diff --git a/frags/wXWbdiOBW5w.json b/frags/wXWbdiOBW5w.json
new file mode 100644
index 0000000000000000000000000000000000000000..b208363fa302f3ff00e522545b8dcbd2bf4008f5
--- /dev/null
+++ b/frags/wXWbdiOBW5w.json
@@ -0,0 +1 @@
+[495, 1510, 1720, 2430, 2908]
\ No newline at end of file
diff --git a/frags/xA00vkxG3lE.json b/frags/xA00vkxG3lE.json
new file mode 100644
index 0000000000000000000000000000000000000000..d9b113f13d13583d6519aaeaef18847cc9c3bcf3
--- /dev/null
+++ b/frags/xA00vkxG3lE.json
@@ -0,0 +1 @@
+[0, 33, 290, 603, 2352, 2894, 3337]
\ No newline at end of file
diff --git a/frags/xbDqd-dVVb0.json b/frags/xbDqd-dVVb0.json
new file mode 100644
index 0000000000000000000000000000000000000000..0635785ee54777066d48352614912a74583c6542
--- /dev/null
+++ b/frags/xbDqd-dVVb0.json
@@ -0,0 +1 @@
+[0, 20, 73, 107, 162, 219, 246, 285, 313, 327, 346, 366, 405, 416, 441, 556, 621, 668, 706, 763, 1516, 1652, 1698, 1717, 1756, 1867, 1927, 2065, 2166, 2253]
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diff --git a/frags/xxydY73V9bQ.json b/frags/xxydY73V9bQ.json
new file mode 100644
index 0000000000000000000000000000000000000000..e35123809a77092cac1e6cf4225d34564522b9b1
--- /dev/null
+++ b/frags/xxydY73V9bQ.json
@@ -0,0 +1 @@
+[599, 1119, 1621, 1992, 2289, 2398, 2502, 2808, 3030, 3412, 3609, 3877, 4364, 4742]
\ No newline at end of file
diff --git a/frags/yESTOkh6nQE.json b/frags/yESTOkh6nQE.json
new file mode 100644
index 0000000000000000000000000000000000000000..d590829e471fa36c5a69def1709929becdc9d36f
--- /dev/null
+++ b/frags/yESTOkh6nQE.json
@@ -0,0 +1 @@
+[0, 15, 107, 199, 370, 699, 882, 1146, 1238, 1440, 1538, 1844, 2021, 2114, 2193, 2264, 2370, 2506, 2686, 2738, 2773, 2816, 2878, 2946, 3022, 3155, 3221]
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diff --git a/frags/yKa-KxY-YJk.json b/frags/yKa-KxY-YJk.json
new file mode 100644
index 0000000000000000000000000000000000000000..c453266d01a0092637f373746b513f05bd66e32e
--- /dev/null
+++ b/frags/yKa-KxY-YJk.json
@@ -0,0 +1 @@
+[0, 250, 546, 857, 1051, 1169, 1219, 1355, 1430, 1550, 1633, 1855, 2865]
\ No newline at end of file
diff --git a/frags/ySqVVEBTy2o.json b/frags/ySqVVEBTy2o.json
new file mode 100644
index 0000000000000000000000000000000000000000..097ac4736aae8b748072d0441f229e962f40cc19
--- /dev/null
+++ b/frags/ySqVVEBTy2o.json
@@ -0,0 +1 @@
+[132, 298, 313, 380, 471, 786, 841, 1157, 1348, 1641, 1886, 1942, 2746, 2845, 3319, 3567, 3748]
\ No newline at end of file
diff --git a/frags/yYto-sIfHjo.json b/frags/yYto-sIfHjo.json
new file mode 100644
index 0000000000000000000000000000000000000000..7e1a77978786a5984179b3434066f40e104a9713
--- /dev/null
+++ b/frags/yYto-sIfHjo.json
@@ -0,0 +1 @@
+[0, 37, 82, 130, 210, 291, 363, 535, 714, 730, 1080, 1484, 1651, 1956, 2043, 2116, 2264, 2298, 2447, 2517, 2590, 2739, 2887, 2944]
\ No newline at end of file
diff --git a/frags/ydyiq1Z22gc.json b/frags/ydyiq1Z22gc.json
new file mode 100644
index 0000000000000000000000000000000000000000..24009eece62ac41a68388058711cc986c1cf623e
--- /dev/null
+++ b/frags/ydyiq1Z22gc.json
@@ -0,0 +1 @@
+[207, 379, 403, 470, 1286, 1380, 1868, 2525, 2783, 3228, 3321, 4254, 4337, 4361]
\ No newline at end of file
diff --git a/frags/yiSZecIWBIc.json b/frags/yiSZecIWBIc.json
new file mode 100644
index 0000000000000000000000000000000000000000..b012f9721d63308097f4276f5167827ea9fb9296
--- /dev/null
+++ b/frags/yiSZecIWBIc.json
@@ -0,0 +1 @@
+[0, 145, 187, 239, 354, 404, 489, 612, 734, 990, 1052, 1157, 1235, 1312, 1666, 1725]
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diff --git a/frags/yndgIDO0zQQ.json b/frags/yndgIDO0zQQ.json
new file mode 100644
index 0000000000000000000000000000000000000000..2044e78c4b5189d33d6f55f3771d49423982cf1c
--- /dev/null
+++ b/frags/yndgIDO0zQQ.json
@@ -0,0 +1 @@
+[95, 124, 358, 751, 1093, 1335, 2191, 2382, 2426, 2717]
\ No newline at end of file
diff --git a/frags/zGDTt9Q3vyM.json b/frags/zGDTt9Q3vyM.json
new file mode 100644
index 0000000000000000000000000000000000000000..7290f03f6cfe0296a76fe5ecaf39e39a152a5545
--- /dev/null
+++ b/frags/zGDTt9Q3vyM.json
@@ -0,0 +1 @@
+[251, 306, 326, 1027, 1536, 2316]
\ No newline at end of file
diff --git a/frags/zPGh2bBeIgM.json b/frags/zPGh2bBeIgM.json
new file mode 100644
index 0000000000000000000000000000000000000000..dfc7d20cdd852e61bedcbdbc930132f14d944274
--- /dev/null
+++ b/frags/zPGh2bBeIgM.json
@@ -0,0 +1 @@
+[0, 138, 478, 532, 728, 880, 1053, 1178, 1288, 1548, 1658, 1805, 1885, 1996, 2101, 2208, 2380, 2449, 2565, 2676, 2744, 2822, 2891, 2950, 3057, 3121, 3190, 3235, 3269, 3385, 3488]
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diff --git a/frags/zYzEmBlJ77s.json b/frags/zYzEmBlJ77s.json
new file mode 100644
index 0000000000000000000000000000000000000000..9f96e19ca575f2aa590f3f8e834dd0a2c2a40698
--- /dev/null
+++ b/frags/zYzEmBlJ77s.json
@@ -0,0 +1 @@
+[0, 30, 200, 513, 772, 887, 1915, 2044, 2826, 2952, 3040, 3112, 3279, 3353, 3388, 3473, 3563]
\ No newline at end of file
diff --git a/frags/z_xyx-z6arc.json b/frags/z_xyx-z6arc.json
new file mode 100644
index 0000000000000000000000000000000000000000..6fbce62f6e81130a606a2e3932cd561bd5d191c9
--- /dev/null
+++ b/frags/z_xyx-z6arc.json
@@ -0,0 +1 @@
+[109, 478, 910, 1456, 1585, 2059, 2502, 2584, 3097]
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diff --git a/transcripts/-Pg11JHzUTo.json b/transcripts/-Pg11JHzUTo.json
new file mode 100644
index 0000000000000000000000000000000000000000..9203d7c8ac61b5e7e523506fb35315280c02264b
--- /dev/null
+++ b/transcripts/-Pg11JHzUTo.json
@@ -0,0 +1 @@
+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.96}, {"text": "[RUSTLING]", "start": 1.96, "duration": 1.47}, {"text": "[CLICKING]", "start": 3.43, "duration": 2.94}, {"text": "NORVIN RICHARDS: OK.", "start": 11.76, "duration": 1.0}, {"text": "So last time, we ended on\none of these cliffhangers.", "start": 12.76, "duration": 5.16}, {"text": "And so I rushed you through\na bunch of Japanese data.", "start": 17.92, "duration": 3.6}, {"text": "And then we got to this new\nbit of linguistic technology--", "start": 21.52, "duration": 4.665}, {"text": "[BUZZING] that's\ngoing to be annoying--", "start": 26.185, "duration": 2.535}, {"text": "this new bit of\nlinguistic technology", "start": 28.72, "duration": 1.68}, {"text": "and went through it pretty fast.", "start": 30.4, "duration": 2.91}, {"text": "So what I want to do is do the\nrun up to that again a little", "start": 33.31, "duration": 4.2}, {"text": "more carefully and show you what\nit is that we're talking about.", "start": 37.51, "duration": 3.378}, {"text": "What we were talking\nabout at the end", "start": 40.888, "duration": 1.542}, {"text": "was the position of accent\nin Japanese compounds.", "start": 42.43, "duration": 4.0}, {"text": "So here are a bunch of\ncompound nouns in Japanese.", "start": 46.43, "duration": 4.26}, {"text": "And the observation\nwas that when", "start": 50.69, "duration": 2.24}, {"text": "you have a compound\nconsisting of two parts,", "start": 52.93, "duration": 5.85}, {"text": "the result always\nhas one accent.", "start": 58.78, "duration": 1.92}, {"text": "It has accent on one\nparticular syllable.", "start": 60.7, "duration": 3.09}, {"text": "The accented\nsyllable doesn't have", "start": 63.79, "duration": 2.25}, {"text": "to be the accented syllable in\neither of the original parts", "start": 66.04, "duration": 4.44}, {"text": "of the compound.", "start": 70.48, "duration": 0.88}, {"text": "So \"raw egg,\" which is the\nfirst example in this slide--", "start": 71.36, "duration": 3.77}, {"text": "\"raw\" and \"egg\"--\nthey have accents", "start": 75.13, "duration": 3.89}, {"text": "where they have accents.", "start": 79.02, "duration": 1.0}, {"text": "\"Raw\" has an accent\non the first syllable.", "start": 80.02, "duration": 2.16}, {"text": "\"Egg\" has an accent on\nthe second syllable.", "start": 82.18, "duration": 1.92}, {"text": "But \"raw egg\" has an accent\non the syllable which is not", "start": 84.1, "duration": 3.0}, {"text": "normally accented in \"egg.\"", "start": 87.1, "duration": 2.73}, {"text": "What we said was there is\na set of rules for where", "start": 89.83, "duration": 4.11}, {"text": "accent goes in these compounds.", "start": 93.94, "duration": 2.49}, {"text": "And the rules go\nsomething like this.", "start": 96.43, "duration": 2.88}, {"text": "There's only going\nto be one accent.", "start": 99.31, "duration": 2.07}, {"text": "It needs to be next to the\nboundary between the words.", "start": 101.38, "duration": 3.99}, {"text": "And if possible, it should\nbe on the second word.", "start": 105.37, "duration": 2.49}, {"text": "That is, it should be after\nthe boundary between the words.", "start": 107.86, "duration": 3.18}, {"text": "But you don't do that if that\nwould result in the accent", "start": 111.04, "duration": 3.06}, {"text": "being on the last syllable.", "start": 114.1, "duration": 1.35}, {"text": "So the general pattern is the\none you're getting in \"French", "start": 115.45, "duration": 3.66}, {"text": "fry\" up there--\n\"furaido POteto\"--", "start": 119.11, "duration": 2.43}, {"text": "where you get accent at the\nbeginning of the second half", "start": 121.54, "duration": 3.42}, {"text": "of the compound, \"potato.\"", "start": 124.96, "duration": 1.35}, {"text": "Yeah.", "start": 126.31, "duration": 1.62}, {"text": "That's what you get in most of\nthe examples on the preceding", "start": 127.93, "duration": 2.609}, {"text": "slide.", "start": 130.539, "duration": 0.5}, {"text": "If we go back to\nthe preceding slide,", "start": 131.039, "duration": 1.851}, {"text": "you can see that in\n\"raw egg,\" right?", "start": 132.89, "duration": 1.608}, {"text": "It's at the beginning of \"egg.\"", "start": 134.498, "duration": 1.292}, {"text": "And you can see it\nin \"field mouse.\"", "start": 135.79, "duration": 1.23}, {"text": "It's at the\nbeginning of \"mouse.\"", "start": 137.02, "duration": 1.375}, {"text": "And you're also getting\nit in \"French fry.\"", "start": 138.395, "duration": 2.945}, {"text": "But there's this coherent\nclass of exceptions.", "start": 141.34, "duration": 3.84}, {"text": "If the second half\nof the compound", "start": 145.18, "duration": 2.43}, {"text": "is only one syllable\nlong, then you", "start": 147.61, "duration": 2.22}, {"text": "don't put accent\non the second half.", "start": 149.83, "duration": 1.56}, {"text": "You put it at the end\nof the first half.", "start": 151.39, "duration": 2.53}, {"text": "So Kagawa prefecture-- \"kagawa\"\nis the name of a place.", "start": 153.92, "duration": 4.79}, {"text": "And it's got accent\non its first syllable.", "start": 158.71, "duration": 2.7}, {"text": "But the expression for\n\"Kagawa prefecture\"", "start": 161.41, "duration": 3.15}, {"text": "has accent at almost\nat the boundary.", "start": 164.56, "duration": 2.907}, {"text": "It's right before the\nboundary between them,", "start": 167.467, "duration": 1.833}, {"text": "not on the second half of\nthe compound, unusually,", "start": 169.3, "duration": 2.725}, {"text": "because the second\nhalf of the compound", "start": 172.025, "duration": 1.625}, {"text": "is only one syllable long.", "start": 173.65, "duration": 1.11}, {"text": "So we get \"kagaWAken.\"", "start": 174.76, "duration": 2.093}, {"text": "Yeah.", "start": 176.853, "duration": 2.367}, {"text": "I'm telling you all this\nnot just to educate you", "start": 179.22, "duration": 2.79}, {"text": "in what a cool and complicated\nlanguage Japanese is,", "start": 182.01, "duration": 3.42}, {"text": "but to show you\nthat there are cases", "start": 185.43, "duration": 2.13}, {"text": "of cool and\ncomplicated phenomena", "start": 187.56, "duration": 2.37}, {"text": "that can be fruitfully\nthought of as a series", "start": 189.93, "duration": 3.51}, {"text": "of things that you're trying\nto do which are in conflict", "start": 193.44, "duration": 2.94}, {"text": "with each other sometimes.", "start": 196.38, "duration": 1.5}, {"text": "So Japanese wants the accent\nto be on the second word", "start": 197.88, "duration": 4.86}, {"text": "and next to the boundary\nbetween the words.", "start": 202.74, "duration": 2.07}, {"text": "But it also wants\nit not to be final.", "start": 204.81, "duration": 2.88}, {"text": "And if it can't have all\nof those things at once,", "start": 207.69, "duration": 3.96}, {"text": "like in \"Kagawa\nprefecture,\" it has", "start": 211.65, "duration": 2.16}, {"text": "to decide, do I care more\nabout it not being final,", "start": 213.81, "duration": 2.97}, {"text": "or do I care more about it\nbeing on the second word?", "start": 216.78, "duration": 2.19}, {"text": "And Japanese cares more about\nit not being final, right?", "start": 218.97, "duration": 3.96}, {"text": "So it retracts it\nfrom the second word", "start": 222.93, "duration": 1.71}, {"text": "to the end of the first word.", "start": 224.64, "duration": 2.828}, {"text": "Does anybody still read--", "start": 227.468, "duration": 1.042}, {"text": "Isaac Asimov had these\nstories, the robot stories.", "start": 228.51, "duration": 3.02}, {"text": "He had a book, I, Robot.", "start": 231.53, "duration": 1.75}, {"text": "It was a series of stories.", "start": 233.28, "duration": 1.442}, {"text": "Some of you have heard\nof them, at least?", "start": 234.722, "duration": 1.708}, {"text": "Yeah.", "start": 236.43, "duration": 0.5}, {"text": "So they feature robots that\nhave these laws governing", "start": 236.93, "duration": 4.9}, {"text": "how they work.", "start": 241.83, "duration": 0.93}, {"text": "And the laws act like\nthese kinds of laws.", "start": 242.76, "duration": 2.22}, {"text": "So there's the first law.", "start": 244.98, "duration": 1.89}, {"text": "And then there's the second law.", "start": 246.87, "duration": 1.47}, {"text": "And the rule for\nthe second law is", "start": 248.34, "duration": 1.417}, {"text": "you must obey the second\nlaw unless it comes", "start": 249.757, "duration": 1.881}, {"text": "in conflict with the first law.", "start": 251.638, "duration": 1.292}, {"text": "Then you disobey the second law\nand do the first law, right?", "start": 252.93, "duration": 2.16}, {"text": "And there's a third\nlaw, which you", "start": 255.09, "duration": 1.617}, {"text": "should do unless it\nconflicts with the first", "start": 256.707, "duration": 1.833}, {"text": "or the second law.", "start": 258.54, "duration": 1.08}, {"text": "So this is like that, right?", "start": 259.62, "duration": 1.77}, {"text": "So Japanese wants the accent\nto be on the second word, oh,", "start": 261.39, "duration": 5.37}, {"text": "unless that's going to\nmake the accent final.", "start": 266.76, "duration": 2.01}, {"text": "Then you don't do that.", "start": 268.77, "duration": 2.07}, {"text": "Does that make sense?", "start": 270.84, "duration": 2.64}, {"text": "That's a way-- or to put\nthat another way, don't", "start": 273.48, "duration": 4.05}, {"text": "put the accent on\nthe last syllable", "start": 277.53, "duration": 1.62}, {"text": "is more important than put\nthe accent on the second word.", "start": 279.15, "duration": 3.205}, {"text": "That's the picture\nthat we end up with.", "start": 282.355, "duration": 1.625}, {"text": "So you get \"kagaWAken\" with the\naccent at the end of \"kagawa\"", "start": 283.98, "duration": 6.84}, {"text": "and not \"kagawaKEN.\"", "start": 290.82, "duration": 2.46}, {"text": "You don't put accent at the end.", "start": 293.28, "duration": 4.53}, {"text": "There's a standard\nway of representing", "start": 297.81, "duration": 1.92}, {"text": "these kinds of facts, these\nbodies of facts, which", "start": 299.73, "duration": 2.67}, {"text": "involves this table\nthat I've got here", "start": 302.4, "duration": 2.25}, {"text": "at the bottom of the slide.", "start": 304.65, "duration": 2.43}, {"text": "This was an approach\nto phonology that was", "start": 307.08, "duration": 2.85}, {"text": "invented by people who--", "start": 309.93, "duration": 3.93}, {"text": "one of them in\nparticular, Alan Prince,", "start": 313.86, "duration": 2.1}, {"text": "is a brilliant, brilliant man.", "start": 315.96, "duration": 2.4}, {"text": "But he enjoys\nintimidating people.", "start": 318.36, "duration": 2.02}, {"text": "And so instead of\ncalling this a table,", "start": 320.38, "duration": 2.72}, {"text": "he decided to call it a tableau.", "start": 323.1, "duration": 2.28}, {"text": "So he gives it a\nFrench name in order", "start": 325.38, "duration": 3.03}, {"text": "to be as intimidating\nas possible.", "start": 328.41, "duration": 2.64}, {"text": "So I'll adopt that because\nthat's what phonologists,", "start": 331.05, "duration": 4.89}, {"text": "linguists standardly\ncall these objects.", "start": 335.94, "duration": 2.68}, {"text": "This is a tableau.", "start": 338.62, "duration": 1.85}, {"text": "And what the tableau\nrepresents is this interplay", "start": 340.47, "duration": 3.21}, {"text": "between the different\nlaws that are governing", "start": 343.68, "duration": 2.67}, {"text": "where the accent goes.", "start": 346.35, "duration": 2.16}, {"text": "The idea is the most important\nlaws are toward the left.", "start": 348.51, "duration": 4.05}, {"text": "And the least important\nlaws are toward the right.", "start": 352.56, "duration": 3.57}, {"text": "And what you do is\nimagine all of the places", "start": 356.13, "duration": 2.82}, {"text": "where you could put the accent.", "start": 358.95, "duration": 1.47}, {"text": "And you ask yourself, how does\nthat placement of the accent", "start": 360.42, "duration": 4.74}, {"text": "square with the\nvarious different laws?", "start": 365.16, "duration": 2.88}, {"text": "The little asterisks mark places\nwhere one of the candidates,", "start": 368.04, "duration": 4.71}, {"text": "one of the options\nyou're considering,", "start": 372.75, "duration": 3.12}, {"text": "violates one of the laws.", "start": 375.87, "duration": 2.17}, {"text": "So for example, the first one,\nwhich kept both of the accents", "start": 378.04, "duration": 5.09}, {"text": "in the parts of the compound,\njust kept them both,", "start": 383.13, "duration": 4.29}, {"text": "violates the most\nimportant law, which is", "start": 387.42, "duration": 1.74}, {"text": "you may only have one accent.", "start": 389.16, "duration": 1.38}, {"text": "So it gets a star right there.", "start": 390.54, "duration": 2.38}, {"text": "And that eliminates that\none from competition", "start": 392.92, "duration": 2.12}, {"text": "because it's violated the most\nimportant law, the one that's", "start": 395.04, "duration": 3.66}, {"text": "furthest on the left.", "start": 398.7, "duration": 2.14}, {"text": "And then what I've done\nis consider examples", "start": 400.84, "duration": 3.56}, {"text": "where the accent is-- it's a\nfour-syllable word, so we're", "start": 404.4, "duration": 2.43}, {"text": "considering putting the single\naccent on any of the four", "start": 406.83, "duration": 3.21}, {"text": "syllables.", "start": 410.04, "duration": 0.96}, {"text": "The first two, which\nhave the accent", "start": 411.0, "duration": 3.6}, {"text": "on the first or the\nsecond syllable,", "start": 414.6, "duration": 1.5}, {"text": "violate the second\nlaw, which says", "start": 416.1, "duration": 1.43}, {"text": "put the accent near the\nboundary between the two", "start": 417.53, "duration": 2.0}, {"text": "halves of the compound.", "start": 419.53, "duration": 1.2}, {"text": "So those are ones in\nwhich the accent is not", "start": 420.73, "duration": 3.62}, {"text": "on a syllable that's\nnext to the boundary.", "start": 424.35, "duration": 3.28}, {"text": "And then the next to last one,\nwhich is the one that wins--", "start": 427.63, "duration": 5.51}, {"text": "that's the one that obeys\nall of the conditions", "start": 433.14, "duration": 2.492}, {"text": "except for the least\nimportant one, which", "start": 435.632, "duration": 1.708}, {"text": "is it's best to put your\naccent on the last word, right?", "start": 437.34, "duration": 3.96}, {"text": "You notice, there is\nno perfect candidate.", "start": 443.91, "duration": 2.31}, {"text": "There isn't anything that\ndoesn't have any stars.", "start": 446.22, "duration": 2.82}, {"text": "What the tableau\ndoes is allow us", "start": 449.04, "duration": 1.59}, {"text": "to think in a\nformal way about how", "start": 450.63, "duration": 5.1}, {"text": "you satisfy conditions that are\nnot compatible with each other.", "start": 455.73, "duration": 3.488}, {"text": "And I just realized I\nget to take this off.", "start": 459.218, "duration": 1.792}, {"text": "I keep forgetting that.", "start": 461.01, "duration": 2.67}, {"text": "Yeah.", "start": 463.68, "duration": 1.42}, {"text": "So that's what the tableau\nis meant to represent.", "start": 465.1, "duration": 2.67}, {"text": "Are there are questions\nabout the tableau?", "start": 467.77, "duration": 2.31}, {"text": "There's a standard way\nto represent the fact", "start": 470.08, "duration": 2.67}, {"text": "that the winner is\nthat next to last one", "start": 472.75, "duration": 2.587}, {"text": "there, where the stress is\non the next to last syllable,", "start": 475.337, "duration": 2.333}, {"text": "the accent is on the\nnext to last syllable,", "start": 477.67, "duration": 1.792}, {"text": "which is to put a pointing\nfinger next to it like that.", "start": 479.462, "duration": 2.778}, {"text": "This is the one that wins.", "start": 482.24, "duration": 2.54}, {"text": "Optimality theory-- this\napproach to phonology", "start": 484.78, "duration": 4.2}, {"text": "is called optimality theory.", "start": 488.98, "duration": 1.54}, {"text": "And I don't know.", "start": 490.52, "duration": 1.91}, {"text": "I guess they just\nliked the font that", "start": 492.43, "duration": 1.65}, {"text": "had the pointing finger in it.", "start": 494.08, "duration": 1.25}, {"text": "So they decided to use it.", "start": 495.33, "duration": 2.264}, {"text": "OK?", "start": 497.594, "duration": 0.543}, {"text": "This is an approach.", "start": 498.137, "duration": 0.833}, {"text": "Yeah?", "start": 498.97, "duration": 0.936}, {"text": "STUDENT: Question about--\nthere is an accent on--", "start": 499.906, "duration": 4.804}, {"text": "how do we know there's\nan accent on \"ken\"", "start": 504.71, "duration": 2.86}, {"text": "if it just never shows up\nbecause every time [INAUDIBLE]??", "start": 507.57, "duration": 3.023}, {"text": "NORVIN RICHARDS: Oh, you\nmean why am I putting", "start": 510.593, "duration": 1.917}, {"text": "an accent on \"ken\" over there?", "start": 512.51, "duration": 1.919}, {"text": "STUDENT: Because every\ntime \"ken\" shows up,", "start": 514.429, "duration": 2.341}, {"text": "one syllable is at the end.", "start": 516.77, "duration": 2.23}, {"text": "So there's no-- so it's\nalways the final accent.", "start": 519.0, "duration": 3.13}, {"text": "So how do we know\nthere's an accent?", "start": 522.13, "duration": 1.5}, {"text": "NORVIN RICHARDS: Yeah,\nthat's a very good point.", "start": 523.63, "duration": 2.56}, {"text": "It is possible to\npronounce \"ken\" by itself,", "start": 526.19, "duration": 2.6}, {"text": "not as part of a compound.", "start": 528.79, "duration": 1.93}, {"text": "So if you want to talk about\n\"the prefecture,\" it's a word.", "start": 530.72, "duration": 2.87}, {"text": "It means \"prefecture,\"\nwhich is like a state.", "start": 533.59, "duration": 3.18}, {"text": "It's an administrative\nsubdivision of Japan.", "start": 536.77, "duration": 3.54}, {"text": "And it's possible to\nsay that word by itself.", "start": 540.31, "duration": 1.993}, {"text": "STUDENT: So unbounded.", "start": 542.303, "duration": 0.917}, {"text": "NORVIN RICHARDS: Sorry?", "start": 543.22, "duration": 0.958}, {"text": "STUDENT: So it's unfounded?", "start": 544.178, "duration": 1.672}, {"text": "NORVIN RICHARDS: It's?", "start": 545.85, "duration": 2.17}, {"text": "STUDENT: It's unbounded?", "start": 548.02, "duration": 1.0}, {"text": "NORVIN RICHARDS:\n\"ken\" is unbounded?", "start": 549.02, "duration": 2.28}, {"text": "I don't think I\nknow what you mean.", "start": 551.3, "duration": 2.23}, {"text": "Oh, it's not a bound morpheme.", "start": 553.53, "duration": 1.25}, {"text": "That's right.", "start": 554.78, "duration": 0.3}, {"text": "It can be a free morpheme.", "start": 555.08, "duration": 1.14}, {"text": "Yes, yes.", "start": 556.22, "duration": 0.718}, {"text": "That's right.", "start": 556.938, "duration": 0.542}, {"text": "So you can say in Japanese,\n\"The prefecture is large\"", "start": 557.48, "duration": 4.02}, {"text": "or whatever.", "start": 561.5, "duration": 1.24}, {"text": "And then you can show\nthat it's accented, yeah.", "start": 562.74, "duration": 4.42}, {"text": "Good question.", "start": 567.16, "duration": 0.94}, {"text": "There are other questions\npeople have about this?", "start": 568.1, "duration": 3.6}, {"text": "OK.", "start": 571.7, "duration": 0.99}, {"text": "So this is just meant to\nillustrate the workings", "start": 572.69, "duration": 3.48}, {"text": "of optimality theory.", "start": 576.17, "duration": 2.67}, {"text": "Why am I showing you this one?", "start": 578.84, "duration": 2.03}, {"text": "I'm not sure.", "start": 580.87, "duration": 0.91}, {"text": "OK.", "start": 581.78, "duration": 1.27}, {"text": "Oh, I see.", "start": 583.05, "duration": 0.96}, {"text": "This is a similar\ntableau for \"French fry.\"", "start": 584.01, "duration": 3.48}, {"text": "So this has the\nsame constraints,", "start": 587.49, "duration": 3.99}, {"text": "these things that I put\nin all caps up at the top.", "start": 591.48, "duration": 4.05}, {"text": "In this case, you do\nend up with accent", "start": 595.53, "duration": 3.54}, {"text": "at the beginning of\npotato on the second word.", "start": 599.07, "duration": 2.58}, {"text": "That actually is a\nperfect candidate.", "start": 601.65, "duration": 1.96}, {"text": "So this is an example in\nwhich none of the laws", "start": 603.61, "duration": 3.38}, {"text": "are violated by\nthe best candidate.", "start": 606.99, "duration": 2.767}, {"text": "The laws aren't in\nconflict with each other.", "start": 609.757, "duration": 1.833}, {"text": "So you can put accent\nat the beginning", "start": 611.59, "duration": 1.583}, {"text": "of the last word, \"potato.\"", "start": 613.173, "duration": 2.277}, {"text": "And it won't be final.", "start": 615.45, "duration": 1.71}, {"text": "Yeah, yeah?", "start": 617.16, "duration": 1.77}, {"text": "STUDENT: So for example, if this\nperfect candidate didn't exist,", "start": 618.93, "duration": 3.294}, {"text": "and you were having to\nchoose between the first", "start": 622.224, "duration": 1.958}, {"text": "and the third--", "start": 624.182, "duration": 0.748}, {"text": "NORVIN RICHARDS: Yeah.", "start": 624.93, "duration": 0.36}, {"text": "STUDENT: --you\nwould want to choose", "start": 625.29, "duration": 1.458}, {"text": "the third because it violates\na rule that's less important.", "start": 626.748, "duration": 2.644}, {"text": "NORVIN RICHARDS: Yeah,\nthat's absolutely right.", "start": 629.392, "duration": 1.958}, {"text": "So if, for some reason,\nthat fourth candidate", "start": 631.35, "duration": 2.52}, {"text": "were impossible-- say,\nthere was another very high", "start": 633.87, "duration": 2.52}, {"text": "ranking constraint-- don't put\naccent on \"potato,\" then yes.", "start": 636.39, "duration": 7.59}, {"text": "The third would win.", "start": 643.98, "duration": 1.26}, {"text": "That's right.", "start": 645.24, "duration": 0.75}, {"text": "And actually, we can\nsee that by looking", "start": 645.99, "duration": 2.518}, {"text": "at the behavior of \"kagaWAken.\"", "start": 648.508, "duration": 1.292}, {"text": "So if we eliminate the\noption of putting accent", "start": 649.8, "duration": 4.08}, {"text": "on the last word, that's\nwhere the accent goes.", "start": 653.88, "duration": 2.52}, {"text": "It goes at the end\nof the first word.", "start": 656.4, "duration": 2.23}, {"text": "So it's the best\nyou can do, right?", "start": 658.63, "duration": 3.32}, {"text": "Still near the boundary,\nstill only one accent, just", "start": 661.95, "duration": 4.007}, {"text": "didn't manage to\naccent the last word,", "start": 665.957, "duration": 1.583}, {"text": "which is what you'd like to do.", "start": 667.54, "duration": 1.292}, {"text": "But it's not high on\nyour list of constraints.", "start": 668.832, "duration": 3.048}, {"text": "Yep.", "start": 671.88, "duration": 0.855}, {"text": "Does that make sense?", "start": 672.735, "duration": 1.675}, {"text": "So this is an approach to\nthinking about phonology.", "start": 674.41, "duration": 4.1}, {"text": "Optimality theory\nis the name for it.", "start": 678.51, "duration": 2.68}, {"text": "It says-- in a way, it's\na comforting theory--", "start": 681.19, "duration": 2.9}, {"text": "It says, \"Do the best you can.\"", "start": 684.09, "duration": 1.6}, {"text": "You have all of these things.", "start": 685.69, "duration": 1.418}, {"text": "Probably, all of\nyou have encountered", "start": 687.108, "duration": 1.542}, {"text": "things like this\nin other domains", "start": 688.65, "duration": 1.68}, {"text": "at MIT if you've ever dealt\nwith engineering problems.", "start": 690.33, "duration": 2.25}, {"text": "There are probably cases\nwhere you have various things", "start": 692.58, "duration": 3.008}, {"text": "that you want to achieve.", "start": 695.588, "duration": 1.042}, {"text": "And you can't\noptimize all of them.", "start": 696.63, "duration": 2.46}, {"text": "You have to decide which\nones are the most important.", "start": 699.09, "duration": 3.04}, {"text": "And the idea here is that\nlanguage is like that.", "start": 702.13, "duration": 2.33}, {"text": "There are cases where\nyou have to decide", "start": 704.46, "duration": 2.55}, {"text": "among your various\ndesiderata which", "start": 707.01, "duration": 3.84}, {"text": "ones you care about the most.", "start": 710.85, "duration": 2.1}, {"text": "The hope in optimality\ntheory is that we'll", "start": 712.95, "duration": 2.22}, {"text": "end up with a list of these\nconstraints, these laws,", "start": 715.17, "duration": 4.98}, {"text": "these rules that\nwill be universal.", "start": 720.15, "duration": 2.77}, {"text": "And the differences\nbetween languages", "start": 722.92, "duration": 2.87}, {"text": "are just a matter\nof deciding what", "start": 725.79, "duration": 2.07}, {"text": "order the different\nconstraints are in.", "start": 727.86, "duration": 2.55}, {"text": "So there could be languages\nin which the one accent", "start": 730.41, "duration": 6.36}, {"text": "rule is very low ranked and\nthe first candidate maybe wins,", "start": 736.77, "duration": 5.07}, {"text": "right?", "start": 741.84, "duration": 0.5}, {"text": "You could imagine a\nlanguage like that.", "start": 742.34, "duration": 2.29}, {"text": "Tokyo Japanese\ndoesn't work that way.", "start": 744.63, "duration": 2.17}, {"text": "So differences between\nlanguages are all a matter", "start": 746.8, "duration": 2.24}, {"text": "of reranking the constraints.", "start": 749.04, "duration": 1.86}, {"text": "That's the mission statement\nof optimality theory,", "start": 750.9, "duration": 3.27}, {"text": "is to try to figure out how\nthe world could work that way.", "start": 754.17, "duration": 2.8}, {"text": "Yeah?", "start": 756.97, "duration": 0.5}, {"text": "OK.", "start": 759.905, "duration": 0.5}, {"text": "Optimality theory\nwas partly inspired", "start": 763.13, "duration": 1.95}, {"text": "by the discovery of these\nkinds of conspiracies", "start": 765.08, "duration": 2.933}, {"text": "that we started talking\nabout when I was showing you", "start": 768.013, "duration": 2.167}, {"text": "some stuff about Yawelmani.", "start": 770.18, "duration": 1.32}, {"text": "And now we've seen another\nexample from Japanese.", "start": 771.5, "duration": 3.06}, {"text": "For Yawelmani, the\nconspiracy was,", "start": 774.56, "duration": 2.76}, {"text": "I don't want three\nconsonants in a row.", "start": 777.32, "duration": 2.22}, {"text": "And I'll do various\nthings to achieve that.", "start": 779.54, "duration": 2.67}, {"text": "We said you could state rules\ngoverning the various things.", "start": 782.21, "duration": 2.97}, {"text": "And maybe in a\nsense, you should.", "start": 785.18, "duration": 2.23}, {"text": "But you-- the idea is, let's\ntry to keep sight of the fact", "start": 787.41, "duration": 3.073}, {"text": "that all of these\nrules are trying", "start": 790.483, "duration": 1.417}, {"text": "to achieve the same thing.", "start": 791.9, "duration": 1.62}, {"text": "We want to also capture\nthat kind of a fact.", "start": 793.52, "duration": 2.67}, {"text": "And there's something similar\ngoing on here in Japanese.", "start": 796.19, "duration": 3.03}, {"text": "One of the rules, the\nhighest ranking rule,", "start": 799.22, "duration": 3.09}, {"text": "was \"Don't have more than\none accent in a word.\"", "start": 802.31, "duration": 4.44}, {"text": "And what we saw last time was\nthat there are various things", "start": 806.75, "duration": 4.44}, {"text": "that Japanese does\nto achieve this", "start": 811.19, "duration": 2.67}, {"text": "depending on the situation.", "start": 813.86, "duration": 2.29}, {"text": "So there are words\nlike \"gurai,\" which", "start": 816.15, "duration": 5.39}, {"text": "I think I translated last time\nas even, which are accented.", "start": 821.54, "duration": 3.99}, {"text": "And if you attach them\nto another word that's", "start": 825.53, "duration": 2.01}, {"text": "also accented, you delete\nthe accent on the first word,", "start": 827.54, "duration": 2.833}, {"text": "in the word you're\nattaching \"gurai\" to.", "start": 830.373, "duration": 1.667}, {"text": "And there are other words,\nlike \"made,\" which means \"to,\"", "start": 832.04, "duration": 2.715}, {"text": "or \"up to,\" \"as far as,\"\nwhich are accented but only", "start": 834.755, "duration": 4.095}, {"text": "if they are attached\nto unaccented words.", "start": 838.85, "duration": 3.87}, {"text": "And then we've done all this\ntalking about compounds.", "start": 842.72, "duration": 3.09}, {"text": "These are all different\nkinds of examples in which", "start": 845.81, "duration": 2.55}, {"text": "different things happen.", "start": 848.36, "duration": 1.02}, {"text": "There are different\nstrategies, right?", "start": 849.38, "duration": 1.583}, {"text": "So for \"gurai,\" it's \"Delete\nthe accent on the word", "start": 850.963, "duration": 2.917}, {"text": "you've attached 'gurai' to.\"", "start": 853.88, "duration": 1.8}, {"text": "For \"made,\" it's\n\"Delete the accent on", "start": 855.68, "duration": 1.89}, {"text": "'made' for the compounds.\"", "start": 857.57, "duration": 1.5}, {"text": "We've now talked\nabout this computation", "start": 859.07, "duration": 2.163}, {"text": "that you go through to\ntry to figure out where", "start": 861.233, "duration": 1.917}, {"text": "the single accent should go.", "start": 863.15, "duration": 1.56}, {"text": "But what all of these\nthings are doing", "start": 864.71, "duration": 1.59}, {"text": "is trying to arrange for there\nto just be a single accent.", "start": 866.3, "duration": 3.06}, {"text": "And one of the virtues\nof optimality theory", "start": 869.36, "duration": 1.86}, {"text": "is that it allows us to make\nthat part of our analysis.", "start": 871.22, "duration": 5.07}, {"text": "If we just stated\nthese rules, we'd", "start": 876.29, "duration": 2.64}, {"text": "be losing sight of the\nfact that these rules all", "start": 878.93, "duration": 2.28}, {"text": "seem to be trying to\nachieve the same thing.", "start": 881.21, "duration": 2.258}, {"text": "That's one of the things people\nwho work on optimality theory", "start": 883.468, "duration": 2.542}, {"text": "are trying to get.", "start": 886.01, "duration": 0.93}, {"text": "And then of course,\nthe goal is to try", "start": 886.94, "duration": 1.32}, {"text": "to understand why we\nhave the constraints", "start": 888.26, "duration": 1.59}, {"text": "that we have and not others.", "start": 889.85, "duration": 1.26}, {"text": "That's another thing people\nwho work on this try to do.", "start": 891.11, "duration": 2.58}, {"text": "Yes.", "start": 899.29, "duration": 0.5}, {"text": "I just said that and that.", "start": 899.79, "duration": 2.5}, {"text": "So remember, Yawelmani, which\nwas \"Avoid strings of three", "start": 902.29, "duration": 3.5}, {"text": "consonants either by inserting\nvowels or by deleting", "start": 905.79, "duration": 3.42}, {"text": "'h' if you have an 'h'.\"", "start": 909.21, "duration": 3.12}, {"text": "So I've been saying we could\njust state these rules.", "start": 912.33, "duration": 6.03}, {"text": "But we'd be missing\na generalization.", "start": 918.36, "duration": 1.98}, {"text": "Yawelmani is trying to avoid\nthree consonants in a row.", "start": 920.34, "duration": 2.43}, {"text": "Japanese is trying to avoid\ntwo accents in a single word.", "start": 922.77, "duration": 4.59}, {"text": "Maybe it's obvious.", "start": 927.36, "duration": 0.87}, {"text": "We don't want to miss\ngeneralizations like that.", "start": 928.23, "duration": 2.29}, {"text": "We want to find them\nand understand them.", "start": 930.52, "duration": 4.34}, {"text": "So similar kind of thing that\nwe could think about here--", "start": 934.86, "duration": 4.02}, {"text": "we've talked now a couple\nof times about Polish.", "start": 938.88, "duration": 2.73}, {"text": "Polish is one of the\nnumber of languages", "start": 941.61, "duration": 1.92}, {"text": "in which if you have\ncertain kinds of consonants", "start": 943.53, "duration": 3.51}, {"text": "at the ends of words,\nconsonants like \"b,\"", "start": 947.04, "duration": 2.31}, {"text": "and \"d,\" and \"g,\" and\n\"z,\" we convince ourselves", "start": 949.35, "duration": 2.4}, {"text": "that they devoice.", "start": 951.75, "duration": 0.81}, {"text": "They become voiceless\nat the ends of words.", "start": 952.56, "duration": 2.61}, {"text": "That allows us to capture\nvarious kinds of facts", "start": 955.17, "duration": 2.61}, {"text": "about what happens to Polish\nwords when they become plural--", "start": 957.78, "duration": 2.94}, {"text": "namely, that consonants that\nsound voiceless when they're", "start": 960.72, "duration": 5.28}, {"text": "at the ends of words\nbecome voiced sometimes", "start": 966.0, "duration": 3.24}, {"text": "when they're no longer at\nthe end of words, we decided.", "start": 969.24, "duration": 2.4}, {"text": "That's because they're\nunderlyingly voiced.", "start": 971.64, "duration": 2.64}, {"text": "And they devoice when\nthey're at the ends of words.", "start": 974.28, "duration": 4.45}, {"text": "So this is all familiar.", "start": 978.73, "duration": 1.55}, {"text": "You all remember Polish?", "start": 980.28, "duration": 1.465}, {"text": "It's not just Polish.", "start": 981.745, "duration": 0.875}, {"text": "There are lots of\nlanguages that do this.", "start": 982.62, "duration": 3.73}, {"text": "And so what I'm inviting you\nto do at the end of this slide", "start": 986.35, "duration": 3.68}, {"text": "is to imagine two kinds of\nstories about Polish-- one", "start": 990.03, "duration": 3.15}, {"text": "that would say, yeah, final\nconsonants devoice in Polish,", "start": 993.18, "duration": 3.18}, {"text": "and another that\nwould say, well, there", "start": 996.36, "duration": 2.01}, {"text": "are four rules, actually.", "start": 998.37, "duration": 1.11}, {"text": "There's a rule that says\n\"b\" voices when it's final,", "start": 999.48, "duration": 2.73}, {"text": "and a rule that says \"d\"\ndevoices when it's final,", "start": 1002.21, "duration": 2.31}, {"text": "and a rule that says \"g\"\ndevoices when it's-- yeah?", "start": 1004.52, "duration": 3.27}, {"text": "Both of those would capture\nall of the Polish facts.", "start": 1007.79, "duration": 2.85}, {"text": "One of them is clearly better.", "start": 1010.64, "duration": 2.59}, {"text": "So we want to understand why\nwe get the particular phenomena", "start": 1013.23, "duration": 4.43}, {"text": "that we do in Polish.", "start": 1017.66, "duration": 1.23}, {"text": "Is it clear to everybody\nthat it would be better", "start": 1018.89, "duration": 2.58}, {"text": "to do things that way?", "start": 1021.47, "duration": 1.84}, {"text": "And what we're doing\nhere is similar.", "start": 1023.31, "duration": 4.32}, {"text": "Why would it be better?", "start": 1027.63, "duration": 3.29}, {"text": "What would be wrong--", "start": 1030.92, "duration": 1.31}, {"text": "why is it better to be able to\nsay final consonants devoice", "start": 1032.23, "duration": 3.369}, {"text": "than to say, well, we\nhave these four rules.", "start": 1035.599, "duration": 4.301}, {"text": "Yeah, Faith?", "start": 1039.9, "duration": 0.59}, {"text": "STUDENT: I think\nyou're addressing", "start": 1040.49, "duration": 1.17}, {"text": "the more general phenomenon.", "start": 1041.66, "duration": 1.288}, {"text": "It's very difficult to\ncatalog every single letter", "start": 1042.948, "duration": 2.904}, {"text": "and to have vowel sound\nas something like that", "start": 1045.852, "duration": 3.872}, {"text": "because you eventually have\na list that's very long.", "start": 1049.724, "duration": 2.329}, {"text": "NORVIN RICHARDS: Yeah.", "start": 1052.053, "duration": 0.917}, {"text": "So it might make\nit easier to make", "start": 1052.97, "duration": 1.44}, {"text": "cross-linguistic comparisons.", "start": 1054.41, "duration": 1.56}, {"text": "Yeah, that's a very good point.", "start": 1055.97, "duration": 1.38}, {"text": "Yeah, yeah.", "start": 1057.35, "duration": 2.58}, {"text": "Yeah?", "start": 1059.93, "duration": 0.5}, {"text": "We also maybe--", "start": 1063.26, "duration": 2.025}, {"text": "I don't know if this is\na good way to say it.", "start": 1065.285, "duration": 1.875}, {"text": "Maybe it is.", "start": 1067.16, "duration": 1.87}, {"text": "We want to understand why\nthe sounds that become", "start": 1069.03, "duration": 4.62}, {"text": "voiceless at the ends of\nwords in Polish are \"b,\"", "start": 1073.65, "duration": 3.195}, {"text": "\"d,\" \"g,\" and \"z,\" and not\n\"b,\" \"d,\" \"a,\" and \"o,\" right?", "start": 1076.845, "duration": 7.845}, {"text": "If we're just making four\nrules for those four letters,", "start": 1084.69, "duration": 3.78}, {"text": "then it's not clear.", "start": 1088.47, "duration": 3.12}, {"text": "There's no reason why\none of those rules", "start": 1091.59, "duration": 2.73}, {"text": "is more natural than the other.", "start": 1094.32, "duration": 1.42}, {"text": "But as I keep saying--", "start": 1095.74, "duration": 1.88}, {"text": "what's happening here in\nPolish is extremely common.", "start": 1097.62, "duration": 2.65}, {"text": "So you get it in Turkish.", "start": 1100.27, "duration": 2.013}, {"text": "You get it in Russian.", "start": 1102.283, "duration": 0.917}, {"text": "You get it in a bunch\nof different languages--", "start": 1103.2, "duration": 2.61}, {"text": "German.", "start": 1105.81, "duration": 1.89}, {"text": "And so we want to\nunderstand why it's common.", "start": 1107.7, "duration": 3.812}, {"text": "And part of understanding\nwhy it's common", "start": 1111.512, "duration": 1.708}, {"text": "is being able to say that that's\na common rule, a standard rule", "start": 1113.22, "duration": 3.66}, {"text": "that we see all over the place.", "start": 1116.88, "duration": 1.66}, {"text": "And then we can get to\nwork on understanding it.", "start": 1118.54, "duration": 2.54}, {"text": "If we just have\nthese four rules,", "start": 1121.08, "duration": 1.44}, {"text": "then it's unclear why those\nfour rules are so common,", "start": 1122.52, "duration": 2.34}, {"text": "whereas \"b,\" \"d,\" \"a,\" and \"o\"\ndevoice at the ends of words", "start": 1124.86, "duration": 4.86}, {"text": "is not at all common.", "start": 1129.72, "duration": 1.117}, {"text": "I don't know of any\nlanguages that do.", "start": 1130.837, "duration": 1.583}, {"text": "Does that make sense?", "start": 1132.42, "duration": 1.71}, {"text": "That's another sense in which\nmaking generalizations is good.", "start": 1134.13, "duration": 3.6}, {"text": "This is becoming a philosophy\nof science question, yeah.", "start": 1137.73, "duration": 2.7}, {"text": "It's like, why is science good?", "start": 1140.43, "duration": 2.13}, {"text": "Why is it good to\nmake generalizations?", "start": 1142.56, "duration": 2.225}, {"text": "Because it helps\nus to understand", "start": 1144.785, "duration": 1.375}, {"text": "the world better, for Faith's\nreason, as well as the reason", "start": 1146.16, "duration": 2.915}, {"text": "I just offered.", "start": 1149.075, "duration": 0.625}, {"text": "Yeah?", "start": 1149.7, "duration": 0.5}, {"text": "STUDENT: Is the vowel still\na vowel when you devoice it?", "start": 1150.2, "duration": 4.168}, {"text": "NORVIN RICHARDS:\nYeah, yes, arguably.", "start": 1154.368, "duration": 1.542}, {"text": "So there are languages\nthat devoice vowels.", "start": 1155.91, "duration": 1.92}, {"text": "Mokilese is one.", "start": 1160.8, "duration": 1.86}, {"text": "Oh, Japanese is another.", "start": 1162.66, "duration": 1.86}, {"text": "So Japanese has a general\nrule devoicing its high vowels", "start": 1164.52, "duration": 7.17}, {"text": "when they are between\nvoiceless consonants, I guess.", "start": 1171.69, "duration": 4.86}, {"text": "So here's the Japanese\nword for \"like.\"", "start": 1176.55, "duration": 4.71}, {"text": "And it's pronounced\n\"suki,\" \"suki.\"", "start": 1181.26, "duration": 2.73}, {"text": "So the oo isn't pronounced.", "start": 1183.99, "duration": 1.65}, {"text": "You don't say \"soo-kee\"\nunless you're being very slow", "start": 1185.64, "duration": 3.18}, {"text": "and careful.", "start": 1188.82, "duration": 1.74}, {"text": "And it's still a\nvowel in the sense", "start": 1190.56, "duration": 3.178}, {"text": "that your tongue and the\nrest of your vocal tract", "start": 1193.738, "duration": 2.042}, {"text": "is still in the\nconfiguration that it", "start": 1195.78, "duration": 1.23}, {"text": "would be if your vocal\nchords were vibrating.", "start": 1197.01, "duration": 1.92}, {"text": "But they aren't.", "start": 1198.93, "duration": 2.25}, {"text": "So yeah, there arguably\nare voiceless vowels.", "start": 1201.18, "duration": 2.88}, {"text": "Yes, Joseph?", "start": 1204.06, "duration": 0.6}, {"text": "STUDENT: What if you were\nputting an affix after that,", "start": 1204.66, "duration": 2.25}, {"text": "which is \"i\" is high, too?", "start": 1206.91, "duration": 1.47}, {"text": "So what would happen?", "start": 1208.38, "duration": 1.56}, {"text": "NORVIN RICHARDS: Oh.", "start": 1209.94, "duration": 1.14}, {"text": "So in this particular\nexample, there", "start": 1211.08, "duration": 1.62}, {"text": "aren't any affixes you can add\nto \"suki\" to devoice the vowel.", "start": 1212.7, "duration": 5.1}, {"text": "But let me think of an example.", "start": 1217.8, "duration": 5.82}, {"text": "Yeah.", "start": 1226.62, "duration": 0.5}, {"text": "So \"tatsu\"-- so\nthis is not high.", "start": 1227.12, "duration": 8.013}, {"text": "So it doesn't devoice.", "start": 1235.133, "duration": 0.917}, {"text": "This is the verb \"to stand.\"", "start": 1236.05, "duration": 3.09}, {"text": "The more polite\nversion of this--", "start": 1239.14, "duration": 4.36}, {"text": "no, no, no, no.", "start": 1243.5, "duration": 0.7}, {"text": "That's not what I want to do.", "start": 1244.2, "duration": 2.833}, {"text": "Let me try to think\nof an example.", "start": 1247.033, "duration": 1.417}, {"text": "Let me try to think\nof an example that", "start": 1248.45, "duration": 1.583}, {"text": "does what you want.", "start": 1250.033, "duration": 1.147}, {"text": "But there aren't any examples\nthat will work with \"suki.\"", "start": 1251.18, "duration": 3.33}, {"text": "Yeah.", "start": 1254.51, "duration": 2.88}, {"text": "OK, so when I think\nof an example,", "start": 1257.39, "duration": 2.115}, {"text": "at 3:00 in the morning,\nI'll give you a call.", "start": 1259.505, "duration": 1.875}, {"text": "Leave your phone number\nand think of that.", "start": 1261.38, "duration": 4.05}, {"text": "There's got to be a\nstraightforward way to do this.", "start": 1265.43, "duration": 2.14}, {"text": "Hmm, this is going\nto bother me now.", "start": 1267.57, "duration": 2.51}, {"text": "Yeah.", "start": 1270.08, "duration": 0.795}, {"text": "Other questions about this?", "start": 1270.875, "duration": 1.125}, {"text": "Try to think of\nquestions while I", "start": 1276.175, "duration": 1.375}, {"text": "try to think of examples\nthat do what Joseph wants.", "start": 1277.55, "duration": 2.91}, {"text": "Because the past tense suffix\nin Japanese-- oh, oh, oh.", "start": 1280.46, "duration": 3.57}, {"text": "[JAPANESE] oh, yeah, OK.", "start": 1284.03, "duration": 1.23}, {"text": "Here's one.", "start": 1285.26, "duration": 0.51}, {"text": "Adjectives in Japanese.", "start": 1288.65, "duration": 3.33}, {"text": "So this is the word\nfor new, \"atarashii.\"", "start": 1291.98, "duration": 5.46}, {"text": "And the negative of it,\n\"atarashiku nai\" ends--", "start": 1297.44, "duration": 8.14}, {"text": "so there's a \"ku\" that you\nadd to make the negative form.", "start": 1305.58, "duration": 3.65}, {"text": "And it ends up putting this\nvowel between voiceless sounds.", "start": 1309.23, "duration": 4.41}, {"text": "And then yes, it devoices.", "start": 1313.64, "duration": 1.44}, {"text": "So it goes from \"atarashii\"\nto \"atarashiku nai,\"", "start": 1315.08, "duration": 3.99}, {"text": "\"atarashiku nai,\" or the\npast tense, actually.", "start": 1319.07, "duration": 3.96}, {"text": "If you want to say\nsomething was new,", "start": 1323.03, "duration": 1.68}, {"text": "it's \"atarashii\" [JAPANESE].", "start": 1324.71, "duration": 1.95}, {"text": "So again, the \"i\"\nthat's after the \"sh\"", "start": 1326.66, "duration": 3.07}, {"text": "devoices because there's\na voiceless sound after.", "start": 1329.73, "duration": 2.66}, {"text": "Good.", "start": 1332.39, "duration": 0.91}, {"text": "Phew!", "start": 1333.3, "duration": 0.68}, {"text": "Now I won't call you\nat 2:00 in the morning.", "start": 1333.98, "duration": 2.57}, {"text": "You have any\nquestions about this?", "start": 1336.55, "duration": 2.409}, {"text": "OK.", "start": 1338.959, "duration": 1.421}, {"text": "OK.", "start": 1340.38, "duration": 2.35}, {"text": "So let's go back now to\nthe English plural suffix", "start": 1342.73, "duration": 6.3}, {"text": "and review something that\nwe have talked about.", "start": 1349.03, "duration": 4.35}, {"text": "But in the light of all\nof the things that we've", "start": 1353.38, "duration": 2.16}, {"text": "talked about since then, I hope\nit'll become a little clearer.", "start": 1355.54, "duration": 3.76}, {"text": "So again, we're talking about\nthe regular English plural", "start": 1359.3, "duration": 3.35}, {"text": "suffix.", "start": 1362.65, "duration": 0.66}, {"text": "Stop thinking about \"oxen\"\nand \"fish\" and \"sheep.\"", "start": 1363.31, "duration": 3.36}, {"text": "\"Cats\" and \"dogs\" and \"bushes\"--", "start": 1366.67, "duration": 2.31}, {"text": "we decided the underlying\nform of the plural suffix", "start": 1368.98, "duration": 2.25}, {"text": "is a \"z,\" right?", "start": 1371.23, "duration": 0.87}, {"text": "And it undergoes various\nkinds of sound changes", "start": 1372.1, "duration": 3.96}, {"text": "depending on what's before it.", "start": 1376.06, "duration": 2.16}, {"text": "So you add \"z\" to all three\nof these underlyingly.", "start": 1378.22, "duration": 4.29}, {"text": "And then there are\ngeneralizations like English", "start": 1382.51, "duration": 2.73}, {"text": "doesn't like words that\nend in a \"z\" that's", "start": 1385.24, "duration": 2.28}, {"text": "preceded by a voiceless sound.", "start": 1387.52, "duration": 2.43}, {"text": "And words don't get to end in\ntwo strident consonants, where", "start": 1389.95, "duration": 5.34}, {"text": "stridents are things\nlike the \"sh\" and the \"z\"", "start": 1395.29, "duration": 2.97}, {"text": "that's at the end\nof \"bushes,\" yeah?", "start": 1398.26, "duration": 4.08}, {"text": "So those are generalizations.", "start": 1402.34, "duration": 1.65}, {"text": "But we said one of\nthe attractive things", "start": 1403.99, "duration": 2.075}, {"text": "about this way of thinking\nabout the English plural", "start": 1406.065, "duration": 2.125}, {"text": "is that these are\ngeneralizations", "start": 1408.19, "duration": 1.375}, {"text": "that just seem to hold\nabout English generally.", "start": 1409.565, "duration": 2.195}, {"text": "English doesn't\nhave any words that", "start": 1411.76, "duration": 1.53}, {"text": "end in a \"z\" preceded\nby a voiceless sound.", "start": 1413.29, "duration": 2.46}, {"text": "And we can rely on\nEnglish phonology", "start": 1415.75, "duration": 2.37}, {"text": "to demand that you do something\nif you add \"z\" to cat.", "start": 1418.12, "duration": 3.415}, {"text": "And again, we've\nsaid this before.", "start": 1424.48, "duration": 3.54}, {"text": "I just want to say it again\na little more clearly.", "start": 1428.02, "duration": 2.52}, {"text": "There are these conditions.", "start": 1430.54, "duration": 1.68}, {"text": "And then there are\nalso these procedures", "start": 1432.22, "duration": 2.34}, {"text": "for repairing these violations.", "start": 1434.56, "duration": 2.07}, {"text": "So what do you do about the\nfact that you add a \"z\" to cat?", "start": 1436.63, "duration": 4.29}, {"text": "Well, you devoice\nthe \"z,\" right?", "start": 1440.92, "duration": 3.0}, {"text": "If the condition just says\nyou can't have a \"z\" preceded", "start": 1443.92, "duration": 2.55}, {"text": "by something voiceless,\nthere are various things", "start": 1446.47, "duration": 2.34}, {"text": "you could have done\nto fix that problem.", "start": 1448.81, "duration": 1.98}, {"text": "You could have voiced\nthe \"d,\" right?", "start": 1450.79, "duration": 2.46}, {"text": "So the plural of \"cat\"\ncould be \"cads,\" right?", "start": 1453.25, "duration": 2.25}, {"text": "That would be a\ngood English word.", "start": 1455.5, "duration": 2.58}, {"text": "Or you could add a vowel like\nyou do in \"bushes,\" right?", "start": 1458.08, "duration": 3.39}, {"text": "The plural of \"cat\"\ncould be \"cat-es.\"", "start": 1461.47, "duration": 1.95}, {"text": "There are various things\nthat would fix that problem", "start": 1463.42, "duration": 3.72}, {"text": "if that's the problem.", "start": 1467.14, "duration": 0.99}, {"text": "But this is the\nthing that you do.", "start": 1468.13, "duration": 1.83}, {"text": "Yeah, it's like when we\nwere talking about Yawelmani", "start": 1469.96, "duration": 2.4}, {"text": "We said you can't have\nthree consonants in a row.", "start": 1472.36, "duration": 2.11}, {"text": "What do you do about it?", "start": 1474.47, "duration": 1.08}, {"text": "Well, it depends on\nthe situation, right?", "start": 1475.55, "duration": 1.873}, {"text": "So if one of them is an\n\"h,\" you get rid of the \"h.\"", "start": 1477.423, "duration": 2.167}, {"text": "If not, then you insert\na vowel in this position", "start": 1479.59, "duration": 2.79}, {"text": "and not that position.", "start": 1482.38, "duration": 1.34}, {"text": "It's similar thing.", "start": 1483.72, "duration": 3.98}, {"text": "So this is all the way of\nsaying it's worthwhile, maybe,", "start": 1487.7, "duration": 6.47}, {"text": "to distinguish between the\nphonotactic considerations", "start": 1494.17, "duration": 4.5}, {"text": "or the well-formedness\nconsiderations that tell you", "start": 1498.67, "duration": 2.55}, {"text": "this language doesn't like\nthree consonants in a row,", "start": 1501.22, "duration": 3.12}, {"text": "or two accented\nsyllables in a word,", "start": 1504.34, "duration": 1.98}, {"text": "or words ending in a \"z\"\npreceded by a voiceless sound.", "start": 1506.32, "duration": 4.29}, {"text": "There's that condition.", "start": 1510.61, "duration": 1.59}, {"text": "And then there's how\ndo you repair it?", "start": 1512.2, "duration": 2.7}, {"text": "What kind of a\nrepair do you use?", "start": 1514.9, "duration": 2.37}, {"text": "So there's the\nwell-formedness condition.", "start": 1517.27, "duration": 2.19}, {"text": "And then there's the repair.", "start": 1519.46, "duration": 1.36}, {"text": "So in this particular\ncase, the procedures", "start": 1520.82, "duration": 2.0}, {"text": "are devoice and insert schwa.", "start": 1522.82, "duration": 4.17}, {"text": "There's a particularly striking\nbit of evidence for this way", "start": 1526.99, "duration": 5.76}, {"text": "of dividing things\nup, this distinction", "start": 1532.75, "duration": 3.33}, {"text": "that I'm drawing between\nwell-formedness conditions", "start": 1536.08, "duration": 2.79}, {"text": "on words, on the one hand,\nand types of possible repair", "start": 1538.87, "duration": 4.53}, {"text": "on the other.", "start": 1543.4, "duration": 1.26}, {"text": "We need to think about\nboth of those things", "start": 1544.66, "duration": 1.89}, {"text": "if we're going to describe\nwhat the language is doing.", "start": 1546.55, "duration": 3.57}, {"text": "This is a classic\ntest from 1957.", "start": 1550.12, "duration": 3.06}, {"text": "I mentioned it in\nclass before, but I", "start": 1553.18, "duration": 1.553}, {"text": "wanted to talk about it a\nlittle more now that we've", "start": 1554.733, "duration": 2.167}, {"text": "drawn this distinction.", "start": 1556.9, "duration": 1.89}, {"text": "So Jean Berko, later\nJean Berko Gleason,", "start": 1558.79, "duration": 5.28}, {"text": "did this work in\n1957 with children.", "start": 1564.07, "duration": 3.63}, {"text": "She was demonstrating that\nthey know these generalizations", "start": 1567.7, "duration": 3.66}, {"text": "about plurals even with words\nthey've never heard before.", "start": 1571.36, "duration": 4.06}, {"text": "So she would show them\npictures like this one.", "start": 1575.42, "duration": 2.033}, {"text": "This is one of her pictures.", "start": 1577.453, "duration": 1.167}, {"text": "She said \"This is a wug.\"", "start": 1578.62, "duration": 2.28}, {"text": "And then she would show them\ntwo pictures of the same thing.", "start": 1580.9, "duration": 4.53}, {"text": "And she would say, \"Now\nthere are two of them.", "start": 1585.43, "duration": 2.61}, {"text": "There are two\"-- and children\nwere supposed to say \"wugs\"", "start": 1588.04, "duration": 7.8}, {"text": "even though they'd never heard\nanybody say \"wug\" before,", "start": 1595.84, "duration": 2.57}, {"text": "right?", "start": 1598.41, "duration": 0.5}, {"text": "So Jean Berko Gleason, Jean\nBerko made up a bunch of words.", "start": 1598.91, "duration": 3.77}, {"text": "She worked hard to make sure\nthey were not real words.", "start": 1602.68, "duration": 2.43}, {"text": "And then she drew\nmany cute pictures", "start": 1605.11, "duration": 2.55}, {"text": "and showed children singulars\nand plurals and said,", "start": 1607.66, "duration": 2.99}, {"text": "OK, here's the singular.", "start": 1610.65, "duration": 1.0}, {"text": "What's the plural?", "start": 1611.65, "duration": 1.14}, {"text": "And the kids responded.", "start": 1612.79, "duration": 2.562}, {"text": "And she wrote down\ntheir responses.", "start": 1615.352, "duration": 1.458}, {"text": "And their responses,\ninterestingly,", "start": 1616.81, "duration": 1.98}, {"text": "were accurate in one way,\nand sometimes inaccurate", "start": 1618.79, "duration": 4.14}, {"text": "in another, which is\ninteresting to think about.", "start": 1622.93, "duration": 2.257}, {"text": "So she was working with\nchildren who were five years old", "start": 1625.187, "duration": 2.333}, {"text": "and children who\nwere seven years old.", "start": 1627.52, "duration": 1.963}, {"text": "What she discovered\nwas that by the time", "start": 1629.483, "duration": 1.667}, {"text": "they were five years old,\nthey are, in a sense,", "start": 1631.15, "duration": 1.958}, {"text": "perfect, in the sense that all\nof the words that they came up", "start": 1633.108, "duration": 4.552}, {"text": "with were phonotactically\nwell formed English words.", "start": 1637.66, "duration": 3.94}, {"text": "So here are three of\nBerko's words-- \"hif,\"", "start": 1641.6, "duration": 3.26}, {"text": "\"fas,\" and \"muz,\" yeah?", "start": 1644.86, "duration": 2.51}, {"text": "And I think everybody\ndid \"wug\" perfectly.", "start": 1647.37, "duration": 3.73}, {"text": "Everybody said the plural\nof \"wug\" is \"wugs.\"", "start": 1651.1, "duration": 2.73}, {"text": "But there were other cases\nwhere children would say,", "start": 1653.83, "duration": 3.48}, {"text": "sometimes, things like the\nplural of \"hif\" is \"hifes,\"", "start": 1657.31, "duration": 3.51}, {"text": "or the plural of \"fas\" is\n\"fas,\" or the plural of \"muz\"", "start": 1660.82, "duration": 3.72}, {"text": "is \"muz.\"", "start": 1664.54, "duration": 3.2}, {"text": "These are all words where--", "start": 1667.74, "duration": 2.438}, {"text": "and then there were\nother kinds of mistakes", "start": 1670.178, "duration": 1.792}, {"text": "that children didn't make.", "start": 1671.97, "duration": 1.14}, {"text": "So nobody said that the\nplural \"wug\" was \"wuks,\"", "start": 1673.11, "duration": 4.89}, {"text": "or that the plural of\n\"wook\" is \"wookz,\" right?", "start": 1678.0, "duration": 4.83}, {"text": "Or that the plural of\nfas is \"fas-z,\" yeah?", "start": 1682.83, "duration": 4.8}, {"text": "What were children doing?", "start": 1687.63, "duration": 1.2}, {"text": "Well, children know\nif you show them", "start": 1688.83, "duration": 2.34}, {"text": "something that's underlyingly--\nyou give them \"hif,\" which", "start": 1691.17, "duration": 3.84}, {"text": "for some reason I'm spelling\nbackwards-- you give them \"hif\"", "start": 1695.01, "duration": 2.585}, {"text": "and you ask them\nthe plural, they", "start": 1697.595, "duration": 1.375}, {"text": "know that you're\nsupposed to add a \"z.\"", "start": 1698.97, "duration": 2.64}, {"text": "And they know that English\ndoesn't allow words", "start": 1701.61, "duration": 2.61}, {"text": "that end in a \"z\" preceded\nby a voiceless sound.", "start": 1704.22, "duration": 3.78}, {"text": "But some of these five\nand seven-year-olds", "start": 1708.0, "duration": 1.92}, {"text": "were a little fuzzy on\nthe possible repairs.", "start": 1709.92, "duration": 2.37}, {"text": "None of them said, \"Oh,\nyeah, It's hifz,\" right?", "start": 1715.29, "duration": 3.45}, {"text": "But I just said this.", "start": 1718.74, "duration": 2.19}, {"text": "If the only problem\nis, well, this word", "start": 1720.93, "duration": 2.49}, {"text": "ends in a voiceless\nsound followed", "start": 1723.42, "duration": 1.5}, {"text": "by a \"z,\" in fact,\nwhat you're supposed", "start": 1724.92, "duration": 2.67}, {"text": "to do is devoice the \"z.\"", "start": 1727.59, "duration": 1.77}, {"text": "That's what an adult would do.", "start": 1729.36, "duration": 1.53}, {"text": "So the plural of\n\"hif\" is \"hifs,\" yeah?", "start": 1730.89, "duration": 2.4}, {"text": "But if you were instead\nto insert a schwa,", "start": 1733.29, "duration": 4.44}, {"text": "well, that would\nfix it, too, right?", "start": 1737.73, "duration": 2.13}, {"text": "So now the \"z\" is preceded\nby a voiced sound.", "start": 1739.86, "duration": 3.81}, {"text": "The plural of \"hif\"\nis \"hif-ez,\" yeah?", "start": 1743.67, "duration": 1.652}, {"text": "And there were some kids who\nwere going through a stage who", "start": 1745.322, "duration": 2.458}, {"text": "were entertaining that\npossibility, that that was", "start": 1747.78, "duration": 2.4}, {"text": "the correct repair for that.", "start": 1750.18, "duration": 1.98}, {"text": "So what Berko found was\nthat children universally", "start": 1752.16, "duration": 6.0}, {"text": "knew the phonotactics, right?", "start": 1758.16, "duration": 2.04}, {"text": "They knew that English\ndoesn't allow words", "start": 1760.2, "duration": 3.3}, {"text": "that end in a \"z\" preceded\nby a voiceless sound.", "start": 1763.5, "duration": 2.43}, {"text": "But they made intriguing\nmistakes of various kinds--", "start": 1765.93, "duration": 5.22}, {"text": "not very often.", "start": 1771.15, "duration": 1.042}, {"text": "Most of the kids just\ndid everything perfectly.", "start": 1772.192, "duration": 1.958}, {"text": "But every so often,\nshe would get", "start": 1774.15, "duration": 0.99}, {"text": "kids who made some mistakes.", "start": 1775.14, "duration": 1.2}, {"text": "And the mistakes\nwere of this class.", "start": 1776.34, "duration": 2.22}, {"text": "That is, mistakes\nwhere they knew", "start": 1778.56, "duration": 3.03}, {"text": "that there needed to be a\nrepair but got the repair wrong.", "start": 1781.59, "duration": 3.52}, {"text": "Similarly for \"muz,\"\nthis was a kid who--", "start": 1785.11, "duration": 3.86}, {"text": "the singular is \"muz,\"\nand the kid knows", "start": 1788.97, "duration": 3.6}, {"text": "that you need to add a \"z.\"", "start": 1792.57, "duration": 1.26}, {"text": "And the kid knows that you\ncan't have two stridents", "start": 1793.83, "duration": 2.125}, {"text": "at the end of a word.", "start": 1795.955, "duration": 1.025}, {"text": "The correct answer,\nthe adult's answer,", "start": 1796.98, "duration": 2.16}, {"text": "is to insert a schwa\nso the plural of \"muz\"", "start": 1799.14, "duration": 2.67}, {"text": "will be \"muzes.\"", "start": 1801.81, "duration": 0.96}, {"text": "But deleting the \"z,\" one of the\n\"z\"s-- hard to know which one--", "start": 1802.77, "duration": 5.28}, {"text": "also fixes that problem.", "start": 1808.05, "duration": 1.54}, {"text": "And so that was a\nkid who thought,", "start": 1809.59, "duration": 2.21}, {"text": "yeah, I'll delete a \"z,\" yeah?", "start": 1811.8, "duration": 1.92}, {"text": "Yeah, Joseph?", "start": 1813.72, "duration": 1.218}, {"text": "STUDENT: Is the deletion\nof a consonant viewed", "start": 1814.938, "duration": 2.962}, {"text": "as [INAUDIBLE]?", "start": 1817.9, "duration": 1.36}, {"text": "NORVIN RICHARDS: As\nsomething that English does?", "start": 1819.26, "duration": 2.0}, {"text": "Yeah, no.", "start": 1821.26, "duration": 0.75}, {"text": "So English-- there\naren't, I don't think,", "start": 1822.01, "duration": 2.01}, {"text": "any English nouns that form\ntheir plural by adding a \"z\"", "start": 1824.02, "duration": 6.03}, {"text": "and deleting something\nbefore the \"z.\"", "start": 1830.05, "duration": 1.745}, {"text": "I don't believe\nthat ever happens.", "start": 1831.795, "duration": 3.085}, {"text": "This is me slowing\ndown while I try", "start": 1834.88, "duration": 1.98}, {"text": "to think of English nouns,\nof which I know several,", "start": 1836.86, "duration": 2.55}, {"text": "but I can't think\nof any that do that.", "start": 1839.41, "duration": 3.3}, {"text": "Yeah.", "start": 1842.71, "duration": 1.02}, {"text": "Yeah.", "start": 1843.73, "duration": 1.23}, {"text": "OK.", "start": 1844.96, "duration": 1.53}, {"text": "Yeah, so is this clear?", "start": 1846.49, "duration": 1.74}, {"text": "Another reason to\ndraw this distinction", "start": 1848.23, "duration": 1.74}, {"text": "between, on the one hand, what\nI was calling phonotactics,", "start": 1849.97, "duration": 3.0}, {"text": "these rules for which kinds\nof sounds can be where,", "start": 1852.97, "duration": 3.04}, {"text": "and on the other\nhand, the repairs--", "start": 1856.01, "duration": 1.89}, {"text": "so the kids that\nBerko was working with", "start": 1857.9, "duration": 3.23}, {"text": "knew the phonotactics, but\nwere sometimes fuzzy on what", "start": 1861.13, "duration": 2.97}, {"text": "the correct repairs were.", "start": 1864.1, "duration": 2.583}, {"text": "Yeah.", "start": 1866.683, "duration": 1.887}, {"text": "OK.", "start": 1868.57, "duration": 1.65}, {"text": "So, moral-- yet again, need\nto distinguish between,", "start": 1870.22, "duration": 2.633}, {"text": "on the one hand,\nthe phonotactics,", "start": 1872.853, "duration": 1.417}, {"text": "and on the other hand, the\nparticular sound changes,", "start": 1874.27, "duration": 2.4}, {"text": "the repairs that enforce\nthe phonotactics.", "start": 1876.67, "duration": 1.96}, {"text": "It's apparently possible to know\none of those but not the other.", "start": 1878.63, "duration": 5.53}, {"text": "OK.", "start": 1884.16, "duration": 1.04}, {"text": "That ends the chapter.", "start": 1885.2, "duration": 3.17}, {"text": "Now we're going to talk\nabout something else.", "start": 1888.37, "duration": 2.967}, {"text": "So are there any\nquestions about that?", "start": 1891.337, "duration": 1.583}, {"text": "Is that clear?", "start": 1892.92, "duration": 1.212}, {"text": "OK.", "start": 1894.132, "duration": 1.848}, {"text": "We've already done some of\nthis, but I want to do more.", "start": 1895.98, "duration": 3.0}, {"text": "We've been talking\nabout how there", "start": 1898.98, "duration": 3.75}, {"text": "are some kinds of sound changes\nthat are natural because they", "start": 1902.73, "duration": 4.11}, {"text": "apply to natural\nclasses of things", "start": 1906.84, "duration": 2.1}, {"text": "that can be almost circular.", "start": 1908.94, "duration": 4.56}, {"text": "So I quickly introduced\nyou to the word stridents", "start": 1913.5, "duration": 4.41}, {"text": "because the generalization\nabout English plurals", "start": 1917.91, "duration": 2.79}, {"text": "is that two stridents can't\nend a word in English.", "start": 1920.7, "duration": 3.51}, {"text": "And that's why you introduce\na schwa just in case", "start": 1924.21, "duration": 2.85}, {"text": "you're in danger of\nhaving two stridents", "start": 1927.06, "duration": 1.77}, {"text": "at the end of your word, yeah.", "start": 1928.83, "duration": 3.54}, {"text": "The word strident has\nan acoustic definition.", "start": 1932.37, "duration": 3.48}, {"text": "They are fricatives that have\nlots of high frequency noise.", "start": 1935.85, "duration": 3.57}, {"text": "But it's of interest\nthat there are phenomena", "start": 1939.42, "duration": 3.57}, {"text": "like the allomorphy\nin English plurals", "start": 1942.99, "duration": 2.49}, {"text": "that make reference\nto that acoustic fact.", "start": 1945.48, "duration": 2.55}, {"text": "That's apparently something\nthat a language can care about--", "start": 1948.03, "duration": 3.69}, {"text": "how much high frequency\nnoise you have at once.", "start": 1951.72, "duration": 2.263}, {"text": "It's also something that varies\nfrom language to language.", "start": 1953.983, "duration": 2.417}, {"text": "There are languages that\nare perfectly happy to have", "start": 1956.4, "duration": 2.43}, {"text": "long strings of stridents.", "start": 1958.83, "duration": 1.86}, {"text": "English just isn't one of them.", "start": 1960.69, "duration": 2.25}, {"text": "Yeah.", "start": 1962.94, "duration": 2.49}, {"text": "So we've already done, as I\nsaid, some talking about this.", "start": 1965.43, "duration": 3.62}, {"text": "So when I was first\nintroducing you to consonants", "start": 1969.05, "duration": 2.11}, {"text": "or introducing you\nto vowels, you'd", "start": 1971.16, "duration": 2.31}, {"text": "already met consonants at\nsome point in your life.", "start": 1973.47, "duration": 2.1}, {"text": "But we were talking about them\nin a particular systematic way.", "start": 1975.57, "duration": 3.6}, {"text": "We talked about various ways\nof classifying them, saying", "start": 1979.17, "duration": 4.89}, {"text": "there are some consonants\nthat are fricatives", "start": 1984.06, "duration": 2.28}, {"text": "and some consonants\nthat are stops,", "start": 1986.34, "duration": 1.68}, {"text": "or saying there are some\nconsonants that are voiced", "start": 1988.02, "duration": 2.19}, {"text": "and some consonants\nthat are voiceless.", "start": 1990.21, "duration": 2.2}, {"text": "So what I want to do\ntoday is to introduce you", "start": 1992.41, "duration": 2.51}, {"text": "to some other kinds\nof classification.", "start": 1994.92, "duration": 2.01}, {"text": "And I'll, as much\nas possible, try", "start": 1996.93, "duration": 1.733}, {"text": "to show you places\nwhere languages", "start": 1998.663, "duration": 1.417}, {"text": "care about a particular\nclass of sounds.", "start": 2000.08, "duration": 3.42}, {"text": "Again, this is all in the\nservice of making it easier", "start": 2003.5, "duration": 3.84}, {"text": "for us to understand why\ncertain kinds of sound changes", "start": 2007.34, "duration": 2.85}, {"text": "are natural and others are not.", "start": 2010.19, "duration": 5.13}, {"text": "OK.", "start": 2015.32, "duration": 0.5}, {"text": "So here's one that\nwe've already seen.", "start": 2015.82, "duration": 4.02}, {"text": "There are sounds that are nasal.", "start": 2019.84, "duration": 1.335}, {"text": "This is a contrast\nthat I believe", "start": 2023.88, "duration": 2.205}, {"text": "I have introduced you to before,\nbut let me introduce you to it", "start": 2026.085, "duration": 2.625}, {"text": "again.", "start": 2028.71, "duration": 0.57}, {"text": "There's a distinction--", "start": 2029.28, "duration": 2.37}, {"text": "I think I brought this\nup last time, actually.", "start": 2031.65, "duration": 2.1}, {"text": "There's a distinction, when\nwe talk about consonants,", "start": 2033.75, "duration": 3.03}, {"text": "between what are\ncalled sonorants", "start": 2036.78, "duration": 2.88}, {"text": "and what are called obstruents.", "start": 2039.66, "duration": 1.99}, {"text": "So these are opposites\nof each other.", "start": 2041.65, "duration": 1.88}, {"text": "I hope I have the word\n\"obstruent\" on a later slide.", "start": 2043.53, "duration": 3.01}, {"text": "But just in case I don't, there\nare these two kinds of sounds--", "start": 2046.54, "duration": 4.04}, {"text": "obstruents and sonorants.", "start": 2050.58, "duration": 4.26}, {"text": "And the distinction\nbetween them has", "start": 2054.84, "duration": 1.98}, {"text": "to do with whether\nyou are building up", "start": 2056.82, "duration": 2.879}, {"text": "pressure in the oral cavity.", "start": 2059.699, "duration": 2.411}, {"text": "So the sonorants are the\nnasals and the liquids", "start": 2062.11, "duration": 4.879}, {"text": "and the glides, the\nconsonants in which there's", "start": 2066.989, "duration": 2.94}, {"text": "no pressure building\nup in the oral cavity,", "start": 2069.929, "duration": 3.21}, {"text": "whereas the\nobstruents-- those are", "start": 2073.139, "duration": 2.011}, {"text": "the stops and the fricatives,\nthe oral stops and fricatives.", "start": 2075.15, "duration": 3.54}, {"text": "Those are the sounds in which\nthere is pressure building up", "start": 2078.69, "duration": 2.58}, {"text": "in the oral cavity.", "start": 2081.27, "duration": 0.99}, {"text": "For a stop, it's because, well,\nyou've stopped the flow of air", "start": 2082.26, "duration": 3.0}, {"text": "at the mouth.", "start": 2085.26, "duration": 0.899}, {"text": "And so pressure is building up.", "start": 2086.159, "duration": 1.56}, {"text": "And for a fricative,\nwell, you haven't", "start": 2087.719, "duration": 1.583}, {"text": "stopped the flow of air,\nbut you're constricting it.", "start": 2089.302, "duration": 2.167}, {"text": "That's how you make a fricative.", "start": 2091.469, "duration": 1.531}, {"text": "And so pressure is building\nup in the oral cavity.", "start": 2093.0, "duration": 2.469}, {"text": "And when I say pressure is\nbuilding up in the oral cavity,", "start": 2095.469, "duration": 2.721}, {"text": "what I mean is that phoneticists\nhave put instruments", "start": 2098.19, "duration": 3.99}, {"text": "inside people's mouths to\nmeasure air pressure to find", "start": 2102.18, "duration": 3.42}, {"text": "out what happens.", "start": 2105.6, "duration": 0.84}, {"text": "And they have discovered\nthat this is true, yeah.", "start": 2106.44, "duration": 3.29}, {"text": "So I try not to lie\nto you in this class", "start": 2109.73, "duration": 2.233}, {"text": "any more than I can help it.", "start": 2111.963, "duration": 1.167}, {"text": "But in this particular\ncase, what I'm saying", "start": 2113.13, "duration": 1.86}, {"text": "is absolutely true.", "start": 2114.99, "duration": 0.9}, {"text": "OK, so there are sonorants\nand there are obstruents.", "start": 2119.285, "duration": 2.815}, {"text": "We have already talked about\nthe classification of sounds", "start": 2122.1, "duration": 2.4}, {"text": "into voiced and\nvoiceless sounds.", "start": 2124.5, "duration": 1.41}, {"text": "So the red sounds on\nthis slide are voiced.", "start": 2125.91, "duration": 2.85}, {"text": "And as you can see, in\nthis cross-cut-- some", "start": 2128.76, "duration": 1.86}, {"text": "of the other classifications.", "start": 2130.62, "duration": 1.208}, {"text": "So you can be an obstruent,\nlike a stop or a fricative,", "start": 2131.828, "duration": 5.602}, {"text": "and you can be either\nvoiced or voiceless.", "start": 2137.43, "duration": 2.71}, {"text": "So English stops can\nbe voiced or voiceless.", "start": 2140.14, "duration": 3.32}, {"text": "English fricatives can\nbe voiced or voiceless.", "start": 2143.46, "duration": 2.76}, {"text": "English sonorants,\ninterestingly,", "start": 2146.22, "duration": 1.89}, {"text": "can only be voiced.", "start": 2148.11, "duration": 1.32}, {"text": "They cannot be voiceless.", "start": 2149.43, "duration": 1.98}, {"text": "We have sonorants\nlike \"l,\" like \"l,\"", "start": 2151.41, "duration": 3.42}, {"text": "but we don't have a\nvoiceless version of \"l.\"", "start": 2154.83, "duration": 2.035}, {"text": "We talked about this\nwhen we were first", "start": 2156.865, "duration": 1.625}, {"text": "going through sounds.", "start": 2158.49, "duration": 1.763}, {"text": "There are languages\nout there that", "start": 2160.253, "duration": 1.417}, {"text": "have a voiceless version of\n\"l,\" that have a \"lh\" sound.", "start": 2161.67, "duration": 3.9}, {"text": "Tibetan has one, for example.", "start": 2165.57, "duration": 1.75}, {"text": "So if you go to Lhasa,\nthe capital of Tibet,", "start": 2167.32, "duration": 2.96}, {"text": "you must learn to\nmake voiceless \"l\"s.", "start": 2170.28, "duration": 3.21}, {"text": "Welsh has a voiceless \"l.\".", "start": 2173.49, "duration": 3.27}, {"text": "They spell it with two \"l\"s.", "start": 2176.76, "duration": 1.8}, {"text": "So if you look at Welsh words,\nyou'll see pairs of \"l\"s.", "start": 2178.56, "duration": 3.21}, {"text": "That's their way of\nspelling a voiceless \"l.\"", "start": 2181.77, "duration": 3.48}, {"text": "So there's a traditional\nWelsh name spelled like this", "start": 2185.25, "duration": 4.56}, {"text": "and pronounced\n\"Lhoyd,\" which has", "start": 2189.81, "duration": 2.85}, {"text": "been borrowed into English twice\nas the name Lloyd and the name", "start": 2192.66, "duration": 4.41}, {"text": "Floyd.", "start": 2197.07, "duration": 2.04}, {"text": "These are both\nattempts to pronounce", "start": 2199.11, "duration": 1.527}, {"text": "\"Lhoyd,\" which we can't\npronounce because we", "start": 2200.637, "duration": 1.833}, {"text": "don't have that sound.", "start": 2202.47, "duration": 2.8}, {"text": "Yeah.", "start": 2205.27, "duration": 0.5}, {"text": "So English has voiced and\nvoiceless obstruents, stops", "start": 2205.77, "duration": 4.295}, {"text": "and fricatives.", "start": 2210.065, "duration": 0.625}, {"text": "But it only has voice sonorants.", "start": 2210.69, "duration": 1.8}, {"text": "That's a very common\nstate of affairs.", "start": 2212.49, "duration": 2.67}, {"text": "If you're going\nto have a voicing", "start": 2215.16, "duration": 1.77}, {"text": "distinction in only one of these\nplaces, it's in the obstruents.", "start": 2216.93, "duration": 3.84}, {"text": "Languages only having\nvoiced sonorants--", "start": 2220.77, "duration": 1.89}, {"text": "that's very common, though\nnot universal, as we've said.", "start": 2222.66, "duration": 4.2}, {"text": "Quick interlude to use\none of these features.", "start": 2229.54, "duration": 4.13}, {"text": "Here are a bunch of verbs that\nyou can make out of adjectives.", "start": 2233.67, "duration": 4.84}, {"text": "So you can take an\nadjective like \"black.\"", "start": 2238.51, "duration": 2.9}, {"text": "And you can make\na verb, \"blacken,\"", "start": 2241.41, "duration": 2.457}, {"text": "which can be either a transitive\nverb or in intransitive verb,", "start": 2243.867, "duration": 2.583}, {"text": "I guess.", "start": 2246.45, "duration": 0.5}, {"text": "So you can blacken the paper\nor blacken the fish, I guess.", "start": 2246.95, "duration": 6.7}, {"text": "It means to make it black.", "start": 2253.65, "duration": 3.54}, {"text": "Similarly, something can whiten\nor lessen or freshen or darken.", "start": 2257.19, "duration": 6.0}, {"text": "You can offer to\nfreshen a drink, say.", "start": 2263.19, "duration": 2.04}, {"text": "It means to make\nit fresh, right?", "start": 2265.23, "duration": 2.79}, {"text": "So there's this \"-en\" that you\ncan add to adjectives to make", "start": 2268.02, "duration": 3.27}, {"text": "verbs.", "start": 2271.29, "duration": 0.63}, {"text": "Does that sound right?", "start": 2271.92, "duration": 2.95}, {"text": "On the other hand, there are\nthese other adjectives which", "start": 2274.87, "duration": 4.7}, {"text": "can't have \"-en,\" yeah?", "start": 2279.57, "duration": 1.68}, {"text": "So the screen of a\ncomputer can darken,", "start": 2281.25, "duration": 6.54}, {"text": "but it cannot \"yellowen,\" yeah?", "start": 2287.79, "duration": 3.52}, {"text": "A piece of paper that gets old--", "start": 2291.31, "duration": 3.08}, {"text": "what you say is\nthat the yellows.", "start": 2294.39, "duration": 1.77}, {"text": "It yellowed with age.", "start": 2296.16, "duration": 1.38}, {"text": "You don't say that it\n\"yellowened,\" yeah?", "start": 2297.54, "duration": 2.46}, {"text": "Similarly, you can't\n\"dimmen\" or \"grayen\"", "start": 2300.0, "duration": 2.67}, {"text": "or \"clearen\" or \"brownen.\"", "start": 2302.67, "duration": 1.923}, {"text": "All of those things--\nif you want to make them", "start": 2304.593, "duration": 1.917}, {"text": "into verbs, you just [SNAPS].", "start": 2306.51, "duration": 1.35}, {"text": "They're verbs, yeah?", "start": 2307.86, "duration": 2.15}, {"text": "Yeah?", "start": 2310.01, "duration": 0.66}, {"text": "Does that sound right?", "start": 2310.67, "duration": 2.1}, {"text": "What's the difference\nbetween \"black,\"", "start": 2312.77, "duration": 2.07}, {"text": "\"white,\" \"less,\" \"fresh,\"\nand \"dark\" on the one hand,", "start": 2314.84, "duration": 4.14}, {"text": "and \"yellow,\" \"dim,\"\n\"gray,\" \"clear,\"", "start": 2318.98, "duration": 4.11}, {"text": "and \"brown\" on the other?", "start": 2323.09, "duration": 3.753}, {"text": "STUDENT: They end with voiceless\nstops in the first line?", "start": 2326.843, "duration": 5.559}, {"text": "NORVIN RICHARDS:\nIn the first line,", "start": 2332.402, "duration": 1.458}, {"text": "\"black,\" \"white,\" and \"dark\"\nend with voiceless stops.", "start": 2333.86, "duration": 3.63}, {"text": "And \"less\" and \"fresh\" end with\nvoiceless fricatives, yeah?", "start": 2337.49, "duration": 4.7}, {"text": "Yeah, yeah.", "start": 2342.19, "duration": 0.81}, {"text": "Yeah, nice.", "start": 2343.0, "duration": 3.34}, {"text": "And \"yellow,\" \"dim,\" \"gray,\"\n\"clear,\" and \"brown\" end in", "start": 2346.34, "duration": 5.035}, {"text": "voiced sounds.", "start": 2351.375, "duration": 0.71}, {"text": "What's the cover term\nfor stops and fricatives?", "start": 2354.6, "duration": 4.377}, {"text": "STUDENT: Obstruents.", "start": 2358.977, "duration": 0.833}, {"text": "NORVIN RICHARDS: Obstruents.", "start": 2359.81, "duration": 1.68}, {"text": "So \"-en\" can be added to\nwords ending in obstruents.", "start": 2361.49, "duration": 4.77}, {"text": "And it can't be\nadded to adjectives", "start": 2366.26, "duration": 2.73}, {"text": "ending in sonorants, yeah?", "start": 2368.99, "duration": 1.74}, {"text": "Another place where it's\nuseful to distinguish sonorants", "start": 2374.29, "duration": 3.99}, {"text": "from obstruents--", "start": 2378.28, "duration": 2.67}, {"text": "Polish plurals-- I think this\nis the last time I will say", "start": 2380.95, "duration": 2.79}, {"text": "anything about Polish plurals.", "start": 2383.74, "duration": 1.62}, {"text": "I can't promise because\nit's a very useful example.", "start": 2385.36, "duration": 3.55}, {"text": "But if you're getting tired of\nPolish plurals, I apologize.", "start": 2388.91, "duration": 2.75}, {"text": "I think we're just\nabout to the end.", "start": 2391.66, "duration": 1.5}, {"text": "On the other hand, if you've\nbecome fond of Polish plurals,", "start": 2393.16, "duration": 2.79}, {"text": "please gaze at this\nslide for a while.", "start": 2395.95, "duration": 3.24}, {"text": "This is your last big chance.", "start": 2399.19, "duration": 2.86}, {"text": "What we said about\nPolish plurals was", "start": 2402.05, "duration": 2.42}, {"text": "that it's useful\nto say that there", "start": 2404.47, "duration": 2.01}, {"text": "are words that end underlyingly\nin sounds like \"g\" and \"b\"", "start": 2406.48, "duration": 3.39}, {"text": "and \"z.\"", "start": 2409.87, "duration": 0.75}, {"text": "And those final\nsounds, \"g\" and \"b\"", "start": 2410.62, "duration": 2.34}, {"text": "and \"z,\" devoice when\nthey're at the ends of words.", "start": 2412.96, "duration": 2.34}, {"text": "So underlying \"wuk,\"\nthe word for \"lye,\"", "start": 2415.3, "duration": 2.91}, {"text": "becomes \"wuk\" if you don't\nadd anything after it.", "start": 2418.21, "duration": 3.46}, {"text": "And same with the\nword for \"club\"", "start": 2421.67, "duration": 1.4}, {"text": "and the word for \"rubble.\"", "start": 2423.07, "duration": 1.56}, {"text": "And I have been\nincautiously saying things", "start": 2424.63, "duration": 1.95}, {"text": "like, \"Polish devoices its final\nconsonants,\" which was a lie.", "start": 2426.58, "duration": 6.55}, {"text": "I think I told you just\nnow that I try not to lie", "start": 2433.13, "duration": 2.87}, {"text": "to you any more than I have to.", "start": 2436.0, "duration": 2.97}, {"text": "It doesn't devoice its\nfinal consonants, right?", "start": 2438.97, "duration": 2.76}, {"text": "Because Polish has\nwords like \"dom,\"", "start": 2441.73, "duration": 3.18}, {"text": "which is the word for house.", "start": 2444.91, "duration": 1.53}, {"text": "And that ends in a\nvoiced sound, right?", "start": 2446.44, "duration": 2.136}, {"text": "\"Dom\" doesn't become \"dom\"\n[pronounced with voicelesss", "start": 2448.576, "duration": 2.25}, {"text": "\"m\"], yeah?", "start": 2450.826, "duration": 2.034}, {"text": "Right?", "start": 2452.86, "duration": 2.02}, {"text": "So it's not the case\nthat final consonants", "start": 2454.88, "duration": 2.13}, {"text": "become voiceless in Polish.", "start": 2457.01, "duration": 2.558}, {"text": "What are the things that\nbecome voiceless in Polish?", "start": 2459.568, "duration": 2.167}, {"text": "Obstruents, yeah?", "start": 2464.69, "duration": 0.93}, {"text": "Stops and fricatives.", "start": 2465.62, "duration": 1.53}, {"text": "Those are the things that\nbecome voiceless in Polish.", "start": 2467.15, "duration": 2.64}, {"text": "Relatedly, Polish is like\nEnglish in having voiced", "start": 2469.79, "duration": 3.75}, {"text": "and voiceless obstruents,\nbut not having", "start": 2473.54, "duration": 3.63}, {"text": "voiced and voiceless sonorants.", "start": 2477.17, "duration": 1.68}, {"text": "So Polish-- the \"m,\" in a sense,\ndoesn't have anywhere to go.", "start": 2478.85, "duration": 4.32}, {"text": "Polish doesn't have that sound.", "start": 2483.17, "duration": 1.41}, {"text": "Common situation.", "start": 2487.97, "duration": 1.3}, {"text": "So it's really final obstruents\nthat are becoming voiceless.", "start": 2489.27, "duration": 3.32}, {"text": "OK, all right.", "start": 2496.11, "duration": 1.35}, {"text": "So that's a reason\nto want to care", "start": 2497.46, "duration": 3.57}, {"text": "about the distinction between\nsonorants and obstruents,", "start": 2501.03, "duration": 3.205}, {"text": "not just because you\nwant to understand", "start": 2504.235, "duration": 1.625}, {"text": "why it's \"whiten\" and\n\"darken\" and \"lessen,\"", "start": 2505.86, "duration": 2.97}, {"text": "but not \"yellowen.\"", "start": 2508.83, "duration": 2.695}, {"text": "It seems to be a\ndistinction that cares", "start": 2511.525, "duration": 1.625}, {"text": "about sonorants and obstruents.", "start": 2513.15, "duration": 1.48}, {"text": "Here's another one.", "start": 2514.63, "duration": 1.46}, {"text": "Polish, which as I've\nsaid now several times,", "start": 2516.09, "duration": 2.67}, {"text": "and I think this might\nbe the last time--", "start": 2518.76, "duration": 2.04}, {"text": "Polish is doing something that\nis very common in languages", "start": 2520.8, "duration": 2.758}, {"text": "of the world.", "start": 2523.558, "duration": 0.542}, {"text": "It's devoicing final obstruents.", "start": 2524.1, "duration": 3.75}, {"text": "That's a thing\nthat happens a lot.", "start": 2527.85, "duration": 1.8}, {"text": "All right.", "start": 2532.98, "duration": 0.5}, {"text": "So phonology so far--\nwe've been doing phonology", "start": 2533.48, "duration": 4.26}, {"text": "for a couple of days now.", "start": 2537.74, "duration": 2.31}, {"text": "It's useful to think of sounds\nas undergoing changes sometimes", "start": 2540.05, "duration": 5.28}, {"text": "driven by sounds coming in\ncontact with each other.", "start": 2545.33, "duration": 3.7}, {"text": "And we can describe these\nchanges in terms of rules.", "start": 2549.03, "duration": 3.29}, {"text": "There's the formalism for rules\nthat I've been showing you.", "start": 2552.32, "duration": 3.42}, {"text": "So we'll say sound A\nchanges into sound B.", "start": 2555.74, "duration": 4.14}, {"text": "The slash introduces\nyou to the environment.", "start": 2559.88, "duration": 3.16}, {"text": "This is a description of\nwhat's happening in Polish,", "start": 2563.04, "duration": 2.558}, {"text": "and Turkish, and\nGerman, and Russian,", "start": 2565.598, "duration": 1.542}, {"text": "and lots of other languages.", "start": 2567.14, "duration": 1.5}, {"text": "Final obstruents-- so if\nyou are an obstruent that", "start": 2568.64, "duration": 3.12}, {"text": "is something which\nis not a sonorant,", "start": 2571.76, "duration": 1.8}, {"text": "you become something\nwhich is not voiced.", "start": 2573.56, "duration": 2.85}, {"text": "If you are at the\nend of a word--", "start": 2576.41, "duration": 2.43}, {"text": "that environment\ndescription is the way", "start": 2578.84, "duration": 2.46}, {"text": "to write at the end of a word.", "start": 2581.3, "duration": 1.35}, {"text": "That hash symbol is the symbol\nfor a boundary between words.", "start": 2582.65, "duration": 3.3}, {"text": "And the underscore is where\nthe change takes place.", "start": 2585.95, "duration": 3.25}, {"text": "So this rule says\nthis change happens", "start": 2589.2, "duration": 4.07}, {"text": "when the sound is\nbefore a word boundary,", "start": 2593.27, "duration": 3.39}, {"text": "or to put it another way, when\nit is at the end of a word.", "start": 2596.66, "duration": 3.09}, {"text": "Does that make sense?", "start": 2599.75, "duration": 1.52}, {"text": "This is a way of writing rules.", "start": 2601.27, "duration": 1.465}, {"text": "These rules are part of our\nknowledge of a language.", "start": 2606.53, "duration": 2.52}, {"text": "So we've talked about this.", "start": 2609.05, "duration": 1.43}, {"text": "As adults, anybody who is\na native speaker of English", "start": 2614.26, "duration": 4.92}, {"text": "knows how to make\nthe plural of \"wug,\"", "start": 2619.18, "duration": 3.06}, {"text": "or how to make the\nplural of \"Bach,\" even.", "start": 2622.24, "duration": 2.82}, {"text": "So how to make plurals\nof words you've", "start": 2625.06, "duration": 3.48}, {"text": "never heard before and even\nwords that end in sounds", "start": 2628.54, "duration": 3.0}, {"text": "that your language\ndoesn't have, right?", "start": 2631.54, "duration": 2.89}, {"text": "So if I insist on calling\nthe composer \"Bach\"--", "start": 2634.43, "duration": 3.92}, {"text": "if I insist on the original\nInupiaq pronunciation", "start": 2638.35, "duration": 3.3}, {"text": "of the word \"qaiaq,\" which\nis kayak, a single person", "start": 2641.65, "duration": 3.72}, {"text": "boat, which in Inupiaq begins\nand ends with a uvular stop--", "start": 2645.37, "duration": 5.44}, {"text": "so if I'm trying to\nimpress you with my ability", "start": 2650.81, "duration": 2.0}, {"text": "to make uvular\nstops and I insist", "start": 2652.81, "duration": 1.74}, {"text": "on calling a kayak a \"qaiaq,\"\nthen my plural for it", "start": 2654.55, "duration": 3.27}, {"text": "is going to be \"qaiaqs,\" right?", "start": 2657.82, "duration": 2.55}, {"text": "So I'm going to\nadd an \"s\" sound.", "start": 2660.37, "duration": 1.38}, {"text": "I'm going to devoice it\nbecause that uvular stop,", "start": 2661.75, "duration": 2.28}, {"text": "although it's a\nsound we don't have", "start": 2664.03, "duration": 1.458}, {"text": "an English-- it's voiceless.", "start": 2665.488, "duration": 1.792}, {"text": "So we're going to\ndevoice after it.", "start": 2667.28, "duration": 3.86}, {"text": "So these rules are part of\nour knowledge of a language.", "start": 2671.14, "duration": 2.55}, {"text": "And we can apply them\nto unfamiliar problems,", "start": 2673.69, "duration": 2.85}, {"text": "unfamiliar words, and\neven unfamiliar sounds.", "start": 2676.54, "duration": 3.69}, {"text": "And I've now tried to\nconvince you the best", "start": 2680.23, "duration": 3.225}, {"text": "way to state these rules,\nsometimes at least,", "start": 2683.455, "duration": 1.875}, {"text": "is in terms of features.", "start": 2685.33, "duration": 1.32}, {"text": "That is, we don't just want\nto list the sounds that", "start": 2686.65, "duration": 3.33}, {"text": "undergo a change.", "start": 2689.98, "duration": 1.32}, {"text": "We want to have these\nfeatures which are ways", "start": 2691.3, "duration": 3.66}, {"text": "of capturing sets of sounds.", "start": 2694.96, "duration": 2.19}, {"text": "We think that there are\nnatural classes of sounds that", "start": 2697.15, "duration": 3.69}, {"text": "undergo particular changes.", "start": 2700.84, "duration": 1.63}, {"text": "So there are sound\nchanges that apply, say,", "start": 2702.47, "duration": 2.09}, {"text": "to obstruents, to sonorants,\nor to vowels, to voiced sounds,", "start": 2704.56, "duration": 4.35}, {"text": "or to voiceless sounds.", "start": 2708.91, "duration": 1.047}, {"text": "We're not just going\nto list the sounds that", "start": 2709.957, "duration": 1.833}, {"text": "undergo sound changes.", "start": 2711.79, "duration": 0.917}, {"text": "We're going to state these\nin terms of features, OK?", "start": 2712.707, "duration": 3.512}, {"text": "And then the other thing\nthat I've introduced you to", "start": 2720.71, "duration": 2.58}, {"text": "is the idea that at\nleast sometimes, it's", "start": 2723.29, "duration": 2.55}, {"text": "fruitful to model these\nkinds of sound changes", "start": 2725.84, "duration": 3.9}, {"text": "as involving ranked constraints.", "start": 2729.74, "duration": 2.76}, {"text": "This was the optimality\ntheory tableaux--", "start": 2732.5, "duration": 3.27}, {"text": "that is, to imagine that\nlanguages have a list of things", "start": 2735.77, "duration": 3.6}, {"text": "that they are trying to achieve.", "start": 2739.37, "duration": 1.63}, {"text": "And it's a list that's\nranked in order of priority.", "start": 2741.0, "duration": 3.77}, {"text": "And you get to\nobserve the interplay", "start": 2744.77, "duration": 2.88}, {"text": "between these\ndifferent priorities", "start": 2747.65, "duration": 1.77}, {"text": "in certain kinds of\ncomplicated cases.", "start": 2749.42, "duration": 2.19}, {"text": "The Japanese accent case was one\nof the ones that we looked at.", "start": 2751.61, "duration": 3.94}, {"text": "OK?", "start": 2755.55, "duration": 2.73}, {"text": "And I think that's it\nfor this review slide.", "start": 2758.28, "duration": 2.198}, {"text": "Was there something else?", "start": 2760.478, "duration": 1.042}, {"text": "Oh, OK.", "start": 2761.52, "duration": 1.29}, {"text": "Is everyone happy\nwith all of this?", "start": 2762.81, "duration": 2.16}, {"text": "Is there any of this that\npeople are looking at and going,", "start": 2764.97, "duration": 1.68}, {"text": "no, wait.", "start": 2766.65, "duration": 0.42}, {"text": "How did-- how did we see that?", "start": 2767.07, "duration": 1.25}, {"text": "Or what does that mean,\nor anything like that?", "start": 2768.32, "duration": 2.38}, {"text": "Just an attempt to make\nsure that we're all", "start": 2770.7, "duration": 2.01}, {"text": "n the same ballpark here.", "start": 2772.71, "duration": 1.53}, {"text": "Yeah?", "start": 2774.24, "duration": 0.802}, {"text": "STUDENT: Could you clarify\nwhat \"feature\" means?", "start": 2775.042, "duration": 1.238}, {"text": "NORVIN RICHARDS: Oh.", "start": 2776.28, "duration": 0.833}, {"text": "All I mean by \"feature\"\nare things like voiced,", "start": 2777.113, "duration": 3.547}, {"text": "or sonorant, or those\nkinds of things.", "start": 2780.66, "duration": 3.29}, {"text": "Yeah, good question.", "start": 2783.95, "duration": 1.42}, {"text": "And a standard\nway to write rules", "start": 2785.37, "duration": 1.8}, {"text": "involves putting features\nin brackets like that.", "start": 2787.17, "duration": 2.55}, {"text": "So the fancy way\nto say something", "start": 2789.72, "duration": 1.71}, {"text": "is voiceless is to say that\nits value for the feature voice", "start": 2791.43, "duration": 4.02}, {"text": "is minus.", "start": 2795.45, "duration": 1.08}, {"text": "So it is not voiced, yeah.", "start": 2796.53, "duration": 1.95}, {"text": "That's all that means.", "start": 2798.48, "duration": 2.61}, {"text": "Yeah?", "start": 2801.09, "duration": 1.48}, {"text": "OK.", "start": 2802.57, "duration": 0.78}, {"text": "When we ask you to\ndo phonology, we", "start": 2803.35, "duration": 2.85}, {"text": "will tell you\nwhether we want you--", "start": 2806.2, "duration": 2.64}, {"text": "to what extent we want\nyou to be formal about how", "start": 2808.84, "duration": 2.31}, {"text": "you write your rules.", "start": 2811.15, "duration": 1.57}, {"text": "So I think the problem\nset that I just sent out", "start": 2812.72, "duration": 3.5}, {"text": "asks you to look around\nfor possible rules in--", "start": 2816.22, "duration": 4.05}, {"text": "what is it?", "start": 2820.27, "duration": 1.75}, {"text": "It's Greenlandic data, I think.", "start": 2822.02, "duration": 3.8}, {"text": "You don't have to sweat\nthis level of formality", "start": 2825.82, "duration": 3.15}, {"text": "in your rules.", "start": 2828.97, "duration": 0.76}, {"text": "So if your rule for\nthat problem set--", "start": 2829.73, "duration": 1.62}, {"text": "so if you think you've\nfigured out what's going on,", "start": 2831.35, "duration": 3.93}, {"text": "you can just tell\nus, more or less.", "start": 2835.28, "duration": 2.44}, {"text": "Don't feel like we're\ngoing to count off", "start": 2837.72, "duration": 2.08}, {"text": "for not using features or not\nwriting your rules this way.", "start": 2839.8, "duration": 4.37}, {"text": "OK.", "start": 2844.17, "duration": 0.5}, {"text": "All right, then.", "start": 2848.81, "duration": 1.8}, {"text": "Now I told you just now--", "start": 2850.61, "duration": 2.855}, {"text": "I tried to convince\nyou earlier--", "start": 2853.465, "duration": 1.375}, {"text": "that there are cases where--", "start": 2854.84, "duration": 3.33}, {"text": "the Japanese accent\ncase was the one", "start": 2858.17, "duration": 1.59}, {"text": "that we spent the\nmost time on, where", "start": 2859.76, "duration": 2.34}, {"text": "it's fruitful to think\nof the phenomenon", "start": 2862.1, "duration": 3.45}, {"text": "as involving a bunch\nof ranked priorities,", "start": 2865.55, "duration": 2.31}, {"text": "a bunch of constraints\nthat are all pulling", "start": 2867.86, "duration": 2.75}, {"text": "in different directions.", "start": 2870.61, "duration": 1.0}, {"text": "And you solve that\nproblem by deciding", "start": 2871.61, "duration": 2.04}, {"text": "which is the most\nimportant one, which", "start": 2873.65, "duration": 2.61}, {"text": "ones are more important than\nwhich other ones, ranking", "start": 2876.26, "duration": 2.25}, {"text": "your various constraints\nwith respect to each other.", "start": 2878.51, "duration": 3.46}, {"text": "There are other\ncases, though, that", "start": 2881.97, "duration": 2.3}, {"text": "are problematic for that way\nof thinking about things.", "start": 2884.27, "duration": 3.99}, {"text": "And there's big literature\non trying to reconcile", "start": 2888.26, "duration": 3.3}, {"text": "these kinds of observations.", "start": 2891.56, "duration": 1.26}, {"text": "On the one hand, the\nobservation that there do", "start": 2892.82, "duration": 2.58}, {"text": "seem to be these conspiracies\nwhere a language is doing", "start": 2895.4, "duration": 3.09}, {"text": "the same thing in a\nvariety of ways, which", "start": 2898.49, "duration": 1.75}, {"text": "is the kind of thing that makes\npeople want to think in terms", "start": 2900.24, "duration": 2.542}, {"text": "of ranked constraints,\nand on the other hand,", "start": 2902.782, "duration": 2.198}, {"text": "the kinds of cases, which\nwe've talked about before,", "start": 2904.98, "duration": 2.27}, {"text": "where it looks more\nlike what's happening", "start": 2907.25, "duration": 1.77}, {"text": "is that you have\na bunch of rules.", "start": 2909.02, "duration": 1.56}, {"text": "And they're applying\nin an order.", "start": 2910.58, "duration": 2.46}, {"text": "And they don't necessarily\nall get obeyed.", "start": 2913.04, "duration": 5.67}, {"text": "We did this on the board--", "start": 2918.71, "duration": 2.8}, {"text": "when was it?", "start": 2921.51, "duration": 0.5}, {"text": "Last time, I think.", "start": 2922.01, "duration": 0.792}, {"text": "But let's do it on the slide\na little more carefully.", "start": 2922.802, "duration": 2.698}, {"text": "So cast your minds back to when\nwe were talking about Lardil.", "start": 2925.5, "duration": 3.98}, {"text": "I tried to convince you--\nwe worked out an analysis", "start": 2929.48, "duration": 2.31}, {"text": "of Lardil in which, again,\nbare nominative singular--", "start": 2931.79, "duration": 5.97}, {"text": "Lardil doesn't mark number.", "start": 2937.76, "duration": 1.23}, {"text": "But bare nominative\nforms of nouns", "start": 2938.99, "duration": 3.93}, {"text": "undergo various kinds\nof sound changes.", "start": 2942.92, "duration": 2.05}, {"text": "So Lardil has words\nthat underlyingly", "start": 2944.97, "duration": 3.23}, {"text": "end in a \"k,\" for example.", "start": 2948.2, "duration": 1.89}, {"text": "And there was a\ngeneral rule in Lardil", "start": 2950.09, "duration": 2.82}, {"text": "that said if you\nhave a word that ends", "start": 2952.91, "duration": 2.64}, {"text": "in a \"k,\" get rid of the \"k.\"", "start": 2955.55, "duration": 2.82}, {"text": "So I'll start\nwriting these down.", "start": 2958.37, "duration": 3.03}, {"text": "Some Lardil rules-- one\nof them was eliminate--", "start": 2961.4, "duration": 3.47}, {"text": "and I won't try to\nwrite them formally.", "start": 2964.87, "duration": 1.66}, {"text": "Eliminate final \"k.\"", "start": 2966.53, "duration": 3.36}, {"text": "So the word that we\nthink is underlyingly", "start": 2969.89, "duration": 3.07}, {"text": "\"wangalk,\" the\nword for boomerang,", "start": 2972.96, "duration": 2.93}, {"text": "in its nominative\nform is \"wangal.\"", "start": 2975.89, "duration": 1.81}, {"text": "And the reason we think\nthat it's underlyingly", "start": 2977.7, "duration": 1.917}, {"text": "\"wangal\" is that if you\nadd any suffixes to it,", "start": 2979.617, "duration": 2.243}, {"text": "you get to see that \"k.\"", "start": 2981.86, "duration": 1.41}, {"text": "So the accusative, I think\nI told you, was [LARDIL]..", "start": 2983.27, "duration": 4.11}, {"text": "So the \"k\" shows up, and\nin other forms as well.", "start": 2987.38, "duration": 4.53}, {"text": "We thought there was\nanother rule that said", "start": 2991.91, "duration": 2.88}, {"text": "a final \"u\" becomes \"a,\" yeah?", "start": 2994.79, "duration": 5.67}, {"text": "And that was why\n\"kandu,\" which is", "start": 3000.46, "duration": 2.97}, {"text": "the word for \"blood\"\nunderlyingly,", "start": 3003.43, "duration": 2.52}, {"text": "becomes \"kanda\"\nin the nominative.", "start": 3005.95, "duration": 2.58}, {"text": "And in the accusative,\nit's [LARDIL]..", "start": 3008.53, "duration": 2.19}, {"text": "That's why we think it\nstarts out as \"kandu.\"", "start": 3010.72, "duration": 3.06}, {"text": "So we have these two rules.", "start": 3013.78, "duration": 1.822}, {"text": "And what we said\nwhen we were doing", "start": 3015.602, "duration": 1.458}, {"text": "Lardil before was\nsomething like we", "start": 3017.06, "duration": 3.38}, {"text": "might want these rules to\napply in a particular order.", "start": 3020.44, "duration": 4.08}, {"text": "In fact, I see that\nI have written them", "start": 3024.52, "duration": 2.13}, {"text": "in the wrong order.", "start": 3026.65, "duration": 2.1}, {"text": "If you were to take the\nword \"ngaluk,\" which", "start": 3028.75, "duration": 4.02}, {"text": "is the underlying\nform for \"story,\"", "start": 3032.77, "duration": 2.28}, {"text": "and apply this rule\nand then this rule,", "start": 3035.05, "duration": 3.46}, {"text": "well then, you would\neliminate the final \"k.\"", "start": 3038.51, "duration": 2.15}, {"text": "That would get you ngalu.", "start": 3040.66, "duration": 1.41}, {"text": "And then you would change\nthe final \"u\" to \"a.\"", "start": 3042.07, "duration": 2.01}, {"text": "And then you would\nget an \"ngala.\"", "start": 3044.08, "duration": 2.01}, {"text": "But that's not, in fact, the\nnominative form for \"story.\"", "start": 3046.09, "duration": 2.91}, {"text": "The nominative form for\nstory is ngalu, yeah?", "start": 3049.0, "duration": 3.06}, {"text": "And so what I said at the\ntime was one way of thinking", "start": 3052.06, "duration": 3.58}, {"text": "about this, a popular way\nof thinking about this", "start": 3055.64, "duration": 2.0}, {"text": "is, to think there\nare these rules.", "start": 3057.64, "duration": 1.92}, {"text": "And it's like an assembly line.", "start": 3059.56, "duration": 2.91}, {"text": "The first station is the\none where you do this,", "start": 3062.47, "duration": 2.91}, {"text": "where you get rid of final \"u.\"", "start": 3065.38, "duration": 1.77}, {"text": "And then after you're done\nwith that, you get handed off", "start": 3067.15, "duration": 3.0}, {"text": "to another place in\nthe assembly line", "start": 3070.15, "duration": 2.61}, {"text": "where they eliminate final \"k.\"", "start": 3072.76, "duration": 2.58}, {"text": "And what's happened with that\n\"ngaluk,\" underlying \"ngaluk,\"", "start": 3075.34, "duration": 3.03}, {"text": "is that it got handed to\nthe first station first.", "start": 3078.37, "duration": 2.19}, {"text": "First station said, well,\nthis word, \"ngaluk\"--", "start": 3080.56, "duration": 2.13}, {"text": "it doesn't end in \"u.\"", "start": 3082.69, "duration": 1.23}, {"text": "I'm not going to do anything.", "start": 3083.92, "duration": 1.47}, {"text": "And then it gets handed\nto the second station.", "start": 3085.39, "duration": 2.352}, {"text": "The second station\nsays, oh, I need", "start": 3087.742, "duration": 1.458}, {"text": "to get rid of the final \"k.\"", "start": 3089.2, "duration": 1.167}, {"text": "It'll be a \"ngalu,\"\nby which point", "start": 3090.367, "duration": 1.831}, {"text": "the people in the first\nstation might have been saying,", "start": 3092.198, "duration": 2.292}, {"text": "wait, wait.", "start": 3094.49, "duration": 0.5}, {"text": "Let us have that back.", "start": 3094.99, "duration": 0.94}, {"text": "But it's too late, was the idea.", "start": 3095.93, "duration": 1.97}, {"text": "Yeah, so these are rules that\napply in a particular order.", "start": 3097.9, "duration": 2.49}, {"text": "That's the way we were\ntalking about Lardil.", "start": 3100.39, "duration": 2.43}, {"text": "Does that all sound\nvaguely familiar?", "start": 3102.82, "duration": 2.34}, {"text": "There are these procedures, and\nthe procedures happen in order.", "start": 3105.16, "duration": 2.625}, {"text": "But if we imagine,\nthinking about things", "start": 3110.53, "duration": 2.21}, {"text": "in an optimality\ntheoretic kind of way,", "start": 3112.74, "duration": 2.34}, {"text": "well, it's not hard to come up\nwith constraints that say this.", "start": 3115.08, "duration": 4.59}, {"text": "Star, final-- I have to\nwrite it in capital letters", "start": 3119.67, "duration": 5.31}, {"text": "because that's what you\ndo in optimality theory.", "start": 3124.98, "duration": 2.01}, {"text": "No final \"k.\"", "start": 3126.99, "duration": 1.56}, {"text": "No final \"u,\" yeah?", "start": 3128.55, "duration": 4.62}, {"text": "And those constraints\nwould look at \"ngaluk\"--", "start": 3133.17, "duration": 2.38}, {"text": "or sorry, \"wangalk,\"\nand they would say,", "start": 3135.55, "duration": 2.07}, {"text": "no, we can't have the final \"k.\"", "start": 3137.62, "duration": 0.92}, {"text": "It'll be one \"wangal.\"", "start": 3138.54, "duration": 0.75}, {"text": "And they would look at \"kandu.\"", "start": 3139.29, "duration": 1.292}, {"text": "And they would say, no,\ncan't have the final \"u.\"", "start": 3140.582, "duration": 2.638}, {"text": "It's got to be \"kanda.\"", "start": 3143.22, "duration": 1.56}, {"text": "It might have other\nconstraints that", "start": 3144.78, "duration": 1.5}, {"text": "are responsible for helping\nyou decide the best thing to do", "start": 3146.28, "duration": 3.24}, {"text": "with \"kandu\" is to change it\nto \"kanda\" instead of \"kandi,\"", "start": 3149.52, "duration": 3.18}, {"text": "or \"kand,\" or any of a\nvariety of other things", "start": 3152.7, "duration": 2.197}, {"text": "you could have done.", "start": 3154.897, "duration": 0.833}, {"text": "So it's not all\nthat hard to have", "start": 3155.73, "duration": 1.65}, {"text": "constraints that say there's\nsomething wrong with \"wangalk.\"", "start": 3157.38, "duration": 2.58}, {"text": "There's something\nwrong with \"kandu.\"", "start": 3159.96, "duration": 3.68}, {"text": "But it's not easy to\nfigure out what to do next.", "start": 3163.64, "duration": 3.76}, {"text": "So if you have those conditions\nthat say Lardil cannot stand", "start": 3167.4, "duration": 3.5}, {"text": "words that end in \"k.\"\nor words that end in \"u,\"", "start": 3170.9, "duration": 4.5}, {"text": "that's the kind of thing we were\nsaying about Japanese accent.", "start": 3175.4, "duration": 2.91}, {"text": "Japanese doesn't like\naccent on the last syllable.", "start": 3178.31, "duration": 4.05}, {"text": "So avoid it if you're\nmaking a compound.", "start": 3182.36, "duration": 2.84}, {"text": "Those generalizations hold for\n\"boomerang\" and for \"blood.\"", "start": 3185.2, "duration": 2.7}, {"text": "But they don't hold for \"story.\"", "start": 3187.9, "duration": 1.65}, {"text": "The one about not having a word\nending in \"u\" doesn't hold.", "start": 3189.55, "duration": 3.3}, {"text": "Yes?", "start": 3192.85, "duration": 1.133}, {"text": "STUDENT: You talked about\nno final \"k,\" no final \"u\"", "start": 3193.983, "duration": 2.167}, {"text": "as being part of\noptimality theory.", "start": 3196.15, "duration": 1.663}, {"text": "NORVIN RICHARDS: Yeah.", "start": 3197.813, "duration": 0.917}, {"text": "STUDENT: Is it possible\nto satisfy both", "start": 3201.34, "duration": 4.69}, {"text": "if you were to do \"ngala\"?", "start": 3206.03, "duration": 2.948}, {"text": "NORVIN RICHARDS: Mm-hmm.", "start": 3208.978, "duration": 2.092}, {"text": "STUDENT: Does optimality theory\nsupport each of the rules?", "start": 3211.07, "duration": 5.622}, {"text": "NORVIN RICHARDS:\nSo that's just it.", "start": 3216.692, "duration": 1.458}, {"text": "It doesn't, right?", "start": 3218.15, "duration": 0.75}, {"text": "So the conditions--\nthe sense in which", "start": 3218.9, "duration": 2.105}, {"text": "it has something\nlike an order is", "start": 3221.005, "duration": 1.375}, {"text": "that the conditions are ranked\nwith respect to each other.", "start": 3222.38, "duration": 2.25}, {"text": "There's the one that's most\nimportant and the one that's", "start": 3224.63, "duration": 2.333}, {"text": "next most important, and so on.", "start": 3226.963, "duration": 2.357}, {"text": "But if we were to\nbuild a tableau,", "start": 3229.32, "duration": 3.59}, {"text": "we would have these\ntwo conditions.", "start": 3232.91, "duration": 3.45}, {"text": "Don't have final \"k.\"", "start": 3236.36, "duration": 2.55}, {"text": "Don't have final \"u.\"", "start": 3238.91, "duration": 5.46}, {"text": "And we would start\noff with \"ngaluk.\"", "start": 3244.37, "duration": 3.48}, {"text": "And we'd consider\nkeeping \"ngaluk.\"", "start": 3247.85, "duration": 2.73}, {"text": "And we'd consider getting\nrid of the \"k\" at the end.", "start": 3250.58, "duration": 4.83}, {"text": "And maybe we'd consider\n\"ngala,\" right?", "start": 3255.41, "duration": 3.06}, {"text": "And this one would get knocked\nout by star final \"k,\" right?", "start": 3258.47, "duration": 4.56}, {"text": "Because it would end in \"k.\"", "start": 3263.03, "duration": 1.44}, {"text": "And this one would get knocked\nout by star final \"u,\" yeah?", "start": 3264.47, "duration": 4.05}, {"text": "And this one would pass\nboth of those conditions.", "start": 3268.52, "duration": 3.28}, {"text": "So if we just did a tableau\nlike this, if we said,", "start": 3271.8, "duration": 2.75}, {"text": "Lardil seems to not like\nthis and not like that,", "start": 3274.55, "duration": 2.16}, {"text": "and we have evidence for\nthat in these other cases,", "start": 3276.71, "duration": 3.43}, {"text": "it seems as though \"ngalu\"\nought to become \"ngala.\"", "start": 3280.14, "duration": 2.93}, {"text": "But that's wrong.", "start": 3283.07, "duration": 1.41}, {"text": "So the fact is this is\nthe one we want to win.", "start": 3284.48, "duration": 3.16}, {"text": "And it's hard to see, once we've\nposited these conditions, how", "start": 3287.64, "duration": 4.91}, {"text": "we can get this to win.", "start": 3292.55, "duration": 1.59}, {"text": "This seems like it ought\nto be better once we've", "start": 3294.14, "duration": 3.09}, {"text": "posited these conditions.", "start": 3297.23, "duration": 1.27}, {"text": "So the puzzle-- and there's\nsomething people work on", "start": 3298.5, "duration": 2.167}, {"text": "is try to figure out,\nwhy is that second one", "start": 3300.667, "duration": 2.503}, {"text": "better than the third one?", "start": 3303.17, "duration": 1.59}, {"text": "Yeah.", "start": 3304.76, "duration": 0.66}, {"text": "STUDENT: How about we rephrase\nthe no final \"u\" rule?", "start": 3305.42, "duration": 2.403}, {"text": "NORVIN RICHARDS: Yeah.", "start": 3307.823, "duration": 0.917}, {"text": "STUDENT: We rephrase it as\nno final \"u\" unless it's", "start": 3308.74, "duration": 2.79}, {"text": "original form ends with a \"k.\"", "start": 3311.53, "duration": 1.56}, {"text": "NORVIN RICHARDS: Ah, OK.", "start": 3313.09, "duration": 1.0}, {"text": "So we could have\na rule that says--", "start": 3314.09, "duration": 1.62}, {"text": "that's nice.", "start": 3315.71, "duration": 0.99}, {"text": "We could say, no final \"u.\"", "start": 3316.7, "duration": 2.68}, {"text": "This is another way of\nsaying what you just said.", "start": 3319.38, "duration": 2.57}, {"text": "No final \"u\" that was\nfinal in original form.", "start": 3321.95, "duration": 7.005}, {"text": "Yep.", "start": 3332.08, "duration": 0.63}, {"text": "So we need more capital\nletters, but it's OK.", "start": 3332.71, "duration": 3.12}, {"text": "So yes, if we state\nit that way, then this", "start": 3335.83, "duration": 6.87}, {"text": "passes that version of it.", "start": 3342.7, "duration": 2.59}, {"text": "And as long as we have some\nother condition that says,", "start": 3345.29, "duration": 2.36}, {"text": "don't change vowels\njust for the fun of it,", "start": 3347.65, "duration": 1.89}, {"text": "don't change \"u\" because you\nwant to, which we surely need,", "start": 3349.54, "duration": 4.3}, {"text": "right?", "start": 3353.84, "duration": 0.5}, {"text": "If you give Lardil\na word that has", "start": 3354.34, "duration": 3.09}, {"text": "an \"u\" in it that's not at the\nend, it's not going to change.", "start": 3357.43, "duration": 4.11}, {"text": "Then yes, then this would win.", "start": 3361.54, "duration": 2.25}, {"text": "That's right.", "start": 3363.79, "duration": 0.84}, {"text": "That is indeed one of the kinds\nof things people do in order", "start": 3364.63, "duration": 3.09}, {"text": "to handle this kind of problem.", "start": 3367.72, "duration": 1.32}, {"text": "They make these conditions\nmore complicated because now", "start": 3369.04, "duration": 5.61}, {"text": "the conditions we've had so\nfar are all about the form that", "start": 3374.65, "duration": 4.17}, {"text": "gets pronounced.", "start": 3378.82, "duration": 1.06}, {"text": "They say things like the\nform that gets pronounced", "start": 3379.88, "duration": 2.36}, {"text": "had better not end in\na \"k,\" or the form that", "start": 3382.24, "duration": 2.07}, {"text": "gets pronounced had better\nnot end in a voiced obstruent", "start": 3384.31, "duration": 2.37}, {"text": "if we're doing Polish,\nor it'd better not", "start": 3386.68, "duration": 2.822}, {"text": "have two stridents at\nthe end of the word", "start": 3389.502, "duration": 1.708}, {"text": "in a language like English.", "start": 3391.21, "duration": 1.597}, {"text": "This is a more\ncomplicated constraint.", "start": 3392.807, "duration": 1.583}, {"text": "It says it had better not\nend in this kind of sound", "start": 3394.39, "duration": 3.66}, {"text": "if it ended in\nthis kind of sound", "start": 3398.05, "duration": 2.55}, {"text": "originally, before we started.", "start": 3400.6, "duration": 3.45}, {"text": "So there's an actual debate\ngoing on in optimality theory", "start": 3404.05, "duration": 4.38}, {"text": "about whether we want to allow\nourselves that power, allowing", "start": 3408.43, "duration": 2.772}, {"text": "constraints that\nmake reference not", "start": 3411.202, "duration": 1.458}, {"text": "just to the pronounced version\nbut to an earlier version.", "start": 3412.66, "duration": 2.553}, {"text": "But you're absolutely right.", "start": 3415.213, "duration": 1.167}, {"text": "That's a move people\nmake, people argue for.", "start": 3416.38, "duration": 3.78}, {"text": "I'm bringing this\nup just to show you", "start": 3420.16, "duration": 1.83}, {"text": "there's this tension\nbetween these two ways", "start": 3421.99, "duration": 2.01}, {"text": "of thinking about phonology.", "start": 3424.0, "duration": 2.07}, {"text": "And you've just raised one\nof the ways, one of the ways", "start": 3426.07, "duration": 3.06}, {"text": "that, indeed, has been\ntaken in the literature", "start": 3429.13, "duration": 2.94}, {"text": "to try to figure out how\nto deal with this tension.", "start": 3432.07, "duration": 3.16}, {"text": "But if you thought\nthat linguistics", "start": 3435.23, "duration": 2.06}, {"text": "was finished, like we\nunderstood everything, no.", "start": 3437.29, "duration": 3.0}, {"text": "Yeah, so this is one\nof the kinds of things", "start": 3440.29, "duration": 2.25}, {"text": "that linguists\nstill fight about--", "start": 3442.54, "duration": 2.22}, {"text": "how to deal with these\nkinds of tensions.", "start": 3444.76, "duration": 1.92}, {"text": "Yes?", "start": 3446.68, "duration": 1.79}, {"text": "STUDENT: I think we can still\nthink of it as an assembly", "start": 3448.47, "duration": 2.57}, {"text": "line.", "start": 3451.04, "duration": 0.5}, {"text": "NORVIN RICHARDS: Yeah.", "start": 3451.54, "duration": 0.917}, {"text": "STUDENT: If we think of\nit as an assembly line,", "start": 3452.457, "duration": 2.413}, {"text": "and we throw at that, we can\nmake it like a priority then.", "start": 3454.87, "duration": 3.91}, {"text": "NORVIN RICHARDS: Uh-huh.", "start": 3458.78, "duration": 1.0}, {"text": "STUDENT: We can make it\nlike an assembly language.", "start": 3459.78, "duration": 2.72}, {"text": "NORVIN RICHARDS: Uh-huh.", "start": 3462.5, "duration": 1.0}, {"text": "STUDENT: We can form rules.", "start": 3463.5, "duration": 1.435}, {"text": "NORVIN RICHARDS: Yes.", "start": 3464.935, "duration": 0.875}, {"text": "STUDENT: Actually\nenforce the priority.", "start": 3465.81, "duration": 1.773}, {"text": "NORVIN RICHARDS: Yeah, yeah.", "start": 3467.583, "duration": 1.167}, {"text": "Yeah, so that is another\nmove that people make.", "start": 3468.75, "duration": 3.12}, {"text": "Sorry, this slide has gone away.", "start": 3471.87, "duration": 1.95}, {"text": "That is another move that\npeople make, where they say,", "start": 3477.98, "duration": 4.15}, {"text": "well, there are various ways\nof interpreting what you just", "start": 3482.13, "duration": 2.69}, {"text": "said.", "start": 3484.82, "duration": 1.02}, {"text": "One move that people made,\nespecially early on when people", "start": 3485.84, "duration": 4.332}, {"text": "were worried about this\nproblem in optimality theory,", "start": 3490.172, "duration": 2.208}, {"text": "was to say we're\ngoing to do something", "start": 3492.38, "duration": 3.48}, {"text": "in optimality theory that\nallows us to simulate", "start": 3495.86, "duration": 2.91}, {"text": "having rules in an order.", "start": 3498.77, "duration": 1.74}, {"text": "So what we'll do is we'll have\na word go through the tableaux", "start": 3500.51, "duration": 4.32}, {"text": "more than once.", "start": 3504.83, "duration": 1.77}, {"text": "Or the conditions can\nbe in different orders", "start": 3506.6, "duration": 4.41}, {"text": "in the different tableaux.", "start": 3511.01, "duration": 1.29}, {"text": "So we'll have a\ntableau first that", "start": 3512.3, "duration": 2.91}, {"text": "says final \"k\" is\nvery bad, let's say.", "start": 3515.21, "duration": 4.23}, {"text": "And it doesn't have\nfinal \"u\" is bad, right?", "start": 3519.44, "duration": 3.84}, {"text": "And then we'll have\nanother tableau", "start": 3523.28, "duration": 1.5}, {"text": "that maybe doesn't have\nfinal \"k\" is very bad,", "start": 3524.78, "duration": 2.07}, {"text": "but has final \"u\" is bad, right?", "start": 3526.85, "duration": 2.49}, {"text": "And that's a way to\nsimulate ordered rules,", "start": 3529.34, "duration": 3.48}, {"text": "basically, is to\nsay we go through", "start": 3532.82, "duration": 1.71}, {"text": "tableaux multiple times.", "start": 3534.53, "duration": 1.59}, {"text": "And the tableaux look\ndifferent from each other.", "start": 3536.12, "duration": 2.095}, {"text": "They have different\nconditions in them,", "start": 3538.215, "duration": 1.625}, {"text": "or they have the conditions\nin different orders.", "start": 3539.84, "duration": 2.0}, {"text": "That's one way to talk about it.", "start": 3541.84, "duration": 1.88}, {"text": "You might have had a\nmore clever idea, though,", "start": 3543.72, "duration": 2.28}, {"text": "which is the tableaux--", "start": 3546.0, "duration": 2.12}, {"text": "I was talking as though these\nrules are ranked with respect", "start": 3548.12, "duration": 4.742}, {"text": "to each other.", "start": 3552.862, "duration": 0.583}, {"text": "You know which ones\nare more important", "start": 3553.445, "duration": 1.583}, {"text": "than which other ones.", "start": 3555.028, "duration": 0.922}, {"text": "But optimality theory--\npeople are generally", "start": 3555.95, "duration": 2.22}, {"text": "talking not as though\nthose happen one at a time.", "start": 3558.17, "duration": 4.65}, {"text": "It's just you're considering\nall these possibilities.", "start": 3562.82, "duration": 2.94}, {"text": "And you decide which one is\nbest by all of these conditions.", "start": 3565.76, "duration": 3.127}, {"text": "You sound like you're thinking\nabout something different", "start": 3568.887, "duration": 2.333}, {"text": "where you would say you'd\ngo back to the simple one", "start": 3571.22, "duration": 3.66}, {"text": "and you'd say, we\nstart with \"ngaluk.\"", "start": 3574.88, "duration": 2.1}, {"text": "And what we want is something\nthat says something like,", "start": 3579.86, "duration": 3.84}, {"text": "well, I should have put\nstar final \"u\" first.", "start": 3583.7, "duration": 3.81}, {"text": "I'll just reverse these.", "start": 3587.51, "duration": 1.635}, {"text": "We have all of our\ncandidates here.", "start": 3594.16, "duration": 2.85}, {"text": "And we first consider\na star final \"u.\"", "start": 3597.01, "duration": 2.92}, {"text": "Uh-oh.", "start": 3599.93, "duration": 0.5}, {"text": "But if we consider\na star final \"u,\"", "start": 3600.43, "duration": 1.77}, {"text": "star final \"u\" will\nlook at \"ngalu,\"", "start": 3602.2, "duration": 1.5}, {"text": "and it will knock it out, right?", "start": 3603.7, "duration": 2.37}, {"text": "So that will be bad right there.", "start": 3606.07, "duration": 2.25}, {"text": "And we won't ever get\nit back if we do that.", "start": 3608.32, "duration": 3.335}, {"text": "So what we want\nis something more", "start": 3611.655, "duration": 1.375}, {"text": "like using the tableaux\nto do something", "start": 3613.03, "duration": 2.7}, {"text": "like ordered rules,\nsomething that says", "start": 3615.73, "duration": 3.51}, {"text": "we look at this first thing.", "start": 3619.24, "duration": 1.2}, {"text": "And we are now basically\ndoing rules in an order.", "start": 3620.44, "duration": 4.778}, {"text": "We look at this first\nthing and we ask ourselves,", "start": 3625.218, "duration": 2.042}, {"text": "what's \"ngaluk\"?", "start": 3627.26, "duration": 0.667}, {"text": "Well, it doesn't\nviolate this first rule.", "start": 3627.927, "duration": 3.443}, {"text": "And so we'll keep it.", "start": 3631.37, "duration": 1.58}, {"text": "And then we'll\nconsider the next rule.", "start": 3632.95, "duration": 2.34}, {"text": "It does violate that rule.", "start": 3635.29, "duration": 1.18}, {"text": "And so we'll change it.", "start": 3636.47, "duration": 0.958}, {"text": "We'll make a minimal\nchange to it.", "start": 3637.428, "duration": 1.552}, {"text": "This is a way of converting\ntableaux into ordered rules,", "start": 3638.98, "duration": 2.8}, {"text": "I think.", "start": 3641.78, "duration": 0.5}, {"text": "That's what we're now doing.", "start": 3642.28, "duration": 2.31}, {"text": "And it could be.", "start": 3644.59, "duration": 2.825}, {"text": "These are all things to\nthink about-- open research", "start": 3647.415, "duration": 2.125}, {"text": "questions.", "start": 3649.54, "duration": 1.78}, {"text": "Cool.", "start": 3651.32, "duration": 1.661}, {"text": "OK, so the goal here\nwas to get all of you", "start": 3652.981, "duration": 2.199}, {"text": "to try to do better than\nlinguistics has so far done.", "start": 3655.18, "duration": 2.62}, {"text": "So right now we\nhave these two ways", "start": 3657.8, "duration": 1.49}, {"text": "of thinking about phonology.", "start": 3659.29, "duration": 1.23}, {"text": "And there are in some kind\nof conflict with each other.", "start": 3660.52, "duration": 2.31}, {"text": "And there's active work\non trying to figure out", "start": 3662.83, "duration": 1.958}, {"text": "how to get them to mesh.", "start": 3664.788, "duration": 1.192}, {"text": "OK.", "start": 3670.74, "duration": 1.35}, {"text": "Cool.", "start": 3672.09, "duration": 1.5}, {"text": "Oops.", "start": 3673.59, "duration": 0.57}, {"text": "Where are we?", "start": 3674.16, "duration": 2.16}, {"text": "Here we are.", "start": 3676.32, "duration": 1.095}, {"text": "Sonorants and\nobstruents, we did that.", "start": 3677.415, "duration": 2.035}, {"text": "We did that.", "start": 3679.45, "duration": 1.233}, {"text": "OK, so let me introduce you--", "start": 3680.683, "duration": 3.647}, {"text": "we're running--\nyeah, yeah, yeah.", "start": 3684.33, "duration": 1.62}, {"text": "Let me introduce you to\nanother class of sounds.", "start": 3685.95, "duration": 6.15}, {"text": "Again, the point is to\nshow you ways in which it's", "start": 3692.1, "duration": 4.62}, {"text": "useful to categorize sounds.", "start": 3696.72, "duration": 1.74}, {"text": "And the way to try to\nconvince you of that", "start": 3698.46, "duration": 1.83}, {"text": "is to show you phenomena that\ncare about certain classes", "start": 3700.29, "duration": 4.14}, {"text": "of sounds and not others.", "start": 3704.43, "duration": 1.98}, {"text": "Here are a bunch of\nArabic nouns together", "start": 3706.41, "duration": 2.79}, {"text": "with their definite article,\nwhich you can see is \"al.\"", "start": 3709.2, "duration": 3.78}, {"text": "English has borrowed a\nbunch of Arabic words", "start": 3712.98, "duration": 2.67}, {"text": "that have kept this \"al.\"", "start": 3715.65, "duration": 1.17}, {"text": "So we have words like \"algebra,\"\nfor example, or \"algorithm,\"", "start": 3716.82, "duration": 3.06}, {"text": "where the \"al-\" at the end\nis this word for \"the.\"", "start": 3719.88, "duration": 4.65}, {"text": "So here are some Arabic\nnouns with the word for \"the\"", "start": 3724.53, "duration": 2.22}, {"text": "in front of them.", "start": 3726.75, "duration": 1.62}, {"text": "But there's this other class of\nnouns, where the word for \"the\"", "start": 3728.37, "duration": 4.62}, {"text": "changes.", "start": 3732.99, "duration": 0.73}, {"text": "It's no longer \"al.\"", "start": 3733.72, "duration": 2.21}, {"text": "What it gets-- it\nstill starts with \"a,\"", "start": 3735.93, "duration": 2.43}, {"text": "but the consonant in it becomes\na copy of the consonant that's", "start": 3738.36, "duration": 3.9}, {"text": "after it.", "start": 3742.26, "duration": 1.42}, {"text": "So the word for sun,\nwhich is [ARABIC]..", "start": 3743.68, "duration": 3.11}, {"text": "The sun is [ARABIC].", "start": 3746.79, "duration": 1.59}, {"text": "It's not \"al-\" [ARABIC].", "start": 3748.38, "duration": 1.908}, {"text": "Here I am pretending\nto speak Arabic.", "start": 3750.288, "duration": 1.542}, {"text": "Is there anyone here who\nactually speaks Arabic?", "start": 3751.83, "duration": 3.45}, {"text": "OK, cool.", "start": 3755.28, "duration": 0.5}, {"text": "I'll just keep pretending, then.", "start": 3755.78, "duration": 2.844}, {"text": "OK.", "start": 3758.624, "duration": 1.306}, {"text": "This is a classic observation.", "start": 3759.93, "duration": 1.25}, {"text": "Arabic linguists noticed\nthis about their language.", "start": 3761.18, "duration": 3.93}, {"text": "They name and noticed\nthe relevant condition", "start": 3765.11, "duration": 3.423}, {"text": "is that there are certain\nkinds of sounds that", "start": 3768.533, "duration": 1.917}, {"text": "get the phenomenon on the right,\nwhere the definite article ends", "start": 3770.45, "duration": 3.51}, {"text": "in a copy of the first\nconsonant of the following noun,", "start": 3773.96, "duration": 4.26}, {"text": "and other consonants\nthat don't do that.", "start": 3778.22, "duration": 1.8}, {"text": "They're called \"moon\nletters\" and \"sun letters\"", "start": 3780.02, "duration": 3.15}, {"text": "in the Arabic\ntradition because well,", "start": 3783.17, "duration": 2.97}, {"text": "\"moon\" is one of the words\nin the column on the left.", "start": 3786.14, "duration": 2.605}, {"text": "And \"sun\" is one of the words\nin the column on the right.", "start": 3788.745, "duration": 2.375}, {"text": "It's a mnemonic for\nthese classes of sounds.", "start": 3791.12, "duration": 3.58}, {"text": "So the moon letters are\nletters like \"kuh,\" and \"fuh,\"", "start": 3794.7, "duration": 3.17}, {"text": "and \"k,\" and \"h,\"\nand glottal stop.", "start": 3797.87, "duration": 4.03}, {"text": "And the sun letters are sounds\nlike \"sh,\" \"d,\" \"z,\" \"n,\"", "start": 3801.9, "duration": 3.84}, {"text": "and \"th.\"", "start": 3805.74, "duration": 0.73}, {"text": "The sun letters-- yes.", "start": 3812.82, "duration": 1.41}, {"text": "The sun letters are the ones\nthat I've got in the box there.", "start": 3814.23, "duration": 4.32}, {"text": "They are what are\ncalled coronals.", "start": 3818.55, "duration": 2.46}, {"text": "So coronals are the\ninterdentals and alveolars", "start": 3821.01, "duration": 3.09}, {"text": "and the postalveolars.", "start": 3824.1, "duration": 1.87}, {"text": "If you think about them--", "start": 3825.97, "duration": 1.53}, {"text": "so feel free to sit there\nmaking those noises to yourself", "start": 3827.5, "duration": 3.5}, {"text": "if you want to--", "start": 3831.0, "duration": 2.21}, {"text": "what all of them do is make\na consonant sound that's", "start": 3833.21, "duration": 3.94}, {"text": "articulated with the tip or\nthe blade of your tongue--", "start": 3837.15, "duration": 2.59}, {"text": "so if the front\nof your tongue is", "start": 3839.74, "duration": 1.61}, {"text": "touching some part of the top\nof your mouth or other places.", "start": 3841.35, "duration": 4.48}, {"text": "So the interdentals--\nyour tongue", "start": 3845.83, "duration": 1.55}, {"text": "is sticking out between your\nteeth, or the alveolars,", "start": 3847.38, "duration": 2.43}, {"text": "or the postalveolars--\nthe tip of your tongue", "start": 3849.81, "duration": 2.67}, {"text": "or the blade of your tongue\nis coming into contact almost", "start": 3852.48, "duration": 3.27}, {"text": "with the top of your mouth as\nopposed to, say, bilabials,", "start": 3855.75, "duration": 4.475}, {"text": "where your tongue can do\nwhatever the heck it feels", "start": 3860.225, "duration": 2.125}, {"text": "like, or velars, which involve\nyour tongue, or uvulars,", "start": 3862.35, "duration": 5.07}, {"text": "which involve your tongue.", "start": 3867.42, "duration": 1.14}, {"text": "But it's the back\nof your tongue, \"k,\"", "start": 3868.56, "duration": 2.46}, {"text": "or \"g,\" as opposed to the\nfront of your tongue, which", "start": 3871.02, "duration": 2.238}, {"text": "is what you're using\nfor things like \"t,\"", "start": 3873.258, "duration": 1.708}, {"text": "and \"d,\" and \"f,\" and\n\"th\" and \"sh\" and \"zh.\"", "start": 3874.966, "duration": 3.824}, {"text": "Is that clear?", "start": 3878.79, "duration": 0.87}, {"text": "That distinction clear?", "start": 3879.66, "duration": 1.68}, {"text": "And Arabic gives this a\nnice illustration of this.", "start": 3881.34, "duration": 6.0}, {"text": "The coronal sounds are the\nones that are the sun letters.", "start": 3887.34, "duration": 3.09}, {"text": "They're the ones where\nthe last consonant", "start": 3890.43, "duration": 3.87}, {"text": "of the definite article\njust becomes a copy", "start": 3894.3, "duration": 2.1}, {"text": "of the following consonant.", "start": 3896.4, "duration": 1.77}, {"text": "Notice that the last consonant\nof the indefinite article", "start": 3898.17, "duration": 2.61}, {"text": "underlyingly is \"l,\"\nwhich is itself coronal.", "start": 3900.78, "duration": 3.6}, {"text": "So it's like the end\nof the definite article", "start": 3904.38, "duration": 3.69}, {"text": "is going to be coronal.", "start": 3908.07, "duration": 1.56}, {"text": "If nothing else happens,\nit's going to be \"l,\"", "start": 3909.63, "duration": 2.353}, {"text": "But if there's a\ncoronal right after it,", "start": 3911.983, "duration": 1.667}, {"text": "it just becomes a copy\nof the following coronal.", "start": 3913.65, "duration": 2.28}, {"text": "Does that make sense?", "start": 3915.93, "duration": 1.8}, {"text": "That's what's going on\nin all of these examples.", "start": 3917.73, "duration": 2.71}, {"text": "So with \"moon,\" and \"mare,\"\nand \"book,\" and \"war,\"", "start": 3920.44, "duration": 2.12}, {"text": "and \"father,\" the \"l\"\nof the definite article", "start": 3922.56, "duration": 3.09}, {"text": "can't become a copy of\nthe following consonant", "start": 3925.65, "duration": 2.64}, {"text": "and remain coronal,\nwhereas in the sun letters,", "start": 3928.29, "duration": 4.08}, {"text": "the ones on the\nright, by copying", "start": 3932.37, "duration": 1.86}, {"text": "the following consonant, the\n\"l\" of the definite article", "start": 3934.23, "duration": 3.24}, {"text": "is still a coronal.", "start": 3937.47, "duration": 2.79}, {"text": "[ELECTRONIC CHIME]", "start": 3940.26, "duration": 0.75}, {"text": "Bling.", "start": 3941.01, "duration": 1.44}, {"text": "Somebody had a great\nidea about that.", "start": 3942.45, "duration": 1.59}, {"text": "So that's what's going on\nin these Arabic examples.", "start": 3946.92, "duration": 2.855}, {"text": "A rule that we could have for\nthe Arabic definite article--", "start": 3952.802, "duration": 2.458}, {"text": "yes, I just said this.", "start": 3955.26, "duration": 0.81}, {"text": "Thank you.", "start": 3956.07, "duration": 0.5}, {"text": "\"l\" is also coronal.", "start": 3956.57, "duration": 1.443}, {"text": "A rule we could have for\nthe Arabic definite article", "start": 3958.013, "duration": 2.167}, {"text": "would say in the\ndefinite article,", "start": 3960.18, "duration": 2.22}, {"text": "an \"l\" becomes a copy of a\nfollowing coronal consonant.", "start": 3962.4, "duration": 4.21}, {"text": "So we have a variable,\nconsonant subscript \"i\"", "start": 3966.61, "duration": 4.1}, {"text": "which says whatever the\nfollowing consonant is if it's", "start": 3970.71, "duration": 3.21}, {"text": "coronal, the \"l' will also\nget the value consonant sub i,", "start": 3973.92, "duration": 5.28}, {"text": "but it'll have the same form\nas the following consonant.", "start": 3979.2, "duration": 3.31}, {"text": "Yeah?", "start": 3982.51, "duration": 0.5}, {"text": "STUDENT: I had a\nquestion about coronals.", "start": 3983.01, "duration": 1.74}, {"text": "So what I noticed\nis the sun letters", "start": 3984.75, "duration": 4.232}, {"text": "are the letters that you can\nmaintain for a long time,", "start": 3988.982, "duration": 2.25}, {"text": "like \"sh,\" and like the\n\"sh,\" like [ARABIC] in sun,", "start": 3991.232, "duration": 4.528}, {"text": "for \"d\" in [ARABIC].", "start": 3995.76, "duration": 2.253}, {"text": "NORVIN RICHARDS: Yeah.", "start": 3998.013, "duration": 0.917}, {"text": "STUDENT: You maintain\nthem for a long time.", "start": 3998.93, "duration": 1.65}, {"text": "NORVIN RICHARDS: Yeah.", "start": 4000.58, "duration": 0.917}, {"text": "STUDENT: And Arabic\nactually has [ARABIC],,", "start": 4001.497, "duration": 2.713}, {"text": "which duplicates one letter.", "start": 4004.21, "duration": 2.173}, {"text": "NORVIN RICHARDS: Yeah.", "start": 4006.383, "duration": 0.917}, {"text": "STUDENT: So what I'm\nthinking is that when", "start": 4007.3, "duration": 2.31}, {"text": "you can duplicate the letter,\nyou just duplicate it.", "start": 4009.61, "duration": 2.275}, {"text": "NORVIN RICHARDS: Uh-huh.", "start": 4011.885, "duration": 0.415}, {"text": "STUDENT: With [ARABIC],,\nand other words.", "start": 4012.3, "duration": 1.81}, {"text": "NORVIN RICHARDS: Yeah.", "start": 4014.11, "duration": 1.14}, {"text": "STUDENT: But for [ARABIC],, just\nthe moon, you can't do that.", "start": 4015.25, "duration": 5.07}, {"text": "NORVIN RICHARDS: Yeah.", "start": 4020.32, "duration": 1.05}, {"text": "But there are--", "start": 4021.37, "duration": 1.14}, {"text": "STUDENT: Do you see what\nI'm saying with that?", "start": 4022.51, "duration": 0.78}, {"text": "NORVIN RICHARDS: I\nsee what you mean.", "start": 4023.29, "duration": 1.542}, {"text": "But look.", "start": 4024.832, "duration": 0.528}, {"text": "There are consonants like \"p,\"\nand \"t,\" and \"k,\" which are all", "start": 4025.36, "duration": 6.87}, {"text": "stops.", "start": 4032.23, "duration": 0.96}, {"text": "But \"t\" is coronal and \"p\"\nand \"k\" are not, right?", "start": 4033.19, "duration": 4.26}, {"text": "And so all of those are\nequally hard to maintain", "start": 4037.45, "duration": 3.42}, {"text": "for a long time, I think.", "start": 4040.87, "duration": 1.32}, {"text": "Or similarly, I think\nwhat we're hoping--", "start": 4042.19, "duration": 1.95}, {"text": "and you can stop me\nif this is not true--", "start": 4044.14, "duration": 2.13}, {"text": "is that if there are Arabic\nwords that start with \"m,\"", "start": 4046.27, "duration": 4.89}, {"text": "you'll get al\nbefore an \"m,\" yeah?", "start": 4051.16, "duration": 4.05}, {"text": "But for Arabic words\nthat start with \"n,\"", "start": 4055.21, "duration": 2.34}, {"text": "you get a copy of the \"n,\" yeah?", "start": 4057.55, "duration": 2.22}, {"text": "And again, those are all\nequally easy to hold on", "start": 4059.77, "duration": 3.57}, {"text": "for a long time.", "start": 4063.34, "duration": 1.02}, {"text": "So this is a good\nexample of science.", "start": 4064.36, "duration": 1.86}, {"text": "You had a good hypothesis.", "start": 4066.22, "duration": 1.39}, {"text": "And now we're\nfinding data, yeah.", "start": 4067.61, "duration": 2.15}, {"text": "And I should have\ncalled on you to do", "start": 4069.76, "duration": 1.77}, {"text": "to say these Arabic words.", "start": 4071.53, "duration": 1.86}, {"text": "Yeah, Joseph?", "start": 4073.39, "duration": 1.233}, {"text": "STUDENT: So you mentioned\nthat the English language", "start": 4074.623, "duration": 3.139}, {"text": "has borrowed quite a\nfew words from Arabic.", "start": 4077.762, "duration": 2.251}, {"text": "NORVIN RICHARDS: Yeah.", "start": 4080.013, "duration": 0.917}, {"text": "STUDENT: And we accidentally\nbrought the definite article", "start": 4080.93, "duration": 4.05}, {"text": "with it.", "start": 4084.98, "duration": 0.89}, {"text": "So the word \"algebra.\"", "start": 4085.87, "duration": 1.1}, {"text": "NORVIN RICHARDS: Yep.", "start": 4086.97, "duration": 1.896}, {"text": "STUDENT: \"Algebra.\"", "start": 4088.866, "duration": 1.416}, {"text": "At least, the\nEnglish pronunciation", "start": 4090.282, "duration": 2.36}, {"text": "starts with coronal.", "start": 4092.642, "duration": 1.575}, {"text": "NORVIN RICHARDS: Oh, yeah.", "start": 4094.217, "duration": 1.083}, {"text": "But in Arabic, I\nthink it doesn't.", "start": 4095.3, "duration": 1.62}, {"text": "So maybe you know.", "start": 4096.92, "duration": 3.359}, {"text": "Do you know know what\n\"algebra\" is in Arabic?", "start": 4100.279, "duration": 2.461}, {"text": "STUDENT: I believe\nit's [ARABIC]..", "start": 4102.74, "duration": 1.688}, {"text": "NORVIN RICHARDS: [ARABIC]", "start": 4104.428, "duration": 1.042}, {"text": "STUDENT: [ARABIC]", "start": 4105.47, "duration": 0.708}, {"text": "NORVIN RICHARDS: Oh, OK.", "start": 4106.178, "duration": 1.062}, {"text": "So I got it backwards.", "start": 4107.24, "duration": 0.989}, {"text": "Yeah, so we kept the \"l,\"\nWe didn't do the change.", "start": 4108.229, "duration": 3.871}, {"text": "So it starts with a \"j,\"\nstarts with a coronal.", "start": 4112.1, "duration": 2.882}, {"text": "But it didn't do the change.", "start": 4114.982, "duration": 1.167}, {"text": "I wonder whether we\nborrowed it before Arabic", "start": 4116.149, "duration": 2.67}, {"text": "did this sound change.", "start": 4118.819, "duration": 1.901}, {"text": "I have no idea.", "start": 4120.72, "duration": 1.349}, {"text": "I don't know enough about\nthe history of Arabic.", "start": 4122.069, "duration": 2.471}, {"text": "Cool.", "start": 4124.54, "duration": 1.73}, {"text": "Yep.", "start": 4126.27, "duration": 0.5}, {"text": "All right.", "start": 4131.609, "duration": 3.141}, {"text": "So this is one rule.", "start": 4134.75, "duration": 2.43}, {"text": "It's a very common rule,\nwhere one sound becomes more", "start": 4137.18, "duration": 3.0}, {"text": "like another sound.", "start": 4140.18, "duration": 1.11}, {"text": "It's called assimilation.", "start": 4141.29, "duration": 2.5}, {"text": "And in this\nparticular case, it's", "start": 4143.79, "duration": 2.75}, {"text": "what's sometimes called\ntotal assimilation, where", "start": 4146.54, "duration": 2.64}, {"text": "one sound just becomes a\ncomplete copy of another sound.", "start": 4149.18, "duration": 3.36}, {"text": "We'll see other cases\nwhere one sound just", "start": 4152.54, "duration": 3.18}, {"text": "changes in ways that\nresemble a nearby sound.", "start": 4155.72, "duration": 4.38}, {"text": "Why do you do assimilation?", "start": 4160.1, "duration": 1.379}, {"text": "Languages do assimilation\nall the time.", "start": 4161.479, "duration": 1.991}, {"text": "And it's not hard to have\npretheoretical notions", "start": 4163.47, "duration": 3.62}, {"text": "about why, right?", "start": 4167.09, "duration": 1.26}, {"text": "You're saving wear and\ntear on your articulators.", "start": 4168.35, "duration": 3.81}, {"text": "So\" making it so that your\narticulators-- your tongue,", "start": 4172.16, "duration": 2.76}, {"text": "your lips, your velum don't have\nto do as much moving around.", "start": 4174.92, "duration": 5.85}, {"text": "Things don't move as far\nor don't move at all.", "start": 4180.77, "duration": 4.572}, {"text": "It probably also makes\nperception easier in the sense", "start": 4185.342, "duration": 2.208}, {"text": "that if you're speaking\nArabic and instead of an \"l\"--", "start": 4187.55, "duration": 6.3}, {"text": "so let's take the sun.", "start": 4193.85, "duration": 2.64}, {"text": "If you know that the word\nfor \"sun\" is [ARABIC],,", "start": 4199.19, "duration": 4.19}, {"text": "and you've got this\nthing before it,", "start": 4203.38, "duration": 4.35}, {"text": "basically, it's\nas though you only", "start": 4207.73, "duration": 2.04}, {"text": "need to give your hearer\nenough information", "start": 4209.77, "duration": 2.31}, {"text": "to help them to\nknow that they're", "start": 4212.08, "duration": 1.74}, {"text": "hearing a definite article\nbefore the word for sun.", "start": 4213.82, "duration": 3.36}, {"text": "And Arabic has\ndecided it's enough", "start": 4217.18, "duration": 3.09}, {"text": "if you hear the glottal stop and\nthe vowel, and then a coronal.", "start": 4220.27, "duration": 5.16}, {"text": "Underlyingly, that\ncoronal, maybe, is an \"l.\"", "start": 4225.43, "duration": 2.55}, {"text": "But as long as we\nkeep it coronal,", "start": 4227.98, "duration": 1.53}, {"text": "we've given the hearer enough\nthat they get to hear it.", "start": 4229.51, "duration": 3.04}, {"text": "And in fact, we give\nthe hearer, in a sense,", "start": 4232.55, "duration": 3.17}, {"text": "two shots at hearing the\nbeginning of the word for sun.", "start": 4235.72, "duration": 3.42}, {"text": "So we'll lengthen that sound.", "start": 4239.14, "duration": 3.78}, {"text": "We'll pronounce it twice.", "start": 4242.92, "duration": 2.43}, {"text": "So we're redistributing\nthe signal, in a way,", "start": 4245.35, "duration": 4.26}, {"text": "to the hearer to make\ntheir life arguably easier,", "start": 4249.61, "duration": 3.818}, {"text": "giving up some of what makes\nthe definite article distinctive", "start": 4253.428, "duration": 2.542}, {"text": "in order to emphasize\nsome of the beginning", "start": 4255.97, "duration": 2.58}, {"text": "of the word for sun.", "start": 4258.55, "duration": 0.84}, {"text": "Yeah.", "start": 4259.39, "duration": 1.95}, {"text": "Questions about any of this?", "start": 4261.34, "duration": 1.48}, {"text": "Yes.", "start": 4262.82, "duration": 0.5}, {"text": "STUDENT: So would\nyou say generally", "start": 4263.32, "duration": 1.458}, {"text": "that the focus is just to\nfacilitate the pronunciation", "start": 4264.778, "duration": 3.202}, {"text": "of the word easier.", "start": 4267.98, "duration": 1.72}, {"text": "NORVIN RICHARDS: So\nI was trying to float", "start": 4269.7, "duration": 2.64}, {"text": "the idea that it's partly to\nmake the pronunciation easier.", "start": 4272.34, "duration": 3.18}, {"text": "It's so that your\narticulators are not having", "start": 4275.52, "duration": 2.34}, {"text": "to move as fast or as far.", "start": 4277.86, "duration": 2.25}, {"text": "But it might also make\nperception, in some ways,", "start": 4280.11, "duration": 4.02}, {"text": "easier in a case like this.", "start": 4284.13, "duration": 2.11}, {"text": "So the idea is we'll give up\nsome of the special properties", "start": 4286.24, "duration": 4.4}, {"text": "of the definite article in\nfavor of emphasizing or holding", "start": 4290.64, "duration": 3.81}, {"text": "for longer the special\nproperties of the word for sun,", "start": 4294.45, "duration": 4.14}, {"text": "or whatever, the\nconsonant that's", "start": 4298.59, "duration": 1.47}, {"text": "at the beginning of\nthe following noun.", "start": 4300.06, "duration": 4.2}, {"text": "So we'll emphasize\nsome parts of the--", "start": 4304.26, "duration": 3.18}, {"text": "in some ways, the least\npredictable part of this.", "start": 4307.44, "duration": 2.07}, {"text": "You presumably hear definite\narticles all the time.", "start": 4309.51, "duration": 2.125}, {"text": "It's not so important that you\nget lots of clues to the fact", "start": 4311.635, "duration": 3.365}, {"text": "that this is a definite article.", "start": 4315.0, "duration": 1.44}, {"text": "The nouns are going to vary.", "start": 4316.44, "duration": 1.56}, {"text": "You'll hear more different\nkinds of nouns, yeah.", "start": 4318.0, "duration": 4.3}, {"text": "Yep.", "start": 4322.3, "duration": 0.72}, {"text": "OK, cool.", "start": 4323.02, "duration": 0.977}, {"text": "This is probably a\ngood place to stop.", "start": 4323.997, "duration": 1.583}, {"text": "So let's stop here.", "start": 4325.58, "duration": 0.792}, {"text": "And have a good weekend.", "start": 4326.372, "duration": 1.878}, {"text": "And I'll see you guys next week.", "start": 4328.25, "duration": 3.43}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 1.095, "duration": 2.325}, {"text": "Commons license.", "start": 3.42, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.81, "duration": 2.21}, {"text": "continue to offer high quality\neducational resources for free.", "start": 7.02, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 11.11, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.68, "duration": 3.96}, {"text": "at ocw.mit.edu.", "start": 17.64, "duration": 0.886}, {"text": "GARY GENSLER:\nToday's a little bit", "start": 24.07, "duration": 1.72}, {"text": "of a discussion about clearing\nand settlement systems.", "start": 25.79, "duration": 5.22}, {"text": "Maybe you feel you've\nheard everything", "start": 31.01, "duration": 1.71}, {"text": "you needed from Jeff\nSprecher when he was asked", "start": 32.72, "duration": 2.55}, {"text": "a question when he was with us.", "start": 35.27, "duration": 2.07}, {"text": "Jeff runs some of\nthe largest clearing", "start": 37.34, "duration": 1.84}, {"text": "houses in the world at\nIntercontinental Exchange", "start": 39.18, "duration": 3.68}, {"text": "not only because he started\nin the energy business,", "start": 42.86, "duration": 4.8}, {"text": "but he has big credit default\nswap clearing houses and energy", "start": 47.66, "duration": 3.99}, {"text": "clearing houses and the like.", "start": 51.65, "duration": 1.98}, {"text": "And he said, well, I don't know\nabout blockchain technology", "start": 53.63, "duration": 4.11}, {"text": "for clearing and settling.", "start": 57.74, "duration": 1.17}, {"text": "But I'm going to try this\nBitcoin project that you all", "start": 58.91, "duration": 3.27}, {"text": "know about and he talked about.", "start": 62.18, "duration": 1.62}, {"text": "But today we're going\nto try to dig into,", "start": 63.8, "duration": 2.477}, {"text": "well, maybe there's something\nthere, because there", "start": 66.277, "duration": 2.083}, {"text": "are projects going on.", "start": 68.36, "duration": 1.65}, {"text": "And why are there projects?", "start": 70.01, "duration": 1.37}, {"text": "They're mostly permissioned\nand not permissionless systems.", "start": 71.38, "duration": 5.2}, {"text": "But I think there's\nsomething there.", "start": 76.58, "duration": 3.58}, {"text": "This will be one of\nthe more optimistic--", "start": 80.16, "duration": 2.4}, {"text": "if you're judging how often\nI get to the maximal side,", "start": 82.56, "duration": 4.56}, {"text": "I think there is probably\nsomething there, at least", "start": 87.12, "duration": 2.42}, {"text": "for permissioned blockchain\nprojects in the clearing", "start": 89.54, "duration": 2.88}, {"text": "and settling.", "start": 92.42, "duration": 2.52}, {"text": "I'm going to-- we'll, of\ncourse, go through the readings.", "start": 94.94, "duration": 3.33}, {"text": "And these are the sort of\ntopics we'll go through.", "start": 98.27, "duration": 2.79}, {"text": "Clearing and settling services--", "start": 101.06, "duration": 1.95}, {"text": "I'm going to try to set this\nstage as to what this is.", "start": 103.01, "duration": 4.32}, {"text": "Frankly, when I was on\nWall Street for 18 years,", "start": 107.33, "duration": 2.88}, {"text": "I couldn't really define\nwhat clearing and settling.", "start": 110.21, "duration": 3.0}, {"text": "Sorry, Ross.", "start": 113.21, "duration": 0.75}, {"text": "You thought I could define\nit when I was on Wall Street?", "start": 113.96, "duration": 2.99}, {"text": "What's that?", "start": 116.95, "duration": 0.84}, {"text": "AUDIENCE: I just strictly know\nsomeone else can't either.", "start": 117.79, "duration": 1.78}, {"text": "GARY GENSLER: Yeah.", "start": 119.57, "duration": 0.792}, {"text": "Yeah.", "start": 120.362, "duration": 0.51}, {"text": "Well, when you're in the\nmerger and acquisition area,", "start": 120.872, "duration": 2.208}, {"text": "you usually don't\nthink about what", "start": 123.08, "duration": 1.83}, {"text": "it means to clear\nsomething and to settle it.", "start": 124.91, "duration": 2.747}, {"text": "And frankly, even\nusually when you're", "start": 127.657, "duration": 1.542}, {"text": "on the trading floor, that's\nsomething somebody else", "start": 129.199, "duration": 2.911}, {"text": "takes care of.", "start": 132.11, "duration": 2.73}, {"text": "Just the nature of--", "start": 134.84, "duration": 1.74}, {"text": "how many people have worked\non trading floors here?", "start": 136.58, "duration": 3.89}, {"text": "All right.", "start": 140.47, "duration": 0.5}, {"text": "So I'm going to have seven\nor eight of you start.", "start": 140.97, "duration": 2.88}, {"text": "And you're on notice now.", "start": 143.85, "duration": 2.46}, {"text": "In about eight to 10 minutes,\nyou're going to help.", "start": 146.31, "duration": 4.18}, {"text": "You might prove what I just said\nto Ross, that you can't define", "start": 150.49, "duration": 3.657}, {"text": "what clearing and settling\nis because somebody else took", "start": 154.147, "duration": 2.333}, {"text": "care of it.", "start": 156.48, "duration": 0.62}, {"text": "But we'll see.", "start": 157.1, "duration": 1.3}, {"text": "We'll see.", "start": 158.4, "duration": 1.74}, {"text": "And then we'll talk about\nblockchain technology", "start": 160.14, "duration": 2.31}, {"text": "applicability, some of the\nprojects that are going on,", "start": 162.45, "duration": 3.61}, {"text": "and then move over to this.", "start": 166.06, "duration": 2.27}, {"text": "There was a reading from\nthe International Swaps", "start": 168.33, "duration": 2.805}, {"text": "and Derivatives\nAssociation, ISDA,", "start": 171.135, "duration": 3.465}, {"text": "what they're doing around\nsmart contracts in this space.", "start": 174.6, "duration": 5.49}, {"text": "But what I want to do\nfirst is a little bit", "start": 180.09, "duration": 2.523}, {"text": "of talking about final\nprojects, because we're", "start": 182.613, "duration": 1.917}, {"text": "at that time of the year.", "start": 184.53, "duration": 1.59}, {"text": "And this is to help.", "start": 186.12, "duration": 3.3}, {"text": "Then I'm going to go through\neight or nine questions.", "start": 189.42, "duration": 3.57}, {"text": "If you haven't already\nthought through your projects,", "start": 192.99, "duration": 4.29}, {"text": "these are eight\nor nine questions", "start": 197.28, "duration": 1.41}, {"text": "that I would think you'd\nwant to think about,", "start": 198.69, "duration": 4.05}, {"text": "which is another way of\nsaying it will probably", "start": 202.74, "duration": 2.07}, {"text": "enhance your performance.", "start": 204.81, "duration": 3.45}, {"text": "What else can I say?", "start": 208.26, "duration": 3.27}, {"text": "And number one-- and it's\na little, small print.", "start": 211.53, "duration": 2.73}, {"text": "I'm sorry.", "start": 214.26, "duration": 0.63}, {"text": "Or no, it's not too bad--", "start": 214.89, "duration": 2.22}, {"text": "is what's the value creation\nproposition, or pain point,", "start": 217.11, "duration": 4.23}, {"text": "if you wish.", "start": 221.34, "duration": 0.76}, {"text": "So are you creating value?", "start": 222.1, "duration": 1.97}, {"text": "Are you solving a pain point?", "start": 224.07, "duration": 1.358}, {"text": "Or as Jeff Sprecher\nwould say, what are you", "start": 225.428, "duration": 1.792}, {"text": "doing that's going to make\nsomething cheaper, faster,", "start": 227.22, "duration": 4.66}, {"text": "better?", "start": 231.88, "duration": 1.73}, {"text": "What's the value proposition?", "start": 233.61, "duration": 1.86}, {"text": "Whatever space.", "start": 235.47, "duration": 1.41}, {"text": "There's two or three groups\nthat are doing trade finance.", "start": 236.88, "duration": 3.44}, {"text": "There's one or two\ndoing payments.", "start": 240.32, "duration": 1.9}, {"text": "There's some group\ndoing commercial--", "start": 242.22, "duration": 4.77}, {"text": "I mean, consumer credit\nrating or so forth.", "start": 246.99, "duration": 4.48}, {"text": "There's a wide variety.", "start": 251.47, "duration": 1.472}, {"text": "There's one or two\ngroups that have", "start": 252.942, "duration": 1.458}, {"text": "come to see me that are doing\nthings outside of finance.", "start": 254.4, "duration": 3.809}, {"text": "But regardless, what's\nthe value proposition?", "start": 258.209, "duration": 4.451}, {"text": "What pain points\nare you addressing?", "start": 262.66, "duration": 2.51}, {"text": "Or as Jeff would say,\nwhat are you going", "start": 265.17, "duration": 1.73}, {"text": "to do better, faster, cheaper?", "start": 266.9, "duration": 3.1}, {"text": "If you can't answer\nthat threshold question,", "start": 270.0, "duration": 3.96}, {"text": "shake it loose.", "start": 273.96, "duration": 1.86}, {"text": "Kick it around.", "start": 275.82, "duration": 1.53}, {"text": "Or move on to a different\nuse case, frankly.", "start": 277.35, "duration": 4.92}, {"text": "Secondly, [INAUDIBLE]\nyou get into,", "start": 282.27, "duration": 1.68}, {"text": "like, what is this\nblockchain technology?", "start": 283.95, "duration": 2.22}, {"text": "What transactions or data\nis going to be recorded?", "start": 286.17, "duration": 4.44}, {"text": "Because this is\nfundamentally, ultimately,", "start": 290.61, "duration": 2.04}, {"text": "a database technology, even\nthe permissionless systems.", "start": 292.65, "duration": 4.48}, {"text": "And you'll see a later\nquestion is why this versus", "start": 297.13, "duration": 3.08}, {"text": "traditional database system?", "start": 300.21, "duration": 1.65}, {"text": "But what transactions,\nwhat data--", "start": 301.86, "duration": 1.95}, {"text": "whether it's health\ncare records,", "start": 303.81, "duration": 2.07}, {"text": "whether it's consumer\ncredit data, supply chain,", "start": 305.88, "duration": 4.38}, {"text": "moving a piece of property\nalong a supply chain,", "start": 310.26, "duration": 3.09}, {"text": "but what is the actual data\nand transactions that you're", "start": 313.35, "duration": 2.88}, {"text": "recording?", "start": 316.23, "duration": 1.32}, {"text": "Questions?", "start": 317.55, "duration": 2.27}, {"text": "What multiple stakeholders\nneed to write and read access", "start": 319.82, "duration": 3.69}, {"text": "to the ledgers?", "start": 323.51, "duration": 1.08}, {"text": "And I underline\nthe word multiple.", "start": 324.59, "duration": 1.8}, {"text": "Because really, when you think\nabout the value proposition", "start": 326.39, "duration": 3.69}, {"text": "of blockchain technology,\nit's about immutable records,", "start": 330.08, "duration": 5.87}, {"text": "or so-called immutable records.", "start": 335.95, "duration": 2.23}, {"text": "That's verifiable,\nimmutable records", "start": 338.18, "duration": 3.45}, {"text": "amongst multiple parties.", "start": 341.63, "duration": 3.46}, {"text": "And it cost extra money.", "start": 345.09, "duration": 1.47}, {"text": "Everything we've been studying\nabout in this semester", "start": 346.56, "duration": 3.15}, {"text": "is about there's\nmore complexity.", "start": 349.71, "duration": 1.62}, {"text": "There's more cost, in some\nway, of this decentralized,", "start": 351.33, "duration": 3.96}, {"text": "even permissioned systems,\ndecentralized system.", "start": 355.29, "duration": 5.01}, {"text": "But you get something for it.", "start": 360.3, "duration": 1.8}, {"text": "You get some verification\nof transactions, of data,", "start": 362.1, "duration": 4.0}, {"text": "of mutability.", "start": 366.1, "duration": 1.97}, {"text": "But you also have\nto have some logic", "start": 368.07, "duration": 2.73}, {"text": "that there's\nmultiple parties that", "start": 370.8, "duration": 1.62}, {"text": "need to both write and read.", "start": 372.42, "duration": 3.18}, {"text": "A distributed database\nthat just does read only--", "start": 375.6, "duration": 3.79}, {"text": "I can read my Bank of\nAmerica bank account.", "start": 379.39, "duration": 3.9}, {"text": "I can see what's in\nthat sort of ledger.", "start": 383.29, "duration": 2.94}, {"text": "It doesn't have to\nbe on a blockchain.", "start": 386.23, "duration": 1.95}, {"text": "So multiple parties writing,\nwhy is that important?", "start": 388.18, "duration": 3.54}, {"text": "Forming consensus,\nin this circumstance.", "start": 391.72, "duration": 4.98}, {"text": "Which specific cost of\nverification or networking", "start": 396.7, "duration": 2.91}, {"text": "are you lowering?", "start": 399.61, "duration": 0.9}, {"text": "We talked about a lot of\nthe verification costs,", "start": 400.51, "duration": 3.27}, {"text": "whether it's privacy,\ncensorship resistance,", "start": 403.78, "duration": 3.57}, {"text": "whether it's some direct cost.", "start": 407.35, "duration": 1.908}, {"text": "Maybe you're going\nright at something", "start": 409.258, "duration": 1.542}, {"text": "that's got a bunch of\neconomic rents in it.", "start": 410.8, "duration": 2.79}, {"text": "So there was a series\nof verification costs", "start": 413.59, "duration": 2.16}, {"text": "we talked about.", "start": 415.75, "duration": 1.71}, {"text": "What networking costs\nare you trying to reduce?", "start": 417.46, "duration": 3.03}, {"text": "There's probably been\nsomething in the order", "start": 424.48, "duration": 1.95}, {"text": "of 4,000 or 5,000 white\npapers, many that you can find.", "start": 426.43, "duration": 5.04}, {"text": "You can't find all of them.", "start": 431.47, "duration": 1.592}, {"text": "But if you're going\nat something that you", "start": 433.062, "duration": 1.708}, {"text": "think a white paper\nhas been written about", "start": 434.77, "duration": 1.89}, {"text": "or a blockchain company\nhas been started on,", "start": 436.66, "duration": 2.58}, {"text": "figure out what the\ncompetition is doing.", "start": 439.24, "duration": 2.84}, {"text": "And for the two groups,\nand it may be more,", "start": 442.08, "duration": 1.84}, {"text": "that are doing something around\ntrade, finance, and supply", "start": 443.92, "duration": 2.7}, {"text": "chain, you know there's a\nbunch of stuff you can read.", "start": 446.62, "duration": 4.11}, {"text": "We'll be studying\nit next Tuesday.", "start": 450.73, "duration": 1.53}, {"text": "Alin?", "start": 452.26, "duration": 0.713}, {"text": "AUDIENCE: Can you give us an\nexample of a networking cost?", "start": 452.973, "duration": 2.417}, {"text": "I'm not sure what that is.", "start": 455.39, "duration": 1.28}, {"text": "GARY GENSLER: So\nnetworking cost is often", "start": 456.67, "duration": 4.02}, {"text": "why people are using\na native token.", "start": 460.69, "duration": 3.48}, {"text": "But networking costs are\nhow to jumpstart a network.", "start": 464.17, "duration": 6.56}, {"text": "Uber jumpstarted a\nnetwork, in a sense,", "start": 470.73, "duration": 3.54}, {"text": "without blockchain technology.", "start": 474.27, "duration": 1.58}, {"text": "But an example of\nnetworking costs", "start": 475.85, "duration": 1.9}, {"text": "are if you walked\nout of the airport", "start": 477.75, "duration": 2.45}, {"text": "and you didn't think any drivers\nare using this application,", "start": 480.2, "duration": 4.59}, {"text": "then you wouldn't be terribly\ninterested in using it.", "start": 484.79, "duration": 3.69}, {"text": "So--", "start": 488.48, "duration": 1.24}, {"text": "AUDIENCE: But who\nincurs the cost?", "start": 489.72, "duration": 3.14}, {"text": "GARY GENSLER: Often the cost\nof building a network can", "start": 492.86, "duration": 3.9}, {"text": "be a tremendous startup cost.", "start": 496.76, "duration": 3.1}, {"text": "So how to start a\nnetwork often is", "start": 499.86, "duration": 2.192}, {"text": "you go to a bunch of\nventure capitalists.", "start": 502.052, "duration": 1.708}, {"text": "You raise money.", "start": 503.76, "duration": 1.25}, {"text": "You advertise.", "start": 505.01, "duration": 1.59}, {"text": "And you try to get participants.", "start": 506.6, "duration": 2.83}, {"text": "And one of the challenges\nof health care records--", "start": 509.43, "duration": 3.47}, {"text": "we don't have our health\ncare experts in here today.", "start": 512.9, "duration": 3.09}, {"text": "I was looking around.", "start": 519.825, "duration": 0.875}, {"text": "We have two students from\nHarvard's public policy", "start": 520.7, "duration": 3.54}, {"text": "school doing graduate work\nand sometimes join us.", "start": 524.24, "duration": 3.93}, {"text": "But health care\nrecords, for instance,", "start": 528.17, "duration": 2.29}, {"text": "there's some really interesting\nblockchain technology", "start": 530.46, "duration": 4.19}, {"text": "solutions.", "start": 534.65, "duration": 1.42}, {"text": "But the networking\nchallenge is how do you", "start": 536.07, "duration": 1.85}, {"text": "get a bunch of medical\nproviders, hospitals, doctors,", "start": 537.92, "duration": 4.58}, {"text": "and users to actually\njoin the network.", "start": 542.5, "duration": 3.85}, {"text": "So that would be an\nexample of network cost", "start": 546.35, "duration": 2.88}, {"text": "is basically adoption often.", "start": 549.23, "duration": 2.165}, {"text": "Does that help?", "start": 551.395, "duration": 0.625}, {"text": "AUDIENCE: Yeah.", "start": 552.02, "duration": 0.625}, {"text": "GARY GENSLER: What are\nthe competitors doing?", "start": 555.39, "duration": 2.34}, {"text": "I'm not looking for plagiarism.", "start": 557.73, "duration": 1.65}, {"text": "But if you're in a space,\npayments or supply chain", "start": 559.38, "duration": 4.2}, {"text": "or consumer credit\nor some others,", "start": 563.58, "duration": 2.55}, {"text": "where there's three or six\nor 10 white papers out there", "start": 566.13, "duration": 2.88}, {"text": "and maybe somebody has\neven raised 20 million", "start": 569.01, "duration": 2.67}, {"text": "or a couple million in an ICO,\nthen it would be interesting.", "start": 571.68, "duration": 5.37}, {"text": "You should feel free\nto look at those.", "start": 577.05, "duration": 1.68}, {"text": "And maybe you'll\nbe informed by it.", "start": 578.73, "duration": 1.74}, {"text": "And you'll say, yeah,\nI'm doing it better.", "start": 580.47, "duration": 1.75}, {"text": "Or they've got it poorly here.", "start": 582.22, "duration": 2.33}, {"text": "Or their project's in Estonia.", "start": 584.55, "duration": 2.52}, {"text": "And I'm going to do a\ndigital ID project in the US.", "start": 587.07, "duration": 3.66}, {"text": "And our regulatory system\nis different than Estonia.", "start": 590.73, "duration": 3.51}, {"text": "But I wouldn't be bashful about\nlooking at the competition.", "start": 594.24, "duration": 3.82}, {"text": "In fact, I would say that's--", "start": 598.06, "duration": 1.34}, {"text": "we're a business school.", "start": 599.4, "duration": 1.0}, {"text": "You always look at\nthe competition.", "start": 600.4, "duration": 1.73}, {"text": "And you see if you can do\neither what they're doing better", "start": 602.13, "duration": 2.91}, {"text": "or what they're doing\nin a different geography", "start": 605.04, "duration": 2.1}, {"text": "or in a little bit\ndifferent market.", "start": 607.14, "duration": 2.36}, {"text": "Back to how Alin likes\nto define things,", "start": 609.5, "duration": 2.25}, {"text": "I've not used the term\nblockchain technology yet", "start": 611.75, "duration": 2.91}, {"text": "on this slide, have I?", "start": 614.66, "duration": 2.46}, {"text": "But why are append-only logs\nat multiple party consensus", "start": 617.12, "duration": 5.82}, {"text": "the best solution?", "start": 622.94, "duration": 2.84}, {"text": "Which kind of goes\nback to why not just", "start": 625.78, "duration": 1.95}, {"text": "a traditional database.", "start": 627.73, "duration": 1.23}, {"text": "But why append-only,\ntimestamped, verifiable logs?", "start": 628.96, "duration": 5.43}, {"text": "They're connected by\ncryptographic hash functions.", "start": 634.39, "duration": 3.03}, {"text": "But why have these logs?", "start": 637.42, "duration": 2.37}, {"text": "And why have multiple\nparties in essence", "start": 639.79, "duration": 1.98}, {"text": "form a consensus about\nthe state of the ledger?", "start": 641.77, "duration": 4.895}, {"text": "Alin?", "start": 646.665, "duration": 0.642}, {"text": "AUDIENCE: Yes.", "start": 647.307, "duration": 0.583}, {"text": "I have a question about the\ntimestamped, apend-only logs.", "start": 647.89, "duration": 3.7}, {"text": "Is that only relevant\nin blockchain,", "start": 651.59, "duration": 2.83}, {"text": "that traditional\ndatabases do not", "start": 654.42, "duration": 1.79}, {"text": "have these kinds of features,\ntimestamp and append-only logs?", "start": 656.21, "duration": 5.53}, {"text": "GARY GENSLER: They\ncan have time--", "start": 661.74, "duration": 3.0}, {"text": "timestamps in essence.", "start": 664.74, "duration": 3.95}, {"text": "In essence, it's innovation\nof the early '90s.", "start": 668.69, "duration": 2.44}, {"text": "And then Satoshi\nNakamoto grabbed it.", "start": 671.13, "duration": 1.94}, {"text": "It was the concept that\nyou take a block of data", "start": 673.07, "duration": 3.45}, {"text": "and you connect it to the next\nblock with a cryptographic hash", "start": 676.52, "duration": 3.6}, {"text": "function.", "start": 680.12, "duration": 0.742}, {"text": "And once you've done\nthat, then it's committed.", "start": 680.862, "duration": 1.958}, {"text": "You can't amend\nanything that's before", "start": 682.82, "duration": 3.23}, {"text": "because it's a unique hash.", "start": 686.05, "duration": 3.41}, {"text": "And traditional databases did\nnot have similar commitment", "start": 689.46, "duration": 4.42}, {"text": "schemes.", "start": 693.88, "duration": 0.5}, {"text": "They do have other\ncommitments schemes, but not", "start": 694.38, "duration": 1.98}, {"text": "this commitment scheme of\ntaking a block of data,", "start": 696.36, "duration": 3.36}, {"text": "having the hash function,\nwhich then means never shall", "start": 699.72, "duration": 4.98}, {"text": "you amend what came before.", "start": 704.7, "duration": 3.82}, {"text": "That's how I understand it.", "start": 708.52, "duration": 1.44}, {"text": "Did you have a different view\non traditional databases?", "start": 709.96, "duration": 3.335}, {"text": "AUDIENCE: Well,\nI guess this gets", "start": 713.295, "duration": 1.375}, {"text": "to the root of the question.", "start": 714.67, "duration": 1.95}, {"text": "Is there something new\nabout blockchain technology?", "start": 716.62, "duration": 2.89}, {"text": "In my opinion, there\nisn't, actually.", "start": 719.51, "duration": 2.54}, {"text": "20 years ago, we knew how to\nmake a traditional database", "start": 722.05, "duration": 4.09}, {"text": "and make it full of power and\nmake it a census protocol,", "start": 726.14, "duration": 3.24}, {"text": "or what people nowadays like to\ncall a permissioned blockchain.", "start": 729.38, "duration": 3.117}, {"text": "So we knew how to do that.", "start": 732.497, "duration": 1.083}, {"text": "And that would give\nyou an append-only log.", "start": 733.58, "duration": 1.792}, {"text": "It's nothing exceptional.", "start": 735.372, "duration": 3.448}, {"text": "GARY GENSLER: Yeah.", "start": 741.808, "duration": 0.792}, {"text": "So there are debates as to\nwhere is the border and boundary", "start": 742.6, "duration": 4.2}, {"text": "between a permissioned\nblockchain", "start": 746.8, "duration": 1.62}, {"text": "and a traditional database.", "start": 748.42, "duration": 2.77}, {"text": "But I've chosen to, at\nleast for this class,", "start": 751.19, "duration": 4.02}, {"text": "a hyperledger fabric, we'll\ncall that a blockchain project.", "start": 755.21, "duration": 4.68}, {"text": "But recognize there are some\nwho would say, well, that's--", "start": 759.89, "duration": 4.08}, {"text": "unless you have a native token,\nit's not really blockchain.", "start": 763.97, "duration": 4.64}, {"text": "Eric.", "start": 768.61, "duration": 0.665}, {"text": "AUDIENCE: --one could call point\nrecent days that the trust is", "start": 769.275, "duration": 7.055}, {"text": "the key attribute that's not\nthe factor in this equation,", "start": 776.33, "duration": 4.43}, {"text": "because you can get a multiple--", "start": 780.76, "duration": 3.53}, {"text": "I mean, multiple party consensus\ndoesn't have value on its own.", "start": 784.29, "duration": 4.66}, {"text": "It's actually multiple\nparty consensus is--", "start": 788.95, "duration": 3.81}, {"text": "it's actually something you had\nto come up as a necessity that", "start": 792.76, "duration": 4.38}, {"text": "stems from the fact\nthat you're dealing", "start": 797.14, "duration": 2.01}, {"text": "with a decentralized arrangement\nin which you're not trusting", "start": 799.15, "duration": 3.81}, {"text": "any of the parties\nthat intervening", "start": 802.96, "duration": 3.98}, {"text": "in the exchange of information.", "start": 806.94, "duration": 1.85}, {"text": "Right?", "start": 808.79, "duration": 0.83}, {"text": "GARY GENSLER: Well, I\nagree with the first half,", "start": 809.62, "duration": 2.4}, {"text": "that you wouldn't even\nwant to use Hyperledger", "start": 812.02, "duration": 4.11}, {"text": "Fabric unless you really\nneed multiple parties writing", "start": 816.13, "duration": 3.75}, {"text": "to the ledger.", "start": 819.88, "duration": 0.99}, {"text": "And I think that does\nseparate it a little bit.", "start": 820.87, "duration": 3.12}, {"text": "You could take an\nOracle database", "start": 823.99, "duration": 1.87}, {"text": "and allow it to be\nmultiple parties, too.", "start": 825.86, "duration": 2.48}, {"text": "But I think that separates it.", "start": 828.34, "duration": 2.79}, {"text": "You might be more the\npurist than I am, Eric.", "start": 835.09, "duration": 2.13}, {"text": "I don't think it has to\nbe completely open, where", "start": 837.22, "duration": 5.0}, {"text": "you don't know all\nthe participants.", "start": 842.22, "duration": 3.49}, {"text": "But even in a\nfinancial-- we'll talk", "start": 845.71, "duration": 1.89}, {"text": "about the Australian\nStock Exchange", "start": 847.6, "duration": 2.49}, {"text": "in a half an hour or so.", "start": 850.09, "duration": 2.54}, {"text": "And when we talk about that,\nthat's a limited closed loop.", "start": 852.63, "duration": 4.6}, {"text": "But they believe that\nthey are actually", "start": 857.23, "duration": 1.83}, {"text": "taking a lot of cost out\nof the verification side.", "start": 859.06, "duration": 3.023}, {"text": "They think they're\ngetting a lot--", "start": 862.083, "duration": 1.417}, {"text": "they're lowering\nverification costs.", "start": 863.5, "duration": 2.25}, {"text": "And they would contend they're\nlowering networking costs,", "start": 865.75, "duration": 2.4}, {"text": "because they don't have\nthe same reconciliations", "start": 868.15, "duration": 2.34}, {"text": "between multiple databases.", "start": 870.49, "duration": 3.06}, {"text": "Now, you might call\nthat verification cost.", "start": 873.55, "duration": 2.04}, {"text": "But I think they would\ncall it both verification", "start": 875.59, "duration": 2.04}, {"text": "and networking cost.", "start": 877.63, "duration": 2.51}, {"text": "There's multiple back offices\nno longer reconciling.", "start": 880.14, "duration": 3.25}, {"text": "If your final project has\na permissionless system", "start": 887.77, "duration": 3.24}, {"text": "with a native token, why\ndo you need a native token?", "start": 891.01, "duration": 3.15}, {"text": "Is it to jumpstart the ICO that\nyou want to raise money for?", "start": 894.16, "duration": 4.29}, {"text": "I'm not averse to that.", "start": 898.45, "duration": 2.07}, {"text": "But at least fess up\nand say that's how", "start": 900.52, "duration": 3.48}, {"text": "we're crowdsourcing this thing.", "start": 904.0, "duration": 1.95}, {"text": "If it's about that\nyou really believe", "start": 905.95, "duration": 2.3}, {"text": "there's some benefit\nto the token economics,", "start": 908.25, "duration": 3.88}, {"text": "that it's an incentive system\nto run your new competition", "start": 912.13, "duration": 4.53}, {"text": "to Uber or an incentive\nsystem for health care records", "start": 916.66, "duration": 3.57}, {"text": "or an incentive system\nfor supply chain,", "start": 920.23, "duration": 3.24}, {"text": "talk about what that\nincentive system is.", "start": 923.47, "duration": 3.34}, {"text": "And are you trying to motivate\njumpstarting the network", "start": 926.81, "duration": 3.47}, {"text": "or maintaining\nthe network later?", "start": 930.28, "duration": 2.93}, {"text": "And it could be both.", "start": 933.21, "duration": 2.098}, {"text": "It could be either.", "start": 935.308, "duration": 0.792}, {"text": "I'm just saying it would be\ngood to have a discussion.", "start": 936.1, "duration": 3.67}, {"text": "Is the native token\njust about crowdfunding?", "start": 939.77, "duration": 3.58}, {"text": "Is the native token\nalso about jumpstarting", "start": 943.35, "duration": 2.58}, {"text": "this network and\nthen an incentive", "start": 945.93, "duration": 1.65}, {"text": "to maintain the network\namongst multiple parties?", "start": 947.58, "duration": 3.0}, {"text": "What trade-offs of scalability,\nperformance, privacy, security,", "start": 954.57, "duration": 3.21}, {"text": "coordination?", "start": 957.78, "duration": 0.84}, {"text": "I'm not asking\nyou to solve that.", "start": 958.62, "duration": 1.89}, {"text": "And in fact, you can even jump\nahead three and five and seven", "start": 960.51, "duration": 3.09}, {"text": "years and assume that\nsome of these things", "start": 963.6, "duration": 2.64}, {"text": "will be taken care of.", "start": 966.24, "duration": 1.74}, {"text": "So recognize that in the\npermissioned blockchains,", "start": 967.98, "duration": 5.13}, {"text": "they seem to have a\nhigher performance, a lot", "start": 973.11, "duration": 2.31}, {"text": "higher performance, than the\nnative token permissionless", "start": 975.42, "duration": 3.28}, {"text": "systems.", "start": 978.7, "duration": 0.93}, {"text": "But if you're proposing a native\ntoken permissionless system,", "start": 979.63, "duration": 4.31}, {"text": "I'd just like a short\ndiscussion of how much", "start": 983.94, "duration": 3.57}, {"text": "these scalability issues matter\nto you, particularly when", "start": 987.51, "duration": 4.95}, {"text": "most of the native token\npermissionless systems", "start": 992.46, "duration": 2.82}, {"text": "can't handle much\nmore than 1,000", "start": 995.28, "duration": 2.64}, {"text": "or a handful 1,000 of\ntransactions a day.", "start": 997.92, "duration": 3.06}, {"text": "It is true that Bitcoin handles\nquite a bit more than that.", "start": 1000.98, "duration": 2.76}, {"text": "But five or 10\ntransactions a second,", "start": 1003.74, "duration": 5.46}, {"text": "is that going to work for\nwhatever your solution is?", "start": 1009.2, "duration": 2.52}, {"text": "In fact, I'd like to see some\ngroups use native tokens.", "start": 1014.81, "duration": 3.17}, {"text": "I want to have a variety of\nthings I read in December", "start": 1017.98, "duration": 3.03}, {"text": "rather than reading\nall permission systems.", "start": 1021.01, "duration": 1.85}, {"text": "And then again, can a\npermissioned blockchain", "start": 1025.96, "duration": 5.21}, {"text": "or traditional\ndatabase adequately", "start": 1031.17, "duration": 1.75}, {"text": "address whatever\nuse case if you do", "start": 1032.92, "duration": 1.919}, {"text": "have a permissionless system?", "start": 1034.839, "duration": 2.191}, {"text": "Thinking about that, how can\nbroad adoption be realized?", "start": 1037.03, "duration": 5.089}, {"text": "Are you going to use a native\ntoken to equip broad adoption?", "start": 1042.119, "duration": 2.5}, {"text": "How are you going to get a\nbunch of hospitals signed on?", "start": 1044.619, "duration": 2.333}, {"text": "How are you going to get a\nbunch of banks signed on?", "start": 1046.952, "duration": 2.248}, {"text": "You're going to do\nlike Jeff Sprecher did", "start": 1049.2, "duration": 1.708}, {"text": "and give 50% of his equity away.", "start": 1050.908, "duration": 2.52}, {"text": "There was that\nconversation he talked", "start": 1053.428, "duration": 1.542}, {"text": "about he had with Goldman\nSachs, that he realized", "start": 1054.97, "duration": 2.31}, {"text": "that was the only way to\nget his business started", "start": 1057.28, "duration": 2.79}, {"text": "in the late 1990s.", "start": 1060.07, "duration": 3.06}, {"text": "But just how are you going\nto get that adoption?", "start": 1063.13, "duration": 5.46}, {"text": "And to the extent, this\nmight be a paragraph,", "start": 1068.59, "duration": 2.67}, {"text": "but what type of customer\ninterface or how might it be", "start": 1071.26, "duration": 3.15}, {"text": "better than other customer UIs?", "start": 1074.41, "duration": 3.108}, {"text": "So these are just\nsome of the things,", "start": 1077.518, "duration": 1.542}, {"text": "if you were thinking\nabout a real business.", "start": 1079.06, "duration": 3.0}, {"text": "And I think that the\nmarket is moving away", "start": 1082.06, "duration": 3.45}, {"text": "from that big,\nfrothy bull market,", "start": 1085.51, "duration": 3.24}, {"text": "where there was as many as\n400 or 500 ICOs a month.", "start": 1088.75, "duration": 3.27}, {"text": "And it was raising anywhere\nfrom 2 to 5 billion a month.", "start": 1092.02, "duration": 3.31}, {"text": "October was about 200 ICOs.", "start": 1099.13, "duration": 2.07}, {"text": "And it was about 800 million.", "start": 1101.2, "duration": 1.59}, {"text": "And I think it's going\nto continue to decline,", "start": 1102.79, "duration": 2.43}, {"text": "partly because they\ndon't all work.", "start": 1105.22, "duration": 2.945}, {"text": "But partly because\npeople are now", "start": 1108.165, "duration": 1.375}, {"text": "getting more rigorous as\nto what's really going on.", "start": 1109.54, "duration": 5.02}, {"text": "If you are using a\npermissioned blockchain,", "start": 1114.56, "duration": 2.127}, {"text": "you don't have to\ntell me whether it's", "start": 1116.687, "duration": 1.583}, {"text": "Hyperledger or Corda.", "start": 1118.27, "duration": 1.118}, {"text": "But if somebody does\nand you have something", "start": 1119.388, "duration": 1.792}, {"text": "thoughtful to say there,\nI'm intrigued to find out", "start": 1121.18, "duration": 3.39}, {"text": "why this one versus that one.", "start": 1124.57, "duration": 2.73}, {"text": "It's really just to show\nyour critical analysis", "start": 1127.3, "duration": 2.88}, {"text": "of this subject.", "start": 1130.18, "duration": 1.63}, {"text": "And if you want\nto prove yourself", "start": 1131.81, "duration": 1.76}, {"text": "on why it's Corda versus\nHyperledger Fabric,", "start": 1133.57, "duration": 3.45}, {"text": "that'll be interesting if\nsomebody has a point of view.", "start": 1137.02, "duration": 2.86}, {"text": "But I'm not looking for that\nlevel of either computer", "start": 1139.88, "duration": 3.56}, {"text": "science knowledge.", "start": 1143.44, "duration": 3.18}, {"text": "This is from a\nbusiness perspective.", "start": 1146.62, "duration": 1.74}, {"text": "Think of me as a\nventure capitalist.", "start": 1148.36, "duration": 1.81}, {"text": "If I was investing, how\nyou pull it together.", "start": 1150.17, "duration": 4.65}, {"text": "So any questions on that?", "start": 1154.82, "duration": 1.45}, {"text": "So we had six or\nseven people that", "start": 1159.0, "duration": 1.89}, {"text": "actually worked in banking.", "start": 1160.89, "duration": 1.55}, {"text": "Who did we have at this table?", "start": 1162.44, "duration": 2.352}, {"text": "Ah.", "start": 1164.792, "duration": 1.466}, {"text": "So what's clearing?", "start": 1166.258, "duration": 0.792}, {"text": "AUDIENCE: If I\nrecall correctly, you", "start": 1171.5, "duration": 1.61}, {"text": "need to prove the identity\nof the other party", "start": 1173.11, "duration": 4.12}, {"text": "in order to make sure\nthat you're sending", "start": 1177.23, "duration": 2.41}, {"text": "the asset to the right--", "start": 1179.64, "duration": 1.0}, {"text": "GARY GENSLER: All right.", "start": 1180.64, "duration": 0.28}, {"text": "So you have to\nprove the identity.", "start": 1180.92, "duration": 1.66}, {"text": "So it's about validating and\nauthenticating an identity.", "start": 1182.58, "duration": 3.56}, {"text": "Anything else in clearing?", "start": 1186.14, "duration": 1.59}, {"text": "Who else worked in trading?", "start": 1187.73, "duration": 1.54}, {"text": "I had somebody back at\nthe back table worked in--", "start": 1189.27, "duration": 2.84}, {"text": "ah.", "start": 1192.11, "duration": 0.536}, {"text": "AUDIENCE: Is it that they\nhave the assets to be traded?", "start": 1192.646, "duration": 3.184}, {"text": "GARY GENSLER: They have\nthe assets to be traded.", "start": 1195.83, "duration": 2.01}, {"text": "Well, most equity markets\ntrade on transaction date", "start": 1197.84, "duration": 3.93}, {"text": "plus two days.", "start": 1201.77, "duration": 2.79}, {"text": "So somewhere in\nthat two days, you", "start": 1204.56, "duration": 2.16}, {"text": "have to confirm\nthey have the asset.", "start": 1206.72, "duration": 2.1}, {"text": "That is correct.", "start": 1208.82, "duration": 0.91}, {"text": "You don't have to do\nit on t plus zero,", "start": 1209.73, "duration": 2.27}, {"text": "normally by t plus 1.", "start": 1212.0, "duration": 2.38}, {"text": "AUDIENCE: I think--", "start": 1214.38, "duration": 0.86}, {"text": "I could be wrong.", "start": 1215.24, "duration": 0.75}, {"text": "But I think you had to do\nas well would be the stock", "start": 1215.99, "duration": 3.06}, {"text": "exchange knowing what is\nthe net exposure that you", "start": 1219.05, "duration": 2.33}, {"text": "have at the [INAUDIBLE].", "start": 1221.38, "duration": 1.0}, {"text": "GARY GENSLER: Net exposure.", "start": 1222.38, "duration": 1.86}, {"text": "Net exposure.", "start": 1224.24, "duration": 0.9}, {"text": "Very key thing.", "start": 1225.14, "duration": 0.97}, {"text": "So there's authentication.", "start": 1226.11, "duration": 1.37}, {"text": "At some point between\nexecution and transaction,", "start": 1227.48, "duration": 4.65}, {"text": "you have to actually know\nyou have the security--", "start": 1232.13, "duration": 2.97}, {"text": "and then net exposure,\nwhich we're going", "start": 1235.1, "duration": 4.16}, {"text": "to look at on another page.", "start": 1239.26, "duration": 2.59}, {"text": "This simple chart of two\npeople cutting the lawns,", "start": 1241.85, "duration": 4.05}, {"text": "but a buyer and seller meet.", "start": 1245.9, "duration": 2.43}, {"text": "But a buyer and seller\nmeet in an exchange", "start": 1248.33, "duration": 3.17}, {"text": "in traditional securities\nmarkets through brokers.", "start": 1251.5, "duration": 4.45}, {"text": "That's called an\ninner mediated access.", "start": 1255.95, "duration": 3.41}, {"text": "In the crypto exchange\nmarkets, those two brokers", "start": 1259.36, "duration": 4.963}, {"text": "on the left-hand side\nand the right-hand side,", "start": 1264.323, "duration": 1.917}, {"text": "the sellers and buyers\nbrokers, don't exist.", "start": 1266.24, "duration": 3.255}, {"text": "In the crypto exchange\nmarkets, basically you", "start": 1272.23, "duration": 3.25}, {"text": "have direct access\nto the market.", "start": 1275.48, "duration": 5.5}, {"text": "But in the traditional\nstock exchanges,", "start": 1280.98, "duration": 1.73}, {"text": "whether it's London,\nTokyo, New York, Beijing--", "start": 1282.71, "duration": 3.315}, {"text": "where's the exchange in India?", "start": 1291.26, "duration": 1.722}, {"text": "AUDIENCE: Mumbai.", "start": 1292.982, "duration": 1.388}, {"text": "GARY GENSLER: Oh,\nit's at Mumbai now?", "start": 1294.37, "duration": 2.35}, {"text": "I forgot.", "start": 1296.72, "duration": 0.87}, {"text": "30 years ago, I visited it\nand walked on the floor.", "start": 1297.59, "duration": 2.87}, {"text": "It was called the Bombay\nStock Exchange back then.", "start": 1300.46, "duration": 3.53}, {"text": "But regardless of where\nthe stock exchange is,", "start": 1303.99, "duration": 2.45}, {"text": "there's some clearing house\nseparate from the stock", "start": 1306.44, "duration": 2.88}, {"text": "exchange doing these functions\nthat we just talked about.", "start": 1309.32, "duration": 5.17}, {"text": "So three steps-- execution.", "start": 1314.49, "duration": 5.75}, {"text": "What's it mean to\nexecute a trade?", "start": 1320.24, "duration": 1.748}, {"text": "Alpha, do you know what\nit means to execute", "start": 1321.988, "duration": 1.792}, {"text": "a trade without reading?", "start": 1323.78, "duration": 1.872}, {"text": "Should I go back?", "start": 1325.652, "duration": 0.708}, {"text": "AUDIENCE: Yeah.", "start": 1326.36, "duration": 0.625}, {"text": "Because I've traded before.", "start": 1329.27, "duration": 1.44}, {"text": "GARY GENSLER: Yeah.", "start": 1330.71, "duration": 1.02}, {"text": "That's why I called on you.", "start": 1331.73, "duration": 1.17}, {"text": "AUDIENCE: We did a great job\nwith a separate execution team.", "start": 1332.9, "duration": 2.5}, {"text": "That helped us with that.", "start": 1335.4, "duration": 1.27}, {"text": "But signing the docs,\nmaking sure that the account", "start": 1336.67, "duration": 5.32}, {"text": "information is all there, if\nit's been done through NSDA.", "start": 1341.99, "duration": 2.48}, {"text": "GARY GENSLER: All right.", "start": 1344.47, "duration": 1.0}, {"text": "So this sounds like it's\nabout derivatives, executing", "start": 1345.47, "duration": 3.27}, {"text": "a derivatives contract.", "start": 1348.74, "duration": 0.99}, {"text": "But what if you're just buying\n100 shares of Apple stock?", "start": 1349.73, "duration": 3.88}, {"text": "What's it mean to\nexecute a trade?", "start": 1353.61, "duration": 2.825}, {"text": "AUDIENCE: To be on the\nphone or on the screen", "start": 1356.435, "duration": 1.875}, {"text": "and agree on a price\nand a quantity.", "start": 1358.31, "duration": 1.52}, {"text": "GARY GENSLER: There you go.", "start": 1359.83, "duration": 1.125}, {"text": "It's just you bid a price.", "start": 1360.955, "duration": 3.015}, {"text": "And somebody hits the\nbid or lifts the offer.", "start": 1363.97, "duration": 4.47}, {"text": "Those are the terms when\nyou're on the phone.", "start": 1368.44, "duration": 2.04}, {"text": "I left your offer.", "start": 1370.48, "duration": 1.59}, {"text": "I hit your bid.", "start": 1372.07, "duration": 1.9}, {"text": "Or at least it\nwas when I did it.", "start": 1373.97, "duration": 2.67}, {"text": "Still?", "start": 1376.64, "duration": 0.78}, {"text": "Or no, maybe not.", "start": 1377.42, "duration": 1.94}, {"text": "What's that?", "start": 1379.36, "duration": 1.23}, {"text": "Still.", "start": 1380.59, "duration": 0.63}, {"text": "All right.", "start": 1381.22, "duration": 1.6}, {"text": "Question?", "start": 1382.82, "duration": 0.5}, {"text": "AUDIENCE: Just not\non the phone anymore.", "start": 1383.32, "duration": 1.928}, {"text": "[LAUGHTER]", "start": 1385.248, "duration": 0.964}, {"text": "GARY GENSLER: Ah, yeah.", "start": 1386.212, "duration": 1.038}, {"text": "That's it.", "start": 1387.25, "duration": 1.31}, {"text": "What's that?", "start": 1388.56, "duration": 0.7}, {"text": "AUDIENCE: You just hit a button.", "start": 1389.26, "duration": 1.38}, {"text": "GARY GENSLER: Just hit a button.", "start": 1390.64, "duration": 0.81}, {"text": "AUDIENCE: I worked on the\n[INAUDIBLE] desk at Goldman", "start": 1391.45, "duration": 2.208}, {"text": "So we didn't talk to anyone.", "start": 1393.658, "duration": 1.532}, {"text": "GARY GENSLER: You\ndidn't talk to anybody?", "start": 1395.19, "duration": 1.985}, {"text": "Can you go months without\ntalking to anybody?", "start": 1397.175, "duration": 1.875}, {"text": "AUDIENCE: No, we\ntalked a little.", "start": 1399.05, "duration": 1.52}, {"text": "GARY GENSLER: What's that?", "start": 1400.57, "duration": 0.42}, {"text": "AUDIENCE: We talked\na little bit.", "start": 1400.99, "duration": 0.952}, {"text": "[? But it was always ?]\n[? kinda ?] weird.", "start": 1401.942, "duration": 0.758}, {"text": "GARY GENSLER: All right.", "start": 1402.7, "duration": 1.35}, {"text": "I guess I'm a dinosaur.", "start": 1404.05, "duration": 2.55}, {"text": "Yeah.", "start": 1406.6, "duration": 0.76}, {"text": "Yeah.", "start": 1407.36, "duration": 0.5}, {"text": "The screens that I used to\nlook at at Goldman Sachs,", "start": 1407.86, "duration": 3.42}, {"text": "it was green.", "start": 1411.28, "duration": 2.84}, {"text": "Yeah, yeah, yeah.", "start": 1414.12, "duration": 0.98}, {"text": "You know.", "start": 1415.1, "duration": 1.7}, {"text": "You know the screens.", "start": 1416.8, "duration": 1.39}, {"text": "Kelly is thinking, what\nis he talking about?", "start": 1418.19, "duration": 2.06}, {"text": "Right?", "start": 1420.25, "duration": 0.5}, {"text": "Look it up on the internet.", "start": 1423.26, "duration": 1.35}, {"text": "[? You're ?] [? fine. ?]\n[? You're ?] [? fine. ?] There", "start": 1424.61, "duration": 2.76}, {"text": "wasn't any color\non those screens.", "start": 1427.37, "duration": 2.91}, {"text": "So execution is\nbasically I buy, you", "start": 1430.28, "duration": 2.82}, {"text": "sell, we agree upon a\nprice, a price and a volume.", "start": 1433.1, "duration": 4.97}, {"text": "That's really what execution is.", "start": 1438.07, "duration": 2.55}, {"text": "But when you execute, you still\nneed to do a few other things.", "start": 1440.62, "duration": 3.55}, {"text": "And it's called\nclearing and settling.", "start": 1444.17, "duration": 1.722}, {"text": "When I was on a trading\nfloor, I couldn't", "start": 1445.892, "duration": 1.708}, {"text": "have told you what\nthe difference was", "start": 1447.6, "duration": 1.542}, {"text": "between clearing and settling.", "start": 1449.142, "duration": 1.378}, {"text": "That was something\nsomebody else did, frankly.", "start": 1450.52, "duration": 3.55}, {"text": "I'll admit it.", "start": 1454.07, "duration": 2.7}, {"text": "They were really\nterrific professionals.", "start": 1456.77, "duration": 1.67}, {"text": "But they had their job.", "start": 1458.44, "duration": 1.02}, {"text": "I had a different job.", "start": 1459.46, "duration": 1.65}, {"text": "Clearing is performing\nall of these functions.", "start": 1461.11, "duration": 3.27}, {"text": "Authenticating\nsomebody is there,", "start": 1464.38, "duration": 2.43}, {"text": "making sure you actually\nhave those securities,", "start": 1466.81, "duration": 2.05}, {"text": "and importantly this\nthing called netting.", "start": 1468.86, "duration": 2.82}, {"text": "How about settlement?", "start": 1471.68, "duration": 1.1}, {"text": "Anybody want to say?", "start": 1472.78, "duration": 0.84}, {"text": "I know it's written up there.", "start": 1473.62, "duration": 1.208}, {"text": "But anybody want\nto just say what--", "start": 1474.828, "duration": 1.852}, {"text": "we've talked about ledgers\nfor seven or 10 weeks now.", "start": 1476.68, "duration": 4.71}, {"text": "What do you think a\nsettlement really means", "start": 1481.39, "duration": 2.34}, {"text": "in the context of a ledger?", "start": 1483.73, "duration": 3.46}, {"text": "Did I see a hand up here?", "start": 1487.19, "duration": 2.1}, {"text": "Yes, I did.", "start": 1489.29, "duration": 0.9}, {"text": "I did see a hand up.", "start": 1490.19, "duration": 1.05}, {"text": "What's settlement?", "start": 1491.24, "duration": 0.75}, {"text": "AUDIENCE: Running the\nentries on the ledger.", "start": 1491.99, "duration": 1.2}, {"text": "What's in, what's out.", "start": 1493.19, "duration": 1.307}, {"text": "GARY GENSLER: Right.", "start": 1494.497, "duration": 0.833}, {"text": "It's making a final\nrecording on a ledger,", "start": 1495.33, "duration": 4.67}, {"text": "finally moving\nsomething on a ledger.", "start": 1500.0, "duration": 2.28}, {"text": "You could be moving the\nownership of an asset", "start": 1502.28, "duration": 4.2}, {"text": "or the ownership of cash.", "start": 1506.48, "duration": 2.46}, {"text": "And when you do both\nat the same time,", "start": 1508.94, "duration": 1.9}, {"text": "it's called delivery\nversus payment, or DVP.", "start": 1510.84, "duration": 2.29}, {"text": "It's just a final change\nof data record on a ledger.", "start": 1516.31, "duration": 5.18}, {"text": "In the old days--", "start": 1521.49, "duration": 1.14}, {"text": "I'm talking about\nbefore I was doing it.", "start": 1522.63, "duration": 2.38}, {"text": "But 40 years to\nhundreds of years", "start": 1525.01, "duration": 2.96}, {"text": "ago, it was\nphysically delivering", "start": 1527.97, "duration": 2.27}, {"text": "a physical piece of paper which\nwas a equity security or a bond", "start": 1530.24, "duration": 4.6}, {"text": "security.", "start": 1534.84, "duration": 1.26}, {"text": "But it all got dematerialized\nstarting in the 1970s.", "start": 1536.1, "duration": 3.75}, {"text": "And by the 1990s,\nit was pretty much--", "start": 1539.85, "duration": 2.1}, {"text": "in this country and the UK--", "start": 1541.95, "duration": 2.31}, {"text": "it was pretty much\ndematerialized securities,", "start": 1544.26, "duration": 4.14}, {"text": "that everything's digitized now\nin the equity markets in nearly", "start": 1548.4, "duration": 4.56}, {"text": "every country that\nyou're all from and maybe", "start": 1552.96, "duration": 3.33}, {"text": "with some small exceptions.", "start": 1556.29, "duration": 2.91}, {"text": "So execution is I buy,\nyou sell, volume price.", "start": 1559.2, "duration": 4.04}, {"text": "We've legally agreed\nto something verbally.", "start": 1563.24, "duration": 3.52}, {"text": "And billions of dollars\ncan trade on the phone", "start": 1566.76, "duration": 4.05}, {"text": "or in the computer.", "start": 1570.81, "duration": 2.52}, {"text": "Legally, it's executed.", "start": 1573.33, "duration": 1.32}, {"text": "Clearing is trying to make\nsure that you actually", "start": 1574.65, "duration": 2.97}, {"text": "have the securities, and\nI actually have the cash.", "start": 1577.62, "duration": 3.16}, {"text": "We do some netting.", "start": 1580.78, "duration": 0.89}, {"text": "We authenticate.", "start": 1581.67, "duration": 1.65}, {"text": "And settlement is actually\nmoving the data on the ledgers.", "start": 1583.32, "duration": 3.36}, {"text": "Three steps.", "start": 1586.68, "duration": 2.34}, {"text": "This is the benefit of netting.", "start": 1589.02, "duration": 1.44}, {"text": "It was just one chart that\nI could find somewhere.", "start": 1590.46, "duration": 2.29}, {"text": "It's actually the\nAustralian Stock Exchange", "start": 1592.75, "duration": 1.94}, {"text": "had it on their website.", "start": 1594.69, "duration": 2.85}, {"text": "But if you have multi-parties\nin the transaction,", "start": 1597.54, "duration": 2.89}, {"text": "which was on the\nleft hand side--", "start": 1600.43, "duration": 1.97}, {"text": "and these are just arrows of\nall the different transactions", "start": 1602.4, "duration": 3.06}, {"text": "that could occur in\none little example--", "start": 1605.46, "duration": 3.39}, {"text": "and instead you interpose\na central intermediary,", "start": 1608.85, "duration": 7.46}, {"text": "you can do a lot of netting.", "start": 1616.31, "duration": 2.53}, {"text": "And look at participant\nC. Participant C", "start": 1618.84, "duration": 2.43}, {"text": "only has an exposure of\nselling 35 of whatever they're", "start": 1621.27, "duration": 4.62}, {"text": "selling, some stock, versus\nall these other transactions.", "start": 1625.89, "duration": 5.04}, {"text": "And this is a very simple case.", "start": 1630.93, "duration": 3.68}, {"text": "But if you have 20 or a hundred\nclearing members that are all", "start": 1634.61, "duration": 6.33}, {"text": "big brokerage houses and\nthey're doing thousands or even", "start": 1640.94, "duration": 3.36}, {"text": "hundreds of thousands\nof trades a day,", "start": 1644.3, "duration": 4.25}, {"text": "you have an awful\nlot of transactions.", "start": 1648.55, "duration": 4.14}, {"text": "And the gross transactions\nversus the net", "start": 1652.69, "duration": 3.06}, {"text": "is quite a difference.", "start": 1655.75, "duration": 1.81}, {"text": "That netting can bring down\nnumbers 90 plus percent", "start": 1657.56, "duration": 4.1}, {"text": "or maybe even 99% or more.", "start": 1661.66, "duration": 3.75}, {"text": "So central intermediaries--", "start": 1665.41, "duration": 2.37}, {"text": "I know this goes against Satoshi\nNakamoto's whole concept--", "start": 1667.78, "duration": 3.28}, {"text": "but central intermediaries came\nabout in the securities market", "start": 1671.06, "duration": 6.31}, {"text": "for a bunch of reasons.", "start": 1677.37, "duration": 1.21}, {"text": "But one of the biggest\nones was netting.", "start": 1678.58, "duration": 5.31}, {"text": "Brotish?", "start": 1683.89, "duration": 2.25}, {"text": "And it's a really\nimportant concept", "start": 1686.14, "duration": 1.85}, {"text": "in the back office\nof Wall Street.", "start": 1687.99, "duration": 1.65}, {"text": "AUDIENCE: I'm not\nfamiliar with the concept.", "start": 1689.64, "duration": 1.833}, {"text": "So [INAUDIBLE].", "start": 1691.473, "duration": 0.897}, {"text": "GARY GENSLER: You're\nsaying you're familiar?", "start": 1692.37, "duration": 1.17}, {"text": "AUDIENCE: I'm not familiar\nwith this concept,", "start": 1693.54, "duration": 1.46}, {"text": "so a clarification question.", "start": 1695.0, "duration": 1.46}, {"text": "GARY GENSLER: Please.", "start": 1696.46, "duration": 1.197}, {"text": "AUDIENCE: When we\ndo netting, it seems", "start": 1697.657, "duration": 1.583}, {"text": "that we are losing\na lot of information", "start": 1699.24, "duration": 2.01}, {"text": "here from the\ngross transactions.", "start": 1701.25, "duration": 1.38}, {"text": "So is it--", "start": 1702.63, "duration": 1.05}, {"text": "GARY GENSLER: That's right.", "start": 1703.68, "duration": 0.42}, {"text": "AUDIENCE: --just the\ntransfer of the asset", "start": 1704.1, "duration": 1.89}, {"text": "is done through the\nnetting, but the records", "start": 1705.99, "duration": 1.95}, {"text": "of all the gross\ntransactions are still there", "start": 1707.94, "duration": 2.1}, {"text": "with the central intermediaries?", "start": 1710.04, "duration": 1.41}, {"text": "GARY GENSLER: Very\ngood question.", "start": 1711.45, "duration": 1.375}, {"text": "So are we losing information?", "start": 1712.825, "duration": 2.405}, {"text": "Or are we just lessening the\nlines of counterparty risk", "start": 1715.23, "duration": 5.88}, {"text": "in the transactions?", "start": 1721.11, "duration": 1.29}, {"text": "And the answer is,\nif done properly,", "start": 1722.4, "duration": 1.89}, {"text": "you still keep the\ninformation of all of these.", "start": 1724.29, "duration": 4.59}, {"text": "And in the real world, this\nis just eight transactions.", "start": 1728.88, "duration": 5.0}, {"text": "It's netted down to four.", "start": 1733.88, "duration": 2.03}, {"text": "Right?", "start": 1735.91, "duration": 0.5}, {"text": "So this is eight transactions\nnetted down to four.", "start": 1736.41, "duration": 2.31}, {"text": "Usually this is millions\nof transactions netted down", "start": 1738.72, "duration": 3.39}, {"text": "to tens of thousands or maybe\nmillions of transactions", "start": 1742.11, "duration": 4.31}, {"text": "literally netted down to, if\nthere was 100 clearing members,", "start": 1746.42, "duration": 4.59}, {"text": "it would be 100\ntransactions, because they'd", "start": 1751.01, "duration": 2.19}, {"text": "each have one net transaction\nper security, per security.", "start": 1753.2, "duration": 8.55}, {"text": "And so you need to\nkeep the information", "start": 1761.75, "duration": 2.25}, {"text": "of the millions of\ntransactions to properly", "start": 1764.0, "duration": 2.43}, {"text": "record for your\ncustomers, for your taxes,", "start": 1766.43, "duration": 3.45}, {"text": "for all sorts of other reasons.", "start": 1769.88, "duration": 3.33}, {"text": "But you've netted down\nfor counterparty reasons.", "start": 1773.21, "duration": 3.06}, {"text": "Does that help?", "start": 1776.27, "duration": 3.0}, {"text": "Question over here.", "start": 1779.27, "duration": 1.12}, {"text": "Sean.", "start": 1780.39, "duration": 0.5}, {"text": "AUDIENCE: I was just curious.", "start": 1780.89, "duration": 2.255}, {"text": "It's very understandable\nfor equities.", "start": 1783.145, "duration": 2.075}, {"text": "But for principal\ncommodities, [? the full ?]", "start": 1785.22, "duration": 2.576}, {"text": "commodity derivatives, for\ninstance in the clearing space,", "start": 1787.796, "duration": 4.264}, {"text": "does it actually involve\nthe physical delivery", "start": 1792.06, "duration": 2.48}, {"text": "of the netted\ncommodity [INAUDIBLE]??", "start": 1794.54, "duration": 5.16}, {"text": "Because there's a different type\nfor delivery, and how that--", "start": 1799.7, "duration": 2.542}, {"text": "GARY GENSLER: OK.", "start": 1802.242, "duration": 0.708}, {"text": "So Sean's asked\nthe question, what", "start": 1802.95, "duration": 1.64}, {"text": "if you're not dealing\nwith digitized assets,", "start": 1804.59, "duration": 2.07}, {"text": "but physical assets?", "start": 1806.66, "duration": 1.33}, {"text": "I think.", "start": 1807.99, "duration": 0.5}, {"text": "You used the word commodity.", "start": 1808.49, "duration": 1.29}, {"text": "But I was presuming\nyou meant physical.", "start": 1809.78, "duration": 2.085}, {"text": "So some of the innovations\nof the 19th century", "start": 1814.76, "duration": 2.61}, {"text": "relate here when\nthey started to have", "start": 1817.37, "duration": 2.37}, {"text": "standardized contracts\nfor commodities", "start": 1819.74, "duration": 3.03}, {"text": "that were held in warehouses.", "start": 1822.77, "duration": 3.84}, {"text": "In essence, to facilitate\nsome of this netting", "start": 1826.61, "duration": 4.94}, {"text": "was also why central\nwarehouses, this clearing", "start": 1831.55, "duration": 3.18}, {"text": "house in the middle in\nphysical commodities,", "start": 1834.73, "duration": 2.16}, {"text": "could be a warehouse that held\nthe gold, held the silver,", "start": 1836.89, "duration": 3.42}, {"text": "held the corn or wheat.", "start": 1840.31, "duration": 2.52}, {"text": "And if they're holding\nthat corn or wheat,", "start": 1842.83, "duration": 2.73}, {"text": "they started to have\nspecifications as to what", "start": 1845.56, "duration": 2.67}, {"text": "standards there were.", "start": 1848.23, "duration": 2.16}, {"text": "In gold and silver,\nit was percent.", "start": 1850.39, "duration": 2.46}, {"text": "It was called the,\nlet's see, assay--", "start": 1852.85, "duration": 6.215}, {"text": "I'm trying to\nremember the word--", "start": 1859.065, "duration": 1.375}, {"text": "but what percent\ngold or silver it is.", "start": 1860.44, "duration": 3.66}, {"text": "But in corn and wheat,\nthere was a more detailed", "start": 1864.1, "duration": 2.97}, {"text": "what's going into the warehouse\nto commoditize it so that it", "start": 1867.07, "duration": 5.61}, {"text": "was a standard contract.", "start": 1872.68, "duration": 2.31}, {"text": "If it's truly physical and not\ncommodity, it's much harder.", "start": 1874.99, "duration": 5.24}, {"text": "Then you can't really net down\nmy house versus Shimon's house.", "start": 1880.23, "duration": 6.06}, {"text": "They're two different houses.", "start": 1886.29, "duration": 2.615}, {"text": "Does that help?", "start": 1888.905, "duration": 2.555}, {"text": "But literally by the\nlate 19th century,", "start": 1891.46, "duration": 2.41}, {"text": "even in the commodities\nspace running out of Chicago,", "start": 1893.87, "duration": 3.33}, {"text": "they figured out\ncentral clearing houses", "start": 1897.2, "duration": 1.94}, {"text": "with a lot of counterparty risk.", "start": 1899.14, "duration": 4.47}, {"text": "So there's an economic\nreason we have", "start": 1903.61, "duration": 1.95}, {"text": "centralized clearing houses.", "start": 1905.56, "duration": 1.41}, {"text": "And the biggest economic\nreason is netting.", "start": 1906.97, "duration": 5.01}, {"text": "And netting lowers something\ncalled counterparty risk.", "start": 1911.98, "duration": 4.35}, {"text": "Instead of having literally\nmillions of transactions,", "start": 1916.33, "duration": 4.2}, {"text": "you'll have thousands.", "start": 1920.53, "duration": 2.13}, {"text": "And you'll have less\ncounterparty risk.", "start": 1922.66, "duration": 1.738}, {"text": "It also lowers one other thing.", "start": 1924.398, "duration": 1.292}, {"text": "So it lowers counterparty risk.", "start": 1925.69, "duration": 1.44}, {"text": "And what is the other\nthing you think it lowers?", "start": 1927.13, "duration": 2.0}, {"text": "Anybody?", "start": 1929.13, "duration": 2.093}, {"text": "AUDIENCE: Transactions cost.", "start": 1931.223, "duration": 1.167}, {"text": "GARY GENSLER: Transactions\ncost because it's efficient.", "start": 1932.39, "duration": 2.292}, {"text": "We used to call it you take\na lot of lines off the page.", "start": 1937.28, "duration": 3.57}, {"text": "So in the old human\ndays, you'd have", "start": 1940.85, "duration": 2.67}, {"text": "to have fewer humans\nactually pushing paper.", "start": 1943.52, "duration": 4.87}, {"text": "Hugo.", "start": 1948.39, "duration": 1.26}, {"text": "AUDIENCE: Another\nclarification question.", "start": 1949.65, "duration": 2.58}, {"text": "So from the participants side,\nso from a hedge fund side", "start": 1952.23, "duration": 3.42}, {"text": "or whatever or a\ntrading desk side,", "start": 1955.65, "duration": 3.965}, {"text": "do they just go about their\nday trading everything?", "start": 1959.615, "duration": 2.125}, {"text": "And then the next day\nthe clearing house", "start": 1961.74, "duration": 2.443}, {"text": "tells them, OK, you made all\nthese transactions yesterday.", "start": 1964.183, "duration": 2.417}, {"text": "But we really only\nneed 35 [INAUDIBLE]..", "start": 1966.6, "duration": 2.82}, {"text": "Or how does it [INAUDIBLE]?", "start": 1969.42, "duration": 2.37}, {"text": "GARY GENSLER: In that\ncase, looking back to this,", "start": 1971.79, "duration": 4.32}, {"text": "you are either the\nbuyer or seller.", "start": 1976.11, "duration": 1.65}, {"text": "And you're dealing\nwith a broker.", "start": 1977.76, "duration": 1.44}, {"text": "So if you're a hedge\nfund, you often", "start": 1979.2, "duration": 4.513}, {"text": "enter into an arrangement\nwith a broker.", "start": 1983.713, "duration": 1.667}, {"text": "And it's called a prime\nbrokerage arrangement.", "start": 1985.38, "duration": 2.26}, {"text": "And you might have a prime\nbrokerage arrangement", "start": 1987.64, "duration": 2.0}, {"text": "with more than one\nWall Street firm.", "start": 1989.64, "duration": 2.04}, {"text": "But you rarely would have\nit with more than three.", "start": 1991.68, "duration": 2.9}, {"text": "So even if I'm doing a\ntrade through Merrill Lynch,", "start": 1994.58, "duration": 2.55}, {"text": "if my prime brokerage\narrangement is", "start": 1997.13, "duration": 1.77}, {"text": "at Goldman Sachs, Merrill is\ngoing to get a commission.", "start": 1998.9, "duration": 6.52}, {"text": "But they're going to give up\nmy prime brokerage arrangements", "start": 2005.42, "duration": 2.55}, {"text": "to Goldman Sachs.", "start": 2007.97, "duration": 0.9}, {"text": "And that helps me, me the hedge\nfund, get more netting as well.", "start": 2008.87, "duration": 4.08}, {"text": "And that's a development\nin the last 20 years,", "start": 2012.95, "duration": 3.15}, {"text": "this concept of prime brokerage.", "start": 2016.1, "duration": 3.57}, {"text": "But to answer your\nquestion, yes.", "start": 2019.67, "duration": 1.59}, {"text": "I go about my business.", "start": 2021.26, "duration": 1.11}, {"text": "I trade all day.", "start": 2022.37, "duration": 1.19}, {"text": "And unless I get a phone call\nor an electronic communication", "start": 2023.56, "duration": 4.57}, {"text": "from my prime brokerage\nsaying you've hit your lines,", "start": 2028.13, "duration": 3.74}, {"text": "you do have credit limits and\nposition limits in essence.", "start": 2031.87, "duration": 5.01}, {"text": "But your prime brokerage--", "start": 2036.88, "duration": 1.77}, {"text": "and I might say, well, I\nneed something moved over.", "start": 2038.65, "duration": 3.0}, {"text": "I need some more credit today.", "start": 2041.65, "duration": 3.57}, {"text": "But yes.", "start": 2045.22, "duration": 0.642}, {"text": "You go about your business\nuntil your prime brokerage", "start": 2045.862, "duration": 2.208}, {"text": "says slow down.", "start": 2048.07, "duration": 2.95}, {"text": "Shimon?", "start": 2051.02, "duration": 0.5}, {"text": "AUDIENCE: But [INAUDIBLE]\nquestion says that", "start": 2051.52, "duration": 2.17}, {"text": "if you're a lot like LTCM--", "start": 2053.69, "duration": 2.89}, {"text": "GARY GENSLER: Long-Term\nCapital Management.", "start": 2056.58, "duration": 1.792}, {"text": "AUDIENCE: --at some point,\nthey were running a balance", "start": 2058.372, "duration": 2.25}, {"text": "sheet of a trillion dollars.", "start": 2060.622, "duration": 1.608}, {"text": "And part of the reason\nwhy, when bankrupt is they", "start": 2062.23, "duration": 2.179}, {"text": "didn't want to use\none prime broker,", "start": 2064.409, "duration": 2.736}, {"text": "because they don't want to\nreveal all their trades.", "start": 2067.145, "duration": 2.125}, {"text": "But then their prime\nbrokers could not", "start": 2069.27, "duration": 2.119}, {"text": "net out their positions, because\nI may hold one leg with you", "start": 2071.389, "duration": 4.181}, {"text": "and another leg with you.", "start": 2075.57, "duration": 3.169}, {"text": "The net may be zero.", "start": 2078.739, "duration": 2.381}, {"text": "But there's no way for\nyou to actually reconcile", "start": 2081.12, "duration": 2.309}, {"text": "that or reconcile that risk.", "start": 2083.429, "duration": 3.241}, {"text": "So it's a real problem.", "start": 2086.67, "duration": 1.94}, {"text": "GARY GENSLER: Long-Term\nCapital Management", "start": 2088.61, "duration": 1.75}, {"text": "was a hedge fund\noperating in Connecticut.", "start": 2090.36, "duration": 4.89}, {"text": "It was founded in\nthe early 1990s", "start": 2095.25, "duration": 2.34}, {"text": "by a man named John\nMeriwether, who", "start": 2097.59, "duration": 2.2}, {"text": "is a very famous trader\nfrom Salomon Brothers", "start": 2099.79, "duration": 3.82}, {"text": "and very successful.", "start": 2103.61, "duration": 1.69}, {"text": "And then he started it with\nsome remarkable finance", "start": 2105.3, "duration": 5.16}, {"text": "faculty from here, at\nMIT, and elsewhere--", "start": 2110.46, "duration": 3.6}, {"text": "Bob Merton, who is\na Nobel laureate.", "start": 2114.06, "duration": 2.94}, {"text": "Brilliant, brilliant\nteam of folks.", "start": 2117.0, "duration": 3.22}, {"text": "But they ran into a little\nchallenge four years later.", "start": 2120.22, "duration": 2.72}, {"text": "They had about $125 billion\nbalance sheet, $4 billion", "start": 2122.94, "duration": 3.81}, {"text": "in capital, and 1.2\ntrillion in swaps.", "start": 2126.75, "duration": 4.05}, {"text": "Why do I know the numbers?", "start": 2130.8, "duration": 1.2}, {"text": "I got the phone call with my\none-year-old sitting on my lap.", "start": 2132.0, "duration": 2.88}, {"text": "And I picked up the phone.", "start": 2134.88, "duration": 1.74}, {"text": "And I said, hello?", "start": 2136.62, "duration": 1.5}, {"text": "And the voice on the other\nline said, Treasury operator.", "start": 2138.12, "duration": 2.67}, {"text": "I've got the Treasury\nsecretary for you.", "start": 2140.79, "duration": 2.04}, {"text": "And I get on the phone.", "start": 2142.83, "duration": 0.99}, {"text": "I go, yes, Bob?", "start": 2143.82, "duration": 1.11}, {"text": "It was Bob Rubin.", "start": 2144.93, "duration": 1.03}, {"text": "It was the Treasury secretary.", "start": 2145.96, "duration": 1.25}, {"text": "Bob, what's up?", "start": 2147.21, "duration": 0.74}, {"text": "It was a Saturday.", "start": 2147.95, "duration": 0.9}, {"text": "Isabel was on my lap.", "start": 2148.85, "duration": 2.13}, {"text": "He says, do you know anything\nabout Long-Term Capital", "start": 2150.98, "duration": 2.61}, {"text": "Management?", "start": 2153.59, "duration": 0.59}, {"text": "He goes through\nsome of the figures.", "start": 2154.18, "duration": 1.87}, {"text": "I'll never forget.", "start": 2156.05, "duration": 0.75}, {"text": "He says, I hear from Alan--", "start": 2156.8, "duration": 2.22}, {"text": "that would be Alan Greenspan,\nwho was the head of the Federal", "start": 2159.02, "duration": 3.07}, {"text": "Reserve--", "start": 2162.09, "duration": 0.53}, {"text": "I hear from Alan that they\nhave over a trillion dollars", "start": 2162.62, "duration": 2.385}, {"text": "of derivatives.", "start": 2165.005, "duration": 1.705}, {"text": "That's Shimon's number.", "start": 2166.71, "duration": 1.76}, {"text": "He says, is that a big number?", "start": 2168.47, "duration": 1.887}, {"text": "Well, you have to understand,\nBob's sense of humor", "start": 2170.357, "duration": 2.083}, {"text": "was quite-- at that moment,\nhe knew it was a big number.", "start": 2172.44, "duration": 4.97}, {"text": "So I flew up the next day.", "start": 2177.41, "duration": 2.58}, {"text": "And with somebody from\nthe Federal Reserve", "start": 2179.99, "duration": 2.64}, {"text": "Bank in New York,\nPeter Fisher, we", "start": 2182.63, "duration": 3.03}, {"text": "sat around the\nconference table looking", "start": 2185.66, "duration": 2.22}, {"text": "at these facts and figures.", "start": 2187.88, "duration": 2.16}, {"text": "And then I got back on the plane\nand flew back to Washington", "start": 2190.04, "duration": 3.81}, {"text": "to be with my family.", "start": 2193.85, "duration": 0.99}, {"text": "The next day was actually Rosh\nHashanah, the Jewish holiday.", "start": 2194.84, "duration": 2.67}, {"text": "And I wasn't going to work.", "start": 2197.51, "duration": 2.72}, {"text": "And I had to call Bob and\nhis deputy, Larry Summers,", "start": 2200.23, "duration": 3.68}, {"text": "up and give them my feedback.", "start": 2203.91, "duration": 2.25}, {"text": "And I said, this\nthing's going down.", "start": 2206.16, "duration": 2.88}, {"text": "Bear Stearns was\ntheir prime brokerage.", "start": 2209.04, "duration": 3.06}, {"text": "And Bear Stearns, who 20\nyears later failed themselves,", "start": 2212.1, "duration": 2.91}, {"text": "but Bear Stearns said, we're\npulling the prime brokerage", "start": 2215.01, "duration": 3.72}, {"text": "account if you can't\npost another half", "start": 2218.73, "duration": 2.73}, {"text": "a billion dollars by Wednesday.", "start": 2221.46, "duration": 2.555}, {"text": "Well, there was\nno way they could", "start": 2224.015, "duration": 1.375}, {"text": "post another half\na billion dollars,", "start": 2225.39, "duration": 1.62}, {"text": "because their $4\nbillion of capital", "start": 2227.01, "duration": 1.83}, {"text": "we could best figure on\nthat Sunday was somewhere", "start": 2228.84, "duration": 2.37}, {"text": "covering around 400 or 500\nmillion at that point in time.", "start": 2231.21, "duration": 5.217}, {"text": "Well, when you have\na lot of leverage,", "start": 2236.427, "duration": 1.583}, {"text": "you have $1.2 trillion of\nderivatives which are all", "start": 2238.01, "duration": 2.85}, {"text": "sort of leveraged in\none way or another", "start": 2240.86, "duration": 1.83}, {"text": "and you've got $125\nbillion balance sheet, even", "start": 2242.69, "duration": 2.97}, {"text": "with the best minds, the\nbest finance faculty--", "start": 2245.66, "duration": 4.21}, {"text": "and they really are\nterrific individuals.", "start": 2249.87, "duration": 2.29}, {"text": "And Meriwether was\nquite a trader.", "start": 2252.16, "duration": 3.28}, {"text": "Sometimes markets\ngo against you.", "start": 2255.44, "duration": 2.95}, {"text": "Correlation risk, liquidity\nrisk, and so forth.", "start": 2258.39, "duration": 3.82}, {"text": "So they pulled the plug\nthe next day, basically.", "start": 2262.21, "duration": 4.88}, {"text": "That's the Long-Term Capital\nManagement story I remember.", "start": 2267.09, "duration": 2.76}, {"text": "But it's just because I\nkind of had to live it.", "start": 2269.85, "duration": 4.29}, {"text": "But to answer your question,\nyou can trade all day", "start": 2274.14, "duration": 3.48}, {"text": "until your prime broker\nsays, Hugo, slow down,", "start": 2277.62, "duration": 4.93}, {"text": "because they're\nextending credit to you--", "start": 2282.55, "duration": 2.43}, {"text": "the prime broker is--", "start": 2284.98, "duration": 3.27}, {"text": "intraday.", "start": 2288.25, "duration": 1.26}, {"text": "And one of the big risks,\none of the big risks", "start": 2289.51, "duration": 2.01}, {"text": "in the financial crisis--", "start": 2291.52, "duration": 1.78}, {"text": "and certainly Ben Bernanke,\nwho is chairing the US Federal", "start": 2293.3, "duration": 3.41}, {"text": "Reserve and others had to deal\nwith it in the middle of 2008--", "start": 2296.71, "duration": 3.48}, {"text": "is most commercial banks,\nso they don't have a broker.", "start": 2300.19, "duration": 3.61}, {"text": "They're banks.", "start": 2303.8, "duration": 0.9}, {"text": "They're the brokers\nthemselves-- were extending", "start": 2304.7, "duration": 2.99}, {"text": "significant amount\nof intraday credit", "start": 2307.69, "duration": 2.46}, {"text": "to each other that, in 2008,\nwasn't terribly well measured", "start": 2310.15, "duration": 6.83}, {"text": "in the repo markets\nand in other markets.", "start": 2316.98, "duration": 3.48}, {"text": "And that's changed subsequently.", "start": 2320.46, "duration": 3.94}, {"text": "But you wouldn't\nhave been a big bank.", "start": 2324.4, "duration": 1.85}, {"text": "You would have probably\nbeen shut down.", "start": 2326.25, "duration": 2.88}, {"text": "Sorry.", "start": 2329.13, "duration": 1.23}, {"text": "Or maybe not.", "start": 2330.36, "duration": 1.8}, {"text": "So netting is the biggest\nbenefit of clearing.", "start": 2332.16, "duration": 4.86}, {"text": "But it's also efficiency\nand taking down", "start": 2337.02, "duration": 3.75}, {"text": "a lot of operating\nlines of code.", "start": 2340.77, "duration": 3.55}, {"text": "This is a chart.", "start": 2344.32, "duration": 0.68}, {"text": "I'm not going to spend\na lot of time on it.", "start": 2345.0, "duration": 1.42}, {"text": "But this is right off the\nAustralian Stock Exchange", "start": 2346.42, "duration": 2.13}, {"text": "website.", "start": 2348.55, "duration": 0.5}, {"text": "And I thought, well,\nwhy not take that?", "start": 2349.05, "duration": 1.92}, {"text": "They have 2 million investors,\nthe market participants", "start": 2350.97, "duration": 4.07}, {"text": "or brokers in a much\nsmaller market than the US.", "start": 2355.04, "duration": 3.12}, {"text": "And Australia has 77 brokers,\nregistered, regulated brokers.", "start": 2358.16, "duration": 6.18}, {"text": "And then they have the clearing\nhouse called CHESS, C-H-E-S-S,", "start": 2364.34, "duration": 4.5}, {"text": "which I can't quite remember\nwhat it all stands for.", "start": 2368.84, "duration": 2.25}, {"text": "But SS is Settlement System.", "start": 2371.09, "duration": 2.4}, {"text": "Clearing house--", "start": 2373.49, "duration": 1.68}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2375.17, "duration": 1.77}, {"text": "GARY GENSLER: What's that?", "start": 2376.94, "duration": 1.96}, {"text": "What's it?", "start": 2378.9, "duration": 0.76}, {"text": "AUDIENCE: Clearing House\nSubregistered System.", "start": 2379.66, "duration": 2.282}, {"text": "GARY GENSLER:\nSubregistered System.", "start": 2381.942, "duration": 1.458}, {"text": "Thank you.", "start": 2383.4, "duration": 0.9}, {"text": "Is it Equity for E?", "start": 2384.3, "duration": 1.59}, {"text": "AUDIENCE: There is none.", "start": 2385.89, "duration": 1.0}, {"text": "GARY GENSLER: There is none.", "start": 2386.89, "duration": 1.71}, {"text": "But they have the Australian\nStock Exchange Clear", "start": 2388.6, "duration": 3.31}, {"text": "and Australia Stock\nExchange Settlement,", "start": 2391.91, "duration": 3.17}, {"text": "because they actually put it\nin two different places, two", "start": 2395.08, "duration": 2.97}, {"text": "different things.", "start": 2398.05, "duration": 1.35}, {"text": "The clearinghouse is doing\nwhat we talked about--", "start": 2399.4, "duration": 2.7}, {"text": "mostly netting, lowering\nthe lines of code,", "start": 2402.1, "duration": 4.75}, {"text": "and then settlement.", "start": 2406.85, "duration": 1.47}, {"text": "And basically, because we're\nin a trade day plus two days,", "start": 2408.32, "duration": 4.38}, {"text": "on the first day is all the\nclearing and the netting.", "start": 2412.7, "duration": 3.74}, {"text": "And you better show up\nwith your securities.", "start": 2416.44, "duration": 2.05}, {"text": "And on the second\nday is settlement.", "start": 2418.49, "duration": 2.67}, {"text": "Electronics and technology\ncould make this simultaneous.", "start": 2421.16, "duration": 3.66}, {"text": "But most market\nparticipants like", "start": 2428.14, "duration": 2.42}, {"text": "to have some ability to do\ngross trading against net's", "start": 2430.56, "duration": 3.49}, {"text": "positions.", "start": 2434.05, "duration": 1.59}, {"text": "So there's a lot of\neconomics and market practice", "start": 2435.64, "duration": 3.39}, {"text": "and structure behind keeping\nsome delayed settlement.", "start": 2439.03, "duration": 4.48}, {"text": "And the markets have\ngrown up around that.", "start": 2443.51, "duration": 1.75}, {"text": "Ross.", "start": 2445.26, "duration": 1.24}, {"text": "AUDIENCE: If it's not delayed,\nif it was instantaneous,", "start": 2446.5, "duration": 4.055}, {"text": "wouldn't that get rid\nof the benefits of net?", "start": 2450.555, "duration": 1.875}, {"text": "And you'd have to have every\ntrade go right through.", "start": 2452.43, "duration": 2.51}, {"text": "So it has to be that you\nwait until the end of the day", "start": 2454.94, "duration": 2.3}, {"text": "or whatever period\n[INTERPOSING VOICES]..", "start": 2457.24, "duration": 1.708}, {"text": "GARY GENSLER: So Ross just\nraised the number one reason,", "start": 2458.948, "duration": 2.912}, {"text": "economic reason, why\nsimultaneous clearing", "start": 2461.86, "duration": 6.21}, {"text": "and settling is not\nthat likely to happen.", "start": 2468.07, "duration": 5.58}, {"text": "The markets have\nbuilt themselves", "start": 2473.65, "duration": 2.01}, {"text": "around the benefits\nof netting and also", "start": 2475.66, "duration": 4.74}, {"text": "stock loan, the ability to\nborrow that security somewhere.", "start": 2480.4, "duration": 4.99}, {"text": "But you're absolutely right.", "start": 2485.39, "duration": 1.83}, {"text": "If there were simultaneous\nexecution and settlement, which", "start": 2487.22, "duration": 4.65}, {"text": "is what the Bitcoin network\nin essence is supposed to be", "start": 2491.87, "duration": 2.97}, {"text": "and blockchain networks can\nbe, then you, in essence,", "start": 2494.84, "duration": 4.133}, {"text": "have to prefund.", "start": 2498.973, "duration": 0.667}, {"text": "Every time Hugo\ntrades, he's going", "start": 2502.37, "duration": 2.14}, {"text": "to have to provide\nhis security to trade.", "start": 2504.51, "duration": 2.12}, {"text": "But then Tom would get\nthe security faster.", "start": 2509.56, "duration": 4.23}, {"text": "It would change the entire\nprime brokerage model.", "start": 2513.79, "duration": 4.0}, {"text": "It doesn't mean markets,\nRoss, couldn't adapt", "start": 2517.79, "duration": 2.4}, {"text": "and be structured that way.", "start": 2520.19, "duration": 2.67}, {"text": "But it would be fundamentally\na different structure.", "start": 2522.86, "duration": 2.37}, {"text": "Is this is a hand up?", "start": 2525.23, "duration": 3.05}, {"text": "AUDIENCE: So the [INAUDIBLE]\nis really big with derivatives.", "start": 2528.28, "duration": 3.39}, {"text": "I don't see it.", "start": 2531.67, "duration": 1.51}, {"text": "I don't see what we use--", "start": 2533.18, "duration": 1.11}, {"text": "I don't see it being a\nprimary issue with equities.", "start": 2534.29, "duration": 3.11}, {"text": "So if you were going to apply\nthis to equities, trading,", "start": 2537.4, "duration": 2.74}, {"text": "any cash instrument\nbasically, I don't", "start": 2540.14, "duration": 3.75}, {"text": "see the huge economic\nvalue for netting.", "start": 2543.89, "duration": 3.63}, {"text": "GARY GENSLER: The huge economic\nbenefit for netting currently", "start": 2547.52, "duration": 4.71}, {"text": "is a lot of\noperational efficiency.", "start": 2552.23, "duration": 3.865}, {"text": "AUDIENCE: Sure.", "start": 2556.095, "duration": 0.625}, {"text": "But if you're going to\nplace that with some--", "start": 2556.72, "duration": 2.75}, {"text": "GARY GENSLER: No.", "start": 2559.47, "duration": 0.71}, {"text": "And then also, because there\nis two day counterparty risk,", "start": 2560.18, "duration": 5.34}, {"text": "you are lowering\nthat two day whatever", "start": 2565.52, "duration": 3.36}, {"text": "measure equity volatility, two\nday equity volatility risk,", "start": 2568.88, "duration": 6.58}, {"text": "usually not collateralized.", "start": 2575.46, "duration": 1.75}, {"text": "AUDIENCE: I'm just\ncommenting on whether this--", "start": 2581.58, "duration": 3.54}, {"text": "you said the price that you pay\nfor replacing this system with", "start": 2585.12, "duration": 7.12}, {"text": "the blockchain based one would\nbe that you cannot net up.", "start": 2592.24, "duration": 3.848}, {"text": "GARY GENSLER: I should have\nsaid something in addition.", "start": 2596.088, "duration": 2.292}, {"text": "And the market\nparticipants would have", "start": 2598.38, "duration": 1.89}, {"text": "to then prefund their trades.", "start": 2600.27, "duration": 2.82}, {"text": "I think the larger thing--", "start": 2603.09, "duration": 3.03}, {"text": "so if I speak in too much\nfinancial technology,", "start": 2606.12, "duration": 3.46}, {"text": "let me say current markets\nare you can sell or buy", "start": 2609.58, "duration": 4.35}, {"text": "a security without owning the\nsecurity or having the cash.", "start": 2613.93, "duration": 5.98}, {"text": "You can buy something\nand not have the cash.", "start": 2619.91, "duration": 2.51}, {"text": "You have to deliver\nthe cash in two days.", "start": 2622.42, "duration": 3.06}, {"text": "And usually by that\nevening or the next day,", "start": 2625.48, "duration": 2.22}, {"text": "you have to show\nyou have the cash.", "start": 2627.7, "duration": 2.88}, {"text": "You can sell a security\nwithout owning the security.", "start": 2630.58, "duration": 2.94}, {"text": "And you only have to\nreally kind of deliver", "start": 2633.52, "duration": 1.8}, {"text": "it, generally speaking,\nthe next day, on t plus 1.", "start": 2635.32, "duration": 5.59}, {"text": "If you went to a true\nsimultaneous clearing settling", "start": 2640.91, "duration": 3.78}, {"text": "and execution market,\nyou'd have to have", "start": 2644.69, "duration": 2.58}, {"text": "the cash and the security\nbefore you execute.", "start": 2647.27, "duration": 4.87}, {"text": "And I think that's the\nlarger piece of it,", "start": 2652.14, "duration": 2.24}, {"text": "much larger than netting.", "start": 2654.38, "duration": 3.277}, {"text": "AUDIENCE: I understand the cash.", "start": 2657.657, "duration": 1.333}, {"text": "But you need the\nsecurity, right?", "start": 2658.99, "duration": 1.59}, {"text": "Because if you're\ngoing to buy it--", "start": 2660.58, "duration": 2.04}, {"text": "if you sell it and\nyou don't have it,", "start": 2662.62, "duration": 2.76}, {"text": "then you know it's going\nto take two days to get one", "start": 2665.38, "duration": 4.76}, {"text": "to cover your first.", "start": 2670.14, "duration": 2.122}, {"text": "GARY GENSLER: So through your\nprime brokerage arrangement--", "start": 2672.262, "duration": 2.458}, {"text": "Hugo, remember, has a couple.", "start": 2674.72, "duration": 1.59}, {"text": "He's a big hedge fund.", "start": 2676.31, "duration": 1.925}, {"text": "And he has what's called\na prime brokerage account.", "start": 2678.235, "duration": 2.125}, {"text": "Not at Bear Stearns\nany longer, but maybe", "start": 2680.36, "duration": 3.21}, {"text": "it's at Goldman Sachs.", "start": 2683.57, "duration": 1.18}, {"text": "He's kind of fancy.", "start": 2684.75, "duration": 1.67}, {"text": "He's getting that.", "start": 2686.42, "duration": 2.95}, {"text": "Then his prime\nbrokerage account,", "start": 2689.37, "duration": 1.85}, {"text": "in his legal contractual\narrangements with them,", "start": 2691.22, "duration": 2.4}, {"text": "they will find that\nsecurity for him, maybe", "start": 2693.62, "duration": 4.82}, {"text": "from some other customer.", "start": 2698.44, "duration": 1.62}, {"text": "Maybe that security is\nheld in somebody else's", "start": 2700.06, "duration": 2.49}, {"text": "what's called a margin account.", "start": 2702.55, "duration": 1.86}, {"text": "And they will enter into\nwhat's called a stock borrow.", "start": 2704.41, "duration": 4.11}, {"text": "But when he executes\non the phone,", "start": 2708.52, "duration": 3.12}, {"text": "he doesn't technically\nalready have that security.", "start": 2711.64, "duration": 3.03}, {"text": "He could be shorting it.", "start": 2714.67, "duration": 1.87}, {"text": "And his prime brokerage\naccount could then go find it", "start": 2716.54, "duration": 3.65}, {"text": "from the Goldman Sachs network.", "start": 2720.19, "duration": 3.36}, {"text": "AUDIENCE: But it's not\nbecause you have plus two.", "start": 2723.55, "duration": 2.27}, {"text": "But it's because\nyou have a broker.", "start": 2725.82, "duration": 1.63}, {"text": "GARY GENSLER: Yes.", "start": 2727.45, "duration": 0.75}, {"text": "That's right, combined\nwith t plus 2.", "start": 2728.2, "duration": 2.933}, {"text": "Let's take this.", "start": 2731.133, "duration": 0.667}, {"text": "And then I'm going to move on.", "start": 2731.8, "duration": 1.26}, {"text": "AUDIENCE: Can you just\ntake that one step further", "start": 2733.06, "duration": 2.042}, {"text": "and explain why that's\nbeneficial broadly", "start": 2735.102, "duration": 2.668}, {"text": "versus just the system\nwe've grown accustomed to?", "start": 2737.77, "duration": 2.18}, {"text": "GARY GENSLER: It's a\nreally good question.", "start": 2739.95, "duration": 1.75}, {"text": "Is this just the system\nwe've grown accustomed to?", "start": 2741.7, "duration": 2.083}, {"text": "Or is it beneficial?", "start": 2743.783, "duration": 1.337}, {"text": "It's hard to tell.", "start": 2745.12, "duration": 0.9}, {"text": "It is definitely\nthe system we've", "start": 2746.02, "duration": 1.53}, {"text": "grown accustomed to over\na couple of centuries.", "start": 2747.55, "duration": 3.15}, {"text": "And as we've gone from\ntransaction date plus five,", "start": 2750.7, "duration": 5.17}, {"text": "which most markets\nwere I'm talking", "start": 2755.87, "duration": 2.63}, {"text": "about 50 and 100\nyears ago, maybe it", "start": 2758.5, "duration": 2.7}, {"text": "was even t plus\n10 at some point.", "start": 2761.2, "duration": 1.83}, {"text": "But t plus five to t plus\nthree to now t plus two,", "start": 2763.03, "duration": 4.82}, {"text": "we've started to challenge that.", "start": 2767.85, "duration": 1.39}, {"text": "But in the US, the\nDepository Trust Corporation", "start": 2769.24, "duration": 2.85}, {"text": "provides same day settlement.", "start": 2772.09, "duration": 2.37}, {"text": "And very few accounts ask\nto do same day settlement.", "start": 2774.46, "duration": 5.84}, {"text": "And I think it might be just\nthey've grown accustomed to it.", "start": 2780.3, "duration": 3.69}, {"text": "But I think there is some\nbenefit in this stock,", "start": 2783.99, "duration": 3.33}, {"text": "loan stock borrow side.", "start": 2787.32, "duration": 3.39}, {"text": "But I stand with\nwhat I said earlier.", "start": 2790.71, "duration": 3.04}, {"text": "I think the market could\nwork the other way.", "start": 2793.75, "duration": 3.35}, {"text": "But it would be\na big adjustment.", "start": 2797.1, "duration": 3.52}, {"text": "And there are some\nbenefits, because then", "start": 2800.62, "duration": 1.89}, {"text": "Hugo, this hedge fund,\nis being extended credit", "start": 2802.51, "duration": 3.27}, {"text": "by his prime brokerage account.", "start": 2805.78, "duration": 2.8}, {"text": "And the prime broker is\nmaking some money on it.", "start": 2808.58, "duration": 2.23}, {"text": "But also Hugo's taking\nrisk in that arrangement.", "start": 2810.81, "duration": 5.16}, {"text": "Prefunding it would\nbe a different model.", "start": 2815.97, "duration": 3.99}, {"text": "Some argue it would have less\nliquidity in the marketplace.", "start": 2819.96, "duration": 3.42}, {"text": "It would make shorting\nstocks a little costlier.", "start": 2823.38, "duration": 4.215}, {"text": "I'm not sure they're right.", "start": 2827.595, "duration": 1.125}, {"text": "But their argument\nis that I'd have", "start": 2828.72, "duration": 1.98}, {"text": "to borrow the securities\nalways, 100%, and halve it off", "start": 2830.7, "duration": 5.22}, {"text": "before I sell, even if I'm\na multi-billion dollar hedge", "start": 2835.92, "duration": 3.84}, {"text": "fund that has some\ncredit worthiness.", "start": 2839.76, "duration": 3.028}, {"text": "Kelly.", "start": 2845.31, "duration": 0.5}, {"text": "AUDIENCE: So the paper mentions\nthat their new system fails", "start": 2845.81, "duration": 5.4}, {"text": "to basically recognize these\nchallenges, such as the fact", "start": 2851.21, "duration": 3.96}, {"text": "that it'd be\nadvantaging the capital", "start": 2855.17, "duration": 1.83}, {"text": "and operational efficiencies.", "start": 2857.0, "duration": 1.632}, {"text": "But it goes on to\nsay that it would", "start": 2858.632, "duration": 1.458}, {"text": "be a step backwards for the\nworld's most liquid market.", "start": 2860.09, "duration": 2.99}, {"text": "So what would necessarily\nbe implications", "start": 2863.08, "duration": 2.92}, {"text": "for illiquid markets?", "start": 2866.0, "duration": 1.62}, {"text": "Would it basically be that\npeople can make trades", "start": 2867.62, "duration": 2.91}, {"text": "without having to interface\nwith extensions of credit?", "start": 2870.53, "duration": 3.745}, {"text": "GARY GENSLER: Are you talking\nabout illiquid markets that", "start": 2874.275, "duration": 2.375}, {"text": "are centrally cleared\nor illiquid markets that", "start": 2876.65, "duration": 2.31}, {"text": "have no central clearing?", "start": 2878.96, "duration": 1.732}, {"text": "AUDIENCE: I guess maybe both.", "start": 2880.692, "duration": 1.208}, {"text": "I'm just trying to understand\nwhat the counter would", "start": 2881.9, "duration": 3.48}, {"text": "be, that saying that there would\nbe advantages, efficiencies", "start": 2885.38, "duration": 3.75}, {"text": "in liquid markets.", "start": 2889.13, "duration": 1.39}, {"text": "But what with the opposite be?", "start": 2890.52, "duration": 3.23}, {"text": "Would there not be implications\nfor the [INAUDIBLE] markets?", "start": 2893.75, "duration": 4.18}, {"text": "GARY GENSLER: So\nKelly's asking--", "start": 2897.93, "duration": 1.533}, {"text": "I don't remember the\ncomment, because it", "start": 2899.463, "duration": 1.667}, {"text": "was in the Australian\nStock Exchange one.", "start": 2901.13, "duration": 3.55}, {"text": "So in non-cleared\nmarkets, things", "start": 2904.68, "duration": 5.75}, {"text": "that are just so\nilliquid-- my house.", "start": 2910.43, "duration": 2.97}, {"text": "It's not cleared.", "start": 2913.4, "duration": 0.84}, {"text": "It's not centrally cleared.", "start": 2914.24, "duration": 2.16}, {"text": "Certain parts of the derivatives\nmarkets aren't centrally clear.", "start": 2916.4, "duration": 3.0}, {"text": "They're not, quote,\n\"liquid\" enough.", "start": 2919.4, "duration": 2.96}, {"text": "So I don't know.", "start": 2922.36, "duration": 0.75}, {"text": "I don't know the comment.", "start": 2923.11, "duration": 1.47}, {"text": "Maybe see me in class.", "start": 2924.58, "duration": 1.17}, {"text": "And I'll look at the comment\nand try to nail it for you.", "start": 2925.75, "duration": 3.33}, {"text": "Is that all right?", "start": 2929.08, "duration": 2.53}, {"text": "So I wanted to put this chart\nup, because it was from 2011.", "start": 2931.61, "duration": 2.91}, {"text": "I remembered it when\nI was at the CFTC.", "start": 2934.52, "duration": 2.55}, {"text": "But somebody at\nthe Fed of Chicago", "start": 2937.07, "duration": 2.22}, {"text": "made this chart about\nthe US clearing systems.", "start": 2939.29, "duration": 3.6}, {"text": "Yellow are all clearing houses.", "start": 2942.89, "duration": 2.81}, {"text": "Red, the SEC, the Federal\nReserve, New York--", "start": 2945.7, "duration": 2.2}, {"text": "AUDIENCE: SBD?", "start": 2951.162, "duration": 1.076}, {"text": "GARY GENSLER: Yeah.", "start": 2952.238, "duration": 0.792}, {"text": "SEC, CFTC, and the\nFederal Reserve.", "start": 2953.03, "duration": 2.16}, {"text": "But they might have--", "start": 2955.19, "duration": 1.9}, {"text": "New York.", "start": 2957.09, "duration": 0.5}, {"text": "I don't even know\nwho New York SB--", "start": 2957.59, "duration": 1.503}, {"text": "AUDIENCE: New York State\nBoard of Derivatives.", "start": 2959.093, "duration": 1.917}, {"text": "GARY GENSLER: Yeah.", "start": 2961.01, "duration": 2.41}, {"text": "Somebody from the\nChicago Fed was", "start": 2963.42, "duration": 1.92}, {"text": "trying to make the case that\nour regulatory system in the US", "start": 2965.34, "duration": 3.42}, {"text": "was a little bit complicated.", "start": 2968.76, "duration": 2.32}, {"text": "And I think this was in\nthe midst of the debate", "start": 2971.08, "duration": 2.27}, {"text": "about Dodd-Frank,\nthat they thought", "start": 2973.35, "duration": 1.65}, {"text": "all oversight of\nclearing houses should", "start": 2975.0, "duration": 2.28}, {"text": "move to the Federal Reserve.", "start": 2977.28, "duration": 1.86}, {"text": "But I remembered the\nchart and found it.", "start": 2979.14, "duration": 1.8}, {"text": "And I wanted to\nshare it with you.", "start": 2980.94, "duration": 1.96}, {"text": "But the yellow are all\nthe clearing houses.", "start": 2982.9, "duration": 2.69}, {"text": "There are a lot of\nclearing houses in the US.", "start": 2985.59, "duration": 2.28}, {"text": "There's one for bonds.", "start": 2987.87, "duration": 1.54}, {"text": "There's one for equities.", "start": 2989.41, "duration": 1.46}, {"text": "There's multiple\nones for derivatives,", "start": 2990.87, "duration": 2.1}, {"text": "both from cash and\ninterest rate derivatives", "start": 2992.97, "duration": 2.58}, {"text": "to energy derivatives to\ncredit default derivatives", "start": 2995.55, "duration": 2.82}, {"text": "and so forth.", "start": 2998.37, "duration": 1.11}, {"text": "There's ones for options.", "start": 2999.48, "duration": 3.6}, {"text": "So I just wanted to lay it out.", "start": 3003.08, "duration": 5.0}, {"text": "Finance is pretty complex.", "start": 3008.08, "duration": 3.22}, {"text": "This is all\ndigitized, by the way.", "start": 3011.3, "duration": 3.9}, {"text": "But in this\ncomplexity, that's also", "start": 3015.2, "duration": 2.76}, {"text": "where I think there's some\nopportunity, whether it's", "start": 3017.96, "duration": 2.61}, {"text": "permissioned blockchain\nand not fully permissioned", "start": 3020.57, "duration": 3.63}, {"text": "list with tokens,\nand inspired by--", "start": 3024.2, "duration": 3.99}, {"text": "the green are exchanges.", "start": 3031.58, "duration": 2.22}, {"text": "And I don't even think they\nput a color up for brokers,", "start": 3033.8, "duration": 2.43}, {"text": "did they?", "start": 3036.23, "duration": 0.5}, {"text": "Because then you'd\nhave hundreds.", "start": 3036.73, "duration": 3.16}, {"text": "There are multiple parties\nsharing ledgers and reconciling", "start": 3039.89, "duration": 4.44}, {"text": "their ledgers.", "start": 3044.33, "duration": 0.84}, {"text": "Reconciliation means\nI keep a ledger.", "start": 3045.17, "duration": 2.04}, {"text": "Tom keeps a ledger.", "start": 3047.21, "duration": 1.3}, {"text": "It's both on our\ndatabase systems.", "start": 3048.51, "duration": 1.97}, {"text": "And we keep testing and ensuring\nthat we have the same records.", "start": 3050.48, "duration": 3.765}, {"text": "This is a system that,\nby its complexity", "start": 3057.03, "duration": 3.09}, {"text": "and by its copies of\nledgers and reconciliation,", "start": 3060.12, "duration": 5.84}, {"text": "has a lot of opportunity\nfor greater efficiency.", "start": 3065.96, "duration": 4.14}, {"text": "And the question is whether\nblockchain technology,", "start": 3070.1, "duration": 2.52}, {"text": "maybe permissioned, can bring\nsome of that efficiency.", "start": 3072.62, "duration": 4.64}, {"text": "That's the thought.", "start": 3077.26, "duration": 1.22}, {"text": "And that's what the\nchart was just trying--", "start": 3078.48, "duration": 1.792}, {"text": "by the way, the Congress\ndidn't agree with the Fed.", "start": 3082.28, "duration": 3.21}, {"text": "They left the authorities\nat the SEC and CFTC.", "start": 3085.49, "duration": 3.06}, {"text": "And those are for\nstories other times.", "start": 3088.55, "duration": 3.33}, {"text": "I personally felt it could\nbe a shared authority.", "start": 3091.88, "duration": 2.7}, {"text": "And we ended up with\nsome shared authorities.", "start": 3094.58, "duration": 2.07}, {"text": "But I thought that the CFTC\nand SEC have domain knowledge.", "start": 3096.65, "duration": 4.36}, {"text": "And it really important to keep\nthe SEC involved in securities", "start": 3101.01, "duration": 3.26}, {"text": "clearing and the CFTC involved\nin derivatives clearing", "start": 3104.27, "duration": 3.99}, {"text": "for that domain knowledge, but\nthat the Federal Reserve also", "start": 3108.26, "duration": 4.71}, {"text": "came in under something called\nTitle VIII of Dodd-Frank.", "start": 3112.97, "duration": 2.73}, {"text": "And they also got authorities.", "start": 3115.7, "duration": 1.74}, {"text": "So we made it more complicated,\nbecause now there's", "start": 3117.44, "duration": 2.88}, {"text": "multiple dotted lines for this.", "start": 3120.32, "duration": 4.11}, {"text": "The Federal Reserve basically\nhas an account with everybody.", "start": 3124.43, "duration": 3.63}, {"text": "Or they have some\noversight of everybody.", "start": 3128.06, "duration": 4.35}, {"text": "So then the question on\nblockchain technology,", "start": 3132.41, "duration": 1.925}, {"text": "could you take the clearing\nhouse out of the middle", "start": 3134.335, "duration": 2.125}, {"text": "and do the thing on the right?", "start": 3136.46, "duration": 2.01}, {"text": "And my question for you all is,\ndo you think the economics--", "start": 3138.47, "duration": 4.03}, {"text": "I'm not talking\nabout the technology.", "start": 3142.5, "duration": 2.07}, {"text": "I'm not talking about\nwhether it's performance.", "start": 3144.57, "duration": 2.36}, {"text": "If you wish, you can go five\nor 10 years down the road", "start": 3146.93, "duration": 2.61}, {"text": "and say it's got all this\nscalability and performance.", "start": 3149.54, "duration": 3.12}, {"text": "Do you think the technology,\nwithout something", "start": 3152.66, "duration": 3.45}, {"text": "in the middle, what's\nthe economics about that?", "start": 3156.11, "duration": 4.14}, {"text": "Anybody?", "start": 3160.25, "duration": 1.95}, {"text": "Eilon?", "start": 3162.2, "duration": 0.77}, {"text": "AUDIENCE: I still want\nto support the left side", "start": 3162.97, "duration": 2.91}, {"text": "for liquid markets\nbecause of the netting.", "start": 3165.88, "duration": 1.765}, {"text": "GARY GENSLER:\nBecause of netting.", "start": 3167.645, "duration": 1.375}, {"text": "AUDIENCE: Yes.", "start": 3169.02, "duration": 0.583}, {"text": "I can't see a\nblockchain solution", "start": 3172.8, "duration": 1.38}, {"text": "working well when\nyou need netting", "start": 3174.18, "duration": 2.67}, {"text": "to enjoy the efficiencies\nof selling and shorting,", "start": 3176.85, "duration": 3.87}, {"text": "shorting basically.", "start": 3180.72, "duration": 0.86}, {"text": "GARY GENSLER: Yeah.", "start": 3181.58, "duration": 0.792}, {"text": "But the question really\nis, can you somehow,", "start": 3182.372, "duration": 3.208}, {"text": "on the right with\nshared ledger, still", "start": 3185.58, "duration": 4.51}, {"text": "get some benefit of netting?", "start": 3190.09, "duration": 2.32}, {"text": "Right?", "start": 3192.41, "duration": 0.5}, {"text": "You're saying you're\ninclined here,", "start": 3192.91, "duration": 2.04}, {"text": "because you want to get the\nnetting for economic reasons.", "start": 3194.95, "duration": 4.87}, {"text": "So as a ledger structure,\ncan you get the netting here?", "start": 3199.82, "duration": 2.87}, {"text": "Shimon?", "start": 3202.69, "duration": 1.93}, {"text": "AUDIENCE: You don't\nneed the netting", "start": 3204.62, "duration": 1.5}, {"text": "if it happens simultaneously.", "start": 3206.12, "duration": 2.97}, {"text": "Netting is it it is basically--", "start": 3209.09, "duration": 3.183}, {"text": "again, with cash instrument.", "start": 3212.273, "duration": 1.167}, {"text": "I'm not talking\nabout derivatives.", "start": 3213.44, "duration": 1.417}, {"text": "Derivatives is a\ndifferent issue.", "start": 3214.857, "duration": 1.853}, {"text": "With cash instruments,\nthe only reason", "start": 3216.71, "duration": 1.62}, {"text": "why you have\ncounterparty risk is", "start": 3218.33, "duration": 1.08}, {"text": "because it's not clear--\nit was my understanding.", "start": 3219.41, "duration": 2.2}, {"text": "Correct me-- is\nbecause you don't", "start": 3221.61, "duration": 2.03}, {"text": "have instantaneous settlement.", "start": 3223.64, "duration": 2.25}, {"text": "If you have a\n[INAUDIBLE] settlement,", "start": 3225.89, "duration": 1.59}, {"text": "then you don't\ncare about netting.", "start": 3227.48, "duration": 1.417}, {"text": "AUDIENCE: You care because you\nface so many transaction fees.", "start": 3228.897, "duration": 2.653}, {"text": "AUDIENCE: No.", "start": 3231.55, "duration": 0.542}, {"text": "But that's going to be\na lot more efficient.", "start": 3232.092, "duration": 1.833}, {"text": "So why-- again, do you think the\n[? real ?] transaction fees are", "start": 3233.925, "duration": 6.645}, {"text": "a big economic issue here?", "start": 3240.57, "duration": 1.73}, {"text": "AUDIENCE: Yes.", "start": 3242.3, "duration": 0.61}, {"text": "That's what I think.", "start": 3242.91, "duration": 1.02}, {"text": "GARY GENSLER: And I'm\nsorry that you don't.", "start": 3243.93, "duration": 2.11}, {"text": "AUDIENCE: So now it's fine.", "start": 3246.04, "duration": 1.18}, {"text": "I don't know.", "start": 3247.22, "duration": 0.542}, {"text": "I mean, I don't know.", "start": 3247.762, "duration": 0.964}, {"text": "For really intense\nhelp, how much", "start": 3248.726, "duration": 2.304}, {"text": "do you pay per transaction with\nthe clearing house and without?", "start": 3251.03, "duration": 4.02}, {"text": "Maybe the net will give you\nonly 10% of the transaction.", "start": 3255.05, "duration": 3.9}, {"text": "But the cost of having\nthe clearing house", "start": 3258.95, "duration": 2.28}, {"text": "is more than 10 times.", "start": 3261.23, "duration": 1.673}, {"text": "AUDIENCE: Maybe.", "start": 3262.903, "duration": 0.667}, {"text": "AUDIENCE: So the economics\ndepends on those numbers,", "start": 3263.57, "duration": 2.19}, {"text": "I think.", "start": 3265.76, "duration": 2.08}, {"text": "GARY GENSLER: Is\nthat a question?", "start": 3267.84, "duration": 2.73}, {"text": "Hugo?", "start": 3270.57, "duration": 0.57}, {"text": "AUDIENCE: Yeah.", "start": 3271.14, "duration": 0.99}, {"text": "So you still can get\nsome of the netting.", "start": 3272.13, "duration": 3.09}, {"text": "Let's just talk about blockchain\ntransactions on Bitcoin.", "start": 3275.22, "duration": 3.03}, {"text": "You can batch transactions.", "start": 3278.25, "duration": 1.86}, {"text": "So you can have multiple\ninputs and multiple outputs.", "start": 3280.11, "duration": 2.85}, {"text": "And that's kind of like netting.", "start": 3282.96, "duration": 1.63}, {"text": "Then you have to\nhave a second system", "start": 3284.59, "duration": 2.092}, {"text": "on top of that that\nkeeps track of what's", "start": 3286.682, "duration": 1.708}, {"text": "going on throughout the day.", "start": 3288.39, "duration": 1.167}, {"text": "And then it just\ndoes the transactions", "start": 3289.557, "duration": 2.873}, {"text": "on a daily basis or an\nhourly basis or whatever.", "start": 3292.43, "duration": 3.64}, {"text": "That takes care of that netting.", "start": 3296.07, "duration": 2.5}, {"text": "Right?", "start": 3298.57, "duration": 0.59}, {"text": "GARY GENSLER: So\nHugo contends maybe", "start": 3299.16, "duration": 1.5}, {"text": "you can get this economic\nthing called netting", "start": 3300.66, "duration": 2.49}, {"text": "and still have a shared\ndistributed ledger.", "start": 3303.15, "duration": 3.42}, {"text": "Or you could do it off chain.", "start": 3306.57, "duration": 3.06}, {"text": "I think, Shimon\nto your question,", "start": 3309.63, "duration": 3.27}, {"text": "this is a big\neconomic thing either", "start": 3312.9, "duration": 2.46}, {"text": "because we've just\ngrown accustomed to it", "start": 3315.36, "duration": 1.86}, {"text": "over a couple centuries or\nit's fundamental to how markets", "start": 3317.22, "duration": 4.14}, {"text": "trade, that we don't prefund.", "start": 3321.36, "duration": 4.1}, {"text": "It's that economics that\nblockchain technology", "start": 3325.46, "duration": 4.31}, {"text": "will challenge.", "start": 3329.77, "duration": 1.92}, {"text": "But we might stay with\na central clearing house", "start": 3331.69, "duration": 2.37}, {"text": "if the economics are that value.", "start": 3334.06, "duration": 1.71}, {"text": "Well, the economics of, in\nessence, not prefunding,", "start": 3335.77, "duration": 5.13}, {"text": "and thus, some\ndelayed settlement.", "start": 3340.9, "duration": 4.49}, {"text": "Whereas in the past, we always\nhad delayed settlement at first", "start": 3345.39, "duration": 2.82}, {"text": "because there was\nso much paperwork.", "start": 3348.21, "duration": 1.89}, {"text": "We had to have\ndelayed settlement.", "start": 3350.1, "duration": 1.98}, {"text": "We went digitized.", "start": 3352.08, "duration": 1.62}, {"text": "And now, really in 2018, we\ndon't need delayed settlement", "start": 3353.7, "duration": 5.78}, {"text": "or batch processing.", "start": 3359.48, "duration": 3.65}, {"text": "So now you've\nexposed, well, wait.", "start": 3363.13, "duration": 1.88}, {"text": "What are the economics?", "start": 3365.01, "duration": 2.66}, {"text": "Tom and then Alin?", "start": 3367.67, "duration": 1.095}, {"text": "AUDIENCE: Could you still\nhave a delayed settlement", "start": 3368.765, "duration": 2.125}, {"text": "with a blockchain system just\nby using a smart contract?", "start": 3370.89, "duration": 3.4}, {"text": "GARY GENSLER: You could.", "start": 3374.29, "duration": 1.0}, {"text": "Absolutely.", "start": 3375.29, "duration": 0.63}, {"text": "AUDIENCE: I mean, you\nstill keep this system", "start": 3375.92, "duration": 3.33}, {"text": "that people are\naccustomed to, but do it", "start": 3379.25, "duration": 3.96}, {"text": "without the economic red\nfor the clearing house's", "start": 3383.21, "duration": 2.7}, {"text": "sides or [INAUDIBLE].", "start": 3385.91, "duration": 1.17}, {"text": "GARY GENSLER: Yes.", "start": 3387.08, "duration": 0.75}, {"text": "And it's what the\nAustralian Stock Exchange", "start": 3387.83, "duration": 3.18}, {"text": "says they are using with the\ndigital asset company, Blythe", "start": 3391.01, "duration": 5.85}, {"text": "Masters' company that's\ntheir outside vendor using", "start": 3396.86, "duration": 2.76}, {"text": "the HyperLedger Fabric.", "start": 3399.62, "duration": 1.29}, {"text": "And they're using the code.", "start": 3400.91, "duration": 1.44}, {"text": "They call a DAML, or Digital\nAsset Machine Language?", "start": 3402.35, "duration": 5.235}, {"text": "I don't know what the M is.", "start": 3407.585, "duration": 1.125}, {"text": "But they call it DAML.", "start": 3408.71, "duration": 2.896}, {"text": "Alin?", "start": 3411.606, "duration": 1.191}, {"text": "AUDIENCE: Yes.", "start": 3412.797, "duration": 0.583}, {"text": "We've said you cannot\nprefund on the right.", "start": 3413.38, "duration": 2.683}, {"text": "Is that correct?", "start": 3416.063, "duration": 0.667}, {"text": "GARY GENSLER: I think you\ncould through smart contracts.", "start": 3421.927, "duration": 2.333}, {"text": "I think you could find this.", "start": 3424.26, "duration": 1.53}, {"text": "But the challenge with just\nthe picture, the picture", "start": 3425.79, "duration": 5.07}, {"text": "suggests there's no\ncentral counterparty", "start": 3430.86, "duration": 2.25}, {"text": "to do all the netting.", "start": 3433.11, "duration": 2.61}, {"text": "And so the question is, can\nyou have this ledger structure", "start": 3435.72, "duration": 3.57}, {"text": "and still find a way to\nnet down all the positions?", "start": 3439.29, "duration": 4.47}, {"text": "AUDIENCE: Well,\nlike Shimon said,", "start": 3443.76, "duration": 1.85}, {"text": "there is no need for that.", "start": 3445.61, "duration": 2.53}, {"text": "You get that implicitly\nby recording everything", "start": 3448.14, "duration": 2.31}, {"text": "and executing.", "start": 3450.45, "duration": 1.222}, {"text": "GARY GENSLER: But if you're\nrecording-- all right.", "start": 3451.672, "duration": 2.083}, {"text": "I'm agreeing with that, too.", "start": 3453.755, "duration": 1.395}, {"text": "But that's where I\nget to if you need", "start": 3455.15, "duration": 1.78}, {"text": "to do Shimon's approach, which\nis simultaneous execution", "start": 3456.93, "duration": 5.43}, {"text": "and settlement, then\nyou need to prefund,", "start": 3462.36, "duration": 2.82}, {"text": "even if that prefunding\nis by nanoseconds.", "start": 3465.18, "duration": 2.37}, {"text": "But you need to prefund.", "start": 3467.55, "duration": 1.827}, {"text": "AUDIENCE: Not necessarily.", "start": 3469.377, "duration": 1.083}, {"text": "You could, sort of\noptimistically, you", "start": 3470.46, "duration": 1.97}, {"text": "could post a transaction that\nsays, I want to buy a stock.", "start": 3472.43, "duration": 3.465}, {"text": "And I'm not going\nto prove to you", "start": 3475.895, "duration": 1.375}, {"text": "that I have money to buy it.", "start": 3477.27, "duration": 1.71}, {"text": "You record it, if you were\nsaying optimistically.", "start": 3478.98, "duration": 2.92}, {"text": "And later on--", "start": 3481.9, "duration": 2.838}, {"text": "GARY GENSLER: It depends.", "start": 3484.738, "duration": 1.042}, {"text": "The word record-- let me use\na different word, settle.", "start": 3485.78, "duration": 4.42}, {"text": "Settlement means final\nlegal rights have moved", "start": 3490.2, "duration": 3.27}, {"text": "from one party to another.", "start": 3493.47, "duration": 2.91}, {"text": "So the word settlement\nhas a meaning that I just", "start": 3496.38, "duration": 2.39}, {"text": "want to come back to.", "start": 3498.77, "duration": 1.29}, {"text": "It means I'm\nrecording on a ledger", "start": 3500.06, "duration": 2.67}, {"text": "that I no longer\nhave legal rights.", "start": 3502.73, "duration": 2.34}, {"text": "So this alpha has\nlegal rights to it.", "start": 3505.07, "duration": 1.82}, {"text": "And I think you would have\nto prefund if you were", "start": 3509.58, "duration": 2.5}, {"text": "doing true settlement ledgers.", "start": 3512.08, "duration": 2.4}, {"text": "AUDIENCE: Sure, sure.", "start": 3514.48, "duration": 1.62}, {"text": "I guess I'm saying it seems like\nyou could simulate the clearing", "start": 3516.1, "duration": 2.76}, {"text": "house.", "start": 3518.86, "duration": 1.56}, {"text": "In the right side\nof this picture,", "start": 3520.42, "duration": 2.022}, {"text": "the clearing house\njust distributed", "start": 3522.442, "duration": 1.458}, {"text": "using the consensus protocol.", "start": 3523.9, "duration": 1.17}, {"text": "GARY GENSLER: Right.", "start": 3525.07, "duration": 0.87}, {"text": "I think you're right\nthat you could.", "start": 3525.94, "duration": 2.653}, {"text": "But if you're going\nall the way to where", "start": 3528.593, "duration": 1.667}, {"text": "Shimon is, like Bitcoin, and\nyou're doing final settlement,", "start": 3530.26, "duration": 4.33}, {"text": "final settlement\nrecordation, then I", "start": 3534.59, "duration": 2.58}, {"text": "think you have to prefund.", "start": 3537.17, "duration": 2.087}, {"text": "A couple of questions over here.", "start": 3539.257, "duration": 1.333}, {"text": "Eric, Ross.", "start": 3540.59, "duration": 2.11}, {"text": "AUDIENCE: The reason that the\nprefunding was [INAUDIBLE]", "start": 3542.7, "duration": 3.77}, {"text": "performed in the validation of\nthe block process, because--", "start": 3546.47, "duration": 5.192}, {"text": "GARY GENSLER: It could.", "start": 3551.662, "duration": 0.958}, {"text": "I said it could even be\ndone during the nanoseconds.", "start": 3552.62, "duration": 2.49}, {"text": "But it has to be done before\nyou move the settlement.", "start": 3555.11, "duration": 3.27}, {"text": "And that's what's\ncalled clearing.", "start": 3558.38, "duration": 2.76}, {"text": "So it's a question of whether\nyou have simultaneous execution", "start": 3561.14, "duration": 2.94}, {"text": "and settlement, or you still\nhave execution, clearing,", "start": 3564.08, "duration": 4.05}, {"text": "settlement, even if\nseparated by seconds,", "start": 3568.13, "duration": 3.76}, {"text": "but still literally\nget granular.", "start": 3571.89, "duration": 3.36}, {"text": "I apologize.", "start": 3575.25, "duration": 0.75}, {"text": "This stuff is that granular.", "start": 3576.0, "duration": 3.38}, {"text": "Back here.", "start": 3579.38, "duration": 1.93}, {"text": "And then I'm going to move on.", "start": 3581.31, "duration": 2.07}, {"text": "AUDIENCE: Why do you\nconsider prefunding--", "start": 3583.38, "duration": 2.483}, {"text": "maybe you don't.", "start": 3585.863, "duration": 0.667}, {"text": "But it seems simply\nyou consider prefunding", "start": 3586.53, "duration": 2.785}, {"text": "before you're\nallowed to transact", "start": 3589.315, "duration": 1.375}, {"text": "a negative economically.", "start": 3590.69, "duration": 1.822}, {"text": "GARY GENSLER: I\nshouldn't sound that way.", "start": 3592.512, "duration": 1.708}, {"text": "It's just that for\na couple years,", "start": 3594.22, "duration": 2.33}, {"text": "we've had delayed settlement.", "start": 3596.55, "duration": 2.89}, {"text": "And so I'm saying if you are\na proponent of a system that", "start": 3599.44, "duration": 4.31}, {"text": "has simultaneous\nexecution and settlement,", "start": 3603.75, "duration": 4.64}, {"text": "you just have to deal with it.", "start": 3608.39, "duration": 1.42}, {"text": "You're changing\nthe economic models", "start": 3609.81, "duration": 1.91}, {"text": "that have been so common\nin the capital markets.", "start": 3611.72, "duration": 4.0}, {"text": "And when you take\nthat on, you just", "start": 3615.72, "duration": 1.46}, {"text": "have to think through what are\nthe economics of that shift,", "start": 3617.18, "duration": 5.06}, {"text": "from in essence a\ndelayed settlement,", "start": 3622.24, "duration": 3.04}, {"text": "thus modest but\nreal counterparty", "start": 3625.28, "duration": 2.94}, {"text": "risk that Hugo's got a prime\nbroker and he's got that,", "start": 3628.22, "duration": 3.9}, {"text": "and moving to this new\nmodel in capital markets.", "start": 3632.12, "duration": 4.26}, {"text": "So I shouldn't come\nacross as negative.", "start": 3636.38, "duration": 2.1}, {"text": "But I'm saying at least\nit's a hurdle that you've", "start": 3638.48, "duration": 3.84}, {"text": "got an adoption curve that's\ngoing to be a challenge,", "start": 3642.32, "duration": 3.0}, {"text": "I think, at a minimum.", "start": 3645.32, "duration": 2.39}, {"text": "DTCC, when I first\nspoke to them--", "start": 3651.55, "duration": 2.67}, {"text": "and I've had a lively, ongoing\ndialogue with the folks", "start": 3654.22, "duration": 4.26}, {"text": "there on an occasional basis.", "start": 3658.48, "duration": 3.63}, {"text": "This was the biggest\nissue they raised.", "start": 3662.11, "duration": 1.86}, {"text": "They said they looked\nat blockchain technology", "start": 3663.97, "duration": 2.67}, {"text": "starting several years ago.", "start": 3666.64, "duration": 2.31}, {"text": "They talked to\ntheir customer base.", "start": 3668.95, "duration": 2.13}, {"text": "And they couldn't find that\ntheir customer base really", "start": 3671.08, "duration": 2.25}, {"text": "wanted to go to simultaneous\nexecution and settlement.", "start": 3673.33, "duration": 3.66}, {"text": "They have same day settlement.", "start": 3676.99, "duration": 1.44}, {"text": "But it's end of day settlement.", "start": 3678.43, "duration": 1.56}, {"text": "So there's still several hours.", "start": 3679.99, "duration": 3.263}, {"text": "But they said, we\ndon't have a lot", "start": 3683.253, "duration": 1.417}, {"text": "of customers that really\nwant simultaneous execution", "start": 3684.67, "duration": 3.72}, {"text": "and settlement.", "start": 3688.39, "duration": 1.29}, {"text": "Now, that was commenting\non the demand side.", "start": 3689.68, "duration": 2.965}, {"text": "It's another\nquestion whether you", "start": 3692.645, "duration": 1.375}, {"text": "could adopt this lower cost,\ndo something, and change", "start": 3694.02, "duration": 3.48}, {"text": "your capital market.", "start": 3697.5, "duration": 0.92}, {"text": "So this is another look at it.", "start": 3703.26, "duration": 3.12}, {"text": "This is also from the\nAustralian Stock Exchange,", "start": 3706.38, "duration": 2.7}, {"text": "I think, website if I remember.", "start": 3709.08, "duration": 1.48}, {"text": "But maybe it was\nanother website.", "start": 3710.56, "duration": 1.52}, {"text": "The question is, could you\ntake out these middle parts?", "start": 3712.08, "duration": 2.79}, {"text": "This is like\nblockchain architecture", "start": 3714.87, "duration": 2.31}, {"text": "for clearing\ncentral counterparty", "start": 3717.18, "duration": 3.0}, {"text": "and the central\nsecurities depository.", "start": 3720.18, "duration": 2.31}, {"text": "Because there's also somebody\nwho's got the central registry,", "start": 3722.49, "duration": 4.61}, {"text": "and that central registry\nare the two things.", "start": 3727.1, "duration": 2.17}, {"text": "Could you take this\nout completely?", "start": 3729.27, "duration": 2.37}, {"text": "That was the\nquestion, in a sense.", "start": 3731.64, "duration": 3.87}, {"text": "So here are the projects that\nare actually live or being", "start": 3735.51, "duration": 3.81}, {"text": "explored.", "start": 3739.32, "duration": 0.51}, {"text": "And we're going to\ntalk a little bit", "start": 3739.83, "duration": 1.5}, {"text": "about Australian Stock\nExchange in the few minutes we", "start": 3741.33, "duration": 4.0}, {"text": "have left.", "start": 3745.33, "duration": 0.5}, {"text": "But this Australian\nstock Exchange Project", "start": 3745.83, "duration": 3.15}, {"text": "started in 2016.", "start": 3748.98, "duration": 1.65}, {"text": "A bunch of requests\nfor proposals,", "start": 3750.63, "duration": 1.71}, {"text": "like higher digital\nasset holding,", "start": 3752.34, "duration": 2.08}, {"text": "they're actually\nactively working on it.", "start": 3754.42, "duration": 1.94}, {"text": "It's a 25-year-old system.", "start": 3756.36, "duration": 2.41}, {"text": "And Jeff Sprecher said it, too.", "start": 3758.77, "duration": 1.43}, {"text": "He said, you know, they\nhad a legacy system", "start": 3760.2, "duration": 2.16}, {"text": "they needed to replace.", "start": 3762.36, "duration": 1.11}, {"text": "They decided to go with the\nnew technology of the day.", "start": 3763.47, "duration": 3.48}, {"text": "But Jeff wasn't\nconvinced they had to.", "start": 3766.95, "duration": 3.23}, {"text": "But they feel that it\nwas the right thing", "start": 3770.18, "duration": 3.06}, {"text": "to do, to go with that\nnew technology of the day.", "start": 3773.24, "duration": 5.01}, {"text": "They believe-- and they've\nput out reports as recently", "start": 3778.25, "duration": 3.72}, {"text": "as several weeks ago.", "start": 3781.97, "duration": 1.86}, {"text": "They believe they're\non the right path", "start": 3783.83, "duration": 1.71}, {"text": "and that 15 or 20 years from\nnow, every clearing house", "start": 3785.54, "duration": 2.85}, {"text": "will be using what\nthey would consider", "start": 3788.39, "duration": 1.68}, {"text": "a permissioned\nblockchain solution,", "start": 3790.07, "duration": 2.25}, {"text": "because it will so significantly\nlower the back office", "start": 3792.32, "duration": 4.71}, {"text": "costs for their\nmarket participants", "start": 3797.03, "duration": 2.97}, {"text": "who are now holding records.", "start": 3800.0, "duration": 2.01}, {"text": "Each bank, was it 77 members\nfrom an earlier-- yeah.", "start": 3802.01, "duration": 5.61}, {"text": "Each bank has to hold records.", "start": 3807.62, "duration": 2.31}, {"text": "It could be held\nin a shared ledger.", "start": 3809.93, "duration": 2.82}, {"text": "And they would lower\nthe reconciliation cost.", "start": 3812.75, "duration": 2.49}, {"text": "And they believe\nthe second advantage", "start": 3815.24, "duration": 1.74}, {"text": "is using smart contracts.", "start": 3816.98, "duration": 1.65}, {"text": "Now, are they exactly\nthe smart contracts", "start": 3818.63, "duration": 2.94}, {"text": "like on the Ethereum network?", "start": 3821.57, "duration": 1.6}, {"text": "No, because they don't\nhave a native token.", "start": 3823.17, "duration": 2.93}, {"text": "They don't have a DAP\nand a native token.", "start": 3826.1, "duration": 2.07}, {"text": "But it's still automating\ncertain processes,", "start": 3828.17, "duration": 3.24}, {"text": "automating certain I'll call\nit back office processes.", "start": 3831.41, "duration": 5.1}, {"text": "So they're very committed to it.", "start": 3836.51, "duration": 1.62}, {"text": "And they're going to\nroll it out in 2020.", "start": 3838.13, "duration": 2.82}, {"text": "And then, for 12 months,\nrun it simultaneous", "start": 3840.95, "duration": 4.26}, {"text": "with their legacy system.", "start": 3845.21, "duration": 2.38}, {"text": "So their cut over for\nassuring that it's resilient", "start": 3847.59, "duration": 6.39}, {"text": "is at 12 month test.", "start": 3853.98, "duration": 2.67}, {"text": "Most major market\ninfrastructures", "start": 3856.65, "duration": 1.86}, {"text": "that roll things out do not roll\nsimultaneously for 12 months.", "start": 3858.51, "duration": 3.34}, {"text": "But they all roll simultaneous.", "start": 3861.85, "duration": 2.36}, {"text": "Whether it's a month,\nwhether it's 90 days,", "start": 3864.21, "duration": 4.17}, {"text": "you can't cut over the back\noffice of the New York Stock", "start": 3868.38, "duration": 2.82}, {"text": "Exchange and just\ntest it for one day.", "start": 3871.2, "duration": 4.17}, {"text": "Or you can.", "start": 3875.37, "duration": 1.12}, {"text": "It's just kind of\nchoppy and a big risk.", "start": 3876.49, "duration": 4.454}, {"text": "AUDIENCE: Quick question.", "start": 3880.944, "duration": 1.146}, {"text": "Are they going to use a stable\ncoin to settle the transaction?", "start": 3882.09, "duration": 3.195}, {"text": "How are they going to\nsettle the transaction?", "start": 3885.285, "duration": 1.875}, {"text": "Because I can see how you\nissue securities digitally.", "start": 3887.16, "duration": 2.208}, {"text": "But you cannot issue cash.", "start": 3889.368, "duration": 1.372}, {"text": "GARY GENSLER: So\nthis is very good.", "start": 3890.74, "duration": 1.13}, {"text": "It's very good.", "start": 3891.87, "duration": 0.625}, {"text": "So all of these\nclearing houses, they", "start": 3892.495, "duration": 4.445}, {"text": "are the final custodian\nfor the security.", "start": 3896.94, "duration": 3.9}, {"text": "Securities are dematerialized,\nmeaning they're all digital.", "start": 3900.84, "duration": 4.06}, {"text": "And so those digital\nassets are held on a ledger", "start": 3904.9, "duration": 2.99}, {"text": "and what's called\nthe golden record.", "start": 3907.89, "duration": 2.82}, {"text": "This is the words used in\nthe securities business.", "start": 3910.71, "duration": 2.61}, {"text": "The gold record or the\ngolden record, meaning it", "start": 3913.32, "duration": 2.82}, {"text": "is the legal,\nverifiable thing you", "start": 3916.14, "duration": 2.943}, {"text": "can go to in a court of law.", "start": 3919.083, "duration": 1.167}, {"text": "And it says, this\nis who owns this.", "start": 3920.25, "duration": 1.77}, {"text": "Alpha owns it.", "start": 3922.02, "duration": 0.78}, {"text": "Not Hugo.", "start": 3922.8, "duration": 2.28}, {"text": "Sorry.", "start": 3925.08, "duration": 1.71}, {"text": "You're working with Goldman\nSachs, though, right?", "start": 3926.79, "duration": 2.16}, {"text": "That golden record is\nthere for securities.", "start": 3931.77, "duration": 3.06}, {"text": "Who has the golden\nrecord for cash?", "start": 3934.83, "duration": 2.085}, {"text": "AUDIENCE: The central bank?", "start": 3936.915, "duration": 1.125}, {"text": "GARY GENSLER: The central\nbank or the fractional banking", "start": 3938.04, "duration": 3.66}, {"text": "system, their commercial\nbank subledger.", "start": 3941.7, "duration": 2.7}, {"text": "Clearing houses\naround the globe would", "start": 3947.37, "duration": 1.92}, {"text": "like to be able to have direct\naccess to central bank money.", "start": 3949.29, "duration": 4.99}, {"text": "And they currently do not in\nany of the major jurisdictions", "start": 3954.28, "duration": 3.82}, {"text": "that I know.", "start": 3958.1, "duration": 0.57}, {"text": "I think.", "start": 3958.67, "duration": 1.28}, {"text": "So what Australia does now,\nthis is what they do now.", "start": 3959.95, "duration": 4.84}, {"text": "They net everybody down.", "start": 3964.79, "duration": 2.01}, {"text": "They get to t plus two.", "start": 3966.8, "duration": 1.32}, {"text": "They're on that second day.", "start": 3968.12, "duration": 1.26}, {"text": "Everything's netted down.", "start": 3969.38, "duration": 1.11}, {"text": "And they're about to do\nthe whole closing out.", "start": 3970.49, "duration": 3.86}, {"text": "One second before they do\nthe security settlement,", "start": 3974.35, "duration": 3.3}, {"text": "they do the cash settlement.", "start": 3977.65, "duration": 2.65}, {"text": "They call this Delivery\nVersus Payment, DVP.", "start": 3980.3, "duration": 3.082}, {"text": "But they're a clearing house.", "start": 3983.382, "duration": 1.208}, {"text": "And they do not want to take\nrisk with the central bank.", "start": 3984.59, "duration": 3.41}, {"text": "They take all the money\nand settle all the cash", "start": 3988.0, "duration": 3.42}, {"text": "with the Royal Bank of\nAustralia, RBA I guess.", "start": 3991.42, "duration": 3.75}, {"text": "Do I have the right name?", "start": 3995.17, "duration": 1.11}, {"text": "Or is it a different-- is RBA\none of the banks in Australia?", "start": 3996.28, "duration": 4.02}, {"text": "But they settle all the cash.", "start": 4000.3, "duration": 2.01}, {"text": "And just within a\nsecond, they settle.", "start": 4002.31, "duration": 3.48}, {"text": "We think of it as DVP.", "start": 4005.79, "duration": 1.44}, {"text": "But it's actually\ntechnically not.", "start": 4007.23, "duration": 2.13}, {"text": "Inside their clearing\nsystems, they", "start": 4009.36, "duration": 4.02}, {"text": "have a form of\nAustralian dollars", "start": 4013.38, "duration": 2.16}, {"text": "that is effectively digitally,\nin their system, digital money.", "start": 4015.54, "duration": 7.05}, {"text": "In essence, what\nthey're doing is", "start": 4022.59, "duration": 1.5}, {"text": "clearing their internal digital\nmoney versus Royal Bank money.", "start": 4024.09, "duration": 7.407}, {"text": "AUDIENCE: Thank you.", "start": 4031.497, "duration": 0.833}, {"text": "GARY GENSLER: All right.", "start": 4032.33, "duration": 1.19}, {"text": "Sorry.", "start": 4033.52, "duration": 1.23}, {"text": "So these other projects--", "start": 4034.75, "duration": 1.41}, {"text": "Estonia, the Tallinn\nStock Exchange,", "start": 4036.16, "duration": 3.15}, {"text": "is exploring proxy\nvoting and registration.", "start": 4039.31, "duration": 2.38}, {"text": "What's interesting-- who runs\nthe Estonian Stock Exchange?", "start": 4041.69, "duration": 5.39}, {"text": "NASDAQ.", "start": 4047.08, "duration": 1.35}, {"text": "NASDAQ.", "start": 4048.43, "duration": 1.6}, {"text": "So NASDAQ runs it.", "start": 4050.03, "duration": 2.33}, {"text": "And they're doing this project.", "start": 4052.36, "duration": 1.35}, {"text": "NASDAQ announced and went\nlive in 2015 on an illiquid.", "start": 4053.71, "duration": 4.74}, {"text": "So Kelly, you asked me\nabout illiquids earlier.", "start": 4058.45, "duration": 3.2}, {"text": "NASDAQ started a blockchain\ntechnology platform in 2015", "start": 4061.65, "duration": 6.1}, {"text": "on private securities,\nwhich were not--", "start": 4067.75, "duration": 3.39}, {"text": "they certainly weren't liquid.", "start": 4071.14, "duration": 2.28}, {"text": "I don't know enough about\nwhat they did there as", "start": 4073.42, "duration": 2.37}, {"text": "to how illiquid they were.", "start": 4075.79, "duration": 2.58}, {"text": "But they felt, all right, this\nis a place we could do this.", "start": 4078.37, "duration": 5.01}, {"text": "And it's still gone live.", "start": 4083.38, "duration": 2.795}, {"text": "It's got very little use.", "start": 4086.175, "duration": 1.945}, {"text": "But it's still there.", "start": 4088.12, "duration": 1.445}, {"text": "And they say\nthey're going to try", "start": 4089.565, "duration": 1.375}, {"text": "to do it for mutual funds,\nwhen you and I can just", "start": 4090.94, "duration": 3.78}, {"text": "by interest in mutual funds.", "start": 4094.72, "duration": 3.3}, {"text": "And NASDAQ's going to\noffer that to mutual funds,", "start": 4098.02, "duration": 4.29}, {"text": "partly because\nmutual funds aren't", "start": 4102.31, "duration": 1.98}, {"text": "in DTCC from what I understand.", "start": 4104.29, "duration": 4.109}, {"text": "The others are just\nreally some tests.", "start": 4108.399, "duration": 5.321}, {"text": "Japan Exchange Group for\nthe Tokyo Stock Exchange", "start": 4113.72, "duration": 2.87}, {"text": "has done some tests.", "start": 4116.59, "duration": 1.26}, {"text": "They've written papers.", "start": 4117.85, "duration": 1.002}, {"text": "They're sort of\ninteresting papers.", "start": 4118.852, "duration": 1.458}, {"text": "The last one was\nearlier this year.", "start": 4120.31, "duration": 3.419}, {"text": "They're really trying it\njust on post trade matching.", "start": 4123.729, "duration": 4.111}, {"text": "One of the securities firms\nin Japan, I can't remember,", "start": 4127.84, "duration": 2.97}, {"text": "is really pressing the Tokyo\nStock Exchange to do this.", "start": 4130.81, "duration": 3.81}, {"text": "So there's some local commercial\npolitics that are going on.", "start": 4134.62, "duration": 3.98}, {"text": "I can't remember\nwhich exchange is--", "start": 4138.6, "duration": 2.83}, {"text": "not exchange.", "start": 4141.43, "duration": 0.719}, {"text": "One of the brokerage houses\nis pushing them to do it.", "start": 4142.149, "duration": 4.591}, {"text": "All permissioned systems.", "start": 4146.74, "duration": 1.57}, {"text": "No, to my knowledge,\npermissionless systems.", "start": 4148.31, "duration": 4.65}, {"text": "Let's talk about ISDA for\na few minutes, derivatives", "start": 4152.96, "duration": 3.53}, {"text": "common domain model.", "start": 4156.49, "duration": 4.26}, {"text": "One of my former commissioner's\ncolleagues, Scott O'Malia,", "start": 4160.75, "duration": 3.81}, {"text": "runs ISDA.", "start": 4164.56, "duration": 1.08}, {"text": "That's a international\ntrade organization.", "start": 4169.689, "duration": 2.79}, {"text": "It's largely, largely\ndominated by the 16 big banks", "start": 4172.479, "duration": 5.041}, {"text": "around the globe that\nprobably transact 98% or 99%", "start": 4177.52, "duration": 5.58}, {"text": "of derivatives around the globe.", "start": 4183.1, "duration": 3.45}, {"text": "And it was started in the\n1980s to do all the forms,", "start": 4186.55, "duration": 3.809}, {"text": "all the forms to enter into the\nlegal contractual obligations", "start": 4190.359, "duration": 3.781}, {"text": "called swaps.", "start": 4194.14, "duration": 1.84}, {"text": "And over the years,\nit's transitioned.", "start": 4195.98, "duration": 3.78}, {"text": "It's also an advocacy group.", "start": 4199.76, "duration": 1.74}, {"text": "And it lobbies\nvarious regulators", "start": 4201.5, "duration": 2.97}, {"text": "in Europe and the US and Asia.", "start": 4204.47, "duration": 2.37}, {"text": "But they've, a year or so\nago, said, wait a minute.", "start": 4206.84, "duration": 2.13}, {"text": "We could take a lot of the back\noffice of swaps, particularly", "start": 4208.97, "duration": 5.93}, {"text": "swaps that are not going\ninto clearing houses.", "start": 4214.9, "duration": 3.03}, {"text": "So it's called the non-cleared\nor uncleared swaps.", "start": 4217.93, "duration": 2.91}, {"text": "And maybe we can\ncreate smart contracts", "start": 4220.84, "duration": 3.48}, {"text": "to automate a bunch\nof contractual terms.", "start": 4224.32, "duration": 2.79}, {"text": "So that's the\nsecond bullet point.", "start": 4227.11, "duration": 1.75}, {"text": "And they contracted out.", "start": 4228.86, "duration": 1.43}, {"text": "They put out a\nrequest for proposal,", "start": 4230.29, "duration": 2.19}, {"text": "basically, for\nsomebody to come up", "start": 4232.48, "duration": 2.22}, {"text": "with machine readable\nstandard representation.", "start": 4234.7, "duration": 3.27}, {"text": "Call it code, a\nscripting language.", "start": 4237.97, "duration": 3.33}, {"text": "I can't remember if it's--", "start": 4241.3, "duration": 1.92}, {"text": "oh, it's written in JavaScript.", "start": 4243.22, "duration": 1.98}, {"text": "So written in Java\nand JavaScript,", "start": 4245.2, "duration": 2.451}, {"text": "a standard machine readable\ncode of various events.", "start": 4247.651, "duration": 5.499}, {"text": "If it's a 20-year swap that's\ngoing to pay every quarter 80", "start": 4253.15, "duration": 4.68}, {"text": "quarterly payments, each of\nthose quarterly payments,", "start": 4257.83, "duration": 4.83}, {"text": "fixed versus floating\npayments, is somehow", "start": 4262.66, "duration": 3.15}, {"text": "put into machine readable code.", "start": 4265.81, "duration": 2.48}, {"text": "And Scott and ISDA's\nview was, if we", "start": 4268.29, "duration": 3.28}, {"text": "could get a broad consensus and\npublish that machine readable", "start": 4271.57, "duration": 4.44}, {"text": "code that everybody agrees on,\nmaybe that machine readable", "start": 4276.01, "duration": 3.39}, {"text": "code could take the\nplace of legal contracts.", "start": 4279.4, "duration": 3.99}, {"text": "ISDA, for 30 plus years, one\nof their lines of business", "start": 4283.39, "duration": 3.76}, {"text": "is creating those\nlegal contracts.", "start": 4287.15, "duration": 3.44}, {"text": "Maybe we can get a\nstep ahead of this", "start": 4290.59, "duration": 2.4}, {"text": "and get consensus amongst\nthese 16 big banks.", "start": 4292.99, "duration": 5.18}, {"text": "There's about 100,000\nusers of swaps", "start": 4298.17, "duration": 3.07}, {"text": "when you say all the customers.", "start": 4301.24, "duration": 1.59}, {"text": "It's not measured in\nthe tens of millions.", "start": 4302.83, "duration": 3.04}, {"text": "I doubt anybody in\nthis room personally", "start": 4305.87, "duration": 2.12}, {"text": "has a 20-year or 10-year swap.", "start": 4307.99, "duration": 2.88}, {"text": "But I don't want to embarrass.", "start": 4310.87, "duration": 1.56}, {"text": "Maybe somebody does.", "start": 4312.43, "duration": 2.49}, {"text": "But it's an institutional\nproduct, largely.", "start": 4314.92, "duration": 4.52}, {"text": "That's their product.", "start": 4319.44, "duration": 1.41}, {"text": "And it covers new\ntransactions, rate resets,", "start": 4320.85, "duration": 3.03}, {"text": "partial terminations,\nas I listed up there.", "start": 4323.88, "duration": 5.05}, {"text": "Questions?", "start": 4328.93, "duration": 1.58}, {"text": "And it's definitely very\nmuch inspired by Ethereum", "start": 4330.51, "duration": 4.87}, {"text": "and smart contracts and DAPs.", "start": 4335.38, "duration": 3.88}, {"text": "But in essence, it's not\nreally blockchain technology.", "start": 4339.26, "duration": 5.1}, {"text": "It's inspired by it, in a sense.", "start": 4344.36, "duration": 2.01}, {"text": "AUDIENCE: They're just rewriting\nthe contracts instead of--", "start": 4346.37, "duration": 3.69}, {"text": "they think they can have more\nspecificity and certainty", "start": 4350.06, "duration": 3.35}, {"text": "of about what the contract\nmeans by writing it in contract.", "start": 4353.41, "duration": 3.61}, {"text": "GARY GENSLER: And importantly,\nimportantly, efficiency--", "start": 4357.02, "duration": 3.55}, {"text": "to automate that which\nhumans are still doing, even", "start": 4360.57, "duration": 3.96}, {"text": "if it's in written contract.", "start": 4364.53, "duration": 2.37}, {"text": "So it's also automation\nthat's inspiring them.", "start": 4366.9, "duration": 2.23}, {"text": "But you're absolutely right.", "start": 4372.413, "duration": 1.167}, {"text": "It's taking legal contract,\ngetting into machine readable", "start": 4373.58, "duration": 3.45}, {"text": "JavaScript code, getting\nconsensus on what that code is,", "start": 4377.03, "duration": 4.29}, {"text": "getting some courts\nto recognize it.", "start": 4381.32, "duration": 2.688}, {"text": "And then you won't\neven need to write", "start": 4384.008, "duration": 1.542}, {"text": "some of this, a rate reset\nor a partial termination,", "start": 4385.55, "duration": 3.96}, {"text": "into the contract.", "start": 4389.51, "duration": 1.62}, {"text": "You'd be referencing this.", "start": 4391.13, "duration": 4.34}, {"text": "The longer term\nobjective is to say maybe", "start": 4395.47, "duration": 2.31}, {"text": "we can put even more\nof it right into code.", "start": 4397.78, "duration": 5.843}, {"text": "AUDIENCE: People would have\nto pool their money somewhere.", "start": 4403.623, "duration": 2.417}, {"text": "It's like we were\ntalking about, right?", "start": 4406.04, "duration": 1.25}, {"text": "GARY GENSLER: That's correct.", "start": 4407.29, "duration": 0.47}, {"text": "AUDIENCE: It's going\nto execute itself,", "start": 4407.76, "duration": 1.56}, {"text": "which is going to have to be\na pool of money somewhere.", "start": 4409.32, "duration": 2.292}, {"text": "GARY GENSLER: That you might\nhave to some prefund or self", "start": 4411.612, "duration": 2.968}, {"text": "fund or something.", "start": 4414.58, "duration": 1.83}, {"text": "Let me go back\nhere, and then up.", "start": 4416.41, "duration": 2.24}, {"text": "AUDIENCE: If they're using\nblockchain on it, it can't be--", "start": 4418.65, "duration": 3.8}, {"text": "GARY GENSLER: They call\nit a blockchain project.", "start": 4422.45, "duration": 2.0}, {"text": "But it's a--", "start": 4424.45, "duration": 2.17}, {"text": "I think I've tried to\ncapture the essence of what", "start": 4426.62, "duration": 2.81}, {"text": "I think they have here.", "start": 4429.43, "duration": 1.15}, {"text": "It's definitely\nblockchain inspired.", "start": 4430.58, "duration": 1.67}, {"text": "I'm just not sure it's really\nstored on a blockchain.", "start": 4432.25, "duration": 2.27}, {"text": "AUDIENCE: Yeah.", "start": 4434.52, "duration": 0.625}, {"text": "Because if you look at\ncredit default swap,", "start": 4435.145, "duration": 2.885}, {"text": "you have to reference a credit\nrating somewhere digitally.", "start": 4438.03, "duration": 2.485}, {"text": "And wherever that's referenced\ndigitally, if someone makes", "start": 4440.515, "duration": 2.955}, {"text": "a mistake, does a\ntransaction period that's", "start": 4443.47, "duration": 2.52}, {"text": "based on that mistake\nand it's fixed,", "start": 4445.99, "duration": 1.955}, {"text": "someone's going to have\nto be able to reverse", "start": 4447.945, "duration": 1.875}, {"text": "that transaction.", "start": 4449.82, "duration": 1.425}, {"text": "GARY GENSLER: So\nwhat's raised is", "start": 4451.245, "duration": 1.375}, {"text": "what about if it's referencing\nsome oracle, referencing", "start": 4452.62, "duration": 4.14}, {"text": "some price source,\nand there's an error.", "start": 4456.76, "duration": 2.88}, {"text": "I believe, as I\nunderstand it, they're", "start": 4459.64, "duration": 1.8}, {"text": "writing some of that\ninto the code as well.", "start": 4461.44, "duration": 2.86}, {"text": "So if it's referencing a\nprice off the New York Stock", "start": 4464.3, "duration": 2.33}, {"text": "Exchange, how it does\nthat, what open API", "start": 4466.63, "duration": 3.45}, {"text": "it references, how it pulls it.", "start": 4470.08, "duration": 4.11}, {"text": "And they're trying\nto say, let's make", "start": 4474.19, "duration": 4.05}, {"text": "sure that it's what's\nreally verifiable.", "start": 4478.24, "duration": 2.013}, {"text": "There's one more slide\non this that will help.", "start": 4480.253, "duration": 1.917}, {"text": "This is their steps.", "start": 4482.17, "duration": 1.05}, {"text": "This is their publicly\ndisclosed five steps.", "start": 4483.22, "duration": 3.78}, {"text": "This was in an October paper.", "start": 4487.0, "duration": 1.56}, {"text": "It wasn't part of your reading.", "start": 4488.56, "duration": 2.37}, {"text": "But select the parts of\nderivatives contracts first.", "start": 4490.93, "duration": 2.4}, {"text": "Automation would be worthwhile.", "start": 4493.33, "duration": 1.292}, {"text": "They're effective.", "start": 4494.622, "duration": 0.75}, {"text": "It's efficient.", "start": 4495.372, "duration": 0.628}, {"text": "Let's find something\nwe can automate.", "start": 4496.0, "duration": 2.17}, {"text": "Ross, that's their key driver.", "start": 4498.17, "duration": 2.81}, {"text": "Then try to express it the legal\nterms in a more formalized way.", "start": 4500.98, "duration": 5.7}, {"text": "Get some standardization\nabout the law.", "start": 4506.68, "duration": 3.19}, {"text": "Get that be represented\nas functions,", "start": 4509.87, "duration": 2.5}, {"text": "meaning computer code.", "start": 4512.37, "duration": 2.49}, {"text": "So where can we be\nefficient and automate?", "start": 4514.86, "duration": 1.76}, {"text": "Where can we take\nthe legal words", "start": 4516.62, "duration": 1.68}, {"text": "and get agreement,\nput it into code,", "start": 4518.3, "duration": 2.94}, {"text": "combine that into templates?", "start": 4521.24, "duration": 1.89}, {"text": "I think some of this\nis referencing oracles.", "start": 4523.13, "duration": 3.3}, {"text": "And then validate that\nthe templates actually", "start": 4526.43, "duration": 2.67}, {"text": "work and, ultimately, even\nget some courts of law", "start": 4529.1, "duration": 3.3}, {"text": "to accept them.", "start": 4532.4, "duration": 1.56}, {"text": "That's their game plan.", "start": 4533.96, "duration": 1.71}, {"text": "Shimon?", "start": 4540.829, "duration": 0.578}, {"text": "AUDIENCE: I was thinking\nthat there is potentially", "start": 4541.407, "duration": 2.083}, {"text": "huge implications beyond\nefficiency, right?", "start": 4543.49, "duration": 2.31}, {"text": "Because if you're at\nTreasury or Goldman Sachs", "start": 4545.8, "duration": 4.79}, {"text": "signs a contract with\nsomeone at Orange County,", "start": 4550.59, "duration": 5.36}, {"text": "their ability to\nassess what is actually", "start": 4555.95, "duration": 1.74}, {"text": "written in the 30-page contract\nwas minimal or will be minimal.", "start": 4557.69, "duration": 6.15}, {"text": "But it's a lot easier to do\nrisk management or assessment", "start": 4563.84, "duration": 4.59}, {"text": "if you could just\nuse it as an API.", "start": 4568.43, "duration": 4.23}, {"text": "And you have an\noutside company's", "start": 4572.66, "duration": 2.07}, {"text": "basically providing you\nwith the risk analysis.", "start": 4574.73, "duration": 1.97}, {"text": "Right?", "start": 4576.7, "duration": 0.927}, {"text": "GARY GENSLER: I agree with that.", "start": 4577.627, "duration": 1.333}, {"text": "We're still very much\nat the early days.", "start": 4578.96, "duration": 2.23}, {"text": "But I think this is an\ninteresting, real, live thing.", "start": 4581.19, "duration": 3.02}, {"text": "There's a lot of\nmoney behind this.", "start": 4584.21, "duration": 2.89}, {"text": "The markets are hundreds\nof trillions of dollars.", "start": 4587.1, "duration": 3.16}, {"text": "If my former colleague\nand ISDA pulls this off,", "start": 4590.26, "duration": 3.28}, {"text": "they'll probably drive\nsome efficiency automation.", "start": 4593.54, "duration": 2.46}, {"text": "They might lower some\ncounterparty risk and event", "start": 4596.0, "duration": 2.82}, {"text": "risk or crisis risk.", "start": 4598.82, "duration": 3.06}, {"text": "I think you could embed\nthese into true blockchain", "start": 4601.88, "duration": 2.76}, {"text": "technology.", "start": 4604.64, "duration": 0.9}, {"text": "But I'm not sure it's\ndependent upon it.", "start": 4605.54, "duration": 3.21}, {"text": "The automation of\na smart contract.", "start": 4608.75, "duration": 3.09}, {"text": "Next Tuesday, next\nTuesday there's", "start": 4611.84, "duration": 2.49}, {"text": "a couple extra readings.", "start": 4614.33, "duration": 1.23}, {"text": "We swapped out some readings.", "start": 4615.56, "duration": 1.31}, {"text": "It's trade finance.", "start": 4616.87, "duration": 1.27}, {"text": "Thank you.", "start": 4618.14, "duration": 0.84}, {"text": "[APPLAUSE]", "start": 4618.98, "duration": 3.35}]
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+[{"text": "The following\ncontent is provided", "start": 0.57, "duration": 1.8}, {"text": "by MIT OpenCourseWare under\na Creative Commons license.", "start": 2.37, "duration": 3.96}, {"text": "Additional information\nabout our license", "start": 6.33, "duration": 2.1}, {"text": "and MIT OpenCourseWare\nin general", "start": 8.43, "duration": 2.37}, {"text": "is available at ocw.mit.edu.", "start": 10.8, "duration": 4.07}, {"text": "TAFT BROOME: I say, look,\nI'm writing a term paper", "start": 14.87, "duration": 3.34}, {"text": "on your article, you know?", "start": 18.21, "duration": 2.13}, {"text": "I'd like to ask you\na few questions,", "start": 20.34, "duration": 3.56}, {"text": "because when it comes\nto engineering ethics,", "start": 23.9, "duration": 2.16}, {"text": "there's about a--", "start": 26.06, "duration": 1.46}, {"text": "if it's strictly engineering\nethics as opposed", "start": 27.52, "duration": 3.49}, {"text": "to other kinds--", "start": 31.01, "duration": 2.35}, {"text": "I mean, the more\ngeneral ethics, there's", "start": 33.36, "duration": 3.06}, {"text": "a 90% chance that I\nwill know the author who", "start": 36.42, "duration": 4.05}, {"text": "you're talking about.", "start": 40.47, "duration": 1.312}, {"text": "Tell you a little bit\nwhere they're coming from", "start": 41.782, "duration": 1.958}, {"text": "and invite you to call them up.", "start": 43.74, "duration": 1.72}, {"text": "OK.", "start": 48.65, "duration": 0.96}, {"text": "We've got a good day today.", "start": 49.61, "duration": 3.18}, {"text": "What I'd like to do is to--", "start": 52.79, "duration": 1.6}, {"text": "I'm giving your papers back.", "start": 54.39, "duration": 1.67}, {"text": "What I'd like to do is\nto review the papers,", "start": 56.06, "duration": 2.32}, {"text": "but I want your permission.", "start": 58.38, "duration": 2.09}, {"text": "What I want to do is to\nmake an anonymous review,", "start": 60.47, "duration": 3.0}, {"text": "but I want to make it public.", "start": 63.47, "duration": 2.01}, {"text": "I want to read it\nout to everybody.", "start": 65.48, "duration": 1.86}, {"text": "Nobody will know who said what.", "start": 67.34, "duration": 1.95}, {"text": "AUDIENCE: But there's\nonly two of us.", "start": 72.008, "duration": 1.542}, {"text": "[LAUGHTER]", "start": 73.55, "duration": 0.63}, {"text": "TAFT BROOME: Well, they\ndon't know which one of you--", "start": 74.18, "duration": 2.298}, {"text": "I'll tell you what.", "start": 76.478, "duration": 0.792}, {"text": "It's not--", "start": 77.27, "duration": 0.6}, {"text": "AUDIENCE: It doesn't--\nI don't care.", "start": 77.87, "duration": 1.83}, {"text": "TAFT BROOME: Well, let's\nsee-- let's see how it goes.", "start": 79.7, "duration": 2.208}, {"text": "There's nothing in\nhere that's going to--", "start": 81.908, "duration": 1.709}, {"text": "AUDIENCE: No.", "start": 83.617, "duration": 0.708}, {"text": "TAFT BROOME: --that\nI have to say", "start": 84.325, "duration": 1.375}, {"text": "that's going to be-- you know.", "start": 85.7, "duration": 1.25}, {"text": "Anything that's-- let me use\nsome judgment and see how it", "start": 90.05, "duration": 5.18}, {"text": "goes.", "start": 95.23, "duration": 2.31}, {"text": "And-- OK.", "start": 97.54, "duration": 12.9}, {"text": "Now what I want you to do\nis I'm going to-- the grade", "start": 110.44, "duration": 2.34}, {"text": "that I have put down here is\nnot the grade for the paper", "start": 112.78, "duration": 5.34}, {"text": "you gave me.", "start": 118.12, "duration": 2.0}, {"text": "The grade that I put down here\nis for your second draft that", "start": 120.12, "duration": 6.12}, {"text": "will respond to my comments.", "start": 126.24, "duration": 1.86}, {"text": "AUDIENCE: OK.", "start": 128.1, "duration": 1.602}, {"text": "TAFT BROOME: And\nthat you can save.", "start": 129.702, "duration": 1.458}, {"text": "You don't give back to\nme, but you can save,", "start": 131.16, "duration": 2.19}, {"text": "but you can talk\nto me about it, OK?", "start": 133.35, "duration": 4.0}, {"text": "As we go along.", "start": 137.35, "duration": 0.71}, {"text": "In other words, I want to--", "start": 138.06, "duration": 1.515}, {"text": "I said at the\nbeginning of class,", "start": 139.575, "duration": 1.485}, {"text": "I want to see\nimprovement, all right?", "start": 141.06, "duration": 2.462}, {"text": "So I want you to feel\nlike you can doctor", "start": 143.522, "duration": 1.708}, {"text": "this thing up a little bit.", "start": 145.23, "duration": 2.67}, {"text": "OK.", "start": 147.9, "duration": 0.72}, {"text": "I marked good in several\ncases on both papers,", "start": 148.62, "duration": 3.03}, {"text": "mainly because--", "start": 151.65, "duration": 2.85}, {"text": "not because you made good\nobservations, which you did,", "start": 154.5, "duration": 4.05}, {"text": "and good thoughts.", "start": 158.55, "duration": 0.915}, {"text": "You gave me some good thoughts.", "start": 159.465, "duration": 1.292}, {"text": "But I was actually surprised,\npositively surprised", "start": 160.757, "duration": 2.623}, {"text": "by the good thoughts that\nboth of you had put in here.", "start": 163.38, "duration": 3.42}, {"text": "But it was little\nthings like that you", "start": 166.8, "duration": 2.28}, {"text": "did get a reference that\nI had not brought in", "start": 169.08, "duration": 2.73}, {"text": "and you did it on your own.", "start": 171.81, "duration": 1.3}, {"text": "That was good, OK?", "start": 173.11, "duration": 1.49}, {"text": "And for example, I\ndidn't make a distinction", "start": 174.6, "duration": 5.13}, {"text": "between act and\nrule utilitarianism,", "start": 179.73, "duration": 4.47}, {"text": "and you all figured that out.", "start": 184.2, "duration": 2.58}, {"text": "That's the kind of\nstuff I'm looking for.", "start": 186.78, "duration": 3.18}, {"text": "Another one is an anomaly\nthat's just in the field.", "start": 189.96, "duration": 4.23}, {"text": "Let me tell you-- let me\ngive you something that", "start": 194.19, "duration": 2.67}, {"text": "will cause you to remember it.", "start": 196.86, "duration": 2.22}, {"text": "It's a little game that you\ncan play with three-year-olds.", "start": 199.08, "duration": 3.33}, {"text": "You ever played-- y'all\nplay around with kids?", "start": 202.41, "duration": 2.37}, {"text": "Three-year-olds, four-year-olds.", "start": 204.78, "duration": 1.51}, {"text": "It's a little game,\nbut it is very--", "start": 206.29, "duration": 2.42}, {"text": "my experience with\ntelling it, with playing", "start": 208.71, "duration": 2.4}, {"text": "this game with these little\nkids is very, very interesting.", "start": 211.11, "duration": 4.96}, {"text": "And that is you say, what\nhas a big head, red eyes,", "start": 216.07, "duration": 7.65}, {"text": "and eats rocks?", "start": 223.72, "duration": 2.0}, {"text": "Kid says, I don't know.", "start": 225.72, "duration": 1.23}, {"text": "You say, a big-headed,\nred-eyed rock eater.", "start": 226.95, "duration": 3.3}, {"text": "[LAUGHTER]", "start": 230.25, "duration": 1.2}, {"text": "Kid says, OK.", "start": 231.45, "duration": 1.16}, {"text": "Then you say, what has\na big head, yellow eyes,", "start": 232.61, "duration": 4.42}, {"text": "and eats rocks?", "start": 237.03, "duration": 2.21}, {"text": "And the kid says, a big-headed,\nyellow-eyed rock eater.", "start": 239.24, "duration": 4.86}, {"text": "You say, no.", "start": 244.1, "duration": 1.29}, {"text": "They only come in red.", "start": 245.39, "duration": 1.08}, {"text": "[LAUGHTER]", "start": 246.47, "duration": 1.23}, {"text": "Now my experience is\nthat four-year-olds", "start": 247.7, "duration": 3.765}, {"text": "will see the point to that.", "start": 251.465, "duration": 1.185}, {"text": "That's just the way life is, OK?", "start": 252.65, "duration": 2.774}, {"text": "All right?", "start": 255.424, "duration": 2.806}, {"text": "Now in ethics, you will\nfind a lot of this.", "start": 258.23, "duration": 2.94}, {"text": "You'll find deontological\nethics, but nobody--", "start": 261.17, "duration": 3.33}, {"text": "very few people--\nnot a lot of people", "start": 264.5, "duration": 1.59}, {"text": "talk about ontological ethics.", "start": 266.09, "duration": 3.75}, {"text": "Don't be bothered by that, OK?", "start": 269.84, "duration": 2.58}, {"text": "And there'll be a lot of those.", "start": 272.42, "duration": 2.77}, {"text": "There'll be a lot of them.", "start": 275.19, "duration": 1.172}, {"text": "Let me see if I can\nthink of another one.", "start": 276.362, "duration": 1.708}, {"text": "They'll talk about\nconsequentialists", "start": 285.32, "duration": 1.5}, {"text": "and non-consequentialists,\nbut there's another one.", "start": 286.82, "duration": 3.03}, {"text": "I'll think of it before\nthe class is over.", "start": 289.85, "duration": 1.75}, {"text": "But there are a lot of\nthese little anomalies.", "start": 291.6, "duration": 2.18}, {"text": "Just don't let them bother\nyou, but pick them up.", "start": 293.78, "duration": 2.46}, {"text": "Pick them up.", "start": 296.24, "duration": 0.99}, {"text": "OK.", "start": 297.23, "duration": 1.62}, {"text": "Another thing is that this\ncase is more properly called", "start": 298.85, "duration": 5.04}, {"text": "the A7D case than the A7 case.", "start": 303.89, "duration": 5.322}, {"text": "AUDIENCE: What does that mean?", "start": 309.212, "duration": 1.858}, {"text": "TAFT BROOME: It's the\nnomenclature for the break.", "start": 311.07, "duration": 3.993}, {"text": "AUDIENCE: OK.", "start": 315.063, "duration": 0.542}, {"text": "TAFT BROOME: Now here's a very\nsignificant teaching point.", "start": 322.24, "duration": 5.56}, {"text": "Very significant teaching\npoint for this kind of class.", "start": 327.8, "duration": 4.46}, {"text": "On the one hand, a\nprescription for behavior", "start": 332.26, "duration": 5.85}, {"text": "is made more\ncompelling, I agree,", "start": 338.11, "duration": 4.26}, {"text": "if you use two very\ndifferent approaches", "start": 342.37, "duration": 2.43}, {"text": "and come up with the\nsame prescription.", "start": 344.8, "duration": 2.73}, {"text": "That is very compelling.", "start": 347.53, "duration": 2.99}, {"text": "But in ethics, there's no\nreason that two prescriptions", "start": 350.52, "duration": 4.12}, {"text": "should be the same.", "start": 354.64, "duration": 3.27}, {"text": "If you get different\nprescriptions,", "start": 357.91, "duration": 1.76}, {"text": "you don't have to say,\nyou need more work.", "start": 359.67, "duration": 3.48}, {"text": "That's the way it can end.", "start": 363.15, "duration": 3.17}, {"text": "OK, what you're really looking\nfor is the defensibility of it.", "start": 366.32, "duration": 4.25}, {"text": "So I could give\nyou a classic case,", "start": 370.57, "duration": 3.35}, {"text": "one that I think you should\nthink over, and probably one", "start": 373.92, "duration": 2.73}, {"text": "that you've thought over before.", "start": 376.65, "duration": 1.95}, {"text": "It doesn't have a name, but\nyou've seen it in movies.", "start": 378.6, "duration": 5.16}, {"text": "A ship sinks.", "start": 383.76, "duration": 3.76}, {"text": "Some people escape\nin a lifeboat.", "start": 387.52, "duration": 3.18}, {"text": "There are 10 people\nin the lifeboat.", "start": 390.7, "duration": 2.49}, {"text": "There's food enough for\n10 people for a week,", "start": 393.19, "duration": 4.83}, {"text": "but they don't expect to\nbe picked up for a month.", "start": 398.02, "duration": 2.4}, {"text": "Well, you can come up with\na whole lot of solutions", "start": 404.09, "duration": 3.63}, {"text": "that are very different, even\nopposite, and all of them", "start": 407.72, "duration": 4.14}, {"text": "are equally defensible.", "start": 411.86, "duration": 3.34}, {"text": "You can come up with\nsome solutions--", "start": 415.2, "duration": 2.1}, {"text": "you can come up--\nyou can come up", "start": 417.3, "duration": 2.1}, {"text": "with a solution\nthat is defensible.", "start": 419.4, "duration": 2.71}, {"text": "I can come up with\nthe same solution,", "start": 422.11, "duration": 2.31}, {"text": "but it's not defensible.", "start": 424.42, "duration": 1.227}, {"text": "OK?", "start": 428.63, "duration": 0.94}, {"text": "All right.", "start": 429.57, "duration": 0.5}, {"text": "So in an engineering class, we--", "start": 430.07, "duration": 3.72}, {"text": "well, let's put it this way.", "start": 437.863, "duration": 1.167}, {"text": "In undergraduate\nengineering, there", "start": 439.03, "duration": 3.96}, {"text": "is such a thing as the answer\nin the back of the book.", "start": 442.99, "duration": 4.31}, {"text": "The operative word is the.", "start": 447.3, "duration": 3.14}, {"text": "OK?", "start": 450.44, "duration": 0.75}, {"text": "In graduate, you're\ngoing to find", "start": 451.19, "duration": 2.04}, {"text": "you can get more than one\nanswer and there's costs", "start": 453.23, "duration": 2.97}, {"text": "and benefits on either side.", "start": 456.2, "duration": 3.28}, {"text": "Out there, a lot of good\nanswers, a lot of bad answers.", "start": 459.48, "duration": 5.41}, {"text": "And what is going to count\nmost in many situations", "start": 464.89, "duration": 4.08}, {"text": "is like it is here.", "start": 468.97, "duration": 1.758}, {"text": "It's your argument.", "start": 470.728, "duration": 0.792}, {"text": "And that's going to be because--", "start": 475.16, "duration": 2.325}, {"text": "and this is one thing that\nI try to direct my class to,", "start": 477.485, "duration": 3.735}, {"text": "because people just will not\nknow, no matter what you say,", "start": 481.22, "duration": 13.02}, {"text": "what the right answer is.", "start": 494.24, "duration": 1.8}, {"text": "The question-- let\nme tell you a story.", "start": 496.04, "duration": 2.1}, {"text": "I've got another story.", "start": 498.14, "duration": 1.14}, {"text": "Let me just tell this story.", "start": 499.28, "duration": 2.67}, {"text": "I'm a young assistant\nprofessor, and I'm down there--", "start": 501.95, "duration": 3.51}, {"text": "and I go down to NASA\nLangley Research Center.", "start": 505.46, "duration": 3.51}, {"text": "This is in Hampton, Virginia.", "start": 508.97, "duration": 2.387}, {"text": "Know about it?", "start": 511.357, "duration": 0.583}, {"text": "AUDIENCE: I worked there.", "start": 511.94, "duration": 1.042}, {"text": "TAFT BROOME: Oh.", "start": 512.982, "duration": 0.708}, {"text": "AUDIENCE: [INAUDIBLE]\nfor summer-- two summer", "start": 513.69, "duration": 1.875}, {"text": "internships.", "start": 515.565, "duration": 0.545}, {"text": "TAFT BROOME: Really?", "start": 516.11, "duration": 0.833}, {"text": "What division.", "start": 516.943, "duration": 0.722}, {"text": "AUDIENCE: The space projects\n[INAUDIBLE],, so yeah.", "start": 517.665, "duration": 4.75}, {"text": "In the building where the\nMercury astronauts were", "start": 522.415, "duration": 2.135}, {"text": "[INAUDIBLE].", "start": 524.55, "duration": 0.96}, {"text": "TAFT BROOME: Whoa.", "start": 525.51, "duration": 1.17}, {"text": "I was down there in the\nlate '70s and almost all", "start": 526.68, "duration": 4.59}, {"text": "through the '80s.", "start": 531.27, "duration": 1.56}, {"text": "I had grants with them\nfor about 12 years.", "start": 532.83, "duration": 1.89}, {"text": "And I had a\nrelationship down there", "start": 537.27, "duration": 1.74}, {"text": "where I was going down there\nso often that what I'd do", "start": 539.01, "duration": 3.66}, {"text": "is rent a house.", "start": 542.67, "duration": 0.75}, {"text": "I'd take students with me.", "start": 543.42, "duration": 1.95}, {"text": "We'd live in the house, work.", "start": 545.37, "duration": 3.33}, {"text": "And I did that eight\nor nine years, I guess.", "start": 548.7, "duration": 5.61}, {"text": "And so we would all get in\nthe car and ride down there.", "start": 559.38, "duration": 6.23}, {"text": "And I had this little\nspeech I'd give.", "start": 565.61, "duration": 4.108}, {"text": "I was unmarried\nat the time, and I", "start": 569.718, "duration": 2.842}, {"text": "would tell them,\nwhatever happens", "start": 572.56, "duration": 2.31}, {"text": "in Hampton stays in Hampton.", "start": 574.87, "duration": 5.53}, {"text": "I don't want any students\ncoming back to Howard, saying,", "start": 580.4, "duration": 2.37}, {"text": "I saw Dr. Broome--", "start": 582.77, "duration": 2.805}, {"text": "I said, whatever happens\ndown here stays down there.", "start": 585.575, "duration": 2.865}, {"text": "So one year we were\nriding down there.", "start": 588.44, "duration": 3.9}, {"text": "I was riding down\nthere with four--", "start": 592.34, "duration": 1.47}, {"text": "three students.", "start": 593.81, "duration": 0.84}, {"text": "Four students.", "start": 594.65, "duration": 1.41}, {"text": "Three students.", "start": 596.06, "duration": 1.65}, {"text": "And I made my little speech.", "start": 597.71, "duration": 3.21}, {"text": "They agreed with it.", "start": 600.92, "duration": 1.54}, {"text": "And then one of them said,\ndoes that go for us too?", "start": 602.46, "duration": 4.31}, {"text": "And I thought,\nthere's never a case", "start": 606.77, "duration": 1.74}, {"text": "where I'd go back to Howard\nand tell what students did.", "start": 608.51, "duration": 2.37}, {"text": "I don't care what they did.", "start": 610.88, "duration": 1.14}, {"text": "I just thought, do it.", "start": 612.02, "duration": 2.51}, {"text": "And so I said, yeah, I\nguess it goes for you too.", "start": 614.53, "duration": 4.5}, {"text": "So they started lighting\nup these reefers.", "start": 619.03, "duration": 1.75}, {"text": "And I said, oh my god.", "start": 623.69, "duration": 2.73}, {"text": "What have I got myself into?", "start": 626.42, "duration": 1.47}, {"text": "Then the police came.", "start": 627.89, "duration": 2.13}, {"text": "It was because\nthey were speeding.", "start": 630.02, "duration": 1.44}, {"text": "And there's a place in Virginia.", "start": 635.737, "duration": 1.333}, {"text": "I'm going to tell you right now.", "start": 637.07, "duration": 1.333}, {"text": "It's called-- it's called--", "start": 638.403, "duration": 5.029}, {"text": "what's it called?", "start": 643.432, "duration": 0.708}, {"text": "I can't think of it right now,\nbut there's a place in Virginia", "start": 646.387, "duration": 2.583}, {"text": "where if the police\nget you for speeding,", "start": 648.97, "duration": 2.37}, {"text": "they don't give you\na ticket on the spot.", "start": 651.34, "duration": 2.25}, {"text": "They take you about\n10 miles off the road", "start": 653.59, "duration": 1.95}, {"text": "to a special place where\nyou have to fill out a form", "start": 655.54, "duration": 3.81}, {"text": "and you have to pay in cash.", "start": 659.35, "duration": 2.5}, {"text": "They took us off.", "start": 661.85, "duration": 0.715}, {"text": "I said, I know\nI'm going to jail.", "start": 662.565, "duration": 1.375}, {"text": "[LAUGHTER]", "start": 663.94, "duration": 1.87}, {"text": "That was 30 years ago.", "start": 665.81, "duration": 1.61}, {"text": "But the story is that\none day, I went to what's", "start": 667.42, "duration": 7.14}, {"text": "called a division meeting.", "start": 674.56, "duration": 1.53}, {"text": "This was the structures\nand dynamics division.", "start": 676.09, "duration": 3.63}, {"text": "And I had to go to all\nof the division meetings.", "start": 679.72, "duration": 3.09}, {"text": "And it got me spirited\nin there that day.", "start": 682.81, "duration": 5.61}, {"text": "So imagine a room.", "start": 688.42, "duration": 3.0}, {"text": "There's about 100 engineers.", "start": 691.42, "duration": 2.13}, {"text": "95 of them have PhDs.", "start": 693.55, "duration": 2.28}, {"text": "They called the place a\ncampus when I was there.", "start": 695.83, "duration": 3.39}, {"text": "And these engineers were\nup making a presentation,", "start": 699.22, "duration": 4.91}, {"text": "and the chief was\nsitting on the side", "start": 704.13, "duration": 3.27}, {"text": "and started quizzing\nthem about it.", "start": 707.4, "duration": 4.01}, {"text": "And it got mean in there.", "start": 711.41, "duration": 3.95}, {"text": "And he hit his\nfist on the table,", "start": 715.36, "duration": 4.12}, {"text": "and it kept going\nround and round.", "start": 719.48, "duration": 2.57}, {"text": "And so that was my\nfirst meeting, I think.", "start": 722.05, "duration": 3.0}, {"text": "And I said, my god, if I have\nto make a presentation in here,", "start": 725.05, "duration": 4.65}, {"text": "I'm just going to have to\ndread it, because it was awful.", "start": 729.7, "duration": 4.17}, {"text": "Awful is the word.", "start": 733.87, "duration": 3.38}, {"text": "So after that, it\nwas lunch time.", "start": 737.25, "duration": 2.7}, {"text": "Went to the cafeteria.", "start": 739.95, "duration": 3.18}, {"text": "And this man sat at this long\ntable after he got his tray.", "start": 743.13, "duration": 5.46}, {"text": "Sat at this long\ntable, and nobody", "start": 748.59, "duration": 2.91}, {"text": "sat with him at that table,\nnot from the division,", "start": 751.5, "duration": 3.63}, {"text": "not from any place else.", "start": 755.13, "duration": 1.508}, {"text": "Everybody went someplace else,\nexcept he's sitting over there", "start": 756.638, "duration": 2.542}, {"text": "by himself.", "start": 759.18, "duration": 1.86}, {"text": "So I came up with my\ntray and I said, look,", "start": 761.04, "duration": 4.47}, {"text": "I said, you mind some company?", "start": 765.51, "duration": 2.59}, {"text": "No.", "start": 768.1, "duration": 0.5}, {"text": "He said no.", "start": 768.6, "duration": 1.29}, {"text": "And so I said, well,\nI'm down here just", "start": 769.89, "duration": 2.31}, {"text": "for-- as you know,\njust for the summer.", "start": 772.2, "duration": 2.8}, {"text": "Maybe next summer too.", "start": 775.0, "duration": 1.07}, {"text": "But I said, this is\nan opportunity for me", "start": 776.07, "duration": 3.24}, {"text": "to learn something.", "start": 779.31, "duration": 1.795}, {"text": "I said, it was a pretty\nmean meeting we just had.", "start": 781.105, "duration": 5.505}, {"text": "And I said to him--", "start": 786.61, "duration": 1.53}, {"text": "I said, not only that, but\nlet's call a spade a spade.", "start": 788.14, "duration": 7.47}, {"text": "I said, all those PhDs in\nthere that you are tearing up,", "start": 795.61, "duration": 3.6}, {"text": "and you don't even hold a\nPhD or a masters from MIT.", "start": 799.21, "duration": 5.26}, {"text": "I said, how do when they're\nright or when they're wrong?", "start": 807.14, "duration": 3.84}, {"text": "And he said, being right\nor wrong is not the issue.", "start": 810.98, "duration": 3.805}, {"text": "He said, it's a\nquestion of commitment.", "start": 814.785, "duration": 1.625}, {"text": "What are they willing\nto put their careers on?", "start": 816.41, "duration": 2.761}, {"text": "He said, so I put\nthe heat on them.", "start": 819.171, "duration": 3.149}, {"text": "And what I'm looking\nfor is, number one,", "start": 822.32, "duration": 2.69}, {"text": "whether or not they're going\nto stand by what they said", "start": 825.01, "duration": 2.43}, {"text": "or whether they're going\nto start backpedaling.", "start": 827.44, "duration": 3.06}, {"text": "And number two, whether\nanybody sitting out there", "start": 830.5, "duration": 3.09}, {"text": "is going to join them or\nbe glad it's not then.", "start": 833.59, "duration": 3.987}, {"text": "He said, you watched them.", "start": 837.577, "duration": 1.083}, {"text": "He said, I put them\nunder pressure.", "start": 838.66, "duration": 2.64}, {"text": "After a while, they\nstarted backpedaling,", "start": 841.3, "duration": 2.37}, {"text": "and nobody came to\ntheir aid, so we're not", "start": 843.67, "duration": 2.61}, {"text": "going with those results.", "start": 846.28, "duration": 1.825}, {"text": "They're probably right.", "start": 848.105, "duration": 2.735}, {"text": "But we're not going with that.", "start": 850.84, "duration": 2.19}, {"text": "He said, if they\nstood up to me--", "start": 853.03, "duration": 3.81}, {"text": "he said, this is government.", "start": 856.84, "duration": 1.702}, {"text": "They're know there's going\nto be a rift coming around", "start": 858.542, "duration": 2.208}, {"text": "in a year or so, OK?", "start": 860.75, "duration": 2.918}, {"text": "These guys-- he's\ngoing to fire them.", "start": 863.668, "duration": 1.542}, {"text": "He said, but look.", "start": 868.68, "duration": 2.1}, {"text": "He said, if they had stood up\nto me and if a couple of them", "start": 870.78, "duration": 2.97}, {"text": "out of the audience stood up\nand stood with them, he said,", "start": 873.75, "duration": 2.97}, {"text": "that's what we're\ngoing to go with.", "start": 876.72, "duration": 1.68}, {"text": "The thing might go up and\ncome back down, explode.", "start": 878.4, "duration": 2.7}, {"text": "He said, but that's\nthe business we're in.", "start": 881.1, "duration": 2.55}, {"text": "This is the real\nworld of engineering.", "start": 883.65, "duration": 1.967}, {"text": "It's the commitment that counts.", "start": 885.617, "duration": 1.333}, {"text": "And we've got good\npeople out here.", "start": 889.86, "duration": 1.89}, {"text": "And if they are\nwilling to commit,", "start": 891.75, "duration": 2.73}, {"text": "then the United\nStates will say, when", "start": 894.48, "duration": 3.63}, {"text": "the thing goes up and\nexplodes, they will say,", "start": 898.11, "duration": 2.28}, {"text": "here's some more money.", "start": 900.39, "duration": 1.11}, {"text": "Try it again.", "start": 901.5, "duration": 3.22}, {"text": "But if we have\nthe right answers,", "start": 904.72, "duration": 2.33}, {"text": "it's not the whole story.", "start": 907.05, "duration": 1.65}, {"text": "It's not even the main\nstory, particularly", "start": 908.7, "duration": 1.86}, {"text": "if you're talking\nabout space where", "start": 910.56, "duration": 2.115}, {"text": "you don't have a tradition.", "start": 912.675, "duration": 1.125}, {"text": "Everything you're doing\nis for the first time.", "start": 913.8, "duration": 2.88}, {"text": "So that's the real world.", "start": 916.68, "duration": 1.75}, {"text": "Now the good news is--", "start": 918.43, "duration": 2.51}, {"text": "the bad news is that\nundergraduate education is not", "start": 920.94, "duration": 2.26}, {"text": "like that.", "start": 923.2, "duration": 0.5}, {"text": "Semi depends on who\nyour major professor is.", "start": 927.41, "duration": 3.21}, {"text": "Graduate education is not\nlike that in engineering.", "start": 930.62, "duration": 3.72}, {"text": "But from day one,\nethics education", "start": 934.34, "duration": 2.31}, {"text": "is like that, because--", "start": 936.65, "duration": 2.63}, {"text": "we want a good answer.", "start": 939.28, "duration": 1.15}, {"text": "Now don't get me wrong, OK?", "start": 940.43, "duration": 2.04}, {"text": "But it's that argument\nup to it and whether", "start": 942.47, "duration": 2.94}, {"text": "or not as I'm grading it and as\nany other professor would grade", "start": 945.41, "duration": 3.87}, {"text": "it whether or not I would commit\nme and my kids to your answers,", "start": 949.28, "duration": 7.686}, {"text": "to your analysis,\nbecause my kids are going", "start": 956.966, "duration": 2.876}, {"text": "to have to cross that bridge.", "start": 959.842, "duration": 1.208}, {"text": "And so I'm interested that you\ngot everything written down,", "start": 963.63, "duration": 5.43}, {"text": "but there's got to be something\nunder it that's compelling.", "start": 969.06, "duration": 3.6}, {"text": "And that is impossible to\ngrade, but I can tell you", "start": 972.66, "duration": 3.69}, {"text": "whether or not it's there.", "start": 976.35, "duration": 1.6}, {"text": "I can tell you whether\nor not I feel it.", "start": 977.95, "duration": 2.7}, {"text": "And most importantly,\neven if I don't feel it,", "start": 980.65, "duration": 3.477}, {"text": "I've been out here\nlong enough to know", "start": 984.127, "duration": 1.583}, {"text": "whether somebody else will.", "start": 985.71, "duration": 2.62}, {"text": "I will say, yeah, there\nare some people out here", "start": 988.33, "duration": 2.0}, {"text": "that would really feel this.", "start": 990.33, "duration": 2.47}, {"text": "But that takes time.", "start": 992.8, "duration": 2.06}, {"text": "My objective in this class is\nnot to meet that objective.", "start": 994.86, "duration": 4.89}, {"text": "It's the first time you've had\nan engineering ethics course,", "start": 999.75, "duration": 4.35}, {"text": "and if this was a\nsequence, then I", "start": 1004.1, "duration": 2.52}, {"text": "would expect it the next time.", "start": 1006.62, "duration": 1.918}, {"text": "It's my objective in this\nclass to talk about it.", "start": 1008.538, "duration": 2.042}, {"text": "Let's see.", "start": 1016.215, "duration": 0.5}, {"text": "Yes.", "start": 1022.23, "duration": 0.785}, {"text": "A few comments.", "start": 1023.015, "duration": 0.625}, {"text": "Immanuel Kant takes his\ncategorical imperative", "start": 1028.55, "duration": 5.97}, {"text": "and states it three or\nfour different ways.", "start": 1034.52, "duration": 2.26}, {"text": "Now I think you\nall picked that up.", "start": 1036.78, "duration": 2.15}, {"text": "There's a subtlety\nin one of them.", "start": 1038.93, "duration": 3.939}, {"text": "The golden rule is one\nof those statements.", "start": 1042.869, "duration": 2.581}, {"text": "So tie that in to Kant.", "start": 1045.45, "duration": 3.48}, {"text": "He explicitly says\nthat the golden rule", "start": 1048.93, "duration": 4.23}, {"text": "is a legitimate statement of\nthe categorical imperative.", "start": 1053.16, "duration": 4.301}, {"text": "So what that means is that out\nof the different formulations", "start": 1060.95, "duration": 4.35}, {"text": "of his categorical imperative,\nyou can pick any one of them.", "start": 1065.3, "duration": 4.58}, {"text": "I'm not too sure\nthat a philosopher", "start": 1069.88, "duration": 2.13}, {"text": "would say that one is\nbetter than the other.", "start": 1072.01, "duration": 2.37}, {"text": "Just different ways of\nstating the thing properly,", "start": 1074.38, "duration": 2.477}, {"text": "because it's a\ncomplicated sort of thing.", "start": 1076.857, "duration": 1.708}, {"text": "I guess you all know which\none is my preference, treating", "start": 1081.58, "duration": 3.54}, {"text": "people as means to ends.", "start": 1085.12, "duration": 3.24}, {"text": "That's my preference.", "start": 1088.36, "duration": 1.77}, {"text": "The first one is a\nlittle bit convoluted.", "start": 1090.13, "duration": 4.47}, {"text": "Frankly, I like it,\nbecause he's really", "start": 1094.6, "duration": 1.98}, {"text": "trying-- he's really saying\nwhat I think he really means,", "start": 1096.58, "duration": 2.61}, {"text": "and that is he's\ntrying to connect", "start": 1099.19, "duration": 1.8}, {"text": "this categorical imperative\nto first principles of logic.", "start": 1100.99, "duration": 3.66}, {"text": "So that's important to you.", "start": 1107.89, "duration": 2.3}, {"text": "I think the main\nimportance of that to you", "start": 1114.06, "duration": 2.79}, {"text": "is that now you\ncan see what counts", "start": 1116.85, "duration": 3.03}, {"text": "as a fundamental idea as opposed\nto a theory that's incremental.", "start": 1119.88, "duration": 9.24}, {"text": "You can now say that, well,\nnow I know what the Nobel--", "start": 1129.12, "duration": 3.15}, {"text": "if there was a Nobel Prize for\nphilosophy, which there isn't--", "start": 1132.27, "duration": 4.04}, {"text": "even though philosophers\nhave gotten Nobel Prizes--", "start": 1136.31, "duration": 2.125}, {"text": "for what?", "start": 1140.94, "duration": 0.66}, {"text": "AUDIENCE: For peace?", "start": 1141.6, "duration": 1.29}, {"text": "TAFT BROOME: I think maybe\nyou can count some of them--", "start": 1142.89, "duration": 5.01}, {"text": "all of them who got it for\npeace were philosophers or doing", "start": 1147.9, "duration": 2.85}, {"text": "philosophy, even some of\nthe chemists who did it.", "start": 1150.75, "duration": 5.01}, {"text": "But Sartre.", "start": 1155.76, "duration": 3.98}, {"text": "Jump off from Sartre.", "start": 1159.74, "duration": 2.418}, {"text": "He's a philosopher.", "start": 1162.158, "duration": 0.792}, {"text": "He got it.", "start": 1162.95, "duration": 0.97}, {"text": "He got it, and some others, but\nthey got it from literature.", "start": 1163.92, "duration": 4.22}, {"text": "But they were doing\nphilosophy in the literature.", "start": 1168.14, "duration": 3.03}, {"text": "And Sartre-- I think is the way\na Frenchman would pronounce it.", "start": 1171.17, "duration": 2.93}, {"text": "I think I can get away\nwith saying \"Sar-truh\"--", "start": 1174.1, "duration": 3.91}, {"text": "is someone that I\nwould like to cover.", "start": 1178.01, "duration": 4.7}, {"text": "OK.", "start": 1182.71, "duration": 0.5}, {"text": "And we can read--", "start": 1185.89, "duration": 2.19}, {"text": "the good thing\nabout doing Sartre", "start": 1188.08, "duration": 1.62}, {"text": "is that his plays-- you can\nread his plays overnight.", "start": 1189.7, "duration": 6.06}, {"text": "They're real short.", "start": 1195.76, "duration": 2.31}, {"text": "And we can talk about what--", "start": 1198.07, "duration": 4.8}, {"text": "but he is--", "start": 1202.87, "duration": 1.83}, {"text": "Sartre is a Frenchman.", "start": 1204.7, "duration": 1.23}, {"text": "He is in a different category.", "start": 1205.93, "duration": 2.79}, {"text": "He's going to tell you things\njust by what I just did.", "start": 1208.72, "duration": 2.685}, {"text": "He's going to tell a story.", "start": 1211.405, "duration": 1.125}, {"text": "Out of that, you've got to\nsynthesize what the message is.", "start": 1212.53, "duration": 3.136}, {"text": "[INAUDIBLE]", "start": 1215.666, "duration": 0.936}, {"text": "Let's see if I can\nmake some more.", "start": 1219.88, "duration": 3.318}, {"text": "AUDIENCE: Professor\nBroome, so there", "start": 1223.198, "duration": 1.812}, {"text": "are three ways to look at it.", "start": 1225.01, "duration": 1.83}, {"text": "If we're doing an analysis,\nI know we probably", "start": 1226.84, "duration": 3.2}, {"text": "won't have an assignment like\nwe do where we're specifically", "start": 1230.04, "duration": 2.5}, {"text": "told to take this approach.", "start": 1232.54, "duration": 1.32}, {"text": "But is it OK just to choose\nour favorite and pick one?", "start": 1233.86, "duration": 3.09}, {"text": "In theory, should they all\ncome to the same conclusion?", "start": 1236.95, "duration": 2.825}, {"text": "TAFT BROOME: There's no\nreason that they should all", "start": 1239.775, "duration": 2.125}, {"text": "come to the same conclusion.", "start": 1241.9, "duration": 1.298}, {"text": "AUDIENCE: OK.", "start": 1243.198, "duration": 0.542}, {"text": "So we could phrase\nit in a different way", "start": 1243.74, "duration": 2.79}, {"text": "and come up with something\ncompletely different,", "start": 1246.53, "duration": 2.0}, {"text": "depending on which\ninterpretation", "start": 1248.53, "duration": 1.86}, {"text": "we'd like or choose to use, or\nthink is the most appropriate.", "start": 1250.39, "duration": 2.76}, {"text": "TAFT BROOME: What\nI hope is that you", "start": 1253.15, "duration": 1.5}, {"text": "have enough experiences\nwithin this class", "start": 1254.65, "duration": 1.71}, {"text": "that you will find\nthat you can come up", "start": 1256.36, "duration": 3.51}, {"text": "with two opposite even\nconclusions that are well", "start": 1259.87, "duration": 4.2}, {"text": "grounded.", "start": 1264.07, "duration": 1.95}, {"text": "AUDIENCE: And we should\nwrite about both of them", "start": 1266.02, "duration": 2.16}, {"text": "and have the same\ndefensibility for both of them.", "start": 1268.18, "duration": 3.63}, {"text": "TAFT BROOME: OK,\nyou're putting me in--", "start": 1271.81, "duration": 1.65}, {"text": "AUDIENCE: My\nquestion is, since we", "start": 1273.46, "duration": 2.1}, {"text": "talked about wanting to have the\npassion behind the conclusion,", "start": 1275.56, "duration": 5.22}, {"text": "should we--", "start": 1280.78, "duration": 2.25}, {"text": "does that mean we should\nonly write about the approach", "start": 1283.03, "duration": 3.3}, {"text": "that gives us that passion--", "start": 1286.33, "duration": 1.38}, {"text": "TAFT BROOME: No.", "start": 1287.71, "duration": 0.21}, {"text": "AUDIENCE: --and that argument?", "start": 1287.92, "duration": 0.54}, {"text": "No.", "start": 1288.46, "duration": 0.3}, {"text": "TAFT BROOME: No.", "start": 1288.76, "duration": 0.667}, {"text": "AUDIENCE: OK.", "start": 1289.427, "duration": 0.563}, {"text": "TAFT BROOME: Because this\nthing takes time, OK?", "start": 1289.99, "duration": 3.52}, {"text": "It takes time.", "start": 1293.51, "duration": 0.775}, {"text": "This is going to\nbe an assignment", "start": 1294.285, "duration": 1.375}, {"text": "that I'm going to make\nbefore the class is over.", "start": 1295.66, "duration": 3.33}, {"text": "And the most important thing--", "start": 1298.99, "duration": 2.947}, {"text": "not the most important\nthing, but what", "start": 1301.937, "duration": 1.583}, {"text": "I'm going to take\nout of it today", "start": 1303.52, "duration": 3.21}, {"text": "is something that the\noffice says early on,", "start": 1306.73, "duration": 7.05}, {"text": "right at the end of his preface.", "start": 1313.78, "duration": 4.5}, {"text": "He calls it forward,\n[INAUDIBLE] forward.", "start": 1318.28, "duration": 4.29}, {"text": "And this is Wolfram von\nEschenbach's Parzival.", "start": 1322.57, "duration": 5.135}, {"text": "It's part of the\nArthurian mythology.", "start": 1330.99, "duration": 2.37}, {"text": "But this is a German\nwho's writing it.", "start": 1337.57, "duration": 4.11}, {"text": "And you're probably most\nfamiliar with Thomas Malory's.", "start": 1341.68, "duration": 6.925}, {"text": "It was called Morte d'Arthur,\nKing Arthur's story.", "start": 1348.605, "duration": 3.185}, {"text": "You know, Guinevere\nand all of that.", "start": 1351.79, "duration": 3.31}, {"text": "You're probably most\nfamiliar with that.", "start": 1355.1, "duration": 2.06}, {"text": "They are pretty much different\nversions of the same story,", "start": 1357.16, "duration": 6.22}, {"text": "and you'll find many of the same\ncharacters in these stories.", "start": 1363.38, "duration": 5.56}, {"text": "But both the translators,\nboth of the ones that I have,", "start": 1368.94, "duration": 9.56}, {"text": "this one and the\none of Morte Arthur,", "start": 1378.5, "duration": 4.35}, {"text": "start out by telling\nyou that, well, I", "start": 1382.85, "duration": 3.24}, {"text": "could translate this thing\nback into plain English,", "start": 1386.09, "duration": 7.48}, {"text": "but I won't because [INAUDIBLE].", "start": 1393.57, "duration": 3.745}, {"text": "He says, because\nif you just read it", "start": 1397.315, "duration": 3.475}, {"text": "in the vernacular of the\ntime, that after a while,", "start": 1400.79, "duration": 8.13}, {"text": "maybe page 30, maybe page\n50, it'll sound right.", "start": 1408.92, "duration": 5.82}, {"text": "And you've already had that\nexperience with Shakespeare.", "start": 1414.74, "duration": 4.53}, {"text": "You read Shakespeare,\nbut you were like--", "start": 1419.27, "duration": 4.35}, {"text": "the first time you read it,\nyou would say, good god.", "start": 1423.62, "duration": 2.77}, {"text": "Why didn't the teacher give\nme plain English Shakespeare?", "start": 1426.39, "duration": 4.19}, {"text": "Well, if they gave\nyou Shakespeare--", "start": 1430.58, "duration": 1.8}, {"text": "and after a while,\nsomething magic happens.", "start": 1432.38, "duration": 3.07}, {"text": "The stuff sounds like--", "start": 1435.45, "duration": 1.39}, {"text": "you feel like you've\nlearned a language, right?", "start": 1436.84, "duration": 2.11}, {"text": "Something happens, and\nthat's what happened.", "start": 1438.95, "duration": 1.53}, {"text": "That's what happens.", "start": 1440.48, "duration": 0.833}, {"text": "And I took that long\nexplanation to come back", "start": 1441.313, "duration": 2.377}, {"text": "to tell you that that's what\nhappens in this kind of course.", "start": 1443.69, "duration": 2.52}, {"text": "You're learning\nsomething very new,", "start": 1446.21, "duration": 2.13}, {"text": "and it'll take a while to\nget in the rhythm of it,", "start": 1448.34, "duration": 4.48}, {"text": "particularly with complexities.", "start": 1452.82, "duration": 2.12}, {"text": "After a while, you'll say,\nwell, yeah, it is complex,", "start": 1454.94, "duration": 2.64}, {"text": "but I see a way through this.", "start": 1457.58, "duration": 1.92}, {"text": "Let's see.", "start": 1464.15, "duration": 0.96}, {"text": "Many of the comments that I\nhad were pretty much the same.", "start": 1465.11, "duration": 2.58}, {"text": "And-- oh, another issue is\nwith the utilitarian approach.", "start": 1476.85, "duration": 9.28}, {"text": "It's a little bit\nforgiving in terms of your", "start": 1489.97, "duration": 3.12}, {"text": "being able to\npredict consequences.", "start": 1493.09, "duration": 2.76}, {"text": "You don't have to\nbe exactly this.", "start": 1495.85, "duration": 2.755}, {"text": "If you read Stuart\n[? Milliner, ?] what", "start": 1498.605, "duration": 1.625}, {"text": "they're saying is, your\nbest judgment at the time.", "start": 1500.23, "duration": 2.46}, {"text": "So you make your\njudgment at the time.", "start": 1506.04, "duration": 1.788}, {"text": "You don't have to take into in.", "start": 1507.828, "duration": 1.292}, {"text": "You know-- you see, that's\nwhat really comes into account", "start": 1509.12, "duration": 5.97}, {"text": "with engineering.", "start": 1515.09, "duration": 2.19}, {"text": "You're going to build a bridge.", "start": 1517.28, "duration": 1.74}, {"text": "You're going to build that\nbridge for a life of 100 years.", "start": 1519.02, "duration": 4.29}, {"text": "Now you're supposed\nto tell me what", "start": 1523.31, "duration": 2.13}, {"text": "the consequences\nare to everybody", "start": 1525.44, "duration": 1.5}, {"text": "who crosses that bridge?", "start": 1526.94, "duration": 1.08}, {"text": "You've got to make\nsome kind of judgement,", "start": 1530.39, "duration": 1.75}, {"text": "a reasonable\njudgement that is not", "start": 1532.14, "duration": 4.5}, {"text": "so much defensible as it is--", "start": 1536.64, "duration": 2.55}, {"text": "I'm going to use\nthe term commitable.", "start": 1539.19, "duration": 2.27}, {"text": "You think that other\npeople will say, yeah,", "start": 1541.46, "duration": 2.98}, {"text": "we'll go along with this.", "start": 1544.44, "duration": 2.13}, {"text": "And that's why there's--", "start": 1546.57, "duration": 2.99}, {"text": "and when it comes\nto engineering,", "start": 1549.56, "duration": 1.84}, {"text": "you won't find this\nin many of the texts.", "start": 1551.4, "duration": 1.83}, {"text": "I don't think you'll find\nit in any of them, frankly.", "start": 1553.23, "duration": 2.25}, {"text": "But I'll tell you\nright now, which", "start": 1555.48, "duration": 1.417}, {"text": "is one of the most compelling\nrationales an engineer can", "start": 1556.897, "duration": 6.593}, {"text": "give for doing x as opposed\nto y that works almost--", "start": 1563.49, "duration": 5.08}, {"text": "if it applies, works\nalmost all the time.", "start": 1568.57, "duration": 4.85}, {"text": "We always do it that way.", "start": 1573.42, "duration": 2.4}, {"text": "Tradition.", "start": 1575.82, "duration": 2.05}, {"text": "OK, so you've got a\ncitizen group in here,", "start": 1577.87, "duration": 2.61}, {"text": "and they want to\nknow why you want", "start": 1580.48, "duration": 1.98}, {"text": "to put the nuclear\nwaste dump over", "start": 1582.46, "duration": 1.68}, {"text": "there as opposed to over there.", "start": 1584.14, "duration": 2.16}, {"text": "And then you come up with\nsome kind of a formula,", "start": 1586.3, "duration": 3.75}, {"text": "and they don't\nunderstand the formula,", "start": 1590.05, "duration": 2.985}, {"text": "and they're mad about it, OK?", "start": 1593.035, "duration": 3.045}, {"text": "If you are able to\ntell their rightly,", "start": 1596.08, "duration": 2.4}, {"text": "and all the other\nengineers in the room", "start": 1598.48, "duration": 1.65}, {"text": "go along with it, that that\nformula is what we always use,", "start": 1600.13, "duration": 5.593}, {"text": "you're going to go a\nlong way with that.", "start": 1605.723, "duration": 1.667}, {"text": "Scientists can't\nget away with that,", "start": 1607.39, "duration": 4.345}, {"text": "because there's always\na formula that's", "start": 1611.735, "duration": 1.625}, {"text": "better than the old ones.", "start": 1613.36, "duration": 3.37}, {"text": "But engineers traditionally\nis a good one.", "start": 1616.73, "duration": 2.283}, {"text": "And you can use that in ethics.", "start": 1619.013, "duration": 1.292}, {"text": "OK.", "start": 1623.49, "duration": 1.59}, {"text": "Let's see.", "start": 1625.08, "duration": 0.6}, {"text": "Oh, lastly, the story turns.", "start": 1625.68, "duration": 8.88}, {"text": "I'm going to leave that\none to more discussion", "start": 1638.41, "duration": 3.042}, {"text": "as we go along the\nclass, because I", "start": 1641.452, "duration": 1.458}, {"text": "plan to do more of that.", "start": 1642.91, "duration": 2.5}, {"text": "So when you do your draft two--", "start": 1645.41, "duration": 2.87}, {"text": "and I'm going to ask you to make\ndraft two a copy of draft one", "start": 1648.28, "duration": 9.15}, {"text": "so that you can look back\nand see your progress.", "start": 1657.43, "duration": 2.64}, {"text": "Don't amend it.", "start": 1660.07, "duration": 2.25}, {"text": "Don't edit draft one, OK?", "start": 1662.32, "duration": 3.96}, {"text": "So as time goes\nalong, see if you", "start": 1666.28, "duration": 2.4}, {"text": "will go back and change anything\nyou said about the story turns.", "start": 1668.68, "duration": 4.385}, {"text": "OK.", "start": 1681.62, "duration": 0.5}, {"text": "Did I step on anybody's toes?", "start": 1682.12, "duration": 1.74}, {"text": "Any comments, questions?", "start": 1690.84, "duration": 2.373}, {"text": "This was the homework.", "start": 1693.213, "duration": 0.917}, {"text": "OK.", "start": 1702.24, "duration": 0.5}, {"text": "Let's do some\nunfinished-- well, no.", "start": 1702.74, "duration": 1.65}, {"text": "Let me give you more time.", "start": 1704.39, "duration": 1.083}, {"text": "OK.", "start": 1743.83, "duration": 2.46}, {"text": "Unfinished business\nand then new business,", "start": 1746.29, "duration": 3.06}, {"text": "better stated since you all\nlove parliamentary procedure", "start": 1749.35, "duration": 9.085}, {"text": "so much.", "start": 1758.435, "duration": 0.5}, {"text": "You have experience with\nparliamentary bodies?", "start": 1762.58, "duration": 4.06}, {"text": "AUDIENCE: Not much.", "start": 1766.64, "duration": 1.05}, {"text": "I think high school,\nlike student council", "start": 1767.69, "duration": 2.01}, {"text": "was the most [INAUDIBLE].", "start": 1769.7, "duration": 2.07}, {"text": "Yeah.", "start": 1771.77, "duration": 1.41}, {"text": "TAFT BROOME: Maybe\nwe should do more.", "start": 1773.18, "duration": 3.44}, {"text": "I was chair of the Faculty\nSenate at Howard for six years.", "start": 1776.62, "duration": 4.17}, {"text": "Now senates are usually at\nuniversities either a senate,", "start": 1780.79, "duration": 6.87}, {"text": "a committee of the faculty\nthat does certain things", "start": 1787.66, "duration": 3.51}, {"text": "and represents the\nfaculty to the president.", "start": 1791.17, "duration": 4.34}, {"text": "At Howard, the senate is a--", "start": 1795.51, "duration": 6.87}, {"text": "consists of all of the faculty,\nall the full-time faculty.", "start": 1802.38, "duration": 4.59}, {"text": "And it also consists\nof the president", "start": 1806.97, "duration": 2.13}, {"text": "and the dean, those ex\nofficio members, without vote.", "start": 1809.1, "duration": 4.38}, {"text": "And this senate, all\nof its committees", "start": 1813.48, "duration": 2.88}, {"text": "and all of its meetings\nare presided over", "start": 1816.36, "duration": 1.95}, {"text": "by a faculty person.", "start": 1818.31, "duration": 2.01}, {"text": "And the senate reports\nto the board of trustees", "start": 1820.32, "duration": 4.65}, {"text": "through the president.", "start": 1824.97, "duration": 2.31}, {"text": "So they give the document\nto the president,", "start": 1827.28, "duration": 3.39}, {"text": "and the president is compelled\nto give it to the board.", "start": 1830.67, "duration": 3.72}, {"text": "Now the president can decide\nhow to give it to the board.", "start": 1834.39, "duration": 3.195}, {"text": "But nevertheless, that's\nthe way it operates.", "start": 1837.585, "duration": 1.875}, {"text": "The point I'm trying\nto make is that try", "start": 1839.46, "duration": 4.71}, {"text": "to imagine an engineer with a\ngavel, parliamentary procedure", "start": 1844.17, "duration": 4.92}, {"text": "at a university where you've\ngot a law school, a department", "start": 1849.09, "duration": 5.16}, {"text": "of business.", "start": 1854.25, "duration": 1.92}, {"text": "And I'll tell you the\nhardest ones to preside over.", "start": 1856.17, "duration": 3.043}, {"text": "We've got a medical\nschool for surgeons.", "start": 1859.213, "duration": 1.667}, {"text": "Every surgeon knows\nexactly the way", "start": 1864.44, "duration": 3.39}, {"text": "he or she knows it's got to\ngo, and you can't tell them", "start": 1867.83, "duration": 4.51}, {"text": "one way or the other.", "start": 1872.34, "duration": 2.38}, {"text": "The lawyers, there's a\nway to deal with them.", "start": 1874.72, "duration": 4.53}, {"text": "Well, they operate with the law\na lot like they do with ethics.", "start": 1879.25, "duration": 4.86}, {"text": "If one lawyer believes\nA, another one", "start": 1884.11, "duration": 1.65}, {"text": "believes B. So when the\none who's believing A", "start": 1885.76, "duration": 3.0}, {"text": "is tearing you up,\nfind one that--", "start": 1888.76, "duration": 2.04}, {"text": "[LAUGHTER]", "start": 1890.8, "duration": 3.3}, {"text": "--that will use\napproach B. Right.", "start": 1894.1, "duration": 3.21}, {"text": "So now you're beginning to\nsee what connection that I", "start": 1897.31, "duration": 2.73}, {"text": "am going to make matters\nbetween law and ethics.", "start": 1900.04, "duration": 3.3}, {"text": "There's a whole\nlot of connection.", "start": 1903.34, "duration": 1.68}, {"text": "And depending on what\ncountry you're in--", "start": 1905.02, "duration": 4.17}, {"text": "depending on what\ncountry are you in,", "start": 1909.19, "duration": 2.7}, {"text": "you may find that there's\nno difference between law", "start": 1911.89, "duration": 2.58}, {"text": "and ethics.", "start": 1914.47, "duration": 2.79}, {"text": "You may go to the Middle\nEast, and the judges", "start": 1917.26, "duration": 4.59}, {"text": "have on clerical outfits with\nthe Quran in front of them,", "start": 1921.85, "duration": 6.54}, {"text": "and they're doing--", "start": 1928.39, "duration": 2.387}, {"text": "they don't see any difference\nbetween law, ethics,", "start": 1930.777, "duration": 2.083}, {"text": "and religion.", "start": 1932.86, "duration": 0.99}, {"text": "No difference.", "start": 1933.85, "duration": 0.69}, {"text": "It's all the same.", "start": 1934.54, "duration": 2.16}, {"text": "OK.", "start": 1936.7, "duration": 1.02}, {"text": "So where was I?", "start": 1937.72, "duration": 2.1}, {"text": "Oh, we don't want\nto do old business.", "start": 1939.82, "duration": 2.16}, {"text": "Unfinished business.", "start": 1941.98, "duration": 1.29}, {"text": "What were we doing last?", "start": 1943.27, "duration": 1.5}, {"text": "I don't think we finished it.", "start": 1944.77, "duration": 2.01}, {"text": "Chap-- oh.", "start": 1946.78, "duration": 0.72}, {"text": "AUDIENCE: We had started\ntalking about Ford Pinto.", "start": 1947.5, "duration": 2.55}, {"text": "TAFT BROOME: Ford Pinto.", "start": 1950.05, "duration": 1.68}, {"text": "Now there was something I\nthink is unfinished about that,", "start": 1951.73, "duration": 3.87}, {"text": "about our discussion on that.", "start": 1955.6, "duration": 2.64}, {"text": "We talked about Ford, but we\ndidn't talk about any persons.", "start": 1958.24, "duration": 3.6}, {"text": "Now I want to put\nthe question to you.", "start": 1964.61, "duration": 3.36}, {"text": "First let me put an\nobservation to you,", "start": 1967.97, "duration": 3.45}, {"text": "that in law, a corporation\nhas the status of a person.", "start": 1971.42, "duration": 9.05}, {"text": "So that means a corporation\ncan commit a crime.", "start": 1980.47, "duration": 4.18}, {"text": "A corporation can be\npunished for the crime,", "start": 1984.65, "duration": 3.26}, {"text": "even though nobody\nin the corporation", "start": 1987.91, "duration": 3.48}, {"text": "has been found guilty of\ncommitting any crime, OK?", "start": 1991.39, "duration": 2.76}, {"text": "We agree on that?", "start": 1994.15, "duration": 0.78}, {"text": "AUDIENCE: Mm-hmm.", "start": 1994.93, "duration": 0.43}, {"text": "TAFT BROOME: All right.", "start": 1995.36, "duration": 0.958}, {"text": "If you find a better,\nsharper statement", "start": 1996.318, "duration": 2.062}, {"text": "and bring it in next\nclass, we'll amend it,", "start": 1998.38, "duration": 2.43}, {"text": "is what I just said.", "start": 2000.81, "duration": 1.78}, {"text": "OK.", "start": 2002.59, "duration": 1.73}, {"text": "When engineering ethics\nwas really invented back", "start": 2004.32, "duration": 4.83}, {"text": "in the early, early '70s--", "start": 2009.15, "duration": 3.33}, {"text": "did I give y'all a history\nof engineering ethics yet", "start": 2012.48, "duration": 2.67}, {"text": "or the STS movement?", "start": 2015.15, "duration": 1.412}, {"text": "AUDIENCE: Yes, you did.", "start": 2016.562, "duration": 0.958}, {"text": "TAFT BROOME: OK.", "start": 2017.52, "duration": 1.77}, {"text": "Then one of the--", "start": 2019.29, "duration": 1.17}, {"text": "there were two great hopes\nof the scholars, mainly", "start": 2020.46, "duration": 4.95}, {"text": "the philosophers in it.", "start": 2025.41, "duration": 4.05}, {"text": "One great hope was\nthat someone would", "start": 2029.46, "duration": 3.81}, {"text": "be able to discover\na new ethic, maybe", "start": 2033.27, "duration": 8.39}, {"text": "from a utilitarian\nvariety, maybe", "start": 2041.66, "duration": 5.1}, {"text": "from a categorical or\nthe ontological variety.", "start": 2046.76, "duration": 6.629}, {"text": "Maybe a new variety.", "start": 2053.389, "duration": 1.388}, {"text": "But a lot of people\nthought they would", "start": 2054.777, "duration": 1.583}, {"text": "be able to find a new ethic.", "start": 2056.36, "duration": 2.1}, {"text": "I'm not so sure that they did.", "start": 2058.46, "duration": 1.92}, {"text": "AUDIENCE: Meaning a new\nmoral standard on which", "start": 2060.38, "duration": 3.89}, {"text": "to base decisions?", "start": 2064.27, "duration": 1.119}, {"text": "TAFT BROOME: Yeah.", "start": 2065.389, "duration": 0.75}, {"text": "Actually, they did, and I'll\ntell you about one or two", "start": 2071.74, "duration": 2.72}, {"text": "that I think they might have\ndone, or we might have done.", "start": 2074.46, "duration": 5.051}, {"text": "So that was one of\nthe great hopes.", "start": 2079.511, "duration": 1.458}, {"text": "Another great hope\nwas to be able to give", "start": 2080.969, "duration": 5.491}, {"text": "a corporation moral agency.", "start": 2086.46, "duration": 3.659}, {"text": "The hope was to be able to\nsay that a corporation did", "start": 2093.81, "duration": 2.97}, {"text": "the wrong thing.", "start": 2096.78, "duration": 0.93}, {"text": "And there was this paper\nthat was written by one of--", "start": 2100.45, "duration": 8.88}, {"text": "I'll call him out One of\nthe giants in the field,", "start": 2109.33, "duration": 2.26}, {"text": "his name is John Ladd,\nL-A-D-D. John Ladd is", "start": 2111.59, "duration": 8.17}, {"text": "in semi-retirement.", "start": 2119.76, "duration": 2.25}, {"text": "I guess he's about 80 now,\nbut he's still active.", "start": 2122.01, "duration": 3.39}, {"text": "Still writes.", "start": 2125.4, "duration": 0.935}, {"text": "Still comes to meetings.", "start": 2126.335, "duration": 1.0}, {"text": "John Ladd wrote this\npaper, and what it said", "start": 2130.23, "duration": 3.78}, {"text": "was that there's nothing\nin any moral tradition that", "start": 2134.01, "duration": 5.34}, {"text": "would allow the assignment of\nmoral agency to a corporation.", "start": 2139.35, "duration": 6.97}, {"text": "As a matter of fact, he said,\nthere's only one assignment", "start": 2146.32, "duration": 3.51}, {"text": "that you can make to a group\nas opposed to an individual.", "start": 2149.83, "duration": 5.67}, {"text": "You want to take a wild\nguess as to what group that", "start": 2155.5, "duration": 2.43}, {"text": "is, a collection of\npersons that has moral--", "start": 2157.93, "duration": 3.33}, {"text": "that has moral agency,\na collection as opposed", "start": 2161.26, "duration": 4.89}, {"text": "to an individual?", "start": 2166.15, "duration": 1.05}, {"text": "If you make a wild guess,\nyou'll probably be right.", "start": 2171.62, "duration": 2.57}, {"text": "AUDIENCE: A religion?", "start": 2174.19, "duration": 1.36}, {"text": "TAFT BROOME: No.", "start": 2175.55, "duration": 2.645}, {"text": "AUDIENCE: A religion?", "start": 2178.195, "duration": 1.455}, {"text": "TAFT BROOME: Nope.", "start": 2179.65, "duration": 1.95}, {"text": "That's a good one,\nbecause you would", "start": 2181.6, "duration": 1.5}, {"text": "think that because of the\nhierarchical arrangement", "start": 2183.1, "duration": 2.73}, {"text": "that-- no.", "start": 2185.83, "duration": 1.59}, {"text": "Family, because the kids--", "start": 2187.42, "duration": 3.747}, {"text": "the parents are\nresponsible for what--", "start": 2191.167, "duration": 1.583}, {"text": "morally responsible for\nthe kid's moral behavior,", "start": 2192.75, "duration": 4.38}, {"text": "he argued.", "start": 2197.13, "duration": 0.84}, {"text": "And I don't remember\nanybody arguing back on it.", "start": 2197.97, "duration": 3.06}, {"text": "Now this is John\nLadd talking, OK?", "start": 2201.03, "duration": 2.385}, {"text": "If you ever decide to do\nanything with John Ladd,", "start": 2206.22, "duration": 3.18}, {"text": "I'll give you his phone number.", "start": 2209.4, "duration": 2.317}, {"text": "I have to look at\nup, but I've got it,", "start": 2211.717, "duration": 1.583}, {"text": "and I've got his home\nphone number too.", "start": 2213.3, "duration": 1.625}, {"text": "We could call him up.", "start": 2214.925, "duration": 1.015}, {"text": "He'd really like to talk to you.", "start": 2215.94, "duration": 2.7}, {"text": "So that pretty much killed it,\nthat corporations could not", "start": 2218.64, "duration": 3.72}, {"text": "have moral agency.", "start": 2222.36, "duration": 1.56}, {"text": "Now I'm going to\ntalk about a way", "start": 2223.92, "duration": 1.86}, {"text": "to make corporations\nhave moral agency.", "start": 2225.78, "duration": 2.932}, {"text": "It's going to be\nnew, but I'm going", "start": 2228.712, "duration": 1.458}, {"text": "to put that towards\nthe end of the course.", "start": 2230.17, "duration": 2.79}, {"text": "All right.", "start": 2232.96, "duration": 1.64}, {"text": "So when we talked about\nthe Ford Pinto case,", "start": 2234.6, "duration": 4.29}, {"text": "I remember us talking a lot\nabout Ford and the Ford Pinto,", "start": 2238.89, "duration": 5.67}, {"text": "but I don't remember us\ntalking about individuals.", "start": 2244.56, "duration": 5.04}, {"text": "Were they any\nindividual behaviors", "start": 2249.6, "duration": 2.19}, {"text": "in there that we should\ndiscuss, and then", "start": 2251.79, "duration": 4.08}, {"text": "characterize that behavior as\neither moral, immoral, ethical,", "start": 2255.87, "duration": 3.06}, {"text": "or unethical?", "start": 2258.93, "duration": 2.4}, {"text": "Any difference between\nmorals and ethics?", "start": 2261.33, "duration": 2.34}, {"text": "Oh.", "start": 2266.45, "duration": 2.63}, {"text": "See, that's one thing that\nis typical of this course.", "start": 2269.08, "duration": 4.36}, {"text": "Typically, you get\nhalfway through the course", "start": 2273.44, "duration": 2.07}, {"text": "before somebody will define\nwhat the course means.", "start": 2275.51, "duration": 2.67}, {"text": "[LAUGHTER]", "start": 2278.18, "duration": 4.08}, {"text": "OK, that's not unusual at all,\nbut it's about time for us", "start": 2282.26, "duration": 3.21}, {"text": "to get a little sophisticated\nabout those two words.", "start": 2285.47, "duration": 4.62}, {"text": "OK, so I'll give you a\nchance to look them up first,", "start": 2290.09, "duration": 2.55}, {"text": "and then I'll tell\nyou what's going on.", "start": 2292.64, "duration": 3.06}, {"text": "Yeah.", "start": 2295.7, "duration": 1.733}, {"text": "Are there any individuals\nthat we need to talk about", "start": 2297.433, "duration": 2.167}, {"text": "in this Ford Pinto case?", "start": 2299.6, "duration": 1.05}, {"text": "Did they name any,\nor did they just", "start": 2300.65, "duration": 1.53}, {"text": "talk about engineers generally?", "start": 2302.18, "duration": 4.44}, {"text": "AUDIENCE: In our little\nblurb, they name one.", "start": 2306.62, "duration": 2.325}, {"text": "They name Echold, the\nDirector of Automotive Safety.", "start": 2308.945, "duration": 3.992}, {"text": "TAFT BROOME: Yeah, what\ndid they say about Echold?", "start": 2312.937, "duration": 2.083}, {"text": "AUDIENCE: He is the one who\nactually issued the study", "start": 2315.02, "duration": 2.208}, {"text": "with the cost-benefit\nanalysis, concluding", "start": 2317.228, "duration": 2.772}, {"text": "that it was more costly to\nadd in the safety feature.", "start": 2320.0, "duration": 5.043}, {"text": "TAFT BROOME: OK.", "start": 2325.043, "duration": 0.667}, {"text": "AUDIENCE: But he's\none character.", "start": 2329.175, "duration": 1.535}, {"text": "TAFT BROOME: Yeah.", "start": 2330.71, "duration": 0.75}, {"text": "AUDIENCE: I would\nsay another one--", "start": 2331.46, "duration": 1.458}, {"text": "it's not mentioned\nin the article--", "start": 2332.918, "duration": 1.632}, {"text": "is Iacocca, who\nsaid we need to make", "start": 2334.55, "duration": 4.47}, {"text": "a vehicle that's\nless than $2,000", "start": 2339.02, "duration": 1.66}, {"text": "and less than 2,000 pounds.", "start": 2340.68, "duration": 1.816}, {"text": "We've got to do it.", "start": 2342.496, "duration": 2.724}, {"text": "TAFT BROOME: OK Lee Iacocca,\ninterestingly enough", "start": 2345.22, "duration": 3.94}, {"text": "after that, I think you all\nprobably know better than I,", "start": 2349.16, "duration": 3.53}, {"text": "became quite a corporate\nhero in America.", "start": 2352.69, "duration": 2.295}, {"text": "AUDIENCE: Yeah.", "start": 2354.985, "duration": 0.625}, {"text": "TAFT BROOME: Yeah.", "start": 2357.37, "duration": 0.75}, {"text": "Well, Echold.", "start": 2361.69, "duration": 3.24}, {"text": "Now what do you think\nEchold would say--", "start": 2364.93, "duration": 2.01}, {"text": "if Echold came in here, what\ndo you think Echold would say--", "start": 2366.94, "duration": 3.57}, {"text": "how he would say--", "start": 2370.51, "duration": 1.17}, {"text": "would he defend what he did?", "start": 2371.68, "duration": 1.29}, {"text": "And could you\ndefend what he did?", "start": 2378.56, "duration": 2.97}, {"text": "And could you\ncriticize what he did?", "start": 2381.53, "duration": 4.68}, {"text": "And you can play\ndevil's advocate.", "start": 2386.21, "duration": 1.83}, {"text": "You can give me both arguments.", "start": 2388.04, "duration": 1.62}, {"text": "AUDIENCE: So I assume he\nwould defend what he did,", "start": 2396.03, "duration": 2.72}, {"text": "saying that it was-- that\ncost-benefit analysis,", "start": 2398.75, "duration": 3.94}, {"text": "which assigns cost to\nhuman life, is legitimate,", "start": 2402.69, "duration": 5.03}, {"text": "and it's a practice and used--", "start": 2407.72, "duration": 1.943}, {"text": "TAFT BROOME: It's tradition.", "start": 2409.663, "duration": 1.167}, {"text": "AUDIENCE: --by-- yeah, by\nengineers and engineering", "start": 2410.83, "duration": 5.76}, {"text": "managers in deciding whether\na rescue is acceptable.", "start": 2416.59, "duration": 2.94}, {"text": "TAFT BROOME: All right,\nlet's play a game.", "start": 2419.53, "duration": 1.75}, {"text": "Suppose I'm Echold, and I\nhire you not as my lawyer,", "start": 2421.28, "duration": 3.59}, {"text": "but as my ethicist.", "start": 2424.87, "duration": 2.01}, {"text": "And I'm going before\nan ethical review,", "start": 2426.88, "duration": 2.67}, {"text": "and you've got to present\nmy case, two of y'all.", "start": 2429.55, "duration": 3.3}, {"text": "[LAUGHTER]", "start": 2432.85, "duration": 1.305}, {"text": "And you've got to ground this.", "start": 2435.46, "duration": 2.04}, {"text": "Just can't say,\ngive me an opinion.", "start": 2437.5, "duration": 2.35}, {"text": "How would you ground it?", "start": 2439.85, "duration": 1.0}, {"text": "AUDIENCE: I would\nprobably ground it", "start": 2440.85, "duration": 1.5}, {"text": "in the fact that a manager,\nthat it's their responsibility--", "start": 2442.35, "duration": 3.76}, {"text": "I think we discussed this\na little bit last time--", "start": 2446.11, "duration": 2.37}, {"text": "to worry about money.", "start": 2448.48, "duration": 1.32}, {"text": "As a manager, that's my\nethical responsibility", "start": 2449.8, "duration": 5.64}, {"text": "to conduct the study that is\ngoing to accurately tell you", "start": 2455.44, "duration": 3.95}, {"text": "how this is going to affect\nthe company's finances.", "start": 2459.39, "duration": 3.32}, {"text": "TAFT BROOME: So how\ncan you justify it?", "start": 2462.71, "duration": 1.92}, {"text": "Is that your personal theory,\nor is there some theory", "start": 2464.63, "duration": 2.88}, {"text": "out here you can reference?", "start": 2467.51, "duration": 1.749}, {"text": "Well, you can probably use\nsomething of a content nature.", "start": 2475.13, "duration": 2.4}, {"text": "Not exactly [? Kant, ?]\nbut talk about a contract.", "start": 2477.53, "duration": 2.35}, {"text": "Do you have an obligation?", "start": 2479.88, "duration": 1.16}, {"text": "That's a principle.", "start": 2481.04, "duration": 0.863}, {"text": "Is there a principle\nthat you have", "start": 2481.903, "duration": 1.417}, {"text": "to live up to your contract?", "start": 2483.32, "duration": 1.53}, {"text": "AUDIENCE: No, that\nis the contract", "start": 2484.85, "duration": 2.46}, {"text": "that I have with the country--", "start": 2487.31, "duration": 1.36}, {"text": "with the company\nwhen I took this job.", "start": 2488.67, "duration": 1.79}, {"text": "That was the contract.", "start": 2493.015, "duration": 1.065}, {"text": "I'm worried about money, bottom\nline, making this thing work.", "start": 2494.08, "duration": 3.442}, {"text": "And that's my contract.", "start": 2497.522, "duration": 3.211}, {"text": "TAFT BROOME: OK.", "start": 2500.733, "duration": 0.667}, {"text": "Now we have to worry that\nafter you've said that,", "start": 2501.4, "duration": 4.335}, {"text": "that there's an opposing\npoint of view that's going", "start": 2505.735, "duration": 2.22}, {"text": "to give a different answer.", "start": 2507.955, "duration": 1.125}, {"text": "AUDIENCE: Oh, yeah.", "start": 2509.08, "duration": 0.57}, {"text": "TAFT BROOME: Utilitarian.", "start": 2509.65, "duration": 1.042}, {"text": "[LAUGHTER]", "start": 2510.692, "duration": 1.448}, {"text": "And that the interesting\npart about that", "start": 2512.14, "duration": 2.67}, {"text": "is that your customers\nare most likely going", "start": 2514.81, "duration": 2.04}, {"text": "to use your utilitarian,\nbecause that affects them.", "start": 2516.85, "duration": 3.325}, {"text": "That's the way they're\ngoing to see it.", "start": 2520.175, "duration": 1.625}, {"text": "OK.", "start": 2524.32, "duration": 0.61}, {"text": "So probably Echold or\nsomebody in Echold's position", "start": 2524.93, "duration": 5.96}, {"text": "would typically say\nwhat you just said,", "start": 2530.89, "duration": 4.1}, {"text": "but I would add something to it.", "start": 2534.99, "duration": 2.74}, {"text": "We've already said\nthis in the class.", "start": 2537.73, "duration": 2.6}, {"text": "We've already seen it.", "start": 2540.33, "duration": 1.17}, {"text": "And that is that the ethical\nresponsibility beyond that", "start": 2541.5, "duration": 5.01}, {"text": "is at a higher level.", "start": 2546.51, "duration": 1.14}, {"text": "OK?", "start": 2550.61, "duration": 0.78}, {"text": "Now let me give you\nsomething that will come", "start": 2551.39, "duration": 5.04}, {"text": "into play once you say that.", "start": 2556.43, "duration": 2.62}, {"text": "And I've done my job.", "start": 2559.05, "duration": 2.96}, {"text": "The utilitarian responsibility\nis at the higher level.", "start": 2562.01, "duration": 4.08}, {"text": "Let's play that again.", "start": 2569.79, "duration": 1.13}, {"text": "My job is the ontological.", "start": 2570.92, "duration": 4.2}, {"text": "I have a principle.", "start": 2575.12, "duration": 2.73}, {"text": "Live up to my contracts.", "start": 2577.85, "duration": 3.84}, {"text": "I made a deal.", "start": 2581.69, "duration": 2.92}, {"text": "The contract was legal.", "start": 2584.61, "duration": 1.533}, {"text": "AUDIENCE: Wait, what's the--", "start": 2586.143, "duration": 1.599}, {"text": "what role are you playing now?", "start": 2587.742, "duration": 1.628}, {"text": "TAFT BROOME: I don't\nknow which role--", "start": 2589.37, "duration": 1.583}, {"text": "I'm playing Echold's role.", "start": 2590.953, "duration": 1.777}, {"text": "AUDIENCE: OK.", "start": 2592.73, "duration": 0.6}, {"text": "And then what's the contract?", "start": 2593.33, "duration": 2.22}, {"text": "TAFT BROOME: The contract\nis my job description.", "start": 2595.55, "duration": 2.52}, {"text": "AUDIENCE: OK.", "start": 2598.07, "duration": 2.23}, {"text": "TAFT BROOME: Which\nhas legal force,", "start": 2600.3, "duration": 1.55}, {"text": "because the corporation\nis incorporated.", "start": 2601.85, "duration": 3.42}, {"text": "That is that there exists a\ncontract between the entity", "start": 2605.27, "duration": 6.42}, {"text": "and society.", "start": 2611.69, "duration": 0.75}, {"text": "So you can play that game\nstraight down the line.", "start": 2616.15, "duration": 2.82}, {"text": "There's a contract between\nthe entity and society", "start": 2618.97, "duration": 2.64}, {"text": "in the Articles\nof Incorporation.", "start": 2621.61, "duration": 2.1}, {"text": "And that is a\nhierarchical organization,", "start": 2627.5, "duration": 4.05}, {"text": "and my position in\nthe hierarchy has", "start": 2631.55, "duration": 2.64}, {"text": "a name and a responsibility,\nor a mission.", "start": 2634.19, "duration": 3.48}, {"text": "To live up to that\nprinciple, I have", "start": 2640.4, "duration": 2.61}, {"text": "to live up to that mission.", "start": 2643.01, "duration": 2.73}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2648.698, "duration": 1.819}, {"text": "TAFT BROOME: Pardon?", "start": 2650.517, "duration": 0.833}, {"text": "Again?", "start": 2651.35, "duration": 0.3}, {"text": "AUDIENCE: [INAUDIBLE]\nbreak a contract.", "start": 2651.65, "duration": 1.625}, {"text": "TAFT BROOME: Now to\nbreak a contract--", "start": 2653.275, "duration": 1.735}, {"text": "now we're in the gray area\nbetween ethics and law.", "start": 2659.48, "duration": 4.45}, {"text": "And if we shift too\nmuch to the law area,", "start": 2663.93, "duration": 1.93}, {"text": "you'll know it, because I won't\nknow what I'm talking about.", "start": 2665.86, "duration": 2.5}, {"text": "[LAUGHTER]", "start": 2668.36, "duration": 3.21}, {"text": "OK?", "start": 2671.57, "duration": 1.39}, {"text": "But I do know that to break\na contract, both parties", "start": 2672.96, "duration": 4.79}, {"text": "to the contract have\nto agree to break,", "start": 2677.75, "duration": 3.12}, {"text": "unless you break a leg\nor something like that.", "start": 2680.87, "duration": 3.6}, {"text": "But it takes some\nagreement, all right?", "start": 2684.47, "duration": 5.34}, {"text": "So your point is\ngoing to-- your point", "start": 2689.81, "duration": 2.25}, {"text": "is going to be included\nin what I'm about to say.", "start": 2692.06, "duration": 2.31}, {"text": "I don't if this is in this\nparticular textbook or not,", "start": 2702.2, "duration": 2.95}, {"text": "but it's something that's in\nprobably enough engineering", "start": 2705.15, "duration": 10.13}, {"text": "ethics textbooks or in\nenough ethics textbooks,", "start": 2715.28, "duration": 3.96}, {"text": "or in enough textbooks on\nscience, scientific ethics,", "start": 2719.24, "duration": 5.97}, {"text": "which is mostly research\nethics, that this", "start": 2725.21, "duration": 4.285}, {"text": "is something you have to know.", "start": 2729.495, "duration": 1.25}, {"text": "It's called the\nNuremberg principle.", "start": 2730.745, "duration": 12.906}, {"text": "Anybody want to give a lecture?", "start": 2750.598, "duration": 1.292}, {"text": "All right.", "start": 2756.27, "duration": 1.08}, {"text": "Nuremberg.", "start": 2757.35, "duration": 0.6}, {"text": "The Nuremberg trials,\nthat's where it comes from.", "start": 2757.95, "duration": 2.79}, {"text": "Now this is interesting.", "start": 2765.18, "duration": 2.97}, {"text": "Try to read some law--", "start": 2768.15, "duration": 1.2}, {"text": "I'll try to read\nlaw, because I have", "start": 2769.35, "duration": 2.005}, {"text": "to argue with lawyers at dinner\nall the time on weekends.", "start": 2771.355, "duration": 2.375}, {"text": "I just found-- when my wife\nand I go out with friends,", "start": 2777.3, "duration": 5.13}, {"text": "a third of them are\nlawyers and a third of them", "start": 2782.43, "duration": 2.25}, {"text": "are psychiatrists.", "start": 2784.68, "duration": 3.24}, {"text": "The other third vary.", "start": 2787.92, "duration": 2.7}, {"text": "But I don't defend myself\nagainst the psychiatrists.", "start": 2790.62, "duration": 3.24}, {"text": "[LAUGHTER]", "start": 2793.86, "duration": 3.213}, {"text": "And it just was very strange\nthat my wife's first husband", "start": 2799.2, "duration": 5.94}, {"text": "is a psychiatrist.", "start": 2805.14, "duration": 2.02}, {"text": "But all of these\nother psychiatrists", "start": 2807.16, "duration": 1.58}, {"text": "are friends that I\nhad before I met her.", "start": 2808.74, "duration": 2.7}, {"text": "And I guess they like\npracticing on me.", "start": 2811.44, "duration": 3.8}, {"text": "[INAUDIBLE]", "start": 2815.24, "duration": 1.36}, {"text": "But that's significant,\nbecause when", "start": 2816.6, "duration": 3.75}, {"text": "we talk about the\nNuremberg principle,", "start": 2820.35, "duration": 2.07}, {"text": "there's some really fundamental\nstuff-- fundamental stuff", "start": 2822.42, "duration": 3.12}, {"text": "in there about the law that\nis taken directly from ethics.", "start": 2825.54, "duration": 5.92}, {"text": "See, there's two kinds of law.", "start": 2831.46, "duration": 3.167}, {"text": "Anybody know lawyers,\nhang out with lawyers?", "start": 2834.627, "duration": 1.833}, {"text": "You should sometime.", "start": 2839.757, "duration": 2.113}, {"text": "You'd get them to talk--", "start": 2841.87, "duration": 1.0}, {"text": "I mean, if you can\nstop them from talking.", "start": 2842.87, "duration": 1.75}, {"text": "But there are two kinds of law.", "start": 2844.62, "duration": 3.335}, {"text": "One is called natural law\nand the other one is--", "start": 2852.16, "duration": 6.327}, {"text": "I'm trying to think of the name.", "start": 2858.487, "duration": 1.333}, {"text": "It's not exactly scientific law.", "start": 2859.82, "duration": 1.92}, {"text": "What's the other one called?", "start": 2861.74, "duration": 2.718}, {"text": "I get these names--", "start": 2864.458, "duration": 0.792}, {"text": "I wasn't prepared to talk\nabout this today, but now", "start": 2865.25, "duration": 2.52}, {"text": "that it's come up, I'm\ngoing to go through it,", "start": 2867.77, "duration": 1.917}, {"text": "and they will amend it\nnext class, or add to it,", "start": 2869.687, "duration": 2.043}, {"text": "or whatever we need to.", "start": 2871.73, "duration": 1.38}, {"text": "But look up the other kind.", "start": 2873.11, "duration": 1.316}, {"text": "The natural law basically\nsays that law and ethics--", "start": 2877.76, "duration": 4.23}, {"text": "law should never disobey\nethical principles.", "start": 2881.99, "duration": 3.51}, {"text": "Should always be supported\nby ethical principles.", "start": 2885.5, "duration": 6.651}, {"text": "Most law that's done\nin the United States", "start": 2892.151, "duration": 2.469}, {"text": "it's not natural\nlaw, but both came up", "start": 2894.62, "duration": 10.03}, {"text": "in the Nuremberg principles.", "start": 2904.65, "duration": 2.187}, {"text": "Now what happened in\nthe Nuremberg principle", "start": 2906.837, "duration": 1.833}, {"text": "was that the\ndefendants were Nazis.", "start": 2908.67, "duration": 4.965}, {"text": "Big Nazis.", "start": 2916.91, "duration": 1.5}, {"text": "And their basic defense was\nthat they were following orders,", "start": 2918.41, "duration": 10.22}, {"text": "that in their country--", "start": 2928.63, "duration": 3.93}, {"text": "it's almost the same thing we're\ntalking about now with Ford,", "start": 2932.56, "duration": 4.56}, {"text": "that the government had a\nresponsibility to the people,", "start": 2937.12, "duration": 7.14}, {"text": "and that there was a hierarchy,\nand that if anybody at the top", "start": 2944.26, "duration": 4.41}, {"text": "did something that was morally\nwrong, then punish him.", "start": 2948.67, "duration": 4.44}, {"text": "The rest of us were doing what\nwe were legally required to do.", "start": 2953.11, "duration": 5.22}, {"text": "What they said-- and what\nhappened was in the end--", "start": 2964.05, "duration": 3.27}, {"text": "or what happened was that\nthey wound up into a quandary,", "start": 2967.32, "duration": 11.08}, {"text": "because the West wanted to\nsay that what they had done", "start": 2978.4, "duration": 9.6}, {"text": "was to commit a crime\nagainst humanity,", "start": 2988.0, "duration": 4.14}, {"text": "of which each person in the\nhierarchy was responsible.", "start": 2992.14, "duration": 3.185}, {"text": "And defense-- and not all of the\ndefendants had the same lawyer.", "start": 3002.12, "duration": 10.79}, {"text": "There was this one lawyer.", "start": 3012.91, "duration": 2.7}, {"text": "As a matter of fact, if you\nsee this movie called Judgement", "start": 3015.61, "duration": 3.12}, {"text": "at Nuremberg, the lawyer\nwas played by Max--", "start": 3018.73, "duration": 8.73}, {"text": "anybody remember his last name?", "start": 3031.51, "duration": 2.68}, {"text": "Lawyer.", "start": 3034.19, "duration": 2.51}, {"text": "He got the Academy Award that\nyear for Best Supporting Actor.", "start": 3036.7, "duration": 4.81}, {"text": "The lawyer said,\nyes, they committed--", "start": 3041.51, "duration": 6.65}, {"text": "they were not only\nfollowing their orders,", "start": 3048.16, "duration": 1.75}, {"text": "but yes, they committed,\neach one of them,", "start": 3049.91, "duration": 1.83}, {"text": "a crime against humanity.", "start": 3051.74, "duration": 1.41}, {"text": "Then he came up with a\nbrilliant remark to that.", "start": 3055.83, "duration": 3.21}, {"text": "You can't punish a person for\nbreaking a law that you just", "start": 3061.8, "duration": 4.84}, {"text": "made.", "start": 3066.64, "duration": 0.5}, {"text": "At the time they did\nit, there was no law", "start": 3069.75, "duration": 1.89}, {"text": "called crime against humanity.", "start": 3071.64, "duration": 1.943}, {"text": "So what the West\nfinally did was they", "start": 3077.37, "duration": 3.45}, {"text": "came up with all of these films\nfrom the concentration camps", "start": 3080.82, "duration": 4.95}, {"text": "and used those films pretty\nmuch like the OJ case.", "start": 3085.77, "duration": 4.84}, {"text": "Just bear down on\npublic opinion.", "start": 3090.61, "duration": 2.64}, {"text": "So what they did in the end,\nthey got pretty much support", "start": 3093.25, "duration": 4.58}, {"text": "from the rest of the world.", "start": 3097.83, "duration": 3.4}, {"text": "That's the way that\nthing came down.", "start": 3101.23, "duration": 1.88}, {"text": "It came down-- check\nthe spelling on this.", "start": 3103.11, "duration": 5.83}, {"text": "I had not prepared for this,\nbut it's called My Lai.", "start": 3108.94, "duration": 8.85}, {"text": "It was in Vietnam.", "start": 3117.79, "duration": 1.53}, {"text": "It was a Vietnam case\nwhere an American--", "start": 3119.32, "duration": 3.78}, {"text": "where American soldiers killed\nthese civilians, men, women,", "start": 3123.1, "duration": 4.24}, {"text": "and children.", "start": 3127.34, "duration": 1.88}, {"text": "And Lieutenant Calley said that\nhe was merely following orders.", "start": 3129.22, "duration": 7.035}, {"text": "And what the scholars did--", "start": 3140.02, "duration": 1.56}, {"text": "I'm not going to talk\nabout the law anymore.", "start": 3141.58, "duration": 2.61}, {"text": "What the scholars did\nwas they came back", "start": 3144.19, "duration": 2.31}, {"text": "to the Nuremberg\nprinciple and said", "start": 3146.5, "duration": 3.39}, {"text": "that an officer is responsible\nfor what he or she does,", "start": 3149.89, "duration": 7.09}, {"text": "regardless of the orders.", "start": 3156.98, "duration": 3.18}, {"text": "The sergeant and the rest of\nthe men should follow orders.", "start": 3160.16, "duration": 4.77}, {"text": "They divided the house.", "start": 3164.93, "duration": 1.005}, {"text": "So now if we apply\nthis thinking to Ford,", "start": 3170.24, "duration": 5.01}, {"text": "what we would tell\nEchold is that being", "start": 3175.25, "duration": 6.45}, {"text": "a professional\nemployee as opposed", "start": 3181.7, "duration": 4.77}, {"text": "to a technical or other\nkind of an employee,", "start": 3186.47, "duration": 3.18}, {"text": "you are responsible for what\nyou do, orders notwithstanding.", "start": 3189.65, "duration": 8.098}, {"text": "OK.", "start": 3197.748, "duration": 0.5}, {"text": "All right.", "start": 3203.86, "duration": 0.5}, {"text": "So now what I'm\ngoing to do is I just", "start": 3204.36, "duration": 2.28}, {"text": "thought rather\nthan all of us just", "start": 3206.64, "duration": 3.15}, {"text": "saying, we'll revisit\nthis the next time,", "start": 3209.79, "duration": 5.36}, {"text": "I'm going to make a\nlighthearted assignment,", "start": 3215.15, "duration": 4.08}, {"text": "and that is that you become\nfamiliar with the Nuremberg", "start": 3219.23, "duration": 4.44}, {"text": "principle, the Calley case,\nand see if you can apply it", "start": 3223.67, "duration": 5.37}, {"text": "to the Ford Pinto case,\nand whatever corrections", "start": 3229.04, "duration": 3.03}, {"text": "need to be made at the\nnext class on anything", "start": 3232.07, "duration": 5.04}, {"text": "that I said in this class,\nor even the following class,", "start": 3237.11, "duration": 6.88}, {"text": "that it'll be everybody's\nresponsibility to get it right.", "start": 3243.99, "duration": 3.245}, {"text": "But I think that I'm\n99% on all of this.", "start": 3249.98, "duration": 2.535}, {"text": "AUDIENCE: [INAUDIBLE]?", "start": 3255.482, "duration": 1.01}, {"text": "TAFT BROOME: Yes?", "start": 3256.492, "duration": 0.708}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3257.2, "duration": 0.992}, {"text": "TAFT BROOME: Which one?", "start": 3258.192, "duration": 0.958}, {"text": "This one?", "start": 3259.15, "duration": 2.34}, {"text": "This one?", "start": 3261.49, "duration": 0.78}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3262.27, "duration": 1.428}, {"text": "TAFT BROOME: It's\nin a lot of movies.", "start": 3263.698, "duration": 1.542}, {"text": "AUDIENCE: The one with\nJack Nicholson from--", "start": 3265.24, "duration": 3.856}, {"text": "the military movie.", "start": 3269.096, "duration": 1.446}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3270.542, "duration": 2.892}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3273.434, "duration": 3.74}, {"text": "AUDIENCE: A Few Good Men?", "start": 3277.174, "duration": 1.042}, {"text": "[INAUDIBLE] Jack\nNicholson [INAUDIBLE]..", "start": 3278.216, "duration": 2.451}, {"text": "TAFT BROOME: Jack\nNicholson, you said?", "start": 3280.667, "duration": 1.583}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3282.25, "duration": 3.09}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3285.34, "duration": 0.88}, {"text": "AUDIENCE: [INAUDIBLE]\nTom Cruise.", "start": 3286.22, "duration": 3.164}, {"text": "AUDIENCE: Tom Cruise.", "start": 3289.384, "duration": 0.916}, {"text": "TAFT BROOME: Tom--\nwhat's the name of it?", "start": 3290.3, "duration": 1.89}, {"text": "AUDIENCE: A Few Good Men.", "start": 3292.19, "duration": 1.29}, {"text": "TAFT BROOME: A Few Good Men.", "start": 3293.48, "duration": 1.573}, {"text": "AUDIENCE: There\nwas a trial there.", "start": 3295.053, "duration": 1.417}, {"text": "There was some\n[INAUDIBLE] in Guantanamo.", "start": 3299.38, "duration": 8.54}, {"text": "TAFT BROOME: Yes.", "start": 3307.92, "duration": 0.72}, {"text": "Oh, in Guantanamo.", "start": 3308.64, "duration": 1.71}, {"text": "Whoa.", "start": 3310.35, "duration": 0.745}, {"text": "AUDIENCE: [INAUDIBLE] then\nget off on [INAUDIBLE]..", "start": 3311.095, "duration": 24.379}, {"text": "And I think [INAUDIBLE].", "start": 3335.474, "duration": 2.316}, {"text": "TAFT BROOME: There\nwas another one", "start": 3354.223, "duration": 1.417}, {"text": "that I didn't see starring Gene\nHackman and Denzel Washington", "start": 3355.64, "duration": 5.16}, {"text": "where Denzel is captain\nof this nuclear sub,", "start": 3360.8, "duration": 3.656}, {"text": "and Hackman gives him\nthe order to fire.", "start": 3364.456, "duration": 2.219}, {"text": "I don't know the\nname of that film.", "start": 3369.54, "duration": 2.832}, {"text": "AUDIENCE: I've seen it.", "start": 3372.372, "duration": 0.958}, {"text": "[INAUDIBLE]", "start": 3373.33, "duration": 1.35}, {"text": "TAFT BROOME: Now\nI guess you know", "start": 3374.68, "duration": 2.445}, {"text": "I'm susceptible to talking\nabout films in class.", "start": 3377.125, "duration": 2.545}, {"text": "[LAUGHTER]", "start": 3379.67, "duration": 0.5}, {"text": "So if you see any of\nthese films and you", "start": 3380.17, "duration": 2.79}, {"text": "want to make a five-minute\nreport on the film,", "start": 3382.96, "duration": 2.1}, {"text": "that is legitimate\nfor this class.", "start": 3385.06, "duration": 1.675}, {"text": "That was another one.", "start": 3389.44, "duration": 1.2}, {"text": "I'll tell you another one\nthat goes back a little", "start": 3395.26, "duration": 3.03}, {"text": "early for you all.", "start": 3398.29, "duration": 1.02}, {"text": "When Ronald Reagan\nwas president,", "start": 3404.32, "duration": 3.79}, {"text": "there was a military\nevent in the Red Sea.", "start": 3408.11, "duration": 5.24}, {"text": "And Reagan came on\nnational television", "start": 3416.27, "duration": 5.54}, {"text": "and said that only\nhe as president", "start": 3421.81, "duration": 5.13}, {"text": "had the authority to order\na military person in combat", "start": 3426.94, "duration": 8.43}, {"text": "to use nuclear weapons, but he\nwas delegating his authority", "start": 3435.37, "duration": 7.61}, {"text": "in the Red Sea to\nthe ship captain.", "start": 3442.98, "duration": 2.21}, {"text": "Now I'll tell you why I\nremember that so well,", "start": 3449.89, "duration": 5.02}, {"text": "because when I saw him come\non television and say that,", "start": 3454.91, "duration": 4.23}, {"text": "I was in an airplane\nthat was getting ready", "start": 3459.14, "duration": 2.79}, {"text": "to land at [? Darain, ?]\nwhich is on the Red Sea.", "start": 3461.93, "duration": 9.12}, {"text": "I was on my way to\nChina and we were--", "start": 3471.05, "duration": 2.76}, {"text": "actually, it was\n[? Darain. ?] That's", "start": 3473.81, "duration": 1.98}, {"text": "where I was going, [? Darain. ?]", "start": 3475.79, "duration": 2.52}, {"text": "And we were just about 20\nminutes out before they", "start": 3478.31, "duration": 6.0}, {"text": "said, prepare to land.", "start": 3484.31, "duration": 1.74}, {"text": "And [INAUDIBLE].", "start": 3486.05, "duration": 0.832}, {"text": "I'm looking over there,\nlooking at the Red Sea.", "start": 3486.882, "duration": 1.958}, {"text": "My god.", "start": 3488.84, "duration": 0.63}, {"text": "I said, am I going to\nbe in a nuclear war?", "start": 3489.47, "duration": 5.11}, {"text": "But I remember that.", "start": 3494.58, "duration": 2.18}, {"text": "So yes, these\nsituations are not--", "start": 3496.76, "duration": 7.355}, {"text": "I would like to call\nthem real, but I", "start": 3504.115, "duration": 2.815}, {"text": "think that they are more\nthan realistic, if you", "start": 3506.93, "duration": 5.02}, {"text": "can follow my meeting in that.", "start": 3511.95, "duration": 2.22}, {"text": "What do you do when the\ndelegation of authority", "start": 3516.72, "duration": 3.48}, {"text": "goes down to ship commanders\nfor a nuclear war,", "start": 3520.2, "duration": 4.86}, {"text": "to launch a nuclear\nweapon in defense?", "start": 3525.06, "duration": 1.83}, {"text": "Now you begin to talk\nabout these issues.", "start": 3529.91, "duration": 1.77}, {"text": "Somebody is\nresponsible, no matter", "start": 3531.68, "duration": 1.68}, {"text": "who gave them the authority.", "start": 3533.36, "duration": 1.563}, {"text": "OK.", "start": 3539.475, "duration": 0.5}, {"text": "I think I'm happy with this\ndiscussion on the Ford Pinto.", "start": 3543.05, "duration": 2.55}, {"text": "AUDIENCE: Can I bring\nup one topic on it?", "start": 3550.57, "duration": 2.17}, {"text": "TAFT BROOME: I'm\ngoing to bring up--", "start": 3552.74, "duration": 1.5}, {"text": "I just thought of another topic\nI'm going to bring up on it.", "start": 3554.24, "duration": 1.98}, {"text": "Go ahead.", "start": 3556.22, "duration": 0.36}, {"text": "Actually, it's a story\nI'm going to tell.", "start": 3556.58, "duration": 1.8}, {"text": "AUDIENCE: Well, so\nI've been trying", "start": 3558.38, "duration": 2.9}, {"text": "to find a way to say\nthat the actions of Ford", "start": 3561.28, "duration": 5.28}, {"text": "in producing and\nselling the Pintos", "start": 3566.56, "duration": 1.8}, {"text": "is not morally defensible.", "start": 3568.36, "duration": 2.4}, {"text": "And what I came\nup with was to say", "start": 3570.76, "duration": 1.47}, {"text": "that even though the utilitarian\ncost-benefit analysis said", "start": 3572.23, "duration": 6.64}, {"text": "it was not worth it to\nadd the safety feature", "start": 3578.87, "duration": 5.27}, {"text": "and to sell the car, what\nthey didn't think about", "start": 3584.14, "duration": 3.3}, {"text": "was informed consent.", "start": 3587.44, "duration": 1.57}, {"text": "So they didn't respect\nthe moral agency", "start": 3589.01, "duration": 2.3}, {"text": "of the public to decide about\nthe risk they were [INAUDIBLE]..", "start": 3591.31, "duration": 4.41}, {"text": "Is that an appropriate issue\nto bring into this case?", "start": 3595.72, "duration": 5.63}, {"text": "TAFT BROOME: That's\na good question.", "start": 3601.35, "duration": 1.63}, {"text": "That's a good question.", "start": 3602.98, "duration": 1.73}, {"text": "Now informed consent-- I\nwant y'all to know that term.", "start": 3604.71, "duration": 5.37}, {"text": "Informed consent comes\nout of medical ethics,", "start": 3610.08, "duration": 8.46}, {"text": "because now you're talking\nabout your physician", "start": 3618.54, "duration": 5.85}, {"text": "not only getting your consent\nfor some kind of procedure,", "start": 3624.39, "duration": 6.57}, {"text": "but the physician giving\nyou some lessons on what", "start": 3630.96, "duration": 2.85}, {"text": "you're doing.", "start": 3633.81, "duration": 2.81}, {"text": "Now a little bit of US history.", "start": 3636.62, "duration": 2.655}, {"text": "When I was a kid,\nyou just did not--", "start": 3642.54, "duration": 6.24}, {"text": "you just did not criticize\nwhat a doctor said.", "start": 3648.78, "duration": 4.85}, {"text": "Just totally unheard of.", "start": 3653.63, "duration": 1.87}, {"text": "It was almost bordering\non the religious.", "start": 3655.5, "duration": 3.72}, {"text": "You just did not\nquestion your doctor.", "start": 3659.22, "duration": 2.72}, {"text": "And getting a second\nopinion would have been--", "start": 3661.94, "duration": 3.645}, {"text": "would have been unthinkable.", "start": 3665.585, "duration": 3.035}, {"text": "During the late '60s,\nthat began to turn around,", "start": 3668.62, "duration": 6.94}, {"text": "mainly because--", "start": 3675.56, "duration": 1.17}, {"text": "now everything I've said\nis empirically testable.", "start": 3676.73, "duration": 3.13}, {"text": "I doubt if anybody would\ndispute what I just said.", "start": 3679.86, "duration": 5.57}, {"text": "Now you might get\na little dispute,", "start": 3685.43, "duration": 1.5}, {"text": "but anybody who would\ndispute what I'm about to say", "start": 3686.93, "duration": 2.28}, {"text": "would understand clearly what\nI'm saying and why I said it,", "start": 3689.21, "duration": 3.33}, {"text": "and that is that things began\nto turn around when the women's", "start": 3692.54, "duration": 4.77}, {"text": "movement began to\ngive women more", "start": 3697.31, "duration": 8.38}, {"text": "recognition for their\nresponsibilities", "start": 3705.69, "duration": 8.15}, {"text": "and thoughts and abilities.", "start": 3713.84, "duration": 3.77}, {"text": "Which meant that you now\nhave women who had children", "start": 3717.61, "duration": 4.86}, {"text": "and who are reading books about\nhow to care for their children.", "start": 3722.47, "duration": 3.16}, {"text": "They just weren't\nconsulting the doctors.", "start": 3725.63, "duration": 2.91}, {"text": "And if the doctor said something\nthat they didn't believe it,", "start": 3728.54, "duration": 3.12}, {"text": "consult another one.", "start": 3731.66, "duration": 1.47}, {"text": "So out of that, you\nget the STS movement,", "start": 3733.13, "duration": 3.36}, {"text": "and medical ethics then began\nto start talking about informed", "start": 3736.49, "duration": 3.99}, {"text": "consent being a moral\ndimension to a relationship", "start": 3740.48, "duration": 3.57}, {"text": "between physician and patient.", "start": 3744.05, "duration": 3.58}, {"text": "Now if you apply informed\nconsent to engineering,", "start": 3750.79, "duration": 9.83}, {"text": "you run into not a theoretical,\nbut an applications problem,", "start": 3760.62, "duration": 5.54}, {"text": "that in most cases\nin utilitarianism", "start": 3766.16, "duration": 7.75}, {"text": "you can't find all of\nthe affected parties.", "start": 3773.91, "duration": 4.81}, {"text": "And informed consent is so\neasy, because it's the patient", "start": 3778.72, "duration": 4.6}, {"text": "or the patient's mother.", "start": 3783.32, "duration": 1.913}, {"text": "Could be the\npatient's father too,", "start": 3785.233, "duration": 1.417}, {"text": "but you see what I'm saying.", "start": 3786.65, "duration": 1.167}, {"text": "We're talking about a role\nin the family that you play", "start": 3787.817, "duration": 2.883}, {"text": "[INAUDIBLE].", "start": 3790.7, "duration": 1.42}, {"text": "All right?", "start": 3792.12, "duration": 0.5}, {"text": "So informed consent then, all--", "start": 3792.62, "duration": 6.7}, {"text": "except for one case--", "start": 3799.32, "duration": 1.38}, {"text": "well, not one case,\nbut one case that I'm", "start": 3800.7, "duration": 1.77}, {"text": "going to bring in the class--", "start": 3802.47, "duration": 2.58}, {"text": "and I'm not going to\ntell you which one it is,", "start": 3805.05, "duration": 2.502}, {"text": "but I'm going to bring\none in the class.", "start": 3807.552, "duration": 2.338}, {"text": "Informed consent in engineering\nusually gets diffused.", "start": 3809.89, "duration": 4.88}, {"text": "Now, in this case, that you--", "start": 3814.77, "duration": 2.73}, {"text": "informed consent, how\nwould you apply it", "start": 3817.5, "duration": 10.75}, {"text": "to the Ford Pinto case?", "start": 3828.25, "duration": 1.39}, {"text": "AUDIENCE: Well, one option is\nthat one of the engineers who", "start": 3833.22, "duration": 5.63}, {"text": "knew of the test results, knew\nthat the car would explode", "start": 3838.85, "duration": 4.44}, {"text": "if hit in a certain way,\ncould at least write", "start": 3843.29, "duration": 5.66}, {"text": "a memo to an authority that\nmaybe wasn't being told", "start": 3848.95, "duration": 4.51}, {"text": "about these things,\nlike a higher manager,", "start": 3853.46, "duration": 3.59}, {"text": "and hope that an\naction would be taken.", "start": 3857.05, "duration": 2.43}, {"text": "And then if that didn't do\nanything, contact a news agency", "start": 3859.48, "duration": 5.161}, {"text": "and say, I want to blow the\nwhistle on this car that's", "start": 3864.641, "duration": 4.599}, {"text": "about to be in production.", "start": 3869.24, "duration": 2.052}, {"text": "TAFT BROOME: All right.", "start": 3871.292, "duration": 0.958}, {"text": "Now I've never heard that\nargument applied before Pinto,", "start": 3872.25, "duration": 7.63}, {"text": "but what I'm saying is you're\nbringing up something that's", "start": 3879.88, "duration": 2.91}, {"text": "causing my mind to turn around.", "start": 3882.79, "duration": 2.347}, {"text": "Maybe this is a good project.", "start": 3885.137, "duration": 1.208}, {"text": "Whether or not there\nis some action that", "start": 3889.53, "duration": 6.15}, {"text": "is short of\nwhistleblower that gets", "start": 3895.68, "duration": 6.98}, {"text": "the consent of the\naffected parties", "start": 3902.66, "duration": 4.74}, {"text": "is appropriate to this case,\nand my instincts tell me it is.", "start": 3907.4, "duration": 4.305}, {"text": "AUDIENCE: I mean, now we\nhave the Consumer Report.", "start": 3911.705, "duration": 2.805}, {"text": "So if a car is produced\nand really unsafe,", "start": 3914.51, "duration": 3.83}, {"text": "that word gets out.", "start": 3918.34, "duration": 1.32}, {"text": "And when people buy cars,\nthey can [INAUDIBLE]", "start": 3919.66, "duration": 3.066}, {"text": "and see how unsafe it is.", "start": 3922.726, "duration": 1.804}, {"text": "So maybe that's the correction\non something like this.", "start": 3924.53, "duration": 2.25}, {"text": "TAFT BROOME: Why don't\nyou give it some thought?", "start": 3926.78, "duration": 2.0}, {"text": "AUDIENCE: OK.", "start": 3928.78, "duration": 0.807}, {"text": "TAFT BROOME: Everybody\ngive it some thought.", "start": 3929.587, "duration": 1.833}, {"text": "I think this requires\na little thought.", "start": 3931.42, "duration": 1.625}, {"text": "I don't know that anybody\nhas thought of that one.", "start": 3933.045, "duration": 3.045}, {"text": "I've not seen anything on it.", "start": 3936.09, "duration": 1.27}, {"text": "I do know that--", "start": 3941.68, "duration": 1.14}, {"text": "let's put it this way.", "start": 3942.82, "duration": 1.98}, {"text": "What you're really\nbringing up is", "start": 3944.8, "duration": 9.45}, {"text": "you're suggesting that there\nis a continuum somewhere", "start": 3954.25, "duration": 4.18}, {"text": "between whistleblowing and what\nthey call public understanding", "start": 3958.43, "duration": 3.87}, {"text": "of engineering.", "start": 3962.3, "duration": 2.6}, {"text": "And that's a formal term.", "start": 3964.9, "duration": 1.23}, {"text": "There's an office at\nthe National Academy", "start": 3966.13, "duration": 1.8}, {"text": "of Engineering called Public\nUnderstanding of Engineering.", "start": 3967.93, "duration": 2.7}, {"text": "There's an office\nat the National", "start": 3970.63, "duration": 2.04}, {"text": "Academy of Sciences\ncalled Public", "start": 3972.67, "duration": 1.53}, {"text": "Understanding of Science.", "start": 3974.2, "duration": 3.0}, {"text": "And so a person could\ninform them, you might say,", "start": 3977.2, "duration": 11.28}, {"text": "which is not--", "start": 3988.48, "duration": 0.87}, {"text": "I don't if this is the\nsame thing as going--", "start": 3989.35, "duration": 2.16}, {"text": "I haven't given this thought.", "start": 3991.51, "duration": 1.77}, {"text": "I don't know who\nhas given a thought.", "start": 3993.28, "duration": 1.59}, {"text": "My instincts tell me nobody's\ngiven it a thought, because I", "start": 3994.87, "duration": 3.63}, {"text": "would have read it by now.", "start": 3998.5, "duration": 2.92}, {"text": "So give it some thought.", "start": 4001.42, "duration": 1.52}, {"text": "And even if you don't come up\nwith a conclusion, if you come", "start": 4002.94, "duration": 4.05}, {"text": "up with some more\nquestions or comments", "start": 4006.99, "duration": 2.37}, {"text": "as the course goes\nalong, throw them in.", "start": 4009.36, "duration": 4.254}, {"text": "OK.", "start": 4013.614, "duration": 2.488}, {"text": "OK.", "start": 4016.102, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4021.456, "duration": 0.974}, {"text": "TAFT BROOME: Yeah?", "start": 4022.43, "duration": 1.43}, {"text": "AUDIENCE: When I [INAUDIBLE].", "start": 4023.86, "duration": 1.34}, {"text": "AUDIENCE: They passed the\n20-mile-per-hour test,", "start": 4043.35, "duration": 2.37}, {"text": "but in two years, there was\ngoing to be a new standard that", "start": 4045.72, "duration": 2.81}, {"text": "was 21 miles per\nhour [INAUDIBLE]..", "start": 4048.53, "duration": 3.515}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 4052.045, "duration": 3.415}, {"text": "Is that a federal\nstandard or something", "start": 4055.46, "duration": 2.373}, {"text": "that's required by\nthe [INAUDIBLE]??", "start": 4057.833, "duration": 2.617}, {"text": "TAFT BROOME: That was a\nfederal standard, right?", "start": 4060.45, "duration": 2.0}, {"text": "AUDIENCE: Mm-hmm.", "start": 4062.45, "duration": 0.48}, {"text": "TAFT BROOME: Yeah, that was\nnot a professional engineering", "start": 4062.93, "duration": 2.52}, {"text": "standard.", "start": 4065.45, "duration": 1.824}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4067.274, "duration": 3.076}, {"text": "TAFT BROOME: Now there are\ntwo things I can say on that.", "start": 4083.687, "duration": 2.333}, {"text": "And probably whatever\nyou have in mind,", "start": 4086.02, "duration": 3.57}, {"text": "if you have a thought on\nthis, put it on the table.", "start": 4089.59, "duration": 3.27}, {"text": "We'll probably buy it.", "start": 4092.86, "duration": 1.14}, {"text": "Well, you're in a case almost\nlike this Nuremberg case,", "start": 4096.64, "duration": 3.2}, {"text": "you know?", "start": 4099.84, "duration": 0.78}, {"text": "Somebody's supposed to--\nsomebody guilty of a crime", "start": 4100.62, "duration": 3.06}, {"text": "before the act was made a crime.", "start": 4103.68, "duration": 5.5}, {"text": "They performed the act\nbefore it was made--", "start": 4109.18, "duration": 2.19}, {"text": "that's one.", "start": 4111.37, "duration": 1.995}, {"text": "Then there's another one that I\nwant to bring up in this class.", "start": 4113.365, "duration": 2.625}, {"text": "I was talking-- we've\ngot to get out of here,", "start": 4115.99, "duration": 2.43}, {"text": "but I was talking to somebody--", "start": 4118.42, "duration": 1.59}, {"text": "let me give you--", "start": 4127.09, "duration": 0.96}, {"text": "do we have an assignment?", "start": 4128.05, "duration": 2.309}, {"text": "We still have to do\nthe two nuclear cases.", "start": 4130.359, "duration": 4.247}, {"text": "So that's your assignment.", "start": 4134.606, "duration": 1.083}, {"text": "We still have to do Chernobyl\nand Three Mile Island.", "start": 4135.689, "duration": 5.281}, {"text": "OK, so that's next time.", "start": 4140.97, "duration": 1.08}, {"text": "This is Thursday?", "start": 4142.05, "duration": 1.152}, {"text": "AUDIENCE: Mm-hmm.", "start": 4143.202, "duration": 1.296}, {"text": "TAFT BROOME: All right.", "start": 4144.498, "duration": 1.706}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4146.204, "duration": 3.485}, {"text": "TAFT BROOME: Ah,\nnow let me do that,", "start": 4149.689, "duration": 1.744}, {"text": "and then let me put\nthis-- if I have time, put", "start": 4151.433, "duration": 1.917}, {"text": "this other issue on the board.", "start": 4153.35, "duration": 2.2}, {"text": "OK.", "start": 4155.55, "duration": 0.5}, {"text": "I want everybody\nto read this book,", "start": 4158.67, "duration": 1.598}, {"text": "and I'm going to give\nyou a month to do it.", "start": 4160.268, "duration": 1.792}, {"text": "Let me see.", "start": 4167.88, "duration": 0.66}, {"text": "A month, a month, a month.", "start": 4168.54, "duration": 1.29}, {"text": "Where would a month put us?", "start": 4169.83, "duration": 2.21}, {"text": "How about three weeks?", "start": 4172.04, "duration": 0.93}, {"text": "Because the first\n50 pages is going", "start": 4182.529, "duration": 1.921}, {"text": "to be like reading Shakespeare.", "start": 4184.45, "duration": 2.369}, {"text": "It's going to be a\nlittle laborious.", "start": 4186.819, "duration": 1.5}, {"text": "That's why I'm giving\nyou a lot of time.", "start": 4188.319, "duration": 2.231}, {"text": "But after that, it\nrolls right out.", "start": 4190.55, "duration": 4.04}, {"text": "Today is the 9th.", "start": 4194.59, "duration": 4.53}, {"text": "What about April 1?", "start": 4199.12, "duration": 3.15}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4202.27, "duration": 1.38}, {"text": "TAFT BROOME: April-- oh, OK.", "start": 4203.65, "duration": 4.63}, {"text": "Why not the first class\nafter spring break?", "start": 4208.28, "duration": 2.04}, {"text": "So April 1 is Saturday,\nso that will be April 4.", "start": 4213.2, "duration": 6.0}, {"text": "OK.", "start": 4222.11, "duration": 1.052}, {"text": "I'm going to give you--", "start": 4223.162, "duration": 0.958}, {"text": "I'm going to give you--", "start": 4224.12, "duration": 0.958}, {"text": "OK.", "start": 4231.89, "duration": 1.17}, {"text": "Now it's important to\nget the spelling right,", "start": 4233.06, "duration": 4.39}, {"text": "because there is Parzival, and\nit's by Wolfram von Eschenbach.", "start": 4237.45, "duration": 29.36}, {"text": "And I would like\nfor you to get--", "start": 4266.81, "duration": 2.31}, {"text": "there's more than\none translation,", "start": 4269.12, "duration": 7.04}, {"text": "and the translations\nare different.", "start": 4276.16, "duration": 1.748}, {"text": "But I would like for you to get\nthe one that's Penguin Classic.", "start": 4281.82, "duration": 2.685}, {"text": "It's one of the\nPenguin Classics.", "start": 4291.95, "duration": 3.33}, {"text": "And this particular translator\nis named Attao, A-T-T-A-O.", "start": 4295.28, "duration": 17.01}, {"text": "The main reason for choosing\nAttao is to choose one so that", "start": 4312.29, "duration": 3.96}, {"text": "we have the same one, because\nthe translations will vary.", "start": 4316.25, "duration": 4.29}, {"text": "OK.", "start": 4328.07, "duration": 0.5}, {"text": "So get that one, and we'll\ndiscuss it first class", "start": 4328.57, "duration": 2.85}, {"text": "after the spring break.", "start": 4331.42, "duration": 0.99}, {"text": "Like I said, the first 50\npages, don't be put off.", "start": 4335.77, "duration": 3.96}, {"text": "It's like reading\nShakespeare the first time.", "start": 4339.73, "duration": 2.25}, {"text": "It's a little bit, you know--", "start": 4341.98, "duration": 3.873}, {"text": "let me just open\na page at random.", "start": 4345.853, "duration": 1.417}, {"text": "\"There was a heathen\nnamed Flegetanis--", "start": 4352.87, "duration": 4.44}, {"text": "Flegetanis who was highly\nrenowned for his acquirements.\"", "start": 4357.31, "duration": 5.42}, {"text": "Acquirements.", "start": 4362.73, "duration": 1.68}, {"text": "\"The same physicus was\ndescended from Solomon.\"", "start": 4364.41, "duration": 6.35}, {"text": "Don't worry about physicus.", "start": 4370.76, "duration": 1.35}, {"text": "You'll get it, OK?", "start": 4372.11, "duration": 3.12}, {"text": "In other words, don't even\nlook for a dictionary--", "start": 4375.23, "duration": 9.06}, {"text": "I mean, a dictionary.", "start": 4384.29, "duration": 2.59}, {"text": "Just read this author's\nforward and he'll tell you", "start": 4386.88, "duration": 4.31}, {"text": "how to get through this book.", "start": 4391.19, "duration": 2.88}, {"text": "And after this, it'll\nknock your socks off.", "start": 4394.07, "duration": 4.89}, {"text": "If you get Parzival\nmixed up with Parsifal--", "start": 4398.96, "duration": 3.51}, {"text": "P-A-R-S-I-F-A-L-- it's the\nsame mythical character.", "start": 4402.47, "duration": 6.38}, {"text": "Pretty much the same\nstory, but different.", "start": 4408.85, "duration": 4.41}, {"text": "Very different.", "start": 4413.26, "duration": 2.31}, {"text": "And Parsifal is-- it's time\nto go, just about time to go.", "start": 4415.57, "duration": 5.42}, {"text": "Parsifal is the name of\na great German opera,", "start": 4420.99, "duration": 8.57}, {"text": "and he's one of the characters.", "start": 4429.56, "duration": 2.46}, {"text": "And Lohengrin is his son.", "start": 4432.02, "duration": 4.06}, {"text": "And that's a whole\ndifferent thing.", "start": 4436.08, "duration": 6.34}, {"text": "It's been turned around.", "start": 4442.42, "duration": 1.77}, {"text": "Then there's Percival.", "start": 4444.19, "duration": 3.18}, {"text": "Same knight.", "start": 4447.37, "duration": 2.28}, {"text": "Pretty much-- there's\na Venn diagram.", "start": 4449.65, "duration": 2.55}, {"text": "There's overlapping stories.", "start": 4452.2, "duration": 1.29}, {"text": "A lot in the middle is\nthe same, but there's", "start": 4453.49, "duration": 2.16}, {"text": "a lot on the edges\nthat are different.", "start": 4455.65, "duration": 3.01}, {"text": "Percival is the same knight\nin King Arthur's Round Table.", "start": 4458.66, "duration": 5.45}, {"text": "It's Parzival, but the stories\ntell it different a little bit.", "start": 4464.11, "duration": 4.617}, {"text": "A little bit.", "start": 4468.727, "duration": 3.343}, {"text": "But I want you to read that one.", "start": 4472.07, "duration": 1.86}, {"text": "And by the time you've\nfinished it, we will start--", "start": 4473.93, "duration": 4.83}, {"text": "and I do have time to do this.", "start": 4478.76, "duration": 1.64}, {"text": "That what we have done so\nfar is that we've looked at--", "start": 4484.19, "duration": 12.19}, {"text": "in the Greek\ntradition, we've looked", "start": 4496.38, "duration": 4.97}, {"text": "at consequentialist approaches.", "start": 4501.35, "duration": 6.72}, {"text": "At least one\nconsequentialist approach.", "start": 4508.07, "duration": 2.34}, {"text": "One non-consequentialist\napproach", "start": 4510.41, "duration": 2.73}, {"text": "or principled approach,\ndeontological approach.", "start": 4513.14, "duration": 4.05}, {"text": "Then we're going to\nlook at virtue ethics.", "start": 4517.19, "duration": 7.3}, {"text": "And under that, we're going\nto look at narrative ethics.", "start": 4524.49, "duration": 8.82}, {"text": "And then actually,\nwhat I'm going to do--", "start": 4533.31, "duration": 5.26}, {"text": "this gets a little complicated.", "start": 4538.57, "duration": 1.42}, {"text": "This narrative ethics is\ngoing to be non-Greek, OK?", "start": 4539.99, "duration": 7.25}, {"text": "And then we're going to--", "start": 4547.24, "duration": 2.04}, {"text": "remember the two paintings.", "start": 4549.28, "duration": 2.25}, {"text": "We had The School at Athens.", "start": 4551.53, "duration": 1.83}, {"text": "All of this is in The School\nof Athens except this one.", "start": 4553.36, "duration": 4.98}, {"text": "This one goes out and\ndoes something else.", "start": 4558.34, "duration": 3.4}, {"text": "Then we're going to go\nlook at the painting, which", "start": 4561.74, "duration": 3.41}, {"text": "is The Mass at\nBolsena, and we're", "start": 4565.15, "duration": 3.83}, {"text": "going to look at the\nRoman point of view.", "start": 4568.98, "duration": 4.24}, {"text": "And we're going to look\nat all of these cases,", "start": 4573.22, "duration": 4.77}, {"text": "but through the lens\nof codes of ethics.", "start": 4577.99, "duration": 6.3}, {"text": "We're going to go back to\neach one of these cases", "start": 4587.73, "duration": 2.7}, {"text": "and see what the code\nhas-- what if some code has", "start": 4590.43, "duration": 2.85}, {"text": "to say about it.", "start": 4593.28, "duration": 1.84}, {"text": "So that will be towards the end.", "start": 4595.12, "duration": 2.26}, {"text": "And I do not plan to spend\na whole lot of time on this,", "start": 4597.38, "duration": 4.09}, {"text": "but I plan to spend\na whole lot of time", "start": 4601.47, "duration": 2.07}, {"text": "on this, a whole\nlot of time on this.", "start": 4603.54, "duration": 2.22}, {"text": "Not so much on this,\nnot so much on that,", "start": 4605.76, "duration": 2.52}, {"text": "but a whole lot of time on that.", "start": 4608.28, "duration": 3.32}, {"text": "And when we start doing\nthe narrative ethics,", "start": 4611.6, "duration": 5.14}, {"text": "we will need characters\nfrom mythology.", "start": 4616.74, "duration": 4.02}, {"text": "And we'll have at\nleast one mythology", "start": 4620.76, "duration": 2.01}, {"text": "that we can all\nanchor ourselves on.", "start": 4622.77, "duration": 3.19}, {"text": "And I would like to have\nsome other mythologies.", "start": 4625.96, "duration": 4.08}, {"text": "And it would be fun for you\nto read some mythologies", "start": 4630.04, "duration": 3.6}, {"text": "from some cultures that you\ndon't know anything about.", "start": 4633.64, "duration": 4.9}, {"text": "Or if you know\nsomething about them,", "start": 4643.63, "duration": 1.5}, {"text": "let's make sure\nthey're not Western.", "start": 4645.13, "duration": 1.5}, {"text": "OK?", "start": 4651.61, "duration": 1.79}, {"text": "Well, that's it for today.", "start": 4653.4, "duration": 1.11}, {"text": "Thank you.", "start": 4654.51, "duration": 1.52}]
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+[{"text": "[SQUEAKING]\n[RUSTLING] [CLICKING]", "start": 0.0, "duration": 15.08}, {"text": "JOHN DOLHUN: Good\nafternoon, everyone.", "start": 15.08, "duration": 2.32}, {"text": "Welcome to The Ellen Swallow\nRichards lab part two.", "start": 17.4, "duration": 5.06}, {"text": "There is-- the room will\nbe a little bit more", "start": 22.46, "duration": 2.46}, {"text": "sparsely populated today.", "start": 24.92, "duration": 1.74}, {"text": "I wonder why.", "start": 26.66, "duration": 1.35}, {"text": "Lab reports are due, right?", "start": 28.01, "duration": 1.53}, {"text": "So we're going to get started.", "start": 32.479, "duration": 2.921}, {"text": "And I'm going to start off by\ntalking about probably the most", "start": 35.4, "duration": 5.57}, {"text": "important parameter in measuring\nthe health of the river,", "start": 40.97, "duration": 5.07}, {"text": "and that's the dissolved\noxygen. So when", "start": 46.04, "duration": 3.99}, {"text": "we look at the dissolved\noxygen concentrations", "start": 50.03, "duration": 4.05}, {"text": "out there, for a river\nto really be healthy,", "start": 54.08, "duration": 4.74}, {"text": "we're looking for something\ngreater than probably about 8", "start": 58.82, "duration": 3.88}, {"text": "PPM.", "start": 62.7, "duration": 0.5}, {"text": "If the concentrations\nfall down to 5 or less,", "start": 73.52, "duration": 4.44}, {"text": "then you'll start to see the\nfish move around erratically,", "start": 77.96, "duration": 3.66}, {"text": "because they're trying\nto get their oxygen.", "start": 81.62, "duration": 2.85}, {"text": "So less than or equal to\n5, and we have some stress", "start": 84.47, "duration": 9.48}, {"text": "placed on the aquatic life.", "start": 93.95, "duration": 2.25}, {"text": "If the dissolved\noxygen concentration", "start": 96.2, "duration": 2.43}, {"text": "goes below 2, even\nfor an hour or two,", "start": 98.63, "duration": 9.827}, {"text": "you're going to have fish kills.", "start": 108.457, "duration": 1.333}, {"text": "So let's take a\nmoment to actually see", "start": 117.07, "duration": 4.08}, {"text": "how this oxygen\ngets into the water,", "start": 121.15, "duration": 2.88}, {"text": "and this is the big picture.", "start": 124.03, "duration": 2.89}, {"text": "So if you look at this, you've\ngot two processes going on.", "start": 126.92, "duration": 4.43}, {"text": "You've got the oxygen coming\nin from the atmosphere,", "start": 131.35, "duration": 3.51}, {"text": "and it's diffusing\ninto the water system.", "start": 134.86, "duration": 3.75}, {"text": "You also have down below, you've\ngot aerobic biodegradation", "start": 138.61, "duration": 5.04}, {"text": "taking place.", "start": 143.65, "duration": 2.02}, {"text": "So we've got oxygen\ndiffusing into the water,", "start": 145.67, "duration": 13.16}, {"text": "and then we've got\naerobic biodegradation.", "start": 158.83, "duration": 7.37}, {"text": "These are the two main\nprocesses that are taking place,", "start": 171.28, "duration": 5.79}, {"text": "and both of these\nprocesses are going--", "start": 177.07, "duration": 4.53}, {"text": "they have different kinetics,\nyet they're coupled together,", "start": 181.6, "duration": 4.5}, {"text": "coupled in the sense that if\naerobic biodegradation uses up", "start": 186.1, "duration": 4.62}, {"text": "the oxygen, more oxygen\nwill start to dissolve in.", "start": 190.72, "duration": 4.68}, {"text": "There's a transfer\ndriving force that", "start": 195.4, "duration": 2.34}, {"text": "actually lets more oxygen\ndissolve into the water.", "start": 197.74, "duration": 2.76}, {"text": "The rate at which\noxygen is dissolving", "start": 203.85, "duration": 5.78}, {"text": "is actually proportional\nto the deficit of oxygen", "start": 209.63, "duration": 4.65}, {"text": "that's in the river.", "start": 214.28, "duration": 1.32}, {"text": "And that deficit is equal\nto the equilibrium level", "start": 222.49, "duration": 8.26}, {"text": "that we would expect\nminus the actual level", "start": 230.75, "duration": 4.5}, {"text": "that we actually find.", "start": 235.25, "duration": 1.5}, {"text": "So the amounts of oxygen\nthat we're talking about", "start": 246.34, "duration": 2.87}, {"text": "are very tiny.", "start": 249.21, "duration": 2.22}, {"text": "And there was a\nbrilliant chemist", "start": 251.43, "duration": 3.06}, {"text": "by the name of William Henry,\nwho actually, back in 1803,", "start": 254.49, "duration": 15.26}, {"text": "came out with Henry's Law.", "start": 269.75, "duration": 2.52}, {"text": "And what Henry's Law\nsays is very simple.", "start": 279.51, "duration": 5.17}, {"text": "The solubility of a dissolved\ngas in a body of water", "start": 284.68, "duration": 13.74}, {"text": "is proportional to\nthe partial pressure", "start": 298.42, "duration": 3.06}, {"text": "of that gas over the water.", "start": 301.48, "duration": 2.4}, {"text": "There's even a Henry's\nLaw constant here,", "start": 308.35, "duration": 2.67}, {"text": "and there are tables of these.", "start": 311.02, "duration": 2.73}, {"text": "There are thousands of them.", "start": 313.75, "duration": 1.53}, {"text": "For every solvent, for every\ngas, for every temperature", "start": 315.28, "duration": 4.23}, {"text": "combination that\nyou can think of,", "start": 319.51, "duration": 2.06}, {"text": "there is a Henry Law constant\nthat you can plug in.", "start": 321.57, "duration": 4.58}, {"text": "Let's think about, what\nis the partial pressure", "start": 326.15, "duration": 3.18}, {"text": "of oxygen on any given day?", "start": 329.33, "duration": 2.86}, {"text": "How do we calculate that?", "start": 332.19, "duration": 1.19}, {"text": "Yes, yeah.", "start": 344.1, "duration": 1.05}, {"text": "Alec.", "start": 345.15, "duration": 0.66}, {"text": "AUDIENCE: So if you\nhave total pressure,", "start": 345.81, "duration": 1.77}, {"text": "and then you know the\nmakeup of the atmosphere.", "start": 347.58, "duration": 2.34}, {"text": "You can just break it down.", "start": 349.92, "duration": 2.2}, {"text": "So say your pressure\nis 1 atmosphere", "start": 352.12, "duration": 2.08}, {"text": "and you have 20% oxygen in\nthe at-- that's not right.", "start": 354.2, "duration": 3.49}, {"text": "But 20% oxygen in\nthe atmosphere,", "start": 357.69, "duration": 2.22}, {"text": "your oxygen would be\ncontributing 0.20 atmospheres", "start": 359.91, "duration": 3.423}, {"text": "to the pressure [INAUDIBLE].", "start": 363.333, "duration": 1.167}, {"text": "JOHN DOLHUN: Very good.", "start": 364.5, "duration": 1.08}, {"text": "Very good, Alec.", "start": 365.58, "duration": 1.38}, {"text": "So Alec said that you've got\n20.9% oxygen in the atmosphere.", "start": 366.96, "duration": 5.38}, {"text": "So we can convert\nthat to a decimal.", "start": 372.34, "duration": 3.29}, {"text": "Partial pressure of\noxygen on any given day", "start": 375.63, "duration": 2.61}, {"text": "would be the percent\nof oxygen that's", "start": 378.24, "duration": 3.81}, {"text": "in the atmosphere times\nthe atmospheric pressure", "start": 382.05, "duration": 5.61}, {"text": "on that particular day minus\nthe pressure of the water vapor", "start": 387.66, "duration": 6.96}, {"text": "that we're talking about.", "start": 394.62, "duration": 2.44}, {"text": "So that gives us\na handle on this.", "start": 397.06, "duration": 5.315}, {"text": "I want to show you\nprobably the simplest", "start": 402.375, "duration": 2.565}, {"text": "example of Henry's Law.", "start": 404.94, "duration": 2.61}, {"text": "I brought a bottle of Coke\nhere, and these are hard, right,", "start": 407.55, "duration": 6.81}, {"text": "because they pack them--", "start": 414.36, "duration": 1.47}, {"text": "there's a head of carbon\ndioxide gas over the liquid.", "start": 415.83, "duration": 5.14}, {"text": "Now when I open this, I'm\ngoing to release the gas,", "start": 420.97, "duration": 3.15}, {"text": "so the partial pressure of\nCO2 over this liquid is gone.", "start": 424.12, "duration": 3.65}, {"text": "We should start to see bubbles\ncoming out of the solution,", "start": 427.77, "duration": 2.88}, {"text": "right?", "start": 430.65, "duration": 1.809}, {"text": "[HISSING]", "start": 432.459, "duration": 1.581}, {"text": "Oh good, it's not an\nexplosive one, so that's good.", "start": 434.04, "duration": 6.66}, {"text": "So there are the bubbles of\nthe dissolved carbon dioxide", "start": 440.7, "duration": 4.14}, {"text": "gas starting to come out.", "start": 444.84, "duration": 2.13}, {"text": "And that's a simple\nexample of Henry's Law.", "start": 446.97, "duration": 4.08}, {"text": "Can anybody think of a\nmore complex example?", "start": 451.05, "duration": 2.565}, {"text": "Anybody a diver here?", "start": 460.94, "duration": 4.54}, {"text": "Kelly, you're a diver?", "start": 465.48, "duration": 1.02}, {"text": "AUDIENCE: Oh, no,\nI'm just [INAUDIBLE]..", "start": 466.5, "duration": 1.667}, {"text": "JOHN DOLHUN: OK.", "start": 468.167, "duration": 1.813}, {"text": "When you--", "start": 469.98, "duration": 0.82}, {"text": "AUDIENCE: Yeah.", "start": 470.8, "duration": 1.43}, {"text": "It's like the bends, right?", "start": 472.23, "duration": 1.21}, {"text": "Because as you go down\nfurther, the pressure", "start": 473.44, "duration": 3.47}, {"text": "increases so that more nitrogen\ncan dissolve in your blood,", "start": 476.91, "duration": 6.65}, {"text": "you said?", "start": 483.56, "duration": 0.61}, {"text": "JOHN DOLHUN: Yeah, very good.", "start": 484.17, "duration": 1.29}, {"text": "Yeah, so you've got\ngases in your blood.", "start": 485.46, "duration": 2.255}, {"text": "And when you go\ndown, when you're", "start": 487.715, "duration": 1.375}, {"text": "diving down under\na great pressure,", "start": 489.09, "duration": 3.22}, {"text": "when you start your ascent,\nall of those gas bubbles", "start": 492.31, "duration": 5.28}, {"text": "are going to come out.", "start": 497.59, "duration": 1.62}, {"text": "And they have to go somewhere.", "start": 499.21, "duration": 1.26}, {"text": "They could migrate\nanywhere in your body,", "start": 500.47, "duration": 2.46}, {"text": "and it could cause a rash.", "start": 502.93, "duration": 3.16}, {"text": "It could cause some\ntype of joint pain.", "start": 506.09, "duration": 3.47}, {"text": "You could end up with\nparalysis, even death.", "start": 509.56, "duration": 3.28}, {"text": "So divers have to really,\nreally time their ascent.", "start": 512.84, "duration": 4.67}, {"text": "That there's a name for that.", "start": 517.51, "duration": 1.529}, {"text": "Kelly said the bends.", "start": 519.039, "duration": 1.651}, {"text": "That's one of the names.", "start": 520.69, "duration": 1.504}, {"text": "It's also called DCS,\nDecompression Sickness.", "start": 525.62, "duration": 4.995}, {"text": "That's a great example\nof Henry's Law.", "start": 542.41, "duration": 4.65}, {"text": "What about if we think about\ntemperature and dissolved", "start": 547.06, "duration": 5.31}, {"text": "oxygen?", "start": 552.37, "duration": 1.47}, {"text": "Let's actually take\na look at that.", "start": 553.84, "duration": 2.07}, {"text": "Here is a graph of oxygen\nconcentration and temperature.", "start": 560.63, "duration": 4.47}, {"text": "What stands out to you here?", "start": 565.1, "duration": 1.59}, {"text": "Sean?", "start": 576.71, "duration": 0.5}, {"text": "AUDIENCE: It decreases\nexponentially with temperature.", "start": 577.21, "duration": 3.57}, {"text": "JOHN DOLHUN: Yeah, as\nthe water is warming up,", "start": 580.78, "duration": 2.04}, {"text": "look what's happening\nto the dissolved oxygen.", "start": 582.82, "duration": 3.76}, {"text": "Why do you think\nthat's happening?", "start": 586.58, "duration": 1.906}, {"text": "And why, when the water is\ncold, can we hold so much oxygen", "start": 592.95, "duration": 6.09}, {"text": "in that cold water?", "start": 599.04, "duration": 3.14}, {"text": "Kelly.", "start": 602.18, "duration": 0.75}, {"text": "AUDIENCE: Is it because, as\nthe temperature increases,", "start": 602.93, "duration": 2.82}, {"text": "the average kinetic\nenergy of the molecules", "start": 605.75, "duration": 2.495}, {"text": "increases, and the\ndistribution broadens,", "start": 608.245, "duration": 2.665}, {"text": "so more oxygen has\nthe ability to escape?", "start": 610.91, "duration": 5.13}, {"text": "JOHN DOLHUN: Good, good.", "start": 616.04, "duration": 1.155}, {"text": "As the temperature increases,\nthe kinetic energy of the water", "start": 617.195, "duration": 3.675}, {"text": "molecules is\nincreasing, and they're", "start": 620.87, "duration": 2.37}, {"text": "starting-- think about\nwhen you boil water.", "start": 623.24, "duration": 3.12}, {"text": "Bam, they're bubbling out.", "start": 626.36, "duration": 2.43}, {"text": "That hydrogen bonding\nnetwork is gone.", "start": 628.79, "duration": 2.61}, {"text": "All those intermolecular\nforces of attraction are gone.", "start": 631.4, "duration": 3.51}, {"text": "Now think about this side when\nthe water gets really cold", "start": 634.91, "duration": 4.44}, {"text": "and you form this\nhydrogen bonding network.", "start": 639.35, "duration": 5.82}, {"text": "I mean, it expands, right?", "start": 645.17, "duration": 2.13}, {"text": "Pipes break.", "start": 647.3, "duration": 0.9}, {"text": "That's why our pipes break.", "start": 648.2, "duration": 1.35}, {"text": "It's because of the hydrogen\nbonding in the ice crystals", "start": 649.55, "duration": 3.225}, {"text": "when they expand out.", "start": 652.775, "duration": 1.635}, {"text": "But look at the crevices\nhere in these things.", "start": 654.41, "duration": 3.74}, {"text": "So the oxygen molecules can\nswim in and out of those,", "start": 658.15, "duration": 3.43}, {"text": "and they can become weakly\ntrapped and pinned in.", "start": 661.58, "duration": 3.3}, {"text": "And there you've got\na dramatic increase", "start": 664.88, "duration": 4.82}, {"text": "in the amount of oxygen that can\ndissolve in the colder waters.", "start": 669.7, "duration": 5.32}, {"text": "The other thing to keep in mind\nabout the water is the heat", "start": 675.02, "duration": 5.94}, {"text": "capacity of water\nis much greater", "start": 680.96, "duration": 2.7}, {"text": "than the heat capacity of air.", "start": 683.66, "duration": 2.43}, {"text": "It takes a lot more\nenergy to change", "start": 686.09, "duration": 2.61}, {"text": "the temperature of water.", "start": 688.7, "duration": 2.05}, {"text": "I mean, you can--", "start": 690.75, "duration": 1.875}, {"text": "I've gone out when\nit's 85 degrees,", "start": 692.625, "duration": 2.265}, {"text": "and I want to go for a\nswim across from my house.", "start": 694.89, "duration": 2.94}, {"text": "And I jump in, and\nit's only 67 in there.", "start": 697.83, "duration": 3.36}, {"text": "So the water hasn't caught up\nto the temperature of the air.", "start": 701.19, "duration": 3.63}, {"text": "Now there are a lot of\ndifferent equations out there", "start": 707.87, "duration": 6.4}, {"text": "that actually would\nlet us calculate", "start": 714.27, "duration": 2.85}, {"text": "the potential of a body of water\nto hold oxygen, theoretically,", "start": 717.12, "duration": 5.31}, {"text": "how much could be out\nthere on a given day.", "start": 722.43, "duration": 2.89}, {"text": "And the more complex\nthe equation,", "start": 725.32, "duration": 2.54}, {"text": "the better the results.", "start": 727.86, "duration": 1.8}, {"text": "I found a couple\nempirical, simple equations", "start": 729.66, "duration": 3.18}, {"text": "that give really good results,\nso I'm going to go with these.", "start": 732.84, "duration": 4.44}, {"text": "And they're all based on\naltitude and temperature.", "start": 737.28, "duration": 4.42}, {"text": "If you look at\nthe equation, it's", "start": 741.7, "duration": 2.24}, {"text": "all about the\natmospheric pressure,", "start": 743.94, "duration": 3.04}, {"text": "the water vapor pressure, and\nthe temperature of the water,", "start": 746.98, "duration": 4.86}, {"text": "which is in Celsius.", "start": 751.84, "duration": 2.04}, {"text": "So if we look at that\nequation, if the pressure,", "start": 753.88, "duration": 5.87}, {"text": "the atmospheric\npressure goes up, right,", "start": 759.75, "duration": 3.4}, {"text": "what happens to the dissolved\noxygen concentration?", "start": 763.15, "duration": 2.98}, {"text": "If you're trying to\ncalculate the saturated level", "start": 773.74, "duration": 2.37}, {"text": "of dissolved oxygen, and\nthe pressure goes up,", "start": 776.11, "duration": 3.96}, {"text": "the atmospheric\npressure, what happens", "start": 780.07, "duration": 1.8}, {"text": "to the DO concentration?", "start": 781.87, "duration": 1.5}, {"text": "I promise this is\nnot a trick question.", "start": 787.48, "duration": 3.66}, {"text": "This is-- Alec.", "start": 791.14, "duration": 1.232}, {"text": "AUDIENCE: It increases.", "start": 792.372, "duration": 0.958}, {"text": "JOHN DOLHUN: It\nabsolutely increases.", "start": 793.33, "duration": 1.92}, {"text": "Yeah.", "start": 795.25, "duration": 0.9}, {"text": "Now what happens if we\nhave a high water vapor", "start": 796.15, "duration": 2.73}, {"text": "pressure that day?", "start": 798.88, "duration": 2.82}, {"text": "You might be on a\nmountaintop stream.", "start": 801.7, "duration": 2.31}, {"text": "Water vapor pressure\nis very high.", "start": 804.01, "duration": 1.72}, {"text": "What happens to the DO?", "start": 805.73, "duration": 1.16}, {"text": "Someone?", "start": 811.41, "duration": 0.5}, {"text": "AUDIENCE: Decreases.", "start": 811.91, "duration": 0.93}, {"text": "JOHN DOLHUN: Sam, decreases.", "start": 812.84, "duration": 1.26}, {"text": "Good.", "start": 814.1, "duration": 1.77}, {"text": "And the other situation, which\nif the river temperature is", "start": 815.87, "duration": 4.32}, {"text": "high, then it's\nintuitive, right?", "start": 820.19, "duration": 3.33}, {"text": "Your DO is going to be smaller.", "start": 823.52, "duration": 5.1}, {"text": "So that's how you\nuse those equations.", "start": 828.62, "duration": 2.25}, {"text": "And then what you can\ndo with the equation", "start": 830.87, "duration": 2.04}, {"text": "is you can calculate a thing\ncalled the percent saturation", "start": 832.91, "duration": 4.65}, {"text": "level, which is the actual DO\nthat you get in the lab divided", "start": 837.56, "duration": 7.46}, {"text": "by the potential of\nwater to hold oxygen", "start": 845.02, "duration": 4.65}, {"text": "based on the temperature\nand pressure above.", "start": 849.67, "duration": 2.85}, {"text": "And that saturated\nlevel is going", "start": 852.52, "duration": 1.83}, {"text": "to tell us a lot about the\ncondition of the water.", "start": 854.35, "duration": 4.56}, {"text": "Usually-- I mean, you could\nhave from 90% to 110%,", "start": 858.91, "duration": 4.53}, {"text": "something like that.", "start": 863.44, "duration": 0.96}, {"text": "That's normal.", "start": 864.4, "duration": 1.14}, {"text": "If you get to 120%\nor greater, that's", "start": 865.54, "duration": 4.38}, {"text": "a problem, because there\nare different diseases", "start": 869.92, "duration": 3.03}, {"text": "that the fish can--", "start": 872.95, "duration": 1.32}, {"text": "they have an oxygen bubble\ndisease fish can get", "start": 874.27, "duration": 3.685}, {"text": "if it becomes too saturated.", "start": 877.955, "duration": 2.191}, {"text": "So this is something that\nyou'll do these calculations,", "start": 880.146, "duration": 4.654}, {"text": "and the TAs will\ncarry a pH meter.", "start": 884.8, "duration": 3.78}, {"text": "They'll record the\nair temperature,", "start": 888.58, "duration": 2.46}, {"text": "the atmospheric\npressure, the river water", "start": 891.04, "duration": 3.63}, {"text": "temperature each\nday you go down,", "start": 894.67, "duration": 1.89}, {"text": "and they'll put that\non the whiteboard.", "start": 896.56, "duration": 2.37}, {"text": "Here is some simple\ndata that will", "start": 898.93, "duration": 5.52}, {"text": "allow you to\ninterpolate the water", "start": 904.45, "duration": 1.89}, {"text": "vapor pressures based\non temperatures.", "start": 906.34, "duration": 5.32}, {"text": "And you can go in\nbetween these, and you'll", "start": 911.66, "duration": 1.83}, {"text": "get very good results.", "start": 913.49, "duration": 1.92}, {"text": "If you can't find it on here,\nyou could use this equation.", "start": 915.41, "duration": 3.82}, {"text": "But the T here is the\ntemperature of air,", "start": 919.23, "duration": 3.96}, {"text": "and it's in Kelvin.", "start": 923.19, "duration": 2.16}, {"text": "And back here, this\nis the temperature", "start": 925.35, "duration": 2.16}, {"text": "of the river in Celsius.", "start": 927.51, "duration": 1.96}, {"text": "So don't get confused with that.", "start": 929.47, "duration": 3.73}, {"text": "And now I'd like to spend\na few minutes talking", "start": 933.2, "duration": 2.85}, {"text": "about the actual method that\nwe're going to use in this lab.", "start": 936.05, "duration": 6.39}, {"text": "This method was\nactually discovered", "start": 942.44, "duration": 2.25}, {"text": "by a graduate student by the\nname of Winkler back in 1888.", "start": 944.69, "duration": 10.81}, {"text": "And the method has\nwithstood time.", "start": 955.5, "duration": 3.39}, {"text": "What he did is he developed this\nseries of oxidation reduction", "start": 958.89, "duration": 4.11}, {"text": "equations to actually\nmeasure the dissolved oxygen", "start": 963.0, "duration": 6.09}, {"text": "concentration in saltwater.", "start": 969.09, "duration": 3.21}, {"text": "And he came up with this\nseries of equations.", "start": 972.3, "duration": 3.06}, {"text": "And it's been 130 years,\nand this is still here.", "start": 975.36, "duration": 4.38}, {"text": "Today they have the fancy\ndissolved oxygen meters,", "start": 979.74, "duration": 3.81}, {"text": "which we're not using,\nbut you can just", "start": 983.55, "duration": 1.71}, {"text": "drop it in and get your DO.", "start": 985.26, "duration": 3.24}, {"text": "They used this method to\ncalibrate those meters today.", "start": 988.5, "duration": 4.44}, {"text": "So you're using--\nyou're going to be", "start": 992.94, "duration": 1.5}, {"text": "doing the real chemistry here.", "start": 994.44, "duration": 2.22}, {"text": "The whole method is\nbased on that if you've", "start": 996.66, "duration": 5.08}, {"text": "got oxygen in the\nwater, iodide is", "start": 1001.74, "duration": 3.99}, {"text": "going to get oxidized\nto iodine, and you're", "start": 1005.73, "duration": 3.12}, {"text": "going to be able to titrate the\niodine with sodium thiosulfate.", "start": 1008.85, "duration": 4.56}, {"text": "So let's just go through the\nmethod just a little bit here.", "start": 1013.41, "duration": 5.74}, {"text": "So we start with\nmanganese sulfate,", "start": 1019.15, "duration": 2.57}, {"text": "and we form a white precipitate.", "start": 1021.72, "duration": 2.94}, {"text": "But if oxygen is\npresent in the water,", "start": 1024.66, "duration": 3.9}, {"text": "oxygen is an\noxidizing agent here.", "start": 1028.56, "duration": 3.18}, {"text": "It's going to oxidize\nthis manganese hydroxide", "start": 1031.74, "duration": 4.41}, {"text": "to this tetravalent\nmanganic species.", "start": 1036.15, "duration": 5.41}, {"text": "So you've got manganese over\nhere, which is a plus 2,", "start": 1041.56, "duration": 4.61}, {"text": "and over here,\nyou've got a plus 4.", "start": 1046.17, "duration": 4.04}, {"text": "There are a couple--", "start": 1050.21, "duration": 0.93}, {"text": "in the literature, there's\nsome argument about this.", "start": 1051.14, "duration": 3.07}, {"text": "Some people feel the\nspecies is a trivalent,", "start": 1054.21, "duration": 3.86}, {"text": "and they're saying it's MnOH3.", "start": 1058.07, "duration": 2.71}, {"text": "So on this side, you'd have a\ntrivalent manganese species.", "start": 1063.35, "duration": 5.37}, {"text": "Other people are\nsaying no, it's MnO2.", "start": 1068.72, "duration": 4.0}, {"text": "It's a hydrated form of mnO2.", "start": 1072.72, "duration": 1.715}, {"text": "It's tetravalent.", "start": 1077.9, "duration": 1.92}, {"text": "What I've done is I've\ncombined both these", "start": 1079.82, "duration": 3.03}, {"text": "to give you this manganic\nspecies here, which works.", "start": 1082.85, "duration": 4.44}, {"text": "This is tetravalent.", "start": 1087.29, "duration": 2.4}, {"text": "So notice that when\nyou've formed this,", "start": 1089.69, "duration": 2.37}, {"text": "this is like a brown flock.", "start": 1092.06, "duration": 3.27}, {"text": "You've captured the\noxygen at this point.", "start": 1095.33, "duration": 4.04}, {"text": "Now you've got to dissolve\nthat, so we add sulfuric acid", "start": 1099.37, "duration": 4.92}, {"text": "to dissolve that\nbrown precipitate.", "start": 1104.29, "duration": 3.0}, {"text": "And then there's\niodide in there.", "start": 1107.29, "duration": 3.6}, {"text": "So this oxidized manganese\nwill oxidize iodide to iodine.", "start": 1110.89, "duration": 9.54}, {"text": "We can then detect it\nwith sodium thiosulfate,", "start": 1120.43, "duration": 3.75}, {"text": "and the iodine gets reduced\nback down to iodide.", "start": 1124.18, "duration": 5.07}, {"text": "If you look at this, for every\noxygen, every one oxygen,", "start": 1129.25, "duration": 4.26}, {"text": "you make to manganic species.", "start": 1133.51, "duration": 3.41}, {"text": "Each manganic species\ngives you one I2,", "start": 1136.92, "duration": 3.85}, {"text": "and each I2 requires\ntwo thiosulfate.", "start": 1140.77, "duration": 3.81}, {"text": "So that's a 4 to 1 ratio,\nthiosulfate to oxygen.", "start": 1144.58, "duration": 10.83}, {"text": "So let's take a look at\nyour first day, which", "start": 1155.41, "duration": 3.17}, {"text": "is the standardization\nof the thiosulfate.", "start": 1158.58, "duration": 4.71}, {"text": "We have to know exactly what\nthe concentration of that", "start": 1163.29, "duration": 3.18}, {"text": "is when we titrate the river\nwater to actually get-- to home", "start": 1166.47, "duration": 4.91}, {"text": "in on the exact concentration.", "start": 1171.38, "duration": 2.5}, {"text": "So we're going to be using a\nprimary standard, potassium", "start": 1173.88, "duration": 4.95}, {"text": "biiodate.", "start": 1178.83, "duration": 0.5}, {"text": "Does anybody know what the\nqualities of a primary standard", "start": 1187.66, "duration": 4.99}, {"text": "are?", "start": 1192.65, "duration": 0.5}, {"text": "When you pick a\nprimary standard,", "start": 1199.39, "duration": 1.8}, {"text": "it's pretty important.", "start": 1201.19, "duration": 1.14}, {"text": "You want something that\nhas certain properties.", "start": 1202.33, "duration": 4.58}, {"text": "Anybody ever worked\nwith a primary standard?", "start": 1206.91, "duration": 2.025}, {"text": "No?", "start": 1211.76, "duration": 2.73}, {"text": "OK, well, first thing,\nnotice how big this is.", "start": 1214.49, "duration": 4.815}, {"text": "It has a very high\nformula weight.", "start": 1219.305, "duration": 2.715}, {"text": "So that's actually a good thing.", "start": 1222.02, "duration": 2.565}, {"text": "Not all primary\nstandards have that.", "start": 1224.585, "duration": 4.235}, {"text": "When you mass it\nout, you're going", "start": 1228.82, "duration": 1.83}, {"text": "to have less error on\nthe balance because", "start": 1230.65, "duration": 2.88}, {"text": "of the mass of this thing.", "start": 1233.53, "duration": 2.1}, {"text": "Also, it has to be\nsomething that's pure.", "start": 1235.63, "duration": 4.56}, {"text": "And this is like 99.9% pure.", "start": 1240.19, "duration": 5.46}, {"text": "The other thing is\nyou need something", "start": 1245.65, "duration": 2.82}, {"text": "that does not have any\nwater vapor attached,", "start": 1248.47, "duration": 3.33}, {"text": "no attached water.", "start": 1251.8, "duration": 2.01}, {"text": "The TAs put this in the oven.", "start": 1253.81, "duration": 2.49}, {"text": "So no hydrated water.", "start": 1256.3, "duration": 5.79}, {"text": "And then the final\nthing is, you want--", "start": 1265.52, "duration": 3.09}, {"text": "it should be stable at room\ntemperature and when heated.", "start": 1268.61, "duration": 3.9}, {"text": "And oftentimes we'll\nlook at the cost, too.", "start": 1283.36, "duration": 2.28}, {"text": "That's another factor\nthat comes into play.", "start": 1285.64, "duration": 2.808}, {"text": "But what you're\ngoing to do is you're", "start": 1288.448, "duration": 1.542}, {"text": "going to weigh out\n0.0818 grams of this.", "start": 1289.99, "duration": 4.96}, {"text": "And if you divide by the\nmolecular weight of that,", "start": 1294.95, "duration": 2.45}, {"text": "you'll get moles.", "start": 1297.4, "duration": 1.8}, {"text": "And you're going to\nmake a 100-mil solution.", "start": 1299.2, "duration": 2.83}, {"text": "So divide that by 0.1\nliters, and you'll", "start": 1302.03, "duration": 3.14}, {"text": "get your concentration.", "start": 1305.17, "duration": 1.95}, {"text": "You're actually making up\nsomething like a 0.0021 molar", "start": 1307.12, "duration": 5.64}, {"text": "solution of that standard.", "start": 1312.76, "duration": 4.3}, {"text": "And then you're going to\nuse that to standardize", "start": 1317.06, "duration": 4.49}, {"text": "your thiosulfate.", "start": 1321.55, "duration": 2.84}, {"text": "We're also going to be using\nstarch in this reaction.", "start": 1324.39, "duration": 3.73}, {"text": "So why do you think\nwe need to use starch", "start": 1328.12, "duration": 2.9}, {"text": "when we're titrating something?", "start": 1331.02, "duration": 2.063}, {"text": "Alec.", "start": 1337.82, "duration": 0.8}, {"text": "AUDIENCE: Starch\nreacts with iodide,", "start": 1338.62, "duration": 1.69}, {"text": "and it creates the\nblue color so that when", "start": 1340.31, "duration": 3.15}, {"text": "we react-- when\nwe were titrating,", "start": 1343.46, "duration": 1.975}, {"text": "it could turn really pale.", "start": 1345.435, "duration": 1.235}, {"text": "JOHN DOLHUN: OK.", "start": 1346.67, "duration": 0.36}, {"text": "AUDIENCE: So it was really hard\nto tell if it was clear or not.", "start": 1347.03, "duration": 2.625}, {"text": "So I think the starch helps\nindicate whether or not", "start": 1349.655, "duration": 2.175}, {"text": "you've gotten rid of\nall of the iodide.", "start": 1351.83, "duration": 2.19}, {"text": "Iodide, yeah.", "start": 1354.02, "duration": 0.99}, {"text": "JOHN DOLHUN: Good.", "start": 1355.01, "duration": 0.75}, {"text": "Good.", "start": 1355.76, "duration": 0.31}, {"text": "That's very good.", "start": 1356.07, "duration": 0.73}, {"text": "So starch actually reacts\nwith iodide and iodine,", "start": 1356.8, "duration": 4.06}, {"text": "gives you that blue-black color.", "start": 1360.86, "duration": 1.44}, {"text": "So if you're titrating\nsomething yellow to clear,", "start": 1362.3, "duration": 3.75}, {"text": "sometimes it might\nbe harder to see.", "start": 1366.05, "duration": 3.22}, {"text": "So what Alec said\nwas your solution", "start": 1369.27, "duration": 5.1}, {"text": "actually reacts with starch.", "start": 1374.37, "duration": 4.28}, {"text": "So I actually brought some\nof the solution in here,", "start": 1378.65, "duration": 3.94}, {"text": "and I brought a\npiece of bread in.", "start": 1382.59, "duration": 1.83}, {"text": "I don't know if this\nis going to work,", "start": 1384.42, "duration": 2.01}, {"text": "but bread has starch\nin it, doesn't it?", "start": 1386.43, "duration": 3.87}, {"text": "So I'm going to put\nsomeone on this bread.", "start": 1390.3, "duration": 3.33}, {"text": "Wow.", "start": 1393.63, "duration": 1.93}, {"text": "Look at that blue black.", "start": 1395.56, "duration": 1.52}, {"text": "So something's going on here.", "start": 1397.08, "duration": 1.77}, {"text": "It's reacting with\nthe starch, right?", "start": 1398.85, "duration": 2.87}, {"text": "Can I have a volunteer?", "start": 1401.72, "duration": 2.67}, {"text": "Some brave person?", "start": 1404.39, "duration": 3.34}, {"text": "I know you're all\ntired, but one of you.", "start": 1407.73, "duration": 2.01}, {"text": "One of you, come up.", "start": 1409.74, "duration": 2.84}, {"text": "Come on up, Maida.", "start": 1412.58, "duration": 1.59}, {"text": "Maida, right?", "start": 1414.17, "duration": 1.29}, {"text": "It's Maida, right?", "start": 1418.21, "duration": 0.96}, {"text": "AUDIENCE: Yes.", "start": 1419.17, "duration": 0.24}, {"text": "JOHN DOLHUN: OK.", "start": 1419.41, "duration": 0.75}, {"text": "Maida, stand up front here.", "start": 1420.16, "duration": 2.41}, {"text": "So what we're going to do is\nwe're going to open this up.", "start": 1422.57, "duration": 3.56}, {"text": "And put a pair of\nthese on, Maida.", "start": 1426.13, "duration": 4.87}, {"text": "And I'm going to let\nyou hold this beaker", "start": 1431.0, "duration": 7.34}, {"text": "and face your fellow students.", "start": 1438.34, "duration": 2.31}, {"text": "And just hold it nice and--", "start": 1440.65, "duration": 2.58}, {"text": "and what we're\ngoing to do is we're", "start": 1445.834, "duration": 1.546}, {"text": "going to add something to it.", "start": 1447.38, "duration": 1.95}, {"text": "It's clear, right?", "start": 1449.33, "duration": 1.69}, {"text": "OK, keep your eye on the beaker.", "start": 1451.02, "duration": 3.9}, {"text": "Maida, don't drop\nbut whatever you do.", "start": 1454.92, "duration": 1.67}, {"text": "AUDIENCE: I won't drop it.", "start": 1456.59, "duration": 0.27}, {"text": "JOHN DOLHUN: OK.", "start": 1456.86, "duration": 0.667}, {"text": "[CHUCKLES]", "start": 1457.527, "duration": 0.823}, {"text": "OK.", "start": 1462.63, "duration": 1.95}, {"text": "So keep your eye on that beaker.", "start": 1464.58, "duration": 2.037}, {"text": "Don't take your\neyes off the beaker.", "start": 1470.03, "duration": 1.74}, {"text": "Now what-- don't worry.", "start": 1478.68, "duration": 1.715}, {"text": "Keep watching it, Maida.", "start": 1480.395, "duration": 1.465}, {"text": "Don't get nervous.", "start": 1481.86, "duration": 0.75}, {"text": "Oh!", "start": 1482.61, "duration": 1.28}, {"text": "Now that's what\nI'm talking about.", "start": 1483.89, "duration": 2.23}, {"text": "You see that?", "start": 1486.12, "duration": 1.31}, {"text": "This is what we're\ntalking about.", "start": 1487.43, "duration": 2.23}, {"text": "And I mean, you're titrating.", "start": 1489.66, "duration": 1.79}, {"text": "You can't see the end point.", "start": 1491.45, "duration": 1.17}, {"text": "You put this in, now that\nlast drop of titrant,", "start": 1492.62, "duration": 3.78}, {"text": "it's going to turn it clear.", "start": 1496.4, "duration": 2.01}, {"text": "You're going to be able\nto see your titration.", "start": 1498.41, "duration": 2.315}, {"text": "And thank you very much, Maida.", "start": 1500.725, "duration": 2.305}, {"text": "So what's going on\nwith the starch?", "start": 1508.8, "duration": 3.12}, {"text": "Let's take a look at this.", "start": 1511.92, "duration": 2.58}, {"text": "Starch is made up of\nabout 25% amylose, which", "start": 1514.5, "duration": 5.67}, {"text": "is the linear helical form.", "start": 1520.17, "duration": 2.88}, {"text": "And it also is made up about\n75% of the branched amylopectin.", "start": 1523.05, "duration": 5.87}, {"text": "What happens is we have\niodine and iodide present", "start": 1528.92, "duration": 5.535}, {"text": "in our solution, and when\nthose two come together,", "start": 1534.455, "duration": 5.065}, {"text": "they actually form\nthis pentaiodide anion.", "start": 1539.52, "duration": 5.07}, {"text": "So you've got some\nI2, some I minus.", "start": 1544.59, "duration": 6.39}, {"text": "Remember, I2 is amber.", "start": 1550.98, "duration": 2.67}, {"text": "I minus is clear.", "start": 1553.65, "duration": 1.95}, {"text": "When you get these\ntwo together and they", "start": 1555.6, "duration": 4.06}, {"text": "insert into this helix, the\namylose helix of starch,", "start": 1559.66, "duration": 5.04}, {"text": "and what amylose does is it\nforces the pentaiodide anion", "start": 1564.7, "duration": 4.86}, {"text": "to go in linearly\ninto that helix.", "start": 1569.56, "duration": 3.37}, {"text": "Then the energy spacings change.", "start": 1572.93, "duration": 3.46}, {"text": "So you've got-- the way the\nwavelength of light hits", "start": 1576.39, "duration": 2.96}, {"text": "that, you're going\nto see blue black.", "start": 1579.35, "duration": 2.19}, {"text": "It's all happening inside of\nthe starch with the amylose.", "start": 1581.54, "duration": 3.6}, {"text": "That's the key thing.", "start": 1585.14, "duration": 1.5}, {"text": "There are different people--", "start": 1586.64, "duration": 1.57}, {"text": "some people still\nbelieve it's I3 minus.", "start": 1588.21, "duration": 4.07}, {"text": "There's somebody else out\nthere saying no, no, it's", "start": 1592.28, "duration": 2.28}, {"text": "a polyiodide.", "start": 1594.56, "duration": 2.04}, {"text": "There's always going to be\nsome controversy in the--", "start": 1596.6, "duration": 3.57}, {"text": "but they're working on it.", "start": 1600.17, "duration": 2.1}, {"text": "I like I5.", "start": 1602.27, "duration": 1.74}, {"text": "And someone actually\nmade an inorganic complex", "start": 1604.01, "duration": 6.3}, {"text": "to make it look like starch,\nand they proved it was I5.", "start": 1610.31, "duration": 5.61}, {"text": "But even after this\npaper came out,", "start": 1615.92, "duration": 1.8}, {"text": "there's still a lot\nof controversy, so.", "start": 1617.72, "duration": 2.4}, {"text": "So for your standardization,\npretty simple.", "start": 1622.88, "duration": 4.807}, {"text": "You're going to go\nthrough, and you're", "start": 1627.687, "duration": 1.583}, {"text": "going to just\nfollow these steps.", "start": 1629.27, "duration": 1.65}, {"text": "The TAs will go through\nthis with you, very simple.", "start": 1630.92, "duration": 3.33}, {"text": "And you're going to\nstart off with probably", "start": 1634.25, "duration": 2.49}, {"text": "something like this, kind\nof like a reddish solution.", "start": 1636.74, "duration": 5.91}, {"text": "And then you're going to\nstart adding your thiosulfate.", "start": 1642.65, "duration": 6.87}, {"text": "And gradually, your titrating\nthe iodine in this solution", "start": 1649.52, "duration": 5.46}, {"text": "to iodide.", "start": 1654.98, "duration": 1.8}, {"text": "So here you've got a\nmore yellow solution.", "start": 1656.78, "duration": 2.425}, {"text": "What you want to do is you want\nto find a spot when it turns", "start": 1661.725, "duration": 5.055}, {"text": "yellow to add your starch.", "start": 1666.78, "duration": 3.8}, {"text": "And the starch has to be\nbubbly hot on the hot plate.", "start": 1670.58, "duration": 3.96}, {"text": "And if you add it\ntoo early, there's", "start": 1674.54, "duration": 4.61}, {"text": "so much iodine in\nthere, it's going", "start": 1679.15, "duration": 1.77}, {"text": "to destroy the starch complex.", "start": 1680.92, "duration": 2.28}, {"text": "You won't get a reaction.", "start": 1683.2, "duration": 2.22}, {"text": "But if you wait until it's\nso pale yellow, what happens,", "start": 1685.42, "duration": 4.945}, {"text": "Thomas?", "start": 1690.365, "duration": 0.5}, {"text": "AUDIENCE: It turns blue.", "start": 1692.85, "duration": 1.0}, {"text": "It makes the complex\nsuccessfully,", "start": 1693.85, "duration": 2.14}, {"text": "it turns it dark blue.", "start": 1695.99, "duration": 1.68}, {"text": "JOHN DOLHUN: It\nturns it dark blue.", "start": 1697.67, "duration": 2.37}, {"text": "Yeah.", "start": 1700.04, "duration": 0.69}, {"text": "But if you wait\ntoo long, right--", "start": 1700.73, "duration": 2.357}, {"text": "AUDIENCE: [? I ?] [? mean, ?]\nif you add too much, [INAUDIBLE]", "start": 1703.087, "duration": 2.583}, {"text": "JOHN DOLHUN: Did you--", "start": 1705.67, "duration": 0.95}, {"text": "you had a reaction\nyesterday where your starch", "start": 1706.62, "duration": 2.35}, {"text": "was an globules, right?", "start": 1708.97, "duration": 1.71}, {"text": "Is that--", "start": 1710.68, "duration": 0.87}, {"text": "AUDIENCE: Oh yeah.", "start": 1711.55, "duration": 0.952}, {"text": "It formed a film because\nwe didn't keep it hot.", "start": 1712.502, "duration": 3.36}, {"text": "JOHN DOLHUN: Oh, the\nstarch was not hot enough.", "start": 1715.862, "duration": 1.958}, {"text": "OK, that explains that.", "start": 1717.82, "duration": 1.76}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1719.58, "duration": 0.94}, {"text": "JOHN DOLHUN: Yeah.", "start": 1720.52, "duration": 0.45}, {"text": "AUDIENCE: We put\nit in and stirred,", "start": 1720.97, "duration": 0.973}, {"text": "and it made a bunch of little\nblue specks that [INAUDIBLE]..", "start": 1721.943, "duration": 2.957}, {"text": "JOHN DOLHUN: Yes, yes.", "start": 1724.9, "duration": 1.32}, {"text": "Yeah, I've seen that before.", "start": 1726.22, "duration": 1.51}, {"text": "So you want to keep your starch\nhot, and just be patient.", "start": 1727.73, "duration": 5.12}, {"text": "And then you just take a\nplastic pasture pipette,", "start": 1732.85, "duration": 4.17}, {"text": "take a swig of it,\nshoot it in, and you", "start": 1737.02, "duration": 2.64}, {"text": "should get your blue black.", "start": 1739.66, "duration": 1.95}, {"text": "And then look.", "start": 1741.61, "duration": 1.96}, {"text": "You've got your blue black.", "start": 1743.57, "duration": 1.55}, {"text": "You put that last drop\nof thiosulfate in,", "start": 1745.12, "duration": 2.61}, {"text": "and you've got your\nclear solution.", "start": 1747.73, "duration": 2.71}, {"text": "So you turn around, and\nyou're writing this down", "start": 1750.44, "duration": 2.0}, {"text": "in your notebooks, right,\nand then you look back,", "start": 1752.44, "duration": 4.53}, {"text": "but it's starting to\nturn blue black again.", "start": 1756.97, "duration": 2.49}, {"text": "What should you do?", "start": 1759.46, "duration": 0.98}, {"text": "What would you do?", "start": 1763.49, "duration": 0.86}, {"text": "AUDIENCE: Add another\ndrop of titrant.", "start": 1768.84, "duration": 2.482}, {"text": "JOHN DOLHUN: Add\nanother drop of titrant.", "start": 1771.322, "duration": 1.708}, {"text": "That's what I would do, Thomas.", "start": 1773.03, "duration": 2.04}, {"text": "But it's not correct.", "start": 1775.07, "duration": 1.13}, {"text": "AUDIENCE: [LAUGHS]", "start": 1776.2, "duration": 0.75}, {"text": "JOHN DOLHUN: But I\nwould do the same thing.", "start": 1776.95, "duration": 1.792}, {"text": "I would add another\ndrop of titrant.", "start": 1778.742, "duration": 1.698}, {"text": "AUDIENCE: Oh, what if it\njust turned blue by itself,", "start": 1780.44, "duration": 1.49}, {"text": "[INAUDIBLE] and you're\njust [INAUDIBLE]", "start": 1781.93, "duration": 1.625}, {"text": "JOHN DOLHUN: There's a side\nreaction going on in the air.", "start": 1783.555, "duration": 2.855}, {"text": "When you get this\nclear, you've got", "start": 1786.41, "duration": 2.1}, {"text": "all iodide present in there.", "start": 1788.51, "duration": 2.74}, {"text": "But what happens is--", "start": 1791.25, "duration": 1.04}, {"text": "so you've got iodide\nthere, but you also", "start": 1795.18, "duration": 4.83}, {"text": "have oxygen in the air.", "start": 1800.01, "duration": 1.44}, {"text": "And the oxygen is oxidizing\nthe iodide to iodine,", "start": 1804.86, "duration": 10.23}, {"text": "and we don't want this\niodine coming from the air.", "start": 1815.09, "duration": 3.36}, {"text": "We want it only from\nthe river water,", "start": 1818.45, "duration": 2.16}, {"text": "right, from the\noxygen in the river.", "start": 1820.61, "duration": 2.34}, {"text": "So this is a side reaction that\ncan go on if you let it set.", "start": 1822.95, "duration": 4.38}, {"text": "So just ignore it.", "start": 1827.33, "duration": 1.68}, {"text": "Just take your end point,\nyour final neutralization,", "start": 1829.01, "duration": 6.66}, {"text": "and you're good.", "start": 1835.67, "duration": 2.37}, {"text": "Take a look at the\nstoichiometry here.", "start": 1838.04, "duration": 2.76}, {"text": "One biiodate make six I2.", "start": 1840.8, "duration": 4.775}, {"text": "Each I2 reacts with\ntwo thiosulfate.", "start": 1845.575, "duration": 4.445}, {"text": "So it's 12 to 1\nthiosulfate to biiodate.", "start": 1850.02, "duration": 5.695}, {"text": "What you're going\nto do is you're", "start": 1855.715, "duration": 1.375}, {"text": "going to do three trials,\nand they all should agree to", "start": 1857.09, "duration": 4.05}, {"text": "within 2% or 3%.", "start": 1861.14, "duration": 2.22}, {"text": "If they don't, do an\nextra trial or two.", "start": 1863.36, "duration": 3.42}, {"text": "And what you're\ngoing to do is you're", "start": 1866.78, "duration": 2.1}, {"text": "going to find your mean,\nyour standard deviation,", "start": 1868.88, "duration": 2.85}, {"text": "and your confidence\nintervals and then give all", "start": 1871.73, "duration": 2.64}, {"text": "that information to your TA.", "start": 1874.37, "duration": 2.16}, {"text": "Yesterday the TAs\ndid a beautiful job.", "start": 1876.53, "duration": 2.16}, {"text": "They put everybody's on\nan Excel spreadsheet,", "start": 1878.69, "duration": 3.0}, {"text": "had it all averaged out.", "start": 1881.69, "duration": 1.96}, {"text": "They really did a\ngood job yesterday.", "start": 1883.65, "duration": 2.37}, {"text": "The students really homed in\non the exact concentration", "start": 1886.02, "duration": 4.25}, {"text": "of the thiosulfate.", "start": 1890.27, "duration": 2.42}, {"text": "So it's pretty simple.", "start": 1892.69, "duration": 1.71}, {"text": "You do your calculations\nright there in the lab.", "start": 1894.4, "duration": 3.06}, {"text": "And then you have a choice\nof using the class average", "start": 1897.46, "duration": 3.51}, {"text": "or using your own results for\nthe dissolved oxygen that will", "start": 1900.97, "duration": 3.99}, {"text": "take place on the next day.", "start": 1904.96, "duration": 1.38}, {"text": "So collection of water samples.", "start": 1911.62, "duration": 2.4}, {"text": "So you're going to be going\nto the river for day two.", "start": 1914.02, "duration": 3.66}, {"text": "And we have these poles.", "start": 1917.68, "duration": 2.82}, {"text": "If you have long arms,\nyou'll take a short poll.", "start": 1920.5, "duration": 5.66}, {"text": "If you're short and\nhave short arms,", "start": 1926.16, "duration": 2.53}, {"text": "then we have real long poles.", "start": 1928.69, "duration": 1.8}, {"text": "They're like hockey sticks.", "start": 1930.49, "duration": 2.28}, {"text": "So you get your stick, and what\nyou do is you insert your--", "start": 1932.77, "duration": 6.21}, {"text": "your BOD bottle snaps into\nthe clip that I've got inside.", "start": 1938.98, "duration": 3.85}, {"text": "You take the stopper\nout, and then you", "start": 1942.83, "duration": 2.3}, {"text": "go to the edge of the dock.", "start": 1945.13, "duration": 1.77}, {"text": "Don't fall in, and\ndon't push anybody, OK.", "start": 1946.9, "duration": 5.25}, {"text": "Remember the cyanobacteria\nand all that out there.", "start": 1952.15, "duration": 3.93}, {"text": "And take gloves with\nyou, because when", "start": 1956.08, "duration": 2.82}, {"text": "you put this under water, it's\ngot to be completely submerged.", "start": 1958.9, "duration": 3.84}, {"text": "You have to reach over the dock.", "start": 1962.74, "duration": 2.04}, {"text": "You've got to stopper\nit underwater.", "start": 1964.78, "duration": 2.28}, {"text": "So you've got to have\ngloves with you, all right.", "start": 1967.06, "duration": 2.85}, {"text": "So I stoppered mine underwater.", "start": 1969.91, "duration": 2.13}, {"text": "I bring it up, take it out,\nand then I look at the--", "start": 1972.04, "duration": 5.46}, {"text": "I take the bottle,\nand I do this test.", "start": 1977.5, "duration": 3.9}, {"text": "I don't see any bubbles.", "start": 1981.4, "duration": 2.01}, {"text": "That's a good sign.", "start": 1983.41, "duration": 1.66}, {"text": "That means it's perfect.", "start": 1985.07, "duration": 1.8}, {"text": "If you see bubbles, you've\nintroduced more oxygen", "start": 1986.87, "duration": 3.47}, {"text": "in there.", "start": 1990.34, "duration": 0.78}, {"text": "Your DO concentrations\nare going to be too high.", "start": 1991.12, "duration": 2.91}, {"text": "Pour it out, and restart again.", "start": 1994.03, "duration": 2.95}, {"text": "OK, so that's the collection.", "start": 1996.98, "duration": 3.0}, {"text": "Then you bring the\nstuff back to the lab,", "start": 1999.98, "duration": 2.87}, {"text": "and you're going to treat\nthe bottles in the lab.", "start": 2002.85, "duration": 5.502}, {"text": "This here is wrong.", "start": 2008.352, "duration": 3.438}, {"text": "You don't want to use these\ndigital pipetters to treat", "start": 2011.79, "duration": 3.66}, {"text": "the water, because you'll\nbe introducing oxygen", "start": 2015.45, "duration": 3.8}, {"text": "into those water bottles.", "start": 2019.25, "duration": 1.39}, {"text": "What you're going to use is\nyour 10-mL glass pipette.", "start": 2020.64, "duration": 4.8}, {"text": "And what we're\ngoing to do here is", "start": 2025.44, "duration": 4.23}, {"text": "each pair of students\nwill have four bottles.", "start": 2029.67, "duration": 3.63}, {"text": "So you're going to--", "start": 2033.3, "duration": 1.32}, {"text": "first, you're going to treat it\nwith the manganese sulfate, 2", "start": 2034.62, "duration": 4.11}, {"text": "mLs of manganese sulfate.", "start": 2038.73, "duration": 1.41}, {"text": "That's the first reaction\non that oxidation reduction", "start": 2040.14, "duration": 3.57}, {"text": "Winkler series.", "start": 2043.71, "duration": 1.89}, {"text": "And the way you do it\nis-- what I would do", "start": 2045.6, "duration": 2.19}, {"text": "is I would take up 10\nmils of manganese sulfate", "start": 2047.79, "duration": 4.38}, {"text": "to prevent any airflow, any air.", "start": 2052.17, "duration": 3.14}, {"text": "And then what you're\ngoing to do is you're", "start": 2055.31, "duration": 1.75}, {"text": "going to take the stopper out.", "start": 2057.06, "duration": 1.95}, {"text": "You're going to go just below\nthe surface of the liquid", "start": 2059.01, "duration": 3.57}, {"text": "and put in 2 mils.", "start": 2062.58, "duration": 2.099}, {"text": "And then your partner\ncan stopper it.", "start": 2064.679, "duration": 1.921}, {"text": "You go to the next one.", "start": 2066.6, "duration": 1.079}, {"text": "You do all four of them.", "start": 2067.679, "duration": 1.861}, {"text": "The last 2 mils in here,\nshoot it into waste.", "start": 2069.54, "duration": 3.96}, {"text": "And then do the same thing\nwith the alkaline-iodide-azide", "start": 2073.5, "duration": 3.719}, {"text": "reagent, 2 mils in each bottle.", "start": 2077.219, "duration": 2.821}, {"text": "And you should look at\nthe bottle at this point.", "start": 2080.04, "duration": 4.949}, {"text": "After you add those\nreagents, there", "start": 2084.989, "duration": 1.741}, {"text": "should not be any bubbles.", "start": 2086.73, "duration": 2.28}, {"text": "If there's a bubble, it\nmeans you've introduced air,", "start": 2089.01, "duration": 3.45}, {"text": "and your DO values will\nbe higher by doing that.", "start": 2092.46, "duration": 5.2}, {"text": "So once you've treated with\nthese two steps here, you've", "start": 2097.66, "duration": 6.59}, {"text": "essentially trapped\nthe oxygen. You're", "start": 2104.25, "duration": 2.31}, {"text": "going to have this\nbrown flock like this.", "start": 2106.56, "duration": 3.52}, {"text": "Now you just shake that\na bit, and then you're", "start": 2110.08, "duration": 4.92}, {"text": "going to dissolve it now\nby adding sulfuric acid, 28", "start": 2115.0, "duration": 3.93}, {"text": "drops of sulfuric.", "start": 2118.93, "duration": 1.8}, {"text": "Acid for the sulfuric, you\ndon't go below the surface.", "start": 2120.73, "duration": 2.94}, {"text": "You just open the lid,\nand you drip, drip it in.", "start": 2123.67, "duration": 3.66}, {"text": "The acid is heavy.", "start": 2127.33, "duration": 0.99}, {"text": "It's going to fall right to\nthe bottom of the bottle.", "start": 2128.32, "duration": 2.97}, {"text": "And now you should\nhave a bubble in there.", "start": 2131.29, "duration": 4.68}, {"text": "You will have a bubble\nafter you add the sulfuric,", "start": 2135.97, "duration": 2.76}, {"text": "and that's OK.", "start": 2138.73, "duration": 2.53}, {"text": "So when you're done with\nthis, you're ready to titrate.", "start": 2141.26, "duration": 3.86}, {"text": "And we've got to-- we're\nsupposed to titrate 200 mils.", "start": 2145.12, "duration": 4.59}, {"text": "That's what you titrated when\nyou did your standardization as", "start": 2149.71, "duration": 3.27}, {"text": "well.", "start": 2152.98, "duration": 1.67}, {"text": "But we've got to make\nup for the 4 mils", "start": 2154.65, "duration": 5.81}, {"text": "that we added there\nin the beginning.", "start": 2160.46, "duration": 2.91}, {"text": "We've displaced something there.", "start": 2163.37, "duration": 2.33}, {"text": "So you want to titrate\n200 mLs times--", "start": 2165.7, "duration": 5.46}, {"text": "you've got a 300 mL BOD bottle,\nand you've taken and added", "start": 2171.16, "duration": 6.84}, {"text": "4 mLs of stuff to it.", "start": 2178.0, "duration": 2.81}, {"text": "So if you do the math\nto make up for that,", "start": 2180.81, "duration": 2.69}, {"text": "you really have to\ntitrate 203 mLs.", "start": 2183.5, "duration": 4.28}, {"text": "So there's a couple\nways you could do this.", "start": 2187.78, "duration": 3.07}, {"text": "You can use a 100-mL graduated\ncylinder, and the error on that", "start": 2190.85, "duration": 6.13}, {"text": "is about plus or minus 0.5.", "start": 2196.98, "duration": 2.97}, {"text": "You fill that up twice,\nput that in your container.", "start": 2199.95, "duration": 4.33}, {"text": "The last 3 mils, you could\nuse this for accuracy", "start": 2204.28, "duration": 5.13}, {"text": "to get your last 3 mLs\nin, and then you're good.", "start": 2209.41, "duration": 4.02}, {"text": "But you can also\njust titrate 200 mLs", "start": 2213.43, "duration": 5.46}, {"text": "and then multiply your answer\nby a correction factor, which", "start": 2218.89, "duration": 4.53}, {"text": "would be 203 over 200.", "start": 2223.42, "duration": 4.56}, {"text": "And that will give you the same\nanswer as titrating the 203.", "start": 2227.98, "duration": 11.12}, {"text": "So the math is\npretty simple here.", "start": 2239.1, "duration": 2.97}, {"text": "You're converting the\nmoles of your titrant", "start": 2242.07, "duration": 3.15}, {"text": "to moles of oxygen,\ngrams of oxygen.", "start": 2245.22, "duration": 3.69}, {"text": "You divide by the liters.", "start": 2248.91, "duration": 2.61}, {"text": "If you're doing 200\nmLs, that's 0.2 liters.", "start": 2251.52, "duration": 4.74}, {"text": "And then you get your\nmilligrams per liter in PPM.", "start": 2256.26, "duration": 4.1}, {"text": "I kept mentioning\nwe're using the--", "start": 2266.88, "duration": 4.08}, {"text": "we've got to add this\nalkaline-azide solution.", "start": 2270.96, "duration": 3.21}, {"text": "We're actually using\nthe azide modification", "start": 2274.17, "duration": 3.24}, {"text": "of the Winkler method.", "start": 2277.41, "duration": 2.3}, {"text": "And what is that?", "start": 2279.71, "duration": 2.15}, {"text": "Well, there are NOx\ngases in the atmosphere.", "start": 2281.86, "duration": 7.42}, {"text": "What's the nastiest NOx\ngas that you can think of?", "start": 2289.28, "duration": 3.66}, {"text": "I'll give you a hint.", "start": 2305.67, "duration": 2.11}, {"text": "It's a big greenhouse\ngas, and it's not CO2.", "start": 2307.78, "duration": 5.801}, {"text": "AUDIENCE: Ozone?", "start": 2313.581, "duration": 1.749}, {"text": "JOHN DOLHUN: Ozone is\na gas up there, yeah.", "start": 2315.33, "duration": 2.94}, {"text": "But that protects us.", "start": 2318.27, "duration": 2.34}, {"text": "Our ozone layer is a\nlayer of protection.", "start": 2320.61, "duration": 4.94}, {"text": "But what's-- yes.", "start": 2325.55, "duration": 1.14}, {"text": "AUDIENCE: Is it NO2 or--", "start": 2326.69, "duration": 3.685}, {"text": "JOHN DOLHUN: The other way.", "start": 2330.375, "duration": 1.125}, {"text": "AUDIENCE: Or N O?", "start": 2331.5, "duration": 0.81}, {"text": "I know that [INAUDIBLE]", "start": 2332.31, "duration": 3.24}, {"text": "JOHN DOLHUN: All right,\nplease don't laugh at this.", "start": 2335.55, "duration": 3.86}, {"text": "It's laughing gas, N2O.", "start": 2339.41, "duration": 4.3}, {"text": "You're all-- I\nmean, the atmosphere", "start": 2343.71, "duration": 2.12}, {"text": "is loaded with laughing gas.", "start": 2345.83, "duration": 2.39}, {"text": "I know.", "start": 2348.22, "duration": 0.76}, {"text": "Everybody's laughing now.", "start": 2348.98, "duration": 2.46}, {"text": "It's great.", "start": 2351.44, "duration": 1.2}, {"text": "Where does it come from, N2O?", "start": 2352.64, "duration": 2.79}, {"text": "All the fertilizer.", "start": 2355.43, "duration": 2.01}, {"text": "1% of all the\nfertilizer in the world", "start": 2357.44, "duration": 3.12}, {"text": "goes up in the atmosphere\nas laughing gas.", "start": 2360.56, "duration": 2.73}, {"text": "It's not from a\ndentist's office.", "start": 2363.29, "duration": 1.98}, {"text": "It's from fertilizer.", "start": 2365.27, "duration": 1.28}, {"text": "I know.", "start": 2366.55, "duration": 1.39}, {"text": "I don't want to\nthink about dentists.", "start": 2367.94, "duration": 1.83}, {"text": "I was just at one yesterday.", "start": 2369.77, "duration": 1.59}, {"text": "I don't like dentists.", "start": 2371.36, "duration": 2.52}, {"text": "But every ton of laughing\ngas that's in the atmosphere.", "start": 2373.88, "duration": 7.36}, {"text": "is like 300 tons of CO2.", "start": 2381.24, "duration": 4.04}, {"text": "And it stays up there\nfor over 100 years.", "start": 2385.28, "duration": 3.58}, {"text": "And what does it do?", "start": 2388.86, "duration": 2.49}, {"text": "Well, who said ozone back there?", "start": 2391.35, "duration": 7.65}, {"text": "There you are.", "start": 2399.0, "duration": 0.78}, {"text": "OK.", "start": 2399.78, "duration": 1.41}, {"text": "Laughing gas reacts\nwith ozone, and it", "start": 2401.19, "duration": 3.93}, {"text": "forms dinitrogen dioxide.", "start": 2405.12, "duration": 2.47}, {"text": "And this dinitrogen dioxide\nonly lasts for about an hour.", "start": 2410.5, "duration": 5.07}, {"text": "And immediately, the N2O2\nreacts with air and water", "start": 2415.57, "duration": 11.52}, {"text": "to form nitrites.", "start": 2427.09, "duration": 0.99}, {"text": "And here we are talking about\ngreenhouse gas in the world,", "start": 2435.76, "duration": 5.35}, {"text": "and this is affecting our little\ntiny reaction in the Charles", "start": 2441.11, "duration": 3.62}, {"text": "River experiment, because these\nnitrites, look what they do.", "start": 2444.73, "duration": 4.59}, {"text": "They get in and oxidize\niodide to iodine.", "start": 2449.32, "duration": 3.96}, {"text": "And we don't want\nour iodine coming", "start": 2453.28, "duration": 2.31}, {"text": "from some reaction from laughing\ngas, right, from nitrite.", "start": 2455.59, "duration": 4.92}, {"text": "We want it coming from\nthe oxygen in the river.", "start": 2460.51, "duration": 3.24}, {"text": "So we add sodium azide.", "start": 2463.75, "duration": 3.12}, {"text": "And that zaps the\nnitrites, convert them", "start": 2466.87, "duration": 3.24}, {"text": "to harmless nitrogen and water.", "start": 2470.11, "duration": 3.21}, {"text": "So that's the theory\nbehind why we're", "start": 2473.32, "duration": 5.69}, {"text": "using the azide modification.", "start": 2479.01, "duration": 1.98}, {"text": "All that for these nitrites.", "start": 2480.99, "duration": 2.22}, {"text": "So let's talk for a moment\nabout pH, pH in natural waters.", "start": 2486.84, "duration": 6.45}, {"text": "Let's see here.", "start": 2493.29, "duration": 1.323}, {"text": "Pulling down some board, here.", "start": 2494.613, "duration": 1.932}, {"text": "Who knows the definition of pH?", "start": 2500.42, "duration": 2.01}, {"text": "Remember your chemical\nprinciples from a long time a--", "start": 2513.49, "duration": 2.695}, {"text": "Alec.", "start": 2516.185, "duration": 0.5}, {"text": "AUDIENCE: I think it was log\nof concentration of hydrogen", "start": 2516.685, "duration": 3.075}, {"text": "ions, [INAUDIBLE] ions.", "start": 2519.76, "duration": 1.062}, {"text": "JOHN DOLHUN: Very good.", "start": 2520.822, "duration": 0.958}, {"text": "The negative log of the\nconcentration of the hydrogen", "start": 2521.78, "duration": 2.81}, {"text": "ions.", "start": 2524.59, "duration": 1.126}, {"text": "So pH.", "start": 2525.716, "duration": 0.5}, {"text": "And I mean, you all know\nthe pH scale is 0 to 14,", "start": 2532.99, "duration": 3.24}, {"text": "and acid is less than 7.", "start": 2536.23, "duration": 2.79}, {"text": "And I hope you know what color\nlitmus paper changes, right,", "start": 2539.02, "duration": 3.39}, {"text": "with pH.", "start": 2542.41, "duration": 0.505}, {"text": "That was a question on a\nTV show with Regis Philbin,", "start": 2545.68, "duration": 4.29}, {"text": "You Want to Be a Millionaire.", "start": 2549.97, "duration": 1.92}, {"text": "A guy actually got up to\nthe million dollar question.", "start": 2551.89, "duration": 4.4}, {"text": "And I happened to turn\nit on just at that point,", "start": 2556.29, "duration": 4.14}, {"text": "and they ask him,\nwhat color does", "start": 2560.43, "duration": 1.65}, {"text": "litmus paper change in base?", "start": 2562.08, "duration": 3.39}, {"text": "And the guy said,\noh, I don't know,", "start": 2565.47, "duration": 3.12}, {"text": "but can I call my lifeline?", "start": 2568.59, "duration": 2.52}, {"text": "And they said yes.", "start": 2571.11, "duration": 1.38}, {"text": "So he called this\nprestigious biologist", "start": 2572.49, "duration": 3.12}, {"text": "at one of the\nCalifornia universities.", "start": 2575.61, "duration": 3.18}, {"text": "And they said red.", "start": 2578.79, "duration": 1.98}, {"text": "[LAUGHTER]", "start": 2580.77, "duration": 1.23}, {"text": "And the guy answers red, and\nhe loses the million dollars.", "start": 2582.0, "duration": 4.514}, {"text": "Oh, I was beside myself.", "start": 2586.514, "duration": 3.346}, {"text": "So if you remember anything,\nremember what color", "start": 2589.86, "duration": 2.8}, {"text": "litmus paper is in acid.", "start": 2592.66, "duration": 2.66}, {"text": "But in the river, the pH\ncan go from 6.5 to 8.5.", "start": 2595.32, "duration": 9.12}, {"text": "And the pH effects everything,\nfrom the solubility of metals--", "start": 2604.44, "duration": 6.36}, {"text": "if it gets too acidic\nout there in the river,", "start": 2610.8, "duration": 3.585}, {"text": "the metals become more soluble,\nmercury, cadmium, arsenic,", "start": 2614.385, "duration": 6.355}, {"text": "all those metals.", "start": 2620.74, "duration": 1.26}, {"text": "So the fish uptake the\nmetals, and we eat the fish.", "start": 2622.0, "duration": 3.3}, {"text": "And with global warming,\nthe acidity of the rivers", "start": 2625.3, "duration": 3.39}, {"text": "is gradually drifting\nvery slightly lower.", "start": 2628.69, "duration": 5.52}, {"text": "It also affects the\nforms of phosphorous.", "start": 2634.21, "duration": 3.18}, {"text": "So remember, you've\ngot PO4 to the 3 minus.", "start": 2637.39, "duration": 4.92}, {"text": "But if it's slightly\nacidic, you might", "start": 2642.31, "duration": 2.64}, {"text": "have the hydrogen phosphate\nor the dihydrogen phosphate.", "start": 2644.95, "duration": 7.86}, {"text": "Or you could end up\nwith phosphoric acid,", "start": 2656.17, "duration": 4.58}, {"text": "depending on how acidic it gets.", "start": 2660.75, "duration": 3.4}, {"text": "What about\nphotosynthesis and pH?", "start": 2664.15, "duration": 2.741}, {"text": "Where are my biologists\nat, my resident bi--", "start": 2669.87, "duration": 4.7}, {"text": "there must be somebody\nin bio in here.", "start": 2674.57, "duration": 2.22}, {"text": "Come on.", "start": 2676.79, "duration": 2.37}, {"text": "Don't be afraid.", "start": 2679.16, "duration": 2.07}, {"text": "Yes.", "start": 2681.23, "duration": 1.17}, {"text": "There you are.", "start": 2682.4, "duration": 1.35}, {"text": "What's the equation\nfor photosynthesis?", "start": 2683.75, "duration": 3.696}, {"text": "AUDIENCE: Water\nand carbon dioxide.", "start": 2687.446, "duration": 1.634}, {"text": "JOHN DOLHUN: Good, good.", "start": 2689.08, "duration": 1.0}, {"text": "Water and carbon dioxide.", "start": 2690.08, "duration": 2.07}, {"text": "Let's just write that\ndown for a moment.", "start": 2692.15, "duration": 1.95}, {"text": "So CO2 plus water,\nlittle bit of sun.", "start": 2697.95, "duration": 10.07}, {"text": "AUDIENCE: Oxygen and glucose.", "start": 2708.02, "duration": 2.1}, {"text": "JOHN DOLHUN: Oxygen\nand sugars, good.", "start": 2710.12, "duration": 2.64}, {"text": "So CH2O, n.", "start": 2712.76, "duration": 1.85}, {"text": "So does the pH go up or\ndown during photosynthesis?", "start": 2720.23, "duration": 4.77}, {"text": "I mean, it's like\na 50/50 chance.", "start": 2729.06, "duration": 2.105}, {"text": "Sean, you want to\nanswer, don't you?", "start": 2736.63, "duration": 2.92}, {"text": "AUDIENCE: I would\nsay the pH goes up.", "start": 2739.55, "duration": 2.97}, {"text": "JOHN DOLHUN: It goes up?", "start": 2742.52, "duration": 1.0}, {"text": "OK.", "start": 2743.52, "duration": 0.88}, {"text": "Anyone else?", "start": 2744.4, "duration": 0.78}, {"text": "Alec?", "start": 2745.18, "duration": 0.795}, {"text": "AUDIENCE: It goes down?", "start": 2745.975, "duration": 1.125}, {"text": "JOHN DOLHUN: It goes down?", "start": 2747.1, "duration": 0.75}, {"text": "OK.", "start": 2747.85, "duration": 0.39}, {"text": "[LAUGHTER]", "start": 2748.24, "duration": 0.54}, {"text": "There you go.", "start": 2748.78, "duration": 0.72}, {"text": "I told you it's\nlike a 50/50, right?", "start": 2749.5, "duration": 2.85}, {"text": "All right, let's do a\nlittle experiment with this.", "start": 2752.35, "duration": 3.78}, {"text": "I'm going to pour\nmyself a drink here.", "start": 2758.68, "duration": 1.99}, {"text": "This is good stuff.", "start": 2764.38, "duration": 1.26}, {"text": "It's not Gatorade,\nI can tell you that.", "start": 2771.15, "duration": 1.68}, {"text": "This is a classic test in\nthe medical profession,", "start": 2776.175, "duration": 4.845}, {"text": "if you're going to medical\nschool, for breath.", "start": 2781.02, "duration": 3.0}, {"text": "And when I'm doing this,\nyou cannot make me laugh.", "start": 2784.02, "duration": 4.14}, {"text": "If you make me\nlaugh, I'm dead, OK.", "start": 2788.16, "duration": 2.51}, {"text": "Please.", "start": 2790.67, "duration": 1.06}, {"text": "I'm going to play some\nmusic to relax myself here.", "start": 2791.73, "duration": 4.81}, {"text": "Let me just-- let me see\nif we can get this on here.", "start": 2796.54, "duration": 4.28}, {"text": "OK.", "start": 2800.82, "duration": 0.72}, {"text": "There we go.", "start": 2801.54, "duration": 0.71}, {"text": "So I'm breathing into this.", "start": 2805.34, "duration": 2.12}, {"text": "We don't hear any\nmusic coming out.", "start": 2811.45, "duration": 3.9}, {"text": "Going to--", "start": 2815.35, "duration": 1.572}, {"text": "[MUSIC PLAYING]", "start": 2816.922, "duration": 4.268}, {"text": "There we go.", "start": 2821.19, "duration": 0.56}, {"text": "You're making me laugh, Sean.", "start": 2830.41, "duration": 1.62}, {"text": "I may have to have you come\nup and help me with this.", "start": 2835.79, "duration": 2.34}, {"text": "[MUSIC PLAYING]", "start": 2838.13, "duration": 3.96}, {"text": "I may not be OK.", "start": 2861.41, "duration": 1.663}, {"text": "The color's supposed to change.", "start": 2863.073, "duration": 1.292}, {"text": "[MUSIC PLAYING]", "start": 2864.365, "duration": 3.757}, {"text": "There we are.", "start": 2879.53, "duration": 1.15}, {"text": "Good?", "start": 2880.68, "duration": 2.3}, {"text": "I'm OK.", "start": 2882.98, "duration": 0.72}, {"text": "So what just happened?", "start": 2887.46, "duration": 2.52}, {"text": "AUDIENCE: You blew carbon\ndioxide into the water.", "start": 2892.888, "duration": 2.042}, {"text": "JOHN DOLHUN: I blew carbon\ndioxide in the water.", "start": 2894.93, "duration": 2.07}, {"text": "So we've got CO2 plus\nwater going to what?", "start": 2897.0, "duration": 8.764}, {"text": "Yeah.", "start": 2909.48, "duration": 0.71}, {"text": "AUDIENCE: Carbonic acid.", "start": 2910.19, "duration": 1.0}, {"text": "JOHN DOLHUN: Carbonic acid.", "start": 2911.19, "duration": 1.125}, {"text": "Good.", "start": 2912.315, "duration": 0.81}, {"text": "H2CO3, which breaks down\ninto H plus plus bicarbonate.", "start": 2913.125, "duration": 8.025}, {"text": "Now photosynthesis needs\ncarbon dioxide, right?", "start": 2924.29, "duration": 5.56}, {"text": "So we take that out\nof the equation,", "start": 2929.85, "duration": 2.77}, {"text": "which means we're also\ntaking out the H plus.", "start": 2932.62, "duration": 5.01}, {"text": "So does the pH go up or down?", "start": 2937.63, "duration": 2.066}, {"text": "AUDIENCE: Up.", "start": 2939.696, "duration": 0.914}, {"text": "JOHN DOLHUN: Alec?", "start": 2940.61, "duration": 1.19}, {"text": "Up, up, up.", "start": 2941.8, "duration": 1.19}, {"text": "OK?", "start": 2942.99, "duration": 0.66}, {"text": "Good.", "start": 2943.65, "duration": 0.96}, {"text": "And pollution and\npH, same thing.", "start": 2944.61, "duration": 3.37}, {"text": "If you've got pollution,\nyou've got all this vegetation.", "start": 2947.98, "duration": 3.5}, {"text": "So you've got photosynthesis,\nso the pH is going to be up.", "start": 2951.48, "duration": 3.66}, {"text": "This is Lassen Lake, Volcanic\nNational Park, pH 2, 2.0.", "start": 2957.88, "duration": 7.84}, {"text": "You do not want to stick\nyour foot into this lake.", "start": 2965.72, "duration": 3.35}, {"text": "And then you've got some\nsafety of the chemicals, which", "start": 2969.07, "duration": 4.83}, {"text": "the most serious is the\nazide reagent, which", "start": 2973.9, "duration": 4.68}, {"text": "it's a neurological toxin.", "start": 2978.58, "duration": 2.52}, {"text": "And if you ingest it,\nit can cause death.", "start": 2981.1, "duration": 3.52}, {"text": "So please be careful with that.", "start": 2984.62, "duration": 3.29}, {"text": "Sulfuric acid, you\nknow how bad that is.", "start": 2987.91, "duration": 2.94}, {"text": "You don't want to get it\nin your respiratory system.", "start": 2990.85, "duration": 2.67}, {"text": "And the manganese\nsulfate seems innocuous,", "start": 2993.52, "duration": 4.41}, {"text": "but it attacks the\ncentral nervous system,", "start": 2997.93, "duration": 3.18}, {"text": "targets blood and kidneys.", "start": 3001.11, "duration": 2.62}, {"text": "So be careful with that.", "start": 3003.73, "duration": 1.52}, {"text": "Sodium thiosulfate is\na respiratory irritant,", "start": 3005.25, "duration": 5.04}, {"text": "can cause breathing problems.", "start": 3010.29, "duration": 3.04}, {"text": "So if you feel like you're\nhaving breathing issues,", "start": 3013.33, "duration": 3.77}, {"text": "it could be that.", "start": 3017.1, "duration": 1.17}, {"text": "Biiodate can burn your eyes.", "start": 3018.27, "duration": 2.88}, {"text": "Very, very dangerous\nstuff around your eyes.", "start": 3021.15, "duration": 3.36}, {"text": "So all of these things, you\nhave to be careful with.", "start": 3024.51, "duration": 3.52}, {"text": "OK.", "start": 3028.03, "duration": 0.53}, {"text": "So we'll see you Thursday\nfor the last lecture", "start": 3028.56, "duration": 2.85}, {"text": "in this series.", "start": 3031.41, "duration": 1.85}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.41}, {"text": "[RUSTLING]", "start": 2.41, "duration": 1.446}, {"text": "[CLICKING]", "start": 3.856, "duration": 2.892}, {"text": "PROFESSOR: So we're talking\nabout relative orientation, one", "start": 12.07, "duration": 5.58}, {"text": "of the second of four\nproblems in photogrammetry", "start": 17.65, "duration": 5.61}, {"text": "relevant to binocular stereo,\nas well as motion vision", "start": 23.26, "duration": 5.46}, {"text": "structure, structure\nfrom motion.", "start": 28.72, "duration": 2.16}, {"text": "And we developed a solution.", "start": 30.88, "duration": 4.38}, {"text": "And we're wondering\nabout circumstances", "start": 35.26, "duration": 2.67}, {"text": "where that won't work.", "start": 37.93, "duration": 1.77}, {"text": "And in particular,\nare there surfaces", "start": 39.7, "duration": 5.5}, {"text": "where we can't determine\nthe relative orientation?", "start": 45.2, "duration": 3.81}, {"text": "And we got there.", "start": 49.01, "duration": 3.42}, {"text": "We found that there\nwere quadric surfaces", "start": 52.43, "duration": 19.48}, {"text": "in that family of surfaces.", "start": 71.91, "duration": 2.01}, {"text": "Now, keep in mind that this is\nin a coordinate system that's", "start": 73.92, "duration": 6.12}, {"text": "been specially lined up to\nmake the equation simple.", "start": 80.04, "duration": 3.69}, {"text": "So this is, first of all,\nthe center is at the origin.", "start": 83.73, "duration": 5.535}, {"text": "And the axes are lined up.", "start": 93.14, "duration": 1.95}, {"text": "So in a more general case,\nwe'd have a more complicated", "start": 97.91, "duration": 4.5}, {"text": "looking equation,\nwhere we don't just", "start": 102.41, "duration": 3.21}, {"text": "have the second order terms.", "start": 105.62, "duration": 1.59}, {"text": "But we also have first order\nterms and zeroth order terms,", "start": 107.21, "duration": 4.59}, {"text": "constants.", "start": 111.8, "duration": 1.24}, {"text": "But in classifying the shapes,\nthis is a convenient form.", "start": 113.04, "duration": 8.71}, {"text": "And we noted that if we have\nall positive signs, then", "start": 121.75, "duration": 8.889}, {"text": "we have an ellipsoid.", "start": 130.639, "duration": 1.441}, {"text": "And if A, and B, and C are\nthe same, then it's a sphere.", "start": 132.08, "duration": 4.77}, {"text": "If we have one\nnegative sign, we have", "start": 136.85, "duration": 3.45}, {"text": "a hyperboloid of one sheet.", "start": 140.3, "duration": 2.43}, {"text": "If we have two\nnegative signs, we", "start": 146.48, "duration": 4.89}, {"text": "have a hyperboloid\nof two sheets.", "start": 151.37, "duration": 2.07}, {"text": "And if we have three\nnegative signs,", "start": 153.44, "duration": 4.72}, {"text": "then we don't have\nany real locus.", "start": 158.16, "duration": 4.41}, {"text": "But if we extend it\nto complex numbers,", "start": 162.57, "duration": 2.95}, {"text": "then we can talk about\nan imaginary ellipsoid.", "start": 165.52, "duration": 4.41}, {"text": "Now, the particular\nequation we got", "start": 169.93, "duration": 4.11}, {"text": "from the problem of\nrelative orientation", "start": 174.04, "duration": 4.08}, {"text": "fell in this category.", "start": 178.12, "duration": 4.02}, {"text": "And actually, the\nway we can get there", "start": 182.14, "duration": 2.97}, {"text": "is to note that it didn't\nhave a constant term.", "start": 185.11, "duration": 4.0}, {"text": "So it was second\norder, but it only", "start": 189.11, "duration": 2.6}, {"text": "had the second order term\nand the first order term.", "start": 191.71, "duration": 3.03}, {"text": "And so think of it as\nan equation like that.", "start": 194.74, "duration": 4.53}, {"text": "And that means that R\nequals 0 is the solution.", "start": 206.48, "duration": 6.59}, {"text": "And so that point\nis on the surface.", "start": 213.07, "duration": 8.03}, {"text": "And what was that again?", "start": 221.1, "duration": 1.62}, {"text": "Well, that was the origin\nof the right-hand system.", "start": 222.72, "duration": 2.535}, {"text": "Or in the case of\nmotion vision, that's", "start": 231.58, "duration": 5.09}, {"text": "the place where the\ncamera is at time 2.", "start": 236.67, "duration": 3.75}, {"text": "So that's interesting.", "start": 240.42, "duration": 3.27}, {"text": "That means that\nthis weird surface", "start": 243.69, "duration": 2.46}, {"text": "is one where we actually have\nto be on it with our right eye,", "start": 246.15, "duration": 6.75}, {"text": "or move on it, in the\nmotion vision case.", "start": 252.9, "duration": 5.17}, {"text": "Well, it turns out\nthat in addition,", "start": 258.07, "duration": 10.34}, {"text": "if we plug in a minus B for\nR, that's also a solution.", "start": 268.41, "duration": 5.28}, {"text": "And what is that?", "start": 273.69, "duration": 1.4}, {"text": "Well, if we move left along\nthe baseline by B, then", "start": 275.09, "duration": 4.86}, {"text": "we're at the origin of the\nleft-hand coordinate system.", "start": 279.95, "duration": 6.34}, {"text": "So actually, that surface\nhas to go through both eyes,", "start": 286.29, "duration": 4.12}, {"text": "so to speak.", "start": 290.41, "duration": 1.26}, {"text": "Or in the case of motion vision,\nwe have to start on the surface", "start": 291.67, "duration": 3.59}, {"text": "and end up back on the surface.", "start": 295.26, "duration": 2.13}, {"text": "And this shouldn't\nbe surprising,", "start": 297.39, "duration": 1.5}, {"text": "because everything should\nbe symmetrical between left", "start": 298.89, "duration": 3.39}, {"text": "and right.", "start": 302.28, "duration": 0.69}, {"text": "It just so happens\nthat we picked", "start": 302.97, "duration": 1.65}, {"text": "the right-hand coordinate\nsystem as our reference.", "start": 304.62, "duration": 3.93}, {"text": "But we would expect\nthe same to be", "start": 308.55, "duration": 3.03}, {"text": "true of the left-hand\ncoordinate system.", "start": 311.58, "duration": 2.53}, {"text": "OK.", "start": 314.11, "duration": 0.5}, {"text": "In addition, because this is\na homogeneous equation, i.e.", "start": 314.61, "duration": 7.24}, {"text": "some polynomial in R is equal\nto 0 with no constant term,", "start": 326.29, "duration": 5.52}, {"text": "there's no scaling.", "start": 331.81, "duration": 2.46}, {"text": "We can't tell the\nsize of the vector.", "start": 334.27, "duration": 1.9}, {"text": "So R equals kb is also\na solution, right?", "start": 336.17, "duration": 7.16}, {"text": "If R equal to B as a solution,\nor R equal to minus B,", "start": 343.33, "duration": 3.93}, {"text": "then R equal to kb is.", "start": 347.26, "duration": 1.87}, {"text": "And that means that the whole\nbaseline is in the surface.", "start": 349.13, "duration": 3.05}, {"text": "So this has a number\nof implications.", "start": 356.58, "duration": 2.16}, {"text": "One of them is, it suggests\nthat, well, maybe this is", "start": 358.74, "duration": 4.28}, {"text": "a rare case.", "start": 363.02, "duration": 1.17}, {"text": "How likely is it that you're\non the surface with both camera", "start": 364.19, "duration": 5.7}, {"text": "positions and the whole baseline\nbetween them is on the surface?", "start": 369.89, "duration": 6.15}, {"text": "The other thing it means is\nthat it's a ruled surface.", "start": 376.04, "duration": 3.0}, {"text": "That is, we can draw lines\nin the surface, which", "start": 382.23, "duration": 4.92}, {"text": "of course, we can't do in the\ncase of the ellipsoid, right?", "start": 387.15, "duration": 3.57}, {"text": "If we draw a tangent, it touches\nthe surface at one place.", "start": 390.72, "duration": 3.57}, {"text": "And then, it goes\noff into space.", "start": 394.29, "duration": 2.4}, {"text": "But apparently, the surface\nwe're interested in is ruled.", "start": 396.69, "duration": 5.52}, {"text": "And that means, without doing\nall the detailed algebra,", "start": 402.21, "duration": 6.21}, {"text": "it has to be that one.", "start": 408.42, "duration": 1.44}, {"text": "Because neither one\nof these two is ruled.", "start": 409.86, "duration": 5.76}, {"text": "Also once we've\ndecided that it's", "start": 415.62, "duration": 3.15}, {"text": "a hyperboloid of one sheet,\nwe know that it actually", "start": 418.77, "duration": 3.54}, {"text": "has two rulings.", "start": 422.31, "duration": 3.18}, {"text": "That is, at any\ngiven point, we can", "start": 425.49, "duration": 3.66}, {"text": "draw a line that stays in the\nsurface going in one direction.", "start": 429.15, "duration": 5.85}, {"text": "And there's a second\none that crosses it.", "start": 435.0, "duration": 2.85}, {"text": "So that's pretty interesting.", "start": 437.85, "duration": 2.16}, {"text": "And that corresponds\nto the method", "start": 440.01, "duration": 3.33}, {"text": "used to manufacture\ntables, chairs,", "start": 443.34, "duration": 2.85}, {"text": "what have you out of\nstraight sticks where", "start": 446.19, "duration": 3.135}, {"text": "you use two sticks that cross.", "start": 449.325, "duration": 2.505}, {"text": "And so it's interesting\nthat we find this surface.", "start": 451.83, "duration": 7.71}, {"text": "OK.", "start": 459.54, "duration": 2.37}, {"text": "It seems like a\nvery special case.", "start": 461.91, "duration": 2.24}, {"text": "Why are we worrying about it?", "start": 464.15, "duration": 2.31}, {"text": "Well, the thing is that\nthis is the general equation", "start": 466.46, "duration": 3.39}, {"text": "for the quadric.", "start": 469.85, "duration": 0.96}, {"text": "But it also covers a large\nnumber of special cases.", "start": 470.81, "duration": 5.97}, {"text": "Parabolic hyperboloids\nand whatnot--", "start": 476.78, "duration": 2.19}, {"text": "you can find the whole list\nof these special cases online.", "start": 478.97, "duration": 4.65}, {"text": "I won't go through all of\nthem, just focus on one", "start": 483.62, "duration": 3.18}, {"text": "in particular, which is planar.", "start": 486.8, "duration": 4.11}, {"text": "Now, we know that this is the\nequation of a plane in 3D.", "start": 497.53, "duration": 5.61}, {"text": "And if we take a second equation\nof some other plane in 3D,", "start": 503.14, "duration": 7.77}, {"text": "now both of these are\nlinear in X, Y and Z.", "start": 510.91, "duration": 4.41}, {"text": "But if we multiply\nthe two of them,", "start": 515.32, "duration": 4.13}, {"text": "then the product\nwill be equal to 0.", "start": 519.45, "duration": 4.589}, {"text": "And what is that\nequation describing?", "start": 524.039, "duration": 4.081}, {"text": "Well, it's describing\nthose two planes.", "start": 528.12, "duration": 3.12}, {"text": "And if we multiply it\nout, we get a quadric.", "start": 531.24, "duration": 3.15}, {"text": "We get something that has up\nto second order terms in X, Y", "start": 534.39, "duration": 4.41}, {"text": "and Z. And so curiously,\na surface like that", "start": 538.8, "duration": 7.56}, {"text": "falls into this category.", "start": 546.36, "duration": 4.02}, {"text": "And planar surfaces are\npretty common in the world.", "start": 550.38, "duration": 2.74}, {"text": "So we need to worry about that.", "start": 553.12, "duration": 1.82}, {"text": "Now, it turns out that for these\nto have no constant to them,", "start": 557.47, "duration": 6.3}, {"text": "one of the planes has to\npass through the origin", "start": 563.77, "duration": 5.1}, {"text": "of the right system and the\norigin of the left system.", "start": 568.87, "duration": 3.1}, {"text": "In other words, has to\npass through the baseline.", "start": 571.97, "duration": 2.09}, {"text": "And so one of the planes\nis an epipolar plane.", "start": 574.06, "duration": 3.6}, {"text": "And what's the image\nof an epipolar plane?", "start": 582.12, "duration": 2.79}, {"text": "It's a straight line, right?", "start": 584.91, "duration": 1.35}, {"text": "Because it's coming\nright through your eye.", "start": 586.26, "duration": 2.49}, {"text": "And so you're seeing it edge on.", "start": 588.75, "duration": 2.01}, {"text": "And so that's not\nparticularly interesting,", "start": 590.76, "duration": 3.12}, {"text": "because we don't see\nany of its surface.", "start": 593.88, "duration": 2.82}, {"text": "But the other\nplane is arbitrary.", "start": 596.7, "duration": 2.29}, {"text": "The other plane can be anything.", "start": 598.99, "duration": 1.67}, {"text": "And that's scary, because\nthat means that potentially,", "start": 600.66, "duration": 3.96}, {"text": "when we're looking\nat a planar surface,", "start": 604.62, "duration": 3.33}, {"text": "we end up with this ambiguity.", "start": 607.95, "duration": 2.55}, {"text": "And it's not just a problem\nfor binocular stereo", "start": 610.5, "duration": 3.66}, {"text": "and reconstructing\ntopographic maps.", "start": 614.16, "duration": 3.31}, {"text": "But it's a problem\nfor motion vision", "start": 617.47, "duration": 2.69}, {"text": "as well, recovering\nstructure from motion.", "start": 620.16, "duration": 2.28}, {"text": "Because the two problems\nare really the same,", "start": 622.44, "duration": 3.54}, {"text": "mathematically.", "start": 625.98, "duration": 2.49}, {"text": "And well, we'll pretty\nmuch stop there--", "start": 628.47, "duration": 2.61}, {"text": "except that we\nhaven't really looked", "start": 634.03, "duration": 3.87}, {"text": "at how the geometry\naffects things beyond this.", "start": 637.9, "duration": 6.73}, {"text": "So in particular,\nit seems unlikely", "start": 644.63, "duration": 4.55}, {"text": "that we would run\ninto this situation.", "start": 649.18, "duration": 1.74}, {"text": "Because you have all these\nspecial circumstances.", "start": 650.92, "duration": 3.84}, {"text": "But maybe your real surface is\npretty close to one of these.", "start": 654.76, "duration": 6.39}, {"text": "And then, you won't run\ninto this problem exactly.", "start": 661.15, "duration": 4.89}, {"text": "But you have large noise\namplification, high noise gain.", "start": 666.04, "duration": 3.54}, {"text": "So we would like to stay\naway from that situation.", "start": 669.58, "duration": 4.47}, {"text": "And it turns out that\nthe field of view", "start": 674.05, "duration": 3.72}, {"text": "has a big influence on that.", "start": 677.77, "duration": 1.9}, {"text": "So I won't be proving\nanything about that.", "start": 679.67, "duration": 3.81}, {"text": "But basically, if we have\na large field of view,", "start": 683.48, "duration": 3.42}, {"text": "then this problem becomes much\nmore well-posed, much more", "start": 686.9, "duration": 5.12}, {"text": "stable.", "start": 692.02, "duration": 0.78}, {"text": "If we have only a narrow,\nsmall patch on the surface,", "start": 692.8, "duration": 4.47}, {"text": "the chance that\nthat patch happens", "start": 697.27, "duration": 2.79}, {"text": "to be very similar to\none of these is high.", "start": 700.06, "duration": 3.76}, {"text": "And so it's pretty unstable.", "start": 703.82, "duration": 3.17}, {"text": "So high field of view--", "start": 706.99, "duration": 2.13}, {"text": "a large field of view.", "start": 709.12, "duration": 1.18}, {"text": "And so that led to\nsome amusing things.", "start": 710.3, "duration": 4.62}, {"text": "One of them was that people\nfigured this out pretty early", "start": 714.92, "duration": 2.96}, {"text": "when they started doing\naerial photography.", "start": 717.88, "duration": 2.64}, {"text": "But they didn't have\nthe lens technology", "start": 720.52, "duration": 3.45}, {"text": "to build something that had\nincredibly high quality image", "start": 723.97, "duration": 5.37}, {"text": "reproduction, which\nthey needed so they", "start": 729.34, "duration": 1.89}, {"text": "could see a lot of detail.", "start": 731.23, "duration": 2.64}, {"text": "Low radial distortions--\nso they didn't", "start": 733.87, "duration": 2.43}, {"text": "have the image distorted, and\nalso a large field of view.", "start": 736.3, "duration": 3.67}, {"text": "So what they did was, they\nstuck a bunch of cameras", "start": 739.97, "duration": 2.69}, {"text": "together into a very\nrigid structure.", "start": 742.66, "duration": 6.61}, {"text": "So there was a set\nof steel beams.", "start": 749.27, "duration": 7.38}, {"text": "And you stuck these\ncameras on there.", "start": 756.65, "duration": 2.13}, {"text": "And they are called\nthe spider heads,", "start": 758.78, "duration": 2.4}, {"text": "because spiders have eight eyes.", "start": 761.18, "duration": 2.67}, {"text": "And so there's a similarity\nto this solution.", "start": 763.85, "duration": 4.78}, {"text": "Of course, it doesn't\nmean now that you", "start": 768.63, "duration": 1.79}, {"text": "have to calibrate these\ncameras relative to one another", "start": 770.42, "duration": 3.07}, {"text": "so that out of the\nindividual pictures,", "start": 773.49, "duration": 2.36}, {"text": "you can compose a\nmosaic picture as", "start": 775.85, "duration": 3.18}, {"text": "if it was taken\nby a single camera", "start": 779.03, "duration": 2.4}, {"text": "with a wide field of view.", "start": 781.43, "duration": 1.47}, {"text": "But it makes it clear that this\nwas a well-known problem going", "start": 782.9, "duration": 3.75}, {"text": "back 100 years.", "start": 786.65, "duration": 1.8}, {"text": "At least from a\npractical point of view,", "start": 788.45, "duration": 2.43}, {"text": "the mathematics\ntook a bit later.", "start": 790.88, "duration": 4.24}, {"text": "OK.", "start": 795.12, "duration": 1.17}, {"text": "Relative orientation\nstructure from motion--", "start": 796.29, "duration": 2.82}, {"text": "that was number 2.", "start": 799.11, "duration": 2.7}, {"text": "Let's go on to number 3.", "start": 801.81, "duration": 1.66}, {"text": "And as we go along, we\ndo less and less detail,", "start": 803.47, "duration": 5.63}, {"text": "because a lot of the basic\nideas are common to all of this.", "start": 809.1, "duration": 4.56}, {"text": "OK, so relative\norientation-- let's", "start": 813.66, "duration": 2.7}, {"text": "go on to interior orientation,\nwhich is basically", "start": 816.36, "duration": 9.64}, {"text": "camera calibration.", "start": 826.0, "duration": 1.35}, {"text": "And you'll say, oh,\nbut we did that.", "start": 831.26, "duration": 3.24}, {"text": "Well, we had one idea, which\nwas using vanishing points.", "start": 834.5, "duration": 7.83}, {"text": "So the problem was finding X0,\nY0 and F, the principal point", "start": 842.33, "duration": 8.91}, {"text": "and the principal distance.", "start": 851.24, "duration": 1.71}, {"text": "And we had one\nway of doing that,", "start": 852.95, "duration": 1.84}, {"text": "which was to image a\nrectangular brick shape.", "start": 854.79, "duration": 6.17}, {"text": "So our calibration\nlogic could be a brick", "start": 860.96, "duration": 4.35}, {"text": "machined more carefully.", "start": 865.31, "duration": 1.33}, {"text": "But that was the basic idea.", "start": 866.64, "duration": 2.36}, {"text": "And that works.", "start": 869.0, "duration": 2.88}, {"text": "It's not very accurate.", "start": 871.88, "duration": 2.28}, {"text": "It's hard to make\nit very accurate.", "start": 874.16, "duration": 2.5}, {"text": "And so what we want is\na more general method.", "start": 876.66, "duration": 5.13}, {"text": "Also we need to take into\naccount radial distortion.", "start": 881.79, "duration": 4.41}, {"text": "And the method that we developed\nusing a rectangular brick", "start": 891.93, "duration": 4.47}, {"text": "doesn't lend itself\nto that very well.", "start": 896.4, "duration": 2.71}, {"text": "So what's this about\nradial distortion?", "start": 899.11, "duration": 2.1}, {"text": "Well, I mentioned that\nwe can make these glass", "start": 901.21, "duration": 3.53}, {"text": "analog computers that are so\npowerful in redirecting rays", "start": 904.74, "duration": 4.71}, {"text": "into just the right direction\nso they come to fine focus", "start": 909.45, "duration": 4.23}, {"text": "and give us a very\ndetailed image,", "start": 913.68, "duration": 2.28}, {"text": "but there are trade-offs,\nall kinds of trade offs.", "start": 915.96, "duration": 3.76}, {"text": "And I mentioned\nthat in fact, it's", "start": 919.72, "duration": 1.85}, {"text": "impossible to make\na perfect lens.", "start": 921.57, "duration": 2.52}, {"text": "And you basically have to\ndecide what you're going", "start": 924.09, "duration": 2.82}, {"text": "to put up with, and what not.", "start": 926.91, "duration": 2.52}, {"text": "And radial distortion is\nsomething that generally,", "start": 929.43, "duration": 4.54}, {"text": "unless you are taking a picture\nof an architectural structure", "start": 933.97, "duration": 2.9}, {"text": "with lots of straight lines,\nyou don't notice much.", "start": 936.87, "duration": 3.34}, {"text": "So if you're taking pictures of\npeople, and forests, and cats", "start": 940.21, "duration": 4.46}, {"text": "to post on YouTube,\nit doesn't really", "start": 944.67, "duration": 2.07}, {"text": "matter that there's\nsome radial distortion.", "start": 946.74, "duration": 1.83}, {"text": "Because nobody will\never notice it.", "start": 948.57, "duration": 1.96}, {"text": "And so in designing lenses,\na lot of the other problems", "start": 950.53, "duration": 4.19}, {"text": "were reduced in difficulty by\nallowing radial distortion,", "start": 954.72, "duration": 6.88}, {"text": "which basically just\nmeans that there's", "start": 961.6, "duration": 2.57}, {"text": "some point in the image--", "start": 964.17, "duration": 2.67}, {"text": "the center of distortion.", "start": 966.84, "duration": 1.74}, {"text": "And when we express coordinates\nin polar coordinates,", "start": 974.19, "duration": 4.77}, {"text": "then the image doesn't\nappear where it should.", "start": 978.96, "duration": 3.89}, {"text": "But it appears somewhere\nelse along that line.", "start": 982.85, "duration": 5.23}, {"text": "And that error\nvaries with radius.", "start": 988.08, "duration": 5.61}, {"text": "And it typically is\napproximated using a polynomial.", "start": 993.69, "duration": 7.67}, {"text": "So the usual notation\nis something like this.", "start": 1001.36, "duration": 4.629}, {"text": "So you can see\nthat delta x delta", "start": 1024.579, "duration": 1.941}, {"text": "y is proportional to x and y.", "start": 1026.52, "duration": 2.67}, {"text": "So it is a vector that's\nparallel to the radius vector.", "start": 1029.19, "duration": 8.09}, {"text": "So it is along that radial line.", "start": 1037.28, "duration": 3.51}, {"text": "And then, the lowest\norder term is r squared.", "start": 1040.79, "duration": 7.44}, {"text": "And why is that?", "start": 1048.23, "duration": 1.92}, {"text": "Well, I'll leave that for a\npotential homework problem.", "start": 1050.15, "duration": 3.87}, {"text": "Why is it we're not including\nk0 of r, or something?", "start": 1054.02, "duration": 5.67}, {"text": "Then, the next term\nis after the fourth.", "start": 1059.69, "duration": 3.81}, {"text": "And in many cases,\nthe first term", "start": 1063.5, "duration": 3.33}, {"text": "is good enough to\nget you somewhere.", "start": 1066.83, "duration": 3.3}, {"text": "And so often, we only\nfind that first term.", "start": 1070.13, "duration": 4.2}, {"text": "Yeah, towards the edge.", "start": 1074.33, "duration": 2.1}, {"text": "But those coefficients\ntend to be very small.", "start": 1076.43, "duration": 3.135}, {"text": "So if you buy a telephoto\nlens from, say, Zeiss,", "start": 1083.48, "duration": 8.4}, {"text": "you get with it a plot\nof the radial distortion.", "start": 1091.88, "duration": 6.09}, {"text": "And they're hand calibrated.", "start": 1097.97, "duration": 2.31}, {"text": "That's why you pay a lot\nof money for those lenses.", "start": 1100.28, "duration": 3.6}, {"text": "And you'll see that there's\nthis quadratic rise.", "start": 1103.88, "duration": 6.03}, {"text": "But there's also a\nhigher order drop.", "start": 1109.91, "duration": 2.61}, {"text": "And that's usually taken\ncare of by that second term.", "start": 1112.52, "duration": 4.11}, {"text": "So yeah, the distortion\ngets worse a lot", "start": 1116.63, "duration": 3.3}, {"text": "as you go out towards\nthe corners of the image.", "start": 1119.93, "duration": 2.46}, {"text": "And it's not much of\nan issue in the center.", "start": 1122.39, "duration": 2.79}, {"text": "In machine vision, often, we can\nget away just with a first term", "start": 1128.975, "duration": 6.485}, {"text": "quadratic, just make it simple.", "start": 1135.46, "duration": 1.5}, {"text": "Now, how do you measure this?", "start": 1141.76, "duration": 5.55}, {"text": "Well, a famous method\nused in the past", "start": 1147.31, "duration": 4.64}, {"text": "is the method of plumb lines.", "start": 1151.95, "duration": 2.22}, {"text": "So you go into an area with lots\nof space like a parking garage.", "start": 1154.17, "duration": 4.74}, {"text": "And you take some\nstring and some weights.", "start": 1158.91, "duration": 2.565}, {"text": "And you hang the weights\nalong those strings.", "start": 1164.54, "duration": 5.67}, {"text": "And why do you do this?", "start": 1170.21, "duration": 1.3}, {"text": "Well, because now, first\nof all, the strings", "start": 1171.51, "duration": 2.99}, {"text": "will be straight lines.", "start": 1174.5, "duration": 2.1}, {"text": "They'll be stretched\nout by the wire.", "start": 1176.6, "duration": 2.34}, {"text": "And then, they'll be parallel,\nbecause presumably, gravity", "start": 1178.94, "duration": 3.21}, {"text": "points in the same\ndirection in those places.", "start": 1182.15, "duration": 4.81}, {"text": "They're not far enough apart.", "start": 1186.96, "duration": 1.235}, {"text": "And then, you take\na picture of that.", "start": 1191.72, "duration": 2.68}, {"text": "And then, your picture might\nlook, if you exaggerated,", "start": 1194.4, "duration": 5.21}, {"text": "might look like that.", "start": 1199.61, "duration": 1.05}, {"text": "And so first of all, you can\nsee that there's a distortion.", "start": 1203.99, "duration": 2.93}, {"text": "And then also, you can\nsee what type it is.", "start": 1206.92, "duration": 2.73}, {"text": "This is called\nbarrel distortion,", "start": 1209.65, "duration": 2.46}, {"text": "because it looks like\nthe staves on a barrel.", "start": 1212.11, "duration": 4.56}, {"text": "In some cases, you\nmight find the opposite.", "start": 1216.67, "duration": 2.88}, {"text": "And that's called the\npincushion distortion.", "start": 1222.49, "duration": 2.64}, {"text": "I guess we don't do\nmuch sewing by hand", "start": 1227.69, "duration": 3.1}, {"text": "anymore in our\nmodern world, anyway.", "start": 1230.79, "duration": 4.44}, {"text": "So that may seem like\na strange concept.", "start": 1235.23, "duration": 2.25}, {"text": "But people used to need a\nway to put away their pins.", "start": 1237.48, "duration": 3.96}, {"text": "And they had a little cushion.", "start": 1241.44, "duration": 1.68}, {"text": "And the shape of the cushion\nis the shape that we see there.", "start": 1243.12, "duration": 5.74}, {"text": "So they're pins\non the sine of k1.", "start": 1248.86, "duration": 4.1}, {"text": "And the other thing\nis, of course,", "start": 1252.96, "duration": 1.48}, {"text": "once you've got\nthese images, you", "start": 1254.44, "duration": 2.12}, {"text": "can look at the radius of\ncurvature of these lines.", "start": 1256.56, "duration": 4.32}, {"text": "And you use them to estimate k1.", "start": 1260.88, "duration": 5.17}, {"text": "But we'll do it by actual\nmeasurement of images.", "start": 1266.05, "duration": 4.98}, {"text": "One subtle point\nhere is, do we want", "start": 1271.03, "duration": 3.51}, {"text": "to go from undistorted\ncoordinates to distorted?", "start": 1274.54, "duration": 9.29}, {"text": "In other words, we'll take\nour perspective projection", "start": 1283.83, "duration": 3.39}, {"text": "equation.", "start": 1287.22, "duration": 0.81}, {"text": "That tells us where\nthings should appear.", "start": 1288.03, "duration": 2.46}, {"text": "And then, we look at the image\nto see where they actually", "start": 1290.49, "duration": 2.82}, {"text": "appear.", "start": 1293.31, "duration": 0.63}, {"text": "And then, we fit this polynomial\napproximation to that.", "start": 1293.94, "duration": 5.28}, {"text": "Or do we want to go from the\ndistorted to the undistorted,", "start": 1299.22, "duration": 7.74}, {"text": "again using a polynomial?", "start": 1306.96, "duration": 2.79}, {"text": "And why might we\nwant to do that?", "start": 1309.75, "duration": 2.173}, {"text": "Well, because the\ndistorted is something", "start": 1311.923, "duration": 1.667}, {"text": "we actually can measure.", "start": 1313.59, "duration": 1.72}, {"text": "We don't have a way of measuring\nthe undistorted quantities", "start": 1315.31, "duration": 3.8}, {"text": "directly.", "start": 1319.11, "duration": 2.03}, {"text": "So the two are\nrelated, of course,", "start": 1321.14, "duration": 3.12}, {"text": "by what's called the\nseries inversion.", "start": 1324.26, "duration": 3.09}, {"text": "Not a surprise that\nthat's what it's called.", "start": 1329.89, "duration": 2.94}, {"text": "But it's not something\nthat's usually taught.", "start": 1332.83, "duration": 4.92}, {"text": "And it's not entirely trivial.", "start": 1337.75, "duration": 2.19}, {"text": "But you can automate it\nand use some algorithm that", "start": 1339.94, "duration": 5.8}, {"text": "will take you from\nthe polynomial going", "start": 1345.74, "duration": 2.31}, {"text": "in one direction to\nthe polynomial going", "start": 1348.05, "duration": 2.58}, {"text": "in the other direction.", "start": 1350.63, "duration": 2.06}, {"text": "The way it affects\nus is that it affects", "start": 1352.69, "duration": 2.97}, {"text": "what coordinate\nsystem we want to do", "start": 1355.66, "duration": 2.19}, {"text": "the final optimization in.", "start": 1357.85, "duration": 2.27}, {"text": "Because obviously,\nit's going to be easier", "start": 1363.62, "duration": 3.72}, {"text": "to do the optimization\nin one of those,", "start": 1367.34, "duration": 4.48}, {"text": "depending on which\nway around you've", "start": 1371.82, "duration": 1.79}, {"text": "expressed the polynomial.", "start": 1373.61, "duration": 2.25}, {"text": "And I guess we're going\nto try and minimize", "start": 1375.86, "duration": 2.79}, {"text": "the error in the image plane.", "start": 1378.65, "duration": 2.05}, {"text": "So from that point\nof view, it may", "start": 1380.7, "duration": 3.05}, {"text": "be that we want to go from\nundistorted to distorted.", "start": 1383.75, "duration": 3.78}, {"text": "But we'll hang onto that.", "start": 1387.53, "duration": 2.01}, {"text": "So okay.", "start": 1389.54, "duration": 3.46}, {"text": "By the way, radial\ndistortion-- how", "start": 1393.0, "duration": 3.97}, {"text": "about tangential distortion?", "start": 1396.97, "duration": 1.68}, {"text": "Well fortunately, we don't have\nto worry about that anymore.", "start": 1402.5, "duration": 5.33}, {"text": "But just for reference, this\nis what it would look like.", "start": 1407.83, "duration": 7.02}, {"text": "No, sorry.", "start": 1417.38, "duration": 0.95}, {"text": "Minus y plus x.", "start": 1418.33, "duration": 2.055}, {"text": "Again, polynomial--\nsomething growing with power", "start": 1424.61, "duration": 4.14}, {"text": "of the radius in the image.", "start": 1428.75, "duration": 1.768}, {"text": "So it's not a problem in\nthe middle of the image.", "start": 1430.518, "duration": 2.042}, {"text": "And then, it gets worse\nwhen you get to the corners.", "start": 1432.56, "duration": 3.31}, {"text": "And now, it's in a\ndirection that's orthogonal.", "start": 1435.87, "duration": 2.75}, {"text": "So delta x delta y--", "start": 1438.62, "duration": 1.89}, {"text": "that vector in 2D--", "start": 1440.51, "duration": 1.86}, {"text": "is now perpendicular\nto this vector,", "start": 1442.37, "duration": 2.97}, {"text": "to the vector xy, right?", "start": 1445.34, "duration": 1.445}, {"text": "So if we take the direct\nproduct, you can see here.", "start": 1446.785, "duration": 2.125}, {"text": "So that used to be a problem,\nbecause imaging systems were", "start": 1448.91, "duration": 6.27}, {"text": "electromagnetic\nvacuum tube apparatus.", "start": 1455.18, "duration": 3.12}, {"text": "And in addition to\nradial distortion,", "start": 1458.3, "duration": 2.97}, {"text": "they would have\ntangential distortion", "start": 1461.27, "duration": 2.31}, {"text": "based on exactly how you placed\nthose electromagnets, and so", "start": 1463.58, "duration": 3.42}, {"text": "on.", "start": 1467.0, "duration": 0.9}, {"text": "It's not a problem\nin modern devices,", "start": 1467.9, "duration": 3.57}, {"text": "because the chip has\nperfect geometry.", "start": 1471.47, "duration": 3.81}, {"text": "And the lenses, if they're\nrotationally symmetric,", "start": 1475.28, "duration": 5.01}, {"text": "only have radial distortion.", "start": 1480.29, "duration": 2.43}, {"text": "But just be aware of\nthe fact that it's", "start": 1482.72, "duration": 3.12}, {"text": "called radial distortion.", "start": 1485.84, "duration": 1.17}, {"text": "Because there's another one.", "start": 1487.01, "duration": 2.64}, {"text": "There are some\nadditional factors", "start": 1489.65, "duration": 3.3}, {"text": "that we're ignoring,\nbecause they're small,", "start": 1492.95, "duration": 4.77}, {"text": "and because they depend on the\nquality of the lens assembly.", "start": 1497.72, "duration": 5.61}, {"text": "One is called decentering.", "start": 1503.33, "duration": 2.03}, {"text": "And so in particular, if\nthe center of distortion", "start": 1509.69, "duration": 5.76}, {"text": "is not the same as\nyour principal point,", "start": 1515.45, "duration": 3.42}, {"text": "so you're distorting\nabout a point", "start": 1518.87, "duration": 1.68}, {"text": "other than what\nyou would normally", "start": 1520.55, "duration": 2.13}, {"text": "consider the center of the\nimage as far as perspective", "start": 1522.68, "duration": 2.52}, {"text": "projection is\nconcerned, then you're", "start": 1525.2, "duration": 1.86}, {"text": "going to get an offset\nthat depends on position.", "start": 1527.06, "duration": 4.76}, {"text": "And usually, it's very small.", "start": 1531.82, "duration": 2.55}, {"text": "Because usually, things are\nassembled accurately enough", "start": 1534.37, "duration": 6.23}, {"text": "for that not to be a problem.", "start": 1540.6, "duration": 1.84}, {"text": "But if you want to do\nreally high quality", "start": 1542.44, "duration": 2.18}, {"text": "work like aerial\nphotography, then you", "start": 1544.62, "duration": 2.22}, {"text": "do need to include that.", "start": 1546.84, "duration": 1.26}, {"text": "Another thing to consider is\nif the image plane is tilted.", "start": 1552.47, "duration": 5.46}, {"text": "So here's our lens.", "start": 1557.93, "duration": 2.04}, {"text": "And now, your image-- of course,\nit won't be tilted that much.", "start": 1559.97, "duration": 2.7}, {"text": "But it's a mechanical\nthing that somebody built.", "start": 1562.67, "duration": 4.2}, {"text": "So there's a possibility\nthat there'll", "start": 1566.87, "duration": 1.98}, {"text": "be some small error there.", "start": 1568.85, "duration": 1.69}, {"text": "And that, of course, means\nthat the magnification", "start": 1570.54, "duration": 2.63}, {"text": "isn't quite constant across.", "start": 1573.17, "duration": 2.67}, {"text": "And the focus will\nalso be an issue.", "start": 1575.84, "duration": 3.1}, {"text": "But if it's a very\nsmall effect, the focus", "start": 1578.94, "duration": 1.91}, {"text": "won't be affected much.", "start": 1580.85, "duration": 1.05}, {"text": "But it will still\nintroduce a distortion.", "start": 1581.9, "duration": 2.7}, {"text": "And it turns out that\nthese two are related.", "start": 1584.6, "duration": 4.09}, {"text": "So if you want to, you can\nhave a more complicated model", "start": 1588.69, "duration": 6.35}, {"text": "for distortion.", "start": 1595.04, "duration": 1.8}, {"text": "We're not going to do that.", "start": 1596.84, "duration": 1.23}, {"text": "But it turns out\nin the end, when", "start": 1598.07, "duration": 2.22}, {"text": "we do the nonlinear\noptimization,", "start": 1600.29, "duration": 1.89}, {"text": "you can have whatever you want.", "start": 1602.18, "duration": 3.58}, {"text": "We're going to start off with\nsome closed form formulas.", "start": 1605.76, "duration": 5.33}, {"text": "But at the end, we're just\ngoing to throw up our hands", "start": 1611.09, "duration": 2.25}, {"text": "and say, oh, this is a\ndifficult nonlinear problem.", "start": 1613.34, "duration": 2.58}, {"text": "We'll just give it to\none of those packages.", "start": 1615.92, "duration": 2.25}, {"text": "And at that point, your\nmodel of distortion", "start": 1618.17, "duration": 2.88}, {"text": "can be more complicated\nwithout high penalty,", "start": 1621.05, "duration": 3.66}, {"text": "other than overfitting\nproblems, like you've", "start": 1624.71, "duration": 3.0}, {"text": "put in so many\nparameters that it's", "start": 1627.71, "duration": 2.46}, {"text": "going to specifically tune it to\nyour experimental measurements.", "start": 1630.17, "duration": 5.07}, {"text": "And the resulting apparent\nhigh accuracy is bogus.", "start": 1635.24, "duration": 6.54}, {"text": "But beyond that, we can\nhave more complicated--", "start": 1641.78, "duration": 3.57}, {"text": "so what's the strategy?", "start": 1645.35, "duration": 1.2}, {"text": "So what we're going to follow is\nsize camera calibration method", "start": 1646.55, "duration": 6.33}, {"text": "with some modifications.", "start": 1652.88, "duration": 3.84}, {"text": "Yeah.", "start": 1656.72, "duration": 0.51}, {"text": "Well, that's a good question.", "start": 1657.23, "duration": 2.1}, {"text": "Because we find that\nmechanical adjustments and fine", "start": 1659.33, "duration": 5.01}, {"text": "tuning at the\nmanufacturer is expensive.", "start": 1664.34, "duration": 3.96}, {"text": "Software solutions\ntend to be cheap.", "start": 1668.3, "duration": 2.91}, {"text": "And so in modern times,\nit's been mostly a matter", "start": 1671.21, "duration": 3.15}, {"text": "of extending the\nmodel of distortion", "start": 1674.36, "duration": 2.85}, {"text": "and having a couple\nmore parameters to tune.", "start": 1677.21, "duration": 3.84}, {"text": "In the past, it was indeed\na matter of fine tuning", "start": 1681.05, "duration": 5.82}, {"text": "when you manufactured.", "start": 1686.87, "duration": 2.13}, {"text": "It wasn't done for anything\nexcept aerial photography,", "start": 1689.0, "duration": 3.45}, {"text": "where you want the geometry\nto be absolutely straight.", "start": 1692.45, "duration": 3.51}, {"text": "And they would have\nfine adjustments.", "start": 1695.96, "duration": 3.45}, {"text": "And if you tweaked any of\nthem, your warranty was dead.", "start": 1699.41, "duration": 4.15}, {"text": "So naturally, they spent a lot\nof effort to get it squared up.", "start": 1703.56, "duration": 9.14}, {"text": "And in some cases, the fix\nwas not actually adjusting", "start": 1712.7, "duration": 8.27}, {"text": "the tilt of the image\nplane, but introducing", "start": 1720.97, "duration": 2.79}, {"text": "a prism wedge, a\nvery small angle", "start": 1723.76, "duration": 3.93}, {"text": "that would compensate for it.", "start": 1727.69, "duration": 2.19}, {"text": "And you'd measure how much tilt\nthere is in the image plane,", "start": 1729.88, "duration": 5.31}, {"text": "and then go to the\nstoreroom and pick out", "start": 1735.19, "duration": 3.05}, {"text": "the compensating\nelement that would just", "start": 1738.24, "duration": 3.54}, {"text": "get rid of that component.", "start": 1741.78, "duration": 3.19}, {"text": "OK.", "start": 1744.97, "duration": 2.28}, {"text": "So Tsai came up\nwith this scheme.", "start": 1747.25, "duration": 5.37}, {"text": "And it involves, as you might\nimagine, a calibration object.", "start": 1752.62, "duration": 4.92}, {"text": "And the calibration\nobject could be anything", "start": 1760.94, "duration": 2.13}, {"text": "that you know coordinates\non very accurately.", "start": 1763.07, "duration": 2.88}, {"text": "And we'll have to make a\ndistinction between planar", "start": 1765.95, "duration": 4.17}, {"text": "calibration objects,\nwhich obviously", "start": 1770.12, "duration": 3.3}, {"text": "are easier to make and\nkeep in the storeroom,", "start": 1773.42, "duration": 3.84}, {"text": "and make very accurately using\nlithographic reproduction", "start": 1777.26, "duration": 5.79}, {"text": "methods, or\nthree-dimensional calibration", "start": 1783.05, "duration": 4.2}, {"text": "objects like the rectangular\nbrick that we talked about,", "start": 1787.25, "duration": 4.53}, {"text": "which are harder to make,\nharder to maintain accurately.", "start": 1791.78, "duration": 7.23}, {"text": "And then on the other hand,\nthey have some advantages", "start": 1799.01, "duration": 4.08}, {"text": "in terms of calibration.", "start": 1803.09, "duration": 1.23}, {"text": "So there's a tension there.", "start": 1804.32, "duration": 3.64}, {"text": "So we get correspondences,\nthis time between image points", "start": 1807.96, "duration": 6.46}, {"text": "and known points on this\nthree-dimensional object.", "start": 1814.42, "duration": 4.16}, {"text": "Now, what makes it not quite\nso easy as when we were talking", "start": 1818.58, "duration": 6.23}, {"text": "about the vanishing\npoint method is", "start": 1824.81, "duration": 4.59}, {"text": "that we're unlikely to\nbe able to determine,", "start": 1829.4, "duration": 8.97}, {"text": "by getting a tape measure,\nwhat the relationship is", "start": 1838.37, "duration": 4.5}, {"text": "between the calibration\nobject and the camera.", "start": 1842.87, "duration": 3.39}, {"text": "So they're sitting on the floor.", "start": 1846.26, "duration": 2.31}, {"text": "We take a picture of it,\nput the camera on a tripod.", "start": 1848.57, "duration": 4.26}, {"text": "And we can go out,\nand we can measure", "start": 1852.83, "duration": 1.59}, {"text": "how far is the first\npoint on that object.", "start": 1854.42, "duration": 4.12}, {"text": "But then, how is it\nrotated in space?", "start": 1858.54, "duration": 3.41}, {"text": "And it's just not practical,\nparticularly since you", "start": 1861.95, "duration": 2.58}, {"text": "don't actually know where\nthe center of projection", "start": 1864.53, "duration": 2.91}, {"text": "is, that front nodal point\nthat we talked about when we're", "start": 1867.44, "duration": 3.51}, {"text": "talking about image projection.", "start": 1870.95, "duration": 1.68}, {"text": "And so that means that we need\nto add exterior orientation.", "start": 1872.63, "duration": 7.14}, {"text": "So rather than find just\nthe interior orientation", "start": 1883.6, "duration": 8.53}, {"text": "of the camera as we did when\nwe used vanishing points,", "start": 1892.13, "duration": 2.82}, {"text": "now we're going to solve\nthe problem of figuring out", "start": 1894.95, "duration": 4.26}, {"text": "where the calibration object is\nin space and how it's rotated,", "start": 1899.21, "duration": 3.75}, {"text": "as well as finding\nthe camera parameters.", "start": 1902.96, "duration": 2.67}, {"text": "And that produces much\nmore accurate results,", "start": 1905.63, "duration": 2.91}, {"text": "because there aren't\nany external measurement", "start": 1908.54, "duration": 4.05}, {"text": "errors, or errors\nbecause we don't", "start": 1912.59, "duration": 3.36}, {"text": "know, in this complicated\nlens with many elements,", "start": 1915.95, "duration": 3.9}, {"text": "exactly where is the\nfront nodal point.", "start": 1919.85, "duration": 2.19}, {"text": "It's not like there's a\nlittle mark on the side.", "start": 1922.04, "duration": 6.38}, {"text": "Because there can't\nbe a mark on the side.", "start": 1928.42, "duration": 2.13}, {"text": "It's right inside the lens.", "start": 1930.55, "duration": 1.32}, {"text": "So how would you denote it?", "start": 1931.87, "duration": 4.11}, {"text": "OK.", "start": 1935.98, "duration": 2.04}, {"text": "So let's see.", "start": 1938.02, "duration": 3.06}, {"text": "So that makes it more\ncomplicated, right?", "start": 1941.08, "duration": 2.64}, {"text": "Because interior orientation\nhas three degrees of freedom,", "start": 1943.72, "duration": 8.4}, {"text": "if we ignore distortion\nfor the moment.", "start": 1952.12, "duration": 3.525}, {"text": "And how about\nexterior orientation?", "start": 1958.81, "duration": 2.43}, {"text": "Well, that's translation\nand rotation.", "start": 1961.24, "duration": 3.84}, {"text": "The translation and\nrotation position,", "start": 1965.08, "duration": 2.67}, {"text": "the calibration object.", "start": 1967.75, "duration": 1.68}, {"text": "So that's six\ndegrees of freedom.", "start": 1969.43, "duration": 2.13}, {"text": "So we've taken something\nthat's pretty simple only,", "start": 1974.14, "duration": 4.25}, {"text": "has three unknowns.", "start": 1978.39, "duration": 2.07}, {"text": "And we've turned it into\nsomething that has nine.", "start": 1980.46, "duration": 2.49}, {"text": "But it does actually\nmake the problem simpler", "start": 1982.95, "duration": 4.35}, {"text": "and produces much\nmore accurate results.", "start": 1987.3, "duration": 4.42}, {"text": "OK.", "start": 1991.72, "duration": 0.5}, {"text": "So in the interior\norientation, we", "start": 1992.22, "duration": 5.61}, {"text": "have the good old prospective\nprediction equation.", "start": 1997.83, "duration": 2.91}, {"text": "OK.", "start": 2011.76, "duration": 0.5}, {"text": "So xc, yc, zc is in\ncamera coordinates.", "start": 2012.26, "duration": 9.78}, {"text": "So if we know some point in\nthe camera coordinate system,", "start": 2022.04, "duration": 3.36}, {"text": "we can calculate the\nposition of the image.", "start": 2025.4, "duration": 4.145}, {"text": "And x0, y0, f--", "start": 2036.84, "duration": 3.57}, {"text": "that's the interior orientation.", "start": 2040.41, "duration": 4.06}, {"text": "Right?", "start": 2044.47, "duration": 0.5}, {"text": "It's the principle point\nand the principle distance.", "start": 2044.97, "duration": 2.82}, {"text": "OK.", "start": 2052.48, "duration": 1.83}, {"text": "Now, the strategy\nhere is going to be", "start": 2054.31, "duration": 3.48}, {"text": "that we try to eliminate\nsome parameters that we don't", "start": 2057.79, "duration": 5.099}, {"text": "like that are difficult to deal\nwith, like radial distortion.", "start": 2062.889, "duration": 3.31}, {"text": "So we're going to try\nand find a method that,", "start": 2066.199, "duration": 2.601}, {"text": "right away, modifies the\nmeasurements in such a way", "start": 2068.8, "duration": 4.41}, {"text": "that the results are not\ndependent on radial distortion,", "start": 2073.21, "duration": 3.42}, {"text": "and then get closed\nform solution for some", "start": 2076.63, "duration": 3.15}, {"text": "of the parameters out of\nall of these parameters,", "start": 2079.78, "duration": 3.76}, {"text": "and then finally,\nwhen we no longer", "start": 2083.54, "duration": 2.449}, {"text": "can find closed form solutions,\nresort to number crunching.", "start": 2085.989, "duration": 5.291}, {"text": "And so why do we even\nbother with this?", "start": 2091.28, "duration": 2.49}, {"text": "Well, because the\nnumerical methods", "start": 2093.77, "duration": 3.32}, {"text": "minimize some quantity\nwhich has multiple minima.", "start": 2097.09, "duration": 4.11}, {"text": "And we want the true one.", "start": 2101.2, "duration": 3.3}, {"text": "We don't want to get stuck\nin the wrong local minimum.", "start": 2104.5, "duration": 3.39}, {"text": "And so we need a\ngood initial guess.", "start": 2107.89, "duration": 2.73}, {"text": "And this is how we get\nthe good initial guess.", "start": 2110.62, "duration": 2.89}, {"text": "So in the process,\nwe're allowed to violate", "start": 2113.51, "duration": 2.39}, {"text": "many of the principles\nthat we've established,", "start": 2115.9, "duration": 2.79}, {"text": "because this isn't\ngoing to be the answer.", "start": 2118.69, "duration": 2.41}, {"text": "This is our first guess for\nthe number crunching iterative", "start": 2121.1, "duration": 3.41}, {"text": "solution.", "start": 2124.51, "duration": 1.18}, {"text": "And so for example, we said\nthat we should be minimizing", "start": 2125.69, "duration": 4.49}, {"text": "the error in image position.", "start": 2130.18, "duration": 2.1}, {"text": "But that's very\nhard to do directly.", "start": 2132.28, "duration": 3.37}, {"text": "So we're going to minimize\nsome other area that is related", "start": 2135.65, "duration": 3.38}, {"text": "to the image position error.", "start": 2139.03, "duration": 2.31}, {"text": "And that's OK, because we're\nnot going to stop there.", "start": 2141.34, "duration": 4.69}, {"text": "This is just to get\nthe initial condition.", "start": 2146.03, "duration": 2.96}, {"text": "OK.", "start": 2148.99, "duration": 0.54}, {"text": "So the xIyI-- that could be just\nthe row and column in the image", "start": 2149.53, "duration": 7.77}, {"text": "sensor.", "start": 2157.3, "duration": 2.07}, {"text": "Or it could be millimeters\nfrom some reference point.", "start": 2159.37, "duration": 2.67}, {"text": "But it's very convenient to just\nuse the row and column numbers.", "start": 2162.04, "duration": 5.31}, {"text": "And then for f, well, f\ncould be in millimeters.", "start": 2167.35, "duration": 4.18}, {"text": "But it could also be in pixels.", "start": 2171.53, "duration": 3.92}, {"text": "Suppose that our\npixels are square.", "start": 2175.45, "duration": 2.61}, {"text": "And we just use the\nrow and column number", "start": 2178.06, "duration": 2.07}, {"text": "as coordinates for\nimage position.", "start": 2180.13, "duration": 4.37}, {"text": "Then it's very convenient\nto express f in pixel size.", "start": 2184.5, "duration": 5.64}, {"text": "It's 1,000 pixels.", "start": 2190.14, "duration": 1.48}, {"text": "Why?", "start": 2191.62, "duration": 0.5}, {"text": "Well, because when we apply\nthe perspective projection", "start": 2192.12, "duration": 3.21}, {"text": "equation, then the units\nabove and below match.", "start": 2195.33, "duration": 4.21}, {"text": "And so we can use any units we\nwant-- millimeters or pixels.", "start": 2199.54, "duration": 5.66}, {"text": "So OK.", "start": 2205.2, "duration": 2.31}, {"text": "Now, so there are\nthree parameters here.", "start": 2207.51, "duration": 3.3}, {"text": "And then, we add\nto that exterior.", "start": 2210.81, "duration": 3.6}, {"text": "And that of course, is\nrotation and translation.", "start": 2214.41, "duration": 3.01}, {"text": "And so we have a vector\nfor the camera, which", "start": 2217.42, "duration": 4.76}, {"text": "is going to be a rotated\nversion of vector for scene", "start": 2222.18, "duration": 5.49}, {"text": "plus some translation.", "start": 2227.67, "duration": 2.95}, {"text": "So this is again, the camera.", "start": 2230.62, "duration": 3.12}, {"text": "And so that's, of\ncourse, the xc,", "start": 2233.74, "duration": 1.514}, {"text": "yc, zc we've talked\nabout over here.", "start": 2235.254, "duration": 3.996}, {"text": "And this is the scene, or\nobject, or world coordinate,", "start": 2239.25, "duration": 5.61}, {"text": "or whatever you want to call.", "start": 2244.86, "duration": 1.38}, {"text": "It's not really a world\ncoordinate system.", "start": 2246.24, "duration": 3.54}, {"text": "It's a coordinate system\nin the calibration object.", "start": 2249.78, "duration": 2.43}, {"text": "So we know the calibration\nobject very accurately.", "start": 2252.21, "duration": 3.06}, {"text": "And we know its coordinates\nrelative to some system that's", "start": 2255.27, "duration": 4.17}, {"text": "embedded in that object, like\nmaybe the corner of that cube,", "start": 2259.44, "duration": 3.45}, {"text": "or rectangular brick.", "start": 2262.89, "duration": 3.5}, {"text": "OK.", "start": 2266.39, "duration": 0.5}, {"text": "Now as I said, we're going to\nignore our better instincts.", "start": 2266.89, "duration": 7.67}, {"text": "And for a start, we're going\nto use rotation matrices here.", "start": 2274.56, "duration": 6.045}, {"text": "2, 3r, 2 xsyszs.", "start": 2286.05, "duration": 4.665}, {"text": "OK, so this, of\ncourse, is a coordinate", "start": 2298.83, "duration": 2.61}, {"text": "in the collaboration object\nin its own coordinate system.", "start": 2301.44, "duration": 4.77}, {"text": "And then, we're\ngoing to rotate that.", "start": 2306.21, "duration": 1.74}, {"text": "And then, we're moving the\nobject out by this distance.", "start": 2307.95, "duration": 4.75}, {"text": "And of course,\nthat's the unknown.", "start": 2312.7, "duration": 3.87}, {"text": "This is unknown.", "start": 2316.57, "duration": 0.74}, {"text": "And that is unknown.", "start": 2317.31, "duration": 1.33}, {"text": "And as I mentioned before,\nwe're using the equations", "start": 2318.64, "duration": 3.77}, {"text": "in a weird way.", "start": 2322.41, "duration": 2.01}, {"text": "Because normally, you\nwould use these equations", "start": 2324.42, "duration": 2.88}, {"text": "to take a position in\nthe calibration object", "start": 2327.3, "duration": 3.3}, {"text": "and transform it into a\nposition in the camera object.", "start": 2330.6, "duration": 2.91}, {"text": "That's what their\npurpose in life is.", "start": 2333.51, "duration": 2.25}, {"text": "But we're turning\nthis upside down.", "start": 2335.76, "duration": 4.41}, {"text": "Those are the things we know.", "start": 2340.17, "duration": 1.86}, {"text": "And we don't know\nwhat this matrix is.", "start": 2342.03, "duration": 2.1}, {"text": "And we don't know\nwhat that vector is.", "start": 2344.13, "duration": 1.95}, {"text": "And so those are the things\nwe're going to try and recover.", "start": 2346.08, "duration": 3.555}, {"text": "OK.", "start": 2356.19, "duration": 0.5}, {"text": "So now, we combine interior\norientation and exterior", "start": 2356.69, "duration": 3.87}, {"text": "orientation.", "start": 2360.56, "duration": 1.17}, {"text": "And what we get is--", "start": 2361.73, "duration": 1.65}, {"text": "and a similar equation for y.", "start": 2383.91, "duration": 2.325}, {"text": "r21 xs plus r22 ys plus--", "start": 2388.915, "duration": 7.685}, {"text": "and then, the bottom is\nexactly the same as up there.", "start": 2396.6, "duration": 5.84}, {"text": "OK.", "start": 2402.44, "duration": 1.08}, {"text": "And again, written\nthat way, it basically", "start": 2403.52, "duration": 3.9}, {"text": "allows us to map from\ncoordinates in the calibration", "start": 2407.42, "duration": 3.06}, {"text": "objects to image coordinates.", "start": 2410.48, "duration": 2.25}, {"text": "But we want to use it instead to\nrecover as many of these things", "start": 2412.73, "duration": 4.47}, {"text": "as we can.", "start": 2417.2, "duration": 0.66}, {"text": "OK.", "start": 2421.6, "duration": 0.5}, {"text": "Now, I mentioned that\nit'd be convenient to get", "start": 2433.59, "duration": 3.45}, {"text": "rid of the problems of radial\ndistortion and fine tune things", "start": 2437.04, "duration": 6.78}, {"text": "right at the end to\nget those coefficients.", "start": 2443.82, "duration": 2.91}, {"text": "And also it turns out\nto be difficult to get", "start": 2446.73, "duration": 4.905}, {"text": "f at first, and tz.", "start": 2451.635, "duration": 3.075}, {"text": "So f occurs here.", "start": 2454.71, "duration": 4.65}, {"text": "Now, one way we\ncan deal with that", "start": 2459.36, "duration": 2.46}, {"text": "is to look only at the\ndirection in the image.", "start": 2461.82, "duration": 3.67}, {"text": "So I guess it\ndisappeared up there.", "start": 2465.49, "duration": 3.71}, {"text": "But if we work in\npolar coordinates,", "start": 2469.2, "duration": 6.1}, {"text": "radial distortion just\nchanges the length.", "start": 2475.3, "duration": 4.62}, {"text": "It doesn't change the angle.", "start": 2479.92, "duration": 2.01}, {"text": "Similarly, if I change\nthe principle distance f,", "start": 2481.93, "duration": 3.39}, {"text": "all that happens is that the\nimage gets magnified with f.", "start": 2485.32, "duration": 3.78}, {"text": "And so it moves radially.", "start": 2489.1, "duration": 2.34}, {"text": "And the same happens if I change\nthe distance z to the object.", "start": 2491.44, "duration": 5.22}, {"text": "All that happens is the\nmagnification changes.", "start": 2496.66, "duration": 2.76}, {"text": "And so again, we're\nmoving along the radius.", "start": 2499.42, "duration": 3.61}, {"text": "So the idea is,\nlet's do something", "start": 2503.03, "duration": 3.68}, {"text": "to deal with that angle and\nforget the radial distance", "start": 2506.71, "duration": 6.21}, {"text": "in this polar coordinate system.", "start": 2512.92, "duration": 1.99}, {"text": "And so for example,\nwe can do this.", "start": 2514.91, "duration": 4.29}, {"text": "We can divide these\ntwo equations, right?", "start": 2519.2, "duration": 5.62}, {"text": "Because now, we've\ngotten rid of f.", "start": 2524.82, "duration": 3.75}, {"text": "We have a new equation\nthat doesn't involve f.", "start": 2528.57, "duration": 2.76}, {"text": "And let's see.", "start": 2531.33, "duration": 1.83}, {"text": "xs plus-- and we also\nhave gotten rid of tz.", "start": 2533.16, "duration": 11.095}, {"text": "23 zs plus ty.", "start": 2547.91, "duration": 4.29}, {"text": "Right?", "start": 2552.2, "duration": 0.5}, {"text": "So tz occurs here and there.", "start": 2552.7, "duration": 3.99}, {"text": "And those two terms cancel.", "start": 2556.69, "duration": 1.96}, {"text": "And so we're just\nleft with tx and ty.", "start": 2558.65, "duration": 3.36}, {"text": "So we've combined two\nequations, two constraints.", "start": 2562.01, "duration": 5.54}, {"text": "We get a new one, which has\nfewer of the unknowns in it.", "start": 2567.55, "duration": 3.9}, {"text": "So it's going to\nbe easier to find.", "start": 2571.45, "duration": 1.6}, {"text": "So now, we cross-multiply.", "start": 2573.05, "duration": 2.42}, {"text": "And we gather up terms.", "start": 2575.47, "duration": 2.19}, {"text": "And we get xs yi prime r11.", "start": 2577.66, "duration": 7.29}, {"text": "And I'm gathering up terms\nin such a way that it's clear", "start": 2584.95, "duration": 4.29}, {"text": "what are the unknowns.", "start": 2589.24, "duration": 2.58}, {"text": "And of course, in our\ncase here, the unknowns", "start": 2591.82, "duration": 4.02}, {"text": "are the components\nof r, and tx and ty.", "start": 2595.84, "duration": 7.89}, {"text": "xs-- that's going to be--\nwell, these two are equal.", "start": 2608.38, "duration": 23.83}, {"text": "And if I bring this\nover to the other side,", "start": 2632.21, "duration": 3.58}, {"text": "I get this minus that equals 0.", "start": 2635.79, "duration": 1.95}, {"text": "So there's an equation.", "start": 2637.74, "duration": 1.23}, {"text": "And let's look at that equation\nto see what's in there.", "start": 2638.97, "duration": 3.07}, {"text": "So first of all,\nxs and ys and zs--", "start": 2642.04, "duration": 4.4}, {"text": "that's coordinate and\nthe calibration object.", "start": 2646.44, "duration": 2.34}, {"text": "We know those.", "start": 2648.78, "duration": 1.53}, {"text": "Then, we've got xi\nprime and yi prime.", "start": 2650.31, "duration": 3.12}, {"text": "Those are image coordinates.", "start": 2653.43, "duration": 1.86}, {"text": "And we've measured those.", "start": 2655.29, "duration": 1.9}, {"text": "So the things in\nparentheses are known.", "start": 2657.19, "duration": 4.28}, {"text": "OK, just a second.", "start": 2661.47, "duration": 1.17}, {"text": "And what's unknown are r11,\nr12, et cetera, et cetera.", "start": 2662.64, "duration": 3.49}, {"text": "So this is a linear\nequation in those unknowns.", "start": 2666.13, "duration": 2.54}, {"text": "Oh, OK.", "start": 2668.67, "duration": 0.9}, {"text": "They are these things.", "start": 2672.98, "duration": 1.89}, {"text": "So let me just--", "start": 2674.87, "duration": 1.0}, {"text": "yeah.", "start": 2680.04, "duration": 0.5}, {"text": "Thanks for pointing that out.", "start": 2680.54, "duration": 1.26}, {"text": "So in order to do\nthis, we need to know", "start": 2681.8, "duration": 4.05}, {"text": "where the principal point is\nso we can subtract it out.", "start": 2685.85, "duration": 3.84}, {"text": "And of course, we don't\nactually know where it is.", "start": 2689.69, "duration": 2.31}, {"text": "But for this purpose, we\njust need an approximation.", "start": 2692.0, "duration": 5.44}, {"text": "And so we can take the\ncenter of the image sensor.", "start": 2697.44, "duration": 4.31}, {"text": "Unless we know better, we can\ntake half the number of rows", "start": 2701.75, "duration": 6.51}, {"text": "and half the number of\ncolumns, and put it there.", "start": 2708.26, "duration": 3.2}, {"text": "Now, that's going\nto be a problem", "start": 2711.46, "duration": 3.65}, {"text": "if we're dealing with\nimage points that", "start": 2715.11, "duration": 1.86}, {"text": "are right close to it, because\nthe directions to those points", "start": 2716.97, "duration": 3.57}, {"text": "is going to be affected a lot\nby any small error in our guess", "start": 2720.54, "duration": 4.14}, {"text": "at what the principal point is.", "start": 2724.68, "duration": 2.16}, {"text": "So what we do is--", "start": 2726.84, "duration": 2.19}, {"text": "and what Tsai doesn't\nmention is that we throw away", "start": 2729.03, "duration": 10.8}, {"text": "all of the\ncorrespondences that are", "start": 2739.83, "duration": 2.88}, {"text": "close to the assumed\ncenter of the image, right?", "start": 2742.71, "duration": 4.05}, {"text": "Because if we're dealing\nwith the direction of a ray", "start": 2746.76, "duration": 3.24}, {"text": "out here, and this center is\nwrong by some small amount,", "start": 2750.0, "duration": 4.17}, {"text": "that's not going to have a\nhuge effect on the direction.", "start": 2754.17, "duration": 2.82}, {"text": "But if we're dealing\nwith a point in here", "start": 2756.99, "duration": 2.25}, {"text": "and we move the\ncenter, that's going", "start": 2759.24, "duration": 1.95}, {"text": "to have a large\neffect on its angle.", "start": 2761.19, "duration": 2.01}, {"text": "So we're cheating\nby saying, oh, we", "start": 2763.2, "duration": 5.04}, {"text": "have a guess at\nwhat x0 and y0 are--", "start": 2768.24, "duration": 2.97}, {"text": "the principal point, which in\nfact we're trying to determine.", "start": 2771.21, "duration": 3.03}, {"text": "But it's OK, because it's\nonly an approximation.", "start": 2774.24, "duration": 4.59}, {"text": "And we don't use\nthe data where it", "start": 2778.83, "duration": 3.39}, {"text": "matters, where that effect\nwould be the most severe.", "start": 2782.22, "duration": 3.52}, {"text": "So OK.", "start": 2785.74, "duration": 3.03}, {"text": "So we subtract out--\nwe reference everything", "start": 2788.77, "duration": 4.94}, {"text": "to the image center that we\nassume is close to x0 and y0.", "start": 2793.71, "duration": 4.53}, {"text": "And then, we get this linear\nequation, the unknowns.", "start": 2798.24, "duration": 4.02}, {"text": "And we get one of\nthese equations", "start": 2802.26, "duration": 1.83}, {"text": "for every correspondence, right?", "start": 2804.09, "duration": 2.49}, {"text": "So every time we say, oh,\nthis point in the image", "start": 2806.58, "duration": 3.66}, {"text": "is that point on the\ncalibration object,", "start": 2810.24, "duration": 3.27}, {"text": "we can write down one\nof these equations.", "start": 2813.51, "duration": 2.82}, {"text": "And of course, the xs and\nyI's will change as we go.", "start": 2819.1, "duration": 7.08}, {"text": "OK.", "start": 2831.59, "duration": 0.5}, {"text": "Now, it's a linear equation.", "start": 2832.09, "duration": 2.04}, {"text": "And how many do we need?", "start": 2834.13, "duration": 3.75}, {"text": "Of course, with\njust one, we can't", "start": 2837.88, "duration": 1.56}, {"text": "solve, because we've\ngot a bunch of unknowns.", "start": 2839.44, "duration": 3.1}, {"text": "So we need to count how\nmany unknowns we have.", "start": 2842.54, "duration": 3.47}, {"text": "OK.", "start": 2849.62, "duration": 0.5}, {"text": "So now, we got\nrid of some stuff.", "start": 2850.12, "duration": 3.78}, {"text": "So what's left?", "start": 2853.9, "duration": 1.15}, {"text": "So what's left is--", "start": 2855.05, "duration": 3.45}, {"text": "so those appear in\nthere, as do these.", "start": 2858.5, "duration": 5.5}, {"text": "And tx appears, and ty.", "start": 2864.0, "duration": 3.87}, {"text": "So what doesn't appear?", "start": 2867.87, "duration": 1.56}, {"text": "Well, so out of\nall of the unknowns", "start": 2869.43, "duration": 10.94}, {"text": "we're trying to solve for,\nthese are the ones that", "start": 2880.37, "duration": 3.85}, {"text": "appear in the equation.", "start": 2884.22, "duration": 1.05}, {"text": "There are eight.", "start": 2885.27, "duration": 2.34}, {"text": "That seems to make sense.", "start": 2887.61, "duration": 1.77}, {"text": "Eight of those.", "start": 2889.38, "duration": 0.94}, {"text": "And then, there's a\nbunch more that we don't.", "start": 2890.32, "duration": 3.05}, {"text": "Now, keep in mind that we're\nnot enforcing orthonormality", "start": 2893.37, "duration": 5.73}, {"text": "of the matrix, right?", "start": 2899.1, "duration": 7.14}, {"text": "Because we're\npretending that those", "start": 2906.24, "duration": 2.35}, {"text": "are nine unrelated\nnumbers, not three degrees", "start": 2908.59, "duration": 6.0}, {"text": "of freedom of rotation.", "start": 2914.59, "duration": 2.02}, {"text": "So there are really\nsix numbers here,", "start": 2916.61, "duration": 2.69}, {"text": "when we know that rotation only\nhas three degrees of freedom.", "start": 2919.3, "duration": 3.61}, {"text": "Now as for these other three\nhere, if we ever get these six,", "start": 2922.91, "duration": 5.27}, {"text": "we should be able to get\nthis one by cross-product,", "start": 2928.18, "duration": 2.79}, {"text": "because we know that the\nrows of the rotation matrix", "start": 2930.97, "duration": 4.11}, {"text": "are orthogonal.", "start": 2935.08, "duration": 1.51}, {"text": "And so if you find\na vector that's", "start": 2936.59, "duration": 2.84}, {"text": "orthogonal to row 1\nand row 2, then it's", "start": 2939.43, "duration": 2.73}, {"text": "going to be parallel\nto row 3, right?", "start": 2942.16, "duration": 2.87}, {"text": "And so cross-product\nor the first two rows", "start": 2945.03, "duration": 3.33}, {"text": "gives us something that's\nparallel to the third row.", "start": 2948.36, "duration": 2.38}, {"text": "So we can recover\nthis one afterwards.", "start": 2950.74, "duration": 3.92}, {"text": "But right now, we're\nnot even enforcing", "start": 2954.66, "duration": 2.22}, {"text": "that this is supposed\nto be a unit vector.", "start": 2956.88, "duration": 3.3}, {"text": "This is supposed to\nbe a unit vector.", "start": 2960.18, "duration": 2.01}, {"text": "And these two vectors are\nsupposed to be orthogonal.", "start": 2962.19, "duration": 2.55}, {"text": "We're just going\nto go with this.", "start": 2964.74, "duration": 2.43}, {"text": "OK, the eight unknowns-- so\nthat suggests eight equations", "start": 2967.17, "duration": 4.71}, {"text": "are needed, eight\ncorrespondences.", "start": 2971.88, "duration": 2.8}, {"text": "But that's not quite true,\nbecause this equation", "start": 2974.68, "duration": 2.75}, {"text": "is homogeneous.", "start": 2977.43, "duration": 2.34}, {"text": "The result is equal to 0.", "start": 2979.77, "duration": 3.43}, {"text": "And we all learn how to\ndo a linear equations.", "start": 2983.2, "duration": 4.23}, {"text": "I don't know about\nyour education,", "start": 2987.43, "duration": 1.8}, {"text": "but typically, there's\nnot much emphasis", "start": 2989.23, "duration": 1.86}, {"text": "on homogeneous equations.", "start": 2991.09, "duration": 1.8}, {"text": "And they come up quite\na bit in machine vision.", "start": 2992.89, "duration": 2.43}, {"text": "So it's important to know\nwhat to do with them.", "start": 2995.32, "duration": 3.82}, {"text": "So one feature of a\nhomogeneous equation", "start": 2999.14, "duration": 2.48}, {"text": "is that the linear combination\nof some variables equals 0.", "start": 3001.62, "duration": 5.37}, {"text": "If I double all the variables,\nit'll still equal 0.", "start": 3006.99, "duration": 3.96}, {"text": "So there's a scale factor\nissue that I cannot,", "start": 3010.95, "duration": 4.17}, {"text": "from the homogeneous equation,\nfigure out what the scale", "start": 3015.12, "duration": 4.92}, {"text": "factor is.", "start": 3020.04, "duration": 2.13}, {"text": "And well, then a\nmethod of solution", "start": 3022.17, "duration": 3.0}, {"text": "is, take one of the unknowns.", "start": 3025.17, "duration": 2.34}, {"text": "And just set it to\nwhatever you want.", "start": 3027.51, "duration": 2.29}, {"text": "So for example, here we\nmight say ty equals 1, right?", "start": 3029.8, "duration": 7.37}, {"text": "Why?", "start": 3037.17, "duration": 0.5}, {"text": "Well, because whatever\nthe solution is,", "start": 3037.67, "duration": 2.16}, {"text": "I can scale it so\nthat ty equals 1.", "start": 3039.83, "duration": 3.21}, {"text": "And conversely, if I get a\nsolution with ty equals 1,", "start": 3043.04, "duration": 4.11}, {"text": "then I have some multiple\nof the true solution.", "start": 3047.15, "duration": 3.84}, {"text": "And the equation doesn't\ntell me what multiple.", "start": 3050.99, "duration": 3.06}, {"text": "I can't figure that\nout from that equation.", "start": 3054.05, "duration": 2.14}, {"text": "So this is a way to proceed.", "start": 3056.19, "duration": 5.33}, {"text": "OK.", "start": 3061.52, "duration": 0.6}, {"text": "So that then reduces\nit to linear equations", "start": 3062.12, "duration": 4.86}, {"text": "in seven unknowns, right?", "start": 3066.98, "duration": 4.08}, {"text": "Because I've fixed one of them.", "start": 3071.06, "duration": 3.54}, {"text": "And so that means that I\nneed seven correspondences.", "start": 3074.6, "duration": 3.2}, {"text": "So your calibration\nobject should", "start": 3081.39, "duration": 2.46}, {"text": "have seven points that are\neasily identified, preferably", "start": 3083.85, "duration": 8.28}, {"text": "from any point of view.", "start": 3092.13, "duration": 1.41}, {"text": "And that means you probably\nneed more than seven,", "start": 3093.54, "duration": 2.46}, {"text": "because some of\nthem will be hidden.", "start": 3096.0, "duration": 2.84}, {"text": "So let's see.", "start": 3098.84, "duration": 0.59}, {"text": "So if you have a\ncube, you typically", "start": 3099.43, "duration": 3.15}, {"text": "hide from a general position\none of the eight sides.", "start": 3102.58, "duration": 4.29}, {"text": "You'd be left with seven.", "start": 3106.87, "duration": 1.68}, {"text": "Oh, that's a nice match.", "start": 3108.55, "duration": 1.32}, {"text": "So a cube is not a bad\ncalibration object.", "start": 3109.87, "duration": 3.46}, {"text": "OK.", "start": 3113.33, "duration": 0.5}, {"text": "So then out of this, we get some\nmultiple of the true solution.", "start": 3113.83, "duration": 5.37}, {"text": "We get r11 prime,\nr12 prime, and so on.", "start": 3119.2, "duration": 4.83}, {"text": "So this method of solving\nthe homogeneous equations", "start": 3134.31, "duration": 4.31}, {"text": "will give us that.", "start": 3138.62, "duration": 0.87}, {"text": "Oh, so by the way, if we have\nexactly seven correspondences,", "start": 3139.49, "duration": 4.41}, {"text": "we're going to end up with\nseven linear equations and seven", "start": 3143.9, "duration": 2.52}, {"text": "unknowns.", "start": 3146.42, "duration": 0.51}, {"text": "And we know how to\nsolve those using--", "start": 3146.93, "duration": 2.07}, {"text": "I don't know-- Gaussian\nelimination, or MATLAB,", "start": 3149.0, "duration": 3.12}, {"text": "or whatever you want.", "start": 3152.12, "duration": 1.53}, {"text": "What happens if we have more\nthan seven correspondences?", "start": 3153.65, "duration": 2.37}, {"text": "First of all, that's desirable.", "start": 3156.02, "duration": 1.68}, {"text": "The more correspondences\nyou have,", "start": 3157.7, "duration": 1.95}, {"text": "the tighter your solution,\nthe smaller the error is.", "start": 3159.65, "duration": 3.63}, {"text": "And with seven correspondences,\nyou will get a perfect fit.", "start": 3163.28, "duration": 6.36}, {"text": "Does it mean you have no error?", "start": 3169.64, "duration": 1.56}, {"text": "No.", "start": 3171.2, "duration": 0.63}, {"text": "But if you take more\ncorrespondences,", "start": 3171.83, "duration": 2.22}, {"text": "you can estimate the error.", "start": 3174.05, "duration": 1.57}, {"text": "So it's not only that\nyou get a better answer,", "start": 3175.62, "duration": 2.42}, {"text": "but you also get an estimate\nof what's wrong with it.", "start": 3178.04, "duration": 2.67}, {"text": "So typically, you'd\nuse more than seven.", "start": 3180.71, "duration": 3.24}, {"text": "And that means that your\nsystem of linear equations", "start": 3183.95, "duration": 2.4}, {"text": "is overdetermined.", "start": 3186.35, "duration": 1.23}, {"text": "And then, you use least squares,\npseudo inverse, standard stuff", "start": 3187.58, "duration": 5.73}, {"text": "to find the best solution.", "start": 3193.31, "duration": 3.45}, {"text": "OK.", "start": 3196.76, "duration": 0.5}, {"text": "But whether it's seven or\nmore, now we have this.", "start": 3197.26, "duration": 5.22}, {"text": "And we have to figure out\nwhat the actual solution is.", "start": 3202.48, "duration": 4.11}, {"text": "Well, we know that these are\nsupposed to be unit vectors.", "start": 3206.59, "duration": 4.0}, {"text": "So we can calculate\na scale factor.", "start": 3210.59, "duration": 1.67}, {"text": "So we can compute a scale factor\nto make those be unit vectors.", "start": 3235.12, "duration": 5.83}, {"text": "And oh, what if those\ntwo don't agree?", "start": 3240.95, "duration": 2.82}, {"text": "Well, that's a\ngood sanity check.", "start": 3243.77, "duration": 2.34}, {"text": "If you do this, and you\nfind that those two scale", "start": 3246.11, "duration": 4.44}, {"text": "factors aren't\napproximately the same,", "start": 3250.55, "duration": 2.56}, {"text": "then there's something\nseriously wrong.", "start": 3253.11, "duration": 3.74}, {"text": "For example, you\nhave misidentified", "start": 3256.85, "duration": 2.13}, {"text": "the correspondences.", "start": 3258.98, "duration": 1.38}, {"text": "You thought this was the point\non the corner of the cube", "start": 3260.36, "duration": 2.79}, {"text": "on the left, but it wasn't.", "start": 3263.15, "duration": 1.71}, {"text": "Then, these will come\nout different, typically.", "start": 3264.86, "duration": 3.15}, {"text": "In practice, they won't\never be exactly the same.", "start": 3268.01, "duration": 3.19}, {"text": "So you can take the\naverage, if you like.", "start": 3271.2, "duration": 3.14}, {"text": "And so now, we can\nscale this vector", "start": 3274.34, "duration": 3.91}, {"text": "to turn it into this one.", "start": 3278.25, "duration": 2.8}, {"text": "OK.", "start": 3281.05, "duration": 0.5}, {"text": "So what we've done\nnow is, we have", "start": 3281.55, "duration": 3.36}, {"text": "a first estimate of everything\nexcept f and tz and radial", "start": 3284.91, "duration": 10.68}, {"text": "distortion.", "start": 3295.59, "duration": 1.74}, {"text": "And this was closed form.", "start": 3297.33, "duration": 2.76}, {"text": "If we do pseudo inverse,\nthat's a closed form solution.", "start": 3300.09, "duration": 5.59}, {"text": "OK.", "start": 3305.68, "duration": 1.74}, {"text": "So next step is going\nto be finding f and tz.", "start": 3307.42, "duration": 5.39}, {"text": "But while we're\nhere, we're trying", "start": 3312.81, "duration": 5.19}, {"text": "to make these unit vectors\nlike they're supposed to.", "start": 3318.0, "duration": 2.64}, {"text": "But we haven't really enforced\nthat they're orthogonal.", "start": 3320.64, "duration": 2.88}, {"text": "So that'll be another check.", "start": 3323.52, "duration": 5.32}, {"text": "So you could take r11 prime,\nr21 prime, et cetera, r22 prime.", "start": 3328.84, "duration": 7.65}, {"text": "So this is supposed\nto be equal to 0.", "start": 3339.81, "duration": 3.54}, {"text": "And again, if it's not, then\nthat's a potential problem.", "start": 3343.35, "duration": 6.06}, {"text": "In practice, it'll\nnever be exactly 0.", "start": 3349.41, "duration": 3.66}, {"text": "But if it's large,\nthen that means,", "start": 3353.07, "duration": 1.65}, {"text": "again, something went\nwrong in your calculation.", "start": 3354.72, "duration": 3.15}, {"text": "But we're going to need the full\nrotational matrix in a moment.", "start": 3357.87, "duration": 5.5}, {"text": "And so that means we're going\nto take the first two row", "start": 3363.37, "duration": 2.6}, {"text": "and take their cross-product.", "start": 3365.97, "duration": 1.44}, {"text": "But if these aren't\northogonal, then we're", "start": 3367.41, "duration": 3.09}, {"text": "going to get some\nsort of messy matrix", "start": 3370.5, "duration": 2.82}, {"text": "that's not\northonormal, and so on.", "start": 3373.32, "duration": 3.27}, {"text": "So squaring up-- so\nwe have two vectors.", "start": 3376.59, "duration": 9.64}, {"text": "And they're\napproximately orthogonal.", "start": 3386.23, "duration": 2.25}, {"text": "How do we get a pair of\nvectors that is orthogonal,", "start": 3388.48, "duration": 3.27}, {"text": "and that's as close as possible\nto the two vectors we start--", "start": 3391.75, "duration": 3.27}, {"text": "so what is the nearest\nset of orthogonal vectors?", "start": 3395.02, "duration": 3.94}, {"text": "So let's throw it this way.", "start": 3398.96, "duration": 1.91}, {"text": "Here are two vectors,\nthose first two rows", "start": 3404.01, "duration": 2.73}, {"text": "of the rotation matrix.", "start": 3406.74, "duration": 1.08}, {"text": "And they're not\nquite orthogonal.", "start": 3407.82, "duration": 2.07}, {"text": "And now, we want to make some\nsmall adjustment so that we get", "start": 3409.89, "duration": 11.42}, {"text": "new vectors that orthogonal.", "start": 3421.31, "duration": 2.28}, {"text": "And then, we take\ntheir cross-product.", "start": 3423.59, "duration": 1.95}, {"text": "And we have the complete\nrotation matrix.", "start": 3425.54, "duration": 2.84}, {"text": "By the way, heaven\nforbid that we end up", "start": 3428.38, "duration": 2.01}, {"text": "with a reflection matrix.", "start": 3430.39, "duration": 3.438}, {"text": "That's something we\nwant to worry about.", "start": 3433.828, "duration": 1.842}, {"text": "Now, if we are the ones\ntaking the cross-product,", "start": 3435.67, "duration": 2.13}, {"text": "we can make sure that it's a\nrotation, not a reflection.", "start": 3437.8, "duration": 5.11}, {"text": "OK.", "start": 3442.91, "duration": 0.5}, {"text": "Well, it turns out--", "start": 3443.41, "duration": 2.67}, {"text": "and this is boring\nleast squares--", "start": 3446.08, "duration": 2.37}, {"text": "that the smallest\nadjustment is the following.", "start": 3448.45, "duration": 2.7}, {"text": "That is, the adjustment in\na is in the direction b.", "start": 3461.23, "duration": 4.68}, {"text": "And the adjustment in b\nis in the direction a.", "start": 3465.91, "duration": 2.67}, {"text": "And so now, how big is k?", "start": 3472.51, "duration": 6.59}, {"text": "That's the only\nremaining question.", "start": 3479.1, "duration": 1.515}, {"text": "All right.", "start": 3487.43, "duration": 0.55}, {"text": "We want the new vectors\nto be orthogonal.", "start": 3487.98, "duration": 2.41}, {"text": "And so there's the equation.", "start": 3490.39, "duration": 2.36}, {"text": "And we have to solve for k.", "start": 3492.75, "duration": 2.31}, {"text": "So you get a dot b plus a\ndot a plus b dot b into k", "start": 3495.06, "duration": 8.82}, {"text": "plus k squared into\na dot b equals 0.", "start": 3503.88, "duration": 7.51}, {"text": "So there's a quadratic for k.", "start": 3511.39, "duration": 4.02}, {"text": "Solve for k and iterate.", "start": 3515.41, "duration": 1.98}, {"text": "Well, if we get the\nexact right value of k,", "start": 3525.55, "duration": 4.09}, {"text": "we don't have to iterate.", "start": 3529.64, "duration": 1.05}, {"text": "But we'll see in a second,\nthat's actually not", "start": 3530.69, "duration": 3.24}, {"text": "going to happen.", "start": 3533.93, "duration": 1.32}, {"text": "Why?", "start": 3535.25, "duration": 0.57}, {"text": "Well, look at this quadratic.", "start": 3535.82, "duration": 1.62}, {"text": "The first term and the last term\nare 0 at the solution, right?", "start": 3537.44, "duration": 5.97}, {"text": "We want them to be orthogonal.", "start": 3543.41, "duration": 2.14}, {"text": "And so near the\nsolution, those two terms", "start": 3545.55, "duration": 4.37}, {"text": "are going to be very small.", "start": 3549.92, "duration": 1.84}, {"text": "And so this is going to\nbe a nasty, numerically", "start": 3551.76, "duration": 5.48}, {"text": "unstable quadratic equation.", "start": 3557.24, "duration": 1.89}, {"text": "We're not used to that.", "start": 3559.13, "duration": 1.03}, {"text": "We're used to seeing more\ncomplicated equations", "start": 3560.16, "duration": 2.39}, {"text": "being nasty.", "start": 3562.55, "duration": 1.95}, {"text": "But this is one case where\nthe quadratic actually fails.", "start": 3564.5, "duration": 4.3}, {"text": "And so instead of solving\nthe quadratic, we do that.", "start": 3568.8, "duration": 10.766}, {"text": "Where does that come from?", "start": 3582.422, "duration": 1.388}, {"text": "Well, suppose that k\nis very small already.", "start": 3583.81, "duration": 4.16}, {"text": "Then, k squared times a\ndot b is even smaller.", "start": 3587.97, "duration": 3.85}, {"text": "So forget that.", "start": 3591.82, "duration": 1.41}, {"text": "And then, solve the rest for k.", "start": 3593.23, "duration": 3.0}, {"text": "And if you need a\nsolution, those two", "start": 3596.23, "duration": 1.89}, {"text": "are going to be unit vectors--", "start": 3598.12, "duration": 1.75}, {"text": "a dot a plus b dot b is 2.", "start": 3599.87, "duration": 1.94}, {"text": "And so you get minus\na dot b over 2.", "start": 3601.81, "duration": 4.05}, {"text": "And that's why I said iterate,\nbecause rather than try", "start": 3605.86, "duration": 3.33}, {"text": "to solve that quadratic\nvery accurately,", "start": 3609.19, "duration": 2.82}, {"text": "you just solve that\nsimple equation", "start": 3612.01, "duration": 3.3}, {"text": "and iterate it a\ncouple of times.", "start": 3615.31, "duration": 1.455}, {"text": "So instead of using\nthe standard formula", "start": 3619.72, "duration": 11.23}, {"text": "for the solutions\nof a quadratic,", "start": 3630.95, "duration": 2.49}, {"text": "we use this approximation.", "start": 3633.44, "duration": 1.95}, {"text": "Anyone awake out there?", "start": 3640.19, "duration": 2.07}, {"text": "[CHUCKLES]", "start": 3642.26, "duration": 1.68}, {"text": "Is that your standard\nformula for solutions", "start": 3643.94, "duration": 2.76}, {"text": "that are quadratic?", "start": 3646.7, "duration": 2.22}, {"text": "OK, probably not.", "start": 3648.92, "duration": 1.74}, {"text": "But believe it or\nnot, that is a formula", "start": 3650.66, "duration": 3.18}, {"text": "for the solutions\nof a quadratic.", "start": 3653.84, "duration": 1.84}, {"text": "And it's sad that\nwe don't know this.", "start": 3655.68, "duration": 2.18}, {"text": "So what's the other one?", "start": 3657.86, "duration": 1.44}, {"text": "Well it's, minus\nb plus or minus--", "start": 3659.3, "duration": 2.28}, {"text": "right?", "start": 3665.31, "duration": 0.5}, {"text": "So this is the\none we all taught.", "start": 3665.81, "duration": 2.64}, {"text": "It turns out, this\nis also a formula.", "start": 3668.45, "duration": 3.27}, {"text": "And the way you can check it is\nthat if you have the two roots,", "start": 3671.72, "duration": 4.23}, {"text": "x1 x2 product is\nsupposed to be c over a.", "start": 3675.95, "duration": 6.9}, {"text": "x1 plus x2 is b minus b over a.", "start": 3682.85, "duration": 5.19}, {"text": "So you can easily check\nthat both of these formulas", "start": 3691.22, "duration": 3.96}, {"text": "are right by checking the roots\nproduct and sum of the roots.", "start": 3695.18, "duration": 5.79}, {"text": "So why do I bring this up?", "start": 3700.97, "duration": 2.71}, {"text": "Well, in this formula\nhere, depending", "start": 3703.68, "duration": 3.23}, {"text": "on the plus or the\nminus that you're using,", "start": 3706.91, "duration": 5.07}, {"text": "you may be subtracting nearly\nthe same size quantities.", "start": 3711.98, "duration": 4.34}, {"text": "And we know that since\ncomputers can't represent", "start": 3716.32, "duration": 2.88}, {"text": "real numbers exactly,\nthere is going", "start": 3719.2, "duration": 3.33}, {"text": "to be a loss of precision.", "start": 3722.53, "duration": 1.89}, {"text": "So if you have 2.111111, and you\nsubtract 2.111 with a 2 in it", "start": 3724.42, "duration": 6.63}, {"text": "somewhere, you get\na very small number.", "start": 3731.05, "duration": 2.22}, {"text": "And you know that\nyou can't really", "start": 3733.27, "duration": 1.59}, {"text": "trust that number, because it\nonly has a limited precision.", "start": 3734.86, "duration": 4.27}, {"text": "So every time in the case\nof real solutions, one", "start": 3739.13, "duration": 6.32}, {"text": "of the two answers you\nget is rather poor, right?", "start": 3745.45, "duration": 3.42}, {"text": "Because in one of the two cases,\nthese two have opposite signs.", "start": 3748.87, "duration": 4.518}, {"text": "And every time you subtract\ntwo floating point numbers,", "start": 3753.388, "duration": 2.292}, {"text": "you lose precision.", "start": 3755.68, "duration": 2.97}, {"text": "The trick is that\nthe signs over here", "start": 3758.65, "duration": 2.91}, {"text": "are the opposite of\nthe ones over here.", "start": 3761.56, "duration": 2.07}, {"text": "So you get one of your\nsolutions from this one", "start": 3763.63, "duration": 2.73}, {"text": "where the signs match.", "start": 3766.36, "duration": 1.5}, {"text": "And then, you get\nthe other one--", "start": 3767.86, "duration": 1.68}, {"text": "I guess I should have\nwritten it this way.", "start": 3769.54, "duration": 2.4}, {"text": "And you get the other\nsolution from this one.", "start": 3771.94, "duration": 2.64}, {"text": "And this is how you get accurate\nsolutions to quadratics.", "start": 3774.58, "duration": 3.54}, {"text": "So little side note there.", "start": 3778.12, "duration": 2.46}, {"text": "So we could have used this\nto get a good answer for k.", "start": 3780.58, "duration": 4.2}, {"text": "But a very simple method\nis just that iteration.", "start": 3784.78, "duration": 4.41}, {"text": "And you can see that k\nwill eventually tend to 0.", "start": 3789.19, "duration": 4.89}, {"text": "And then, when you're\nsatisfied that it's", "start": 3794.08, "duration": 3.66}, {"text": "small enough for numerical\nprecision on your computer,", "start": 3797.74, "duration": 3.18}, {"text": "you can stop.", "start": 3800.92, "duration": 1.66}, {"text": "OK.", "start": 3802.58, "duration": 0.5}, {"text": "So that was the tweaking of\nthe rotation matrix components.", "start": 3803.08, "duration": 4.69}, {"text": "So now, we have a\nreplacement for r11--", "start": 3807.77, "duration": 3.38}, {"text": "that first row and\nthe second row--", "start": 3811.15, "duration": 2.46}, {"text": "that are actually orthogonal.", "start": 3813.61, "duration": 3.18}, {"text": "And then, we can get the third\nrow by cross-multiplying.", "start": 3816.79, "duration": 3.78}, {"text": "And we have a full\nrotation matrix.", "start": 3820.57, "duration": 2.28}, {"text": "Remember, though, that this\nisn't the final answer.", "start": 3822.85, "duration": 2.19}, {"text": "Because we haven't followed\nour rules about how to do this,", "start": 3825.04, "duration": 6.46}, {"text": "how to get accurate results.", "start": 3831.5, "duration": 1.55}, {"text": "OK.", "start": 3833.05, "duration": 1.02}, {"text": "This is a good time to talk\nabout the planar target case.", "start": 3834.07, "duration": 2.91}, {"text": "So planar targets are very\nattractive from the point", "start": 3840.51, "duration": 4.2}, {"text": "of view of being easy\nto make, easy to store,", "start": 3844.71, "duration": 4.83}, {"text": "and having high accuracy.", "start": 3849.54, "duration": 2.37}, {"text": "And so for example, if you had\nyour wheels aligned recently,", "start": 3851.91, "duration": 5.61}, {"text": "you might have been at a\nplace that uses machine", "start": 3857.52, "duration": 2.76}, {"text": "vision for wheel alignment.", "start": 3860.28, "duration": 1.6}, {"text": "And what they do is, they\nmount a calibration target", "start": 3861.88, "duration": 3.29}, {"text": "on the wheel, and\nthen rotate the wheel,", "start": 3865.17, "duration": 4.5}, {"text": "or rotate the steering wheel\nto measure two different axes.", "start": 3869.67, "duration": 4.09}, {"text": "And what's that\ntarget look like?", "start": 3873.76, "duration": 2.25}, {"text": "Well, it has a\npattern on it that", "start": 3876.01, "duration": 3.44}, {"text": "has a feature that it's very\npossible to get incredibly high", "start": 3879.45, "duration": 5.55}, {"text": "accurate position of corners\nof the pattern to 1/100", "start": 3885.0, "duration": 4.44}, {"text": "of a pixel, even better than\nwith our edge finding methods.", "start": 3889.44, "duration": 5.16}, {"text": "And how is it mounted?", "start": 3894.6, "duration": 2.07}, {"text": "It's planar.", "start": 3896.67, "duration": 0.76}, {"text": "It's mounted on the side\nof the wheel at an angle.", "start": 3897.43, "duration": 2.42}, {"text": "But it's planar.", "start": 3899.85, "duration": 0.96}, {"text": "And why are they using planar?", "start": 3900.81, "duration": 1.27}, {"text": "Well, because it's possible to\ncheaply manufacture incredibly", "start": 3902.08, "duration": 4.4}, {"text": "accurate planar patterns.", "start": 3906.48, "duration": 2.16}, {"text": "But there's a downside.", "start": 3908.64, "duration": 1.59}, {"text": "And so let's talk about that.", "start": 3910.23, "duration": 4.03}, {"text": "So here's our planar target.", "start": 3914.26, "duration": 1.535}, {"text": "And I guess we call this\ncoordinate system s.", "start": 3919.08, "duration": 2.865}, {"text": "And we can construct a\ncoordinate system there.", "start": 3925.22, "duration": 5.87}, {"text": "It makes sense to construct\nit this way, where x and y are", "start": 3931.09, "duration": 3.28}, {"text": "in the plane of the target,\nand all of your coordinates", "start": 3934.37, "duration": 2.7}, {"text": "are known in xs and\nys, and zs is 0.", "start": 3937.07, "duration": 6.27}, {"text": "That's the direction\nperpendicular to the target.", "start": 3943.34, "duration": 2.76}, {"text": "Well then, we can follow the\nsame methodology up there.", "start": 3946.1, "duration": 4.05}, {"text": "Except now, there are\ncertain terms that", "start": 3950.15, "duration": 2.55}, {"text": "don't matter anymore, like r13.", "start": 3952.7, "duration": 4.05}, {"text": "It gets multiplied by zs.", "start": 3956.75, "duration": 1.84}, {"text": "R23, r33-- none of\nthose occur anymore.", "start": 3958.59, "duration": 6.35}, {"text": "OK.", "start": 3983.98, "duration": 0.5}, {"text": "So we get this equation\ninstead, because that term in zs", "start": 3984.48, "duration": 4.2}, {"text": "drops out.", "start": 3988.68, "duration": 1.83}, {"text": "So big deal.", "start": 3990.51, "duration": 1.08}, {"text": "And now, we cross-multiply.", "start": 3991.59, "duration": 1.59}, {"text": "And instead of getting\nthe equation up there,", "start": 3993.18, "duration": 2.808}, {"text": "we get the slightly\nsimpler equation.", "start": 3995.988, "duration": 1.542}, {"text": "OK.", "start": 4023.5, "duration": 0.5}, {"text": "And again, same thing.", "start": 4024.0, "duration": 2.88}, {"text": "The things in parentheses\nare measurements,", "start": 4026.88, "duration": 2.28}, {"text": "the things we know.", "start": 4029.16, "duration": 2.01}, {"text": "Then, r11, r12, et\ncetera are things--", "start": 4031.17, "duration": 2.43}, {"text": "they're the unknowns\nthat we're looking for.", "start": 4033.6, "duration": 2.97}, {"text": "But now, there are fewer.", "start": 4036.57, "duration": 1.17}, {"text": "So now, if we list the unknowns,\nthere are six instead of eight.", "start": 4037.74, "duration": 14.63}, {"text": "And since these are\nhomogeneous equations again,", "start": 4055.72, "duration": 5.85}, {"text": "we turn them into\ninhomogeneous equations", "start": 4061.57, "duration": 3.18}, {"text": "by setting one of the\nparameters equal to 1.", "start": 4064.75, "duration": 3.9}, {"text": "And then, we have five\nequations and five unknowns.", "start": 4068.65, "duration": 4.24}, {"text": "So one great feature\nof this approach", "start": 4072.89, "duration": 2.75}, {"text": "is that we only need five\ncorrespondences now instead", "start": 4075.64, "duration": 4.48}, {"text": "of seven.", "start": 4080.12, "duration": 0.6}, {"text": "And again, usually,\nwe would use more", "start": 4083.59, "duration": 2.4}, {"text": "and use least squares to get\na more accurate solution.", "start": 4085.99, "duration": 3.06}, {"text": "Oh, by the way, what\nhappens if, just by chance,", "start": 4094.18, "duration": 4.86}, {"text": "ty in the real\nworld is actually 0,", "start": 4099.04, "duration": 2.88}, {"text": "that there's no translation\nin the y direction?", "start": 4101.92, "duration": 2.859}, {"text": "Well then, this method is\ngoing to have a problem.", "start": 4104.779, "duration": 4.211}, {"text": "It means that all\nyour other parameters", "start": 4108.99, "duration": 2.039}, {"text": "are going to be huge,\nand probably inaccurate.", "start": 4111.029, "duration": 3.521}, {"text": "So that's something about\nthis approach to solving", "start": 4114.55, "duration": 2.72}, {"text": "a homogeneous equation.", "start": 4117.27, "duration": 2.129}, {"text": "What do you do then?", "start": 4119.399, "duration": 1.0}, {"text": "Well, set tx equal to 1.", "start": 4120.399, "duration": 2.241}, {"text": "So I'm presenting it this way.", "start": 4122.64, "duration": 4.5}, {"text": "But actually, to get a\nnumerically good solution,", "start": 4127.14, "duration": 4.99}, {"text": "you would want to\ncheck the result.", "start": 4132.13, "duration": 2.36}, {"text": "And if it's the case that ty\nis actually very close to 0,", "start": 4134.49, "duration": 4.89}, {"text": "then switch to the other one.", "start": 4139.38, "duration": 2.11}, {"text": "And so I didn't make a\npoint of that before.", "start": 4141.49, "duration": 2.989}, {"text": "But OK.", "start": 4144.479, "duration": 1.365}, {"text": "Well before, we recovered\nthe full rotation matrix just", "start": 4148.439, "duration": 4.71}, {"text": "by squaring up\ntwo of the vectors", "start": 4153.149, "duration": 2.731}, {"text": "and then taking a cross-product.", "start": 4155.88, "duration": 1.95}, {"text": "And so here, hmm.", "start": 4157.83, "duration": 3.12}, {"text": "Now, we've only got the top 2 by\n2 piece of the rotation matrix.", "start": 4160.95, "duration": 10.26}, {"text": "And so I won't write\ndown the solution,", "start": 4171.21, "duration": 2.412}, {"text": "because that's what\nyou're supposed", "start": 4173.622, "duration": 1.458}, {"text": "to do in the homework problem.", "start": 4175.08, "duration": 1.25}, {"text": "So OK.", "start": 4176.33, "duration": 3.42}, {"text": "So let's suppose that we can\ndo this either for planar", "start": 4179.75, "duration": 3.27}, {"text": "or nonplanar.", "start": 4183.02, "duration": 2.1}, {"text": "But you can see how this is\ndifferent for the planar case", "start": 4185.12, "duration": 5.73}, {"text": "clearly.", "start": 4190.85, "duration": 1.95}, {"text": "Now, there's another subtlety\nthat I didn't bother with,", "start": 4192.8, "duration": 4.38}, {"text": "because it's not really\nrelevant anymore today.", "start": 4197.18, "duration": 2.76}, {"text": "But in the old days,\nyou weren't quite", "start": 4199.94, "duration": 5.15}, {"text": "sure about the\nrelationship the aspect", "start": 4205.09, "duration": 1.95}, {"text": "ratio of the stepping\nin the x direction", "start": 4207.04, "duration": 2.64}, {"text": "and the stepping\nin the y direction.", "start": 4209.68, "duration": 1.65}, {"text": "Because they were produced\nby very different effects.", "start": 4211.33, "duration": 3.49}, {"text": "So one of them was just lines.", "start": 4214.82, "duration": 2.9}, {"text": "And this is true\neven of CCD and CMOS", "start": 4217.72, "duration": 3.3}, {"text": "sensors, which were pixel--", "start": 4221.02, "duration": 1.89}, {"text": "they were sensors,\ndiscrete sensors.", "start": 4222.91, "duration": 2.88}, {"text": "But the way they were read out\nusually was in an analog form.", "start": 4225.79, "duration": 4.08}, {"text": "So you took the discrete signal\nout of your row of sensors,", "start": 4229.87, "duration": 4.26}, {"text": "turned it into an analog form.", "start": 4234.13, "duration": 1.77}, {"text": "And then, a bot in the computer\nchopped it up and digitized it,", "start": 4235.9, "duration": 4.5}, {"text": "but not in any way related\nto the size of the pixel step", "start": 4240.4, "duration": 5.04}, {"text": "in the row, right?", "start": 4245.44, "duration": 1.44}, {"text": "The frame grabber\nhad its own clock.", "start": 4246.88, "duration": 3.75}, {"text": "And so as a result, the spacing\nhorizontally and the spacing", "start": 4250.63, "duration": 4.74}, {"text": "vertically were controlled\nby different things.", "start": 4255.37, "duration": 2.13}, {"text": "The spacing vertically was--", "start": 4257.5, "duration": 1.53}, {"text": "I've got different\nrows in my sensor.", "start": 4259.03, "duration": 1.98}, {"text": "I know exactly what that is.", "start": 4261.01, "duration": 1.68}, {"text": "And horizontally,\nit was, well, what's", "start": 4262.69, "duration": 2.01}, {"text": "the relationship between\nthe clock in the frame grab", "start": 4264.7, "duration": 3.54}, {"text": "and the clock in the camera?", "start": 4268.24, "duration": 2.55}, {"text": "And so we needed\nanother parameter", "start": 4270.79, "duration": 4.68}, {"text": "that scaled x relative to y.", "start": 4275.47, "duration": 3.66}, {"text": "And it turns out that you\ncouldn't find that parameter", "start": 4279.13, "duration": 3.3}, {"text": "with a planar target.", "start": 4282.43, "duration": 2.19}, {"text": "And it makes a bit of\na mess of the algebra.", "start": 4284.62, "duration": 3.51}, {"text": "So I didn't want to go there\nbecause today, of course, you", "start": 4288.13, "duration": 3.48}, {"text": "look at the\nmanufacturer's spec sheet.", "start": 4291.61, "duration": 1.8}, {"text": "And you know exactly what the\naspect ratio is of the stepping", "start": 4293.41, "duration": 3.45}, {"text": "in the x and the y direction.", "start": 4296.86, "duration": 1.98}, {"text": "But again, it\nbrings out the fact", "start": 4298.84, "duration": 1.71}, {"text": "that the planar\ntarget is different.", "start": 4300.55, "duration": 3.77}, {"text": "OK.", "start": 4304.32, "duration": 0.72}, {"text": "What's left to do?", "start": 4305.04, "duration": 1.06}, {"text": "Well, we don't know f.", "start": 4306.1, "duration": 1.22}, {"text": "And we don't know tz.", "start": 4307.32, "duration": 2.37}, {"text": "And we also don't other things.", "start": 4309.69, "duration": 4.05}, {"text": "But let's focus on that.", "start": 4313.74, "duration": 1.41}, {"text": "How do we find them?", "start": 4318.59, "duration": 0.98}, {"text": "Well, we use the same equations.", "start": 4319.57, "duration": 3.24}, {"text": "And I won't write them out\nagain, just multiply them out.", "start": 4322.81, "duration": 5.8}, {"text": "So this is just a perspective\nprojection equation,", "start": 4328.61, "duration": 2.75}, {"text": "where we combine interior\nwith exterior orientation.", "start": 4331.36, "duration": 3.72}, {"text": "And you can see that now, we\nneed the full rotation matrix.", "start": 4345.3, "duration": 3.83}, {"text": "And it'd be good if it\nwas really orthonormal.", "start": 4349.13, "duration": 2.97}, {"text": "And again, the\nterms in parentheses", "start": 4357.09, "duration": 2.52}, {"text": "are the ones that we\nknow at this point.", "start": 4359.61, "duration": 3.525}, {"text": "And so the unknowns, of\ncourse, are f and tz.", "start": 4374.47, "duration": 5.73}, {"text": "So this is a simpler problem\nthan the one we had before.", "start": 4383.69, "duration": 3.64}, {"text": "So this stuff-- all of this,\nwe can calculate, right?", "start": 4387.33, "duration": 5.28}, {"text": "Because we've got the\nimage measurements.", "start": 4392.61, "duration": 2.06}, {"text": "And at this point, we've got\ntx and ty, and the components", "start": 4394.67, "duration": 4.59}, {"text": "of the rotation metric.", "start": 4399.26, "duration": 0.96}, {"text": "So we can calculate all of that.", "start": 4400.22, "duration": 1.65}, {"text": "We can calculate all of this.", "start": 4401.87, "duration": 3.48}, {"text": "And we just need to solve for f.", "start": 4405.35, "duration": 2.73}, {"text": "And that means we actually need\nonly one correspondence, right?", "start": 4408.08, "duration": 10.84}, {"text": "Because from one correspondence,\nwe get these two equations.", "start": 4418.92, "duration": 4.92}, {"text": "And we're looking\nfor two unknowns.", "start": 4423.84, "duration": 2.14}, {"text": "So now, of course in practice,\nwe would never do that.", "start": 4425.98, "duration": 2.91}, {"text": "We would use all of\nthe correspondences", "start": 4428.89, "duration": 1.94}, {"text": "we can lay our hands on\nand do least squares.", "start": 4430.83, "duration": 2.74}, {"text": "But the minimum number is 1.", "start": 4433.57, "duration": 2.82}, {"text": "OK.", "start": 4436.39, "duration": 0.5}, {"text": "So that gives us f and tz.", "start": 4436.89, "duration": 4.29}, {"text": "And there is a\nlittle problem here,", "start": 4441.18, "duration": 2.56}, {"text": "though, which is that\nI need depth variation.", "start": 4443.74, "duration": 9.47}, {"text": "So it's very tempting to do this\nwith your calibration target.", "start": 4457.57, "duration": 3.37}, {"text": "So here's the image plane.", "start": 4460.94, "duration": 1.94}, {"text": "Here's your planar\ncalibration target.", "start": 4462.88, "duration": 2.37}, {"text": "And here's the lens.", "start": 4465.25, "duration": 1.125}, {"text": "All right.", "start": 4471.753, "duration": 0.697}, {"text": "This seems like a\nnice arrangement.", "start": 4475.78, "duration": 2.07}, {"text": "And what's wrong with that?", "start": 4486.99, "duration": 1.63}, {"text": "Well, we know that\nperspective projection", "start": 4488.62, "duration": 9.3}, {"text": "has in it multiplication\nby f and division by z.", "start": 4497.92, "duration": 4.86}, {"text": "So if we double f and\ndouble z, nothing happens.", "start": 4502.78, "duration": 5.22}, {"text": "That's a scale factor ambiguity.", "start": 4508.0, "duration": 2.49}, {"text": "So that means that in this case,\nyou cannot discover f and tz", "start": 4510.49, "duration": 5.19}, {"text": "separately.", "start": 4515.68, "duration": 2.89}, {"text": "You can only\ndetermine the ratio.", "start": 4518.57, "duration": 1.56}, {"text": "And that's, of course,\nunsatisfactory.", "start": 4524.77, "duration": 2.22}, {"text": "And so what you need to do\nis have variations in depth.", "start": 4526.99, "duration": 8.23}, {"text": "And there's issues\nabout how much,", "start": 4535.22, "duration": 3.39}, {"text": "and what's the best, and so on.", "start": 4538.61, "duration": 1.63}, {"text": "But basically, it's\nnot going to work", "start": 4540.24, "duration": 2.75}, {"text": "if it's perpendicular\nto the optical axis.", "start": 4542.99, "duration": 4.2}, {"text": "And this could be--", "start": 4547.19, "duration": 0.93}, {"text": "I don't know-- 45\ndegrees, 60 degrees,", "start": 4548.12, "duration": 2.32}, {"text": "depending on what\nyou're trying to do.", "start": 4550.44, "duration": 1.92}, {"text": "And if you go into the place\nwhere they do your wheel", "start": 4552.36, "duration": 4.01}, {"text": "alignment if they're\nusing machine vision,", "start": 4556.37, "duration": 2.28}, {"text": "you'll see that when they\nmount the calibration", "start": 4558.65, "duration": 2.85}, {"text": "target on the wheel--", "start": 4561.5, "duration": 1.2}, {"text": "so they have a camera\nlooking down parallel", "start": 4562.7, "duration": 2.52}, {"text": "to the axis of the car--", "start": 4565.22, "duration": 2.88}, {"text": "and they mount this thing\non the side of the wheel", "start": 4568.1, "duration": 2.32}, {"text": "so it has to stick out.", "start": 4570.42, "duration": 1.04}, {"text": "But instead of mounting\nit perpendicular", "start": 4571.46, "duration": 2.01}, {"text": "so that you get the\nbest view in the camera,", "start": 4573.47, "duration": 2.97}, {"text": "they're mounted at 45 degrees.", "start": 4576.44, "duration": 2.4}, {"text": "And why?", "start": 4578.84, "duration": 1.05}, {"text": "Because exterior orientation is\nambiguous if you don't do that.", "start": 4579.89, "duration": 5.79}, {"text": "You can only determine\nthe ratio of f over tz.", "start": 4585.68, "duration": 2.97}, {"text": "You can't determine\nf and tz separately.", "start": 4588.65, "duration": 4.87}, {"text": "OK.", "start": 4593.52, "duration": 0.5}, {"text": "Now, we're almost done.", "start": 4594.02, "duration": 1.21}, {"text": "We've got estimates of\nmost of the parameters.", "start": 4595.23, "duration": 4.55}, {"text": "So what's missing?", "start": 4602.8, "duration": 1.09}, {"text": "What's missing is\nthe principal point", "start": 4603.89, "duration": 5.33}, {"text": "and the radial distortion.", "start": 4609.22, "duration": 4.59}, {"text": "So it turns out,\nno one's come up", "start": 4613.81, "duration": 3.61}, {"text": "with a way of\nclosed form solution", "start": 4617.42, "duration": 2.67}, {"text": "for the principal point.", "start": 4620.09, "duration": 1.53}, {"text": "And so we just give up\nat this point and say,", "start": 4621.62, "duration": 2.61}, {"text": "okay, now we need to do\nthe nonlinear optimization.", "start": 4624.23, "duration": 12.91}, {"text": "And the idea is that here has\nan error between xI and xp.", "start": 4640.33, "duration": 8.225}, {"text": "OK.", "start": 4658.92, "duration": 0.5}, {"text": "So if we have all\nof these parameters,", "start": 4659.42, "duration": 2.41}, {"text": "we can calculate forward from\nsome position in the world", "start": 4661.83, "duration": 3.71}, {"text": "to some position in the image.", "start": 4665.54, "duration": 2.1}, {"text": "And that means,\nthen, we would hope", "start": 4667.64, "duration": 3.855}, {"text": "that that was going to lie\nright on top of the image", "start": 4671.495, "duration": 3.495}, {"text": "point we actually measured.", "start": 4674.99, "duration": 1.33}, {"text": "So the calibration object\nwill have a bunch of points", "start": 4676.32, "duration": 4.16}, {"text": "that are easily identified.", "start": 4680.48, "duration": 1.53}, {"text": "And then, you look\nat point number 3.", "start": 4682.01, "duration": 2.55}, {"text": "And you pump it through\nthe rotation translation", "start": 4684.56, "duration": 4.44}, {"text": "perspective projection.", "start": 4689.0, "duration": 1.65}, {"text": "It gives you a predicted\nposition in the image.", "start": 4690.65, "duration": 2.7}, {"text": "And you saw it somewhere else.", "start": 4693.35, "duration": 2.34}, {"text": "And that's an error.", "start": 4695.69, "duration": 1.36}, {"text": "And that's the thing\nyou're trying to minimize.", "start": 4697.05, "duration": 2.04}, {"text": "And so I can write it this way.", "start": 4713.94, "duration": 2.37}, {"text": "That's what I would hope.", "start": 4716.31, "duration": 1.41}, {"text": "And of course, in terms of\nleast squares minimization,", "start": 4717.72, "duration": 2.79}, {"text": "I would just take the sum of\nsquares of those two terms.", "start": 4720.51, "duration": 3.54}, {"text": "And how do I get the xp and yp?", "start": 4724.05, "duration": 4.44}, {"text": "Well, I apply the rotation\nmatrix to translation matrix", "start": 4728.49, "duration": 4.53}, {"text": "and the principle point\ninformation that I have,", "start": 4733.02, "duration": 4.47}, {"text": "as well as the\nradial distortion.", "start": 4737.49, "duration": 3.01}, {"text": "So now, I have something that\ndepends on r, t, x0, y0, f, k1,", "start": 4740.5, "duration": 13.67}, {"text": "possibly k2, maybe some more.", "start": 4754.17, "duration": 2.97}, {"text": "So I've got a whole\nbunch of parameters.", "start": 4757.14, "duration": 2.19}, {"text": "And now, I have this huge\nminimization problem.", "start": 4759.33, "duration": 4.36}, {"text": "And as we mentioned\nlast time, there's", "start": 4763.69, "duration": 3.59}, {"text": "this wonderful package\ninvented eons ago that does it.", "start": 4767.28, "duration": 7.52}, {"text": "And what's it called?", "start": 4774.8, "duration": 4.17}, {"text": "LMdiff.", "start": 4778.97, "duration": 2.28}, {"text": "And it's in the MINPACK in the\noriginal Fortran, if you like.", "start": 4781.25, "duration": 11.97}, {"text": "But it's been translated\ninto lots of other languages.", "start": 4793.22, "duration": 4.91}, {"text": "And of course, it's built\ninto MATLAB and whatever.", "start": 4798.13, "duration": 4.13}, {"text": "So now, we just set up\nthis least squares problem", "start": 4802.26, "duration": 4.92}, {"text": "where we're trying to come as\nclose as possible to satisfying", "start": 4807.18, "duration": 3.45}, {"text": "a bunch of equations\nof this form, one", "start": 4810.63, "duration": 2.67}, {"text": "pair for every correspondence.", "start": 4813.3, "duration": 3.69}, {"text": "And we do it by tweaking\nthese parameters.", "start": 4816.99, "duration": 3.78}, {"text": "Well, there's this\nlittle problem here.", "start": 4820.77, "duration": 2.27}, {"text": "R is highly redundant.", "start": 4826.125, "duration": 2.565}, {"text": "It has nine numbers, and only\nthree degrees of freedom.", "start": 4828.69, "duration": 5.11}, {"text": "And so we could try and\nimpose the constraint.", "start": 4833.8, "duration": 2.51}, {"text": "So this package works for\nunconstrained minimization.", "start": 4836.31, "duration": 3.87}, {"text": "And so imposing R transpose R\nequals I, and determinant of R", "start": 4849.31, "duration": 7.53}, {"text": "equals 1 plus 1--\nthat's going to be hard.", "start": 4856.84, "duration": 2.71}, {"text": "So what to do instead?", "start": 4859.55, "duration": 1.35}, {"text": "Well, what Tsai did\nwas Euler angles.", "start": 4860.9, "duration": 3.83}, {"text": "And what you can do\ninstead is Gibbs vector,", "start": 4869.47, "duration": 5.18}, {"text": "which is-- let's see.", "start": 4874.65, "duration": 1.62}, {"text": "Omega hat-- so this so this is\na nonredundant representation.", "start": 4876.27, "duration": 6.792}, {"text": "There are only three numbers.", "start": 4883.062, "duration": 1.208}, {"text": "That's the good part.", "start": 4884.27, "duration": 0.99}, {"text": "It has singularities.", "start": 4885.26, "duration": 1.35}, {"text": "That's the bad part.", "start": 4886.61, "duration": 1.95}, {"text": "This one is nonredundant.", "start": 4888.56, "duration": 2.355}, {"text": "It has three numbers.", "start": 4890.915, "duration": 1.975}, {"text": "The bad part is that it blows\nup if you rotate 380 degrees.", "start": 4892.89, "duration": 9.15}, {"text": "Now, if you know\nthat's not going", "start": 4902.04, "duration": 3.77}, {"text": "to happen because of the way you\nset up the calibration object,", "start": 4905.81, "duration": 3.57}, {"text": "then that's a perfectly\nacceptable way of proceeding.", "start": 4909.38, "duration": 3.57}, {"text": "That works pretty well.", "start": 4912.95, "duration": 1.68}, {"text": "The other one is, of course,\nto use unit quaternions, which", "start": 4914.63, "duration": 8.54}, {"text": "have no singularity.", "start": 4923.17, "duration": 1.62}, {"text": "Right.", "start": 4930.03, "duration": 0.5}, {"text": "So we can use that for\nthe parameterization", "start": 4930.53, "duration": 3.6}, {"text": "of quaternions.", "start": 4934.13, "duration": 1.05}, {"text": "Unfortunately, it's\nredundant, right?", "start": 4935.18, "duration": 3.6}, {"text": "Because there are four numbers\nfor three degrees of freedom.", "start": 4938.78, "duration": 3.82}, {"text": "But what you can do\nis really simple.", "start": 4942.6, "duration": 1.82}, {"text": "You add another equation.", "start": 4947.68, "duration": 3.63}, {"text": "So there's going to\nbe an error term that", "start": 4951.31, "duration": 3.81}, {"text": "is proportional to the\ndifference between the size", "start": 4955.12, "duration": 2.94}, {"text": "of this quaternion and 1.", "start": 4958.06, "duration": 1.77}, {"text": "And you can determine how\nstrongly that's enforced.", "start": 4959.83, "duration": 7.09}, {"text": "And as you turn that up,\nyou get the solution.", "start": 4966.92, "duration": 3.23}, {"text": "So that's one\nimplementation that", "start": 4973.09, "duration": 2.57}, {"text": "works very well\nindependent of conditions", "start": 4975.66, "duration": 4.38}, {"text": "like avoiding 180 degrees.", "start": 4980.04, "duration": 3.58}, {"text": "Now, Levenberg-Marquardt\nfinds local extrema.", "start": 4983.62, "duration": 5.51}, {"text": "So if you put it down in the\nwrong place in parameter space,", "start": 4989.13, "duration": 4.44}, {"text": "it'll be perfectly happy to walk\ninto some other local minima.", "start": 4993.57, "duration": 4.41}, {"text": "And that's why we had\nto do all the other work", "start": 4997.98, "duration": 2.79}, {"text": "to get an approximate\nsolution first.", "start": 5000.77, "duration": 3.96}, {"text": "Otherwise, we could have done\naway with all of that stuff", "start": 5004.73, "duration": 2.94}, {"text": "and just start there.", "start": 5007.67, "duration": 0.97}, {"text": "But we can't.", "start": 5008.64, "duration": 3.436}, {"text": "A very important question is\nnoise sensitivity, or what", "start": 5012.076, "duration": 7.564}, {"text": "we've been calling noise gain.", "start": 5019.64, "duration": 1.65}, {"text": "And we alluded to it\nin several places,", "start": 5024.93, "duration": 2.49}, {"text": "like over here where the\ncalibration plane, if it's", "start": 5027.42, "duration": 3.09}, {"text": "perpendicular to the\noptical axis, then the noise", "start": 5030.51, "duration": 3.54}, {"text": "gain on f and tz is huge--", "start": 5034.05, "duration": 2.64}, {"text": "infinite-- while the ratio\nis perfectly well-determined.", "start": 5036.69, "duration": 4.5}, {"text": "But it's hard to say\nsomething general because", "start": 5041.19, "duration": 7.87}, {"text": "of this numerical optimization,\nand because these methods here", "start": 5049.06, "duration": 5.76}, {"text": "were approximate.", "start": 5054.82, "duration": 1.47}, {"text": "They didn't enforce the\nconditions directly.", "start": 5056.29, "duration": 3.43}, {"text": "So how do you address\nthe noise gain issue?", "start": 5059.72, "duration": 4.82}, {"text": "Well, as happens in\nmany cases where all you", "start": 5064.54, "duration": 2.49}, {"text": "have is a numerical method--", "start": 5067.03, "duration": 2.7}, {"text": "and this is where the\nadvantage of an analytic method", "start": 5069.73, "duration": 2.61}, {"text": "comes to the fore--", "start": 5072.34, "duration": 1.41}, {"text": "if you only have a\nnumerical method,", "start": 5073.75, "duration": 1.77}, {"text": "you can use Monte Carlo methods.", "start": 5075.52, "duration": 1.92}, {"text": "So how do you do that?", "start": 5077.44, "duration": 1.72}, {"text": "Well, you take your\nmeasured image positions.", "start": 5079.16, "duration": 3.02}, {"text": "And you add some noise of\nknown statistical properties.", "start": 5082.18, "duration": 5.58}, {"text": "You add some Gaussian noise,\nnoise with some known variance", "start": 5087.76, "duration": 10.1}, {"text": "or standard deviation.", "start": 5097.86, "duration": 3.0}, {"text": "And you do the computation.", "start": 5100.86, "duration": 1.98}, {"text": "And you get a different answer.", "start": 5102.84, "duration": 2.23}, {"text": "And you do this many times.", "start": 5105.07, "duration": 1.85}, {"text": "And you look at the statistical\nproperties of the answer.", "start": 5106.92, "duration": 4.74}, {"text": "And you look at its\nstandard deviation.", "start": 5111.66, "duration": 3.18}, {"text": "And then, the ratio is\nthe noise gain, right?", "start": 5114.84, "duration": 3.78}, {"text": "Very straightforward method.", "start": 5118.62, "duration": 2.01}, {"text": "Once you've written the\ncode to solve this problem,", "start": 5120.63, "duration": 3.21}, {"text": "you just take the inputs\nand you fiddle with them,", "start": 5123.84, "duration": 4.29}, {"text": "and do this many, many times.", "start": 5128.13, "duration": 1.71}, {"text": "And each time you get an answer.", "start": 5129.84, "duration": 1.62}, {"text": "And then, you look at the\ndistribution of the answer", "start": 5131.46, "duration": 2.34}, {"text": "in the parameter space.", "start": 5133.8, "duration": 1.77}, {"text": "And that way, you can\ndo what normally you", "start": 5135.57, "duration": 4.92}, {"text": "would do if you had\nan analytic solution.", "start": 5140.49, "duration": 3.95}, {"text": "And this is how you\nfind out things like--", "start": 5144.44, "duration": 2.65}, {"text": "that this absolutely\ndoes not work.", "start": 5147.09, "duration": 2.65}, {"text": "If the calibration\nplane is perpendicular", "start": 5149.74, "duration": 3.06}, {"text": "to the optical axis, you\nget a huge noise gain", "start": 5152.8, "duration": 3.18}, {"text": "in a certain direction\nin parameter space.", "start": 5155.98, "duration": 2.76}, {"text": "And you find out that the\nhigher order coefficients", "start": 5158.74, "duration": 4.65}, {"text": "of radial distortion past k2\nare very poorly determined,", "start": 5163.39, "duration": 6.54}, {"text": "that they're very sensitive to\nany kind of noise measurement.", "start": 5169.93, "duration": 3.79}, {"text": "So it's probably not\nworth trying to get them.", "start": 5173.72, "duration": 3.56}, {"text": "Oh.", "start": 5177.28, "duration": 1.51}, {"text": "OK.", "start": 5178.79, "duration": 0.5}, {"text": "So what are we going to do\nnext after you come back", "start": 5179.29, "duration": 4.26}, {"text": "is go, again, one level up.", "start": 5183.55, "duration": 3.1}, {"text": "So we started off\nreal low-level stuff.", "start": 5186.65, "duration": 2.39}, {"text": "Then, we went to this\nintermediate stuff.", "start": 5189.04, "duration": 2.592}, {"text": "The next thing\nwe're going to do is", "start": 5191.632, "duration": 1.458}, {"text": "talk about representation\nof shape, and recognition,", "start": 5193.09, "duration": 4.59}, {"text": "and determining the\nattitude in space.", "start": 5197.68, "duration": 2.73}, {"text": "So it's parallel to\nwhat we did in 2D.", "start": 5200.41, "duration": 2.4}, {"text": "When we were doing the patterns,\nwe did recognition and attitude", "start": 5202.81, "duration": 4.26}, {"text": "determination in 2D.", "start": 5207.07, "duration": 2.13}, {"text": "Now, we're going to do it in 3D.", "start": 5209.2, "duration": 1.62}, {"text": "And we've got all the\ntools for it, now,", "start": 5210.82, "duration": 2.34}, {"text": "to talk about rotation in 3D.", "start": 5213.16, "duration": 2.14}, {"text": "So have a good holiday.", "start": 5215.3, "duration": 6.01}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 0.85, "duration": 2.37}, {"text": "Commons license.", "start": 3.22, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.61, "duration": 2.21}, {"text": "continue to offer high-quality\neducational resources for free.", "start": 6.82, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 10.91, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.48, "duration": 3.96}, {"text": "at ocw.mit.edu.", "start": 17.44, "duration": 0.873}, {"text": "TADGE DRYJA: Today,\nI'm going to talk", "start": 22.948, "duration": 1.542}, {"text": "about signatures and all\nsorts of different signature", "start": 24.49, "duration": 5.28}, {"text": "kind of things.", "start": 29.77, "duration": 0.72}, {"text": "In the problem set, you're\nworking with signatures,", "start": 30.49, "duration": 2.853}, {"text": "but you're working with\nhash-based signatures, which", "start": 33.343, "duration": 2.167}, {"text": "are not actually used\nin bitcoin at all.", "start": 35.51, "duration": 2.895}, {"text": "But we'll talk about those.", "start": 38.405, "duration": 1.175}, {"text": "OK.", "start": 39.58, "duration": 0.5}, {"text": "So if you've gotten\nthrough the homework,", "start": 40.08, "duration": 3.55}, {"text": "there's lamport\nsignatures, right?", "start": 43.63, "duration": 3.18}, {"text": "These are hash-based signatures.", "start": 46.81, "duration": 2.23}, {"text": "And they use hash functions.", "start": 49.04, "duration": 2.97}, {"text": "So it's fairly straightforward.", "start": 52.01, "duration": 1.93}, {"text": "You can understand them.", "start": 53.94, "duration": 1.0}, {"text": "There's nothing\nsuper crazy going on.", "start": 54.94, "duration": 2.41}, {"text": "The code is fairly compact.", "start": 57.35, "duration": 1.37}, {"text": "So that's cool.", "start": 58.72, "duration": 1.11}, {"text": "What are some disadvantages\nof these lamport signatures?", "start": 59.83, "duration": 3.51}, {"text": "Does anyone-- yeah?", "start": 63.34, "duration": 2.002}, {"text": "AUDIENCE: You can\nonly use it once.", "start": 65.342, "duration": 1.458}, {"text": "TADGE DRYJA: Yeah.", "start": 66.8, "duration": 0.61}, {"text": "OK.", "start": 67.41, "duration": 0.5}, {"text": "So plus.", "start": 67.91, "duration": 1.135}, {"text": "This is hashes.", "start": 69.045, "duration": 0.625}, {"text": "That's cool.", "start": 69.67, "duration": 0.81}, {"text": "One-time use.", "start": 70.48, "duration": 3.09}, {"text": "Other possible disadvantages of\nthem relative to other systems,", "start": 73.57, "duration": 5.26}, {"text": "if you're aware.", "start": 78.83, "duration": 1.52}, {"text": "Another is they're kind of\nhuge, kind of big, right?", "start": 80.35, "duration": 6.07}, {"text": "You can deal with it.", "start": 86.42, "duration": 1.66}, {"text": "But if you were\nlooking in the forge,", "start": 88.08, "duration": 2.66}, {"text": "or that file with\nthe signatures,", "start": 90.74, "duration": 2.52}, {"text": "it's like, what, 8K\nfor a signature--", "start": 93.26, "duration": 4.67}, {"text": "8 kilobytes-- kind of big.", "start": 97.93, "duration": 2.59}, {"text": "Keys are 16 kilobytes--", "start": 100.52, "duration": 1.95}, {"text": "kind of annoying.", "start": 102.47, "duration": 0.93}, {"text": "Private keys are\nalso 16 kilobytes.", "start": 103.4, "duration": 3.39}, {"text": "So yes, sig 8K,\n16K priv/pub key.", "start": 106.79, "duration": 8.29}, {"text": "So that's some disadvantages.", "start": 115.08, "duration": 3.72}, {"text": "So since I don't\nhave slides, I'm", "start": 118.8, "duration": 2.02}, {"text": "gonna make this more\nfun and interactive.", "start": 120.82, "duration": 3.99}, {"text": "What are some solutions\nfor these problems?", "start": 124.81, "duration": 3.12}, {"text": "So we can actually\nmitigate/solve", "start": 127.93, "duration": 3.78}, {"text": "both of these things to\na pretty good extent.", "start": 131.71, "duration": 3.57}, {"text": "So how about the first\none, one-time use?", "start": 135.28, "duration": 2.19}, {"text": "What would be a\nfairly obvious way", "start": 137.47, "duration": 2.7}, {"text": "to mitigate the\none-time use problem?", "start": 140.17, "duration": 2.92}, {"text": "And don't think the\nanswer is too stupid.", "start": 143.09, "duration": 3.813}, {"text": "It may be a fairly stupid\nanswer, and it might work.", "start": 146.903, "duration": 2.167}, {"text": "So yeah?", "start": 149.07, "duration": 1.07}, {"text": "AUDIENCE: Not actually revealing\npieces of your private key?", "start": 150.14, "duration": 3.06}, {"text": "Instead, reveal something else.", "start": 153.2, "duration": 4.103}, {"text": "TADGE DRYJA: There's\nprobably some clever way.", "start": 157.303, "duration": 1.917}, {"text": "But that might be too clever.", "start": 159.22, "duration": 1.56}, {"text": "Something really simple for,\nOK, I can only use a key once.", "start": 160.78, "duration": 6.42}, {"text": "How can I use a \"key,\" quote\nunquote, more than once?", "start": 167.2, "duration": 2.65}, {"text": "Yeah?", "start": 169.85, "duration": 0.5}, {"text": "AUDIENCE: Make another one.", "start": 170.35, "duration": 0.7}, {"text": "TADGE DRYJA: Yeah.", "start": 171.05, "duration": 0.28}, {"text": "You can make another key.", "start": 171.33, "duration": 1.21}, {"text": "So you could say, well, I've\ngot this 16 kilobyte public key.", "start": 172.54, "duration": 3.96}, {"text": "Well, I'm going to make\na 32 kilobyte public key.", "start": 176.5, "duration": 3.55}, {"text": "And it's just two public\nkeys stuck together.", "start": 180.05, "duration": 2.99}, {"text": "And now, when I\nmake a signature,", "start": 186.55, "duration": 1.86}, {"text": "I just put an extra\nbit in the front.", "start": 188.41, "duration": 2.13}, {"text": "And I say, well, this\nsignature is using key 0", "start": 190.54, "duration": 3.33}, {"text": "or this signature\nis using key 1,", "start": 193.87, "duration": 1.62}, {"text": "and it's got the\nwhole signature after.", "start": 195.49, "duration": 2.61}, {"text": "And then you look through\nthis 32 kilobyte public key,", "start": 198.1, "duration": 3.18}, {"text": "and you say, OK, well,\nit starts with a zero,", "start": 201.28, "duration": 2.28}, {"text": "so that means it's using the\nfirst key, the first subkey", "start": 203.56, "duration": 4.53}, {"text": "in this 32 byte\npublic key block.", "start": 208.09, "duration": 2.49}, {"text": "And in this case,\nit's using one,", "start": 210.58, "duration": 1.76}, {"text": "so that means it's\nusing the latter subkey.", "start": 212.34, "duration": 3.588}, {"text": "So that would work.", "start": 215.928, "duration": 0.792}, {"text": "That would let you use\nyour public key twice,", "start": 216.72, "duration": 4.3}, {"text": "at the cost of doubling\nyour public key size, which", "start": 221.02, "duration": 3.24}, {"text": "is not really great, right?", "start": 224.26, "duration": 3.783}, {"text": "And it's not very efficient.", "start": 228.043, "duration": 1.167}, {"text": "But it does sort of work.", "start": 229.21, "duration": 2.01}, {"text": "OK.", "start": 231.22, "duration": 0.57}, {"text": "Any clever ways to do\nit more efficiently?", "start": 231.79, "duration": 6.91}, {"text": "Or wait.", "start": 238.7, "duration": 1.07}, {"text": "So OK, also, I'll give\nyou sort of a hint.", "start": 239.77, "duration": 4.56}, {"text": "In this case, let's say this is\npub sub 0 and pub sub 1, right?", "start": 244.33, "duration": 5.88}, {"text": "And then, your 32 byte\npubkey is just them", "start": 250.21, "duration": 3.57}, {"text": "concatenated together, right--", "start": 253.78, "duration": 1.95}, {"text": "pub0, pub1.", "start": 255.73, "duration": 1.2}, {"text": "What would happen to the private\nkeys in this case, right?", "start": 260.24, "duration": 7.03}, {"text": "How would private\nkeys work here?", "start": 267.27, "duration": 2.73}, {"text": "Same expansion of size, I guess.", "start": 270.0, "duration": 4.65}, {"text": "Can anyone think of a way to\nmitigate the expansion of size", "start": 274.65, "duration": 5.55}, {"text": "of private keys in this case?", "start": 280.2, "duration": 2.21}, {"text": "So the private keys are\nthe preimages here, right?", "start": 282.41, "duration": 3.13}, {"text": "They lead into these\npublic key blocks.", "start": 285.54, "duration": 3.293}, {"text": "So you could just\nsay, OK, well, I", "start": 288.833, "duration": 1.417}, {"text": "have twice the size private\nkey leading into twice the size", "start": 290.25, "duration": 3.75}, {"text": "public key.", "start": 294.0, "duration": 1.05}, {"text": "Could you do that\nmore efficiently?", "start": 295.05, "duration": 1.47}, {"text": "Yeah?", "start": 296.52, "duration": 0.5}, {"text": "AUDIENCE: Could you just\nhash the private key", "start": 297.02, "duration": 2.05}, {"text": "so that you have two\nhashes instead of one?", "start": 299.07, "duration": 3.54}, {"text": "TADGE DRYJA: Yes.", "start": 302.61, "duration": 1.79}, {"text": "So let's say you\nhave this 16k block,", "start": 304.4, "duration": 4.07}, {"text": "and you want this to\nturn into two public key.", "start": 308.47, "duration": 3.77}, {"text": "So that's the basic\ngood way to do it.", "start": 312.24, "duration": 3.28}, {"text": "And it sort of\nturns in like that.", "start": 315.52, "duration": 2.21}, {"text": "How exactly-- what's\nthe way you do that?", "start": 317.73, "duration": 3.385}, {"text": "AUDIENCE: You can keep the\nsame private key as before", "start": 321.115, "duration": 2.525}, {"text": "and just add something like\nzero or one to indicate--", "start": 323.64, "duration": 2.91}, {"text": "TADGE DRYJA: Yeah.", "start": 326.55, "duration": 0.99}, {"text": "So this is a hash\nfunction, right?", "start": 327.54, "duration": 2.15}, {"text": "And so before, we just said,\nOK, hash of this is block 0,", "start": 329.69, "duration": 4.63}, {"text": "this is block 1,\nthis is block 2.", "start": 334.32, "duration": 2.25}, {"text": "So the idea of pub--", "start": 336.57, "duration": 3.702}, {"text": "let's see.", "start": 340.272, "duration": 0.998}, {"text": "Is this visible?", "start": 341.27, "duration": 1.19}, {"text": "This might be too small, right?", "start": 342.46, "duration": 1.827}, {"text": "AUDIENCE: Yes.", "start": 344.287, "duration": 0.583}, {"text": "TADGE DRYJA: Yes, OK.", "start": 344.87, "duration": 0.975}, {"text": "Let me make this bigger.", "start": 345.845, "duration": 1.635}, {"text": "Sorry.", "start": 350.68, "duration": 1.78}, {"text": "OK.", "start": 352.46, "duration": 0.5}, {"text": "So in these diagrams, you've\ngot your private key right now.", "start": 352.96, "duration": 7.72}, {"text": "And it's in these big blocks.", "start": 360.68, "duration": 1.35}, {"text": "And there's 256 of them,\nbut let's keep it small.", "start": 362.03, "duration": 3.91}, {"text": "And the idea is these are 32\nbyte blocks with random numbers", "start": 365.94, "duration": 2.72}, {"text": "in it.", "start": 368.66, "duration": 0.75}, {"text": "And then you hash it\nto get your public key.", "start": 369.41, "duration": 2.7}, {"text": "So we say, OK, pub2--", "start": 375.29, "duration": 2.542}, {"text": "and this is public, this\nis private, and, let's say,", "start": 377.832, "duration": 3.598}, {"text": "secret--", "start": 381.43, "duration": 1.98}, {"text": "pub2 is just the hash\nof secret2, right?", "start": 383.41, "duration": 6.64}, {"text": "But yeah.", "start": 390.05, "duration": 0.5}, {"text": "What we could do is we could\nsort of have two different hash", "start": 390.55, "duration": 2.5}, {"text": "functions.", "start": 393.05, "duration": 1.49}, {"text": "And then a real\nsimple way to make", "start": 394.54, "duration": 2.22}, {"text": "a whole bunch of\ndifferent hash functions", "start": 396.76, "duration": 1.89}, {"text": "is we define, OK,\nwell hash0 is defined", "start": 398.65, "duration": 4.53}, {"text": "as the hash function of whatever\nyour input x is concatenated", "start": 403.18, "duration": 5.13}, {"text": "with the number 0.", "start": 408.31, "duration": 1.92}, {"text": "And then hash1, we define\nas just x comma 1 and so on.", "start": 410.23, "duration": 6.03}, {"text": "And this is actually secure.", "start": 416.26, "duration": 1.41}, {"text": "You could do this.", "start": 417.67, "duration": 1.59}, {"text": "Any questions or\npossible objections?", "start": 419.26, "duration": 3.085}, {"text": "AUDIENCE: I was thinking that if\nsomeone knew the hash function", "start": 422.345, "duration": 2.625}, {"text": "you're using, wouldn't\nthey only define", "start": 424.97, "duration": 1.793}, {"text": "x because they know that it\nwon't help with [INAUDIBLE] x.", "start": 426.763, "duration": 2.417}, {"text": "[INAUDIBLE]", "start": 429.18, "duration": 0.52}, {"text": "TADGE DRYJA: Yes.", "start": 429.7, "duration": 0.72}, {"text": "Yes.", "start": 430.42, "duration": 0.69}, {"text": "So there's no real entropy\nor secrets in this 0 and 1.", "start": 431.11, "duration": 8.03}, {"text": "But it's purely\nriding on x, right?", "start": 439.14, "duration": 3.28}, {"text": "But the idea is,\nwell, if I do this,", "start": 442.42, "duration": 3.72}, {"text": "and I say, OK, well\npub2 is the hash", "start": 446.14, "duration": 4.74}, {"text": "of secret2 concatenated with\n0, yeah, if you know secret2,", "start": 450.88, "duration": 4.01}, {"text": "you can go back.", "start": 454.89, "duration": 1.4}, {"text": "Because 0 is obvious.", "start": 456.29, "duration": 1.04}, {"text": "But the idea is if you don't\nknow secret2, the fact that you", "start": 457.33, "duration": 2.88}, {"text": "know the last byte of the hash\ninput doesn't really help you.", "start": 460.21, "duration": 4.83}, {"text": "Because there's all this\ndata that you don't know.", "start": 465.04, "duration": 3.36}, {"text": "And so you're not going to\nbe able to find a preimage.", "start": 468.4, "duration": 2.25}, {"text": "You're like, OK, I\nknow the preimage", "start": 470.65, "duration": 1.89}, {"text": "to public2 ends with a 0 byte.", "start": 472.54, "duration": 3.0}, {"text": "What are the other 32 bytes\nthat come before that?", "start": 475.54, "duration": 3.54}, {"text": "You still can't go back\nto make a preimage.", "start": 479.08, "duration": 2.324}, {"text": "AUDIENCE: But it feels\nlike there's some sort of--", "start": 481.404, "duration": 4.211}, {"text": "what's the word-- you'd make a\nsimilar statement saying, oh,", "start": 485.615, "duration": 2.855}, {"text": "if the last byte\nis not important,", "start": 488.47, "duration": 1.89}, {"text": "then the second-to-last byte is\nnot important, either, right?", "start": 490.36, "duration": 3.24}, {"text": "TADGE DRYJA: So the\nattack is I've got pub2,", "start": 497.95, "duration": 2.67}, {"text": "which is a 32 byte hash output.", "start": 500.62, "duration": 2.7}, {"text": "I want to find\nwhat this thing is.", "start": 503.32, "duration": 4.5}, {"text": "Now, I do know what the\nlast byte is, right?", "start": 507.82, "duration": 1.98}, {"text": "It's going to be,\nlet's say, 33 bytes,", "start": 509.8, "duration": 2.52}, {"text": "and the last byte is a 0.", "start": 512.32, "duration": 2.46}, {"text": "And this is going to\nbe some random numbers", "start": 514.78, "duration": 2.79}, {"text": "all the way back.", "start": 517.57, "duration": 0.93}, {"text": "So I have some insight\ninto what the preimage is.", "start": 518.5, "duration": 5.039}, {"text": "I know the last byte is a 0.", "start": 523.539, "duration": 2.431}, {"text": "But that doesn't\nhelp because I don't", "start": 525.97, "duration": 1.98}, {"text": "know all the bytes before that.", "start": 527.95, "duration": 3.21}, {"text": "So I can't really do--", "start": 531.16, "duration": 2.97}, {"text": "I can't sign because I\nneed to be able to reveal", "start": 534.13, "duration": 2.64}, {"text": "all these things.", "start": 536.77, "duration": 1.175}, {"text": "And the way the hash\nfunctions, if it's a good hash", "start": 537.945, "duration": 2.125}, {"text": "function, the fact that you\nknow some part of the preimage", "start": 540.07, "duration": 3.652}, {"text": "shouldn't give you insight\ninto the other parts", "start": 543.722, "duration": 1.958}, {"text": "of the preimage.", "start": 545.68, "duration": 1.59}, {"text": "Because it looks really random.", "start": 547.27, "duration": 1.66}, {"text": "And adding stuff to the end\nhere shouldn't reveal anything.", "start": 548.93, "duration": 5.45}, {"text": "There are hash functions\nwhere this can be dangerous,", "start": 554.38, "duration": 2.28}, {"text": "and you can consider those like\nbroken hash functions, where", "start": 556.66, "duration": 3.18}, {"text": "if I concatenate a lot\nof known data at the end,", "start": 559.84, "duration": 2.85}, {"text": "it might give me properties of\nthe public key that I can find.", "start": 562.69, "duration": 4.42}, {"text": "[INAUDIBLE],, as far as\nwe know, it works fine.", "start": 567.11, "duration": 2.96}, {"text": "Most of the hash functions\nwork fine this way.", "start": 570.07, "duration": 2.37}, {"text": "So yeah, you can do this.", "start": 572.44, "duration": 2.31}, {"text": "And then you can\nsay, OK, well, I'm", "start": 574.75, "duration": 1.62}, {"text": "going to use hash function\n0 to make pubkey 0, right?", "start": 576.37, "duration": 6.34}, {"text": "This is pubkey 0.", "start": 582.71, "duration": 1.31}, {"text": "And if I use hash function\n1, I make pubkey 1.", "start": 584.02, "duration": 6.45}, {"text": "Now I have a 16 kilobyte--\nlet me erase this--", "start": 590.47, "duration": 5.44}, {"text": "so now what I can do\nis I can say, OK, well,", "start": 598.152, "duration": 1.833}, {"text": "I have a 16 kilobyte\nsecret key, private key,", "start": 599.985, "duration": 4.005}, {"text": "but I have a 32\nkilobyte public key", "start": 603.99, "duration": 6.06}, {"text": "that I can use twice\nthat has two subkeys", "start": 610.05, "duration": 1.877}, {"text": "so I don't have to store as\nmuch of my private key data.", "start": 611.927, "duration": 2.333}, {"text": "So that's cool.", "start": 614.26, "duration": 0.99}, {"text": "That makes it quite\na bit more efficient.", "start": 615.25, "duration": 2.978}, {"text": "Does anyone have an idea of how\nto get it even more efficient", "start": 618.228, "duration": 2.542}, {"text": "for private key storage?", "start": 620.77, "duration": 1.0}, {"text": "You can actually get\nit very efficient", "start": 624.26, "duration": 3.22}, {"text": "using this kind of idea.", "start": 627.48, "duration": 2.928}, {"text": "Any ideas?", "start": 630.408, "duration": 0.952}, {"text": "Yeah.", "start": 635.644, "duration": 0.956}, {"text": "Well, you--", "start": 636.6, "duration": 0.71}, {"text": "So some hints.", "start": 640.22, "duration": 2.16}, {"text": "This is pretty useful, right?", "start": 642.38, "duration": 1.62}, {"text": "The idea is, well,\neven if you know", "start": 644.0, "duration": 2.19}, {"text": "what the sort of suffix\nof all these things", "start": 646.19, "duration": 3.36}, {"text": "are, if you don't\nknow x, you're not", "start": 649.55, "duration": 1.74}, {"text": "going to be able to find\nthe preimage, right?", "start": 651.29, "duration": 3.45}, {"text": "So maybe add some\nmore stuff here.", "start": 654.74, "duration": 2.8}, {"text": "Any idea?", "start": 657.54, "duration": 0.5}, {"text": "Oh, yeah?", "start": 661.64, "duration": 0.96}, {"text": "AUDIENCE: Could\nyou hash the index?", "start": 662.6, "duration": 1.96}, {"text": "TADGE DRYJA: Right.", "start": 664.56, "duration": 1.05}, {"text": "Right.", "start": 665.61, "duration": 0.5}, {"text": "So instead of just\nsaying 0 and 1,", "start": 666.11, "duration": 4.1}, {"text": "we can say here, well, why\nnot just have one chunk?", "start": 670.21, "duration": 4.44}, {"text": "And there's one chunk, and\nit's got random number x.", "start": 674.65, "duration": 10.86}, {"text": "Well, this is hash x comma 0.", "start": 685.51, "duration": 2.37}, {"text": "This is hash x comma 1.", "start": 687.88, "duration": 3.96}, {"text": "This is hash x comma 2.", "start": 691.84, "duration": 3.49}, {"text": "OK.", "start": 695.33, "duration": 0.5}, {"text": "So yeah.", "start": 695.83, "duration": 0.5}, {"text": "So what you can do is you can--", "start": 696.33, "duration": 4.27}, {"text": "this was before, right,\nwhere I said, OK, yeah,", "start": 700.6, "duration": 3.09}, {"text": "but this is basically how to\ndo a 32 byte private key where", "start": 703.69, "duration": 5.01}, {"text": "your private key is\nactually quite small,", "start": 708.7, "duration": 2.34}, {"text": "and you just derive\nall of the public keys", "start": 711.04, "duration": 4.29}, {"text": "by adding numbers at the\nend, concatenating them", "start": 715.33, "duration": 3.78}, {"text": "into your hash.", "start": 719.11, "duration": 0.88}, {"text": "And now you're like, OK, cool.", "start": 719.99, "duration": 1.25}, {"text": "I have a 32 byte\nprivate key, and I", "start": 721.24, "duration": 3.18}, {"text": "can make enormous\npublic keys from them,", "start": 724.42, "duration": 2.22}, {"text": "and it's still secure, right?", "start": 726.64, "duration": 1.62}, {"text": "Because I can add whatever\nnumber I want here.", "start": 728.26, "duration": 3.15}, {"text": "And I can do this\na million times,", "start": 731.41, "duration": 2.078}, {"text": "and no one will be able to find\nthe preimage, even though I'm", "start": 733.488, "duration": 2.542}, {"text": "giving you all these\nrelated hashes, right?", "start": 736.03, "duration": 2.55}, {"text": "It's x comma 0, x comma\n1, x comma a million.", "start": 738.58, "duration": 3.32}, {"text": "I can give you millions of them.", "start": 741.9, "duration": 1.44}, {"text": "And each time I do it,\nit doesn't give you", "start": 743.34, "duration": 2.05}, {"text": "any insight into how\nto find what x is--", "start": 745.39, "duration": 2.49}, {"text": "if it's a good hash function.", "start": 747.88, "duration": 1.717}, {"text": "So that's really powerful.", "start": 749.597, "duration": 1.083}, {"text": "And now I can say, OK, the\nprivate key problem is solved.", "start": 750.68, "duration": 2.84}, {"text": "I have 0 of 1 growth\nin my private key.", "start": 753.52, "duration": 3.9}, {"text": "I can make as many public\nkeys as I want, never", "start": 757.42, "duration": 2.25}, {"text": "gets any bigger.", "start": 759.67, "duration": 0.9}, {"text": "Cool.", "start": 760.57, "duration": 1.542}, {"text": "Still have this problem with\nthe public keys, though.", "start": 762.112, "duration": 2.208}, {"text": "Let's say I want\nto sign four times.", "start": 764.32, "duration": 2.5}, {"text": "OK.", "start": 766.82, "duration": 0.5}, {"text": "Well, I make a 64\nkilobyte pubkey.", "start": 767.32, "duration": 3.637}, {"text": "Now I can sign four times.", "start": 774.64, "duration": 1.63}, {"text": "Great.", "start": 776.27, "duration": 0.5}, {"text": "But my public key size expands\nwith the number of signatures", "start": 776.77, "duration": 4.05}, {"text": "I ever want to do.", "start": 780.82, "duration": 3.28}, {"text": "Any ideas on how you\ncould mitigate that", "start": 784.1, "duration": 3.15}, {"text": "or how you could still\nmake a usable system,", "start": 787.25, "duration": 2.88}, {"text": "despite this fact?", "start": 790.13, "duration": 0.93}, {"text": "There's a couple\ndifferent techniques.", "start": 794.41, "duration": 3.86}, {"text": "Any ideas?", "start": 798.27, "duration": 0.5}, {"text": "OK.", "start": 801.0, "duration": 0.5}, {"text": "So one would be\nevery time I sign,", "start": 801.5, "duration": 3.68}, {"text": "I also sign my next pubkey.", "start": 805.18, "duration": 4.65}, {"text": "You can do that.", "start": 809.83, "duration": 1.71}, {"text": "It's got some downsides, right?", "start": 811.54, "duration": 1.62}, {"text": "So the idea is I first publish\none 16 kilobyte pubkey.", "start": 813.16, "duration": 4.38}, {"text": "And then I say, OK, when I sign,\nI'm going to sign my message.", "start": 817.54, "duration": 4.08}, {"text": "And concatenated to that\nmessage will be my next pubkey.", "start": 821.62, "duration": 3.99}, {"text": "And so I'm signing something\nand also indicating", "start": 825.61, "duration": 2.43}, {"text": "what my next public key\nwill be that I sign with.", "start": 828.04, "duration": 3.15}, {"text": "Then I can still maintain\na small private key", "start": 831.19, "duration": 2.97}, {"text": "and then keep signing.", "start": 834.16, "duration": 1.41}, {"text": "The problem is, in order\nfor someone to verify,", "start": 835.57, "duration": 3.12}, {"text": "they're going to need to look at\nall of my previous signatures,", "start": 838.69, "duration": 2.68}, {"text": "right?", "start": 841.37, "duration": 0.5}, {"text": "So if I'm saying, hey,\nhere's my 500th public key", "start": 841.87, "duration": 3.56}, {"text": "that I'm signing with,\nhere's the message,", "start": 845.43, "duration": 1.75}, {"text": "you're going to have to go back\nand look at my entire history", "start": 847.18, "duration": 2.542}, {"text": "of signing, which is not great.", "start": 849.722, "duration": 4.278}, {"text": "OK.", "start": 854.0, "duration": 0.5}, {"text": "So other ideas of how to\ndeal with large pubkeys?", "start": 854.5, "duration": 4.918}, {"text": "What's a way you could do this?", "start": 859.418, "duration": 1.292}, {"text": "So hints.", "start": 863.5, "duration": 2.07}, {"text": "Is there any kind\nof data function", "start": 865.57, "duration": 3.13}, {"text": "we've seen here where it takes\nan arbitrary sized amount", "start": 868.7, "duration": 2.87}, {"text": "of data and outputs\na fixed size?", "start": 871.57, "duration": 3.06}, {"text": "[LAUGHING]", "start": 874.63, "duration": 1.98}, {"text": "In fact, it's the\nonly thing we've", "start": 876.61, "duration": 1.64}, {"text": "been talking about so far.", "start": 878.25, "duration": 2.5}, {"text": "So what would you do to make\nyour public keys smaller?", "start": 880.75, "duration": 3.117}, {"text": "AUDIENCE: Hash.", "start": 883.867, "duration": 0.625}, {"text": "TADGE DRYJA: Hash them.", "start": 884.492, "duration": 0.958}, {"text": "Right.", "start": 885.45, "duration": 0.58}, {"text": "OK.", "start": 886.03, "duration": 0.5}, {"text": "So you say, well,\nyeah, 32 byte pubkey.", "start": 886.53, "duration": 3.09}, {"text": "Well, you just\ncommit to the pubkey", "start": 889.62, "duration": 2.43}, {"text": "with the hash of the\nwhole thing, right?", "start": 892.05, "duration": 2.52}, {"text": "And I say, well, I've got\nmy 16 kilobyte by pubkey.", "start": 894.57, "duration": 7.47}, {"text": "I just hash it, right?", "start": 902.04, "duration": 2.54}, {"text": "And now I have a\n32 byte public key.", "start": 904.58, "duration": 5.02}, {"text": "And I've committed.", "start": 909.6, "duration": 1.64}, {"text": "That works, right?", "start": 911.24, "duration": 0.76}, {"text": "I've committed to my public key.", "start": 912.0, "duration": 2.16}, {"text": "However, when I sign, I need\nto provide the whole public key", "start": 914.16, "duration": 5.83}, {"text": "in order for you to verify.", "start": 919.99, "duration": 1.58}, {"text": "I need to provide this\nwhole 16 original pubkey,", "start": 921.57, "duration": 3.58}, {"text": "original version pubkey,\nafter when I sign.", "start": 925.15, "duration": 2.47}, {"text": "So now my signature goes\nfrom 8K to, what, 24K.", "start": 927.62, "duration": 7.26}, {"text": "So I haven't really made\nit more efficient, right,", "start": 934.88, "duration": 3.65}, {"text": "in that the total thing with\npublic keys and signatures", "start": 938.53, "duration": 4.31}, {"text": "stays the same size--", "start": 942.84, "duration": 1.84}, {"text": "actually, slightly larger.", "start": 944.68, "duration": 1.98}, {"text": "But this is kind of a game.", "start": 946.66, "duration": 1.56}, {"text": "Because the public\nkey, it might be", "start": 948.22, "duration": 5.04}, {"text": "like I'm showing it\nto you beforehand,", "start": 953.26, "duration": 2.79}, {"text": "and we're\nspace-constrained there.", "start": 956.05, "duration": 1.645}, {"text": "And then, when I'm\ndoing the signature,", "start": 957.695, "duration": 1.625}, {"text": "I have more space or time\nor something like that.", "start": 959.32, "duration": 2.64}, {"text": "So this is actually useful.", "start": 961.96, "duration": 1.29}, {"text": "And actually, this\ntechnique is used", "start": 963.25, "duration": 1.77}, {"text": "in Bitcoin and all\ndifferent cryptocurrencies,", "start": 965.02, "duration": 4.38}, {"text": "where you can call\nthis a pubkey hash--", "start": 969.4, "duration": 2.82}, {"text": "pubkey hash, or they say PKH.", "start": 977.66, "duration": 3.64}, {"text": "And the main benefit\nis size, right?", "start": 981.3, "duration": 2.262}, {"text": "You could say, well, if I've\ngot a really big pubkey,", "start": 983.562, "duration": 2.208}, {"text": "I can commit to it by sending\nto the hash of the pubkey.", "start": 985.77, "duration": 3.27}, {"text": "And then, when I\nlater want to sign,", "start": 989.04, "duration": 2.19}, {"text": "I reveal the actual pubkey.", "start": 991.23, "duration": 2.55}, {"text": "You can do it that way.", "start": 993.78, "duration": 1.24}, {"text": "OK.", "start": 995.02, "duration": 0.5}, {"text": "So then this is\npretty cool, right?", "start": 995.52, "duration": 2.85}, {"text": "We've now taken our system,\nwhich had fairly large--", "start": 998.37, "duration": 4.47}, {"text": "16 kilobyte-- private\nkeys, turned them", "start": 1002.84, "duration": 2.82}, {"text": "into 32 byte private keys.", "start": 1005.66, "duration": 1.35}, {"text": "Great.", "start": 1007.01, "duration": 0.6}, {"text": "And also, this is 0\nof 1-- never expands.", "start": 1007.61, "duration": 3.36}, {"text": "Awesome.", "start": 1010.97, "duration": 1.08}, {"text": "We've taken a system with\nlarge, potentially huge--", "start": 1012.05, "duration": 3.63}, {"text": "32 kilobyte, 64\nkilobyte-- public keys.", "start": 1015.68, "duration": 3.45}, {"text": "We've got it down to 32 bytes.", "start": 1019.13, "duration": 1.95}, {"text": "Awesome.", "start": 1021.08, "duration": 0.55}, {"text": "OK.", "start": 1021.63, "duration": 0.5}, {"text": "We've now made this thing\nmuch more efficient, much more", "start": 1022.13, "duration": 3.449}, {"text": "useful.", "start": 1025.579, "duration": 0.871}, {"text": "The problem-- the\nsignatures are still big.", "start": 1026.45, "duration": 2.43}, {"text": "They actually got\na little bit bigger", "start": 1028.88, "duration": 2.37}, {"text": "because they include the full\npublic key in the signature.", "start": 1031.25, "duration": 3.24}, {"text": "And let's say we had\none of these things,", "start": 1034.49, "duration": 3.45}, {"text": "where we make a\nbunch of public keys", "start": 1037.94, "duration": 2.25}, {"text": "and commit to them\nat the outset.", "start": 1040.19, "duration": 1.919}, {"text": "So you say, OK, I've got\na 64 kilobyte pubkey.", "start": 1042.109, "duration": 3.781}, {"text": "I can commit to the whole\nthing by hashing it.", "start": 1045.89, "duration": 2.52}, {"text": "However, then, when I reveal and\nwant to give you a signature,", "start": 1048.41, "duration": 4.05}, {"text": "my signature is now\nwhatever it'll be--", "start": 1052.46, "duration": 4.59}, {"text": "72, right?", "start": 1057.05, "duration": 1.55}, {"text": "The signature would\nbe 72 kilobytes--", "start": 1058.6, "duration": 3.22}, {"text": "kind of huge.", "start": 1061.82, "duration": 3.27}, {"text": "So I can add a bunch\nof keys, but I'm just", "start": 1065.09, "duration": 3.48}, {"text": "sort of pushing the\nproblem somewhere else--", "start": 1068.57, "duration": 2.13}, {"text": "into the signature, right?", "start": 1070.7, "duration": 1.98}, {"text": "There's a better way to\ncommit to many public keys.", "start": 1072.68, "duration": 3.24}, {"text": "It's maybe not super obvious\nunless you've seen it before.", "start": 1075.92, "duration": 3.9}, {"text": "But if you have,\ndo you know what", "start": 1079.82, "duration": 2.17}, {"text": "the better way to commit\nto many public keys is?", "start": 1081.99, "duration": 3.692}, {"text": "Or you could come up\nwith it on the spot,", "start": 1085.682, "duration": 1.708}, {"text": "and it'd be like, wow,\nyou should have gotten", "start": 1087.39, "duration": 1.875}, {"text": "this stuff named after you.", "start": 1089.265, "duration": 3.345}, {"text": "Any idea?", "start": 1092.61, "duration": 1.12}, {"text": "OK.", "start": 1093.73, "duration": 1.28}, {"text": "So what you can do--", "start": 1095.01, "duration": 2.13}, {"text": "it's a little non-obvious--", "start": 1097.14, "duration": 1.86}, {"text": "you can make a tree, right?", "start": 1099.0, "duration": 2.1}, {"text": "So the idea is instead\nof just saying,", "start": 1101.1, "duration": 2.76}, {"text": "oh, I'm going to take all\nfour of my big pubkeys,", "start": 1103.86, "duration": 4.23}, {"text": "stick them all in a row, take\nthe hash of that whole thing", "start": 1108.09, "duration": 3.15}, {"text": "and publish that\nas my public hash,", "start": 1111.24, "duration": 2.37}, {"text": "I'm going to have a little\nbit more complex design.", "start": 1113.61, "duration": 3.18}, {"text": "And that design\nis a binary tree.", "start": 1116.79, "duration": 4.07}, {"text": "OK.", "start": 1120.86, "duration": 0.83}, {"text": "So the idea is here are my four\npublic keys that take up 64K", "start": 1121.69, "duration": 4.53}, {"text": "each.", "start": 1126.22, "duration": 1.29}, {"text": "I can make these\nintermediate hashes.", "start": 1127.51, "duration": 2.04}, {"text": "So I make a binary tree\nwhere I say, OK, this", "start": 1129.55, "duration": 2.76}, {"text": "is the hash of the first\ntwo keys stuck together.", "start": 1132.31, "duration": 4.26}, {"text": "This is the hash of the second\ntwo keys stuck together.", "start": 1136.57, "duration": 4.25}, {"text": "The top is the hash of these\ntwo intermediate hashes", "start": 1140.82, "duration": 3.6}, {"text": "stuck together.", "start": 1144.42, "duration": 2.37}, {"text": "And then, this top\nis my root, which is", "start": 1146.79, "duration": 3.72}, {"text": "equivalent to my pubkey hash.", "start": 1150.51, "duration": 2.25}, {"text": "And so I can publish this,\nand it commits me to all four", "start": 1152.76, "duration": 4.68}, {"text": "of my public keys.", "start": 1157.44, "duration": 2.58}, {"text": "So it might not be obvious.", "start": 1160.02, "duration": 4.56}, {"text": "Do you see any\nadvantages that this", "start": 1164.58, "duration": 1.83}, {"text": "could have over just\nconcatenating all four", "start": 1166.41, "duration": 3.12}, {"text": "of the keys and hashing it?", "start": 1169.53, "duration": 1.2}, {"text": "Yes?", "start": 1170.73, "duration": 0.31}, {"text": "AUDIENCE: I'm confused.", "start": 1171.04, "duration": 0.958}, {"text": "Where is your\nprivate key in this?", "start": 1171.998, "duration": 1.972}, {"text": "TADGE DRYJA: The private\nkey is down here, right?", "start": 1173.97, "duration": 2.65}, {"text": "The private key is not shown.", "start": 1176.62, "duration": 1.44}, {"text": "But I have a private key.", "start": 1178.06, "duration": 1.76}, {"text": "It turns into these pubkeys.", "start": 1179.82, "duration": 2.303}, {"text": "And we can use the\ntechnique here,", "start": 1182.123, "duration": 1.417}, {"text": "where we just have, really,\none 32 byte private key", "start": 1183.54, "duration": 4.11}, {"text": "and create all the different\nchunks of all the public keys", "start": 1187.65, "duration": 3.66}, {"text": "by concatenating\ndifferent indices.", "start": 1191.31, "duration": 2.79}, {"text": "Yes?", "start": 1194.1, "duration": 0.5}, {"text": "AUDIENCE: You can do [INAUDIBLE]\nsystems and log-in time instead", "start": 1194.6, "duration": 3.28}, {"text": "of linear time.", "start": 1197.88, "duration": 1.24}, {"text": "TADGE DRYJA: Yeah, exactly.", "start": 1199.12, "duration": 1.59}, {"text": "I can prove that, hey,\nthis is public key 0, which", "start": 1200.71, "duration": 4.17}, {"text": "is in here, this root hash, and\nI don't have to reveal all four", "start": 1204.88, "duration": 6.03}, {"text": "in order to do it.", "start": 1210.91, "duration": 1.22}, {"text": "So yeah.", "start": 1212.13, "duration": 1.24}, {"text": "Did someone else have,\nprobably, the same idea?", "start": 1213.37, "duration": 2.27}, {"text": "Yeah, OK.", "start": 1215.64, "duration": 0.86}, {"text": "OK.", "start": 1216.5, "duration": 0.5}, {"text": "So how are we going to do that?", "start": 1217.0, "duration": 2.61}, {"text": "You obviously know.", "start": 1222.21, "duration": 0.86}, {"text": "Anyone else?", "start": 1223.07, "duration": 0.6}, {"text": "Yeah.", "start": 1223.67, "duration": 1.15}, {"text": "AUDIENCE: So assuming you\nwanted the public key 0,", "start": 1224.82, "duration": 2.62}, {"text": "you would publish that and\n1, and also hash of 2, 3.", "start": 1227.44, "duration": 4.24}, {"text": "TADGE DRYJA: Right, yeah.", "start": 1231.68, "duration": 1.47}, {"text": "And then you can\nprove up to the top.", "start": 1233.15, "duration": 2.65}, {"text": "So I have little colors.", "start": 1235.8, "duration": 1.43}, {"text": "So the idea is the verifier\nwho's verifying the signature,", "start": 1237.23, "duration": 6.51}, {"text": "he already knows\nthe root, right?", "start": 1243.74, "duration": 2.94}, {"text": "Because you've pre-published\nthat as your public key,", "start": 1246.68, "duration": 2.45}, {"text": "as your public key root\nand your public key hash.", "start": 1249.13, "duration": 2.32}, {"text": "And then that\nverifier is provided", "start": 1251.45, "duration": 2.85}, {"text": "with public key 0 saying,\nhey, here's a signature.", "start": 1254.3, "duration": 3.09}, {"text": "Here's the message.", "start": 1257.39, "duration": 1.12}, {"text": "Here is public key 0.", "start": 1258.51, "duration": 2.36}, {"text": "So you've got both\nof these things.", "start": 1260.87, "duration": 1.59}, {"text": "Now, the prover needs to\nprove that public key 0 is", "start": 1262.46, "duration": 5.19}, {"text": "contained within the root.", "start": 1267.65, "duration": 2.22}, {"text": "And to do that, the only two\nthings the prover needs to add", "start": 1269.87, "duration": 3.99}, {"text": "is pub1--", "start": 1273.86, "duration": 2.52}, {"text": "OK, so the prover says,\nhere's public key 1.", "start": 1276.38, "duration": 5.13}, {"text": "That allows the verifier\nto compute this.", "start": 1281.51, "duration": 4.26}, {"text": "And then the prover\nsays, hey, here's", "start": 1285.77, "duration": 1.74}, {"text": "hash 2, 3, which allows the\nverifier to compute the root", "start": 1287.51, "duration": 4.68}, {"text": "and then check that it's equal.", "start": 1292.19, "duration": 1.61}, {"text": "So yeah, you only need two extra\nhashes instead of all four.", "start": 1293.8, "duration": 2.5}, {"text": "So saves some space.", "start": 1296.3, "duration": 2.827}, {"text": "It doesn't save that much\nspace when you only have four.", "start": 1299.127, "duration": 2.333}, {"text": "It saves a lot of space\nwhen you have 1,000, right?", "start": 1301.46, "duration": 4.08}, {"text": "So you can add 0 of n elements.", "start": 1305.54, "duration": 3.51}, {"text": "And the root stays\nthe same size.", "start": 1309.05, "duration": 2.28}, {"text": "The root stays 32\nbytes, regardless", "start": 1311.33, "duration": 1.86}, {"text": "of how many leaf nodes you have.", "start": 1313.19, "duration": 2.81}, {"text": "And you can prove an\nelement with log n--", "start": 1316.0, "duration": 2.11}, {"text": "oh, those parentheses\nare wrong--", "start": 1318.11, "duration": 2.066}, {"text": "0 log n intermediate hashes.", "start": 1320.176, "duration": 2.164}, {"text": "So if you have 1,000 keys,\nyour root stays 32 bytes,", "start": 1322.34, "duration": 4.17}, {"text": "and your proofs are going to\nbe not too, too big, right--", "start": 1326.51, "duration": 4.32}, {"text": "320 bytes of overhead,\nwhich is a bunch smaller", "start": 1330.83, "duration": 4.17}, {"text": "than a signature, right?", "start": 1335.0, "duration": 2.55}, {"text": "So this is really cool.", "start": 1337.55, "duration": 1.03}, {"text": "And you can use this\nmuch more practically", "start": 1338.58, "duration": 2.87}, {"text": "than the raw lamport\nsignatures that", "start": 1341.45, "duration": 2.7}, {"text": "were in the first problem set.", "start": 1344.15, "duration": 1.53}, {"text": "Because those, if\nyou're just doing", "start": 1345.68, "duration": 4.08}, {"text": "one key and one signature,\nit's about the same size.", "start": 1349.76, "duration": 2.88}, {"text": "But this actually lets\nyou use it multiple times,", "start": 1352.64, "duration": 2.28}, {"text": "lets you store a much\nsmaller private key,", "start": 1354.92, "duration": 2.31}, {"text": "commit to much\nsmaller public keys.", "start": 1357.23, "duration": 1.95}, {"text": "It's a more usable system.", "start": 1359.18, "duration": 1.56}, {"text": "The signatures, though, still\nare kind of huge, right?", "start": 1360.74, "duration": 5.332}, {"text": "Your signatures are going\nto be a little over 8", "start": 1366.072, "duration": 1.958}, {"text": "kilobytes, which is OK, right?", "start": 1368.03, "duration": 1.59}, {"text": "Computers can deal\nwith 8 kilobytes.", "start": 1369.62, "duration": 2.07}, {"text": "That's called a Merkle\ntree made by Ralph Merkle", "start": 1371.69, "duration": 3.54}, {"text": "in '76 or something.", "start": 1375.23, "duration": 3.45}, {"text": "And it was originally made\nfor exactly that purpose.", "start": 1378.68, "duration": 3.14}, {"text": "Anyway, so these are\ncalled Merkle trees.", "start": 1381.82, "duration": 3.08}, {"text": "Ralph Merkle.", "start": 1384.9, "duration": 2.22}, {"text": "He doesn't really\nwork on crypto now.", "start": 1387.12, "duration": 1.905}, {"text": "He works on biotech\nstuff now, I think.", "start": 1389.025, "duration": 2.565}, {"text": "Anyway.", "start": 1391.59, "duration": 0.866}, {"text": "But he's cool.", "start": 1392.456, "duration": 1.557}, {"text": "And he gets, like,\neverything named after him.", "start": 1394.013, "duration": 1.917}, {"text": "So you will see the\nword Merkle everywhere.", "start": 1395.93, "duration": 2.26}, {"text": "And it's, you know, he\ninvented something cool.", "start": 1398.19, "duration": 2.97}, {"text": "Awesome.", "start": 1401.16, "duration": 0.713}, {"text": "This is one of the\nkind of things,", "start": 1401.873, "duration": 1.417}, {"text": "though, where it\nseems like, yeah,", "start": 1403.29, "duration": 1.2}, {"text": "I might have been able\nto think of that, right?", "start": 1404.49, "duration": 1.46}, {"text": "It's sort of a binary\ntree and hash functions.", "start": 1405.95, "duration": 2.32}, {"text": "It's nothing that crazy.", "start": 1408.27, "duration": 2.29}, {"text": "But so there's all\nsorts of Merkle trees.", "start": 1410.56, "duration": 2.15}, {"text": "You can make a different thing.", "start": 1412.71, "duration": 2.73}, {"text": "It's used in Bitcoin.", "start": 1415.44, "duration": 0.89}, {"text": "It's used in a bunch of\ndifferent cryptocurrencies.", "start": 1416.33, "duration": 3.19}, {"text": "Oh, cool.", "start": 1419.52, "duration": 1.23}, {"text": "It's a very powerful way\nto take a whole bunch", "start": 1420.75, "duration": 5.31}, {"text": "of different things and commit\nto them in one small thing.", "start": 1426.06, "duration": 2.71}, {"text": "OK.", "start": 1428.77, "duration": 0.5}, {"text": "So this is very cool.", "start": 1429.27, "duration": 1.26}, {"text": "But we can do better.", "start": 1430.53, "duration": 1.83}, {"text": "And so the next things are\nthings that I definitely", "start": 1432.36, "duration": 2.46}, {"text": "would never have thought\nof because it's much more", "start": 1434.82, "duration": 3.36}, {"text": "complex than just, like,\nhey, let's use a binary tree", "start": 1438.18, "duration": 2.22}, {"text": "with hashes.", "start": 1440.4, "duration": 2.13}, {"text": "And I will mention\nRSA and then go", "start": 1442.53, "duration": 2.73}, {"text": "into ECDSA and elliptic curve\n[INAUDIBLE] signatures, which", "start": 1445.26, "duration": 5.25}, {"text": "do different things and are not\nbased on just hash functions.", "start": 1450.51, "duration": 4.502}, {"text": "So I'll talk about\nRSA for a few minutes,", "start": 1455.012, "duration": 1.708}, {"text": "and then we'll have a little\nbreak, like intermission.", "start": 1456.72, "duration": 2.347}, {"text": "And then we'll go into\nelliptic curve stuff.", "start": 1459.067, "duration": 1.833}, {"text": "OK.", "start": 1460.9, "duration": 0.5}, {"text": "So RSA was invented by locals.", "start": 1461.4, "duration": 1.86}, {"text": "The R is Ron--", "start": 1463.26, "duration": 1.53}, {"text": "no, I think the R\nstands for Rivest,", "start": 1464.79, "duration": 1.5}, {"text": "but Ron Rivest is at\nCSAIL, and he's still", "start": 1466.29, "duration": 3.58}, {"text": "working on cool crypto stuff.", "start": 1469.87, "duration": 2.36}, {"text": "It's not used in Bitcoin\nor any currency, actually--", "start": 1472.23, "duration": 2.73}, {"text": "well, any currently\noperating cryptocurrency.", "start": 1474.96, "duration": 3.6}, {"text": "Because the signatures\nand keys are", "start": 1478.56, "duration": 4.32}, {"text": "a bit larger than the\nlater systems we'll see--", "start": 1482.88, "duration": 2.67}, {"text": "smaller than the hash-based\nthings, but still a bit larger.", "start": 1485.55, "duration": 4.95}, {"text": "Was used in chaumian\nblinded cash.", "start": 1490.5, "duration": 1.92}, {"text": "Because you can do blinded\nsignatures, where you say,", "start": 1492.42, "duration": 2.65}, {"text": "OK, I'm going to have you\nsign something for me,", "start": 1495.07, "duration": 3.202}, {"text": "and then after you\ngive me the signature,", "start": 1498.272, "duration": 1.708}, {"text": "I can pull apart the signature.", "start": 1499.98, "duration": 4.02}, {"text": "Because I'll have\nyou sign something", "start": 1504.0, "duration": 1.65}, {"text": "that you don't know what\nyou're signing, right?", "start": 1505.65, "duration": 2.22}, {"text": "I'm going to mask this\nmessage and blind it", "start": 1507.87, "duration": 2.76}, {"text": "so that you sign the\nmessage, and then I", "start": 1510.63, "duration": 1.92}, {"text": "can get your signature\non the real message", "start": 1512.55, "duration": 2.76}, {"text": "without you knowing\nwhat you signed.", "start": 1515.31, "duration": 1.77}, {"text": "So basically, the idea\nis, well, I actually", "start": 1517.08, "duration": 2.46}, {"text": "have message prime equals\nmessage plus randomness.", "start": 1519.54, "duration": 6.69}, {"text": "And I say, hey, can\nyou sign m prime?", "start": 1526.23, "duration": 1.98}, {"text": "And you say, OK.", "start": 1528.21, "duration": 0.78}, {"text": "I produce a signature on m\nprime with my private key.", "start": 1528.99, "duration": 4.98}, {"text": "And we'll call that s prime.", "start": 1533.97, "duration": 2.4}, {"text": "And then what I can do\nis I can s equals s prime", "start": 1536.37, "duration": 5.05}, {"text": "minus the randomness,\nor, really, some function", "start": 1541.42, "duration": 3.63}, {"text": "of that randomness.", "start": 1545.05, "duration": 1.47}, {"text": "And now I have a signature.", "start": 1546.52, "duration": 1.72}, {"text": "And this is a valid\nsignature on m.", "start": 1548.24, "duration": 3.29}, {"text": "So that's kind of cool.", "start": 1551.53, "duration": 1.23}, {"text": "It's like, hey, can you\nsign this message for me?", "start": 1552.76, "duration": 2.042}, {"text": "And we're not going to tell\nyou what you're signing.", "start": 1554.802, "duration": 2.868}, {"text": "It seems sort of\nuseless, like why would I", "start": 1557.67, "duration": 1.75}, {"text": "sign something I have no\nidea what I'm signing?", "start": 1559.42, "duration": 2.01}, {"text": "But it can be used in that\nchaumian blinded cash.", "start": 1561.43, "duration": 3.75}, {"text": "Because I then have a proof\nthat, well, this bank didn't", "start": 1565.18, "duration": 2.97}, {"text": "know what they were signing,\nbut they signed this,", "start": 1568.15, "duration": 2.4}, {"text": "and this is their signature,\nand they gave it to me.", "start": 1570.55, "duration": 3.0}, {"text": "And I can use that as a\nthing to represent money.", "start": 1573.55, "duration": 3.54}, {"text": "There's all sorts of cool\nthings you can do with this.", "start": 1577.09, "duration": 2.25}, {"text": "The basic setup of RSA is make\ntwo prime numbers, p and q.", "start": 1579.34, "duration": 5.55}, {"text": "And then compute n, which\nis the product p times q.", "start": 1584.89, "duration": 3.99}, {"text": "So this seems fairly\nstraightforward, right?", "start": 1588.88, "duration": 2.52}, {"text": "It's not too hard.", "start": 1591.4, "duration": 1.26}, {"text": "Everyone knows what\nprime numbers are.", "start": 1592.66, "duration": 1.923}, {"text": "Now you have this composite\nnumber, p times q.", "start": 1594.583, "duration": 1.917}, {"text": "How do I make a leading\nquestion for the next slide?", "start": 1599.47, "duration": 3.57}, {"text": "Does this have any relation to\nthings that we've looked at?", "start": 1603.04, "duration": 3.492}, {"text": "This doesn't look at all\nlike a hash function, right?", "start": 1606.532, "duration": 2.208}, {"text": "But are there any properties\nsimilar to a hash function", "start": 1608.74, "duration": 2.34}, {"text": "here?", "start": 1611.08, "duration": 0.5}, {"text": "Yeah?", "start": 1614.23, "duration": 1.765}, {"text": "AUDIENCE: It's hard\nto route the image.", "start": 1615.995, "duration": 1.625}, {"text": "It's hard to [INAUDIBLE].", "start": 1617.62, "duration": 1.24}, {"text": "TADGE DRYJA: Yeah.", "start": 1618.86, "duration": 0.84}, {"text": "It's a one-way function\nin that if I know p and q,", "start": 1619.7, "duration": 2.87}, {"text": "I can compute n, right?", "start": 1622.57, "duration": 2.04}, {"text": "But given n, I can't\nnecessarily find p and q, right?", "start": 1624.61, "duration": 4.2}, {"text": "If they're small,\nsure, I just check.", "start": 1628.81, "duration": 1.95}, {"text": "And there's all sorts of\nalgorithms to find factors.", "start": 1630.76, "duration": 3.39}, {"text": "But if p and q are pretty big,\nlike hundreds of bits long", "start": 1634.15, "duration": 3.87}, {"text": "or thousands of\nbits long, finding n", "start": 1638.02, "duration": 2.67}, {"text": "may be impractical, whereas\nif p and q are really long,", "start": 1640.69, "duration": 3.69}, {"text": "finding the product of both of\nthem will be very practical.", "start": 1644.38, "duration": 2.79}, {"text": "Even if huge, multiplying\ntwo integers is really easy.", "start": 1647.17, "duration": 4.78}, {"text": "So this is a one-way function\nbut not a hash function.", "start": 1651.95, "duration": 2.93}, {"text": "And so a lot of these signature\nsystems use one-way functions,", "start": 1654.88, "duration": 3.66}, {"text": "but trickier one-way functions\nthat aren't hash functions,", "start": 1658.54, "duration": 3.27}, {"text": "and still have cool\nthings that you can do.", "start": 1661.81, "duration": 4.0}, {"text": "So I'm not going to go\ninto RSA in super detail.", "start": 1665.81, "duration": 3.95}, {"text": "I'm going to run\nthrough it really quick,", "start": 1669.76, "duration": 2.157}, {"text": "and you'll be like,\nhuh, how does that work?", "start": 1671.917, "duration": 1.833}, {"text": "But if you think it's\ninteresting, you can look it up", "start": 1673.75, "duration": 2.48}, {"text": "and then maybe you go\nto CSAIL and ask Ron", "start": 1676.23, "duration": 1.75}, {"text": "how it works, although maybe\ntry to look it up first.", "start": 1677.98, "duration": 2.37}, {"text": "He's probably explained\nit a lot of times.", "start": 1680.35, "duration": 1.75}, {"text": "But it has different properties.", "start": 1684.88, "duration": 1.72}, {"text": "So you could say, I'm\ngoing to use this p times", "start": 1686.6, "duration": 2.45}, {"text": "q equals n as a hash function\nand make a lamport signature", "start": 1689.05, "duration": 3.39}, {"text": "out of it where my private key\nis a whole bunch of p and q", "start": 1692.44, "duration": 4.41}, {"text": "pairs, and my public key is\na whole bunch of n's, and I", "start": 1696.85, "duration": 3.15}, {"text": "reveal them and stuff.", "start": 1700.0, "duration": 1.59}, {"text": "You could do that.", "start": 1701.59, "duration": 0.87}, {"text": "That would work.", "start": 1702.46, "duration": 1.89}, {"text": "But you can do much\nmore powerful things", "start": 1704.35, "duration": 1.89}, {"text": "because of the mathematical\nproperties of these things.", "start": 1706.24, "duration": 3.12}, {"text": "So yeah, I'm just going to\ngo through it really fast.", "start": 1709.36, "duration": 3.23}, {"text": "But if you know anything,\nthis is kind of cool.", "start": 1712.59, "duration": 2.89}, {"text": "The idea is you can do a\nbunch of multiplication", "start": 1715.48, "duration": 5.25}, {"text": "and exponential modulo n.", "start": 1720.73, "duration": 2.85}, {"text": "And so because n\nis almost prime,", "start": 1723.58, "duration": 4.23}, {"text": "there's some\ninteresting properties,", "start": 1727.81, "duration": 1.83}, {"text": "where if you know\nthe factors of n,", "start": 1729.64, "duration": 3.54}, {"text": "you have these\nshortcuts you can do.", "start": 1733.18, "duration": 1.785}, {"text": "And someone who doesn't\nknow the factors of n", "start": 1734.965, "duration": 1.875}, {"text": "can't do these shortcuts.", "start": 1736.84, "duration": 1.45}, {"text": "So you publish e, which is\na constant-- this is sort", "start": 1738.29, "duration": 3.8}, {"text": "of a parameter system.", "start": 1742.09, "duration": 2.4}, {"text": "So RSA is used today\nall over the place.", "start": 1744.49, "duration": 2.07}, {"text": "If your computer\nis open and you've", "start": 1746.56, "duration": 2.22}, {"text": "been using the web in\nthe last five seconds,", "start": 1748.78, "duration": 1.89}, {"text": "your computer has\nperformed RSA calculations.", "start": 1750.67, "duration": 3.36}, {"text": "Every time you connect to a\nwebsite, you're doing RSA.", "start": 1754.03, "duration": 4.35}, {"text": "So generally, it's 65537.", "start": 1758.38, "duration": 2.822}, {"text": "They just make this up.", "start": 1761.202, "duration": 0.958}, {"text": "You could also use\nthree-- some small number.", "start": 1762.16, "duration": 3.64}, {"text": "And then d is a number\nthat you can compute", "start": 1765.8, "duration": 2.87}, {"text": "if you know what p and q are.", "start": 1768.67, "duration": 1.86}, {"text": "So this is sort of the\nprivate key, right?", "start": 1770.53, "duration": 3.51}, {"text": "p and q itself can be\nseen as the private key.", "start": 1774.04, "duration": 2.7}, {"text": "But you can actually\ncompute this d number", "start": 1776.74, "duration": 2.34}, {"text": "and then discard p and q.", "start": 1779.08, "duration": 4.02}, {"text": "And so this is how you\ncompute d or whatever.", "start": 1783.1, "duration": 2.22}, {"text": "But the idea is n is your public\nkey, and d is your private key.", "start": 1785.32, "duration": 4.17}, {"text": "e is always the same, and p and\nq, you can discard afterwards.", "start": 1789.49, "duration": 2.94}, {"text": "And then what you can do--", "start": 1792.43, "duration": 1.31}, {"text": "and not going to get into\nit-- but you can say, OK,", "start": 1793.74, "duration": 4.28}, {"text": "my signature s is\nmessage, right--", "start": 1798.02, "duration": 2.57}, {"text": "I can take the hash\nand make a message m--", "start": 1800.59, "duration": 2.475}, {"text": "message to the d power modulo n.", "start": 1803.065, "duration": 3.765}, {"text": "And if I verify, if I take that\nsignature to the e power modulo", "start": 1806.83, "duration": 4.11}, {"text": "n, it should equal\nm again, which", "start": 1810.94, "duration": 2.1}, {"text": "is crazy and kind of awesome.", "start": 1813.04, "duration": 3.72}, {"text": "Because the idea\nis to sign, OK, I", "start": 1816.76, "duration": 1.77}, {"text": "just raised to\nthe d power mod n.", "start": 1818.53, "duration": 2.13}, {"text": "It's going to be some number\non the same size as n, right?", "start": 1820.66, "duration": 3.96}, {"text": "And then I give that to someone.", "start": 1824.62, "duration": 2.61}, {"text": "They take that signature\nto the 65537 power modulo", "start": 1827.23, "duration": 5.52}, {"text": "m again and see if m--", "start": 1832.75, "duration": 2.73}, {"text": "the message-- comes back out.", "start": 1835.48, "duration": 1.32}, {"text": "And if it does,\nthey know I signed,", "start": 1836.8, "duration": 2.46}, {"text": "and I have the private\nkey that corresponds to n.", "start": 1839.26, "duration": 4.32}, {"text": "Now, the cool thing is I can\nuse this any number of times.", "start": 1843.58, "duration": 3.66}, {"text": "I can use the same\nthing a bazillion times", "start": 1847.24, "duration": 3.39}, {"text": "with different m's, and\nthat doesn't give any help", "start": 1850.63, "duration": 4.26}, {"text": "on how to factor n\nor how to compute d.", "start": 1854.89, "duration": 3.63}, {"text": "So this was late 70s, also,\nRSA, and one of the first,", "start": 1858.52, "duration": 5.8}, {"text": "hey, we can do better\nthan hash functions.", "start": 1864.32, "duration": 3.11}, {"text": "It was developed at\naround the same time", "start": 1867.43, "duration": 3.63}, {"text": "as hash-based signatures.", "start": 1871.06, "duration": 1.74}, {"text": "All of these things were sort\nof coming out at the same time.", "start": 1872.8, "duration": 3.03}, {"text": "You can do lots of cool\nstuff because there's", "start": 1875.83, "duration": 2.82}, {"text": "these properties where we\ncan make m prime plus m", "start": 1878.65, "duration": 6.45}, {"text": "and take the exponentiation of\nall that, and it still works.", "start": 1885.1, "duration": 3.97}, {"text": "OK.", "start": 1889.07, "duration": 0.5}, {"text": "So that's really cool.", "start": 1889.57, "duration": 0.917}, {"text": "You can do lots of cool stuff.", "start": 1890.487, "duration": 1.873}, {"text": "But this is also\nnot used in Bitcoin.", "start": 1892.36, "duration": 4.08}, {"text": "One of the things is the size.", "start": 1896.44, "duration": 1.5}, {"text": "So key sizes are smaller\nthan with lamport signatures.", "start": 1897.94, "duration": 4.86}, {"text": "And they're often about\n2 kilobits, or 256 bytes,", "start": 1902.8, "duration": 5.477}, {"text": "which is fine.", "start": 1908.277, "duration": 0.583}, {"text": "And that's the same\nsize as signatures.", "start": 1908.86, "duration": 3.04}, {"text": "So if you use your web browser--", "start": 1911.9, "duration": 1.535}, {"text": "secure-- well, how secure?", "start": 1916.2, "duration": 3.52}, {"text": "Certificate, valid.", "start": 1919.72, "duration": 1.23}, {"text": "Oh, this browser\nmight not show me.", "start": 1920.95, "duration": 2.75}, {"text": "OK, never mind.", "start": 1923.7, "duration": 1.563}, {"text": "AUDIENCE: In\nFirefox, it'll do it.", "start": 1925.263, "duration": 1.417}, {"text": "TADGE DRYJA: In Firefox,\nit tells you more.", "start": 1926.68, "duration": 2.29}, {"text": "OK.", "start": 1928.97, "duration": 0.5}, {"text": "Well, anyway, anyway, anyway.", "start": 1929.47, "duration": 1.56}, {"text": "But yeah, there's RSA keys in,\nbasically, every certificate", "start": 1931.03, "duration": 5.22}, {"text": "for web browsers and websites.", "start": 1936.25, "duration": 1.77}, {"text": "And they're generally\n2,048 bits long.", "start": 1938.02, "duration": 3.04}, {"text": "That's seen as pretty secure.", "start": 1941.06, "duration": 2.78}, {"text": "Even 1,024 bits has\nnot been hacked.", "start": 1943.84, "duration": 3.66}, {"text": "But people think\nit probably could", "start": 1947.5, "duration": 1.5}, {"text": "be by a very motivated actor.", "start": 1949.0, "duration": 2.72}, {"text": "So this is decent size.", "start": 1951.72, "duration": 2.83}, {"text": "One thing about RSA is that it's\na little tricky to implement,", "start": 1954.55, "duration": 2.583}, {"text": "right?", "start": 1957.133, "duration": 0.5}, {"text": "There's a whole bunch\nof weird math there.", "start": 1957.633, "duration": 1.807}, {"text": "It's not like the\nlamport signatures,", "start": 1959.44, "duration": 2.1}, {"text": "where it's like, OK, I have a\nhash function, use it, right?", "start": 1961.54, "duration": 2.87}, {"text": "It's kind of hard\nto shoot yourself", "start": 1964.41, "duration": 1.51}, {"text": "in the foot with the\nlamport signature scheme.", "start": 1965.92, "duration": 3.15}, {"text": "You can, right, but\nit's sort of obvious", "start": 1969.07, "duration": 1.89}, {"text": "if you do, so if you're\ndoing the homework", "start": 1970.96, "duration": 1.32}, {"text": "and it just doesn't work\nat all, and you're like,", "start": 1972.28, "duration": 2.042}, {"text": "oh, I was hashing twice, or,\noh, I was reversing the order,", "start": 1974.322, "duration": 3.358}, {"text": "or it just didn't work.", "start": 1977.68, "duration": 4.62}, {"text": "But there's no subtle ways\nwhere, oh, I was off by one,", "start": 1982.3, "duration": 2.85}, {"text": "and now it reveals\nall my private keys.", "start": 1985.15, "duration": 2.04}, {"text": "That's hard to do, whereas in\nRSA, it's actually quite easy.", "start": 1987.19, "duration": 4.08}, {"text": "If your p and q\nvalues, for example--", "start": 1991.27, "duration": 2.82}, {"text": "what's a really crazy gotcha--", "start": 1994.09, "duration": 2.43}, {"text": "if p or q minus 1-- so if\np minus 1 or q minus 1--", "start": 1996.52, "duration": 4.89}, {"text": "is smooth-- essentially, a\nnumber that's highly composite", "start": 2001.41, "duration": 2.91}, {"text": "has many small factors--", "start": 2004.32, "duration": 2.01}, {"text": "you can find\nsomeone's private key.", "start": 2006.33, "duration": 2.13}, {"text": "You can factor it.", "start": 2008.46, "duration": 1.13}, {"text": "So it's not just that p\nand q have to be prime.", "start": 2009.59, "duration": 2.26}, {"text": "P minus 1 and q minus 1\nhave to be not too unprime.", "start": 2011.85, "duration": 5.85}, {"text": "It can't be a power\nof two or something.", "start": 2017.7, "duration": 2.178}, {"text": "Otherwise, you can\nlose your privacy.", "start": 2019.878, "duration": 1.542}, {"text": "So there's all sorts of crazy\nthings that happen with RSA.", "start": 2021.42, "duration": 5.28}, {"text": "Bitcoin and other coins use\nelliptic curve signatures,", "start": 2026.7, "duration": 2.94}, {"text": "which I'll talk about next,\nthat are sort of displacing RSA,", "start": 2029.64, "duration": 6.12}, {"text": "in many cases.", "start": 2035.76, "duration": 0.94}, {"text": "So it hasn't really taken\noff for web certificates", "start": 2036.7, "duration": 7.67}, {"text": "but a lot of other types of\nencryption, signing, things", "start": 2044.37, "duration": 2.85}, {"text": "like that.", "start": 2047.22, "duration": 0.54}, {"text": "Cryptocurrencies are also one of\nthe big uses of elliptic curve", "start": 2047.76, "duration": 3.39}, {"text": "signatures because\nthey're somewhat more", "start": 2051.15, "duration": 2.58}, {"text": "powerful and somewhat\nsmaller and really cool.", "start": 2053.73, "duration": 2.94}, {"text": "And we will talk about\nthose in three minutes.", "start": 2056.67, "duration": 3.42}, {"text": "So intermission, three minutes.", "start": 2060.09, "duration": 2.609}, {"text": "Stretch.", "start": 2062.699, "duration": 1.951}, {"text": "Ask random questions.", "start": 2064.65, "duration": 1.299}, {"text": "Talk to the neighbors.", "start": 2065.949, "duration": 1.591}, {"text": "OK.", "start": 2067.54, "duration": 0.5}, {"text": "So they're using\nthese elliptic curves,", "start": 2068.04, "duration": 4.619}, {"text": "which are curves of\nthe form y squared", "start": 2072.659, "duration": 2.131}, {"text": "plus x cubed plus some\ncoefficient x squared", "start": 2074.79, "duration": 3.36}, {"text": "plus some constant.", "start": 2078.15, "duration": 3.089}, {"text": "And in the case of\nBitcoin, it's very simple.", "start": 2081.239, "duration": 2.431}, {"text": "It's y squared equals\nx cubed plus 7.", "start": 2083.67, "duration": 3.29}, {"text": "And that's the\ncurve Bitcoin uses.", "start": 2086.96, "duration": 2.38}, {"text": "And this is what it looks\nlike if you plot it.", "start": 2089.34, "duration": 2.96}, {"text": "And that seems really simple.", "start": 2092.3, "duration": 2.62}, {"text": "We can totally understand that.", "start": 2094.92, "duration": 1.319}, {"text": "But it gets a little weird.", "start": 2096.239, "duration": 1.981}, {"text": "With elliptic curves, you have\nthese points on the curves,", "start": 2098.22, "duration": 4.11}, {"text": "right?", "start": 2102.33, "duration": 0.54}, {"text": "And another property is if\nyou draw a straight line that", "start": 2102.87, "duration": 3.66}, {"text": "intersects this curve--", "start": 2106.53, "duration": 1.933}, {"text": "you could also draw\na line which doesn't", "start": 2108.463, "duration": 1.667}, {"text": "intersect at all, fine--", "start": 2110.13, "duration": 1.088}, {"text": "but if you draw a line\nthat intersects the curve,", "start": 2111.218, "duration": 2.042}, {"text": "it will intersect\nin three places.", "start": 2113.26, "duration": 3.315}, {"text": "So if I draw a line here, it\nintersects these three dots.", "start": 2116.575, "duration": 2.375}, {"text": "If I draw a line here,\nit intersects here, here,", "start": 2118.95, "duration": 2.61}, {"text": "and then it'll intersect\nsomewhere down here.", "start": 2121.56, "duration": 1.96}, {"text": "It'll intersect in three\nplaces unless I take a tangent.", "start": 2123.52, "duration": 3.17}, {"text": "If I draw, and I try\nto be like, oh, I'm", "start": 2126.69, "duration": 1.74}, {"text": "going only intersect\nin two, well, I", "start": 2128.43, "duration": 1.8}, {"text": "can take a tangent\nhere, and it'll", "start": 2130.23, "duration": 2.25}, {"text": "intersect in one more place.", "start": 2132.48, "duration": 1.68}, {"text": "What we can do, though,\nis we can say, well,", "start": 2134.16, "duration": 2.27}, {"text": "if you intersect at a\ntangent, that's kind", "start": 2136.43, "duration": 1.75}, {"text": "of like intersecting twice.", "start": 2138.18, "duration": 2.713}, {"text": "We can deal with that.", "start": 2140.893, "duration": 0.917}, {"text": "AUDIENCE: What if you\ndraw a vertical line?", "start": 2141.81, "duration": 1.827}, {"text": "TADGE DRYJA: If you draw a\nvertical-- oh, yeah, vertical", "start": 2143.637, "duration": 2.333}, {"text": "line, then there's\na point at infinity,", "start": 2145.97, "duration": 1.74}, {"text": "which shouldn't happen.", "start": 2147.71, "duration": 1.788}, {"text": "AUDIENCE: But\ninfinity is included--", "start": 2149.498, "duration": 1.572}, {"text": "TADGE DRYJA: Yeah.", "start": 2151.07, "duration": 0.315}, {"text": "AUDIENCE: --in the set\nof points on the curve?", "start": 2151.385, "duration": 1.995}, {"text": "So it's like there's\nthree points, anyway.", "start": 2153.38, "duration": 1.75}, {"text": "TADGE DRYJA: Yeah.", "start": 2155.13, "duration": 1.16}, {"text": "There's a point up there--", "start": 2156.29, "duration": 1.66}, {"text": "sort of.", "start": 2157.95, "duration": 0.5}, {"text": "In the practice of\nsigning and stuff,", "start": 2161.15, "duration": 1.77}, {"text": "you probably shouldn't hit it.", "start": 2162.92, "duration": 2.99}, {"text": "Yeah.", "start": 2165.91, "duration": 2.38}, {"text": "But so what we do is we say,\nOK, well, three points in a line", "start": 2168.29, "duration": 4.02}, {"text": "equals zero.", "start": 2172.31, "duration": 2.32}, {"text": "And so if we take this\npoint plus this point", "start": 2174.63, "duration": 3.96}, {"text": "plus this point, that's zero.", "start": 2178.59, "duration": 1.98}, {"text": "Another way to say that is\nP plus Q minus R equals 0,", "start": 2180.57, "duration": 4.98}, {"text": "or P plus Q equals negative\nR. And another property is", "start": 2185.55, "duration": 4.95}, {"text": "the negation of a point\nis just that same point", "start": 2190.5, "duration": 4.29}, {"text": "with the y-coordinate flipped.", "start": 2194.79, "duration": 2.37}, {"text": "So if this is\nnegative R, we just", "start": 2197.16, "duration": 3.0}, {"text": "go down to the\nbottom side of this,", "start": 2200.16, "duration": 2.22}, {"text": "and this is positive\nR. Similarly, minus P", "start": 2202.38, "duration": 2.477}, {"text": "would be here.", "start": 2204.857, "duration": 0.583}, {"text": "Minus Q would be here.", "start": 2205.44, "duration": 1.56}, {"text": "And if you had a point Z here,\nnegative Z would be up here.", "start": 2207.0, "duration": 4.83}, {"text": "This is how it's constructed.", "start": 2211.83, "duration": 1.74}, {"text": "However, we don't actually\nuse these nice curves.", "start": 2213.57, "duration": 4.89}, {"text": "We chop them up in\nmodulo something.", "start": 2218.46, "duration": 2.318}, {"text": "Yeah?", "start": 2220.778, "duration": 0.5}, {"text": "AUDIENCE: You have P plus Q\nequals negative R. Should it", "start": 2221.278, "duration": 2.402}, {"text": "be positive R?", "start": 2223.68, "duration": 0.829}, {"text": "TADGE DRYJA: No.", "start": 2228.05, "duration": 2.37}, {"text": "In this case, R is up here.", "start": 2230.42, "duration": 1.17}, {"text": "Right.", "start": 2231.59, "duration": 1.77}, {"text": "In this case--", "start": 2233.36, "duration": 1.56}, {"text": "P. Wait, hold on.", "start": 2234.92, "duration": 2.55}, {"text": "[INTERPOSING VOICES]", "start": 2237.47, "duration": 0.882}, {"text": "TADGE DRYJA: Oh, shoot.", "start": 2238.352, "duration": 0.958}, {"text": "Sorry.", "start": 2239.31, "duration": 0.5}, {"text": "P plus Q equals R. Right.", "start": 2239.81, "duration": 1.98}, {"text": "Sorry.", "start": 2241.79, "duration": 2.05}, {"text": "OK.", "start": 2243.84, "duration": 0.5}, {"text": "Never mind.", "start": 2244.34, "duration": 0.8}, {"text": "Yeah.", "start": 2245.14, "duration": 1.04}, {"text": "The picture is correct.", "start": 2246.18, "duration": 3.31}, {"text": "But so basically,\nP plus Q equals R", "start": 2249.49, "duration": 5.512}, {"text": "because R is down here.", "start": 2255.002, "duration": 0.958}, {"text": "Sorry.", "start": 2255.96, "duration": 0.5}, {"text": "Yeah, that's why.", "start": 2256.46, "duration": 1.14}, {"text": "OK.", "start": 2257.6, "duration": 0.52}, {"text": "This is R. This is\nnegative R. So yeah,", "start": 2258.12, "duration": 2.43}, {"text": "P plus Q equals R,\nnot negative R. Sorry.", "start": 2260.55, "duration": 7.17}, {"text": "When you want to multiply\na point, you can.", "start": 2267.72, "duration": 3.03}, {"text": "Because you can take\na tangent, right?", "start": 2270.75, "duration": 1.962}, {"text": "So you can add\nthese points, right?", "start": 2272.712, "duration": 1.458}, {"text": "You can say, OK, I want\nthe sum of P and Q,", "start": 2274.17, "duration": 2.88}, {"text": "which will be down here--", "start": 2277.05, "duration": 1.45}, {"text": "R. I want 2P, for example.", "start": 2278.5, "duration": 4.82}, {"text": "Well, with 2P, I\ncan take a tangent", "start": 2283.32, "duration": 2.55}, {"text": "and then find\nwhere it intersects", "start": 2285.87, "duration": 1.59}, {"text": "and then go down\nbelow the curve.", "start": 2287.46, "duration": 1.99}, {"text": "So for example, if this\nis G, I say OK, well, G", "start": 2289.45, "duration": 3.65}, {"text": "starts here, take the tangent,\nfind where it intersects", "start": 2293.1, "duration": 3.3}, {"text": "and then drop down.", "start": 2296.4, "duration": 1.44}, {"text": "And this is 2G.", "start": 2297.84, "duration": 2.01}, {"text": "So it's a simple\nway to say, well,", "start": 2299.85, "duration": 3.015}, {"text": "I'm not really multiplying.", "start": 2302.865, "duration": 1.125}, {"text": "I'm just adding it\nto itself, which is", "start": 2303.99, "duration": 1.77}, {"text": "sort of what multiplication is.", "start": 2305.76, "duration": 1.853}, {"text": "And I can do this\nagain and again.", "start": 2307.613, "duration": 1.417}, {"text": "So I say, oh, I want 4G.", "start": 2309.03, "duration": 1.59}, {"text": "I take the tangent at 2G,\nfind the intersection here,", "start": 2310.62, "duration": 3.08}, {"text": "drop down.", "start": 2313.7, "duration": 0.67}, {"text": "OK.", "start": 2314.37, "duration": 0.5}, {"text": "Here's 4G.", "start": 2314.87, "duration": 0.97}, {"text": "Take the tangent\nhere, it'll go--", "start": 2315.84, "duration": 2.19}, {"text": "I can keep doing that\nand get 2G, 4G, 8G.", "start": 2318.03, "duration": 3.6}, {"text": "And if I want intermediate\nthings, like, well, I want 3G,", "start": 2321.63, "duration": 4.83}, {"text": "well, I draw a line between G\nand 2G, find the intersection,", "start": 2326.46, "duration": 5.21}, {"text": "and find the sum.", "start": 2331.67, "duration": 1.48}, {"text": "So yeah?", "start": 2333.15, "duration": 0.84}, {"text": "Yes?", "start": 2333.99, "duration": 0.5}, {"text": "AUDIENCE: When you find\nthe intersection of that", "start": 2334.49, "duration": 2.88}, {"text": "[INAUDIBLE] the intersection\nof the modulo of something,", "start": 2337.37, "duration": 2.333}, {"text": "does it just--", "start": 2339.703, "duration": 0.537}, {"text": "TADGE DRYJA: Yeah, yeah.", "start": 2340.24, "duration": 1.0}, {"text": "So the pictures look\nnice, in this case, right?", "start": 2341.24, "duration": 3.922}, {"text": "It's like, hey,\nthere's this curve.", "start": 2345.162, "duration": 1.458}, {"text": "And it looks so simple.", "start": 2346.62, "duration": 1.87}, {"text": "And we can graphically\ndo it on graph paper.", "start": 2348.49, "duration": 2.48}, {"text": "But when you're actually\ndoing it on the computer,", "start": 2350.97, "duration": 2.31}, {"text": "it looks more like this.", "start": 2353.28, "duration": 1.68}, {"text": "Everything is modulo\nsome giant prime number.", "start": 2354.96, "duration": 3.93}, {"text": "You could still draw lines.", "start": 2358.89, "duration": 1.41}, {"text": "It's just that the curve is now\nall these crazy-looking dots.", "start": 2360.3, "duration": 4.26}, {"text": "And you still have that\nsymmetry from the y-axis.", "start": 2364.56, "duration": 4.29}, {"text": "But the way the computer does\nit is all modulo a number.", "start": 2368.85, "duration": 3.21}, {"text": "So it doesn't actually\nmap to a nice curve.", "start": 2372.06, "duration": 5.71}, {"text": "So the fun thing about\nwhen you're doing modulo", "start": 2377.77, "duration": 2.6}, {"text": "is all the properties\nstay the same, right?", "start": 2380.37, "duration": 3.522}, {"text": "With regular numbers,\nyou can still", "start": 2383.892, "duration": 1.458}, {"text": "do addition,\nmultiplication, division", "start": 2385.35, "duration": 2.31}, {"text": "all modulo some number, and\nit still all works, right?", "start": 2387.66, "duration": 3.84}, {"text": "So same with this.", "start": 2391.5, "duration": 2.1}, {"text": "You still have the same\ndraw a line between P and Q,", "start": 2393.6, "duration": 4.2}, {"text": "and you get to here.", "start": 2397.8, "duration": 1.98}, {"text": "And then you flip over the\ny-axis, and now this is R.", "start": 2399.78, "duration": 5.46}, {"text": "Similarly, you can\ntake a tangent--", "start": 2405.24, "duration": 2.43}, {"text": "although a tangent is harder\nto visually see because there's", "start": 2407.67, "duration": 2.94}, {"text": "no obvious curve here--", "start": 2410.61, "duration": 2.34}, {"text": "but the equations work the same.", "start": 2412.95, "duration": 2.15}, {"text": "OK.", "start": 2415.1, "duration": 0.5}, {"text": "So you don't need to know\nexactly why these things work", "start": 2415.6, "duration": 5.26}, {"text": "or curves.", "start": 2420.86, "duration": 0.5}, {"text": "But we're going to go through\nwhat you can do with these", "start": 2421.36, "duration": 3.18}, {"text": "and what properties you have.", "start": 2424.54, "duration": 1.28}, {"text": "OK.", "start": 2425.82, "duration": 0.5}, {"text": "So we've defined these\npoints on a curve", "start": 2426.32, "duration": 4.16}, {"text": "and how this curve works.", "start": 2430.48, "duration": 1.38}, {"text": "And then we also have\nregular old numbers, right?", "start": 2431.86, "duration": 3.66}, {"text": "So what we'll do from now\non is say, like a and b,", "start": 2435.52, "duration": 4.0}, {"text": "our lowercase numbers,\nthese are scalars.", "start": 2439.52, "duration": 2.24}, {"text": "Scalars just means\nregular old numbers.", "start": 2441.76, "duration": 3.12}, {"text": "The uppercase A and B will refer\nto points on the curve, OK?", "start": 2444.88, "duration": 4.43}, {"text": "So from now on, lowercase\nis regular number,", "start": 2449.31, "duration": 2.77}, {"text": "uppercase is point\non this curve,", "start": 2452.08, "duration": 2.07}, {"text": "or point on this mashed-up thing\nthat we still call a curve.", "start": 2454.15, "duration": 4.528}, {"text": "OK.", "start": 2458.678, "duration": 0.832}, {"text": "So I'll go through what\noperations we can do,", "start": 2459.51, "duration": 2.19}, {"text": "and then we can see\nwhat use those have.", "start": 2461.7, "duration": 3.39}, {"text": "So first, scalars.", "start": 2465.09, "duration": 2.1}, {"text": "You can add, subtract,\nmultiply, divide.", "start": 2467.19, "duration": 1.8}, {"text": "You can do whatever\nyou want, right?", "start": 2468.99, "duration": 1.5}, {"text": "These are just regular\nnumbers, like five or 17 or 22.", "start": 2470.49, "duration": 4.37}, {"text": "Everything's OK, right?", "start": 2474.86, "duration": 2.23}, {"text": "Easy.", "start": 2477.09, "duration": 0.69}, {"text": "Everything here is integers.", "start": 2477.78, "duration": 1.167}, {"text": "We're doing modulo\nsome big prime number,", "start": 2478.947, "duration": 2.583}, {"text": "so there's no decimal points.", "start": 2481.53, "duration": 3.068}, {"text": "I think in this class,\nwe'll probably never", "start": 2484.598, "duration": 1.792}, {"text": "have to use floating\npoint, which is great,", "start": 2486.39, "duration": 2.31}, {"text": "because floating point\nalways scares me.", "start": 2488.7, "duration": 3.66}, {"text": "It's also uint.", "start": 2492.36, "duration": 1.35}, {"text": "These are like\nunsigned integers.", "start": 2493.71, "duration": 1.467}, {"text": "You can do it with signed.", "start": 2495.177, "duration": 1.083}, {"text": "But since you're\nmodulo some big number,", "start": 2496.26, "duration": 3.21}, {"text": "it's like unsigned\nnumbers that loop around.", "start": 2499.47, "duration": 2.91}, {"text": "So it's really\nnice for computers.", "start": 2502.38, "duration": 1.53}, {"text": "Computers deal very\nwell with these things.", "start": 2503.91, "duration": 1.5}, {"text": "Computers are good at\nfloating point, as well.", "start": 2505.41, "duration": 1.62}, {"text": "But the thing is,\nin cryptography,", "start": 2507.03, "duration": 1.65}, {"text": "a lot of times floating point\nends up with error, right,", "start": 2508.68, "duration": 2.84}, {"text": "where you're pretty\nclose, but you've", "start": 2511.52, "duration": 3.43}, {"text": "got some fixed amount of\ndecimal places you can store.", "start": 2514.95, "duration": 3.72}, {"text": "Your floating point goes\nout to some precision.", "start": 2518.67, "duration": 2.34}, {"text": "And then error can accumulate.", "start": 2521.01, "duration": 1.47}, {"text": "And in a lot of cryptography,\nyou want zero error, right?", "start": 2522.48, "duration": 3.99}, {"text": "Like in a hash function,\nit's pretty exact.", "start": 2526.47, "duration": 3.03}, {"text": "So a lot of times,\nthe cryptography,", "start": 2529.5, "duration": 2.64}, {"text": "you use integers instead of\nfloating point or rational", "start": 2532.14, "duration": 2.82}, {"text": "numbers.", "start": 2534.96, "duration": 1.15}, {"text": "OK.", "start": 2536.11, "duration": 0.5}, {"text": "So with scalars, these\nare just regular integers,", "start": 2536.61, "duration": 3.99}, {"text": "natural numbers even.", "start": 2540.6, "duration": 1.92}, {"text": "You can do these.", "start": 2542.52, "duration": 0.96}, {"text": "All the operations,\nyou're familiar with.", "start": 2543.48, "duration": 2.46}, {"text": "That's fairly straightforward.", "start": 2545.94, "duration": 2.13}, {"text": "With points.", "start": 2548.07, "duration": 1.23}, {"text": "So you can add and\nsubtract the points, right?", "start": 2549.3, "duration": 3.66}, {"text": "We showed how you\ndo that visually.", "start": 2552.96, "duration": 3.06}, {"text": "And then the equations\nfor it, the computer", "start": 2556.02, "duration": 2.01}, {"text": "can do that pretty quick.", "start": 2558.03, "duration": 1.78}, {"text": "However, this is not defined.", "start": 2559.81, "duration": 1.82}, {"text": "Multiplication and division\nwith two points is undefined.", "start": 2561.63, "duration": 4.69}, {"text": "It's just not clear\nhow you do it.", "start": 2566.32, "duration": 2.722}, {"text": "It's not something in\nthis system, right?", "start": 2569.042, "duration": 1.708}, {"text": "It's a group.", "start": 2570.75, "duration": 0.65}, {"text": "You've got one operation.", "start": 2571.4, "duration": 1.81}, {"text": "You don't have this other one.", "start": 2573.21, "duration": 1.842}, {"text": "So you can add and\nsubtract points,", "start": 2575.052, "duration": 1.458}, {"text": "but you can't multiply them.", "start": 2576.51, "duration": 1.92}, {"text": "Any questions about this?", "start": 2578.43, "duration": 1.39}, {"text": "This is pretty important.", "start": 2579.82, "duration": 3.19}, {"text": "Make sense?", "start": 2583.01, "duration": 0.98}, {"text": "Yes?", "start": 2583.99, "duration": 0.5}, {"text": "AUDIENCE: In the previous case,\nwhen you were adding points,", "start": 2584.49, "duration": 3.61}, {"text": "what is defined as addition?", "start": 2588.1, "duration": 1.28}, {"text": "Are you adding only\nthe y components?", "start": 2589.38, "duration": 3.25}, {"text": "TADGE DRYJA: You use both\nthe x and y-coordinates", "start": 2592.63, "duration": 2.21}, {"text": "to add, right?", "start": 2594.84, "duration": 0.88}, {"text": "So when you're doing\nit in the computer,", "start": 2598.093, "duration": 1.667}, {"text": "you're saying,\nOK, well, what are", "start": 2599.76, "duration": 1.375}, {"text": "the x- and y-coordinates of P?", "start": 2601.135, "duration": 1.53}, {"text": "What are the x- and\ny-coordinates of Q?", "start": 2602.665, "duration": 1.625}, {"text": "Find the slope here and\nwhere it intersects the axis.", "start": 2607.98, "duration": 3.46}, {"text": "And then see where it'll\nintersect the curve", "start": 2611.44, "duration": 2.12}, {"text": "at another point.", "start": 2613.56, "duration": 1.055}, {"text": "AUDIENCE: Addition Is literally\ndefined as compute that point.", "start": 2614.615, "duration": 3.675}, {"text": "It is not a function of adding\nthe x- and y-coordinates.", "start": 2618.29, "duration": 3.11}, {"text": "AUDIENCE: Gotcha.", "start": 2621.4, "duration": 0.83}, {"text": "TADGE DRYJA: Yeah.", "start": 2622.23, "duration": 0.75}, {"text": "Well, I mean-- yeah.", "start": 2622.98, "duration": 2.4}, {"text": "But the equation would be--", "start": 2625.38, "duration": 2.52}, {"text": "since the computer doesn't\nactually look at the curve,", "start": 2627.9, "duration": 2.25}, {"text": "you just say, OK.", "start": 2630.15, "duration": 0.99}, {"text": "Find the Px- and y-coordinate.", "start": 2631.14, "duration": 1.56}, {"text": "Find the Qx- and y-coordinate.", "start": 2632.7, "duration": 1.5}, {"text": "Find the slope, and then\nfind where it intersects,", "start": 2634.2, "duration": 3.21}, {"text": "and then compute for that for R.", "start": 2637.41, "duration": 6.39}, {"text": "OK.", "start": 2643.8, "duration": 0.5}, {"text": "So yeah.", "start": 2644.3, "duration": 1.47}, {"text": "You can add and subtract.", "start": 2645.77, "duration": 1.2}, {"text": "You cannot multiply and\ndivide these points.", "start": 2646.97, "duration": 2.79}, {"text": "Sounds good?", "start": 2649.76, "duration": 0.66}, {"text": "Any other questions?", "start": 2650.42, "duration": 1.25}, {"text": "Yes?", "start": 2651.67, "duration": 0.655}, {"text": "AUDIENCE: How\nwould you subtract?", "start": 2652.325, "duration": 1.375}, {"text": "TADGE DRYJA: Ah.", "start": 2653.7, "duration": 1.29}, {"text": "You just go down, right?", "start": 2654.99, "duration": 3.93}, {"text": "So if I want P minus Q, I\nshould say P plus negative Q.", "start": 2658.92, "duration": 3.96}, {"text": "And negative Q is just right\nhere, right down on the axis.", "start": 2662.88, "duration": 3.15}, {"text": "So I say, OK, I want\nP minus Q. I go here.", "start": 2666.03, "duration": 1.95}, {"text": "Find it.", "start": 2667.98, "duration": 0.75}, {"text": "It's going to be\nup there somewhere.", "start": 2668.73, "duration": 3.19}, {"text": "So yeah.", "start": 2671.92, "duration": 0.5}, {"text": "You just add the\nnegative of the number.", "start": 2672.42, "duration": 4.63}, {"text": "I guess that's another thing.", "start": 2677.05, "duration": 3.42}, {"text": "Minus B-- negative B-- is\nalso an operation I can do.", "start": 2680.47, "duration": 2.85}, {"text": "I can negate something,\nwhich lets me do subtraction.", "start": 2683.32, "duration": 4.288}, {"text": "AUDIENCE: For those of\nyou with math backgrounds,", "start": 2687.608, "duration": 2.042}, {"text": "this is defining\na group operation", "start": 2689.65, "duration": 1.88}, {"text": "on the field of natural\nnumbers, modulo--", "start": 2691.53, "duration": 2.807}, {"text": "TADGE DRYJA: Which is a big one.", "start": 2694.337, "duration": 1.333}, {"text": "AUDIENCE: --and using\nthis elliptic curve.", "start": 2695.67, "duration": 1.28}, {"text": "So this is A. And the\nonly thing that's defined", "start": 2696.95, "duration": 2.39}, {"text": "is addition and subtraction\nand not multiplication.", "start": 2699.34, "duration": 2.3}, {"text": "TADGE DRYJA: Right.", "start": 2701.64, "duration": 1.45}, {"text": "You can do the same\ngroup operations", "start": 2703.09, "duration": 1.83}, {"text": "without using elliptic curves.", "start": 2704.92, "duration": 1.5}, {"text": "And so you can just\ndo exponential modulo", "start": 2706.42, "duration": 2.49}, {"text": "big prime number.", "start": 2708.91, "duration": 1.53}, {"text": "I'm going to use\ncurves because it's", "start": 2710.44, "duration": 1.5}, {"text": "what is used in all\nthe actual systems.", "start": 2711.94, "duration": 3.66}, {"text": "But you can sort of forget about\nthe curve after this, right?", "start": 2715.6, "duration": 3.78}, {"text": "You can say, well, look, we just\nhave these uppercase variables", "start": 2719.38, "duration": 5.76}, {"text": "and these lowercase variables.", "start": 2725.14, "duration": 1.32}, {"text": "And the fact that it's on a\ncurve, we can sort of abstract", "start": 2726.46, "duration": 2.61}, {"text": "away and just know that we\nhave these different types,", "start": 2729.07, "duration": 2.58}, {"text": "essentially.", "start": 2731.65, "duration": 0.81}, {"text": "And when you're in the\ncomputer, you're just like,", "start": 2732.46, "duration": 1.65}, {"text": "yeah, that's a point.", "start": 2734.11, "duration": 0.99}, {"text": "That's a scalar.", "start": 2735.1, "duration": 0.87}, {"text": "Here are the\noperations I can do,", "start": 2735.97, "duration": 1.7}, {"text": "and I just run the functions.", "start": 2737.67, "duration": 2.15}, {"text": "OK.", "start": 2739.82, "duration": 0.5}, {"text": "So the next part, when you\nmix scalars and points,", "start": 2740.32, "duration": 5.76}, {"text": "so mixed operations.", "start": 2746.08, "duration": 1.92}, {"text": "You cannot add a point and an\ninteger or subtract a point", "start": 2748.0, "duration": 6.48}, {"text": "and an integer.", "start": 2754.48, "duration": 0.9}, {"text": "That's not defined, right?", "start": 2755.38, "duration": 1.11}, {"text": "You say, OK, here's\nthis point p minus 7.", "start": 2756.49, "duration": 3.81}, {"text": "Well, does that mean\nmove the x-axis?", "start": 2760.3, "duration": 1.83}, {"text": "Does that mean move the y?", "start": 2762.13, "duration": 1.71}, {"text": "It's not defined.", "start": 2763.84, "duration": 1.48}, {"text": "However, you can do this, right?", "start": 2765.32, "duration": 2.09}, {"text": "You can multiply and divide.", "start": 2767.41, "duration": 2.61}, {"text": "So you can say, well,\nA times 2, well,", "start": 2770.02, "duration": 3.51}, {"text": "you take the tangent, right?", "start": 2773.53, "duration": 1.17}, {"text": "It's just A plus A. Or A times\n7, is we just break it down as", "start": 2774.7, "duration": 4.38}, {"text": "A plus A plus A plus A 17 times.", "start": 2779.08, "duration": 2.64}, {"text": "We can also divide,\nwhich is a little weird", "start": 2781.72, "duration": 1.86}, {"text": "because we have to\nfind the inverse of B", "start": 2783.58, "duration": 4.02}, {"text": "and then multiply by that--", "start": 2787.6, "duration": 2.04}, {"text": "the multiplicative inverse\nof B modulo the order.", "start": 2789.64, "duration": 4.185}, {"text": "But anyway, you can do these.", "start": 2793.825, "duration": 2.133}, {"text": "This is a little\ntrickier because you", "start": 2795.958, "duration": 1.542}, {"text": "have to compute what, like,\nB to the negative 1 is", "start": 2797.5, "duration": 2.31}, {"text": "and multiply by that.", "start": 2799.81, "duration": 1.11}, {"text": "You can do it.", "start": 2800.92, "duration": 0.84}, {"text": "So you can do these things where\nyou have points times scalars.", "start": 2801.76, "duration": 3.708}, {"text": "But you cannot add.", "start": 2805.468, "duration": 0.792}, {"text": "Yeah?", "start": 2806.26, "duration": 0.18}, {"text": "AUDIENCE: So 2A is\nbasically joining", "start": 2806.44, "duration": 1.67}, {"text": "the tangent to A,\n[INAUDIBLE] beginning.", "start": 2808.11, "duration": 2.37}, {"text": "TADGE DRYJA: Yep.", "start": 2810.48, "duration": 0.82}, {"text": "So that was here.", "start": 2811.3, "duration": 2.76}, {"text": "If this is G, this is 2G.", "start": 2814.06, "duration": 1.74}, {"text": "Find the tangent, find the\nintersection, and then negate.", "start": 2815.8, "duration": 4.34}, {"text": "OK.", "start": 2820.14, "duration": 0.5}, {"text": "So you can do that.", "start": 2820.64, "duration": 2.62}, {"text": "That's cool.", "start": 2823.26, "duration": 0.5}, {"text": "You cannot do that.", "start": 2823.76, "duration": 2.46}, {"text": "OK.", "start": 2826.22, "duration": 0.5}, {"text": "So roster of\noperations we can do.", "start": 2826.72, "duration": 3.82}, {"text": "This is it.", "start": 2830.54, "duration": 1.15}, {"text": "And this is sort of,\nif you think of that,", "start": 2831.69, "duration": 1.91}, {"text": "you can do all\nthese cool things.", "start": 2833.6, "duration": 1.81}, {"text": "It's sort of amazing,\nall the crazy things", "start": 2835.41, "duration": 1.85}, {"text": "you can do with just\nthese operations, right?", "start": 2837.26, "duration": 2.43}, {"text": "With regular numbers, you\ncan do whatever you want.", "start": 2839.69, "duration": 2.32}, {"text": "That's obvious.", "start": 2842.01, "duration": 1.37}, {"text": "And with these points, you\ncan add and subtract them.", "start": 2843.38, "duration": 2.88}, {"text": "And when you mix, you\ncan multiply and divide.", "start": 2846.26, "duration": 3.12}, {"text": "And that's it.", "start": 2849.38, "duration": 1.21}, {"text": "OK.", "start": 2850.59, "duration": 0.5}, {"text": "Any questions so far?", "start": 2851.09, "duration": 3.24}, {"text": "You don't have to worry too\nmuch about the curves and all", "start": 2854.33, "duration": 2.945}, {"text": "of the math and stuff.", "start": 2857.275, "duration": 1.105}, {"text": "But you just sort of say,\nOK, here's my toolbox.", "start": 2858.38, "duration": 2.725}, {"text": "Here's what I can do.", "start": 2861.105, "duration": 0.875}, {"text": "OK.", "start": 2864.95, "duration": 0.5}, {"text": "Any questions?", "start": 2865.45, "duration": 0.583}, {"text": "Good?", "start": 2866.033, "duration": 1.337}, {"text": "So now what we can do is we\ncan define a one-way function", "start": 2867.37, "duration": 5.38}, {"text": "sort of like a hash function,\nsort of like multiplying", "start": 2872.75, "duration": 3.24}, {"text": "p times q to get n.", "start": 2875.99, "duration": 3.27}, {"text": "What we will need,\nin addition to this,", "start": 2879.26, "duration": 2.13}, {"text": "is everyone pick some point on\nthe curve, and we call it G.", "start": 2881.39, "duration": 3.78}, {"text": "And it's random.", "start": 2885.17, "duration": 0.96}, {"text": "And we want it to be\nsomewhat verifiably random.", "start": 2886.13, "duration": 2.64}, {"text": "We just all have to\nagree on a point.", "start": 2888.77, "duration": 3.45}, {"text": "And we'll call this\nthe generator point.", "start": 2892.22, "duration": 3.54}, {"text": "Another property is that, since\nit's all modulo, this number,", "start": 2895.76, "duration": 4.53}, {"text": "if B is too big, you'll\nwrap around, right,", "start": 2900.29, "duration": 3.66}, {"text": "because it's all modulo, this n.", "start": 2903.95, "duration": 2.43}, {"text": "So it's called a\ngenerator point because--", "start": 2906.38, "duration": 2.31}, {"text": "and every point on\nthe curve can be one--", "start": 2908.69, "duration": 1.86}, {"text": "if you keep, say,\n2G, 3G, 4G, 5G,", "start": 2910.55, "duration": 3.24}, {"text": "eventually, you'll\nget back to G, right?", "start": 2913.79, "duration": 3.57}, {"text": "It's all finite.", "start": 2917.36, "duration": 3.48}, {"text": "OK so does anyone\nhave an idea, OK,", "start": 2920.84, "duration": 3.24}, {"text": "how would we make some\ncool one-way function", "start": 2924.08, "duration": 3.99}, {"text": "given these operations\nand the fact", "start": 2928.07, "duration": 1.89}, {"text": "that we have an\nagreed-upon point?", "start": 2929.96, "duration": 3.29}, {"text": "It's not super obvious,\nbut it's actually", "start": 2933.25, "duration": 1.89}, {"text": "fairly straightforward.", "start": 2935.14, "duration": 1.71}, {"text": "Once you see it,\nyou're like, oh.", "start": 2936.85, "duration": 1.452}, {"text": "Any ideas?", "start": 2941.02, "duration": 0.51}, {"text": "Yeah.", "start": 2941.53, "duration": 0.18}, {"text": "AUDIENCE: So you\ntake your point G,", "start": 2941.71, "duration": 1.575}, {"text": "and you multiply\nit by some scalar,", "start": 2943.285, "duration": 2.65}, {"text": "and you publish where the\npoint is [INAUDIBLE] scalars.", "start": 2945.935, "duration": 3.615}, {"text": "TADGE DRYJA: Yep, yep.", "start": 2949.55, "duration": 1.71}, {"text": "OK.", "start": 2951.26, "duration": 0.5}, {"text": "So your private key--", "start": 2951.76, "duration": 1.87}, {"text": "let's say private\nkey, lowercase a,", "start": 2953.63, "duration": 2.09}, {"text": "it's just some 256 bit\nrandom number, scalar,", "start": 2955.72, "duration": 3.21}, {"text": "exactly the same as 32 bytes\nlike in a lamport signature.", "start": 2958.93, "duration": 4.56}, {"text": "And your public key\nis just a times G.", "start": 2963.49, "duration": 2.85}, {"text": "And your public key is\nnow a point on a curve.", "start": 2966.34, "duration": 4.47}, {"text": "We're going to call\nit uppercase A.", "start": 2970.81, "duration": 1.47}, {"text": "And you have a 32 byte\nx-coordinate, right--", "start": 2972.28, "duration": 3.06}, {"text": "because the x\ndimension is 256 bits--", "start": 2975.34, "duration": 3.2}, {"text": "32 byte y-coordinate.", "start": 2978.54, "duration": 1.39}, {"text": "So it's 64 bytes--", "start": 2979.93, "duration": 1.32}, {"text": "pretty small.", "start": 2981.25, "duration": 0.9}, {"text": "Anyone have another\nquick optimization", "start": 2982.15, "duration": 3.27}, {"text": "on how you could reduce this?", "start": 2985.42, "duration": 2.1}, {"text": "So there's a lot of\noptimization going on", "start": 2987.52, "duration": 2.91}, {"text": "in all these different\ncryptocurrency systems.", "start": 2990.43, "duration": 1.98}, {"text": "Because they don't\nscale too well.", "start": 2992.41, "duration": 1.417}, {"text": "But any idea of how\nto get that down?", "start": 2993.827, "duration": 4.765}, {"text": "AUDIENCE: Can you hash it?", "start": 2998.592, "duration": 1.64}, {"text": "TADGE DRYJA: You could.", "start": 3000.232, "duration": 0.958}, {"text": "So you could hash it.", "start": 3001.19, "duration": 0.875}, {"text": "You'd make it into 32 bytes.", "start": 3002.065, "duration": 3.395}, {"text": "There's a more useful way.", "start": 3005.46, "duration": 3.428}, {"text": "But if you hash it, you still\nhave to reveal it later, right?", "start": 3008.888, "duration": 2.542}, {"text": "So it helps, making\na pubkey hash.", "start": 3011.43, "duration": 2.76}, {"text": "And that's what\nBitcoin did initially", "start": 3014.19, "duration": 2.45}, {"text": "is you'd have the\n64 byte public keys.", "start": 3016.64, "duration": 3.34}, {"text": "And then you'd send\nto the hash of them.", "start": 3019.98, "duration": 2.34}, {"text": "There's a nicer way.", "start": 3022.32, "duration": 3.18}, {"text": "Any ideas?", "start": 3025.5, "duration": 0.97}, {"text": "OK.", "start": 3026.47, "duration": 0.5}, {"text": "So the thing is it's\nsymmetric, right?", "start": 3026.97, "duration": 4.8}, {"text": "So the curve is symmetric\nabout the x-axis.", "start": 3031.77, "duration": 4.86}, {"text": "Any ideas?", "start": 3039.49, "duration": 1.26}, {"text": "yes.", "start": 3040.75, "duration": 0.63}, {"text": "AUDIENCE: Could you just code\none of the x- or y-coordinates", "start": 3041.38, "duration": 2.5}, {"text": "and say which side?", "start": 3043.88, "duration": 1.068}, {"text": "TADGE DRYJA: Right.", "start": 3044.948, "duration": 0.792}, {"text": "So you take the x-coordinate\nand encode that.", "start": 3045.74, "duration": 3.903}, {"text": "And then just that one bit--", "start": 3049.643, "duration": 1.167}, {"text": "4-- it's on the top.", "start": 3050.81, "duration": 0.98}, {"text": "It's on the bottom.", "start": 3051.79, "duration": 1.24}, {"text": "And then let them figure out\nexactly where it is, right?", "start": 3053.03, "duration": 3.18}, {"text": "So you can encode the\nx-coordinate only and 1 bit", "start": 3056.21, "duration": 2.55}, {"text": "for y, and then you're\ndown to 33 bytes.", "start": 3058.76, "duration": 2.61}, {"text": "It's a little annoying\nbecause the 33 bytes, well,", "start": 3061.37, "duration": 2.46}, {"text": "one of those bytes\nis going to be empty.", "start": 3063.83, "duration": 2.33}, {"text": "It's just going to have one\nbit in it for up or down.", "start": 3066.16, "duration": 2.62}, {"text": "But whatever.", "start": 3068.78, "duration": 1.42}, {"text": "So you can do that, and\nthat's also really cool.", "start": 3070.2, "duration": 3.0}, {"text": "OK.", "start": 3073.2, "duration": 0.86}, {"text": "Any questions so far?", "start": 3074.06, "duration": 3.15}, {"text": "AUDIENCE: Could you encode\na [INAUDIBLE] and same", "start": 3077.21, "duration": 4.1}, {"text": "up and down?", "start": 3081.31, "duration": 0.942}, {"text": "Could you just encode\nan [INAUDIBLE]??", "start": 3082.252, "duration": 1.884}, {"text": "TADGE DRYJA: Huh.", "start": 3084.136, "duration": 1.414}, {"text": "Probably.", "start": 3085.55, "duration": 1.17}, {"text": "But I don't think\nit would be smaller.", "start": 3086.72, "duration": 3.03}, {"text": "I think you'd have to\nprobably have the same size", "start": 3089.75, "duration": 2.16}, {"text": "if you use some other\ncoordinate system.", "start": 3091.91, "duration": 1.667}, {"text": "Hm.", "start": 3096.11, "duration": 1.68}, {"text": "Yeah, you could encode a slope--", "start": 3097.79, "duration": 2.117}, {"text": "AUDIENCE: Yeah, the [INAUDIBLE].", "start": 3099.907, "duration": 1.333}, {"text": "TADGE DRYJA: And you\nsay it intersects,", "start": 3101.24, "duration": 1.625}, {"text": "and it's at the slope, and\nwhich side of the axis?", "start": 3102.865, "duration": 2.095}, {"text": "AUDIENCE: Yeah, and if it\ncrosses multiple times,", "start": 3104.96, "duration": 1.74}, {"text": "which one of the--", "start": 3106.7, "duration": 0.75}, {"text": "TADGE DRYJA: You probably could.", "start": 3107.45, "duration": 0.9}, {"text": "I think you would\nend up the same size.", "start": 3108.35, "duration": 1.82}, {"text": "But yeah.", "start": 3110.17, "duration": 0.545}, {"text": "But it might be faster\nfor some things.", "start": 3110.715, "duration": 1.625}, {"text": "There's all sorts of\ndifferent encodings.", "start": 3112.34, "duration": 2.37}, {"text": "AUDIENCE: I guarantee that you\nhave an integer in the end.", "start": 3114.71, "duration": 3.28}, {"text": "TADGE DRYJA: Yeah.", "start": 3117.99, "duration": 0.805}, {"text": "So you might not\nbe on the curve.", "start": 3118.795, "duration": 1.375}, {"text": "But there's a\nsimilar problem here", "start": 3120.17, "duration": 1.47}, {"text": "where it might not\nbe on the curve.", "start": 3121.64, "duration": 1.68}, {"text": "You can encode a point\nthat's also off the curve.", "start": 3123.32, "duration": 3.04}, {"text": "And so when you actually\nget a public key,", "start": 3126.36, "duration": 2.57}, {"text": "like over the wire\nin these systems,", "start": 3128.93, "duration": 2.585}, {"text": "the first thing\nyou usually do is", "start": 3131.515, "duration": 1.375}, {"text": "make sure this is\na valid public key,", "start": 3132.89, "duration": 1.542}, {"text": "and it's actually on the curve.", "start": 3134.432, "duration": 1.785}, {"text": "Because there's a lot\nof points that aren't.", "start": 3136.217, "duration": 1.833}, {"text": "And sometimes you can screw\naround with the code that way.", "start": 3138.05, "duration": 2.64}, {"text": "Yeah?", "start": 3140.69, "duration": 0.13}, {"text": "AUDIENCE: Can you define the\nscalar multiplication again?", "start": 3140.82, "duration": 2.42}, {"text": "how does it go?", "start": 3143.24, "duration": 0.77}, {"text": "TADGE DRYJA: OK.", "start": 3144.01, "duration": 0.667}, {"text": "So scalar multiplication--\na times G is, basically,", "start": 3144.677, "duration": 4.443}, {"text": "break it out as G plus G\nplus G plus G plus G a times.", "start": 3149.12, "duration": 3.84}, {"text": "And G plus G is find\nthe tangent of G", "start": 3152.96, "duration": 3.93}, {"text": "and then find the\nintersection, right?", "start": 3156.89, "duration": 3.09}, {"text": "So this is G. This is 2G,\nright-- tangent, intersect,", "start": 3159.98, "duration": 4.89}, {"text": "and then the negation.", "start": 3164.87, "duration": 2.07}, {"text": "And so you just do\nthat a bazillion times.", "start": 3166.94, "duration": 3.87}, {"text": "However, since you can\nfind 2G and then you", "start": 3170.81, "duration": 3.09}, {"text": "can double 2G to get 4G\nand double 4G to get 8G,", "start": 3173.9, "duration": 3.42}, {"text": "you can come up with\npowers of 2 of G", "start": 3177.32, "duration": 2.82}, {"text": "and then add those\npowers of 2 to do", "start": 3180.14, "duration": 2.1}, {"text": "a much more efficient addition\nso that you can practically", "start": 3182.24, "duration": 4.41}, {"text": "make--", "start": 3186.65, "duration": 0.92}, {"text": "because little a is going to\nbe some huge decimal 50-digit", "start": 3187.57, "duration": 5.32}, {"text": "number or whatever.", "start": 3192.89, "duration": 1.4}, {"text": "So you're going to have\nto do this two, four, six,", "start": 3194.29, "duration": 3.16}, {"text": "eight binary expansion\nand then add them all up.", "start": 3197.45, "duration": 3.37}, {"text": "OK.", "start": 3200.82, "duration": 1.4}, {"text": "Yeah?", "start": 3202.22, "duration": 2.35}, {"text": "AUDIENCE: You're chucking\neverything into some grain size", "start": 3204.57, "duration": 5.29}, {"text": "to get these.", "start": 3209.86, "duration": 0.94}, {"text": "You're [INAUDIBLE]\na continuous curve.", "start": 3210.8, "duration": 1.842}, {"text": "TADGE DRYJA: Yes.", "start": 3212.642, "duration": 0.708}, {"text": "AUDIENCE: It feels like if you\nhave 306 bits in the original,", "start": 3213.35, "duration": 4.28}, {"text": "you shouldn't be able to get all\nthe way down to 32 bits, right?", "start": 3217.63, "duration": 3.18}, {"text": "Because you just want\nto make sure that you--", "start": 3220.81, "duration": 2.02}, {"text": "TADGE DRYJA: This?", "start": 3222.83, "duration": 0.877}, {"text": "AUDIENCE: Yeah.", "start": 3223.707, "duration": 0.625}, {"text": "If you removed a\nbyte of precision,", "start": 3226.58, "duration": 2.57}, {"text": "would you actually\nbe losing any power?", "start": 3229.15, "duration": 3.49}, {"text": "TADGE DRYJA: What you can do\na little-- what you can do", "start": 3232.64, "duration": 2.94}, {"text": "is you can just\nsay, look, I'm only", "start": 3235.58, "duration": 2.94}, {"text": "going to allow public keys\nthat are on the top, positive y", "start": 3238.52, "duration": 7.62}, {"text": "component.", "start": 3246.14, "duration": 0.93}, {"text": "And everything\nelse is disallowed.", "start": 3247.07, "duration": 2.475}, {"text": "You could have that as\na rule of your system,", "start": 3249.545, "duration": 1.875}, {"text": "and then you can get\nrid of the y bit.", "start": 3251.42, "duration": 3.39}, {"text": "But the thing is\nthe y-coordinate", "start": 3254.81, "duration": 4.62}, {"text": "does affect some of the\nthings like signatures, things", "start": 3259.43, "duration": 3.673}, {"text": "that you'll later use.", "start": 3263.103, "duration": 0.917}, {"text": "So you can just say, OK, look,\nimplicitly y bit is positive.", "start": 3264.02, "duration": 4.56}, {"text": "And you lose 1 bit of security.", "start": 3268.58, "duration": 3.66}, {"text": "Because there is a\ndifference between", "start": 3272.24, "duration": 2.01}, {"text": "the positive and negative\nthing if you're doing signing.", "start": 3274.25, "duration": 3.492}, {"text": "But yeah.", "start": 3277.742, "duration": 0.718}, {"text": "And so some systems do do that.", "start": 3278.46, "duration": 2.49}, {"text": "And it makes things easier.", "start": 3280.95, "duration": 1.39}, {"text": "There's some signing\nsystems that do that.", "start": 3282.34, "duration": 1.84}, {"text": "OK.", "start": 3284.18, "duration": 0.5}, {"text": "I'm going to go\nto the next part.", "start": 3284.68, "duration": 2.31}, {"text": "ECDSA is used in bitcoin.", "start": 3290.69, "duration": 1.92}, {"text": "I'm actually not\ngoing to explain it.", "start": 3292.61, "duration": 3.4}, {"text": "It's a worse signature system.", "start": 3296.01, "duration": 2.39}, {"text": "So the reason why this was\nused was the better system", "start": 3298.4, "duration": 4.02}, {"text": "was patented.", "start": 3302.42, "duration": 2.07}, {"text": "And so there's a clearer, more\nobvious, cleaner, more powerful", "start": 3304.49, "duration": 6.69}, {"text": "signature system that was\npatented by this German guy,", "start": 3311.18, "duration": 3.06}, {"text": "Claus Schnorr.", "start": 3314.24, "duration": 0.93}, {"text": "And so no one used it, or\nmaybe a few people used it.", "start": 3315.17, "duration": 2.49}, {"text": "But in general, with open\nsource things and web standards,", "start": 3317.66, "duration": 4.2}, {"text": "patents are really\nhard to work with.", "start": 3321.86, "duration": 3.73}, {"text": "And so all the\ncryptographers said,", "start": 3325.59, "duration": 1.55}, {"text": "well, we'll make\nthis other system", "start": 3327.14, "duration": 2.22}, {"text": "that's different enough that it\ndoesn't infringe on the patent.", "start": 3329.36, "duration": 3.18}, {"text": "And it's kind of ugly.", "start": 3332.54, "duration": 3.66}, {"text": "It does work as a\nsignature scheme.", "start": 3336.2, "duration": 2.52}, {"text": "But actually, I'm\ngoing to explain", "start": 3338.72, "duration": 2.04}, {"text": "the Schnorr signatures,\nwhich make a lot more sense,", "start": 3340.76, "duration": 5.34}, {"text": "are easier to understand\nand manipulate,", "start": 3346.1, "duration": 2.31}, {"text": "and the patent has expired,\nso we can all use it.", "start": 3348.41, "duration": 2.43}, {"text": "And it will probably\nbe going into Bitcoin.", "start": 3350.84, "duration": 2.94}, {"text": "And some cryptocurrencies\nuse Schnorr signatures.", "start": 3353.78, "duration": 2.71}, {"text": "I think Monero uses a\nSchnorr-like signature.", "start": 3356.49, "duration": 5.69}, {"text": "But Bitcoin will\nprobably be putting it", "start": 3362.18, "duration": 3.3}, {"text": "into Bitcoin in the\nnext year or so.", "start": 3365.48, "duration": 2.65}, {"text": "So all these things will\nbe much more applicable,", "start": 3368.13, "duration": 2.09}, {"text": "and you can use them.", "start": 3370.22, "duration": 1.09}, {"text": "And there's code out.", "start": 3371.31, "duration": 0.875}, {"text": "You can use them now.", "start": 3372.185, "duration": 1.435}, {"text": "OK.", "start": 3373.62, "duration": 0.5}, {"text": "Yeah.", "start": 3374.12, "duration": 0.29}, {"text": "Sorry.", "start": 3374.41, "duration": 0.598}, {"text": "Patent has expired--\nfree to use the better", "start": 3375.008, "duration": 1.792}, {"text": "algo that must not be named.", "start": 3376.8, "duration": 1.55}, {"text": "So yeah.", "start": 3378.35, "duration": 2.002}, {"text": "People don't call it\nSchnorr signature as much.", "start": 3380.352, "duration": 1.958}, {"text": "Because it's like, well, this\nis the guy who prevented us", "start": 3382.31, "duration": 2.49}, {"text": "from using this for 20 years.", "start": 3384.8, "duration": 4.1}, {"text": "And there's modifications to it.", "start": 3388.9, "duration": 2.4}, {"text": "OK.", "start": 3391.3, "duration": 0.5}, {"text": "So the elliptic curve signature,\nfor lack of a better name.", "start": 3391.8, "duration": 4.55}, {"text": "This is something\nof a simplification.", "start": 3396.35, "duration": 2.01}, {"text": "And there's reading\nabout how you can really", "start": 3398.36, "duration": 2.64}, {"text": "do it the right way.", "start": 3401.0, "duration": 0.907}, {"text": "But this does give\nyou the right idea.", "start": 3401.907, "duration": 1.583}, {"text": "And for a single signer,\nthis is secure, and it works.", "start": 3403.49, "duration": 4.68}, {"text": "But later things, you might want\nto actually add other stuff.", "start": 3408.17, "duration": 2.88}, {"text": "So the idea is you've got\nyour message m, right?", "start": 3411.05, "duration": 3.31}, {"text": "Same as in lamport,\nsame as in RSA, you've", "start": 3414.36, "duration": 2.21}, {"text": "got a message m and a\nprivate key lowercase a.", "start": 3416.57, "duration": 3.05}, {"text": "And your public key is\na times G, like we said.", "start": 3419.62, "duration": 4.135}, {"text": "And then, when you want\nto sign, you actually", "start": 3423.755, "duration": 1.875}, {"text": "make a one-time use key\npair for the signature only.", "start": 3425.63, "duration": 4.86}, {"text": "And they usually call that k.", "start": 3430.49, "duration": 2.04}, {"text": "And k is a new random number.", "start": 3432.53, "duration": 3.12}, {"text": "It's the private key.", "start": 3435.65, "duration": 1.5}, {"text": "And you're going to\nmultiply it by G.", "start": 3437.15, "duration": 3.158}, {"text": "And they call this R.\nI don't know why they", "start": 3440.308, "duration": 1.792}, {"text": "use these letters, but anyway.", "start": 3442.1, "duration": 3.36}, {"text": "K times G is R. R is the other\npublic key you're using just", "start": 3445.46, "duration": 5.22}, {"text": "for this signature.", "start": 3450.68, "duration": 3.04}, {"text": "And then the signature itself\nis quite straightforward.", "start": 3453.72, "duration": 3.45}, {"text": "As the signer, you\ncompute s, which is k--", "start": 3457.17, "duration": 3.42}, {"text": "this new private key\nyou just made up--", "start": 3460.59, "duration": 2.16}, {"text": "minus the hash of your\nmessage concatenated with R,", "start": 3462.75, "duration": 4.41}, {"text": "this public key-- so you encode\nthe public key in 33 bytes,", "start": 3467.16, "duration": 2.83}, {"text": "stick it in there--", "start": 3469.99, "duration": 0.92}, {"text": "multiplied by a, your\nnormal private key.", "start": 3470.91, "duration": 4.74}, {"text": "And then your\nsignature is the pair--", "start": 3475.65, "duration": 2.34}, {"text": "the R point and the s scalar.", "start": 3477.99, "duration": 3.0}, {"text": "This is a little bit\nof a bunch to process.", "start": 3480.99, "duration": 2.4}, {"text": "But it's actually\nnot too bad, right?", "start": 3483.39, "duration": 2.76}, {"text": "This is a scalar--", "start": 3486.15, "duration": 0.96}, {"text": "32 bytes-- that you made up.", "start": 3487.11, "duration": 1.38}, {"text": "The hash, this is a message,\nalso going to be however long.", "start": 3488.49, "duration": 5.91}, {"text": "This is 33 bytes.", "start": 3494.4, "duration": 0.948}, {"text": "You concatenate them\ntogether-- hash.", "start": 3495.348, "duration": 1.542}, {"text": "You end up with\nanother 32 byte scalar.", "start": 3496.89, "duration": 3.66}, {"text": "You multiply those two scalars.", "start": 3500.55, "duration": 2.77}, {"text": "So actually, the only\nelliptic curve operation", "start": 3503.32, "duration": 3.44}, {"text": "here is calculating what R is.", "start": 3506.76, "duration": 2.4}, {"text": "When you're actually\ncalculating s,", "start": 3509.16, "duration": 1.65}, {"text": "this is all just scalar,\nso it's very fast.", "start": 3510.81, "duration": 3.03}, {"text": "So in terms of practical\ncomputer stuff,", "start": 3513.84, "duration": 2.25}, {"text": "doing these operations is a\nlittle bit on the slow side.", "start": 3516.09, "duration": 3.63}, {"text": "Because you're doing those\npoint additions quite a number", "start": 3519.72, "duration": 2.55}, {"text": "of times.", "start": 3522.27, "duration": 1.89}, {"text": "So a decent code,\na decent CPU, can", "start": 3524.16, "duration": 3.27}, {"text": "do on the order of thousands\nof these types of operations", "start": 3527.43, "duration": 5.67}, {"text": "per second, which is decent.", "start": 3533.1, "duration": 3.51}, {"text": "You can do a decent amount,\nbut it is kind of slow.", "start": 3536.61, "duration": 2.58}, {"text": "And it's considerably\nslower than hash functions.", "start": 3539.19, "duration": 2.58}, {"text": "You can do a million iterations\nof a hash function per second", "start": 3541.77, "duration": 3.0}, {"text": "on a core, or you can\ndo, maybe, 1,000 or 2,000", "start": 3544.77, "duration": 2.58}, {"text": "of this kind of thing, so\nstill pretty fast but slower.", "start": 3547.35, "duration": 4.63}, {"text": "And so this signing procedure,\nthis takes a bit of time.", "start": 3551.98, "duration": 4.605}, {"text": "This takes, actually,\nvery little time.", "start": 3556.585, "duration": 1.625}, {"text": "Because you're just subtracting\nand multiplying 32 byte scalar", "start": 3558.21, "duration": 4.89}, {"text": "integers, which is much faster.", "start": 3563.1, "duration": 2.71}, {"text": "OK.", "start": 3565.81, "duration": 0.5}, {"text": "So does this make sense?", "start": 3566.31, "duration": 2.99}, {"text": "We'll go a little bit of\nhow you can't forge this.", "start": 3569.3, "duration": 2.45}, {"text": "OK.", "start": 3571.75, "duration": 0.5}, {"text": "Sorry.", "start": 3572.25, "duration": 0.5}, {"text": "So first verification.", "start": 3572.75, "duration": 0.93}, {"text": "Sorry.", "start": 3573.68, "duration": 0.6}, {"text": "So how would you, if\nanyone knows or can think,", "start": 3574.28, "duration": 4.86}, {"text": "how would you\nverify this, right?", "start": 3579.14, "duration": 3.87}, {"text": "I know their public key--", "start": 3583.01, "duration": 1.45}, {"text": "capital A, which is\nlittle a times G--", "start": 3584.46, "duration": 2.96}, {"text": "and then they're\ngiving me a message m,", "start": 3587.42, "duration": 1.92}, {"text": "and they're giving me a\nsignature, which is R and s.", "start": 3589.34, "duration": 2.46}, {"text": "And they've computed\nit this way.", "start": 3591.8, "duration": 2.1}, {"text": "I can't verify this\nequation myself", "start": 3593.9, "duration": 3.12}, {"text": "because I don't know what k is.", "start": 3597.02, "duration": 1.59}, {"text": "I don't know what\nlittle a is, right?", "start": 3598.61, "duration": 1.95}, {"text": "I'm just given R, s, m, and big\nA. So how would I verify this?", "start": 3600.56, "duration": 8.91}, {"text": "AUDIENCE: Can I, for example,\ntake the hash of the message,", "start": 3609.47, "duration": 4.04}, {"text": "use R, and then try\nrandom a's and that--", "start": 3613.51, "duration": 7.614}, {"text": "on, sorry.", "start": 3621.124, "duration": 1.126}, {"text": "TADGE DRYJA: Yeah.", "start": 3622.25, "duration": 0.75}, {"text": "Do you have one?", "start": 3623.0, "duration": 1.35}, {"text": "AUDIENCE: So trying random is\nprobably [INAUDIBLE] because--", "start": 3624.35, "duration": 2.5}, {"text": "TADGE DRYJA:\nThere's a lot, yeah.", "start": 3626.85, "duration": 0.835}, {"text": "AUDIENCE: --there's too many.", "start": 3627.685, "duration": 1.208}, {"text": "The old one that\nyou don't know it.", "start": 3628.893, "duration": 1.657}, {"text": "But I think one more thing\nyou could do is take little s", "start": 3630.55, "duration": 3.36}, {"text": "and multiply it by big G.", "start": 3633.91, "duration": 1.962}, {"text": "TADGE DRYJA: Yes.", "start": 3635.872, "duration": 0.708}, {"text": "AUDIENCE: And then do some--", "start": 3636.58, "duration": 1.07}, {"text": "TADGE DRYJA: Yeah.", "start": 3637.65, "duration": 0.78}, {"text": "So the basic idea--\nyeah, you're right.", "start": 3638.43, "duration": 2.89}, {"text": "Multiply this side\nby G. Then you also", "start": 3641.32, "duration": 2.31}, {"text": "have to multiply the\nother side by G, right?", "start": 3643.63, "duration": 2.7}, {"text": "So you say, OK, well,\nas the verifier--", "start": 3646.33, "duration": 3.84}, {"text": "I've got R, I've got s--", "start": 3650.17, "duration": 1.562}, {"text": "I multiply s by\nG, and now I have", "start": 3651.732, "duration": 1.858}, {"text": "to multiply this side by G.\nAnd what'll that look like?", "start": 3653.59, "duration": 4.21}, {"text": "Well, what's k times G?", "start": 3657.8, "duration": 1.964}, {"text": "AUDIENCE: R.", "start": 3659.764, "duration": 0.5}, {"text": "TADGE DRYJA: R. What's\nlittle a times G?", "start": 3660.264, "duration": 3.226}, {"text": "Big A. So yeah.", "start": 3663.49, "duration": 3.65}, {"text": "I want to verify.", "start": 3667.14, "duration": 1.95}, {"text": "I want to verify that\nthis equation was used,", "start": 3669.09, "duration": 2.4}, {"text": "right-- s equals k minus\nthis hash times little a.", "start": 3671.49, "duration": 3.63}, {"text": "Multiply both sides\nby G, I get s times G", "start": 3675.12, "duration": 2.37}, {"text": "equals k times G minus the\nhash thing times little a times", "start": 3677.49, "duration": 4.17}, {"text": "G. This is big A. This is R.", "start": 3681.66, "duration": 4.41}, {"text": "Hey, now I know everything\nhere as the verifier, right?", "start": 3686.07, "duration": 3.42}, {"text": "I know what s time G is.", "start": 3689.49, "duration": 1.062}, {"text": "I know what R is.", "start": 3690.552, "duration": 0.708}, {"text": "I know what big A is.", "start": 3691.26, "duration": 1.23}, {"text": "I know what's going\ninto this hash function.", "start": 3692.49, "duration": 3.103}, {"text": "And so I just say, OK.", "start": 3695.593, "duration": 0.917}, {"text": "Well, I rearrange it a little,\nand I say, is R equal to this?", "start": 3696.51, "duration": 7.62}, {"text": "And if it is, that's\na good signature.", "start": 3704.13, "duration": 2.22}, {"text": "If it's not, it's\nnot a good signature.", "start": 3706.35, "duration": 4.27}, {"text": "Any questions about this?", "start": 3710.62, "duration": 1.28}, {"text": "Does this makes sense, mostly?", "start": 3711.9, "duration": 4.95}, {"text": "So for the verification, it's\na bit more CPU-intense, right?", "start": 3719.85, "duration": 4.77}, {"text": "You're given a scalar.", "start": 3724.62, "duration": 1.41}, {"text": "You multiply by G. You\nalso have to multiply A--", "start": 3726.03, "duration": 7.24}, {"text": "this is actually more costly--", "start": 3733.27, "duration": 1.45}, {"text": "you have to multiply\nA by this hash.", "start": 3734.72, "duration": 2.15}, {"text": "The reason that's\nmore costly-- it's", "start": 3736.87, "duration": 1.5}, {"text": "still a scalar times a point.", "start": 3738.37, "duration": 2.29}, {"text": "The thing is, since G is\nused for multiplying a lot,", "start": 3740.66, "duration": 4.4}, {"text": "you precompute all sorts\nof coefficients times G,", "start": 3745.06, "duration": 4.65}, {"text": "and you store them in RAM\nor in your CPU somewhere.", "start": 3749.71, "duration": 4.88}, {"text": "So multiplying by G\nis a little bit faster", "start": 3754.59, "duration": 1.78}, {"text": "because you do it a lot,\nyou can precompute a lot,", "start": 3756.37, "duration": 2.25}, {"text": "whereas multiplying by A is\ndifferent each time for all", "start": 3758.62, "duration": 2.55}, {"text": "the different signatures.", "start": 3761.17, "duration": 1.44}, {"text": "So this is a little\nbit slower, in general.", "start": 3762.61, "duration": 2.73}, {"text": "So it takes a little\nbit more CPU time", "start": 3765.34, "duration": 2.85}, {"text": "to verify a signature\nthan to create one,", "start": 3768.19, "duration": 3.63}, {"text": "something like twice as much.", "start": 3771.82, "duration": 1.84}, {"text": "But still, you can\ndo this pretty fast.", "start": 3773.66, "duration": 2.03}, {"text": "On a modern computer, you can\ndo thousands of these a second.", "start": 3775.69, "duration": 3.31}, {"text": "OK.", "start": 3779.0, "duration": 0.5}, {"text": "Any questions so far?", "start": 3779.5, "duration": 1.68}, {"text": "I'll go a little bit into why\nthis is not forgible, right?", "start": 3781.18, "duration": 4.62}, {"text": "So I want to forge a signature.", "start": 3785.8, "duration": 3.42}, {"text": "Well, I don't know little a.", "start": 3789.22, "duration": 5.76}, {"text": "But why don't I make up\na k and compute s and R?", "start": 3794.98, "duration": 3.45}, {"text": "But I need a, right?", "start": 3798.43, "duration": 2.04}, {"text": "So I'm going to say, OK,\nthis is the equation I want.", "start": 3800.47, "duration": 2.67}, {"text": "I'll just make up my own\nk and make up my own k, s,", "start": 3803.14, "duration": 4.98}, {"text": "that'll satisfy this.", "start": 3808.12, "duration": 2.88}, {"text": "Without a, I really can't\nmake a valid s, right?", "start": 3811.0, "duration": 2.67}, {"text": "I can make something up here.", "start": 3813.67, "duration": 1.275}, {"text": "But I can't compute it because\nI don't know here, right?", "start": 3818.41, "duration": 3.99}, {"text": "I can try to grind through hash\nfunctions, but it won't work.", "start": 3822.4, "duration": 2.86}, {"text": "The basic problem\nis if I make up an s", "start": 3825.26, "duration": 2.78}, {"text": "and solve for R, right--", "start": 3828.04, "duration": 2.82}, {"text": "I can say, well,\nI know what R is--", "start": 3830.86, "duration": 1.92}, {"text": "but the thing is R is in\nthe hash function, as well.", "start": 3832.78, "duration": 3.633}, {"text": "It's the one-wayness of\nthe hash function that", "start": 3836.413, "duration": 1.917}, {"text": "actually breaks this, right?", "start": 3838.33, "duration": 2.812}, {"text": "So I could say, well,\nlet me solve for R. Well,", "start": 3841.142, "duration": 1.958}, {"text": "R is the hash of m and R\ntimes a plus s times G.", "start": 3843.1, "duration": 7.61}, {"text": "If I can come up with a\nvalid R here, I can do this.", "start": 3850.71, "duration": 3.27}, {"text": "The problem is R is defined\nby the hash of R in this case.", "start": 3853.98, "duration": 5.67}, {"text": "I can't compute this, and I\ncan't cancel this out, right?", "start": 3859.65, "duration": 2.98}, {"text": "So you can see just like, OK,\nI need to solve for R. Well,", "start": 3862.63, "duration": 3.29}, {"text": "but it's already in here.", "start": 3865.92, "duration": 1.53}, {"text": "I'm stuck.", "start": 3867.45, "duration": 0.99}, {"text": "If I don't know k, I can't come\nup with a signature, either.", "start": 3868.44, "duration": 4.04}, {"text": "OK.", "start": 3877.11, "duration": 0.5}, {"text": "There is one footgun\nwith EC signatures.", "start": 3877.61, "duration": 3.33}, {"text": "If you use the same R value\nfor different signatures", "start": 3880.94, "duration": 5.22}, {"text": "with the same pubkey, you\nreveal your private key.", "start": 3886.16, "duration": 3.97}, {"text": "So k has to be random\nand new every time.", "start": 3890.13, "duration": 3.29}, {"text": "If you look through\nthe equation,", "start": 3896.515, "duration": 1.375}, {"text": "you'll see how you can solve--", "start": 3897.89, "duration": 1.815}, {"text": "if you have two of the same\nk's with different s's--", "start": 3899.705, "duration": 5.445}, {"text": "you can solve for k.", "start": 3905.15, "duration": 1.62}, {"text": "And then, once you\nsolve for k given", "start": 3906.77, "duration": 5.14}, {"text": "this, if you know\nwhat k is, you can", "start": 3911.91, "duration": 3.12}, {"text": "find what little a is,\nright, as a verifier.", "start": 3915.03, "duration": 2.37}, {"text": "You can say, well,\nyou gave me s.", "start": 3917.4, "duration": 2.28}, {"text": "That's part of the signature.", "start": 3919.68, "duration": 1.41}, {"text": "I know this whole coefficient.", "start": 3921.09, "duration": 2.67}, {"text": "If I know k, I can solve for\nlittle a by dividing this out.", "start": 3923.76, "duration": 3.65}, {"text": "So always use a new k value.", "start": 3927.41, "duration": 1.81}, {"text": "There have been many\ncases where people don't.", "start": 3929.22, "duration": 2.76}, {"text": "Probably the most famous one\nis PlayStation 3 used ECDSA.", "start": 3931.98, "duration": 5.04}, {"text": "And they used a fixed k value\nfor signing all their code.", "start": 3937.02, "duration": 3.45}, {"text": "And that allowed people to\ncalculate their private keys", "start": 3940.47, "duration": 2.85}, {"text": "and then run pirated games.", "start": 3943.32, "duration": 2.55}, {"text": "That was actually\nthe first time I", "start": 3945.87, "duration": 1.53}, {"text": "learned about elliptic\ncurve signatures,", "start": 3947.4, "duration": 2.194}, {"text": "in 2010 or something.", "start": 3949.594, "duration": 4.076}, {"text": "So actually, there's\ninteresting tutorials", "start": 3953.67, "duration": 2.13}, {"text": "written by the hackers who\nbroke Playstation 3 about how", "start": 3955.8, "duration": 3.03}, {"text": "this works.", "start": 3958.83, "duration": 0.76}, {"text": "And that's when I\nfirst read about it.", "start": 3959.59, "duration": 2.91}, {"text": "OK.", "start": 3962.5, "duration": 0.5}, {"text": "We're almost out of time.", "start": 3963.0, "duration": 3.37}, {"text": "Any questions about\nthis stuff so far?", "start": 3966.37, "duration": 3.72}, {"text": "OK.", "start": 3970.09, "duration": 1.25}, {"text": "So this is a\nsignature algorithm.", "start": 3971.34, "duration": 4.447}, {"text": "It's like, OK, fine.", "start": 3975.787, "duration": 0.833}, {"text": "This works.", "start": 3976.62, "duration": 0.51}, {"text": "I can sign, same as lamport\nsignatures, same as RSA.", "start": 3977.13, "duration": 3.33}, {"text": "What's really nice about\nthe elliptic curve stuff", "start": 3980.46, "duration": 2.07}, {"text": "is you can do more\nthan just signatures.", "start": 3982.53, "duration": 4.05}, {"text": "There's all sorts of\nfun things you can do.", "start": 3986.58, "duration": 2.31}, {"text": "And it seems like a\nfairly unexplored area", "start": 3988.89, "duration": 2.49}, {"text": "in that I've found\nfun things that you", "start": 3991.38, "duration": 3.06}, {"text": "can do that I guess are novel.", "start": 3994.44, "duration": 2.25}, {"text": "And I'm not an expert\non this at all.", "start": 3996.69, "duration": 1.92}, {"text": "It's just that it's a\nfairly new area of research", "start": 3998.61, "duration": 2.19}, {"text": "in how to do cool\nbitcoiny cryptocurrency", "start": 4000.8, "duration": 3.12}, {"text": "things with these curves\nand points and stuff.", "start": 4003.92, "duration": 2.37}, {"text": "So I'll go through a couple\nfun things you can do.", "start": 4006.29, "duration": 5.61}, {"text": "Fun with points.", "start": 4011.9, "duration": 1.18}, {"text": "OK.", "start": 4013.08, "duration": 0.5}, {"text": "So I'm not using an asterisk.", "start": 4013.58, "duration": 2.07}, {"text": "Just b times G.\nSo let's say Alice", "start": 4015.65, "duration": 4.23}, {"text": "has a public key A. Bob\nhas a public key B, right,", "start": 4019.88, "duration": 4.74}, {"text": "which is little a times G\nor little b times G. Well,", "start": 4024.62, "duration": 4.68}, {"text": "this is weird.", "start": 4029.3, "duration": 1.17}, {"text": "Little a times big B--", "start": 4030.47, "duration": 2.5}, {"text": "Alice's private key multiplied\nby Bob's public key--", "start": 4032.97, "duration": 3.32}, {"text": "you can do that, right?--", "start": 4036.29, "duration": 2.19}, {"text": "is equal to Bob's private\nkey times Alice's public", "start": 4038.48, "duration": 3.37}, {"text": "key, right?", "start": 4041.85, "duration": 1.74}, {"text": "It's commutative.", "start": 4043.59, "duration": 0.72}, {"text": "The multiplication\nis commutative.", "start": 4044.31, "duration": 1.55}, {"text": "That's weird, right?", "start": 4045.86, "duration": 1.17}, {"text": "It's just a times G times\nb, which is the same--", "start": 4047.03, "duration": 3.438}, {"text": "or it doesn't matter\nthe order-- it's", "start": 4050.468, "duration": 1.542}, {"text": "the same as b times G times a,\nwhich is the same as a times", "start": 4052.01, "duration": 4.35}, {"text": "b times G. And let's\ncall that C. C-- this", "start": 4056.36, "duration": 3.96}, {"text": "is called a Diffie-Hellman\nkey exchange point.", "start": 4060.32, "duration": 2.63}, {"text": "Diffie and Hellman are two also\nlate-'70s PhD students who came", "start": 4062.95, "duration": 4.6}, {"text": "up with all this cool stuff.", "start": 4067.55, "duration": 1.92}, {"text": "No, wait.", "start": 4069.47, "duration": 1.438}, {"text": "Diffie was a PhD student.", "start": 4070.908, "duration": 1.042}, {"text": "Hellman was his advisor?", "start": 4071.95, "duration": 1.0}, {"text": "I don't remember.", "start": 4072.95, "duration": 1.02}, {"text": "Anyway, they came\nup with this idea.", "start": 4073.97, "duration": 3.57}, {"text": "And this is a shared point.", "start": 4077.54, "duration": 1.8}, {"text": "What would this be useful for?", "start": 4079.34, "duration": 3.11}, {"text": "It's actually super useful.", "start": 4082.45, "duration": 1.62}, {"text": "Can you think of like, oh, OK.", "start": 4084.07, "duration": 1.415}, {"text": "We can do this.", "start": 4085.485, "duration": 0.625}, {"text": "We can compute C. Why\nwould we want to do that?", "start": 4086.11, "duration": 3.06}, {"text": "Any applications\nyou can think of?", "start": 4089.17, "duration": 2.276}, {"text": "Yeah?", "start": 4091.446, "duration": 0.956}, {"text": "AUDIENCE: Trying to share\nkeys with people without both", "start": 4092.402, "duration": 2.868}, {"text": "of them knowing who\nthey are and evaluating", "start": 4095.27, "duration": 1.912}, {"text": "the other set of keys.", "start": 4097.182, "duration": 1.482}, {"text": "TADGE DRYJA: Yeah.", "start": 4098.664, "duration": 0.75}, {"text": "It's really cool to share keys.", "start": 4099.414, "duration": 2.565}, {"text": "So this is also done if\nyou have a web browser.", "start": 4101.979, "duration": 3.63}, {"text": "I think it's all elliptic curve\nDiffie-Hellman now, mostly.", "start": 4105.609, "duration": 2.851}, {"text": "But if you have a web browser\nand you go to a website,", "start": 4108.46, "duration": 2.28}, {"text": "this is happening, basically,\nfor every HTTPS request.", "start": 4110.74, "duration": 4.56}, {"text": "Because you can\nuse C as a sort of", "start": 4115.3, "duration": 2.25}, {"text": "shared key and encrypt\nthings with it.", "start": 4117.55, "duration": 4.2}, {"text": "The idea is big A can be public.", "start": 4121.75, "duration": 3.87}, {"text": "Big B can be public.", "start": 4125.62, "duration": 2.909}, {"text": "Point C will not be public.", "start": 4128.529, "duration": 1.801}, {"text": "The only way to\ncompute it is to know", "start": 4130.33, "duration": 1.8}, {"text": "either Alice's private\nkey-- little a--", "start": 4132.13, "duration": 2.849}, {"text": "or Bob's private key, little b.", "start": 4134.979, "duration": 3.811}, {"text": "Even though you can\nsee the public keys,", "start": 4138.79, "duration": 3.48}, {"text": "you can't compute C from\njust the public keys, right?", "start": 4142.27, "duration": 4.2}, {"text": "Because big A times big\nB, that's not defined.", "start": 4146.47, "duration": 5.759}, {"text": "You can't multiply the points.", "start": 4152.229, "duration": 1.681}, {"text": "You have to multiply\nthe point by a scalar.", "start": 4153.91, "duration": 2.76}, {"text": "And since you don't\nknow the scalars", "start": 4156.67, "duration": 1.59}, {"text": "from viewing this\nexchange, you can't", "start": 4158.26, "duration": 2.19}, {"text": "compute C. But Alice and\nBob can both compute C.", "start": 4160.45, "duration": 3.36}, {"text": "So this is really useful.", "start": 4163.81, "duration": 1.9}, {"text": "You can compute C. You\ncan use it for encryption.", "start": 4165.71, "duration": 4.519}, {"text": "You can use it to prove you\nare who you say you are.", "start": 4170.229, "duration": 3.09}, {"text": "You can use it as an\ninteractive verification", "start": 4173.319, "duration": 2.881}, {"text": "where you say, OK, I'm Bob.", "start": 4176.2, "duration": 2.1}, {"text": "I'm going to make random point.", "start": 4178.3, "duration": 3.38}, {"text": "I'm going to give that to you.", "start": 4181.68, "duration": 1.25}, {"text": "Prove you know your\nprivate key-- little a--", "start": 4182.93, "duration": 3.75}, {"text": "by telling me what C is, right?", "start": 4186.68, "duration": 3.759}, {"text": "So I can make a random\nkey here, give it to you.", "start": 4190.439, "duration": 4.441}, {"text": "You return C. I verify that\nthat's the right C. And I say,", "start": 4194.88, "duration": 3.46}, {"text": "OK, well you must know little a.", "start": 4198.34, "duration": 2.12}, {"text": "You haven't shown me\na little a, but you've", "start": 4200.46, "duration": 2.64}, {"text": "proven that you know it,\nso proof of knowledge", "start": 4203.1, "duration": 2.16}, {"text": "of the private key.", "start": 4205.26, "duration": 1.42}, {"text": "So you can use that for\nlogins instead of passwords.", "start": 4206.68, "duration": 4.32}, {"text": "And it's much simpler\nthan a signature.", "start": 4211.0, "duration": 2.28}, {"text": "So that's really cool.", "start": 4213.28, "duration": 2.9}, {"text": "All sorts of things\nyou can do with that.", "start": 4216.18, "duration": 1.74}, {"text": "The last part, you can\nhave fun with points.", "start": 4217.92, "duration": 2.07}, {"text": "And I use this in my software.", "start": 4219.99, "duration": 2.7}, {"text": "So you say, OK, well,\nthere's a public key A.", "start": 4222.69, "duration": 2.4}, {"text": "There's a public\nkey B. And we'll", "start": 4225.09, "duration": 2.34}, {"text": "define D as the sum of\nthese two public keys.", "start": 4227.43, "duration": 5.16}, {"text": "The thing is if you're\nsumming these two public keys,", "start": 4232.59, "duration": 2.52}, {"text": "it's commutative,\nand it is the same", "start": 4235.11, "duration": 1.71}, {"text": "as saying the sum of the two\nprivate keys times G, right?", "start": 4236.82, "duration": 5.07}, {"text": "a times G plus b times\nG is the same as a plus", "start": 4241.89, "duration": 4.02}, {"text": "b times G, which is another\nreally cool property.", "start": 4245.91, "duration": 4.74}, {"text": "So what if I compute\nthis public key D,", "start": 4250.65, "duration": 3.66}, {"text": "and I say I want a\nsignature from public key D?", "start": 4254.31, "duration": 5.1}, {"text": "You can.", "start": 4259.41, "duration": 0.72}, {"text": "And you so the\nprivate key, little d,", "start": 4260.13, "duration": 1.77}, {"text": "which can sign for this, is\njust little a plus little b.", "start": 4261.9, "duration": 5.16}, {"text": "So you can make a combined key.", "start": 4267.06, "duration": 2.132}, {"text": "And then either party--", "start": 4269.192, "duration": 0.958}, {"text": "Alice has little a,\nBob has a little b--", "start": 4270.15, "duration": 4.11}, {"text": "and they could reveal\nit to each other", "start": 4274.26, "duration": 1.74}, {"text": "and allow the other person to\nmake a signature with D later.", "start": 4276.0, "duration": 3.75}, {"text": "I use this in the lightning\nnetwork software I've had,", "start": 4284.4, "duration": 2.61}, {"text": "where, basically, you say,\nlook, we'll compute D,", "start": 4287.01, "duration": 3.66}, {"text": "and I can give you the\nprivate key, right?", "start": 4290.67, "duration": 5.48}, {"text": "I'm Bob.", "start": 4296.15, "duration": 0.6}, {"text": "And I say, OK, here's point b.", "start": 4296.75, "duration": 2.58}, {"text": "Here's point a.", "start": 4299.33, "duration": 0.94}, {"text": "We add them together.", "start": 4300.27, "duration": 1.43}, {"text": "And then, Alice, if I give\nyou my private key, now", "start": 4301.7, "duration": 3.33}, {"text": "you can sign, but\nI can't, right?", "start": 4305.03, "duration": 2.52}, {"text": "So I'll give you\nthe private key to D", "start": 4307.55, "duration": 3.06}, {"text": "from some information I have.", "start": 4310.61, "duration": 1.56}, {"text": "Or you could give me\nthe private key to D", "start": 4312.17, "duration": 1.86}, {"text": "by sharing little a with me.", "start": 4314.03, "duration": 2.34}, {"text": "So this is another\nuseful thing where", "start": 4316.37, "duration": 1.65}, {"text": "you can have something\nwhere both parties know", "start": 4318.02, "duration": 2.13}, {"text": "that neither party can\nsign unless they give them", "start": 4320.15, "duration": 2.97}, {"text": "something.", "start": 4323.12, "duration": 1.99}, {"text": "And you can use that for bitcoin\naddresses, things like that.", "start": 4325.11, "duration": 4.34}, {"text": "Before you even\nget to signatures,", "start": 4329.45, "duration": 2.16}, {"text": "you can share keys and stuff.", "start": 4331.61, "duration": 1.39}, {"text": "There's all sorts\nof super fun things", "start": 4333.0, "duration": 2.39}, {"text": "you can do with these points\nand curves and systems.", "start": 4335.39, "duration": 3.3}, {"text": "Multisignatures-- I put\na link to a PDF file", "start": 4338.69, "duration": 4.17}, {"text": "that's very recent and kind\nof overkill and over my head,", "start": 4342.86, "duration": 3.9}, {"text": "as well.", "start": 4346.76, "duration": 1.77}, {"text": "But you can do signatures where\nyou aggregate the signatures.", "start": 4348.53, "duration": 3.07}, {"text": "But", "start": 4351.6, "duration": 0.5}, {"text": "There's ways to\nsay, OK, well, I'm", "start": 4352.1, "duration": 2.233}, {"text": "going to add all these\nR points, and I'm", "start": 4354.333, "duration": 1.667}, {"text": "going to add all these s points.", "start": 4356.0, "duration": 1.333}, {"text": "And I can have\nsignatures that are", "start": 4357.333, "duration": 2.567}, {"text": "from a bunch of\ndifferent people that", "start": 4359.9, "duration": 1.92}, {"text": "collapse into the same\nsize as a single signature.", "start": 4361.82, "duration": 3.12}, {"text": "And I can verify that they're\nall signing the same thing", "start": 4364.94, "duration": 2.55}, {"text": "or, possibly, that they're\nall signing different things.", "start": 4367.49, "duration": 2.37}, {"text": "So I have 10\ndifferent signatures", "start": 4369.86, "duration": 2.55}, {"text": "from different people\nsigning different messages.", "start": 4372.41, "duration": 2.85}, {"text": "But I can add up\nall the s values.", "start": 4375.26, "duration": 1.96}, {"text": "I have to keep the R values.", "start": 4377.22, "duration": 1.22}, {"text": "But now these 10 signatures,\ninstead of being 64 bytes", "start": 4378.44, "duration": 3.27}, {"text": "each are more like\n32 bites each.", "start": 4381.71, "duration": 2.13}, {"text": "And there's one extra 32\nbyte value for all of them.", "start": 4383.84, "duration": 3.52}, {"text": "So there's a lot\nof really cool ways", "start": 4387.36, "duration": 1.61}, {"text": "you can combine things,\nmake things smaller,", "start": 4388.97, "duration": 3.36}, {"text": "make things really versatile,\nwhere we can share keys,", "start": 4392.33, "duration": 2.59}, {"text": "things like that,\nwhich you can't", "start": 4394.92, "duration": 2.33}, {"text": "do with hash-based\nsignatures, hash functions.", "start": 4397.25, "duration": 3.42}, {"text": "And so it's really fun.", "start": 4400.67, "duration": 1.5}, {"text": "One worry is that if\nquantum computers ever", "start": 4402.17, "duration": 2.07}, {"text": "become really a thing, all\nthis stuff stops working.", "start": 4404.24, "duration": 2.61}, {"text": "All the elliptic curve\nstuff doesn't work anymore.", "start": 4406.85, "duration": 2.22}, {"text": "You can figure out what\npeople's private keys are,", "start": 4409.07, "duration": 2.88}, {"text": "whereas hash stuff, hash\nthings like lamport signatures,", "start": 4411.95, "duration": 2.37}, {"text": "still work.", "start": 4414.32, "duration": 1.74}, {"text": "So there's some talk\nof hey, we should", "start": 4416.06, "duration": 2.4}, {"text": "prepare for if that ever happens\nand make efficient, effective", "start": 4418.46, "duration": 3.9}, {"text": "hash-based signatures\nand use them", "start": 4422.36, "duration": 2.16}, {"text": "in something like\nBitcoin or Ethereum.", "start": 4424.52, "duration": 2.088}, {"text": "People haven't yet because\nthe overhead is really high.", "start": 4426.608, "duration": 2.292}, {"text": "It's really big.", "start": 4428.9, "duration": 2.04}, {"text": "The real thing is\nall these fun things", "start": 4430.94, "duration": 1.77}, {"text": "might disappear in\nthe next 10, 20 years.", "start": 4432.71, "duration": 2.56}, {"text": "Who knows?", "start": 4435.27, "duration": 0.5}, {"text": "But there's lots of cool stuff.", "start": 4435.77, "duration": 1.11}, {"text": "What do we do with this?", "start": 4436.88, "duration": 1.0}, {"text": "So we're not going\nto do anything yet", "start": 4437.88, "duration": 1.88}, {"text": "in terms of problem sets.", "start": 4439.76, "duration": 1.59}, {"text": "It's a little hard to\nprogram it directly.", "start": 4441.35, "duration": 2.19}, {"text": "But there's libraries.", "start": 4443.54, "duration": 1.19}, {"text": "And the libraries\nhave fairly easy use,", "start": 4444.73, "duration": 1.625}, {"text": "where it's multiply\nby G is a function,", "start": 4446.355, "duration": 2.625}, {"text": "and multiply by this\npoint is a function.", "start": 4448.98, "duration": 2.16}, {"text": "So this is groundwork for\ncool stuff you can do.", "start": 4451.14, "duration": 2.0}, {"text": "And it's really nice\nbecause it's a new area.", "start": 4453.14, "duration": 2.28}, {"text": "And I'm not an expert on this,\nbut I've come up with stuff", "start": 4455.42, "duration": 3.15}, {"text": "that people have cited me on.", "start": 4458.57, "duration": 2.07}, {"text": "And they're like, yeah, I guess\nno one thought of that before.", "start": 4460.64, "duration": 2.71}, {"text": "There's a lot of things.", "start": 4463.35, "duration": 1.89}, {"text": "There's one very\nrecent one called", "start": 4465.24, "duration": 1.52}, {"text": "Taproot, where it's one line.", "start": 4466.76, "duration": 1.693}, {"text": "You're like, oh, yeah.", "start": 4468.453, "duration": 0.917}, {"text": "That works.", "start": 4469.37, "duration": 1.38}, {"text": "And it's just these sort of\nelliptic curve operations.", "start": 4470.75, "duration": 3.18}, {"text": "It's like, yeah, that works.", "start": 4473.93, "duration": 1.29}, {"text": "That's really useful.", "start": 4475.22, "duration": 1.132}, {"text": "How did no one think of that?", "start": 4476.352, "duration": 1.208}, {"text": "It's one line.", "start": 4477.56, "duration": 0.81}, {"text": "Wow.", "start": 4478.37, "duration": 0.81}, {"text": "So there's just\nnot a ton of people", "start": 4479.18, "duration": 1.14}, {"text": "working on this kind of stuff.", "start": 4480.32, "duration": 1.25}, {"text": "And so it's kind of fun.", "start": 4481.57, "duration": 1.92}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 1.01, "duration": 2.34}, {"text": "Commons license.", "start": 3.35, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.74, "duration": 2.21}, {"text": "continue to offer high quality\neducational resources for free.", "start": 6.95, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 11.04, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.61, "duration": 3.96}, {"text": "at ocw.mit.edu.", "start": 17.57, "duration": 0.893}, {"text": "GARY GENSLER: I\njust want to say how", "start": 23.471, "duration": 2.019}, {"text": "touched I am that you\nare all still here.", "start": 25.49, "duration": 3.39}, {"text": "I really-- you know, there's a\nlot of shopping opportunities", "start": 28.88, "duration": 4.05}, {"text": "in the MIT courses.", "start": 32.93, "duration": 4.71}, {"text": "And that you have come\nback and not shaken", "start": 37.64, "duration": 3.33}, {"text": "loose after reading\nSatoshi Nakamoto's", "start": 40.97, "duration": 4.83}, {"text": "peer-to-peer Bitcoin paper,\nor maybe you just came back", "start": 45.8, "duration": 5.88}, {"text": "to see whether I was going to\ncrash and burn describing it.", "start": 51.68, "duration": 4.99}, {"text": "But what we're going to try to\ndo in the next three classes,", "start": 56.67, "duration": 4.28}, {"text": "just to frame it,\nis really give you", "start": 60.95, "duration": 2.46}, {"text": "some of the technical\nunderpinnings", "start": 63.41, "duration": 3.3}, {"text": "of blockchain technology\nthrough the lens of Bitcoin.", "start": 66.71, "duration": 3.75}, {"text": "Bitcoin is just the first use\ncase of blockchain technology.", "start": 70.46, "duration": 5.56}, {"text": "So if I often say Bitcoin\nthis or Bitcoin that,", "start": 76.02, "duration": 3.35}, {"text": "it's really largely--", "start": 79.37, "duration": 1.68}, {"text": "not entirely--\nlargely applicable", "start": 81.05, "duration": 2.19}, {"text": "to blockchain technology.", "start": 83.24, "duration": 2.28}, {"text": "My feeling is I'm only about\neight or nine months ahead", "start": 85.52, "duration": 3.39}, {"text": "of all of you.", "start": 88.91, "duration": 1.08}, {"text": "I may have spent my\nwhole professional life", "start": 89.99, "duration": 3.0}, {"text": "around finance and\npublic service,", "start": 92.99, "duration": 3.27}, {"text": "and I can talk a lot\nabout markets and about", "start": 96.26, "duration": 2.88}, {"text": "public policy, but\nMIT has given me", "start": 99.14, "duration": 3.12}, {"text": "the gift of thinking about\nblockchain technology.", "start": 102.26, "duration": 4.23}, {"text": "And I'm trying to return that\ngift a little bit for you all.", "start": 106.49, "duration": 3.92}, {"text": "And I have a few\ncomputer scientists", "start": 110.41, "duration": 1.72}, {"text": "in the room that are\ngoing to bail me out", "start": 112.13, "duration": 1.71}, {"text": "if I don't get this right.", "start": 113.84, "duration": 1.83}, {"text": "Sabrina, and then, oh, I\nsee Alin is putting up his--", "start": 115.67, "duration": 3.955}, {"text": "do you all know Alin?", "start": 119.625, "duration": 0.875}, {"text": "He's actually a PhD student\nat MIT, computer science.", "start": 120.5, "duration": 3.72}, {"text": "So somebody gets to that\npart of their life--", "start": 124.22, "duration": 5.124}, {"text": "AUDIENCE: Terrible life choice.", "start": 129.344, "duration": 1.292}, {"text": "GARY GENSLER: Yeah, yeah.", "start": 130.636, "duration": 1.714}, {"text": "What was that?", "start": 132.35, "duration": 0.828}, {"text": "AUDIENCE: Terrible life choice.", "start": 133.178, "duration": 1.292}, {"text": "GARY GENSLER:\nTerrible life choice.", "start": 134.47, "duration": 1.84}, {"text": "Yeah.", "start": 136.31, "duration": 2.02}, {"text": "But he's going to\nbail us all out.", "start": 138.33, "duration": 2.18}, {"text": "But the reason that I think it's\nrelevant not to just belabor", "start": 140.51, "duration": 5.055}, {"text": "it, is I really believe\nthe only way that any of us", "start": 145.565, "duration": 3.675}, {"text": "can get to ground truths is\nto know a little bit about how", "start": 149.24, "duration": 3.9}, {"text": "the inner workings of\nthis technology are.", "start": 153.14, "duration": 3.57}, {"text": "You're not going to\nhave to do an algorithm", "start": 156.71, "duration": 2.73}, {"text": "or actually do a hash function,\nbut to know underneath it.", "start": 159.44, "duration": 4.223}, {"text": "And then you can\nstep away and say", "start": 163.663, "duration": 1.417}, {"text": "I no longer need to know how\nthe carburetor on the car works,", "start": 165.08, "duration": 3.42}, {"text": "but I know what a carburetor is.", "start": 168.5, "duration": 2.12}, {"text": "Or, you know, whatever\nanalogy you want.", "start": 170.62, "duration": 5.32}, {"text": "So with that little\nbit, as opposed", "start": 175.94, "duration": 4.02}, {"text": "to sort of all of that\nSocratic cold calling", "start": 179.96, "duration": 2.52}, {"text": "that I did last\nclass, because money,", "start": 182.48, "duration": 3.12}, {"text": "Fiat currency is\nsomething at the core,", "start": 185.6, "duration": 3.51}, {"text": "and ledgers is at the\ncore of a Sloan student's", "start": 189.11, "duration": 3.96}, {"text": "either education or background,\nthis a little less of the core.", "start": 193.07, "duration": 3.75}, {"text": "If today's and the next\ncouple of lectures,", "start": 196.82, "duration": 2.28}, {"text": "if you can work with me then\nI want you to interrupt me", "start": 199.1, "duration": 3.18}, {"text": "anytime you've got a question.", "start": 202.28, "duration": 1.95}, {"text": "I'm not going to do\nmuch cold calling.", "start": 204.23, "duration": 2.61}, {"text": "I don't want you\nto relax too much.", "start": 206.84, "duration": 1.74}, {"text": "I still want you to do the\nreadings the next three", "start": 208.58, "duration": 2.4}, {"text": "classes.", "start": 210.98, "duration": 1.14}, {"text": "But just raise your\nhand, stop me, say, well,", "start": 212.12, "duration": 2.98}, {"text": "but what is that all about.", "start": 215.1, "duration": 2.64}, {"text": "And that just sort\nof we can work", "start": 217.74, "duration": 2.42}, {"text": "a little bit different\non these next classes.", "start": 220.16, "duration": 4.78}, {"text": "So, as I'm always going\nto be doing, consistency.", "start": 224.94, "duration": 5.05}, {"text": "What are the study questions?", "start": 229.99, "duration": 2.39}, {"text": "So really, what are\nthe design features?", "start": 232.38, "duration": 1.95}, {"text": "What are the key design\nfeatures of this new technology,", "start": 234.33, "duration": 3.54}, {"text": "blockchain.", "start": 237.87, "duration": 1.41}, {"text": "And I put a few on the syllabus.", "start": 239.28, "duration": 2.64}, {"text": "And we're going to go through\nall this today and next week.", "start": 241.92, "duration": 3.72}, {"text": "Cryptography,\nappend-only, timestamps", "start": 245.64, "duration": 4.32}, {"text": "blocks, distributed consensus\nalgorithms, and networking.", "start": 249.96, "duration": 4.47}, {"text": "I list four.", "start": 254.43, "duration": 2.04}, {"text": "Later in this lecture,\nyou'll see 8 or 10 that--", "start": 256.47, "duration": 3.609}, {"text": "I guess it's 10 that we're\ngoing to really dig dig into.", "start": 260.079, "duration": 4.651}, {"text": "Can I just get a sense\nof the class and this", "start": 264.73, "duration": 1.88}, {"text": "is not for Talita or\nSabrina to write down", "start": 266.61, "duration": 2.67}, {"text": "notes about participation.", "start": 269.28, "duration": 3.33}, {"text": "Is it a decent assumption,\ndid most or all of you", "start": 272.61, "duration": 3.24}, {"text": "at least read Nakamoto's paper?", "start": 275.85, "duration": 2.44}, {"text": "All right.", "start": 278.29, "duration": 0.5}, {"text": "Good.", "start": 278.79, "duration": 1.02}, {"text": "All right, great.", "start": 279.81, "duration": 2.19}, {"text": "Just a sense, how many of you\nfelt you got at least half", "start": 282.0, "duration": 3.42}, {"text": "of it, maybe less than 2/3,\nbut at least half of it?", "start": 285.42, "duration": 4.41}, {"text": "All right, pretty good.", "start": 289.83, "duration": 1.67}, {"text": "When I first read it,\nI was right with you.", "start": 291.5, "duration": 1.98}, {"text": "So it's all right.", "start": 293.48, "duration": 1.552}, {"text": "Alin you got more than\nhalf of it, right?", "start": 295.032, "duration": 1.708}, {"text": "AUDIENCE: I read it\nfive years ago, so.", "start": 296.74, "duration": 1.87}, {"text": "GARY GENSLER: You read\nit five years ago.", "start": 298.61, "duration": 1.11}, {"text": "Yeah, yeah, yeah.", "start": 299.72, "duration": 0.97}, {"text": "Yeah, life choices,\ntalk about it.", "start": 300.69, "duration": 4.3}, {"text": "All right.", "start": 304.99, "duration": 2.69}, {"text": "And you're taking this class.", "start": 307.68, "duration": 2.0}, {"text": "Good, good.", "start": 309.68, "duration": 2.7}, {"text": "So we'll go through\neach of those.", "start": 312.38, "duration": 1.71}, {"text": "And then more\nspecifically, we're", "start": 314.09, "duration": 2.4}, {"text": "going to peel back\nthe cryptography.", "start": 316.49, "duration": 2.61}, {"text": "The two main cryptographic\nalgorithms, or these words", "start": 319.1, "duration": 5.73}, {"text": "that you'll hear sometimes,\ncryptographic primitives--", "start": 324.83, "duration": 3.87}, {"text": "Alin, what is a\ncryptographic primitive?", "start": 328.7, "duration": 2.07}, {"text": "AUDIENCE: Oh, it's\na wild beasts.", "start": 330.77, "duration": 1.79}, {"text": "There are so many of them.", "start": 332.56, "duration": 1.34}, {"text": "GARY GENSLER: Yeah, but what's\nthe two words together mean?", "start": 333.9, "duration": 2.77}, {"text": "AUDIENCE: Well,\nthat's I'm saying.", "start": 336.67, "duration": 1.05}, {"text": "It could be anything.", "start": 337.72, "duration": 0.5}, {"text": "It could be a hash function,\ncould be encryption function,", "start": 338.22, "duration": 2.37}, {"text": "could be a very powerful\ncomputation scheme,", "start": 340.59, "duration": 1.7}, {"text": "it could be a data outsourcing\nscheme, could be a data access", "start": 342.29, "duration": 2.542}, {"text": "privacy access.", "start": 344.832, "duration": 1.238}, {"text": "GARY GENSLER: But\nit's anything that", "start": 346.07, "duration": 1.5}, {"text": "basically protects\nthe communication", "start": 347.57, "duration": 2.04}, {"text": "in the presence of adversaries.", "start": 349.61, "duration": 1.51}, {"text": "AUDIENCE: Well\nit's also something", "start": 351.12, "duration": 1.417}, {"text": "that you can use to prove that\ncomputation was done correctly", "start": 352.537, "duration": 2.893}, {"text": "on trusted servers.", "start": 355.43, "duration": 1.03}, {"text": "It's not just communication,\nit's also computation.", "start": 356.46, "duration": 3.2}, {"text": "GARY GENSLER: So\ncommunications and computation", "start": 359.66, "duration": 2.64}, {"text": "that needs to be\nprotected or verified,", "start": 362.3, "duration": 3.79}, {"text": "have some form of\ncryptographic algorithm,", "start": 366.09, "duration": 3.6}, {"text": "which happens to be called\na cryptographic primitive.", "start": 369.69, "duration": 2.58}, {"text": "The two main ones--", "start": 372.27, "duration": 1.953}, {"text": "and there's a third one\nwe'll talk about later", "start": 374.223, "duration": 1.917}, {"text": "in the semester-- but the two\nmain ones, hash functions,", "start": 376.14, "duration": 4.17}, {"text": "just as a working knowledge of\nblockchain is worthy to know,", "start": 380.31, "duration": 3.66}, {"text": "and we're going to get--\neverybody's going to get there.", "start": 383.97, "duration": 2.958}, {"text": "We're going to all\nget there to where", "start": 386.928, "duration": 1.542}, {"text": "you have some sense of\nwhat a hash function is.", "start": 388.47, "duration": 2.76}, {"text": "And then this whole concept\nof digital signatures,", "start": 391.23, "duration": 2.71}, {"text": "which relates to\nasymmetric cryptography.", "start": 393.94, "duration": 3.26}, {"text": "Those two are very fundamental\nto blockchain technology.", "start": 397.2, "duration": 4.803}, {"text": "Later in the semester,\nwe'll talk a little bit", "start": 402.003, "duration": 1.917}, {"text": "about zero knowledge\nproofs, but they're not", "start": 403.92, "duration": 3.42}, {"text": "as fundamental to the\nfirst application.", "start": 407.34, "duration": 3.84}, {"text": "And so that's why\nthey're kind of--", "start": 411.18, "duration": 2.45}, {"text": "and they help make things\nverifiable and immutable.", "start": 413.63, "duration": 2.8}, {"text": "And that's the business\nside, the market side.", "start": 416.43, "duration": 1.95}, {"text": "Why does it matter?", "start": 418.38, "duration": 2.155}, {"text": "Otherwise, like, who cares\nwhat's in the carburetor", "start": 420.535, "duration": 2.125}, {"text": "if it doesn't matter?", "start": 422.66, "duration": 3.35}, {"text": "And then how does this\nall relate to the double", "start": 426.01, "duration": 2.23}, {"text": "spend problem?", "start": 428.24, "duration": 0.87}, {"text": "I can cold call on this.", "start": 429.11, "duration": 1.89}, {"text": "Isabella, do you remember\nwhat the double spending", "start": 431.0, "duration": 2.1}, {"text": "problem was from?", "start": 433.1, "duration": 1.92}, {"text": "AUDIENCE: It was when they\nwould use the same coin,", "start": 435.02, "duration": 3.003}, {"text": "I guess, and they would\nuse it multiple places", "start": 438.023, "duration": 1.917}, {"text": "and other digital\nwallets [INAUDIBLE]..", "start": 439.94, "duration": 2.42}, {"text": "GARY GENSLER: All right.", "start": 442.36, "duration": 1.0}, {"text": "So in essence, a\ndouble spend is when", "start": 443.36, "duration": 2.37}, {"text": "you have a piece of information\nand you use it twice.", "start": 445.73, "duration": 4.65}, {"text": "And we happen to call this\npiece of information \"money,\"", "start": 450.38, "duration": 2.55}, {"text": "but you use it twice.", "start": 452.93, "duration": 1.68}, {"text": "You can send an email to\ntwo people and that's OK.", "start": 454.61, "duration": 3.413}, {"text": "I mean, it's a\nlittle embarrassing", "start": 458.023, "duration": 1.417}, {"text": "if you're sending it to\none friend telling them", "start": 459.44, "duration": 2.71}, {"text": "you're available for\ndinner and the other friend", "start": 462.15, "duration": 2.0}, {"text": "thought you told them\nyou weren't available.", "start": 464.15, "duration": 2.4}, {"text": "But you can still\nsend it to two places.", "start": 466.55, "duration": 2.58}, {"text": "But in the system of money,\nit's a critical thing", "start": 469.13, "duration": 2.82}, {"text": "that you don't use it twice.", "start": 471.95, "duration": 3.99}, {"text": "The readings, was\nthe demo helpful?", "start": 475.94, "duration": 4.1}, {"text": "I mean, we're going to\ndo a lot more on that.", "start": 480.04, "duration": 2.19}, {"text": "I watched that demo\nlast November, December.", "start": 482.23, "duration": 2.948}, {"text": "That was one of the\nfirst things I watched.", "start": 485.178, "duration": 1.792}, {"text": "From an MIT student.", "start": 486.97, "duration": 2.56}, {"text": "I don't know if\nyou knew Bosworth.", "start": 489.53, "duration": 3.53}, {"text": "And I found it very\nhelpful, so I'm glad.", "start": 493.06, "duration": 2.52}, {"text": "And I see it's actually\nthat demo is on a Stanford", "start": 495.58, "duration": 3.33}, {"text": "blockchain course as well,\nso the West Coast, one", "start": 498.91, "duration": 3.57}, {"text": "of our competitors is\nusing an MIT product.", "start": 502.48, "duration": 2.505}, {"text": "And so we're going to just\ndo a slight review of what", "start": 507.49, "duration": 4.05}, {"text": "we did in class 2.", "start": 511.54, "duration": 1.24}, {"text": "And then we're going to\ntalk about the key design", "start": 512.78, "duration": 2.389}, {"text": "features, hash functions,\nas I mentioned,", "start": 515.169, "duration": 2.671}, {"text": "what is an append-only log,\nblock headers and Merkle trees,", "start": 517.84, "duration": 6.18}, {"text": "and asymmetric cryptography\nand digital signatures.", "start": 524.02, "duration": 2.31}, {"text": "Crazy.", "start": 526.33, "duration": 0.5}, {"text": "We're going to cover\nall five of those today.", "start": 526.83, "duration": 4.43}, {"text": "And then you're going\nto tell me how we did.", "start": 531.26, "duration": 2.36}, {"text": "Oh, Bitcoin addresses,\nwhich is just a small thing.", "start": 533.62, "duration": 2.46}, {"text": "Six, actually.", "start": 536.08, "duration": 2.67}, {"text": "So last time, for those of\nyou that weren't with us,", "start": 538.75, "duration": 3.27}, {"text": "we talked about money.", "start": 542.02, "duration": 1.29}, {"text": "And again, money is\njust a social construct,", "start": 543.31, "duration": 2.67}, {"text": "or an economic\nconsensus mechanism.", "start": 545.98, "duration": 2.46}, {"text": "We're going to talk\na lot about consensus", "start": 548.44, "duration": 2.22}, {"text": "next Tuesday when we\ntalk about the consensus", "start": 550.66, "duration": 2.73}, {"text": "protocol on Bitcoin.", "start": 553.39, "duration": 1.65}, {"text": "But remember, money itself\nis just a consensus.", "start": 555.04, "duration": 3.3}, {"text": "There was a question\non Tuesday, I", "start": 558.34, "duration": 3.87}, {"text": "think Alin actually\nhad asked this question", "start": 562.21, "duration": 2.16}, {"text": "about well, what\ndoes it mean to be", "start": 564.37, "duration": 2.16}, {"text": "a liability in the central bank?", "start": 566.53, "duration": 1.74}, {"text": "Why is money, what does\nthat actually mean?", "start": 568.27, "duration": 3.46}, {"text": "And I said it just means that\nsomebody else will accept it.", "start": 571.73, "duration": 2.58}, {"text": "It's a social consensus\nbecause it's not", "start": 574.31, "duration": 2.81}, {"text": "that they're going to\ngive you anything else.", "start": 577.12, "duration": 2.28}, {"text": "It's just that you can\nget a bank deposit,", "start": 579.4, "duration": 1.77}, {"text": "you can pay your taxes, you\ncan use it at Starbucks,", "start": 581.17, "duration": 3.63}, {"text": "if in fact, you've already\ngotten a cup of coffee.", "start": 584.8, "duration": 2.82}, {"text": "If you remember, it's only\nlegal tender for a debt.", "start": 587.62, "duration": 4.87}, {"text": "And so forth.", "start": 592.49, "duration": 1.25}, {"text": "Fiat money is just\nin that long line.", "start": 593.74, "duration": 3.21}, {"text": "But it's had its challenges\nand instabilities.", "start": 596.95, "duration": 2.16}, {"text": "It doesn't mean it's\ngoing to go away.", "start": 599.11, "duration": 2.29}, {"text": "I'm not a Bitcoin maximalist who\nthinks that Fiat currencies are", "start": 601.4, "duration": 3.29}, {"text": "going to go away.", "start": 604.69, "duration": 0.73}, {"text": "But Fiat currencies have their\ninstabilities, particularly", "start": 605.42, "duration": 2.99}, {"text": "around weak monetary policy.", "start": 608.41, "duration": 4.96}, {"text": "In essence, when you debase a\ncurrency and allow a lot of it", "start": 613.37, "duration": 2.91}, {"text": "to be issued, or usually\naround unstable fiscal policy.", "start": 616.28, "duration": 4.25}, {"text": "So either the government\nis spending a lot,", "start": 620.53, "duration": 2.86}, {"text": "the King is off to foreign\nwars, and the Bank of England", "start": 623.39, "duration": 3.87}, {"text": "was actually set up in the\nlate 17th century in essence", "start": 627.26, "duration": 3.45}, {"text": "to control the currency\nwhen the King was--", "start": 630.71, "duration": 3.24}, {"text": "of England, I think--", "start": 633.95, "duration": 0.9}, {"text": "was in wars with\nFrance, if I can recall.", "start": 634.85, "duration": 2.97}, {"text": "A lot of banks, central\nbanks, were set up right", "start": 637.82, "duration": 2.73}, {"text": "about when a sovereign was\noff debasing a currency", "start": 640.55, "duration": 3.81}, {"text": "and spending too much at war.", "start": 644.36, "duration": 3.19}, {"text": "Ledgers, we talked\nabout ledgers,", "start": 647.55, "duration": 1.67}, {"text": "how critical ledgers are.", "start": 649.22, "duration": 1.95}, {"text": "In essence, ledgers are\na way to keep records.", "start": 651.17, "duration": 4.56}, {"text": "And those records could\neither be transaction records", "start": 655.73, "duration": 3.12}, {"text": "or balance records.", "start": 658.85, "duration": 1.16}, {"text": "We'll see that Bitcoin is set up\nas a transaction ledger system.", "start": 660.01, "duration": 5.71}, {"text": "Later we're going to be\ntalking about other blockchain", "start": 665.72, "duration": 2.25}, {"text": "technologies that are set\nup as balance ledgers.", "start": 667.97, "duration": 2.37}, {"text": "So one should not just\nthink immutability", "start": 670.34, "duration": 4.35}, {"text": "that there's only\none way to do this.", "start": 674.69, "duration": 2.01}, {"text": "But transactions and ledgers\nare at the core of Bitcoin.", "start": 676.7, "duration": 4.95}, {"text": "And central banking is of\ncourse, built on ledgers.", "start": 681.65, "duration": 3.87}, {"text": "The master ledger of the\ncentral bank, and then", "start": 685.52, "duration": 1.98}, {"text": "the commercial banks have\nsort of the sub-ledgers.", "start": 687.5, "duration": 3.06}, {"text": "And then you can think\nsometimes your digital wallet,", "start": 690.56, "duration": 2.52}, {"text": "maybe Starbucks has yet\na third tier ledger.", "start": 693.08, "duration": 3.87}, {"text": "We obviously live in an\nelectronic age already.", "start": 696.95, "duration": 2.97}, {"text": "We know this.", "start": 699.92, "duration": 1.23}, {"text": "There's been many\nefforts, they've", "start": 701.15, "duration": 1.74}, {"text": "all died until Bitcoin\nto crack that riddle", "start": 702.89, "duration": 3.87}, {"text": "that we talked about,\npeer-to-peer money", "start": 706.76, "duration": 4.99}, {"text": "without a central authority.", "start": 711.75, "duration": 2.165}, {"text": "And later in the\nsemester when we", "start": 713.915, "duration": 1.375}, {"text": "talk about what\nare the use cases,", "start": 715.29, "duration": 5.48}, {"text": "that's going to\nbe the core thing.", "start": 720.77, "duration": 1.88}, {"text": "It's why I'm not a maximalist.", "start": 722.65, "duration": 1.79}, {"text": "I'm not sure in\nevery circumstance", "start": 724.44, "duration": 3.01}, {"text": "a central intermediary\nisn't necessarily so bad.", "start": 727.45, "duration": 5.23}, {"text": "And this is not\na value judgment.", "start": 732.68, "duration": 1.56}, {"text": "It's just pure money and\nmarkets and so forth.", "start": 734.24, "duration": 3.15}, {"text": "But in some circumstances,\ndecentralization really", "start": 737.39, "duration": 2.6}, {"text": "will compete and beat the\ncentralized intermediary.", "start": 739.99, "duration": 4.48}, {"text": "So let's talk about his little\npaper, which of course he", "start": 744.47, "duration": 5.63}, {"text": "was modest, or she was modest.", "start": 750.1, "duration": 3.51}, {"text": "Please remind me, we don't\nknow who Nakamoto is or was,", "start": 753.61, "duration": 5.31}, {"text": "or a group of people.", "start": 758.92, "duration": 1.35}, {"text": "\"I've been working on\na new electronic cash", "start": 760.27, "duration": 2.82}, {"text": "system that's fully peer-to-peer\nwith no trusted third party.\"", "start": 763.09, "duration": 3.63}, {"text": "So you've seen\nthis slide before.", "start": 769.59, "duration": 3.36}, {"text": "But a time stamped\nappend-only log.", "start": 772.95, "duration": 2.85}, {"text": "Just think blocks of data.", "start": 775.8, "duration": 2.39}, {"text": "To kind of oversimplify, but\nit's got a name, blockchain.", "start": 778.19, "duration": 5.23}, {"text": "And I don't think--\ndid Satoshi's paper,", "start": 783.42, "duration": 1.71}, {"text": "you all read it in the\nlast few days, I of course", "start": 785.13, "duration": 3.12}, {"text": "read it again yesterday just\nto make sure I remembered it,", "start": 788.25, "duration": 3.96}, {"text": "I don't remember that he ever\nused the word blockchain.", "start": 792.21, "duration": 2.49}, {"text": "Am I right about that?", "start": 794.7, "duration": 1.68}, {"text": "Right.", "start": 796.38, "duration": 0.89}, {"text": "So the words\nblockchain are really--", "start": 797.27, "duration": 2.5}, {"text": "have been sort of layered\nover his innovation.", "start": 799.77, "duration": 5.76}, {"text": "So information, blocks going on.", "start": 805.53, "duration": 2.85}, {"text": "And that leads to\nbasically a database.", "start": 808.38, "duration": 3.4}, {"text": "But it's the blocks of data.", "start": 811.78, "duration": 1.92}, {"text": "Bitcoin right now is\nabout 550,000 blocks,", "start": 813.7, "duration": 4.14}, {"text": "and the blocks are added on\naverage every 10 minutes.", "start": 817.84, "duration": 4.79}, {"text": "And we'll talk about why it's\nevery 10 minutes, and not", "start": 822.63, "duration": 3.07}, {"text": "only why Satoshi Nakamoto\nmade it every 10 minutes", "start": 825.7, "duration": 4.12}, {"text": "but how they maintain that.", "start": 829.82, "duration": 1.73}, {"text": "Other blockchains like Ethereum\nit's about every seven seconds.", "start": 831.55, "duration": 3.94}, {"text": "So don't get too caught\nup that it's all the same.", "start": 835.49, "duration": 4.34}, {"text": "And there's some technologists,\nhere Silvio Micali", "start": 839.83, "duration": 4.35}, {"text": "is working on Algorand\nand that's even tighter,", "start": 844.18, "duration": 3.09}, {"text": "less than seven seconds.", "start": 847.27, "duration": 1.66}, {"text": "So there's not one way.", "start": 848.93, "duration": 2.24}, {"text": "There's multiple designs on\nhow often blocks are added.", "start": 851.17, "duration": 3.87}, {"text": "But let's start with Bitcoin.", "start": 855.04, "duration": 2.92}, {"text": "Secured by yes,\nguess what, those two", "start": 857.96, "duration": 2.88}, {"text": "cryptographic primitives,\nhash functions", "start": 860.84, "duration": 2.91}, {"text": "and digital signatures.", "start": 863.75, "duration": 3.36}, {"text": "Lose anybody yet?", "start": 867.11, "duration": 1.54}, {"text": "Yeah?", "start": 868.65, "duration": 0.5}, {"text": "Maybe.", "start": 869.15, "duration": 1.2}, {"text": "And then there's a\nconsensus for agreement.", "start": 870.35, "duration": 4.28}, {"text": "The whole debate\nusually about databases", "start": 874.63, "duration": 3.27}, {"text": "is who gets to change the data.", "start": 877.9, "duration": 3.73}, {"text": "And this is true\nin all databases.", "start": 881.63, "duration": 1.98}, {"text": "In its essence, it's\nusually centralized.", "start": 883.61, "duration": 2.37}, {"text": "But in blockchain, it's all\na sudden, well, maybe it's", "start": 885.98, "duration": 2.25}, {"text": "not centralized.", "start": 888.23, "duration": 1.26}, {"text": "Who gets to add that next bit\nof information, that next block?", "start": 889.49, "duration": 3.71}, {"text": "And the consensus agreement is--", "start": 893.2, "duration": 2.32}, {"text": "which we'll discuss\nnext Tuesday--", "start": 895.52, "duration": 1.62}, {"text": "is about that very issue.", "start": 897.14, "duration": 2.22}, {"text": "And I think there was\na little pretty picture", "start": 899.36, "duration": 2.18}, {"text": "of that done in slides before.", "start": 901.54, "duration": 2.415}, {"text": "But I'm going to I'm going\nto delay that discussion", "start": 903.955, "duration": 2.125}, {"text": "until next Tuesday.", "start": 906.08, "duration": 2.07}, {"text": "And hopefully you'll\nall come back.", "start": 908.15, "duration": 2.32}, {"text": "So what are the key features?", "start": 910.47, "duration": 2.94}, {"text": "And I might do a\nlittle cold calling.", "start": 913.41, "duration": 2.16}, {"text": "Do you remember any\nkey feature, Tom?", "start": 915.57, "duration": 2.54}, {"text": "From the papers?", "start": 918.11, "duration": 2.06}, {"text": "AUDIENCE: Oh, boy.", "start": 920.17, "duration": 1.152}, {"text": "GARY GENSLER: It's all right.", "start": 921.322, "duration": 1.208}, {"text": "AUDIENCE: Yeah.", "start": 922.53, "duration": 0.65}, {"text": "You know, the hash function.", "start": 923.18, "duration": 1.183}, {"text": "GARY GENSLER: Hash function.", "start": 924.363, "duration": 1.167}, {"text": "Any other key features?", "start": 925.53, "duration": 1.128}, {"text": "Let's see how many.", "start": 926.658, "duration": 0.792}, {"text": "I'm going to have\n10 on this page.", "start": 927.45, "duration": 1.795}, {"text": "AUDIENCE: A private\nand a public key.", "start": 929.245, "duration": 1.56}, {"text": "GARY GENSLER: What is that?", "start": 930.805, "duration": 1.125}, {"text": "AUDIENCE: Private\nand public keys.", "start": 931.93, "duration": 2.373}, {"text": "Private and public--", "start": 934.303, "duration": 0.833}, {"text": "GARY GENSLER: Oh,\nprivate and public key.", "start": 935.136, "duration": 1.524}, {"text": "Yes.", "start": 936.66, "duration": 0.5}, {"text": "So asymmetric cryptography,\nor private and public keying.", "start": 937.16, "duration": 3.88}, {"text": "Yes, hash functions, yes,\nprivate and public key.", "start": 941.04, "duration": 2.54}, {"text": "Any other kind of\nkey design features,", "start": 943.58, "duration": 3.31}, {"text": "or words you didn't understand?", "start": 946.89, "duration": 1.92}, {"text": "Maybe that's another\nway to put it.", "start": 948.81, "duration": 2.18}, {"text": "Leandro.", "start": 950.99, "duration": 0.707}, {"text": "AUDIENCE: Addresses.", "start": 951.697, "duration": 0.833}, {"text": "GARY GENSLER: What's that?", "start": 952.53, "duration": 0.61}, {"text": "AUDIENCE: Addresses.", "start": 953.14, "duration": 0.75}, {"text": "GARY GENSLER: Bitcoin addresses.", "start": 953.89, "duration": 1.333}, {"text": "Three.", "start": 955.223, "duration": 0.947}, {"text": "AUDIENCE: Timestamp server.", "start": 956.17, "duration": 1.16}, {"text": "GARY GENSLER: Timestamp server.", "start": 957.33, "duration": 1.08}, {"text": "That's four of the things.", "start": 958.41, "duration": 1.09}, {"text": "This is going well.", "start": 959.5, "duration": 2.11}, {"text": "[INAUDIBLE]", "start": 961.61, "duration": 0.5}, {"text": "AUDIENCE: Double payments.", "start": 962.11, "duration": 1.7}, {"text": "GARY GENSLER: Double\npayment is something", "start": 963.81, "duration": 2.61}, {"text": "that it's trying to address.", "start": 966.42, "duration": 2.61}, {"text": "It's not really\na design feature,", "start": 969.03, "duration": 1.71}, {"text": "but it's a-- they have a\nsolution for double payment,", "start": 970.74, "duration": 2.505}, {"text": "so I'll give you\na credit for it.", "start": 973.245, "duration": 1.445}, {"text": "But it's--", "start": 974.69, "duration": 1.34}, {"text": "AUDIENCE: Miners.", "start": 976.03, "duration": 0.82}, {"text": "GARY GENSLER: All right.", "start": 976.85, "duration": 1.0}, {"text": "So Hugo says miners, which\nis really the consensus.", "start": 977.85, "duration": 4.32}, {"text": "So I'll say that the\ndesign feature is", "start": 982.17, "duration": 3.0}, {"text": "the consensus or proof of work.", "start": 985.17, "duration": 2.07}, {"text": "Kelly.", "start": 987.24, "duration": 0.5}, {"text": "AUDIENCE: The full node\nversus the lightweight node.", "start": 987.74, "duration": 2.417}, {"text": "GARY GENSLER: Right.", "start": 990.157, "duration": 0.833}, {"text": "So very interesting,\nthis concept of nodes.", "start": 990.99, "duration": 3.06}, {"text": "And Satoshi actually\ntalks about full nodes", "start": 994.05, "duration": 3.24}, {"text": "or lightweight nodes.", "start": 997.29, "duration": 1.2}, {"text": "In essence, how much\ninformation has to be stored.", "start": 998.49, "duration": 3.512}, {"text": "I want to reserve that.", "start": 1002.002, "duration": 0.958}, {"text": "Kelly, please remind me\nwhen we talk about block", "start": 1002.96, "duration": 2.28}, {"text": "headers to come back to that.", "start": 1005.24, "duration": 1.78}, {"text": "But nodes in the network is a\nvery important design feature.", "start": 1007.02, "duration": 4.26}, {"text": "Over here.", "start": 1011.28, "duration": 0.5}, {"text": "AUDIENCE: The Merkle\ntree structure.", "start": 1011.78, "duration": 2.43}, {"text": "The Merkle tree structure.", "start": 1014.21, "duration": 1.77}, {"text": "GARY GENSLER: Merkle\ntree structure.", "start": 1015.98, "duration": 1.69}, {"text": "So Merkle tree structure is a\nway to compress a lot of data,", "start": 1017.67, "duration": 4.85}, {"text": "and also to sort\nthrough that data.", "start": 1022.52, "duration": 2.13}, {"text": "Uh-oh.", "start": 1024.65, "duration": 0.83}, {"text": "No, Sabrina's not going\nto clean me out here.", "start": 1025.48, "duration": 3.04}, {"text": "Merkle tree structure is there.", "start": 1028.52, "duration": 1.589}, {"text": "We're going to talk about that.", "start": 1030.109, "duration": 1.292}, {"text": "Two more.", "start": 1031.401, "duration": 1.001}, {"text": "AUDIENCE: Nonce.", "start": 1032.402, "duration": 0.667}, {"text": "GARY GENSLER: What's that?", "start": 1033.069, "duration": 0.601}, {"text": "The", "start": 1033.67, "duration": 0.305}, {"text": "AUDIENCE: Nonce.", "start": 1033.975, "duration": 0.765}, {"text": "GARY GENSLER: Nodes.", "start": 1034.74, "duration": 1.079}, {"text": "All right.", "start": 1035.819, "duration": 0.5}, {"text": "What's that?", "start": 1036.319, "duration": 0.471}, {"text": "AUDIENCE: Nonce.", "start": 1036.79, "duration": 0.5}, {"text": "GARY GENSLER: Nonce.", "start": 1037.29, "duration": 0.529}, {"text": "The nonce.", "start": 1037.819, "duration": 0.701}, {"text": "OK.", "start": 1038.52, "duration": 0.61}, {"text": "So a nonce.", "start": 1039.13, "duration": 1.449}, {"text": "Anybody know what\nthe word nonce is?", "start": 1040.579, "duration": 2.101}, {"text": "A year ago I didn't.", "start": 1042.68, "duration": 1.929}, {"text": "So this-- so we're\nall getting there.", "start": 1044.609, "duration": 1.791}, {"text": "What, do I have a look, do\nyou know what a nonce is?", "start": 1049.52, "duration": 2.74}, {"text": "Yeah.", "start": 1052.26, "duration": 2.115}, {"text": "AUDIENCE: In the\nactual protocol,", "start": 1054.375, "duration": 1.375}, {"text": "it's essentially a guess\nfor the miners to kind of--", "start": 1055.75, "duration": 3.55}, {"text": "GARY GENSLER: So\nthe word \"nonce\"", "start": 1059.3, "duration": 1.48}, {"text": "means a random number\nthat is used once.", "start": 1060.78, "duration": 3.25}, {"text": "N for number, and \"once.\"", "start": 1064.03, "duration": 4.6}, {"text": "It's a number that's\nrandom and it's used once.", "start": 1068.63, "duration": 4.86}, {"text": "That's how I've learned it.", "start": 1073.49, "duration": 1.574}, {"text": "Whew.", "start": 1075.064, "duration": 2.606}, {"text": "And so one more, because\nthis is great, actually.", "start": 1077.67, "duration": 3.636}, {"text": "AUDIENCE: Peer-to-peer.", "start": 1081.306, "duration": 1.134}, {"text": "GARY GENSLER: Remind\nme your first name.", "start": 1082.44, "duration": 1.08}, {"text": "AUDIENCE: Pria.", "start": 1083.52, "duration": 0.615}, {"text": "GARY GENSLER: Pria.", "start": 1084.135, "duration": 0.792}, {"text": "Peer-to-peer.", "start": 1084.927, "duration": 1.583}, {"text": "All right.", "start": 1086.51, "duration": 0.5}, {"text": "So this is what I have.", "start": 1087.01, "duration": 1.77}, {"text": "Cryptographic hash functions.", "start": 1088.78, "duration": 1.6}, {"text": "We're going to go through\nthese in more detail.", "start": 1090.38, "duration": 2.51}, {"text": "Timestamped append-only logs,\nblock headers and Merkle trees.", "start": 1092.89, "duration": 5.79}, {"text": "So Merkle trees were discussed.", "start": 1098.68, "duration": 1.51}, {"text": "But we need to actually\nsay what information", "start": 1100.19, "duration": 2.39}, {"text": "is kept at the head of the block\nas opposed to all the body.", "start": 1102.58, "duration": 5.16}, {"text": "And some of that's just to\nmake it more manageable.", "start": 1107.74, "duration": 4.59}, {"text": "Asymmetric cryptography,\nwhich is this public key,", "start": 1112.33, "duration": 2.73}, {"text": "private key, and signatures.", "start": 1115.06, "duration": 3.16}, {"text": "The Bitcoin\naddresses themselves,", "start": 1118.22, "duration": 2.94}, {"text": "which interestingly are a little\nbit different than public keys.", "start": 1121.16, "duration": 4.26}, {"text": "And then I breach break\nbecause in the next,", "start": 1125.42, "duration": 3.793}, {"text": "we're going to talk about next\nTuesday, the proof of work,", "start": 1129.213, "duration": 2.417}, {"text": "the miners, the then the\nnodes, the nonces, they're", "start": 1131.63, "duration": 4.1}, {"text": "are all in that little topic.", "start": 1135.73, "duration": 3.89}, {"text": "There's actually in Bitcoin\na really important protocol", "start": 1139.62, "duration": 3.74}, {"text": "is how information gets\npropagated on the internet.", "start": 1143.36, "duration": 3.18}, {"text": "Just the network communication.", "start": 1146.54, "duration": 2.07}, {"text": "It's not written about a lot.", "start": 1148.61, "duration": 1.32}, {"text": "You won't read a lot about it\nin Nathaniel Popper's Digital", "start": 1149.93, "duration": 2.94}, {"text": "Gold or all the\nother popular books,", "start": 1152.87, "duration": 2.43}, {"text": "but it is an important\nthing to remind ourselves", "start": 1155.3, "duration": 2.79}, {"text": "that information has to\npropagate around the internet", "start": 1158.09, "duration": 3.51}, {"text": "and all these transactions have\nto communicate with each other.", "start": 1161.6, "duration": 3.78}, {"text": "There's currently about 10,000\nnodes on the Bitcoin network.", "start": 1165.38, "duration": 5.17}, {"text": "We don't know where\nall of them are,", "start": 1170.55, "duration": 1.76}, {"text": "but they're probably in\n180 different countries.", "start": 1172.31, "duration": 3.24}, {"text": "And so it's just--", "start": 1175.55, "duration": 1.41}, {"text": "also the networking and\ncommunication matters.", "start": 1176.96, "duration": 3.73}, {"text": "And it matters to\nthe economics a lot.", "start": 1180.69, "duration": 3.51}, {"text": "There's a native currency.", "start": 1184.2, "duration": 1.4}, {"text": "This is interesting that it was\nthe one thing that no one said.", "start": 1185.6, "duration": 2.76}, {"text": "That's an actual\ntechnological design feature.", "start": 1188.36, "duration": 4.59}, {"text": "It's not only that he\ncreated a currency,", "start": 1192.95, "duration": 2.94}, {"text": "but the native currency is\npart of the economic incentive", "start": 1195.89, "duration": 3.45}, {"text": "system.", "start": 1199.34, "duration": 1.32}, {"text": "And we'll have\nsome fun with that.", "start": 1200.66, "duration": 2.7}, {"text": "In essence, he\nsaid that when you", "start": 1203.36, "duration": 2.16}, {"text": "mine and did the proof\nof work, you created", "start": 1205.52, "duration": 4.62}, {"text": "and you've got some native\ncurrency called Bitcoin.", "start": 1210.14, "duration": 2.58}, {"text": "So he created an economic\nincentive system.", "start": 1212.72, "duration": 3.18}, {"text": "Whomever Satoshi\nNakamoto was or is", "start": 1215.9, "duration": 3.07}, {"text": "knew a lot about economics,\nas well as technology.", "start": 1218.97, "duration": 2.81}, {"text": "Yes.", "start": 1221.78, "duration": 0.54}, {"text": "AUDIENCE: I just wanted to\nquickly add to what you said.", "start": 1222.32, "duration": 2.333}, {"text": "So it's not only that he\ncreated this native currency,", "start": 1224.653, "duration": 2.287}, {"text": "but wants the finite supply\nhas reached, the currency can", "start": 1226.94, "duration": 3.21}, {"text": "be distributed as\na transaction fee,", "start": 1230.15, "duration": 2.28}, {"text": "which I think is very\nimportant in [INAUDIBLE]..", "start": 1232.43, "duration": 2.37}, {"text": "GARY GENSLER: And remind\nme your first name?", "start": 1234.8, "duration": 1.14}, {"text": "AUDIENCE: Daniel.", "start": 1235.94, "duration": 0.78}, {"text": "GARY GENSLER: So\nwhat Daniel just said", "start": 1236.72, "duration": 1.583}, {"text": "is really interesting.", "start": 1238.303, "duration": 1.627}, {"text": "Not only to take light of\nthis individual or individuals", "start": 1239.93, "duration": 4.23}, {"text": "that did this.", "start": 1244.16, "duration": 1.42}, {"text": "But this world of Bitcoin\nand other cryptocurrencies", "start": 1245.58, "duration": 6.1}, {"text": "creates a unit of account\nthat could be valued.", "start": 1251.68, "duration": 5.2}, {"text": "And once it's valued, you have\nsort of a native currency.", "start": 1256.88, "duration": 3.59}, {"text": "But as Daniel\nsaid, Nakamoto also", "start": 1260.47, "duration": 2.46}, {"text": "said there would\nbe a finite limit.", "start": 1262.93, "duration": 3.48}, {"text": "It happens to be\n21 million Bitcoin", "start": 1266.41, "duration": 2.74}, {"text": "is the most that it\ncan be, and we'll", "start": 1269.15, "duration": 2.46}, {"text": "get there around the year 2040.", "start": 1271.61, "duration": 3.47}, {"text": "Does anyone know how many\nBitcoin there are right now?", "start": 1275.08, "duration": 2.61}, {"text": "About half of you\nwere investing in it.", "start": 1277.69, "duration": 2.39}, {"text": "Hugh?", "start": 1280.08, "duration": 0.61}, {"text": "Hugo?", "start": 1280.69, "duration": 1.14}, {"text": "About 17 million\nBitcoin right now.", "start": 1281.83, "duration": 3.63}, {"text": "And all 17 million have\ncome from this process", "start": 1285.46, "duration": 3.69}, {"text": "of proof of work and mining.", "start": 1289.15, "duration": 2.1}, {"text": "Initially it was 50\nBitcoin every 10 minutes,", "start": 1291.25, "duration": 3.87}, {"text": "roughly every 10 minutes.", "start": 1295.12, "duration": 1.92}, {"text": "Then it went down\nto 25, and we're now", "start": 1297.04, "duration": 3.0}, {"text": "at 12 and a half Bitcoin.", "start": 1300.04, "duration": 2.24}, {"text": "And does anyone know what\ntoday's value purported--", "start": 1302.28, "duration": 3.25}, {"text": "I always should say\npurported value of Bitcoin,", "start": 1305.53, "duration": 2.4}, {"text": "because I don't\nknow if we can trust", "start": 1307.93, "duration": 1.5}, {"text": "some of those websites that\nsay with the values are.", "start": 1309.43, "duration": 3.97}, {"text": "What is it?", "start": 1313.4, "duration": 0.72}, {"text": "AUDIENCE: $6,500.", "start": 1314.12, "duration": 0.75}, {"text": "GARY GENSLER: So\n$6,500 of Bitcoin", "start": 1314.87, "duration": 2.61}, {"text": "at 12 and a half\nBitcoin to mine a block.", "start": 1317.48, "duration": 2.505}, {"text": "So you see that\nit's about $80,000", "start": 1322.77, "duration": 3.21}, {"text": "US is the reward to\nmine a block, right?", "start": 1325.98, "duration": 6.76}, {"text": "So he created an\nincentive system", "start": 1332.74, "duration": 3.41}, {"text": "that initially, if you\ngot 50 Bitcoin and they", "start": 1336.15, "duration": 2.85}, {"text": "weren't worth a penny, you\nwould not commit that much.", "start": 1339.0, "duration": 5.48}, {"text": "You had to be a hobbyist,\nbasically, in 2009,", "start": 1344.48, "duration": 3.15}, {"text": "or a cyberpunk, or\njust kind of curious.", "start": 1347.63, "duration": 4.63}, {"text": "Because you weren't\ngetting much incentive.", "start": 1352.26, "duration": 2.16}, {"text": "If in fact it's\nworth 6,500 today,", "start": 1354.42, "duration": 2.34}, {"text": "you're getting $80,000 if you\nactually successfully mine", "start": 1356.76, "duration": 5.16}, {"text": "a block.", "start": 1361.92, "duration": 1.93}, {"text": "And then there's the\ntransaction inputs and outputs.", "start": 1363.85, "duration": 2.55}, {"text": "Think about a check, who signs\nit, where you move money.", "start": 1366.4, "duration": 6.98}, {"text": "There's something called the\nunspent transaction ledger.", "start": 1373.38, "duration": 2.51}, {"text": "So this is the ledger part.", "start": 1375.89, "duration": 1.978}, {"text": "So when you think--", "start": 1377.868, "duration": 0.792}, {"text": "I think of the\ntechnology, I think", "start": 1378.66, "duration": 2.28}, {"text": "of cryptography,\nwhich is kind of all", "start": 1380.94, "duration": 2.43}, {"text": "that stuff at the top which\nwe're going to discuss today.", "start": 1383.37, "duration": 3.82}, {"text": "Secondly, the\nconsensus mechanism.", "start": 1387.19, "duration": 2.42}, {"text": "In essence, that's\nthat key question", "start": 1389.61, "duration": 2.22}, {"text": "of any database, who gets\nto amend the database?", "start": 1391.83, "duration": 3.93}, {"text": "Who gets to decide to change the\nstate of what we all agreed to?", "start": 1395.76, "duration": 7.51}, {"text": "And then thirdly, is the ledger,\nor the transaction ledger,", "start": 1403.27, "duration": 3.63}, {"text": "which we're not\ngoing to deep dive", "start": 1406.9, "duration": 2.04}, {"text": "into the scripting\nlanguage, but we", "start": 1408.94, "duration": 1.65}, {"text": "are next Thursday going\nto talk a little bit", "start": 1410.59, "duration": 1.92}, {"text": "about the underlying scripting.", "start": 1412.51, "duration": 2.67}, {"text": "Does that give you a path\nthat's all this cryptography,", "start": 1415.18, "duration": 4.5}, {"text": "the consensus, and\nthen the transactions.", "start": 1419.68, "duration": 2.38}, {"text": "Yes.", "start": 1422.06, "duration": 0.5}, {"text": "AUDIENCE: I have a question.", "start": 1422.56, "duration": 0.433}, {"text": "GARY GENSLER: And\nyour first name?", "start": 1422.993, "duration": 1.417}, {"text": "If everybody just\nsays first name.", "start": 1424.41, "duration": 1.42}, {"text": "AUDIENCE: Oh.", "start": 1425.83, "duration": 0.542}, {"text": "I'm just curious, so\nyou mentioned that--", "start": 1426.372, "duration": 2.068}, {"text": "GARY GENSLER: I'm curious\nabout your first name.", "start": 1428.44, "duration": 2.34}, {"text": "AUDIENCE: Sean.", "start": 1430.78, "duration": 1.22}, {"text": "GARY GENSLER: All right.", "start": 1432.0, "duration": 1.0}, {"text": "AUDIENCE: So just\ncurious, you mentioned", "start": 1433.0, "duration": 1.667}, {"text": "that the block value is\nroughly $80,000 US as of now.", "start": 1434.667, "duration": 4.503}, {"text": "So just curious, in\nterms of the CPU power,", "start": 1439.17, "duration": 2.93}, {"text": "the electricity that will be\nconsumed to mine the block,", "start": 1442.1, "duration": 3.2}, {"text": "how much does that translate\nto equivalent US dollar terms?", "start": 1445.3, "duration": 4.79}, {"text": "GARY GENSLER: So the\nquestion that's asked", "start": 1450.09, "duration": 1.75}, {"text": "is how much electricity is\nbeing consumed for that miner", "start": 1451.84, "duration": 6.17}, {"text": "to get that reward,\nthat $80,000.", "start": 1458.01, "duration": 3.84}, {"text": "And I'm going to try to\nanswer in one minute.", "start": 1461.85, "duration": 3.3}, {"text": "But we'll come back to this\nlater in the semester about", "start": 1465.15, "duration": 3.54}, {"text": "economics, and blockchain\neconomics, and mining", "start": 1468.69, "duration": 2.85}, {"text": "economics.", "start": 1471.54, "duration": 0.63}, {"text": "But what has happened\nover these 10 years", "start": 1472.17, "duration": 3.36}, {"text": "is more and more\ncomputers are being used,", "start": 1475.53, "duration": 4.36}, {"text": "or are trying to\nmine for the Bitcoin.", "start": 1479.89, "duration": 5.3}, {"text": "And so today in the most\nrecent research I've seen", "start": 1485.19, "duration": 4.95}, {"text": "is that the probability\nof winning a block--", "start": 1490.14, "duration": 3.21}, {"text": "there's so much-- is it\nmeasured in terahashes?", "start": 1493.35, "duration": 4.05}, {"text": "I can't remember the numbers.", "start": 1497.4, "duration": 2.1}, {"text": "But it's how many terahashes,\nwhich, is it 15 zeros", "start": 1499.5, "duration": 6.68}, {"text": "Is a terahash?", "start": 1506.18, "duration": 1.28}, {"text": "Is it that, or is it 12?", "start": 1507.46, "duration": 2.77}, {"text": "Well, in any event,\nthere's so many hashes", "start": 1510.23, "duration": 2.37}, {"text": "being done a second, x\nnumber of terahashes,", "start": 1512.6, "duration": 4.2}, {"text": "that your probability\nof winning is quite low.", "start": 1516.8, "duration": 3.83}, {"text": "And so what's happened\nis most nodes and miners", "start": 1520.63, "duration": 2.42}, {"text": "have entered into agreements\ncalled mining pools, where", "start": 1523.05, "duration": 3.66}, {"text": "they smooth out the\nrisk and everybody", "start": 1526.71, "duration": 2.37}, {"text": "shares in the rewards.", "start": 1529.08, "duration": 2.07}, {"text": "But those economics\nwe'll talk about later,", "start": 1531.15, "duration": 2.55}, {"text": "it's thought to be that\nyou need electricity", "start": 1533.7, "duration": 2.97}, {"text": "cost around $0.03 a kilowatt\nhour to be successful.", "start": 1536.67, "duration": 4.28}, {"text": "And in most parts\nof the world you", "start": 1540.95, "duration": 1.48}, {"text": "can't get electricity for\n$0.03 a kilowatt hour.", "start": 1542.43, "duration": 3.85}, {"text": "So you would put\nyour mining rigs", "start": 1546.28, "duration": 2.27}, {"text": "where you can get\nlow cost electricity", "start": 1548.55, "duration": 2.7}, {"text": "or where you possibly can--", "start": 1551.25, "duration": 4.45}, {"text": "you can get it legally low\ncost or illegally low cost.", "start": 1555.7, "duration": 3.75}, {"text": "So there are a\nlot of mining rigs", "start": 1559.45, "duration": 2.15}, {"text": "and in jurisdictions where there\nmay be local officials that", "start": 1561.6, "duration": 3.21}, {"text": "are allowing those\nmining rigs, and instead", "start": 1564.81, "duration": 2.46}, {"text": "of $0.03 a kilowatt hour\nto the electric company", "start": 1567.27, "duration": 2.92}, {"text": "it's $0.01 to $0.02\ncents a kilowatt hour", "start": 1570.19, "duration": 2.03}, {"text": "to the local\ngovernment officials.", "start": 1572.22, "duration": 3.72}, {"text": "And the two largest\nmining pools are in China.", "start": 1575.94, "duration": 3.24}, {"text": "And the third is in Russia.", "start": 1579.18, "duration": 2.5}, {"text": "But we'll get into\nthe sort of economics", "start": 1581.68, "duration": 2.58}, {"text": "and at least some theories about\nwhy some are where they are.", "start": 1584.26, "duration": 6.06}, {"text": "So cryptography.", "start": 1590.32, "duration": 3.16}, {"text": "So Alin's probably\ngoing to clean me up.", "start": 1593.48, "duration": 1.85}, {"text": "It's not just communication in\nthe presence of adversaries,", "start": 1595.33, "duration": 3.06}, {"text": "it's also computation in\nthe presence of adversaries.", "start": 1598.39, "duration": 3.89}, {"text": "That would be good.", "start": 1602.28, "duration": 2.05}, {"text": "And we talked about-- we're\nnot going to deep dive.", "start": 1604.33, "duration": 3.06}, {"text": "If you remember, even in ancient\ntimes if you were going to war", "start": 1607.39, "duration": 4.14}, {"text": "there was this\nwonderful little way", "start": 1611.53, "duration": 1.86}, {"text": "that you could do cryptography.", "start": 1613.39, "duration": 1.65}, {"text": "And then anybody who's\nseen imitation games", "start": 1615.04, "duration": 7.26}, {"text": "about the British breaking\ninto the German codes,", "start": 1622.3, "duration": 3.618}, {"text": "even though they\nshould have probably", "start": 1625.918, "duration": 1.542}, {"text": "given more credit to the Polish\ngovernment that had probably", "start": 1627.46, "duration": 4.5}, {"text": "broken into it in the 1930s,\nbut Turing did great work.", "start": 1631.96, "duration": 4.26}, {"text": "And then we're going to talk\nabout asymmetric cryptography", "start": 1636.22, "duration": 2.67}, {"text": "today.", "start": 1638.89, "duration": 1.15}, {"text": "All right.", "start": 1640.04, "duration": 0.8}, {"text": "What is a hash function?", "start": 1640.84, "duration": 3.03}, {"text": "A hash function, and these are\njust words that I think of it,", "start": 1643.87, "duration": 4.26}, {"text": "I think of it as a\nfingerprint for data.", "start": 1648.13, "duration": 2.07}, {"text": "But it has certain properties.", "start": 1652.94, "duration": 2.5}, {"text": "The one that you'll\nsee throughout", "start": 1655.44, "duration": 1.73}, {"text": "is that it takes\ninputs of input x.", "start": 1657.17, "duration": 4.02}, {"text": "It maps that input of\nany size to a fixed size.", "start": 1661.19, "duration": 5.01}, {"text": "So one that we use\nhere in the US,", "start": 1666.2, "duration": 1.86}, {"text": "one hash function we all\nuse is zip codes, in a way.", "start": 1668.06, "duration": 3.65}, {"text": "It's five digits,\nit's a fixed size.", "start": 1671.71, "duration": 2.14}, {"text": "I know I'm doing this as a loose\nhand, how can I think of it.", "start": 1673.85, "duration": 4.65}, {"text": "But zip codes.", "start": 1678.5, "duration": 0.99}, {"text": "You might have 50,000 people\nor 5,000 people all living", "start": 1679.49, "duration": 3.78}, {"text": "in one postal district.", "start": 1683.27, "duration": 2.82}, {"text": "And you can map them to zip\ncodes, and it's a fixed let.", "start": 1686.09, "duration": 4.82}, {"text": "Now, I don't know whether my\nfriends in the computer science", "start": 1690.91, "duration": 3.15}, {"text": "departments-- but it's an\nearly sense of a hash function.", "start": 1694.06, "duration": 4.17}, {"text": "I just wanted to say there are\ntangible things in our life", "start": 1698.23, "duration": 3.81}, {"text": "that act like hash functions.", "start": 1702.04, "duration": 2.4}, {"text": "Problem with zip codes\nis it will not in any way", "start": 1704.44, "duration": 2.94}, {"text": "be a secure hash function.", "start": 1707.38, "duration": 2.01}, {"text": "And you'll see that in a minute.", "start": 1709.39, "duration": 1.85}, {"text": "But it does take--", "start": 1711.24, "duration": 1.66}, {"text": "you can be a 300-pound\nperson or a 30-pound kid", "start": 1712.9, "duration": 6.63}, {"text": "and you still map into\nthe same zip code.", "start": 1719.53, "duration": 3.03}, {"text": "It's deterministic.", "start": 1725.43, "duration": 1.17}, {"text": "It's always the same.", "start": 1726.6, "duration": 1.39}, {"text": "So if you take a\ncertain set of data,", "start": 1727.99, "duration": 2.81}, {"text": "it will always give\nyou the same hash.", "start": 1730.8, "duration": 2.43}, {"text": "And that's relevant\nto the background.", "start": 1733.23, "duration": 5.04}, {"text": "And you can\nefficiently compute it.", "start": 1738.27, "duration": 1.53}, {"text": "You don't want to take\na year to do this.", "start": 1739.8, "duration": 1.708}, {"text": "You've got to do it in\nshort periods of time.", "start": 1741.508, "duration": 2.672}, {"text": "And in Bitcoin's case,\nit's done in nanoseconds", "start": 1744.18, "duration": 4.11}, {"text": "or less, because they're one\ncomputer, one CPU can do--", "start": 1748.29, "duration": 6.23}, {"text": "can't remember, probably--\nhow many millions a second?", "start": 1754.52, "duration": 3.7}, {"text": "AUDIENCE: Couple of\nterahashes a second.", "start": 1758.22, "duration": 1.86}, {"text": "GARY GENSLER: Couple\nof terahashes a second.", "start": 1760.08, "duration": 3.42}, {"text": "So it's a remarkably\nefficient algorithm.", "start": 1763.5, "duration": 4.59}, {"text": "And so a bunch of\nmathematicians-- and hashing", "start": 1768.09, "duration": 3.69}, {"text": "started in the 1950s\nand '60s, but the ones", "start": 1771.78, "duration": 2.73}, {"text": "that we're talking about\nhere are much more recent.", "start": 1774.51, "duration": 2.61}, {"text": "But it's really\nterrifically talented", "start": 1777.12, "duration": 3.6}, {"text": "scientists, mathematicians,\ncomputer scientists,", "start": 1780.72, "duration": 2.91}, {"text": "and sometimes the National\nInstitute Standards", "start": 1783.63, "duration": 2.43}, {"text": "of Technology here in the US\nworking on hash functions.", "start": 1786.06, "duration": 3.88}, {"text": "So it takes a array of any size,\nputs it into a fixed number--", "start": 1789.94, "duration": 4.58}, {"text": "I think zip codes for a minute--", "start": 1794.52, "duration": 3.06}, {"text": "it's deterministic.", "start": 1797.58, "duration": 1.02}, {"text": "It's always-- you only live\nin one zip code, in a sense.", "start": 1798.6, "duration": 4.11}, {"text": "And it's very efficient.", "start": 1802.71, "duration": 1.71}, {"text": "But now what are its\ncryptographic properties?", "start": 1804.42, "duration": 2.28}, {"text": "Because a zip code\nwouldn't make it.", "start": 1806.7, "duration": 2.16}, {"text": "It just wouldn't.", "start": 1808.86, "duration": 2.45}, {"text": "Well, the computer\nscientists use", "start": 1811.31, "duration": 2.22}, {"text": "this term preimage resistant.", "start": 1813.53, "duration": 2.22}, {"text": "I would just say\nit's one way, you", "start": 1815.75, "duration": 3.04}, {"text": "can only go one way, meaning\nit's infeasible to determine", "start": 1818.79, "duration": 5.96}, {"text": "the input from the output.", "start": 1824.75, "duration": 2.13}, {"text": "It's infeasible to determine\nthe x from the hash of x.", "start": 1826.88, "duration": 5.7}, {"text": "Does anybody know why I use\nthe word infeasible rather than", "start": 1832.58, "duration": 3.36}, {"text": "impossible?", "start": 1835.94, "duration": 1.925}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1837.865, "duration": 0.875}, {"text": "GARY GENSLER: First name?", "start": 1838.74, "duration": 0.51}, {"text": "AUDIENCE: Brotish.", "start": 1839.25, "duration": 0.75}, {"text": "GARY GENSLER: Brotish", "start": 1840.0, "duration": 1.57}, {"text": "AUDIENCE: Because we can\ndo it with brute force.", "start": 1841.57, "duration": 2.265}, {"text": "GARY GENSLER: So you might be\nable to use it brute force.", "start": 1843.835, "duration": 2.375}, {"text": "What do you mean by brute\nforce, just so everybody--", "start": 1846.21, "duration": 1.68}, {"text": "AUDIENCE: Try all the options.", "start": 1847.89, "duration": 1.26}, {"text": "GARY GENSLER: Try all options.", "start": 1849.15, "duration": 1.25}, {"text": "But as I understand it, a\nsort of tenet of cryptography", "start": 1853.55, "duration": 3.42}, {"text": "for centuries is not to have\nit mathematically impossible,", "start": 1856.97, "duration": 6.87}, {"text": "the point is getting\nit so infeasible", "start": 1863.84, "duration": 2.58}, {"text": "that your adversary can't\neither get the communication", "start": 1866.42, "duration": 4.18}, {"text": "or so forth.", "start": 1870.6, "duration": 1.75}, {"text": "So hash functions,\nI just say this", "start": 1872.35, "duration": 2.33}, {"text": "because you can't assume\nthat Bitcoin can't be broken.", "start": 1874.68, "duration": 3.27}, {"text": "We all call it immutable.", "start": 1877.95, "duration": 1.35}, {"text": "It is immutable.", "start": 1879.3, "duration": 1.38}, {"text": "Until the hash functions\nthat are inside of Bitcoin", "start": 1880.68, "duration": 5.31}, {"text": "might be broken.", "start": 1885.99, "duration": 1.29}, {"text": "And even Satoshi wrote\nabout this in 2010.", "start": 1887.28, "duration": 2.82}, {"text": "He got emails.", "start": 1890.1, "duration": 1.03}, {"text": "There's this wonderful\nbook if any of you", "start": 1891.13, "duration": 2.0}, {"text": "want that I mentioned in\nthe bookshelf at the end", "start": 1893.13, "duration": 2.67}, {"text": "of the syllabus, he said, well\nwhat if a SHA-256, which is", "start": 1895.8, "duration": 4.32}, {"text": "the hash function, gets broken?", "start": 1900.12, "duration": 2.55}, {"text": "And his answer, by\nthe way, was well,", "start": 1902.67, "duration": 3.33}, {"text": "there will be a better\nhash function at that time.", "start": 1906.0, "duration": 3.09}, {"text": "Whatever that is, we'll\nhash the entire system,", "start": 1909.09, "duration": 5.38}, {"text": "whatever that is.", "start": 1914.47, "duration": 0.95}, {"text": "Because remember, you can\ntake something of any size,", "start": 1915.42, "duration": 2.88}, {"text": "hash it with a new\nsystem, and move forward.", "start": 1918.3, "duration": 2.86}, {"text": "And so he or she felt\nin this wonderful email", "start": 1921.16, "duration": 4.37}, {"text": "is that Bitcoin actually\ncould transition to a new hash", "start": 1925.53, "duration": 5.01}, {"text": "function as long as you\nhad a little bit of time", "start": 1930.54, "duration": 5.1}, {"text": "before it was all corrupted.", "start": 1935.64, "duration": 2.48}, {"text": "Kelly.", "start": 1938.12, "duration": 0.5}, {"text": "AUDIENCE: Is this what his\narticle called the Gambler's", "start": 1938.62, "duration": 2.292}, {"text": "Ruin problem?", "start": 1940.912, "duration": 1.828}, {"text": "Is that we you're describing?", "start": 1942.74, "duration": 2.03}, {"text": "GARY GENSLER: The\nGambler's Ruin problem.", "start": 1944.77, "duration": 1.93}, {"text": "AUDIENCE: The probability that\nan attacker could catch up", "start": 1946.7, "duration": 3.09}, {"text": "to recreating it.", "start": 1949.79, "duration": 3.182}, {"text": "GARY GENSLER: OK.", "start": 1952.972, "duration": 0.708}, {"text": "AUDIENCE: That's something else.", "start": 1953.68, "duration": 1.8}, {"text": "That's--", "start": 1955.48, "duration": 0.945}, {"text": "GARY GENSLER: Will you\nspeak a little louder?", "start": 1956.425, "duration": 1.875}, {"text": "AUDIENCE: Yeah.", "start": 1958.3, "duration": 0.625}, {"text": "So that's the-- you\nwant to sort of assess", "start": 1958.925, "duration": 5.055}, {"text": "how hard it is to fork Bitcoin.", "start": 1963.98, "duration": 1.53}, {"text": "If I have a lot of\ncomputational power,", "start": 1965.51, "duration": 1.89}, {"text": "how hard is it for\nme to create a fork?", "start": 1967.4, "duration": 2.01}, {"text": "And Satoshi does an analysis\nat the end of the paper--", "start": 1969.41, "duration": 2.91}, {"text": "GARY GENSLER: Oh, I apologize.", "start": 1972.32, "duration": 1.35}, {"text": "You're talking\nabout in his paper.", "start": 1973.67, "duration": 1.72}, {"text": "Yes.", "start": 1975.39, "duration": 0.5}, {"text": "In his paper, he's\ntalking about how hard", "start": 1975.89, "duration": 2.64}, {"text": "it is computationally to\ndo what some people call", "start": 1978.53, "duration": 2.43}, {"text": "a 51% attack, to basically\ntake over all the nodes.", "start": 1980.96, "duration": 4.377}, {"text": "And that part of his\npaper we're going", "start": 1985.337, "duration": 1.583}, {"text": "to talk about next Tuesday.", "start": 1986.92, "duration": 1.73}, {"text": "But it's basically, can\nyou take over the nodes?", "start": 1988.65, "duration": 3.418}, {"text": "I was talking about\na separate thing,", "start": 1992.068, "duration": 1.542}, {"text": "can you break the cryptography.", "start": 1993.61, "duration": 1.995}, {"text": "And he doesn't write\nabout that in his paper.", "start": 1995.605, "duration": 1.875}, {"text": "He writes about it in an email\nabout 10 months later or so.", "start": 1997.48, "duration": 5.18}, {"text": "Second key cryptographic thing.", "start": 2002.66, "duration": 2.28}, {"text": "So we said one is it's one way.", "start": 2004.94, "duration": 2.67}, {"text": "The other thing is this\nconcept of collision resistant.", "start": 2007.61, "duration": 5.67}, {"text": "I presume if everybody in this\nroom told me your birthdays,", "start": 2013.28, "duration": 3.9}, {"text": "there's multiple\npeople in this room", "start": 2017.18, "duration": 1.59}, {"text": "who have the same birthday.", "start": 2018.77, "duration": 2.62}, {"text": "And in fact, if we got it\npast 26 people in a room", "start": 2021.39, "duration": 3.09}, {"text": "it's over 50% chance that two\nof you have the same birthday.", "start": 2024.48, "duration": 4.23}, {"text": "We don't need to get to 183\npeople in the room, which is", "start": 2028.71, "duration": 4.8}, {"text": "half of the days of the year.", "start": 2033.51, "duration": 1.38}, {"text": "We can get to about 26 or 7.", "start": 2034.89, "duration": 2.52}, {"text": "And similarly, the key thing is\nis that two sets of data are--", "start": 2037.41, "duration": 10.33}, {"text": "it's again, infeasible\nthat x and y would", "start": 2047.74, "duration": 2.88}, {"text": "hash to the same thing.", "start": 2050.62, "duration": 1.349}, {"text": "It's not impossible.", "start": 2051.969, "duration": 1.571}, {"text": "It's infeasible.", "start": 2053.54, "duration": 1.67}, {"text": "And if you look at the\nhistory of hash functions,", "start": 2055.21, "duration": 2.55}, {"text": "this is usually the thing,\nthat at some point in time", "start": 2057.76, "duration": 3.28}, {"text": "these hash functions will\nnot be collision resistant.", "start": 2061.04, "duration": 2.389}, {"text": "Some quantum computing\nwill come along,", "start": 2063.429, "duration": 2.25}, {"text": "or something will come along.", "start": 2065.679, "duration": 1.841}, {"text": "But for now you can put\nsomething of any size in", "start": 2067.52, "duration": 4.24}, {"text": "and they're independent.", "start": 2071.76, "duration": 4.64}, {"text": "They also look terribly random.", "start": 2076.4, "duration": 1.71}, {"text": "It's called an avalanche\neffect, meaning", "start": 2078.11, "duration": 4.04}, {"text": "you change one little\ndifference and the whole thing", "start": 2082.15, "duration": 3.0}, {"text": "looks different.", "start": 2085.15, "duration": 0.91}, {"text": "So when you noticed\non that little video,", "start": 2086.06, "duration": 1.73}, {"text": "if you changed one thing,\nit all looked so different.", "start": 2087.79, "duration": 3.97}, {"text": "And why that's important\nis it makes it more secure.", "start": 2091.76, "duration": 4.42}, {"text": "And then there's something\ncalled puzzle friendliness.", "start": 2096.18, "duration": 2.25}, {"text": "Even if you know a\nlittle bit of the input,", "start": 2098.43, "duration": 1.792}, {"text": "it doesn't mean that you're\ngoing to get the output.", "start": 2100.222, "duration": 3.188}, {"text": "I put these up here not\nfor you to know them.", "start": 2103.41, "duration": 2.85}, {"text": "You're not going to get tested.", "start": 2106.26, "duration": 1.92}, {"text": "If you go into\nbusiness, as Elon,", "start": 2108.18, "duration": 2.657}, {"text": "you've started, when you\nprobably haven't thought,", "start": 2110.837, "duration": 2.083}, {"text": "well, collision\nresistant this or that.", "start": 2112.92, "duration": 3.64}, {"text": "But I just wanted\nyou to know there", "start": 2116.56, "duration": 1.53}, {"text": "is a bunch of cryptography\nunderneath this.", "start": 2118.09, "duration": 3.77}, {"text": "And the key is it is\nnot 100% immutable.", "start": 2121.86, "duration": 9.83}, {"text": "It's probably one in,\nyou know, I don't know,", "start": 2131.69, "duration": 6.97}, {"text": "a quadrillion immutable.", "start": 2138.66, "duration": 1.6}, {"text": "But there's still-- these\nthings could be broken.", "start": 2140.26, "duration": 2.79}, {"text": "And quantum computing and\nsomething else might--", "start": 2143.05, "duration": 2.85}, {"text": "Alin.", "start": 2145.9, "duration": 0.58}, {"text": "AUDIENCE: The actual probability\nshould be actually 1 over 2", "start": 2146.48, "duration": 2.57}, {"text": "to the power of 128.", "start": 2149.05, "duration": 2.49}, {"text": "So much more than\none quadrillion.", "start": 2151.54, "duration": 4.05}, {"text": "GARY GENSLER: So it's 1\nover 10 to about the 40th.", "start": 2155.59, "duration": 2.73}, {"text": "How'd I do?", "start": 2162.0, "duration": 1.95}, {"text": "My math all right?", "start": 2163.95, "duration": 1.87}, {"text": "All right.", "start": 2165.82, "duration": 0.5}, {"text": "And anybody who's interested\ncan come to office hours.", "start": 2169.56, "duration": 2.79}, {"text": "So it's highly\nunlikely to be broken.", "start": 2174.9, "duration": 3.63}, {"text": "But I think it's always\nworthwhile to say, well,", "start": 2178.53, "duration": 2.46}, {"text": "no, there's some outward--", "start": 2180.99, "duration": 1.7}, {"text": "it's not as bounded\nas you think.", "start": 2182.69, "duration": 3.48}, {"text": "So what is it used for?", "start": 2186.17, "duration": 2.42}, {"text": "In many places it's used\nfor names, and references,", "start": 2188.59, "duration": 2.99}, {"text": "and pointers, and in\nsomething called commitments.", "start": 2191.58, "duration": 3.68}, {"text": "In Bitcoin, it's used for\npointers because one block", "start": 2195.26, "duration": 3.66}, {"text": "points to another block.", "start": 2198.92, "duration": 2.58}, {"text": "But it's also used\nin commitments.", "start": 2201.5, "duration": 4.8}, {"text": "You'll hear these words.", "start": 2206.3, "duration": 1.65}, {"text": "We're not going to\ndelve into them.", "start": 2207.95, "duration": 1.86}, {"text": "But the headers and the\nMerkle trees use something", "start": 2209.81, "duration": 2.61}, {"text": "called SHA 256, which\nis a standard which", "start": 2212.42, "duration": 4.35}, {"text": "is literally 256 bits long.", "start": 2216.77, "duration": 5.97}, {"text": "That's like zeros and\nones for 256 registries.", "start": 2222.74, "duration": 6.16}, {"text": "But a Bitcoin address actually--", "start": 2228.9, "duration": 2.39}, {"text": "Satoshi Nakamoto\nthrew on a loop.", "start": 2231.29, "duration": 4.14}, {"text": "I'm glad to debate why, but\nhe uses two hash functions", "start": 2235.43, "duration": 4.78}, {"text": "for Bitcoin addresses.", "start": 2240.21, "duration": 1.47}, {"text": "The one thing I saw\nthat he actually", "start": 2241.68, "duration": 2.07}, {"text": "wrote about it is he\nsaid if one of them", "start": 2243.75, "duration": 1.72}, {"text": "is broken at least the other\none is less likely to be broken.", "start": 2245.47, "duration": 4.02}, {"text": "So as I've read\nabout it, I think", "start": 2249.49, "duration": 2.48}, {"text": "in his own voice is you have\nto hash something twice.", "start": 2251.97, "duration": 4.21}, {"text": "And he was just making\nit that much more secure,", "start": 2256.18, "duration": 2.36}, {"text": "even knowing it was one out\nof 10 to the 40th chance.", "start": 2258.54, "duration": 4.15}, {"text": "AUDIENCE: Which is\nastronomically low, so.", "start": 2262.69, "duration": 2.197}, {"text": "GARY GENSLER: Right.", "start": 2264.887, "duration": 0.833}, {"text": "So.", "start": 2265.72, "duration": 2.42}, {"text": "So remember, where's Caroline?", "start": 2268.14, "duration": 1.64}, {"text": "I remember-- there we are.", "start": 2269.78, "duration": 2.05}, {"text": "You asked me about, I\nthought I had set it", "start": 2271.83, "duration": 2.073}, {"text": "up for today, which you\nwere good to remind me", "start": 2273.903, "duration": 1.917}, {"text": "for Tuesday, what's the\nlongest running hash,", "start": 2275.82, "duration": 4.77}, {"text": "time stamped hash?", "start": 2280.59, "duration": 2.2}, {"text": "AUDIENCE: That is\na great question.", "start": 2282.79, "duration": 4.17}, {"text": "GARY GENSLER: Thank\nyou for the compliment.", "start": 2286.96, "duration": 3.51}, {"text": "AUDIENCE: The answer is--", "start": 2290.47, "duration": 1.71}, {"text": "yeah, I don't know\nthat phonetically,", "start": 2292.18, "duration": 2.64}, {"text": "so I'm not sure if I'm\ntotally butchering this one.", "start": 2294.82, "duration": 2.72}, {"text": "But it came out of Bell Labs\nwith Stuart Haber and Surety.", "start": 2297.54, "duration": 5.39}, {"text": "GARY GENSLER: There he is.", "start": 2302.93, "duration": 2.12}, {"text": "Yeah.", "start": 2305.05, "duration": 1.11}, {"text": "So Haber and his\ncolleague-- yes.", "start": 2306.16, "duration": 4.02}, {"text": "You got it.", "start": 2310.18, "duration": 1.022}, {"text": "AUDIENCE: That's my roommate.", "start": 2311.202, "duration": 1.208}, {"text": "GARY GENSLER:\nThat's you roommate.", "start": 2312.41, "duration": 1.417}, {"text": "Terrific.", "start": 2313.827, "duration": 1.843}, {"text": "So I'm just trying to say it\nwasn't Bitcoin that had it.", "start": 2315.67, "duration": 5.37}, {"text": "He did this in 1991.", "start": 2321.04, "duration": 2.85}, {"text": "But by 1995, they started\na company called Surety.", "start": 2323.89, "duration": 2.79}, {"text": "I don't think it\ntook off that much.", "start": 2326.68, "duration": 1.5}, {"text": "It's not competing with Apple\nfor the largest market cap", "start": 2328.18, "duration": 3.12}, {"text": "or anything like\nthat or Facebook.", "start": 2331.3, "duration": 4.5}, {"text": "But every week in\nthe notices section,", "start": 2335.8, "duration": 3.51}, {"text": "you can see a hash literally.", "start": 2339.31, "duration": 5.95}, {"text": "It's time stamped because\nit's in the New York Times.", "start": 2345.26, "duration": 3.69}, {"text": "And it's a hash, all those\nfunky digits and everything", "start": 2348.95, "duration": 5.37}, {"text": "of all the information\ncame before it.", "start": 2354.32, "duration": 2.23}, {"text": "And they're basically\nhashing any document.", "start": 2356.55, "duration": 3.54}, {"text": "Any document that you want\na timestamp in that week,", "start": 2360.09, "duration": 2.74}, {"text": "you put it in.", "start": 2362.83, "duration": 1.13}, {"text": "One follows another,\nand that's a blockchain.", "start": 2363.96, "duration": 2.82}, {"text": "It's not about money.", "start": 2366.78, "duration": 1.47}, {"text": "There's no native\ncurrency and so forth.", "start": 2368.25, "duration": 5.69}, {"text": "I believe that\nHaber and Stornetta", "start": 2373.94, "duration": 3.2}, {"text": "are three of the eight or nine\nfootnotes in the Satoshi paper.", "start": 2377.14, "duration": 3.87}, {"text": "Maybe it's four of them.", "start": 2381.01, "duration": 2.16}, {"text": "So he gets his credit.", "start": 2383.17, "duration": 2.24}, {"text": "And if you go to his\nwebsite, Stuart Haber,", "start": 2385.41, "duration": 2.28}, {"text": "I think he says,\nblockchain's co-founder", "start": 2387.69, "duration": 3.68}, {"text": "on his personal website.", "start": 2391.37, "duration": 2.87}, {"text": "Who knew?", "start": 2394.24, "duration": 0.64}, {"text": "So here, we get-- this\nwas in the National", "start": 2397.45, "duration": 2.19}, {"text": "Institute, the NIST paper.", "start": 2399.64, "duration": 3.03}, {"text": "But timestamp append-only\nlogs in Bitcoin or blockchain.", "start": 2402.67, "duration": 5.23}, {"text": "What is put together is the\nheader, the top information.", "start": 2407.9, "duration": 6.18}, {"text": "And if I can go past the visual\nand just say, what's there?", "start": 2414.08, "duration": 5.92}, {"text": "There's five pieces\nof key information.", "start": 2420.0, "duration": 2.22}, {"text": "The version, it doesn't\nchange that often.", "start": 2422.22, "duration": 2.19}, {"text": "But there is a version number.", "start": 2424.41, "duration": 2.79}, {"text": "The previous block's\nhash, so it's", "start": 2427.2, "duration": 3.85}, {"text": "some information about all the\nblocks that came before it.", "start": 2431.05, "duration": 6.23}, {"text": "The Merkle Root hash, which does\nanybody want to tell me what", "start": 2437.28, "duration": 5.23}, {"text": "that does, the Merkle Root?", "start": 2442.51, "duration": 1.89}, {"text": "AUDIENCE: So it essentially\nposts the transactions", "start": 2449.047, "duration": 2.083}, {"text": "in the bottom most\nlayer of the tree", "start": 2451.13, "duration": 2.47}, {"text": "and then creates\nthe [INAUDIBLE] hash", "start": 2453.6, "duration": 1.61}, {"text": "of each of the transactions.", "start": 2455.21, "duration": 2.55}, {"text": "GARY GENSLER: So if I go back\nto this nice little picture,", "start": 2457.76, "duration": 5.47}, {"text": "the yellow box at the bottom\nup each of these blocks", "start": 2463.23, "duration": 2.69}, {"text": "is all the transactions.", "start": 2465.92, "duration": 1.2}, {"text": "There could be upwards to 1,000,\n2,000 transactions in a block.", "start": 2467.12, "duration": 4.32}, {"text": "So there's blockchain\nconcept, 1,000, 2,000.", "start": 2471.44, "duration": 4.86}, {"text": "There's means and methods\nwell before Nakamoto's paper", "start": 2476.3, "duration": 4.28}, {"text": "about how to compress that,\nhow to keep that information", "start": 2480.58, "duration": 2.85}, {"text": "a little bit tidier.", "start": 2483.43, "duration": 2.28}, {"text": "And that uses this thing\ncalled Merkle Roots.", "start": 2485.71, "duration": 3.83}, {"text": "The five items right at the top,\nwhat's called the block header,", "start": 2489.54, "duration": 5.67}, {"text": "doesn't have the\n1,000 transactions.", "start": 2495.21, "duration": 3.21}, {"text": "And earlier, Kelly,\nyou had asked me", "start": 2498.42, "duration": 2.1}, {"text": "about full nodes\nand light nodes.", "start": 2500.52, "duration": 5.78}, {"text": "A light node or a\nwallet that anyone here", "start": 2506.3, "duration": 3.34}, {"text": "could download on\nyour cell phone", "start": 2509.64, "duration": 4.29}, {"text": "probably does not\ndownload the millions", "start": 2513.93, "duration": 3.99}, {"text": "of transactions\nthat have happened", "start": 2517.92, "duration": 2.16}, {"text": "in the history of Bitcoin.", "start": 2520.08, "duration": 1.89}, {"text": "You are unlikely to download\nwhat's called a full node.", "start": 2521.97, "duration": 4.17}, {"text": "But you might download\nall the headers,", "start": 2526.14, "duration": 3.13}, {"text": "this bit of information\nthat's all of the headers.", "start": 2529.27, "duration": 3.68}, {"text": "All of the\ninformation in Bitcoin", "start": 2532.95, "duration": 1.59}, {"text": "is still not that large.", "start": 2534.54, "duration": 1.21}, {"text": "It's less than 200 gigs.", "start": 2535.75, "duration": 3.11}, {"text": "But all of the headers, I\nthink, is single digit gigs.", "start": 2538.86, "duration": 4.26}, {"text": "I can't remember if it's four\nor six gigabytes right now.", "start": 2543.12, "duration": 3.06}, {"text": "What is the number?", "start": 2546.18, "duration": 1.31}, {"text": "AUDIENCE: The\nheader is 80 bytes.", "start": 2547.49, "duration": 1.375}, {"text": "So it's 80 bytes\ntimes 500,000, which", "start": 2548.865, "duration": 1.725}, {"text": "is 50 megabytes, 60\nmegabytes of headers.", "start": 2550.59, "duration": 3.42}, {"text": "GARY GENSLER: So\nit's 60 megabytes,", "start": 2554.01, "duration": 1.49}, {"text": "so it's much smaller as\nopposed to like 180 gig.", "start": 2555.5, "duration": 7.37}, {"text": "So Satoshi was\nthinking in advance.", "start": 2562.87, "duration": 3.81}, {"text": "And every blockchain that\nyou're going to work on,", "start": 2566.68, "duration": 2.43}, {"text": "likely, I mean, there might\nbe some, this concept of it's", "start": 2569.11, "duration": 4.86}, {"text": "really keeping the security\nby a little bit of information", "start": 2573.97, "duration": 3.18}, {"text": "in something called a\nheader and then pushing", "start": 2577.15, "duration": 2.7}, {"text": "all the meat of the\ntransaction and data down.", "start": 2579.85, "duration": 3.06}, {"text": "And this is really\nimportant when", "start": 2582.91, "duration": 1.47}, {"text": "you get to like\nEthereum where there's", "start": 2584.38, "duration": 1.59}, {"text": "a lot of data, a\nlot of computation", "start": 2585.97, "duration": 3.63}, {"text": "down in each of these blocks.", "start": 2589.6, "duration": 1.89}, {"text": "It's sort of like\nif Stuart Haber", "start": 2591.49, "duration": 4.86}, {"text": "had a lot of documents and\npictures and everything.", "start": 2596.35, "duration": 3.51}, {"text": "You don't have to\nhave all the picture", "start": 2599.86, "duration": 1.59}, {"text": "quality and a whole movie.", "start": 2601.45, "duration": 1.86}, {"text": "You can actually\nhash a whole movie,", "start": 2603.31, "duration": 1.92}, {"text": "and you still get\nthese 256 bits.", "start": 2605.23, "duration": 3.18}, {"text": "So whoops.", "start": 2611.02, "duration": 4.4}, {"text": "So the header has the previous\nhash, this Merkle Root,", "start": 2615.42, "duration": 3.39}, {"text": "which is just a way to\nget all the transactions.", "start": 2618.81, "duration": 2.58}, {"text": "Just think of a Merkle\nRoot as a way to grab", "start": 2621.39, "duration": 1.95}, {"text": "2,000 transactions in a way.", "start": 2623.34, "duration": 3.3}, {"text": "A timestamp, that one's easy.", "start": 2626.64, "duration": 1.89}, {"text": "We can get that.", "start": 2628.53, "duration": 2.07}, {"text": "Difficulty target, anybody\nknow what blockchain,", "start": 2630.6, "duration": 7.38}, {"text": "Bitcoin tried to\ndo to make it more", "start": 2637.98, "duration": 2.25}, {"text": "or less difficult over time?", "start": 2640.23, "duration": 2.644}, {"text": "No.", "start": 2642.874, "duration": 0.756}, {"text": "Brodish, we've heard.", "start": 2643.63, "duration": 2.802}, {"text": "AUDIENCE: [INAUDIBLE]\ntime but such", "start": 2646.432, "duration": 1.458}, {"text": "that it stays with creating\na block every 10 minutes.", "start": 2647.89, "duration": 3.52}, {"text": "So with more\ncomputational power,", "start": 2651.41, "duration": 1.69}, {"text": "it gets harder to find a block.", "start": 2653.1, "duration": 2.2}, {"text": "GARY GENSLER: So it's\nharder to find a block,", "start": 2655.3, "duration": 1.99}, {"text": "the more miners there are.", "start": 2657.29, "duration": 3.02}, {"text": "So every block header\nneeds to have some what's", "start": 2660.31, "duration": 2.76}, {"text": "called a difficulty target.", "start": 2663.07, "duration": 2.25}, {"text": "How difficult is the\nmining going to be?", "start": 2665.32, "duration": 1.98}, {"text": "Since we're talking about\nmining next Tuesday,", "start": 2667.3, "duration": 3.06}, {"text": "these all bring me back\nto difficulty target.", "start": 2670.36, "duration": 4.55}, {"text": "And then what's a nonce?", "start": 2674.91, "duration": 3.606}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2678.516, "duration": 1.974}, {"text": "GARY GENSLER: What's that?", "start": 2680.49, "duration": 1.6}, {"text": "AUDIENCE: Just a random number.", "start": 2682.09, "duration": 1.523}, {"text": "GARY GENSLER: A random\nnumber that's used one.", "start": 2683.613, "duration": 1.917}, {"text": "Number once, nonce.", "start": 2685.53, "duration": 1.135}, {"text": "And that's hash functions.", "start": 2690.58, "duration": 3.54}, {"text": "How'd we do?", "start": 2694.12, "duration": 1.075}, {"text": "We're a little off the skids.", "start": 2695.195, "duration": 1.385}, {"text": "We are MIT.", "start": 2696.58, "duration": 1.38}, {"text": "Yes?", "start": 2697.96, "duration": 0.89}, {"text": "AUDIENCE: I have a question.", "start": 2698.85, "duration": 1.167}, {"text": "The number of characters in\nthe hash is equal to your--", "start": 2700.017, "duration": 3.303}, {"text": "GARY GENSLER: The\noutput, not the input.", "start": 2703.32, "duration": 2.158}, {"text": "AUDIENCE: No.", "start": 2705.478, "duration": 0.542}, {"text": "No.", "start": 2706.02, "duration": 0.5}, {"text": "They put the number of\ncharacters in the hash", "start": 2706.52, "duration": 2.8}, {"text": "is limited, right?", "start": 2709.32, "duration": 0.8}, {"text": "So that's a pool of\nfunctions that you have.", "start": 2710.12, "duration": 2.607}, {"text": "When you have many,\nmany transactions,", "start": 2712.727, "duration": 1.583}, {"text": "that's like a flow, right?", "start": 2714.31, "duration": 1.745}, {"text": "So internally, you're just\nconsuming and consuming hashes", "start": 2716.055, "duration": 2.375}, {"text": "up to a point where you're\ngoing going to repeat that hash,", "start": 2718.43, "duration": 3.43}, {"text": "right?", "start": 2721.86, "duration": 0.5}, {"text": "So how do you know\nfor the same has,", "start": 2722.36, "duration": 2.98}, {"text": "you have two\ndifferent information,", "start": 2725.34, "duration": 2.52}, {"text": "to which information\nyou're referring to?", "start": 2727.86, "duration": 2.89}, {"text": "GARY GENSLER: So could you help\nme pronounce your first name?", "start": 2730.75, "duration": 2.982}, {"text": "AUDIENCE: Diermo.", "start": 2733.732, "duration": 0.708}, {"text": "GARY GENSLER: Diermo, has\nasked the right question.", "start": 2734.44, "duration": 3.78}, {"text": "He's say, well, how do you know?", "start": 2738.22, "duration": 1.71}, {"text": "Especially as you have more\nand more time and more and more", "start": 2739.93, "duration": 3.0}, {"text": "time, you might get the\nsame output of a hash", "start": 2742.93, "duration": 5.1}, {"text": "from different inputs.", "start": 2748.03, "duration": 2.628}, {"text": "And if you recall--", "start": 2750.658, "duration": 0.792}, {"text": "wait.", "start": 2754.59, "duration": 0.77}, {"text": "Somebody does recall.", "start": 2755.36, "duration": 1.08}, {"text": "Now before Brodish,\nin front of Brodish.", "start": 2756.44, "duration": 3.54}, {"text": "AUDIENCE: The papers\nmentioned that it's", "start": 2759.98, "duration": 2.34}, {"text": "possible that two the hash\nof x equal to hash of y.", "start": 2762.32, "duration": 5.88}, {"text": "But if the miners are\nworking at the same time,", "start": 2768.2, "duration": 5.4}, {"text": "if the same information are not\ntreated at the same exact time,", "start": 2773.6, "duration": 3.63}, {"text": "it won't be a problem because\nthen they just continue just", "start": 2777.23, "duration": 4.635}, {"text": "like two different--", "start": 2781.865, "duration": 1.665}, {"text": "GARY GENSLER: So you're correct\nas it relates to mining.", "start": 2783.53, "duration": 4.18}, {"text": "But there is another\npiece of it as well", "start": 2787.71, "duration": 2.12}, {"text": "is that the hash\nfunction, if it's", "start": 2789.83, "duration": 1.86}, {"text": "a good cryptographic\nsecure hash function,", "start": 2791.69, "duration": 2.73}, {"text": "is what's called collision\nresistant where what you're", "start": 2794.42, "duration": 2.91}, {"text": "saying is so\ninfeasible, in fact,", "start": 2797.33, "duration": 3.1}, {"text": "1 divided by 10 to the 40th,\nthat's a 1 with 40 zeroes", "start": 2800.43, "duration": 5.49}, {"text": "after it.", "start": 2805.92, "duration": 0.65}, {"text": "It's so infeasible to happen,\nit's possible but infeasible", "start": 2806.57, "duration": 5.87}, {"text": "to happen.", "start": 2812.44, "duration": 2.04}, {"text": "What you're referencing\nis what if two parties", "start": 2814.48, "duration": 3.39}, {"text": "solve the cryptographic puzzle\nas opposed to a collision.", "start": 2817.87, "duration": 5.52}, {"text": "And because of the difficulty,\nthey just got at the same time.", "start": 2823.39, "duration": 4.78}, {"text": "Please.", "start": 2828.17, "duration": 0.745}, {"text": "AUDIENCE: It seems like\na dumb question but--", "start": 2828.915, "duration": 1.875}, {"text": "GARY GENSLER: No.", "start": 2830.79, "duration": 0.26}, {"text": "There's no dumb questions\nwhen it comes to this.", "start": 2831.05, "duration": 2.32}, {"text": "I really mean that.", "start": 2833.37, "duration": 1.73}, {"text": "AUDIENCE: The timestamps\nattributed, so is it", "start": 2835.1, "duration": 3.48}, {"text": "from the whole system or?", "start": 2838.58, "duration": 2.03}, {"text": "GARY GENSLER: So timestamps are\nnot a particularly important", "start": 2840.61, "duration": 3.97}, {"text": "part of Bitcoin.", "start": 2844.58, "duration": 1.07}, {"text": "They are timestamped.", "start": 2845.65, "duration": 2.42}, {"text": "But sometimes if somebody\nputs something off", "start": 2848.07, "duration": 2.23}, {"text": "and it's off by a few minutes\nor even up to two hours,", "start": 2850.3, "duration": 4.99}, {"text": "there's a check\nin the technology", "start": 2855.29, "duration": 3.69}, {"text": "in the scripting function\nif the timestamp's off", "start": 2858.98, "duration": 3.69}, {"text": "more than a couple hours.", "start": 2862.67, "duration": 1.87}, {"text": "So literally, it's\nnot that precise.", "start": 2864.54, "duration": 3.86}, {"text": "Having said that, the real way\nthat timestamping happens is", "start": 2868.4, "duration": 3.57}, {"text": "if a block is mined and it's the\n540,000th block and it's sort", "start": 2871.97, "duration": 6.57}, {"text": "of accepted in all the nodes,\nthese 10,000 nodes start mining", "start": 2878.54, "duration": 3.87}, {"text": "the 540,000 and 1st\nblock, in essence,", "start": 2882.41, "duration": 5.72}, {"text": "it's just think of it\nas almost like a stack.", "start": 2888.13, "duration": 4.05}, {"text": "And so what's, in essence, more\nrelevant than the actual time", "start": 2892.18, "duration": 4.74}, {"text": "that's in the\nheader, and they all", "start": 2896.92, "duration": 1.71}, {"text": "have a timestamp in\nthe header, but what's", "start": 2898.63, "duration": 4.43}, {"text": "more relevant is the\norder of the blocks,", "start": 2903.06, "duration": 3.88}, {"text": "and, most importantly,\nthe previous block hash.", "start": 2906.94, "duration": 3.42}, {"text": "Yes?", "start": 2913.71, "duration": 0.5}, {"text": "AUDIENCE: I would say that\nwithout the timestamps,", "start": 2914.21, "duration": 2.083}, {"text": "you cannot do this\ndifficulty readjustment.", "start": 2916.293, "duration": 2.607}, {"text": "The timestamps are\nvery important.", "start": 2918.9, "duration": 1.71}, {"text": "If you don't have\ntimestamps on the block,", "start": 2920.61, "duration": 2.04}, {"text": "you cannot do the\ndifficulty readjustment,", "start": 2922.65, "duration": 2.4}, {"text": "which is necessary to keep the\nrate of blocks 10 minutes after", "start": 2925.05, "duration": 3.44}, {"text": "[INAUDIBLE].", "start": 2928.49, "duration": 0.63}, {"text": "GARY GENSLER: I'm going\nto partially agree", "start": 2929.12, "duration": 1.75}, {"text": "with you because the difficulty\nadjustment happens every two", "start": 2930.87, "duration": 3.32}, {"text": "weeks.", "start": 2934.19, "duration": 0.55}, {"text": "So even if any one individual\nor five or six timestamps", "start": 2934.74, "duration": 3.89}, {"text": "are a little goofed\nup in the two weeks,", "start": 2938.63, "duration": 3.43}, {"text": "the algorithm is basically\nlooking over the course", "start": 2942.06, "duration": 3.12}, {"text": "of about 2,000 blocks.", "start": 2945.18, "duration": 2.67}, {"text": "AUDIENCE: Yeah.", "start": 2947.85, "duration": 0.84}, {"text": "So a little goofed up is fine.", "start": 2948.69, "duration": 1.84}, {"text": "But you need the timestamp.", "start": 2950.53, "duration": 1.437}, {"text": "GARY GENSLER: You\nneed the timestamps.", "start": 2951.967, "duration": 1.583}, {"text": "But it's more important\nis basically the--", "start": 2953.55, "duration": 4.74}, {"text": "here, I'll go back a slide.", "start": 2958.29, "duration": 2.02}, {"text": "It's the order of the blocks.", "start": 2960.31, "duration": 3.26}, {"text": "Please.", "start": 2963.57, "duration": 1.25}, {"text": "AUDIENCE: Going back to when\nwe talked about collisions.", "start": 2964.82, "duration": 3.06}, {"text": "The paper didn't\nreally go into detail,", "start": 2967.88, "duration": 2.16}, {"text": "but it said like in\naddition to how unlikely", "start": 2970.04, "duration": 2.55}, {"text": "it is with to the power of 128\nthat even if there were two", "start": 2972.59, "duration": 4.92}, {"text": "that hashed to the\nsame kind of has digest", "start": 2977.51, "duration": 3.39}, {"text": "that it would be\nunlikely that they'd", "start": 2980.9, "duration": 2.01}, {"text": "both be valid in the context.", "start": 2982.91, "duration": 1.5}, {"text": "So given what's a valid\nblockchain transaction", "start": 2984.41, "duration": 4.01}, {"text": "that that could\neven further reduce", "start": 2988.42, "duration": 1.57}, {"text": "the likelihood of any\nproblems, which there", "start": 2989.99, "duration": 2.16}, {"text": "wasn't a lot of detail as to\nwhy the blockchain context would", "start": 2992.15, "duration": 5.044}, {"text": "even make two hashes of the\nsame value even more unlikely", "start": 2997.194, "duration": 4.406}, {"text": "because of the context.", "start": 3001.6, "duration": 1.383}, {"text": "GARY GENSLER: I want to hold\nthat question for Tuesday.", "start": 3005.868, "duration": 2.292}, {"text": "But it has to do with rather\nthan the collision issue, what", "start": 3008.16, "duration": 3.87}, {"text": "the paper is talking about is\nif two miners solve the puzzle.", "start": 3012.03, "duration": 5.53}, {"text": "And that doesn't mean that\nthey got identical hashes", "start": 3017.56, "duration": 3.45}, {"text": "because the puzzle is not\ngeared to getting an exact hash.", "start": 3021.01, "duration": 6.96}, {"text": "The Bitcoin puzzle is\nhaving a certain number", "start": 3027.97, "duration": 3.33}, {"text": "of leading zeros.", "start": 3031.3, "duration": 1.86}, {"text": "So it's literally\nstarted, I think,", "start": 3033.16, "duration": 2.28}, {"text": "it was nine or 10 leading zeros.", "start": 3035.44, "duration": 2.19}, {"text": "I'm talking about 10 years ago.", "start": 3037.63, "duration": 1.9}, {"text": "And now, you have to hash\nto something with, I think,", "start": 3039.53, "duration": 2.36}, {"text": "it's about 20 or\n26 leading zeros.", "start": 3041.89, "duration": 3.78}, {"text": "Meaning it's gotten\nmore and more difficult,", "start": 3045.67, "duration": 2.43}, {"text": "and the result of\nthe hash has to have", "start": 3048.1, "duration": 1.68}, {"text": "a bunch of leading zeros,\nwhat you saw in that video.", "start": 3049.78, "duration": 3.72}, {"text": "I'm sorry.", "start": 3053.5, "duration": 0.81}, {"text": "AUDIENCE: I have a question on\nhow the hash, the [INAUDIBLE]", "start": 3054.31, "duration": 3.3}, {"text": "hash comes about.", "start": 3057.61, "duration": 1.13}, {"text": "So if it's only hashing\nthe transactions,", "start": 3058.74, "duration": 3.68}, {"text": "how does it change when the hash\nof the previous block changes?", "start": 3062.42, "duration": 4.906}, {"text": "GARY GENSLER: OK, so, Addy.", "start": 3067.326, "duration": 3.774}, {"text": "It reminds me of\nthat old television", "start": 3071.1, "duration": 1.78}, {"text": "show with Johnny Carson.", "start": 3072.88, "duration": 1.29}, {"text": "And you just did a great\nsetup for the comedian.", "start": 3074.17, "duration": 2.23}, {"text": "So thank you.", "start": 3076.4, "duration": 2.69}, {"text": "So I'm going to go\nto Merkle Roots.", "start": 3079.09, "duration": 2.77}, {"text": "So Merkle Roots, which\nare a binary data tree,", "start": 3081.86, "duration": 3.86}, {"text": "looks something like this.", "start": 3085.72, "duration": 2.65}, {"text": "If one had 1,000 transactions,\nI wouldn't have a pretty slide.", "start": 3088.37, "duration": 5.24}, {"text": "So this only goes\nto four levels.", "start": 3093.61, "duration": 2.67}, {"text": "But think of four\ntransactions at the bottom.", "start": 3096.28, "duration": 4.01}, {"text": "They're each hashed.", "start": 3100.29, "duration": 2.63}, {"text": "And then you concatenate.", "start": 3102.92, "duration": 2.48}, {"text": "You put the two hashes together.", "start": 3105.4, "duration": 1.5}, {"text": "You hash that.", "start": 3106.9, "duration": 0.87}, {"text": "You keep going up the tray.", "start": 3107.77, "duration": 1.89}, {"text": "If you had 1,000 transactions,\nbecause that's 2 to the 10th", "start": 3109.66, "duration": 6.12}, {"text": "roughly, then you'd have\n10 levels of this tray.", "start": 3115.78, "duration": 5.06}, {"text": "And so that's what happens.", "start": 3120.84, "duration": 1.65}, {"text": "And literally, the mining pull\noperators are doing this a lot", "start": 3122.49, "duration": 4.47}, {"text": "for the nodes.", "start": 3126.96, "duration": 1.54}, {"text": "But in the Bitcoin\ncore application,", "start": 3128.5, "duration": 5.41}, {"text": "in software that\nanybody in this room", "start": 3133.91, "duration": 2.86}, {"text": "could download the\nsoftware if you wished.", "start": 3136.77, "duration": 2.22}, {"text": "There is software that helps,\ntakes transactions, puts them", "start": 3138.99, "duration": 4.54}, {"text": "basically into this binary\ntree called a Merkle tree,", "start": 3143.53, "duration": 3.51}, {"text": "uses hash functions, and\nbasically skinnies it", "start": 3147.04, "duration": 3.18}, {"text": "all the way up to the top.", "start": 3150.22, "duration": 1.495}, {"text": "Does that--", "start": 3151.715, "duration": 1.936}, {"text": "AUDIENCE: I think\nwhat my question was", "start": 3153.651, "duration": 1.829}, {"text": "that given that this\nstructure exists,", "start": 3155.48, "duration": 4.28}, {"text": "how does the root hash change\nwith the previous block?", "start": 3159.76, "duration": 4.08}, {"text": "So basically, we saw\nthat if you change", "start": 3163.84, "duration": 2.73}, {"text": "the hash of the previous\nblock, all the blocks forward", "start": 3166.57, "duration": 2.82}, {"text": "will get invalidated\nbecause the hash changes.", "start": 3169.39, "duration": 2.82}, {"text": "But it doesn't seem to\nuse the previous hash.", "start": 3172.21, "duration": 2.17}, {"text": "GARY GENSLER: So I'm going\nto repeat the question.", "start": 3174.38, "duration": 2.083}, {"text": "Does the Merkle Root\nthat is basically", "start": 3176.463, "duration": 2.957}, {"text": "a summary of the\n10,000 transactions", "start": 3179.42, "duration": 3.18}, {"text": "that are in a block change if\nthe rest of the header changes", "start": 3182.6, "duration": 5.47}, {"text": "or the previous block change?", "start": 3188.07, "duration": 2.37}, {"text": "And the answer is no.", "start": 3190.44, "duration": 3.52}, {"text": "It only changes if some of the\ndata in the 10,000 transactions", "start": 3193.96, "duration": 4.05}, {"text": "change.", "start": 3198.01, "duration": 2.46}, {"text": "And so a Merkle Root\nwill change if you", "start": 3200.47, "duration": 4.31}, {"text": "put different\ntransactions in the mix", "start": 3204.78, "duration": 3.03}, {"text": "or, as is really important,\none of the incentives.", "start": 3207.81, "duration": 4.07}, {"text": "You get your 12 and\n1/2 bitcoins today", "start": 3211.88, "duration": 3.4}, {"text": "in what's called a\nCoinbase transaction.", "start": 3215.28, "duration": 3.13}, {"text": "And so one of these\n1,000 transactions", "start": 3218.41, "duration": 2.42}, {"text": "is the payment to the miner.", "start": 3220.83, "duration": 4.32}, {"text": "So the Merkle Root\nwould be different", "start": 3225.15, "duration": 2.1}, {"text": "depending upon who wins.", "start": 3227.25, "duration": 1.405}, {"text": "But that wasn't your question.", "start": 3231.36, "duration": 1.61}, {"text": "I'm just saying.", "start": 3232.97, "duration": 0.81}, {"text": "But Merkle Roots are\na very efficient way", "start": 3233.78, "duration": 3.51}, {"text": "to take thousands\nof transactions,", "start": 3237.29, "duration": 2.49}, {"text": "store it up, have one spot.", "start": 3239.78, "duration": 2.03}, {"text": "Please.", "start": 3244.32, "duration": 0.96}, {"text": "AUDIENCE: So the order of\nthe different transaction", "start": 3245.28, "duration": 2.79}, {"text": "has to be exactly the\nsame for everyone that", "start": 3248.07, "duration": 3.36}, {"text": "is hashing, right?", "start": 3251.43, "duration": 1.85}, {"text": "GARY GENSLER: No, actually not.", "start": 3253.28, "duration": 1.58}, {"text": "So if you're hashing, and\nyou're running a mining rig,", "start": 3254.86, "duration": 3.35}, {"text": "and Elon's running a mining\nrig, if Elon solves the puzzle", "start": 3258.21, "duration": 7.18}, {"text": "and propagates it\nout on the network,", "start": 3265.39, "duration": 1.92}, {"text": "and people start mining\non top of Elon's block", "start": 3267.31, "duration": 2.67}, {"text": "because they say,\nwell, he's finished.", "start": 3269.98, "duration": 2.2}, {"text": "You're not-- you're just\ngoing to probably start mining", "start": 3272.18, "duration": 3.38}, {"text": "on the top of his block\nand look in something", "start": 3275.56, "duration": 2.64}, {"text": "called the mempool.", "start": 3278.2, "duration": 0.93}, {"text": "The memory pool is\nthis network of all", "start": 3279.13, "duration": 3.12}, {"text": "the free floating transactions.", "start": 3282.25, "duration": 1.83}, {"text": "You'll scoop up the next\nset of transactions.", "start": 3284.08, "duration": 2.99}, {"text": "AUDIENCE: And so\nhow can we validate", "start": 3287.07, "duration": 2.73}, {"text": "that all the transaction\nhe wrote are the real ones?", "start": 3289.8, "duration": 4.84}, {"text": "GARY GENSLER: All\nright, so validation,", "start": 3294.64, "duration": 2.34}, {"text": "which is more next Thursday,\nbut I'll give it a shot.", "start": 3296.98, "duration": 2.79}, {"text": "No, no, no.", "start": 3299.77, "duration": 0.63}, {"text": "It's a good question.", "start": 3300.4, "duration": 1.78}, {"text": "Every transaction-- or\nactually, you're setting me up,", "start": 3302.18, "duration": 4.27}, {"text": "digital signatures.", "start": 3306.45, "duration": 1.35}, {"text": "There you go.", "start": 3307.8, "duration": 0.69}, {"text": "Thank you.", "start": 3308.49, "duration": 0.6}, {"text": "Did you have a question or\nI'm going to on to digital.", "start": 3309.09, "duration": 2.61}, {"text": "So the second\ncryptographic thing,", "start": 3311.7, "duration": 2.16}, {"text": "and we're going to keep\ngoing back and forth,", "start": 3313.86, "duration": 2.01}, {"text": "hash functions are basically a\nway to compress a lot of data,", "start": 3315.87, "duration": 3.78}, {"text": "have a fingerprint, make sure\nthat it's basically commitment.", "start": 3319.65, "duration": 5.79}, {"text": "Digital signatures, well,\nremember that little graph", "start": 3325.44, "duration": 2.37}, {"text": "that we had Alice and Bob?", "start": 3327.81, "duration": 2.56}, {"text": "Alice wants to send a note to\nBob and just say, hello, Bob.", "start": 3330.37, "duration": 4.47}, {"text": "She wants to encrypt it.", "start": 3334.84, "duration": 2.23}, {"text": "She encrypts it with Bob's\npublic key, sends it to him.", "start": 3337.07, "duration": 4.28}, {"text": "He decrypts it with\nhis private key.", "start": 3341.35, "duration": 1.92}, {"text": "You might say, oh my god,\nGensler, what's a private key?", "start": 3343.27, "duration": 3.03}, {"text": "What's a public key?", "start": 3346.3, "duration": 1.54}, {"text": "In cryptography, it's a way to\nkind of scramble information.", "start": 3347.84, "duration": 3.86}, {"text": "I know.", "start": 3351.7, "duration": 0.51}, {"text": "I'm really making this like--", "start": 3352.21, "duration": 3.03}, {"text": "So if we went back to\nthat little mechanism", "start": 3355.24, "duration": 4.89}, {"text": "the Romans used or we used what\nthe Germans used in the Enigma", "start": 3360.13, "duration": 3.84}, {"text": "machine, they were\nsymmetric cryptography.", "start": 3363.97, "duration": 5.69}, {"text": "Both people had the key.", "start": 3369.66, "duration": 2.16}, {"text": "The key was the Enigma\nmachine with five rotors.", "start": 3371.82, "duration": 5.01}, {"text": "In the 1970s, some wonderful\ntechnologist here and elsewhere", "start": 3376.83, "duration": 5.49}, {"text": "basically said, well, what\nif the key isn't the same?", "start": 3382.32, "duration": 3.88}, {"text": "Because the adversary\ncould steal the key.", "start": 3386.2, "duration": 2.99}, {"text": "What if it's not symmetric\nbut it's asymmetric?", "start": 3389.19, "duration": 2.47}, {"text": "There's a private\nkey and a public key.", "start": 3391.66, "duration": 2.22}, {"text": "In essence, there's\ntwo keys that have", "start": 3393.88, "duration": 2.16}, {"text": "some mathematical relationship.", "start": 3396.04, "duration": 3.19}, {"text": "And the math between\nthese two keys", "start": 3399.23, "duration": 2.19}, {"text": "don't matter for\na class like this.", "start": 3401.42, "duration": 2.37}, {"text": "But know that the public key and\nthe private key link together.", "start": 3403.79, "duration": 6.35}, {"text": "They're bonded together.", "start": 3410.14, "duration": 2.86}, {"text": "But the critical thing is\nabout digital signatures,", "start": 3413.0, "duration": 4.59}, {"text": "there's three functions.", "start": 3417.59, "duration": 1.41}, {"text": "You have to generate a key pair.", "start": 3419.0, "duration": 1.66}, {"text": "And when a key\npair is generated,", "start": 3420.66, "duration": 2.09}, {"text": "a public key and a private key\nare generated at the same time.", "start": 3422.75, "duration": 5.64}, {"text": "And they need a random\nnumber to go into it.", "start": 3428.39, "duration": 3.277}, {"text": "And one of the things\nthat makes a lot", "start": 3431.667, "duration": 1.583}, {"text": "of Bitcoin and other\nwallets insecure,", "start": 3433.25, "duration": 5.11}, {"text": "and it's probably why\nsome have been hacked,", "start": 3438.36, "duration": 2.75}, {"text": "the wallets, not Bitcoin,\nis because they don't have", "start": 3441.11, "duration": 2.86}, {"text": "good random number generation.", "start": 3443.97, "duration": 2.04}, {"text": "Yes, Brodish?", "start": 3446.01, "duration": 3.06}, {"text": "I saw-- I was at a\nconference last week", "start": 3449.07, "duration": 1.98}, {"text": "where a technologist from the\nUniversity of Pennsylvania", "start": 3451.05, "duration": 4.74}, {"text": "had done a survey of\n150 hedge funds, mining", "start": 3455.79, "duration": 3.81}, {"text": "companies, and Bitcoin wallet\ncompanies and the like.", "start": 3459.6, "duration": 3.96}, {"text": "So they actually let a\ncybersecurity individual", "start": 3463.56, "duration": 3.27}, {"text": "get inside and do a survey of\n150 what you would consider", "start": 3466.83, "duration": 4.26}, {"text": "really committed, high end\nusers of Bitcoin, miners", "start": 3471.09, "duration": 4.41}, {"text": "and hedge funds and\ncrypto exchanges.", "start": 3475.5, "duration": 5.1}, {"text": "And it was horrifying,\ntheir cyber security", "start": 3480.6, "duration": 2.77}, {"text": "as to what they're doing\nwith their private keys.", "start": 3483.37, "duration": 4.16}, {"text": "Before he even got to the\nprivate keys, many of them", "start": 3487.53, "duration": 2.25}, {"text": "didn't really have a secure way\nto create the random numbers", "start": 3489.78, "duration": 3.72}, {"text": "to create their private keys.", "start": 3493.5, "duration": 2.35}, {"text": "So it's just a piece.", "start": 3495.85, "duration": 1.85}, {"text": "When somebody says they have\nreally good private key,", "start": 3497.7, "duration": 2.4}, {"text": "public key, in the\nback of your mind,", "start": 3500.1, "duration": 3.0}, {"text": "just know there's got to be\nsome way to do a random number", "start": 3503.1, "duration": 2.79}, {"text": "generation.", "start": 3505.89, "duration": 0.81}, {"text": "That's the only\nmath that I'm going", "start": 3506.7, "duration": 1.68}, {"text": "to ask you to remember of that.", "start": 3508.38, "duration": 2.21}, {"text": "There is a signature function.", "start": 3513.49, "duration": 1.71}, {"text": "And the key thing is\na signature creates.", "start": 3515.2, "duration": 2.88}, {"text": "You can create a\ndigital signature", "start": 3518.08, "duration": 2.58}, {"text": "from a message\nand a private key.", "start": 3520.66, "duration": 1.94}, {"text": "So if Kelly has a\nprivate key and wants", "start": 3525.24, "duration": 3.63}, {"text": "to send a secret message to\nsomebody across the room--", "start": 3528.87, "duration": 4.27}, {"text": "Isabella, you want a\nmessage from Kelly?", "start": 3533.14, "duration": 1.67}, {"text": "Kelly's going to\ntake the message.", "start": 3537.61, "duration": 2.64}, {"text": "You got this, Kelly?", "start": 3540.25, "duration": 1.6}, {"text": "You're going to\ntake the message,", "start": 3541.85, "duration": 1.62}, {"text": "and you're going to sign\nit with a private key.", "start": 3543.47, "duration": 3.83}, {"text": "You send it over to Isabella.", "start": 3547.3, "duration": 3.93}, {"text": "How's Isabella know\nthat it was from you?", "start": 3551.23, "duration": 3.43}, {"text": "AUDIENCE: She has to\ndecrypt it with her key.", "start": 3554.66, "duration": 4.68}, {"text": "GARY GENSLER: She's\ngot to verify it.", "start": 3559.34, "duration": 1.56}, {"text": "So there's a function called\na verification function,", "start": 3560.9, "duration": 2.82}, {"text": "and it comes back just yes, no.", "start": 3563.72, "duration": 2.46}, {"text": "I mean, it might\nsay it differently.", "start": 3566.18, "duration": 2.1}, {"text": "But it's just a yes, no.", "start": 3568.28, "duration": 1.65}, {"text": "It's a verification function.", "start": 3569.93, "duration": 1.83}, {"text": "Isabella-- you want\nto do this with me--", "start": 3571.76, "duration": 2.63}, {"text": "is going to verify\nyour signature", "start": 3574.39, "duration": 2.8}, {"text": "is valid for this\nmessage because you", "start": 3577.19, "duration": 3.76}, {"text": "have the public key.", "start": 3580.95, "duration": 1.87}, {"text": "So you're right.", "start": 3582.82, "duration": 0.92}, {"text": "Isabella has your public key.", "start": 3583.74, "duration": 3.14}, {"text": "But using your public key, she\ncan verify that the signature.", "start": 3586.88, "duration": 4.7}, {"text": "It's magical math.", "start": 3591.58, "duration": 2.56}, {"text": "Well, it's not magical math.", "start": 3594.14, "duration": 1.32}, {"text": "It's real math.", "start": 3595.46, "duration": 1.8}, {"text": "But it's not math we need\nto study in this class.", "start": 3597.26, "duration": 3.42}, {"text": "Yes, Hugo?", "start": 3600.68, "duration": 1.61}, {"text": "AUDIENCE: Back to\ngenerating the key pair.", "start": 3602.29, "duration": 1.75}, {"text": "GARY GENSLER: Yeah?", "start": 3604.04, "duration": 0.9}, {"text": "AUDIENCE: So they're\nboth generated", "start": 3604.94, "duration": 1.18}, {"text": "from the random number?", "start": 3606.12, "duration": 1.01}, {"text": "One is not-- like\nthe private is not", "start": 3607.13, "duration": 2.55}, {"text": "determined by the public\nkey or the other way around?", "start": 3609.68, "duration": 3.927}, {"text": "GARY GENSLER: The public--", "start": 3613.607, "duration": 1.083}, {"text": "you can think of it--", "start": 3614.69, "duration": 1.74}, {"text": "in Bitcoin, it uses an\nelliptic curve cryptography.", "start": 3616.43, "duration": 5.18}, {"text": "And you can think of it\nas that the private key", "start": 3621.61, "duration": 3.94}, {"text": "is based on the random number.", "start": 3625.55, "duration": 4.92}, {"text": "To be more technical,\nthe random number", "start": 3630.47, "duration": 5.3}, {"text": "is what gets you\nto the public key.", "start": 3635.77, "duration": 2.49}, {"text": "But I think of it\nas the private key", "start": 3638.26, "duration": 1.85}, {"text": "is almost the random number,\nand then the public key", "start": 3640.11, "duration": 2.44}, {"text": "is generated along with it.", "start": 3642.55, "duration": 1.44}, {"text": "AUDIENCE: So [INAUDIBLE].", "start": 3643.99, "duration": 3.15}, {"text": "GARY GENSLER: Yes.", "start": 3647.14, "duration": 2.553}, {"text": "AUDIENCE: So you pick a\nrandom number actually", "start": 3649.693, "duration": 1.917}, {"text": "between 0 and 256,\nthat's your private key.", "start": 3651.61, "duration": 3.275}, {"text": "To pick a public\nkey, you derive it", "start": 3654.885, "duration": 1.945}, {"text": "directly from the private key.", "start": 3656.83, "duration": 1.83}, {"text": "In fact, all you do is you\nexponentiate another number", "start": 3658.66, "duration": 2.67}, {"text": "by the private key.", "start": 3661.33, "duration": 2.47}, {"text": "So you can think\nof the public key", "start": 3663.8, "duration": 1.58}, {"text": "as a one way function\nof the private key.", "start": 3665.38, "duration": 3.03}, {"text": "So given a public key, you\ncannot recover the private key.", "start": 3668.41, "duration": 2.893}, {"text": "If you could, then you could\nsign, potentially disastrous.", "start": 3671.303, "duration": 2.417}, {"text": "GARY GENSLER: And instead of\nexponentiation, in Bitcoin,", "start": 3676.38, "duration": 2.49}, {"text": "it uses a function called\nthe elliptic curve.", "start": 3678.87, "duration": 4.17}, {"text": "So what properties?", "start": 3683.04, "duration": 1.11}, {"text": "And these are the key\neconomic properties as well as", "start": 3684.15, "duration": 2.52}, {"text": "cryptographic properties.", "start": 3686.67, "duration": 1.74}, {"text": "Basically, it's infeasible.", "start": 3688.41, "duration": 1.71}, {"text": "And again, I use\nthe word infeasible.", "start": 3690.12, "duration": 1.98}, {"text": "I didn't say impossible,\neven though Eileen", "start": 3692.1, "duration": 2.85}, {"text": "might want to tell me\nthat it's 1 over 10", "start": 3694.95, "duration": 2.55}, {"text": "to the 40th of something.", "start": 3697.5, "duration": 1.77}, {"text": "But it's infeasible to find a\nprivate key from a public key,", "start": 3699.27, "duration": 3.57}, {"text": "so reverse engineer.", "start": 3702.84, "duration": 2.23}, {"text": "AUDIENCE: So even if you\ncan't find the private key,", "start": 3705.07, "duration": 3.0}, {"text": "like in the case of\nKelly and Isabella,", "start": 3708.07, "duration": 2.6}, {"text": "if I knew Kelly's\npublic key, could I", "start": 3710.67, "duration": 4.65}, {"text": "send a message to Isabella\nimpersonating Kelly?", "start": 3715.32, "duration": 4.3}, {"text": "GARY GENSLER: No.", "start": 3719.62, "duration": 1.91}, {"text": "You need to do a signature--", "start": 3721.53, "duration": 3.804}, {"text": "if you please just\nrun your eye up there.", "start": 3725.334, "duration": 2.856}, {"text": "To do a digital\nsignature, you need", "start": 3728.19, "duration": 2.04}, {"text": "a private key and a message.", "start": 3730.23, "duration": 2.1}, {"text": "And it's a function of the\nmessage and the private key.", "start": 3732.33, "duration": 3.18}, {"text": "Let's call it complex math.", "start": 3739.88, "duration": 2.79}, {"text": "That digital signature was\ncreated from the private key.", "start": 3742.67, "duration": 7.58}, {"text": "And the public key was\ncreated from the private key.", "start": 3750.25, "duration": 4.08}, {"text": "And to oversimplify the reason\nthat the verify function", "start": 3754.33, "duration": 3.39}, {"text": "works is because both\nthe digital signature", "start": 3757.72, "duration": 4.61}, {"text": "and the public key\nthat Isabella has--", "start": 3762.33, "duration": 2.37}, {"text": "Isabella has this\ndigital signature,", "start": 3764.7, "duration": 3.11}, {"text": "and she has the public key,\nand she has the message.", "start": 3767.81, "duration": 4.185}, {"text": "The math is such\nthat, basically,", "start": 3774.5, "duration": 3.06}, {"text": "the private key, if you wish,\nalmost like factors out.", "start": 3777.56, "duration": 5.53}, {"text": "But think of two functions.", "start": 3783.09, "duration": 2.72}, {"text": "Isabella has Kelly's\npublic key, the message,", "start": 3785.81, "duration": 3.36}, {"text": "the digital signature.", "start": 3789.17, "duration": 1.32}, {"text": "It either verifies\nor it doesn't.", "start": 3790.49, "duration": 1.81}, {"text": "But she never has to\nsee the private key.", "start": 3792.3, "duration": 2.45}, {"text": "And in fact, Kelly\ndoes not want her", "start": 3794.75, "duration": 1.65}, {"text": "to ever see the private key.", "start": 3796.4, "duration": 2.16}, {"text": "AUDIENCE: Eric, maybe\njust to simplify", "start": 3798.56, "duration": 3.79}, {"text": "the way the validation of\nthe digital signature works", "start": 3802.35, "duration": 4.36}, {"text": "is Kelly's message is run\nthrough a hash function which", "start": 3806.71, "duration": 5.86}, {"text": "generates a hash.", "start": 3812.57, "duration": 1.44}, {"text": "And it's encrypted\nwith her private key.", "start": 3814.01, "duration": 3.78}, {"text": "Then the message encrypted\nand the digital signature", "start": 3817.79, "duration": 3.48}, {"text": "goes to Isabella.", "start": 3821.27, "duration": 1.54}, {"text": "Isabella, what she does is\nusing the same hash function", "start": 3822.81, "duration": 3.02}, {"text": "to run it with the document\nto generate the hash function", "start": 3825.83, "duration": 4.02}, {"text": "and uses the public key of\nKelly to unencrypt the signature", "start": 3829.85, "duration": 4.2}, {"text": "and compare those two hashes.", "start": 3834.05, "duration": 1.8}, {"text": "If those two hashes\ncorrespond that", "start": 3835.85, "duration": 1.86}, {"text": "means that the message\nbelongs to Kelly", "start": 3837.71, "duration": 3.36}, {"text": "and it hasn't been\ntampered with.", "start": 3841.07, "duration": 1.77}, {"text": "So that's the more or\nless the simplification", "start": 3842.84, "duration": 2.58}, {"text": "of the digital\nsignature process.", "start": 3845.42, "duration": 4.29}, {"text": "AUDIENCE: I don't know if--", "start": 3849.71, "duration": 2.06}, {"text": "GARY GENSLER: So I mean,\nthe key is basically", "start": 3851.77, "duration": 2.29}, {"text": "that there's a scheme\nunrelated to Bitcoin", "start": 3854.06, "duration": 2.88}, {"text": "that exists for many other\nreasons on the internet,", "start": 3856.94, "duration": 3.24}, {"text": "many other reasons in\ncommerce and at war", "start": 3860.18, "duration": 5.31}, {"text": "that this public key,\nprivate key cryptography.", "start": 3865.49, "duration": 4.65}, {"text": "And it's not simply\njust going back,", "start": 3870.14, "duration": 3.15}, {"text": "it's not just simply\nAlice sending something.", "start": 3873.29, "duration": 2.64}, {"text": "It's also digital signatures.", "start": 3875.93, "duration": 2.43}, {"text": "You generate the key pair.", "start": 3878.36, "duration": 1.89}, {"text": "Everything in Bitcoin,\neverything in Ethereum", "start": 3880.25, "duration": 2.52}, {"text": "has key pairs, public\nkey and private key,", "start": 3882.77, "duration": 3.1}, {"text": "a digital signature.", "start": 3885.87, "duration": 1.28}, {"text": "But, Kelly, never\nlose your private key.", "start": 3887.15, "duration": 4.28}, {"text": "You got that?", "start": 3891.43, "duration": 0.63}, {"text": "Do not.", "start": 3892.06, "duration": 0.907}, {"text": "And by the way, you have to\ncreate it with a good random", "start": 3892.967, "duration": 2.333}, {"text": "number generator because most\nsophisticated hedge funds", "start": 3895.3, "duration": 3.57}, {"text": "around the world aren't.", "start": 3898.87, "duration": 1.393}, {"text": "So you're going to\nbe better than those.", "start": 3900.263, "duration": 1.667}, {"text": "That's what I learned at a\nconference I was at recently.", "start": 3901.93, "duration": 3.03}, {"text": "And then there's a\nverification function.", "start": 3904.96, "duration": 3.09}, {"text": "AUDIENCE: A quick question about\nthe random number generator", "start": 3908.05, "duration": 2.52}, {"text": "and the verification function.", "start": 3910.57, "duration": 2.07}, {"text": "So is there any third\nparty generating", "start": 3912.64, "duration": 3.51}, {"text": "the generator or the generator\nis a function already existing", "start": 3916.15, "duration": 6.96}, {"text": "and already there?", "start": 3923.11, "duration": 3.53}, {"text": "GARY GENSLER: So the question\nis, if random number generation", "start": 3926.64, "duration": 3.81}, {"text": "is so important, are\nthere outside parties that", "start": 3930.45, "duration": 3.03}, {"text": "have good software, in essence,\nto produce the random number", "start": 3933.48, "duration": 3.24}, {"text": "generation?", "start": 3936.72, "duration": 0.66}, {"text": "And the answer is\nyes, and there's", "start": 3937.38, "duration": 1.417}, {"text": "some that are not so good.", "start": 3938.797, "duration": 1.643}, {"text": "And yes, some good\nlaptops have it.", "start": 3940.44, "duration": 3.15}, {"text": "At the heart, I\nwant to skip ahead.", "start": 3943.59, "duration": 3.51}, {"text": "Elliptic curve digital\nsignature algorithm,", "start": 3947.1, "duration": 3.0}, {"text": "that's the actual algorithm\nthat Bitcoin uses to take", "start": 3950.1, "duration": 4.08}, {"text": "the private key and so forth.", "start": 3954.18, "duration": 2.7}, {"text": "But many of the wallets, if you\ndownload a wallet application", "start": 3956.88, "duration": 7.11}, {"text": "to hold your Bitcoin,\nto hold your Litecoin,", "start": 3963.99, "duration": 2.31}, {"text": "to hold some other coin,\nthat wallet application", "start": 3966.3, "duration": 3.09}, {"text": "has a random number\ngeneration software.", "start": 3969.39, "duration": 6.38}, {"text": "I can't attest to all the random\nnumber generation software.", "start": 3975.77, "duration": 3.54}, {"text": "I'm not a cyber security expert.", "start": 3979.31, "duration": 3.09}, {"text": "But there's probably\na range of some", "start": 3982.4, "duration": 1.95}, {"text": "that are a little bit more.", "start": 3984.35, "duration": 3.62}, {"text": "There's stronger ones.", "start": 3987.97, "duration": 1.77}, {"text": "The key to random\nnumber generation", "start": 3989.74, "duration": 1.62}, {"text": "is if you're generating\nany length that it truly", "start": 3991.36, "duration": 4.14}, {"text": "is not clumpier,\nthat there's let's", "start": 3995.5, "duration": 5.21}, {"text": "say it's what maximum\nentropy, and that you really", "start": 4000.71, "duration": 4.45}, {"text": "don't have any clumps.", "start": 4005.16, "duration": 2.69}, {"text": "If it all clumps\nin one area, then", "start": 4007.85, "duration": 2.5}, {"text": "that's not great randomness.", "start": 4010.35, "duration": 1.753}, {"text": "So I just want to\nfinish because there's", "start": 4012.103, "duration": 1.667}, {"text": "one other thing we're\ngoing to chat about", "start": 4013.77, "duration": 1.708}, {"text": "to lay the groundwork\nis Bitcoin addresses.", "start": 4015.478, "duration": 3.752}, {"text": "I put that up.", "start": 4019.23, "duration": 0.81}, {"text": "You can look at\nthe slides later.", "start": 4020.04, "duration": 2.1}, {"text": "The details don't matter much.", "start": 4022.14, "duration": 3.03}, {"text": "But the key thing is that\nwhen you hear somebody talk", "start": 4025.17, "duration": 2.76}, {"text": "about public keys and Bitcoin\naddresses, colloquially,", "start": 4027.93, "duration": 5.1}, {"text": "we all reference them the same.", "start": 4033.03, "duration": 2.22}, {"text": "They're actually not.", "start": 4035.25, "duration": 2.53}, {"text": "The technology that Nakamoto\ndid was he uses the public key.", "start": 4037.78, "duration": 7.3}, {"text": "He literally hashed it twice,\nonce with this hash function", "start": 4045.08, "duration": 5.91}, {"text": "called SHA256,\nanother hash function,", "start": 4050.99, "duration": 4.14}, {"text": "then concatenates, and puts a\nlittle check sum at the end,", "start": 4055.13, "duration": 4.85}, {"text": "and then uses something\ncalled a base 58 to make", "start": 4059.98, "duration": 2.64}, {"text": "it even shorter.", "start": 4062.62, "duration": 2.8}, {"text": "I've gone back and read\nsome of Nakamoto's emails", "start": 4065.42, "duration": 3.06}, {"text": "for the two years after\nhe published all this", "start": 4068.48, "duration": 3.15}, {"text": "and I've read other things.", "start": 4071.63, "duration": 1.59}, {"text": "My understanding is the reason\nthere is two hash functions", "start": 4073.22, "duration": 3.3}, {"text": "and actually two\ndifferent ones was just", "start": 4076.52, "duration": 2.43}, {"text": "to make everything\na bit more secure.", "start": 4078.95, "duration": 3.31}, {"text": "Also, a public key is very long.", "start": 4082.26, "duration": 2.23}, {"text": "It's about 512 bits.", "start": 4084.49, "duration": 3.36}, {"text": "And so you can shrink\nthe data and make", "start": 4087.85, "duration": 2.58}, {"text": "the data more compressed\nby hashing it,", "start": 4090.43, "duration": 4.89}, {"text": "which took it to 256 bits.", "start": 4095.32, "duration": 2.31}, {"text": "He hashes it twice, and\nthen he does this base 58", "start": 4097.63, "duration": 3.37}, {"text": "and makes it even\na little tighter.", "start": 4101.0, "duration": 3.77}, {"text": "So for all purposes, you\ncould go ahead and just use", "start": 4104.77, "duration": 3.629}, {"text": "public key and Bitcoin\naddress is the same.", "start": 4108.399, "duration": 2.571}, {"text": "But remember back in\nthe mind, oh, actually,", "start": 4110.97, "duration": 3.679}, {"text": "they're a little different.", "start": 4114.649, "duration": 1.54}, {"text": "Bitcoin addresses are a little\nbit more secure supposedly,", "start": 4116.189, "duration": 4.84}, {"text": "unless of course somebody\nhas hacked into your wallet", "start": 4121.029, "duration": 2.851}, {"text": "and figured out all\nthese little details.", "start": 4123.88, "duration": 3.059}, {"text": "A Bitcoin address\nis a little bit", "start": 4126.939, "duration": 2.701}, {"text": "like the signatures on these\nnotes we talked about, right?", "start": 4129.64, "duration": 5.339}, {"text": "Remember what an-- half of you\ndon't use checking accounts.", "start": 4134.979, "duration": 4.141}, {"text": "But these are early\nforms of checks.", "start": 4139.12, "duration": 3.39}, {"text": "And there's a signature\non the bottom.", "start": 4142.51, "duration": 1.86}, {"text": "That's really kind\nof a Bitcoin address.", "start": 4144.37, "duration": 4.05}, {"text": "I'm sorry, the signature\nis the digital signature.", "start": 4148.42, "duration": 3.55}, {"text": "The address, the Bitcoin\naddress is who it's paid for.", "start": 4151.97, "duration": 3.58}, {"text": "And I promise last slide.", "start": 4155.55, "duration": 2.162}, {"text": "We're going to be talking\nabout this next week.", "start": 4157.712, "duration": 1.958}, {"text": "Transactions, all\nthat stuff that", "start": 4159.67, "duration": 2.34}, {"text": "rolls up into the Merkle trees.", "start": 4162.01, "duration": 2.04}, {"text": "All that little itty bitty\nimportant information,", "start": 4164.05, "duration": 3.929}, {"text": "they basically have an input\nand an output, the input", "start": 4167.979, "duration": 5.151}, {"text": "and a lock time.", "start": 4173.13, "duration": 1.74}, {"text": "But the input is a\nprevious transaction.", "start": 4174.87, "duration": 4.35}, {"text": "This uniquely identifies,\nbasically, money.", "start": 4179.22, "duration": 5.49}, {"text": "And you're going to\nsend value in Satoshis.", "start": 4184.71, "duration": 2.05}, {"text": "He named the unit of\ncount for himself.", "start": 4189.609, "duration": 4.901}, {"text": "There's a lot of Satoshis\nin every one Bitcoin.", "start": 4194.51, "duration": 2.4}, {"text": "That's why we don't hear\nmuch about Satoshis.", "start": 4196.91, "duration": 2.1}, {"text": "But there's 10 to the 8th\nSatoshis in every one Bitcoin.", "start": 4199.01, "duration": 5.55}, {"text": "So when you actually\nenter in the computer", "start": 4204.56, "duration": 2.01}, {"text": "code in a transaction,\nyou're doing it in Satoshis.", "start": 4206.57, "duration": 5.31}, {"text": "And it's sent to a public key.", "start": 4211.88, "duration": 1.86}, {"text": "That's a coin.", "start": 4213.74, "duration": 1.59}, {"text": "That is what the incentive\nsystem's all about.", "start": 4215.33, "duration": 3.31}, {"text": "Any other questions?", "start": 4221.64, "duration": 3.02}, {"text": "And this is just I know.", "start": 4224.66, "duration": 1.49}, {"text": "There's a lot.", "start": 4226.15, "duration": 1.58}, {"text": "I wonder how many of you are\ngoing to come back on Thursday.", "start": 4227.73, "duration": 3.64}, {"text": "No.", "start": 4231.37, "duration": 0.5}, {"text": "Let me say this.", "start": 4231.87, "duration": 1.42}, {"text": "It's not just that we're at MIT.", "start": 4233.29, "duration": 1.55}, {"text": "But we are at MIT.", "start": 4234.84, "duration": 1.14}, {"text": "Come on.", "start": 4235.98, "duration": 1.71}, {"text": "Everybody in this room can get\nthese kind of key concepts.", "start": 4237.69, "duration": 5.64}, {"text": "The key questions\nthat we talked about", "start": 4243.33, "duration": 2.46}, {"text": "were timestamped\nappend-only logs.", "start": 4245.79, "duration": 2.64}, {"text": "Does anybody want\nto tell me what a--", "start": 4248.43, "duration": 1.89}, {"text": "if this class here in\nthe next seven minutes", "start": 4250.32, "duration": 2.67}, {"text": "can get these two\nconcepts, that's", "start": 4252.99, "duration": 2.19}, {"text": "all we talked about\nfor the last hour.", "start": 4255.18, "duration": 1.86}, {"text": "So I don't know your\nname in the orange shirt.", "start": 4257.04, "duration": 4.392}, {"text": "AUDIENCE: Andrew.", "start": 4261.432, "duration": 0.808}, {"text": "GARY GENSLER: What's that?", "start": 4262.24, "duration": 1.083}, {"text": "Andrew?", "start": 4263.323, "duration": 0.507}, {"text": "Andrew, what's time\nappend-only logs?", "start": 4263.83, "duration": 2.43}, {"text": "AUDIENCE: Timestamped\nappend-only logs is essentially", "start": 4266.26, "duration": 2.7}, {"text": "a record of\ntransactions or a block", "start": 4268.96, "duration": 2.13}, {"text": "as blockchain uses\nit with a time.", "start": 4271.09, "duration": 2.745}, {"text": "And that can't be\nchanged in the future.", "start": 4273.835, "duration": 1.725}, {"text": "So you can only add\non transactions.", "start": 4275.56, "duration": 1.5}, {"text": "GARY GENSLER: So it's\nkind of immutable because", "start": 4277.06, "duration": 1.958}, {"text": "of all this cryptography.", "start": 4279.018, "duration": 2.132}, {"text": "Stuart Haber was making it in\na timestamped append-only log.", "start": 4281.15, "duration": 5.16}, {"text": "And he was placing it where?", "start": 4286.31, "duration": 1.785}, {"text": "Carolyn, you still with me?", "start": 4288.095, "duration": 1.125}, {"text": "Where was Haber putting it?", "start": 4289.22, "duration": 1.868}, {"text": "AUDIENCE: New York Times.", "start": 4291.088, "duration": 1.042}, {"text": "GARY GENSLER: New York Times.", "start": 4292.13, "duration": 1.208}, {"text": "There you go in the\nclassified section.", "start": 4293.338, "duration": 1.887}, {"text": "So it's just it's a bunch of\nblocks of data compressed up.", "start": 4297.78, "duration": 5.112}, {"text": "So we talked about\nsomething called", "start": 4302.892, "duration": 1.458}, {"text": "Merkle trees and Merkle Roots.", "start": 4304.35, "duration": 2.1}, {"text": "Just think about as that's a\nway to take a lot of information", "start": 4306.45, "duration": 3.09}, {"text": "and compress it but also\nmake it searchable later", "start": 4309.54, "duration": 4.29}, {"text": "because 1,000 transactions,\nwhen we talk next week,", "start": 4313.83, "duration": 3.22}, {"text": "you have to be able to verify.", "start": 4317.05, "duration": 1.75}, {"text": "Somebody asked me about\nhow to verify, right?", "start": 4318.8, "duration": 2.89}, {"text": "When you go back to verify, you\nneed an index number to find it", "start": 4321.69, "duration": 4.14}, {"text": "in that Merkle tree situation.", "start": 4325.83, "duration": 3.04}, {"text": "And it's secured\nthrough hash functions.", "start": 4328.87, "duration": 1.69}, {"text": "Anybody want to tell me\nthat easiest lay definition", "start": 4330.56, "duration": 2.31}, {"text": "of the hash function?", "start": 4332.87, "duration": 1.35}, {"text": "Jennifer?", "start": 4336.93, "duration": 2.54}, {"text": "AUDIENCE: It's like\na mapping can be", "start": 4339.47, "duration": 3.23}, {"text": "so members can get to just one.", "start": 4342.7, "duration": 3.58}, {"text": "GARY GENSLER: Right.", "start": 4346.28, "duration": 1.18}, {"text": "You could take a picture of this\nclassroom and everybody exactly", "start": 4347.46, "duration": 5.31}, {"text": "and they could map\nit into something.", "start": 4352.77, "duration": 2.908}, {"text": "I don't know.", "start": 4355.678, "duration": 0.542}, {"text": "Would a QR code be\na form of a hash?", "start": 4356.22, "duration": 2.49}, {"text": "Not cryptographically secure.", "start": 4361.34, "duration": 1.87}, {"text": "But is it a hash?", "start": 4363.21, "duration": 1.228}, {"text": "AUDIENCE: It's more of a\ndifferent representation", "start": 4364.438, "duration": 2.042}, {"text": "of some data rather than\nbinary you're using.", "start": 4366.48, "duration": 3.11}, {"text": "GARY GENSLER: All right,\nso I failed that one.", "start": 4369.59, "duration": 3.26}, {"text": "AUDIENCE: It often\nstores hashes.", "start": 4372.85, "duration": 2.767}, {"text": "GARY GENSLER: So\ncryptographic hash function", "start": 4375.617, "duration": 1.833}, {"text": "is a way to take not\nonly a lot of information", "start": 4377.45, "duration": 2.58}, {"text": "and put it into a fixed\nform, but the key thing here", "start": 4380.03, "duration": 3.57}, {"text": "is the hash functions are\nwhat tie the blocks together", "start": 4383.6, "duration": 3.39}, {"text": "because hash functions can\npoint to previous information.", "start": 4386.99, "duration": 4.09}, {"text": "And as the video showed, if you\nchange any of the underlying", "start": 4391.08, "duration": 3.92}, {"text": "information, the hash changes.", "start": 4395.0, "duration": 3.19}, {"text": "So what does that give you?", "start": 4398.19, "duration": 2.9}, {"text": "It basically secures the data.", "start": 4401.09, "duration": 2.6}, {"text": "You know if somebody\nhas tampered.", "start": 4403.69, "duration": 2.01}, {"text": "So the only reason to really\nlearn about hash functions", "start": 4405.7, "duration": 4.08}, {"text": "is it's to say, oh, I get it.", "start": 4409.78, "duration": 2.01}, {"text": "This is one of the ways to\nmake this data tamper proof.", "start": 4411.79, "duration": 5.28}, {"text": "Go on.", "start": 4417.07, "duration": 0.59}, {"text": "AUDIENCE: I have a question\nabout a theoretical event where", "start": 4417.66, "duration": 3.17}, {"text": "a better hash function\nis found than the SHA256.", "start": 4420.83, "duration": 6.6}, {"text": "How would that be implemented\ninto the Bitcoin network", "start": 4427.43, "duration": 2.58}, {"text": "practically?", "start": 4430.01, "duration": 1.26}, {"text": "There needs to be\na consensus and--", "start": 4431.27, "duration": 2.04}, {"text": "GARY GENSLER: So how\nwould any relevant change", "start": 4433.31, "duration": 4.65}, {"text": "be adopted into Bitcoin\nis always a challenge", "start": 4437.96, "duration": 3.21}, {"text": "because it's a\ndecentralized network.", "start": 4441.17, "duration": 3.18}, {"text": "And all decentralized\nnetworks have a little bit", "start": 4444.35, "duration": 3.3}, {"text": "of a governance challenge.", "start": 4447.65, "duration": 1.56}, {"text": "The governance challenge is,\nhow do you do software updates?", "start": 4449.21, "duration": 3.64}, {"text": "We all know that on our\nlaptops, our iPhones,", "start": 4452.85, "duration": 4.19}, {"text": "there's probably software\nupdates going on here now", "start": 4457.04, "duration": 3.0}, {"text": "unbeknownst to me, right?", "start": 4460.04, "duration": 2.16}, {"text": "They're probably just\nApple has dropped.", "start": 4462.2, "duration": 1.83}, {"text": "I mean, who knows what\nthey're doing in here, right?", "start": 4464.03, "duration": 2.67}, {"text": "And Uber, I really, one of my\nfavorites, who knows what's", "start": 4466.7, "duration": 3.36}, {"text": "happening inside this phone.", "start": 4470.06, "duration": 1.39}, {"text": "But the commercial enterprise,\nthe central authority", "start": 4471.45, "duration": 5.18}, {"text": "has a way to update\nthe software.", "start": 4476.63, "duration": 1.65}, {"text": "We probably sign\nsome terms of use", "start": 4478.28, "duration": 2.28}, {"text": "that allows them to do that.", "start": 4480.56, "duration": 2.06}, {"text": "In a decentralized\nnetwork like this,", "start": 4482.62, "duration": 3.31}, {"text": "there has to be consensus.", "start": 4485.93, "duration": 2.28}, {"text": "And so the only way\nreally to update", "start": 4488.21, "duration": 2.94}, {"text": "the software for a new hash\nfunction or for most everything", "start": 4491.15, "duration": 4.51}, {"text": "else is, in essence,\nthat the nodes,", "start": 4495.66, "duration": 4.35}, {"text": "the operators of the software\ncollectively in a consensus", "start": 4500.01, "duration": 3.21}, {"text": "form adopt it.", "start": 4503.22, "duration": 1.5}, {"text": "So it's another way that\nnot only is the data", "start": 4504.72, "duration": 5.33}, {"text": "immutable because of these hash\nfunctions but the software is.", "start": 4510.05, "duration": 5.04}, {"text": "And that comes both\nwith benefits and costs.", "start": 4515.09, "duration": 3.7}, {"text": "Some people would say\nthat's a bug of blockchain.", "start": 4518.79, "duration": 2.22}, {"text": "Some people would\nsay it's a feature.", "start": 4521.01, "duration": 1.895}, {"text": "You can come to\nyour own judgment", "start": 4522.905, "duration": 1.375}, {"text": "over the course\nof this semester.", "start": 4524.28, "duration": 1.83}, {"text": "But the software\nis harder to update", "start": 4526.11, "duration": 3.67}, {"text": "than software in\ncentralized authorities", "start": 4529.78, "duration": 3.39}, {"text": "because centralized\nauthorities just say--", "start": 4533.17, "duration": 2.28}, {"text": "they just push the--", "start": 4535.45, "duration": 2.872}, {"text": "now sometimes you have\nto click and say update.", "start": 4538.322, "duration": 1.958}, {"text": "But don't be naive.", "start": 4544.02, "duration": 1.11}, {"text": "Not every software do you click.", "start": 4545.13, "duration": 4.02}, {"text": "I mean, there's some\nthat's just happening.", "start": 4549.15, "duration": 2.31}, {"text": "But here, you've got\nto have consensus.", "start": 4551.46, "duration": 2.538}, {"text": "I know it didn't\nanswer your question", "start": 4553.998, "duration": 1.542}, {"text": "about the hash function.", "start": 4555.54, "duration": 1.302}, {"text": "But if it were a hash function\nthat had to be updated", "start": 4556.842, "duration": 2.208}, {"text": "and everybody said they\nhad to quickly update it,", "start": 4559.05, "duration": 4.84}, {"text": "there's interesting\ndebates about this,", "start": 4563.89, "duration": 2.95}, {"text": "but you wouldn't need to\ngo back over all 540,000", "start": 4566.84, "duration": 3.3}, {"text": "previous blocks.", "start": 4570.14, "duration": 2.64}, {"text": "You could just hash all 540,000\nblocks, 180 gigabytes to one", "start": 4572.78, "duration": 6.33}, {"text": "256 or maybe it's\nthen a different,", "start": 4579.11, "duration": 4.05}, {"text": "and then you'd have that.", "start": 4583.16, "duration": 2.11}, {"text": "And it would be tamper proof.", "start": 4585.27, "duration": 2.08}, {"text": "So those are the key things.", "start": 4587.35, "duration": 1.32}, {"text": "That's what we covered really.", "start": 4588.67, "duration": 1.56}, {"text": "What we're going to cover next\nTuesday is consensus protocol.", "start": 4590.23, "duration": 5.04}, {"text": "We've talked a lot\nabout proof of work", "start": 4595.27, "duration": 1.59}, {"text": "here because everybody thinks\nof Bitcoin about proof of work.", "start": 4596.86, "duration": 4.99}, {"text": "But we're going to talk about\nproof of work, the nodes,", "start": 4601.85, "duration": 2.51}, {"text": "and the native currency.", "start": 4604.36, "duration": 1.452}, {"text": "And then next\nThursday, we're going", "start": 4605.812, "duration": 1.458}, {"text": "to talk about transactions.", "start": 4607.27, "duration": 1.71}, {"text": "Again, I try to break\ndown this technology.", "start": 4608.98, "duration": 3.86}, {"text": "If you want to forget\nabout this lecture,", "start": 4612.84, "duration": 1.71}, {"text": "and you're going to\ngo, oh my god, it", "start": 4614.55, "duration": 1.56}, {"text": "was like going to\nthe dentist, you", "start": 4616.11, "duration": 3.057}, {"text": "can tell your friends\nthat you actually know", "start": 4619.167, "duration": 1.833}, {"text": "something about cryptography.", "start": 4621.0, "duration": 1.29}, {"text": "It is called cryptocurrencies.", "start": 4622.29, "duration": 2.37}, {"text": "So how could we not know\nsomething about cryptography?", "start": 4624.66, "duration": 2.55}, {"text": "But it's basically\nthose three things.", "start": 4627.21, "duration": 1.92}, {"text": "It's cryptography.", "start": 4629.13, "duration": 1.6}, {"text": "It's a consensus mechanism\nand the transactions.", "start": 4630.73, "duration": 3.68}, {"text": "So right?", "start": 4634.41, "duration": 0.57}, {"text": "Cryptography, consensus\nmechanism, transactions.", "start": 4634.98, "duration": 3.815}, {"text": "And we will get through it.", "start": 4638.795, "duration": 1.125}, {"text": "And then you'll see\nthis matters to finance", "start": 4639.92, "duration": 2.59}, {"text": "and whether it's\ngot any use cases.", "start": 4642.51, "duration": 1.77}, {"text": "So thank you.", "start": 4644.28, "duration": 2.12}]
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+[{"text": "The following\ncontent is provided", "start": 0.61, "duration": 1.83}, {"text": "by MIT OpenCourseWare under\na Creative Commons license.", "start": 2.44, "duration": 3.9}, {"text": "Additional information about our\nlicense and MIT OpenCourseWare,", "start": 6.34, "duration": 3.78}, {"text": "in general, is available\nat OCW.MIT.edu.", "start": 10.12, "duration": 2.61}, {"text": "GEORGE CHURCH: OK,\nso welcome tonight,", "start": 22.51, "duration": 3.36}, {"text": "a very special lecture for\nme tonight in more ways", "start": 25.87, "duration": 4.18}, {"text": "than I can express.", "start": 30.05, "duration": 1.49}, {"text": "This is the last of my\nlectures, but I look forward", "start": 31.54, "duration": 2.22}, {"text": "to your lectures coming up.", "start": 33.76, "duration": 2.73}, {"text": "I really do.", "start": 36.49, "duration": 0.7}, {"text": "I've heard from the\nTFs, and from what", "start": 37.19, "duration": 1.82}, {"text": "I've seen from talking\nto many of you,", "start": 39.01, "duration": 2.14}, {"text": "this is going to be a really\namazing set of projects", "start": 41.15, "duration": 3.38}, {"text": "this year, more\nthan any other year.", "start": 44.53, "duration": 3.06}, {"text": "Anyway, last week, we asked what\ncan biology do for computing?", "start": 47.59, "duration": 7.77}, {"text": "And this week is going to be\na little less nuts and bolts", "start": 55.36, "duration": 3.93}, {"text": "than usual.", "start": 59.29, "duration": 0.69}, {"text": "The entire course--\nas you all understand,", "start": 59.98, "duration": 1.89}, {"text": "you're all self-selected\nto life survey", "start": 61.87, "duration": 2.399}, {"text": "courses, at least this one,\nbecause you're still here.", "start": 64.269, "duration": 3.781}, {"text": "And tonight's going to be more\nof a survey than ever before,", "start": 68.05, "duration": 3.856}, {"text": "and it's going to be talking\nabout topics for which we don't", "start": 71.906, "duration": 2.954}, {"text": "have answers for the most part.", "start": 74.86, "duration": 4.59}, {"text": "There'll be some interesting\ndetails along the way.", "start": 79.45, "duration": 3.63}, {"text": "But anyway, instead of what\nbiology can do for computing,", "start": 83.08, "duration": 3.96}, {"text": "this is more about what\nbiology and computing can", "start": 87.04, "duration": 2.52}, {"text": "do for the world.", "start": 89.56, "duration": 1.11}, {"text": "That's really what\nwe want to do,", "start": 90.67, "duration": 2.13}, {"text": "and also, the\nhigher level network", "start": 92.8, "duration": 2.61}, {"text": "models that we can build since\nthis is network number three.", "start": 95.41, "duration": 3.84}, {"text": "So we'll start out--", "start": 99.25, "duration": 1.46}, {"text": "we've been talking mainly about\ncellular models as our highest", "start": 100.71, "duration": 3.73}, {"text": "level of networking,\nand so we'll", "start": 104.44, "duration": 1.5}, {"text": "talk about multicellular\nmodels, in particular,", "start": 105.94, "duration": 3.22}, {"text": "the sort of multicellular\nmodels that you get that involve", "start": 109.16, "duration": 3.02}, {"text": "sensory integration and\nintegration of higher levels,", "start": 112.18, "duration": 6.93}, {"text": "and then all the way up to\nmulti-organ systems, where", "start": 119.11, "duration": 4.11}, {"text": "we'll take an example\nfrom the atomic scale,", "start": 123.22, "duration": 3.9}, {"text": "all the way up to\norgan system failure.", "start": 127.12, "duration": 4.77}, {"text": "And then we'll go from there.", "start": 131.89, "duration": 2.85}, {"text": "So let's start with\nmulticellular models.", "start": 134.74, "duration": 2.76}, {"text": "And this is something that I--", "start": 137.5, "duration": 4.38}, {"text": "I'll show you a few slides\nthat will remind you", "start": 141.88, "duration": 2.43}, {"text": "of the first lecture.", "start": 144.31, "duration": 1.282}, {"text": "They either were taken\nfrom the first lecture--", "start": 145.592, "duration": 1.958}, {"text": "in this case, this is a wildly\ndifferent author, and approach,", "start": 147.55, "duration": 3.43}, {"text": "and so forth, but\nit's the same lesson", "start": 150.98, "duration": 1.982}, {"text": "as from the first\nlecture, which is", "start": 152.962, "duration": 1.458}, {"text": "we not only have these\nexponential curves going", "start": 154.42, "duration": 2.19}, {"text": "through the 1900s, but\nthey're super exponential.", "start": 156.61, "duration": 2.19}, {"text": "They go up, and the\ntrend lines you get", "start": 158.8, "duration": 1.68}, {"text": "depend on which set of points\nyou use, the steepest one being", "start": 160.48, "duration": 3.21}, {"text": "the most recent one, 1995.", "start": 163.69, "duration": 2.31}, {"text": "And this basically\nis part of when", "start": 166.0, "duration": 1.74}, {"text": "it is that we will\nhave computing power", "start": 167.74, "duration": 2.85}, {"text": "that might be on the order of\nan integrated human neural net.", "start": 170.59, "duration": 5.67}, {"text": "We talked about neural nets\nlast time as a metaphor,", "start": 176.26, "duration": 2.76}, {"text": "or as an algorithm,\nbut when will", "start": 179.02, "duration": 3.24}, {"text": "we actually have a\ncomputer that has", "start": 182.26, "duration": 3.27}, {"text": "the capability of the\nhuman cerebral cortex,", "start": 185.53, "duration": 5.4}, {"text": "or entire integrated\nnervous system?", "start": 190.93, "duration": 2.19}, {"text": "And the basis of\nthose calculations", "start": 193.12, "duration": 2.4}, {"text": "that Moravec made,\nand in lecture one", "start": 195.52, "duration": 3.96}, {"text": "Kurzweil was the\nsuper exponential", "start": 199.48, "duration": 2.55}, {"text": "curve that I showed.", "start": 202.03, "duration": 1.35}, {"text": "Moravec made them\nbased on his studies", "start": 203.38, "duration": 3.33}, {"text": "on how the retina works.", "start": 206.71, "duration": 2.83}, {"text": "And I think those\nof you who have", "start": 209.54, "duration": 4.16}, {"text": "done a lot of\ncomputer programming,", "start": 213.7, "duration": 2.82}, {"text": "that understanding\nhow the retina works", "start": 216.52, "duration": 4.23}, {"text": "is probably one of\nthe more intuitive", "start": 220.75, "duration": 2.13}, {"text": "of our various human senses, in\nthe sense that you can program", "start": 222.88, "duration": 5.19}, {"text": "an algorithm that might do in\nthe lower right of slide four", "start": 228.07, "duration": 3.85}, {"text": "here, edge or motion detection.", "start": 231.92, "duration": 2.45}, {"text": "When a frog sees a fly, black\nand white, high contrast,", "start": 234.37, "duration": 4.77}, {"text": "zoom across its visual\nfield, something goes off.", "start": 239.14, "duration": 4.2}, {"text": "And you could write an\nalgorithm that could do that,", "start": 243.34, "duration": 2.49}, {"text": "given a few frames\nof any kind of form.", "start": 245.83, "duration": 4.3}, {"text": "So anyway, but there's been\nliterature on the subject.", "start": 250.13, "duration": 3.75}, {"text": "And when you go through even\nthe best algorithms right now", "start": 253.88, "duration": 3.11}, {"text": "for doing these\nkind of calculations", "start": 256.99, "duration": 2.43}, {"text": "and you figure out how\nlong it takes to do--", "start": 259.42, "duration": 5.04}, {"text": "the retina is doing about 10\nmillion detections per second.", "start": 264.46, "duration": 4.62}, {"text": "And then you scale up from\nthat 0.02 gram chunk of retina", "start": 269.08, "duration": 5.94}, {"text": "up to the 1,500\ngram human brain,", "start": 275.02, "duration": 4.05}, {"text": "then you get the extrapolation\nthat was in the previous slide.", "start": 279.07, "duration": 3.61}, {"text": "I think this is interesting\nboth as an introduction", "start": 282.68, "duration": 2.283}, {"text": "to the kind of algorithms we'd\nlike to think about when we", "start": 284.963, "duration": 2.417}, {"text": "think about integrating\na multicellular system,", "start": 287.38, "duration": 3.57}, {"text": "but also in terms of\nwhere the compute power", "start": 290.95, "duration": 4.5}, {"text": "both biological and\ncomputational is going.", "start": 295.45, "duration": 3.06}, {"text": "Do we want to engineer\nbiological systems", "start": 298.51, "duration": 3.99}, {"text": "to keep up with these silicon\nor whatever other computational", "start": 302.5, "duration": 4.77}, {"text": "system we're using a\ndecade or so from now.", "start": 307.27, "duration": 5.77}, {"text": "Now, so I said that\nthe visual system", "start": 313.04, "duration": 4.25}, {"text": "is a relatively intuitive\ncomputational system", "start": 317.29, "duration": 2.94}, {"text": "to program.", "start": 320.23, "duration": 1.36}, {"text": "In contrast, I would say\nthe olfactory system is less", "start": 321.59, "duration": 3.78}, {"text": "intuitive, at least for me.", "start": 325.37, "duration": 2.61}, {"text": "We know now quite a bit\nabout the molecular biology", "start": 327.98, "duration": 3.36}, {"text": "of the system.", "start": 331.34, "duration": 0.6}, {"text": "There are 1,000 receptors.", "start": 331.94, "duration": 1.47}, {"text": "It's probably one of the largest\nclasses of genomic repeated", "start": 333.41, "duration": 5.04}, {"text": "proteins.", "start": 338.45, "duration": 1.71}, {"text": "And these receptors\nare in the same family", "start": 340.16, "duration": 2.94}, {"text": "as the receptors that are\nthe major class of drug", "start": 343.1, "duration": 2.7}, {"text": "receptors, the G protein\ncoupled receptors.", "start": 345.8, "duration": 3.57}, {"text": "And there is\nbasically one receptor", "start": 349.37, "duration": 2.73}, {"text": "per cell, which is\nquite a trick, right?", "start": 352.1, "duration": 1.98}, {"text": "Because you got one receptor\nfrom mom and one from dad.", "start": 354.08, "duration": 2.88}, {"text": "And you've got\nthousands of receptors.", "start": 356.96, "duration": 2.28}, {"text": "But there's basically\none per cell.", "start": 359.24, "duration": 3.3}, {"text": "And they detect olfactory\nmolecule concentrations", "start": 362.54, "duration": 7.8}, {"text": "over about seven logs, where\nthey can detect a concentration", "start": 370.34, "duration": 11.16}, {"text": "threshold with a particular\nstandard deviation.", "start": 381.5, "duration": 4.74}, {"text": "Now this is the\nbeginnings of the model,", "start": 386.24, "duration": 1.8}, {"text": "just stating the fact\nthat you know about it.", "start": 388.04, "duration": 2.61}, {"text": "When you look at the\nneuroanatomy, you've got this--", "start": 390.65, "duration": 4.575}, {"text": "the odorant molecules\ndown at the very bottom", "start": 395.225, "duration": 1.875}, {"text": "of this figure, cilia\nolfactory neurons, which is", "start": 397.1, "duration": 4.8}, {"text": "a primary signal transduction.", "start": 401.9, "duration": 2.73}, {"text": "This thing goes up where it's\nintegrated in the glomeruli.", "start": 404.63, "duration": 4.11}, {"text": "And you can think of\nthis like the neural nets", "start": 408.74, "duration": 2.24}, {"text": "that we're talking\nabout last time, where", "start": 410.98, "duration": 1.708}, {"text": "you had these interneurons.", "start": 412.688, "duration": 1.512}, {"text": "You had the extra layer that\nwe showed was so important.", "start": 414.2, "duration": 7.08}, {"text": "And the thing that's\namazing about this system", "start": 421.28, "duration": 2.07}, {"text": "are lodged in these\nfour basic olfactory", "start": 423.35, "duration": 5.94}, {"text": "facts, which I take from\nHopfield's work, which", "start": 429.29, "duration": 3.81}, {"text": "is really just like this is the\nsame Hopfield that introduced", "start": 433.1, "duration": 3.63}, {"text": "us to or really championed\nthe concept of neural nets", "start": 436.73, "duration": 3.81}, {"text": "as a computational\nalgorithmic metaphor.", "start": 440.54, "duration": 3.36}, {"text": "And here, the idea is you have\nodor and memory recognition.", "start": 443.9, "duration": 6.51}, {"text": "You have background\nelimination, just", "start": 450.41, "duration": 2.7}, {"text": "like how your eyes adapt\nto a mostly red room,", "start": 453.11, "duration": 5.43}, {"text": "your nose is great, or\nwhole olfactory system", "start": 458.54, "duration": 3.87}, {"text": "is great at adapting\nto background odorants.", "start": 462.41, "duration": 4.8}, {"text": "So you have one known and\none unknown thoroughly mixed.", "start": 467.21, "duration": 4.62}, {"text": "Number three, you can\nhave component separation.", "start": 471.83, "duration": 2.73}, {"text": "You can have a few\ndifferent odors at once.", "start": 474.56, "duration": 3.12}, {"text": "You have odor separation\nwhere you have unknowns.", "start": 477.68, "duration": 5.535}, {"text": "I mean, the combination of\nthese is quite remarkable.", "start": 486.53, "duration": 4.24}, {"text": "So the basis of the model that\nHopfield has proposed is this.", "start": 490.77, "duration": 7.82}, {"text": "You have a coverage for\neach of the i receptors,", "start": 498.59, "duration": 4.38}, {"text": "where i goes from 1 to 1,000.", "start": 502.97, "duration": 2.1}, {"text": "This will vary depending\non the organism.", "start": 505.07, "duration": 2.01}, {"text": "Mice have twice as many as\nwe do, probably, and so on.", "start": 507.08, "duration": 3.31}, {"text": "But the coverage of\neach of those receptors", "start": 510.39, "duration": 6.14}, {"text": "is equal to the minimum\ncoverage for the concentration", "start": 516.53, "duration": 8.52}, {"text": "of the target, where let's\nsay the target is the target", "start": 525.05, "duration": 2.49}, {"text": "odorant that you're looking for\nover the concentration that's", "start": 527.54, "duration": 4.47}, {"text": "the threshold for firing\nthat neuron for that target,", "start": 532.01, "duration": 3.87}, {"text": "threshold of t.", "start": 535.88, "duration": 1.62}, {"text": "And you multiply that times\neither one or some fraction.", "start": 537.5, "duration": 3.72}, {"text": "It's 1 if you really\nhit the target.", "start": 541.22, "duration": 3.93}, {"text": "And it's this fraction for\nthat particular receptor", "start": 545.15, "duration": 4.47}, {"text": "and that particular target.", "start": 549.62, "duration": 1.53}, {"text": "You've got some crosstalk.", "start": 551.15, "duration": 1.47}, {"text": "And the amount of\ncrosstalk you can", "start": 552.62, "duration": 2.64}, {"text": "think of this as a field\nof receptors, which", "start": 555.26, "duration": 5.77}, {"text": "all have variable binding.", "start": 561.03, "duration": 2.06}, {"text": "And that binding is over\nthe six or seven logs here.", "start": 563.09, "duration": 4.12}, {"text": "And this just reflects\nthat same thing", "start": 567.21, "duration": 1.925}, {"text": "that we were talking about.", "start": 569.135, "duration": 1.125}, {"text": "So the total number\nof inputs going", "start": 572.96, "duration": 4.26}, {"text": "to the next layer in the\nneural net, the coverage here,", "start": 577.22, "duration": 2.97}, {"text": "is the sum of this target signal\nplus the background signal.", "start": 580.19, "duration": 7.33}, {"text": "So the first term is target.", "start": 587.52, "duration": 1.25}, {"text": "And the right hand\nterm is the background.", "start": 588.77, "duration": 1.99}, {"text": "And so you can see they have the\nsame form, the same threshold,", "start": 590.76, "duration": 2.96}, {"text": "and concentration. c sub b is\nconcentration of background.", "start": 593.72, "duration": 3.705}, {"text": "Now, so let's see\nhow this plays out", "start": 603.63, "duration": 3.66}, {"text": "when you actually try this\nout in an olfactory processing", "start": 607.29, "duration": 6.51}, {"text": "problem.", "start": 613.8, "duration": 0.66}, {"text": "Here you have an odor space.", "start": 614.46, "duration": 3.03}, {"text": "And what you have here\nis 80 different neurons", "start": 617.49, "duration": 5.67}, {"text": "is the y-axis at the\ntop of slide seven.", "start": 623.16, "duration": 3.63}, {"text": "And then across the x-axis\nis time in milliseconds going", "start": 626.79, "duration": 6.93}, {"text": "from 0 to 800 milliseconds.", "start": 633.72, "duration": 1.65}, {"text": "And this is all modeled on\nfairly realistic parameters", "start": 635.37, "duration": 5.67}, {"text": "based on experiments.", "start": 641.04, "duration": 2.7}, {"text": "And so what you have here\nis 80 adapting neurons.", "start": 643.74, "duration": 2.85}, {"text": "And what you're doing is\ntwo sniffs of a mixed odor.", "start": 646.59, "duration": 2.67}, {"text": "That's what this\nis modeling, OK?", "start": 649.26, "duration": 3.66}, {"text": "First, you have a 100 to 500\nmilliseconds, the range from--", "start": 652.92, "duration": 6.57}, {"text": "so you can see that something's\nhappening at 100 milliseconds.", "start": 659.49, "duration": 3.33}, {"text": "And up to 500 you\nhave a mixed odor,", "start": 662.82, "duration": 2.34}, {"text": "which is 50 parts of x\nplus 1,000 parts of y,", "start": 665.16, "duration": 4.17}, {"text": "or 1,000 times y.", "start": 669.33, "duration": 5.22}, {"text": "And then 500 milliseconds\nyou change this ratio very", "start": 674.55, "duration": 3.63}, {"text": "slightly, you see?", "start": 678.18, "duration": 0.96}, {"text": "You just up x by 75 and\ny up from 1,000 to 1,100.", "start": 679.14, "duration": 8.21}, {"text": "OK, so that's the paradigm,\n50 and 1,000 to 75 and 1,100.", "start": 687.35, "duration": 6.06}, {"text": "And the sniff at 100\nmilliseconds, that first one,", "start": 693.41, "duration": 3.93}, {"text": "that mixed odorant, it activates\nmore than half the neurons.", "start": 697.34, "duration": 5.35}, {"text": "So this is not like\nyour retina, where", "start": 702.69, "duration": 2.48}, {"text": "if you have a\nsingle point source", "start": 705.17, "duration": 2.01}, {"text": "it will activate that one\nbroad cell, or maybe a center", "start": 707.18, "duration": 4.89}, {"text": "surround effect.", "start": 712.07, "duration": 2.31}, {"text": "But it's really activating\nhalf of the neurons, OK?", "start": 714.38, "duration": 3.45}, {"text": "And then the changed sniff at\n500 milliseconds-- remember,", "start": 717.83, "duration": 3.09}, {"text": "just these two small changes--", "start": 720.92, "duration": 2.07}, {"text": "is almost invisible, right?", "start": 722.99, "duration": 3.36}, {"text": "So that's what you're\nseeing right here,", "start": 726.35, "duration": 5.37}, {"text": "OK, is this huge,\nswamping amount.", "start": 731.72, "duration": 4.68}, {"text": "But then in B-- so that's\nwhat happened in A. B,", "start": 736.4, "duration": 5.55}, {"text": "you've now plotting instead\nof individual neurons,", "start": 741.95, "duration": 4.71}, {"text": "you're doing the instantaneous\nrate in hertz, OK?", "start": 746.66, "duration": 3.81}, {"text": "And now, you can see\nthe second sniff here", "start": 750.47, "duration": 7.74}, {"text": "at the 500 milliseconds,\nwhich even though you really", "start": 758.21, "duration": 2.85}, {"text": "can't see it in the\ncorresponding point", "start": 761.06, "duration": 1.782}, {"text": "where you're looking at all\nthese individual neurons.", "start": 762.842, "duration": 2.208}, {"text": "And so you can see that\neven a 20% spread in one", "start": 765.05, "duration": 6.27}, {"text": "of these parameters is enough\nto get this kind of easily", "start": 771.32, "duration": 5.55}, {"text": "detectable signal.", "start": 776.87, "duration": 2.4}, {"text": "Now, that's an example\nof a simulation.", "start": 779.27, "duration": 2.46}, {"text": "That's not a simulation of\na particular experimental", "start": 781.73, "duration": 3.12}, {"text": "dataset, but it's based\non experimental datasets.", "start": 784.85, "duration": 3.06}, {"text": "And the code, this\nis not Mathematica,", "start": 787.91, "duration": 1.92}, {"text": "this is Matlab,\nwhich we all wish", "start": 789.83, "duration": 2.22}, {"text": "we could have interchangeably\ntaught in this course.", "start": 792.05, "duration": 2.88}, {"text": "And you can see here in\ngreen are the comments.", "start": 794.93, "duration": 2.28}, {"text": "And you can see\nsome of the things", "start": 797.21, "duration": 1.47}, {"text": "that we've been\ntalking about here.", "start": 798.68, "duration": 1.458}, {"text": "The number of receptor\ntypes is actually", "start": 803.673, "duration": 1.667}, {"text": "here 2,000 instead of 1,000.", "start": 805.34, "duration": 2.04}, {"text": "You see the target,\nremember, I said", "start": 807.38, "duration": 2.34}, {"text": "could be some random number\nthat goes over six logarithms.", "start": 809.72, "duration": 3.995}, {"text": "Well, the way\nthat's done here is", "start": 813.715, "duration": 1.375}, {"text": "here's a random number\ngenerated and you generate", "start": 815.09, "duration": 4.628}, {"text": "as the log of the target.", "start": 819.718, "duration": 1.042}, {"text": "And then, you get the target\nby taking the exponential.", "start": 820.76, "duration": 2.292}, {"text": "It's very straightforward and\nthe code goes on from there.", "start": 823.052, "duration": 4.828}, {"text": "OK, now this brings us to\na very interesting point.", "start": 827.88, "duration": 4.88}, {"text": "Since these three\nlectures on networks,", "start": 832.76, "duration": 2.622}, {"text": "and in a certain sense,\nthe whole course,", "start": 835.382, "duration": 1.708}, {"text": "is building towards systems\nbiology network models.", "start": 837.09, "duration": 4.16}, {"text": "And for these\nmodels to be useful,", "start": 841.25, "duration": 1.92}, {"text": "in the same sense that\nthe models we have", "start": 843.17, "duration": 1.832}, {"text": "for X-ray crystallography,\nand the models", "start": 845.002, "duration": 1.708}, {"text": "we've had for genome\ninterpretation in terms", "start": 846.71, "duration": 2.61}, {"text": "of homology, and\nsequence folding,", "start": 849.32, "duration": 3.42}, {"text": "and so forth needed\nto be shared.", "start": 852.74, "duration": 3.72}, {"text": "The models, even\nmore than the data,", "start": 856.46, "duration": 1.95}, {"text": "need to be shareable\nbecause in a certain sense,", "start": 858.41, "duration": 4.23}, {"text": "even modest\nmanipulation of the data", "start": 862.64, "duration": 2.94}, {"text": "usually involves some\ngood model behind it.", "start": 865.58, "duration": 2.323}, {"text": "And so these are some\nof the work groups", "start": 867.903, "duration": 1.667}, {"text": "that are working on\ndifferent modeling schemes.", "start": 869.57, "duration": 3.27}, {"text": "In particular, I\nshould point out", "start": 872.84, "duration": 2.535}, {"text": "that BioSpice is\nnow DARPA BioSpice,", "start": 875.375, "duration": 3.195}, {"text": "and SBML is kind of a\ngrowing part of that.", "start": 878.57, "duration": 3.0}, {"text": "System Biology Markup Language\nis a way of sharing this data.", "start": 881.57, "duration": 3.66}, {"text": "And as yet, there's not\nthe kind of convention", "start": 885.23, "duration": 3.6}, {"text": "that we have in\ncrystallography and DNA", "start": 888.83, "duration": 3.24}, {"text": "sequencing where you submit--", "start": 892.07, "duration": 1.818}, {"text": "at the time that\nyou publish a paper,", "start": 893.888, "duration": 1.542}, {"text": "you submit your data\nand model, data/model,", "start": 895.43, "duration": 4.41}, {"text": "with an accession number\nto the database or else", "start": 899.84, "duration": 2.58}, {"text": "you don't get it published.", "start": 902.42, "duration": 1.14}, {"text": "We're nowhere near that now\nfor the rest of biology.", "start": 903.56, "duration": 2.43}, {"text": "But these kind of\nefforts, probably,", "start": 905.99, "duration": 2.22}, {"text": "are moving in that direction.", "start": 908.21, "duration": 1.27}, {"text": "And you can see that the\nfeatures of each of these", "start": 909.48, "duration": 3.115}, {"text": "are some of the\nthings that we've", "start": 912.595, "duration": 1.375}, {"text": "been talking about before.", "start": 913.97, "duration": 1.083}, {"text": "You've got stochastic\nmodeling, kinetic modeling,", "start": 915.053, "duration": 3.927}, {"text": "enzyme receptor cell geometry,\nneural nets, and so on.", "start": 918.98, "duration": 11.37}, {"text": "This is by no means\ncomprehensive.", "start": 930.35, "duration": 1.96}, {"text": "And there are hypertext\nlinks here if you really", "start": 932.31, "duration": 2.0}, {"text": "want to dig into them.", "start": 934.31, "duration": 1.38}, {"text": "And some of the\nplatforms that they've", "start": 935.69, "duration": 1.83}, {"text": "been thinking about different\nways of making it slightly less", "start": 937.52, "duration": 4.74}, {"text": "system-dependent.", "start": 942.26, "duration": 1.17}, {"text": "Everyone has their attempts.", "start": 943.43, "duration": 2.1}, {"text": "Obviously, Windows is\nnot system-independent.", "start": 945.53, "duration": 4.89}, {"text": "So that's two very\nbrief examples", "start": 950.42, "duration": 3.0}, {"text": "of multicellular models, both\nof them being neural models", "start": 953.42, "duration": 5.55}, {"text": "kind of building from what we\nwere thinking about last time.", "start": 958.97, "duration": 2.67}, {"text": "But now we're going to a\ncompletely different kind", "start": 961.64, "duration": 2.22}, {"text": "of multicellular model, all the\nway up from individual effects", "start": 963.86, "duration": 5.19}, {"text": "that a single nucleotide-- how\nmuch effect a single nucleotide", "start": 969.05, "duration": 3.45}, {"text": "can have on a whole organ\nsystem, which in this case", "start": 972.5, "duration": 3.48}, {"text": "will be cardiovascular.", "start": 975.98, "duration": 1.96}, {"text": "So we go from--.", "start": 977.94, "duration": 2.33}, {"text": "And there are a number of\nphysiome and cardiome projects", "start": 980.27, "duration": 5.79}, {"text": "that are of active interest.", "start": 986.06, "duration": 2.77}, {"text": "Just like the\nprevious slides that I", "start": 992.44, "duration": 1.95}, {"text": "showed showing all the ways\nof sharing system models,", "start": 994.39, "duration": 2.94}, {"text": "many of these efforts are kind\nof loose consortium alliances", "start": 997.33, "duration": 6.12}, {"text": "where people have put together\ndifferent models either to deal", "start": 1003.45, "duration": 4.44}, {"text": "with the anatomy,\nphysiology, or sometimes,", "start": 1007.89, "duration": 4.98}, {"text": "a integration of molecular to\ncellular, cellular to, say,", "start": 1012.87, "duration": 7.71}, {"text": "neural or muscular, and all\nthe way up to fluid dynamics", "start": 1020.58, "duration": 4.71}, {"text": "and so on.", "start": 1025.29, "duration": 3.069}, {"text": "So let's start with a\nsingle base-pair change.", "start": 1028.359, "duration": 3.951}, {"text": "And I start with\nthis one because you", "start": 1032.31, "duration": 2.683}, {"text": "should feel comfortable\nwith it at this point.", "start": 1034.993, "duration": 1.917}, {"text": "We mentioned it briefly before.", "start": 1036.91, "duration": 3.05}, {"text": "We'll talk about it\nin more detail now.", "start": 1039.96, "duration": 2.04}, {"text": "This is the single\nnucleotide polymorphism,", "start": 1042.0, "duration": 2.589}, {"text": "which causes the change of the\nbeta subunit of hemoglobin,", "start": 1044.589, "duration": 5.751}, {"text": "which is a tetramer,\nto go from a glutamate,", "start": 1050.34, "duration": 6.69}, {"text": "normally, in most people at\nposition six of the beta chain,", "start": 1057.03, "duration": 3.42}, {"text": "to a valine.", "start": 1060.45, "duration": 2.52}, {"text": "So that's the purple\nset of tetramers.", "start": 1062.97, "duration": 3.21}, {"text": "Or to tryptophan, and that's\nthe cyan set on the far right.", "start": 1066.18, "duration": 5.22}, {"text": "And this, from combinations\nof X-ray crystallography", "start": 1071.4, "duration": 8.27}, {"text": "and three-dimensional\nmodeling, and this", "start": 1079.67, "duration": 2.19}, {"text": "is not speculation, just based\non primary sequence data,", "start": 1081.86, "duration": 3.09}, {"text": "even though the primary sequence\nhere is very, very close,", "start": 1084.95, "duration": 3.12}, {"text": "just a single nucleotide and\na single amino acid change.", "start": 1088.07, "duration": 4.33}, {"text": "Nevertheless, these\nauthors have been", "start": 1092.4, "duration": 2.21}, {"text": "building this from the\ncrystallographic data", "start": 1094.61, "duration": 4.23}, {"text": "where not only do you care\nabout the tetramer itself,", "start": 1098.84, "duration": 3.36}, {"text": "but how the tetramers\ninteract with one another", "start": 1102.2, "duration": 2.61}, {"text": "to make these long, fibrous\nchains, which are considerably", "start": 1104.81, "duration": 3.69}, {"text": "more stable in the sickle cell.", "start": 1108.5, "duration": 2.82}, {"text": "And what you see here is sort\nof the valine substitution", "start": 1111.32, "duration": 7.86}, {"text": "is locked in one\nkind of conformation", "start": 1119.18, "duration": 2.58}, {"text": "and the tryptophan in another.", "start": 1121.76, "duration": 2.53}, {"text": "And you can see\nhow these authors", "start": 1124.29, "duration": 2.81}, {"text": "have decided how a\npotential fiber can", "start": 1127.1, "duration": 4.02}, {"text": "form in the different cases.", "start": 1131.12, "duration": 2.16}, {"text": "Now those fibers, in\none way or another,", "start": 1137.11, "duration": 2.76}, {"text": "which is not totally\nmapped out, but you", "start": 1139.87, "duration": 5.52}, {"text": "affect the efficiency of\nthe hemoglobin slightly", "start": 1145.39, "duration": 5.35}, {"text": "and the shape of the\ncell much more radically.", "start": 1150.74, "duration": 3.2}, {"text": "And this combination\nresults in the cell,", "start": 1153.94, "duration": 5.26}, {"text": "especially under any kind\nof stress, either oxidative", "start": 1159.2, "duration": 3.89}, {"text": "or other metabolic\nstress, becoming sickled.", "start": 1163.09, "duration": 2.82}, {"text": "So you can have a combination\nof cells which have", "start": 1165.91, "duration": 3.42}, {"text": "varying degrees of sickling.", "start": 1169.33, "duration": 1.68}, {"text": "Here in this microscopic\nslide on the left,", "start": 1171.01, "duration": 6.42}, {"text": "you have both the sickle\ncell and the normal cell side", "start": 1177.43, "duration": 2.7}, {"text": "by side.", "start": 1180.13, "duration": 2.08}, {"text": "I think when we built up the\nred blood cell metabolic model,", "start": 1182.21, "duration": 3.05}, {"text": "we talked about some of the\nnon-metabolic considerations", "start": 1185.26, "duration": 2.79}, {"text": "of that, which were that its\nfunction is to transport oxygen", "start": 1188.05, "duration": 4.23}, {"text": "and so forth.", "start": 1192.28, "duration": 2.4}, {"text": "And what we're talking about now\nis more a cell membrane issue.", "start": 1194.68, "duration": 3.65}, {"text": "This is on slide 13, where the\ninternal environment, which", "start": 1198.33, "duration": 5.35}, {"text": "is the hemoglobin, is\ngreatly affecting now", "start": 1203.68, "duration": 2.37}, {"text": "the external environment,\nwhich is the hemodynamic flow", "start": 1206.05, "duration": 3.12}, {"text": "in the capillaries.", "start": 1209.17, "duration": 3.15}, {"text": "So this falls under\nthe heading now", "start": 1215.68, "duration": 2.16}, {"text": "of how is it that we can go from\nthat single nucleotide change", "start": 1217.84, "duration": 3.72}, {"text": "to a very dramatic\nmorphological change?", "start": 1221.56, "duration": 2.16}, {"text": "In this case, it's\npathological, but you", "start": 1223.72, "duration": 2.25}, {"text": "could imagine that in the hands\nof evolutionary adaptation,", "start": 1225.97, "duration": 4.917}, {"text": "an organism could take\nthis and run with it.", "start": 1230.887, "duration": 1.833}, {"text": "Maybe not sickle cell mutation,\nbut some other one that", "start": 1232.72, "duration": 2.46}, {"text": "causes some other morphological\nchange in some other cell", "start": 1235.18, "duration": 2.88}, {"text": "or complex aggregate of cells.", "start": 1238.06, "duration": 3.06}, {"text": "Because here you can see a whole\nvariety of different shapes", "start": 1241.12, "duration": 6.63}, {"text": "of red blood cells.", "start": 1247.75, "duration": 2.043}, {"text": "And remember, these red\nblood cells are very simple.", "start": 1249.793, "duration": 2.167}, {"text": "They have no macromolecular\n[INAUDIBLE],, no DNA, no RNA,", "start": 1251.96, "duration": 4.94}, {"text": "so we're really just talking\nabout a bag of proteins which", "start": 1256.9, "duration": 2.64}, {"text": "are greatly affected by\nthese different conditions", "start": 1259.54, "duration": 4.05}, {"text": "or enzyme deficiencies.", "start": 1263.59, "duration": 1.87}, {"text": "So the system models\nthat were built up,", "start": 1265.46, "duration": 1.82}, {"text": "where we had the kinetic\nparameters for the enzymes,", "start": 1267.28, "duration": 4.17}, {"text": "here can, in principle, be\nmodeled on the impact it would", "start": 1271.45, "duration": 4.65}, {"text": "have on the osmolarity, or the\nother membrane properties that", "start": 1276.1, "duration": 5.22}, {"text": "were listed in the\nprevious slide,", "start": 1281.32, "duration": 1.59}, {"text": "or the sickling that\nwas in two slides back.", "start": 1282.91, "duration": 2.34}, {"text": "So from a single\nnucleotide polymorphism,", "start": 1296.68, "duration": 5.13}, {"text": "we've gone from this\nthree-dimensional fiber", "start": 1301.81, "duration": 2.43}, {"text": "of hemoglobin to a change in\nthe three-dimensional structure", "start": 1304.24, "duration": 5.76}, {"text": "of this biconcave\ndisk to a sickle disk.", "start": 1310.0, "duration": 7.02}, {"text": "But you can also go,\nsort of in parallel,", "start": 1317.02, "duration": 2.52}, {"text": "the same single-nucleotide\npolymorphism, or some like it,", "start": 1319.54, "duration": 3.42}, {"text": "can take you up to\npathogen resistance.", "start": 1322.96, "duration": 2.79}, {"text": "We've already mentioned that\nsickle cell hemoglobin can take", "start": 1325.75, "duration": 3.75}, {"text": "you to malarial resistance.", "start": 1329.5, "duration": 2.19}, {"text": "But in addition, you\ncan get components", "start": 1331.69, "duration": 7.32}, {"text": "of the enzymatic\nmetabolic pathway,", "start": 1339.01, "duration": 3.85}, {"text": "such as the one that we\nmodeled a few lectures back,", "start": 1342.86, "duration": 6.08}, {"text": "such as glutathione peroxidase.", "start": 1348.94, "duration": 1.69}, {"text": "This is part of the\nredox components.", "start": 1350.63, "duration": 4.52}, {"text": "And here, erythrocytes\nthat are heterozygous", "start": 1355.15, "duration": 3.96}, {"text": "for this particular\nallele should", "start": 1359.11, "duration": 7.12}, {"text": "be more efficient in\nsheltering the cell membrane", "start": 1366.23, "duration": 2.16}, {"text": "from irreversible oxidation\nin binding hemoglobin caused", "start": 1368.39, "duration": 2.7}, {"text": "by the oxidant\nstress that's exerted", "start": 1371.09, "duration": 2.04}, {"text": "by the malarial parasite.", "start": 1373.13, "duration": 4.53}, {"text": "And what they observe\nhere is actually", "start": 1377.66, "duration": 2.25}, {"text": "an interaction between these\ntwo possible haplotypes.", "start": 1379.91, "duration": 7.56}, {"text": "So it's actually, you can think\nof it as a pair of haplotypes.", "start": 1387.47, "duration": 2.61}, {"text": "It's the one is\nthe hemoglobin AS,", "start": 1390.08, "duration": 4.8}, {"text": "the one we've been talking\nabout for sickling,", "start": 1394.88, "duration": 3.12}, {"text": "and then, this\nglutathione peroxidase.", "start": 1398.0, "duration": 2.88}, {"text": "And so you can imagine, that\nsince both of these things", "start": 1400.88, "duration": 2.76}, {"text": "interact with malaria\nparasite, that your genotype", "start": 1403.64, "duration": 3.39}, {"text": "will depend--", "start": 1407.03, "duration": 0.87}, {"text": "I'm sorry, your phenotype\nin respect to malaria", "start": 1407.9, "duration": 2.16}, {"text": "will depend on the alleles\nthat you have at both cases.", "start": 1410.06, "duration": 3.517}, {"text": "So you can-- here, you can\nhave an A over S heterozygote", "start": 1413.577, "duration": 2.333}, {"text": "and a two over one heterozygote.", "start": 1415.91, "duration": 3.337}, {"text": "And so that's something to\ntake into account when you're", "start": 1419.247, "duration": 2.333}, {"text": "trying to do any kind of\npredictive modeling or modeling", "start": 1421.58, "duration": 4.59}, {"text": "to explain the functional\ngenomics that you", "start": 1426.17, "duration": 3.03}, {"text": "have in a patient who's\na compound heterozygote", "start": 1429.2, "duration": 2.64}, {"text": "like that.", "start": 1431.84, "duration": 1.54}, {"text": "So now, the third pathway.", "start": 1433.38, "duration": 2.21}, {"text": "Now, from single-- the same\nset of single nucleotide", "start": 1435.59, "duration": 2.37}, {"text": "polymorphisms that\naffect either hemoglobin", "start": 1437.96, "duration": 1.83}, {"text": "or one of the major enzymes\nin the red blood cell.", "start": 1439.79, "duration": 3.01}, {"text": "Now, on to cell morphology.", "start": 1442.8, "duration": 3.5}, {"text": "On to pathogen interaction.", "start": 1446.3, "duration": 3.39}, {"text": "And finally, to\ninteraction with drugs.", "start": 1449.69, "duration": 1.98}, {"text": "We talked about\npharmacogenomics.", "start": 1451.67, "duration": 1.62}, {"text": "Here's another example where you\nhave the drug-induced oxidative", "start": 1453.29, "duration": 6.36}, {"text": "hemolysis that you occur\nwith certain enzymopathies", "start": 1459.65, "duration": 4.68}, {"text": "like glucose-6-phosphate\ndehydrogenase.", "start": 1464.33, "duration": 4.14}, {"text": "This enzyme, glucose-6-phosphate\ndehydrogenase,", "start": 1468.47, "duration": 4.08}, {"text": "interacts with drugs\nsuch as primaquine.", "start": 1472.55, "duration": 4.11}, {"text": "And it disrupts mitochondrial\nfunction, heme biosynthesis,", "start": 1476.66, "duration": 6.04}, {"text": "and so forth, and so on.", "start": 1482.7, "duration": 3.0}, {"text": "This is a very\nsignificant consideration", "start": 1485.7, "duration": 6.02}, {"text": "with a long list\nof 20-some drugs", "start": 1491.72, "duration": 2.7}, {"text": "that has to be taken\nto account when", "start": 1494.42, "duration": 2.04}, {"text": "you have any of a variety of\nred blood cell enzyme changes.", "start": 1496.46, "duration": 7.03}, {"text": "So we've got these three\neffects of a limited number", "start": 1503.49, "duration": 4.67}, {"text": "of single nucleotide\npolymorphisms.", "start": 1508.16, "duration": 3.15}, {"text": "How do you make this\ntransition from--", "start": 1511.31, "duration": 5.55}, {"text": "and they're all\nsomewhat interconnected.", "start": 1516.86, "duration": 1.71}, {"text": "Part of the reason it's\nresistant to malaria", "start": 1518.57, "duration": 1.833}, {"text": "is because it's less\neffective in its cell", "start": 1520.403, "duration": 1.947}, {"text": "shape, and its ability to\ntransport oxygen, and do", "start": 1522.35, "duration": 5.4}, {"text": "its metabolism.", "start": 1527.75, "duration": 1.7}, {"text": "And same thing with\ndrug sensitivity.", "start": 1529.45, "duration": 3.01}, {"text": "How are these changes\nin the hemoglobin--", "start": 1532.46, "duration": 7.29}, {"text": "might they be reflected in\nthe three-dimensional shape", "start": 1539.75, "duration": 2.94}, {"text": "of the erythrocyte,\nwhich is a kind", "start": 1542.69, "duration": 2.67}, {"text": "of a membrane-bound compartment?", "start": 1545.36, "duration": 2.58}, {"text": "And here's a model that\nstruck me as interesting.", "start": 1547.94, "duration": 2.58}, {"text": "It's not been that\nextensively tested since 1998.", "start": 1550.52, "duration": 5.62}, {"text": "But the idea is that Band3--", "start": 1556.14, "duration": 2.69}, {"text": "this is one of those\nnames that just comes out", "start": 1558.83, "duration": 2.43}, {"text": "of the molecular\nbiologist literature,", "start": 1561.26, "duration": 3.06}, {"text": "that they ran a\ngel, and they count", "start": 1564.32, "duration": 2.01}, {"text": "the bands, and number three.", "start": 1566.33, "duration": 1.77}, {"text": "And it turns out it's about 10%\nof the red blood cell membrane.", "start": 1568.1, "duration": 5.28}, {"text": "It's a very abundant protein.", "start": 1573.38, "duration": 3.27}, {"text": "And it's responsible\nfor the equilibration", "start": 1576.65, "duration": 4.02}, {"text": "of anions such as carbonate and\nchloride across the red blood", "start": 1580.67, "duration": 3.81}, {"text": "cell membrane.", "start": 1584.48, "duration": 1.26}, {"text": "It's not a pump, it just\nkind of allows these anions", "start": 1585.74, "duration": 3.42}, {"text": "to go across because\nthe pump here", "start": 1589.16, "duration": 2.04}, {"text": "is the pumps that are\ninvolved in proton", "start": 1591.2, "duration": 2.97}, {"text": "and there's also\nsodium potassium.", "start": 1594.17, "duration": 3.57}, {"text": "And that's what your ATP in the\nred blood cell is going for.", "start": 1597.74, "duration": 2.58}, {"text": "And these are just kind\nof following along.", "start": 1600.32, "duration": 1.792}, {"text": "The idea here is that if\nyou change the degree--", "start": 1604.46, "duration": 9.73}, {"text": "let's see, I think this\nis covered in more detail.", "start": 1614.19, "duration": 3.248}, {"text": "No, sorry.", "start": 1617.438, "duration": 1.332}, {"text": "The mechanism of\naction here is greatly", "start": 1622.405, "duration": 3.265}, {"text": "affected by its\ndisulfide effects.", "start": 1625.67, "duration": 3.18}, {"text": "And if you change the redox\ncomponents in the red blood", "start": 1628.85, "duration": 4.74}, {"text": "cell, you get just a slight\nchange in conformation", "start": 1633.59, "duration": 3.81}, {"text": "of this molecule.", "start": 1637.4, "duration": 1.44}, {"text": "And then that can result\nin a net difference", "start": 1638.84, "duration": 3.3}, {"text": "between the cross-sectional area\nof this protein on the outside", "start": 1642.14, "duration": 3.9}, {"text": "and the inside, which\ntranslates into a net change--", "start": 1646.04, "duration": 3.78}, {"text": "since the phospholipids\ndon't exchange,", "start": 1649.82, "duration": 4.457}, {"text": "or the rate constant for\nthe phospholipid exchange", "start": 1654.277, "duration": 2.083}, {"text": "is slow and known,\nthen this results", "start": 1656.36, "duration": 2.4}, {"text": "in a conformational change.", "start": 1658.76, "duration": 7.14}, {"text": "Anyway, that's the model.", "start": 1665.9, "duration": 2.94}, {"text": "That connects the\nsingle nucleotide to--", "start": 1668.84, "duration": 3.06}, {"text": "could connect it to the\nthree-dimensional structure", "start": 1671.9, "duration": 3.0}, {"text": "of the cell.", "start": 1674.9, "duration": 0.87}, {"text": "Then you want to connect the\nthree-dimensional structure", "start": 1675.77, "duration": 2.333}, {"text": "of the cell to its ability\nto carry out its function", "start": 1678.103, "duration": 3.457}, {"text": "in the capillaries.", "start": 1681.56, "duration": 1.26}, {"text": "And its function there\nis to allow the fusion", "start": 1682.82, "duration": 3.57}, {"text": "of oxygen and carbon dioxide.", "start": 1686.39, "duration": 6.18}, {"text": "So here, each of these cells is\nshaped by a mechanical process.", "start": 1702.52, "duration": 6.03}, {"text": "A mechanical process\nhere, you can", "start": 1708.55, "duration": 1.8}, {"text": "take the known or the\nmeasurable mechanical properties", "start": 1710.35, "duration": 5.67}, {"text": "of a red blood cell\nand subject them", "start": 1716.02, "duration": 3.21}, {"text": "to a method called finite\nelements analysis where", "start": 1719.23, "duration": 5.94}, {"text": "you're solving these partial\ndifferentiable equations.", "start": 1725.17, "duration": 4.62}, {"text": "And you can calculate the\nexchange of the oxygen--", "start": 1729.79, "duration": 5.71}, {"text": "alveolar just refers to--\nthis would be in the lungs.", "start": 1739.27, "duration": 2.455}, {"text": "This would be a small\ncapillary in the lungs.", "start": 1741.725, "duration": 1.875}, {"text": "And you can see\nthe capillary now,", "start": 1743.6, "duration": 1.417}, {"text": "the endothelial walls are close\nenough so that the red blood", "start": 1745.017, "duration": 2.653}, {"text": "cells are basically\ndeformed in their shape", "start": 1747.67, "duration": 3.158}, {"text": "as they go through there.", "start": 1750.828, "duration": 1.042}, {"text": "And the exact shapes that\nare compatible with this", "start": 1751.87, "duration": 2.82}, {"text": "will determine the rate that\nthese little arrows that", "start": 1754.69, "duration": 2.55}, {"text": "go from the oxygen on the\noutside the lung epithelium", "start": 1757.24, "duration": 4.23}, {"text": "get through to the blood cell.", "start": 1761.47, "duration": 2.89}, {"text": "So that's a reference that\ndeals with that kind of problem.", "start": 1764.36, "duration": 6.77}, {"text": "Now, as we start thinking about\nbuilding up a larger system", "start": 1771.13, "duration": 8.45}, {"text": "model, the other parts of\nthe system, each of them--", "start": 1779.58, "duration": 2.52}, {"text": "so we've got a red\nblood cell model,", "start": 1782.1, "duration": 1.5}, {"text": "it's the metabolic model.", "start": 1783.6, "duration": 1.042}, {"text": "In principle, it could also be\na shape model and a diffusion", "start": 1784.642, "duration": 4.358}, {"text": "model.", "start": 1789.0, "duration": 1.26}, {"text": "But the other\nparts of the system", "start": 1790.26, "duration": 3.1}, {"text": "typically involve muscle cells.", "start": 1793.36, "duration": 4.65}, {"text": "They have the smooth muscles\nthroughout the entire arterial", "start": 1798.01, "duration": 9.82}, {"text": "and venous system, and most\nsignificantly, the heart", "start": 1807.83, "duration": 4.99}, {"text": "muscles.", "start": 1812.82, "duration": 0.93}, {"text": "And so here you have an example\nof action potential in one", "start": 1813.75, "duration": 6.12}, {"text": "of the ventricular\ncells of the dog heart.", "start": 1819.87, "duration": 3.51}, {"text": "And it includes all the\ncomponents that at least we,", "start": 1823.38, "duration": 4.35}, {"text": "since this is not an entire\ncourse on ventricular heart", "start": 1827.73, "duration": 6.73}, {"text": "modeling.", "start": 1834.46, "duration": 2.43}, {"text": "This is the sort of\nparameters, in terms", "start": 1836.89, "duration": 2.34}, {"text": "of all the I to the currents for\neach of the different potassium", "start": 1839.23, "duration": 3.39}, {"text": "channels to K, all of--\neach of the ones at I", "start": 1842.62, "duration": 3.36}, {"text": "sub K was all potassium.", "start": 1845.98, "duration": 2.7}, {"text": "And then there's some in sodium,\nand sodium and calcium, calcium", "start": 1848.68, "duration": 3.87}, {"text": "potassium, sodium alone.", "start": 1852.55, "duration": 2.057}, {"text": "And so each of these things,\nthat internal storage", "start": 1854.607, "duration": 2.083}, {"text": "of calcium [INAUDIBLE] from\none subcellular compartment", "start": 1856.69, "duration": 3.21}, {"text": "to another and so on.", "start": 1859.9, "duration": 3.31}, {"text": "You get the idea.", "start": 1863.21, "duration": 0.71}, {"text": "Each of these things has to\nhave the parameters measured.", "start": 1863.92, "duration": 3.21}, {"text": "And any of that are\nabsent, you have", "start": 1867.13, "duration": 3.03}, {"text": "to have reasonable ways\nof getting surrogates.", "start": 1870.16, "duration": 6.51}, {"text": "And so this is just\nthe sort of data", "start": 1876.67, "duration": 3.66}, {"text": "that would go into the other\nmajor type of cell that", "start": 1880.33, "duration": 4.14}, {"text": "comes into this\ncardiovascular modeling.", "start": 1884.47, "duration": 4.92}, {"text": "And finally, you can\nintegrate this up", "start": 1889.39, "duration": 3.87}, {"text": "to a fairly complete system.", "start": 1893.26, "duration": 2.76}, {"text": "It's obviously not\ncomplete until you", "start": 1896.02, "duration": 1.56}, {"text": "get to the whole organism,\nbut higher level,", "start": 1897.58, "duration": 2.88}, {"text": "and how we're talking about\nwhole body recirculation.", "start": 1900.46, "duration": 3.8}, {"text": "This NSR group, this\nis a hypertext link", "start": 1904.26, "duration": 3.28}, {"text": "for this particular model\nwhich you can download.", "start": 1907.54, "duration": 3.39}, {"text": "And it has a\nfour-chambered heart.", "start": 1910.93, "duration": 1.57}, {"text": "We were just talking\nabout one ventricular", "start": 1912.5, "duration": 2.12}, {"text": "cell on the previous slide.", "start": 1914.62, "duration": 1.68}, {"text": "But that would be--", "start": 1916.3, "duration": 1.8}, {"text": "if we look at the second\nbox from the top here,", "start": 1918.1, "duration": 2.88}, {"text": "this is where the heart and\nlung model would fit in there.", "start": 1920.98, "duration": 4.15}, {"text": "It's got seven different organs,\nwhich include kidney, liver,", "start": 1925.13, "duration": 3.17}, {"text": "lower limbs, and so forth\ndown at the bottom part", "start": 1928.3, "duration": 2.84}, {"text": "of this diagram.", "start": 1931.14, "duration": 1.85}, {"text": "And you get the picture.", "start": 1932.99, "duration": 1.19}, {"text": "Each of these things, you're\nmodeling the volumes and flows,", "start": 1934.18, "duration": 9.51}, {"text": "Now, this is systems biology.", "start": 1943.69, "duration": 2.1}, {"text": "This is really kind of a\nrenaissance of interest", "start": 1945.79, "duration": 3.75}, {"text": "in physiology, which is what it\nwould have been called before.", "start": 1949.54, "duration": 2.79}, {"text": "And there are some really\ninteresting mysteries out there", "start": 1952.33, "duration": 4.47}, {"text": "to be solved that are really\nonly solvable, or possibly only", "start": 1956.8, "duration": 4.77}, {"text": "solvable, at the system level.", "start": 1961.57, "duration": 1.35}, {"text": "You never know,\nsomebody could come up", "start": 1962.92, "duration": 2.22}, {"text": "and say, oh, yeah,\nthis is really", "start": 1965.14, "duration": 1.59}, {"text": "well understood immunology\nand that answers everything.", "start": 1966.73, "duration": 3.61}, {"text": "But even if it's some\nkind of immunology,", "start": 1970.34, "duration": 4.967}, {"text": "you still have to say,\nhow does it play out?", "start": 1975.307, "duration": 1.833}, {"text": "And what happens is we've\nbeen talking about sickle cell", "start": 1977.14, "duration": 2.333}, {"text": "disease, and you can\nhave fairly mild pain", "start": 1979.473, "duration": 3.487}, {"text": "as one of the major symptoms.", "start": 1982.96, "duration": 2.17}, {"text": "But then all of a\nsudden, out of nowhere,", "start": 1985.13, "duration": 1.85}, {"text": "you'll get this\nmulti-organ system failure", "start": 1986.98, "duration": 2.49}, {"text": "where almost every major\norgan in that previous slide,", "start": 1989.47, "duration": 4.38}, {"text": "lungs and so forth,\nfill up with fluid", "start": 1993.85, "duration": 1.74}, {"text": "and you have a very\nhigh chance of dying.", "start": 1995.59, "duration": 3.492}, {"text": "And this could happen to\nevery one of us in this room", "start": 1999.082, "duration": 2.208}, {"text": "because it's not\nrestricted to sickle cell.", "start": 2001.29, "duration": 2.55}, {"text": "If any of you have severe\nburn, or car crash, major bone", "start": 2003.84, "duration": 7.14}, {"text": "injuries, and so forth,\nyou have a very good chance", "start": 2010.98, "duration": 2.61}, {"text": "of getting into\nmulti-organ system failure.", "start": 2013.59, "duration": 2.44}, {"text": "And it really isn't\nknown how that plays out.", "start": 2016.03, "duration": 3.47}, {"text": "I mean, not even that-- not\njust a quantitative model,", "start": 2019.5, "duration": 2.79}, {"text": "but even qualitatively.", "start": 2022.29, "duration": 2.73}, {"text": "So I think this is something--\nthere are projects now", "start": 2025.02, "duration": 4.2}, {"text": "to get genomic data collection,\nboth genetic and expression", "start": 2029.22, "duration": 5.4}, {"text": "data, and time will tell whether\nthat is actually the best", "start": 2034.62, "duration": 5.85}, {"text": "route to solving that mystery.", "start": 2040.47, "duration": 2.3}, {"text": "So that was multi-organ.", "start": 2042.77, "duration": 1.57}, {"text": "Now we're talking\nabout multi-organism.", "start": 2044.34, "duration": 3.09}, {"text": "After you've built up\nan entire organism,", "start": 2047.43, "duration": 4.26}, {"text": "then you want to\nknow how it acts", "start": 2051.69, "duration": 1.98}, {"text": "at the next level of network\nanalysis, which is how does it", "start": 2053.67, "duration": 4.89}, {"text": "fit in with other organisms?", "start": 2058.56, "duration": 3.929}, {"text": "None of us, almost\nno organism, really", "start": 2062.489, "duration": 3.841}, {"text": "belongs in ecological\nniche all by itself.", "start": 2066.33, "duration": 3.36}, {"text": "And some of the modeling we\nare taught in this course", "start": 2069.69, "duration": 5.969}, {"text": "could be called simulation.", "start": 2075.659, "duration": 2.071}, {"text": "And probably one of the\nlongest-lasting computer", "start": 2077.73, "duration": 6.09}, {"text": "games in the world, and\none of the most successful,", "start": 2083.82, "duration": 4.62}, {"text": "I've heard, is The Sims.", "start": 2088.44, "duration": 4.11}, {"text": "It started with SimCity in--", "start": 2092.55, "duration": 1.98}, {"text": "SimCity in '87.", "start": 2097.44, "duration": 1.08}, {"text": "And then this particular\none illustrated here", "start": 2100.995, "duration": 1.875}, {"text": "is SimLife, which is all\nabout ecological modeling.", "start": 2102.87, "duration": 3.6}, {"text": "And it's not entirely\ndifferent from what", "start": 2106.47, "duration": 2.4}, {"text": "a serious ecological-modeling\nprogram would do.", "start": 2108.87, "duration": 3.66}, {"text": "It certainly has a lot of\nthe interesting parameters", "start": 2112.53, "duration": 2.34}, {"text": "such as the lifespan here.", "start": 2114.87, "duration": 3.54}, {"text": "You're doing demographics\nhere so you have the lifespan,", "start": 2118.41, "duration": 3.48}, {"text": "the amount of food needed,\nthe size, kind of vision,", "start": 2121.89, "duration": 6.96}, {"text": "roaming, so forth, of all these\ndifferent kinds of animals.", "start": 2128.85, "duration": 3.45}, {"text": "You can have plants, you\nhave herbivores, carnivores,", "start": 2135.09, "duration": 3.87}, {"text": "and so on.", "start": 2138.96, "duration": 0.97}, {"text": "And then you can set up\nthe population sizes,", "start": 2139.93, "duration": 2.63}, {"text": "and then it will do\nsimulations based", "start": 2142.56, "duration": 3.42}, {"text": "on that, where each individual\nanimal is tracked in terms", "start": 2145.98, "duration": 5.46}, {"text": "of its position and quantity.", "start": 2151.44, "duration": 2.13}, {"text": "And as you would expect,\nas the carnivores build up,", "start": 2153.57, "duration": 5.79}, {"text": "then they knock\ndown the herbivores,", "start": 2159.36, "duration": 1.5}, {"text": "and the plants go\nup, and so forth.", "start": 2160.86, "duration": 3.3}, {"text": "And it goes through\nthese cycles.", "start": 2164.16, "duration": 2.52}, {"text": "And so this is basically\na stochastic model,", "start": 2166.68, "duration": 2.31}, {"text": "just like the stochastic models\nthat we had for molecules,", "start": 2168.99, "duration": 4.74}, {"text": "but here, at the organism level.", "start": 2173.73, "duration": 2.28}, {"text": "And what's happening here in\nthe slower right-hand section", "start": 2176.01, "duration": 3.15}, {"text": "is you've got little\ngreen plants getting", "start": 2179.16, "duration": 3.42}, {"text": "eaten by herbivores, and\nthe herbivores getting", "start": 2182.58, "duration": 2.58}, {"text": "eaten by carnivores.", "start": 2185.16, "duration": 1.2}, {"text": "Now, hopefully, this\ncourse has already", "start": 2189.05, "duration": 6.16}, {"text": "or will inspire you to\nreally think globally.", "start": 2195.21, "duration": 4.89}, {"text": "To think not only\nglobally in terms", "start": 2200.1, "duration": 2.4}, {"text": "of how little pieces\nof molecular tools", "start": 2202.5, "duration": 5.52}, {"text": "fit together into\nsystems and networks,", "start": 2208.02, "duration": 2.73}, {"text": "but how our systems\nand networks we model", "start": 2210.75, "duration": 2.85}, {"text": "fit into the big picture of what\nare really important problems.", "start": 2213.6, "duration": 4.83}, {"text": "Maybe a slightly\nimproved Viagra is not", "start": 2218.43, "duration": 6.12}, {"text": "in the same category as\na new tuberculosis drug", "start": 2224.55, "duration": 3.78}, {"text": "or maybe it is.", "start": 2228.33, "duration": 0.75}, {"text": "I mean, you decide for yourself\nwhat is thinking globally.", "start": 2229.08, "duration": 4.05}, {"text": "But you have to act\nlocally, and that's", "start": 2233.13, "duration": 1.74}, {"text": "what we're doing in this class.", "start": 2234.87, "duration": 1.292}, {"text": "When we're thinking\nglobally, and we're", "start": 2239.07, "duration": 1.71}, {"text": "thinking about\necological systems,", "start": 2240.78, "duration": 2.46}, {"text": "we're thinking about the\nlithosphere, for the most part,", "start": 2243.24, "duration": 5.25}, {"text": "and its interaction\nwith the hydrosphere.", "start": 2248.49, "duration": 3.66}, {"text": "The lithosphere is\nmostly silicon dioxide,", "start": 2252.15, "duration": 7.88}, {"text": "a tiny bit of carbon, and it\ngets very hot, very quickly.", "start": 2260.03, "duration": 4.85}, {"text": "So only the top 0.1%, that's\nthe top four kilometers of it,", "start": 2264.88, "duration": 7.88}, {"text": "is survivable in any type\nof organism we know of.", "start": 2272.76, "duration": 3.75}, {"text": "About 110 degrees centigrade\nis where organisms start", "start": 2276.51, "duration": 3.21}, {"text": "having a great deal of trouble.", "start": 2279.72, "duration": 2.22}, {"text": "You and I would have\ntrouble before that.", "start": 2281.94, "duration": 1.8}, {"text": "The biosphere here\nis about 3 times 10", "start": 2287.57, "duration": 3.44}, {"text": "to the 15th grams, my\nestimate for marine organisms.", "start": 2291.01, "duration": 10.14}, {"text": "And maybe 10 to the 18th grams\nfor all land plants and animals", "start": 2301.15, "duration": 6.06}, {"text": "and microorganisms.", "start": 2307.21, "duration": 2.94}, {"text": "The microbial hydrosphere\nhere is about 10", "start": 2310.15, "duration": 6.275}, {"text": "to the 21st milliliters,\nwhich works out about 10", "start": 2316.425, "duration": 5.155}, {"text": "to the 27th cells.", "start": 2321.58, "duration": 1.38}, {"text": "A phenomenal number of\nthese cells, about 10", "start": 2322.96, "duration": 1.97}, {"text": "to the 26th of those\ncells is a single species,", "start": 2324.93, "duration": 2.71}, {"text": "which is prochlorococcus,\nwhich is responsible for maybe", "start": 2327.64, "duration": 5.07}, {"text": "about 50% of the\nEarth's photosynthesis.", "start": 2332.71, "duration": 3.96}, {"text": "A lot of that photosynthesis\ndoes not end up in fixed carbon", "start": 2336.67, "duration": 3.99}, {"text": "because it is\nimmediately consumed", "start": 2340.66, "duration": 2.91}, {"text": "by one of its other\npredators, basically.", "start": 2343.57, "duration": 7.5}, {"text": "But there's really quite a\nlot of cells out there which,", "start": 2351.07, "duration": 7.027}, {"text": "to the extent that\nthey're well-mixed,", "start": 2358.097, "duration": 1.583}, {"text": "and they're not-- of course,\nit's not perfectly mixed,", "start": 2359.68, "duration": 2.25}, {"text": "all the Pacific and\nAtlantic and so forth.", "start": 2361.93, "duration": 1.84}, {"text": "But it's a considerably\nmore well-mixed,", "start": 2363.77, "duration": 2.09}, {"text": "say, than the\nlithosphere organisms,", "start": 2365.86, "duration": 1.62}, {"text": "where you have organisms down\na kilometer into the ground.", "start": 2367.48, "duration": 3.91}, {"text": "They don't move\naround very rapidly.", "start": 2371.39, "duration": 3.51}, {"text": "So when you have a\npopulation of that size", "start": 2374.9, "duration": 1.75}, {"text": "as you remember from one\nof our first lectures", "start": 2376.65, "duration": 1.96}, {"text": "on population size, the\neffect of population size", "start": 2378.61, "duration": 2.91}, {"text": "determines the rate of drift and\nthe optimality of the organism.", "start": 2381.52, "duration": 8.058}, {"text": "So one of the things\nthat we do, when", "start": 2389.578, "duration": 1.542}, {"text": "we've been talking about\nmining the biosphere, one", "start": 2391.12, "duration": 3.54}, {"text": "of the things that\nwe're looking for", "start": 2394.66, "duration": 1.5}, {"text": "are new tools that we can\nuse for nanoengineering.", "start": 2396.16, "duration": 7.38}, {"text": "And kind of one of my pet ones\nthat I'm becoming interested", "start": 2403.54, "duration": 3.63}, {"text": "in, we don't work\non the same thing,", "start": 2407.17, "duration": 1.5}, {"text": "but it is kind of interesting,\nis a set of-- we mentioned this", "start": 2408.67, "duration": 4.2}, {"text": "briefly in the drug protein\ninteraction lecture where--", "start": 2412.87, "duration": 5.845}, {"text": "but I don't think I mentioned\nthis particular one-- where", "start": 2418.715, "duration": 2.375}, {"text": "you have polyketides\nthat go together.", "start": 2421.09, "duration": 3.21}, {"text": "It's another polymer that\nhas certain similarities", "start": 2424.3, "duration": 3.75}, {"text": "to the basic polymers\nwe talked about,", "start": 2428.05, "duration": 1.62}, {"text": "but each step in it had\nto have a protein enzyme--", "start": 2429.67, "duration": 4.32}, {"text": "an enzymatic domain\nto accomplish that.", "start": 2433.99, "duration": 2.56}, {"text": "And so one of these\nis tetracycline.", "start": 2436.55, "duration": 2.0}, {"text": "And this is one of\nthe more aromatic kind", "start": 2438.55, "duration": 2.49}, {"text": "of coupled-aromatic\ncompounds that's", "start": 2441.04, "duration": 1.86}, {"text": "made because you have\nthese [INAUDIBLE]", "start": 2442.9, "duration": 2.04}, {"text": "and aromatases in addition\nto the polymerization steps.", "start": 2444.94, "duration": 5.31}, {"text": "And so you make this\nthing that looks", "start": 2450.25, "duration": 2.1}, {"text": "kind of like a poly\naromatic hydrocarbon.", "start": 2452.35, "duration": 3.6}, {"text": "And also in nature, you will\nfind, in soot, in forest fires,", "start": 2455.95, "duration": 5.25}, {"text": "in all kinds of\nnatural phenomena,", "start": 2461.2, "duration": 1.77}, {"text": "you will find polycyclic\naromatic hydrocarbons, which", "start": 2462.97, "duration": 4.44}, {"text": "some of you may know about\nas the potent carcinogens,", "start": 2467.41, "duration": 3.3}, {"text": "but they're also just\nnatural components.", "start": 2470.71, "duration": 3.96}, {"text": "But they also-- you\ncan start to see this", "start": 2474.67, "duration": 2.37}, {"text": "looks a little bit like the\nbuckyballs and buckytubes", "start": 2477.04, "duration": 2.61}, {"text": "that we talked\nabout when we were", "start": 2479.65, "duration": 1.375}, {"text": "talking about\nmolecular-type transistors.", "start": 2481.025, "duration": 3.545}, {"text": "So the possibility of mining\nthe biosphere for enzymes", "start": 2484.57, "duration": 5.22}, {"text": "that act to\nsynthesize or degrade", "start": 2489.79, "duration": 2.16}, {"text": "this class of\ncompounds, I think,", "start": 2491.95, "duration": 1.56}, {"text": "would be just an example.", "start": 2493.51, "duration": 1.42}, {"text": "We could list many others.", "start": 2494.93, "duration": 1.2}, {"text": "But the part of it is\njust to dream, to imagine,", "start": 2496.13, "duration": 3.02}, {"text": "what it is would like\nto find out there.", "start": 2499.15, "duration": 2.44}, {"text": "And if there's an\nabundant source of it,", "start": 2501.59, "duration": 5.36}, {"text": "then you should be able to--", "start": 2506.95, "duration": 1.77}, {"text": "abundant source of, say,\nthe compound, in this case,", "start": 2508.72, "duration": 2.29}, {"text": "you need to be able to find\na microorganism and an enzyme", "start": 2511.01, "duration": 4.02}, {"text": "that goes with that\nbecause there's a truly", "start": 2515.03, "duration": 2.03}, {"text": "phenomenal amount of diversity.", "start": 2517.06, "duration": 2.13}, {"text": "Another very important\nglobal consideration,", "start": 2522.37, "duration": 3.21}, {"text": "rather than just mining\nit for new tools,", "start": 2525.58, "duration": 3.03}, {"text": "is thinking about ways that\neither we could engineer", "start": 2528.61, "duration": 2.91}, {"text": "or accidentally mess\nup our entire planet,", "start": 2531.52, "duration": 5.37}, {"text": "as we could be doing with\nglobal warming or could do.", "start": 2536.89, "duration": 5.91}, {"text": "And perhaps it's naive\nto think that we actually", "start": 2542.8, "duration": 3.06}, {"text": "are having such a\nbig effect because we", "start": 2545.86, "duration": 1.83}, {"text": "know that global warming changes\nperiodically over millennia.", "start": 2547.69, "duration": 4.41}, {"text": "But it is very clear\nfrom the record", "start": 2555.11, "duration": 4.92}, {"text": "just exactly how much carbon\ndioxide we are releasing", "start": 2560.03, "duration": 2.38}, {"text": "and it makes sense, that it\nis consistent with the kind", "start": 2562.41, "duration": 3.848}, {"text": "of temperature\nchanges that have been", "start": 2566.258, "duration": 1.542}, {"text": "observed since the\nIndustrial Revolution.", "start": 2567.8, "duration": 2.73}, {"text": "In any case, when you\nlook at, in particular,", "start": 2570.53, "duration": 5.26}, {"text": "the Southern Ocean--", "start": 2575.79, "duration": 2.06}, {"text": "up at the top of slide 27--", "start": 2577.85, "duration": 2.108}, {"text": "you can see there is a\nfew places, in particular,", "start": 2579.958, "duration": 2.042}, {"text": "Southern Ocean seems like\nit's a prime candidate where", "start": 2582.0, "duration": 2.33}, {"text": "you have high nutrients\nbut low chlorophyll.", "start": 2584.33, "duration": 3.18}, {"text": "And you say, well, why would\nyou have high nutrients", "start": 2587.51, "duration": 2.22}, {"text": "but very little of the\nchlorophyll around,", "start": 2589.73, "duration": 5.2}, {"text": "which is a tipoff that you have\nthe photosynthetic bacteria.", "start": 2594.93, "duration": 5.24}, {"text": "And the reason is that\nyou have a limitation", "start": 2600.17, "duration": 3.33}, {"text": "of some micronutrient.", "start": 2603.5, "duration": 1.17}, {"text": "Micronutrient means it's not\nneeded in the vast quantities", "start": 2604.67, "duration": 4.68}, {"text": "that you need nitrogen,\nphosphorus, carbon, oxygen,", "start": 2609.35, "duration": 2.92}, {"text": "and so on.", "start": 2612.27, "duration": 1.2}, {"text": "So iron, typically, is\nthe limiting micronutrient", "start": 2613.47, "duration": 2.6}, {"text": "in the Southern Ocean.", "start": 2616.07, "duration": 1.26}, {"text": "And so there actually have\nbeen little pilot experiments", "start": 2617.33, "duration": 3.48}, {"text": "to drop iron off the\nbacks of huge tankers.", "start": 2620.81, "duration": 4.08}, {"text": "And there are now at\nleast seven patents", "start": 2624.89, "duration": 2.37}, {"text": "that have been filed\non doing this in order", "start": 2627.26, "duration": 2.46}, {"text": "to balance out the carbon\ncredits for different nations.", "start": 2629.72, "duration": 4.02}, {"text": "This is potentially a very big\nbit of terrestrial engineering", "start": 2633.74, "duration": 3.96}, {"text": "that might happen.", "start": 2637.7, "duration": 1.14}, {"text": "It involves trying to\nchange phytoplankton.", "start": 2638.84, "duration": 5.4}, {"text": "And as this line here\nbegins to point out,", "start": 2644.24, "duration": 4.21}, {"text": "even though\nphytoplankton are only 1%", "start": 2648.45, "duration": 2.6}, {"text": "of the total global\nbiomass, it's about 50%", "start": 2651.05, "duration": 2.7}, {"text": "of the carbon fixation.", "start": 2653.75, "duration": 3.19}, {"text": "What is the source of\nthis 50-fold anomaly?", "start": 2656.94, "duration": 2.63}, {"text": "Why is it that even\nthough it's doing--", "start": 2659.57, "duration": 4.96}, {"text": "how is it doing 50% of\nthe carbon fixation?", "start": 2664.53, "duration": 1.88}, {"text": "And what's happening\nis a lot of the carbon", "start": 2666.41, "duration": 2.34}, {"text": "is going right back\nout after being fixed.", "start": 2668.75, "duration": 3.693}, {"text": "Instead of settling to\nthe bottom of the ocean", "start": 2672.443, "duration": 1.917}, {"text": "and never bothering us\nagain, it gets returned.", "start": 2674.36, "duration": 5.67}, {"text": "And the exact modeling\nof that requires", "start": 2680.03, "duration": 2.25}, {"text": "a much deeper knowledge\nof exactly what organisms", "start": 2682.28, "duration": 3.18}, {"text": "are present in the ocean.", "start": 2685.46, "duration": 1.35}, {"text": "One of the problems\nwith this however,", "start": 2686.81, "duration": 1.78}, {"text": "is a genomic problem, in\na certain sense, which", "start": 2688.59, "duration": 4.16}, {"text": "is that very few\nof these organisms", "start": 2692.75, "duration": 3.93}, {"text": "can be cultivated\nin the laboratory.", "start": 2696.68, "duration": 2.16}, {"text": "On the order of 99.9% of the\norganisms that you sample", "start": 2698.84, "duration": 3.39}, {"text": "from the ocean,\nor from the soil,", "start": 2702.23, "duration": 1.95}, {"text": "a number of different\nenvironments,", "start": 2704.18, "duration": 2.91}, {"text": "do not grow well\nin the laboratory.", "start": 2707.09, "duration": 2.26}, {"text": "So if you were to\nstudy them, some people", "start": 2709.35, "duration": 3.77}, {"text": "are feeling that the best\nroute to studying them", "start": 2713.12, "duration": 2.76}, {"text": "is going directly for--", "start": 2715.88, "duration": 3.15}, {"text": "looking at their genomes,\nwithout necessarily", "start": 2719.03, "duration": 2.07}, {"text": "being able to grow\nthem in the laboratory.", "start": 2721.1, "duration": 2.532}, {"text": "Now, when we talk\nabout this problem of--", "start": 2726.41, "duration": 4.44}, {"text": "even if we fertilize\nthe oceans, and we", "start": 2730.85, "duration": 3.93}, {"text": "can model this whole procedure,\nI won't go into details.", "start": 2734.78, "duration": 2.46}, {"text": "But if there are predators\nthere that take the fixed carbon", "start": 2737.24, "duration": 10.15}, {"text": "and turn it back\ninto carbon dioxide,", "start": 2747.39, "duration": 2.43}, {"text": "you want to be able\nto monitor that.", "start": 2749.82, "duration": 2.37}, {"text": "Now, of course, the ocean\nis a large, complex set", "start": 2752.19, "duration": 3.48}, {"text": "of prokaryotic\nautotrophs that are, say,", "start": 2755.67, "duration": 3.87}, {"text": "photosynthetic bacteria, and\neukaryotic photosynthetic", "start": 2759.54, "duration": 2.91}, {"text": "bacteria, and prokaryotic\nand eukaryotic predators", "start": 2762.45, "duration": 5.76}, {"text": "of various sorts.", "start": 2768.21, "duration": 1.36}, {"text": "And this is, I think, one\nof the more interesting", "start": 2769.57, "duration": 2.9}, {"text": "predator-prey differential\nequation models.", "start": 2772.47, "duration": 6.09}, {"text": "It's almost the same as many\nof the other differential", "start": 2778.56, "duration": 2.82}, {"text": "equations that we did from\nthe first lecture on growth.", "start": 2781.38, "duration": 5.5}, {"text": "We did the logistic\nequation, some", "start": 2786.88, "duration": 2.3}, {"text": "of the ones we did on\nrepressor function, and so on.", "start": 2789.18, "duration": 2.838}, {"text": "But the thing that's kind of\ninteresting about this one", "start": 2792.018, "duration": 2.292}, {"text": "is it's not simply a\nsingle-cell bacteria", "start": 2794.31, "duration": 5.85}, {"text": "being eaten by a\nsingle-celled heterotroph,", "start": 2800.16, "duration": 3.15}, {"text": "let's say, a blue-green\nalgae being eaten", "start": 2803.31, "duration": 1.71}, {"text": "by a single-cell heterotroph.", "start": 2805.02, "duration": 1.47}, {"text": "Here, they are\nboth multicellular.", "start": 2806.49, "duration": 2.45}, {"text": "They're sort of the\nminimal multicellular.", "start": 2808.94, "duration": 1.75}, {"text": "But because they\nare-- so Chlorella", "start": 2810.69, "duration": 2.55}, {"text": "is one of the smallest\nplants, multicellular plants.", "start": 2813.24, "duration": 2.79}, {"text": "And Brachionus is a small\nrotifer, a multicellular", "start": 2816.03, "duration": 7.89}, {"text": "animal.", "start": 2823.92, "duration": 0.595}, {"text": "Because they're\nmulti-cellular, though,", "start": 2824.515, "duration": 1.625}, {"text": "now you have the demographic\nmortality and fecundity", "start": 2826.14, "duration": 5.55}, {"text": "of each of these things\nthat has to be modeled in.", "start": 2831.69, "duration": 2.43}, {"text": "That's the m and the\nlambda for Brachionus.", "start": 2834.12, "duration": 4.83}, {"text": "And so this plays into these\nequations where you have here,", "start": 2838.95, "duration": 6.45}, {"text": "in the upper-right\nof slide 28, the rate", "start": 2845.4, "duration": 3.3}, {"text": "of change of nitrogen\nwith respect to time,", "start": 2848.7, "duration": 5.43}, {"text": "and concentration of Chlorella.", "start": 2854.13, "duration": 2.82}, {"text": "So nitrogen is N,\nChlorella is C.", "start": 2856.95, "duration": 3.42}, {"text": "The R is the Brachionus\nthat are reproducing", "start": 2860.37, "duration": 7.59}, {"text": "and B are the Brachionus\nwhich are the total.", "start": 2867.96, "duration": 3.43}, {"text": "And you can see each of these\nequations and how it plays out.", "start": 2871.39, "duration": 3.02}, {"text": "Now this is how--", "start": 2874.41, "duration": 1.53}, {"text": "and the way they play\nit out here is you do it", "start": 2875.94, "duration": 2.7}, {"text": "by dilution rate, delta, here.", "start": 2878.64, "duration": 2.82}, {"text": "And the dilution rate is shown\nalong the horizontal x-axis", "start": 2881.46, "duration": 11.49}, {"text": "for each of these\nthree plots here.", "start": 2892.95, "duration": 2.04}, {"text": "And what they're modeling\nis on the far left,", "start": 2894.99, "duration": 4.44}, {"text": "the nitrogen concentration as\na function of dilution rate.", "start": 2899.43, "duration": 7.36}, {"text": "And you can see you get these\ndifferent sectors of behavior.", "start": 2906.79, "duration": 7.85}, {"text": "When you look at\nthe Chlorella, this", "start": 2914.64, "duration": 1.74}, {"text": "is a green, photosynthetic,\nmulticellular organism,", "start": 2916.38, "duration": 4.59}, {"text": "in units of millions of\ncells per milliliter,", "start": 2920.97, "duration": 2.79}, {"text": "that can take different--", "start": 2923.76, "duration": 3.86}, {"text": "it take different\npathways here where,", "start": 2927.62, "duration": 4.15}, {"text": "as a function of\ndilution rate, you", "start": 2931.77, "duration": 1.65}, {"text": "get this bifurcation\nwhere you get", "start": 2933.42, "duration": 2.19}, {"text": "a huge split in the possible\nconcentrations of Chlorella", "start": 2935.61, "duration": 7.77}, {"text": "is the one curve and the\nBrachionus, the predator,", "start": 2943.38, "duration": 3.84}, {"text": "is the other curve.", "start": 2947.22, "duration": 1.095}, {"text": "This kind of bifurcation\nis the sort of thing", "start": 2948.315, "duration": 1.875}, {"text": "we talked about earlier,\nboth in the logistic equation", "start": 2950.19, "duration": 4.62}, {"text": "and in the\nself-exclusion modeling.", "start": 2954.81, "duration": 10.1}, {"text": "And in the upper-right-hand,\nhere's our friend", "start": 2964.91, "duration": 4.38}, {"text": "the coefficient of\nvariation in percent,", "start": 2969.29, "duration": 2.03}, {"text": "ranging from 0 to 80 or\nso on the vertical axis", "start": 2971.32, "duration": 4.84}, {"text": "and the dilution rate.", "start": 2976.16, "duration": 1.57}, {"text": "And again, you can see that you\nget a peak in the dilution rate", "start": 2977.73, "duration": 4.82}, {"text": "at around 0.75.", "start": 2982.55, "duration": 1.92}, {"text": "The bottom two are models, and\nthe upper right is the data.", "start": 2984.47, "duration": 5.08}, {"text": "You can actually see, when\nyou run real Chlorella", "start": 2989.55, "duration": 2.33}, {"text": "and Brachionus in here, that you\ndo get a peak just as you would", "start": 2991.88, "duration": 3.27}, {"text": "predict in this kind\nof bifurcation analysis", "start": 2995.15, "duration": 2.145}, {"text": "in kinetic modeling.", "start": 2997.295, "duration": 2.385}, {"text": "That's due to-- where you\nget interesting behavior", "start": 2999.68, "duration": 5.28}, {"text": "in this complicated-- or this\nfairly simple model ecosystem", "start": 3004.96, "duration": 4.08}, {"text": "where you just have two species.", "start": 3009.04, "duration": 1.92}, {"text": "In the ocean, of course,\nyou have a lot more.", "start": 3010.96, "duration": 4.11}, {"text": "Now, that's out\nin the wide world", "start": 3015.07, "duration": 2.16}, {"text": "where you have 10\nto the 26 cells.", "start": 3017.23, "duration": 3.66}, {"text": "But inside every one of us\nin this room, no offense,", "start": 3020.89, "duration": 3.42}, {"text": "but there are about 10 times\nas many non-human cells", "start": 3024.31, "duration": 4.86}, {"text": "in each of us as\nare human cells.", "start": 3029.17, "duration": 2.88}, {"text": "And we have our own ecology.", "start": 3032.05, "duration": 2.97}, {"text": "And there is a literature\nwhere certain organisms", "start": 3035.02, "duration": 4.95}, {"text": "we know cause\ndiseases, and they're", "start": 3039.97, "duration": 1.77}, {"text": "put into one category,\ninfectious diseases,", "start": 3041.74, "duration": 3.24}, {"text": "but then there's\nanother set that", "start": 3044.98, "duration": 1.47}, {"text": "takes some time to sort out.", "start": 3046.45, "duration": 1.69}, {"text": "And you can see here\nare candidate diseases", "start": 3048.14, "duration": 1.97}, {"text": "and candidate organisms.", "start": 3050.11, "duration": 1.41}, {"text": "And all these little bars\nthat are going in here", "start": 3051.52, "duration": 2.46}, {"text": "are references that\nyou can look up", "start": 3053.98, "duration": 3.33}, {"text": "where maybe it's not\nan airtight case yet,", "start": 3057.31, "duration": 3.21}, {"text": "or maybe it's not\neven-- maybe there's", "start": 3060.52, "duration": 1.8}, {"text": "controversial or\ndiscredited [INAUDIBLE],,", "start": 3062.32, "duration": 2.79}, {"text": "but these are links where,\neventually, this will be", "start": 3065.11, "duration": 2.88}, {"text": "called an infectious disease.", "start": 3067.99, "duration": 2.01}, {"text": "Helicobacter pylori\ncauses stomach ulcers.", "start": 3070.0, "duration": 2.52}, {"text": "I think that fact's\nbasically already accepted.", "start": 3072.52, "duration": 2.415}, {"text": "Some Australian\ndoctor named Marshall", "start": 3077.98, "duration": 2.28}, {"text": "decided to drink a\nbunch of Helicobacter", "start": 3080.26, "duration": 1.833}, {"text": "to prove to his colleagues,\nwho didn't believe", "start": 3082.093, "duration": 1.917}, {"text": "any stomach ulcers were caused\nby Helicobacter, much less all", "start": 3084.01, "duration": 2.82}, {"text": "of them.", "start": 3086.83, "duration": 0.81}, {"text": "And he drank it, he cured\nhimself, he drank it again.", "start": 3087.64, "duration": 4.32}, {"text": "And he caused stomach\nulcers in himself.", "start": 3091.96, "duration": 5.46}, {"text": "And hopefully, none\nof you will volunteer", "start": 3097.42, "duration": 4.14}, {"text": "to do similar things with\nsome of these other nasty guys", "start": 3101.56, "duration": 3.63}, {"text": "here because I think some\nof the list of things", "start": 3105.19, "duration": 2.7}, {"text": "that they cause are a little\nmore serious than stomach", "start": 3107.89, "duration": 2.43}, {"text": "ulcers, and the cures\nare a little less obvious", "start": 3110.32, "duration": 2.67}, {"text": "than the cures for a\ngram-negative bacterium", "start": 3112.99, "duration": 2.25}, {"text": "like Helicobacter.", "start": 3115.24, "duration": 3.6}, {"text": "There have been\nvarious efforts started", "start": 3118.84, "duration": 2.76}, {"text": "to actually mine what's the\nconnection with genomics", "start": 3121.6, "duration": 4.35}, {"text": "and computational biology?", "start": 3125.95, "duration": 1.26}, {"text": "To mine the transcriptome\nfor evidence of these.", "start": 3127.21, "duration": 5.13}, {"text": "You can look for\nbacteria very easily", "start": 3132.34, "duration": 1.8}, {"text": "because they have ribosomal RNA\ncomponents which you can PCR.", "start": 3134.14, "duration": 5.52}, {"text": "Viruses are more complicated\nbecause they're not conserved,", "start": 3139.66, "duration": 5.94}, {"text": "or they don't have any\nuniversally conserved element", "start": 3145.6, "duration": 2.79}, {"text": "like ribosomal RNA.", "start": 3148.39, "duration": 1.59}, {"text": "But there have been\nefforts to look", "start": 3149.98, "duration": 3.93}, {"text": "for what's present in the\nhuman transcriptome that's not", "start": 3153.91, "duration": 2.613}, {"text": "present in the human genome.", "start": 3156.523, "duration": 1.167}, {"text": "The human genome is something\nhighly purified and cloned", "start": 3157.69, "duration": 4.38}, {"text": "and so forth, while\nthe transcriptome", "start": 3162.07, "duration": 2.1}, {"text": "is whatever cells they\nground up that day and they.", "start": 3164.17, "duration": 4.38}, {"text": "And indeed, lurking in there\nare many of these hepatitis,", "start": 3168.55, "duration": 4.26}, {"text": "papilloma, Epstein-Barr virus,\nretroviral-like elements which", "start": 3172.81, "duration": 4.92}, {"text": "are not present in the\nhuman genome as yet.", "start": 3177.73, "duration": 2.55}, {"text": "Human genome is not\ncompletely finished.", "start": 3180.28, "duration": 2.11}, {"text": "So that's still\nan escape clause.", "start": 3182.39, "duration": 1.94}, {"text": "But basically, these are smoking\nguns for at least commensals.", "start": 3184.33, "duration": 6.33}, {"text": "Microorganisms and viruses that\nare living in tissues, some", "start": 3190.66, "duration": 5.1}, {"text": "of them may be tissue-specific.", "start": 3195.76, "duration": 1.86}, {"text": "Some of them, subset, may\nactually cause disease.", "start": 3197.62, "duration": 2.723}, {"text": "And that's the\nwhole problem then,", "start": 3200.343, "duration": 1.417}, {"text": "is sorting out cause and effect.", "start": 3201.76, "duration": 1.75}, {"text": "We know how it's been\ndone, heroically,", "start": 3203.51, "duration": 3.95}, {"text": "with Helicobacter\npylori, but how do", "start": 3207.46, "duration": 1.5}, {"text": "we do it with the other ones?", "start": 3208.96, "duration": 1.208}, {"text": "Some of them will have\ntissue-culture models.", "start": 3210.168, "duration": 1.957}, {"text": "At the time this slide\nwas done, but so--", "start": 3216.43, "duration": 4.68}, {"text": "this is just illustrating\nkind of the flow", "start": 3221.11, "duration": 4.68}, {"text": "of nucleic acid information\nthat comes in about--", "start": 3225.79, "duration": 6.24}, {"text": "that was capable of being\nmined for new microorganisms,", "start": 3232.03, "duration": 3.39}, {"text": "new viruses that might be\npresent in a tissue-specific", "start": 3235.42, "duration": 3.0}, {"text": "fashion, might be pathogens.", "start": 3238.42, "duration": 2.83}, {"text": "These are some of the\nmost popular sequences", "start": 3241.25, "duration": 2.12}, {"text": "from which we're mining.", "start": 3243.37, "duration": 1.44}, {"text": "Obviously, human was\npopular at times [INAUDIBLE]", "start": 3244.81, "duration": 4.71}, {"text": "the human genome was in place.", "start": 3249.52, "duration": 1.72}, {"text": "Here's Brachionus,\nour friend, which", "start": 3251.24, "duration": 1.76}, {"text": "was pretty high up on this\nlist, considering most of you", "start": 3253.0, "duration": 2.73}, {"text": "probably didn't hear about\nBrachionus before this lecture.", "start": 3255.73, "duration": 2.47}, {"text": "Now you've heard of it twice.", "start": 3258.2, "duration": 1.79}, {"text": "There just was a spurt\nin sequencing interest.", "start": 3259.99, "duration": 3.45}, {"text": "And of course, HIV\nis the winner year", "start": 3263.44, "duration": 2.49}, {"text": "after year because of the\nimportance of resequencing it", "start": 3265.93, "duration": 3.15}, {"text": "for new mutations.", "start": 3269.08, "duration": 2.32}, {"text": "And it really has a record\nnumber of new mutations.", "start": 3271.4, "duration": 4.52}, {"text": "And we've talked about\nHIV from a variety", "start": 3275.92, "duration": 7.2}, {"text": "of different standpoints.", "start": 3283.12, "duration": 2.28}, {"text": "One of them is\npolymerase, is protease,", "start": 3285.4, "duration": 2.88}, {"text": "is drug targets, and as a\nsource of drug resistance.", "start": 3288.28, "duration": 4.44}, {"text": "And that you can follow\nup that model, that sort", "start": 3292.72, "duration": 3.83}, {"text": "of atomic-scale\nprotein modeling,", "start": 3296.55, "duration": 2.92}, {"text": "where you're looking\nfor new drugs", "start": 3299.47, "duration": 4.62}, {"text": "where the polymerase,\nthe mutant polymerase,", "start": 3304.09, "duration": 2.16}, {"text": "will not be resistant\nto the new drug.", "start": 3306.25, "duration": 2.01}, {"text": "But you can also monitor\nat the population scale.", "start": 3308.26, "duration": 2.34}, {"text": "As HIV goes to a\nparticular patient,", "start": 3310.6, "duration": 3.39}, {"text": "or to a population of patients,\nhow does the drug resistance", "start": 3313.99, "duration": 6.54}, {"text": "change as a function of time?", "start": 3320.53, "duration": 1.65}, {"text": "Here, the horizontal axis\nis in days, up to 30 days,", "start": 3322.18, "duration": 3.66}, {"text": "and then the vertical\naxis is the titers", "start": 3325.84, "duration": 9.59}, {"text": "of the viruses [INAUDIBLE]\nas a function of time.", "start": 3335.43, "duration": 4.69}, {"text": "And what you have here is\nrates of exponential increase.", "start": 3340.12, "duration": 8.65}, {"text": "These are all on\nlogarithmic scales.", "start": 3348.77, "duration": 2.73}, {"text": "And where you're\nmodeling such a thing", "start": 3351.5, "duration": 2.52}, {"text": "as the clearance to the\nimmune system and so forth.", "start": 3354.02, "duration": 3.623}, {"text": "Originally, this\nvirus was thought", "start": 3357.643, "duration": 1.417}, {"text": "to be a very slowly replicating\nvirus, almost cryptic.", "start": 3359.06, "duration": 6.96}, {"text": "And then later\nwas found out this", "start": 3366.02, "duration": 1.38}, {"text": "is actually a very rapidly\nreplicating, but immune system", "start": 3367.4, "duration": 3.24}, {"text": "is very rapidly responding.", "start": 3370.64, "duration": 3.177}, {"text": "Just each of these\nmodels we've gone through", "start": 3373.817, "duration": 1.833}, {"text": "has a set of parameters\nthat it goes along with.", "start": 3375.65, "duration": 2.26}, {"text": "In a certain sense,\nthere's quite a bit", "start": 3377.91, "duration": 1.7}, {"text": "you can learn about a model just\nby seeing what parameters are", "start": 3379.61, "duration": 3.06}, {"text": "present or absent, whether\nthey're experimentally", "start": 3382.67, "duration": 3.63}, {"text": "determined, how\naccurately, and so on.", "start": 3386.3, "duration": 2.52}, {"text": "And model parameters here are\nmortality rate of uninfected", "start": 3388.82, "duration": 4.86}, {"text": "CD4+ T-cells, same thing\nfor infected cells,", "start": 3393.68, "duration": 4.235}, {"text": "and they can have different\n[INAUDIBLE] you can see", "start": 3397.915, "duration": 2.125}, {"text": "on the far right that there's a\nhuge difference between a diet", "start": 3400.04, "duration": 4.26}, {"text": "of 1/4 per day versus\n[INAUDIBLE] and so on.", "start": 3404.3, "duration": 5.95}, {"text": "There's rates for getting\ninfected, rates of virus loss,", "start": 3410.25, "duration": 5.0}, {"text": "production, threshold value for\nremission, so on and so forth.", "start": 3415.25, "duration": 10.65}, {"text": "And these are\nimportant parameters", "start": 3425.9, "duration": 3.35}, {"text": "for how the virus\npopulation changes", "start": 3429.25, "duration": 4.29}, {"text": "within a person\nor the population.", "start": 3433.54, "duration": 2.268}, {"text": "How it spreads\nthrough the population", "start": 3435.808, "duration": 1.542}, {"text": "depends on, in many cases, on\nthe herd immunity and so forth.", "start": 3437.35, "duration": 7.21}, {"text": "And we get into issues\nof public health.", "start": 3444.56, "duration": 2.99}, {"text": "It's almost a truism that\nmost of the additional quality", "start": 3450.87, "duration": 9.24}, {"text": "years of life, quality-adjusted\nlife years here,", "start": 3460.11, "duration": 3.66}, {"text": "QALY, that we have in the\nworld the fact that our life", "start": 3463.77, "duration": 5.19}, {"text": "expectancy is so much\nlonger and so forth,", "start": 3468.96, "duration": 1.77}, {"text": "are mainly public health\ndecisions that have been made,", "start": 3470.73, "duration": 4.53}, {"text": "not so much pharmaceutical.", "start": 3475.26, "duration": 1.8}, {"text": "Such things as clean water\nhave made a huge impact.", "start": 3481.04, "duration": 7.06}, {"text": "And so we need to think--", "start": 3488.1, "duration": 1.46}, {"text": "but even when you think about\nthe pharmaceutical aspects,", "start": 3489.56, "duration": 2.895}, {"text": "it needs to be thought of\nin a public health sense.", "start": 3492.455, "duration": 2.125}, {"text": "And a surprising amount\nof public health officials", "start": 3494.58, "duration": 3.47}, {"text": "in even the most developed\nnations, maybe most of them", "start": 3498.05, "duration": 5.25}, {"text": "do not have formal\neducation in public health.", "start": 3503.3, "duration": 2.34}, {"text": "And so I urge you all to get at\nleast some education in this.", "start": 3505.64, "duration": 4.68}, {"text": "Because in this, we have--", "start": 3510.32, "duration": 2.16}, {"text": "here, they're trying\nto build and have", "start": 3512.48, "duration": 3.57}, {"text": "built quantitative models,\nnot only for the kinetics", "start": 3516.05, "duration": 5.17}, {"text": "which a disease will go\nthrough a population or even", "start": 3521.22, "duration": 2.66}, {"text": "through an individual, but the\nway that you make decisions.", "start": 3523.88, "duration": 6.52}, {"text": "And this is having an impact\non the way decisions are--", "start": 3530.4, "duration": 2.66}, {"text": "how these different\nprojects are prioritized.", "start": 3533.06, "duration": 2.52}, {"text": "At any given time,\nyou might have", "start": 3535.58, "duration": 1.74}, {"text": "hundreds of different\ncandidate vaccines, which", "start": 3537.32, "duration": 4.5}, {"text": "is one of the major, very\neffective public health", "start": 3541.82, "duration": 3.99}, {"text": "strategies.", "start": 3545.81, "duration": 2.49}, {"text": "And this is the way\nthey prioritize it.", "start": 3548.3, "duration": 2.05}, {"text": "So the level one, saves\nmoney and it improves life.", "start": 3550.35, "duration": 3.68}, {"text": "So that's almost a no-brainer.", "start": 3554.03, "duration": 3.72}, {"text": "Then you have different levels.", "start": 3557.75, "duration": 1.39}, {"text": "We have it might cost\na $10,000, or $100,000", "start": 3559.14, "duration": 5.21}, {"text": "per quality-adjusted\nlife year saved.", "start": 3564.35, "duration": 2.565}, {"text": "And so the level one\ncandidates are cytomegalovirus,", "start": 3570.2, "duration": 3.66}, {"text": "and therapeutic vaccines.", "start": 3573.86, "duration": 2.4}, {"text": "These are not aimed at\nan infectious disease,", "start": 3576.26, "duration": 2.46}, {"text": "they're for diabetes, rheumatoid\narthritis, multiple sclerosis,", "start": 3578.72, "duration": 3.78}, {"text": "various bacterial ones.", "start": 3582.5, "duration": 1.695}, {"text": "And of course, HIV was\nnot even in this study", "start": 3584.195, "duration": 1.875}, {"text": "because it was such a\nhigh priority already", "start": 3586.07, "duration": 3.96}, {"text": "within the NIH.", "start": 3590.03, "duration": 0.72}, {"text": "So is there a role for genomics\nand computational biology,", "start": 3595.773, "duration": 2.417}, {"text": "the title of this course,\nin this vaccine research", "start": 3598.19, "duration": 3.09}, {"text": "and development?", "start": 3601.28, "duration": 1.56}, {"text": "I think the answer\nis yes, but it", "start": 3602.84, "duration": 2.25}, {"text": "requires a great deal of\ncreativity and resourcefulness", "start": 3605.09, "duration": 2.85}, {"text": "on all of your parts.", "start": 3607.94, "duration": 2.19}, {"text": "There are new opportunities\nwith DNA vaccines where", "start": 3610.13, "duration": 3.6}, {"text": "you can have one or more\nDNAs shot intramuscularly", "start": 3613.73, "duration": 4.29}, {"text": "or a variety of other ways.", "start": 3618.02, "duration": 2.73}, {"text": "What is delivered\nby the DNA vaccine", "start": 3620.75, "duration": 2.25}, {"text": "can be various so-called\nintracellular vaccines,", "start": 3623.0, "duration": 4.74}, {"text": "which can either act through\ncell-mediated immunity", "start": 3627.74, "duration": 2.37}, {"text": "or in some other\nway intracellularly.", "start": 3630.11, "duration": 2.88}, {"text": "RNAi is a rapidly emerging\nway of delivering things", "start": 3632.99, "duration": 8.49}, {"text": "that may not be\nclassically considered", "start": 3641.48, "duration": 2.82}, {"text": "therapeutics or vaccines.", "start": 3644.3, "duration": 2.97}, {"text": "The concept of multiplexing--", "start": 3647.27, "duration": 2.49}, {"text": "many of us have received\nmultiple vaccines at a time.", "start": 3649.76, "duration": 7.68}, {"text": "Typically, every\nyear, your flu vaccine", "start": 3657.44, "duration": 1.89}, {"text": "will have two or\nthree strains in it.", "start": 3659.33, "duration": 1.84}, {"text": "But as you can see from\nthis middle article,", "start": 3661.17, "duration": 4.85}, {"text": "the diversity of\ncertain diseases,", "start": 3666.02, "duration": 1.86}, {"text": "like HIV and influenza, almost\ndemand attention from genomics.", "start": 3667.88, "duration": 5.46}, {"text": "The diversity that can occur,\neither from year to year", "start": 3673.34, "duration": 3.42}, {"text": "or throughout the entire\nglobal set of viruses.", "start": 3676.76, "duration": 8.29}, {"text": "Another opportunity\nis when we have", "start": 3685.05, "duration": 2.69}, {"text": "vectors for, say,\narthropod vectors,", "start": 3687.74, "duration": 4.38}, {"text": "insect vectors like mosquito.", "start": 3692.12, "duration": 1.95}, {"text": "And we have opportunities\nto hit malaria and all", "start": 3694.07, "duration": 6.0}, {"text": "the different life stages.", "start": 3700.07, "duration": 1.347}, {"text": "There are multiple life\nstages within humans", "start": 3701.417, "duration": 1.833}, {"text": "and multiple stages\nwithin the insect vector.", "start": 3703.25, "duration": 5.19}, {"text": "And now, the genomics\nof these two just", "start": 3708.44, "duration": 2.28}, {"text": "came out recently, in the same\nweek, in Nature and Science.", "start": 3710.72, "duration": 6.03}, {"text": "This provides a whole new\nset of inspirations for work", "start": 3716.75, "duration": 4.767}, {"text": "that can be done on these.", "start": 3721.517, "duration": 1.083}, {"text": "I think we should take\na little break now,", "start": 3722.6, "duration": 2.4}, {"text": "and we'll wrap up the\ntalk after that break.", "start": 3725.0, "duration": 4.25}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.44}, {"text": "[RUSTLING]", "start": 2.44, "duration": 1.464}, {"text": "[CLICKING]", "start": 3.904, "duration": 1.464}, {"text": "MARKUS KLUTE: Welcome back\nto 8.20, Special Relativity.", "start": 19.07, "duration": 3.17}, {"text": "So in this section,\nwe're going to review", "start": 22.24, "duration": 3.26}, {"text": "the content of the\nmaterial, but underlined", "start": 25.5, "duration": 3.0}, {"text": "with a few questions and\nexamples, very similar", "start": 28.5, "duration": 3.0}, {"text": "to the previous section.", "start": 31.5, "duration": 1.44}, {"text": "It's just this one is\ninterleaved with activities.", "start": 32.94, "duration": 4.61}, {"text": "So let me start by bringing\nback two of those Einstein", "start": 37.55, "duration": 4.77}, {"text": "quotes, which nicely relate\nto each other in a sense", "start": 42.32, "duration": 3.17}, {"text": "that they feed off each other.", "start": 45.49, "duration": 2.72}, {"text": "The first one is, \"I\nhave no special talent.", "start": 48.21, "duration": 2.9}, {"text": "I'm only passionately curious.\"", "start": 51.11, "duration": 3.03}, {"text": "Albert Einstein.", "start": 54.14, "duration": 1.32}, {"text": "And the second one, \"It is\na miracle that curiosity", "start": 55.46, "duration": 3.75}, {"text": "survives formal education.\"", "start": 59.21, "duration": 1.98}, {"text": "And I [LAUGHS] sincerely\nhope that I didn't stop", "start": 61.19, "duration": 2.49}, {"text": "your curiosity\nwith this lecture--", "start": 63.68, "duration": 2.91}, {"text": "quite the opposite.", "start": 66.59, "duration": 1.763}, {"text": "Like we discussed here,\nit's just the starting point", "start": 68.353, "duration": 2.167}, {"text": "of a wider discussion\nof general relativity", "start": 70.52, "duration": 2.55}, {"text": "in your education at MIT\nin the Physics Department.", "start": 73.07, "duration": 3.09}, {"text": "You could learn about quantum\nmechanics, quantum field", "start": 76.16, "duration": 2.82}, {"text": "theories.", "start": 78.98, "duration": 0.78}, {"text": "And a lot of physics\nis out there,", "start": 79.76, "duration": 2.53}, {"text": "which is super exciting\nand interesting.", "start": 82.29, "duration": 5.75}, {"text": "So it basically\nneeds your curiosity", "start": 88.04, "duration": 2.46}, {"text": "in order to tackle challenging\nquestions in physics today.", "start": 90.5, "duration": 3.87}, {"text": "We started the\ndiscussion looking", "start": 97.1, "duration": 2.1}, {"text": "at the background\nwhich led Einstein", "start": 99.2, "duration": 2.85}, {"text": "to make his discoveries.", "start": 102.05, "duration": 2.31}, {"text": "And specifically the\nyear 1905, in which", "start": 104.36, "duration": 3.06}, {"text": "he was able to come out with\nfive papers, all breakthrough", "start": 107.42, "duration": 6.45}, {"text": "papers, including the theory\nof special relativity.", "start": 113.87, "duration": 4.68}, {"text": "His career didn't stop there.", "start": 118.55, "duration": 2.12}, {"text": "He developed the general\ntheory of relativity", "start": 120.67, "duration": 4.64}, {"text": "and published a paper\non this in 1915.", "start": 125.31, "duration": 3.949}, {"text": "And his fame as a\nphysicist really", "start": 129.259, "duration": 2.311}, {"text": "comes out of the predictions\nhe made at that time.", "start": 131.57, "duration": 3.81}, {"text": "So we set the context\nof this class,", "start": 137.89, "duration": 2.42}, {"text": "and we started with a question\nof Galilean transformation and", "start": 140.31, "duration": 5.43}, {"text": "whether or not you can\ntell in a moving train car", "start": 145.74, "duration": 6.42}, {"text": "whether or not this is\nactually moving or stationary.", "start": 152.16, "duration": 3.3}, {"text": "And we demonstrated that\ntime and acceleration", "start": 155.46, "duration": 3.54}, {"text": "is invariant in the\nGalilean transformation.", "start": 159.0, "duration": 2.94}, {"text": "And then, therefore, since you\ncannot distinguish the strength", "start": 161.94, "duration": 5.88}, {"text": "of a force in two reference\nframes which move to each other", "start": 167.82, "duration": 4.17}, {"text": "with moderate velocity, you\ncannot tell whether or not", "start": 171.99, "duration": 4.63}, {"text": "the train car is moving or not.", "start": 176.62, "duration": 2.74}, {"text": "Very important are the\ndevelopment of clocks and times", "start": 179.36, "duration": 3.33}, {"text": "and signal processing\nof the time.", "start": 182.69, "duration": 2.7}, {"text": "And we discussed this in the\ncontext of trains and train", "start": 185.39, "duration": 2.82}, {"text": "lines, but also in Einstein\nliving in the city of Bern,", "start": 188.21, "duration": 3.93}, {"text": "with a large number\nof clock towers", "start": 192.14, "duration": 3.06}, {"text": "which needed synchronization.", "start": 195.2, "duration": 1.44}, {"text": "And even working in\nthe patent office", "start": 196.64, "duration": 3.99}, {"text": "certainly confronted him with\nthose questions all the time.", "start": 200.63, "duration": 4.18}, {"text": "So time is suspect.", "start": 204.81, "duration": 1.04}, {"text": "That is really the\nkey to moving out", "start": 205.85, "duration": 4.38}, {"text": "from Galilean transformation\ninto Newtonian mechanics", "start": 210.23, "duration": 3.39}, {"text": "to special relativity.", "start": 213.62, "duration": 4.8}, {"text": "When we classify or when\nwe look at specific series,", "start": 218.42, "duration": 5.04}, {"text": "we have to understand that\nthey live within a context,", "start": 223.46, "duration": 2.64}, {"text": "within a range of validity.", "start": 226.1, "duration": 2.38}, {"text": "And so classical\nmechanics is not wrong", "start": 228.48, "duration": 2.06}, {"text": "because it breaks down\nat large velocities.", "start": 230.54, "duration": 3.96}, {"text": "It's just only correct in\nthe frame of slow velocities.", "start": 234.5, "duration": 4.17}, {"text": "And special relativity\nalso has its limitations,", "start": 238.67, "duration": 4.68}, {"text": "as in it only describes\nreference frames or scenarios", "start": 243.35, "duration": 4.77}, {"text": "in which there is no\nacceleration between two", "start": 248.12, "duration": 2.91}, {"text": "reference frames.", "start": 251.03, "duration": 0.93}, {"text": "Going back to the question\nof the time, Michelson--", "start": 254.57, "duration": 4.41}, {"text": "and a number of other\nexperiments leading to the very", "start": 258.98, "duration": 2.46}, {"text": "same direction--", "start": 261.44, "duration": 1.89}, {"text": "was trying to\nestablish that there", "start": 263.33, "duration": 2.445}, {"text": "is an ether wind, a medium\nin which light is moving.", "start": 265.775, "duration": 3.135}, {"text": "And his experiment,\nat the time, failed", "start": 268.91, "duration": 2.76}, {"text": "to demonstrate that\nether actually exists.", "start": 271.67, "duration": 3.39}, {"text": "His experiment used a light\nsource and a couple of mirrors", "start": 275.06, "duration": 2.88}, {"text": "in order to show\ninterference patterns.", "start": 277.94, "duration": 4.11}, {"text": "And those interference patterns\ndidn't manifest themselves.", "start": 282.05, "duration": 3.28}, {"text": "So he thought for a long time\nthat his experiment is limited", "start": 285.33, "duration": 3.62}, {"text": "or that he has made a mistake.", "start": 288.95, "duration": 2.38}, {"text": "But it turns out that\nether indeed doesn't exist.", "start": 291.33, "duration": 4.04}, {"text": "Einstein tackled this problem\nby making two postulates.", "start": 295.37, "duration": 3.24}, {"text": "The first one is the\nprinciple of relativity,", "start": 298.61, "duration": 5.16}, {"text": "that there is no preferred\nreference frame if you want;", "start": 303.77, "duration": 3.06}, {"text": "and the second, that the\nspeed of light is constant--", "start": 306.83, "duration": 3.61}, {"text": "and constant and the same\nin all reference frames.", "start": 310.44, "duration": 3.03}, {"text": "And in this class we use\nthose two postulates in order", "start": 313.47, "duration": 2.69}, {"text": "to derive everything we know\nabout special relativity.", "start": 316.16, "duration": 3.54}, {"text": "So we looked at\nthe implications.", "start": 322.485, "duration": 1.375}, {"text": "And the implications\nstarted from time dilation,", "start": 323.86, "duration": 2.13}, {"text": "length contractions.", "start": 325.99, "duration": 0.9}, {"text": "We were able to derive the\nLorentz factor and Lorentz", "start": 326.89, "duration": 3.36}, {"text": "transformation.", "start": 330.25, "duration": 1.35}, {"text": "And we did this by showing\nthis light clock here,", "start": 331.6, "duration": 3.42}, {"text": "where you observe a ticking\nclock in which there", "start": 335.02, "duration": 3.9}, {"text": "is two mirrors and\nlight bouncing back.", "start": 338.92, "duration": 2.37}, {"text": "And each time there\nis a bounce, we", "start": 341.29, "duration": 2.16}, {"text": "count this as one\ntick of the clock.", "start": 343.45, "duration": 2.98}, {"text": "So if the clock is\nmoving, the light", "start": 346.43, "duration": 1.73}, {"text": "has to travel a longer distance.", "start": 348.16, "duration": 1.65}, {"text": "And hence time is delayed.", "start": 349.81, "duration": 4.05}, {"text": "And from just the\ngeometry of this problem,", "start": 353.86, "duration": 2.67}, {"text": "we were able to derive\nthis gamma factor here--", "start": 356.53, "duration": 3.57}, {"text": "1 over square root of\n1 minus beta squared.", "start": 360.1, "duration": 2.37}, {"text": "The beta is velocity\nover the speed of light.", "start": 362.47, "duration": 3.406}, {"text": "So as the first activity\nin today's class,", "start": 365.876, "duration": 2.424}, {"text": "I want you to think\nabout a clock which", "start": 368.3, "duration": 3.05}, {"text": "is moving with a\nphoton, a clock which is", "start": 371.35, "duration": 2.64}, {"text": "moving with the speed of light.", "start": 373.99, "duration": 1.65}, {"text": "And also discuss why isn't\nit possible to go faster", "start": 375.64, "duration": 3.39}, {"text": "than the speed of light.", "start": 379.03, "duration": 1.08}, {"text": "And why can you not\njust keep accelerating?", "start": 380.11, "duration": 3.3}, {"text": "So think about\nthis a little bit.", "start": 383.41, "duration": 1.65}, {"text": "In the live class we\nwill have a discussion.", "start": 385.06, "duration": 2.7}, {"text": "But just come up with\nsome sort of answer", "start": 387.76, "duration": 2.97}, {"text": "of why this is the case.", "start": 390.73, "duration": 1.633}, {"text": "So here we have, in\nthe class, actually", "start": 396.44, "duration": 2.31}, {"text": "showed that there\nis a real speed", "start": 398.75, "duration": 1.38}, {"text": "limit, that if you\ntry to go faster,", "start": 400.13, "duration": 2.85}, {"text": "past [INAUDIBLE]\nvelocity, you run", "start": 402.98, "duration": 1.59}, {"text": "against a boundary,\na real speed limit.", "start": 404.57, "duration": 4.3}, {"text": "If you think about keeping\naccelerating, giving", "start": 408.87, "duration": 2.03}, {"text": "more energy, you\nfind that the amount", "start": 410.9, "duration": 2.16}, {"text": "of energy you need in order to\ngo faster and faster, faster,", "start": 413.06, "duration": 3.84}, {"text": "doesn't get you to velocities\nwhich are faster and faster.", "start": 416.9, "duration": 3.09}, {"text": "And again, you enter a speed\nlimit-- the speed of light.", "start": 419.99, "duration": 4.02}, {"text": "An important topic\nin understanding", "start": 429.28, "duration": 1.86}, {"text": "some of the paradoxes\nin special relativity,", "start": 431.14, "duration": 2.37}, {"text": "and some of the\nconfusion, is the concept", "start": 433.51, "duration": 2.34}, {"text": "of the relativity\nof simultaneity.", "start": 435.85, "duration": 2.775}, {"text": "Now, it can be illustrated quite\nnicely in this example here,", "start": 438.625, "duration": 3.165}, {"text": "where you have a carriage train\ncar with light being emitted", "start": 441.79, "duration": 5.13}, {"text": "and clocks which record those\nevents at each end of the train", "start": 446.92, "duration": 5.55}, {"text": "car.", "start": 452.47, "duration": 1.05}, {"text": "For the stationary person,\nthose clocks will tick in sync.", "start": 453.52, "duration": 4.12}, {"text": "They will always show the\nsame tick and the same time.", "start": 457.64, "duration": 4.25}, {"text": "But for somebody who's observing\nthis train from a platform,", "start": 461.89, "duration": 4.89}, {"text": "or somebody who's moving\nwith a relative velocity", "start": 466.78, "duration": 2.61}, {"text": "towards this train car, you\nwill see those clocks not", "start": 469.39, "duration": 3.36}, {"text": "ticking at the same time.", "start": 472.75, "duration": 2.24}, {"text": "So the clear evidence\nis given in this picture", "start": 474.99, "duration": 3.62}, {"text": "again, where you see that\nthe light's being emitted", "start": 478.61, "duration": 2.505}, {"text": "in the center, but one side\nof the train car is hit first", "start": 481.115, "duration": 3.405}, {"text": "and the second side\nis hit afterwards.", "start": 484.52, "duration": 2.83}, {"text": "So you see that the\nleading clock lags.", "start": 487.35, "duration": 2.84}, {"text": "The leading clock in\nthis example lags behind.", "start": 490.19, "duration": 3.37}, {"text": "And so what you find\nhere is that events which", "start": 493.56, "duration": 2.15}, {"text": "are observed simultaneously\nfor one observer--", "start": 495.71, "duration": 3.42}, {"text": "in this case, the person\ninside the carriage--", "start": 499.13, "duration": 5.07}, {"text": "they will not be simultaneous\nfor an observer who's moving", "start": 504.2, "duration": 4.56}, {"text": "with a relative velocity.", "start": 508.76, "duration": 2.23}, {"text": "And that led us to the\nunderstanding of the pole", "start": 510.99, "duration": 3.679}, {"text": "in the barn paradox, where,\nin one example, the event", "start": 514.669, "duration": 6.061}, {"text": "of the front of the pole\nhitting the back of the barn", "start": 520.73, "duration": 4.02}, {"text": "and the event of the\nback of the pole hitting", "start": 524.75, "duration": 2.52}, {"text": "the front of the barn,\nthey are simultaneously", "start": 527.27, "duration": 2.61}, {"text": "for the barn owner.", "start": 529.88, "duration": 1.29}, {"text": "But they're not simultaneously\nhappening for the person", "start": 531.17, "duration": 3.81}, {"text": "who's carrying the pole.", "start": 534.98, "duration": 3.6}, {"text": "In this case, the event of\nhitting the back of the barn", "start": 538.58, "duration": 7.08}, {"text": "is simultaneous to an event\nwhere the back of the pole", "start": 545.66, "duration": 2.94}, {"text": "is still sticking\nout of the barn.", "start": 548.6, "duration": 1.62}, {"text": "So there is a\nclear disagreement.", "start": 550.22, "duration": 1.53}, {"text": "But the disagreement\ncan be resolved", "start": 551.75, "duration": 2.04}, {"text": "by understanding that\nsimultaneous events are not", "start": 553.79, "duration": 3.75}, {"text": "necessarily simultaneous\nto two observers.", "start": 557.54, "duration": 5.59}, {"text": "Then we moved on to a\nvariety of other paradoxes", "start": 563.13, "duration": 5.01}, {"text": "in special relativity.", "start": 568.14, "duration": 1.5}, {"text": "And the most famous likely\nis the twin paradox,", "start": 569.64, "duration": 3.48}, {"text": "where we discussed that a person\nmoving away and then returning", "start": 573.12, "duration": 5.85}, {"text": "is younger than the person\nwho actually stayed at rest.", "start": 578.97, "duration": 3.96}, {"text": "And we discussed that we were\nable to use time dilation", "start": 582.93, "duration": 4.98}, {"text": "or length contraction in order\nto quantitatively figure out", "start": 587.91, "duration": 3.36}, {"text": "the difference in time.", "start": 591.27, "duration": 1.9}, {"text": "But we also discussed\nthat the person", "start": 593.17, "duration": 1.74}, {"text": "who is moving away\nand then coming back", "start": 594.91, "duration": 5.2}, {"text": "needs to describe the journey in\ntwo different reference frames.", "start": 600.11, "duration": 4.81}, {"text": "And from the fact that\nyou don't consistently can", "start": 604.92, "duration": 2.25}, {"text": "describe this sequence\nof events as two", "start": 607.17, "duration": 3.2}, {"text": "reference frames\ncan see the paradox", "start": 610.37, "duration": 3.33}, {"text": "and the extra confusion.", "start": 613.7, "duration": 5.01}, {"text": "So here we have\nanother activity--", "start": 618.71, "duration": 2.37}, {"text": "an asymmetric travel.", "start": 621.08, "duration": 1.74}, {"text": "So we discussed also the example\nwhere two people move away", "start": 622.82, "duration": 3.93}, {"text": "and then they come back\nin a symmetric fashion.", "start": 626.75, "duration": 2.44}, {"text": "But here we want\nto discuss the case", "start": 629.19, "duration": 1.64}, {"text": "where there are three trends.", "start": 630.83, "duration": 1.56}, {"text": "Carol stays on Earth.", "start": 632.39, "duration": 1.41}, {"text": "Bob moves to Star 1.", "start": 633.8, "duration": 1.59}, {"text": "And Alice moves to Star 2.", "start": 635.39, "duration": 2.34}, {"text": "The distance to Star 1 is longer\nthan the distance to Star 2.", "start": 637.73, "duration": 6.69}, {"text": "So the question is, in this\njourney, they both start", "start": 644.42, "duration": 5.16}, {"text": "and they both return at\nthe same time for Carol.", "start": 649.58, "duration": 3.63}, {"text": "But which of the\ntwins is the youngest?", "start": 653.21, "duration": 3.88}, {"text": "So again, I invite you\nto just work this out.", "start": 657.09, "duration": 2.49}, {"text": "You can use some numbers if\nyou want a quantitative answer.", "start": 659.58, "duration": 4.2}, {"text": "Or you can just reason\nabout [INAUDIBLE]..", "start": 663.78, "duration": 2.52}, {"text": "The answer here is that Bob\nis the youngest of the three", "start": 670.07, "duration": 6.81}, {"text": "once they return to Earth.", "start": 676.88, "duration": 3.27}, {"text": "And the reason for this is\nthe distance he has to travel", "start": 680.15, "duration": 3.13}, {"text": "is the longest.", "start": 683.28, "duration": 0.8}, {"text": "Hence the velocity he has\nto travel in is the largest.", "start": 684.08, "duration": 3.81}, {"text": "And hence the effect of\ntime dilation for him", "start": 687.89, "duration": 2.7}, {"text": "is the biggest.", "start": 690.59, "duration": 1.02}, {"text": "And therefore he's going to\nbe the youngest of the three.", "start": 691.61, "duration": 3.12}, {"text": "All right.", "start": 700.67, "duration": 0.96}, {"text": "We had a rather long discussion\nabout waves and light, Doppler", "start": 701.63, "duration": 4.77}, {"text": "effect, and relativistic\nDoppler effect.", "start": 706.4, "duration": 3.66}, {"text": "Here, just as a\nreminder, the wave", "start": 710.06, "duration": 2.01}, {"text": "equation for an electric\nfield in a vacuum.", "start": 712.07, "duration": 2.37}, {"text": "And the solution to\nthe wave equation", "start": 714.44, "duration": 2.49}, {"text": "is use the second derivative\nwith space and time.", "start": 716.93, "duration": 5.95}, {"text": "And the solution\nsimply can be expressed", "start": 722.88, "duration": 2.03}, {"text": "as a cosine, which is a\nfunction of space and time.", "start": 724.91, "duration": 4.22}, {"text": "We have talked about\nlight quite a bit.", "start": 729.13, "duration": 2.5}, {"text": "And just as\nreminder, [INAUDIBLE]", "start": 731.63, "duration": 1.85}, {"text": "the energy of photon is\nrelated via the Planck-Einstein", "start": 733.48, "duration": 3.81}, {"text": "relation to the frequency.", "start": 737.29, "duration": 2.82}, {"text": "So the higher the frequency,\nthe higher the energy.", "start": 740.11, "duration": 6.005}, {"text": "The higher the frequency,\nthe higher the energy.", "start": 746.115, "duration": 2.485}, {"text": "And here, in this\npicture, you can", "start": 748.6, "duration": 3.03}, {"text": "see the effect of\nthe Doppler effect,", "start": 751.63, "duration": 2.865}, {"text": "where, when you have\na moving source,", "start": 754.495, "duration": 3.075}, {"text": "the observer sees the\nwaveline modified.", "start": 757.57, "duration": 2.73}, {"text": "Objects which move\ntowards us are", "start": 763.44, "duration": 2.82}, {"text": "blueshifted, starting\nfrom white light,", "start": 766.26, "duration": 3.51}, {"text": "or green light in this example.", "start": 769.77, "duration": 1.86}, {"text": "And objects that move away\nfrom us are redshifted.", "start": 771.63, "duration": 3.45}, {"text": "The effect can be\nused, for example,", "start": 775.08, "duration": 3.12}, {"text": "in speed measurements of cars.", "start": 778.2, "duration": 3.45}, {"text": "It can also be used in order\nto measure speed or distances", "start": 781.65, "duration": 3.03}, {"text": "of stars moving away from us.", "start": 784.68, "duration": 2.58}, {"text": "And so that defines,\nthen, the concept", "start": 787.26, "duration": 2.07}, {"text": "of redshift, which is simply\nthe ratio of the difference", "start": 789.33, "duration": 7.05}, {"text": "in wavelength divided\nby the wavelength as", "start": 796.38, "duration": 3.48}, {"text": "observed by the observer.", "start": 799.86, "duration": 2.4}, {"text": "So here there's two\nconcept questions.", "start": 802.26, "duration": 1.96}, {"text": "The first one is, is\nthe wave equation,", "start": 804.22, "duration": 3.27}, {"text": "which you can see\nthere as an example,", "start": 807.49, "duration": 1.61}, {"text": "invariant under\nLorentz transformation?", "start": 809.1, "duration": 3.15}, {"text": "And the second question is,\nhow about the solutions?", "start": 812.25, "duration": 2.67}, {"text": "Are the solutions\nto the wave equation", "start": 814.92, "duration": 2.01}, {"text": "invariant under\nLorentz transformation?", "start": 816.93, "duration": 2.9}, {"text": "So I'll have you\nwork this out again.", "start": 819.83, "duration": 2.27}, {"text": "And the answers are yes and no.", "start": 822.1, "duration": 6.7}, {"text": "The wave equation is invariant.", "start": 828.8, "duration": 2.04}, {"text": "The wave equation\ndescribes the physics.", "start": 830.84, "duration": 3.65}, {"text": "It explains how electric\nand magnetic fields change.", "start": 834.49, "duration": 3.64}, {"text": "And the laws of physics\nneed to be invariant", "start": 838.13, "duration": 3.45}, {"text": "under Lorentz transformation.", "start": 841.58, "duration": 1.29}, {"text": "Otherwise they\nwill not be valid.", "start": 842.87, "duration": 1.74}, {"text": "They will violate the postulate\nwe just made that all reference", "start": 844.61, "duration": 3.81}, {"text": "frames are equal to each other.", "start": 848.42, "duration": 2.55}, {"text": "However, the solutions of the\nwave equation-- light itself--", "start": 850.97, "duration": 3.17}, {"text": "is not invariant under\nLorentz transformation.", "start": 854.14, "duration": 2.76}, {"text": "We've just discussed\nredshift and blueshift,", "start": 856.9, "duration": 2.97}, {"text": "which means that the wavelength\nand frequency of light", "start": 859.87, "duration": 2.25}, {"text": "changes with respect to the\nobserver, or for each observer.", "start": 862.12, "duration": 4.17}, {"text": "So the solutions-- light--", "start": 866.29, "duration": 1.83}, {"text": "are not invariant under\nLorentz transformation.", "start": 868.12, "duration": 4.493}, {"text": "And then we went a little\nbit into particle physics.", "start": 872.613, "duration": 2.167}, {"text": "And I have to apologize\nfor my own preference.", "start": 874.78, "duration": 2.88}, {"text": "But elementary\nparticles, as they", "start": 877.66, "duration": 1.97}, {"text": "have been reproduced\nor observed,", "start": 879.63, "duration": 1.45}, {"text": "are typically moving at\nrather large velocities.", "start": 881.08, "duration": 2.89}, {"text": "So they are very good\nexamples to study", "start": 883.97, "duration": 1.88}, {"text": "effects of special relativity.", "start": 885.85, "duration": 2.46}, {"text": "We looked at energy, the\ntotal energy m0 gamma c", "start": 888.31, "duration": 3.21}, {"text": "squared, which also\ncan be expressed", "start": 891.52, "duration": 2.49}, {"text": "as the energy of the rest\nenergy of the particle,", "start": 894.01, "duration": 3.27}, {"text": "m0 c squared, plus\nthe kinetic energy.", "start": 897.28, "duration": 2.82}, {"text": "And we looked at\nthe total energy", "start": 900.1, "duration": 1.83}, {"text": "as being invariant, one\nof those invariants,", "start": 901.93, "duration": 3.75}, {"text": "as equal to the total\nmomenta squared.", "start": 905.68, "duration": 3.22}, {"text": "The total energy squared is\nequal to the total momentum", "start": 908.9, "duration": 2.45}, {"text": "squared times c squared\nplus the rest mass squared", "start": 911.35, "duration": 3.21}, {"text": "times c to the fourth power.", "start": 914.56, "duration": 2.05}, {"text": "And then we went through a\nlarger number of examples,", "start": 916.61, "duration": 3.37}, {"text": "from accelerating electrons\nto composite particles.", "start": 919.98, "duration": 3.36}, {"text": "We talked about deuteron\nphoton absorption and emission,", "start": 923.34, "duration": 4.15}, {"text": "the creation of particle, the\ncreation of antiparticles,", "start": 927.49, "duration": 3.86}, {"text": "and the scattering of particles.", "start": 931.35, "duration": 2.17}, {"text": "So here we had another example.", "start": 933.52, "duration": 2.06}, {"text": "Oops-- without the solution.", "start": 935.58, "duration": 3.69}, {"text": "In 1995, at Fermilab, a\nproton-antiproton collider,", "start": 939.27, "duration": 4.44}, {"text": "the Tevatron, top\nquarks were discovered.", "start": 943.71, "duration": 3.42}, {"text": "And we measured the top\nquark mass to 175 GeV.", "start": 947.13, "duration": 4.83}, {"text": "The center of mass\nenergy at the Tevatron", "start": 951.96, "duration": 2.16}, {"text": "was 1.8, and later almost\n2 tera-electronvolt,", "start": 954.12, "duration": 4.62}, {"text": "and clearly sufficient for the\nproduction of top and antitop.", "start": 958.74, "duration": 3.99}, {"text": "But what is the minimal energy\nin order for this process", "start": 962.73, "duration": 2.91}, {"text": "to occur?", "start": 965.64, "duration": 1.63}, {"text": "And here we went through\na number of examples.", "start": 967.27, "duration": 3.68}, {"text": "The minimal energy-- sorry.", "start": 970.95, "duration": 1.47}, {"text": "I have to work this out again.", "start": 972.42, "duration": 2.16}, {"text": "The minimal energy required\ncan be derived or extracted", "start": 974.58, "duration": 5.49}, {"text": "in the center of mass frame,\nwhere the top and antitop are", "start": 980.07, "duration": 3.27}, {"text": "produced at rest.", "start": 983.34, "duration": 1.66}, {"text": "And if you do this--\nin this example,", "start": 985.0, "duration": 1.56}, {"text": "the proton in this\ncollider experiment--", "start": 986.56, "duration": 2.97}, {"text": "the experiment is\nalready conducted", "start": 989.53, "duration": 1.79}, {"text": "in the center of mass frame.", "start": 991.32, "duration": 1.44}, {"text": "So the minimal energy\nis simply 2 times", "start": 992.76, "duration": 3.0}, {"text": "the top mass times c square,\nor 2 times gamma times the mass", "start": 995.76, "duration": 3.45}, {"text": "of the proton times c\nsquare, which gives you", "start": 999.21, "duration": 2.1}, {"text": "a gamma factor of 175.", "start": 1001.31, "duration": 3.07}, {"text": "But the likelihood\nto actually observe", "start": 1004.38, "duration": 2.93}, {"text": "a top quark and a antitop\nquark at that energy, 175 GeV", "start": 1007.31, "duration": 6.76}, {"text": "proton or antiproton\nenergy, is rather 0.", "start": 1014.07, "duration": 4.77}, {"text": "And the reason for this has\nto do with the structure", "start": 1018.84, "duration": 2.7}, {"text": "of the proton.", "start": 1021.54, "duration": 1.08}, {"text": "The actual interaction between\nthe proton and the antiproton", "start": 1022.62, "duration": 2.999}, {"text": "is such that the quarks and\nantiquarks inside the proton,", "start": 1025.619, "duration": 5.25}, {"text": "and also the gluons, interact.", "start": 1030.869, "duration": 1.861}, {"text": "And they only carry a\nfraction of the momentum", "start": 1032.73, "duration": 2.31}, {"text": "and the energy of the proton.", "start": 1035.04, "duration": 1.35}, {"text": "And hence this\nminimal calculation", "start": 1036.39, "duration": 2.25}, {"text": "is insufficient to get a\nsufficient cross-section", "start": 1038.64, "duration": 2.79}, {"text": "likelihood for top quarks and\nantiquarks to be produced.", "start": 1041.43, "duration": 3.929}, {"text": "But that is particle physics\nand goes beyond the scope", "start": 1045.359, "duration": 3.061}, {"text": "of this lecture.", "start": 1048.42, "duration": 2.22}, {"text": "One last point, which leads\nsometimes to confusion,", "start": 1050.64, "duration": 3.06}, {"text": "is the concept of conserved\nand invariant properties.", "start": 1053.7, "duration": 4.96}, {"text": "When we look at the\nmeaning of the word,", "start": 1058.66, "duration": 2.6}, {"text": "invariant means never-changing.", "start": 1061.26, "duration": 2.37}, {"text": "And in the concept of\nspecial relativity,", "start": 1063.63, "duration": 2.43}, {"text": "properties are invariant\nwhen they do not", "start": 1066.06, "duration": 2.49}, {"text": "change under Lorentz\ntransformation or Galilean", "start": 1068.55, "duration": 3.99}, {"text": "transformation, as we\ndiscussed earlier in the class.", "start": 1072.54, "duration": 3.63}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.495}, {"text": "[RUSTLING]", "start": 2.495, "duration": 1.497}, {"text": "[CLICKING]", "start": 3.992, "duration": 1.497}, {"text": "CASEY RODRIGUEZ: OK, so let's\ncontinue our study of sequences", "start": 13.99, "duration": 3.173}, {"text": "of real numbers.", "start": 17.163, "duration": 0.667}, {"text": "So we've seen special types of\nsequences, monotone sequences,", "start": 24.24, "duration": 3.9}, {"text": "before.", "start": 28.14, "duration": 0.51}, {"text": "And then in the\nprevious lecture,", "start": 28.65, "duration": 4.12}, {"text": "we looked at sequences\nobtained from sequences,", "start": 32.77, "duration": 6.45}, {"text": "namely the sequences that give\nyou the lim sup and lim inf.", "start": 39.22, "duration": 2.958}, {"text": "And we showed that\nthese are actually", "start": 42.178, "duration": 1.542}, {"text": "limits of subsequences.", "start": 43.72, "duration": 3.453}, {"text": "Now I'm going to\ndefine what looks", "start": 47.173, "duration": 1.417}, {"text": "like a new class of sequences.", "start": 48.59, "duration": 5.88}, {"text": "But we'll see it's actually not.", "start": 54.47, "duration": 1.74}, {"text": "These are called\nCauchy sequences.", "start": 56.21, "duration": 1.83}, {"text": "So \"coe-shee\"-- not\n\"couch-ee,\" not \"cawt-shee\"--", "start": 62.45, "duration": 7.33}, {"text": "Cauchy, so a French guy.", "start": 69.78, "duration": 3.15}, {"text": "So it's pronounced Cauchy and\nprobably not even pronounced", "start": 72.93, "duration": 3.03}, {"text": "like that.", "start": 75.96, "duration": 0.5}, {"text": "It's probably got a\ndifferent pronunciation", "start": 76.46, "duration": 8.04}, {"text": "by people who\nactually speak French.", "start": 84.5, "duration": 1.98}, {"text": "So what is the definition\nof a Cauchy sequence?", "start": 86.48, "duration": 2.655}, {"text": "A Cauchy sequence,\nintuitively, it's", "start": 89.135, "duration": 3.945}, {"text": "a sequence so that if you go\nfar enough out in the sequence,", "start": 93.08, "duration": 5.28}, {"text": "any two entries in that\nsequence are close together.", "start": 98.36, "duration": 4.35}, {"text": "So convergent sequences\nhad the property", "start": 102.71, "duration": 2.61}, {"text": "that if you go far enough out,\nthe entries in the sequence", "start": 105.32, "duration": 3.66}, {"text": "are getting close\nto a real number.", "start": 108.98, "duration": 2.76}, {"text": "Cauchy sequence is\nthat any two entries", "start": 111.74, "duration": 2.58}, {"text": "are close to each other.", "start": 114.32, "duration": 1.305}, {"text": "So a Cauchy sequence, so\nwe say a sequence is Cauchy", "start": 118.72, "duration": 12.87}, {"text": "if we're all epsilon\npositive, there", "start": 131.59, "duration": 6.9}, {"text": "exists an M,\nnatural number, such", "start": 138.49, "duration": 3.54}, {"text": "that if n is bigger\nthan or equal to M and k", "start": 142.03, "duration": 7.54}, {"text": "is bigger than or equal\nto M, then xn minus xk", "start": 149.57, "duration": 6.895}, {"text": "is less than epsilon.", "start": 156.465, "duration": 0.875}, {"text": "So maybe not write if.", "start": 161.05, "duration": 2.33}, {"text": "I mean, it's the same\nstatement, but since it looks--", "start": 163.38, "duration": 2.49}, {"text": "so it'll look a little more\nlike previous statements", "start": 165.87, "duration": 4.25}, {"text": "when we put a \"for all\" there.", "start": 170.12, "duration": 1.25}, {"text": "So you have a definition here.", "start": 174.07, "duration": 3.345}, {"text": "It's the definition\nof a new thing.", "start": 180.99, "duration": 3.43}, {"text": "You should now try\nto look at an example", "start": 184.42, "duration": 2.88}, {"text": "and then possibly negate the\ndefinition to see if you really", "start": 187.3, "duration": 2.82}, {"text": "understand it.", "start": 190.12, "duration": 1.15}, {"text": "So an example of\na Cauchy sequence", "start": 191.27, "duration": 3.02}, {"text": "is x of n equals 1 over\nn, our favorite sequence.", "start": 194.29, "duration": 6.37}, {"text": "So let's prove this.", "start": 200.66, "duration": 2.27}, {"text": "So all we have is\nthe definition.", "start": 202.93, "duration": 1.96}, {"text": "So we have to verify that\nx of n equals 1 over n", "start": 204.89, "duration": 3.41}, {"text": "verifies the definition\nof being Cauchy.", "start": 208.3, "duration": 3.78}, {"text": "So just like when we try to\nprove something is convergent,", "start": 212.08, "duration": 2.7}, {"text": "which is a \"for all\" epsilon\nstatement, the first thing", "start": 214.78, "duration": 3.51}, {"text": "you have to do is let\nepsilon be positive.", "start": 218.29, "duration": 3.43}, {"text": "And then I have to choose M\nand show that that capital", "start": 221.72, "duration": 2.48}, {"text": "M produces this statement here.", "start": 224.2, "duration": 3.76}, {"text": "So choose M, a natural\nnumber, so that 1 over M", "start": 227.96, "duration": 9.17}, {"text": "is less than epsilon over 2.", "start": 237.13, "duration": 2.13}, {"text": "So I could phrase that as\ncapital M being bigger than 2", "start": 239.26, "duration": 3.33}, {"text": "over epsilon, but I'm going\nto phrase it this way.", "start": 242.59, "duration": 4.05}, {"text": "Now we have to show\nthat it works-- namely,", "start": 246.64, "duration": 2.34}, {"text": "if I take n bigger than\nor equal to capital M", "start": 248.98, "duration": 2.16}, {"text": "and k bigger than or\nequal to a capital M,", "start": 251.14, "duration": 2.13}, {"text": "then this difference\nis less than epsilon.", "start": 253.27, "duration": 2.67}, {"text": "Then if n is bigger\nthan or equal to M,", "start": 255.94, "duration": 5.97}, {"text": "k is bigger than or equal to M,\nand I look at 1 over n minus 1", "start": 261.91, "duration": 4.71}, {"text": "over k, this is less than\nor equal to, by the triangle", "start": 266.62, "duration": 4.47}, {"text": "inequality, the\nabsolute value of each", "start": 271.09, "duration": 3.45}, {"text": "of these added together, which\nis just 1 over n plus 1 over k.", "start": 274.54, "duration": 5.01}, {"text": "And since these are both\nbigger than or equal to M,", "start": 279.55, "duration": 3.06}, {"text": "each 1 is less than\nor equal to 1 over M 1", "start": 282.61, "duration": 3.705}, {"text": "over M, so I get 2 over M,\nwhich, by our choice of M,", "start": 286.315, "duration": 4.635}, {"text": "is less than epsilon.", "start": 290.95, "duration": 3.41}, {"text": "So x of n equals 1 over n is an\nexample of a Cauchy sequence.", "start": 294.36, "duration": 7.33}, {"text": "So let's negate the\ndefinition, and then we'll", "start": 301.69, "duration": 8.68}, {"text": "look at an example of a\nsequence which is not Cauchy.", "start": 310.37, "duration": 2.23}, {"text": "And as you'll probably guess, if\nthis is our favorite sequence,", "start": 312.6, "duration": 2.625}, {"text": "which converges, our favorite\nsequence which doesn't converge", "start": 315.225, "duration": 4.535}, {"text": "will be an example of a\nsequence which is not Cauchy.", "start": 319.76, "duration": 3.885}, {"text": "And this should shouldn't\ncome as a surprise.", "start": 323.645, "duration": 1.875}, {"text": "Because, again, a sequence\nwhich is Cauchy, if you", "start": 325.52, "duration": 4.56}, {"text": "go far enough out,\nany two entries", "start": 330.08, "duration": 3.33}, {"text": "are close to each other.", "start": 333.41, "duration": 1.74}, {"text": "But if we look at, for\nexample, the sequence minus 1", "start": 335.15, "duration": 2.22}, {"text": "to the n, which is just\nminus 1 plus 1 minus 1,", "start": 337.37, "duration": 2.64}, {"text": "any two entries will differ by--", "start": 340.01, "duration": 4.987}, {"text": "or you can always\nchoose two entries--", "start": 344.997, "duration": 1.583}, {"text": "that differ by 2 in distance.", "start": 346.58, "duration": 5.83}, {"text": "So let's negate this\ndefinition to get what it means", "start": 352.41, "duration": 8.47}, {"text": "for something not to be Cauchy.", "start": 360.88, "duration": 2.4}, {"text": "So we'll not write all that out.", "start": 363.28, "duration": 3.42}, {"text": "So x of n is not Cauchy if--", "start": 373.45, "duration": 4.65}, {"text": "so every time we\nsee a \"for all,\"", "start": 378.1, "duration": 2.19}, {"text": "it becomes \"there exists.\"", "start": 380.29, "duration": 3.75}, {"text": "If there exists a bad\nepsilon 0 positive", "start": 384.04, "duration": 5.1}, {"text": "such that for all\nM, a natural number,", "start": 389.14, "duration": 4.89}, {"text": "you can find two entries\nfurther out than M", "start": 394.03, "duration": 4.68}, {"text": "that are greater than epsilon\n0 distance to each other.", "start": 398.71, "duration": 3.28}, {"text": "So there exists n bigger\nthan or equal to M", "start": 401.99, "duration": 3.44}, {"text": "and k bigger than or equal to\nM such that x of n minus x of k", "start": 405.43, "duration": 7.68}, {"text": "is bigger than or equal\nto this bad epsilon.", "start": 413.11, "duration": 1.89}, {"text": "OK", "start": 417.72, "duration": 2.53}, {"text": "Again, the definition\nof Cauchy means", "start": 420.25, "duration": 3.03}, {"text": "that, as long as I go far\nenough out in the sequence,", "start": 423.28, "duration": 8.33}, {"text": "this distance is supposed\nto be less than epsilon.", "start": 431.61, "duration": 2.72}, {"text": "So for all epsilon positive,\nthere exists a capital M", "start": 434.33, "duration": 3.13}, {"text": "so that I have this picture.", "start": 437.46, "duration": 1.62}, {"text": "If I choose x sub k plus\n1, then it should also", "start": 439.08, "duration": 4.53}, {"text": "be within distance epsilon\nto x sub n or x sub k.", "start": 443.61, "duration": 5.22}, {"text": "So they're getting closer\nand closer together.", "start": 448.83, "duration": 2.58}, {"text": "The negation means that they're\nnot getting closer and closer", "start": 451.41, "duration": 3.27}, {"text": "together to each other.", "start": 454.68, "duration": 1.15}, {"text": "So there exists\nsome small distance", "start": 455.83, "duration": 3.27}, {"text": "so that you can always go as\nfar out as you want and find", "start": 459.1, "duration": 4.13}, {"text": "two entries that are greater\nthan epsilon 0 distance", "start": 463.23, "duration": 4.47}, {"text": "to each other.", "start": 467.7, "duration": 0.78}, {"text": "So what's an example of that?", "start": 471.51, "duration": 2.06}, {"text": "Like I said, the sequence\nminus 1 to the n is not Cauchy.", "start": 473.57, "duration": 13.18}, {"text": "That just doesn't look right.", "start": 497.04, "duration": 1.32}, {"text": "There we go.", "start": 498.36, "duration": 0.63}, {"text": "Now it is.", "start": 503.98, "duration": 0.78}, {"text": "So this is not Cauchy.", "start": 507.94, "duration": 1.35}, {"text": "So that means there should\nexist some bad epsilon 0.", "start": 509.29, "duration": 4.769}, {"text": "So I can go as far\nout as I want and find", "start": 514.059, "duration": 2.881}, {"text": "two entries in the sequence\ndiffering from each other", "start": 516.94, "duration": 3.239}, {"text": "by epsilon 0 in distance.", "start": 520.179, "duration": 2.201}, {"text": "So basically, I can\nalways find two entries", "start": 522.38, "duration": 6.56}, {"text": "in the sequence which\ndiffer from each other by 2.", "start": 528.94, "duration": 3.6}, {"text": "So that'll be my bad epsilon 0.", "start": 532.54, "duration": 3.51}, {"text": "So if you like, here's a proof.", "start": 536.05, "duration": 3.96}, {"text": "Choose epsilon 0 equals 2.", "start": 540.01, "duration": 3.855}, {"text": "Let M be a natural number.", "start": 546.83, "duration": 1.42}, {"text": "So now we have to find\nan element of entries", "start": 548.25, "duration": 3.98}, {"text": "in the sequence further out than\nM whose distance to each other", "start": 552.23, "duration": 3.412}, {"text": "is bigger than or equal to 2.", "start": 555.642, "duration": 1.208}, {"text": "We can just take M plus\n1 and capital M. Choose n", "start": 556.85, "duration": 8.24}, {"text": "equals M and k equals M plus 1.", "start": 565.09, "duration": 4.59}, {"text": "So these are both bigger\nthan or equal to M.", "start": 569.68, "duration": 3.87}, {"text": "Then minus 1 to the\nn minus 1 to the k,", "start": 573.55, "duration": 5.52}, {"text": "this is equal to 1 minus minus\n1 after I factor out a minus 1", "start": 579.07, "duration": 8.15}, {"text": "to the capital M,\nwhich equals 2.", "start": 587.22, "duration": 2.19}, {"text": "So minus 1 to the\nn is not Cauchy.", "start": 593.95, "duration": 4.095}, {"text": "So I, at the beginning,\nsaid that this", "start": 605.75, "duration": 3.69}, {"text": "will look like a definition\nof a new type of sequence,", "start": 609.44, "duration": 4.71}, {"text": "but it's not, really.", "start": 614.15, "duration": 1.59}, {"text": "So as it turns out, the\nelements of the sequence", "start": 615.74, "duration": 11.9}, {"text": "are getting closer\nand closer together", "start": 627.64, "duration": 2.37}, {"text": "as you go far enough out.", "start": 630.01, "duration": 3.01}, {"text": "So", "start": 633.02, "duration": 0.5}, {"text": "They're all kind of clustering\nnear each other, which kind of", "start": 633.52, "duration": 2.94}, {"text": "makes you think they're all\nclustering near something", "start": 636.46, "duration": 2.31}, {"text": "in the real number line.", "start": 638.77, "duration": 2.64}, {"text": "And therefore, maybe, the\nsequence is convergent.", "start": 641.41, "duration": 3.21}, {"text": "Now, this is true--\nand we'll prove this--", "start": 644.62, "duration": 5.75}, {"text": "that a sequence is Cauchy if\nand only if it's convergent.", "start": 650.37, "duration": 3.63}, {"text": "Now, this is true only\nfor the real numbers.", "start": 654.0, "duration": 2.43}, {"text": "And I'll say a little bit\nabout this in a minute--", "start": 656.43, "duration": 2.947}, {"text": "or not only true for\nthe real numbers,", "start": 659.377, "duration": 1.583}, {"text": "but it's not true for\nthe rational numbers.", "start": 660.96, "duration": 3.73}, {"text": "And I'll get to that\nin just a second.", "start": 664.69, "duration": 1.84}, {"text": "So what we're going to prove\nis that a sequence is Cauchy if", "start": 666.53, "duration": 3.56}, {"text": "and only if it is convergent.", "start": 670.09, "duration": 2.98}, {"text": "So the first thing\nI want to show", "start": 673.07, "duration": 5.85}, {"text": "is that Cauchy\nsequences are bounded.", "start": 678.92, "duration": 6.775}, {"text": "So the proof of this\nstatement is essentially", "start": 695.36, "duration": 3.45}, {"text": "the same as the proof\nthat convergent sequences", "start": 698.81, "duration": 5.35}, {"text": "are bounded.", "start": 704.16, "duration": 0.5}, {"text": "So let me draw a picture that\ngoes along with this proof.", "start": 704.66, "duration": 3.97}, {"text": "So as long as I\ngo far enough out,", "start": 708.63, "duration": 2.51}, {"text": "there exists an M so\nthat for all n bigger", "start": 711.14, "duration": 6.39}, {"text": "than or equal to capital\nM, I can say this.", "start": 717.53, "duration": 2.67}, {"text": "Let's look at this entry x\nof M. Then for all n bigger", "start": 720.2, "duration": 4.2}, {"text": "than or equal to capital\nM, all of the other entries", "start": 724.4, "duration": 2.49}, {"text": "have to be within a certain\ndistance to x sub n,", "start": 726.89, "duration": 3.6}, {"text": "based on the\ndefinition of Cauchy.", "start": 730.49, "duration": 2.67}, {"text": "So let's say I make\nthat distance 1.", "start": 733.16, "duration": 3.39}, {"text": "And let's say 0's over\nhere, just for this picture.", "start": 740.51, "duration": 3.39}, {"text": "So then for all n\nfor all n bigger", "start": 743.9, "duration": 4.5}, {"text": "than or equal to capital M,\nx sub n lies in this interval", "start": 748.4, "duration": 2.815}, {"text": "here.", "start": 751.215, "duration": 0.5}, {"text": "And therefore, we'll get\nthat x of n is bounded.", "start": 754.45, "duration": 9.11}, {"text": "So the way this picture looks,\nI'm going to write it this way.", "start": 763.56, "duration": 3.14}, {"text": "It's 1 plus 1.", "start": 766.7, "duration": 1.08}, {"text": "Now, that handles all n bigger\nthan or equal to capital M.", "start": 770.66, "duration": 3.45}, {"text": "So we just need to deal\nwith the first capital", "start": 774.11, "duration": 2.495}, {"text": "M minus 1 other guy.", "start": 776.605, "duration": 3.355}, {"text": "So maybe there's capital\nM minus 1 is over here.", "start": 779.96, "duration": 4.74}, {"text": "Capital X sub 1 is over there.", "start": 784.7, "duration": 1.59}, {"text": "Capital X sub 2 is over here.", "start": 786.29, "duration": 1.81}, {"text": "So then our bound\nwill just be this one,", "start": 788.1, "duration": 3.05}, {"text": "which handles all of the n\nbigger than or equal to M", "start": 791.15, "duration": 2.88}, {"text": "plus the absolute values of\nthese guys that we missed.", "start": 794.03, "duration": 6.105}, {"text": "So since xn is\nCauchy, there exists", "start": 804.81, "duration": 10.33}, {"text": "and M, a natural number,\nsuch that for all n", "start": 815.14, "duration": 4.91}, {"text": "bigger than or equal\nto M, and k bigger", "start": 820.05, "duration": 4.92}, {"text": "than or equal to M, x sub n\nminus x sub k is less than 1", "start": 824.97, "duration": 9.16}, {"text": "in distance.", "start": 834.13, "duration": 2.38}, {"text": "So this is certainly\ntrue for k equals", "start": 836.51, "duration": 3.41}, {"text": "capital M. So this\nimplies for all n bigger", "start": 839.92, "duration": 4.83}, {"text": "than or equal to M, x\nsub n minus x sub capital", "start": 844.75, "duration": 4.29}, {"text": "M is less than 1.", "start": 849.04, "duration": 2.16}, {"text": "So now, if I use the\ntriangle inequality,", "start": 851.2, "duration": 4.74}, {"text": "I can show that the\nprevious implies", "start": 855.94, "duration": 2.85}, {"text": "that for all n bigger\nthan or equal to M,", "start": 858.79, "duration": 2.31}, {"text": "if I look at the absolute\nvalue of x sub n,", "start": 861.1, "duration": 2.43}, {"text": "this is equal to x sub n minus\nx sub capital M plus capital M.", "start": 863.53, "duration": 8.49}, {"text": "And this is less than or\nequal to the absolute value", "start": 872.02, "duration": 2.31}, {"text": "of this guy plus the\nabsolute value of this guy.", "start": 874.33, "duration": 5.97}, {"text": "And this is bounded by 1.", "start": 880.3, "duration": 1.95}, {"text": "So in summary, I've shown\nthat for all n bigger", "start": 886.69, "duration": 5.84}, {"text": "than or equal to this\nfixed integer, capital M, x", "start": 892.53, "duration": 5.02}, {"text": "sub n is less than or\nequal to x sub capital", "start": 897.55, "duration": 5.9}, {"text": "M in absolute value plus 1.", "start": 903.45, "duration": 4.537}, {"text": "So that's for all\nlittle n bigger than", "start": 907.987, "duration": 1.583}, {"text": "or equal to capital\nM. So now I just", "start": 909.57, "duration": 1.5}, {"text": "need to pick a big enough number\nthat bounds the first capital M", "start": 911.07, "duration": 7.21}, {"text": "entries that are not\ncovered by this inequality.", "start": 918.28, "duration": 3.24}, {"text": "Capital M is fixed.", "start": 921.52, "duration": 1.005}, {"text": "So let B be the absolute\nvalue of x sub 1", "start": 926.83, "duration": 5.52}, {"text": "plus absolute value of x sub\n2 plus this fixed number now.", "start": 932.35, "duration": 11.42}, {"text": "Then for all n bigger than\nor equal to capital M,", "start": 947.49, "duration": 4.4}, {"text": "I have, by this\ninequality up here--", "start": 951.89, "duration": 3.28}, {"text": "this is a sum of\nnon-negative numbers,", "start": 958.56, "duration": 1.945}, {"text": "so this number is\ncertainly bigger than", "start": 960.505, "duration": 1.625}, {"text": "or equal to just this part.", "start": 962.13, "duration": 1.425}, {"text": "And if I have n bigger than\nequal to 1 and less than M,", "start": 969.39, "duration": 9.22}, {"text": "then x of n, the absolute\nvalue of this guy", "start": 978.61, "duration": 5.51}, {"text": "is going to be one of these\nthat appears here, which", "start": 984.12, "duration": 2.73}, {"text": "is certainly less than\nor equal to if I add", "start": 986.85, "duration": 3.54}, {"text": "on this number and the\nothers, which is less than", "start": 990.39, "duration": 3.63}, {"text": "or equal to B. So now I've found\na B which is non-negative which", "start": 994.02, "duration": 5.08}, {"text": "bounds all the absolute values.", "start": 999.1, "duration": 1.59}, {"text": "And therefore, this proves\nthat the sequence is bounded.", "start": 1000.69, "duration": 4.17}, {"text": "So we've shown that a\nCauchy sequence is bounded.", "start": 1014.16, "duration": 4.65}, {"text": "And so what I'm now going\nto show is the following.", "start": 1021.47, "duration": 10.879}, {"text": "So again, all of the entries\nare getting close to each other.", "start": 1032.349, "duration": 3.75}, {"text": "They're kind of clustering\nnear each other.", "start": 1036.099, "duration": 2.161}, {"text": "So it kind of feels like\nthey want to converge.", "start": 1038.26, "duration": 5.349}, {"text": "And this next theorem\nsays that, well,", "start": 1043.609, "duration": 2.341}, {"text": "if you've identified a\nlimit along a subsequence,", "start": 1045.95, "duration": 3.93}, {"text": "then, in fact, the entire\nsequence converges.", "start": 1049.88, "duration": 2.95}, {"text": "So of course, this is not true\nfor an arbitrary sequence.", "start": 1052.83, "duration": 3.45}, {"text": "If a subsequence converges--", "start": 1056.28, "duration": 2.99}, {"text": "or I should say, for\nan arbitrary sequence,", "start": 1059.27, "duration": 3.27}, {"text": "it's not true that a\nsubsequence converging implies", "start": 1062.54, "duration": 2.64}, {"text": "a full sequence converging.", "start": 1065.18, "duration": 1.92}, {"text": "We have minus 1 to the n for\nwhich a subsequence converges,", "start": 1067.1, "duration": 4.56}, {"text": "but the whole sequence\ndoes not converge.", "start": 1071.66, "duration": 2.13}, {"text": "But if we make the\nadditional hypothesis", "start": 1073.79, "duration": 2.4}, {"text": "that the sequence is\nCauchy, then the sequence", "start": 1076.19, "duration": 3.39}, {"text": "converges if and only if\nthat subsequence converges.", "start": 1079.58, "duration": 3.76}, {"text": "So the statement of the\ntheorem is following.", "start": 1083.34, "duration": 2.72}, {"text": "If x sub n is Cauchy and there\nexists a subsequence which", "start": 1092.38, "duration": 22.24}, {"text": "is converging to some number--", "start": 1114.62, "duration": 3.06}, {"text": "call it x-- then the whole\nsequence converges to x.", "start": 1117.68, "duration": 12.355}, {"text": "So what I was saying right\nbefore I stated this theorem is", "start": 1133.5, "duration": 2.79}, {"text": "that if I hide this\npart and just say,", "start": 1136.29, "duration": 1.83}, {"text": "there exists a subsequence\nwhich is converging to x,", "start": 1138.12, "duration": 3.48}, {"text": "this does not imply that the\nfull sequence converges to x.", "start": 1141.6, "duration": 2.67}, {"text": "Because we had this example\nof minus 1 to the n.", "start": 1144.27, "duration": 2.79}, {"text": "But if I also assume\nthe sequence is Cauchy,", "start": 1147.06, "duration": 3.84}, {"text": "then it does follow that\nCauchy plus subsequence", "start": 1150.9, "duration": 3.21}, {"text": "converging implies the\nfull sequence converges.", "start": 1154.11, "duration": 2.61}, {"text": "So I want to show that\nxn converges to x.", "start": 1161.96, "duration": 4.56}, {"text": "So want to show--", "start": 1166.52, "duration": 1.275}, {"text": "and we're going to do this\njust by using the definition,", "start": 1176.18, "duration": 5.13}, {"text": "by verifying this\nthrough the definition,", "start": 1181.31, "duration": 1.89}, {"text": "not using the squeeze theorem\nor anything like that.", "start": 1183.2, "duration": 3.818}, {"text": "So let epsilon be positive.", "start": 1187.018, "duration": 4.102}, {"text": "Since xn is Cauchy, there\nexist M0, a natural number", "start": 1198.26, "duration": 17.53}, {"text": "such that for all n\nbigger than or equal to M0", "start": 1215.79, "duration": 4.53}, {"text": "and k bigger than\nor equal to M0, x", "start": 1220.32, "duration": 6.825}, {"text": "sub n minus x sub k is\nless than epsilon over 2.", "start": 1227.145, "duration": 5.055}, {"text": "Why this epsilon over 2?", "start": 1232.2, "duration": 3.0}, {"text": "Or why should you\nnot be surprised?", "start": 1235.2, "duration": 1.53}, {"text": "Well, we have two\nassumptions here.", "start": 1236.73, "duration": 1.99}, {"text": "So like we did when we did\nconvergence of products", "start": 1238.72, "duration": 5.51}, {"text": "of sequences and so on,\nwhich had two assumptions,", "start": 1244.23, "duration": 4.86}, {"text": "namely two sequences converged\nto something, typically,", "start": 1249.09, "duration": 3.27}, {"text": "that means we'll have\ntwo integers coming.", "start": 1252.36, "duration": 1.8}, {"text": "We'll choose a bigger integer\nand then some inequalities", "start": 1254.16, "duration": 4.14}, {"text": "to get an epsilon.", "start": 1258.3, "duration": 0.94}, {"text": "So that's a little bit\nof a rambling answer", "start": 1259.24, "duration": 3.08}, {"text": "to why we get an epsilon over 2\nhere, or why we put one there.", "start": 1262.32, "duration": 4.92}, {"text": "Since the subsequence-- so this\nsubsequence converges to x--", "start": 1272.69, "duration": 7.23}, {"text": "there exists another\ninteger, M sub 1 such", "start": 1288.67, "duration": 4.92}, {"text": "that if k is bigger than\nor equal to M sub 1,", "start": 1293.59, "duration": 7.95}, {"text": "then x sub n sub k minus x\nis less than epsilon over 2.", "start": 1301.54, "duration": 9.3}, {"text": "So maybe I should have used\na different letter here.", "start": 1310.84, "duration": 2.97}, {"text": "Let's use a little m.", "start": 1313.81, "duration": 1.865}, {"text": "Because I don't\nwant you to think", "start": 1315.675, "duration": 1.375}, {"text": "these have to be the same k.", "start": 1317.05, "duration": 1.38}, {"text": "So now we'll choose an integer\nbigger than both M1 and M2", "start": 1327.95, "duration": 7.95}, {"text": "and show that it works.", "start": 1335.9, "duration": 1.42}, {"text": "Choose M to be M0 plus M1.", "start": 1337.32, "duration": 5.87}, {"text": "Now we need to show this works.", "start": 1359.47, "duration": 2.04}, {"text": "And if n is bigger than\nor equal to M, so let me,", "start": 1361.51, "duration": 11.62}, {"text": "actually, make a\nfirst observation", "start": 1373.13, "duration": 6.02}, {"text": "before I go to the n bigger\nthan or equal to capital M.", "start": 1379.15, "duration": 3.57}, {"text": "Then, since n sub k is bigger\nthan or equal to k for all", "start": 1382.72, "duration": 10.63}, {"text": "of k, a natural number-- just\nbecause the n sub k is there", "start": 1393.35, "duration": 2.94}, {"text": "in increasing\nsequence of integers,", "start": 1396.29, "duration": 2.84}, {"text": "which starts at least at 1--", "start": 1399.13, "duration": 1.68}, {"text": "and since n sub k is bigger\nthan or equal to k for all k,", "start": 1404.43, "duration": 3.69}, {"text": "this implies that the integer\nn sub capital M is bigger", "start": 1408.12, "duration": 5.4}, {"text": "than or equal to\nM, which, remember,", "start": 1413.52, "duration": 1.59}, {"text": "is M0 plus M1, which\nimplies that n sub M is", "start": 1415.11, "duration": 5.97}, {"text": "bigger than or equal\nto M0 and n sub M is", "start": 1421.08, "duration": 4.11}, {"text": "bigger than or equal to M1.", "start": 1425.19, "duration": 2.82}, {"text": "So I just wanted to make\nthis preliminary observation.", "start": 1428.01, "duration": 6.3}, {"text": "And now we'll go to showing\nthat this capital M works.", "start": 1434.31, "duration": 2.835}, {"text": "So now, if n is bigger\nthan or equal to capital", "start": 1440.36, "duration": 2.34}, {"text": "M, and I look at x sub n\nminus x, an absolute value,", "start": 1442.7, "duration": 5.47}, {"text": "and add and subtract x sub n\ncapital M capital M minus x", "start": 1448.17, "duration": 12.44}, {"text": "and use the triangle\ninequality, then--", "start": 1460.61, "duration": 13.75}, {"text": "so since n is bigger than\nor equal to capital M, which", "start": 1474.36, "duration": 3.66}, {"text": "is bigger than or\nequal to M0, that", "start": 1478.02, "duration": 2.34}, {"text": "means n is bigger\nthan or equal to M0.", "start": 1480.36, "duration": 2.85}, {"text": "And then n sub M we just showed\nis bigger than or equal to 0.", "start": 1483.21, "duration": 3.75}, {"text": "So by this inequality, I\nget that the first term", "start": 1486.96, "duration": 5.88}, {"text": "is less than epsilon over 2.", "start": 1492.84, "duration": 2.94}, {"text": "And now, so M is\ncertainly bigger than", "start": 1495.78, "duration": 6.06}, {"text": "or equal to M sub 1.", "start": 1501.84, "duration": 2.04}, {"text": "And therefore, I will get that\nthis part is less than epsilon", "start": 1503.88, "duration": 6.06}, {"text": "over 2 because of\nthis inequality.", "start": 1509.94, "duration": 4.24}, {"text": "So that choice of\ncapital M works.", "start": 1514.18, "duration": 8.47}, {"text": "And now, we'll\nprove the following,", "start": 1527.78, "duration": 8.02}, {"text": "that a sequence is convergent\nif and only if it's Cauchy.", "start": 1535.8, "duration": 3.75}, {"text": "So this is a two-way street.", "start": 1567.14, "duration": 1.75}, {"text": "So we need to show the\nleft implies the right", "start": 1568.89, "duration": 3.38}, {"text": "and then the right\nimplies the left.", "start": 1572.27, "duration": 1.665}, {"text": "So this direction\nis, in fact, easy.", "start": 1580.8, "duration": 9.757}, {"text": "Based on what we've done--", "start": 1590.557, "duration": 1.083}, {"text": "I shouldn't say it's easy--", "start": 1591.64, "duration": 1.14}, {"text": "but what we've done so\nfar, it quickly follows.", "start": 1592.78, "duration": 2.97}, {"text": "So we're assuming\nx sub n is Cauchy.", "start": 1602.31, "duration": 3.14}, {"text": "I'm trying to show\nit's convergent.", "start": 1605.45, "duration": 1.47}, {"text": "So if x sub n is\nCauchy, this implies", "start": 1612.25, "duration": 2.91}, {"text": "that x sub n is bounded,\nthe sequence is bounded,", "start": 1615.16, "duration": 7.08}, {"text": "which implies by the\nBolzano-Weierstrass theorem", "start": 1622.24, "duration": 3.48}, {"text": "that x sub n has a\nconvergent subsequence.", "start": 1625.72, "duration": 15.11}, {"text": "And by the theorem\nwe just proved,", "start": 1640.83, "duration": 1.89}, {"text": "if a Cauchy sequence has\na convergent subsequence,", "start": 1642.72, "duration": 3.81}, {"text": "it must be convergent.", "start": 1646.53, "duration": 1.32}, {"text": "Now, for the converse\ndirection, that xn", "start": 1656.05, "duration": 3.39}, {"text": "is convergent implies xn\nis Cauchy, well, so this", "start": 1659.44, "duration": 5.13}, {"text": "should not come as a surprise.", "start": 1664.57, "duration": 1.26}, {"text": "Let me draw a picture.", "start": 1665.83, "duration": 0.917}, {"text": "Let's suppose x sub\nn is converging to x,", "start": 1670.51, "duration": 5.35}, {"text": "and epsilon is positive.", "start": 1675.86, "duration": 1.77}, {"text": "Then, since the\nxn's are converging", "start": 1680.55, "duration": 3.0}, {"text": "to x, if I draw a\nlittle interval around x", "start": 1683.55, "duration": 9.3}, {"text": "of total length epsilon--", "start": 1692.85, "duration": 3.07}, {"text": "so x minus epsilon over 2\nand x plus epsilon over 2--", "start": 1695.92, "duration": 3.38}, {"text": "then I will find, as long\nas so then there exists M", "start": 1699.3, "duration": 5.61}, {"text": "so that, for all n bigger\nthan or equal to capital M,", "start": 1704.91, "duration": 4.89}, {"text": "all of the x sub n's\nlie in this interval.", "start": 1709.8, "duration": 5.67}, {"text": "They all lie in this\ninterval because they", "start": 1721.54, "duration": 1.75}, {"text": "have to be within\ndistance epsilon over 2", "start": 1723.29, "duration": 1.8}, {"text": "to x if the xn's\nare converging to x.", "start": 1725.09, "duration": 5.46}, {"text": "And since they lie\nin this interval,", "start": 1730.55, "duration": 1.86}, {"text": "the distance between\nany two of them", "start": 1732.41, "duration": 2.37}, {"text": "can only be as big as the\nlength of the interval, which", "start": 1734.78, "duration": 2.7}, {"text": "is epsilon.", "start": 1737.48, "duration": 2.79}, {"text": "So this is essentially\nthe picture", "start": 1740.27, "duration": 3.78}, {"text": "of why a convergence\nsequence has to be Cauchy.", "start": 1744.05, "duration": 2.67}, {"text": "So now let's turn this\npicture into math.", "start": 1746.72, "duration": 1.8}, {"text": "We have to verify xn is\nCauchy through the definition.", "start": 1753.2, "duration": 2.34}, {"text": "That's all we have.", "start": 1755.54, "duration": 1.02}, {"text": "So let epsilon be positive.", "start": 1756.56, "duration": 3.48}, {"text": "Since the xn's\nconverge to x, there", "start": 1760.04, "duration": 4.32}, {"text": "exists an integer M sub\n0, a natural number,", "start": 1764.36, "duration": 3.84}, {"text": "such that for all n bigger\nthan or equal to M sub 0, x", "start": 1768.2, "duration": 5.64}, {"text": "sub n minus x is less\nthan epsilon over 2.", "start": 1773.84, "duration": 3.42}, {"text": "And so we'll choose the M\nfor our definition of Cauchy", "start": 1782.86, "duration": 4.65}, {"text": "to be this M sub 0.", "start": 1787.51, "duration": 1.41}, {"text": "And if n is bigger\nthan or equal to M", "start": 1792.52, "duration": 3.66}, {"text": "and k is bigger\nthan or equal to M", "start": 1796.18, "duration": 3.51}, {"text": "and I look at the absolute\nvalue of x sub n minus x sub k", "start": 1799.69, "duration": 4.62}, {"text": "and add and subtract x and\nuse the triangle inequality,", "start": 1804.31, "duration": 4.14}, {"text": "this is less than\nor equal to x sub", "start": 1808.45, "duration": 1.65}, {"text": "n minus x, an absolute\nvalue, plus x minus x sub k.", "start": 1810.1, "duration": 6.93}, {"text": "Each of these is less\nthan epsilon over 2", "start": 1817.03, "duration": 5.1}, {"text": "since n is bigger than\nor equal to capital M,", "start": 1822.13, "duration": 1.988}, {"text": "and k is bigger than\nor equal to capital M.", "start": 1824.118, "duration": 1.792}, {"text": "So this is less than epsilon\nover 2 plus epsilon over 2", "start": 1825.91, "duration": 4.2}, {"text": "equals epsilon.", "start": 1830.11, "duration": 1.29}, {"text": "And therefore, xn is Cauchy.", "start": 1831.4, "duration": 1.5}, {"text": "Now I want to make\na brief remark", "start": 1837.23, "duration": 4.5}, {"text": "about the previous theorem.", "start": 1841.73, "duration": 3.24}, {"text": "So remember how this\nwhole story started off?", "start": 1847.94, "duration": 3.18}, {"text": "There was something wrong with\nthe rational numbers, namely,", "start": 1856.07, "duration": 5.06}, {"text": "they didn't contain\nthe square root of 2.", "start": 1861.13, "duration": 2.76}, {"text": "So we couldn't solve\nthe algebraic equation", "start": 1863.89, "duration": 2.34}, {"text": "x squared minus 2 equals 0.", "start": 1866.23, "duration": 2.79}, {"text": "But this also, then,\nturned into the rationals", "start": 1869.02, "duration": 4.74}, {"text": "not being complete in\nthe sense of order.", "start": 1873.76, "duration": 3.72}, {"text": "Not every non-empty\nbounded set had a supremum.", "start": 1877.48, "duration": 3.348}, {"text": "It didn't have the least\nupper bound property.", "start": 1880.828, "duration": 1.917}, {"text": "But you can also interpret this\nlack of having square root of 2", "start": 1885.7, "duration": 5.16}, {"text": "as somehow saying\nthat the rationals are", "start": 1890.86, "duration": 6.24}, {"text": "incomplete in this sense.", "start": 1897.1, "duration": 1.93}, {"text": "So hopefully, at the\nend of this class,", "start": 1899.03, "duration": 3.747}, {"text": "we'll be able to get\nto metrics basis.", "start": 1902.777, "duration": 1.583}, {"text": "But so what do I mean by that?", "start": 1904.36, "duration": 4.03}, {"text": "Let's say I look\nat this statement", "start": 1908.39, "duration": 1.82}, {"text": "now within the universe\nof rational numbers.", "start": 1910.21, "duration": 4.87}, {"text": "So now, if this sequence\nis rational numbers--", "start": 1919.26, "duration": 19.03}, {"text": "meaning sequences are only\nsequences of rational numbers,", "start": 1938.29, "duration": 4.07}, {"text": "limits are only elements\nof the rational numbers,", "start": 1942.36, "duration": 5.01}, {"text": "epsilon is only a rational\nnumber, and so on-- then", "start": 1947.37, "duration": 5.1}, {"text": "we still have many\nof the same theorems", "start": 1952.47, "duration": 2.01}, {"text": "that we proved--\nnot all of them,", "start": 1954.48, "duration": 2.22}, {"text": "and I'll indicate\nwhich ones don't hold.", "start": 1956.7, "duration": 3.28}, {"text": "But if we only\nwork in rationals,", "start": 1959.98, "duration": 1.55}, {"text": "then we always do have a\nconvergence implies Cauchy,", "start": 1961.53, "duration": 11.38}, {"text": "meaning convergent\nsequences are Cauchy.", "start": 1972.91, "duration": 4.23}, {"text": "But Cauchy sequences are\nnot necessarily convergent.", "start": 1977.14, "duration": 13.74}, {"text": "Again, what's the\nexample here, or what's", "start": 1990.88, "duration": 8.44}, {"text": "the intuitive example?", "start": 1999.32, "duration": 1.17}, {"text": "Take x sub n so\nthat x of n is in Q.", "start": 2000.49, "duration": 11.05}, {"text": "And now viewed in the\nuniverse of real numbers,", "start": 2011.54, "duration": 6.62}, {"text": "x sub n's converge to root 2.", "start": 2018.16, "duration": 1.815}, {"text": "Then such a sequence would\nbe a Cauchy sequence.", "start": 2026.59, "duration": 4.38}, {"text": "We just proved that, basically.", "start": 2030.97, "duration": 2.34}, {"text": "So such a sequence would\nbe a Cauchy sequence", "start": 2033.31, "duration": 2.19}, {"text": "of rational numbers.", "start": 2035.5, "duration": 1.71}, {"text": "However, it would not converge\nin the set of rational numbers.", "start": 2037.21, "duration": 3.95}, {"text": "It would converge to\nthe square root of 2,", "start": 2041.16, "duration": 1.75}, {"text": "which is not a rational number.", "start": 2042.91, "duration": 1.87}, {"text": "So because the square root of\n2 is not a rational number,", "start": 2044.78, "duration": 5.04}, {"text": "this shows that the\nrational numbers do not", "start": 2049.82, "duration": 1.919}, {"text": "have this completeness property\nthat Cauchy sequences converge.", "start": 2051.739, "duration": 4.68}, {"text": "So there's a whole,\nstill, to this day, kind", "start": 2062.34, "duration": 4.87}, {"text": "of industry of studying\nspaces for which Cauchy", "start": 2067.21, "duration": 4.35}, {"text": "is equivalent to convergent.", "start": 2071.56, "duration": 2.55}, {"text": "These are called\ncomplete metric spaces.", "start": 2074.11, "duration": 1.799}, {"text": "And then if you add a\nlittle more structure,", "start": 2075.909, "duration": 1.833}, {"text": "they're called Banach\nspaces and so on,", "start": 2077.742, "duration": 4.147}, {"text": "which are very important,\nnot just in math", "start": 2081.889, "duration": 1.75}, {"text": "but also for\nformulating rigorously", "start": 2083.639, "duration": 6.27}, {"text": "a lot of the\nunderlying assumptions", "start": 2089.909, "duration": 6.421}, {"text": "for mathematical physics.", "start": 2096.33, "duration": 1.86}, {"text": "So if we're just looking\ninside the rationals,", "start": 2101.96, "duration": 2.76}, {"text": "it does not follow that Cauchy\nsequences always converge.", "start": 2104.72, "duration": 3.48}, {"text": "And now let's just\nstop for a minute", "start": 2108.2, "duration": 1.8}, {"text": "and take stock of why this\nwas true for the real numbers.", "start": 2110.0, "duration": 3.43}, {"text": "What did we use going back?", "start": 2113.43, "duration": 1.756}, {"text": "So if you really go\nback to the proof", "start": 2115.186, "duration": 8.374}, {"text": "of the Bolzano-Weierstrass--\nso that's what we used here", "start": 2123.56, "duration": 3.57}, {"text": "to show that Cauchy\nsequences converge--", "start": 2127.13, "duration": 2.25}, {"text": "we use the fact that the lim sup\nand the lim inf always exists.", "start": 2132.11, "duration": 5.37}, {"text": "And lim sup and lim\ninf, first off, they're", "start": 2137.48, "duration": 3.63}, {"text": "defined to be sups and\ninfs, which may not always", "start": 2141.11, "duration": 2.16}, {"text": "exist as rational numbers,\nas we've already shown.", "start": 2143.27, "duration": 2.88}, {"text": "So that's definitely a\nproblem already there.", "start": 2146.15, "duration": 5.28}, {"text": "But even more so, when we prove\nthat every bounded monotone", "start": 2151.43, "duration": 4.02}, {"text": "sequence converges,\nwhat we showed", "start": 2155.45, "duration": 2.76}, {"text": "was that this limit is\nactually a sup of a certain set", "start": 2158.21, "duration": 3.27}, {"text": "or an inf of a certain set,\nwhich, again, may or may not", "start": 2161.48, "duration": 2.843}, {"text": "exist if we're just looking\nin the rational numbers.", "start": 2164.323, "duration": 2.167}, {"text": "Because the rational numbers do\nnot have the least upper bound", "start": 2166.49, "duration": 2.7}, {"text": "property.", "start": 2169.19, "duration": 1.23}, {"text": "So it really is the least\nupper bound property", "start": 2170.42, "duration": 4.17}, {"text": "that gives us\nconvergence equivalent", "start": 2174.59, "duration": 3.66}, {"text": "to Cauchy for the real numbers.", "start": 2178.25, "duration": 2.17}, {"text": "So for R, the least\nupper bound property is--", "start": 2180.42, "duration": 12.492}, {"text": "it has to be because\nthat's the main thing that", "start": 2192.912, "duration": 1.958}, {"text": "separates the two fields,\nbut I'm just reiterating this", "start": 2194.87, "duration": 4.89}, {"text": "here--", "start": 2199.76, "duration": 1.56}, {"text": "is the reason why convergent\nis equivalent to Cauchy.", "start": 2201.32, "duration": 12.1}, {"text": "Now that I've proved that Cauchy\nis equivalent to convergence,", "start": 2227.75, "duration": 5.49}, {"text": "maybe you'll ask, then why\ndid we introduce it at all?", "start": 2233.24, "duration": 2.73}, {"text": "If these two notions\nare the same,", "start": 2238.48, "duration": 4.96}, {"text": "why even introduce\nthem if they're just", "start": 2243.44, "duration": 2.19}, {"text": "convergent sequences already?", "start": 2245.63, "duration": 2.23}, {"text": "And the reason is because to\nshow that a sequence converges,", "start": 2247.86, "duration": 6.59}, {"text": "you have to somehow\nhave your hands", "start": 2254.45, "duration": 1.86}, {"text": "on a candidate for the limit.", "start": 2256.31, "duration": 4.47}, {"text": "If you want to prove\nthat xn converges,", "start": 2260.78, "duration": 4.71}, {"text": "you have to somehow come up\nwith an x that it converges to.", "start": 2265.49, "duration": 3.39}, {"text": "And it's not always\nclear how to find that x.", "start": 2268.88, "duration": 6.234}, {"text": "But Cauchy, although it's\nequivalent to a convergent", "start": 2275.114, "duration": 3.306}, {"text": "in the set of real\nnumbers, doesn't", "start": 2278.42, "duration": 3.45}, {"text": "require you to find a\ncandidate for convergence.", "start": 2281.87, "duration": 5.28}, {"text": "All it requires\nyou to do is show", "start": 2287.15, "duration": 2.67}, {"text": "that, as long as you\ngo far enough out,", "start": 2289.82, "duration": 3.61}, {"text": "any two entries in the\nsequence are close together", "start": 2293.43, "duration": 4.98}, {"text": "without requiring you\nto come up with a limit.", "start": 2298.41, "duration": 2.62}, {"text": "See, computing limits\nis quite difficult.", "start": 2301.03, "duration": 2.15}, {"text": "We're about to do series.", "start": 2303.18, "duration": 1.71}, {"text": "And there's maybe, I don't\nknow, five series people", "start": 2304.89, "duration": 3.15}, {"text": "can compute explicitly.", "start": 2308.04, "duration": 1.937}, {"text": "But you do know that there's\na ton of other series", "start": 2309.977, "duration": 2.083}, {"text": "that are actually convergent,\neven though you don't know what", "start": 2312.06, "duration": 2.7}, {"text": "the limit as.", "start": 2314.76, "duration": 1.32}, {"text": "And why do you know that?", "start": 2316.08, "duration": 1.65}, {"text": "This is exactly\nbecause and exactly", "start": 2317.73, "duration": 2.16}, {"text": "why people thought\nof Cauchy sequences", "start": 2319.89, "duration": 3.96}, {"text": "to begin with in\nmuch of analysis.", "start": 2323.85, "duration": 2.59}, {"text": "So again, just to\nsummarize this,", "start": 2326.44, "duration": 5.33}, {"text": "convergent sequences are nice.", "start": 2331.77, "duration": 1.47}, {"text": "But in practice, it's\ndifficult to get your hands", "start": 2333.24, "duration": 2.94}, {"text": "on what could be a\nlimit of a sequence,", "start": 2336.18, "duration": 2.1}, {"text": "especially if that sequence\nis pretty complicated.", "start": 2338.28, "duration": 3.37}, {"text": "So if you're trying to show\na certain sequence converges,", "start": 2341.65, "duration": 3.5}, {"text": "it suffices, by what we've done\nhere, to show that it's Cauchy.", "start": 2345.15, "duration": 4.18}, {"text": "And that's a little bit\neasier to do because that just", "start": 2349.33, "duration": 3.51}, {"text": "requires you to work with\nthe original sequence.", "start": 2352.84, "duration": 2.485}, {"text": "You don't have to\ncome up with a limit.", "start": 2355.325, "duration": 1.625}, {"text": "You can just take your sequence\nand start playing directly", "start": 2356.95, "duration": 4.41}, {"text": "with the entries rather than\ntry to come up with a limit", "start": 2361.36, "duration": 6.01}, {"text": "explicitly.", "start": 2367.37, "duration": 0.93}, {"text": "So that's what we're\ngoing to move on to", "start": 2372.02, "duration": 2.46}, {"text": "is series now, which,\nas I said a minute ago,", "start": 2374.48, "duration": 5.46}, {"text": "is original reason why\npeople started developing", "start": 2379.94, "duration": 8.81}, {"text": "the foundations of\nanalysis, what we're talking", "start": 2388.75, "duration": 2.248}, {"text": "about right now, to begin with.", "start": 2390.998, "duration": 1.292}, {"text": "Because they were just kind\nof doing very formal things", "start": 2395.64, "duration": 6.33}, {"text": "that ended up not\nmaking sense, like they", "start": 2401.97, "duration": 5.07}, {"text": "were adding infinitely\nmany positive numbers", "start": 2407.04, "duration": 2.94}, {"text": "and coming up with\na negative number.", "start": 2409.98, "duration": 3.048}, {"text": "Well, that can't be right.", "start": 2413.028, "duration": 1.252}, {"text": "So all of this was\ncreated, discovered--", "start": 2414.28, "duration": 7.31}, {"text": "however you want to phrase it--", "start": 2421.59, "duration": 1.56}, {"text": "to put on rigorous\nfoundations this next topic,", "start": 2423.15, "duration": 6.143}, {"text": "which is series.", "start": 2429.293, "duration": 0.667}, {"text": "And you dealt with\nseries in calculus,", "start": 2435.2, "duration": 3.51}, {"text": "so you know what a series is.", "start": 2438.71, "duration": 1.885}, {"text": "Maybe you don't\nremember all the proofs", "start": 2440.595, "duration": 1.625}, {"text": "of the properties of series.", "start": 2442.22, "duration": 1.35}, {"text": "But suffice it to say, series\nis a pretty good motivation", "start": 2443.57, "duration": 6.16}, {"text": "since it's one of the most\nuseful things that comes out", "start": 2449.73, "duration": 4.375}, {"text": "of math.", "start": 2454.105, "duration": 0.5}, {"text": "Series expansions are\nhow you solve ODEs, PDEs,", "start": 2458.79, "duration": 6.21}, {"text": "Taylor expansions.", "start": 2465.0, "duration": 1.02}, {"text": "All these things are, in\nsome sense, a form of series.", "start": 2466.02, "duration": 3.33}, {"text": "So being able to justify\nthem as being real things", "start": 2469.35, "duration": 5.25}, {"text": "is a necessity.", "start": 2474.6, "duration": 2.56}, {"text": "So the definition of\na series, for now,", "start": 2477.16, "duration": 8.66}, {"text": "really is just this symbol\nI'm about to write down.", "start": 2485.82, "duration": 2.7}, {"text": "So given a sequence\nx sub n, the symbol--", "start": 2488.52, "duration": 8.945}, {"text": "or maybe I'll just sometimes\nwrite just the sum x sub n--", "start": 2505.13, "duration": 3.105}, {"text": "is what's called the series\nassociated to the sequence", "start": 2510.8, "duration": 9.31}, {"text": "x sub n.", "start": 2520.11, "duration": 0.56}, {"text": "So right now, that's\njust a symbol.", "start": 2523.607, "duration": 1.458}, {"text": "We're going to interpret\nthis as a real number", "start": 2527.6, "duration": 2.46}, {"text": "in the following situation.", "start": 2530.06, "duration": 1.53}, {"text": "We say that the\nseries converges,", "start": 2535.04, "duration": 13.34}, {"text": "if the following sequence\ngiven by s sub m equals--", "start": 2548.38, "duration": 20.51}, {"text": "so s sub m, this is the\nelement of the sequence.", "start": 2574.06, "duration": 3.06}, {"text": "And what is it?", "start": 2577.12, "duration": 0.84}, {"text": "It is the actual sum.", "start": 2577.96, "duration": 1.93}, {"text": "So this is not a formal thing.", "start": 2579.89, "duration": 1.38}, {"text": "This is just a finite\nsum from n equals 1 to m.", "start": 2581.27, "duration": 3.56}, {"text": "So this is-- so this sequence\nnow, m equals 1 to infinity.", "start": 2584.83, "duration": 10.24}, {"text": "And these guys we call\npartial sums converges.", "start": 2600.0, "duration": 14.07}, {"text": "So right now, if we just\nhave a sequence x sub n,", "start": 2616.87, "duration": 5.04}, {"text": "the series associated to that\nsequence is just a symbol.", "start": 2621.91, "duration": 4.5}, {"text": "We say that this\nseries converges", "start": 2626.41, "duration": 1.8}, {"text": "if this sequence of\npartial sums converge", "start": 2628.21, "duration": 4.72}, {"text": "and if s is this limit.", "start": 2632.93, "duration": 9.43}, {"text": "And we write s is\nequal to the series", "start": 2651.81, "duration": 13.26}, {"text": "and treat the series\nnow as a number.", "start": 2665.07, "duration": 1.8}, {"text": "So in general, if\nI have a sequence,", "start": 2677.03, "duration": 1.98}, {"text": "I just have this formal\nsymbol, which I'm writing down,", "start": 2679.01, "duration": 3.73}, {"text": "which I call a series\nassociated to it.", "start": 2682.74, "duration": 2.96}, {"text": "In the case that the sequence\nof partial sums converges,", "start": 2685.7, "duration": 3.85}, {"text": "then I actually identify this\nseries with a real number", "start": 2689.55, "duration": 3.585}, {"text": "and treat it as a real number.", "start": 2693.135, "duration": 1.25}, {"text": "And so the way\nI've written this,", "start": 2699.12, "duration": 3.96}, {"text": "the series is starting at 1.", "start": 2703.08, "duration": 1.44}, {"text": "But it doesn't\nnecessarily have to.", "start": 2704.52, "duration": 2.01}, {"text": "So just by shifting the index--", "start": 2706.53, "duration": 4.905}, {"text": "so let me just say here\nthat we don't necessarily", "start": 2716.08, "duration": 9.69}, {"text": "have to start a\nseries at n equals 1.", "start": 2725.77, "duration": 9.63}, {"text": "So this could be\nsum from n equals 0", "start": 2735.4, "duration": 2.25}, {"text": "to infinity, in which case, we\nhave a sequence starting now", "start": 2737.65, "duration": 3.0}, {"text": "at x sub 0.", "start": 2740.65, "duration": 1.53}, {"text": "Or this could be starting\nat 2, in which place", "start": 2742.18, "duration": 3.24}, {"text": "the sequence of x sub\nn starts at n equals 2.", "start": 2745.42, "duration": 3.12}, {"text": "And then the sequence\nof partial sums", "start": 2748.54, "duration": 2.43}, {"text": "would start at not m\nequals 1 but m equals 0", "start": 2750.97, "duration": 3.3}, {"text": "or m equals 2, depending\non where the series starts.", "start": 2754.27, "duration": 3.57}, {"text": "So some examples.", "start": 2760.86, "duration": 0.84}, {"text": "The series sum from n equals\n1 to infinity 1 over n", "start": 2765.18, "duration": 8.93}, {"text": "plus 1 times n, this\nis a convergent series.", "start": 2774.11, "duration": 7.47}, {"text": "So why is this?", "start": 2786.01, "duration": 1.935}, {"text": "So let's look at the proof.", "start": 2787.945, "duration": 1.125}, {"text": "So we look at the\nm-th partial sum--", "start": 2789.07, "duration": 2.7}, {"text": "this is the sum from n equals\n1 to m of 1 over n plus 1n.", "start": 2791.77, "duration": 6.93}, {"text": "And this is equal to--", "start": 2798.7, "duration": 2.73}, {"text": "now, if I write 1 over n plus\n1 times n as 1 over n minus 1", "start": 2801.43, "duration": 15.11}, {"text": "over n plus 1, this is\nnow the sum of 1 over n", "start": 2816.54, "duration": 4.98}, {"text": "plus-- these are finite sums,\nso I can always split them up.", "start": 2821.52, "duration": 3.87}, {"text": "This should be a minus.", "start": 2827.747, "duration": 0.958}, {"text": "And so now, this is\nequal to 1 plus 1/2", "start": 2831.64, "duration": 2.91}, {"text": "plus 1 over m minus 1/2\nplus 1/3 plus 1 over m", "start": 2834.55, "duration": 12.0}, {"text": "plus 1 over n plus 1.", "start": 2846.55, "duration": 4.41}, {"text": "And you see all of these cancel.", "start": 2850.96, "duration": 4.02}, {"text": "And all that's left is\n1 minus 1 over m plus 1.", "start": 2854.98, "duration": 5.82}, {"text": "So the m-th partial sum is equal\nto 1 minus 1 over m plus 1.", "start": 2860.8, "duration": 5.01}, {"text": "And therefore, the\nsequence of partial sums", "start": 2865.81, "duration": 7.48}, {"text": "is the limit as m\ngoes to infinity", "start": 2873.29, "duration": 1.62}, {"text": "of this, which is just 1.", "start": 2874.91, "duration": 2.2}, {"text": "And therefore, this\nseries converges.", "start": 2877.11, "duration": 2.84}, {"text": "Now, our favorite sequence,\nwhich does not converge,", "start": 2889.61, "duration": 4.44}, {"text": "will give us a series\nwhich does not converge.", "start": 2894.05, "duration": 2.64}, {"text": "So let's look at sum from n\nequals 1 to infinity minus 1", "start": 2896.69, "duration": 5.55}, {"text": "to the n.", "start": 2902.24, "duration": 1.2}, {"text": "This does not converge.", "start": 2903.44, "duration": 3.06}, {"text": "So what's the proof?", "start": 2909.532, "duration": 0.833}, {"text": "The m-th partial sum,\nthis is equal to minus 1", "start": 2913.1, "duration": 6.24}, {"text": "plus 1 plus minus 1 up until\nI get minus 1 to the m.", "start": 2919.34, "duration": 6.14}, {"text": "And therefore, this is always\nequal to one of two things.", "start": 2928.61, "duration": 6.45}, {"text": "If m is odd, then I have an\nodd number of these guys.", "start": 2935.06, "duration": 7.61}, {"text": "And therefore, the\nminuses and pluses", "start": 2942.67, "duration": 4.38}, {"text": "cancel, just leaving\na minus 1 in the end--", "start": 2947.05, "duration": 3.75}, {"text": "this last one, the odd one.", "start": 2950.8, "duration": 1.44}, {"text": "And m is odd and 0 if m is even.", "start": 2955.9, "duration": 5.86}, {"text": "If I add up an even\nnumber of these terms,", "start": 2961.76, "duration": 4.2}, {"text": "then all of the minus\n1's and 1's cancel out,", "start": 2965.96, "duration": 2.23}, {"text": "so I just get 0.", "start": 2968.19, "duration": 1.49}, {"text": "And therefore, this sequence,\nwhich is just minus 1", "start": 2969.68, "duration": 10.25}, {"text": "for m odd, 0 for m\neven, does not converge.", "start": 2979.93, "duration": 11.487}, {"text": "And therefore, the\nseries does not converge.", "start": 2991.417, "duration": 1.833}, {"text": "So when I write this,\nthis is just a symbol.", "start": 2993.25, "duration": 3.0}, {"text": "This is just chalk\non a chalkboard.", "start": 2996.25, "duration": 1.838}, {"text": "It doesn't mean anything.", "start": 2998.088, "duration": 1.042}, {"text": "So let's go to another\nseries, which does converge.", "start": 3006.32, "duration": 6.0}, {"text": "And this is kind of\nthe one to which we", "start": 3012.32, "duration": 5.22}, {"text": "compare all other series,\nessentially, as you'll see.", "start": 3017.54, "duration": 4.98}, {"text": "You have all these series tests\nthat you remember, hopefully,", "start": 3022.52, "duration": 3.18}, {"text": "from calculus that tell you\nwhen a series converges.", "start": 3025.7, "duration": 7.0}, {"text": "But maybe, if you\nremember the proof", "start": 3032.7, "duration": 2.58}, {"text": "or don't, how you do\nthat is you converge it", "start": 3035.28, "duration": 2.46}, {"text": "to one series, which\nyou do know how to sum.", "start": 3037.74, "duration": 2.58}, {"text": "So it was just by pure luck we\nwere able to compute the sum,", "start": 3040.32, "duration": 5.34}, {"text": "or compute the explicit\nseries for this guy.", "start": 3045.66, "duration": 4.71}, {"text": "Another one which we can do\nthat for is geometric series.", "start": 3050.37, "duration": 3.64}, {"text": "So the theorem is if\nI have a real number", "start": 3054.01, "duration": 4.22}, {"text": "with absolute value less\nthan 1, then the series", "start": 3058.23, "duration": 7.77}, {"text": "starting now at 0 R\nto the n converges.", "start": 3066.0, "duration": 7.23}, {"text": "And I can actually compute\nthe sum of this series.", "start": 3073.23, "duration": 6.57}, {"text": "And this is 1 over 1 minus r.", "start": 3079.8, "duration": 3.09}, {"text": "So what's the proof?", "start": 3088.775, "duration": 2.595}, {"text": "Let's look at the partial sums.", "start": 3091.37, "duration": 2.46}, {"text": "And we can actually\ncompute these, as well,", "start": 3093.83, "duration": 4.23}, {"text": "just as we were able to\ndo for the first example.", "start": 3098.06, "duration": 2.55}, {"text": "We compute that the sum from n\nequals 0 to m of r to the m--", "start": 3105.63, "duration": 6.44}, {"text": "now, you can prove\nthis by induction.", "start": 3112.07, "duration": 2.94}, {"text": "I cannot exactly\nremember if I did this--", "start": 3115.01, "duration": 2.52}, {"text": "I believe I did-- in\nthe second lecture", "start": 3120.44, "duration": 1.8}, {"text": "on induction, first or second\nlecture on the induction.", "start": 3122.24, "duration": 2.52}, {"text": "But if I add up some\nnumber raised to the n-th--", "start": 3124.76, "duration": 4.41}, {"text": "so this should be to the n--", "start": 3129.17, "duration": 2.91}, {"text": "power from 0 to m, this\nis equal to 1 minus r", "start": 3132.08, "duration": 3.36}, {"text": "to the m plus 1 over 1 minus r.", "start": 3135.44, "duration": 5.23}, {"text": "And I guess two lectures\nago, we proved that", "start": 3140.67, "duration": 5.46}, {"text": "if the absolute value--", "start": 3146.13, "duration": 1.96}, {"text": "so let me state this now.", "start": 3148.09, "duration": 2.585}, {"text": "Two lectures ago, we proved\nthat if the absolute value of r", "start": 3158.49, "duration": 7.8}, {"text": "is less than 1, then limit as,\nlet's make it m, of r to the m", "start": 3166.29, "duration": 9.12}, {"text": "equals 0, which implies that--", "start": 3175.41, "duration": 7.37}, {"text": "so this was the\nm-th partial sum--", "start": 3182.78, "duration": 4.33}, {"text": "which implies that the limit as\nm goes to infinity of s sub m", "start": 3187.11, "duration": 4.82}, {"text": "equals the limit as m goes to\ninfinity of this thing, which", "start": 3191.93, "duration": 4.29}, {"text": "is, if you like--", "start": 3196.22, "duration": 1.05}, {"text": "so that plus 1 there just\nmultiplies r to the m by r.", "start": 3200.25, "duration": 4.62}, {"text": "And using the algebraic\nfacts we proved", "start": 3204.87, "duration": 5.04}, {"text": "about limits is 1\nminus r time 0 over 1", "start": 3209.91, "duration": 2.7}, {"text": "minus r, which equals\n1 over 1 minus r.", "start": 3212.61, "duration": 3.93}, {"text": "So now you ask about the other.", "start": 3222.756, "duration": 3.534}, {"text": "What about r bigger than 1?", "start": 3226.29, "duration": 2.43}, {"text": "Well, when r equals\nminus 1, then we", "start": 3232.57, "duration": 2.73}, {"text": "get the second\nexample we looked at.", "start": 3235.3, "duration": 4.14}, {"text": "If we get r equals 1, then\nthat's just summing up 1,", "start": 3239.44, "duration": 4.89}, {"text": "and I'll leave it to you\nto check that that does not", "start": 3244.33, "duration": 3.24}, {"text": "converge, that the sequence of\npartial sums, if I just sum up", "start": 3247.57, "duration": 3.72}, {"text": "1 from n equals 0 to\nm, is equal 2n plus 1,", "start": 3251.29, "duration": 5.53}, {"text": "which does not converge.", "start": 3256.82, "duration": 1.0}, {"text": "And let me make just a\nkind of silly comment.", "start": 3272.67, "duration": 3.33}, {"text": "And maybe I didn't\nexplicitly make", "start": 3276.0, "duration": 2.16}, {"text": "this comment about sequences.", "start": 3278.16, "duration": 2.01}, {"text": "Maybe I forgot to\ndo that, as well.", "start": 3280.17, "duration": 1.81}, {"text": "So for a sequence, you could\nstart your sequence not", "start": 3281.98, "duration": 8.24}, {"text": "necessarily at the first entry.", "start": 3290.22, "duration": 1.95}, {"text": "Maybe you look at a, if you\nlike, new sequence where--", "start": 3292.17, "duration": 3.78}, {"text": "well, so we know from\nsequences that subsequences", "start": 3300.05, "duration": 4.24}, {"text": "of convergent\nsequences converge.", "start": 3304.29, "duration": 1.68}, {"text": "So if I, instead of looking at\nthe whole sequence, start at,", "start": 3305.97, "duration": 6.01}, {"text": "let's say, x100 and\nthen go x101, x102,", "start": 3311.98, "duration": 3.98}, {"text": "and that's the\nsequence I look at,", "start": 3315.96, "duration": 1.74}, {"text": "well, that's a subsequence\nof the original one, which,", "start": 3317.7, "duration": 2.79}, {"text": "if it converges, implies\nthat subsequence converges.", "start": 3320.49, "duration": 2.92}, {"text": "So all that is to say--", "start": 3323.41, "duration": 3.35}, {"text": "and for this simple way of\nobtaining this new sequence--", "start": 3326.76, "duration": 4.74}, {"text": "all of that is to say\nthat to understand", "start": 3331.5, "duration": 5.04}, {"text": "if a sequence\nconverges, I don't have", "start": 3336.54, "duration": 1.86}, {"text": "to consider what happens for\nthe first finitely many terms", "start": 3338.4, "duration": 5.58}, {"text": "in the sequence,\nmeaning a sequence x", "start": 3343.98, "duration": 5.33}, {"text": "sub n converges if and only if\na sequence starting now at say,", "start": 3349.31, "duration": 5.57}, {"text": "n equals 100-- and 101, 102,\n103 and so on-- converges.", "start": 3354.88, "duration": 5.49}, {"text": "And the same is true for series,\nthat a series converges if", "start": 3360.37, "duration": 6.73}, {"text": "and only if a series\nconverges, now,", "start": 3367.1, "duration": 4.68}, {"text": "starting at a different\npoint along the sequence.", "start": 3371.78, "duration": 2.95}, {"text": "So this is the\nfollowing theorem.", "start": 3374.73, "duration": 4.52}, {"text": "Let xn be a sequence, and let\ncapital M be a natural number.", "start": 3383.34, "duration": 15.29}, {"text": "Then n equals 1 to\ninfinity of x sub n.", "start": 3398.63, "duration": 8.01}, {"text": "This converges if and only\nif the sequence, now starting", "start": 3406.64, "duration": 5.25}, {"text": "at capital M,\nconverges, meaning when", "start": 3411.89, "duration": 6.29}, {"text": "I have to decide whether\na series converges or not,", "start": 3418.18, "duration": 3.03}, {"text": "it doesn't matter\nwhat's going on", "start": 3421.21, "duration": 2.46}, {"text": "for the first\nfinitely many terms.", "start": 3423.67, "duration": 3.01}, {"text": "What matters is\nwhat's going on as I", "start": 3426.68, "duration": 1.79}, {"text": "keep adding terms from\nfurther and further out", "start": 3428.47, "duration": 4.467}, {"text": "of this sequence.", "start": 3432.937, "duration": 0.708}, {"text": "And what's the proof?", "start": 3436.57, "duration": 0.93}, {"text": "The proof is just\nexpressing the partial sums", "start": 3437.5, "duration": 2.93}, {"text": "for this guy in terms of the\npartial sums for this guy.", "start": 3440.43, "duration": 3.48}, {"text": "So a partial sum satisfied\nfor all m, sum from n", "start": 3443.91, "duration": 18.46}, {"text": "equals 1 to m, and now\nx sub n as sum from n", "start": 3462.37, "duration": 9.67}, {"text": "equals capital M to m\nx sub n plus sum from n", "start": 3472.04, "duration": 6.63}, {"text": "equals 1 to capital\nM minus 1 x sub n.", "start": 3478.67, "duration": 6.35}, {"text": "So this is now just\na fixed number.", "start": 3485.02, "duration": 2.32}, {"text": "So this is a sequence of\npartial sums corresponding", "start": 3487.34, "duration": 4.94}, {"text": "to this series.", "start": 3492.28, "duration": 1.92}, {"text": "This is a sequence of\npartial sums corresponding", "start": 3494.2, "duration": 2.28}, {"text": "to this series.", "start": 3496.48, "duration": 0.99}, {"text": "And this is just a fixed number.", "start": 3497.47, "duration": 2.01}, {"text": "Therefore, if this\nconverges, then this side", "start": 3499.48, "duration": 3.78}, {"text": "converges to this plus this--", "start": 3503.26, "duration": 4.86}, {"text": "so maybe I'm going\na little quick.", "start": 3508.12, "duration": 2.25}, {"text": "But so if this\nconverges, then this", "start": 3510.37, "duration": 4.29}, {"text": "converges to this\nminus this number.", "start": 3514.66, "duration": 3.31}, {"text": "And if this converges, then\nthis sequence of partial sums", "start": 3517.97, "duration": 5.36}, {"text": "converges to this limit\nplus this fixed number.", "start": 3523.33, "duration": 5.67}, {"text": "And that's all I'm\ngoing to write.", "start": 3529.0, "duration": 1.65}, {"text": "Now, coming back to the\nusefulness of Cauchy sequences,", "start": 3538.72, "duration": 15.74}, {"text": "this is kind of\nwhere they really", "start": 3554.46, "duration": 5.0}, {"text": "become useful is in\nthe study of series.", "start": 3559.46, "duration": 2.91}, {"text": "Because again, it's\ndifficult to sum.", "start": 3565.58, "duration": 2.41}, {"text": "So when I keep talking\nsaying the word sum a series,", "start": 3567.99, "duration": 2.81}, {"text": "I'm talking about find\nthe limit of partial sums.", "start": 3570.8, "duration": 5.055}, {"text": "But because we have this\nequivalence between Cauchy", "start": 3578.45, "duration": 2.79}, {"text": "sequences and\nconvergent sequences,", "start": 3581.24, "duration": 3.63}, {"text": "to decide if a series\nis convergent or not,", "start": 3584.87, "duration": 3.96}, {"text": "we can just decide if, in some\nsense, it's Cauchy or not.", "start": 3588.83, "duration": 5.02}, {"text": "So let me make this definition.", "start": 3593.85, "duration": 5.39}, {"text": "We say that a series x sub\nn is Cauchy if the sequence", "start": 3599.24, "duration": 10.41}, {"text": "of partial sums--", "start": 3609.65, "duration": 1.17}, {"text": "again, I'm just going to\nput an m up top because this", "start": 3610.82, "duration": 8.66}, {"text": "may start at 0 or n equals 1\nor something-- so the sequence", "start": 3619.48, "duration": 4.11}, {"text": "of partial sums is Cauchy.", "start": 3623.59, "duration": 7.73}, {"text": "And so let me just restate\nwhat we proved for sequences", "start": 3636.84, "duration": 5.67}, {"text": "in terms of series.", "start": 3642.51, "duration": 1.62}, {"text": "So we proved that every\nCauchy sequence is convergent.", "start": 3644.13, "duration": 4.15}, {"text": "So a series is Cauchy means that\nthe sequence of partial sums", "start": 3648.28, "duration": 7.73}, {"text": "is Cauchy.", "start": 3656.01, "duration": 0.78}, {"text": "But we've proven that Cauchy\nsequences are convergent.", "start": 3656.79, "duration": 3.79}, {"text": "So if this is Cauchy, then\nit's convergent and vice versa.", "start": 3660.58, "duration": 4.32}, {"text": "So based on what we've\nproven already for sequences,", "start": 3664.9, "duration": 6.99}, {"text": "it follows that--", "start": 3671.89, "duration": 1.985}, {"text": "and this just\nfollows immediately", "start": 3673.875, "duration": 1.375}, {"text": "from what we've proven\nalready, so I'm not even", "start": 3675.25, "duration": 1.958}, {"text": "going to write a proof--", "start": 3677.208, "duration": 1.672}, {"text": "a series is Cauchy if and only\nif the series is convergent--", "start": 3678.88, "duration": 7.11}, {"text": "again, because both\nare defined in terms", "start": 3688.57, "duration": 2.04}, {"text": "of the sequence of partial\nsums associated to the series.", "start": 3690.61, "duration": 3.03}, {"text": "And we've already proven the\nequivalence between Cauchy", "start": 3693.64, "duration": 2.85}, {"text": "and convergence for sequences.", "start": 3696.49, "duration": 3.54}, {"text": "Now, let me write what\nit means to be Cauchy", "start": 3710.74, "duration": 3.0}, {"text": "in a slightly different way.", "start": 3713.74, "duration": 3.435}, {"text": "And it's the following.", "start": 3723.66, "duration": 1.29}, {"text": "So before, we had that\na sequence is Cauchy,", "start": 3731.86, "duration": 5.13}, {"text": "intuitively, if the\nelements of the sequence", "start": 3736.99, "duration": 3.63}, {"text": "are getting close to each other.", "start": 3740.62, "duration": 2.07}, {"text": "Now, for a series to be\nCauchy, the intuitive way", "start": 3742.69, "duration": 3.87}, {"text": "to think about it is\nthat the tail of the sum", "start": 3746.56, "duration": 3.9}, {"text": "is getting small, is\ngetting arbitrarily", "start": 3750.46, "duration": 3.72}, {"text": "small, the tail of the\nsum being if I add up", "start": 3754.18, "duration": 3.93}, {"text": "finitely many numbers\nfar enough out.", "start": 3758.11, "duration": 2.88}, {"text": "So a series is\nCauchy if and only", "start": 3760.99, "duration": 4.48}, {"text": "if all epsilon positive there\nexist to M, a natural number,", "start": 3765.47, "duration": 7.86}, {"text": "such that for all integers\nl bigger than m, which", "start": 3773.33, "duration": 7.35}, {"text": "is bigger than or equal to\ncapital M, the sum from n", "start": 3780.68, "duration": 7.92}, {"text": "equals n plus 1\nto l of x sub n--", "start": 3788.6, "duration": 4.71}, {"text": "so this is a sum involving\nterms that are pretty far out", "start": 3793.31, "duration": 4.53}, {"text": "there, at least all\nindexed by something bigger", "start": 3797.84, "duration": 4.44}, {"text": "than or equal to capital M--", "start": 3802.28, "duration": 1.65}, {"text": "is less than epsilon.", "start": 3803.93, "duration": 1.86}, {"text": "So a series is Cauchy\nif you're adding up", "start": 3805.79, "duration": 3.39}, {"text": "smaller and smaller pieces, not\nindividual pieces but actual", "start": 3809.18, "duration": 4.29}, {"text": "adding those up.", "start": 3813.47, "duration": 1.29}, {"text": "So I'll leave it to you to do--", "start": 3824.74, "duration": 5.16}, {"text": "they're both pretty\neasy-- but this direction,", "start": 3829.9, "duration": 3.25}, {"text": "I'll leave it to\nyou as an exercise.", "start": 3833.15, "duration": 1.85}, {"text": "And it'll follow\nimmediately from what", "start": 3835.0, "duration": 4.29}, {"text": "I'm going to write for,\nessentially, this direction.", "start": 3839.29, "duration": 3.57}, {"text": "So let's suppose-- and\nlet's make things concrete,", "start": 3846.45, "duration": 8.2}, {"text": "starting somewhere-- let's\nsuppose this sum is Cauchy.", "start": 3854.65, "duration": 2.535}, {"text": "And we want to prove now\nthat it has this property.", "start": 3861.08, "duration": 4.23}, {"text": "So let epsilon be positive.", "start": 3865.31, "duration": 5.3}, {"text": "We now want to produce\nsome capital number", "start": 3870.61, "duration": 1.75}, {"text": "M so that this holds.", "start": 3872.36, "duration": 2.01}, {"text": "So since the sequence of\npartial sums s sub m is Cauchy--", "start": 3883.73, "duration": 8.49}, {"text": "that's what it means for\nthe series to be Cauchy--", "start": 3892.22, "duration": 3.99}, {"text": "there exists a natural\nnumber, capital M,", "start": 3896.21, "duration": 4.14}, {"text": "such that for all M\nbigger than or equal to M0", "start": 3900.35, "duration": 9.75}, {"text": "and l bigger than or equal\nto M0, s sub m minus s", "start": 3910.1, "duration": 13.5}, {"text": "sub l is less than epsilon.", "start": 3923.6, "duration": 2.04}, {"text": "So we're actually going to\ntake capital M to be this M0.", "start": 3931.72, "duration": 4.47}, {"text": "Choose M to be M0.", "start": 3936.19, "duration": 8.65}, {"text": "Then, if l is\nbigger than m, which", "start": 3944.84, "duration": 6.77}, {"text": "is bigger than or equal to\nM, which is equal to M0,", "start": 3951.61, "duration": 6.12}, {"text": "if I look at this sum from n\nequals m plus 1 to l x sub n,", "start": 3957.73, "duration": 7.98}, {"text": "I can write--", "start": 3965.71, "duration": 2.568}, {"text": "so this is absolute value.", "start": 3968.278, "duration": 1.272}, {"text": "So in fact, let me remove\nthe absolute value so", "start": 3973.73, "duration": 2.09}, {"text": "that this becomes pretty clear.", "start": 3975.82, "duration": 1.71}, {"text": "I can write this sum\nas the l-th partial sum", "start": 3980.54, "duration": 4.29}, {"text": "minus the n-th partial sum.", "start": 3984.83, "duration": 3.42}, {"text": "Because the l-th partial sum\nsums from n equals 1 up to l.", "start": 3988.25, "duration": 4.32}, {"text": "The m-th partial sums\nfrom n equals 1 up to m.", "start": 3992.57, "duration": 3.27}, {"text": "So the sum containing only the\nterms between n plus 1 and l", "start": 3995.84, "duration": 4.05}, {"text": "is the difference of these guys.", "start": 3999.89, "duration": 1.395}, {"text": "So now I'll put it\non absolute values.", "start": 4003.91, "duration": 3.79}, {"text": "And this thing,\nbecause l and m are", "start": 4007.7, "duration": 2.46}, {"text": "bigger than or equal to capital\nM, which is equal to M0,", "start": 4010.16, "duration": 3.09}, {"text": "and because I have\nthis inequality,", "start": 4013.25, "duration": 2.4}, {"text": "this is less than epsilon.", "start": 4015.65, "duration": 1.83}, {"text": "And the converse\ndirection, again, it", "start": 4017.48, "duration": 1.74}, {"text": "follows immediately,\nessentially,", "start": 4019.22, "duration": 1.74}, {"text": "from this equality here.", "start": 4020.96, "duration": 3.54}, {"text": "So to check whether\na series converges,", "start": 4028.57, "duration": 2.97}, {"text": "I don't have to somehow come up\nwith a limit for this series,", "start": 4031.54, "duration": 6.69}, {"text": "a sum for this series.", "start": 4038.23, "duration": 3.21}, {"text": "I can just prove\nthat the tail can", "start": 4041.44, "duration": 3.72}, {"text": "be made arbitrarily\nsmall, as long", "start": 4045.16, "duration": 1.95}, {"text": "as I go far enough\nout in the series.", "start": 4047.11, "duration": 3.105}, {"text": "And from this, we get a pretty\nsimple elementary property,", "start": 4065.97, "duration": 7.98}, {"text": "so a theorem.", "start": 4073.95, "duration": 0.78}, {"text": "If a series converges, then\nthis implies that the limit as n", "start": 4080.19, "duration": 14.98}, {"text": "goes to infinity of x sub\nn of the sequence you used", "start": 4095.17, "duration": 5.88}, {"text": "to obtain the series equals 0.", "start": 4101.05, "duration": 3.36}, {"text": "So this should fall in line\nwith a series being convergent", "start": 4104.41, "duration": 6.9}, {"text": "if and only if it satisfies this\nproperty here, which is somehow", "start": 4111.31, "duration": 3.87}, {"text": "saying the tail of the sum is\ngetting smaller and smaller,", "start": 4115.18, "duration": 4.719}, {"text": "which means you can't be adding\nup big things as you go on", "start": 4119.899, "duration": 5.75}, {"text": "out in the series.", "start": 4125.649, "duration": 1.516}, {"text": "So proof.", "start": 4133.399, "duration": 0.541}, {"text": "So we'll show this by a\nsimple epsilon M definition.", "start": 4139.02, "duration": 10.549}, {"text": "So suppose xn converges.", "start": 4149.569, "duration": 6.96}, {"text": "Then xn the series is Cauchy.", "start": 4159.56, "duration": 5.945}, {"text": "And now I'm going to verify this\nusing the epsilon M definition.", "start": 4168.87, "duration": 4.59}, {"text": "Let epsilon be positive.", "start": 4176.76, "duration": 1.44}, {"text": "Since xn is Cauchy,\nthis implies that there", "start": 4180.76, "duration": 6.36}, {"text": "exists a natural number M0\nsuch that for all l bigger", "start": 4187.12, "duration": 7.38}, {"text": "than or equal to m\nbigger than or equal M0,", "start": 4194.5, "duration": 4.11}, {"text": "I have that condition there,\nsum from n equals m plus 1", "start": 4198.61, "duration": 9.4}, {"text": "to l x sub n is\nless than epsilon.", "start": 4208.01, "duration": 3.66}, {"text": "Choose M to be M0 plus 1.", "start": 4220.74, "duration": 5.06}, {"text": "So why M0 plus 1\nbut not exactly M0?", "start": 4229.16, "duration": 2.76}, {"text": "Just because, basically,\nwhat I'm going to do", "start": 4231.92, "duration": 2.76}, {"text": "is I'm going to take l\nto be equal to m plus 1.", "start": 4234.68, "duration": 2.85}, {"text": "And the index gets shifted by 1.", "start": 4237.53, "duration": 2.91}, {"text": "Then if m is bigger\nthan or equal to M,", "start": 4243.32, "duration": 5.52}, {"text": "I get that the absolute\nvalue of x sub m--", "start": 4248.84, "duration": 3.3}, {"text": "maybe instead of\nsaying limit as n", "start": 4255.38, "duration": 3.57}, {"text": "goes to infinity, I'll write\nlimit as m goes to infinity,", "start": 4258.95, "duration": 2.68}, {"text": "it's just a change in\nthe dummy variable-- this", "start": 4261.63, "duration": 2.21}, {"text": "is equal to the sum from\nn equals m to m x sub n.", "start": 4263.84, "duration": 11.88}, {"text": "And so I've shifted this.", "start": 4275.72, "duration": 2.11}, {"text": "So now little m is bigger than\nor equal to capital M0 plus 1.", "start": 4277.83, "duration": 5.6}, {"text": "So you could write this as,\nif you like, m minus 1 plus 1.", "start": 4283.43, "duration": 4.17}, {"text": "So little m minus 1 is\nbigger than or equal to M0.", "start": 4287.6, "duration": 4.56}, {"text": "So by this inequality,\nthis is less than epsilon.", "start": 4292.16, "duration": 2.64}, {"text": "So we see that if a series\nconverges the terms,", "start": 4312.96, "duration": 5.19}, {"text": "the individual terms, x\nsub n must converge to 0.", "start": 4318.15, "duration": 6.03}, {"text": "So there's another reason why\nthis series minus 1 to the n", "start": 4324.18, "duration": 4.5}, {"text": "does not converge.", "start": 4328.68, "duration": 1.98}, {"text": "Because those terms\ndo not converge.", "start": 4330.66, "duration": 1.53}, {"text": "And this also tells us that\nfor this geometric series, when", "start": 4335.64, "duration": 4.08}, {"text": "r is greater than or equal\nto 1 in absolute value,", "start": 4339.72, "duration": 3.802}, {"text": "the series does not converge.", "start": 4343.522, "duration": 1.208}, {"text": "It does not converge.", "start": 4354.25, "duration": 2.64}, {"text": "And the proof is--", "start": 4356.89, "duration": 0.78}, {"text": "and we proved this, in fact,\nI think, a few lectures ago,", "start": 4361.24, "duration": 6.71}, {"text": "as well, that if the absolute\nvalue of r is bigger than 1,", "start": 4367.95, "duration": 5.79}, {"text": "then the limit as n goes\nto infinity of r to the n,", "start": 4373.74, "duration": 5.1}, {"text": "this limit does not exist.", "start": 4378.84, "duration": 3.56}, {"text": "We showed it's, in\nfact, unbounded.", "start": 4385.55, "duration": 3.39}, {"text": "r to the n is an\nunbounded sequence.", "start": 4388.94, "duration": 6.23}, {"text": "So it does not convert.", "start": 4395.17, "duration": 6.71}, {"text": "So I'm using that\ntheorem over there", "start": 4401.88, "duration": 3.21}, {"text": "in a little bit roundabout way.", "start": 4405.09, "duration": 1.35}, {"text": "Let me restate this\ntheorem over here.", "start": 4417.89, "duration": 1.68}, {"text": "This theorem says if\nthe series converges,", "start": 4419.57, "duration": 6.55}, {"text": "then this limit equals 0.", "start": 4426.12, "duration": 4.49}, {"text": "Now, this statement is logically\nequivalent to the negation", "start": 4430.61, "duration": 6.15}, {"text": "of the converse, or there's\nan actual word for that,", "start": 4436.76, "duration": 5.76}, {"text": "but I can't remember--", "start": 4442.52, "duration": 1.95}, {"text": "namely that the negation of this\nimplies the negation of this.", "start": 4444.47, "duration": 8.43}, {"text": "So a logically equivalent way\nto rewrite that statement over", "start": 4452.9, "duration": 6.06}, {"text": "there is that if this\nlimit does not equal to 0--", "start": 4458.96, "duration": 12.94}, {"text": "so if it doesn't exist at\nall, that's also fine--", "start": 4471.9, "duration": 4.68}, {"text": "this implies that\ndoes not converge.", "start": 4476.58, "duration": 6.57}, {"text": "So this restatement of\nthe theorem over there", "start": 4483.15, "duration": 4.92}, {"text": "is really what I used here.", "start": 4488.07, "duration": 3.84}, {"text": "All right.", "start": 4496.35, "duration": 0.5}, {"text": "And I think I'll stop there.", "start": 4496.85, "duration": 2.59}, {"text": "Next time, we'll see\nthat this theorem here", "start": 4499.44, "duration": 4.7}, {"text": "is a one-way street.", "start": 4504.14, "duration": 1.39}, {"text": "And I think you covered\nthis example in, probably,", "start": 4505.53, "duration": 2.93}, {"text": "calculus, namely that\none-way street in the sense", "start": 4508.46, "duration": 3.72}, {"text": "that if x then converges,\nthen this limit is 0.", "start": 4512.18, "duration": 3.63}, {"text": "But the converse does not hold.", "start": 4515.81, "duration": 2.22}, {"text": "Namely, it is not true\nthat if this limit", "start": 4518.03, "duration": 3.93}, {"text": "is 0, then this converges.", "start": 4521.96, "duration": 3.48}, {"text": "And we'll see the famed\nharmonic series next time.", "start": 4525.44, "duration": 6.23}]
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+[{"text": "MARKUS KLUTE: Welcome back\nto 8.20, special relativity.", "start": 12.98, "duration": 2.58}, {"text": "Let's start here\nwith a short summary.", "start": 15.56, "duration": 2.86}, {"text": "We have seen through\nexperimental measurements", "start": 18.42, "duration": 2.09}, {"text": "that there is no ether, that\nelectromagnetic waves travels", "start": 20.51, "duration": 4.11}, {"text": "through vacuum.", "start": 24.62, "duration": 2.31}, {"text": "We have discussed the concept of\nthe relativity of simultaneity,", "start": 26.93, "duration": 5.25}, {"text": "meaning that two events\nmight occur simultaneous", "start": 32.18, "duration": 4.14}, {"text": "to one reference-- in\none reference frame,", "start": 36.32, "duration": 1.77}, {"text": "to one observer, while\nthey're not to another.", "start": 38.09, "duration": 4.32}, {"text": "In the last two videos,\nwe looked at clocks.", "start": 42.41, "duration": 3.06}, {"text": "And we've seen that\nmoving clocks run slow.", "start": 45.47, "duration": 2.67}, {"text": "We've also seen that moving\nobjects appear smaller.", "start": 48.14, "duration": 3.84}, {"text": "They're lengths contract.", "start": 51.98, "duration": 2.42}, {"text": "We found that the\ntime of a moving clock", "start": 54.4, "duration": 5.94}, {"text": "is related to the time\nin the clock at rest", "start": 60.34, "duration": 3.3}, {"text": "with a gamma factor\nbecause it's time dilation.", "start": 63.64, "duration": 3.21}, {"text": "And, for the length, we\nhave seen that there is a 1", "start": 66.85, "duration": 2.67}, {"text": "over gamma dependency,\nlength contraction.", "start": 69.52, "duration": 3.78}, {"text": "The entire discussion was\nbased on Einstein's postulates.", "start": 73.3, "duration": 3.81}, {"text": "We simply used\nEinstein's postulates.", "start": 77.11, "duration": 2.46}, {"text": "And then we looked at\nexperiments of clocks.", "start": 79.57, "duration": 3.3}, {"text": "Now, you might argue that\nthe setup of the clock", "start": 82.87, "duration": 2.07}, {"text": "is actually what's\ntricking us here,", "start": 84.94, "duration": 1.86}, {"text": "but I can tell you\nthat is not the case.", "start": 86.8, "duration": 1.9}, {"text": "As you have seen for\nthe muon, the muon", "start": 88.7, "duration": 1.625}, {"text": "doesn't know about\noptical clocks.", "start": 90.325, "duration": 1.785}, {"text": "It just decays based\non its own properties.", "start": 92.11, "duration": 4.44}, {"text": "I think it's fair to say that\nPoincar\u00e9 and Lorentz came", "start": 96.55, "duration": 3.18}, {"text": "to similar conclusions about\nthe same time as Einstein did.", "start": 99.73, "duration": 4.85}, {"text": "Delta t at rest and delta L at\nrest, the time and the length,", "start": 104.58, "duration": 4.08}, {"text": "are also sometimes called\nthe proper time and length.", "start": 108.66, "duration": 3.72}, {"text": "In German-- and I actually\nprefer this a bit--", "start": 112.38, "duration": 2.73}, {"text": "we use the word eigen,\nwhich means own.", "start": 115.11, "duration": 2.61}, {"text": "So it's basically the time,\nthe own time of the object,", "start": 117.72, "duration": 3.39}, {"text": "the object being addressed.", "start": 121.11, "duration": 3.57}, {"text": "So we can now ask, [INAUDIBLE]\nseen time is suspect.", "start": 124.68, "duration": 4.92}, {"text": "What is not suspect?", "start": 129.6, "duration": 1.17}, {"text": "What are the observables\nwhich are invariant?", "start": 130.77, "duration": 3.6}, {"text": "And, by this, I mean\nthe observables,", "start": 134.37, "duration": 2.048}, {"text": "when we have two\ndifferent reference frames", "start": 136.418, "duration": 1.792}, {"text": "and we have a conversation,\nwe do actually", "start": 138.21, "duration": 2.19}, {"text": "agree in a conversation\nabout an observation we have.", "start": 140.4, "duration": 7.074}, {"text": "We have seen we\ncannot agree on time,", "start": 147.474, "duration": 2.396}, {"text": "and we cannot agree on the\nlength in the direction", "start": 149.87, "duration": 2.61}, {"text": "in which we are moving.", "start": 152.48, "duration": 2.22}, {"text": "So can I ask, for\nexample, what happens", "start": 154.7, "duration": 1.95}, {"text": "to the width or the height?", "start": 156.65, "duration": 3.27}, {"text": "If I put a train on a train\ntrack and it's fast moving,", "start": 159.92, "duration": 3.57}, {"text": "is that contracted or even\nexpanded or changing at all?", "start": 163.49, "duration": 4.0}, {"text": "The answer is no.", "start": 167.49, "duration": 1.31}, {"text": "Similarly, if I put a\ntrain track on a track", "start": 168.8, "duration": 3.06}, {"text": "and I go very fast\ninto a tunnel,", "start": 171.86, "duration": 2.91}, {"text": "does the height of\nthe tunnel change?", "start": 174.77, "duration": 2.53}, {"text": "Also here the answer is no.", "start": 177.3, "duration": 2.37}, {"text": "And we can verify this\nlater quantitatively.", "start": 179.67, "duration": 6.11}, {"text": "In summary, transverse\ndimensions are not affected.", "start": 185.78, "duration": 3.0}, {"text": "They are not suspect.", "start": 188.78, "duration": 1.38}, {"text": "We can agree in a\nconversation of two people", "start": 190.16, "duration": 2.7}, {"text": "in different reference\nframes about the height", "start": 192.86, "duration": 2.76}, {"text": "and the width of a train.", "start": 195.62, "duration": 2.01}, {"text": "That's good.", "start": 197.63, "duration": 0.79}, {"text": "But what else is invariant?", "start": 198.42, "duration": 3.04}, {"text": "So here I want you to\nconsider the time and distance", "start": 201.46, "duration": 2.49}, {"text": "between two events or\nmaybe even three events", "start": 203.95, "duration": 2.88}, {"text": "observed from different\nreference frames.", "start": 206.83, "duration": 2.4}, {"text": "And we introduce or reintroduce\nour characters Alice and Bob", "start": 209.23, "duration": 3.51}, {"text": "and add Carol to this.", "start": 212.74, "duration": 1.21}, {"text": "So we're going to have three\nreference frames of three", "start": 213.95, "duration": 3.23}, {"text": "observers in this discussion.", "start": 217.18, "duration": 3.69}, {"text": "So I want you to look\nat this one here.", "start": 220.87, "duration": 1.72}, {"text": "So assume that Bob\nhas a clock, and it's", "start": 222.59, "duration": 3.5}, {"text": "moving with a velocity v. And\nAlice is observing Bob's clock.", "start": 226.09, "duration": 5.66}, {"text": "We have done this before.", "start": 231.75, "duration": 1.72}, {"text": "Now, we want to also\nadd Carol to this.", "start": 233.47, "duration": 2.28}, {"text": "And Carol is moving with\nthree times the velocity", "start": 235.75, "duration": 2.85}, {"text": "and is also observing\nBob's clock.", "start": 238.6, "duration": 3.15}, {"text": "What I want you to do is\nlook at this property here.", "start": 241.75, "duration": 7.22}, {"text": "So we have seen that\nthe height is invariant.", "start": 248.97, "duration": 3.59}, {"text": "So let's look at what\nhappens if I calculate", "start": 252.56, "duration": 2.52}, {"text": "2 times the height squared, and\nI use x and t, time and space,", "start": 255.08, "duration": 5.939}, {"text": "in order to express\nthe height, all right?", "start": 261.019, "duration": 3.151}, {"text": "Again, this is an opportunity to\nstop the clock, stop the video,", "start": 264.17, "duration": 5.31}, {"text": "and work this out\non a piece of paper.", "start": 269.48, "duration": 4.35}, {"text": "So it turns out\nit's not that hard.", "start": 273.83, "duration": 2.97}, {"text": "We basically find that 4\ntimes the height squared", "start": 276.8, "duration": 2.61}, {"text": "is equal to--", "start": 279.41, "duration": 1.315}, {"text": "maybe it is hard--", "start": 280.725, "duration": 2.185}, {"text": "c squared times t\nsquared minus x squared.", "start": 282.91, "duration": 2.97}, {"text": "And, since the height\nis an invariant,", "start": 285.88, "duration": 2.94}, {"text": "this property, c squared,\nthe speed of light squared,", "start": 288.82, "duration": 3.63}, {"text": "times the time squared minus\nx squared, is invariant.", "start": 292.45, "duration": 3.87}, {"text": "So we can think about them\nas delta t and delta x.", "start": 296.32, "duration": 4.11}, {"text": "When we look at the difference\nin time and the difference", "start": 300.43, "duration": 3.03}, {"text": "in space between two events--", "start": 303.46, "duration": 1.59}, {"text": "Professor Klute\nentered the class.", "start": 308.09, "duration": 2.01}, {"text": "And, at the other\nend of the class,", "start": 310.1, "duration": 1.47}, {"text": "Professor Klute exploded.", "start": 311.57, "duration": 2.01}, {"text": "If I do the delta t and the\ndelta x between the two--", "start": 313.58, "duration": 3.3}, {"text": "we square them and\nsubtract them--", "start": 316.88, "duration": 2.4}, {"text": "that is an observation\nwe can all agree on.", "start": 319.28, "duration": 2.4}, {"text": "Whether or not you're\nstationary in the classroom", "start": 321.68, "duration": 2.58}, {"text": "or you're passing by really\nquickly with your spacecraft,", "start": 324.26, "duration": 3.18}, {"text": "that observation is\nsomething we can agree on.", "start": 327.44, "duration": 2.8}, {"text": "And it's invariant.", "start": 330.24, "duration": 1.1}, {"text": "This property is called\nthe invariant interval.", "start": 331.34, "duration": 4.25}]
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+[{"text": "The following content is\nprovided by MIT OpenCourseWare", "start": 1.0, "duration": 2.0}, {"text": "under a Creative", "start": 3.0, "duration": 1.0}, {"text": "Commons license.", "start": 4.0, "duration": 1.0}, {"text": "Additional information\nabout our license and MIT", "start": 5.0, "duration": 4.0}, {"text": "OpenCourseWare in general, is\navailable at ocw.mit.edu.", "start": 9.0, "duration": 5.0}, {"text": "PROFESSOR:", "start": 14.0, "duration": 1.0}, {"text": "Good afternoon.", "start": 15.0, "duration": 4.0}, {"text": "Now that all you turkeys are\nback from Thanksgiving.", "start": 26.0, "duration": 4.0}, {"text": "I shouldn't have said that.", "start": 30.0, "duration": 1.0}, {"text": "How was Thanksgiving?", "start": 31.0, "duration": 3.0}, {"text": "Good.", "start": 34.0, "duration": 3.0}, {"text": "As I'm wrapping up the sleep\nand dreams thing, I should look", "start": 37.0, "duration": 4.0}, {"text": "around and see whether people\nlook like they're awake.", "start": 41.0, "duration": 4.0}, {"text": "How many people discharged a\nsubstantial amount of their", "start": 45.0, "duration": 3.0}, {"text": "sleep debt over the\nlast few days?", "start": 48.0, "duration": 5.0}, {"text": "Good.\nThe rest of you are\nstill rolling around.", "start": 53.0, "duration": 0.0}, {"text": "I am going -- I'm going,\nbut I'm coming back.", "start": 58.0, "duration": 5.0}, {"text": "I think I'm going to depart a\nlittle from the organization of", "start": 67.0, "duration": 6.0}, {"text": "the lecture that's on the\nlecture notes, and I will trust", "start": 73.0, "duration": 5.0}, {"text": "on your talents to figure out\nwhere -- I might even point out", "start": 78.0, "duration": 5.0}, {"text": "where I've gone to -- but I'm\ngoing to re-organize things a", "start": 83.0, "duration": 4.0}, {"text": "bit, because it occurred to me\nthat I can organize at least", "start": 87.0, "duration": 5.0}, {"text": "the first part of the lecture\nin the form of a sort of a", "start": 92.0, "duration": 10.0}, {"text": "summary statement about Freud,\nwho I'm going to abandon", "start": 102.0, "duration": 4.0}, {"text": "fairly shortly here.", "start": 106.0, "duration": 2.0}, {"text": "And I can work two examples --\none of them about dreams and", "start": 108.0, "duration": 5.0}, {"text": "one of them about abnormal\npsych, where Freud or Freud's", "start": 113.0, "duration": 9.0}, {"text": "followers are wrong\nin both cases.", "start": 122.0, "duration": 2.0}, {"text": "But in one case, we can do this\nbusiness that I've been doing", "start": 124.0, "duration": 5.0}, {"text": "for the last few lectures of\nsaying look, we can salvage", "start": 129.0, "duration": 2.0}, {"text": "something important out of\nFreud's ideas, and in the other", "start": 131.0, "duration": 5.0}, {"text": "case, which will turn out to be\nthe abnormal psych case, we'll", "start": 136.0, "duration": 3.0}, {"text": "say that, in this case, Freud's\nfollowers are simply wrong.", "start": 139.0, "duration": 4.0}, {"text": "And have been superceded\nby later work.", "start": 143.0, "duration": 8.0}, {"text": "So let me start by picking\nup in sleep and dreamland", "start": 151.0, "duration": 5.0}, {"text": "talking about dreams.", "start": 156.0, "duration": 6.0}, {"text": "Well, I won't ask if anybody\nhad any good dreams over the", "start": 162.0, "duration": 3.0}, {"text": "course of their catching up\non sleep over Thanksgiving.", "start": 165.0, "duration": 4.0}, {"text": "I know what I'll ask.", "start": 172.0, "duration": 1.0}, {"text": "I will ask how many people\ndid sleep and dream", "start": 173.0, "duration": 3.0}, {"text": "stuff in recitation?", "start": 176.0, "duration": 2.0}, {"text": "Not many.", "start": 178.0, "duration": 1.0}, {"text": "OK.\nHow many people can remember?", "start": 179.0, "duration": 0.0}, {"text": "Not many.", "start": 182.0, "duration": 1.0}, {"text": "Oh, good, good,\nthat's encouraging.", "start": 183.0, "duration": 2.0}, {"text": "All right, that allows me to\nask one of the things that", "start": 188.0, "duration": 6.0}, {"text": "tends to surprise people\nsometimes is that there's a", "start": 194.0, "duration": 3.0}, {"text": "fair degree of commonality\nin at least some of the", "start": 197.0, "duration": 4.0}, {"text": "dreams that people have.", "start": 201.0, "duration": 2.0}, {"text": "They seem like such\nidiosyncratic personalized", "start": 203.0, "duration": 5.0}, {"text": "stories, that it's surprising\nto discover that some of the", "start": 208.0, "duration": 3.0}, {"text": "plot lines go across\nindividuals.", "start": 211.0, "duration": 6.0}, {"text": "It's a weird state, right.", "start": 217.0, "duration": 1.0}, {"text": "I mean it's clear there\nare weird aspects of", "start": 218.0, "duration": 3.0}, {"text": "the sleeping state.", "start": 221.0, "duration": 2.0}, {"text": "The normal laws of physics seem\nto be suspendable -- you can", "start": 223.0, "duration": 7.0}, {"text": "fly sometimes, do\nthings like that.", "start": 230.0, "duration": 4.0}, {"text": "You can fall for hours and\nhours and never hit the ground.", "start": 234.0, "duration": 6.0}, {"text": "The normal laws of reality\ntesting or the awake state of", "start": 240.0, "duration": 4.0}, {"text": "reality testing seems to be up,\nbecause you can fly and it", "start": 244.0, "duration": 3.0}, {"text": "doesn't strike you as weird.", "start": 247.0, "duration": 2.0}, {"text": "When you wake up you say that\nwas weird, but if you think", "start": 249.0, "duration": 2.0}, {"text": "about it, while you were flying\naround or doing whatever other", "start": 251.0, "duration": 4.0}, {"text": "video game kind of thing you\nwere doing in your dreams,", "start": 255.0, "duration": 2.0}, {"text": "yeah, that was just\nthe way things were.", "start": 257.0, "duration": 3.0}, {"text": "If you have the same problem\nwith reality testing, when", "start": 260.0, "duration": 4.0}, {"text": "you're awake you end up in the\npart of the course on abnormal", "start": 264.0, "duration": 8.0}, {"text": "psych that we'll get\nto in a minute.", "start": 272.0, "duration": 1.0}, {"text": "It's diagnostic of having a\nvariety of forms of mental", "start": 273.0, "duration": 5.0}, {"text": "illness if you cannot tell\nthe difference between dream", "start": 278.0, "duration": 5.0}, {"text": "state and awake state,\nthat's not healthy.", "start": 283.0, "duration": 3.0}, {"text": "When you're dreaming you\ncan't tell, but you're", "start": 286.0, "duration": 2.0}, {"text": "not clinically insane.", "start": 288.0, "duration": 2.0}, {"text": "There was one other sense in\nwhich it was different from the", "start": 295.0, "duration": 4.0}, {"text": "awake state that I wanted to\nmake sure that I mentioned, but", "start": 299.0, "duration": 3.0}, {"text": "now I don't remember\nwhat it is.", "start": 302.0, "duration": 2.0}, {"text": "Oh, yes, just to point out that\nthe transfer from experience to", "start": 304.0, "duration": 6.0}, {"text": "episodic memory does not\nwork well for dreaming.", "start": 310.0, "duration": 4.0}, {"text": "This is why you forget your\ndreams so readily is that you", "start": 314.0, "duration": 3.0}, {"text": "know when you wake up that\ndream is just sort of there", "start": 317.0, "duration": 3.0}, {"text": "sitting around in some sort of\nshort-term buffer, and if you", "start": 320.0, "duration": 2.0}, {"text": "don't do something like write\nit down or repeat it yourself", "start": 322.0, "duration": 3.0}, {"text": "you discover that those normal\nmechanisms that take your", "start": 325.0, "duration": 6.0}, {"text": "experiences and transfer them\ninto some sort of", "start": 331.0, "duration": 3.0}, {"text": "long-term memory, they're\njust not working.", "start": 334.0, "duration": 5.0}, {"text": "So, that said, let's see if\nwe can conjure up--yup?", "start": 339.0, "duration": 5.0}, {"text": "AUDIENCE: Especially when\npeople say they know", "start": 344.0, "duration": 3.0}, {"text": "they're dreaming.", "start": 347.0, "duration": 2.0}, {"text": "PROFESSOR: All the stuff about\ndifferent states of sleep and", "start": 349.0, "duration": 6.0}, {"text": "awakeness should be seen as\nnot absolutely categorical.", "start": 355.0, "duration": 5.0}, {"text": "So there are these borderline\nstates -- the sort of jargony", "start": 360.0, "duration": 3.0}, {"text": "term is liminal states where\nyou're in between being", "start": 363.0, "duration": 5.0}, {"text": "asleep and awake.", "start": 368.0, "duration": 4.0}, {"text": "In the course of a normal\nnight's sleep, you'd probably", "start": 372.0, "duration": 2.0}, {"text": "wake up out of REM sleep and\ndifferent bits of you are", "start": 374.0, "duration": 3.0}, {"text": "coming online at different\ntimes, and you may be aware,", "start": 377.0, "duration": 4.0}, {"text": "still asleep, but I'm\nnot quite asleep.", "start": 381.0, "duration": 2.0}, {"text": "How many people have had the\nexperience of saying I'm waking", "start": 383.0, "duration": 3.0}, {"text": "up here and I want to know\nhow the story comes out?", "start": 386.0, "duration": 6.0}, {"text": "Yeah, yeah.", "start": 392.0, "duration": 2.0}, {"text": "It's always cause you're\nwaking up at the good parts.", "start": 394.0, "duration": 2.0}, {"text": "Or how many of you have the\nother experience, which I think", "start": 396.0, "duration": 3.0}, {"text": "maybe what you're getting to\nwhich is I'm asleep here and", "start": 399.0, "duration": 4.0}, {"text": "this dream is not a good dream\nand it's time to wake", "start": 403.0, "duration": 3.0}, {"text": "up out of this dream.", "start": 406.0, "duration": 1.0}, {"text": "I'm going to wake myself up.", "start": 407.0, "duration": 2.0}, {"text": "Fewer.", "start": 409.0, "duration": 1.0}, {"text": "Now, are there people here\nwho are experts at what's", "start": 410.0, "duration": 4.0}, {"text": "known as lucid dreaming?", "start": 414.0, "duration": 2.0}, {"text": "Lucid dreaming is a sort of a\nhalfway state where people", "start": 416.0, "duration": 4.0}, {"text": "claim to be able to control the\nplot line of their dreams.", "start": 420.0, "duration": 9.0}, {"text": "There are books in the\nbookstore that will both claim", "start": 429.0, "duration": 3.0}, {"text": "that they can train you to do\nthis, and maybe you", "start": 432.0, "duration": 2.0}, {"text": "can, I don't know.", "start": 434.0, "duration": 1.0}, {"text": "It sounds good.", "start": 435.0, "duration": 1.0}, {"text": "I mean all those people who\nsaid, oh man, I woke up and", "start": 436.0, "duration": 4.0}, {"text": "I wanted to hear out\nthe thing came out.", "start": 440.0, "duration": 2.0}, {"text": "If you'd go and train yourself\nto be a lucid dreamer maybe", "start": 442.0, "duration": 3.0}, {"text": "you can go and keep it going.", "start": 445.0, "duration": 2.0}, {"text": "I have these extremely\nfrustrating dreams that I'm", "start": 450.0, "duration": 4.0}, {"text": "sure a good analyst would have\na field day with, but I choose", "start": 454.0, "duration": 5.0}, {"text": "to think that they are\nbasically nice, simple,", "start": 459.0, "duration": 3.0}, {"text": "transparent dreams.", "start": 462.0, "duration": 3.0}, {"text": "I like to ski, I dream about\nskiing, but in my dreams I", "start": 465.0, "duration": 4.0}, {"text": "spend a great deal of time\ngetting up the mountain", "start": 469.0, "duration": 4.0}, {"text": "and I never get to ski.", "start": 473.0, "duration": 4.0}, {"text": "I get to the top and the snow\nmelts or something like that.", "start": 477.0, "duration": 4.0}, {"text": "No, I don't want to hear your\ninterpretation of what this is", "start": 481.0, "duration": 3.0}, {"text": "all really about or anything --\nI can do that, too, and make", "start": 484.0, "duration": 4.0}, {"text": "up all those good stories.", "start": 488.0, "duration": 1.0}, {"text": "But in any case, I sometimes\nthink I'm going to get one of", "start": 489.0, "duration": 4.0}, {"text": "these lucid dreaming books\nbecause dammit, before I die", "start": 493.0, "duration": 4.0}, {"text": "I'm going to get to ski\ndown that mountain.", "start": 497.0, "duration": 3.0}, {"text": "The conditions are always a\ngreat, look a lot better than", "start": 500.0, "duration": 2.0}, {"text": "they do in the northeast when\nyou actually go skiing.", "start": 502.0, "duration": 3.0}, {"text": "So, let us consider a\ncouple of plot lines.", "start": 509.0, "duration": 6.0}, {"text": "Some of the things, there's\na sort of element that show", "start": 515.0, "duration": 2.0}, {"text": "up in people's dreams.", "start": 517.0, "duration": 1.0}, {"text": "How many people have\nhad falling dreams?", "start": 518.0, "duration": 4.0}, {"text": "How how many people have\never hit the ground?", "start": 522.0, "duration": 3.0}, {"text": "Usually you don't hit the\nground, right -- you wake up", "start": 525.0, "duration": 3.0}, {"text": "just before you hit the ground.", "start": 528.0, "duration": 2.0}, {"text": "Oh, there's a whole raft of\nsort of pseudo-scientific", "start": 530.0, "duration": 5.0}, {"text": "nonsense about--.", "start": 535.0, "duration": 2.0}, {"text": "How many people have ever\nbeen killed in their dreams?", "start": 537.0, "duration": 3.0}, {"text": "A fair number.", "start": 540.0, "duration": 1.0}, {"text": "Well, that's presumably a\ncounter examples to the theory", "start": 541.0, "duration": 3.0}, {"text": "that if you die you in your\ndreams you die for real.", "start": 544.0, "duration": 4.0}, {"text": "It's one of those\ngreat assertions.", "start": 548.0, "duration": 1.0}, {"text": "How would you know\nthat was true?", "start": 549.0, "duration": 3.0}, {"text": "Right.", "start": 552.0, "duration": 1.0}, {"text": "What were your dreaming about?", "start": 553.0, "duration": 2.0}, {"text": "I don't know, I'm dead.", "start": 555.0, "duration": 1.0}, {"text": "But typically, typically people\nreport that you wake up just", "start": 558.0, "duration": 6.0}, {"text": "before you get killed by the\nwhatever it is that's", "start": 564.0, "duration": 5.0}, {"text": "going to kill you.", "start": 569.0, "duration": 1.0}, {"text": "But the plot lines get\nmore elaborate than that.", "start": 570.0, "duration": 3.0}, {"text": "How many people have had dreams\n-- this is typically a dream of", "start": 573.0, "duration": 5.0}, {"text": "grade school, the grade school\nera where you show up in school", "start": 578.0, "duration": 5.0}, {"text": "inappropriately dressed\nin some fashion.", "start": 583.0, "duration": 4.0}, {"text": "All right, anybody care to\ndescribe one of those?", "start": 587.0, "duration": 6.0}, {"text": "Sorry, I heard a--.", "start": 593.0, "duration": 3.0}, {"text": "Somebody wave a hand if you\nwant to actually tell us the", "start": 596.0, "duration": 2.0}, {"text": "-- you don't have to\ntell us your dream.", "start": 598.0, "duration": 2.0}, {"text": "It's fine.", "start": 600.0, "duration": 2.0}, {"text": "Nobody wants to-- How\ninappropriate was it?", "start": 602.0, "duration": 4.0}, {"text": "I mean it doesn't get much more\ninappropriate than I was buck", "start": 606.0, "duration": 3.0}, {"text": "naked, I suppose, which is the\nstand-- My version of it", "start": 609.0, "duration": 3.0}, {"text": "happened to be that -- I still\nvividly remember what must have", "start": 612.0, "duration": 3.0}, {"text": "been a kindergarten dream\nbecause I ended up in my", "start": 615.0, "duration": 3.0}, {"text": "kindergarten classroom of\ndriving down the street from my", "start": 618.0, "duration": 4.0}, {"text": "house to my school in my crib,\nwhich presumably, by the time I", "start": 622.0, "duration": 6.0}, {"text": "was in kindergarten I was long\nout, and I ended up in school", "start": 628.0, "duration": 4.0}, {"text": "in my crib in my pj's.", "start": 632.0, "duration": 4.0}, {"text": "All right, so you don't\nhave to tell us what", "start": 636.0, "duration": 2.0}, {"text": "you weren't wearing.", "start": 638.0, "duration": 3.0}, {"text": "There is a characteristic of\nthis dream which is that once", "start": 641.0, "duration": 6.0}, {"text": "you get there, once you end\nup in class, what happens?", "start": 647.0, "duration": 6.0}, {"text": "Anybody got any intuition about\nthe common plot line here?", "start": 653.0, "duration": 4.0}, {"text": "AUDIENCE: People\npoint and laugh.", "start": 663.0, "duration": 1.0}, {"text": "PROFESSOR: Oh, people\npoint and laugh.", "start": 664.0, "duration": 3.0}, {"text": "Do you believe it?", "start": 667.0, "duration": 0.0}, {"text": "Where's the inappropriately\ndressed crowd?", "start": 672.0, "duration": 2.0}, {"text": "Raise your hand if you were\nin the inappropriately", "start": 674.0, "duration": 1.0}, {"text": "dressed class.", "start": 675.0, "duration": 1.0}, {"text": "It's dropped, the\nnumbers are dropping.", "start": 676.0, "duration": 3.0}, {"text": "OK, not inappropriately\ndressed right now, this", "start": 679.0, "duration": 2.0}, {"text": "is in your dreams.", "start": 681.0, "duration": 1.0}, {"text": "Inappropriately dressed.", "start": 682.0, "duration": 1.0}, {"text": "How many people agreed that\nwhat happened was they", "start": 683.0, "duration": 3.0}, {"text": "pointed and laughed?", "start": 686.0, "duration": 2.0}, {"text": "No, it's only in Russia.", "start": 688.0, "duration": 3.0}, {"text": "The characteristic form of this\ndream is that nobody notices.", "start": 691.0, "duration": 6.0}, {"text": "I mean that's not to say that\nyou're weird for having the", "start": 697.0, "duration": 3.0}, {"text": "variant -- either that\nor you're making it", "start": 700.0, "duration": 1.0}, {"text": "up, I don't know.", "start": 701.0, "duration": 1.0}, {"text": "But that you would think, I\nwould think if I showed up,", "start": 702.0, "duration": 5.0}, {"text": "if I drove my crib in here,\neverybody's going to point", "start": 707.0, "duration": 3.0}, {"text": "and they're going to laugh.", "start": 710.0, "duration": 2.0}, {"text": "But they don't.", "start": 712.0, "duration": 1.0}, {"text": "This is assumed to be some sort\nof a school anxiety dream.", "start": 713.0, "duration": 4.0}, {"text": "School anxiety dreams of\nsome sort are quite common.", "start": 717.0, "duration": 3.0}, {"text": "They also morph as\nyou get older.", "start": 720.0, "duration": 2.0}, {"text": "So, how many people have had\na dream of the form where", "start": 722.0, "duration": 8.0}, {"text": "-- well, all right,\nlet's rephrase this.", "start": 730.0, "duration": 3.0}, {"text": "We'll get the form out of you.", "start": 733.0, "duration": 2.0}, {"text": "Has anybody had what they\nwould consider to be", "start": 735.0, "duration": 2.0}, {"text": "an exam anxiety dream?", "start": 737.0, "duration": 5.0}, {"text": "Anybody willing to\ndescribe that?", "start": 742.0, "duration": 1.0}, {"text": "I don't think they mostly\ninvolve being grossly", "start": 743.0, "duration": 3.0}, {"text": "inappropriately dressed.", "start": 746.0, "duration": 2.0}, {"text": "Yeah, OK.", "start": 748.0, "duration": 1.0}, {"text": "AUDIENCE: Before the psych\nmid-term I started [INAUDIBLE]", "start": 749.0, "duration": 4.0}, {"text": "psychological theories that\ndon't actually exist.", "start": 753.0, "duration": 4.0}, {"text": "PROFESSOR: Psychological\n-- that's a novel", "start": 757.0, "duration": 2.0}, {"text": "form of the dream.", "start": 759.0, "duration": 3.0}, {"text": "Any good ones?", "start": 762.0, "duration": 1.0}, {"text": "Well, I won't ask you that.", "start": 763.0, "duration": 2.0}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 765.0, "duration": 2.0}, {"text": "AUDIENCE: OK, so one version\nis the I overslept and", "start": 767.0, "duration": 4.0}, {"text": "you missed the exam.", "start": 771.0, "duration": 2.0}, {"text": "Variance thereon?", "start": 773.0, "duration": 2.0}, {"text": "Yeah.\nAUDIENCE: I slept until about\nan hour before the exam.", "start": 775.0, "duration": 0.0}, {"text": "Woke up and didn't\nstudy [INAUDIBLE].", "start": 778.0, "duration": 3.0}, {"text": "PROFESSOR: OK, I haven't\nstudied enough for the exam,", "start": 781.0, "duration": 2.0}, {"text": "and perhaps because --\nsomething is going", "start": 783.0, "duration": 3.0}, {"text": "to make it uh-oh.", "start": 786.0, "duration": 1.0}, {"text": "Yeah.", "start": 787.0, "duration": 1.0}, {"text": "They all pointed at you and\nlaughed at you, right.", "start": 788.0, "duration": 2.0}, {"text": "AUDIENCE: The exam was\nin some other language.", "start": 790.0, "duration": 3.0}, {"text": "PROFESSOR: Yeah,\nwell that happens.", "start": 793.0, "duration": 3.0}, {"text": "Yeah, the exam was in\nanother language.", "start": 796.0, "duration": 2.0}, {"text": "How many people have had the\nversion where you realize in", "start": 798.0, "duration": 5.0}, {"text": "your dream that you have an\nexam in this course and you've", "start": 803.0, "duration": 4.0}, {"text": "never been to the course?", "start": 807.0, "duration": 3.0}, {"text": "Medieval French -- I've got the\nMedieval French exam, I've", "start": 810.0, "duration": 5.0}, {"text": "never taken Medieval French.", "start": 815.0, "duration": 2.0}, {"text": "Or there are also versions of\nthis where you get to the exam", "start": 817.0, "duration": 7.0}, {"text": "and you realize that there's\nsomething about the exam -- the", "start": 824.0, "duration": 2.0}, {"text": "different language thing is a\ngood example of this where you", "start": 826.0, "duration": 3.0}, {"text": "look at the exam and you\nrealize there's no way", "start": 829.0, "duration": 1.0}, {"text": "I'm passing this exam.", "start": 830.0, "duration": 2.0}, {"text": "Not because you didn't make up\nthe right psych theory, but", "start": 832.0, "duration": 3.0}, {"text": "because I can't see the page in\nsome weird way, or sometimes --", "start": 835.0, "duration": 9.0}, {"text": "oh, somebody was telling me\nthis morning of a great version", "start": 844.0, "duration": 2.0}, {"text": "where I realize I'm going to be\nlate to the exam and it's down", "start": 846.0, "duration": 4.0}, {"text": "the other end of the infinite\ncorridor, and the infinite", "start": 850.0, "duration": 3.0}, {"text": "corridor really is infinite.", "start": 853.0, "duration": 4.0}, {"text": "You're just going\ndown it forever.", "start": 857.0, "duration": 2.0}, {"text": "Anyway, if you haven't had that\ndream don't worry, you will.", "start": 859.0, "duration": 6.0}, {"text": "When I was an undergrad\nat Princeton, somebody", "start": 865.0, "duration": 3.0}, {"text": "did a study of this.", "start": 868.0, "duration": 1.0}, {"text": "25% of the freshman class, 50%\nof the sophomore class, 75% of", "start": 869.0, "duration": 7.0}, {"text": "the junior class, and you\ncan see where this goes.", "start": 876.0, "duration": 3.0}, {"text": "It's an extremely common\ncollege era type dream.", "start": 879.0, "duration": 5.0}, {"text": "And it doesn't get\nbetter after that.", "start": 884.0, "duration": 1.0}, {"text": "All that happens is that,\nif you stay in academia,", "start": 885.0, "duration": 4.0}, {"text": "is that the form moves.", "start": 889.0, "duration": 2.0}, {"text": "Any number of my colleagues\nhave reported dreams where the", "start": 891.0, "duration": 6.0}, {"text": "-- this is the grad school\nversion coming up here -- the", "start": 897.0, "duration": 6.0}, {"text": "dream where your thesis\ncommittee comes to you and says", "start": 903.0, "duration": 4.0}, {"text": "it was a big mistake, we're\ntaking the PhD back, or that", "start": 907.0, "duration": 4.0}, {"text": "you have to take your oral\nexams over again -- the thing", "start": 911.0, "duration": 3.0}, {"text": "you crammed for months and then\nforgot all of it the next week,", "start": 914.0, "duration": 4.0}, {"text": "or something like that.", "start": 918.0, "duration": 1.0}, {"text": "And then if you end up in my\nposition actually teaching, it", "start": 919.0, "duration": 4.0}, {"text": "just flips around the exam\nanxiety dream where you have", "start": 923.0, "duration": 7.0}, {"text": "dreams where you get up in\nfront of the class and you", "start": 930.0, "duration": 3.0}, {"text": "realize Medieval French, I\ndon't know anything about", "start": 933.0, "duration": 3.0}, {"text": "Medieval French, what do you\nmean I'm supposed to talk", "start": 936.0, "duration": 2.0}, {"text": "about Medieval French\nfor the next hour?", "start": 938.0, "duration": 3.0}, {"text": "Now you may think that having\nanxiety dreams about not", "start": 941.0, "duration": 4.0}, {"text": "knowing what you're talking\nabout is not that far from", "start": 945.0, "duration": 3.0}, {"text": "reality in the case of some\nof us who -- I won't say", "start": 948.0, "duration": 4.0}, {"text": "more about that anymore.", "start": 952.0, "duration": 3.0}, {"text": "But there are these sort\nof common themes that", "start": 955.0, "duration": 4.0}, {"text": "run through dreams.", "start": 959.0, "duration": 1.0}, {"text": "People have known this forever,\nand people have attempted to", "start": 960.0, "duration": 3.0}, {"text": "interpret dreams forever.", "start": 963.0, "duration": 2.0}, {"text": "So there's dream\ninterpretation in the Bible.", "start": 965.0, "duration": 4.0}, {"text": "I'm sure in whatever culture\nyou or your ancestors came", "start": 969.0, "duration": 3.0}, {"text": "from there's a canon of\ndream interpretation.", "start": 972.0, "duration": 5.0}, {"text": "Have I mentioned Lucretius's\ngreat book De Rerum Natura,", "start": 977.0, "duration": 6.0}, {"text": "On the Nature of Things?", "start": 983.0, "duration": 3.0}, {"text": "Yeah.\nMaybe.", "start": 986.0, "duration": 0.0}, {"text": "Some people think so, some\npeople don't think so.", "start": 987.0, "duration": 2.0}, {"text": "Oh well, what you gonna do?", "start": 989.0, "duration": 3.0}, {"text": "Roman author, and it really is\nabout the nature of things.", "start": 992.0, "duration": 4.0}, {"text": "It's everything, you know, it's\n1801 and 801 and 900, and it's", "start": 996.0, "duration": 4.0}, {"text": "all rolled in one\ngreat big book.", "start": 1000.0, "duration": 3.0}, {"text": "But he's got a nice dream\ntheory in there in which he", "start": 1003.0, "duration": 3.0}, {"text": "says that lawyers dream of\ncourt cases and sailors are", "start": 1006.0, "duration": 5.0}, {"text": "wrestling with the winds and\nthings of that sort suggesting,", "start": 1011.0, "duration": 3.0}, {"text": "as Freud would later suggest\nthat every dream reflects", "start": 1014.0, "duration": 3.0}, {"text": "something about the\npreceding day.", "start": 1017.0, "duration": 4.0}, {"text": "Oh, let me say\nsomething about that.", "start": 1021.0, "duration": 3.0}, {"text": "I think I'm jumping ahead\nin my handout again.", "start": 1024.0, "duration": 2.0}, {"text": "Oh well.", "start": 1026.0, "duration": 2.0}, {"text": "This was always assumed\nanecdotally to be true.", "start": 1028.0, "duration": 4.0}, {"text": "You may have had\nthis experience.", "start": 1035.0, "duration": 1.0}, {"text": "You do something all day and\nyou dream about it all night.", "start": 1036.0, "duration": 5.0}, {"text": "There wasn't much data on this.", "start": 1044.0, "duration": 2.0}, {"text": "Bob Stickgold at Harvard Med\nhas now gone off and collected", "start": 1046.0, "duration": 5.0}, {"text": "some beautiful data on this.", "start": 1051.0, "duration": 1.0}, {"text": "What he did was he got people\nto play Tetris, a lot Tetris.", "start": 1052.0, "duration": 6.0}, {"text": "Then he sent them to bed with\nlittle wires on their head and", "start": 1058.0, "duration": 5.0}, {"text": "when they went into REM sleep\nhe kicked them -- pow -- what", "start": 1063.0, "duration": 2.0}, {"text": "are you dreaming about?", "start": 1065.0, "duration": 1.0}, {"text": "Oh man, bricks,\nthey're falling, man.", "start": 1066.0, "duration": 3.0}, {"text": "Nice clear evidence --\nof course, there's a", "start": 1072.0, "duration": 3.0}, {"text": "non-Tetris control group.", "start": 1075.0, "duration": 2.0}, {"text": "You kick them, oh I'm flying\ndown the infinite corridor.", "start": 1077.0, "duration": 2.0}, {"text": "You know, something else.", "start": 1079.0, "duration": 1.0}, {"text": "The Tetris group\ndreamed about Tetris.", "start": 1080.0, "duration": 3.0}, {"text": "The coolest thing about\nStickgold's experiment is that", "start": 1083.0, "duration": 5.0}, {"text": "he tested a population of\namnesics -- patients with the", "start": 1088.0, "duration": 4.0}, {"text": "same basic problem as HM.", "start": 1092.0, "duration": 3.0}, {"text": "Remember HM, no new\nlong-term memories.", "start": 1095.0, "duration": 3.0}, {"text": "Learn how to play Tetris?", "start": 1098.0, "duration": 1.0}, {"text": "Grr.", "start": 1099.0, "duration": 1.0}, {"text": "What are you doing?\nI'm playing Tetris.", "start": 1100.0, "duration": 0.0}, {"text": "Five minutes later.", "start": 1101.0, "duration": 1.0}, {"text": "What were you doing?", "start": 1102.0, "duration": 1.0}, {"text": "I don't know.", "start": 1103.0, "duration": 1.0}, {"text": "Right, doesn't\nremember any of this.", "start": 1104.0, "duration": 1.0}, {"text": "So he takes these amnesics,\nthey play Tetris for a while,", "start": 1105.0, "duration": 4.0}, {"text": "they're having a great time.", "start": 1109.0, "duration": 1.0}, {"text": "You send them to bed,\nyou kick them in the", "start": 1110.0, "duration": 2.0}, {"text": "middle of the night.", "start": 1112.0, "duration": 1.0}, {"text": "What are you dreaming about?", "start": 1113.0, "duration": 1.0}, {"text": "Oh, bricks, bricks, the\nbricks are falling.", "start": 1114.0, "duration": 2.0}, {"text": "They were dreaming about Tetris\neven though they didn't", "start": 1116.0, "duration": 3.0}, {"text": "remember ever having\nplayed Tetris.", "start": 1119.0, "duration": 3.0}, {"text": "That was pretty cool.", "start": 1122.0, "duration": 1.0}, {"text": "Anyway, there's now\nexperimental evidence for this", "start": 1123.0, "duration": 2.0}, {"text": "notion that your dreams\nincorporate material from", "start": 1125.0, "duration": 5.0}, {"text": "the preceding days.", "start": 1130.0, "duration": 1.0}, {"text": "Freud asserted that all dreams\nincorporated something", "start": 1131.0, "duration": 3.0}, {"text": "from the preceding day.", "start": 1134.0, "duration": 1.0}, {"text": "Is that absolutely true?", "start": 1135.0, "duration": 1.0}, {"text": "Well, that's one of those\nassertions like all snowflakes", "start": 1136.0, "duration": 6.0}, {"text": "are different, that's\nkind of hard to prove.", "start": 1142.0, "duration": 3.0}, {"text": "But certainly material\nfrom the preceding day", "start": 1145.0, "duration": 3.0}, {"text": "gets incorporated.", "start": 1148.0, "duration": 1.0}, {"text": "Is that a hand?", "start": 1149.0, "duration": 1.0}, {"text": "That is a hand.\nAUDIENCE: I was just wondering,\nso there an experiment done", "start": 1150.0, "duration": 0.0}, {"text": "where they had these\nanimals running through", "start": 1154.0, "duration": 3.0}, {"text": "the [INAUDIBLE].", "start": 1157.0, "duration": 1.0}, {"text": "PROFESSOR: Oh, yes, thank\nyou for reminding me.", "start": 1158.0, "duration": 3.0}, {"text": "AUDIENCE: I was just\nwondering that [INAUDIBLE],", "start": 1161.0, "duration": 3.0}, {"text": "when they were in,", "start": 1164.0, "duration": 2.0}, {"text": "when the [UNINTELLIGIBLE],\ntheir brains, I mean is a fMRI", "start": 1166.0, "duration": 6.0}, {"text": "where it's showing activity--", "start": 1172.0, "duration": 3.0}, {"text": "PROFESSOR: Answer's pretty\ngood, she's going to give", "start": 1175.0, "duration": 2.0}, {"text": "the rest of the story here.", "start": 1177.0, "duration": 2.0}, {"text": "None of you guys are\nfrom that lab, right?", "start": 1179.0, "duration": 3.0}, {"text": "It's done here.", "start": 1182.0, "duration": 2.0}, {"text": "So, if you look in the brain\nof, in the hippocampus of a", "start": 1184.0, "duration": 7.0}, {"text": "rat, what you discover is the\nhippocampus not only is there", "start": 1191.0, "duration": 4.0}, {"text": "encoding the rat's episodic\nmemories in some sense maybe", "start": 1195.0, "duration": 3.0}, {"text": "but, it's also serving\nas a spatial map.", "start": 1198.0, "duration": 3.0}, {"text": "So when a rat learns a maze, it\ndevelops a map of that maze, in", "start": 1201.0, "duration": 7.0}, {"text": "effect, in its hippocampus, and\nit develops cells that are", "start": 1208.0, "duration": 3.0}, {"text": "so-called place -- it's got\nplace cells and the place cells", "start": 1211.0, "duration": 3.0}, {"text": "develop responses that are\nspecific to a specific place.", "start": 1214.0, "duration": 3.0}, {"text": "So, the rat's running around in\na maze, and this cell goes off", "start": 1217.0, "duration": 4.0}, {"text": "right here -- nananana -- go\nover here, different cell goes", "start": 1221.0, "duration": 3.0}, {"text": "off -- nananana -- go over\nhere, different cell goes off.", "start": 1224.0, "duration": 3.0}, {"text": "And as the rat learns the maze,\nyou, the experimenter, can", "start": 1227.0, "duration": 3.0}, {"text": "watch the rat learning this\nbecause you can watch cells in", "start": 1230.0, "duration": 4.0}, {"text": "the hippocampus lighting\nup in order, in effect.", "start": 1234.0, "duration": 4.0}, {"text": "So now the rat does this\nall day -- nananana.", "start": 1238.0, "duration": 2.0}, {"text": "OK, the rat goes to sleep,\nthe rat goes into REM sleep.", "start": 1240.0, "duration": 3.0}, {"text": "All mammalian species, except\nfor the spiny anteater -- don't", "start": 1243.0, "duration": 4.0}, {"text": "ask me why I know that -- all\nmammalian species", "start": 1247.0, "duration": 3.0}, {"text": "have REM sleep.", "start": 1250.0, "duration": 1.0}, {"text": "So you kick the rat, you\nask the rat what he", "start": 1251.0, "duration": 2.0}, {"text": "was dreaming about.", "start": 1253.0, "duration": 2.0}, {"text": "Rat doesn't say nothing.", "start": 1255.0, "duration": 3.0}, {"text": "But, if you're recording from\nhis hippocampus while he's", "start": 1258.0, "duration": 3.0}, {"text": "asleep, what you see is the\nsame cells lighting", "start": 1261.0, "duration": 3.0}, {"text": "up in order again.", "start": 1264.0, "duration": 2.0}, {"text": "Who knows what the rat's\nactually experiencing, but", "start": 1266.0, "duration": 3.0}, {"text": "what the rat's hippocampus is\ndoing is running the maze.", "start": 1269.0, "duration": 4.0}, {"text": "This is, first of all, part of\nthe argument for sleep having", "start": 1273.0, "duration": 5.0}, {"text": "something to do with\nconsolidation of memory and", "start": 1278.0, "duration": 2.0}, {"text": "learning, and it's also an\nargument for the possibility at", "start": 1280.0, "duration": 6.0}, {"text": "least that the rats are\ndreaming away there, too.", "start": 1286.0, "duration": 7.0}, {"text": "Well now, arguably Freud's\ngreatest work is Interpretation", "start": 1293.0, "duration": 8.0}, {"text": "of Dreams -- that's the name of\nthe book -- big, fat book.", "start": 1301.0, "duration": 2.0}, {"text": "Still kind of fun to read but\nit's kind of long -- from 1900.", "start": 1303.0, "duration": 5.0}, {"text": "Remember that Freud was writing\nbefore we knew any of this", "start": 1308.0, "duration": 3.0}, {"text": "stuff about REM sleep or\nanything of that sort.", "start": 1311.0, "duration": 4.0}, {"text": "And what Freud thought was\nhappening was that pressure", "start": 1315.0, "duration": 8.0}, {"text": "was building up in\nyour unconscious.", "start": 1323.0, "duration": 3.0}, {"text": "So let's switch from sort of\nit dungeon model to sort", "start": 1326.0, "duration": 3.0}, {"text": "of a plumbing model.", "start": 1329.0, "duration": 1.0}, {"text": "Well, we've got the boiler\ndown in the dungeon and it's", "start": 1330.0, "duration": 3.0}, {"text": "building up pressure -- this\nrepressed material that", "start": 1333.0, "duration": 3.0}, {"text": "we've been talking about.", "start": 1336.0, "duration": 1.0}, {"text": "It's building up pressure and\nit's going to blow the roof off", "start": 1337.0, "duration": 3.0}, {"text": "the whole building unless we\nvent some of the pressure.", "start": 1340.0, "duration": 3.0}, {"text": "And so you've got to be able\nto -- whoosh -- get some", "start": 1343.0, "duration": 3.0}, {"text": "of that out of there.", "start": 1346.0, "duration": 1.0}, {"text": "One of the ways to do it is\ndreams -- to release this", "start": 1347.0, "duration": 7.0}, {"text": "while you're asleep.", "start": 1354.0, "duration": 2.0}, {"text": "Now what Freud said was that\ndreams start when some hunk of", "start": 1356.0, "duration": 8.0}, {"text": "the preceding day, that he\ncalled the day residue, some", "start": 1364.0, "duration": 6.0}, {"text": "idea, some activity, some\nsomething made an association", "start": 1370.0, "duration": 5.0}, {"text": "with something down in\nyour repressed -- in", "start": 1375.0, "duration": 5.0}, {"text": "your unconscious.", "start": 1380.0, "duration": 2.0}, {"text": "And that allowed this\nunconscious prisoner to try", "start": 1382.0, "duration": 2.0}, {"text": "and make a break for freedom.", "start": 1384.0, "duration": 2.0}, {"text": "The form of that break would be\nan effort to fulfill this", "start": 1389.0, "duration": 6.0}, {"text": "repressed wish, if you like --\nthat's why it was called wish", "start": 1395.0, "duration": 3.0}, {"text": "fulfillment -- meant that you\nwere going to try to fulfill", "start": 1398.0, "duration": 13.0}, {"text": "one of these repressed wishes\nwhile you were asleep.", "start": 1411.0, "duration": 5.0}, {"text": "There's a problem with that,\nsaid Freud, which is if you", "start": 1416.0, "duration": 6.0}, {"text": "take the materials out -- the\nrepressed material to be this", "start": 1422.0, "duration": 4.0}, {"text": "stuff that's repressed because\nit's unacceptable to you, to", "start": 1426.0, "duration": 4.0}, {"text": "the conscious you, to the ego,\nwhat's going to happen if you", "start": 1430.0, "duration": 3.0}, {"text": "start dreaming about it?", "start": 1433.0, "duration": 1.0}, {"text": "Well, we've already gotten\npart of the answer here.", "start": 1434.0, "duration": 2.0}, {"text": "Many people here have had\ndreams so awful that", "start": 1436.0, "duration": 4.0}, {"text": "they've deliberately woken\nthemselves up out of them.", "start": 1440.0, "duration": 4.0}, {"text": "Now most of those dreams, I\nwould imagine, were dreams", "start": 1444.0, "duration": 5.0}, {"text": "where the monster's about to\nput the bite on you or", "start": 1449.0, "duration": 2.0}, {"text": "something like that.", "start": 1451.0, "duration": 2.0}, {"text": "What Freud said is that look,\nif you were going to start", "start": 1453.0, "duration": 3.0}, {"text": "dreaming about, oh, let's\ndismember my little brother", "start": 1456.0, "duration": 3.0}, {"text": "-- oh, look at his little guts.", "start": 1459.0, "duration": 3.0}, {"text": "Stuff like that, that would\nbe really gross and really", "start": 1462.0, "duration": 3.0}, {"text": "disturbing and you would say\nto yourself, I don't want", "start": 1465.0, "duration": 3.0}, {"text": "to be having this dream.", "start": 1468.0, "duration": 1.0}, {"text": "And you would wake up.", "start": 1469.0, "duration": 1.0}, {"text": "So what you need to do\nis to disguise the", "start": 1470.0, "duration": 4.0}, {"text": "material in the dream.", "start": 1474.0, "duration": 2.0}, {"text": "So you've got, said Freud, the\nlatent content of the dream", "start": 1476.0, "duration": 5.0}, {"text": "that you don't know about.", "start": 1481.0, "duration": 3.0}, {"text": "The latent content is the\nrepressed material that's", "start": 1484.0, "duration": 7.0}, {"text": "trying to be vented out.", "start": 1491.0, "duration": 2.0}, {"text": "What you see is the manifest\ncontent, which is the", "start": 1493.0, "duration": 10.0}, {"text": "storyline of the dream.", "start": 1503.0, "duration": 3.0}, {"text": "It's hidden material -- it is\nhiding the latent content from", "start": 1506.0, "duration": 5.0}, {"text": "you so that you can sleep.", "start": 1511.0, "duration": 2.0}, {"text": "Freud argued that the primary\nrole of the sort of sleep", "start": 1513.0, "duration": 4.0}, {"text": "mechanism was to protect the\nsleeper, to keep you asleep and", "start": 1517.0, "duration": 4.0}, {"text": "allow you to sleep, and allow\nthis sort of venting of", "start": 1521.0, "duration": 4.0}, {"text": "repressed steam to take place.", "start": 1525.0, "duration": 7.0}, {"text": "Were you to show up in analysis\nthe reason your dreams would", "start": 1532.0, "duration": 4.0}, {"text": "be, what Freud called the royal\nroad to the unconscious, was if", "start": 1536.0, "duration": 3.0}, {"text": "you could work back from the\nmanifest content to the latent", "start": 1539.0, "duration": 3.0}, {"text": "content, which was a job of\nanalysis, not a job of picking", "start": 1542.0, "duration": 4.0}, {"text": "up some supermarket guide to\nyour dreams, but a job of", "start": 1546.0, "duration": 3.0}, {"text": "working with you\nand an analyst.", "start": 1549.0, "duration": 2.0}, {"text": "But if you could go back from\nthe manifest content to the", "start": 1551.0, "duration": 2.0}, {"text": "latent content, you'd know\nsomething about what it", "start": 1553.0, "duration": 3.0}, {"text": "was that was bugging you.", "start": 1556.0, "duration": 2.0}, {"text": "Now the fact that, like\nrepression as a whole, the fact", "start": 1558.0, "duration": 3.0}, {"text": "that you have these disguised\ndreams all the time doesn't", "start": 1561.0, "duration": 4.0}, {"text": "mean that you're somehow\nsick and diseased.", "start": 1565.0, "duration": 3.0}, {"text": "It means that's part,\nagain, of what it means", "start": 1568.0, "duration": 2.0}, {"text": "to be human for Freud.", "start": 1570.0, "duration": 2.0}, {"text": "You're going to need\nrepression, you're going to", "start": 1572.0, "duration": 1.0}, {"text": "need to be able to bubble off\nsome of this repressed energy,", "start": 1573.0, "duration": 4.0}, {"text": "and dreams are a nice\nsafe way to do it.", "start": 1577.0, "duration": 5.0}, {"text": "That's an interesting theory,\nbut it runs into some major", "start": 1582.0, "duration": 4.0}, {"text": "problems, which, of course,\nFreud didn't know about because", "start": 1586.0, "duration": 2.0}, {"text": "he died in 1939 and REM\nwasn't discovered for another", "start": 1588.0, "duration": 4.0}, {"text": "couple of decades or so.", "start": 1592.0, "duration": 1.0}, {"text": "When REM is discovered it\nbecomes a lot harder to believe", "start": 1593.0, "duration": 5.0}, {"text": "that you are boiling up this\nlittle poof of repressed energy", "start": 1598.0, "duration": 6.0}, {"text": "every ninety minutes\nlike clockwork.", "start": 1604.0, "duration": 5.0}, {"text": "That's a bit surprising.", "start": 1609.0, "duration": 2.0}, {"text": "Well, that's a bit surprising.", "start": 1611.0, "duration": 2.0}, {"text": "More surprising is if you look\nat babies, a one month old is", "start": 1613.0, "duration": 5.0}, {"text": "REMing a great deal more\nthan you're REMing.", "start": 1618.0, "duration": 3.0}, {"text": "How much repressed stuff\ndoes a one month old", "start": 1621.0, "duration": 2.0}, {"text": "baby have to deal with?", "start": 1623.0, "duration": 2.0}, {"text": "Not much.\nHow about a lion?", "start": 1625.0, "duration": 0.0}, {"text": "Lions, they REM all the time.", "start": 1627.0, "duration": 2.0}, {"text": "Apparently predators show more\nREM than prey, as I recall.", "start": 1629.0, "duration": 3.0}, {"text": "So yeah, all the mammals are\nsitting there doing this REM", "start": 1632.0, "duration": 4.0}, {"text": "thing, right, you know lions,\nexcept for like Scar in the", "start": 1636.0, "duration": 5.0}, {"text": "Lion King and stuff like that.", "start": 1641.0, "duration": 2.0}, {"text": "There's not a lot of repressed\nwork that a lion presumably", "start": 1643.0, "duration": 4.0}, {"text": "has to deal with.", "start": 1647.0, "duration": 1.0}, {"text": "Or a cow -- cows don't REM that\nmuch, but you know, ah, I", "start": 1648.0, "duration": 5.0}, {"text": "really wanted to\nhurt the grass.", "start": 1653.0, "duration": 2.0}, {"text": "I feel bad about the\n-- I don't know.", "start": 1655.0, "duration": 4.0}, {"text": "So presumably, now what's going\non when you dream and when you", "start": 1659.0, "duration": 13.0}, {"text": "go into REM is that there are\ncenters down in your brain stem", "start": 1672.0, "duration": 3.0}, {"text": "that spray of vast amount of\nactivity up into cortex and", "start": 1675.0, "duration": 8.0}, {"text": "light it up as though you were\nawake -- that's what you", "start": 1683.0, "duration": 3.0}, {"text": "end up seeing in REM.", "start": 1686.0, "duration": 1.0}, {"text": "One of the senses in which\nFreud was right is the sense", "start": 1691.0, "duration": 4.0}, {"text": "in which dreaming does\nprotect the sleeper.", "start": 1695.0, "duration": 6.0}, {"text": "If you light up -- you're\ntrying to go to sleep, right,", "start": 1701.0, "duration": 4.0}, {"text": "and I light up cortex by coming\ninto your room, turning on all", "start": 1705.0, "duration": 3.0}, {"text": "the lights and turning the\nstereo way up, you have", "start": 1708.0, "duration": 3.0}, {"text": "trouble sleeping.", "start": 1711.0, "duration": 2.0}, {"text": "Well your brain's doing the\nsame kind of thing when you go", "start": 1713.0, "duration": 2.0}, {"text": "into REM sleep, but you've got\nto do something with all that", "start": 1715.0, "duration": 4.0}, {"text": "cortical activity or you're\njust going to wake up.", "start": 1719.0, "duration": 3.0}, {"text": "So you turn it into this\nstoryline for who knows who", "start": 1722.0, "duration": 3.0}, {"text": "to watch on the big wide\nscreen TV in your brain.", "start": 1725.0, "duration": 5.0}, {"text": "In that sense you do\nend up protecting your", "start": 1730.0, "duration": 7.0}, {"text": "sleep by dreaming.", "start": 1737.0, "duration": 2.0}, {"text": "In fact, many -- Freud wasn't\nthinking about alarm clocks,", "start": 1739.0, "duration": 5.0}, {"text": "but an example of this would\nbe how many of you have", "start": 1744.0, "duration": 2.0}, {"text": "incorporated your alarm clock\ninto a dream and managed to", "start": 1746.0, "duration": 5.0}, {"text": "successfully stay asleep?", "start": 1751.0, "duration": 4.0}, {"text": "Well that's sort of a\nnon-Freudian sense in", "start": 1755.0, "duration": 3.0}, {"text": "which the dream engine is\nprotecting your sleep.", "start": 1758.0, "duration": 5.0}, {"text": "I want to stay asleep here,\nthere's a loud noise, well I", "start": 1763.0, "duration": 2.0}, {"text": "don't know where this loud\nnoise is coming from, my brain", "start": 1765.0, "duration": 2.0}, {"text": "stem's making these loud noises\nall the time, so let's just", "start": 1767.0, "duration": 4.0}, {"text": "pretend it's from the inside\nand not the outside and we can", "start": 1771.0, "duration": 4.0}, {"text": "dream that we're getting up.", "start": 1775.0, "duration": 2.0}, {"text": "Right, dream that\nwe're getting up.", "start": 1777.0, "duration": 1.0}, {"text": "We'll dream that we're going to\nclass and taking the exam and", "start": 1778.0, "duration": 3.0}, {"text": "then we wake up and it really\nis halfway through -- don't do", "start": 1781.0, "duration": 3.0}, {"text": "this at the final, please.", "start": 1784.0, "duration": 2.0}, {"text": "It's so lame.", "start": 1786.0, "duration": 2.0}, {"text": "Particularly since the\nexam's at -- the 900", "start": 1788.0, "duration": 3.0}, {"text": "final's 1:30, right?", "start": 1791.0, "duration": 1.0}, {"text": "Got plenty of time\nto wake up by 1:30.", "start": 1792.0, "duration": 2.0}, {"text": "But every year somebody wanders\nin at like 2:30, 3:00 o'clock", "start": 1794.0, "duration": 6.0}, {"text": "with the big bags under\nthe eyes, right.", "start": 1800.0, "duration": 2.0}, {"text": "So you do sort of believe\nthem -- I just woke up.", "start": 1802.0, "duration": 4.0}, {"text": "Well, good, sit down, see\nif you can see the exam.", "start": 1806.0, "duration": 5.0}, {"text": "Anyway, so there's that sense\nin which Freud had a point that", "start": 1811.0, "duration": 6.0}, {"text": "sleep was protecting the\ndreamer. but is there", "start": 1817.0, "duration": 2.0}, {"text": "any meaning to it?", "start": 1819.0, "duration": 2.0}, {"text": "Is there any sense in which\nthere there's meaning", "start": 1821.0, "duration": 3.0}, {"text": "in your dreams.", "start": 1824.0, "duration": 2.0}, {"text": "I mean after all you are\ndreaming because your brain", "start": 1826.0, "duration": 3.0}, {"text": "stem decided to throw all the\nswitches in your visual cortex", "start": 1829.0, "duration": 5.0}, {"text": "or something and you're\nbusy trying to stay asleep.", "start": 1834.0, "duration": 3.0}, {"text": "I think there is a sense in\nwhich you might be able to", "start": 1837.0, "duration": 3.0}, {"text": "argue that you could get\nsomething meaningful at a dream", "start": 1840.0, "duration": 3.0}, {"text": "-- you're not just looking\nat static on the brain.", "start": 1843.0, "duration": 3.0}, {"text": "Actually, I thought of a way to\ndemo this, but I didn't bring", "start": 1846.0, "duration": 3.0}, {"text": "any of the props because I only\nsaw it when I saw this thing.", "start": 1849.0, "duration": 3.0}, {"text": "So, a piece of paper -- I've\nprobably got a piece of paper.", "start": 1852.0, "duration": 4.0}, {"text": "Who's got a coin on them?", "start": 1856.0, "duration": 2.0}, {"text": "Somebody have a coin?", "start": 1858.0, "duration": 2.0}, {"text": "Let's see if I can\nmake this work.", "start": 1860.0, "duration": 2.0}, {"text": "That looks pretty so far.", "start": 1865.0, "duration": 3.0}, {"text": "And I also need a pencil.", "start": 1868.0, "duration": 1.0}, {"text": "Somebody have a pencil --\nit works better with a", "start": 1869.0, "duration": 2.0}, {"text": "pencil than with a pen.", "start": 1871.0, "duration": 1.0}, {"text": "Oh my goodness, it's coming all\nthe way from the cheap seats.", "start": 1872.0, "duration": 2.0}, {"text": "Visual search.", "start": 1878.0, "duration": 3.0}, {"text": "Oh, you wanted to do\nthis because -- he's", "start": 1881.0, "duration": 2.0}, {"text": "got a fancy coin.", "start": 1883.0, "duration": 1.0}, {"text": "This is very cool here.", "start": 1884.0, "duration": 2.0}, {"text": "All right, pencil,\ngot a pencil?", "start": 1889.0, "duration": 2.0}, {"text": "Here we go.", "start": 1891.0, "duration": 1.0}, {"text": "OK, this is my brain.", "start": 1892.0, "duration": 3.0}, {"text": "Thank you.", "start": 1900.0, "duration": 3.0}, {"text": "Didn't you have something\nelse you needed to do today?", "start": 1903.0, "duration": 4.0}, {"text": "Well actually, it's just\nmy cortex -- it can", "start": 1907.0, "duration": 2.0}, {"text": "just be my cortex.", "start": 1909.0, "duration": 0.0}, {"text": "Well that's my\ncortex under there.", "start": 1915.0, "duration": 1.0}, {"text": "This is my brain stem.", "start": 1916.0, "duration": 2.0}, {"text": "So now I will spray activity\nacross my cortex here, and", "start": 1918.0, "duration": 4.0}, {"text": "let's see if this\nsort of works.", "start": 1922.0, "duration": 1.0}, {"text": "It looks like\nsquat, doesn't it?", "start": 1931.0, "duration": 3.0}, {"text": "Well you know what?", "start": 1934.0, "duration": 2.0}, {"text": "That's a really\nboring dorkey demo.", "start": 1936.0, "duration": 2.0}, {"text": "It's a fidelity issue.", "start": 1941.0, "duration": 1.0}, {"text": "I can see what-- Use\na different pencil?", "start": 1942.0, "duration": 5.0}, {"text": "A wooden pencil.", "start": 1947.0, "duration": 1.0}, {"text": "No, no, no, no.", "start": 1948.0, "duration": 1.0}, {"text": "It looks just fine from here.", "start": 1949.0, "duration": 2.0}, {"text": "Here, we'll try the other side\nup, see if that works any", "start": 1951.0, "duration": 3.0}, {"text": "better but I don't\nthink it will.", "start": 1954.0, "duration": 3.0}, {"text": "Do it at more of an angle?", "start": 1957.0, "duration": 2.0}, {"text": "Hold the pencil up\nmore of an angle.", "start": 1959.0, "duration": 2.0}, {"text": "All right, we'll try\nthis one more time.", "start": 1961.0, "duration": 2.0}, {"text": "Oh look, maybe we're\ngetting -- I don't know,", "start": 1963.0, "duration": 3.0}, {"text": "what are we getting?", "start": 1966.0, "duration": 1.0}, {"text": "We're getting nothing.", "start": 1967.0, "duration": 4.0}, {"text": "We're getting nothing that\nyou're going to see.", "start": 1971.0, "duration": 1.0}, {"text": "Oh yeah, no, you can sort\nof see something but", "start": 1972.0, "duration": 2.0}, {"text": "it's really boring.", "start": 1974.0, "duration": 1.0}, {"text": "Well that was lovely.", "start": 1975.0, "duration": 1.0}, {"text": "Here we go.", "start": 1976.0, "duration": 0.0}, {"text": "Here's what I was doing that\ndidn't work but makes a", "start": 1990.0, "duration": 4.0}, {"text": "brilliant model anyway.", "start": 1994.0, "duration": 3.0}, {"text": "You can try this for yourself.", "start": 1997.0, "duration": 2.0}, {"text": "If you stick a coin under a\npiece of paper and rub a pencil", "start": 1999.0, "duration": 4.0}, {"text": "over it, you can actually\nsee the shape of the", "start": 2003.0, "duration": 3.0}, {"text": "pattern on the coin.", "start": 2006.0, "duration": 2.0}, {"text": "Anybody here ever done brass\nrubbing or greystone rubbing", "start": 2008.0, "duration": 3.0}, {"text": "or any of that sort of--?", "start": 2011.0, "duration": 2.0}, {"text": "No.", "start": 2013.0, "duration": 1.0}, {"text": "A few people.\nAll right.", "start": 2014.0, "duration": 0.0}, {"text": "Look, the point is that by\nspraying random noise across a", "start": 2015.0, "duration": 5.0}, {"text": "structured object, in effect, I\ncan see something", "start": 2020.0, "duration": 3.0}, {"text": "of the structure.", "start": 2023.0, "duration": 2.0}, {"text": "Boy, this took more minutes\nthan it should have.", "start": 2025.0, "duration": 4.0}, {"text": "By spraying random noise from\nyour brain stem, across your", "start": 2029.0, "duration": 4.0}, {"text": "particular brain, the\nparticular dreams that you get", "start": 2033.0, "duration": 4.0}, {"text": "are going to say something\nabout that underlying", "start": 2037.0, "duration": 2.0}, {"text": "structure.", "start": 2039.0, "duration": 1.0}, {"text": "So, Attila the Hun, when he was\ndreaming was not dreaming about", "start": 2040.0, "duration": 12.0}, {"text": "trains going into tunnels or\nstuff like that, because", "start": 2052.0, "duration": 4.0}, {"text": "Attila the Hun didn't know\nanything about trains.", "start": 2056.0, "duration": 3.0}, {"text": "You dream about trains, they\nmay or may not -- trains going", "start": 2059.0, "duration": 3.0}, {"text": "into tunnels, you know it's\nsort of a classic supermarket", "start": 2062.0, "duration": 3.0}, {"text": "dream analysis image\nof a sexual dream or", "start": 2065.0, "duration": 3.0}, {"text": "something like that.", "start": 2068.0, "duration": 1.0}, {"text": "It may or may not be a sexual\ndream, but the content of that", "start": 2069.0, "duration": 3.0}, {"text": "dream, that set of imagery, is\na function of your", "start": 2072.0, "duration": 5.0}, {"text": "particular brain.", "start": 2077.0, "duration": 1.0}, {"text": "If your dream about Tetris\nafter playing Tetris all day,", "start": 2078.0, "duration": 3.0}, {"text": "it's because you were playing\nthe Tetris, not because", "start": 2081.0, "duration": 2.0}, {"text": "somebody else was\nplaying Tetris.", "start": 2083.0, "duration": 1.0}, {"text": "So it could well be if you\nthought you had a process for", "start": 2084.0, "duration": 5.0}, {"text": "going back from the storyline\nthat's there to protect you", "start": 2089.0, "duration": 5.0}, {"text": "from waking up with all that\nnoise in your head to the", "start": 2094.0, "duration": 4.0}, {"text": "underlying structure of your\nmind, if you had a process that", "start": 2098.0, "duration": 4.0}, {"text": "you thought worked, then it\nfollows that you might actually", "start": 2102.0, "duration": 3.0}, {"text": "get some sort of interesting\nmeaning out of your dreams.", "start": 2105.0, "duration": 3.0}, {"text": "Now it's quite a leap to\ndecide that you actually", "start": 2108.0, "duration": 2.0}, {"text": "know how to do this.", "start": 2110.0, "duration": 1.0}, {"text": "Analysts think they do.", "start": 2111.0, "duration": 2.0}, {"text": "People who write guides\nto dream interpretation", "start": 2113.0, "duration": 3.0}, {"text": "think they do.", "start": 2116.0, "duration": 3.0}, {"text": "I think I'll just leave it at\nthat as an exercise for the", "start": 2119.0, "duration": 4.0}, {"text": "reader to go and decide whether\nor not they've got deep", "start": 2123.0, "duration": 3.0}, {"text": "meaning in their dreams.", "start": 2126.0, "duration": 4.0}, {"text": "So that's an example where\nFreud didn't know the", "start": 2130.0, "duration": 6.0}, {"text": "subsequent hundred years of\nsleep research, so if you", "start": 2136.0, "duration": 5.0}, {"text": "actually read Interpretation of\nDreams, a lot of it would sound", "start": 2141.0, "duration": 3.0}, {"text": "kind of odd at this point.", "start": 2144.0, "duration": 1.0}, {"text": "But the core ideas that sleep\nneeds to protect you, keep you", "start": 2145.0, "duration": 6.0}, {"text": "asleep and that it's sort of a\nre-packaging of this activity", "start": 2151.0, "duration": 7.0}, {"text": "of your mind, those seem to be\ncore ideas that can still do a", "start": 2158.0, "duration": 6.0}, {"text": "certain amount of work for us.", "start": 2164.0, "duration": 2.0}, {"text": "Now a place where the effort to\napply Freudian ideas did not", "start": 2166.0, "duration": 5.0}, {"text": "pan out is in the treatment\nof schizophrenia.", "start": 2171.0, "duration": 6.0}, {"text": "So I'm going to jump to talking\nabout that, and I may or may", "start": 2177.0, "duration": 3.0}, {"text": "not manage to jump back to the\nother things that I claimed I", "start": 2180.0, "duration": 2.0}, {"text": "was going to jump back to.", "start": 2182.0, "duration": 2.0}, {"text": "But I might.", "start": 2184.0, "duration": 2.0}, {"text": "So, in the middle part of 20th\ncentury, mental hospitals in", "start": 2190.0, "duration": 12.0}, {"text": "the U.S. were filled with\nchronic schizophrenics.", "start": 2202.0, "duration": 6.0}, {"text": "Schizophrenia is an extremely\ndisabling disease when", "start": 2208.0, "duration": 5.0}, {"text": "it's in its florid state.", "start": 2213.0, "duration": 3.0}, {"text": "So, schizophrenia, the word\ncomes from split mind.", "start": 2216.0, "duration": 5.0}, {"text": "As it says on the handout, for\nfive points free on the final", "start": 2221.0, "duration": 5.0}, {"text": "exam probably, not the\nsame thing as a multiple", "start": 2226.0, "duration": 5.0}, {"text": "personality disorder.", "start": 2231.0, "duration": 2.0}, {"text": "The split in the mind is a\nsplit that 19th century", "start": 2233.0, "duration": 5.0}, {"text": "psychiatry saw between\nemotional life and", "start": 2238.0, "duration": 4.0}, {"text": "cognitive life.", "start": 2242.0, "duration": 1.0}, {"text": "It is, in fact, sort of an\nunfortunate term because it", "start": 2243.0, "duration": 3.0}, {"text": "does make people think that\nit's the same thing as multiple", "start": 2246.0, "duration": 4.0}, {"text": "personality disorder.", "start": 2250.0, "duration": 1.0}, {"text": "It's not.", "start": 2251.0, "duration": 3.0}, {"text": "Multiple personality patients\ncan actually function at least", "start": 2254.0, "duration": 5.0}, {"text": "somewhat in the world\nreasonably well.", "start": 2259.0, "duration": 4.0}, {"text": "Floridly schizophrenic patients\ndo not work well out there in", "start": 2263.0, "duration": 5.0}, {"text": "the world, that's why they\nend up hospitalized.", "start": 2268.0, "duration": 3.0}, {"text": "The sorts of symptoms that you\nget are hallucinations, hearing", "start": 2271.0, "duration": 7.0}, {"text": "voices, paranoid delusions\noften of vast conspiracies", "start": 2278.0, "duration": 6.0}, {"text": "to control your mind.", "start": 2284.0, "duration": 2.0}, {"text": "You can see this as sort of\nan adaptive response, right.", "start": 2286.0, "duration": 2.0}, {"text": "If your mind, if some chunk of\nyou, in a sense, knows that", "start": 2288.0, "duration": 5.0}, {"text": "your mind is out of control,\nit's not an unreasonable", "start": 2293.0, "duration": 5.0}, {"text": "irrational thought to believe\nthat somebody else is", "start": 2298.0, "duration": 3.0}, {"text": "doing this to you.", "start": 2301.0, "duration": 3.0}, {"text": "So it may, in some sense, be\nreasonable to think, to imagine", "start": 2304.0, "duration": 4.0}, {"text": "how people could come to\nbelieve that their mind", "start": 2308.0, "duration": 2.0}, {"text": "is being controlled\nby somebody else.", "start": 2310.0, "duration": 3.0}, {"text": "The sorts of things that led to\nthe notion of a dissocation --", "start": 2313.0, "duration": 5.0}, {"text": "I shouldn't say dissociation --\nof a split between cognition", "start": 2318.0, "duration": 3.0}, {"text": "and emotion, another\ncharacteristic of", "start": 2321.0, "duration": 3.0}, {"text": "schizophrenia is so-called\ninappropriate affect.", "start": 2324.0, "duration": 3.0}, {"text": "That's just jargon for\nshowing the wrong emotions", "start": 2327.0, "duration": 4.0}, {"text": "at the wrong time.", "start": 2331.0, "duration": 1.0}, {"text": "The sort of classic symptom\nis laughing at the funeral.", "start": 2332.0, "duration": 5.0}, {"text": "You know, if you're just\nyucking it up at graveside or", "start": 2337.0, "duration": 4.0}, {"text": "something like that, people\nwill think that that is not", "start": 2341.0, "duration": 5.0}, {"text": "normal, and it is, in fact,\none of the characteristics", "start": 2346.0, "duration": 5.0}, {"text": "of schizophrenia.", "start": 2351.0, "duration": 2.0}, {"text": "And that schizophrenia's sort\nof a messy diagnosis -- not", "start": 2353.0, "duration": 3.0}, {"text": "every schizophrenic has every\none of these symptoms.", "start": 2356.0, "duration": 5.0}, {"text": "But you can imagine that by\nthe time you're gripped by", "start": 2361.0, "duration": 7.0}, {"text": "fantastical thoughts and\nconspiracy theories and you're", "start": 2368.0, "duration": 4.0}, {"text": "hearing voices and seeing\nthings that aren't there, that", "start": 2372.0, "duration": 3.0}, {"text": "this is pretty disabling stuff.", "start": 2375.0, "duration": 6.0}, {"text": "It's not so disabling that\nyou can't be out there in", "start": 2388.0, "duration": 2.0}, {"text": "the world, by the way.", "start": 2390.0, "duration": 1.0}, {"text": "When I was a graduate student,\nthe MIT Department was", "start": 2391.0, "duration": 4.0}, {"text": "called psychology.", "start": 2395.0, "duration": 1.0}, {"text": "One of the reasons, though\nperhaps not one of the more", "start": 2396.0, "duration": 4.0}, {"text": "serious reasons, for changing\nthe name was that my doctoral", "start": 2400.0, "duration": 5.0}, {"text": "advisor who was chair of the\ndepartment got tired of getting", "start": 2405.0, "duration": 2.0}, {"text": "phone calls from people who\nwanted to know about stuff like", "start": 2407.0, "duration": 5.0}, {"text": "abnormal psychology, which\nnobody at the MIT Department", "start": 2412.0, "duration": 3.0}, {"text": "ever did anything with.", "start": 2415.0, "duration": 1.0}, {"text": "So he would always get the\nphone call or his secretary", "start": 2416.0, "duration": 3.0}, {"text": "would get the phone call and\nshe was instructed to say,", "start": 2419.0, "duration": 3.0}, {"text": "don't call us, they do\nthat stuff at Harvard.", "start": 2422.0, "duration": 5.0}, {"text": "I remember one time when I was\na grad student that rather than", "start": 2427.0, "duration": 5.0}, {"text": "phoning up, one of these people\ncame to the lab and he wandered", "start": 2432.0, "duration": 3.0}, {"text": "into the lab and said that he\nknew that we were controlling", "start": 2435.0, "duration": 5.0}, {"text": "his mind with microwaves beamed\nfrom this location and he", "start": 2440.0, "duration": 5.0}, {"text": "wanted us to stop right now.", "start": 2445.0, "duration": 4.0}, {"text": "I'm there sort of uh-oh.", "start": 2449.0, "duration": 3.0}, {"text": "But my advisor with great\npresence of mind I thought,", "start": 2452.0, "duration": 7.0}, {"text": "walked over to the biggest rack\nof equipment in the lab, threw", "start": 2459.0, "duration": 3.0}, {"text": "the biggest switch he could\nfind, said there, does", "start": 2462.0, "duration": 4.0}, {"text": "that feel better?", "start": 2466.0, "duration": 1.0}, {"text": "The guy said yes and left.", "start": 2467.0, "duration": 5.0}, {"text": "I'm not sure I recommend this\nas a treatment for delusional", "start": 2472.0, "duration": 4.0}, {"text": "patients, but it worked in this\n-- and then we changed the", "start": 2476.0, "duration": 3.0}, {"text": "name of the department.", "start": 2479.0, "duration": 1.0}, {"text": "In any case, it can be very\ndisabling and it often can", "start": 2483.0, "duration": 7.0}, {"text": "lead to hospitalization.", "start": 2490.0, "duration": 3.0}, {"text": "What would Freud\nhave said about it?", "start": 2493.0, "duration": 1.0}, {"text": "What Freud said about it was\nthese are not patients that I", "start": 2494.0, "duration": 4.0}, {"text": "want to deal with, basically.", "start": 2498.0, "duration": 1.0}, {"text": "He doesn't write extensively\nabout schizophrenia and says in", "start": 2499.0, "duration": 6.0}, {"text": "various places that look,\nif you're going to do", "start": 2505.0, "duration": 2.0}, {"text": "psychoanalysis, the first thing\nyou need is a patient that", "start": 2507.0, "duration": 3.0}, {"text": "you can at least talk to.", "start": 2510.0, "duration": 1.0}, {"text": "Anna O.", "start": 2511.0, "duration": 2.0}, {"text": "With her collection of\nhysterical symptoms may have", "start": 2513.0, "duration": 2.0}, {"text": "been in psychiatric trouble\nsome variety, but you could", "start": 2515.0, "duration": 7.0}, {"text": "talk to her about it.", "start": 2522.0, "duration": 1.0}, {"text": "You could engage\nin this dialogue.", "start": 2523.0, "duration": 3.0}, {"text": "If you've got a patient who is\ndelusional and hallucinating", "start": 2526.0, "duration": 7.0}, {"text": "there's not much Freud thought\nyou could do with them.", "start": 2533.0, "duration": 3.0}, {"text": "However, his followers thought\nyou could and developed a", "start": 2536.0, "duration": 7.0}, {"text": "theory growing out of Freudian\npsychodynamic ideas of where", "start": 2543.0, "duration": 7.0}, {"text": "schizophrenia came from.", "start": 2550.0, "duration": 2.0}, {"text": "So in the mid-20th century,\npsychiatric hospitals were", "start": 2552.0, "duration": 5.0}, {"text": "filled with schizophrenics and\nfilled with good Freudianly", "start": 2557.0, "duration": 4.0}, {"text": "trained analysts\nattempting to treat them.", "start": 2561.0, "duration": 4.0}, {"text": "What they thought the cause was\nthe so-called schizophrenogenic", "start": 2565.0, "duration": 5.0}, {"text": "parent, typically Mother.", "start": 2570.0, "duration": 3.0}, {"text": "Schizophrenogenic\nis a great word.", "start": 2573.0, "duration": 5.0}, {"text": "It's somebody who\ngenerates schizophrenia.", "start": 2578.0, "duration": 4.0}, {"text": "Anyway, a schizophrenogenic\nmother, what was the problem", "start": 2582.0, "duration": 4.0}, {"text": "here, the problem was what the\ntherapists perceived as a", "start": 2586.0, "duration": 6.0}, {"text": "double-bind situation that\nthe mother was somehow", "start": 2592.0, "duration": 4.0}, {"text": "putting the child in.", "start": 2596.0, "duration": 1.0}, {"text": "The mother was saying come\nhere, come here, come here, go", "start": 2597.0, "duration": 3.0}, {"text": "away, go away, go away, I love\nyou, I love you, I love you,", "start": 2600.0, "duration": 1.0}, {"text": "get away, get away, get away.", "start": 2601.0, "duration": 2.0}, {"text": "Somehow both saying come near\nme and get away from me at one", "start": 2603.0, "duration": 4.0}, {"text": "and the same time, and\nthat this was literally", "start": 2607.0, "duration": 3.0}, {"text": "driving the child mad.", "start": 2610.0, "duration": 2.0}, {"text": "Now why would they have come\nup with such a theory?", "start": 2612.0, "duration": 2.0}, {"text": "One of the reasons was that\nonset of schizophrenia is quite", "start": 2614.0, "duration": 8.0}, {"text": "typically late adolescence,\nearly adulthood.", "start": 2622.0, "duration": 3.0}, {"text": "Oh, that reminds me to\nreiterate or iterate for the", "start": 2625.0, "duration": 4.0}, {"text": "first time, if I haven't\nmentioned it yet -- no, I", "start": 2629.0, "duration": 2.0}, {"text": "think I did mention it.", "start": 2631.0, "duration": 2.0}, {"text": "Remember what I was saying\nabout psychiatric hypochondria", "start": 2633.0, "duration": 4.0}, {"text": "-- the notion that if I sit\naround and lecture about", "start": 2637.0, "duration": 6.0}, {"text": "psychiatric disorders, you\nshouldn't go and be feeling", "start": 2643.0, "duration": 5.0}, {"text": "your brain for the rest of the\nterm saying oh man, I'm going", "start": 2648.0, "duration": 4.0}, {"text": "to wake up with a dissociative\ndisorder tomorrow and that's", "start": 2652.0, "duration": 2.0}, {"text": "going to progress to\nschizophrenia and dimentia and", "start": 2654.0, "duration": 2.0}, {"text": "I'm going to be dead.", "start": 2656.0, "duration": 3.0}, {"text": "The fact that schizophrenia has\na typical onset in a population", "start": 2659.0, "duration": 7.0}, {"text": "of about your age doesn't mean\nthat tomorrow we're going", "start": 2666.0, "duration": 3.0}, {"text": "to have 300 schizophrenic\nstudents in this class.", "start": 2669.0, "duration": 4.0}, {"text": "It does happen.", "start": 2673.0, "duration": 1.0}, {"text": "What convinced me\n-- a small aside.", "start": 2677.0, "duration": 7.0}, {"text": "When you're discussing abnormal\nbehavior, which we are now,", "start": 2684.0, "duration": 4.0}, {"text": "there are two senses of that.", "start": 2688.0, "duration": 4.0}, {"text": "One sense of that is all\nbehaviors that you care", "start": 2692.0, "duration": 3.0}, {"text": "to measure have some\nvariability in them.", "start": 2695.0, "duration": 3.0}, {"text": "You can simply assert\nthat everybody above two", "start": 2698.0, "duration": 5.0}, {"text": "standard deviations or\nsomething is abnormal.", "start": 2703.0, "duration": 3.0}, {"text": "We'll see as we go along that\nthere are times when that is", "start": 2713.0, "duration": 2.0}, {"text": "not an unreasonable\nthing to do.", "start": 2715.0, "duration": 4.0}, {"text": "There are other times when\nit's a whacky thing to do.", "start": 2719.0, "duration": 4.0}, {"text": "All right, for a wacky example,\nvirtually everybody here is", "start": 2723.0, "duration": 4.0}, {"text": "abnormal in that sense,\nbut then the axis is", "start": 2727.0, "duration": 2.0}, {"text": "SAT score, right.", "start": 2729.0, "duration": 2.0}, {"text": "Most of you are up here in the\nupper tail of the distribution.", "start": 2731.0, "duration": 3.0}, {"text": "Sure it's abnormal but\nwe don't consider it as", "start": 2734.0, "duration": 2.0}, {"text": "pathological, right?", "start": 2736.0, "duration": 2.0}, {"text": "At least not in this community.", "start": 2738.0, "duration": 2.0}, {"text": "So the other possibility is\nthat sure, the normal", "start": 2743.0, "duration": 4.0}, {"text": "population is distributed like\nthis, but there is a disease", "start": 2747.0, "duration": 5.0}, {"text": "state of some sort that looks\nlike this that's essentially", "start": 2752.0, "duration": 3.0}, {"text": "discontinuous with\nthe normal state.", "start": 2755.0, "duration": 4.0}, {"text": "Arguments have been made,\nnotably by a psychiatrist in", "start": 2759.0, "duration": 6.0}, {"text": "the '60s whose name is probably\npronounced something like", "start": 2765.0, "duration": 4.0}, {"text": "Shosh -- a Hungarian name.", "start": 2769.0, "duration": 2.0}, {"text": "Anybody happen to know\nthe right answer?", "start": 2771.0, "duration": 3.0}, {"text": "Anyway, Thomas Szasz will\ndo or Shosh or something.", "start": 2774.0, "duration": 5.0}, {"text": "In any case, he made the\nargument that in a book", "start": 2779.0, "duration": 4.0}, {"text": "entitled Being Sane in an\nInsane World, that", "start": 2783.0, "duration": 3.0}, {"text": "schizophrenia was simply a way\nto adapt to the fact that the", "start": 2786.0, "duration": 3.0}, {"text": "Russians had lots of bombs and\nwe had lots of bombs and we", "start": 2789.0, "duration": 3.0}, {"text": "were all going to blow each\nother up, and that it was", "start": 2792.0, "duration": 2.0}, {"text": "just one position on\nthis normal curve.", "start": 2794.0, "duration": 5.0}, {"text": "It's an interesting argument.", "start": 2799.0, "duration": 2.0}, {"text": "But if you actually see\nsomebody in the midst of a", "start": 2801.0, "duration": 5.0}, {"text": "florid schizophrenic break from\nreality, it's hard to believe.", "start": 2806.0, "duration": 7.0}, {"text": "I had, when I was an\nundergraduate, the roommate", "start": 2813.0, "duration": 3.0}, {"text": "of a close friend of\nmine had such a break.", "start": 2816.0, "duration": 4.0}, {"text": "It's unmistakable -- it's\nat once fascinating and", "start": 2820.0, "duration": 4.0}, {"text": "deeply frightening.", "start": 2824.0, "duration": 2.0}, {"text": "This was a friend of ours who\nbecame delusional -- she was", "start": 2826.0, "duration": 4.0}, {"text": "hallucinating, she absolutely\ncouldn't function, and was", "start": 2830.0, "duration": 6.0}, {"text": "scaring the heck out of her\nroommate and she eventually", "start": 2836.0, "duration": 3.0}, {"text": "-- actually, she\neventually did fine.", "start": 2839.0, "duration": 5.0}, {"text": "We caught up with her like\ntwenty years later, and people", "start": 2844.0, "duration": 4.0}, {"text": "do recover from schizophrenia\nand she was doing quite", "start": 2848.0, "duration": 3.0}, {"text": "well, thank you.\nBut in any case, she was the\ndata point, that at least", "start": 2851.0, "duration": 0.0}, {"text": "for me, argued strongly for\nthe notion that this is a", "start": 2855.0, "duration": 4.0}, {"text": "different state, not just\na position on a continuum.", "start": 2859.0, "duration": 9.0}, {"text": "In any case, the psychiatrists\nwere busy trying to treat", "start": 2868.0, "duration": 4.0}, {"text": "this with sor of Freudian\npsychotherapeutic techniques.", "start": 2872.0, "duration": 6.0}, {"text": "It wasn't working.", "start": 2878.0, "duration": 2.0}, {"text": "This wasn't because they were\nbad people -- these were", "start": 2880.0, "duration": 2.0}, {"text": "well-intentioned people doing\nthe best by their lights that", "start": 2882.0, "duration": 5.0}, {"text": "they could, it just\nwasn't working.", "start": 2887.0, "duration": 1.0}, {"text": "It was a case where the\ntheory was just wrong.", "start": 2888.0, "duration": 3.0}, {"text": "Oh, one of the engines that\nmoved theory away from this,", "start": 2891.0, "duration": 4.0}, {"text": "by the way, were parent\nadvocacy groups.", "start": 2895.0, "duration": 5.0}, {"text": "You've got to imagine that\nhaving a seriously ill child,", "start": 2900.0, "duration": 7.0}, {"text": "whether that's a physical\nillness or a mental", "start": 2907.0, "duration": 2.0}, {"text": "illness, is very traumatic\nfor parents, period.", "start": 2909.0, "duration": 5.0}, {"text": "But imagine how you would feel\nif the leading theory was that", "start": 2914.0, "duration": 6.0}, {"text": "this was your fault, that you\nhad done this to your child.", "start": 2920.0, "duration": 5.0}, {"text": "Not intentionally, of course,\nbut it was you who had done it.", "start": 2925.0, "duration": 4.0}, {"text": "Parents simply\ndidn't believe it.", "start": 2929.0, "duration": 2.0}, {"text": "And as science started to\nemerge suggesting that in", "start": 2931.0, "duration": 3.0}, {"text": "schizophrenia's case it was\nmuch more like a brain disease", "start": 2934.0, "duration": 3.0}, {"text": "than like the product of bad\nmothering, that groups, funding", "start": 2937.0, "duration": 8.0}, {"text": "groups -- you know, the guys\nwho send you lots of mail at", "start": 2945.0, "duration": 3.0}, {"text": "this time of year saying send\nus your check and we'll support", "start": 2948.0, "duration": 3.0}, {"text": "good research on this disease\nthat disease or whatever, a", "start": 2951.0, "duration": 5.0}, {"text": "number of these groups powered\nby parents of schizophrenics", "start": 2956.0, "duration": 4.0}, {"text": "were helping to move the\nresearch away from the notion", "start": 2960.0, "duration": 3.0}, {"text": "of a schizophrenogenic mother.", "start": 2963.0, "duration": 2.0}, {"text": "But what really did it\nwas it just didn't work.", "start": 2965.0, "duration": 2.0}, {"text": "Nobody could make\nthis story work.", "start": 2967.0, "duration": 4.0}, {"text": "The psychiatric hospitals are\nno longer filled with", "start": 2971.0, "duration": 7.0}, {"text": "schizophrenic patients, and\nthat's not because of a great", "start": 2978.0, "duration": 4.0}, {"text": "breakthrough in Freudian\npsychotherapy, it's", "start": 2982.0, "duration": 3.0}, {"text": "because of drugs.", "start": 2985.0, "duration": 2.0}, {"text": "In the '50s drugs like\nThorazine, Chlorpromazine", "start": 2987.0, "duration": 4.0}, {"text": "is the technical name,\ncame on the market.", "start": 2991.0, "duration": 5.0}, {"text": "In this particular case these\nare drugs that block dopamine", "start": 2996.0, "duration": 6.0}, {"text": "receptors -- dopamine's a neuro\ntransmitter, the receptor on", "start": 3002.0, "duration": 3.0}, {"text": "the other side of the synapse.", "start": 3005.0, "duration": 2.0}, {"text": "Thorazine decreased the uptake\nof dopamine, and that served to", "start": 3007.0, "duration": 10.0}, {"text": "ameliorate the florid symptoms\nof schizophrenia,", "start": 3017.0, "duration": 4.0}, {"text": "in particular.", "start": 3021.0, "duration": 1.0}, {"text": "You put somebody on Thorazine\nand they didn't hallucinate", "start": 3022.0, "duration": 3.0}, {"text": "anymore, and their paranoid\ndilusions slipped away.", "start": 3025.0, "duration": 5.0}, {"text": "Oh, let me tell you another\nanecdote about schizophrenics.", "start": 3030.0, "duration": 5.0}, {"text": "Schizophrenics I have known.", "start": 3035.0, "duration": 2.0}, {"text": "We had a very interesting woman\nwho was the librarian in the", "start": 3037.0, "duration": 5.0}, {"text": "department here some years ago\n-- PhD Classicist and also, she", "start": 3042.0, "duration": 10.0}, {"text": "was schizophrenic and\nsuccessfully medicated and", "start": 3052.0, "duration": 6.0}, {"text": "functioned well as the psych\ndepartment librarian", "start": 3058.0, "duration": 5.0}, {"text": "when on medication.", "start": 3063.0, "duration": 3.0}, {"text": "Anytime I tell you the root of\nsomething like schizophrenia,", "start": 3066.0, "duration": 3.0}, {"text": "the Latin and Greek roots of\nthese words, it's because I'm", "start": 3069.0, "duration": 3.0}, {"text": "remembering what she taught me.", "start": 3072.0, "duration": 3.0}, {"text": "But she would slip off\nof her medication.", "start": 3075.0, "duration": 4.0}, {"text": "You could tell when she was\nslipping off her medication", "start": 3079.0, "duration": 3.0}, {"text": "because her handwriting, her\nhandwritten notes would start", "start": 3082.0, "duration": 3.0}, {"text": "getting smaller and smaller\nand longer and longer.", "start": 3085.0, "duration": 2.0}, {"text": "She developed this\nmicro-writing and very", "start": 3087.0, "duration": 4.0}, {"text": "extensive writing, and\nthen the content would", "start": 3091.0, "duration": 2.0}, {"text": "start to slip, too.", "start": 3093.0, "duration": 2.0}, {"text": "And she would also start -- if\nit got dim in the library you", "start": 3095.0, "duration": 4.0}, {"text": "knew you were in for trouble\nbecause she became photophobic.", "start": 3099.0, "duration": 4.0}, {"text": "One of the interesting problems\nhere and one of the problems in", "start": 3103.0, "duration": 3.0}, {"text": "treatment was that as she fell\noff her medicine she", "start": 3106.0, "duration": 3.0}, {"text": "became paranoid.", "start": 3109.0, "duration": 1.0}, {"text": "What was the nature\nof her paranoia?", "start": 3110.0, "duration": 2.0}, {"text": "The nature of her paranoia was\nthat people wanted to control", "start": 3112.0, "duration": 3.0}, {"text": "her brain using chemicals.", "start": 3115.0, "duration": 1.0}, {"text": "Well that was exactly true.", "start": 3116.0, "duration": 2.0}, {"text": "But if we would tell her, you\ngotta start taking your", "start": 3118.0, "duration": 3.0}, {"text": "medicine, that was just\nevidence for her that we", "start": 3121.0, "duration": 3.0}, {"text": "were trying to control her\nbrain, which was true.", "start": 3124.0, "duration": 3.0}, {"text": "So it wasn't even really --\nit's very tricky stuff.", "start": 3127.0, "duration": 4.0}, {"text": "I mean it's funny and\nsad at the same time.", "start": 3131.0, "duration": 3.0}, {"text": "Eventually, she was no longer\nable to control this and", "start": 3134.0, "duration": 4.0}, {"text": "was no longer able to hold\nthe job, which was sad.", "start": 3138.0, "duration": 6.0}, {"text": "But it's also a real issue, a\nreal medical ethics issue.", "start": 3144.0, "duration": 5.0}, {"text": "When the hospitals were emptied\nby these drugs, the promise was", "start": 3149.0, "duration": 6.0}, {"text": "that supports would be placed\nin the community that would it", "start": 3155.0, "duration": 3.0}, {"text": "make it possible for medicated\nschizophrenics to function.", "start": 3158.0, "duration": 7.0}, {"text": "It's not a cure because the\nmedicines are imperfect.", "start": 3165.0, "duration": 2.0}, {"text": "For instance, it's not the case\nthat dopamine -- the problem in", "start": 3167.0, "duration": 4.0}, {"text": "schizophrenia isn't that\ndopamine is bad stuff and if", "start": 3171.0, "duration": 3.0}, {"text": "you have lots of it\nyou're in trouble.", "start": 3174.0, "duration": 2.0}, {"text": "It is clear that in\nschizophrenia, bits of the", "start": 3176.0, "duration": 3.0}, {"text": "brain are awash in too much\ndopamine, but if you wipe out", "start": 3179.0, "duration": 4.0}, {"text": "-- if you just blanket, push\ndown dopamine, other bits of", "start": 3183.0, "duration": 3.0}, {"text": "the brain which really like\ndopamine are starved for it.", "start": 3186.0, "duration": 4.0}, {"text": "The sorts of symptoms that you\nget when dopamine is removed", "start": 3190.0, "duration": 4.0}, {"text": "from these chunks of the brain\nare the symptoms of Parkinson's", "start": 3194.0, "duration": 2.0}, {"text": "disease -- muscle tremors, an\ninability to initiate", "start": 3196.0, "duration": 4.0}, {"text": "voluntary activity.", "start": 3200.0, "duration": 2.0}, {"text": "So a patient overmedicated on\nThorazine isn't hallucinating", "start": 3202.0, "duration": 5.0}, {"text": "anymore, but is also\nsort of inert.", "start": 3207.0, "duration": 3.0}, {"text": "So it's not trivial to\njust say take this pill,", "start": 3210.0, "duration": 3.0}, {"text": "great you're cured.", "start": 3213.0, "duration": 1.0}, {"text": "It was clear that management\nwas going to be needed.", "start": 3214.0, "duration": 3.0}, {"text": "It was clear in many cases that\npeople were going to need", "start": 3217.0, "duration": 2.0}, {"text": "housing that was like sort of\nhalfway housing, not complete", "start": 3219.0, "duration": 4.0}, {"text": "independence, but you could be\nout in the world and you", "start": 3223.0, "duration": 5.0}, {"text": "wouldn't need to be\nhospitalized anymore but you'd", "start": 3228.0, "duration": 2.0}, {"text": "need some sort of\ncontinuing care.", "start": 3230.0, "duration": 2.0}, {"text": "The problem is that we've\nsystematically not given", "start": 3232.0, "duration": 5.0}, {"text": "enough, basically money\nand resources to that.", "start": 3237.0, "duration": 4.0}, {"text": "The result is there are numbers\nof imperfectly -- perfect", "start": 3241.0, "duration": 8.0}, {"text": "medication isn't out there yet\n-- but inadequately medicated,", "start": 3249.0, "duration": 7.0}, {"text": "unsuccessfully medicated\npatients who ought to be cared", "start": 3256.0, "duration": 3.0}, {"text": "for, but who are not being\ncared for for by the system.", "start": 3259.0, "duration": 5.0}, {"text": "Schizophrenics are\nover-represented in the", "start": 3268.0, "duration": 2.0}, {"text": "homeless population because if\nyou are not successfully", "start": 3270.0, "duration": 5.0}, {"text": "medicated it's hard to hold a\njob, it's hard to keep an", "start": 3275.0, "duration": 5.0}, {"text": "apartment or something\nlike that and you end", "start": 3280.0, "duration": 3.0}, {"text": "up on the street.", "start": 3283.0, "duration": 1.0}, {"text": "That loops back to this issue\nabout your paranoid delusion", "start": 3284.0, "duration": 3.0}, {"text": "about somebody trying\nto control your mind.", "start": 3287.0, "duration": 3.0}, {"text": "When is it OK then, now that\nyou're on the street, now that", "start": 3290.0, "duration": 4.0}, {"text": "you're floridly schizophrenic\nagain, when is it OK for us as", "start": 3294.0, "duration": 4.0}, {"text": "a society to come in and say\nguess what, we don't care that", "start": 3298.0, "duration": 3.0}, {"text": "you think we're trying to\ncontrol your mind, we're going", "start": 3301.0, "duration": 2.0}, {"text": "to medicate you whether you\nwant to or not because", "start": 3303.0, "duration": 3.0}, {"text": "it's for your own good.", "start": 3306.0, "duration": 2.0}, {"text": "You can argue yeah, it's for\nyour own good, but there's lots", "start": 3308.0, "duration": 3.0}, {"text": "of things that -- you know, I\nmight decide it's for your own", "start": 3311.0, "duration": 3.0}, {"text": "good that you should sleep\neight hours a night.", "start": 3314.0, "duration": 2.0}, {"text": "Do I get to enforce that?", "start": 3316.0, "duration": 2.0}, {"text": "No, I don't.", "start": 3318.0, "duration": 2.0}, {"text": "If I decide that it's good for\nyou to take a drug that is", "start": 3320.0, "duration": 4.0}, {"text": "going to, in fact, control your\nmind, when do I get to do that,", "start": 3324.0, "duration": 4.0}, {"text": "and this ends up in court\nregularly, and it ends up on", "start": 3328.0, "duration": 3.0}, {"text": "talk radio all the time, right,\nbecause it's a sort of thing", "start": 3331.0, "duration": 3.0}, {"text": "that yakking head talk radio\nloves to get excited about.", "start": 3334.0, "duration": 3.0}, {"text": "You know some judge declares\nthat some clearly schizophrenic", "start": 3337.0, "duration": 6.0}, {"text": "individual has a constitutional\nright to live under a bridge", "start": 3343.0, "duration": 5.0}, {"text": "yelling obscenities at you,\nand talk radio goes nuts.", "start": 3348.0, "duration": 7.0}, {"text": "It's an interesting question.", "start": 3355.0, "duration": 2.0}, {"text": "It's not a question\nwith an easy answer.", "start": 3357.0, "duration": 3.0}, {"text": "When do you get to decide that\nyou're allowed to take control", "start": 3360.0, "duration": 4.0}, {"text": "over somebody else's\nmental life?", "start": 3364.0, "duration": 6.0}, {"text": "At the present, the view of\nschizophrenia is, as I say,", "start": 3370.0, "duration": 9.0}, {"text": "much more that it's a\ndistinct state of brain", "start": 3379.0, "duration": 2.0}, {"text": "disease of some sort.", "start": 3381.0, "duration": 1.0}, {"text": "What might cause it?", "start": 3382.0, "duration": 1.0}, {"text": "Well, the fact that a pill that\nreduces the effects of dopamine", "start": 3383.0, "duration": 7.0}, {"text": "does something tends to suggest\nto people that there's a", "start": 3390.0, "duration": 2.0}, {"text": "biological cause there.", "start": 3392.0, "duration": 3.0}, {"text": "In the case of schizophrenia\nthat well maybe true, but it's", "start": 3395.0, "duration": 2.0}, {"text": "important to note that that\ndoesn't need to be true.", "start": 3397.0, "duration": 3.0}, {"text": "Things that are cured or\nsymptoms that are cured by", "start": 3400.0, "duration": 4.0}, {"text": "pills aren't necessarily\nsymptoms that are caused by bad", "start": 3404.0, "duration": 4.0}, {"text": "genes or bacteria or some\nbiological story like that.", "start": 3408.0, "duration": 5.0}, {"text": "A perfectly nice example\nis motion sickness.", "start": 3413.0, "duration": 3.0}, {"text": "You go on an airplane, you get\nbounced around, you throw up.", "start": 3416.0, "duration": 3.0}, {"text": "What are you going\nto do about this?", "start": 3419.0, "duration": 2.0}, {"text": "Well, you can take scopolamine\nor meclizine that's Bonine --", "start": 3421.0, "duration": 4.0}, {"text": "Bonine is meclizine and\ndramamine is scopolamine -- two", "start": 3425.0, "duration": 4.0}, {"text": "perfectly nice drugs that\naffect your vestibular system,", "start": 3429.0, "duration": 4.0}, {"text": "and they will keep you\nfrom getting motion sick.", "start": 3433.0, "duration": 3.0}, {"text": "That's not because you've got\nbad motion sickness genes or", "start": 3436.0, "duration": 3.0}, {"text": "you got the motion\nsickness bacteria.", "start": 3439.0, "duration": 3.0}, {"text": "It's a biological treatment,\nif you like, for", "start": 3442.0, "duration": 3.0}, {"text": "an environmentally\ncaused disorder.", "start": 3445.0, "duration": 4.0}, {"text": "I point that out only to make\nthe point that what cures or", "start": 3449.0, "duration": 6.0}, {"text": "treats a disorder doesn't\nnecessarily tell you", "start": 3455.0, "duration": 3.0}, {"text": "what the cause is.", "start": 3458.0, "duration": 2.0}, {"text": "There's not one-to-one mapping\nthere -- that's important", "start": 3460.0, "duration": 4.0}, {"text": "to keep in mind.", "start": 3464.0, "duration": 2.0}, {"text": "But the drugs certainly do\nhelp with the symptoms.", "start": 3466.0, "duration": 2.0}, {"text": "What psychopharmacologists\nwork on a lot now is getting", "start": 3468.0, "duration": 6.0}, {"text": "drugs that work better.", "start": 3474.0, "duration": 2.0}, {"text": "All right, we want to reduce\ndopamine here but not here.", "start": 3476.0, "duration": 3.0}, {"text": "Well it turns out that there's\na bunch of different dopamine", "start": 3479.0, "duration": 3.0}, {"text": "receptors -- let's make a drug\nthat only acts at this location", "start": 3482.0, "duration": 3.0}, {"text": "and not at this location.", "start": 3485.0, "duration": 2.0}, {"text": "That's a sort of project that\npsychopharmacology works", "start": 3487.0, "duration": 5.0}, {"text": "on at the present time.", "start": 3492.0, "duration": 2.0}, {"text": "But I want to go back and talk\nabout the possible causes of", "start": 3494.0, "duration": 6.0}, {"text": "mental illness, but I'll do\nthat after we take a", "start": 3500.0, "duration": 4.0}, {"text": "brief break here.", "start": 3504.0, "duration": 1.0}, {"text": "OK.", "start": 3609.0, "duration": 1.0}, {"text": "What I want to do with the\nremaining portion, probably all", "start": 3610.0, "duration": 6.0}, {"text": "of the remaining portion, of\ntoday's lecture is to make two", "start": 3616.0, "duration": 5.0}, {"text": "points, which I have\nalready alluded to.", "start": 3621.0, "duration": 4.0}, {"text": "One of them is that there are\nmultiple roots into mental", "start": 3625.0, "duration": 4.0}, {"text": "illness, not just any sort of\nsingle root, and you're going", "start": 3629.0, "duration": 4.0}, {"text": "to need to work this out\non a case-by-case basis.", "start": 3633.0, "duration": 3.0}, {"text": "The other related point is that\nthe border between normal and", "start": 3636.0, "duration": 6.0}, {"text": "abnormal is not necessarily\na sharp clearly marked one.", "start": 3642.0, "duration": 4.0}, {"text": "Oh, by the way, if you're\ninterested in this latter", "start": 3646.0, "duration": 4.0}, {"text": "point, there's an article in\ntoday's New York Times science", "start": 3650.0, "duration": 4.0}, {"text": "section about really exactly\nthis point in the context of", "start": 3654.0, "duration": 4.0}, {"text": "eating disorders -- a topic\nthat I hope to get to before", "start": 3658.0, "duration": 3.0}, {"text": "the end of the course -- where\nit's very important to be", "start": 3661.0, "duration": 6.0}, {"text": "able to give a label to\npsychiatric conditions.", "start": 3667.0, "duration": 6.0}, {"text": "Why is that important?", "start": 3673.0, "duration": 2.0}, {"text": "In part it's important because\nthird party payers will pay if", "start": 3675.0, "duration": 5.0}, {"text": "you have a disorder, but they\nwon't pay if you're", "start": 3680.0, "duration": 3.0}, {"text": "just feeling a little\nscrewed up, right.", "start": 3683.0, "duration": 3.0}, {"text": "So you gotta have a\nlabeled disorder.", "start": 3686.0, "duration": 2.0}, {"text": "So, there's been a big movement\nwithin the American Psychiatric", "start": 3688.0, "duration": 5.0}, {"text": "establishment to come up with\nclear diagnostic criteria.", "start": 3693.0, "duration": 4.0}, {"text": "The nice thing about, you know\nyou go into your pediatrician", "start": 3697.0, "duration": 3.0}, {"text": "and getting a throat culture\nfor strep is that I can grow it", "start": 3700.0, "duration": 5.0}, {"text": "in the lab, and if you got\nstrep you got strep, and I'd", "start": 3705.0, "duration": 4.0}, {"text": "give you something for strep.", "start": 3709.0, "duration": 2.0}, {"text": "Mental illness is almost\nnever like that.", "start": 3711.0, "duration": 4.0}, {"text": "You got some collection of\nsymptoms, are they adequate", "start": 3715.0, "duration": 3.0}, {"text": "to get you the definition\nof this disease?", "start": 3718.0, "duration": 5.0}, {"text": "The Times article is pointing\nout that therapists are having", "start": 3723.0, "duration": 6.0}, {"text": "a real problems with people who\nany idiot can see has, let's", "start": 3729.0, "duration": 5.0}, {"text": "say, an eating disorder, but\nthe official criteria for", "start": 3734.0, "duration": 4.0}, {"text": "anorexia nervosa, the eating\ndisorder of self-starvation,", "start": 3738.0, "duration": 6.0}, {"text": "are you have to have boom,\nboom, boom, boom and boom.", "start": 3744.0, "duration": 3.0}, {"text": "Well, if you're missing\nthat boom, you can't", "start": 3747.0, "duration": 3.0}, {"text": "make the diagnosis.", "start": 3750.0, "duration": 2.0}, {"text": "What do you call them now?", "start": 3752.0, "duration": 2.0}, {"text": "Anyway, so today's New York\nTimes science section,", "start": 3754.0, "duration": 2.0}, {"text": "go check it out.", "start": 3756.0, "duration": 2.0}, {"text": "In the meantime, let us return\nto 1900 to talk a bit about", "start": 3758.0, "duration": 5.0}, {"text": "possible causes of\nmental illness.", "start": 3763.0, "duration": 4.0}, {"text": "In 1900 half the patients in\nAmerican mental hospitals", "start": 3767.0, "duration": 7.0}, {"text": "had a disorder known as\ndementia paralytica.", "start": 3774.0, "duration": 3.0}, {"text": "This is the bad stuff.", "start": 3777.0, "duration": 2.0}, {"text": "It's a disorder that starts\nwith mania and grandiosity", "start": 3779.0, "duration": 5.0}, {"text": "as its symptoms.", "start": 3784.0, "duration": 1.0}, {"text": "If you think that you are Jesus\nand that you can turn water", "start": 3789.0, "duration": 6.0}, {"text": "into wine and stuff like that,\nexcept in the rare case where", "start": 3795.0, "duration": 4.0}, {"text": "that turns out to be true or\nsomething, it's a psychiatric", "start": 3799.0, "duration": 6.0}, {"text": "symptom and it would be a\nmanic symptom of some sort.", "start": 3805.0, "duration": 7.0}, {"text": "If you think you're the\nreincarnation of Napoleon and", "start": 3812.0, "duration": 3.0}, {"text": "this time you're going to get\nthe invasion of Russia right or", "start": 3815.0, "duration": 4.0}, {"text": "something like that, you know,\nthat's the sort of thing that", "start": 3819.0, "duration": 2.0}, {"text": "gets you into psychiatric care.", "start": 3821.0, "duration": 3.0}, {"text": "In the case of dimentia\nparalytica, it then", "start": 3824.0, "duration": 5.0}, {"text": "proceeded to the other\ntwo bits of the name.", "start": 3829.0, "duration": 2.0}, {"text": "Dementia, people became\ndemented, they then became", "start": 3831.0, "duration": 4.0}, {"text": "paralyzed, lost control their\nmuscles and then they died.", "start": 3835.0, "duration": 3.0}, {"text": "This is not a good disorder.", "start": 3838.0, "duration": 4.0}, {"text": "It has disappeared essentially.", "start": 3842.0, "duration": 2.0}, {"text": "Why?", "start": 3844.0, "duration": 3.0}, {"text": "Does anybody happen\nto know the answer?", "start": 3847.0, "duration": 4.0}, {"text": "Yes.", "start": 3851.0, "duration": 1.0}, {"text": "Which person?", "start": 3852.0, "duration": 2.0}, {"text": "What are you looking\nbehind you for?", "start": 3854.0, "duration": 2.0}, {"text": "How many people are\nwearing witchy hats?", "start": 3856.0, "duration": 3.0}, {"text": "How long have you thought\nyou were a witch?", "start": 3862.0, "duration": 5.0}, {"text": "Anyway, you were saying.", "start": 3867.0, "duration": 2.0}, {"text": "AUDIENCE: This is caused by\nbacteria I think, or something", "start": 3869.0, "duration": 6.0}, {"text": "that they like [INAUDIBLE].", "start": 3875.0, "duration": 2.0}, {"text": "PROFESSOR: Well, all right.", "start": 3877.0, "duration": 2.0}, {"text": "The problem is people know\ntoo much around here.", "start": 3879.0, "duration": 3.0}, {"text": "You can fish around for all\nsorts of interesting answers,", "start": 3882.0, "duration": 3.0}, {"text": "like one of the possible\nreasons for a diagnosis to", "start": 3885.0, "duration": 2.0}, {"text": "disappear is you fractionate\nthe disorder into a bunch of", "start": 3887.0, "duration": 3.0}, {"text": "other stuff and we've now\nrenamed it and this is now", "start": 3890.0, "duration": 3.0}, {"text": "called Alzheimers and\na few other things.", "start": 3893.0, "duration": 2.0}, {"text": "But no, in fact, this is\nan outside pathogen.", "start": 3895.0, "duration": 2.0}, {"text": "In this case, dementia\nparalytica was the result of", "start": 3897.0, "duration": 6.0}, {"text": "tertiary third stage syphilis.", "start": 3903.0, "duration": 3.0}, {"text": "The reason you don't see it\nanymore is that nobody gets to", "start": 3906.0, "duration": 3.0}, {"text": "third stage syphilis anymore.", "start": 3909.0, "duration": 2.0}, {"text": "If you show up with symptoms of\nsyphilis somebody treats you.", "start": 3911.0, "duration": 4.0}, {"text": "This was the result, by\nthe time the organism had", "start": 3915.0, "duration": 3.0}, {"text": "gotten to your brain and\nchewed up your brain.", "start": 3918.0, "duration": 3.0}, {"text": "So it disappeared\nwith treatment.", "start": 3923.0, "duration": 3.0}, {"text": "But it points out is that one\nof the roots to mental illness", "start": 3926.0, "duration": 5.0}, {"text": "is an assault, a biological\nassault from the outside.", "start": 3931.0, "duration": 6.0}, {"text": "So there are theories, unproven\ntheories that a rise in autism,", "start": 3941.0, "duration": 7.0}, {"text": "that's been seen in this\ncountry over the last couple of", "start": 3948.0, "duration": 3.0}, {"text": "generations, is due to some\nsort of external insult to the", "start": 3951.0, "duration": 4.0}, {"text": "nervous system, not clear what\nit is, but there are proposals", "start": 3955.0, "duration": 5.0}, {"text": "out there that something\nthat we're doing to the", "start": 3960.0, "duration": 1.0}, {"text": "environment is causing\nmore autism, for example.", "start": 3961.0, "duration": 5.0}, {"text": "But this is an example of\na clearly biologically", "start": 3968.0, "duration": 3.0}, {"text": "rooted mental illness.", "start": 3971.0, "duration": 5.0}, {"text": "Perhaps the extreme other end\nof the scale would be -- well,", "start": 3978.0, "duration": 7.0}, {"text": "it's more like a triangle.", "start": 3985.0, "duration": 1.0}, {"text": "We could have biology, we could\nhave an environmental disorder,", "start": 3986.0, "duration": 11.0}, {"text": "and we could have what you\nmight consider to be a", "start": 3997.0, "duration": 3.0}, {"text": "societally defined disorder.", "start": 4000.0, "duration": 3.0}, {"text": "The distinction here is this is\na case where the environment", "start": 4003.0, "duration": 5.0}, {"text": "somehow really does make you\ninsane, and this is a case", "start": 4008.0, "duration": 4.0}, {"text": "where we take the normal\ndistribution and declare the", "start": 4012.0, "duration": 4.0}, {"text": "upper tail of the distribution\nto be a psychopathology", "start": 4016.0, "duration": 4.0}, {"text": "of some sort.", "start": 4020.0, "duration": 2.0}, {"text": "So let's look for examples\nof both of these.", "start": 4022.0, "duration": 3.0}, {"text": "A perfectly nice example -- not\nnice -- an example of an", "start": 4025.0, "duration": 3.0}, {"text": "environmental disorder would be\nwhat was called shell-shock in", "start": 4028.0, "duration": 7.0}, {"text": "World War I and would now\nprobably be more generally", "start": 4035.0, "duration": 4.0}, {"text": "lumped under the category of\ntraumatic stress disorder.", "start": 4039.0, "duration": 4.0}, {"text": "Exposure to extreme stress and\nbeing shot at can produce", "start": 4043.0, "duration": 12.0}, {"text": "a range of disabling\npsychiatric symptoms.", "start": 4055.0, "duration": 4.0}, {"text": "So, in World War I when people\nwere fighting this insane", "start": 4059.0, "duration": 6.0}, {"text": "warfare of having vast numbers\nof people in entrenched", "start": 4065.0, "duration": 5.0}, {"text": "positions shelling each other\nand just charging at each", "start": 4070.0, "duration": 5.0}, {"text": "other, some fraction\nof the population of", "start": 4075.0, "duration": 5.0}, {"text": "soldiers cracked up.", "start": 4080.0, "duration": 2.0}, {"text": "They just couldn't function.", "start": 4082.0, "duration": 2.0}, {"text": "They would cry hysterically,\nthey would just lie there", "start": 4084.0, "duration": 3.0}, {"text": "and not do anything.", "start": 4087.0, "duration": 3.0}, {"text": "The first reaction of the\nmilitary to such things is", "start": 4090.0, "duration": 5.0}, {"text": "to decide that this is\ninsubordination and to shoot", "start": 4095.0, "duration": 3.0}, {"text": "you or something of that sort\nfor failing to obey orders.", "start": 4098.0, "duration": 4.0}, {"text": "But it became clear to medical\nfolks during World War I that", "start": 4102.0, "duration": 6.0}, {"text": "this was not a voluntary act,\nthis was a psychiatric problem.", "start": 4108.0, "duration": 5.0}, {"text": "They went and pulled people\nback behind the lines, worked", "start": 4118.0, "duration": 4.0}, {"text": "very hard to treat them so that\nthey could return them to the", "start": 4122.0, "duration": 3.0}, {"text": "war in a sort of a sick irony.", "start": 4125.0, "duration": 4.0}, {"text": "But this is a disorder that\nis clearly environmental.", "start": 4129.0, "duration": 7.0}, {"text": "Now there's probably some --\nnot everybody who's placed", "start": 4136.0, "duration": 4.0}, {"text": "under stress produces a post\ntraumatic stress disorder, so", "start": 4140.0, "duration": 5.0}, {"text": "it's clear that there's some\nunderlying variation of unknown", "start": 4145.0, "duration": 4.0}, {"text": "nature that makes some people\nvulnerable to it and", "start": 4149.0, "duration": 3.0}, {"text": "some people not.", "start": 4152.0, "duration": 1.0}, {"text": "But the precipitating cause\nhere is environmental.", "start": 4153.0, "duration": 4.0}, {"text": "Now this is something that's\na topic of a lot of current", "start": 4157.0, "duration": 4.0}, {"text": "interest in psychiatry and\nin clinical psychology.", "start": 4161.0, "duration": 6.0}, {"text": "Because as it's been\nappreciated that this sort of", "start": 4167.0, "duration": 4.0}, {"text": "trauma does produce psychiatric\nsymptoms, efforts are made to", "start": 4171.0, "duration": 8.0}, {"text": "prevent this when it's clear\nit's going to happen.", "start": 4179.0, "duration": 3.0}, {"text": "So, first responders, the\npolice and firemen who are", "start": 4182.0, "duration": 6.0}, {"text": "going to be the first guys that\ncrash scenes or into burning", "start": 4188.0, "duration": 3.0}, {"text": "buildings, are going to see\nreally terrible stuff, and it's", "start": 4191.0, "duration": 5.0}, {"text": "known that that's going to\nproduce a collection of", "start": 4196.0, "duration": 5.0}, {"text": "psychiatric symptoms.", "start": 4201.0, "duration": 1.0}, {"text": "So, an interesting question is\nwell if you know that, what", "start": 4202.0, "duration": 5.0}, {"text": "could you do perhaps to\nameliorate the situation?", "start": 4207.0, "duration": 4.0}, {"text": "One very popular idea has been\nthat after a crisis -- I mean", "start": 4211.0, "duration": 5.0}, {"text": "you hear this all the time when\nsomething really bad happens", "start": 4216.0, "duration": 7.0}, {"text": "like a school shooting or\nsomething, one of the things", "start": 4223.0, "duration": 3.0}, {"text": "you do is you immediately pour\nin a bunch of therapists, and", "start": 4226.0, "duration": 2.0}, {"text": "the idea is is you get people\ntogether to talk about it.", "start": 4228.0, "duration": 4.0}, {"text": "One particular modality of\ntherapy is you basically get", "start": 4232.0, "duration": 3.0}, {"text": "all your firefighters who were\nat this scene into a room", "start": 4235.0, "duration": 5.0}, {"text": "together to talk it through,\nand that this has been proposed", "start": 4240.0, "duration": 5.0}, {"text": "as a mechanism for preventing\nthese stress disorders.", "start": 4245.0, "duration": 4.0}, {"text": "Unfortunately, a big study\ncame out last year suggesting", "start": 4249.0, "duration": 4.0}, {"text": "sounds lovely, doesn't work.", "start": 4253.0, "duration": 3.0}, {"text": "Not that it does anything\nparticularly bad or anything,", "start": 4256.0, "duration": 3.0}, {"text": "it just doesn't work.", "start": 4259.0, "duration": 2.0}, {"text": "What it points out is that the\nstate of the art is a little", "start": 4265.0, "duration": 5.0}, {"text": "like the problem I was talking\nabout with Freudian attempts", "start": 4270.0, "duration": 2.0}, {"text": "to explain schizophrenia.", "start": 4272.0, "duration": 4.0}, {"text": "These are difficult problems\nwhere good well-meaning", "start": 4276.0, "duration": 5.0}, {"text": "clinicians try stuff out that\ndoesn't necessarily work.", "start": 4281.0, "duration": 4.0}, {"text": "Very hard to get a clear\nfeeling from this, from reading", "start": 4285.0, "duration": 3.0}, {"text": "the popular press where you get\none miracle cure after the", "start": 4288.0, "duration": 4.0}, {"text": "other and then the miracle cure\nfades away, but it fades away", "start": 4292.0, "duration": 4.0}, {"text": "in the literature somewhere --\nyou don't get to see this very", "start": 4296.0, "duration": 2.0}, {"text": "clearly if you just sit there\nreading the science section", "start": 4298.0, "duration": 5.0}, {"text": "of Time magazine or\nsomething of that sort.", "start": 4303.0, "duration": 5.0}, {"text": "Anyway, so third stage syphilis\nmunches up your mind, trench", "start": 4308.0, "duration": 7.0}, {"text": "warfare munches up your mind.", "start": 4315.0, "duration": 3.0}, {"text": "Are there diseases that are\ndefined purely by society", "start": 4318.0, "duration": 7.0}, {"text": "and what does that mean?", "start": 4325.0, "duration": 3.0}, {"text": "Are those legitimate?", "start": 4328.0, "duration": 1.0}, {"text": "Well, let's talk about one\nthat's not terribly legitimate.", "start": 4329.0, "duration": 3.0}, {"text": "I don't think anybody here is\ndeeply familiar with the", "start": 4332.0, "duration": 4.0}, {"text": "disorder called drapetomania.", "start": 4336.0, "duration": 3.0}, {"text": "Any drapetomania experts?", "start": 4339.0, "duration": 3.0}, {"text": "No.", "start": 4342.0, "duration": 1.0}, {"text": "OK.", "start": 4343.0, "duration": 2.0}, {"text": "Any Greek scholars?", "start": 4345.0, "duration": 3.0}, {"text": "No.\nSo we're not going to\nget anybody to tell", "start": 4348.0, "duration": 0.0}, {"text": "us what the root is.", "start": 4350.0, "duration": 1.0}, {"text": "So, it's not a manic\ndesire to put up drapes.", "start": 4351.0, "duration": 4.0}, {"text": "It's drapeto comes from a\nGreek root having to do", "start": 4355.0, "duration": 5.0}, {"text": "with wandering off, and the\nmania's the mania part.", "start": 4360.0, "duration": 5.0}, {"text": "So it's an insane\ndesire to wander away.", "start": 4365.0, "duration": 3.0}, {"text": "All right, that sounds\nlike it could be insane.", "start": 4368.0, "duration": 3.0}, {"text": "This is a disorder discovered\nby a doctor named Cartwright", "start": 4371.0, "duration": 6.0}, {"text": "in Louisiana in the 1840s.", "start": 4377.0, "duration": 5.0}, {"text": "He writes about it in a\nbook endearingly titled,", "start": 4382.0, "duration": 4.0}, {"text": "Peculiarities of\nthe Negro Race.", "start": 4386.0, "duration": 3.0}, {"text": "So you need to think --\nall right, time to review", "start": 4389.0, "duration": 4.0}, {"text": "your AP American history.", "start": 4393.0, "duration": 2.0}, {"text": "Right, 1840s, Louisiana.", "start": 4395.0, "duration": 3.0}, {"text": "If you are a member of the\nnegro race you are what?", "start": 4398.0, "duration": 5.0}, {"text": "A slave.", "start": 4403.0, "duration": 1.0}, {"text": "If you are a slave\nyou might do what?", "start": 4404.0, "duration": 2.0}, {"text": "Well you might wander\noff or run away.", "start": 4410.0, "duration": 6.0}, {"text": "It wasn't that Cartwright\ndiscovered this.", "start": 4416.0, "duration": 2.0}, {"text": "People knew that\nslaves ran away.", "start": 4418.0, "duration": 2.0}, {"text": "But rather like earlier\nattitudes towards people", "start": 4420.0, "duration": 4.0}, {"text": "cracking up on the battlefield,\nthe standard attitude towards", "start": 4424.0, "duration": 3.0}, {"text": "the slave that ran away\nwas that's a bad slave.", "start": 4427.0, "duration": 5.0}, {"text": "Right, he's just bad, and what\nwe should do is catch him", "start": 4432.0, "duration": 5.0}, {"text": "and beat him and put\nhim back to work.", "start": 4437.0, "duration": 3.0}, {"text": "Cartwright was an odd sort of\nliberal from the sound of it in", "start": 4440.0, "duration": 5.0}, {"text": "the sense that he said, no,\nno, no, no, no -- they're", "start": 4445.0, "duration": 4.0}, {"text": "not bad, they're sick.", "start": 4449.0, "duration": 2.0}, {"text": "Because after all, as he\nunderstood it, the proper place", "start": 4451.0, "duration": 5.0}, {"text": "for a slave for an African\nAmerican was to be", "start": 4456.0, "duration": 5.0}, {"text": "a slave, right?", "start": 4461.0, "duration": 1.0}, {"text": "So if you wandered off,\nyou weren't being a", "start": 4462.0, "duration": 6.0}, {"text": "healthy, normal slave.", "start": 4468.0, "duration": 1.0}, {"text": "You'd gone up here somewhere\nand you were being abnormal.", "start": 4469.0, "duration": 4.0}, {"text": "He also, by the way, had a\nlovely biological theory about", "start": 4473.0, "duration": 3.0}, {"text": "the cause of this, which\nwas decarbonized blood.", "start": 4476.0, "duration": 5.0}, {"text": "I don't know, it sounds like it\nwould do something bad to me.", "start": 4481.0, "duration": 3.0}, {"text": "And he had a treatment regimen.", "start": 4488.0, "duration": 2.0}, {"text": "Remember that the standard\ntreatment for a slave who ran", "start": 4490.0, "duration": 3.0}, {"text": "away was catch him, beat him\nand put him back to work.", "start": 4493.0, "duration": 6.0}, {"text": "Cartwright said, when you catch\nhim, what you need to do is", "start": 4499.0, "duration": 6.0}, {"text": "slap some oil in with a broad\nleather strap and", "start": 4505.0, "duration": 4.0}, {"text": "put him to work.", "start": 4509.0, "duration": 1.0}, {"text": "All right, so the treatment\ndidn't sound all", "start": 4510.0, "duration": 2.0}, {"text": "that different.", "start": 4512.0, "duration": 1.0}, {"text": "In any case, it's a pretty\nclear case of a disorder", "start": 4513.0, "duration": 7.0}, {"text": "defined entirely by society.", "start": 4520.0, "duration": 4.0}, {"text": "There's not a -- I don't\nknow, decarbonized", "start": 4524.0, "duration": 2.0}, {"text": "blood not withstanding.", "start": 4526.0, "duration": 1.0}, {"text": "There's not an organism there.", "start": 4527.0, "duration": 4.0}, {"text": "There's not -- well, you can\nthink of the environment as", "start": 4531.0, "duration": 3.0}, {"text": "causing the slave to run\naway, but not in the sense", "start": 4534.0, "duration": 3.0}, {"text": "of causing a disorder.", "start": 4537.0, "duration": 2.0}, {"text": "We would consider this to be\nessentially a normal -- we'd be", "start": 4539.0, "duration": 4.0}, {"text": "with Thomas Szasz on that,\nthat's a sane reaction to an", "start": 4543.0, "duration": 2.0}, {"text": "insane world, perhaps, to be\na slave and to run away.", "start": 4545.0, "duration": 7.0}, {"text": "Now, you might argue that we\ndon't do that anymore, but", "start": 4552.0, "duration": 5.0}, {"text": "if you were to, say, OK,\nwhat this is, is weight.", "start": 4557.0, "duration": 5.0}, {"text": "Let's make this normal\ndistribution weight.", "start": 4562.0, "duration": 4.0}, {"text": "The Surgeon General is\nperfectly happy and all sorts", "start": 4566.0, "duration": 5.0}, {"text": "of outfits are perfectly happy\nto declare that if you're above", "start": 4571.0, "duration": 3.0}, {"text": "this level whatever it\nis, you're abnormal,", "start": 4574.0, "duration": 3.0}, {"text": "you're overweight.", "start": 4577.0, "duration": 3.0}, {"text": "And there are plenty of\ntheories, folks psychological", "start": 4580.0, "duration": 4.0}, {"text": "and otherwise, that basically\ngive a psychiatric spin to", "start": 4584.0, "duration": 4.0}, {"text": "what's going on there, right.", "start": 4588.0, "duration": 2.0}, {"text": "If you've heard theories of\nobesity being -- there are pop", "start": 4590.0, "duration": 6.0}, {"text": "theories that oh, they're\novercompensating -- that", "start": 4596.0, "duration": 3.0}, {"text": "they're eating to substitute\nfor the lack of love in their", "start": 4599.0, "duration": 2.0}, {"text": "life, or it's a lack of\nself-control, or it's because", "start": 4601.0, "duration": 5.0}, {"text": "they have gene for fatness.", "start": 4606.0, "duration": 4.0}, {"text": "All of this might be\ntrue at some level.", "start": 4610.0, "duration": 2.0}, {"text": "I'm not casting any doubt\non the particular theory,", "start": 4612.0, "duration": 6.0}, {"text": "that's a separate topic.", "start": 4618.0, "duration": 2.0}, {"text": "But you gotta realize that what\nyou're doing is taking an", "start": 4620.0, "duration": 3.0}, {"text": "essentially normal distribution\nwith the exception of some very", "start": 4623.0, "duration": 4.0}, {"text": "few -- there are a small\nnumber of clear pathologies", "start": 4627.0, "duration": 4.0}, {"text": "of weight regulation.", "start": 4631.0, "duration": 1.0}, {"text": "Mostly what you're doing is\ntaking one tail of the", "start": 4632.0, "duration": 3.0}, {"text": "distribution, declaring it\nto be abnormal, and putting", "start": 4635.0, "duration": 3.0}, {"text": "an explanation on it.", "start": 4638.0, "duration": 3.0}, {"text": "How you understand that\nis culturally dependent.", "start": 4641.0, "duration": 7.0}, {"text": "How we talk about obesity\nis in part defined by how", "start": 4648.0, "duration": 3.0}, {"text": "we talk about beauty.", "start": 4651.0, "duration": 2.0}, {"text": "In cultures where obesity is\nconsidered beautiful, you don't", "start": 4653.0, "duration": 5.0}, {"text": "get theories that say it's\nan abnormality, right?", "start": 4658.0, "duration": 4.0}, {"text": "So in some fashion we\ndo this all the time.", "start": 4662.0, "duration": 5.0}, {"text": "In the remaining time, what I\nwant to do, and then I'll loop", "start": 4671.0, "duration": 4.0}, {"text": "back to this point, is look on\nyour handout on page three.", "start": 4675.0, "duration": 7.0}, {"text": "Let's do a little bit of\narmchair diagnosis here.", "start": 4682.0, "duration": 5.0}, {"text": "We don't have much time.", "start": 4687.0, "duration": 1.0}, {"text": "Quickly read these three\nvignettes and quickly decide", "start": 4688.0, "duration": 5.0}, {"text": "where they lie on the scale\nfrom fine to very weird.", "start": 4693.0, "duration": 5.0}, {"text": "I'm deliberately using very\ncasual language there in order", "start": 4698.0, "duration": 4.0}, {"text": "to suggest that you not think\ndeeply about whether or not", "start": 4702.0, "duration": 4.0}, {"text": "you're giving them a\npsychiatric diagnosis", "start": 4706.0, "duration": 2.0}, {"text": "here, I just want to know\nwhether they're nuts.", "start": 4708.0, "duration": 2.0}, {"text": "We'll collect a little data.", "start": 4716.0, "duration": 1.0}, {"text": "How are we going to\ncollect this data?", "start": 4717.0, "duration": 2.0}, {"text": "Don't cheat off your neighbors,\nplease, and [? wavel ?]", "start": 4744.0, "duration": 3.0}, {"text": "in when you're done.", "start": 4747.0, "duration": 1.0}, {"text": "How many people are done?", "start": 4748.0, "duration": 3.0}, {"text": "Most people are done.\nOK, good enough.", "start": 4751.0, "duration": 0.0}, {"text": "In the interest of getting some\ndata relatively quickly, let's", "start": 4754.0, "duration": 3.0}, {"text": "group between -- let's do\naluminum hat boy, Jim.", "start": 4757.0, "duration": 13.0}, {"text": "How many people gave him a\nsort of 1-3, he's fine?", "start": 4770.0, "duration": 5.0}, {"text": "4-7 he's a little weird.", "start": 4775.0, "duration": 3.0}, {"text": "I take it we got a lot of\npopulation-- All right.", "start": 4778.0, "duration": 3.0}, {"text": "So Jim's here.", "start": 4785.0, "duration": 1.0}, {"text": "How about Jack there at\nthe bottom -- we'll", "start": 4789.0, "duration": 3.0}, {"text": "come back to Sam.", "start": 4792.0, "duration": 1.0}, {"text": "How many people thought\nJack was in the 1-3", "start": 4793.0, "duration": 2.0}, {"text": "he's fine category?", "start": 4795.0, "duration": 2.0}, {"text": "A bunch of people.\nHow many people thought\nhe's in the 4-7 category?", "start": 4800.0, "duration": 0.0}, {"text": "A bunch more people.", "start": 4804.0, "duration": 2.0}, {"text": "Let's give him some hash\nmarks here so we can", "start": 4806.0, "duration": 2.0}, {"text": "tell the difference.", "start": 4808.0, "duration": 3.0}, {"text": "So this is -- what is his name?", "start": 4811.0, "duration": 1.0}, {"text": "Jack.", "start": 4812.0, "duration": 1.0}, {"text": "How many people thought\nhe was very weird?", "start": 4817.0, "duration": 2.0}, {"text": "So only a very few.", "start": 4819.0, "duration": 2.0}, {"text": "So, you can, in fact -- so Jim\nis sort of the guy who came to", "start": 4821.0, "duration": 4.0}, {"text": "my lab all those years ago, and\nJack can be found in Harvard", "start": 4825.0, "duration": 3.0}, {"text": "Square any time selling some\nfar left newspaper and yelling", "start": 4828.0, "duration": 4.0}, {"text": "at you about the fact that\nwe're all controlled by", "start": 4832.0, "duration": 3.0}, {"text": "something, and we just consider\nthem to be sort of weird but", "start": 4835.0, "duration": 3.0}, {"text": "kind of -- this is in the\nrealm of free speech.", "start": 4838.0, "duration": 3.0}, {"text": "All right, let's\ntake a look at Sam.", "start": 4841.0, "duration": 3.0}, {"text": "How many people thought\nSam's just fine?", "start": 4844.0, "duration": 5.0}, {"text": "OK.", "start": 4849.0, "duration": 1.0}, {"text": "How many thought Sam was\njust in the middle?", "start": 4850.0, "duration": 3.0}, {"text": "OK.", "start": 4853.0, "duration": 1.0}, {"text": "How many thought that\nSam was pretty weird?", "start": 4854.0, "duration": 3.0}, {"text": "All right, so that looks--\nI need some space here.", "start": 4857.0, "duration": 5.0}, {"text": "Well actually, lots of fines,\na few less in the middles,", "start": 4870.0, "duration": 3.0}, {"text": "and almost as many weird.", "start": 4873.0, "duration": 4.0}, {"text": "Pretty wide\ndistribution, right.", "start": 4877.0, "duration": 2.0}, {"text": "The other two are\nvery heavily skewed.", "start": 4879.0, "duration": 3.0}, {"text": "Could somebody in\nthe fine department", "start": 4882.0, "duration": 4.0}, {"text": "explain why he's fine?", "start": 4886.0, "duration": 3.0}, {"text": "Yes, find person.", "start": 4889.0, "duration": 1.0}, {"text": "AUDIENCE: I think he's weird, I\njust don't think he's disabled.", "start": 4890.0, "duration": 3.0}, {"text": "PROFESSOR: I need somebody\nwho thinks he's fine, fine.", "start": 4893.0, "duration": 3.0}, {"text": "Yes.", "start": 4896.0, "duration": 2.0}, {"text": "Yes, you pink person.", "start": 4898.0, "duration": 1.0}, {"text": "AUDIENCE: He's just a stamp\ncollector -- he sounds fine.", "start": 4902.0, "duration": 3.0}, {"text": "PROFESSOR: A stamp collector.", "start": 4905.0, "duration": 2.0}, {"text": "All right.", "start": 4907.0, "duration": 2.0}, {"text": "The trick here is there is a\ntwo-word variation between what", "start": 4909.0, "duration": 6.0}, {"text": "half of you have and what\nthe other half of you have.", "start": 4915.0, "duration": 3.0}, {"text": "Let's see if that\nmakes a difference.", "start": 4918.0, "duration": 5.0}, {"text": "The people who don't have the\nstamp collector one know the", "start": 4923.0, "duration": 3.0}, {"text": "difference, which is that one\nhalf of you have his major", "start": 4926.0, "duration": 7.0}, {"text": "passion is collecting stamps,\nand the other have his major", "start": 4933.0, "duration": 4.0}, {"text": "passion is collecting\nwomen's undergarments.", "start": 4937.0, "duration": 1.0}, {"text": "Right.", "start": 4942.0, "duration": 2.0}, {"text": "That is the only\ndifference here.", "start": 4944.0, "duration": 2.0}, {"text": "Yes?", "start": 4946.0, "duration": 1.0}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4947.0, "duration": 10.0}, {"text": "PROFESSOR: You know, actually\nthat's lovely because I", "start": 4957.0, "duration": 2.0}, {"text": "could probably expand\nthe description.", "start": 4959.0, "duration": 6.0}, {"text": "If I said he used to write all\nof his relatives and asked them", "start": 4965.0, "duration": 4.0}, {"text": "to send him used stamps, nobody\nwould think that was weird.", "start": 4969.0, "duration": 5.0}, {"text": "If I said he used to write to\nall his relatives and asked", "start": 4974.0, "duration": 3.0}, {"text": "them to send used underwear,\nthat's really weird, right?", "start": 4977.0, "duration": 5.0}, {"text": "If I changed it a little more\nto say -- what is his name?", "start": 4985.0, "duration": 4.0}, {"text": "Sam was a shy, withdrawn man,\nthe president of the Haines", "start": 4989.0, "duration": 5.0}, {"text": "underwear company and at the\ncorporate headquarters he had", "start": 4994.0, "duration": 5.0}, {"text": "the big underwear exhibit\nor something, then he", "start": 4999.0, "duration": 3.0}, {"text": "becomes less weird.", "start": 5002.0, "duration": 2.0}, {"text": "Given the time, let me just\nreiterate the point that what", "start": 5004.0, "duration": 5.0}, {"text": "this is intended to illustrate\nis that the border between what", "start": 5009.0, "duration": 4.0}, {"text": "makes you weird and what\nmakes you just a little", "start": 5013.0, "duration": 5.0}, {"text": "different is not clear.", "start": 5018.0, "duration": 4.0}, {"text": "It's not something that we\ncan define nice and sharply.", "start": 5022.0, "duration": 2.0}, {"text": "See you Thursday.", "start": 5024.0, "duration": 3.0}]
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+[{"text": "[SQUEAKING]\n[RUSTLING] [CLICKING]", "start": 0.0, "duration": 6.279}, {"text": "NORVIN RICHARDS:\nSigned languages--", "start": 11.109, "duration": 1.971}, {"text": "there are a bunch\nof signed languages.", "start": 13.08, "duration": 3.48}, {"text": "I've listed three of them\nhere, but there are many.", "start": 16.56, "duration": 3.15}, {"text": "And maybe the first\nthing to say about them,", "start": 19.71, "duration": 2.7}, {"text": "I can remember a\ntime when I believed,", "start": 22.41, "duration": 4.44}, {"text": "as a child, that signed\nlanguages were basically", "start": 26.85, "duration": 2.55}, {"text": "just codes--", "start": 29.4, "duration": 1.44}, {"text": "coded versions of\nspoken languages.", "start": 30.84, "duration": 3.18}, {"text": "When I was a kid,\nyou were sometimes", "start": 34.02, "duration": 1.5}, {"text": "taught ASL signs for things\nevery so often in class,", "start": 35.52, "duration": 4.902}, {"text": "sort of the way\nyou would be taught", "start": 40.422, "duration": 1.458}, {"text": "the occasional Spanish\nword in class or whatever.", "start": 41.88, "duration": 2.428}, {"text": "It's like, here's the word\nin a foreign language.", "start": 44.308, "duration": 2.042}, {"text": "Let's all learn this word.", "start": 46.35, "duration": 2.97}, {"text": "Unlike Spanish, the impression\nI was given by my teachers-- who", "start": 49.32, "duration": 2.675}, {"text": "may actually have\nbelieved this--", "start": 51.995, "duration": 1.375}, {"text": "was that the way you spoke\nASL was to speak English,", "start": 53.37, "duration": 3.12}, {"text": "but to use your hands.", "start": 56.49, "duration": 1.23}, {"text": "So like every English word\nhad an ASL translation.", "start": 57.72, "duration": 4.11}, {"text": "And there is\nsomething like that.", "start": 61.83, "duration": 1.57}, {"text": "It's called Signed\nExact English.", "start": 63.4, "duration": 2.33}, {"text": "But it is not the standard\nlanguage used by the deaf.", "start": 65.73, "duration": 4.38}, {"text": "The deaf use something\ncalled American Sign Language", "start": 70.11, "duration": 2.4}, {"text": "in America.", "start": 72.51, "duration": 1.116}, {"text": "Another way to\nmake this point may", "start": 77.28, "duration": 1.77}, {"text": "be that signed\nlanguages are not just", "start": 79.05, "duration": 2.1}, {"text": "coded versions of the spoken\nlanguages that are around them,", "start": 81.15, "duration": 3.39}, {"text": "is that American-- to point out\nthat American Sign Language is", "start": 84.54, "duration": 5.07}, {"text": "fairly closely related to French\nSign Language, which I won't", "start": 89.61, "duration": 4.14}, {"text": "try to pronounce in French\nbecause I don't speak French,", "start": 93.75, "duration": 3.06}, {"text": "for historical reasons.", "start": 96.81, "duration": 2.23}, {"text": "The first schools for\nthe deaf in America", "start": 99.04, "duration": 2.78}, {"text": "were established by\npeople from France", "start": 101.82, "duration": 1.937}, {"text": "who had established schools\nfor the deaf in France", "start": 103.757, "duration": 2.083}, {"text": "and began establishing\nthem here.", "start": 105.84, "duration": 1.44}, {"text": "So American Sign Language is\na descendant of French Sign", "start": 107.28, "duration": 3.51}, {"text": "Language, and it is unrelated\nto British Sign Language", "start": 110.79, "duration": 2.46}, {"text": "and quite different from it.", "start": 113.25, "duration": 1.32}, {"text": "So go ahead and\nmake all the jokes", "start": 114.57, "duration": 2.615}, {"text": "you want about American\nEnglish and British English", "start": 117.185, "duration": 2.125}, {"text": "being different, but they're\nmore similar to each other", "start": 119.31, "duration": 2.292}, {"text": "than either is to French.", "start": 121.602, "duration": 1.488}, {"text": "But American Sign Language is\nmore similar to French Sign", "start": 123.09, "duration": 3.69}, {"text": "Language than it is to\nBritish Sign Language", "start": 126.78, "duration": 2.46}, {"text": "because American Sign\nLanguage is not English.", "start": 129.24, "duration": 2.25}, {"text": "It's another\nlanguage, one which is", "start": 131.49, "duration": 2.4}, {"text": "spoken with your body,\nespecially your hands.", "start": 133.89, "duration": 2.385}, {"text": "Yes, I just said that.", "start": 139.473, "duration": 0.917}, {"text": "Thank you.", "start": 140.39, "duration": 2.382}, {"text": "Another way to make\nthe same point,", "start": 142.772, "duration": 1.458}, {"text": "there are big\ngrammatical differences", "start": 144.23, "duration": 1.59}, {"text": "between ASL and English, some\nof which we'll be exploring.", "start": 145.82, "duration": 3.18}, {"text": "Here's one.", "start": 149.0, "duration": 0.5}, {"text": "In English has\novert wh-movement.", "start": 149.5, "duration": 2.51}, {"text": "Remember wh-movement?", "start": 152.01, "duration": 2.67}, {"text": "So in \"Who did John see?\"", "start": 154.68, "duration": 2.03}, {"text": "Lots of other languages,\nlike Mandarin, don't.", "start": 156.71, "duration": 2.82}, {"text": "And in this regard, ASL\nis more like Mandarin", "start": 159.53, "duration": 2.97}, {"text": "than it is like English.", "start": 162.5, "duration": 1.44}, {"text": "It's actually a blend.", "start": 163.94, "duration": 1.35}, {"text": "You can do either one.", "start": 165.29, "duration": 1.44}, {"text": "But there's a very natural\nway to ask wh-questions", "start": 166.73, "duration": 2.91}, {"text": "in ASL, which looks\nsomething like this.", "start": 169.64, "duration": 4.72}, {"text": "Here's a guy who\nis about to say,", "start": 174.36, "duration": 1.73}, {"text": "I think, \"Who did John see?\"", "start": 176.09, "duration": 3.94}, {"text": "\"John\"- \"saw\"- \"who?\"", "start": 180.03, "duration": 1.56}, {"text": "Yeah, so I'll get him\nto sign that again.", "start": 181.59, "duration": 2.55}, {"text": "So \"John saw who?\"", "start": 184.14, "duration": 2.85}, {"text": "And \"who\" is signed like this.", "start": 186.99, "duration": 1.68}, {"text": "That's the ASL for \"who.\"", "start": 188.67, "duration": 2.4}, {"text": "There's another thing he's\ndoing, which we'll talk about.", "start": 191.07, "duration": 2.85}, {"text": "Part of signing\na question in ASL", "start": 193.92, "duration": 4.063}, {"text": "is not just what you\ndo with your hands,", "start": 197.983, "duration": 1.667}, {"text": "but what you do with your face.", "start": 199.65, "duration": 1.38}, {"text": "You're required to\nlook puzzled as you", "start": 201.03, "duration": 3.12}, {"text": "ask these particular\nkinds of questions--", "start": 204.15, "duration": 1.93}, {"text": "and so to tilt your head\nand furrow your brow.", "start": 206.08, "duration": 2.45}, {"text": "And there's some\nvery careful work", "start": 208.53, "duration": 2.79}, {"text": "on where, exactly, you're\nrequired to tilt your head", "start": 211.32, "duration": 2.515}, {"text": "and furrow your brow.", "start": 213.835, "duration": 0.875}, {"text": "It turns out to be\nvery interesting.", "start": 214.71, "duration": 1.63}, {"text": "It isn't just you do that\nfor the whole question.", "start": 216.34, "duration": 2.06}, {"text": "You do that for certain\nparts of the question.", "start": 218.4, "duration": 1.917}, {"text": "And linguists who work\non signed languages", "start": 220.317, "duration": 2.733}, {"text": "do work on what's going on.", "start": 223.05, "duration": 1.8}, {"text": "I'll put a link to this.", "start": 224.85, "duration": 1.58}, {"text": "This is a corpus of American\nSign Language utterances", "start": 226.43, "duration": 3.94}, {"text": "by the folks over\nthere at BU who", "start": 230.37, "duration": 3.39}, {"text": "have a center for studying ASL.", "start": 233.76, "duration": 3.108}, {"text": "There's a lot of really\ninteresting data in here, which", "start": 236.868, "duration": 2.292}, {"text": "is tagged, as you can see.", "start": 239.16, "duration": 1.53}, {"text": "Anyway, I'll put a link\nto this on our website.", "start": 240.69, "duration": 3.01}, {"text": "So this is Carol Neidle,\nwho's done a lot of really", "start": 243.7, "duration": 2.53}, {"text": "interesting work on ASL.", "start": 246.23, "duration": 1.0}, {"text": "Back into full screen mode.", "start": 250.285, "duration": 1.125}, {"text": "I'm sorry, I'm going\nto do a lot of this", "start": 251.41, "duration": 1.05}, {"text": "because we're going to be going\nback and forth between videos", "start": 252.46, "duration": 2.542}, {"text": "and my slides.", "start": 255.002, "duration": 1.418}, {"text": "And I am low tech.", "start": 256.42, "duration": 1.151}, {"text": "If I were higher tech, I\nwould have figured out a way", "start": 257.571, "duration": 2.208}, {"text": "to incorporate the\nvideos into the slides,", "start": 259.779, "duration": 1.771}, {"text": "but that's why this is the\nlinguistics department and not", "start": 261.55, "duration": 3.07}, {"text": "some other department.", "start": 264.62, "duration": 2.19}, {"text": "OK, so ASL is not English.", "start": 266.81, "duration": 1.953}, {"text": "It's not English because it's\nnot all that closely related", "start": 268.763, "duration": 2.417}, {"text": "to British sign language,\nand it's also not English", "start": 271.18, "duration": 2.28}, {"text": "because, well, it has\nwh- [INAUDIBLE] too,", "start": 273.46, "duration": 1.845}, {"text": "like, English standard way\nto ask \"Who did John see?,\"", "start": 275.305, "duration": 2.505}, {"text": "the word order is,\n\"John saw who?\"", "start": 277.81, "duration": 1.58}, {"text": "That's not to say that\nsign languages aren't", "start": 282.01, "duration": 1.86}, {"text": "in some kind of contact\nwith spoken languages.", "start": 283.87, "duration": 1.917}, {"text": "So typically, if you're a deaf\nperson growing up in America,", "start": 285.787, "duration": 7.413}, {"text": "you have some kind of\nrelationship with ASL.", "start": 293.2, "duration": 2.67}, {"text": "What kind of relationship\ndepends on the circumstances.", "start": 295.87, "duration": 3.19}, {"text": "So it's not at all\nuncommon for deaf children", "start": 299.06, "duration": 2.39}, {"text": "to be the deaf children\nof hearing parents,", "start": 301.45, "duration": 1.95}, {"text": "and then their parents\nhave to do some hustling", "start": 303.4, "duration": 2.588}, {"text": "and be careful to make sure that\ntheir children have a chance", "start": 305.988, "duration": 2.542}, {"text": "to learn ASL.", "start": 308.53, "duration": 2.4}, {"text": "Some children of hearing\nparents will try to learn ASL", "start": 310.93, "duration": 2.76}, {"text": "themselves and raise\ntheir children in ASL.", "start": 313.69, "duration": 2.94}, {"text": "But, of course that's quite\ndifficult, to learn quickly", "start": 316.63, "duration": 3.78}, {"text": "a language like ASL.", "start": 320.41, "duration": 1.5}, {"text": "I say \"quickly\" because\nif you didn't know ASL", "start": 321.91, "duration": 2.893}, {"text": "before you realized that you\nhad a deaf child, well, then,", "start": 324.803, "duration": 2.417}, {"text": "you need to hurry up and\nlearn it fairly fast.", "start": 327.22, "duration": 2.37}, {"text": "And that's a difficult\nposition for parents to be in.", "start": 329.59, "duration": 3.1}, {"text": "So there are some barriers with\nrespect to how much resources", "start": 332.69, "duration": 4.22}, {"text": "these people have,\nwhether they can", "start": 336.91, "duration": 2.64}, {"text": "do that in time for their kids\nto be exposed to ASL the way", "start": 339.55, "duration": 3.903}, {"text": "you need to be exposed\nto your first language.", "start": 343.453, "duration": 1.917}, {"text": "They're the deaf kids\nwho-- and then, there", "start": 345.37, "duration": 1.8}, {"text": "are deaf kids who are lucky\nenough to be around native ASL", "start": 347.17, "duration": 2.88}, {"text": "signers from a very early age.", "start": 350.05, "duration": 1.98}, {"text": "Now, the upshot of all\nthis is that if you're deaf", "start": 352.03, "duration": 3.338}, {"text": "and you're growing up\nin the United States,", "start": 355.368, "duration": 1.792}, {"text": "you probably have some\nkind of relation to ASL.", "start": 357.16, "duration": 2.01}, {"text": "Maybe you become\na fluent speaker.", "start": 359.17, "duration": 1.44}, {"text": "That's one hope.", "start": 360.61, "duration": 4.165}, {"text": "But you also have some kind\nof relationship with English.", "start": 364.775, "duration": 2.375}, {"text": "You're surrounded by people\nwho are communicating", "start": 367.15, "duration": 2.7}, {"text": "with each other in English.", "start": 369.85, "duration": 1.17}, {"text": "And so there are what you\ncould think of as borrowings", "start": 371.02, "duration": 2.7}, {"text": "between gestures of\nhearing people around you", "start": 373.72, "duration": 3.93}, {"text": "and the gestures that\nare used in the sign.", "start": 377.65, "duration": 5.22}, {"text": "Maybe one of the\nclearest examples", "start": 382.87, "duration": 1.47}, {"text": "of this, the pronoun for \"I\" in\nAmerican Sign Language is this.", "start": 384.34, "duration": 3.3}, {"text": "You point at your own chest.", "start": 387.64, "duration": 2.25}, {"text": "The pronoun for \"I\" in\nJapanese Sign Language is this.", "start": 389.89, "duration": 3.03}, {"text": "You point at your own nose.", "start": 392.92, "duration": 1.86}, {"text": "That's borrowing\nfrom the standard way", "start": 394.78, "duration": 3.96}, {"text": "to point to yourself\nin these places.", "start": 398.74, "duration": 2.2}, {"text": "So in Japan, and a\nlot of Asia, I think,", "start": 400.94, "duration": 2.39}, {"text": "the way to point to yourself\nis to point at your own nose,", "start": 403.33, "duration": 4.44}, {"text": "whereas in America, the standard\nway to point to yourself", "start": 407.77, "duration": 3.0}, {"text": "is to point at your chest.", "start": 410.77, "duration": 1.083}, {"text": "So we could think of\nthis as borrowing,", "start": 411.853, "duration": 1.625}, {"text": "if we wanted to,\nsome kind of contact", "start": 413.478, "duration": 1.582}, {"text": "between the spoken language\nand the sign language.", "start": 415.06, "duration": 3.495}, {"text": "From very early on--", "start": 422.61, "duration": 1.2}, {"text": "one of the first\ndays, I think-- we", "start": 423.81, "duration": 1.548}, {"text": "talked about Saussure and\nthe idea of the arbitrariness", "start": 425.358, "duration": 2.292}, {"text": "of the sign, the observation\nthat the fact that this", "start": 427.65, "duration": 3.12}, {"text": "is called a \"table\"\nis an arbitrary fact.", "start": 430.77, "duration": 3.7}, {"text": "There's nothing\nabout it that demands", "start": 434.47, "duration": 2.51}, {"text": "that it be called a table.", "start": 436.98, "duration": 1.163}, {"text": "It could have been\ncalled \"chair\",", "start": 438.143, "duration": 1.417}, {"text": "and the fact that it's called\na table is an accident.", "start": 439.56, "duration": 2.67}, {"text": "The fact that we call it a table\nin English but that in another", "start": 442.23, "duration": 2.79}, {"text": "language it could be called\na \"mesa,\" or a [NON-ENGLISH],,", "start": 445.02, "duration": 2.55}, {"text": "or a bunch of other things.", "start": 447.57, "duration": 3.03}, {"text": "Yeah, languages get to\narbitrarily decide what", "start": 450.6, "duration": 3.12}, {"text": "they're going to call things.", "start": 453.72, "duration": 1.71}, {"text": "Even in spoken languages--", "start": 455.43, "duration": 1.29}, {"text": "I think we said this before--", "start": 456.72, "duration": 1.54}, {"text": "there are places where the\nway a word is pronounced", "start": 458.26, "duration": 7.43}, {"text": "has some kind of connection\nwith what it refers to.", "start": 465.69, "duration": 3.03}, {"text": "The classic example\nof this is names", "start": 468.72, "duration": 1.74}, {"text": "for birds, which are\nnot always, but often", "start": 470.46, "duration": 3.03}, {"text": "imitations of the\ncall of the bird.", "start": 473.49, "duration": 2.01}, {"text": "So a little chickadee\nis named after the thing", "start": 475.5, "duration": 3.058}, {"text": "that a chickadee says.", "start": 478.558, "duration": 0.917}, {"text": "It sounds like it's\nsaying \"chickadee,\"", "start": 479.475, "duration": 1.725}, {"text": "if you listen to a chickadee.", "start": 481.2, "duration": 2.19}, {"text": "Or Passamaquoddy, the word\nfor \"Great Horned Owl,\"", "start": 483.39, "duration": 3.6}, {"text": "is [NON-ENGLISH],, which\nis a pretty good imitation", "start": 486.99, "duration": 2.97}, {"text": "of an owl.", "start": 489.96, "duration": 1.2}, {"text": "So there are some\nthings like that", "start": 491.16, "duration": 1.56}, {"text": "where people seem\nto be imitating", "start": 492.72, "duration": 1.74}, {"text": "the sounds made by something.", "start": 494.46, "duration": 4.11}, {"text": "In ASL, of course, your\nsounds are not relevant.", "start": 498.57, "duration": 5.16}, {"text": "In a sense, you have\na lot of chances", "start": 503.73, "duration": 1.92}, {"text": "to have non-arbitrary signs.", "start": 505.65, "duration": 2.22}, {"text": "So there are signs\nthat really do", "start": 507.87, "duration": 2.22}, {"text": "look like you're\nimitating the thing,", "start": 510.09, "duration": 2.55}, {"text": "trying to make an\nimage of the thing.", "start": 512.64, "duration": 1.99}, {"text": "So here's \"book.\"", "start": 514.63, "duration": 1.297}, {"text": "That's \"book.\"", "start": 515.927, "duration": 0.583}, {"text": "You can see why that's\nthe word for \"book.\"", "start": 516.51, "duration": 2.31}, {"text": "Or this is \"tree,\"\nand you can see", "start": 518.82, "duration": 2.187}, {"text": "why that's the word for \"tree.\"", "start": 521.007, "duration": 1.292}, {"text": "It's a picture of a tree.", "start": 522.299, "duration": 1.411}, {"text": "This is the kind of\nthing that gets people", "start": 523.71, "duration": 3.03}, {"text": "to think that ASL is basically\na very sophisticated version", "start": 526.74, "duration": 3.72}, {"text": "of charades, that people are\njust trying to imitate things,", "start": 530.46, "duration": 4.53}, {"text": "and then you're done.", "start": 534.99, "duration": 1.27}, {"text": "But of course, that's not it.", "start": 536.26, "duration": 1.7}, {"text": "Signs are just as\narbitrary in ASL", "start": 537.96, "duration": 2.19}, {"text": "as they are in any\nspoken language.", "start": 540.15, "duration": 1.56}, {"text": "That is to say they're\nmostly arbitrary,", "start": 541.71, "duration": 2.07}, {"text": "with some other cases\nlike \"chickadee\"", "start": 543.78, "duration": 2.34}, {"text": "for English or \"book\"\nfor ASL, cases where it's", "start": 546.12, "duration": 3.48}, {"text": "possible to imitate something.", "start": 549.6, "duration": 1.71}, {"text": "There's a fair amount\nof work on the phonology", "start": 553.83, "duration": 1.98}, {"text": "of signed languages-- which,\nwhen I say it that way,", "start": 555.81, "duration": 2.67}, {"text": "sounds like a bad joke.", "start": 558.48, "duration": 1.51}, {"text": "I mean, what does that mean,\nthe phonology of sign languages?", "start": 559.99, "duration": 3.2}, {"text": "But it's actually, there's this\nreally cool stuff that people", "start": 563.19, "duration": 2.73}, {"text": "have observed about, if you\nthink of phonology as being", "start": 565.92, "duration": 3.93}, {"text": "the study of how basic units\ncan be combined to make slightly", "start": 569.85, "duration": 4.89}, {"text": "larger units-- so OK,\nfor spoken languages,", "start": 574.74, "duration": 2.58}, {"text": "those units are sounds--", "start": 577.32, "duration": 1.56}, {"text": "and we make all kinds of\nobservations about the rules", "start": 578.88, "duration": 2.37}, {"text": "for how those things\nget to combine.", "start": 581.25, "duration": 2.25}, {"text": "And cast your mind back to when\nI was showing you some Lardil", "start": 583.5, "duration": 2.79}, {"text": "data, and I said, we\nconvinced ourselves", "start": 586.29, "duration": 3.09}, {"text": "that it was useful to think\nthat the accusative forms were", "start": 589.38, "duration": 4.32}, {"text": "a more reliable guide\nto the underlying forms", "start": 593.7, "duration": 4.23}, {"text": "than the nominative forms were.", "start": 597.93, "duration": 1.68}, {"text": "That's what we ended\nup saying for Lardil.", "start": 599.61, "duration": 2.47}, {"text": "So we wanted to say, -in is\nbeing added to the underlying", "start": 602.08, "duration": 4.4}, {"text": "form of the noun, which\nfor \"woman\" is \"bidngen\"", "start": 606.48, "duration": 3.06}, {"text": "and for \"fish\" is \"yak.\"", "start": 609.54, "duration": 2.64}, {"text": "And if you ask a Lardil speaker,\nwhat's your word for fish,", "start": 612.18, "duration": 2.67}, {"text": "they're not going to say \"yak.\"", "start": 614.85, "duration": 1.77}, {"text": "They're going to say \"yaga.\"", "start": 616.62, "duration": 1.26}, {"text": "But that's because, although\nthe Lardil word for fish is", "start": 617.88, "duration": 4.05}, {"text": "underlyingly \"yak,\" Lardil\nalso has a basic rule--", "start": 621.93, "duration": 3.6}, {"text": "a bunch of rules--", "start": 625.53, "duration": 0.9}, {"text": "that lengthen\nmonosyllabic words.", "start": 626.43, "duration": 2.16}, {"text": "And we talked about\nvarious rules of this kind.", "start": 628.59, "duration": 2.76}, {"text": "They add different\nthings depending", "start": 631.35, "duration": 1.86}, {"text": "on what the monosyllabic word\nends in, what sound it ends in,", "start": 633.21, "duration": 4.38}, {"text": "with the upshot that \"yak\"\nis not a possible Lardil", "start": 637.59, "duration": 4.14}, {"text": "word because it's too short.", "start": 641.73, "duration": 1.83}, {"text": "And Lardil, therefore,\nlengthens it", "start": 643.56, "duration": 2.64}, {"text": "if you haven't added\nanything to it.", "start": 646.2, "duration": 1.665}, {"text": "So if you've made it\naccusative, you're fine.", "start": 647.865, "duration": 1.875}, {"text": "It's two syllables long,\n\"yaga,\" and you're all done.", "start": 649.74, "duration": 2.557}, {"text": "But if you wanted\nit to be nominative,", "start": 652.297, "duration": 1.583}, {"text": "you weren't going to add any\nsuffixes to it, well, then,", "start": 653.88, "duration": 1.98}, {"text": "you need to add another\nvowel because it's too short.", "start": 655.86, "duration": 1.95}, {"text": "That was the picture of\nLardil that we ended up with.", "start": 657.81, "duration": 2.07}, {"text": "Does that sound even\nfaintly familiar?", "start": 659.88, "duration": 1.583}, {"text": "That's what we\nwere talking about.", "start": 661.463, "duration": 1.837}, {"text": "That's a story about\nLardil that says", "start": 663.3, "duration": 1.95}, {"text": "Lardil is like many languages\nin having what's called", "start": 665.25, "duration": 2.55}, {"text": "a minimal word requirement.", "start": 667.8, "duration": 1.44}, {"text": "That is, in Lardil, it\nsays Lardil words can't", "start": 669.24, "duration": 3.12}, {"text": "be just one syllable long.", "start": 672.36, "duration": 1.142}, {"text": "If you have a word\nthat's going to end up", "start": 673.502, "duration": 1.708}, {"text": "being one syllable long,\nyou do something to it", "start": 675.21, "duration": 1.71}, {"text": "to make it longer.", "start": 676.92, "duration": 0.75}, {"text": "ASL has also been argued to\nhave a minimal word requirement,", "start": 680.1, "duration": 3.78}, {"text": "and the argument goes like this.", "start": 683.88, "duration": 1.35}, {"text": "There are signs that, if\nthey're by themselves,", "start": 685.23, "duration": 3.36}, {"text": "they involve a movement\nwhich is often short.", "start": 688.59, "duration": 2.31}, {"text": "But then, that\nmovement goes away", "start": 690.9, "duration": 1.74}, {"text": "if they're made part\nof a larger word.", "start": 692.64, "duration": 2.02}, {"text": "So here's the ASL for \"think.\"", "start": 694.66, "duration": 3.43}, {"text": "You take your finger, you\nmove it towards your temple,", "start": 698.09, "duration": 3.91}, {"text": "and touch yourself in\nthe temple briefly.", "start": 702.0, "duration": 1.74}, {"text": "Yeah, that's \"think\" and\n[INAUDIBLE] \"I think.\"", "start": 703.74, "duration": 3.45}, {"text": "And here is \"shocked.\"", "start": 707.19, "duration": 1.313}, {"text": "So \"shocked\" starts with\nyour finger at your temple,", "start": 708.503, "duration": 2.167}, {"text": "where it would be\nfor \"think,\" and then", "start": 710.67, "duration": 1.625}, {"text": "it has a second\ncomponent, \"shocked.\"", "start": 712.295, "duration": 2.455}, {"text": "\"I'm shocked.\"", "start": 714.75, "duration": 0.93}, {"text": "Yeah, so \"think,\" one way\nto think about \"think\"", "start": 715.68, "duration": 5.46}, {"text": "is just having your\nhand in a position.", "start": 721.14, "duration": 2.37}, {"text": "That's too small.", "start": 723.51, "duration": 1.32}, {"text": "That's like a\nmonosyllable in Lardil.", "start": 724.83, "duration": 2.01}, {"text": "And so you add something.", "start": 726.84, "duration": 1.26}, {"text": "You add emotion.", "start": 728.1, "duration": 0.84}, {"text": "Your hand moves\ntowards your temple.", "start": 728.94, "duration": 2.58}, {"text": "But if you're adding,\nif you're making", "start": 731.52, "duration": 1.74}, {"text": "\"shocked,\" which is \"think\"\nplus something else--", "start": 733.26, "duration": 2.85}, {"text": "that's kind of like the\naccusative of \"fish\"--", "start": 736.11, "duration": 2.13}, {"text": "then it's OK to just start\nwith your hand at your temple", "start": 738.24, "duration": 2.55}, {"text": "and then do the second half.", "start": 740.79, "duration": 1.35}, {"text": "You don't have to add\nthat motion to your hand.", "start": 742.14, "duration": 3.84}, {"text": "And the suggestion that's been\nmade in the literature on ASL", "start": 745.98, "duration": 3.18}, {"text": "phonology is this is like\na minimal word requirement.", "start": 749.16, "duration": 3.55}, {"text": "So Diane Brentari has suggested\nASL signs have a minimal word", "start": 752.71, "duration": 4.76}, {"text": "requirement.", "start": 757.47, "duration": 0.72}, {"text": "She doesn't say \"like Lardil.\"", "start": 758.19, "duration": 1.25}, {"text": "I forget what minimal word\nlanguage she's talking about.", "start": 759.44, "duration": 2.81}, {"text": "So they have to contain at\nleast one move, is her idea.", "start": 762.25, "duration": 3.68}, {"text": "\"Think\" Is the ASL version of\nthe Lardil word for \"fish.\"", "start": 765.93, "duration": 3.21}, {"text": "Remember Polish obstruents?", "start": 773.33, "duration": 2.82}, {"text": "I like this class because\nI think I promised you", "start": 776.15, "duration": 2.197}, {"text": "that I was never, ever again\ngoing to talk about Polish,", "start": 778.347, "duration": 2.333}, {"text": "and so I apologize.", "start": 780.68, "duration": 2.15}, {"text": "It's the last day.", "start": 782.83, "duration": 0.88}, {"text": "You don't have to hear\nany more about Polish.", "start": 783.71, "duration": 1.875}, {"text": "Sorry, go ahead.", "start": 785.585, "duration": 0.755}, {"text": "AUDIENCE: I just\nhave a question.", "start": 786.34, "duration": 1.06}, {"text": "NORVIN RICHARDS: Yeah.", "start": 787.4, "duration": 0.917}, {"text": "AUDIENCE: Are there other words\nthat have \"think\" something?", "start": 788.317, "duration": 3.033}, {"text": "NORVIN RICHARDS:\nOh, dear, now we", "start": 791.35, "duration": 1.8}, {"text": "get beyond my very modest\nknowledge about ASL.", "start": 793.15, "duration": 2.82}, {"text": "I don't know.", "start": 795.97, "duration": 0.66}, {"text": "Are you thinking that\nmight be the only one?", "start": 796.63, "duration": 2.85}, {"text": "AUDIENCE: Well, I think,\nagain, if you, I guess,", "start": 799.48, "duration": 3.71}, {"text": "look at compound words, there\nis definitely the ability", "start": 803.19, "duration": 3.18}, {"text": "to pair them with other things.", "start": 806.37, "duration": 3.26}, {"text": "So I was just wondering\nif that's a common way", "start": 809.63, "duration": 3.33}, {"text": "to just show surprise,\nmaybe confusion.", "start": 812.96, "duration": 4.17}, {"text": "NORVIN RICHARDS:\nOh, you mean having", "start": 817.13, "duration": 1.5}, {"text": "this as part of a larger sign?", "start": 818.63, "duration": 1.95}, {"text": "Yeah, so Brentari's\ndiscussion certainly makes", "start": 820.58, "duration": 2.522}, {"text": "it sound like there\nare a bunch of these.", "start": 823.102, "duration": 1.708}, {"text": "\"Shocked\" is the\nexamples she uses,", "start": 824.81, "duration": 1.503}, {"text": "and I'm afraid I don't\nknow any other examples", "start": 826.313, "duration": 1.917}, {"text": "off the top of my head.", "start": 828.23, "duration": 0.81}, {"text": "I'll try to find the paper\nthat I got this from,", "start": 829.04, "duration": 2.01}, {"text": "and I can put it on the\nwebsite so you can take a look.", "start": 831.05, "duration": 3.7}, {"text": "So here I am signing\nthings at you, yeah.", "start": 834.75, "duration": 4.48}, {"text": "Polish-- last time, I promise,\nwe will talk about Polish.", "start": 839.23, "duration": 2.52}, {"text": "Polish obstruents, so\nstops and fricatives--", "start": 841.75, "duration": 4.2}, {"text": "we convinced\nourselves that Polish", "start": 845.95, "duration": 1.59}, {"text": "has what's called final\nvoicing, cross-linguistically", "start": 847.54, "duration": 2.31}, {"text": "extraordinarily common, a\nphenomenon in which, if you", "start": 849.85, "duration": 4.17}, {"text": "have a voiced obstruent\nat the end of a word,", "start": 854.02, "duration": 3.88}, {"text": "it becomes voiceless.", "start": 857.9, "duration": 1.08}, {"text": "So if you look at the\nplurals of these nouns,", "start": 858.98, "duration": 2.94}, {"text": "then you can see that before\nthe plural suffix \"i\",", "start": 861.92, "duration": 2.54}, {"text": "you can have both\nvoiced and voiceless", "start": 864.46, "duration": 2.79}, {"text": "stops and fricatives-- in\nthe last example, \"nose\"", "start": 867.25, "duration": 2.85}, {"text": "and \"rubble,\"\nplural of \"rubble,\"", "start": 870.1, "duration": 1.95}, {"text": "which, hopefully, none of\nus will meet any time soon.", "start": 872.05, "duration": 3.7}, {"text": "But that if you don't have the\nplural, all of these obstruents", "start": 875.75, "duration": 2.75}, {"text": "are voiceless if they're\nat the end of a word", "start": 878.5, "duration": 1.875}, {"text": "because Polish has\nfinal devoicing.", "start": 880.375, "duration": 2.295}, {"text": "This was part of the argument\nthat we need to posit", "start": 882.67, "duration": 3.09}, {"text": "an underlying representation for\na word like \"lye,\" let's say--", "start": 885.76, "duration": 3.39}, {"text": "the second line there--\nwhich ends in a voiced stop,", "start": 889.15, "duration": 4.59}, {"text": "because that gives us the best--", "start": 893.74, "duration": 2.7}, {"text": "well, the best\nmatch on the data.", "start": 896.44, "duration": 1.848}, {"text": "So it allows us to account\nfor the fact that the plural", "start": 898.288, "duration": 2.292}, {"text": "of \"bow\" and \"lye\" look\ndifferent from each other--", "start": 900.58, "duration": 2.89}, {"text": "they're \"wuki\" and \"wugi\"--", "start": 903.47, "duration": 1.58}, {"text": "even though the\nsingulars look the same.", "start": 905.05, "duration": 2.258}, {"text": "So this is what we were doing\nback when we were doing Polish,", "start": 907.308, "duration": 2.542}, {"text": "Yeah?", "start": 909.85, "duration": 0.96}, {"text": "Have I triggered your\nPolish flashbacks?", "start": 910.81, "duration": 2.68}, {"text": "OK, so it has voiced\nobstruents, but they're", "start": 913.49, "duration": 2.272}, {"text": "limited in where they can go.", "start": 915.762, "duration": 1.208}, {"text": "They can't go at\nthe ends of words.", "start": 916.97, "duration": 2.69}, {"text": "Here's an observation about\nthe distribution of finger", "start": 919.66, "duration": 2.25}, {"text": "wiggling in the ASL sign.", "start": 921.91, "duration": 1.68}, {"text": "So sometimes when\nyou make an ASL sign,", "start": 923.59, "duration": 1.86}, {"text": "you wiggle your fingers.", "start": 925.45, "duration": 1.26}, {"text": "There are ASL signs in which\nthere isn't much movement,", "start": 926.71, "duration": 3.242}, {"text": "or just one of Brentari's\nshortened ones,", "start": 929.952, "duration": 1.708}, {"text": "like the word for\n\"color,\" which is this.", "start": 931.66, "duration": 1.83}, {"text": "So you put your\nhand to your chin,", "start": 933.49, "duration": 1.86}, {"text": "and you wiggle your fingers.", "start": 935.35, "duration": 2.46}, {"text": "There are also signs where\nyour hands are moving", "start": 937.81, "duration": 3.81}, {"text": "and the wiggling is\nhappening during the move,", "start": 941.62, "duration": 2.1}, {"text": "like go up in flames,\nwhere your hands are rising", "start": 943.72, "duration": 3.7}, {"text": "and your fingers are wiggling.", "start": 947.42, "duration": 1.25}, {"text": "That's how you do\ngo up in flames.", "start": 948.67, "duration": 2.07}, {"text": "So ASL signs can have\nfinger wiggling in them,", "start": 950.74, "duration": 2.61}, {"text": "but there are imaginable\nsigns that you don't get.", "start": 953.35, "duration": 2.58}, {"text": "So you could\nimagine a sign where", "start": 955.93, "duration": 2.52}, {"text": "your fingers would wiggle,\nand then you would move.", "start": 958.45, "duration": 2.7}, {"text": "It would be like\ngo up in flames,", "start": 961.15, "duration": 2.088}, {"text": "except you would wiggle first\nbefore you began moving--", "start": 963.238, "duration": 2.292}, {"text": "or in which you moved\nand then, having reached", "start": 965.53, "duration": 2.28}, {"text": "your destination,\nyou did a long move--", "start": 967.81, "duration": 2.28}, {"text": "not one of your short\nmoves, but a long move--", "start": 970.09, "duration": 2.265}, {"text": "did your move, and then\nwiggled your fingers.", "start": 972.355, "duration": 1.875}, {"text": "But there aren't\nany signs like that.", "start": 974.23, "duration": 2.46}, {"text": "So finger wiggling\nis either confined", "start": 976.69, "duration": 5.13}, {"text": "to the position\nat the end of one", "start": 981.82, "duration": 2.13}, {"text": "of Brentari's short movements,\nor if your hands are moving", "start": 983.95, "duration": 2.85}, {"text": "over a longer distance like in\n\"go up in flames,\" well, you", "start": 986.8, "duration": 3.28}, {"text": "have to wiggle the whole time.", "start": 990.08, "duration": 1.25}, {"text": "Similar observation\nabout hand shape change.", "start": 995.66, "duration": 2.707}, {"text": "So there are signs where your\nhands just do a short move", "start": 998.367, "duration": 2.333}, {"text": "and then change their hand\nshape, like \"understand,\" where", "start": 1000.7, "duration": 4.08}, {"text": "your hand moves into position\nand then, put up one finger,", "start": 1004.78, "duration": 2.7}, {"text": "\"understand,\" or \"old\", where\nyour hand starts at your chin", "start": 1007.48, "duration": 5.48}, {"text": "and moves as it moves away\nfrom your chin-- \"old.\"", "start": 1012.96, "duration": 2.25}, {"text": "Yeah?", "start": 1015.21, "duration": 1.17}, {"text": "AUDIENCE: You're talking about\nother mental concepts being", "start": 1016.38, "duration": 5.58}, {"text": "expressed in sign\nlanguage and understand--", "start": 1021.96, "duration": 3.31}, {"text": "so it also starts at the temple?", "start": 1025.27, "duration": 2.007}, {"text": "NORVIN RICHARDS: Yeah,\nso I think, right, I", "start": 1027.277, "duration": 1.792}, {"text": "think there are a number of--", "start": 1029.069, "duration": 1.591}, {"text": "not surprising, maybe\na number of mental.", "start": 1030.66, "duration": 1.885}, {"text": "So \"forget\" is another one.", "start": 1032.545, "duration": 1.125}, {"text": "This is \"forget,\" where you wipe\nsomething off of your brain,", "start": 1033.67, "duration": 3.35}, {"text": "yeah, using your middle finger.", "start": 1037.02, "duration": 3.7}, {"text": "Your middle finger is\nalso used for being sick.", "start": 1040.72, "duration": 3.8}, {"text": "So yeah, there are\na bunch of signs,", "start": 1044.52, "duration": 1.5}, {"text": "that use your head that\nhave to do with what's", "start": 1046.02, "duration": 2.053}, {"text": "going on in your head.", "start": 1048.073, "duration": 0.917}, {"text": "Yeah, that's right.", "start": 1048.99, "duration": 1.11}, {"text": "That's right.", "start": 1050.1, "duration": 1.482}, {"text": "OK, so ASL has finger\nwiggling, but there", "start": 1051.582, "duration": 3.196}, {"text": "are limits on where\nfinger wiggling can go.", "start": 1054.778, "duration": 1.792}, {"text": "It goes during the\nmotion, or it goes right", "start": 1056.57, "duration": 1.792}, {"text": "after one of Brentari's\nshort movements.", "start": 1058.362, "duration": 2.198}, {"text": "Hand shape change is the same.", "start": 1060.56, "duration": 1.38}, {"text": "It goes after one of\nBrentari's short movements,", "start": 1061.94, "duration": 1.62}, {"text": "like in \"understand,\" or it\ngoes during the movement,", "start": 1063.56, "duration": 1.83}, {"text": "like in \"old.\"", "start": 1065.39, "duration": 0.9}, {"text": "Yeah, but there aren't--", "start": 1066.29, "duration": 1.99}, {"text": "did I say this in\nthe next slide?", "start": 1068.28, "duration": 1.58}, {"text": "Yeah, again, you can\nimagine a sign where--", "start": 1069.86, "duration": 3.36}, {"text": "which would be like \"old\" where\nyou would start with one hand", "start": 1073.22, "duration": 2.79}, {"text": "shape, you change\nshapes, and then move,", "start": 1076.01, "duration": 3.54}, {"text": "or where you would move along\ndistance and then change", "start": 1079.55, "duration": 2.37}, {"text": "shapes, but there aren't\nany signs like that.", "start": 1081.92, "duration": 3.7}, {"text": "And so people have\nsuggested, yeah,", "start": 1085.62, "duration": 1.76}, {"text": "just like a phonologist has\nto be able to say things like,", "start": 1087.38, "duration": 2.76}, {"text": "this is a language that has\nvoiced obstruents but not", "start": 1090.14, "duration": 3.42}, {"text": "at the ends of words-- there are\nlimits on where they can go--", "start": 1093.56, "duration": 2.94}, {"text": "ASL has finger wiggling, and\nit has hand shape change,", "start": 1096.5, "duration": 3.27}, {"text": "but it has rules about where\nthey can go in the sign.", "start": 1099.77, "duration": 2.49}, {"text": "And then, of course,\nyou want to know why--", "start": 1102.26, "duration": 1.95}, {"text": "like why, what constrains\nthese to where they go.", "start": 1104.21, "duration": 3.18}, {"text": "But when I say that there's\nwork on ASL phonology, ,", "start": 1107.39, "duration": 2.76}, {"text": "this is what I mean--", "start": 1110.15, "duration": 0.972}, {"text": "there's people\ntrying to figure out", "start": 1111.122, "duration": 1.458}, {"text": "what makes something a\npossible well-formed ASL sign.", "start": 1112.58, "duration": 3.81}, {"text": "It turns out there\nare limits on this.", "start": 1116.39, "duration": 3.24}, {"text": "One observation,\nactually, that people", "start": 1119.63, "duration": 2.82}, {"text": "have made as they\ndo this work, there", "start": 1122.45, "duration": 2.79}, {"text": "are compounds or\npolymorphemic signs,", "start": 1125.24, "duration": 4.062}, {"text": "which you can tell they're\npolymorphemic because they", "start": 1129.302, "duration": 2.208}, {"text": "appear to violate these rules.", "start": 1131.51, "duration": 1.21}, {"text": "So I just said, there aren't\nany signs where you first", "start": 1132.72, "duration": 2.25}, {"text": "finger wiggle and then move.", "start": 1134.97, "duration": 2.98}, {"text": "Here's an apparent\ncounterexample to that.", "start": 1137.95, "duration": 1.75}, {"text": "There's a word \"hypnotist,\"\nwhich goes like this.", "start": 1139.7, "duration": 3.105}, {"text": "But that's a two-morpheme sign.", "start": 1145.43, "duration": 2.52}, {"text": "So it's \"hypnotize\"-- which is\na Brentari short movement plus", "start": 1147.95, "duration": 5.04}, {"text": "finger wiggling-- and\nthen there's a suffix,", "start": 1152.99, "duration": 2.61}, {"text": "which is the agentive suffix.", "start": 1155.6, "duration": 1.86}, {"text": "You use it to make--", "start": 1157.46, "duration": 1.38}, {"text": "you attach it to nouns to\nmake people who do that now.", "start": 1158.84, "duration": 2.47}, {"text": "So it's a hypnotist.", "start": 1161.31, "duration": 1.97}, {"text": "So \"hypnotist\" by itself looks\nlike you're finger wiggling", "start": 1163.28, "duration": 4.11}, {"text": "and then moving.", "start": 1167.39, "duration": 0.93}, {"text": "But that's because there's\na morpheme boundary", "start": 1168.32, "duration": 1.56}, {"text": "between those two things.", "start": 1169.88, "duration": 0.95}, {"text": "So within a morpheme,\nyou can think of it", "start": 1170.83, "duration": 1.708}, {"text": "as a bisyllabic\nword if you want.", "start": 1172.538, "duration": 1.822}, {"text": "So in the first syllable,\nyou're doing finger wiggling", "start": 1174.36, "duration": 2.48}, {"text": "the same way you're doing\nfinger wiggling in color.", "start": 1176.84, "duration": 3.75}, {"text": "And then there's a\nsecond move, which", "start": 1180.59, "duration": 1.8}, {"text": "involves moving your hands.", "start": 1182.39, "duration": 1.23}, {"text": "ASL has one-handed\nsigns, like \"understand,\"", "start": 1189.39, "duration": 3.48}, {"text": "and it also has two-handed\nsigns, like \"go up in flames.\"", "start": 1192.87, "duration": 5.29}, {"text": "There's an interesting\nrestriction in two-handed signs", "start": 1198.16, "duration": 2.25}, {"text": "on the second hand.", "start": 1200.41, "duration": 1.05}, {"text": "So the second hand\neither has to stay still,", "start": 1201.46, "duration": 2.73}, {"text": "like in tree, where one hand\nmoves and the other hand", "start": 1204.19, "duration": 3.24}, {"text": "just stays there in the\nbackground for the first sign,", "start": 1207.43, "duration": 3.75}, {"text": "or it does the same\nthing as the other hand.", "start": 1211.18, "duration": 3.24}, {"text": "So \"teach,\" both your hands\nare doing the same thing.", "start": 1214.42, "duration": 3.87}, {"text": "I love the sign for \"teach.\"", "start": 1218.29, "duration": 1.8}, {"text": "I want to do this\nwhen I teach now.", "start": 1220.09, "duration": 3.33}, {"text": "Or bicycle, where your hands\nare doing the same thing,", "start": 1223.42, "duration": 2.652}, {"text": "but they're out of\nphase with each other.", "start": 1226.072, "duration": 1.708}, {"text": "So they're both\ngoing in circles.", "start": 1227.78, "duration": 2.79}, {"text": "Which is kind of\ninteresting because--", "start": 1230.57, "duration": 1.88}, {"text": "so and that's it, right?", "start": 1232.45, "duration": 1.62}, {"text": "So there aren't\nASL signs in which", "start": 1234.07, "duration": 2.882}, {"text": "one hand is doing one\nthing and the other hand,", "start": 1236.952, "duration": 1.958}, {"text": "is doing a completely\ndifferent thing.", "start": 1238.91, "duration": 2.4}, {"text": "And it's not because--", "start": 1241.31, "duration": 1.97}, {"text": "does that make sense?", "start": 1243.28, "duration": 1.32}, {"text": "So your hands can't\nboth be moving and doing", "start": 1244.6, "duration": 3.57}, {"text": "different things.", "start": 1248.17, "duration": 2.05}, {"text": "Which is interesting, because it\nis actually physically possible", "start": 1250.22, "duration": 2.75}, {"text": "to violate this, to have your\ntwo hands both moving and doing", "start": 1252.97, "duration": 3.48}, {"text": "different things, in poetry.", "start": 1256.45, "duration": 1.59}, {"text": "So there's a video which\nI'll try to show you now", "start": 1258.04, "duration": 3.18}, {"text": "of an ASL poet, guy\nnamed Clayton Valli, who", "start": 1261.22, "duration": 4.26}, {"text": "wrote many poems in ASL.", "start": 1265.48, "duration": 1.26}, {"text": "There are a lot\nof YouTube videos", "start": 1266.74, "duration": 1.62}, {"text": "of him performing his poems.", "start": 1268.36, "duration": 2.4}, {"text": "And this one is\ncalled \"Snowflake.\"", "start": 1270.76, "duration": 2.97}, {"text": "And what he does in it--", "start": 1273.73, "duration": 3.14}, {"text": "the reason I'm going\nto show you the video", "start": 1276.87, "duration": 1.75}, {"text": "is that I can't physically\ndo it very well.", "start": 1278.62, "duration": 1.92}, {"text": "I'll show you what he does.", "start": 1280.54, "duration": 1.83}, {"text": "But I'll tell you\nwhat he's about to do,", "start": 1282.37, "duration": 2.02}, {"text": "just so you can see it.", "start": 1284.39, "duration": 1.67}, {"text": "With one hand, he's doing\nthe sign for \"snowflake\"--", "start": 1286.06, "duration": 3.53}, {"text": "which is a snowflake falling.", "start": 1289.59, "duration": 1.95}, {"text": "And, then with the other\nhand, he's signing one-handed", "start": 1291.54, "duration": 2.31}, {"text": "versions of--", "start": 1293.85, "duration": 1.243}, {"text": "I may not get the order right--", "start": 1295.093, "duration": 1.292}, {"text": "white, cold, beautiful.", "start": 1298.98, "duration": 6.32}, {"text": "And he's doing this as\nthis hand is moving.", "start": 1305.3, "duration": 1.94}, {"text": "So this hand is moving, and\nwith the other hand, he's going,", "start": 1307.24, "duration": 2.5}, {"text": "white, cold, beautiful.", "start": 1309.74, "duration": 1.56}, {"text": "And as you can see, I can't\nphysically do this, but he can.", "start": 1311.3, "duration": 3.24}, {"text": "Let me show you him doing it.", "start": 1314.54, "duration": 1.23}, {"text": "Let me get it.", "start": 1318.47, "duration": 2.732}, {"text": "Where is he?", "start": 1321.202, "duration": 0.608}, {"text": "Yeah, so here's Clayton Valli.", "start": 1321.81, "duration": 1.297}, {"text": "And I think I paused it in\nmore or less the right place,", "start": 1323.107, "duration": 2.333}, {"text": "and we have to watch\nthis for a little bit.", "start": 1325.44, "duration": 1.792}, {"text": "So he's about to sign\nabout looking out", "start": 1327.232, "duration": 2.438}, {"text": "the window at a snowy day.", "start": 1329.67, "duration": 1.71}, {"text": "The snow is coming down.", "start": 1331.38, "duration": 2.43}, {"text": "And now I think\nit's about to come.", "start": 1333.81, "duration": 2.47}, {"text": "Here's the snow piled up.", "start": 1336.28, "duration": 1.07}, {"text": "Come on, Clayton.", "start": 1341.014, "duration": 1.066}, {"text": "Yeah, here it is.", "start": 1346.732, "duration": 0.708}, {"text": "There's the snowflake\nfalling, and", "start": 1347.44, "duration": 1.92}, {"text": "white, beautiful, cold,\nyeah, with his other hand.", "start": 1349.36, "duration": 4.56}, {"text": "So it's physically\npossible to do that,", "start": 1353.92, "duration": 3.63}, {"text": "at least if you're Clayton\nValli, if you're a fluent ASL", "start": 1357.55, "duration": 2.82}, {"text": "signer.", "start": 1360.37, "duration": 1.62}, {"text": "But there aren't any\nASL signs that do it.", "start": 1361.99, "duration": 2.17}, {"text": "It's one of those rules\nthat you break in order", "start": 1364.16, "duration": 4.13}, {"text": "to perform poetry.", "start": 1368.29, "duration": 2.07}, {"text": "So I'll put a link to that.", "start": 1370.36, "duration": 3.18}, {"text": "I'll put link to that poem on\nthe website so you can see.", "start": 1373.54, "duration": 2.76}, {"text": "Yeah?", "start": 1376.3, "duration": 0.5}, {"text": "AUDIENCE: I feel\nlike that might just", "start": 1376.8, "duration": 0.91}, {"text": "be because most people\naren't capable of doing", "start": 1377.71, "duration": 2.49}, {"text": "that, like do a\ncircle with one hand", "start": 1380.2, "duration": 2.523}, {"text": "and a square with the other.", "start": 1382.723, "duration": 1.167}, {"text": "Most people can't do that.", "start": 1383.89, "duration": 1.3}, {"text": "NORVIN RICHARDS:\nSo I think it's one", "start": 1385.19, "duration": 1.58}, {"text": "of those things that probably\nrequires practice, right?", "start": 1386.77, "duration": 2.55}, {"text": "And question, is this something\nthat any ASL signer could just", "start": 1389.32, "duration": 4.23}, {"text": "do cold without any trouble?", "start": 1393.55, "duration": 2.43}, {"text": "If they saw the\nClayton Valli video,", "start": 1395.98, "duration": 1.77}, {"text": "they'd be like, oh, yeah,\nand then they would do it,", "start": 1397.75, "duration": 3.15}, {"text": "and I can't do it because\nI'm not a fluent ASL signer?", "start": 1400.9, "duration": 2.46}, {"text": "Or whether it's because Clayton\nValli practiced in his room", "start": 1403.36, "duration": 3.263}, {"text": "hour after hour\nand eventually got", "start": 1406.623, "duration": 1.417}, {"text": "to where he could get\nhis hands to do that?", "start": 1408.04, "duration": 2.34}, {"text": "Yeah, right.", "start": 1410.38, "duration": 0.84}, {"text": "So I think you're right.", "start": 1411.22, "duration": 1.35}, {"text": "It's not exactly that.", "start": 1412.57, "duration": 1.03}, {"text": "It's not surprising\nthat ASL isn't", "start": 1413.6, "duration": 1.64}, {"text": "full of signs that are like\nthis, with your two hands doing", "start": 1415.24, "duration": 2.82}, {"text": "two different things.", "start": 1418.06, "duration": 1.72}, {"text": "But it's interesting that\nit is physically possible", "start": 1419.78, "duration": 2.84}, {"text": "to learn to do it.", "start": 1422.62, "duration": 1.62}, {"text": "Yeah?", "start": 1424.24, "duration": 1.08}, {"text": "AUDIENCE: I think that it's in\ncontrast to the signing rule.", "start": 1425.32, "duration": 4.08}, {"text": "It's one of the first things\nyou learn in an ASL class.", "start": 1429.4, "duration": 2.714}, {"text": "And I believe that\nis where you should", "start": 1432.114, "duration": 2.629}, {"text": "focus all your attention,\non the dominant hand.", "start": 1434.743, "duration": 3.16}, {"text": "NORVIN RICHARDS:\nYeah, yeah, yeah.", "start": 1437.903, "duration": 1.417}, {"text": "So I mean, you're\nabsolutely right.", "start": 1439.32, "duration": 3.33}, {"text": "What happens is that\nthe non-dominant hand", "start": 1442.65, "duration": 2.25}, {"text": "either copies the\ndominant hand or just", "start": 1444.9, "duration": 2.01}, {"text": "sits still, like in \"tree.\"", "start": 1446.91, "duration": 3.15}, {"text": "And so you think this is\nsomething somebody deliberately", "start": 1450.06, "duration": 3.51}, {"text": "did?", "start": 1453.57, "duration": 0.51}, {"text": "They decided that ASL\nshould work this way?", "start": 1454.08, "duration": 2.455}, {"text": "It'd be interesting to see.", "start": 1456.535, "duration": 1.125}, {"text": "I have no idea.", "start": 1457.66, "duration": 0.65}, {"text": "I'm doing all this\ntalk about ASL.", "start": 1458.31, "duration": 2.01}, {"text": "I started by saying, there\nare many sign languages.", "start": 1460.32, "duration": 2.88}, {"text": "I don't know whether this is\ntrue in every sign language.", "start": 1463.2, "duration": 2.79}, {"text": "I haven't heard\nof a sign language", "start": 1465.99, "duration": 1.5}, {"text": "in which your hands are\nallowed to move independently", "start": 1467.49, "duration": 2.208}, {"text": "of each other.", "start": 1469.698, "duration": 1.012}, {"text": "So it'd be interesting to\nsee how universal this is.", "start": 1470.71, "duration": 2.37}, {"text": "Yeah?", "start": 1473.08, "duration": 0.5}, {"text": "Is there a left-handed versus\nright-handed version of ASL?", "start": 1473.58, "duration": 5.22}, {"text": "No, I mean if, so\nI'm right-handed,", "start": 1478.8, "duration": 3.33}, {"text": "and so this is my\nversion of \"tree.\"", "start": 1482.13, "duration": 1.5}, {"text": "If I were left-handed this\nwould be my version of \"tree.\"", "start": 1483.63, "duration": 2.85}, {"text": "And they mean the same\nthing, as far as I can tell.", "start": 1486.48, "duration": 2.67}, {"text": "Similarly, for the signs\nthat use both hands--", "start": 1489.15, "duration": 3.81}, {"text": "I mean, this is a consequence\nof these facts about the signs", "start": 1492.96, "duration": 2.91}, {"text": "that we've been talking about--\nfor the signs that use both", "start": 1495.87, "duration": 2.458}, {"text": "hands, like \"teach,\" if I'm--", "start": 1498.328, "duration": 3.354}, {"text": "somebody described this\nto me as the equivalent", "start": 1501.682, "duration": 1.958}, {"text": "of talking with your\nmouth full-- if I'm", "start": 1503.64, "duration": 1.667}, {"text": "busy with my right hand,\nif I'm holding something", "start": 1505.307, "duration": 2.713}, {"text": "or whatever, then I\ncan sign \"teach\" just", "start": 1508.02, "duration": 1.98}, {"text": "with my other hand, and\nyou don't lose anything,", "start": 1510.0, "duration": 3.3}, {"text": "in a sense.", "start": 1513.3, "duration": 2.16}, {"text": "You might if there's also a\nsign that's just like this.", "start": 1515.46, "duration": 3.93}, {"text": "And Valli, actually,\nin this video,", "start": 1519.39, "duration": 2.632}, {"text": "is doing something like that.", "start": 1522.022, "duration": 1.208}, {"text": "The sign for \"cold\"\nuses both hands.", "start": 1523.23, "duration": 4.62}, {"text": "They're both moving.", "start": 1527.85, "duration": 1.59}, {"text": "But because his right hand\nis busy doing \"snowflake,\"", "start": 1529.44, "duration": 3.01}, {"text": "he does a one-handed\nversion of \"cold,\" yeah.", "start": 1532.45, "duration": 3.16}, {"text": "Yeah, OK, and I alluded\nto this a second ago.", "start": 1541.18, "duration": 4.55}, {"text": "There's a lot of work\non the use of parts", "start": 1545.73, "duration": 1.77}, {"text": "of the body other\nthan your hands, so", "start": 1547.5, "duration": 1.44}, {"text": "your non-manual component.", "start": 1548.94, "duration": 1.083}, {"text": "There's facial expressions\nthat are involved in doing", "start": 1550.023, "duration": 2.787}, {"text": "certain kinds of things.", "start": 1552.81, "duration": 1.0}, {"text": "So as I said, in\nwh-questions in ASL,", "start": 1553.81, "duration": 3.5}, {"text": "wh-questions require\nyou to furrow your brow", "start": 1557.31, "duration": 3.06}, {"text": "and look puzzled.", "start": 1560.37, "duration": 1.41}, {"text": "And there's all this interesting\nwork on where, exactly, you're", "start": 1561.78, "duration": 2.647}, {"text": "required to do that.", "start": 1564.427, "duration": 0.833}, {"text": "As I said, ASL is a\nwh-in-situ language,", "start": 1565.26, "duration": 4.455}, {"text": "or it has the option\nof wh in situ.", "start": 1569.715, "duration": 2.235}, {"text": "And I do have chalk\ntoday, which is nice.", "start": 1571.95, "duration": 3.16}, {"text": "So apparently,\nwhat that means is", "start": 1575.11, "duration": 3.5}, {"text": "that if you're doing the ASL for\n\"You gave what to the teacher?\"", "start": 1578.61, "duration": 14.07}, {"text": "where just pretend that\nall of this is ASL,", "start": 1592.68, "duration": 3.03}, {"text": "you're required to\nlook puzzled here--", "start": 1595.71, "duration": 3.66}, {"text": "that is, from the\nbeginning of the question", "start": 1599.37, "duration": 2.13}, {"text": "until you get to the wh word.", "start": 1601.5, "duration": 1.68}, {"text": "And then you're allowed\nto relax your face.", "start": 1603.18, "duration": 3.45}, {"text": "And if this is an embedded\nquestion like, I don't know--", "start": 1606.63, "duration": 3.195}, {"text": "so if I'm saying the\nASL for, \"I don't know", "start": 1613.96, "duration": 2.06}, {"text": "what you gave to the teacher\"--", "start": 1616.02, "duration": 2.1}, {"text": "well, then, this is still true.", "start": 1618.12, "duration": 1.53}, {"text": "You sign \"I don't know\" without\ndoing a wh- facial expression,", "start": 1619.65, "duration": 3.57}, {"text": "but you do one for this part.", "start": 1623.22, "duration": 1.89}, {"text": "So from the beginning of the\nquestion to the wh- word,", "start": 1625.11, "duration": 3.21}, {"text": "you're required to look puzzled.", "start": 1628.32, "duration": 2.28}, {"text": "Just kind of cool there's\nthis work on this.", "start": 1630.6, "duration": 4.08}, {"text": "Or similarly, there's a negation\nin facial expression in ASL.", "start": 1634.68, "duration": 4.035}, {"text": "And so negation--", "start": 1638.715, "duration": 1.665}, {"text": "ASL has a word for \"not.\"", "start": 1640.38, "duration": 2.1}, {"text": "It's this.", "start": 1642.48, "duration": 1.87}, {"text": "And so if I want to sign--", "start": 1644.35, "duration": 2.93}, {"text": "oh, sorry.", "start": 1647.28, "duration": 0.99}, {"text": "AUDIENCE: So does that mean that\nthe facial expressions we make", "start": 1648.27, "duration": 2.78}, {"text": "when [INAUDIBLE] are\nrelated to [INAUDIBLE]", "start": 1651.05, "duration": 5.582}, {"text": "face and interaction\nwith others?", "start": 1656.632, "duration": 3.278}, {"text": "Because I would think it's\nsomething that's unique,", "start": 1659.91, "duration": 2.84}, {"text": "like when you're\nconfused, to make", "start": 1662.75, "duration": 2.32}, {"text": "an expression with your face.", "start": 1665.07, "duration": 2.01}, {"text": "Is it just related to\nthe fact that you're", "start": 1667.08, "duration": 2.154}, {"text": "talking with someone you want\nto understand you're confused.", "start": 1669.234, "duration": 2.5}, {"text": "Or is it [INAUDIBLE]?", "start": 1671.734, "duration": 1.886}, {"text": "NORVIN RICHARDS: These are all\nreally interesting questions", "start": 1673.62, "duration": 1.38}, {"text": "to which I don't\nknow the answers.", "start": 1675.0, "duration": 1.417}, {"text": "One possibility is that the\npuzzled facial expression,", "start": 1676.417, "duration": 4.163}, {"text": "the wh- facial\nexpression in ASL,", "start": 1680.58, "duration": 1.95}, {"text": "it's a little bit the\ntwo pronouns for \"I\"", "start": 1682.53, "duration": 3.12}, {"text": "that I was talking\nabout earlier--", "start": 1685.65, "duration": 1.47}, {"text": "that this is \"I\" in ASL, and\nthis is \"I\" in Japanese Sign", "start": 1687.12, "duration": 2.82}, {"text": "Language, and that maybe\nthat's connected to gestures", "start": 1689.94, "duration": 2.55}, {"text": "that hearing people make that\nspeakers of sign languages", "start": 1692.49, "duration": 4.59}, {"text": "are using in a different way.", "start": 1697.08, "duration": 1.45}, {"text": "So you're right, I might, if I\nwere asking you a wh- question,", "start": 1698.53, "duration": 3.41}, {"text": "look puzzled.", "start": 1701.94, "duration": 1.96}, {"text": "I don't have to look puzzled\nto ask you a wh-question,", "start": 1703.9, "duration": 2.72}, {"text": "and there are no particular\nrestrictions on when I should", "start": 1706.62, "duration": 3.69}, {"text": "look puzzled--", "start": 1710.31, "duration": 0.99}, {"text": "where during my question\nI should look puzzled.", "start": 1711.3, "duration": 2.67}, {"text": "But in ASL, there are.", "start": 1713.97, "duration": 1.68}, {"text": "You actually have\nto do this, and you", "start": 1715.65, "duration": 1.8}, {"text": "have to do it at\nthe right points,", "start": 1717.45, "duration": 2.07}, {"text": "in the right points\nof the wh- question.", "start": 1719.52, "duration": 3.48}, {"text": "So their use of\nfacial expressions", "start": 1723.0, "duration": 2.76}, {"text": "is a little more sophisticated,\nI guess, or rule-governed,", "start": 1725.76, "duration": 3.81}, {"text": "than they have been shown to\nbe, anyway, for speaking people.", "start": 1729.57, "duration": 4.17}, {"text": "Now, maybe all this\nshows is that there", "start": 1733.74, "duration": 2.31}, {"text": "hasn't been enough work\non facial expressions", "start": 1736.05, "duration": 2.79}, {"text": "for spoken languages.", "start": 1738.84, "duration": 1.08}, {"text": "We're all obsessed\nwith the sounds,", "start": 1739.92, "duration": 2.22}, {"text": "but for ASL, there's all\nthis clever work on what you", "start": 1742.14, "duration": 3.18}, {"text": "do with the rest of your body.", "start": 1745.32, "duration": 1.32}, {"text": "Yeah, good question.", "start": 1746.64, "duration": 3.22}, {"text": "Similarly, there's a\nnegation facial expression.", "start": 1749.86, "duration": 2.61}, {"text": "So if I want to say, \"I'm\nnot deaf,\" I can sign,", "start": 1752.47, "duration": 3.99}, {"text": "\"I,\" \"not,\" and \"deaf.\"", "start": 1756.46, "duration": 4.2}, {"text": "or I can point at myself and\nshake my head as I sign \"deaf.\"", "start": 1760.66, "duration": 7.74}, {"text": "So I don't have to use\nthe sign for \"not\" at all.", "start": 1768.4, "duration": 3.36}, {"text": "By shaking my head,\nI convey negation", "start": 1771.76, "duration": 3.81}, {"text": "without using the negation sign.", "start": 1775.57, "duration": 2.435}, {"text": "So there are facial expressions\nfor both of these things.", "start": 1778.005, "duration": 2.375}, {"text": "I don't know what\nhappens when they", "start": 1780.38, "duration": 1.458}, {"text": "combine because, presumably,\nyou can ask negative questions.", "start": 1781.838, "duration": 3.164}, {"text": "I guess you can do all of these\nthings with your head at once.", "start": 1785.002, "duration": 2.583}, {"text": "One of the other properties\nof signed languages", "start": 1790.84, "duration": 4.57}, {"text": "which is cool and there's\na lot of work on it", "start": 1795.41, "duration": 3.59}, {"text": "is the use of loci\nin space to refer.", "start": 1799.0, "duration": 3.4}, {"text": "So an English\nsentence like \"Trump", "start": 1802.4, "duration": 2.3}, {"text": "told Biden that he\nwould win\" is ambiguous.", "start": 1804.7, "duration": 4.32}, {"text": "So \"he\" could refer to Trump,\nor to Biden, or to anybody else,", "start": 1809.02, "duration": 5.34}, {"text": "in principle.", "start": 1814.36, "duration": 1.01}, {"text": "It has to refer to\nsome male person.", "start": 1815.37, "duration": 1.93}, {"text": "It could refer to\neither of these people.", "start": 1817.3, "duration": 2.79}, {"text": "If you were going to\nsign this in ASL--", "start": 1820.09, "duration": 2.7}, {"text": "and I'm not going to.", "start": 1822.79, "duration": 1.148}, {"text": "I don't know enough\nASL, but I can tell you", "start": 1823.938, "duration": 1.792}, {"text": "the basic ideas about how this\nwould work-- first of all,", "start": 1825.73, "duration": 2.89}, {"text": "you would need what are\ncalled \"name signs.\"", "start": 1828.62, "duration": 2.48}, {"text": "So you would need to sign the\nnames \"Trump\" and \"Biden\".", "start": 1831.1, "duration": 3.75}, {"text": "The simple way to do that\nis by finger spelling.", "start": 1834.85, "duration": 2.67}, {"text": "So there are correspondents\nto all of the letters.", "start": 1837.52, "duration": 5.377}, {"text": "You can sign all of the letters\nof the English alphabet.", "start": 1842.897, "duration": 2.333}, {"text": "So you could sign T-R-U-M-P,\nonly you'd do it faster if you", "start": 1845.23, "duration": 4.2}, {"text": "knew ASL.", "start": 1849.43, "duration": 2.64}, {"text": "But there are also what are\ncalled \"name signs,\" which", "start": 1852.07, "duration": 2.25}, {"text": "are signs that are just\nsigns for particular people--", "start": 1854.32, "duration": 2.85}, {"text": "typically famous people,\nor people who are deaf,", "start": 1857.17, "duration": 3.87}, {"text": "I think, generally end\nup with name signs.", "start": 1861.04, "duration": 3.96}, {"text": "Name signs are often based--", "start": 1865.0, "duration": 1.77}, {"text": "they often contain the first\nletter of the person's name.", "start": 1866.77, "duration": 3.21}, {"text": "I had a classmate in\ngrad school who was deaf.", "start": 1869.98, "duration": 2.1}, {"text": "He's now a professor at\nGallaudet University.", "start": 1872.08, "duration": 3.42}, {"text": "His name was Gaurav in\nEnglish, and his ASL sign", "start": 1875.5, "duration": 3.638}, {"text": "involved the letter G, which is\nthe first letter of his name,", "start": 1879.138, "duration": 2.542}, {"text": "put on the chest.", "start": 1881.68, "duration": 0.99}, {"text": "Sorry, so that's Gaurav in ASL.", "start": 1882.67, "duration": 3.66}, {"text": "The name sign for\n\"Noam Chomsky,\"", "start": 1886.33, "duration": 1.47}, {"text": "which is one of the few\nother signs I know, is this.", "start": 1887.8, "duration": 3.24}, {"text": "So it's a C. When I\nfirst saw it, I was like,", "start": 1891.04, "duration": 2.442}, {"text": "what, they think\nhe's an alcoholic?", "start": 1893.482, "duration": 1.458}, {"text": "What is the deal?", "start": 1894.94, "duration": 1.87}, {"text": "It turns out to be based\non the sign for \"God.\"", "start": 1896.81, "duration": 2.54}, {"text": "So it's \"God\" with a C.", "start": 1899.35, "duration": 1.54}, {"text": "[LAUGHTER]", "start": 1900.89, "duration": 0.5}, {"text": "It's Noam Chomsky.", "start": 1901.39, "duration": 0.96}, {"text": "It was invented by someone\nwith the proper level", "start": 1902.35, "duration": 2.31}, {"text": "of respect for Noam Chomsky.", "start": 1904.66, "duration": 2.77}, {"text": "The name of sign for\nTrump, there are apparently", "start": 1907.43, "duration": 2.0}, {"text": "various name signs for Trump.", "start": 1909.43, "duration": 1.208}, {"text": "One of them is this--", "start": 1910.638, "duration": 0.877}, {"text": "[LAUGHTER]", "start": 1911.515, "duration": 2.965}, {"text": "Or this, that's another one.", "start": 1914.98, "duration": 3.45}, {"text": "For Biden, I was looking,\nand apparently, there", "start": 1918.43, "duration": 2.928}, {"text": "isn't general agreement on\nwhat the name sign for Biden", "start": 1921.358, "duration": 2.292}, {"text": "ought to be.", "start": 1923.65, "duration": 0.5}, {"text": "One of them is this,\nwhich is apparently", "start": 1924.15, "duration": 2.08}, {"text": "supposed to be a gesture\nthat indicates that he likes", "start": 1926.23, "duration": 3.06}, {"text": "to wear sunglasses, I guess.", "start": 1929.29, "duration": 2.22}, {"text": "It's connected to the fact\nthat he has sunglasses a lot.", "start": 1931.51, "duration": 2.55}, {"text": "By now, there must be\na name sign for Biden", "start": 1934.06, "duration": 2.01}, {"text": "because, of course, he's\nsurrounded by interpreters", "start": 1936.07, "duration": 3.06}, {"text": "when he's talking, you hope.", "start": 1939.13, "duration": 2.22}, {"text": "But anyway, if you wanted\nto say-- bless you-- in ASL,", "start": 1941.35, "duration": 2.598}, {"text": "\"Trump told Biden that he\nwould win,\" you'd sign Trump,", "start": 1943.948, "duration": 2.292}, {"text": "and you'd sign Biden, and\nyou would put them in places.", "start": 1946.24, "duration": 2.85}, {"text": "So you'd say \"Trump,\" and you'd\nput Trump here, and Biden,", "start": 1949.09, "duration": 3.09}, {"text": "put Biden here.", "start": 1952.18, "duration": 1.23}, {"text": "And then you would say,\nhe told him that he--", "start": 1953.41, "duration": 4.532}, {"text": "and then you would\neither point at Trump,", "start": 1957.942, "duration": 1.708}, {"text": "or you would point at Biden--", "start": 1959.65, "duration": 1.26}, {"text": "would win.", "start": 1960.91, "duration": 1.33}, {"text": "So the ASL versions of the\nsentence are not ambiguous.", "start": 1962.24, "duration": 2.66}, {"text": "So you make it clear.", "start": 1964.9, "duration": 2.55}, {"text": "You've either pointed at Trump,\nor you've pointed at Biden.", "start": 1967.45, "duration": 2.67}, {"text": "So he always refers to\nsomeone in particular.", "start": 1970.12, "duration": 2.22}, {"text": "Or, if what I want\nto convey to you", "start": 1972.34, "duration": 2.04}, {"text": "is \"Trump told Biden that\nObama would win,\" well,", "start": 1974.38, "duration": 2.16}, {"text": "then, I need to sign\n\"Biden,\" \"Obama,\"", "start": 1976.54, "duration": 1.65}, {"text": "and put \"Obama\" somewhere else.", "start": 1978.19, "duration": 1.5}, {"text": "You can have many, many people\nin front of you in space.", "start": 1979.69, "duration": 3.075}, {"text": "I believe people who have\nstudied this have not", "start": 1985.63, "duration": 2.37}, {"text": "found limits on how much space,\nhow much subdividing of space", "start": 1988.0, "duration": 3.51}, {"text": "you can do in front of you.", "start": 1991.51, "duration": 1.56}, {"text": "I don't know how\nhard they've tried,", "start": 1993.07, "duration": 1.5}, {"text": "but yeah, it's\ncertainly not just two.", "start": 1994.57, "duration": 2.925}, {"text": "You can have lots of\npronouns in front of you.", "start": 1997.495, "duration": 3.735}, {"text": "There are even fancier\nthings you can do.", "start": 2001.23, "duration": 1.912}, {"text": "I was just reading\na paper about this.", "start": 2003.142, "duration": 1.583}, {"text": "This is kind of astonishing.", "start": 2004.725, "duration": 1.695}, {"text": "So if I want to say something\nin ASL like \"Most of my students", "start": 2006.42, "duration": 3.78}, {"text": "came to class,\" what I do is I\nstart by signing \"my students,\"", "start": 2010.2, "duration": 5.41}, {"text": "and then I put my\nstudents in a circle.", "start": 2015.61, "duration": 2.25}, {"text": "So I have my students, and\nthen I establish a circle", "start": 2017.86, "duration": 2.69}, {"text": "that all of my students are in.", "start": 2020.55, "duration": 1.392}, {"text": "And then I'm going to make\nthe sign for \"most,\" which", "start": 2021.942, "duration": 2.208}, {"text": "I think is something like this.", "start": 2024.15, "duration": 1.39}, {"text": "And then I describe\na smaller circle", "start": 2025.54, "duration": 2.3}, {"text": "that's part of the circle that\nI've just described for you.", "start": 2027.84, "duration": 2.94}, {"text": "And then I would\nsign, \"went to class.\"", "start": 2030.78, "duration": 2.44}, {"text": "So I make my circle that\nhas all the students,", "start": 2033.22, "duration": 3.87}, {"text": "And then I have a\nsubset of that that's--", "start": 2037.09, "duration": 1.91}, {"text": "I draw the kinds of\nVenn diagram-y things", "start": 2039.0, "duration": 2.07}, {"text": "we were talking about before.", "start": 2041.07, "duration": 1.933}, {"text": "Here are the students.", "start": 2043.003, "duration": 0.917}, {"text": "And the cool thing\nabout this is now,", "start": 2043.92, "duration": 1.77}, {"text": "what I've got in front of me is\na space that's got my students,", "start": 2045.69, "duration": 3.029}, {"text": "and it's subdivided into\na larger space that's", "start": 2048.719, "duration": 3.174}, {"text": "got most of my students,\nthe ones who came to class,", "start": 2051.893, "duration": 2.167}, {"text": "and a smaller space that's\ngot the students who", "start": 2054.06, "duration": 2.04}, {"text": "didn't come to class.", "start": 2056.1, "duration": 1.15}, {"text": "So the next\nsentence, apparently,", "start": 2057.25, "duration": 1.909}, {"text": "can be \"They stayed home,\"\npointing at the ones who", "start": 2059.159, "duration": 4.471}, {"text": "didn't come to class.", "start": 2063.63, "duration": 1.529}, {"text": "In English, if I say \"Most\nof my students came to class,", "start": 2065.159, "duration": 3.601}, {"text": "they stayed home,\" I'm\ncontradicting myself.", "start": 2068.76, "duration": 5.72}, {"text": "And there's something\ninteresting going on here.", "start": 2074.48, "duration": 2.0}, {"text": "When we were talking\nabout pronouns,", "start": 2076.48, "duration": 1.5}, {"text": "we just breezed by them, right?", "start": 2077.98, "duration": 1.73}, {"text": "Pronouns, well,\nthey refer to people", "start": 2079.71, "duration": 1.86}, {"text": "who are salient or whatever.", "start": 2081.57, "duration": 2.76}, {"text": "Certainly, if I pass a bunch\nof students on the Infinite", "start": 2084.33, "duration": 5.24}, {"text": "Corridor, I could remark to\nyou, \"They're on their way", "start": 2089.57, "duration": 2.25}, {"text": "to class.\"", "start": 2091.82, "duration": 0.5}, {"text": "We don't have to have been\ntalking about them before.", "start": 2092.32, "duration": 2.208}, {"text": "They're just there in the world.", "start": 2094.528, "duration": 1.381}, {"text": "I get to assume that\nyou're thinking about them.", "start": 2095.909, "duration": 2.311}, {"text": "But if I say \"Most\nof my students", "start": 2098.22, "duration": 2.33}, {"text": "came to class,\" well, that--", "start": 2100.55, "duration": 2.67}, {"text": "I mean, I'm telling you\nthat they're my students,", "start": 2103.22, "duration": 2.4}, {"text": "and that most of\nthem came to class,", "start": 2105.62, "duration": 1.71}, {"text": "and then there were the\nones who didn't, right?", "start": 2107.33, "duration": 2.1}, {"text": "I mean, that's what that means.", "start": 2109.43, "duration": 1.482}, {"text": "But I still don't get to\nrefer to the ones who didn't", "start": 2110.912, "duration": 2.208}, {"text": "come to class with \"they.\"", "start": 2113.12, "duration": 1.29}, {"text": "\"They\" has to refer to the\nones who did come to class.", "start": 2114.41, "duration": 2.25}, {"text": "But in ASL, I get\nto point at them.", "start": 2116.66, "duration": 3.12}, {"text": "And so I get to refer\nto them right away.", "start": 2119.78, "duration": 2.08}, {"text": "Joseph?", "start": 2121.86, "duration": 1.38}, {"text": "AUDIENCE: So the \"Most of\nmy students came to class.\"", "start": 2123.24, "duration": 3.14}, {"text": "NORVIN RICHARDS: Yeah.", "start": 2126.38, "duration": 1.66}, {"text": "AUDIENCE: Because [INAUDIBLE]\nthe quantifier \"most,\"", "start": 2128.04, "duration": 3.585}, {"text": "you're describing a subset.", "start": 2131.625, "duration": 1.785}, {"text": "But doesn't it\nconservatively mean you", "start": 2133.41, "duration": 1.95}, {"text": "get to ignore the [INAUDIBLE]?", "start": 2135.36, "duration": 2.77}, {"text": "NORVIN RICHARDS: So if\nwe didn't know about ASL,", "start": 2138.13, "duration": 2.0}, {"text": "I might have said, why don't I\nget to refer to that other set?", "start": 2140.13, "duration": 4.685}, {"text": "And you might have\nsaid, ah, it's", "start": 2144.815, "duration": 1.375}, {"text": "because of the\nconservativity of \"most.\"", "start": 2146.19, "duration": 1.862}, {"text": "Yeah, that would have been a\npretty plausible thing to say,", "start": 2148.052, "duration": 2.458}, {"text": "and it's maybe even right.", "start": 2150.51, "duration": 2.22}, {"text": "But the fact that in ASL you\ncan refer to them with a pronoun", "start": 2152.73, "duration": 3.0}, {"text": "suggests that\nmaybe it's actually", "start": 2155.73, "duration": 1.86}, {"text": "something else going on.", "start": 2157.59, "duration": 1.135}, {"text": "There's all kinds of stuff\nlike this in spoken languages,", "start": 2158.725, "duration": 2.375}, {"text": "by the way.", "start": 2161.1, "duration": 0.37}, {"text": "It's not just about modifiers.", "start": 2161.47, "duration": 1.25}, {"text": "And so like-- old observation--", "start": 2162.72, "duration": 2.91}, {"text": "if I say, John has a\nchild; she's five--", "start": 2165.63, "duration": 5.94}, {"text": "that's fine.", "start": 2171.57, "duration": 1.02}, {"text": "And \"she,\" you\nprobably figure it's", "start": 2172.59, "duration": 1.56}, {"text": "the child I'm talking about.", "start": 2174.15, "duration": 1.62}, {"text": "If I say, \"John\nis a parent; she's", "start": 2175.77, "duration": 3.15}, {"text": "five,\" that's a weird\nthing for me to say,", "start": 2178.92, "duration": 4.0}, {"text": "even though by saying,\n\"John is a parent,\"", "start": 2182.92, "duration": 1.95}, {"text": "I'm telling you that\nJohn has a child, right?", "start": 2184.87, "duration": 2.01}, {"text": "That's what that means,\nbut it doesn't help.", "start": 2186.88, "duration": 2.31}, {"text": "[LAUGHS] So we're limited\nin how we can use pronouns.", "start": 2189.19, "duration": 4.15}, {"text": "I'm sorry.", "start": 2193.34, "duration": 0.5}, {"text": "You had a point\nyou wanted to make.", "start": 2193.84, "duration": 1.552}, {"text": "AUDIENCE: Is there\nany finer distinction,", "start": 2195.392, "duration": 1.708}, {"text": "like with [INAUDIBLE] say, I\nget most of my students who", "start": 2197.1, "duration": 3.6}, {"text": "don't come to class because--", "start": 2200.7, "duration": 1.82}, {"text": "NORVIN RICHARDS: I\nbelieve you can, then,", "start": 2202.52, "duration": 1.74}, {"text": "draw subparts of these.", "start": 2204.26, "duration": 1.96}, {"text": "I'll put that paper\non the website, too.", "start": 2206.22, "duration": 1.97}, {"text": "You can--", "start": 2208.19, "duration": 0.54}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 2208.73, "duration": 0.48}, {"text": "NORVIN RICHARDS: Yeah,\nthere's all kinds of stuff", "start": 2209.21, "duration": 1.29}, {"text": "that you can do with space.", "start": 2210.5, "duration": 1.143}, {"text": "Again, I don't know what\nthe limits of it are,", "start": 2211.643, "duration": 1.917}, {"text": "but it would be really\ninteresting to find out.", "start": 2213.56, "duration": 1.958}, {"text": "Yeah, they can do more\nreferring to sets and subsets", "start": 2215.518, "duration": 2.424}, {"text": "than we can do because they\nhave the advantage that they've", "start": 2217.942, "duration": 2.458}, {"text": "got a blackboard.", "start": 2220.4, "duration": 2.01}, {"text": "They get to point out\nwhere everything is.", "start": 2222.41, "duration": 2.63}, {"text": "Yeah?", "start": 2225.04, "duration": 0.5}, {"text": "AUDIENCE: OK, so\nthat seems pretty", "start": 2225.54, "duration": 2.06}, {"text": "different from spoken English.", "start": 2227.6, "duration": 1.603}, {"text": "NORVIN RICHARDS: Yeah.", "start": 2229.203, "duration": 0.917}, {"text": "AUDIENCE: [INAUDIBLE] shapes\nthat individual's perception", "start": 2230.12, "duration": 3.298}, {"text": "of the world into\ncertain [INAUDIBLE]..", "start": 2233.418, "duration": 2.172}, {"text": "But is their written form of\ncommunication very different", "start": 2235.59, "duration": 4.21}, {"text": "from a non-deaf individual's?", "start": 2239.8, "duration": 1.44}, {"text": "Or are they similar?", "start": 2241.24, "duration": 0.98}, {"text": "NORVIN RICHARDS: Oh, OK.", "start": 2242.22, "duration": 1.0}, {"text": "So there have been\nvarious attempts", "start": 2243.22, "duration": 1.5}, {"text": "to come up with writing systems\nthat are indigenous to ASL,", "start": 2244.72, "duration": 3.57}, {"text": "and I don't think\nany of them have", "start": 2248.29, "duration": 1.5}, {"text": "gained a lot of popularity.", "start": 2249.79, "duration": 3.79}, {"text": "So when linguists are\nwriting papers about ASL,", "start": 2253.58, "duration": 5.51}, {"text": "what they typically do is--", "start": 2259.09, "duration": 1.303}, {"text": "I mean, I did a parody\nof it over here--", "start": 2260.393, "duration": 1.667}, {"text": "that if you want to write an\nexample sentence that's like,", "start": 2262.06, "duration": 3.33}, {"text": "\"I saw a tree,\" for \"tree,\"\nyou're going to write--", "start": 2265.39, "duration": 3.12}, {"text": "for this sign, you're going\nto write the English word", "start": 2268.51, "duration": 3.45}, {"text": "\"tree\" in all capital letters.", "start": 2271.96, "duration": 1.38}, {"text": "So you use all capital letters\nto indicate that you're", "start": 2273.34, "duration": 2.25}, {"text": "talking about signs.", "start": 2275.59, "duration": 2.16}, {"text": "And then, they'll\nannotate these,", "start": 2277.75, "duration": 1.59}, {"text": "if you're interested\nin indicating things", "start": 2279.34, "duration": 2.61}, {"text": "about facial position,\nand facial expression,", "start": 2281.95, "duration": 2.26}, {"text": "and things like\nthat, there are ways", "start": 2284.21, "duration": 1.5}, {"text": "of annotating that\nto show you're", "start": 2285.71, "duration": 1.4}, {"text": "doing the wh- facial\nexpression or whatever.", "start": 2287.11, "duration": 3.39}, {"text": "As far as actual\nASL speakers go,", "start": 2290.5, "duration": 2.92}, {"text": "my understanding is that they\ntypically don't write in ASL.", "start": 2293.42, "duration": 3.8}, {"text": "So dictionaries, you can find\ndictionaries of ASL online.", "start": 2297.22, "duration": 3.39}, {"text": "They have lots of\nvideos, or they'll", "start": 2300.61, "duration": 2.34}, {"text": "have pictures of one\nframe after another of--", "start": 2302.95, "duration": 4.37}, {"text": "so there isn't-- literacy among\nthe deaf is apparently a really", "start": 2307.32, "duration": 4.69}, {"text": "serious problem, as you\nmight imagine, right?", "start": 2312.01, "duration": 2.13}, {"text": "So somebody who's\nprofoundly deaf,", "start": 2314.14, "duration": 1.89}, {"text": "who hasn't heard a sound--", "start": 2316.03, "duration": 4.13}, {"text": "learning to spell if you\ncan hear is hard enough.", "start": 2320.16, "duration": 4.21}, {"text": "Learning to spell if all of the\nsymbols that you're being asked", "start": 2324.37, "duration": 4.86}, {"text": "to write just don't represent\nanything for you at all,", "start": 2329.23, "duration": 4.29}, {"text": "it's going to be a nightmare.", "start": 2333.52, "duration": 1.3}, {"text": "And so although ASL\nnative signers typically", "start": 2334.82, "duration": 4.58}, {"text": "write in English, it's\napparently very hard,", "start": 2339.4, "duration": 2.665}, {"text": "as you might imagine.", "start": 2342.065, "duration": 0.875}, {"text": "Yeah.", "start": 2342.94, "duration": 1.77}, {"text": "Yeah?", "start": 2344.71, "duration": 1.48}, {"text": "Points about this?", "start": 2346.19, "duration": 1.86}, {"text": "OK.", "start": 2348.05, "duration": 0.5}, {"text": "Oh, OK, so yeah,\nthis has all been", "start": 2353.05, "duration": 2.04}, {"text": "about space and other\nthings to do with your body.", "start": 2355.09, "duration": 2.23}, {"text": "I wanted to show\nyou one other video.", "start": 2357.32, "duration": 3.63}, {"text": "So there's another phenomenon\nthat people use when they are", "start": 2360.95, "duration": 3.05}, {"text": "telling stories or talking\nabout multiple people,", "start": 2364.0, "duration": 3.123}, {"text": "which is what's\ncalled \"role shift\"--", "start": 2367.123, "duration": 1.542}, {"text": "that's what people who\nwork on it call it--", "start": 2368.665, "duration": 2.145}, {"text": "where you'll shift your body.", "start": 2370.81, "duration": 1.86}, {"text": "People do this in\nspoken language,", "start": 2372.67, "duration": 1.737}, {"text": "too, but again, in ASL,\nit's apparently more", "start": 2374.407, "duration": 1.833}, {"text": "or less obligatory.", "start": 2376.24, "duration": 0.99}, {"text": "You'll shift your\nbody to represent", "start": 2377.23, "duration": 1.92}, {"text": "the different characters\nthat you're talking about.", "start": 2379.15, "duration": 3.78}, {"text": "And I'll show you a story\nwhere somebody does this.", "start": 2382.93, "duration": 4.68}, {"text": "It is a story about\nthrowing a stick for a dog,", "start": 2387.61, "duration": 2.25}, {"text": "and one of the nice\nthings about it", "start": 2389.86, "duration": 2.28}, {"text": "is that there's no\nneed at all to explain", "start": 2392.14, "duration": 1.74}, {"text": "what the guy is talking about.", "start": 2393.88, "duration": 2.3}, {"text": "Maybe at the beginning\na little bit.", "start": 2396.18, "duration": 1.5}, {"text": "He's going for a\nwalk with his dog.", "start": 2397.68, "duration": 2.19}, {"text": "No, stop that!", "start": 2403.22, "duration": 1.1}, {"text": "OK, so there's his dog, right?", "start": 2411.93, "duration": 2.1}, {"text": "[LAUGHS] And there's him.", "start": 2414.03, "duration": 1.95}, {"text": "[LAUGHS] Yeah, so\nhe's doing role shift.", "start": 2415.98, "duration": 2.25}, {"text": "He's going to get a stick.", "start": 2418.23, "duration": 1.82}, {"text": "Yeah, and there's the dog again.", "start": 2420.05, "duration": 3.043}, {"text": "The dog's all excited.", "start": 2423.093, "duration": 0.917}, {"text": "There's the guy.", "start": 2424.01, "duration": 0.667}, {"text": "He throws the stick.", "start": 2424.677, "duration": 2.363}, {"text": "Phew, clunk.", "start": 2427.04, "duration": 3.42}, {"text": "And here comes the dog.", "start": 2430.46, "duration": 1.59}, {"text": "And so--", "start": 2432.05, "duration": 0.72}, {"text": "[LAUGHTER]", "start": 2432.77, "duration": 3.114}, {"text": "I'm showing this to you partly\nbecause it's a cute story--", "start": 2438.853, "duration": 2.417}, {"text": "\"Thank you,\" he says.", "start": 2441.27, "duration": 2.305}, {"text": "I'm showing that to you partly\nbecause it's a cute story,", "start": 2443.575, "duration": 2.375}, {"text": "but also because it's a\ngood example of role shift.", "start": 2445.95, "duration": 2.125}, {"text": "So he's-- oh, there's\nClayton Valli again--", "start": 2448.075, "duration": 2.175}, {"text": "a good example of role shift.", "start": 2450.25, "duration": 1.34}, {"text": "So he's using his body to go\nback and forth between being", "start": 2451.59, "duration": 2.82}, {"text": "the dog and being the person.", "start": 2454.41, "duration": 1.23}, {"text": "And apparently, this\nis a standard thing", "start": 2455.64, "duration": 1.667}, {"text": "that you do if you do ASL, if\nyou're a native speaker of ASL.", "start": 2457.307, "duration": 4.183}, {"text": "It's part of being a fluent\nsigner as opposed to being", "start": 2461.49, "duration": 2.64}, {"text": "someone who knows a bit of ASL.", "start": 2464.13, "duration": 1.62}, {"text": "Full screen mode,\nthat's what I want.", "start": 2469.068, "duration": 1.542}, {"text": "OK.", "start": 2473.322, "duration": 0.908}, {"text": "So this was what I wanted to\ntry to show you about ASL.", "start": 2474.23, "duration": 5.17}, {"text": "So just to review, ASL, American\nSign Language, it's a language.", "start": 2479.4, "duration": 5.1}, {"text": "It's a language spoken here in\nAmerica by many deaf people.", "start": 2484.5, "duration": 4.42}, {"text": "It is not English.", "start": 2488.92, "duration": 1.91}, {"text": "It's not any form of English.", "start": 2490.83, "duration": 1.59}, {"text": "It's not charades, and\nit's not English with all", "start": 2492.42, "duration": 2.64}, {"text": "of the words replaced\nby signs, which is what", "start": 2495.06, "duration": 2.19}, {"text": "I believed when I was a kid.", "start": 2497.25, "duration": 2.555}, {"text": "It's a language that's\nquite different from English", "start": 2499.805, "duration": 2.125}, {"text": "in various ways, as\nI've tried to show you.", "start": 2501.93, "duration": 3.72}, {"text": "There's a lot of\ninteresting work on ASL.", "start": 2505.65, "duration": 3.06}, {"text": "A lot of it is on ASL phonology,\nwhere by \"phonology,\" we", "start": 2508.71, "duration": 3.51}, {"text": "mean what we always meant\nby phonology, I guess,", "start": 2512.22, "duration": 2.79}, {"text": "which is the rules for how\nthe articulations work.", "start": 2515.01, "duration": 3.12}, {"text": "So phonology up\nuntil now has all", "start": 2518.13, "duration": 3.3}, {"text": "been about what you're\ndoing with your vocal tract", "start": 2521.43, "duration": 2.44}, {"text": "and what the rules are for what\nyour vocal tract is allowed", "start": 2523.87, "duration": 2.458}, {"text": "to do here or there in a word.", "start": 2526.328, "duration": 3.052}, {"text": "There is an ASL\nversion of this where", "start": 2529.38, "duration": 2.13}, {"text": "people try to understand what\nare the various articulations", "start": 2531.51, "duration": 3.0}, {"text": "your fingers, your hands, your\nwrists, the rest of your body,", "start": 2534.51, "duration": 4.53}, {"text": "what are those\nparts of you allowed", "start": 2539.04, "duration": 1.83}, {"text": "to do at different\npoints in the sign?", "start": 2540.87, "duration": 3.48}, {"text": "And then, as I\nsaid, there's a lot", "start": 2544.35, "duration": 1.53}, {"text": "of interest in the use\nof parts of your body", "start": 2545.88, "duration": 1.65}, {"text": "other than your hands.", "start": 2547.53, "duration": 0.917}, {"text": "Lots of work on facial\nexpression and on role shift,", "start": 2548.447, "duration": 2.233}, {"text": "shifting your shifting\nyour body back and forth.", "start": 2550.68, "duration": 2.52}, {"text": "And that's what I wanted\nto tell you about ASL.", "start": 2553.2, "duration": 3.02}, {"text": "Any questions about any of that?", "start": 2556.22, "duration": 3.58}, {"text": "Then we are done.", "start": 2559.8, "duration": 1.11}, {"text": "You officially know\neverything about 24.900.", "start": 2560.91, "duration": 2.7}, {"text": "So 24.900, you know\neverything about linguistics.", "start": 2563.61, "duration": 2.17}, {"text": "[LAUGHTER]", "start": 2565.78, "duration": 0.5}, {"text": "No, actually, that's false.", "start": 2566.28, "duration": 2.17}, {"text": "But one of the main\ngoals of this class--", "start": 2568.45, "duration": 2.485}, {"text": "this class has\nhad several goals,", "start": 2570.935, "duration": 1.375}, {"text": "but one of the main\ngoals of this class", "start": 2572.31, "duration": 1.625}, {"text": "has been to convince\nyou that there", "start": 2573.935, "duration": 1.705}, {"text": "are some interesting mysteries\nhaving to do with how language", "start": 2575.64, "duration": 3.42}, {"text": "works and that, if you take\nmore linguistics classes,", "start": 2579.06, "duration": 3.182}, {"text": "you might get to learn more\nabout how those mysteries work.", "start": 2582.242, "duration": 2.458}, {"text": "If you take even more\nlinguistics classes,", "start": 2584.7, "duration": 1.83}, {"text": "then you could be the person\nwho solves these mysteries", "start": 2586.53, "duration": 2.61}, {"text": "for the rest of us,\nwhich would be great.", "start": 2589.14, "duration": 2.24}, {"text": "One of the nice things\nabout linguistics--", "start": 2591.38, "duration": 1.75}, {"text": "I think I've said this before--", "start": 2593.13, "duration": 1.38}, {"text": "it's a field that's\nbeen around for a while.", "start": 2594.51, "duration": 2.52}, {"text": "We have some results.", "start": 2597.03, "duration": 1.27}, {"text": "But it's not all that hard,\neven in an intro class,", "start": 2598.3, "duration": 2.57}, {"text": "to bring you right up to the\nedge of what we understand", "start": 2600.87, "duration": 3.18}, {"text": "and invite you to look down into\nthe abyss and ask yourself how", "start": 2604.05, "duration": 3.72}, {"text": "you could build a bridge-- this\nmetaphor is getting away from", "start": 2607.77, "duration": 2.58}, {"text": "me--", "start": 2610.35, "duration": 1.35}, {"text": "how you could move\nfurther, how you", "start": 2611.7, "duration": 1.86}, {"text": "could get further\nfrom where we are.", "start": 2613.56, "duration": 1.902}, {"text": "So I hope that at\nleast some of you", "start": 2615.462, "duration": 1.458}, {"text": "will be inspired to want to\ndo that because we need people", "start": 2616.92, "duration": 2.7}, {"text": "to go out there and\nsolve the mysteries that", "start": 2619.62, "duration": 2.01}, {"text": "haven't been solved.", "start": 2621.63, "duration": 1.8}, {"text": "Questions about any of that?", "start": 2623.43, "duration": 3.162}, {"text": "All right, then, we are done.", "start": 2626.592, "duration": 1.208}, {"text": "Go forth.", "start": 2627.8, "duration": 1.17}, {"text": "Do your class evaluations.", "start": 2628.97, "duration": 1.558}, {"text": "So we're ending early, so\nyou'll have a good half", "start": 2630.528, "duration": 2.042}, {"text": "hour to think hard about what\nyou want to write in your class", "start": 2632.57, "duration": 3.15}, {"text": "evaluations.", "start": 2635.72, "duration": 0.81}, {"text": "And thanks very much.", "start": 2636.53, "duration": 3.132}, {"text": "[APPLAUSE]", "start": 2639.662, "duration": 1.678}, {"text": "Thank you.", "start": 2641.34, "duration": 0.5}, {"text": "Thank you, thank you.", "start": 2645.645, "duration": 0.875}, {"text": "Go out and enjoy the day.", "start": 2646.52, "duration": 2.39}]
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+[{"text": "ANNOUNCER: The\nfollowing content is", "start": 0.0, "duration": 1.52}, {"text": "provided by MIT OpenCourseWare\nunder a Creative Commons", "start": 1.52, "duration": 3.33}, {"text": "License.", "start": 4.85, "duration": 0.9}, {"text": "Additional information\nabout our license", "start": 5.75, "duration": 2.25}, {"text": "and MIT OpenCourseWare\nin general", "start": 8.0, "duration": 2.37}, {"text": "is available at ocw.mit.edu.", "start": 10.37, "duration": 4.632}, {"text": "JEREMY WOLFE: OK.", "start": 15.002, "duration": 0.708}, {"text": "We could continue.", "start": 15.71, "duration": 2.53}, {"text": "Last time I was\ntalking about cognition", "start": 18.24, "duration": 2.06}, {"text": "and framing the argument in\npart in saying that we're not", "start": 20.3, "duration": 5.79}, {"text": "like computers even\nthough computers", "start": 26.09, "duration": 2.31}, {"text": "are nice metaphors for various\naspects of cognitive function.", "start": 28.4, "duration": 4.38}, {"text": "We could continue that today.", "start": 32.78, "duration": 1.83}, {"text": "When you get an\noff-the-shelf computer,", "start": 34.61, "duration": 2.07}, {"text": "you expect that its basic way\nof thinking is going to be--", "start": 36.68, "duration": 7.98}, {"text": "it's there.", "start": 44.66, "duration": 0.96}, {"text": "You might have to\nput programs on it", "start": 45.62, "duration": 3.57}, {"text": "to teach it to do\nspecific things,", "start": 49.19, "duration": 1.65}, {"text": "but you don't have to\neducate its motherboard", "start": 50.84, "duration": 2.61}, {"text": "or something of that sort.", "start": 53.45, "duration": 1.71}, {"text": "With kids, it's not\nclear that that's", "start": 55.16, "duration": 2.37}, {"text": "the case, that if you take\nan off-the-shelf baby,", "start": 57.53, "duration": 3.19}, {"text": "it's not clear that\nthat baby is thinking", "start": 60.72, "duration": 4.019}, {"text": "the way that an\nadult is thinking,", "start": 64.739, "duration": 1.711}, {"text": "and that's really what I\nwant to talk about today.", "start": 66.45, "duration": 6.57}, {"text": "Let me put up a\npicture that I can then", "start": 73.02, "duration": 2.37}, {"text": "return to multiple times.", "start": 75.39, "duration": 3.57}, {"text": "If this is age and we're\ninterested in development, what", "start": 78.96, "duration": 6.6}, {"text": "we were talking about last time\nis the adult state, something", "start": 85.56, "duration": 6.0}, {"text": "about the adult state.", "start": 91.56, "duration": 1.38}, {"text": "What we want to know in\nstudying cognitive development--", "start": 92.94, "duration": 4.67}, {"text": "or any development is,\nwhat's the starting point?", "start": 97.61, "duration": 5.35}, {"text": "If you have a newborn baby,\nis that baby starting at 0", "start": 102.96, "duration": 3.66}, {"text": "or does that baby come with\nan innate endowment that", "start": 106.62, "duration": 3.12}, {"text": "allows them--", "start": 109.74, "duration": 1.87}, {"text": "that gets them on the way\ntowards the adult state?", "start": 111.61, "duration": 4.25}, {"text": "And then what does the\ntransition from the kid state", "start": 115.86, "duration": 7.8}, {"text": "to the adult state look like?", "start": 123.66, "duration": 2.94}, {"text": "Does it look like some\ngradual improvement?", "start": 126.6, "duration": 3.3}, {"text": "Does it look like\nsome step function?", "start": 129.9, "duration": 2.89}, {"text": "It might be useful to describe\nfrom the realm of vision", "start": 132.79, "duration": 6.17}, {"text": "a couple of examples just\nto show you what this means.", "start": 138.96, "duration": 4.95}, {"text": "If you want to know what a\nbaby sees, if you go and--", "start": 143.91, "duration": 3.57}, {"text": "we'll go over here.", "start": 147.48, "duration": 0.81}, {"text": "If you give yourself--\nget yourself a newborn", "start": 148.29, "duration": 3.09}, {"text": "off-the-shelf baby\nand give them--", "start": 151.38, "duration": 3.51}, {"text": "well, you can't give\nthem an eye chart", "start": 154.89, "duration": 1.77}, {"text": "to read because they can't read.", "start": 156.66, "duration": 1.44}, {"text": "So you give them the\nilliterate E chart,", "start": 158.1, "duration": 3.87}, {"text": "as it's called in\nthe trade, and--", "start": 161.97, "duration": 3.42}, {"text": "whoops, well, now and so on.", "start": 165.39, "duration": 4.98}, {"text": "And you ask them which\nway the letters point,", "start": 170.37, "duration": 3.0}, {"text": "the kid doesn't tell\nyou anything useful", "start": 173.37, "duration": 2.25}, {"text": "because the kid can't\nanswer that question.", "start": 175.62, "duration": 2.1}, {"text": "However, conveniently enough, if\nyou take-- even a newborn baby,", "start": 177.72, "duration": 8.76}, {"text": "as young as you can test\nthem, and put them in front", "start": 186.48, "duration": 3.21}, {"text": "of a couple of screens,\na little peephole here--", "start": 189.69, "duration": 5.58}, {"text": "you guys can all be babies,\nand I, the experimenter,", "start": 195.27, "duration": 4.16}, {"text": "would be looking out at\nyou through this peephole,", "start": 199.43, "duration": 2.29}, {"text": "if you put black and white\nbars on one screen and you put", "start": 201.72, "duration": 5.67}, {"text": "on the other screen a gray of\nthe same average luminance--", "start": 207.39, "duration": 4.27}, {"text": "So if this is 0 and that's 100,\nthis is 50 all over the place,", "start": 211.66, "duration": 4.92}, {"text": "if the baby can see the bars,\nconveniently enough, that baby", "start": 216.58, "duration": 4.02}, {"text": "will look at the bars.", "start": 220.6, "duration": 2.23}, {"text": "And if you are\nlooking at the baby,", "start": 222.83, "duration": 3.74}, {"text": "you can figure out-- move\nthe bars from side to side,", "start": 226.57, "duration": 2.97}, {"text": "from trial to trial,\nyou can figure out", "start": 229.54, "duration": 2.13}, {"text": "where that baby\nis looking and you", "start": 231.67, "duration": 2.13}, {"text": "can figure out where\nthe bars are based", "start": 233.8, "duration": 2.01}, {"text": "on where the baby is looking.", "start": 235.81, "duration": 1.86}, {"text": "That's known as a preferential\nlooking method, very useful", "start": 237.67, "duration": 3.0}, {"text": "in infant research.", "start": 240.67, "duration": 3.81}, {"text": "And what you discover, if\nyou do experiments like this,", "start": 244.48, "duration": 3.81}, {"text": "studying infant\nvisual acuity, is", "start": 248.29, "duration": 2.91}, {"text": "that babies don't start at 0.", "start": 251.2, "duration": 2.73}, {"text": "Babies don't start--\nnewborn baby isn't blind.", "start": 253.93, "duration": 4.29}, {"text": "Newborn baby can see something.", "start": 258.22, "duration": 2.4}, {"text": "If normal adult vision\nis around 20/20,", "start": 260.62, "duration": 4.35}, {"text": "newborn baby vision\nis around 24/100.", "start": 264.97, "duration": 3.84}, {"text": "It's the big E at the top\nof the eye chart, roughly.", "start": 268.81, "duration": 4.97}, {"text": "And the progression from the\ninfant state to the adult state", "start": 273.78, "duration": 7.56}, {"text": "is a gradual, relatively\nsteady increase", "start": 281.34, "duration": 3.51}, {"text": "over about the first\ncouple of years of life.", "start": 284.85, "duration": 3.45}, {"text": "Every month, you get roughly\nthe same kind of improvement", "start": 288.3, "duration": 4.44}, {"text": "until you hit the adult level.", "start": 292.74, "duration": 2.79}, {"text": "So not a zero starting point\nand a gradual improvement", "start": 295.53, "duration": 5.76}, {"text": "to adult levels.", "start": 301.29, "duration": 1.24}, {"text": "Now let's take a different\nexample from the same realm.", "start": 302.53, "duration": 3.38}, {"text": "Remember, you've got two eyes.", "start": 305.91, "duration": 1.8}, {"text": "The difference is in those two\neyes are a depth cue, known", "start": 307.71, "duration": 3.78}, {"text": "as binocular stereopsis.", "start": 311.49, "duration": 1.68}, {"text": "Well, the cue is\nbinocular disparity,", "start": 313.17, "duration": 1.74}, {"text": "the ability is stereoscopic\ndepth perception.", "start": 314.91, "duration": 3.93}, {"text": "If you test a baby--", "start": 318.84, "duration": 2.25}, {"text": "so babies, it turns\nout, also like", "start": 321.09, "duration": 2.16}, {"text": "things that stand\nout in depth better", "start": 323.25, "duration": 1.65}, {"text": "than they like flat stuff.", "start": 324.9, "duration": 1.39}, {"text": "So if you show a baby bars\nstanding out in depth,", "start": 326.29, "duration": 3.41}, {"text": "a newborn baby gives you squat.", "start": 329.7, "duration": 5.28}, {"text": "To all appearances, there\nis no binocular stereovision", "start": 334.98, "duration": 3.9}, {"text": "in a newborn baby.", "start": 338.88, "duration": 4.26}, {"text": "And for about the first three\nto five months, nothing happens.", "start": 343.14, "duration": 5.61}, {"text": "And then, over a very\nshort period of time--", "start": 348.75, "duration": 3.63}, {"text": "I should get rid of\nthis other step function", "start": 352.38, "duration": 1.98}, {"text": "just to not confuse matters.", "start": 354.36, "duration": 3.09}, {"text": "Over a very short\nperiod of time,", "start": 357.45, "duration": 2.13}, {"text": "performance rises to\nessentially the adult level", "start": 359.58, "duration": 4.2}, {"text": "as if this was waiting for\nsomething to get wired up", "start": 363.78, "duration": 4.77}, {"text": "in the brain-- when it got\nwired up in the brain, bingo,", "start": 368.55, "duration": 2.61}, {"text": "the kid is fine.", "start": 371.16, "duration": 1.59}, {"text": "Oh, by the way, if you\nare a woman person,", "start": 372.75, "duration": 3.33}, {"text": "you got there first.", "start": 376.08, "duration": 1.56}, {"text": "It turns out to be a\nreliable sex difference", "start": 377.64, "duration": 2.76}, {"text": "that females get binocular\nstereovision a month", "start": 380.4, "duration": 4.86}, {"text": "or so before males.", "start": 385.26, "duration": 2.15}, {"text": "Does this make any\ndifference to anything?", "start": 387.41, "duration": 1.75}, {"text": "No, but we've found\nit years and years ago", "start": 389.16, "duration": 1.79}, {"text": "when I was a grad student,\nso I still remember it.", "start": 390.95, "duration": 3.37}, {"text": "So these are two of the\nvarious possibilities", "start": 394.32, "duration": 2.87}, {"text": "for a function like this--", "start": 397.19, "duration": 1.44}, {"text": "for a developmental course.", "start": 398.63, "duration": 2.4}, {"text": "And we're going to look at--", "start": 401.03, "duration": 2.58}, {"text": "we're going to talk about\nthree specific realms", "start": 403.61, "duration": 5.55}, {"text": "of cognitive development\nin which there", "start": 409.16, "duration": 5.79}, {"text": "are classic demonstrations\nof children doing things", "start": 414.95, "duration": 4.26}, {"text": "differently than\nadults do them, and I", "start": 419.21, "duration": 3.42}, {"text": "will try to take\neach of those apart", "start": 422.63, "duration": 2.64}, {"text": "and to give you\nsome idea of what's", "start": 425.27, "duration": 3.15}, {"text": "the starting point,\nwhat's the ending point,", "start": 428.42, "duration": 2.19}, {"text": "and how do we get between those.", "start": 430.61, "duration": 1.86}, {"text": "The three, which are\noutlined on the handout,", "start": 432.47, "duration": 6.042}, {"text": "have to do with number,\nso-called childhood animism,", "start": 438.512, "duration": 5.238}, {"text": "and egocentric behavior.", "start": 443.75, "duration": 2.14}, {"text": "Let me describe each of\nthese problems to you in turn", "start": 445.89, "duration": 6.8}, {"text": "and then we'll take\neach of them apart.", "start": 452.69, "duration": 3.57}, {"text": "The classic-- these\nare all demonstrations", "start": 456.26, "duration": 3.15}, {"text": "that originally come\nfrom the work of Jean", "start": 459.41, "duration": 4.44}, {"text": "Piaget, the great\nearly-mid 20th-century", "start": 463.85, "duration": 7.35}, {"text": "developmental psychologist,\nwho, among other things", "start": 471.2, "duration": 3.42}, {"text": "bequeathed to us a great\ncollection of phenomena that", "start": 474.62, "duration": 6.12}, {"text": "show striking differences\nbetween the way kids behave", "start": 480.74, "duration": 2.73}, {"text": "and the way adults behave and\nthat cry out for explanation.", "start": 483.47, "duration": 3.33}, {"text": "So here would be one of them.", "start": 486.8, "duration": 1.68}, {"text": "These are M&Ms, let us say.", "start": 488.48, "duration": 3.4}, {"text": "[VOCALIZING]", "start": 491.88, "duration": 2.28}, {"text": "That will do.", "start": 495.591, "duration": 1.079}, {"text": "Oh, I'm running out of space\nhere for my M&Ms. Well,", "start": 500.6, "duration": 3.84}, {"text": "people over there\ncan't see them.", "start": 504.44, "duration": 2.61}, {"text": "Can you see that M&M?", "start": 507.05, "duration": 3.15}, {"text": "Wait a second, I'll\nput them down here.", "start": 510.2, "duration": 3.12}, {"text": "That'll work.", "start": 513.32, "duration": 0.659}, {"text": "There we go.", "start": 516.89, "duration": 0.8}, {"text": "Don't worry about\nthese M&Ms. OK.", "start": 517.69, "duration": 5.43}, {"text": "This is another one of those\nforced choice kind of things.", "start": 523.12, "duration": 2.98}, {"text": "So think hard about this.", "start": 526.1, "duration": 1.65}, {"text": "Are there more\nM&Ms here or here?", "start": 527.75, "duration": 3.56}, {"text": "How many vote up?", "start": 531.31, "duration": 2.55}, {"text": "That's good.", "start": 533.86, "duration": 2.74}, {"text": "However, if you were three,\nfour, five, maybe even six,", "start": 536.6, "duration": 5.51}, {"text": "you'd stay here.", "start": 542.11, "duration": 1.68}, {"text": "You would be perfectly happy.", "start": 543.79, "duration": 2.58}, {"text": "You think, that's\ngood, that's nice.", "start": 546.37, "duration": 2.73}, {"text": "It makes math a little\nmore difficult here at MIT,", "start": 549.1, "duration": 2.79}, {"text": "but you should--", "start": 551.89, "duration": 2.19}, {"text": "but we shouldn't\nstifle your creativity.", "start": 554.08, "duration": 1.95}, {"text": "That's good.", "start": 556.03, "duration": 2.79}, {"text": "And so the first\nobvious thought is,", "start": 558.82, "duration": 2.46}, {"text": "well, the kid's just not quite\nunderstanding the question.", "start": 561.28, "duration": 4.18}, {"text": "It's a language-y kind of thing.", "start": 565.46, "duration": 1.88}, {"text": "We're saying, \"where is more?\"", "start": 567.34, "duration": 1.68}, {"text": "And they're saying\n\"Which is longer?\"", "start": 569.02, "duration": 2.32}, {"text": "So that's why it's important\nthat you use M&Ms. You say, OK,", "start": 571.34, "duration": 3.69}, {"text": "kid, which pile would you like?", "start": 575.03, "duration": 4.08}, {"text": "Kid says, I want this pile.", "start": 579.11, "duration": 1.707}, {"text": "Why do you want this pile?", "start": 580.817, "duration": 1.083}, {"text": "Well, there's more there.", "start": 581.9, "duration": 1.84}, {"text": "Ah.", "start": 583.74, "duration": 0.5}, {"text": "And, in fact, this\nis why you shouldn't", "start": 586.785, "duration": 1.625}, {"text": "be born to a psychologist,\nbecause your psychologist", "start": 588.41, "duration": 3.78}, {"text": "dad is always tricking\nyou out of the candy", "start": 592.19, "duration": 2.19}, {"text": "by playing this game on you.", "start": 594.38, "duration": 1.62}, {"text": "It works.", "start": 596.0, "duration": 1.91}, {"text": "You teach this\nstuff long enough--", "start": 597.91, "duration": 1.9}, {"text": "because this is really true.", "start": 599.81, "duration": 1.35}, {"text": "And then you've got yourself\nlike a three-year-old kid", "start": 601.16, "duration": 3.21}, {"text": "and you mess with his\nbrain and yeah, it's true.", "start": 604.37, "duration": 2.37}, {"text": "[LAUGHTER]", "start": 606.74, "duration": 1.656}, {"text": "This is good stuff.", "start": 608.396, "duration": 1.194}, {"text": "So you want to know what's--", "start": 612.23, "duration": 1.44}, {"text": "the question here, of course,\nis then, what's going on?", "start": 613.67, "duration": 3.96}, {"text": "This is part of a\ngeneral problem.", "start": 617.63, "duration": 2.49}, {"text": "If you take-- so let's\ntake a fat beaker.", "start": 620.12, "duration": 3.72}, {"text": "Here's a big fat beaker\nwith this much fluid in it.", "start": 623.84, "duration": 3.27}, {"text": "Now I pour that into\na narrow beaker.", "start": 627.11, "duration": 2.61}, {"text": "The water-- the fluid level is--", "start": 629.72, "duration": 3.06}, {"text": "STUDENTS: Higher.", "start": 632.78, "duration": 0.835}, {"text": "JEREMY WOLFE: Higher.", "start": 633.615, "duration": 0.875}, {"text": "Is there more fluid now than\nthere was when it was here?", "start": 634.49, "duration": 4.35}, {"text": "No.", "start": 638.84, "duration": 1.8}, {"text": "Does a little kid\nthink there is?", "start": 640.64, "duration": 2.34}, {"text": "Yes.", "start": 642.98, "duration": 1.05}, {"text": "If you let the little kid pour\nit back into the big bowl now,", "start": 644.03, "duration": 3.48}, {"text": "he thinks there's less now.", "start": 647.51, "duration": 1.62}, {"text": "Take a ball of clay,\nroll it out into a snake,", "start": 649.13, "duration": 3.78}, {"text": "there's more clay,\nsays the little kid.", "start": 652.91, "duration": 1.8}, {"text": "Squish it back together,\nnow there's less.", "start": 654.71, "duration": 2.19}, {"text": "These are so-called\nconservation problems.", "start": 656.9, "duration": 2.49}, {"text": "We're particularly\ninterested in the version", "start": 659.39, "duration": 2.01}, {"text": "that has to do with number.", "start": 661.4, "duration": 1.62}, {"text": "How come they think, in this\ncase, that 5 is bigger than 6?", "start": 663.02, "duration": 5.94}, {"text": "Second problem is what's\ncalled childhood animism.", "start": 668.96, "duration": 5.71}, {"text": "The classic Piagetian version\nwould involve something like--", "start": 674.67, "duration": 7.97}, {"text": "well, something exactly like\nhis so-called three-mountain", "start": 682.64, "duration": 4.65}, {"text": "apparatus where he\nhad a tabletop--", "start": 687.29, "duration": 4.92}, {"text": "he's from Switzerland,\nso he's into the Alps.", "start": 692.21, "duration": 2.76}, {"text": "So it's a tabletop\nversion of the Alps.", "start": 694.97, "duration": 2.34}, {"text": "And on the Alps, are things\nlike-- that's a river,", "start": 697.31, "duration": 4.02}, {"text": "and that's a hut.", "start": 701.33, "duration": 3.225}, {"text": "[LAUGHTER]", "start": 704.555, "duration": 2.475}, {"text": "It's-- yeah, it's where\nthe pie-maker lives, right?", "start": 707.03, "duration": 4.17}, {"text": "[LAUGHTER]", "start": 711.2, "duration": 1.275}, {"text": "So anyway.", "start": 712.475, "duration": 0.735}, {"text": "But the point is that\nyou're sitting here", "start": 713.21, "duration": 1.74}, {"text": "looking at this thing.", "start": 714.95, "duration": 0.99}, {"text": "You're like a three-year-old\nor something looking at this.", "start": 715.94, "duration": 3.21}, {"text": "And mom's over there\non the other side.", "start": 719.15, "duration": 3.4}, {"text": "You can see mom.", "start": 722.55, "duration": 1.79}, {"text": "And the question\nthat you're asked", "start": 724.34, "duration": 3.45}, {"text": "is, can your mother\nsee the river?", "start": 727.79, "duration": 3.06}, {"text": "And you say, yeah, sure.", "start": 730.85, "duration": 1.89}, {"text": "As if the fact that you\ncould see the river makes", "start": 732.74, "duration": 5.31}, {"text": "you think that she\ncan see the river.", "start": 738.05, "duration": 1.74}, {"text": "As if you couldn't\ntake her point of view.", "start": 739.79, "duration": 2.475}, {"text": "At least Piaget thought\nthat the problem here", "start": 742.265, "duration": 1.875}, {"text": "is that you can't quite take\nsomebody else's point of view.", "start": 744.14, "duration": 2.55}, {"text": "My favorite anecdotal version of\nthis is a story of a little kid", "start": 746.69, "duration": 5.16}, {"text": "out to eat with his brother\nat some burger place.", "start": 751.85, "duration": 5.28}, {"text": "Little kid wants more French\nfries, and so he does this.", "start": 757.13, "duration": 5.88}, {"text": "On the theory, presumably, if\nI can't see what I'm doing,", "start": 763.01, "duration": 3.96}, {"text": "you can't see what I'm doing.", "start": 766.97, "duration": 2.54}, {"text": "So there-- most people\ndon't do that by the time", "start": 769.51, "duration": 3.79}, {"text": "they reach adulthood.", "start": 773.3, "duration": 2.1}, {"text": "So there's something\nto explain there.", "start": 775.4, "duration": 2.22}, {"text": "That's childhood-- that's\nnot childhood animism at all,", "start": 777.62, "duration": 5.67}, {"text": "actually.", "start": 783.29, "duration": 0.69}, {"text": "That's egocentric behavior.", "start": 783.98, "duration": 2.41}, {"text": "Sorry.", "start": 786.39, "duration": 0.5}, {"text": "I misspoke.", "start": 786.89, "duration": 1.44}, {"text": "That's the third example\nthat we'll get to.", "start": 788.33, "duration": 2.31}, {"text": "So egocentric, that\nmakes more sense.", "start": 790.64, "duration": 2.67}, {"text": "Egocentric is the inability to\nsee things from somebody else's", "start": 793.31, "duration": 4.14}, {"text": "vantage point.", "start": 797.45, "duration": 1.022}, {"text": "So I've just described\nto you the problem", "start": 798.472, "duration": 1.708}, {"text": "of childhood egocentrism.", "start": 800.18, "duration": 2.25}, {"text": "Childhood animism is\na tendency to declare", "start": 802.43, "duration": 5.82}, {"text": "things to be alive that you\nwould not declare to be alive.", "start": 808.25, "duration": 3.72}, {"text": "Is the cat alive?", "start": 811.97, "duration": 1.02}, {"text": "Yeah, fine.", "start": 812.99, "duration": 0.9}, {"text": "Is the sun alive?", "start": 813.89, "duration": 0.76}, {"text": "Yes.", "start": 814.65, "duration": 0.5}, {"text": "Is the cloud-- are\nthe clouds alive?", "start": 815.15, "duration": 1.56}, {"text": "Yes.", "start": 816.71, "duration": 0.5}, {"text": "Little kids will assert that\nand you typically will not.", "start": 817.21, "duration": 4.33}, {"text": "That's animism.", "start": 821.54, "duration": 2.46}, {"text": "Piaget understood that as a\nproblem with mapping concepts", "start": 824.0, "duration": 4.86}, {"text": "onto a discrete set of\nentities out in the world,", "start": 828.86, "duration": 3.43}, {"text": "and so we'll take a\nlook at that, too.", "start": 832.29, "duration": 4.04}, {"text": "So, number, animism,\negocentric behavior, those", "start": 836.33, "duration": 4.5}, {"text": "are the things that I\nwant to talk about today.", "start": 840.83, "duration": 2.26}, {"text": "Let's start with number.", "start": 843.09, "duration": 4.94}, {"text": "And let's start by taking\napart the idea of number a bit", "start": 848.03, "duration": 7.62}, {"text": "because you and I tend\nto think of number as--", "start": 855.65, "duration": 4.27}, {"text": "there's five of those things,\nand six of those things.", "start": 863.64, "duration": 4.25}, {"text": "Number-- the concept of\nnumber, the idea of number", "start": 867.89, "duration": 2.82}, {"text": "can be broken down into three\ndifferent bits, at least.", "start": 870.71, "duration": 5.02}, {"text": "And let's see if I\ncan do this right.", "start": 875.73, "duration": 2.46}, {"text": "Whoop.", "start": 878.19, "duration": 1.06}, {"text": "Oh.", "start": 879.25, "duration": 0.5}, {"text": "Well, they went by.", "start": 879.75, "duration": 0.81}, {"text": "How many warthogs were there?", "start": 880.56, "duration": 3.4}, {"text": "Six?", "start": 883.96, "duration": 0.5}, {"text": "Who knows?", "start": 884.46, "duration": 0.27}, {"text": "Some number.", "start": 884.73, "duration": 0.54}, {"text": "Wait a second.", "start": 885.27, "duration": 0.49}, {"text": "Let's try this again.", "start": 885.76, "duration": 0.875}, {"text": "STUDENT: Eight.", "start": 889.317, "duration": 0.625}, {"text": "JEREMY WOLFE: All right.", "start": 889.942, "duration": 1.238}, {"text": "Nine, eight.", "start": 891.18, "duration": 2.9}, {"text": "Seven.", "start": 894.08, "duration": 0.91}, {"text": "Some number like that.", "start": 894.99, "duration": 1.17}, {"text": "It wasn't 115, but\nhow about this?", "start": 896.16, "duration": 3.02}, {"text": "STUDENTS: Two.", "start": 899.18, "duration": 0.7}, {"text": "JEREMY WOLFE: Yeah, OK.", "start": 899.88, "duration": 0.958}, {"text": "That's good.", "start": 900.838, "duration": 1.032}, {"text": "Whoops.", "start": 901.87, "duration": 0.5}, {"text": "How about this?", "start": 902.37, "duration": 0.96}, {"text": "STUDENTS: Three.", "start": 903.33, "duration": 1.195}, {"text": "JEREMY WOLFE: Whoops.", "start": 904.525, "duration": 0.875}, {"text": "How about that?", "start": 905.4, "duration": 0.41}, {"text": "That was a--", "start": 905.81, "duration": 0.5}, {"text": "[LAUGHTER]", "start": 906.31, "duration": 1.46}, {"text": "How about this?", "start": 907.77, "duration": 0.885}, {"text": "This is data.", "start": 908.655, "duration": 1.065}, {"text": "If you do this\ntask, what you find", "start": 912.24, "duration": 4.59}, {"text": "is that people are essentially\nperfect for 1, 2, and 3, maybe", "start": 916.83, "duration": 3.96}, {"text": "4.", "start": 920.79, "duration": 0.57}, {"text": "And then it falls off.", "start": 921.36, "duration": 1.2}, {"text": "They start-- I think\nthe answer was 8 before,", "start": 922.56, "duration": 2.28}, {"text": "but sometimes you'll say\n7, sometimes you say 9.", "start": 924.84, "duration": 2.49}, {"text": "And so your percent correct,\nbeing absolutely correct", "start": 927.33, "duration": 2.7}, {"text": "will systematically fall off.", "start": 930.03, "duration": 2.92}, {"text": "And if I put 1,500\nwarthogs up there,", "start": 932.95, "duration": 2.27}, {"text": "you'll just not get\nit right at all.", "start": 935.22, "duration": 2.59}, {"text": "Similarly, if I was to\nmeasure not percent correct,", "start": 937.81, "duration": 2.72}, {"text": "but reaction time, the\nreaction time for 1, 2, 3, 4", "start": 940.53, "duration": 4.21}, {"text": "would be essentially\nflat, and then", "start": 944.74, "duration": 3.45}, {"text": "start to roughly\nlinearly increase.", "start": 948.19, "duration": 3.03}, {"text": "That linear increase could be--", "start": 951.22, "duration": 2.25}, {"text": "for a number like\n8, could either", "start": 953.47, "duration": 1.92}, {"text": "be due to some\ncounting operation.", "start": 955.39, "duration": 2.13}, {"text": "Or how many people--", "start": 957.52, "duration": 2.762}, {"text": "somebody tell-- somebody who\nthinks they saw eight of them,", "start": 960.282, "duration": 2.458}, {"text": "tell me how they\nfigured that out.", "start": 962.74, "duration": 2.04}, {"text": "Yeah?", "start": 964.78, "duration": 1.29}, {"text": "STUDENT: You saw a line\nof 5 and a 2 and 1.", "start": 966.07, "duration": 2.55}, {"text": "JEREMY WOLFE: A line\nof 5 and 2 and 1.", "start": 968.62, "duration": 2.38}, {"text": "OK.", "start": 971.0, "duration": 1.01}, {"text": "That's-- yeah, yeah.", "start": 972.01, "duration": 1.313}, {"text": "STUDENT: Well, it kind of\ncame after they went away.", "start": 973.323, "duration": 2.167}, {"text": "JEREMY WOLFE: Oh, OK, yes.", "start": 975.49, "duration": 0.76}, {"text": "If I was doing this as\na proper experiment,", "start": 976.25, "duration": 1.827}, {"text": "I would have masked\nit so you couldn't", "start": 978.077, "duration": 1.583}, {"text": "count like the afterimage\nor the iconic memory.", "start": 979.66, "duration": 2.82}, {"text": "So there-- yep.", "start": 982.48, "duration": 2.323}, {"text": "STUDENT: Just\nrecall the picture?", "start": 984.803, "duration": 2.519}, {"text": "JEREMY WOLFE: OK.", "start": 987.322, "duration": 0.708}, {"text": "So you were also dumping\nit out of iconic memory", "start": 988.03, "duration": 2.093}, {"text": "in some fashion.", "start": 990.123, "duration": 0.667}, {"text": "But the answer I was\nfishing for is something", "start": 990.79, "duration": 2.16}, {"text": "like the 5, 2, and 1 thing.", "start": 992.95, "duration": 2.13}, {"text": "You can count those\ndisplays, and in fact,", "start": 995.08, "duration": 1.807}, {"text": "the people who got them back\nlater might have done this,", "start": 996.887, "duration": 2.333}, {"text": "too, by more typically saying,\noh, there's one group of four,", "start": 999.22, "duration": 4.23}, {"text": "there's another group of four.", "start": 1003.45, "duration": 1.89}, {"text": "This ability to handle small\nnumbers is called subitizing.", "start": 1005.34, "duration": 4.08}, {"text": "And it works for small\nnumbers like 1, 2, 3, 4.", "start": 1009.42, "duration": 3.87}, {"text": "You have some\nimmediate appreciation", "start": 1013.29, "duration": 1.83}, {"text": "of that number-- of\nthose small numbers.", "start": 1015.12, "duration": 3.61}, {"text": "That's different than your\nappreciation of 8 or 17 or 150.", "start": 1018.73, "duration": 6.95}, {"text": "OK, that's one\nwarthog demonstration.", "start": 1025.68, "duration": 5.399}, {"text": "How about, which one\nhas more warthogs?", "start": 1031.079, "duration": 3.421}, {"text": "How many vote that\nthere were more here?", "start": 1038.04, "duration": 2.71}, {"text": "How many vote that\nthere were more here?", "start": 1040.75, "duration": 1.68}, {"text": "Yeah, OK, you got that.", "start": 1042.43, "duration": 1.49}, {"text": "You knew-- how many\nwarthogs were there here?", "start": 1043.92, "duration": 2.37}, {"text": "A lot, yeah.", "start": 1049.26, "duration": 1.98}, {"text": "And how many warthogs were here?", "start": 1051.24, "duration": 2.73}, {"text": "A lot, but not as many.", "start": 1053.97, "duration": 1.41}, {"text": "Well, you can go back.", "start": 1055.38, "duration": 1.45}, {"text": "There we go.", "start": 1056.83, "duration": 0.685}, {"text": "You could count\nthese, obviously,", "start": 1057.515, "duration": 1.375}, {"text": "but you didn't count them.", "start": 1058.89, "duration": 1.41}, {"text": "And you didn't subitize them.", "start": 1060.3, "duration": 1.77}, {"text": "What you did was got\nsome general impression", "start": 1062.07, "duration": 2.85}, {"text": "of their numerosity because--", "start": 1064.92, "duration": 2.42}, {"text": "well, this is-- if you go back\nto the perception chapter,", "start": 1070.66, "duration": 4.19}, {"text": "this is another Weber's\nlaw kind of thing,", "start": 1074.85, "duration": 2.01}, {"text": "or the money example\nfrom last time.", "start": 1076.86, "duration": 3.3}, {"text": "You can also decide something\nabout how many things there", "start": 1080.16, "duration": 5.07}, {"text": "by a ratio comparison.", "start": 1085.23, "duration": 4.08}, {"text": "There's more here than here.", "start": 1089.31, "duration": 2.58}, {"text": "If there were 750 here and 745\nhere, you wouldn't know that.", "start": 1091.89, "duration": 6.3}, {"text": "There has to be a critical\nproportional difference", "start": 1098.19, "duration": 3.42}, {"text": "between the two.", "start": 1101.61, "duration": 0.93}, {"text": "But given a\nproportional difference,", "start": 1102.54, "duration": 1.98}, {"text": "this is something\nlike 2 to 1, it", "start": 1104.52, "duration": 2.22}, {"text": "doesn't matter how\nmany things there are.", "start": 1106.74, "duration": 1.71}, {"text": "You simply know that there's\nmore here and less here.", "start": 1108.45, "duration": 2.43}, {"text": "That's a crude\nsense of numerosity.", "start": 1110.88, "duration": 4.53}, {"text": "The variety of--\nwhat we typically", "start": 1115.41, "duration": 4.2}, {"text": "think of when we think about\nnumbers is counting things.", "start": 1119.61, "duration": 2.7}, {"text": "And that's the third property.", "start": 1122.31, "duration": 1.59}, {"text": "So here, you can count them.", "start": 1123.9, "duration": 1.5}, {"text": "Somebody can go and figure out\nexactly how many warthogs there", "start": 1125.4, "duration": 2.76}, {"text": "are there.", "start": 1128.16, "duration": 0.78}, {"text": "You just have to go through\nand use your counting ability", "start": 1128.94, "duration": 5.72}, {"text": "to figure that out.", "start": 1134.66, "duration": 3.55}, {"text": "You have that ability.", "start": 1138.21, "duration": 1.99}, {"text": "It seems to be critically\npiggybacked on your ability--", "start": 1140.2, "duration": 4.16}, {"text": "on linguistic ability.", "start": 1144.36, "duration": 3.21}, {"text": "Recent interesting evidence\nfor that comes from--", "start": 1147.57, "duration": 3.2}, {"text": "I don't know how to\npronounce it properly,", "start": 1150.77, "duration": 1.75}, {"text": "but something like\nthe Piraha tribe", "start": 1152.52, "duration": 2.16}, {"text": "in the Amazon, their number\nterms consist of 1, 2, and more", "start": 1154.68, "duration": 7.68}, {"text": "than that.", "start": 1162.36, "duration": 1.17}, {"text": "And the result is that they bomb\ntasks that require counting.", "start": 1163.53, "duration": 9.15}, {"text": "They can do subitizing tasks,\nthey can do numerosity tasks,", "start": 1172.68, "duration": 5.28}, {"text": "but they don't do\ncounting tasks.", "start": 1177.96, "duration": 2.91}, {"text": "And they will fail--", "start": 1180.87, "duration": 1.62}, {"text": "they fail versions of\nthe M&M task, in effect.", "start": 1182.49, "duration": 2.95}, {"text": "You say, which of\nthese boxes has--", "start": 1185.44, "duration": 4.11}, {"text": "do you want-- they've\ngot fish in them", "start": 1189.55, "duration": 1.65}, {"text": "or something like that\nand one has a little label", "start": 1191.2, "duration": 1.95}, {"text": "with, I think, four\nfish on the top", "start": 1193.15, "duration": 1.458}, {"text": "and another has five\nfish on the top.", "start": 1194.608, "duration": 1.552}, {"text": "And as far as these\nguys are concerned,", "start": 1196.16, "duration": 1.73}, {"text": "it's all just got lots of fish.", "start": 1197.89, "duration": 3.36}, {"text": "What you see here is a\ntask where they were--", "start": 1201.25, "duration": 4.125}, {"text": "this was the\nexperimenter's marks,", "start": 1205.375, "duration": 2.085}, {"text": "and the Piraha person was\nasked to just copy it so one.", "start": 1207.46, "duration": 6.18}, {"text": "I make one mark, two, I can\nmake that two marks, three.", "start": 1213.64, "duration": 3.81}, {"text": "That's just a bunch, I'll\nmake a bunch of marks.", "start": 1217.45, "duration": 3.36}, {"text": "Once you got out of\nthe subitizing range,", "start": 1220.81, "duration": 1.86}, {"text": "they simply didn't do\nsimply do the task.", "start": 1222.67, "duration": 3.78}, {"text": "I think I put\nthese guys on the--", "start": 1226.45, "duration": 3.505}, {"text": "this article from which\nI stole this picture", "start": 1229.955, "duration": 2.015}, {"text": "may live on the website.", "start": 1231.97, "duration": 1.56}, {"text": "I seem to remember that\nthat was one of the things", "start": 1233.53, "duration": 2.34}, {"text": "that I posted there.", "start": 1235.87, "duration": 2.29}, {"text": "So, what do kids have\nand how does that", "start": 1238.16, "duration": 2.6}, {"text": "tie into the M&M problem?", "start": 1240.76, "duration": 3.88}, {"text": "Well, turns out that\nlittle kids have--", "start": 1244.64, "duration": 5.01}, {"text": "babies have this\nnumerosity, Weber's law,", "start": 1249.65, "duration": 6.21}, {"text": "comparison kind of\nnumerosity ability.", "start": 1255.86, "duration": 2.55}, {"text": "And here's an experiment\ndone by Shu and Liz Spelke", "start": 1258.41, "duration": 4.11}, {"text": "up at Harvard that illustrates\nthat you're a baby,", "start": 1262.52, "duration": 4.89}, {"text": "you're looking at this,\nand every now and then,", "start": 1267.41, "duration": 3.81}, {"text": "the display changes.", "start": 1271.22, "duration": 1.29}, {"text": "Boink.", "start": 1272.51, "duration": 0.63}, {"text": "Yeah, OK, there's\nanother bunch of dots.", "start": 1273.14, "duration": 3.39}, {"text": "And another bunch of dots.", "start": 1276.53, "duration": 1.92}, {"text": "And what I'm doing is I, the\nexperimenter, and measuring", "start": 1278.45, "duration": 3.03}, {"text": "how long you look at this.", "start": 1281.48, "duration": 2.49}, {"text": "And I'm changing the shape and\nthe distribution of these guys,", "start": 1283.97, "duration": 3.18}, {"text": "but I'm not changing the number.", "start": 1287.15, "duration": 2.4}, {"text": "And you are slowly\ngetting bored.", "start": 1289.55, "duration": 3.9}, {"text": "Or to be more technical\nabout it, you're habituating.", "start": 1293.45, "duration": 3.33}, {"text": "You may recall that from\nthe learning chapter.", "start": 1296.78, "duration": 5.118}, {"text": "I don't think we talked about\nit in the chapter-- well,", "start": 1301.898, "duration": 2.292}, {"text": "we can talk about it right now.", "start": 1304.19, "duration": 3.51}, {"text": "Oh, a bunch of people\noriented to that.", "start": 1307.7, "duration": 2.64}, {"text": "And now those people\nare having no problem", "start": 1314.06, "duration": 1.98}, {"text": "at all seeing back out again.", "start": 1316.04, "duration": 2.61}, {"text": "That's habituation.", "start": 1318.65, "duration": 1.35}, {"text": "You do it, babies do it, slugs\ndo it, everybody does it.", "start": 1320.0, "duration": 2.91}, {"text": "It's great.", "start": 1322.91, "duration": 1.32}, {"text": "Useful technique, because the\nbaby's sitting here saying,", "start": 1324.23, "duration": 3.15}, {"text": "this is all more\nor less the same", "start": 1327.38, "duration": 2.35}, {"text": "and it's just not\nthat interesting.", "start": 1329.73, "duration": 3.68}, {"text": "Whoa, wait a second, that's\ninteresting, says the baby.", "start": 1333.41, "duration": 5.07}, {"text": "And the baby says\nit by looking more.", "start": 1338.48, "duration": 2.79}, {"text": "What happens here is that\nlooking time goes down,", "start": 1341.27, "duration": 5.92}, {"text": "down, down, down, is the number\non each trial stays the same.", "start": 1347.19, "duration": 2.99}, {"text": "Then when you jump from\n8 to 16, the baby says,", "start": 1350.18, "duration": 2.312}, {"text": "hey, something's happened, I've\ngot to take a look at this.", "start": 1352.492, "duration": 2.458}, {"text": "Do 16 for a while and blah,\nblah, blah, blah, blah, blah,", "start": 1354.95, "duration": 2.1}, {"text": "blah, blah.", "start": 1357.05, "duration": 0.5}, {"text": "And what this tells\nyou is that the baby", "start": 1357.55, "duration": 3.82}, {"text": "could tell the difference\nbetween 8 and 16.", "start": 1361.37, "duration": 3.06}, {"text": "The reason for changing the\nshape and the distribution", "start": 1364.43, "duration": 3.15}, {"text": "and the density\nand stuff like that", "start": 1367.58, "duration": 1.71}, {"text": "is to make sure that that's\nnot what you're picking up on.", "start": 1369.29, "duration": 3.46}, {"text": "And Shu and Spelke were\ncareful about that.", "start": 1372.75, "duration": 2.83}, {"text": "So what you're picking\nup on here is numerosity.", "start": 1375.58, "duration": 5.3}, {"text": "Babies can do that, but\nif you go from 8 to 9,", "start": 1380.88, "duration": 6.87}, {"text": "nothing happens here.", "start": 1387.75, "duration": 1.75}, {"text": "In fact, if you go from 8 to\n12, a 50% increase in dots,", "start": 1389.5, "duration": 3.59}, {"text": "nothing happens here with--", "start": 1393.09, "duration": 3.068}, {"text": "how old are these babies?", "start": 1396.158, "duration": 1.042}, {"text": "Six-month-old babies.", "start": 1397.2, "duration": 1.62}, {"text": "So 8 to 16, a 2-to-1 change,\nthat babies pick up on.", "start": 1398.82, "duration": 4.3}, {"text": "So, one thing we know--", "start": 1403.12, "duration": 2.51}, {"text": "let me get my graph back here--", "start": 1405.63, "duration": 3.19}, {"text": "Oops.", "start": 1408.82, "duration": 0.5}, {"text": "Graph, come back, graph.", "start": 1409.32, "duration": 1.98}, {"text": "Get my graph back down here.", "start": 1411.3, "duration": 3.4}, {"text": "So we know that if we're\ntalking about number,", "start": 1414.7, "duration": 3.11}, {"text": "the starting spot isn't 0\nfor number-sense in infants.", "start": 1417.81, "duration": 10.68}, {"text": "The numerosity piece, some\nchunk of the numerosity piece", "start": 1428.49, "duration": 5.84}, {"text": "is there for starters.", "start": 1434.33, "duration": 1.68}, {"text": "Perhaps more dramatically,\nthe subitizing piece is there,", "start": 1436.01, "duration": 5.82}, {"text": "and the subitizing\npiece is there along", "start": 1441.83, "duration": 3.03}, {"text": "with what seems to be an\ninnate mathematical ability.", "start": 1444.86, "duration": 6.45}, {"text": "Little kids can\nadd and subtract.", "start": 1451.31, "duration": 2.55}, {"text": "Babies can add and subtract.", "start": 1453.86, "duration": 2.88}, {"text": "This was a surprise.", "start": 1456.74, "duration": 3.09}, {"text": "And I can-- this is\nwork done by Karen Wynn", "start": 1459.83, "duration": 4.26}, {"text": "and it is worth making\nthe historical note", "start": 1464.09, "duration": 3.39}, {"text": "that she was a TA for this\ncourse once upon a time,", "start": 1467.48, "duration": 4.71}, {"text": "now a professor at Yale.", "start": 1472.19, "duration": 1.35}, {"text": "But in any case, she\nfigured out that babies", "start": 1473.54, "duration": 3.57}, {"text": "can add and subtract.", "start": 1477.11, "duration": 1.08}, {"text": "Look, if you ask a\nbaby, what's 1 plus 1?", "start": 1478.19, "duration": 3.33}, {"text": "You get much the same answers.", "start": 1481.52, "duration": 1.48}, {"text": "If you ask the baby, which\nway is the E pointing?", "start": 1483.0, "duration": 2.75}, {"text": "You gotta get clever\nabout this sort of thing.", "start": 1485.75, "duration": 2.38}, {"text": "And here's how Karen\ngot clever about it.", "start": 1488.13, "duration": 3.96}, {"text": "So, you're looking at a screen.", "start": 1492.09, "duration": 1.56}, {"text": "You're a little baby looking\nat a screen like this,", "start": 1493.65, "duration": 4.44}, {"text": "and you see a hand come\nin with an object--", "start": 1498.09, "duration": 3.12}, {"text": "[VOCALIZING] sticking-- it\nprobably wasn't a warthog,", "start": 1501.21, "duration": 3.93}, {"text": "but I had this\nwarthog lying around", "start": 1505.14, "duration": 2.28}, {"text": "as an image on my\ncomputer for some reason.", "start": 1507.42, "duration": 2.68}, {"text": "OK.", "start": 1510.1, "duration": 0.5}, {"text": "So-- eh, and you see a hand\ncome in with another one.", "start": 1510.6, "duration": 4.72}, {"text": "OK.", "start": 1515.32, "duration": 0.5}, {"text": "You got a pretty good\nidea what's going on here.", "start": 1515.82, "duration": 2.79}, {"text": "So if I lift the screen--", "start": 1518.61, "duration": 3.81}, {"text": "[VOCALIZING] what do\nyou expect to see?", "start": 1522.42, "duration": 3.91}, {"text": "[LAUGHTER]", "start": 1526.33, "duration": 2.39}, {"text": "All right.", "start": 1528.72, "duration": 0.6}, {"text": "Now let's-- we\ncan do this again.", "start": 1529.32, "duration": 2.34}, {"text": "Whoop.", "start": 1531.66, "duration": 0.81}, {"text": "Whoop.", "start": 1532.47, "duration": 0.54}, {"text": "OK.", "start": 1533.01, "duration": 0.535}, {"text": "The speed would be\nthe same, of course,", "start": 1533.545, "duration": 1.625}, {"text": "I just didn't want to keep\nsliding them in slowly.", "start": 1535.17, "duration": 3.69}, {"text": "I'll move to screen again.", "start": 1538.86, "duration": 3.15}, {"text": "They you are.", "start": 1542.01, "duration": 1.38}, {"text": "[LAUGHTER]", "start": 1543.39, "duration": 2.7}, {"text": "And the baby will respond\nto this by looking longer.", "start": 1546.09, "duration": 5.25}, {"text": "The baby will say--", "start": 1551.34, "duration": 1.64}, {"text": "the baby will say.", "start": 1552.98, "duration": 0.91}, {"text": "Who knows what\nthe baby will say?", "start": 1553.89, "duration": 1.375}, {"text": "But the baby is apparently,\nin effect, saying,", "start": 1555.265, "duration": 2.267}, {"text": "I put one thing in there,\nso two things are in there.", "start": 1557.532, "duration": 2.208}, {"text": "I guess two-- there\nmust be two stuffs.", "start": 1559.74, "duration": 2.29}, {"text": "Two warthogs back there.", "start": 1562.03, "duration": 1.67}, {"text": "Lift it up, and now\nthere's only one warthog,", "start": 1563.7, "duration": 2.82}, {"text": "and this violates the\nrules of the universe", "start": 1566.52, "duration": 2.47}, {"text": "and I better look\nat this for a while", "start": 1568.99, "duration": 1.82}, {"text": "to figure out what's going on.", "start": 1570.81, "duration": 2.37}, {"text": "And you can use this technique\nto show that babies can do--", "start": 1573.18, "duration": 10.39}, {"text": "I have a subtraction one here?", "start": 1583.57, "duration": 1.25}, {"text": "I forget.", "start": 1584.82, "duration": 1.405}, {"text": "No, that's going to--", "start": 1586.225, "duration": 0.875}, {"text": "I did that already.", "start": 1587.1, "duration": 2.73}, {"text": "Yeah, yeah, yeah.", "start": 1589.83, "duration": 1.5}, {"text": "Did habituate.", "start": 1591.33, "duration": 1.26}, {"text": "Oh, nope.", "start": 1592.59, "duration": 1.47}, {"text": "It works for monkeys, too.", "start": 1594.06, "duration": 1.21}, {"text": "We'll talk about\nthat in a minute.", "start": 1595.27, "duration": 1.68}, {"text": "But you can do this--\nyou can do addition,", "start": 1596.95, "duration": 2.062}, {"text": "you can do subtraction.", "start": 1599.012, "duration": 0.958}, {"text": "So subtraction.", "start": 1599.97, "duration": 1.32}, {"text": "You put-- you have\nthe two things here,", "start": 1601.29, "duration": 2.59}, {"text": "you put down the\nscreen, the hand", "start": 1603.88, "duration": 2.37}, {"text": "comes in and pulls one out.", "start": 1606.25, "duration": 2.64}, {"text": "When the screen comes up,\nthe baby expects to see one.", "start": 1608.89, "duration": 3.36}, {"text": "If the baby sees zero\nor the baby sees two,", "start": 1612.25, "duration": 2.91}, {"text": "the baby says, something\nweird is going on here", "start": 1615.16, "duration": 2.865}, {"text": "and I need to I need to\nthink about this for a while.", "start": 1618.025, "duration": 4.875}, {"text": "Now, if you do this\nwith big numbers", "start": 1622.9, "duration": 2.52}, {"text": "outside of the subitizing\nrange, you don't get the result.", "start": 1625.42, "duration": 3.84}, {"text": "So you stick 15\nwarthogs back there", "start": 1629.26, "duration": 2.49}, {"text": "and you lift up the screen\nand there's 13 warthogs", "start": 1631.75, "duration": 3.66}, {"text": "and the kid says, I don't care.", "start": 1635.41, "duration": 2.85}, {"text": "Once you get above\nabout three with babies,", "start": 1638.26, "duration": 4.44}, {"text": "it doesn't work anymore.", "start": 1642.7, "duration": 1.3}, {"text": "So what you get is evidence\nfor subitizing being present", "start": 1644.0, "duration": 10.16}, {"text": "and some addition\nand subtraction", "start": 1654.16, "duration": 3.93}, {"text": "kind of operation\nfor essentially", "start": 1658.09, "duration": 3.09}, {"text": "as early as you want to test it.", "start": 1661.18, "duration": 1.41}, {"text": "You can also get these\nabilities in animals--", "start": 1662.59, "duration": 2.97}, {"text": "that's what this\nslide is intended", "start": 1665.56, "duration": 2.61}, {"text": "to remind me to tell you.", "start": 1668.17, "duration": 2.52}, {"text": "Animals, certainly\nmacaque monkeys", "start": 1670.69, "duration": 3.06}, {"text": "will show numerosity\neffects and they can also", "start": 1673.75, "duration": 3.78}, {"text": "do this Karen Wynn-style math.", "start": 1677.53, "duration": 3.39}, {"text": "They prefer eggplants.", "start": 1680.92, "duration": 1.89}, {"text": "At least Mark Hauser's\nmonkeys like eggplant,", "start": 1682.81, "duration": 3.81}, {"text": "so that's why they\nare eggplants here.", "start": 1686.62, "duration": 2.04}, {"text": "And you worry about\ndoing this in the lab", "start": 1688.66, "duration": 2.28}, {"text": "because maybe your\nlab monkeys have", "start": 1690.94, "duration": 1.98}, {"text": "led this elaborately studied\nlife and are kind of smart.", "start": 1692.92, "duration": 4.38}, {"text": "So Hauser went down to this\nisland in the Caribbean", "start": 1697.3, "duration": 4.02}, {"text": "where he's got a free-ranging\ntroop of monkeys,", "start": 1701.32, "duration": 2.79}, {"text": "and then you have to coax\nthem into playing your game.", "start": 1704.11, "duration": 3.81}, {"text": "So you're hanging--\nthere's this great video", "start": 1707.92, "duration": 2.22}, {"text": "that Mark has of monkeys.", "start": 1710.14, "duration": 2.34}, {"text": "He's hanging out\nwith his eggplants,", "start": 1712.48, "duration": 2.79}, {"text": "and then he's starting to\ndo this eggplant puppet", "start": 1715.27, "duration": 2.64}, {"text": "show with the macaque is looking\nlonger at the weird ones.", "start": 1717.91, "duration": 4.44}, {"text": "And the guy put\ntwo eggplants there", "start": 1722.35, "duration": 2.16}, {"text": "and there's only one\nthere now, now what?", "start": 1724.51, "duration": 2.34}, {"text": "Hope he's going to feed me some\nof these eggplants eventually.", "start": 1726.85, "duration": 2.7}, {"text": "But in any case,\nmonkeys can do the task.", "start": 1729.55, "duration": 2.31}, {"text": "Monkeys will look\nlonger at things", "start": 1731.86, "duration": 2.22}, {"text": "that violate their expectation.", "start": 1734.08, "duration": 3.97}, {"text": "However, monkeys\ndon't count, at least", "start": 1738.05, "duration": 3.41}, {"text": "they don't count the way\nthat you and I count.", "start": 1741.46, "duration": 3.03}, {"text": "And this goes for great apes.", "start": 1744.49, "duration": 3.3}, {"text": "Let's go find the brightest\nbeast other than humans", "start": 1747.79, "duration": 3.48}, {"text": "that we can.", "start": 1751.27, "duration": 1.65}, {"text": "There's at least one chimp who's\nbeen trained for 20 years--", "start": 1752.92, "duration": 6.87}, {"text": "oh, I misspoke when I talked\nabout this in concourse.", "start": 1759.79, "duration": 2.4}, {"text": "I said he'd been\ntrained for nine years", "start": 1762.19, "duration": 1.625}, {"text": "and never gotten past 20.", "start": 1763.815, "duration": 1.345}, {"text": "It's worse than that.", "start": 1765.16, "duration": 1.23}, {"text": "He's been trained for\n20 years and he's never", "start": 1766.39, "duration": 1.89}, {"text": "gotten past nine.", "start": 1768.28, "duration": 2.22}, {"text": "He can count to nine--", "start": 1770.5, "duration": 1.15}, {"text": "do pretty good stuff\nup to nine, but he's", "start": 1771.65, "duration": 2.42}, {"text": "doing this by basically\nassociation learning.", "start": 1774.07, "duration": 4.41}, {"text": "Up you go.", "start": 1778.48, "duration": 1.2}, {"text": "And let's turn that on\nand let it come back up.", "start": 1779.68, "duration": 4.25}, {"text": "You can train the\nmonkey to realize", "start": 1783.93, "duration": 2.85}, {"text": "that this sign or this graphic\nor something means nine things,", "start": 1786.78, "duration": 7.2}, {"text": "but this is very different\nfrom what you and I can do.", "start": 1793.98, "duration": 4.14}, {"text": "It didn't take you 20 years\nand you got well beyond nine.", "start": 1798.12, "duration": 5.16}, {"text": "Counting seems to be heavily\ndependent on two things.", "start": 1803.28, "duration": 5.71}, {"text": "One is language and the other is\nan act of inductive reasoning.", "start": 1808.99, "duration": 5.3}, {"text": "And you can see\ncounting happening,", "start": 1814.29, "duration": 2.97}, {"text": "the development of counting\nin a series of steps.", "start": 1817.26, "duration": 8.76}, {"text": "Kids, as they are\nlearning language,", "start": 1826.02, "duration": 3.21}, {"text": "learn that there is\nthis game about saying,", "start": 1829.23, "duration": 9.12}, {"text": "1, 2, 3, 4, and so on that\nparents really like to play.", "start": 1838.35, "duration": 8.61}, {"text": "If you start counting, they'll\ngive you the cookies and stuff.", "start": 1846.96, "duration": 6.15}, {"text": "Good things happen.", "start": 1853.11, "duration": 2.82}, {"text": "They don't have\nany particular clue", "start": 1855.93, "duration": 1.65}, {"text": "that this-- initially that\nthis maps on to anything", "start": 1857.58, "duration": 4.47}, {"text": "in particular.", "start": 1862.05, "duration": 3.93}, {"text": "And so what you get with\ntwo-and-a-half-year-old kids is", "start": 1865.98, "duration": 5.04}, {"text": "a two-and-a-half-year-old kid,\nif you ask for one cookie,", "start": 1871.02, "duration": 5.31}, {"text": "will give you one cookie.", "start": 1876.33, "duration": 1.68}, {"text": "But if you ask for\nanything else--", "start": 1878.01, "duration": 1.79}, {"text": "give me two cookies,\ngive me four cookies,", "start": 1879.8, "duration": 1.75}, {"text": "give me whatever, they'll\ngive you some random--", "start": 1881.55, "duration": 2.45}, {"text": "here, have some cookies.", "start": 1884.0, "duration": 1.51}, {"text": "It's one and other stuff.", "start": 1885.51, "duration": 3.03}, {"text": "Eventually, they learn\nto map the counting", "start": 1888.54, "duration": 5.85}, {"text": "onto the subitizing range and\nthen start blowing it later.", "start": 1894.39, "duration": 6.13}, {"text": "So if you have little\nsibs or cousins", "start": 1900.52, "duration": 4.197}, {"text": "or stuff that you've\nhung around with,", "start": 1904.717, "duration": 1.583}, {"text": "you may have seen\nthem counting things.", "start": 1906.3, "duration": 3.42}, {"text": "1, 2, 3, 4, 5, 7, 12.", "start": 1909.72, "duration": 6.72}, {"text": "And they've got this notion\nthat the numbers keep", "start": 1916.44, "duration": 2.28}, {"text": "going in some fashion,\nbut once you get out", "start": 1918.72, "duration": 1.92}, {"text": "of the small numbers,\nit's not terribly clear", "start": 1920.64, "duration": 2.91}, {"text": "what's going on there.", "start": 1923.55, "duration": 1.65}, {"text": "But even in this\nstage, you can start", "start": 1925.2, "duration": 2.79}, {"text": "to see the development of\nsomething more sophisticated.", "start": 1927.99, "duration": 4.05}, {"text": "Six.", "start": 1932.04, "duration": 0.84}, {"text": "They may not know\nhow many sixes.", "start": 1932.88, "duration": 1.83}, {"text": "They know 6 is a lot of stuff.", "start": 1934.71, "duration": 2.74}, {"text": "If you ask for six\ncookies, you'll", "start": 1937.45, "duration": 1.61}, {"text": "get some arbitrary\nnumber of cookies.", "start": 1939.06, "duration": 4.54}, {"text": "But if you ask a little kid--", "start": 1943.6, "duration": 2.66}, {"text": "if I take a lot of\ncookies and I add a few,", "start": 1949.14, "duration": 6.06}, {"text": "do I still have\na lot of cookies?", "start": 1955.2, "duration": 2.94}, {"text": "Kid says, yeah.", "start": 1958.14, "duration": 1.47}, {"text": "Yeah that works.", "start": 1959.61, "duration": 1.59}, {"text": "Kid says-- and so all right.", "start": 1961.2, "duration": 1.81}, {"text": "So we know that.", "start": 1963.01, "duration": 1.02}, {"text": "OK, now, if I have six cookies,\ncan you give me six cookies?", "start": 1964.03, "duration": 5.4}, {"text": "Some random number of cookies.", "start": 1969.43, "duration": 1.27}, {"text": "OK.", "start": 1970.7, "duration": 0.5}, {"text": "If I have six\ncookies and I give--", "start": 1971.2, "duration": 2.46}, {"text": "and I add some more cookies,\ndo I still have six cookies?", "start": 1973.66, "duration": 4.63}, {"text": "No.", "start": 1978.29, "duration": 0.5}, {"text": "You've got a lot of cookies, but\nit's not the same \"a lot of.\"", "start": 1978.79, "duration": 3.63}, {"text": "So even when they don't really\nknow how many cookies you've", "start": 1982.42, "duration": 3.27}, {"text": "got, they have the notion\nthat the number names", "start": 1985.69, "duration": 7.89}, {"text": "are naming something specific.", "start": 1993.58, "duration": 2.85}, {"text": "They don't quite get\nwhat it is, but it's", "start": 1996.43, "duration": 1.71}, {"text": "something specific in a way\nthat a term like \"a lot\" is not.", "start": 1998.14, "duration": 4.86}, {"text": "Eventually, you make\nthe breakthrough", "start": 2003.0, "duration": 5.82}, {"text": "that you can count, basically.", "start": 2008.82, "duration": 3.66}, {"text": "And that you can keep--", "start": 2012.48, "duration": 1.42}, {"text": "and if you add one\nto each of them,", "start": 2013.9, "duration": 2.36}, {"text": "you can just keep\ndoing this forever.", "start": 2016.26, "duration": 2.26}, {"text": "This is-- again, I don't\nknow how much you hang around", "start": 2018.52, "duration": 2.57}, {"text": "with little kids or\nremember your own experience", "start": 2021.09, "duration": 3.24}, {"text": "because this is getting old\nenough that you might actually", "start": 2024.33, "duration": 2.52}, {"text": "remember this state yourself,\nof asking what the biggest", "start": 2026.85, "duration": 5.1}, {"text": "number in the world is?", "start": 2031.95, "duration": 1.74}, {"text": "Anybody remember asking what the\nbiggest number in the world is?", "start": 2033.69, "duration": 3.06}, {"text": "Yeah, all right.", "start": 2036.75, "duration": 1.08}, {"text": "Most of you got-- that's the\nproblem with MIT students,", "start": 2037.83, "duration": 2.46}, {"text": "they figured all this stuff out\nwhen they were like two instead", "start": 2040.29, "duration": 2.34}, {"text": "of--", "start": 2042.63, "duration": 0.36}, {"text": "[LAUGHTER]", "start": 2042.99, "duration": 0.6}, {"text": "So anyway.", "start": 2043.59, "duration": 1.517}, {"text": "You have little kids want\nto know what the biggest", "start": 2045.107, "duration": 2.083}, {"text": "number in the world is.", "start": 2047.19, "duration": 0.969}, {"text": "And so you say to the\nlittle kid, well, what", "start": 2048.159, "duration": 1.461}, {"text": "do you think the biggest\nnumber in the world is?", "start": 2049.62, "duration": 2.19}, {"text": "Well, it's a million.", "start": 2051.81, "duration": 2.7}, {"text": "OK.", "start": 2054.51, "duration": 0.689}, {"text": "What happens if we\nhad a million plus 1?", "start": 2055.199, "duration": 3.96}, {"text": "Is there a number for that?", "start": 2059.159, "duration": 1.23}, {"text": "[MUMMBLING] There's a\nmillion and one, I guess.", "start": 2060.389, "duration": 1.958}, {"text": "Well, I guess a million\nand one is the biggest", "start": 2062.347, "duration": 1.917}, {"text": "number in the world.", "start": 2064.264, "duration": 1.33}, {"text": "Always, we're adding it.", "start": 2065.594, "duration": 1.155}, {"text": "A million and two.", "start": 2066.749, "duration": 1.111}, {"text": "And you can keep doing\nthis for a while.", "start": 2067.86, "duration": 1.667}, {"text": "Eventually, around the time when\nyou get in this conversation,", "start": 2069.527, "duration": 3.402}, {"text": "the kid catches on to the\nnotion that you can always", "start": 2072.929, "duration": 5.371}, {"text": "get a bigger one.", "start": 2078.3, "duration": 1.919}, {"text": "And this is really-- this\nleads to very boring car rides,", "start": 2080.219, "duration": 4.261}, {"text": "sometimes.", "start": 2084.48, "duration": 1.77}, {"text": "Do you want to see\nhow high I can count?", "start": 2086.25, "duration": 1.77}, {"text": "That's a kind of cute game\nwith a three-year-old.", "start": 2088.02, "duration": 2.82}, {"text": "Oh, look, he can get\nall the way to 20.", "start": 2090.84, "duration": 2.16}, {"text": "By the time you get a four or\nfive-year-old, million and one,", "start": 2093.0, "duration": 3.55}, {"text": "million and two,\nmillion and three.", "start": 2096.55, "duration": 2.06}, {"text": "OK, we've made it to\nCalifornia, kid, shut up!", "start": 2098.61, "duration": 3.36}, {"text": "So, what you get is,\nyou've got this base--", "start": 2101.97, "duration": 5.46}, {"text": "you've got this basic numeric\ncompetence or core knowledge,", "start": 2107.43, "duration": 3.78}, {"text": "as Liz Spelke would\ncall it, and then you're", "start": 2111.21, "duration": 5.37}, {"text": "waiting for the\ndevelopment of language.", "start": 2116.58, "duration": 3.06}, {"text": "When you get language, you can\nthen get this counting piece", "start": 2119.64, "duration": 3.6}, {"text": "to work.", "start": 2123.24, "duration": 0.51}, {"text": "When you got the\ncounting piece to work,", "start": 2123.75, "duration": 1.667}, {"text": "you can combine it\nwith your ability", "start": 2125.417, "duration": 1.663}, {"text": "to make the inductive leap\nthat numbers go on forever.", "start": 2127.08, "duration": 4.498}, {"text": "And then you're in a\nposition to go off to school", "start": 2131.578, "duration": 2.042}, {"text": "and learn some math.", "start": 2133.62, "duration": 1.96}, {"text": "So the ability-- I mean,\nthere's, in a sense,", "start": 2135.58, "duration": 2.99}, {"text": "not an adult level of\nnumerical competence.", "start": 2138.57, "duration": 2.64}, {"text": "You guys it's know more\nabout numbers than I know,", "start": 2141.21, "duration": 2.81}, {"text": "I would imagine.", "start": 2144.02, "duration": 1.66}, {"text": "But the ability to go off\nand learn that kind of math", "start": 2145.68, "duration": 3.29}, {"text": "is based on this\ncore knowledge that", "start": 2148.97, "duration": 3.12}, {"text": "waiting on language before\nyou can make the leap to--", "start": 2152.09, "duration": 5.436}, {"text": "ability to use to\ndo 18 or whatever.", "start": 2157.526, "duration": 6.064}, {"text": "So, it's an example,\nif you like,", "start": 2163.59, "duration": 3.66}, {"text": "of the synergistic\ncombination of information", "start": 2167.25, "duration": 2.45}, {"text": "from a couple of\ndifferent realms.", "start": 2169.7, "duration": 1.89}, {"text": "Let's switch to the problem\nof childhood animism that is--", "start": 2171.59, "duration": 8.43}, {"text": "if you're not completely\nconfused from my earlier", "start": 2180.02, "duration": 2.34}, {"text": "misspeaking, animism\nis the tendency to say,", "start": 2182.36, "duration": 3.09}, {"text": "is the sun alive?", "start": 2185.45, "duration": 1.71}, {"text": "Yes.", "start": 2187.16, "duration": 0.6}, {"text": "Are clouds alive?", "start": 2187.76, "duration": 1.38}, {"text": "Yes.", "start": 2189.14, "duration": 0.87}, {"text": "That seems quite different\nfrom what you and I do.", "start": 2190.01, "duration": 6.15}, {"text": "One might wonder exactly\nhow different it really is.", "start": 2196.16, "duration": 6.28}, {"text": "Does it really reflect\na fundamental problem", "start": 2202.44, "duration": 2.79}, {"text": "with the concept alive?", "start": 2205.23, "duration": 3.99}, {"text": "It's not that obvious how you\nmap these the concept like that", "start": 2209.22, "duration": 4.92}, {"text": "even as an adult.", "start": 2214.14, "duration": 1.5}, {"text": "Perhaps straight-- easier to\nthink about in connection with", "start": 2215.64, "duration": 5.85}, {"text": "dead--", "start": 2221.49, "duration": 2.07}, {"text": "mapping dead onto a discrete set\nof things is not that trivial.", "start": 2223.56, "duration": 4.71}, {"text": "Is a rock dead?", "start": 2228.27, "duration": 2.49}, {"text": "Probably not because\nit was never alive.", "start": 2230.76, "duration": 3.12}, {"text": "Is George Washington dead?", "start": 2233.88, "duration": 2.82}, {"text": "That seems about right.", "start": 2236.7, "duration": 1.11}, {"text": "Is he dead in the same\nway that something--", "start": 2237.81, "duration": 3.54}, {"text": "that a cat that\njust recently died?", "start": 2241.35, "duration": 4.38}, {"text": "The sphere is dead now, is that\nthe same is that the same--", "start": 2245.73, "duration": 3.3}, {"text": "how about a dinosaur?", "start": 2249.03, "duration": 1.89}, {"text": "Or the dinosaurs.", "start": 2250.92, "duration": 1.29}, {"text": "Are the dinosaurs dead?", "start": 2252.21, "duration": 1.118}, {"text": "Well, yes, they're dead\nbut they're also extinct,", "start": 2253.328, "duration": 2.042}, {"text": "which is somehow different.", "start": 2255.37, "duration": 2.99}, {"text": "Or to use an example\nfrom driving around,", "start": 2258.36, "duration": 3.67}, {"text": "now that my kids have\ngotten out of the counting", "start": 2262.03, "duration": 2.0}, {"text": "to a million stage--", "start": 2264.03, "duration": 2.52}, {"text": "I don't know how we got on\nthe subject of what is alive?", "start": 2266.55, "duration": 4.81}, {"text": "Maybe because I was\nthinking about this lecture.", "start": 2271.36, "duration": 2.0}, {"text": "But anyway, my 10th grader asked\nmy 3rd grader, is fire alive?", "start": 2273.36, "duration": 8.136}, {"text": "Ah, well, I don't know\nabout the 3rd grader,", "start": 2281.496, "duration": 3.354}, {"text": "but it took dad in the front\nseat a surprisingly long time", "start": 2284.85, "duration": 3.33}, {"text": "to figure-- well, dad knew\nthat the answer is no,", "start": 2288.18, "duration": 3.66}, {"text": "but the principled reason\nwhy it's no takes--", "start": 2291.84, "duration": 3.78}, {"text": "took me a couple\nof beats to get to,", "start": 2295.62, "duration": 2.88}, {"text": "because when a fire breathes,\nit grows, it reproduces, it", "start": 2298.5, "duration": 5.31}, {"text": "can die, it can do\nall those good things.", "start": 2303.81, "duration": 2.93}, {"text": "Turns out that in\n10th grade biology,", "start": 2306.74, "duration": 1.55}, {"text": "they teach you that if\nyou're going to be alive,", "start": 2308.29, "duration": 2.0}, {"text": "you've got to be made of\ncells, and fire is not", "start": 2310.29, "duration": 4.86}, {"text": "made of cells except that-- then\nyou get into 11th grade English", "start": 2315.15, "duration": 5.28}, {"text": "and you read some sci-fi novel\nwhere this thing is alive", "start": 2320.43, "duration": 3.42}, {"text": "but it's just a force field\nin deep space or something", "start": 2323.85, "duration": 3.783}, {"text": "like that, I don't know\nwhat to do about that.", "start": 2327.633, "duration": 1.917}, {"text": "But concepts like alive\nare pretty complex stuff,", "start": 2329.55, "duration": 7.2}, {"text": "and the fact that a kid doesn't\nmap it exactly the same way", "start": 2336.75, "duration": 2.55}, {"text": "you map it may not\nbe that definitive.", "start": 2339.3, "duration": 2.64}, {"text": "Does the kid have a concept\nat all that they can use?", "start": 2341.94, "duration": 3.432}, {"text": "That's what we\nreally want to know.", "start": 2345.372, "duration": 1.458}, {"text": "What's really going on there.", "start": 2346.83, "duration": 1.9}, {"text": "So maybe we ought to ask\nthe question a little bit", "start": 2348.73, "duration": 3.77}, {"text": "differently.", "start": 2352.5, "duration": 0.99}, {"text": "Kid has some notion of\nwhat alive things do.", "start": 2353.49, "duration": 3.51}, {"text": "So suppose we ask a\nkid, does a cat breathe?", "start": 2357.0, "duration": 7.53}, {"text": "Yeah.", "start": 2364.53, "duration": 0.84}, {"text": "Cat breathes.", "start": 2365.37, "duration": 0.72}, {"text": "How about a cow?", "start": 2366.09, "duration": 1.57}, {"text": "Yeah, a cow breathes.", "start": 2367.66, "duration": 1.88}, {"text": "How about the sun?", "start": 2369.54, "duration": 2.31}, {"text": "I don't think so.", "start": 2371.85, "duration": 0.78}, {"text": "The moon?", "start": 2372.63, "duration": 0.57}, {"text": "No.", "start": 2373.2, "duration": 0.3}, {"text": "The clouds?", "start": 2373.5, "duration": 0.6}, {"text": "No.", "start": 2374.1, "duration": 0.5}, {"text": "So that-- and you can do\nthe same thing with babies.", "start": 2374.6, "duration": 4.03}, {"text": "Not asking the babies,\nbut talking about--", "start": 2378.63, "duration": 2.7}, {"text": "does a cat-- can\na cat have babies?", "start": 2381.33, "duration": 3.42}, {"text": "Yeah, sure.", "start": 2384.75, "duration": 0.84}, {"text": "Can the sun have babies?", "start": 2385.59, "duration": 1.98}, {"text": "No.", "start": 2387.57, "duration": 1.71}, {"text": "And you get the feeling\nthat there's a concept there", "start": 2389.28, "duration": 2.97}, {"text": "that they're just not using\nthe word alive the way that you", "start": 2392.25, "duration": 5.73}, {"text": "and I are using it.", "start": 2397.98, "duration": 1.26}, {"text": "Well, maybe all\nyou're looking at here", "start": 2399.24, "duration": 2.58}, {"text": "is the fact that they don't\nactually have a concept.", "start": 2401.82, "duration": 2.64}, {"text": "What they have is a long\nlist of learned instances.", "start": 2404.46, "duration": 2.25}, {"text": "They all hang out at these fancy\nupper-middle-class preschools", "start": 2406.71, "duration": 3.75}, {"text": "where they get taught, kitty\nhas babies, cow has babies,", "start": 2410.46, "duration": 3.81}, {"text": "and they never\nget taught sun has", "start": 2414.27, "duration": 1.8}, {"text": "babies because the sun\ndoesn't have babies.", "start": 2416.07, "duration": 1.95}, {"text": "And so they learn\nall this stuff.", "start": 2418.02, "duration": 1.418}, {"text": "Maybe it's not a concept.", "start": 2419.438, "duration": 1.042}, {"text": "Maybe it's just a\nlist of instances.", "start": 2420.48, "duration": 1.95}, {"text": "How can we figure this out?", "start": 2422.43, "duration": 1.63}, {"text": "Well Sue Carey did an experiment\nwhere what she did was", "start": 2424.06, "duration": 5.33}, {"text": "she taught kids something new.", "start": 2429.39, "duration": 2.55}, {"text": "She said, see this cat?", "start": 2431.94, "duration": 3.69}, {"text": "This cat has a momentum.", "start": 2435.63, "duration": 3.09}, {"text": "And you have an momentum.", "start": 2438.72, "duration": 1.89}, {"text": "And the cow has a momentum.", "start": 2440.61, "duration": 2.43}, {"text": "Now, how about the sheep?", "start": 2443.04, "duration": 3.06}, {"text": "Think it's got momentum?", "start": 2446.1, "duration": 2.43}, {"text": "It's probably got momentum.", "start": 2448.53, "duration": 1.59}, {"text": "And the dog?", "start": 2450.12, "duration": 1.68}, {"text": "Yeah, the dog's probably\ngot-- well, how about a fish?", "start": 2451.8, "duration": 4.11}, {"text": "Yeah, probably.", "start": 2455.91, "duration": 0.99}, {"text": "Could be.", "start": 2456.9, "duration": 0.75}, {"text": "Worm?", "start": 2457.65, "duration": 0.75}, {"text": "I don't know.", "start": 2458.4, "duration": 1.185}, {"text": "A rock?", "start": 2459.585, "duration": 0.855}, {"text": "Nah, a rock doesn't\nhave momentum.", "start": 2460.44, "duration": 2.16}, {"text": "How about a sun?", "start": 2462.6, "duration": 1.17}, {"text": "Nah, sun doesn't\nhave a momentum.", "start": 2463.77, "duration": 1.71}, {"text": "You don't have one\neither, it turns out.", "start": 2465.48, "duration": 2.31}, {"text": "She wanted a real\nbiological term, but she--", "start": 2467.79, "duration": 2.49}, {"text": "I think it's some weird\nmembrane that an insect has", "start": 2470.28, "duration": 2.49}, {"text": "or something like that.", "start": 2472.77, "duration": 1.12}, {"text": "But the point was that\nit wasn't something", "start": 2473.89, "duration": 2.12}, {"text": "that you would\nhave ever learned.", "start": 2476.01, "duration": 1.38}, {"text": "It's a new piece of knowledge.", "start": 2477.39, "duration": 1.87}, {"text": "And if you say that\nthings in this category,", "start": 2479.26, "duration": 3.56}, {"text": "things in the category that is\nare encompassed by cats, cows,", "start": 2482.82, "duration": 4.69}, {"text": "and you all have\nthis, who else has it?", "start": 2487.51, "duration": 3.65}, {"text": "And little kids, three,\nfour-year-old kids,", "start": 2491.16, "duration": 2.52}, {"text": "map this in a plausible\nkind of a way.", "start": 2493.68, "duration": 3.94}, {"text": "So it might map\nsomething like mammal,", "start": 2497.62, "duration": 2.12}, {"text": "it might map\nsomething like animal.", "start": 2499.74, "duration": 2.19}, {"text": "I don't remember\nif any of her kids", "start": 2501.93, "duration": 1.65}, {"text": "mapped something like\nalive, in which case,", "start": 2503.58, "duration": 2.047}, {"text": "they would assert that a tree\nhad it, too, or something.", "start": 2505.627, "duration": 2.333}, {"text": "But it maps a concept that\nhas a biological ring to it.", "start": 2507.96, "duration": 8.29}, {"text": "What's the difference\nbetween the childhood", "start": 2516.25, "duration": 2.51}, {"text": "use of these concepts and the\nadult use of these concepts?", "start": 2518.76, "duration": 2.73}, {"text": "It seems to be, in\nthis case, education.", "start": 2521.49, "duration": 3.39}, {"text": "You go to school to\nlearn the right concepts.", "start": 2524.88, "duration": 3.69}, {"text": "In this sense, there\nis no firm adult state.", "start": 2528.57, "duration": 4.86}, {"text": "I mean, my job here is to\nteach you a collection of facts", "start": 2533.43, "duration": 4.44}, {"text": "and the right concepts\nin psychology,", "start": 2537.87, "duration": 4.98}, {"text": "but I can teach\nyou some of them,", "start": 2542.85, "duration": 1.71}, {"text": "and I keep learning new ones.", "start": 2544.56, "duration": 1.65}, {"text": "And the adult bar\nkeeps drifting there.", "start": 2546.21, "duration": 4.53}, {"text": "So you go off to\nlearn these concepts,", "start": 2550.74, "duration": 2.82}, {"text": "but you don't learn to\nhave a concept, per se.", "start": 2553.56, "duration": 4.35}, {"text": "What the kid is\ndoing, well actually,", "start": 2557.91, "duration": 2.64}, {"text": "it's rather similar to\nwhat we're doing here.", "start": 2560.55, "duration": 2.17}, {"text": "The kid is mustering the\ndata that is available to him", "start": 2562.72, "duration": 7.56}, {"text": "and working with a\nconcept as long--", "start": 2570.28, "duration": 3.79}, {"text": "so what do you think the concept\nof alive is for a little kid?", "start": 2574.07, "duration": 3.89}, {"text": "What do you think goes into it\nthat causes little kids to give", "start": 2577.96, "duration": 4.35}, {"text": "the wrong answer when asked\nby Piaget what's alive", "start": 2582.31, "duration": 4.08}, {"text": "and what's not?", "start": 2586.39, "duration": 0.84}, {"text": "What's the critical\ndifference between your notion", "start": 2587.23, "duration": 2.88}, {"text": "of alive that you\npicked up in 10th grade", "start": 2590.11, "duration": 2.37}, {"text": "biology and a four-year-old's\nnotion of alive?", "start": 2592.48, "duration": 6.03}, {"text": "Anybody?", "start": 2598.51, "duration": 0.6}, {"text": "Yeah?", "start": 2599.11, "duration": 0.5}, {"text": "STUDENT: Something alive\nis something that moves", "start": 2599.61, "duration": 2.41}, {"text": "and you didn't see how--", "start": 2602.02, "duration": 1.988}, {"text": "JEREMY WOLFE: Yeah.", "start": 2604.008, "duration": 0.792}, {"text": "So moving on its own\nseems to be an import--", "start": 2604.8, "duration": 3.3}, {"text": "so cars aren't\nalive because you've", "start": 2608.1, "duration": 1.8}, {"text": "got to make them\nmove in some fashion,", "start": 2609.9, "duration": 2.91}, {"text": "but self-produced\nmotion seems to be", "start": 2612.81, "duration": 5.578}, {"text": "an important part of the\ndefinition-- and the sun", "start": 2618.388, "duration": 2.042}, {"text": "and the clouds and the moon seem\nto scooch around in the sky,", "start": 2620.43, "duration": 4.02}, {"text": "particularly if you're\ndriving in that car,", "start": 2624.45, "duration": 2.82}, {"text": "in ways that suggest\nthat it might be alive.", "start": 2627.27, "duration": 3.005}, {"text": "It gets a little\nmore complicated", "start": 2630.275, "duration": 1.375}, {"text": "because kids have also\nlearned that trees are alive,", "start": 2631.65, "duration": 3.06}, {"text": "and outside of\nLord of the Rings,", "start": 2634.71, "duration": 2.22}, {"text": "trees don't do much in the\nway of wandering around.", "start": 2636.93, "duration": 3.87}, {"text": "But growing on your\nown is good, too.", "start": 2640.8, "duration": 3.18}, {"text": "And that would be part of\nthe biological definition,", "start": 2643.98, "duration": 3.51}, {"text": "but it's the self-produced\nmotion thing that kids regard--", "start": 2647.49, "duration": 3.48}, {"text": "that kids overuse\nin their definition,", "start": 2650.97, "duration": 3.51}, {"text": "seemingly, that you don't use.", "start": 2654.48, "duration": 2.52}, {"text": "You can see, if\nyou get transcripts", "start": 2657.0, "duration": 2.34}, {"text": "of little kids using\nlanguage, you can see--", "start": 2659.34, "duration": 4.86}, {"text": "you can get a feeling\nfor this little scientist", "start": 2664.2, "duration": 2.55}, {"text": "aspect of childhood concept.", "start": 2666.75, "duration": 3.39}, {"text": "Well, concept formation\nand concept verification.", "start": 2670.14, "duration": 4.14}, {"text": "So here, from the\n\"What is alive?\"", "start": 2674.28, "duration": 3.96}, {"text": "literature, is a kid who\nis asked, are rocks alive?", "start": 2678.24, "duration": 7.68}, {"text": "And the answer is\nyes, rocks are alive,", "start": 2685.92, "duration": 4.71}, {"text": "but they're only alive\nuntil you step on them,", "start": 2690.63, "duration": 2.52}, {"text": "and then they die, which\nis kind of reasonable.", "start": 2693.15, "duration": 4.29}, {"text": "The kid's got presumably some\nexperience with other things", "start": 2697.44, "duration": 2.61}, {"text": "like that.", "start": 2700.05, "duration": 0.94}, {"text": "This ant, the ant's alive.", "start": 2700.99, "duration": 2.27}, {"text": "Step on it and it's\nnot alive anymore.", "start": 2703.26, "duration": 2.82}, {"text": "And he can actually--\nand this kid", "start": 2706.08, "duration": 2.61}, {"text": "produces some evidence in\nfavor of this theory, which", "start": 2708.69, "duration": 4.41}, {"text": "is, if you look on a path, how\nbig are the rocks on average?", "start": 2713.1, "duration": 7.91}, {"text": "I can take a walk in the woods,\ndown a rocky kind of path--", "start": 2721.01, "duration": 3.538}, {"text": "there are rocks on there.", "start": 2724.548, "duration": 1.042}, {"text": "They're small rocks.", "start": 2725.59, "duration": 1.14}, {"text": "You look off across\nat the mountains.", "start": 2726.73, "duration": 3.45}, {"text": "How big are the rocks?", "start": 2730.18, "duration": 1.87}, {"text": "Well, they're huge.", "start": 2732.05, "duration": 1.1}, {"text": "What's going on here?", "start": 2733.15, "duration": 1.18}, {"text": "Well, on a path, people\nare walking all the time,", "start": 2734.33, "duration": 2.31}, {"text": "so the rocks die real young\nand they never get to grow big.", "start": 2736.64, "duration": 4.46}, {"text": "Whereas the rocks off the\npath out in the mountains,", "start": 2741.1, "duration": 2.97}, {"text": "they got to grow to\nbe really big rocks.", "start": 2744.07, "duration": 2.31}, {"text": "It's not a correct\ntheory, but you", "start": 2746.38, "duration": 2.58}, {"text": "can see the kid using\nthe data he's got,", "start": 2748.96, "duration": 3.96}, {"text": "a certain amount of data there.", "start": 2752.92, "duration": 1.74}, {"text": "If I step on it, it dies.", "start": 2754.66, "duration": 3.09}, {"text": "Maybe that's what\nhappens to rocks,", "start": 2757.75, "duration": 1.74}, {"text": "and people step more here\nthan they step there,", "start": 2759.49, "duration": 2.76}, {"text": "so big rocks, little rocks--\nit all hangs together,", "start": 2762.25, "duration": 2.67}, {"text": "I got a great theory here.", "start": 2764.92, "duration": 1.74}, {"text": "Or another one.", "start": 2766.66, "duration": 4.17}, {"text": "Are rocks alive?", "start": 2770.83, "duration": 0.97}, {"text": "Yes.", "start": 2771.8, "duration": 0.5}, {"text": "Can they have babies?", "start": 2772.3, "duration": 1.11}, {"text": "Yes.", "start": 2773.41, "duration": 0.69}, {"text": "Are all rocks alive?", "start": 2774.1, "duration": 1.15}, {"text": "No.", "start": 2775.25, "duration": 0.5}, {"text": "Some rocks are dead.", "start": 2775.75, "duration": 1.08}, {"text": "How can you tell\nif a rock is dead?", "start": 2776.83, "duration": 2.71}, {"text": "Well, the dead ones\njust lie there.", "start": 2779.54, "duration": 3.56}, {"text": "This is capturing the notion\nof-- that motion is important", "start": 2783.1, "duration": 4.95}, {"text": "in little kids' definitions\nof the notion of aliveness,", "start": 2788.05, "duration": 5.7}, {"text": "and then--", "start": 2793.75, "duration": 2.592}, {"text": "I don't know how\nmany rocks you saw", "start": 2796.342, "duration": 1.458}, {"text": "moving under their own power.", "start": 2797.8, "duration": 2.19}, {"text": "But in any case, you can\nsee the little scientist", "start": 2799.99, "duration": 4.56}, {"text": "aspect of this.", "start": 2804.55, "duration": 0.87}, {"text": "OK, so what's the\nstarting point here?", "start": 2805.42, "duration": 2.235}, {"text": "The concepts that\nyou're building", "start": 2810.22, "duration": 5.37}, {"text": "seem to have some foundations\nthat can be picked up very", "start": 2815.59, "duration": 3.87}, {"text": "early and are probably innate.", "start": 2819.46, "duration": 1.95}, {"text": "I'll just talk about\ntwo of them here.", "start": 2821.41, "duration": 2.67}, {"text": "So concepts about\nthings like aliveness.", "start": 2824.08, "duration": 3.75}, {"text": "If you're going to decide\nthat a thing is alive,", "start": 2827.83, "duration": 3.51}, {"text": "you need, for starters, to\nknow that it is a thing.", "start": 2831.34, "duration": 3.43}, {"text": "So you need to have some\nnotion of an object.", "start": 2834.77, "duration": 5.66}, {"text": "And the other thing\nyou need is some notion", "start": 2840.43, "duration": 5.07}, {"text": "that objects, classes of\nobjects, have essences.", "start": 2845.5, "duration": 4.2}, {"text": "This is-- I think it's on\nthe handout somewhere as--", "start": 2849.7, "duration": 4.23}, {"text": "did I write-- yes.", "start": 2853.93, "duration": 2.61}, {"text": "Oh yes, towards the bottom\nof page 2, says essence,", "start": 2856.54, "duration": 2.613}, {"text": "and there's a reference\nto Susan Gelman's work", "start": 2859.153, "duration": 1.917}, {"text": "on psychological essentialism.", "start": 2861.07, "duration": 1.95}, {"text": "The notion of an\nessence is a property", "start": 2863.02, "duration": 3.48}, {"text": "that's not visible, or at\nleast not currently visible.", "start": 2866.5, "duration": 5.67}, {"text": "It's gotta be-- in order to\nhave these category things,", "start": 2872.17, "duration": 4.02}, {"text": "you've got to have the\nnotion that objects", "start": 2876.19, "duration": 4.26}, {"text": "continue to have properties\neven if you can't see that.", "start": 2880.45, "duration": 3.76}, {"text": "So, for example-- well, I\nwon't embarrass anybody,", "start": 2884.21, "duration": 3.41}, {"text": "but there are people here\npresently who are not moving,", "start": 2887.62, "duration": 6.69}, {"text": "who are not, to all\nappearances, growing.", "start": 2894.31, "duration": 3.16}, {"text": "I can't tell from this distance\nwhether they're made of cells", "start": 2897.47, "duration": 2.563}, {"text": "and they don't\nappear to be having", "start": 2900.033, "duration": 1.417}, {"text": "babies or anything like that.", "start": 2901.45, "duration": 2.11}, {"text": "Nevertheless, I assume\nthat they are alive.", "start": 2903.56, "duration": 5.94}, {"text": "That's part of their\nessence, that this aliveness", "start": 2909.5, "duration": 4.62}, {"text": "is something that I\nattribute to that object", "start": 2914.12, "duration": 3.3}, {"text": "without being able to see it.", "start": 2917.42, "duration": 1.47}, {"text": "Now what's the evidence\nthat little kids have that?", "start": 2918.89, "duration": 4.418}, {"text": "Well, I'll tell you\nthat, and then before--", "start": 2923.308, "duration": 1.792}, {"text": "and then we'll go\non have a break", "start": 2925.1, "duration": 1.375}, {"text": "and then we'll go on to the\nproblem of egocentric behavior.", "start": 2926.475, "duration": 3.615}, {"text": "So, I need a tube.", "start": 2930.09, "duration": 4.89}, {"text": "This is-- let's start with\nevidence that children know--", "start": 2934.98, "duration": 4.55}, {"text": "babies know something\nabout objects.", "start": 2939.53, "duration": 3.4}, {"text": "So here's a tube.", "start": 2942.93, "duration": 3.23}, {"text": "If I was doing this\nright, I'd show you", "start": 2946.16, "duration": 2.25}, {"text": "that there's\nnothing in the tube.", "start": 2948.41, "duration": 2.1}, {"text": "And it's-- and then I would\ntake a stuffed animal--", "start": 2950.51, "duration": 5.02}, {"text": "here's a duck.", "start": 2963.68, "duration": 1.66}, {"text": "OK.", "start": 2965.34, "duration": 0.5}, {"text": "So we take the duck.", "start": 2965.84, "duration": 2.31}, {"text": "And he's a squishy duck, so I'm\ngoing to stuff him in the tube.", "start": 2968.15, "duration": 7.77}, {"text": "And then-- so the baby's\nwatching all this cool stuff", "start": 2975.92, "duration": 3.24}, {"text": "happening here.", "start": 2979.16, "duration": 0.66}, {"text": "This is a-- little baby\nis watching this stuff.", "start": 2979.82, "duration": 2.41}, {"text": "And then I take Nemo or\nwhatever, my little plush Nemo,", "start": 2982.23, "duration": 8.0}, {"text": "and I stuff him in the tube.", "start": 2990.23, "duration": 3.99}, {"text": "You're with me so far, babies?", "start": 2994.22, "duration": 2.7}, {"text": "Now, I reach into the tube\nand I pull out the fish.", "start": 2996.92, "duration": 15.72}, {"text": "And you, being good\nbabies, stare at this.", "start": 3012.64, "duration": 4.26}, {"text": "You say, this is\nweird stuff because I", "start": 3016.9, "duration": 3.96}, {"text": "saw the duck go in first--", "start": 3020.86, "duration": 1.74}, {"text": "and this is not quite\nLiz Spelke's experiment.", "start": 3022.6, "duration": 3.69}, {"text": "I realize I'm getting the\nmethods a little screwed up,", "start": 3026.29, "duration": 2.25}, {"text": "but the principle is right.", "start": 3028.54, "duration": 1.74}, {"text": "I saw the duck go in,\nthen the fish went in,", "start": 3030.28, "duration": 3.12}, {"text": "and I know about objects.", "start": 3033.4, "duration": 2.22}, {"text": "Objects do not interpenetrate.", "start": 3035.62, "duration": 3.36}, {"text": "Objects are solid things.", "start": 3038.98, "duration": 3.75}, {"text": "If the fish is out here,\nwhere'd the duck go?", "start": 3042.73, "duration": 4.65}, {"text": "And Spelke has done a\nseries of experiments", "start": 3047.38, "duration": 2.37}, {"text": "like this that suggest that\nkids know about object--", "start": 3049.75, "duration": 4.5}, {"text": "babies.", "start": 3054.25, "duration": 0.76}, {"text": "Young babies, as early as you\ncan successfully test them.", "start": 3055.01, "duration": 3.27}, {"text": "So getting very close to\nbeing at the starting point.", "start": 3058.28, "duration": 3.59}, {"text": "Know about objects, and know a\nfew things about those objects,", "start": 3061.87, "duration": 5.44}, {"text": "notably things like that\nobjects don't interpenetrate.", "start": 3067.31, "duration": 3.51}, {"text": "They don't know\neverything about objects.", "start": 3070.82, "duration": 2.14}, {"text": "So they don't, for instance--", "start": 3072.96, "duration": 2.12}, {"text": "if you set up some\nfish and ducky", "start": 3075.08, "duration": 2.4}, {"text": "kind of thing that violates\nthe law of gravity,", "start": 3077.48, "duration": 3.77}, {"text": "kid doesn't care.", "start": 3081.25, "duration": 1.053}, {"text": "They don't seem\nto be particularly", "start": 3082.303, "duration": 1.417}, {"text": "sensitive to gravity.", "start": 3083.72, "duration": 2.19}, {"text": "Yet, a two-year-old or\nso in his high chair,", "start": 3085.91, "duration": 2.52}, {"text": "two-year-old in the high\nchair thinks gravity is great.", "start": 3088.43, "duration": 2.73}, {"text": "Here's the hot dog.", "start": 3091.16, "duration": 3.3}, {"text": "Oh, yeah, OK.", "start": 3094.46, "duration": 0.9}, {"text": "So dad picks up the hot dog\nand puts it back on the plate", "start": 3095.36, "duration": 3.45}, {"text": "and the kid drops it\nagain because he's", "start": 3098.81, "duration": 1.975}, {"text": "got a-- he's a little\nscientist, right?", "start": 3100.785, "duration": 1.625}, {"text": "You gotta check that gravity\nis still-- you'll get there.", "start": 3102.41, "duration": 2.895}, {"text": "Mom knows about gravity, but her\nbaby doesn't know about it yet.", "start": 3107.9, "duration": 4.95}, {"text": "Her baby looks at gravity\ndemonstrations and says,", "start": 3112.85, "duration": 2.413}, {"text": "this is really boring.", "start": 3115.263, "duration": 0.917}, {"text": "But her baby knows\nthat the duck cannot--", "start": 3116.18, "duration": 3.96}, {"text": "that the fish cannot\ngo through the duck.", "start": 3120.14, "duration": 2.91}, {"text": "It just would be bad\nnews for the duck.", "start": 3123.05, "duration": 4.25}, {"text": "Babies don't care about\ninertia either, things", "start": 3127.3, "duration": 2.25}, {"text": "like objects in motion continue\nin motion unless acted on by--", "start": 3129.55, "duration": 4.02}, {"text": "tell that to a baby, the\nbaby says, yeah, right.", "start": 3133.57, "duration": 2.61}, {"text": "Don't care about that.", "start": 3136.18, "duration": 1.26}, {"text": "But I know that the fish\ndoes not go through the duck.", "start": 3137.44, "duration": 4.57}, {"text": "So that's this\nnotion of objects.", "start": 3142.01, "duration": 2.37}, {"text": "What about essence?", "start": 3144.38, "duration": 0.86}, {"text": "Well, essence is harder to\nget to in early childhood.", "start": 3145.24, "duration": 6.78}, {"text": "It's harder to ask the question.", "start": 3152.02, "duration": 1.38}, {"text": "But by the time you get to--", "start": 3153.4, "duration": 2.8}, {"text": "how old are we in\nthis experiment?", "start": 3159.13, "duration": 2.98}, {"text": "You're like two or\nthree years old,", "start": 3162.11, "duration": 1.73}, {"text": "but you're doing\nsomething like this.", "start": 3163.84, "duration": 1.99}, {"text": "You take the duck and\nyou say, see this duck?", "start": 3165.83, "duration": 7.04}, {"text": "What we're going to\ndo is we're going", "start": 3172.87, "duration": 1.56}, {"text": "to do an operation on the duck.", "start": 3174.43, "duration": 1.38}, {"text": "I promise it's not\ngoing to hurt the duck,", "start": 3175.81, "duration": 1.89}, {"text": "but we're going to\ntake off his skin", "start": 3177.7, "duration": 1.98}, {"text": "and we're going to put\nraccoon skin on him.", "start": 3179.68, "duration": 3.18}, {"text": "He's going to look\njust like a raccoon.", "start": 3182.86, "duration": 2.325}, {"text": "Now is there-- OK.", "start": 3187.7, "duration": 1.17}, {"text": "OK.", "start": 3191.39, "duration": 0.57}, {"text": "Is this a duck or a raccoon?", "start": 3191.96, "duration": 2.91}, {"text": "And as soon as the\nkid can meaningfully", "start": 3194.87, "duration": 1.86}, {"text": "answer the question for you,\nthe kid will say, that's a duck.", "start": 3196.73, "duration": 3.18}, {"text": "I mean, you dressed him up like\na raccoon, but he's a duck.", "start": 3199.91, "duration": 3.03}, {"text": "Inside, he's got duck essence--\nhe doesn't say anything", "start": 3202.94, "duration": 3.06}, {"text": "about duck essence, but\nhe knows that there's", "start": 3206.0, "duration": 2.25}, {"text": "a core of duckenss that is not\ndependent on looking exactly", "start": 3208.25, "duration": 5.01}, {"text": "like a duck.", "start": 3213.26, "duration": 1.8}, {"text": "Moreover-- oh, it says--\nthis, by the way, is--", "start": 3215.06, "duration": 4.95}, {"text": "how many of you are familiar\nwith the classic Pep\u00e9 Le Pew", "start": 3220.01, "duration": 5.55}, {"text": "cartoons?", "start": 3225.56, "duration": 2.07}, {"text": "Yeah, there's Cartoon\nNetwork stuff.", "start": 3227.63, "duration": 1.5}, {"text": "So the basic plot there's\na whole bunch of these,", "start": 3229.13, "duration": 2.042}, {"text": "but the basic plot\nis always the same.", "start": 3231.172, "duration": 1.648}, {"text": "Pep\u00e9 Le Pew is a French\nskunk, a French lover skunk.", "start": 3232.82, "duration": 8.37}, {"text": "And this cat, female cat, gets\na white stripe down her back", "start": 3241.19, "duration": 5.88}, {"text": "by some paint or\nsomething like that.", "start": 3247.07, "duration": 2.26}, {"text": "And Pep\u00e9 spends the next five\nminutes of the cartoon chasing", "start": 3249.33, "duration": 4.4}, {"text": "her around, trying to\nget her to fall in love,", "start": 3253.73, "duration": 2.35}, {"text": "and she doesn't want to\nfall in love because she", "start": 3256.08, "duration": 2.0}, {"text": "knows he's a skunk and she\nknows that she's not a skunk.", "start": 3258.08, "duration": 2.79}, {"text": "What's funny about\nthis, the reason", "start": 3260.87, "duration": 2.13}, {"text": "this is funny for\nlittle kids, is", "start": 3263.0, "duration": 1.8}, {"text": "that little kids know\nthat the fact that she's", "start": 3264.8, "duration": 3.93}, {"text": "got a white stripe down her\ndoesn't make her into a skunk.", "start": 3268.73, "duration": 3.63}, {"text": "She's still a cat who happens\nto look like s skunk and isn't", "start": 3272.36, "duration": 4.56}, {"text": "that funny because the skunk\nis chasing around after her", "start": 3276.92, "duration": 3.073}, {"text": "and getting hit in the head\nwith bats and stuff like that,", "start": 3279.993, "duration": 2.417}, {"text": "and all those good things\nhappen in cartoons.", "start": 3282.41, "duration": 3.54}, {"text": "So, not only do kids\nknow that things", "start": 3285.95, "duration": 3.51}, {"text": "have an essence like\nthat, they are also--", "start": 3289.46, "duration": 2.7}, {"text": "well, to be a little recursive\nhere, their innate nativists,", "start": 3292.16, "duration": 4.59}, {"text": "it appears.", "start": 3296.75, "duration": 1.2}, {"text": "They believe that these\nproperties came with the system", "start": 3297.95, "duration": 3.99}, {"text": "and were not learned.", "start": 3301.94, "duration": 1.14}, {"text": "So Susan Gelman did\na clever experiment", "start": 3303.08, "duration": 3.08}, {"text": "where what she did was she\nsaid, see this kangaroo?", "start": 3306.16, "duration": 4.712}, {"text": "This can be a kangaroo\nas well as a duck,", "start": 3310.872, "duration": 1.708}, {"text": "I'm sure, but anyway.", "start": 3312.58, "duration": 0.875}, {"text": "Take this kangaroo,\nthis is a baby kangaroo.", "start": 3313.455, "duration": 3.565}, {"text": "It's a newborn kangaroo.", "start": 3317.02, "duration": 2.55}, {"text": "And you know what\nwe're going to do?", "start": 3319.57, "duration": 1.5}, {"text": "We're going to\ntake her and we're", "start": 3321.07, "duration": 1.47}, {"text": "going to give her to the goats.", "start": 3322.54, "duration": 2.67}, {"text": "And she's going to get\nraised by the goats.", "start": 3325.21, "duration": 4.71}, {"text": "And now she's all grown up.", "start": 3329.92, "duration": 2.76}, {"text": "Let me ask you a few\nquestions about her.", "start": 3332.68, "duration": 2.94}, {"text": "Does she have a pouch?", "start": 3335.62, "duration": 2.64}, {"text": "Well, yeah, sure, that's\npretty straightforward.", "start": 3338.26, "duration": 2.79}, {"text": "That's not the\ninteresting question.", "start": 3341.05, "duration": 1.56}, {"text": "The interesting\nquestion is, is she", "start": 3342.61, "duration": 2.76}, {"text": "going to be a\nhopper or a climber?", "start": 3345.37, "duration": 4.23}, {"text": "And little kids, two,\nthree-year-old kids, will say,", "start": 3349.6, "duration": 4.35}, {"text": "it's going to be a climber.", "start": 3353.95, "duration": 2.205}, {"text": "It's going to be a hopper--", "start": 3356.155, "duration": 1.125}, {"text": "I gotta get it right\nhere, otherwise", "start": 3357.28, "duration": 1.53}, {"text": "you'll be hopelessly--\nit's going to be a hopper.", "start": 3358.81, "duration": 2.28}, {"text": "It was a kangaroo at\nbirth, kangaroos hop.", "start": 3361.09, "duration": 3.81}, {"text": "It's part of their essence.", "start": 3364.9, "duration": 1.66}, {"text": "The fact that she\nlived with the goats", "start": 3366.56, "duration": 6.42}, {"text": "isn't going to change that.", "start": 3372.98, "duration": 2.19}, {"text": "This is the amusement value\nof the Disney Tarzan cartoon.", "start": 3375.17, "duration": 7.14}, {"text": "Right Tarzan gets\nraised by a gorilla--", "start": 3382.31, "duration": 2.61}, {"text": "by the gorillas.", "start": 3384.92, "duration": 0.9}, {"text": "He thinks-- how many\nhave you seen that?", "start": 3385.82, "duration": 3.178}, {"text": "Oh man, when did that come out?", "start": 3388.998, "duration": 1.292}, {"text": "It must have come--", "start": 3390.29, "duration": 1.982}, {"text": "I guess it-- all right.", "start": 3392.272, "duration": 0.958}, {"text": "I gotta calibrate\nmy Disneyness here.", "start": 3393.23, "duration": 2.99}, {"text": "Which Disney movies\ncame out when you", "start": 3396.22, "duration": 1.93}, {"text": "were of an age to watch them?", "start": 3398.15, "duration": 3.066}, {"text": "STUDENTS: Aladdin.", "start": 3401.216, "duration": 1.207}, {"text": "JEREMY WOLFE: Aladdin.", "start": 3402.423, "duration": 0.917}, {"text": "Oh, you were too old\nwhen Tarzan came out.", "start": 3403.34, "duration": 4.47}, {"text": "Oh, so you're the\nAladdin cohort.", "start": 3407.81, "duration": 5.7}, {"text": "Jungle-- Jungle Book came\nout when I was a kid.", "start": 3413.51, "duration": 3.39}, {"text": "Not-- well, no not quite.", "start": 3416.9, "duration": 2.13}, {"text": "Actually, Jungle\nBook-- the one that it", "start": 3419.03, "duration": 2.76}, {"text": "was-- the ones that came\nout when I was a kid", "start": 3421.79, "duration": 2.07}, {"text": "were things like\nSword in the Stone.", "start": 3423.86, "duration": 1.65}, {"text": "I thought that was great.", "start": 3425.51, "duration": 3.05}, {"text": "That was good stuff.", "start": 3428.56, "duration": 1.45}, {"text": "And don't claim that I was a\nkid when Snow White came out,", "start": 3430.01, "duration": 3.5}, {"text": "that was my father.", "start": 3433.51, "duration": 1.35}, {"text": "[LAUGHTER]", "start": 3434.86, "duration": 0.66}, {"text": "But anyway.", "start": 3435.52, "duration": 1.77}, {"text": "So in Jungle Book--", "start": 3437.29, "duration": 2.52}, {"text": "Jungle Book.", "start": 3439.81, "duration": 0.54}, {"text": "In-- well, The\nJungle Book works.", "start": 3440.35, "duration": 1.41}, {"text": "Right Jungle Book\nworks, but Tarzan works.", "start": 3441.76, "duration": 2.97}, {"text": "You get raised by\nthe wild animals,", "start": 3444.73, "duration": 1.86}, {"text": "but you're essentially a human,\nand that eventually catches up", "start": 3446.59, "duration": 8.05}, {"text": "with you.", "start": 3454.64, "duration": 0.5}, {"text": "Actually, kids are incorrect\nnativists because they believe", "start": 3455.14, "duration": 7.02}, {"text": "things that turn\nout-- and it's true", "start": 3462.16, "duration": 1.5}, {"text": "that the kangaroo\nwill probably hop even", "start": 3463.66, "duration": 1.98}, {"text": "if it gets raised by a goat.", "start": 3465.64, "duration": 4.95}, {"text": "But suppose you are--", "start": 3470.59, "duration": 2.34}, {"text": "so suppose we have\nhere a Chinese baby.", "start": 3472.93, "duration": 3.81}, {"text": "And we take this Chinese\nbaby and we bring it", "start": 3476.74, "duration": 4.02}, {"text": "to the United States and\nit's raised in California.", "start": 3480.76, "duration": 6.72}, {"text": "Will that-- when\nthat kid grows up,", "start": 3487.48, "duration": 3.24}, {"text": "will she be able\nto speak Chinese?", "start": 3490.72, "duration": 2.76}, {"text": "STUDENT: Depends.", "start": 3493.48, "duration": 0.89}, {"text": "JEREMY WOLFE: Depends.", "start": 3494.37, "duration": 0.917}, {"text": "Depends on the-- right?", "start": 3495.287, "duration": 1.043}, {"text": "STUDENT: If it's in California--", "start": 3496.33, "duration": 1.373}, {"text": "JEREMY WOLFE: In\nCalifornia, yeah.", "start": 3497.703, "duration": 1.417}, {"text": "It depends on the neighborhood.", "start": 3499.12, "duration": 1.65}, {"text": "But kids aren't quite clear\non these demographic issues", "start": 3500.77, "duration": 6.143}, {"text": "to the same way.", "start": 3506.913, "duration": 0.667}, {"text": "But a little kid will\nfigure, incorrectly,", "start": 3507.58, "duration": 4.08}, {"text": "that language is one of\nthese essential properties.", "start": 3511.66, "duration": 3.93}, {"text": "That if you're Chinese,\nthat means you can speak--", "start": 3515.59, "duration": 2.533}, {"text": "you might be able to\nspeak English, too.", "start": 3518.123, "duration": 1.667}, {"text": "You could learn that,\nthey can figure that out.", "start": 3519.79, "duration": 1.958}, {"text": "But that you'd be-- you'd\nhave a privileged ability", "start": 3521.748, "duration": 3.382}, {"text": "to speak Chinese because, after\nall, you were a Chinese kid,", "start": 3525.13, "duration": 4.59}, {"text": "and that ought to work.", "start": 3529.72, "duration": 1.98}, {"text": "If you're a Chinese\nkid who grew up", "start": 3531.7, "duration": 2.31}, {"text": "in an Anglo linguistic\nenvironment,", "start": 3534.01, "duration": 2.753}, {"text": "you may have\ndiscovered that there", "start": 3536.763, "duration": 1.417}, {"text": "were plenty of your\nrelatives who also thought", "start": 3538.18, "duration": 1.917}, {"text": "you should be able\nto speak Chinese,", "start": 3540.097, "duration": 1.773}, {"text": "but that's a different issue.", "start": 3541.87, "duration": 2.34}, {"text": "In any case, little\nkids start certainly", "start": 3544.21, "duration": 4.83}, {"text": "with a notion of\nobjectness, and probably", "start": 3549.04, "duration": 5.37}, {"text": "quite early with the notion\nthat objects have essences,", "start": 3554.41, "duration": 3.15}, {"text": "and then they build on that\nin this little scientist", "start": 3557.56, "duration": 3.21}, {"text": "kind of a way to get closer\nand closer to what we consider", "start": 3560.77, "duration": 6.45}, {"text": "to be the adult concept of\nwhatever alive or kangaroo", "start": 3567.22, "duration": 5.49}, {"text": "or any of those sorts of things.", "start": 3572.71, "duration": 4.67}, {"text": "That here's a case where the\nadult state is not particularly", "start": 3577.38, "duration": 3.1}, {"text": "fixed, but where,\nnevertheless, what you're", "start": 3580.48, "duration": 5.85}, {"text": "doing is you're elaborating\non juvenile concepts,", "start": 3586.33, "duration": 2.58}, {"text": "not suddenly\ndiscovering the notion", "start": 3588.91, "duration": 1.92}, {"text": "that there is such a\nthing as a concept.", "start": 3590.83, "duration": 3.42}, {"text": "OK, I want to do\negocentrism still,", "start": 3594.25, "duration": 2.07}, {"text": "but I will start doing that\nwhen that thing says 3:10.", "start": 3596.32, "duration": 4.92}, {"text": "If you can count.", "start": 3601.24, "duration": 1.757}, {"text": "[SIDE CONVERSATION]", "start": 3602.997, "duration": 3.976}, {"text": "OK.", "start": 3788.72, "duration": 1.65}, {"text": "Whoops!", "start": 3790.37, "duration": 1.35}, {"text": "I'm a minute later than\nI claimed I would be.", "start": 3791.72, "duration": 2.31}, {"text": "Oh well.", "start": 3794.03, "duration": 2.25}, {"text": "Let us talk about egocentrism.", "start": 3796.28, "duration": 2.44}, {"text": "So, you will recall that\nthe basic problem here", "start": 3798.72, "duration": 5.72}, {"text": "was that the kid seemed unable\nto take the point of view", "start": 3804.44, "duration": 4.468}, {"text": "of another-- in this\ncase, the mother", "start": 3808.908, "duration": 1.542}, {"text": "on the other side of this table.", "start": 3810.45, "duration": 2.15}, {"text": "The kid asked about things\nlike the river and the hut,", "start": 3812.6, "duration": 5.85}, {"text": "claimed that the\nmom could see them", "start": 3818.45, "duration": 1.71}, {"text": "even though mom\ncouldn't see them,", "start": 3820.16, "duration": 1.8}, {"text": "only the kid could see them.", "start": 3821.96, "duration": 1.29}, {"text": "You can get kids to perform\nquite well on this task", "start": 3826.11, "duration": 4.02}, {"text": "if you come from\nNebraska instead", "start": 3830.13, "duration": 3.15}, {"text": "of coming from the Alps.", "start": 3833.28, "duration": 1.62}, {"text": "So in one version\nof this experiment--", "start": 3834.9, "duration": 4.15}, {"text": "so for your-- how does this--", "start": 3839.05, "duration": 2.88}, {"text": "so I think the answer is that\nfour-year-olds fail this.", "start": 3841.93, "duration": 4.76}, {"text": "You can get three year-olds to\nbe successful in an equivalent", "start": 3846.69, "duration": 4.41}, {"text": "task if what you do is just\nsimplify the situation.", "start": 3851.1, "duration": 5.255}, {"text": "So there's a\nversion of this that", "start": 3856.355, "duration": 1.375}, {"text": "may have a picture in the\nbook still, I don't remember,", "start": 3857.73, "duration": 2.292}, {"text": "of a city block with a car in it\nand a Sesame Street character,", "start": 3860.022, "duration": 6.168}, {"text": "and you drive Grover around\nthe block or something", "start": 3866.19, "duration": 2.94}, {"text": "and ask questions about\nthat much simpler situation.", "start": 3869.13, "duration": 3.15}, {"text": "And then the kid can\nsuccessfully answer questions", "start": 3872.28, "duration": 4.98}, {"text": "from the vantage point of the\nmother as if part of the issue", "start": 3877.26, "duration": 5.94}, {"text": "here was that the task\nwas just too complicated.", "start": 3883.2, "duration": 4.985}, {"text": "Oh, I never mentioned the M&Ms\nare under there somewhere.", "start": 3888.185, "duration": 2.375}, {"text": "I never mentioned, well, why is\nit that the kids bombed the M&M", "start": 3890.56, "duration": 2.52}, {"text": "task?", "start": 3893.08, "duration": 0.5}, {"text": "That seems to be the case--", "start": 3893.58, "duration": 1.39}, {"text": "an issue where\nyou're asking kids", "start": 3894.97, "duration": 3.6}, {"text": "who haven't gotten to the\ncounting-- successful counting", "start": 3898.57, "duration": 2.91}, {"text": "stage to do this, and\nthey can't do it either", "start": 3901.48, "duration": 2.64}, {"text": "with the numerosity or\nthe subitizing piece,", "start": 3904.12, "duration": 1.95}, {"text": "so they fail the task.", "start": 3906.07, "duration": 1.23}, {"text": "If you make the M&M task--", "start": 3907.3, "duration": 2.37}, {"text": "if you put that into\neither the numerosity range", "start": 3909.67, "duration": 2.52}, {"text": "or the subitizing\nrange, little kids", "start": 3912.19, "duration": 2.1}, {"text": "will succeed in doing the task.", "start": 3914.29, "duration": 1.93}, {"text": "So if you say, would you rather\nhave this pile with two M&Ms", "start": 3916.22, "duration": 4.34}, {"text": "or three M&Ms?", "start": 3920.56, "duration": 1.71}, {"text": "Little kids don't bomb that.", "start": 3922.27, "duration": 1.68}, {"text": "They bomb five versus six or six\nversus eight, things like that.", "start": 3923.95, "duration": 5.73}, {"text": "And a similar thing seems\nto be going on here,", "start": 3929.68, "duration": 2.46}, {"text": "that the task is,\nin some fashion,", "start": 3932.14, "duration": 3.72}, {"text": "a little too\ncomplicated for them.", "start": 3935.86, "duration": 1.65}, {"text": "How far can we push this back?", "start": 3937.51, "duration": 2.19}, {"text": "Well if you take two-year-olds--", "start": 3939.7, "duration": 2.74}, {"text": "suppose you take two-year-olds\nand you give them", "start": 3942.44, "duration": 2.0}, {"text": "a pair of sunglasses.", "start": 3944.44, "duration": 1.64}, {"text": "Put the sunglasses on the kid,\nkid looks around for a while.", "start": 3946.08, "duration": 3.45}, {"text": "Now we take the sunglasses--", "start": 3949.53, "duration": 1.892}, {"text": "they may have been\nmirrored shades, even,", "start": 3951.422, "duration": 1.708}, {"text": "and anyway, you put\nthe sunglasses on mommy", "start": 3953.13, "duration": 2.61}, {"text": "and you ask, can mommy see you?", "start": 3955.74, "duration": 3.21}, {"text": "Well, you can't see mommy's eyes\nanymore because of the glasses,", "start": 3958.95, "duration": 3.87}, {"text": "but the kid-- even a\ntwo-year-old will be able", "start": 3962.82, "duration": 2.43}, {"text": "to say, yes indeed, mommy can\nsee me even though I cannot see", "start": 3965.25, "duration": 3.15}, {"text": "mommy's eyes.", "start": 3968.4, "duration": 0.81}, {"text": "Normally, if mommy\nis doing this,", "start": 3969.21, "duration": 2.38}, {"text": "it's a pretty good bet\nthat mommy can't see you,", "start": 3971.59, "duration": 3.86}, {"text": "and that's the root of a\nlot of entertaining games.", "start": 3975.45, "duration": 3.97}, {"text": "But they can manage to\nsolve the problem at the--", "start": 3979.42, "duration": 5.344}, {"text": "if it's simplified to the\npoint of sunglasses on or off.", "start": 3987.402, "duration": 5.958}, {"text": "And this, if I can see\nyou, can see me thing,", "start": 3993.36, "duration": 4.92}, {"text": "you can see, as you get\nmore and more complicated,", "start": 3998.28, "duration": 3.24}, {"text": "that it takes you\nlonger and longer", "start": 4001.52, "duration": 3.99}, {"text": "to solve the more and more\ncomplicated versions of it.", "start": 4005.51, "duration": 2.44}, {"text": "You don't remember what it was\nlike to be thinking when you", "start": 4007.95, "duration": 4.59}, {"text": "were a two-year-old,\nbut you may remember", "start": 4012.54, "duration": 1.74}, {"text": "a stage later in your life\nwhen it was not clear to you", "start": 4014.28, "duration": 4.44}, {"text": "how mirrors worked.", "start": 4018.72, "duration": 2.6}, {"text": "If A can see B, B\ncan see in a mirror?", "start": 4021.32, "duration": 3.34}, {"text": "This is the thing that amuses\nearly school-aged kids often.", "start": 4024.66, "duration": 5.918}, {"text": "You can see around the corner--", "start": 4030.578, "duration": 1.292}, {"text": "I can see dad around\nthe corner there.", "start": 4031.87, "duration": 2.99}, {"text": "I bet he can't see me\nand it comes as a shock", "start": 4034.86, "duration": 2.94}, {"text": "that dad can see you because\nthe mirror works both ways.", "start": 4037.8, "duration": 4.21}, {"text": "And then there are more\ncomplicated arrangements", "start": 4042.01, "duration": 2.0}, {"text": "with keyholes and\nstuff like that", "start": 4044.01, "duration": 3.42}, {"text": "where it takes even\nlonger to be able to take", "start": 4047.43, "duration": 2.267}, {"text": "the point of view of the\nperson on the other side.", "start": 4049.697, "duration": 2.083}, {"text": "So some examples--\nsome aspect of this", "start": 4051.78, "duration": 2.01}, {"text": "is simply a matter\nof complexity.", "start": 4053.79, "duration": 4.48}, {"text": "In fact, Paul Bloom\nand his student--", "start": 4058.27, "duration": 3.98}, {"text": "actually, I should mention, Paul\nBloom is married to Karen Wynn.", "start": 4062.25, "duration": 3.63}, {"text": "They were both students--", "start": 4065.88, "duration": 1.5}, {"text": "both TAs for this\ncourse, and are", "start": 4067.38, "duration": 2.49}, {"text": "now both professors at Yale.", "start": 4069.87, "duration": 1.35}, {"text": "Anyway, Paul works on similar\nsorts of problems and talks", "start": 4071.22, "duration": 3.18}, {"text": "about the curse of\nknowledge that shows up", "start": 4074.4, "duration": 4.02}, {"text": "in adult behavior, too.", "start": 4078.42, "duration": 1.5}, {"text": "That it's very difficult,\nit's often very difficult", "start": 4079.92, "duration": 3.75}, {"text": "to remember that somebody else\ndoesn't know what you know.", "start": 4083.67, "duration": 5.16}, {"text": "And so it's a problem\nfor me teaching.", "start": 4088.83, "duration": 6.84}, {"text": "The things that are\nhardest to teach", "start": 4095.67, "duration": 1.54}, {"text": "are the things that I\ndon't know anything about.", "start": 4097.21, "duration": 2.0}, {"text": "That's not surprising.", "start": 4099.21, "duration": 1.26}, {"text": "The second hardest\ncategory are things", "start": 4100.47, "duration": 1.8}, {"text": "that I know too much about\nbecause it's hard to remember", "start": 4102.27, "duration": 4.95}, {"text": "how little about vision.", "start": 4107.22, "duration": 2.309}, {"text": "How can it be that\nyou haven't actually", "start": 4109.529, "duration": 2.58}, {"text": "spent the last 18 years\nof your life bathed", "start": 4112.109, "duration": 3.691}, {"text": "in visual phenomenology?", "start": 4115.8, "duration": 2.01}, {"text": "I forget that from time--\nyou can try using that", "start": 4117.81, "duration": 2.28}, {"text": "as an excuse on the\nexam, but forget it,", "start": 4120.09, "duration": 2.55}, {"text": "we'll still take the points off.", "start": 4122.64, "duration": 1.469}, {"text": "So that turns out\nto be an example", "start": 4124.109, "duration": 2.908}, {"text": "of the curse of knowledge.", "start": 4127.017, "duration": 1.083}, {"text": "Or another example would be--", "start": 4128.1, "duration": 4.17}, {"text": "if you've ever been\ngiving somebody directions", "start": 4132.27, "duration": 2.79}, {"text": "while you're sitting\nnext to them in the car,", "start": 4135.06, "duration": 2.49}, {"text": "you might discover that\nyou go past the street", "start": 4137.55, "duration": 2.104}, {"text": "where they were\nsupposed to turn,", "start": 4139.654, "duration": 1.375}, {"text": "because you knew you were\nsupposed to turn there", "start": 4141.029, "duration": 2.37}, {"text": "and you just forgot that\nthey wouldn't know that,", "start": 4143.399, "duration": 2.88}, {"text": "and that's why you were sitting\nthere supposedly giving them", "start": 4146.279, "duration": 3.241}, {"text": "directions.", "start": 4149.52, "duration": 0.78}, {"text": "It's hard, even for\nadults, necessarily,", "start": 4150.3, "duration": 4.11}, {"text": "it's hard for adults\nsometimes to take the vantage", "start": 4154.41, "duration": 2.76}, {"text": "point of another person.", "start": 4157.17, "duration": 5.41}, {"text": "Now one of the great\nexamples of this", "start": 4162.58, "duration": 5.66}, {"text": "in kid behavior,\na paradigm that's", "start": 4168.24, "duration": 3.69}, {"text": "yielded an awful\nlot of research,", "start": 4171.93, "duration": 2.25}, {"text": "which gives you some\ninsight into this,", "start": 4174.18, "duration": 2.07}, {"text": "if you like this curse\nof knowledge problem,", "start": 4176.25, "duration": 2.729}, {"text": "is what's known as\nthe false belief task.", "start": 4178.979, "duration": 4.691}, {"text": "And, well, the first\nfalse belief you need", "start": 4183.67, "duration": 2.24}, {"text": "is that this is Big\nBird from Sesame Street.", "start": 4185.91, "duration": 4.65}, {"text": "All right, so here's\nhow a typical--", "start": 4190.56, "duration": 2.31}, {"text": "here's how a typical\nfalse belief task", "start": 4192.87, "duration": 3.09}, {"text": "experiment might work.", "start": 4195.96, "duration": 1.83}, {"text": "Big Bird-- you're watching this.", "start": 4197.79, "duration": 2.58}, {"text": "Big Bird comes into the\nscene, and he has candy.", "start": 4200.37, "duration": 5.52}, {"text": "And he puts the candy\nin-- what is this?", "start": 4205.89, "duration": 2.816}, {"text": "This is the refrigerator.", "start": 4208.706, "duration": 1.124}, {"text": "He puts the candy in the\nrefrigerator and he goes out.", "start": 4209.83, "duration": 3.755}, {"text": "Now, I didn't draw--", "start": 4217.02, "duration": 2.73}, {"text": "I didn't draw\nGrover or whatever,", "start": 4219.75, "duration": 2.7}, {"text": "but Grover comes in, takes the\ncandy out of the refrigerator,", "start": 4222.45, "duration": 7.75}, {"text": "and puts it in the drawer.", "start": 4230.2, "duration": 3.72}, {"text": "Now, Big Bird comes back\nin, he didn't see this,", "start": 4233.92, "duration": 4.68}, {"text": "but you saw this.", "start": 4238.6, "duration": 1.14}, {"text": "Big Bird comes back in, and you\nare asked, where will Big Bird", "start": 4239.74, "duration": 6.93}, {"text": "look for the candy?", "start": 4246.67, "duration": 2.91}, {"text": "And your answer, if\nyou're a four-year-old,", "start": 4249.58, "duration": 3.63}, {"text": "is that Big Bird will\nlook in the drawer.", "start": 4253.21, "duration": 3.06}, {"text": "You cannot somehow access\nthe fact that Big Bird thinks", "start": 4256.27, "duration": 6.57}, {"text": "in his brain that the candy\nis in the fridge when you", "start": 4262.84, "duration": 10.17}, {"text": "updated--", "start": 4273.01, "duration": 0.81}, {"text": "your knowledge\nabout the candy, you", "start": 4273.82, "duration": 4.23}, {"text": "updated his knowledge about the\ncandy, too, in some fashion.", "start": 4278.05, "duration": 7.63}, {"text": "Now there are endless\nversion owns of this--", "start": 4285.68, "duration": 5.1}, {"text": "this is a task that\nfour-year-olds will fail--", "start": 4290.78, "duration": 3.8}, {"text": "younger than four will fail,\nolder than four roughly", "start": 4294.58, "duration": 2.71}, {"text": "will tend to get.", "start": 4297.29, "duration": 3.06}, {"text": "There are endless\ntasks that look at this", "start": 4300.35, "duration": 2.1}, {"text": "and try to break it apart,\nsee what's going on here", "start": 4302.45, "duration": 3.36}, {"text": "in developing this ability\nto take into account what is", "start": 4305.81, "duration": 3.93}, {"text": "in the mind of another person--", "start": 4309.74, "duration": 3.54}, {"text": "or bird, as the case may be.", "start": 4313.28, "duration": 3.96}, {"text": "This is sometimes talked\nabout as mind-reading,", "start": 4317.24, "duration": 2.76}, {"text": "and is sometimes described\nas the major problem--", "start": 4320.0, "duration": 3.03}, {"text": "or the major social\nproblem in autism,", "start": 4323.03, "duration": 2.7}, {"text": "that may be one of the\nreasons that autistic adults--", "start": 4325.73, "duration": 5.07}, {"text": "kids and adults\nhave a real problem", "start": 4330.8, "duration": 2.52}, {"text": "relating to other\npeople is an inability", "start": 4333.32, "duration": 3.24}, {"text": "to understand that other people\nhave mental states, which", "start": 4336.56, "duration": 5.22}, {"text": "you have that ability.", "start": 4341.78, "duration": 1.44}, {"text": "But-- now here, you failed--\nyou as a four-year-old", "start": 4343.22, "duration": 4.47}, {"text": "have failed to\nmanage to keep track", "start": 4347.69, "duration": 2.04}, {"text": "of Big Bird's mental state.", "start": 4349.73, "duration": 1.71}, {"text": "OK, well let's do a\nvariation on this.", "start": 4351.44, "duration": 2.44}, {"text": "So here's a variation where you\ndon't see that initial scene.", "start": 4353.88, "duration": 4.31}, {"text": "And now you are asked to guess--", "start": 4361.22, "duration": 7.74}, {"text": "the candy is either\nhere or here.", "start": 4368.96, "duration": 3.87}, {"text": "Where do you think that\nthe candy might be?", "start": 4372.83, "duration": 5.82}, {"text": "Well, you say, 50/50.", "start": 4378.65, "duration": 3.39}, {"text": "Well, I think the\ncandy is in the drawer.", "start": 4382.04, "duration": 2.49}, {"text": "OK.", "start": 4384.53, "duration": 0.54}, {"text": "Now Big Bird comes\nin and you're told,", "start": 4385.07, "duration": 1.83}, {"text": "well, you know, Big Bird\nthinks it's in the fridge.", "start": 4386.9, "duration": 5.64}, {"text": "Where's Big Bird going to look?", "start": 4392.54, "duration": 2.52}, {"text": "And the answer now is, even\nif you're as young as three,", "start": 4395.06, "duration": 3.39}, {"text": "that you say Big Bird is\ngoing to look in the fridge.", "start": 4398.45, "duration": 3.46}, {"text": "Your guess isn't strong\nenough to overwrite", "start": 4401.91, "duration": 4.85}, {"text": "your understanding of what's\ngoing on in Big Bird's head.", "start": 4406.76, "duration": 2.64}, {"text": "This tells you\nsomething important.", "start": 4409.4, "duration": 1.5}, {"text": "This tells you immediately\nthat you can know something", "start": 4410.9, "duration": 3.66}, {"text": "about the contents--", "start": 4414.56, "duration": 1.86}, {"text": "that you're capable\nunderstanding something", "start": 4416.42, "duration": 2.28}, {"text": "about the contents\nof Big Bird's head.", "start": 4418.7, "duration": 2.76}, {"text": "It's not a complete\nblank to you.", "start": 4421.46, "duration": 3.51}, {"text": "Even younger than\nthat, little kids", "start": 4424.97, "duration": 2.85}, {"text": "can see somebody\nplaying with a banana,", "start": 4427.82, "duration": 3.42}, {"text": "pretending it's a\nphone, and you ask,", "start": 4431.24, "duration": 3.39}, {"text": "does he know that\nit's not a phone?", "start": 4434.63, "duration": 3.99}, {"text": "And yeah, yeah, the\ntwo-year-old will tell,", "start": 4438.62, "duration": 2.04}, {"text": "you, yeah, he's just pretending.", "start": 4440.66, "duration": 1.68}, {"text": "And you can have the\nnotion that somebody else", "start": 4442.34, "duration": 3.12}, {"text": "could pretend to--", "start": 4445.46, "duration": 3.39}, {"text": "pretend something.", "start": 4448.85, "duration": 1.17}, {"text": "So again, you can\npush this notion", "start": 4450.02, "duration": 1.44}, {"text": "of being able to read minds\nback earlier if it gets simpler.", "start": 4451.46, "duration": 5.46}, {"text": "And maybe this isn't\nreally about the contents", "start": 4456.92, "duration": 3.84}, {"text": "of Big Bird's mind at all.", "start": 4460.76, "duration": 2.74}, {"text": "Here's a cute version of the\nexperiment done by Debbie", "start": 4463.5, "duration": 2.435}, {"text": "Zaitchik once upon a time.", "start": 4465.935, "duration": 2.055}, {"text": "Big Bird comes in-- this is the\noriginal false memory game--", "start": 4467.99, "duration": 3.09}, {"text": "false belief game.", "start": 4471.08, "duration": 2.37}, {"text": "Big Bird comes in, puts\nthe candy in the fridge,", "start": 4473.45, "duration": 3.24}, {"text": "but this time, Big Bird\ntakes out his camera", "start": 4476.69, "duration": 3.51}, {"text": "and he photographs it.", "start": 4480.2, "duration": 2.49}, {"text": "So he's got a picture of it.", "start": 4482.69, "duration": 1.59}, {"text": "There's the candy in the fridge.", "start": 4488.74, "duration": 2.48}, {"text": "Now, Big Bird goes out.", "start": 4491.22, "duration": 4.05}, {"text": "And Grover comes in, moves\nthe candy to the drawer.", "start": 4495.27, "duration": 4.08}, {"text": "You now know that the\ncandy is in the drawer.", "start": 4499.35, "duration": 2.52}, {"text": "Big Bird comes in.", "start": 4501.87, "duration": 1.23}, {"text": "You are asked, where's Big Bird\ngoing to look for the candy?", "start": 4503.1, "duration": 4.47}, {"text": "Even though Big Bird has\ntaken a picture of it,", "start": 4507.57, "duration": 3.21}, {"text": "even though there's now\na physical instantiation", "start": 4510.78, "duration": 2.79}, {"text": "of the contents of\nBig Bird's mind,", "start": 4513.57, "duration": 2.43}, {"text": "you still say it's\nin the drawer.", "start": 4516.0, "duration": 1.83}, {"text": "You as a four-year-old are still\nunable to keep track of this.", "start": 4517.83, "duration": 4.2}, {"text": "This suggests that\nmaybe the problem", "start": 4522.03, "duration": 1.86}, {"text": "is less with your ability to\nsee into somebody else's mind", "start": 4523.89, "duration": 4.14}, {"text": "and more with something like\nthe capacity of your working", "start": 4528.03, "duration": 4.65}, {"text": "memory.", "start": 4532.68, "duration": 1.21}, {"text": "So if you think about it, this\nis very parallel to a Loftus", "start": 4533.89, "duration": 3.05}, {"text": "experiment I talked about either\nlast time or the time before.", "start": 4536.94, "duration": 2.91}, {"text": "You see somebody go\nthrough a yield sign.", "start": 4539.85, "duration": 2.49}, {"text": "You later hear that\nit was a stop sign.", "start": 4542.34, "duration": 4.01}, {"text": "And you believe--\nyou come to have", "start": 4546.35, "duration": 2.21}, {"text": "a false memory or a false\nbelief, if you like,", "start": 4548.56, "duration": 2.31}, {"text": "that it really was a stop sign.", "start": 4550.87, "duration": 2.07}, {"text": "Because we've managed to somehow\noverwrite your memory here.", "start": 4552.94, "duration": 4.83}, {"text": "Maybe, in this case,\nwhat you're dealing with", "start": 4557.77, "duration": 2.13}, {"text": "is not the development--", "start": 4559.9, "duration": 2.16}, {"text": "a qualitative\nchange where you're", "start": 4562.06, "duration": 2.13}, {"text": "seeing a change in the ability\nto see into somebody else's", "start": 4564.19, "duration": 3.39}, {"text": "mind, but a big\nenough working memory", "start": 4567.58, "duration": 2.28}, {"text": "that you can keep\ntrack of the task.", "start": 4569.86, "duration": 3.28}, {"text": "So another case where the\ndevelopment here waits", "start": 4573.14, "duration": 4.82}, {"text": "on the development of another\nability, a separate ability,", "start": 4577.96, "duration": 5.28}, {"text": "in this case, working memory.", "start": 4583.24, "duration": 2.76}, {"text": "OK, that's as good a place\nto stop as any, so I'll stop.", "start": 4586.0, "duration": 5.15}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 1.09, "duration": 2.37}, {"text": "Commons license.", "start": 3.46, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.85, "duration": 2.21}, {"text": "continue to offer high quality\neducational resources for free.", "start": 7.06, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 11.15, "duration": 2.54}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.69, "duration": 3.96}, {"text": "at ocw.mit.edu.", "start": 17.65, "duration": 0.9}, {"text": "TADGE DRYJA: Today we're going\nto talk about synchronization--", "start": 22.52, "duration": 2.7}, {"text": "how all these different\nnodes on the network", "start": 25.22, "duration": 2.73}, {"text": "come to consensus,\nhow they link up.", "start": 27.95, "duration": 3.84}, {"text": "So it's sort of bringing\nit all together.", "start": 31.79, "duration": 1.75}, {"text": "So so far in these\nlectures we've", "start": 33.54, "duration": 2.57}, {"text": "talked about signatures,\nmining and blocks, transactions", "start": 36.11, "duration": 4.8}, {"text": "and scripts.", "start": 40.91, "duration": 1.11}, {"text": "And now we're going to\nput it all together.", "start": 42.02, "duration": 1.967}, {"text": "How does this all actually work?", "start": 43.987, "duration": 1.333}, {"text": "What do all these components\ncome together to do?", "start": 45.32, "duration": 2.41}, {"text": "And how does this\nmake this cool money?", "start": 47.73, "duration": 4.16}, {"text": "Quick recap on\nsignatures that I think", "start": 51.89, "duration": 2.97}, {"text": "you got the idea\nfrom the homeworks,", "start": 54.86, "duration": 2.31}, {"text": "from the lectures-- you have\nthese public and private keys.", "start": 57.17, "duration": 3.81}, {"text": "This key pair where you\ngenerate the private key,", "start": 60.98, "duration": 2.52}, {"text": "you distribute the public key.", "start": 63.5, "duration": 2.252}, {"text": "The private key\ncan sign a message.", "start": 65.752, "duration": 2.548}, {"text": "And anyone can verify, given\nthe triple public key, message,", "start": 68.3, "duration": 5.94}, {"text": "signature group.", "start": 74.24, "duration": 1.842}, {"text": "This is useful for\nlots of things--", "start": 76.082, "duration": 1.458}, {"text": "providing identity, ownership,\nall sorts of things.", "start": 77.54, "duration": 2.85}, {"text": "And it's better than\npaper signatures.", "start": 80.39, "duration": 1.86}, {"text": "Paper signatures don't\nreally sign the message.", "start": 82.25, "duration": 3.87}, {"text": "They just sort of\nsign the paper.", "start": 86.12, "duration": 2.61}, {"text": "So if you change some\npart of a document,", "start": 88.73, "duration": 3.36}, {"text": "the signature still\nsort of looks OK.", "start": 92.09, "duration": 1.89}, {"text": "Maybe you can see--", "start": 93.98, "duration": 1.11}, {"text": "you want the paper\nto not be tampered.", "start": 95.09, "duration": 2.76}, {"text": "But you can sign a\nblank piece of paper", "start": 97.85, "duration": 2.67}, {"text": "and then add all this\ntext on afterwards.", "start": 100.52, "duration": 2.64}, {"text": "You can't do that\nwith these systems.", "start": 103.16, "duration": 3.22}, {"text": "So signatures are really cool.", "start": 106.38, "duration": 1.51}, {"text": "And they are sort of a necessary\nthing for this network to work.", "start": 107.89, "duration": 5.87}, {"text": "So mining and blocks--", "start": 113.76, "duration": 1.21}, {"text": "I think you sort of got the idea\nwith the Lamport signatures.", "start": 114.97, "duration": 2.91}, {"text": "If you've looked at the\ncurrent problem set,", "start": 117.88, "duration": 3.0}, {"text": "it makes a lot of sense.", "start": 120.88, "duration": 2.31}, {"text": "You change it nonce, hash a\nbunch of times while you change", "start": 123.19, "duration": 3.37}, {"text": "a nonce a bunch of times.", "start": 126.56, "duration": 1.13}, {"text": "Try to get a low output.", "start": 127.69, "duration": 1.87}, {"text": "So you get the idea of mining.", "start": 129.56, "duration": 1.64}, {"text": "You're proving work\nby repeatedly going", "start": 131.2, "duration": 3.72}, {"text": "through different nonces, trying\nto find a certain hash output", "start": 134.92, "duration": 3.27}, {"text": "that there's no shortcut to.", "start": 138.19, "duration": 1.8}, {"text": "You just have the\nguess and check.", "start": 139.99, "duration": 2.25}, {"text": "And now if you include\nthe previous data", "start": 142.24, "duration": 2.1}, {"text": "as part of your input\nto that hash function,", "start": 144.34, "duration": 2.73}, {"text": "you can make a chain of work.", "start": 147.07, "duration": 2.43}, {"text": "And that's what we call\na blockchain I guess.", "start": 149.5, "duration": 3.72}, {"text": "Any questions on this so far?", "start": 153.22, "duration": 1.735}, {"text": "It's the basic idea\nfrom two lectures ago.", "start": 154.955, "duration": 4.165}, {"text": "Cool.", "start": 159.12, "duration": 1.76}, {"text": "And a recap of what\nNeha said yesterday--", "start": 160.88, "duration": 3.935}, {"text": "there's transactions\nand scripts.", "start": 164.815, "duration": 1.375}, {"text": "I'm not going to go\ninto scripts too much", "start": 166.19, "duration": 2.61}, {"text": "yet, because in practice,\n99% of the scripts", "start": 168.8, "duration": 5.07}, {"text": "are just checking a\npublic key signature.", "start": 173.87, "duration": 2.94}, {"text": "You can do all sorts of other\ncrazy things with the scripts.", "start": 176.81, "duration": 4.35}, {"text": "But almost nobody does yet.", "start": 181.16, "duration": 2.85}, {"text": "Basically they say, OK, I'm\nsending to a public key hash.", "start": 184.01, "duration": 2.85}, {"text": "When I spend from it, I\nreveal the public key,", "start": 186.86, "duration": 2.43}, {"text": "check that the hash\nmatches, check a signature.", "start": 189.29, "duration": 3.602}, {"text": "And transactions have\ninputs and outputs.", "start": 192.892, "duration": 1.708}, {"text": "We went over this yesterday.", "start": 194.6, "duration": 1.26}, {"text": "Just a sort of\nreal-world numbers,", "start": 195.86, "duration": 6.26}, {"text": "this is how big\nthings are, \"ish,\"", "start": 202.12, "duration": 3.3}, {"text": "so a transaction ID\nand index to point", "start": 205.42, "duration": 3.39}, {"text": "to a previous transaction.", "start": 208.81, "duration": 1.47}, {"text": "The transaction ID is 32 bytes.", "start": 210.28, "duration": 2.19}, {"text": "The index is encoded as a\nfour byte, so 32-bit integer,", "start": 212.47, "duration": 4.207}, {"text": "which is kind of overkill,\nbecause I think the most that", "start": 216.677, "duration": 2.333}, {"text": "there's ever--", "start": 219.01, "duration": 0.935}, {"text": "the most outputs\nthere's ever been", "start": 219.945, "duration": 1.675}, {"text": "is like 1,000 or something.", "start": 221.62, "duration": 1.86}, {"text": "So you really don't need it to\nbe able to go up to 4 billion.", "start": 223.48, "duration": 3.96}, {"text": "But that's how it is.", "start": 227.44, "duration": 2.01}, {"text": "The signature ends up\nbeing about 100 bytes", "start": 229.45, "duration": 2.13}, {"text": "because you have to provide\nthe public key, which is either", "start": 231.58, "duration": 3.42}, {"text": "33 or 65.", "start": 235.0, "duration": 2.19}, {"text": "And then the signature itself\nis encoded to something", "start": 237.19, "duration": 2.34}, {"text": "like 70 bytes.", "start": 239.53, "duration": 1.83}, {"text": "Both of those things could\nbe much more efficient.", "start": 241.36, "duration": 2.68}, {"text": "But they're not yet.", "start": 244.04, "duration": 2.422}, {"text": "And the output is\nactually a lot smaller.", "start": 246.462, "duration": 1.708}, {"text": "An output, the script--", "start": 248.17, "duration": 1.56}, {"text": "the main thing is\nyour public key hash,", "start": 249.73, "duration": 2.38}, {"text": "which in Bitcoin is 20 bytes.", "start": 252.11, "duration": 2.15}, {"text": "And then you have those\nother little opcodes,", "start": 254.26, "duration": 2.25}, {"text": "which it adds a\nfew bytes, and then", "start": 256.51, "duration": 1.829}, {"text": "your amount, which is--\nso all amounts in Bitcoin", "start": 258.339, "duration": 3.12}, {"text": "are encoded as 8-byte,\nsigned 64-bit integers.", "start": 261.459, "duration": 3.946}, {"text": "So you can have\npretty high precision.", "start": 265.405, "duration": 2.875}, {"text": "And that's also overkill, since\nall the bitcoins ever mined,", "start": 268.28, "duration": 4.22}, {"text": "put together--", "start": 272.5, "duration": 1.62}, {"text": "if you added them all up, it's\nnowhere near 64 bits to the 64.", "start": 274.12, "duration": 4.98}, {"text": "It's like 2 to the 40 something.", "start": 279.1, "duration": 4.46}, {"text": "So it's also kind of\noverkill but yeah, whatever.", "start": 283.56, "duration": 2.62}, {"text": "So this ends up being for a one\ninput, one output transaction,", "start": 286.18, "duration": 4.32}, {"text": "less than 200 bytes.", "start": 290.5, "duration": 1.14}, {"text": "So that's a message,\npretty small.", "start": 294.3, "duration": 2.04}, {"text": "You can broadcast it\naround the network.", "start": 296.34, "duration": 2.646}, {"text": "Inputs point to old\noutputs, have signatures.", "start": 298.986, "duration": 2.074}, {"text": "Outputs have scripts\nand coin amounts.", "start": 301.06, "duration": 2.91}, {"text": "So what do we do with\nall these things?", "start": 303.97, "duration": 1.66}, {"text": "What is the mining process?", "start": 305.63, "duration": 1.73}, {"text": "So in the homework,\nyou're mining your name.", "start": 307.36, "duration": 3.198}, {"text": "You connect to the\nserver, figure out", "start": 310.558, "duration": 1.542}, {"text": "with the last block was, put\nyour name on, put a nonce,", "start": 312.1, "duration": 2.88}, {"text": "and continue to mine.", "start": 314.98, "duration": 1.71}, {"text": "That's not super useful,\nunless you want to prove that", "start": 316.69, "duration": 2.25}, {"text": "you're-- hey, this is me.", "start": 318.94, "duration": 3.0}, {"text": "In Bitcoin, the\nbasic idea is users", "start": 321.94, "duration": 2.28}, {"text": "are making these transactions.", "start": 324.22, "duration": 1.32}, {"text": "Transactions are moving coins\nfrom one place to another,", "start": 325.54, "duration": 2.98}, {"text": "from one key to another.", "start": 328.52, "duration": 2.3}, {"text": "They make the transactions, they\nsign them, and they broadcast.", "start": 330.82, "duration": 3.42}, {"text": "I'll get in to what\n\"broadcast\" means.", "start": 334.24, "duration": 2.62}, {"text": "So in the current\nproblem set, there's", "start": 336.86, "duration": 2.39}, {"text": "one server, which is not really\na robust distributed system,", "start": 339.25, "duration": 5.25}, {"text": "as people may have\nseen yesterday", "start": 344.5, "duration": 1.98}, {"text": "from about 1:30 to 3:00 PM,\nwhen the whole thing went down.", "start": 346.48, "duration": 5.91}, {"text": "In Bitcoin, it's\ncompletely peer-to-peer.", "start": 352.39, "duration": 3.09}, {"text": "Every node is the same.", "start": 355.48, "duration": 1.56}, {"text": "They're all listening\nfor people connecting in.", "start": 357.04, "duration": 2.14}, {"text": "They're all connecting\nout to other nodes.", "start": 359.18, "duration": 3.86}, {"text": "And they broadcast.", "start": 363.04, "duration": 0.92}, {"text": "So if someone sends\nyou a message,", "start": 363.96, "duration": 1.45}, {"text": "you'll pass it on to\nall the other people.", "start": 365.41, "duration": 2.38}, {"text": "So it's called a gossip network.", "start": 367.79, "duration": 2.3}, {"text": "In practice, it works OK.", "start": 370.09, "duration": 2.22}, {"text": "It's fairly heavy load\non some network traffic,", "start": 372.31, "duration": 2.88}, {"text": "but you can make transactions,\nsign them, broadcast them.", "start": 375.19, "duration": 3.69}, {"text": "And then someone,\nthe miner, takes", "start": 378.88, "duration": 3.31}, {"text": "all these recent\ntransactions that they've", "start": 382.19, "duration": 2.4}, {"text": "seen, and puts them into a\nblock, and then does some work.", "start": 384.59, "duration": 4.34}, {"text": "So those transactions\nare now confirmed,", "start": 388.93, "duration": 2.15}, {"text": "and people can build\nthe next block.", "start": 391.08, "duration": 3.46}, {"text": "So the only difference from\nthe current problem set", "start": 394.54, "duration": 2.3}, {"text": "is instead of putting\nyour name in, you put--", "start": 396.84, "duration": 3.6}, {"text": "you can put your name-- but\nyou also put all these messages", "start": 400.44, "duration": 2.85}, {"text": "that you've seen recently.", "start": 403.29, "duration": 1.62}, {"text": "And so you commit\nto them that way.", "start": 404.91, "duration": 2.25}, {"text": "You could do it by just\nsticking them all in,", "start": 407.16, "duration": 2.77}, {"text": "but instead, there's a bit\nmore advanced way to do it.", "start": 409.93, "duration": 4.85}, {"text": "You use what's called\na block header.", "start": 414.78, "duration": 2.67}, {"text": "So yeah, the block header\nitself is the message.", "start": 417.45, "duration": 2.97}, {"text": "So similar to the problem\nset, it's the block header", "start": 420.42, "duration": 2.67}, {"text": "that you need to hash to get a\nlow output value, not the block", "start": 423.09, "duration": 3.39}, {"text": "itself, which is\nkind of interesting.", "start": 426.48, "duration": 2.56}, {"text": "And the headers have a hash\nof all the transactions", "start": 429.04, "duration": 3.297}, {"text": "in the blocks.", "start": 432.337, "duration": 0.583}, {"text": "So you don't just put\nall the transactions", "start": 432.92, "duration": 1.81}, {"text": "into one big megabyte\ndata structure,", "start": 434.73, "duration": 2.82}, {"text": "hash the whole thing, and\nthen try to get a low output.", "start": 437.55, "duration": 2.31}, {"text": "You actually do some\nintermediate steps first.", "start": 439.86, "duration": 2.605}, {"text": "And what's interesting\nis it's actually", "start": 442.465, "duration": 1.625}, {"text": "just the headers that\nmake a chain, not", "start": 444.09, "duration": 1.95}, {"text": "the blocks themselves.", "start": 446.04, "duration": 1.54}, {"text": "So instead of blockchain, you\ncould call it a headerchain.", "start": 447.58, "duration": 2.86}, {"text": "So I'll talk about headers.", "start": 450.44, "duration": 2.82}, {"text": "The headers are 80 bytes.", "start": 453.26, "duration": 1.69}, {"text": "And they're actually quite\nsimilar to the blocks", "start": 454.95, "duration": 2.7}, {"text": "in problem set 2.", "start": 457.65, "duration": 1.25}, {"text": "So the main three\ncomponents are you've", "start": 458.9, "duration": 2.14}, {"text": "got the previous hash, the\nMerkle root, and the nonce.", "start": 461.04, "duration": 2.55}, {"text": "And so this is like\nin the problem set.", "start": 463.59, "duration": 1.9}, {"text": "You start with\nthe previous hash.", "start": 465.49, "duration": 1.85}, {"text": "Then you have data that\nyou're actually committing to.", "start": 467.34, "duration": 3.733}, {"text": "And then you have\nsome data that doesn't", "start": 471.073, "duration": 1.667}, {"text": "have any actual meaning,\njust to get the work done.", "start": 472.74, "duration": 3.22}, {"text": "So I can-- to reference, if\nyou look through the work", "start": 475.96, "duration": 4.43}, {"text": "people are doing right\nnow, this is all public,", "start": 480.39, "duration": 3.39}, {"text": "the current problem set.", "start": 483.78, "duration": 1.65}, {"text": "There's a previous\nhash, which is basically", "start": 485.43, "duration": 2.04}, {"text": "the hash of the line above it.", "start": 487.47, "duration": 2.29}, {"text": "And then there's some data\nyou're committing to, in this", "start": 489.76, "duration": 2.66}, {"text": "case people's user names, and\nthen some non-meaningful data", "start": 492.42, "duration": 4.62}, {"text": "here with just random numbers\nand stuff it looks like--", "start": 497.04, "duration": 6.04}, {"text": "so very similar.", "start": 503.08, "duration": 1.72}, {"text": "Any questions about this idea?", "start": 504.8, "duration": 1.25}, {"text": "Cool.", "start": 510.38, "duration": 0.5}, {"text": "So we use a Merkle root, which\nI think I talked about last week", "start": 513.97, "duration": 4.1}, {"text": "Monday, instead of\njust concatenating", "start": 518.07, "duration": 3.219}, {"text": "all the transactions and\nhashing them in together.", "start": 521.289, "duration": 2.401}, {"text": "You could do that.", "start": 523.69, "duration": 0.84}, {"text": "That actually would work.", "start": 524.53, "duration": 1.042}, {"text": "It wouldn't make\na huge difference.", "start": 525.572, "duration": 1.993}, {"text": "But this is a\nlittle nicer if you", "start": 527.565, "duration": 1.375}, {"text": "want to prove that a\ntransaction was in this block,", "start": 528.94, "duration": 4.11}, {"text": "without giving the whole block.", "start": 533.05, "duration": 2.79}, {"text": "So the idea is I\nhave these TXIDs.", "start": 535.84, "duration": 3.24}, {"text": "And a TXID, transaction ID, is\njust a hash of the transaction.", "start": 539.08, "duration": 5.46}, {"text": "Stick all the components of\nthe transaction into bytes,", "start": 544.54, "duration": 2.91}, {"text": "hash that, and you've\ngot what's called a TXID.", "start": 547.45, "duration": 2.22}, {"text": "And that's how you\nrefer to transactions.", "start": 549.67, "duration": 2.26}, {"text": "You hash these two together to\nget this intermediate point.", "start": 555.06, "duration": 3.76}, {"text": "Do the same thing\nup to the root.", "start": 558.82, "duration": 2.16}, {"text": "And so you can't change any of\nthese little transaction IDs", "start": 560.98, "duration": 4.44}, {"text": "without changing\nthe Merkle root.", "start": 565.42, "duration": 1.86}, {"text": "So it commits to\nall the transactions", "start": 567.28, "duration": 2.97}, {"text": "just the same way it would\nif you just concatenated them", "start": 570.25, "duration": 3.152}, {"text": "all together and hashed that.", "start": 573.402, "duration": 1.208}, {"text": "So it really-- we'll go in\nto, later, why this is useful.", "start": 577.15, "duration": 5.25}, {"text": "But in many cases, it really\ndoesn't help too much.", "start": 582.4, "duration": 4.76}, {"text": "Any getting questions\nabout Merkle, Merkle tree?", "start": 587.16, "duration": 2.21}, {"text": "Good.", "start": 589.37, "duration": 1.99}, {"text": "So the actual Bitcoin headers,\nwhich many things use,", "start": 591.36, "duration": 4.87}, {"text": "has a couple of fields.", "start": 596.23, "duration": 1.11}, {"text": "Some of them are\nactually not very useful.", "start": 597.34, "duration": 3.51}, {"text": "But the main two are previous\nhash, Merkle root, nonce.", "start": 600.85, "duration": 4.35}, {"text": "And then there's-- I'll\ntalk about the other things.", "start": 605.2, "duration": 2.26}, {"text": "So there's also a version\nfield right at the beginning.", "start": 607.46, "duration": 2.84}, {"text": "It's 4 bytes.", "start": 610.3, "duration": 1.7}, {"text": "It indicates block version.", "start": 612.0, "duration": 1.75}, {"text": "It's not clear what that's going\nto be used for in the future.", "start": 613.75, "duration": 3.78}, {"text": "It used to be used for sort\nof signaling protocol changes.", "start": 617.53, "duration": 3.44}, {"text": "I'm not sure that's going to\nbe the case going forward,", "start": 620.97, "duration": 2.53}, {"text": "because it didn't really\nwork very well for that.", "start": 623.5, "duration": 3.94}, {"text": "So right now I think they all\nstart like 02 and then a bunch", "start": 627.44, "duration": 3.53}, {"text": "of zeros.", "start": 630.97, "duration": 1.32}, {"text": "And that's the current\nversion, whatever that means.", "start": 632.29, "duration": 3.82}, {"text": "And if you mine something\nwith a different version,", "start": 636.11, "duration": 4.31}, {"text": "everyone will accept it.", "start": 640.42, "duration": 1.54}, {"text": "But there'll be like these\nwarnings that show up", "start": 641.96, "duration": 2.0}, {"text": "in your Bitcoin log files that\nsay, warning, unknown version", "start": 643.96, "duration": 4.56}, {"text": "detected.", "start": 648.52, "duration": 1.92}, {"text": "The idea is maybe, well, if the\ninversion increases or changes,", "start": 650.44, "duration": 3.27}, {"text": "maybe there's some new rules\nin this system, or new opcodes,", "start": 653.71, "duration": 3.87}, {"text": "or new something going on.", "start": 657.58, "duration": 1.663}, {"text": "And you're not aware\nof it, so you might", "start": 659.243, "duration": 1.667}, {"text": "need to upgrade your software.", "start": 660.91, "duration": 2.37}, {"text": "That was the idea anyway.", "start": 663.28, "duration": 2.77}, {"text": "In practice, what happens is--", "start": 666.05, "duration": 1.668}, {"text": "you'll see in your\nlogs all the time,", "start": 667.718, "duration": 1.542}, {"text": "that like, unknown\nversion detected.", "start": 669.26, "duration": 2.1}, {"text": "And it's just someone\njust set random numbers", "start": 671.36, "duration": 2.67}, {"text": "in the version field.", "start": 674.03, "duration": 1.41}, {"text": "And it doesn't seem to mean\nanything, so not super useful.", "start": 675.44, "duration": 4.24}, {"text": "Previous hash, just\nlike in the problem set,", "start": 679.68, "duration": 2.01}, {"text": "it's the hash of the\nprevious block, 32 bytes.", "start": 681.69, "duration": 3.22}, {"text": "Merkle root, as described\na few slides before--", "start": 684.91, "duration": 2.79}, {"text": "hash of all the\ntransactions in the block.", "start": 687.7, "duration": 1.86}, {"text": "Time, actually kind of complex--", "start": 692.458, "duration": 3.372}, {"text": "I'm not going to go into\nthe whole thing right here.", "start": 695.83, "duration": 3.33}, {"text": "So far we haven't really\ntalked about time.", "start": 699.16, "duration": 2.43}, {"text": "Does anyone know why we'd\nwant time in these headers?", "start": 701.59, "duration": 6.65}, {"text": "Yeah.", "start": 711.2, "duration": 0.5}, {"text": "AUDIENCE: You had\nmentioned earlier", "start": 711.7, "duration": 1.458}, {"text": "that you don't accept blocks\nbetween a certain interval", "start": 713.158, "duration": 3.512}, {"text": "if they were too late.", "start": 716.67, "duration": 1.788}, {"text": "TADGE DRYJA: Right.", "start": 718.458, "duration": 0.792}, {"text": "So it makes sense intuitively\nthat like if someone says, hey,", "start": 719.25, "duration": 3.6}, {"text": "I mined this in 1987.", "start": 722.85, "duration": 3.33}, {"text": "It's like well,\nthat seems crazy.", "start": 726.18, "duration": 2.46}, {"text": "Or if someone says,\nhere's a block.", "start": 728.64, "duration": 1.71}, {"text": "It came out in 2046.", "start": 730.35, "duration": 2.03}, {"text": "Like, this doesn't\nmake any sense.", "start": 732.38, "duration": 3.58}, {"text": "So intuitively,\nyeah, you shouldn't", "start": 735.96, "duration": 1.82}, {"text": "accept things that have\nsome crazy date that's", "start": 737.78, "duration": 2.22}, {"text": "clearly wrong.", "start": 740.0, "duration": 1.26}, {"text": "But why?", "start": 741.26, "duration": 0.87}, {"text": "Why do we need time at all?", "start": 742.13, "duration": 1.19}, {"text": "Yeah.", "start": 745.66, "duration": 0.5}, {"text": "AUDIENCE: If you want\nto lock the transaction", "start": 746.16, "duration": 1.875}, {"text": "until a certain time.", "start": 748.035, "duration": 1.795}, {"text": "TADGE DRYJA: Yeah, you could\nsay, here's a transaction,", "start": 749.83, "duration": 3.13}, {"text": "and I don't want it to\nbe valid before August 1.", "start": 752.96, "duration": 4.08}, {"text": "And so then, you could say,\nif it goes into a block,", "start": 757.04, "duration": 4.03}, {"text": "and that block has a\ntimestamp before August 1,", "start": 761.07, "duration": 3.5}, {"text": "consider the block invalid.", "start": 764.57, "duration": 1.86}, {"text": "You could.", "start": 766.43, "duration": 2.1}, {"text": "You can also do timestamping\nbased just on block height.", "start": 768.53, "duration": 3.45}, {"text": "But what's the main-- does\nanyone know the main reason", "start": 771.98, "duration": 2.26}, {"text": "to have height here?", "start": 774.24, "duration": 1.1}, {"text": "Yeah.", "start": 775.34, "duration": 0.615}, {"text": "AUDIENCE: Is it\nbecause if they're", "start": 775.955, "duration": 1.417}, {"text": "a competing transaction?", "start": 777.372, "duration": 1.548}, {"text": "And then you would\npick one or the other.", "start": 778.92, "duration": 4.76}, {"text": "TADGE DRYJA: So the competing\ntransactions, when they get in,", "start": 783.68, "duration": 2.64}, {"text": "they sort of get into a block.", "start": 786.32, "duration": 1.57}, {"text": "And that sort of solves\nthat competition.", "start": 787.89, "duration": 2.035}, {"text": "So you have two\ntransactions that", "start": 789.925, "duration": 1.375}, {"text": "both are mutually exclusive.", "start": 791.3, "duration": 2.35}, {"text": "Well, if they're both in the\nsame Merkle root and both", "start": 793.65, "duration": 2.683}, {"text": "in the same block,\nthen that block", "start": 796.333, "duration": 1.417}, {"text": "is considered invalid,\nbecause it's like,", "start": 797.75, "duration": 2.04}, {"text": "hey, you've given me a block.", "start": 799.79, "duration": 1.8}, {"text": "It's got two things that\ncan't both exist here.", "start": 801.59, "duration": 2.55}, {"text": "So throw the block away.", "start": 804.14, "duration": 2.88}, {"text": "If you find two blocks\nthat both seem to have--", "start": 807.02, "duration": 3.5}, {"text": "that sort of collide.", "start": 810.52, "duration": 1.36}, {"text": "They're both pointing to the--", "start": 811.88, "duration": 1.47}, {"text": "they've both got the\nsame previous hash.", "start": 813.35, "duration": 1.92}, {"text": "So they're both in the same\nheight, we call, of the chain.", "start": 815.27, "duration": 5.28}, {"text": "You could say, oh, well,\nwhichever one came out first.", "start": 820.55, "duration": 4.095}, {"text": "I'll look at the\ntimestamp and say, OK,", "start": 824.645, "duration": 1.625}, {"text": "the block that came out\nfirst will be the valid one.", "start": 826.27, "duration": 3.51}, {"text": "But the problem is this\nis claimed block creation.", "start": 829.78, "duration": 3.9}, {"text": "You can put whatever 4\nbytes you want in there.", "start": 833.68, "duration": 2.91}, {"text": "And so you can always\nsay, oh, I just", "start": 836.59, "duration": 1.98}, {"text": "wanted it exactly 1 second\nafter the previous block.", "start": 838.57, "duration": 3.12}, {"text": "It just took me a\nwhile to broadcast it.", "start": 841.69, "duration": 3.69}, {"text": "So you can't really\ntrust the timestamp", "start": 845.38, "duration": 2.25}, {"text": "to see which came first.", "start": 847.63, "duration": 1.83}, {"text": "If you could, you wouldn't need\nall this crazy mining stuff.", "start": 849.46, "duration": 2.55}, {"text": "And transactions themselves\ncould just have a timestamp.", "start": 852.01, "duration": 3.51}, {"text": "And you wouldn't need\nthis whole structure.", "start": 855.52, "duration": 2.34}, {"text": "So the fundamental\nreason you're mining", "start": 857.86, "duration": 2.19}, {"text": "is we can't trust people to\nsay when they did something.", "start": 860.05, "duration": 4.593}, {"text": "You can always say, no,\nthis transaction came first.", "start": 864.643, "duration": 2.167}, {"text": "No, this came first.", "start": 866.81, "duration": 1.64}, {"text": "So the real reason\nfor this blockchain", "start": 868.45, "duration": 1.71}, {"text": "is, OK, we know which\ncame before what.", "start": 870.16, "duration": 3.282}, {"text": "AUDIENCE: In practice,\nwhich one happens?", "start": 873.442, "duration": 1.708}, {"text": "Do people just lie and say\nit happened a second later?", "start": 875.15, "duration": 2.39}, {"text": "Or is it [INAUDIBLE]?", "start": 877.54, "duration": 1.328}, {"text": "TADGE DRYJA: Oh, in\npractice the timestamps", "start": 878.868, "duration": 1.792}, {"text": "are pretty unreliable.", "start": 880.66, "duration": 3.15}, {"text": "They can be off by minutes.", "start": 883.81, "duration": 4.52}, {"text": "It can be before the\nprevious block's time.", "start": 888.33, "duration": 2.32}, {"text": "And that's OK.", "start": 890.65, "duration": 2.4}, {"text": "It seems intuitively like, well,\nthat should just be a rule.", "start": 893.05, "duration": 2.937}, {"text": "And it probably-- it would have\nbeen cool if it was a rule and", "start": 895.987, "duration": 2.583}, {"text": "made things simpler\nfrom the beginning.", "start": 898.57, "duration": 2.1}, {"text": "But if you're pointing\nto a previous block,", "start": 900.67, "duration": 3.75}, {"text": "I'm building on top of it.", "start": 904.42, "duration": 1.41}, {"text": "And the previous block\ncame out at 10:15.", "start": 905.83, "duration": 4.04}, {"text": "And I set my timestamp\nto 10:12, 3 minutes prior", "start": 909.87, "duration": 3.73}, {"text": "to the previous block.", "start": 913.6, "duration": 1.41}, {"text": "Logically, that's impossible.", "start": 915.01, "duration": 1.433}, {"text": "I'm referencing\nsomething, and I'm", "start": 916.443, "duration": 1.417}, {"text": "saying I'm coming before it.", "start": 917.86, "duration": 1.62}, {"text": "But the software says that's OK.", "start": 919.48, "duration": 2.522}, {"text": "AUDIENCE: So if we're\ncreating a version,", "start": 922.002, "duration": 1.708}, {"text": "would it be useful to just\nget rid of version and time,", "start": 923.71, "duration": 3.263}, {"text": "like if we're creating\na new blockchain?", "start": 926.973, "duration": 1.667}, {"text": "TADGE DRYJA: So version,\nmaybe you could get rid of,", "start": 928.64, "duration": 2.297}, {"text": "or you could put it somewhere\nin the Merkle root or something.", "start": 930.937, "duration": 2.583}, {"text": "Time actually does have\na really useful purpose.", "start": 933.52, "duration": 2.91}, {"text": "Does anyone, maybe if you know?", "start": 939.15, "duration": 2.54}, {"text": "AUDIENCE: I don't\nknow, but does it", "start": 941.69, "duration": 2.02}, {"text": "play into the\ndifficulty of the mine?", "start": 943.71, "duration": 2.11}, {"text": "Does it?", "start": 945.82, "duration": 0.68}, {"text": "TADGE DRYJA: Yeah, so\nthe main reason for time", "start": 946.5, "duration": 2.85}, {"text": "here is to adjust\nthe difficulty.", "start": 949.35, "duration": 4.47}, {"text": "And that happens\nevery 2,016 blocks.", "start": 953.82, "duration": 3.15}, {"text": "You just look at, OK, how long\ndid this 2,016-block period", "start": 956.97, "duration": 2.94}, {"text": "take according to\nthese timestamps?", "start": 959.91, "duration": 2.88}, {"text": "And if it took two\nweeks, OK, we're good.", "start": 962.79, "duration": 2.29}, {"text": "The difficulty doesn't\nhave to change.", "start": 965.08, "duration": 1.76}, {"text": "If it took three weeks,\nthat means the blocks", "start": 966.84, "duration": 2.61}, {"text": "were coming out very slowly.", "start": 969.45, "duration": 1.62}, {"text": "And we need to reduce\nthe difficulty.", "start": 971.07, "duration": 3.06}, {"text": "If the 2,016 blocks came\nout in one week, that means,", "start": 974.13, "duration": 3.54}, {"text": "wow, people were\nmining really fast.", "start": 977.67, "duration": 2.8}, {"text": "And so we need to\nincrease the difficulty.", "start": 980.47, "duration": 2.04}, {"text": "So there's this negative\nfeedback mechanism", "start": 982.51, "duration": 2.81}, {"text": "based on this time.", "start": 985.32, "duration": 1.8}, {"text": "And it can be tweaked.", "start": 987.12, "duration": 2.31}, {"text": "It's not accurate.", "start": 989.43, "duration": 2.1}, {"text": "You can have things\ncoming in the wrong order.", "start": 991.53, "duration": 2.65}, {"text": "The general rule of thumb--", "start": 994.18, "duration": 1.9}, {"text": "the rule in the software\nis about two hours.", "start": 996.08, "duration": 2.89}, {"text": "If you see something\nthat's two hours off", "start": 998.97, "duration": 2.34}, {"text": "from what your internal clock\nsays, you will reject it.", "start": 1001.31, "duration": 4.86}, {"text": "But that's a huge gap.", "start": 1006.17, "duration": 2.55}, {"text": "Most network systems,\neveryone's got their clocks", "start": 1008.72, "duration": 3.63}, {"text": "to the same second at\nleast, or millisecond.", "start": 1012.35, "duration": 4.65}, {"text": "Two hours is like\nkind of enormous gaps.", "start": 1017.0, "duration": 3.67}, {"text": "But the system works\nOK, because you've", "start": 1020.67, "duration": 2.33}, {"text": "got these really long-term\ndifficulty adjustments that", "start": 1023.0, "duration": 3.359}, {"text": "only happen every 2,016 blocks,\nwhich in practice is something", "start": 1026.359, "duration": 3.451}, {"text": "like two weeks.", "start": 1029.81, "duration": 1.809}, {"text": "So if someone gets\nsomething a few minutes off,", "start": 1031.619, "duration": 3.47}, {"text": "it doesn't really\naffect things too much.", "start": 1035.089, "duration": 2.721}, {"text": "And it's really only used for,\nOK, look at the last 2,016", "start": 1037.81, "duration": 4.269}, {"text": "blocks, two weeks-ish of\nwork, of all these blocks,", "start": 1042.079, "duration": 3.301}, {"text": "and see how fast we\nneed to make things.", "start": 1045.38, "duration": 3.03}, {"text": "So that ties into the next\nfield, which is difficulty.", "start": 1048.41, "duration": 4.86}, {"text": "It's in a sort of weird\nfloating pointlike", "start": 1053.27, "duration": 2.07}, {"text": "format with a mantissa\nand exponent, which", "start": 1055.34, "duration": 3.78}, {"text": "is totally custom.", "start": 1059.12, "duration": 1.29}, {"text": "And you kind of have to write\nyour own code to deal with it.", "start": 1060.41, "duration": 3.21}, {"text": "But it basically\nsays, OK, what does", "start": 1063.62, "duration": 1.95}, {"text": "the number have to-- what does\nthe hash have to be below?", "start": 1065.57, "duration": 2.85}, {"text": "It's not just number of bits.", "start": 1068.42, "duration": 2.37}, {"text": "So in the problem set,\nI said 33 bits of work.", "start": 1070.79, "duration": 4.38}, {"text": "So that's fairly easy to\ndetect, because you just look", "start": 1075.17, "duration": 2.25}, {"text": "for 33 0-bits in the front.", "start": 1077.42, "duration": 2.49}, {"text": "In Bitcoin, it's not\njust number of bits.", "start": 1079.91, "duration": 2.13}, {"text": "It's actually a number\nthat it must be below.", "start": 1082.04, "duration": 2.438}, {"text": "If it were just number\nof bits, the problem", "start": 1084.478, "duration": 1.792}, {"text": "then is your adjustments are\nfairly coarse, because you can", "start": 1086.27, "duration": 3.99}, {"text": "only adjust by a factor of 2.", "start": 1090.26, "duration": 1.86}, {"text": "You can double your\ndifficulty or half it.", "start": 1092.12, "duration": 3.81}, {"text": "But with this, you can have much\nsmaller difficulty adjustments", "start": 1095.93, "duration": 3.66}, {"text": "of like a fraction of a percent.", "start": 1099.59, "duration": 1.35}, {"text": "Yeah, this field is\npretty much useless", "start": 1103.84, "duration": 4.033}, {"text": "since you can calculate\nit from the time", "start": 1107.873, "duration": 1.667}, {"text": "fields of the previous blocks.", "start": 1109.54, "duration": 1.983}, {"text": "So you could just\nhave it be implied.", "start": 1111.523, "duration": 1.542}, {"text": "But it's in there.", "start": 1115.63, "duration": 0.9}, {"text": "And you can just whatever.", "start": 1116.53, "duration": 1.26}, {"text": "It's an extra 4 bytes.", "start": 1117.79, "duration": 2.12}, {"text": "I don't think you\nactually-- like, you", "start": 1119.91, "duration": 2.5}, {"text": "don't have to store it\non a disk if you want,", "start": 1122.41, "duration": 1.92}, {"text": "because you can just figure\nit out from the other things.", "start": 1124.33, "duration": 3.563}, {"text": "AUDIENCE: Wouldn't you\nneed it for [INAUDIBLE]??", "start": 1127.893, "duration": 5.079}, {"text": "TADGE DRYJA: No, because you\ncan figure out what difficulty", "start": 1132.972, "duration": 2.458}, {"text": "is just from the headers.", "start": 1135.43, "duration": 1.042}, {"text": "I mean, it's in there.", "start": 1138.833, "duration": 0.917}, {"text": "I guess it's nice\nif you just want", "start": 1139.75, "duration": 1.92}, {"text": "to validate whether a single\nheader has enough work.", "start": 1141.67, "duration": 5.21}, {"text": "But it's like, how much\nwork does it claim it needs?", "start": 1146.88, "duration": 3.322}, {"text": "And then you can validate it.", "start": 1150.202, "duration": 1.208}, {"text": "But I don't know.", "start": 1151.41, "duration": 1.487}, {"text": "It's in there.", "start": 1152.897, "duration": 0.583}, {"text": "It doesn't-- you could take\nit out and reorganize the code", "start": 1153.48, "duration": 2.587}, {"text": "a little if you\nwanted to optimize it.", "start": 1156.067, "duration": 1.583}, {"text": "But that would change so\nmuch that no one bothers.", "start": 1157.65, "duration": 2.93}, {"text": "AUDIENCE: So when we talk about\nthe adjusting difficulties", "start": 1160.58, "duration": 2.85}, {"text": "and even just showing the\nproblem or proof of work, who", "start": 1163.43, "duration": 4.53}, {"text": "[INAUDIBLE] for\nthe problems that", "start": 1167.96, "duration": 2.22}, {"text": "will go to the central server?", "start": 1170.18, "duration": 3.08}, {"text": "TADGE DRYJA: So in\nthis, it's just everyone", "start": 1173.26, "duration": 1.91}, {"text": "broadcasts their blocks.", "start": 1175.17, "duration": 1.53}, {"text": "So if you've received a block or\nif you found a block yourself,", "start": 1176.7, "duration": 4.44}, {"text": "you just send it to all your\npeers that you're connected to.", "start": 1181.14, "duration": 3.48}, {"text": "And so there's no like, oh,\nthis is the canonical block.", "start": 1184.62, "duration": 5.56}, {"text": "There can be competing\nblocks where you have two", "start": 1190.18, "duration": 2.0}, {"text": "at the same time and just\nstochastically, one of them", "start": 1192.18, "duration": 3.93}, {"text": "will pull ahead,\nbecause, well, randomly.", "start": 1196.11, "duration": 3.0}, {"text": "So you can have\nconflicting things.", "start": 1199.11, "duration": 2.67}, {"text": "Yeah, and then the\nadjustments-- also,", "start": 1201.78, "duration": 1.74}, {"text": "everyone computes\nthe adjustments.", "start": 1203.52, "duration": 2.51}, {"text": "And this is an actually\nvery quick computation,", "start": 1206.03, "duration": 2.56}, {"text": "because you're just looking at--", "start": 1208.59, "duration": 4.08}, {"text": "you're not even looking\nat 2,016 timestamps.", "start": 1212.67, "duration": 2.58}, {"text": "You're basically just\nsaying, OK, if height--", "start": 1215.25, "duration": 2.67}, {"text": "so height is just what\nblock number it is.", "start": 1217.92, "duration": 2.16}, {"text": "So if you're-- right now,\nit's about 500 million.", "start": 1220.08, "duration": 3.76}, {"text": "No, sorry, 500,000.", "start": 1223.84, "duration": 2.325}, {"text": "So you basically\nin the code just", "start": 1226.165, "duration": 1.375}, {"text": "say, well, if\nheight modulo 2,016", "start": 1227.54, "duration": 3.28}, {"text": "is equal to 0, check\nheight minus 2,016's block.", "start": 1230.82, "duration": 7.98}, {"text": "Compare the two timestamps.", "start": 1238.8, "duration": 1.77}, {"text": "Subtract them.", "start": 1240.57, "duration": 1.38}, {"text": "Get a duration.", "start": 1241.95, "duration": 1.86}, {"text": "And then compare that\nduration to two weeks.", "start": 1243.81, "duration": 3.0}, {"text": "And then change the\ndifficulty proportionally.", "start": 1246.81, "duration": 2.77}, {"text": "So it's actually, like,\nsuper quick for everyone", "start": 1249.58, "duration": 2.4}, {"text": "to compute the new difficulty.", "start": 1251.98, "duration": 1.25}, {"text": "And they only do it\nonce every two weeks.", "start": 1253.23, "duration": 2.89}, {"text": "And it, yeah, it's\npretty straightforward.", "start": 1256.12, "duration": 3.15}, {"text": "There are weird\nattacks and stuff.", "start": 1259.27, "duration": 2.42}, {"text": "And it's kind of some weird\noff by 1 errors, where you're--", "start": 1261.69, "duration": 3.51}, {"text": "I don't remember.", "start": 1265.2, "duration": 0.8}, {"text": "Like, it's kind of confusing.", "start": 1266.0, "duration": 1.42}, {"text": "It's also confusing because\nthe test network, which", "start": 1267.42, "duration": 2.73}, {"text": "I haven't gone into but will\nuse probably in two weeks.", "start": 1270.15, "duration": 5.09}, {"text": "There's a Bitcoin test network,\nwhich operates pretty much", "start": 1275.24, "duration": 4.15}, {"text": "exactly the same as\nBitcoin, except everyone", "start": 1279.39, "duration": 2.4}, {"text": "agrees that the coins\nare not worth any money.", "start": 1281.79, "duration": 3.0}, {"text": "What's interesting is it's\nactually called testnet3.", "start": 1284.79, "duration": 3.06}, {"text": "The first two test networks\nhave the same setup.", "start": 1287.85, "duration": 3.69}, {"text": "However, the agreement that\nthey were not worth any money", "start": 1291.54, "duration": 2.43}, {"text": "broke down.", "start": 1293.97, "duration": 2.73}, {"text": "So at testnet1,\nsomeone said, hey,", "start": 1296.7, "duration": 1.83}, {"text": "I'll pay you a bitcoin for\na million testnet coins.", "start": 1298.53, "duration": 4.05}, {"text": "And once people\nsaw this happening,", "start": 1302.58, "duration": 1.53}, {"text": "they said, oh, well,\nyou just ruined testnet.", "start": 1304.11, "duration": 1.5}, {"text": "Now they're worth money.", "start": 1305.61, "duration": 1.29}, {"text": "So we'll go to testnet2.", "start": 1306.9, "duration": 1.14}, {"text": "It happened again.", "start": 1308.04, "duration": 1.18}, {"text": "Testnet3 has had\nsome staying power.", "start": 1309.22, "duration": 1.5}, {"text": "I think people realized that if\nthey try to buy testnet3 coins,", "start": 1310.72, "duration": 4.28}, {"text": "everyone's going to\nleave and go to testnet4.", "start": 1315.0, "duration": 3.365}, {"text": "So it's kind of fun.", "start": 1318.365, "duration": 3.865}, {"text": "I'd actually be OK with testnet3\ncoins being worth money,", "start": 1322.23, "duration": 2.85}, {"text": "because I have many,\nmany thousands of them.", "start": 1325.08, "duration": 5.19}, {"text": "But yeah, so one\ndifference, though,", "start": 1330.27, "duration": 8.2}, {"text": "between the test networks\nand the real network", "start": 1338.47, "duration": 2.3}, {"text": "is the difficulty adjustments.", "start": 1340.77, "duration": 1.83}, {"text": "So I think in the\nfirst test network,", "start": 1342.6, "duration": 3.48}, {"text": "it just worked\nexactly like Bitcoin.", "start": 1346.08, "duration": 2.31}, {"text": "But one of the problems\nwas people would mine,", "start": 1348.39, "duration": 3.21}, {"text": "and the difficulty\nwould increase.", "start": 1351.6, "duration": 2.43}, {"text": "And then people would\nstop mining, say, oh, I'm", "start": 1354.03, "duration": 2.22}, {"text": "going to test out\nmy mining software.", "start": 1356.25, "duration": 2.34}, {"text": "I'll mine a couple\nthousand blocks.", "start": 1358.59, "duration": 2.505}, {"text": "Maybe it only takes me\na day or two to do so,", "start": 1361.095, "duration": 1.875}, {"text": "because I have a very\nfast computer compared", "start": 1362.97, "duration": 2.79}, {"text": "to the rest of the network.", "start": 1365.76, "duration": 1.292}, {"text": "And then I say, OK,\nwell, it works, cool.", "start": 1367.052, "duration": 1.708}, {"text": "I'm going to go to\nthe real network now.", "start": 1368.76, "duration": 1.667}, {"text": "And I leave the test network.", "start": 1370.427, "duration": 1.323}, {"text": "And now the\ndifficulty increased,", "start": 1371.75, "duration": 1.69}, {"text": "because let's say 2,000\nor 4,000 blocks came out.", "start": 1373.44, "duration": 3.12}, {"text": "And they came out very quickly,\nso the difficulty went up.", "start": 1376.56, "duration": 2.85}, {"text": "And then all the\nmining power left.", "start": 1379.41, "duration": 1.77}, {"text": "And so now blocks\naren't coming out.", "start": 1381.18, "duration": 2.37}, {"text": "And since the adjustment\ncan be up or down", "start": 1383.55, "duration": 3.46}, {"text": "but happens based on number\nof blocks, not based on time,", "start": 1387.01, "duration": 5.18}, {"text": "if you have a very high\ndifficulty and the very low", "start": 1392.19, "duration": 3.24}, {"text": "hash rate relative\nto that difficulty,", "start": 1395.43, "duration": 2.67}, {"text": "it can take weeks\nor months or years", "start": 1398.1, "duration": 3.0}, {"text": "for the difficulty to reduce.", "start": 1401.1, "duration": 2.73}, {"text": "So testnet3 put in this\nsort of difficulty nerfing", "start": 1403.83, "duration": 4.26}, {"text": "code, which is probably wrong\nand not what they intended.", "start": 1408.09, "duration": 4.86}, {"text": "And it has this thing where\nlike if 20 minutes have gone by,", "start": 1412.95, "duration": 3.09}, {"text": "the difficulty lowers.", "start": 1416.04, "duration": 1.26}, {"text": "And it's kind of ugly.", "start": 1417.3, "duration": 3.24}, {"text": "So that's the main place\nI've dealt with this field.", "start": 1420.54, "duration": 4.643}, {"text": "One other rule with the\nrestriction-- the difficulty", "start": 1425.183, "duration": 2.167}, {"text": "can go up by at\nmost a factor of 4", "start": 1427.35, "duration": 3.27}, {"text": "and drop by at\nmost a factor of 4.", "start": 1430.62, "duration": 3.15}, {"text": "So if you mine 2,016\nblocks in one day,", "start": 1433.77, "duration": 4.08}, {"text": "the difficulty goes\nup 4x but does not", "start": 1437.85, "duration": 2.07}, {"text": "go up 14x or whatever\nthe implied would.", "start": 1439.92, "duration": 5.83}, {"text": "Any-- go ahead.", "start": 1445.75, "duration": 0.64}, {"text": "AUDIENCE: So the\ndifficulty is definitely", "start": 1446.39, "duration": 1.78}, {"text": "constant for two weeks then?", "start": 1448.17, "duration": 1.69}, {"text": "TADGE DRYJA: Yeah.", "start": 1449.86, "duration": 1.22}, {"text": "Well, sorry, not two weeks--", "start": 1451.08, "duration": 1.32}, {"text": "2,016 blocks, which is generally\naround two weeks, but yeah.", "start": 1452.4, "duration": 4.52}, {"text": "AUDIENCE: So it\nunblocks and blocks,", "start": 1456.92, "duration": 1.68}, {"text": "within literally an\nalmost two-week period,", "start": 1458.6, "duration": 1.5}, {"text": "that difficulty\nwould be the same.", "start": 1460.1, "duration": 1.28}, {"text": "TADGE DRYJA: Yeah, so if you\nactually look at the headers,", "start": 1461.38, "duration": 2.417}, {"text": "this is just the constant.", "start": 1463.797, "duration": 1.108}, {"text": "It just is always the same.", "start": 1464.905, "duration": 1.125}, {"text": "So it's kind of a silly\nfield to be in there.", "start": 1466.03, "duration": 1.875}, {"text": "You never need it, and\nit's always the same.", "start": 1467.905, "duration": 3.57}, {"text": "Any other questions\nabout-- yeah?", "start": 1471.475, "duration": 1.375}, {"text": "AUDIENCE: How many transactions\nare usually [INAUDIBLE]??", "start": 1472.85, "duration": 2.532}, {"text": "TADGE DRYJA: Oh,\nI'll get to that--", "start": 1475.382, "duration": 1.458}, {"text": "right now, a couple\nthousand, 4,000-ish.", "start": 1476.84, "duration": 3.33}, {"text": "We'll get to that I think.", "start": 1480.17, "duration": 2.41}, {"text": "But yeah, in the Merkle root--", "start": 1482.58, "duration": 1.25}, {"text": "so the height of the\nMerkle root's like 12-ish.", "start": 1483.83, "duration": 3.36}, {"text": "And it goes out to maybe\n4,000 transactions,", "start": 1487.19, "duration": 4.26}, {"text": "sometimes more,\nsometimes very few.", "start": 1491.45, "duration": 2.37}, {"text": "You'll find empty\nblocks that just", "start": 1493.82, "duration": 1.74}, {"text": "have one transaction in them.", "start": 1495.56, "duration": 3.43}, {"text": "And that transaction ID just\nbecomes the Merkle root,", "start": 1498.99, "duration": 3.2}, {"text": "because a height--", "start": 1502.19, "duration": 1.14}, {"text": "it's like a height-zero\nMerkle tree,", "start": 1503.33, "duration": 3.06}, {"text": "but yeah, something like that.", "start": 1506.39, "duration": 1.87}, {"text": "And then last-- pretty easy--", "start": 1508.26, "duration": 3.09}, {"text": "there's a nonce, 4 byte.", "start": 1511.35, "duration": 1.7}, {"text": "Anything you want goes in there.", "start": 1513.05, "duration": 1.53}, {"text": "You can think of it\nas a you went 32,", "start": 1514.58, "duration": 3.93}, {"text": "there's no meaning to it.", "start": 1518.51, "duration": 2.34}, {"text": "So does anyone see a problem\nwith this nonce field?", "start": 1520.85, "duration": 5.6}, {"text": "Yeah.", "start": 1526.45, "duration": 0.5}, {"text": "AUDIENCE: It's too small.", "start": 1526.95, "duration": 1.042}, {"text": "TADGE DRYJA: Yeah,\nit's too small.", "start": 1527.992, "duration": 1.698}, {"text": "4 bytes-- even in\nthe homework, people", "start": 1529.69, "duration": 3.83}, {"text": "are using 12 something\nbytes for a nonce.", "start": 1533.52, "duration": 4.44}, {"text": "With only 4 bytes of\nnonce, you can go through 2", "start": 1537.96, "duration": 3.03}, {"text": "to the 32 possibilities,\nwhich is not", "start": 1540.99, "duration": 4.5}, {"text": "enough to mine in\nalmost all cases,", "start": 1545.49, "duration": 2.07}, {"text": "because you're going to need\nto go through 2 to the 70", "start": 1547.56, "duration": 2.73}, {"text": "possibilities to find a block.", "start": 1550.29, "duration": 3.21}, {"text": "So what are some ideas for how\ndo you deal with this problem?", "start": 1553.5, "duration": 3.85}, {"text": "Like, it would be nice\nif it was just 8 bytes.", "start": 1557.35, "duration": 2.57}, {"text": "That'd make things simpler.", "start": 1559.92, "duration": 1.17}, {"text": "But the system is what it is.", "start": 1561.09, "duration": 1.71}, {"text": "It's very hard to change.", "start": 1562.8, "duration": 1.41}, {"text": "How, as a miner, would you\nwork around this issue?", "start": 1564.21, "duration": 4.782}, {"text": "AUDIENCE: Adjust the\nversion and time.", "start": 1568.992, "duration": 1.958}, {"text": "TADGE DRYJA: Yeah, so\nyou can adjust version.", "start": 1570.95, "duration": 1.875}, {"text": "So that may be why sometimes\nweird version numbers come up.", "start": 1572.825, "duration": 3.175}, {"text": "Time is a good one\ntoo, since time--", "start": 1576.0, "duration": 1.875}, {"text": "so yeah, adjust time\nand also Merkle root.", "start": 1581.61, "duration": 2.74}, {"text": "So time, if you're off by a\nfew seconds, nobody cares.", "start": 1584.35, "duration": 7.36}, {"text": "So use the low bits of this time\nfield as part of your nonce.", "start": 1591.71, "duration": 4.89}, {"text": "It's kind of in the wrong\nplace, but you can make chips", "start": 1596.6, "duration": 2.4}, {"text": "to sort of fiddle--", "start": 1599.0, "duration": 1.29}, {"text": "twiddle these bits as well.", "start": 1600.29, "duration": 3.06}, {"text": "What's also nice is that\nevery second you can sort of--", "start": 1603.35, "duration": 3.99}, {"text": "you can do it the wrong way.", "start": 1607.34, "duration": 1.26}, {"text": "And you can say,\noh, I'm just going", "start": 1608.6, "duration": 1.458}, {"text": "to take the least significant\n4 bits of my time field", "start": 1610.058, "duration": 4.392}, {"text": "and just use them as\nnonce space randomly.", "start": 1614.45, "duration": 2.29}, {"text": "What's nice is that the\nactual time progresses by one", "start": 1616.74, "duration": 3.98}, {"text": "bit every second.", "start": 1620.72, "duration": 2.25}, {"text": "So as long as your\nchip has enough space--", "start": 1622.97, "duration": 5.033}, {"text": "so you're like, OK,\nI've got 2 bit to 32", "start": 1628.003, "duration": 1.667}, {"text": "here, another 4 bits here,\nso I'm at 2 to the 36.", "start": 1629.67, "duration": 4.63}, {"text": "If you're chip only goes\nthrough 2 to the 36 hashes", "start": 1634.3, "duration": 3.36}, {"text": "every second, you're good\nbecause the actual time", "start": 1637.66, "duration": 3.0}, {"text": "progresses.", "start": 1640.66, "duration": 2.31}, {"text": "The other way you can do it\nis modify the Merkle root.", "start": 1642.97, "duration": 3.69}, {"text": "And you can do that-- so can\nyou think of ways to modify that", "start": 1646.66, "duration": 5.55}, {"text": "without breaking things?", "start": 1652.21, "duration": 2.472}, {"text": "AUDIENCE: Add or\ndrop the transaction.", "start": 1654.682, "duration": 1.768}, {"text": "TADGE DRYJA: Yeah,\nyou could add or you", "start": 1656.45, "duration": 1.14}, {"text": "could drop a transaction.", "start": 1657.59, "duration": 0.99}, {"text": "So you say, OK, I have\nall these transactions.", "start": 1658.58, "duration": 1.917}, {"text": "I'm going to drop one.", "start": 1660.497, "duration": 1.115}, {"text": "That's got some\ndisadvantages, because it", "start": 1661.612, "duration": 1.708}, {"text": "may pay fees to the miner.", "start": 1663.32, "duration": 1.827}, {"text": "AUDIENCE: Changing the order?", "start": 1665.147, "duration": 1.208}, {"text": "TADGE DRYJA: Yep,\nyou can swap them.", "start": 1666.355, "duration": 1.5}, {"text": "You can just say, OK, well,\nthese two are independent.", "start": 1670.55, "duration": 2.29}, {"text": "I'm going to swap them.", "start": 1672.84, "duration": 1.19}, {"text": "This will change,\nwhich will change that.", "start": 1674.03, "duration": 2.75}, {"text": "So you can swap\ntransactions around.", "start": 1676.78, "duration": 3.19}, {"text": "You can also edit what's called\nthe Coinbase, which I think", "start": 1679.97, "duration": 3.15}, {"text": "is in like one more slide.", "start": 1683.12, "duration": 2.32}, {"text": "So yeah, so there's\na bunch of ways", "start": 1685.44, "duration": 1.535}, {"text": "that you can change things.", "start": 1686.975, "duration": 1.125}, {"text": "And so this is really\nwhere you're going", "start": 1688.1, "duration": 1.7}, {"text": "to have all the variation.", "start": 1689.8, "duration": 1.9}, {"text": "You have 32-bit bytes here.", "start": 1691.7, "duration": 3.44}, {"text": "And just even if it\nwas just swapping,", "start": 1695.14, "duration": 1.663}, {"text": "and if you have 1,000\ntransactions, swap", "start": 1696.803, "duration": 1.667}, {"text": "in whatever order you want--", "start": 1698.47, "duration": 1.39}, {"text": "there's enough sort\nof entropy there", "start": 1699.86, "duration": 1.71}, {"text": "that you'll be able to find it.", "start": 1701.57, "duration": 1.768}, {"text": "So what's interesting is\nthat the nonce is there.", "start": 1703.338, "duration": 2.042}, {"text": "And it's important,\nbecause that's", "start": 1705.38, "duration": 1.417}, {"text": "where sort of the\nhigh-speed mining occurs.", "start": 1706.797, "duration": 4.493}, {"text": "But most mining chips will also\nhave circuitry to modify this,", "start": 1711.29, "duration": 4.32}, {"text": "because they're operating\nso quickly that they", "start": 1715.61, "duration": 2.67}, {"text": "will exhaust the\n4-byte nonce space", "start": 1718.28, "duration": 3.09}, {"text": "in a fraction of a second.", "start": 1721.37, "duration": 2.02}, {"text": "And so they'll have to\nswap two transactions,", "start": 1723.39, "duration": 3.4}, {"text": "recalculate a Merkle root, which\ninvolves a few dozen hashes,", "start": 1726.79, "duration": 5.013}, {"text": "and then go back here.", "start": 1731.803, "duration": 0.917}, {"text": "So it actually doesn't hurt\ntheir efficiency too much,", "start": 1732.72, "duration": 2.25}, {"text": "because, OK, I just did 4\nbillion hash operations.", "start": 1734.97, "duration": 4.01}, {"text": "And then I need to\ndo a few dozen more", "start": 1738.98, "duration": 2.13}, {"text": "to get to the next 4 billion.", "start": 1741.11, "duration": 2.43}, {"text": "So it doesn't hurt\nthings too much.", "start": 1743.54, "duration": 2.17}, {"text": "Also, in Bitcoin-- a\nsort of weird quirk--", "start": 1745.71, "duration": 3.64}, {"text": "it's called SHA-256d.", "start": 1749.35, "duration": 2.47}, {"text": "They do SHA-256.", "start": 1751.82, "duration": 1.56}, {"text": "And then from the output,\nthey do a SHA-256 again,", "start": 1753.38, "duration": 3.8}, {"text": "not sure why.", "start": 1757.18, "duration": 0.63}, {"text": "I think in one person's\nfirst problem set,", "start": 1757.81, "duration": 4.957}, {"text": "they inadvertently were\ndoing the same thing", "start": 1762.767, "duration": 1.833}, {"text": "and was like, yeah, that works.", "start": 1764.6, "duration": 3.11}, {"text": "Satoshi, whoever he\nor she was, or they,", "start": 1767.71, "duration": 2.862}, {"text": "just put that in there.", "start": 1770.572, "duration": 0.958}, {"text": "Any questions about this header\nin this format and anything", "start": 1771.53, "duration": 3.02}, {"text": "about it?", "start": 1774.55, "duration": 1.23}, {"text": "It's pretty compact.", "start": 1775.78, "duration": 0.99}, {"text": "It's 80 bytes.", "start": 1776.77, "duration": 0.81}, {"text": "AUDIENCE: [INAUDIBLE]\nincluding the Merkle root.", "start": 1781.244, "duration": 2.556}, {"text": "So if you end up\nmining something,", "start": 1783.8, "duration": 2.038}, {"text": "you don't have to\nput anything there.", "start": 1785.838, "duration": 1.542}, {"text": "So the only incentive\nis the transaction fees?", "start": 1787.38, "duration": 3.117}, {"text": "TADGE DRYJA: In the\nblock reward, which I'll", "start": 1790.497, "duration": 1.833}, {"text": "get to in a second, but yeah.", "start": 1792.33, "duration": 1.208}, {"text": "That's a good question.", "start": 1797.22, "duration": 1.17}, {"text": "Can you put nothing\nin as a Merkle?", "start": 1798.39, "duration": 2.32}, {"text": "I don't think so.", "start": 1800.71, "duration": 0.72}, {"text": "I'm pretty sure you\nneed one transaction.", "start": 1801.43, "duration": 1.34}, {"text": "AUDIENCE: Oh, that's right.", "start": 1802.77, "duration": 0.61}, {"text": "I mean, you need\nthe base for the--", "start": 1803.38, "duration": 1.84}, {"text": "because even if just did it, you\nneed a [INAUDIBLE] transaction.", "start": 1805.22, "duration": 2.9}, {"text": "TADGE DRYJA: You can do that.", "start": 1808.12, "duration": 0.74}, {"text": "And there's many blocks.", "start": 1808.86, "duration": 1.0}, {"text": "So in the first\nyear or so in 2009,", "start": 1809.86, "duration": 2.87}, {"text": "almost all the blocks are empty\nand only have one transaction,", "start": 1812.73, "duration": 3.15}, {"text": "because no one was using it.", "start": 1815.88, "duration": 1.2}, {"text": "But people were mining.", "start": 1817.08, "duration": 1.41}, {"text": "So it was very similar\nto the problem set, where", "start": 1818.49, "duration": 2.47}, {"text": "everyone's just mining,\nand they're not actually", "start": 1820.96, "duration": 2.0}, {"text": "using the system.", "start": 1822.96, "duration": 0.708}, {"text": "AUDIENCE: Bu then right now--", "start": 1823.668, "duration": 1.902}, {"text": "TADGE DRYJA: Right\nnow there's tons.", "start": 1825.57, "duration": 0.77}, {"text": "AUDIENCE: People aren't doing\nthat just because there's", "start": 1826.34, "duration": 1.36}, {"text": "transaction fees.", "start": 1827.7, "duration": 0.78}, {"text": "TADGE DRYJA: Right now--", "start": 1828.48, "duration": 0.66}, {"text": "AUDIENCE: It's their\nonly incentive?", "start": 1829.14, "duration": 0.81}, {"text": "People just decided--", "start": 1829.95, "duration": 1.14}, {"text": "TADGE DRYJA: No, you\nstill get more bitcoins.", "start": 1831.09, "duration": 2.01}, {"text": "So you still get a reward.", "start": 1833.1, "duration": 1.23}, {"text": "The reason you'll see empty\nblocks now is a little tricky.", "start": 1834.33, "duration": 5.71}, {"text": "We're not sure,\nbecause who knows?", "start": 1840.04, "duration": 2.4}, {"text": "But it's probably because of\nblind mining, where you receive", "start": 1842.44, "duration": 4.97}, {"text": "a block, and you\nhaven't actually", "start": 1847.41, "duration": 3.135}, {"text": "looked through the\ncontents of the block yet.", "start": 1850.545, "duration": 1.875}, {"text": "But you want to\nmine the next block.", "start": 1852.42, "duration": 2.61}, {"text": "But you're not sure what\ntransactions to put in.", "start": 1855.03, "duration": 2.79}, {"text": "You see this 80-byte\nheader, and you're like, oh,", "start": 1857.82, "duration": 2.16}, {"text": "someone find a block.", "start": 1859.98, "duration": 1.46}, {"text": "But you only have\nthe header, and you", "start": 1861.44, "duration": 1.57}, {"text": "want to build on top of it.", "start": 1863.01, "duration": 1.125}, {"text": "You have a bunch of transactions\nyou'd like to put in,", "start": 1866.64, "duration": 2.25}, {"text": "but they may have already been\nput into the previous one.", "start": 1868.89, "duration": 3.283}, {"text": "And so you're like,\nwell, I have no idea", "start": 1872.173, "duration": 1.667}, {"text": "what's in the previous one.", "start": 1873.84, "duration": 1.125}, {"text": "I'm just going to mine a\nblock with nothing in it,", "start": 1874.965, "duration": 2.295}, {"text": "that way I'm sure that\nI'm not going to conflict", "start": 1877.26, "duration": 2.515}, {"text": "with my previous one.", "start": 1879.775, "duration": 0.875}, {"text": "You'll often see a block with\nonly one transaction very soon", "start": 1883.59, "duration": 3.15}, {"text": "after its predecessor block.", "start": 1886.74, "duration": 1.77}, {"text": "AUDIENCE: So like every once\nin a while, it would check.", "start": 1888.51, "duration": 3.543}, {"text": "So you're saying if it happened\nand went to a block really", "start": 1892.053, "duration": 2.417}, {"text": "quickly, there's just more\nlikely to be more transactions.", "start": 1894.47, "duration": 2.727}, {"text": "TADGE DRYJA: Right, right,\nbecause a miner might--", "start": 1897.197, "duration": 2.083}, {"text": "it's actually an optimal\nstrategy for a miner", "start": 1899.28, "duration": 2.29}, {"text": "to say, look, first thing\nI'm going do, download", "start": 1901.57, "duration": 2.04}, {"text": "the 80-byte header.", "start": 1903.61, "duration": 2.97}, {"text": "Figure out if it's got\na valid proof of work.", "start": 1906.58, "duration": 2.07}, {"text": "If it does, I'm\ngoing to just assume", "start": 1908.65, "duration": 2.34}, {"text": "it's valid for the\nnext few seconds,", "start": 1910.99, "duration": 2.43}, {"text": "because it probably is.", "start": 1913.42, "duration": 2.58}, {"text": "And then I'm going to try to\nmine a block on top of that.", "start": 1916.0, "duration": 3.43}, {"text": "Reference this previous block.", "start": 1919.43, "duration": 1.25}, {"text": "Mine a block on top.", "start": 1920.68, "duration": 1.05}, {"text": "The thing is, I have no idea\nwhat's actually in the block.", "start": 1921.73, "duration": 2.85}, {"text": "I have no idea what contributes\nto this Merkle root,", "start": 1924.58, "duration": 2.46}, {"text": "because I haven't even\ndownloaded that data yet.", "start": 1927.04, "duration": 2.82}, {"text": "But I can build on top of\nit, just from the header.", "start": 1929.86, "duration": 3.03}, {"text": "But I can't include\ntransactions,", "start": 1932.89, "duration": 1.47}, {"text": "because I have no idea what\ntransactions are in here,", "start": 1934.36, "duration": 2.25}, {"text": "so they might conflict.", "start": 1936.61, "duration": 1.5}, {"text": "So I'll just mine sort of\nblind for a second or two.", "start": 1938.11, "duration": 3.81}, {"text": "And then download all the\ntransactions, validate it.", "start": 1941.92, "duration": 5.04}, {"text": "And now I can include\nmy transactions", "start": 1946.96, "duration": 1.89}, {"text": "that haven't been included.", "start": 1948.85, "duration": 2.12}, {"text": "And so that happens.", "start": 1950.97, "duration": 2.26}, {"text": "It can be an OK strategy.", "start": 1953.23, "duration": 2.1}, {"text": "Sometimes it can lead to\nyou mining an invalid block.", "start": 1955.33, "duration": 3.54}, {"text": "If someone produces an invalid\nblock, and you just see, oh,", "start": 1958.87, "duration": 3.31}, {"text": "well, it's got proof of work,\nyou grab that header, start", "start": 1962.18, "duration": 3.2}, {"text": "mining on top of it.", "start": 1965.38, "duration": 2.58}, {"text": "No matter what you\nmine, it's going", "start": 1967.96, "duration": 1.52}, {"text": "to be invalid, because it's\npointing to an invalid block.", "start": 1969.48, "duration": 2.98}, {"text": "That happened 2015 or 2016.", "start": 1972.46, "duration": 3.67}, {"text": "The summer of 2015 it happened.", "start": 1976.13, "duration": 2.057}, {"text": "And it was like quite extensive.", "start": 1978.187, "duration": 1.333}, {"text": "It was like seven\nor eight blocks", "start": 1979.52, "duration": 1.41}, {"text": "in a row that were all invalid,\nbecause none of the miners", "start": 1980.93, "duration": 2.94}, {"text": "were actually\nverifying anything.", "start": 1983.87, "duration": 2.31}, {"text": "They were just downloading\nthe headers from each other", "start": 1986.18, "duration": 2.49}, {"text": "and being like, yeah, I\nmean, you did the work.", "start": 1988.67, "duration": 4.05}, {"text": "So they were just\nassuming everyone else", "start": 1992.72, "duration": 2.19}, {"text": "was verifying the Merkle roots.", "start": 1994.91, "duration": 2.45}, {"text": "And yeah, so then it ended--", "start": 1997.36, "duration": 2.81}, {"text": "so they lost 25 times 8,\nhowever many bitcoins.", "start": 2000.17, "duration": 4.94}, {"text": "They lost hundreds of bitcoins,\nwhich at the time was still", "start": 2005.11, "duration": 3.78}, {"text": "worth quite a bit-- and now\nit's worth millions of dollars--", "start": 2008.89, "duration": 3.93}, {"text": "just because they weren't\nactually checking things.", "start": 2012.82, "duration": 2.76}, {"text": "AUDIENCE: If I mine a\nblock and it's empty,", "start": 2015.58, "duration": 2.26}, {"text": "do I decrease my chances\nof being mined afterwards?", "start": 2017.84, "duration": 3.23}, {"text": "TADGE DRYJA: No, actually,\nI would say you'd, sort", "start": 2021.07, "duration": 3.09}, {"text": "of game theoretically, you would\nincrease it, because you're not", "start": 2024.16, "duration": 5.53}, {"text": "depleting the mempool.", "start": 2029.69, "duration": 1.99}, {"text": "I need to talk about\nthe actual mining", "start": 2031.68, "duration": 1.73}, {"text": "coinbase and mempool and stuff.", "start": 2033.41, "duration": 1.45}, {"text": "But yeah, it's a\ntricky question.", "start": 2034.86, "duration": 1.67}, {"text": "And I'll try to get back to it.", "start": 2036.53, "duration": 1.41}, {"text": "If I don't, bug me again.", "start": 2037.94, "duration": 2.11}, {"text": "TX-- so in this\nMerkle root, you've", "start": 2040.05, "duration": 1.79}, {"text": "got all these transactions.", "start": 2041.84, "duration": 1.32}, {"text": "They have a specified order.", "start": 2043.16, "duration": 2.07}, {"text": "Transaction 0 is the\ncoinbase transaction.", "start": 2045.23, "duration": 2.82}, {"text": "And it's special.", "start": 2048.05, "duration": 1.169}, {"text": "It generates new coins,\nand it takes fees", "start": 2049.219, "duration": 2.746}, {"text": "from all the other\ntransactions in the block.", "start": 2051.965, "duration": 1.875}, {"text": "I think Neha mentioned\nthis yesterday,", "start": 2053.84, "duration": 2.74}, {"text": "where if you have a difference\nbetween the input amounts", "start": 2056.58, "duration": 3.559}, {"text": "and output amounts,\nthat's implicitly a fee.", "start": 2060.139, "duration": 4.091}, {"text": "So if your input--", "start": 2064.23, "duration": 1.86}, {"text": "so here, Neha's thing,\nyou're spending 20 coins.", "start": 2066.09, "duration": 3.29}, {"text": "You've got 5, 10, 4.", "start": 2069.38, "duration": 2.009}, {"text": "Well, there's only 19\ncoins in the output,", "start": 2071.389, "duration": 2.671}, {"text": "so there's an implicit\nfee of 1 coin.", "start": 2074.06, "duration": 4.409}, {"text": "That one coin can go\nto transactions 0.", "start": 2078.469, "duration": 4.351}, {"text": "So transaction 0 has\nessentially no input.", "start": 2082.82, "duration": 4.33}, {"text": "Transaction 0's input\nfield is just empty,", "start": 2087.15, "duration": 3.21}, {"text": "anything you want to put, any\nbytes you want to put in there.", "start": 2090.36, "duration": 2.67}, {"text": "Its output field\ngenerates new coins.", "start": 2093.03, "duration": 2.459}, {"text": "So that's currently\n12 and 1/2 coins.", "start": 2095.489, "duration": 2.101}, {"text": "So currently, if you mine\na block with only TX0,", "start": 2097.59, "duration": 3.54}, {"text": "you get 12 and 1/2 coins.", "start": 2101.13, "duration": 1.41}, {"text": "If you mine a block with\nthousands of transactions,", "start": 2102.54, "duration": 2.28}, {"text": "you get the 12 and 1/2\ncoins plus the difference", "start": 2104.82, "duration": 3.272}, {"text": "between the input and outputs\nof all the other transactions", "start": 2108.092, "duration": 2.458}, {"text": "in the block, which can\nbe even more than 12", "start": 2110.55, "duration": 2.94}, {"text": "and-- which can recently,\nlike in January or December,", "start": 2113.49, "duration": 4.17}, {"text": "there were quite a few blocks\nwhere they're getting 25, 26,", "start": 2117.66, "duration": 3.58}, {"text": "27 coins, because the total\nfees for the entire block", "start": 2121.24, "duration": 3.59}, {"text": "were more than 12 and 1/2 coins,\nwhich is hundreds of thousands", "start": 2124.83, "duration": 4.68}, {"text": "of dollars now.", "start": 2129.51, "duration": 0.72}, {"text": "So it's kind of cool.", "start": 2130.23, "duration": 2.31}, {"text": "The fees have since decreased.", "start": 2132.54, "duration": 1.59}, {"text": "Fees are highly variable.", "start": 2134.13, "duration": 1.65}, {"text": "And we'll talk about fees\nin a few more lectures.", "start": 2135.78, "duration": 3.15}, {"text": "And it's kind of a mess,\nbut it's an evolving area", "start": 2138.93, "duration": 3.87}, {"text": "in this whole network thing.", "start": 2142.8, "duration": 3.6}, {"text": "So you've got your\ncoinbase transaction.", "start": 2146.4, "duration": 2.01}, {"text": "That's important.", "start": 2148.41, "duration": 0.82}, {"text": "That's why people are doing this\nstuff, because they want money.", "start": 2149.23, "duration": 3.32}, {"text": "All the other transactions\ncan be shuffled around.", "start": 2152.55, "duration": 2.76}, {"text": "However, they can\nonly spend outputs", "start": 2155.31, "duration": 3.12}, {"text": "from previous transactions.", "start": 2158.43, "duration": 1.92}, {"text": "And previous means\nthey have an index", "start": 2160.35, "duration": 2.19}, {"text": "within the block that's lower.", "start": 2162.54, "duration": 2.07}, {"text": "So for example, you\nhave transaction", "start": 2164.61, "duration": 2.43}, {"text": "B spends an output of\ntransaction A. Transaction A", "start": 2167.04, "duration": 4.68}, {"text": "must come first in\nthe block ordering.", "start": 2171.72, "duration": 3.12}, {"text": "This makes it so that you can\ngo through in a linear fashion", "start": 2174.84, "duration": 2.7}, {"text": "and validate every\ntransaction in order.", "start": 2177.54, "duration": 2.64}, {"text": "Otherwise, you'd go through,\nsee, OK, transaction 0, I", "start": 2180.18, "duration": 2.973}, {"text": "don't have to validate that.", "start": 2183.153, "duration": 1.167}, {"text": "That's coinbase--\ntransaction 1, transaction 2.", "start": 2184.32, "duration": 2.908}, {"text": "And then you see transaction 3.", "start": 2187.228, "duration": 1.292}, {"text": "It appears to be\nspending something", "start": 2188.52, "duration": 1.92}, {"text": "you've never heard of.", "start": 2190.44, "duration": 2.2}, {"text": "So that would at first--", "start": 2192.64, "duration": 1.5}, {"text": "that would appear to be invalid.", "start": 2194.14, "duration": 1.638}, {"text": "And then maybe you go through\nanother few transactions,", "start": 2195.778, "duration": 2.292}, {"text": "say, oh, this creates the\noutput that this thing I just", "start": 2198.07, "duration": 4.44}, {"text": "saw before spends.", "start": 2202.51, "duration": 1.76}, {"text": "It's sort of out of order.", "start": 2204.27, "duration": 1.36}, {"text": "It makes things very\ncomplicated to validate.", "start": 2205.63, "duration": 2.19}, {"text": "And so this rule ensures that\nif you go through and just check", "start": 2207.82, "duration": 3.9}, {"text": "every transaction in order,\nit'll all make sense.", "start": 2211.72, "duration": 3.64}, {"text": "Yes.", "start": 2215.36, "duration": 0.5}, {"text": "AUDIENCE: Is there any benefit\nmoving earlier or later?", "start": 2215.86, "duration": 2.687}, {"text": "TADGE DRYJA: In the block?", "start": 2218.547, "duration": 1.083}, {"text": "AUDIENCE: Yeah.", "start": 2219.63, "duration": 1.53}, {"text": "TADGE DRYJA: No,\nI don't think so.", "start": 2221.16, "duration": 1.48}, {"text": "I mean, I can't think of one.", "start": 2222.64, "duration": 3.79}, {"text": "Yeah, it's just sort of random.", "start": 2226.43, "duration": 2.36}, {"text": "A lot of times they'll\norganize it by fee rate.", "start": 2228.79, "duration": 2.22}, {"text": "Or by default, they'll\njust organize it", "start": 2231.01, "duration": 2.34}, {"text": "by when they saw them first.", "start": 2233.35, "duration": 1.86}, {"text": "So it's pretty arbitrary.", "start": 2235.21, "duration": 1.535}, {"text": "AUDIENCE: Does\nthat mean that you", "start": 2236.745, "duration": 1.375}, {"text": "have to wait until\nthe transaction", "start": 2238.12, "duration": 1.705}, {"text": "that the major output\nhas been mined,", "start": 2239.825, "duration": 2.03}, {"text": "in order spend that again?", "start": 2241.855, "duration": 1.355}, {"text": "TADGE DRYJA: No,\nalthough if they did,", "start": 2243.21, "duration": 2.98}, {"text": "that would make the software\na lot simpler and easier", "start": 2246.19, "duration": 2.61}, {"text": "to deal with.", "start": 2248.8, "duration": 1.12}, {"text": "But that is not how it works.", "start": 2249.92, "duration": 1.93}, {"text": "So for example-- I'll draw\nit-- you can have a block where", "start": 2256.92, "duration": 6.48}, {"text": "there's-- let's do it this way.", "start": 2263.4, "duration": 1.95}, {"text": "So you have TX0.", "start": 2265.35, "duration": 1.2}, {"text": "There's coinbase transaction,\ntransaction 1, transaction 2,", "start": 2266.55, "duration": 4.68}, {"text": "transaction 3.", "start": 2271.23, "duration": 1.83}, {"text": "And transaction 3 may be\nspending something that", "start": 2273.06, "duration": 3.51}, {"text": "was generated in transaction 1.", "start": 2276.57, "duration": 2.7}, {"text": "That can happen.", "start": 2279.27, "duration": 1.32}, {"text": "So if you make transaction 1\nbroadcast it. it's unconfirmed.", "start": 2280.59, "duration": 4.71}, {"text": "You then make transaction\n3 broadcast it,", "start": 2285.3, "duration": 2.01}, {"text": "spends transaction 1.", "start": 2287.31, "duration": 1.84}, {"text": "The miner can put\nthose in the blocks.", "start": 2289.15, "duration": 1.7}, {"text": "They must put it in order.", "start": 2290.85, "duration": 1.53}, {"text": "So if this happens, you\ncan't switch them in order.", "start": 2292.38, "duration": 3.93}, {"text": "But that's considered OK.", "start": 2296.31, "duration": 1.71}, {"text": "It makes parallel-- it makes\nmulti-core validation more", "start": 2298.02, "duration": 3.66}, {"text": "annoying.", "start": 2301.68, "duration": 1.575}, {"text": "If you said, no, you can only\nuse outputs that have already", "start": 2303.255, "duration": 3.135}, {"text": "been confirmed, then\nthe block validation", "start": 2306.39, "duration": 3.45}, {"text": "becomes embarrassingly\nparallel, because you can just", "start": 2309.84, "duration": 2.4}, {"text": "validate every\ntransaction independently.", "start": 2312.24, "duration": 2.715}, {"text": "That would be kind of nice.", "start": 2314.955, "duration": 1.125}, {"text": "There's other\ninteresting reasons", "start": 2318.756, "duration": 1.644}, {"text": "why this is also useful.", "start": 2320.4, "duration": 2.195}, {"text": "I mean, if I were\ndesigning it, I", "start": 2322.595, "duration": 1.375}, {"text": "would say you have to\nconfirm, because it just", "start": 2323.97, "duration": 1.71}, {"text": "makes things simpler.", "start": 2325.68, "duration": 0.875}, {"text": "But I was not Satoshi.", "start": 2326.555, "duration": 2.175}, {"text": "So yeah, the order\nis fairly arbitrary.", "start": 2328.73, "duration": 1.83}, {"text": "Any other questions about block\nordering, Merkle root stuff?", "start": 2330.56, "duration": 2.5}, {"text": "And then we're going to\nhave a quick intermission", "start": 2333.06, "duration": 2.042}, {"text": "right at the halfway point.", "start": 2335.102, "duration": 1.132}, {"text": "Sounds good, so\n256-second break.", "start": 2338.98, "duration": 5.42}, {"text": "So now I'll talk about the\nsynchronization process.", "start": 2344.4, "duration": 2.67}, {"text": "How does this actually\nwork in the software", "start": 2347.07, "duration": 3.15}, {"text": "when you download Bitcoin?", "start": 2350.22, "duration": 1.92}, {"text": "So first, you download Bitcoin.", "start": 2352.14, "duration": 2.16}, {"text": "You go to bitcoin.org.", "start": 2354.3, "duration": 2.16}, {"text": "of Your friend hands you\na USB drive and says,", "start": 2356.46, "duration": 2.62}, {"text": "hey, I got some good stuff, man,\nthis new thing called Bitcoin.", "start": 2359.08, "duration": 3.95}, {"text": "And so you've got the\nBitcoin EXE file or DMG file,", "start": 2363.03, "duration": 4.08}, {"text": "or the binary, or the code.", "start": 2367.11, "duration": 1.592}, {"text": "And you want to know what's\nbeen going on for the last nine", "start": 2368.702, "duration": 2.458}, {"text": "years?", "start": 2371.16, "duration": 1.35}, {"text": "So first, you\ndownload the binary,", "start": 2372.51, "duration": 1.5}, {"text": "or you compile the code.", "start": 2374.01, "duration": 1.38}, {"text": "And you verify all the GPG\nsignatures of this code,", "start": 2375.39, "duration": 4.367}, {"text": "if you want to do this securely.", "start": 2379.757, "duration": 1.333}, {"text": "So I'm sure everyone has their\nPGP keys on the MIT PGP server", "start": 2381.09, "duration": 6.03}, {"text": "and goes to key signing parties\nheld on the weekends, right?", "start": 2387.12, "duration": 4.65}, {"text": "Yeah, no?", "start": 2391.77, "duration": 2.277}, {"text": "AUDIENCE: Keybase is cool.", "start": 2394.047, "duration": 1.083}, {"text": "Base", "start": 2395.13, "duration": 0.39}, {"text": "TADGE DRYJA: Keybase\nis also useful, yeah.", "start": 2395.52, "duration": 1.75}, {"text": "So I have my PGP key\nhash on my business card.", "start": 2397.27, "duration": 3.68}, {"text": "I don't think anyone's\nactually ever used it.", "start": 2400.95, "duration": 3.51}, {"text": "But the Bitcoin nerds\nactually do do this.", "start": 2404.46, "duration": 2.46}, {"text": "And they're very sort\nof annoying about it,", "start": 2406.92, "duration": 5.76}, {"text": "because a really\ngood attack vector", "start": 2412.68, "duration": 3.06}, {"text": "is to get someone to download\ncompromised Bitcoin code.", "start": 2415.74, "duration": 3.69}, {"text": "It's like the best\nattack vector ever", "start": 2419.43, "duration": 1.86}, {"text": "if you're trying to do\nsomething sneaky, mainly just", "start": 2421.29, "duration": 3.84}, {"text": "to steal all the money.", "start": 2425.13, "duration": 1.11}, {"text": "If you get them to download\na Bitcoin binary that you", "start": 2426.24, "duration": 2.55}, {"text": "control, that you put\nsome backdoor code in,", "start": 2428.79, "duration": 4.05}, {"text": "the code can be like two lines.", "start": 2432.84, "duration": 1.33}, {"text": "It's like, open a TCP\nconnection to my computer.", "start": 2434.17, "duration": 4.07}, {"text": "Send me all the private keys.", "start": 2438.24, "duration": 1.56}, {"text": "We're good.", "start": 2439.8, "duration": 0.99}, {"text": "Or if you want to be\nmore sophisticated,", "start": 2440.79, "duration": 3.0}, {"text": "every time they click Send\nand type in their password,", "start": 2443.79, "duration": 2.82}, {"text": "I just change all the addresses\nand all the outputs to me,", "start": 2446.61, "duration": 3.45}, {"text": "and like, every time\nthey try to send money.", "start": 2450.06, "duration": 1.85}, {"text": "To UI sort of shows that they're\nsending money but actually just", "start": 2451.91, "duration": 3.17}, {"text": "send to me.", "start": 2455.08, "duration": 0.5}, {"text": "And they won't find\nout for a little while.", "start": 2455.58, "duration": 1.792}, {"text": "There's a lot of\nthings where you", "start": 2457.372, "duration": 2.228}, {"text": "want to be running the\nright Bitcoin code.", "start": 2459.6, "duration": 3.33}, {"text": "And that's a hard problem.", "start": 2462.93, "duration": 1.77}, {"text": "Because we're sort of\noperating in this Trust List,", "start": 2464.7, "duration": 2.35}, {"text": "decentralized\nnetwork, how do you", "start": 2467.05, "duration": 2.54}, {"text": "get into this in the beginning?", "start": 2469.59, "duration": 2.378}, {"text": "If it's your friend\nand saying, hey, here's", "start": 2471.968, "duration": 1.792}, {"text": "the Bitcoin I'm running.", "start": 2473.76, "duration": 1.0}, {"text": "I know this is good.", "start": 2474.76, "duration": 0.86}, {"text": "Then it works.", "start": 2475.62, "duration": 0.787}, {"text": "But just a website-- what if\nsomeone hacks the website--", "start": 2476.407, "duration": 2.333}, {"text": "things like that?", "start": 2478.74, "duration": 0.93}, {"text": "It's like a huge rabbit hole.", "start": 2479.67, "duration": 1.35}, {"text": "And you can try to worry\nabout it for years.", "start": 2481.02, "duration": 4.02}, {"text": "But anyway, you\ndownload the binary,", "start": 2485.04, "duration": 1.5}, {"text": "assume you've somehow\ngotten the binary,", "start": 2486.54, "duration": 2.04}, {"text": "and you're pretty sure\nit's the right software.", "start": 2488.58, "duration": 2.7}, {"text": "So how do you connect\nto this network?", "start": 2491.28, "duration": 1.71}, {"text": "Well, there are these\nhardcoded DNS seeds in order", "start": 2492.99, "duration": 3.24}, {"text": "to find peers in the beginning.", "start": 2496.23, "duration": 1.44}, {"text": "If you know how DNS works, it's\nhow you look up IP addresses", "start": 2497.67, "duration": 2.97}, {"text": "based on a hostname.", "start": 2500.64, "duration": 1.26}, {"text": "There are some servers that will\nreturn multiple different IP", "start": 2501.9, "duration": 3.09}, {"text": "addresses every\ntime you query them.", "start": 2504.99, "duration": 4.28}, {"text": "And those are IP addresses\nof currently running", "start": 2509.27, "duration": 5.62}, {"text": "Bitcoin nodes.", "start": 2514.89, "duration": 1.152}, {"text": "So the idea is, OK, someone's\nrunning a Bitcoin node.", "start": 2516.042, "duration": 2.208}, {"text": "They've got their DNS server.", "start": 2518.25, "duration": 1.77}, {"text": "You query that DNS server,\nand it will hand you", "start": 2520.02, "duration": 2.55}, {"text": "out some IP addresses.", "start": 2522.57, "duration": 3.15}, {"text": "This is also sort\nof centralized,", "start": 2525.72, "duration": 2.82}, {"text": "slash trusted, slash whatever,\nin that if someone compromises", "start": 2528.54, "duration": 3.96}, {"text": "these four or five\nDNS servers, you", "start": 2532.5, "duration": 2.873}, {"text": "might not be able to connect\nto the Bitcoin network.", "start": 2535.373, "duration": 2.167}, {"text": "So in practice, it's not\ncompletely mathematically", "start": 2537.54, "duration": 2.64}, {"text": "secure in Trust List.", "start": 2540.18, "duration": 1.202}, {"text": "There's all these\nreal-world issues", "start": 2541.382, "duration": 1.458}, {"text": "that's like, how do I know\nI've got the right software?", "start": 2542.84, "duration": 2.44}, {"text": "How do I know I'm connecting\nto the actual Bitcoin network?", "start": 2545.28, "duration": 2.8}, {"text": "What if my ISP is\nblocking me and sending me", "start": 2548.08, "duration": 2.15}, {"text": "to some other network,\nor things like that?", "start": 2550.23, "duration": 3.31}, {"text": "So in practice, it sort\nof works OK right now.", "start": 2553.54, "duration": 2.81}, {"text": "You connect to the DNS seeds.", "start": 2556.35, "duration": 1.56}, {"text": "And then you connect\nto a Bitcoin node,", "start": 2557.91, "duration": 2.4}, {"text": "and you ask for headers.", "start": 2560.31, "duration": 1.11}, {"text": "You say, hey, I just showed up.", "start": 2561.42, "duration": 3.72}, {"text": "I know about one header.", "start": 2565.14, "duration": 1.35}, {"text": "There's a hardcoded header in\nthe code called the genesis", "start": 2566.49, "duration": 3.21}, {"text": "block that Satoshi did.", "start": 2569.7, "duration": 2.82}, {"text": "And you say, hey, I've\ngot this genesis block.", "start": 2572.52, "duration": 2.01}, {"text": "Do you know anything that builds\nabove this genesis block, that", "start": 2574.53, "duration": 3.6}, {"text": "comes after?", "start": 2578.13, "duration": 1.35}, {"text": "And they say, yes, I\nactually know 500,000 headers", "start": 2579.48, "duration": 3.108}, {"text": "that come after it.", "start": 2582.588, "duration": 0.792}, {"text": "And they'll start\nsending it to you.", "start": 2583.38, "duration": 2.04}, {"text": "They send it to you in\na couple of thousand", "start": 2585.42, "duration": 2.08}, {"text": "of headers at a time.", "start": 2587.5, "duration": 2.21}, {"text": "And then you start to download\nall those and verify them.", "start": 2589.71, "duration": 4.56}, {"text": "The header chain,\nyou get it first.", "start": 2594.27, "duration": 2.7}, {"text": "And it's actually very quick.", "start": 2596.97, "duration": 1.53}, {"text": "You can do it in under a minute\nif you have a good internet", "start": 2598.5, "duration": 2.458}, {"text": "connection.", "start": 2600.958, "duration": 0.632}, {"text": "And you verify all the work\nbefore you do anything else.", "start": 2601.59, "duration": 2.4}, {"text": "So this is nice in that\nthe attacker, in order", "start": 2603.99, "duration": 3.21}, {"text": "to sort of make you\ndo more work here,", "start": 2607.2, "duration": 3.45}, {"text": "would have to do a\nlot of proof of work.", "start": 2610.65, "duration": 3.28}, {"text": "But for you, it's very\nquick to verify everything.", "start": 2613.93, "duration": 2.96}, {"text": "Even half a million\nheaders, 30 seconds", "start": 2616.89, "duration": 3.545}, {"text": "if you've got a good internet\nconnection, something", "start": 2620.435, "duration": 2.125}, {"text": "like that, because all you're\ndoing is one hash per header.", "start": 2622.56, "duration": 3.51}, {"text": "You just download the\nheader, check the bits,", "start": 2626.07, "duration": 2.64}, {"text": "check the time, make\nsure the times are", "start": 2628.71, "duration": 1.65}, {"text": "like progressing reasonably.", "start": 2630.36, "duration": 2.67}, {"text": "If the times keep going\nbackwards for like,", "start": 2633.03, "duration": 2.24}, {"text": "I think it's 10 blocks, then\nyou consider it invalid.", "start": 2635.27, "duration": 4.025}, {"text": "But your computer\ncan actually do this.", "start": 2639.295, "duration": 1.625}, {"text": "It's 500,000 hash functions.", "start": 2640.92, "duration": 1.74}, {"text": "And I'm sure if you've\nseen for the problem set,", "start": 2642.66, "duration": 2.46}, {"text": "you can do that in a few\nseconds in many cases.", "start": 2645.12, "duration": 3.19}, {"text": "So you can verify the work\ndone throughout the entirety", "start": 2648.31, "duration": 2.99}, {"text": "of the Bitcoin's\nexistence pretty quickly.", "start": 2651.3, "duration": 4.22}, {"text": "So then you've got\n500,000 headers.", "start": 2655.52, "duration": 2.4}, {"text": "And now you need to actually\ndownload the blocks.", "start": 2657.92, "duration": 4.19}, {"text": "Any questions about\nheader synchronization?", "start": 2662.11, "duration": 4.34}, {"text": "Seems pretty\nstraight-- oh, yeah.", "start": 2666.45, "duration": 1.692}, {"text": "AUDIENCE: Can you\ncatch any of that work,", "start": 2668.142, "duration": 1.708}, {"text": "since you're going to see some\nof these every time you sync?", "start": 2669.85, "duration": 3.95}, {"text": "TADGE DRYJA: Well, yeah,\nyou save it to disk.", "start": 2673.8, "duration": 2.02}, {"text": "So you don't have to, like,\nif you shut your computer off,", "start": 2675.82, "duration": 2.84}, {"text": "turn it on the next\ntime, you've already", "start": 2678.66, "duration": 1.77}, {"text": "got all those headers on disk.", "start": 2680.43, "duration": 1.25}, {"text": "Basically, you save them to\ndisk once you've verified them.", "start": 2681.68, "duration": 3.61}, {"text": "So you download a\ncouple thousand.", "start": 2685.29, "duration": 1.42}, {"text": "It builds linearly,\nso it's nice for you", "start": 2686.71, "duration": 1.667}, {"text": "to like download them, validate,\nand as you validate, write them", "start": 2688.377, "duration": 2.666}, {"text": "to disk.", "start": 2691.043, "duration": 0.517}, {"text": "And then when you start\nbackup, they're on disk.", "start": 2691.56, "duration": 2.25}, {"text": "You trust your own disk.", "start": 2693.81, "duration": 1.08}, {"text": "If someone goes in\nand modifies things", "start": 2694.89, "duration": 1.77}, {"text": "on disk between running of\nBitcoin, all bets are off.", "start": 2696.66, "duration": 5.28}, {"text": "So you sort of\nimplicitly trust that.", "start": 2701.94, "duration": 2.31}, {"text": "So yeah, that's pretty\nquick, works well.", "start": 2704.25, "duration": 2.742}, {"text": "Then you get to\nthe real hard part,", "start": 2706.992, "duration": 1.458}, {"text": "where you now have to\nvalidate all these signatures", "start": 2708.45, "duration": 2.19}, {"text": "and download all\nthese transactions.", "start": 2710.64, "duration": 1.927}, {"text": "Any other questions?", "start": 2712.567, "duration": 0.833}, {"text": "Good?", "start": 2713.4, "duration": 2.1}, {"text": "So then it's called IBD,\ninitial block download.", "start": 2715.5, "duration": 3.652}, {"text": "So you get the headers first.", "start": 2719.152, "duration": 1.208}, {"text": "That's quick.", "start": 2720.36, "duration": 0.93}, {"text": "Now you start asking\nyour peers, hey, here's", "start": 2721.29, "duration": 3.06}, {"text": "this header from\n2009, block height 1.", "start": 2724.35, "duration": 5.16}, {"text": "Here's the header.", "start": 2729.51, "duration": 0.75}, {"text": "Can you give me the full block?", "start": 2730.26, "duration": 3.0}, {"text": "I have the header.", "start": 2733.26, "duration": 0.99}, {"text": "What are all the things that\ngo into the Merkle root?", "start": 2734.25, "duration": 3.2}, {"text": "So you request\nblocks from peers.", "start": 2737.45, "duration": 2.5}, {"text": "You match the transaction lists,\nthe Merkle root and the header.", "start": 2739.95, "duration": 3.06}, {"text": "And you process each\ntransaction in order.", "start": 2743.01, "duration": 1.89}, {"text": "So download it.", "start": 2744.9, "duration": 1.59}, {"text": "Say, OK, here's all\nthese transactions.", "start": 2746.49, "duration": 1.72}, {"text": "Let me take the\nhash of all of them.", "start": 2748.21, "duration": 1.97}, {"text": "Compute the Merkle root.", "start": 2750.18, "duration": 1.68}, {"text": "Make sure it matches\nthe Merkle root", "start": 2751.86, "duration": 1.98}, {"text": "I see in the header\nI've already gotten.", "start": 2753.84, "duration": 2.7}, {"text": "And now process\neach transaction.", "start": 2756.54, "duration": 2.8}, {"text": "So what do we do to\nprocess transactions?", "start": 2759.34, "duration": 3.61}, {"text": "So you've got this UTXO DB.", "start": 2762.95, "duration": 3.3}, {"text": "So this is unspent\ntransaction output.", "start": 2766.25, "duration": 3.97}, {"text": "So all the cool--", "start": 2770.22, "duration": 1.55}, {"text": "I'm sure in like 2030, there\nwill be a new slang term", "start": 2771.77, "duration": 3.21}, {"text": "where we'll just\ncall money UTXOs,", "start": 2774.98, "duration": 2.14}, {"text": "like, hey I've\ngot a lot of UTXO.", "start": 2777.12, "duration": 2.068}, {"text": "I mean, I'm already doing that.", "start": 2779.188, "duration": 1.292}, {"text": "And I'm pretty ahead\nof the times, so.", "start": 2780.48, "duration": 1.94}, {"text": "So you've got this\ndatabase, which", "start": 2785.02, "duration": 1.75}, {"text": "is basically a key-value store.", "start": 2786.77, "duration": 2.64}, {"text": "And it just has\ntransaction ID index--", "start": 2789.41, "duration": 3.99}, {"text": "so this sort of how\nyou reference inputs", "start": 2793.4, "duration": 4.65}, {"text": "in Bitcoin, the transaction\nID index as the key.", "start": 2798.05, "duration": 3.33}, {"text": "And then the value\nis just the output,", "start": 2801.38, "duration": 3.42}, {"text": "the scriptsig and 8-byte amount.", "start": 2804.8, "duration": 5.2}, {"text": "So it's pretty compact.", "start": 2810.0, "duration": 1.077}, {"text": "You've got all these key values.", "start": 2811.077, "duration": 1.333}, {"text": "And it's using level DB.", "start": 2812.41, "duration": 2.16}, {"text": "But you could use some other\nkey-value store database.", "start": 2814.57, "duration": 2.72}, {"text": "And the idea is, OK, every\ntime you get a transaction,", "start": 2817.29, "duration": 3.18}, {"text": "validate all the inputs.", "start": 2820.47, "duration": 1.357}, {"text": "Make sure all the\nsignatures are good.", "start": 2821.827, "duration": 1.583}, {"text": "Make sure it's spending\nthings that actually", "start": 2823.41, "duration": 2.13}, {"text": "exist in your UTXO set.", "start": 2825.54, "duration": 1.71}, {"text": "And delete those inputs\nfrom your UTXO DB.", "start": 2830.13, "duration": 3.74}, {"text": "You say, OK, this\ntransaction is spending", "start": 2833.87, "duration": 1.93}, {"text": "these inputs, so delete.", "start": 2835.8, "duration": 1.723}, {"text": "So [INAUDIBLE], sorry.", "start": 2837.523, "duration": 0.917}, {"text": "First, make sure the\ntransaction's valid,", "start": 2838.44, "duration": 2.46}, {"text": "given your current UTXO DB.", "start": 2840.9, "duration": 1.95}, {"text": "So validate that all\nthese inputs exist.", "start": 2842.85, "duration": 2.97}, {"text": "Validate all the\nsignatures are correct.", "start": 2845.82, "duration": 2.63}, {"text": "Then you're saying, OK,\nthis transaction is good.", "start": 2848.45, "duration": 2.85}, {"text": "Now I modify my database by\ndeleting all the inputs that", "start": 2851.3, "duration": 4.23}, {"text": "are consumed and adding\nall these new outputs", "start": 2855.53, "duration": 4.92}, {"text": "for the transaction.", "start": 2860.45, "duration": 2.83}, {"text": "So this modifies the\ndatabase in place.", "start": 2863.28, "duration": 2.85}, {"text": "And you're sort of\nconstantly reading", "start": 2866.13, "duration": 2.25}, {"text": "from it to validate\ninputs, and then writing", "start": 2868.38, "duration": 5.06}, {"text": "to it to delete inputs,\nand then writing to it", "start": 2873.44, "duration": 2.52}, {"text": "again to add outputs.", "start": 2875.96, "duration": 2.49}, {"text": "So it doesn't seem too bad.", "start": 2878.45, "duration": 2.49}, {"text": "But there's a lot\nof disk access.", "start": 2880.94, "duration": 2.06}, {"text": "And the UTXO DB is a key-value\nstore with a lot of keys.", "start": 2883.0, "duration": 3.28}, {"text": "The values are very small.", "start": 2886.28, "duration": 1.41}, {"text": "So it's not like a\ncrazy database problem,", "start": 2887.69, "duration": 3.21}, {"text": "if anyone's interested\nin databases and stuff.", "start": 2890.9, "duration": 3.6}, {"text": "But it can be slow.", "start": 2894.5, "duration": 1.59}, {"text": "And we want to\nreally optimize it.", "start": 2896.09, "duration": 2.6}, {"text": "So when you think the\ninitial block download,", "start": 2898.69, "duration": 3.63}, {"text": "you're doing this\n300 million times.", "start": 2902.32, "duration": 1.53}, {"text": "So there's about 300 million\ntransactions historically.", "start": 2903.85, "duration": 4.27}, {"text": "So you're validating signature,\ndeleting input, adding", "start": 2908.12, "duration": 3.02}, {"text": "output, 300 million times.", "start": 2911.14, "duration": 1.63}, {"text": "It ends up being about 170\ngigabytes of downloads.", "start": 2912.77, "duration": 3.23}, {"text": "And then the end\nresult, when you're", "start": 2916.0, "duration": 1.5}, {"text": "done modifying this\ndatabase, is that you", "start": 2917.5, "duration": 3.66}, {"text": "have 55 million transaction\noutputs remaining.", "start": 2921.16, "duration": 3.18}, {"text": "And it's about 3.2\ngigabytes of disk use.", "start": 2924.34, "duration": 3.91}, {"text": "So yeah, but you had to download\nthat 170 gigabytes to get", "start": 2928.25, "duration": 4.85}, {"text": "to the 3.2-gigabyte\nend state, because most", "start": 2933.1, "duration": 3.75}, {"text": "of the transactions that\nhave been created and most", "start": 2936.85, "duration": 2.22}, {"text": "of the outputs have\nthen later been spent.", "start": 2939.07, "duration": 2.82}, {"text": "So there's a lot of churn.", "start": 2941.89, "duration": 3.04}, {"text": "So yeah, of the 300 million--", "start": 2944.93, "duration": 1.827}, {"text": "sorry, these are not\nthe same numbers.", "start": 2946.757, "duration": 1.583}, {"text": "I was actually looking.", "start": 2948.34, "duration": 1.37}, {"text": "How many transaction\noutputs have been created", "start": 2949.71, "duration": 2.127}, {"text": "throughout all of Bitcoin?", "start": 2951.837, "duration": 1.083}, {"text": "And I couldn't find the number.", "start": 2952.92, "duration": 1.292}, {"text": "And I didn't want to write\nsoftware to figure it out.", "start": 2954.212, "duration": 2.908}, {"text": "But you can certainly figure\nit out from the blockchain.", "start": 2957.12, "duration": 5.34}, {"text": "But yeah, this is\ntransaction outputs.", "start": 2962.46, "duration": 2.46}, {"text": "How many total\ntransactions have TXOs?", "start": 2964.92, "duration": 2.548}, {"text": "I'm not sure.", "start": 2967.468, "duration": 0.542}, {"text": "But yeah, so it's pretty big.", "start": 2968.01, "duration": 1.65}, {"text": "But it's reasonable.", "start": 2969.66, "duration": 0.99}, {"text": "Like, we can do this\non today's computers.", "start": 2970.65, "duration": 1.75}, {"text": "If you've got a decent\nlaptop, this is possible.", "start": 2972.4, "duration": 2.3}, {"text": "This total time taken\ndepends on a lot of factors.", "start": 2974.7, "duration": 4.14}, {"text": "Has anyone actually done\ninitial block download", "start": 2978.84, "duration": 2.28}, {"text": "and synced to Bitcoin\nnode, and like,", "start": 2981.12, "duration": 1.62}, {"text": "want to say about how\nquickly they did it or?", "start": 2982.74, "duration": 2.747}, {"text": "OK, James, how long did it take?", "start": 2985.487, "duration": 1.333}, {"text": "AUDIENCE: For 0.15, it's\nactually quite quick.", "start": 2986.82, "duration": 3.72}, {"text": "On a spinning disk it will\ntake about six hours maybe.", "start": 2990.54, "duration": 3.577}, {"text": "TADGE DRYJA: On a spinning disk?", "start": 2994.117, "duration": 1.333}, {"text": "AUDIENCE: Yeah, yeah, with the\nnew one, it's really quick.", "start": 2995.45, "duration": 3.31}, {"text": "TADGE DRYJA:\nBecause I run 0.15.1", "start": 2998.76, "duration": 1.83}, {"text": "on a laptop with\na spinning disk,", "start": 3000.59, "duration": 1.8}, {"text": "and it'll take like overnight\nto just sync up a week or so.", "start": 3002.39, "duration": 4.83}, {"text": "It's really slow,\nbut I don't know.", "start": 3007.22, "duration": 1.47}, {"text": "AUDIENCE: Like, my\nmum tried to start it,", "start": 3008.69, "duration": 1.18}, {"text": "and it did it from scratch.", "start": 3009.87, "duration": 1.125}, {"text": "It did it in like eight hours.", "start": 3010.995, "duration": 1.402}, {"text": "TADGE DRYJA: Wow, cool, so eight\nhours to do the whole thing--", "start": 3012.397, "duration": 2.583}, {"text": "anyone else have tried it?", "start": 3014.98, "duration": 3.15}, {"text": "Yeah.", "start": 3018.13, "duration": 0.5}, {"text": "AUDIENCE: A while back\nit took me a week.", "start": 3018.63, "duration": 2.16}, {"text": "TADGE DRYJA: Yeah, a\nwhile back it took a week.", "start": 3020.79, "duration": 1.958}, {"text": "So the software has been\nimproved quite a bit.", "start": 3022.748, "duration": 2.522}, {"text": "So if you downloaded it--", "start": 3025.27, "duration": 2.84}, {"text": "like, I first\ndownloaded it in 2011.", "start": 3028.11, "duration": 1.89}, {"text": "And it took overnight\nto download everything.", "start": 3030.0, "duration": 2.75}, {"text": "And the download\nwas vastly smaller.", "start": 3032.75, "duration": 1.6}, {"text": "It was less than a gigabyte to\ndownload the entire blockchain.", "start": 3034.35, "duration": 2.61}, {"text": "So what's interesting\nis that the time taken", "start": 3036.96, "duration": 2.97}, {"text": "for initial block download\nover the last seven years", "start": 3039.93, "duration": 4.38}, {"text": "has been somewhat constant\nin that the blockchain gets", "start": 3044.31, "duration": 3.03}, {"text": "bigger and bigger.", "start": 3047.34, "duration": 0.75}, {"text": "But there's all\nthese optimizations", "start": 3048.09, "duration": 1.8}, {"text": "to the code and the databases.", "start": 3049.89, "duration": 2.1}, {"text": "And so that sort of keeps pace.", "start": 3051.99, "duration": 3.17}, {"text": "Although actually, I'd say\nrecently it's gotten faster,", "start": 3055.16, "duration": 2.67}, {"text": "because like 0.15--", "start": 3057.83, "duration": 1.9}, {"text": "wait, 0.11 or 0.12 had\na big speed-up as well.", "start": 3059.73, "duration": 4.1}, {"text": "AUDIENCE: They completely\nrefactored the net web code.", "start": 3063.83, "duration": 2.355}, {"text": "It used to be couples\nof the synchronization.", "start": 3066.185, "duration": 1.875}, {"text": "And then they decoupled it.", "start": 3068.06, "duration": 1.125}, {"text": "TADGE DRYJA: Yeah, I think\nthat was mostly Cory, right?", "start": 3069.185, "duration": 3.105}, {"text": "So Cory Fields, who\nalso works for the DCI,", "start": 3072.29, "duration": 2.91}, {"text": "helped to refactor the\ncode, make it a lot faster.", "start": 3075.2, "duration": 3.45}, {"text": "There's definitely still\noptimizations, a lot of cool--", "start": 3078.65, "duration": 4.44}, {"text": "a lot of it's pretty low-level\ntweaks kind of stuff.", "start": 3083.09, "duration": 3.03}, {"text": "But some of them are\npretty big things.", "start": 3086.12, "duration": 1.83}, {"text": "Most of the big things,\nlow-hanging fruit,", "start": 3087.95, "duration": 1.75}, {"text": "has already been gotten.", "start": 3089.7, "duration": 1.67}, {"text": "The worry is that long-term,\nthis just keeps going up.", "start": 3091.37, "duration": 3.84}, {"text": "As the blockchain gets\nbigger and longer,", "start": 3095.21, "duration": 2.678}, {"text": "it's going to take heart.", "start": 3097.888, "duration": 1.042}, {"text": "It's going to be\nharder to validate.", "start": 3098.93, "duration": 1.95}, {"text": "It can be parallelized\nto some extent.", "start": 3100.88, "duration": 2.34}, {"text": "But there's also network I/O\nconcerns, things like that.", "start": 3103.22, "duration": 3.54}, {"text": "So it's tricky but doable.", "start": 3106.76, "duration": 3.0}, {"text": "Any questions about\ninitial block download?", "start": 3109.76, "duration": 4.6}, {"text": "Good?", "start": 3114.36, "duration": 1.77}, {"text": "So here's a question.", "start": 3116.13, "duration": 3.0}, {"text": "You've got this UTXO DB.", "start": 3119.13, "duration": 2.22}, {"text": "What about this 170 gigabytes?", "start": 3121.35, "duration": 1.34}, {"text": "Do you have to store it?", "start": 3122.69, "duration": 1.0}, {"text": "Or can you delete it?", "start": 3123.69, "duration": 2.912}, {"text": "This you can't delete, right?", "start": 3126.602, "duration": 1.208}, {"text": "So you think this is OK?", "start": 3131.16, "duration": 2.65}, {"text": "Yeah, you can maybe\ndelete some of this.", "start": 3133.81, "duration": 1.79}, {"text": "Actually, there's\na lot of research", "start": 3135.6, "duration": 1.458}, {"text": "into maybe we can delete\nthis, accumulators, cool stuff", "start": 3137.058, "duration": 5.112}, {"text": "like that.", "start": 3142.17, "duration": 0.92}, {"text": "It would be really cool to have\nsome kind of data structure", "start": 3143.09, "duration": 2.56}, {"text": "where we can keep adding these--", "start": 3145.65, "duration": 2.31}, {"text": "we can add, remove, and\nprove, and then seek,", "start": 3147.96, "duration": 3.63}, {"text": "and see if something's\nin there, where it either", "start": 3151.59, "duration": 2.578}, {"text": "is like constant size, or login\nsize, or something like that.", "start": 3154.168, "duration": 2.542}, {"text": "That'd be really cool.", "start": 3156.71, "duration": 0.917}, {"text": "There are constructions\nlike that,", "start": 3157.627, "duration": 2.513}, {"text": "but they don't work for what\nwe're trying to do right now.", "start": 3160.14, "duration": 2.803}, {"text": "But there's a lot of\nresearch into that.", "start": 3162.943, "duration": 1.667}, {"text": "If anyone here finds\nsome cool data structure", "start": 3164.61, "duration": 2.46}, {"text": "that you can use for the UTXO\nDB that doesn't keep growing", "start": 3167.07, "duration": 4.22}, {"text": "linear at size of the number\nof keys, everyone in Bitcoin", "start": 3171.29, "duration": 3.46}, {"text": "will sing your praises forever.", "start": 3174.75, "duration": 3.99}, {"text": "But it's an active\nresearch area.", "start": 3178.74, "duration": 2.04}, {"text": "So pruning-- by default-- oh,\nthat should be a K, not an M,", "start": 3180.78, "duration": 5.43}, {"text": "sorry.", "start": 3186.21, "duration": 0.58}, {"text": "There's only 500K\nblocks, not 500M.", "start": 3186.79, "duration": 2.97}, {"text": "Anyway, by default, your client\nwill download all these blocks", "start": 3189.76, "duration": 4.16}, {"text": "and store them on the disk.", "start": 3193.92, "duration": 1.8}, {"text": "And that's important\nbecause what if someone", "start": 3195.72, "duration": 2.88}, {"text": "else requests them from you?", "start": 3198.6, "duration": 3.42}, {"text": "Everyone starts out as a noob.", "start": 3202.02, "duration": 1.62}, {"text": "Someone else comes\nand says, hey, guys,", "start": 3203.64, "duration": 1.86}, {"text": "I just downloaded Bitcoin.", "start": 3205.5, "duration": 2.25}, {"text": "What's going on for\nthe last nine years?", "start": 3207.75, "duration": 2.41}, {"text": "And you might want\nto give them blocks", "start": 3210.16, "duration": 1.7}, {"text": "to let them into the system.", "start": 3211.86, "duration": 3.35}, {"text": "So you can serve to\nothers who are doing IBD.", "start": 3215.21, "duration": 2.29}, {"text": "However, if you want, and\nyour hard drive's small,", "start": 3217.5, "duration": 2.48}, {"text": "or you have an SSD\nor something, you", "start": 3219.98, "duration": 1.63}, {"text": "can prune and delete the\nblocks after you've done IBD,", "start": 3221.61, "duration": 3.93}, {"text": "with no loss of security.", "start": 3225.54, "duration": 3.57}, {"text": "Anyone think of\ndownsides doing so?", "start": 3229.11, "duration": 3.0}, {"text": "Not really, right?", "start": 3238.14, "duration": 1.65}, {"text": "The only real downside\nis sort of this.", "start": 3239.79, "duration": 3.28}, {"text": "Well, not everyone can prune.", "start": 3243.07, "duration": 1.61}, {"text": "If everyone prunes, no new\nentrants to the system.", "start": 3244.68, "duration": 4.448}, {"text": "So it's a little\nbit of a tricky sort", "start": 3249.128, "duration": 1.542}, {"text": "of seed versus leech\nkind of problem,", "start": 3250.67, "duration": 3.21}, {"text": "where someone's got to be\nthere to serve up these blocks.", "start": 3253.88, "duration": 3.442}, {"text": "You don't have to trust them.", "start": 3257.322, "duration": 1.208}, {"text": "You're still validating\nall the work,", "start": 3258.53, "duration": 1.95}, {"text": "validating all the signatures.", "start": 3260.48, "duration": 1.59}, {"text": "They can't do anything bad.", "start": 3262.07, "duration": 2.37}, {"text": "But someone's got to be there\nto provide the network capacity.", "start": 3264.44, "duration": 4.057}, {"text": "And so it is tricky.", "start": 3268.497, "duration": 0.833}, {"text": "Like, most of the\nnodes on the network", "start": 3269.33, "duration": 1.68}, {"text": "are behind people's cable\nmodem firewall kind of thing.", "start": 3271.01, "duration": 3.3}, {"text": "So you can't actually\nconnect to them and download.", "start": 3274.31, "duration": 2.55}, {"text": "And if you run a node\nthat does allow people", "start": 3276.86, "duration": 2.46}, {"text": "to connect in and\nserve them blocks,", "start": 3279.32, "duration": 2.315}, {"text": "people will download\nquite a bit.", "start": 3281.635, "duration": 1.375}, {"text": "So I have one in the\noffice over there.", "start": 3283.01, "duration": 3.72}, {"text": "It ends up sending out about\nthree terabytes a month,", "start": 3286.73, "duration": 4.87}, {"text": "which is a lot.", "start": 3291.6, "duration": 0.84}, {"text": "Like, it's dozens of gigabytes\na day, 20, 30, I don't know.", "start": 3292.44, "duration": 5.36}, {"text": "So yeah, people are doing this.", "start": 3297.8, "duration": 1.77}, {"text": "People are connecting in and\ndownloading all the blocks,", "start": 3299.57, "duration": 2.64}, {"text": "either through IBD\nor just keeping up", "start": 3302.21, "duration": 1.86}, {"text": "with current transactions.", "start": 3304.07, "duration": 1.44}, {"text": "So yeah, pruning is possible.", "start": 3305.51, "duration": 1.95}, {"text": "But not everyone can do it, so\nit's sort of an unsolved issue", "start": 3307.46, "duration": 5.29}, {"text": "there.", "start": 3312.75, "duration": 0.5}, {"text": "There's a lot of\nresearch into how", "start": 3313.25, "duration": 1.417}, {"text": "we can do partial\npruning, where, OK, I'm", "start": 3314.667, "duration": 2.333}, {"text": "going to only store the last\nmonth's worth of blocks, which", "start": 3317.0, "duration": 3.18}, {"text": "is mostly what people do,\nbecause a lot of people", "start": 3320.18, "duration": 2.28}, {"text": "have intermittent connectivity,\nwhere they'll turn off", "start": 3322.46, "duration": 2.85}, {"text": "their node and then start it\nback up again a few days later.", "start": 3325.31, "duration": 2.91}, {"text": "And they just need to catch\nup with the last few blocks.", "start": 3328.22, "duration": 3.71}, {"text": "So pruning's cool.", "start": 3331.93, "duration": 0.75}, {"text": "That's been in since\n0.12 or something.", "start": 3332.68, "duration": 3.57}, {"text": "So I'll go through--", "start": 3336.25, "duration": 2.52}, {"text": "in practice, if you go\nto your Bitcoin node,", "start": 3338.77, "duration": 3.12}, {"text": "what does that actually store?", "start": 3341.89, "duration": 1.36}, {"text": "And if you just go to\nyour Bitcoin folder,", "start": 3343.25, "duration": 1.83}, {"text": "which in Unix-type OS's is\nlike home directory /.Bitcoin--", "start": 3345.08, "duration": 4.38}, {"text": "total random aside,\nI don't like how", "start": 3352.03, "duration": 2.46}, {"text": "they put a dot in front of all\nthe really important folders.", "start": 3354.49, "duration": 3.6}, {"text": "It's like they hide all the\nimportant things, like your GPG", "start": 3358.09, "duration": 2.76}, {"text": "folder, It's got a dot.", "start": 3360.85, "duration": 1.03}, {"text": "And your Bitcoin\nfolder's got a dot.", "start": 3361.88, "duration": 1.55}, {"text": "But like, downloads doesn't.", "start": 3363.43, "duration": 1.725}, {"text": "And like, who cares about that?", "start": 3365.155, "duration": 3.585}, {"text": "Anyway, so if you just\nls in your folder,", "start": 3368.74, "duration": 4.26}, {"text": "here's all the files.", "start": 3373.0, "duration": 1.62}, {"text": "And we'll just go\nthrough it real quick.", "start": 3374.62, "duration": 2.8}, {"text": "Here's the files,\nand I'll describe.", "start": 3377.42, "duration": 1.67}, {"text": "So there's a banlist.dat.", "start": 3379.09, "duration": 2.76}, {"text": "This is a list of IP\naddresses that you have", "start": 3381.85, "duration": 2.16}, {"text": "banned, because they're bad.", "start": 3384.01, "duration": 3.18}, {"text": "They're doing something weird.", "start": 3387.19, "duration": 1.36}, {"text": "So I'll get to it at the end.", "start": 3388.55, "duration": 1.37}, {"text": "I sort of am thinking of making\na ban list for the problem set,", "start": 3389.92, "duration": 3.72}, {"text": "because there are some nodes\nthat are doing non-good things.", "start": 3393.64, "duration": 3.27}, {"text": "That was what caused\nyesterday's outage.", "start": 3396.91, "duration": 3.48}, {"text": "Someone was connecting.", "start": 3400.39, "duration": 1.02}, {"text": "Although it was really my\nfault, because the server code", "start": 3401.41, "duration": 2.333}, {"text": "was not verifying\ninputs correctly.", "start": 3403.743, "duration": 2.287}, {"text": "But yeah, in Bitcoin,\nyou verify everything.", "start": 3406.03, "duration": 2.31}, {"text": "If people start sending you\nnonsense data, or they say,", "start": 3408.34, "duration": 2.49}, {"text": "hey, here's a block,\nand it's wrong,", "start": 3410.83, "duration": 1.59}, {"text": "or hey, here's a transaction,\nand the signatures are wrong,", "start": 3412.42, "duration": 3.51}, {"text": "you'll pretty quickly ban\nthem, because it's like, well,", "start": 3415.93, "duration": 3.67}, {"text": "if they're making a mistake--", "start": 3419.6, "duration": 1.687}, {"text": "it's computer.", "start": 3421.287, "duration": 0.583}, {"text": "There's no excuse\nfor making a mistake.", "start": 3421.87, "duration": 2.92}, {"text": "So either their software is\njust different than mine,", "start": 3424.79, "duration": 2.242}, {"text": "or something's wrong with their\nsoftware or their hardware,", "start": 3427.032, "duration": 2.458}, {"text": "I don't know.", "start": 3429.49, "duration": 0.542}, {"text": "But they're wasting my time.", "start": 3430.032, "duration": 1.738}, {"text": "They're sending\nme nonsense-- ban.", "start": 3431.77, "duration": 2.43}, {"text": "So you have your own ban list.", "start": 3434.2, "duration": 2.14}, {"text": "Then the blue ones are folders.", "start": 3436.34, "duration": 1.78}, {"text": "I'll talk about those later.", "start": 3438.12, "duration": 2.47}, {"text": "But you have peers.dat,\nwhich is good nodes.", "start": 3440.59, "duration": 2.76}, {"text": "So it's quite a\nbit, 4 megabytes.", "start": 3443.35, "duration": 2.31}, {"text": "And you keep track of here's\nall the different nodes", "start": 3445.66, "duration": 3.12}, {"text": "I've connected to for\nthe duration of however", "start": 3448.78, "duration": 3.57}, {"text": "long I've been using Bitcoin.", "start": 3452.35, "duration": 1.98}, {"text": "I keep track of all\ntheir IP addresses,", "start": 3454.33, "duration": 2.19}, {"text": "how much uptime they've had,\nwhat I've downloaded from them.", "start": 3456.52, "duration": 4.0}, {"text": "And so I sort of sort them and\nput the good ones at the top.", "start": 3460.52, "duration": 2.75}, {"text": "And like, OK, here's all\nthe different Bitcoin nodes.", "start": 3463.27, "duration": 3.06}, {"text": "So next time I start\nup Bitcoin, I'm", "start": 3466.33, "duration": 1.98}, {"text": "going to try to connect to them.", "start": 3468.31, "duration": 2.01}, {"text": "So this makes the\nnetwork very robust,", "start": 3470.32, "duration": 1.74}, {"text": "because everyone\nremembers everyone else.", "start": 3472.06, "duration": 2.46}, {"text": "And then when they need to--", "start": 3474.52, "duration": 1.2}, {"text": "if there's a network\ndisruption, maybe half the nodes", "start": 3475.72, "duration": 2.61}, {"text": "go off the network,\nyou can still", "start": 3478.33, "duration": 2.13}, {"text": "try to connect to all the rest.", "start": 3480.46, "duration": 1.98}, {"text": "And also peers will share their\npeers files, not directly,", "start": 3482.44, "duration": 4.47}, {"text": "but they'll sort of take\nrandom samplings of this file", "start": 3486.91, "duration": 2.49}, {"text": "and share it with each other,\nso that everyone sort of", "start": 3489.4, "duration": 2.25}, {"text": "knows about everyone else.", "start": 3491.65, "duration": 2.86}, {"text": "Then there's a wallet.dat,\nwhich is very important,", "start": 3494.51, "duration": 3.38}, {"text": "because that's got all\nyour precious UTXOs.", "start": 3497.89, "duration": 3.31}, {"text": "And we'll talk about\nwallets Monday, I think.", "start": 3501.2, "duration": 4.29}, {"text": "There's a bitcoin.conf,\nlittle config file.", "start": 3505.49, "duration": 2.28}, {"text": "You can set some settings\nand things like that;", "start": 3507.77, "duration": 2.865}, {"text": "a debug file, which shows\nall these weird messages;", "start": 3510.635, "duration": 3.705}, {"text": "and a mempool.dat.", "start": 3514.34, "duration": 1.41}, {"text": "So the mempool is a transaction\nyou've seen that you've not", "start": 3515.75, "duration": 4.38}, {"text": "seen in a block yet.", "start": 3520.13, "duration": 1.38}, {"text": "So people are\nbroadcasting transactions.", "start": 3521.51, "duration": 2.67}, {"text": "And you store them.", "start": 3524.18, "duration": 1.68}, {"text": "It used to be just in memory,\nhence the word \"mempool.\"", "start": 3525.86, "duration": 2.957}, {"text": "Now it's more like disk\npool, because you actually", "start": 3528.817, "duration": 2.083}, {"text": "store them on disk, because it\nsaves a little speed when you", "start": 3530.9, "duration": 3.27}, {"text": "shut down and start up again.", "start": 3534.17, "duration": 1.68}, {"text": "So any questions about just\nwhat all these files are doing?", "start": 3535.85, "duration": 3.27}, {"text": "Makes sense, so now the folders.", "start": 3542.467, "duration": 1.333}, {"text": "Chainstate blocks\nand database-- so any", "start": 3546.57, "duration": 2.28}, {"text": "guesses onto how\nbig these things are", "start": 3548.85, "duration": 2.37}, {"text": "based on previous slides or?", "start": 3551.22, "duration": 2.78}, {"text": "So how big is\nchainstate, for example?", "start": 3554.0, "duration": 1.97}, {"text": "Yes?", "start": 3558.83, "duration": 0.5}, {"text": "AUDIENCE: 3 gigs.", "start": 3559.33, "duration": 2.59}, {"text": "TADGE DRYJA: Yeah, 3 gigs.", "start": 3561.92, "duration": 2.23}, {"text": "This is a UTXO set, 3-ish gigs.", "start": 3564.15, "duration": 2.822}, {"text": "This is all the blocks.", "start": 3566.972, "duration": 0.958}, {"text": "What?", "start": 3567.93, "duration": 0.5}, {"text": "Oh, no.", "start": 3568.43, "duration": 0.958}, {"text": "And then database,\nactually, I have no idea.", "start": 3572.547, "duration": 1.833}, {"text": "Does anyone know what that is?", "start": 3574.38, "duration": 1.33}, {"text": "There's a database folder, and\nit's got one little log file.", "start": 3575.71, "duration": 3.14}, {"text": "And it's like 80 kilobytes.", "start": 3578.85, "duration": 1.56}, {"text": "I don't know what it is.", "start": 3580.41, "duration": 1.76}, {"text": "Do you guys know?", "start": 3582.17, "duration": 1.38}, {"text": "Yeah, I don't know.", "start": 3583.55, "duration": 2.08}, {"text": "But there's a blocks folder,\nand that's got all the blocks.", "start": 3585.63, "duration": 2.71}, {"text": "And that's your\nhuge amount of data.", "start": 3588.34, "duration": 4.1}, {"text": "And this is the UTXO\nset, not too bad.", "start": 3592.44, "duration": 2.83}, {"text": "So yeah, you can look in it.", "start": 3595.27, "duration": 2.02}, {"text": "It's reasonable but\nyeah, it's kind of big.", "start": 3597.29, "duration": 3.537}, {"text": "So any questions\nabout the data stuff?", "start": 3600.827, "duration": 1.583}, {"text": "I'm going to go into\nblockchain as a database,", "start": 3602.41, "duration": 2.25}, {"text": "real quick at the end.", "start": 3604.66, "duration": 2.13}, {"text": "So it's 186 gigabytes,\nor alternatively, you", "start": 3606.79, "duration": 3.69}, {"text": "can think of it as\njust 3 gigabytes.", "start": 3610.48, "duration": 1.83}, {"text": "But it's a really\ncrummy database.", "start": 3612.31, "duration": 1.707}, {"text": "So I've heard a\nlot that blockchain", "start": 3614.017, "duration": 1.458}, {"text": "is going to change the world.", "start": 3615.475, "duration": 1.275}, {"text": "And it's like a database\nthat's shared among everyone.", "start": 3616.75, "duration": 2.34}, {"text": "And you can query things.", "start": 3619.09, "duration": 1.975}, {"text": "It's a really bad database.", "start": 3621.065, "duration": 1.125}, {"text": "So for example,\nI'm going to have", "start": 3622.19, "duration": 2.96}, {"text": "some fun interactive\nquestions, where some of these", "start": 3625.15, "duration": 5.67}, {"text": "are answerable.", "start": 3630.82, "duration": 0.87}, {"text": "Some of these are not.", "start": 3631.69, "duration": 2.25}, {"text": "And I'm posing the question\nto my Bitcoin node.", "start": 3633.94, "duration": 3.567}, {"text": "So I posed this question\nto my Bitcoin node.", "start": 3637.507, "duration": 1.833}, {"text": "Hey, remember transaction\n9e95c3 dot, dot, dot,", "start": 3639.34, "duration": 3.63}, {"text": "from back in 2014?", "start": 3642.97, "duration": 1.89}, {"text": "And how do you think the\nBitcoin node will answer?", "start": 3644.86, "duration": 3.31}, {"text": "Will it answer, or\nwill it not be able to?", "start": 3648.17, "duration": 3.47}, {"text": "Any ideas?", "start": 3651.64, "duration": 0.64}, {"text": "Yeah.", "start": 3652.28, "duration": 0.5}, {"text": "AUDIENCE: Wait, where does\none be easiest [INAUDIBLE]??", "start": 3652.78, "duration": 2.415}, {"text": "TADGE DRYJA: 183 plus 3,\nso the total data usage", "start": 3658.1, "duration": 4.02}, {"text": "on this computer is 186 gigs.", "start": 3662.12, "duration": 3.176}, {"text": "The rest are kind of small.", "start": 3665.296, "duration": 3.776}, {"text": "AUDIENCE: What do you mean?", "start": 3669.072, "duration": 1.586}, {"text": "TADGE DRYJA: So I mean like,\nwhen you're using Bitcoin,", "start": 3670.658, "duration": 2.292}, {"text": "you've got 186 gigs\non your hard drive", "start": 3672.95, "duration": 2.73}, {"text": "or your SSD devoted to Bitcoin.", "start": 3675.68, "duration": 4.2}, {"text": "So you've got this 186-gigabyte\ndatabase, essentially.", "start": 3679.88, "duration": 4.02}, {"text": "But it's a really\ncrummy database.", "start": 3683.9, "duration": 2.43}, {"text": "And it can't do a lot of the\nthings you might expect it to.", "start": 3686.33, "duration": 3.34}, {"text": "So for example, this--", "start": 3689.67, "duration": 1.97}, {"text": "arbitrary transaction\nfrom the past-- you say,", "start": 3691.64, "duration": 1.98}, {"text": "hey, there was this transaction\na couple of years ago.", "start": 3693.62, "duration": 3.3}, {"text": "Give me the\ninformation about it.", "start": 3696.92, "duration": 1.86}, {"text": "And what do you think the\nresponse from the full node is?", "start": 3698.78, "duration": 2.395}, {"text": "AUDIENCE: It's valid.", "start": 3701.175, "duration": 0.875}, {"text": "TADGE DRYJA: What, sorry?", "start": 3702.05, "duration": 0.607}, {"text": "AUDIENCE: It's\nvalid or not valid.", "start": 3702.657, "duration": 1.193}, {"text": "TADGE DRYJA: It's\nvalid or not valid.", "start": 3703.85, "duration": 1.08}, {"text": "Any other ideas?", "start": 3704.93, "duration": 0.667}, {"text": "AUDIENCE: What's the header?", "start": 3705.597, "duration": 1.553}, {"text": "TADGE DRYJA: What, sorry?", "start": 3707.15, "duration": 0.585}, {"text": "AUDIENCE: What's the\nheader of [INAUDIBLE]??", "start": 3707.735, "duration": 1.185}, {"text": "TADGE DRYJA: It asks\ninstead for a header.", "start": 3708.92, "duration": 2.09}, {"text": "Any other ideas?", "start": 3711.01, "duration": 0.75}, {"text": "Yeah, so sort of that--\nit'll say, remember TX disk?", "start": 3711.76, "duration": 4.14}, {"text": "No, it's somewhere\nin the blocks maybe,", "start": 3715.9, "duration": 2.19}, {"text": "but I have no idea where.", "start": 3718.09, "duration": 1.41}, {"text": "It's not in the chainstate.", "start": 3719.5, "duration": 2.03}, {"text": "So it just stores the blocks.", "start": 3721.53, "duration": 2.49}, {"text": "Like, here's this block.", "start": 3724.02, "duration": 2.44}, {"text": "Here's that block, in line.", "start": 3726.46, "duration": 1.71}, {"text": "And if you say, hey,\nthere's this transaction.", "start": 3728.17, "duration": 2.66}, {"text": "OK, go look for it.", "start": 3730.83, "duration": 1.57}, {"text": "Oh, 2014, well, that might\nbe somewhere in the middle.", "start": 3732.4, "duration": 4.91}, {"text": "But yeah, if you don't know\nwhat block it's in, forget it.", "start": 3737.31, "duration": 3.352}, {"text": "So it does have an\nindex of blocks.", "start": 3740.662, "duration": 1.458}, {"text": "It'll tell you a block,\nbut transaction, no luck.", "start": 3742.12, "duration": 2.33}, {"text": "Yeah.", "start": 3744.45, "duration": 0.5}, {"text": "AUDIENCE: So it pretty much\ntells you if it exists,", "start": 3744.95, "duration": 1.894}, {"text": "and that's it.", "start": 3746.844, "duration": 0.636}, {"text": "TADGE DRYJA: It won't even\ntell you if this exists.", "start": 3747.48, "duration": 1.99}, {"text": "It has no idea.", "start": 3749.47, "duration": 0.625}, {"text": "AUDIENCE: What's the\n[INAUDIBLE] in the block though?", "start": 3750.095, "duration": 2.635}, {"text": "TADGE DRYJA: I might\nhave made that up.", "start": 3752.73, "duration": 2.377}, {"text": "So if you're saying, hey,\nhere's this transaction.", "start": 3755.107, "duration": 2.083}, {"text": "Do you remember it?", "start": 3757.19, "duration": 0.58}, {"text": "Does it exist?", "start": 3757.77, "duration": 0.7}, {"text": "I don't know.", "start": 3758.47, "duration": 1.14}, {"text": "Yeah.", "start": 3759.61, "duration": 0.5}, {"text": "AUDIENCE: If you ask-- if you\nquery about a certain block,", "start": 3760.11, "duration": 2.938}, {"text": "will it be able to?", "start": 3763.048, "duration": 0.792}, {"text": "TADGE DRYJA: Yes, and I'll--", "start": 3763.84, "duration": 1.557}, {"text": "yeah, good question.", "start": 3765.397, "duration": 0.833}, {"text": "But I'll get to that.", "start": 3766.23, "duration": 1.08}, {"text": "I think it's in\nthe later slides.", "start": 3767.31, "duration": 1.45}, {"text": "But yes, if you create\nyour base on a block hash,", "start": 3768.76, "duration": 4.13}, {"text": "then it does have\nthat in the database.", "start": 3772.89, "duration": 1.99}, {"text": "And it'll be able\nto get it for you.", "start": 3774.88, "duration": 1.5}, {"text": "Yeah, James.", "start": 3776.38, "duration": 0.67}, {"text": "AUDIENCE: I know what the\ndatabase directory does.", "start": 3777.05, "duration": 2.09}, {"text": "TADGE DRYJA: You know what\nthe database directory does.", "start": 3779.14, "duration": 1.6}, {"text": "AUDIENCE: Yeah,\nit's the journaling", "start": 3780.74, "duration": 1.5}, {"text": "for the other databases.", "start": 3782.24, "duration": 1.375}, {"text": "TADGE DRYJA: Journaling\nfor other databases--", "start": 3783.615, "duration": 1.875}, {"text": "OK, I didn't-- yeah, cool.", "start": 3785.49, "duration": 1.65}, {"text": "It's very small, so I\nguess it helps things work.", "start": 3787.14, "duration": 3.65}, {"text": "So this one-- do you\nknow this transaction?", "start": 3790.79, "duration": 3.03}, {"text": "No.", "start": 3793.82, "duration": 0.81}, {"text": "How about this?", "start": 3794.63, "duration": 1.95}, {"text": "Well, I've got this output.", "start": 3796.58, "duration": 3.06}, {"text": "It's still there in the UTX--\nlike, someone spent here.", "start": 3799.64, "duration": 4.59}, {"text": "It's like, this a\ntransaction in the first one.", "start": 3804.23, "duration": 2.34}, {"text": "It's an op_return output.", "start": 3806.57, "duration": 1.35}, {"text": "So it's got some extra data.", "start": 3807.92, "duration": 1.44}, {"text": "But op_return\nmeans it's invalid.", "start": 3809.36, "duration": 1.86}, {"text": "It can't spend it.", "start": 3811.22, "duration": 0.93}, {"text": "Can you tell me\nwhat the data is?", "start": 3812.15, "duration": 2.052}, {"text": "Do you think it'll be able to?", "start": 3814.202, "duration": 2.438}, {"text": "If you query, hey,\nhere's this output,", "start": 3816.64, "duration": 3.66}, {"text": "what do you think\nthe response will be?", "start": 3820.3, "duration": 3.04}, {"text": "Yea, nay?", "start": 3823.34, "duration": 2.031}, {"text": "Nay, OK, I'm seeing nays.", "start": 3825.371, "duration": 1.359}, {"text": "Yeah.", "start": 3826.73, "duration": 0.81}, {"text": "Nope.", "start": 3827.54, "duration": 0.545}, {"text": "If it's an op_return output,\neven though it's unspent,", "start": 3828.085, "duration": 2.545}, {"text": "well, it's unspendable.", "start": 3830.63, "duration": 1.65}, {"text": "So you don't put it\nin the UTXO database,", "start": 3832.28, "duration": 2.94}, {"text": "because you just see, oh, this\noutput, op_return is in there.", "start": 3835.22, "duration": 3.495}, {"text": "Don't bother putting it in.", "start": 3838.715, "duration": 1.125}, {"text": "No one will ever be\nable to spend it.", "start": 3839.84, "duration": 2.08}, {"text": "So there's no\nreason to put it in.", "start": 3841.92, "duration": 1.76}, {"text": "So op_returns are\nused to sort of commit", "start": 3843.68, "duration": 2.1}, {"text": "to data and all these\ndifferent protocols.", "start": 3845.78, "duration": 2.19}, {"text": "But the actual normal\ncode won't store them.", "start": 3847.97, "duration": 5.817}, {"text": "Anything else?", "start": 3853.787, "duration": 0.583}, {"text": "Next one, this one--", "start": 3854.37, "duration": 3.0}, {"text": "hey, I have a public key.", "start": 3857.37, "duration": 2.438}, {"text": "And here's the hash\nof my public key.", "start": 3859.808, "duration": 1.542}, {"text": "This is essentially an address.", "start": 3861.35, "duration": 1.292}, {"text": "So we didn't talk\nabout addresses.", "start": 3862.642, "duration": 1.523}, {"text": "But the Bitcoin addresses\nthat start with like a 1,", "start": 3864.165, "duration": 2.335}, {"text": "and then have these\nalphanumeric stuff--", "start": 3866.5, "duration": 3.2}, {"text": "it's just a different\nencoding, slightly shorter", "start": 3869.7, "duration": 2.01}, {"text": "than hexadecimal,\nfor a pubkey hash.", "start": 3871.71, "duration": 2.52}, {"text": "So you say, hey, I've got this.", "start": 3874.23, "duration": 2.07}, {"text": "I have a private key.", "start": 3876.3, "duration": 0.99}, {"text": "I just computed the public key.", "start": 3877.29, "duration": 1.36}, {"text": "I hashed it.", "start": 3878.65, "duration": 0.78}, {"text": "I got this.", "start": 3879.43, "duration": 1.53}, {"text": "Do I have any money?", "start": 3880.96, "duration": 1.23}, {"text": "I think I did.", "start": 3882.19, "duration": 1.06}, {"text": "I don't remember.", "start": 3883.25, "duration": 0.77}, {"text": "But I remember my private key.", "start": 3884.02, "duration": 1.08}, {"text": "I backed that up.", "start": 3885.1, "duration": 0.708}, {"text": "That was the important part.", "start": 3885.808, "duration": 1.722}, {"text": "Everyone says keep\nyour private keys.", "start": 3887.53, "duration": 1.92}, {"text": "So I have my private key.", "start": 3889.45, "duration": 1.74}, {"text": "But all this data and\nall this blockchain", "start": 3891.19, "duration": 2.85}, {"text": "stuff, I lost my computer.", "start": 3894.04, "duration": 1.317}, {"text": "But I have my private,\nso I've got my money.", "start": 3895.357, "duration": 1.833}, {"text": "How many coins do I have?", "start": 3897.19, "duration": 1.17}, {"text": "How many outputs?", "start": 3898.36, "duration": 2.22}, {"text": "What do you think the\nfull node will tell you?", "start": 3900.58, "duration": 4.73}, {"text": "Yeah, any ideas?", "start": 3905.31, "duration": 2.82}, {"text": "It'll say, I don't know.", "start": 3908.13, "duration": 1.638}, {"text": "Well, you're going to have\nto search through everything", "start": 3909.768, "duration": 2.292}, {"text": "in chainstate.", "start": 3912.06, "duration": 1.98}, {"text": "And it doesn't index based on\nthe public key script, only", "start": 3914.04, "duration": 3.0}, {"text": "the transaction ID index there.", "start": 3917.04, "duration": 1.98}, {"text": "It's a key-value store, and the\nkey is this 36-byte txid:index.", "start": 3919.02, "duration": 5.49}, {"text": "So this is a very real problem.", "start": 3924.51, "duration": 2.1}, {"text": "Like, OK, I backed up my key.", "start": 3926.61, "duration": 1.65}, {"text": "Or I took my private keys\nto some other computer", "start": 3928.26, "duration": 2.37}, {"text": "or something like that.", "start": 3930.63, "duration": 2.23}, {"text": "And this is fairly--", "start": 3932.86, "duration": 0.928}, {"text": "it's gotten a lot faster.", "start": 3933.788, "duration": 1.042}, {"text": "It used to take hours,\nwhere you had a hard drive,", "start": 3934.83, "duration": 3.15}, {"text": "and you're like, OK, import\na key to this wallet.", "start": 3937.98, "duration": 3.12}, {"text": "And it's like, well, when\ndid you do transactions?", "start": 3941.1, "duration": 2.33}, {"text": "It has to look through the\nentire blockchain, [INAUDIBLE]", "start": 3943.43, "duration": 2.63}, {"text": "and linearly, to see if\nany of these transactions", "start": 3946.06, "duration": 3.05}, {"text": "have an output that matches\nthat, and then says,", "start": 3949.11, "duration": 2.74}, {"text": "oh, yeah, you got\nmoney back in 2013.", "start": 3951.85, "duration": 1.7}, {"text": "Oh, then you spent it--", "start": 3953.55, "duration": 2.3}, {"text": "and sort of replays\nthings, because it", "start": 3955.85, "duration": 2.61}, {"text": "doesn't have an address index.", "start": 3958.46, "duration": 1.25}, {"text": "Next one-- this is an example.", "start": 3962.53, "duration": 2.41}, {"text": "How many coins-- so you say,\nhey, here's this output,", "start": 3964.94, "duration": 3.41}, {"text": "this transaction:1, how\nmany coins does it have?", "start": 3968.35, "duration": 3.51}, {"text": "Will the full node be\nable to tell you this?", "start": 3971.86, "duration": 3.11}, {"text": "Yea, nay?", "start": 3974.97, "duration": 2.57}, {"text": "I'm seeing a bunch of nays.", "start": 3977.54, "duration": 2.3}, {"text": "No, it will.", "start": 3979.84, "duration": 1.07}, {"text": "Yeah, this is the\none thing it can do.", "start": 3980.91, "duration": 3.7}, {"text": "So if you say, hey, 7434,\ndot, dot, dot, colon 1,", "start": 3984.61, "duration": 3.803}, {"text": "it'll know that.", "start": 3988.413, "duration": 0.667}, {"text": "That's in the UTXO DB,\nbecause that's the key", "start": 3989.08, "duration": 3.15}, {"text": "that the UTXO DB sorts by.", "start": 3992.23, "duration": 2.17}, {"text": "So yep, this is a UTXO.", "start": 3994.4, "duration": 2.6}, {"text": "It's unspent.", "start": 3997.0, "duration": 0.72}, {"text": "And it has a bunch of coins.", "start": 3997.72, "duration": 2.457}, {"text": "And this is fairly recent.", "start": 4000.177, "duration": 1.083}, {"text": "I was just looking through.", "start": 4001.26, "duration": 1.125}, {"text": "Someone got a couple\nmillion bucks worth, cool.", "start": 4002.385, "duration": 2.775}, {"text": "Is that a million?", "start": 4005.16, "duration": 0.888}, {"text": "Man.", "start": 4006.048, "duration": 2.922}, {"text": "Yeah, it's a new UTXO\nset, hasn't been spent,", "start": 4008.97, "duration": 2.43}, {"text": "and you can sort quickly\nbased on txid:index pair.", "start": 4011.4, "duration": 3.81}, {"text": "So I think this is in\nsome software called", "start": 4015.21, "duration": 2.97}, {"text": "an outpoint, where it's\nlike, you concatenate them.", "start": 4018.18, "duration": 2.61}, {"text": "And it ends up being 36 bytes.", "start": 4020.79, "duration": 2.52}, {"text": "This is 32 bytes.", "start": 4023.31, "duration": 0.81}, {"text": "This is 4.", "start": 4024.12, "duration": 0.795}, {"text": "So you sort of have\na 36-byte outpoint,", "start": 4024.915, "duration": 2.145}, {"text": "which describes what goes\ninto the UTXO database.", "start": 4027.06, "duration": 3.14}, {"text": "AUDIENCE: But once\nit gets respent,", "start": 4030.2, "duration": 1.776}, {"text": "it's hard to find it again.", "start": 4031.976, "duration": 1.374}, {"text": "TADGE DRYJA: Yeah,\nonce this is spent,", "start": 4033.35, "duration": 1.98}, {"text": "you delete it from the UTXO, and\nyou won't remember it anymore.", "start": 4035.33, "duration": 3.328}, {"text": "It'll just be, hey, you, how\nmany coins does this have?", "start": 4038.658, "duration": 2.292}, {"text": "You're like, well-- well,\nyou can still answer it.", "start": 4040.95, "duration": 2.28}, {"text": "You say \"none.\"", "start": 4043.23, "duration": 1.91}, {"text": "If it's spent, and you say, how\nmany coins does this guy have?", "start": 4045.14, "duration": 3.34}, {"text": "None.", "start": 4048.48, "duration": 0.5}, {"text": "It's not in the UTXO set.", "start": 4048.98, "duration": 1.042}, {"text": "Yeah, so the previous one--", "start": 4052.695, "duration": 1.125}, {"text": "I just copied these randomly.", "start": 4053.82, "duration": 1.208}, {"text": "So any questions about what is\nstored and what is not stored?", "start": 4058.01, "duration": 3.78}, {"text": "Basically, keeps\ntrack of UTXOs, and it", "start": 4064.41, "duration": 2.81}, {"text": "keeps track of historic\nblocks in order", "start": 4067.22, "duration": 1.75}, {"text": "to give them to people.", "start": 4068.97, "duration": 1.028}, {"text": "And it keeps after the headers.", "start": 4069.998, "duration": 1.292}, {"text": "The headers ends up being small.", "start": 4071.29, "duration": 1.43}, {"text": "All the headers\ntotal is like, what?", "start": 4072.72, "duration": 1.55}, {"text": "40 megs, something like that.", "start": 4074.27, "duration": 3.03}, {"text": "So yeah, you can\nadd further indices.", "start": 4077.3, "duration": 3.17}, {"text": "You could write software to\nanswer all these questions", "start": 4080.47, "duration": 2.84}, {"text": "very quickly.", "start": 4083.31, "duration": 2.1}, {"text": "But that's not what\nBitcoin does by default.", "start": 4085.41, "duration": 3.09}, {"text": "Those types of indices would\ntake a lot of extra space", "start": 4088.5, "duration": 3.72}, {"text": "and add a lot of CPU\nor things like that.", "start": 4092.22, "duration": 3.22}, {"text": "So a very common thing\nis an address index,", "start": 4095.44, "duration": 3.08}, {"text": "so people can ask if\nthey have any money.", "start": 4098.52, "duration": 1.77}, {"text": "So the second to last\none, where you say,", "start": 4100.29, "duration": 2.29}, {"text": "hey, I have this key hash.", "start": 4102.58, "duration": 2.787}, {"text": "Do I have any money?", "start": 4105.367, "duration": 0.833}, {"text": "Do I have any transactions?", "start": 4106.2, "duration": 1.65}, {"text": "Having an address\nindex is actually", "start": 4107.85, "duration": 2.129}, {"text": "pretty useful for\na lot of things,", "start": 4109.979, "duration": 2.261}, {"text": "for example, importing keys or\nlike web wallet kind of things.", "start": 4112.24, "duration": 4.84}, {"text": "But Bitcoin by default doesn't\ndo it, because, well, why?", "start": 4117.08, "duration": 5.518}, {"text": "You can make arguments that\nit would be actually useful", "start": 4122.598, "duration": 2.292}, {"text": "to have in the normal\ncode, but we don't.", "start": 4124.89, "duration": 4.219}, {"text": "Any other questions about\nwhat indices, what it can do,", "start": 4129.109, "duration": 3.591}, {"text": "what it cannot do?", "start": 4132.7, "duration": 1.93}, {"text": "Somewhat counterintuitive in\nmany cases, where you say, hey,", "start": 4134.63, "duration": 2.87}, {"text": "here's this transaction.", "start": 4137.5, "duration": 1.0}, {"text": "And you can't actually find it.", "start": 4138.5, "duration": 2.68}, {"text": "Or you have to scan through 180\ngigabytes in order to find it.", "start": 4141.18, "duration": 4.58}, {"text": "So wait, James, I\nhave a question.", "start": 4145.76, "duration": 1.53}, {"text": "So how big is an address index\nfor what you were working on?", "start": 4147.29, "duration": 4.7}, {"text": "AUDIENCE: Usually, equal to\nthe size of the chain inside.", "start": 4151.99, "duration": 2.81}, {"text": "TADGE DRYJA: Wow, so it\ncould be hundreds of gigs.", "start": 4154.8, "duration": 2.44}, {"text": "Yeah.", "start": 4157.24, "duration": 0.514}, {"text": "AUDIENCE: It only takes what?", "start": 4157.754, "duration": 1.208}, {"text": "At least for Bitcoin, it\ntakes usually multiple weeks", "start": 4158.962, "duration": 2.598}, {"text": "to generate.", "start": 4161.56, "duration": 0.698}, {"text": "TADGE DRYJA: Weeks to generate?", "start": 4162.258, "duration": 1.292}, {"text": "I bet you, well--", "start": 4163.55, "duration": 0.772}, {"text": "AUDIENCE: Although [INAUDIBLE]\nusually takes a few days", "start": 4164.322, "duration": 2.292}, {"text": "on the inside, which is\nwhat [INAUDIBLE] takes--", "start": 4166.614, "duration": 3.016}, {"text": "weeks.", "start": 4169.63, "duration": 0.87}, {"text": "TADGE DRYJA: Well,\nthat's inside.", "start": 4170.5, "duration": 1.62}, {"text": "So the other thing is, these\nare like fairly involved sort", "start": 4172.12, "duration": 5.13}, {"text": "of CSE software\nengineering problems.", "start": 4177.25, "duration": 2.1}, {"text": "And optimization really works.", "start": 4179.35, "duration": 2.16}, {"text": "If you download like Bitcoin\n0.9, it'll still work.", "start": 4181.51, "duration": 4.83}, {"text": "But you're never\ngoing to catch up.", "start": 4186.34, "duration": 1.889}, {"text": "Maybe not never, I don't know.", "start": 4188.229, "duration": 1.5}, {"text": "If you have a fast computer, but\nit'll take months and months.", "start": 4189.729, "duration": 3.21}, {"text": "And as people have been\nupdating the software", "start": 4192.939, "duration": 2.071}, {"text": "and making it faster,\nmaking it more efficient,", "start": 4195.01, "duration": 2.22}, {"text": "now it's quite fast.", "start": 4197.23, "duration": 1.08}, {"text": "And you can sync the\nwhole thing in a few hours", "start": 4198.31, "duration": 3.48}, {"text": "on a good computer.", "start": 4201.79, "duration": 2.02}, {"text": "So address index is one\nof those things where", "start": 4203.81, "duration": 1.97}, {"text": "it hasn't had like the full\nforce of all these Bitcoin", "start": 4205.78, "duration": 3.15}, {"text": "protocol coder people on it,\nbecause it's sort of seen", "start": 4208.93, "duration": 3.158}, {"text": "as like, well, yeah that's kind\nof a fun feature if you want.", "start": 4212.088, "duration": 2.542}, {"text": "But it's not like a\ncore utility of Bitcoin.", "start": 4214.63, "duration": 4.27}, {"text": "So yeah, it is a database,\nmaybe not the best way", "start": 4218.9, "duration": 4.14}, {"text": "to think of it though.", "start": 4223.04, "duration": 1.8}, {"text": "Don't think of the blockchain as\nlike a global shared database,", "start": 4224.84, "duration": 2.64}, {"text": "because it sort of is.", "start": 4227.48, "duration": 0.99}, {"text": "But it's a fairly\nspecific database", "start": 4228.47, "duration": 2.1}, {"text": "that isn't useful for\nmany other things.", "start": 4230.57, "duration": 3.9}, {"text": "Yeah, and it's also untrusted.", "start": 4234.47, "duration": 1.63}, {"text": "Another part of why\nis it's untrusted.", "start": 4236.1, "duration": 3.15}, {"text": "Most of these things\nexist so that they", "start": 4239.25, "duration": 2.31}, {"text": "can be used over the\npeer-to-peer peer network.", "start": 4241.56, "duration": 2.01}, {"text": "If you request a block,\nI'll give it to you.", "start": 4243.57, "duration": 2.04}, {"text": "If you give me a\ntransaction, I'll", "start": 4245.61, "duration": 1.53}, {"text": "match it against my UTXO set.", "start": 4247.14, "duration": 2.438}, {"text": "But an address index\ndoesn't work that way.", "start": 4249.578, "duration": 1.792}, {"text": "It's sort of trusted.", "start": 4251.37, "duration": 0.875}, {"text": "I can easily omit things.", "start": 4252.245, "duration": 2.555}, {"text": "If you say, hey, I've got a key.", "start": 4254.8, "duration": 1.49}, {"text": "What are the transactions\ninvolved with this key?", "start": 4256.29, "duration": 2.12}, {"text": "I can omit things very\neasily, and there's", "start": 4258.41, "duration": 1.75}, {"text": "no way for you to\nprove it or verify it.", "start": 4260.16, "duration": 2.49}, {"text": "So your DB queries aren't really\ngiven out to network peers.", "start": 4262.65, "duration": 4.17}, {"text": "And network peers are scary.", "start": 4266.82, "duration": 1.21}, {"text": "And you need to ban\nthem if they act funny.", "start": 4268.03, "duration": 3.16}, {"text": "And this happens all the time.", "start": 4271.19, "duration": 1.25}, {"text": "If you look through\nBitcoin logs,", "start": 4272.44, "duration": 1.92}, {"text": "and you have a node that's\nup, every few seconds, you're", "start": 4274.36, "duration": 2.748}, {"text": "going to be disconnecting\nfrom someone or banning them,", "start": 4277.108, "duration": 2.292}, {"text": "because they're doing something\ncrazy, trying to hack into you", "start": 4279.4, "duration": 2.94}, {"text": "or whatever.", "start": 4282.34, "duration": 1.11}, {"text": "So basically, all\nyou're doing is", "start": 4283.45, "duration": 1.56}, {"text": "you're providing headers,\nblocks, transactions.", "start": 4285.01, "duration": 2.94}, {"text": "And you're sharing the\nother IPs and nodes.", "start": 4287.95, "duration": 2.45}, {"text": "You try to simplify it.", "start": 4290.4, "duration": 2.79}, {"text": "Other questions?", "start": 4293.19, "duration": 1.59}, {"text": "Yeah, bad database, good for\nconsensus, it kind of works.", "start": 4294.78, "duration": 3.75}, {"text": "Everyone's got\nthe same UTXO set,", "start": 4298.53, "duration": 2.55}, {"text": "even though they\nall really would", "start": 4301.08, "duration": 1.62}, {"text": "like to change that UTXO set.", "start": 4302.7, "duration": 1.57}, {"text": "I would much rather\neveryone had a UTXO", "start": 4304.27, "duration": 1.85}, {"text": "set where I had\nthose 27-coin UTXO.", "start": 4306.12, "duration": 4.66}, {"text": "So almost everyone\nin the systems", "start": 4310.78, "duration": 1.79}, {"text": "would rather there was\na different UTXO set.", "start": 4312.57, "duration": 2.97}, {"text": "And yet, they all managed to\nagree on a single UTXO set,", "start": 4315.54, "duration": 3.16}, {"text": "so pretty cool.", "start": 4318.7, "duration": 2.15}]
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@@ -0,0 +1 @@
+[{"text": "[CLICKING]", "start": 0.0, "duration": 1.95}, {"text": "[RUSTLING]", "start": 1.95, "duration": 0.5}, {"text": "[SQUEAKING]", "start": 2.45, "duration": 1.96}, {"text": "[CLICKING]", "start": 4.41, "duration": 1.96}, {"text": "MICHAEL SIPSER: OK.", "start": 25.03, "duration": 1.8}, {"text": "Hi, everybody.", "start": 26.83, "duration": 1.3}, {"text": "Let's get started.", "start": 28.13, "duration": 0.785}, {"text": "So, it's been a while since\nwe came together in a lecture.", "start": 31.91, "duration": 6.14}, {"text": "Last week, we had the holiday.", "start": 38.05, "duration": 1.68}, {"text": "We had the midterm.", "start": 39.73, "duration": 2.49}, {"text": "So with that, what\nhave we been doing?", "start": 42.22, "duration": 5.1}, {"text": "We finished the first half of\nthe course about two weeks ago,", "start": 47.32, "duration": 5.22}, {"text": "where we talked\nabout-- we were talking", "start": 52.54, "duration": 2.1}, {"text": "about computability theory.", "start": 54.64, "duration": 1.77}, {"text": "We have shifted into\nthe second half,", "start": 56.41, "duration": 2.1}, {"text": "talking about complexity theory.", "start": 58.51, "duration": 2.53}, {"text": "So get your mind back to that.", "start": 61.04, "duration": 3.83}, {"text": "We discussed the various\ndifferent models and ways", "start": 64.87, "duration": 7.8}, {"text": "of measuring complexity\non different models--", "start": 72.67, "duration": 3.9}, {"text": "at least in terms of the\namount of time that's used.", "start": 76.57, "duration": 2.43}, {"text": "And in the end, we settled on\nthe one-tape Turing machine,", "start": 79.0, "duration": 3.1}, {"text": "which is the same model\nwe had been working", "start": 82.1, "duration": 1.82}, {"text": "with in the first\nhalf of the course,", "start": 83.92, "duration": 1.89}, {"text": "and argued that though\nthe measures of complexity", "start": 85.81, "duration": 5.64}, {"text": "are going to differ somewhat\nfrom model to model,", "start": 91.45, "duration": 2.22}, {"text": "they're not going to differ by\nmore than a polynomial amount.", "start": 93.67, "duration": 4.38}, {"text": "And so, since the\nkinds of questions", "start": 98.05, "duration": 2.37}, {"text": "we're going to be\nasking are going", "start": 100.42, "duration": 2.34}, {"text": "to be, basically, whether\nproblems are polynomial or not,", "start": 102.76, "duration": 4.44}, {"text": "it's not going to really\nmatter which model we", "start": 107.2, "duration": 2.43}, {"text": "pick among reasonable\ndeterministic models.", "start": 109.63, "duration": 3.06}, {"text": "And so, the one-tape Turing\nmachine is a reasonable choice.", "start": 112.69, "duration": 5.22}, {"text": "Given that, we defined\ntime complexity classes,", "start": 117.91, "duration": 3.02}, {"text": "the TIME[T(n)] classes.", "start": 120.93, "duration": 1.86}, {"text": "We defined the class P,\nwhich was invariant among all", "start": 122.79, "duration": 4.89}, {"text": "of those different deterministic\nmodels in the sense", "start": 127.68, "duration": 2.79}, {"text": "that it didn't matter\nwhich model we choose,", "start": 130.47, "duration": 2.138}, {"text": "we were going to end\nup with the same class", "start": 132.608, "duration": 1.792}, {"text": "P. So that argues\nfor its naturalness.", "start": 134.4, "duration": 3.69}, {"text": "And we gave an example of\nthis path problem being in P.", "start": 138.09, "duration": 3.06}, {"text": "And we kind of ended that\nlecture before the midterm", "start": 141.15, "duration": 2.91}, {"text": "with the discussion of this\nHamiltonian path problem.", "start": 144.06, "duration": 2.86}, {"text": "So we're going to come\nback to that today.", "start": 146.92, "duration": 2.33}, {"text": "So today, we're going to\nlook at non-non-deterministic", "start": 149.25, "duration": 2.25}, {"text": "complexity; define the\nclasses' non-deterministic time", "start": 151.5, "duration": 5.34}, {"text": "or NTIME; talk about the class\nNP, the P versus NP problem--", "start": 156.84, "duration": 5.32}, {"text": "which one of the very famous\nunsolved problems in our field;", "start": 162.16, "duration": 4.07}, {"text": "and look at dynamic programming,\none of the most basic algorithm", "start": 166.23, "duration": 4.215}, {"text": "- polynomial-time algorithms and\npolynomial-time reproducibility", "start": 170.445, "duration": 2.975}, {"text": "- moving toward our\ndiscussion of NP completeness,", "start": 173.42, "duration": 3.89}, {"text": "which we will\nbegin next lecture.", "start": 177.31, "duration": 3.77}, {"text": "So with that, let's move\ninto today's content, which", "start": 181.08, "duration": 5.3}, {"text": "is, well, just a quick review.", "start": 186.38, "duration": 3.9}, {"text": "As I mentioned, we defined\nthe time complexity class.", "start": 190.28, "duration": 4.14}, {"text": "The time complexity\nclass is a collection", "start": 194.42, "duration": 2.37}, {"text": "of all of the\nlanguages that you can", "start": 196.79, "duration": 10.17}, {"text": "solve in a certain time\nbound, within a certain amount", "start": 206.96, "duration": 4.08}, {"text": "of time.", "start": 211.04, "duration": 0.91}, {"text": "So the time n-squared,\nfor example,", "start": 211.95, "duration": 4.34}, {"text": "is all of the languages\nor all of the problems", "start": 216.29, "duration": 3.66}, {"text": "that you can solve\nin n-squared time.", "start": 219.95, "duration": 2.22}, {"text": "We're identifying problems\nwith languages here.", "start": 222.17, "duration": 3.09}, {"text": "And the class P\nis the collection", "start": 225.26, "duration": 2.73}, {"text": "of all problems\nthat you can solve", "start": 227.99, "duration": 1.56}, {"text": "or all languages that you\ncan solve in polynomial time.", "start": 229.55, "duration": 2.89}, {"text": "So it's the union over\nall time n to the k--", "start": 232.44, "duration": 2.93}, {"text": "so n-squared, n-cubed, n to\nthe fifth power, and so on.", "start": 235.37, "duration": 5.01}, {"text": "Union out of all\nof those bounds.", "start": 240.38, "duration": 4.25}, {"text": "The associated languages,\nthat's the class P.", "start": 244.63, "duration": 4.15}, {"text": "And we gave an example,\nthis path problem.", "start": 248.78, "duration": 3.18}, {"text": "We gave an algorithm for path.", "start": 251.96, "duration": 2.73}, {"text": "And then, we introduced this\nHamiltonian path problem.", "start": 254.69, "duration": 4.089}, {"text": "So if you remember?", "start": 258.779, "duration": 4.041}, {"text": "Instead of just asking\ngiven a graph, whether you", "start": 262.82, "duration": 3.03}, {"text": "can get from s to t, now we want\nto know can I get from s to t,", "start": 265.85, "duration": 4.53}, {"text": "but visit every other\nnode along the way.", "start": 270.38, "duration": 3.88}, {"text": "So find a path that goes\nthrough everything else", "start": 274.26, "duration": 4.46}, {"text": "and gets from s to t.", "start": 278.72, "duration": 1.41}, {"text": "And I should say also\nit's a simple path,", "start": 282.78, "duration": 3.67}, {"text": "so you're only allowed to go\nthrough every node just once.", "start": 286.45, "duration": 4.88}, {"text": "And now, the question\nfor this problem", "start": 291.33, "duration": 7.99}, {"text": "is can we solve that\nproblem in polynomial time.", "start": 299.32, "duration": 4.92}, {"text": "Can we somehow modify\nthe algorithm for path", "start": 304.24, "duration": 2.55}, {"text": "to give us an algorithm\nthat solves Hamiltonian path", "start": 306.79, "duration": 3.06}, {"text": "in polynomial time?", "start": 309.85, "duration": 1.35}, {"text": "Of course, we could\nsolve Hamiltonian path", "start": 311.2, "duration": 3.24}, {"text": "with an exponential algorithm\nby trying all possible paths.", "start": 314.44, "duration": 4.14}, {"text": "And that will give\na correct algorithm,", "start": 318.58, "duration": 2.7}, {"text": "but there are exponentially many\ndifferent paths and trying them", "start": 321.28, "duration": 4.08}, {"text": "all will not give a\npolynomial time algorithm.", "start": 325.36, "duration": 2.83}, {"text": "So the interesting\nproblem is can we", "start": 328.19, "duration": 1.79}, {"text": "solve that without doing\nthat brute force searching", "start": 329.98, "duration": 3.09}, {"text": "through all possible paths.", "start": 333.07, "duration": 3.0}, {"text": "And that's a problem that\nno one knows the answer to.", "start": 336.07, "duration": 5.32}, {"text": "Despite lots of\neffort, people have not", "start": 341.39, "duration": 1.74}, {"text": "succeeded in finding\nan algorithm for that.", "start": 343.13, "duration": 2.32}, {"text": "But on the other hand,\nwe don't have any idea", "start": 345.45, "duration": 3.11}, {"text": "how do you prove there\nis no such algorithm.", "start": 348.56, "duration": 3.182}, {"text": "I mean, it's conceivable that\none could prove such a thing,", "start": 351.742, "duration": 2.458}, {"text": "but we just don't\nknow how to do it.", "start": 354.2, "duration": 3.19}, {"text": "And so, that problem is\nan unsolved problem and I", "start": 357.39, "duration": 6.59}, {"text": "just-- this isn't\nreally a note to myself.", "start": 363.98, "duration": 3.51}, {"text": "What's kind of\namazing, and this is", "start": 367.49, "duration": 1.92}, {"text": "what we're going to be showing\nover the next few lectures,", "start": 369.41, "duration": 2.58}, {"text": "that there would be very\nsurprising consequences if you", "start": 371.99, "duration": 3.9}, {"text": "could find a way to\nsolve Hamiltonian path", "start": 375.89, "duration": 3.09}, {"text": "in polynomial time.", "start": 378.98, "duration": 1.97}, {"text": "Because what that\nwould immediately yield", "start": 380.95, "duration": 3.27}, {"text": "is the polynomial time way of,\nsay, factoring large numbers", "start": 384.22, "duration": 3.99}, {"text": "or solving a large\nnumber of other problems", "start": 388.21, "duration": 3.0}, {"text": "that we don't know how to\nsolve in polynomial time.", "start": 391.21, "duration": 3.87}, {"text": "So as we mentioned,\nfactoring is a problem", "start": 395.08, "duration": 3.9}, {"text": "that we only know at\npresent how to solve", "start": 398.98, "duration": 2.19}, {"text": "with an exponential algorithm.", "start": 401.17, "duration": 2.43}, {"text": "And it doesn't seem\nto have anything", "start": 403.6, "duration": 1.5}, {"text": "to do with the\nHamiltonian path problem.", "start": 405.1, "duration": 2.82}, {"text": "Seem very different.", "start": 407.92, "duration": 1.29}, {"text": "But, yet, if you can\nsolve Hamiltonian path", "start": 409.21, "duration": 2.97}, {"text": "in polynomial time, then\nyou can factor numbers", "start": 412.18, "duration": 2.4}, {"text": "in polynomial time.", "start": 414.58, "duration": 1.42}, {"text": "And so, we'll see how\nto make that connection.", "start": 416.0, "duration": 3.8}, {"text": "That's what we're\nbuilding toward", "start": 419.8, "duration": 1.83}, {"text": "with the next few lectures.", "start": 421.63, "duration": 3.88}, {"text": "OK.", "start": 425.51, "duration": 1.75}, {"text": "So happy to take any comments\nand questions on that,", "start": 427.26, "duration": 4.19}, {"text": "or we'll just move on,\nif you have any questions", "start": 431.45, "duration": 3.63}, {"text": "on our little review.", "start": 435.08, "duration": 3.25}, {"text": "Well, send questions\nalong and we", "start": 438.33, "duration": 1.95}, {"text": "can stop at the end of various\nslides to try to answer them.", "start": 440.28, "duration": 4.95}, {"text": "And, of course,\nwrite to the TAs,", "start": 445.23, "duration": 2.34}, {"text": "who can take your questions\nwhile I'm lecturing.", "start": 447.57, "duration": 4.98}, {"text": "OK.", "start": 452.55, "duration": 1.86}, {"text": "So to start this\noff, we're going", "start": 454.41, "duration": 1.77}, {"text": "to have to talk about\nnon-deterministic complexity", "start": 456.18, "duration": 3.81}, {"text": "as a variation of\ndeterministic complexity.", "start": 459.99, "duration": 3.94}, {"text": "So first of all,\nall of the machines", "start": 463.93, "duration": 4.76}, {"text": "in this part of the course\nand the languages, everything", "start": 468.69, "duration": 2.79}, {"text": "is going to be decidable\nand all the machines", "start": 471.48, "duration": 2.13}, {"text": "are going to be deciders.", "start": 473.61, "duration": 1.06}, {"text": "So what do we mean when we have\na non-deterministic machine", "start": 474.67, "duration": 2.458}, {"text": "which is a decider?", "start": 477.128, "duration": 1.942}, {"text": "And that just simply means\nthat all of the branches--", "start": 479.07, "duration": 4.12}, {"text": "it's not just the machine\nhalts on every input,", "start": 483.19, "duration": 2.67}, {"text": "but all of the branches\nhalt on every input.", "start": 485.86, "duration": 3.63}, {"text": "So the non-deterministic\nmachine is non-deterministic,", "start": 489.49, "duration": 2.25}, {"text": "it has lots of\npossible branches.", "start": 491.74, "duration": 1.88}, {"text": "They all have to halt--", "start": 493.62, "duration": 2.16}, {"text": "all of them-- on every input.", "start": 495.78, "duration": 1.95}, {"text": "That's what makes a\nnon-deterministic machine", "start": 497.73, "duration": 1.93}, {"text": "a decider.", "start": 499.66, "duration": 1.1}, {"text": "And you're going to convert\na non-deterministic decider", "start": 500.76, "duration": 3.33}, {"text": "into a deterministic decider.", "start": 504.09, "duration": 2.4}, {"text": "But the question is, how much\ntime would that introduce?", "start": 506.49, "duration": 3.15}, {"text": "How much extra time\nis that going to cost?", "start": 509.64, "duration": 2.16}, {"text": "And the only way\nthat people know", "start": 511.8, "duration": 1.44}, {"text": "at the present time\nfor that conversion", "start": 513.24, "duration": 3.72}, {"text": "would be to do an\nexponential increase.", "start": 516.96, "duration": 4.26}, {"text": "Basically, to try all\npossible branches.", "start": 521.22, "duration": 2.13}, {"text": "And that's, of\ncourse, very slow.", "start": 523.35, "duration": 3.53}, {"text": "So first, let's\nunderstand what we", "start": 526.88, "duration": 5.16}, {"text": "mean by the time used by a\nnon-deterministic machine.", "start": 532.04, "duration": 3.93}, {"text": "And what we mean\nby the time used", "start": 535.97, "duration": 3.39}, {"text": "is, we're looking at\neach individual branch", "start": 539.36, "duration": 2.64}, {"text": "individually, separately.", "start": 542.0, "duration": 3.76}, {"text": "So a non-deterministic\nmachine, we'll say,", "start": 545.76, "duration": 3.38}, {"text": "runs in a certain amount of\ntime if all of the branches", "start": 549.14, "duration": 3.96}, {"text": "halt within that amount of time.", "start": 553.1, "duration": 4.01}, {"text": "So what we do not mean that\nthe total amount of usage,", "start": 557.11, "duration": 6.53}, {"text": "the total amount of effort\nby adding up all the branches", "start": 563.64, "duration": 3.51}, {"text": "is at most T of n.", "start": 567.15, "duration": 1.8}, {"text": "It's just that each branch\nindividually uses at most", "start": 568.95, "duration": 3.48}, {"text": "T of n.", "start": 572.43, "duration": 1.05}, {"text": "That's just going to\nbe our definition.", "start": 573.48, "duration": 1.9}, {"text": "And it's going to turn\nout to be the right way", "start": 575.38, "duration": 2.99}, {"text": "to look at this to\nget something useful.", "start": 578.37, "duration": 1.92}, {"text": "So now we're going to define\nthe analogous complexity", "start": 586.18, "duration": 11.54}, {"text": "class associated to\nnon-deterministic computation,", "start": 597.72, "duration": 4.23}, {"text": "which we'll call\nnon-deterministic time.", "start": 601.95, "duration": 2.73}, {"text": "So non-deterministic time T of\nn is the set of all languages", "start": 604.68, "duration": 5.78}, {"text": "that you can do with a\nnon-deterministic machine that", "start": 610.46, "duration": 3.24}, {"text": "runs in order T of n time.", "start": 613.7, "duration": 3.33}, {"text": "Just think back\nto the definition", "start": 617.03, "duration": 2.79}, {"text": "we had for deterministic\ncomplexity, the time class--", "start": 619.82, "duration": 4.71}, {"text": "or sometimes people\ncall it dtime", "start": 624.53, "duration": 1.71}, {"text": "to emphasize the difference.", "start": 626.24, "duration": 1.36}, {"text": "But let's just say we're\ncalling it in this course", "start": 627.6, "duration": 2.63}, {"text": "time versus ntime.", "start": 630.23, "duration": 1.96}, {"text": "So TIME[T(n)] is all of the\nlanguage that you can do with", "start": 632.19, "duration": 3.66}, {"text": "the one-tape Turing machine\nthat's deterministic.", "start": 635.85, "duration": 3.95}, {"text": "But this here is a\nnon-deterministic Turing", "start": 639.8, "duration": 2.22}, {"text": "machine for\nnon-deterministic time.", "start": 642.02, "duration": 4.45}, {"text": "So the picture that is\ngood to have in your head", "start": 646.47, "duration": 3.89}, {"text": "here would be if you\nthink of non-determinism", "start": 650.36, "duration": 5.43}, {"text": "in terms of a computation\ntree thinking of all", "start": 655.79, "duration": 3.09}, {"text": "the different branches\nof the non-determinism.", "start": 658.88, "duration": 3.9}, {"text": "All of those\nbranches have to halt", "start": 662.78, "duration": 2.76}, {"text": "and they have to halt\nwithin the time bound.", "start": 665.54, "duration": 3.68}, {"text": "So imagine, here,\nthis is T of n time.", "start": 669.22, "duration": 2.57}, {"text": "All of the branches have to halt\nwithin T of n steps for this,", "start": 671.79, "duration": 3.96}, {"text": "a non-deterministic Turing\nmachine to be running in T of n", "start": 675.75, "duration": 2.97}, {"text": "time and to be doing a language\nin the NTIME[T(n)] class.", "start": 678.72, "duration": 3.9}, {"text": "And by analogy with\nwhat we did before,", "start": 685.15, "duration": 2.85}, {"text": "the class NP is the\ncollection of all languages", "start": 688.0, "duration": 9.15}, {"text": "that you can do\nnon-deterministically", "start": 697.15, "duration": 2.16}, {"text": "in polynomial time.", "start": 699.31, "duration": 3.39}, {"text": "So it's the union over all\nof the ntime classes where", "start": 702.7, "duration": 4.82}, {"text": "the bound is polynomial.", "start": 707.52, "duration": 1.35}, {"text": "OK, so a lot of this\nshould look very familiar,", "start": 712.16, "duration": 3.72}, {"text": "but we've just added a\nbunch of non-deterministic", "start": 715.88, "duration": 3.48}, {"text": "and a bunch of Ns in place.", "start": 719.36, "duration": 2.94}, {"text": "But the definitions\nare very similar.", "start": 722.3, "duration": 3.87}, {"text": "And one of the motivations we\nhad for looking at the class P", "start": 726.17, "duration": 4.8}, {"text": "was that it did not depend\non the choice of model,", "start": 730.97, "duration": 4.29}, {"text": "as long as the model was\ndeterministic and reasonable.", "start": 735.26, "duration": 2.85}, {"text": "And the class NP is\nalso going to not", "start": 738.11, "duration": 3.93}, {"text": "depend on the\nchoice of model, as", "start": 742.04, "duration": 2.28}, {"text": "long as it's a reasonable\nnon-deterministic model.", "start": 744.32, "duration": 4.65}, {"text": "So it's again a\nvery natural class", "start": 748.97, "duration": 3.81}, {"text": "to look at from a\nmathematical standpoint.", "start": 752.78, "duration": 2.37}, {"text": "And it also captures something\ninteresting, kind of,", "start": 755.15, "duration": 4.53}, {"text": "from a practical\nstandpoint - which", "start": 759.68, "duration": 1.53}, {"text": "we're going to talk about\nover the next couple of slides", "start": 761.21, "duration": 2.49}, {"text": "- which is that it captures the\nproblems where you can easily", "start": 763.7, "duration": 3.63}, {"text": "verify when you're a\nmember of the language.", "start": 767.33, "duration": 5.78}, {"text": "OK, so we'll talk about that.", "start": 773.11, "duration": 1.26}, {"text": "But if you take, for example,\nthe Hamiltonian path problem.", "start": 774.37, "duration": 5.34}, {"text": "When you find a member\nof the language,", "start": 779.71, "duration": 3.13}, {"text": "so that is a graph that\ndoes have a Hamiltonian", "start": 782.84, "duration": 3.92}, {"text": "path from s to t,\nyou can easily verify", "start": 786.76, "duration": 3.9}, {"text": "that's true by simply\nexhibiting the path.", "start": 790.66, "duration": 3.8}, {"text": "Not all problems can be\nverified in that way.", "start": 794.46, "duration": 3.9}, {"text": "But the problems that are in\nNP have that special feature--", "start": 798.36, "duration": 4.32}, {"text": "that when you have a\nmember of the language,", "start": 802.68, "duration": 2.46}, {"text": "there's a way to verify\nthat you're a member.", "start": 805.14, "duration": 2.377}, {"text": "So we're going to talk about\nthat, because that's really", "start": 807.517, "duration": 2.333}, {"text": "the key to understanding NP--", "start": 809.85, "duration": 2.97}, {"text": "this notion of verification.", "start": 812.82, "duration": 3.11}, {"text": "OK, so let me go-- there\nwas a good question here.", "start": 815.93, "duration": 3.752}, {"text": "Let me just see if I\nwant to answer that.", "start": 819.682, "duration": 1.708}, {"text": "Yeah, I mean, this is a little\nbit of a longer question", "start": 824.33, "duration": 4.05}, {"text": "than I want to fully\nrespond to but--", "start": 828.38, "duration": 4.41}, {"text": "well, let's turn to my\nnext slide, which maybe", "start": 832.79, "duration": 2.64}, {"text": "sort bringing that out anyway.", "start": 835.43, "duration": 3.138}, {"text": "Actually, it's a couple\nof slides from now.", "start": 838.568, "duration": 1.792}, {"text": "But I'll get to that point.", "start": 840.36, "duration": 1.22}, {"text": "So let's look at Hamiltonian,\nthe hampath problem.", "start": 844.38, "duration": 2.9}, {"text": "And what I'm going to show is\nthe Hamiltonian path problem", "start": 847.28, "duration": 3.09}, {"text": "is in NP.", "start": 850.37, "duration": 1.13}, {"text": "And I'm going to walk\nyou through this one", "start": 851.5, "duration": 1.75}, {"text": "kind of slowly.", "start": 853.25, "duration": 1.62}, {"text": "So the Hamiltonian\npath problem, remember,", "start": 854.87, "duration": 1.8}, {"text": "we don't know if it's\nin P. But it is in NP.", "start": 856.67, "duration": 5.67}, {"text": "So it's in one of these.", "start": 862.34, "duration": 1.32}, {"text": "You can solve Hamiltonian\npath in polynomial time", "start": 863.66, "duration": 3.78}, {"text": "if you're a\nnon-deterministic machine.", "start": 867.44, "duration": 1.89}, {"text": "Why is that?", "start": 872.2, "duration": 1.15}, {"text": "Well, it's because of the\nparallelism of non-determinism,", "start": 873.35, "duration": 8.46}, {"text": "which allows you\nto kind of check", "start": 881.81, "duration": 1.4}, {"text": "all of the paths on\ndifferent branches.", "start": 883.21, "duration": 3.72}, {"text": "So let me first describe how I\nwould write down the algorithm.", "start": 886.93, "duration": 5.61}, {"text": "And then, we'll kind of try\nto unpack that and understand", "start": 892.54, "duration": 3.66}, {"text": "how that actually looks in\nterms of the Turing machine's", "start": 896.2, "duration": 5.43}, {"text": "computation.", "start": 901.63, "duration": 2.03}, {"text": "So first of all, taking the\nHamiltonian path problem,", "start": 903.66, "duration": 4.45}, {"text": "you are given an input\nnow, which is a graph", "start": 908.11, "duration": 2.67}, {"text": "and the nodes s and t where\nI'm trying to figure out", "start": 910.78, "duration": 3.27}, {"text": "is that Hamiltonian path--", "start": 914.05, "duration": 2.01}, {"text": "again, which visits\nall the nodes,", "start": 916.06, "duration": 2.28}, {"text": "which takes you from s to t.", "start": 918.34, "duration": 3.75}, {"text": "And we're trying to make now\na non-deterministic machine,", "start": 922.09, "duration": 3.78}, {"text": "which is going to accept all\nsuch inputs which have a path.", "start": 925.87, "duration": 8.16}, {"text": "So the way this\nnon-deterministic machine", "start": 934.03, "duration": 2.24}, {"text": "is going to work\nis it's basically", "start": 936.27, "duration": 2.79}, {"text": "going to use its non-determinism\nto try all possible paths", "start": 939.06, "duration": 5.49}, {"text": "on the different branches.", "start": 944.55, "duration": 2.75}, {"text": "And the way I'll\nspecify that is to say,", "start": 947.3, "duration": 3.06}, {"text": "non-deterministically,\nwe're going", "start": 950.36, "duration": 1.71}, {"text": "to write down a candidate\npath which is just", "start": 952.07, "duration": 4.32}, {"text": "going to be a\nsequence of m nodes,", "start": 956.39, "duration": 3.21}, {"text": "where we will say that's\nthe total number of nodes", "start": 959.6, "duration": 2.31}, {"text": "of the graph.", "start": 961.91, "duration": 0.81}, {"text": "Remember, a Hamiltonian path,\nbecause it visits every node,", "start": 962.72, "duration": 3.75}, {"text": "is going to be a path with\nexactly m nodes in it.", "start": 966.47, "duration": 2.85}, {"text": "So I'm going to write\ndown a sequence of nodes", "start": 971.903, "duration": 1.917}, {"text": "as a candidate path.", "start": 973.82, "duration": 2.41}, {"text": "And I'm\nnon-deterministically going", "start": 976.23, "duration": 1.8}, {"text": "to choose every possible\nsequence in this way.", "start": 978.03, "duration": 4.29}, {"text": "If you'd like to think\nof the guessing metaphor", "start": 985.37, "duration": 2.31}, {"text": "for non-determinism,\nyou can think", "start": 987.68, "duration": 2.37}, {"text": "of the non-deterministic\nmachine as guessing", "start": 990.05, "duration": 3.09}, {"text": "the right path, which is going\nto be the Hamiltonian path", "start": 993.14, "duration": 3.18}, {"text": "from s to t.", "start": 996.32, "duration": 0.78}, {"text": "But I think for\nthis discussion, it", "start": 997.1, "duration": 2.43}, {"text": "might be more helpful\nto think about all", "start": 999.53, "duration": 2.31}, {"text": "of the different branches\nof the non-determinism.", "start": 1001.84, "duration": 4.403}, {"text": "Because that's\nperhaps more useful", "start": 1006.243, "duration": 1.417}, {"text": "when we're thinking about\nit in terms of the time.", "start": 1007.66, "duration": 2.52}, {"text": "I think you'll get used\nto thinking about it.", "start": 1010.18, "duration": 2.34}, {"text": "You should be used\nto thinking about it", "start": 1012.52, "duration": 1.86}, {"text": "in many of the different\nways. but maybe", "start": 1014.38, "duration": 2.16}, {"text": "the computation\ntree of all branches", "start": 1016.54, "duration": 2.67}, {"text": "might be the more\nhelpful one here.", "start": 1019.21, "duration": 2.38}, {"text": "So now after we write\ndown a candidate path", "start": 1021.59, "duration": 3.749}, {"text": "sequence of nodes,\nnow I have to check", "start": 1025.339, "duration": 3.921}, {"text": "that this really is a path.", "start": 1029.26, "duration": 3.559}, {"text": "And the way I'm going to do that\nis to say, well, now if I have", "start": 1032.819, "duration": 2.76}, {"text": "just a sequence of\nnodes written down, what", "start": 1035.579, "duration": 2.191}, {"text": "does it mean for it to be a\nHamiltonian path from s to t?", "start": 1037.77, "duration": 3.66}, {"text": "Well, it better start with s\nand end with t, first of all.", "start": 1041.43, "duration": 4.98}, {"text": "And we have to make sure\nthat every step of the way", "start": 1046.41, "duration": 4.48}, {"text": "is actually an edge.", "start": 1050.89, "duration": 2.7}, {"text": "So each pair vi to vi plus 1\nhas to be an edge in the graph.", "start": 1053.59, "duration": 5.515}, {"text": "Otherwise, that\nsequence of nodes", "start": 1059.105, "duration": 1.375}, {"text": "is not going to be a legitimate\nHamiltonian path from s to t.", "start": 1060.48, "duration": 3.9}, {"text": "And it has to be a simple path.", "start": 1064.38, "duration": 2.31}, {"text": "You can't be repeating nodes.", "start": 1066.69, "duration": 1.56}, {"text": "These four conditions\ntogether will", "start": 1071.1, "duration": 1.92}, {"text": "guarantee that we have\na Hamiltonian path.", "start": 1073.02, "duration": 3.45}, {"text": "And once we have written\ndown a candidate sequence,", "start": 1076.47, "duration": 5.05}, {"text": "we can just check that the\nsequence actually works.", "start": 1081.52, "duration": 2.43}, {"text": "At this second stage\nof the algorithm,", "start": 1086.75, "duration": 5.07}, {"text": "non-determinism isn't necessary.", "start": 1091.82, "duration": 2.11}, {"text": "This is going to be a\ndeterministic phase.", "start": 1093.93, "duration": 2.36}, {"text": "But stage one of\nthe algorithm is", "start": 1096.29, "duration": 3.03}, {"text": "going to be a non-deterministic\nphase where it's writing down", "start": 1099.32, "duration": 2.94}, {"text": "all possible paths.", "start": 1102.26, "duration": 1.68}, {"text": "Now, I'm going to try\nto unpack that for you", "start": 1103.94, "duration": 2.4}, {"text": "so you can actually visualize\nhow the machine is doing this.", "start": 1106.34, "duration": 3.78}, {"text": "And then, of course,\nyou know on each branch", "start": 1112.81, "duration": 2.94}, {"text": "of the non-determinism,\nyou're going", "start": 1115.75, "duration": 1.98}, {"text": "to check to see whether the\nconditions have been satisfied.", "start": 1117.73, "duration": 3.72}, {"text": "And on that branch, if the\nconditions were not satisfied,", "start": 1121.45, "duration": 4.41}, {"text": "that branch is going to reject.", "start": 1125.86, "duration": 1.89}, {"text": "Of course, one of the other\nbranches might yet accept,", "start": 1127.75, "duration": 2.25}, {"text": "so that's how\nnon-determinism works.", "start": 1130.0, "duration": 4.96}, {"text": "OK?", "start": 1134.96, "duration": 0.5}, {"text": "So I'd like to visualize\nthis as the tree", "start": 1135.46, "duration": 16.56}, {"text": "of the different branches of the\ncomputation of m on its input.", "start": 1152.02, "duration": 6.91}, {"text": "So here is our non-deterministic\nTuring machine.", "start": 1158.93, "duration": 4.62}, {"text": "Which?", "start": 1163.55, "duration": 0.5}, {"text": "This one.", "start": 1164.05, "duration": 1.35}, {"text": "And you provide it with\nthe input G, s, and t.", "start": 1165.4, "duration": 5.64}, {"text": "And how is the machine\nactually working?", "start": 1171.04, "duration": 3.64}, {"text": "So when I say\nnon-deterministically write", "start": 1174.68, "duration": 2.3}, {"text": "down a sequence of m nodes--", "start": 1176.98, "duration": 3.33}, {"text": "look, this is getting into\na little bit more detail", "start": 1180.31, "duration": 4.2}, {"text": "than I would normally\nthink about it,", "start": 1184.51, "duration": 1.92}, {"text": "because we try to tend to think\nabout things at a higher level.", "start": 1186.43, "duration": 2.88}, {"text": "But just to get us\nstarted, I think", "start": 1189.31, "duration": 2.94}, {"text": "it's good to think about\nthis with a bit more detail.", "start": 1192.25, "duration": 4.94}, {"text": "So let's think of the m nodes\nas being numbered, having", "start": 1197.19, "duration": 4.91}, {"text": "labels numbered 1 through m.", "start": 1202.1, "duration": 3.532}, {"text": "And I'm going to think\nabout them being labeled", "start": 1205.632, "duration": 1.958}, {"text": "by their binary sequences.", "start": 1207.59, "duration": 2.37}, {"text": "We're going to write\ndown those nodes.", "start": 1209.96, "duration": 1.8}, {"text": "That's how the machine is\ngoing to have to operate", "start": 1211.76, "duration": 2.82}, {"text": "on those numbers for the nodes.", "start": 1214.58, "duration": 2.58}, {"text": "We'll think about them as\nbeing written in binary.", "start": 1217.16, "duration": 2.7}, {"text": "And now, as the machine is\ngoing to be writing down,", "start": 1219.86, "duration": 3.06}, {"text": "let's say, the node v1.", "start": 1222.92, "duration": 3.31}, {"text": "So it's\nnon-deterministically picking", "start": 1226.23, "duration": 2.04}, {"text": "the first node of the sequence.", "start": 1228.27, "duration": 1.86}, {"text": "What does that\nactually mean in terms", "start": 1230.13, "duration": 2.34}, {"text": "of the step-by-step processing\nof the Turing machine m?", "start": 1232.47, "duration": 8.67}, {"text": "Well, it's going to be\nguessing via a sequence", "start": 1241.14, "duration": 4.53}, {"text": "of non-deterministic moves,\nthe bits that represent", "start": 1245.67, "duration": 7.15}, {"text": "the number of the node for v1.", "start": 1252.82, "duration": 4.83}, {"text": "For example, v1 might be the\nnode number 5 in the graph.", "start": 1257.65, "duration": 6.02}, {"text": "Of course,\nnon-deterministically,", "start": 1263.67, "duration": 1.56}, {"text": "the machine is on\ndifferent branches,", "start": 1265.23, "duration": 1.83}, {"text": "picking all different\npossible choices for v1.", "start": 1267.06, "duration": 3.42}, {"text": "Those are going to be the\ndifferent branches here.", "start": 1270.48, "duration": 3.75}, {"text": "But one of the\nbranches might be--", "start": 1274.23, "duration": 3.03}, {"text": "and what I'm really\nrepresenting here, these are--", "start": 1277.26, "duration": 3.893}, {"text": "I probably could have written\nthis down on the slide", "start": 1281.153, "duration": 2.167}, {"text": "here in tiny font.", "start": 1283.32, "duration": 2.07}, {"text": "But these are like\nthe 0, 1 choices.", "start": 1285.39, "duration": 3.048}, {"text": "That's why it's sort\nof a binary tree", "start": 1288.438, "duration": 1.542}, {"text": "here for writing\ndown the bits of v1.", "start": 1289.98, "duration": 7.24}, {"text": "So here maybe this could be\n101, representing the number", "start": 1297.22, "duration": 6.81}, {"text": "5, which might be the very\nfirst node that I'm writing down", "start": 1304.03, "duration": 4.47}, {"text": "in my sequence.", "start": 1308.5, "duration": 1.75}, {"text": "Some other branch is going\nto write down node number 6.", "start": 1310.25, "duration": 2.34}, {"text": "Some other branch is going\nto write down node number 2.", "start": 1312.59, "duration": 2.37}, {"text": "Because\nnon-deterministically, we're", "start": 1314.96, "duration": 1.5}, {"text": "making all possible\nchoices for v1.", "start": 1316.46, "duration": 2.4}, {"text": "That's what I'm trying to\nshow in this little part", "start": 1318.86, "duration": 3.09}, {"text": "of the computation\nof m on this input.", "start": 1321.95, "duration": 5.04}, {"text": "So then, after it's\nfinished writing down", "start": 1326.99, "duration": 3.92}, {"text": "the description of the\nnode for its choice for v1,", "start": 1330.91, "duration": 6.75}, {"text": "it goes down to\nchoose what v2 is.", "start": 1337.66, "duration": 2.97}, {"text": "Again, non-deterministically,\nso there's", "start": 1340.63, "duration": 1.71}, {"text": "going to be more branches for\neach possible choice of v2.", "start": 1342.34, "duration": 7.99}, {"text": "And so on, node after node.", "start": 1350.33, "duration": 3.93}, {"text": "Then, it's going to finally\nget to the last node, vm.", "start": 1354.26, "duration": 2.55}, {"text": "It's going to write down\nlots of choices for vm.", "start": 1356.81, "duration": 2.97}, {"text": "And at this point here, we\nhave completed the first stage", "start": 1359.78, "duration": 5.04}, {"text": "of the algorithm.", "start": 1364.82, "duration": 0.94}, {"text": "Now, there's some\nhuge tree of all", "start": 1365.76, "duration": 2.63}, {"text": "of the possible choices\nfor the V's that", "start": 1368.39, "duration": 2.61}, {"text": "have shown up at this point.", "start": 1371.0, "duration": 2.4}, {"text": "OK?", "start": 1373.4, "duration": 1.58}, {"text": "And now, we're going to\nmove into the second phase.", "start": 1374.98, "duration": 3.87}, {"text": "So following this,\nthere's going to be,", "start": 1378.85, "duration": 4.32}, {"text": "here, a bunch of deterministic\nsteps of the machine.", "start": 1383.17, "duration": 8.92}, {"text": "So no more branching\nis needed because here,", "start": 1392.09, "duration": 5.1}, {"text": "we've written down--\nat this point,", "start": 1397.19, "duration": 2.55}, {"text": "we've reached a point in\neach of those locations,", "start": 1399.74, "duration": 5.67}, {"text": "where we've chosen\none of the candidates,", "start": 1405.41, "duration": 3.27}, {"text": "one of the possible branches--", "start": 1408.68, "duration": 2.22}, {"text": "one of the possible paths\nthrough the graph, I'm sorry.", "start": 1410.9, "duration": 6.45}, {"text": "So here, we're guessing\npotential paths in the graph.", "start": 1417.35, "duration": 6.61}, {"text": "And now, we're going to\ncheck that we actually", "start": 1423.96, "duration": 2.51}, {"text": "have picked a path that's a\nHamiltonian path from s to t.", "start": 1426.47, "duration": 5.85}, {"text": "OK?", "start": 1432.32, "duration": 0.51}, {"text": "So each one of these\nbranches is now", "start": 1432.83, "duration": 2.46}, {"text": "going to end up\naccepting or rejecting.", "start": 1435.29, "duration": 1.83}, {"text": "And the whole\noverall computation", "start": 1437.12, "duration": 1.92}, {"text": "is going to accept if\nat least one of them", "start": 1439.04, "duration": 2.31}, {"text": "ended up accepting,\nwhich means you actually", "start": 1441.35, "duration": 2.22}, {"text": "found a Hamiltonian path.", "start": 1443.57, "duration": 2.84}, {"text": "OK?", "start": 1446.41, "duration": 0.5}, {"text": "I don't know if that's helpful\nto you or not, but that is--", "start": 1446.91, "duration": 5.7}, {"text": "if there's any questions\non this, let's see.", "start": 1452.61, "duration": 3.85}, {"text": "Question on is there something--", "start": 1456.46, "duration": 2.605}, {"text": "trying to draw a connection here\nbetween this and computation", "start": 1463.75, "duration": 4.92}, {"text": "histories.", "start": 1468.67, "duration": 2.16}, {"text": "I mean, there is a pattern\nhere that does come up often", "start": 1470.83, "duration": 3.48}, {"text": "where you want to check\nthat something starts right,", "start": 1474.31, "duration": 3.84}, {"text": "ends right, and that all of\nthe intermediates are right.", "start": 1478.15, "duration": 2.88}, {"text": "So I think there is some\ndeeper connection here.", "start": 1481.03, "duration": 7.38}, {"text": "Probably too hard\nto explain but that", "start": 1488.41, "duration": 3.69}, {"text": "has something to do with this\nHamiltonian path problem.", "start": 1492.1, "duration": 3.39}, {"text": "Why are we using\nbinary representation?", "start": 1498.3, "duration": 2.09}, {"text": "Well, we're going\nto talk about--", "start": 1500.39, "duration": 3.987}, {"text": "the algorithm would\nhave worked equally well", "start": 1504.377, "duration": 1.833}, {"text": "if we used base three\nor base five or base 20", "start": 1506.21, "duration": 6.42}, {"text": "as a way of writing down\nour labels for the nodes.", "start": 1512.63, "duration": 5.37}, {"text": "But in a sense,\nit doesn't matter.", "start": 1518.0, "duration": 3.74}, {"text": "The alphabet has to be finite\nthough, so that's true.", "start": 1521.74, "duration": 3.09}, {"text": "I mean, that's why it's not just\nin a single step of the Turing", "start": 1524.83, "duration": 3.69}, {"text": "machine that you would pick\nthe node the choice for v1.", "start": 1528.52, "duration": 7.17}, {"text": "You really have to go\nto a sequence of steps.", "start": 1535.69, "duration": 2.13}, {"text": "Because each of the\nbranches of the machine", "start": 1537.82, "duration": 4.29}, {"text": "only has a fixed\nnumber of choices.", "start": 1542.11, "duration": 2.08}, {"text": "So you can't, in a single\nstep of the Turing machine,", "start": 1544.19, "duration": 3.29}, {"text": "pick all the different\npossibilities for v1.", "start": 1547.48, "duration": 2.318}, {"text": "That has to go\nthrough a sequence.", "start": 1549.798, "duration": 1.417}, {"text": "OK.", "start": 1554.09, "duration": 0.5}, {"text": "Now, let me do a second example,\nthe problem of composites.", "start": 1559.15, "duration": 4.62}, {"text": "So the language\nof all composites", "start": 1563.77, "duration": 3.24}, {"text": "are all of the non-primes,\nwritten as binary numbers", "start": 1567.01, "duration": 3.12}, {"text": "again.", "start": 1570.13, "duration": 0.61}, {"text": "So we'll talk about the base and\nthe representation in a second.", "start": 1570.74, "duration": 3.8}, {"text": "But just imagine these\nare all of the numbers", "start": 1574.54, "duration": 3.87}, {"text": "that are not prime.", "start": 1578.41, "duration": 1.92}, {"text": "And that language is easily\nseen to be a member of NP.", "start": 1580.33, "duration": 3.93}, {"text": "Here is, again, the\nalgorithm for that.", "start": 1586.92, "duration": 2.19}, {"text": "Given x, we want to accept x,\nif it's not a prime number.", "start": 1592.45, "duration": 6.01}, {"text": "So it has some\nnon-trivial factor.", "start": 1598.46, "duration": 1.865}, {"text": "So first, the way the\nnon-deterministic machine", "start": 1605.02, "duration": 2.64}, {"text": "is going to work is it's\ngoing to guess that factor.", "start": 1607.66, "duration": 2.32}, {"text": "So non-deterministically,\nit's going", "start": 1609.98, "duration": 1.55}, {"text": "to try every possible factor.", "start": 1611.53, "duration": 3.78}, {"text": "Y is going to be a\nnumber between 1 and x.", "start": 1615.31, "duration": 3.53}, {"text": "But not including 1.", "start": 1618.84, "duration": 2.22}, {"text": "You have to be an\ninteresting factor,", "start": 1621.06, "duration": 1.68}, {"text": "so not including one\nin the number itself.", "start": 1622.74, "duration": 2.47}, {"text": "So something\nstrictly in between.", "start": 1625.21, "duration": 2.52}, {"text": "And we're going to then--", "start": 1627.73, "duration": 1.17}, {"text": "after we've\nnon-deterministically chosen y,", "start": 1628.9, "duration": 3.02}, {"text": "then we're going to test to\nsee if y is really a factor.", "start": 1631.92, "duration": 6.34}, {"text": "So we'll see if y divides evenly\ninto x with a remainder of 0.", "start": 1638.26, "duration": 5.696}, {"text": "If that branch successfully\npicked the right y,", "start": 1643.956, "duration": 3.154}, {"text": "it's going to accept.", "start": 1647.11, "duration": 2.29}, {"text": "And some other branch where it\nmight have picked the wrong y,", "start": 1649.4, "duration": 3.42}, {"text": "will not.", "start": 1652.82, "duration": 1.29}, {"text": "And if x is really\na composite number,", "start": 1654.11, "duration": 3.69}, {"text": "some branch will\nfind the factor.", "start": 1657.8, "duration": 3.66}, {"text": "Now, the base doesn't matter.", "start": 1661.46, "duration": 2.0}, {"text": "Could have used base 10, because\nyou can convert from one base", "start": 1663.46, "duration": 4.7}, {"text": "to another.", "start": 1668.16, "duration": 1.3}, {"text": "So this is really in terms\nof our representation", "start": 1669.46, "duration": 2.87}, {"text": "of the number.", "start": 1672.33, "duration": 1.86}, {"text": "But I do want to make one\npoint here, that changing--", "start": 1674.19, "duration": 3.987}, {"text": "we don't want to write\nthe number in unary--", "start": 1678.177, "duration": 1.833}, {"text": "writing the number of\nk as a sequence of k1s.", "start": 1683.4, "duration": 4.29}, {"text": "That's not really a base.", "start": 1687.69, "duration": 2.29}, {"text": "That's just an exponential\nrepresentation for the number", "start": 1689.98, "duration": 2.69}, {"text": "and that changes the game.", "start": 1692.67, "duration": 1.89}, {"text": "Because if you make the\ninput exponentially larger,", "start": 1694.56, "duration": 5.88}, {"text": "then it's going to change\nwhether the algorithm", "start": 1700.44, "duration": 4.35}, {"text": "relative to that exponentially\nlarger input is polynomial", "start": 1704.79, "duration": 3.54}, {"text": "or not.", "start": 1708.33, "duration": 1.23}, {"text": "So an algorithm that might have\nbeen exponential originally", "start": 1709.56, "duration": 5.352}, {"text": "when the number's\nwritten in binary", "start": 1714.912, "duration": 1.458}, {"text": "might become polynomial if the\nnumbers are written in unary.", "start": 1716.37, "duration": 2.5}, {"text": "And I do want to\nmention as a side note,", "start": 1721.64, "duration": 1.98}, {"text": "that the composites language--", "start": 1723.62, "duration": 3.24}, {"text": "or primes, for that matter--", "start": 1726.86, "duration": 1.86}, {"text": "both are NP.", "start": 1728.72, "duration": 3.96}, {"text": "But we won't cover that.", "start": 1732.68, "duration": 1.5}, {"text": "So whereas the Hamiltonian\npath problem is not", "start": 1734.18, "duration": 4.11}, {"text": "known whether it's NP, the\nprimes and composites problem", "start": 1738.29, "duration": 4.2}, {"text": "are NP.", "start": 1742.49, "duration": 1.95}, {"text": "So that was known.", "start": 1744.44, "duration": 0.75}, {"text": "That was actually a very\nbig result in the field.", "start": 1745.19, "duration": 2.94}, {"text": "Solved by folks at one of the\nIndian Institute of Technology", "start": 1748.13, "duration": 7.89}, {"text": "back about almost\n20 years ago now.", "start": 1756.02, "duration": 2.671}, {"text": "So let's turn here, to\ntrying to get an intuitive", "start": 1763.44, "duration": 3.87}, {"text": "feeling for P and NP.", "start": 1767.31, "duration": 1.44}, {"text": "And we'll return now to this\nnotion of NP corresponding", "start": 1768.75, "duration": 4.41}, {"text": "to easy verifiability.", "start": 1773.16, "duration": 1.65}, {"text": "NP are the languages where you\ncan easily verify membership", "start": 1778.8, "duration": 3.69}, {"text": "quickly.", "start": 1782.49, "duration": 1.14}, {"text": "I'll try to explain\nwhat that means.", "start": 1783.63, "duration": 2.07}, {"text": "In contrast, P are the languages\nwhere you can test membership", "start": 1785.7, "duration": 4.83}, {"text": "quickly.", "start": 1790.53, "duration": 1.29}, {"text": "By quickly, I'm using\npolynomial time.", "start": 1791.82, "duration": 6.12}, {"text": "That's going to be,\nfor us, that's what", "start": 1797.94, "duration": 3.21}, {"text": "quickly means in this course.", "start": 1801.15, "duration": 1.62}, {"text": "In the case of the\nHamiltonian path problem,", "start": 1807.65, "duration": 4.23}, {"text": "the way you verify\nthe membership", "start": 1811.88, "duration": 2.1}, {"text": "is you give the path.", "start": 1813.98, "duration": 2.55}, {"text": "In the case of the\ncomposites, the way", "start": 1816.53, "duration": 1.708}, {"text": "you verify the membership\nis you give the factor.", "start": 1818.238, "duration": 2.042}, {"text": "In those two cases,\nand in general,", "start": 1822.96, "duration": 4.39}, {"text": "when we have a\nproblem that's in NP,", "start": 1827.35, "duration": 2.57}, {"text": "we think of this\nverification as having--", "start": 1829.92, "duration": 5.43}, {"text": "we give it a special name,\ncalled a certificate,", "start": 1835.35, "duration": 2.91}, {"text": "or sometimes a\nshort certificate,", "start": 1838.26, "duration": 2.28}, {"text": "to emphasize the polynomiality\nof the certificate.", "start": 1840.54, "duration": 3.33}, {"text": "It's like a way of\nproving that you're", "start": 1843.87, "duration": 2.73}, {"text": "a member of the language.", "start": 1846.6, "duration": 1.215}, {"text": "In the case of COMPOSITES,\nthe proof is the factor.", "start": 1851.05, "duration": 3.5}, {"text": "In the case of\nHAMPATH, the proof", "start": 1854.55, "duration": 1.86}, {"text": "is the path, the\nHamiltonian path.", "start": 1856.41, "duration": 4.67}, {"text": "Contrast that, for example,\nif you had a prime number.", "start": 1861.08, "duration": 3.045}, {"text": "Proving a number is composite\nis easy because you just", "start": 1867.57, "duration": 2.66}, {"text": "exhibit the factor.", "start": 1870.23, "duration": 1.74}, {"text": "How would you prove\nthat a number is prime?", "start": 1871.97, "duration": 3.5}, {"text": "What's the short\ncertificate of proving", "start": 1875.47, "duration": 4.74}, {"text": "that some number has no factor?", "start": 1880.21, "duration": 2.94}, {"text": "That's not so obvious.", "start": 1883.15, "duration": 2.38}, {"text": "In fact, there are\nways of doing it,", "start": 1885.53, "duration": 1.5}, {"text": "which I'm not going to get\ninto in the case of testing", "start": 1887.03, "duration": 2.87}, {"text": "of numbers prime.", "start": 1889.9, "duration": 2.01}, {"text": "And now it's even known to be\nin P, so that's even better.", "start": 1891.91, "duration": 4.56}, {"text": "But there's no obvious way\nof proving that a number is", "start": 1896.47, "duration": 3.95}, {"text": "prime with a short certificate.", "start": 1900.42, "duration": 2.16}, {"text": "This concept of\nbeing able to verify", "start": 1905.19, "duration": 3.66}, {"text": "when you are a member\nof the language, that's", "start": 1908.85, "duration": 2.28}, {"text": "key to understanding NP.", "start": 1911.13, "duration": 3.74}, {"text": "That's the intuition you\nneed to develop and hopefully", "start": 1914.87, "duration": 3.3}, {"text": "take away from today's\nlecture, or at least", "start": 1918.17, "duration": 2.28}, {"text": "by thinking about it,\nreading the book, and so on.", "start": 1920.45, "duration": 3.12}, {"text": "If you compare these\ntwo classes, P and NP.", "start": 1927.33, "duration": 4.206}, {"text": "P, first of all, is going\nto be a subset of NP,", "start": 1931.536, "duration": 3.624}, {"text": "both in terms of the\nway we defined it", "start": 1935.16, "duration": 2.13}, {"text": "because, deterministic\nmachines are", "start": 1937.29, "duration": 1.95}, {"text": "a special case of\nnon-deterministic machines.", "start": 1939.24, "duration": 3.43}, {"text": "But also if you want to think\nabout testing membership,", "start": 1942.67, "duration": 2.93}, {"text": "if you can test\nmembership easily", "start": 1945.6, "duration": 2.1}, {"text": "then you can certainly verify\nit in terms of the certificate.", "start": 1947.7, "duration": 3.242}, {"text": "You don't even need it.", "start": 1950.942, "duration": 0.958}, {"text": "The certificate is\nirrelevant at that point.", "start": 1951.9, "duration": 1.86}, {"text": "Because whatever\nthe certificate is,", "start": 1953.76, "duration": 2.1}, {"text": "you can still test\nyourself whether the input", "start": 1955.86, "duration": 4.38}, {"text": "is in the language or not.", "start": 1960.24, "duration": 1.74}, {"text": "The big question,\nas I mentioned,", "start": 1967.01, "duration": 1.6}, {"text": "is whether these two\nclasses are the same.", "start": 1968.61, "duration": 3.03}, {"text": "So does being able to verify\nmembership quickly, say", "start": 1971.64, "duration": 5.24}, {"text": "with one of these certificates,\nallow you to dispense", "start": 1976.88, "duration": 3.09}, {"text": "with the certificate?", "start": 1979.97, "duration": 0.93}, {"text": "Not even need a\ncertificate and just test", "start": 1980.9, "duration": 1.95}, {"text": "it for yourself whether\nyou're in the language.", "start": 1982.85, "duration": 3.42}, {"text": "And do that in polynomial time.", "start": 1986.27, "duration": 4.3}, {"text": "That's the question.", "start": 1990.57, "duration": 1.74}, {"text": "For a problem like\nHamiltonian path,", "start": 1992.31, "duration": 4.27}, {"text": "do you need to\nsearch for the answer", "start": 1996.58, "duration": 2.7}, {"text": "if you're doing it\ndeterministically?", "start": 1999.28, "duration": 1.77}, {"text": "Or can you somehow\navoid that and just", "start": 2001.05, "duration": 5.52}, {"text": "come up with the answer\ndirectly with a polynomial time", "start": 2006.57, "duration": 4.38}, {"text": "solution?", "start": 2010.95, "duration": 1.83}, {"text": "Nobody knows the answer to that.", "start": 2012.78, "duration": 2.52}, {"text": "And it goes back, at this\npoint, quite a long time.", "start": 2015.3, "duration": 2.4}, {"text": "It's almost 60 years now.", "start": 2017.7, "duration": 1.65}, {"text": "That problem has\nbeen around 60 years.", "start": 2023.1, "duration": 3.64}, {"text": "No, that would be 50 years.", "start": 2026.74, "duration": 1.29}, {"text": "No, 50 years, almost 50 years.", "start": 2028.03, "duration": 1.8}, {"text": "Most people believe that\nP is different from NP.", "start": 2036.77, "duration": 2.34}, {"text": "In other words, that\nthere are problems in P--", "start": 2039.11, "duration": 2.25}, {"text": "in NP which are not\nin P. A candidate", "start": 2041.36, "duration": 3.72}, {"text": "would be the Hamiltonian\npath problem.", "start": 2045.08, "duration": 3.07}, {"text": "But it seems to be very\nhard to prove that.", "start": 2048.15, "duration": 4.08}, {"text": "And part of the\nreason is, how do you", "start": 2052.23, "duration": 1.759}, {"text": "prove that a problem\nlike Hamiltonian path", "start": 2053.989, "duration": 3.841}, {"text": "does not have a\npolynomial time algorithm.", "start": 2057.83, "duration": 3.869}, {"text": "It's very tricky to do\nthat, because the class", "start": 2061.699, "duration": 2.221}, {"text": "of polynomial time algorithms\nis a very rich class.", "start": 2063.92, "duration": 2.61}, {"text": "Polynomial time algorithms\nare very powerful.", "start": 2066.53, "duration": 3.6}, {"text": "And to try to prove--\nthere's no clever way", "start": 2070.13, "duration": 2.54}, {"text": "of solving the\nHamiltonian path problem.", "start": 2072.67, "duration": 2.549}, {"text": "It just seems to be beyond\nour present day mathematics.", "start": 2075.219, "duration": 3.232}, {"text": "I believe someday somebody's\ngoing to solve it.", "start": 2078.451, "duration": 1.958}, {"text": "But so far, no\none has succeeded.", "start": 2080.409, "duration": 5.526}, {"text": "So what I thought\nwe would do is--", "start": 2085.935, "duration": 2.005}, {"text": "I think I have a check-in here.", "start": 2087.94, "duration": 1.92}, {"text": "Yes.", "start": 2089.86, "duration": 1.049}, {"text": "And then we'll stop for a break.", "start": 2090.909, "duration": 1.366}, {"text": "Let's look at the complementary\nproblem, HAMPATH complement.", "start": 2094.78, "duration": 4.5}, {"text": "You're in the language now\nif you don't have a path.", "start": 2103.66, "duration": 4.52}, {"text": "So is that complementary\nproblem in NP?", "start": 2108.18, "duration": 2.504}, {"text": "For that to be\nthe case, we would", "start": 2115.39, "duration": 2.13}, {"text": "need to have short certificates\nof when a graph does not", "start": 2117.52, "duration": 5.19}, {"text": "have a Hamiltonian path.", "start": 2122.71, "duration": 3.36}, {"text": "I leave it to you.", "start": 2129.5, "duration": 1.04}, {"text": "There are three choices.", "start": 2130.54, "duration": 1.0}, {"text": "OK?", "start": 2134.33, "duration": 2.27}, {"text": "Going to stop here, so make\nsure you get your participation", "start": 2136.6, "duration": 3.06}, {"text": "credit here.", "start": 2139.66, "duration": 0.78}, {"text": "I'm going to end\nthe polling now.", "start": 2142.98, "duration": 3.255}, {"text": "Interesting.", "start": 2146.235, "duration": 0.5}, {"text": "[LAUGHS] So the\nmajority is wrong.", "start": 2146.735, "duration": 2.325}, {"text": "Well, not wrong, we don't know.", "start": 2149.06, "duration": 1.73}, {"text": "I think the only fair\nanswer to this question", "start": 2156.95, "duration": 1.95}, {"text": "is C. Because we don't\nknow whether or not", "start": 2158.9, "duration": 5.4}, {"text": "we can give short\ncertificates for a graph", "start": 2164.3, "duration": 2.07}, {"text": "not to have a Hamiltonian path.", "start": 2166.37, "duration": 2.19}, {"text": "If P equaled NP, then you\ncan test in polynomial time", "start": 2168.56, "duration": 6.47}, {"text": "whether a graph has\na Hamiltonian path.", "start": 2175.03, "duration": 2.94}, {"text": "And then the computation\nitself would be a certificate,", "start": 2177.97, "duration": 2.64}, {"text": "whether it has a path or\nwhether it doesn't have a path.", "start": 2180.61, "duration": 3.037}, {"text": "Because it would be something\nthat you can check easily.", "start": 2183.647, "duration": 2.333}, {"text": "Since we don't know for sure\nthat P is different from NP,", "start": 2188.95, "duration": 6.75}, {"text": "P could be equal to\nNP, then it's possible", "start": 2195.7, "duration": 2.55}, {"text": "that we could give\na short certificate.", "start": 2198.25, "duration": 5.26}, {"text": "Namely, the computation of\nthe polynomial algorithm.", "start": 2203.51, "duration": 4.27}, {"text": "So the only really reasonable\nanswer to this question", "start": 2207.78, "duration": 6.92}, {"text": "is that we don't know.", "start": 2214.7, "duration": 0.93}, {"text": "Just ponder that.", "start": 2219.06, "duration": 1.41}, {"text": "Those of you who answered\nyes, however, need to go back.", "start": 2223.92, "duration": 4.98}, {"text": "And I put this here\nexplicitly because I", "start": 2228.9, "duration": 3.57}, {"text": "know this is a confusion\nfor, well I can", "start": 2232.47, "duration": 5.71}, {"text": "see, for quite a few of you.", "start": 2238.18, "duration": 1.44}, {"text": "When we have\nnon-deterministic computation", "start": 2245.31, "duration": 2.655}, {"text": "and you have a\nnon-deterministic machine,", "start": 2247.965, "duration": 2.055}, {"text": "you can't simply\ninvert the answer", "start": 2250.02, "duration": 3.69}, {"text": "and get back a\nnon-deterministic machine.", "start": 2253.71, "duration": 2.25}, {"text": "Non-determinism does\nnot work that way.", "start": 2255.96, "duration": 3.28}, {"text": "If you remember, the complement\nof a pushdown automaton", "start": 2259.24, "duration": 6.56}, {"text": "is not a pushdown automaton.", "start": 2265.8, "duration": 1.41}, {"text": "If you have a\nnon-deterministic machine", "start": 2269.97, "duration": 2.01}, {"text": "and you invert all of\nthe responses on each", "start": 2271.98, "duration": 2.64}, {"text": "of the branches, it's not going\nto be recognizing or deciding", "start": 2274.62, "duration": 5.28}, {"text": "the complementary language.", "start": 2279.9, "duration": 1.155}, {"text": "I think that this\nis something you--", "start": 2287.15, "duration": 2.01}, {"text": "if you answered yes, you\nneed to go back and make", "start": 2289.16, "duration": 3.96}, {"text": "sure you understand why yes\nis not a reasonable answer", "start": 2293.12, "duration": 5.31}, {"text": "to this question.", "start": 2298.43, "duration": 1.05}, {"text": "Because that's not how\nnon-determinism works.", "start": 2299.48, "duration": 2.74}, {"text": "So you have a not\ncomplete understanding", "start": 2302.22, "duration": 4.41}, {"text": "of non-determinism.", "start": 2306.63, "duration": 0.96}, {"text": "And that's going to be really\nimportant for us going forward.", "start": 2307.59, "duration": 3.24}, {"text": "I really urge you to figure out\nand understand why yes is not", "start": 2310.83, "duration": 5.01}, {"text": "a good answer to this check-in.", "start": 2315.84, "duration": 2.94}, {"text": "OK, so I think we will--", "start": 2318.78, "duration": 1.69}, {"text": "we can talk about that\nmore over the break.", "start": 2320.47, "duration": 4.85}, {"text": "And so we'll return\nhere in five minutes.", "start": 2325.32, "duration": 5.805}, {"text": "Somebody's asking about--\ncan infinite sequences", "start": 2335.32, "duration": 6.15}, {"text": "be generated by the machine.", "start": 2341.47, "duration": 1.17}, {"text": "When we're talking\nabout, especially", "start": 2345.64, "duration": 4.88}, {"text": "in the complexity section of the\ncourse, all of the computations", "start": 2350.52, "duration": 3.48}, {"text": "are going to be bounded in time.", "start": 2354.0, "duration": 3.102}, {"text": "So we're not going to be\nthinking about infinite runs", "start": 2357.102, "duration": 2.208}, {"text": "of the machine.", "start": 2359.31, "duration": 0.625}, {"text": "That's not going to\nbe relevant for us.", "start": 2359.935, "duration": 1.635}, {"text": "So let's not think about that.", "start": 2361.57, "duration": 2.66}, {"text": "How does a Turing\nmachine perform division?", "start": 2364.23, "duration": 1.905}, {"text": "How does a Turing\nmachine perform division?", "start": 2368.98, "duration": 1.89}, {"text": "Well, how do you\nperform division?", "start": 2370.87, "duration": 3.72}, {"text": "[LAUGHS] Long division is an\noperation that can run in--", "start": 2374.59, "duration": 8.04}, {"text": "the long division procedure\nthat you learn in grade school,", "start": 2382.63, "duration": 3.9}, {"text": "you can implement that\non a Turing machine.", "start": 2386.53, "duration": 3.57}, {"text": "Yes, a Turing machine\ncan definitely perform--", "start": 2390.1, "duration": 2.52}, {"text": "do long division, or\ndivision of one integer", "start": 2392.62, "duration": 2.13}, {"text": "by another in polynomial time.", "start": 2394.75, "duration": 2.67}, {"text": "Another question.", "start": 2404.062, "duration": 0.708}, {"text": "Can we generally say,\ntry dividing y by x?", "start": 2404.77, "duration": 3.99}, {"text": "Or do we have to enumerate\na string of length y", "start": 2408.76, "duration": 2.61}, {"text": "and cross off every-- no.", "start": 2411.37, "duration": 1.085}, {"text": "I think that's\nthe same question.", "start": 2412.455, "duration": 1.375}, {"text": "I mean, if you have\nnumbers written in binary,", "start": 2418.43, "duration": 2.41}, {"text": "how would you do the division?", "start": 2420.84, "duration": 1.25}, {"text": "You're not going to\nuse long division.", "start": 2422.09, "duration": 5.46}, {"text": "Anything such as\nthe thing that's", "start": 2427.55, "duration": 2.7}, {"text": "proposed here by the\nquestioner is going", "start": 2430.25, "duration": 4.53}, {"text": "to be an exponential algorithm.", "start": 2434.78, "duration": 1.78}, {"text": "So don't do it that way.", "start": 2436.56, "duration": 1.16}, {"text": "Why does primes in P--", "start": 2446.79, "duration": 2.04}, {"text": "composites in P not\nimply primes in P?", "start": 2448.83, "duration": 2.85}, {"text": "It does imply.", "start": 2451.68, "duration": 1.73}, {"text": "If composites are in P,\nthen primes is in P as well.", "start": 2453.41, "duration": 4.39}, {"text": "When you have a\ndeterministic machine,", "start": 2457.8, "duration": 2.82}, {"text": "you can flip the answer.", "start": 2460.62, "duration": 1.62}, {"text": "When you have a\nnon-deterministic machine,", "start": 2462.24, "duration": 2.19}, {"text": "you may not be able\nto flip the answer.", "start": 2464.43, "duration": 1.9}, {"text": "So deterministic machine\njust having a single branch,", "start": 2466.33, "duration": 4.55}, {"text": "you can make another\ndeterministic machine", "start": 2470.88, "duration": 1.77}, {"text": "that runs in the same\namount of time that does", "start": 2472.65, "duration": 2.13}, {"text": "the complementary language.", "start": 2474.78, "duration": 1.89}, {"text": "Because for\ndeterministic machines,", "start": 2476.67, "duration": 4.5}, {"text": "just like for deciders in\nthe computability section,", "start": 2481.17, "duration": 4.47}, {"text": "you can just invert the answer.", "start": 2485.64, "duration": 2.77}, {"text": "There is an analogy here\nbetween P and decidability,", "start": 2488.41, "duration": 5.09}, {"text": "and NP and recognizability.", "start": 2493.5, "duration": 2.19}, {"text": "It's not an airtight\nanalogy here,", "start": 2495.69, "duration": 2.82}, {"text": "but there is some\nrelationship there.", "start": 2498.51, "duration": 2.19}, {"text": "Somebody's asking me, what\nare the implications of P", "start": 2504.62, "duration": 2.19}, {"text": "equal to NP?", "start": 2506.81, "duration": 1.44}, {"text": "Lots of implications.", "start": 2508.25, "duration": 2.37}, {"text": "Too long to enumerate now.", "start": 2510.62, "duration": 1.35}, {"text": "But, for example, you\nwould be able to break", "start": 2511.97, "duration": 3.63}, {"text": "basically all cryptosystems that\nI'm aware of, if P equal to NP.", "start": 2515.6, "duration": 5.725}, {"text": "So we would have a\nlot of consequences.", "start": 2521.325, "duration": 1.625}, {"text": "Somebody's asking,\nso composites--", "start": 2525.5, "duration": 2.7}, {"text": "primality and\ncompositeness testing", "start": 2528.2, "duration": 1.92}, {"text": "is solvable in polynomial time.", "start": 2530.12, "duration": 1.8}, {"text": "But factoring,\ninterestingly enough,", "start": 2531.92, "duration": 2.67}, {"text": "is not known to be solvable\nin polynomial time.", "start": 2534.59, "duration": 2.4}, {"text": "We may talk about this a little\nbit toward the end of the term", "start": 2542.187, "duration": 2.583}, {"text": "if we have time.", "start": 2544.77, "duration": 0.667}, {"text": "The algorithms for testing\nwhether a number is", "start": 2548.83, "duration": 3.21}, {"text": "prime or composite\nin polynomial time", "start": 2552.04, "duration": 3.15}, {"text": "do not operate by\nlooking for factors.", "start": 2555.19, "duration": 2.7}, {"text": "They operate in an entirely\ndifferent way, basically", "start": 2557.89, "duration": 3.51}, {"text": "by showing that a number is\nprime or composite by looking", "start": 2561.4, "duration": 5.49}, {"text": "at certain properties\nof that number.", "start": 2566.89, "duration": 1.68}, {"text": "But without testing\nwhether it has--", "start": 2568.57, "duration": 2.55}, {"text": "testing, but without\nfinding a factor.", "start": 2571.12, "duration": 2.82}, {"text": "Another question\nhere about asking", "start": 2583.9, "duration": 5.49}, {"text": "when we talk about\nencodings, do we", "start": 2589.39, "duration": 1.83}, {"text": "have to say how we\nencode numbers, values?", "start": 2591.22, "duration": 2.995}, {"text": "No, we don't have to.", "start": 2594.215, "duration": 0.875}, {"text": "We usually don't have to get\ninto spelling out encodings,", "start": 2595.09, "duration": 4.68}, {"text": "as long as they're\nreasonable encodings.", "start": 2599.77, "duration": 2.31}, {"text": "So you don't have to usually.", "start": 2602.08, "duration": 2.948}, {"text": "We're going to be talking about\nthings at a high enough level", "start": 2605.028, "duration": 2.542}, {"text": "that the specific encodings\nare not going to matter.", "start": 2607.57, "duration": 4.5}, {"text": "Let's return to the\nrest of our lecture.", "start": 2612.07, "duration": 5.61}, {"text": "When we talk about, say,\nthis P versus NP problem.", "start": 2617.68, "duration": 8.76}, {"text": "And how do you show\nthat a problem might not", "start": 2626.44, "duration": 6.86}, {"text": "be solvable in P, like the\nHamiltonian path problem?", "start": 2633.3, "duration": 4.89}, {"text": "Many people who are not\npractitioners in the field,", "start": 2638.19, "duration": 10.62}, {"text": "know about the P\nversus NP problems--", "start": 2648.81, "duration": 2.61}, {"text": "over the years, I've\ngotten many, many emails", "start": 2651.42, "duration": 3.48}, {"text": "and physical letters\nfrom people about that.", "start": 2654.9, "duration": 4.575}, {"text": "Since I've spent\nsome time thinking--", "start": 2662.55, "duration": 1.74}, {"text": "I'm known as having spent\nsome time thinking about it.", "start": 2664.29, "duration": 4.83}, {"text": "People claim to\nsolve the problem,", "start": 2669.12, "duration": 2.64}, {"text": "solve P is NP, the P versus NP\nproblem, by basically saying,", "start": 2671.76, "duration": 6.87}, {"text": "problems like Hamiltonian path\nor other similar problems,", "start": 2678.63, "duration": 9.59}, {"text": "basically there's clearly no way\nto solve them without searching", "start": 2688.22, "duration": 3.99}, {"text": "through a lot of possibilities.", "start": 2692.21, "duration": 1.35}, {"text": "And then they go through\na big, long analysis", "start": 2693.56, "duration": 1.875}, {"text": "showing that there\nare exponentially", "start": 2695.435, "duration": 1.515}, {"text": "many possibilities.", "start": 2696.95, "duration": 2.04}, {"text": "A lot of the proofs that\nclaim to solve P versus NP,", "start": 2708.01, "duration": 2.97}, {"text": "they all look like that.", "start": 2710.98, "duration": 1.26}, {"text": "You only have to look--", "start": 2712.24, "duration": 1.23}, {"text": "somewhere in that\npaper, there's going", "start": 2713.47, "duration": 1.8}, {"text": "to be a statement along the\nlines, \"to solve this problem,", "start": 2715.27, "duration": 6.34}, {"text": "clearly you have\nto do it this way.\"", "start": 2721.61, "duration": 4.27}, {"text": "And that's the flaw\nin the reasoning.", "start": 2725.88, "duration": 2.73}, {"text": "Because just like for\nthe factoring problem--", "start": 2728.61, "duration": 4.32}, {"text": "just like for the\ncompositeness testing problem,", "start": 2732.93, "duration": 3.72}, {"text": "you don't necessarily\nhave to solve it", "start": 2736.65, "duration": 1.92}, {"text": "by searching for factors.", "start": 2738.57, "duration": 1.375}, {"text": "There might be some\nother way to do it.", "start": 2739.945, "duration": 1.625}, {"text": "You might be able to\nsolve the Hamiltonian path", "start": 2741.57, "duration": 2.82}, {"text": "problem without searching\nfor Hamiltonian paths.", "start": 2744.39, "duration": 2.28}, {"text": "There might be some other\nprocess that you can use,", "start": 2746.67, "duration": 2.47}, {"text": "which would give you the answer.", "start": 2749.14, "duration": 3.35}, {"text": "The class of polynomial\ntime algorithms", "start": 2752.49, "duration": 1.76}, {"text": "is very rich, can do\nmany, many things.", "start": 2754.25, "duration": 3.23}, {"text": "And I wanted to present to\nyou one of the most important", "start": 2757.48, "duration": 5.12}, {"text": "polynomial time algorithms.", "start": 2762.6, "duration": 1.62}, {"text": "In a sense, you can\nmake a certain argument", "start": 2764.22, "duration": 2.97}, {"text": "that this is the most\nfundamental polynomial time", "start": 2767.19, "duration": 5.61}, {"text": "algorithm.", "start": 2772.8, "duration": 0.96}, {"text": "Some people might\nargue with me on that.", "start": 2773.76, "duration": 3.03}, {"text": "And that's a process called\ndynamic programming, which", "start": 2776.79, "duration": 4.06}, {"text": "I'm sure some of you\nhave seen already", "start": 2780.85, "duration": 1.77}, {"text": "in your algorithms classes,\nand some of you may not have.", "start": 2782.62, "duration": 5.55}, {"text": "Since you have a\nhomework problem on it,", "start": 2788.17, "duration": 2.17}, {"text": "I want to spend a little\ntime describing it to you.", "start": 2790.34, "duration": 3.57}, {"text": "And that's useful for solving\nthis A CFG problem, which", "start": 2793.91, "duration": 5.33}, {"text": "you may remember from the\nfirst half of the course,", "start": 2799.24, "duration": 2.64}, {"text": "involving testing if a\ngrammar generates a string.", "start": 2801.88, "duration": 6.27}, {"text": "So you remember\nthis A CFG problem?", "start": 2808.15, "duration": 1.95}, {"text": "You're giving a grammar,\ncontext-free grammar,", "start": 2810.1, "duration": 3.67}, {"text": "and a string.", "start": 2813.77, "duration": 0.87}, {"text": "And I want to know, is it in\nthe language of the grammar.", "start": 2814.64, "duration": 3.7}, {"text": "So that's going to turn out to\nbe solvable in polynomial time,", "start": 2818.34, "duration": 4.08}, {"text": "but only with kind of\na clever algorithm.", "start": 2822.42, "duration": 2.756}, {"text": "Remember, it's decidable.", "start": 2829.0, "duration": 3.35}, {"text": "We decided it by\nmaking sure that you", "start": 2832.35, "duration": 3.06}, {"text": "are converting the grammar\nin Chomsky normal form.", "start": 2835.41, "duration": 3.33}, {"text": "Then all the derivations\nhave a certain length.", "start": 2838.74, "duration": 2.82}, {"text": "You just try all the possible\nderivations of that length,", "start": 2841.56, "duration": 3.0}, {"text": "and you accept if any of\nthose derivations generate w.", "start": 2844.56, "duration": 2.96}, {"text": "You may remember that from\nthe first half of the course.", "start": 2851.54, "duration": 3.15}, {"text": "That immediately\ngives an NP type", "start": 2857.66, "duration": 3.86}, {"text": "algorithm for this language.", "start": 2861.52, "duration": 2.76}, {"text": "Because basically, you\nnon-deterministically--", "start": 2864.28, "duration": 4.937}, {"text": "instead of trying the\nmost sequentially, all", "start": 2869.217, "duration": 1.833}, {"text": "of these derivations,\nyou try them", "start": 2871.05, "duration": 1.53}, {"text": "in parallel\nnon-deterministically.", "start": 2872.58, "duration": 2.37}, {"text": "So non-deterministically,\nyou pick some derivation", "start": 2874.95, "duration": 3.33}, {"text": "of that length.", "start": 2878.28, "duration": 1.72}, {"text": "And you accept it if\nit generates the input.", "start": 2880.0, "duration": 3.29}, {"text": "This classically\nfits our model of NP.", "start": 2883.29, "duration": 8.783}, {"text": "You can think of it as\nguessing the derivation", "start": 2892.073, "duration": 1.917}, {"text": "and checking that it works.", "start": 2893.99, "duration": 1.32}, {"text": "Or, in parallel, writing down\nall possible derivations.", "start": 2895.31, "duration": 3.9}, {"text": "But this A CFG\nproblem is classically", "start": 2899.21, "duration": 6.87}, {"text": "an NP problem, a problem in NP.", "start": 2906.08, "duration": 3.345}, {"text": "And if you just imagine--", "start": 2912.95, "duration": 3.27}, {"text": "then what's going to\nbe the certificate?", "start": 2916.22, "duration": 2.52}, {"text": "If you found an input that's\nin the language, that's", "start": 2918.74, "duration": 3.15}, {"text": "generated by the grammar, the\ncertificate is the derivation.", "start": 2921.89, "duration": 3.68}, {"text": "So if you look at\nit that way, you", "start": 2925.57, "duration": 1.43}, {"text": "might think, well, that's\nthe best you can do.", "start": 2927.0, "duration": 2.31}, {"text": "This is going to be\nan NP problem, in NP,", "start": 2929.31, "duration": 2.58}, {"text": "and is not going to\nbe a way of avoiding", "start": 2931.89, "duration": 2.04}, {"text": "searching for the derivation.", "start": 2933.93, "duration": 1.29}, {"text": "But that's not true.", "start": 2935.22, "duration": 1.447}, {"text": "There is a way of avoiding\nsearching for the derivation.", "start": 2936.667, "duration": 2.333}, {"text": "You can build up the derivation\nusing dynamic programming.", "start": 2939.0, "duration": 4.41}, {"text": "And so that's what I\nwanted to describe for you,", "start": 2943.41, "duration": 3.81}, {"text": "how that works.", "start": 2947.22, "duration": 0.777}, {"text": "Also partly because\nit's a homework problem.", "start": 2947.997, "duration": 1.833}, {"text": "And I think dynamic programming\nis a very important algorithm.", "start": 2949.83, "duration": 4.313}, {"text": "Before we describe what\ndynamic programming is,", "start": 2958.09, "duration": 7.85}, {"text": "which is very\nsimple, by the way,", "start": 2965.94, "duration": 2.73}, {"text": "let's try to work up to\nit by making an attempt", "start": 2968.67, "duration": 2.79}, {"text": "to solve this problem just\nusing ordinary recursion.", "start": 2971.46, "duration": 3.0}, {"text": "How would we solve\nthe A CFG problem?", "start": 2977.14, "duration": 2.98}, {"text": "So you're given grammar,\nyou're given an input.", "start": 2980.12, "duration": 3.52}, {"text": "Let's assume the grammar\nis in Chomsky normal form.", "start": 2983.64, "duration": 3.15}, {"text": "That's going to be useful.", "start": 2989.61, "duration": 1.45}, {"text": "So it's a Chomsky\nnormal form grammar.", "start": 2991.06, "duration": 2.15}, {"text": "And we want to see how to\ntest if you can generate w.", "start": 2993.21, "duration": 6.227}, {"text": "And it's going to be\nrecursive algorithm.", "start": 2999.437, "duration": 1.708}, {"text": "The recursive algorithm is going\nto actually solve something", "start": 3001.145, "duration": 4.545}, {"text": "slightly more general.", "start": 3005.69, "duration": 1.8}, {"text": "I'm going to give\nyou the grammar.", "start": 3007.49, "duration": 1.47}, {"text": "I'm going to give\nyou the string.", "start": 3008.96, "duration": 1.54}, {"text": "And I'm also going to allow you\nto start at some other variable", "start": 3010.5, "duration": 4.31}, {"text": "besides the start variable.", "start": 3014.81, "duration": 1.74}, {"text": "I'm going to give\nyou some variable, R,", "start": 3016.55, "duration": 2.79}, {"text": "and I know I want to know, can\nI generate w starting at R?", "start": 3019.34, "duration": 3.78}, {"text": "So that's my slightly\nmore general problem,", "start": 3026.88, "duration": 1.99}, {"text": "which is going to be\nuseful in the recursion.", "start": 3028.87, "duration": 2.17}, {"text": "So the input now\nto this algorithm", "start": 3033.72, "duration": 2.91}, {"text": "is the grammar, the input,\nand the starting variable.", "start": 3036.63, "duration": 4.498}, {"text": "And now how is the\nalgorithm going to work?", "start": 3041.128, "duration": 1.792}, {"text": "It's going to try to\ntest, can I get to--", "start": 3042.92, "duration": 3.45}, {"text": "is there some\nderivation, pictured here", "start": 3046.37, "duration": 2.55}, {"text": "as the parse tree,\nfor w starting at R?", "start": 3048.92, "duration": 4.08}, {"text": "That's what the algorithm\nis trying to answer.", "start": 3053.0, "duration": 2.9}, {"text": "Can I get w from R?", "start": 3055.9, "duration": 2.85}, {"text": "The way it's going to do that\nis it's going to try to divide w", "start": 3058.75, "duration": 5.86}, {"text": "into the two strings\nin all possible ways.", "start": 3064.61, "duration": 6.25}, {"text": "Which sounds like it might\nbe exponential, but it isn't.", "start": 3070.86, "duration": 4.43}, {"text": "There's only a polynomial\nnumber of ways to divide", "start": 3075.29, "duration": 3.51}, {"text": "the string into two substrings.", "start": 3078.8, "duration": 3.93}, {"text": "Just of order n, just depending\nwhere you make that cut.", "start": 3082.73, "duration": 2.79}, {"text": "So that's not too bad.", "start": 3089.48, "duration": 1.15}, {"text": "There's a polynomial,\nthere's only n ways", "start": 3090.63, "duration": 2.03}, {"text": "of making that division.", "start": 3092.66, "duration": 1.14}, {"text": "And also I'm going to try every\npossible rule that comes from R", "start": 3093.8, "duration": 10.63}, {"text": "that generates two variables.", "start": 3104.43, "duration": 1.52}, {"text": "So these are what's allowed\nin Chomsky normal form,", "start": 3105.95, "duration": 3.34}, {"text": "R goes to ST.", "start": 3109.29, "duration": 3.99}, {"text": "For each possible way\nof cutting w into x, y,", "start": 3113.28, "duration": 4.2}, {"text": "and for each\npossible rule, R goes", "start": 3117.48, "duration": 1.71}, {"text": "to ST, I'm going to see,\nrecursively, can I get", "start": 3119.19, "duration": 5.24}, {"text": "from S to x, and from T to y.", "start": 3124.43, "duration": 4.32}, {"text": "So I'm going to use\nmy recursion now.", "start": 3128.75, "duration": 1.71}, {"text": "Now that I have smaller\nstrings instead of w,", "start": 3130.46, "duration": 6.57}, {"text": "I can apply recursion and\ntry to answer it that way.", "start": 3137.03, "duration": 4.55}, {"text": "And this algorithm will work.", "start": 3141.58, "duration": 2.4}, {"text": "If I found a way to cut w\ninto x, y, and I found a rule,", "start": 3143.98, "duration": 4.83}, {"text": "R goes to ST such that S\ngenerates x and T generates y,", "start": 3148.81, "duration": 4.5}, {"text": "then I'm good.", "start": 3153.31, "duration": 1.61}, {"text": "I know I can generate w from R.", "start": 3154.92, "duration": 4.93}, {"text": "And if there's no way of\ncutting w up to satisfy that,", "start": 3159.85, "duration": 4.2}, {"text": "or if I can't find any\nway to divide w into x, y,", "start": 3164.05, "duration": 6.99}, {"text": "and a rule R goes\nto ST which makes", "start": 3171.04, "duration": 2.31}, {"text": "this work, if all\npossible ways fail", "start": 3173.35, "duration": 2.76}, {"text": "then you can't get from R to w.", "start": 3176.11, "duration": 2.19}, {"text": "And then you can decide the\noriginal A CFG problem now,", "start": 3182.23, "duration": 3.21}, {"text": "by starting from\nthe start variable,", "start": 3185.44, "duration": 1.56}, {"text": "instead of just\nany old R. You plug", "start": 3187.0, "duration": 2.175}, {"text": "in the start variable for R.", "start": 3189.175, "duration": 2.145}, {"text": "So this algorithm works, and\nit can be used to solve A CFG.", "start": 3191.32, "duration": 8.36}, {"text": "But the question is,\nis it polynomial?", "start": 3199.68, "duration": 2.69}, {"text": "And it's not.", "start": 3202.37, "duration": 2.52}, {"text": "Because every time you're\ndoing the recursion,", "start": 3204.89, "duration": 5.13}, {"text": "you're essentially adding\nanother factor of n.", "start": 3210.02, "duration": 3.94}, {"text": "Because here, as we pointed\nout, this is a factor of n.", "start": 3213.96, "duration": 2.76}, {"text": "But that's happening every time\nyou're doing a recursive level.", "start": 3216.72, "duration": 3.3}, {"text": "And you can imagine, I'm just\ndoing a very crude analysis", "start": 3220.02, "duration": 3.96}, {"text": "here, depending upon\nhow you divide w up.", "start": 3223.98, "duration": 3.18}, {"text": "But roughly speaking,\nit's going to get", "start": 3227.16, "duration": 1.77}, {"text": "divided in half each\ntime, so there's", "start": 3228.93, "duration": 2.19}, {"text": "going to be log n levels.", "start": 3231.12, "duration": 2.1}, {"text": "So that means you're\ngoing to be multiplying n", "start": 3233.22, "duration": 2.79}, {"text": "by itself log n\ntimes, or give you", "start": 3236.01, "duration": 2.61}, {"text": "an n to the log n algorithm.", "start": 3238.62, "duration": 3.41}, {"text": "That's not polynomial,\nbecause polynomials", "start": 3242.03, "duration": 2.28}, {"text": "end with a constant,\nfor some fixed constant.", "start": 3244.31, "duration": 2.82}, {"text": "n to the log n is not\ngoing to be polynomial.", "start": 3247.13, "duration": 2.7}, {"text": "This is not a\npolynomial algorithm.", "start": 3249.83, "duration": 3.94}, {"text": "Instead, you're going to have to\ndo something just a little bit", "start": 3253.77, "duration": 3.6}, {"text": "more clever.", "start": 3257.37, "duration": 2.81}, {"text": "It's going to be\nthe same basic idea,", "start": 3260.18, "duration": 2.52}, {"text": "but relying on one\nlittle observation.", "start": 3262.7, "duration": 3.57}, {"text": "And the little\nobservation is that when--", "start": 3266.27, "duration": 6.14}, {"text": "this non-polynomial\nimplementation", "start": 3272.41, "duration": 3.09}, {"text": "that I've just described\nis actually pretty dumb.", "start": 3275.5, "duration": 5.41}, {"text": "Because it's doing a lot\nof recomputation of things", "start": 3280.91, "duration": 2.94}, {"text": "that it's already solved.", "start": 3283.85, "duration": 1.53}, {"text": "Why is that?", "start": 3285.38, "duration": 2.39}, {"text": "Because if you\nlook at the number", "start": 3287.77, "duration": 4.13}, {"text": "of possible different\nsubproblems here,", "start": 3291.9, "duration": 4.35}, {"text": "once I give you G\nand I give you w,", "start": 3296.25, "duration": 5.82}, {"text": "how many different subproblems\nof G, S, and T are there?", "start": 3302.07, "duration": 6.63}, {"text": "The number of strings\nhere, all of those strings", "start": 3312.14, "duration": 3.81}, {"text": "are going to be substrings of w.", "start": 3315.95, "duration": 1.77}, {"text": "There's only roughly n\nsquared substrings of w.", "start": 3317.72, "duration": 4.77}, {"text": "I'm always going\nto be generating,", "start": 3322.49, "duration": 1.56}, {"text": "in a subproblem here,\nsome substring of w", "start": 3324.05, "duration": 3.09}, {"text": "from some starting\nvariable in the grammar.", "start": 3327.14, "duration": 4.22}, {"text": "So because there aren't that\nmany different substrings,", "start": 3331.36, "duration": 2.37}, {"text": "and not that many different\nstarting variables,", "start": 3333.73, "duration": 3.27}, {"text": "the total number of\npossible problems", "start": 3337.0, "duration": 2.64}, {"text": "that this algorithm is going\nto be called on to solve", "start": 3339.64, "duration": 2.49}, {"text": "is going to be, in total,\na polynomial number", "start": 3342.13, "duration": 2.618}, {"text": "of different subproblems.", "start": 3344.748, "duration": 1.042}, {"text": "There aren't very many of them.", "start": 3345.79, "duration": 1.292}, {"text": "It's only something\nlike order of n squared.", "start": 3347.082, "duration": 2.758}, {"text": "So if the algorithm is running\nfor exponentially long time,", "start": 3349.84, "duration": 4.2}, {"text": "it's solving the same\nsubproblem over and over again.", "start": 3354.04, "duration": 3.86}, {"text": "That's dumb.", "start": 3357.9, "duration": 3.01}, {"text": "Why don't you just remember\nwhen you solve the subproblem,", "start": 3360.91, "duration": 3.09}, {"text": "so you don't solve it again?", "start": 3364.0, "duration": 1.29}, {"text": "Doing that enhanced\nrecursion where", "start": 3368.48, "duration": 4.08}, {"text": "you remember the problems\nyou've already solved,", "start": 3372.56, "duration": 3.617}, {"text": "it's called dynamic programming.", "start": 3376.177, "duration": 1.333}, {"text": "I don't know why it has such\na confusing name like that.", "start": 3377.51, "duration": 4.898}, {"text": "Actually it's called by\nseveral different things.", "start": 3382.408, "duration": 2.042}, {"text": "But anyway, that's known\nas dynamic programming.", "start": 3384.45, "duration": 3.62}, {"text": "It's recursion plus the memory.", "start": 3388.07, "duration": 4.33}, {"text": "And here is just\nrepeating myself.", "start": 3392.4, "duration": 3.41}, {"text": "There are not very many\ndifferent substrings,", "start": 3395.81, "duration": 4.11}, {"text": "so every time in your\nrecursion somewhere,", "start": 3399.92, "duration": 3.037}, {"text": "you're going to be\nworking with a substring.", "start": 3402.957, "duration": 1.833}, {"text": "So there's not that many\ndifferent subproblems", "start": 3404.79, "duration": 1.94}, {"text": "that you can possibly solve.", "start": 3406.73, "duration": 1.44}, {"text": "And just remember when\nyou solve the subproblem,", "start": 3408.17, "duration": 3.39}, {"text": "and not solve it again.", "start": 3411.56, "duration": 2.16}, {"text": "Let me just show you that\nalgorithm again here,", "start": 3413.72, "duration": 3.75}, {"text": "with the little modification.", "start": 3417.47, "duration": 2.46}, {"text": "So first of all,\nlet me give you--", "start": 3419.93, "duration": 3.9}, {"text": "this is the same algorithm\nfrom the previous slide.", "start": 3423.83, "duration": 2.13}, {"text": "I'm just repeating it here\nwithout all the other stuff", "start": 3425.96, "duration": 2.25}, {"text": "so we can look at it directly.", "start": 3428.21, "duration": 2.31}, {"text": "Dividing it into x and y\nfor each possible rule.", "start": 3430.52, "duration": 4.74}, {"text": "And then recurse.", "start": 3435.26, "duration": 0.72}, {"text": "I'm going to add a little\nstep 0 beforehand, which", "start": 3438.68, "duration": 7.78}, {"text": "says, if I have G, w, and R,\nlet me just check first if I've", "start": 3446.46, "duration": 5.59}, {"text": "already solved that one before.", "start": 3452.05, "duration": 2.35}, {"text": "So I have to keep track of\nthe ones I've already solved.", "start": 3454.4, "duration": 3.26}, {"text": "That's not too bad,\nbecause there's", "start": 3457.66, "duration": 1.5}, {"text": "only order n squared possible\ndifferent ones that I", "start": 3459.16, "duration": 3.6}, {"text": "could be called on to solve.", "start": 3462.76, "duration": 1.653}, {"text": "So I'm just going to\nhave a little table where", "start": 3464.413, "duration": 1.917}, {"text": "I'm going to remember those.", "start": 3466.33, "duration": 1.53}, {"text": "And then every time I get a\nnew one, I get one to solve,", "start": 3467.86, "duration": 3.4}, {"text": "I'll check.", "start": 3471.26, "duration": 0.5}, {"text": "Is it on that table?", "start": 3471.76, "duration": 1.23}, {"text": "And what's the answer?", "start": 3472.99, "duration": 1.63}, {"text": "So I won't have to rerun those.", "start": 3474.62, "duration": 2.99}, {"text": "I'm going to be basically\npruning that tree so", "start": 3477.61, "duration": 4.11}, {"text": "that it has only a\npolynomial number of leaves.", "start": 3481.72, "duration": 2.23}, {"text": "And so the total\nsize of that tree", "start": 3483.95, "duration": 1.76}, {"text": "now is going to be polynomial.", "start": 3485.71, "duration": 4.06}, {"text": "And so that's going to yield\na polynomial running time.", "start": 3489.77, "duration": 2.358}, {"text": "This, by the way,\nI only learned this", "start": 3492.128, "duration": 1.542}, {"text": "myself, I'm sure you guys all\nknow this who have taken this", "start": 3493.67, "duration": 2.458}, {"text": "in the algorithms course,\nhas a special name called", "start": 3496.128, "duration": 3.032}, {"text": "memoization.", "start": 3499.16, "duration": 1.74}, {"text": "Not memorization.", "start": 3500.9, "duration": 2.13}, {"text": "Came from the same root,\nI think, but memoization,", "start": 3503.03, "duration": 3.03}, {"text": "which is somehow remembering\nthe results of a computation", "start": 3506.06, "duration": 3.688}, {"text": "so you don't have to repeat it.", "start": 3509.748, "duration": 1.292}, {"text": "The total number\nof calls is going", "start": 3514.833, "duration": 1.417}, {"text": "to be, at most, n squared, to\nthis algorithm, because you're", "start": 3516.25, "duration": 3.0}, {"text": "never going to be redoing\nwork that you've done already.", "start": 3519.25, "duration": 5.55}, {"text": "And when you actually have to go\nthrough it, the running time--", "start": 3524.8, "duration": 4.335}, {"text": "the total amount of time\nthat you're going to need", "start": 3536.88, "duration": 2.13}, {"text": "is going to be\npolynomial altogether.", "start": 3539.01, "duration": 1.71}, {"text": "I don't remember what\nmy check-in is on this.", "start": 3544.61, "duration": 3.73}, {"text": "Oh yeah.", "start": 3548.34, "duration": 0.84}, {"text": "This is somehow related.", "start": 3549.18, "duration": 1.32}, {"text": "And feel free to\nask questions too,", "start": 3550.5, "duration": 2.16}, {"text": "while you're thinking\nabout this check-in.", "start": 3552.66, "duration": 3.45}, {"text": "But the check-in\nsays here, we've", "start": 3556.11, "duration": 3.06}, {"text": "solved the A CFG problem\nin polynomial time.", "start": 3559.17, "duration": 3.69}, {"text": "Does that tell us that every\ncontext-free language itself", "start": 3562.86, "duration": 5.96}, {"text": "is also solvable\nin polynomial time?", "start": 3568.82, "duration": 3.15}, {"text": "Just mull that over, and\nplease give me an answer to it.", "start": 3571.97, "duration": 5.268}, {"text": "I hope you do better\non this check-in", "start": 3577.238, "duration": 1.542}, {"text": "than you did on the last one.", "start": 3578.78, "duration": 2.85}, {"text": "But anyway, why don't you go\nahead and think about that.", "start": 3581.63, "duration": 4.13}, {"text": "I can take some questions\nin the meantime.", "start": 3585.76, "duration": 1.75}, {"text": "Somebody is asking here--", "start": 3591.89, "duration": 1.175}, {"text": "actually, I'm getting\nseveral questions on this.", "start": 3596.02, "duration": 3.12}, {"text": "Why isn't it order n\ncubed or something greater", "start": 3599.14, "duration": 3.48}, {"text": "than order n squared\nbecause of the variables?", "start": 3602.62, "duration": 4.24}, {"text": "The variables don't depend on n.", "start": 3606.86, "duration": 3.29}, {"text": "When you're given-- well,\nactually that's not true.", "start": 3610.15, "duration": 8.11}, {"text": "No.", "start": 3618.26, "duration": 1.37}, {"text": "You are right.", "start": 3619.63, "duration": 1.21}, {"text": "Because the grammar\nis part of the input.", "start": 3623.87, "duration": 4.31}, {"text": "So you might have as many\nas n different variables", "start": 3628.18, "duration": 3.26}, {"text": "in the given grammar.", "start": 3631.44, "duration": 1.89}, {"text": "So you are right.", "start": 3633.33, "duration": 1.65}, {"text": "There is potentially--\nthe grammar might", "start": 3634.98, "duration": 5.49}, {"text": "be half the size of the input,\nand the input to the grammar w", "start": 3640.47, "duration": 3.57}, {"text": "might be half the\nsize of the input.", "start": 3644.04, "duration": 1.678}, {"text": "So I didn't think about\nthat, but you're correct.", "start": 3645.718, "duration": 2.042}, {"text": "There are potentially\ndifferent numbers", "start": 3647.76, "duration": 4.53}, {"text": "of variables in\ndifferent grammars,", "start": 3652.29, "duration": 1.81}, {"text": "so you have to add an\nextra factor, which", "start": 3654.1, "duration": 2.45}, {"text": "would be at most the\nsize of the input,", "start": 3656.55, "duration": 2.46}, {"text": "because that's as many variables\nas you could possibly have.", "start": 3659.01, "duration": 2.74}, {"text": "So it really should be, I think,\norder n cubed to take that", "start": 3661.75, "duration": 7.22}, {"text": "into account as well.", "start": 3668.97, "duration": 1.47}, {"text": "Plus all of the work\nthat needs to happen", "start": 3670.44, "duration": 1.98}, {"text": "in terms of dividing things up.", "start": 3672.42, "duration": 2.058}, {"text": "On a one-tape Turing\nmachine, there's", "start": 3674.478, "duration": 1.542}, {"text": "going to be some extra\nwork just to carry out", "start": 3676.02, "duration": 2.73}, {"text": "some of these individual steps,\nbecause with a single tape", "start": 3678.75, "duration": 3.63}, {"text": "things are sometimes\na little awkward.", "start": 3682.38, "duration": 1.65}, {"text": "I think the total\nrunning time is", "start": 3684.03, "duration": 1.17}, {"text": "going to end up being\nsomething like n", "start": 3685.2, "duration": 1.583}, {"text": "to the 4th or into the 5th\non a one-tape Turing machine.", "start": 3686.783, "duration": 2.407}, {"text": "But that's a good point.", "start": 3692.67, "duration": 1.05}, {"text": "Somebody's saying, how can we\nbe storing n squared strings", "start": 3698.07, "duration": 3.18}, {"text": "in finite time?", "start": 3701.25, "duration": 1.32}, {"text": "I'm not saying finite time.", "start": 3702.57, "duration": 1.59}, {"text": "We have polynomial time.", "start": 3704.16, "duration": 1.23}, {"text": "Every stage of this\nalgorithm is allowed", "start": 3705.39, "duration": 3.48}, {"text": "to run for polynomially\nmany steps.", "start": 3708.87, "duration": 1.56}, {"text": "As long as it's\nclearly polynomial,", "start": 3710.43, "duration": 1.83}, {"text": "we can just write that\ndown as a single stage.", "start": 3712.26, "duration": 1.935}, {"text": "Part two should say--", "start": 3718.91, "duration": 2.69}, {"text": "oh.", "start": 3721.6, "duration": 1.47}, {"text": "There's a typo here.", "start": 3723.07, "duration": 0.85}, {"text": "So use D. Thank you.", "start": 3723.92, "duration": 2.135}, {"text": "That is a typo.", "start": 3726.055, "duration": 1.095}, {"text": "I'm afraid if I change it\non my original slide here,", "start": 3734.013, "duration": 2.167}, {"text": "things will break in\nsome horrible way.", "start": 3736.18, "duration": 2.46}, {"text": "Let's just see.", "start": 3738.64, "duration": 0.99}, {"text": "Did I completely wreck my slide?", "start": 3739.63, "duration": 2.66}, {"text": "No, that's good.", "start": 3742.29, "duration": 2.24}, {"text": "Yeah, thank you.", "start": 3744.53, "duration": 0.99}, {"text": "Good point.", "start": 3745.52, "duration": 0.6}, {"text": "Oops.", "start": 3753.08, "duration": 2.02}, {"text": "OK, how's our check-in doing?", "start": 3755.1, "duration": 3.74}, {"text": "I think you're just\nabout all done.", "start": 3758.84, "duration": 3.78}, {"text": "Spent a lot of time on this.", "start": 3762.62, "duration": 1.41}, {"text": "End polling.", "start": 3764.03, "duration": 0.765}, {"text": "As you may remember from the\nfirst half of the course--", "start": 3771.46, "duration": 3.43}, {"text": "so the answer is A, indeed.", "start": 3774.89, "duration": 2.75}, {"text": "Remember that we showed\nA CFG is decidable,", "start": 3777.64, "duration": 4.29}, {"text": "and therefore each\ncontext-free language", "start": 3781.93, "duration": 1.98}, {"text": "itself is decidable,\njust because you", "start": 3783.91, "duration": 3.06}, {"text": "can plug in a specific grammar\ninto the A CFG problem.", "start": 3786.97, "duration": 4.47}, {"text": "The very same\nreasoning works here.", "start": 3791.44, "duration": 3.93}, {"text": "If you have a context-free\nlanguage, it has a grammar.", "start": 3795.37, "duration": 3.63}, {"text": "You can plug that grammar\ninto the A CFG problem.", "start": 3799.0, "duration": 3.24}, {"text": "And then, that's\npolynomial time,", "start": 3802.24, "duration": 1.89}, {"text": "you're going to get\na polynomial time", "start": 3804.13, "duration": 1.77}, {"text": "algorithm for that language.", "start": 3805.9, "duration": 4.8}, {"text": "Good to review that.", "start": 3810.7, "duration": 1.965}, {"text": "It's the same thing, same\nargument we used before.", "start": 3812.665, "duration": 2.625}, {"text": "I don't want to spend\na lot of time on this.", "start": 3822.327, "duration": 1.833}, {"text": "There's another way of looking\nat dynamic programming.", "start": 3824.16, "duration": 2.66}, {"text": "We'll talk about this again\nmaybe in a lecture, probably", "start": 3826.82, "duration": 3.78}, {"text": "next lecture, just because I you\nhave a homework problem on it.", "start": 3830.6, "duration": 4.62}, {"text": "If you've seen dynamic\nprogramming before,", "start": 3835.22, "duration": 2.138}, {"text": "this is going to be easy.", "start": 3837.358, "duration": 1.042}, {"text": "If you haven't seen it\nbefore, it's going to be,", "start": 3838.4, "duration": 2.0}, {"text": "I think, probably a\nlittle challenging.", "start": 3840.4, "duration": 2.05}, {"text": "Another way of looking\nat dynamic programming", "start": 3846.34, "duration": 2.4}, {"text": "is the so-called bottom-up\nversion of dynamic programming.", "start": 3848.74, "duration": 3.21}, {"text": "And what that would\nmean is, you solve", "start": 3851.95, "duration": 2.82}, {"text": "all of the subproblems first.", "start": 3854.77, "duration": 2.31}, {"text": "You solve all the smaller\nsubproblems before you", "start": 3857.08, "duration": 2.46}, {"text": "solve the larger subproblems.", "start": 3859.54, "duration": 1.56}, {"text": "It's here on the slide.", "start": 3865.42, "duration": 1.085}, {"text": "I'm not sure I want\nto talk it through.", "start": 3866.505, "duration": 1.625}, {"text": "But basically, you solve\nthe subproblems here", "start": 3868.13, "duration": 5.75}, {"text": "where, start with\nstrings of length 1,", "start": 3873.88, "duration": 5.82}, {"text": "and then from that you\nbuild up to subproblems", "start": 3879.7, "duration": 2.67}, {"text": "with the substrings are\nof length 2, and then 3,", "start": 3882.37, "duration": 3.24}, {"text": "and so on.", "start": 3885.61, "duration": 0.91}, {"text": "And each of those only relies\non the smaller previously solved", "start": 3886.52, "duration": 3.98}, {"text": "subproblems.", "start": 3890.5, "duration": 1.05}, {"text": "So you can, kind of\nin a systematic way,", "start": 3891.55, "duration": 3.3}, {"text": "solve all the larger and\nlarger subproblems for larger", "start": 3894.85, "duration": 4.41}, {"text": "and larger substrings.", "start": 3899.26, "duration": 3.15}, {"text": "That gives kind of a\ndifferent perspective", "start": 3902.41, "duration": 1.89}, {"text": "on dynamic programming.", "start": 3904.3, "duration": 1.56}, {"text": "And for different\nproblems, sometimes it's", "start": 3905.86, "duration": 2.85}, {"text": "better to think about either\nthis sort of top-down recursion", "start": 3908.71, "duration": 3.21}, {"text": "based process, or the\nbottom-up process that I'm", "start": 3911.92, "duration": 4.65}, {"text": "describing here.", "start": 3916.57, "duration": 1.83}, {"text": "They're really\ncompletely equivalent.", "start": 3918.4, "duration": 1.89}, {"text": "The version that's described\nfor this particular algorithm,", "start": 3923.6, "duration": 4.18}, {"text": "which appears in the\ntextbook, is actually", "start": 3927.78, "duration": 1.82}, {"text": "the bottom-up algorithm.", "start": 3929.6, "duration": 1.69}, {"text": "So you shouldn't be confused\nif you see something there", "start": 3931.29, "duration": 2.7}, {"text": "which looks somewhat different.", "start": 3933.99, "duration": 1.77}, {"text": "You basically solve all\npossible subproblems,", "start": 3938.3, "duration": 5.16}, {"text": "basically filling out a table.", "start": 3943.46, "duration": 2.43}, {"text": "Let me not say anything\nmore about that here,", "start": 3945.89, "duration": 3.96}, {"text": "since we're running a\nlittle short on time.", "start": 3949.85, "duration": 2.04}, {"text": "There are really\ntwo perspectives", "start": 3954.505, "duration": 1.375}, {"text": "on dynamic programming.", "start": 3955.88, "duration": 3.35}, {"text": "So moving on from there,\nlet's shift gears.", "start": 3959.23, "duration": 4.98}, {"text": "Leave context-free languages\nand dynamic programming behind.", "start": 3966.9, "duration": 5.13}, {"text": "And so I'm moving toward\nunderstanding P and NP.", "start": 3972.03, "duration": 6.5}, {"text": "And for that, we will\nintroduce a new problem called", "start": 3978.53, "duration": 5.31}, {"text": "the satisfiability problem.", "start": 3983.84, "duration": 1.35}, {"text": "And that's one we're going\nto spend a lot of time on.", "start": 3985.19, "duration": 4.59}, {"text": "If you tuned out a little bit\nduring the dynamic programming", "start": 3989.78, "duration": 4.26}, {"text": "discussion, time to\nget back on board.", "start": 3994.04, "duration": 3.75}, {"text": "The satisfiability\nproblem is going", "start": 4001.99, "duration": 2.37}, {"text": "to be a computational\nproblem that we're", "start": 4004.36, "duration": 6.29}, {"text": "going to be working on.", "start": 4010.65, "duration": 1.08}, {"text": "And it has to do\nwith Boolean formula.", "start": 4011.73, "duration": 3.16}, {"text": "So these are expressions,\nlike arithmetical formula,", "start": 4014.89, "duration": 3.62}, {"text": "like x plus y times\nz, but instead", "start": 4018.51, "duration": 4.47}, {"text": "of using numerical\nvariables, we're", "start": 4022.98, "duration": 4.23}, {"text": "going to be using Boolean\nvariables that take", "start": 4027.21, "duration": 2.7}, {"text": "on Boolean values, true, false.", "start": 4029.91, "duration": 1.95}, {"text": "Or sometimes\nrepresented by 1 and 0.", "start": 4031.86, "duration": 2.535}, {"text": "The operators that\nwe're going to be using", "start": 4038.66, "duration": 2.01}, {"text": "are going to be the and,\nor, and negation operations.", "start": 4040.67, "duration": 3.54}, {"text": "And, or, not.", "start": 4044.21, "duration": 0.9}, {"text": "I'm going to say such a\nformula, such a Boolean formula,", "start": 4048.59, "duration": 4.64}, {"text": "we're going to call\nit satisfiable--", "start": 4053.23, "duration": 1.59}, {"text": "we'll do an example\nin a second--", "start": 4054.82, "duration": 2.1}, {"text": "if that formula value\nevaluates to true", "start": 4056.92, "duration": 5.52}, {"text": "if you make some assignment\nof values to its variables.", "start": 4062.44, "duration": 5.38}, {"text": "So just like arithmetical\nformula will have some value", "start": 4067.82, "duration": 4.16}, {"text": "if you plug in values\nfor the variables,", "start": 4071.98, "duration": 3.99}, {"text": "Boolean formula is\ngoing to have some value", "start": 4075.97, "duration": 2.22}, {"text": "if you plug in Boolean\nvalues for its variables.", "start": 4078.19, "duration": 2.94}, {"text": "And I want to know,\nis there some way", "start": 4081.13, "duration": 1.68}, {"text": "to plug in values which makes\nthe whole thing evaluate", "start": 4082.81, "duration": 2.67}, {"text": "to true.", "start": 4085.48, "duration": 1.59}, {"text": "The formula itself\nis going to evaluate", "start": 4087.07, "duration": 1.92}, {"text": "to either true or false, and\nI wanted to evaluate to true.", "start": 4088.99, "duration": 3.39}, {"text": "Here is our example.", "start": 4097.84, "duration": 1.229}, {"text": "Let's take the formula,\nphi, which is x or y,", "start": 4099.069, "duration": 5.87}, {"text": "and x complement--", "start": 4104.939, "duration": 2.821}, {"text": "or, not x or not y.", "start": 4107.76, "duration": 2.58}, {"text": "So the notation x with a\nbar over it, x complement,", "start": 4110.34, "duration": 4.769}, {"text": "is just x bar, not x.", "start": 4115.109, "duration": 4.83}, {"text": "It's just the way\nif you're familiar", "start": 4119.939, "duration": 2.161}, {"text": "with the other notation,\nthe not operation, which", "start": 4122.1, "duration": 5.04}, {"text": "just inverts 1s and 0s.", "start": 4127.14, "duration": 1.809}, {"text": "We're going to write it with\na bar instead of the negation", "start": 4132.33, "duration": 2.819}, {"text": "symbol.", "start": 4135.149, "duration": 1.5}, {"text": "I'm assuming that you've\nall seen Boolean algebra,", "start": 4136.649, "duration": 2.58}, {"text": "Boolean arithmetic before,\nwhere the and operation is only", "start": 4139.229, "duration": 5.431}, {"text": "true if both inputs are true.", "start": 4144.66, "duration": 3.0}, {"text": "These are going to be binary\nand operations and binary", "start": 4147.66, "duration": 2.4}, {"text": "or operations.", "start": 4150.06, "duration": 2.1}, {"text": "Or is going to be true\nif either input is true.", "start": 4152.16, "duration": 2.85}, {"text": "And not is true if its\nsingle input is false.", "start": 4155.01, "duration": 4.25}, {"text": "Oops, just looked at the answer.", "start": 4159.26, "duration": 3.12}, {"text": "Here I want to know, for\nthis Boolean formula,", "start": 4162.38, "duration": 3.51}, {"text": "here is it satisfiable.", "start": 4165.89, "duration": 2.52}, {"text": "Is there some way to assign\nvalues to the variables", "start": 4168.41, "duration": 4.3}, {"text": "to make this formula\nevaluate to true?", "start": 4172.71, "duration": 4.769}, {"text": "So for example, let's\njust try things.", "start": 4177.479, "duration": 1.971}, {"text": "Let's make x and y both true.", "start": 4179.45, "duration": 2.65}, {"text": "So x is true and y is true.", "start": 4182.1, "duration": 2.7}, {"text": "So x or y, well that's\ngood, that's true.", "start": 4184.8, "duration": 3.11}, {"text": "But now we have to do an and, so\nwe need both sides to be true.", "start": 4187.91, "duration": 4.319}, {"text": "So now we have x complement--\nwell we said we said x is true,", "start": 4192.229, "duration": 3.671}, {"text": "so x complement is false,\ny complement is false.", "start": 4195.9, "duration": 2.93}, {"text": "False or false is false.", "start": 4198.83, "duration": 2.44}, {"text": "So now we have a true and false.", "start": 4201.27, "duration": 1.79}, {"text": "That's going to be false.", "start": 4203.06, "duration": 1.72}, {"text": "We did not find a\nsatisfying assignment.", "start": 4204.78, "duration": 1.88}, {"text": "But maybe there's another one.", "start": 4206.66, "duration": 1.36}, {"text": "And in fact, there is.", "start": 4208.02, "duration": 1.25}, {"text": "If you make x true and y\nfalse, then both of these parts", "start": 4209.27, "duration": 4.26}, {"text": "will evaluate to true, and\nthen you'll have true and true.", "start": 4213.53, "duration": 3.39}, {"text": "So we found a satisfying\nassignment to this formula.", "start": 4216.92, "duration": 2.46}, {"text": "It is, in fact, satisfiable.", "start": 4219.38, "duration": 3.19}, {"text": "So if you say x is\n1 and y is 0, yes.", "start": 4222.57, "duration": 2.9}, {"text": "This is satisfiable.", "start": 4225.47, "duration": 3.06}, {"text": "Now the problem of testing\nfor a Boolean formula,", "start": 4228.53, "duration": 2.48}, {"text": "if it is satisfiable, is\ngoing to be the SAT language.", "start": 4231.01, "duration": 3.9}, {"text": "It's a set.", "start": 4234.91, "duration": 0.64}, {"text": "It's a collection of\nsatisfiable Boolean formula.", "start": 4235.55, "duration": 4.11}, {"text": "And testing whether\nyou're in SAT or not", "start": 4239.66, "duration": 2.28}, {"text": "is going to be an important\ncomputational problem.", "start": 4241.94, "duration": 4.44}, {"text": "There was an amazing\ntheorem which", "start": 4249.58, "duration": 7.41}, {"text": "really got this\nwhole subject going,", "start": 4256.99, "duration": 2.88}, {"text": "discovered independently by\nSteve Cook in North America", "start": 4259.87, "duration": 5.85}, {"text": "and Leonid Levin in the former\nSoviet Union, almost exactly at", "start": 4265.72, "duration": 4.98}, {"text": "the same time, which made a\nconnection between this one", "start": 4270.7, "duration": 3.99}, {"text": "problem and all of\nthe problems in NP.", "start": 4274.69, "duration": 4.17}, {"text": "By solving this one\nsatisfiability problem", "start": 4278.86, "duration": 3.72}, {"text": "in polynomial\ntime, it allows you", "start": 4282.58, "duration": 5.64}, {"text": "to solve all of the problems\nin NP in polynomial time.", "start": 4288.22, "duration": 4.79}, {"text": "So if you could solve\nthis problem set in P,", "start": 4293.01, "duration": 3.23}, {"text": "then Hamiltonian path\nis also solvable in P.", "start": 4296.24, "duration": 5.56}, {"text": "If you step back and think about\nthat, it's kind of amazing.", "start": 4301.8, "duration": 2.5}, {"text": "And the method that\nwe're going to introduce", "start": 4306.82, "duration": 2.19}, {"text": "is called polynomial\ntime reducibility.", "start": 4309.01, "duration": 3.93}, {"text": "Let's do a quick\ncheck-in on this.", "start": 4312.94, "duration": 1.65}, {"text": "This should be an easy one.", "start": 4314.59, "duration": 3.03}, {"text": "Why don't you just think\nabout, is SAT, the SAT problem", "start": 4317.62, "duration": 2.91}, {"text": "that we just described\nhere, is that in NP?", "start": 4320.53, "duration": 1.89}, {"text": "Three seconds.", "start": 4326.857, "duration": 0.583}, {"text": "You all there?", "start": 4330.86, "duration": 1.71}, {"text": "OK.", "start": 4332.57, "duration": 0.93}, {"text": "Ending polling.", "start": 4333.5, "duration": 0.72}, {"text": "Hopefully you're getting\nthe intuition for NP", "start": 4341.24, "duration": 3.0}, {"text": "that these are the\nproblems-- to be in NP means", "start": 4344.24, "duration": 4.08}, {"text": "that when you're a\nmember of the language,", "start": 4348.32, "duration": 2.49}, {"text": "there's a short proof or a\nshort certificate of membership.", "start": 4350.81, "duration": 3.51}, {"text": "And in this case,\nthe short certificate", "start": 4354.32, "duration": 1.92}, {"text": "that the formula is\nsatisfiable is the assignment,", "start": 4356.24, "duration": 3.1}, {"text": "which makes it true, also called\nthe satisfying assignment.", "start": 4359.34, "duration": 4.55}, {"text": "So yes, this is an NP language,\nlanguage that's in NP.", "start": 4363.89, "duration": 3.245}, {"text": "There are a lot of things that\nwe don't know in the subject,", "start": 4371.55, "duration": 2.5}, {"text": "but this isn't one of them.", "start": 4374.05, "duration": 2.04}, {"text": "We do know that SAT is in NP.", "start": 4376.09, "duration": 2.97}, {"text": "So let's talk about\nour method for showing", "start": 4379.06, "duration": 3.51}, {"text": "this remarkable\nfact that, if you", "start": 4382.57, "duration": 9.58}, {"text": "can solve SAT in polynomial\ntime, then all of NP", "start": 4392.15, "duration": 3.6}, {"text": "is solvable in polynomial time.", "start": 4395.75, "duration": 1.68}, {"text": "And it uses this notion of\npolynomial time reducibility,", "start": 4397.43, "duration": 4.02}, {"text": "which is just like\nmapping reducibility", "start": 4401.45, "duration": 2.49}, {"text": "that I hope you've all\ngrown to know and love", "start": 4403.94, "duration": 2.94}, {"text": "in the first half of the course.", "start": 4406.88, "duration": 1.74}, {"text": "But now, the reduction has to\noperate in polynomial time.", "start": 4408.62, "duration": 4.38}, {"text": "So it's the same picture that\nwe had before, mapping A to B,", "start": 4413.0, "duration": 5.13}, {"text": "transforming A questions\nto B questions.", "start": 4418.13, "duration": 2.16}, {"text": "But now the transformation\nhas to operate quickly.", "start": 4420.29, "duration": 3.91}, {"text": "And we get that if A is\npolynomial time reducible to B,", "start": 4424.2, "duration": 5.33}, {"text": "and B is polynomial time, then\nA is also polynomial time.", "start": 4429.53, "duration": 4.47}, {"text": "Same pattern as before.", "start": 4434.0, "duration": 1.74}, {"text": "If A is reducible to B and\nB is easy, then A is easy.", "start": 4435.74, "duration": 5.58}, {"text": "Here is kind of the\nessence of the idea,", "start": 4441.32, "duration": 4.92}, {"text": "or at least the outline of the\nidea of this Cook and Levin", "start": 4446.24, "duration": 5.04}, {"text": "theorem.", "start": 4451.28, "duration": 0.96}, {"text": "That if satisfiable is in\nP, then everything in NP", "start": 4452.24, "duration": 3.48}, {"text": "can be done in P. Which\nis because, we will", "start": 4455.72, "duration": 2.76}, {"text": "show that all problems\nin NP are polynomial time", "start": 4458.48, "duration": 4.77}, {"text": "reducible to SAT.", "start": 4463.25, "duration": 3.39}, {"text": "That's the amazing fact.", "start": 4466.64, "duration": 1.8}, {"text": "So therefore, if you\ncan bring SAT down", "start": 4468.44, "duration": 3.39}, {"text": "into P by using this reduction,\nit brings everything else along", "start": 4471.83, "duration": 3.87}, {"text": "with it, everything\nis reducible to SAT.", "start": 4475.7, "duration": 2.97}, {"text": "So we just have to\nshow how to do that.", "start": 4478.67, "duration": 3.42}, {"text": "There is an analogy that\nwe had in the first half", "start": 4482.09, "duration": 2.19}, {"text": "of the course, in one of\nour homework problems,", "start": 4484.28, "duration": 1.958}, {"text": "if you may remember.", "start": 4486.238, "duration": 1.282}, {"text": "We showed that A TM has\nthe very special property", "start": 4487.52, "duration": 6.12}, {"text": "that all Turing\nrecognizable languages are", "start": 4493.64, "duration": 2.94}, {"text": "mapping reducible to it.", "start": 4496.58, "duration": 2.81}, {"text": "I think that was problem 2,\nor 2a, either in problem set 3", "start": 4499.39, "duration": 8.27}, {"text": "or problem set 2.", "start": 4507.66, "duration": 2.01}, {"text": "I think problem set 3.", "start": 4509.67, "duration": 2.67}, {"text": "That every Turing\nrecognizable language", "start": 4512.34, "duration": 2.73}, {"text": "is polynomial time\nreducible to A TM.", "start": 4515.07, "duration": 2.52}, {"text": "And so, very similar picture.", "start": 4517.59, "duration": 2.85}, {"text": "And there's a lot\nof analogies here", "start": 4520.44, "duration": 2.04}, {"text": "that you can draw between\nthe computability section", "start": 4522.48, "duration": 4.44}, {"text": "and the complexity section.", "start": 4526.92, "duration": 2.85}, {"text": "With that, I know we're\njust about out of time.", "start": 4529.77, "duration": 2.56}, {"text": "So let's just quick review\nof what we've done here.", "start": 4532.33, "duration": 6.41}, {"text": "I will stick around for\nquestions for a while.", "start": 4538.74, "duration": 3.82}, {"text": "Is there a--", "start": 4542.56, "duration": 2.935}, {"text": "OK, that's a good question.", "start": 4545.495, "duration": 1.125}, {"text": "Is there a regular\nreduction analogy version", "start": 4546.62, "duration": 5.88}, {"text": "to mapping reducibility?", "start": 4552.5, "duration": 2.28}, {"text": "We had the general reduction\nfor the computability section.", "start": 4554.78, "duration": 5.77}, {"text": "And we had the mapping reduction\nfor the computability section.", "start": 4560.55, "duration": 2.94}, {"text": "Here, we're only going\nto be focusing now", "start": 4563.49, "duration": 3.42}, {"text": "on the mapping reduction.", "start": 4566.91, "duration": 1.92}, {"text": "So polynomial time\nreduction is, by assumption,", "start": 4568.83, "duration": 3.39}, {"text": "going to be a mapping reduction.", "start": 4572.22, "duration": 1.44}, {"text": "Yes, there is a general\npolynomial time reduction", "start": 4573.66, "duration": 4.8}, {"text": "notion as well.", "start": 4578.46, "duration": 0.765}, {"text": "This is not required,\nbut if you are", "start": 4582.45, "duration": 2.2}, {"text": "curious about the\ngeneral reduction", "start": 4584.65, "duration": 2.88}, {"text": "and how to precisely\nformulate that,", "start": 4587.53, "duration": 2.04}, {"text": "it actually appears in chapter\n6 under Turing reducibility.", "start": 4589.57, "duration": 5.28}, {"text": "That's the general notion\nof reducibility spelled out", "start": 4594.85, "duration": 2.67}, {"text": "in a formal way.", "start": 4597.52, "duration": 1.05}, {"text": "And there's polynomial time\nTuring reducibility as well.", "start": 4598.57, "duration": 3.61}, {"text": "We're not going to talk\nabout it in this course.", "start": 4602.18, "duration": 3.185}, {"text": "Other questions?", "start": 4609.44, "duration": 2.84}, {"text": "Does NP correspond\nexactly to verification", "start": 4612.28, "duration": 4.44}, {"text": "in polynomial time?", "start": 4616.72, "duration": 3.18}, {"text": "For me to answer that\nas a precise question,", "start": 4619.9, "duration": 2.22}, {"text": "we have to have a precise\ndefinition of verification.", "start": 4622.12, "duration": 3.06}, {"text": "But with the right\ndefinition, the answer is yes.", "start": 4625.18, "duration": 6.24}, {"text": "So you can define a verifier\nas a polynomial time algorithm", "start": 4631.42, "duration": 6.27}, {"text": "that gives a\ncertificate, that takes", "start": 4637.69, "duration": 3.18}, {"text": "a certificate and an\ninput to the language,", "start": 4640.87, "duration": 2.28}, {"text": "and will accept if\nthat certificate is", "start": 4643.15, "duration": 7.74}, {"text": "a valid certificate\nfor that input.", "start": 4650.89, "duration": 2.82}, {"text": "This is actually\ndiscussed in chapter,", "start": 4653.71, "duration": 2.34}, {"text": "I think, 9 of the text.", "start": 4656.05, "duration": 4.075}, {"text": "Now I'm forgetting already,\nwhat's where in the book.", "start": 4667.95, "duration": 2.28}, {"text": "But yeah, you can think of\nNP in terms of verification", "start": 4670.23, "duration": 4.17}, {"text": "as the definition.", "start": 4674.4, "duration": 1.14}, {"text": "Is proving P equal NP the same\nas proving that a polynom--", "start": 4679.84, "duration": 4.71}, {"text": "actually, I can even make the--", "start": 4684.55, "duration": 1.95}, {"text": "if you want, you can\npost public comments too.", "start": 4686.5, "duration": 5.33}, {"text": "I should have done\nthat in other cases.", "start": 4691.83, "duration": 2.31}, {"text": "Is proving P equal NP\nthe same as proving", "start": 4694.14, "duration": 2.61}, {"text": "that a polynomial\ntime non-deterministic", "start": 4696.75, "duration": 2.35}, {"text": "Turing machine N has a\npolynomial time deterministic?", "start": 4699.1, "duration": 4.31}, {"text": "Yeah.", "start": 4706.115, "duration": 0.5}, {"text": "Suppose we prove that P equals\nNP, which is the minority view,", "start": 4709.66, "duration": 6.77}, {"text": "I would say, the\nsmall minority view.", "start": 4716.43, "duration": 4.265}, {"text": "There are some\npeople who believe", "start": 4720.695, "duration": 1.375}, {"text": "that that is entirely possible,\nand might even be the case.", "start": 4722.07, "duration": 4.89}, {"text": "But that's a very small group.", "start": 4726.96, "duration": 3.06}, {"text": "But yeah, if you\nprove P equal NP,", "start": 4730.02, "duration": 2.7}, {"text": "that's the same as saying\nthat every non-deterministic", "start": 4732.72, "duration": 3.24}, {"text": "polynomial time Turing\nmachine is going", "start": 4735.96, "duration": 2.67}, {"text": "to have a companion\ndeterministic polynomial", "start": 4738.63, "duration": 3.72}, {"text": "time Turing machine which\ndoes the same language.", "start": 4742.35, "duration": 2.67}, {"text": "That's exactly what it means.", "start": 4745.02, "duration": 2.51}, {"text": "Bye bye, everybody.", "start": 4747.53, "duration": 2.36}]
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+[{"text": "How is everyone doing today?", "start": 17.5, "duration": 2.002}, {"text": "[CHEERING]", "start": 19.502, "duration": 2.769}, {"text": "You know why there's\na lot of excitement,", "start": 22.271, "duration": 1.702}, {"text": "and I saw the silent\npraise, because I", "start": 23.973, "duration": 2.135}, {"text": "know what this means, recently,\nand I'm doing more and more.", "start": 26.108, "duration": 5.205}, {"text": "You guys are excited, because\nwe are celebrating something", "start": 31.313, "duration": 3.204}, {"text": "on Friday.", "start": 34.517, "duration": 1.101}, {"text": "We are celebrating knowledge,\nwe are celebrating chemistry,", "start": 35.618, "duration": 6.339}, {"text": "and we are celebrating\nhow much we've", "start": 41.957, "duration": 3.537}, {"text": "learned in the last month.", "start": 45.494, "duration": 1.335}, {"text": "It's called exam three.", "start": 46.829, "duration": 1.668}, {"text": "Woo.", "start": 48.497, "duration": 0.734}, {"text": "It's a midterm.", "start": 49.231, "duration": 1.368}, {"text": "Thank you for that.", "start": 50.599, "duration": 0.935}, {"text": "What I thought we'd\ndo today instead of--", "start": 58.574, "duration": 2.769}, {"text": "again, I mentioned\nthis on Monday.", "start": 61.343, "duration": 3.304}, {"text": "You guys just had\nThanksgiving, you're back,", "start": 64.647, "duration": 3.603}, {"text": "and now we've got a test.", "start": 68.25, "duration": 1.402}, {"text": "And I know you've got a\nlot of other stuff going on", "start": 69.652, "duration": 2.102}, {"text": "too at this time.", "start": 71.754, "duration": 0.767}, {"text": "So instead of throwing\nsomething in that we're not", "start": 72.521, "duration": 2.102}, {"text": "going to test you on, what\nI wanted to do with today", "start": 74.623, "duration": 2.569}, {"text": "was just to kind of feel our\noneness with the concepts.", "start": 77.192, "duration": 4.704}, {"text": "All right?", "start": 81.896, "duration": 0.935}, {"text": "And so I want to go\nover the concepts that", "start": 82.831, "duration": 3.17}, {"text": "are going to be potentially\non the exam on Friday,", "start": 86.001, "duration": 5.306}, {"text": "and I'll talk about\nthose concepts,", "start": 91.307, "duration": 2.235}, {"text": "and we'll do a\ncouple of problems", "start": 93.542, "duration": 1.368}, {"text": "here and there as we go.", "start": 94.91, "duration": 1.635}, {"text": "OK, so those are the metrics,\nthe specs, for exam three.", "start": 96.545, "duration": 5.571}, {"text": "But on Monday, I finished\nwith two minutes left,", "start": 106.221, "duration": 3.671}, {"text": "and I said, hey,\nthere's one more", "start": 109.892, "duration": 1.367}, {"text": "kind of acid-base definition.", "start": 111.259, "duration": 1.736}, {"text": "You won't be tested on it,\nbut it's the most general,", "start": 112.995, "duration": 2.202}, {"text": "and I've got to\ngive Lewis his due.", "start": 115.197, "duration": 1.835}, {"text": "So I just wanted to\njust show you like that.", "start": 117.032, "duration": 2.937}, {"text": "You won't be tested on\nLewis acids and bases,", "start": 119.969, "duration": 2.969}, {"text": "but I did throw this\nin there, and so", "start": 122.938, "duration": 2.67}, {"text": "I want to just, for one or two\nmore minutes, talk about this.", "start": 125.608, "duration": 3.603}, {"text": "Right?", "start": 129.211, "duration": 0.5}, {"text": "These are the things you\nare responsible for knowing.", "start": 129.711, "duration": 2.203}, {"text": "So an Arrhenius acid-base--", "start": 131.914, "duration": 1.768}, {"text": "OH, H plus.", "start": 133.682, "duration": 1.101}, {"text": "Bronsted-Lowry.", "start": 134.783, "duration": 1.969}, {"text": "It's proton transfer.", "start": 136.752, "duration": 2.736}, {"text": "And then there's\nLewis, who broasted", "start": 139.588, "duration": 1.802}, {"text": "these guys, because\nhe said, uh-uh,", "start": 141.39, "duration": 4.571}, {"text": "and this is the most general way\nto think about acids and bases.", "start": 145.961, "duration": 4.238}, {"text": "It is the most general.", "start": 150.199, "duration": 1.201}, {"text": "It is quite powerful, because\nyou go back to say this one,", "start": 151.4, "duration": 8.275}, {"text": "and so if this is a--", "start": 159.675, "duration": 3.136}, {"text": "what if we mix this with this?", "start": 162.811, "duration": 4.004}, {"text": "So here we have H.", "start": 166.815, "duration": 2.236}, {"text": "Now, remember, Lewis had all\nthe dots all over the place.", "start": 169.051, "duration": 2.903}, {"text": "He loved dots, and so\nthey're all over the place.", "start": 171.954, "duration": 3.47}, {"text": "And that's what if you had\nthis, this is a Lewis acid,", "start": 175.424, "duration": 4.771}, {"text": "because it is ready to receive.", "start": 180.195, "duration": 4.538}, {"text": "What is it ready to receive?", "start": 184.733, "duration": 1.702}, {"text": "No more atoms, only electrons.", "start": 186.435, "duration": 3.07}, {"text": "It is the most general\nway to think about it.", "start": 189.505, "duration": 3.136}, {"text": "All right?", "start": 192.641, "duration": 1.101}, {"text": "And this would be a\nLewis base, because it", "start": 193.742, "duration": 3.504}, {"text": "is ready to give a\npair of electrons", "start": 197.246, "duration": 4.104}, {"text": "and form a bond together.", "start": 201.35, "duration": 1.501}, {"text": "And that's what they do,\nor that's what they can do.", "start": 202.851, "duration": 3.737}, {"text": "So a Lewis acid and a Lewis\nbase is the most general form,", "start": 206.588, "duration": 4.705}, {"text": "and you really get rid of--", "start": 211.293, "duration": 1.502}, {"text": "so for Lewis, it's all\nabout electron transfer,", "start": 212.795, "duration": 4.471}, {"text": "electron pair transfer, pair\ntransfer, or bonds if you're--", "start": 217.266, "duration": 5.938}, {"text": "I'm just going to make it\nas general as possible.", "start": 223.204, "duration": 2.77}, {"text": "If you're going to mix\nan acid and a base,", "start": 225.974, "duration": 1.936}, {"text": "which I'll do in a\nsecond, it's a pair.", "start": 227.91, "duration": 2.869}, {"text": "Electron transfer is\nwhat it's all about,", "start": 230.779, "duration": 3.871}, {"text": "and what happens here?", "start": 234.65, "duration": 2.569}, {"text": "Well, you don't have\nany chemical identity,", "start": 237.219, "duration": 3.337}, {"text": "no more chemical identity.", "start": 240.556, "duration": 1.935}, {"text": "So it's full.", "start": 245.861, "duration": 0.734}, {"text": "You don't need the\nhydrogens anymore.", "start": 246.595, "duration": 1.568}, {"text": "You don't need the OH's.", "start": 248.163, "duration": 1.735}, {"text": "It's totally general.", "start": 249.898, "duration": 1.869}, {"text": "And this really opens\nit up, because now you", "start": 251.767, "duration": 2.336}, {"text": "can look at gases, liquid,\nsolids, all forms of matter,", "start": 254.103, "duration": 3.103}, {"text": "all elements in the table, and\nyou can think about them as", "start": 257.206, "duration": 2.435}, {"text": "whether they're going\nto have an acid-like", "start": 259.641, "duration": 2.169}, {"text": "or a base-like character in\nterms of electron transfer.", "start": 261.81, "duration": 2.97}, {"text": "So here's the general-- if you\nhad a Lewis acid and a Lewis", "start": 264.78, "duration": 4.671}, {"text": "base, and you mix them together.", "start": 269.451, "duration": 3.003}, {"text": "Then, you can see that\nif you got an electron", "start": 272.454, "duration": 3.904}, {"text": "pair that could then go--", "start": 276.358, "duration": 1.301}, {"text": "that one of them wants it,\nand the other can give it,", "start": 277.659, "duration": 2.236}, {"text": "and they can form\na bond, then that", "start": 279.895, "duration": 2.569}, {"text": "would be how you think about\nmixing a Lewis acid and a Lewis", "start": 282.464, "duration": 2.803}, {"text": "base.", "start": 285.267, "duration": 0.501}, {"text": "And again, this\nwon't be on the exam,", "start": 285.768, "duration": 3.203}, {"text": "but I just had to\ngive Lewis his due.", "start": 288.971, "duration": 3.736}, {"text": "OK, Lewis acids and bases\nare all about the electrons.", "start": 292.707, "duration": 5.206}, {"text": "And then the other thing I\ndidn't get to do on Monday", "start": 297.913, "duration": 2.202}, {"text": "was my Why This Matters,\nand so I want to do that.", "start": 300.115, "duration": 2.069}, {"text": "Now hair is very much affected\nby the softness of water.", "start": 302.184, "duration": 3.87}, {"text": "But instead of me showing\nyou lots of pictures of hair", "start": 308.891, "duration": 5.038}, {"text": "that I found randomly on the\ninternet, googling soft water,", "start": 313.929, "duration": 5.472}, {"text": "hard water, different\nforms of water, hair,", "start": 319.401, "duration": 4.004}, {"text": "I'm showing you pipes, because\nthat's much more actually", "start": 323.405, "duration": 3.237}, {"text": "relevant in terms of like, for\nexample, whether you can get", "start": 326.642, "duration": 2.469}, {"text": "water into your house at all.", "start": 329.111, "duration": 2.402}, {"text": "All right?", "start": 331.513, "duration": 0.901}, {"text": "And this is a real problem.", "start": 332.414, "duration": 2.736}, {"text": "If you have hard\nwater what it means", "start": 335.15, "duration": 1.835}, {"text": "is you've got\nminerals in the water.", "start": 336.985, "duration": 3.037}, {"text": "Right?", "start": 340.022, "duration": 0.734}, {"text": "Things like magnesium and\ncalcium ions are in the water.", "start": 340.756, "duration": 3.837}, {"text": "And what happens is, if you run\nthat through pipes, they tend", "start": 344.593, "duration": 3.937}, {"text": "to react and form and deposit.", "start": 348.53, "duration": 4.071}, {"text": "And you get these deposits\nof very, very hard mineral", "start": 352.601, "duration": 2.569}, {"text": "deposits around the edges that\neventually look like this.", "start": 355.17, "duration": 3.203}, {"text": "That's not a good thing.", "start": 358.373, "duration": 1.702}, {"text": "And so you need to soften the\nwater, and that's something", "start": 360.075, "duration": 3.537}, {"text": "you may have heard of.", "start": 363.612, "duration": 1.501}, {"text": "But now you really know how\nto think about it, because you", "start": 365.113, "duration": 2.403}, {"text": "can think about it in\nterms of all of the things", "start": 367.516, "duration": 2.069}, {"text": "that you've learned.", "start": 369.585, "duration": 2.469}, {"text": "And just as an example,\nif one of those minerals", "start": 372.054, "duration": 4.538}, {"text": "that's a problem is calcium--", "start": 376.592, "duration": 2.035}, {"text": "oh, it is, right?", "start": 378.627, "duration": 1.568}, {"text": "Magnesium is another one\nthat can cause this in pipes.", "start": 380.195, "duration": 5.205}, {"text": "You've got to somehow\ntake it out of the water", "start": 385.4, "duration": 3.571}, {"text": "or at least make it into a form\nthat makes it like insoluble,", "start": 388.971, "duration": 4.871}, {"text": "so it'll just flow, and\nit won't have a chance", "start": 393.842, "duration": 2.469}, {"text": "to come around and deposit on\nthe edge there of the pipe.", "start": 396.311, "duration": 5.306}, {"text": "And so what do you do?", "start": 401.617, "duration": 1.101}, {"text": "Well, you add, for example--", "start": 402.718, "duration": 2.502}, {"text": "oh, we've done this before.", "start": 405.22, "duration": 1.568}, {"text": "Right?", "start": 406.788, "duration": 0.501}, {"text": "What if I add soda,\nsomething called soda ash?", "start": 407.289, "duration": 4.004}, {"text": "Oh, we know what that is.", "start": 411.293, "duration": 1.635}, {"text": "That's Na2CO3, and that\nwill give me some ions.", "start": 412.928, "duration": 8.475}, {"text": "It'll give me some\nNa pluses, and it'll", "start": 421.403, "duration": 2.769}, {"text": "give me some CO3 2 minuses,\nand those are in aqueous.", "start": 424.172, "duration": 5.473}, {"text": "Now, this is all\npart of the stuff", "start": 429.645, "duration": 1.635}, {"text": "that we've been talking about.", "start": 431.28, "duration": 1.234}, {"text": "You're dissociating this\nto get ions in solution,", "start": 432.514, "duration": 2.436}, {"text": "but why do I want these ions?", "start": 434.95, "duration": 3.337}, {"text": "That's a water softener.", "start": 438.287, "duration": 1.735}, {"text": "Why?", "start": 440.022, "duration": 0.567}, {"text": "Because now you can see it.", "start": 440.589, "duration": 1.568}, {"text": "Right?", "start": 442.157, "duration": 0.501}, {"text": "Because this one\nhere, this one here", "start": 442.658, "duration": 3.403}, {"text": "is going to remove the calcium.", "start": 446.061, "duration": 3.437}, {"text": "So if I've got these\ncalcium, these minerals,", "start": 449.498, "duration": 2.369}, {"text": "in the water making it hard\nwater which leads to that", "start": 451.867, "duration": 4.037}, {"text": "and wreaks havoc on\nyour hair, then you", "start": 455.904, "duration": 4.204}, {"text": "get a little of this\nin there, and you're", "start": 460.108, "duration": 1.801}, {"text": "going to react with the calcium.", "start": 461.909, "duration": 1.403}, {"text": "Why?", "start": 463.312, "duration": 0.5}, {"text": "It's because of\nwhat we already saw.", "start": 463.812, "duration": 1.969}, {"text": "If I have this--", "start": 465.781, "duration": 1.968}, {"text": "this is something we've already\nlooked at-- if I have calcium 2", "start": 467.749, "duration": 3.17}, {"text": "plus, and I have some\nbicarbonate in there,", "start": 470.919, "duration": 3.137}, {"text": "CO3 minus, then we know that\nI can get precipitates, Ca--", "start": 474.056, "duration": 6.506}, {"text": "this is just what we looked\nat in the goody bag, right--", "start": 480.562, "duration": 2.503}, {"text": "plus CO2 plus H2O.", "start": 483.065, "duration": 4.404}, {"text": "That's the same kind of reaction\nthat we looked at already.", "start": 487.469, "duration": 3.504}, {"text": "We have calcium carbonate,\ncalcium carbonate.", "start": 490.973, "duration": 3.136}, {"text": "Why?", "start": 494.109, "duration": 0.601}, {"text": "Well, because this is\ngoing to give me these.", "start": 494.71, "duration": 3.536}, {"text": "This is a source for those\nwhich then eats up some calcium.", "start": 498.246, "duration": 5.239}, {"text": "And you think, well, now this\ncan take the calcium ions out,", "start": 503.485, "duration": 4.671}, {"text": "so that it runs through.", "start": 508.156, "duration": 2.369}, {"text": "That's what you want to do here.", "start": 510.525, "duration": 1.634}, {"text": "That's how you soften water.", "start": 512.159, "duration": 2.07}, {"text": "Well, you can add lime which\ngives me a source of OH minus,", "start": 514.229, "duration": 3.871}, {"text": "and that takes\nout the magnesium.", "start": 518.1, "duration": 2.401}, {"text": "And these are ways to change\nthe chemistry of water,", "start": 520.501, "duration": 2.537}, {"text": "so that you don't have\nas many ions, mineral,", "start": 523.038, "duration": 2.97}, {"text": "these calcium and magnesium\nions floating around that cause", "start": 526.008, "duration": 3.336}, {"text": "problems.", "start": 529.344, "duration": 1.368}, {"text": "So that was my Why This\nMatters, and now we", "start": 530.712, "duration": 1.835}, {"text": "turn to what I started\nwith which is exam three.", "start": 532.547, "duration": 3.304}, {"text": "Oh, look at that.", "start": 535.851, "duration": 2.702}, {"text": "I look at that, and\nthat's just happiness.", "start": 538.553, "duration": 3.003}, {"text": "Look at all those topics--", "start": 541.556, "duration": 1.936}, {"text": "X-rays XRD, defects, glasses,\nreaction rates, solubility,", "start": 543.492, "duration": 7.307}, {"text": "aqueous solutions, acids/bases.", "start": 550.799, "duration": 4.538}, {"text": "It's all there.", "start": 555.337, "duration": 1.535}, {"text": "It's all there, and it's all\nthere in you, and if not,", "start": 556.872, "duration": 6.206}, {"text": "you've got two days.", "start": 563.078, "duration": 2.903}, {"text": "So please, make it be there.", "start": 565.981, "duration": 4.337}, {"text": "Let's go through this.", "start": 570.318, "duration": 1.268}, {"text": "Let's go through this.", "start": 571.586, "duration": 0.935}, {"text": "I'm going to go through\nthis topic right there.", "start": 572.521, "duration": 1.935}, {"text": "So I'm going to tell\nyou the concepts that I", "start": 574.456, "duration": 2.035}, {"text": "want to make sure you know.", "start": 576.491, "duration": 1.201}, {"text": "OK, so here's the first one.", "start": 581.096, "duration": 1.168}, {"text": "So it's X-rays, and XRD.", "start": 582.264, "duration": 4.137}, {"text": "So what do I want you to know?", "start": 586.401, "duration": 2.202}, {"text": "Well, for example,\nI want you to know", "start": 588.603, "duration": 2.703}, {"text": "about how you have\ncharacteristic, characteristic,", "start": 591.306, "duration": 6.573}, {"text": "characteristic X-rays,\nand remember this?", "start": 597.879, "duration": 6.54}, {"text": "This comes from\nthose transitions.", "start": 604.419, "duration": 1.802}, {"text": "Right?", "start": 606.221, "duration": 0.5}, {"text": "So you get like the K and the\nL and the M. We say et cetera.", "start": 606.721, "duration": 6.307}, {"text": "We never really did\net cetera, but we've", "start": 613.028, "duration": 2.235}, {"text": "got a lot of K and L lines\nwe looked at, alpha, beta,", "start": 615.263, "duration": 7.541}, {"text": "but there's also the continuous.", "start": 622.804, "duration": 1.969}, {"text": "Right?", "start": 624.773, "duration": 0.5}, {"text": "So this was in--", "start": 625.273, "duration": 1.168}, {"text": "if you want-- this would be in\nthe topic of X-ray generation,", "start": 626.441, "duration": 4.571}, {"text": "and there's that Bremsstrahlung\nword that means breaking.", "start": 631.012, "duration": 9.243}, {"text": "Right?", "start": 640.255, "duration": 2.236}, {"text": "So if you just want\nto look at this,", "start": 642.491, "duration": 3.136}, {"text": "you might have a\ncurve that looks--", "start": 645.627, "duration": 2.436}, {"text": "OK, so we had things like this.", "start": 648.063, "duration": 1.501}, {"text": "Right?", "start": 649.564, "duration": 0.801}, {"text": "Oh, I'm going to try to\nmake it not look too bad,", "start": 650.365, "duration": 5.939}, {"text": "and there's another\none, and so on.", "start": 656.304, "duration": 3.938}, {"text": "And remember, so this would\nbe like intensity, intensity,", "start": 660.242, "duration": 6.573}, {"text": "and this would be like maybe a\nlambda going that way or maybe", "start": 666.815, "duration": 5.405}, {"text": "energy going that\nway or frequency.", "start": 672.22, "duration": 3.704}, {"text": "Right?", "start": 675.924, "duration": 0.5}, {"text": "Those would be like the x-axis,\nand these are those lines.", "start": 676.424, "duration": 5.306}, {"text": "Those are the lines, and they\ncome from the transitions", "start": 681.73, "duration": 3.069}, {"text": "that you get from like\nthe K level to the L level", "start": 684.799, "duration": 4.105}, {"text": "to the M level.", "start": 688.904, "duration": 0.9}, {"text": "Right?", "start": 689.804, "duration": 0.501}, {"text": "Remember, if you get the energy\nhigh enough of an incident", "start": 690.305, "duration": 5.606}, {"text": "electron onto a\ntarget, metal, then you", "start": 695.911, "duration": 6.006}, {"text": "can knock out electrons\nfrom that 1s shell.", "start": 701.917, "duration": 3.703}, {"text": "And then something\ncascades down,", "start": 705.62, "duration": 1.702}, {"text": "and that emits these lines here.", "start": 707.322, "duration": 1.935}, {"text": "So that'd be like K alpha,\nK alpha, K beta, et cetera.", "start": 709.257, "duration": 5.105}, {"text": "But then, you also,\neven at lower energies,", "start": 714.362, "duration": 2.837}, {"text": "even if you don't\nhave enough energy", "start": 717.199, "duration": 1.468}, {"text": "to knock out a 1s\nelectron, you still", "start": 718.667, "duration": 2.736}, {"text": "can slow an electron down as\nit goes through a metal atom.", "start": 721.403, "duration": 3.703}, {"text": "And that's where you get\nthis continuous spectrum", "start": 725.106, "duration": 3.737}, {"text": "and that limit of how much of\nthat type of X-ray you get.", "start": 728.843, "duration": 4.538}, {"text": "And it just depends\non the incident,", "start": 733.381, "duration": 2.403}, {"text": "on the voltage, on the\nmaximum incident electron", "start": 735.784, "duration": 3.537}, {"text": "you fire at it.", "start": 739.321, "duration": 0.634}, {"text": "So that's those\nfirst two topics.", "start": 739.955, "duration": 2.269}, {"text": "OK?", "start": 742.224, "duration": 2.202}, {"text": "Well, oh, we also did\nX-ray diffraction.", "start": 744.426, "duration": 5.172}, {"text": "Oh, that's fun, diffraction.", "start": 749.598, "duration": 3.903}, {"text": "OK, and this involves\nunderstanding Bragg,", "start": 753.501, "duration": 4.638}, {"text": "the Bragg condition, and\nalso selection rules.", "start": 758.139, "duration": 5.372}, {"text": "So let's just take a look at\nan example of the diffraction", "start": 767.549, "duration": 4.938}, {"text": "and selection rules.", "start": 772.487, "duration": 0.834}, {"text": "OK?", "start": 773.321, "duration": 0.501}, {"text": "So what would I want?", "start": 773.822, "duration": 1.234}, {"text": "So these are like\nthe kind of concepts", "start": 775.056, "duration": 1.769}, {"text": "that I want you to know about.", "start": 776.825, "duration": 2.502}, {"text": "How might it play out?", "start": 779.327, "duration": 0.968}, {"text": "So like, OK, so here's like\nan example of a spectrum.", "start": 780.295, "duration": 5.339}, {"text": "Now, that's an X-ray spectrum\nfor MgFeO4, magnesium ferrite,", "start": 785.634, "duration": 7.607}, {"text": "and it's a kind of steel.", "start": 793.241, "duration": 3.103}, {"text": "And you put it in, you\nmake a powder of it,", "start": 796.344, "duration": 1.769}, {"text": "and and you throw\nsome X-rays on it.", "start": 798.113, "duration": 2.269}, {"text": "Oh no, you throw just\none type of X-ray on it.", "start": 800.382, "duration": 3.837}, {"text": "All right?", "start": 804.219, "duration": 0.5}, {"text": "So for these X-ray\nspectra, what happened?", "start": 804.719, "duration": 2.102}, {"text": "I threw some K alpha on it,\nI showed right there, you", "start": 806.821, "duration": 3.504}, {"text": "got to say what you got.", "start": 810.325, "duration": 1.935}, {"text": "All right?", "start": 812.26, "duration": 1.135}, {"text": "You've got to know at\nleast the source of X-rays", "start": 813.395, "duration": 3.003}, {"text": "has this wavelength.", "start": 816.398, "duration": 2.469}, {"text": "Good.", "start": 818.867, "duration": 1.067}, {"text": "And if I have that\nspectrum, and say,", "start": 819.934, "duration": 1.802}, {"text": "what's the lattice constant?", "start": 821.736, "duration": 2.836}, {"text": "What's the structure?", "start": 824.572, "duration": 1.168}, {"text": "I can get that.", "start": 825.74, "duration": 1.569}, {"text": "How would I get that?", "start": 827.309, "duration": 0.867}, {"text": "How would I get that?", "start": 828.176, "duration": 0.868}, {"text": "So I would take this\nspectrum, and notice something", "start": 829.044, "duration": 5.705}, {"text": "is very much pointed out to\nme, a peak and a number, 35.5.", "start": 834.749, "duration": 5.139}, {"text": "Right?", "start": 839.888, "duration": 0.5}, {"text": "That's the 2 theta\nvalue for the 311 peak.", "start": 840.388, "duration": 4.204}, {"text": "Well, I think I'll\ntake that as a hint.", "start": 844.592, "duration": 2.103}, {"text": "Maybe I should think about that\nnumber, and OK, so let's see.", "start": 846.695, "duration": 3.503}, {"text": "From Bragg, so from\nBragg, you know", "start": 850.198, "duration": 4.905}, {"text": "that you got n lambda\nequals 2d sine theta,", "start": 855.103, "duration": 8.675}, {"text": "and remember that had to do with\nconstructive and destructive", "start": 863.778, "duration": 3.103}, {"text": "interference of waves, the\nwaves being the X-rays.", "start": 866.881, "duration": 3.037}, {"text": "And then we said, well, n is 1\nin our class, so that's just 1", "start": 869.918, "duration": 5.105}, {"text": "in 3,091.", "start": 875.023, "duration": 0.734}, {"text": "It doesn't have to be.", "start": 875.757, "duration": 1.201}, {"text": "You could have interference\noff of two planes down,", "start": 876.958, "duration": 3.07}, {"text": "three planes down,\nbut in this class,", "start": 880.028, "duration": 1.535}, {"text": "we're just doing the two\nplanes next to each other.", "start": 881.563, "duration": 2.135}, {"text": "So n is 1.", "start": 883.698, "duration": 1.135}, {"text": "OK?", "start": 884.833, "duration": 1.468}, {"text": "Now, I'll take that angle, and\nI'll round it to 18 degrees.", "start": 886.301, "duration": 3.837}, {"text": "So I'm going to say for theta\nequals 18 degrees, then--", "start": 890.138, "duration": 6.073}, {"text": "oh, wait, why is it 18?", "start": 896.211, "duration": 2.936}, {"text": "Because that's 2 theta.", "start": 899.147, "duration": 1.802}, {"text": "Right?", "start": 900.949, "duration": 0.5}, {"text": "Because remember, we\ntake spectra in 2 theta,", "start": 901.449, "duration": 2.569}, {"text": "but the theta in\nBragg is 1 theta.", "start": 904.018, "duration": 2.336}, {"text": "OK, that wasn't too hard.", "start": 906.354, "duration": 2.903}, {"text": "But now, I've got, let's see,\nsine theta is around 0.3,", "start": 909.257, "duration": 7.174}, {"text": "and oh, I got lambda.", "start": 916.431, "duration": 3.303}, {"text": "Lambda equals 1.54 nanometers,\nand so I can actually", "start": 919.734, "duration": 7.274}, {"text": "plug in now.", "start": 927.008, "duration": 2.002}, {"text": "I didn't even need the peak.", "start": 929.01, "duration": 2.002}, {"text": "I'm just plugging in the Bragg\ncondition, and I've got d.", "start": 931.012, "duration": 6.373}, {"text": "d equals 2.52\nAngstroms, so I'm done.", "start": 937.385, "duration": 5.939}, {"text": "No.", "start": 943.324, "duration": 1.235}, {"text": "No, I'm not done, because\nthe question says,", "start": 944.559, "duration": 2.336}, {"text": "what's the lattice constant?", "start": 946.895, "duration": 2.269}, {"text": "What's the lattice constant?", "start": 949.164, "duration": 1.167}, {"text": "This d, I didn't say--", "start": 950.331, "duration": 3.003}, {"text": "I did something very bad--", "start": 953.334, "duration": 1.202}, {"text": "I didn't say what d--", "start": 954.536, "duration": 2.636}, {"text": "d is in hkl.", "start": 957.172, "duration": 2.669}, {"text": "That's what an XRD does.", "start": 959.841, "duration": 3.87}, {"text": "XRD, that's a different\nthan diffraction, but the d,", "start": 963.711, "duration": 4.071}, {"text": "in Bragg, is the distance\nbetween the mirror planes", "start": 967.782, "duration": 4.204}, {"text": "that are scattering.", "start": 971.986, "duration": 1.836}, {"text": "All right?", "start": 973.822, "duration": 0.634}, {"text": "And so that's some\ncuts in the crystal.", "start": 974.456, "duration": 3.837}, {"text": "That's some hkl, and\nwe know from that era", "start": 978.293, "duration": 4.838}, {"text": "that there is an equation\nfor cubic crystals", "start": 983.131, "duration": 4.204}, {"text": "that gives us hkl\nwhich is a divided", "start": 987.335, "duration": 3.47}, {"text": "by the square root of h squared\nplus k squared plus l squared.", "start": 990.805, "duration": 8.008}, {"text": "And that is the lattice\nconstant of the crystal,", "start": 998.813, "duration": 7.574}, {"text": "and that would be the\ndistance between any planes,", "start": 1006.387, "duration": 3.337}, {"text": "any set of planes,\nin the crystal,", "start": 1009.724, "duration": 2.169}, {"text": "and that's what we need.", "start": 1011.893, "duration": 1.301}, {"text": "Now, I can use that,\ncombine it with the d,", "start": 1013.194, "duration": 5.739}, {"text": "and I can get that the lattice\nconstant is 8.38 Angstroms.", "start": 1018.933, "duration": 5.005}, {"text": "Good.", "start": 1023.938, "duration": 1.468}, {"text": "But the second question is--", "start": 1025.406, "duration": 2.635}, {"text": "you don't even need to do\nany math to answer that--", "start": 1028.041, "duration": 2.703}, {"text": "what is the lattice structure?", "start": 1030.744, "duration": 2.771}, {"text": "Here, we simply go to\nour selection rules,", "start": 1033.515, "duration": 3.169}, {"text": "and we know from before if\nthey're all even or all odd--", "start": 1036.684, "duration": 7.241}, {"text": "so here we have, let's\nsee, all these peaks--", "start": 1043.925, "duration": 1.867}, {"text": "220, 311, 400.", "start": 1045.792, "duration": 3.905}, {"text": "You can see, they're\nalways all even,", "start": 1049.697, "duration": 1.635}, {"text": "or they're always all odd.", "start": 1051.332, "duration": 1.302}, {"text": "From our selection rules,\nwhat kind of crystal is that?", "start": 1052.634, "duration": 2.569}, {"text": "It's got to be FCC.", "start": 1058.006, "duration": 2.202}, {"text": "All right?", "start": 1060.208, "duration": 0.834}, {"text": "It's got to be FCC.", "start": 1061.042, "duration": 1.768}, {"text": "So that's the answer\nto that question,", "start": 1062.81, "duration": 3.104}, {"text": "just from looking at\nthe peaks that you get", "start": 1065.914, "duration": 2.268}, {"text": "and matching them with the\nselection rules that you know,", "start": 1068.182, "duration": 3.637}, {"text": "that we've already talked about.", "start": 1071.819, "duration": 1.335}, {"text": "You could also, if you\ndidn't have the planes--", "start": 1075.823, "duration": 3.003}, {"text": "so this is an example, where\nyou're given all these planes.", "start": 1078.826, "duration": 3.17}, {"text": "You're given all these hkls,\nbut what if instead it's", "start": 1081.996, "duration": 2.303}, {"text": "like the one we had in class?", "start": 1084.299, "duration": 2.068}, {"text": "We went through this in class.", "start": 1086.367, "duration": 1.235}, {"text": "Here, I'm not given the planes.", "start": 1087.602, "duration": 1.301}, {"text": "I'm given instead\njust two theta values.", "start": 1088.903, "duration": 4.738}, {"text": "Well now, you've got to go\nand use the procedure of XRD,", "start": 1093.641, "duration": 4.271}, {"text": "and I'm not going\nto do that again.", "start": 1097.912, "duration": 1.468}, {"text": "We've already done\nthat pretty thoroughly,", "start": 1099.38, "duration": 2.603}, {"text": "but that's what you\nwould have to do here,", "start": 1101.983, "duration": 2.169}, {"text": "where you create your columns.", "start": 1104.152, "duration": 2.035}, {"text": "Remember the columns?", "start": 1106.187, "duration": 1.935}, {"text": "All right?", "start": 1108.122, "duration": 1.702}, {"text": "So you would simply make your\ncolumns, you make your sign,", "start": 1109.824, "duration": 2.436}, {"text": "your thetas, your 2 theta\ntheta sine squared thetas.", "start": 1112.26, "duration": 4.805}, {"text": "And then you normalize,\nyou take the lowest one,", "start": 1117.065, "duration": 3.97}, {"text": "and you normalize to 1.", "start": 1121.035, "duration": 3.27}, {"text": "Clear fractions, and then\nfind the hkl combinations,", "start": 1124.305, "duration": 3.103}, {"text": "and that's how you would\ngo from this to getting,", "start": 1127.408, "duration": 3.237}, {"text": "for example, the planes.", "start": 1130.645, "duration": 2.569}, {"text": "So those are some\nexamples of things", "start": 1133.214, "duration": 2.336}, {"text": "I want you to be able to\ndo with X-rays and XRD.", "start": 1135.55, "duration": 3.603}, {"text": "Let's move on.", "start": 1139.153, "duration": 1.735}, {"text": "Let's go to the next topic.", "start": 1140.888, "duration": 1.135}, {"text": "Let's do defects.", "start": 1142.023, "duration": 2.035}, {"text": "How about this, defects,\nbecause as we said,", "start": 1144.058, "duration": 5.205}, {"text": "it's just like life,\ncrystals, defects", "start": 1149.263, "duration": 2.903}, {"text": "are what make them interesting.", "start": 1152.166, "duration": 1.669}, {"text": "It's the same.", "start": 1153.835, "duration": 0.867}, {"text": "Everything, it's\nall about defects,", "start": 1154.702, "duration": 2.002}, {"text": "imperfections, those are\nthe interesting and exciting", "start": 1156.704, "duration": 2.703}, {"text": "things, so we've got to know\nabout them in chemistry,", "start": 1159.407, "duration": 3.47}, {"text": "of course.", "start": 1162.877, "duration": 2.87}, {"text": "So we've talked about a bunch\nof different kinds of defects.", "start": 1165.747, "duration": 3.136}, {"text": "The first one that\nwe talked about", "start": 1168.883, "duration": 2.169}, {"text": "were vacancies, vacancies, and\nthese could be interstitial.", "start": 1171.052, "duration": 8.075}, {"text": "These fall into the category of\npoint defects, point defects,", "start": 1181.996, "duration": 5.639}, {"text": "right?", "start": 1187.635, "duration": 0.501}, {"text": "You could also have\ninterstitial point defects,", "start": 1191.039, "duration": 4.471}, {"text": "interstitial or substitutional.", "start": 1195.51, "duration": 4.538}, {"text": "Those are the different\nkinds of defects we've", "start": 1203.184, "duration": 1.935}, {"text": "talked about for point defects.", "start": 1205.119, "duration": 2.236}, {"text": "Also, by the way, if it's an\nionic point defect, ionic point", "start": 1207.355, "duration": 4.137}, {"text": "defect, you need\nto make sure you", "start": 1211.492, "duration": 6.507}, {"text": "have charge neutrality, charge\nneutrality, plus two types.", "start": 1217.999, "duration": 7.974}, {"text": "There's Frenkel, and\nthere's Schottky.", "start": 1228.776, "duration": 2.303}, {"text": "You can think about\nSchottky, you remove,", "start": 1231.079, "duration": 4.971}, {"text": "but you've got to remove them\nin a way that's charge-balanced.", "start": 1236.05, "duration": 3.504}, {"text": "Right?", "start": 1239.554, "duration": 0.5}, {"text": "So in Schottky, you remove.", "start": 1240.054, "duration": 2.336}, {"text": "In an ionic crystal,\nyou've got to keep charge.", "start": 1242.39, "duration": 1.968}, {"text": "That's a new thing you've\ngot to keep track of.", "start": 1244.358, "duration": 2.269}, {"text": "And so if we had--", "start": 1246.627, "duration": 1.102}, {"text": "I'll go to this picture.", "start": 1247.729, "duration": 2.535}, {"text": "Well, you should\nknow this picture.", "start": 1250.264, "duration": 1.902}, {"text": "This is an important picture.", "start": 1252.166, "duration": 1.201}, {"text": "We showed it a lot--", "start": 1253.367, "duration": 1.102}, {"text": "vacancy, interstitial,\nself-interstitial,", "start": 1254.469, "duration": 3.069}, {"text": "substitutional.", "start": 1257.538, "duration": 1.035}, {"text": "And then if it's ionic,\nnow all of a sudden,", "start": 1258.573, "duration": 2.068}, {"text": "you've got charges in\nthere, and so you've just", "start": 1260.641, "duration": 2.103}, {"text": "got to make sure\nthings remain neutral.", "start": 1262.744, "duration": 2.936}, {"text": "Right?", "start": 1265.68, "duration": 0.901}, {"text": "In Schottky, you would remove\natoms to balance the charge,", "start": 1266.581, "duration": 4.371}, {"text": "and in Frenkel,\nyou move an atom.", "start": 1270.952, "duration": 2.869}, {"text": "Schottky remove, Frenkel move.", "start": 1276.524, "duration": 3.136}, {"text": "That just occurred to me,\nthat that's the same word", "start": 1279.66, "duration": 4.071}, {"text": "with just re in front of it.", "start": 1283.731, "duration": 2.736}, {"text": "That's exciting.", "start": 1286.467, "duration": 1.402}, {"text": "Well, so if I were to ask\nyou, for example, if I were to", "start": 1287.869, "duration": 2.736}, {"text": "ask you this.", "start": 1290.605, "duration": 1.268}, {"text": "You diffuse chromium into\none side of the ionic crystal", "start": 1291.873, "duration": 5.939}, {"text": "alumina to make it red\nand titanium on the other.", "start": 1297.812, "duration": 3.603}, {"text": "Would you expect oxygen\nvacancies, aluminum vacancies,", "start": 1301.415, "duration": 2.703}, {"text": "or no vacancies in each case?", "start": 1304.118, "duration": 4.371}, {"text": "Just follow the charge,\nfollow the charge.", "start": 1308.489, "duration": 6.473}, {"text": "So for example, if\nI had alumina, O3.", "start": 1314.962, "duration": 5.072}, {"text": "Well, if I were\nLewis, if I were Lewis", "start": 1320.034, "duration": 3.871}, {"text": "I would see this as 2Al3 plus.", "start": 1323.905, "duration": 6.406}, {"text": "Right?", "start": 1330.311, "duration": 0.501}, {"text": "This is how he saw ionic bonds.", "start": 1330.812, "duration": 3.536}, {"text": "Ah, I want to make\nsure this is clear.", "start": 1334.348, "duration": 7.174}, {"text": "I'm going to start over.", "start": 1341.522, "duration": 1.468}, {"text": "So I would have 2Al3 plus, and\nthen I would have a 3O2 minus.", "start": 1342.99, "duration": 9.777}, {"text": "Remember, O likes to\nbe 2 minus, and so", "start": 1352.767, "duration": 4.604}, {"text": "if I were to introduce\nsomething like Cr2O3,", "start": 1357.371, "duration": 6.006}, {"text": "well, this is 2Cr3 plus, so this\nis 2Cr3 plus, and 3O2 minus.", "start": 1363.377, "duration": 12.746}, {"text": "So if I substitute\naluminum with chromium,", "start": 1376.123, "duration": 5.473}, {"text": "then I'm charge-balanced.", "start": 1381.596, "duration": 2.369}, {"text": "Right?", "start": 1383.965, "duration": 0.5}, {"text": "I'm OK.", "start": 1384.465, "duration": 0.701}, {"text": "But if I substitute titanium,\nTiO2 is Ti4 plus and 2O2 minus,", "start": 1385.166, "duration": 11.778}, {"text": "you know this just\nfrom the formula.", "start": 1396.944, "duration": 1.802}, {"text": "Because if oxygen is 2 minus,\nthis thing's got to be neutral,", "start": 1398.746, "duration": 3.337}, {"text": "and so that's Ti4 plus.", "start": 1402.083, "duration": 2.636}, {"text": "But now, if I put a Ti\nin there, and I get one", "start": 1404.719, "duration": 2.636}, {"text": "in for an aluminum, I've\nknocked the charge by 1.", "start": 1407.355, "duration": 5.438}, {"text": "Right?", "start": 1412.793, "duration": 2.503}, {"text": "So this gives us\nan extra charge,", "start": 1415.296, "duration": 8.041}, {"text": "and that means you've\ngot to create vacancies,", "start": 1423.337, "duration": 2.636}, {"text": "create aluminum vacancies.", "start": 1425.973, "duration": 3.37}, {"text": "It's the only way to do it.", "start": 1429.343, "duration": 2.436}, {"text": "So for every three titanium\natoms that I put in,", "start": 1431.779, "duration": 2.436}, {"text": "I've got to take an\naluminum one out.", "start": 1434.215, "duration": 1.702}, {"text": "Right?", "start": 1435.917, "duration": 0.5}, {"text": "Otherwise, I'm not going\nto have charge balance,", "start": 1436.417, "duration": 2.903}, {"text": "not going to have\ncharge balance.", "start": 1439.32, "duration": 1.368}, {"text": "Right?", "start": 1440.688, "duration": 1.335}, {"text": "So that would be an example of\nplaying with an ionic crystal,", "start": 1442.023, "duration": 4.404}, {"text": "but remember, we also\nhad stress-strain curves.", "start": 1446.427, "duration": 2.736}, {"text": "Because when we talked\nabout line defects,", "start": 1449.163, "duration": 5.806}, {"text": "we talked about how that's a way\nfor metals and other materials", "start": 1454.969, "duration": 3.87}, {"text": "to undergo deformation.", "start": 1458.839, "duration": 1.402}, {"text": "And then we said,\nwell, how are we", "start": 1460.241, "duration": 1.702}, {"text": "going to conceptualize\nthese things happening,", "start": 1461.943, "duration": 4.437}, {"text": "and we did it with the\nstress-strain curve", "start": 1466.38, "duration": 1.735}, {"text": "and the mechanical\nresponse of materials.", "start": 1468.115, "duration": 2.469}, {"text": "So we learned about\nstress-strain curves", "start": 1470.584, "duration": 2.203}, {"text": "and fracture points,\nfracture and plastic", "start": 1472.787, "duration": 9.342}, {"text": "versus elastic regimes.", "start": 1482.129, "duration": 4.872}, {"text": "OK, I'll give an\nexample in a sec.", "start": 1487.001, "duration": 3.503}, {"text": "OK?", "start": 1490.504, "duration": 0.501}, {"text": "And finally, the last\nthing we did with defects", "start": 1493.841, "duration": 1.969}, {"text": "is we talked about\ntheir activation.", "start": 1495.81, "duration": 2.135}, {"text": "And so we know if something\nis thermally activated,", "start": 1497.945, "duration": 4.271}, {"text": "as are point defects, vacancies\nare thermally activated,", "start": 1502.216, "duration": 5.472}, {"text": "so are other types\nof point defects.", "start": 1507.688, "duration": 2.77}, {"text": "And we said that we need\nan Arrhenius relationship,", "start": 1510.458, "duration": 3.203}, {"text": "and that requires\nknowledge of an activation", "start": 1513.661, "duration": 3.904}, {"text": "energy for the defect to form.", "start": 1517.565, "duration": 2.702}, {"text": "So that was another\nreally important concept", "start": 1520.267, "duration": 3.037}, {"text": "that we covered.", "start": 1523.304, "duration": 0.767}, {"text": "Right?", "start": 1524.071, "duration": 0.834}, {"text": "So for example, here is like\na defect formation energy", "start": 1524.905, "duration": 4.538}, {"text": "question.", "start": 1529.443, "duration": 0.501}, {"text": "So let me go over here, stay\nwith this side, where I've got", "start": 1533.18, "duration": 5.639}, {"text": "some defects.", "start": 1538.819, "duration": 2.67}, {"text": "So one thing I\nwant to make clear,", "start": 1541.489, "duration": 4.004}, {"text": "the fraction of vacancies.", "start": 1545.493, "duration": 1.801}, {"text": "We talked about this.", "start": 1547.294, "duration": 0.868}, {"text": "We talked about an\nArrhenius behavior,", "start": 1548.162, "duration": 2.469}, {"text": "Arrhenius-like behavior, and\nthe fraction of vacancies", "start": 1550.631, "duration": 3.504}, {"text": "was the number of vacancies over\nthe number of possible sites.", "start": 1554.135, "duration": 4.971}, {"text": "That makes a lot of sense.", "start": 1559.106, "duration": 1.535}, {"text": "Now, if it's\nArrhenius, then this", "start": 1560.641, "duration": 1.735}, {"text": "is some constant times e to the\nminus activation energy divided", "start": 1562.376, "duration": 4.238}, {"text": "by KBT, where we use\nthe Boltzmann constant", "start": 1566.614, "duration": 4.07}, {"text": "if it's per atom.", "start": 1570.684, "duration": 2.236}, {"text": "Right?", "start": 1572.92, "duration": 1.768}, {"text": "So per vacancy, that activation\nenergy would be per vacancy.", "start": 1574.688, "duration": 4.305}, {"text": "But when I first introduced\nthis, I simply let a be 1,", "start": 1578.993, "duration": 4.438}, {"text": "but a is a constant.", "start": 1583.431, "duration": 2.235}, {"text": "This is a constant,\nand it can be whatever.", "start": 1585.666, "duration": 5.139}, {"text": "It's a constant.", "start": 1590.805, "duration": 0.767}, {"text": "It's called the\nanthropic factor,", "start": 1591.572, "duration": 4.671}, {"text": "and it's a constant related\nto as you would have", "start": 1596.243, "duration": 3.304}, {"text": "in any Arrhenius-like behavior.", "start": 1599.547, "duration": 2.602}, {"text": "Right?", "start": 1602.149, "duration": 1.235}, {"text": "Remember how it's like\na frequency factor,", "start": 1603.384, "duration": 2.669}, {"text": "this is related to all\nsorts of complexities", "start": 1606.053, "duration": 3.404}, {"text": "that we don't need to know about\nrelated to how vacancies form.", "start": 1609.457, "duration": 3.37}, {"text": "It's a constant that's in\nthere, and I let it be 1,", "start": 1612.827, "duration": 2.135}, {"text": "but I want to make sure\nwe put it in explicitly.", "start": 1614.962, "duration": 2.469}, {"text": "This n is the number\nof possible sites.", "start": 1621.902, "duration": 2.77}, {"text": "Right?", "start": 1624.672, "duration": 0.5}, {"text": "So maybe it's the number of\nlattice sites in the crystal,", "start": 1625.172, "duration": 4.538}, {"text": "number of possible sites.", "start": 1629.71, "duration": 1.301}, {"text": "But you might get\nthis could be related", "start": 1631.011, "duration": 3.07}, {"text": "to, for example, or to or\nfrom, things like the grams", "start": 1634.081, "duration": 9.376}, {"text": "that you have of something\nor maybe the volume", "start": 1643.457, "duration": 6.073}, {"text": "or the moles, et cetera.", "start": 1649.53, "duration": 1.034}, {"text": "Right?", "start": 1650.564, "duration": 0.501}, {"text": "So these are the kinds\nof problems we've done.", "start": 1651.065, "duration": 3.937}, {"text": "That gives you a sense of\nhow many sites did you have.", "start": 1655.002, "duration": 4.938}, {"text": "Right?", "start": 1659.94, "duration": 0.968}, {"text": "It could be per\ncentimeter cubed.", "start": 1660.908, "duration": 2.603}, {"text": "It could be per moles.", "start": 1663.511, "duration": 2.235}, {"text": "You go back and forth.", "start": 1665.746, "duration": 1.635}, {"text": "How much stuff do I have?", "start": 1667.381, "duration": 2.402}, {"text": "It's that kind of\nback and forth.", "start": 1669.783, "duration": 2.37}, {"text": "If I had a problem like this,\nthen I know I can set it up,", "start": 1672.153, "duration": 4.004}, {"text": "because I've got\ntwo temperatures.", "start": 1676.157, "duration": 2.836}, {"text": "You see the key here,\nthe concentration of 10", "start": 1678.993, "duration": 2.802}, {"text": "to the cubed per\ncentimeter cubed,", "start": 1681.795, "duration": 3.304}, {"text": "so don't let that throw you off.", "start": 1685.099, "duration": 1.334}, {"text": "It's simply two equations,\nwhere a bunch of stuff cancels.", "start": 1686.433, "duration": 4.472}, {"text": "Right?", "start": 1690.905, "duration": 1.001}, {"text": "So the fraction\nof vacancies, fv1,", "start": 1691.906, "duration": 4.904}, {"text": "would be 10 to the\n3rd divided by fv2,", "start": 1696.81, "duration": 4.705}, {"text": "and that's going to be 10 to\nthe 3rd over 10 to the 16th,", "start": 1701.515, "duration": 4.538}, {"text": "because the number\nof stuff cancels.", "start": 1706.053, "duration": 4.304}, {"text": "Right?", "start": 1710.357, "duration": 0.501}, {"text": "I didn't change that.", "start": 1710.858, "duration": 1.468}, {"text": "But this pre-factor cancels too.", "start": 1712.326, "duration": 2.336}, {"text": "You can put it there, A times\ne to the minus ea divided by KB", "start": 1714.662, "duration": 8.341}, {"text": "times 300 Kelvin--\nremember, so it was Kelvin--", "start": 1723.003, "duration": 3.771}, {"text": "divided by A times to the\nminus ea divided by KB times", "start": 1726.774, "duration": 8.909}, {"text": "the other temperature,\n900 Kelvin.", "start": 1735.683, "duration": 3.503}, {"text": "Right?", "start": 1739.186, "duration": 0.734}, {"text": "And so those cancel,\nthe stuff related to n", "start": 1739.92, "duration": 4.772}, {"text": "cancels, and I can just take\nthe number of vacancies.", "start": 1744.692, "duration": 3.069}, {"text": "Right?", "start": 1747.761, "duration": 0.668}, {"text": "So that's what's nice about\nhaving something like this.", "start": 1748.429, "duration": 1.768}, {"text": "You have two temperatures\nand a whole bunch of stuff", "start": 1750.197, "duration": 2.302}, {"text": "can cancel, and you can figure\nout then the activation energy", "start": 1752.499, "duration": 5.106}, {"text": "which doesn't change.", "start": 1757.605, "duration": 2.102}, {"text": "The activation energy is simply\nthe energy that you need,", "start": 1759.707, "duration": 3.803}, {"text": "so you can now solve for ea,\nand I think you get something", "start": 1763.51, "duration": 5.74}, {"text": "like 2.3 electron volts.", "start": 1769.25, "duration": 2.268}, {"text": "Remember that you could\nalso have plotted it.", "start": 1771.518, "duration": 2.403}, {"text": "You'd know that\nin this equation,", "start": 1773.921, "duration": 2.536}, {"text": "in the Arrhenius relationship,\nif you take the log,", "start": 1776.457, "duration": 3.804}, {"text": "then you have the minus\n1 over T relationship.", "start": 1780.261, "duration": 4.804}, {"text": "So remember that?", "start": 1785.065, "duration": 1.669}, {"text": "So if you take the\nT versus the log,", "start": 1786.734, "duration": 3.77}, {"text": "then you're going to get that.", "start": 1790.504, "duration": 2.102}, {"text": "Right?", "start": 1792.606, "duration": 2.269}, {"text": "We like plots, when we\nthink about Arrhenius,", "start": 1794.875, "duration": 2.169}, {"text": "because it makes it easier.", "start": 1797.044, "duration": 1.134}, {"text": "We can make it linear,\nwhere the slope of this", "start": 1798.178, "duration": 3.237}, {"text": "is minus ea, the slope, minus\nea over KB, in this case.", "start": 1801.415, "duration": 7.908}, {"text": "Right?", "start": 1809.323, "duration": 0.5}, {"text": "So we talked about these\nare all kinds of things", "start": 1809.823, "duration": 2.203}, {"text": "that we talked about.", "start": 1812.026, "duration": 1.034}, {"text": "And finally, getting\nto this stress-strain,", "start": 1813.06, "duration": 1.802}, {"text": "what if we looked at this?", "start": 1814.862, "duration": 1.835}, {"text": "This is the stress-strain,\nso now we're here.", "start": 1816.697, "duration": 3.303}, {"text": "We just did this.", "start": 1820.0, "duration": 1.135}, {"text": "We talked about that.", "start": 1821.135, "duration": 0.901}, {"text": "We talked about this,\nso stress-strain.", "start": 1822.036, "duration": 2.369}, {"text": "So if you were to be given\nplots like this, you should know", "start": 1824.405, "duration": 4.404}, {"text": "which one is most\nbrittle, which one", "start": 1828.809, "duration": 1.535}, {"text": "is the stiffest, the\nmost resistant to", "start": 1830.344, "duration": 2.936}, {"text": "changing elastically, and\nwhich one is the most ductile?", "start": 1833.28, "duration": 5.839}, {"text": "You can see that\nthe stiffest one", "start": 1839.119, "duration": 2.136}, {"text": "is going to be the one\nthat's the most resistant to", "start": 1841.255, "duration": 4.404}, {"text": "elastic deformation.", "start": 1845.659, "duration": 1.201}, {"text": "That's that linear\npart, that first part.", "start": 1846.86, "duration": 2.47}, {"text": "So there, it's\ngoing to be material", "start": 1849.33, "duration": 2.202}, {"text": "A. It's going to be A, because\nit's got the highest slope.", "start": 1851.532, "duration": 4.704}, {"text": "Right?", "start": 1856.236, "duration": 1.068}, {"text": "OK.", "start": 1857.304, "duration": 1.535}, {"text": "How about the most brittle?", "start": 1858.839, "duration": 1.134}, {"text": "Well, that's the one\nthat's going to break.", "start": 1859.973, "duration": 3.471}, {"text": "So it sort of looks like--", "start": 1863.444, "duration": 1.601}, {"text": "without deforming, without being\nable to undergo defamation,", "start": 1865.045, "duration": 3.404}, {"text": "that's brittleness.", "start": 1868.449, "duration": 1.968}, {"text": "It's going to crack\nbefore doing anything.", "start": 1870.417, "duration": 2.369}, {"text": "So that's B, right?", "start": 1872.786, "duration": 1.135}, {"text": "That's B.", "start": 1873.921, "duration": 1.468}, {"text": "And then the most ductile will\nbe the one that has the most", "start": 1875.389, "duration": 2.936}, {"text": "plastic deformation, because\nthat's what ductility is,", "start": 1878.325, "duration": 3.237}, {"text": "so that's going to be C. OK?", "start": 1881.562, "duration": 3.603}, {"text": "So remember\nstress-strain curves.", "start": 1885.165, "duration": 1.502}, {"text": "You've got this elastic\npart here, that's linear,", "start": 1886.667, "duration": 3.603}, {"text": "and then if it's a material--\nnot all materials have", "start": 1890.27, "duration": 4.004}, {"text": "plastic defamation.", "start": 1894.274, "duration": 2.736}, {"text": "Some are going to\nbreak before they", "start": 1897.01, "duration": 1.902}, {"text": "start deforming plastically, but\nif it can deform plastically,", "start": 1898.912, "duration": 4.038}, {"text": "then it's going to\nhave that yield point.", "start": 1902.95, "duration": 2.769}, {"text": "Right?", "start": 1905.719, "duration": 0.501}, {"text": "The yield stress, where then\nit starts becoming non-linear,", "start": 1906.22, "duration": 2.936}, {"text": "and then finally, it\nfractures somewhere else.", "start": 1909.156, "duration": 5.005}, {"text": "OK?", "start": 1914.161, "duration": 0.5}, {"text": "So those are\nstress-strain curves.", "start": 1914.661, "duration": 2.269}, {"text": "OK, let's move on.", "start": 1916.93, "duration": 3.404}, {"text": "Now, oh, with the next topic--", "start": 1920.334, "duration": 7.607}, {"text": "oh boy, I'm going to\nrun out of real estate--", "start": 1927.941, "duration": 4.004}, {"text": "we've got glasses, and here,\nthe most important thing", "start": 1931.945, "duration": 9.109}, {"text": "to know about is the curve.", "start": 1941.054, "duration": 2.737}, {"text": "That's how it all started.", "start": 1943.791, "duration": 1.167}, {"text": "Right?", "start": 1944.958, "duration": 0.501}, {"text": "I'm calling it The Curve.", "start": 1945.459, "duration": 1.401}, {"text": "Let's go all caps,\nbecause it's The Curve,", "start": 1946.86, "duration": 4.071}, {"text": "and what I mean by The\nCurve is the volume", "start": 1950.931, "duration": 3.17}, {"text": "per mole versus temperature.", "start": 1954.101, "duration": 6.373}, {"text": "We also talked about the\neffects of cooling rate,", "start": 1960.474, "duration": 10.077}, {"text": "and we also talked about\nthe effects of modifiers,", "start": 1970.551, "duration": 8.909}, {"text": "and in particular how the\nmodifier changes the viscosity", "start": 1979.46, "duration": 6.473}, {"text": "because it cuts the pasta.", "start": 1985.933, "duration": 2.469}, {"text": "OK, so but the framing of these\nconcepts was in The Curve,", "start": 1988.402, "duration": 6.406}, {"text": "and that's this one.", "start": 1994.808, "duration": 0.834}, {"text": "Oh, I have a picture of it.", "start": 1995.642, "duration": 1.435}, {"text": "There it is.", "start": 1997.077, "duration": 1.668}, {"text": "OK, they did specific--\nwe do volume per mole", "start": 1998.745, "duration": 2.369}, {"text": "is how we're looking at it in\nthis class, so volume per mole", "start": 2001.114, "duration": 2.47}, {"text": "versus temperature.", "start": 2003.584, "duration": 2.269}, {"text": "Now remember, if it's a\ncrystal, where am I going to go?", "start": 2005.853, "duration": 4.971}, {"text": "Let's go here.", "start": 2010.824, "duration": 1.568}, {"text": "If it's a crystal, then you've\ngot one melting point that", "start": 2012.392, "duration": 5.072}, {"text": "only depends on the material.", "start": 2017.464, "duration": 4.271}, {"text": "It only depends on the material,\nso that melting point is Tm,", "start": 2021.735, "duration": 6.44}, {"text": "and it's going to have a\nbig volume change as it goes", "start": 2028.175, "duration": 3.47}, {"text": "from liquid to crystal solid.", "start": 2031.645, "duration": 3.57}, {"text": "OK?", "start": 2035.215, "duration": 1.135}, {"text": "And so for example, I'm just\nbasically replotting it,", "start": 2036.35, "duration": 5.372}, {"text": "but you would have something\nlike this and something", "start": 2041.722, "duration": 2.869}, {"text": "like this and\nsomething like this,", "start": 2044.591, "duration": 2.269}, {"text": "and that's your melting point.", "start": 2046.86, "duration": 3.37}, {"text": "This would be the liquid,\nand this would be the solid,", "start": 2050.23, "duration": 2.936}, {"text": "and you know that, if it's\ngoing to undergo this big volume", "start": 2053.166, "duration": 2.47}, {"text": "change.", "start": 2055.636, "duration": 0.967}, {"text": "Then, it's the melting\npoint and it's a crystal.", "start": 2056.603, "duration": 3.237}, {"text": "But then we say, well,\nbut if it can't find--", "start": 2059.84, "duration": 2.736}, {"text": "by crystal I mean in opposition\nto glass, which we know", "start": 2062.576, "duration": 4.137}, {"text": "doesn't just mean your windows.", "start": 2066.713, "duration": 1.769}, {"text": "It means any amorphous material,\nmeaning it's not crystalline.", "start": 2068.482, "duration": 3.869}, {"text": "It didn't find the\nlattice structure.", "start": 2072.351, "duration": 2.537}, {"text": "Remember those three\nreasons, the musical chairs?", "start": 2074.888, "duration": 2.836}, {"text": "Whatever you're trying\nto crystallize, atoms", "start": 2077.724, "duration": 1.836}, {"text": "or molecules, they weren't able\nto find all the lattice sites,", "start": 2079.56, "duration": 4.003}, {"text": "not even withstanding\nsome defects here.", "start": 2083.563, "duration": 2.636}, {"text": "They simply couldn't do\nit, and so it's amorphous,", "start": 2086.199, "duration": 3.104}, {"text": "and it's a glass.", "start": 2089.303, "duration": 1.668}, {"text": "And in that case,\nwhat happens is it", "start": 2090.971, "duration": 3.235}, {"text": "super cools and then\nbecomes a solid at something", "start": 2094.206, "duration": 8.377}, {"text": "called the glass\ntransition temperature.", "start": 2102.583, "duration": 1.634}, {"text": "Which unlike the crystal\ncan have different values,", "start": 2104.217, "duration": 4.205}, {"text": "and those values can depend on\nthings like the cooling rate.", "start": 2108.422, "duration": 3.537}, {"text": "So if I cool it slower,\nif I cool it slower--", "start": 2111.959, "duration": 5.672}, {"text": "remember this is faster,\nfaster, slower, and please,", "start": 2117.631, "duration": 6.406}, {"text": "do not confuse time\nwith this axis.", "start": 2124.037, "duration": 2.469}, {"text": "This is just temperature.", "start": 2126.506, "duration": 1.669}, {"text": "So we can use the same--", "start": 2128.175, "duration": 1.968}, {"text": "this is volume per mole-- we can\nuse the same The Plot to think", "start": 2130.143, "duration": 4.939}, {"text": "about modifiers as well.", "start": 2135.082, "duration": 2.168}, {"text": "Because it's not-- this is\njust one plot, one curve", "start": 2137.25, "duration": 4.004}, {"text": "and another.", "start": 2141.254, "duration": 1.001}, {"text": "This happened to\nbe cooled slower,", "start": 2142.255, "duration": 1.869}, {"text": "so it was able to\nsuper cool more,", "start": 2144.124, "duration": 2.836}, {"text": "before it locked\nin the disorder,", "start": 2146.96, "duration": 2.169}, {"text": "and the other one's faster.", "start": 2149.129, "duration": 1.635}, {"text": "You could also imagine\nif you cut the pasta,", "start": 2150.764, "duration": 2.836}, {"text": "you change the viscosity.", "start": 2153.6, "duration": 3.07}, {"text": "And so now you're\nchanging something else", "start": 2156.67, "duration": 1.868}, {"text": "about the glass using\nchemistry, and you're", "start": 2158.538, "duration": 2.136}, {"text": "allowing it to find those\nlattice sites more easily.", "start": 2160.674, "duration": 3.437}, {"text": "You're allowing it to try\nto become crystalline,", "start": 2164.111, "duration": 2.035}, {"text": "to try to close pack\njust a little bit more.", "start": 2166.146, "duration": 2.736}, {"text": "So you can also get this,\nby cutting the pasta you", "start": 2168.882, "duration": 3.003}, {"text": "can get these kinds of changes.", "start": 2171.885, "duration": 3.403}, {"text": "So those are the things we\ntalked about with glass.", "start": 2175.288, "duration": 4.004}, {"text": "Now, next, we talked\nabout reactions.", "start": 2179.292, "duration": 6.741}, {"text": "OK.", "start": 2186.033, "duration": 0.5}, {"text": "What do we need to know about\nreactions, reaction rates?", "start": 2194.274, "duration": 7.441}, {"text": "So we want to know the order\nof some general reaction,", "start": 2201.715, "duration": 7.507}, {"text": "like aA plus bB--", "start": 2209.222, "duration": 2.67}, {"text": "remember this--\ngoes to cC plus dD.", "start": 2211.892, "duration": 3.737}, {"text": "And we want to know\nthe rate from--", "start": 2218.832, "duration": 8.075}, {"text": "basically, it's the\nmass conservation,", "start": 2226.907, "duration": 2.702}, {"text": "so from the coefficients.", "start": 2229.609, "duration": 3.437}, {"text": "OK, so that would\nbe, for example,", "start": 2233.046, "duration": 2.369}, {"text": "like minus 1 over a, d(A), dt--", "start": 2235.415, "duration": 4.104}, {"text": "that's a rate-- equals minus\n1 over b d(B), dt, et cetera.", "start": 2239.519, "duration": 6.44}, {"text": "Now, those come from\nthe coefficients,", "start": 2250.097, "duration": 2.068}, {"text": "but the rate law does not,\nthe rate law does not.", "start": 2252.165, "duration": 5.906}, {"text": "So these are simply\ninstantaneous rates,", "start": 2258.071, "duration": 2.202}, {"text": "but now I say, no, I\nwant a rate law that", "start": 2260.273, "duration": 2.837}, {"text": "gives me the dependence on these\nconcentrations at any time.", "start": 2263.11, "duration": 6.973}, {"text": "So the rate law would\nbe, for example,", "start": 2273.854, "duration": 6.339}, {"text": "like rate equals k times\nA to the m, B to the n.", "start": 2280.193, "duration": 9.143}, {"text": "Now, here's the thing.", "start": 2289.336, "duration": 2.335}, {"text": "These come from experiments.", "start": 2291.671, "duration": 4.572}, {"text": "Very important\ndistinction, right?", "start": 2301.481, "duration": 2.803}, {"text": "Those come from\nexperiments, and so you", "start": 2304.284, "duration": 2.836}, {"text": "could get the rate with\nrespect to A which would be--", "start": 2307.12, "duration": 2.536}, {"text": "I'm sorry.", "start": 2309.656, "duration": 0.601}, {"text": "The order with respect\nto A would be m,", "start": 2310.257, "duration": 3.336}, {"text": "the order with respect\nto B would be n,", "start": 2313.593, "duration": 2.169}, {"text": "and the overall\norder of the reaction", "start": 2315.762, "duration": 2.403}, {"text": "is m plus n, the overall order.", "start": 2318.165, "duration": 3.103}, {"text": "And then, we had one more\nitem here of conceptually", "start": 2324.604, "duration": 4.338}, {"text": "what I want you to know about,\nwhich is that the rate also", "start": 2328.942, "duration": 3.27}, {"text": "depends on temperature.", "start": 2332.212, "duration": 2.469}, {"text": "Sorry, the rate\nconstant, rate constant", "start": 2334.681, "duration": 5.005}, {"text": "depends on temperature.", "start": 2339.686, "duration": 3.07}, {"text": "So if I were to now\nsay, well, OK, I", "start": 2342.756, "duration": 2.235}, {"text": "want to know something about\nthe order of a reaction,", "start": 2344.991, "duration": 2.303}, {"text": "you might get a table like\nthis, and we did this in class.", "start": 2347.294, "duration": 3.77}, {"text": "You might get a\ntable just like this.", "start": 2351.064, "duration": 1.769}, {"text": "Here's a reaction.", "start": 2352.833, "duration": 0.934}, {"text": "It's W and X and Y,\nand it goes to Z.", "start": 2353.767, "duration": 4.638}, {"text": "Don't let the fact that you have\nthree reactants throw you off.", "start": 2358.405, "duration": 3.537}, {"text": "You've got a certain\nnumber of reactants,", "start": 2361.942, "duration": 1.701}, {"text": "they've got their coefficients,\nand they go to some product.", "start": 2363.643, "duration": 4.071}, {"text": "And now, you're given\nexperimental data, so", "start": 2367.714, "duration": 2.836}, {"text": "from this data, you\ncan get the order", "start": 2370.55, "duration": 3.07}, {"text": "of the reaction with respect\nto each one of these.", "start": 2373.62, "duration": 3.203}, {"text": "Right?", "start": 2376.823, "duration": 0.934}, {"text": "And that would then give you,\nof course, the overall order.", "start": 2377.757, "duration": 3.037}, {"text": "So let's see.", "start": 2380.794, "duration": 0.7}, {"text": "If we were to look at that\ndata, then what would we get?", "start": 2381.494, "duration": 6.006}, {"text": "So what you want to do in\nthese kinds of situations is,", "start": 2387.5, "duration": 7.308}, {"text": "first of all, don't panic.", "start": 2394.808, "duration": 2.402}, {"text": "By the way, on an exam,\nin general, don't panic,", "start": 2397.21, "duration": 2.603}, {"text": "and if you have a question,\nyou can ask a question,", "start": 2399.813, "duration": 2.202}, {"text": "but also show us what you know.", "start": 2402.015, "duration": 2.97}, {"text": "We will give you-- as you\nI hope have seen already--", "start": 2404.985, "duration": 2.903}, {"text": "we will give you as much\ncredit as we can for sharing", "start": 2407.888, "duration": 2.769}, {"text": "what you know.", "start": 2410.657, "duration": 0.601}, {"text": "You don't have to get everything\nright to get a lot of points.", "start": 2411.258, "duration": 3.536}, {"text": "Please share your knowledge.", "start": 2414.794, "duration": 3.137}, {"text": "So in this case, what\nwould the knowledge be?", "start": 2417.931, "duration": 1.969}, {"text": "Well, it would be that\nI want to compare stuff,", "start": 2419.9, "duration": 1.968}, {"text": "like trial 1 and 2.", "start": 2421.868, "duration": 1.502}, {"text": "And if I do that, you see,\nOK, trial 1, trial 2, then two", "start": 2423.37, "duration": 4.604}, {"text": "of them stay constant,\nbut W doubles.", "start": 2427.974, "duration": 3.137}, {"text": "OK?", "start": 2431.111, "duration": 0.967}, {"text": "So comparing 1 versus 2, you\ngot W goes to 2 two times,", "start": 2432.078, "duration": 12.012}, {"text": "but the rate is\nsame, so you know", "start": 2444.09, "duration": 4.572}, {"text": "the order is 0 with respect to\nW. But if I compare 1 versus 3,", "start": 2448.662, "duration": 9.809}, {"text": "then you know that,\nlet's see, x goes to 3x", "start": 2458.471, "duration": 6.273}, {"text": "and the rate goes to 3x,\nand so the order is 1.", "start": 2464.744, "duration": 9.743}, {"text": "And then finally, for Y--", "start": 2474.487, "duration": 2.136}, {"text": "I will just jump to it--", "start": 2476.623, "duration": 2.002}, {"text": "the order is 2, and you can\ndo that just by find one", "start": 2478.625, "duration": 6.773}, {"text": "where only Y changes.", "start": 2485.398, "duration": 2.236}, {"text": "You don't have to\nnecessarily find one", "start": 2487.634, "duration": 2.669}, {"text": "where just one changes.", "start": 2490.303, "duration": 1.335}, {"text": "Right?", "start": 2491.638, "duration": 2.002}, {"text": "Because if you knew\none is first order--", "start": 2493.64, "duration": 4.137}, {"text": "if you knew one, and then you\nhad another one, and they both", "start": 2497.777, "duration": 2.503}, {"text": "changed.", "start": 2500.28, "duration": 0.467}, {"text": "But maybe the rate\ndidn't change,", "start": 2500.747, "duration": 1.401}, {"text": "then you know they must have\nboth the same order, if they", "start": 2502.148, "duration": 2.403}, {"text": "change in opposite ways.", "start": 2504.551, "duration": 1.635}, {"text": "Right?", "start": 2506.186, "duration": 0.667}, {"text": "So you can get into\nthis in different ways,", "start": 2506.853, "duration": 1.768}, {"text": "just looking at these\nchanges from one to another", "start": 2508.621, "duration": 4.305}, {"text": "and thinking about\nwhat must happen", "start": 2512.926, "duration": 2.402}, {"text": "in terms of the\nrate law, in terms", "start": 2515.328, "duration": 1.635}, {"text": "of what you wrote out here.", "start": 2516.963, "duration": 2.069}, {"text": "But you could also ask\nquestions like with reactions,", "start": 2522.302, "duration": 5.405}, {"text": "OK, this is first order.", "start": 2527.707, "duration": 1.535}, {"text": "What's the dependence\nof the concentration", "start": 2529.242, "duration": 1.769}, {"text": "over time as a function\nof the rate constant?", "start": 2531.011, "duration": 2.635}, {"text": "Well, that just goes back to our\nunderstanding of the integrated", "start": 2533.646, "duration": 5.039}, {"text": "rate equation.", "start": 2538.685, "duration": 1.234}, {"text": "Right?", "start": 2539.919, "duration": 0.734}, {"text": "And so let's see, oh\nboy, now I need to find--", "start": 2540.653, "duration": 6.34}, {"text": "I'm going to go--", "start": 2546.993, "duration": 1.402}, {"text": "I hate to do this, XRD.", "start": 2548.395, "duration": 1.735}, {"text": "I hate to do this, but\nsometimes being first carries", "start": 2550.13, "duration": 8.575}, {"text": "a consequence.", "start": 2558.705, "duration": 0.801}, {"text": "OK.", "start": 2562.742, "duration": 1.635}, {"text": "So in this case--", "start": 2564.377, "duration": 1.235}, {"text": "first of all, by the\nway, you look at reaction", "start": 2565.612, "duration": 1.902}, {"text": "like that, you're like, well\nOK, from the coefficients", "start": 2567.514, "duration": 2.235}, {"text": "and the mass balance stuff, you\nknow that the change in oxygen,", "start": 2569.749, "duration": 3.671}, {"text": "for example, with\ntime, the instantaneous", "start": 2573.42, "duration": 2.202}, {"text": "rate would equal minus the\nchange in MO2 with time.", "start": 2575.622, "duration": 7.774}, {"text": "Well, that's not what\nthe question asked.", "start": 2583.396, "duration": 1.702}, {"text": "The question says\nit's first order.", "start": 2585.098, "duration": 2.469}, {"text": "So that's enough, because\nthis means that if I integrate", "start": 2587.567, "duration": 8.208}, {"text": "the rate law then-- first of\nall, if it's first order--", "start": 2595.775, "duration": 4.305}, {"text": "then d of MO2 with\nrespect to time", "start": 2600.08, "duration": 5.238}, {"text": "must equal some constant\ntimes the concentration of MO2", "start": 2605.318, "duration": 6.24}, {"text": "to the 1, first order.", "start": 2611.558, "duration": 3.904}, {"text": "And so now, if I\nintegrate this, I", "start": 2615.462, "duration": 2.135}, {"text": "take this concentration over\nhere, I put the dt over there.", "start": 2617.597, "duration": 3.136}, {"text": "You integrate it.", "start": 2620.733, "duration": 0.835}, {"text": "You've got all the\nintegrated rate laws.", "start": 2621.568, "duration": 1.668}, {"text": "We've gone through this already.", "start": 2623.236, "duration": 1.568}, {"text": "You know that you\nget that the log--", "start": 2624.804, "duration": 3.837}, {"text": "oh, we do logs--", "start": 2628.641, "duration": 1.669}, {"text": "are this MO2 equals the log\nof some starting concentration", "start": 2630.31, "duration": 7.941}, {"text": "minus Kt.", "start": 2638.251, "duration": 1.835}, {"text": "OK?", "start": 2640.086, "duration": 2.002}, {"text": "Why do we do that?", "start": 2642.088, "duration": 0.768}, {"text": "Because we like plotting\nthings, linear things.", "start": 2642.856, "duration": 2.469}, {"text": "We love linear.", "start": 2645.325, "duration": 3.036}, {"text": "So remember, we did this.", "start": 2648.361, "duration": 1.902}, {"text": "We went from these\nintegrated rate", "start": 2650.263, "duration": 1.902}, {"text": "laws to plots and\nback and forth,", "start": 2652.165, "duration": 2.235}, {"text": "and so that's also\nvery important.", "start": 2654.4, "duration": 2.636}, {"text": "OK.", "start": 2657.036, "duration": 1.268}, {"text": "Now finally, so the\nlast couple of things.", "start": 2658.304, "duration": 4.104}, {"text": "And I'm purposely giving these\nlast ones a little less time,", "start": 2662.408, "duration": 3.137}, {"text": "because they're the ones that\nwe've seen very recently,", "start": 2665.545, "duration": 2.636}, {"text": "and these are the\nones that we haven't", "start": 2668.181, "duration": 1.568}, {"text": "seen for almost a month.", "start": 2669.749, "duration": 2.136}, {"text": "Right?", "start": 2671.885, "duration": 1.635}, {"text": "Yeah, but you still gotta\nknow about solubility,", "start": 2673.52, "duration": 5.138}, {"text": "and so for solubility,\nremember what we did is we did", "start": 2678.658, "duration": 3.504}, {"text": "equilibrium and Le Chatelier,\nand we did the equilibrium", "start": 2682.162, "duration": 8.742}, {"text": "constants, the K's.", "start": 2690.904, "duration": 3.136}, {"text": "Like for example, Ksp is\nthe solubility product,", "start": 2694.04, "duration": 4.972}, {"text": "solubility product constant.", "start": 2699.012, "duration": 3.17}, {"text": "Right?", "start": 2702.182, "duration": 1.201}, {"text": "And then we also did\nice tables, and then we", "start": 2703.383, "duration": 6.373}, {"text": "talked about the common ion.", "start": 2709.756, "duration": 1.368}, {"text": "And so as an example,\nif I were to tell you,", "start": 2716.296, "duration": 2.469}, {"text": "well, OK, I'm going\nto take BaCl2.", "start": 2718.765, "duration": 2.803}, {"text": "I might have done this\none in class already.", "start": 2721.568, "duration": 2.035}, {"text": "If I add BaCl2 to a\nsaturated solution of BaSO4,", "start": 2723.603, "duration": 3.57}, {"text": "why does it cause precipitation?", "start": 2727.173, "duration": 3.937}, {"text": "Answer-- because\nof the common ion", "start": 2731.11, "duration": 1.669}, {"text": "effect, but you could\nwrite these out.", "start": 2732.779, "duration": 3.437}, {"text": "So you write out your\nsaturated solution,", "start": 2736.216, "duration": 3.336}, {"text": "so you write out\nyour BaSO4, and you", "start": 2739.552, "duration": 3.57}, {"text": "see that BaSO4 solid will\ngo to Ba2 plus in solution", "start": 2743.122, "duration": 10.911}, {"text": "plus SO4 2 minus in solution.", "start": 2754.033, "duration": 3.904}, {"text": "And so the common\nion effect tells you", "start": 2757.937, "duration": 2.836}, {"text": "that if I now add something else\nthat has something in common", "start": 2760.773, "duration": 3.971}, {"text": "with one of these, that\ngives me an ion in common,", "start": 2764.744, "duration": 3.237}, {"text": "then because of Le\nChatelier, you're", "start": 2767.981, "duration": 1.501}, {"text": "going to drive the\nreaction the other way.", "start": 2769.482, "duration": 3.036}, {"text": "That precipitates, because\nit forms a solid BaSO4.", "start": 2772.518, "duration": 2.436}, {"text": "So I've just done that.", "start": 2774.954, "duration": 0.934}, {"text": "Right?", "start": 2775.888, "duration": 0.501}, {"text": "I've given you BaCl2 which\ngives you a source of Ba2 plus,", "start": 2776.389, "duration": 3.837}, {"text": "and how do you figure\nout if you were", "start": 2780.226, "duration": 1.535}, {"text": "given amounts what happens,\nwhat the new equilibrium is?", "start": 2781.761, "duration": 5.105}, {"text": "You use ICE.", "start": 2786.866, "duration": 1.101}, {"text": "Right?", "start": 2787.967, "duration": 0.501}, {"text": "You use the ICE tables.", "start": 2788.468, "duration": 3.003}, {"text": "OK.", "start": 2791.471, "duration": 1.101}, {"text": "And then finally, we talked\nabout acids and bases.", "start": 2792.572, "duration": 5.639}, {"text": "Oh, I really hate to erase\ndefects, but here we go.", "start": 2798.211, "duration": 6.373}, {"text": "Defects are gone.", "start": 2804.584, "duration": 0.934}, {"text": "Arrhenius, I'm so sorry.", "start": 2805.518, "duration": 2.503}, {"text": "That was painful.", "start": 2808.021, "duration": 2.035}, {"text": "And the last topic here\nis acids and bases,", "start": 2810.056, "duration": 4.671}, {"text": "and this is the most recent\none, and so what do we have?", "start": 2814.727, "duration": 7.441}, {"text": "Well, got the acid equilibrium\nconstant, the base.", "start": 2822.168, "duration": 4.738}, {"text": "We did water.", "start": 2826.906, "duration": 2.469}, {"text": "We did pH.", "start": 2829.375, "duration": 1.602}, {"text": "Oh, we did p anything.", "start": 2830.977, "duration": 2.269}, {"text": "Right?", "start": 2833.246, "duration": 0.6}, {"text": "p equals negative log\nof the thing, pKa, pKb.", "start": 2833.846, "duration": 6.04}, {"text": "OK, and then we did, like\nfor example, the definitions,", "start": 2843.056, "duration": 5.305}, {"text": "so Arrhenius versus\nBronsted-Lowry definitions.", "start": 2848.361, "duration": 8.742}, {"text": "And so for example, if you're\ngiven a solution-- this is one,", "start": 2857.103, "duration": 3.737}, {"text": "just a simple\nexample of an acid--", "start": 2860.84, "duration": 4.071}, {"text": "and it's HOCN, and\nyou're given the acid.", "start": 2864.911, "duration": 2.002}, {"text": "And you know the pH,\nso you're given that.", "start": 2866.913, "duration": 3.203}, {"text": "Then the pH from that\ninformation you can get that", "start": 2870.116, "duration": 6.039}, {"text": "the concentration of H plus--\nwhich is also a H3O plus--", "start": 2876.155, "duration": 4.305}, {"text": "is 1.7 times 10 to the\nminus 3 moles per liter.", "start": 2880.46, "duration": 5.805}, {"text": "That's from the pH,\nand if you have that,", "start": 2886.265, "duration": 5.873}, {"text": "then you can go to the\nKa definition, which", "start": 2892.138, "duration": 5.105}, {"text": "is H plus concentration OCN\nminus divided by the acid HOCN", "start": 2897.243, "duration": 9.143}, {"text": "concentration, and\nyou've got it all.", "start": 2906.386, "duration": 2.535}, {"text": "Because if you're right the\nequilibrium equation, which", "start": 2908.921, "duration": 3.838}, {"text": "is what Ka describes, the\nequilibrium of this acid", "start": 2912.759, "duration": 5.572}, {"text": "dissociating into\nions, dissociating", "start": 2918.331, "duration": 4.037}, {"text": "into H plus and OCN minus,\nand so you can get Ka.", "start": 2922.368, "duration": 2.97}, {"text": "OK.", "start": 2925.338, "duration": 0.5}, {"text": "So what I hope is that\nthis got us in the mood,", "start": 2925.838, "duration": 2.57}, {"text": "that this got us all kind of\non the right page with respect", "start": 2928.408, "duration": 2.535}, {"text": "to these topics.", "start": 2930.943, "duration": 0.701}, {"text": "You've got two days.", "start": 2931.644, "duration": 1.368}]
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+[{"text": "MARKUS KLUTE: Welcome back\nto 8.20 Special Relativity.", "start": 7.56, "duration": 2.79}, {"text": "In this short\nvideo, you're going", "start": 10.35, "duration": 2.01}, {"text": "to see how special\nrelativity, here shown as SR,", "start": 12.36, "duration": 4.98}, {"text": "fits into the general\nlandscape of physics theories.", "start": 17.34, "duration": 3.72}, {"text": "Very likely you have listened\nto 8.01 last semester", "start": 21.06, "duration": 4.92}, {"text": "or some previous time\nin your career at MIT.", "start": 25.98, "duration": 3.48}, {"text": "And once we enter the discussion\nof special relativity,", "start": 29.46, "duration": 5.79}, {"text": "it might seem to you\nthat what you learned", "start": 35.25, "duration": 2.52}, {"text": "there was simply incorrect.", "start": 37.77, "duration": 2.4}, {"text": "A better way to look at this\nis that each of those physics", "start": 40.17, "duration": 3.78}, {"text": "theories, they have\na range of validity,", "start": 43.95, "duration": 3.63}, {"text": "a range in which the\ntheory works and describes", "start": 47.58, "duration": 4.38}, {"text": "physical phenomena.", "start": 51.96, "duration": 1.77}, {"text": "And so here in this\npicture, I'd like", "start": 53.73, "duration": 2.37}, {"text": "to point out that even\nspecial relativity has", "start": 56.1, "duration": 4.17}, {"text": "its own range of validity.", "start": 60.27, "duration": 2.22}, {"text": "But let's start with\nclassical mechanics.", "start": 62.49, "duration": 2.59}, {"text": "So classical mechanics\ndescribes the motion", "start": 65.08, "duration": 2.87}, {"text": "of objects, a collision of\nobjects, a rotation of objects.", "start": 67.95, "duration": 4.17}, {"text": "In 8.02, you are\nstudying electrodynamics.", "start": 72.12, "duration": 4.32}, {"text": "But you do that typically at MIT\nin those courses at velocities", "start": 76.44, "duration": 4.26}, {"text": "which are modest--", "start": 80.7, "duration": 0.9}, {"text": "small velocities,\nsmall velocities", "start": 81.6, "duration": 2.13}, {"text": "compared to the speed of light.", "start": 83.73, "duration": 2.22}, {"text": "Once you accelerate,\nonce you have velocities", "start": 85.95, "duration": 3.45}, {"text": "which are really, really large,\nthen the description breaks.", "start": 89.4, "duration": 4.14}, {"text": "The validity of those\ntheories breaks.", "start": 93.54, "duration": 2.28}, {"text": "And that's where special\nrelativity comes in.", "start": 95.82, "duration": 2.76}, {"text": "And it's especially\nimportant when", "start": 98.58, "duration": 1.71}, {"text": "you discuss very fast moving\nbodies, fast moving reference", "start": 100.29, "duration": 4.74}, {"text": "frames, or behavior of light.", "start": 105.03, "duration": 2.83}, {"text": "And so this is what\nspecial relativity does.", "start": 107.86, "duration": 2.01}, {"text": "The range of validity is\nbasically fast-moving phenomena", "start": 109.87, "duration": 5.15}, {"text": "with high speed.", "start": 115.02, "duration": 2.23}, {"text": "But special relativity\nby itself doesn't", "start": 117.25, "duration": 2.07}, {"text": "help you to understand,\nfor example,", "start": 119.32, "duration": 1.8}, {"text": "object of small scales.", "start": 121.12, "duration": 1.35}, {"text": "In order to have a\nproper description here,", "start": 122.47, "duration": 2.46}, {"text": "you need to study\nquantum mechanics.", "start": 124.93, "duration": 2.19}, {"text": "If you have object\nof very mass large", "start": 127.12, "duration": 2.549}, {"text": "or with large\naccelerations, you need", "start": 129.669, "duration": 3.181}, {"text": "to enter a generalized\nview, general relativity.", "start": 132.85, "duration": 5.82}, {"text": "And if you, for example,\ncombine high velocities", "start": 138.67, "duration": 2.85}, {"text": "and small scales, you have to\nstudy quantum field theories.", "start": 141.52, "duration": 4.23}, {"text": "So the point of\nthis slide is really", "start": 145.75, "duration": 2.19}, {"text": "to point out that special\nrelativity has a specific use", "start": 147.94, "duration": 3.34}, {"text": "case.", "start": 151.28, "duration": 0.5}, {"text": "It's limited.", "start": 151.78, "duration": 1.71}, {"text": "It describes\nfast-moving objects.", "start": 153.49, "duration": 2.85}, {"text": "It doesn't describe\nlarge accelerations.", "start": 156.34, "duration": 3.16}, {"text": "So that is the\ngeneralization you get when", "start": 159.5, "duration": 2.42}, {"text": "you study general relativity.", "start": 161.92, "duration": 3.6}, {"text": "So in summary,\nspecial relativity", "start": 165.52, "duration": 2.09}, {"text": "is a complete description\nof physical phenomena", "start": 167.61, "duration": 3.45}, {"text": "at high speed.", "start": 171.06, "duration": 1.38}, {"text": "It is consistent\nwith 8.01 and 8.02.", "start": 172.44, "duration": 2.25}, {"text": "And you will later see that\nwhenever we find integration", "start": 174.69, "duration": 3.45}, {"text": "of motion for object\nat high speed,", "start": 178.14, "duration": 5.21}, {"text": "if we use smaller\nvelocities, we'll", "start": 183.35, "duration": 3.25}, {"text": "find the solutions\nof 8.01 and 8.02.", "start": 186.6, "duration": 4.218}, {"text": "When we combine\nspecial relativity", "start": 190.818, "duration": 3.072}, {"text": "with quantum mechanics,\nit describes quantum field", "start": 193.89, "duration": 2.28}, {"text": "theories.", "start": 196.17, "duration": 0.9}, {"text": "And as I was saying,\nthe generalization", "start": 197.07, "duration": 2.43}, {"text": "of special relativity, SR,\nis general relativity, GR.", "start": 199.5, "duration": 4.85}]
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+[{"text": "The following\ncontent is provided", "start": 0.57, "duration": 1.8}, {"text": "by MIT OpenCourseWare under\na Creative Commons license.", "start": 2.37, "duration": 3.96}, {"text": "Additional information\nabout our license", "start": 6.33, "duration": 2.1}, {"text": "and MIT OpenCourseWare\nin general", "start": 8.43, "duration": 2.37}, {"text": "is available at ocw.mit.edu.", "start": 10.8, "duration": 1.93}, {"text": "JON GRUDEN: Dr.\nJoel Moses, who is", "start": 15.63, "duration": 3.87}, {"text": "going to give us a talk\nthat will clarify and get us", "start": 19.5, "duration": 9.38}, {"text": "to think deeply about\nthe nature of engineering", "start": 28.88, "duration": 3.13}, {"text": "as a learning discipline.", "start": 32.01, "duration": 2.2}, {"text": "I think he'll talk\nless about engineering", "start": 34.21, "duration": 2.82}, {"text": "as a professional society,\nwhich is what a lot of people", "start": 37.03, "duration": 5.04}, {"text": "talk about when they talk\nengineering or as a profession.", "start": 42.07, "duration": 5.36}, {"text": "And I think he's going\nto talk less about it", "start": 47.43, "duration": 2.64}, {"text": "as a practice of work.", "start": 50.07, "duration": 6.265}, {"text": "In other words,\nsociology of work.", "start": 56.335, "duration": 1.695}, {"text": "We're not going to talk a\nwhole lot about what engineers", "start": 58.03, "duration": 3.65}, {"text": "do when they go on the job.", "start": 61.68, "duration": 1.22}, {"text": "We're going to talk about\nwhat we call a learning", "start": 62.9, "duration": 3.502}, {"text": "discipline [INAUDIBLE].", "start": 66.402, "duration": 1.168}, {"text": "Incidentally, that's\nthe focus about this.", "start": 67.57, "duration": 2.772}, {"text": "So we got a lot to follow up on.", "start": 70.342, "duration": 3.297}, {"text": "There's different points.", "start": 73.639, "duration": 3.301}, {"text": "And as I said, I'm teaching\nthis course, Engineering Ethics,", "start": 76.94, "duration": 3.47}, {"text": "as an engagement of two learning\ndisciplines, engineering", "start": 80.41, "duration": 2.96}, {"text": "and ethics.", "start": 83.37, "duration": 0.96}, {"text": "So I got a little\nbit on the ethics,", "start": 84.33, "duration": 1.5}, {"text": "and I'm putting lot\nmore on the engineering,", "start": 85.83, "duration": 2.205}, {"text": "and we'll cover\nother [? things. ?]", "start": 88.035, "duration": 2.995}, {"text": "So with that, I\nthink you're ready.", "start": 91.03, "duration": 5.13}, {"text": "JOEL MOSES: Right.", "start": 96.16, "duration": 0.75}, {"text": "JON GRUDEN: OK.", "start": 96.91, "duration": 0.635}, {"text": "JOEL MOSES: OK.", "start": 97.545, "duration": 0.625}, {"text": "So the emphasis here is going to\nbe a philosophy of engineering", "start": 98.17, "duration": 4.11}, {"text": "as opposed to ethics.", "start": 102.28, "duration": 0.93}, {"text": "Ethics can be drawn from that.", "start": 103.21, "duration": 2.32}, {"text": "So how would you classify\nengineering again?", "start": 105.53, "duration": 3.17}, {"text": "Metaphysics.", "start": 108.7, "duration": 1.12}, {"text": "JON GRUDEN: Metaphysics--", "start": 109.82, "duration": 1.55}, {"text": "JOEL MOSES: Epistemology.", "start": 111.37, "duration": 0.45}, {"text": "JON GRUDEN: Epistemology.", "start": 111.82, "duration": 0.84}, {"text": "JOEL MOSES: OK.", "start": 112.66, "duration": 0.625}, {"text": "This is really more about\nmetaphysics and epistemology", "start": 113.285, "duration": 2.465}, {"text": "than it is about ethics.", "start": 115.75, "duration": 1.05}, {"text": "So I won't have too many\nreferences because this is--", "start": 122.32, "duration": 3.84}, {"text": "I didn't spend my life\ntrying to remember", "start": 126.16, "duration": 3.75}, {"text": "everybody who said what.", "start": 129.91, "duration": 1.17}, {"text": "But this is my belief.", "start": 131.08, "duration": 2.88}, {"text": "I think there's a lot of\ntruth to what I have to say.", "start": 133.96, "duration": 3.66}, {"text": "OK, so here we're going\nto ask a question,", "start": 137.62, "duration": 2.67}, {"text": "how do different countries\nthink about engineering?", "start": 140.29, "duration": 3.45}, {"text": "Attitudes.", "start": 143.74, "duration": 2.22}, {"text": "Germany and Japan have\nrelatively positive attitudes", "start": 145.96, "duration": 2.97}, {"text": "on engineering.", "start": 148.93, "duration": 1.38}, {"text": "Britain, much less positive.", "start": 150.31, "duration": 2.19}, {"text": "And in Britain, an engineer\nis someone who runs--", "start": 152.5, "duration": 4.26}, {"text": "who operates engines.", "start": 156.76, "duration": 1.185}, {"text": "In France, contrast,\nthe word \"ingenieur\"", "start": 160.66, "duration": 4.23}, {"text": "is very similar to the\nword for \"ingenious,\"", "start": 164.89, "duration": 2.88}, {"text": "ingenieur or something.", "start": 167.77, "duration": 1.41}, {"text": "I can't pronounce it\nnecessarily very well.", "start": 169.18, "duration": 2.13}, {"text": "Much more positive\nattitude toward engineering", "start": 171.31, "duration": 3.33}, {"text": "than in Britain.", "start": 174.64, "duration": 0.75}, {"text": "Where do we get most\nof our ideas from?", "start": 175.39, "duration": 3.63}, {"text": "Britain.", "start": 179.02, "duration": 1.86}, {"text": "But nevertheless, there is a\nclear difference in the US.", "start": 180.88, "duration": 3.22}, {"text": "No, no.", "start": 184.1, "duration": 0.5}, {"text": "I'd like the lights\non, if you don't mind.", "start": 184.6, "duration": 2.94}, {"text": "There's a clear difference\nin US with Britain", "start": 187.54, "duration": 3.42}, {"text": "we're not quite as positive\nthan it is in Japan,", "start": 190.96, "duration": 2.8}, {"text": "but not as negative\nas in Britain.", "start": 193.76, "duration": 1.82}, {"text": "Somewhere in the middle.", "start": 195.58, "duration": 2.85}, {"text": "So what's our\nclaim-- our thesis?", "start": 198.43, "duration": 2.4}, {"text": "National cultural\nvalues, especially", "start": 200.83, "duration": 2.07}, {"text": "the dominant philosophies\nin a particular country", "start": 202.9, "duration": 3.325}, {"text": "has a great deal to do with\nthese difference in attitudes", "start": 206.225, "duration": 2.375}, {"text": "toward engineering.", "start": 208.6, "duration": 1.32}, {"text": "That's one belief that I have.", "start": 209.92, "duration": 3.12}, {"text": "Also another belief--\na general belief", "start": 213.04, "duration": 2.37}, {"text": "is, there's no right answer.", "start": 215.41, "duration": 3.24}, {"text": "Everything depends on context,\nthere's a context change.", "start": 218.65, "duration": 3.51}, {"text": "Cultures change slowly\nbut they do change.", "start": 222.16, "duration": 4.18}, {"text": "And so for example, if you\ncompare American attitudes", "start": 226.34, "duration": 4.01}, {"text": "toward manufacturing in the\n'60s and then in the '80s", "start": 230.35, "duration": 4.83}, {"text": "and then in this decade,\nthere are a lot of differences", "start": 235.18, "duration": 2.4}, {"text": "because the competitive issues.", "start": 237.58, "duration": 1.99}, {"text": "So it's not a static\nsituation at all.", "start": 239.57, "duration": 3.815}, {"text": "So continuing to a discussion\nof these cultural attitudes.", "start": 249.86, "duration": 7.25}, {"text": "Yeah, compare engineering to\nmedicine, law, and business--", "start": 257.11, "duration": 4.56}, {"text": "MBA type education.", "start": 261.67, "duration": 2.13}, {"text": "The kids that come\nto MIT have been", "start": 266.92, "duration": 2.71}, {"text": "viewed as not entirely,\nbut largely lower", "start": 269.63, "duration": 4.47}, {"text": "middle class or\nmaybe middle class", "start": 274.1, "duration": 2.04}, {"text": "people who are aspiring to\nmove up in the economic chain.", "start": 276.14, "duration": 4.17}, {"text": "Now let's say they have moved\nup in the economic chain.", "start": 280.31, "duration": 3.69}, {"text": "Do they want their kids\nto go into engineering?", "start": 284.0, "duration": 3.36}, {"text": "Do mommies and daddies want\ntheir-- what do they want?", "start": 287.36, "duration": 2.49}, {"text": "They want them to become--", "start": 289.85, "duration": 3.32}, {"text": "and maybe MBAs, right?", "start": 293.17, "duration": 3.16}, {"text": "Now that's not true\nin every country.", "start": 296.33, "duration": 3.18}, {"text": "In Japan, the engineers are\nmore highly valued than lawyers,", "start": 299.51, "duration": 3.12}, {"text": "I would dare say.", "start": 302.63, "duration": 2.88}, {"text": "In India too.", "start": 305.51, "duration": 2.19}, {"text": "In the US, parents want\ntheir children become", "start": 307.7, "duration": 1.89}, {"text": "doctors, lawyers and MBA.", "start": 309.59, "duration": 2.47}, {"text": "If you want more\nwomen and minorities", "start": 312.06, "duration": 1.97}, {"text": "to enter engineering,\nyou can concentrate", "start": 314.03, "duration": 2.955}, {"text": "on getting women minorities\ninto engineering.", "start": 316.985, "duration": 1.875}, {"text": "But will also pay to\nimprove the general attitude", "start": 318.86, "duration": 2.61}, {"text": "toward engineering.", "start": 321.47, "duration": 0.93}, {"text": "It's not bad, but\nit's not as good", "start": 325.34, "duration": 2.46}, {"text": "as it is in other countries.", "start": 327.8, "duration": 2.35}, {"text": "Now you can go too far.", "start": 330.15, "duration": 1.55}, {"text": "In Germany, if you are\na professor, doctor,", "start": 331.7, "duration": 4.14}, {"text": "you go into a company\nin the United States,", "start": 335.84, "duration": 2.038}, {"text": "they'll say, what does he know?", "start": 337.878, "duration": 1.292}, {"text": "He's an academic, et cetera.", "start": 339.17, "duration": 1.8}, {"text": "In Germany, they'll\nsay, yes, sir.", "start": 340.97, "duration": 1.95}, {"text": "Absolutely.", "start": 342.92, "duration": 0.81}, {"text": "Yes, sir.", "start": 343.73, "duration": 0.6}, {"text": "We do what you say.", "start": 344.33, "duration": 1.74}, {"text": "You can go too far.", "start": 346.07, "duration": 2.1}, {"text": "But in another aspect\nwhere problems show up", "start": 348.17, "duration": 4.11}, {"text": "is in Britain or in England.", "start": 352.28, "duration": 2.1}, {"text": "The lords-- if you\nare aristocracy, well,", "start": 354.38, "duration": 3.36}, {"text": "if you have a big company,\nyou need an aristocrat", "start": 357.74, "duration": 2.31}, {"text": "to become the CEO.", "start": 360.05, "duration": 0.847}, {"text": "What do they know\nabout that business?", "start": 360.897, "duration": 1.583}, {"text": "Not lots.", "start": 362.48, "duration": 1.11}, {"text": "But they are aristocrats.", "start": 363.59, "duration": 1.35}, {"text": "By golly, they\ndeserve to be CEOs.", "start": 364.94, "duration": 3.06}, {"text": "That's not necessarily\nthe best thing.", "start": 368.0, "duration": 2.53}, {"text": "So you have problems in\nBritain in technology.", "start": 370.53, "duration": 3.23}, {"text": "Now let me switch\ngears a little bit.", "start": 377.63, "duration": 1.93}, {"text": "And this is getting closer\nto my real interest.", "start": 379.56, "duration": 4.04}, {"text": "Who are the two greatest\nphilosophers in antiquity?", "start": 383.6, "duration": 5.0}, {"text": "It's Plato and Aristotle.", "start": 388.6, "duration": 1.39}, {"text": "Well, I could have said\nMoses and Aristotle,", "start": 389.99, "duration": 1.95}, {"text": "but that requires\nanother lecture.", "start": 391.94, "duration": 4.28}, {"text": "A quote.", "start": 396.22, "duration": 0.61}, {"text": "Plato is Moses writing\nin attic Greek.", "start": 401.58, "duration": 2.475}, {"text": "I didn't make that one up,\nbut that's a side discussion.", "start": 408.98, "duration": 5.86}, {"text": "So the two greatest\nphilosophers in antiquity", "start": 414.84, "duration": 2.315}, {"text": "are Plato and Aristotle.", "start": 417.155, "duration": 2.295}, {"text": "We're talking about 380 BCE.", "start": 419.45, "duration": 2.22}, {"text": "Aristotle was Plato's student.", "start": 421.67, "duration": 1.83}, {"text": "Makes life interesting.", "start": 423.5, "duration": 2.01}, {"text": "Have a very different attitude\non math, science, problem", "start": 425.51, "duration": 2.88}, {"text": "solving, design, organization.", "start": 428.39, "duration": 1.83}, {"text": "And these differences\nbetween Plato and Aristotle", "start": 430.22, "duration": 3.0}, {"text": "show up in the next 2,400 years\nagain and again and again.", "start": 433.22, "duration": 5.58}, {"text": "It's as if somehow\nor other these", "start": 438.8, "duration": 2.28}, {"text": "are the two poles of\nways of thinking deeply", "start": 441.08, "duration": 4.68}, {"text": "about a lot of important issues.", "start": 445.76, "duration": 4.88}, {"text": "Aristotle was\ninterested in science.", "start": 450.64, "duration": 3.4}, {"text": "If you look at what is\nhe known for in biology?", "start": 454.04, "duration": 3.66}, {"text": "Does anybody--\nthe classification", "start": 457.7, "duration": 5.63}, {"text": "of things and the species,\net cetera, families.", "start": 463.33, "duration": 4.92}, {"text": "Oh, he was a born classifier.", "start": 468.25, "duration": 2.98}, {"text": "Now how did he get--", "start": 471.23, "duration": 1.7}, {"text": "he got money to send people out\nthroughout the Greek islands", "start": 472.93, "duration": 6.92}, {"text": "and to get him all the\nvarious kinds of flowers,", "start": 479.85, "duration": 3.0}, {"text": "plants, different kinds of\nanimals and what have you", "start": 482.85, "duration": 3.54}, {"text": "so he could classify it all.", "start": 486.39, "duration": 1.65}, {"text": "Where did he get the money\nto send all these people out?", "start": 488.04, "duration": 2.43}, {"text": "He had a student--", "start": 490.47, "duration": 1.26}, {"text": "famous student, Aristotle did.", "start": 491.73, "duration": 2.61}, {"text": "Who was his student?", "start": 494.34, "duration": 1.84}, {"text": "AUDIENCE: Alexander the Great.", "start": 496.18, "duration": 1.25}, {"text": "JOEL MOSES: You got it.", "start": 497.43, "duration": 0.57}, {"text": "Alexander the Great.", "start": 498.0, "duration": 0.99}, {"text": "You know how much money he got\nout of Alexander the Great?", "start": 498.99, "duration": 2.88}, {"text": "30 talents of gold.", "start": 501.87, "duration": 2.63}, {"text": "Yeah, I know, multimillion\ndollars, 30 talents of gold", "start": 504.5, "duration": 4.78}, {"text": "that he spent to\ndo this research.", "start": 509.28, "duration": 4.12}, {"text": "And what did he do?", "start": 513.4, "duration": 0.96}, {"text": "He came up with structures\nfor classifying.", "start": 514.36, "duration": 2.49}, {"text": "What do we call this-- what\ndo I call these structures?", "start": 524.148, "duration": 2.292}, {"text": "These are called\ntree structures.", "start": 526.44, "duration": 1.375}, {"text": "So in his biology work, he\ncreates this classification", "start": 534.91, "duration": 3.97}, {"text": "structure.", "start": 538.88, "duration": 0.5}, {"text": "We still use it.", "start": 539.38, "duration": 0.93}, {"text": "But it turns out that\neverything he did--", "start": 544.28, "duration": 3.6}, {"text": "his mode of thought--", "start": 547.88, "duration": 0.99}, {"text": "everything turned out to\nhave this kind of a diagram.", "start": 548.87, "duration": 2.8}, {"text": "So let's look at the world\naccording to Aristotle.", "start": 551.67, "duration": 5.0}, {"text": "Tip of the world is God.", "start": 556.67, "duration": 2.58}, {"text": "But there is no God.", "start": 559.25, "duration": 1.56}, {"text": "This is called\nthe unmoved mover.", "start": 560.81, "duration": 3.98}, {"text": "Ring a bell?", "start": 564.79, "duration": 1.26}, {"text": "Everything in the world\nis somewhere in the tree.", "start": 566.05, "duration": 4.02}, {"text": "You take a snapshot, you\nknow where everything is.", "start": 573.16, "duration": 3.99}, {"text": "Advance one second, things\nmove, but they're still", "start": 577.15, "duration": 4.41}, {"text": "in a tree structure.", "start": 581.56, "duration": 1.44}, {"text": "Maybe it's slightly different\none, but it's a tree structure.", "start": 583.0, "duration": 2.96}, {"text": "Little problem with this\nAristotelian physics.", "start": 585.96, "duration": 3.01}, {"text": "He cannot express the notion\nwhich is Newton's law,", "start": 588.97, "duration": 6.54}, {"text": "an object in motion remains in\nmotion unless there's a force", "start": 595.51, "duration": 2.79}, {"text": "applied.", "start": 598.3, "duration": 1.08}, {"text": "The concept of motion\ndoesn't exist because all", "start": 599.38, "duration": 3.72}, {"text": "what you have are snapshots.", "start": 603.1, "duration": 2.52}, {"text": "So a thing is always somewhere.", "start": 605.62, "duration": 2.37}, {"text": "It ain't moving.", "start": 607.99, "duration": 2.48}, {"text": "Now you take another\nsnapshot, it's somewhere else.", "start": 610.47, "duration": 2.31}, {"text": "There was something happen,\nwe don't talk about that.", "start": 612.78, "duration": 3.66}, {"text": "But nevertheless, the\npoint I'm trying to make", "start": 616.44, "duration": 2.13}, {"text": "is, in back of Aristotle's\nmind is this notion.", "start": 618.57, "duration": 3.63}, {"text": "And it explains everything.", "start": 622.2, "duration": 2.84}, {"text": "Aristotelian logic.", "start": 625.04, "duration": 2.16}, {"text": "You got it.", "start": 627.2, "duration": 1.29}, {"text": "My guess is, Aristotelian\nethics will have this character.", "start": 628.49, "duration": 2.7}, {"text": "I haven't studied that.", "start": 631.19, "duration": 1.77}, {"text": "My guess is,\nAristotelian, I think,", "start": 632.96, "duration": 1.77}, {"text": "has that character because\nthat's how I Aristotle thought.", "start": 634.73, "duration": 4.45}, {"text": "Everything breaks\ndown, decomposes.", "start": 639.18, "duration": 2.82}, {"text": "Those things get decomposed.", "start": 642.0, "duration": 1.68}, {"text": "Things get into finer\nand finer detail.", "start": 643.68, "duration": 2.7}, {"text": "Empiricism rules.", "start": 646.38, "duration": 1.47}, {"text": "Details matter.", "start": 647.85, "duration": 0.87}, {"text": "Top-down tree structures.", "start": 652.67, "duration": 1.8}, {"text": "He's a reductionist par\nexcellence, loves science.", "start": 654.47, "duration": 5.67}, {"text": "Plato, very different.", "start": 660.14, "duration": 3.125}, {"text": "He's not a scientist,\nhe's a mathematician.", "start": 665.88, "duration": 4.4}, {"text": "Plato describes\nhimself as a geometer.", "start": 670.28, "duration": 2.683}, {"text": "Actually proved the\ntheorem in geometry.", "start": 672.963, "duration": 1.667}, {"text": "He is an idealist.", "start": 677.17, "duration": 3.65}, {"text": "Ideal forms.", "start": 680.82, "duration": 1.21}, {"text": "Remember how many different\nkinds of perfect bodies", "start": 682.03, "duration": 4.76}, {"text": "there are?", "start": 686.79, "duration": 1.05}, {"text": "Things that are ideal.", "start": 687.84, "duration": 2.97}, {"text": "Abstract thinker.", "start": 690.81, "duration": 2.22}, {"text": "Details?", "start": 693.03, "duration": 0.63}, {"text": "Nah.", "start": 693.66, "duration": 1.59}, {"text": "Abstract thinking.", "start": 695.25, "duration": 2.43}, {"text": "What kind of structure does\nhe have in back of his mind?", "start": 697.68, "duration": 2.685}, {"text": "These kinds of pyramids\nare called layered systems.", "start": 706.8, "duration": 2.325}, {"text": "So what's Plato's\nmost famous book?", "start": 714.24, "duration": 4.83}, {"text": "The Republic.", "start": 719.07, "duration": 2.1}, {"text": "Here is society in The Republic.", "start": 721.17, "duration": 3.21}, {"text": "At the tip of the society is a--", "start": 724.38, "duration": 3.866}, {"text": "you remember?", "start": 728.246, "duration": 1.834}, {"text": "Philosopher king.", "start": 730.08, "duration": 1.183}, {"text": "That's right.", "start": 731.263, "duration": 0.542}, {"text": "That this level of people\nwho work together-- they're", "start": 737.1, "duration": 3.0}, {"text": "not individualistic.", "start": 740.1, "duration": 1.11}, {"text": "This is highly\nindividualistically oriented.", "start": 741.21, "duration": 2.43}, {"text": "I'm not saying Aristotle\nwas as individualistic", "start": 743.64, "duration": 2.46}, {"text": "as people became later.", "start": 746.1, "duration": 2.47}, {"text": "But that lends itself\nto individualism.", "start": 748.57, "duration": 2.75}, {"text": "These people are together.", "start": 751.32, "duration": 3.03}, {"text": "This is communism before Marx.", "start": 754.35, "duration": 3.39}, {"text": "These are called the guardians.", "start": 757.74, "duration": 3.62}, {"text": "And they are the top\nlayer of this society--", "start": 761.36, "duration": 3.33}, {"text": "the perfect society.", "start": 764.69, "duration": 3.42}, {"text": "And also called the gold layer.", "start": 768.11, "duration": 2.88}, {"text": "And therefore, this is\nsilver and this is bronze.", "start": 770.99, "duration": 3.42}, {"text": "And people here wind\nup in this level", "start": 774.41, "duration": 4.11}, {"text": "because they couldn't pass\ncertain educational levels.", "start": 778.52, "duration": 5.83}, {"text": "And they wind up in here\nbecause intermediate educational", "start": 784.35, "duration": 3.02}, {"text": "level-- the smartest people,\nthe ones who pass all the tests,", "start": 787.37, "duration": 3.78}, {"text": "they wind up in here.", "start": 791.15, "duration": 1.33}, {"text": "And the absolute smartest\nperson at any given time", "start": 792.48, "duration": 2.18}, {"text": "is the philosopher king.", "start": 794.66, "duration": 2.77}, {"text": "And the key is here, these guys\nare absolutely worked together.", "start": 797.43, "duration": 4.53}, {"text": "It's only a theorist\nlike Plato could", "start": 801.96, "duration": 2.7}, {"text": "make an unbelievable\nmistake about society,", "start": 804.66, "duration": 3.09}, {"text": "which is what he did.", "start": 807.75, "duration": 1.62}, {"text": "In order to be sure\nthat these guardians who", "start": 809.37, "duration": 3.93}, {"text": "determine who passes a test\nwon't give their own children", "start": 813.3, "duration": 6.3}, {"text": "an unfair advantage,\nhe wanted to be", "start": 819.6, "duration": 2.91}, {"text": "sure they didn't know who\ntheir own children were.", "start": 822.51, "duration": 2.73}, {"text": "Therefore, all the women\nin here are at large.", "start": 825.24, "duration": 4.21}, {"text": "No one gets married\nto a particular person", "start": 829.45, "duration": 4.31}, {"text": "because then they'd\nknow who was the father.", "start": 833.76, "duration": 2.1}, {"text": "Only a theorist could\nmake this mistake.", "start": 838.77, "duration": 3.87}, {"text": "There's nothing\nperfect about this.", "start": 842.64, "duration": 1.69}, {"text": "It's just an entirely different\nway of thinking-- abstraction,", "start": 844.33, "duration": 4.01}, {"text": "reductionism.", "start": 848.34, "duration": 3.48}, {"text": "Plato was a member of\nthe Greek aristocracy.", "start": 851.82, "duration": 4.89}, {"text": "Of course, his party\nfell out of favor,", "start": 856.71, "duration": 3.45}, {"text": "and he got pretty pissed off.", "start": 860.16, "duration": 3.76}, {"text": "Maybe you can cut that out.", "start": 863.92, "duration": 2.58}, {"text": "He got quite unhappy at\nthe killing of Socrates", "start": 866.5, "duration": 4.46}, {"text": "at the fact that his party lost,\net cetera, with the Athenians.", "start": 870.96, "duration": 4.32}, {"text": "And he tried to create an\nideal society insistently,", "start": 875.28, "duration": 7.32}, {"text": "but that didn't work.", "start": 882.6, "duration": 1.35}, {"text": "But in any case, it's an\nentirely different way", "start": 883.95, "duration": 2.73}, {"text": "of thinking is my claim.", "start": 886.68, "duration": 2.76}, {"text": "There isn't anything right.", "start": 889.44, "duration": 3.22}, {"text": "And engineering-- let's\ngo back to engineering--", "start": 892.66, "duration": 2.73}, {"text": "needs both science\nand mathematics.", "start": 895.39, "duration": 2.79}, {"text": "And my claim is mathematics\nis a different-- is ideal,", "start": 898.18, "duration": 3.12}, {"text": "science is empirical.", "start": 901.3, "duration": 1.68}, {"text": "You need both the abstract\ncapability from science", "start": 902.98, "duration": 3.33}, {"text": "and the reductionist\nworldview of mathematics.", "start": 906.31, "duration": 4.74}, {"text": "And if you have a society\nthat is highly empirical,", "start": 911.05, "duration": 2.97}, {"text": "like the British\nemphasizing science,", "start": 914.02, "duration": 2.37}, {"text": "you may not get\ngood engineering.", "start": 916.39, "duration": 1.71}, {"text": "If you have a society it's\ntoo heavily abstract--", "start": 918.1, "duration": 3.06}, {"text": "that's unlikely--", "start": 921.16, "duration": 1.86}, {"text": "then you probably\nalso won't work.", "start": 923.02, "duration": 1.54}, {"text": "I can't think of an\nexample like that quite.", "start": 924.56, "duration": 2.15}, {"text": "But a society that has\nboth working for it,", "start": 926.71, "duration": 4.53}, {"text": "like the Germans or the\nJapanese, then engineering", "start": 931.24, "duration": 4.88}, {"text": "will flourish.", "start": 936.12, "duration": 0.96}, {"text": "That's my argument.", "start": 937.08, "duration": 0.975}, {"text": "Here is a structure.", "start": 943.05, "duration": 3.28}, {"text": "I claim that when Americans\ntalk about hierarchies,", "start": 946.33, "duration": 3.72}, {"text": "they usually think this\nway, almost entirely.", "start": 950.05, "duration": 4.05}, {"text": "But this is also a hierarchy.", "start": 954.1, "duration": 1.32}, {"text": "People here are in some sense\nhigher than people there.", "start": 958.0, "duration": 2.89}, {"text": "Likewise, people here are\nhigher than that, et cetera.", "start": 960.89, "duration": 2.9}, {"text": "This philosopher king\nis the highest of all.", "start": 963.79, "duration": 2.68}, {"text": "Give me an organization\nthat is modeled like that.", "start": 966.47, "duration": 3.92}, {"text": "AUDIENCE: A university.", "start": 973.36, "duration": 1.378}, {"text": "JOEL MOSES: A university.", "start": 974.738, "duration": 1.042}, {"text": "Exactly.", "start": 975.78, "duration": 2.44}, {"text": "And this is the--", "start": 978.22, "duration": 3.44}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 981.66, "duration": 1.527}, {"text": "JOEL MOSES: Provost.", "start": 983.187, "duration": 0.833}, {"text": "AUDIENCE: Provost.", "start": 984.02, "duration": 1.872}, {"text": "JOEL MOSES: Yeah.", "start": 985.892, "duration": 0.708}, {"text": "This is the provost.", "start": 986.6, "duration": 1.16}, {"text": "These are the deans,\ndepartment heads, faculty.", "start": 987.76, "duration": 3.93}, {"text": "Or maybe these are\nthe full professors,", "start": 991.69, "duration": 2.07}, {"text": "associate professors,\nand assistant professor.", "start": 993.76, "duration": 2.94}, {"text": "It's a pure\nthree-layered hierarchy.", "start": 996.7, "duration": 2.95}, {"text": "And in olden times,\nall the full professors", "start": 999.65, "duration": 2.55}, {"text": "would get together and\nmake decisions as a body.", "start": 1002.2, "duration": 6.88}, {"text": "What happened in a critical\nyear for University in 1807,", "start": 1009.08, "duration": 4.89}, {"text": "is that there was\nthis character--", "start": 1013.97, "duration": 3.0}, {"text": "forget his name right now--", "start": 1016.97, "duration": 3.36}, {"text": "in the hospital in Berlin\nand he had this notion", "start": 1020.33, "duration": 4.769}, {"text": "that he had to split\nthe surgeons from the--", "start": 1025.099, "duration": 4.74}, {"text": "who are the guys\nwho checked to see", "start": 1029.839, "duration": 3.23}, {"text": "if the stuff was done right?", "start": 1033.069, "duration": 1.601}, {"text": "The pathologist.", "start": 1034.67, "duration": 1.142}, {"text": "They were constantly\nfighting each other.", "start": 1035.812, "duration": 1.708}, {"text": "Pathologist saying,\nyou made a mistake.", "start": 1037.52, "duration": 1.625}, {"text": "The surgeon said, no, no, no.", "start": 1039.145, "duration": 1.208}, {"text": "I did perfect.", "start": 1040.353, "duration": 0.766}, {"text": "Don't tell me I made a mistake.", "start": 1041.119, "duration": 1.831}, {"text": "So he created departments.", "start": 1042.95, "duration": 2.159}, {"text": "And departments break\nup the university", "start": 1045.109, "duration": 3.481}, {"text": "and break up this structure.", "start": 1048.59, "duration": 2.64}, {"text": "So this was in Berlin in 1807.", "start": 1051.23, "duration": 2.34}, {"text": "And by 1880, again in\nthe medical school,", "start": 1053.57, "duration": 4.53}, {"text": "this was at Johns Hopkins.", "start": 1058.1, "duration": 3.34}, {"text": "And in 1885, it\nmade it to Harvard.", "start": 1061.44, "duration": 3.0}, {"text": "And ever since, we've had\nit in the United States.", "start": 1064.44, "duration": 5.22}, {"text": "But where did the\nUniversity get their idea", "start": 1069.66, "duration": 2.85}, {"text": "how to organize things?", "start": 1072.51, "duration": 2.92}, {"text": "You said last time, the\noriginal universities", "start": 1075.43, "duration": 3.27}, {"text": "like Bologna and Paris--", "start": 1078.7, "duration": 2.54}, {"text": "especially Paris and Oxford\nwere associated with what?", "start": 1081.24, "duration": 3.997}, {"text": "AUDIENCE: Well the way I said\nit was that they were associated", "start": 1085.237, "duration": 2.583}, {"text": "with the Holy Roman Empire.", "start": 1087.82, "duration": 1.68}, {"text": "JOEL MOSES: Holy Roman Empire.", "start": 1089.5, "duration": 1.32}, {"text": "You're getting close.", "start": 1090.82, "duration": 1.29}, {"text": "So where does this come from?", "start": 1092.11, "duration": 3.24}, {"text": "The church.", "start": 1095.35, "duration": 1.44}, {"text": "The Pope.", "start": 1096.79, "duration": 1.2}, {"text": "The Cardinals.", "start": 1097.99, "duration": 1.14}, {"text": "The bishops.", "start": 1099.13, "duration": 0.67}, {"text": "The priests.", "start": 1099.8, "duration": 0.5}, {"text": "Now let me tell you, Moses\nwas the original Platonist.", "start": 1103.22, "duration": 4.83}, {"text": "This shows up in the Bible.", "start": 1108.05, "duration": 1.125}, {"text": "How did it show up in the Bible?", "start": 1113.447, "duration": 1.333}, {"text": "AUDIENCE: As the fathers.", "start": 1120.54, "duration": 1.47}, {"text": "JOEL MOSES: Close.", "start": 1122.01, "duration": 0.75}, {"text": "High priests, the kohanim,\nthe priests, the Levis,", "start": 1122.76, "duration": 8.02}, {"text": "the Israelites.", "start": 1130.78, "duration": 1.02}, {"text": "You want to talk\nabout neural networks?", "start": 1134.39, "duration": 1.625}, {"text": "It ain't quite like that,\nbut you're getting close.", "start": 1140.41, "duration": 3.81}, {"text": "So we see examples.", "start": 1144.22, "duration": 2.67}, {"text": "In the West, Plato and\nhis mode of thought", "start": 1146.89, "duration": 5.86}, {"text": "was dominant until about 1,300.", "start": 1152.75, "duration": 6.8}, {"text": "And what happened?", "start": 1159.55, "duration": 1.92}, {"text": "What happened was starting--\nlet me guess, around 1150,", "start": 1161.47, "duration": 5.85}, {"text": "people rediscovered Aristotle.", "start": 1167.32, "duration": 2.79}, {"text": "His writings were lost.", "start": 1170.11, "duration": 1.47}, {"text": "And the rediscovery\nstarted with the Arabs.", "start": 1174.52, "duration": 6.17}, {"text": "They had access to Aristotle's\nwritings from the Middle East.", "start": 1180.69, "duration": 4.5}, {"text": "And it went through\npeople like Maimonides.", "start": 1185.19, "duration": 6.03}, {"text": "And then finally, it went\nthrough St. Thomas Aquinas", "start": 1191.22, "duration": 3.51}, {"text": "around 1250, let me guess.", "start": 1194.73, "duration": 2.1}, {"text": "And by 1250, St. Thomas\nthen redefined Catholicism", "start": 1196.83, "duration": 6.15}, {"text": "to be more in line with\nAristotelian logical,", "start": 1202.98, "duration": 6.26}, {"text": "rational, somewhat\nmore individualistic--", "start": 1209.24, "duration": 3.3}, {"text": "not so much science based.", "start": 1215.09, "duration": 1.13}, {"text": "I don't think it's St.\nThomas really cared", "start": 1216.22, "duration": 1.75}, {"text": "much for the science.", "start": 1217.97, "duration": 1.35}, {"text": "But that whole\ndevelopment beginning 1250", "start": 1219.32, "duration": 3.84}, {"text": "led, eventually, to the\nRenaissance to a science mode", "start": 1223.16, "duration": 5.4}, {"text": "emphasis, et cetera,\net cetera, et cetera.", "start": 1228.56, "duration": 2.64}, {"text": "And that's why the name\nof the rows that we", "start": 1231.2, "duration": 3.15}, {"text": "were talking about last time\nare such an interesting book.", "start": 1234.35, "duration": 3.57}, {"text": "Because it was written\nfor about this time when", "start": 1237.92, "duration": 3.96}, {"text": "the transition from Platonic\nthought or Neoplatonic thought", "start": 1241.88, "duration": 4.05}, {"text": "of the church to\nAristotelian thought", "start": 1245.93, "duration": 2.52}, {"text": "could be influenced\none way or the other.", "start": 1248.45, "duration": 4.02}, {"text": "And that's why the\nmurders occurred", "start": 1252.47, "duration": 3.03}, {"text": "when people read Aristotle's\nlogic, which book had", "start": 1255.5, "duration": 4.68}, {"text": "a tremendous influence\non the way people", "start": 1260.18, "duration": 2.61}, {"text": "were thinking in the\nRenaissance and beyond.", "start": 1262.79, "duration": 2.91}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 1269.463, "duration": 0.917}, {"text": "This is going to be an\nassignment [INAUDIBLE]..", "start": 1270.38, "duration": 1.958}, {"text": "JOEL MOSES: OK, there he is.", "start": 1272.338, "duration": 2.962}, {"text": "Sean Connery is the guy who\nfigures out who killed and why.", "start": 1275.3, "duration": 5.37}, {"text": "AUDIENCE: And he was roughly--", "start": 1284.62, "duration": 1.62}, {"text": "brings a conflation\nof several characters", "start": 1286.24, "duration": 1.93}, {"text": "who are roughly William\n[INAUDIBLE],, wouldn't you say?", "start": 1288.17, "duration": 2.292}, {"text": "JOEL MOSES: I don't if he\nwas William [INAUDIBLE],,", "start": 1290.805, "duration": 2.125}, {"text": "but the author\nobviously made it up.", "start": 1292.93, "duration": 4.92}, {"text": "But he had a point.", "start": 1297.85, "duration": 1.41}, {"text": "And I think that's the point.", "start": 1299.26, "duration": 1.65}, {"text": "That here is a\ntremendous sea change", "start": 1300.91, "duration": 3.06}, {"text": "in Western thinking\nfrom a Neoplatonic--", "start": 1303.97, "duration": 2.76}, {"text": "I'm not saying Plato is right.", "start": 1306.73, "duration": 2.03}, {"text": "It's different.", "start": 1308.76, "duration": 0.97}, {"text": "And it has advantage in\nsome cases, disadvantage", "start": 1309.73, "duration": 2.16}, {"text": "in other cases.", "start": 1311.89, "duration": 1.14}, {"text": "A tremendous sea change\ngoing on in mode of thought.", "start": 1313.03, "duration": 5.51}, {"text": "So this guy was trying to hold\nback and say, no, no, no, no.", "start": 1318.54, "duration": 2.5}, {"text": "Let's keep the order.", "start": 1321.04, "duration": 1.86}, {"text": "In a sense, this\nslide coming up,", "start": 1328.86, "duration": 3.45}, {"text": "Catholic Church historically\ninfluenced by Neoplatonic.", "start": 1332.31, "duration": 2.768}, {"text": "Organizational hierarchies\nlargely layered.", "start": 1335.078, "duration": 1.792}, {"text": "Pope, college of Cardinal,\nsynods of bishops.", "start": 1336.87, "duration": 3.6}, {"text": "Aristotle's closer\nto Protestant.", "start": 1340.47, "duration": 2.34}, {"text": "And Protestantism is closer\nto science, et cetera.", "start": 1345.5, "duration": 5.93}, {"text": "It's more network\noriented as supposed", "start": 1351.43, "duration": 2.04}, {"text": "to centralize hierarchies.", "start": 1353.47, "duration": 1.38}, {"text": "Lends itself to more\nnetwork distributed things.", "start": 1354.85, "duration": 4.8}, {"text": "And that's the final comment.", "start": 1359.65, "duration": 1.71}, {"text": "Be careful, dear student.", "start": 1361.36, "duration": 1.23}, {"text": "Not all hierarchies are alike.", "start": 1362.59, "duration": 1.5}, {"text": "Americans think all\nhierarchies are like this.", "start": 1364.09, "duration": 4.08}, {"text": "But here is an example,\nthis is hierarchical", "start": 1368.17, "duration": 2.46}, {"text": "in a different way.", "start": 1370.63, "duration": 1.6}, {"text": "And it has advantages\nand disadvantages.", "start": 1372.23, "duration": 2.45}, {"text": "I would claim-- I don't\nif I do it in the slides--", "start": 1374.68, "duration": 2.37}, {"text": "that Japanese organizations\nare more like this", "start": 1377.05, "duration": 2.43}, {"text": "than they are like that.", "start": 1379.48, "duration": 1.08}, {"text": "Internally, locally,\nthey are tree structured.", "start": 1380.56, "duration": 2.94}, {"text": "But there is a way of looking at\nthe structure of the firm which", "start": 1383.5, "duration": 4.35}, {"text": "has this character as well.", "start": 1387.85, "duration": 4.13}, {"text": "Because Japan does have\nthat set of approaches.", "start": 1391.98, "duration": 4.53}, {"text": "So philosophy and religion\nintimately connected,", "start": 1399.88, "duration": 4.36}, {"text": "intimately connected\nto ways of thinking.", "start": 1404.24, "duration": 4.213}, {"text": "Engineering is\ngoing to flourish--", "start": 1408.453, "duration": 1.417}, {"text": "I said this before-- in nations\nthat have both a holistic, as", "start": 1409.87, "duration": 2.87}, {"text": "well as reductionistic model.", "start": 1412.74, "duration": 1.26}, {"text": "So Plato is the ultimate\nholistic thinker, but also", "start": 1414.0, "duration": 4.74}, {"text": "rational.", "start": 1418.74, "duration": 0.6}, {"text": "So in contrast to\nmysticism, which", "start": 1419.34, "duration": 2.91}, {"text": "tends to be holistic and\nnot necessarily rational,", "start": 1422.25, "duration": 3.93}, {"text": "Plato is rational.", "start": 1426.18, "duration": 1.9}, {"text": "But he also tends to\nthink holistically.", "start": 1428.08, "duration": 3.74}, {"text": "So these guys all work together.", "start": 1431.82, "duration": 2.68}, {"text": "It's the whole.", "start": 1434.5, "duration": 1.31}, {"text": "We are trying to\nimprove this society.", "start": 1435.81, "duration": 3.923}, {"text": "AUDIENCE: I have a question.", "start": 1439.733, "duration": 1.167}, {"text": "JOEL MOSES: Sure.", "start": 1440.9, "duration": 0.708}, {"text": "AUDIENCE: The Platonic\nmodel over there.", "start": 1444.19, "duration": 3.122}, {"text": "JOEL MOSES: Yeah.", "start": 1447.312, "duration": 0.708}, {"text": "AUDIENCE: When we talk\nabout the university.", "start": 1448.02, "duration": 3.313}, {"text": "Let's talk about the\nuniversity, but this time", "start": 1451.333, "duration": 1.917}, {"text": "is talking about it in\nterms of curriculum.", "start": 1453.25, "duration": 3.23}, {"text": "And let's talk about how\nwe organize the curriculum.", "start": 1456.48, "duration": 3.36}, {"text": "Now let's talk about\ntwo kinds of curriculum.", "start": 1459.84, "duration": 3.88}, {"text": "General education and\nspecial education.", "start": 1463.72, "duration": 5.2}, {"text": "It's just occurred\nto me that maybe we", "start": 1468.92, "duration": 1.74}, {"text": "could think of general\neducation in the Platonic model,", "start": 1470.66, "duration": 2.62}, {"text": "because--", "start": 1473.28, "duration": 0.5}, {"text": "JOEL MOSES: That's\nthe way it was.", "start": 1473.78, "duration": 1.43}, {"text": "AUDIENCE: --at each\nlevel, everybody", "start": 1475.21, "duration": 1.6}, {"text": "knows a little bit of\nsomething about it.", "start": 1476.81, "duration": 2.148}, {"text": "JOEL MOSES: But\nthat's exactly right.", "start": 1478.958, "duration": 1.542}, {"text": "When you think of Middle\nAges, the university", "start": 1480.5, "duration": 2.97}, {"text": "taught either quadrillion or\nthe four things, the rhetoric", "start": 1483.47, "duration": 4.41}, {"text": "and geometry.", "start": 1487.88, "duration": 1.83}, {"text": "And everybody was\nlearning the same thing.", "start": 1489.71, "duration": 2.37}, {"text": "AUDIENCE: Yes.", "start": 1492.08, "duration": 1.2}, {"text": "JOEL MOSES: The specialization\nstarts occurring", "start": 1493.28, "duration": 3.29}, {"text": "with the medical schools.", "start": 1496.57, "duration": 2.99}, {"text": "The medical system said, we\nneed you to understand anatomy.", "start": 1499.56, "duration": 3.78}, {"text": "It isn't one of the four things\nthat everybody is taught.", "start": 1503.34, "duration": 3.81}, {"text": "So the medical schools force\nthe issue on specialization.", "start": 1507.15, "duration": 3.57}, {"text": "And they force the issue\non department structure.", "start": 1510.72, "duration": 3.37}, {"text": "There was no department\nstructure in the Middle Ages.", "start": 1514.09, "duration": 3.87}, {"text": "All the professors were--", "start": 1517.96, "duration": 1.32}, {"text": "full professors were alike.", "start": 1519.28, "duration": 1.8}, {"text": "And they would teach\ntheir courses all right.", "start": 1521.08, "duration": 2.19}, {"text": "But they'd get together\nfor lunch or whatever.", "start": 1523.27, "duration": 3.15}, {"text": "We work together.", "start": 1526.42, "duration": 1.74}, {"text": "We're in it together.", "start": 1528.16, "duration": 3.3}, {"text": "Oh, now, they would\nmake money by asking", "start": 1531.46, "duration": 2.58}, {"text": "the students to pay tuition\nif they attend their classes.", "start": 1534.04, "duration": 3.42}, {"text": "But it seems like the\ndepartmental structure really", "start": 1537.46, "duration": 3.69}, {"text": "made it an absolute sea change\nin the nature of the research", "start": 1541.15, "duration": 4.86}, {"text": "university.", "start": 1546.01, "duration": 0.87}, {"text": "So how does Germany get\nto have this holistic and", "start": 1551.02, "duration": 2.64}, {"text": "reductionistic thing?", "start": 1553.66, "duration": 2.49}, {"text": "Partly because Germany\nis Catholic in the South,", "start": 1556.15, "duration": 3.39}, {"text": "Protestant in the North.", "start": 1559.54, "duration": 1.29}, {"text": "And they have melded\nthe two views.", "start": 1560.83, "duration": 3.81}, {"text": "I'm not saying Catholicism\nis super Platonic,", "start": 1564.64, "duration": 3.39}, {"text": "it's more Platonic\nthan it is not.", "start": 1568.03, "duration": 3.99}, {"text": "They've melded these views.", "start": 1572.02, "duration": 2.82}, {"text": "And you could argue, well,\npeople say, how did Nazism", "start": 1574.84, "duration": 3.0}, {"text": "succeed when the Germans\nare so highly educated", "start": 1577.84, "duration": 4.32}, {"text": "and this, that, and\nthe other thing?", "start": 1582.16, "duration": 1.75}, {"text": "And the answer is\nHitler beat them up", "start": 1583.91, "duration": 2.06}, {"text": "and he tried to\nbreak the melding.", "start": 1585.97, "duration": 2.58}, {"text": "He tried to get the Southern\npoint of view become dominant", "start": 1588.55, "duration": 6.6}, {"text": "over the northern view.", "start": 1595.15, "duration": 1.98}, {"text": "Rather than melding,\nbreak the melding.", "start": 1597.13, "duration": 3.33}, {"text": "And he took a while,\nbut he succeeded.", "start": 1600.46, "duration": 3.58}, {"text": "And so the Germans\nbehaved in ways", "start": 1604.04, "duration": 2.57}, {"text": "that were surprising to\npeople who knew them.", "start": 1606.61, "duration": 3.17}, {"text": "The Japanese have three\ndominant religions", "start": 1609.78, "duration": 2.46}, {"text": "and have the most\nflexible culture", "start": 1612.24, "duration": 4.74}, {"text": "in terms of attitudes\ntoward reductionism holism.", "start": 1616.98, "duration": 2.67}, {"text": "They could switch on a dime.", "start": 1619.65, "duration": 4.41}, {"text": "AUDIENCE: On this point.", "start": 1624.06, "duration": 1.06}, {"text": "JOEL MOSES: Yeah.", "start": 1625.12, "duration": 1.545}, {"text": "AUDIENCE: You have to say\nsomething special about Germany", "start": 1626.665, "duration": 2.375}, {"text": "when it comes to the\nuniversity, the research they", "start": 1629.04, "duration": 1.944}, {"text": "do in Germany.", "start": 1630.984, "duration": 0.716}, {"text": "JOEL MOSES: Yes.", "start": 1631.7, "duration": 0.667}, {"text": "AUDIENCE: Because everybody else\nwas talking about handing down", "start": 1632.367, "duration": 2.753}, {"text": "traditional knowledge.", "start": 1635.12, "duration": 2.25}, {"text": "I mean, nobody was\nadding to Aristotle.", "start": 1637.37, "duration": 3.78}, {"text": "JOEL MOSES: No, that changed.", "start": 1641.15, "duration": 1.83}, {"text": "Indeed.", "start": 1642.98, "duration": 0.9}, {"text": "So what the first wave,\nsay between St. Thomas", "start": 1643.88, "duration": 4.08}, {"text": "and say 1550-1600,\nthe first wave,", "start": 1647.96, "duration": 4.53}, {"text": "they viewed the Greeks whom\nthey rediscovered as God.", "start": 1652.49, "duration": 5.37}, {"text": "I mean what they said went.", "start": 1657.86, "duration": 3.04}, {"text": "So let me give you an example.", "start": 1660.9, "duration": 2.01}, {"text": "I may have the numbers wrong\nbut the idea is just right.", "start": 1662.91, "duration": 3.08}, {"text": "So when Aristotle said--", "start": 1665.99, "duration": 1.83}, {"text": "and Aristotle, remember,\nwas somebody who'd", "start": 1667.82, "duration": 2.665}, {"text": "gathered a lot of information.", "start": 1670.485, "duration": 1.25}, {"text": "And he had these\n30 talents of gold", "start": 1671.735, "duration": 1.74}, {"text": "that allowed them\nto do these things.", "start": 1673.475, "duration": 1.665}, {"text": "When Aristotle said that\na fly had eight legs,", "start": 1675.14, "duration": 3.39}, {"text": "no one bothered to check.", "start": 1678.53, "duration": 3.72}, {"text": "Well, the flies have six legs.", "start": 1682.25, "duration": 1.95}, {"text": "Oh, maybe he said six\nand they have eight.", "start": 1684.2, "duration": 1.89}, {"text": "But whatever it was,\nthey got it wrong.", "start": 1686.09, "duration": 1.92}, {"text": "No one checked because\nAristotle said so.", "start": 1688.01, "duration": 4.01}, {"text": "In medicine for hundreds\nof thousands years,", "start": 1692.02, "duration": 3.15}, {"text": "Galen's book on medicine--", "start": 1695.17, "duration": 2.25}, {"text": "Galen said, I tell\nyou what to do.", "start": 1697.42, "duration": 2.15}, {"text": "You take the blood out, you\ngive them these root extracts.", "start": 1699.57, "duration": 4.42}, {"text": "None of which works.", "start": 1703.99, "duration": 1.44}, {"text": "But Galen said, I\nknow what I'm doing.", "start": 1705.43, "duration": 2.67}, {"text": "And he wrote at that time\nperiod through the Middle Ages,", "start": 1708.1, "duration": 3.48}, {"text": "that's what they did.", "start": 1711.58, "duration": 1.27}, {"text": "No one bothered to check.", "start": 1712.85, "duration": 3.4}, {"text": "Science begins slowly\nbut surely around,", "start": 1716.25, "duration": 3.87}, {"text": "let's say, 1600 suddenly.", "start": 1720.12, "duration": 2.49}, {"text": "And they are doing experiments.", "start": 1722.61, "duration": 1.535}, {"text": "In the Middle Ages, they\nweren't doing experiments.", "start": 1724.145, "duration": 2.125}, {"text": "They were buying\nAristotle's line.", "start": 1726.27, "duration": 3.21}, {"text": "The philosopher was telling\nyou to do this, it is.", "start": 1729.48, "duration": 4.92}, {"text": "It's only later that\nthey actually changed.", "start": 1734.4, "duration": 3.28}, {"text": "But the fact is that\nthey Aristotle was", "start": 1737.68, "duration": 2.24}, {"text": "a necessary bridge between\nthe Neoplatonic thought", "start": 1739.92, "duration": 4.47}, {"text": "of the Dark Ages and the first\nMillennium, say, after Christ.", "start": 1744.39, "duration": 5.04}, {"text": "And it was a necessary bridge\nto allow the science to develop.", "start": 1749.43, "duration": 5.715}, {"text": "So Germany and Japan\nhave a positive attitude", "start": 1761.63, "duration": 2.1}, {"text": "toward engineering.", "start": 1763.73, "duration": 1.11}, {"text": "And in the 1980s, when we were\nlosing in the car manufacturing", "start": 1764.84, "duration": 5.46}, {"text": "to the Germans and the\nJapanese, especially Japanese,", "start": 1770.3, "duration": 3.0}, {"text": "we were really trying\nto figure out why is it", "start": 1773.3, "duration": 2.07}, {"text": "that they were doing so well.", "start": 1775.37, "duration": 1.32}, {"text": "And again, I would say it's a\nlittle bit of this issue coming", "start": 1776.69, "duration": 3.87}, {"text": "up.", "start": 1780.56, "duration": 0.81}, {"text": "That is here, we were highly\nindividualistic, weren't", "start": 1781.37, "duration": 4.56}, {"text": "working as teams as well.", "start": 1785.93, "duration": 1.54}, {"text": "We learned the Japanese\nworked in teams.", "start": 1787.47, "duration": 2.46}, {"text": "And so we picked up on some of\nthese things in the early '90s.", "start": 1789.93, "duration": 2.9}, {"text": "Teamwork, dah, dah,\ndah, dah, dah, dah.", "start": 1792.83, "duration": 2.49}, {"text": "Did we really understand\nhow the Japanese work?", "start": 1795.32, "duration": 2.43}, {"text": "No.", "start": 1797.75, "duration": 1.26}, {"text": "But we made a fair progress.", "start": 1799.01, "duration": 2.82}, {"text": "I mean, all cars nowadays,\nbased on teamwork", "start": 1801.83, "duration": 2.967}, {"text": "and a number of other\nthings we've picked up", "start": 1804.797, "duration": 1.833}, {"text": "from the Japanese,\nreally are better", "start": 1806.63, "duration": 2.31}, {"text": "than they were otherwise.", "start": 1808.94, "duration": 1.59}, {"text": "Now it turns out the Japanese\ndidn't stop improving", "start": 1810.53, "duration": 3.57}, {"text": "and we didn't realize that.", "start": 1814.1, "duration": 2.85}, {"text": "So what's happening\nin the automobile", "start": 1816.95, "duration": 1.79}, {"text": "industry in the United\nStates is that they", "start": 1818.74, "duration": 1.75}, {"text": "have taken their understanding\nof the Toyota process,", "start": 1820.49, "duration": 3.75}, {"text": "as it's called.", "start": 1824.24, "duration": 1.95}, {"text": "The lean manufacturing\nis another term for it.", "start": 1826.19, "duration": 2.617}, {"text": "That they've taken\ntheir understanding", "start": 1828.807, "duration": 1.583}, {"text": "and they've made\nit into a religion.", "start": 1830.39, "duration": 2.43}, {"text": "You do this, you do that.", "start": 1832.82, "duration": 2.04}, {"text": "Reduce waste.", "start": 1834.86, "duration": 1.5}, {"text": "You do just in time.", "start": 1836.36, "duration": 1.44}, {"text": "You do this, you do that.", "start": 1837.8, "duration": 2.25}, {"text": "The Japanese-- the Toyota\npeople have figured out,", "start": 1840.05, "duration": 2.17}, {"text": "hey, you know, that doesn't\nwork as well as we should.", "start": 1842.22, "duration": 2.84}, {"text": "For example, it used\nto be that the Toyota", "start": 1845.06, "duration": 4.98}, {"text": "people had this line where you\nbasically put the car together.", "start": 1850.04, "duration": 4.81}, {"text": "And the idea was that things\nmove without stopping.", "start": 1854.85, "duration": 5.51}, {"text": "Now if anybody screwed up, your\njob as somebody on the line", "start": 1860.36, "duration": 4.44}, {"text": "it's to pull the\ncord, stop the line,", "start": 1864.8, "duration": 2.7}, {"text": "fix the thing at its\nsource-- not at the end when", "start": 1867.5, "duration": 2.55}, {"text": "it's hard to fix.", "start": 1870.05, "duration": 1.15}, {"text": "Fix it at its source,\nand then continue.", "start": 1871.2, "duration": 3.95}, {"text": "Well, these lines were very\nlong and they had maybe 50", "start": 1875.15, "duration": 3.09}, {"text": "different people on the line.", "start": 1878.24, "duration": 1.53}, {"text": "And these poor Japanese\nwho noticed an error,", "start": 1879.77, "duration": 3.66}, {"text": "they were afraid.", "start": 1883.43, "duration": 1.05}, {"text": "Oh, my God.", "start": 1884.48, "duration": 1.08}, {"text": "We stopped this 50 person line.", "start": 1885.56, "duration": 3.06}, {"text": "Maybe I shouldn't.", "start": 1888.62, "duration": 1.52}, {"text": "Oh, I'm scared.", "start": 1890.14, "duration": 1.46}, {"text": "I'm not going to do it.", "start": 1891.6, "duration": 1.13}, {"text": "So they figured this out.", "start": 1892.73, "duration": 2.85}, {"text": "They said, hey, we can't\nhave a 50-person line moving", "start": 1895.58, "duration": 4.26}, {"text": "without having\neverything just in time.", "start": 1899.84, "duration": 4.44}, {"text": "No stacking up of\nanything, blah, blah, blah.", "start": 1904.28, "duration": 3.31}, {"text": "And if we really want to\nfix the error at its source,", "start": 1907.59, "duration": 2.63}, {"text": "we're going to have to break\nit up into lines of maybe 10.", "start": 1910.22, "duration": 3.69}, {"text": "Now psychologically, you're\nmore likely to pull the cord", "start": 1913.91, "duration": 3.63}, {"text": "when you should, et cetera.", "start": 1917.54, "duration": 2.01}, {"text": "Did the Americans\nunderstand this?", "start": 1919.55, "duration": 1.59}, {"text": "No.", "start": 1921.14, "duration": 0.57}, {"text": "Because they had the rules.", "start": 1921.71, "duration": 3.51}, {"text": "They're following\nthe rules of 1988.", "start": 1925.22, "duration": 2.01}, {"text": "And by 1998, they were\nfalling behinder and behinder.", "start": 1927.23, "duration": 2.64}, {"text": "We learned from the\nJapanese, but not enough.", "start": 1933.52, "duration": 2.04}, {"text": "Now of all the major\nmanufacturing countries", "start": 1942.18, "duration": 3.42}, {"text": "in the world, England\nhad the most problem.", "start": 1945.6, "duration": 4.66}, {"text": "So not only is it largely\na Protestant country,", "start": 1950.26, "duration": 4.1}, {"text": "so it means--", "start": 1954.36, "duration": 1.095}, {"text": "there's nothing wrong\nwith that, obviously.", "start": 1955.455, "duration": 1.935}, {"text": "But it means that you are\nmore likely to be here,", "start": 1957.39, "duration": 3.09}, {"text": "everything is more\nindividualistic,", "start": 1960.48, "duration": 2.55}, {"text": "reductionistic, science based.", "start": 1963.03, "duration": 1.89}, {"text": "Not so much engineering\nbecause you have", "start": 1964.92, "duration": 2.67}, {"text": "both of these things going on.", "start": 1967.59, "duration": 2.4}, {"text": "In addition to which, they\nstill have this remnant", "start": 1969.99, "duration": 2.94}, {"text": "of the hierarchy from the Middle\nAges because of aristocracy.", "start": 1972.93, "duration": 4.32}, {"text": "So they don't have\nthe mode of thought,", "start": 1977.25, "duration": 2.1}, {"text": "but they have this thing--", "start": 1979.35, "duration": 4.6}, {"text": "really problematic.", "start": 1983.95, "duration": 1.5}, {"text": "And so what happened in the\nautomobile industry in England?", "start": 1985.45, "duration": 3.77}, {"text": "It got bought out.", "start": 1989.22, "duration": 2.66}, {"text": "I mean Ford owns--", "start": 1991.88, "duration": 1.26}, {"text": "they own Jaguar.", "start": 1996.395, "duration": 1.575}, {"text": "The Germans own Land\nRover or something.", "start": 1997.97, "duration": 4.83}, {"text": "Mercedes owns one\nof the companies.", "start": 2002.8, "duration": 2.19}, {"text": "So basically,\nthere's nothing left.", "start": 2004.99, "duration": 1.878}, {"text": "I mean, they just\nlost out completely", "start": 2006.868, "duration": 1.542}, {"text": "on the automobile part.", "start": 2008.41, "duration": 0.99}, {"text": "So they have just as many\nsmart people, tinkerers people", "start": 2013.51, "duration": 3.75}, {"text": "come up with ideas.", "start": 2017.26, "duration": 1.59}, {"text": "But when it comes down\nto a sizable business,", "start": 2018.85, "duration": 2.43}, {"text": "then you run into this issue of,\nwe better get a lord in there.", "start": 2021.28, "duration": 3.42}, {"text": "And it doesn't necessarily\nwork very well.", "start": 2024.7, "duration": 3.04}, {"text": "So obviously, they do very\nwell in certain issues", "start": 2027.74, "duration": 3.14}, {"text": "like insurance and variety\nof other kinds of things.", "start": 2030.88, "duration": 2.8}, {"text": "But when it comes\ndown to things that", "start": 2033.68, "duration": 2.33}, {"text": "require depth of\nengineering and large scale,", "start": 2036.01, "duration": 4.65}, {"text": "they have really done poorly.", "start": 2040.66, "duration": 1.89}, {"text": "So the US gets much of\nits philosophy, at least,", "start": 2048.54, "duration": 4.31}, {"text": "from Britain.", "start": 2052.85, "duration": 1.74}, {"text": "So to some degree, engineering\nis not as highly valued", "start": 2054.59, "duration": 3.45}, {"text": "as doctor, lawyer, MBA.", "start": 2058.04, "duration": 2.67}, {"text": "But we do better\nthan the British", "start": 2060.71, "duration": 1.949}, {"text": "because we don't have a\nclass structure mentality.", "start": 2062.659, "duration": 2.52}, {"text": "And many of our\ntechnological firms", "start": 2065.179, "duration": 3.361}, {"text": "are run by their\nfounders, at least,", "start": 2068.54, "duration": 1.5}, {"text": "initially and others\nwho may have an MBA.", "start": 2070.04, "duration": 2.76}, {"text": "But they appreciate the\ntechnology to a large degree,", "start": 2072.8, "duration": 4.71}, {"text": "and so we do better.", "start": 2077.51, "duration": 3.27}, {"text": "Now we do even better?", "start": 2080.78, "duration": 1.737}, {"text": "I think the answer is yes.", "start": 2082.517, "duration": 1.083}, {"text": "But it's not going to be\neasy to make the transition.", "start": 2083.6, "duration": 2.22}, {"text": "So I've taken you to here, 1300.", "start": 2089.389, "duration": 6.6}, {"text": "People realized that there was\na conflict between those two.", "start": 2095.989, "duration": 2.641}, {"text": "Because Aristotle\nwas rediscovered", "start": 2098.63, "duration": 3.14}, {"text": "and the university professors\nsaid, now, wait a minute.", "start": 2101.77, "duration": 4.72}, {"text": "These different\nmodes of thought.", "start": 2106.49, "duration": 2.95}, {"text": "So there became a controversy.", "start": 2109.44, "duration": 2.325}, {"text": "It was called the nominalism\nversus realism controversy.", "start": 2111.765, "duration": 12.215}, {"text": "You ever hear that term?", "start": 2123.98, "duration": 2.69}, {"text": "About somewhere in the\n1300s, I would guess.", "start": 2126.67, "duration": 4.38}, {"text": "Now which one of these\nguys, Plato or Aristotle,", "start": 2131.05, "duration": 6.99}, {"text": "is likely to be the realist?", "start": 2138.04, "duration": 1.515}, {"text": "A-ha.", "start": 2144.54, "duration": 1.28}, {"text": "Trick question.", "start": 2145.82, "duration": 2.14}, {"text": "It's Plato.", "start": 2147.96, "duration": 1.38}, {"text": "So let me explain what\nthe issue here is.", "start": 2149.34, "duration": 3.74}, {"text": "Lambda calculus.", "start": 2153.08, "duration": 0.705}, {"text": "The meaning of a name in\nlambda calculus is nothing.", "start": 2157.76, "duration": 5.81}, {"text": "X is an X. It could\njust as well be", "start": 2163.57, "duration": 1.8}, {"text": "a Y. That's the Aristotelian\nposition in the 14th century,", "start": 2165.37, "duration": 6.9}, {"text": "nominalism.", "start": 2172.27, "duration": 1.8}, {"text": "Names don't mean anything.", "start": 2174.07, "duration": 3.19}, {"text": "Realism says, the\nname might tell you", "start": 2177.26, "duration": 3.57}, {"text": "something about the person or\nbut the future of this person.", "start": 2180.83, "duration": 6.2}, {"text": "Boy, names mean a lot.", "start": 2187.03, "duration": 2.43}, {"text": "They convey the reality\nof the situation.", "start": 2189.46, "duration": 3.96}, {"text": "They get at the essence\nof the person, maybe.", "start": 2193.42, "duration": 2.16}, {"text": "Plato.", "start": 2198.99, "duration": 2.8}, {"text": "A chair isn't just a chair.", "start": 2201.79, "duration": 2.25}, {"text": "Think of Shakespeare, a rose\nis a rose by any other name,", "start": 2204.04, "duration": 2.61}, {"text": "nominalist position.", "start": 2206.65, "duration": 2.31}, {"text": "A chair is a representative\nof the ideal chair in heaven.", "start": 2208.96, "duration": 6.625}, {"text": "The fact that it's a\nchair means that there's", "start": 2215.585, "duration": 1.875}, {"text": "a direct correspondence\nto the ideal.", "start": 2217.46, "duration": 1.95}, {"text": "This thing is a copy.", "start": 2219.41, "duration": 1.17}, {"text": "It's not as good,\nbut it's a chair.", "start": 2220.58, "duration": 3.15}, {"text": "It has some chairness to it.", "start": 2223.73, "duration": 3.47}, {"text": "So once I learned that the\ncorrespondent named chair", "start": 2227.2, "duration": 3.06}, {"text": "to the chairness of a\nthing that's a chair,", "start": 2230.26, "duration": 3.24}, {"text": "there's reality\nattached to the name.", "start": 2233.5, "duration": 2.55}, {"text": "I wouldn't say that\nAristotle and Plato would", "start": 2238.855, "duration": 1.875}, {"text": "argue quite this way in 400 BC.", "start": 2240.73, "duration": 2.76}, {"text": "But in 1400 BC, the professors\nare getting this way", "start": 2243.49, "duration": 5.73}, {"text": "as their descendants,\nif you will--", "start": 2249.22, "duration": 2.04}, {"text": "intellectual descendants.", "start": 2251.26, "duration": 1.53}, {"text": "This was a big issue and\nit shows up in the Bible", "start": 2252.79, "duration": 4.26}, {"text": "when Moses says to\nGod, now, if you're", "start": 2257.05, "duration": 2.25}, {"text": "going to send me down\nto Pharaoh, what should", "start": 2259.3, "duration": 2.13}, {"text": "I tell him and the Jewish--", "start": 2261.43, "duration": 1.99}, {"text": "the other Hebrews,\nwhat's your name?", "start": 2263.42, "duration": 3.62}, {"text": "And boy, you\nremember the answer?", "start": 2267.04, "duration": 2.01}, {"text": "What a weird answer.", "start": 2269.05, "duration": 2.83}, {"text": "I am that I am.", "start": 2271.88, "duration": 2.192}, {"text": "Is that a name?", "start": 2274.072, "duration": 2.058}, {"text": "No.", "start": 2276.13, "duration": 0.98}, {"text": "There's somebody who doesn't\nwant to tell you the name", "start": 2277.11, "duration": 4.22}, {"text": "because the name would reveal\ntoo much of the essence.", "start": 2281.33, "duration": 3.72}, {"text": "And this is in essence it's\nindescribable, has no limit.", "start": 2285.05, "duration": 4.06}, {"text": "Therefore, attaching a name\nto it is too restrictive.", "start": 2289.11, "duration": 4.52}, {"text": "This is a person who\nbelieves that name really", "start": 2296.16, "duration": 2.33}, {"text": "represents reality of a kind.", "start": 2298.49, "duration": 3.51}, {"text": "Therefore, don't get--", "start": 2302.0, "duration": 1.8}, {"text": "God, no name.", "start": 2303.8, "duration": 2.79}, {"text": "Be careful with the name.", "start": 2306.59, "duration": 1.2}, {"text": "Be very careful.", "start": 2307.79, "duration": 0.93}, {"text": "It really is circumscribing\nto much, this notion.", "start": 2308.72, "duration": 5.09}, {"text": "AUDIENCE: That brings\nto mind, since we", "start": 2313.81, "duration": 2.15}, {"text": "can talk about\nfilms in this class,", "start": 2315.96, "duration": 1.48}, {"text": "I don't know if you're familiar\nwith this film called Pi.", "start": 2317.44, "duration": 3.176}, {"text": "Yeah?", "start": 2320.616, "duration": 1.864}, {"text": "But it's a young\nmathematician, a genius,", "start": 2322.48, "duration": 4.91}, {"text": "who is trying to figure out\nsome patterns in the number pi", "start": 2327.39, "duration": 5.65}, {"text": "as you take it out.", "start": 2333.04, "duration": 1.392}, {"text": "JOEL MOSES: Yeah.", "start": 2334.432, "duration": 0.708}, {"text": "AUDIENCE: [INAUDIBLE]\nbeing able to predict", "start": 2335.14, "duration": 5.395}, {"text": "the future within it.", "start": 2340.535, "duration": 0.875}, {"text": "He's being accosted\nby all of these people", "start": 2341.41, "duration": 2.4}, {"text": "from the stock market\nand everything.", "start": 2343.81, "duration": 1.93}, {"text": "And he winds up with this\nrabbi who wants him to tell--", "start": 2345.74, "duration": 8.68}, {"text": "wants him to say that\nthere's a pattern in pi", "start": 2354.42, "duration": 5.58}, {"text": "after so many numbers,\nand then it repeats.", "start": 2360.0, "duration": 3.39}, {"text": "And it is the name of God.", "start": 2363.39, "duration": 2.55}, {"text": "Now I never understood\nthat part of the film.", "start": 2365.94, "duration": 3.7}, {"text": "JOEL MOSES: So that brings\nup a different issue.", "start": 2369.64, "duration": 2.0}, {"text": "I wasn't going to bring\nit up, but now that you", "start": 2371.64, "duration": 1.958}, {"text": "mentioned this, I'll tell you.", "start": 2373.598, "duration": 1.412}, {"text": "So this is Moses\nway of thinking.", "start": 2375.01, "duration": 4.66}, {"text": "Abstract, don't bother\nme with details.", "start": 2379.67, "duration": 3.79}, {"text": "The rabbis actually\nlearned from the Greeks.", "start": 2383.46, "duration": 3.74}, {"text": "You see, Alexander the Great\nattacks the Middle East", "start": 2387.2, "duration": 2.7}, {"text": "around 322 BC.", "start": 2389.9, "duration": 3.18}, {"text": "So they come after that.", "start": 2393.08, "duration": 1.828}, {"text": "They're affected by the Greeks.", "start": 2394.908, "duration": 1.292}, {"text": "They won't admit it\nnecessarily, but they", "start": 2396.2, "duration": 1.68}, {"text": "effected by the Greeks.", "start": 2397.88, "duration": 0.958}, {"text": "They become ultra empirical,\nultra rational, logical.", "start": 2398.838, "duration": 6.482}, {"text": "Not so much\nindividualistic, but they", "start": 2405.32, "duration": 2.04}, {"text": "take on a lot of\nAristotelian kind", "start": 2407.36, "duration": 2.1}, {"text": "of way of looking at things.", "start": 2409.46, "duration": 2.55}, {"text": "And become even more so in\nthe case of my Maimonides.", "start": 2412.01, "duration": 3.88}, {"text": "When Aristotle's whose writings\nwere rediscovered by the Arabs,", "start": 2415.89, "duration": 5.12}, {"text": "he spoke Arabic and\nhe learned from them.", "start": 2421.01, "duration": 3.36}, {"text": "And he modified Judaism\nto become even more", "start": 2424.37, "duration": 5.28}, {"text": "logical, rational, rule based.", "start": 2429.65, "duration": 6.09}, {"text": "He has axioms.", "start": 2435.74, "duration": 1.23}, {"text": "He's got 13 axioms.", "start": 2436.97, "duration": 2.7}, {"text": "It's amazing.", "start": 2439.67, "duration": 1.38}, {"text": "But where do the Jews\nrediscover Aristotle?", "start": 2441.05, "duration": 6.91}, {"text": "Because they have.", "start": 2447.96, "duration": 2.54}, {"text": "And it comes back to\nwhat you were saying.", "start": 2450.5, "duration": 2.74}, {"text": "In mysticism, Kabbalah.", "start": 2453.24, "duration": 3.31}, {"text": "What's Kabbalah spend\na lot of its time on?", "start": 2456.55, "duration": 3.27}, {"text": "The name of God.", "start": 2459.82, "duration": 0.945}, {"text": "God is without end.", "start": 2464.04, "duration": 1.05}, {"text": "There's only one God.", "start": 2465.09, "duration": 1.35}, {"text": "And boy, if you only\nknew the name of God,", "start": 2466.44, "duration": 3.03}, {"text": "this would be so\npowerful a weapon", "start": 2469.47, "duration": 3.515}, {"text": "because you can\nget all the power", "start": 2472.985, "duration": 1.375}, {"text": "of the universe in your hand.", "start": 2474.36, "duration": 0.99}, {"text": "And you've got to\nbe very careful.", "start": 2475.35, "duration": 1.417}, {"text": "You can't do that.", "start": 2476.767, "duration": 1.313}, {"text": "You've got to shy\naway from that.", "start": 2478.08, "duration": 1.71}, {"text": "It's one of the key issues.", "start": 2482.34, "duration": 1.48}, {"text": "So to the extent\nthat mysticism, which", "start": 2483.82, "duration": 2.9}, {"text": "exists in every\nreligion on Earth,", "start": 2486.72, "duration": 3.87}, {"text": "is the closest analog\nwe now have in religion,", "start": 2490.59, "duration": 2.67}, {"text": "I would say, to\nPlatonic thought.", "start": 2493.26, "duration": 5.94}, {"text": "Not quite there, but it\ncarries some of the same ideas.", "start": 2499.2, "duration": 4.26}, {"text": "AUDIENCE: Do you think we're\ntrying to get that idea today", "start": 2503.46, "duration": 2.63}, {"text": "in the word icon?", "start": 2506.09, "duration": 2.1}, {"text": "JOEL MOSES: I don't know.", "start": 2508.19, "duration": 1.59}, {"text": "AUDIENCE: Because it's\nsupposed to be that looks", "start": 2509.78, "duration": 2.65}, {"text": "like what it references.", "start": 2512.43, "duration": 2.1}, {"text": "JOEL MOSES: Yeah,\nbut you see, think", "start": 2514.53, "duration": 1.5}, {"text": "of the mosaic commandment.", "start": 2516.03, "duration": 2.67}, {"text": "Do not make a graven image.", "start": 2518.7, "duration": 2.38}, {"text": "So if you want to\nhave God be abstract--", "start": 2521.08, "duration": 2.36}, {"text": "and the mystics do.", "start": 2523.44, "duration": 2.94}, {"text": "If you want God be abstract\nyou can't have a real icon.", "start": 2526.38, "duration": 4.7}, {"text": "That goes against abstraction.", "start": 2531.08, "duration": 1.62}, {"text": "And now you've\ngot it down there.", "start": 2532.7, "duration": 1.92}, {"text": "This is what God looks--\nno, no, no, no, no.", "start": 2534.62, "duration": 2.1}, {"text": "Can't have that.", "start": 2536.72, "duration": 1.41}, {"text": "Can't have that.", "start": 2538.13, "duration": 1.17}, {"text": "See Moses really was\nan abstract thinker.", "start": 2539.3, "duration": 2.91}, {"text": "There's one God,\nno graven image.", "start": 2542.21, "duration": 3.78}, {"text": "Be careful with the name.", "start": 2545.99, "duration": 2.64}, {"text": "Do not take the\nLord's name in vain.", "start": 2548.63, "duration": 2.07}, {"text": "I say, that's simpler than\nwhat people had in mind.", "start": 2550.7, "duration": 3.75}, {"text": "Don't ever use the Lord's\nname because then you", "start": 2554.45, "duration": 4.64}, {"text": "are attached to much specificity\nto this abstract notion.", "start": 2559.09, "duration": 8.48}, {"text": "So to continue the path.", "start": 2567.57, "duration": 2.73}, {"text": "This is 14th century.", "start": 2570.3, "duration": 2.58}, {"text": "In the 18th century,\nare Hume and Kant.", "start": 2572.88, "duration": 8.62}, {"text": "So let's say this is about\n1700 and this is about 1775.", "start": 2581.5, "duration": 6.57}, {"text": "A lot of things happen\naround 1776, it turns out.", "start": 2588.07, "duration": 5.01}, {"text": "What is Hume saying,\namong other things?", "start": 2593.08, "duration": 4.02}, {"text": "He's British, Kant's German.", "start": 2597.1, "duration": 1.98}, {"text": "And from now on, the\nBritish and the Germans", "start": 2599.08, "duration": 2.25}, {"text": "are going to be\nfighting each other.", "start": 2601.33, "duration": 1.5}, {"text": "And they're fighting\nover this set of issues.", "start": 2602.83, "duration": 3.94}, {"text": "Hume says, a baby is\nborn \"tabula rasa\"--", "start": 2606.77, "duration": 3.66}, {"text": "I think he got the\nterm from Aristotle--", "start": 2610.43, "duration": 2.4}, {"text": "which means the baby\ndoesn't know anything,", "start": 2612.83, "duration": 3.01}, {"text": "complete clean slate, and\neverything is learned.", "start": 2615.84, "duration": 4.81}, {"text": "Everything is learned.", "start": 2620.65, "duration": 2.54}, {"text": "The biologist would argue.", "start": 2623.19, "duration": 4.76}, {"text": "Their claim would be, hey, these\ngenes really have an impact.", "start": 2627.95, "duration": 3.19}, {"text": "No, no, no.", "start": 2631.14, "duration": 0.58}, {"text": "For him, a baby, clean slate.", "start": 2631.72, "duration": 3.68}, {"text": "And that's the British view,\nwhich emphasizes logic,", "start": 2635.4, "duration": 5.7}, {"text": "rationality of that kind.", "start": 2641.1, "duration": 2.16}, {"text": "Kant comes in, and what's\nthe name of his famous book?", "start": 2643.26, "duration": 4.99}, {"text": "Critique of Pure Reason.", "start": 2648.25, "duration": 2.87}, {"text": "Because Hume is the\nultimate pure reason view.", "start": 2651.12, "duration": 6.04}, {"text": "You have axioms.", "start": 2657.16, "duration": 1.5}, {"text": "You have deduction mechanisms.", "start": 2658.66, "duration": 2.04}, {"text": "And everything\nfollows from that.", "start": 2660.7, "duration": 2.76}, {"text": "No, no, no, no, no, Kant says.", "start": 2663.46, "duration": 3.48}, {"text": "Pure reason doesn't explain the\nworld very well, or not enough.", "start": 2666.94, "duration": 4.86}, {"text": "And he believes in\nbuilt in things.", "start": 2671.8, "duration": 5.97}, {"text": "I forget exactly\nwhat he calls them.", "start": 2677.77, "duration": 2.91}, {"text": "What is Kantian categories?", "start": 2680.68, "duration": 4.62}, {"text": "You have built in categories.", "start": 2685.3, "duration": 2.73}, {"text": "So if you look at\ncognitive science nowadays", "start": 2688.03, "duration": 5.04}, {"text": "and you ask the question,\nhow does a child", "start": 2693.07, "duration": 3.6}, {"text": "manage to see things?", "start": 2696.67, "duration": 2.79}, {"text": "We know that they have\nbuilt in mechanisms", "start": 2699.46, "duration": 3.48}, {"text": "for seeing certain things.", "start": 2702.94, "duration": 1.35}, {"text": "There's a famous paper written\nby one of our colleagues", "start": 2704.29, "duration": 3.12}, {"text": "which says, what the fly's\neye tells the fly's brain--", "start": 2707.41, "duration": 6.658}, {"text": "is that what it is?", "start": 2714.068, "duration": 0.792}, {"text": "Yeah, I think that's what it is.", "start": 2714.86, "duration": 1.333}, {"text": "What the fly's eye\ntell the fly's brain.", "start": 2716.193, "duration": 2.567}, {"text": "And what they did was\nthey would put electrodes", "start": 2718.76, "duration": 2.76}, {"text": "into the fly's\nbrain and they would", "start": 2721.52, "duration": 2.85}, {"text": "see when things would light up.", "start": 2724.37, "duration": 2.34}, {"text": "And they would send\nimages across the field", "start": 2726.71, "duration": 2.91}, {"text": "of view of the fly.", "start": 2729.62, "duration": 1.05}, {"text": "And it turns out that if\nyou had something which", "start": 2730.67, "duration": 4.68}, {"text": "looked like this and it went\nthrough the field of view", "start": 2735.35, "duration": 3.87}, {"text": "of the eye and it moved,\nthen certain kinds of things", "start": 2739.22, "duration": 3.36}, {"text": "would light up.", "start": 2742.58, "duration": 1.2}, {"text": "You see, those neurons\nin the fly's eye I", "start": 2743.78, "duration": 3.96}, {"text": "we're looking for\nthings like that moving.", "start": 2747.74, "duration": 3.29}, {"text": "Because that could be a--", "start": 2751.03, "duration": 3.58}, {"text": "that could be something\nthat it could eat.", "start": 2754.61, "duration": 2.1}, {"text": "Now is this a fly's eye?", "start": 2756.71, "duration": 2.49}, {"text": "What the-- oh, I'm sorry.", "start": 2759.2, "duration": 4.8}, {"text": "It's a frog.", "start": 2764.0, "duration": 0.93}, {"text": "What the frog's I\ntells the frog's brain.", "start": 2764.93, "duration": 2.19}, {"text": "And what's the frog want to do?", "start": 2767.12, "duration": 1.53}, {"text": "Eat flies.", "start": 2768.65, "duration": 2.25}, {"text": "So you see something moving\nlike that, that's a fly.", "start": 2770.9, "duration": 5.73}, {"text": "So this thing was\ntrained, built in category", "start": 2776.63, "duration": 3.3}, {"text": "to look for that kind of stuff.", "start": 2779.93, "duration": 2.16}, {"text": "And I don't know what\nwe are trained to do,", "start": 2782.09, "duration": 3.45}, {"text": "but the assumption that we\nhave built in categories", "start": 2785.54, "duration": 2.94}, {"text": "has a lot of truth here.", "start": 2788.48, "duration": 2.13}, {"text": "This is a more of a Platonic\nview-- not purely Platonic,", "start": 2790.61, "duration": 3.66}, {"text": "but more of a Platonic view\nthan an Aristotelian view,", "start": 2794.27, "duration": 3.3}, {"text": "which would say it's\nreally just logic.", "start": 2797.57, "duration": 3.94}, {"text": "It all follows\nfrom a few axioms.", "start": 2801.51, "duration": 2.22}, {"text": "And so when you\nsee Lord Russell--", "start": 2803.73, "duration": 2.25}, {"text": "you may have heard Lord\nRussell, a famous logician", "start": 2805.98, "duration": 2.4}, {"text": "mathematician in\nthe 20th century", "start": 2808.38, "duration": 3.03}, {"text": "and the Cambridge\nprofessor-- say,", "start": 2811.41, "duration": 2.16}, {"text": "I can't understand\nthese Germans.", "start": 2813.57, "duration": 1.74}, {"text": "I mean, Kant, who\ncan understand him?", "start": 2815.31, "duration": 1.98}, {"text": "Of course, other\nphilosophers will say,", "start": 2817.29, "duration": 2.11}, {"text": "Kant's the greatest philosopher\nin the last 200 or 300 years.", "start": 2819.4, "duration": 3.92}, {"text": "But the British, especially,\nthe Cambridge school, just they", "start": 2823.32, "duration": 3.69}, {"text": "don't get it.", "start": 2827.01, "duration": 1.26}, {"text": "They don't understand it.", "start": 2828.27, "duration": 1.33}, {"text": "So this different mode of\nthought, which is my opinion,", "start": 2829.6, "duration": 3.45}, {"text": "goes way back to\nAristotle and Plato.", "start": 2833.05, "duration": 1.88}, {"text": "Different ways of\nthinking about the world.", "start": 2834.93, "duration": 1.95}, {"text": "Even though Aristotle\nwas Plato's student,", "start": 2836.88, "duration": 2.64}, {"text": "they didn't see eye to eye.", "start": 2839.52, "duration": 1.2}, {"text": "So what does this have\nto do with engineering?", "start": 2843.88, "duration": 2.462}, {"text": "Well, let me go back.", "start": 2855.21, "duration": 2.53}, {"text": "So I think Taft introduced\nthis as being a different way", "start": 2857.74, "duration": 6.23}, {"text": "of looking at engineering.", "start": 2863.97, "duration": 2.235}, {"text": "People who write about\nengineering philosophy", "start": 2866.205, "duration": 1.875}, {"text": "tend to emphasize what\nmakes engineering unique,", "start": 2868.08, "duration": 3.245}, {"text": "different from science,\ndifferent from mathematics,", "start": 2871.325, "duration": 2.125}, {"text": "different from social science.", "start": 2873.45, "duration": 2.48}, {"text": "Design, for example,\nmakes engineering unique.", "start": 2875.93, "duration": 3.37}, {"text": "Well, I want to argue.", "start": 2879.3, "duration": 2.55}, {"text": "I think engineering\nisn't that unique.", "start": 2881.85, "duration": 2.61}, {"text": "Because in a sense, everybody\ndesigns in a university.", "start": 2884.46, "duration": 4.83}, {"text": "So let's talk about\nwhat they design.", "start": 2889.29, "duration": 5.55}, {"text": "And philosophers care\nabout design issues.", "start": 2894.84, "duration": 2.8}, {"text": "But in a sense, this approach\nis systems engineering.", "start": 2897.64, "duration": 6.68}, {"text": "Take a problem, break it up\ninto pods, keep doing it.", "start": 2904.32, "duration": 2.862}, {"text": "Blah, blah, blah.", "start": 2907.182, "duration": 0.708}, {"text": "All the great American systems\nengineers think this way.", "start": 2907.89, "duration": 4.63}, {"text": "This approach is maybe more\nof the way mathematicians", "start": 2912.52, "duration": 3.6}, {"text": "like to solve problems.", "start": 2916.12, "duration": 1.08}, {"text": "Take a problem, abstract it.", "start": 2917.2, "duration": 2.04}, {"text": "Make it even more abstract.", "start": 2919.24, "duration": 1.83}, {"text": "Get it down to\nsomething so simple", "start": 2921.07, "duration": 1.56}, {"text": "that you can actually\nsolve the abstract problem.", "start": 2922.63, "duration": 2.76}, {"text": "And now specialized to\na particular solution.", "start": 2925.39, "duration": 4.42}, {"text": "Here, get it down to the\nsimplest thing, which", "start": 2929.81, "duration": 4.92}, {"text": "you can solve and back it up.", "start": 2934.73, "duration": 1.92}, {"text": "This one, no, move\nit up and then down.", "start": 2936.65, "duration": 3.87}, {"text": "No, no.", "start": 2940.52, "duration": 0.632}, {"text": "These guys say, no, no.", "start": 2941.152, "duration": 0.958}, {"text": "Down then up.", "start": 2942.11, "duration": 1.97}, {"text": "Different way of\nlooking at things.", "start": 2944.08, "duration": 2.81}, {"text": "And nobody is absolutely\nright all the time.", "start": 2946.89, "duration": 2.37}, {"text": "So let's talk about design,\norganization, et cetera.", "start": 2953.06, "duration": 4.88}, {"text": "So I claim design is of interest\nto every field in the universe.", "start": 2957.94, "duration": 6.44}, {"text": "Writers, composers, artists,\nobviously, architects.", "start": 2964.38, "duration": 3.09}, {"text": "Biologists nowadays.", "start": 2967.47, "duration": 2.73}, {"text": "Maybe physicist\nnot so much though.", "start": 2970.2, "duration": 1.83}, {"text": "I don't know.", "start": 2972.03, "duration": 0.66}, {"text": "I mean, they could\nsay, look, we're", "start": 2972.69, "duration": 1.665}, {"text": "not trying to figure\nout the nature of design", "start": 2974.355, "duration": 1.875}, {"text": "because we really only\ncare about one design.", "start": 2976.23, "duration": 1.95}, {"text": "How did God do it\nin the first place?", "start": 2978.18, "duration": 3.33}, {"text": "So design variation, which is\nthe interesting thing to me,", "start": 2981.51, "duration": 4.32}, {"text": "how do you maintain\nflexibility in a design", "start": 2985.83, "duration": 2.94}, {"text": "so you can make changes easily?", "start": 2988.77, "duration": 1.41}, {"text": "It's things that's not an issue.", "start": 2990.18, "duration": 2.04}, {"text": "Biologists care about\ndesign variation", "start": 2992.22, "duration": 1.86}, {"text": "because development and\nevolution, things of that sort.", "start": 2994.08, "duration": 2.94}, {"text": "But physicists, less so.", "start": 2997.02, "duration": 4.23}, {"text": "So bottom line, you have to\nlook hard to find a field which", "start": 3001.25, "duration": 3.51}, {"text": "isn't interested in\ndesign, and therefore,", "start": 3004.76, "duration": 3.45}, {"text": "has some relationship\nto engineering.", "start": 3008.21, "duration": 2.44}, {"text": "So the claim is\nthat legacy views--", "start": 3019.47, "duration": 2.6}, {"text": "and lots there are\ndifferent legacies.", "start": 3022.07, "duration": 1.98}, {"text": "We, as humans, have a legacy.", "start": 3024.05, "duration": 1.92}, {"text": "We're limited by our\nability to solve problems.", "start": 3025.97, "duration": 4.2}, {"text": "The phrase 7 plus or\nminus 2 ring a bell?", "start": 3030.17, "duration": 3.84}, {"text": "You've heard it, right?", "start": 3034.01, "duration": 1.38}, {"text": "But you haven't and you haven't?", "start": 3035.39, "duration": 2.88}, {"text": "So there was a psychologist\nhere at MIT 50 years ago,", "start": 3038.27, "duration": 3.16}, {"text": "his name was George Miller.", "start": 3041.43, "duration": 1.49}, {"text": "And he wrote a paper called The\nMagic Number, 7 Plus or Minus", "start": 3042.92, "duration": 2.88}, {"text": "2.", "start": 3045.8, "duration": 1.11}, {"text": "And The Magic Number,\n7 Plus or Minus 2", "start": 3046.91, "duration": 3.45}, {"text": "is based on experiments\nthat he did with people.", "start": 3050.36, "duration": 3.88}, {"text": "Now ring a bell?", "start": 3054.24, "duration": 1.85}, {"text": "And what do you think--", "start": 3056.09, "duration": 2.06}, {"text": "how many different\nthings you can remember?", "start": 3058.15, "duration": 2.01}, {"text": "It could be numbers.", "start": 3060.16, "duration": 0.91}, {"text": "It could be words.", "start": 3061.07, "duration": 0.86}, {"text": "How many different things\nyou could remember at a time.", "start": 3061.93, "duration": 2.43}, {"text": "And people can go\nbetween five and nine,", "start": 3064.36, "duration": 3.18}, {"text": "depending on the individual, et\ncetera, et cetera, et cetera.", "start": 3067.54, "duration": 3.46}, {"text": "So here is a legacy--", "start": 3071.0, "duration": 1.44}, {"text": "a restriction that we inherit\nas humans, assuming he's", "start": 3072.44, "duration": 4.19}, {"text": "right, of course.", "start": 3076.63, "duration": 1.59}, {"text": "And he seems to be.", "start": 3078.22, "duration": 2.95}, {"text": "But there are other\nlegacies-- other things", "start": 3081.17, "duration": 2.06}, {"text": "that restrict our\nability to do things.", "start": 3083.23, "duration": 1.91}, {"text": "One is the country\nwe were born in.", "start": 3085.14, "duration": 3.37}, {"text": "Maybe our religion,\ncertainly our education.", "start": 3088.51, "duration": 3.03}, {"text": "If we're trained as electrical\nengineers or civil engineers", "start": 3091.54, "duration": 3.15}, {"text": "or mathematicians, that'll\nhave a way of affecting it.", "start": 3094.69, "duration": 3.15}, {"text": "I'm certainly affected by having\nbeen trained in mathematics", "start": 3097.84, "duration": 3.54}, {"text": "because, remember,\nthis guy isn't", "start": 3101.38, "duration": 1.77}, {"text": "things like a mathematician.", "start": 3103.15, "duration": 1.95}, {"text": "That's a logician.", "start": 3105.1, "duration": 0.81}, {"text": "That's a funny kind\nof mathematician.", "start": 3105.91, "duration": 2.22}, {"text": "So let's look at\nmathematics, which I", "start": 3111.07, "duration": 1.68}, {"text": "a little bit about the history.", "start": 3112.75, "duration": 2.07}, {"text": "Especially in the 19th\ncentury, British mathematicians", "start": 3114.82, "duration": 3.57}, {"text": "didn't do well in\nthe 19th century", "start": 3118.39, "duration": 1.98}, {"text": "because there was so\nin love with Newton.", "start": 3120.37, "duration": 4.84}, {"text": "So what they did was\nthey went into the study", "start": 3125.21, "duration": 2.34}, {"text": "of differentiable\nequations, special cases,", "start": 3127.55, "duration": 2.53}, {"text": "the differentiable equations.", "start": 3130.08, "duration": 1.25}, {"text": "Even more special cases\nof solution differentiable", "start": 3131.33, "duration": 2.492}, {"text": "equations, this that\nand the other thing.", "start": 3133.822, "duration": 1.708}, {"text": "And they got stuck in\nthere and they really", "start": 3135.53, "duration": 2.25}, {"text": "didn't make much progress.", "start": 3137.78, "duration": 1.29}, {"text": "And again, it shows\nthe empirical aspects--", "start": 3139.07, "duration": 2.46}, {"text": "it's special cases, empiricism\nare very closely connected.", "start": 3141.53, "duration": 5.22}, {"text": "On the other hand,\nthe Germans, who", "start": 3146.75, "duration": 1.65}, {"text": "I claim have this more\nabstract view of things,", "start": 3148.4, "duration": 2.88}, {"text": "they made enormous\nprogress certainly", "start": 3151.28, "duration": 4.05}, {"text": "by the mid-19th\ncentury in algebra.", "start": 3155.33, "duration": 3.54}, {"text": "Algebraic geometry, algebraic\ntopology, abstract algebra,", "start": 3158.87, "duration": 4.11}, {"text": "blah, blah, blah.", "start": 3162.98, "duration": 1.56}, {"text": "All of which\nemphasize abstraction,", "start": 3164.54, "duration": 2.35}, {"text": "which is a consistent with\ntheir content philosophy.", "start": 3166.89, "duration": 3.02}, {"text": "Which again, is consistent\nwith Platonic way", "start": 3169.91, "duration": 2.25}, {"text": "of looking at things,\net cetera, et cetera.", "start": 3172.16, "duration": 4.23}, {"text": "And these guys want out in\nterms of most of mathematics.", "start": 3176.39, "duration": 4.1}, {"text": "Not all.", "start": 3180.49, "duration": 0.87}, {"text": "Certainly, logic--\nthe kind of stuff", "start": 3181.36, "duration": 1.98}, {"text": "that we study in\ncomputer science, logic", "start": 3183.34, "duration": 1.68}, {"text": "and combinatorics\nis more like this.", "start": 3185.02, "duration": 2.86}, {"text": "But the stuff we don't study\nin computer science that", "start": 3187.88, "duration": 2.51}, {"text": "is real mathematics,\ntopology, geometry--", "start": 3190.39, "duration": 3.72}, {"text": "well, we do a little bit\nof algebraic geometry.", "start": 3194.11, "duration": 2.16}, {"text": "Algebra.", "start": 3196.27, "duration": 2.25}, {"text": "Even analysis tends to be much\nmore abstract, much more based", "start": 3198.52, "duration": 3.9}, {"text": "on these kinds of notions.", "start": 3202.42, "duration": 3.99}, {"text": "So I would say, by the mid\n20th century certainly,", "start": 3206.41, "duration": 3.193}, {"text": "most mathematicians followed\nthe German approach.", "start": 3209.603, "duration": 2.042}, {"text": "It doesn't mean\nthe German approach", "start": 3211.645, "duration": 1.535}, {"text": "is right for everything.", "start": 3213.18, "duration": 1.0}, {"text": "I keep saying, there\nis no right answer.", "start": 3214.18, "duration": 3.03}, {"text": "But let me tell you, you\ncan take this too far.", "start": 3217.21, "duration": 2.91}, {"text": "The French took it too far.", "start": 3220.12, "duration": 2.56}, {"text": "So one of the\nproblems you can run", "start": 3222.68, "duration": 2.61}, {"text": "into if you're\ngoing to be abstract", "start": 3225.29, "duration": 1.74}, {"text": "is to say, well, I'm going to\nmake lots and lots and lots", "start": 3227.03, "duration": 2.55}, {"text": "and lots and lots and lots and\nlots and lots of abstractions.", "start": 3229.58, "duration": 2.64}, {"text": "And I had the\nwhole power with 20", "start": 3232.22, "duration": 2.64}, {"text": "different-- actually in\nsoftware, we see this a lot", "start": 3234.86, "duration": 2.19}, {"text": "now.", "start": 3237.05, "duration": 0.86}, {"text": "If people building in one\nsoftware layer above a layer,", "start": 3237.91, "duration": 3.07}, {"text": "they go nuts.", "start": 3240.98, "duration": 1.26}, {"text": "The idea is to have relatively\nfew layers that really", "start": 3242.24, "duration": 3.69}, {"text": "add something, rather\nthan lots and layers that", "start": 3245.93, "duration": 2.76}, {"text": "add very little.", "start": 3248.69, "duration": 0.93}, {"text": "And if you're a logician,\nthen you buy into the notion", "start": 3249.62, "duration": 3.18}, {"text": "that abstraction\nis a good thing.", "start": 3252.8, "duration": 1.72}, {"text": "but if you carry\nit to the extreme,", "start": 3254.52, "duration": 2.15}, {"text": "then you will have\nso many layers", "start": 3256.67, "duration": 1.51}, {"text": "you just get lost completely.", "start": 3258.18, "duration": 1.46}, {"text": "You don't really say anything.", "start": 3259.64, "duration": 2.07}, {"text": "That's what happened\nin mid 20th century.", "start": 3261.71, "duration": 2.88}, {"text": "In France, there was a movement\ncalled the Bourbaki school.", "start": 3264.59, "duration": 4.9}, {"text": "The Bourbaki was one\nof Napoleon's generals.", "start": 3269.49, "duration": 3.33}, {"text": "They made up the name.", "start": 3272.82, "duration": 1.66}, {"text": "A bunch of mathematicians\nwrote under the name Bourbaki", "start": 3274.48, "duration": 4.61}, {"text": "And they read did--\nthey re-approved", "start": 3279.09, "duration": 3.77}, {"text": "a lot of mathematics\nthat was already", "start": 3282.86, "duration": 2.07}, {"text": "known from a fundamental\npoint of view of set theory", "start": 3284.93, "duration": 3.84}, {"text": "and logic.", "start": 3288.77, "duration": 0.84}, {"text": "And this had an\neffect, for example,", "start": 3289.61, "duration": 2.52}, {"text": "on education k-12 in the '60s\nand '70s when we did new math.", "start": 3292.13, "duration": 5.66}, {"text": "That was those guys in\nthe American context.", "start": 3297.79, "duration": 5.2}, {"text": "So Bourbaki was going to\nrevolutionize the teaching", "start": 3302.99, "duration": 3.62}, {"text": "and research and\nmathematics by redoing it", "start": 3306.61, "duration": 2.58}, {"text": "all from a very\nfundamental point of view.", "start": 3309.19, "duration": 2.11}, {"text": "Lots and lots and lots\nand lots and lots and lots", "start": 3311.3, "duration": 2.06}, {"text": "of abstractions.", "start": 3313.36, "duration": 1.53}, {"text": "And eventually, people\nsaid, this is nuts.", "start": 3314.89, "duration": 3.33}, {"text": "This is absolutely insane.", "start": 3318.22, "duration": 1.66}, {"text": "Get rid of those guys.", "start": 3319.88, "duration": 1.127}, {"text": "And they stopped doing it.", "start": 3321.007, "duration": 1.083}, {"text": "Don't go crazy\nover abstractions.", "start": 3327.94, "duration": 3.27}, {"text": "Some are good, too\nmany is too many.", "start": 3331.21, "duration": 3.3}, {"text": "So back to an issue I discussed\nalready, manufacturing.", "start": 3338.04, "duration": 5.02}, {"text": "I'll read it with you.", "start": 3348.93, "duration": 1.02}, {"text": "US Manufacturers\nin the 1980s were", "start": 3349.95, "duration": 1.92}, {"text": "very concerned over the\nability of the Japanese", "start": 3351.87, "duration": 2.25}, {"text": "to manufacture cars more\ncheaply with higher quality", "start": 3354.12, "duration": 2.88}, {"text": "than the Americans.", "start": 3357.0, "duration": 1.05}, {"text": "The German produced cars\nwith greater performance", "start": 3358.05, "duration": 2.85}, {"text": "than the Americans.", "start": 3360.9, "duration": 0.93}, {"text": "Not necessarily higher\nquality or cheaper, but better", "start": 3361.83, "duration": 3.06}, {"text": "performance.", "start": 3364.89, "duration": 0.82}, {"text": "And so caught between those two.", "start": 3365.71, "duration": 4.31}, {"text": "Then we started looking\nat the Toyota process.", "start": 3370.02, "duration": 3.22}, {"text": "And I got to tell you a story.", "start": 3373.24, "duration": 1.32}, {"text": "There was a joint\nToyota-GM plant", "start": 3374.56, "duration": 5.03}, {"text": "in California called NUMMI.", "start": 3379.59, "duration": 2.25}, {"text": "I don't know why it was called\nNUMMI, had some meaning.", "start": 3381.84, "duration": 3.45}, {"text": "And basically, an\nexisting GM plant", "start": 3385.29, "duration": 3.21}, {"text": "took over all the union labor\nthat they had in the plant.", "start": 3388.5, "duration": 3.57}, {"text": "And they retaught them,\nwith Japanese managers,", "start": 3392.07, "duration": 3.33}, {"text": "how to do things.", "start": 3395.4, "duration": 1.68}, {"text": "And the quality went way up.", "start": 3397.08, "duration": 2.25}, {"text": "The production rate went way up.", "start": 3399.33, "duration": 2.47}, {"text": "And GM sent all their vice\npresidents to go in there", "start": 3401.8, "duration": 2.96}, {"text": "and investigate.", "start": 3404.76, "duration": 0.81}, {"text": "What did these guys\ndo with our plant?", "start": 3405.57, "duration": 2.88}, {"text": "They're working with us.", "start": 3408.45, "duration": 1.128}, {"text": "They did something.", "start": 3409.578, "duration": 0.792}, {"text": "It all works.", "start": 3410.37, "duration": 1.26}, {"text": "And I talked to one guy who\nhad seen the plant six times.", "start": 3411.63, "duration": 5.79}, {"text": "And he said, I don't\nsee anything different.", "start": 3417.42, "duration": 2.64}, {"text": "They do the same thing we do.", "start": 3420.06, "duration": 1.53}, {"text": "What is going on?", "start": 3421.59, "duration": 0.9}, {"text": "I mean, why-- I can't\nfigure this out.", "start": 3422.49, "duration": 2.41}, {"text": "So finally, he admitted--\nhe said, OK, OK.", "start": 3424.9, "duration": 3.8}, {"text": "Let the guys who run the plant--", "start": 3428.7, "duration": 1.86}, {"text": "the Japanese guy-- give me a\nthree-hour lecture as to what", "start": 3430.56, "duration": 6.11}, {"text": "they think is different.", "start": 3436.67, "duration": 1.68}, {"text": "So he finally, after\nsix visits to the plant,", "start": 3438.35, "duration": 2.49}, {"text": "when he didn't get it, OK,\ngot a three-hour lecture.", "start": 3440.84, "duration": 2.97}, {"text": "And then his eyes lit up.", "start": 3443.81, "duration": 3.03}, {"text": "It was such a different\nway of thinking.", "start": 3446.84, "duration": 2.23}, {"text": "He just couldn't see it.", "start": 3449.07, "duration": 1.79}, {"text": "Simply could not see it.", "start": 3450.86, "duration": 2.43}, {"text": "But once explained,\nit made sense.", "start": 3453.29, "duration": 3.79}, {"text": "So it was a different\nway of looking at things.", "start": 3457.08, "duration": 3.35}, {"text": "And we learn from them.", "start": 3460.43, "duration": 3.42}, {"text": "And I claim that the reason\nthat they were successful", "start": 3463.85, "duration": 4.16}, {"text": "is they looked at the production\nprocess in a more abstract way.", "start": 3468.01, "duration": 5.63}, {"text": "And that fits in with\nthe national cultural", "start": 3473.64, "duration": 3.45}, {"text": "of value, my claim.", "start": 3477.09, "duration": 3.06}, {"text": "In Germany, where quality\nwasn't so much the issue.", "start": 3480.15, "duration": 4.02}, {"text": "It was mastery of details.", "start": 3484.17, "duration": 1.74}, {"text": "The German mastery of details\nis a big deal of that culture.", "start": 3485.91, "duration": 6.675}, {"text": "Meister is what they call\nthem, meister, uber meister.", "start": 3492.585, "duration": 5.985}, {"text": "And that gave him the ability\nto do things better and better.", "start": 3498.57, "duration": 4.0}, {"text": "Some people actually claimed\nthe Germans lost World War II", "start": 3502.57, "duration": 3.29}, {"text": "because they were too wedded\nto this notion of mastery.", "start": 3505.86, "duration": 3.09}, {"text": "So they have all these great\nguys on their production plants", "start": 3508.95, "duration": 3.69}, {"text": "making tanks.", "start": 3512.64, "duration": 2.04}, {"text": "Well, each one of them makes\na slightly different tank", "start": 3514.68, "duration": 3.87}, {"text": "based on his way\nof doing things.", "start": 3518.55, "duration": 2.367}, {"text": "He won't listen to anybody else.", "start": 3520.917, "duration": 1.333}, {"text": "You make the tank this way.", "start": 3522.25, "duration": 1.89}, {"text": "So the Germans went into\nbattle against Russia", "start": 3524.14, "duration": 2.54}, {"text": "with a whole slew of tanks,\nwhich are fine and dandy.", "start": 3526.68, "duration": 3.93}, {"text": "Each of them worked very\nwell, until for some reason,", "start": 3530.61, "duration": 2.58}, {"text": "some part failed.", "start": 3533.19, "duration": 1.77}, {"text": "And they had a problem getting\nany parts because all the parts", "start": 3534.96, "duration": 2.64}, {"text": "were different.", "start": 3537.6, "duration": 1.75}, {"text": "Whereas, the Americans\nmade the same tank", "start": 3539.35, "duration": 2.37}, {"text": "over and over and over again.", "start": 3541.72, "duration": 1.56}, {"text": "And by golly, there\nwas no problem", "start": 3543.28, "duration": 1.8}, {"text": "with interchangeable parts.", "start": 3545.08, "duration": 3.08}, {"text": "Anyways, probably\nnot the only reason", "start": 3548.16, "duration": 1.9}, {"text": "they lost, but maybe\none of the reasons.", "start": 3550.06, "duration": 3.39}, {"text": "So we learned from the\nJapanese, who are still ahead,", "start": 3553.45, "duration": 2.82}, {"text": "as I said before.", "start": 3556.27, "duration": 2.05}, {"text": "And one of the things\nwe learned was wrong.", "start": 3558.32, "duration": 4.26}, {"text": "So one of the things\nwe thought we learned", "start": 3562.58, "duration": 2.12}, {"text": "is how to organize firms, which\nwe realized were hierarchical.", "start": 3564.7, "duration": 7.13}, {"text": "But as they grew, we\nallowed the hierarchy", "start": 3571.83, "duration": 3.04}, {"text": "to grow into many, many levels.", "start": 3574.87, "duration": 3.76}, {"text": "And so we said, no, no, no.", "start": 3578.63, "duration": 1.4}, {"text": "The way to understand\nthe Japanese", "start": 3580.03, "duration": 2.16}, {"text": "is they don't have\nmiddle managers.", "start": 3582.19, "duration": 3.67}, {"text": "Let's get rid of\nthe middle managers.", "start": 3585.86, "duration": 2.68}, {"text": "Well, what it really,\nto me, explains", "start": 3588.54, "duration": 2.91}, {"text": "is we don't understand\nmiddle management.", "start": 3591.45, "duration": 2.86}, {"text": "What's the role of\na middle manager?", "start": 3594.31, "duration": 1.67}, {"text": "Well, in the American way, a\nrole of the middle managers", "start": 3595.98, "duration": 2.34}, {"text": "to check up on people.", "start": 3598.32, "duration": 1.92}, {"text": "Are you doing what you're\nsupposed to be doing?", "start": 3600.24, "duration": 2.04}, {"text": "Are you screwing up?", "start": 3602.28, "duration": 3.0}, {"text": "Oh, that's not the role\nof a middle manager.", "start": 3605.28, "duration": 1.85}, {"text": "The role of a middle\nmanager is, is there", "start": 3607.13, "duration": 1.708}, {"text": "any way I can help you?", "start": 3608.838, "duration": 1.692}, {"text": "Can I teach you what it\nis that you need to know?", "start": 3610.53, "duration": 4.11}, {"text": "On the next project--", "start": 3614.64, "duration": 1.74}, {"text": "I mean, it's a\ndifferent attitude", "start": 3616.38, "duration": 2.79}, {"text": "toward the role\nof middle manager.", "start": 3619.17, "duration": 1.5}, {"text": "You can have fewer levels\nof middle management", "start": 3620.67, "duration": 2.79}, {"text": "if you recognize what\nthe proper role is.", "start": 3623.46, "duration": 2.79}, {"text": "But if you simply say, middle\nmanagement is just at waste,", "start": 3626.25, "duration": 3.36}, {"text": "just added fat,\nlet's get rid of it.", "start": 3629.61, "duration": 2.79}, {"text": "You're going to get run\nyourself into some difficulty.", "start": 3632.4, "duration": 2.25}, {"text": "And I think many companies have.", "start": 3634.65, "duration": 1.77}, {"text": "So what saved us in the\n'90s is the line here.", "start": 3641.04, "duration": 5.1}, {"text": "The two problems.", "start": 3646.14, "duration": 1.2}, {"text": "Problem number one\nis that Japanese got", "start": 3647.34, "duration": 2.64}, {"text": "hurt by the real estate bubble.", "start": 3649.98, "duration": 3.28}, {"text": "In 1988 or '89, the\ngovernment of New Zealand", "start": 3653.26, "duration": 7.17}, {"text": "sold its embassy\nin downtown Tokyo.", "start": 3660.43, "duration": 5.11}, {"text": "And the value of real\nestate was so high,", "start": 3665.54, "duration": 1.92}, {"text": "they were able to zero\nout their national debt.", "start": 3667.46, "duration": 2.49}, {"text": "The value of the few\nacres in downtown Tokyo", "start": 3672.53, "duration": 3.96}, {"text": "near the Emperor's palace was\nequal to the assessed value", "start": 3676.49, "duration": 6.81}, {"text": "of California.", "start": 3683.3, "duration": 2.45}, {"text": "I mean, it was out of sight.", "start": 3685.75, "duration": 1.98}, {"text": "And did they have a bubble.", "start": 3687.73, "duration": 2.4}, {"text": "And then the\nJapanese don't allow", "start": 3690.13, "duration": 2.31}, {"text": "themselves to let the banks\ngo out of business readily.", "start": 3692.44, "duration": 2.85}, {"text": "And therefore, they just took\nyears and years and years", "start": 3695.29, "duration": 3.3}, {"text": "to get out of this.", "start": 3698.59, "duration": 1.11}, {"text": "And they're just starting\nto come out of it.", "start": 3699.7, "duration": 2.2}, {"text": "And so that helped the\nAmericans in the '90s.", "start": 3701.9, "duration": 2.48}, {"text": "They didn't have the Japanese--", "start": 3704.38, "duration": 1.71}, {"text": "the same Japanese\nto compete with.", "start": 3706.09, "duration": 1.77}, {"text": "And what hurt the\nGermans in the '90s", "start": 3707.86, "duration": 2.16}, {"text": "was reunification with East\nGermany, where the West", "start": 3710.02, "duration": 2.67}, {"text": "Germans had to\nsend a lot of money", "start": 3712.69, "duration": 1.86}, {"text": "over to make the East Germans\nappear a little closer", "start": 3714.55, "duration": 4.14}, {"text": "in terms of their economic\nstatus to the West Germans.", "start": 3718.69, "duration": 3.81}, {"text": "And so they got hurt that way.", "start": 3722.5, "duration": 2.41}, {"text": "On the other hand,\nnow, as you could say,", "start": 3724.91, "duration": 2.28}, {"text": "well, so we're doing\nfine against these guys.", "start": 3727.19, "duration": 3.27}, {"text": "But they're coming\nback is my argument.", "start": 3730.46, "duration": 2.82}, {"text": "But now everybody is worried\nabout China and India.", "start": 3733.28, "duration": 2.93}, {"text": "And it's not clear exactly\nhow these different modes", "start": 3736.21, "duration": 3.51}, {"text": "of thought and\nvariations on them", "start": 3739.72, "duration": 2.25}, {"text": "are going to deal with the\nchallenge from a billion three", "start": 3741.97, "duration": 3.75}, {"text": "or whatever the number\nis of people in China", "start": 3745.72, "duration": 2.7}, {"text": "and the Indian challenge.", "start": 3748.42, "duration": 2.25}, {"text": "I'm not predicting the future.", "start": 3750.67, "duration": 1.38}, {"text": "I'm just saying that this\nway of thinking about it", "start": 3752.05, "duration": 3.15}, {"text": "tends to clarify, at\nleast in my thinking, what", "start": 3755.2, "duration": 4.86}, {"text": "has been going on, even as\nrecently as a decade ago.", "start": 3760.06, "duration": 3.04}, {"text": "But in terms of predicting\nthe future, it's not as good.", "start": 3763.1, "duration": 4.04}, {"text": "End.", "start": 3769.675, "duration": 0.5}, {"text": "JON GRUDEN: I hope\nyou stay up there.", "start": 3774.168, "duration": 1.542}, {"text": "We got some more questions.", "start": 3775.71, "duration": 3.615}, {"text": "JOEL MOSES: OK.", "start": 3779.325, "duration": 0.625}, {"text": "JON GRUDEN: Or comments.", "start": 3779.95, "duration": 1.35}, {"text": "Let's have a little\nmore discussion.", "start": 3781.3, "duration": 3.268}, {"text": "AUDIENCE: Could we hear a little\nbit more about the Toyota-GM", "start": 3784.568, "duration": 2.542}, {"text": "you said that--", "start": 3787.11, "duration": 0.57}, {"text": "JOEL MOSES: NUMMI plant.", "start": 3787.68, "duration": 1.003}, {"text": "AUDIENCE: --the manager went\nout there and could see--", "start": 3788.683, "duration": 2.187}, {"text": "JOEL MOSES: The vice president\nwent out there, yeah.", "start": 3790.87, "duration": 2.167}, {"text": "AUDIENCE: --three hours, and\nwhat were the differences?", "start": 3793.037, "duration": 3.531}, {"text": "JOEL MOSES: He may not realize\nthe importance of things", "start": 3796.568, "duration": 2.292}, {"text": "like just in time.", "start": 3798.86, "duration": 1.71}, {"text": "I mean, things were\nbeing delivered,", "start": 3800.57, "duration": 2.55}, {"text": "but they got deliveries\nin GM plants too.", "start": 3803.12, "duration": 2.79}, {"text": "But the fact that\ntheir deliveries", "start": 3805.91, "duration": 1.59}, {"text": "were relatively few and\nspecialized to the cars just", "start": 3807.5, "duration": 4.68}, {"text": "now being worked on, maybe\nsomething he may have missed.", "start": 3812.18, "duration": 4.77}, {"text": "Now mind you, this is the guy\nwho came a year later here", "start": 3816.95, "duration": 3.15}, {"text": "and gave a talk at Kresge.", "start": 3820.1, "duration": 1.65}, {"text": "And he said, well,\nI got my MBA at MIT.", "start": 3821.75, "duration": 2.67}, {"text": "And then he had a\nbriefcase with him.", "start": 3824.42, "duration": 2.29}, {"text": "He threw out the\ncontents of a briefcase.", "start": 3826.71, "duration": 2.0}, {"text": "It was a bunch of books.", "start": 3828.71, "duration": 1.9}, {"text": "And he says, these are\nthe books they taught me.", "start": 3830.61, "duration": 3.17}, {"text": "Now, in the automobile\nbusiness, we", "start": 3833.78, "duration": 1.95}, {"text": "have recalls for\nthings that don't work.", "start": 3835.73, "duration": 2.31}, {"text": "MIT should have a recall.", "start": 3838.04, "duration": 2.4}, {"text": "And for free, they\nshould re-educate us.", "start": 3840.44, "duration": 4.34}, {"text": "He was a character.", "start": 3844.78, "duration": 1.93}, {"text": "So after he learned these\nthings, he saw the light.", "start": 3846.71, "duration": 4.08}, {"text": "The trouble is, I said earlier--\nand maybe you missed it,", "start": 3850.79, "duration": 2.46}, {"text": "Tony-- is that in some\nsense, it became a religion", "start": 3853.25, "duration": 3.78}, {"text": "after a while.", "start": 3857.03, "duration": 0.78}, {"text": "These are the seven\nsteps to heaven.", "start": 3857.81, "duration": 3.11}, {"text": "And we didn't realize the\nJapanese were constantly", "start": 3860.92, "duration": 3.37}, {"text": "tinkering with the\nprocess and they", "start": 3864.29, "duration": 1.68}, {"text": "were improving and improving.", "start": 3865.97, "duration": 1.29}, {"text": "And even the Germans got better.", "start": 3867.26, "duration": 2.85}, {"text": "I mean, what happened\nwas that of all", "start": 3870.11, "duration": 2.82}, {"text": "the firms, the worst performing\nin terms of quality and cost--", "start": 3872.93, "duration": 6.15}, {"text": "well, not so much quality,\nbut certainly cost--", "start": 3879.08, "duration": 2.16}, {"text": "were Daimler-Benz Mercedes.", "start": 3881.24, "duration": 2.31}, {"text": "And the president Mercedes\ncalled up president of MIT", "start": 3883.55, "duration": 2.375}, {"text": "in '88 or '89 and he said,\nyou can't publish that result.", "start": 3885.925, "duration": 3.715}, {"text": "You're going to be\nlike a laughing stock.", "start": 3889.64, "duration": 2.28}, {"text": "You can't tell me a Mercedes\nis the worst performing plant", "start": 3891.92, "duration": 3.6}, {"text": "on Earth.", "start": 3895.52, "duration": 1.23}, {"text": "Well, we published\nthe result anyway.", "start": 3896.75, "duration": 1.83}, {"text": "And this guy got canned.", "start": 3898.58, "duration": 1.07}, {"text": "And the new guy came in.", "start": 3899.65, "duration": 1.0}, {"text": "He says, I'm going to\nmake every vice president", "start": 3900.65, "duration": 2.12}, {"text": "of the company read that book.", "start": 3902.77, "duration": 2.86}, {"text": "So he got the religion.", "start": 3905.63, "duration": 1.35}, {"text": "And they all did because once\nyou show what the numbers are--", "start": 3906.98, "duration": 3.81}, {"text": "a little dose of reality--", "start": 3910.79, "duration": 2.37}, {"text": "it made a big difference\nin the automobile industry.", "start": 3913.16, "duration": 3.62}, {"text": "AUDIENCE: I read somewhere and--", "start": 3916.78, "duration": 1.67}, {"text": "maybe I'm thinking\nof something else.", "start": 3918.45, "duration": 0.93}, {"text": "We're talking about\nlean manufacturing?", "start": 3919.38, "duration": 1.64}, {"text": "JOEL MOSES: Yes, it's exactly\nwhat we're talking about.", "start": 3921.02, "duration": 2.292}, {"text": "AUDIENCE: If you're on a\ncertain level of the hierarchy,", "start": 3923.312, "duration": 3.143}, {"text": "you don't move up?", "start": 3926.455, "duration": 1.383}, {"text": "Is that true?", "start": 3927.838, "duration": 1.69}, {"text": "Because if you're his friend\nand you do a certain job,", "start": 3929.528, "duration": 3.052}, {"text": "you do it really well, maybe you\nget a different kind of reward.", "start": 3932.58, "duration": 3.12}, {"text": "But you won't be promoted to--", "start": 3935.7, "duration": 1.8}, {"text": "JOEL MOSES: So the promotion\nprocess, to remind you,", "start": 3937.5, "duration": 2.53}, {"text": "you don't have very many levels.", "start": 3940.03, "duration": 2.78}, {"text": "So one of the\nthings that happens", "start": 3942.81, "duration": 1.65}, {"text": "is promotions, if they\ndo occur, are slow.", "start": 3944.46, "duration": 3.45}, {"text": "Americans love to\nbe promoted fast.", "start": 3947.91, "duration": 3.6}, {"text": "I want to be promoted fast.", "start": 3951.51, "duration": 3.36}, {"text": "Two or three years on the\njob and I want out of here.", "start": 3954.87, "duration": 2.85}, {"text": "Leave all the mess\nto my successor.", "start": 3957.72, "duration": 2.73}, {"text": "So the Japanese move slowly.", "start": 3960.45, "duration": 3.99}, {"text": "Now in terms of promotion,\nwhat happens is first off,", "start": 3964.44, "duration": 6.24}, {"text": "they retire early,\n55, unless they", "start": 3970.68, "duration": 2.97}, {"text": "happen to be senior management.", "start": 3973.65, "duration": 1.65}, {"text": "Then they can retire\nat 60 or 65 maybe.", "start": 3975.3, "duration": 2.46}, {"text": "But 55 is a normal\nretirement age", "start": 3977.76, "duration": 2.25}, {"text": "for so-called salaried workers.", "start": 3980.01, "duration": 2.04}, {"text": "And what happens is they move\nover to a subsidiary company.", "start": 3982.05, "duration": 5.7}, {"text": "And a subsidiary company\nknows that they better", "start": 3987.75, "duration": 2.28}, {"text": "hire some of these\nguys otherwise", "start": 3990.03, "duration": 2.52}, {"text": "they're not going to remain\nas part of the supply chain", "start": 3992.55, "duration": 3.36}, {"text": "as much.", "start": 3995.91, "duration": 0.75}, {"text": "So slower promotions-- not\nnonexistent, but slower", "start": 3996.66, "duration": 3.72}, {"text": "promotions.", "start": 4000.38, "duration": 0.63}, {"text": "Some people don't get\npromoted, but they", "start": 4001.01, "duration": 2.01}, {"text": "don't get demoted either.", "start": 4003.02, "duration": 2.07}, {"text": "They get given a chair\nfurther away from the action.", "start": 4005.09, "duration": 8.11}, {"text": "So in principle, everybody in\na given level at the company", "start": 4013.2, "duration": 3.56}, {"text": "is at a given level\nof the company.", "start": 4016.76, "duration": 2.16}, {"text": "But when you listen\nto people, you", "start": 4018.92, "duration": 3.03}, {"text": "listen only to a few of them.", "start": 4021.95, "duration": 2.1}, {"text": "The others can\ntalk all they want,", "start": 4024.05, "duration": 2.25}, {"text": "nobody's going to pay\nmuch attention to--", "start": 4026.3, "duration": 1.95}, {"text": "everybody realizes that\nwithin this particular level,", "start": 4028.25, "duration": 3.54}, {"text": "all these guys who are 40\nyears old, two or three of them", "start": 4031.79, "duration": 2.91}, {"text": "are really the\nones to listen to.", "start": 4034.7, "duration": 2.67}, {"text": "It's a complicated game.", "start": 4037.37, "duration": 2.31}, {"text": "But again, very much\nrelated to this issue.", "start": 4039.68, "duration": 3.93}, {"text": "Whereas, the fast promotion, if\nyou have 20 different levels,", "start": 4043.61, "duration": 3.42}, {"text": "you want to go through,\n[SHUFFLING SOUND]..", "start": 4047.03, "duration": 4.41}, {"text": "And again, also\nthe salary ratio,", "start": 4051.44, "duration": 2.76}, {"text": "we worry about how high the\nratio is in the United States.", "start": 4054.2, "duration": 3.39}, {"text": "Several to one between a CEO\nand the lowest paid worker.", "start": 4057.59, "duration": 3.63}, {"text": "But maybe only a\ndozen to one in Japan.", "start": 4061.22, "duration": 3.27}, {"text": "I mean, it's a\ndifferent attitude.", "start": 4064.49, "duration": 1.68}, {"text": "And again, the attitude of,\nwe're all in it together.", "start": 4066.17, "duration": 3.12}, {"text": "We are the Toyota team.", "start": 4069.29, "duration": 2.64}, {"text": "And we are going to beat\nout, not only GM and Ford,", "start": 4071.93, "duration": 3.93}, {"text": "but Nissan and Honda.", "start": 4075.86, "duration": 3.21}, {"text": "On the other hand,\nwe're going to cooperate", "start": 4079.07, "duration": 1.92}, {"text": "between Toyota and Nissan.", "start": 4080.99, "duration": 1.65}, {"text": "We're going to cooperate on\nprocesses, not on products.", "start": 4082.64, "duration": 3.3}, {"text": "We're going to cooperate\non business practices,", "start": 4085.94, "duration": 2.675}, {"text": "on knowledge.", "start": 4088.615, "duration": 0.835}, {"text": "But not things\nthat are intimately", "start": 4089.45, "duration": 2.22}, {"text": "tied to our products.", "start": 4091.67, "duration": 2.05}, {"text": "So there is an attitude about\nwhat's to be cooperated on", "start": 4093.72, "duration": 3.259}, {"text": "and what's to be competed on.", "start": 4096.979, "duration": 1.59}, {"text": "And it is a very different\nway of doing business.", "start": 4098.569, "duration": 3.991}, {"text": "And it works some of the\ntime, not all the time.", "start": 4102.56, "duration": 3.419}, {"text": "Nothing works all the time.", "start": 4105.979, "duration": 2.178}, {"text": "You hear that?", "start": 4108.157, "duration": 0.583}, {"text": "AUDIENCE: Can I ask\nyou about your claim", "start": 4112.135, "duration": 2.795}, {"text": "that design isn't as\nunique as engineering.", "start": 4114.93, "duration": 2.766}, {"text": "JOEL MOSES: Of course not.", "start": 4117.696, "duration": 1.083}, {"text": "AUDIENCE: Which I agree with.", "start": 4121.46, "duration": 2.189}, {"text": "But so then I wonder,\nhow do you think", "start": 4123.649, "duration": 2.491}, {"text": "about defining engineering?", "start": 4126.14, "duration": 3.87}, {"text": "I guess you would say\njust engineering is", "start": 4130.01, "duration": 2.67}, {"text": "closer than to what\nsystems philosophers do.", "start": 4132.68, "duration": 4.74}, {"text": "But [INAUDIBLE].", "start": 4137.42, "duration": 0.99}, {"text": "JOEL MOSES: No,\nsystems philosophers", "start": 4138.41, "duration": 1.5}, {"text": "worry about all kinds of systems\nor organizational systems.", "start": 4139.91, "duration": 3.75}, {"text": "All kind of things.", "start": 4143.66, "duration": 0.869}, {"text": "What engineers\ntend to do is they", "start": 4144.529, "duration": 1.861}, {"text": "use their knowledge of math,\nscience, and engineering", "start": 4146.39, "duration": 4.53}, {"text": "science in order to develop\nproducts, processes,", "start": 4150.92, "duration": 4.0}, {"text": "systems for society.", "start": 4154.92, "duration": 1.828}, {"text": "There are certain kinds--", "start": 4156.748, "duration": 1.042}, {"text": "AUDIENCE: --specific purpose.", "start": 4157.79, "duration": 1.321}, {"text": "JOEL MOSES: Absolutely.", "start": 4159.111, "duration": 0.958}, {"text": "Absolutely.", "start": 4160.069, "duration": 0.5}, {"text": "AUDIENCE: OK.", "start": 4160.569, "duration": 0.643}, {"text": "JOEL MOSES: Absolutely.", "start": 4161.212, "duration": 0.958}, {"text": "But see, in a sense,\nso is design and music.", "start": 4162.17, "duration": 4.38}, {"text": "But the musician\ndoesn't necessarily", "start": 4166.55, "duration": 2.58}, {"text": "rely on his\nunderstanding of physics.", "start": 4169.13, "duration": 1.86}, {"text": "He doesn't rely on\nenergy as a variable.", "start": 4170.99, "duration": 4.96}, {"text": "AUDIENCE: That's\n[? definitely ?] strange.", "start": 4175.95, "duration": 1.75}, {"text": "Like, music isn't\nnecessarily constrained--", "start": 4177.7, "duration": 1.86}, {"text": "JOEL MOSES: It's\nconstrained in some ways,", "start": 4179.56, "duration": 1.45}, {"text": "but not in other ways.", "start": 4181.01, "duration": 0.78}, {"text": "Let me give you an\nexample of constraint.", "start": 4181.79, "duration": 1.708}, {"text": "So I was taking music\nappreciation 101.", "start": 4183.498, "duration": 3.231}, {"text": "And a student got\nup in the course", "start": 4186.729, "duration": 2.401}, {"text": "and he said, Professor,\nI don't understand.", "start": 4189.13, "duration": 2.439}, {"text": "How did Mozart manage to\nwrite so many symphonies", "start": 4191.569, "duration": 2.21}, {"text": "when he was so constrained\nby the sonata form, ABA?", "start": 4193.779, "duration": 4.771}, {"text": "The professor's answer\nwas, because Mozart", "start": 4198.55, "duration": 2.49}, {"text": "was so constrained\nby the sonata form,", "start": 4201.04, "duration": 1.602}, {"text": "he was able to\nwrite lots of music.", "start": 4202.642, "duration": 1.458}, {"text": "Constraints can be good.", "start": 4208.09, "duration": 2.97}, {"text": "Constraints can be good.", "start": 4211.06, "duration": 1.75}, {"text": "So computer scientists\nactually have a problem.", "start": 4212.81, "duration": 2.64}, {"text": "They're not so\nconstrained by physics", "start": 4215.45, "duration": 1.91}, {"text": "and so they can try anything.", "start": 4217.36, "duration": 1.92}, {"text": "And boy, they bollocks it up.", "start": 4219.28, "duration": 1.41}, {"text": "They get overly complex\nsoftware without realizing it.", "start": 4220.69, "duration": 3.69}, {"text": "And after a while, they can't\nmake any further changes.", "start": 4224.38, "duration": 2.94}, {"text": "I'll give you an example\nof overly complex software.", "start": 4227.32, "duration": 2.55}, {"text": "So Jimmy Carter was president\nbefore you were born,", "start": 4229.87, "duration": 2.91}, {"text": "but I remember him well.", "start": 4232.78, "duration": 2.97}, {"text": "I'm sure Taft does too.", "start": 4235.75, "duration": 1.5}, {"text": "And he was not the smartest guy.", "start": 4237.25, "duration": 3.48}, {"text": "He was an engineer, so not\nnecessarily the smartest", "start": 4240.73, "duration": 2.7}, {"text": "politician.", "start": 4243.43, "duration": 0.58}, {"text": "Now one of the\nthings he decided he", "start": 4244.01, "duration": 1.61}, {"text": "was going to do because he\nbelieved in truth and all that", "start": 4245.62, "duration": 3.12}, {"text": "is he was going to\nallow people to call him", "start": 4248.74, "duration": 2.22}, {"text": "on the radio on\nSaturday afternoons", "start": 4250.96, "duration": 1.95}, {"text": "and ask any question they want.", "start": 4252.91, "duration": 2.05}, {"text": "So a lady called up\nand she said, well,", "start": 4254.96, "duration": 2.75}, {"text": "I get Social Security.", "start": 4257.71, "duration": 2.55}, {"text": "And Social Security\nhas updated, my check", "start": 4260.26, "duration": 2.88}, {"text": "is increased relative\nto inflation.", "start": 4263.14, "duration": 2.34}, {"text": "In those days, inflation\nwas quite high.", "start": 4265.48, "duration": 1.77}, {"text": "And it's done once a year.", "start": 4267.25, "duration": 2.67}, {"text": "Because inflation is so\nhigh, it would really", "start": 4269.92, "duration": 1.98}, {"text": "help me a lot if it\nwere done twice a year.", "start": 4271.9, "duration": 4.56}, {"text": "He said, OK, I'll look into it.", "start": 4276.46, "duration": 2.19}, {"text": "So months later, some\nenterprising journalists said,", "start": 4278.65, "duration": 3.0}, {"text": "whatever happened to\nthat lady's question?", "start": 4281.65, "duration": 2.94}, {"text": "And Carter had to own up.", "start": 4284.59, "duration": 1.62}, {"text": "He said, well, we\nasked the people at HHS", "start": 4286.21, "duration": 4.11}, {"text": "where they can do this.", "start": 4290.32, "duration": 1.18}, {"text": "And they said, well, if they\ntry doing that they couldn't", "start": 4291.5, "duration": 3.455}, {"text": "guarantee that the checks would\ncome out because the system was", "start": 4294.955, "duration": 2.625}, {"text": "so complicated, the ramification\nof that little change", "start": 4297.58, "duration": 2.67}, {"text": "could create such a havoc\nthat they dare not do it.", "start": 4300.25, "duration": 3.12}, {"text": "That's overly complicated.", "start": 4303.37, "duration": 1.845}, {"text": "A minute to go, guys,\naccording to that watch.", "start": 4310.34, "duration": 2.79}, {"text": "JON GRUDEN: Well, thanks again.", "start": 4316.63, "duration": 1.98}, {"text": "And next week, we\nare off Tuesday.", "start": 4318.61, "duration": 3.32}, {"text": "Is that right?", "start": 4321.93, "duration": 0.81}, {"text": "JOEL MOSES: Yes, because\nTuesday's a Monday.", "start": 4322.74, "duration": 2.28}, {"text": "JON GRUDEN: Tuesday's a Monday?", "start": 4325.02, "duration": 1.68}, {"text": "OK, well, then first\nthing I need to know", "start": 4326.7, "duration": 2.31}, {"text": "is, what kind of\npublication rights", "start": 4329.01, "duration": 4.3}, {"text": "are you going to give\nus with these slides", "start": 4333.31, "duration": 2.43}, {"text": "since I've got\nthem on my machine?", "start": 4335.74, "duration": 2.35}, {"text": "Can we send them to the?", "start": 4338.09, "duration": 1.04}, {"text": "JOEL MOSES: Oh, absolutely.", "start": 4339.13, "duration": 1.9}, {"text": "JON GRUDEN: All right, then I'll\ntake responsibility for that.", "start": 4341.03, "duration": 3.45}, {"text": "I have a grading scheme.", "start": 4344.48, "duration": 2.68}, {"text": "And I'll be frank\nwith you, I really", "start": 4347.16, "duration": 2.88}, {"text": "don't want to put it in concrete\nuntil you talk about it.", "start": 4350.04, "duration": 4.33}, {"text": "Now I want to be able to reveal\nsome of my subconscious to you", "start": 4354.37, "duration": 4.75}, {"text": "before we do this.", "start": 4359.12, "duration": 1.21}, {"text": "You want to look at partly\na Democratic process.", "start": 4363.55, "duration": 5.37}, {"text": "And I emphasize partly.", "start": 4368.92, "duration": 3.285}, {"text": "And you could say what you\nthink is right, what you", "start": 4372.205, "duration": 2.125}, {"text": "think is fair, unfair about it.", "start": 4374.33, "duration": 2.38}, {"text": "The [INAUDIBLE],, what I'm\nreally looking for you to say", "start": 4376.71, "duration": 3.66}, {"text": "is, well, look, Dr.\nGruden, this latest scheme", "start": 4380.37, "duration": 3.27}, {"text": "here is not as tough as\nwe feel it should be.", "start": 4383.64, "duration": 2.88}, {"text": "We want a more\nrigorous class in here.", "start": 4386.52, "duration": 2.16}, {"text": "We want to do x, y, z.", "start": 4388.68, "duration": 1.45}, {"text": "I'm really looking for you\nto add something to this.", "start": 4390.13, "duration": 3.35}, {"text": "You don't have to do that.", "start": 4393.48, "duration": 1.495}, {"text": "But if you think\nsomething's unfair about it,", "start": 4394.975, "duration": 1.875}, {"text": "I want to hear about it.", "start": 4396.85, "duration": 1.07}, {"text": "And wherever I go\nfrom there, I want", "start": 4397.92, "duration": 2.76}, {"text": "to be able to say,\nwell, I heard from them.", "start": 4400.68, "duration": 2.52}, {"text": "They won't do it, but\nI heard from them,", "start": 4403.2, "duration": 2.1}, {"text": "if that's what it\nreally comes down to it.", "start": 4405.3, "duration": 3.19}, {"text": "Your next assignment-- how\nyou doing with this work?", "start": 4408.49, "duration": 3.52}, {"text": "AUDIENCE: Oh, gosh.", "start": 4412.01, "duration": 0.82}, {"text": "My book, something\nhappened with the mail,", "start": 4412.83, "duration": 1.75}, {"text": "but they're resending it.", "start": 4414.58, "duration": 1.042}, {"text": "I should get it in\na couple of days.", "start": 4415.622, "duration": 1.678}, {"text": "JON GRUDEN: OK.", "start": 4417.3, "duration": 0.42}, {"text": "AUDIENCE: So actually,\ndefinitely about next Thursday,", "start": 4417.72, "duration": 2.179}, {"text": "I would think.", "start": 4419.899, "duration": 0.371}, {"text": "JON GRUDEN: Oh, that far away?", "start": 4420.27, "duration": 1.25}, {"text": "AUDIENCE: Well, we can share.", "start": 4422.6, "duration": 1.235}, {"text": "AUDIENCE: I have\nyour email, so I", "start": 4423.835, "duration": 1.375}, {"text": "can [? work ?] on getting it\nin the next couple of days.", "start": 4425.21, "duration": 2.333}, {"text": "JON GRUDEN: Well, I\nhave another copy.", "start": 4427.543, "duration": 2.347}, {"text": "I'll loan you my copy.", "start": 4429.89, "duration": 2.35}, {"text": "I have, actually, an older\nversion in my office.", "start": 4432.24, "duration": 2.673}, {"text": "I'll give you the\nupdated version.", "start": 4434.913, "duration": 1.417}, {"text": "What I want you to\ndo is read two cases,", "start": 4436.33, "duration": 1.667}, {"text": "since we have so much time.", "start": 4437.997, "duration": 1.143}, {"text": "I want you to read\nthe Ford Pinto case.", "start": 4439.14, "duration": 5.28}, {"text": "And I want you to read\nthe Challenger case.", "start": 4444.42, "duration": 5.232}, {"text": "Next week, we'll start\nconverging on something", "start": 4452.89, "duration": 5.67}, {"text": "much more high quality\nwith the ethics.", "start": 4458.56, "duration": 3.51}, {"text": "And then we're going to\nstart putting the ethics", "start": 4462.07, "duration": 2.25}, {"text": "and the engineering together.", "start": 4464.32, "duration": 2.19}, {"text": "And my assignment for next\nweek-- for the following week--", "start": 4466.51, "duration": 4.07}, {"text": "will be turn in\nthe first analysis.", "start": 4470.58, "duration": 5.635}, {"text": "And I'll give you the\nformat, tell you how to write", "start": 4476.215, "duration": 3.255}, {"text": "and see what's done.", "start": 4479.47, "duration": 1.95}, {"text": "Once you get my methods\ndown, then we'll", "start": 4481.42, "duration": 3.51}, {"text": "start talking about\na little education.", "start": 4484.93, "duration": 3.09}, {"text": "You'll start doing it your way.", "start": 4488.02, "duration": 3.05}, {"text": "Also, you want to sign that you\nlistened and watched this film.", "start": 4491.07, "duration": 4.73}, {"text": "[INAUDIBLE]", "start": 4495.8, "duration": 3.47}, {"text": "OK, that's it.", "start": 4499.27, "duration": 2.03}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.936}, {"text": "[RUSTLING]", "start": 1.936, "duration": 1.452}, {"text": "[CLICKING]", "start": 3.388, "duration": 1.936}, {"text": "JASON KU: Welcome, everybody,\nto the second-to-last lecture", "start": 13.08, "duration": 3.24}, {"text": "of 6.006.", "start": 16.32, "duration": 2.67}, {"text": "In this lecture,\nwe've mostly covered", "start": 18.99, "duration": 2.88}, {"text": "all of the testable\nmaterial that we're", "start": 21.87, "duration": 2.7}, {"text": "going to have on the\nfinal, or on quiz 3.", "start": 24.57, "duration": 6.21}, {"text": "Today, really what\nwe're talking about", "start": 30.78, "duration": 1.949}, {"text": "is putting into context\nall the material", "start": 32.729, "duration": 2.821}, {"text": "that we've learned over\nthe course of the term", "start": 35.55, "duration": 4.37}, {"text": "at a high level and talk about\nwhere we can go from here", "start": 39.92, "duration": 4.32}, {"text": "in terms of other theory\nclasses and other classes", "start": 44.24, "duration": 2.82}, {"text": "in the department that are\nrelated to this material.", "start": 47.06, "duration": 2.28}, {"text": "Now, most things\nin the department", "start": 49.34, "duration": 2.4}, {"text": "are in some way related\nto this material.", "start": 51.74, "duration": 2.5}, {"text": "And so that's why there's\na foundational course.", "start": 54.24, "duration": 2.805}, {"text": "But we're going to try to talk\nabout it from a high level", "start": 57.045, "duration": 2.375}, {"text": "and talk about how some\nfuture things that you", "start": 59.42, "duration": 5.849}, {"text": "might be interested relate.", "start": 65.269, "duration": 1.421}, {"text": "OK, so we started out\nthe term, in lecture one,", "start": 66.69, "duration": 4.73}, {"text": "talking about 6.006, and\nwe had four main goals", "start": 71.42, "duration": 4.05}, {"text": "that we had for our course--\nreally three main goals", "start": 75.47, "duration": 5.64}, {"text": "Does anyone remember\nwhat those goals were?", "start": 81.11, "duration": 2.43}, {"text": "So you got to the\nlast one first.", "start": 89.16, "duration": 2.52}, {"text": "The first one was to solve\nhard computational problems,", "start": 91.68, "duration": 4.32}, {"text": "to be able to solve problems.", "start": 96.0, "duration": 3.06}, {"text": "So this is kind of like the\n\"let's make an algorithm\"", "start": 99.06, "duration": 4.65}, {"text": "part of the course.", "start": 103.71, "duration": 2.58}, {"text": "1, solve hard\ncomputational problems.", "start": 106.29, "duration": 4.845}, {"text": "I guess \"hard\" here maybe\nshould be in quotes because we", "start": 116.62, "duration": 4.11}, {"text": "saw in the last\nlecture what hard", "start": 120.73, "duration": 2.28}, {"text": "means in a technical sense.", "start": 123.01, "duration": 2.67}, {"text": "Hard could mean that there's\nno efficient algorithm that we", "start": 125.68, "duration": 5.67}, {"text": "know how to solve a problem on.", "start": 131.35, "duration": 1.787}, {"text": "That's getting a little\nbit of ahead of ourselves.", "start": 133.137, "duration": 2.083}, {"text": "Computational problems\nwith algorithms", "start": 135.22, "duration": 2.43}, {"text": "is really the key\npart about this goal.", "start": 137.65, "duration": 2.37}, {"text": "It's kind of the\nsame goal that you", "start": 140.02, "duration": 1.65}, {"text": "have in a class like\n6.0001 or 6.009.", "start": 141.67, "duration": 4.56}, {"text": "You're trying to\nconvince a computer", "start": 146.23, "duration": 2.16}, {"text": "that you solved a problem\non a finite set of inputs.", "start": 148.39, "duration": 6.54}, {"text": "But really what\nthis class is about", "start": 154.93, "duration": 2.25}, {"text": "is two other things, which\nis more about communication", "start": 157.18, "duration": 4.5}, {"text": "to people rather than computers.", "start": 161.68, "duration": 2.52}, {"text": "Your algorithm might be\ncorrect or efficient,", "start": 164.2, "duration": 3.81}, {"text": "but you need to be able to\ncommunicate that to humans.", "start": 168.01, "duration": 2.25}, {"text": "And that's what the\nother two goals are.", "start": 170.26, "duration": 2.46}, {"text": "So second one is\nargue correctness.", "start": 172.72, "duration": 8.43}, {"text": "Basically, the thing that\nI'm doing to my inputs", "start": 181.15, "duration": 4.47}, {"text": "is always going to lead\nme to a correct output.", "start": 185.62, "duration": 2.235}, {"text": "No matter what input I\ngive it, any valid input--", "start": 190.58, "duration": 2.56}, {"text": "there could be an infinite\nspace of possible inputs,", "start": 193.14, "duration": 3.6}, {"text": "and in this class,\nthat's the case,", "start": 196.74, "duration": 1.59}, {"text": "because we want our input size\nto grow arbitrarily large--", "start": 198.33, "duration": 4.44}, {"text": "we need to be able\nto argue correctness", "start": 202.77, "duration": 1.89}, {"text": "that it's going to return\nme the correct thing", "start": 204.66, "duration": 2.28}, {"text": "no matter what my inputs are.", "start": 206.94, "duration": 2.53}, {"text": "And in order to do that, that's\nessentially-- that's 6.042.", "start": 209.47, "duration": 4.67}, {"text": "This whole class has\nbasically been applied 6.042.", "start": 214.14, "duration": 4.8}, {"text": "I've given you some\nprocedures, and you", "start": 218.94, "duration": 3.42}, {"text": "have to prove things\nabout these procedures.", "start": 222.36, "duration": 1.89}, {"text": "Or most of the time,\nwe proved it for you,", "start": 224.25, "duration": 2.85}, {"text": "and then you've used\nthem as black boxes.", "start": 227.1, "duration": 2.31}, {"text": "But that's a lot of what\nthis class is about.", "start": 229.41, "duration": 4.68}, {"text": "And the third one\nis efficiency--", "start": 234.09, "duration": 1.94}, {"text": "argue that it's \"good,\"\nfor lack of a better thing.", "start": 238.61, "duration": 4.09}, {"text": "This is efficiency.", "start": 242.7, "duration": 1.63}, {"text": "What does \"good\" mean?", "start": 244.33, "duration": 2.69}, {"text": "Well, that was hard to know\nat the beginning of our class.", "start": 247.02, "duration": 3.48}, {"text": "And so we set up this model\nof computation, a framework,", "start": 250.5, "duration": 3.65}, {"text": "through which we could\ndetermine how good or bad", "start": 254.15, "duration": 3.99}, {"text": "our algorithms were by saying--", "start": 258.14, "duration": 2.1}, {"text": "by defining a model of\ncomputation, saying what things", "start": 260.24, "duration": 3.27}, {"text": "we can do in constant time, and\nthen just building off of that.", "start": 263.51, "duration": 4.65}, {"text": "So this is basically our\nmodel plus some asymptotics", "start": 268.16, "duration": 7.202}, {"text": "or something like that.", "start": 275.362, "duration": 0.958}, {"text": "Ran out of space.", "start": 279.84, "duration": 1.51}, {"text": "What?", "start": 281.35, "duration": 0.69}, {"text": "AUDIENCE: It's\nabout scalability.", "start": 282.04, "duration": 1.375}, {"text": "JASON KU: Yeah, this\nis about scalability.", "start": 283.415, "duration": 2.635}, {"text": "A model of computation tells\nus how much time we can spend,", "start": 286.05, "duration": 4.26}, {"text": "but it's compared\nto our input size.", "start": 290.31, "duration": 3.03}, {"text": "This is always about,\nhow does our algorithm", "start": 293.34, "duration": 3.51}, {"text": "perform relative to the rate\nthat our problem size grows?", "start": 296.85, "duration": 4.92}, {"text": "And so that's what\nwe mean by \"good.\"", "start": 301.77, "duration": 2.01}, {"text": "And in this class, we don't\ntend to talk about constant size", "start": 303.78, "duration": 3.81}, {"text": "problems.", "start": 307.59, "duration": 1.02}, {"text": "It's about how algorithms\ncan scale as you", "start": 308.61, "duration": 4.02}, {"text": "have arbitrarily large inputs.", "start": 312.63, "duration": 1.8}, {"text": "That's why we need\nrecursion and induction", "start": 314.43, "duration": 2.8}, {"text": "to be able to prove things\nabout our algorithms,", "start": 317.23, "duration": 2.0}, {"text": "because they're for arbitrary n.", "start": 319.23, "duration": 2.73}, {"text": "And that's why we need this\nrelative-to-input size,", "start": 321.96, "duration": 5.49}, {"text": "the growth factor of our\nalgorithm's performance,", "start": 327.45, "duration": 4.11}, {"text": "relative to the input.", "start": 331.56, "duration": 1.9}, {"text": "OK, and then the\nlast thing is, to me,", "start": 333.46, "duration": 5.91}, {"text": "one of the most\nimportant things,", "start": 339.37, "duration": 2.0}, {"text": "is communicating these\nthings to another human.", "start": 341.37, "duration": 3.66}, {"text": "So communication is key here.", "start": 345.03, "duration": 6.42}, {"text": "If you can always\nwrite good code", "start": 351.45, "duration": 2.13}, {"text": "that's always\nright, good for you.", "start": 353.58, "duration": 2.91}, {"text": "I can't do that all the time.", "start": 356.49, "duration": 3.44}, {"text": "But that might mean\nthat you can be very--", "start": 359.93, "duration": 4.38}, {"text": "a competent, independent\ncomputer programmer.", "start": 364.31, "duration": 4.47}, {"text": "But you are going to be limited\nin what you can do if you're", "start": 368.78, "duration": 5.73}, {"text": "only able to rely on yourself.", "start": 374.51, "duration": 3.63}, {"text": "A lot about computer science\nis working with others", "start": 378.14, "duration": 3.87}, {"text": "to solve computational problems.", "start": 382.01, "duration": 1.662}, {"text": "And when you're\nworking with others", "start": 383.672, "duration": 1.458}, {"text": "to solve computational\nproblems, you", "start": 385.13, "duration": 2.162}, {"text": "need to be able to\ncommunicate with them,", "start": 387.292, "duration": 1.708}, {"text": "and you need to be able\nto communicate them both", "start": 389.0, "duration": 2.49}, {"text": "what it is you're doing and\nwhy it is you're doing it--", "start": 391.49, "duration": 5.1}, {"text": "that you're doing the correct\nthing and that it's efficient.", "start": 396.59, "duration": 3.7}, {"text": "And so that's a big part\nabout what this course is.", "start": 400.29, "duration": 3.74}, {"text": "At the end of the\nday, on your quiz,", "start": 404.03, "duration": 2.31}, {"text": "if you write down Python\nscript for a correct algorithm,", "start": 406.34, "duration": 6.39}, {"text": "but we don't know\nwhat it's doing,", "start": 412.73, "duration": 1.98}, {"text": "but it's correct,\nwe're not going", "start": 414.71, "duration": 1.98}, {"text": "to give you full points on that,\nbecause you're not satisfying", "start": 416.69, "duration": 4.44}, {"text": "the conditions of this class.", "start": 421.13, "duration": 3.06}, {"text": "It's really about the\ncommunication here.", "start": 424.19, "duration": 2.42}, {"text": "OK, so just to review,\nsince we've not", "start": 426.61, "duration": 5.23}, {"text": "discussed how the most recent\nlecture fits into your problem", "start": 431.84, "duration": 6.12}, {"text": "sets.", "start": 437.96, "duration": 0.72}, {"text": "We didn't have any problem\nsets that covered complexity,", "start": 438.68, "duration": 5.39}, {"text": "so how does that fit in?", "start": 444.07, "duration": 1.25}, {"text": "Well, argue that the ways that\nwe're solving our problems", "start": 445.32, "duration": 3.45}, {"text": "are good.", "start": 448.77, "duration": 1.14}, {"text": "What we proved in the last\nlecture was that most problems", "start": 449.91, "duration": 2.73}, {"text": "cannot be solved good.", "start": 452.64, "duration": 3.32}, {"text": "They can't be solved\nin polynomial time", "start": 455.96, "duration": 2.76}, {"text": "with respect to the\nsize of your input.", "start": 458.72, "duration": 2.62}, {"text": "However, most of the\nproblems that we think about,", "start": 461.34, "duration": 4.67}, {"text": "in a sense, I can prove to\nyou that it's a yes solution.", "start": 466.01, "duration": 5.82}, {"text": "I can show you a simple\npath in this graph that", "start": 471.83, "duration": 4.08}, {"text": "has a certain length.", "start": 475.91, "duration": 2.01}, {"text": "Or I can show you a subset\nthat sums to a certain value", "start": 477.92, "duration": 3.84}, {"text": "in a particular problem.", "start": 481.76, "duration": 1.56}, {"text": "I can give you a\ncertificate that I", "start": 483.32, "duration": 1.83}, {"text": "can prove to you in a\nreasonable amount of time", "start": 485.15, "duration": 2.91}, {"text": "that, yes, I can\nprove to you that this", "start": 488.06, "duration": 2.16}, {"text": "is-- the answer to\nthis thing is correct.", "start": 490.22, "duration": 2.67}, {"text": "And that's what we talked\nabout in the last lecture.", "start": 492.89, "duration": 3.99}, {"text": "So not always \"good\"\nalgorithms to solve problems,", "start": 496.88, "duration": 23.33}, {"text": "but many problems we think\nabout can be either checked", "start": 520.21, "duration": 22.06}, {"text": "in polynomial time--", "start": 542.27, "duration": 2.73}, {"text": "this is the concept of having\na certificate that I could give", "start": 548.48, "duration": 3.24}, {"text": "you of polynomial\nsize that could", "start": 551.72, "duration": 1.89}, {"text": "be checked in polynomial time--", "start": 553.61, "duration": 2.43}, {"text": "in a sense, that's a way--", "start": 556.04, "duration": 2.62}, {"text": "check-- checked in\npolynomial time.", "start": 558.66, "duration": 3.86}, {"text": "This leads to our class\nof decision problems, NP.", "start": 562.52, "duration": 4.05}, {"text": "Or it can be solved by brute\nforce in exponential time.", "start": 566.57, "duration": 13.62}, {"text": "Most of the things that we've\ntalked about in this class", "start": 580.19, "duration": 2.46}, {"text": "fall into one of\nthese two categories.", "start": 582.65, "duration": 2.38}, {"text": "We can just brute force\nover the combinatorial space", "start": 585.03, "duration": 2.51}, {"text": "of possible outputs and check\nto see if they're correct.", "start": 587.54, "duration": 4.19}, {"text": "Or I can give you a certificate\nbasically saying, look,", "start": 591.73, "duration": 6.82}, {"text": "I can solve--", "start": 598.55, "duration": 0.65}, {"text": "actually, anything\nthat's of this form", "start": 599.2, "duration": 1.737}, {"text": "can be checked in this\nform, because there's", "start": 600.937, "duration": 1.833}, {"text": "only a polynomial number of\nthings to check-- or, sorry,", "start": 602.77, "duration": 2.8}, {"text": "an exponential possible\nnumber of certificates", "start": 605.57, "duration": 2.54}, {"text": "of polynomial length to check.", "start": 608.11, "duration": 2.4}, {"text": "But basically, this is\nsaying that the problems", "start": 610.51, "duration": 2.94}, {"text": "that we think of mostly fall\ninto these two categories.", "start": 613.45, "duration": 3.64}, {"text": "And so there usually\nare algorithms to solve", "start": 617.09, "duration": 3.17}, {"text": "the problems that\nwe care about, even", "start": 620.26, "duration": 4.45}, {"text": "if most random problems\nin terms of bit strings", "start": 624.71, "duration": 4.8}, {"text": "that we gave an analysis\nin the last lecture", "start": 629.51, "duration": 2.97}, {"text": "actually prove that most random\nproblems are not solvable.", "start": 632.48, "duration": 3.57}, {"text": "In a sense, the problems we\nthink about are not random.", "start": 638.57, "duration": 3.61}, {"text": "They kind of have this\nstructure that they", "start": 642.18, "duration": 1.79}, {"text": "can be checked pretty quickly.", "start": 643.97, "duration": 2.36}, {"text": "OK, so that's what\nwe mean when we", "start": 646.33, "duration": 3.4}, {"text": "are talking about complexity.", "start": 649.73, "duration": 1.8}, {"text": "For the purposes of\nthe final, you'll", "start": 651.53, "duration": 2.52}, {"text": "be able to see on your\nfinal exam practice problems", "start": 654.05, "duration": 5.1}, {"text": "that we're going to give you,\nmost of what we cover in terms", "start": 659.15, "duration": 6.3}, {"text": "of material on the final\nthat will be testing", "start": 665.45, "duration": 3.75}, {"text": "the lecture 19 material will\nbe in terms of the definitions.", "start": 669.2, "duration": 5.25}, {"text": "Do you understand what the\ndecision problem class NP is?", "start": 674.45, "duration": 4.89}, {"text": "EXP is?", "start": 679.34, "duration": 1.29}, {"text": "Do you know how these\nrelate to each other?", "start": 680.63, "duration": 2.04}, {"text": "EXP is definitely a\nsuperset of NP here.", "start": 682.67, "duration": 4.95}, {"text": "NP nestles inside here.", "start": 687.62, "duration": 1.65}, {"text": "They could be\nequal-- probably not.", "start": 689.27, "duration": 2.58}, {"text": "Those are the types of\nthings that we would address.", "start": 691.85, "duration": 3.63}, {"text": "Knowing a directionality\nof a reduction.", "start": 695.48, "duration": 3.21}, {"text": "If you have a problem\nA and a problem", "start": 698.69, "duration": 5.64}, {"text": "B, and I know that this one\nis difficult by some measure--", "start": 704.33, "duration": 8.96}, {"text": "I already happened to\nknow that it's very hard,", "start": 713.29, "duration": 3.78}, {"text": "like NP-hard or\nsomething like that.", "start": 717.07, "duration": 2.43}, {"text": "If this is a problem that\nI'm interested in knowing", "start": 719.5, "duration": 3.33}, {"text": "the complexity about,\nand I can prove", "start": 722.83, "duration": 2.73}, {"text": "that I can solve it if I\nhad a black box to solve B--", "start": 725.56, "duration": 6.15}, {"text": "any black box to\nsolve B, and I could", "start": 731.71, "duration": 2.22}, {"text": "make this reduction\nin polynomial time,", "start": 733.93, "duration": 3.32}, {"text": "and if this is hard, that\nmeans this can't be--", "start": 737.25, "duration": 3.98}, {"text": "that means that if\nthis is hard, then", "start": 743.77, "duration": 2.4}, {"text": "I better not be able to solve\nthis in polynomial time,", "start": 746.17, "duration": 3.69}, {"text": "because then I would be able to\nsolve this in polynomial time.", "start": 749.86, "duration": 2.65}, {"text": "So that's basically\nthe type of argument", "start": 752.51, "duration": 3.32}, {"text": "usually in a\ntrue/false question we", "start": 755.83, "duration": 1.77}, {"text": "might have on the\nfinal exam for you", "start": 757.6, "duration": 2.85}, {"text": "to kind of understand the basic\nhigh-level definitions involved", "start": 760.45, "duration": 4.68}, {"text": "in what was talked\nabout in lecture 19.", "start": 765.13, "duration": 4.02}, {"text": "Hardness-- the very most\ndifficult problems of these", "start": 769.15, "duration": 3.72}, {"text": "classes--", "start": 772.87, "duration": 0.72}, {"text": "and completeness--\nsorry, anything harder", "start": 773.59, "duration": 3.75}, {"text": "than things in these classes.", "start": 777.34, "duration": 1.95}, {"text": "Whereas completeness is\nthe ones that are in this", "start": 779.29, "duration": 3.03}, {"text": "set, but at least as hard as\nanything in those classes.", "start": 782.32, "duration": 3.57}, {"text": "So that's just to give\nyou a brief overview", "start": 785.89, "duration": 3.45}, {"text": "of the only material\nthat hasn't been tested", "start": 789.34, "duration": 3.36}, {"text": "but might be tested\non the final.", "start": 792.7, "duration": 3.21}, {"text": "So when we don't have\na good algorithm,", "start": 795.91, "duration": 4.17}, {"text": "we can actually prove\nthat it probably", "start": 800.08, "duration": 4.74}, {"text": "doesn't have a good algorithm.", "start": 804.82, "duration": 2.37}, {"text": "And that's a problem\nthat you'll be", "start": 807.19, "duration": 2.94}, {"text": "able to solve in\nfuture classes, if you", "start": 810.13, "duration": 2.46}, {"text": "continue along this track.", "start": 812.59, "duration": 1.78}, {"text": "OK, so what's the actual\ncontent that we talked about?", "start": 814.37, "duration": 4.34}, {"text": "This is a very\nhigh-level overview", "start": 818.71, "duration": 1.68}, {"text": "of why we're taking this class,\nwhy you're taking this class.", "start": 820.39, "duration": 3.27}, {"text": "But what is the content\nwe actually covered?", "start": 823.66, "duration": 2.91}, {"text": "I like to break it up into\nthree units and, in a sense,", "start": 826.57, "duration": 5.77}, {"text": "two subunits.", "start": 832.34, "duration": 1.95}, {"text": "So quiz 1 material and quiz 2\nmaterial was about showing you", "start": 834.29, "duration": 10.02}, {"text": "some nice black boxes.", "start": 844.31, "duration": 2.1}, {"text": "Basically, if I'm going to have\ninputs of non-constant size,", "start": 846.41, "duration": 3.81}, {"text": "it's going to be useful for\nme to be able to find things", "start": 850.22, "duration": 3.78}, {"text": "among those elements.", "start": 854.0, "duration": 2.24}, {"text": "So that's really what\nquiz 1 is all about--", "start": 856.24, "duration": 3.67}, {"text": "data structures\nfor finding things", "start": 859.91, "duration": 10.41}, {"text": "in non-constant size database.", "start": 870.32, "duration": 17.92}, {"text": "Sure.", "start": 888.24, "duration": 0.85}, {"text": "And when we were\nstoring these things,", "start": 889.09, "duration": 2.07}, {"text": "we want to support maybe two\ndifferent types of queries--", "start": 891.16, "duration": 3.135}, {"text": "ones that were intrinsic to\nthe items, what the items were,", "start": 899.52, "duration": 4.44}, {"text": "and ones based on what--\nan extrinsic order", "start": 903.96, "duration": 3.18}, {"text": "was placed on these items.", "start": 907.14, "duration": 3.21}, {"text": "And that was a way in\nwhich we broke down,", "start": 910.35, "duration": 3.033}, {"text": "how should I approach\nlooking at this problem?", "start": 913.383, "duration": 1.917}, {"text": "I want to be able to\nsupport queries and maintain", "start": 915.3, "duration": 2.97}, {"text": "an extrinsic order\non these things.", "start": 918.27, "duration": 1.65}, {"text": "I might want a sequence.", "start": 919.92, "duration": 2.17}, {"text": "This is a sequence\nextrinsic order.", "start": 922.09, "duration": 8.0}, {"text": "Or I want to be able to look\nup, is this thing in my set,", "start": 933.03, "duration": 6.13}, {"text": "by a key that we identify,\nwith a unique key.", "start": 939.16, "duration": 4.48}, {"text": "So this is some intrinsic\nqueries, and often order.", "start": 943.64, "duration": 7.29}, {"text": "A hash table doesn't maintain\nany order on my keys.", "start": 954.69, "duration": 4.35}, {"text": "But it does support\nintrinsic queries--", "start": 959.04, "duration": 1.89}, {"text": "is this thing in my set or not?", "start": 960.93, "duration": 1.99}, {"text": "But we did show you\nother set data structures", "start": 962.92, "duration": 2.48}, {"text": "that do support an\nintrinsic order that", "start": 965.4, "duration": 2.76}, {"text": "allows me to see what the next\nlarger and the next previous--", "start": 968.16, "duration": 4.17}, {"text": "the next larger and the next\nsmaller item is in my set.", "start": 972.33, "duration": 7.81}, {"text": "So here's a summary of those\ndata structures that we had.", "start": 980.14, "duration": 4.87}, {"text": "I'm not going to go into\nhow to use these things", "start": 985.01, "duration": 3.09}, {"text": "or how to choose\nfrom among them here.", "start": 988.1, "duration": 2.64}, {"text": "That's what your quiz 1\nreview lecture was all about.", "start": 990.74, "duration": 5.97}, {"text": "But basically, the idea here\nis, if we have a sequence,", "start": 996.71, "duration": 3.97}, {"text": "most of the time when\nyou're programming,", "start": 1000.68, "duration": 3.4}, {"text": "being able to push and\npop at the end of a list", "start": 1004.08, "duration": 3.24}, {"text": "is pretty good.", "start": 1007.32, "duration": 0.87}, {"text": "Which is why Python, the\nmost fundamental data", "start": 1008.19, "duration": 3.15}, {"text": "structure that you have,\nis a list, because it's", "start": 1011.34, "duration": 3.21}, {"text": "a super useful thing.", "start": 1014.55, "duration": 1.26}, {"text": "I just want to store\na bunch of things,", "start": 1015.81, "duration": 1.89}, {"text": "have random access to the,\nsay, 10th element to my thing,", "start": 1017.7, "duration": 6.81}, {"text": "but I'm not necessarily\nhaving to dynamically update", "start": 1024.51, "duration": 4.53}, {"text": "the order of these\nthings dynamically.", "start": 1029.04, "duration": 4.14}, {"text": "I don't necessarily\nhave to insert something", "start": 1033.18, "duration": 2.04}, {"text": "in the middle of the list.", "start": 1035.22, "duration": 1.47}, {"text": "But most of the\ntime, what I can do", "start": 1036.69, "duration": 1.649}, {"text": "is put it at the end of the\nlist and maybe swap it down", "start": 1038.339, "duration": 3.451}, {"text": "into place if I need to.", "start": 1041.79, "duration": 2.579}, {"text": "So that's why a list\nis super useful.", "start": 1044.369, "duration": 2.46}, {"text": "A sequence AVL tree,\nuseful, but not", "start": 1046.829, "duration": 4.801}, {"text": "as ubiquitous as a linked list--", "start": 1051.63, "duration": 1.89}, {"text": "I mean, as a dynamic\narray, sorry.", "start": 1053.52, "duration": 2.43}, {"text": "I said linked list,\nI meant Python list,", "start": 1055.95, "duration": 2.88}, {"text": "which is a dynamic array.", "start": 1058.83, "duration": 2.31}, {"text": "So the dynamic\narray tended to be,", "start": 1061.14, "duration": 2.28}, {"text": "in your coding practice, your\nmost common sequence data", "start": 1063.42, "duration": 4.5}, {"text": "structure here.", "start": 1067.92, "duration": 1.08}, {"text": "Though, we can get pretty\ngood for this insert", "start": 1069.0, "duration": 3.39}, {"text": "in the middle operation\nwith the sequence AVL.", "start": 1072.39, "duration": 2.94}, {"text": "OK, then on the set\ndata structure side,", "start": 1075.33, "duration": 3.63}, {"text": "I categorize these things into\na couple different categories", "start": 1078.96, "duration": 4.265}, {"text": "here in terms of the operations\nwe can support on these things.", "start": 1083.225, "duration": 2.625}, {"text": "These are all intrinsic\noperations-- finding things,", "start": 1085.85, "duration": 2.8}, {"text": "inserting, deleting things.", "start": 1088.65, "duration": 1.53}, {"text": "I think of the first three as\nbeing dictionary operations.", "start": 1090.18, "duration": 4.41}, {"text": "I want to just look up\nwhether something's there.", "start": 1094.59, "duration": 4.11}, {"text": "Whereas the last two are\norder-preserving operations,", "start": 1098.7, "duration": 5.22}, {"text": "where it matters what the order\nof these things are stored in.", "start": 1103.92, "duration": 4.14}, {"text": "And so as you can see from\nthe asymptotic complexity", "start": 1108.06, "duration": 6.54}, {"text": "of the various operations\nhere, the hash table", "start": 1114.6, "duration": 2.73}, {"text": "is actually super good if you\nwant the dictionary oper--", "start": 1117.33, "duration": 3.36}, {"text": "if you just want to support\ndictionary operations.", "start": 1120.69, "duration": 3.79}, {"text": "But in the cases where you need\nto maintain order dynamically,", "start": 1124.48, "duration": 3.68}, {"text": "a set AVL is the way to go.", "start": 1128.16, "duration": 3.43}, {"text": "But if you don't\nneed it dynamic,", "start": 1131.59, "duration": 1.41}, {"text": "but you still need\nthose order operations,", "start": 1133.0, "duration": 1.98}, {"text": "a sorted array is\njust good enough", "start": 1134.98, "duration": 2.01}, {"text": "if you don't need to\nchange what they are.", "start": 1136.99, "duration": 2.61}, {"text": "So that's a quick overview of\nquiz 1-type data structures", "start": 1139.6, "duration": 7.47}, {"text": "material.", "start": 1147.07, "duration": 1.32}, {"text": "But then we used most\nof these data structures", "start": 1148.39, "duration": 3.36}, {"text": "to get faster sorting algorithms\nin different contexts.", "start": 1151.75, "duration": 3.335}, {"text": "Basically, everything\non this list", "start": 1158.76, "duration": 2.25}, {"text": "involved making a data structure\nand exploiting that data", "start": 1161.01, "duration": 4.65}, {"text": "structure to get a\nbetter running time,", "start": 1165.66, "duration": 1.8}, {"text": "all except for\nmerge sort, really.", "start": 1167.46, "duration": 3.32}, {"text": "The first two we presented\nin terms of a priority queue,", "start": 1170.78, "duration": 4.95}, {"text": "whether we used a sorted\narray or an array.", "start": 1175.73, "duration": 2.97}, {"text": "We represented it at\nthe end of lecture eight", "start": 1178.7, "duration": 6.1}, {"text": "to get n-squared running time.", "start": 1184.8, "duration": 1.8}, {"text": "We generalized that down\nto n log n by using a heap.", "start": 1186.6, "duration": 3.78}, {"text": "That was a nice optimization.", "start": 1190.38, "duration": 2.1}, {"text": "But we also got interesting\ndata structures using an--", "start": 1192.48, "duration": 4.38}, {"text": "I mean, interesting sorting\nalgorithms using an AVL tree", "start": 1196.86, "duration": 3.87}, {"text": "because of the\npower of maintaining", "start": 1200.73, "duration": 1.98}, {"text": "a dynamic order over time.", "start": 1202.71, "duration": 2.58}, {"text": "But then exploiting a direct\naccess array to be able to sort", "start": 1205.29, "duration": 5.79}, {"text": "in linear time for\nsmall-bounded--", "start": 1211.08, "duration": 3.78}, {"text": "bounded in terms of\nthe input, polynomially", "start": 1214.86, "duration": 2.67}, {"text": "bounded in terms of the\ninput-- ranges of numbers.", "start": 1217.53, "duration": 3.09}, {"text": "So we leverage that direct axis\narray to get counting sort.", "start": 1220.62, "duration": 5.13}, {"text": "And then we kind of\namplified that effect", "start": 1225.75, "duration": 4.56}, {"text": "by sorting on a bunch\nof digits multiple times", "start": 1230.31, "duration": 4.08}, {"text": "to get basically polynomial\nblow-up in terms of the numbers", "start": 1234.39, "duration": 4.53}, {"text": "that we could sort\nin linear time.", "start": 1238.92, "duration": 2.65}, {"text": "So that's an overview of\nthe content of quiz 1.", "start": 1241.57, "duration": 4.956}, {"text": "In quiz 2, we were kind\nof like, OK, now you", "start": 1246.526, "duration": 4.954}, {"text": "know how to find things\nwithin a set of just", "start": 1251.48, "duration": 5.73}, {"text": "a flat list of things, you can\nput it in a data structure.", "start": 1257.21, "duration": 3.21}, {"text": "But in a sense, a graph is a\nspecial kind of data structure", "start": 1260.42, "duration": 4.29}, {"text": "that relates the different\nthings in your input.", "start": 1264.71, "duration": 4.23}, {"text": "So if you've got a\nbunch of vertices,", "start": 1268.94, "duration": 5.13}, {"text": "there's a relation now\nbetween those vertices", "start": 1274.07, "duration": 3.03}, {"text": "that are your edges.", "start": 1277.1, "duration": 1.3}, {"text": "And this is a super\nuseful framework", "start": 1278.4, "duration": 2.24}, {"text": "in talking about\ndiscrete systems,", "start": 1280.64, "duration": 2.34}, {"text": "because you can\nthink of a vertex", "start": 1282.98, "duration": 2.07}, {"text": "as a state of your system, and\nthen connect these transitions", "start": 1285.05, "duration": 4.11}, {"text": "as a graph.", "start": 1289.16, "duration": 1.26}, {"text": "That's the reason why--", "start": 1290.42, "duration": 2.61}, {"text": "I mean, graphs are\nawesome, but they're", "start": 1293.03, "duration": 2.94}, {"text": "awesome because they\ncan be used to model", "start": 1295.97, "duration": 2.17}, {"text": "so many different\nthings within our world.", "start": 1298.14, "duration": 2.45}, {"text": "It's not just about\nroad networks.", "start": 1300.59, "duration": 3.9}, {"text": "It can also be about playing\nyour favorite turn-based game,", "start": 1304.49, "duration": 5.38}, {"text": "like Tilt.", "start": 1309.87, "duration": 1.8}, {"text": "OK, so we talked about a lot\nof different types of problems", "start": 1311.67, "duration": 3.86}, {"text": "that you could solve,\nvarious algorithms,", "start": 1315.53, "duration": 1.8}, {"text": "with a focus on a bunch of\ndifferent ways of solving", "start": 1317.33, "duration": 3.96}, {"text": "single-source shortest paths.", "start": 1321.29, "duration": 2.34}, {"text": "And again, just like\nthe sorting algorithms", "start": 1323.63, "duration": 1.943}, {"text": "and just like the\ndata structures,", "start": 1325.573, "duration": 1.417}, {"text": "we presented multiple\nof them, because we", "start": 1326.99, "duration": 3.93}, {"text": "had this trade-off of\ngenerality of the graph", "start": 1330.92, "duration": 3.39}, {"text": "that they apply to contrasted\nwith the running time.", "start": 1334.31, "duration": 4.93}, {"text": "So I guess, in\nparticular, the top line", "start": 1339.24, "duration": 7.55}, {"text": "there is, in some sense,\nthe most restrictive.", "start": 1346.79, "duration": 2.82}, {"text": "We don't have any\ncycles in our graph.", "start": 1349.61, "duration": 1.89}, {"text": "That's a very special\ntype of graph,", "start": 1351.5, "duration": 1.5}, {"text": "and we're able to\nget linear time.", "start": 1353.0, "duration": 3.08}, {"text": "But then even if we do\nhave cycles in our graph,", "start": 1356.08, "duration": 2.1}, {"text": "we can do better if we\nhave a bound on the weights", "start": 1358.18, "duration": 3.24}, {"text": "in our thing, whether they be--", "start": 1361.42, "duration": 3.84}, {"text": "there's an easy conversion\nto a linear time algorithm", "start": 1365.26, "duration": 2.49}, {"text": "via an unweighted process,\nor whether these things are", "start": 1367.75, "duration": 3.42}, {"text": "non-negative, so there can't\nbe negative weight cycles,", "start": 1371.17, "duration": 2.31}, {"text": "and we don't have\nto deal with that.", "start": 1373.48, "duration": 1.56}, {"text": "OK, so that's quiz 2 material.", "start": 1375.04, "duration": 3.93}, {"text": "And then quiz 3\nmaterial was kind", "start": 1378.97, "duration": 3.3}, {"text": "of applying this graph material\nto a recursive framework.", "start": 1382.27, "duration": 5.64}, {"text": "What was our\nrecursive framework?", "start": 1387.91, "duration": 1.53}, {"text": "Everyone say it with me.", "start": 1389.44, "duration": 1.14}, {"text": "AUDIENCE: Dynamic programming.", "start": 1390.58, "duration": 1.1}, {"text": "JASON KU: Dynamic\nprogramming, and the framework", "start": 1391.68, "duration": 2.0}, {"text": "was SRT BOT, right?", "start": 1393.68, "duration": 2.09}, {"text": "Missing a letter,\nbut SORT BOT, right?", "start": 1395.77, "duration": 2.94}, {"text": "You can actually\nthink of the quiz 3", "start": 1398.71, "duration": 2.97}, {"text": "material as really an\napplication of the graph", "start": 1401.68, "duration": 4.92}, {"text": "material.", "start": 1406.6, "duration": 2.26}, {"text": "What are we doing in SORT BOT?", "start": 1408.86, "duration": 2.18}, {"text": "We're defining a\nset of subproblems.", "start": 1411.04, "duration": 3.31}, {"text": "These are a set of\nvertices in a graph.", "start": 1414.35, "duration": 2.97}, {"text": "What is the relationship doing?", "start": 1417.32, "duration": 1.92}, {"text": "It's saying, what\nare the relation", "start": 1419.24, "duration": 3.93}, {"text": "between the\nsubproblems, essentially", "start": 1423.17, "duration": 2.31}, {"text": "defining the edges of a graph?", "start": 1425.48, "duration": 3.29}, {"text": "And then this topological\norder and the base cases,", "start": 1428.77, "duration": 3.81}, {"text": "all of these things\nare just saying,", "start": 1432.58, "duration": 1.89}, {"text": "what is the problem that I\nwant to solve on this graph?", "start": 1434.47, "duration": 2.73}, {"text": "And how do I compute\nthat for things that", "start": 1437.2, "duration": 4.38}, {"text": "don't have any outgoing edges?", "start": 1441.58, "duration": 3.09}, {"text": "I need to start writing\non the board again.", "start": 1444.67, "duration": 2.28}, {"text": "This is graphs.", "start": 1446.95, "duration": 2.64}, {"text": "There was sorting in here, too.", "start": 1449.59, "duration": 5.34}, {"text": "This is basically\nan application.", "start": 1454.93, "duration": 1.8}, {"text": "OK, graphs was\nbasically a relationship", "start": 1461.07, "duration": 3.31}, {"text": "on these non-constant things.", "start": 1464.38, "duration": 1.95}, {"text": "So this was kind of\nlike useful black boxes", "start": 1470.16, "duration": 5.54}, {"text": "that you can just bundle up\nand stick in some inputs,", "start": 1475.7, "duration": 4.03}, {"text": "stick out some outputs,\nand you're golden.", "start": 1479.73, "duration": 3.47}, {"text": "Whereas quiz 3 was\nvery different,", "start": 1483.2, "duration": 2.79}, {"text": "the material in quiz\n3 is very different.", "start": 1485.99, "duration": 1.74}, {"text": "Dynamic programming, while\nit was, in some sense,", "start": 1487.73, "duration": 11.76}, {"text": "related to this graph material--", "start": 1499.49, "duration": 1.43}, {"text": "I'm constructing a graph--", "start": 1500.92, "duration": 1.98}, {"text": "I have to construct that graph.", "start": 1502.9, "duration": 1.71}, {"text": "There's a creative process in\ntrying to construct that graph.", "start": 1504.61, "duration": 4.05}, {"text": "I don't give you\na set of vertices.", "start": 1508.66, "duration": 1.53}, {"text": "Usually what I give\nyou are a set of--", "start": 1510.19, "duration": 3.99}, {"text": "a sequence or\nsomething like that.", "start": 1514.18, "duration": 1.59}, {"text": "And you have to construct\nvertices, subproblems,", "start": 1515.77, "duration": 4.07}, {"text": "that will be able to be\nrelated in a recursive way", "start": 1519.84, "duration": 3.03}, {"text": "so you can solve the problem.", "start": 1522.87, "duration": 1.42}, {"text": "This is a very much\nmore difficult thing", "start": 1524.29, "duration": 3.05}, {"text": "than these other\nthings, I think,", "start": 1527.34, "duration": 1.86}, {"text": "because there's a lot\nmore creativity in this.", "start": 1529.2, "duration": 3.36}, {"text": "In the same way\nthat just applying--", "start": 1532.56, "duration": 2.97}, {"text": "reducing to the graph algorithms\nwe have is fairly easy.", "start": 1535.53, "duration": 4.3}, {"text": "But actually doing some\ngraph transformations", "start": 1539.83, "duration": 3.08}, {"text": "to change the shape\nof the graph so", "start": 1542.91, "duration": 1.98}, {"text": "that you can apply\nthese algorithms, that's", "start": 1544.89, "duration": 2.25}, {"text": "a harder thing to do.", "start": 1547.14, "duration": 3.18}, {"text": "The difficulty with these\ntwo sets of materials", "start": 1550.32, "duration": 3.21}, {"text": "is very similar.", "start": 1553.53, "duration": 1.65}, {"text": "Figuring out what\nthe graph should be,", "start": 1555.18, "duration": 1.778}, {"text": "figuring out what the\nsubproblems should be", "start": 1556.958, "duration": 1.792}, {"text": "and how they relate, is really\nthe entire part of the--", "start": 1558.75, "duration": 3.846}, {"text": "the entire difficulty with\nsolving problems recursively.", "start": 1562.596, "duration": 4.794}, {"text": "And we've only given you a\ntaste of solving problems", "start": 1567.39, "duration": 2.82}, {"text": "recursively.", "start": 1570.21, "duration": 2.26}, {"text": "In future classes,\nlike 6.046, which", "start": 1572.47, "duration": 4.83}, {"text": "is the follow-on to this one in\nthe undergraduate curriculum,", "start": 1577.3, "duration": 4.19}, {"text": "this is all about\nintroduction to algorithms.", "start": 1581.49, "duration": 2.15}, {"text": "The next one's about design\nand analysis of algorithms.", "start": 1583.64, "duration": 3.57}, {"text": "It's quite a bit more\ndifficult, because we've mostly", "start": 1587.21, "duration": 6.92}, {"text": "left it to you to use the\nthings that we gave you", "start": 1594.13, "duration": 5.58}, {"text": "or make your own\nalgorithms based", "start": 1599.71, "duration": 2.64}, {"text": "on this very nice\ncookbook-like framework", "start": 1602.35, "duration": 4.56}, {"text": "that you can plug in a\nrecursive algorithm to.", "start": 1606.91, "duration": 2.7}, {"text": "Now actually, that\ncookbook is super", "start": 1609.61, "duration": 1.71}, {"text": "nice for any way of looking\nat a problem recursively,", "start": 1611.32, "duration": 4.89}, {"text": "but while in\ndynamic programming,", "start": 1616.21, "duration": 7.09}, {"text": "the inductive hypothesis of\ncombining your subproblems", "start": 1623.3, "duration": 5.43}, {"text": "is almost trivial,\nin other types", "start": 1628.73, "duration": 4.12}, {"text": "of recursive algorithms, that's\nnot necessarily the case.", "start": 1632.85, "duration": 4.27}, {"text": "Especially when\ninstead of looking", "start": 1637.12, "duration": 2.0}, {"text": "at all possible\nchoices, for example,", "start": 1639.12, "duration": 3.44}, {"text": "in a greedy algorithm\nwhere you're just", "start": 1642.56, "duration": 1.82}, {"text": "looking at one of the choices,\nthe locally best thing,", "start": 1644.38, "duration": 3.24}, {"text": "and recursing forward, you're\nnot doing all the work.", "start": 1647.62, "duration": 3.93}, {"text": "You're not locally\nbrute-forcing.", "start": 1651.55, "duration": 1.5}, {"text": "Your locally picking an optimal\nthing locally and hoping that", "start": 1653.05, "duration": 4.02}, {"text": "will lead you to good thing.", "start": 1657.07, "duration": 1.56}, {"text": "That's a much harder algorithmic\nparadigm to operate under.", "start": 1658.63, "duration": 5.88}, {"text": "And so that's more\nlike the material", "start": 1664.51, "duration": 2.61}, {"text": "that you'll be talking\nabout in 6.046.", "start": 1667.12, "duration": 3.06}, {"text": "So that's 006, a very quick\noverview of the content of this", "start": 1670.18, "duration": 9.38}, {"text": "class.", "start": 1679.56, "duration": 1.24}, {"text": "And we really like the structure\nof how this class is laid out,", "start": 1680.8, "duration": 4.43}, {"text": "because it gives you a\nfundamental idea of the things", "start": 1685.23, "duration": 2.91}, {"text": "people use to store information\non a computer and a sense", "start": 1688.14, "duration": 5.85}, {"text": "of how you solve\nproblems computationally", "start": 1693.99, "duration": 2.7}, {"text": "and how to argue that they're\ncorrect and efficient.", "start": 1696.69, "duration": 3.09}, {"text": "That's really what\nthis problem--", "start": 1699.78, "duration": 1.86}, {"text": "this course is about.", "start": 1701.64, "duration": 4.01}, {"text": "And if you feel like you\nenjoy this kind of stuff,", "start": 1705.65, "duration": 4.73}, {"text": "that's where you\ngo to take 6.046.", "start": 1710.38, "duration": 4.68}, {"text": "And 6.046 was actually\nthe first algorithms class", "start": 1715.06, "duration": 4.02}, {"text": "I ever took here at MIT,\nas a grad student actually.", "start": 1719.08, "duration": 4.665}, {"text": "This was hard for me.", "start": 1726.37, "duration": 2.94}, {"text": "It's actually hard to look at\nthese problems, these types,", "start": 1729.31, "duration": 4.08}, {"text": "and think in a\ncomputational way,", "start": 1733.39, "duration": 2.01}, {"text": "especially having not\ntaken this class, 6.006.", "start": 1735.4, "duration": 4.05}, {"text": "So hopefully you guys are\nall in a better position", "start": 1739.45, "duration": 2.97}, {"text": "than I was when I took it.", "start": 1742.42, "duration": 2.09}, {"text": "There's two ways I like to\nthink of the content in 6.046.", "start": 1744.51, "duration": 4.77}, {"text": "One is kind of just as\nan extension of 006.", "start": 1749.28, "duration": 3.6}, {"text": "It's the natural\nfollow-on to the things", "start": 1752.88, "duration": 1.92}, {"text": "that we do in this class.", "start": 1754.8, "duration": 1.77}, {"text": "They still talk about\ndata structures.", "start": 1756.57, "duration": 2.677}, {"text": "This isn't the core part of\n046, but they do touch on data", "start": 1763.15, "duration": 4.88}, {"text": "structures for\nmore complicated--", "start": 1768.03, "duration": 3.15}, {"text": "that have more complicated\nanalyses involved in them.", "start": 1771.18, "duration": 2.79}, {"text": "It's really about--\nusually in 046,", "start": 1773.97, "duration": 4.02}, {"text": "stating what the algorithm\nis doing is not so hard.", "start": 1777.99, "duration": 4.93}, {"text": "Basically, giving\nyou the algorithm,", "start": 1782.92, "duration": 3.06}, {"text": "number one here, is\nnot so difficult,", "start": 1785.98, "duration": 3.21}, {"text": "to state what's happening\nin the algorithm.", "start": 1789.19, "duration": 3.24}, {"text": "But the number two\nand number three here,", "start": 1792.43, "duration": 3.3}, {"text": "arguing that that thing is\ncorrect and arguing that thing", "start": 1795.73, "duration": 3.33}, {"text": "is efficient, that's where the\ncomplexity comes in in 046.", "start": 1799.06, "duration": 5.37}, {"text": "The analysis part is quite a\nbit more complicated in 046 than", "start": 1804.43, "duration": 3.93}, {"text": "in 006.", "start": 1808.36, "duration": 1.56}, {"text": "So they solve a problem called\nunion-find and give a much--", "start": 1809.92, "duration": 7.32}, {"text": "we talked a little bit\nabout amortization.", "start": 1817.24, "duration": 2.46}, {"text": "This goes into a much better-- a\nmuch more formal way of proving", "start": 1819.7, "duration": 4.59}, {"text": "things run in amortized time.", "start": 1824.29, "duration": 5.55}, {"text": "So this is basically\namortization via what", "start": 1829.84, "duration": 8.85}, {"text": "we call a potential analysis.", "start": 1838.69, "duration": 1.68}, {"text": "It's basically\nmaking that notion", "start": 1846.03, "duration": 5.022}, {"text": "that we talked about\nwhen we were talking", "start": 1851.052, "duration": 1.708}, {"text": "about dynamic arrays of, we're\nnot doing this expensive thing", "start": 1852.76, "duration": 4.38}, {"text": "too often.", "start": 1857.14, "duration": 1.17}, {"text": "Basically what we\ndo is we keep track", "start": 1858.31, "duration": 1.86}, {"text": "of the cost of all\nsequence of operations", "start": 1860.17, "duration": 2.97}, {"text": "and prove that the\naverage cost is small.", "start": 1863.14, "duration": 3.6}, {"text": "That's kind of what this\npotential analysis is doing.", "start": 1866.74, "duration": 3.498}, {"text": "It's a little bit\nmore formal process", "start": 1870.238, "duration": 1.542}, {"text": "for making that argument\na little more formal.", "start": 1871.78, "duration": 3.99}, {"text": "Right.", "start": 1875.77, "duration": 0.5}, {"text": "OK.", "start": 1876.27, "duration": 0.5}, {"text": "So then on the\ngraph side, this is", "start": 1876.77, "duration": 2.57}, {"text": "kind of an extension of\nquiz 1-type material.", "start": 1879.34, "duration": 3.27}, {"text": "This is, what is this\nunion-find data structure?", "start": 1882.61, "duration": 2.53}, {"text": "It's basically-- it's\na set type thing, where", "start": 1885.14, "duration": 6.26}, {"text": "I can make a set of\njust a single element,", "start": 1891.4, "duration": 5.9}, {"text": "I can take two sets, merge\nthem together, make them", "start": 1897.3, "duration": 4.92}, {"text": "their union, and then\ngiven an object, I say,", "start": 1902.22, "duration": 5.22}, {"text": "which set am I part of,\nessentially by electing", "start": 1907.44, "duration": 4.53}, {"text": "a leader within\na set and saying,", "start": 1911.97, "duration": 1.95}, {"text": "return me a pointer to that one.", "start": 1913.92, "duration": 3.36}, {"text": "And so this can be useful\nin dynamically maintaining,", "start": 1917.28, "duration": 3.45}, {"text": "say, the connected components\nin a dynamically changing graph", "start": 1920.73, "duration": 5.04}, {"text": "supporting the query of,\nam I in the same component", "start": 1925.77, "duration": 3.75}, {"text": "as this other guy?", "start": 1929.52, "duration": 1.83}, {"text": "That could be a very useful\nthing to know about a graph", "start": 1931.35, "duration": 2.52}, {"text": "as it's changing.", "start": 1933.87, "duration": 0.93}, {"text": "So that's an application\nof this problem.", "start": 1934.8, "duration": 2.34}, {"text": "And they get\nnear-constant performance", "start": 1937.14, "duration": 3.18}, {"text": "for a lot of these queries.", "start": 1940.32, "duration": 1.68}, {"text": "It's not quite,\nbut pretty close.", "start": 1942.0, "duration": 3.36}, {"text": "OK, on the graph\nside, they solve", "start": 1945.36, "duration": 2.01}, {"text": "a number of very useful\nproblems on graphs.", "start": 1947.37, "duration": 4.98}, {"text": "Minimum Spanning\nTree-- so I'm trying", "start": 1952.35, "duration": 3.42}, {"text": "to find a tree connecting\nall of the vertices", "start": 1955.77, "duration": 3.96}, {"text": "in a connected\ncomponent of my graph.", "start": 1959.73, "duration": 2.46}, {"text": "And I'm trying to find--\nin a weighted graph,", "start": 1962.19, "duration": 1.98}, {"text": "I'm trying to find\nthe spanning tree that", "start": 1964.17, "duration": 2.79}, {"text": "has minimum total weight.", "start": 1966.96, "duration": 2.28}, {"text": "So that's a problem--", "start": 1969.24, "duration": 1.78}, {"text": "a fundamental problem in\nweighted-graph algorithms.", "start": 1971.02, "duration": 4.61}, {"text": "They've solved this\nvia a greedy algorithm.", "start": 1975.63, "duration": 4.05}, {"text": "And network flows\nand I guess cuts.", "start": 1979.68, "duration": 10.68}, {"text": "So this is-- what is this?", "start": 1990.36, "duration": 1.67}, {"text": "This is, I'm given\na weighted graph.", "start": 1992.03, "duration": 3.81}, {"text": "Basically, each of the weights\ncorrespond to a capacity.", "start": 1995.84, "duration": 5.28}, {"text": "I could push water\nthrough along this edge.", "start": 2001.12, "duration": 2.76}, {"text": "And I may be given a source\nvertex and a sink vertex.", "start": 2003.88, "duration": 4.95}, {"text": "And I want to say, I\nwant to shove water", "start": 2008.83, "duration": 2.67}, {"text": "through the source\nvertex along the edges", "start": 2011.5, "duration": 4.32}, {"text": "with their various capacities.", "start": 2015.82, "duration": 2.07}, {"text": "And I'll get some\namount of water", "start": 2017.89, "duration": 2.25}, {"text": "on the other end in the source.", "start": 2020.14, "duration": 3.0}, {"text": "So the question is, what's\nthe most amount of water", "start": 2023.14, "duration": 3.332}, {"text": "that I can push through this?", "start": 2026.472, "duration": 1.208}, {"text": "Well, I could build\nthat pipe network", "start": 2027.68, "duration": 2.963}, {"text": "with the different things and\njust do this experimentally.", "start": 2030.643, "duration": 2.417}, {"text": "I just stick a bunch of--", "start": 2033.06, "duration": 1.96}, {"text": "maybe-- I'm a\nmechanical engineer,", "start": 2035.02, "duration": 1.8}, {"text": "so that maybe makes sense to me.", "start": 2036.82, "duration": 1.62}, {"text": "But you want to be able to\njust look at those numbers", "start": 2038.44, "duration": 2.76}, {"text": "and be able to tell me how\nmuch water can I push through.", "start": 2041.2, "duration": 3.06}, {"text": "That's what the max flow in\na network is talking about.", "start": 2044.26, "duration": 4.47}, {"text": "And we give you some polynomial\ntime algorithms in this class,", "start": 2048.73, "duration": 3.33}, {"text": "basically incremental algorithms\nthat, kind of like Dijkstra,", "start": 2052.06, "duration": 4.26}, {"text": "or kind of like Bellman-Ford,\nwill incrementally update", "start": 2056.32, "duration": 5.76}, {"text": "estimates to--", "start": 2062.08, "duration": 3.24}, {"text": "of a max flow and\nimprove them over time.", "start": 2065.32, "duration": 3.629}, {"text": "Then on the, basically,\ndesign paradigms,", "start": 2071.98, "duration": 10.5}, {"text": "you've got more involved making\nyour own divide-and-conquer", "start": 2082.48, "duration": 4.11}, {"text": "algorithms, dynamic programming\nalgorithms, greedy algorithms.", "start": 2086.59, "duration": 11.34}, {"text": "Basically, they go\na lot more in depth", "start": 2097.93, "duration": 2.97}, {"text": "in terms of how to design these\nalgorithms and these paradigms", "start": 2100.9, "duration": 3.39}, {"text": "than we do in this class.", "start": 2104.29, "duration": 2.79}, {"text": "And then the last thing is--", "start": 2107.08, "duration": 3.09}, {"text": "we only touched on complexity.", "start": 2110.17, "duration": 3.81}, {"text": "And in a sense, 046 is only\ngoing to touch on complexity.", "start": 2113.98, "duration": 4.42}, {"text": "It's a very big field.", "start": 2118.4, "duration": 2.12}, {"text": "But it will give\nyou the tools to be", "start": 2120.52, "duration": 3.59}, {"text": "able to prove that something is\nNP-hard, whereas we just kind", "start": 2124.11, "duration": 4.02}, {"text": "of say that, oh, there's this\nthing called a reduction.", "start": 2128.13, "duration": 3.96}, {"text": "We didn't give you any\nproblems in which you actually", "start": 2132.09, "duration": 4.23}, {"text": "had to reduce one\nproblem to another.", "start": 2136.32, "duration": 2.29}, {"text": "And you'll do a lot\nmore of that here.", "start": 2138.61, "duration": 2.13}, {"text": "So, reductions.", "start": 2140.74, "duration": 3.62}, {"text": "So in a big sense, 046 is\nreally just a natural extension", "start": 2144.36, "duration": 8.06}, {"text": "to the 006 material, plus\nsome additional stuff,", "start": 2152.42, "duration": 3.307}, {"text": "which I'm going to\nget to in a second.", "start": 2155.727, "duration": 1.583}, {"text": "Yeah, question?", "start": 2157.31, "duration": 0.63}, {"text": "AUDIENCE: Do you want\nto add randomization", "start": 2157.94, "duration": 1.75}, {"text": "for time paradigms?", "start": 2159.69, "duration": 1.67}, {"text": "JASON KU: I'm going\nto talk about that", "start": 2161.36, "duration": 1.89}, {"text": "slightly in a separate--", "start": 2163.25, "duration": 2.43}, {"text": "I'll get to your question\nin just a second.", "start": 2165.68, "duration": 1.98}, {"text": "I like to think of it as\na separate topic, which", "start": 2167.66, "duration": 3.75}, {"text": "I will go into right now.", "start": 2171.41, "duration": 2.19}, {"text": "The separate topic I like\nto think of it as, instead", "start": 2173.6, "duration": 3.3}, {"text": "of being the natural extension\nto the things in the 006 units,", "start": 2176.9, "duration": 6.14}, {"text": "what I'm going to do is kind\nof relax either what it means", "start": 2183.04, "duration": 5.8}, {"text": "to have a correct algorithm\nor relax what it means to--", "start": 2188.84, "duration": 4.315}, {"text": "what my model of computation is.", "start": 2195.78, "duration": 3.33}, {"text": "So 006, this is kind of\nas an extension of 006.", "start": 2199.11, "duration": 12.19}, {"text": "And this is kind of\nlike 6.046 as change", "start": 2211.3, "duration": 11.67}, {"text": "my definition of what it means\nto be correct or efficient.", "start": 2222.97, "duration": 3.904}, {"text": "So we've already kind of done\nthis a little bit in 006.", "start": 2230.59, "duration": 10.9}, {"text": "Basically, one of the\nthings that we can do,", "start": 2241.49, "duration": 2.05}, {"text": "which is what the question\nthat a student asked a question", "start": 2243.54, "duration": 3.47}, {"text": "about, was about\nrandomized algorithms,", "start": 2247.01, "duration": 2.1}, {"text": "which is a big part\nof 046 actually--", "start": 2249.11, "duration": 3.69}, {"text": "randomized analysis\nof algorithms", "start": 2252.8, "duration": 3.81}, {"text": "that are not deterministic.", "start": 2256.61, "duration": 1.8}, {"text": "It's not guaranteed that\nit'll give you the same output", "start": 2258.41, "duration": 2.73}, {"text": "every time or not\nguaranteed that it", "start": 2261.14, "duration": 2.79}, {"text": "will do the same\ncomputations over the course", "start": 2263.93, "duration": 2.94}, {"text": "of the algorithm every time.", "start": 2266.87, "duration": 1.8}, {"text": "But it exploits\nsome randomization.", "start": 2268.67, "duration": 2.01}, {"text": "And in 006, this is--", "start": 2281.65, "duration": 2.34}, {"text": "we've mostly not touched on\nthis, except in one area.", "start": 2283.99, "duration": 3.54}, {"text": "Where did we use randomization?", "start": 2287.53, "duration": 2.67}, {"text": "In hashing, right?", "start": 2290.2, "duration": 2.07}, {"text": "When we used hashing,\nwhat were we doing?", "start": 2292.27, "duration": 3.81}, {"text": "We changed the definition\nof correct versus efficient.", "start": 2296.08, "duration": 3.15}, {"text": "We didn't really change the\ndefinition, what we did was", "start": 2299.23, "duration": 2.97}, {"text": "we said that it was OK that\nsometimes our algorithm was", "start": 2302.2, "duration": 4.5}, {"text": "slower than we--", "start": 2306.7, "duration": 2.56}, {"text": "than on-- in expectation.", "start": 2309.26, "duration": 2.94}, {"text": "That's what we meant there.", "start": 2312.2, "duration": 1.73}, {"text": "We're relaxing the\nidea of efficient,", "start": 2313.93, "duration": 2.92}, {"text": "but we're still saying\nit's good, because most", "start": 2316.85, "duration": 1.98}, {"text": "of the time it is good.", "start": 2318.83, "duration": 2.22}, {"text": "So there's two types of\nrandomized algorithms.", "start": 2321.05, "duration": 3.81}, {"text": "They have these\nweird names based", "start": 2324.86, "duration": 2.34}, {"text": "on betting regions of\nthe world, shall we say?", "start": 2327.2, "duration": 4.86}, {"text": "There are-- this is L-O?", "start": 2332.06, "duration": 5.998}, {"text": "Los Vegas?", "start": 2338.058, "duration": 1.302}, {"text": "It is Las, OK, Vegas algorithms.", "start": 2339.36, "duration": 5.31}, {"text": "These are always correct,\nbut probably efficient.", "start": 2344.67, "duration": 9.308}, {"text": "In a sense, that's\nwhat hashing is.", "start": 2358.86, "duration": 3.12}, {"text": "I'm always going to give\nyou the right thing,", "start": 2361.98, "duration": 3.12}, {"text": "whether this thing\nis in my set or not.", "start": 2365.1, "duration": 2.04}, {"text": "But some of the time,\nit's inefficient.", "start": 2367.14, "duration": 3.27}, {"text": "I have to look through\na chain of length", "start": 2370.41, "duration": 2.46}, {"text": "of-- that's linear in the size\nof the things that I'm storing.", "start": 2372.87, "duration": 3.24}, {"text": "And this is in contrast to\na Monte Carlo algorithm,", "start": 2376.11, "duration": 7.78}, {"text": "which is always efficient for\nsome definition of efficient,", "start": 2383.89, "duration": 8.21}, {"text": "but only probably correct.", "start": 2392.1, "duration": 1.74}, {"text": "And I mean, I could define you a\nhash table that has Monte Carlo", "start": 2398.64, "duration": 4.53}, {"text": "semantics instead.", "start": 2403.17, "duration": 1.74}, {"text": "Say, for example, I\nsay that I'm going--", "start": 2404.91, "duration": 3.925}, {"text": "it's going to be exactly\nthe same as a hash table,", "start": 2408.835, "duration": 2.925}, {"text": "except instead of storing\nall the things that", "start": 2411.76, "duration": 2.4}, {"text": "collide in a place, I just\nstore the first two, say.", "start": 2414.16, "duration": 4.29}, {"text": "Well, actually, that's actually\ngoing to be always efficient.", "start": 2421.75, "duration": 3.15}, {"text": "I'm going to look\nthrough the things", "start": 2424.9, "duration": 1.5}, {"text": "and see if it's in there.", "start": 2426.4, "duration": 2.72}, {"text": "And the chains that I'm storing\nthere only have two things.", "start": 2429.12, "duration": 3.393}, {"text": "It's going to be\nalways efficient.", "start": 2432.513, "duration": 1.417}, {"text": "It's always going to\ngive me constant time.", "start": 2433.93, "duration": 2.22}, {"text": "But some of the time, it's\ngoing to be the wrong thing,", "start": 2436.15, "duration": 2.51}, {"text": "because I'm not storing\neverything in that chain.", "start": 2438.66, "duration": 2.97}, {"text": "So there's some probability that\nthat's not going to be correct.", "start": 2441.63, "duration": 3.57}, {"text": "And so that's a\ndifferent kind of--", "start": 2445.2, "duration": 2.28}, {"text": "maybe I want my hash\ntables to always be fast,", "start": 2447.48, "duration": 2.85}, {"text": "but I can afford to be\nwrong some of the time.", "start": 2450.33, "duration": 4.018}, {"text": "I don't know.", "start": 2454.348, "duration": 0.542}, {"text": "In practice, this is actually\nsometimes a good trade-off", "start": 2454.89, "duration": 3.0}, {"text": "in real systems.", "start": 2457.89, "duration": 2.01}, {"text": "Sometimes it's OK to be\nwrong some of the times,", "start": 2459.9, "duration": 2.59}, {"text": "if we get good performance.", "start": 2462.49, "duration": 2.74}, {"text": "OK, but generally can do better\nif you allow randomization.", "start": 2465.23, "duration": 18.54}, {"text": "And by better I mean, usually\nwe can get faster bounds", "start": 2483.77, "duration": 4.35}, {"text": "on a lot of problems if we allow\nrandomization and things aren't", "start": 2488.12, "duration": 4.65}, {"text": "necessarily always correct\nor always efficient.", "start": 2492.77, "duration": 3.9}, {"text": "So this is a big area in\n046 that requires a lot more", "start": 2496.67, "duration": 5.46}, {"text": "analysis using randomness\nand probability.", "start": 2502.13, "duration": 5.49}, {"text": "So if you need some\nprimers on that--", "start": 2507.62, "duration": 5.29}, {"text": "we didn't have a lot of this in\n006, but if you go on to 046,", "start": 2512.91, "duration": 4.735}, {"text": "that's going to be a really\nimportant thing for you", "start": 2517.645, "duration": 2.125}, {"text": "to brush up on.", "start": 2519.77, "duration": 2.37}, {"text": "The next part on 006 is kind\nof changing what our definition", "start": 2522.14, "duration": 5.97}, {"text": "of correct or efficient means.", "start": 2528.11, "duration": 2.1}, {"text": "I mean, we've\nrestricted ourselves", "start": 2530.21, "duration": 2.64}, {"text": "in this class to a class\nof problems where we only", "start": 2532.85, "duration": 3.27}, {"text": "talk about integers.", "start": 2536.12, "duration": 2.91}, {"text": "But there's tons of\nproblems in this world,", "start": 2539.03, "duration": 1.87}, {"text": "especially in\nscientific computing,", "start": 2540.9, "duration": 2.0}, {"text": "where I want to be able to find\nout what this real number is.", "start": 2542.9, "duration": 5.61}, {"text": "And I can't even store a\nreal number on my computer.", "start": 2548.51, "duration": 3.44}, {"text": "So what the hell, Jason?", "start": 2551.95, "duration": 1.51}, {"text": "What are you talking about?", "start": 2553.46, "duration": 2.25}, {"text": "I can't do that on a computer.", "start": 2555.71, "duration": 1.71}, {"text": "But what I can do is\nbasically compute things", "start": 2557.42, "duration": 4.26}, {"text": "in a numerical sense--\nnumerical algorithms.", "start": 2561.68, "duration": 4.11}, {"text": "And in 046, a lot of times\nwe put this in the context", "start": 2569.02, "duration": 3.69}, {"text": "of continuous optimization,\ncontinuous being the opportune", "start": 2572.71, "duration": 9.18}, {"text": "word here, not discrete systems.", "start": 2581.89, "duration": 1.86}, {"text": "You have a continuum of\npossible solutions, real numbers", "start": 2583.75, "duration": 4.47}, {"text": "essentially.", "start": 2588.22, "duration": 1.71}, {"text": "How do we do this on a computer\nthat's a discrete system?", "start": 2589.93, "duration": 2.415}, {"text": "Basically, in 046\nwhat you can do,", "start": 2596.35, "duration": 4.2}, {"text": "and in other numerical methods\nclasses, what you can say is,", "start": 2600.55, "duration": 3.87}, {"text": "well, I know that you can't\nreturn me a real number.", "start": 2604.42, "duration": 3.87}, {"text": "I got that.", "start": 2608.29, "duration": 0.63}, {"text": "Or you can maybe have\na model of computation", "start": 2608.92, "duration": 2.97}, {"text": "that allows integers\nto represent", "start": 2611.89, "duration": 2.88}, {"text": "other kinds of real numbers,\nlike radicals or rationals", "start": 2614.77, "duration": 3.632}, {"text": "or something like that.", "start": 2618.402, "duration": 0.958}, {"text": "And I can do\nmanipulations on those.", "start": 2619.36, "duration": 1.86}, {"text": "But really what these\nalgorithms are usually about", "start": 2621.22, "duration": 2.82}, {"text": "is computing real\nnumbers not completely,", "start": 2624.04, "duration": 4.62}, {"text": "but to some bounded precision.", "start": 2628.66, "duration": 2.91}, {"text": "And I pay for that precision.", "start": 2631.57, "duration": 2.76}, {"text": "The more bits of precision\nI want on my number,", "start": 2634.33, "duration": 3.12}, {"text": "I have to pay for them.", "start": 2637.45, "duration": 1.58}, {"text": "So this is basic--", "start": 2639.03, "duration": 1.93}, {"text": "I think of these as\nan approximation--", "start": 2640.96, "duration": 1.95}, {"text": "approximation of real\nnumber to some precision,", "start": 2645.73, "duration": 15.87}, {"text": "and I pay for\nprecision with time.", "start": 2661.6, "duration": 11.89}, {"text": "So let's say I wanted to compute\nthe square root of a number.", "start": 2673.49, "duration": 3.83}, {"text": "I could have an algorithm\njust like the algorithms--", "start": 2677.32, "duration": 3.33}, {"text": "or I guess division,\nright, long division.", "start": 2680.65, "duration": 4.35}, {"text": "You all know the algorithm\nof long division.", "start": 2685.0, "duration": 2.4}, {"text": "You put the quotient under\nhere with these-- an AB", "start": 2687.4, "duration": 4.56}, {"text": "and you get the C\non top or whatever.", "start": 2691.96, "duration": 3.157}, {"text": "That's an algorithm.", "start": 2695.117, "duration": 0.833}, {"text": "That's a procedure using\nessentially small numbers.", "start": 2695.95, "duration": 3.81}, {"text": "I'm only talking about\nthe digits zero to nine", "start": 2699.76, "duration": 2.79}, {"text": "here when I'm doing\nthat algorithm.", "start": 2702.55, "duration": 1.92}, {"text": "So it's a procedure\nthat only uses", "start": 2704.47, "duration": 2.67}, {"text": "small integers to\ncompute arbitrary", "start": 2707.14, "duration": 2.97}, {"text": "precision of a division.", "start": 2710.11, "duration": 3.48}, {"text": "So that's an\nalgorithm, and I have", "start": 2713.59, "duration": 1.44}, {"text": "to pay time to get more digits.", "start": 2715.03, "duration": 3.66}, {"text": "So that's an\nexample of this kind", "start": 2718.69, "duration": 3.45}, {"text": "of-- how we live in the\nworld of real numbers", "start": 2722.14, "duration": 3.75}, {"text": "when all we have is\na discrete system.", "start": 2725.89, "duration": 3.16}, {"text": "And then the last category\nI'd like to talk about here", "start": 2729.05, "duration": 4.76}, {"text": "is really approximation\nalgorithms.", "start": 2733.81, "duration": 3.42}, {"text": "Whereas this is kind of an\napproximation algorithm,", "start": 2740.83, "duration": 2.7}, {"text": "I'm approximating\nmy outputs, this", "start": 2743.53, "duration": 2.34}, {"text": "is an approximation algorithm\nfrom the standpoint of,", "start": 2745.87, "duration": 4.81}, {"text": "well, there's a lot of problems\nthat I can't solve efficiently.", "start": 2750.68, "duration": 3.11}, {"text": "They're NP-hard.", "start": 2753.79, "duration": 0.75}, {"text": "They're in EXP or\neven harder problems.", "start": 2754.54, "duration": 6.15}, {"text": "But maybe I'm OK with not\ngetting the optimal solution.", "start": 2760.69, "duration": 5.49}, {"text": "So this is in the domain\nof optimization problems.", "start": 2766.18, "duration": 2.915}, {"text": "So most of the\ndynamic programming", "start": 2775.09, "duration": 3.182}, {"text": "problems that we gave you\nwere optimization problems.", "start": 2778.272, "duration": 2.208}, {"text": "They're the shortest\npaths problems.", "start": 2780.48, "duration": 1.23}, {"text": "Those are optimization problems.", "start": 2781.71, "duration": 1.333}, {"text": "Basically, the possible outputs\nare ranked in some way--", "start": 2783.043, "duration": 3.827}, {"text": "the distance of a path that you\nreturn or something like that.", "start": 2786.87, "duration": 5.34}, {"text": "They're ranked in some way.", "start": 2792.21, "duration": 1.36}, {"text": "There is an optimal one--", "start": 2793.57, "duration": 1.49}, {"text": "the one with the smallest\nmetric or something like that.", "start": 2795.06, "duration": 3.45}, {"text": "Well, in an approximation\nalgorithm what I do is, OK,", "start": 2801.05, "duration": 2.55}, {"text": "I get that it's computationally\ndifficult for you", "start": 2803.6, "duration": 3.12}, {"text": "to give me the longest\nsimple path in this graph,", "start": 2806.72, "duration": 3.27}, {"text": "or the shortest possible route\nfor my traveling salesman,", "start": 2809.99, "duration": 3.69}, {"text": "but maybe that's OK.", "start": 2813.68, "duration": 4.05}, {"text": "I mean, my engineering\nSpidey-sense", "start": 2817.73, "duration": 3.39}, {"text": "tells me that\nwithin 10% is fine.", "start": 2821.12, "duration": 3.36}, {"text": "So maybe instead of giving\nme the most optimal thing,", "start": 2824.48, "duration": 3.99}, {"text": "can I give you an\nalgorithm that's", "start": 2828.47, "duration": 1.44}, {"text": "guaranteed to be within\na certain distance", "start": 2829.91, "duration": 2.61}, {"text": "from the optimal thing?", "start": 2832.52, "duration": 2.49}, {"text": "Usually, we're looking for\nconstant factor approximations", "start": 2835.01, "duration": 2.85}, {"text": "which have low\nconstant, or maybe", "start": 2837.86, "duration": 4.77}, {"text": "even have to do for worse\nif such things don't exist.", "start": 2842.63, "duration": 3.39}, {"text": "OK, so that's\napproximation algorithms.", "start": 2846.02, "duration": 2.55}, {"text": "Can we get close to an optimal\nsolution in polynomial time?", "start": 2848.57, "duration": 4.96}, {"text": "OK.", "start": 2853.53, "duration": 1.55}, {"text": "And then the last way we could\nchange things in, especially", "start": 2855.08, "duration": 4.35}, {"text": "future classes, though sometimes\nthey talk about this in 046", "start": 2859.43, "duration": 3.54}, {"text": "as well, is we could change\nthe model of computation.", "start": 2862.97, "duration": 3.9}, {"text": "We could basically change\nsomething about our computer", "start": 2866.87, "duration": 3.27}, {"text": "to be put in some other weird\nparadigm of solving problems", "start": 2870.14, "duration": 4.77}, {"text": "with more power\nessentially, or you're", "start": 2874.91, "duration": 2.633}, {"text": "in a situation where\nthere's less power.", "start": 2877.543, "duration": 1.667}, {"text": "OK, so change in the\nmodel of computation.", "start": 2879.21, "duration": 2.985}, {"text": "So what we've been talking\nto you in terms of model", "start": 2892.59, "duration": 3.78}, {"text": "of computation is our word-RAM--", "start": 2896.37, "duration": 2.05}, {"text": "word-RAM.", "start": 2898.42, "duration": 0.5}, {"text": "And that essentially says I\ncan do arithmetic operations,", "start": 2901.83, "duration": 3.69}, {"text": "and I can look up stuff in\nmy memory in constant time.", "start": 2905.52, "duration": 2.79}, {"text": "And but if I allocate\na certain amount,", "start": 2908.31, "duration": 2.618}, {"text": "I have to pay that amount\nand that kind of thing.", "start": 2910.928, "duration": 2.042}, {"text": "So that's this word-RAM model.", "start": 2912.97, "duration": 3.35}, {"text": "But in actuality, all\nof your computers,", "start": 2916.32, "duration": 4.17}, {"text": "it's a lot easier\nfor me to figure--", "start": 2920.49, "duration": 2.85}, {"text": "to find and read memory\nthat's on my CPU in a register", "start": 2923.34, "duration": 5.43}, {"text": "than it is for me to go out\nto the hard disk, ask this--", "start": 2928.77, "duration": 3.3}, {"text": "well, in my day, it used to be\nthis movable mechanical head", "start": 2932.07, "duration": 4.02}, {"text": "that had to go and scan\nover a bit on a CD-ROM drive", "start": 2936.09, "duration": 4.71}, {"text": "and actually read\nwhat that thing was.", "start": 2940.8, "duration": 5.13}, {"text": "So we can add\ncomplexity to our model", "start": 2945.93, "duration": 3.12}, {"text": "to better account for the costs\nof operations on my machine.", "start": 2949.05, "duration": 5.55}, {"text": "One of those models is\ncalled the cache model--", "start": 2954.6, "duration": 2.76}, {"text": "cache model.", "start": 2961.83, "duration": 2.49}, {"text": "It's basically a\nhierarchy of memory.", "start": 2964.32, "duration": 4.5}, {"text": "I have my registers\non board my CPU.", "start": 2968.82, "duration": 3.42}, {"text": "I have maybe an L1 cache\nthat's close to my CPU.", "start": 2972.24, "duration": 3.87}, {"text": "Then I have another\nset of caches", "start": 2976.11, "duration": 1.44}, {"text": "and another set of\ncaches maybe out to RAM.", "start": 2977.55, "duration": 2.76}, {"text": "And reading from a hard disk, a\nsolid state drive of some kind,", "start": 2980.31, "duration": 3.21}, {"text": "that's the slowest\nthing to access.", "start": 2983.52, "duration": 2.82}, {"text": "And I can put a cost associated\nwith each of those things.", "start": 2986.34, "duration": 3.48}, {"text": "And instead of having to--", "start": 2989.82, "duration": 1.53}, {"text": "having all of our operations\nbe said to be constant,", "start": 2991.35, "duration": 6.41}, {"text": "the constants are\nactually different,", "start": 2997.76, "duration": 2.1}, {"text": "and I have to pay\nfor that difference.", "start": 2999.86, "duration": 2.43}, {"text": "And so that's\nextending our model", "start": 3002.29, "duration": 1.92}, {"text": "to be a little bit more\nrealistic to our machine.", "start": 3004.21, "duration": 2.94}, {"text": "Another one is we have\ncomputers right now that", "start": 3007.15, "duration": 4.47}, {"text": "operate in classical\nphysics, that exploit", "start": 3011.62, "duration": 3.3}, {"text": "things in classical physics.", "start": 3014.92, "duration": 1.77}, {"text": "But in actuality,\nour world allows", "start": 3016.69, "duration": 4.59}, {"text": "for even more complicated\ntypes of operations,", "start": 3021.28, "duration": 6.03}, {"text": "like quantum operations, where\nyou're exploiting entanglement", "start": 3027.31, "duration": 3.48}, {"text": "and superposition\nof different atoms", "start": 3030.79, "duration": 3.19}, {"text": "to potentially get operations\nthat I can act on my data that", "start": 3033.98, "duration": 5.31}, {"text": "are actually provably stronger\nthan the classical models", "start": 3039.29, "duration": 3.72}, {"text": "in some sense.", "start": 3043.01, "duration": 1.65}, {"text": "So this is a huge\nreason why there's", "start": 3044.66, "duration": 3.9}, {"text": "a lot of work\nbeing done in, say,", "start": 3048.56, "duration": 2.58}, {"text": "lots of industry research\nfacilities in figuring out", "start": 3051.14, "duration": 5.82}, {"text": "these models.", "start": 3056.96, "duration": 0.63}, {"text": "Because maybe if you can make\na big enough quantum computer,", "start": 3057.59, "duration": 3.16}, {"text": "you can break encryption and\nstuff in polynomial time.", "start": 3060.75, "duration": 3.05}, {"text": "And that's something that\nmaybe the NSA is interested in.", "start": 3063.8, "duration": 2.82}, {"text": "And I'm not going\nto go into that.", "start": 3066.62, "duration": 2.07}, {"text": "But, you know.", "start": 3068.69, "duration": 2.7}, {"text": "I mean, some people--", "start": 3071.39, "duration": 1.41}, {"text": "you look at artificial\nintelligence and things like", "start": 3072.8, "duration": 2.4}, {"text": "discussions around\nartificial intelligence,", "start": 3075.2, "duration": 2.43}, {"text": "my brain might be doing things\nthat a classical computer", "start": 3077.63, "duration": 6.8}, {"text": "cannot.", "start": 3084.43, "duration": 1.86}, {"text": "It could be using quantum\nsuperposition in some way.", "start": 3086.29, "duration": 3.6}, {"text": "And our computers that are\nin your phone and your laptop", "start": 3089.89, "duration": 4.257}, {"text": "and things like that aren't\nexploiting those operations,", "start": 3094.147, "duration": 2.333}, {"text": "so how could we ever\nget intelligence,", "start": 3096.48, "duration": 1.583}, {"text": "because in some sense, our\nbrains are more powerful.", "start": 3098.063, "duration": 3.557}, {"text": "And so a lot of what AI\nshould be looking into", "start": 3101.62, "duration": 3.45}, {"text": "is, what is the actual model\nof computation of our brains", "start": 3105.07, "duration": 4.98}, {"text": "that can give us the\npower to have sentience?", "start": 3110.05, "duration": 3.96}, {"text": "OK, so that's kind\nof quantum computing.", "start": 3114.01, "duration": 2.43}, {"text": "I don't know much\nabout it actually.", "start": 3116.44, "duration": 2.28}, {"text": "And then there's things like,\nmaybe I have more than one CPU.", "start": 3118.72, "duration": 6.23}, {"text": "I mean, most computers--\nall the computers you have,", "start": 3124.95, "duration": 2.71}, {"text": "even the ones in your phone,\nprobably have multiple cores.", "start": 3127.66, "duration": 3.42}, {"text": "In a sense, you have lots\nof CPUs running in parallel.", "start": 3131.08, "duration": 3.67}, {"text": "So this is like par--", "start": 3134.75, "duration": 2.37}, {"text": "there's one R in parallel?", "start": 3137.12, "duration": 1.415}, {"text": "Parallel computing basically\nsays, it's cheap for me", "start": 3148.08, "duration": 3.33}, {"text": "to make another\ncomputer potentially.", "start": 3151.41, "duration": 3.24}, {"text": "If I have two computers\nrunning on the same problem,", "start": 3154.65, "duration": 3.48}, {"text": "maybe I can get a\ntwo-fold speed-up on my--", "start": 3158.13, "duration": 3.642}, {"text": "on the time in which it\ntakes to solve my problem.", "start": 3161.772, "duration": 4.898}, {"text": "Now, suppose I had then 100\nCPUs running on a machine.", "start": 3166.67, "duration": 5.28}, {"text": "Maybe I can get\n100-fold speed-up.", "start": 3171.95, "duration": 1.74}, {"text": "And actually, in real\nlife, 100-fold speed-up", "start": 3173.69, "duration": 4.45}, {"text": "makes a difference.", "start": 3178.14, "duration": 1.86}, {"text": "It's, am I waiting for\nthis for 10 minutes?", "start": 3180.0, "duration": 3.06}, {"text": "Or am I waiting for\nthis for 1,000 minutes?", "start": 3183.06, "duration": 4.05}, {"text": "That's, like, all day.", "start": 3187.11, "duration": 1.92}, {"text": "I don't want to do that.", "start": 3189.03, "duration": 1.11}, {"text": "Maybe it's on weeks.", "start": 3190.14, "duration": 1.08}, {"text": "I don't even remember.", "start": 3191.22, "duration": 1.83}, {"text": "But parallel computing, if I\ncan get a 100-fold speed-up,", "start": 3193.05, "duration": 3.99}, {"text": "that might be a huge win.", "start": 3197.04, "duration": 1.83}, {"text": "But for some problems,\nit's not possible--", "start": 3198.87, "duration": 3.91}, {"text": "if I have k CPUs, can I\nget a k-factor speed-up?", "start": 3202.78, "duration": 6.42}, {"text": "It's not always possible to do.", "start": 3209.2, "duration": 3.19}, {"text": "And so parallel computing\nis another paradigm", "start": 3212.39, "duration": 2.94}, {"text": "in which there's a lot of\ninteresting theory going on.", "start": 3215.33, "duration": 5.59}, {"text": "There's a lot of\ncomplications there,", "start": 3220.92, "duration": 1.76}, {"text": "because there are a\ncouple different models.", "start": 3222.68, "duration": 2.34}, {"text": "You can have multicore\nset-up, where", "start": 3225.02, "duration": 1.77}, {"text": "you have a lot of computers\nthat are accessing", "start": 3226.79, "duration": 2.01}, {"text": "the same bank of memory.", "start": 3228.8, "duration": 2.13}, {"text": "And then you don't want them\nall to be reading and writing", "start": 3230.93, "duration": 2.76}, {"text": "from them at different times,\nbecause you don't necessarily", "start": 3233.69, "duration": 3.03}, {"text": "know what their state is,\nand you get these collisions,", "start": 3236.72, "duration": 2.653}, {"text": "which are something\nthat you really have", "start": 3239.373, "duration": 1.667}, {"text": "to think about in this world.", "start": 3241.04, "duration": 2.28}, {"text": "Or you have situations\nwhere maybe I", "start": 3243.32, "duration": 2.64}, {"text": "have a bunch of\nnano-flies or something", "start": 3245.96, "duration": 3.03}, {"text": "that are going around, and\nthey have very small computer", "start": 3248.99, "duration": 3.06}, {"text": "brains themselves.", "start": 3252.05, "duration": 3.06}, {"text": "But they can talk to each\nother and pass information", "start": 3255.11, "duration": 2.552}, {"text": "to each other, but\nthey don't have access", "start": 3257.662, "duration": 1.708}, {"text": "to one central network\nrepository of information.", "start": 3259.37, "duration": 2.86}, {"text": "That's what we call a\ndistributed parallel system,", "start": 3262.23, "duration": 3.23}, {"text": "where all of the\nCPUs that you have", "start": 3265.46, "duration": 3.48}, {"text": "can interact with each\nother maybe locally,", "start": 3268.94, "duration": 2.79}, {"text": "but don't have access to\nthe same memory system.", "start": 3271.73, "duration": 4.15}, {"text": "So they have to work\ntogether to learn information", "start": 3275.88, "duration": 4.88}, {"text": "about the system.", "start": 3280.76, "duration": 1.08}, {"text": "OK, so that's a brief overview\nof the different directions", "start": 3281.84, "duration": 6.42}, {"text": "this class, 6.006,\nand theory in general,", "start": 3288.26, "duration": 3.27}, {"text": "could lead you-- into a huge\narray of different branches", "start": 3291.53, "duration": 4.29}, {"text": "theory and different\nproblems that you", "start": 3295.82, "duration": 2.46}, {"text": "could address with different\ntypes of computers.", "start": 3298.28, "duration": 3.51}, {"text": "So I know this is a very\nhigh-level lecture and maybe", "start": 3301.79, "duration": 5.43}, {"text": "less-applied than some\nof you might like.", "start": 3307.22, "duration": 3.51}, {"text": "But I hope this gives you a good\nunderstanding of the directions", "start": 3310.73, "duration": 4.8}, {"text": "you can go after this\nclass that I think", "start": 3315.53, "duration": 3.87}, {"text": "are really excited in terms\nof how to solve problems", "start": 3319.4, "duration": 3.72}, {"text": "computationally.", "start": 3323.12, "duration": 1.77}, {"text": "So with that, I'd\nlike to end there.", "start": 3324.89, "duration": 4.52}]
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+[{"text": "The following\ncontent is provided", "start": 0.57, "duration": 1.8}, {"text": "by MIT OpenCourseWare under\na Creative Commons license.", "start": 2.37, "duration": 3.96}, {"text": "Additional information\nabout our license,", "start": 6.33, "duration": 2.1}, {"text": "and MIT OpenCourseWare\nin general,", "start": 8.43, "duration": 2.37}, {"text": "is available at ocw.mit.edu.", "start": 10.8, "duration": 1.94}, {"text": "TAFT BROOME: Yeah,\nthe internet--", "start": 15.33, "duration": 3.09}, {"text": "I was really trying to--", "start": 18.42, "duration": 2.91}, {"text": "push is not the word, but\nsomething close to push,", "start": 21.33, "duration": 3.27}, {"text": "Doctor Ing to do\nsomething on that.", "start": 24.6, "duration": 5.35}, {"text": "So one of the things\nabout the internet", "start": 29.95, "duration": 1.86}, {"text": "is that we've\nproduced a generation,", "start": 31.81, "duration": 15.777}, {"text": "and the \"we\" is the world.", "start": 47.587, "duration": 1.083}, {"text": "Let me tell you\nwhat I mean by that.", "start": 51.25, "duration": 2.15}, {"text": "Now, I don't know if I ever\ntold you I was in South Africa,", "start": 53.4, "duration": 6.44}, {"text": "and I was up in Lesotho.", "start": 59.84, "duration": 3.79}, {"text": "And I'm riding down this road\nand it's total desolation,", "start": 63.63, "duration": 9.29}, {"text": "total.", "start": 72.92, "duration": 0.5}, {"text": "We're up in the mountains--\ntotal desolation.", "start": 73.42, "duration": 3.06}, {"text": "And all of a sudden,\nthere's this guy", "start": 76.48, "duration": 1.59}, {"text": "walking along the side of\nthe road with a cellphone.", "start": 78.07, "duration": 4.64}, {"text": "And I asked my driver, said, who\nis he talking to, somebody back", "start": 82.71, "duration": 4.5}, {"text": "at his village?", "start": 87.21, "duration": 0.67}, {"text": "He said, no, he's\nprobably talking", "start": 87.88, "duration": 1.417}, {"text": "to a relative in France.", "start": 89.297, "duration": 1.378}, {"text": "So when I say \"we\"\nand I mean the world,", "start": 93.54, "duration": 2.79}, {"text": "I really mean we have produced\na generation that is probably", "start": 96.33, "duration": 9.48}, {"text": "in some ways wired into the\ninternet and other things", "start": 105.81, "duration": 6.06}, {"text": "that I am not wired into,\nand that you all are probably", "start": 111.87, "duration": 3.57}, {"text": "just--", "start": 115.44, "duration": 1.89}, {"text": "I don't even know if\nI count you all in it.", "start": 117.33, "duration": 2.91}, {"text": "STUDENT: We didn't have\nit in our childhood.", "start": 120.24, "duration": 2.98}, {"text": "[INAUDIBLE] happen after hours.", "start": 123.22, "duration": 2.91}, {"text": "So I think that must be\ndifferent [INAUDIBLE]..", "start": 126.13, "duration": 2.844}, {"text": "TAFT BROOME: And what\nI've gotten from students", "start": 134.442, "duration": 3.288}, {"text": "is a basic moral sensibility\nabout the internet", "start": 137.73, "duration": 8.56}, {"text": "that I don't have, and\nthat I can argue against.", "start": 146.29, "duration": 4.23}, {"text": "But they have a basic\nsentimentality about it,", "start": 150.52, "duration": 4.03}, {"text": "which I think gives\nrise to all ethics.", "start": 154.55, "duration": 1.67}, {"text": "You have to have a sentiment.", "start": 156.22, "duration": 1.94}, {"text": "You have to have a\npassion about something.", "start": 158.16, "duration": 1.83}, {"text": "You have to feel something.", "start": 159.99, "duration": 1.71}, {"text": "And one of them is\nthat no matter what", "start": 161.7, "duration": 3.112}, {"text": "the law says, whatever\nyou can get from the net", "start": 164.812, "duration": 1.958}, {"text": "belongs to you.", "start": 166.77, "duration": 0.63}, {"text": "It's like free water out\npast the 12-mile limit.", "start": 167.4, "duration": 5.7}, {"text": "There's a sensibility they\nhave that no matter what", "start": 173.1, "duration": 3.06}, {"text": "you put up there,\nonce it gets up there,", "start": 176.16, "duration": 2.82}, {"text": "it's in public domain.", "start": 178.98, "duration": 2.41}, {"text": "And I say, no.", "start": 181.39, "duration": 0.613}, {"text": "You know what I mean, I'm able\nto argue all of that stuff.", "start": 182.003, "duration": 2.417}, {"text": "And they, OK, they\nbelieve what I-- but I", "start": 184.42, "duration": 1.79}, {"text": "look at them in their\nfaces after I've argued.", "start": 186.21, "duration": 2.28}, {"text": "They're not buying it.", "start": 188.49, "duration": 3.08}, {"text": "And the only argument that I can\ngive to them that confuses them", "start": 191.57, "duration": 3.99}, {"text": "is the one where\nI say that I ran", "start": 195.56, "duration": 4.32}, {"text": "into this undergraduate\nstudent one day at Howard.", "start": 199.88, "duration": 4.26}, {"text": "It was a Chemical\nEngineering major.", "start": 204.14, "duration": 1.53}, {"text": "I hadn't had him in the\nclass, but I knew him.", "start": 205.67, "duration": 2.352}, {"text": "He's walking down the\nhall with a guitar.", "start": 208.022, "duration": 1.708}, {"text": "I said, I didn't know\nyou play the guitar.", "start": 209.73, "duration": 1.75}, {"text": "He said, well I\nplay at the guitar.", "start": 211.48, "duration": 1.49}, {"text": "I'm not really good at\nit, but I write songs.", "start": 212.97, "duration": 1.875}, {"text": "I said, oh, really?", "start": 214.845, "duration": 1.115}, {"text": "So he opens up his\nguitar and pulls out,", "start": 215.96, "duration": 1.95}, {"text": "shows me this little sheet of\npaper, about that much of it,", "start": 217.91, "duration": 4.11}, {"text": "as a song.", "start": 222.02, "duration": 1.68}, {"text": "I said, oh, how nice.", "start": 223.7, "duration": 1.56}, {"text": "He sold it to Prince.", "start": 225.26, "duration": 1.62}, {"text": "So I said, how much\ndid you make for that?", "start": 226.88, "duration": 2.8}, {"text": "And it was about\ntwice the salary", "start": 229.68, "duration": 2.42}, {"text": "I make in a year, what he got\nfrom that, royalties and all.", "start": 232.1, "duration": 5.93}, {"text": "So I say now, if you wrote\na song and it's yours,", "start": 241.06, "duration": 5.34}, {"text": "I don't care if you spent\n12 years on it or 12 minutes", "start": 246.4, "duration": 3.63}, {"text": "on it.", "start": 250.03, "duration": 2.07}, {"text": "Do you want everybody\ndownloading your song?", "start": 252.1, "duration": 4.979}, {"text": "And they will sit and think.", "start": 257.079, "duration": 1.861}, {"text": "And they've got\nproblems with that.", "start": 258.94, "duration": 3.66}, {"text": "But I still think that\nthere's a possibility", "start": 262.6, "duration": 2.82}, {"text": "we have to contend with a\nsensibility about the net", "start": 265.42, "duration": 7.77}, {"text": "that my generation was\ndeveloping about robots.", "start": 273.19, "duration": 4.35}, {"text": "So my generation was\nabout willing to say", "start": 277.54, "duration": 2.46}, {"text": "that a robot was sentient,\nnot really that the robot was", "start": 280.0, "duration": 4.71}, {"text": "sentient, but that we could\nhave feelings for a machine.", "start": 284.71, "duration": 3.99}, {"text": "And I don't think we ever quite\ngot there, mainly because we're", "start": 292.03, "duration": 3.27}, {"text": "dying off first.", "start": 295.3, "duration": 2.58}, {"text": "But I don't know, if\nyou ever meet somebody", "start": 297.88, "duration": 5.3}, {"text": "my age or older, ask them what\nthey feel about their car.", "start": 303.18, "duration": 3.48}, {"text": "They might feel that--", "start": 310.01, "duration": 1.732}, {"text": "STUDENT: What do you predict?", "start": 311.742, "duration": 1.728}, {"text": "TAFT BROOME: Well, I mean,\nsome people feel about a car,", "start": 313.47, "duration": 2.57}, {"text": "they get out and kiss the engine\nif you let them, it wasn't hot.", "start": 316.04, "duration": 3.0}, {"text": "I mean, they feel\nsentimentality about it.", "start": 319.04, "duration": 4.35}, {"text": "So I don't know it's\nan interesting thing", "start": 323.39, "duration": 1.8}, {"text": "to speculate about.", "start": 325.19, "duration": 1.44}, {"text": "The important thing for this\nclass is to speculate about it.", "start": 326.63, "duration": 4.02}, {"text": "Keep it in mind.", "start": 330.65, "duration": 1.05}, {"text": "Watch people.", "start": 331.7, "duration": 0.87}, {"text": "Ask them questions, because\nyour arguments may not", "start": 332.57, "duration": 2.46}, {"text": "sink in with them past\nthe rational level.", "start": 335.03, "duration": 2.97}, {"text": "What I want to do today\nis go into some depth", "start": 342.09, "duration": 2.22}, {"text": "on these codes of ethics, but\nI want to entertain Q&A first.", "start": 344.31, "duration": 2.94}, {"text": "Any burning issues,\noutstanding stuff?", "start": 350.55, "duration": 2.175}, {"text": "STUDENT: Related to\nthe codes of ethics?", "start": 359.48, "duration": 2.37}, {"text": "TAFT BROOME:\nRelated to anything,", "start": 361.85, "duration": 1.96}, {"text": "so that I can start\ninto the code of ethics", "start": 363.81, "duration": 2.63}, {"text": "with a clear conscience.", "start": 366.44, "duration": 2.042}, {"text": "STUDENT: I have to\nshow you something,", "start": 368.482, "duration": 1.583}, {"text": "I brought this to\nshow you Professor,", "start": 370.065, "duration": 3.115}, {"text": "because [INAUDIBLE] were\nstudying the legal applications", "start": 373.18, "duration": 3.705}, {"text": "of genetic engineering.", "start": 376.885, "duration": 1.335}, {"text": "It's like, I'm showing him--", "start": 378.22, "duration": 2.39}, {"text": "TAFT BROOME: Ethics, as\nI believe most engineers", "start": 380.61, "duration": 2.43}, {"text": "understand and practice it--", "start": 383.04, "duration": 3.38}, {"text": "hot dog-- involves the carefully\ncalculated, responsible", "start": 386.42, "duration": 4.2}, {"text": "application of well-understood\nprinciples in accordance", "start": 390.62, "duration": 4.8}, {"text": "with established public\nand professional standards", "start": 395.42, "duration": 3.21}, {"text": "to produce results that are both\nsafe and beneficial to society.", "start": 398.63, "duration": 6.13}, {"text": "STUDENT: But this man's argument\nis actually you cannot call", "start": 404.76, "duration": 2.51}, {"text": "genetic--", "start": 407.27, "duration": 0.75}, {"text": "what's done with gene,\ngenetic engineering.", "start": 408.02, "duration": 2.52}, {"text": "These people who manipulate the\ngenetic material of organisms,", "start": 410.54, "duration": 3.48}, {"text": "they can't assume--", "start": 414.02, "duration": 1.87}, {"text": "they can't say\nthis is a safe way.", "start": 415.89, "duration": 2.228}, {"text": "And no [INAUDIBLE].", "start": 418.118, "duration": 0.792}, {"text": "There's so much\nuncertainty you really", "start": 418.91, "duration": 1.583}, {"text": "can't call it engineering\nwas his main argument.", "start": 420.493, "duration": 2.327}, {"text": "But I thought it\nwas interesting.", "start": 422.82, "duration": 1.693}, {"text": "TAFT BROOME: Could you write\ndown the source for me?", "start": 424.513, "duration": 2.167}, {"text": "STUDENT: Yeah.", "start": 426.68, "duration": 0.583}, {"text": "STUDENT: [INAUDIBLE] engineering\nimplies ethical responsibility.", "start": 427.263, "duration": 3.737}, {"text": "STUDENT: Exactly, so\n[INAUDIBLE] interesting.", "start": 431.0, "duration": 3.37}, {"text": "TAFT BROOME: Yeah, that's an\nargument, if you'll recall--", "start": 434.37, "duration": 4.325}, {"text": "you have no reason\nto recall this", "start": 438.695, "duration": 1.375}, {"text": "because it was the very,\nvery, very last thing I said,", "start": 440.07, "duration": 2.88}, {"text": "but when we went to\nthe Norwegian lecture,", "start": 442.95, "duration": 9.0}, {"text": "my very last recommendation was\nthat we think about competency.", "start": 451.95, "duration": 6.91}, {"text": "We define competency in terms\nof the good, not competent,", "start": 458.86, "duration": 5.07}, {"text": "and then ask whether it's\ngood, but it is not competent", "start": 463.93, "duration": 4.22}, {"text": "unless it is also good.", "start": 468.15, "duration": 2.91}, {"text": "And the group didn't\nseem to want to spend", "start": 471.06, "duration": 4.2}, {"text": "much time on that part.", "start": 475.26, "duration": 1.14}, {"text": "They wanted to spend time on\nthe character development.", "start": 476.4, "duration": 5.53}, {"text": "But that part was\nsignificant because--", "start": 481.93, "duration": 9.498}, {"text": "well, for two reasons.", "start": 491.428, "duration": 0.917}, {"text": "Well, let me just\nsay for one reason,", "start": 497.928, "duration": 1.542}, {"text": "if I want to put the\n[INAUDIBLE] in that way.", "start": 499.47, "duration": 2.29}, {"text": "And that is that if\nyou take the ethics out", "start": 501.76, "duration": 5.56}, {"text": "of the definition of\ncompetency, what you", "start": 507.32, "duration": 1.95}, {"text": "have is a lower-order\nstandard for competence.", "start": 509.27, "duration": 7.19}, {"text": "You don't have to be\nreally good at what", "start": 516.46, "duration": 1.89}, {"text": "you do because let's say, for\nexample, three children come", "start": 518.35, "duration": 6.73}, {"text": "in here and one of them has\ngot a disease that we'll all", "start": 525.08, "duration": 3.0}, {"text": "catch in 10 minutes.", "start": 528.08, "duration": 2.55}, {"text": "Well, one way to\nsolve the problem--", "start": 530.63, "duration": 1.5}, {"text": "kill all the children.", "start": 532.13, "duration": 1.83}, {"text": "I wouldn't call that competent.", "start": 533.96, "duration": 3.9}, {"text": "OK, so I want to say\nthat competency really", "start": 537.86, "duration": 3.33}, {"text": "includes ethics as a condition.", "start": 541.19, "duration": 5.46}, {"text": "Because it not only means that\nyou have to be really highly", "start": 546.65, "duration": 5.04}, {"text": "competent, but you build in\ncompetence into the culture,", "start": 551.69, "duration": 4.68}, {"text": "that people do not look for\nthe one that's not ethical.", "start": 556.37, "duration": 5.04}, {"text": "And I guess I put the other one\nin there because it actually", "start": 561.41, "duration": 3.75}, {"text": "means the same thing.", "start": 565.16, "duration": 1.03}, {"text": "It goes back to my lecture,\nagain, about Faust--", "start": 566.19, "duration": 3.41}, {"text": "that if you leave\nout the ethics part,", "start": 569.6, "duration": 1.92}, {"text": "you're going to get what you\ncall a competent solution,", "start": 571.52, "duration": 2.82}, {"text": "but it would be\nsomething you don't want.", "start": 574.34, "duration": 3.9}, {"text": "The monkey's paw again--", "start": 578.24, "duration": 3.12}, {"text": "so I think the monkey's paw\nreally defines competency", "start": 581.36, "duration": 3.9}, {"text": "without ethics.", "start": 585.26, "duration": 2.58}, {"text": "And that's something\nthat nobody wants,", "start": 587.84, "duration": 3.99}, {"text": "even though you\nhave agreed a priori", "start": 591.83, "duration": 5.302}, {"text": "on the terms of the contract.", "start": 597.132, "duration": 1.208}, {"text": "So those are my\narguments about that.", "start": 600.88, "duration": 4.09}, {"text": "So yeah, I'd like\nto see that paper.", "start": 604.97, "duration": 2.61}, {"text": "And I'd like to--\nactually, I'm trying", "start": 607.58, "duration": 1.88}, {"text": "to get Stephanie\nBird in here to talk.", "start": 609.46, "duration": 3.63}, {"text": "She does ethics and science.", "start": 613.09, "duration": 4.29}, {"text": "So she wants to talk about\nthose kinds of issues, too.", "start": 617.38, "duration": 2.73}, {"text": "And I want to bring her in\nhere to talk about these issues", "start": 620.11, "duration": 2.7}, {"text": "because I think when you say\nwhat something is, you clarify", "start": 622.81, "duration": 4.275}, {"text": "it by saying what it is not.", "start": 627.085, "duration": 2.995}, {"text": "So we're not talking\nabout ethics and science,", "start": 630.08, "duration": 2.09}, {"text": "but how do we know?", "start": 632.17, "duration": 1.28}, {"text": "Well, let's have a lecture\non ethics and science.", "start": 633.45, "duration": 4.06}, {"text": "So what you'll find\nin ethics and science", "start": 637.51, "duration": 5.12}, {"text": "is two categories of\nissues, basically.", "start": 642.63, "duration": 6.24}, {"text": "One is ethics in research.", "start": 648.87, "duration": 3.57}, {"text": "Research ethics, which\nis what I talked about,", "start": 652.44, "duration": 2.49}, {"text": "is today almost\nalways considered", "start": 654.93, "duration": 3.0}, {"text": "research ethics in\nsciences, even though it", "start": 657.93, "duration": 2.34}, {"text": "can include anything else.", "start": 660.27, "duration": 1.93}, {"text": "But all of the\nissues have come up", "start": 662.2, "duration": 1.97}, {"text": "with big scientists\nmaking gross violations", "start": 664.17, "duration": 5.55}, {"text": "of your basic sense of ethics.", "start": 669.72, "duration": 4.11}, {"text": "The other category\nhas to do with what", "start": 673.83, "duration": 2.88}, {"text": "I would call political issues--", "start": 676.71, "duration": 3.69}, {"text": "abortion--", "start": 680.4, "duration": 2.093}, {"text": "STUDENT: Should we\nbe doing it at all?", "start": 682.493, "duration": 1.583}, {"text": "[INTERPOSING VOICES]", "start": 684.076, "duration": 0.833}, {"text": "TAFT BROOME: --stem cells.", "start": 684.909, "duration": 1.121}, {"text": "That's right, should\nwe be doing it at all.", "start": 686.03, "duration": 4.8}, {"text": "And some people\nwill tell you if you", "start": 690.83, "duration": 3.06}, {"text": "get four philosophers in\nthis room, one of them", "start": 693.89, "duration": 4.61}, {"text": "will say that those issues\nreally aren't ethical issues,", "start": 698.5, "duration": 8.42}, {"text": "they are scientific issues.", "start": 706.92, "duration": 2.25}, {"text": "Because we want a scientific\ndefinition of a human being.", "start": 709.17, "duration": 4.673}, {"text": "We all agree that we shouldn't\nbe doing these things", "start": 713.843, "duration": 2.167}, {"text": "to human beings, but is that\na human being, that fetus", "start": 716.01, "duration": 6.67}, {"text": "or whatever?", "start": 722.68, "duration": 1.56}, {"text": "And so that person will say,\nI'm done, walk out of the room--", "start": 724.24, "duration": 4.31}, {"text": "not that he doesn't\nwant to talk about it,", "start": 728.55, "duration": 1.75}, {"text": "but it's not ethics\nfor him or her.", "start": 730.3, "duration": 1.86}, {"text": "STUDENT: And others\nwill say [INAUDIBLE]", "start": 736.17, "duration": 5.74}, {"text": "is a matter of definition,\nnot just science.", "start": 741.91, "duration": 4.38}, {"text": "That's the other side\nof that [INAUDIBLE]..", "start": 746.29, "duration": 1.792}, {"text": "TAFT BROOME: That's\non the other side is--", "start": 748.082, "duration": 1.75}, {"text": "STUDENT: That's why it doesn't--", "start": 749.832, "duration": 1.512}, {"text": "[INAUDIBLE] the\ndefinition [INAUDIBLE]..", "start": 751.344, "duration": 4.936}, {"text": "TAFT BROOME: There got to be--", "start": 756.28, "duration": 1.25}, {"text": "STUDENT: [INAUDIBLE]\nYeah, I mean, I think so.", "start": 757.53, "duration": 4.08}, {"text": "I would say that it's not--", "start": 761.61, "duration": 1.74}, {"text": "science has to agree upon,\nscientists as a community", "start": 766.37, "duration": 3.105}, {"text": "have to agree upon the\ndefinition and the starting", "start": 769.475, "duration": 2.722}, {"text": "point [INAUDIBLE].", "start": 772.197, "duration": 2.733}, {"text": "There's not a series of\nexperiments that can be done.", "start": 774.93, "duration": 3.64}, {"text": "I mean, it all\ninvolves [INAUDIBLE]", "start": 778.57, "duration": 4.849}, {"text": "about what possibly\n[INAUDIBLE] I definitely", "start": 783.419, "duration": 5.891}, {"text": "have not [INAUDIBLE]\nbeginning of [INAUDIBLE]..", "start": 789.31, "duration": 6.45}, {"text": "TAFT BROOME: Well,\nthat takes time, right?", "start": 795.76, "duration": 4.36}, {"text": "I mean, you have\nto sit out, and you", "start": 800.12, "duration": 1.52}, {"text": "have to think about that one.", "start": 801.64, "duration": 2.22}, {"text": "Actually, what I say\nis, first of all,", "start": 803.86, "duration": 4.93}, {"text": "it is a philosophical\nargument because it belongs", "start": 808.79, "duration": 2.358}, {"text": "to the category of metaphysics.", "start": 811.148, "duration": 1.292}, {"text": "You're talking about how are you\ngoing to divide the world up.", "start": 812.44, "duration": 5.04}, {"text": "And the scientific\ndefinition can only", "start": 817.48, "duration": 6.72}, {"text": "contribute one part of that.", "start": 824.2, "duration": 1.71}, {"text": "The other thing about it is that\nthe affected parties are not", "start": 832.47, "duration": 4.22}, {"text": "only the fetus.", "start": 836.69, "duration": 2.535}, {"text": "You've got the mother,\nyou've got the father.", "start": 839.225, "duration": 1.875}, {"text": "You've got a whole\nbunch of other people", "start": 841.1, "duration": 1.86}, {"text": "who are concerned\nabout all that.", "start": 842.96, "duration": 1.8}, {"text": "Then the more you step into the\npolitical domain on this issue,", "start": 844.76, "duration": 5.01}, {"text": "the more you get into\nthe religious domain.", "start": 849.77, "duration": 2.67}, {"text": "So you've got to start\ndividing the house there.", "start": 852.44, "duration": 2.0}, {"text": "What are we going\nto talk about here?", "start": 854.44, "duration": 1.542}, {"text": "We're going to use faith as\nan appeal, a legitimate source", "start": 855.982, "duration": 5.788}, {"text": "of appeal?", "start": 861.77, "duration": 0.5}, {"text": "Or we're going to\nstay with reason?", "start": 862.27, "duration": 3.0}, {"text": "So you've got to continue\nto divide the house.", "start": 865.27, "duration": 1.98}, {"text": "And once you do that, still\nhaven't solved the problem.", "start": 867.25, "duration": 2.46}, {"text": "So I think that\nhaving her in here--", "start": 872.77, "duration": 4.41}, {"text": "I owe her a paper\nby the way, one", "start": 877.18, "duration": 3.27}, {"text": "that I'm reading for her,\nnot one that I've written.", "start": 880.45, "duration": 2.85}, {"text": "So that would be helpful, and\nI hope you all have the stomach", "start": 883.3, "duration": 2.94}, {"text": "for one lecture on this.", "start": 886.24, "duration": 3.2}, {"text": "You might.", "start": 889.44, "duration": 0.54}, {"text": "And then, we'll talk about\nwhether or not any of it's", "start": 892.992, "duration": 2.208}, {"text": "genetic engineering, or whether\nit's really bioengineering.", "start": 895.2, "duration": 5.63}, {"text": "Because you are\nmaking something,", "start": 900.83, "duration": 4.24}, {"text": "like you take clay and\nmake bricks, or like", "start": 905.07, "duration": 3.21}, {"text": "you take iron and make steel.", "start": 908.28, "duration": 2.1}, {"text": "You're making something.", "start": 910.38, "duration": 1.05}, {"text": "STUDENT: There's\na design process.", "start": 911.43, "duration": 2.332}, {"text": "TAFT BROOME: There's a\ndesign process involved.", "start": 913.762, "duration": 1.958}, {"text": "STUDENT: [INAUDIBLE].", "start": 915.72, "duration": 3.093}, {"text": "STUDENT: It's not very\nwell understood, maybe,", "start": 918.813, "duration": 1.917}, {"text": "[INAUDIBLE] It's not based\non sound science yet.", "start": 920.73, "duration": 6.058}, {"text": "No one really quite\nunderstands what's", "start": 926.788, "duration": 1.583}, {"text": "going to happen\nwhen [INAUDIBLE]..", "start": 928.371, "duration": 4.659}, {"text": "STUDENT: The [? grid ?] building\nisn't well understood, then.", "start": 933.03, "duration": 4.08}, {"text": "There's lots of\nengineering practices", "start": 937.11, "duration": 1.74}, {"text": "that are not standard\n[INAUDIBLE] totally uncertain.", "start": 938.85, "duration": 5.121}, {"text": "So I wonder if the\nauthor of that article", "start": 943.971, "duration": 2.099}, {"text": "would say that wasn't\nengineering until [INAUDIBLE]..", "start": 946.07, "duration": 5.22}, {"text": "Because that goes against\na lot of the definition", "start": 951.29, "duration": 2.234}, {"text": "that we discussed in this class.", "start": 953.524, "duration": 1.491}, {"text": "[INAUDIBLE]", "start": 955.015, "duration": 0.994}, {"text": "TAFT BROOME: Well, I'm\ngiving consideration", "start": 964.46, "duration": 3.63}, {"text": "to all of this in\nmy research work.", "start": 968.09, "duration": 2.52}, {"text": "And I haven't finished it.", "start": 970.61, "duration": 2.41}, {"text": "But where I am now\nis that it goes back", "start": 973.02, "duration": 4.828}, {"text": "to the Manhattan Project.", "start": 977.848, "duration": 1.042}, {"text": "Actually, it goes back\nbefore the Manhattan Project.", "start": 978.89, "duration": 2.25}, {"text": "It goes back, really, to radar.", "start": 981.14, "duration": 4.41}, {"text": "And that's when scientists\nwere doing engineering.", "start": 985.55, "duration": 5.15}, {"text": "So if you get a scientist\nwho is doing engineering,", "start": 990.7, "duration": 5.05}, {"text": "basically they might\nnot do it right.", "start": 995.75, "duration": 2.04}, {"text": "So you can call it\nengineering, I think,", "start": 997.79, "duration": 4.29}, {"text": "but it's not what I would call\nsophisticated engineering.", "start": 1002.08, "duration": 3.63}, {"text": "Because it's like when\nengineers sometimes do science.", "start": 1005.71, "duration": 3.96}, {"text": "I think a good example\nof that is the invention", "start": 1009.67, "duration": 4.5}, {"text": "of thermodynamics.", "start": 1014.17, "duration": 2.37}, {"text": "If you're looking at the history\nof thermodynamics, engineers,", "start": 1016.54, "duration": 4.7}, {"text": "boilers, and boilers\nfor trains, developed", "start": 1021.24, "duration": 7.65}, {"text": "a science using what scientists\nwould call herky jerky methods.", "start": 1028.89, "duration": 4.15}, {"text": "And so that's what I'm\ntrying to reconcile now.", "start": 1036.849, "duration": 3.701}, {"text": "And I think I'll\nhave it reconciled", "start": 1040.55, "duration": 2.24}, {"text": "before the month is out,\nbut what happens to a thing", "start": 1042.79, "duration": 4.799}, {"text": "when it is practiced\nby a non-practitioner.", "start": 1047.589, "duration": 4.931}, {"text": "Here's is a good example.", "start": 1052.52, "duration": 1.83}, {"text": "I'll tell you a good example.", "start": 1054.35, "duration": 1.21}, {"text": "I was getting on the\nelevator with this researcher", "start": 1055.56, "duration": 4.78}, {"text": "here at MIT who is doing\nresearch on systems.", "start": 1060.34, "duration": 7.39}, {"text": "Actually, I was getting\non the elevator with him", "start": 1067.73, "duration": 2.0}, {"text": "at the airport.", "start": 1069.73, "duration": 0.63}, {"text": "We ran into each\nother at the airport.", "start": 1070.36, "duration": 2.07}, {"text": "And he's going to this\nconference on systems.", "start": 1072.43, "duration": 4.42}, {"text": "There's another person here\nat MIT who's the president", "start": 1076.85, "duration": 2.76}, {"text": "of the organization,\nnamed Pat Hale, H-A-L-E.", "start": 1079.61, "duration": 3.79}, {"text": "Don't know if you\nknow [INAUDIBLE]..", "start": 1083.4, "duration": 3.08}, {"text": "And we were discussing that,\nand he had organized a session.", "start": 1086.48, "duration": 6.83}, {"text": "And so I said, what did you\norganize your session on?", "start": 1093.31, "duration": 5.62}, {"text": "And really what he\nsaid was that he", "start": 1098.93, "duration": 5.77}, {"text": "belongs to the first generation\nof systems engineers.", "start": 1104.7, "duration": 3.54}, {"text": "I said, hold up--", "start": 1108.24, "duration": 1.155}, {"text": "what are you talking about?", "start": 1109.395, "duration": 1.125}, {"text": "Systems engineering had been\naround before you were around.", "start": 1110.52, "duration": 2.76}, {"text": "He says, no, they were all\nthis engineer, or that business", "start": 1113.28, "duration": 6.6}, {"text": "person, or the\nother doing systems.", "start": 1119.88, "duration": 3.45}, {"text": "But we are the first ones who\nare really systems engineers.", "start": 1123.33, "duration": 3.42}, {"text": "Everybody who was my teacher,\nmy faculty advisor, all", "start": 1126.75, "duration": 3.57}, {"text": "of these people were people\nwho were doing engineering,", "start": 1130.32, "duration": 3.49}, {"text": "but they mainly had it\nfrom this perspective", "start": 1133.81, "duration": 2.21}, {"text": "of another discipline.", "start": 1136.02, "duration": 1.93}, {"text": "And so we want to\norganize the young people", "start": 1137.95, "duration": 2.69}, {"text": "to start developing a\npurely systems idea.", "start": 1140.64, "duration": 5.14}, {"text": "And so I think that tells a\nstory about a lot of things.", "start": 1145.78, "duration": 3.59}, {"text": "It tells it about\nengineering ethics", "start": 1149.37, "duration": 1.5}, {"text": "because the people involved were\nbasically mostly philosophers,", "start": 1150.87, "duration": 7.43}, {"text": "and they got some engineers,\nand half of the engineers", "start": 1158.3, "duration": 2.7}, {"text": "were practicing engineers.", "start": 1161.0, "duration": 1.83}, {"text": "Many of them had\nbeen whistleblowers.", "start": 1162.83, "duration": 2.07}, {"text": "Half of them were\nacademic engineers.", "start": 1164.9, "duration": 4.18}, {"text": "So who becomes the first\nengineering ethicist?", "start": 1169.08, "duration": 3.51}, {"text": "Well, I felt that\nway when I came out.", "start": 1176.087, "duration": 1.583}, {"text": "I felt that I was\nin a generation that", "start": 1177.67, "duration": 1.583}, {"text": "was the first person--", "start": 1179.253, "duration": 2.217}, {"text": "not the first person, but in\nthe first generation at least--", "start": 1181.47, "duration": 2.55}, {"text": "not the first age\ngeneration, but", "start": 1184.02, "duration": 3.39}, {"text": "in the first\nacademic generation,", "start": 1187.41, "duration": 3.0}, {"text": "who was doing engineering\nethics with a combined approach", "start": 1190.41, "duration": 7.24}, {"text": "that on occasion\ndeveloped something", "start": 1197.65, "duration": 3.75}, {"text": "that was different from the\ntwo things that made it.", "start": 1201.4, "duration": 3.42}, {"text": "And you can do that by\nadding to or violating", "start": 1204.82, "duration": 3.42}, {"text": "one of the principles of one of\nthe participating disciplines.", "start": 1208.24, "duration": 6.33}, {"text": "And an example of\nthat is the one", "start": 1214.57, "duration": 1.8}, {"text": "where I talk about\nthe virtue ethics", "start": 1216.37, "duration": 3.69}, {"text": "from the standpoint\nof what I had first", "start": 1220.06, "duration": 2.04}, {"text": "called African ethics,\nbut now I have realized", "start": 1222.1, "duration": 2.91}, {"text": "that it's all around the world.", "start": 1225.01, "duration": 1.99}, {"text": "There's this whole other point\nof view that non-Western.", "start": 1227.0, "duration": 3.73}, {"text": "And so the question is,\nand my colleagues at Howard", "start": 1230.73, "duration": 3.36}, {"text": "are debating me, is\nthis an extension", "start": 1234.09, "duration": 3.6}, {"text": "of Greek ethics, Western ethics,\nor is this something different?", "start": 1237.69, "duration": 6.467}, {"text": "So I think that one\nmakes a big mistake when", "start": 1251.54, "duration": 8.51}, {"text": "one defines competency\nin a manner that does not", "start": 1260.05, "duration": 3.69}, {"text": "have a moral dimension.", "start": 1263.74, "duration": 2.29}, {"text": "And scientists argue-- this\nused to be a big issue,", "start": 1266.03, "duration": 2.51}, {"text": "then I get on to the point\nof the codes of ethics--", "start": 1268.54, "duration": 6.35}, {"text": "there were big debates\nin the '70s and '80s", "start": 1278.82, "duration": 4.38}, {"text": "over the question, is\nscience value free?", "start": 1283.2, "duration": 5.7}, {"text": "Then it got narrowed\ndown to truth.", "start": 1288.9, "duration": 2.175}, {"text": "Squirrel got a nut--", "start": 1293.97, "duration": 1.65}, {"text": "is there value in that,\nsomebody would argue.", "start": 1295.62, "duration": 5.29}, {"text": "So truth can be\nseparate from values.", "start": 1300.91, "duration": 5.46}, {"text": "You have to ask yourself,\nif truth was not", "start": 1306.37, "duration": 4.65}, {"text": "separate from\nvalues, why would we", "start": 1311.02, "duration": 1.5}, {"text": "need two different\nwords, truth and value?", "start": 1312.52, "duration": 4.08}, {"text": "STUDENT: That makes sense.", "start": 1322.929, "duration": 1.083}, {"text": "TAFT BROOME: So my take on it\nhas come out-- since you all", "start": 1328.52, "duration": 4.71}, {"text": "got me on this road.", "start": 1333.23, "duration": 1.53}, {"text": "I didn't ask for this.", "start": 1334.76, "duration": 2.7}, {"text": "My take on it is that\ntruth is value free.", "start": 1337.46, "duration": 13.45}, {"text": "You can think about\na truthful statement", "start": 1350.91, "duration": 6.31}, {"text": "and then make a value\njudgment about it separately.", "start": 1357.22, "duration": 5.1}, {"text": "But then I come back and say,\nwhat is scientific truth?", "start": 1362.32, "duration": 3.45}, {"text": "What is scientific truth?", "start": 1369.74, "duration": 3.85}, {"text": "And then there's a book,\ntwo books, three books--", "start": 1373.59, "duration": 4.41}, {"text": "well, let's say two--", "start": 1380.85, "duration": 0.875}, {"text": "that I hadn't intended to\nlecture about, but why not?", "start": 1385.07, "duration": 4.14}, {"text": "One is called Patterns\nof Discovery by Hanson.", "start": 1397.37, "duration": 31.32}, {"text": "And the other is called--", "start": 1428.69, "duration": 3.075}, {"text": "let me start talking, then\nit'll come to my mind.", "start": 1440.42, "duration": 2.697}, {"text": "I didn't prepare for this.", "start": 1443.117, "duration": 1.083}, {"text": "STUDENT: Is it Kuhn?", "start": 1447.483, "duration": 0.938}, {"text": "TAFT BROOME: Kuhn,\nThomas Kuhn, The Nature", "start": 1448.421, "duration": 1.809}, {"text": "of Scientific Revolutions.", "start": 1450.23, "duration": 2.114}, {"text": "STUDENT: I think it might\neven be the structure.", "start": 1457.57, "duration": 2.0}, {"text": "TAFT BROOME: Structure\nof Scientific Revolution.", "start": 1459.57, "duration": 3.215}, {"text": "STUDENT: Still haven't\nfinished it, but--", "start": 1462.785, "duration": 1.94}, {"text": "now", "start": 1479.48, "duration": 1.492}, {"text": "TAFT BROOME: Both, of\nthem talk about something", "start": 1480.972, "duration": 1.958}, {"text": "called worldview.", "start": 1482.93, "duration": 2.04}, {"text": "Both of them talk about\nsomething called gestalt.", "start": 1484.97, "duration": 6.66}, {"text": "So both of them will\ntalk about this figure,", "start": 1491.63, "duration": 14.51}, {"text": "and you would not believe\nthat this figure has", "start": 1506.14, "duration": 8.48}, {"text": "a name called the Necker cube.", "start": 1514.62, "duration": 2.025}, {"text": "Because a Swedish\npsychologist studied it.", "start": 1519.21, "duration": 4.72}, {"text": "I mean, we do it in\nengineering from day one,", "start": 1523.93, "duration": 3.6}, {"text": "this thing here, if for no\nother reason than you'll", "start": 1527.53, "duration": 3.51}, {"text": "extend this out, call that x,\nextend this up, call that y,", "start": 1531.04, "duration": 2.685}, {"text": "extend this out and\ncall that z, won't you?", "start": 1533.725, "duration": 3.255}, {"text": "If for no other reason.", "start": 1536.98, "duration": 1.56}, {"text": "Now, what they'll do is they'll\nask if A is in front of B,", "start": 1541.84, "duration": 5.04}, {"text": "or is B in front of A?", "start": 1546.88, "duration": 1.31}, {"text": "Your mind can switch them.", "start": 1551.55, "duration": 1.536}, {"text": "You can get both.", "start": 1559.9, "duration": 1.12}, {"text": "It takes a minute.", "start": 1561.02, "duration": 3.18}, {"text": "Is this thing coming out of the\nboard and down to the right,", "start": 1564.2, "duration": 4.08}, {"text": "or is it coming out of the\nboard and up to the left?", "start": 1568.28, "duration": 2.625}, {"text": "Well, the point is that we're\ndealing with gestalt here.", "start": 1575.63, "duration": 4.94}, {"text": "And the whole range of\na choice of gestalts", "start": 1580.57, "duration": 6.66}, {"text": "is called world view.", "start": 1587.23, "duration": 1.96}, {"text": "So if you choose to see\nthat A is in front of B,", "start": 1589.19, "duration": 2.3}, {"text": "and then you see a lot\nof different things", "start": 1591.49, "duration": 1.8}, {"text": "with the same kind of\nchoice, that whole thing", "start": 1593.29, "duration": 3.84}, {"text": "forms your world view.", "start": 1597.13, "duration": 1.9}, {"text": "And somebody coming\nin the door may", "start": 1599.03, "duration": 3.17}, {"text": "have a different or\noverlapping world view.", "start": 1602.2, "duration": 4.29}, {"text": "Now, what they say is that\nevery learned discipline", "start": 1606.49, "duration": 2.76}, {"text": "has its world view.", "start": 1609.25, "duration": 5.09}, {"text": "And that you can walk\ninto a class and get", "start": 1614.34, "duration": 3.68}, {"text": "lost when you are right, but\nyou're just looking at it", "start": 1618.02, "duration": 5.472}, {"text": "from a different point.", "start": 1623.492, "duration": 0.958}, {"text": "You're looking at B\nas being behind A.", "start": 1624.45, "duration": 2.43}, {"text": "Everybody else is looking\nat A in front of B", "start": 1626.88, "duration": 3.87}, {"text": "because that's the\nworldview associated", "start": 1630.75, "duration": 1.86}, {"text": "with this learned discipline.", "start": 1632.61, "duration": 1.565}, {"text": "So what they say, then, is that\nwhen you talk about the truth,", "start": 1641.39, "duration": 7.85}, {"text": "that's one thing.", "start": 1649.24, "duration": 0.73}, {"text": "But when you talk\nabout scientific truth", "start": 1649.97, "duration": 1.82}, {"text": "in the context of a\nscientific world view,", "start": 1651.79, "duration": 5.14}, {"text": "you're talking about looking\nat it this way as opposed", "start": 1656.93, "duration": 3.94}, {"text": "to another way.", "start": 1660.87, "duration": 1.59}, {"text": "You're not talking about\nalways looking at the truth.", "start": 1662.46, "duration": 3.03}, {"text": "And so therefore, you\nhave put a value judgment", "start": 1665.49, "duration": 3.35}, {"text": "on why you want to look\nat it that way as opposed", "start": 1668.84, "duration": 3.62}, {"text": "to the other.", "start": 1672.46, "duration": 0.97}, {"text": "And that value judgment\nhas moral implications.", "start": 1673.43, "duration": 5.07}, {"text": "So I go before these people and\nsay, yeah, truth is value free,", "start": 1678.5, "duration": 3.74}, {"text": "but scientific truth isn't\nbecause you have chosen, then,", "start": 1682.24, "duration": 5.96}, {"text": "to look at it a certain\nway when you could", "start": 1688.2, "duration": 1.86}, {"text": "have looked at it another way.", "start": 1690.06, "duration": 4.68}, {"text": "And then what Kuhn\ncomes along and says", "start": 1694.74, "duration": 2.67}, {"text": "is, that's how we get paradigm\nshifts in the disciplines.", "start": 1697.41, "duration": 4.14}, {"text": "Somebody says we all better\nlook at it the other way.", "start": 1701.55, "duration": 2.67}, {"text": "And when everybody starts\nchanging their worldview,", "start": 1709.5, "duration": 2.67}, {"text": "when they look at the same\nthing and actually see", "start": 1712.17, "duration": 3.87}, {"text": "something different, then\nyou've got a paradigm shift.", "start": 1716.04, "duration": 6.125}, {"text": "And now you talk\nabout why people", "start": 1722.165, "duration": 1.375}, {"text": "get Nobel Prizes, why\npeople write dissertations,", "start": 1723.54, "duration": 7.58}, {"text": "Master's theses.", "start": 1731.12, "duration": 0.69}, {"text": "Thomas Kuhn was actually here.", "start": 1748.64, "duration": 1.29}, {"text": "STUDENT: There was [INAUDIBLE].", "start": 1756.832, "duration": 1.479}, {"text": "TAFT BROOME: He wrote\nit back in the '40s.", "start": 1761.27, "duration": 3.72}, {"text": "He was a historian.", "start": 1764.99, "duration": 1.69}, {"text": "He was a historian.", "start": 1766.68, "duration": 1.159}, {"text": "And he uses that thesis\nto do history of science.", "start": 1783.26, "duration": 5.86}, {"text": "And that thesis\nthen tells him how", "start": 1789.12, "duration": 2.97}, {"text": "to break up the errors,\nand that between this error", "start": 1792.09, "duration": 3.84}, {"text": "and that there was\na paradigm shift.", "start": 1795.93, "duration": 2.16}, {"text": "And the paradigm\nshift was like that.", "start": 1798.09, "duration": 2.31}, {"text": "And this stuff is\nvery interesting.", "start": 1803.96, "duration": 2.82}, {"text": "We look at it, and\neverybody agrees", "start": 1806.78, "duration": 2.16}, {"text": "that this, in fact, is a cube.", "start": 1808.94, "duration": 1.29}, {"text": "I don't care how\nmany people you get.", "start": 1810.23, "duration": 1.75}, {"text": "I mean, you ask them\nwhat do they see,", "start": 1811.98, "duration": 1.583}, {"text": "and everybody will\nagree that it's a cute.", "start": 1813.563, "duration": 2.967}, {"text": "Just think about.", "start": 1816.53, "duration": 2.76}, {"text": "And this is what Hanson does.", "start": 1819.29, "duration": 3.87}, {"text": "He says, just think about it.", "start": 1823.16, "duration": 1.29}, {"text": "I asked you what did you see?", "start": 1824.45, "duration": 2.22}, {"text": "I didn't ask you\nwhat this represents.", "start": 1826.67, "duration": 2.445}, {"text": "I asked you, what\ndo you actually see?", "start": 1829.115, "duration": 2.835}, {"text": "Everybody says, \"a cube.\"", "start": 1831.95, "duration": 2.208}, {"text": "it's not a cube.", "start": 1834.158, "duration": 0.667}, {"text": "It's 12 lines on a flat surface.", "start": 1837.66, "duration": 3.6}, {"text": "Actually, what your brain\nsees is not even a line,", "start": 1841.26, "duration": 3.15}, {"text": "it's a bitmap.", "start": 1844.41, "duration": 1.96}, {"text": "You've got white dots\nand black dots in there.", "start": 1846.37, "duration": 3.3}, {"text": "So your brain is\ndoing all of this work", "start": 1849.67, "duration": 3.36}, {"text": "to organize what you experience\nso that you can understand it,", "start": 1853.03, "duration": 4.62}, {"text": "so you can get\nmeaning out of it.", "start": 1857.65, "duration": 3.227}, {"text": "Well, basically, this\nis not even a cube.", "start": 1860.877, "duration": 1.708}, {"text": "Now, there's an artist\nthat deals with this issue.", "start": 1869.01, "duration": 3.54}, {"text": "Now I'm going to tell\nyou who this artist is.", "start": 1879.47, "duration": 2.8}, {"text": "And I'm going to tell\nyou that only one or two", "start": 1882.27, "duration": 6.25}, {"text": "pieces of his work\ncome through to me,", "start": 1888.52, "duration": 3.55}, {"text": "but maybe you see Mondrian.", "start": 1892.07, "duration": 1.23}, {"text": "Because Mondrian knows how\nto draw and color a Necker", "start": 1900.4, "duration": 3.69}, {"text": "cube so that looks flat, whereas\nPicasso can use 6 to 10 of them", "start": 1904.09, "duration": 12.93}, {"text": "to draw your face.", "start": 1917.02, "duration": 0.765}, {"text": "STUDENT: [INAUDIBLE]?", "start": 1927.483, "duration": 0.994}, {"text": "Completely different?", "start": 1936.96, "duration": 1.82}, {"text": "And they always use the example,\nif you're on a train moving,", "start": 1938.78, "duration": 3.73}, {"text": "and you throw a ball in\nthe air, it looks to you", "start": 1942.51, "duration": 2.0}, {"text": "like it goes straight up\nand down when actually, it's", "start": 1944.51, "duration": 2.208}, {"text": "taking the shape of a\nparabola, like in a different", "start": 1946.718, "duration": 2.672}, {"text": "[INAUDIBLE].", "start": 1949.39, "duration": 1.68}, {"text": "TAFT BROOME: Right.", "start": 1951.07, "duration": 1.09}, {"text": "STUDENT: So I think\na lot about that,", "start": 1952.16, "duration": 1.67}, {"text": "what is [INAUDIBLE] if it's real\nto you that it goes straight up", "start": 1953.83, "duration": 4.87}, {"text": "and down, for me looking\nat it from a distance--", "start": 1958.7, "duration": 2.402}, {"text": "TAFT BROOME: Well, that's\nthe kind of thinking that we", "start": 1965.04, "duration": 2.25}, {"text": "need to do in this class--", "start": 1967.29, "duration": 1.05}, {"text": "I mean, not that we\nhaven't been doing it.", "start": 1968.34, "duration": 1.75}, {"text": "But what is truth?", "start": 1970.09, "duration": 5.77}, {"text": "STUDENT: [INAUDIBLE].", "start": 1975.86, "duration": 1.523}, {"text": "TAFT BROOME: Well,\nlet's play with that.", "start": 1977.383, "duration": 1.667}, {"text": "What do you mean absolute?", "start": 1979.05, "duration": 3.21}, {"text": "STUDENT: Is there one\nuniversal truth for everyone?", "start": 1982.26, "duration": 4.725}, {"text": "TAFT BROOME: What does\nthe word \"truth\" mean?", "start": 1986.985, "duration": 1.875}, {"text": "All right.", "start": 1991.86, "duration": 0.57}, {"text": "Well, Aristotle played\naround with that question.", "start": 1995.46, "duration": 5.72}, {"text": "Plato did, too, and\nthey went very far.", "start": 2001.18, "duration": 4.83}, {"text": "They went at least--", "start": 2006.01, "duration": 2.83}, {"text": "accomplished 50%\nof the question.", "start": 2008.84, "duration": 3.39}, {"text": "And the rest of us have\naccomplished, added to that.", "start": 2012.23, "duration": 3.06}, {"text": "Maybe we're at 90%, 95%.", "start": 2015.29, "duration": 3.72}, {"text": "Let's speculate on that.", "start": 2019.01, "duration": 1.14}, {"text": "What do we mean by that?", "start": 2022.75, "duration": 1.56}, {"text": "Plato said one thing about it.", "start": 2024.31, "duration": 4.387}, {"text": "You want me to talk?", "start": 2028.697, "duration": 0.833}, {"text": "STUDENT: I want you to talk.", "start": 2029.53, "duration": 1.983}, {"text": "TAFT BROOME: OK.", "start": 2031.513, "duration": 0.667}, {"text": "[INAUDIBLE] Plato said-- we're\ntalking about what is truth.", "start": 2032.18, "duration": 6.19}, {"text": "And I don't consider\nthat a diversion.", "start": 2038.37, "duration": 2.42}, {"text": "I wanted to talk about\ncodes of ethics today.", "start": 2040.79, "duration": 4.24}, {"text": "Frankly, the question\nof what is truth", "start": 2045.03, "duration": 1.79}, {"text": "is more interesting\nthan codes of ethics.", "start": 2046.82, "duration": 3.352}, {"text": "But I'm looking at the clock.", "start": 2050.172, "duration": 1.208}, {"text": "We've got time.", "start": 2051.38, "duration": 1.93}, {"text": "We've got time.", "start": 2053.31, "duration": 0.71}, {"text": "This is what a philosophy\nclass is supposed to be--", "start": 2054.02, "duration": 4.23}, {"text": "supposed to be 75% ad hoc.", "start": 2058.25, "duration": 2.04}, {"text": "I wouldn't say that\nabout a math class.", "start": 2063.25, "duration": 2.085}, {"text": "OK, let me start talking,\nbut I want you all", "start": 2069.1, "duration": 5.11}, {"text": "to take over the conversation\nif you can get to it.", "start": 2074.21, "duration": 7.88}, {"text": "Let me start with Plato.", "start": 2082.09, "duration": 1.14}, {"text": "Plato said, well, let's\nnot talk about truth first.", "start": 2083.23, "duration": 5.87}, {"text": "Let's talk about\nsomething else first.", "start": 2089.1, "duration": 3.18}, {"text": "Let's talk about knowledge.", "start": 2092.28, "duration": 1.14}, {"text": "What is knowledge?", "start": 2093.42, "duration": 1.14}, {"text": "And Plato said, well, knowledge\nis a statement-- that is,", "start": 2099.51, "duration": 7.51}, {"text": "a sentence that's\neither true or false,", "start": 2107.02, "duration": 5.17}, {"text": "and that there are two kinds\nof knowledge, statements.", "start": 2112.19, "duration": 5.03}, {"text": "One is a statement that agrees\nwith other knowledge statements", "start": 2117.22, "duration": 11.74}, {"text": "according to the rules\nof logic and reason.", "start": 2128.96, "duration": 2.34}, {"text": "And that's called\nrational knowledge.", "start": 2139.25, "duration": 4.48}, {"text": "The other one is a\nstatement that agrees", "start": 2143.73, "duration": 4.98}, {"text": "with observation or experience.", "start": 2148.71, "duration": 2.46}, {"text": "I'll put observation, but\nI don't mean just the eye.", "start": 2151.17, "duration": 2.77}, {"text": "I mean all of the five senses.", "start": 2153.94, "duration": 1.25}, {"text": "So there's a cup of\ncoffee on the table.", "start": 2162.26, "duration": 3.53}, {"text": "That's a statement of knowledge.", "start": 2165.79, "duration": 1.333}, {"text": "STUDENT: Isn't that\na statement of fact?", "start": 2171.76, "duration": 1.667}, {"text": "TAFT BROOME: No, it's the\nsame thing as a [INAUDIBLE]..", "start": 2173.427, "duration": 2.291}, {"text": "It's an observation of a fact.", "start": 2175.718, "duration": 1.922}, {"text": "It's a statement that describes\nan observation of a fact,", "start": 2177.64, "duration": 3.56}, {"text": "or it is a fact because\nit is information", "start": 2181.2, "duration": 5.1}, {"text": "that is coming to\nmy brain of the type", "start": 2186.3, "duration": 3.09}, {"text": "that I call sensory information.", "start": 2189.39, "duration": 1.83}, {"text": "And then what I\nwould speculate on", "start": 2194.65, "duration": 1.79}, {"text": "is that that sensory\ninformation comes", "start": 2196.44, "duration": 2.52}, {"text": "from someplace outside of the\nmind, call it \"real world.\"", "start": 2198.96, "duration": 5.76}, {"text": "So a knowledge statement--", "start": 2207.5, "duration": 3.18}, {"text": "well, you might\ncome along and say,", "start": 2210.68, "duration": 2.43}, {"text": "I said this was a cup of coffee.", "start": 2213.11, "duration": 2.33}, {"text": "I analyze it.", "start": 2215.44, "duration": 0.617}, {"text": "There's some coffee\nin it, but there's", "start": 2216.057, "duration": 1.583}, {"text": "really strychnine in there.", "start": 2217.64, "duration": 2.28}, {"text": "Pretty soon,\n[INAUDIBLE] the room.", "start": 2219.92, "duration": 4.08}, {"text": "So Plato doesn't have\nany problems with that.", "start": 2224.0, "duration": 4.6}, {"text": "Plato says that you can improve\nupon your knowledge statements,", "start": 2228.6, "duration": 5.85}, {"text": "and in the limit,\nyou get the truth.", "start": 2234.45, "duration": 8.65}, {"text": "That's why Plato was very happy\nto say we pursue the truth,", "start": 2243.1, "duration": 6.8}, {"text": "but we make knowledge claims.", "start": 2249.9, "duration": 3.87}, {"text": "You do the same thing when\nit comes to value judgments.", "start": 2253.77, "duration": 6.6}, {"text": "You make a value judgment and\nin the limit, you get the good.", "start": 2260.37, "duration": 3.12}, {"text": "So now, this is called\nrational knowledge,", "start": 2268.21, "duration": 5.78}, {"text": "and this is called\nempirical knowledge.", "start": 2273.99, "duration": 12.82}, {"text": "You can also say values, value\njudgments, and get the good.", "start": 2286.81, "duration": 5.57}, {"text": "And then Plato says that if\nyou put these two together,", "start": 2296.79, "duration": 7.58}, {"text": "and imagine that this limit does\nexist, what do you think Plato", "start": 2304.37, "duration": 10.65}, {"text": "or what do you think pretty much\n90% of the philosophers that", "start": 2315.02, "duration": 3.758}, {"text": "are out here-- what do\nyou think they would", "start": 2318.778, "duration": 1.792}, {"text": "call the truth and the good?", "start": 2320.57, "duration": 3.405}, {"text": "If there's something out\nthere that is perfect--", "start": 2328.6, "duration": 4.41}, {"text": "yes, that's Plato's theology.", "start": 2333.01, "duration": 2.49}, {"text": "He calls this God.", "start": 2335.5, "duration": 2.74}, {"text": "STUDENT: [INAUDIBLE] in\nthere somewhere, too?", "start": 2338.24, "duration": 2.3}, {"text": "TAFT BROOME: Values,\nthat's aesthetic value.", "start": 2340.54, "duration": 2.97}, {"text": "STUDENT: I have a question\nabout rational knowledge.", "start": 2351.891, "duration": 4.264}, {"text": "So rational knowledge, we said,\nagrees with other [INAUDIBLE]..", "start": 2356.155, "duration": 12.335}, {"text": "TAFT BROOME: Well, it's\nhard to put in words.", "start": 2368.49, "duration": 2.76}, {"text": "Let me give you\na starting point.", "start": 2371.25, "duration": 2.67}, {"text": "Mathematics is\nrational knowledge.", "start": 2373.92, "duration": 3.19}, {"text": "It makes no reference to\nexperience or to objects.", "start": 2377.11, "duration": 4.8}, {"text": "You ready for this?", "start": 2385.09, "duration": 0.81}, {"text": "Can you see this up at the top?", "start": 2390.54, "duration": 3.09}, {"text": "STUDENT: [INAUDIBLE].", "start": 2393.63, "duration": 1.147}, {"text": "TAFT BROOME: I'll tell you what.", "start": 2394.777, "duration": 1.333}, {"text": "STUDENT: That's good.", "start": 2403.082, "duration": 1.318}, {"text": "[INAUDIBLE] my mind [INAUDIBLE].", "start": 2404.4, "duration": 2.305}, {"text": "So like math, saying that the\nderivative of the natural log", "start": 2411.61, "duration": 7.002}, {"text": "is whatever it is, is\nknowledge, but it makes no sense", "start": 2418.612, "duration": 8.428}, {"text": "unless you know what\n\"derivative\" means", "start": 2427.04, "duration": 3.533}, {"text": "or what \"natural log\" means.", "start": 2430.573, "duration": 1.167}, {"text": "TAFT BROOME: You've\ngot definitions.", "start": 2431.74, "duration": 1.98}, {"text": "Start with definitions.", "start": 2433.72, "duration": 2.89}, {"text": "You've got symbols.", "start": 2436.61, "duration": 1.908}, {"text": "You've got rules for\nputting them together.", "start": 2438.518, "duration": 1.792}, {"text": "You call that syntax.", "start": 2440.31, "duration": 3.27}, {"text": "And then you have rules\nfor deducing other symbols.", "start": 2443.58, "duration": 5.22}, {"text": "You call that semantics.", "start": 2448.8, "duration": 1.66}, {"text": "So now we're talking\nabout deducing a theorem", "start": 2450.46, "duration": 3.2}, {"text": "from an axiom.", "start": 2453.66, "duration": 3.09}, {"text": "STUDENT: [INAUDIBLE] but\nit's not-- it can't just be", "start": 2456.75, "duration": 2.64}, {"text": "[INAUDIBLE].", "start": 2459.39, "duration": 1.41}, {"text": "TAFT BROOME: Right, or I'm\ngoing to be a little bit more--", "start": 2460.8, "duration": 3.45}, {"text": "it is not empirical.", "start": 2464.25, "duration": 1.29}, {"text": "I don't want to say\nthat it can or possibly.", "start": 2468.35, "duration": 2.4}, {"text": "We throw that all out.", "start": 2470.75, "duration": 1.32}, {"text": "It's all mental,\nand it's all reason.", "start": 2472.07, "duration": 4.686}, {"text": "STUDENT: I also think of\nEinstein's paper [INAUDIBLE]??", "start": 2476.756, "duration": 2.832}, {"text": "He talks about\nEuclidean geometry,", "start": 2482.42, "duration": 1.77}, {"text": "and how you talk about a\nlot [INAUDIBLE] exists.", "start": 2484.19, "duration": 2.49}, {"text": "Can you observe a line?", "start": 2486.68, "duration": 1.284}, {"text": "Because it's infinitely small--", "start": 2487.964, "duration": 1.464}, {"text": "TAFT BROOME: Right.", "start": 2489.428, "duration": 0.792}, {"text": "[INTERPOSING VOICES]", "start": 2490.22, "duration": 0.91}, {"text": "STUDENT: So it's not something\nthat you can really observe.", "start": 2491.13, "duration": 1.985}, {"text": "And a point is the same thing.", "start": 2493.115, "duration": 1.588}, {"text": "You can't really observe,\nempirically measure a point.", "start": 2494.703, "duration": 3.209}, {"text": "It doesn't really\nexist [INAUDIBLE]..", "start": 2497.912, "duration": 2.261}, {"text": "TAFT BROOME: Right.", "start": 2505.678, "duration": 0.792}, {"text": "I could put a rock\nhere, and then", "start": 2506.47, "duration": 1.86}, {"text": "a smaller rock, and a smaller\none, and a smaller one.", "start": 2508.33, "duration": 3.6}, {"text": "We could even go down\nto an atomic particle,", "start": 2511.93, "duration": 4.59}, {"text": "and keep going.", "start": 2516.52, "duration": 0.77}, {"text": "We still haven't got a point.", "start": 2517.29, "duration": 1.66}, {"text": "But we can still\ntalk about a point.", "start": 2518.95, "duration": 2.625}, {"text": "STUDENT: Right.", "start": 2521.575, "duration": 0.625}, {"text": "[INAUDIBLE]", "start": 2522.2, "duration": 1.65}, {"text": "TAFT BROOME: And\nall kinds of stuff.", "start": 2523.85, "duration": 1.5}, {"text": "That's right.", "start": 2528.188, "duration": 0.542}, {"text": "So what Kant wanted to do is\ntake that kind of thinking out", "start": 2532.67, "duration": 3.3}, {"text": "of the scientific\nrealm, and say,", "start": 2535.97, "duration": 4.23}, {"text": "I want to base a value\njudgment strictly off", "start": 2540.2, "duration": 6.47}, {"text": "of the rational process,\nstrictly mental.", "start": 2546.67, "duration": 3.96}, {"text": "And Mill said, I want to make a\nrational judgment strictly out", "start": 2550.63, "duration": 5.07}, {"text": "of the empirical thinking--\nknowledge, statements.", "start": 2555.7, "duration": 5.68}, {"text": "So they took all of\nthis stuff and put it", "start": 2561.38, "duration": 1.79}, {"text": "into the value domain.", "start": 2563.17, "duration": 1.11}, {"text": "Now, let's talk some more\nabout empirical knowledge.", "start": 2569.19, "duration": 4.22}, {"text": "Let's talk some more.", "start": 2584.13, "duration": 2.07}, {"text": "There is a genre of story\nthat all start the same way.", "start": 2586.2, "duration": 9.4}, {"text": "They end slightly differently,\nbut they all start the same,", "start": 2595.6, "duration": 5.465}, {"text": "and we can get a\nlot out of this.", "start": 2601.065, "duration": 1.375}, {"text": "You're driving along someplace.", "start": 2605.85, "duration": 4.49}, {"text": "Look down, something\nlooks funny about your car", "start": 2610.34, "duration": 5.6}, {"text": "or for whatever reason, you\nget off 95, the main highway.", "start": 2615.94, "duration": 3.39}, {"text": "You get on some little road,\ngoing down this little road.", "start": 2619.33, "duration": 3.96}, {"text": "And then there are no houses, no\ngas stations, just driving down", "start": 2623.29, "duration": 6.527}, {"text": "this little road.", "start": 2629.817, "duration": 0.708}, {"text": "It's getting dark,\nthe car stops,", "start": 2630.525, "duration": 3.493}, {"text": "and the road comes to an\nend, and there's nothing", "start": 2634.018, "duration": 2.042}, {"text": "there but the woods.", "start": 2636.06, "duration": 2.97}, {"text": "And for some reason, you\ndecide to get out of your car", "start": 2639.03, "duration": 3.27}, {"text": "and walk through the woods.", "start": 2642.3, "duration": 1.14}, {"text": "You've got to run into\nsomething-- shopping center.", "start": 2643.44, "duration": 4.32}, {"text": "You run into a monastery.", "start": 2647.76, "duration": 1.5}, {"text": "And you knock on the\ndoor, and hear a voice", "start": 2652.1, "duration": 4.19}, {"text": "on the other side\ntalking to you.", "start": 2656.29, "duration": 2.85}, {"text": "And there's a little window in\nthe door, a little window where", "start": 2659.14, "duration": 3.35}, {"text": "you can basically pass.", "start": 2662.49, "duration": 1.66}, {"text": "And everybody can\nspeak the same English.", "start": 2664.15, "duration": 4.63}, {"text": "Now, all of the stories\nstart the same way.", "start": 2671.47, "duration": 2.43}, {"text": "I'm going to tell two of them.", "start": 2673.9, "duration": 2.16}, {"text": "Now, one of them is that they\ntell you to go away at first.", "start": 2679.42, "duration": 5.638}, {"text": "You say you're hungry,\nyou need a place to sleep.", "start": 2685.058, "duration": 2.042}, {"text": "And they tell you to go away.", "start": 2687.1, "duration": 1.26}, {"text": "You keep knocking on\nand banging on the door.", "start": 2688.36, "duration": 3.48}, {"text": "And all of a sudden, that little\nwindow falls open by itself.", "start": 2691.84, "duration": 8.25}, {"text": "Nobody opened it,\nit just falls open,", "start": 2700.09, "duration": 1.57}, {"text": "and you get a peek inside.", "start": 2701.66, "duration": 1.083}, {"text": "And you look in there,\nand everything is yellow--", "start": 2705.41, "duration": 8.74}, {"text": "floor, walls, the ceiling,\nchairs, the desk, their food,", "start": 2714.15, "duration": 8.04}, {"text": "their skin, their\neyes, their hair.", "start": 2722.19, "duration": 3.24}, {"text": "Everything is yellow.", "start": 2725.43, "duration": 1.515}, {"text": "Everything is yellow.", "start": 2730.87, "duration": 1.47}, {"text": "Then you say, why is\neverything yellow?", "start": 2735.04, "duration": 4.0}, {"text": "They don't have the word\n\"yellow\" in their vocabulary.", "start": 2739.04, "duration": 3.643}, {"text": "Then you reach in your\nhand, and let's say", "start": 2746.85, "duration": 3.39}, {"text": "you had a pen that\nhad red ink in it.", "start": 2750.24, "duration": 1.96}, {"text": "So you squirt some\nred ink in there.", "start": 2752.2, "duration": 2.42}, {"text": "All of a sudden, two words\ncomes into their vocabulary", "start": 2754.62, "duration": 2.91}, {"text": "at the same time--\n\"red\" and \"yellow.\"", "start": 2757.53, "duration": 1.8}, {"text": "Then they get to\ntalk, and then they", "start": 2764.71, "duration": 1.98}, {"text": "find the word \"color\" to\naccount for both of them,", "start": 2766.69, "duration": 2.4}, {"text": "and to distinguish\ncolor from other things.", "start": 2769.09, "duration": 2.4}, {"text": "But they had yellow in\nfront of them all along,", "start": 2771.49, "duration": 3.33}, {"text": "but they couldn't see it.", "start": 2774.82, "duration": 1.65}, {"text": "Or they could see it,\ncouldn't distinguish it.", "start": 2776.47, "duration": 4.937}, {"text": "Only when that got that\nother color in there could", "start": 2781.407, "duration": 2.083}, {"text": "they distinguish it.", "start": 2783.49, "duration": 0.833}, {"text": "But then red and yellow\ncome in their language", "start": 2784.323, "duration": 3.037}, {"text": "at the same time.", "start": 2787.36, "duration": 0.96}, {"text": "So now, that's what Kuhn\nis talking about when", "start": 2792.98, "duration": 2.88}, {"text": "he says a new paradigm.", "start": 2795.86, "duration": 3.33}, {"text": "He's not saying that somebody\nis going to show you something", "start": 2799.19, "duration": 2.5}, {"text": "that you've never seen before.", "start": 2801.69, "duration": 2.35}, {"text": "What he's going to say\nis you're going to say,", "start": 2804.04, "duration": 3.56}, {"text": "I don't know what word to\nuse about my experience", "start": 2807.6, "duration": 3.6}, {"text": "with this thing.", "start": 2811.2, "duration": 0.78}, {"text": "It was here all along,\nbut did I see it?", "start": 2811.98, "duration": 7.51}, {"text": "No.", "start": 2819.49, "duration": 0.5}, {"text": "Then you have to find a\nlot of different words", "start": 2819.99, "duration": 1.917}, {"text": "to describe what you did see.", "start": 2821.907, "duration": 2.223}, {"text": "And you still won't.", "start": 2824.13, "duration": 1.675}, {"text": "And you'll wind up\nspeaking with people", "start": 2825.805, "duration": 1.625}, {"text": "call \"tongues,\" very abstract.", "start": 2827.43, "duration": 1.745}, {"text": "It's only when the other\none came in there that you", "start": 2829.175, "duration": 2.125}, {"text": "could see both of them.", "start": 2831.3, "duration": 0.958}, {"text": "Now let's get to Einstein--", "start": 2840.28, "duration": 3.03}, {"text": "same story.", "start": 2843.31, "duration": 2.94}, {"text": "You're at the monastery.", "start": 2846.25, "duration": 2.25}, {"text": "The monks won't let you in.", "start": 2848.5, "duration": 3.21}, {"text": "The door opens up.", "start": 2851.71, "duration": 3.02}, {"text": "This time, you look in there\nand all of the monks are blind.", "start": 2854.73, "duration": 6.44}, {"text": "You don't ask them a\nquestion about generations.", "start": 2865.98, "duration": 2.61}, {"text": "They've always been blind.", "start": 2871.23, "duration": 1.232}, {"text": "Everybody's been blind.", "start": 2872.462, "duration": 0.958}, {"text": "So what you do is you finally\ntalk them into letting you in.", "start": 2876.16, "duration": 8.55}, {"text": "And when you get\nin there, you find", "start": 2884.71, "duration": 4.07}, {"text": "that there's a rack in a\ncloset, a rack of t-shirts.", "start": 2888.78, "duration": 3.645}, {"text": "Now, all of the t-shirts are the\nsame size, smell the same way,", "start": 2896.3, "duration": 5.9}, {"text": "made out of the same material.", "start": 2902.2, "duration": 2.61}, {"text": "They are all the\nsame except that they", "start": 2904.81, "duration": 2.16}, {"text": "have different colors, but\nthe blind man can't see it.", "start": 2906.97, "duration": 2.25}, {"text": "The blind man cannot\ndistinguish one from the other.", "start": 2912.75, "duration": 2.738}, {"text": "He's sitting there.", "start": 2915.488, "duration": 0.792}, {"text": "He knows he pulls out one,\nand they're all the same.", "start": 2916.28, "duration": 2.167}, {"text": "You can tell that half of them\nare dark red and the other half", "start": 2921.43, "duration": 6.06}, {"text": "are white.", "start": 2927.49, "duration": 0.54}, {"text": "They can't see it, but there's\none thing the blind men know,", "start": 2930.63, "duration": 3.93}, {"text": "and that is that when\nthey put on some t-shirts", "start": 2934.56, "duration": 5.7}, {"text": "and sit out in the\nsun, they get warm.", "start": 2940.26, "duration": 1.77}, {"text": "And when they put\non other t-shirts,", "start": 2942.03, "duration": 2.265}, {"text": "they sit out under the sun\nand they don't get warm.", "start": 2944.295, "duration": 2.125}, {"text": "They stay a little bit cool.", "start": 2946.42, "duration": 2.83}, {"text": "You go in there and say,\nwell, wear the red ones", "start": 2949.25, "duration": 3.328}, {"text": "when you want to get warm\nand wear the white ones", "start": 2952.578, "duration": 2.042}, {"text": "when you want to get cool.", "start": 2954.62, "duration": 1.083}, {"text": "They don't know what\nyou're talking about.", "start": 2955.703, "duration": 2.607}, {"text": "Einstein calls\nthat \"hyperspace,\"", "start": 2958.31, "duration": 3.54}, {"text": "says that we have five senses.", "start": 2961.85, "duration": 5.22}, {"text": "If we had a sixth one, we\ncould perceive other things.", "start": 2967.07, "duration": 4.87}, {"text": "With our five\nsenses, we can still", "start": 2971.94, "duration": 2.31}, {"text": "perceive some of those\nthings, but their behaviors", "start": 2974.25, "duration": 3.57}, {"text": "don't fit in the patterns,\nlike these traces of particles", "start": 2977.82, "duration": 5.38}, {"text": "they see, these\nparticle physicists", "start": 2983.2, "duration": 2.42}, {"text": "see even to this day.", "start": 2985.62, "duration": 2.01}, {"text": "They know that they're\nthere, but they", "start": 2987.63, "duration": 2.1}, {"text": "don't behave according\nto Newton's laws,", "start": 2989.73, "duration": 5.28}, {"text": "to Einstein's special\ntheory of relativity.", "start": 2995.01, "duration": 2.82}, {"text": "As a matter of fact, there's\nno pattern that you can see.", "start": 2997.83, "duration": 3.33}, {"text": "And so what they say\nis that a pattern", "start": 3001.16, "duration": 2.52}, {"text": "would exist if some\nalien came down", "start": 3003.68, "duration": 2.67}, {"text": "here with a sixth sense who\ncould perceive something", "start": 3006.35, "duration": 5.41}, {"text": "like that.", "start": 3011.76, "duration": 0.75}, {"text": "We don't have the sixth sense.", "start": 3012.51, "duration": 1.68}, {"text": "We know that this thing\nis behaving like this.", "start": 3014.19, "duration": 4.75}, {"text": "So here's what Einstein and\nthese physicists try to do--", "start": 3018.94, "duration": 4.01}, {"text": "what they try to do is\nwrite a position vector,", "start": 3022.95, "duration": 5.19}, {"text": "not just in x, y, z, and\nsay that these are dependent", "start": 3028.14, "duration": 5.01}, {"text": "variables, and they're\nall dependent on time.", "start": 3033.15, "duration": 3.3}, {"text": "Einstein comes back and\nsays, let's put in alpha,", "start": 3036.45, "duration": 6.57}, {"text": "call it the fourth\ndimension, do our arithmetic,", "start": 3043.02, "duration": 3.54}, {"text": "and we will be able to\naccount for that behavior", "start": 3046.56, "duration": 3.51}, {"text": "even though we don't\nbelong or can't", "start": 3050.07, "duration": 1.8}, {"text": "sense the rest of\nthis hyperspace,", "start": 3051.87, "duration": 2.19}, {"text": "just like the blind\nmen can account", "start": 3054.06, "duration": 3.87}, {"text": "for the difference in t-shirts\nby going out in the sun,", "start": 3057.93, "duration": 5.6}, {"text": "but can't see the difference\nor otherwise perceived it.", "start": 3063.53, "duration": 4.05}, {"text": "So that's what hyperspace is.", "start": 3067.58, "duration": 3.34}, {"text": "It's an attempt to\naccount for something", "start": 3070.92, "duration": 1.89}, {"text": "you can't fully perceive--\nyou can't perceive but you", "start": 3072.81, "duration": 4.68}, {"text": "can perceive the effects.", "start": 3077.49, "duration": 3.22}, {"text": "So what you say is that in order\nto understand this position", "start": 3080.71, "duration": 3.5}, {"text": "vector, you have to\nspeculate another dimension.", "start": 3084.21, "duration": 5.5}, {"text": "And if you do your math right,\nyou'll get right answers.", "start": 3089.71, "duration": 4.6}, {"text": "Better stated, you\nwill find a pattern.", "start": 3094.31, "duration": 1.71}, {"text": "And then you use this\nalpha to fit in so", "start": 3098.8, "duration": 3.03}, {"text": "that you fit into the pattern.", "start": 3101.83, "duration": 2.41}, {"text": "And if that has a predictive\nquality, then you've got a law.", "start": 3104.24, "duration": 7.35}, {"text": "STUDENT: [INAUDIBLE]", "start": 3111.59, "duration": 3.3}, {"text": "TAFT BROOME: You just\nhave to live with it,", "start": 3114.89, "duration": 1.94}, {"text": "like the blind men just\nhave to live with the fact.", "start": 3116.83, "duration": 2.64}, {"text": "STUDENT: [INAUDIBLE].", "start": 3119.47, "duration": 2.287}, {"text": "TAFT BROOME: And\nthey're not even sure", "start": 3121.757, "duration": 1.583}, {"text": "before they go out\nwhich ones are.", "start": 3123.34, "duration": 3.695}, {"text": "So you take two\nor three of them,", "start": 3127.035, "duration": 1.375}, {"text": "you go out you put them on, take\na chance that one of them will.", "start": 3128.41, "duration": 3.22}, {"text": "But you've tied\ndown things a bit.", "start": 3131.63, "duration": 2.025}, {"text": "You've got a science.", "start": 3133.655, "duration": 0.875}, {"text": "They've got a science in\nthere, in that monastery.", "start": 3134.53, "duration": 4.67}, {"text": "So that's where you get a lot\nof this abstract thinking coming", "start": 3142.53, "duration": 3.66}, {"text": "along later, with people\nlike Kierkegaard and Sartre.", "start": 3146.19, "duration": 7.2}, {"text": "Let me see if I can\nget my French right.", "start": 3153.39, "duration": 2.61}, {"text": "I qualified in French, but I\ndon't count myself as a person", "start": 3156.0, "duration": 2.73}, {"text": "who knows French, but\n\"Sahrt,\" S-A-R-T-R-E.", "start": 3158.73, "duration": 3.3}, {"text": "I feel more comfortable\nin saying \"Sar-tre.\"", "start": 3162.03, "duration": 2.062}, {"text": "Sartre won the\nNobel Prize twice.", "start": 3167.19, "duration": 5.85}, {"text": "I think he won it three times,\nbut he turned it down one time.", "start": 3173.04, "duration": 3.12}, {"text": "These are people who talk\nabout existentialism.", "start": 3178.96, "duration": 5.97}, {"text": "And if you go talk\nto a Zen Buddhist,", "start": 3193.17, "duration": 6.24}, {"text": "he or she will\ntalk about Nirvana.", "start": 3199.41, "duration": 2.415}, {"text": "And if you talk to\nEinstein, or any", "start": 3206.26, "duration": 3.24}, {"text": "of his intellectual descendants,\nhe will talk about hyperspace.", "start": 3209.5, "duration": 5.28}, {"text": "There's a lot of similarity\nin those concepts,", "start": 3217.97, "duration": 10.56}, {"text": "a lot of similarity\nin those concepts.", "start": 3228.53, "duration": 1.83}, {"text": "And there is Kierkegaard who'll\ntalk about existentialism,", "start": 3230.36, "duration": 7.29}, {"text": "and then he does the same\nthing that these two guys did,", "start": 3237.65, "duration": 5.04}, {"text": "when they looked at knowledge\nand truth, values and the good,", "start": 3242.69, "duration": 5.46}, {"text": "and you look at\nknowledge in terms", "start": 3248.15, "duration": 1.44}, {"text": "of empirical knowledge\nand rational knowledge,", "start": 3249.59, "duration": 2.13}, {"text": "these people talk about\nactually empirical values", "start": 3251.72, "duration": 4.14}, {"text": "and rational values.", "start": 3255.86, "duration": 3.36}, {"text": "So Kierkegaard comes\nalong and says,", "start": 3259.22, "duration": 2.19}, {"text": "let's stretch out hyperspace.", "start": 3261.41, "duration": 2.7}, {"text": "Can we talk about good\nand bad in hyperspace?", "start": 3264.11, "duration": 2.82}, {"text": "In other words, not\njust the real world,", "start": 3266.93, "duration": 2.85}, {"text": "but things that you cannot\ntotally observe but that are", "start": 3269.78, "duration": 2.97}, {"text": "there anyway?", "start": 3272.75, "duration": 2.76}, {"text": "And you get a lot of sympathy\nfrom that if you go over", "start": 3275.51, "duration": 2.67}, {"text": "to the Art Department.", "start": 3278.18, "duration": 1.466}, {"text": "You don't have to go to\nthe School of Religion.", "start": 3282.492, "duration": 1.958}, {"text": "You go to the Art\nDepartment, Ballet.", "start": 3284.45, "duration": 5.01}, {"text": "They'll tell you there's\na hyperspace out there.", "start": 3289.46, "duration": 2.43}, {"text": "There's a hyper world out\nthere, and that some people are", "start": 3291.89, "duration": 3.96}, {"text": "in touch with it, and most\nof the rest of us aren't.", "start": 3295.85, "duration": 2.58}, {"text": "And they don't know\nwhat it is out there,", "start": 3304.3, "duration": 3.18}, {"text": "but they know when you've\ngot it, like the monks did.", "start": 3307.48, "duration": 4.17}, {"text": "They knew when you\nhad the red shirt,", "start": 3311.65, "duration": 3.618}, {"text": "but they didn't know about\nred and white shirts.", "start": 3315.268, "duration": 3.407}, {"text": "But they know when\nyou've got it,", "start": 3318.675, "duration": 1.375}, {"text": "and those are the ones\nyou call the geniuses.", "start": 3320.05, "duration": 2.58}, {"text": "Not genius in\nterms of intellect,", "start": 3322.63, "duration": 1.44}, {"text": "but just people\nwho've just got it.", "start": 3324.07, "duration": 3.61}, {"text": "Some people just\ngot it, and they", "start": 3327.68, "duration": 2.27}, {"text": "can touch that other world.", "start": 3329.95, "duration": 2.85}, {"text": "Ancient people knew\nabout this stuff.", "start": 3332.8, "duration": 1.605}, {"text": "Tell you how they\nknew about it--", "start": 3339.855, "duration": 1.375}, {"text": "they knew it in a way that\nwe call it very concrete.", "start": 3344.24, "duration": 3.5}, {"text": "They knew about it in\nterms of consciousness", "start": 3347.74, "duration": 1.86}, {"text": "and unconsciousness.", "start": 3349.6, "duration": 1.34}, {"text": "They knew about the dream state.", "start": 3354.44, "duration": 2.07}, {"text": "And when I say \"ancient,\" I'm\ntalking about beyond way back.", "start": 3361.52, "duration": 6.25}, {"text": "I'm talking about\n10,000 years ago.", "start": 3367.77, "duration": 8.58}, {"text": "I'm talking about even\nprobably before that,", "start": 3376.35, "duration": 2.52}, {"text": "but when human beings\nbegan to have dreams.", "start": 3378.87, "duration": 5.24}, {"text": "They say some\nanimals have dreams--", "start": 3384.11, "duration": 2.52}, {"text": "dogs.", "start": 3386.63, "duration": 0.93}, {"text": "STUDENT: Wait, they know a\nparticular point in time when", "start": 3387.56, "duration": 3.2}, {"text": "[INAUDIBLE]?", "start": 3390.76, "duration": 2.0}, {"text": "TAFT BROOME: I don't\nknow, but they speculate--", "start": 3392.76, "duration": 2.04}, {"text": "STUDENT: [INAUDIBLE]\nfirst start recording.", "start": 3394.8, "duration": 3.08}, {"text": "TAFT BROOME: They know\nwhen dreams became a factor", "start": 3397.88, "duration": 5.61}, {"text": "in your daily life.", "start": 3403.49, "duration": 3.36}, {"text": "They know that,\nbecause they were", "start": 3406.85, "duration": 1.53}, {"text": "able to see what we call\nreligious artifacts and burial.", "start": 3408.38, "duration": 5.94}, {"text": "I think burial was what the\ncultural archaeologists say", "start": 3414.32, "duration": 4.44}, {"text": "is the first, then cave drawings\non walls, art, but burial--", "start": 3418.76, "duration": 7.18}, {"text": "the notion that somebody\ndeserves some kind of ceremony", "start": 3425.94, "duration": 7.2}, {"text": "after they died, and\nhave to be buried,", "start": 3433.14, "duration": 2.4}, {"text": "and something goes into\nthe grave with them", "start": 3435.54, "duration": 2.49}, {"text": "to notice the notion that\nthere is another world.", "start": 3438.03, "duration": 2.94}, {"text": "And the other world\nthat they thought", "start": 3440.97, "duration": 1.62}, {"text": "was that you are just\ngoing to the dream state,", "start": 3442.59, "duration": 3.6}, {"text": "and you'll never\nget out of it now,", "start": 3446.19, "duration": 4.69}, {"text": "and that the dream\nstate was just", "start": 3450.88, "duration": 1.53}, {"text": "as valid as a conscious state.", "start": 3452.41, "duration": 4.29}, {"text": "The price we pay for saying\nthat the dream state is not", "start": 3456.7, "duration": 4.68}, {"text": "worth anything unless you've\ngot a real mental problem--", "start": 3461.38, "duration": 5.01}, {"text": "the price we pay for that is\nthat we forget the obvious,", "start": 3466.39, "duration": 3.03}, {"text": "and that is that our conscious\nminds can't be entirely trusted", "start": 3469.42, "duration": 4.5}, {"text": "because there are a lot of\ntruths that are in our mind", "start": 3473.92, "duration": 2.25}, {"text": "that our conscious minds\ndo not want to face.", "start": 3476.17, "duration": 1.875}, {"text": "And we put them\nin our unconscious", "start": 3478.045, "duration": 1.785}, {"text": "and they come out in dreams\nin the forms of dragons,", "start": 3479.83, "duration": 2.82}, {"text": "and trolls, and all that.", "start": 3482.65, "duration": 3.4}, {"text": "So there is truth down there.", "start": 3486.05, "duration": 2.43}, {"text": "That's what the mythic\nhero has got to do.", "start": 3488.48, "duration": 3.17}, {"text": "He's got to kill that dragon.", "start": 3491.65, "duration": 2.27}, {"text": "That's the symbol.", "start": 3493.92, "duration": 0.78}, {"text": "That is the metaphor for solving\nyour biggest problems in life.", "start": 3494.7, "duration": 4.17}, {"text": "You have to say\nthat you've got all", "start": 3498.87, "duration": 1.74}, {"text": "of the truth necessary\nto solve this problem.", "start": 3500.61, "duration": 1.93}, {"text": "But some of it you\nhave hidden, so you", "start": 3502.54, "duration": 2.77}, {"text": "have to go down in\nthe unconscious,", "start": 3505.31, "duration": 1.47}, {"text": "get it, bring it up to\nconsciousness, and make it fit,", "start": 3506.78, "duration": 4.8}, {"text": "mostly morally.", "start": 3511.58, "duration": 1.6}, {"text": "Because a lot of the\nthings you have hidden down", "start": 3513.18, "duration": 2.0}, {"text": "there don't fit\nbecause you don't", "start": 3515.18, "duration": 1.83}, {"text": "want to accept the\nmoral truth of it.", "start": 3517.01, "duration": 3.06}, {"text": "Notice I said \"moral truth.\"", "start": 3520.07, "duration": 3.488}, {"text": "So there are truths down there.", "start": 3523.558, "duration": 1.292}, {"text": "So what the primitive-- that's\nthe word I'm looking for--", "start": 3524.85, "duration": 5.56}, {"text": "beyond ancient--\nprimitive human beings", "start": 3530.41, "duration": 5.21}, {"text": "understood the two\ndifferent worlds", "start": 3535.62, "duration": 3.6}, {"text": "and they believed\nthat both were valid.", "start": 3539.22, "duration": 2.58}, {"text": "And that whatever was\ndown in one, some of them", "start": 3541.8, "duration": 4.47}, {"text": "had mirror images of\nwhat was up in the other.", "start": 3546.27, "duration": 4.44}, {"text": "But there were other\nthings, and you had", "start": 3550.71, "duration": 2.01}, {"text": "to learn how to live in both.", "start": 3552.72, "duration": 2.58}, {"text": "And there was always\none individual", "start": 3555.3, "duration": 3.83}, {"text": "that understood both of them.", "start": 3559.13, "duration": 4.482}, {"text": "You know what they called them?", "start": 3563.612, "duration": 2.725}, {"text": "Go ahead and say it.", "start": 3566.337, "duration": 0.833}, {"text": "STUDENT: I've heard you\nsay \"shaman\" before.", "start": 3567.17, "duration": 1.92}, {"text": "TAFT BROOME: Yeah, the shaman.", "start": 3569.09, "duration": 1.68}, {"text": "Shaman understands those\ntwo different worlds", "start": 3574.37, "duration": 4.77}, {"text": "and can navigate them.", "start": 3579.14, "duration": 4.5}, {"text": "And so hyperspace-- let's\ntake this thing one more time,", "start": 3583.64, "duration": 11.677}, {"text": "and then we'll try one\nor two of these codes", "start": 3595.317, "duration": 1.833}, {"text": "before we get out of here.", "start": 3597.15, "duration": 2.65}, {"text": "Hyperspace-- let's go back to\nknowledge in the first place.", "start": 3599.8, "duration": 3.85}, {"text": "Go back to knowledge.", "start": 3603.65, "duration": 1.135}, {"text": "We're talking now about there's\na term of art in philosophy,", "start": 3607.7, "duration": 7.52}, {"text": "and it's called--", "start": 3615.22, "duration": 1.335}, {"text": "I'm putting it in quotes because\nI want you to memorize this--", "start": 3616.555, "duration": 3.535}, {"text": "it's called the\n\"mind-body problem.\"", "start": 3620.09, "duration": 6.365}, {"text": "Now, the mind-body\nproblem is this--", "start": 3634.57, "duration": 3.31}, {"text": "we know that there\nexists a mind.", "start": 3637.88, "duration": 2.16}, {"text": "Does there exist the body?", "start": 3640.04, "duration": 1.19}, {"text": "Or is the mind just\ntelling you that things", "start": 3644.59, "duration": 4.11}, {"text": "are going on, and\nsomehow or another,", "start": 3648.7, "duration": 3.38}, {"text": "you believe that there's a\nphysical world out here that", "start": 3652.08, "duration": 3.27}, {"text": "will be there even\nif you're dead?", "start": 3655.35, "duration": 1.68}, {"text": "Believe it or not, there's\na lot of serious debate", "start": 3660.417, "duration": 2.083}, {"text": "about all that right\nnow, whether or not", "start": 3662.5, "duration": 3.18}, {"text": "there's only the mind.", "start": 3665.68, "duration": 1.8}, {"text": "The thing that you've\ngot to take seriously", "start": 3671.998, "duration": 1.792}, {"text": "about it is some of the\nbest thinkers, at least", "start": 3673.79, "duration": 2.94}, {"text": "that the Western\nworld has ever had,", "start": 3676.73, "duration": 3.2}, {"text": "have tried to tackle this thing.", "start": 3679.93, "duration": 3.09}, {"text": "Descartes tried to tackle it.", "start": 3683.02, "duration": 3.08}, {"text": "He got a big chunk of it.", "start": 3686.1, "duration": 1.305}, {"text": "You remember what it was?", "start": 3687.405, "duration": 1.75}, {"text": "STUDENT: I think,\ntherefore I am.", "start": 3689.155, "duration": 1.375}, {"text": "TAFT BROOME: There it is.", "start": 3690.53, "duration": 2.25}, {"text": "He said there is\none world for sure,", "start": 3692.78, "duration": 2.43}, {"text": "and that you do exist\nbecause it's in your mind.", "start": 3695.21, "duration": 3.0}, {"text": "Your mind exists now.", "start": 3698.21, "duration": 1.9}, {"text": "Why?", "start": 3700.11, "duration": 0.5}, {"text": "Because you think.", "start": 3700.61, "duration": 2.64}, {"text": "Do you think?", "start": 3703.25, "duration": 1.087}, {"text": "Yeah, I think.", "start": 3704.337, "duration": 0.583}, {"text": "Then they start\nplaying games with you.", "start": 3708.26, "duration": 4.29}, {"text": "Well, what about this desk?", "start": 3712.55, "duration": 1.44}, {"text": "How do you know you're\nnot just dreaming it?", "start": 3713.99, "duration": 2.37}, {"text": "How do you know that this\nisn't, in fact, the desk?", "start": 3716.36, "duration": 2.25}, {"text": "Because I can play\na game with you,", "start": 3718.61, "duration": 1.657}, {"text": "and I can make this\nthing out of water,", "start": 3720.267, "duration": 2.723}, {"text": "and you just won't know the\ndifference until you touch it.", "start": 3722.99, "duration": 3.0}, {"text": "So I can manipulate your world.", "start": 3728.64, "duration": 4.19}, {"text": "What do you know?", "start": 3732.83, "duration": 1.89}, {"text": "Is this valid, this\nbusiness of observation,", "start": 3734.72, "duration": 6.93}, {"text": "or is it just you and your mind?", "start": 3741.65, "duration": 1.92}, {"text": "There is some other thinking\nthat the only valid statement", "start": 3746.28, "duration": 4.1}, {"text": "you can make about knowledge is\nyour mind, but not your mind,", "start": 3750.38, "duration": 7.26}, {"text": "because what you say is yours\nis only part of a whole.", "start": 3757.64, "duration": 2.73}, {"text": "All of this has to do with--", "start": 3774.24, "duration": 3.88}, {"text": "this finds its way into ethical\nthought one way or another.", "start": 3778.12, "duration": 3.42}, {"text": "And like I said, if you\nread Kierkegaard, A-A-R-D,", "start": 3784.3, "duration": 11.58}, {"text": "some of these other people\ndealing with that hyperspace.", "start": 3795.88, "duration": 10.73}, {"text": "There any artists that deal\nwith hyperspaces and all", "start": 3806.61, "duration": 2.46}, {"text": "of this stuff.", "start": 3809.07, "duration": 0.72}, {"text": "Can you imagine a\nfourth dimension?", "start": 3813.03, "duration": 2.097}, {"text": "I thought I couldn't\nimagine one until I", "start": 3824.173, "duration": 1.667}, {"text": "met-- until I had\nthis discussion", "start": 3825.84, "duration": 2.7}, {"text": "with a cousin of mine.", "start": 3828.54, "duration": 2.88}, {"text": "Well, this cousin of mine has\nthe same mentality as a shaman.", "start": 3831.42, "duration": 4.71}, {"text": "He was diagnosed as\nschizophrenic, long time,", "start": 3839.23, "duration": 4.54}, {"text": "20, 30 years ago, 40 years ago.", "start": 3843.77, "duration": 4.04}, {"text": "He had all of the\nmakings of a shaman.", "start": 3850.32, "duration": 6.66}, {"text": "He had a terrible\nexperience as a child,", "start": 3856.98, "duration": 4.91}, {"text": "and he never had a job.", "start": 3861.89, "duration": 5.0}, {"text": "Lives at home with his mother.", "start": 3866.89, "duration": 1.25}, {"text": "I was sitting there.", "start": 3874.06, "duration": 2.04}, {"text": "His mother asked me to\ngo talk to him one day.", "start": 3876.1, "duration": 3.023}, {"text": "I went, and sat down,\nand talked to him.", "start": 3879.123, "duration": 1.667}, {"text": "I said, we don't have to\ntalk if you don't want to.", "start": 3880.79, "duration": 3.828}, {"text": "He said, I want to.", "start": 3884.618, "duration": 0.792}, {"text": "I said, well, everybody\nsays you've got a problem.", "start": 3885.41, "duration": 4.56}, {"text": "What's your problem?", "start": 3889.97, "duration": 2.65}, {"text": "He said, sometimes\nhe goes to sleep", "start": 3892.62, "duration": 7.53}, {"text": "and he doesn't wake\nup for a month.", "start": 3900.15, "duration": 3.46}, {"text": "And he's not laying in\nthe bed for a month.", "start": 3903.61, "duration": 1.792}, {"text": "He's walking around,\ntalking it, but he", "start": 3905.402, "duration": 1.625}, {"text": "said he's in the dream state.", "start": 3907.027, "duration": 1.263}, {"text": "Then he comes out of it.", "start": 3913.26, "duration": 1.56}, {"text": "He only knows that he\nwas in the dream state", "start": 3914.82, "duration": 1.88}, {"text": "when he comes out of it.", "start": 3916.7, "duration": 1.99}, {"text": "It's like the yellow.", "start": 3918.69, "duration": 1.76}, {"text": "He only knows there's red--", "start": 3920.45, "duration": 2.433}, {"text": "STUDENT: [INAUDIBLE].", "start": 3922.883, "duration": 3.387}, {"text": "TAFT BROOME: People\ntell him he has", "start": 3926.27, "duration": 3.24}, {"text": "a distorted concept of time.", "start": 3929.51, "duration": 1.605}, {"text": "But there are some\ntalents that he has.", "start": 3934.64, "duration": 6.45}, {"text": "And one of those talents\nis the talent that--", "start": 3941.09, "duration": 2.7}, {"text": "I got the what was his\nname problem again.", "start": 3950.3, "duration": 2.82}, {"text": "The book and the movie is called\n\"The Picture of Dorian Gray.\"", "start": 3956.9, "duration": 11.18}, {"text": "What's the author's name?", "start": 3968.08, "duration": 1.407}, {"text": "STUDENT: Oscar Wilde.", "start": 3969.487, "duration": 0.875}, {"text": "TAFT BROOME: Oscar Wilde,\nyes, yeah, Oscar Wilde.", "start": 3973.55, "duration": 3.15}, {"text": "There's a movie that I've gotten\nalso, that's written in French.", "start": 3981.98, "duration": 4.79}, {"text": "I haven't looked at it.", "start": 3986.77, "duration": 1.703}, {"text": "I looked at it\nonce on television,", "start": 3988.473, "duration": 1.417}, {"text": "and I went and ordered it.", "start": 3989.89, "duration": 1.942}, {"text": "It's got subtitles.", "start": 3991.832, "duration": 3.658}, {"text": "And there's this\nyoung artist who falls", "start": 3995.49, "duration": 5.25}, {"text": "in love with this young girl.", "start": 4000.74, "duration": 3.59}, {"text": "And he tries to paint her\nand he can't get it right.", "start": 4004.33, "duration": 6.25}, {"text": "He says he just can't\nbring out her inner beauty.", "start": 4010.58, "duration": 3.922}, {"text": "Every time he paints\nher, she looks", "start": 4014.502, "duration": 1.458}, {"text": "like \"Picture of Dorian Gray--\"\nit looks like something else.", "start": 4015.96, "duration": 5.76}, {"text": "So he says he knows\nof this old man that", "start": 4021.72, "duration": 5.36}, {"text": "lives up in the hills\nwho's a famous artist.", "start": 4027.08, "duration": 4.23}, {"text": "And he's an artist\nwho's just got it.", "start": 4031.31, "duration": 2.64}, {"text": "Everybody says there's\nartists, and then there's", "start": 4033.95, "duration": 2.34}, {"text": "some people just got it.", "start": 4036.29, "duration": 1.42}, {"text": "So he says, he's\na friend of mine.", "start": 4037.71, "duration": 2.45}, {"text": "I'm going to take\nyou up to his house", "start": 4040.16, "duration": 2.55}, {"text": "and I'm going to ask\nhim to paint you.", "start": 4042.71, "duration": 3.59}, {"text": "So he goes up to this\nman's house, small villa.", "start": 4046.3, "duration": 3.9}, {"text": "Man's there with his wife.", "start": 4050.2, "duration": 2.01}, {"text": "And the old man\nis very reluctant", "start": 4052.21, "duration": 2.4}, {"text": "to take on this job\nof painting this girl.", "start": 4054.61, "duration": 4.03}, {"text": "And there's a real\nnice line in there", "start": 4058.64, "duration": 2.76}, {"text": "where the old man says, well,\nif when I start painting her,", "start": 4061.4, "duration": 5.81}, {"text": "I don't know what\nthe paint on my brush", "start": 4067.21, "duration": 4.47}, {"text": "is going to do when\nit hits the canvas.", "start": 4071.68, "duration": 2.97}, {"text": "You may not like what you see.", "start": 4074.65, "duration": 1.44}, {"text": "And it goes on.", "start": 4078.86, "duration": 0.91}, {"text": "And at the end, the last scene,\nhe's completed the painting.", "start": 4079.77, "duration": 4.46}, {"text": "He puts the cover\nover the painting.", "start": 4084.23, "duration": 3.09}, {"text": "He takes a sledgehammer,\nand he breaks", "start": 4087.32, "duration": 3.48}, {"text": "a hole in the brick wall.", "start": 4090.8, "duration": 2.547}, {"text": "He takes the painting-- we never\nsee the painting-- he puts it", "start": 4093.347, "duration": 2.583}, {"text": "in the hole, and\nhe got some water,", "start": 4095.93, "duration": 2.31}, {"text": "and he covers the hole back up.", "start": 4098.24, "duration": 1.949}, {"text": "In other words, he was able\nto capture her \"true self,\"", "start": 4100.189, "duration": 5.75}, {"text": "and she looked like a beast.", "start": 4105.939, "duration": 2.701}, {"text": "And he just could not give\nthat picture to that young boy", "start": 4108.64, "duration": 2.94}, {"text": "because it would\ntear his heart out.", "start": 4111.58, "duration": 2.069}, {"text": "That's the whole\npoint of the thing.", "start": 4113.649, "duration": 1.5}, {"text": "The whole point of the\nthing is that some people,", "start": 4115.149, "duration": 2.521}, {"text": "like my cousin, can\nsee that inner you.", "start": 4117.67, "duration": 4.78}, {"text": "And I don't like the\n[INAUDIBLE] because I don't", "start": 4122.45, "duration": 2.0}, {"text": "want him to see [INAUDIBLE].", "start": 4124.45, "duration": 2.97}, {"text": "But we got along, so I\nguess it's not so bad.", "start": 4127.42, "duration": 3.22}, {"text": "But he doesn't have\nthe skill to put brush", "start": 4130.64, "duration": 5.089}, {"text": "to paint and paint to canvas.", "start": 4135.729, "duration": 3.811}, {"text": "And I tried to tell him,\nhe developed poetic skills.", "start": 4139.54, "duration": 3.689}, {"text": "And all poetic skills--", "start": 4143.229, "duration": 2.331}, {"text": "you don't have to rhyme.", "start": 4145.56, "duration": 1.0}, {"text": "But if he can see those things\nin people, then he is special.", "start": 4149.109, "duration": 3.451}, {"text": "He's got a special talent.", "start": 4152.56, "duration": 3.549}, {"text": "And a lot of artists\nare like that--", "start": 4156.109, "duration": 2.011}, {"text": "Jackson Pollock.", "start": 4161.04, "duration": 0.84}, {"text": "STUDENT: Does he see\nthe world differently?", "start": 4166.55, "duration": 2.34}, {"text": "TAFT BROOME: I would not\ngo to an ice cream parlor", "start": 4168.89, "duration": 2.16}, {"text": "with Jackson Pollock.", "start": 4171.05, "duration": 1.229}, {"text": "But in other words, what I\nthink is healthy for us to say", "start": 4175.49, "duration": 7.11}, {"text": "is that so far as our senses are\nconcerned, some of these people", "start": 4182.6, "duration": 2.82}, {"text": "are in hyperspace.", "start": 4185.42, "duration": 1.635}, {"text": "They're perceiving\nthings that we", "start": 4187.055, "duration": 1.375}, {"text": "could perceive if we could\npurge our unconsciousnesses", "start": 4188.43, "duration": 4.139}, {"text": "of their demons, and\nreconcile all that's", "start": 4192.569, "duration": 2.791}, {"text": "down there with our conscious,\nand our reason, and our morals.", "start": 4195.36, "duration": 3.66}, {"text": "And that's what's supposed to\nhappen when you become wise,", "start": 4199.02, "duration": 3.09}, {"text": "that you're supposed\nto be able to purge", "start": 4202.11, "duration": 3.12}, {"text": "your unconscious of\nall of his demons.", "start": 4205.23, "duration": 2.49}, {"text": "Carl Jung said that.", "start": 4207.72, "duration": 1.89}, {"text": "And he said it happens\nonly in the old,", "start": 4209.61, "duration": 2.64}, {"text": "because in order for the\nrest of us, the non-shaman,", "start": 4212.25, "duration": 3.54}, {"text": "for the rest of us to do\nit and remain healthy,", "start": 4215.79, "duration": 4.5}, {"text": "we have to see death.", "start": 4220.29, "duration": 2.91}, {"text": "And when we see the Grim\nReaper not far away,", "start": 4223.2, "duration": 3.09}, {"text": "then these demons just\ndon't mean that much.", "start": 4226.29, "duration": 3.9}, {"text": "And if we can find a\nmoral way to accept them--", "start": 4230.19, "duration": 5.285}, {"text": "you know what I\nmean by moral way", "start": 4235.475, "duration": 1.375}, {"text": "to accept the stuff\nthat's down there?", "start": 4236.85, "duration": 1.583}, {"text": "Well, one that's\nunforgettable is", "start": 4241.475, "duration": 1.375}, {"text": "Freud when he talked\nabout how a boy can", "start": 4242.85, "duration": 3.93}, {"text": "have a sexual attraction\nto his mother.", "start": 4246.78, "duration": 1.68}, {"text": "Well, that's kept down\nin the unconscious", "start": 4251.052, "duration": 1.708}, {"text": "because that's\nmorally unacceptable.", "start": 4252.76, "duration": 4.08}, {"text": "So there's a demon down there.", "start": 4256.84, "duration": 2.1}, {"text": "But if you're getting\nold, and the Grim Reaper", "start": 4258.94, "duration": 2.522}, {"text": "is right over there,\nyou don't know", "start": 4261.462, "duration": 1.458}, {"text": "when you're going, that\nbecomes no longer significant.", "start": 4262.92, "duration": 3.748}, {"text": "You could bring that to\nconsciousness and deal with it.", "start": 4266.668, "duration": 2.292}, {"text": "So a wise person is purged,\nis unconscious of all", "start": 4268.96, "duration": 3.32}, {"text": "these demons, and takes on some\nof these skills of the shaman,", "start": 4272.28, "duration": 3.63}, {"text": "and can see into certain\nkinds of hyperspace.", "start": 4275.91, "duration": 4.59}, {"text": "In this class-- I wouldn't say\nthis in an engineering class,", "start": 4292.61, "duration": 2.5}, {"text": "but in this class, I'm\nno longer in the mood", "start": 4295.11, "duration": 1.833}, {"text": "to talk about codes of ethics.", "start": 4296.943, "duration": 1.418}, {"text": "So I have to make\nthat an assignment.", "start": 4300.95, "duration": 2.91}, {"text": "We have a surprise.", "start": 4303.86, "duration": 1.17}, {"text": "Did you read your email?", "start": 4305.03, "duration": 1.32}, {"text": "We have a visitor\ncoming on Tuesday.", "start": 4306.35, "duration": 1.77}, {"text": "What is definite is\nthat apparently, he had", "start": 4312.06, "duration": 5.01}, {"text": "asked about a class like this.", "start": 4317.07, "duration": 2.28}, {"text": "This is a visitor from\nthe Netherlands, chairman", "start": 4319.35, "duration": 5.64}, {"text": "of a department, of an\nEngineering Department,", "start": 4324.99, "duration": 4.59}, {"text": "apparently part of this whole\nreconstruction of education", "start": 4329.58, "duration": 5.91}, {"text": "in Europe.", "start": 4335.49, "duration": 1.95}, {"text": "And engineering ethics is\ngetting on everybody's agenda", "start": 4337.44, "duration": 5.52}, {"text": "over there.", "start": 4342.96, "duration": 1.79}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.98}, {"text": "[RUSTLING]", "start": 1.98, "duration": 1.485}, {"text": "[CLICKING]", "start": 3.465, "duration": 6.935}, {"text": "MATTHEW VANDER\nHEIDEN: Last time, we", "start": 10.4, "duration": 1.95}, {"text": "discussed standard reduction\npotential, this E0 prime value,", "start": 12.35, "duration": 5.58}, {"text": "that really is a\nway to quantitate", "start": 17.93, "duration": 2.4}, {"text": "the propensity of a molecule\nto accept or donate electrons.", "start": 20.33, "duration": 5.61}, {"text": "And this is useful to think\nabout how energy is transduced", "start": 25.94, "duration": 4.65}, {"text": "in biological systems.", "start": 30.59, "duration": 1.23}, {"text": "Because remember, as I have\nnow tried to stress many times,", "start": 31.82, "duration": 6.57}, {"text": "how energy is moved\nthrough biology", "start": 38.39, "duration": 3.21}, {"text": "is largely about oxidation\nand reduction reactions", "start": 41.6, "duration": 4.41}, {"text": "involving carbon and\nultimately oxygen.", "start": 46.01, "duration": 3.9}, {"text": "And so remember that oxidation\nof carbon is favorable.", "start": 49.91, "duration": 6.0}, {"text": "That is removing\nelectrons from the carbon", "start": 55.91, "duration": 2.55}, {"text": "and giving them to\noxygen, exactly what we", "start": 58.46, "duration": 2.79}, {"text": "described for burning\nwood or burning gasoline.", "start": 61.25, "duration": 3.3}, {"text": "And so that's why coming\nfrom the most reduced", "start": 64.55, "duration": 3.12}, {"text": "carbon like fatty acids\nor other reduced carbon", "start": 67.67, "duration": 3.24}, {"text": "like carbohydrates,\nnot as reduced", "start": 70.91, "duration": 1.92}, {"text": "as fatty acids, that oxidizing\nthat carbon releases energy.", "start": 72.83, "duration": 6.13}, {"text": "And of course, it means\nthat storing carbon", "start": 78.96, "duration": 3.08}, {"text": "as reduced carbon either as\ncarbohydrates or fatty acids", "start": 82.04, "duration": 4.14}, {"text": "is a way to store\nenergy for later.", "start": 86.18, "duration": 3.06}, {"text": "And so moving from left to\nright, equilibrium strongly", "start": 89.24, "duration": 5.95}, {"text": "favors moving to the right.", "start": 95.19, "duration": 1.35}, {"text": "That means that delta\nG is less than 0", "start": 96.54, "duration": 3.75}, {"text": "for the oxidation of carbon.", "start": 100.29, "duration": 2.74}, {"text": "Or we can describe this\nas moving from a smaller", "start": 103.03, "duration": 3.23}, {"text": "standard reduction potential\nto a larger standard reduction", "start": 106.26, "duration": 3.78}, {"text": "potential because, remember, the\nrelationship between the change", "start": 110.04, "duration": 4.53}, {"text": "in standard reduction\npotential is related", "start": 114.57, "duration": 2.22}, {"text": "to the equilibrium\nconstant or delta G0 prime,", "start": 116.79, "duration": 4.873}, {"text": "which is also related\nto the equilibrium", "start": 121.663, "duration": 1.667}, {"text": "constant by the above formula.", "start": 123.33, "duration": 4.03}, {"text": "And so we closed last time by\nsaying that with this formula", "start": 127.36, "duration": 5.87}, {"text": "we know that, if we move from\na smaller standard reduction", "start": 133.23, "duration": 2.73}, {"text": "potential-- that is donate\nelectrons from a smaller", "start": 135.96, "duration": 2.52}, {"text": "standard reduction potential\nto a larger standard reduction", "start": 138.48, "duration": 3.39}, {"text": "potential-- that that\nnumber, that difference,", "start": 141.87, "duration": 3.96}, {"text": "will then be positive, which\nis the opposite of delta G", "start": 145.83, "duration": 5.31}, {"text": "because of that formula.", "start": 151.14, "duration": 1.07}, {"text": "And so a positive change in\nstandard reduction potential,", "start": 152.21, "duration": 2.8}, {"text": "moving from lower to\nhigher, equilibrium", "start": 155.01, "duration": 4.8}, {"text": "is going to favor\nthat direction--", "start": 159.81, "duration": 3.39}, {"text": "should make sense from\neverything we discussed before.", "start": 163.2, "duration": 4.23}, {"text": "And of course, that\nchange tells you", "start": 167.43, "duration": 1.83}, {"text": "the propensity of\nelectron transfer", "start": 169.26, "duration": 2.61}, {"text": "that ultimately is going to\nbe favorable at equilibrium.", "start": 171.87, "duration": 3.99}, {"text": "However, exactly as we\ndiscussed for delta G,", "start": 175.86, "duration": 4.68}, {"text": "whether an exact\nreaction is favorable", "start": 180.54, "duration": 2.67}, {"text": "is still going to be\ndependent on delta G.", "start": 183.21, "duration": 2.46}, {"text": "And so the change in\nstandard reduction potential", "start": 185.67, "duration": 2.43}, {"text": "tells you about the\nequilibrium constant,", "start": 188.1, "duration": 2.01}, {"text": "and so which direction\nis going to be", "start": 190.11, "duration": 2.1}, {"text": "net favorable at equilibrium.", "start": 192.21, "duration": 2.13}, {"text": "However, what actually\nhappens is still", "start": 194.34, "duration": 2.61}, {"text": "going to depend on conditions\nfor all the reasons", "start": 196.95, "duration": 2.88}, {"text": "we talked about previously.", "start": 199.83, "duration": 2.48}, {"text": "Still, this change in\nstandard reduction potential", "start": 202.31, "duration": 2.89}, {"text": "is still a useful\nconcept to think about", "start": 205.2, "duration": 3.6}, {"text": "because it tells us about\nhow energy transfer can", "start": 208.8, "duration": 3.45}, {"text": "occur across redox pairs.", "start": 212.25, "duration": 2.46}, {"text": "And that will be\nuseful in thinking", "start": 214.71, "duration": 2.7}, {"text": "about this process of\noxidative phosphorylation", "start": 217.41, "duration": 3.24}, {"text": "and how cells really couple\nelectron transfer to oxygen", "start": 220.65, "duration": 5.19}, {"text": "as a way to do lots\nof useful things", "start": 225.84, "duration": 4.23}, {"text": "in cells, including making ATP.", "start": 230.07, "duration": 4.99}, {"text": "Now, one point I want\nto come back to again,", "start": 235.06, "duration": 2.78}, {"text": "which we discussed at length\nwhen we talked about changes", "start": 237.84, "duration": 4.83}, {"text": "in free energy and how\nthat worked for pathways,", "start": 242.67, "duration": 3.51}, {"text": "is that, remember, we discussed\nthat, if we start with wood", "start": 246.18, "duration": 4.41}, {"text": "or oil and all in one\nstep burn it to CO2,", "start": 250.59, "duration": 4.02}, {"text": "it releases a certain\namount of energy.", "start": 254.61, "duration": 2.669}, {"text": "Or we can break that\ninto individual steps,", "start": 257.279, "duration": 2.641}, {"text": "as we did in glycolysis.", "start": 259.92, "duration": 2.34}, {"text": "The same amount of\nenergy is released.", "start": 262.26, "duration": 1.77}, {"text": "But by breaking into\nindividual steps,", "start": 264.03, "duration": 2.59}, {"text": "we can now capture that\nenergy as intermediates", "start": 266.62, "duration": 3.13}, {"text": "such that we can, say,\nfavorably synthesize ATP", "start": 269.75, "duration": 3.22}, {"text": "at a high ATP/ADP\nratio in cells.", "start": 272.97, "duration": 2.7}, {"text": "The exact same thing is true\nabout any of these electron", "start": 275.67, "duration": 3.18}, {"text": "transfers.", "start": 278.85, "duration": 1.2}, {"text": "There is the change in\nstandard reduction potential.", "start": 280.05, "duration": 2.82}, {"text": "Or the change in free energy\nas one moves from electron", "start": 282.87, "duration": 4.71}, {"text": "transfer from one\nacceptor to one donor", "start": 287.58, "duration": 3.09}, {"text": "is the same if\nyou go in one step", "start": 290.67, "duration": 2.4}, {"text": "or in many different steps.", "start": 293.07, "duration": 2.26}, {"text": "And so by doing these\nstepwise electron transfers", "start": 295.33, "duration": 5.02}, {"text": "in exactly the same way we\ndiscussed about for glycolysis,", "start": 300.35, "duration": 4.71}, {"text": "we can capture that energy\nrelease in smaller packets.", "start": 305.06, "duration": 3.99}, {"text": "And this is a way to basically\nbetter harness this energy", "start": 309.05, "duration": 3.45}, {"text": "release to do useful\nthings for cells.", "start": 312.5, "duration": 3.0}, {"text": "Ultimately, you'll see\nit's how you make ATP,", "start": 315.5, "duration": 1.98}, {"text": "but it can do\nother work as well,", "start": 317.48, "duration": 2.04}, {"text": "generate heat, move\nions, et cetera.", "start": 319.52, "duration": 3.24}, {"text": "And so this is really what\nI want to discuss today.", "start": 322.76, "duration": 5.28}, {"text": "But it's important to remember\nthese concepts when we think", "start": 328.04, "duration": 4.64}, {"text": "through how these systems work.", "start": 332.68, "duration": 2.34}, {"text": "And so we've now\nspent several lectures", "start": 335.02, "duration": 3.3}, {"text": "discussing the chemical\ndetails of how we can oxidize.", "start": 338.32, "duration": 4.32}, {"text": "First, we discussed\ncarbohydrates.", "start": 342.64, "duration": 1.72}, {"text": "Then we discussed fatty acids.", "start": 344.36, "duration": 2.16}, {"text": "And what we saw is that\nmany of the electrons that", "start": 346.52, "duration": 4.04}, {"text": "are lost from the\ncarbon oxidation", "start": 350.56, "duration": 3.18}, {"text": "are used to generate molecules\nsuch as NADH or FADH2", "start": 353.74, "duration": 9.09}, {"text": "and effectively charge up\na ratio, if you will, of", "start": 362.83, "duration": 6.6}, {"text": "reduce oxidized cofactors.", "start": 369.43, "duration": 3.54}, {"text": "And these molecules then donate\nthose electrons, ultimately,", "start": 372.97, "duration": 4.68}, {"text": "to oxygen. And it's that,\nhow you couple those electron", "start": 377.65, "duration": 5.61}, {"text": "transfers from these\ncarriers to oxygen,", "start": 383.26, "duration": 3.99}, {"text": "ultimately is what\noxidative phosphorylation is", "start": 387.25, "duration": 2.79}, {"text": "about as a way to allow cells\nto convert this energy released", "start": 390.04, "duration": 7.62}, {"text": "into a biologically useful form.", "start": 397.66, "duration": 3.84}, {"text": "Now, effectively,\nthe way biology", "start": 401.5, "duration": 1.86}, {"text": "does this is by using that\nfavorable electron transfer", "start": 403.36, "duration": 5.37}, {"text": "to oxygen to charge a battery.", "start": 408.73, "duration": 3.57}, {"text": "So really oxidative\nphosphorylation, if you will,", "start": 412.3, "duration": 4.87}, {"text": "is about a biological battery.", "start": 417.17, "duration": 2.52}, {"text": "And it's really\nthe same concepts", "start": 419.69, "duration": 1.98}, {"text": "that you may have\nlearned in other courses", "start": 421.67, "duration": 2.16}, {"text": "about how chemical\nbatteries work.", "start": 423.83, "duration": 2.202}, {"text": "And so let's just\nthink about that.", "start": 426.032, "duration": 1.458}, {"text": "What is a battery?", "start": 427.49, "duration": 1.71}, {"text": "Well, a battery is two different\nsolutions of ions usually", "start": 429.2, "duration": 4.59}, {"text": "that is separated\ninto two compartments.", "start": 433.79, "duration": 4.17}, {"text": "It has a unit of volts.", "start": 437.96, "duration": 4.11}, {"text": "That's exactly\nwhat the units are", "start": 442.07, "duration": 2.49}, {"text": "for this change in standard\nreduction potential is volts.", "start": 444.56, "duration": 4.7}, {"text": "By using that voltage to run\na current between the two", "start": 449.26, "duration": 4.59}, {"text": "compartments, you can do work.", "start": 453.85, "duration": 2.88}, {"text": "And if you short circuit\na battery, of course,", "start": 456.73, "duration": 3.03}, {"text": "you can get some heat.", "start": 459.76, "duration": 2.16}, {"text": "And so how are\nthese really made?", "start": 461.92, "duration": 3.54}, {"text": "Well, you basically just\nneed to get that voltage.", "start": 465.46, "duration": 3.78}, {"text": "You need to have something that\ninsulates between those two", "start": 469.24, "duration": 3.33}, {"text": "compartments.", "start": 472.57, "duration": 0.57}, {"text": "And you can then\ncontrol electron flow", "start": 473.14, "duration": 2.82}, {"text": "from one side of the\ncircuit to the other.", "start": 475.96, "duration": 3.11}, {"text": "And it's exactly the same\nissue that happens in biology,", "start": 479.07, "duration": 4.36}, {"text": "except biology\nneeds some insulator", "start": 483.43, "duration": 3.42}, {"text": "between two compartments.", "start": 486.85, "duration": 1.74}, {"text": "How do we create different\ncompartments in cells?", "start": 488.59, "duration": 2.58}, {"text": "Well, we create\nthem with membranes.", "start": 491.17, "duration": 2.62}, {"text": "And so an important function\nof membranes in cells,", "start": 493.79, "duration": 4.31}, {"text": "other than things like\nseparating cellular contents", "start": 498.1, "duration": 3.75}, {"text": "from the outside\nworld or breaking up", "start": 501.85, "duration": 2.43}, {"text": "different organelles,\nis that cells actually", "start": 504.28, "duration": 2.94}, {"text": "require a membrane.", "start": 507.22, "duration": 1.59}, {"text": "They're essential\nfor life because they", "start": 508.81, "duration": 3.51}, {"text": "are what allows an insulation\nbetween two aqueous", "start": 512.32, "duration": 4.17}, {"text": "compartments in a way\nthat you can build", "start": 516.49, "duration": 2.22}, {"text": "a biological battery that is\nreally central to how life uses", "start": 518.71, "duration": 6.3}, {"text": "energy as a way to do work.", "start": 525.01, "duration": 2.62}, {"text": "And so life creates a voltage,\nwhich I'm going to call delta", "start": 527.63, "duration": 5.66}, {"text": "psi, delta pH-- we'll come\nback to that in a little bit--", "start": 533.29, "duration": 3.03}, {"text": "to basically couple favorable\nelectron transfer from, say,", "start": 536.32, "duration": 10.36}, {"text": "an electron carrier\nlike NAD/NADH to oxygen,", "start": 546.68, "duration": 9.0}, {"text": "so reoxidizing NADH to\nreduce oxygen to water.", "start": 555.68, "duration": 6.52}, {"text": "That is moving from a lower\nto a higher standard reduction", "start": 562.2, "duration": 5.43}, {"text": "potential that's favorable.", "start": 567.63, "duration": 2.04}, {"text": "Delta G0 prime is negative.", "start": 569.67, "duration": 2.73}, {"text": "Net transfer is favorable.", "start": 572.4, "duration": 2.4}, {"text": "This can be coupled to doing\nsome work that otherwise would", "start": 574.8, "duration": 7.26}, {"text": "be unfavorable, in this\ncase pumping protons", "start": 582.06, "duration": 3.15}, {"text": "from one side of the\nmembrane to another.", "start": 585.21, "duration": 2.64}, {"text": "By pumping protons to one side\nof a membrane or the other,", "start": 587.85, "duration": 4.62}, {"text": "you create a voltage\nmembrane potential, often", "start": 592.47, "duration": 4.14}, {"text": "abbreviated delta psi.", "start": 596.61, "duration": 1.89}, {"text": "It's also a pH gradient,\nso delta H. The protons", "start": 598.5, "duration": 5.52}, {"text": "have lower pH on one side of\nthe membrane than the other.", "start": 604.02, "duration": 4.42}, {"text": "And it's this charging of a\nbattery at a membrane that", "start": 608.44, "duration": 3.86}, {"text": "is what is captured by oxidative\nphosphorylation, what's", "start": 612.3, "duration": 4.32}, {"text": "typically referred to as that\nprocess, as a way to make ATP.", "start": 616.62, "duration": 4.86}, {"text": "But of course, this\nis a useful thing.", "start": 621.48, "duration": 2.71}, {"text": "It's a battery.", "start": 624.19, "duration": 0.74}, {"text": "And so it can also do\nother work for cells.", "start": 624.93, "duration": 6.34}, {"text": "Now, I just want\nto say and really", "start": 631.27, "duration": 4.31}, {"text": "stress that this is really\ncritical, this process.", "start": 635.58, "duration": 4.65}, {"text": "And it's really central to\nhow energy works for cells.", "start": 640.23, "duration": 4.92}, {"text": "You will see that,\neffectively, this", "start": 645.15, "duration": 3.0}, {"text": "is the key steps\nin photosynthesis,", "start": 648.15, "duration": 2.88}, {"text": "do exactly the same thing.", "start": 651.03, "duration": 1.93}, {"text": "It's how mitochondria work.", "start": 652.96, "duration": 1.76}, {"text": "It's also how bacteria work.", "start": 654.72, "duration": 3.21}, {"text": "And really prokaryotes end\nup doing this at their plasma", "start": 657.93, "duration": 5.43}, {"text": "membranes, whereas mitochondria\nand chloroplasts end up", "start": 663.36, "duration": 4.86}, {"text": "doing this at intracellular\nmembranes in eukaryotes.", "start": 668.22, "duration": 4.71}, {"text": "But ultimately,\nit's the same idea", "start": 672.93, "duration": 3.24}, {"text": "of charging this biological\nbattery that really allows", "start": 676.17, "duration": 5.19}, {"text": "cells to convert, do\nenergy conversions", "start": 681.36, "duration": 4.32}, {"text": "in a way that's useful for\nthem to allow otherwise", "start": 685.68, "duration": 7.38}, {"text": "unfavorable things\nto happen in cells.", "start": 693.06, "duration": 3.66}, {"text": "Now, this works\nlargely because you", "start": 696.72, "duration": 3.81}, {"text": "have this insulating\nmembrane system, which is,", "start": 700.53, "duration": 4.26}, {"text": "of course, made of lipids.", "start": 704.79, "duration": 2.83}, {"text": "Lipids are what separates\nthe two compartments.", "start": 707.62, "duration": 2.54}, {"text": "Remember, we discussed earlier\nthat these lipid bilayers", "start": 710.16, "duration": 3.93}, {"text": "are useful because they\ncreate a hydrophobic interface", "start": 714.09, "duration": 5.67}, {"text": "between two aqueous\ncompartments.", "start": 719.76, "duration": 2.91}, {"text": "It's also useful\nbecause lipids are", "start": 722.67, "duration": 2.55}, {"text": "poor conductors of electrons.", "start": 725.22, "duration": 3.16}, {"text": "And so this really ends up\nbeing the insulating system", "start": 728.38, "duration": 5.0}, {"text": "that makes this work.", "start": 733.38, "duration": 1.99}, {"text": "Now, in the previous\nlecture, we discussed", "start": 735.37, "duration": 5.53}, {"text": "a lot about the polar\nand non-polar properties", "start": 740.9, "duration": 4.77}, {"text": "of phospholipids really\nallow them to assemble", "start": 745.67, "duration": 3.42}, {"text": "into these membrane barriers.", "start": 749.09, "duration": 2.55}, {"text": "And I just want to\ndo a slight diversion", "start": 751.64, "duration": 2.52}, {"text": "to revisit this in\nthe context of how", "start": 754.16, "duration": 2.79}, {"text": "this works for bioenergetics.", "start": 756.95, "duration": 4.72}, {"text": "So remember, you have\nthis lipid bilayer where", "start": 761.67, "duration": 4.38}, {"text": "you separate two\naqueous compartments", "start": 766.05, "duration": 13.16}, {"text": "with this hydrophobic membrane.", "start": 779.21, "duration": 2.22}, {"text": "In this membrane are\nthese phospholipids,", "start": 781.43, "duration": 6.42}, {"text": "where you have these polar head\ngroups with two lipid tails.", "start": 787.85, "duration": 5.31}, {"text": "You can look back to a\nformer lecture where I drew", "start": 793.16, "duration": 3.36}, {"text": "and we discussed what\nthose phospholipids", "start": 796.52, "duration": 3.15}, {"text": "are in great detail.", "start": 799.67, "duration": 1.71}, {"text": "But it's really having that\npolar, non-polar interface", "start": 801.38, "duration": 3.93}, {"text": "that allows you to form\nthese bilayers that's", "start": 805.31, "duration": 2.4}, {"text": "creating this separation between\nthe aqueous compartments,", "start": 807.71, "duration": 4.56}, {"text": "but also this insulator that\nallows a battery to be built", "start": 812.27, "duration": 4.83}, {"text": "across the membrane.", "start": 817.1, "duration": 3.06}, {"text": "Now, there are several\nconsequences, though,", "start": 820.16, "duration": 4.61}, {"text": "to this system that is worth\nthinking about at least", "start": 824.77, "duration": 4.23}, {"text": "in terms of how lipids\nand membranes work.", "start": 829.0, "duration": 4.83}, {"text": "Now, a consequence of\nthis is that, if we're", "start": 833.83, "duration": 2.46}, {"text": "going to create\nthis system, now we", "start": 836.29, "duration": 2.19}, {"text": "create a system where we\nhave issues with transport", "start": 838.48, "duration": 6.8}, {"text": "across from one\ncompartment to another.", "start": 845.28, "duration": 4.12}, {"text": "Now, this, of course,\nis an opportunity", "start": 849.4, "duration": 1.79}, {"text": "for a layer of regulation\nbecause it also", "start": 851.19, "duration": 4.14}, {"text": "allows then these\nconditions where", "start": 855.33, "duration": 1.65}, {"text": "you could have different\nchemical conditions,", "start": 856.98, "duration": 2.63}, {"text": "say, different ATP/ADP\nratios, NAD/NADH ratios", "start": 859.61, "duration": 3.43}, {"text": "in the different compartments,\nwhich, of course,", "start": 863.04, "duration": 2.5}, {"text": "for all the thermodynamic\nreasons we've already discussed", "start": 865.54, "duration": 2.39}, {"text": "can make things more or\nless favorable to occur", "start": 867.93, "duration": 3.33}, {"text": "in different\ncompartments in cells.", "start": 871.26, "duration": 2.67}, {"text": "But it also means\nmetabolism then", "start": 873.93, "duration": 2.1}, {"text": "has to have ways to transport\nstuff across these membranes.", "start": 876.03, "duration": 4.05}, {"text": "And we've discussed\nthis a couple of times.", "start": 880.08, "duration": 2.16}, {"text": "A few examples--\nI talked briefly", "start": 882.24, "duration": 1.92}, {"text": "about the pyruvate carrier.", "start": 884.16, "duration": 1.77}, {"text": "That is, if glycolysis\nis happening", "start": 885.93, "duration": 1.95}, {"text": "in this compartment\nin the cytosol", "start": 887.88, "duration": 2.25}, {"text": "and we need to get the pyruvate\ninside the mitochondria", "start": 890.13, "duration": 3.18}, {"text": "across a membrane for the\npyruvate dehydrogenase", "start": 893.31, "duration": 3.81}, {"text": "reaction, now you needed this\npyruvate carrier molecule.", "start": 897.12, "duration": 3.18}, {"text": "And it turns out that\nthat transport process", "start": 900.3, "duration": 1.89}, {"text": "is an opportunity\nfor regulation,", "start": 902.19, "duration": 2.01}, {"text": "but it still needs to occur.", "start": 904.2, "duration": 2.43}, {"text": "We discussed the\ncarnitine shuttle, right?", "start": 906.63, "duration": 2.73}, {"text": "Fatty acid, we generate\nfatty acyl-CoAs", "start": 909.36, "duration": 4.53}, {"text": "from breakdown of\nlipids in one side", "start": 913.89, "duration": 3.24}, {"text": "in the cytosolic compartment.", "start": 917.13, "duration": 1.38}, {"text": "We need to get those fatty\nacyl-CoAs into the mitochondria", "start": 918.51, "duration": 3.66}, {"text": "where they can be oxidized\nby fatty acid oxidation.", "start": 922.17, "duration": 2.91}, {"text": "And that required that\ncarnitine shuttle system.", "start": 925.08, "duration": 3.99}, {"text": "Now, ultimately, what mediates\nthis transport is, of course,", "start": 929.07, "duration": 5.19}, {"text": "proteins that can sit within\nthis membrane bilayer.", "start": 934.26, "duration": 6.6}, {"text": "And you can imagine\nyou can have proteins", "start": 940.86, "duration": 1.83}, {"text": "that span the\nmembrane bilayer, such", "start": 942.69, "duration": 2.19}, {"text": "that there's hydrophilic\nsurfaces that", "start": 944.88, "duration": 2.52}, {"text": "are on either face of the\nmembrane and hydrophobic", "start": 947.4, "duration": 3.93}, {"text": "residues in the middle\nwith various ways", "start": 951.33, "duration": 2.61}, {"text": "to make channels and other\ntransport mechanisms to get", "start": 953.94, "duration": 3.54}, {"text": "things from one side of\nthe membrane to the other,", "start": 957.48, "duration": 2.7}, {"text": "all right?", "start": 960.18, "duration": 0.93}, {"text": "Or you could have complexes that\nfloat freely within the lipid", "start": 961.11, "duration": 3.87}, {"text": "bilayer, such that there's\na hydrophilic surface that", "start": 964.98, "duration": 3.69}, {"text": "faces one compartment and a\nhydrophobic surface that faces", "start": 968.67, "duration": 4.2}, {"text": "the inside of the membrane.", "start": 972.87, "duration": 2.77}, {"text": "Now, having these complexes\nwill become very important", "start": 975.64, "duration": 5.21}, {"text": "for ways in which one can\nregulate processes that", "start": 980.85, "duration": 4.86}, {"text": "occur either within the\nmembrane or by moving things", "start": 985.71, "duration": 2.34}, {"text": "across membranes, like\ngenerating moving protons", "start": 988.05, "duration": 3.39}, {"text": "and generating a\nvoltage, or even", "start": 991.44, "duration": 5.91}, {"text": "move large things like\nproteins across the membrane.", "start": 997.35, "duration": 3.0}, {"text": "But it has additional\nconsequences because it now", "start": 1000.35, "duration": 4.05}, {"text": "means that the properties\nof the membrane", "start": 1004.4, "duration": 2.28}, {"text": "also matter somewhat as well.", "start": 1006.68, "duration": 2.71}, {"text": "And this brings us back\nto the other discussion", "start": 1009.39, "duration": 2.15}, {"text": "we had in the last lecture.", "start": 1011.54, "duration": 1.68}, {"text": "And that is how the various\nproperties of the fatty acids", "start": 1013.22, "duration": 4.14}, {"text": "that exist within this\nhydrophobic membrane area also,", "start": 1017.36, "duration": 6.36}, {"text": "now, can really\nmatter because they're", "start": 1023.72, "duration": 2.849}, {"text": "going to affect things\nabout how leaky this", "start": 1026.569, "duration": 3.361}, {"text": "is as an insulator between\nthe two compartments,", "start": 1029.93, "duration": 3.48}, {"text": "as well as how fluid\nthe membrane is,", "start": 1033.41, "duration": 2.28}, {"text": "such that things\nlike these proteins", "start": 1035.69, "duration": 2.429}, {"text": "can actually move within\nthis hydrophobic barrier", "start": 1038.119, "duration": 5.071}, {"text": "between the two compartments.", "start": 1043.19, "duration": 2.7}, {"text": "In other words, the fatty\nacid composition, as well as", "start": 1045.89, "duration": 13.52}, {"text": "the lipid species\nthemselves, that", "start": 1059.41, "duration": 4.29}, {"text": "is which phospholipid, other\npolar hydrophobic lipid", "start": 1063.7, "duration": 7.23}, {"text": "species analogous to\nphospholipids that form up", "start": 1070.93, "duration": 3.72}, {"text": "membranes, can change\nproperties such as how leaky", "start": 1074.65, "duration": 4.35}, {"text": "the membrane is or how\nfluid the membrane is.", "start": 1079.0, "duration": 6.03}, {"text": "You can imagine, if you have a\nreally rigid membrane surface,", "start": 1085.03, "duration": 4.35}, {"text": "you're not going to get\nany flow of materials.", "start": 1089.38, "duration": 3.25}, {"text": "It's not going to be very\nleaky, which might be great", "start": 1092.63, "duration": 2.538}, {"text": "if you want to build an\ninsulator between the two", "start": 1095.168, "duration": 2.042}, {"text": "compartments.", "start": 1097.21, "duration": 0.96}, {"text": "But it's going to be very\ndifficult to regulate transport", "start": 1098.17, "duration": 3.42}, {"text": "across that compartment.", "start": 1101.59, "duration": 1.68}, {"text": "And so nature has come up with\na bunch of different solutions", "start": 1103.27, "duration": 3.72}, {"text": "for how to play with fatty acid\nand other lipid composition", "start": 1106.99, "duration": 5.01}, {"text": "to change the\nproperties of membranes.", "start": 1112.0, "duration": 2.49}, {"text": "We don't have time to get\ninto that in great detail", "start": 1114.49, "duration": 2.58}, {"text": "in this course, but I\nwant you to appreciate", "start": 1117.07, "duration": 1.89}, {"text": "that these things exist.", "start": 1118.96, "duration": 1.92}, {"text": "But one thing I want to\ndiscuss is that often,", "start": 1120.88, "duration": 2.58}, {"text": "when you see phospholipids\ndrawn like this,", "start": 1123.46, "duration": 3.15}, {"text": "they're drawn in this\nway where the polar head", "start": 1126.61, "duration": 2.07}, {"text": "group is a circle.", "start": 1128.68, "duration": 1.47}, {"text": "And then they'll draw the\ntwo lipids tails often", "start": 1130.15, "duration": 3.51}, {"text": "with a kink in one\nof the lipid tails.", "start": 1133.66, "duration": 2.37}, {"text": "That's because many times\nphospholipids, of the two lipid", "start": 1136.03, "duration": 3.12}, {"text": "tails, one is saturated.", "start": 1139.15, "duration": 2.31}, {"text": "And one has a\nmonounsaturation in it.", "start": 1141.46, "duration": 4.32}, {"text": "And I just want to go\nback to the models here.", "start": 1145.78, "duration": 2.85}, {"text": "Remember, the monounsaturated,\nthe double bond,", "start": 1148.63, "duration": 2.94}, {"text": "ends up being this\ncis double bond.", "start": 1151.57, "duration": 3.22}, {"text": "And so here's two fatty acids.", "start": 1154.79, "duration": 3.98}, {"text": "If you put these here in with\nthe head groups on one side--", "start": 1158.77, "duration": 4.5}, {"text": "so this would be esterified to\nthe glycerol, the phospholipid,", "start": 1163.27, "duration": 3.63}, {"text": "you end up getting this\nkink in the membrane, which", "start": 1166.9, "duration": 2.85}, {"text": "is much different than\ntwo straight chains.", "start": 1169.75, "duration": 2.82}, {"text": "You can imagine that\nwithin the membrane", "start": 1172.57, "duration": 1.89}, {"text": "itself this ends up basically\nnot letting those lipid tails", "start": 1174.46, "duration": 5.22}, {"text": "pack quite so tightly in the\nmembrane, which certainly", "start": 1179.68, "duration": 3.48}, {"text": "contributes to an\nability to have space", "start": 1183.16, "duration": 3.93}, {"text": "to put other stuff in\nthe membrane to allow", "start": 1187.09, "duration": 2.58}, {"text": "other processes to happen.", "start": 1189.67, "duration": 2.85}, {"text": "Now, recall that\nthere's other ways", "start": 1192.52, "duration": 2.67}, {"text": "we can modulate the\nproperties of fatty acids,", "start": 1195.19, "duration": 6.02}, {"text": "introduce more double bonds,\nchain length, et cetera.", "start": 1201.21, "duration": 4.45}, {"text": "And different organisms\nuse different strategies", "start": 1205.66, "duration": 3.89}, {"text": "to deal with this.", "start": 1209.55, "duration": 1.48}, {"text": "And so plants,\nremember, have all kinds", "start": 1211.03, "duration": 4.79}, {"text": "of polyunsaturated fatty acids,\njust like we talked about", "start": 1215.82, "duration": 5.1}, {"text": "with plant oils being\nliquid at room temperature.", "start": 1220.92, "duration": 3.36}, {"text": "Having more polyunsaturated\nfatty acids in their lipid", "start": 1224.28, "duration": 5.58}, {"text": "tails is one way\nplants use to keep", "start": 1229.86, "duration": 4.17}, {"text": "their membranes more fluid.", "start": 1234.03, "duration": 2.58}, {"text": "Animals, remember, have\nmore saturated fatty acids.", "start": 1236.61, "duration": 4.08}, {"text": "All right, those\nsaturated fatty acids--", "start": 1240.69, "duration": 3.6}, {"text": "less double bonds, going\nto be higher melting", "start": 1244.29, "duration": 3.9}, {"text": "temperature, more likely to\nbe solid at room temperature.", "start": 1248.19, "duration": 3.94}, {"text": "So that's not going to be very\ngood for membrane fluidity.", "start": 1252.13, "duration": 2.54}, {"text": "And it turns out animals\nuse a different strategy", "start": 1254.67, "duration": 3.72}, {"text": "to keep membrane\nfluidity that's not", "start": 1258.39, "duration": 2.16}, {"text": "polyunsaturated fatty acids.", "start": 1260.55, "duration": 2.13}, {"text": "And that is that they\nincorporate this molecule shown", "start": 1262.68, "duration": 3.15}, {"text": "here on the slide,\nwhich is cholesterol,", "start": 1265.83, "duration": 3.7}, {"text": "which you're well aware of.", "start": 1269.53, "duration": 1.5}, {"text": "And so animals use you\nsterols, like cholesterol,", "start": 1271.03, "duration": 4.04}, {"text": "as a way to keep their\nmembranes more fluid.", "start": 1275.07, "duration": 4.3}, {"text": "And so that cholesterol that\nis present in animal products", "start": 1279.37, "duration": 5.33}, {"text": "is not there to give\nyou heart attacks.", "start": 1284.7, "duration": 2.05}, {"text": "It's really there\nas a way animals use", "start": 1286.75, "duration": 2.57}, {"text": "to keep their membranes fluid.", "start": 1289.32, "duration": 2.13}, {"text": "And this is really,\nat heart, why", "start": 1291.45, "duration": 2.19}, {"text": "plants are cholesterol\nfree foods and animals have", "start": 1293.64, "duration": 3.93}, {"text": "cholesterol.", "start": 1297.57, "duration": 1.08}, {"text": "And it's because animals\nuse cholesterol as a way", "start": 1298.65, "duration": 2.88}, {"text": "to keep their membranes\nfluid, whereas plants", "start": 1301.53, "duration": 2.34}, {"text": "use a different strategy,\npolyunsaturated fatty acids.", "start": 1303.87, "duration": 5.1}, {"text": "All right, now,\nultimately setting up", "start": 1308.97, "duration": 5.12}, {"text": "the system this way is\nimportant because it allows", "start": 1314.09, "duration": 3.63}, {"text": "for these flexible\nmembranes that", "start": 1317.72, "duration": 1.68}, {"text": "can enable ion and other\ntransport between compartments,", "start": 1319.4, "duration": 4.53}, {"text": "as well as hold a charge so that\nyou can form this battery which", "start": 1323.93, "duration": 6.72}, {"text": "allows oxidative phosphorylation\nor other processes to occur", "start": 1330.65, "duration": 4.17}, {"text": "where you can\ncharge this membrane", "start": 1334.82, "duration": 2.25}, {"text": "and ultimately use that\nvoltage to do work,", "start": 1337.07, "duration": 5.67}, {"text": "like make ATP, all right?", "start": 1342.74, "duration": 3.39}, {"text": "Now, how this membrane\ncharging occurs,", "start": 1346.13, "duration": 5.32}, {"text": "again, is really taking\nadvantage of favorable electron", "start": 1351.45, "duration": 4.86}, {"text": "transfer across a\nseries of redox pairs,", "start": 1356.31, "duration": 4.8}, {"text": "ultimately, to oxygen or\nanother good electron acceptor.", "start": 1361.11, "duration": 4.86}, {"text": "And it's really that\nfavorable electron transfer", "start": 1365.97, "duration": 3.48}, {"text": "that's being coupled to\nthis pumping of proton ions", "start": 1369.45, "duration": 3.93}, {"text": "to charge a battery.", "start": 1373.38, "duration": 2.19}, {"text": "That's the oxidation part.", "start": 1375.57, "duration": 2.16}, {"text": "And then that battery doing work\nsuch as driving favorable ADP", "start": 1377.73, "duration": 6.48}, {"text": "to ATP conversion,\nthe phosphorylation", "start": 1384.21, "duration": 3.93}, {"text": "part of oxidative\nphosphorylation,", "start": 1388.14, "duration": 2.91}, {"text": "is the type of work\nthat you can then", "start": 1391.05, "duration": 3.57}, {"text": "do once you generate this\nchemical battery, although not", "start": 1394.62, "duration": 4.17}, {"text": "the only work you can\ndo with that battery.", "start": 1398.79, "duration": 2.13}, {"text": "And it's why this\nis so much more", "start": 1400.92, "duration": 1.41}, {"text": "flexible than just making ATP.", "start": 1402.33, "duration": 3.83}, {"text": "All right, so\nultimately this process", "start": 1406.16, "duration": 5.67}, {"text": "by coupling transfer\nof electrons", "start": 1411.83, "duration": 3.69}, {"text": "from favorable\noxidation of carbon", "start": 1415.52, "duration": 2.34}, {"text": "to charge up these other\nelectron carriers that", "start": 1417.86, "duration": 3.51}, {"text": "ultimately transfer to\noxygen is a major way", "start": 1421.37, "duration": 5.37}, {"text": "that life uses nutrient\noxidation to convert it", "start": 1426.74, "duration": 5.61}, {"text": "to biologically useful energy.", "start": 1432.35, "duration": 2.46}, {"text": "And this is where we get to this\nprocess of what is typically", "start": 1434.81, "duration": 4.44}, {"text": "referred to as oxidative\nphosphorylation, which", "start": 1439.25, "duration": 8.28}, {"text": "is a concept or a process that\nwas often abbreviated oxphos.", "start": 1447.53, "duration": 7.32}, {"text": "And it was discovered by or\nfirst described by a gentleman", "start": 1454.85, "duration": 4.5}, {"text": "by the name of Peter Mitchell.", "start": 1459.35, "duration": 1.44}, {"text": "And like many novel or\nrevolutionary ideas,", "start": 1464.59, "duration": 4.56}, {"text": "when Peter Mitchell first\ndescribed or proposed", "start": 1469.15, "duration": 3.09}, {"text": "the processes I'm about\nto tell you about,", "start": 1472.24, "duration": 2.1}, {"text": "his ideas were\ninitially dismissed.", "start": 1474.34, "duration": 4.26}, {"text": "It was thought at the time, when\npeople were thinking about how", "start": 1478.6, "duration": 3.3}, {"text": "do you couple metabolism to,\nsay, charge up your ATP/ADP", "start": 1481.9, "duration": 3.93}, {"text": "ratio, that that\nprocess would work", "start": 1485.83, "duration": 3.45}, {"text": "via the oxidative\nphosphorylation type reactions", "start": 1489.28, "duration": 4.35}, {"text": "that we otherwise\ndescribed, things", "start": 1493.63, "duration": 2.28}, {"text": "like what happens at the GAPDH\nstep or the succinic thiokinase", "start": 1495.91, "duration": 3.75}, {"text": "step in the TCA cycle.", "start": 1499.66, "duration": 2.1}, {"text": "Those are two examples\nwhere we could directly", "start": 1501.76, "duration": 2.58}, {"text": "couple the oxidation of carbon\nto a phosphorylation event that", "start": 1504.34, "duration": 6.48}, {"text": "ultimately allowed us\nto favorably produce", "start": 1510.82, "duration": 3.72}, {"text": "ATP to maintain an\nATP/ADP ratio that's high", "start": 1514.54, "duration": 5.52}, {"text": "and is present in cells.", "start": 1520.06, "duration": 3.03}, {"text": "However, what Peter\nMitchell described", "start": 1523.09, "duration": 2.67}, {"text": "was really this\nbattery phenomena", "start": 1525.76, "duration": 3.45}, {"text": "that we're talking about.", "start": 1529.21, "duration": 1.54}, {"text": "And it turned out\nto be largely right", "start": 1530.75, "duration": 2.75}, {"text": "and represents something\nthat's actually", "start": 1533.5, "duration": 2.88}, {"text": "quite unique about\nbiological processes", "start": 1536.38, "duration": 4.23}, {"text": "even if you think about other\nbiological processes that", "start": 1540.61, "duration": 2.64}, {"text": "occur.", "start": 1543.25, "duration": 0.84}, {"text": "And that is what he\nproposed was the oxidation", "start": 1544.09, "duration": 6.45}, {"text": "and phosphorylation events were\nactually separate processes.", "start": 1550.54, "duration": 13.72}, {"text": "That is nature does not have\nto have these two things touch", "start": 1564.26, "duration": 5.07}, {"text": "in order for them to work.", "start": 1569.33, "duration": 2.04}, {"text": "That is that you use\noxidation to create", "start": 1571.37, "duration": 5.1}, {"text": "this battery as one event.", "start": 1576.47, "duration": 2.31}, {"text": "So oxidation generates this\npotential across a membrane.", "start": 1583.56, "duration": 12.9}, {"text": "And then that potential\nacross a membrane", "start": 1596.46, "duration": 3.93}, {"text": "is a totally separate event,\ncan drive phosphorylation, ATP,", "start": 1600.39, "duration": 22.24}, {"text": "or do other work,\nultimately making", "start": 1622.63, "duration": 2.46}, {"text": "this a more flexible\nsystem for biology.", "start": 1625.09, "duration": 3.69}, {"text": "And so turns out, as I said\nbefore, in a prokaryotic cell--", "start": 1628.78, "duration": 5.26}, {"text": "so this here is some\nkind of prokaryote, OK?", "start": 1634.04, "duration": 6.44}, {"text": "Prokaryotes have a membrane\nthat separates them", "start": 1640.48, "duration": 3.15}, {"text": "from the outside world.", "start": 1643.63, "duration": 1.24}, {"text": "This cell membrane effectively\ncouples that oxidation step", "start": 1644.87, "duration": 5.75}, {"text": "to the pumping of protons.", "start": 1650.62, "duration": 1.95}, {"text": "That creates a battery\nat the cell membrane", "start": 1652.57, "duration": 9.2}, {"text": "of the prokaryote.", "start": 1661.77, "duration": 1.65}, {"text": "And separate in\nspace, that can then", "start": 1663.42, "duration": 4.11}, {"text": "be used to drive\nATP synthesis or do", "start": 1667.53, "duration": 5.91}, {"text": "other work that's useful to\nmaintain that prokaryotic cell.", "start": 1673.44, "duration": 6.98}, {"text": "Now, in eukaryotes, this\nprocess occurs at membranes", "start": 1680.42, "duration": 9.52}, {"text": "within the mitochondria.", "start": 1689.94, "duration": 1.24}, {"text": "So this here is a\nmitochondria, OK?", "start": 1691.18, "duration": 3.71}, {"text": "So just to remind you of some\nvery basic cell biology--", "start": 1694.89, "duration": 6.12}, {"text": "and so, remember, mitochondria\nhave two membranes.", "start": 1701.01, "duration": 3.13}, {"text": "So there's this outer\nmitochondrial membrane,", "start": 1704.14, "duration": 10.94}, {"text": "outer mitochondrial membrane.", "start": 1715.08, "duration": 1.98}, {"text": "And then there's this inner\nmitochondrial membrane,", "start": 1717.06, "duration": 7.14}, {"text": "so two membranes in\nthe mitochondria.", "start": 1724.2, "duration": 2.73}, {"text": "Remember, there's\nthis matrix space.", "start": 1726.93, "duration": 5.45}, {"text": "The cytosol would be out here.", "start": 1732.38, "duration": 2.64}, {"text": "And then there's this space\nbetween the two membranes", "start": 1735.02, "duration": 4.23}, {"text": "called the intermembrane\nspace, intermembrane space", "start": 1739.25, "duration": 15.18}, {"text": "between the two membranes.", "start": 1754.43, "duration": 2.26}, {"text": "If you'll recall, many of these\noxidation reactions, the TCA", "start": 1756.69, "duration": 5.0}, {"text": "cycle, fatty acid oxidation,\npyruvate dehydrogenase step,", "start": 1761.69, "duration": 5.07}, {"text": "all of those were happening in\nthe matrix of the mitochondria.", "start": 1766.76, "duration": 4.08}, {"text": "Remember, glycolysis\nwas in the cytosol,", "start": 1770.84, "duration": 2.55}, {"text": "but all these other\nprocesses were", "start": 1773.39, "duration": 2.07}, {"text": "happening in the matrix\nof the mitochondria.", "start": 1775.46, "duration": 2.37}, {"text": "And really what's going\non is that this battery is", "start": 1777.83, "duration": 4.11}, {"text": "being charged across this inner\nmitochondrial membrane, OK?", "start": 1781.94, "duration": 4.98}, {"text": "So protons are being pumped\ninto the inner mitochondrial", "start": 1786.92, "duration": 3.63}, {"text": "membrane into the intermembrane\nspace of the mitochondria", "start": 1790.55, "duration": 5.13}, {"text": "and then used to synthesize\nATP in the matrix", "start": 1795.68, "duration": 5.49}, {"text": "of the mitochondria.", "start": 1801.17, "duration": 1.92}, {"text": "Now, part of this came,\nmany people know-- remember,", "start": 1803.09, "duration": 3.96}, {"text": "mitochondria have their\nown DNA, et cetera.", "start": 1807.05, "duration": 2.59}, {"text": "And so really where\npeople thought,", "start": 1809.64, "duration": 2.9}, {"text": "think eukaryotic cells\ncame from is basically", "start": 1812.54, "duration": 3.36}, {"text": "the mitochondria is an enslaved\nbacteria or an obligate", "start": 1815.9, "duration": 5.16}, {"text": "captured symbiont, if you\nwill, where one cell engulfed", "start": 1821.06, "duration": 4.98}, {"text": "a different prokaryotic cell.", "start": 1826.04, "duration": 2.44}, {"text": "And if you track this, think\nof the inner mitochondrial", "start": 1828.48, "duration": 6.13}, {"text": "membrane as a enslaved\nprokaryotic cell,", "start": 1834.61, "duration": 4.68}, {"text": "you can see that\nyou're generating", "start": 1839.29, "duration": 1.8}, {"text": "this membrane potential\nacross the inner mitochondrial", "start": 1841.09, "duration": 10.35}, {"text": "membrane, which is\nreally equivalent", "start": 1851.44, "duration": 2.22}, {"text": "to the bacterial membrane of\nthe enslaved prokaryotic cell.", "start": 1853.66, "duration": 5.67}, {"text": "In both cases, it's\ncreating this battery", "start": 1859.33, "duration": 3.66}, {"text": "at a membrane, the inner\nmitochondrial membrane", "start": 1862.99, "duration": 2.55}, {"text": "or the bacterial membrane of\na prokaryote, that is then", "start": 1865.54, "duration": 3.09}, {"text": "being used to\nseparately in space", "start": 1868.63, "duration": 4.2}, {"text": "use that gradient to do\nwork, such as synthesize ATP.", "start": 1872.83, "duration": 4.53}, {"text": "So if I draw this more\nexplicitly as this here", "start": 1881.41, "duration": 7.84}, {"text": "being the membrane--", "start": 1889.25, "duration": 1.84}, {"text": "so the inner\nmitochondrial membrane", "start": 1891.09, "duration": 4.87}, {"text": "of a mitochondria or\nthe bacterial membrane", "start": 1895.96, "duration": 9.64}, {"text": "of a prokaryotic\ncell, such that this", "start": 1905.6, "duration": 2.49}, {"text": "is outside the bacteria,\nthat's inside the bacteria.", "start": 1908.09, "duration": 3.88}, {"text": "This is the intermembrane\nspace often referred to", "start": 1911.97, "duration": 4.13}, {"text": "as the cytosol side.", "start": 1916.1, "duration": 2.49}, {"text": "Of course, there's another outer\nmitochondrial membrane here", "start": 1918.59, "duration": 3.27}, {"text": "that, for the sake\nof this class,", "start": 1921.86, "duration": 2.53}, {"text": "you can just think of as\nbeing generally permeable.", "start": 1924.39, "duration": 3.18}, {"text": "This would be the matrix inside\nof the inner mitochondrial", "start": 1927.57, "duration": 3.29}, {"text": "membrane.", "start": 1930.86, "duration": 1.12}, {"text": "And so all this NADH\nis being generated", "start": 1931.98, "duration": 7.34}, {"text": "from nutrient\noxidation TCA cycle,", "start": 1939.32, "duration": 3.06}, {"text": "fatty acid oxidation,\npyruvate dehydrogenase,", "start": 1942.38, "duration": 2.31}, {"text": "whatever, within the matrix\nor within the bacteria.", "start": 1944.69, "duration": 3.33}, {"text": "Those electrons are ultimately\nbeing transferred from NADH,", "start": 1952.43, "duration": 6.93}, {"text": "reoxidizing it to NAD, to\nreduce oxygen to water.", "start": 1959.36, "duration": 6.37}, {"text": "This is favorable.", "start": 1965.73, "duration": 2.64}, {"text": "This is, therefore,\ncoupled to pumping protons.", "start": 1968.37, "duration": 6.84}, {"text": "That creates a membrane\npotential and gradient", "start": 1975.21, "duration": 9.65}, {"text": "across this membrane,\nwhich can be", "start": 1984.86, "duration": 4.17}, {"text": "used to do work such as\ndriving the synthesis of ATP", "start": 1989.03, "duration": 13.91}, {"text": "for other work.", "start": 2002.94, "duration": 1.63}, {"text": "So this all has to happen\nat the same membrane,", "start": 2004.57, "duration": 4.0}, {"text": "but this process does not\nhave to touch that process.", "start": 2008.57, "duration": 4.79}, {"text": "It's coupled because\nyou create this battery,", "start": 2013.36, "duration": 3.3}, {"text": "this membrane potential\nand pH gradient, that", "start": 2016.66, "duration": 5.52}, {"text": "can be used elsewhere\nalong the membrane", "start": 2022.18, "duration": 3.39}, {"text": "to do some kind of work.", "start": 2025.57, "duration": 3.29}, {"text": "Now, I draw this is\ndelta psi, delta pH.", "start": 2028.86, "duration": 2.48}, {"text": "You can imagine, if\nyou're moving protons,", "start": 2031.34, "duration": 2.41}, {"text": "you're going to\ncreate a voltage.", "start": 2033.75, "duration": 2.67}, {"text": "You're also going to\ncreate a pH gradient.", "start": 2036.42, "duration": 2.552}, {"text": "It turns out I don't\nhave time to discuss", "start": 2038.972, "duration": 1.708}, {"text": "this further in the class.", "start": 2040.68, "duration": 1.083}, {"text": "A lot is written\nabout how to think", "start": 2041.763, "duration": 2.307}, {"text": "about this membrane potential\nas either a true voltage", "start": 2044.07, "duration": 5.25}, {"text": "or as a pH gradient.", "start": 2049.32, "duration": 1.62}, {"text": "It turns out that\nthey're useful to think", "start": 2050.94, "duration": 1.949}, {"text": "about in different ways\nfor different processes.", "start": 2052.889, "duration": 2.895}, {"text": "But if you're\ninterested in this,", "start": 2055.784, "duration": 1.375}, {"text": "there's certainly lots written\nabout this on various papers", "start": 2057.159, "duration": 4.131}, {"text": "and texts on bioenergetics.", "start": 2061.29, "duration": 2.099}, {"text": "And I would encourage you\nto read more about that.", "start": 2063.389, "duration": 3.491}, {"text": "OK.", "start": 2066.88, "duration": 1.255}, {"text": "All right, what\nI want to do next", "start": 2068.135, "duration": 1.375}, {"text": "then is discuss each\nof these processes", "start": 2069.51, "duration": 3.03}, {"text": "in turn, that is\nhow does this work", "start": 2072.54, "duration": 2.31}, {"text": "and how does that work,\nto really understand", "start": 2074.85, "duration": 6.17}, {"text": "what's going on in\nmitochondria and bacteria", "start": 2081.02, "duration": 3.719}, {"text": "to carry out this process of\noxidative phosphorylation.", "start": 2084.739, "duration": 4.631}, {"text": "So first, let's talk here.", "start": 2089.37, "duration": 1.91}, {"text": "First, how does one use\nfavorable electron transfer", "start": 2091.28, "duration": 14.91}, {"text": "to make this membrane potential?", "start": 2106.19, "duration": 10.4}, {"text": "Obviously, if we're\ngoing to pump protons", "start": 2116.59, "duration": 3.27}, {"text": "against a gradient, such that\nwe have different concentration", "start": 2119.86, "duration": 4.92}, {"text": "of protons on either\nside of the membrane,", "start": 2124.78, "duration": 2.01}, {"text": "that's going to\nrequire energy input.", "start": 2126.79, "duration": 2.64}, {"text": "And that energy is going to\ncome from favorable electron", "start": 2129.43, "duration": 3.91}, {"text": "transfer.", "start": 2133.34, "duration": 0.5}, {"text": "And really this process is\ntaking electrons from, say,", "start": 2136.65, "duration": 12.84}, {"text": "a cofactor like NADH, and\nultimately transferring", "start": 2149.49, "duration": 10.64}, {"text": "those electrons to\noxygen to get water.", "start": 2160.13, "duration": 5.05}, {"text": "The standard reduction\npotential of NAD/NADH", "start": 2165.18, "duration": 4.14}, {"text": "is less than the\nstandard reduction", "start": 2169.32, "duration": 2.7}, {"text": "potential of oxygen and water.", "start": 2172.02, "duration": 2.22}, {"text": "That means that equilibrium\nis going to favor electron", "start": 2174.24, "duration": 3.78}, {"text": "transport in this direction.", "start": 2178.02, "duration": 2.4}, {"text": "To say it another way,\nrelative to oxygen-water,", "start": 2180.42, "duration": 4.75}, {"text": "NAD/NADH is a better\nelectron donor.", "start": 2185.17, "duration": 2.96}, {"text": "Oxygen-water is a better\nelectron acceptor pair.", "start": 2188.13, "duration": 4.35}, {"text": "And so by this electron\ntransfer being favorable,", "start": 2192.48, "duration": 4.98}, {"text": "it can be used then\nto release energy", "start": 2197.46, "duration": 5.31}, {"text": "coupled to other processes,\nsuch as moving protons", "start": 2202.77, "duration": 3.99}, {"text": "and make that otherwise\nunfavorable process favorable.", "start": 2206.76, "duration": 4.77}, {"text": "Now, you'll note\nthat, in doing this,", "start": 2211.53, "duration": 3.6}, {"text": "we now regenerate the\noxidized cofactor NAD+.", "start": 2215.13, "duration": 4.38}, {"text": "And so that solves our electron\nbalance problem for glycolysis,", "start": 2219.51, "duration": 5.49}, {"text": "solves any electron\nbalance problem", "start": 2225.0, "duration": 2.91}, {"text": "that would exist for fatty\nacid oxidation or the TCA cycle", "start": 2227.91, "duration": 4.47}, {"text": "in the mitochondria.", "start": 2232.38, "duration": 1.47}, {"text": "Because ultimately,\nthose electrons", "start": 2233.85, "duration": 1.77}, {"text": "are being given to\noxygen. And so oxygen,", "start": 2235.62, "duration": 3.18}, {"text": "being this final\nelectron acceptor,", "start": 2238.8, "duration": 3.23}, {"text": "being stoichiometrically\nproduced to generate water,", "start": 2242.03, "duration": 4.59}, {"text": "is effectively water being\nthe alternative waste product", "start": 2246.62, "duration": 3.93}, {"text": "to, say, lactate\nor ethanol that we", "start": 2250.55, "duration": 2.07}, {"text": "saw in fermentation, all right?", "start": 2252.62, "duration": 3.9}, {"text": "Now, as we started the\nlecture with and discussed", "start": 2256.52, "duration": 2.76}, {"text": "in glycolysis, if we do this\nin one step, it's favorable.", "start": 2259.28, "duration": 3.84}, {"text": "But it's also favorable if we\ndo it in lots of little steps.", "start": 2263.12, "duration": 5.49}, {"text": "By doing it and lots\nof little steps,", "start": 2268.61, "duration": 1.96}, {"text": "just like we did\nin glycolysis, we", "start": 2270.57, "duration": 2.24}, {"text": "can break up that\nenergy release in a way", "start": 2272.81, "duration": 2.37}, {"text": "to allow us to do\nmore work, right?", "start": 2275.18, "duration": 2.88}, {"text": "So in glycolysis, we could\nturn carbohydrate into CO2--", "start": 2278.06, "duration": 6.62}, {"text": "one step, burning wood,\nrelease a lot of light and heat", "start": 2284.68, "duration": 3.24}, {"text": "all in one step.", "start": 2287.92, "duration": 1.59}, {"text": "That can be used to do work.", "start": 2289.51, "duration": 1.59}, {"text": "But it was more efficient to\nbreak it up into little steps", "start": 2291.1, "duration": 3.0}, {"text": "where we could then\ncapture intermediates", "start": 2294.1, "duration": 1.8}, {"text": "that made ATP synthase favorable\ndespite high ATP/ADP ratio.", "start": 2295.9, "duration": 4.95}, {"text": "Same idea here, we could\ntransfer this all in one step.", "start": 2300.85, "duration": 3.45}, {"text": "But instead, you break\nit up into a bunch", "start": 2304.3, "duration": 2.07}, {"text": "of individual steps, which can\nthen be coupled individually", "start": 2306.37, "duration": 4.68}, {"text": "to pumping protons\nacross the membrane", "start": 2311.05, "duration": 2.44}, {"text": "to generate more efficiently\nthis delta PSI delta pH", "start": 2313.49, "duration": 4.49}, {"text": "to charge this battery.", "start": 2317.98, "duration": 2.28}, {"text": "And so this occurs across a\nseries of electron carriers,", "start": 2320.26, "duration": 6.36}, {"text": "multi-protein complexes,\nelectron carriers,", "start": 2326.62, "duration": 3.24}, {"text": "called the electron\ntransport chain.", "start": 2329.86, "duration": 2.79}, {"text": "And you can think of this\nelectron transport chain", "start": 2335.75, "duration": 2.72}, {"text": "as being entirely analogous\nto what we already", "start": 2338.47, "duration": 2.85}, {"text": "talked about when\nwe talked about how", "start": 2341.32, "duration": 2.34}, {"text": "pyruvate dehydrogenase\nor alpha-ketoglutarate", "start": 2343.66, "duration": 2.43}, {"text": "dehydrogenase works when we\ntalked about the TCA cycle.", "start": 2346.09, "duration": 3.24}, {"text": "Remember, these had these\ndifferent protein complexes,", "start": 2349.33, "duration": 3.15}, {"text": "this E1, E2, E3,\nwhere electrons were", "start": 2352.48, "duration": 2.94}, {"text": "transferred across this chain.", "start": 2355.42, "duration": 1.83}, {"text": "It's exactly the same\nidea here, a number", "start": 2357.25, "duration": 2.76}, {"text": "of multi-polypeptide\nencoded protein complexes", "start": 2360.01, "duration": 4.89}, {"text": "that come together to hold\na bunch of electron carriers", "start": 2364.9, "duration": 4.86}, {"text": "that break up the energy\nrelease, if you will,", "start": 2369.76, "duration": 3.64}, {"text": "as we oxidize NADH and\nreduce oxygen and transfer", "start": 2373.4, "duration": 5.48}, {"text": "those electrons along the chain\nwith the complexes themselves", "start": 2378.88, "duration": 4.56}, {"text": "coupling the favorable\nelectron transfer to the moving", "start": 2383.44, "duration": 3.6}, {"text": "of protons against a gradient\nacross the membrane to work.", "start": 2387.04, "duration": 5.0}, {"text": "And so for this electron\ntransport chain to work,", "start": 2392.04, "duration": 3.66}, {"text": "we obviously need a bunch\nof electron carriers.", "start": 2395.7, "duration": 3.3}, {"text": "And why you need more\nthan one electron carrier", "start": 2399.0, "duration": 2.22}, {"text": "should now be obvious.", "start": 2401.22, "duration": 1.53}, {"text": "Because having\ndifferent carriers that", "start": 2402.75, "duration": 2.52}, {"text": "sit at different\nstandard reduction", "start": 2405.27, "duration": 2.88}, {"text": "potentials is going\nto be useful if we", "start": 2408.15, "duration": 4.23}, {"text": "want to build a chain such that\nwe can have favorable oxidation", "start": 2412.38, "duration": 5.88}, {"text": "and reduction to move electrons\nin a favorable direction", "start": 2418.26, "duration": 3.54}, {"text": "and couple that to\nprocesses that allow", "start": 2421.8, "duration": 4.41}, {"text": "us to charge this battery.", "start": 2426.21, "duration": 2.76}, {"text": "And so it turns out that\nfor this electron transport", "start": 2428.97, "duration": 2.85}, {"text": "chain to work--", "start": 2431.82, "duration": 1.38}, {"text": "well, we know about some\nof our electron carriers.", "start": 2433.2, "duration": 2.47}, {"text": "So we've discussed NAD, NADH.", "start": 2435.67, "duration": 4.22}, {"text": "There's FAD, FADH2.", "start": 2439.89, "duration": 3.38}, {"text": "There was lipoic acid.", "start": 2443.27, "duration": 1.2}, {"text": "Lipoic acid is not part of\nthe electron transport chain.", "start": 2447.8, "duration": 5.66}, {"text": "NAD, NADH is a donor.", "start": 2453.46, "duration": 1.43}, {"text": "You'll see FAD can be part of\nthe electron transport chain,", "start": 2454.89, "duration": 4.2}, {"text": "but there's a different--", "start": 2459.09, "duration": 1.65}, {"text": "or there's additional\nelectron carriers.", "start": 2460.74, "duration": 1.77}, {"text": "I want to discuss those now.", "start": 2462.51, "duration": 2.65}, {"text": "So another important\none is something called", "start": 2465.16, "duration": 2.81}, {"text": "FMN or Flavin Mononucleotide.", "start": 2467.97, "duration": 5.636}, {"text": "What FMN, or Flavin\nMononucleotide is, is it's", "start": 2476.89, "duration": 4.47}, {"text": "effectively FAD.", "start": 2481.36, "duration": 2.91}, {"text": "But it's a FAD not in\na dinucleotide state,", "start": 2484.27, "duration": 3.48}, {"text": "but a mononucleotide state.", "start": 2487.75, "duration": 2.2}, {"text": "So if you take FAD and you\nremove an AMP group from it,", "start": 2489.95, "duration": 3.68}, {"text": "what you're left with is FMN.", "start": 2493.63, "duration": 2.79}, {"text": "So just to remind you to\nbe explicit about this--", "start": 2496.42, "duration": 4.045}, {"text": "so.", "start": 2500.465, "duration": 0.5}, {"text": "So you have this flavin group\nattached to this ribitol group", "start": 2550.76, "duration": 5.29}, {"text": "with a phosphate on it.", "start": 2556.05, "duration": 1.5}, {"text": "If I put another phosphate and\nan adenine nucleotide here,", "start": 2557.55, "duration": 3.12}, {"text": "an AMP group attached\nhere, that would be FAD.", "start": 2560.67, "duration": 3.48}, {"text": "This would be FMN, nucleotide\ninstead of a dinucleotide.", "start": 2564.15, "duration": 4.89}, {"text": "This is FMN in\nthe oxidized form.", "start": 2569.04, "duration": 6.42}, {"text": "And just like FAD, it can\naccept an electron pair.", "start": 2575.46, "duration": 8.07}, {"text": "So here's our hydride\nion, two electrons", "start": 2583.53, "duration": 5.145}, {"text": "if we just draw here the\nmiddle part of the molecule.", "start": 2588.675, "duration": 3.505}, {"text": "And so this here would be\nFMNH2 or the reduced form", "start": 2600.87, "duration": 16.54}, {"text": "of this electron carrier, OK?", "start": 2617.41, "duration": 5.03}, {"text": "So flavin mononucleotide--\npart of the electron transport", "start": 2622.44, "duration": 4.88}, {"text": "chain.", "start": 2627.32, "duration": 0.94}, {"text": "Now, note FMN, FAD,\nNAD, all of these things", "start": 2628.26, "duration": 4.43}, {"text": "are two electron\ncarriers, right?", "start": 2632.69, "duration": 2.43}, {"text": "We disguise the\nmechanism of all of them,", "start": 2635.12, "duration": 2.7}, {"text": "just reminded you of\nit, these hydride ion", "start": 2637.82, "duration": 2.4}, {"text": "transfers, two\nelectron carriers.", "start": 2640.22, "duration": 2.56}, {"text": "It turns out the electron\ntransport chain also", "start": 2642.78, "duration": 3.14}, {"text": "uses metal ions as\nelectron carriers.", "start": 2645.92, "duration": 3.21}, {"text": "And so-- lots of minerals in\nour diet, things like iron.", "start": 2649.13, "duration": 3.69}, {"text": "It turns out elemental iron\nis a great electron carrier.", "start": 2652.82, "duration": 3.42}, {"text": "And it's very important for\nelectron transport chain.", "start": 2656.24, "duration": 5.08}, {"text": "Now, elemental metals\nare one electron carrier.", "start": 2661.32, "duration": 5.45}, {"text": "And so there's a few ways\nyou incorporate iron.", "start": 2666.77, "duration": 3.72}, {"text": "One is something called\niron sulfur clusters.", "start": 2670.49, "duration": 3.45}, {"text": "And so iron sulfur clusters\nis, within a protein,", "start": 2673.94, "duration": 4.17}, {"text": "you have some cysteine residues.", "start": 2678.11, "duration": 2.47}, {"text": "And those cysteine residues\ncan coordinate an iron atom.", "start": 2683.1, "duration": 6.07}, {"text": "And so that iron atom can sit\nin the 3+ versus 2+ state,", "start": 2689.17, "duration": 8.24}, {"text": "oxidized, reduced.", "start": 2697.41, "duration": 1.335}, {"text": "So reduction of the iron--", "start": 2702.86, "duration": 1.92}, {"text": "oxidation of the iron, OK?", "start": 2704.78, "duration": 3.0}, {"text": "So one electron carrier--", "start": 2707.78, "duration": 1.86}, {"text": "move one electron that way.", "start": 2709.64, "duration": 2.1}, {"text": "Also, ion sits within\nmolecules called cytochromes.", "start": 2711.74, "duration": 7.35}, {"text": "So what are cytochromes?", "start": 2719.09, "duration": 1.98}, {"text": "This is an iron atom\nthat's basically", "start": 2721.07, "duration": 3.87}, {"text": "chelated into a porphyrin\nvery similar to what", "start": 2724.94, "duration": 3.54}, {"text": "you saw for hemoglobin.", "start": 2728.48, "duration": 2.05}, {"text": "And so you have an iron 2+ or 3+\nthat's chelated here into this", "start": 2730.53, "duration": 24.34}, {"text": "porphyrin ring structure.", "start": 2754.87, "duration": 2.27}, {"text": "OK.", "start": 2769.05, "duration": 0.99}, {"text": "Lots of conjugated double\nbond systems in it,", "start": 2770.04, "duration": 2.52}, {"text": "this should look very similar.", "start": 2772.56, "duration": 1.85}, {"text": "Porphyrin is the thing on\nthe outside, coordinates iron", "start": 2774.41, "duration": 2.53}, {"text": "atom in the middle.", "start": 2776.94, "duration": 1.08}, {"text": "That can move between the 2+\nand the 3+ state just like we do", "start": 2778.02, "duration": 2.88}, {"text": "for iron sulfur clusters, so\ncarry electrons be oxidized", "start": 2780.9, "duration": 3.42}, {"text": "or reduced, 3+ or 2+.", "start": 2784.32, "duration": 2.79}, {"text": "And ultimately,\nthis porphyrin can", "start": 2787.11, "duration": 5.64}, {"text": "have some R groups added here,\ncan be associated with it", "start": 2792.75, "duration": 8.18}, {"text": "or bound to cysteine\nresidues within proteins.", "start": 2800.93, "duration": 3.63}, {"text": "Effectively, these molecules\nvarying these R groups", "start": 2804.56, "duration": 4.92}, {"text": "and how it's\nattached to proteins", "start": 2809.48, "duration": 2.49}, {"text": "gives you different families\nof cytochrome is referred", "start": 2811.97, "duration": 4.05}, {"text": "to as cytochrome A, the B type\ncytochromes, and cytochrome C.", "start": 2816.02, "duration": 8.7}, {"text": "These are associated\nwith enzyme complexes,", "start": 2824.72, "duration": 3.0}, {"text": "cytochrome C. It's\nactually covalently bound", "start": 2827.72, "duration": 2.37}, {"text": "to the polypeptide itself.", "start": 2830.09, "duration": 3.54}, {"text": "Basically, these are\nnamed because you", "start": 2833.63, "duration": 2.16}, {"text": "have these different conjugated\nring structures here.", "start": 2835.79, "duration": 5.77}, {"text": "That and how the R groups\nare will slightly change.", "start": 2841.56, "duration": 3.21}, {"text": "So this will absorb\nvisible light.", "start": 2844.77, "duration": 1.53}, {"text": "That will slightly change\nthe absorption spectra.", "start": 2846.3, "duration": 3.34}, {"text": "And so classically, based\non absorption spectra,", "start": 2849.64, "duration": 2.48}, {"text": "these were classified into\nA, B, and C type cytochromes.", "start": 2852.12, "duration": 3.69}, {"text": "And you can imagine,\nby these properties", "start": 2855.81, "duration": 2.04}, {"text": "having slightly different--", "start": 2857.85, "duration": 2.79}, {"text": "affecting the iron in\nways that it slightly", "start": 2860.64, "duration": 2.01}, {"text": "affects its electron\ntransport properties.", "start": 2862.65, "duration": 2.97}, {"text": "Of course, hemoglobin\nalmost certainly", "start": 2865.62, "duration": 2.82}, {"text": "evolved from these molecules\nas oxygen carrying ways", "start": 2868.44, "duration": 4.11}, {"text": "in multicellular life.", "start": 2872.55, "duration": 1.8}, {"text": "But of course, the original\nuse was as electron carriers", "start": 2874.35, "duration": 3.845}, {"text": "for the processes\nhere that we're", "start": 2878.195, "duration": 1.375}, {"text": "going to talk about, to\nhold that iron as a way", "start": 2879.57, "duration": 2.13}, {"text": "to control electron transport\nacross these electron transport", "start": 2881.7, "duration": 4.47}, {"text": "chains.", "start": 2886.17, "duration": 1.53}, {"text": "All right, so that's iron.", "start": 2887.7, "duration": 1.11}, {"text": "It turns out iron is\nnot the only metal that", "start": 2888.81, "duration": 3.03}, {"text": "can be used to do this.", "start": 2891.84, "duration": 1.69}, {"text": "And so cells also use copper.", "start": 2893.53, "duration": 3.11}, {"text": "And so histidine can coordinate\na copper that can move between", "start": 2896.64, "duration": 15.76}, {"text": "an oxidized and reduced state,\nso copper 2+ reduced to copper", "start": 2912.4, "duration": 3.81}, {"text": "+, copper + to copper 2+ or\ncopper + oxidized to copper 2+,", "start": 2916.21, "duration": 5.28}, {"text": "another one electron carrier.", "start": 2921.49, "duration": 2.76}, {"text": "And so iron and copper can\nact as one electron carriers.", "start": 2924.25, "duration": 4.887}, {"text": "And so you have these\ntwo electron carriers.", "start": 2929.137, "duration": 1.833}, {"text": "Here's a bunch of metals\nas one electron carriers.", "start": 2930.97, "duration": 2.67}, {"text": "Obviously, you need ways\nto carry both one and two", "start": 2933.64, "duration": 4.235}, {"text": "electrons if you're\ngoing to move", "start": 2937.875, "duration": 1.375}, {"text": "electrons between these\ndifferent carriers.", "start": 2939.25, "duration": 2.94}, {"text": "And an important molecule\nto do that is something", "start": 2942.19, "duration": 3.51}, {"text": "called coenzyme Q. Coenzyme Q--", "start": 2945.7, "duration": 6.46}, {"text": "sometimes referred to\nas ubiquinone ubiquinol,", "start": 2952.16, "duration": 9.87}, {"text": "because it's ubiquitous, often\nabbreviated co-Q. Many of you", "start": 2962.03, "duration": 7.168}, {"text": "have probably heard\nof the supplement", "start": 2969.198, "duration": 1.542}, {"text": "CoQ10, very popular\nsupplement out there.", "start": 2970.74, "duration": 4.17}, {"text": "CoQ10 is basically a\nversion of coenzyme Q,", "start": 2974.91, "duration": 3.93}, {"text": "ubiquinone, ubiquinol.", "start": 2978.84, "duration": 2.13}, {"text": "What this looks\nlike is as follows.", "start": 2980.97, "duration": 1.65}, {"text": "So this here is ubiquinone,\nthe oxidized form.", "start": 3003.75, "duration": 8.72}, {"text": "So this middle part\nis the quinone.", "start": 3012.47, "duration": 3.39}, {"text": "And then you have these\ndecorations on the outside,", "start": 3015.86, "duration": 2.85}, {"text": "including this R group.", "start": 3018.71, "duration": 1.53}, {"text": "This R group is typically\na long acyl tail.", "start": 3020.24, "duration": 3.15}, {"text": "If it's 10 carbons long,\nthat's CoQ10 supplement.", "start": 3023.39, "duration": 4.14}, {"text": "Having this long\nacyl chain makes this", "start": 3027.53, "duration": 2.28}, {"text": "a very hydrophobic molecule.", "start": 3029.81, "duration": 1.71}, {"text": "And it actually lives\nwithin the membrane itself", "start": 3031.52, "duration": 4.02}, {"text": "as an electron carrier.", "start": 3035.54, "duration": 1.77}, {"text": "And so this ubiquinone can\npick up an electron as well as", "start": 3037.31, "duration": 8.645}, {"text": "a proton.", "start": 3045.955, "duration": 0.5}, {"text": "Whoops.", "start": 3049.192, "duration": 0.5}, {"text": "And so by picking\nup one electron,", "start": 3057.49, "duration": 6.79}, {"text": "it can then basically go here\nto this semiquinone stabilized", "start": 3064.28, "duration": 20.83}, {"text": "free radical state\nand then pick up", "start": 3085.11, "duration": 2.46}, {"text": "a second electron to go\nto the fully reduced form.", "start": 3087.57, "duration": 6.965}, {"text": "ubiquinol.", "start": 3105.55, "duration": 0.63}, {"text": "OK.", "start": 3111.18, "duration": 0.9}, {"text": "So one electronic carrier\nand two electron carrier--", "start": 3112.08, "duration": 3.72}, {"text": "so basically, it can\ncarry two electrons", "start": 3115.8, "duration": 4.05}, {"text": "from the oxidized,\nthe reduced form,", "start": 3119.85, "duration": 1.86}, {"text": "but can transfer them\nas single electrons", "start": 3121.71, "duration": 3.3}, {"text": "by going through this stabilized\nfree radical ubiquinone state.", "start": 3125.01, "duration": 6.24}, {"text": "And so, basically, these\nvarious electron carriers", "start": 3131.25, "duration": 3.15}, {"text": "are associated with\nthese protein complexes", "start": 3134.4, "duration": 4.41}, {"text": "within this electron transport\nchain that ultimately works", "start": 3138.81, "duration": 3.93}, {"text": "to couple favorable\nelectron transport down", "start": 3142.74, "duration": 3.6}, {"text": "the chain to pumping protons\nto generate this potential", "start": 3146.34, "duration": 4.32}, {"text": "across the membrane.", "start": 3150.66, "duration": 2.67}, {"text": "All right, so this\nprocess occurs, again,", "start": 3153.33, "duration": 14.59}, {"text": "at the bacterial membrane or\nthe inner mitochondrial membrane", "start": 3167.92, "duration": 3.93}, {"text": "and, in animals\nand most organisms,", "start": 3171.85, "duration": 9.49}, {"text": "operates with four large\nmulti-subunit protein", "start": 3181.34, "duration": 9.15}, {"text": "complexes, all right?", "start": 3190.49, "duration": 2.85}, {"text": "Each of these protein complexes\nhas multiple polypeptides,", "start": 3193.34, "duration": 6.6}, {"text": "as I said.", "start": 3199.94, "duration": 0.5}, {"text": "It's coming together to form\nthese complexes just like we", "start": 3200.44, "duration": 2.47}, {"text": "described for pH, for instance.", "start": 3202.91, "duration": 2.49}, {"text": "Most of the\ncomponents of this are", "start": 3205.4, "duration": 2.28}, {"text": "encoded in the nuclear\ngenome, but a subset of these", "start": 3207.68, "duration": 3.48}, {"text": "are encoded in the\nmitochondrial genome.", "start": 3211.16, "duration": 2.34}, {"text": "Now, what exactly is encoded in\ndifferent mitochondrial genomes", "start": 3213.5, "duration": 3.18}, {"text": "varies by organisms.", "start": 3216.68, "duration": 2.01}, {"text": "But across organisms,\nit's basically", "start": 3218.69, "duration": 3.27}, {"text": "mostly complex components\nof these protein complexes.", "start": 3221.96, "duration": 5.25}, {"text": "And so this is why\nmitochondrial DNA is retained.", "start": 3227.21, "duration": 2.58}, {"text": "It's kind of this vestige of\nthis symbiotic relationship.", "start": 3229.79, "duration": 3.36}, {"text": "The mitochondria have\nretained some of the ability", "start": 3233.15, "duration": 2.88}, {"text": "to control their own\nenergy transduction, sort", "start": 3236.03, "duration": 3.495}, {"text": "of core components\nof these complexes.", "start": 3239.525, "duration": 2.985}, {"text": "There is one soluble protein.", "start": 3242.51, "duration": 3.51}, {"text": "So these complexes are\nembedded within the membrane.", "start": 3246.02, "duration": 3.39}, {"text": "There's also one\nsoluble protein that's", "start": 3249.41, "duration": 2.91}, {"text": "associated with the membrane.", "start": 3252.32, "duration": 1.71}, {"text": "And then there's\ncoenzyme Q, which also", "start": 3254.03, "duration": 5.16}, {"text": "floats within the membrane.", "start": 3259.19, "duration": 2.27}, {"text": "So that's in the membrane.", "start": 3261.46, "duration": 4.14}, {"text": "These are embedded\nin the membrane.", "start": 3265.6, "duration": 3.572}, {"text": "And then there's a\nsoluble protein that's", "start": 3269.172, "duration": 1.708}, {"text": "associated with the membrane.", "start": 3270.88, "duration": 1.53}, {"text": "OK, now I want to discuss the\ndetails of what these protein", "start": 3311.39, "duration": 4.26}, {"text": "complexes are and also few\ncomments about how they work.", "start": 3315.65, "duration": 8.14}, {"text": "So if this is the\ninner membrane space", "start": 3323.79, "duration": 2.36}, {"text": "and this is the\nmatrix side, that'd", "start": 3326.15, "duration": 2.01}, {"text": "be out or in if we're\ndiscussing a prokaryote.", "start": 3328.16, "duration": 6.3}, {"text": "The first is we have something\ncalled complex I, also", "start": 3334.46, "duration": 18.8}, {"text": "referred to as NADH oxidase\nbecause it oxidizes NADH back", "start": 3353.26, "duration": 13.335}, {"text": "to NAD.", "start": 3366.595, "duration": 0.5}, {"text": "NADH oxidase is a giant complex\ngreater than 900 kilodaltons", "start": 3371.53, "duration": 8.49}, {"text": "in total.", "start": 3380.02, "duration": 1.095}, {"text": "It has more than 25\nindividual protein subunits,", "start": 3381.115, "duration": 10.115}, {"text": "contains some flavin\nmononucleotides as well as", "start": 3391.23, "duration": 6.18}, {"text": "some iron sulfur clusters\nas electron carriers.", "start": 3397.41, "duration": 5.34}, {"text": "And it is the least\nwell-understood", "start": 3402.75, "duration": 4.62}, {"text": "of all of the protein complexes.", "start": 3407.37, "duration": 1.68}, {"text": "In fact, it is still\na major field of study", "start": 3409.05, "duration": 4.47}, {"text": "to try to understand how\nNAD oxidase really works.", "start": 3413.52, "duration": 4.41}, {"text": "But it effectively is one of the\ncomplexes that can pump protons", "start": 3417.93, "duration": 5.19}, {"text": "across the membrane as those\ntwo electrons are transferred", "start": 3423.12, "duration": 4.65}, {"text": "through the complex from NADH\nultimately to coenzyme Q that", "start": 3427.77, "duration": 9.3}, {"text": "exists within the membrane.", "start": 3437.07, "duration": 3.65}, {"text": "OK, the next complex\ndiscuss is complex II.", "start": 3440.72, "duration": 13.29}, {"text": "Complex II is succinate\ndehydrogenase, the exact enzyme", "start": 3454.01, "duration": 10.43}, {"text": "that we heard about\nfrom the TCA cycle.", "start": 3464.44, "duration": 3.39}, {"text": "So what does succinate\ndehydrogenase do?", "start": 3467.83, "duration": 3.69}, {"text": "Remember, it converts\nfumarate to succinate.", "start": 3471.52, "duration": 3.24}, {"text": "It gave those electrons\nto FAD to make FADH2.", "start": 3474.76, "duration": 9.44}, {"text": "Well, that occurs\nwithin this complex,", "start": 3484.2, "duration": 3.22}, {"text": "which can also reoxidize the\nFADH2 with those two electrons", "start": 3487.42, "duration": 6.59}, {"text": "and give them,\nalso, to coenzyme Q", "start": 3494.01, "duration": 4.53}, {"text": "that sits within the membrane.", "start": 3498.54, "duration": 3.25}, {"text": "So I want to point out that\nthis, ultimately, you will see,", "start": 3501.79, "duration": 6.02}, {"text": "is why it is that electron\ntransfer from NADH and FADH2", "start": 3507.81, "duration": 6.72}, {"text": "has different energy yields.", "start": 3514.53, "duration": 3.27}, {"text": "And so the electron transfer\nfrom NADH to ubiquinone", "start": 3517.8, "duration": 6.45}, {"text": "is more of a change in\nstandard reduction potential", "start": 3524.25, "duration": 3.78}, {"text": "than from FADH2 to ubiquinone.", "start": 3528.03, "duration": 3.42}, {"text": "Why use FADH2?", "start": 3531.45, "duration": 2.01}, {"text": "Well, because, remember when\nwe did electron transfers,", "start": 3533.46, "duration": 3.57}, {"text": "we used, when we\noxidized a carbon, say,", "start": 3537.03, "duration": 8.34}, {"text": "in a carbohydrate to a ketone,\nwe tended to use NAD+/NADH", "start": 3545.37, "duration": 9.99}, {"text": "as the electron transport pair.", "start": 3555.36, "duration": 3.63}, {"text": "So this change in\nstandard reduction", "start": 3558.99, "duration": 2.25}, {"text": "potential is such that we\ncan make that reaction work", "start": 3561.24, "duration": 4.92}, {"text": "and ultimately drive that.", "start": 3566.16, "duration": 1.98}, {"text": "It turns out that putting\na double bond in--", "start": 3568.14, "duration": 6.18}, {"text": "this going from a not oxidizing\nan alcohol to a ketone,", "start": 3574.32, "duration": 6.09}, {"text": "but oxidizing the carbon\nto a double bond--", "start": 3580.41, "duration": 2.97}, {"text": "that basically you\nneed a different change", "start": 3583.38, "duration": 7.13}, {"text": "in standard reduction potential\nto carry out that reaction", "start": 3590.51, "duration": 4.53}, {"text": "and make it work.", "start": 3595.04, "duration": 2.1}, {"text": "FADH/FADH2 sits at a\nhigher standard reduction", "start": 3597.14, "duration": 4.53}, {"text": "potential than NAD/NADH.", "start": 3601.67, "duration": 2.91}, {"text": "And so that means to\nfurther transfer them", "start": 3604.58, "duration": 3.51}, {"text": "to something further\ndownstream, like coenzyme Q,", "start": 3608.09, "duration": 6.588}, {"text": "there's a bigger change in\nstandard reduction potential", "start": 3614.678, "duration": 2.292}, {"text": "here.", "start": 3616.97, "duration": 0.5}, {"text": "That can be used\nto drive protons.", "start": 3617.47, "duration": 1.66}, {"text": "There's not enough\nof a change here.", "start": 3619.13, "duration": 1.71}, {"text": "You can't use that\nto drive protons.", "start": 3620.84, "duration": 2.28}, {"text": "And it's because of\nthese differences", "start": 3623.12, "duration": 2.28}, {"text": "in what's actually being\noxidized that ultimately leads", "start": 3625.4, "duration": 3.96}, {"text": "to this difference in energetics\nwhen we think about FADH2", "start": 3629.36, "duration": 6.39}, {"text": "versus NADH and how\nmuch ATP equivalence", "start": 3635.75, "duration": 4.05}, {"text": "that they might have for cells.", "start": 3639.8, "duration": 2.48}, {"text": "All right, once electrons\nare in the ubiquinone pool", "start": 3642.28, "duration": 7.57}, {"text": "or coenzyme Q pool, they can now\nbe transferred to complex III.", "start": 3649.85, "duration": 8.13}, {"text": "So complex III is also referred\nto as cytochrome C reductase.", "start": 3657.98, "duration": 13.86}, {"text": "You'll see why in a second.", "start": 3671.84, "duration": 2.4}, {"text": "It's a 250 kilodalton complex.", "start": 3674.24, "duration": 5.67}, {"text": "There are 10 subunits.", "start": 3679.91, "duration": 3.9}, {"text": "It has a bunch of B type\nand C type cytochromes,", "start": 3683.81, "duration": 11.91}, {"text": "as well as some iron\nsulfur clusters.", "start": 3695.72, "duration": 5.17}, {"text": "Shown here on the\nslide from a textbook", "start": 3700.89, "duration": 2.7}, {"text": "is a picture of complex III and\nwhat it actually looks like.", "start": 3703.59, "duration": 7.14}, {"text": "Fairly well-understood\nhow it works,", "start": 3710.73, "duration": 3.6}, {"text": "this coupling of basically\nelectron transfer through the Q", "start": 3714.33, "duration": 4.11}, {"text": "pool can pump protons.", "start": 3718.44, "duration": 2.385}, {"text": "And this ultimately\nallows transfer", "start": 3724.47, "duration": 4.47}, {"text": "of electrons to this\nsmall soluble protein that", "start": 3728.94, "duration": 6.12}, {"text": "lives in the intermembrane space\nor associated with the outside", "start": 3735.06, "duration": 3.54}, {"text": "of the bacteria\ncalled cytochrome C--", "start": 3738.6, "duration": 3.45}, {"text": "or outside in the intermembrane\nspace called cytochrome C.", "start": 3742.05, "duration": 3.6}, {"text": "Cytochrome C is a 13\nkilodalton protein.", "start": 3745.65, "duration": 9.19}, {"text": "It's a very small\nhighly conserved protein", "start": 3754.84, "duration": 3.68}, {"text": "with a C type\ncytochrome commonly used", "start": 3758.52, "duration": 2.753}, {"text": "because it's found across\nmany, many different types", "start": 3761.273, "duration": 2.167}, {"text": "of organisms.", "start": 3763.44, "duration": 0.73}, {"text": "And so it's been sequenced\nfrom many, many organisms", "start": 3764.17, "duration": 3.26}, {"text": "as a way to identify\nevolutionary relationships.", "start": 3767.43, "duration": 3.12}, {"text": "And then cytochrome\nC, this is also", "start": 3770.55, "duration": 2.04}, {"text": "why it's called cytochrome\nC reductase because it's", "start": 3772.59, "duration": 2.82}, {"text": "reducing cytochrome C\nto transfer electrons", "start": 3775.41, "duration": 4.23}, {"text": "along the chain, ultimately to\nthe final complex, complex IV.", "start": 3779.64, "duration": 7.56}, {"text": "Complex IV-- also referred\nto as cytochrome C oxidase.", "start": 3787.2, "duration": 7.38}, {"text": "And this is ultimately the place\nwhere electrons are transferred", "start": 3794.58, "duration": 6.21}, {"text": "to reduce oxygen to water.", "start": 3800.79, "duration": 3.91}, {"text": "So this is 160 kilodalton\nprotein complex", "start": 3804.7, "duration": 5.6}, {"text": "with 13 subunits, uses A\ntype cytochromes and copper", "start": 3810.3, "duration": 15.67}, {"text": "as electron carriers\nand, ultimately,", "start": 3825.97, "duration": 4.74}, {"text": "allows you to get electrons\nfrom cytochrome C to oxygen.", "start": 3830.71, "duration": 4.44}, {"text": "And so here, again,\nfrom the textbook", "start": 3835.15, "duration": 2.19}, {"text": "is a picture of complex\nIV and what it looks like.", "start": 3837.34, "duration": 5.85}, {"text": "Also, fairly well-understood--\nalso couples electron transport", "start": 3843.19, "duration": 5.4}, {"text": "to proton pumping.", "start": 3848.59, "duration": 3.55}, {"text": "And so this is effectively\nthe electron transport chain", "start": 3852.14, "duration": 5.91}, {"text": "as it exists in mitochondria.", "start": 3858.05, "duration": 1.95}, {"text": "And you can draw it a different\nway as I will do here.", "start": 3860.0, "duration": 5.65}, {"text": "So here's complex I, allows\noxidation of NADH back to NAD+.", "start": 3865.65, "duration": 10.06}, {"text": "That oxidation can be\ncoupled to reduction of FMN.", "start": 3880.89, "duration": 7.59}, {"text": "Ultimately, those are passed\nthrough some iron sulfur", "start": 3888.48, "duration": 15.02}, {"text": "clusters leading to the\nreduction of ubiquinone.", "start": 3903.5, "duration": 9.12}, {"text": "And in the process,\nthis electron transport", "start": 3912.62, "duration": 5.04}, {"text": "can pump on the order\nof four protons,", "start": 3917.66, "duration": 3.06}, {"text": "or at least that's\nwhat's estimated.", "start": 3920.72, "duration": 2.43}, {"text": "Complex II, which is succinate\ndehydrogenase from the TCA", "start": 3923.15, "duration": 6.36}, {"text": "cycle, really converts\nsuccinate to fumarate.", "start": 3929.51, "duration": 8.39}, {"text": "That oxidation reaction\nwithin the complex", "start": 3937.9, "duration": 7.08}, {"text": "leads to the reduction\nof FAD to FADH2.", "start": 3944.98, "duration": 5.62}, {"text": "That can be reoxidized\nthrough iron,", "start": 3950.6, "duration": 9.57}, {"text": "ultimately driving the\nreduction of coenzyme Q", "start": 3960.17, "duration": 8.54}, {"text": "from ubiquinone to ubiquinol.", "start": 3968.71, "duration": 2.73}, {"text": "That ubiquinone to you\nubiquinol in something", "start": 3971.44, "duration": 4.32}, {"text": "called the Q pool\nwithin the membrane", "start": 3975.76, "duration": 4.2}, {"text": "can then be reoxidized\nin complex III.", "start": 3979.96, "duration": 12.35}, {"text": "That reoxidized in\ncomplex III puts electrons", "start": 3992.31, "duration": 6.36}, {"text": "through complex III that\ncan be coupled to pumping", "start": 3998.67, "duration": 3.9}, {"text": "on the order of two protons.", "start": 4002.57, "duration": 3.36}, {"text": "Those electrons are transferred\nto cytochrome C. Ultimately,", "start": 4005.93, "duration": 6.09}, {"text": "those electrons are transferred\nto copper in complex IV", "start": 4012.02, "duration": 8.78}, {"text": "to cytochrome A and,\nultimately, oxygen to water,", "start": 4020.8, "duration": 8.04}, {"text": "reducing oxygen to\nwater and pumping", "start": 4028.84, "duration": 3.23}, {"text": "on the order of four protons.", "start": 4032.07, "duration": 4.2}, {"text": "And so you can see here\nthat, basically, this", "start": 4036.27, "duration": 6.12}, {"text": "is a series of oxidation\nand reduction reactions", "start": 4042.39, "duration": 4.53}, {"text": "that happens across these\ncomplexes, such that complex I,", "start": 4046.92, "duration": 5.34}, {"text": "the transfer electrons from\nthe Q pool through complex III.", "start": 4052.26, "duration": 2.91}, {"text": "And complex IV can pump\nprotons across the membrane", "start": 4055.17, "duration": 4.83}, {"text": "and generate this\ndelta psi delta", "start": 4060.0, "duration": 2.4}, {"text": "pH that can be used to do work.", "start": 4062.4, "duration": 2.58}, {"text": "And it's really the favorable\ntransfer of electrons", "start": 4064.98, "duration": 2.7}, {"text": "either from NAD/NADH or the\noxidation of the succinate", "start": 4067.68, "duration": 3.9}, {"text": "to fumarate with those electrons\nbeing given to oxygen to drive", "start": 4071.58, "duration": 4.62}, {"text": "this process.", "start": 4076.2, "duration": 2.26}, {"text": "And so really just to schematize\nthis, in a way, is that,", "start": 4078.46, "duration": 9.58}, {"text": "if this is our membrane, NAD+ to\nNADH gives electrons to complex", "start": 4088.04, "duration": 11.04}, {"text": "I, which goes to coenzyme Q,\nwhich goes to complex III,", "start": 4099.08, "duration": 5.58}, {"text": "which goes to cytochrome\nC, which goes to complex IV", "start": 4104.66, "duration": 4.17}, {"text": "and reduces oxygen to water.", "start": 4108.83, "duration": 5.489}, {"text": "That is one way to carry\nout this set of reactions.", "start": 4114.319, "duration": 3.931}, {"text": "The other way is we\ncan convert fumarate--", "start": 4118.25, "duration": 5.045}, {"text": "sorry, succinate to fumarate.", "start": 4123.295, "duration": 5.335}, {"text": "That's the FAD.", "start": 4128.63, "duration": 1.89}, {"text": "That's complex II, also\ngives it to the Q pool.", "start": 4130.52, "duration": 3.87}, {"text": "And so you can see that\nthe electron transport", "start": 4134.39, "duration": 2.4}, {"text": "chain would be complex I, Q,\nIII C, IV or II Q, III, C IV.", "start": 4136.79, "duration": 6.0}, {"text": "It is not I, II, III, IV.", "start": 4142.79, "duration": 2.37}, {"text": "It is actually I to Q or II\nto Q, ultimately going to III.", "start": 4145.16, "duration": 6.606}, {"text": "Now, the way protons\nare pumped is a process", "start": 4151.766, "duration": 4.104}, {"text": "that I don't have time this\nyear to discuss in class.", "start": 4155.87, "duration": 3.42}, {"text": "I will post something\non Stellar that is just", "start": 4159.29, "duration": 2.52}, {"text": "a short section from the\ntextbook that describes", "start": 4161.81, "duration": 3.18}, {"text": "at least what is known about\nhow that process works,", "start": 4164.99, "duration": 3.869}, {"text": "such as the Q cycle,\nbasically how oxidation", "start": 4168.859, "duration": 4.141}, {"text": "and reduction of coenzyme\nQ, which will take protons", "start": 4173.0, "duration": 4.05}, {"text": "on and off the molecule on\neither side of the membrane,", "start": 4177.05, "duration": 2.61}, {"text": "can be used to show how this\ncan be coupled to proton", "start": 4179.66, "duration": 4.68}, {"text": "pumping across the membrane.", "start": 4184.34, "duration": 2.86}, {"text": "And you can read that\nif you're interested.", "start": 4187.2, "duration": 3.97}, {"text": "OK.", "start": 4191.17, "duration": 1.59}, {"text": "Now, a couple other\npoints about this, this", "start": 4192.76, "duration": 6.13}, {"text": "works because you're\nmoving from a lower", "start": 4198.89, "duration": 6.56}, {"text": "to a higher standard reduction\npotential across the chain.", "start": 4205.45, "duration": 3.36}, {"text": "And it turns out oxygen is\na particularly good electron", "start": 4208.81, "duration": 4.53}, {"text": "acceptor.", "start": 4213.34, "duration": 1.2}, {"text": "And this is really why oxygen\nand respiration is really", "start": 4214.54, "duration": 3.78}, {"text": "so vital to a lot of the\nway energy transduction", "start": 4218.32, "duration": 3.96}, {"text": "works in metabolism.", "start": 4222.28, "duration": 1.86}, {"text": "Oxygen is now abundant.", "start": 4224.14, "duration": 1.62}, {"text": "And being a great electron\nacceptor is why it's used.", "start": 4225.76, "duration": 2.5}, {"text": "But of course, oxygen\nwas not abundant", "start": 4228.26, "duration": 1.94}, {"text": "2 and 1/2 billion years ago.", "start": 4230.2, "duration": 2.4}, {"text": "And it doesn't have to be\noxygen for this to work.", "start": 4232.6, "duration": 4.6}, {"text": "If you have another\nelectron acceptor that", "start": 4237.2, "duration": 3.02}, {"text": "basically makes this\nprocess favorable,", "start": 4240.22, "duration": 2.76}, {"text": "that can work just as well.", "start": 4242.98, "duration": 1.54}, {"text": "And in fact, that happens\nstill in some very extreme", "start": 4244.52, "duration": 3.98}, {"text": "environments.", "start": 4248.5, "duration": 1.17}, {"text": "This so-called\nchemosynthesis basically", "start": 4249.67, "duration": 2.94}, {"text": "can use other\nelectronic acceptors", "start": 4252.61, "duration": 3.6}, {"text": "to drive the\nenergetics of cells.", "start": 4256.21, "duration": 3.09}, {"text": "And you really just\nneed the right ways", "start": 4259.3, "duration": 4.76}, {"text": "to build an electron transport\nchain to make this whole system", "start": 4264.06, "duration": 3.66}, {"text": "work, such you can build a\nbattery and use it to do work,", "start": 4267.72, "duration": 3.43}, {"text": "OK?", "start": 4271.15, "duration": 0.5}, {"text": "So oxygen-- commonly used\nbecause it's abundant and good", "start": 4271.65, "duration": 3.42}, {"text": "at it, but it's not the\nonly way that this can work.", "start": 4275.07, "duration": 3.18}, {"text": "And there are\nexamples in biology", "start": 4278.25, "duration": 1.56}, {"text": "where oxygen is not used, that\nthere is other acceptors that", "start": 4279.81, "duration": 4.02}, {"text": "are used instead.", "start": 4283.83, "duration": 2.15}, {"text": "Now, I also want to note, as\nI've alluded to in discussing", "start": 4285.98, "duration": 3.45}, {"text": "complex II, this FAD/FADH2.", "start": 4289.43, "duration": 4.14}, {"text": "So when we talk about\nthat in the TCA cycle", "start": 4293.57, "duration": 3.69}, {"text": "or in fatty acid\noxidation, we discuss it", "start": 4297.26, "duration": 3.09}, {"text": "as if it's kind of like\nNAD/NADH, but it's not.", "start": 4300.35, "duration": 3.69}, {"text": "NAD/NADH are basically\ncofactors that", "start": 4304.04, "duration": 4.29}, {"text": "move around between enzymes.", "start": 4308.33, "duration": 1.77}, {"text": "Fad/fadh2 are not free.", "start": 4310.1, "duration": 4.83}, {"text": "They're electron carriers that\nare part of protein complexes,", "start": 4314.93, "duration": 4.56}, {"text": "like what we described up here.", "start": 4319.49, "duration": 3.51}, {"text": "And they're part of enzymes\nlike succinate dehydrogenase.", "start": 4323.0, "duration": 2.97}, {"text": "So complex II just happens to be\nan FAD/FADH2 containing enzyme", "start": 4325.97, "duration": 7.2}, {"text": "that's part of the TCA cycle and\npart of the electron transport", "start": 4333.17, "duration": 3.81}, {"text": "chain as a way to transfer\nelectrons in the TCA cycle", "start": 4336.98, "duration": 3.9}, {"text": "into the Q pool\nvia this succinate", "start": 4340.88, "duration": 3.91}, {"text": "to fumarate conversion.", "start": 4344.79, "duration": 2.21}, {"text": "Acyl-CoA dehydrogenase,\nthe FAD/FADH2 enzyme", "start": 4347.0, "duration": 3.66}, {"text": "we discussed in\nfatty acid oxidation,", "start": 4350.66, "duration": 2.37}, {"text": "could easily be drawn instead\nin electron transport chain that", "start": 4353.03, "duration": 3.99}, {"text": "goes acyl-CoA dehydrogenase,\ncoenzyme Q, III, C, IV,", "start": 4357.02, "duration": 4.83}, {"text": "just like we can say\nsuccinate to fumarate", "start": 4361.85, "duration": 2.01}, {"text": "is the same as complex\nII, Q, III, C, IV, OK?", "start": 4363.86, "duration": 4.02}, {"text": "And so there's really lots of\nalternative electron transport", "start": 4367.88, "duration": 3.66}, {"text": "chains that involve these\nFAD/FADH2 containing enzymes", "start": 4371.54, "duration": 4.29}, {"text": "that really sit in the membrane\nand directly transfer electrons", "start": 4375.83, "duration": 4.02}, {"text": "to the Q pool.", "start": 4379.85, "duration": 3.93}, {"text": "Ultimately, the\ngoal of all of this", "start": 4383.78, "duration": 2.64}, {"text": "is, of course, to create\nthis delta psi delta", "start": 4386.42, "duration": 3.84}, {"text": "pH, which can be used to charge\nthis battery that then can then", "start": 4390.26, "duration": 4.53}, {"text": "be done to do work.", "start": 4394.79, "duration": 2.05}, {"text": "And so this work includes\nthe phosphorylation of ATP.", "start": 4396.84, "duration": 5.27}, {"text": "And so if we charge\nthis battery,", "start": 4402.11, "duration": 3.09}, {"text": "we can now use this as a way to\ncouple current in this battery", "start": 4405.2, "duration": 11.05}, {"text": "to phosphorylate ADP to make\nATP, the phosphorylation part", "start": 4416.25, "duration": 5.43}, {"text": "of oxidative phosphorylation.", "start": 4421.68, "duration": 3.15}, {"text": "Now, this occurs also by a\nlarge protein complex sometimes", "start": 4424.83, "duration": 3.9}, {"text": "referred to as complex\nV. But remember,", "start": 4428.73, "duration": 3.48}, {"text": "complex V, or this ATP\nsynthase machinery,", "start": 4432.21, "duration": 3.48}, {"text": "is not really part of the\nelectron transport chain.", "start": 4435.69, "duration": 3.03}, {"text": "It is separate in space and\nis basically something, a way,", "start": 4438.72, "duration": 4.17}, {"text": "to utilize this delta psi\ndelta pH across the membrane", "start": 4442.89, "duration": 4.56}, {"text": "to drive ATP synthesis.", "start": 4447.45, "duration": 4.14}, {"text": "All right, how does this\ncomplex V or ATP synthesis work?", "start": 4451.59, "duration": 7.6}, {"text": "So this is also a\nlarge protein complex,", "start": 4462.37, "duration": 6.83}, {"text": "sits within the same\nmembrane, of course,", "start": 4469.2, "duration": 3.1}, {"text": "because it has to utilize the\nmembrane potential to function.", "start": 4472.3, "duration": 4.34}, {"text": "And the so-called\ncomplex V is also", "start": 4491.05, "duration": 7.88}, {"text": "referred to as the ATP\nsynthase or the F0 F1 ATPase.", "start": 4498.93, "duration": 13.82}, {"text": "And basically, if this is\nthe intermembrane space,", "start": 4512.75, "duration": 6.44}, {"text": "this is the inner\nmitochondrial membrane.", "start": 4519.19, "duration": 3.46}, {"text": "This is the matrix.", "start": 4522.65, "duration": 2.59}, {"text": "You have a protein\ncomplex that sits", "start": 4525.24, "duration": 4.12}, {"text": "within the membrane called F0.", "start": 4529.36, "duration": 4.23}, {"text": "It's actually FO.", "start": 4533.59, "duration": 1.83}, {"text": "The O stands for a\nOligomycin because there's", "start": 4535.42, "duration": 4.05}, {"text": "a drug called oligomycin\nthat inhibits the FO,", "start": 4539.47, "duration": 3.0}, {"text": "or F0, part of the molecule.", "start": 4542.47, "duration": 3.78}, {"text": "And then there's\nthis F1 component", "start": 4546.25, "duration": 3.45}, {"text": "that is associated with\nthe F0 component that", "start": 4549.7, "duration": 3.06}, {"text": "sits on the matrix\nside of the membrane.", "start": 4552.76, "duration": 2.19}, {"text": "And it is effectively\nthe machine", "start": 4554.95, "duration": 3.3}, {"text": "that phosphorylates\nor interconverts", "start": 4558.25, "duration": 6.58}, {"text": "ATP and ADP on the matrix\nside of the membrane.", "start": 4564.83, "duration": 6.25}, {"text": "Now, it's pretty well-understood\nhow this system works.", "start": 4571.08, "duration": 4.02}, {"text": "And basically, F1\nworks by a process", "start": 4575.1, "duration": 2.69}, {"text": "called rotational catalysis.", "start": 4577.79, "duration": 3.57}, {"text": "How this works was awarded\nthe Nobel Prize in 1997,", "start": 4581.36, "duration": 3.51}, {"text": "figured out not\nall that long ago.", "start": 4584.87, "duration": 3.06}, {"text": "And basically, this is F1 is\na large protein complex where", "start": 4587.93, "duration": 4.83}, {"text": "you have a gamma\nsubunit that is attached", "start": 4592.76, "duration": 3.72}, {"text": "to F0 the couples, basically,\nproton pumping to this gamma", "start": 4596.48, "duration": 5.04}, {"text": "subunit to literally\nturn the F1 component", "start": 4601.52, "duration": 5.34}, {"text": "and change the confirmation\nof attached regions, parts,", "start": 4606.86, "duration": 6.18}, {"text": "of this F1 machine.", "start": 4613.04, "duration": 2.79}, {"text": "Because it turns\nout you can have", "start": 4615.83, "duration": 1.44}, {"text": "three different conformations\nof the rest of F1,", "start": 4617.27, "duration": 3.78}, {"text": "the so-called L, or Loose,\nconformation, the T,", "start": 4621.05, "duration": 3.33}, {"text": "or Tight, conformation, or\nthe O, or Open, conformation.", "start": 4624.38, "duration": 5.1}, {"text": "And so in the open conformation,\nADP and phosphate or ATP", "start": 4629.48, "duration": 14.81}, {"text": "can exchange in and out of\nthis complex, all right?", "start": 4644.29, "duration": 6.59}, {"text": "In the loose confirmation,\nyou basically", "start": 4650.88, "duration": 3.84}, {"text": "have ADP and phosphate bound.", "start": 4654.72, "duration": 3.78}, {"text": "And in the tight\nconformation, this", "start": 4658.5, "duration": 5.13}, {"text": "is favored to synthesize ATP.", "start": 4663.63, "duration": 6.27}, {"text": "And so you can envision that\nwhat actually happens here", "start": 4669.9, "duration": 5.61}, {"text": "is that you first\nhave ADP and ATP", "start": 4675.51, "duration": 4.47}, {"text": "bind in this open conformation.", "start": 4679.98, "duration": 5.86}, {"text": "Protons are moved.", "start": 4690.82, "duration": 1.83}, {"text": "You get rotation around\nthe gamma subunit.", "start": 4692.65, "duration": 4.03}, {"text": "That changes the\nconformation of the O subunit", "start": 4696.68, "duration": 3.93}, {"text": "to the loose subunit.", "start": 4700.61, "duration": 1.35}, {"text": "So now, you have\nADP plus PI bound.", "start": 4701.96, "duration": 4.08}, {"text": "Another proton moves,\nchanges the conformation", "start": 4706.04, "duration": 4.83}, {"text": "of the loose subunit into\nthe tight confirmation.", "start": 4710.87, "duration": 5.16}, {"text": "Now, ATP synthase is favored.", "start": 4716.03, "duration": 4.77}, {"text": "Another proton moves, comes\nback to the open conformation.", "start": 4720.8, "duration": 6.12}, {"text": "ATP is released\nfrom the molecule,", "start": 4726.92, "duration": 2.7}, {"text": "and you can run another\nrotational catalysis cycle", "start": 4729.62, "duration": 3.3}, {"text": "again to ultimately drive\nATP to ATP synthase using", "start": 4732.92, "duration": 5.82}, {"text": "this transfer of protons\nacross the F0 subunit", "start": 4738.74, "duration": 5.01}, {"text": "to ultimately rotate this\nmachine to synthesize ATP.", "start": 4743.75, "duration": 6.41}, {"text": "Now, the way F0 works\nis within the membrane--", "start": 4750.16, "duration": 4.05}, {"text": "and this is always\nhard to draw--", "start": 4754.21, "duration": 3.93}, {"text": "you basically have\na central complex", "start": 4758.14, "duration": 13.98}, {"text": "with another set of\ncomplexes around it", "start": 4772.12, "duration": 2.58}, {"text": "that, within that, have\ntwo half-channels that", "start": 4774.7, "duration": 4.23}, {"text": "are open to either\nside of the membrane.", "start": 4778.93, "duration": 3.85}, {"text": "And so if you look at\nthis from the top view,", "start": 4782.78, "duration": 3.0}, {"text": "so looking at it\nstraight down, you'd", "start": 4785.78, "duration": 2.21}, {"text": "have this central piece\nwith this external piece", "start": 4787.99, "duration": 4.41}, {"text": "with the two half-channels that\nbasically can rotate around", "start": 4792.4, "duration": 5.61}, {"text": "the central stalk.", "start": 4798.01, "duration": 1.53}, {"text": "This is hooked up to\nthe gamma subunit of F1", "start": 4799.54, "duration": 3.21}, {"text": "in which drives\nrotational catalysis.", "start": 4802.75, "duration": 2.94}, {"text": "And how this works\nis that attached", "start": 4805.69, "duration": 2.01}, {"text": "to this inner piece that is\nopen to the half-channels", "start": 4807.7, "duration": 5.52}, {"text": "is an aspartate residue.", "start": 4813.22, "duration": 3.85}, {"text": "So this is an aspartic\nacid residue that's there.", "start": 4817.07, "duration": 4.28}, {"text": "And recall that aspartic\nacid, it's an acid.", "start": 4821.35, "duration": 5.46}, {"text": "So it can pick up a\nproton or release a proton", "start": 4826.81, "duration": 6.25}, {"text": "from its acid group\ndepending on the pH", "start": 4833.06, "duration": 4.53}, {"text": "on either side of the membrane.", "start": 4837.59, "duration": 1.93}, {"text": "And so, remember,\nthere's a different pH", "start": 4839.52, "duration": 2.51}, {"text": "on the two sides\nof the membrane.", "start": 4842.03, "duration": 4.15}, {"text": "And it's really that\ndifference in pH", "start": 4846.18, "duration": 4.37}, {"text": "that will allow favorable\nturning around this center", "start": 4850.55, "duration": 6.09}, {"text": "stalk.", "start": 4856.64, "duration": 1.07}, {"text": "And so the pH in the\nintermembrane space is lower.", "start": 4857.71, "duration": 4.42}, {"text": "So that means you're\nmore likely to favor", "start": 4862.13, "duration": 3.03}, {"text": "protonation of the aspartate.", "start": 4865.16, "duration": 2.37}, {"text": "It can then rotate, such as the\nchannel, that aspartate, is now", "start": 4867.53, "duration": 3.39}, {"text": "exposed to the other\nchannel, to the matrix side.", "start": 4870.92, "duration": 2.67}, {"text": "There, the pH is higher,\nso favors deprotonation.", "start": 4873.59, "duration": 3.81}, {"text": "And basically, this will\ndrive motion of this piece", "start": 4877.4, "duration": 5.16}, {"text": "around the central stalk.", "start": 4882.56, "duration": 1.71}, {"text": "That being coupled to\nthe gamma subunit of F1", "start": 4884.27, "duration": 3.95}, {"text": "will cause the rotation\nof the F1 subunit changing", "start": 4888.22, "duration": 5.29}, {"text": "the attached conformation of\nthe rest of the complex to favor", "start": 4893.51, "duration": 4.38}, {"text": "ATP synthesis.", "start": 4897.89, "duration": 1.53}, {"text": "And it's really this is\nhow moving of protons back", "start": 4899.42, "duration": 5.25}, {"text": "from the intermembrane\nspace to the matrix", "start": 4904.67, "duration": 2.4}, {"text": "can drive the synthesis of\nATP, the phosphorylation", "start": 4907.07, "duration": 3.51}, {"text": "part of this process.", "start": 4910.58, "duration": 3.64}, {"text": "And so now you\nhave a full picture", "start": 4914.22, "duration": 2.06}, {"text": "of how carbon oxidation really\nreleases energy in a way that's", "start": 4916.28, "duration": 5.29}, {"text": "coupled to do work in biology.", "start": 4921.57, "duration": 2.33}, {"text": "So we can, of course,\ncouple this directly,", "start": 4923.9, "duration": 2.22}, {"text": "as we did at GAPDH or\nsuccinic thiokinase.", "start": 4926.12, "duration": 3.93}, {"text": "But mostly, it's captured to\ncharge up these NAD/NADH ratios", "start": 4930.05, "duration": 5.58}, {"text": "where favorable\nelectron transport can", "start": 4935.63, "duration": 2.49}, {"text": "be used to make this delta psi\ndelta pH in a membrane that", "start": 4938.12, "duration": 3.87}, {"text": "can be used also to synthesize\nATP despite a high ATP/ADP", "start": 4941.99, "duration": 4.29}, {"text": "ratio because that battery can\nbe used to drive this machine.", "start": 4946.28, "duration": 8.46}, {"text": "Now, I want to point out\nthat the ATP synthase is just", "start": 4954.74, "duration": 3.0}, {"text": "like any other enzyme\nin any pathway.", "start": 4957.74, "duration": 3.13}, {"text": "And that is, if\nconditions are right,", "start": 4960.87, "duration": 1.82}, {"text": "there's no reason\nthat this machine", "start": 4962.69, "duration": 2.4}, {"text": "has to drive ATP synthesis.", "start": 4965.09, "duration": 2.07}, {"text": "It could also\nconsume ATP as a way", "start": 4967.16, "duration": 3.72}, {"text": "to create a proton gradient.", "start": 4970.88, "duration": 2.52}, {"text": "That is use ATP\nhydrolysis to pump", "start": 4973.4, "duration": 4.05}, {"text": "protons in the\nopposite direction", "start": 4977.45, "duration": 2.22}, {"text": "into the intermembrane space.", "start": 4979.67, "duration": 2.165}, {"text": "Well, why would\nyou ever do that?", "start": 4981.835, "duration": 1.375}, {"text": "Well, you would do that\nbecause having this battery", "start": 4983.21, "duration": 2.82}, {"text": "is useful because ATP is\nnot the only way that cells", "start": 4986.03, "duration": 3.93}, {"text": "can use energy to do work.", "start": 4989.96, "duration": 1.98}, {"text": "It turns out that having\na membrane potential", "start": 4991.94, "duration": 2.85}, {"text": "is useful for other things.", "start": 4994.79, "duration": 1.28}, {"text": "So if you're in\ncourse nine, you know", "start": 4996.07, "duration": 1.72}, {"text": "that action potentials are\ncarried, basically electricity", "start": 4997.79, "duration": 3.72}, {"text": "along cells.", "start": 5001.51, "duration": 1.74}, {"text": "What is that?", "start": 5003.25, "duration": 0.63}, {"text": "That is basically changing\nmembrane potentials", "start": 5003.88, "duration": 2.49}, {"text": "across cells.", "start": 5006.37, "duration": 1.5}, {"text": "More generally,\nmembrane potentials", "start": 5007.87, "duration": 1.71}, {"text": "can be used to do lots\nof other types of work.", "start": 5009.58, "duration": 3.45}, {"text": "And so ATP is only one way that\ncells can use biological energy", "start": 5013.03, "duration": 7.29}, {"text": "because it can be\ncoupled to otherwise", "start": 5020.32, "duration": 1.62}, {"text": "unfavorable reactions.", "start": 5021.94, "duration": 1.68}, {"text": "But you can also\ncouple ion gradients", "start": 5023.62, "duration": 2.34}, {"text": "to unfavorable reactions\nand use that to do work--", "start": 5025.96, "duration": 4.3}, {"text": "and so lots of useful\nways that delta psi delta", "start": 5030.26, "duration": 4.04}, {"text": "pH can be used by cells.", "start": 5034.3, "duration": 5.32}, {"text": "And so what are some of these?", "start": 5039.62, "duration": 1.37}, {"text": "Well, the first one is this\ncan be used to generate heat.", "start": 5040.99, "duration": 5.98}, {"text": "So if you're checking\nyour phone right now,", "start": 5046.97, "duration": 2.84}, {"text": "your phone is obviously\na very useful device", "start": 5049.81, "duration": 2.31}, {"text": "to do all kinds of work for you.", "start": 5052.12, "duration": 2.16}, {"text": "You can read whatever\nyou want on your phone,", "start": 5054.28, "duration": 2.43}, {"text": "use it to call people.", "start": 5056.71, "duration": 1.795}, {"text": "Well, what happens\nif you short circuit", "start": 5058.505, "duration": 1.625}, {"text": "the battery in your phone?", "start": 5060.13, "duration": 1.35}, {"text": "Well, it'll get really hot.", "start": 5061.48, "duration": 1.89}, {"text": "And the same thing happens here.", "start": 5063.37, "duration": 2.73}, {"text": "Rather than use this delta\npsi delta pH to generate ATP,", "start": 5066.1, "duration": 4.38}, {"text": "if I just put a hole\nin the membrane,", "start": 5070.48, "duration": 3.6}, {"text": "something referred to as\nan uncoupling protein, UCP,", "start": 5074.08, "duration": 3.9}, {"text": "Uncoupling Protein, this will\njust allow the leak of protons", "start": 5077.98, "duration": 4.53}, {"text": "back across the membrane.", "start": 5082.51, "duration": 2.37}, {"text": "Well, that's short\ncircuiting the battery.", "start": 5084.88, "duration": 2.55}, {"text": "Energy has to be\ndissipated somewhere,", "start": 5087.43, "duration": 1.74}, {"text": "and it's dissipated as heat.", "start": 5089.17, "duration": 2.76}, {"text": "And this is effectively ways in\nwhich biology can create heat.", "start": 5091.93, "duration": 6.36}, {"text": "And so uncoupling proteins are\nexpressed in a tissue called", "start": 5098.29, "duration": 2.94}, {"text": "brown fat in mammals.", "start": 5101.23, "duration": 2.34}, {"text": "Brown fat is a way\nto generate heat.", "start": 5103.57, "duration": 3.33}, {"text": "And it's one way that we\nmaintain our body temperatures.", "start": 5106.9, "duration": 3.3}, {"text": "Now, the system is imperfect.", "start": 5110.2, "duration": 1.53}, {"text": "And lots of cells,\nall metabolism,", "start": 5111.73, "duration": 2.64}, {"text": "generates some heat.", "start": 5114.37, "duration": 1.53}, {"text": "If you've ever done\ncomposting, you", "start": 5115.9, "duration": 1.86}, {"text": "know your compost pile gets hot.", "start": 5117.76, "duration": 2.31}, {"text": "That's because the\norganisms there", "start": 5120.07, "duration": 1.59}, {"text": "that are metabolized in the\nmaterial in the compost pile", "start": 5121.66, "duration": 3.27}, {"text": "are generating some heat.", "start": 5124.93, "duration": 1.347}, {"text": "And that's because\nmembranes aren't perfect.", "start": 5126.277, "duration": 1.833}, {"text": "They're somewhat leaky.", "start": 5128.11, "duration": 1.95}, {"text": "Now, as humans, we work hard\nto maintain a constant body", "start": 5130.06, "duration": 3.87}, {"text": "temperature.", "start": 5133.93, "duration": 1.02}, {"text": "And there's actually a\nhuge amount of energy", "start": 5134.95, "duration": 2.04}, {"text": "that goes into just maintaining\nour body temperature.", "start": 5136.99, "duration": 3.55}, {"text": "But you can imagine\nhow efficiently", "start": 5140.54, "duration": 2.54}, {"text": "we couple these processes will\ndetermine how many calories we", "start": 5143.08, "duration": 4.68}, {"text": "need to maintain heat.", "start": 5147.76, "duration": 2.04}, {"text": "And that's actually a\ntheory of weight control,", "start": 5149.8, "duration": 2.31}, {"text": "that those of us\nout there who have", "start": 5152.11, "duration": 2.07}, {"text": "less well-coupled\nmitochondria can", "start": 5154.18, "duration": 1.92}, {"text": "eat more because they waste\nmore energy in generating", "start": 5156.1, "duration": 3.18}, {"text": "heat than those of us who are\nreally efficient in doing this.", "start": 5159.28, "duration": 3.37}, {"text": "And in fact, there's\ndrugs that allow", "start": 5162.65, "duration": 1.76}, {"text": "you to uncouple\nelectron transport", "start": 5164.41, "duration": 3.47}, {"text": "generation of delta psi\ndelta pH from utilizing", "start": 5167.88, "duration": 3.66}, {"text": "that membrane potential.", "start": 5171.54, "duration": 2.16}, {"text": "And these are great\nweight loss drugs.", "start": 5173.7, "duration": 2.195}, {"text": "Dinitrophenol was used middle\npart of the last century", "start": 5175.895, "duration": 5.155}, {"text": "as a weight loss agent.", "start": 5181.05, "duration": 1.16}, {"text": "It was very effective.", "start": 5182.21, "duration": 1.76}, {"text": "The problem is it's also\nincredibly dangerous", "start": 5183.97, "duration": 2.11}, {"text": "because people will die.", "start": 5186.08, "duration": 1.0}, {"text": "Because it turns out, if\nyou uncouple this process", "start": 5187.08, "duration": 2.16}, {"text": "and you don't have enough\nATP, you die really fast.", "start": 5189.24, "duration": 3.04}, {"text": "And so don't use that\ndrug, but it illustrates", "start": 5192.28, "duration": 3.47}, {"text": "how you can use this\nbattery to generate", "start": 5195.75, "duration": 3.06}, {"text": "heat, another form of energy.", "start": 5198.81, "duration": 3.46}, {"text": "Another big one is\nmembrane transport.", "start": 5202.27, "duration": 4.37}, {"text": "So if I want to concentrate\nsomething-- and this", "start": 5210.4, "duration": 2.9}, {"text": "could be moving proteins.", "start": 5213.3, "duration": 3.72}, {"text": "Or it could be\nmoving other ions,", "start": 5217.02, "duration": 2.91}, {"text": "like in an action potential.", "start": 5219.93, "duration": 3.95}, {"text": "Those are unfavorable\nprocesses, right?", "start": 5223.88, "duration": 1.86}, {"text": "I'm causing dissociation\nof ions across membranes", "start": 5225.74, "duration": 4.68}, {"text": "or moving protein from one\nside of a membrane to another.", "start": 5230.42, "duration": 3.6}, {"text": "One can couple those transfer\nprocesses to these delta psi", "start": 5234.02, "duration": 4.77}, {"text": "delta pH as well.", "start": 5238.79, "duration": 1.63}, {"text": "And in fact, protein\nimport in the mitochondria", "start": 5240.42, "duration": 2.99}, {"text": "depends very much on\na membrane potential", "start": 5243.41, "duration": 3.27}, {"text": "to get those proteins in.", "start": 5246.68, "duration": 1.86}, {"text": "The mitochondria is\nan important site", "start": 5248.54, "duration": 1.89}, {"text": "of calcium storage for cells.", "start": 5250.43, "duration": 2.46}, {"text": "Calcium is concentrated\nin the mitochondria.", "start": 5252.89, "duration": 2.31}, {"text": "And that concentration\ncan be driven", "start": 5255.2, "duration": 2.37}, {"text": "by this membrane potential.", "start": 5257.57, "duration": 2.5}, {"text": "And of course, this\npotential can also", "start": 5260.07, "duration": 2.63}, {"text": "use to power lots of shuttles,\nlike the carnitine shuttle,", "start": 5262.7, "duration": 4.08}, {"text": "and actually create\nsituations where", "start": 5266.78, "duration": 2.07}, {"text": "you have different conditions\nacross membranes as a way", "start": 5268.85, "duration": 3.42}, {"text": "to favor different chemistries.", "start": 5272.27, "duration": 3.51}, {"text": "And so the last thing\nI want to mention", "start": 5275.78, "duration": 1.65}, {"text": "is, in fact, these\nshuttles, which is just ways", "start": 5277.43, "duration": 3.87}, {"text": "that one can couple\nmembrane potential to drive", "start": 5281.3, "duration": 3.96}, {"text": "other things, can also be\nreally important for how", "start": 5285.26, "duration": 3.33}, {"text": "metabolism works.", "start": 5288.59, "duration": 1.68}, {"text": "And I just want to illustrate\none aspect of this.", "start": 5290.27, "duration": 2.68}, {"text": "So if I draw here\nmy mitochondria--", "start": 5292.95, "duration": 3.323}, {"text": "let me draw it up here.", "start": 5296.273, "duration": 3.387}, {"text": "If I draw a\nmitochondria, so here's", "start": 5299.66, "duration": 7.32}, {"text": "all these processes\nare happening here", "start": 5306.98, "duration": 3.48}, {"text": "where we have electron\ntransport generating", "start": 5310.46, "duration": 4.17}, {"text": "a potential across the\nintermitochondrial membrane", "start": 5314.63, "duration": 3.69}, {"text": "that can be used\nto synthesize ATP.", "start": 5318.32, "duration": 4.78}, {"text": "Well, this synthesis is\noccurring in the mitochondria.", "start": 5323.1, "duration": 4.59}, {"text": "But ultimately, I need\nto get that ATP out", "start": 5327.69, "duration": 4.32}, {"text": "into the cytosol for it\nto be useful for the cell", "start": 5332.01, "duration": 5.25}, {"text": "to run otherwise unfavorable\nprocesses in the cytosol.", "start": 5337.26, "duration": 3.51}, {"text": "And so one needs a\ntransporter for this.", "start": 5340.77, "duration": 2.1}, {"text": "There's some transporter\ncalled the adenine nucleotide", "start": 5342.87, "duration": 2.25}, {"text": "transporter.", "start": 5345.12, "duration": 1.32}, {"text": "And this partially takes\nadvantage of the fact", "start": 5346.44, "duration": 3.48}, {"text": "that there's a charge\ndifference between ATP and ADP", "start": 5349.92, "duration": 4.43}, {"text": "to actually couple membrane\npotential to exchange", "start": 5354.35, "duration": 3.87}, {"text": "of ATP/ADP between the cytosol\nand the mitochondrial matrix.", "start": 5358.22, "duration": 6.15}, {"text": "Now, there's other issues we'll\ntalk about next time as well.", "start": 5364.37, "duration": 3.13}, {"text": "And so, remember,\nsome metabolism", "start": 5367.5, "duration": 2.57}, {"text": "is happening in the cytosol.", "start": 5370.07, "duration": 2.55}, {"text": "So glycolysis turning\nglucose into pyruvate", "start": 5372.62, "duration": 8.46}, {"text": "is occurring in the cytosol.", "start": 5381.08, "duration": 1.77}, {"text": "We've already discussed.", "start": 5382.85, "duration": 1.0}, {"text": "That means you got\nto get pyruvate", "start": 5383.85, "duration": 1.417}, {"text": "in the mitochondria\nfor the PDH reaction,", "start": 5385.267, "duration": 2.353}, {"text": "but this is also generating\nNADH in the cytosol.", "start": 5387.62, "duration": 4.35}, {"text": "And if that NADH needs\nto transfer its electrons", "start": 5391.97, "duration": 3.36}, {"text": "to oxygen, we also\nhave to get that", "start": 5395.33, "duration": 1.68}, {"text": "NADH into the mitochondrial\nmatrix or, more correctly,", "start": 5397.01, "duration": 5.16}, {"text": "transfer those electrons into\nthe mitochondrial matrix.", "start": 5402.17, "duration": 2.92}, {"text": "It turns out cells maintain\ndistinct NAD/NADH pools", "start": 5405.09, "duration": 3.68}, {"text": "in the mitochondria\nand the cytosol.", "start": 5408.77, "duration": 1.89}, {"text": "That's part of the\nconditions that", "start": 5410.66, "duration": 1.62}, {"text": "make different reactions\nfavorable in each compartment.", "start": 5412.28, "duration": 5.28}, {"text": "And how cells do that,\ntransfer those electrons", "start": 5417.56, "duration": 3.75}, {"text": "into the mitochondria, ends up\nbeing another important thing", "start": 5421.31, "duration": 3.75}, {"text": "that has to be transport that's\ndriven across these membranes", "start": 5425.06, "duration": 3.57}, {"text": "where one can use\ndelta psi delta pH.", "start": 5428.63, "duration": 3.09}, {"text": "And we'll talk about that at\nthe start of the next lecture.", "start": 5431.72, "duration": 2.77}, {"text": "Thanks.", "start": 5434.49, "duration": 1.55}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.984}, {"text": "[RUSTLING]", "start": 1.984, "duration": 2.48}, {"text": "[CLICKING]", "start": 4.464, "duration": 3.472}, {"text": "MARKUS KLUTE: Welcome back\nto 8.20, Special Relativity.", "start": 19.35, "duration": 3.022}, {"text": "In this section, you're\ngoing to take a journey", "start": 22.372, "duration": 1.958}, {"text": "through our solar\nsystem and beyond.", "start": 24.33, "duration": 2.97}, {"text": "1977 marks the first flight\nof the Voyager program.", "start": 27.3, "duration": 3.48}, {"text": "Voyager is an MIT-led program\nwith the original mission", "start": 30.78, "duration": 4.44}, {"text": "to study planetary systems.", "start": 35.22, "duration": 2.55}, {"text": "Now, Voyager 1 and Voyager\n2, two spacecrafts,", "start": 37.77, "duration": 3.57}, {"text": "are studying the\ninterstellar space.", "start": 41.34, "duration": 2.58}, {"text": "Those two probes are\nstill sending back now,", "start": 43.92, "duration": 2.85}, {"text": "more than 40 years\nlater, information", "start": 46.77, "duration": 3.03}, {"text": "about measurement of their\nsurroundings back to Earth.", "start": 49.8, "duration": 4.41}, {"text": "Those are the two furthest-away\nobjects we were able to send.", "start": 54.21, "duration": 4.62}, {"text": "What we have here in 8.20--", "start": 58.83, "duration": 1.86}, {"text": "and it's IAP, so we are a\nlittle bit more ambitious--", "start": 60.69, "duration": 3.89}, {"text": "our mission is to bring\nus to Alpha Centauri.", "start": 64.58, "duration": 3.21}, {"text": "Alpha Centauri is the\nclosest star and planetary", "start": 67.79, "duration": 3.06}, {"text": "system to our solar system.", "start": 70.85, "duration": 3.3}, {"text": "It's actually not just one\nstar, but multiple stars.", "start": 74.15, "duration": 3.18}, {"text": "And our journey brings\nus to Proxima B,", "start": 77.33, "duration": 3.42}, {"text": "which is a planet in the\nAlpha Centauri system.", "start": 80.75, "duration": 5.11}, {"text": "So we have a very\nfancy spacecraft.", "start": 85.86, "duration": 2.52}, {"text": "It's able to travel with a\nconstant velocity of 0.943 c,", "start": 88.38, "duration": 5.33}, {"text": "speed of light.", "start": 93.71, "duration": 2.01}, {"text": "The gamma factor is 3, and the\npath which it's going to take", "start": 95.72, "duration": 5.07}, {"text": "is 5 light years long.", "start": 100.79, "duration": 2.91}, {"text": "Alice is our ground control.", "start": 103.7, "duration": 3.72}, {"text": "She is going to stay on Earth.", "start": 107.42, "duration": 1.59}, {"text": "And Bob is going to take this\njourney with Virgin Galactic.", "start": 109.01, "duration": 4.71}, {"text": "After some time, Bob is\ngoing to arrive on Proxima B.", "start": 113.72, "duration": 4.46}, {"text": "So your first challenge\nis to now calculate", "start": 118.18, "duration": 4.39}, {"text": "how long does this trip\ntake from Alice's and Bob's", "start": 122.57, "duration": 3.84}, {"text": "perspective?", "start": 126.41, "duration": 1.87}, {"text": "So I ask you to stop the video\nhere and just work this out.", "start": 128.28, "duration": 3.5}, {"text": "So for Alice, the time\nneeded is 5 light years", "start": 134.64, "duration": 3.93}, {"text": "divided by 0.9, by\nthe velocity of 0.943,", "start": 138.57, "duration": 3.75}, {"text": "times the speed of light.", "start": 142.32, "duration": 1.38}, {"text": "And that gives us 5.3 years.", "start": 143.7, "duration": 2.79}, {"text": "So after 5.3 years, Alice\nis observing Bob's arrival", "start": 146.49, "duration": 5.58}, {"text": "on Proxima B. For Bob,\nthe length of this path", "start": 152.07, "duration": 4.9}, {"text": "is Lorentz contracted--", "start": 156.97, "duration": 3.3}, {"text": "5 light years\ndivided by 3, which", "start": 160.27, "duration": 2.19}, {"text": "is the gamma factor, which\nresults to 1.67 light years.", "start": 162.46, "duration": 5.04}, {"text": "So for him, the journey\ntakes only 1.77 years--", "start": 167.5, "duration": 4.11}, {"text": "1.67 light years divided by\n0.943 times the speed of light.", "start": 171.61, "duration": 5.77}, {"text": "So apparently, the time\nexperienced by Alice and Bob", "start": 177.38, "duration": 4.31}, {"text": "for the very same\njourney is different.", "start": 181.69, "duration": 3.01}, {"text": "So this now is the\nfirst part, where", "start": 184.7, "duration": 1.79}, {"text": "we enter discussions\nof paradoxes", "start": 186.49, "duration": 4.2}, {"text": "in special relativity.", "start": 190.69, "duration": 1.44}, {"text": "And this will bring\nus, ultimately,", "start": 192.13, "duration": 1.68}, {"text": "to an understanding of the twin\nparadox later in this course.", "start": 193.81, "duration": 4.91}]
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+[{"text": "The following\ncontent is provided", "start": 0.61, "duration": 1.83}, {"text": "by MIT OpenCourseWare under\na Creative Commons license.", "start": 2.44, "duration": 3.9}, {"text": "Additional information\nabout our license", "start": 6.34, "duration": 2.13}, {"text": "and MIT OpenCourseWare\nin general", "start": 8.47, "duration": 2.4}, {"text": "is available at ocw.mit.edu.", "start": 10.87, "duration": 1.86}, {"text": "GEORGE CHURCH: OK, ready.", "start": 17.17, "duration": 3.24}, {"text": "OK.", "start": 20.41, "duration": 1.68}, {"text": "So welcome to the third phase\nof our omics discussion.", "start": 22.09, "duration": 7.148}, {"text": "Someone pointed out\nthat I should point out", "start": 29.238, "duration": 1.792}, {"text": "[? this shirt ?] says\nomics not comics.", "start": 31.03, "duration": 4.08}, {"text": "So we've covered genomics and\nlast time transcriptomics,", "start": 35.11, "duration": 4.23}, {"text": "and today we introduce a very\nimportant all-inclusive subject", "start": 39.34, "duration": 3.66}, {"text": "of proteomics.", "start": 43.0, "duration": 2.16}, {"text": "We'll connect it to last\nweek's through the vehicle", "start": 45.16, "duration": 3.66}, {"text": "of focusing on motifs\nthat are involved", "start": 48.82, "duration": 4.98}, {"text": "in protein interactions\nwith the two nucleic acid", "start": 53.8, "duration": 4.65}, {"text": "macromolecules.", "start": 58.45, "duration": 2.16}, {"text": "So we're going to be covering,\njust as we introduced", "start": 60.61, "duration": 3.93}, {"text": "RNA omics with RNA\nstructure, we're", "start": 64.54, "duration": 4.11}, {"text": "going to spend this entire class\ntalking about protein three", "start": 68.65, "duration": 2.61}, {"text": "dimensional structure, how\nyou get at it experimentally", "start": 71.26, "duration": 3.15}, {"text": "and computationally\nand its implications", "start": 74.41, "duration": 2.64}, {"text": "for the binding of small\nmolecules such as drugs.", "start": 77.05, "duration": 5.01}, {"text": "We will in short order get\nto the scary pumpkin-like", "start": 82.06, "duration": 5.49}, {"text": "molecule.", "start": 87.55, "duration": 1.9}, {"text": "So the connection to last\nweek was this diagram", "start": 89.45, "duration": 9.53}, {"text": "showing palindromicity in\nthree cases and a direct repeat", "start": 98.98, "duration": 4.38}, {"text": "in the fourth case.", "start": 103.36, "duration": 2.52}, {"text": "And I offered that\nthis might reflect", "start": 105.88, "duration": 2.61}, {"text": "the symmetry of the\nproteins-- of the three", "start": 108.49, "duration": 2.82}, {"text": "dimensional structure\nof the proteins", "start": 111.31, "duration": 2.01}, {"text": "and the three dimensional\nstructure of the nucleic acid", "start": 113.32, "duration": 2.61}, {"text": "and these symmetry\nelements would align.", "start": 115.93, "duration": 1.98}, {"text": "Now in order to introduce\nthese symmetry elements", "start": 117.91, "duration": 2.31}, {"text": "and the possibility\nof having codes", "start": 120.22, "duration": 2.15}, {"text": "that you can at\nleast program, even", "start": 122.37, "duration": 2.77}, {"text": "if they may have been tinkered\nabout during an evolution,", "start": 125.14, "duration": 2.925}, {"text": "the question is to\nwhat extent can we", "start": 128.065, "duration": 1.815}, {"text": "get our hands on these kind of\nprotein and nucleic acid motifs", "start": 129.88, "duration": 4.04}, {"text": "that interact.", "start": 133.92, "duration": 1.45}, {"text": "In order to get at this issue\nof where there is a code--", "start": 135.37, "duration": 4.08}, {"text": "and I just take this as\none of the ways of dealing", "start": 139.45, "duration": 3.42}, {"text": "with the incredible\ncomplexity of proteins", "start": 142.87, "duration": 2.97}, {"text": "is to give this a theme that\nconnects it to the last class", "start": 145.84, "duration": 3.75}, {"text": "and connects, I think, to many\nof the sentiments of people", "start": 149.59, "duration": 2.97}, {"text": "in this sort of\naudience interested", "start": 152.56, "duration": 2.34}, {"text": "in computational biology is\nways of having simple codes.", "start": 154.9, "duration": 4.92}, {"text": "And of course,\nthe way of one way", "start": 159.82, "duration": 2.16}, {"text": "of breaking up proteins\nand thinking about them", "start": 161.98, "duration": 2.07}, {"text": "is these ABCs-- the alpha helix,\nthe beta sheet, and the coil.", "start": 164.05, "duration": 5.01}, {"text": "Each of these can be\ncharacterized by the hydrogen", "start": 169.06, "duration": 2.64}, {"text": "bonds that hold it together.", "start": 171.7, "duration": 1.53}, {"text": "The weak bonds between the\nhydrogens, the nitrogens,", "start": 173.23, "duration": 4.23}, {"text": "and the oxygens.", "start": 177.46, "duration": 1.643}, {"text": "And the alpha\nhelix, these are all", "start": 179.103, "duration": 1.417}, {"text": "kept within the\nhelix with a repeat", "start": 180.52, "duration": 2.76}, {"text": "of 3.6 residues per turn.", "start": 183.28, "duration": 3.81}, {"text": "In the beta sheet, they tend\nto have a longer, straighter", "start": 187.09, "duration": 5.79}, {"text": "chains where there are unpaired\nhydrogen bonds inevitably", "start": 192.88, "duration": 4.38}, {"text": "until you form\nenough chains to form", "start": 197.26, "duration": 2.4}, {"text": "a cyclic structure while the\nalpha helix is immediately", "start": 199.66, "duration": 2.82}, {"text": "helical.", "start": 202.48, "duration": 2.623}, {"text": "There are many different\ntypes of coils.", "start": 205.103, "duration": 1.667}, {"text": "It's a catch-all phrase\nthat includes everything", "start": 206.77, "duration": 2.0}, {"text": "except alpha and beta, but a\nparticularly well-formed type", "start": 208.77, "duration": 4.57}, {"text": "of coil has its own nomenclature\nand parameters is the turn,", "start": 213.34, "duration": 5.19}, {"text": "and the turn is illustrated\nhere at the end of a beta sheet.", "start": 218.53, "duration": 5.58}, {"text": "That beta sheet\nbasically is going", "start": 224.11, "duration": 1.47}, {"text": "in on the lower\nright hand corner", "start": 225.58, "duration": 2.34}, {"text": "in the direction of the arrow.", "start": 227.92, "duration": 1.38}, {"text": "The arrows typically\npoint from the n terminus", "start": 229.3, "duration": 2.52}, {"text": "to the c terminus just\nas in nucleic acids", "start": 231.82, "duration": 3.18}, {"text": "is from five prime\nto three prime.", "start": 235.0, "duration": 1.68}, {"text": "And here it goes\nin the arrow, it", "start": 236.68, "duration": 1.58}, {"text": "turns around very tightly,\nand goes back out again.", "start": 238.26, "duration": 3.82}, {"text": "OK, now how can we use\nthese basic motifs?", "start": 242.08, "duration": 4.02}, {"text": "These are the smallest\nmeaningful units of protein", "start": 246.1, "duration": 4.47}, {"text": "three dimensional structure.", "start": 250.57, "duration": 1.18}, {"text": "How can we use\nthese to recognize", "start": 251.75, "duration": 1.79}, {"text": "other macromolecules, other\nproteins and nucleic acids?", "start": 253.54, "duration": 3.94}, {"text": "So let's connect this to\nthe motifs of last class.", "start": 257.48, "duration": 2.669}, {"text": "We have these motifs\nthat we could find,", "start": 260.149, "duration": 2.871}, {"text": "weight matrices for them by\naligning lots of sequences.", "start": 263.02, "duration": 3.18}, {"text": "Now instead of\naligning sequences,", "start": 266.2, "duration": 1.52}, {"text": "let's see what we can do by\nmutating both the protein", "start": 267.72, "duration": 6.16}, {"text": "part and the nucleic acid part.", "start": 273.88, "duration": 2.19}, {"text": "And in order to do this,\njust as an illustration,", "start": 276.07, "duration": 3.27}, {"text": "let's say we have\nthree zinc fingers.", "start": 279.34, "duration": 1.56}, {"text": "This is a real human and\nmouse DNA binding protein", "start": 280.9, "duration": 6.87}, {"text": "with three zinc\nfingers in a row.", "start": 287.77, "duration": 1.54}, {"text": "So this is an example of the\ndirect repeat or tandem repeat", "start": 289.31, "duration": 2.6}, {"text": "type of symmetry.", "start": 291.91, "duration": 1.11}, {"text": "Remember, there's the direct\nrepeat and the inverted repeat.", "start": 293.02, "duration": 2.76}, {"text": "And in this tandem repeat,\nlet's anchor the two ends", "start": 295.78, "duration": 2.61}, {"text": "and change the middle.", "start": 298.39, "duration": 1.32}, {"text": "Make every possible\npeptide sequence", "start": 299.71, "duration": 1.92}, {"text": "in the middle or randomly\nsample the vast space that", "start": 301.63, "duration": 4.53}, {"text": "might occur in changing\na few, say, six or more", "start": 306.16, "duration": 6.9}, {"text": "key amino acids.", "start": 313.06, "duration": 1.62}, {"text": "And then we know from the\nthree dimensional structure", "start": 314.68, "duration": 3.45}, {"text": "that it interacts mainly with\nthe middle three nucleotides,", "start": 318.13, "duration": 3.3}, {"text": "so let's change\nthose middle three", "start": 321.43, "duration": 1.5}, {"text": "nucleotides to every possible\ntrinucleotide sequence", "start": 322.93, "duration": 3.27}, {"text": "and see quantitatively how much\nthat the different sequences", "start": 326.2, "duration": 5.82}, {"text": "in the protein affect\nthe different sequences", "start": 332.02, "duration": 2.43}, {"text": "in the nucleic acid.", "start": 334.45, "duration": 1.6}, {"text": "So this is not going to be\nby staring at long sequence", "start": 336.05, "duration": 3.427}, {"text": "alignments where we're going\nto get the weight matrices.", "start": 339.477, "duration": 2.333}, {"text": "We can get them by actual\nexperimental measures", "start": 341.81, "duration": 2.48}, {"text": "of the binding in vitro.", "start": 344.29, "duration": 2.943}, {"text": "And so what happens when\nyou do this exercise,", "start": 347.233, "duration": 1.917}, {"text": "the wild type, now this--\nthe wild type sequence", "start": 349.15, "duration": 2.55}, {"text": "is something that\nmay want to recognize", "start": 351.7, "duration": 3.51}, {"text": "a family of sequences.", "start": 355.21, "duration": 1.05}, {"text": "We don't know exactly what\nthe wild type sequence", "start": 356.26, "duration": 2.82}, {"text": "is for this particular DNA\nbinding protein, this zinc", "start": 359.08, "duration": 2.46}, {"text": "finger from human and mouse.", "start": 361.54, "duration": 2.02}, {"text": "But the subsequence\nof the business end,", "start": 363.56, "duration": 2.21}, {"text": "the amino acid subsequence of\nthat recognition alpha helix", "start": 365.77, "duration": 3.72}, {"text": "that's binding into\nthe major groove DNA", "start": 369.49, "duration": 2.46}, {"text": "is shown in the upper\nleft, [? RSVHLTT. ?]", "start": 371.95, "duration": 3.9}, {"text": "And the sequence that it\nmainly binds to-- remember this", "start": 375.85, "duration": 2.418}, {"text": "is a weight matrix.", "start": 378.268, "duration": 0.792}, {"text": "It's not a consensus\nsequence, this TGG.", "start": 379.06, "duration": 3.39}, {"text": "It obviously recognizes a\nvariety of other sequences.", "start": 382.45, "duration": 2.4}, {"text": "So remember, there's\nabout three nucleotides", "start": 384.85, "duration": 2.49}, {"text": "on either side of it that the\nother two zinc fingers bind to.", "start": 387.34, "duration": 3.51}, {"text": "When you try all 64 possible\ntrinucleotides-- remember", "start": 390.85, "duration": 4.347}, {"text": "from the genetic code,\nthis is pure coincidence", "start": 395.197, "duration": 1.958}, {"text": "that these are triplets the\nsame as the genetic code.", "start": 397.155, "duration": 2.545}, {"text": "This just happens to be the\namount of the chunk of DNA", "start": 399.7, "duration": 2.37}, {"text": "that a zinc finger will cover.", "start": 402.07, "duration": 3.39}, {"text": "But it's not coincidence\nthat 4 to the third", "start": 405.46, "duration": 2.28}, {"text": "is still 64, just\nlike the genetic code.", "start": 407.74, "duration": 2.79}, {"text": "And if you run through all\npossible nucleotide sequences", "start": 410.53, "duration": 4.41}, {"text": "for this wild type, you\nfind the winner is TGG,", "start": 414.94, "duration": 3.81}, {"text": "and it has that particular\nbinding constant.", "start": 418.75, "duration": 1.92}, {"text": "The binding constant is\nmeasured in the molarity,", "start": 420.67, "duration": 3.66}, {"text": "roughly where you get half\nmaximal or equilibrium binding.", "start": 424.33, "duration": 4.74}, {"text": "That's 10 to the minus\n9 moles per liter.", "start": 429.07, "duration": 3.9}, {"text": "You can now mutagenize the\npeptide and select for peptides", "start": 432.97, "duration": 4.02}, {"text": "that bind to GCC.", "start": 436.99, "duration": 1.98}, {"text": "Remember, the flanks\nare kept constant.", "start": 438.97, "duration": 2.5}, {"text": "You get two peptides,\nboth bind to the GCC.", "start": 441.47, "duration": 2.78}, {"text": "They both give matrices very\nsimilar to this with very--", "start": 444.25, "duration": 5.58}, {"text": "these are very high\naffinity binding constants", "start": 449.83, "duration": 2.13}, {"text": "just like wild type.", "start": 451.96, "duration": 1.26}, {"text": "You've essentially engineered\nby selection a new specificity", "start": 453.22, "duration": 6.35}, {"text": "and two different\nways of getting it.", "start": 459.57, "duration": 2.13}, {"text": "If you now go for something\nradically different,", "start": 461.7, "duration": 2.34}, {"text": "now no GC--", "start": 464.04, "duration": 1.5}, {"text": "the first one was high GC,\nthe second was pure GC,", "start": 465.54, "duration": 3.6}, {"text": "and then the third\none is pure AT.", "start": 469.14, "duration": 1.95}, {"text": "And you get another peptide\nsequence that binds to that,", "start": 471.09, "duration": 2.993}, {"text": "and you get another\nweight matrix.", "start": 474.083, "duration": 1.417}, {"text": "Now remember, this weight matrix\nis not sequence alignment.", "start": 475.5, "duration": 2.458}, {"text": "This is binding constants\nwhere the weighting of the 64", "start": 477.958, "duration": 5.042}, {"text": "different sequences is based\non how much binding you", "start": 483.0, "duration": 3.03}, {"text": "get for each of the 64.", "start": 486.03, "duration": 1.77}, {"text": "And then for some sequences, all\nthese different trinucleotides", "start": 487.8, "duration": 3.75}, {"text": "all result in a\nrather poor selection", "start": 491.55, "duration": 2.88}, {"text": "for any kind of peptide out of\nall the vast number of peptides", "start": 494.43, "duration": 3.21}, {"text": "you have.", "start": 497.64, "duration": 0.54}, {"text": "None of them do\nparticularly well,", "start": 498.18, "duration": 1.71}, {"text": "and the result is a\nweight matrix here", "start": 499.89, "duration": 3.7}, {"text": "which has very little\ninformation content.", "start": 503.59, "duration": 2.15}, {"text": "So this is a way.", "start": 505.74, "duration": 1.853}, {"text": "It's not the only\nway, but this is", "start": 507.593, "duration": 1.417}, {"text": "a way of getting a really\ngood empirical data set, which", "start": 509.01, "duration": 4.049}, {"text": "in principle, you can combine\nit with similar functions", "start": 513.059, "duration": 3.36}, {"text": "on the flanking ones,\nand you can dial up", "start": 516.419, "duration": 3.271}, {"text": "any sequence of a nucleic acid\nprotein interaction, at least", "start": 519.69, "duration": 5.01}, {"text": "with this class of proteins.", "start": 524.7, "duration": 1.2}, {"text": "Others are a little\nmore problematic.", "start": 525.9, "duration": 2.55}, {"text": "But you can see how this\ncan generate a code even", "start": 528.45, "duration": 2.4}, {"text": "if the actual detailed\namino acid nucleotide", "start": 530.85, "duration": 5.13}, {"text": "interaction is not so simple.", "start": 535.98, "duration": 3.79}, {"text": "So that those are the\nresults of the study.", "start": 539.77, "duration": 2.24}, {"text": "Then I'll show you\njust a snapshot", "start": 542.01, "duration": 2.01}, {"text": "of a schematic of how the\nactual experiments are done.", "start": 544.02, "duration": 3.225}, {"text": "And then finally, I'll\nshow you a little math", "start": 547.245, "duration": 1.875}, {"text": "behind how we got those\napparent binding constants.", "start": 549.12, "duration": 3.21}, {"text": "Remember, in those lower\nbinding constant means", "start": 552.33, "duration": 4.14}, {"text": "you can get the binding\nat a lower concentration,", "start": 556.47, "duration": 3.28}, {"text": "which means a stronger binding.", "start": 559.75, "duration": 2.43}, {"text": "So the way you do\nthe binding here", "start": 562.18, "duration": 1.49}, {"text": "is you take a\nnucleic acid array,", "start": 563.67, "duration": 3.75}, {"text": "similar to the ones we've been\ntalking about in last class.", "start": 567.42, "duration": 2.91}, {"text": "Instead of being single\nstranded, ready to bind", "start": 570.33, "duration": 2.34}, {"text": "fluorescent nucleic acid,\nit's double stranded,", "start": 572.67, "duration": 2.13}, {"text": "ready to bind a fluorescent\nprotein complex.", "start": 574.8, "duration": 3.24}, {"text": "The protein complex in this\ncase is a bacteriophage,", "start": 578.04, "duration": 5.25}, {"text": "which is displaying the\nthree zinc fingers in red.", "start": 583.29, "duration": 3.03}, {"text": "The middle one is the one in\nthe past slide was mutagenized.", "start": 586.32, "duration": 4.86}, {"text": "And similarly, the\narray is combinatoric--", "start": 591.18, "duration": 3.51}, {"text": "every possible DNA sequence\nthat you're interested in", "start": 594.69, "duration": 2.85}, {"text": "is present.", "start": 597.54, "duration": 0.81}, {"text": "And what you do is quantitate\nthe fluorescence of the zinc", "start": 598.35, "duration": 6.12}, {"text": "finger protein\nindirectly by the binding", "start": 604.47, "duration": 4.2}, {"text": "of the covalently-attached\nphage to the antibodies, which", "start": 608.67, "duration": 3.99}, {"text": "are fluorescently labeled\nby [INAUDIBLE] fluorescence.", "start": 612.66, "duration": 2.437}, {"text": "The quantity-- how you relate\nthe fluorescence, the more", "start": 617.84, "duration": 3.57}, {"text": "binding, the more fluorescence.", "start": 621.41, "duration": 1.65}, {"text": "But how you relate that\nto the binding constant", "start": 623.06, "duration": 2.43}, {"text": "we had in the previous\nslide is the subject", "start": 625.49, "duration": 2.85}, {"text": "of this slide number eight.", "start": 628.34, "duration": 2.73}, {"text": "Now we call this the apparent\nequilibrium association", "start": 631.07, "duration": 4.59}, {"text": "constant because\nthese experiments,", "start": 635.66, "duration": 1.92}, {"text": "just like many binding in living\ncells is not at equilibrium.", "start": 637.58, "duration": 6.27}, {"text": "It's a dynamic process\nin the cell and in vitro.", "start": 643.85, "duration": 4.89}, {"text": "There are ways that you\ncan measure the equilibrium", "start": 648.74, "duration": 2.82}, {"text": "constants, but what this\nis apparent in the sense", "start": 651.56, "duration": 3.12}, {"text": "that you need to wash off the\nexcess fluorescence in order", "start": 654.68, "duration": 2.82}, {"text": "to detect the fairly\nlow signal that you", "start": 657.5, "duration": 2.49}, {"text": "get from the specific\nbinding, rather", "start": 659.99, "duration": 3.248}, {"text": "than having fluorescence.", "start": 663.238, "duration": 1.042}, {"text": "You bathe it with 10 to the\nsixford excess of fluorescence.", "start": 664.28, "duration": 4.59}, {"text": "And so as you're\ndoing that wash,", "start": 668.87, "duration": 1.74}, {"text": "you're obviously\nnot at equilibrium.", "start": 670.61, "duration": 1.5}, {"text": "In the end, you take a snapshot\nbefore you wash off everything.", "start": 672.11, "duration": 4.95}, {"text": "And so what you're measuring--\nwhat you're basically measuring", "start": 677.06, "duration": 3.3}, {"text": "is--", "start": 680.36, "duration": 0.93}, {"text": "attempting to measure is\nthe equilibrium constant", "start": 681.29, "duration": 2.1}, {"text": "between protein P\nin the upper left", "start": 683.39, "duration": 2.73}, {"text": "here, DNA D, double\nstranded going", "start": 686.12, "duration": 3.78}, {"text": "to the product, which is this\nP.D associated biomolecular", "start": 689.9, "duration": 5.31}, {"text": "product.", "start": 695.21, "duration": 1.02}, {"text": "And this is basic physical\nchemistry and algebra", "start": 696.23, "duration": 6.0}, {"text": "so that-- so you\nrearrange that to get", "start": 702.23, "duration": 2.37}, {"text": "the association constant.", "start": 704.6, "duration": 1.9}, {"text": "That's what you want.", "start": 706.5, "duration": 1.07}, {"text": "And the fraction of DNA\nmolecules with the protein", "start": 707.57, "duration": 2.34}, {"text": "bounds can be found from this.", "start": 709.91, "duration": 3.0}, {"text": "It's just by definition, the\nfraction DNA molecules protein", "start": 712.91, "duration": 5.55}, {"text": "bound is--", "start": 718.46, "duration": 1.35}, {"text": "the protein bound\nis the numerator.", "start": 719.81, "duration": 2.23}, {"text": "The brackets mean concentration\nin moles per liter,", "start": 722.04, "duration": 2.57}, {"text": "just like we stated.", "start": 724.61, "duration": 1.5}, {"text": "And then divide the\ncomplex by the amount", "start": 726.11, "duration": 3.87}, {"text": "of the fraction, which\nis the total DNA, which", "start": 729.98, "duration": 3.96}, {"text": "is the DNA present in the\ncomplex and the DNA is free.", "start": 733.94, "duration": 2.8}, {"text": "That's the D plus PD.", "start": 736.74, "duration": 2.6}, {"text": "And then you just substitute\nin this definition", "start": 739.34, "duration": 2.82}, {"text": "of the association constant.", "start": 742.16, "duration": 1.71}, {"text": "The definition is\nproduct over reactants,", "start": 743.87, "duration": 5.59}, {"text": "and then you get this\nintermediate term.", "start": 749.46, "duration": 2.26}, {"text": "Which now you cancel out all\nthe concentrations of these,", "start": 751.72, "duration": 3.05}, {"text": "and then you end up with the\nlast term on the far right,", "start": 754.77, "duration": 2.92}, {"text": "which is where if you hold\nthe protein-- if the protein", "start": 757.69, "duration": 4.07}, {"text": "concentration is known,\nthen the whole thing is", "start": 761.76, "duration": 3.09}, {"text": "constant except for\nthe association.", "start": 764.85, "duration": 2.16}, {"text": "So that one over the\nassociation constant", "start": 767.01, "duration": 2.85}, {"text": "is directly related to the\nfraction of DNA molecules", "start": 769.86, "duration": 3.54}, {"text": "with protein bound,\nwhich is directly", "start": 773.4, "duration": 2.82}, {"text": "proportional to the signal\nintensity and fluorescence.", "start": 776.22, "duration": 4.41}, {"text": "So this is how you\nget the numbers that", "start": 780.63, "duration": 1.92}, {"text": "were on that slide.", "start": 782.55, "duration": 1.38}, {"text": "Now let's return\nthe question that", "start": 783.93, "duration": 2.52}, {"text": "connected this talk\nwith the last one, which", "start": 786.45, "duration": 2.01}, {"text": "was the symmetry of DNA\nprotein interactions.", "start": 788.46, "duration": 6.75}, {"text": "We illustrated already one\nof these three zinc finger", "start": 795.21, "duration": 4.29}, {"text": "complexes, as illustrated\non the left hand side here.", "start": 799.5, "duration": 7.35}, {"text": "The double-stranded DNA is in\nblue and the three zinc fingers", "start": 806.85, "duration": 4.41}, {"text": "follow along the major groove,\nthe large groove of the DNA.", "start": 811.26, "duration": 5.56}, {"text": "And the reason the textbook\nis wrong, first of all,", "start": 816.82, "duration": 3.5}, {"text": "it emphasizes the non-helical\npart of the zinc finger.", "start": 820.32, "duration": 2.538}, {"text": "You can barely see the helix\nwith the background there.", "start": 822.858, "duration": 2.292}, {"text": "And also the way it\nloops through the DNA,", "start": 825.15, "duration": 2.242}, {"text": "if you look at this\ncarefully in your textbook,", "start": 827.392, "duration": 1.958}, {"text": "this is actually the\n[? Mount ?] book,", "start": 829.35, "duration": 2.07}, {"text": "it actually interdigitates\nwith a phosphodiester bond,", "start": 831.42, "duration": 2.985}, {"text": "basically going through\nthe base pairs, which", "start": 834.405, "duration": 1.875}, {"text": "is not at all what happens.", "start": 836.28, "duration": 2.1}, {"text": "Similarly, the\nleucine zipper, this", "start": 838.38, "duration": 2.22}, {"text": "is, again, recognition\nwith a helix", "start": 840.6, "duration": 2.31}, {"text": "in the major groove of DNA.", "start": 842.91, "duration": 2.94}, {"text": "Here, you can see\nthat the helix that", "start": 845.85, "duration": 2.64}, {"text": "causes the dimerization\nof proteins-- you", "start": 848.49, "duration": 2.01}, {"text": "can think of this as your really\nmost elementary protein-protein", "start": 850.5, "duration": 3.9}, {"text": "interaction code.", "start": 854.4, "duration": 1.08}, {"text": "A very fundamental one\nthat comes again and again,", "start": 855.48, "duration": 2.61}, {"text": "so-called coil-coil, two\nalpha helices interacting.", "start": 858.09, "duration": 5.13}, {"text": "The direct extension of that,\nalmost coaxial with a coil-coil", "start": 863.22, "duration": 3.72}, {"text": "[? or ?] protein-protein\ninteraction,", "start": 866.94, "duration": 1.56}, {"text": "they go down and touch the DNA.", "start": 868.5, "duration": 2.07}, {"text": "In contrast, the textbook where\nit does the sharp right hand", "start": 870.57, "duration": 3.18}, {"text": "turn and in some way\npoorly schematized there,", "start": 873.75, "duration": 7.32}, {"text": "it goes coaxial to DNA.", "start": 881.07, "duration": 1.62}, {"text": "That's not what happens.", "start": 882.69, "duration": 2.34}, {"text": "The helices are more or\nless direct extensions down", "start": 885.03, "duration": 3.09}, {"text": "from the dimerization\nregion of the protein", "start": 888.12, "duration": 4.5}, {"text": "maintaining almost\nperpendicular to the DNA axis.", "start": 892.62, "duration": 5.1}, {"text": "But again, so on the left\nis the three tandem repeats,", "start": 897.72, "duration": 5.7}, {"text": "and on the right is a dyad\naxis, where the twofold 180", "start": 903.42, "duration": 5.16}, {"text": "degrees symmetry--", "start": 908.58, "duration": 1.74}, {"text": "think of it as rotating\nexactly 180 degrees.", "start": 910.32, "duration": 3.57}, {"text": "This is not a mirror.", "start": 913.89, "duration": 0.9}, {"text": "This is a rotation.", "start": 914.79, "duration": 1.35}, {"text": "Of the DNA on itself\nalso coincides perfectly", "start": 916.14, "duration": 3.87}, {"text": "with the twofold\nsymmetry of the protein", "start": 920.01, "duration": 3.21}, {"text": "association with itself.", "start": 923.22, "duration": 1.57}, {"text": "These are the two\nmajor symmetry classes,", "start": 924.79, "duration": 2.06}, {"text": "and it's amazing how\nmany nucleic acid protein", "start": 926.85, "duration": 3.66}, {"text": "interactions fall into one\nof these two classes-- direct", "start": 930.51, "duration": 2.82}, {"text": "repeat or inverted repeat.", "start": 933.33, "duration": 1.77}, {"text": "And that's the one you find\ndirect and inverted repeats", "start": 935.1, "duration": 2.61}, {"text": "in nucleic acid sequences,\nyou get a little excited.", "start": 937.71, "duration": 3.31}, {"text": "The other reason is\nthe hairpin structures", "start": 941.02, "duration": 4.1}, {"text": "that you found in RNA\nthat we talked about", "start": 945.12, "duration": 2.31}, {"text": "in the last classes,\nthose also are", "start": 947.43, "duration": 2.64}, {"text": "indicated by inverted repeats.", "start": 950.07, "duration": 1.395}, {"text": "So we now have a semi-empirical\nway of computing--", "start": 954.79, "duration": 5.76}, {"text": "in a certain sense, predicting\nnew regulatory protein", "start": 960.55, "duration": 4.32}, {"text": "DNA interactions with\ndouble-stranded DNA.", "start": 964.87, "duration": 2.31}, {"text": "Can we extend this to RNA?", "start": 967.18, "duration": 1.74}, {"text": "This is a much more\ncomplicated situation with RNA", "start": 968.92, "duration": 3.3}, {"text": "because you don't have these\nlong perfect double helices", "start": 972.22, "duration": 2.92}, {"text": "anymore.", "start": 975.14, "duration": 0.5}, {"text": "You have these very\nshort RNA helices", "start": 975.64, "duration": 2.1}, {"text": "that I showed in the\nlast couple of classes.", "start": 977.74, "duration": 2.61}, {"text": "This is transfer RNA, one\nof our favorite molecules", "start": 980.35, "duration": 2.58}, {"text": "here, with the\nanticodon at the bottom", "start": 982.93, "duration": 1.98}, {"text": "of each of the pink structures.", "start": 984.91, "duration": 1.92}, {"text": "And the amino acid acceptor\nthree prime end of that 70-some", "start": 986.83, "duration": 4.59}, {"text": "nucleotide--", "start": 991.42, "duration": 1.8}, {"text": "70 to 80 nucleotide\nnucleic acid.", "start": 993.22, "duration": 2.34}, {"text": "So the pinks are all\nthe tRNAs, and there", "start": 995.56, "duration": 2.22}, {"text": "are at least 20 different\ntypes of amino acid", "start": 997.78, "duration": 2.79}, {"text": "and has 20 types of-- at least\n20 types of transfer RNAs", "start": 1000.57, "duration": 3.3}, {"text": "and 20 types of\nproteins that add", "start": 1003.87, "duration": 2.31}, {"text": "the amino acid onto the three\nprime ends of the transfer RNA.", "start": 1006.18, "duration": 4.17}, {"text": "These break themselves up\ninto two major classes.", "start": 1010.35, "duration": 2.64}, {"text": "These can be recognized\nat the structural level.", "start": 1012.99, "duration": 2.04}, {"text": "Class 1, which is the single\nletter amino acid code", "start": 1015.03, "duration": 3.63}, {"text": "[? CEL, ?] so forth, cysteine,\nglutamate, and so on.", "start": 1018.66, "duration": 4.23}, {"text": "That's one class, which\nare structurally similar.", "start": 1022.89, "duration": 2.28}, {"text": "Class 2 is structurally\ndissimilar to Class 1,", "start": 1025.17, "duration": 3.6}, {"text": "but they are similar\nwithin the class.", "start": 1028.77, "duration": 3.36}, {"text": "Anyway, the point is\nthat they recognize", "start": 1032.13, "duration": 2.443}, {"text": "all different parts\nof the nucleic acid,", "start": 1034.573, "duration": 1.667}, {"text": "not just the anticodon,\nwhich is the code itself,", "start": 1036.24, "duration": 3.24}, {"text": "the trinucleotide code.", "start": 1039.48, "duration": 1.47}, {"text": "Not just the amino\nacid end where", "start": 1040.95, "duration": 1.86}, {"text": "you need the\nrecognize amino acid,", "start": 1042.81, "duration": 3.24}, {"text": "but various points\nalong the transfer RNA.", "start": 1046.05, "duration": 2.88}, {"text": "If you wanted to create a new\ncode, as these authors have,", "start": 1048.93, "duration": 3.66}, {"text": "or to create hybrids between\nthese various things,", "start": 1052.59, "duration": 3.36}, {"text": "you'd have to find homology\namong the proteins or graph", "start": 1055.95, "duration": 4.32}, {"text": "domains of recognition\nbetween each one", "start": 1060.27, "duration": 3.09}, {"text": "or mutagenize\nparticular regions that", "start": 1063.36, "duration": 2.81}, {"text": "are known to interact\nwith the nucleotides", "start": 1066.17, "duration": 1.75}, {"text": "you want to contact,\nand that's been done.", "start": 1067.92, "duration": 3.33}, {"text": "You can arrange to\nmake a new amino acid", "start": 1071.25, "duration": 2.01}, {"text": "by carving the pocket\nthe amino acid recognizes", "start": 1073.26, "duration": 5.73}, {"text": "and grafting on the\nappropriate nucleotides--", "start": 1078.99, "duration": 4.41}, {"text": "the appropriate amino\nacids would recognize, say,", "start": 1083.4, "duration": 2.55}, {"text": "a stop codon.", "start": 1085.95, "duration": 2.25}, {"text": "OK, you've had some\nprogramming experience", "start": 1088.2, "duration": 5.61}, {"text": "that hopefully will prepare\nyou for the real world", "start": 1093.81, "duration": 2.26}, {"text": "of interacting with input and\noutput from various devices.", "start": 1096.07, "duration": 5.53}, {"text": "The topic today is\nproteins, and this", "start": 1105.5, "duration": 2.16}, {"text": "really is the main\ncontact between", "start": 1107.66, "duration": 5.07}, {"text": "the exquisite regulatory\nmechanisms, which", "start": 1112.73, "duration": 2.34}, {"text": "will be the topic\nof the [? network ?]", "start": 1115.07, "duration": 1.72}, {"text": "that we've already touched\nupon, but will really", "start": 1116.79, "duration": 2.0}, {"text": "be the topic of some\nof our network analysis", "start": 1118.79, "duration": 4.56}, {"text": "in the last three lectures.", "start": 1123.35, "duration": 2.64}, {"text": "Here, we need sensors to\nsense the environment.", "start": 1125.99, "duration": 3.6}, {"text": "We need actuators\nto then deliver back", "start": 1129.59, "duration": 2.13}, {"text": "into the environment\nwhat the cell wants to do", "start": 1131.72, "duration": 3.15}, {"text": "or to interact with other cells.", "start": 1134.87, "duration": 2.01}, {"text": "You have to have\nfeedback, synchrony,", "start": 1136.88, "duration": 3.03}, {"text": "so on that you can\nbasically program the almost", "start": 1139.91, "duration": 4.26}, {"text": "digital nucleic acid\nworld inside the cell", "start": 1144.17, "duration": 5.43}, {"text": "but via clearly analog\ninputs and outputs.", "start": 1149.6, "duration": 4.875}, {"text": "So since this is the\nHalloween lecture", "start": 1154.475, "duration": 6.285}, {"text": "and I'm masquerading as\nthe Wolfman, we also--", "start": 1160.76, "duration": 5.4}, {"text": "I've listed some of the scariest\nproteins that I could think of.", "start": 1166.16, "duration": 6.19}, {"text": "And we're going to talk\nabout three of them.", "start": 1172.35, "duration": 3.08}, {"text": "One of them in the slide,\nwhich is the proteins that", "start": 1175.43, "duration": 4.29}, {"text": "are actually involved in\ncausing the symptoms that", "start": 1179.72, "duration": 2.49}, {"text": "come from when you're\nworried about anthrax.", "start": 1182.21, "duration": 3.42}, {"text": "And then we'll talk\nabout HIV yet again,", "start": 1185.63, "duration": 3.93}, {"text": "this time, polymerase mutants\nthat cause drug resistance.", "start": 1189.56, "duration": 4.29}, {"text": "And then ApoE yet again, as\nwe have in the past, this time", "start": 1193.85, "duration": 3.54}, {"text": "talking specifically about\nhow protein structure tells us", "start": 1197.39, "duration": 3.24}, {"text": "the haplotype.", "start": 1200.63, "duration": 1.06}, {"text": "So with anthrax, you start\nout with this simple two", "start": 1201.69, "duration": 3.47}, {"text": "component--", "start": 1205.16, "duration": 1.35}, {"text": "two protein domains here.", "start": 1206.51, "duration": 2.25}, {"text": "They bind to a cellular--", "start": 1208.76, "duration": 2.0}, {"text": "something on your cell surface.", "start": 1210.76, "duration": 1.66}, {"text": "Hopefully not yours,\nbut human cell surface.", "start": 1212.42, "duration": 3.36}, {"text": "And then one of the\ndomains disappears.", "start": 1215.78, "duration": 2.64}, {"text": "And the remaining one\nnow self-assembles", "start": 1218.42, "duration": 1.98}, {"text": "into a seven-mer,\nseven-fold symmetry.", "start": 1220.4, "duration": 2.91}, {"text": "Remember, we were talking about\ntwo-fold rotational symmetry", "start": 1223.31, "duration": 2.657}, {"text": "for the DNA protein interaction.", "start": 1225.967, "duration": 1.333}, {"text": "This is now seven-fold\nrotational symmetry.", "start": 1227.3, "duration": 2.13}, {"text": "That now allows lethal\nfactor, LF, to bind--", "start": 1229.43, "duration": 3.75}, {"text": "still not inside the cell.", "start": 1233.18, "duration": 1.86}, {"text": "But the whole complex\ngets internalized.", "start": 1235.04, "duration": 3.51}, {"text": "Still, topologically, it's as\nif it were outside the cell", "start": 1238.55, "duration": 3.288}, {"text": "when it's inside\nthis little vesicle.", "start": 1241.838, "duration": 1.542}, {"text": "It has to get through\nthat membrane.", "start": 1243.38, "duration": 2.61}, {"text": "But now the pH change that\nhappens when this vesicle goes", "start": 1245.99, "duration": 3.15}, {"text": "in the cell, part of the natural\ncell biological processes", "start": 1249.14, "duration": 3.99}, {"text": "causes some act--", "start": 1253.13, "duration": 1.53}, {"text": "an unfortunate act where,\nnow, the seven-mer complex", "start": 1254.66, "duration": 5.19}, {"text": "of proteins does yet another\nconformational change", "start": 1259.85, "duration": 2.76}, {"text": "and turns into this hairy beast\nthat allows the lethal factor", "start": 1262.61, "duration": 3.81}, {"text": "to get into your\ncell and kill it.", "start": 1266.42, "duration": 1.87}, {"text": "So you can see that\nwhen we're talking", "start": 1268.29, "duration": 2.0}, {"text": "about protein three-dimensional\nstructure, whether we're", "start": 1270.29, "duration": 2.333}, {"text": "predicting it or solving it,\nprotein is not a static object.", "start": 1272.623, "duration": 3.937}, {"text": "Here, it associates\nwith one factor.", "start": 1276.56, "duration": 1.89}, {"text": "It associates seven of itself.", "start": 1278.45, "duration": 2.7}, {"text": "It interacts with lethal factor.", "start": 1281.15, "duration": 1.65}, {"text": "It opens up a whole new channel\nin the membrane, et cetera.", "start": 1282.8, "duration": 3.93}, {"text": "You need to think of\nthese as dynamic systems", "start": 1286.73, "duration": 1.905}, {"text": "with many different states.", "start": 1288.635, "duration": 1.125}, {"text": "We also need to think\nabout time scales.", "start": 1292.57, "duration": 2.85}, {"text": "Many of-- the\nmolecular mechanics", "start": 1295.42, "duration": 2.04}, {"text": "we'll be talking about,\nthe timescale of relevance", "start": 1297.46, "duration": 2.79}, {"text": "is the femtosecond.", "start": 1300.25, "duration": 1.41}, {"text": "You need to be able-- this\nis, well, two nanoseconds.", "start": 1301.66, "duration": 3.51}, {"text": "So 10 to the minus 15th, 10\nto the minus 9th seconds.", "start": 1305.17, "duration": 2.82}, {"text": "That's atomic motion.", "start": 1307.99, "duration": 1.74}, {"text": "The turnover of\nan enzyme that is", "start": 1309.73, "duration": 3.57}, {"text": "the time it takes to\nfor a small molecule,", "start": 1313.3, "duration": 2.82}, {"text": "say, to find and\nbind the enzyme,", "start": 1316.12, "duration": 3.36}, {"text": "to possibly go through\na catalytic step,", "start": 1319.48, "duration": 3.27}, {"text": "and to dissociate as a product.", "start": 1322.75, "duration": 3.27}, {"text": "That's on the order of\nmicroseconds to milliseconds.", "start": 1326.02, "duration": 2.52}, {"text": "And the second range is the time\nthat it takes the molecule to--", "start": 1328.54, "duration": 4.22}, {"text": "the drug or small molecule-- to\ntouch the surface of the cell,", "start": 1332.76, "duration": 2.89}, {"text": "maybe diffuse across the\ncell, and find its target.", "start": 1335.65, "duration": 3.75}, {"text": "Transcription that\nwe talked about,", "start": 1339.4, "duration": 1.62}, {"text": "all of the regulatory mechanisms\nof transcription last time,", "start": 1341.02, "duration": 4.98}, {"text": "the rate of the constant\nfor that process", "start": 1346.0, "duration": 4.17}, {"text": "is around 50\nnucleotides per second.", "start": 1350.17, "duration": 4.59}, {"text": "Not entirely\ncoincidentally, that's", "start": 1354.76, "duration": 1.56}, {"text": "about the rate at which it\nis translated into protein.", "start": 1356.32, "duration": 3.9}, {"text": "These are important numbers,\nbecause a typical gene size", "start": 1360.22, "duration": 3.99}, {"text": "piece, say, after RNA\nsplicing in higher organisms", "start": 1364.21, "duration": 5.01}, {"text": "or naturally, it\nmight be a kilobase.", "start": 1369.22, "duration": 3.6}, {"text": "So that's about a half a minute\nto transcribe and translate.", "start": 1372.82, "duration": 3.78}, {"text": "That could be used as a timer\nin a circuit of these longer", "start": 1379.3, "duration": 4.53}, {"text": "time frames, like cell\ncycle, circadian rhythm,", "start": 1383.83, "duration": 5.19}, {"text": "very long time frames\nin ecological systems", "start": 1389.02, "duration": 3.66}, {"text": "with bamboo and various pests,\nwhich can be not even yearly,", "start": 1392.68, "duration": 7.08}, {"text": "and then development\nand aging, which", "start": 1399.76, "duration": 1.92}, {"text": "can be on the order of hundreds\nof years, at least for humans,", "start": 1401.68, "duration": 4.012}, {"text": "turtles, and whales.", "start": 1405.692, "duration": 0.833}, {"text": "So what we think\nproteins are good for", "start": 1409.42, "duration": 3.9}, {"text": "depends on the accuracy.", "start": 1413.32, "duration": 2.62}, {"text": "And the accuracy\ndepends on the method.", "start": 1415.94, "duration": 1.85}, {"text": "At the very bottom right, we\nhave a very appealing approach,", "start": 1417.79, "duration": 6.7}, {"text": "which is de novo, a\npriori, or ab initio", "start": 1424.49, "duration": 5.99}, {"text": "prediction of\nsecondary-- of protein", "start": 1430.48, "duration": 2.393}, {"text": "three-dimensional structure\nfrom the sequence alone,", "start": 1432.873, "duration": 2.167}, {"text": "which we're getting\nin bucketloads", "start": 1435.04, "duration": 1.417}, {"text": "from the genome projects.", "start": 1436.457, "duration": 1.283}, {"text": "But unfortunately,\naccuracy so far--", "start": 1437.74, "duration": 2.04}, {"text": "and we'll delve into this\nin more detail in a moment--", "start": 1439.78, "duration": 2.31}, {"text": "is on the order of six\nangstroms of difference", "start": 1442.09, "duration": 3.21}, {"text": "between the predicted\nstructure and what it actually", "start": 1445.3, "duration": 2.31}, {"text": "is by the more precise\nmethods up higher on this.", "start": 1447.61, "duration": 3.54}, {"text": "The y-axis here,\nthe vertical axis,", "start": 1451.15, "duration": 3.12}, {"text": "is basically sequence identity\nas you start doing, say,", "start": 1454.27, "duration": 3.57}, {"text": "threading or comparative\nmodeling here as you get--", "start": 1457.84, "duration": 4.71}, {"text": "instead of the ab initio\nor de novo prediction", "start": 1462.55, "duration": 3.87}, {"text": "doesn't require any\nsequence similarity.", "start": 1466.42, "duration": 1.98}, {"text": "If you want to build it based\non previously solved structures,", "start": 1468.4, "duration": 2.97}, {"text": "you need at least 30%, but\nyou're still very far-- say,", "start": 1471.37, "duration": 4.71}, {"text": "3 to 4 angstroms away--", "start": 1476.08, "duration": 1.77}, {"text": "from the native structure.", "start": 1477.85, "duration": 2.25}, {"text": "As you get to 1 Angstrom\nor better in your accuracy,", "start": 1480.1, "duration": 3.18}, {"text": "as you can get from NMR\nand X-ray crystallography,", "start": 1483.28, "duration": 2.76}, {"text": "you now are in a position\nto study catalytic mechanism", "start": 1486.04, "duration": 3.42}, {"text": "and design and improve\nligands, such as drugs.", "start": 1489.46, "duration": 2.67}, {"text": "This is really\nwhere we want to be.", "start": 1492.13, "duration": 1.74}, {"text": "There may be a day where we\ncan do this all from ab initio", "start": 1493.87, "duration": 3.51}, {"text": "prediction or modeling\nat very great distances.", "start": 1497.38, "duration": 2.52}, {"text": "But for now, modeling\nat very short,", "start": 1499.9, "duration": 3.27}, {"text": "say, 80% to 90% amino acid\nsimilarity, is important.", "start": 1503.17, "duration": 3.9}, {"text": "Remember, there's\na-- just like there's", "start": 1507.07, "duration": 2.37}, {"text": "a variety of different\nprotein structures.", "start": 1509.44, "duration": 4.27}, {"text": "This is just an example\nof a vast literature that", "start": 1513.71, "duration": 3.47}, {"text": "exists where you can\nuse some of the methods", "start": 1517.18, "duration": 4.17}, {"text": "that we'll be\ndiscussing in this class", "start": 1521.35, "duration": 5.79}, {"text": "on doing molecular\nmechanics on proteins", "start": 1527.14, "duration": 4.5}, {"text": "and predicting their\nthree-dimensional structure", "start": 1531.64, "duration": 2.58}, {"text": "in complex with\nthe various drugs.", "start": 1534.22, "duration": 3.66}, {"text": "We will contrast this,\nor show the interplay", "start": 1537.88, "duration": 2.37}, {"text": "of the computational\nbiology, that", "start": 1540.25, "duration": 1.65}, {"text": "can be aided by actual\nmeasurements of drug binding,", "start": 1541.9, "duration": 3.66}, {"text": "just as we had actual\nmeasurements of zinc finger", "start": 1545.56, "duration": 2.73}, {"text": "binding to double-stranded DNA.", "start": 1548.29, "duration": 2.19}, {"text": "And ways that you can\ndiscover the small molecules", "start": 1550.48, "duration": 3.3}, {"text": "by a clever use of\nparts of it that you", "start": 1553.78, "duration": 4.065}, {"text": "know bind and parts\nof it that you know", "start": 1557.845, "duration": 2.815}, {"text": "might be variable\nin a chemical sense.", "start": 1560.66, "duration": 5.6}, {"text": "Now, this is what--", "start": 1566.26, "duration": 1.71}, {"text": "just as there is this dynamic\ncompetition between pathogens", "start": 1567.97, "duration": 5.37}, {"text": "and their hosts, there's\nthis similar lethal game", "start": 1573.34, "duration": 5.22}, {"text": "that's played between pathogens\nand the pharmaceutical", "start": 1578.56, "duration": 2.91}, {"text": "industry.", "start": 1581.47, "duration": 0.87}, {"text": "And here, HIV, for which\nthere are many drugs now aimed", "start": 1582.34, "duration": 3.78}, {"text": "either at the protease\nor at the polymerase--", "start": 1586.12, "duration": 3.603}, {"text": "some of the first ones were\naimed at the polymerase,", "start": 1589.723, "duration": 2.167}, {"text": "and so we have a big collection.", "start": 1591.89, "duration": 2.12}, {"text": "This is one of the most\nsequenced molecules on Earth,", "start": 1594.01, "duration": 2.22}, {"text": "which is the HIV gene encoding\nthe reverse transcriptase", "start": 1596.23, "duration": 4.47}, {"text": "polymerase.", "start": 1600.7, "duration": 0.99}, {"text": "And it's been\nsequenced many times", "start": 1601.69, "duration": 1.56}, {"text": "because as a patient\ntakes the drugs,", "start": 1603.25, "duration": 1.86}, {"text": "their population of\nthe AIDS virus changes.", "start": 1605.11, "duration": 3.4}, {"text": "And each of these little\ndiamond-shaped substitution", "start": 1608.51, "duration": 4.91}, {"text": "sites clustered around the\nbinding site in the protein--", "start": 1613.42, "duration": 2.955}, {"text": "the binding site here\nindicated the substrate", "start": 1616.375, "duration": 1.875}, {"text": "is in space filling,\nwhich is the triphosphate", "start": 1618.25, "duration": 2.82}, {"text": "on the upper left\nand that the template", "start": 1621.07, "duration": 4.86}, {"text": "kind of curving around on the\nright-hand side of that space", "start": 1625.93, "duration": 2.61}, {"text": "filling bright green structure.", "start": 1628.54, "duration": 4.14}, {"text": "The protein is in red.", "start": 1632.68, "duration": 2.458}, {"text": "And these little diamonds\nindicate substitutions,", "start": 1635.138, "duration": 2.042}, {"text": "where the nomenclature is\nsingle-letter code for the wild", "start": 1637.18, "duration": 2.94}, {"text": "type, the position in amino\nacids from the end terminus is", "start": 1640.12, "duration": 5.85}, {"text": "the number, and then the third--", "start": 1645.97, "duration": 3.36}, {"text": "or the last far right letter\nis the new amino acids.", "start": 1649.33, "duration": 4.0}, {"text": "So for example, D67N means a\n[? sparcade ?] at position 67", "start": 1653.33, "duration": 4.16}, {"text": "and wild type changes\nto an asparagine.", "start": 1657.49, "duration": 2.58}, {"text": "And that causes a drug\nresistance in the HIV,", "start": 1660.07, "duration": 4.17}, {"text": "with unfortunate\nconsequences for the patient.", "start": 1664.24, "duration": 2.535}, {"text": "We can take-- now, making\nmutations in polymerases", "start": 1672.24, "duration": 5.87}, {"text": "is not entirely of\nnegative consequences.", "start": 1678.11, "duration": 3.28}, {"text": "And I'm going to show you a\nreally beautiful example where", "start": 1681.39, "duration": 3.35}, {"text": "a DNA polymerase-- a very\nsimilar kind of dynamic,", "start": 1684.74, "duration": 4.29}, {"text": "where the DNA polymerase, you\nwant to change it so that it", "start": 1689.03, "duration": 4.29}, {"text": "can now handle what would\nnormally be an inhibitor of DNA", "start": 1693.32, "duration": 6.42}, {"text": "polymerase, a class of\nnucleotides that is incapable", "start": 1699.74, "duration": 8.25}, {"text": "of extending--", "start": 1707.99, "duration": 1.32}, {"text": "capable of being incorporated\ninto the growing replicating", "start": 1709.31, "duration": 5.46}, {"text": "genome, but is not\ncapable of extending.", "start": 1714.77, "duration": 3.39}, {"text": "Is a powerful inhibitor,\nand it's also powerful", "start": 1718.16, "duration": 2.52}, {"text": "sequencing reagent,\nthese dideoxys.", "start": 1720.68, "duration": 2.43}, {"text": "And so one of the\nthings that was noticed", "start": 1723.11, "duration": 5.34}, {"text": "as the sequences of some\nof these polymerases", "start": 1728.45, "duration": 3.753}, {"text": "were being studied, and\nsome of the resistance", "start": 1732.203, "duration": 1.917}, {"text": "mutants, and so\non, it was noticed", "start": 1734.12, "duration": 2.79}, {"text": "that the complex between\nthe nucleotide, whether it's", "start": 1736.91, "duration": 6.15}, {"text": "a deoxynucleotide shown here\nwith a 3 prime hydroxyl, which", "start": 1743.06, "duration": 4.77}, {"text": "could then be extended\nby bringing in the next 5", "start": 1747.83, "duration": 3.96}, {"text": "phosphate.", "start": 1751.79, "duration": 1.62}, {"text": "This hydroxyl is near\nin space to the position", "start": 1753.41, "duration": 4.2}, {"text": "on a phenylalanine\nor a tyrosine,", "start": 1757.61, "duration": 2.58}, {"text": "position 762 of this\npolymerase, which can either--", "start": 1760.19, "duration": 4.65}, {"text": "if it's a tyrosine,\nit has an OH there.", "start": 1764.84, "duration": 4.148}, {"text": "And if it's a phenylalanine,\nyou lose the O", "start": 1768.988, "duration": 1.792}, {"text": "and you just have\na hydrogen there.", "start": 1770.78, "duration": 1.92}, {"text": "And when you have the\nphenylalanine there,", "start": 1772.7, "duration": 5.85}, {"text": "there's a space that--", "start": 1778.55, "duration": 3.51}, {"text": "an appropriate space\nthat accommodates the 3", "start": 1782.06, "duration": 3.15}, {"text": "prime hydroxyl quite well.", "start": 1785.21, "duration": 1.6}, {"text": "But if you now put in\na dideoxy inhibitor,", "start": 1786.81, "duration": 2.69}, {"text": "you now have too\nmuch space in there,", "start": 1789.5, "duration": 2.34}, {"text": "and you start trying\nto fill that space", "start": 1791.84, "duration": 2.49}, {"text": "with other bulky\nmolecules, like water.", "start": 1794.33, "duration": 3.72}, {"text": "And basically, the\nbinding constant,", "start": 1798.05, "duration": 4.14}, {"text": "it becomes much less\nfavorable binding", "start": 1802.19, "duration": 2.58}, {"text": "when you're lacking\nboth oxygens.", "start": 1804.77, "duration": 3.19}, {"text": "So this presented an opportunity\nto engineer some polymerases", "start": 1807.96, "duration": 5.01}, {"text": "which had a phenylalanine\nthere to become", "start": 1812.97, "duration": 5.54}, {"text": "more accepting of the\ndideoxys and hence better", "start": 1818.51, "duration": 3.45}, {"text": "at using disease in DNA\nsequencing chemistry.", "start": 1821.96, "duration": 3.69}, {"text": "And this was simply\nby engineering--", "start": 1825.65, "duration": 2.16}, {"text": "putting in that oxygen there,\nby changing the phenylalanine", "start": 1827.81, "duration": 2.64}, {"text": "to a tyrosine, it now made\na better fit between--", "start": 1830.45, "duration": 5.34}, {"text": "you can think of it as--", "start": 1835.79, "duration": 2.565}, {"text": "you can have either oxygen,\nand by removing this oxygen,", "start": 1838.355, "duration": 3.975}, {"text": "you replace it with an\noxygen on the protein side.", "start": 1842.33, "duration": 5.4}, {"text": "I'm trying to emphasize,\nby a few examples here,", "start": 1847.73, "duration": 2.4}, {"text": "the idea of\ncomplementary surfaces", "start": 1850.13, "duration": 1.89}, {"text": "and how you can engineer them.", "start": 1852.02, "duration": 1.51}, {"text": "This is a beautiful case.", "start": 1853.53, "duration": 1.07}, {"text": "Now, we're talking about\na single atom rather than", "start": 1854.6, "duration": 2.31}, {"text": "the complementary surfaces\nof the nucleic acids we", "start": 1856.91, "duration": 2.1}, {"text": "were talking about before.", "start": 1859.01, "duration": 1.47}, {"text": "This has an 8,000-fold effect\non the specificity of this", "start": 1860.48, "duration": 4.05}, {"text": "polymerase, and a big impact\non the Genome Project.", "start": 1864.53, "duration": 4.08}, {"text": "Now, that's how we\nprogram a particular atom", "start": 1868.61, "duration": 3.0}, {"text": "to achieve an important goal.", "start": 1871.61, "duration": 2.13}, {"text": "And of course, the virus\nhas its own mechanisms", "start": 1873.74, "duration": 2.13}, {"text": "for programming it typically,\nby random mutagenesis", "start": 1875.87, "duration": 3.125}, {"text": "and selection, as\nwe talked about", "start": 1878.995, "duration": 1.375}, {"text": "in the population genetics.", "start": 1880.37, "duration": 1.2}, {"text": "But the way we program\nin general proteins", "start": 1881.57, "duration": 2.67}, {"text": "are either transgenics, where we\nmight overproduce the protein,", "start": 1884.24, "duration": 6.6}, {"text": "or homologous\nrecombination, which", "start": 1890.84, "duration": 1.74}, {"text": "is the ultimate where we go in\nand if the protein is already--", "start": 1892.58, "duration": 3.233}, {"text": "if the gene encoding the\nprotein is already present,", "start": 1895.813, "duration": 2.167}, {"text": "we can change that\nparticular nucleotide in situ", "start": 1897.98, "duration": 2.73}, {"text": "in the correct place so\nit's properly regulated", "start": 1900.71, "duration": 2.31}, {"text": "and everything.", "start": 1903.02, "duration": 0.72}, {"text": "That's a great way to do it.", "start": 1903.74, "duration": 3.42}, {"text": "Point mutants are\nnot the only way", "start": 1907.16, "duration": 1.877}, {"text": "to generate conditional mutants.", "start": 1909.037, "duration": 1.333}, {"text": "Many of them historically were.", "start": 1910.37, "duration": 1.292}, {"text": "But there are ways\nthat you can program,", "start": 1911.662, "duration": 2.158}, {"text": "and conditional, meaning that\nyou can regulate under what", "start": 1913.82, "duration": 2.79}, {"text": "conditions the\nprotein is expressed", "start": 1916.61, "duration": 1.86}, {"text": "or not or active or not\nwith an entire domain,", "start": 1918.47, "duration": 3.78}, {"text": "or with single\nnucleotide polymorphisms.", "start": 1922.25, "duration": 3.72}, {"text": "Now, so this is one way.", "start": 1925.97, "duration": 1.47}, {"text": "This is the nucleic acid way.", "start": 1927.44, "duration": 3.67}, {"text": "Another way is by modulating\nthe activity of the proteins", "start": 1931.11, "duration": 4.76}, {"text": "from the outside with drugs\nor drug-like molecules", "start": 1935.87, "duration": 3.81}, {"text": "and chemical kinetics.", "start": 1939.68, "duration": 1.53}, {"text": "And under the\nsubheadings for that,", "start": 1941.21, "duration": 2.07}, {"text": "you can make these by\ncombinatorial synthesis--", "start": 1943.28, "duration": 2.49}, {"text": "and we'll show an\nexample of that.", "start": 1945.77, "duration": 1.47}, {"text": "But combinatorial synthesis can\nbe based on design principles,", "start": 1947.24, "duration": 3.75}, {"text": "not just completely random.", "start": 1950.99, "duration": 2.46}, {"text": "Usually are.", "start": 1953.45, "duration": 0.608}, {"text": "The design principles\ncan take into account", "start": 1954.058, "duration": 1.792}, {"text": "what you know about the\nnature of the interaction", "start": 1955.85, "duration": 2.55}, {"text": "of similar proteins.", "start": 1958.4, "duration": 3.39}, {"text": "And you can mine\nwhatever biochemical data", "start": 1961.79, "duration": 7.95}, {"text": "that you can collect for\nso-called quantitative", "start": 1969.74, "duration": 2.68}, {"text": "structure activity\nrelationships.", "start": 1972.42, "duration": 1.53}, {"text": "This is a slightly\ndifferent discipline", "start": 1973.95, "duration": 2.61}, {"text": "than the detailed\ncrystallographic", "start": 1976.56, "duration": 5.887}, {"text": "and quantitative studies that\nwe've talked about so far.", "start": 1982.447, "duration": 2.333}, {"text": "Here, you're trying\nto basically mine", "start": 1984.78, "duration": 2.58}, {"text": "through the structures\nof the ligand itself", "start": 1987.36, "duration": 3.96}, {"text": "for the parts of the\nligand that might", "start": 1991.32, "duration": 2.13}, {"text": "be responsible for the\nactivity, the binding", "start": 1993.45, "duration": 2.16}, {"text": "activity or the full biological\nactivity that you see.", "start": 1995.61, "duration": 4.48}, {"text": "So let's look at some\nexamples of single-nucleotide", "start": 2000.09, "duration": 3.23}, {"text": "polymorphisms that we've been\ntalking about before in--", "start": 2003.32, "duration": 4.29}, {"text": "actually, this is a class\nthat we didn't discuss before.", "start": 2007.61, "duration": 4.83}, {"text": "But in previous classes.", "start": 2012.44, "duration": 2.25}, {"text": "But it's related to what\nwe've been talking about.", "start": 2014.69, "duration": 2.76}, {"text": "In the case of the zinc finger,\nwe made an altered specificity.", "start": 2017.45, "duration": 2.783}, {"text": "We made new zinc\nfingers with bind", "start": 2020.233, "duration": 1.417}, {"text": "to completely new\ntrinucleotides.", "start": 2021.65, "duration": 2.85}, {"text": "With the DNA polymerase,\nby changing one amino acid,", "start": 2024.5, "duration": 3.81}, {"text": "we could make it now accept\nalmost four logs better", "start": 2028.31, "duration": 4.14}, {"text": "an inhibitor is very useful.", "start": 2032.45, "duration": 2.47}, {"text": "And here, many\ndifferent-- many of these", "start": 2034.92, "duration": 3.56}, {"text": "are enzymes, where you can\nnot just knock out the enzyme,", "start": 2038.48, "duration": 5.04}, {"text": "but actually make it\nrecognize a new substrate,", "start": 2043.52, "duration": 2.67}, {"text": "or change radically the binding\nconstant and catalytic rate", "start": 2046.19, "duration": 5.489}, {"text": "for new substrates.", "start": 2051.679, "duration": 1.441}, {"text": "And I just have this long\nfine-print slide just", "start": 2056.27, "duration": 2.949}, {"text": "to impress to you-- this\nis actually less than half", "start": 2059.219, "duration": 2.361}, {"text": "of the list--", "start": 2061.58, "duration": 1.74}, {"text": "just how many examples.", "start": 2063.32, "duration": 1.149}, {"text": "These are not that unusual.", "start": 2064.469, "duration": 1.851}, {"text": "And those can be designed\nor naturally occurring.", "start": 2066.32, "duration": 4.589}, {"text": "Now, we're going to take the\nthree-dimensional structure", "start": 2070.909, "duration": 3.991}, {"text": "of proteins and connect it with\nour discussion of haplotypes", "start": 2074.9, "duration": 9.96}, {"text": "and single-nucleotide\npolymorphisms.", "start": 2084.86, "duration": 2.01}, {"text": "And you may recall\nthat with-- one", "start": 2086.87, "duration": 4.23}, {"text": "of the commonly occurring\nsingle-nucleotide", "start": 2091.1, "duration": 4.17}, {"text": "polymorphisms is\nthe ApoE4 allele.", "start": 2095.27, "duration": 4.62}, {"text": "It's present in 20% of\nthe human population.", "start": 2099.89, "duration": 2.13}, {"text": "Even though it has unfortunate\nconsequences, we think,", "start": 2102.02, "duration": 4.41}, {"text": "mainly for Alzheimer's--", "start": 2106.43, "duration": 4.05}, {"text": "it increases the risk of\nAlzheimer's, and probably", "start": 2110.48, "duration": 2.88}, {"text": "increases cardiovascular\nfitness through ApoE refers", "start": 2113.36, "duration": 7.41}, {"text": "to its involvement in\ncholesterol metabolism", "start": 2120.77, "duration": 4.02}, {"text": "and transport.", "start": 2124.79, "duration": 1.17}, {"text": "The ApoE3 allele is\npresent in about 80%,", "start": 2125.96, "duration": 2.91}, {"text": "and is far more common in human\npopulations, but both of these", "start": 2128.87, "duration": 2.94}, {"text": "would be considered\nvery common alleles.", "start": 2131.81, "duration": 2.56}, {"text": "And we also mentioned that\nthe ancestral form of this,", "start": 2134.37, "duration": 3.14}, {"text": "for example, found in\nchimpanzees at nearly 100%,", "start": 2137.51, "duration": 3.48}, {"text": "is this arginine 112,\ninstead of what's now common", "start": 2140.99, "duration": 3.99}, {"text": "in human populations\nwas cysteine 112.", "start": 2144.98, "duration": 2.19}, {"text": "And that was-- one explanation\nfor that might be that it was", "start": 2147.17, "duration": 2.91}, {"text": "physiologically--", "start": 2150.08, "duration": 2.91}, {"text": "our nutritional\nstandards have changed.", "start": 2152.99, "duration": 2.77}, {"text": "We now eat a lot\nmore fatty things.", "start": 2155.76, "duration": 1.67}, {"text": "We live long enough\nto get Alzheimer's.", "start": 2157.43, "duration": 2.14}, {"text": "And so maybe this was\nsomething that was--", "start": 2159.57, "duration": 4.58}, {"text": "this bad allele, E4, was\ngood in chimpanzees that have", "start": 2164.15, "duration": 3.33}, {"text": "different diets or lifespans.", "start": 2167.48, "duration": 2.46}, {"text": "But the other possibility--\nand I can't really", "start": 2169.94, "duration": 3.93}, {"text": "distinguish between\nthese right now--", "start": 2173.87, "duration": 1.98}, {"text": "but another one to\nseriously consider,", "start": 2175.85, "duration": 1.92}, {"text": "not just in this case,\nbut in cases in general,", "start": 2177.77, "duration": 2.22}, {"text": "is you no longer just think\nabout single nucleotides.", "start": 2179.99, "duration": 3.63}, {"text": "You think about haplotypes.", "start": 2183.62, "duration": 1.29}, {"text": "Everything insists\non that DNA strand", "start": 2184.91, "duration": 3.06}, {"text": "has a chance of affecting\neither the expression", "start": 2187.97, "duration": 1.98}, {"text": "level of the protein or\ninsists, on the protein strand,", "start": 2189.95, "duration": 3.63}, {"text": "to fall back and interact.", "start": 2193.58, "duration": 1.98}, {"text": "And you can see that one\nof the nearest amino acids", "start": 2195.56, "duration": 2.67}, {"text": "to this arginine 112, which\nis the main difference", "start": 2198.23, "duration": 3.54}, {"text": "between ApoE4 and ApoE3.", "start": 2201.77, "duration": 2.94}, {"text": "Arginine 61 is the same\non the two alleles.", "start": 2204.71, "duration": 2.49}, {"text": "But you think of this\nas one haplotype,", "start": 2207.2, "duration": 3.12}, {"text": "and in chimpanzees the\nhaplotype, is now threonine 61.", "start": 2210.32, "duration": 3.51}, {"text": "And you can think that\na [? 3R ?] in chimps,", "start": 2213.83, "duration": 5.79}, {"text": "or ancestrally, is not too\ndifferent from [? Rcys. ?] So", "start": 2219.62, "duration": 5.94}, {"text": "the different order.", "start": 2225.56, "duration": 1.69}, {"text": "So it's like this compensating,\ncomplementary mutation,", "start": 2227.25, "duration": 3.26}, {"text": "just like we had in the\noxygens in the polymerase", "start": 2230.51, "duration": 5.97}, {"text": "a couple of slides ago.", "start": 2236.48, "duration": 1.23}, {"text": "And you can think of the\ncompensating mutations--", "start": 2237.71, "duration": 2.042}, {"text": "we had the mutual information\ntheory for doing the theory", "start": 2239.752, "duration": 2.588}, {"text": "structure.", "start": 2242.34, "duration": 0.89}, {"text": "Think of complementary surfaces.", "start": 2243.23, "duration": 1.47}, {"text": "When you think of\nsingle nucleotides,", "start": 2244.7, "duration": 3.18}, {"text": "don't think of them as haplotype\nand possibly complementing", "start": 2247.88, "duration": 5.19}, {"text": "constellations.", "start": 2253.07, "duration": 1.86}, {"text": "Especially, now, this brings\nus to the possible impact", "start": 2254.93, "duration": 5.76}, {"text": "of three-dimensional\nstructure on predicting", "start": 2260.69, "duration": 1.92}, {"text": "deleterious human alleles.", "start": 2262.61, "duration": 1.29}, {"text": "If we suddenly had the sequence\nof everyone in this room", "start": 2263.9, "duration": 3.0}, {"text": "and we wanted our computer\nprogram to prioritize, which", "start": 2266.9, "duration": 3.648}, {"text": "ones should I the attention to?", "start": 2270.548, "duration": 1.292}, {"text": "Which deviations from\nthe most common allele", "start": 2271.84, "duration": 4.35}, {"text": "should I look at first?", "start": 2276.19, "duration": 1.022}, {"text": "Well, you might think of these\nthings in terms of proteins.", "start": 2277.212, "duration": 2.458}, {"text": "We've now gotten to\nthe point in the course", "start": 2279.67, "duration": 1.8}, {"text": "where we're talking\nabout proteins.", "start": 2281.47, "duration": 1.56}, {"text": "You need to think about the\nthree-dimensional structure.", "start": 2283.03, "duration": 2.333}, {"text": "Who's near who in the structure?", "start": 2285.363, "duration": 2.407}, {"text": "You can think about\nbinding sites.", "start": 2287.77, "duration": 1.53}, {"text": "These might be indicated by--", "start": 2289.3, "duration": 1.68}, {"text": "if you know the\nthree-dimensional structure", "start": 2290.98, "duration": 3.27}, {"text": "or you know the\nconservation pattern", "start": 2294.25, "duration": 2.1}, {"text": "in this family of proteins.", "start": 2296.35, "duration": 2.1}, {"text": "You can ask things about charge.", "start": 2298.45, "duration": 2.85}, {"text": "In that last slide,\nwe had the charge", "start": 2301.3, "duration": 1.65}, {"text": "of the arginines being\nnear a compatibly", "start": 2302.95, "duration": 5.55}, {"text": "partial negative charge on\nthe cysteines or threonines.", "start": 2308.5, "duration": 6.6}, {"text": "You can have-- a disulfide is\na very important thing to lose.", "start": 2315.1, "duration": 4.95}, {"text": "They tend to be\nhighly conserved.", "start": 2320.05, "duration": 3.36}, {"text": "If you introduce a proline into\nwhat would normally be an alpha", "start": 2323.41, "duration": 3.81}, {"text": "helix, this is something\nwhere knowledge", "start": 2327.22, "duration": 2.003}, {"text": "of the three-dimensional\nstructure", "start": 2329.223, "duration": 1.417}, {"text": "would say, oh, that proline,\nthis a priori, without any", "start": 2330.64, "duration": 3.3}, {"text": "knowledge of\nconservation, could be", "start": 2333.94, "duration": 2.37}, {"text": "a huge change in the\nthree-dimensional structure.", "start": 2336.31, "duration": 3.93}, {"text": "And then these\nmulti-sequence profiles", "start": 2340.24, "duration": 2.49}, {"text": "are a good way of looking\nat the conservation.", "start": 2342.73, "duration": 4.08}, {"text": "That's a way of prioritizing\nsingle-nucleotide polymorphisms", "start": 2346.81, "duration": 4.02}, {"text": "that might have impact on\npharmacogenomics or disease", "start": 2350.83, "duration": 3.21}, {"text": "in general.", "start": 2354.04, "duration": 1.2}, {"text": "Now, as we integrate that\nwith the chemical diversity", "start": 2355.24, "duration": 4.68}, {"text": "that we can create--", "start": 2359.92, "duration": 0.852}, {"text": "that's going to be the topic\nfor the next few slides,", "start": 2360.772, "duration": 2.208}, {"text": "is how do we create\nchemical diversity?", "start": 2362.98, "duration": 3.75}, {"text": "And I'm going to introduce this,\nthe idea of chemical diversity,", "start": 2366.73, "duration": 3.84}, {"text": "in a way I hope nicely\nconnects to where", "start": 2370.57, "duration": 2.97}, {"text": "we've been with RNA arrays.", "start": 2373.54, "duration": 2.49}, {"text": "RNA arrays, and the\ndouble-stranded RNA array", "start": 2376.03, "duration": 2.79}, {"text": "that we used earlier\nin class today,", "start": 2378.82, "duration": 2.97}, {"text": "can be generated in\na commentorial sense.", "start": 2381.79, "duration": 1.89}, {"text": "You can make an exhaustive set.", "start": 2383.68, "duration": 2.07}, {"text": "Now, typically, those were\nmade where, spatially, they", "start": 2385.75, "duration": 3.03}, {"text": "were isolated.", "start": 2388.78, "duration": 0.81}, {"text": "Each different nucleic\nacid, oligonucleotide,", "start": 2389.59, "duration": 6.06}, {"text": "is present in a different place\nidentifiable to the computer", "start": 2395.65, "duration": 3.15}, {"text": "by its coordinates on an array.", "start": 2398.8, "duration": 2.98}, {"text": "But you can also make\nthem in a big mixture", "start": 2401.78, "duration": 3.77}, {"text": "and use them as a mixture and\ndo selection on them, as we", "start": 2405.55, "duration": 3.06}, {"text": "did with the phage display.", "start": 2408.61, "duration": 2.19}, {"text": "Or you can make them as\na mixture of solid phase", "start": 2410.8, "duration": 3.69}, {"text": "particles and then separate the\n[INAUDIBLE] phase particles out", "start": 2414.49, "duration": 3.18}, {"text": "in some manner.", "start": 2417.67, "duration": 1.68}, {"text": "Solid phase comes up\nagain and again in arrays.", "start": 2419.35, "duration": 2.415}, {"text": "It's very obvious why\nyou have a solid phase.", "start": 2421.765, "duration": 1.875}, {"text": "You want to be able to address\nit by its positions in x and y", "start": 2423.64, "duration": 3.72}, {"text": "on the array.", "start": 2427.36, "duration": 2.34}, {"text": "But the other reason--\ntechnical reasons", "start": 2429.7, "duration": 1.77}, {"text": "are, it's a fantastic way\nof getting purification", "start": 2431.47, "duration": 2.46}, {"text": "of your products\nsimply by washing", "start": 2433.93, "duration": 3.06}, {"text": "rather than doing complicated\npurification procedures.", "start": 2436.99, "duration": 3.3}, {"text": "And it allows you to,\nin the case of beads,", "start": 2440.29, "duration": 2.82}, {"text": "there now-- you can think of\nit as an ultimate and flexible", "start": 2443.11, "duration": 2.64}, {"text": "array.", "start": 2445.75, "duration": 0.63}, {"text": "You can move the beads around\nand put them in new arrays,", "start": 2446.38, "duration": 4.08}, {"text": "and identify them later.", "start": 2450.46, "duration": 2.79}, {"text": "Anyway, so we're going to\nintroduce the general way", "start": 2453.25, "duration": 4.62}, {"text": "of making either--", "start": 2457.87, "duration": 3.36}, {"text": "complex chemicals,\nwhether they're", "start": 2461.23, "duration": 2.43}, {"text": "linear polymers like\nproteins or nucleic acids,", "start": 2463.66, "duration": 3.78}, {"text": "or much more tighter\nand small molecules.", "start": 2467.44, "duration": 7.71}, {"text": "But they have similar\nconcepts that you need.", "start": 2475.15, "duration": 1.943}, {"text": "There's the solid phase\nthat I already talked about.", "start": 2477.093, "duration": 2.167}, {"text": "There's the idea of\nprotecting groups,", "start": 2479.26, "duration": 4.5}, {"text": "and the protecting\ngroups are protecting", "start": 2483.76, "duration": 1.89}, {"text": "against a reactive group.", "start": 2485.65, "duration": 1.38}, {"text": "So the highly\nreactive group here", "start": 2487.03, "duration": 1.95}, {"text": "is the phosphoramidite, which\nis this phosphate nitrogen bond.", "start": 2488.98, "duration": 4.11}, {"text": "This is capable of reacting\nwith just about any nitrogen", "start": 2493.09, "duration": 6.39}, {"text": "or oxygen, such as\nthis-- eventually,", "start": 2499.48, "duration": 1.92}, {"text": "once you do protect this\noxygen at the 5 prime position,", "start": 2501.4, "duration": 3.0}, {"text": "these two oxygens are 5 and\n3, just like the ones we've", "start": 2504.4, "duration": 2.302}, {"text": "been talking about all along.", "start": 2506.702, "duration": 1.208}, {"text": "This is the chemical synthesis\nversion of the polymerase", "start": 2507.91, "duration": 3.24}, {"text": "that we've been talking about.", "start": 2511.15, "duration": 1.41}, {"text": "So you have these\nreactive groups", "start": 2512.56, "duration": 2.04}, {"text": "and the protecting groups.", "start": 2514.6, "duration": 3.06}, {"text": "And those are the\nmajor concepts.", "start": 2517.66, "duration": 2.25}, {"text": "Now, let's go through.", "start": 2519.91, "duration": 1.23}, {"text": "This is-- the topic\nhere is proteins.", "start": 2521.14, "duration": 7.11}, {"text": "And we'll talk more\nabout protein synthesis", "start": 2528.25, "duration": 3.36}, {"text": "as part of\nquantitation next time,", "start": 2531.61, "duration": 2.825}, {"text": "and as part of networks in\nthe last three lectures.", "start": 2534.435, "duration": 2.125}, {"text": "But here's a completely\nsynthetic way", "start": 2536.56, "duration": 1.92}, {"text": "of getting short\npeptides, either", "start": 2538.48, "duration": 3.3}, {"text": "by directly synthesizing\nthe peptides", "start": 2541.78, "duration": 1.77}, {"text": "or synthesizing nucleic acid\nthat encodes that peptide", "start": 2543.55, "duration": 3.75}, {"text": "or interferes with the\nproduction of that peptide.", "start": 2547.3, "duration": 2.19}, {"text": "And you can think of these\nas drug-like molecules.", "start": 2549.49, "duration": 2.94}, {"text": "These are naturally related--", "start": 2552.43, "duration": 2.67}, {"text": "they can be analogs of\nnucleic acids and proteins,", "start": 2555.1, "duration": 2.47}, {"text": "not just straight ones.", "start": 2557.57, "duration": 1.993}, {"text": "And we'll talk\nabout opportunities", "start": 2559.563, "duration": 1.417}, {"text": "for making these analogs.", "start": 2560.98, "duration": 2.55}, {"text": "And so by making analogs\nof known proteins", "start": 2563.53, "duration": 3.57}, {"text": "or nucleic acids, you kind\nof have a more immediate", "start": 2567.1, "duration": 4.13}, {"text": "connection between the thing\nthat your computer instructed", "start": 2571.23, "duration": 3.21}, {"text": "the synthesizer to\nmake and your targets.", "start": 2574.44, "duration": 3.0}, {"text": "Well, if you make\na random chemical,", "start": 2577.44, "duration": 2.182}, {"text": "you don't necessarily\nknow what your target is.", "start": 2579.622, "duration": 1.958}, {"text": "But we'll talk\nabout ways of making", "start": 2581.58, "duration": 1.74}, {"text": "slightly less random chemicals.", "start": 2583.32, "duration": 1.83}, {"text": "But this is one way of\nmaking a direct connection.", "start": 2585.15, "duration": 2.49}, {"text": "And the process is\ncyclic in the sense", "start": 2587.64, "duration": 3.51}, {"text": "that each cycle, you\nreturn, and the polymer", "start": 2591.15, "duration": 4.11}, {"text": "gets a little bit longer.", "start": 2595.26, "duration": 1.11}, {"text": "You start with one monomer\non a solid phase, shown", "start": 2596.37, "duration": 3.21}, {"text": "by these little hexagons on the\nfar right side of the slide.", "start": 2599.58, "duration": 6.36}, {"text": "And you add-- you remove\nthe protecting group", "start": 2605.94, "duration": 4.89}, {"text": "on the immobilized polymer,\none protecting group.", "start": 2610.83, "duration": 3.84}, {"text": "And then you bring in\nthis reactive group,", "start": 2614.67, "duration": 1.86}, {"text": "otherwise protected.", "start": 2616.53, "duration": 1.71}, {"text": "And there's really one major\nproduct that you expect.", "start": 2618.24, "duration": 2.97}, {"text": "You wash off all of the excess.", "start": 2621.21, "duration": 1.65}, {"text": "You now have one longer.", "start": 2622.86, "duration": 1.68}, {"text": "You deprotect.", "start": 2624.54, "duration": 0.87}, {"text": "This DMT group is removed.", "start": 2625.41, "duration": 3.03}, {"text": "And you go back up\nand cycle again.", "start": 2628.44, "duration": 2.64}, {"text": "There may be additional\nsteps, such as oxidation,", "start": 2631.08, "duration": 3.22}, {"text": "which will stabilize the\nnew bond that you've made.", "start": 2634.3, "duration": 2.99}, {"text": "Or you can have a capping\nstep that can soak up", "start": 2637.29, "duration": 5.55}, {"text": "any excess that was left over.", "start": 2642.84, "duration": 2.492}, {"text": "But in general, after you're\ndone with all of these cycles,", "start": 2645.332, "duration": 2.458}, {"text": "then there'll be\na step where you", "start": 2647.79, "duration": 2.31}, {"text": "remove the protecting\ngroups altogether and remove", "start": 2650.1, "duration": 2.7}, {"text": "the polymer from the solid\nphase if you so choose.", "start": 2652.8, "duration": 3.03}, {"text": "Or you leave it there,\nif you have an array.", "start": 2655.83, "duration": 2.67}, {"text": "These are other examples\nof protecting groups.", "start": 2658.5, "duration": 3.09}, {"text": "These are now on the bases.", "start": 2661.59, "duration": 1.44}, {"text": "Some bases don't need\nprotection, like thiamines.", "start": 2663.03, "duration": 2.91}, {"text": "If you have an exocyclic\namine, then you", "start": 2665.94, "duration": 1.89}, {"text": "typically need a benzyl or an\nisobutyryl group in blue here,", "start": 2667.83, "duration": 4.29}, {"text": "are the protecting groups.", "start": 2672.12, "duration": 1.155}, {"text": "I said there's an opportunity\nhere for modifying", "start": 2677.1, "duration": 7.65}, {"text": "the nucleotides or\noligopeptides or other chemicals", "start": 2684.75, "duration": 7.41}, {"text": "to make them so that\nthey're related to, but not", "start": 2692.16, "duration": 4.11}, {"text": "identical in every property,\nto normal constituents", "start": 2696.27, "duration": 5.13}, {"text": "of your body or of a bacterial\ncell that you're aiming at.", "start": 2701.4, "duration": 4.8}, {"text": "And why would you want\nto make derivatives?", "start": 2706.2, "duration": 2.01}, {"text": "Why not make the exact thing?", "start": 2708.21, "duration": 1.47}, {"text": "And the reason you want\nto make derivatives", "start": 2709.68, "duration": 1.26}, {"text": "would be, for example, to\nincrease their stability,", "start": 2710.94, "duration": 2.16}, {"text": "or decrease their stability,\nor make them bind more faster", "start": 2713.1, "duration": 6.0}, {"text": "or more irreversibly.", "start": 2719.1, "duration": 1.41}, {"text": "And examples are, in\nthe previous slide,", "start": 2720.51, "duration": 2.64}, {"text": "you can make modified bases.", "start": 2723.15, "duration": 1.56}, {"text": "And in slide 29 here you can\nchange the backbone itself.", "start": 2724.71, "duration": 3.75}, {"text": "You can change the\nribosomes so that they", "start": 2728.46, "duration": 1.83}, {"text": "have bulky groups that prevent\nthe nucleases from getting in,", "start": 2730.29, "duration": 4.14}, {"text": "or they can exchange oxygen\nfor sulfurs or hydrogens", "start": 2734.43, "duration": 6.72}, {"text": "in order to make the\nphosphodiester backbone itself,", "start": 2741.15, "duration": 3.37}, {"text": "which is where\nnucleus is cleaved,", "start": 2744.52, "duration": 2.51}, {"text": "a less attractive,\nless energetically", "start": 2747.03, "duration": 4.17}, {"text": "favorable substrate.", "start": 2751.2, "duration": 3.0}, {"text": "So now, those are\nchemical processes", "start": 2754.2, "duration": 3.79}, {"text": "that, in a certain sense,\nmimic the normal polymerases", "start": 2757.99, "duration": 3.35}, {"text": "and ribosomes in the cell.", "start": 2761.34, "duration": 2.34}, {"text": "And there are analogous\nprocesses to generate chemical", "start": 2763.68, "duration": 3.42}, {"text": "diversity on smaller molecules.", "start": 2767.1, "duration": 3.48}, {"text": "And then there are,\nanalogous to that,", "start": 2770.58, "duration": 4.23}, {"text": "biological mechanisms by which\nyou can make small molecule", "start": 2774.81, "duration": 5.1}, {"text": "diversity which are less\ncyclic than processes", "start": 2779.91, "duration": 5.55}, {"text": "we just talked about.", "start": 2785.46, "duration": 1.26}, {"text": "These are more a set\nof ordered reactions", "start": 2786.72, "duration": 7.86}, {"text": "that has a conceptual\nrepeat, but in a sense,", "start": 2794.58, "duration": 3.88}, {"text": "you can think of it\nas a linear program", "start": 2798.46, "duration": 2.51}, {"text": "that you go from the\nbeginning to the end.", "start": 2800.97, "duration": 2.74}, {"text": "And that's to make\nthese polyketides, which", "start": 2803.71, "duration": 3.17}, {"text": "are shown on the right-hand\nside of the slide.", "start": 2806.88, "duration": 2.13}, {"text": "A large class of\npharmaceuticals,", "start": 2809.01, "duration": 4.05}, {"text": "including most of\nthe antibiotics,", "start": 2813.06, "duration": 1.89}, {"text": "are made by a fairly\nsmall set of organisms,", "start": 2814.95, "duration": 2.91}, {"text": "such as streptomyces\nin certain plants.", "start": 2817.86, "duration": 2.4}, {"text": "And this process\nby which it's made,", "start": 2820.26, "duration": 2.312}, {"text": "which will be illustrated in\nmore detail in the next slide,", "start": 2822.572, "duration": 2.458}, {"text": "is very akin to\nfatty acid synthesis.", "start": 2825.03, "duration": 2.49}, {"text": "Fatty acids are long\nhydrocarbon chains,", "start": 2827.52, "duration": 2.31}, {"text": "which you can think\nof, adding each two", "start": 2829.83, "duration": 3.03}, {"text": "carbons on that fatty\nacid is a process", "start": 2832.86, "duration": 2.85}, {"text": "akin to the one for making these\npolyketide drug-like molecules.", "start": 2835.71, "duration": 4.56}, {"text": "Another way of\nbiologically making", "start": 2840.27, "duration": 2.31}, {"text": "a very compact structure,\nwhich actually uses ribosomes,", "start": 2842.58, "duration": 5.58}, {"text": "but it uses them to make\nvery tight short peptides", "start": 2848.16, "duration": 5.28}, {"text": "and a precursor that then\nfolds with lots of disulfides", "start": 2853.44, "duration": 3.6}, {"text": "to make this small and\nhighly cross-linked.", "start": 2857.04, "duration": 4.71}, {"text": "Now, the fact that these\ncone snails have gone", "start": 2861.75, "duration": 5.46}, {"text": "have gone to the trouble\nof making hundreds", "start": 2867.21, "duration": 1.83}, {"text": "of these different very\nsmall peptides that", "start": 2869.04, "duration": 2.97}, {"text": "have these properties tells\nyou something about what", "start": 2872.01, "duration": 3.72}, {"text": "it is that you want-- that\ndrug-like molecules have", "start": 2875.73, "duration": 3.9}, {"text": "in common.", "start": 2879.63, "duration": 0.6}, {"text": "And that is, they're small, so\nthey diffuse quickly and get", "start": 2880.23, "duration": 5.85}, {"text": "to their site.", "start": 2886.08, "duration": 1.15}, {"text": "And so you can have\nlarge amounts of them", "start": 2887.23, "duration": 1.79}, {"text": "in a small space.", "start": 2889.02, "duration": 1.03}, {"text": "So you can manufacture\nlots of them.", "start": 2890.05, "duration": 2.06}, {"text": "And then they have to be\nhighly cross-linked in order", "start": 2892.11, "duration": 3.57}, {"text": "to maintain the rigidity.", "start": 2895.68, "duration": 1.38}, {"text": "Because they're small,\nthey have less surface area", "start": 2897.06, "duration": 2.67}, {"text": "to bind to their binding pocket.", "start": 2899.73, "duration": 3.91}, {"text": "So to compensate for that, they\nhave to have a lot of rigidity.", "start": 2903.64, "duration": 3.17}, {"text": "And the thing that\nyou lock in rigidly", "start": 2906.81, "duration": 2.4}, {"text": "has to be the correct structure.", "start": 2909.21, "duration": 1.53}, {"text": "It does you no good to\nhave a rigid structure that", "start": 2910.74, "duration": 2.19}, {"text": "isn't really perfectly\ncomplementary to that surface.", "start": 2912.93, "duration": 3.4}, {"text": "And the third source\nof biological diversity", "start": 2916.33, "duration": 3.74}, {"text": "is one you're probably\nmore familiar with,", "start": 2920.07, "duration": 1.75}, {"text": "which is the immune\nreceptors, the B and T cell", "start": 2921.82, "duration": 2.69}, {"text": "receptors, the antibodies,\nand cell-mediated immunity.", "start": 2924.51, "duration": 5.17}, {"text": "And these use\nrecombination machinery", "start": 2929.68, "duration": 7.52}, {"text": "to program various combinations\nof nucleic acid motifs", "start": 2937.2, "duration": 7.74}, {"text": "that encode protein motifs.", "start": 2944.94, "duration": 1.35}, {"text": "And as they do\nthat recombination,", "start": 2946.29, "duration": 1.74}, {"text": "they have further\ndiversification", "start": 2948.03, "duration": 2.1}, {"text": "that occurs due to a\ntemplate-independent", "start": 2950.13, "duration": 2.61}, {"text": "polymerase,\n[? thermotransferase, ?]", "start": 2952.74, "duration": 2.55}, {"text": "which will extend a few\nnucleotides of completely", "start": 2955.29, "duration": 2.76}, {"text": "random nucleic acid sequence\nthat basically incredibly", "start": 2958.05, "duration": 5.58}, {"text": "accelerates the rate of\nmutagenesis, basically", "start": 2963.63, "duration": 3.06}, {"text": "generating sequence de novo.", "start": 2966.69, "duration": 1.44}, {"text": "This is one of the\nexamples in biology", "start": 2968.13, "duration": 2.46}, {"text": "where you generate\nsequence de novo.", "start": 2970.59, "duration": 2.46}, {"text": "And I think that's very apropos\nof this combinatorial topic.", "start": 2973.05, "duration": 6.99}, {"text": "Now, this is a beautiful\nexample from the previous slide.", "start": 2980.04, "duration": 3.99}, {"text": "Those polyketides\non the far right", "start": 2984.03, "duration": 1.77}, {"text": "now are the star of this slide.", "start": 2985.8, "duration": 2.5}, {"text": "And here, in a certain\nsense, nature has--", "start": 2988.3, "duration": 2.66}, {"text": "and now scientists have--\nengineered protein modules", "start": 2990.96, "duration": 3.51}, {"text": "to make this linear\nsequence of events.", "start": 2994.47, "duration": 4.77}, {"text": "You can think of, here,\nyou're using a linear set", "start": 2999.24, "duration": 3.96}, {"text": "of protein domains to program\nvery complicated series", "start": 3003.2, "duration": 4.08}, {"text": "of chemical reactions, the\nsame way the linear sequence", "start": 3007.28, "duration": 2.37}, {"text": "of messenger RNA\ntells the ribosome", "start": 3009.65, "duration": 2.88}, {"text": "to make a series of\nadditions in the protein.", "start": 3012.53, "duration": 4.15}, {"text": "The ribosome catalytic\ncycle is a cycle,", "start": 3016.68, "duration": 4.55}, {"text": "while this is more\na linear tape,", "start": 3021.23, "duration": 2.97}, {"text": "a linear series of events.", "start": 3024.2, "duration": 2.19}, {"text": "The proteins themselves, these\nlittle arrow-shaped things", "start": 3026.39, "duration": 2.61}, {"text": "with boxes in them\nalong the top,", "start": 3029.0, "duration": 3.15}, {"text": "labeled Module 1 through 6,\nthose proteins are, of course,", "start": 3032.15, "duration": 3.81}, {"text": "made on ribosomes.", "start": 3035.96, "duration": 0.9}, {"text": "But then they act kind of like\nthe solid phase synthesis,", "start": 3036.86, "duration": 3.66}, {"text": "where the acyl carrier\nprotein, ACP in the box,", "start": 3040.52, "duration": 2.64}, {"text": "binds to the first\nmonomer, and it", "start": 3043.16, "duration": 2.91}, {"text": "starts transferring\nit from protein", "start": 3046.07, "duration": 2.64}, {"text": "to protein along this\nmulti-domain huge protein.", "start": 3048.71, "duration": 5.267}, {"text": "And there's actually three\nproteins in a row here.", "start": 3053.977, "duration": 2.083}, {"text": "And each of the steps are taken\nin order along the protein,", "start": 3056.06, "duration": 3.06}, {"text": "and they involve things like a\nsynthase step, where you bring", "start": 3059.12, "duration": 3.09}, {"text": "in another monomer, or a\nketo reductase step, KR,", "start": 3062.21, "duration": 4.08}, {"text": "where you'll bring in--", "start": 3066.29, "duration": 2.25}, {"text": "where you'll reduce one\nof the double bonds,", "start": 3068.54, "duration": 4.8}, {"text": "or an acyltransferase step, AT.", "start": 3073.34, "duration": 3.57}, {"text": "But you can see each of these\nhas a substrate specificity.", "start": 3080.99, "duration": 3.03}, {"text": "And by changing the order\nof substrate specificities,", "start": 3084.02, "duration": 3.45}, {"text": "you can build up a huge\ncombinatorial collection here", "start": 3087.47, "duration": 4.23}, {"text": "in microbial communities,\nand also in the laboratory.", "start": 3091.7, "duration": 6.87}, {"text": "Now, protein interaction.", "start": 3098.57, "duration": 1.65}, {"text": "We're just beginning to\ntalk seriously about protein", "start": 3100.22, "duration": 3.36}, {"text": "interaction assays.", "start": 3103.58, "duration": 2.1}, {"text": "I think many of you\neither are or will", "start": 3105.68, "duration": 3.03}, {"text": "be more and more familiar with\nthe protein interaction assays.", "start": 3108.71, "duration": 4.14}, {"text": "In next class, we'll\ntalk about ways", "start": 3112.85, "duration": 3.72}, {"text": "of getting direct\ninformation on protein", "start": 3116.57, "duration": 2.83}, {"text": "through cross-linking\nand mass spectrometry.", "start": 3119.4, "duration": 2.81}, {"text": "Another way is\nindirectly setting up", "start": 3122.21, "duration": 2.16}, {"text": "these reporter\nassays, where you take", "start": 3124.37, "duration": 2.13}, {"text": "advantage of the binding\nproperties of known proteins", "start": 3126.5, "duration": 3.03}, {"text": "to analyze two unknown proteins.", "start": 3129.53, "duration": 2.88}, {"text": "And so a known protein\nmight be, [INAUDIBLE],,", "start": 3132.41, "duration": 2.52}, {"text": "which binds to DNA, and B42,\nwhich activates transcription", "start": 3134.93, "duration": 4.14}, {"text": "of something for which you\nhave a good visual assay,", "start": 3139.07, "duration": 4.56}, {"text": "like [? URO3, ?] life and death.", "start": 3143.63, "duration": 3.93}, {"text": "And by taking these\ntwo knowns, let's say,", "start": 3147.56, "duration": 3.24}, {"text": "in B42, which have\nknown properties--", "start": 3150.8, "duration": 2.4}, {"text": "but they only exert\ntheir properties", "start": 3153.2, "duration": 2.362}, {"text": "when they're brought\ntogether, and they're only", "start": 3155.562, "duration": 1.958}, {"text": "brought together if the\nunknown proteins or partially", "start": 3157.52, "duration": 2.7}, {"text": "known proteins to which they're\nbound interact with each other.", "start": 3160.22, "duration": 4.24}, {"text": "And so this is a\nso-called two-hybrid assay", "start": 3164.46, "duration": 2.99}, {"text": "and variations on it.", "start": 3167.45, "duration": 2.47}, {"text": "And I think we\nmentioned one where", "start": 3169.92, "duration": 2.54}, {"text": "you can characterize nucleic\nacid-protein interactions", "start": 3172.46, "duration": 2.76}, {"text": "with one hybrid assay.", "start": 3175.22, "duration": 1.38}, {"text": "And here, you can\ninhibit this interaction", "start": 3176.6, "duration": 4.08}, {"text": "between the two knowns--", "start": 3180.68, "duration": 2.91}, {"text": "sorry, unknowns or partially\nknown molecules in blue here.", "start": 3183.59, "duration": 4.38}, {"text": "Here's a TGF beta, a growth\nfactor, and a binding protein.", "start": 3187.97, "duration": 8.07}, {"text": "You can inhibit that with\na particular small molecule", "start": 3196.04, "duration": 3.84}, {"text": "or a collection of\nsmall molecules, which", "start": 3199.88, "duration": 1.98}, {"text": "can be introduced from one of\nthese combinatorial syntheses", "start": 3201.86, "duration": 3.72}, {"text": "into an array of\nthese cellular assays.", "start": 3205.58, "duration": 4.08}, {"text": "And you get this\ninformation about--", "start": 3209.66, "duration": 4.38}, {"text": "you can either\ncollect a big data", "start": 3214.04, "duration": 1.98}, {"text": "set of proteins that interact\nfrom a proteomic scale", "start": 3216.02, "duration": 3.48}, {"text": "experiment, or from molecules\nthat inhibit one or more", "start": 3219.5, "duration": 3.42}, {"text": "of those interactions.", "start": 3222.92, "duration": 1.63}, {"text": "This is a source of\ninformation, which", "start": 3224.55, "duration": 2.69}, {"text": "is intrinsically computational\nin the sense-- well,", "start": 3227.24, "duration": 3.052}, {"text": "in the sense that there's\na large amount of it.", "start": 3230.292, "duration": 1.958}, {"text": "You can model the\nthree-dimensional structure", "start": 3232.25, "duration": 2.37}, {"text": "of this interaction if you have\nsufficient data to do that.", "start": 3234.62, "duration": 2.98}, {"text": "And you can model the impact\nof the small molecules", "start": 3237.6, "duration": 3.14}, {"text": "in a structure\nactivity [? since. ?]", "start": 3240.74, "duration": 2.67}, {"text": "Now, if you look at the top\nright-hand part of slide 34", "start": 3243.41, "duration": 4.98}, {"text": "here, you can see\nthis huge diversity", "start": 3248.39, "duration": 2.4}, {"text": "of all of these\ndifferent colored shapes.", "start": 3250.79, "duration": 1.9}, {"text": "And if you wanted to use these\nin a combinatorial assay,", "start": 3252.69, "duration": 4.88}, {"text": "you'd connect them in\nevery pairwise combination", "start": 3257.57, "duration": 3.39}, {"text": "and try them against your\ntarget by some bioassay.", "start": 3260.96, "duration": 3.57}, {"text": "However, if that\nlibrary is too large", "start": 3264.53, "duration": 3.75}, {"text": "either to make or to screen--", "start": 3268.28, "duration": 1.65}, {"text": "typically, to screen--\nthen what you can do", "start": 3269.93, "duration": 1.95}, {"text": "is, you can study a\npart of the molecule", "start": 3271.88, "duration": 4.0}, {"text": "and see-- and then take the\nsubset of the diversity that", "start": 3275.88, "duration": 4.08}, {"text": "can bind, and then\ntake that subset,", "start": 3279.96, "duration": 7.17}, {"text": "characterize it, and now make\nonly the pairwise combinations", "start": 3287.13, "duration": 3.63}, {"text": "of the two half-molecules.", "start": 3290.76, "duration": 2.71}, {"text": "And generally speaking, if\nthe geometry is fairly rigid,", "start": 3293.47, "duration": 7.25}, {"text": "then the binding\nconstant will get--", "start": 3300.72, "duration": 4.32}, {"text": "will be roughly the product\nof the two binding constants.", "start": 3305.04, "duration": 3.19}, {"text": "So if each one has a very\nlow binding constant,", "start": 3308.23, "duration": 2.66}, {"text": "then it will be roughly\nthe square of that.", "start": 3310.89, "duration": 3.94}, {"text": "And you get some point\nof diminishing returns,", "start": 3314.83, "duration": 3.95}, {"text": "eventually.", "start": 3318.78, "duration": 2.43}, {"text": "So this is an example\nof a strategy where", "start": 3321.21, "duration": 3.03}, {"text": "you use a little bit of\nprior knowledge, which", "start": 3324.24, "duration": 3.66}, {"text": "can be empirical or it could be\npurely computational, about how", "start": 3327.9, "duration": 4.56}, {"text": "to limit your library and\nmake interesting combinations.", "start": 3332.46, "duration": 3.57}, {"text": "Now, we've been talking mainly\nabout the kind of chemical", "start": 3339.86, "duration": 2.94}, {"text": "diversity we can get that's\naimed at the ligands that", "start": 3342.8, "duration": 2.55}, {"text": "combine to target proteins.", "start": 3345.35, "duration": 1.62}, {"text": "But now, we want to talk about\nthe source of information", "start": 3346.97, "duration": 3.81}, {"text": "about those target\nproteins itself,", "start": 3350.78, "duration": 2.08}, {"text": "which is another genomics\nproject, structural genomics.", "start": 3352.86, "duration": 8.39}, {"text": "And typically, we want to select\ntargets for binding drugs,", "start": 3361.25, "duration": 6.0}, {"text": "or select targets for solving\nthe structures of proteins", "start": 3367.25, "duration": 3.51}, {"text": "in order to look at their\nligands in more detail.", "start": 3370.76, "duration": 3.96}, {"text": "And how can we do this?", "start": 3374.72, "duration": 3.18}, {"text": "How can we decide which\ntargets are high on our list", "start": 3377.9, "duration": 2.93}, {"text": "to go for next?", "start": 3380.83, "duration": 1.02}, {"text": "We have hundreds of\nproteins for which we", "start": 3381.85, "duration": 1.8}, {"text": "have three-dimensional\nstructures,", "start": 3383.65, "duration": 1.59}, {"text": "and from some of them,\nwe have information", "start": 3385.24, "duration": 4.53}, {"text": "on what ligands they bind.", "start": 3389.77, "duration": 2.76}, {"text": "But these are\nother criteria that", "start": 3392.53, "duration": 1.68}, {"text": "are sometimes used in the\nfield for target selection.", "start": 3394.21, "duration": 3.96}, {"text": "If they are homologous to\nprevious interesting targets,", "start": 3398.17, "duration": 5.88}, {"text": "then that puts them\nhigh on the short list.", "start": 3404.05, "duration": 4.14}, {"text": "If they are conserved--\nand we've talked about how", "start": 3408.19, "duration": 2.19}, {"text": "important conservation\nis from time to time--", "start": 3410.38, "duration": 3.24}, {"text": "then that might be an approach.", "start": 3413.62, "duration": 3.03}, {"text": "If they're conserved\nand you knock it out,", "start": 3416.65, "duration": 4.99}, {"text": "then you might expect\nthat to be lethal.", "start": 3421.64, "duration": 2.0}, {"text": "And that might make it a good\ntarget for an anti-bacterial.", "start": 3423.64, "duration": 6.87}, {"text": "If you want to limit the action\nof your therapy to the surface", "start": 3430.51, "duration": 8.19}, {"text": "in order to, say, reduce\nthe cross-reaction", "start": 3438.7, "duration": 5.28}, {"text": "with internal molecules,\nyou can sometimes", "start": 3443.98, "duration": 4.29}, {"text": "restrict yourself to the\nsurface-acceptable proteins.", "start": 3448.27, "duration": 3.09}, {"text": "And in fact, a very\nlarge class of drugs", "start": 3451.36, "duration": 2.64}, {"text": "is aimed at surface-accessible\nmembrane proteins.", "start": 3454.0, "duration": 5.5}, {"text": "And so very often, those\nare prioritized high.", "start": 3459.5, "duration": 2.6}, {"text": "There are also-- the\nsurface-acceptable proteins are", "start": 3462.1, "duration": 2.49}, {"text": "important if you're\ntalking about vaccines,", "start": 3464.59, "duration": 3.13}, {"text": "which is an\nincreasingly important--", "start": 3467.72, "duration": 2.78}, {"text": "or diagnostics that\nare non-invasive,", "start": 3470.5, "duration": 4.83}, {"text": "or at least not going to\nthe interior of the cell.", "start": 3475.33, "duration": 4.29}, {"text": "And there are ways,\nsay, with microarrays,", "start": 3479.62, "duration": 2.49}, {"text": "that you can ask which\ngenes are differentially", "start": 3482.11, "duration": 2.07}, {"text": "expressed in the disease state.", "start": 3484.18, "duration": 1.41}, {"text": "And that causes\nhigh prioritization.", "start": 3485.59, "duration": 2.19}, {"text": "Now, once you have that\nprioritization, which", "start": 3487.78, "duration": 2.97}, {"text": "comes from, say,\ngenome sequencing", "start": 3490.75, "duration": 2.97}, {"text": "and some of those\nother facts, then we", "start": 3493.72, "duration": 3.96}, {"text": "would like to have--\nyou've got your target.", "start": 3497.68, "duration": 1.89}, {"text": "You've got your\ngenome sequence--", "start": 3499.57, "duration": 1.83}, {"text": "gene sequence for that target.", "start": 3504.34, "duration": 1.812}, {"text": "How, then, do you get the\nthree-dimensional structure", "start": 3506.152, "duration": 2.208}, {"text": "that helps you design\ndrugs or improve", "start": 3508.36, "duration": 4.32}, {"text": "the drugs that you have?", "start": 3512.68, "duration": 1.65}, {"text": "Well, one very\nattractive approach,", "start": 3514.33, "duration": 7.95}, {"text": "given a protein\nsequence which might", "start": 3522.28, "duration": 2.64}, {"text": "get from their deluge\nof genome sequences,", "start": 3524.92, "duration": 3.51}, {"text": "the practical approach\nmight be to start", "start": 3528.43, "duration": 3.72}, {"text": "with this genome sequence--\nthis gene sequence which", "start": 3532.15, "duration": 2.22}, {"text": "is 99.99% accurate, and try to\npredict the three dimensional", "start": 3534.37, "duration": 5.04}, {"text": "structure of the protein\nand its ligand specificity.", "start": 3539.41, "duration": 3.0}, {"text": "And if you walk\nthrough these, these", "start": 3542.41, "duration": 1.695}, {"text": "are kind of ballpark\nestimates, some of them", "start": 3544.105, "duration": 1.875}, {"text": "better than others.", "start": 3545.98, "duration": 1.08}, {"text": "To get from the\nsequence to exons--", "start": 3547.06, "duration": 1.62}, {"text": "we talked about this before--", "start": 3548.68, "duration": 1.44}, {"text": "might be an 80%.", "start": 3550.12, "duration": 1.945}, {"text": "Remember, these numbers really\nshould be false positives,", "start": 3552.065, "duration": 2.375}, {"text": "false negatives, so on.", "start": 3554.44, "duration": 1.72}, {"text": "But this ballpark, 80%, getting\nto exons, exons to genes.", "start": 3556.16, "duration": 5.51}, {"text": "If you aren't privileged\nenough to have the cDNA,", "start": 3561.67, "duration": 3.99}, {"text": "then this is an\nerror-prone process", "start": 3565.66, "duration": 4.14}, {"text": "with maybe a 30% success rate.", "start": 3569.8, "duration": 4.32}, {"text": "Once you have genes\nknowing it's regulation,", "start": 3574.12, "duration": 2.675}, {"text": "whether it's on or off in\nthe particular cell types", "start": 3576.795, "duration": 2.125}, {"text": "you're interested in, is\nvery difficult right now.", "start": 3578.92, "duration": 4.17}, {"text": "Knowing the motifs\nis barely a start", "start": 3583.09, "duration": 4.32}, {"text": "on getting the full regulation.", "start": 3587.41, "duration": 1.54}, {"text": "So I would say 10% or less.", "start": 3588.95, "duration": 2.72}, {"text": "Once you have a regulated gene,\ngetting the protein sequence", "start": 3591.67, "duration": 2.61}, {"text": "is easy.", "start": 3594.28, "duration": 0.75}, {"text": "That's the genetic code.", "start": 3595.03, "duration": 1.35}, {"text": "Getting from the sequence\nto secondary structure", "start": 3596.38, "duration": 2.73}, {"text": "is easy in the context of\nsome of these other things,", "start": 3599.11, "duration": 4.41}, {"text": "but still, the accuracy\nis only around 77%.", "start": 3603.52, "duration": 3.36}, {"text": "I have next to this the\nreference is [? cast, ?]", "start": 3606.88, "duration": 3.36}, {"text": "which is something\nthat is a competition", "start": 3610.24, "duration": 3.3}, {"text": "for computational assessment\nof three-dimensional structure", "start": 3613.54, "duration": 2.88}, {"text": "prediction for proteins that's\nbeen held since, I think, '94,", "start": 3616.42, "duration": 3.69}, {"text": "and the next one is coming\nup in a couple of months.", "start": 3620.11, "duration": 2.64}, {"text": "And this is kind of the\nbig race or bake-off", "start": 3622.75, "duration": 3.52}, {"text": "between the different methods.", "start": 3626.27, "duration": 1.25}, {"text": "Very exciting.", "start": 3627.52, "duration": 1.29}, {"text": "But unfortunately,\nover decades, it's", "start": 3628.81, "duration": 2.27}, {"text": "still hovering around 77%\nfor secondary structure", "start": 3631.08, "duration": 3.13}, {"text": "and about 25% for ab initio\nthree-dimensional structure.", "start": 3634.21, "duration": 4.8}, {"text": "Then even if you have the\nthree-dimensional structure", "start": 3639.01, "duration": 2.55}, {"text": "at adequate accuracy, getting\nthe ligand specificity", "start": 3641.56, "duration": 3.69}, {"text": "is problematic, and it\ndepends on the ligand.", "start": 3645.25, "duration": 3.51}, {"text": "If it's DNA, it's a good case.", "start": 3648.76, "duration": 1.86}, {"text": "If it's a small molecule, it\ncan be as low as 10% or worse.", "start": 3650.62, "duration": 3.96}, {"text": "Now, since each of\nthese are fairly", "start": 3654.58, "duration": 1.92}, {"text": "independent of\nestimates, you can", "start": 3656.5, "duration": 5.1}, {"text": "get an approximate\noverall accuracy", "start": 3661.6, "duration": 3.34}, {"text": "which is a product of\nall of those, which", "start": 3664.94, "duration": 1.91}, {"text": "is dismally small at 0.0005.", "start": 3666.85, "duration": 6.55}, {"text": "And so it behooves one to use\nas many extra-experimental data", "start": 3673.4, "duration": 5.09}, {"text": "as one can, or improve\nthe algorithms that", "start": 3678.49, "duration": 3.09}, {"text": "are weakest in this journey\nfrom genome sequence", "start": 3681.58, "duration": 4.2}, {"text": "to ligand specificity.", "start": 3685.78, "duration": 3.09}, {"text": "We'll pick up this thread\nright after a break", "start": 3688.87, "duration": 4.32}, {"text": "and carry on to\nactually how we get", "start": 3693.19, "duration": 4.23}, {"text": "the three-dimensional\nstructure, whether it's", "start": 3697.42, "duration": 3.3}, {"text": "predictive or experimental, and\nthe computational tasks there.", "start": 3700.72, "duration": 4.47}, {"text": "Thank you.", "start": 3705.19, "duration": 1.38}, {"text": "Take a break.", "start": 3706.57, "duration": 1.79}]
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+[{"text": "[SQUEAKING][RUSTLING][CLICKING]", "start": 0.0, "duration": 2.42}, {"text": "MATTHEW VANDER\nHEIDEN: Last time, we", "start": 9.68, "duration": 1.88}, {"text": "discussed oxidative\nphosphorylation, which", "start": 11.56, "duration": 3.66}, {"text": "is how to couple the NADH\ngenerated from sugar,", "start": 15.22, "duration": 5.49}, {"text": "fatty acids, et cetera; the\noxidation of carbon as a way", "start": 20.71, "duration": 4.68}, {"text": "to carry out favorable\nelectron transfer to oxygen", "start": 25.39, "duration": 3.81}, {"text": "and use that energy release\nto charge a battery--", "start": 29.2, "duration": 3.45}, {"text": "that is, create\nthis delta psi/delta", "start": 32.65, "duration": 3.24}, {"text": "pH that can subsequently be\nused by the battery to do work,", "start": 35.89, "duration": 5.47}, {"text": "including the synthesis of ADP.", "start": 41.36, "duration": 2.87}, {"text": "And of course, this can occur\nat a physiological ATP/ADP ratio", "start": 44.23, "duration": 4.41}, {"text": "and, therefore, allow\nthe cell to couple ATP", "start": 48.64, "duration": 2.98}, {"text": "to ADP conversion to other\nunfavorable processes", "start": 51.62, "duration": 2.6}, {"text": "in the cell.", "start": 54.22, "duration": 1.54}, {"text": "Now, all of these reactions\noccur at the mitochondria.", "start": 55.76, "duration": 2.69}, {"text": "And I drew, here, a\nschematic mitochondria for us", "start": 58.45, "duration": 3.06}, {"text": "just to start.", "start": 61.51, "duration": 1.06}, {"text": "Remember, the mitochondria\nhas its own genome.", "start": 62.57, "duration": 3.72}, {"text": "This is a vestige of the\nsymbiotic relationship that", "start": 66.29, "duration": 3.89}, {"text": "developed long, long ago, where\ntwo prokaryotes came together,", "start": 70.18, "duration": 5.4}, {"text": "leading to this symbiotic\nrelationship-- but of course,", "start": 75.58, "duration": 5.14}, {"text": "the mitochondrial\nDNA encoding many", "start": 80.72, "duration": 2.45}, {"text": "of the key components of\nthis electron transport chain", "start": 83.17, "duration": 4.14}, {"text": "and ATP synthesis machinery\nthat remains in the mitochondria", "start": 87.31, "duration": 4.17}, {"text": "today.", "start": 91.48, "duration": 1.05}, {"text": "Now, ultimately, this process\ninvolves the reoxidation", "start": 92.53, "duration": 3.84}, {"text": "of NADH back to NAD that occurs,\nthat complex I of the electron", "start": 96.37, "duration": 6.69}, {"text": "transport chain.", "start": 103.06, "duration": 1.35}, {"text": "Those electrons are transferred\ninto the Q pool, which", "start": 104.41, "duration": 2.82}, {"text": "then go into complex III to\ncytochrome c to complex IV,", "start": 107.23, "duration": 3.93}, {"text": "ultimately being transferred\nto oxygen as the final electron", "start": 111.16, "duration": 5.97}, {"text": "acceptor.", "start": 117.13, "duration": 0.72}, {"text": "And it's this process of\nfavorable electron transport--", "start": 117.85, "duration": 3.45}, {"text": "that is, electrons\nmoving from a lower", "start": 121.3, "duration": 2.37}, {"text": "to a higher standard\nreduction potential-- that", "start": 123.67, "duration": 2.52}, {"text": "is coupled to the\npumping of protons", "start": 126.19, "duration": 2.19}, {"text": "and the generation of\nthis delta psi/delta pH.", "start": 128.38, "duration": 3.45}, {"text": "Now, we also discussed complex\nII of the electron transport", "start": 131.83, "duration": 3.63}, {"text": "chain, which is identical\nto succinate dehydrogenase", "start": 135.46, "duration": 3.66}, {"text": "in the TCA cycle.", "start": 139.12, "duration": 1.38}, {"text": "This is involving that\nFAD/FADH2, which can, itself,", "start": 140.5, "duration": 5.52}, {"text": "also transfer electrons\nto the Q pool,", "start": 146.02, "duration": 2.58}, {"text": "ultimately passing\nthose to complex III", "start": 148.6, "duration": 2.34}, {"text": "to cytochrome c to\ncomplex IV, again,", "start": 150.94, "duration": 2.91}, {"text": "with oxygen as\nelectron acceptor,", "start": 153.85, "duration": 2.88}, {"text": "ultimately forming\nwhat is essentially", "start": 156.73, "duration": 2.7}, {"text": "two different variations\non the electron transport", "start": 159.43, "duration": 3.87}, {"text": "chain as a way to generate\ndelta psi/delta pH.", "start": 163.3, "duration": 4.17}, {"text": "Now I show here, on the\nslide, that there's really", "start": 167.47, "duration": 4.62}, {"text": "many versions of this\nelectron transport chain,", "start": 172.09, "duration": 2.94}, {"text": "and another one we discussed\nis shown down here.", "start": 175.03, "duration": 2.44}, {"text": "So up here is the typical one to\nregenerate NAD+ using complex I", "start": 177.47, "duration": 5.75}, {"text": "to the Q pool to III to c to IV.", "start": 183.22, "duration": 2.55}, {"text": "Here's the one involving complex\nII, so dehydrogenase reaction", "start": 185.77, "duration": 5.22}, {"text": "via complex II to the Q\npool, complex III, c, IV.", "start": 190.99, "duration": 4.59}, {"text": "And then there's yet a third one\nhere from fatty acid oxidation.", "start": 195.58, "duration": 3.67}, {"text": "So this is Acyl-CoA\ndehydrogenase.", "start": 199.25, "duration": 2.63}, {"text": "Again, like complex\nII, involves FAD/FADH2.", "start": 201.88, "duration": 4.08}, {"text": "This occurs at the\nmembrane, transfers", "start": 205.96, "duration": 2.91}, {"text": "electrons to the Q\npool to III to c to IV,", "start": 208.87, "duration": 3.12}, {"text": "ultimately reducing\noxygen to water.", "start": 211.99, "duration": 3.16}, {"text": "And so the net effect of\nthese various electron", "start": 215.15, "duration": 3.77}, {"text": "transport chains\nwere shown up here", "start": 218.92, "duration": 2.61}, {"text": "is generating this delta\npsi/delta pH, which", "start": 221.53, "duration": 4.14}, {"text": "can then be used to do work.", "start": 225.67, "duration": 2.47}, {"text": "Now, the cool thing\nis is that this", "start": 228.14, "duration": 2.9}, {"text": "is occurring, in this case,\nat the inner mitochondrial", "start": 231.04, "duration": 2.37}, {"text": "membrane.", "start": 233.41, "duration": 0.82}, {"text": "And so you can do work in\nlots of different ways.", "start": 234.23, "duration": 2.66}, {"text": "It doesn't have to be\nnext to the complex.", "start": 236.89, "duration": 1.75}, {"text": "You have a charge\nacross the membrane that", "start": 238.64, "duration": 1.97}, {"text": "can be used different\nplaces in space,", "start": 240.61, "duration": 2.05}, {"text": "such as so-called complex\nV or the F1F0-ATPase,", "start": 242.66, "duration": 4.19}, {"text": "which can use dissipation\nof that proton gradient", "start": 246.85, "duration": 3.48}, {"text": "to drive that rotational\ncatalysis machine we described", "start": 250.33, "duration": 3.66}, {"text": "last time and, ultimately,\ntake ADP plus phosphate", "start": 253.99, "duration": 3.15}, {"text": "and synthesize ATP.", "start": 257.14, "duration": 2.31}, {"text": "But that's not the\nonly work it can do.", "start": 259.45, "duration": 1.65}, {"text": "You can uncouple\nthe whole thing.", "start": 261.1, "duration": 2.13}, {"text": "We discussed these\nuncoupling proteins,", "start": 263.23, "duration": 2.31}, {"text": "which, effectively,\njust let protons leak", "start": 265.54, "duration": 2.58}, {"text": "back across into the membranes,\nthat short-circuiting", "start": 268.12, "duration": 3.45}, {"text": "this potential.", "start": 271.57, "duration": 1.14}, {"text": "And that's a way\nto generate heat.", "start": 272.71, "duration": 2.61}, {"text": "Other type of work\nwe can do is we", "start": 275.32, "duration": 1.86}, {"text": "can use this proton\ngradient to power", "start": 277.18, "duration": 4.02}, {"text": "the transport of other ions.", "start": 281.2, "duration": 2.67}, {"text": "We discussed this happening\nwith ADP/ATP exchange", "start": 283.87, "duration": 3.96}, {"text": "because, of course,\nADP-to-ATP conversion", "start": 287.83, "duration": 2.64}, {"text": "needed in the cytosol to favor\nunfavorable processes there.", "start": 290.47, "duration": 3.36}, {"text": "Need to exchange those in\nand out of the mitochondria,", "start": 293.83, "duration": 2.29}, {"text": "so you can regenerate ATP with\nthe ATP synthase machinery.", "start": 296.12, "duration": 3.83}, {"text": "And yet another thing\nwe talked about is", "start": 299.95, "duration": 1.68}, {"text": "you can use this as a\nway to concentrate ions,", "start": 301.63, "duration": 2.05}, {"text": "such as calcium.", "start": 303.68, "duration": 1.43}, {"text": "And the mitochondria ends\nup being a major calcium", "start": 305.11, "duration": 2.73}, {"text": "store for cells.", "start": 307.84, "duration": 3.02}, {"text": "Now, we discussed last time\nthat this is great having all", "start": 310.86, "duration": 8.31}, {"text": "of these oxidation\nprocesses-- the TCA cycle,", "start": 319.17, "duration": 2.7}, {"text": "fatty acid oxidation--", "start": 321.87, "duration": 1.62}, {"text": "all occurring in the\nmatrix because it", "start": 323.49, "duration": 1.74}, {"text": "gives a location for\nNAD/NADH to happen where", "start": 325.23, "duration": 4.95}, {"text": "it has easy access to this\nelectron transport machinery", "start": 330.18, "duration": 4.41}, {"text": "and the ability to regenerate\nthe NAD necessary to keep these", "start": 334.59, "duration": 3.96}, {"text": "processes going.", "start": 338.55, "duration": 1.63}, {"text": "But of course, the very first\nprocess we talked about happens", "start": 340.18, "duration": 2.87}, {"text": "in the cytosol, and\nthat's glycolysis.", "start": 343.05, "duration": 2.88}, {"text": "And we discussed how\nyou can bring pyruvate", "start": 345.93, "duration": 2.31}, {"text": "into the mitochondria through\nthis mitochondrial pyruvate", "start": 348.24, "duration": 2.56}, {"text": "carrier.", "start": 350.8, "duration": 1.04}, {"text": "Then it has access to the\npyruvate dehydrogenase", "start": 351.84, "duration": 2.82}, {"text": "reaction, which, of course,\ngenerates acetyl-CoA", "start": 354.66, "duration": 3.14}, {"text": "and NADH in the right place.", "start": 357.8, "duration": 2.51}, {"text": "However, if you go way back to\nwhen we discuss fermentation,", "start": 360.31, "duration": 3.05}, {"text": "remember, the reason we had to\nsend pyruvate to fermentation", "start": 363.36, "duration": 3.66}, {"text": "was to regenerate that\nNAD in the cytosol that's", "start": 367.02, "duration": 4.11}, {"text": "necessary to keep\nglycolysis going.", "start": 371.13, "duration": 3.1}, {"text": "Now, of course, if we're\ngoing to fully oxidize", "start": 374.23, "duration": 3.68}, {"text": "pyruvate carbon in\nthe mitochondria,", "start": 377.91, "duration": 2.31}, {"text": "we still have to solve\nthis electron balance", "start": 380.22, "duration": 3.12}, {"text": "problem for glycolysis.", "start": 383.34, "duration": 2.16}, {"text": "And as we discussed,\nwe can solve that", "start": 385.5, "duration": 2.16}, {"text": "by giving those\nelectrons to oxygen.", "start": 387.66, "duration": 2.13}, {"text": "But now you see that there's\nthis additional complication--", "start": 389.79, "duration": 3.21}, {"text": "is that these electrons\nin the form of NADH", "start": 393.0, "duration": 3.48}, {"text": "need to get inside the\nmitochondrial matrix", "start": 396.48, "duration": 2.94}, {"text": "or get to the electron\ntransport chain", "start": 399.42, "duration": 2.64}, {"text": "as a way to use oxygen\nto ultimately dispose", "start": 402.06, "duration": 4.68}, {"text": "of those electrons.", "start": 406.74, "duration": 1.06}, {"text": "And so, effectively,\nthat NADH needs", "start": 407.8, "duration": 2.6}, {"text": "to be gotten to\ncomplex I, which would", "start": 410.4, "duration": 3.03}, {"text": "be the matrix in the\nway we've drawn it here.", "start": 413.43, "duration": 4.47}, {"text": "Now, really, the way that\nthis happens is not direct.", "start": 417.9, "duration": 6.55}, {"text": "So you don't transport\nNADH from the cytosol", "start": 424.45, "duration": 4.8}, {"text": "into the mitochondria.", "start": 429.25, "duration": 2.34}, {"text": "And that's partially because\none of the benefits, remember,", "start": 431.59, "duration": 4.32}, {"text": "of having compartmentalized\nmetabolism", "start": 435.91, "duration": 2.55}, {"text": "is your ability to have\ndifferent conditions;", "start": 438.46, "duration": 2.8}, {"text": "different ATP/ADP\nratios, NAD/NADH ratios", "start": 441.26, "duration": 3.207}, {"text": "in different\ncompartments because that", "start": 444.467, "duration": 1.583}, {"text": "can favor different chemistry.", "start": 446.05, "duration": 2.02}, {"text": "And so the way that you get\nelectrons into the matrix", "start": 448.07, "duration": 5.78}, {"text": "or get electrons to the\nelectron transport chains", "start": 453.85, "duration": 3.0}, {"text": "doesn't occur directly.", "start": 456.85, "duration": 1.41}, {"text": "You do not transport\nNAD or NADH directly.", "start": 458.26, "duration": 4.11}, {"text": "Instead, you use\nso-called shuttles,", "start": 462.37, "duration": 4.85}, {"text": "which are analogous to some\nof the other shuttles we've", "start": 467.22, "duration": 3.27}, {"text": "talked about, in order to get\nmaterials across membranes.", "start": 470.49, "duration": 3.15}, {"text": "In this case, this\nis a way to get", "start": 473.64, "duration": 1.83}, {"text": "electrons generated\nfrom oxidation", "start": 475.47, "duration": 2.88}, {"text": "reactions in the cytosol--", "start": 478.35, "duration": 1.74}, {"text": "production of NADH in\nthe cytosol, things", "start": 480.09, "duration": 2.31}, {"text": "like glycolysis--", "start": 482.4, "duration": 2.64}, {"text": "to the electron transport chain\nso that they can ultimately", "start": 485.04, "duration": 3.48}, {"text": "be transferred to oxygen.", "start": 488.52, "duration": 3.6}, {"text": "And so these shuttles,\nor redox shuttles,", "start": 492.12, "duration": 8.18}, {"text": "actually come in\nseveral different ways", "start": 500.3, "duration": 3.24}, {"text": "that cells can deal with\ncytosolic electrons.", "start": 503.54, "duration": 4.36}, {"text": "And so these shuttles\nalso, in essence,", "start": 507.9, "duration": 6.33}, {"text": "help cells also establish\nthese different conditions,", "start": 514.23, "duration": 4.62}, {"text": "these different NAD/NADH ratios\nin different compartments.", "start": 518.85, "duration": 3.71}, {"text": "And so you can imagine that the\nshuttles themselves could be", "start": 522.56, "duration": 2.5}, {"text": "regulated as a way to do this.", "start": 525.06, "duration": 2.64}, {"text": "Now, there's two\nmajor redox shuttles", "start": 527.7, "duration": 3.0}, {"text": "that allow you to move\nelectrons from the cytosol", "start": 530.7, "duration": 3.69}, {"text": "into the mitochondria, and we'll\ndiscuss those two here next.", "start": 534.39, "duration": 7.08}, {"text": "These are the two\nthat probably are", "start": 541.47, "duration": 2.1}, {"text": "being looked for if you get\nthis question on an MCAT exam", "start": 543.57, "duration": 5.13}, {"text": "or something like that.", "start": 548.7, "duration": 1.602}, {"text": "They're the ones\nthat are described", "start": 550.302, "duration": 1.458}, {"text": "in the text as the way to\nget electrons to the electron", "start": 551.76, "duration": 3.33}, {"text": "transport chain.", "start": 555.09, "duration": 1.29}, {"text": "But however, as we\ngo through them,", "start": 556.38, "duration": 2.53}, {"text": "you will see that there's\na couple different ways", "start": 558.91, "duration": 2.82}, {"text": "one can do this.", "start": 561.73, "duration": 0.74}, {"text": "They basically involve\noxidation and reduction", "start": 562.47, "duration": 3.24}, {"text": "of a pair of molecules on\neither side of the membrane.", "start": 565.71, "duration": 3.96}, {"text": "And there's lots of ways\nyou can do that in addition", "start": 569.67, "duration": 2.49}, {"text": "to these other shuttles.", "start": 572.16, "duration": 2.13}, {"text": "It'll become more clear\nwhat I mean by this,", "start": 574.29, "duration": 1.95}, {"text": "but I guess I just want you\nto know that these are not", "start": 576.24, "duration": 2.79}, {"text": "the only ways one\ncould shuttle electrons", "start": 579.03, "duration": 2.79}, {"text": "into the mitochondria.", "start": 581.82, "duration": 1.44}, {"text": "These are just the major\nways that have been discussed", "start": 583.26, "duration": 5.19}, {"text": "and are usually\ndiscussed in textbooks.", "start": 588.45, "duration": 4.18}, {"text": "So the first shuttle\nsystem is something called", "start": 592.63, "duration": 4.37}, {"text": "the glycerol phosphate shuttle.", "start": 597.0, "duration": 5.865}, {"text": "And so the glycerol\nphosphate shuttle", "start": 605.49, "duration": 3.42}, {"text": "involves a reaction that\nwe've already discussed.", "start": 608.91, "duration": 4.17}, {"text": "So here's our old friend,\ndihyroxyacetone phosphate", "start": 622.75, "duration": 3.86}, {"text": "from glycolysis.", "start": 626.61, "duration": 2.31}, {"text": "Remember when we talked\nabout the generation of", "start": 628.92, "duration": 3.93}, {"text": "and metabolism of\nglycerol, in order", "start": 632.85, "duration": 1.92}, {"text": "to make triacylglycerides,\nphospholipids--", "start": 634.77, "duration": 2.76}, {"text": "remember we described\nthat you can", "start": 637.53, "duration": 2.61}, {"text": "take dihyroxyacetone phosphate.", "start": 640.14, "duration": 2.19}, {"text": "If you use NADH to reduce\nthat ketone to the alcohol,", "start": 646.54, "duration": 15.72}, {"text": "that generates this\nmolecule, glycerol phosphate.", "start": 662.26, "duration": 5.32}, {"text": "And of course, because\nyou're reducing the ketone", "start": 667.58, "duration": 2.55}, {"text": "to the alcohol, something\nelse has to be oxidized.", "start": 670.13, "duration": 2.34}, {"text": "You reoxidized\nNADH back to NAD+,", "start": 672.47, "duration": 3.96}, {"text": "effectively disposing of\nthose electrons from, say,", "start": 676.43, "duration": 5.18}, {"text": "glycolysis that generated\nNADH to regenerate NAD+.", "start": 681.61, "duration": 6.54}, {"text": "Now, rather than use this\nglycerol phosphate and lipid", "start": 688.15, "duration": 2.73}, {"text": "synthesis, turns out\nthere's a complex that", "start": 690.88, "duration": 3.21}, {"text": "can directly transfer\nthose electrons to FAD", "start": 694.09, "duration": 10.85}, {"text": "to generate FADH2.", "start": 704.94, "duration": 4.8}, {"text": "And this complex sits within the\ninner mitochondrial membrane,", "start": 709.74, "duration": 7.01}, {"text": "facing the cytosolic\nside of the membrane.", "start": 716.75, "duration": 4.29}, {"text": "Here's the inner\nmitochondrial membrane.", "start": 724.232, "duration": 2.028}, {"text": "This would be the matrix.", "start": 726.26, "duration": 2.91}, {"text": "And so transferring\nthose electrons", "start": 729.17, "duration": 2.75}, {"text": "to FAD to reduce\nto FADH2 reoxidizes", "start": 731.92, "duration": 5.17}, {"text": "the glycerol phosphate back\nto dihydroxyacetone phosphate.", "start": 737.09, "duration": 3.83}, {"text": "And of course, in this membrane,\nyou can, in this complex,", "start": 740.92, "duration": 3.6}, {"text": "transfer those electrons\nby oxidizing the FAD", "start": 744.52, "duration": 3.96}, {"text": "and sending them to\nthe coenzyme Q pool.", "start": 748.48, "duration": 4.59}, {"text": "That can take the\nubiquinone, makes ubinquinol.", "start": 753.07, "duration": 3.3}, {"text": "Those electrons can\ngo to complex III.", "start": 756.37, "duration": 2.04}, {"text": "That can go to cytochrome C.\nThey can go to complex IV,", "start": 758.41, "duration": 4.38}, {"text": "ultimately ending up reducing\noxygen to water using oxygen", "start": 762.79, "duration": 8.28}, {"text": "as a final electron acceptor.", "start": 771.07, "duration": 2.19}, {"text": "Again, this is effectively\nanother alternative", "start": 773.26, "duration": 5.07}, {"text": "to the electron transport chain.", "start": 778.33, "duration": 2.29}, {"text": "And so I show that\nhere on the slide.", "start": 780.62, "duration": 1.72}, {"text": "And so we've discussed--", "start": 782.34, "duration": 1.29}, {"text": "the complex II-- this is the\nFAD/FADH2 containing enzyme", "start": 788.83, "duration": 4.92}, {"text": "is complex II.", "start": 793.75, "duration": 1.03}, {"text": "Succinate dehydrogenase sits\nin the inner mitochondrial", "start": 794.78, "duration": 3.41}, {"text": "membrane, converts\nsuccinate to fumarate.", "start": 798.19, "duration": 2.97}, {"text": "Those electrons\nend up on up FADH2,", "start": 801.16, "duration": 3.12}, {"text": "can get transferred\nto the Q pool,", "start": 804.28, "duration": 1.445}, {"text": "reoxidizing FAD to complex III\nto cytochrome C to complex IV", "start": 805.725, "duration": 5.695}, {"text": "to oxygen to water.", "start": 811.42, "duration": 2.61}, {"text": "We already discussed acyl-CoA\ndehydrogenase-- same thing.", "start": 814.03, "duration": 3.51}, {"text": "FADH2 containing reaction in\nthere is also in the membrane--", "start": 817.54, "duration": 3.75}, {"text": "ultimately allows another\nversion electron transport", "start": 821.29, "duration": 2.91}, {"text": "chain.", "start": 824.2, "duration": 0.78}, {"text": "And here's yet a third one\ninvolving an FDA using enzyme.", "start": 824.98, "duration": 4.26}, {"text": "The difference is is that these\nhave the oxidation reduction", "start": 829.24, "duration": 4.62}, {"text": "reaction occurring\non the matrix side--", "start": 833.86, "duration": 2.25}, {"text": "succinate to fumarate\non the matrix side--", "start": 836.11, "duration": 2.79}, {"text": "the introduction\nof a double bond", "start": 838.9, "duration": 2.19}, {"text": "for fatty acid oxidation\nand the matrix side.", "start": 841.09, "duration": 2.52}, {"text": "This one here instead\nfaces the cytosolic side.", "start": 843.61, "duration": 3.51}, {"text": "So glycerol 3 phosphate\ncan be reoxidized", "start": 847.12, "duration": 5.01}, {"text": "to dihydroxyacetone phosphate--", "start": 852.13, "duration": 5.09}, {"text": "looks like I have those arrows\ndrawn backwards, sorry--", "start": 857.22, "duration": 2.75}, {"text": "ultimately sending electrons\ninto this glycerol phosphate", "start": 859.97, "duration": 5.04}, {"text": "shuttle, reducing FADH2,\nwhich can be reoxidized", "start": 865.01, "duration": 4.88}, {"text": "by giving those electrons to\nthe Q pool to complex III,", "start": 869.89, "duration": 3.28}, {"text": "to cytochrome C, to\ncomplex IV, ultimately", "start": 873.17, "duration": 3.23}, {"text": "with water serving as the\nfinal electron acceptor,", "start": 876.4, "duration": 4.5}, {"text": "as I've drawn here.", "start": 880.9, "duration": 2.56}, {"text": "Now, if you notice, if\nwe use this system or any", "start": 883.46, "duration": 5.52}, {"text": "of these systems, these\nalternative FAD/FADH2 using", "start": 888.98, "duration": 5.7}, {"text": "electron transport chains,\nyou don't use complex I.", "start": 894.68, "duration": 4.71}, {"text": "Remember, complex I will pump\na proton, complex II will not.", "start": 899.39, "duration": 5.86}, {"text": "And that means that if you\nuse any of these FADH2 using", "start": 905.25, "duration": 4.88}, {"text": "alternative electron\ntransport chains,", "start": 910.13, "duration": 2.25}, {"text": "you pump fewer protons\ninto the cytosol.", "start": 912.38, "duration": 3.36}, {"text": "And so if you donate the\nelectrons to complex I", "start": 915.74, "duration": 3.84}, {"text": "from the matrix,\nyou pump a proton", "start": 919.58, "duration": 2.7}, {"text": "as you go through\ncomplex I to the Q pool", "start": 922.28, "duration": 2.61}, {"text": "if you go through the\nglycerol phosphate shuttle,", "start": 924.89, "duration": 2.73}, {"text": "you avoid complex I, because you\ngive those electrons directly", "start": 927.62, "duration": 3.93}, {"text": "to the glycerol\nphosphate shuttle.", "start": 931.55, "duration": 1.83}, {"text": "And FAD/FADH2 enzyme--\nthose end up in the Q pool.", "start": 933.38, "duration": 3.51}, {"text": "Less protons are pumped.", "start": 936.89, "duration": 2.07}, {"text": "And this is why sometimes\nin textbooks, you'll", "start": 938.96, "duration": 2.58}, {"text": "see that you get less ATP per\nNADH produced in the cytosol", "start": 941.54, "duration": 4.53}, {"text": "than you get for NADH\nproduced in the mitochondria.", "start": 946.07, "duration": 5.35}, {"text": "And this is one of the\nways that you end up", "start": 951.42, "duration": 3.86}, {"text": "with these accounting yields for\nglucose oxidation-- something", "start": 955.28, "duration": 4.2}, {"text": "we'll talk about in a minute.", "start": 959.48, "duration": 2.95}, {"text": "But the deeper reason for this,\nwhich I want you to appreciate,", "start": 962.43, "duration": 2.96}, {"text": "is because FADH2 has a higher\nstandard reduction potential.", "start": 965.39, "duration": 6.79}, {"text": "So the standard reduction\npotential of FAD/FADH2", "start": 972.18, "duration": 8.03}, {"text": "is greater than it\nis for NAD/NADH.", "start": 980.21, "duration": 4.035}, {"text": "In essence, that\nmeans that there's", "start": 987.7, "duration": 2.37}, {"text": "less change in\nstandard reduction", "start": 990.07, "duration": 1.71}, {"text": "potential for transferring FADH2\nelectrons to oxygen as there is", "start": 991.78, "duration": 6.0}, {"text": "for transferring\nelectrons to oxygen.", "start": 997.78, "duration": 3.51}, {"text": "And so less energy released,\nless protons pumped,", "start": 1001.29, "duration": 3.66}, {"text": "and so that's why you get\nless ATP, if you will,", "start": 1004.95, "duration": 4.65}, {"text": "produced going through the\nglycerol phosphate shuttle.", "start": 1009.6, "duration": 5.0}, {"text": "All right.", "start": 1014.6, "duration": 1.85}, {"text": "Next, I want to discuss\nanother alternative shuttle", "start": 1016.45, "duration": 4.92}, {"text": "to get electrons into\nthe mitochondria.", "start": 1021.37, "duration": 2.56}, {"text": "And this involves much more\nwhat I was alluding to earlier.", "start": 1023.93, "duration": 3.38}, {"text": "And that's oxidation\nand reduction", "start": 1027.31, "duration": 2.19}, {"text": "of a pair of metabolites\nthat are transported", "start": 1029.5, "duration": 3.545}, {"text": "across the membrane on\neither side of the membrane,", "start": 1033.045, "duration": 2.125}, {"text": "effectively moving electrons\nfrom one compartment", "start": 1035.17, "duration": 4.32}, {"text": "in the cell to another.", "start": 1039.49, "duration": 1.9}, {"text": "Now, to understand how this\nshuttle works, I have to--", "start": 1041.39, "duration": 4.365}, {"text": "because it's a little\nmore complicated,", "start": 1045.755, "duration": 1.625}, {"text": "I have to first\ndescribe that there's", "start": 1047.38, "duration": 2.37}, {"text": "a relationship between amino\nacids and alpha-keto acids.", "start": 1049.75, "duration": 5.08}, {"text": "And so, what do I mean by that?", "start": 1054.83, "duration": 1.41}, {"text": "Well, here's a alpha-keto acid\nthat we've talked about a lot.", "start": 1056.24, "duration": 7.91}, {"text": "So this is oxaloacetate.", "start": 1064.15, "duration": 3.45}, {"text": "Remember, it's an alpha\nketo-acid because this ketone", "start": 1067.6, "duration": 3.45}, {"text": "is alpha to this\ncarboxylic acid--", "start": 1071.05, "duration": 5.11}, {"text": "so an alpha-keto acid.", "start": 1076.16, "duration": 2.7}, {"text": "Turns out that\nalpha-keto acids are", "start": 1078.86, "duration": 4.34}, {"text": "related to amino acids\nin the following way.", "start": 1083.2, "duration": 6.73}, {"text": "And so if I take\nthat alpha-keto group", "start": 1089.93, "duration": 3.62}, {"text": "and instead make\nit an amino group,", "start": 1093.55, "duration": 6.23}, {"text": "this here is the\namino acid aspartame.", "start": 1099.78, "duration": 3.81}, {"text": "Now, we'll discuss\nlater in the course", "start": 1109.03, "duration": 2.41}, {"text": "the chemistry that allows\nyou to interconvert", "start": 1111.44, "duration": 2.27}, {"text": "this alpha-keto group\nwith this amino group.", "start": 1113.71, "duration": 2.94}, {"text": "But that's effectively where\nyour amino acids come from--", "start": 1116.65, "duration": 4.05}, {"text": "how your amino acids are related\nto other aspects of carbon", "start": 1120.7, "duration": 5.43}, {"text": "metabolism--", "start": 1126.13, "duration": 0.78}, {"text": "Alpha-keto acids that are\ngenerated in metabolism.", "start": 1126.91, "duration": 3.18}, {"text": "And so there's one example--", "start": 1130.09, "duration": 2.82}, {"text": "oxaloacetate and aspartate, an\nalpha-keto acid, an amino acid.", "start": 1132.91, "duration": 6.4}, {"text": "Here's another one.", "start": 1139.31, "duration": 0.905}, {"text": "So this is alpha-ketoglutarate--", "start": 1149.29, "duration": 2.43}, {"text": "an alpha-keto acid.", "start": 1156.51, "duration": 2.8}, {"text": "And if we change that alpha\ngroup to an amino group,", "start": 1159.31, "duration": 11.46}, {"text": "now we get the amino\nacid glutamate.", "start": 1170.77, "duration": 8.42}, {"text": "All right.", "start": 1179.19, "duration": 0.93}, {"text": "To remind you, the three letter\nabbreviation for aspartate", "start": 1180.12, "duration": 4.26}, {"text": "is a-s-p.", "start": 1184.38, "duration": 1.02}, {"text": "The one letter is D. The\nthree letter abbreviation", "start": 1185.4, "duration": 4.18}, {"text": "for glutamate is g-l-u.", "start": 1189.58, "duration": 3.9}, {"text": "And the one letter\nabbreviation is E.", "start": 1193.48, "duration": 2.79}, {"text": "And I just remind you of that in\ncase I use those abbreviations.", "start": 1196.27, "duration": 4.62}, {"text": "But effectively, you can note\nthat if you couple these swaps", "start": 1200.89, "duration": 5.31}, {"text": "to each other--", "start": 1206.2, "duration": 0.99}, {"text": "that is, if I take\noxaloacetate and turn it", "start": 1207.19, "duration": 4.26}, {"text": "into aspartate while at the\nsame time taking glutamate", "start": 1211.45, "duration": 8.17}, {"text": "and turning it into\nalpha-ketoglutarate,", "start": 1219.62, "duration": 3.66}, {"text": "you can see that that\nis a reaction where", "start": 1223.28, "duration": 4.35}, {"text": "all atoms are conserved.", "start": 1227.63, "duration": 2.07}, {"text": "That is, if I turn this amino\nacid into this alpha-keto acid", "start": 1229.7, "duration": 6.27}, {"text": "while at the same time\nturning that alpha-keto acid", "start": 1235.97, "duration": 2.28}, {"text": "into this amino acid, I have\nnot gained or lost any atoms", "start": 1238.25, "duration": 5.43}, {"text": "or molecules in the process.", "start": 1243.68, "duration": 3.03}, {"text": "And we will see\nlater in the course", "start": 1246.71, "duration": 2.07}, {"text": "that these types\nof interconversions", "start": 1248.78, "duration": 2.07}, {"text": "is exactly how you run\nthese reactions to do", "start": 1250.85, "duration": 6.24}, {"text": "these interconversions\nbetween alpha-keto acids", "start": 1257.09, "duration": 2.22}, {"text": "and amino acids.", "start": 1259.31, "duration": 2.67}, {"text": "OK.", "start": 1261.98, "duration": 0.93}, {"text": "Why am I telling you this now?", "start": 1262.91, "duration": 1.5}, {"text": "Because it turns out this\nis central to understand", "start": 1264.41, "duration": 2.79}, {"text": "the other major shuttle,\nwhich is referred", "start": 1267.2, "duration": 4.65}, {"text": "to as the malate-aspartate\nshuttle as another way", "start": 1271.85, "duration": 10.65}, {"text": "to get electrons and\nNADH from the cytosol", "start": 1282.5, "duration": 4.23}, {"text": "into the mitochondria.", "start": 1286.73, "duration": 2.57}, {"text": "All right.", "start": 1289.3, "duration": 0.5}, {"text": "So how does this happen?", "start": 1289.8, "duration": 1.57}, {"text": "So here if you have--", "start": 1291.37, "duration": 3.69}, {"text": "here's oxaloacetate.", "start": 1300.77, "duration": 2.49}, {"text": "This is occurring up\nhere in the cytosol.", "start": 1303.26, "duration": 5.01}, {"text": "OK.", "start": 1308.27, "duration": 1.05}, {"text": "And if we take oxaloacetate\nin the cytosol and we", "start": 1309.32, "duration": 5.82}, {"text": "utilize the malate\ndehydrogenase reaction", "start": 1315.14, "duration": 6.35}, {"text": "that we heard about\nfrom the TCA cycle--", "start": 1321.49, "duration": 2.265}, {"text": "so basically this is the reverse\nof the malate dehydrogenase", "start": 1332.08, "duration": 3.51}, {"text": "reaction we discussed\nin the TCA cycle.", "start": 1335.59, "duration": 2.37}, {"text": "We're going to reduce this\nketone to the alcohol.", "start": 1337.96, "duration": 3.51}, {"text": "NADH is reoxidized to NAD+.", "start": 1341.47, "duration": 3.96}, {"text": "That will generate malate.", "start": 1345.43, "duration": 13.52}, {"text": "And now we've regenerated NAD+\nin the cytosol by putting those", "start": 1358.95, "duration": 6.87}, {"text": "electrons onto oxaloacetate\nto make malate.", "start": 1365.82, "duration": 4.785}, {"text": "All right.", "start": 1370.605, "duration": 1.455}, {"text": "Now, we can take\nthat malate, send it", "start": 1372.06, "duration": 5.55}, {"text": "across the mitochondrial\nmembranes via transporter", "start": 1377.61, "duration": 12.75}, {"text": "to generate, on the matrix\nside of the membrane,", "start": 1390.36, "duration": 5.11}, {"text": "malate, whereas\nfrom the TCA cycle,", "start": 1395.47, "duration": 10.15}, {"text": "we also have malate\ndehydrogenase that can now", "start": 1405.62, "duration": 15.3}, {"text": "reoxidize that carbon from\nthe alcohol to the ketone", "start": 1420.92, "duration": 11.86}, {"text": "and regenerate\noxaloacetate effectively", "start": 1432.78, "duration": 5.22}, {"text": "by carrying out the same\nreaction through a redox pair", "start": 1438.0, "duration": 4.32}, {"text": "on two sides of the membrane.", "start": 1442.32, "duration": 1.53}, {"text": "Effectively what\nI've done is I've", "start": 1443.85, "duration": 2.05}, {"text": "moved the electrons\nfrom NADH in the cytosol", "start": 1445.9, "duration": 3.44}, {"text": "to now being NADH in the\nmitochondrial matrix, where", "start": 1449.34, "duration": 4.44}, {"text": "this can now donate the\nelectrons to complex I,", "start": 1453.78, "duration": 2.73}, {"text": "to the Q pool, to complex III,\nto cytochrome C, to complex IV,", "start": 1456.51, "duration": 4.95}, {"text": "and ultimately to\noxygen, just like it", "start": 1461.46, "duration": 3.84}, {"text": "would for the TCA cycle.", "start": 1465.3, "duration": 4.05}, {"text": "All right.", "start": 1469.35, "duration": 0.5}, {"text": "Now, the simplest\nthing, of course,", "start": 1469.85, "duration": 2.14}, {"text": "would just be to send\nthe oxaloacetate back out", "start": 1471.99, "duration": 2.48}, {"text": "to the cytosol.", "start": 1474.47, "duration": 2.01}, {"text": "But that's not what happens.", "start": 1476.48, "duration": 1.92}, {"text": "Instead, what happens is\nyou turn that oxaloacetate", "start": 1478.4, "duration": 4.2}, {"text": "into aspartate.", "start": 1482.6, "duration": 2.86}, {"text": "This is an alpha-keto acid.", "start": 1485.46, "duration": 1.62}, {"text": "Turn it into the amino acid.", "start": 1487.08, "duration": 2.28}, {"text": "If you do that, you\nbasically at the same time", "start": 1489.36, "duration": 6.77}, {"text": "turn glutamate into\nalpha-ketoglutarate all right.", "start": 1496.13, "duration": 5.76}, {"text": "Turns out it's that\nalpha-ketoglutarate", "start": 1501.89, "duration": 3.28}, {"text": "that is exchanged when you\nbring malate into the cell.", "start": 1505.17, "duration": 5.72}, {"text": "So malate is exchanged\nfor alpha-ketoglutarate.", "start": 1510.89, "duration": 4.83}, {"text": "And at the same time, you\nexchange the aspartate", "start": 1515.72, "duration": 25.6}, {"text": "for a glutamate.", "start": 1541.32, "duration": 3.24}, {"text": "All right.", "start": 1560.39, "duration": 1.08}, {"text": "So now you can take\nthat aspartame,", "start": 1561.47, "duration": 4.23}, {"text": "turn it back into oxaloacetate.", "start": 1565.7, "duration": 3.66}, {"text": "To do so you need\nto balance this.", "start": 1569.36, "duration": 3.36}, {"text": "So you return your\nalpha-ketoglutarate back", "start": 1572.72, "duration": 6.83}, {"text": "into glutamate.", "start": 1579.55, "duration": 2.07}, {"text": "And effectively, this is the\nmalate aspartate shuttle.", "start": 1581.62, "duration": 11.34}, {"text": "OK.", "start": 1592.96, "duration": 0.57}, {"text": "So electrons from oxaloacetate\nto malate, and then malate back", "start": 1593.53, "duration": 8.06}, {"text": "to oxaloacetate moves\nthe electrons on NADH", "start": 1601.59, "duration": 3.18}, {"text": "from the cytosol into\nthe mitochondria.", "start": 1604.77, "duration": 3.12}, {"text": "To get that malate\nacross the membrane,", "start": 1607.89, "duration": 2.07}, {"text": "you exchange it for\nalpha-ketoglutarate", "start": 1609.96, "duration": 2.43}, {"text": "and to maintain carbon\nbalance across the--", "start": 1612.39, "duration": 3.09}, {"text": "and nitrogen balance--\nacross the whole thing.", "start": 1615.48, "duration": 2.55}, {"text": "At the same time, you\nalso exchange an aspartate", "start": 1618.03, "duration": 3.81}, {"text": "for a glutamate, which allows\nyou to basically interconvert", "start": 1621.84, "duration": 8.33}, {"text": "the oxaloacetate\nand the aspartate", "start": 1630.17, "duration": 3.21}, {"text": "on either side of the\nmembrane via interconverting", "start": 1633.38, "duration": 3.27}, {"text": "glutamate and\nalpha-ketoglutarate.", "start": 1636.65, "duration": 2.79}, {"text": "So somewhat confusing\nsystems, but", "start": 1639.44, "duration": 4.47}, {"text": "recognize that the net\neffect is moving NADH", "start": 1643.91, "duration": 3.93}, {"text": "from one side of the\nmembrane to the other.", "start": 1647.84, "duration": 2.65}, {"text": "And that occurs because you're\ninterconverting to redox pairs", "start": 1650.49, "duration": 4.25}, {"text": "in opposite directions-- in this\ncase oxaloacetate and malate--", "start": 1654.74, "duration": 3.51}, {"text": "on either side of the membrane.", "start": 1658.25, "duration": 2.61}, {"text": "And that's why what\nI alluded to earlier,", "start": 1660.86, "duration": 3.85}, {"text": "you can imagine that\nyou could easily come up", "start": 1664.71, "duration": 3.11}, {"text": "with other shuttle systems\nwhere you have a redox", "start": 1667.82, "duration": 2.61}, {"text": "reaction on one\nside of the membrane", "start": 1670.43, "duration": 1.98}, {"text": "and the reverse of that redox\nreaction on the other side", "start": 1672.41, "duration": 2.4}, {"text": "of the membrane.", "start": 1674.81, "duration": 0.99}, {"text": "And as long as you can\nmaintain carbon balance,", "start": 1675.8, "duration": 2.64}, {"text": "the net effect is moving\nelectrons across the membranes", "start": 1678.44, "duration": 4.14}, {"text": "from one compartment to another.", "start": 1682.58, "duration": 2.34}, {"text": "And that is a way to allow\nyou to generate NADH that's", "start": 1684.92, "duration": 4.89}, {"text": "now in the matrix,\nwhich has access", "start": 1689.81, "duration": 1.95}, {"text": "to complex I of the\nelectron transport chain", "start": 1691.76, "duration": 3.45}, {"text": "as we discussed\nnow several time.", "start": 1695.21, "duration": 5.02}, {"text": "All right.", "start": 1700.23, "duration": 0.9}, {"text": "Now we're ready to go through\nand discuss the accounting", "start": 1701.13, "duration": 5.88}, {"text": "that you see--", "start": 1707.01, "duration": 2.31}, {"text": "the accounting that comes up all\nthe time that is in textbooks", "start": 1713.39, "duration": 4.74}, {"text": "and perhaps you memorized\nfrom previous classes", "start": 1718.13, "duration": 3.03}, {"text": "about how the ATP yield\nworks for different pathways.", "start": 1721.16, "duration": 5.4}, {"text": "So hopefully it's\nclear to you by now", "start": 1726.56, "duration": 1.98}, {"text": "that these numbers that\nyou get are estimates.", "start": 1728.54, "duration": 3.91}, {"text": "And that's because there\nis no direct relationship", "start": 1732.45, "duration": 3.38}, {"text": "between NADH or FADH to NATP.", "start": 1735.83, "duration": 5.05}, {"text": "These interconversions occur\nvia oxidative phosphorylation,", "start": 1740.88, "duration": 3.96}, {"text": "these electron transport\nchains, delta psi/delta pH.", "start": 1744.84, "duration": 3.96}, {"text": "And so all of these\nestimates take", "start": 1748.8, "duration": 2.1}, {"text": "into account various\nassumptions about how efficient", "start": 1750.9, "duration": 4.74}, {"text": "the electron transport chain\nis, oxidative phosphorylation", "start": 1755.64, "duration": 3.18}, {"text": "works, bounded, of\ncourse, by the change", "start": 1758.82, "duration": 4.83}, {"text": "in standard reduction potential,\nwhat's the free energy released", "start": 1763.65, "duration": 3.99}, {"text": "from that?", "start": 1767.64, "duration": 0.87}, {"text": "What's the free energy\nto synthesize ADP to ATP.", "start": 1768.51, "duration": 4.68}, {"text": "Of course, those\nrequire assumptions.", "start": 1773.19, "duration": 2.55}, {"text": "And it's, in the end, why if\nyou read different textbooks", "start": 1775.74, "duration": 4.68}, {"text": "and different sources\nyou will find numbers", "start": 1780.42, "duration": 2.7}, {"text": "that are actually a range.", "start": 1783.12, "duration": 1.69}, {"text": "There is no fixed number\nfor what the equivalent is", "start": 1784.81, "duration": 4.61}, {"text": "of an ATP for an NADH.", "start": 1789.42, "duration": 2.34}, {"text": "And that's because it really\ndepends on several variables.", "start": 1791.76, "duration": 3.19}, {"text": "So let's go through what\nthose variables are,", "start": 1794.95, "duration": 3.56}, {"text": "because if we can\nunderstand that,", "start": 1798.51, "duration": 1.44}, {"text": "you really understand\nhow this system works.", "start": 1799.95, "duration": 3.5}, {"text": "So the first variable--", "start": 1803.45, "duration": 1.97}, {"text": "at least if we're talking\nabout something like glucose,", "start": 1805.42, "duration": 2.79}, {"text": "where we generate\nNADH in the cytosol,", "start": 1808.21, "duration": 3.97}, {"text": "we have to consider\nthe redox shuttles.", "start": 1812.18, "duration": 4.91}, {"text": "And hopefully you appreciate\nnow that you have this need", "start": 1817.09, "duration": 4.02}, {"text": "to regenerate NAD in the cytosol\nto keep glycolysis going.", "start": 1821.11, "duration": 3.45}, {"text": "You got to get those electrons\nsomehow to the electron", "start": 1824.56, "duration": 2.49}, {"text": "transport chain.", "start": 1827.05, "duration": 1.26}, {"text": "And I just described for you two\ndifferent ways you can do that.", "start": 1828.31, "duration": 4.44}, {"text": "Now, if I use the glycerol\nphosphate shuttle,", "start": 1832.75, "duration": 2.22}, {"text": "I'm skipping complex\nI altogether.", "start": 1834.97, "duration": 2.89}, {"text": "And so that's not\npumping any protons.", "start": 1837.86, "duration": 2.18}, {"text": "If I'm using the malate\naspartate shuttle,", "start": 1840.04, "duration": 2.58}, {"text": "well, I have all the energetics\nof doing this gymnastics.", "start": 1842.62, "duration": 3.0}, {"text": "But in the end, now I can use\ncomplex I and pump protons.", "start": 1845.62, "duration": 4.59}, {"text": "And so the yield of ATP,\nif you will-- how many", "start": 1850.21, "duration": 4.5}, {"text": "protons I can pump to generate\ndelta psi/delta pH will", "start": 1854.71, "duration": 4.47}, {"text": "be different if I use\nthe glycerol phosphate", "start": 1859.18, "duration": 2.19}, {"text": "shuttle or a shuttle like\nthe malate aspartate shuttle.", "start": 1861.37, "duration": 5.0}, {"text": "The second variable\nin consideration", "start": 1866.37, "duration": 3.03}, {"text": "is, what is the\nefficiency of proton", "start": 1869.4, "duration": 6.15}, {"text": "pumping by the various electron\ntransport chain ETC complexes?", "start": 1875.55, "duration": 9.12}, {"text": "That's not so straightforward\nand, of course,", "start": 1889.31, "duration": 3.73}, {"text": "is going to depend on\na couple of things.", "start": 1893.04, "duration": 2.81}, {"text": "Remember, we spent a long\ntime talking about ATP/ADP,", "start": 1895.85, "duration": 3.81}, {"text": "and how it's the ratio of\nATP/ADP that was really", "start": 1899.66, "duration": 3.6}, {"text": "the energy there,\nbecause, remember,", "start": 1903.26, "duration": 1.92}, {"text": "thermodynamics is\ndependent on that log", "start": 1905.18, "duration": 3.93}, {"text": "of the reactants over the\nproduct's term in the delta G", "start": 1909.11, "duration": 3.69}, {"text": "equation.", "start": 1912.8, "duration": 1.42}, {"text": "Well, that's true also\nfor the NAD/NADH ratio.", "start": 1914.22, "duration": 4.28}, {"text": "And it's also true for how\nhigh the membrane potential is.", "start": 1918.5, "duration": 3.15}, {"text": "And so how efficient\nthis pumping", "start": 1921.65, "duration": 2.55}, {"text": "is going to be is going\nto be depending on what", "start": 1924.2, "duration": 2.73}, {"text": "is the delta psi to begin with,\nand what is the NAD/NADH ratio", "start": 1926.93, "duration": 3.87}, {"text": "or the FAD/FADH2 ratio,\nbecause all of those things", "start": 1930.8, "duration": 4.89}, {"text": "will affect how much\nfree energy there", "start": 1935.69, "duration": 2.46}, {"text": "is to be able to move protons\nfrom one side of the membrane", "start": 1938.15, "duration": 3.78}, {"text": "to the other.", "start": 1941.93, "duration": 2.61}, {"text": "Once I get those protons\nacross the membrane,", "start": 1944.54, "duration": 2.64}, {"text": "then there's the\nquestion of how--", "start": 1947.18, "duration": 3.3}, {"text": "and for lack of a\nbetter word, I'm", "start": 1950.48, "duration": 1.53}, {"text": "going to say tight the\nmembrane is to proton leak.", "start": 1952.01, "duration": 9.71}, {"text": "That is, you can imagine\nthat to make ATP,", "start": 1961.72, "duration": 3.48}, {"text": "I have to send\nthose protons back", "start": 1965.2, "duration": 2.22}, {"text": "through the ATP synthase,\ncomplex V, F1F0-ATPase,", "start": 1967.42, "duration": 3.51}, {"text": "whatever you want to call it.", "start": 1970.93, "duration": 2.08}, {"text": "And if some of\nthose protons just", "start": 1973.01, "duration": 2.18}, {"text": "leak back across the\nmembrane, well, that's", "start": 1975.19, "duration": 2.97}, {"text": "how we generate heat.", "start": 1978.16, "duration": 1.56}, {"text": "And so how tight\nthat membrane is,", "start": 1979.72, "duration": 2.76}, {"text": "that is how coupled\ndelta psi is,", "start": 1982.48, "duration": 6.9}, {"text": "delta pH is to ATP synthesis\nis another variable.", "start": 1989.38, "duration": 5.95}, {"text": "And of course, the last one is,\nis the efficiency of H+ turning", "start": 1995.33, "duration": 12.85}, {"text": "the F0F1-ATPase, which is the\nsame considerations that we", "start": 2008.18, "duration": 5.55}, {"text": "already talked about\nfor number two.", "start": 2013.73, "duration": 1.5}, {"text": "That is, the higher delta\npsi/delta pH, the more free", "start": 2015.23, "duration": 3.93}, {"text": "energy that's stored there\nand the higher or lower", "start": 2019.16, "duration": 3.69}, {"text": "the ATP/ADP ratio is, the easier\nor harder it is to synthesize", "start": 2022.85, "duration": 6.18}, {"text": "ADP.", "start": 2029.03, "duration": 1.5}, {"text": "And so basically,\nthese different things,", "start": 2030.53, "duration": 4.26}, {"text": "two through four, in\ngeneral takes into account", "start": 2034.79, "duration": 5.25}, {"text": "a term called\ncoupled respiration.", "start": 2040.04, "duration": 5.25}, {"text": "By coupled\nrespiration is really,", "start": 2045.29, "duration": 2.43}, {"text": "how tightly is oxidation--", "start": 2047.72, "duration": 3.15}, {"text": "moving electrons on the electron\ntransport chain to oxygen--", "start": 2050.87, "duration": 3.36}, {"text": "to phosphorylation--\nsynthesizing ATP from ADP?", "start": 2054.23, "duration": 5.46}, {"text": "And so, how tight\nor how well-coupled", "start": 2059.69, "duration": 3.6}, {"text": "is respiration to\nphosphorylation really", "start": 2063.29, "duration": 5.429}, {"text": "is a variable that is going to\nvery much depend on conditions.", "start": 2068.719, "duration": 5.641}, {"text": "And so ultimately,\nto give numbers", "start": 2074.36, "duration": 3.48}, {"text": "for what is the ATP produced\nfrom various oxidation", "start": 2077.84, "duration": 4.29}, {"text": "processes, one has\nto make assumptions", "start": 2082.13, "duration": 2.58}, {"text": "about all of these things,\nhow coupled respiration is", "start": 2084.71, "duration": 2.85}, {"text": "and which redox\nshuttles are used?", "start": 2087.56, "duration": 1.619}, {"text": "If it's something\nlike glycolysis,", "start": 2089.179, "duration": 2.04}, {"text": "it involves the cytosol.", "start": 2091.219, "duration": 2.821}, {"text": "And this is why these\nnumbers are made up.", "start": 2094.04, "duration": 2.13}, {"text": "And it makes no sense in my\nview to memorize these numbers.", "start": 2096.17, "duration": 4.32}, {"text": "But I think it is\nimportant to understand", "start": 2100.49, "duration": 3.54}, {"text": "where those numbers come from.", "start": 2104.03, "duration": 2.14}, {"text": "Because if you understand\nthat, that means you understand", "start": 2106.17, "duration": 2.99}, {"text": "all the assumptions and why\nthe numbers are variable,", "start": 2109.16, "duration": 3.54}, {"text": "you really understand\nthe bioenergetics", "start": 2112.7, "duration": 2.55}, {"text": "of what's going\non in metabolism.", "start": 2115.25, "duration": 2.62}, {"text": "All right.", "start": 2117.87, "duration": 0.5}, {"text": "So now let's go through\none of these calculations", "start": 2118.37, "duration": 3.39}, {"text": "just to fully illustrate\nwhat I'm talking about.", "start": 2121.76, "duration": 3.58}, {"text": "So let's go through the\ncalculation for glycolysis.", "start": 2125.34, "duration": 2.59}, {"text": "So if I run glycolysis and\nturn glucose into two pyruvate.", "start": 2127.93, "duration": 6.97}, {"text": "So what do we get from that?", "start": 2134.9, "duration": 3.2}, {"text": "Of course, we get\n2 ATPs produced", "start": 2138.1, "duration": 4.06}, {"text": "and we get two NADHs\nproduced in the cytosol.", "start": 2142.16, "duration": 6.41}, {"text": "OK.", "start": 2148.57, "duration": 2.37}, {"text": "So this is the cytosol.", "start": 2150.94, "duration": 3.35}, {"text": "This is the mitochondria.", "start": 2154.29, "duration": 1.56}, {"text": "All right?", "start": 2155.85, "duration": 1.45}, {"text": "We're going to completely\noxidize that pyruvate.", "start": 2157.3, "duration": 2.24}, {"text": "We send that pyruvate\ninto the mitochondria.", "start": 2159.54, "duration": 3.6}, {"text": "We run the PDH reaction.", "start": 2167.89, "duration": 2.92}, {"text": "That gives us two\nacetyl-CoA, which", "start": 2170.81, "duration": 3.66}, {"text": "is a yield of two more NADHs.", "start": 2174.47, "duration": 6.49}, {"text": "All right?", "start": 2180.96, "duration": 1.05}, {"text": "If we now take those acetyl-CoAs\nand we burn them completely,", "start": 2182.01, "duration": 5.64}, {"text": "two cycles around the TCA cycle.", "start": 2187.65, "duration": 3.6}, {"text": "OK, now we get two more\nFADH2s and six NADHs--", "start": 2191.25, "duration": 11.93}, {"text": "one FADH2, three NADHs from\neach turn, as well as a GDP.", "start": 2203.18, "duration": 4.53}, {"text": "And so that's a total of two\nFADH2, six NADHs, and two GTPs.", "start": 2207.71, "duration": 6.54}, {"text": "And so now if I come\ntogether, what is our yield?", "start": 2214.25, "duration": 5.19}, {"text": "Well, from the\nmitochondria I've generated", "start": 2219.44, "duration": 3.81}, {"text": "a total of two FADH2s and\nsix, seven, eight NADHs.", "start": 2223.25, "duration": 7.004}, {"text": "And then up here, there's\nan additional two NADHs", "start": 2233.0, "duration": 5.28}, {"text": "that are made in\nthe cytosol, and so", "start": 2238.28, "duration": 2.4}, {"text": "have to access the electron\ntransport chain via a shuttle.", "start": 2240.68, "duration": 5.63}, {"text": "A typical number that's\ngiven is you get 1.58 ATP", "start": 2246.31, "duration": 5.58}, {"text": "for something that has\nto access via shuttle,", "start": 2251.89, "duration": 3.36}, {"text": "or on FADH2, that\nwould make sense,", "start": 2255.25, "duration": 5.52}, {"text": "because FADH2 is really the\nsame as a glycerol phosphate", "start": 2260.77, "duration": 3.6}, {"text": "shuttle.", "start": 2264.37, "duration": 0.87}, {"text": "And so if I do that, that\nwould be three ATP from the two", "start": 2265.24, "duration": 5.34}, {"text": "glycolysis NADHs and three ATP\nfrom the two TCA cycle FADH2s,", "start": 2270.58, "duration": 10.14}, {"text": "because the NADHs produced\nin the matrix can generate", "start": 2280.72, "duration": 5.22}, {"text": "POM protons via complex I.\nOftentimes, that's said to be,", "start": 2285.94, "duration": 3.99}, {"text": "oh, that's about 2 and 1/2 ATP.", "start": 2289.93, "duration": 2.22}, {"text": "So 8 times 2.5 is 20 ATP.", "start": 2292.15, "duration": 3.91}, {"text": "And if we had all\nthese numbers together,", "start": 2296.06, "duration": 1.73}, {"text": "20 plus 3 plus 3 plus 2 plus\n2, that is a total of 30", "start": 2297.79, "duration": 9.42}, {"text": "ATP per glucose that's\ncompletely oxidized to CO2.", "start": 2307.21, "duration": 7.83}, {"text": "OK?", "start": 2315.04, "duration": 1.14}, {"text": "So 26 ATP over here plus another\n2 from GTP plus another 2", "start": 2316.18, "duration": 9.83}, {"text": "from glycolysis is a total\nof 20 ATP per glucose.", "start": 2326.01, "duration": 4.56}, {"text": "That is a number.", "start": 2330.57, "duration": 0.9}, {"text": "It made certain assumptions.", "start": 2331.47, "duration": 1.53}, {"text": "Obviously, if I assume that this\nis not the glycerol phosphate", "start": 2333.0, "duration": 5.4}, {"text": "shuttle but instead the\nmalate aspartate shuttle,", "start": 2338.4, "duration": 2.4}, {"text": "maybe I bump this number up\nby multiplying that by 2.5.", "start": 2340.8, "duration": 4.35}, {"text": "Maybe I use different\nconversion factors.", "start": 2345.15, "duration": 3.09}, {"text": "And if you read\nin textbooks, you", "start": 2348.24, "duration": 2.37}, {"text": "get numbers that\nrange from 30 to 36.", "start": 2350.61, "duration": 3.48}, {"text": "I think the highest I've ever\nseen is 38 ATP per glucose.", "start": 2354.09, "duration": 5.4}, {"text": "And the fact that you\nactually see this range really", "start": 2359.49, "duration": 2.88}, {"text": "reflects the different\nauthors of textbooks,", "start": 2362.37, "duration": 3.66}, {"text": "or whoever writes these things,\nmakes different assumptions", "start": 2366.03, "duration": 3.09}, {"text": "about all of these\nthings over here", "start": 2369.12, "duration": 3.51}, {"text": "to understand how to\nmake these conversions.", "start": 2372.63, "duration": 2.55}, {"text": "But the important thing is\nrealizing that these are not", "start": 2375.18, "duration": 2.4}, {"text": "real numbers.", "start": 2377.58, "duration": 1.64}, {"text": "All right.", "start": 2379.22, "duration": 0.5}, {"text": "Let's quickly go\nthrough and just do", "start": 2379.72, "duration": 2.43}, {"text": "the similar exercise one last\ntime just to come back to.", "start": 2382.15, "duration": 2.94}, {"text": "I'm not going to go\nthrough as much detail.", "start": 2385.09, "duration": 2.52}, {"text": "But we talked about\nthat 6:0 fatty acid", "start": 2387.61, "duration": 3.03}, {"text": "that we did accounting\nfor earlier.", "start": 2390.64, "duration": 2.01}, {"text": "If you look back in your\nnotes, what we wrote down", "start": 2392.65, "duration": 2.79}, {"text": "is that from completely\noxidizing that fully saturated", "start": 2395.44, "duration": 4.77}, {"text": "six carbon fatty acid, we got\none ATP, 11 and ADHDs, and five", "start": 2400.21, "duration": 9.76}, {"text": "FADH2s.", "start": 2409.97, "duration": 0.5}, {"text": "Remember, all these\nare being generated", "start": 2413.96, "duration": 2.3}, {"text": "in the-- all these NADHs\nand FADH2s are already", "start": 2416.26, "duration": 4.59}, {"text": "in the mitochondria.", "start": 2420.85, "duration": 1.47}, {"text": "And so if we just use the\nsame conversion factors", "start": 2422.32, "duration": 3.75}, {"text": "that we used for over there in\nour calculation for glycolysis,", "start": 2426.07, "duration": 5.1}, {"text": "what we get is 27.5 ATP\nfor the NADHs and 7.5 ATP", "start": 2431.17, "duration": 13.11}, {"text": "for the FADH2s, which is\na total of 35 ATP for--", "start": 2444.28, "duration": 10.36}, {"text": "35 plus the one,\nso a total of 36", "start": 2458.13, "duration": 7.19}, {"text": "ATP from complete oxidation\nof our six carbon fatty acid,", "start": 2465.32, "duration": 6.007}, {"text": "which is certainly\ngreater than the 30", "start": 2471.327, "duration": 1.583}, {"text": "ATP we got from complete\noxidation of glucose.", "start": 2472.91, "duration": 4.29}, {"text": "That makes sense.", "start": 2477.2, "duration": 1.53}, {"text": "Fatty acids are more\nreduced than glucose--", "start": 2478.73, "duration": 2.73}, {"text": "more calories, should be\nable to get more from it.", "start": 2481.46, "duration": 3.18}, {"text": "And this calculation\nillustrates that we get that.", "start": 2484.64, "duration": 3.83}, {"text": "The typical\ncalculation in textbook", "start": 2488.47, "duration": 2.64}, {"text": "usually describes complete\noxidation of a 16:0--", "start": 2491.11, "duration": 4.62}, {"text": "a fully saturated 16\ncarbon fatty acid.", "start": 2495.73, "duration": 3.87}, {"text": "That's palmitate.", "start": 2499.6, "duration": 0.93}, {"text": "That's one of the most abundant\nfatty acids in the cell.", "start": 2500.53, "duration": 3.3}, {"text": "This, if you\ncompletely oxidize it,", "start": 2503.83, "duration": 2.52}, {"text": "the number and a\nlot of textbooks", "start": 2506.35, "duration": 2.07}, {"text": "is 106 ATP per palmitate\ncompletely oxidized to CO2.", "start": 2508.42, "duration": 9.12}, {"text": "If you're so inclined,\nyou can go through", "start": 2517.54, "duration": 2.25}, {"text": "and do the calculations yourself\nand see if you agree with that.", "start": 2519.79, "duration": 4.36}, {"text": "But the key point of all of this\naccounting is that none of this", "start": 2524.15, "duration": 3.2}, {"text": "are real numbers.", "start": 2527.35, "duration": 1.63}, {"text": "And I hope you now\nbetter appreciate", "start": 2528.98, "duration": 2.87}, {"text": "what energy really means--", "start": 2531.85, "duration": 2.88}, {"text": "that is, how oxidation of\ncarbon by being favorable", "start": 2534.73, "duration": 4.71}, {"text": "can be coupled either to direct\ncharging of an ATP/ADT ratio", "start": 2539.44, "duration": 6.78}, {"text": "as occurs in the GAPDH\nstep of glycolysis,", "start": 2546.22, "duration": 5.22}, {"text": "as well as the\nsuccinic thiokinase", "start": 2551.44, "duration": 2.94}, {"text": "step of the TCA cycle.", "start": 2554.38, "duration": 1.95}, {"text": "But most energy\ntransduction involves", "start": 2556.33, "duration": 3.18}, {"text": "this charging up\nNAD/NADH ratios,", "start": 2559.51, "duration": 4.29}, {"text": "or reactions that are\ncoupled to FAD/FADH2", "start": 2563.8, "duration": 3.87}, {"text": "via these membrane complexes\nthat ultimately lead", "start": 2567.67, "duration": 4.38}, {"text": "to this favorable\nelectron transport", "start": 2572.05, "duration": 2.88}, {"text": "from lower to higher standard\nreduction potentials.", "start": 2574.93, "duration": 4.77}, {"text": "That favorable\nelectron transport", "start": 2579.7, "duration": 2.46}, {"text": "can be used to create a battery,\na delta psi/delta pH, which", "start": 2582.16, "duration": 3.87}, {"text": "can then be coupled\nto do other work,", "start": 2586.03, "duration": 2.44}, {"text": "including synthesizing ATP at\nthe high ATP/ADP ratio that", "start": 2588.47, "duration": 4.7}, {"text": "can then be used\nby other reactions", "start": 2593.17, "duration": 2.46}, {"text": "in the cell that would otherwise\nbe unfavorable and allow cells", "start": 2595.63, "duration": 4.47}, {"text": "to basically extract\nenergy from its environment", "start": 2600.1, "duration": 3.69}, {"text": "in order to fuel the processes\nthat are unfavorable and are", "start": 2603.79, "duration": 4.74}, {"text": "necessary to sustain life.", "start": 2608.53, "duration": 3.33}, {"text": "All right.", "start": 2611.86, "duration": 1.925}, {"text": "Great.", "start": 2613.785, "duration": 0.5}, {"text": "So thus far, we have\nfocused almost entirely", "start": 2620.51, "duration": 6.76}, {"text": "on how you oxidized carbon\nas a way to release energy.", "start": 2627.27, "duration": 6.89}, {"text": "And that's great.", "start": 2634.16, "duration": 1.43}, {"text": "But of course,\nthat reduced carbon", "start": 2635.59, "duration": 2.29}, {"text": "has to come from\nsomewhere to begin with.", "start": 2637.88, "duration": 3.42}, {"text": "And every one of us\nlearned in grade school", "start": 2641.3, "duration": 3.57}, {"text": "that the energy for all life\nultimately comes from the sun.", "start": 2644.87, "duration": 4.35}, {"text": "And that's, of course,\nphotosynthesis.", "start": 2649.22, "duration": 1.86}, {"text": "And now I want to\nturn to beginning", "start": 2651.08, "duration": 2.52}, {"text": "to discuss photosynthesis\nand how it works.", "start": 2653.6, "duration": 4.51}, {"text": "In other words, how does\nlife harvest solar energy", "start": 2658.11, "duration": 3.77}, {"text": "in a usable form that ultimately\ninvolves using atmospheric CO2,", "start": 2661.88, "duration": 9.67}, {"text": "which gets reduced\nto generate reduced", "start": 2671.55, "duration": 3.99}, {"text": "carbon that, of\ncourse, originally", "start": 2675.54, "duration": 2.52}, {"text": "occurred because plants--", "start": 2678.06, "duration": 2.73}, {"text": "or, any photosynthetic organism\nhas the same issues as us.", "start": 2680.79, "duration": 4.2}, {"text": "That is, to fight\nthermodynamics, maintain,", "start": 2684.99, "duration": 3.66}, {"text": "and survive.", "start": 2688.65, "duration": 1.08}, {"text": "It constantly has to be charging\nan ATP/ADP ratio in order", "start": 2689.73, "duration": 4.68}, {"text": "to fuel the otherwise\nunfavorable processes that", "start": 2694.41, "duration": 3.66}, {"text": "are required to maintain\norder in the cell.", "start": 2698.07, "duration": 4.53}, {"text": "This has to occur during\nthe day when the sun is out", "start": 2702.6, "duration": 2.85}, {"text": "and there's light\nenergy photosynthesis.", "start": 2705.45, "duration": 2.7}, {"text": "But also has to occur\nat night, or at times", "start": 2708.15, "duration": 2.67}, {"text": "when there is no sun.", "start": 2710.82, "duration": 1.5}, {"text": "And so thus, plants basically\nstored energy as reduced carbon", "start": 2712.32, "duration": 6.75}, {"text": "so that they had something\nto eat at night-- that is,", "start": 2719.07, "duration": 2.7}, {"text": "to keep their\nATP/ADP ratios high--", "start": 2721.77, "duration": 2.85}, {"text": "at night so they can do all\nthese catabolic processes", "start": 2724.62, "duration": 3.21}, {"text": "at night.", "start": 2727.83, "duration": 1.38}, {"text": "Now, fortunately\nfor us, the fact", "start": 2729.21, "duration": 3.33}, {"text": "that photosynthetic organisms\nstored all this reduced carbon", "start": 2732.54, "duration": 4.05}, {"text": "allowed other life,\nlike us, to evolve", "start": 2736.59, "duration": 3.36}, {"text": "that is entirely dependent\non photosynthetic organisms", "start": 2739.95, "duration": 5.25}, {"text": "either directly or\nindirectly for food.", "start": 2745.2, "duration": 4.18}, {"text": "And so photosynthesis also is\nthe process that ultimately", "start": 2749.38, "duration": 5.78}, {"text": "oxygenated our atmosphere.", "start": 2755.16, "duration": 4.51}, {"text": "Aerobic life, also something\nthat was necessary for us", "start": 2759.67, "duration": 3.45}, {"text": "to survive because oxygen is\nsuch a key electron acceptor,", "start": 2763.12, "duration": 4.65}, {"text": "really key to our energetics--", "start": 2767.77, "duration": 2.98}, {"text": "well, the fact that\nphotosynthetic organisms", "start": 2770.75, "duration": 2.39}, {"text": "put oxygen in our\natmosphere also", "start": 2773.14, "duration": 3.06}, {"text": "was really essential for aerobic\nlife, us, to ultimately evolve.", "start": 2776.2, "duration": 7.17}, {"text": "And so photosynthesis is often,\nin biochemistry courses, almost", "start": 2783.37, "duration": 5.16}, {"text": "a sidelight and\nforgotten process.", "start": 2788.53, "duration": 3.13}, {"text": "But of course, it is\nreally, really central", "start": 2791.66, "duration": 2.75}, {"text": "to how life works,\nbecause no life", "start": 2794.41, "duration": 2.43}, {"text": "could exist without\nphotosynthesis", "start": 2796.84, "duration": 2.1}, {"text": "and the conditions\nthat allowed aerobic--", "start": 2798.94, "duration": 2.76}, {"text": "most multicellular\nlife that we know", "start": 2801.7, "duration": 2.01}, {"text": "of that's not photosynthetic,\nincluding ourselves,", "start": 2803.71, "duration": 3.18}, {"text": "could not have evolved\nwithout photosynthesis", "start": 2806.89, "duration": 3.24}, {"text": "oxygenating the\natmosphere and generating", "start": 2810.13, "duration": 2.64}, {"text": "all this reduced carbon.", "start": 2812.77, "duration": 1.62}, {"text": "That, really, is where we\nget our energy from as food.", "start": 2814.39, "duration": 4.98}, {"text": "Now, you also learned\nin grade school,", "start": 2819.37, "duration": 3.39}, {"text": "when you learned that life\ndepends on energy of the sun,", "start": 2822.76, "duration": 3.57}, {"text": "that the process\nthat life uses is", "start": 2826.33, "duration": 3.06}, {"text": "this mysterious photosynthesis.", "start": 2829.39, "duration": 3.69}, {"text": "Well, as we go through\nthis over the rest of today", "start": 2833.08, "duration": 2.28}, {"text": "and in the next lecture,\nI want you to appreciate", "start": 2835.36, "duration": 2.43}, {"text": "what photosynthesis is.", "start": 2837.79, "duration": 2.43}, {"text": "And that is how life\nreally takes solar energy", "start": 2840.22, "duration": 5.91}, {"text": "and harvests that energy in\na biologically useful form,", "start": 2846.13, "duration": 4.86}, {"text": "bearing in mind all of the\nconcepts that we've already", "start": 2850.99, "duration": 4.32}, {"text": "talked about, because that will\nultimately help you understand", "start": 2855.31, "duration": 5.8}, {"text": "how that energy from the\nsun is used to make all", "start": 2861.11, "duration": 4.62}, {"text": "this reduced carbon,\nthis carbohydrate and fat", "start": 2865.73, "duration": 3.45}, {"text": "that is energy that we can use\nfor later, and also, of course,", "start": 2869.18, "duration": 4.24}, {"text": "allows how photosynthetic\norganisms can use light", "start": 2873.42, "duration": 3.8}, {"text": "from the sun to just\npower things directly", "start": 2877.22, "duration": 2.46}, {"text": "from that solar battery,\nand ultimately, of course,", "start": 2879.68, "duration": 4.41}, {"text": "you should appreciate that\nthese things all came first.", "start": 2884.09, "duration": 4.94}, {"text": "Photosynthesis\nobviously existed first.", "start": 2889.03, "duration": 2.7}, {"text": "And so most of what we\nalready talked about--", "start": 2891.73, "duration": 2.79}, {"text": "well, we'll draw parallels when\nwe talk about photosynthesis", "start": 2894.52, "duration": 3.18}, {"text": "to the stuff we already know.", "start": 2897.7, "duration": 1.62}, {"text": "Of course, photosynthesis\ncame first.", "start": 2899.32, "duration": 1.97}, {"text": "And the stuff you've\nalready learned about", "start": 2901.29, "duration": 1.75}, {"text": "evolved from photosynthesis.", "start": 2903.04, "duration": 3.45}, {"text": "All right.", "start": 2906.49, "duration": 1.11}, {"text": "Now, like all pathways,\nphotosynthesis also", "start": 2907.6, "duration": 4.17}, {"text": "has to follow the same rules\nand laws of thermodynamics that", "start": 2911.77, "duration": 3.9}, {"text": "were true for all pathways.", "start": 2915.67, "duration": 1.86}, {"text": "So plants and animals have\nto follow the same rules.", "start": 2917.53, "duration": 4.36}, {"text": "And so what is photosynthesis?", "start": 2921.89, "duration": 2.33}, {"text": "Well, it's ultimately CO2\nin the atmosphere that", "start": 2924.22, "duration": 4.62}, {"text": "gets reduced to carbohydrate.", "start": 2928.84, "duration": 4.26}, {"text": "That's classically\nphotosynthesis.", "start": 2936.5, "duration": 1.74}, {"text": "But, of course, plants\nalso make fatty acids.", "start": 2938.24, "duration": 4.83}, {"text": "OK?", "start": 2943.07, "duration": 1.38}, {"text": "This is carbon reduction.", "start": 2944.45, "duration": 4.38}, {"text": "Remember, carbon oxidation\ngenerally is favorable.", "start": 2948.83, "duration": 4.26}, {"text": "Carbon reduction is not.", "start": 2953.09, "duration": 2.25}, {"text": "Delta G naught prime for\nthis is greater than 0.", "start": 2955.34, "duration": 5.49}, {"text": "This direction is favored.", "start": 2960.83, "duration": 1.68}, {"text": "That direction is\nnot, which means", "start": 2962.51, "duration": 2.25}, {"text": "you need energy input\nto reduce that CO2", "start": 2964.76, "duration": 3.99}, {"text": "to carbohydrate or fatty acid.", "start": 2968.75, "duration": 2.19}, {"text": "And of course, it's the sun's\nenergy, the solar energy,", "start": 2970.94, "duration": 4.35}, {"text": "that ultimately must be\ndone to make this favorable.", "start": 2975.29, "duration": 5.24}, {"text": "Now we're reducing carbon.", "start": 2980.53, "duration": 2.43}, {"text": "That means we need\nto add electrons.", "start": 2982.96, "duration": 2.79}, {"text": "Those electrons have\nto come from somewhere.", "start": 2985.75, "duration": 2.68}, {"text": "And so we're\nreducing the carbon.", "start": 2988.43, "duration": 3.32}, {"text": "That means something\nelse has to be oxidized.", "start": 2991.75, "duration": 2.46}, {"text": "Just like when we\noxidized carbon,", "start": 2994.21, "duration": 2.34}, {"text": "those electrons had\nto go somewhere,", "start": 2996.55, "duration": 1.62}, {"text": "something else\nhad to be reduced.", "start": 2998.17, "duration": 2.13}, {"text": "That was pyruvate to\nlactate and fermentation,", "start": 3000.3, "duration": 2.61}, {"text": "or oxygen to water via all of\nthe oxidative phosphorylation", "start": 3002.91, "duration": 5.16}, {"text": "things we just talked about.", "start": 3008.07, "duration": 1.62}, {"text": "And so in this case,\nthose electrons", "start": 3009.69, "duration": 1.5}, {"text": "have to come from somewhere.", "start": 3011.19, "duration": 1.51}, {"text": "And those electrons ultimately,\nfor photosynthesis--", "start": 3012.7, "duration": 4.64}, {"text": "this reduction,\nthe electrons come", "start": 3017.34, "duration": 2.31}, {"text": "from oxidation,\nultimately, of water,", "start": 3019.65, "duration": 6.77}, {"text": "which will generate oxygen.\nAnd this is effectively then", "start": 3026.42, "duration": 7.6}, {"text": "the reverse of what\nyou learned about", "start": 3034.02, "duration": 2.37}, {"text": "for the mitochondrial\nelectron transport.", "start": 3036.39, "duration": 3.45}, {"text": "Why this?", "start": 3039.84, "duration": 1.05}, {"text": "Well, water is very abundant,\nhas been for all of life", "start": 3040.89, "duration": 9.09}, {"text": "on Earth.", "start": 3049.98, "duration": 0.72}, {"text": "Water is-- obviously,\nlife depends on water.", "start": 3050.7, "duration": 4.78}, {"text": "And so you can oxidize\nthe water to generate", "start": 3055.48, "duration": 7.34}, {"text": "oxygen. This will obviously\ngenerate electrons that", "start": 3062.82, "duration": 3.21}, {"text": "can be used to reduce carbon.", "start": 3066.03, "duration": 3.36}, {"text": "And it's effectively the\nphotosynthetic oxidation", "start": 3069.39, "duration": 3.75}, {"text": "of water to make oxygen that\nwas the source of oxygen", "start": 3073.14, "duration": 4.83}, {"text": "in the atmosphere\nthat, really, today", "start": 3077.97, "duration": 3.06}, {"text": "makes aerobic life possible.", "start": 3081.03, "duration": 3.01}, {"text": "Now, of course, the fact that\noxygen is a good electron", "start": 3084.04, "duration": 3.318}, {"text": "acceptor-- we've been\ntalking about this forever.", "start": 3087.358, "duration": 2.042}, {"text": "This means that, of\ncourse, you might", "start": 3089.4, "duration": 2.31}, {"text": "guess that delta G naught\nprime for this process", "start": 3091.71, "duration": 4.47}, {"text": "is not going to be favorable.", "start": 3096.18, "duration": 3.48}, {"text": "To put it another way,\noxygen is a great electron", "start": 3099.66, "duration": 3.03}, {"text": "acceptor and water is\na poor electron donor.", "start": 3102.69, "duration": 3.67}, {"text": "And so, really, the\nway photosynthesis--", "start": 3106.36, "duration": 2.99}, {"text": "the magic of\nphotosynthesis, if you will,", "start": 3109.35, "duration": 2.43}, {"text": "is making water a good electron\ndonor, because, ultimately,", "start": 3111.78, "duration": 8.52}, {"text": "that is what is going\nto make this whole thing", "start": 3120.3, "duration": 3.54}, {"text": "work energetically.", "start": 3123.84, "duration": 2.49}, {"text": "And so you probably could guess\nthat if these processes are", "start": 3126.33, "duration": 7.29}, {"text": "really about these\nelectron transfers,", "start": 3133.62, "duration": 2.37}, {"text": "we need electron carriers.", "start": 3135.99, "duration": 1.77}, {"text": "This is true for\nphotosynthesis, just", "start": 3137.76, "duration": 2.7}, {"text": "as it was true for\noxidative phosphorylation.", "start": 3140.46, "duration": 4.62}, {"text": "But remember, we'll describe\na lot of the same electron", "start": 3145.08, "duration": 2.58}, {"text": "carriers that are used.", "start": 3147.66, "duration": 1.17}, {"text": "But as we described\nthem, remember", "start": 3148.83, "duration": 1.68}, {"text": "that the photosynthesis\ncame first.", "start": 3150.51, "duration": 1.9}, {"text": "And so the other processes, like\nOXPHOS, that use these electron", "start": 3152.41, "duration": 4.13}, {"text": "carriers, use them\nbecause they were first", "start": 3156.54, "duration": 1.95}, {"text": "used in photosynthesis.", "start": 3158.49, "duration": 1.5}, {"text": "And then they were repurposed\nfor oxidative phosphorylation.", "start": 3159.99, "duration": 5.62}, {"text": "Now, to discuss this,\nI want to first start", "start": 3165.61, "duration": 2.76}, {"text": "by introducing an\nelectron carrier that's", "start": 3168.37, "duration": 4.17}, {"text": "important for this that's\nreally a variation on NADH.", "start": 3172.54, "duration": 4.83}, {"text": "And it's an electron\ncarrier that's found in--", "start": 3177.37, "duration": 3.15}, {"text": "excuse me-- all plants,\nall animals, all life,", "start": 3180.52, "duration": 4.53}, {"text": "and is very important\nin anabolic pathways", "start": 3185.05, "duration": 3.39}, {"text": "like photosynthesis.", "start": 3188.44, "duration": 2.52}, {"text": "Remember that anabolism,\nbuilding stuff,", "start": 3190.96, "duration": 2.88}, {"text": "has to be distinct from\ncatabolism, breaking stuff", "start": 3193.84, "duration": 3.18}, {"text": "down, for a number of reasons.", "start": 3197.02, "duration": 1.8}, {"text": "We saw this in glycolysis\nand gluconeogenesis, glycogen", "start": 3198.82, "duration": 3.09}, {"text": "synthesis, glycogen breakdown.", "start": 3201.91, "duration": 2.52}, {"text": "Remember, delta G naught prime\ncan only favor one direction.", "start": 3204.43, "duration": 3.73}, {"text": "And so in the direction\nthat's favorable, it works.", "start": 3208.16, "duration": 2.957}, {"text": "In the other direction to\nactually make it happen,", "start": 3211.117, "duration": 2.083}, {"text": "we have to make delta\nG less than zero.", "start": 3213.2, "duration": 2.57}, {"text": "That has to happen\nby energy addition.", "start": 3215.77, "duration": 1.89}, {"text": "And so now we had to have\nthese separate pathways.", "start": 3217.66, "duration": 3.24}, {"text": "You also need separate\npathways because that", "start": 3220.9, "duration": 1.92}, {"text": "allows separate regulation,\navoids futile cycle,", "start": 3222.82, "duration": 3.45}, {"text": "and enables cells to match\nneeds with processes.", "start": 3226.27, "duration": 3.57}, {"text": "And as we already\ndiscussed, one way", "start": 3229.84, "duration": 2.61}, {"text": "to keep these anabolic and\ncatabolic processes distinct", "start": 3232.45, "duration": 3.21}, {"text": "is by building separate\ncompartments, right?", "start": 3235.66, "duration": 2.07}, {"text": "It's useful to have\nseparate compartments,", "start": 3237.73, "duration": 2.133}, {"text": "different conditions in\ndifferent compartments", "start": 3239.863, "duration": 1.917}, {"text": "that can favor different\nthings happening.", "start": 3241.78, "duration": 3.04}, {"text": "However, not all cells\nhave separate compartments.", "start": 3244.82, "duration": 2.81}, {"text": "Prokaryotes don't.", "start": 3247.63, "duration": 1.5}, {"text": "And you might\nthink of situations", "start": 3249.13, "duration": 2.7}, {"text": "where you clearly\nwant to have two", "start": 3251.83, "duration": 2.61}, {"text": "different types of\nreactions happening", "start": 3254.44, "duration": 1.83}, {"text": "in the same compartment.", "start": 3256.27, "duration": 1.41}, {"text": "And so what if you want to\nboth do oxidation and reduction", "start": 3257.68, "duration": 4.44}, {"text": "in different reactions\nin the same compartment?", "start": 3262.12, "duration": 3.11}, {"text": "Well, clearly you\nneed some way that", "start": 3265.23, "duration": 3.4}, {"text": "will favor some\nreactions being oxidation", "start": 3268.63, "duration": 3.15}, {"text": "and other reactions\nbeing reductions.", "start": 3271.78, "duration": 2.82}, {"text": "And if you simply rely on\nNADH/NAD+ as your oxidant", "start": 3274.6, "duration": 8.34}, {"text": "or your reductant, this\nnow becomes a problem.", "start": 3282.94, "duration": 4.55}, {"text": "All right?", "start": 3287.49, "duration": 1.45}, {"text": "So a solution is, well, let's\nmake a distinct electron", "start": 3288.94, "duration": 4.65}, {"text": "carrier for the oxidation\nreactions in the cells.", "start": 3293.59, "duration": 3.82}, {"text": "So that's what this is.", "start": 3297.41, "duration": 2.72}, {"text": "Turns out, you\nkeep your NAD/NADH", "start": 3300.13, "duration": 2.61}, {"text": "to largely favor the oxidation\nreactions you want to do.", "start": 3302.74, "duration": 4.2}, {"text": "And let's create a different\ncurrency for reduction.", "start": 3306.94, "duration": 3.63}, {"text": "And this currency ends up\nbeing a different molecule,", "start": 3310.57, "duration": 3.756}, {"text": "NADPH/NADP+.", "start": 3314.326, "duration": 0.974}, {"text": "And you use this as a\ncofactor pair for reduction.", "start": 3318.22, "duration": 6.195}, {"text": "Well, what is NADPH?", "start": 3324.415, "duration": 1.965}, {"text": "Well, it's effectively\nthe same thing as NADH.", "start": 3329.51, "duration": 4.62}, {"text": "But now you mark it\nas a separate pool", "start": 3334.13, "duration": 2.64}, {"text": "with a two prime phosphate\non the ADP portion", "start": 3336.77, "duration": 5.52}, {"text": "of the molecule.", "start": 3342.29, "duration": 1.475}, {"text": "Let me draw it out for you.", "start": 3343.765, "duration": 1.125}, {"text": "OK.", "start": 3386.47, "duration": 0.54}, {"text": "So this here is NA--", "start": 3387.01, "duration": 3.39}, {"text": "so if I took this phosphate\noff, this would be NADH,", "start": 3390.4, "duration": 4.2}, {"text": "put a two prime\nphosphate on, now I", "start": 3394.6, "duration": 2.88}, {"text": "mark this as a separate\nmolecule pool, NADPH.", "start": 3397.48, "duration": 4.02}, {"text": "A is an adenine.", "start": 3409.409, "duration": 1.191}, {"text": "Remember, it's a nicotinamide\nadenine dinucleoside.", "start": 3410.6, "duration": 4.03}, {"text": "OK?", "start": 3414.63, "duration": 0.5}, {"text": "So here's a adenine, phosphate,\nphosphate, other nucleoside", "start": 3415.13, "duration": 4.38}, {"text": "with the nicotinamide group.", "start": 3419.51, "duration": 1.59}, {"text": "This here is in\nthe reduced form.", "start": 3421.1, "duration": 2.79}, {"text": "Seen this now a\nmillion times, but we", "start": 3427.48, "duration": 4.52}, {"text": "can oxidize it as possible.", "start": 3432.0, "duration": 2.76}, {"text": "That generates this two\nelectron hydride ion.", "start": 3434.76, "duration": 4.52}, {"text": "So remove two electrons and now\nthis nicotinamide form is here", "start": 3439.28, "duration": 16.22}, {"text": "in the NADP+ or oxidized\nform of the molecule.", "start": 3455.5, "duration": 10.36}, {"text": "And so effectively by marking\nthis as a separate pool with", "start": 3465.86, "duration": 3.44}, {"text": "that two prime phosphate, you\ncan have a different NADH/NAD+", "start": 3469.3, "duration": 6.0}, {"text": "ratio in cells.", "start": 3475.3, "duration": 1.44}, {"text": "Then you have NADH/NADP+\nplus ratio and cells.", "start": 3476.74, "duration": 5.13}, {"text": "Use one co-factor\nfair pair to favor", "start": 3481.87, "duration": 2.64}, {"text": "oxidation and the\nother co-factor pair", "start": 3484.51, "duration": 2.88}, {"text": "to favor reduction.", "start": 3487.39, "duration": 3.1}, {"text": "And so I want to give\na quick aside on NADPH", "start": 3490.49, "duration": 3.99}, {"text": "because it's really\nalso NADPH that", "start": 3494.48, "duration": 3.03}, {"text": "can be very important in keeping\nthe cytosol of cells reduced.", "start": 3497.51, "duration": 5.13}, {"text": "So what do I mean by that?", "start": 3502.64, "duration": 1.26}, {"text": "Well, you remember you\nlearned from Professor Yaffe.", "start": 3503.9, "duration": 3.47}, {"text": "We talked about proteins\nthat you can have", "start": 3507.37, "duration": 3.16}, {"text": "these inside the side cytosol.", "start": 3510.53, "duration": 2.37}, {"text": "You'd have your cystine\nresidues on proteins", "start": 3512.9, "duration": 3.27}, {"text": "be in this reduced form.", "start": 3516.17, "duration": 2.31}, {"text": "And outside the cell, you'd form\nthese disulfide bonds, which", "start": 3518.48, "duration": 4.47}, {"text": "is basically oxidized cystine.", "start": 3522.95, "duration": 2.49}, {"text": "And so in the cytosol, you want\nyour cystine residues reduced.", "start": 3525.44, "duration": 4.71}, {"text": "And outside of the\ncell, you end up", "start": 3530.15, "duration": 1.95}, {"text": "with these disulfide\nbonds on proteins.", "start": 3532.1, "duration": 4.28}, {"text": "Why does cystine tend to get\noxidized outside the cell?", "start": 3536.38, "duration": 4.95}, {"text": "Well, there's lots of\noxygen in our atmosphere.", "start": 3541.33, "duration": 3.09}, {"text": "Oxygen's a good\nelectron acceptor.", "start": 3544.42, "duration": 2.16}, {"text": "It's very good at oxidation.", "start": 3546.58, "duration": 2.07}, {"text": "In fact, that's what gives\nit this property that makes", "start": 3548.65, "duration": 3.45}, {"text": "oxidative phosphorylation work.", "start": 3552.1, "duration": 2.31}, {"text": "And so it turns out\nthat these cystines,", "start": 3554.41, "duration": 3.12}, {"text": "these sulfhydryl groups, like to\ngive their electrons to oxygen.", "start": 3557.53, "duration": 3.36}, {"text": "And that leads to these\nmore oxidized things", "start": 3560.89, "duration": 3.21}, {"text": "outside the cell.", "start": 3564.1, "duration": 1.66}, {"text": "In fact, oxygen is very\ngood at accepting electrons", "start": 3565.76, "duration": 3.2}, {"text": "from lots of donors.", "start": 3568.96, "duration": 1.98}, {"text": "So if you have iron 2+ sitting\naround outside the cell,", "start": 3570.94, "duration": 4.8}, {"text": "oxygen is very good at oxidizing\nthat iron 2+ to iron 3+.", "start": 3575.74, "duration": 6.21}, {"text": "That's rust.", "start": 3581.95, "duration": 1.89}, {"text": "And this process, in the end,\nends up transferring electrons", "start": 3583.84, "duration": 4.29}, {"text": "to oxygen and can generate\nlots of oxygen species,", "start": 3588.13, "duration": 4.72}, {"text": "including oxygen radicals.", "start": 3592.85, "duration": 1.98}, {"text": "And so you can get things\nlike this O2- superoxide,", "start": 3594.83, "duration": 5.17}, {"text": "ultimately hydrogen\nperoxide, also", "start": 3600.0, "duration": 11.17}, {"text": "comes from oxygen\npicking up electrons.", "start": 3611.17, "duration": 4.21}, {"text": "And as you know, very\nreactive molecules like this", "start": 3615.38, "duration": 3.71}, {"text": "can damage membranes,\ndamage proteins, kill cells.", "start": 3619.09, "duration": 4.29}, {"text": "What do we use hydrogen\nperoxide for in daily life?", "start": 3623.38, "duration": 2.55}, {"text": "Use it to clean wounds,\nkills a bunch of bacteria.", "start": 3625.93, "duration": 3.15}, {"text": "And ultimately, production\nof these so-called ROS,", "start": 3629.08, "duration": 5.82}, {"text": "or reactive oxygen\nspecies, in excess", "start": 3634.9, "duration": 7.36}, {"text": "can be very bad for\nbiological systems.", "start": 3642.26, "duration": 2.91}, {"text": "And this is one of\nthe arguments for why", "start": 3645.17, "duration": 2.13}, {"text": "antioxidants are good for us.", "start": 3647.3, "duration": 1.56}, {"text": "They protect us and ourselves\nfrom these reactive oxygen", "start": 3648.86, "duration": 5.04}, {"text": "species.", "start": 3653.9, "duration": 2.04}, {"text": "OK.", "start": 3655.94, "duration": 1.02}, {"text": "Now, cells, of course,\nhave endogenous ways", "start": 3656.96, "duration": 3.3}, {"text": "to deal with this, to keep\ncystines in our cytosol", "start": 3660.26, "duration": 3.3}, {"text": "reduced, to keep our cytosol\nin this reducing environment,", "start": 3663.56, "duration": 2.88}, {"text": "prevent this ROS damage.", "start": 3666.44, "duration": 2.76}, {"text": "And really, if\nyou're going to have", "start": 3669.2, "duration": 2.28}, {"text": "things to deal with these\nreactive molecules, what do", "start": 3671.48, "duration": 2.28}, {"text": "you want?", "start": 3673.76, "duration": 0.42}, {"text": "Well, you want\nsomething that's going", "start": 3674.18, "duration": 1.542}, {"text": "to buffer the damage that\nthese things can cause.", "start": 3675.722, "duration": 4.241}, {"text": "That is, if these\nthings are going", "start": 3679.963, "duration": 1.417}, {"text": "to react with lipids and\nproteins and cause damage", "start": 3681.38, "duration": 3.42}, {"text": "and you want to keep\nthe cytosol reduced,", "start": 3684.8, "duration": 1.71}, {"text": "you really want to have\na series of molecules", "start": 3686.51, "duration": 2.01}, {"text": "that will actually, instead,\nundergo this process before it", "start": 3688.52, "duration": 4.53}, {"text": "can damage critical\nstructures in the cell.", "start": 3693.05, "duration": 2.79}, {"text": "And a key system cells\nuse to do this is", "start": 3695.84, "duration": 2.43}, {"text": "something called glutathione.", "start": 3698.27, "duration": 3.75}, {"text": "So what is glutathione?", "start": 3702.02, "duration": 2.1}, {"text": "Well, glutathione is a\nsmall molecule tripeptide.", "start": 3704.12, "duration": 4.36}, {"text": "All right?", "start": 3708.48, "duration": 0.5}, {"text": "And it's among the most abundant\nsmall molecules found in cells.", "start": 3708.98, "duration": 5.34}, {"text": "And effectively,\nwhat glutathione does", "start": 3714.32, "duration": 2.16}, {"text": "is it serves this purpose\nof reacting with nasty stuff", "start": 3716.48, "duration": 4.2}, {"text": "before it can damage other\nbiomolecules and hurt the cell.", "start": 3720.68, "duration": 5.85}, {"text": "And so by tripeptide,\nwhat it is is it's", "start": 3726.53, "duration": 2.91}, {"text": "a tripeptide of glutamate\nwith a gamma peptide bond", "start": 3729.44, "duration": 5.37}, {"text": "to glycine and then cystine--", "start": 3734.81, "duration": 1.98}, {"text": "so glutamate glycine\ncystine tripeptide", "start": 3736.79, "duration": 4.11}, {"text": "that looks like this.", "start": 3740.9, "duration": 1.29}, {"text": "OK.", "start": 3758.17, "duration": 0.5}, {"text": "So this here is the\namino acid glutamate.", "start": 3758.67, "duration": 4.85}, {"text": "Here's the alpha carbon\nwith the carboxylic acid", "start": 3763.52, "duration": 5.082}, {"text": "and amine groups.", "start": 3768.602, "duration": 0.708}, {"text": "So you would typically think of\nthe peptide bond of glutamate", "start": 3769.31, "duration": 3.18}, {"text": "was in a chain as being\nfrom this nitrogen", "start": 3772.49, "duration": 3.42}, {"text": "to the next amino acid and that\ncarbon to the next amino acid.", "start": 3775.91, "duration": 3.57}, {"text": "But in this case, it uses the\nnitrogen on the side chain,", "start": 3779.48, "duration": 3.73}, {"text": "the so-called\ngamma linkage here,", "start": 3783.21, "duration": 3.35}, {"text": "to form a peptide bond with--", "start": 3786.56, "duration": 2.82}, {"text": "oops, sorry.", "start": 3792.43, "duration": 2.97}, {"text": "This would be glutamic acid.", "start": 3795.4, "duration": 2.22}, {"text": "It uses this gamma\ncarboxylic acid", "start": 3797.62, "duration": 2.79}, {"text": "on the side chain of glutamate\nto form a peptide bond", "start": 3800.41, "duration": 6.38}, {"text": "with glycine.", "start": 3806.79, "duration": 3.0}, {"text": "OK.", "start": 3813.22, "duration": 0.96}, {"text": "So this is glutamate.", "start": 3814.18, "duration": 5.03}, {"text": "This is glycine.", "start": 3819.21, "duration": 2.52}, {"text": "And then this has a\npeptide bond to cystine,", "start": 3821.73, "duration": 18.01}, {"text": "which contributes that\nsulfhydryl group that", "start": 3839.74, "duration": 3.87}, {"text": "can either exist in\nthis reduced form.", "start": 3843.61, "duration": 4.11}, {"text": "Or, if there's two\nof them together,", "start": 3847.72, "duration": 7.06}, {"text": "you can go into\nthis oxidized form.", "start": 3854.78, "duration": 3.56}, {"text": "And so, often, this is drawn as\nglutathione GSH in the reduced", "start": 3858.34, "duration": 6.99}, {"text": "form.", "start": 3865.33, "duration": 1.12}, {"text": "And if you have two glutathione\nmolecules that then basically", "start": 3866.45, "duration": 5.81}, {"text": "form a disulfide bond\nto give you this GSSG", "start": 3872.26, "duration": 4.89}, {"text": "oxidized form of the molecule.", "start": 3877.15, "duration": 3.9}, {"text": "And NADPH plays a\nkey role in the cell,", "start": 3881.05, "duration": 4.38}, {"text": "because that's an\noxidation reduction", "start": 3885.43, "duration": 1.56}, {"text": "reaction in keeping glutathione\nin the reduced form.", "start": 3886.99, "duration": 3.81}, {"text": "So if you have two\nGSH molecules that", "start": 3890.8, "duration": 4.68}, {"text": "can cycle to a oxidized GSSG--", "start": 3895.48, "duration": 4.59}, {"text": "so this is reduced,\nthis is oxidized.", "start": 3900.07, "duration": 6.16}, {"text": "On the other side you can\ncycle those electrons.", "start": 3906.23, "duration": 3.65}, {"text": "If something gets\noxidized, something else", "start": 3909.88, "duration": 1.75}, {"text": "has to be reduced.", "start": 3911.63, "duration": 1.63}, {"text": "So you can have NADP+ and NADPH.", "start": 3913.26, "duration": 5.15}, {"text": "This is reduced.", "start": 3923.65, "duration": 3.01}, {"text": "This is oxidized.", "start": 3926.66, "duration": 1.44}, {"text": "And so by maintaining a\nhigh ratio of NADH to NADP+,", "start": 3928.1, "duration": 6.54}, {"text": "you can keep a high ratio of\nreduced to oxidize glutathione", "start": 3934.64, "duration": 4.95}, {"text": "in the cell and keep the\ncell in a protected reducing", "start": 3939.59, "duration": 4.44}, {"text": "environment where you have these\nglutathione molecules to react", "start": 3944.03, "duration": 5.19}, {"text": "with other things before it\ncauses damage to the cell.", "start": 3949.22, "duration": 4.41}, {"text": "All right.", "start": 3953.63, "duration": 0.88}, {"text": "A little bit of a diversion,\nbut a very important system", "start": 3954.51, "duration": 3.74}, {"text": "that cells use related to\noxidation reduction and NADPH,", "start": 3958.25, "duration": 4.47}, {"text": "and needed a place to talk about\nit somewhere in the course.", "start": 3962.72, "duration": 3.7}, {"text": "All right.", "start": 3966.42, "duration": 0.5}, {"text": "Now back to photosynthesis.", "start": 3966.92, "duration": 3.52}, {"text": "Now, for photosynthesis,\nthis reduced", "start": 3970.44, "duration": 3.65}, {"text": "NADPH molecule's\nof course useful,", "start": 3974.09, "duration": 2.91}, {"text": "because it can serve as\na source of electrons", "start": 3977.0, "duration": 2.97}, {"text": "to donate carbons to reduce CO2.", "start": 3979.97, "duration": 3.69}, {"text": "So if you're going to reduce\nCO2 to make carbohydrate or fat,", "start": 3983.66, "duration": 5.67}, {"text": "you need this\nsource of electrons.", "start": 3989.33, "duration": 1.53}, {"text": "Those can come from NADPH,\nwhich can be oxidized to NADP+.", "start": 3990.86, "duration": 7.16}, {"text": "And so perhaps at\nthis point, you've", "start": 3998.02, "duration": 2.1}, {"text": "already guessed or\nmaybe already know", "start": 4000.12, "duration": 1.92}, {"text": "that photosynthesis uses the\nfavorable electron transfer", "start": 4002.04, "duration": 6.3}, {"text": "from water to generate NADPH.", "start": 4008.34, "duration": 4.35}, {"text": "And to do that, you use\nthe energy of the sun.", "start": 4012.69, "duration": 3.85}, {"text": "Now, of course, if you're going\nto do a favorable electron", "start": 4016.54, "duration": 4.22}, {"text": "transfer, that can be coupled,\njust like we talked about", "start": 4020.76, "duration": 5.46}, {"text": "for oxidative phosphorylation,\nto make delta psi/delta pH.", "start": 4026.22, "duration": 6.42}, {"text": "And if we can use that\nfavorable electron transfer", "start": 4032.64, "duration": 2.91}, {"text": "to make delta psi/delta\npH, we can also", "start": 4035.55, "duration": 2.91}, {"text": "use it to do other work,\nincluding making ATP exactly", "start": 4038.46, "duration": 5.46}, {"text": "as we described for\noxidative phosphorylation.", "start": 4043.92, "duration": 4.62}, {"text": "And at the highest level, this\nis exactly how photosynthesis", "start": 4048.54, "duration": 3.96}, {"text": "traps solar energy\nand uses that energy", "start": 4052.5, "duration": 3.42}, {"text": "to both remake reduced\ncarbon and generates", "start": 4055.92, "duration": 5.9}, {"text": "a battery for the\nphotosynthetic organism that", "start": 4061.82, "duration": 3.15}, {"text": "can be used to make\nATP or do other work,", "start": 4064.97, "duration": 3.42}, {"text": "provided that sun is available.", "start": 4068.39, "duration": 4.02}, {"text": "And so classically,\nphotosynthesis", "start": 4072.41, "duration": 3.36}, {"text": "can really be separated into, I\nguess, two distinct processes.", "start": 4075.77, "duration": 4.32}, {"text": "All right?", "start": 4080.09, "duration": 0.85}, {"text": "So you have this process\nof taking solar energy,", "start": 4080.94, "duration": 8.3}, {"text": "using that solar\nenergy to charge up", "start": 4089.24, "duration": 4.44}, {"text": "a battery, delta psi/delta pH,\nwhich of course can be used", "start": 4093.68, "duration": 4.53}, {"text": "to generate ATP or do other\nwork, and at the same time", "start": 4098.21, "duration": 4.41}, {"text": "gives you an electron\ndonor, NADPH,", "start": 4102.62, "duration": 5.01}, {"text": "that is useful to\ngenerate reduced carbon.", "start": 4107.63, "duration": 4.38}, {"text": "Once you generate, high ATP/ADP\nratio, high NADPH/NADP ratio.", "start": 4112.01, "duration": 8.309}, {"text": "Now we can use that to\nbe couple to do something", "start": 4120.319, "duration": 4.801}, {"text": "else unfavorable.", "start": 4125.12, "duration": 2.25}, {"text": "And that would be\nsomething like reduced CO2", "start": 4127.37, "duration": 4.5}, {"text": "to generate a carbohydrate.", "start": 4131.87, "duration": 2.13}, {"text": "And typically, when we\ntalk about photosynthesis,", "start": 4137.31, "duration": 3.27}, {"text": "the way it's often\ndescribed is how you", "start": 4140.58, "duration": 1.77}, {"text": "reduced CO2 to carbohydrate.", "start": 4142.35, "duration": 1.86}, {"text": "And we'll do that too.", "start": 4144.21, "duration": 1.26}, {"text": "But of course, we'll then see\nonce you have carbohydrates,", "start": 4145.47, "duration": 3.929}, {"text": "obviously, it's just\nfurther reduction of carbon", "start": 4149.399, "duration": 2.401}, {"text": "to make fatty acids and lipids.", "start": 4151.8, "duration": 4.769}, {"text": "We'll discuss later\nhow we can use", "start": 4156.569, "duration": 1.891}, {"text": "those to make amino\nacids, which would", "start": 4158.46, "duration": 1.649}, {"text": "allow you to make proteins.", "start": 4160.109, "duration": 1.691}, {"text": "And, of course, we can also\nstore those carbohydrates", "start": 4161.8, "duration": 7.09}, {"text": "as disaccharides or\npolysaccharides, storage", "start": 4168.89, "duration": 4.03}, {"text": "sugars, which is what plants do.", "start": 4172.92, "duration": 2.22}, {"text": "They make starch, they\nmake sucrose, et cetera,", "start": 4175.14, "duration": 2.79}, {"text": "as a way to store\nthat reduce carbon", "start": 4177.93, "duration": 3.299}, {"text": "so that they can have\na source of energy,", "start": 4181.229, "duration": 3.21}, {"text": "do the oxidation reactions, to\ndeal with their energetic needs", "start": 4184.439, "duration": 3.511}, {"text": "when the sun is not shining.", "start": 4187.95, "duration": 2.76}, {"text": "All right.", "start": 4190.71, "duration": 1.479}, {"text": "So let's break down\nthese two processes.", "start": 4192.189, "duration": 5.961}, {"text": "And so to just be very\nexplicit, the first part", "start": 4198.15, "duration": 3.36}, {"text": "is basically trapping\nenergy to make a battery.", "start": 4201.51, "duration": 4.89}, {"text": "All right?", "start": 4206.4, "duration": 1.14}, {"text": "And so this means that we need\nto generate delta psi/delta", "start": 4207.54, "duration": 4.29}, {"text": "pH via favorable electron\ntransport, exactly what we", "start": 4211.83, "duration": 4.98}, {"text": "describe for OXPHOS.", "start": 4216.81, "duration": 1.15}, {"text": "But, of course,\nphotosynthesis was first.", "start": 4217.96, "duration": 2.24}, {"text": "This would then allow us to use\nATP to fill our energy needs.", "start": 4220.2, "duration": 3.24}, {"text": "And we get NADPH if we set it\nup in the right way, which is", "start": 4223.44, "duration": 4.11}, {"text": "important for carbon reduction.", "start": 4227.55, "duration": 2.81}, {"text": "Then we need to use NADPH\nand ATP via pathways", "start": 4230.36, "duration": 3.81}, {"text": "to describe how we can use that\nto reduce CO2, and ultimately", "start": 4234.17, "duration": 4.2}, {"text": "produce glucose, which allows\nus to store energy for later.", "start": 4238.37, "duration": 4.57}, {"text": "All right.", "start": 4242.94, "duration": 0.5}, {"text": "So that is, at a very high\nlevel, what photosynthesis is.", "start": 4243.44, "duration": 3.45}, {"text": "And, of course, this\noccurs in plants.", "start": 4246.89, "duration": 3.21}, {"text": "All right?", "start": 4250.1, "duration": 1.63}, {"text": "But perhaps more\nimportantly, it also", "start": 4251.73, "duration": 1.95}, {"text": "occurs in algae and other\nunicellular eukaryotes", "start": 4253.68, "duration": 16.51}, {"text": "as well as in prokaryotes--\nphotosynthetic prokaryotes,", "start": 4270.19, "duration": 7.48}, {"text": "bacteria.", "start": 4277.67, "duration": 1.38}, {"text": "And, of course,\nphotosynthetic bacteria,", "start": 4279.05, "duration": 2.82}, {"text": "unicellular eukaryotes, algae--", "start": 4281.87, "duration": 2.34}, {"text": "these really are\nthe heroes of life.", "start": 4284.21, "duration": 2.68}, {"text": "These are the things that life\nstarted from, and generated", "start": 4286.89, "duration": 3.56}, {"text": "the oxygenated\natmosphere, and ultimately", "start": 4290.45, "duration": 2.22}, {"text": "led to the evolution\nof higher plants,", "start": 4292.67, "duration": 2.61}, {"text": "but also enabled the\nformation of animal life,", "start": 4295.28, "duration": 4.38}, {"text": "and really anything that lives\noff of eating other organisms.", "start": 4299.66, "duration": 5.22}, {"text": "Just a few facts\nabout photosynthesis", "start": 4304.88, "duration": 2.73}, {"text": "because it's really quite\nan amazing process--", "start": 4307.61, "duration": 3.7}, {"text": "and so about 10 to the\n17th kilojoules, at least", "start": 4311.31, "duration": 5.54}, {"text": "by some estimate, of energy\nis harvested on our planet", "start": 4316.85, "duration": 7.88}, {"text": "from photosynthesis every year.", "start": 4324.73, "duration": 2.67}, {"text": "Just to give you a perspective\nof what that number means,", "start": 4327.4, "duration": 2.55}, {"text": "that is 10 times the\nworldwide energy use", "start": 4329.95, "duration": 4.23}, {"text": "by all people on Earth.", "start": 4334.18, "duration": 1.35}, {"text": "So if you add up all the\nenergy that we as humans use", "start": 4335.53, "duration": 3.15}, {"text": "in the world, it is tenfold\nless than the amount of energy", "start": 4338.68, "duration": 4.53}, {"text": "that is harvested\nby photosynthesis,", "start": 4343.21, "duration": 4.42}, {"text": "by photosynthetic\norganisms around the world.", "start": 4347.63, "duration": 4.09}, {"text": "Photosynthetic organisms, when\nthey do this, consume CO2.", "start": 4351.72, "duration": 4.83}, {"text": "All right?", "start": 4356.55, "duration": 0.78}, {"text": "So that is removing\nCO2, the greenhouse", "start": 4357.33, "duration": 2.73}, {"text": "gas from our atmosphere.", "start": 4360.06, "duration": 3.76}, {"text": "And this occurs on\na massive scale.", "start": 4363.82, "duration": 3.15}, {"text": "So this is better than any\nman-made engineering solution", "start": 4366.97, "duration": 4.73}, {"text": "that we have come\nup with by far.", "start": 4371.7, "duration": 3.34}, {"text": "And I think this\nreally illustrates", "start": 4375.04, "duration": 3.06}, {"text": "the awesome power\nof biology to solve", "start": 4378.1, "duration": 3.54}, {"text": "some of the biggest problems\nthat face our society today.", "start": 4381.64, "duration": 4.15}, {"text": "So world energy problems--", "start": 4385.79, "duration": 3.14}, {"text": "photosynthesis harnesses\na ton of energy.", "start": 4388.93, "duration": 7.32}, {"text": "Global warming,\ngreenhouse gases--", "start": 4396.25, "duration": 1.98}, {"text": "photosynthesis, better\nthan almost anything", "start": 4398.23, "duration": 2.76}, {"text": "at dealing with these\nCO2 that is produced.", "start": 4400.99, "duration": 5.2}, {"text": "However, this also illustrates\nwhat some of the problems are", "start": 4406.19, "duration": 5.377}, {"text": "and what some of the issues\nare with fossil fuels,", "start": 4411.567, "duration": 2.083}, {"text": "because what are fossil fuels.", "start": 4413.65, "duration": 1.95}, {"text": "Well, they're\neffectively reduced", "start": 4415.6, "duration": 2.19}, {"text": "carbon that is trapped in\nthe ground somewhere, that is", "start": 4417.79, "duration": 4.11}, {"text": "effectively old photosynthesis.", "start": 4421.9, "duration": 2.53}, {"text": "So these are organisms in many,\nmany, many, many years ago", "start": 4424.43, "duration": 5.57}, {"text": "that did photosynthesis,\nmade reduced carbon that", "start": 4430.0, "duration": 3.75}, {"text": "was effectively\ntrapped in the ground.", "start": 4433.75, "duration": 2.73}, {"text": "And so the fact that\nphotosynthesis transducers 10", "start": 4436.48, "duration": 5.49}, {"text": "to 17th kilojoules of energy\nper year and we're using 1/10", "start": 4441.97, "duration": 4.41}, {"text": "of that amount of energy, if\nthat's all coming from fossil", "start": 4446.38, "duration": 3.24}, {"text": "fuels, that means we're\nusing 1/10 of a year's worth", "start": 4449.62, "duration": 4.17}, {"text": "of photosynthesis--\nand, of course,", "start": 4453.79, "duration": 1.68}, {"text": "a year is not entirely\nstored in the ground--", "start": 4455.47, "duration": 2.82}, {"text": "per year.", "start": 4458.29, "duration": 0.69}, {"text": "So that's a lot of energy.", "start": 4458.98, "duration": 1.26}, {"text": "And it really comes down to why\npeople say fossil fuels can't", "start": 4460.24, "duration": 4.47}, {"text": "last forever, and also why the\nnet release of these things", "start": 4464.71, "duration": 6.18}, {"text": "can change our atmosphere,\nbecause, of course,", "start": 4470.89, "duration": 2.67}, {"text": "once upon a time, there was\nmuch more CO2 in the atmosphere.", "start": 4473.56, "duration": 3.81}, {"text": "And photosynthesis,\nover millennia,", "start": 4477.37, "duration": 2.52}, {"text": "trapping these things\nas fossil fuels really", "start": 4479.89, "duration": 3.09}, {"text": "has lowered CO2 in our\natmosphere to the levels", "start": 4482.98, "duration": 3.66}, {"text": "that they exist today,\nand how, basically,", "start": 4486.64, "duration": 4.68}, {"text": "burning fossil fuels on\nthe scale that we are", "start": 4491.32, "duration": 3.63}, {"text": "is able to change\nour atmosphere.", "start": 4494.95, "duration": 4.42}, {"text": "So you can view this both\nas glass half full and glass", "start": 4499.37, "duration": 2.51}, {"text": "half empty.", "start": 4501.88, "duration": 1.2}, {"text": "It really says\nunderstanding photosynthesis", "start": 4503.08, "duration": 2.25}, {"text": "could be a key to solving\nsome of these problems.", "start": 4505.33, "duration": 3.1}, {"text": "But it also points out\nwhy some of these things", "start": 4508.43, "duration": 3.35}, {"text": "might be problems to begin with.", "start": 4511.78, "duration": 2.42}, {"text": "All right.", "start": 4514.2, "duration": 1.11}, {"text": "Now we want to discuss first\nhow photosynthesis traps energy.", "start": 4515.31, "duration": 5.07}, {"text": "And you'll see that it\nis similar to oxidative", "start": 4520.38, "duration": 3.81}, {"text": "phosphorylation in\nmany, many ways.", "start": 4524.19, "duration": 4.87}, {"text": "So it's going to\noccur at a membrane.", "start": 4529.06, "duration": 4.37}, {"text": "All right?", "start": 4533.43, "duration": 1.82}, {"text": "It's going to involve a\nseries of protein complexes", "start": 4535.25, "duration": 8.97}, {"text": "where we're going\nto favor, we're", "start": 4544.22, "duration": 2.37}, {"text": "going to couple\nfavorable electron", "start": 4546.59, "duration": 2.73}, {"text": "transport along a\nelectron transport chain", "start": 4549.32, "duration": 4.44}, {"text": "to favor proton pumping.", "start": 4553.76, "duration": 2.91}, {"text": "That is going to generate\na membrane potential delta", "start": 4556.67, "duration": 5.06}, {"text": "psi/delta pH.", "start": 4561.73, "duration": 0.76}, {"text": "In order to do\nthat, of course, we", "start": 4565.21, "duration": 1.98}, {"text": "need favorable\nelectron transport", "start": 4567.19, "duration": 2.37}, {"text": "from something that is\nlower standard reduction", "start": 4569.56, "duration": 4.8}, {"text": "potential to something that\nis higher standard reduction", "start": 4574.36, "duration": 3.99}, {"text": "potential.", "start": 4578.35, "duration": 0.54}, {"text": "That is what is going\nto make it favorable,", "start": 4578.89, "duration": 2.31}, {"text": "allow proton pumping.", "start": 4581.2, "duration": 2.85}, {"text": "That, when it generates\ndelta psi/delta pH,", "start": 4584.05, "duration": 4.32}, {"text": "we can now harness that\nas a way to synthesize", "start": 4588.37, "duration": 7.19}, {"text": "ATP or do other work, as\nwe've now talked about a lot.", "start": 4595.56, "duration": 6.736}, {"text": "Looks a lot like\noxidative phosphorylation", "start": 4602.296, "duration": 1.75}, {"text": "and it makes sense.", "start": 4604.046, "duration": 1.304}, {"text": "Oxidative phosphorylation\ncame from photosynthesis.", "start": 4605.35, "duration": 4.11}, {"text": "However, there are some\nreally big differences", "start": 4609.46, "duration": 3.09}, {"text": "between the two.", "start": 4612.55, "duration": 1.47}, {"text": "And that is in photosynthesis,\nas I've already alluded", "start": 4614.02, "duration": 3.24}, {"text": "to, the electron donor\nis going to be water,", "start": 4617.26, "duration": 6.45}, {"text": "which will generate oxygen. And\nthe electron acceptor is NADP+,", "start": 4623.71, "duration": 8.25}, {"text": "which will generate NADPH.", "start": 4631.96, "duration": 2.75}, {"text": "And you might now be\nasking, well, how on Earth", "start": 4639.23, "duration": 2.85}, {"text": "can this be possible?", "start": 4642.08, "duration": 1.71}, {"text": "Because, remember, the standard\nreduction potential of NADH", "start": 4643.79, "duration": 10.04}, {"text": "is less than the standard\nreduction potential", "start": 4653.83, "duration": 4.8}, {"text": "of our oxygen water pair.", "start": 4658.63, "duration": 3.69}, {"text": "And it's really this\nthat makes the change", "start": 4662.32, "duration": 4.11}, {"text": "in standard reduction\npotential positive, which", "start": 4666.43, "duration": 3.15}, {"text": "means that delta G is\ngoing to be negative,", "start": 4669.58, "duration": 4.21}, {"text": "which is why electron\ntransport and oxidative", "start": 4673.79, "duration": 2.36}, {"text": "phosphorylation is\nfavorable and can be coupled", "start": 4676.15, "duration": 2.55}, {"text": "to make delta psi/delta pH.", "start": 4678.7, "duration": 3.81}, {"text": "Now, adding a\nphosphate to NAD/NADH", "start": 4682.51, "duration": 4.29}, {"text": "does not change its\nstandard reduction potential", "start": 4686.8, "duration": 3.0}, {"text": "in a way that is at all\nmeaningful to impact", "start": 4689.8, "duration": 3.18}, {"text": "what goes on.", "start": 4692.98, "duration": 1.29}, {"text": "And so this is really where\nenergy input from the sun", "start": 4694.27, "duration": 5.43}, {"text": "becomes critical.", "start": 4699.7, "duration": 1.71}, {"text": "And that is-- it is this light\nenergy from a photon that", "start": 4701.41, "duration": 7.23}, {"text": "in the end makes water\na good electron donor,", "start": 4708.64, "duration": 4.18}, {"text": "such that all of these other\nthings are satisfied that", "start": 4712.82, "duration": 4.1}, {"text": "electron transport is favorable\ngoing from lower to higher", "start": 4716.92, "duration": 4.26}, {"text": "standard reduction potential\nwith NADP+ ultimately being", "start": 4721.18, "duration": 5.91}, {"text": "the final electron acceptor,\nsuch that the change", "start": 4727.09, "duration": 4.5}, {"text": "in standard production\npotential is positive.", "start": 4731.59, "duration": 3.75}, {"text": "And that really is the\nmagic of photosynthesis.", "start": 4735.34, "duration": 5.045}, {"text": "And, of course,\nonce you do that,", "start": 4740.385, "duration": 1.375}, {"text": "now you have delta psi/delta pH.", "start": 4741.76, "duration": 2.07}, {"text": "You can use that to\nmake ATP, do other work", "start": 4743.83, "duration": 2.37}, {"text": "for the photosynthetic organism.", "start": 4746.2, "duration": 1.86}, {"text": "And you also get NADPH,\nwhich is an electron", "start": 4748.06, "duration": 2.31}, {"text": "donor for carbon reduction.", "start": 4750.37, "duration": 2.43}, {"text": "And the net result is that\nyou get this familiar formula", "start": 4752.8, "duration": 6.57}, {"text": "that you learned in grade\nschool for photosynthesis--", "start": 4759.37, "duration": 2.97}, {"text": "CO2 plus water with light goes\nto oxygen plus carbohydrate,", "start": 4762.34, "duration": 9.95}, {"text": "which is, of course, the\nexact opposite of combustion.", "start": 4772.29, "duration": 5.51}, {"text": "We talked a lot about how\nburning wood combustion is", "start": 4777.8, "duration": 5.94}, {"text": "the opposite reaction that's\nfavorable-- lots of energy", "start": 4783.74, "duration": 2.97}, {"text": "released.", "start": 4786.71, "duration": 1.42}, {"text": "And so the energy\ninput here is obviously", "start": 4788.13, "duration": 4.52}, {"text": "the opposite of that to do\nthis opposite of combustion", "start": 4792.65, "duration": 5.79}, {"text": "and stores lots of energy.", "start": 4798.44, "duration": 2.07}, {"text": "All right, so again,\nI want to say why", "start": 4800.51, "duration": 5.32}, {"text": "use water as an electron donor?", "start": 4805.83, "duration": 3.09}, {"text": "Well, because it's abundant.", "start": 4808.92, "duration": 1.26}, {"text": "There's nothing particularly\nspecial about water other", "start": 4810.18, "duration": 3.18}, {"text": "than its abundance, just like\nwe talked about in oxygen is not", "start": 4813.36, "duration": 4.71}, {"text": "really being special\nother than that it's", "start": 4818.07, "duration": 1.92}, {"text": "a good electron\nacceptor and abundant.", "start": 4819.99, "duration": 3.18}, {"text": "You could obviously build\nsystems that do something other", "start": 4823.17, "duration": 3.21}, {"text": "than oxygen and water.", "start": 4826.38, "duration": 2.29}, {"text": "And so there are\nextremophiles out there", "start": 4828.67, "duration": 2.33}, {"text": "that instead do\nhydrogen sulfide to make", "start": 4831.0, "duration": 6.36}, {"text": "reduced sulfur as another--", "start": 4837.36, "duration": 2.78}, {"text": "sorry, oxidize sulfur as a\nway of doing photosynthesis.", "start": 4842.9, "duration": 6.57}, {"text": "Exact same concepts\nwould apply is what", "start": 4849.47, "duration": 2.7}, {"text": "we're going to talk about here.", "start": 4852.17, "duration": 2.97}, {"text": "All right.", "start": 4855.14, "duration": 0.51}, {"text": "Now, the parts of\nphotosynthesis,", "start": 4855.65, "duration": 4.8}, {"text": "as you might guess,\nare spatially distinct.", "start": 4860.45, "duration": 3.43}, {"text": "That is, we're going to generate\ndelta psi/delta pH and NADPH.", "start": 4863.88, "duration": 9.02}, {"text": "Those are basically\nthis electron", "start": 4872.9, "duration": 2.79}, {"text": "transport chain reactions,\ncharge the battery, et cetera.", "start": 4875.69, "duration": 4.27}, {"text": "And then imagine if we're going\nto fix CO2 as carbohydrate.", "start": 4879.96, "duration": 10.12}, {"text": "Well, effectively that's more\nlike what we talked about", "start": 4890.08, "duration": 2.4}, {"text": "with gluconeogenesis.", "start": 4892.48, "duration": 1.65}, {"text": "That's the chemical\nreactions that we just", "start": 4894.13, "duration": 4.83}, {"text": "have to build a pathway\nfor, like gluconeogenesis.", "start": 4898.96, "duration": 3.48}, {"text": "Now these two things\nare often referred", "start": 4902.44, "duration": 2.04}, {"text": "to as the light and dark\nreactions of photosynthesis.", "start": 4904.48, "duration": 11.73}, {"text": "And that's because the\nfirst set of reactions", "start": 4916.21, "duration": 3.15}, {"text": "generating the membrane\npotential and making NADPH", "start": 4919.36, "duration": 3.84}, {"text": "requires solar energy inputs\nor requires light from the sun.", "start": 4923.2, "duration": 4.23}, {"text": "This fixing of CO2, which will\njust use electrons from NADPH", "start": 4927.43, "duration": 5.97}, {"text": "to reduce CO2, can occur--", "start": 4933.4, "duration": 2.868}, {"text": "of course, it can\noccur in the light.", "start": 4936.268, "duration": 1.542}, {"text": "But it doesn't need light.", "start": 4937.81, "duration": 1.21}, {"text": "So it can occur in\nthe light or the dark,", "start": 4939.02, "duration": 1.94}, {"text": "hence called the dark reactions.", "start": 4940.96, "duration": 2.59}, {"text": "And so these light reactions can\nreally be broken up into water", "start": 4943.55, "duration": 5.3}, {"text": "plus NADP+ goes to\nNADPH plus oxygen.", "start": 4948.85, "duration": 10.2}, {"text": "And the dark reactions are NADPH\nplus CO2 goes to carbohydrate", "start": 4959.05, "duration": 11.82}, {"text": "plus NADP+, which of\ncourse gives us our net--", "start": 4970.87, "duration": 7.98}, {"text": "water plus CO2 goes to\ncarbohydrate plus oxygen.", "start": 4978.85, "duration": 9.1}, {"text": "And in the next lecture,\nwhat we'll talk about is", "start": 4987.95, "duration": 2.91}, {"text": "we'll go through\nthe details of how", "start": 4990.86, "duration": 2.7}, {"text": "these light and\ndark reactions work.", "start": 4993.56, "duration": 3.96}, {"text": "But when we do so, bear\nin mind that we're really", "start": 4997.52, "duration": 2.79}, {"text": "going to follow all of\nthe concepts and rules", "start": 5000.31, "duration": 5.04}, {"text": "that we talked about for past\nthermodynamic considerations", "start": 5005.35, "duration": 4.77}, {"text": "of pathways as\nwell as what we've", "start": 5010.12, "duration": 2.49}, {"text": "been discussing about how\noxidative phosphorylation", "start": 5012.61, "duration": 3.21}, {"text": "works.", "start": 5015.82, "duration": 0.75}, {"text": "Thanks.", "start": 5016.57, "duration": 1.55}]
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+[{"text": "The following\ncontent is provided", "start": 0.58, "duration": 1.86}, {"text": "by MIT OpenCourseWare under\na Creative Commons license.", "start": 2.44, "duration": 3.9}, {"text": "Additional information\nabout our license", "start": 6.34, "duration": 2.16}, {"text": "and MIT OpenCourseWare\nin general", "start": 8.5, "duration": 2.37}, {"text": "is available at ocw.mit.edu.", "start": 10.87, "duration": 1.86}, {"text": "GEORGE CHURCH: OK.", "start": 22.81, "duration": 0.75}, {"text": "Welcome back.", "start": 23.56, "duration": 1.35}, {"text": "We're going to go through a very\nspecific example of association", "start": 24.91, "duration": 6.27}, {"text": "studying, illustrating this\nextremely important statistic,", "start": 31.18, "duration": 3.36}, {"text": "the chi-square statistic\nin the simplest case.", "start": 34.54, "duration": 4.62}, {"text": "That simple case will be a\nsingle allele combination,", "start": 39.16, "duration": 6.93}, {"text": "two alleles and two possible\nphenotypic outcomes,", "start": 46.09, "duration": 6.3}, {"text": "HIV resistance and\nHIV non-resistance.", "start": 52.39, "duration": 4.92}, {"text": "So to set up this\nassociation study, which", "start": 57.31, "duration": 2.97}, {"text": "would be computational,\nlet's talk a little bit", "start": 60.28, "duration": 3.51}, {"text": "about the biology here.", "start": 63.79, "duration": 1.199}, {"text": "All viruses need to get\ninto your cells somehow.", "start": 68.89, "duration": 3.66}, {"text": "HIV has a number of\nproteins to which it binds", "start": 72.55, "duration": 4.89}, {"text": "on the surface of your cell.", "start": 77.44, "duration": 1.17}, {"text": "These proteins are not-- they're\nnot designed to bind HIV.", "start": 78.61, "duration": 3.6}, {"text": "They do something else.", "start": 82.21, "duration": 1.27}, {"text": "This is in a family of\nchemokine receptors.", "start": 83.48, "duration": 2.33}, {"text": "This is involved in\nintracellular signaling,", "start": 85.81, "duration": 3.15}, {"text": "and so it's a receptor\nnormally for these chemokines.", "start": 88.96, "duration": 5.4}, {"text": "But it is also a\nreceptor for the virus.", "start": 94.36, "duration": 3.72}, {"text": "And in the human population,\nas we alluded to earlier,", "start": 98.08, "duration": 6.43}, {"text": "there are at least two\nalleles, two common alleles.", "start": 104.51, "duration": 3.32}, {"text": "One of them, the top\none, capital CCR5,", "start": 107.83, "duration": 4.89}, {"text": "has this long,\nopen reading frame.", "start": 112.72, "duration": 1.5}, {"text": "And this you could translate\nby your pearl strip", "start": 114.22, "duration": 2.97}, {"text": "that you wrote for\nthe problem set.", "start": 117.19, "duration": 1.89}, {"text": "And the DNA sequences\nin the middle here", "start": 119.08, "duration": 3.37}, {"text": "and the protein sequence derived\nfrom it is on the top strand.", "start": 122.45, "duration": 5.46}, {"text": "And that's the capital CCR5.", "start": 127.91, "duration": 1.879}, {"text": "And the little delta or\ndeletion Ccr5 is below it.", "start": 129.789, "duration": 4.111}, {"text": "You've locked out 32\nbase pairs, which is not", "start": 133.9, "duration": 3.33}, {"text": "an interval multiple of three.", "start": 137.23, "duration": 1.47}, {"text": "And as you know\nfrom last lecture,", "start": 138.7, "duration": 2.97}, {"text": "that means it's going to be\na different genetic code.", "start": 141.67, "duration": 2.31}, {"text": "At every point downstream, this\nis going to be frame-shifted,", "start": 143.98, "duration": 3.21}, {"text": "and so you get a whole\nnew set of amino acids", "start": 147.19, "duration": 2.29}, {"text": "for the entirety of the rest\nof the carboxy terminus.", "start": 149.48, "duration": 4.92}, {"text": "So this in black\nhere-- so we're showing", "start": 154.4, "duration": 3.23}, {"text": "here in the single-letter code\na somewhat realistic folding", "start": 157.63, "duration": 5.1}, {"text": "of the-- schematic folding\nof the protein, showing here", "start": 162.73, "duration": 3.18}, {"text": "disulfide between two cysteines.", "start": 165.91, "duration": 2.43}, {"text": "Transmembrane region, we\nhave these hydrophobic alpha", "start": 168.34, "duration": 3.66}, {"text": "helices.", "start": 172.0, "duration": 0.84}, {"text": "And finally, in the\nblack amino acids,", "start": 172.84, "duration": 2.94}, {"text": "the C terminus, the\nend of the protein", "start": 175.78, "duration": 2.34}, {"text": "are all substituted in\nthis deletion mutant.", "start": 178.12, "duration": 3.45}, {"text": "Now that is sufficient to\ncause resistance to the virus.", "start": 181.57, "duration": 5.31}, {"text": "It probably has some\neffect on its ability", "start": 186.88, "duration": 2.49}, {"text": "to bind chemokines or react\nto them in some other way.", "start": 189.37, "duration": 4.12}, {"text": "And presumably, this is not--", "start": 193.49, "duration": 3.68}, {"text": "there is some deleterious\neffect we do not know about.", "start": 197.17, "duration": 2.97}, {"text": "But in any case,\nwe can assess this.", "start": 200.14, "duration": 3.075}, {"text": "We can make a genetic\nassay for this.", "start": 203.215, "duration": 2.235}, {"text": "And we can look in\nhuman populations", "start": 205.45, "duration": 4.62}, {"text": "for their resistance to HIV and\nfor the presence of either two", "start": 210.07, "duration": 4.8}, {"text": "alleles of the resistance or\ntwo alleles of the susceptible.", "start": 214.87, "duration": 6.57}, {"text": "Now I'm kind of biasing\nyou here in this.", "start": 221.44, "duration": 2.25}, {"text": "We haven't done the\nassociation study.", "start": 223.69, "duration": 1.633}, {"text": "I really shouldn't be referring\nto it as resistant or not,", "start": 225.323, "duration": 2.417}, {"text": "but I think it helps\nyou visualize it.", "start": 227.74, "duration": 2.61}, {"text": "We'll be rigorous enough\nin the next slide.", "start": 230.35, "duration": 2.11}, {"text": "So here is, if you will,\nthe big allele, right?", "start": 232.46, "duration": 4.85}, {"text": "It's the original.", "start": 237.31, "duration": 1.28}, {"text": "It's the non-deleted allele.", "start": 238.59, "duration": 1.54}, {"text": "So when you do a PCR\nassay where you're", "start": 240.13, "duration": 2.43}, {"text": "amplifying with two primers\nacross the region that", "start": 242.56, "duration": 3.54}, {"text": "could be deleted\nor not, you'll tend", "start": 246.1, "duration": 2.1}, {"text": "to get a large\namplification product.", "start": 248.2, "duration": 2.16}, {"text": "You prime synthesis\nuntil you get something", "start": 250.36, "duration": 3.81}, {"text": "which has 403 base pairs.", "start": 254.17, "duration": 2.185}, {"text": "And there's enough of it\nthat you can display it", "start": 256.355, "duration": 2.0}, {"text": "on electrophoretic gel,\nand it migrates slowly", "start": 258.355, "duration": 2.745}, {"text": "because it's large.", "start": 261.1, "duration": 2.22}, {"text": "If you have a homozygote\nfor the deletion allele--", "start": 263.32, "duration": 2.79}, {"text": "we'll not call it the HIV\nresistance allele just yet--", "start": 266.11, "duration": 4.29}, {"text": "then you'll get a\n371-base-pair PCR product.", "start": 270.4, "duration": 4.8}, {"text": "And if you have\nthe heterozygote,", "start": 275.2, "duration": 1.5}, {"text": "you'll get both, the large and\nthe small allele represented", "start": 276.7, "duration": 3.39}, {"text": "on this electrophoretic assay.", "start": 280.09, "duration": 1.47}, {"text": "A very simple, very robust\nDNA PCR-based assay.", "start": 281.56, "duration": 4.26}, {"text": "So now let's ask whether\none allele or the other", "start": 289.32, "duration": 6.11}, {"text": "is more abundant in people\nwhich are observed to be", "start": 295.43, "duration": 5.25}, {"text": "seropositive or seronegative.", "start": 300.68, "duration": 1.98}, {"text": "Seropositive means\nthat they have", "start": 302.66, "duration": 2.04}, {"text": "circulating antibodies\nin their serum", "start": 304.7, "duration": 2.82}, {"text": "which react positively\nto the HIV virus.", "start": 307.52, "duration": 4.53}, {"text": "And so that's not\nnecessarily, but is commonly", "start": 312.05, "duration": 5.11}, {"text": "associated with being heavily\nexposed to the HIV virus,", "start": 317.16, "duration": 3.26}, {"text": "and therefore\nbasically infected.", "start": 320.42, "duration": 2.28}, {"text": "Seronegative means\nthat you are--", "start": 322.7, "duration": 4.62}, {"text": "it's an indication\nthat you're resistant.", "start": 327.32, "duration": 2.19}, {"text": "Now we could do this as\na two-by-two matrix here", "start": 329.51, "duration": 4.125}, {"text": "of alleles versus\noutcomes, or we", "start": 333.635, "duration": 3.555}, {"text": "could do it as a\nthree-by-two where we", "start": 337.19, "duration": 2.25}, {"text": "have genotypes versus outcomes.", "start": 339.44, "duration": 2.94}, {"text": "The three genotypes are\nbig-big, little-little,", "start": 342.38, "duration": 4.05}, {"text": "and big-little heterozygote.", "start": 346.43, "duration": 1.635}, {"text": "But let's just do it-- just keep\nit simple in terms of alleles.", "start": 348.065, "duration": 2.625}, {"text": "If there is a selective advan--", "start": 350.69, "duration": 2.19}, {"text": "or there's a\nperceivable association", "start": 352.88, "duration": 4.98}, {"text": "between the seropositive,\nseronegative, and the allele,", "start": 357.86, "duration": 3.93}, {"text": "you should be able to see it\nin both the genotype or just", "start": 361.79, "duration": 3.565}, {"text": "the allele.", "start": 365.355, "duration": 0.5}, {"text": "The allele is simpler.", "start": 365.855, "duration": 1.155}, {"text": "It's a two-by-two matrix.", "start": 367.01, "duration": 1.53}, {"text": "And so these are the data,\njust these four boxes here.", "start": 368.54, "duration": 4.68}, {"text": "The big allele is 1,278 observed\nnegative and 1,368 observed", "start": 373.22, "duration": 7.53}, {"text": "positive for a total of 2,646.", "start": 380.75, "duration": 3.06}, {"text": "You can see that\nthere are fewer total", "start": 383.81, "duration": 2.67}, {"text": "in the population surveyed\nof the deletion mutant.", "start": 386.48, "duration": 3.577}, {"text": "This is consistent with the\nclaim that I made all along.", "start": 390.057, "duration": 2.333}, {"text": "It's about 9% in general\nhuman population,", "start": 392.39, "duration": 2.85}, {"text": "and it's 9% of this population.", "start": 395.24, "duration": 1.995}, {"text": "That's good.", "start": 397.235, "duration": 2.005}, {"text": "But now you have to\ncorrect for that.", "start": 399.24, "duration": 1.64}, {"text": "You need to-- you\ncan't just ask,", "start": 400.88, "duration": 3.24}, {"text": "is it more frequent here or not?", "start": 404.12, "duration": 1.47}, {"text": "You have to correct for\nthe actual frequencies", "start": 405.59, "duration": 2.52}, {"text": "in the population.", "start": 408.11, "duration": 0.78}, {"text": "And the way that's done is you\ncalculate another table, which", "start": 408.89, "duration": 6.33}, {"text": "is the expected number of each\nof these combinations of big", "start": 415.22, "duration": 6.6}, {"text": "with seronegative,\nbig with seropositive,", "start": 421.82, "duration": 1.86}, {"text": "and so forth, under\nthe assumption", "start": 423.68, "duration": 2.19}, {"text": "that it's completely random.", "start": 425.87, "duration": 1.965}, {"text": "You know the allele\nfrequencies in the population,", "start": 427.835, "duration": 2.385}, {"text": "but say that they just randomly\nassociated with whether it's", "start": 430.22, "duration": 3.405}, {"text": "seropositive or seronegative.", "start": 433.625, "duration": 1.545}, {"text": "You use these totals\nhere and the frequencies", "start": 435.17, "duration": 2.61}, {"text": "in the population to\ngenerate this expected end", "start": 437.78, "duration": 3.75}, {"text": "of the random assumption.", "start": 441.53, "duration": 1.17}, {"text": "And then you look for\ndeviation of the real ones", "start": 442.7, "duration": 3.09}, {"text": "of the observed\nversus the expected.", "start": 445.79, "duration": 1.715}, {"text": "So any deviation between the\nexpected and the observed", "start": 454.99, "duration": 4.32}, {"text": "is going to be\nsignificant in this.", "start": 459.31, "duration": 1.59}, {"text": "So you want to do is take the\ndifference between the observed", "start": 463.49, "duration": 3.23}, {"text": "and expected.", "start": 466.72, "duration": 0.71}, {"text": "So we're working on\na statistic here,", "start": 467.43, "duration": 2.41}, {"text": "a type of measure\nthat will determine,", "start": 469.84, "duration": 2.28}, {"text": "how far from expectation\nare the observations", "start": 472.12, "duration": 3.36}, {"text": "on the left-hand side\nin this two-by-two?", "start": 475.48, "duration": 3.27}, {"text": "And so for every square\nin the two-by-two,", "start": 478.75, "duration": 3.39}, {"text": "you find a corresponding\nexpected number", "start": 482.14, "duration": 2.64}, {"text": "and you subtract it.", "start": 484.78, "duration": 1.14}, {"text": "That's the starting point.", "start": 485.92, "duration": 1.29}, {"text": "But you don't care whether\nit's negative or positive.", "start": 487.21, "duration": 3.66}, {"text": "You want to make it positive.", "start": 490.87, "duration": 1.51}, {"text": "So the trick we'll often use\nis to take the square of that.", "start": 492.38, "duration": 2.598}, {"text": "So you could take\nthe absolute value.", "start": 494.978, "duration": 1.542}, {"text": "You take the square for the\nchi-square, oddly enough.", "start": 496.52, "duration": 3.11}, {"text": "And then you want to put it\non some kind of standard scale", "start": 499.63, "duration": 3.84}, {"text": "so that when you do a chi-square\nfor any kind of phenomenon,", "start": 503.47, "duration": 3.57}, {"text": "you'll be able to compare.", "start": 507.04, "duration": 1.2}, {"text": "And the way you do that is you\ndivide by the expected number.", "start": 508.24, "duration": 3.63}, {"text": "Or as this puts it on, if\nthese numbers were really huge,", "start": 511.87, "duration": 4.53}, {"text": "this would bring them down.", "start": 516.4, "duration": 3.13}, {"text": "Very small, it'll\nbring the same point.", "start": 519.53, "duration": 2.34}, {"text": "And so you take the sum over\nall the squares in here,", "start": 521.87, "duration": 3.45}, {"text": "and that's 15.6.", "start": 525.32, "duration": 1.94}, {"text": "And that's saying that it\ndeviates from the expectation", "start": 527.26, "duration": 5.89}, {"text": "by this amount normalized as\na fraction of the expected.", "start": 533.15, "duration": 5.49}, {"text": "Now to determine just a little\nsidelight on the chi-square,", "start": 538.64, "duration": 5.34}, {"text": "in order to determine\nthe probability of 15.6", "start": 543.98, "duration": 3.42}, {"text": "being significant,\nwhat does that", "start": 547.4, "duration": 1.41}, {"text": "mean, looking at this at 15.6?", "start": 548.81, "duration": 1.952}, {"text": "You want to turn this\ninto a probability,", "start": 550.762, "duration": 1.708}, {"text": "because probabilities are the\ncommon language that we can all", "start": 552.47, "duration": 2.67}, {"text": "share our surprise at this\nbeing different from expected,", "start": 555.14, "duration": 4.29}, {"text": "the null hypothesis that\nthis is the same as expected.", "start": 559.43, "duration": 2.825}, {"text": "And so in order\nto evaluate that,", "start": 562.255, "duration": 1.375}, {"text": "you have to ask how\nmuch freedom there--", "start": 563.63, "duration": 2.22}, {"text": "degrees of freedom.", "start": 565.85, "duration": 1.18}, {"text": "This is jargon for,\nhow many different ways", "start": 567.03, "duration": 5.26}, {"text": "can these two numbers vary?", "start": 572.29, "duration": 1.72}, {"text": "Well, since we know\nthe total number,", "start": 574.01, "duration": 2.96}, {"text": "when we observe the number of\nCCR5, that fixes in the columns", "start": 576.97, "duration": 7.15}, {"text": "the number of deletions, right?", "start": 584.12, "duration": 1.68}, {"text": "Because it's just going to be\nthe number of big alleles taken", "start": 585.8, "duration": 3.45}, {"text": "from the total.", "start": 589.25, "duration": 1.48}, {"text": "So in a way, the degrees\nof freedom is just one.", "start": 590.73, "duration": 2.18}, {"text": "You fixed this one number, and\nthe other one is now known.", "start": 592.91, "duration": 4.44}, {"text": "And the same thing's true\nfor rows and columns.", "start": 597.35, "duration": 2.08}, {"text": "So the rows minus--", "start": 599.43, "duration": 1.19}, {"text": "it's just one and\nthe columns is one.", "start": 600.62, "duration": 2.49}, {"text": "And so the whole\ndegrees of freedom", "start": 603.11, "duration": 1.83}, {"text": "is the product that rows\nand columns, which is one.", "start": 604.94, "duration": 2.97}, {"text": "So you plug this in.", "start": 607.91, "duration": 0.93}, {"text": "If you look in your\nstandard statistical--", "start": 608.84, "duration": 1.92}, {"text": "or your favorite statistical\nbook or software package, Excel", "start": 610.76, "duration": 3.84}, {"text": "or whatever, you plug\nin this chi-square value", "start": 614.6, "duration": 2.82}, {"text": "and this degrees of freedom,\nand you get this probability,", "start": 617.42, "duration": 2.95}, {"text": "which is very significant.", "start": 620.37, "duration": 1.52}, {"text": "Generally better than 5%\nmeans that you will only", "start": 621.89, "duration": 5.22}, {"text": "be wrong 20% of the time.", "start": 627.11, "duration": 2.32}, {"text": "Some people would prefer to--", "start": 629.43, "duration": 2.69}, {"text": "this means you'll be wrong eight\ntimes in 10,000 or something", "start": 632.12, "duration": 4.21}, {"text": "like that.", "start": 636.33, "duration": 0.5}, {"text": "Very, very infrequently.", "start": 636.83, "duration": 2.64}, {"text": "OK.", "start": 639.47, "duration": 1.17}, {"text": "Now this is great.", "start": 640.64, "duration": 1.84}, {"text": "This is a two-by-two matrix.", "start": 642.48, "duration": 1.25}, {"text": "We found an association.", "start": 643.73, "duration": 1.56}, {"text": "We have a plausible\nmolecular mechanism", "start": 645.29, "duration": 2.79}, {"text": "in the previous slide.", "start": 648.08, "duration": 1.56}, {"text": "But how was it that\nwe pulled CCR5 out", "start": 649.64, "duration": 3.69}, {"text": "of-- this rabbit out of the hat?", "start": 653.33, "duration": 1.5}, {"text": "I mean, why CCR5?", "start": 654.83, "duration": 2.43}, {"text": "There are 40,000-some\ngenes in the human genome.", "start": 657.26, "duration": 3.09}, {"text": "Yes?", "start": 660.35, "duration": 0.57}, {"text": "AUDIENCE: What is it?", "start": 660.92, "duration": 0.875}, {"text": "I was curious as to,\nwhat population is it?", "start": 661.795, "duration": 4.165}, {"text": "I mean, in which there's\nslightly more seropositive", "start": 665.96, "duration": 5.272}, {"text": "or seronegative people.", "start": 671.232, "duration": 0.958}, {"text": "This must be a particular--", "start": 672.19, "duration": 2.754}, {"text": "GEORGE CHURCH: Oh, yeah.", "start": 674.944, "duration": 2.286}, {"text": "This is a case\ncontrol study where", "start": 677.23, "duration": 1.89}, {"text": "you try to get a roughly\nequal number of negatives", "start": 679.12, "duration": 2.88}, {"text": "and positives that are matched\nfor socioeconomic group", "start": 682.0, "duration": 3.45}, {"text": "and race and gender\nand things like that.", "start": 685.45, "duration": 2.37}, {"text": "So that's a setup.", "start": 687.82, "duration": 1.51}, {"text": "But then the-- if there's not\na huge risk ratio for the two", "start": 689.33, "duration": 6.29}, {"text": "alleles, then you'll expect them\nto be close to the population", "start": 695.62, "duration": 2.66}, {"text": "frequency, which means\nthat you can't just", "start": 698.28, "duration": 1.75}, {"text": "look at it on inspection\nand say, oh, yeah.", "start": 700.03, "duration": 2.46}, {"text": "All the seropositive\nare the big allele.", "start": 702.49, "duration": 2.79}, {"text": "We wouldn't need a\nchi-square at that point.", "start": 705.28, "duration": 2.88}, {"text": "But this is pretty close to\nthe population frequency,", "start": 708.16, "duration": 3.79}, {"text": "and so that's why we\nhad to do a chi-square.", "start": 711.95, "duration": 4.0}, {"text": "OK.", "start": 715.95, "duration": 1.5}, {"text": "But the question\nthat we're taking now", "start": 717.45, "duration": 5.73}, {"text": "is, how did we pick CCR5?", "start": 723.18, "duration": 1.45}, {"text": "And I introduced this as\nbeing a putative receptor", "start": 724.63, "duration": 3.56}, {"text": "for the virus, but one of\nthe first pieces of evidence", "start": 728.19, "duration": 2.842}, {"text": "that this was a putative\nreceptor for the virus", "start": 731.032, "duration": 1.958}, {"text": "was this association study.", "start": 732.99, "duration": 2.71}, {"text": "So how was it that it hit\nthe chemokine receptor?", "start": 735.7, "duration": 3.632}, {"text": "Well, you could say, well,\nbecause some kind of hunch", "start": 739.332, "duration": 2.208}, {"text": "about chemokines being\ninvolved in immunology,", "start": 741.54, "duration": 2.49}, {"text": "and immunology being\nimportant in fighting viruses,", "start": 744.03, "duration": 3.69}, {"text": "but that wouldn't suggest\nthat it's an actual receptor.", "start": 747.72, "duration": 2.64}, {"text": "I think these are--", "start": 753.51, "duration": 1.64}, {"text": "there's all kinds of\ninspired guesswork.", "start": 755.15, "duration": 1.93}, {"text": "There's biochemistry happening\nbehind the scene, and so on.", "start": 757.08, "duration": 2.925}, {"text": "But let's just put that\naside for the moment", "start": 760.005, "duration": 2.17}, {"text": "and take the more\ngeneral case that you", "start": 762.175, "duration": 1.625}, {"text": "wanted to test not just\nthis one hypothesis,", "start": 763.8, "duration": 2.64}, {"text": "that CCR5 is involved,\nbut you've implicitly", "start": 766.44, "duration": 2.67}, {"text": "then tested or explicitly\ntested every gene.", "start": 769.11, "duration": 3.812}, {"text": "You've gone through\nevery gene and you've", "start": 772.922, "duration": 1.708}, {"text": "taken either the most\ncommon alleles or you've", "start": 774.63, "duration": 3.12}, {"text": "sequenced your own\ngenome and you've", "start": 777.75, "duration": 1.59}, {"text": "found the alleles that you have,\nwhether they're common or rare.", "start": 779.34, "duration": 3.275}, {"text": "You don't care.", "start": 782.615, "duration": 0.625}, {"text": "And you want to ask,\nwhat's the association?", "start": 783.24, "duration": 2.82}, {"text": "Let's consider the upper\nright-hand panel here", "start": 790.85, "duration": 4.35}, {"text": "where we have some risk ratio,\na fairly subtle one, 1.5.", "start": 795.2, "duration": 5.46}, {"text": "Remember, we were talking\nabout risk ratios of 75", "start": 800.66, "duration": 2.64}, {"text": "in the case of autism.", "start": 803.3, "duration": 1.05}, {"text": "This is just 1.5.", "start": 804.35, "duration": 1.02}, {"text": "Very subtle risk ratio, just\nlike I think in the last one", "start": 805.37, "duration": 4.02}, {"text": "could have been a\nsubtle risk ratio.", "start": 809.39, "duration": 1.86}, {"text": "And the x-axis is going to\nbe the number of alleles", "start": 813.93, "duration": 4.535}, {"text": "that you're\nhypothetically testing.", "start": 818.465, "duration": 2.115}, {"text": "This could be related\nto the number of genes", "start": 820.58, "duration": 1.92}, {"text": "that you're testing,\nor it could be", "start": 822.5, "duration": 1.98}, {"text": "more than the number of\ngenes that you're testing,", "start": 824.48, "duration": 1.56}, {"text": "because you can have more\nthan one allele per gene", "start": 826.04, "duration": 2.04}, {"text": "that you might want to test.", "start": 828.08, "duration": 1.167}, {"text": "Is this allele of this gene\nimportant in this disease,", "start": 829.247, "duration": 3.153}, {"text": "or is this other one?", "start": 832.4, "duration": 1.245}, {"text": "For example, sickle\ncell is important,", "start": 833.645, "duration": 2.085}, {"text": "but various other hemoglobin\nmutations are not.", "start": 835.73, "duration": 3.51}, {"text": "This chemokine deletion is\nimportant and maybe another one", "start": 839.24, "duration": 2.67}, {"text": "isn't.", "start": 841.91, "duration": 0.72}, {"text": "Many chemokine mutations\nwill be neutral.", "start": 842.63, "duration": 3.11}, {"text": "OK.", "start": 845.74, "duration": 0.5}, {"text": "So as you increase the number\nof genes and alleles from--", "start": 846.24, "duration": 3.77}, {"text": "here's 10 to the fourth on up--", "start": 850.01, "duration": 2.67}, {"text": "then the number of sib pairs--", "start": 852.68, "duration": 3.24}, {"text": "so this is a simulation covering\nall kinds of experiments", "start": 855.92, "duration": 4.65}, {"text": "that you could do\nwhere you can use", "start": 860.57, "duration": 3.03}, {"text": "computational\nmethods to help guide", "start": 863.6, "duration": 1.86}, {"text": "the design of experiments.", "start": 865.46, "duration": 2.4}, {"text": "If you did an\nexpensive experiment", "start": 867.86, "duration": 1.59}, {"text": "and you just happened to\nuse too few patients and too", "start": 869.45, "duration": 3.87}, {"text": "many alleles, then you may\nhave misused your resources.", "start": 873.32, "duration": 3.255}, {"text": "You should have maybe done\nfewer alleles and more patients", "start": 876.575, "duration": 2.535}, {"text": "or something like that.", "start": 879.11, "duration": 2.68}, {"text": "And this provides\nsome guidance here.", "start": 881.79, "duration": 1.82}, {"text": "But you can see\nthat in order to get", "start": 883.61, "duration": 1.68}, {"text": "to a very large\nnumber of alleles,", "start": 885.29, "duration": 1.98}, {"text": "you need a fairly\nmodest increase", "start": 887.27, "duration": 1.68}, {"text": "in the number of patients.", "start": 888.95, "duration": 1.09}, {"text": "And that's due to\nthe exponential term", "start": 890.04, "duration": 4.43}, {"text": "that you have in these\nprobability distributions.", "start": 894.47, "duration": 4.69}, {"text": "So you actually--\nbut nevertheless,", "start": 899.16, "duration": 1.97}, {"text": "it's a big deal cost-wise\ngoing up from, say,", "start": 901.13, "duration": 5.49}, {"text": "400 patients to 1,600.", "start": 906.62, "duration": 4.5}, {"text": "Nevertheless, it's\nonly linear in patients", "start": 911.12, "duration": 2.85}, {"text": "while it's exponential in the\nnumber of alleles you can test,", "start": 913.97, "duration": 4.47}, {"text": "so that's the good news.", "start": 918.44, "duration": 2.03}, {"text": "And you can see some\nof these other panels", "start": 920.47, "duration": 1.75}, {"text": "show the effect of\nvarying other parameters.", "start": 922.22, "duration": 4.35}, {"text": "For example, here\non the left you've", "start": 926.57, "duration": 1.92}, {"text": "got varying the population\nfrequency of the allele.", "start": 928.49, "duration": 3.99}, {"text": "As you get to very,\nvery rare alleles", "start": 932.48, "duration": 3.15}, {"text": "on the right hand of the\nhorizontal axis here, then", "start": 935.63, "duration": 4.26}, {"text": "the number of sib pairs--", "start": 939.89, "duration": 4.32}, {"text": "brothers-sisters,\nbrother-brothers", "start": 944.21, "duration": 1.8}, {"text": "that you need-- starts\nto go through the roof.", "start": 946.01, "duration": 2.19}, {"text": "And now it's exponential\non both axes,", "start": 948.2, "duration": 4.86}, {"text": "or that is to say that\nit's a direct relationship.", "start": 953.06, "duration": 2.31}, {"text": "Question?", "start": 955.37, "duration": 0.54}, {"text": "AUDIENCE: What's that\nz value over there?", "start": 955.91, "duration": 1.718}, {"text": "GEORGE CHURCH: Hmm?", "start": 957.628, "duration": 0.792}, {"text": "AUDIENCE: What's that\nz value of over there?", "start": 958.42, "duration": 2.53}, {"text": "GEORGE CHURCH: Oh, that's\nthe population frequency that", "start": 960.95, "duration": 4.345}, {"text": "you're--", "start": 965.295, "duration": 0.5}, {"text": "AUDIENCE: On the bottom?", "start": 965.795, "duration": 1.199}, {"text": "GEORGE CHURCH: Hmm?", "start": 966.994, "duration": 0.946}, {"text": "Well, on-- on the one we were\njust talking about on the left,", "start": 967.94, "duration": 4.86}, {"text": "the population frequency\nis the horizontal axis,", "start": 972.8, "duration": 2.52}, {"text": "and it varies from near unity\nto 10 to the minus nine.", "start": 975.32, "duration": 5.34}, {"text": "It's a very rare\nallele frequency.", "start": 980.66, "duration": 3.3}, {"text": "On the right, the one we\nstarted with, the top right,", "start": 983.96, "duration": 3.78}, {"text": "we just picked 0.5,\nwhich would be very--", "start": 987.74, "duration": 3.24}, {"text": "be around here on the left-hand\nend of the left-hand quadrant.", "start": 990.98, "duration": 4.84}, {"text": "So you pick one of these\nallele frequencies, a fairly--", "start": 995.82, "duration": 2.66}, {"text": "where it's equal\nfrequency of the two", "start": 998.48, "duration": 1.95}, {"text": "alleles in the\npopulation as where you", "start": 1000.43, "duration": 2.62}, {"text": "do the rest of the simulation.", "start": 1003.05, "duration": 1.25}, {"text": "You can think of\nall these panels", "start": 1004.3, "duration": 2.43}, {"text": "could be some\nmulti-dimensional display,", "start": 1006.73, "duration": 1.74}, {"text": "but I wanted to take\nthem out one at a time.", "start": 1008.47, "duration": 2.76}, {"text": "And actually, I did\nall these in Excel", "start": 1011.23, "duration": 3.48}, {"text": "using the equations that are\npresent in this reference", "start": 1014.71, "duration": 3.92}, {"text": "that's given in the slides here.", "start": 1018.63, "duration": 2.44}, {"text": "A good sign of a\nwell-written paper", "start": 1024.53, "duration": 1.77}, {"text": "is for a sort of\naverage individual", "start": 1026.3, "duration": 2.309}, {"text": "to be able to reproduce it.", "start": 1028.609, "duration": 2.891}, {"text": "So we have how many--\nso we've been talking", "start": 1031.5, "duration": 5.2}, {"text": "about new polymorphisms.", "start": 1036.7, "duration": 2.34}, {"text": "In fact, the question that\ncame up during the break", "start": 1039.04, "duration": 2.25}, {"text": "was, if selection and drift\ncause allele frequencies to fix", "start": 1041.29, "duration": 6.779}, {"text": "fairly rapidly, drift\nin small populations,", "start": 1048.069, "duration": 3.511}, {"text": "normal-sized\npopulations will drift", "start": 1051.58, "duration": 1.95}, {"text": "in fairly short evolutionary\ntimes and selection", "start": 1053.53, "duration": 4.303}, {"text": "if you have a high selection\ncoefficient of cost fixation.", "start": 1057.833, "duration": 2.417}, {"text": "Why do we have any allele\nfrequencies at all?", "start": 1060.25, "duration": 1.89}, {"text": "Why isn't everything fixed at\n100% for one particular allele?", "start": 1062.14, "duration": 4.5}, {"text": "And the answer is mutation.", "start": 1066.64, "duration": 1.53}, {"text": "And where all these new\nmutations or polymorphisms", "start": 1068.17, "duration": 2.408}, {"text": "come from-- actually,\nthese should probably", "start": 1070.578, "duration": 1.792}, {"text": "be called mutations,\nbecause most of them", "start": 1072.37, "duration": 2.1}, {"text": "have frequencies less than 1%.", "start": 1074.47, "duration": 2.31}, {"text": "Well, here's a specific model\nwhich doesn't follow all", "start": 1076.78, "duration": 3.103}, {"text": "the assumptions we had before,\nbut we'll use a different--", "start": 1079.883, "duration": 2.417}, {"text": "we'll use a back-of-the-envelope\ncalculation to give you", "start": 1082.3, "duration": 2.333}, {"text": "a feeling for what\nis true for the--", "start": 1084.633, "duration": 3.517}, {"text": "what is likely to be the case\nfor the human population.", "start": 1088.15, "duration": 2.77}, {"text": "So the human population,\nthere's a little bit", "start": 1090.92, "duration": 2.39}, {"text": "of unknown in some\nof these parameters,", "start": 1093.31, "duration": 2.99}, {"text": "so you should take these all\nwith a grain of salt. Actually,", "start": 1096.3, "duration": 2.5}, {"text": "everything I say\nyou should take.", "start": 1098.8, "duration": 1.42}, {"text": "But the number of\npopulations that we've", "start": 1100.22, "duration": 4.25}, {"text": "had since a bottleneck\nin the human population--", "start": 1104.47, "duration": 3.75}, {"text": "maybe there were as few\nas 10 to the fourth humans", "start": 1108.22, "duration": 3.12}, {"text": "at some point or another.", "start": 1111.34, "duration": 2.28}, {"text": "Maybe less.", "start": 1113.62, "duration": 1.68}, {"text": "But since that time, there have\nbeen about 5,000 generations.", "start": 1115.3, "duration": 2.91}, {"text": "And during that\ntime, our population", "start": 1118.21, "duration": 1.68}, {"text": "has now grown to\nsix billion people.", "start": 1119.89, "duration": 2.25}, {"text": "That's the n prime nn.", "start": 1122.14, "duration": 3.57}, {"text": "And the mutation rate, as\nmentioned earlier in response", "start": 1125.71, "duration": 6.073}, {"text": "to a question, is\naround 10 to the minus", "start": 1131.783, "duration": 1.667}, {"text": "eighth per base pair per\ngenome per generation.", "start": 1133.45, "duration": 6.13}, {"text": "And so the genome size\nis about six billion.", "start": 1139.58, "duration": 2.69}, {"text": "Coincidentally, the same\nas the population size.", "start": 1142.27, "duration": 2.16}, {"text": "Total coincidence.", "start": 1144.43, "duration": 1.95}, {"text": "Then 10 to the minus eight\ntimes that number of base pairs", "start": 1146.38, "duration": 3.45}, {"text": "means you have\nabout 60 mutations", "start": 1149.83, "duration": 2.49}, {"text": "or so occurring in a generation.", "start": 1152.32, "duration": 4.99}, {"text": "So you've got a steady\nflow of new mutations.", "start": 1157.31, "duration": 2.74}, {"text": "Now if you take\nthat-- just roughly", "start": 1160.05, "duration": 1.57}, {"text": "speaking, if you take that\nover 5,000 generations,", "start": 1161.62, "duration": 2.31}, {"text": "you've got 60 times 5,000.", "start": 1163.93, "duration": 2.7}, {"text": "You've got a very large number--", "start": 1166.63, "duration": 1.86}, {"text": "on the order of 10 to\nthe fourth mutations", "start": 1168.49, "duration": 3.21}, {"text": "that have accumulated\nin our population.", "start": 1171.7, "duration": 1.93}, {"text": "Assuming relatively\nlittle drift because", "start": 1173.63, "duration": 3.26}, {"text": "of this exponentially growing\npopulation and relatively", "start": 1176.89, "duration": 2.67}, {"text": "little selection, then\nthis is the number", "start": 1179.56, "duration": 3.27}, {"text": "that might have accumulated.", "start": 1182.83, "duration": 1.41}, {"text": "You can do subtle corrections\nfor this exponential growth.", "start": 1184.24, "duration": 4.68}, {"text": "The number of mutations\nyou got at the beginning", "start": 1188.92, "duration": 3.073}, {"text": "will have higher frequency,\nbut there'll be fewer of them,", "start": 1191.993, "duration": 2.417}, {"text": "because population was smaller.", "start": 1194.41, "duration": 1.332}, {"text": "But anyway, you\nget the picture, is", "start": 1195.742, "duration": 1.458}, {"text": "that the total\nnumber of mutations", "start": 1197.2, "duration": 1.89}, {"text": "in any one of this that\nare new since that new--", "start": 1199.09, "duration": 3.27}, {"text": "since 5,000 generations ago\nwill be on the order of 10", "start": 1202.36, "duration": 4.03}, {"text": "to the fourth in your body, not\nall of them doing good for you.", "start": 1206.39, "duration": 5.99}, {"text": "And for each of those\nrare mutations--", "start": 1212.38, "duration": 2.717}, {"text": "they might have a frequency of\nabout 10 to the minus five--", "start": 1215.097, "duration": 2.458}, {"text": "there will be about 10 to\nthe fourth people on Earth", "start": 1221.67, "duration": 4.348}, {"text": "that will share that very\nrare mutation with you.", "start": 1226.018, "duration": 2.042}, {"text": "10 to the minus 5\nsounds very rare,", "start": 1228.06, "duration": 2.782}, {"text": "but when you multiply it\nby six billion people,", "start": 1230.842, "duration": 1.958}, {"text": "there are a lot of people\nwho share that with you.", "start": 1232.8, "duration": 2.34}, {"text": "It's a new mutation.", "start": 1235.14, "duration": 1.85}, {"text": "OK.", "start": 1236.99, "duration": 0.5}, {"text": "So the take-home is--", "start": 1237.49, "duration": 1.49}, {"text": "and this is from\nthis reference here.", "start": 1238.98, "duration": 3.36}, {"text": "High genomic\ndeleterious mutations", "start": 1242.34, "duration": 3.36}, {"text": "accumulate over these 4,000--", "start": 1245.7, "duration": 3.48}, {"text": "some large number\nof generations.", "start": 1249.18, "duration": 1.92}, {"text": "And they would confound\nlinkage methods", "start": 1251.1, "duration": 2.7}, {"text": "and they would\nconfound assumptions", "start": 1253.8, "duration": 2.04}, {"text": "that say that the\ncommon alleles--", "start": 1255.84, "duration": 2.28}, {"text": "common alleles are causative.", "start": 1258.12, "duration": 4.07}, {"text": "OK.", "start": 1262.19, "duration": 0.51}, {"text": "So let's say we've done\nan association study.", "start": 1262.7, "duration": 2.25}, {"text": "Either we've done it\non one gene, picked", "start": 1264.95, "duration": 2.25}, {"text": "one out of the hat\nlike CCR5, or we've", "start": 1267.2, "duration": 2.28}, {"text": "done it on a full genome\nsurvey, 40,000 genes,", "start": 1269.48, "duration": 2.58}, {"text": "all the alleles we know of.", "start": 1272.06, "duration": 3.06}, {"text": "In order to do the latter,\nwe had to have a big patient", "start": 1275.12, "duration": 3.06}, {"text": "population.", "start": 1278.18, "duration": 1.69}, {"text": "But let's say we've done that.", "start": 1279.87, "duration": 1.25}, {"text": "Now we want to prove that\nthat association is--", "start": 1281.12, "duration": 3.9}, {"text": "that great statistic\nthat we got out,", "start": 1285.02, "duration": 1.83}, {"text": "if we have a large enough\npatient population,", "start": 1286.85, "duration": 1.89}, {"text": "is still just a statistic.", "start": 1288.74, "duration": 2.25}, {"text": "What will constitute proof is\nafter we find the association,", "start": 1290.99, "duration": 4.05}, {"text": "we make a copy of that\nmutation, isolated away", "start": 1295.04, "duration": 3.51}, {"text": "from the three million\nother polymorphisms that", "start": 1298.55, "duration": 2.55}, {"text": "are floating around\nin your body,", "start": 1301.1, "duration": 2.77}, {"text": "and we do some kind of test.", "start": 1303.87, "duration": 1.52}, {"text": "Ideally, we would\nmake an isogenic pair", "start": 1305.39, "duration": 3.12}, {"text": "of humans that only differ\nby this one mutation.", "start": 1308.51, "duration": 2.94}, {"text": "That is not generally considered\nmedically feasible or ethical.", "start": 1311.45, "duration": 7.53}, {"text": "But somehow or another, you\ncan do it on human cells", "start": 1318.98, "duration": 2.61}, {"text": "or you can do it in a\nmammalian model system.", "start": 1321.59, "duration": 5.52}, {"text": "But you have to make\nsomething that's", "start": 1327.11, "duration": 1.77}, {"text": "close to isogenic, a\ncopy of this mutation,", "start": 1328.88, "duration": 2.7}, {"text": "and show that it has a\nphenotype that makes sense.", "start": 1331.58, "duration": 3.22}, {"text": "And then, just to make\nsure you haven't introduced", "start": 1334.8, "duration": 2.27}, {"text": "other mutations, the\nreally careful scientists", "start": 1337.07, "duration": 3.24}, {"text": "will then revert that one\npolymorphism and show now", "start": 1340.31, "duration": 3.3}, {"text": "you no longer have\nthat phenotype.", "start": 1343.61, "duration": 2.46}, {"text": "OK.", "start": 1346.07, "duration": 0.96}, {"text": "So let's walk\nthrough an example.", "start": 1347.03, "duration": 4.45}, {"text": "Here's the third\nexample in this lecture", "start": 1351.48, "duration": 4.51}, {"text": "of a very specific\nallele where we've", "start": 1355.99, "duration": 2.8}, {"text": "shown the molecular\nbasis of it, and it's", "start": 1358.79, "duration": 2.22}, {"text": "the second example\nwhere it's not coding,", "start": 1361.01, "duration": 2.148}, {"text": "and it's the second example\nwhere it's going to repeat.", "start": 1363.158, "duration": 2.292}, {"text": "So this is just to--", "start": 1365.45, "duration": 1.71}, {"text": "I'm not giving you a\nrandom sample here.", "start": 1367.16, "duration": 1.71}, {"text": "I'm specifically biasing this\ntowards very interesting genes,", "start": 1368.87, "duration": 4.77}, {"text": "very interesting traits\nthat are associated", "start": 1373.64, "duration": 3.6}, {"text": "with non-coding\nrepetitive alleles.", "start": 1377.24, "duration": 2.91}, {"text": "In this case, the trait\nthat got the attention", "start": 1380.15, "duration": 3.6}, {"text": "of these researchers-- it\nisn't necessarily proven", "start": 1383.75, "duration": 3.12}, {"text": "that this is the relationship.", "start": 1386.87, "duration": 2.37}, {"text": "But the association\nthat was studied", "start": 1389.24, "duration": 1.65}, {"text": "was between anxiety-related\ntraits, anxiety,", "start": 1390.89, "duration": 4.35}, {"text": "and a polymorphism in the\nserotonin transporter.", "start": 1395.24, "duration": 3.6}, {"text": "This is a science paper.", "start": 1398.84, "duration": 3.3}, {"text": "Now the next step\nin this is to--", "start": 1402.14, "duration": 2.4}, {"text": "OK, that was found associated.", "start": 1404.54, "duration": 2.28}, {"text": "There were lots of other alleles\nrandomly being moved around,", "start": 1406.82, "duration": 6.51}, {"text": "because these are humans.", "start": 1413.33, "duration": 1.74}, {"text": "We have no control over who\nmates with who, or very little.", "start": 1415.07, "duration": 4.362}, {"text": "So you get what you're given.", "start": 1422.21, "duration": 1.98}, {"text": "You can do the survey\nas best you can.", "start": 1424.19, "duration": 1.83}, {"text": "But now in order to move it\ntowards a mechanistic basis", "start": 1426.02, "duration": 4.59}, {"text": "and a proof of introducing\njust this one point mutation.", "start": 1430.61, "duration": 3.69}, {"text": "Now what is the mutation\nfound in this case of anxiety", "start": 1434.3, "duration": 3.75}, {"text": "relationship in this\nserotonin transporter?", "start": 1438.05, "duration": 2.74}, {"text": "It's upstream of the first\nRNA encoding axon one.", "start": 1440.79, "duration": 4.34}, {"text": "It is a 44 base pair deletion\nin a repetitive region,", "start": 1445.13, "duration": 3.95}, {"text": "in a region which might be\nresponsible for promoting", "start": 1449.08, "duration": 4.03}, {"text": "transcription.", "start": 1453.11, "duration": 1.65}, {"text": "You have the short and the long\nalleles, just like in the CCR5.", "start": 1454.76, "duration": 3.93}, {"text": "In this case, it's in a\nputative promoter element.", "start": 1458.69, "duration": 2.76}, {"text": "And when you make this\nconstruct and you hook it up", "start": 1461.45, "duration": 3.57}, {"text": "to a luciferase enzymatic\nactivity in vitro,", "start": 1465.02, "duration": 5.95}, {"text": "in cultured cells so\nyou don't actually", "start": 1470.97, "duration": 2.12}, {"text": "have to construct\na mutant human,", "start": 1473.09, "duration": 3.21}, {"text": "you can now see the\nlong allele always", "start": 1476.3, "duration": 2.19}, {"text": "produces higher\nlevels of expression", "start": 1478.49, "duration": 3.33}, {"text": "than the short allele.", "start": 1481.82, "duration": 1.05}, {"text": "And these little error bars\non top of each of the measures", "start": 1482.87, "duration": 5.22}, {"text": "show your statistical measure\nof standard deviation,", "start": 1488.09, "duration": 3.63}, {"text": "as we did in the first lecture.", "start": 1491.72, "duration": 3.195}, {"text": "And if the black mean, which\nis the height of the bar,", "start": 1494.915, "duration": 5.235}, {"text": "is different from the white\nmean by more than a couple", "start": 1500.15, "duration": 3.143}, {"text": "of these standard deviations,\nwhich is the root mean", "start": 1503.293, "duration": 2.167}, {"text": "square of the standard\ndeviations of each", "start": 1505.46, "duration": 3.24}, {"text": "of the measures, then you call\nit statistically significant.", "start": 1508.7, "duration": 4.09}, {"text": "And that's what these\ntriple stars mean.", "start": 1512.79, "duration": 2.0}, {"text": "It's the statistical\nshorthand for this", "start": 1514.79, "duration": 2.37}, {"text": "is statistically significant\nat the cutoff that we're using.", "start": 1517.16, "duration": 3.06}, {"text": "Say, 5%.", "start": 1520.22, "duration": 1.68}, {"text": "Now in this case, it's\nkind of showing off", "start": 1521.9, "duration": 1.86}, {"text": "because every one of\nthem is statistically", "start": 1523.76, "duration": 1.75}, {"text": "significant by two different--", "start": 1525.51, "duration": 4.04}, {"text": "completely different\nassays here.", "start": 1529.55, "duration": 1.56}, {"text": "But the point is\nthis does not prove", "start": 1531.11, "duration": 2.16}, {"text": "that anxiety is meaningfully\nassociated with this.", "start": 1533.27, "duration": 6.27}, {"text": "But it does prove that this\nrepetitive polymorphism", "start": 1539.54, "duration": 5.04}, {"text": "is causally capable of\ndifferential transcription", "start": 1544.58, "duration": 8.25}, {"text": "levels for a reporter gene.", "start": 1552.83, "duration": 2.82}, {"text": "So by introducing it into\na clean cellular system,", "start": 1555.65, "duration": 7.65}, {"text": "you can test at least\npart of the mechanism that", "start": 1563.3, "duration": 3.12}, {"text": "might be involved in the\nassociation that originally", "start": 1566.42, "duration": 2.37}, {"text": "got your attention.", "start": 1568.79, "duration": 2.73}, {"text": "Now as you can\nsee, we're getting", "start": 1571.52, "duration": 2.97}, {"text": "into a fairly mature and fairly\nnew phase of human genetics.", "start": 1574.49, "duration": 6.66}, {"text": "Some of the concepts\nthat are used here", "start": 1581.15, "duration": 1.71}, {"text": "will be useful in a\nvariety of other systems", "start": 1582.86, "duration": 2.58}, {"text": "where we have relatively little\ncontrol over the genetics.", "start": 1585.44, "duration": 3.42}, {"text": "But certainly in humans,\nthere's a very large need.", "start": 1588.86, "duration": 4.65}, {"text": "And where this\nhappened historically", "start": 1593.51, "duration": 2.73}, {"text": "is with Mendelian linkage,\nwhich would involve", "start": 1596.24, "duration": 2.85}, {"text": "very large families with\na complete pedigree,", "start": 1599.09, "duration": 4.86}, {"text": "multi-generation,\ngreat-grandfathers and mothers,", "start": 1603.95, "duration": 3.21}, {"text": "all the way down, hundreds\nof people in a family.", "start": 1607.16, "duration": 3.615}, {"text": "And that's the problem, because\nthere aren't that many diseases", "start": 1610.775, "duration": 2.625}, {"text": "for which you have\nlarge families", "start": 1613.4, "duration": 1.375}, {"text": "with simple Mendelian\ninheritance.", "start": 1614.775, "duration": 1.895}, {"text": "Common diseases tend to\nbe much more complicated,", "start": 1616.67, "duration": 2.34}, {"text": "involving multiple\ngenes simultaneously", "start": 1619.01, "duration": 2.91}, {"text": "and small families.", "start": 1621.92, "duration": 3.36}, {"text": "Then there's linkage\ndisequilibrium,", "start": 1625.28, "duration": 3.72}, {"text": "which depends on\nthese common alleles", "start": 1629.0, "duration": 5.633}, {"text": "where the population has\ngone through a particularly", "start": 1634.633, "duration": 2.167}, {"text": "small bottleneck and where\nyour common allele is", "start": 1636.8, "duration": 3.84}, {"text": "a pretty good distance away\nfrom the causative one.", "start": 1640.64, "duration": 2.76}, {"text": "But it allows you to\nmap it into a ballpark,", "start": 1643.4, "duration": 2.58}, {"text": "and then you hunker down and\ndo the more expensive testing", "start": 1645.98, "duration": 5.22}, {"text": "of hypotheses for all and\nsequencing and looking", "start": 1651.2, "duration": 2.76}, {"text": "for potentially\ncausative alleles.", "start": 1653.96, "duration": 1.728}, {"text": "Once you find a potentially\ncausative allele, something", "start": 1655.688, "duration": 2.292}, {"text": "that looks suspicious,\nmaybe something", "start": 1657.98, "duration": 2.02}, {"text": "that's in a coding region\nthat it's conserved--", "start": 1660.0, "duration": 2.33}, {"text": "that's the first priority,\ndespite all the counterexamples", "start": 1662.33, "duration": 3.18}, {"text": "I've given.", "start": 1665.51, "duration": 1.27}, {"text": "And then you go ahead.", "start": 1666.78, "duration": 1.23}, {"text": "But the problem is that\nyou're at the mercy", "start": 1668.01, "duration": 1.792}, {"text": "of the recombination\nthat might have occurred", "start": 1669.802, "duration": 1.875}, {"text": "in that population, but you get\nto very interesting populations", "start": 1671.677, "duration": 2.803}, {"text": "like people of African\nAmerican descent", "start": 1674.48, "duration": 4.29}, {"text": "where the population\nis very old, hasn't", "start": 1678.77, "duration": 2.88}, {"text": "passed through a\npopulation bottleneck.", "start": 1681.65, "duration": 2.7}, {"text": "The useful linkage\ndisequilibrium", "start": 1684.35, "duration": 2.52}, {"text": "is on a couple of kilobases\nrather than hundreds", "start": 1686.87, "duration": 3.45}, {"text": "of kilobases, so it\nactually is hard to find", "start": 1690.32, "duration": 2.19}, {"text": "things that are linked.", "start": 1692.51, "duration": 1.32}, {"text": "That is to say, insists\nbut not causatives.", "start": 1693.83, "duration": 2.58}, {"text": "Insists to the causative allele.", "start": 1696.41, "duration": 2.97}, {"text": "Instead, you have to look\ndirectly for causative alleles.", "start": 1699.38, "duration": 2.64}, {"text": "And that's where-- now you look\nfor common causative alleles.", "start": 1702.02, "duration": 2.82}, {"text": "This has the problem that\nwe've been talking about,", "start": 1707.765, "duration": 2.125}, {"text": "which is that maybe common\nalleles aren't often causative.", "start": 1709.89, "duration": 4.97}, {"text": "They've been selected out.", "start": 1714.86, "duration": 1.47}, {"text": "So then you get into\nthe scenario, what if we", "start": 1716.33, "duration": 2.07}, {"text": "wanted to look at all alleles?", "start": 1718.4, "duration": 1.53}, {"text": "Well, theoretically, there's\nnothing wrong with that.", "start": 1719.93, "duration": 3.84}, {"text": "It'd be great.", "start": 1723.77, "duration": 1.68}, {"text": "We could do the\nassociation studies.", "start": 1725.45, "duration": 1.62}, {"text": "We'd have to have fairly\nlarge populations.", "start": 1727.07, "duration": 3.24}, {"text": "But you saw it was linear\nwith an exponential increase", "start": 1730.31, "duration": 2.34}, {"text": "in the number of hypotheses, and\nyou could rank those hypotheses", "start": 1732.65, "duration": 3.06}, {"text": "by a priori likelihood and\nso forth, but it's expensive.", "start": 1735.71, "duration": 3.57}, {"text": "And so the discussion\nnow has to include", "start": 1739.28, "duration": 3.54}, {"text": "a little bit of discussion\nof the new technologies that", "start": 1742.82, "duration": 4.29}, {"text": "might make this less expensive,\nand a discussion of how we got", "start": 1747.11, "duration": 3.36}, {"text": "the first genome and how\nthe new technologies might", "start": 1750.47, "duration": 2.43}, {"text": "be a little different.", "start": 1752.9, "duration": 1.68}, {"text": "But we're going to do this\nin the context of computation", "start": 1754.58, "duration": 2.49}, {"text": "in the sense of, how do we\ndeal with random and systematic", "start": 1757.07, "duration": 2.74}, {"text": "errors?", "start": 1759.81, "duration": 0.5}, {"text": "As we plan our\nstrategy for getting", "start": 1760.31, "duration": 3.06}, {"text": "each of our genomes, personal\ngenomes sequence for $1,000", "start": 1763.37, "duration": 3.27}, {"text": "or so, how do we choose\nwhich technology to pursue?", "start": 1766.64, "duration": 4.21}, {"text": "Which ones have the\nlowest intrinsic, random,", "start": 1770.85, "duration": 3.2}, {"text": "and systematic errors?", "start": 1774.05, "duration": 1.3}, {"text": "So we needed to study\nthe first genome", "start": 1775.35, "duration": 1.76}, {"text": "to see, what would we mean by\nrandom and systematic errors?", "start": 1777.11, "duration": 4.08}, {"text": "How many people here know what\nthe difference is already?", "start": 1781.19, "duration": 3.6}, {"text": "A few.", "start": 1787.37, "duration": 0.52}, {"text": "OK.", "start": 1787.89, "duration": 0.5}, {"text": "But anyway, whether you do or\nnot, it's good for the soul", "start": 1788.39, "duration": 3.33}, {"text": "to go through some\nreal examples of this.", "start": 1791.72, "duration": 2.7}, {"text": "A random mutation\nis something which", "start": 1794.42, "duration": 1.74}, {"text": "occurs every time you\ndo the experiment.", "start": 1796.16, "duration": 2.88}, {"text": "You get a different error.", "start": 1799.04, "duration": 2.64}, {"text": "And a systematic\none is something", "start": 1801.68, "duration": 4.56}, {"text": "where if you do it over\nand over the same way,", "start": 1806.24, "duration": 2.32}, {"text": "you'll get the same\nerror or a simple class", "start": 1808.56, "duration": 2.36}, {"text": "of errors occurring more\nthan once, over and over.", "start": 1810.92, "duration": 4.59}, {"text": "So for sequencing, the process\ninvolves picking something", "start": 1815.51, "duration": 4.535}, {"text": "that you want to\nsequence-- we'll", "start": 1820.045, "duration": 1.375}, {"text": "call it a clone or a template.", "start": 1821.42, "duration": 1.53}, {"text": "Then actually doing\nthe sequencing", "start": 1822.95, "duration": 1.86}, {"text": "and then assembling\nthis into a meaningful", "start": 1824.81, "duration": 3.09}, {"text": "interpreted sequence.", "start": 1827.9, "duration": 1.79}, {"text": "And this is an\nexample where we might", "start": 1829.69, "duration": 4.81}, {"text": "have chosen these big clones.", "start": 1834.5, "duration": 6.87}, {"text": "In other words, you might\nfragment the genome up randomly", "start": 1841.37, "duration": 2.55}, {"text": "into large clones of\n100 kilobases called", "start": 1843.92, "duration": 2.22}, {"text": "bacterial artificial\nchromosomes, for example.", "start": 1846.14, "duration": 2.55}, {"text": "And then that's all\nrandom, and so there's", "start": 1848.69, "duration": 2.46}, {"text": "a shotgun of that scale.", "start": 1851.15, "duration": 1.77}, {"text": "And then we break it up\nrandomly into smaller pieces,", "start": 1852.92, "duration": 2.92}, {"text": "which provide us with\nlittle sequences.", "start": 1855.84, "duration": 1.64}, {"text": "And then in the computer,\nwe assemble these by methods", "start": 1857.48, "duration": 2.46}, {"text": "that we'll discuss in\nthe next lecture, which", "start": 1859.94, "duration": 4.47}, {"text": "can take even fairly different\nsequences than assemble them.", "start": 1864.41, "duration": 3.19}, {"text": "In this case, we're talking\nabout very similar sequences.", "start": 1867.6, "duration": 3.44}, {"text": "And then you assemble the little\nsequences into big sequences,", "start": 1871.04, "duration": 2.783}, {"text": "and you assemble\nthe big sequences", "start": 1873.823, "duration": 1.417}, {"text": "into even bigger sequences, and\nthen you have the whole thing.", "start": 1875.24, "duration": 2.67}, {"text": "But you can see there's a lot\nof opportunity for error here.", "start": 1877.91, "duration": 3.468}, {"text": "We make it look\nsimple in this slide,", "start": 1881.378, "duration": 1.542}, {"text": "but we're going to talk about\nrandom and systematic errors", "start": 1882.92, "duration": 3.06}, {"text": "in a moment.", "start": 1885.98, "duration": 2.04}, {"text": "Where did we get\nthose sequences,", "start": 1888.02, "duration": 1.59}, {"text": "those little sequences\nthat we want to assemble?", "start": 1889.61, "duration": 2.73}, {"text": "We're going to go through\na few methods in a moment,", "start": 1892.34, "duration": 2.26}, {"text": "but the most common\none by far I think", "start": 1894.6, "duration": 2.54}, {"text": "that generates over\n90% of the human genome", "start": 1897.14, "duration": 3.24}, {"text": "sequence in the\nlast couple of years", "start": 1900.38, "duration": 2.04}, {"text": "is capillary electrophoresis\nof fluorescently labeled", "start": 1902.42, "duration": 4.71}, {"text": "polymerase terminated products.", "start": 1907.13, "duration": 2.19}, {"text": "When you electrophoresis\nthings, you're", "start": 1909.32, "duration": 2.07}, {"text": "separating DNA fragments,\nwhich are n nucleotides long,", "start": 1911.39, "duration": 5.985}, {"text": "from a DNA fragment which is\nn plus one nucleotides long.", "start": 1917.375, "duration": 3.255}, {"text": "That's a very subtle\ndifference as n gets big.", "start": 1920.63, "duration": 2.4}, {"text": "As n gets big, it\ngets harder and harder", "start": 1923.03, "duration": 2.25}, {"text": "to separate n from n plus one.", "start": 1925.28, "duration": 2.115}, {"text": "As it does so, you start\ngetting all kinds of errors.", "start": 1927.395, "duration": 2.925}, {"text": "The total number of errors here\nin the lower left-hand corner", "start": 1930.32, "duration": 3.99}, {"text": "is the number of insertions\nplus the number of deletions", "start": 1934.31, "duration": 2.43}, {"text": "plus the number of\nsubstitutions plus n, which", "start": 1936.74, "duration": 3.57}, {"text": "is an abbreviation for no call.", "start": 1940.31, "duration": 3.33}, {"text": "It means the software felt\nthat it was so close that it", "start": 1943.64, "duration": 3.36}, {"text": "couldn't call it at all.", "start": 1947.0, "duration": 1.0}, {"text": "It just said it's n.", "start": 1948.0, "duration": 0.83}, {"text": "I don't know whether\nit's an A, C-- it", "start": 1948.83, "duration": 1.583}, {"text": "doesn't know whether it's an A,\nC, G, or T. Calls it a no call.", "start": 1950.413, "duration": 3.977}, {"text": "And so if you look\nthrough this table,", "start": 1954.39, "duration": 2.27}, {"text": "it shows on the vertical axis\nfor each of these six bar", "start": 1956.66, "duration": 7.02}, {"text": "charts is as you go up\non the vertical axis,", "start": 1963.68, "duration": 4.14}, {"text": "you go from very\nshort reads where", "start": 1967.82, "duration": 2.43}, {"text": "it's easy to separate n from\nn plus one electrophoretically", "start": 1970.25, "duration": 2.7}, {"text": "to very long ones where\nyou start accumulating", "start": 1972.95, "duration": 2.55}, {"text": "insertions deletion\nerrors, insertion deletion", "start": 1975.5, "duration": 3.18}, {"text": "substitution, and n.", "start": 1978.68, "duration": 1.56}, {"text": "They all go up with length.", "start": 1980.24, "duration": 1.93}, {"text": "And so you can think of that\nas a random error superimposed", "start": 1982.17, "duration": 4.22}, {"text": "on the systematic error of if\nyou always do the experiments,", "start": 1986.39, "duration": 3.99}, {"text": "the same base pair is always\nat the end of your run,", "start": 1990.38, "duration": 3.24}, {"text": "it's going to always have\na higher random error rate.", "start": 1993.62, "duration": 2.64}, {"text": "So this is kind of a combination\nof random and systematic error.", "start": 1996.26, "duration": 3.04}, {"text": "So let's go through\nsome examples here.", "start": 1999.3, "duration": 3.38}, {"text": "We have just\nisolating the template", "start": 2002.68, "duration": 3.09}, {"text": "to prepare it for sequencing,\nthere are systematic errors.", "start": 2005.77, "duration": 5.58}, {"text": "If you have certain\nkinds of repeats,", "start": 2011.35, "duration": 1.92}, {"text": "long, inverted repeats, or\ncertain kinds of restriction", "start": 2013.27, "duration": 3.09}, {"text": "elements that the bacteria\ndoesn't like or likes", "start": 2016.36, "duration": 2.79}, {"text": "to chew up, then you\nwon't get the clone.", "start": 2019.15, "duration": 3.81}, {"text": "And that would plague the early\npart of the Genome Project,", "start": 2022.96, "duration": 2.55}, {"text": "is you'd keep trying again\nand again the same way,", "start": 2025.51, "duration": 2.612}, {"text": "and you just wouldn't\nget certain clones.", "start": 2028.122, "duration": 1.708}, {"text": "It's as if there\nwas a hole there.", "start": 2029.83, "duration": 1.53}, {"text": "You know that there's\nsomething there,", "start": 2031.36, "duration": 1.583}, {"text": "but you couldn't clone it.", "start": 2032.943, "duration": 2.077}, {"text": "Sequencing-- hairpins can\nform in the single strand", "start": 2035.02, "duration": 3.54}, {"text": "of nucleic acids\nwhere you're trying", "start": 2038.56, "duration": 1.5}, {"text": "to separate n from n plus one.", "start": 2040.06, "duration": 2.04}, {"text": "And those hairpins then take\nout the gel electrophoresis", "start": 2042.1, "duration": 4.89}, {"text": "and make it seem like it's much\nsmaller than it actually is.", "start": 2046.99, "duration": 3.81}, {"text": "Tandem repeats cause\na problem in all three", "start": 2050.8, "duration": 2.76}, {"text": "of these stages in sequencing.", "start": 2053.56, "duration": 3.42}, {"text": "You get some\npolymerase stuttering", "start": 2056.98, "duration": 2.55}, {"text": "and you get little artifacts.", "start": 2059.53, "duration": 2.189}, {"text": "In assembly repeats,\nyou're assembling", "start": 2061.719, "duration": 3.091}, {"text": "by sequence alignment.", "start": 2064.81, "duration": 2.5}, {"text": "If you have a\nrepeat, the repeat's", "start": 2067.31, "duration": 1.46}, {"text": "going to align just\nas well because it's", "start": 2068.77, "duration": 2.34}, {"text": "a repeat within the\ngenome as a repeat", "start": 2071.11, "duration": 2.105}, {"text": "due to experimental repeating,\nand so the alignment", "start": 2073.215, "duration": 2.125}, {"text": "can be off.", "start": 2075.34, "duration": 1.56}, {"text": "The errors that you got\nfrom these earlier steps", "start": 2076.9, "duration": 2.25}, {"text": "make it hard to assemble.", "start": 2079.15, "duration": 1.71}, {"text": "Polymorphisms look like errors.", "start": 2080.86, "duration": 1.71}, {"text": "Chimeric clones means\nyou've got things", "start": 2082.57, "duration": 2.01}, {"text": "that have been misassembled\nearly on here, and so on.", "start": 2084.58, "duration": 7.43}, {"text": "OK.", "start": 2092.01, "duration": 2.66}, {"text": "When we do this random\nselection of big clones", "start": 2094.67, "duration": 5.232}, {"text": "and random selection of\nlittle clones for sequencing,", "start": 2099.902, "duration": 2.208}, {"text": "we want to know when to quit.", "start": 2102.11, "duration": 1.95}, {"text": "Now you could say,\nwell, we're going", "start": 2104.06, "duration": 1.83}, {"text": "to quit once we get\nit all assembled,", "start": 2105.89, "duration": 1.56}, {"text": "but you need to accumulate\na certain amount of data", "start": 2107.45, "duration": 2.67}, {"text": "in advance before you\ntry to assemble it.", "start": 2110.12, "duration": 1.95}, {"text": "And so there are\nvarious calculations", "start": 2112.07, "duration": 3.75}, {"text": "as to when to quit.", "start": 2115.82, "duration": 1.29}, {"text": "And this is related to\nthe Poisson distribution,", "start": 2117.11, "duration": 2.47}, {"text": "but it's not exactly.", "start": 2119.58, "duration": 1.07}, {"text": "And in fact, one of the\nstudies done in 1988", "start": 2120.65, "duration": 4.11}, {"text": "made some poor\nassumptions about--", "start": 2124.76, "duration": 4.23}, {"text": "remember, we mentioned\nin the first lecture", "start": 2128.99, "duration": 3.33}, {"text": "the assumptions of the\nPoisson distribution", "start": 2132.32, "duration": 3.99}, {"text": "that make it an\napproximation-- when", "start": 2136.31, "duration": 1.86}, {"text": "it becomes an approximation\nto a more formal distribution", "start": 2138.17, "duration": 4.14}, {"text": "like the binomial.", "start": 2142.31, "duration": 0.87}, {"text": "Anyway, that approximation,\nyou should be getting,", "start": 2143.18, "duration": 3.24}, {"text": "as you get higher\nand higher coverage,", "start": 2146.42, "duration": 1.71}, {"text": "meaning more and more\nexperimental repeats,", "start": 2148.13, "duration": 4.11}, {"text": "you'll eventually\nfill all the gaps.", "start": 2152.24, "duration": 2.22}, {"text": "And that means you'll get\n100% complete coverage,", "start": 2154.46, "duration": 4.17}, {"text": "and it should asymptotically\napproach that.", "start": 2158.63, "duration": 2.28}, {"text": "Well, if you use the\nPoisson incorrectly,", "start": 2160.91, "duration": 2.94}, {"text": "as authors did in 1988, you\nbasically go off to infinity.", "start": 2163.85, "duration": 4.23}, {"text": "You get 200% coverage, which\nis physically impossible.", "start": 2168.08, "duration": 4.72}, {"text": "But both an earlier\nstudy, which they ignored,", "start": 2172.8, "duration": 2.6}, {"text": "and a more recent\nstudy got it right.", "start": 2175.4, "duration": 2.43}, {"text": "And these are slightly\ndifferent measures,", "start": 2177.83, "duration": 3.18}, {"text": "but they both converge on 100%.", "start": 2181.01, "duration": 3.24}, {"text": "And I urge you to\nlook at that if you're", "start": 2184.25, "duration": 1.98}, {"text": "designing an experiment\nwith simple formula.", "start": 2186.23, "duration": 3.33}, {"text": "On the other hand, if you want\nto design the experiment more", "start": 2189.56, "duration": 2.97}, {"text": "explicit, you eventually\nget to a point", "start": 2192.53, "duration": 2.55}, {"text": "where a simple analytic\nformula won't do,", "start": 2195.08, "duration": 2.73}, {"text": "and you have to do Monte Carlo.", "start": 2197.81, "duration": 1.35}, {"text": "We treated this\nin the first class", "start": 2199.16, "duration": 2.13}, {"text": "of analytic versus numeric\ndifferentiable equations", "start": 2201.29, "duration": 3.54}, {"text": "and then many other cases.", "start": 2204.83, "duration": 1.51}, {"text": "The simulation you\nwant to do is beyond--", "start": 2206.34, "duration": 3.04}, {"text": "is too hard to do analytically.", "start": 2209.38, "duration": 2.9}, {"text": "So Gene Myers set up-- just\nlisted all the things he", "start": 2212.28, "duration": 3.74}, {"text": "thought would be--", "start": 2216.02, "duration": 1.77}, {"text": "could affect the ability to\nassemble a genome sequence.", "start": 2217.79, "duration": 4.68}, {"text": "The read length and types of\nrepeats, and all this stuff", "start": 2222.47, "duration": 5.52}, {"text": "was simulated.", "start": 2227.99, "duration": 1.17}, {"text": "And he cranked the simulation on\nreal human genome size projects", "start": 2229.16, "duration": 4.35}, {"text": "and came to the conclusion\nthat you could do a shotgun", "start": 2233.51, "duration": 2.7}, {"text": "assembly of a mammalian genome.", "start": 2236.21, "duration": 2.25}, {"text": "A company called\nCelera was formed.", "start": 2238.46, "duration": 1.86}, {"text": "Gene Myers was hired\nas the computer guru.", "start": 2240.32, "duration": 4.2}, {"text": "They put together a\nlarge stable of computers", "start": 2244.52, "duration": 2.73}, {"text": "and they started doing this on\nthe human and the mouse genome.", "start": 2247.25, "duration": 3.81}, {"text": "The human genome was in the\nend not done by this method,", "start": 2251.06, "duration": 2.58}, {"text": "but the mouse genome was, and\nit was a pretty good assembly.", "start": 2253.64, "duration": 2.91}, {"text": "So the Drosophila genome\nmissing the Drosophila repeats", "start": 2256.55, "duration": 3.12}, {"text": "was also done by this method.", "start": 2259.67, "duration": 1.69}, {"text": "So this is scaled\nvery gracefully", "start": 2261.36, "duration": 2.51}, {"text": "from the first shotgun sequence,\nwhich was on a four kV plasmid", "start": 2263.87, "duration": 5.61}, {"text": "to mammalian size genomes.", "start": 2269.48, "duration": 3.03}, {"text": "No mammalian genome is\ncompletely sequenced,", "start": 2272.51, "duration": 2.16}, {"text": "so we can't really\ndeclare victory.", "start": 2274.67, "duration": 1.77}, {"text": "But the sort of simulation\nthat he did here", "start": 2276.44, "duration": 3.51}, {"text": "has played out very nicely.", "start": 2279.95, "duration": 1.155}, {"text": "Right here in Boston,\nthere will be--", "start": 2283.76, "duration": 2.22}, {"text": "when we start\nthinking of the future", "start": 2285.98, "duration": 1.5}, {"text": "of sequencing\ntechnology, we would all", "start": 2287.48, "duration": 1.68}, {"text": "like-- this is almost\nuncontroversial as", "start": 2289.16, "duration": 2.88}, {"text": "to how much we desire that the\ngenome not cost $3 billion,", "start": 2292.04, "duration": 4.05}, {"text": "but it costs $1,000.", "start": 2296.09, "duration": 1.83}, {"text": "And now there are\na number of people", "start": 2297.92, "duration": 2.19}, {"text": "who are taking very definite\nsteps to get us to that point.", "start": 2300.11, "duration": 6.87}, {"text": "To understand systematic\nand random errors that", "start": 2306.98, "duration": 3.06}, {"text": "can occur in these\nsteps, let's take", "start": 2310.04, "duration": 2.04}, {"text": "this dideoxy gel electrophoresis\nwe've been talking about here.", "start": 2312.08, "duration": 3.48}, {"text": "You have four different\ncolored terminators.", "start": 2315.56, "duration": 2.1}, {"text": "These is where the polymerase\ncan't go any further", "start": 2317.66, "duration": 3.09}, {"text": "because there's a\nblocking group here,", "start": 2320.75, "duration": 2.782}, {"text": "which is fluorescent labeled.", "start": 2323.532, "duration": 1.208}, {"text": "And if the template\non the far left", "start": 2324.74, "duration": 1.98}, {"text": "here is ready to accept\nan A, you'll get an A.", "start": 2326.72, "duration": 3.6}, {"text": "And this n and n minus\none will separate", "start": 2330.32, "duration": 3.75}, {"text": "on this electrophoresis and\nthe four colors will give you", "start": 2334.07, "duration": 2.97}, {"text": "this four-colored pattern\nwhere the intensity reflects", "start": 2337.04, "duration": 3.66}, {"text": "good termination\nat that position,", "start": 2340.7, "duration": 2.97}, {"text": "and you can basically\ngo along reading it.", "start": 2343.67, "duration": 2.16}, {"text": "G, C, G, G, A, T.", "start": 2345.83, "duration": 2.16}, {"text": "Now this is in the\nwell-behaved part.", "start": 2347.99, "duration": 1.77}, {"text": "An example of a systematic error\nthat you get in this extension", "start": 2349.76, "duration": 3.75}, {"text": "occurs here in the upper\nright-hand corner of slide 40.", "start": 2353.51, "duration": 3.81}, {"text": "Now you've got-- because\nof one of these hairpins", "start": 2357.32, "duration": 2.19}, {"text": "that I mentioned\nbefore, you've got", "start": 2359.51, "duration": 1.458}, {"text": "a pile-up of seven nucleotides\nall at the same position.", "start": 2360.968, "duration": 3.732}, {"text": "A completely\nalternative method that", "start": 2364.7, "duration": 1.542}, {"text": "doesn't involve\ngel electrophoresis", "start": 2366.242, "duration": 1.458}, {"text": "is called pirA\nsequencing, and this", "start": 2367.7, "duration": 2.22}, {"text": "is an equivalent that can be\ndone with fluorescent addition.", "start": 2369.92, "duration": 4.56}, {"text": "Instead of separating\nthem in time", "start": 2374.48, "duration": 2.28}, {"text": "by their size in\nelectrophoresis,", "start": 2376.76, "duration": 2.79}, {"text": "in time you ask serially,\ndo you want an A here?", "start": 2379.55, "duration": 3.57}, {"text": "If yes, then you\nget a little green--", "start": 2383.12, "duration": 2.28}, {"text": "you get a little\npeek of representing", "start": 2385.4, "duration": 3.67}, {"text": "the release of pyrophosphate\nor the incorporation", "start": 2389.07, "duration": 2.67}, {"text": "of fluorescent A.", "start": 2391.74, "duration": 1.315}, {"text": "And then you ask,\ndo you want a T,", "start": 2393.055, "duration": 2.075}, {"text": "and so forth, and you go along.", "start": 2395.13, "duration": 1.32}, {"text": "And each signal means\nyes to the answer", "start": 2396.45, "duration": 3.78}, {"text": "that it's ready for\nthat particular base.", "start": 2400.23, "duration": 2.32}, {"text": "And you can see this\ndoesn't have any problems", "start": 2402.55, "duration": 1.94}, {"text": "with this hairpin region.", "start": 2404.49, "duration": 1.56}, {"text": "So when you have a\nsystematic error,", "start": 2408.69, "duration": 1.5}, {"text": "you have to change\nthe method that you're", "start": 2410.19, "duration": 1.708}, {"text": "using fairly radically.", "start": 2411.898, "duration": 1.772}, {"text": "The opposite strand or a\ncompletely different method.", "start": 2413.67, "duration": 3.765}, {"text": "If you have-- early on,\nwe had huge differences", "start": 2420.23, "duration": 4.05}, {"text": "in intensity of the\nfluorophores and new enzymes", "start": 2424.28, "duration": 3.48}, {"text": "and new fluorophores were\ndeveloped by Tabor and Matthews", "start": 2427.76, "duration": 3.39}, {"text": "and Glaser, and so forth.", "start": 2431.15, "duration": 1.3}, {"text": "And this was a huge advance\nin making everything uniform", "start": 2432.45, "duration": 4.13}, {"text": "and eliminating\nsystematic errors.", "start": 2436.58, "duration": 2.74}, {"text": "So the sort of things that are\non the horizon that hopefully", "start": 2439.32, "duration": 2.63}, {"text": "will be discussed\ntomorrow in Boston,", "start": 2441.95, "duration": 3.09}, {"text": "we've talked about this short\nnumber of base extensions", "start": 2445.04, "duration": 6.06}, {"text": "like power\nsequencing, the longer", "start": 2451.1, "duration": 1.98}, {"text": "extensions in capillary\narrays, which, capillary arrays", "start": 2453.08, "duration": 3.9}, {"text": "are changing from\nlow-end capillaries", "start": 2456.98, "duration": 1.71}, {"text": "into microfabricated chips.", "start": 2458.69, "duration": 3.09}, {"text": "I'll show an example of a\nmass spec in just a moment.", "start": 2461.78, "duration": 2.235}, {"text": "Sequencing by\nhybridization on arrays", "start": 2467.15, "duration": 1.83}, {"text": "will illustrate as a prelude,\nas an example of Affymetrix", "start": 2468.98, "duration": 4.05}, {"text": "technology in this slide.", "start": 2473.03, "duration": 4.83}, {"text": "OK.", "start": 2477.86, "duration": 0.51}, {"text": "So the idea here, this is\nmainly for re-sequencing.", "start": 2478.37, "duration": 4.38}, {"text": "Some of the ways of reducing\nthe cost of sequencing", "start": 2482.75, "duration": 3.03}, {"text": "the human genome will not\napply to sequencing brand", "start": 2485.78, "duration": 2.7}, {"text": "new genomes.", "start": 2488.48, "duration": 0.78}, {"text": "But still, we need\nto pursue them,", "start": 2489.26, "duration": 1.71}, {"text": "because this may be the way that\nwe get the $1,000 human genome,", "start": 2490.97, "duration": 2.91}, {"text": "even if we don't get other ones.", "start": 2493.88, "duration": 2.38}, {"text": "And here, you know the\nsequence, except there's", "start": 2496.26, "duration": 3.47}, {"text": "a possibility that there could\nbe a polymorphism at any base.", "start": 2499.73, "duration": 2.81}, {"text": "Could be any single base\nsubstitution at any base.", "start": 2502.54, "duration": 3.1}, {"text": "And so you don't\nnecessarily know", "start": 2505.64, "duration": 1.695}, {"text": "in advance what the common\nones are or the rare ones,", "start": 2507.335, "duration": 2.355}, {"text": "but you do know the\ncanonical sequence.", "start": 2509.69, "duration": 2.73}, {"text": "And so at every position, you'll\nmake a 25-mer oligonucleotide", "start": 2512.42, "duration": 6.33}, {"text": "which will bind to a\nfluorescently labeled", "start": 2518.75, "duration": 1.77}, {"text": "version of your genome,\nor a piece of your genome.", "start": 2520.52, "duration": 3.39}, {"text": "And this is actually developed\nfor HIV re-sequencing", "start": 2523.91, "duration": 2.85}, {"text": "by Affymetrix.", "start": 2526.76, "duration": 1.41}, {"text": "And at this middle\nposition, you'll", "start": 2528.17, "duration": 3.45}, {"text": "put in all four possible\nsubstitutions, T, G, C, or A.", "start": 2531.62, "duration": 7.165}, {"text": "And you'll consider\neach possible template.", "start": 2538.785, "duration": 6.085}, {"text": "So if you have the\ntemplate, which is-- let's", "start": 2544.87, "duration": 1.88}, {"text": "say these are the\ntwo alleles that", "start": 2546.75, "duration": 1.417}, {"text": "occur in a human population\nor in your sample.", "start": 2548.167, "duration": 3.653}, {"text": "You can have this sequence and\nthen all the variations on it,", "start": 2551.82, "duration": 3.36}, {"text": "stepping along, changing T,\nG, C, A for the first base,", "start": 2555.18, "duration": 4.273}, {"text": "the second base, the\nthird base, and so forth,", "start": 2559.453, "duration": 1.917}, {"text": "till you hit this one.", "start": 2561.37, "duration": 0.917}, {"text": "And this is where the\nreal polymorphism occurs.", "start": 2562.287, "duration": 2.253}, {"text": "And you could have either\nthis as the context", "start": 2564.54, "duration": 2.49}, {"text": "or this as the context.", "start": 2567.03, "duration": 2.28}, {"text": "And this is schematic And\nthis is the real data.", "start": 2569.31, "duration": 3.0}, {"text": "These are real data\ndown here where", "start": 2572.31, "duration": 1.86}, {"text": "you have the context of\nthe A allele or the context", "start": 2574.17, "duration": 2.97}, {"text": "of the C allele.", "start": 2577.14, "duration": 1.05}, {"text": "You can have the homozygotes\nor the heterozygotes.", "start": 2578.19, "duration": 3.45}, {"text": "And in the homozygous A,\nyou can see it lights up", "start": 2581.64, "duration": 3.063}, {"text": "the best, the best\nhybridization when you have", "start": 2584.703, "duration": 1.917}, {"text": "the A in the middle position.", "start": 2586.62, "duration": 1.208}, {"text": "The middle position\nis most sensitive", "start": 2587.828, "duration": 1.552}, {"text": "to hybridization changes.", "start": 2589.38, "duration": 1.87}, {"text": "And for the C, you have\nit in the C row here.", "start": 2591.25, "duration": 5.03}, {"text": "And remember, you're\nchanging all the bases", "start": 2596.28, "duration": 2.13}, {"text": "in every position.", "start": 2598.41, "duration": 0.75}, {"text": "One, two, three, four.", "start": 2599.16, "duration": 0.917}, {"text": "This is the one where the middle\nbase of the middle position", "start": 2600.077, "duration": 3.073}, {"text": "is in the right context.", "start": 2603.15, "duration": 1.63}, {"text": "So this is in the A\ncontext and the C context.", "start": 2604.78, "duration": 2.33}, {"text": "And in the heterozygote, you\nget both the A and the C.", "start": 2607.11, "duration": 3.36}, {"text": "And so this has\nbeen done on HIV.", "start": 2610.47, "duration": 2.25}, {"text": "It's been done on\nBRCA1, on mitochondria.", "start": 2612.72, "duration": 2.01}, {"text": "And now they've applied\nit with whole wafers", "start": 2614.73, "duration": 2.91}, {"text": "to the entire human genome.", "start": 2617.64, "duration": 1.99}, {"text": "And this probably costs on\nthe order of $3 million or so.", "start": 2619.63, "duration": 5.0}, {"text": "Mass spectrometry is\nanother way that's", "start": 2624.63, "duration": 1.77}, {"text": "used, probably not for\nsequencing the whole genome,", "start": 2626.4, "duration": 2.125}, {"text": "but it's used for single\nnucleotide polymorphisms.", "start": 2628.525, "duration": 3.065}, {"text": "This costs on the order\nof $0.50 per polymorphism.", "start": 2631.59, "duration": 5.07}, {"text": "If there's three million\nof them in your genome,", "start": 2636.66, "duration": 3.99}, {"text": "that's a lot of $0.50.", "start": 2640.65, "duration": 3.093}, {"text": "[LAUGHTER]", "start": 2643.743, "duration": 3.387}, {"text": "And here's what it looks\nlike when you read it out.", "start": 2647.13, "duration": 2.55}, {"text": "It's really just\nlike electrophoresis.", "start": 2649.68, "duration": 2.01}, {"text": "You can now separate\nan addition of an A", "start": 2651.69, "duration": 5.43}, {"text": "from an addition of a G. And the\ndifference in mass between an A", "start": 2657.12, "duration": 5.415}, {"text": "and a G, this is\neven more subtle", "start": 2662.535, "duration": 1.395}, {"text": "than the difference of\nan n and an n plus one.", "start": 2663.93, "duration": 1.917}, {"text": "This is just a difference\nbetween an A and a C.", "start": 2665.847, "duration": 1.958}, {"text": "It's detectable in this.", "start": 2667.805, "duration": 1.105}, {"text": "In fact, it's detectable\nand quantitative enough", "start": 2668.91, "duration": 2.67}, {"text": "that you can pool samples.", "start": 2671.58, "duration": 1.332}, {"text": "This is a bit of a stunt,\nbut it's an important stunt", "start": 2672.912, "duration": 2.208}, {"text": "to show that this is really\na very precise method, albeit", "start": 2675.12, "duration": 4.98}, {"text": "still fairly expensive.", "start": 2680.1, "duration": 2.43}, {"text": "Now just in closing,\nI want to give you", "start": 2682.53, "duration": 2.79}, {"text": "the simplest possible\nexample of how we", "start": 2685.32, "duration": 4.26}, {"text": "can search through sequences.", "start": 2689.58, "duration": 1.44}, {"text": "Next week, we'll give you\na much more rigorous way", "start": 2691.02, "duration": 2.083}, {"text": "that you can look\nthrough the sequences", "start": 2693.103, "duration": 1.625}, {"text": "with very extensive differences\nbetween the sequences.", "start": 2694.728, "duration": 2.362}, {"text": "But here, the theme\nof today's talk", "start": 2697.09, "duration": 3.02}, {"text": "is the subtle\npolymorphism differences", "start": 2700.11, "duration": 2.73}, {"text": "that occur between you and me.", "start": 2702.84, "duration": 1.53}, {"text": "And here, one different--\nso generally, you're", "start": 2704.37, "duration": 2.79}, {"text": "looking for exact matches.", "start": 2707.16, "duration": 1.32}, {"text": "And a good way to look\nfor exact matches is--", "start": 2708.48, "duration": 2.97}, {"text": "good ways are hashing, suffix\narrays, and suffix trees", "start": 2711.45, "duration": 3.12}, {"text": "where basically\nin each of these,", "start": 2714.57, "duration": 1.93}, {"text": "you're looking for using\na word, a word either", "start": 2716.5, "duration": 4.61}, {"text": "that's built up and stored\nfrom the end, the suffix,", "start": 2721.11, "duration": 3.72}, {"text": "one letter at a\ntime, or it's a chunk", "start": 2724.83, "duration": 2.7}, {"text": "that you might have as a hash.", "start": 2727.53, "duration": 1.62}, {"text": "And you make up a lookup table.", "start": 2729.15, "duration": 2.142}, {"text": "And the size of\nthat lookup table--", "start": 2731.292, "duration": 1.458}, {"text": "it's a trade-off between\nspeed of searching", "start": 2732.75, "duration": 1.792}, {"text": "and the size of the table.", "start": 2734.542, "duration": 1.268}, {"text": "The size is going to be-- if\nthe word is n nucleotides long,", "start": 2735.81, "duration": 3.568}, {"text": "it's going to be four to the n.", "start": 2739.378, "duration": 1.292}, {"text": "It's going to be the\nstorage space you", "start": 2740.67, "duration": 1.583}, {"text": "have to put on disk\nor RAM, RAM if you", "start": 2742.253, "duration": 3.307}, {"text": "want it to be a fast search.", "start": 2745.56, "duration": 1.35}, {"text": "And so 16 is the magic number,\nsort of in the ballpark", "start": 2746.91, "duration": 3.48}, {"text": "for a human genome,\nbecause four to the 16th", "start": 2750.39, "duration": 2.1}, {"text": "is four billion sequences\nyou can represent.", "start": 2752.49, "duration": 2.91}, {"text": "But it's a huge table.", "start": 2755.4, "duration": 1.27}, {"text": "You have to have a table of\nfour billion times however", "start": 2756.67, "duration": 2.66}, {"text": "many bytes you need to\nstore the positions.", "start": 2759.33, "duration": 4.8}, {"text": "Typically, about four\nbytes of storage.", "start": 2764.13, "duration": 2.34}, {"text": "If you cut back on\nthis a little bit,", "start": 2766.47, "duration": 1.59}, {"text": "you'll end up with\ncollisions where", "start": 2768.06, "duration": 1.458}, {"text": "you'll have two things that\nhave the same hash or suffix.", "start": 2769.518, "duration": 3.792}, {"text": "If you make it--", "start": 2773.31, "duration": 1.62}, {"text": "and that's if you\nmake it smaller.", "start": 2774.93, "duration": 1.423}, {"text": "It'll take less space.", "start": 2776.353, "duration": 0.917}, {"text": "If you make it\nbigger, it'll take", "start": 2777.27, "duration": 1.41}, {"text": "a ridiculous amount of RAM.", "start": 2778.68, "duration": 2.34}, {"text": "And then here's a\nkind of whimsical--", "start": 2781.02, "duration": 4.05}, {"text": "another example of pearl\nwhere you not only want", "start": 2785.07, "duration": 2.43}, {"text": "to find all the mutations\nhere at a very high density--", "start": 2787.5, "duration": 2.61}, {"text": "a ridiculously high density,\nnot one particular base", "start": 2790.11, "duration": 2.97}, {"text": "for every few base pairs.", "start": 2793.08, "duration": 1.538}, {"text": "You not only want to find them,\nbut you want to correct them.", "start": 2794.618, "duration": 2.542}, {"text": "And here, the pearl\ndoes the substitution.", "start": 2797.16, "duration": 2.97}, {"text": "And after gene therapy,\neverybody walks out happy.", "start": 2800.13, "duration": 3.635}, {"text": "OK.", "start": 2803.765, "duration": 0.5}, {"text": "[LAUGHTER]", "start": 2804.265, "duration": 2.095}]
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+[{"text": "MICHALE FEE: OK, good\nmorning, everyone.", "start": 12.896, "duration": 2.964}, {"text": "OK, so today we are\ngoing to continue", "start": 15.86, "duration": 4.95}, {"text": "the process of building\nour equivalent circuit", "start": 20.81, "duration": 2.79}, {"text": "model of a neuron.", "start": 23.6, "duration": 2.46}, {"text": "This model was actually\ndeveloped in the late '40s", "start": 26.06, "duration": 4.98}, {"text": "and early '50s by Alan\nHodgkin and Andrew", "start": 31.04, "duration": 2.31}, {"text": "Huxley, who started working on\nthe problem of understanding", "start": 33.35, "duration": 4.83}, {"text": "how neurons make\naction potentials.", "start": 38.18, "duration": 2.5}, {"text": "And so they studied\nthe squid giant axon,", "start": 40.68, "duration": 3.63}, {"text": "which is actually a\nvery cool preparation,", "start": 44.31, "duration": 2.03}, {"text": "because that axon is actually\nabout a millimeter across,", "start": 46.34, "duration": 4.18}, {"text": "and so you can stick\nwires inside of it.", "start": 50.52, "duration": 3.78}, {"text": "And they did a bunch of\nvery cool experiments", "start": 54.3, "duration": 3.32}, {"text": "to figure out how these\ndifferent ionic conductances", "start": 57.62, "duration": 3.748}, {"text": "and how these different\ncomponents of the circuit", "start": 61.368, "duration": 2.042}, {"text": "work together to make\nan action potential.", "start": 63.41, "duration": 4.95}, {"text": "So that's what we're\ngoing to continue doing,", "start": 68.36, "duration": 3.94}, {"text": "we're going to\nessentially continue", "start": 72.3, "duration": 2.96}, {"text": "describing and motivating\nthe different components", "start": 75.26, "duration": 2.79}, {"text": "of this circuit.", "start": 78.05, "duration": 1.21}, {"text": "So today, we're going to\nget through the process", "start": 79.26, "duration": 4.73}, {"text": "of introducing a\nvoltage-measuring device,", "start": 83.99, "duration": 4.29}, {"text": "a current source, a\ncapacitor, a conductance,", "start": 88.28, "duration": 3.33}, {"text": "and we're going to start\nintroducing a battery, OK?", "start": 91.61, "duration": 5.32}, {"text": "OK.", "start": 96.93, "duration": 0.5}, {"text": "So here's what we want\nto accomplish today.", "start": 97.43, "duration": 4.83}, {"text": "So we want to understand how\nkind of at the simplest level", "start": 102.26, "duration": 3.81}, {"text": "how neurons respond\nto injected currents,", "start": 106.07, "duration": 4.71}, {"text": "we want to understand\nhow membrane", "start": 110.78, "duration": 1.56}, {"text": "capacitance and membrane\nresistance allows neurons", "start": 112.34, "duration": 3.78}, {"text": "to integrate their\ninputs over time,", "start": 116.12, "duration": 2.55}, {"text": "and to filter their inputs or\nsmooth their inputs over time--", "start": 118.67, "duration": 4.2}, {"text": "and that particular model is\ncalled a resistor capacitor", "start": 122.87, "duration": 3.75}, {"text": "model or an RC\nmodel of a neuron.", "start": 126.62, "duration": 4.88}, {"text": "We're going to go through how\nto derive the differential", "start": 131.5, "duration": 2.64}, {"text": "equations that describe that\nmodel-- it's actually quite", "start": 134.14, "duration": 3.54}, {"text": "simple, but some\nof you may not have", "start": 137.68, "duration": 2.58}, {"text": "been through that before,\nso I want to go through it", "start": 140.26, "duration": 2.52}, {"text": "step by step so we\ncan really understand", "start": 142.78, "duration": 2.25}, {"text": "where that comes from.", "start": 145.03, "duration": 2.27}, {"text": "And we're going to learn to\nbasically look at a current--", "start": 147.3, "duration": 4.635}, {"text": "a pattern of current\ninjection, and we", "start": 151.935, "duration": 1.845}, {"text": "should be able to\nintuitively see", "start": 153.78, "duration": 3.0}, {"text": "how the voltage of\nthat neuron responds.", "start": 156.78, "duration": 5.08}, {"text": "And we're going to\nstart working on where", "start": 161.86, "duration": 3.09}, {"text": "the batteries of a neuron\nactually come from, OK?", "start": 164.95, "duration": 4.33}, {"text": "OK.", "start": 169.28, "duration": 0.62}, {"text": "So-- all right.", "start": 169.9, "duration": 1.59}, {"text": "So-- all right.", "start": 171.49, "duration": 3.27}, {"text": "So we're going to basically\ntalk about the following sort", "start": 174.76, "duration": 4.585}, {"text": "of thought experiment, OK?", "start": 179.345, "duration": 1.995}, {"text": "The following conceptual idea.", "start": 181.34, "duration": 1.65}, {"text": "We're going to take\na neuron and we're", "start": 182.99, "duration": 2.31}, {"text": "going to put it in a\nbath of sailing, OK?", "start": 185.3, "duration": 2.79}, {"text": "A saltwater solution that\nrepresents the extracellular", "start": 188.09, "duration": 2.76}, {"text": "solution that neurons--", "start": 190.85, "duration": 3.45}, {"text": "extracellular\nsolution in the brain.", "start": 194.3, "duration": 2.47}, {"text": "And we're going to put an\nelectrode into that neuron", "start": 196.77, "duration": 2.87}, {"text": "so that we can inject\ncurrent, and we're", "start": 199.64, "duration": 2.07}, {"text": "going to put another\nelectrode into the neuron", "start": 201.71, "duration": 2.41}, {"text": "so that we can\nmeasure the voltage,", "start": 204.12, "duration": 1.64}, {"text": "and we're going to study\nhow this neuron responds--", "start": 205.76, "duration": 3.78}, {"text": "how the voltage of the neuron\nresponds to current injections,", "start": 209.54, "duration": 3.41}, {"text": "OK?", "start": 212.95, "duration": 1.9}, {"text": "Now why is it that we\nwant to actually do that?", "start": 214.85, "duration": 3.27}, {"text": "Why is that an interesting or\nimportant experiment to do?", "start": 218.12, "duration": 5.39}, {"text": "Anybody have any\nidea why we would", "start": 223.51, "duration": 2.37}, {"text": "want to actually measure\nvoltage and current", "start": 225.88, "duration": 3.117}, {"text": "for a neuron in the brain?", "start": 228.997, "duration": 1.083}, {"text": "Yes?", "start": 234.73, "duration": 0.5}, {"text": "AUDIENCE: Be able to use the\nmathematical model [INAUDIBLE]", "start": 235.23, "duration": 2.82}, {"text": "provided for us?", "start": 238.05, "duration": 0.94}, {"text": "MICHALE FEE: OK, but\nit's more than just", "start": 238.99, "duration": 3.14}, {"text": "so that we can describe\nit mathematically, right?", "start": 242.13, "duration": 3.63}, {"text": "It's because these things--", "start": 245.76, "duration": 1.65}, {"text": "something about\nvoltage and current", "start": 247.41, "duration": 1.71}, {"text": "are actually relevant to\nhow a neuron functions.", "start": 249.12, "duration": 3.91}, {"text": "Yes?", "start": 253.03, "duration": 0.5}, {"text": "AUDIENCE: Like the\nresistance inside?", "start": 253.53, "duration": 2.61}, {"text": "MICHALE FEE: Yeah.", "start": 256.14, "duration": 0.99}, {"text": "So that's an important\nquantity, but we're", "start": 257.13, "duration": 2.1}, {"text": "looking for something\nmore fundamental,", "start": 259.23, "duration": 1.89}, {"text": "like why is it\nactually important", "start": 261.12, "duration": 2.13}, {"text": "that we understand how voltage\nchanges when a neuron has", "start": 263.25, "duration": 4.05}, {"text": "current injected into it?", "start": 267.3, "duration": 1.69}, {"text": "Habiba?", "start": 268.99, "duration": 0.5}, {"text": "AUDIENCE: Equals [INAUDIBLE]\ndifferent like ion channels,", "start": 269.49, "duration": 2.39}, {"text": "a different set of\nvoltages [INAUDIBLE]..", "start": 271.88, "duration": 3.975}, {"text": "MICHALE FEE: Exactly.", "start": 275.855, "duration": 0.875}, {"text": "So ion channels are\nsensitive to voltage,", "start": 276.73, "duration": 3.49}, {"text": "and the way they function\ndepends very critically", "start": 280.22, "duration": 3.68}, {"text": "on voltage.", "start": 283.9, "duration": 0.93}, {"text": "So many-- if not\nmost-- ion channels", "start": 284.83, "duration": 3.72}, {"text": "are voltage sensitive and are\ncontrolled by voltage, OK?", "start": 288.55, "duration": 6.0}, {"text": "And that's exactly why.", "start": 294.55, "duration": 1.52}, {"text": "So nearly every aspect of\nwhat neurons do in the brain", "start": 296.07, "duration": 4.21}, {"text": "as you're walking around looking\nat things and doing things", "start": 300.28, "duration": 5.16}, {"text": "is controlled by\nvoltage, and that", "start": 305.44, "duration": 1.89}, {"text": "goes through the voltage\nsensitivity of buying channels,", "start": 307.33, "duration": 4.01}, {"text": "OK?", "start": 311.34, "duration": 0.73}, {"text": "But what is it that changes\nthe voltage in a neuron?", "start": 312.07, "duration": 3.63}, {"text": "Yes?", "start": 322.03, "duration": 0.5}, {"text": "AUDIENCE: The action potential.", "start": 322.53, "duration": 2.09}, {"text": "MICHALE FEE: That's\non the output side.", "start": 324.62, "duration": 3.17}, {"text": "Yes?", "start": 327.79, "duration": 0.5}, {"text": "AUDIENCE: Is it\nion concentration?", "start": 328.29, "duration": 2.2}, {"text": "MICHALE FEE: Good.", "start": 330.49, "duration": 1.01}, {"text": "That's correct.", "start": 331.5, "duration": 1.8}, {"text": "I'm looking for something\na little bit different.", "start": 333.3, "duration": 3.78}, {"text": "Habiba?", "start": 337.08, "duration": 0.5}, {"text": "AUDIENCE: Do you have\npumps or [INAUDIBLE]..", "start": 337.58, "duration": 1.99}, {"text": "MICHALE FEE: Yeah, those\nare all good answers.", "start": 339.57, "duration": 2.718}, {"text": "Not quite what I'm looking for.", "start": 342.288, "duration": 1.292}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 343.58, "duration": 2.74}, {"text": "MICHALE FEE: Yes.", "start": 346.32, "duration": 1.56}, {"text": "So the answer is that\nthe voltage of a neuron", "start": 347.88, "duration": 4.17}, {"text": "changes because--", "start": 352.05, "duration": 3.22}, {"text": "the reason current is important\nis because the reason voltage", "start": 355.27, "duration": 3.99}, {"text": "changes in a neuron is because\nother cells are injecting", "start": 359.26, "duration": 4.02}, {"text": "current into our neuron.", "start": 363.28, "duration": 2.31}, {"text": "Sensory inputs are injecting\ncurrent into our neuron, OK?", "start": 365.59, "duration": 4.8}, {"text": "Everything that a neuron\nreceives, all the information", "start": 370.39, "duration": 3.66}, {"text": "that a neuron receives from\nother neurons in the network", "start": 374.05, "duration": 3.33}, {"text": "and from the outside world\ncomes from currents being", "start": 377.38, "duration": 3.36}, {"text": "injected into that neuron, OK?", "start": 380.74, "duration": 3.45}, {"text": "And so it's really\nimportant that we understand", "start": 384.19, "duration": 2.01}, {"text": "how the neuron transforms that\ncurrent input from other cells", "start": 386.2, "duration": 5.61}, {"text": "and from the sensory periphery\ninto voltage changes that", "start": 391.81, "duration": 4.98}, {"text": "then change the behavior\nof ion channels.", "start": 396.79, "duration": 2.88}, {"text": "Is that clear?", "start": 399.67, "duration": 1.05}, {"text": "That link of current\ninputs to voltage output", "start": 400.72, "duration": 4.59}, {"text": "is really crucial,\nand that's why we're", "start": 405.31, "duration": 1.86}, {"text": "doing this experiment, OK?", "start": 407.17, "duration": 1.92}, {"text": "OK, and that's this\npoint right here.", "start": 412.39, "duration": 3.49}, {"text": "OK, so one of the\nfirst things we're", "start": 415.88, "duration": 1.5}, {"text": "going to see when we go\nthrough this analysis", "start": 417.38, "duration": 2.94}, {"text": "is that neurons can\nperform analog integration.", "start": 420.32, "duration": 2.85}, {"text": "They can perform numerical\nintegration over time, OK?", "start": 423.17, "duration": 4.1}, {"text": "That's pretty cool.", "start": 427.27, "duration": 1.86}, {"text": "Voltage is that integral over\ntime of the injected current.", "start": 429.13, "duration": 5.34}, {"text": "To first order.", "start": 434.47, "duration": 1.56}, {"text": "It's the simplest\nbehavior of a neuron.", "start": 436.03, "duration": 2.222}, {"text": "So if you measure the\nvoltage of a neuron", "start": 438.252, "duration": 1.708}, {"text": "and you turn on current and\nyou turn the current on,", "start": 439.96, "duration": 3.45}, {"text": "the voltage of a\nneuron will ramp up,", "start": 443.41, "duration": 3.21}, {"text": "integrating that\ninput over time, OK?", "start": 446.62, "duration": 2.7}, {"text": "Pretty cool.", "start": 449.32, "duration": 1.17}, {"text": "So we're going to\nsee how that happens,", "start": 450.49, "duration": 2.1}, {"text": "why that happens biophysically.", "start": 452.59, "duration": 3.84}, {"text": "OK.", "start": 456.43, "duration": 0.57}, {"text": "So let's come back to\nour neuron in the dish.", "start": 457.0, "duration": 3.0}, {"text": "Let me just explain a little\nbit how you would actually", "start": 460.0, "duration": 2.7}, {"text": "do this experiment.", "start": 462.7, "duration": 0.94}, {"text": "So these electrodes are\nlittle pieces of glass tubing.", "start": 463.64, "duration": 3.15}, {"text": "So you take a fine glass\ntube about a millimeter", "start": 466.79, "duration": 2.27}, {"text": "across you heat it up in\nthe middle over a flame,", "start": 469.06, "duration": 2.91}, {"text": "and you pull it apart when\nit melts in the middle,", "start": 471.97, "duration": 2.64}, {"text": "and it makes a very sharp point.", "start": 474.61, "duration": 2.73}, {"text": "You break off the fine little\nthread of glass that's left,", "start": 477.34, "duration": 4.8}, {"text": "and you have a tube that narrows\ndown to a very sharp point,", "start": 482.14, "duration": 3.3}, {"text": "but it's still a tube, and\nyou can literally just--", "start": 485.44, "duration": 2.935}, {"text": "there are some cells, like in\nthe old days people studied", "start": 488.375, "duration": 2.375}, {"text": "large neurons and in\nsnails where the cells are", "start": 490.75, "duration": 3.453}, {"text": "a millimeter across, you\ncan take an electrode", "start": 494.203, "duration": 1.917}, {"text": "and literally just by hand\npoke it into the cell.", "start": 496.12, "duration": 2.52}, {"text": "And then you fill that\nelectrode with a salt solution,", "start": 498.64, "duration": 4.23}, {"text": "and then you put a wire in\nthe back of that electrode,", "start": 502.87, "duration": 2.64}, {"text": "and you hook it up\nto an amplifier.", "start": 505.51, "duration": 1.93}, {"text": "Now we want to measure\nthe voltage in the cell.", "start": 507.44, "duration": 2.73}, {"text": "Remember, voltage is\nalways voltage difference.", "start": 510.17, "duration": 3.619}, {"text": "We're always measuring\nthe difference", "start": 513.789, "duration": 1.591}, {"text": "between the voltage in one place\nand the voltage somewhere else.", "start": 515.38, "duration": 3.46}, {"text": "So this amplifier\nhas two inputs.", "start": 518.84, "duration": 2.61}, {"text": "It's called a\ndifferential amplifier,", "start": 521.45, "duration": 2.18}, {"text": "and we're going to hook\nthe electrode that's", "start": 523.63, "duration": 2.19}, {"text": "in the cell to\nthe plus terminal,", "start": 525.82, "duration": 1.86}, {"text": "we're going to put\na wire in the bath,", "start": 527.68, "duration": 1.94}, {"text": "hook it to the minus\nterminal, and this amplifier", "start": 529.62, "duration": 2.08}, {"text": "is measuring the difference\nbetween the voltage", "start": 531.7, "duration": 2.61}, {"text": "inside the cell and the\nvoltage outside the cell, OK?", "start": 534.31, "duration": 3.18}, {"text": "Any questions about that?", "start": 537.49, "duration": 2.2}, {"text": "So we're going to take the other\nhalf of that piece of glass", "start": 539.69, "duration": 2.78}, {"text": "that we pulled, fill\nit with salt solution,", "start": 542.47, "duration": 2.675}, {"text": "stick it in the cell, and\nwe're going to hook it up", "start": 545.145, "duration": 2.125}, {"text": "to a current source.", "start": 547.27, "duration": 1.83}, {"text": "Now our current source is\nbasically just a battery, OK?", "start": 549.1, "duration": 4.17}, {"text": "But it's got some\nfancy electronics", "start": 553.27, "duration": 2.17}, {"text": "such that the current that flows\nis equal to whatever value you", "start": 555.44, "duration": 4.73}, {"text": "set, OK?", "start": 560.17, "duration": 4.85}, {"text": "And of course,\nremember, that voltage", "start": 565.02, "duration": 1.955}, {"text": "is in units of volts and\ncurrent is charge per second.", "start": 566.975, "duration": 4.815}, {"text": "Charge is coulombs, so\ncoulombs per second,", "start": 571.79, "duration": 3.36}, {"text": "and that's equal to the unit\nof current, which is amperes.", "start": 575.15, "duration": 4.31}, {"text": "All right.", "start": 579.46, "duration": 0.6}, {"text": "Now let's take a closer look\nat our little spherical neuron,", "start": 580.06, "duration": 4.71}, {"text": "our little neuron.", "start": 584.77, "duration": 1.2}, {"text": "We've chopped all the\ndendrites and axons off,", "start": 585.97, "duration": 2.02}, {"text": "so it's just a little\nsphere, and you can basically", "start": 587.99, "duration": 2.87}, {"text": "model a neuron just like any\nother cell as a spherical shell", "start": 590.86, "duration": 5.61}, {"text": "of insulating material, OK?", "start": 596.47, "duration": 3.27}, {"text": "In this case, a lipid bilayer.", "start": 599.74, "duration": 2.31}, {"text": "This is a phospholipid bilayer.", "start": 602.05, "duration": 3.0}, {"text": "Phospholipids are just little\nfat molecules that have a polar", "start": 605.05, "duration": 3.72}, {"text": "head on one side-- that means\nthey're soluble in water", "start": 608.77, "duration": 2.76}, {"text": "on this side, and they\nhave a non-polar tail,", "start": 611.53, "duration": 3.09}, {"text": "so they don't like to be\nin contact with water,", "start": 614.62, "duration": 2.16}, {"text": "and the two polar\ntails go end to end--", "start": 616.78, "duration": 3.63}, {"text": "sorry, the non-polar\ntails go end to end,", "start": 620.41, "duration": 2.49}, {"text": "the polar heads face\nout into the water.", "start": 622.9, "duration": 3.42}, {"text": "Does that makes sense?", "start": 626.32, "duration": 1.16}, {"text": "And they are very closely\npacked together so", "start": 627.48, "duration": 2.85}, {"text": "that ions can't pass\nthrough that membrane,", "start": 630.33, "duration": 2.55}, {"text": "so it's insulating.", "start": 632.88, "duration": 2.43}, {"text": "It's very thin, it's only\nabout 23 angstroms across, OK?", "start": 635.31, "duration": 4.98}, {"text": "An angstrom is about the\nsize of a hydrogen atom.", "start": 640.29, "duration": 4.81}, {"text": "They're very thin, OK?", "start": 645.1, "duration": 1.93}, {"text": "OK, we have saline inside.", "start": 650.03, "duration": 1.84}, {"text": "What is saline?", "start": 651.87, "duration": 1.85}, {"text": "What is it in our model?", "start": 653.72, "duration": 1.785}, {"text": "Remember on Tuesday what--", "start": 659.22, "duration": 1.662}, {"text": "AUDIENCE: A wire.", "start": 660.882, "duration": 0.708}, {"text": "MICHALE FEE: Good.", "start": 661.59, "duration": 0.75}, {"text": "It's a wire and we have saline\noutside, which is also a wire.", "start": 662.34, "duration": 4.75}, {"text": "So we have two wires separated\nby an insulator, what is that?", "start": 667.09, "duration": 4.07}, {"text": "That's a capacitor, because\nit's two conductors separated", "start": 676.1, "duration": 3.43}, {"text": "by an insulator, OK?", "start": 679.53, "duration": 1.83}, {"text": "So an electrical component\nthat behaves like a capacitor--", "start": 681.36, "duration": 6.085}, {"text": "like if you were to\nbuild one of those,", "start": 687.445, "duration": 1.625}, {"text": "you would take like a\npiece of aluminum foil,", "start": 689.07, "duration": 3.27}, {"text": "put a piece of paper on it, put\nanother piece of aluminum foil", "start": 692.34, "duration": 2.88}, {"text": "next to it, and\nattach wires to that,", "start": 695.22, "duration": 2.85}, {"text": "and you would squeeze the\nstack of aluminum foil paper", "start": 698.07, "duration": 3.51}, {"text": "and aluminum foil together, and\nthat becomes a capacitor, OK?", "start": 701.58, "duration": 3.87}, {"text": "And it has a symbol that\nlooks like this electrically.", "start": 705.45, "duration": 4.31}, {"text": "So this is now our equivalent\ncircuit of this model neuron,", "start": 709.76, "duration": 5.6}, {"text": "OK?", "start": 715.36, "duration": 0.61}, {"text": "It's very simple.", "start": 715.97, "duration": 1.27}, {"text": "It's a capacitor\nwith one wire here", "start": 717.24, "duration": 2.57}, {"text": "that represents the inside of\nthe cell, another wire that", "start": 719.81, "duration": 4.16}, {"text": "represents the\noutside of the cell.", "start": 723.97, "duration": 4.19}, {"text": "We have a current\nsource that connects", "start": 728.16, "duration": 2.52}, {"text": "the outside of the cell\nto the inside of the cell.", "start": 730.68, "duration": 3.03}, {"text": "When we turn on\nthe current source,", "start": 733.71, "duration": 1.47}, {"text": "it takes charges\nfrom inside of here", "start": 735.18, "duration": 4.08}, {"text": "and sticks them\nthrough the electrode", "start": 739.26, "duration": 3.45}, {"text": "and pumps them into the cell.", "start": 742.71, "duration": 2.28}, {"text": "Does that makes sense?", "start": 744.99, "duration": 2.91}, {"text": "This is our-- this is sort\nof a simplified symbol", "start": 747.9, "duration": 5.06}, {"text": "for a voltage-measuring device.", "start": 752.96, "duration": 2.73}, {"text": "The voltage difference\nbetween the inside of the cell", "start": 755.69, "duration": 2.94}, {"text": "and the outside of the cell\nis what we're measuring here,", "start": 758.63, "duration": 3.03}, {"text": "and that difference is called\nthe membrane potential.", "start": 761.66, "duration": 3.27}, {"text": "It's the voltage difference\nbetween the inside", "start": 764.93, "duration": 3.63}, {"text": "and the outside of the\nmembrane, all right?", "start": 768.56, "duration": 2.91}, {"text": "Any questions about that?", "start": 771.47, "duration": 1.5}, {"text": "Yes?", "start": 772.97, "duration": 0.7}, {"text": "AUDIENCE: There's a narrow\nresistance for [INAUDIBLE]..", "start": 773.67, "duration": 2.3}, {"text": "MICHALE FEE: What's that?", "start": 775.97, "duration": 0.757}, {"text": "AUDIENCE: The resistance for--", "start": 776.727, "duration": 1.193}, {"text": "MICHALE FEE: Yes,\nbut we're going", "start": 777.92, "duration": 0.69}, {"text": "to do it one piece at a time.", "start": 778.61, "duration": 1.39}, {"text": "So we're going to\nstart with a capacitor.", "start": 780.0, "duration": 1.96}, {"text": "The resistor will\ncome in a few slides.", "start": 781.96, "duration": 2.38}, {"text": "Yes?", "start": 787.75, "duration": 1.348}, {"text": "AUDIENCE: So the [INAUDIBLE].", "start": 789.098, "duration": 1.437}, {"text": "MICHALE FEE: Exactly.", "start": 797.455, "duration": 0.875}, {"text": "So we've simplified our\nneurons so that it's", "start": 798.33, "duration": 2.46}, {"text": "just an insulating shell, OK?", "start": 800.79, "duration": 3.51}, {"text": "No ion channels, no\ncurrent anywhere else.", "start": 804.3, "duration": 2.79}, {"text": "If we want to inject current\ninto this simple model neuron,", "start": 807.09, "duration": 3.93}, {"text": "we have to inject it through\nthis electrode here, OK?", "start": 811.02, "duration": 3.68}, {"text": "So we're just going down\nto the very simplest case,", "start": 814.7, "duration": 5.03}, {"text": "because this is already\nkind of interesting enough", "start": 819.73, "duration": 3.05}, {"text": "to understand just by itself.", "start": 822.78, "duration": 1.41}, {"text": "Yes?", "start": 824.19, "duration": 0.806}, {"text": "AUDIENCE: So if the cell's\nacting as a capacitor,", "start": 824.996, "duration": 2.174}, {"text": "is their energy stored\nin their myelin?", "start": 827.17, "duration": 3.805}, {"text": "MICHALE FEE: The\nenergy is stored", "start": 830.975, "duration": 1.375}, {"text": "in the electric field\nthat crosses the bilayer,", "start": 832.35, "duration": 1.92}, {"text": "and I'll get to\nthat in a second.", "start": 834.27, "duration": 1.375}, {"text": "Any other questions?", "start": 839.48, "duration": 1.05}, {"text": "OK, great questions.", "start": 840.53, "duration": 2.338}, {"text": "All right, so what happens\nwhen we inject current", "start": 842.868, "duration": 2.042}, {"text": "into our neuron?", "start": 844.91, "duration": 0.78}, {"text": "As I said, the current\nsource is pulling charges", "start": 845.69, "duration": 4.05}, {"text": "from the outside and pumping\nthem into the inside,", "start": 849.74, "duration": 4.196}, {"text": "all right?", "start": 853.936, "duration": 2.736}, {"text": "So what happens when goes on?", "start": 856.672, "duration": 6.498}, {"text": "So what we're doing is we\nare injecting current-- let's", "start": 863.17, "duration": 2.66}, {"text": "say this is our capacitor.", "start": 865.83, "duration": 1.75}, {"text": "There are charges, there\nare ions on the inside", "start": 867.58, "duration": 5.35}, {"text": "that are just up against the\ninside of the cell membrane.", "start": 872.93, "duration": 3.45}, {"text": "There are charges\non the outside, OK?", "start": 876.38, "duration": 3.87}, {"text": "And when we inject a charge\nfrom the outside to the inside--", "start": 880.25, "duration": 3.31}, {"text": "let's put one of those\ncharges right here.", "start": 883.56, "duration": 2.15}, {"text": "And we're going to push it\ninto this cell, when you inject", "start": 885.71, "duration": 2.75}, {"text": "a charge, you get\nan excessive charge", "start": 888.46, "duration": 3.64}, {"text": "on the inside of the\ncell membrane, OK?", "start": 892.1, "duration": 3.96}, {"text": "And what does that do?", "start": 896.06, "duration": 1.2}, {"text": "You now have more positive\ncharges inside than outside,", "start": 897.26, "duration": 4.86}, {"text": "like-charges repel--", "start": 902.12, "duration": 2.38}, {"text": "so it pushes one\nof those charges", "start": 904.5, "duration": 2.27}, {"text": "away from the outside\nof the membrane.", "start": 906.77, "duration": 3.683}, {"text": "Does that makes sense?", "start": 910.453, "duration": 0.917}, {"text": "OK, that's kind of interesting.", "start": 913.88, "duration": 1.52}, {"text": "We took a charge, we pushed\nit in, and a charge comes out.", "start": 915.4, "duration": 8.25}, {"text": "Right?", "start": 923.65, "duration": 1.02}, {"text": "We have a current flowing.", "start": 924.67, "duration": 1.62}, {"text": "We have charges coming\nin and charges leaving.", "start": 926.29, "duration": 3.07}, {"text": "We have a current flowing\nthrough an insulator.", "start": 929.36, "duration": 2.77}, {"text": "How is that possible?", "start": 932.13, "duration": 2.38}, {"text": "It's a capacitive current, OK?", "start": 934.51, "duration": 2.24}, {"text": "No charges are actually\npassing through the insulator,", "start": 936.75, "duration": 3.9}, {"text": "but it looks like you\nhave a current flowing.", "start": 940.65, "duration": 3.42}, {"text": "That's called a\ncapacitive current.", "start": 944.07, "duration": 2.4}, {"text": "And we represent that in\nour diagram by a current", "start": 946.47, "duration": 4.85}, {"text": "I sub C, capacitive current that\nflows through the capacitor.", "start": 951.32, "duration": 4.32}, {"text": "Pretty cool, right?", "start": 955.64, "duration": 1.3}, {"text": "You have a current flowing\nthrough an insulator.", "start": 956.94, "duration": 2.21}, {"text": "That's what a capacitor is.", "start": 959.15, "duration": 3.03}, {"text": "OK.", "start": 962.18, "duration": 1.29}, {"text": "Now notice that you\nhave a charge imbalance.", "start": 963.47, "duration": 2.82}, {"text": "You have three positive\ncharges here and only", "start": 966.29, "duration": 2.82}, {"text": "one positive charge here.", "start": 969.11, "duration": 2.35}, {"text": "So there is an excess of two\npositive charges on the inside.", "start": 971.46, "duration": 2.87}, {"text": "That's because we added a\npositive charge to the inside", "start": 974.33, "duration": 3.0}, {"text": "and took away a positive\ncharge from the outside,", "start": 977.33, "duration": 2.31}, {"text": "so that leaves a charge\nimbalance of 2, OK?", "start": 979.64, "duration": 4.04}, {"text": "What do you get between positive\ncharge and negative charge", "start": 983.68, "duration": 3.73}, {"text": "if you hold them\nnext to each other?", "start": 987.41, "duration": 2.04}, {"text": "What is there in between?", "start": 989.45, "duration": 2.61}, {"text": "AUDIENCE: It's attraction.", "start": 992.06, "duration": 1.422}, {"text": "MICHALE FEE: Good,\nit's attraction,", "start": 993.482, "duration": 1.458}, {"text": "but what is it that\ncauses that attraction?", "start": 994.94, "duration": 2.07}, {"text": "Remember yesterday, we talked\nabout a something on a charge", "start": 997.01, "duration": 3.87}, {"text": "produces a force, what is it?", "start": 1000.88, "duration": 1.298}, {"text": "AUDIENCE: Electric field.", "start": 1002.178, "duration": 1.042}, {"text": "MICHALE FEE: Good.", "start": 1003.22, "duration": 0.75}, {"text": "So there's an electric\nfield between the positive--", "start": 1003.97, "duration": 3.6}, {"text": "the excess positive charges here\nand the excess negative charges", "start": 1007.57, "duration": 3.66}, {"text": "here, OK?", "start": 1011.23, "duration": 1.56}, {"text": "That's an electric\nfield, all right?", "start": 1012.79, "duration": 3.0}, {"text": "And that electric\nfield stores energy.", "start": 1015.79, "duration": 2.35}, {"text": "How do you know there's\nenergy in this system, though?", "start": 1018.14, "duration": 2.54}, {"text": "What could you do to\ndemonstrate that there is", "start": 1020.68, "duration": 2.19}, {"text": "energy stored in that system?", "start": 1022.87, "duration": 3.76}, {"text": "Any ideas?", "start": 1026.63, "duration": 0.83}, {"text": "You have two plates, two\nmetal plates, let's say,", "start": 1027.46, "duration": 2.95}, {"text": "in the metal version of this.", "start": 1030.41, "duration": 1.76}, {"text": "Separated by an insulator.", "start": 1032.17, "duration": 1.98}, {"text": "What would happen if you\npulled away the insulator?", "start": 1034.15, "duration": 4.13}, {"text": "Those two things would do\nthat again, but louder--", "start": 1038.28, "duration": 2.49}, {"text": "boom.", "start": 1040.77, "duration": 0.87}, {"text": "What does that take\nto make that sound?", "start": 1041.64, "duration": 3.959}, {"text": "Energy, OK?", "start": 1045.599, "duration": 1.711}, {"text": "So there's energy stored\nin that electric field.", "start": 1050.04, "duration": 3.34}, {"text": "So there's a charge imbalance,\nthere's an electric field.", "start": 1053.38, "duration": 2.45}, {"text": "What does an electric field over\nsome distance correspond to?", "start": 1055.83, "duration": 5.098}, {"text": "AUDIENCE: A voltage difference.", "start": 1060.928, "duration": 1.292}, {"text": "MICHALE FEE: A voltage\ndifference, OK?", "start": 1062.22, "duration": 3.004}, {"text": "Now, there's a charge imbalance\nand a voltage difference,", "start": 1068.46, "duration": 3.19}, {"text": "and they're proportional\nto each other.", "start": 1071.65, "duration": 2.41}, {"text": "So there's a\nproportionality constant", "start": 1074.06, "duration": 2.45}, {"text": "that's called the\ncapacitance, all right?", "start": 1076.51, "duration": 3.32}, {"text": "If you can put a lot of charge\nand have a small voltage", "start": 1079.83, "duration": 5.16}, {"text": "difference, that's\na big capacitor.", "start": 1084.99, "duration": 2.25}, {"text": "Now you can get a big capacitor\njust by having a big area.", "start": 1087.24, "duration": 2.5}, {"text": "You can see, you can have a lot\nof charges with a small voltage", "start": 1089.74, "duration": 3.38}, {"text": "difference if you have big\nplates on your capacitor, OK?", "start": 1093.12, "duration": 5.49}, {"text": "So the capacitance is actually\nproportional to the area", "start": 1098.61, "duration": 3.15}, {"text": "of the plates,\nand it's inversely", "start": 1101.76, "duration": 1.5}, {"text": "proportional to the\ndistance between them.", "start": 1103.26, "duration": 2.8}, {"text": "It's a very thin\nmembrane, which means", "start": 1106.06, "duration": 3.2}, {"text": "you can get a lot of\ncapacitance in a tiny area, OK?", "start": 1109.26, "duration": 4.44}, {"text": "That's pretty cool.", "start": 1113.7, "duration": 3.23}, {"text": "All right, any questions?", "start": 1116.93, "duration": 2.98}, {"text": "So charge is coulombs, and there\nare 6 times 10 to the charges", "start": 1119.91, "duration": 4.17}, {"text": "in a coulomb, the\nelemental charges, electron", "start": 1124.08, "duration": 2.94}, {"text": "or monovalent ion charges.", "start": 1127.02, "duration": 4.888}, {"text": "Voltage is in units of\nvolts, and the capacitance", "start": 1131.908, "duration": 2.042}, {"text": "is in units of farads.", "start": 1133.95, "duration": 1.32}, {"text": "Any questions?", "start": 1138.72, "duration": 2.3}, {"text": "All right.", "start": 1141.02, "duration": 1.62}, {"text": "So we have our relation between\nvoltage difference and charge", "start": 1142.64, "duration": 4.7}, {"text": "difference.", "start": 1147.34, "duration": 1.43}, {"text": "And what we're\ngoing to do is we're", "start": 1148.77, "duration": 2.23}, {"text": "going to calculate this\ncapacitive current.", "start": 1151.0, "duration": 3.48}, {"text": "How do you think\nwe would calculate", "start": 1154.48, "duration": 2.28}, {"text": "the capacitive current?", "start": 1156.76, "duration": 1.02}, {"text": "Well, the capacitive\ncurrent is just", "start": 1161.31, "duration": 3.34}, {"text": "the rate at which the charge\nimbalance is changing, right?", "start": 1164.65, "duration": 5.25}, {"text": "Current is just charge\nper unit of time.", "start": 1169.9, "duration": 3.26}, {"text": "OK?", "start": 1173.16, "duration": 0.5}, {"text": "So we're going to calculate the\ncapacitive current as the time", "start": 1173.66, "duration": 3.68}, {"text": "rate of change of the charge--", "start": 1177.34, "duration": 1.56}, {"text": "and I've dropped\nthe deltas here.", "start": 1178.9, "duration": 2.67}, {"text": "So capacitive current\nis dQ/dt, all right?", "start": 1181.57, "duration": 4.91}, {"text": "And remember that Q is just\nCV, so the capacitive current", "start": 1186.48, "duration": 4.245}, {"text": "is just C dV/dt, and\nthe Vm here represents", "start": 1190.725, "duration": 3.765}, {"text": "the membrane potential, OK?", "start": 1194.49, "duration": 2.64}, {"text": "So the capacitive current\nthrough a membrane", "start": 1197.13, "duration": 3.63}, {"text": "is just the capacitance\ntimes the time rate of change", "start": 1200.76, "duration": 3.36}, {"text": "of the membrane potential.", "start": 1204.12, "duration": 3.75}, {"text": "Any questions?", "start": 1207.87, "duration": 2.168}, {"text": "OK.", "start": 1210.038, "duration": 0.932}, {"text": "Pretty straightforward.", "start": 1210.97, "duration": 1.96}, {"text": "Now what we're\ngoing to do now is", "start": 1212.93, "duration": 2.51}, {"text": "we're going to relate\nthe injected charge", "start": 1215.44, "duration": 4.17}, {"text": "to the-- sorry, the injected\ncurrent to the capacitor.", "start": 1219.61, "duration": 3.12}, {"text": "And what does Kirchhoff's\ncurrent law tell us?", "start": 1222.73, "duration": 2.95}, {"text": "It tells us that the amount of\ncurrent going into this wire", "start": 1225.68, "duration": 3.29}, {"text": "has to be equal to the amount\nof current leaving that wire.", "start": 1228.97, "duration": 3.86}, {"text": "OK?", "start": 1232.83, "duration": 0.5}, {"text": "So we can write that\ndown as follows.", "start": 1233.33, "duration": 2.39}, {"text": "The difference in sign here is\nbecause the electrode current", "start": 1235.72, "duration": 3.6}, {"text": "is defined as positive\ninward, the capacitive current", "start": 1239.32, "duration": 3.54}, {"text": "is defined as positive outward.", "start": 1242.86, "duration": 4.108}, {"text": "OK?", "start": 1246.968, "duration": 0.5}, {"text": "So you can see that\nwe just calculated", "start": 1254.95, "duration": 3.0}, {"text": "the capacitive\ncurrent, it's C dV/dt,", "start": 1257.95, "duration": 2.16}, {"text": "so we can just\nplug that in here,", "start": 1260.11, "duration": 2.07}, {"text": "and now we see this\nvery simple relation", "start": 1262.18, "duration": 2.19}, {"text": "between the injected\ncurrent and the voltage.", "start": 1264.37, "duration": 3.88}, {"text": "And again, the current\nhas unit of amperes,", "start": 1274.75, "duration": 2.21}, {"text": "which is coulombs per second.", "start": 1276.96, "duration": 1.32}, {"text": "OK, so we have that.", "start": 1280.8, "duration": 2.31}, {"text": "Now we have a\ndifferential equation", "start": 1283.11, "duration": 1.83}, {"text": "that describes the relation\nbetween current and voltage,", "start": 1284.94, "duration": 2.46}, {"text": "we can just integrate\nit to get the solution.", "start": 1287.4, "duration": 5.19}, {"text": "So that membrane\npotential will just", "start": 1292.59, "duration": 2.34}, {"text": "be some initial membrane\npotential at time 0", "start": 1294.93, "duration": 4.2}, {"text": "plus 1 over C integral over\ntime of the injected current.", "start": 1299.13, "duration": 6.06}, {"text": "Just integrate both sides.", "start": 1310.89, "duration": 1.41}, {"text": "You get V here, you get\nintegral of I there,", "start": 1312.3, "duration": 3.06}, {"text": "and divide both sides\nby C. Any questions?", "start": 1315.36, "duration": 8.848}, {"text": "It's either really\nconfusing or really obvious.", "start": 1324.208, "duration": 4.362}, {"text": "Yeah?", "start": 1328.57, "duration": 0.5}, {"text": "Everybody OK?", "start": 1329.07, "duration": 1.66}, {"text": "All right, good.", "start": 1330.73, "duration": 1.28}, {"text": "Now what is this?", "start": 1332.01, "duration": 0.9}, {"text": "What is the integral\nof current over time?", "start": 1332.91, "duration": 4.96}, {"text": "AUDIENCE: It's\ncharge [INAUDIBLE]", "start": 1337.87, "duration": 1.66}, {"text": "MICHALE FEE: Good.", "start": 1339.53, "duration": 0.75}, {"text": "It's the amount of charge\nyou injected between time", "start": 1340.28, "duration": 3.0}, {"text": "0 and time t, right?", "start": 1343.28, "duration": 2.4}, {"text": "And what is the amount of charge\nyou inject-- if I tell you", "start": 1345.68, "duration": 5.07}, {"text": "that I injected an amount of\ncharge delta Q, how much did", "start": 1350.75, "duration": 4.44}, {"text": "I change the voltage?", "start": 1355.19, "duration": 0.94}, {"text": "Delta V is delta Q over\nC, and that's exactly.", "start": 1363.38, "duration": 2.58}, {"text": "So the voltage is just\nthe starting voltage", "start": 1365.96, "duration": 2.91}, {"text": "plus delta voltage.", "start": 1368.87, "duration": 2.87}, {"text": "Does that makes sense?", "start": 1371.74, "duration": 2.38}, {"text": "This integral here is just--", "start": 1374.12, "duration": 2.88}, {"text": "that part is just\nthe amount of charge", "start": 1377.0, "duration": 2.43}, {"text": "you injected divided by C gives\nyou the change in the voltage.", "start": 1379.43, "duration": 3.66}, {"text": "So the voltage is just the\nstarting voltage plus delta V,", "start": 1383.09, "duration": 5.25}, {"text": "OK?", "start": 1388.34, "duration": 1.21}, {"text": "Yes?", "start": 1389.55, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1390.05, "duration": 1.838}, {"text": "MICHALE FEE: What's that?", "start": 1391.888, "duration": 1.042}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1392.93, "duration": 0.983}, {"text": "MICHALE FEE: Oh.", "start": 1393.913, "duration": 0.667}, {"text": "Because this equation\nhere just came from here.", "start": 1394.58, "duration": 5.76}, {"text": "That was our charge--", "start": 1400.34, "duration": 1.51}, {"text": "our relation between charge\nbalance and voltage difference.", "start": 1401.85, "duration": 4.28}, {"text": "Yeah?", "start": 1406.13, "duration": 0.5}, {"text": "If it's not clear, just\nplease ask, thank you.", "start": 1410.41, "duration": 2.41}, {"text": "OK.", "start": 1415.99, "duration": 1.01}, {"text": "There we go.", "start": 1417.0, "duration": 0.73}, {"text": "So what is the\ninterval constant?", "start": 1417.73, "duration": 7.31}, {"text": "It's just some constant\ntimes time, right?", "start": 1425.04, "duration": 2.94}, {"text": "So our voltage is just\nsome initial voltage", "start": 1427.98, "duration": 3.27}, {"text": "plus the injected current\nover C times time.", "start": 1431.25, "duration": 4.51}, {"text": "And so you can see where\nthis comes from, right?", "start": 1435.76, "duration": 2.24}, {"text": "When you turn the\ncurrent on, the voltage", "start": 1438.0, "duration": 2.34}, {"text": "just increases\nlinearly over time", "start": 1440.34, "duration": 3.81}, {"text": "with a slope that's given\nby the current divided", "start": 1444.15, "duration": 4.44}, {"text": "by the capacitance.", "start": 1448.59, "duration": 1.566}, {"text": "OK?", "start": 1450.156, "duration": 0.5}, {"text": "All right, any questions?", "start": 1458.782, "duration": 4.038}, {"text": "You guys are being very quiet.", "start": 1462.82, "duration": 1.49}, {"text": "This is the point where\nI start feeling nervous,", "start": 1464.31, "duration": 3.0}, {"text": "I went too fast.", "start": 1467.31, "duration": 1.0}, {"text": "Yes?", "start": 1468.31, "duration": 0.8}, {"text": "AUDIENCE: You continually\ndraw the curve for a while--", "start": 1469.11, "duration": 2.25}, {"text": "MICHALE FEE: Yep.", "start": 1471.36, "duration": 0.708}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1472.068, "duration": 2.012}, {"text": "MICHALE FEE: Yes, it does.", "start": 1474.08, "duration": 1.75}, {"text": "And it breaks at\nabout a volt or so.", "start": 1475.83, "duration": 7.09}, {"text": "Because the electric\nfield gets so strong,", "start": 1482.92, "duration": 2.55}, {"text": "it literally just\nrips the atoms apart", "start": 1485.47, "duration": 3.09}, {"text": "in the molecules of\nthe lipid bilayer.", "start": 1488.56, "duration": 1.795}, {"text": "Yes?", "start": 1493.95, "duration": 0.5}, {"text": "AUDIENCE: Why do you [INAUDIBLE]", "start": 1494.45, "duration": 1.378}, {"text": "MICHALE FEE: Sorry,\nI shouldn't say--", "start": 1495.828, "duration": 1.542}, {"text": "it doesn't rip the atoms apart,\nit rips the molecules apart.", "start": 1497.37, "duration": 4.37}, {"text": "You need much higher\nelectric fields to do that.", "start": 1501.74, "duration": 2.91}, {"text": "Yes?", "start": 1504.65, "duration": 0.81}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1505.46, "duration": 5.268}, {"text": "MICHALE FEE: Oh.", "start": 1510.728, "duration": 0.667}, {"text": "Because we're integrating\nfrom time 0 to time t.", "start": 1511.395, "duration": 6.045}, {"text": "We want to know the\nvoltage at time t, OK?", "start": 1517.44, "duration": 4.02}, {"text": "We're starting at 0, we're\nintegrating the current", "start": 1521.46, "duration": 2.64}, {"text": "from time 0 to time t,\nwhich is where we're wanting", "start": 1524.1, "duration": 5.56}, {"text": "to know the voltage, right?", "start": 1529.66, "duration": 1.33}, {"text": "So you have to integrate\nthe current from 0 to t.", "start": 1530.99, "duration": 3.02}, {"text": "We can't use t in here.\nt is the endpoint.", "start": 1534.01, "duration": 5.33}, {"text": "Yeah.", "start": 1539.34, "duration": 0.64}, {"text": "Does that makes sense?", "start": 1539.98, "duration": 0.998}, {"text": "Good question, thank you.", "start": 1540.978, "duration": 1.042}, {"text": "OK, everybody all right?", "start": 1550.18, "duration": 1.41}, {"text": "I'm going to stand here until\nI hear one more question.", "start": 1551.59, "duration": 4.18}, {"text": "Yes?", "start": 1555.77, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1556.27, "duration": 4.213}, {"text": "MICHALE FEE: Oh, here.", "start": 1560.483, "duration": 0.917}, {"text": "Because it's a\ncurrent of value I0.", "start": 1561.4, "duration": 4.44}, {"text": "Great question.", "start": 1565.84, "duration": 1.95}, {"text": "Yes?", "start": 1567.79, "duration": 0.5}, {"text": "AUDIENCE: So to maintain this\nconstant current [INAUDIBLE]", "start": 1568.29, "duration": 3.22}, {"text": "the amount of [INAUDIBLE]\nyou're pumping it and--", "start": 1571.51, "duration": 3.76}, {"text": "MICHALE FEE: Yes.", "start": 1575.27, "duration": 1.14}, {"text": "That's right.", "start": 1576.41, "duration": 0.63}, {"text": "This-- OK, I should have\nmaybe been more clear.", "start": 1577.04, "duration": 2.88}, {"text": "This current source has a\nknob on it that I get to set.", "start": 1579.92, "duration": 4.23}, {"text": "I get to like--", "start": 1584.15, "duration": 2.52}, {"text": "there would be an\napp now, and I'd", "start": 1586.67, "duration": 1.47}, {"text": "pull out my current\nsource app and I", "start": 1588.14, "duration": 2.22}, {"text": "type in 10 milliamps, boom.", "start": 1590.36, "duration": 1.578}, {"text": "And this thing-- because\nthere's a Bluetooth connection", "start": 1591.938, "duration": 2.292}, {"text": "to this thing, and it like sets\nthis thing to 10 milliamps,", "start": 1594.23, "duration": 3.18}, {"text": "and it just keeps pumping\n10 milliamps until you tell", "start": 1597.41, "duration": 2.55}, {"text": "it to do something else, OK?", "start": 1599.96, "duration": 4.16}, {"text": "Yes?", "start": 1604.12, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE] make the\nright direction instead of it", "start": 1604.62, "duration": 3.07}, {"text": "being constant current\nstate that usually--", "start": 1607.69, "duration": 2.617}, {"text": "MICHALE FEE: Oh, OK.", "start": 1610.307, "duration": 0.833}, {"text": "AUDIENCE: --that would\ncreate some weird kind of--", "start": 1611.14, "duration": 2.86}, {"text": "MICHALE FEE: Sure.", "start": 1614.0, "duration": 1.15}, {"text": "Yeah.", "start": 1615.15, "duration": 0.5}, {"text": "What would that be, actually?", "start": 1615.65, "duration": 1.23}, {"text": "If you put in a linear\nramp in current?", "start": 1616.88, "duration": 2.805}, {"text": "It would be a parabolic\nvoltage profile.", "start": 1619.685, "duration": 2.715}, {"text": "Yeah, very good.", "start": 1622.4, "duration": 1.2}, {"text": "That's exactly it.", "start": 1623.6, "duration": 1.23}, {"text": "This current profile that\nyou-- this voltage profile", "start": 1624.83, "duration": 4.8}, {"text": "is literally just the numerical\nintegral of this function.", "start": 1629.63, "duration": 4.03}, {"text": "So all you have to\ndo is look at this", "start": 1633.66, "duration": 1.67}, {"text": "and integrate it in\nyour head, and you can", "start": 1635.33, "duration": 2.16}, {"text": "see what the voltage does, OK?", "start": 1637.49, "duration": 3.18}, {"text": "Great.", "start": 1640.67, "duration": 0.75}, {"text": "That's exactly right.", "start": 1641.42, "duration": 1.56}, {"text": "So let's do another example.", "start": 1642.98, "duration": 1.3}, {"text": "Let's put in a current pulse.", "start": 1644.28, "duration": 2.0}, {"text": "So we start at zero current,\nwe step it up to I0,", "start": 1646.28, "duration": 2.88}, {"text": "we hold it there for tau,\nthen we turn the current off.", "start": 1649.16, "duration": 3.42}, {"text": "So let's start our\nneuron right here.", "start": 1652.58, "duration": 2.1}, {"text": "What's going to happen?", "start": 1654.68, "duration": 1.782}, {"text": "What's your name?", "start": 1656.462, "duration": 0.708}, {"text": "I'm going to ask you\nto do this problem.", "start": 1657.17, "duration": 2.25}, {"text": "What-- yeah.", "start": 1659.42, "duration": 0.79}, {"text": "AUDIENCE: Sammy.", "start": 1660.21, "duration": 0.668}, {"text": "MICHALE FEE: Sammy.", "start": 1660.878, "duration": 0.792}, {"text": "What's this voltage going to do?", "start": 1661.67, "duration": 2.778}, {"text": "AUDIENCE: So I'd say constant.", "start": 1664.448, "duration": 1.482}, {"text": "MICHALE FEE: Good.", "start": 1665.93, "duration": 0.75}, {"text": "Because it's zero current.", "start": 1666.68, "duration": 1.503}, {"text": "Then what's going to happen?", "start": 1668.183, "duration": 1.167}, {"text": "AUDIENCE: And it's\ngoing to [INAUDIBLE]", "start": 1669.35, "duration": 1.26}, {"text": "MICHALE FEE: Good.", "start": 1670.61, "duration": 0.75}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1671.36, "duration": 1.77}, {"text": "MICHALE FEE: Good.", "start": 1673.13, "duration": 1.164}, {"text": "AUDIENCE: And then the\n[INAUDIBLE] go back to constant", "start": 1674.294, "duration": 3.361}, {"text": "at that point.", "start": 1677.655, "duration": 0.965}, {"text": "MICHALE FEE: Awesome.", "start": 1678.62, "duration": 1.08}, {"text": "That's it.", "start": 1679.7, "duration": 0.67}, {"text": "It's that simple.", "start": 1680.37, "duration": 2.87}, {"text": "OK?", "start": 1683.24, "duration": 2.515}, {"text": "Good.", "start": 1685.755, "duration": 2.795}, {"text": "All right.", "start": 1688.55, "duration": 0.57}, {"text": "Now somebody brought\nup resistors.", "start": 1689.12, "duration": 1.62}, {"text": "Who brought up ion conductances?", "start": 1690.74, "duration": 2.28}, {"text": "Somebody mentioned that.", "start": 1693.02, "duration": 1.68}, {"text": "So that's the next thing\nwe're going to add.", "start": 1697.33, "duration": 2.01}, {"text": "This is sort of the zero\norder model of a neuron.", "start": 1699.34, "duration": 4.24}, {"text": "It has the simplest view and\nit's often not so bad, OK?", "start": 1703.58, "duration": 4.46}, {"text": "For short periods of time.", "start": 1708.04, "duration": 1.96}, {"text": "But neurons actually have\nion channels, all right?", "start": 1710.0, "duration": 3.68}, {"text": "Allow current to flow\nthrough the membrane.", "start": 1713.68, "duration": 2.86}, {"text": "So we're going to start\ntoday by analyzing", "start": 1716.54, "duration": 1.76}, {"text": "the case of the simplest\nkind of ion channel", "start": 1718.3, "duration": 2.58}, {"text": "which is the kind of ion channel\nyou get when you take a needle", "start": 1720.88, "duration": 2.73}, {"text": "and you poke a hole\nin the membrane, OK?", "start": 1723.61, "duration": 4.06}, {"text": "It's called the leak\nor a hole, all right?", "start": 1727.67, "duration": 4.36}, {"text": "And we're going to analyze\nwhat our neuron does", "start": 1732.03, "duration": 2.65}, {"text": "when you do that.", "start": 1734.68, "duration": 0.73}, {"text": "So what we're going to find\nis that the ion channel--", "start": 1735.41, "duration": 5.08}, {"text": "a leak conductance, it can\nbe represented in our model", "start": 1740.49, "duration": 3.91}, {"text": "simply by a resistor, OK?", "start": 1744.4, "duration": 4.67}, {"text": "And we're going to have our\ncapacitive current, membrane", "start": 1749.07, "duration": 3.15}, {"text": "capacitive current, and a\nmembrane ionic current that's", "start": 1752.22, "duration": 4.08}, {"text": "due to ions flowing through ion\nchannels in the membrane, OK?", "start": 1756.3, "duration": 4.4}, {"text": "And that current will be--", "start": 1764.41, "duration": 1.66}, {"text": "we're going to call that\nour leak resistance,", "start": 1766.07, "duration": 3.06}, {"text": "and that current will\nbe our leak current, OK?", "start": 1769.13, "duration": 6.6}, {"text": "So now, Kirchhoff's\ncurrent law tells us what?", "start": 1775.73, "duration": 2.76}, {"text": "That the leak current plus\nthe capacitive current", "start": 1778.49, "duration": 3.57}, {"text": "has to equal the injected\ncurrent, all right?", "start": 1782.06, "duration": 3.668}, {"text": "We know the capacitive\ncurrent is just C dV/dt,", "start": 1790.71, "duration": 3.15}, {"text": "so we just plug that\nin, and now we have I", "start": 1793.86, "duration": 2.28}, {"text": "leak plus C dV/dt equals the\ninjected electrode current.", "start": 1796.14, "duration": 4.02}, {"text": "That is called membrane\nionic current, that", "start": 1802.79, "duration": 3.09}, {"text": "is called membrane\ncapacitive current,", "start": 1805.88, "duration": 2.62}, {"text": "and that is our\nelectrode current.", "start": 1808.5, "duration": 2.73}, {"text": "There's a sign convention\nin neuroscience,", "start": 1811.23, "duration": 4.5}, {"text": "which is that membrane\nionic currents that", "start": 1815.73, "duration": 2.87}, {"text": "are outward from the\ninside of the cell", "start": 1818.6, "duration": 2.25}, {"text": "to the outside of the cell\nmembrane are positive in sign.", "start": 1820.85, "duration": 4.56}, {"text": "Positive charges leaving the\ncell have a positive sign.", "start": 1825.41, "duration": 4.31}, {"text": "It's just convention, it\ncould have been the other way.", "start": 1829.72, "duration": 3.29}, {"text": "But you have to choose\nsomething, so that's what--", "start": 1833.01, "duration": 4.12}, {"text": "I think it was Hodgkin\nand Huxley, actually,", "start": 1837.13, "duration": 2.73}, {"text": "who decided that.", "start": 1839.86, "duration": 2.13}, {"text": "Inward currents, positive\ncharges entering the cell", "start": 1841.99, "duration": 2.7}, {"text": "through the membrane going\nthis way from extracellular", "start": 1844.69, "duration": 2.46}, {"text": "to intracellular, are\ndefined as negative.", "start": 1847.15, "duration": 4.383}, {"text": "Electrode currents,\nthe other way.", "start": 1851.533, "duration": 1.417}, {"text": "Electrode current--\ninward current is--", "start": 1852.95, "duration": 2.46}, {"text": "into the cell is positive.", "start": 1855.41, "duration": 2.072}, {"text": "OK, so we're going to poke\na hole in our membrane", "start": 1860.86, "duration": 2.58}, {"text": "and we're going to model that\nion channel using Ohm's law.", "start": 1863.44, "duration": 5.42}, {"text": "So the leak current is just\nmembrane potential divided", "start": 1868.86, "duration": 3.3}, {"text": "by resistance, leak resistance.", "start": 1872.16, "duration": 3.06}, {"text": "So what do we get if\nwe plug this into our--", "start": 1879.95, "duration": 2.9}, {"text": "I leak plus I capacitance?", "start": 1882.85, "duration": 2.2}, {"text": "Capacitive equals\ninjected current.", "start": 1885.05, "duration": 2.52}, {"text": "We get V membrane potential,\nVm over RL plus C dV/dt", "start": 1887.57, "duration": 5.07}, {"text": "equals injected current, OK?", "start": 1892.64, "duration": 3.655}, {"text": "We multiply both sides by\nresistance, we get V plus RC--", "start": 1899.07, "duration": 6.39}, {"text": "that why it's\ncalled an RC model--", "start": 1905.46, "duration": 2.86}, {"text": "dV/dt equals leak\nresistance times", "start": 1908.32, "duration": 3.94}, {"text": "the injected current, all right?", "start": 1912.26, "duration": 4.1}, {"text": "Now that's looking a\nlittle complicated,", "start": 1916.36, "duration": 2.38}, {"text": "but we're going to\nsimplify things now.", "start": 1918.74, "duration": 3.2}, {"text": "Tau-- I'm sorry, RC is\nresistance times capacitance,", "start": 1921.94, "duration": 4.03}, {"text": "and it turns out, that\nhas units of time.", "start": 1925.97, "duration": 3.3}, {"text": "And so we're going\nto call that tau--", "start": 1929.27, "duration": 3.84}, {"text": "got a little ahead of myself.", "start": 1933.11, "duration": 1.657}, {"text": "That's called tau,\nwe're going to make", "start": 1934.767, "duration": 1.583}, {"text": "that substitution in a minute.", "start": 1936.35, "duration": 2.57}, {"text": "But first we're going to\ncalculate the steady state", "start": 1938.92, "duration": 2.25}, {"text": "solution to that\nlittle equation, OK?", "start": 1941.17, "duration": 2.88}, {"text": "So bear with me, hang\non, it's all going", "start": 1944.05, "duration": 2.487}, {"text": "to make sense in a minute.", "start": 1946.537, "duration": 1.083}, {"text": "Does anyone know how to\ncalculate the steady state", "start": 1950.947, "duration": 2.083}, {"text": "solution of a\ndifferential equation?", "start": 1953.03, "duration": 2.62}, {"text": "Yes?", "start": 1955.65, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1956.15, "duration": 1.14}, {"text": "MICHALE FEE: Good.", "start": 1957.29, "duration": 0.75}, {"text": "What's your name?", "start": 1958.04, "duration": 0.57}, {"text": "AUDIENCE: Rebecca.", "start": 1958.61, "duration": 0.75}, {"text": "MICHALE FEE: Rebecca.", "start": 1959.36, "duration": 1.55}, {"text": "So you said the derivative--", "start": 1960.91, "duration": 1.96}, {"text": "so let's do that.", "start": 1962.87, "duration": 1.4}, {"text": "Set dV/dt equal to 0.", "start": 1964.27, "duration": 1.58}, {"text": "And what do you find?", "start": 1968.55, "duration": 2.09}, {"text": "Sorry, we flashed\nthe answer up there.", "start": 1970.64, "duration": 1.85}, {"text": "What do you get if you\nsaid dV/dt equals 0?", "start": 1972.49, "duration": 3.636}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1976.126, "duration": 1.734}, {"text": "MICHALE FEE: Good.", "start": 1977.86, "duration": 0.93}, {"text": "So you inject some\ncurrent, we're", "start": 1978.79, "duration": 2.9}, {"text": "going to hold the current\nconstant, let's say, OK?", "start": 1981.69, "duration": 2.84}, {"text": "We've put some current in\nand we hold it constant.", "start": 1984.53, "duration": 4.19}, {"text": "The voltage will change,\nand eventually things", "start": 1988.72, "duration": 2.49}, {"text": "will settle down and\nthe dV/dt will go to 0.", "start": 1991.21, "duration": 4.42}, {"text": "At that point, we\nknow the voltage.", "start": 1995.63, "duration": 2.55}, {"text": "It's just RL times Ie.", "start": 1998.18, "duration": 3.66}, {"text": "What is the voltage equals\nresistance times current?", "start": 2001.84, "duration": 3.18}, {"text": "What is that?", "start": 2005.02, "duration": 1.087}, {"text": "AUDIENCE: Ohm's law.", "start": 2006.107, "duration": 0.833}, {"text": "MICHALE FEE: Ohm's law.", "start": 2006.94, "duration": 2.25}, {"text": "It's just when we inject\ncurrent, a bunch of stuff", "start": 2009.19, "duration": 4.6}, {"text": "happens, and when\nthe dust settles,", "start": 2013.79, "duration": 3.93}, {"text": "the voltage difference is\njust the injected current", "start": 2017.72, "duration": 3.86}, {"text": "divided by the resistance.", "start": 2021.58, "duration": 3.51}, {"text": "Does that makes sense?", "start": 2025.09, "duration": 1.33}, {"text": "Yes?", "start": 2026.42, "duration": 0.5}, {"text": "AUDIENCE: Where is [INAUDIBLE]", "start": 2026.92, "duration": 5.647}, {"text": "MICHALE FEE: Well, right\nnow we just took a needle", "start": 2032.567, "duration": 2.083}, {"text": "and poked a hole in our cell.", "start": 2034.65, "duration": 2.73}, {"text": "So--", "start": 2037.38, "duration": 1.07}, {"text": "AUDIENCE: How big the hole is?", "start": 2038.45, "duration": 1.25}, {"text": "MICHALE FEE: Yep, exactly.", "start": 2039.7, "duration": 1.79}, {"text": "It's how big the hole is.", "start": 2041.49, "duration": 2.04}, {"text": "Now cells-- real cells\ndo have leak channels.", "start": 2043.53, "duration": 4.42}, {"text": "They're actually\nion channels that", "start": 2047.95, "duration": 3.68}, {"text": "leak kind of any\nion that's in there.", "start": 2051.63, "duration": 2.96}, {"text": "It's not very common.", "start": 2054.59, "duration": 3.708}, {"text": "And you'll see why in a minute.", "start": 2058.298, "duration": 1.292}, {"text": "Actually, that's not quite true.", "start": 2062.87, "duration": 3.269}, {"text": "There are ion channels that\nlook essentially like leaks,", "start": 2066.139, "duration": 4.941}, {"text": "and it turns out\nthat the ion channels", "start": 2071.08, "duration": 4.309}, {"text": "that many neurotransmitter\nreceptors like", "start": 2075.389, "duration": 4.201}, {"text": "glutamate and acetylcholine,\nthe ion channels actually", "start": 2079.59, "duration": 4.379}, {"text": "look like little leaks.", "start": 2083.969, "duration": 1.381}, {"text": "They pass multiple ions that\nmakes them look like leaks.", "start": 2085.35, "duration": 4.86}, {"text": "OK.", "start": 2095.69, "duration": 0.82}, {"text": "So in steady state, the membrane\npotential goes to RL times Ie,", "start": 2096.51, "duration": 5.7}, {"text": "and we call that voltage\nsomething special, V infinity,", "start": 2102.21, "duration": 4.47}, {"text": "because it's the voltage that\nthe system reaches at time", "start": 2106.68, "duration": 4.26}, {"text": "equals infinity, OK?", "start": 2110.94, "duration": 3.82}, {"text": "Any questions about that?", "start": 2114.76, "duration": 1.09}, {"text": "OK.", "start": 2118.57, "duration": 0.5}, {"text": "So we're going to just rewrite\nthis equation as Vm plus tau", "start": 2119.07, "duration": 5.58}, {"text": "dV/dt equals V infinity.", "start": 2124.65, "duration": 2.02}, {"text": "And that equation we're\ngoing to see over and over", "start": 2126.67, "duration": 3.5}, {"text": "and over again in this class\nin many different contexts, all", "start": 2130.17, "duration": 3.88}, {"text": "right?", "start": 2134.05, "duration": 0.5}, {"text": "It's a first order linear\ndifferential equation", "start": 2134.55, "duration": 2.28}, {"text": "and it's very powerful, so I\nwant you to get used to it.", "start": 2136.83, "duration": 5.87}, {"text": "So what does this mean?", "start": 2142.7, "duration": 3.4}, {"text": "So let's rewrite this\nequation a little bit.", "start": 2146.1, "duration": 2.31}, {"text": "Let's move this term\nto the other side", "start": 2148.41, "duration": 3.65}, {"text": "and divide both sides by\ntau, and here's what you get.", "start": 2152.06, "duration": 3.0}, {"text": "dV/dt equals minus\n1 over tau V minus--", "start": 2155.06, "duration": 4.89}, {"text": "times V minus V infinity.", "start": 2159.95, "duration": 3.885}, {"text": "OK?", "start": 2163.835, "duration": 2.795}, {"text": "Now let's take a look at what\nthe derivative dV/dt looks", "start": 2166.63, "duration": 3.89}, {"text": "like as a function of voltage.", "start": 2170.52, "duration": 1.28}, {"text": "Yes?", "start": 2171.8, "duration": 0.5}, {"text": "AUDIENCE: So why\ncouldn't we have said", "start": 2172.3, "duration": 1.583}, {"text": "we didn't mean to [INAUDIBLE].", "start": 2173.883, "duration": 2.377}, {"text": "MICHALE FEE: V infinity\nis defined as RL times Ie.", "start": 2180.22, "duration": 5.334}, {"text": "AUDIENCE: Oh, so\nthat's a [INAUDIBLE]..", "start": 2185.554, "duration": 1.796}, {"text": "MICHALE FEE: It's a definition.", "start": 2187.35, "duration": 1.41}, {"text": "Sorry, I should have put\nlike three lines there", "start": 2188.76, "duration": 3.14}, {"text": "to indicate that\nit's the definition.", "start": 2191.9, "duration": 1.71}, {"text": "AUDIENCE: OK.", "start": 2193.61, "duration": 0.88}, {"text": "MICHALE FEE: Yeah.", "start": 2194.49, "duration": 0.75}, {"text": "Sorry, that's a very\nimportant question.", "start": 2195.24, "duration": 2.45}, {"text": "What's your name?", "start": 2197.69, "duration": 0.986}, {"text": "AUDIENCE: Rishi.", "start": 2198.676, "duration": 0.894}, {"text": "MICHALE FEE: Rishi.", "start": 2199.57, "duration": 0.54}, {"text": "OK.", "start": 2200.11, "duration": 0.5}, {"text": "I'm going to make an\nattempt to remember names.", "start": 2200.61, "duration": 2.765}, {"text": "So is everyone clear about that?", "start": 2206.09, "duration": 2.03}, {"text": "V infinity is defined\nas the resistance", "start": 2208.12, "duration": 4.3}, {"text": "times this injected current.", "start": 2212.42, "duration": 1.66}, {"text": "So the injected current, when we\ninject current into our neuron,", "start": 2214.08, "duration": 4.7}, {"text": "you're changing V infinity, OK?", "start": 2218.78, "duration": 3.37}, {"text": "You're controlling it.", "start": 2222.15, "duration": 1.953}, {"text": "Does that makes sense?", "start": 2224.103, "duration": 0.917}, {"text": "OK.", "start": 2228.57, "duration": 0.62}, {"text": "So let's look at how\nthe derivative changes", "start": 2229.19, "duration": 2.848}, {"text": "as a function of voltage,\nit's very simple.", "start": 2232.038, "duration": 1.792}, {"text": "Bear with me.", "start": 2233.83, "duration": 0.7}, {"text": "All of this is\ngoing to crystallize", "start": 2234.53, "duration": 2.49}, {"text": "in your mind in one beautiful\nconstruct very shortly.", "start": 2237.02, "duration": 4.2}, {"text": "Yes?", "start": 2241.22, "duration": 0.843}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2242.063, "duration": 3.381}, {"text": "MICHALE FEE: Yep.", "start": 2245.444, "duration": 2.116}, {"text": "Resistance times capacitance\nhas units time, OK?", "start": 2247.56, "duration": 5.72}, {"text": "And so we call it tau.", "start": 2253.28, "duration": 1.47}, {"text": "Tau is just a constant, OK?", "start": 2254.75, "duration": 2.97}, {"text": "So hang on, bear with me.", "start": 2257.72, "duration": 2.89}, {"text": "The derivative is a\nfunction of voltage.", "start": 2260.61, "duration": 3.94}, {"text": "And at V equals V infinity,\nthe derivative is 0, right?", "start": 2264.55, "duration": 5.3}, {"text": "That's the definition\nof the infinity,", "start": 2273.42, "duration": 2.11}, {"text": "it's the voltage at which\nthe derivative is 0.", "start": 2275.53, "duration": 4.046}, {"text": "Yeah?", "start": 2279.576, "duration": 2.814}, {"text": "And the voltage is less than\nV infinity, the derivative", "start": 2282.39, "duration": 7.1}, {"text": "is positive, right?", "start": 2289.49, "duration": 3.78}, {"text": "When the voltage is\nbelow the infinity,", "start": 2293.27, "duration": 2.4}, {"text": "the derivative of\nvoltage is positive.", "start": 2295.67, "duration": 2.25}, {"text": "So what is the voltage doing?", "start": 2297.92, "duration": 2.9}, {"text": "It's approaching V infinity.", "start": 2300.82, "duration": 2.17}, {"text": "If the voltage is\nabove V infinity,", "start": 2302.99, "duration": 3.1}, {"text": "voltage greater than V infinity,\nthe derivative is negative.", "start": 2306.09, "duration": 4.5}, {"text": "So voltage does what?", "start": 2310.59, "duration": 2.365}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2312.955, "duration": 0.875}, {"text": "MICHALE FEE: Yes, but it's--", "start": 2313.83, "duration": 1.04}, {"text": "AUDIENCE: Approaches--", "start": 2314.87, "duration": 0.917}, {"text": "MICHALE FEE: It\napproaches V infinity.", "start": 2315.787, "duration": 2.073}, {"text": "So no matter where\nvoltage is, it's", "start": 2317.86, "duration": 2.0}, {"text": "always approaching V infinity.", "start": 2319.86, "duration": 1.44}, {"text": "If it's below V infinity,\nthe slope is positive,", "start": 2321.3, "duration": 2.61}, {"text": "and it approaches V infinity.", "start": 2323.91, "duration": 1.83}, {"text": "If it's above V infinity,\nthe slope is negative,", "start": 2325.74, "duration": 4.26}, {"text": "and it approaches V\ninfinity from above.", "start": 2330.0, "duration": 3.24}, {"text": "Pretty cool, right?", "start": 2333.24, "duration": 1.47}, {"text": "So V is always just\nrelaxing toward V infinity.", "start": 2334.71, "duration": 4.98}, {"text": "And how does it get there?", "start": 2339.69, "duration": 1.29}, {"text": "Does it go linearly?", "start": 2340.98, "duration": 1.65}, {"text": "Well, you can see\nthat the slope--", "start": 2342.63, "duration": 1.68}, {"text": "the rate at which\nit approaches V", "start": 2344.31, "duration": 1.74}, {"text": "infinity is proportional to how\nfar away it is from V infinity.", "start": 2346.05, "duration": 4.58}, {"text": "And so it doesn't just go vroom,\nboom, crash into V infinity,", "start": 2350.63, "duration": 3.34}, {"text": "it kind of slowly\napproaches V infinity, OK?", "start": 2353.97, "duration": 8.39}, {"text": "Anybody know what that\nfunction is called?", "start": 2362.36, "duration": 3.53}, {"text": "AUDIENCE: Exponential.", "start": 2365.89, "duration": 1.0}, {"text": "MICHALE FEE: It's an\nexponential, good.", "start": 2366.89, "duration": 3.54}, {"text": "And it approaches with\na timescale of tau.", "start": 2370.43, "duration": 6.49}, {"text": "So if tau is small,\nit approaches quickly.", "start": 2376.92, "duration": 3.51}, {"text": "If tau is long, it\napproaches slow.", "start": 2380.43, "duration": 2.17}, {"text": "You can see that if tau is\nbig, the derivatives are small.", "start": 2382.6, "duration": 5.37}, {"text": "If tau is small, the derivatives\nare bigger, all right?", "start": 2387.97, "duration": 4.034}, {"text": "Any questions about that?", "start": 2400.28, "duration": 1.455}, {"text": "Yes?", "start": 2401.735, "duration": 1.245}, {"text": "AUDIENCE: So a\ntau usually is a--", "start": 2402.98, "duration": 2.231}, {"text": "MICHALE FEE: Sorry,\nsay it again?", "start": 2405.211, "duration": 1.375}, {"text": "AUDIENCE: --times\nequals to tau--", "start": 2406.586, "duration": 1.704}, {"text": "MICHALE FEE: Yes.", "start": 2408.29, "duration": 0.708}, {"text": "AUDIENCE: --is V\ninfinity plus 1 over e.", "start": 2408.998, "duration": 3.092}, {"text": "MICHALE FEE: At time tau, the--", "start": 2412.09, "duration": 3.556}, {"text": "AUDIENCE: Times V0.", "start": 2415.646, "duration": 1.374}, {"text": "MICHALE FEE: At time tau--", "start": 2417.02, "duration": 1.5}, {"text": "at time 0, the difference\nbetween V infinity-- sorry, V", "start": 2418.52, "duration": 3.48}, {"text": "and V infinity is\nV0 minus V infinity.", "start": 2422.0, "duration": 3.33}, {"text": "At time tau, that\ninitial difference", "start": 2425.33, "duration": 2.49}, {"text": "drops by about a third.", "start": 2427.82, "duration": 1.5}, {"text": "AUDIENCE: OK.", "start": 2429.32, "duration": 0.69}, {"text": "MICHALE FEE: About 1 over e,\nwhich I think is 2.7-something,", "start": 2430.01, "duration": 4.21}, {"text": "OK?", "start": 2434.22, "duration": 0.83}, {"text": "So in 1 tau, this\nvoltage difference", "start": 2435.05, "duration": 2.55}, {"text": "falls by about a--\ndrops by about a third.", "start": 2437.6, "duration": 2.65}, {"text": "And in another tau, it\ndrops by another third,", "start": 2440.25, "duration": 2.77}, {"text": "it keeps going, OK?", "start": 2443.02, "duration": 3.95}, {"text": "All right.", "start": 2446.97, "duration": 0.5}, {"text": "So let's just write down\nthe general solution.", "start": 2447.47, "duration": 3.606}, {"text": "The general solution\nfor the case", "start": 2451.076, "duration": 2.274}, {"text": "where you have constant\ncurrent, that voltage difference", "start": 2453.35, "duration": 9.35}, {"text": "from the voltage at\ntime t to V infinity", "start": 2462.7, "duration": 2.67}, {"text": "is just equal to the initial\nvoltage difference times e", "start": 2465.37, "duration": 2.77}, {"text": "to the minus t over tau, OK?", "start": 2468.14, "duration": 3.635}, {"text": "So if t is equal to tau, then\nthis is e to the minus 1,", "start": 2474.55, "duration": 5.4}, {"text": "so the voltage difference will\nbe 1/3 of the original voltage", "start": 2479.95, "duration": 3.78}, {"text": "difference.", "start": 2483.73, "duration": 0.9}, {"text": "Is that clear?", "start": 2484.63, "duration": 2.66}, {"text": "OK.", "start": 2487.29, "duration": 0.5}, {"text": "So now let's see what this\nlooks like in our neuron.", "start": 2487.79, "duration": 4.14}, {"text": "We have our neuron, we\nhave a current pulse,", "start": 2491.93, "duration": 2.39}, {"text": "we have zero current,\nwe turn the current", "start": 2494.32, "duration": 2.94}, {"text": "on to I0 at this time, we\nhold the current constant,", "start": 2497.26, "duration": 3.71}, {"text": "and we turn current off at\nthis time right here, OK?", "start": 2500.97, "duration": 4.69}, {"text": "So what does the voltage do?", "start": 2505.66, "duration": 2.82}, {"text": "Let's go step by step.", "start": 2508.48, "duration": 2.1}, {"text": "The first thing\nis that voltage--", "start": 2510.58, "duration": 1.89}, {"text": "sorry-- the current controls\nwhat in that equation?", "start": 2512.47, "duration": 3.525}, {"text": "The current controls V infinity.", "start": 2518.902, "duration": 4.168}, {"text": "So we can plot V\ninfinity immediately,", "start": 2523.07, "duration": 2.03}, {"text": "because V infinity is\njust the resistance", "start": 2525.1, "duration": 2.34}, {"text": "times the injected current.", "start": 2527.44, "duration": 1.36}, {"text": "So what does V\ninfinity look like?", "start": 2528.8, "duration": 1.42}, {"text": "It's constant here, and then\nwhat happens to V infinity?", "start": 2533.23, "duration": 3.678}, {"text": "AUDIENCE: Increases.", "start": 2536.908, "duration": 2.632}, {"text": "MICHALE FEE: It increases,\nthat's correct, but--", "start": 2539.54, "duration": 2.408}, {"text": "AUDIENCE: It'll\njust be [INAUDIBLE]..", "start": 2541.948, "duration": 1.542}, {"text": "MICHALE FEE: Good.", "start": 2543.49, "duration": 0.75}, {"text": "It will just be the\nresistance times the current.", "start": 2544.24, "duration": 2.08}, {"text": "Resistance is a constant, so V\ninfinity will just go up here,", "start": 2546.32, "duration": 4.566}, {"text": "right?", "start": 2550.886, "duration": 0.5}, {"text": "Good.", "start": 2551.386, "duration": 0.5}, {"text": "It'll go up, and then it\nstays constant at R times I.", "start": 2551.886, "duration": 7.414}, {"text": "And then at this\npoint, the current", "start": 2559.3, "duration": 2.75}, {"text": "goes back to 0, so V infinity\nis resistance time 0,", "start": 2562.05, "duration": 5.37}, {"text": "so V infinity drops back to 0.", "start": 2567.42, "duration": 3.88}, {"text": "Does that makes sense?", "start": 2571.3, "duration": 1.42}, {"text": "That's V infinity, that's\nnot the voltage of the cell.", "start": 2572.72, "duration": 4.44}, {"text": "That's the steady state\nvoltage of the cell.", "start": 2577.16, "duration": 3.72}, {"text": "So now what does voltage\nof the cell actually do?", "start": 2580.88, "duration": 3.89}, {"text": "So let's start our\nvoltage here at 0.", "start": 2587.47, "duration": 3.868}, {"text": "What happens?", "start": 2591.338, "duration": 0.542}, {"text": "Good.", "start": 2595.72, "duration": 1.02}, {"text": "What is it doing?", "start": 2596.74, "duration": 1.73}, {"text": "AUDIENCE: Approaching\nfrom infinity.", "start": 2598.47, "duration": 1.5}, {"text": "MICHALE FEE: Good.", "start": 2599.97, "duration": 0.78}, {"text": "It approaches.", "start": 2600.75, "duration": 1.21}, {"text": "So V at every point\nis relaxing toward V", "start": 2601.96, "duration": 5.69}, {"text": "infinity exponentially, right?", "start": 2607.65, "duration": 3.64}, {"text": "And that looks like--", "start": 2611.29, "duration": 1.08}, {"text": "at some time constant, and that\nlooks like this, all right?", "start": 2612.37, "duration": 7.31}, {"text": "Now what happens here?", "start": 2619.68, "duration": 2.505}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2622.185, "duration": 0.975}, {"text": "MICHALE FEE: Good.", "start": 2623.16, "duration": 0.75}, {"text": "Because V infinity\nsuddenly change to 0,", "start": 2623.91, "duration": 3.27}, {"text": "and so V relaxes toward\nV infinity exponentially", "start": 2627.18, "duration": 3.39}, {"text": "with some time constant.", "start": 2630.57, "duration": 1.56}, {"text": "OK?", "start": 2637.366, "duration": 0.5}, {"text": "Any questions?", "start": 2641.22, "duration": 1.177}, {"text": "OK.", "start": 2647.87, "duration": 0.5}, {"text": "Now this-- that is our\nRC model neuron, OK?", "start": 2652.08, "duration": 6.61}, {"text": "Resistance times\ncapacitance-- they", "start": 2658.69, "duration": 1.63}, {"text": "got a resistor and a\ncapacitor, but the solutions", "start": 2660.32, "duration": 4.06}, {"text": "are just exponential decays\ntoward some steady state", "start": 2664.38, "duration": 3.36}, {"text": "solution.", "start": 2667.74, "duration": 2.75}, {"text": "Now it turns out\nthat an RC system,", "start": 2670.49, "duration": 4.62}, {"text": "a first order linear system\nacts like a filter, OK?", "start": 2675.11, "duration": 5.54}, {"text": "So remember, our neuron\nthat just has a capacitor", "start": 2680.65, "duration": 4.86}, {"text": "is an integrator, it\nintegrates over time.", "start": 2685.51, "duration": 3.15}, {"text": "When you add a\nresistor, this thing--", "start": 2688.66, "duration": 3.3}, {"text": "it's kind of integrating\nhere, but then it", "start": 2691.96, "duration": 2.25}, {"text": "gets tired and stops\nintegrating, OK?", "start": 2694.21, "duration": 3.42}, {"text": "It relaxes to some steady state.", "start": 2697.63, "duration": 4.23}, {"text": "So this actually\nlooks like a filter.", "start": 2701.86, "duration": 3.89}, {"text": "It takes time to\nrespond to something.", "start": 2705.75, "duration": 4.07}, {"text": "So that system responds well to\nthings that are changing slowly", "start": 2709.82, "duration": 5.73}, {"text": "in time, and it responds\nvery weakly to things that", "start": 2715.55, "duration": 3.6}, {"text": "are changing rapidly in time.", "start": 2719.15, "duration": 2.26}, {"text": "So here's an example--", "start": 2721.41, "duration": 1.16}, {"text": "I'll put together\nthis demonstration.", "start": 2722.57, "duration": 3.78}, {"text": "In red is the injected current.", "start": 2726.35, "duration": 1.93}, {"text": "So if you have long pulses\nof injected current,", "start": 2728.28, "duration": 3.77}, {"text": "the time constant of this\ngarners about 10 milliseconds--", "start": 2732.05, "duration": 3.24}, {"text": "I think this is probably a--", "start": 2735.29, "duration": 1.64}, {"text": "what is that, a 50 or\n100-millisecond pulse?", "start": 2736.93, "duration": 2.82}, {"text": "80--", "start": 2739.75, "duration": 0.5}, {"text": "AUDIENCE: Nanofarads.", "start": 2740.25, "duration": 0.875}, {"text": "MICHALE FEE: Yeah.", "start": 2741.125, "duration": 1.1}, {"text": "You can see that in\nblue is the voltage,", "start": 2742.225, "duration": 2.165}, {"text": "it relaxes toward V infinity.", "start": 2744.39, "duration": 3.28}, {"text": "And then the current goes\noff, it relaxes back.", "start": 2747.67, "duration": 2.33}, {"text": "And you can see that the\nvoltage is responding very well", "start": 2750.0, "duration": 3.51}, {"text": "to the current injection.", "start": 2753.51, "duration": 1.71}, {"text": "But now let's make\nreally short pulses", "start": 2755.22, "duration": 3.2}, {"text": "that are much shorter than tau.", "start": 2758.42, "duration": 2.34}, {"text": "You can see that\nthe voltage starts", "start": 2760.76, "duration": 3.87}, {"text": "relaxing toward V infinity,\nbut it doesn't get very far,", "start": 2764.63, "duration": 2.397}, {"text": "and all of a sudden the\ncurrent's turned off", "start": 2767.027, "duration": 1.833}, {"text": "and it relaxes back.", "start": 2768.86, "duration": 1.68}, {"text": "And so you can plot the\npeak voltage response", "start": 2770.54, "duration": 2.91}, {"text": "as a function of the\nwidth of these pulses,", "start": 2773.45, "duration": 2.77}, {"text": "and you can see that for long\npulses, it responds very well,", "start": 2776.22, "duration": 4.43}, {"text": "but for short pulses--", "start": 2780.65, "duration": 1.87}, {"text": "really responds at all.", "start": 2782.52, "duration": 1.79}, {"text": "And that's called a\nlow pass filter, OK?", "start": 2784.31, "duration": 3.87}, {"text": "It responds well to\nslowly-changing things,", "start": 2788.18, "duration": 3.66}, {"text": "but barely responds to\nrapidly-changing things.", "start": 2791.84, "duration": 3.37}, {"text": "So it's passing low frequencies,\nlow pass filter, OK?", "start": 2795.21, "duration": 5.441}, {"text": "All right.", "start": 2803.34, "duration": 0.73}, {"text": "Any questions?", "start": 2804.07, "duration": 0.69}, {"text": "That was a lot of\nstuff all at once.", "start": 2804.76, "duration": 1.78}, {"text": "Yes?", "start": 2806.54, "duration": 0.5}, {"text": "AUDIENCE: I'm just curious,\nlike on what order is", "start": 2807.04, "duration": 2.86}, {"text": "the capacitance for nanofarads?", "start": 2809.9, "duration": 3.13}, {"text": "MICHALE FEE: OK.", "start": 2813.03, "duration": 1.07}, {"text": "It's 10 nanofarads per--", "start": 2814.1, "duration": 3.66}, {"text": "1 microfarads per\nsquare centimeter.", "start": 2817.76, "duration": 2.23}, {"text": "10 nanofarads per\nsquare millimeter, OK?", "start": 2819.99, "duration": 3.963}, {"text": "We're going to get to\nthat in a second, that's", "start": 2823.953, "duration": 1.917}, {"text": "a great question.", "start": 2825.87, "duration": 1.24}, {"text": "We're going to get to what\nthe actual numbers look like", "start": 2827.11, "duration": 2.84}, {"text": "for real neurons, OK?", "start": 2829.95, "duration": 3.24}, {"text": "I think you had a question.", "start": 2833.19, "duration": 1.45}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2834.64, "duration": 2.455}, {"text": "MICHALE FEE: Sorry,\nsay it again?", "start": 2837.095, "duration": 1.375}, {"text": "AUDIENCE: Past [INAUDIBLE]?", "start": 2838.47, "duration": 1.4}, {"text": "Is that [INAUDIBLE]\nreacts to [INAUDIBLE]??", "start": 2839.87, "duration": 2.925}, {"text": "MICHALE FEE: What happens\nis it reacts to it,", "start": 2842.795, "duration": 1.875}, {"text": "but because it's\nchanging kind of linearly", "start": 2844.67, "duration": 2.97}, {"text": "at these short times,\nit doesn't get very far.", "start": 2847.64, "duration": 2.58}, {"text": "If the current stays\non for a long time,", "start": 2850.22, "duration": 1.84}, {"text": "you can see it has exactly\nthe same profile here,", "start": 2852.06, "duration": 3.23}, {"text": "but it just has time\nto reach V infinity.", "start": 2855.29, "duration": 2.512}, {"text": "Here, it doesn't have\ntime to reach V infinity,", "start": 2857.802, "duration": 1.958}, {"text": "it just gets a little bit away\nfrom 0 and then it decays back.", "start": 2859.76, "duration": 6.83}, {"text": "Yes?", "start": 2866.59, "duration": 0.76}, {"text": "AUDIENCE: Are there other sorts\nof filters for non-responses", "start": 2867.35, "duration": 2.812}, {"text": "like [INAUDIBLE]?", "start": 2870.162, "duration": 2.768}, {"text": "MICHALE FEE: You can build\ndifferent kinds of filters", "start": 2872.93, "duration": 2.76}, {"text": "from circuits of neurons,\nbut neurons themselves", "start": 2875.69, "duration": 3.3}, {"text": "tend to be high pass filters.", "start": 2878.99, "duration": 4.17}, {"text": "You can-- sorry,\nlow pass filters.", "start": 2883.16, "duration": 2.2}, {"text": "You can make-- so you can put in\ndifferent kinds of ion channels", "start": 2885.36, "duration": 5.48}, {"text": "that change the\nproperties of neurons,", "start": 2890.84, "duration": 3.24}, {"text": "but sort of to first\norder, you should think", "start": 2894.08, "duration": 2.1}, {"text": "of neurons as low pass filters.", "start": 2896.18, "duration": 1.86}, {"text": "Yeah?", "start": 2901.976, "duration": 0.984}, {"text": "AUDIENCE: Can you\nshow the [INAUDIBLE]", "start": 2902.96, "duration": 8.322}, {"text": "MICHALE FEE: I\nwrote it like this--", "start": 2911.282, "duration": 1.458}, {"text": "you can write it as V equals V\ninfinity plus this other stuff,", "start": 2912.74, "duration": 3.24}, {"text": "but I wrote it like this because\nwhat you should really be", "start": 2915.98, "duration": 2.64}, {"text": "seeing here is that the\nvoltage difference from--", "start": 2918.62, "duration": 3.99}, {"text": "time between the voltage and V\ninfinity decays exponentially.", "start": 2922.61, "duration": 5.62}, {"text": "So the distance you are\nfrom V infinity decays", "start": 2928.23, "duration": 3.14}, {"text": "exponentially, OK?", "start": 2931.37, "duration": 2.604}, {"text": "It makes it more\nobvious that you're", "start": 2936.72, "duration": 1.66}, {"text": "decaying toward V infinity, OK?", "start": 2938.38, "duration": 4.535}, {"text": "Yes?", "start": 2946.8, "duration": 1.15}, {"text": "AUDIENCE: If you were to arrange\nlike the physical properties", "start": 2947.95, "duration": 2.542}, {"text": "of the neuron itself,\nyou [INAUDIBLE]", "start": 2950.492, "duration": 5.378}, {"text": "MICHALE FEE: Not-- not really.", "start": 2955.87, "duration": 1.53}, {"text": "Not simply.", "start": 2957.4, "duration": 1.02}, {"text": "You can put in\ncertain ion channels", "start": 2958.42, "duration": 3.63}, {"text": "that could make a neuron less\nresponsive at low frequencies,", "start": 2962.05, "duration": 7.9}, {"text": "OK?", "start": 2969.95, "duration": 0.5}, {"text": "So you can make them kind of\nresponsive to some middle range", "start": 2970.45, "duration": 4.17}, {"text": "of frequencies\nthat won't respond", "start": 2974.62, "duration": 2.645}, {"text": "to very high\nfrequencies and they", "start": 2977.265, "duration": 1.375}, {"text": "won't respond much to\nvery low frequencies,", "start": 2978.64, "duration": 4.4}, {"text": "but for the most\npart, again, just", "start": 2983.04, "duration": 2.04}, {"text": "you should-- at this point,\nlet's just think of them", "start": 2985.08, "duration": 2.25}, {"text": "as low pass filters.", "start": 2987.33, "duration": 2.88}, {"text": "We're going to start\nadding fancy stuff", "start": 2990.21, "duration": 2.73}, {"text": "to our neuron that's going\nto make it more complicated.", "start": 2992.94, "duration": 5.17}, {"text": "So don't get too\nhung up on this.", "start": 2998.11, "duration": 2.96}, {"text": "All right, let me\njust make this point.", "start": 3001.07, "duration": 2.924}, {"text": "This one right\nhere, V equals tau--", "start": 3003.994, "duration": 3.636}, {"text": "V plus tau dV/dt equals V\ninfinity appears everywhere,", "start": 3007.63, "duration": 4.03}, {"text": "it's ubiquitous in physics,\nchemistry, biology, we'll", "start": 3011.66, "duration": 6.26}, {"text": "be using it in multiple\ndifferent contexts", "start": 3017.92, "duration": 2.46}, {"text": "in different parts of\nthe class, and in--", "start": 3020.38, "duration": 4.41}, {"text": "computation, OK?", "start": 3024.79, "duration": 2.13}, {"text": "And even slightly more\ncomplicated versions of this,", "start": 3026.92, "duration": 5.85}, {"text": "like the Michaelis-Menten\nequations in chemistry,", "start": 3032.77, "duration": 4.73}, {"text": "you can kind of understand\nthem in simple terms.", "start": 3037.5, "duration": 2.38}, {"text": "If you like have\na handle on this,", "start": 3039.88, "duration": 3.41}, {"text": "other slightly more\ncomplicated things", "start": 3043.29, "duration": 1.98}, {"text": "become much more intuitive, OK?", "start": 3045.27, "duration": 4.09}, {"text": "All right, so try\nto really make sure", "start": 3049.36, "duration": 3.9}, {"text": "that you understand\nthis equation", "start": 3053.26, "duration": 3.99}, {"text": "and how we derived it, OK?", "start": 3057.25, "duration": 5.0}, {"text": "OK, let's talk about\nthe origin of this--", "start": 3062.25, "duration": 2.79}, {"text": "the timescale of a neuron.", "start": 3065.04, "duration": 1.47}, {"text": "So the tau of a neuron--", "start": 3066.51, "duration": 1.86}, {"text": "of most neurons is about\n100 milliseconds to--", "start": 3068.37, "duration": 3.09}, {"text": "sorry, 10 milliseconds\nto 100 milliseconds,", "start": 3071.46, "duration": 2.19}, {"text": "kind of in that range.", "start": 3073.65, "duration": 1.6}, {"text": "And it comes from the values\nof resistance and capacitance", "start": 3075.25, "duration": 3.35}, {"text": "of a neuron.", "start": 3078.6, "duration": 1.39}, {"text": "So a resistor-- the\nresistance of a neuron--", "start": 3079.99, "duration": 4.67}, {"text": "range of 100 million ohms, OK?", "start": 3084.66, "duration": 5.11}, {"text": "And the capacitance is about\n10 to the minus 10 ohms", "start": 3089.77, "duration": 3.74}, {"text": "or about 100 picofarads.", "start": 3093.51, "duration": 4.13}, {"text": "And you multiply those\ntwo things together", "start": 3097.64, "duration": 2.14}, {"text": "and you get a time constant\nof about 10 milliseconds, OK?", "start": 3099.78, "duration": 5.13}, {"text": "So what that means is if you\ninject current into a neuron,", "start": 3104.91, "duration": 4.6}, {"text": "it takes about 10 to\n100 milliseconds for it", "start": 3109.51, "duration": 2.91}, {"text": "to fully respond to\nthat step of current.", "start": 3112.42, "duration": 5.59}, {"text": "The voltage will\njump up and relax", "start": 3118.01, "duration": 2.25}, {"text": "to the new V infinity in about\n10 to 100 milliseconds, OK?", "start": 3120.26, "duration": 5.25}, {"text": "So let's take a\nlittle bit closer", "start": 3125.51, "duration": 1.68}, {"text": "look at the resistance-- what\nthis resistance in capacitance", "start": 3127.19, "duration": 3.81}, {"text": "looks like in a neuron.", "start": 3131.0, "duration": 3.42}, {"text": "So we've described the\nrelation between leak current", "start": 3134.42, "duration": 4.28}, {"text": "and voltage as current equals\nvoltage over resistance,", "start": 3138.7, "duration": 6.15}, {"text": "but rather than using resistance\nto think about currents flowing", "start": 3144.85, "duration": 4.96}, {"text": "through a membrane, it's\nmuch more useful, usually,", "start": 3149.81, "duration": 3.48}, {"text": "to think about something\ncalled conductance,", "start": 3153.29, "duration": 2.44}, {"text": "and conductance is just\n1 over resistance, OK?", "start": 3155.73, "duration": 3.82}, {"text": "So conductance, G-- and we use\nthe simple G for conductance--", "start": 3159.55, "duration": 4.24}, {"text": "it's equal to 1 over resistance.", "start": 3163.79, "duration": 1.83}, {"text": "So now we can write\nOhm's law as I", "start": 3165.62, "duration": 2.34}, {"text": "equals G times V. Resistance\nhas units of ohms, G--", "start": 3167.96, "duration": 7.86}, {"text": "conductance has units of\ninverse ohms or siemens", "start": 3175.82, "duration": 2.91}, {"text": "is the SI unit for conductance.", "start": 3178.73, "duration": 4.2}, {"text": "So if we have\nconductances, if we", "start": 3182.93, "duration": 3.41}, {"text": "have two-- let's say two ion\nchannels in the membrane,", "start": 3186.34, "duration": 4.06}, {"text": "they operate in parallel.", "start": 3190.4, "duration": 1.43}, {"text": "Current flows through\nthem separately, right?", "start": 3191.83, "duration": 3.295}, {"text": "They're not in series, like\nit flows through one and then", "start": 3195.125, "duration": 2.375}, {"text": "flows through the other, right?", "start": 3197.5, "duration": 1.57}, {"text": "They are in parallel--\nthe current can flow", "start": 3199.07, "duration": 3.08}, {"text": "through both like\nthis up in parallel.", "start": 3202.15, "duration": 4.06}, {"text": "And we can write down the\ncurrent using Kirchhoff's law,", "start": 3206.21, "duration": 3.95}, {"text": "the total current\nis just the sum", "start": 3210.16, "duration": 2.04}, {"text": "of the current through those two\nseparate conductances, right?", "start": 3212.2, "duration": 3.93}, {"text": "Now the total current is--", "start": 3216.13, "duration": 2.01}, {"text": "we can just expand this\nin terms of the inductance", "start": 3218.14, "duration": 2.7}, {"text": "of each one of those.", "start": 3220.84, "duration": 0.91}, {"text": "So the total current is G1\ntimes the voltage difference", "start": 3221.75, "duration": 5.81}, {"text": "plus G2 times the\nvoltage difference", "start": 3227.56, "duration": 3.12}, {"text": "for this conductance.", "start": 3230.68, "duration": 2.93}, {"text": "So the total current is just--", "start": 3233.61, "duration": 1.88}, {"text": "you factor out the V, the total\ncurrent is just G1 plus G2,", "start": 3235.49, "duration": 4.23}, {"text": "so we can write down the total\nconductance as just G1 plus G2.", "start": 3239.72, "duration": 6.19}, {"text": "Does that makes sense?", "start": 3245.91, "duration": 1.38}, {"text": "So conductances in\nparallel add together.", "start": 3247.29, "duration": 2.94}, {"text": "So if we have a piece\nof membrane that's", "start": 3253.563, "duration": 1.667}, {"text": "got some ion channels\nin it-- or holes,", "start": 3255.23, "duration": 3.63}, {"text": "and we add another piece of\nmembrane that kind of has", "start": 3258.86, "duration": 2.22}, {"text": "the same density\nof ion channels,", "start": 3261.08, "duration": 2.36}, {"text": "you have twice the\nholes, twice the current,", "start": 3263.44, "duration": 2.64}, {"text": "and twice the conductance.", "start": 3266.08, "duration": 1.42}, {"text": "So we can write the current\nas conductance times membrane", "start": 3273.23, "duration": 3.17}, {"text": "potential, but we can\nrewrite that conductance", "start": 3276.4, "duration": 2.61}, {"text": "as the area times that\nconductance per unit area,", "start": 3279.01, "duration": 4.67}, {"text": "and that's called specific\nmembrane conductance--", "start": 3283.68, "duration": 3.52}, {"text": "in this case, it's a leak,\nso we call it specific leak", "start": 3287.2, "duration": 2.34}, {"text": "conductance, and it has units\nof conductance per area.", "start": 3289.54, "duration": 4.44}, {"text": "We multiply that by the area and\nwe get that total conductance.", "start": 3297.7, "duration": 5.37}, {"text": "Any questions about this?", "start": 3303.07, "duration": 1.26}, {"text": "No?", "start": 3309.077, "duration": 0.5}, {"text": "So you can see that\nwe can now plot", "start": 3312.92, "duration": 4.27}, {"text": "the current through the membrane\nas a function of voltage.", "start": 3317.19, "duration": 4.75}, {"text": "This is called a\nIV current plotted", "start": 3321.94, "duration": 3.14}, {"text": "as a function of voltage.", "start": 3325.08, "duration": 1.09}, {"text": "You can see that the\ncurrent is linear", "start": 3326.17, "duration": 2.707}, {"text": "as a function of voltage, right?", "start": 3328.877, "duration": 1.333}, {"text": "That's just Ohm's law.", "start": 3330.21, "duration": 3.02}, {"text": "And you can see that for a\nlow conductance, G is small,", "start": 3333.23, "duration": 2.95}, {"text": "so the slope is small.", "start": 3336.18, "duration": 2.2}, {"text": "For a high conductance,\nyou get a lot", "start": 3338.38, "duration": 2.38}, {"text": "of current for a little bit\nof voltage, and so the--", "start": 3340.76, "duration": 2.7}, {"text": "deeper, OK?", "start": 3343.46, "duration": 1.61}, {"text": "So if you plot current versus\nvoltage, you get a curve,", "start": 3345.07, "duration": 3.51}, {"text": "and the slope of that curve is\njust equal to the conductance,", "start": 3348.58, "duration": 5.834}, {"text": "all right?", "start": 3354.414, "duration": 2.386}, {"text": "OK.", "start": 3356.8, "duration": 0.54}, {"text": "Now let's look at capacitance.", "start": 3357.34, "duration": 2.86}, {"text": "The total current through these\ntwo capacitors in parallel", "start": 3360.2, "duration": 4.4}, {"text": "is just the current through\none capacitor plus the current", "start": 3364.6, "duration": 2.54}, {"text": "through the other.", "start": 3367.14, "duration": 1.02}, {"text": "We can write the current through\neach capacitor separately.", "start": 3368.16, "duration": 2.64}, {"text": "I total equals C1\ndV/dt plus C2 dV/dt.", "start": 3370.8, "duration": 5.28}, {"text": "Factor out the dV/dt and you get\nthat the total current is just", "start": 3376.08, "duration": 2.97}, {"text": "C1 plus C2 dV/dt.", "start": 3379.05, "duration": 2.27}, {"text": "So the total capacitance is\nthe sum of the capacitances.", "start": 3381.32, "duration": 4.09}, {"text": "So if you have a\npatch of membrane,", "start": 3385.41, "duration": 2.16}, {"text": "you measure the capacitance, if\nyou put another one next to it,", "start": 3387.57, "duration": 3.52}, {"text": "you'll get the sum of\nthose two capacitances.", "start": 3391.09, "duration": 2.73}, {"text": "So the capacitance\nalso scales with area.", "start": 3393.82, "duration": 2.855}, {"text": "So we can write down the\ntotal membrane capacitance", "start": 3399.27, "duration": 3.32}, {"text": "as capacitance per unit area\ntimes the area of the cell,", "start": 3402.59, "duration": 5.91}, {"text": "right?", "start": 3408.5, "duration": 1.88}, {"text": "And the area of a cell is\nlike the-- if it's a sphere,", "start": 3410.38, "duration": 3.27}, {"text": "it's 4 pi r squared\nwhere is the radius, OK?", "start": 3413.65, "duration": 5.37}, {"text": "All right.", "start": 3419.02, "duration": 0.5}, {"text": "And here's the-- this\nC sub m is called", "start": 3419.52, "duration": 3.24}, {"text": "this specific\nmembrane capacitance,", "start": 3422.76, "duration": 2.82}, {"text": "and it's 10 nanofarads per\nsquare millimeter, all right?", "start": 3425.58, "duration": 6.0}, {"text": "OK, now, I want to show\nyou something really cool.", "start": 3431.58, "duration": 3.28}, {"text": "We have a cell that has\na membrane with some--", "start": 3434.86, "duration": 3.59}, {"text": "this cell has some time\nconstant-- remember,", "start": 3438.45, "duration": 1.95}, {"text": "10 milliseconds.", "start": 3440.4, "duration": 1.99}, {"text": "Now you might think,\noh, the capacitance", "start": 3442.39, "duration": 3.89}, {"text": "of the cell depends on\nhow big it is, right?", "start": 3446.28, "duration": 2.88}, {"text": "And so the time\nconstant will change", "start": 3449.16, "duration": 1.98}, {"text": "depending on how big the\ncell is, you might think.", "start": 3451.14, "duration": 3.51}, {"text": "But let's actually\ncalculate the time", "start": 3454.65, "duration": 1.59}, {"text": "constant from this capacitance\nand this conductance, OK?", "start": 3456.24, "duration": 4.99}, {"text": "So here we go.", "start": 3461.23, "duration": 1.08}, {"text": "Time constant C. R is just 1\nover the conductance, right?", "start": 3462.31, "duration": 6.42}, {"text": "So the time constant\nis capacitance", "start": 3468.73, "duration": 1.77}, {"text": "divided by conductance--\ntotal capacitance", "start": 3470.5, "duration": 2.49}, {"text": "divided by total conductance.", "start": 3472.99, "duration": 2.91}, {"text": "But you can rewrite this\ncapacitance as capacitance", "start": 3475.9, "duration": 2.96}, {"text": "per unit area\ntimes area, you can", "start": 3478.86, "duration": 2.28}, {"text": "rewrite that conductance\nas conductance per unit", "start": 3481.14, "duration": 3.81}, {"text": "area times the area of the\ncell, and the areas cancel.", "start": 3484.95, "duration": 5.68}, {"text": "And so the time constant\nis just that capacitance", "start": 3490.63, "duration": 3.96}, {"text": "per unit area of the membrane\ndivided by the conductance", "start": 3494.59, "duration": 3.18}, {"text": "per unit area of the membrane.", "start": 3497.77, "duration": 2.11}, {"text": "And what that means is that\nthe time constant of a cell--", "start": 3499.88, "duration": 3.59}, {"text": "nothing to do with the cell.", "start": 3503.47, "duration": 1.91}, {"text": "The time constant is the\nmembrane time constant,", "start": 3505.38, "duration": 3.49}, {"text": "and it's a property\nonly of the membrane.", "start": 3508.87, "duration": 2.295}, {"text": "That's pretty cool, right?", "start": 3514.11, "duration": 1.16}, {"text": "Any questions about that?", "start": 3523.126, "duration": 1.454}, {"text": "Now in a more\ncomplicated neuron where", "start": 3533.6, "duration": 2.82}, {"text": "you have a soma and\ndendrites and axons,", "start": 3536.42, "duration": 3.06}, {"text": "different parts of the cell\ncan have different conductance", "start": 3539.48, "duration": 5.83}, {"text": "per unit area-- like\nmore ion channels", "start": 3545.31, "duration": 2.25}, {"text": "out here on the dendrite\nand maybe fewer on the soma.", "start": 3547.56, "duration": 3.45}, {"text": "And so one part of a cell can\nhave a different membrane time", "start": 3551.01, "duration": 3.69}, {"text": "constant than some other\npart of the cell, OK?", "start": 3554.7, "duration": 4.17}, {"text": "But again, it's a\nproperty of the membrane.", "start": 3558.87, "duration": 2.01}, {"text": "Any questions about that?", "start": 3567.478, "duration": 1.042}, {"text": "Yes?", "start": 3568.52, "duration": 0.774}, {"text": "AUDIENCE: So in that case,\nlike different time constants,", "start": 3569.294, "duration": 3.011}, {"text": "do you have to like consider\nflow between different areas?", "start": 3572.305, "duration": 2.845}, {"text": "MICHALE FEE: You sure do.", "start": 3575.15, "duration": 1.43}, {"text": "Absolutely.", "start": 3576.58, "duration": 0.91}, {"text": "That's one of the\ninteresting things about--", "start": 3577.49, "duration": 4.17}, {"text": "when cells have multiple--", "start": 3581.66, "duration": 1.782}, {"text": "they have different\nproperties, you", "start": 3583.442, "duration": 1.458}, {"text": "have current flowing\nbetween them,", "start": 3584.9, "duration": 2.04}, {"text": "but you have to understand\nthis kind of basic stuff", "start": 3586.94, "duration": 3.45}, {"text": "before you even get anywhere\nclose to understanding a more", "start": 3590.39, "duration": 2.91}, {"text": "complicated neuron, right?", "start": 3593.3, "duration": 1.94}, {"text": "OK.", "start": 3598.67, "duration": 1.96}, {"text": "So we're going to add a\nnew component to our model.", "start": 3600.63, "duration": 3.925}, {"text": "It's a battery, and it's\ngoing to solve one really", "start": 3607.37, "duration": 4.71}, {"text": "fatal problem with this model.", "start": 3612.08, "duration": 2.97}, {"text": "What's the problem\nwith this model?", "start": 3615.05, "duration": 2.94}, {"text": "Can anyone see--", "start": 3617.99, "duration": 0.8}, {"text": "I'm kind of showing\nit right here.", "start": 3618.79, "duration": 1.78}, {"text": "What happens to this neuron\nif I turn the current off?", "start": 3625.37, "duration": 4.91}, {"text": "It goes back to zero.", "start": 3630.28, "duration": 1.05}, {"text": "And in order to get the voltage\nto go different from zero,", "start": 3636.24, "duration": 2.55}, {"text": "I have to inject current\nthrough my current source.", "start": 3638.79, "duration": 4.67}, {"text": "Without me, the experimenter\nwith an electrode in it", "start": 3643.46, "duration": 3.39}, {"text": "injecting current, this neuron\nliterally just sits at zero", "start": 3646.85, "duration": 3.27}, {"text": "and stays there, all right?", "start": 3650.12, "duration": 3.09}, {"text": "It's actually a good model\nof a dead neuron, OK?", "start": 3653.21, "duration": 2.96}, {"text": "So in order to change that, we\nneed to add a battery here, OK?", "start": 3659.17, "duration": 5.175}, {"text": "And that battery is going\nto power this thing up,", "start": 3668.15, "duration": 3.12}, {"text": "so now it can change\nits own voltage.", "start": 3671.27, "duration": 2.44}, {"text": "And then things start\ngetting really interesting.", "start": 3676.71, "duration": 2.52}, {"text": "So how can these\nbatteries allow a neuron", "start": 3679.23, "duration": 2.64}, {"text": "to change its own voltage?", "start": 3681.87, "duration": 2.08}, {"text": "Well, the way a neuron controls\nits own voltage is it has ion", "start": 3683.95, "duration": 4.55}, {"text": "channels-- conductances--", "start": 3688.5, "duration": 2.22}, {"text": "that have little knobs\non them that the cell", "start": 3690.72, "duration": 3.0}, {"text": "can control called voltage.", "start": 3693.72, "duration": 5.42}, {"text": "So these conductances\nare voltage-dependent,", "start": 3699.14, "duration": 3.18}, {"text": "and now the cell\nconnects these batteries", "start": 3702.32, "duration": 2.88}, {"text": "to its inside wire at different\ntimes in different ways.", "start": 3705.2, "duration": 5.97}, {"text": "So let's say we want to\nmake an action potential.", "start": 3711.17, "duration": 2.43}, {"text": "So we have a battery that's\ngot a positive voltage,", "start": 3713.6, "duration": 2.78}, {"text": "we have a battery that's\ngot a negative voltage,", "start": 3716.38, "duration": 2.61}, {"text": "and we make an action potential\nby connecting the back", "start": 3718.99, "duration": 4.77}, {"text": "to the inside of the cell by\nturning on this conductance,", "start": 3723.76, "duration": 4.32}, {"text": "and then we're going\nto connect the battery", "start": 3728.08, "duration": 2.85}, {"text": "with a negative\nvoltage to our cell,", "start": 3730.93, "duration": 2.19}, {"text": "and we're going to do\nthat one after the other.", "start": 3733.12, "duration": 2.4}, {"text": "So watch this.", "start": 3735.52, "duration": 1.62}, {"text": "We're going to connect\nthe positive battery", "start": 3739.72, "duration": 2.16}, {"text": "and the voltage\nis going to go up;", "start": 3741.88, "duration": 2.005}, {"text": "we're going to turn off\nthe positive battery,", "start": 3743.885, "duration": 1.875}, {"text": "connect the negative battery,\nthe voltage goes down;", "start": 3745.76, "duration": 3.29}, {"text": "and then we're going to\nturn off both batteries,", "start": 3749.05, "duration": 3.02}, {"text": "and the voltage\njust relaxes, OK?", "start": 3752.07, "duration": 4.54}, {"text": "Cool, right?", "start": 3756.61, "duration": 1.19}, {"text": "So now the neuron can\ncontrol its own voltage.", "start": 3757.8, "duration": 4.38}, {"text": "But before we do that, we need\nto put batteries in our neuron,", "start": 3762.18, "duration": 4.734}, {"text": "OK?", "start": 3766.914, "duration": 2.036}, {"text": "All right.", "start": 3768.95, "duration": 0.5}, {"text": "So anybody know what the-- yes?", "start": 3769.45, "duration": 3.206}, {"text": "AUDIENCE: [INAUDIBLE]\nWhat does that [INAUDIBLE]", "start": 3772.656, "duration": 7.852}, {"text": "MICHALE FEE: Good, we're\ngoing to get to that.", "start": 3780.508, "duration": 1.917}, {"text": "That was-- exact next question.", "start": 3782.425, "duration": 2.575}, {"text": "What is it that makes\na battery in a neuron?", "start": 3785.0, "duration": 3.546}, {"text": "Yeah?", "start": 3788.546, "duration": 0.934}, {"text": "AUDIENCE: Well I mean, like,\nyou have like something, right?", "start": 3789.48, "duration": 2.964}, {"text": "Even in like--", "start": 3792.444, "duration": 0.786}, {"text": "MICHALE FEE: Good.", "start": 3793.23, "duration": 0.29}, {"text": "AUDIENCE: --concentration\ngradient--", "start": 3793.52, "duration": 1.16}, {"text": "MICHALE FEE: Good.", "start": 3794.68, "duration": 0.75}, {"text": "AUDIENCE: --so that\ngive us a [INAUDIBLE]", "start": 3795.43, "duration": 2.04}, {"text": "MICHALE FEE: Here.", "start": 3797.47, "duration": 0.75}, {"text": "You give the rest\nof the lecture.", "start": 3798.22, "duration": 2.49}, {"text": "That's exactly right.", "start": 3800.71, "duration": 1.89}, {"text": "OK?", "start": 3802.6, "duration": 0.54}, {"text": "Well concentration gradients.", "start": 3803.14, "duration": 2.62}, {"text": "There's one more thing we need.", "start": 3805.76, "duration": 2.51}, {"text": "Concentration gradients\nby themselves don't do it.", "start": 3808.27, "duration": 3.06}, {"text": "We need ion channels that are\npermeable only to certain ions,", "start": 3811.33, "duration": 4.87}, {"text": "OK?", "start": 3816.2, "duration": 0.5}, {"text": "And that's what we're\ngoing to do now.", "start": 3816.7, "duration": 1.583}, {"text": "So you need\nconcentration gradients", "start": 3820.84, "duration": 2.03}, {"text": "and ion-selective\npermeability, OK?", "start": 3822.87, "duration": 2.49}, {"text": "So we're going to\ngo through that.", "start": 3825.36, "duration": 3.01}, {"text": "So let's take a beaker,\nfill it with water,", "start": 3828.37, "duration": 3.5}, {"text": "have a membrane,\ndividing it into two.", "start": 3831.87, "duration": 2.7}, {"text": "We're going to have an\nelectrode on one side,", "start": 3834.57, "duration": 2.1}, {"text": "we measure the voltage\ndifference-- sorry,", "start": 3836.67, "duration": 2.16}, {"text": "we have an electron\non both sides,", "start": 3838.83, "duration": 1.44}, {"text": "we hook it up to our\ndifferential amplifier,", "start": 3840.27, "duration": 2.04}, {"text": "and measure the voltage\ndifference on the two sides,", "start": 3842.31, "duration": 2.79}, {"text": "OK?", "start": 3845.1, "duration": 1.29}, {"text": "Then we're going to put--", "start": 3846.39, "duration": 3.355}, {"text": "we're going to take a--", "start": 3853.05, "duration": 1.53}, {"text": "we're going to buy some\npotassium chloride from sigma,", "start": 3854.58, "duration": 4.24}, {"text": "we're going to take\na spoonful of it", "start": 3858.82, "duration": 1.58}, {"text": "and dump it into this\nside of the beaker.", "start": 3860.4, "duration": 3.06}, {"text": "Stir it up, and now you're going\nto have lots of potassium ions", "start": 3863.46, "duration": 4.17}, {"text": "and chloride ions on this\nside of the beaker, right?", "start": 3867.63, "duration": 2.35}, {"text": "Now we're going to\ntake a needle and poke", "start": 3872.85, "duration": 2.7}, {"text": "a hole in that membrane.", "start": 3875.55, "duration": 2.11}, {"text": "That becomes a leak,\na leak channel.", "start": 3877.66, "duration": 3.8}, {"text": "It's a non-specific--\na non-selective pore", "start": 3881.46, "duration": 3.48}, {"text": "that passes any iron, OK?", "start": 3884.94, "duration": 4.167}, {"text": "So what's going to happen?", "start": 3889.107, "duration": 1.083}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3894.375, "duration": 2.335}, {"text": "MICHALE FEE: Good.", "start": 3896.71, "duration": 0.78}, {"text": "The ions are going to diffuse.", "start": 3897.49, "duration": 2.207}, {"text": "From where to where?", "start": 3899.697, "duration": 0.833}, {"text": "Somebody else.", "start": 3900.53, "duration": 1.14}, {"text": "AUDIENCE: To the\nlower concentration.", "start": 3901.67, "duration": 1.8}, {"text": "MICHALE FEE: To the lower\nconcentration, good.", "start": 3903.47, "duration": 1.917}, {"text": "So some of those ions are going\nto diffuse from here to here.", "start": 3905.387, "duration": 2.843}, {"text": "And we can plot the potassium--\nlet's focus on potassium now.", "start": 3908.23, "duration": 3.902}, {"text": "We're going to plot-- we\ncan plot the potassium", "start": 3912.132, "duration": 1.958}, {"text": "concentration on\nthis side over time", "start": 3914.09, "duration": 2.62}, {"text": "and on this side over time.", "start": 3916.71, "duration": 1.91}, {"text": "By the way, this\nside of the beaker", "start": 3918.62, "duration": 2.91}, {"text": "is going to represent the\ninside of the neuron, which", "start": 3921.53, "duration": 2.37}, {"text": "has lots of\npotassium, and this is", "start": 3923.9, "duration": 2.01}, {"text": "going to represent the\noutside of our neuron, which", "start": 3925.91, "duration": 2.34}, {"text": "has very little potassium, OK?", "start": 3928.25, "duration": 3.09}, {"text": "So if we plot that potassium\nconcentration on this side,", "start": 3931.34, "duration": 3.94}, {"text": "it's going to\nincrease over time.", "start": 3935.28, "duration": 1.88}, {"text": "It's going to take a long--", "start": 3937.16, "duration": 1.32}, {"text": "and the concentration\nhere will decrease", "start": 3938.48, "duration": 2.13}, {"text": "and eventually they'll meet\nin the middle somewhere.", "start": 3940.61, "duration": 3.63}, {"text": "They'll become equal.", "start": 3944.24, "duration": 3.005}, {"text": "And that's going to take\na really long time, right?", "start": 3947.245, "duration": 2.125}, {"text": "Because it takes a\nlong time for this half", "start": 3949.37, "duration": 2.58}, {"text": "of this spoonful of\npotassium chloride", "start": 3951.95, "duration": 1.86}, {"text": "to diffuse to the other side.", "start": 3953.81, "duration": 2.386}, {"text": "Yeah?", "start": 3956.196, "duration": 2.874}, {"text": "OK.", "start": 3959.07, "duration": 2.73}, {"text": "Now let's get a\ndifferent kind of needle,", "start": 3961.8, "duration": 4.79}, {"text": "a very special needle.", "start": 3966.59, "duration": 1.47}, {"text": "It's really small\nand poke a hole", "start": 3968.06, "duration": 3.15}, {"text": "in the membrane that\nis only big enough", "start": 3971.21, "duration": 2.64}, {"text": "to pass potassium ions\nbut not chloride ions.", "start": 3973.85, "duration": 2.91}, {"text": "So what's going to happen now?", "start": 3979.68, "duration": 1.25}, {"text": "Yeah?", "start": 3986.49, "duration": 0.5}, {"text": "Somebody-- yes?", "start": 3986.99, "duration": 3.93}, {"text": "AUDIENCE: Half of it\nflows to the other side--", "start": 3990.92, "duration": 2.36}, {"text": "MICHALE FEE: Good.", "start": 3993.28, "duration": 0.75}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3994.03, "duration": 3.61}, {"text": "MICHALE FEE: Good.", "start": 3997.64, "duration": 1.44}, {"text": "So some potassium ions are going\nto diffuse through this pore", "start": 3999.08, "duration": 6.06}, {"text": "and go to the other side.", "start": 4005.14, "duration": 3.32}, {"text": "And what's going to happen\nis if we plot the potassium", "start": 4008.46, "duration": 2.31}, {"text": "concentration here, it\nwill decrease-- sorry--", "start": 4010.77, "duration": 3.18}, {"text": "over here it will\nincrease a little bit,", "start": 4013.95, "duration": 2.43}, {"text": "and the potassium\nconcentration on this side", "start": 4016.38, "duration": 2.04}, {"text": "will decrease a little bit,\nbut then it will stop changing,", "start": 4018.42, "duration": 3.45}, {"text": "and it will never\ncome to equilibrium.", "start": 4021.87, "duration": 3.82}, {"text": "It will also take a very short\ntime for that equilibrium", "start": 4025.69, "duration": 2.96}, {"text": "to happen, because\njust a few potassium", "start": 4028.65, "duration": 1.86}, {"text": "ions need to go to the\nother side before it stops.", "start": 4030.51, "duration": 4.37}, {"text": "So why does the concentration\nstop changing here?", "start": 4034.88, "duration": 3.48}, {"text": "Well, it's because\nthe potassium current", "start": 4038.36, "duration": 3.03}, {"text": "from this side to this\nside goes to zero,", "start": 4041.39, "duration": 2.93}, {"text": "and it goes to\nzero very quickly.", "start": 4044.32, "duration": 1.375}, {"text": "So why is that?", "start": 4051.07, "duration": 0.81}, {"text": "Well, one hint to the\nanswer to that question", "start": 4054.86, "duration": 6.53}, {"text": "comes if we look at the voltage\ndifference between the two", "start": 4061.39, "duration": 2.91}, {"text": "sides.", "start": 4064.3, "duration": 0.5}, {"text": "So what you see is that the\nvoltage difference started", "start": 4064.8, "duration": 3.22}, {"text": "at 0, and when we poked\nthat hole, all of a sudden", "start": 4068.02, "duration": 6.23}, {"text": "there was a rapidly-developing\nvoltage difference", "start": 4074.25, "duration": 2.67}, {"text": "across the two sides, OK?", "start": 4076.92, "duration": 3.55}, {"text": "Why does that\nvoltage go negative?", "start": 4084.21, "duration": 4.14}, {"text": "Anybody?", "start": 4088.35, "duration": 2.45}, {"text": "What happened when these\npositive charges started", "start": 4090.8, "duration": 3.14}, {"text": "diffusing from this\nside to this side?", "start": 4093.94, "duration": 4.175}, {"text": "AUDIENCE: Didn't\nyou say it can bond", "start": 4098.115, "duration": 1.5}, {"text": "to the positive and\nnegative charge [INAUDIBLE]", "start": 4099.615, "duration": 4.864}, {"text": "MICHALE FEE: Basically this\nis like a capacitor, right?", "start": 4104.479, "duration": 2.46}, {"text": "And some charges diffused\nfrom here to here,", "start": 4106.939, "duration": 3.991}, {"text": "some positive charges\ndiffused from here to here,", "start": 4110.93, "duration": 2.849}, {"text": "that charges up this side, and\nso the voltage is positive.", "start": 4113.779, "duration": 3.87}, {"text": "We put positive charge--\nmore positive charges here,", "start": 4117.649, "duration": 2.551}, {"text": "the voltage here goes up, OK?", "start": 4120.2, "duration": 3.715}, {"text": "So if the voltage here is\nhigher than the voltage here--", "start": 4127.31, "duration": 7.219}, {"text": "we're plotting V1 minus\nV2, the voltage here", "start": 4134.529, "duration": 3.601}, {"text": "is lower than the\nvoltage here, and so this", "start": 4138.13, "duration": 4.29}, {"text": "is going negative, OK?", "start": 4142.42, "duration": 3.369}, {"text": "And that voltage difference,\nthat negative voltage here,", "start": 4149.25, "duration": 3.84}, {"text": "positive voltage here,\nwhat does that do?", "start": 4153.09, "duration": 3.79}, {"text": "It repels, it makes--\nthe positive side", "start": 4156.88, "duration": 2.97}, {"text": "starts repelling which ions?", "start": 4159.85, "duration": 3.25}, {"text": "It's repelling positive ions.", "start": 4163.1, "duration": 2.509}, {"text": "So it keeps more potassium\nions from diffusing", "start": 4165.609, "duration": 4.231}, {"text": "through the hole.", "start": 4169.84, "duration": 2.823}, {"text": "Does that makes sense?", "start": 4172.663, "duration": 0.917}, {"text": "Blank stares.", "start": 4183.83, "duration": 1.41}, {"text": "Are we OK?", "start": 4185.24, "duration": 1.57}, {"text": "OK, good.", "start": 4186.81, "duration": 1.9}, {"text": "And it continues to drop until\nit reaches a constant voltage,", "start": 4188.71, "duration": 4.859}, {"text": "and that's called the\nequilibrium potential, OK?", "start": 4193.569, "duration": 2.476}, {"text": "The voltage changes until\nit comes to equilibrium,", "start": 4196.045, "duration": 3.075}, {"text": "and that voltage difference\nis called the equilibrium", "start": 4199.12, "duration": 2.64}, {"text": "potential.", "start": 4201.76, "duration": 2.4}, {"text": "And that voltage difference\nis a battery, OK?", "start": 4204.16, "duration": 6.5}, {"text": "And I'm going to--", "start": 4210.66, "duration": 0.84}, {"text": "we're going to\nexplain a little bit--", "start": 4211.5, "duration": 2.43}, {"text": "I think it's in the next\nlecture, the one that's", "start": 4213.93, "duration": 2.76}, {"text": "on tape that explains how\nyou actually can justify", "start": 4216.69, "duration": 4.17}, {"text": "representing that as a battery.", "start": 4220.86, "duration": 1.95}, {"text": "But right now, I'm\ngoing to show you", "start": 4222.81, "duration": 2.4}, {"text": "how to calculate what that\nvoltage difference actually", "start": 4225.21, "duration": 3.6}, {"text": "is-- what's the size\nof the battery, how", "start": 4228.81, "duration": 2.1}, {"text": "big is the battery, OK?", "start": 4230.91, "duration": 3.49}, {"text": "So you can see that when ions--", "start": 4234.4, "duration": 2.67}, {"text": "positive ions defuse to this\nside, this voltage goes up,", "start": 4237.07, "duration": 2.88}, {"text": "you have a voltage gradient that\ncorresponds to a field pointing", "start": 4239.95, "duration": 4.26}, {"text": "in this direction.", "start": 4244.21, "duration": 2.25}, {"text": "And that electric field pushes\nagainst the ions-- remember,", "start": 4246.46, "duration": 3.7}, {"text": "we talked about drift\nin an electric field,", "start": 4250.16, "duration": 2.4}, {"text": "so when those ions are\ntrying to diffuse across,", "start": 4252.56, "duration": 2.57}, {"text": "that electric field is\nliterally dragging them back", "start": 4255.13, "duration": 3.87}, {"text": "to this side, right?", "start": 4259.0, "duration": 5.16}, {"text": "So we have a current flowing\nthis way from diffusion,", "start": 4264.16, "duration": 4.32}, {"text": "and we have a current\nflowing that way from being", "start": 4268.48, "duration": 3.51}, {"text": "dragged in the electric field.", "start": 4271.99, "duration": 1.42}, {"text": "And so we can calculate that\nvoltage difference because", "start": 4273.41, "duration": 6.19}, {"text": "at equilibrium, the current\nflowing this way from diffusion", "start": 4279.6, "duration": 3.3}, {"text": "has to equal the current\nflowing that way from drift", "start": 4282.9, "duration": 5.95}, {"text": "in an electric field, OK?", "start": 4288.85, "duration": 1.41}, {"text": "So one way to\ncalculate this is we're", "start": 4290.26, "duration": 3.78}, {"text": "going to calculate the\ncurrent due to drift,", "start": 4294.04, "duration": 3.45}, {"text": "current due to\ndiffusion, add those up,", "start": 4297.49, "duration": 2.11}, {"text": "and that's equal to the\ntotal, and at equilibrium,", "start": 4299.6, "duration": 2.87}, {"text": "that has to equal to 0, right?", "start": 4302.47, "duration": 3.86}, {"text": "So what I'm showing\nyou now is just", "start": 4306.33, "duration": 4.11}, {"text": "sort of the\nframework for how you", "start": 4310.44, "duration": 1.59}, {"text": "would calculate this using this\ndrift and diffusion equation.", "start": 4312.03, "duration": 6.84}, {"text": "So we have Ohm's\nlaw that tells us", "start": 4318.87, "duration": 3.33}, {"text": "how the voltage\ndifference produces", "start": 4322.2, "duration": 3.03}, {"text": "a current due to drift, and we\nhave Fick's law that tells us", "start": 4325.23, "duration": 3.69}, {"text": "how much current is\ndue to diffusion,", "start": 4328.92, "duration": 3.6}, {"text": "and you can set the sum of\nthose two things to equal zero,", "start": 4332.52, "duration": 5.76}, {"text": "all right?", "start": 4338.28, "duration": 1.308}, {"text": "And so this is the\nway it would look.", "start": 4339.588, "duration": 1.542}, {"text": "I don't expect you to follow\nanything on this slide", "start": 4341.13, "duration": 3.96}, {"text": "just except to see that it\ncan be done in this way, OK?", "start": 4345.09, "duration": 4.05}, {"text": "So you don't even have\nto write this down, OK?", "start": 4349.14, "duration": 5.1}, {"text": "So the drift current\nis proportion-- it's", "start": 4354.24, "duration": 2.46}, {"text": "some constant times voltage.", "start": 4356.7, "duration": 3.21}, {"text": "Fisk's law is some constant\ntimes that concentration", "start": 4359.91, "duration": 4.44}, {"text": "gradient, remember that.", "start": 4364.35, "duration": 1.785}, {"text": "And we just set those two things\nequal and solve for delta V,", "start": 4366.135, "duration": 4.613}, {"text": "and that's what you find.", "start": 4370.748, "duration": 1.042}, {"text": "What you find is the delta V\nis just some constant times", "start": 4371.79, "duration": 2.88}, {"text": "the log of the difference\nin concentrations", "start": 4374.67, "duration": 3.66}, {"text": "on the inside and outside, OK?", "start": 4378.33, "duration": 4.664}, {"text": "Now it turns out, there's a\nway of calculating this that's", "start": 4382.994, "duration": 3.226}, {"text": "much simpler and\nmore elegant, and I'm", "start": 4386.22, "duration": 2.76}, {"text": "going to show you\nthat calculation, OK?", "start": 4388.98, "duration": 4.15}, {"text": "Yes?", "start": 4393.13, "duration": 0.509}, {"text": "AUDIENCE: And so like\nthe concentrations inside", "start": 4393.639, "duration": 1.958}, {"text": "and outside, like at the\n[INAUDIBLE] beginning of the--", "start": 4395.597, "duration": 2.785}, {"text": "MICHALE FEE: Yes,\nat the beginning.", "start": 4398.382, "duration": 1.458}, {"text": "And the answer is that the\nconcentrations don't change", "start": 4399.84, "duration": 3.24}, {"text": "very much through this\nprocess, so you can even", "start": 4403.08, "duration": 2.64}, {"text": "ignore that change, OK?", "start": 4405.72, "duration": 3.15}, {"text": "All right, everybody got this?", "start": 4408.87, "duration": 2.29}, {"text": "All right.", "start": 4411.16, "duration": 0.5}, {"text": "So here's how we're\ngoing to calculate", "start": 4411.66, "duration": 1.86}, {"text": "an alternative\nway of calculating", "start": 4413.52, "duration": 1.59}, {"text": "this voltage difference,\njust really beautiful.", "start": 4415.11, "duration": 4.55}, {"text": "We're going to use the\nBoltzmann equation.", "start": 4419.66, "duration": 1.76}, {"text": "The Boltzmann equation\ntells the probability", "start": 4421.42, "duration": 3.87}, {"text": "of a particle\nbeing in two states", "start": 4425.29, "duration": 3.06}, {"text": "as a function of the energy\ndifference between those two", "start": 4428.35, "duration": 2.93}, {"text": "states.", "start": 4431.28, "duration": 0.5}, {"text": "And one of those states is going\nto correspond to a particle", "start": 4431.78, "duration": 2.78}, {"text": "being on the left side of the\nbeaker or inside of our cell,", "start": 4434.56, "duration": 4.14}, {"text": "and that particle being\noutside of our cell", "start": 4438.7, "duration": 3.072}, {"text": "or on the other\nside of the beaker.", "start": 4441.772, "duration": 1.458}, {"text": "And those two, left\nside and right side,", "start": 4443.23, "duration": 2.55}, {"text": "have different energies, OK?", "start": 4445.78, "duration": 2.82}, {"text": "So our system has two\nstates, a high-energy state", "start": 4448.6, "duration": 3.39}, {"text": "and a low-energy state.", "start": 4451.99, "duration": 1.47}, {"text": "Boltzmann equation just\nsays the probability", "start": 4453.46, "duration": 2.058}, {"text": "of being in state 1 divided\nby the probability of being", "start": 4455.518, "duration": 2.292}, {"text": "in state 2 is just e to the\nminus energy difference divided", "start": 4457.81, "duration": 4.24}, {"text": "by kT.", "start": 4462.05, "duration": 0.5}, {"text": "k is the Boltzmann\nconstant, T is temperature--", "start": 4465.21, "duration": 2.61}, {"text": "this is the same kT\nthat we talked about", "start": 4467.82, "duration": 1.89}, {"text": "in the last lecture.", "start": 4469.71, "duration": 0.84}, {"text": "Now, you can see if the\ntemperature is very low,", "start": 4473.45, "duration": 3.05}, {"text": "all those particles are--", "start": 4476.5, "duration": 1.2}, {"text": "if the temperature is 0,\nthey're not being jostled,", "start": 4477.7, "duration": 2.16}, {"text": "they're just sitting\nthere quietly.", "start": 4479.86, "duration": 2.49}, {"text": "They can't move, they\ncan't get into state 1,", "start": 4482.35, "duration": 2.37}, {"text": "they just sit in state 2, OK?", "start": 4484.72, "duration": 3.3}, {"text": "So the probability of\nbeing in state 1 divided", "start": 4488.02, "duration": 1.95}, {"text": "by the probability of\nbeing in state 2 is 0, OK?", "start": 4489.97, "duration": 4.28}, {"text": "If kT is 0, this is\na very big number,", "start": 4494.25, "duration": 3.4}, {"text": "e to the minus big number is 0.", "start": 4497.65, "duration": 1.88}, {"text": "Now let's say that\nwe heat things up", "start": 4502.04, "duration": 1.77}, {"text": "a bit so that now kT gets big.", "start": 4503.81, "duration": 3.48}, {"text": "So the Katie actually gets\napproximately the same size", "start": 4507.29, "duration": 5.4}, {"text": "as the energy difference\nbetween our two states.", "start": 4512.69, "duration": 3.96}, {"text": "So now some of\nthose particles can", "start": 4516.65, "duration": 1.55}, {"text": "get jostled over into state 1.", "start": 4518.2, "duration": 3.25}, {"text": "And we can write down--", "start": 4525.21, "duration": 1.92}, {"text": "we can just calculate--", "start": 4527.13, "duration": 1.56}, {"text": "you can see now that the\nprobability of being in state 1", "start": 4528.69, "duration": 2.49}, {"text": "is--", "start": 4531.18, "duration": 0.84}, {"text": "divided by the probability\nof being in state 2", "start": 4532.02, "duration": 1.95}, {"text": "is bigger than 0 now.", "start": 4533.97, "duration": 1.92}, {"text": "You can actually\njust calculate it.", "start": 4535.89, "duration": 1.83}, {"text": "If the energy difference\nis just twice kT, then", "start": 4537.72, "duration": 4.05}, {"text": "energy difference,\n2kT divided by kT,", "start": 4541.77, "duration": 4.11}, {"text": "that ratio of probabilities\nis just e to the minus 2, OK?", "start": 4545.88, "duration": 4.428}, {"text": "If the energy difference is\nbigger, then you can see,", "start": 4553.55, "duration": 3.69}, {"text": "that probability\nratio is smaller.", "start": 4557.24, "duration": 1.86}, {"text": "The probability\nof being a state 1", "start": 4559.1, "duration": 1.53}, {"text": "goes to 0 if you\nincrease that energy.", "start": 4560.63, "duration": 3.385}, {"text": "If you make that\nenergy difference very", "start": 4564.015, "duration": 1.625}, {"text": "small at temperature\nkT, you'd see", "start": 4565.64, "duration": 2.94}, {"text": "that if the energy difference\nis about the same as kT,", "start": 4568.58, "duration": 4.57}, {"text": "then the probability\nof being at state 1", "start": 4573.15, "duration": 1.68}, {"text": "is equal to the\nprobability in state 2.", "start": 4574.83, "duration": 1.83}, {"text": "Those particles just\njostle back and forth", "start": 4576.66, "duration": 2.79}, {"text": "between the two states.", "start": 4579.45, "duration": 2.43}, {"text": "OK, so we're ready to do this.", "start": 4581.88, "duration": 2.53}, {"text": "Ratio of probabilities\nis e to the minus energy", "start": 4584.41, "duration": 2.4}, {"text": "difference over KT.", "start": 4586.81, "duration": 1.06}, {"text": "What's the energy of a\nparticle here versus here?", "start": 4587.87, "duration": 3.08}, {"text": "Well, that's a charged\nparticle, the energy difference", "start": 4590.95, "duration": 2.25}, {"text": "is just given by the\nvoltage difference.", "start": 4593.2, "duration": 2.85}, {"text": "So energy is charged\ntimes voltage where", "start": 4596.05, "duration": 2.85}, {"text": "Q is the charge of an ion.", "start": 4598.9, "duration": 2.136}, {"text": "The ratio of probabilities\nis e to the--", "start": 4601.036, "duration": 2.674}, {"text": "Q times voltage\ndifference over kT.", "start": 4603.71, "duration": 2.325}, {"text": "Take the log of\nboth sides, solve", "start": 4610.33, "duration": 2.07}, {"text": "for the voltage difference,\nV in minus V out", "start": 4612.4, "duration": 2.91}, {"text": "equals minus kT over Q times the\nlog of the probability ratio,", "start": 4615.31, "duration": 5.13}, {"text": "but the probability is\njust this concentration.", "start": 4620.44, "duration": 5.16}, {"text": "And so we can write\nthis as delta V--", "start": 4625.6, "duration": 3.75}, {"text": "the voltage difference\nis equal to kT", "start": 4629.35, "duration": 3.56}, {"text": "over Q, which is 25 millivolts,\ntimes the log of the ratio", "start": 4632.91, "duration": 5.43}, {"text": "of potassium concentration\noutside to potassium", "start": 4638.34, "duration": 3.12}, {"text": "concentration inside.", "start": 4641.46, "duration": 2.54}, {"text": "And that's exactly\nthe same equation", "start": 4644.0, "duration": 2.16}, {"text": "that we get if you do that much\nmore complicated derivation", "start": 4646.16, "duration": 4.5}, {"text": "based on Fick's law and\nOhm's law, balancing Fick's", "start": 4650.66, "duration": 4.41}, {"text": "law and Ohm's law, OK?", "start": 4655.07, "duration": 3.72}, {"text": "And this is equilibrium\npotential here,", "start": 4658.79, "duration": 2.13}, {"text": "not electric field.", "start": 4660.92, "duration": 3.2}, {"text": "OK, so let's take a look\nat potassium concentrations", "start": 4664.12, "duration": 2.49}, {"text": "in a real cell.", "start": 4666.61, "duration": 2.09}, {"text": "This is actually from\nsquid giant axon.", "start": 4668.7, "duration": 1.77}, {"text": "400 millimolar inside.", "start": 4670.47, "duration": 1.98}, {"text": "So 20 millimolar outside, so\nthere's a lot of potassium", "start": 4672.45, "duration": 3.75}, {"text": "inside of a cell, not\nvery much outside.", "start": 4676.2, "duration": 3.39}, {"text": "Plug those into our equation.", "start": 4679.59, "duration": 1.77}, {"text": "kT over Q is 25,000\nmillimolar-- temperature", "start": 4681.36, "duration": 2.73}, {"text": "at room temperature.", "start": 4684.09, "duration": 2.89}, {"text": "The log of that concentration\nratio is minus 3,", "start": 4686.98, "duration": 3.33}, {"text": "so ek is minus 75 millivolts.", "start": 4690.31, "duration": 2.12}, {"text": "That means if we start\nwith a lot of potassium", "start": 4692.43, "duration": 1.98}, {"text": "inside of our cell, open up a\npotassium-selective channel,", "start": 4694.41, "duration": 5.7}, {"text": "what happens?", "start": 4700.11, "duration": 1.17}, {"text": "Potassium diffuses out\nthrough that channel", "start": 4701.28, "duration": 4.73}, {"text": "and the voltage goes\nto minus 75 millivolts.", "start": 4706.01, "duration": 4.45}, {"text": "How do you know it's negative?", "start": 4710.46, "duration": 1.35}, {"text": "Like, I always can't remember\nwhether this is concentration", "start": 4711.81, "duration": 3.0}, {"text": "inside or outside, outside\nover inside, I don't know.", "start": 4714.81, "duration": 3.01}, {"text": "But the point is, you don't\nactually have to know,", "start": 4717.82, "duration": 2.145}, {"text": "because you can just\nlook at it and see", "start": 4719.965, "duration": 1.625}, {"text": "the answer what sign it is.", "start": 4721.59, "duration": 2.49}, {"text": "If you have positive ions--", "start": 4724.08, "duration": 1.85}, {"text": "a high concentration of positive\nions inside, they diffuse out,", "start": 4725.93, "duration": 4.87}, {"text": "the voltage inside of the\ncell when positive ions leave", "start": 4730.8, "duration": 4.17}, {"text": "is going to do what?", "start": 4734.97, "duration": 2.66}, {"text": "It's going to go down, so\nthat's why it's minus, OK?", "start": 4737.63, "duration": 4.41}, {"text": "So-- the battery\nand in those video", "start": 4742.04, "duration": 4.46}, {"text": "modules that I\nrecorded for you, it's", "start": 4746.5, "duration": 2.82}, {"text": "going to explain how you\nactually incorporate that", "start": 4749.32, "duration": 2.94}, {"text": "into a battery in\nour circuit model.", "start": 4752.26, "duration": 3.78}, {"text": "And so we've done\nall of these things,", "start": 4756.04, "duration": 1.84}, {"text": "we've looked at how membrane\ncapacitance and resistance", "start": 4757.88, "duration": 2.39}, {"text": "allows neurons to\nintegrate over time,", "start": 4760.27, "duration": 2.85}, {"text": "we've learned how to write down\nthe differential equations,", "start": 4763.12, "duration": 2.62}, {"text": "we're now able to just\nlook at a current input", "start": 4765.74, "duration": 2.78}, {"text": "and figure out the\nvoltage change,", "start": 4768.52, "duration": 2.01}, {"text": "and we now understand where\nthe batteries in a neuron", "start": 4770.53, "duration": 2.79}, {"text": "come from.", "start": 4773.32, "duration": 1.79}]
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+[{"text": "YUFEI ZHAO: We've been\nspending the past few lectures", "start": 16.602, "duration": 2.208}, {"text": "discussing Szemeredi's\nRegularity Lemma.", "start": 18.81, "duration": 2.94}, {"text": "And one of the\nfirst applications", "start": 21.75, "duration": 2.31}, {"text": "that we discussed of\nthe Regularity Lemma", "start": 24.06, "duration": 2.67}, {"text": "is the triangle removal Lemma.", "start": 26.73, "duration": 2.85}, {"text": "So today, I want to\nrevisit this topic", "start": 29.58, "duration": 2.16}, {"text": "and show you a strengthening\nof the Removal Lemma", "start": 31.74, "duration": 3.12}, {"text": "for which new regularity\ntechniques are needed.", "start": 34.86, "duration": 3.0}, {"text": "But first, recall the\ngraph removal Lemma.", "start": 42.03, "duration": 3.06}, {"text": "In the graph removal Lemma,\nwe have that for every graph H", "start": 57.69, "duration": 5.9}, {"text": "and epsilon bigger than zero,\nthere exists some delta such", "start": 63.59, "duration": 6.45}, {"text": "that if an N vertex graph\nhas fewer than delta", "start": 70.04, "duration": 14.69}, {"text": "and to the number of vertices\nof H, many copies of H,", "start": 84.73, "duration": 10.54}, {"text": "then it can be made H-free by\nremoving fewer than epsilon N", "start": 95.27, "duration": 18.35}, {"text": "squared edges.", "start": 113.62, "duration": 0.9}, {"text": "Even in the case when\nH is a triangle, when", "start": 118.23, "duration": 2.835}, {"text": "this is called a triangle\nremoval Lemma, even", "start": 121.065, "duration": 1.875}, {"text": "in that case, basically\nthe regularity method", "start": 122.94, "duration": 3.39}, {"text": "is more or less the only\nway that we currently", "start": 126.33, "duration": 1.95}, {"text": "know how to prove this theorem.", "start": 128.28, "duration": 2.1}, {"text": "So we saw this a\nfew lectures ago.", "start": 130.38, "duration": 3.93}, {"text": "What I would like\nto discuss today", "start": 134.31, "duration": 2.01}, {"text": "is a variant of\nthis result where", "start": 136.32, "duration": 3.33}, {"text": "instead of considering\ncopies of H,", "start": 139.65, "duration": 4.38}, {"text": "we're now considering\ninduced copies of H. OK?", "start": 144.03, "duration": 5.43}, {"text": "So this is the induced\ngraph removal Lemma", "start": 149.46, "duration": 5.55}, {"text": "where the only difference is\nthat the hypothesis is now", "start": 155.01, "duration": 4.77}, {"text": "going to be changed to\ninduced copies of H.", "start": 159.78, "duration": 5.13}, {"text": "And the conclusion\nis that you can", "start": 164.91, "duration": 1.68}, {"text": "make the graph induced H-free.", "start": 166.59, "duration": 4.74}, {"text": "So let me remind\nyou, the difference", "start": 171.33, "duration": 1.59}, {"text": "between the induced\ngraph subgraph", "start": 172.92, "duration": 2.94}, {"text": "and the usual subgraph.", "start": 175.86, "duration": 3.18}, {"text": "So we say that H is an induced\ncopy of G, induced subgraph", "start": 179.04, "duration": 13.18}, {"text": "of G. If one can obtain H from\nG by deleting vertices of G.", "start": 192.22, "duration": 30.622}, {"text": "You're not allowed\nto delete edges,", "start": 222.842, "duration": 1.458}, {"text": "but only allowed\nto delete vertices.", "start": 224.3, "duration": 2.61}, {"text": "So in other words,\nthe four cycle", "start": 226.91, "duration": 8.61}, {"text": "is not an induced\nsubgraph because, well,", "start": 235.52, "duration": 9.69}, {"text": "if you select four vertices, you\ndon't generate this four cycle.", "start": 245.21, "duration": 3.06}, {"text": "You get extra edges.", "start": 248.27, "duration": 1.02}, {"text": "So it is a subgraph, but\nnot an induced subgraph.", "start": 249.29, "duration": 2.77}, {"text": "So it is a theorem, the\ninduced graph removal Lemma.", "start": 260.05, "duration": 3.24}, {"text": "So it's a theorem,\nand let's discuss", "start": 263.29, "duration": 1.5}, {"text": "how we may prove that theorem.", "start": 264.79, "duration": 1.43}, {"text": "Question.", "start": 266.22, "duration": 0.5}, {"text": "OK, question is, why is it\nstronger than the graph removal", "start": 270.55, "duration": 2.45}, {"text": "lemma?", "start": 273.0, "duration": 1.81}, {"text": "So it's not stronger, but\nwe'll see the relationship", "start": 274.81, "duration": 5.25}, {"text": "between the two.", "start": 280.06, "duration": 1.21}, {"text": "So I claim that it is more\ndifficult to do this theorem.", "start": 281.27, "duration": 5.06}, {"text": "Any more questions?", "start": 286.33, "duration": 2.61}, {"text": "So let's pretend for a second\nthat whatever's in here", "start": 288.94, "duration": 8.38}, {"text": "is not quite true.", "start": 297.32, "duration": 1.285}, {"text": "So here's an example.", "start": 298.605, "duration": 0.875}, {"text": "For example, if your H is\nthree isolated vertices.", "start": 306.11, "duration": 8.25}, {"text": "So what is that saying?", "start": 314.36, "duration": 1.53}, {"text": "We're looking at\ncopies of H which", "start": 315.89, "duration": 2.34}, {"text": "are three isolated vertices.", "start": 318.23, "duration": 1.47}, {"text": "So really you are looking at\ntriangles in g complement.", "start": 319.7, "duration": 6.63}, {"text": "So this is exactly the\ntriangle removal lemma", "start": 326.33, "duration": 3.71}, {"text": "in the complement of g, but\nyou can't get rid of these guys", "start": 330.04, "duration": 5.26}, {"text": "by removing edges.", "start": 335.3, "duration": 1.38}, {"text": "So we need to make\nthe modification", "start": 336.68, "duration": 1.68}, {"text": "where instead of\nremoving these edges,", "start": 338.36, "duration": 2.22}, {"text": "we need to both remove and\nadd by adding or deleting.", "start": 340.58, "duration": 7.5}, {"text": "So maybe at the same time.", "start": 351.49, "duration": 1.268}, {"text": "So you're allowed to add some\nedges, delete some edges.", "start": 352.758, "duration": 2.292}, {"text": "But in total, you change no more\nthan epsilon n squared edges.", "start": 355.05, "duration": 3.738}, {"text": "So those are sometimes also\nknown as the edit distance.", "start": 358.788, "duration": 2.292}, {"text": "You're allowed to change edges.", "start": 365.69, "duration": 2.84}, {"text": "So you can add edges\nand delete edges.", "start": 368.53, "duration": 2.28}, {"text": "Any questions about\nthe statement?", "start": 376.09, "duration": 1.85}, {"text": "All right, so let's\nthink about how would you", "start": 380.88, "duration": 3.67}, {"text": "prove this result following\nthe proof that we did", "start": 384.55, "duration": 3.21}, {"text": "for the triangle removal lemma.", "start": 387.76, "duration": 2.9}, {"text": "So let's pretend that\nwe go through this proof", "start": 390.66, "duration": 2.68}, {"text": "and think about\nwhat could go wrong.", "start": 393.34, "duration": 1.89}, {"text": "So remember in the application\nof the removal lemma,", "start": 395.23, "duration": 2.61}, {"text": "so the recipe has three steps.", "start": 397.84, "duration": 2.41}, {"text": "The first step we\ndo a partition.", "start": 400.25, "duration": 2.204}, {"text": "So we partition applying\nSzemeredi's regularity lemma", "start": 405.42, "duration": 3.8}, {"text": "to this partition.", "start": 409.22, "duration": 1.67}, {"text": "And the second step\nis do a cleaning,", "start": 410.89, "duration": 5.51}, {"text": "and the two key things\nthat happen in the cleaning", "start": 416.4, "duration": 3.42}, {"text": "is we remove low density pairs\nof parts and irregular pairs.", "start": 419.82, "duration": 11.31}, {"text": "And the third step\nwe claim that once we", "start": 433.94, "duration": 2.44}, {"text": "do the cleaning, once\nwe remove those edges,", "start": 436.38, "duration": 3.51}, {"text": "the resulting\ngraphs should be H3.", "start": 439.89, "duration": 2.34}, {"text": "Because if we're not H3, then\nby considering the vertex parts", "start": 442.23, "duration": 4.74}, {"text": "where H lie and applying\nthe counting lemma,", "start": 446.97, "duration": 2.49}, {"text": "you can generate many\nmore copies of H.", "start": 449.46, "duration": 3.97}, {"text": "So these were the three\nmain steps in the proof", "start": 453.43, "duration": 2.12}, {"text": "of the triangle removal lemma.", "start": 455.55, "duration": 1.98}, {"text": "So let's see what\nhappens when we", "start": 457.53, "duration": 2.52}, {"text": "try to apply this strategy\nto the induced version.", "start": 460.05, "duration": 3.48}, {"text": "I mean, the partition you still\ndo the regularity partition.", "start": 463.53, "duration": 4.23}, {"text": "Nothing really changes there.", "start": 467.76, "duration": 2.61}, {"text": "So let's see in the\ncleaning step what happens.", "start": 470.37, "duration": 4.05}, {"text": "For low density pairs--", "start": 474.42, "duration": 2.04}, {"text": "well, so now we need to think\nabout not just low density", "start": 476.46, "duration": 2.79}, {"text": "pairs, but also\nhigh density pairs.", "start": 479.25, "duration": 2.45}, {"text": "Because in the induced, we\nthink about edges and non-edges", "start": 481.7, "duration": 3.07}, {"text": "at the same time.", "start": 484.77, "duration": 1.18}, {"text": "So you might think of a\nstrategy which is like the edge", "start": 485.95, "duration": 3.08}, {"text": "density is less than n.", "start": 489.03, "duration": 2.43}, {"text": "So less than epsilon, then\nyou remove all those edges.", "start": 491.46, "duration": 4.02}, {"text": "And if the edge density is\nbigger than 1 plus epsilon,", "start": 495.48, "duration": 2.97}, {"text": "then you add all\nof those edges in.", "start": 498.45, "duration": 3.65}, {"text": "So this is the\nnatural generalization", "start": 502.1, "duration": 1.76}, {"text": "of our strategy for\ntriangle removal", "start": 503.86, "duration": 1.96}, {"text": "lemma for the induced setting.", "start": 505.82, "duration": 1.58}, {"text": "So so far,\neverything's still OK.", "start": 507.4, "duration": 3.17}, {"text": "But now what would you do\nfor the irregular pairs?", "start": 510.57, "duration": 2.92}, {"text": "That's problematic.", "start": 517.97, "duration": 3.06}, {"text": "Previously for\ntriangle removal lemma,", "start": 521.03, "duration": 2.79}, {"text": "we just said if a pair is\nirregular, get rid of that pair", "start": 523.82, "duration": 3.45}, {"text": "and it will never show\nup in the counting stage.", "start": 527.27, "duration": 4.17}, {"text": "But that strategy\nno longer works.", "start": 531.44, "duration": 3.1}, {"text": "Because for example, if\nyour graph H being counted", "start": 534.54, "duration": 5.33}, {"text": "is this here, you do the\nregularity partition,", "start": 539.87, "duration": 8.76}, {"text": "and one of your\npairs is irregular.", "start": 548.63, "duration": 3.92}, {"text": "So you, let's say, get rid of\nall those edges in between.", "start": 552.55, "duration": 3.69}, {"text": "Then maybe you have\nsome embedding of H", "start": 556.24, "duration": 4.44}, {"text": "where you are going to\nuse the removed edges.", "start": 560.68, "duration": 5.225}, {"text": "And now you don't\nhave a counting lemma.", "start": 570.01, "duration": 4.03}, {"text": "You cannot say, I found this\ncopy of H in my changed graph.", "start": 574.04, "duration": 7.03}, {"text": "And by the counting lemma I\ncould get many copies of H", "start": 581.07, "duration": 2.58}, {"text": "because you have no control over\nthis irregular pair anymore.", "start": 583.65, "duration": 3.97}, {"text": "So the fact that you\nhave to add and remove", "start": 587.62, "duration": 3.26}, {"text": "makes it unclear\nwhat to do here,", "start": 590.88, "duration": 1.78}, {"text": "and this is a big obstacle\nin the application", "start": 592.66, "duration": 2.15}, {"text": "of the regularity lemma to\nthe induced removal lemma", "start": 594.81, "duration": 4.56}, {"text": "application.", "start": 599.37, "duration": 2.94}, {"text": "Any questions about\nthis obstacle?", "start": 602.31, "duration": 2.04}, {"text": "So make sure you understand\nwhy this is an issue.", "start": 608.55, "duration": 2.39}, {"text": "Otherwise you won't\nreally appreciate", "start": 610.94, "duration": 2.9}, {"text": "what will happen next.", "start": 613.84, "duration": 2.71}, {"text": "So somehow we need to find some\nkind of regularity partition", "start": 616.55, "duration": 5.08}, {"text": "to get no irregular pairs.", "start": 621.63, "duration": 3.54}, {"text": "So the question\nis, is there a way", "start": 625.17, "duration": 4.61}, {"text": "to partition so that there\nare no irregular pairs?", "start": 629.78, "duration": 6.8}, {"text": "For those of you who have\nstarted your homework", "start": 642.13, "duration": 2.4}, {"text": "problem on time, you realize\nthat the answer is no.", "start": 644.53, "duration": 4.62}, {"text": "So one of the\nhomework problems is", "start": 649.15, "duration": 1.62}, {"text": "for you to show that for\nthe specific graph known", "start": 650.77, "duration": 2.93}, {"text": "as the half graph.", "start": 653.7, "duration": 1.0}, {"text": "So there was an\nexample in homework", "start": 658.11, "duration": 2.478}, {"text": "that for the half graph--", "start": 660.588, "duration": 1.042}, {"text": "so you'll see in the\nhomework what this graph is--", "start": 668.665, "duration": 3.135}, {"text": "you cannot partition it so that\nyou get rid of all irregular", "start": 671.8, "duration": 3.25}, {"text": "pairs.", "start": 675.05, "duration": 0.5}, {"text": "Irregular pairs are\nnecessary in the statement", "start": 675.55, "duration": 2.79}, {"text": "of regularity lemma.", "start": 678.34, "duration": 1.31}, {"text": "So what I want to show\nyou today is a way", "start": 682.24, "duration": 2.1}, {"text": "to do what's called a strong\nregularity lemma in which you", "start": 684.34, "duration": 5.06}, {"text": "obtain a somewhat different\nconsequence that will allow", "start": 689.4, "duration": 3.6}, {"text": "you to get rid of\nirregular pairs", "start": 693.0, "duration": 2.438}, {"text": "in the more restricted setting.", "start": 695.438, "duration": 1.292}, {"text": "So this is the issue,\nthe irregular pairs.", "start": 699.73, "duration": 2.37}, {"text": "Before telling you what\nthis regularity lemma is,", "start": 708.42, "duration": 2.37}, {"text": "I want to give you a\nsmall generalization", "start": 710.79, "duration": 4.26}, {"text": "of the induced graph removal\nlemma, or just a different way", "start": 715.05, "duration": 3.3}, {"text": "to think about the statement.", "start": 718.35, "duration": 2.19}, {"text": "And you can think of it as\na colorful version instead", "start": 720.54, "duration": 3.18}, {"text": "of induced where you\nhave edges and no edges.", "start": 723.72, "duration": 5.25}, {"text": "You can also have colored edges.", "start": 728.97, "duration": 2.1}, {"text": "So colorful removal\nlemma, although this name", "start": 731.07, "duration": 3.12}, {"text": "is not standard.", "start": 734.19, "duration": 1.11}, {"text": "So colorful-- so when\nwe talk about graphs,", "start": 741.58, "duration": 4.03}, {"text": "it's colorful graph\nremoval lemma.", "start": 745.61, "duration": 3.43}, {"text": "So for every k, r, and epsilon,\nthere exists delta such", "start": 749.04, "duration": 8.45}, {"text": "that if curly H is a set of\nr edge of the complete graph", "start": 757.49, "duration": 20.53}, {"text": "on little k vertices.", "start": 778.02, "duration": 2.57}, {"text": "So edge coloring just\nmeans using r colors", "start": 780.59, "duration": 3.21}, {"text": "to color the edges.", "start": 783.8, "duration": 0.9}, {"text": "So there are no restrictions\nabout what are allowed,", "start": 784.7, "duration": 2.83}, {"text": "what are not allowed.", "start": 787.53, "duration": 0.92}, {"text": "So just a set of\npossible r colorings.", "start": 788.45, "duration": 3.843}, {"text": "Then if the complete graph--", "start": 792.293, "duration": 9.707}, {"text": "say it slightly differently.", "start": 807.823, "duration": 1.167}, {"text": "So then every r edge coloring\nof the complete graph", "start": 808.99, "duration": 15.66}, {"text": "on n vertices with fewer than\ndelta fraction of its k vertex", "start": 824.65, "duration": 18.2}, {"text": "subsets, say k vertex subgraphs,\nbelonging to the script H.", "start": 842.85, "duration": 17.46}, {"text": "So every such graph can be made\ncurly H free by recoloring,", "start": 860.31, "duration": 14.36}, {"text": "so using the same r colors, a\nfewer than epsilon fraction.", "start": 874.67, "duration": 15.04}, {"text": "So less than epsilon fraction\nof the edges of this kn.", "start": 889.71, "duration": 11.0}, {"text": "So in particular, the\nversion that we just stated,", "start": 903.36, "duration": 3.18}, {"text": "the induced version, so the\ninduced graph removal lemma,", "start": 906.54, "duration": 9.72}, {"text": "is the same as having two\ncolors and H having exactly one", "start": 916.26, "duration": 15.19}, {"text": "red-blue coloring of k\nof the complete graph", "start": 931.45, "duration": 13.17}, {"text": "on the same number\nof vertices as H.", "start": 944.62, "duration": 4.16}, {"text": "So you color red the edges\nand blue the non-edges,", "start": 948.78, "duration": 3.15}, {"text": "for instance.", "start": 951.93, "duration": 1.72}, {"text": "And you're saying, I want to\ncolor the big complete graph", "start": 953.65, "duration": 5.03}, {"text": "with red and blue in such a way\nthat there are very few copies", "start": 958.68, "duration": 4.08}, {"text": "of that pattern.", "start": 962.76, "duration": 1.14}, {"text": "So then I can recolor\nthe red and blue", "start": 963.9, "duration": 1.83}, {"text": "in a small number of places to\nget rid of all such patterns.", "start": 965.73, "duration": 4.02}, {"text": "So having a colored\npattern somewhere", "start": 969.75, "duration": 2.19}, {"text": "in your graph in this\ncomplete graph coloring", "start": 971.94, "duration": 2.67}, {"text": "is the same as having\nan induced subgraph.", "start": 974.61, "duration": 4.56}, {"text": "Yeah?", "start": 979.17, "duration": 0.58}, {"text": "AUDIENCE: So after done--", "start": 979.75, "duration": 1.38}, {"text": "like the statement after done\nis a really long sentence.", "start": 981.13, "duration": 2.846}, {"text": "Can I--", "start": 983.976, "duration": 0.584}, {"text": "YUFEI ZHAO: Yeah, OK.", "start": 984.56, "duration": 3.46}, {"text": "So every r edge coloring of kn\nwith a small number of patterns", "start": 988.02, "duration": 9.36}, {"text": "can be made h-free by recoloring\na small fraction of the edges.", "start": 997.38, "duration": 6.33}, {"text": "So like in a triangle\nremoval lemma,", "start": 1003.71, "duration": 1.92}, {"text": "every graph with a small\nnumber of triangles", "start": 1005.63, "duration": 3.54}, {"text": "can be made\ntriangle-free by removing", "start": 1009.17, "duration": 2.37}, {"text": "a small number of edges.", "start": 1011.54, "duration": 1.17}, {"text": "Any other questions?", "start": 1018.02, "duration": 3.69}, {"text": "So this is a restatement of\nthe induced removal lemma", "start": 1021.71, "duration": 5.369}, {"text": "with a bit more generality.", "start": 1027.079, "duration": 3.27}, {"text": "It's OK if you like\nthis one more or less,", "start": 1030.349, "duration": 2.611}, {"text": "but let's talk about the\ninduced version from now on.", "start": 1032.96, "duration": 2.85}, {"text": "But the same proofs that\nI will talk about also", "start": 1035.81, "duration": 2.64}, {"text": "applies to this version where\nyou have somewhat more colors.", "start": 1038.45, "duration": 4.26}, {"text": "So the variant of the\nregularity lemma that we'll need", "start": 1046.349, "duration": 4.591}, {"text": "is known as a strong\nregularity lemma.", "start": 1050.94, "duration": 2.43}, {"text": "To state the strong\nregularity lemma,", "start": 1067.32, "duration": 1.89}, {"text": "let me recall a notion that came\nup in the proof of Szemeredi's", "start": 1069.21, "duration": 3.21}, {"text": "regularity lemma.", "start": 1072.42, "duration": 2.4}, {"text": "And this was the\nnotion of an energy.", "start": 1074.82, "duration": 2.92}, {"text": "So recall that if you have\na partition, denoted P. So", "start": 1077.74, "duration": 7.19}, {"text": "if this is a partition of\nthe vertex set of a graph, G,", "start": 1084.93, "duration": 7.05}, {"text": "and here n is the\nnumber of vertices,", "start": 1091.98, "duration": 5.79}, {"text": "we defined this notion of energy\nto be this quantity denoted", "start": 1097.77, "duration": 11.62}, {"text": "q, which is basically a\nsquared mean of the densities", "start": 1109.39, "duration": 7.4}, {"text": "between vertex parts\nappropriately normalized", "start": 1116.79, "duration": 5.22}, {"text": "if the vertexes do not\nall have the same size.", "start": 1122.01, "duration": 4.92}, {"text": "In the proof of Szemeredi's\nregularity lemma,", "start": 1132.86, "duration": 5.83}, {"text": "there was an important\nenergy increment", "start": 1138.69, "duration": 2.07}, {"text": "step which says that if you have\nsome partition p that is not", "start": 1140.76, "duration": 11.49}, {"text": "epsilon regular, then there\nexists a refinement, Q.", "start": 1152.25, "duration": 12.068}, {"text": "And this refinement has\nthe property that Q has", "start": 1164.318, "duration": 5.602}, {"text": "a small number of pieces, or\nnot too large as a function of P", "start": 1169.92, "duration": 7.52}, {"text": "So it's bounded at\nleast in terms of P.", "start": 1177.44, "duration": 3.73}, {"text": "But also if P is not epsilon\nregular, then the energy of Q", "start": 1181.17, "duration": 7.2}, {"text": "is significantly larger than\nthe energy of P. So remember,", "start": 1188.37, "duration": 6.79}, {"text": "this was an important step in\nthe proof of regularity lemma.", "start": 1195.16, "duration": 3.42}, {"text": "So to state the strong\nregularity lemma,", "start": 1203.13, "duration": 4.25}, {"text": "we need that notion of energy.", "start": 1207.38, "duration": 1.918}, {"text": "And the statement of the\nstrong regularity lemma,", "start": 1209.298, "duration": 2.042}, {"text": "if you've never seen this\nkind of thing before,", "start": 1211.34, "duration": 1.958}, {"text": "will seem a bit\nintimidating at first", "start": 1213.298, "duration": 1.582}, {"text": "because it involves a whole\nsequence of parameters.", "start": 1214.88, "duration": 4.35}, {"text": "But we'll get used to it.", "start": 1219.23, "duration": 1.41}, {"text": "So instead of one\nepsilon parameter,", "start": 1223.88, "duration": 2.91}, {"text": "now you have a sequence\nof positive epsilons.", "start": 1226.79, "duration": 9.155}, {"text": "And part of the strength\nof this regularity lemma", "start": 1235.945, "duration": 2.085}, {"text": "is that depending on the\napplication you have in mind,", "start": 1238.03, "duration": 3.09}, {"text": "you can make the sequence\ngo to zero pretty quickly.", "start": 1241.12, "duration": 3.45}, {"text": "Thereby increasing the strength\nof the regularity lemma.", "start": 1244.57, "duration": 4.24}, {"text": "So there exists some m\nbound, which depends only", "start": 1248.81, "duration": 4.94}, {"text": "on your epsilons such that\nevery graph has not just one,", "start": 1253.75, "duration": 14.21}, {"text": "but now we're going to get a\npair of vertex partitions P", "start": 1267.96, "duration": 8.21}, {"text": "and Q with the\nfollowing properties.", "start": 1276.17, "duration": 6.76}, {"text": "So first, P refines--", "start": 1282.93, "duration": 4.25}, {"text": "so Q refines P. So it's\na pair of partitions,", "start": 1287.18, "duration": 9.81}, {"text": "one refining the other.", "start": 1296.99, "duration": 1.66}, {"text": "The number of parts\nof Q is bounded", "start": 1302.4, "duration": 2.85}, {"text": "just like in the usual\nregularity lemma.", "start": 1305.25, "duration": 2.01}, {"text": "The partition P\nepsilon 0 regular.", "start": 1310.07, "duration": 4.89}, {"text": "And here is the new part\nthat's the most important one.", "start": 1317.72, "duration": 4.63}, {"text": "Q is very epsilon regular.", "start": 1322.35, "duration": 4.87}, {"text": "So it's not just\nepsilon 0 regular,", "start": 1327.22, "duration": 2.03}, {"text": "it's epsilon sub the number\nof parts of P regular.", "start": 1329.25, "duration": 4.16}, {"text": "So you should think of\nthis as extremely regular", "start": 1336.33, "duration": 7.05}, {"text": "because you get to choose what\nthe sequence of epsilon is.", "start": 1343.38, "duration": 4.9}, {"text": "And finally, the energy\ndifference between P and Q", "start": 1348.28, "duration": 4.44}, {"text": "is not too big.", "start": 1352.72, "duration": 1.26}, {"text": "This is the statement of\nthe strong regularity lemma.", "start": 1363.69, "duration": 3.14}, {"text": "It produces for you\nnot just one partition,", "start": 1366.83, "duration": 1.92}, {"text": "but a pair of partitions.", "start": 1368.75, "duration": 2.03}, {"text": "And in this pair\nof partitions, you", "start": 1370.78, "duration": 2.02}, {"text": "have one partition, P,\nwhich is similar to the one", "start": 1372.8, "duration": 4.68}, {"text": "that we obtained from\nSzemeredi's regularity lemma", "start": 1377.48, "duration": 2.18}, {"text": "is some epsilon 0 regular, but\nwe also get a refinement Q.", "start": 1379.66, "duration": 6.49}, {"text": "And this Q is extremely regular.", "start": 1386.15, "duration": 5.1}, {"text": "So you can think\nthat is P, then Q", "start": 1391.25, "duration": 8.26}, {"text": "is an extremely\nregular refinement", "start": 1399.51, "duration": 2.53}, {"text": "of P. Any questions\nabout the statement", "start": 1402.04, "duration": 6.17}, {"text": "of the strong regularity lemma?", "start": 1408.21, "duration": 1.75}, {"text": "So the sequence of\nepsilons gives you", "start": 1413.86, "duration": 1.75}, {"text": "flexibility on how to apply it,\nbut let's see how to prove it.", "start": 1415.61, "duration": 4.2}, {"text": "And the proof is once you\nunderstand how this works,", "start": 1419.81, "duration": 3.99}, {"text": "conceptually it's pretty short.", "start": 1423.8, "duration": 3.27}, {"text": "But let me do it slowly\nso that we can appreciate", "start": 1427.07, "duration": 3.3}, {"text": "this sequence of epsilons.", "start": 1430.37, "duration": 4.6}, {"text": "And the idea is that we\nwill repeatedly apply", "start": 1434.97, "duration": 3.3}, {"text": "Szemeredi's regularity lemma.", "start": 1438.27, "duration": 1.3}, {"text": "So start with the\nregularity lemma.", "start": 1446.03, "duration": 2.48}, {"text": "We'll apply it\nrepeatedly to generate", "start": 1448.51, "duration": 4.47}, {"text": "a sequence of partitions.", "start": 1452.98, "duration": 3.56}, {"text": "So first, let me remind you\na statement of Szemeredi's", "start": 1456.54, "duration": 5.08}, {"text": "regularity lemma.", "start": 1461.62, "duration": 0.99}, {"text": "This is slightly\ndifferent from the one", "start": 1462.61, "duration": 1.71}, {"text": "that we stated, but comes\nout of the same proof.", "start": 1464.32, "duration": 4.01}, {"text": "So for every epsilon,\nthere exists some m0", "start": 1468.33, "duration": 5.11}, {"text": "which depends on epsilon such\nthat for every partition P0,", "start": 1473.44, "duration": 8.06}, {"text": "so starting with\nsome partition--", "start": 1481.5, "duration": 5.03}, {"text": "so actually, let me\nstart with just P.", "start": 1486.53, "duration": 1.98}, {"text": "So if you start with some\npartition of the vertex set", "start": 1488.51, "duration": 6.41}, {"text": "of g, there exists a refinement\nP prime of P into at most--", "start": 1494.92, "duration": 15.67}, {"text": "OK, so the refinement has is\nsuch that with each part of P", "start": 1510.59, "duration": 16.93}, {"text": "refined into at\nmost m0 parts such", "start": 1527.52, "duration": 11.44}, {"text": "that P prime, the new\npartition, is epsilon regular.", "start": 1538.96, "duration": 5.69}, {"text": "So this is a statement of\nSzemeredi's regularity lemma", "start": 1552.47, "duration": 2.43}, {"text": "that we will apply repeatedly.", "start": 1554.9, "duration": 1.95}, {"text": "So in the version that\nwe've seen before,", "start": 1556.85, "duration": 2.02}, {"text": "we would start with\na trivial partition.", "start": 1558.87, "duration": 3.63}, {"text": "And applying\nrefinements repeatedly", "start": 1562.5, "duration": 3.24}, {"text": "in the proof to get a partition\ninto a bounded number of parts", "start": 1565.74, "duration": 4.14}, {"text": "such that the final\npartition is epsilon regular.", "start": 1569.88, "duration": 4.2}, {"text": "But instead, in the proof\nof the regularity lemma", "start": 1574.08, "duration": 2.94}, {"text": "if you start with not\na trivial partition", "start": 1577.02, "duration": 2.16}, {"text": "but start with a given partition\nand run this exact same proof,", "start": 1579.18, "duration": 4.92}, {"text": "you find this consequence.", "start": 1584.1, "duration": 2.28}, {"text": "Except now you can guarantee\nthat the final partition", "start": 1586.38, "duration": 2.94}, {"text": "is a refinement of the\none that you are given.", "start": 1589.32, "duration": 2.25}, {"text": "So let's apply the\nstatement, and we obtain", "start": 1595.88, "duration": 7.06}, {"text": "a sequence of partitions of g--", "start": 1602.94, "duration": 7.7}, {"text": "the vertex set of g--", "start": 1610.64, "duration": 1.82}, {"text": "starting with P0 being a\ntrivial partition, and so on.", "start": 1612.46, "duration": 14.79}, {"text": "Such that each partition,\neach P sub i plus 1", "start": 1627.25, "duration": 10.08}, {"text": "refines the previous\none, and such", "start": 1637.33, "duration": 12.61}, {"text": "that each P sub i plus 1 is\nepsilon sub a P sub i regular.", "start": 1649.94, "duration": 9.43}, {"text": "So you apply the regularity\nlemma with parameter", "start": 1662.36, "duration": 3.1}, {"text": "based on the number of\nparts you currently have.", "start": 1665.46, "duration": 3.69}, {"text": "Applied to the\ncurrent partition,", "start": 1669.15, "duration": 1.86}, {"text": "you get a finer partition\nthat's extremely regular.", "start": 1671.01, "duration": 5.81}, {"text": "And you also know\nthat the number", "start": 1676.82, "duration": 2.1}, {"text": "of parts of the new\npartition is bounded in terms", "start": 1678.92, "duration": 5.43}, {"text": "of the previous partition.", "start": 1684.35, "duration": 2.387}, {"text": "All right.", "start": 1703.138, "duration": 2.977}, {"text": "Any questions so far?", "start": 1706.115, "duration": 0.875}, {"text": "So now we get this\nsequence of partitions.", "start": 1711.51, "duration": 4.28}, {"text": "We can keep on doing this.", "start": 1715.79, "duration": 1.53}, {"text": "So g could be arbitrarily\nlarge, but eventually we", "start": 1717.32, "duration": 5.83}, {"text": "will be able to obtain\nthe last condition here,", "start": 1723.15, "duration": 2.83}, {"text": "which is the only thing\nthat is missing so far.", "start": 1725.98, "duration": 3.19}, {"text": "So since the energy is\nbounded between 0 and 1,", "start": 1729.17, "duration": 10.34}, {"text": "there exists some i at\nmost 1 over epsilon 0", "start": 1739.51, "duration": 7.14}, {"text": "such that the energy goes\nup by less than epsilon 0.", "start": 1746.65, "duration": 9.21}, {"text": "Because otherwise your\nenergy would exceed 1.", "start": 1766.39, "duration": 2.31}, {"text": "So now let's set\nP to be this Pi,", "start": 1773.37, "duration": 5.22}, {"text": "and Q to be this,\nthe refinement--", "start": 1778.59, "duration": 5.33}, {"text": "the next term in the partition.", "start": 1783.92, "duration": 1.75}, {"text": "And what we find is that the--", "start": 1790.47, "duration": 4.21}, {"text": "so then you have basically\nall the conditions.", "start": 1794.68, "duration": 2.43}, {"text": "So p is epsilon 0 regular,\nbecause it is epsilon--", "start": 1797.11, "duration": 5.97}, {"text": "the previous term, which is\nat most epsilon 0 regular.", "start": 1803.08, "duration": 4.79}, {"text": "And you have this one as\nwell, and this one as well.", "start": 1807.87, "duration": 4.1}, {"text": "And we want to show that\nthe number of parts of Q", "start": 1811.97, "duration": 2.73}, {"text": "is bounded.", "start": 1814.7, "duration": 2.26}, {"text": "And that's basically\nbecause each time there", "start": 1816.96, "duration": 2.35}, {"text": "was a bound on the number\nof parts which depends only", "start": 1819.31, "duration": 3.48}, {"text": "on the regularity\nparameters, and you're", "start": 1822.79, "duration": 2.1}, {"text": "repeating that bound a\nbounded number of times.", "start": 1824.89, "duration": 3.09}, {"text": "So Q is-- so it's bounded as\na function of the sequence", "start": 1830.52, "duration": 14.09}, {"text": "of epsilons-- this infinite\nvector of epsilons,", "start": 1844.61, "duration": 2.4}, {"text": "but it is a bounded number.", "start": 1847.01, "duration": 2.17}, {"text": "You're only iterating this\nbound a bounded number of times.", "start": 1849.18, "duration": 5.143}, {"text": "And that finishes the proof.", "start": 1854.323, "duration": 1.167}, {"text": "Any questions?", "start": 1860.946, "duration": 1.417}, {"text": "It may be somewhat mysterious\nto you right now why we do this,", "start": 1869.77, "duration": 3.41}, {"text": "so we'll get that\napplication a second.", "start": 1873.18, "duration": 1.66}, {"text": "But for now, I just want to\ncomment a bit on the bounds.", "start": 1874.84, "duration": 3.17}, {"text": "Of course, the bounds depend\non what epsilon i's do you use.", "start": 1886.09, "duration": 6.04}, {"text": "And typically, you\nwant the epsilon i's", "start": 1892.13, "duration": 1.77}, {"text": "to decrease with more\nparts that you have.", "start": 1893.9, "duration": 3.45}, {"text": "And with almost all\nreasonable applications", "start": 1897.35, "duration": 2.67}, {"text": "of this regularity lemma,\nthe strong regularity lemma--", "start": 1900.02, "duration": 4.43}, {"text": "so for example, with epsilon\ni being some epsilon divided", "start": 1904.45, "duration": 8.51}, {"text": "by, let's say, i plus 1 or\nany polynomial of the i's--", "start": 1912.96, "duration": 5.18}, {"text": "or you can even let it decay\nquicker than that, as well.", "start": 1918.14, "duration": 4.09}, {"text": "You see, basically what\nhappens is that you", "start": 1922.23, "duration": 4.08}, {"text": "are applying this m0 bound.", "start": 1926.31, "duration": 3.0}, {"text": "m0 applied in succession\n1 over epsilon times.", "start": 1935.3, "duration": 10.06}, {"text": "In the regularity lemma, we\nsaw that the m0 that comes out", "start": 1949.25, "duration": 4.55}, {"text": "of Szemeredi's graph regularity\nlemma is the tower function.", "start": 1953.8, "duration": 3.33}, {"text": "So the tower function,\nthat's a tower of i", "start": 1959.872, "duration": 4.098}, {"text": "is defined to be the exponential\nfunction iterated i times.", "start": 1963.97, "duration": 8.356}, {"text": "So of course, I'm\nbeing somewhat loose", "start": 1972.326, "duration": 1.594}, {"text": "here with the exact dependence,\nbut you get the idea", "start": 1973.92, "duration": 3.33}, {"text": "that now we want to apply\nthe tower function i times.", "start": 1977.25, "duration": 4.8}, {"text": "Instead of iterating\nthe exponential i times,", "start": 1995.22, "duration": 2.13}, {"text": "now you iterate the\ntower function i times.", "start": 1997.35, "duration": 3.03}, {"text": "And some of you laughing, this\nis an incredibly large number.", "start": 2000.38, "duration": 2.912}, {"text": "It's even larger than\nthe tower function.", "start": 2003.292, "duration": 1.708}, {"text": "So in literature, especially\naround the regularity lemma,", "start": 2009.49, "duration": 4.04}, {"text": "this function where you\niterate the tower function i", "start": 2013.53, "duration": 3.49}, {"text": "times is given the name wowzer.", "start": 2017.02, "duration": 2.853}, {"text": "[LAUGHTER] As in, wow,\nthis is a huge number.", "start": 2019.873, "duration": 7.407}, {"text": "So it's a step up in\nthe Ackerman hierarchy.", "start": 2027.28, "duration": 3.12}, {"text": "So if you repeat the\nwowzer function i times,", "start": 2030.4, "duration": 3.08}, {"text": "you move up one ladder\nin the Ackerman hierarchy", "start": 2033.48, "duration": 3.16}, {"text": "and this hierarchy of\nrapidly growing functions.", "start": 2036.64, "duration": 4.42}, {"text": "But in any case, it's bounded\nand that's good enough for us.", "start": 2041.06, "duration": 2.5}, {"text": "Any questions so far?", "start": 2050.695, "duration": 0.875}, {"text": "Yeah?", "start": 2056.38, "duration": 0.57}, {"text": "AUDIENCE: What do you\ncall like [INAUDIBLE]", "start": 2056.95, "duration": 2.907}, {"text": "YUFEI ZHAO: Yes, so\nquestion is, what do you", "start": 2059.857, "duration": 1.833}, {"text": "call wowzer iterated?", "start": 2061.69, "duration": 2.23}, {"text": "I'm not aware of a\nstandard name for that.", "start": 2063.92, "duration": 3.25}, {"text": "Actually, even the\nname wowzer somehow", "start": 2067.17, "duration": 1.81}, {"text": "is very common in the\ncombinatorics community,", "start": 2068.98, "duration": 3.159}, {"text": "but I think most people\noutside this community", "start": 2072.139, "duration": 2.06}, {"text": "will not recognize this word.", "start": 2074.199, "duration": 1.311}, {"text": "Any more questions?", "start": 2080.139, "duration": 2.25}, {"text": "So another way it's a step\nup in Ackerman hierarchy.", "start": 2082.389, "duration": 3.756}, {"text": "So it's enumerated one,\ntwo, three, four, you know,", "start": 2086.145, "duration": 2.125}, {"text": "if you keep going up.", "start": 2088.27, "duration": 0.9}, {"text": "All right.", "start": 2092.994, "duration": 3.346}, {"text": "Another remark about this\nstrong regularity lemma", "start": 2096.34, "duration": 4.95}, {"text": "is that it will be\nconvenient for us-- actually,", "start": 2101.29, "duration": 3.62}, {"text": "some are more essential compared\nto our previous applications--", "start": 2104.91, "duration": 3.04}, {"text": "to make the parts equitable.", "start": 2107.95, "duration": 1.962}, {"text": "So P and Q equitable.", "start": 2113.15, "duration": 5.56}, {"text": "And basically, the parts\nare such that all the--", "start": 2118.71, "duration": 3.465}, {"text": "the partitions are such that\nall the parts have basically", "start": 2122.175, "duration": 2.893}, {"text": "the same number of vertices.", "start": 2125.068, "duration": 1.167}, {"text": "So I won't make it\nprecise, but you can do it.", "start": 2126.235, "duration": 4.25}, {"text": "It's not too hard to do it.", "start": 2130.485, "duration": 1.125}, {"text": "And you can prove\nit similar to how", "start": 2131.61, "duration": 3.57}, {"text": "I described how to modify the\nproof of the regularity level.", "start": 2135.18, "duration": 3.85}, {"text": "So I won't belabor\nthat point, but we'll", "start": 2139.03, "duration": 2.21}, {"text": "use the equitable version.", "start": 2141.24, "duration": 1.23}, {"text": "All right, so how does one\nuse this regularity lemma?", "start": 2145.79, "duration": 4.97}, {"text": "Let me state a\ncorollary, and let", "start": 2150.76, "duration": 2.7}, {"text": "me call this a corollary\nstar because you actually", "start": 2153.46, "duration": 2.39}, {"text": "need to do some work\nto get it to follow", "start": 2155.85, "duration": 2.58}, {"text": "from the strong\nregularity lemma.", "start": 2158.43, "duration": 1.45}, {"text": "But the corollary is\nthe version that we", "start": 2159.88, "duration": 1.667}, {"text": "will apply that if you\nstart with a decreasing", "start": 2161.547, "duration": 4.873}, {"text": "sequence of this epsilon,\nthen there exists a delta such", "start": 2166.42, "duration": 10.795}, {"text": "that the following is true.", "start": 2177.215, "duration": 1.125}, {"text": "Every n vertex graph has an\nequitable vertex partition,", "start": 2182.65, "duration": 18.71}, {"text": "call it i through the\nk, and a subset Wi", "start": 2201.36, "duration": 10.17}, {"text": "of each Vi such that the\nfollowing properties hold.", "start": 2211.53, "duration": 8.05}, {"text": "First, all the W's\nare fairly large.", "start": 2219.58, "duration": 5.38}, {"text": "They're at least\nconstant proportion", "start": 2224.96, "duration": 2.11}, {"text": "of the total vertex set.", "start": 2227.07, "duration": 1.47}, {"text": "Between every pair of Wi Wj,\nit is epsilon sub k regular.", "start": 2233.04, "duration": 9.48}, {"text": "And this is the point\nI want to emphasize.", "start": 2250.89, "duration": 1.75}, {"text": "So here there are not you\nregular pairs anymore.", "start": 2252.64, "duration": 2.72}, {"text": "So it is every.", "start": 2255.36, "duration": 1.81}, {"text": "So no irregular pairs\nbetween the Wi's,", "start": 2261.274, "duration": 3.596}, {"text": "and also we need\nto include the case", "start": 2264.87, "duration": 3.87}, {"text": "when i equals the j, as well.", "start": 2268.74, "duration": 2.16}, {"text": "So each Wi is\nregular with itself.", "start": 2270.9, "duration": 2.595}, {"text": "And furthermore, the edge\ndensities between the V's are", "start": 2277.06, "duration": 8.79}, {"text": "similar to the edge densities\nbetween the corresponding W's.", "start": 2285.85, "duration": 5.97}, {"text": "And here it is for\nmost pairs for all", "start": 2291.82, "duration": 6.24}, {"text": "but at most epsilon\nk square pairs.", "start": 2298.06, "duration": 5.49}, {"text": "Epsilon 0, yeah.", "start": 2310.32, "duration": 1.425}, {"text": "At most epsilon 0.", "start": 2311.745, "duration": 1.115}, {"text": "Any questions about\nthe statement?", "start": 2320.66, "duration": 1.745}, {"text": "So let me show you\nhow you could deduce", "start": 2337.44, "duration": 3.51}, {"text": "the corollary from the\nstrong regularity lemma.", "start": 2340.95, "duration": 3.57}, {"text": "So first, let me\ndraw your picture.", "start": 2356.95, "duration": 1.77}, {"text": "So here you have a\nregularity partition.", "start": 2363.07, "duration": 3.276}, {"text": "And so these are your\nV's, and inside each V", "start": 2371.01, "duration": 7.145}, {"text": "I find a W such that\nif I look at the edge", "start": 2378.155, "duration": 12.185}, {"text": "sets between pairwise\nblue sets, including", "start": 2390.34, "duration": 3.01}, {"text": "the blue sets with themselves,\nit is always very regular.", "start": 2393.35, "duration": 5.6}, {"text": "And also, the edge densities\nbetween the blue sets", "start": 2398.95, "duration": 5.67}, {"text": "is mostly very\nsimilar to the edge", "start": 2404.62, "duration": 2.97}, {"text": "density between their\nambient white sets.", "start": 2407.59, "duration": 2.52}, {"text": "OK, so let me say a few words--", "start": 2420.04, "duration": 1.87}, {"text": "I won't go into\ntoo many details--", "start": 2421.91, "duration": 1.97}, {"text": "about how you might\ndeduce this corollary", "start": 2423.88, "duration": 2.4}, {"text": "from the strong\nregularity lemma.", "start": 2426.28, "duration": 2.19}, {"text": "So first let me\ndo something which", "start": 2431.28, "duration": 2.04}, {"text": "is slightly simpler, which\nis to not yet require", "start": 2433.32, "duration": 6.51}, {"text": "that the blue sets, Wi's,\nare regular with themselves.", "start": 2439.83, "duration": 4.496}, {"text": "So without requiring this\nas regular so we can obtain", "start": 2451.48, "duration": 8.15}, {"text": "the Wi's by picking\na uniform random part", "start": 2459.63, "duration": 14.03}, {"text": "of the final partition,\nQ, inside each part of P", "start": 2473.66, "duration": 14.21}, {"text": "in the strong regularity lemma.", "start": 2487.87, "duration": 1.77}, {"text": "So you have the strong\nregularity lemma,", "start": 2495.92, "duration": 1.92}, {"text": "which produces for you a\npair of partitions like that.", "start": 2497.84, "duration": 6.24}, {"text": "So it produces for you\na pair of partitions.", "start": 2504.08, "duration": 2.94}, {"text": "And what we will do is to pick\none of these guys as my W,", "start": 2507.02, "duration": 6.54}, {"text": "pick one of these\nguys at random,", "start": 2513.56, "duration": 1.488}, {"text": "and pick one of\nthose guys at random.", "start": 2515.048, "duration": 1.542}, {"text": "Because W is so extremely\nregular, most of these pairs", "start": 2520.73, "duration": 5.89}, {"text": "will be regular.", "start": 2526.62, "duration": 3.12}, {"text": "So with high\nprobability, you will not", "start": 2529.74, "duration": 3.87}, {"text": "encounter any\nirregular pairs if you", "start": 2533.61, "duration": 5.19}, {"text": "pick the W's randomly as parts\nof Q. So that's the key point.", "start": 2538.8, "duration": 6.77}, {"text": "Here we're using that\nQ is extremely regular.", "start": 2545.57, "duration": 3.27}, {"text": "So all the Wi Wj is\nregular for all i not equal", "start": 2560.93, "duration": 6.49}, {"text": "to j with high probability.", "start": 2567.42, "duration": 2.298}, {"text": "But the other thing that we\nwould like is that the edge", "start": 2573.55, "duration": 2.94}, {"text": "densities between the W's\nare similar to those between", "start": 2576.49, "duration": 4.32}, {"text": "the V's.", "start": 2580.81, "duration": 1.93}, {"text": "And for that, we will use this\ncondition about their energies", "start": 2582.74, "duration": 3.28}, {"text": "being very similar\nto each other.", "start": 2586.02, "duration": 1.53}, {"text": "So the third\nconsequence, C, is--", "start": 2590.65, "duration": 6.15}, {"text": "it's a consequence\nof the energy bound.", "start": 2596.8, "duration": 5.4}, {"text": "Because recall that in our proof\nof the Szemeredi regularity", "start": 2610.82, "duration": 3.69}, {"text": "lemma there was\nan interpretation", "start": 2614.51, "duration": 2.22}, {"text": "of the energy as\nthe second moment", "start": 2616.73, "duration": 7.13}, {"text": "of a certain random\nvariable which we called z.", "start": 2623.86, "duration": 3.48}, {"text": "And using that interpretation,\nI can write down", "start": 2631.64, "duration": 3.19}, {"text": "this expression like that.", "start": 2634.83, "duration": 5.49}, {"text": "We are here assuming\nfor simplicity", "start": 2640.32, "duration": 3.54}, {"text": "that Q is completely\nequitable, so all the parts", "start": 2643.86, "duration": 4.17}, {"text": "have exactly the same size.", "start": 2648.03, "duration": 1.62}, {"text": "Z of Q is defined to be the\nedge density between Vi and Vj", "start": 2649.65, "duration": 6.09}, {"text": "for random ij.", "start": 2655.74, "duration": 5.27}, {"text": "So this is a random variable z.", "start": 2661.01, "duration": 2.76}, {"text": "So you pick pair\nof parts uniformly,", "start": 2663.77, "duration": 4.64}, {"text": "or maybe with some weights\nif they're not exactly equal.", "start": 2668.41, "duration": 2.7}, {"text": "And you evaluate\nthe edge density.", "start": 2671.11, "duration": 3.37}, {"text": "So this energy difference\nis the difference", "start": 2674.48, "duration": 3.17}, {"text": "between the second moments.", "start": 2677.65, "duration": 1.68}, {"text": "And because Q is\na refinement of P,", "start": 2679.33, "duration": 7.38}, {"text": "it is the case that this\ndifference of L2 norms", "start": 2686.71, "duration": 9.16}, {"text": "is equal to the second\nmoment of the difference", "start": 2695.87, "duration": 4.99}, {"text": "of the random variables.", "start": 2700.86, "duration": 1.62}, {"text": "So we saw a version\nof this earlier", "start": 2702.48, "duration": 2.28}, {"text": "when we were discussing\nvariance in the context", "start": 2704.76, "duration": 3.15}, {"text": "of the proof of the\nsimilar irregularity lemma.", "start": 2707.91, "duration": 2.61}, {"text": "Here it's basically the same.", "start": 2710.52, "duration": 1.29}, {"text": "You can either look at this\ninequality part by part of V,", "start": 2711.81, "duration": 4.62}, {"text": "or if you like to be\na bit more abstract", "start": 2716.43, "duration": 4.62}, {"text": "then this is actually a\ncase of Pythagorean theorem.", "start": 2721.05, "duration": 3.12}, {"text": "If you view these as vectors\nin a certain vector space,", "start": 2729.91, "duration": 4.44}, {"text": "then you have some\northogonality.", "start": 2734.35, "duration": 1.75}, {"text": "So you have this sum\nof squares identity.", "start": 2736.1, "duration": 4.278}, {"text": "Where does part A come from?", "start": 2745.86, "duration": 1.932}, {"text": "So part A, we want the parts,\nthat Wi's to be not too small,", "start": 2747.792, "duration": 4.548}, {"text": "but that comes from a bound\non the number of parts of Q.", "start": 2752.34, "duration": 23.221}, {"text": "So so far this more or\nless proves the corollary", "start": 2775.561, "duration": 3.249}, {"text": "except for that we\nsimplified our lives", "start": 2778.81, "duration": 4.24}, {"text": "by requiring just that the i\nnot equal to j, the Vi Vj's are", "start": 2783.05, "duration": 6.63}, {"text": "regular.", "start": 2789.68, "duration": 1.42}, {"text": "But in the statement\nup there, we also want", "start": 2791.1, "duration": 2.7}, {"text": "the Vi's-- so the Wi's ice to\nbe regular with themselves,", "start": 2793.8, "duration": 3.85}, {"text": "which will be important\nfor application.", "start": 2797.65, "duration": 3.79}, {"text": "So I won't explain how to do\nthat, and part of the reason", "start": 2801.44, "duration": 4.23}, {"text": "is that this is also one\nof your homework problems.", "start": 2805.67, "duration": 3.5}, {"text": "So in one of the homework\nproblems problem set 3,", "start": 2809.17, "duration": 2.75}, {"text": "you were asked to prove\nthat every graph has", "start": 2811.92, "duration": 3.51}, {"text": "a subset of vertices that is of\nleast constant proportion such", "start": 2815.43, "duration": 5.67}, {"text": "that it is regular with itself.", "start": 2821.1, "duration": 3.78}, {"text": "And the methods\nyou use there will", "start": 2824.88, "duration": 1.89}, {"text": "be applicable to handle the\nsituation over here, as well.", "start": 2826.77, "duration": 5.44}, {"text": "So putting all of these\ningredients together,", "start": 2832.21, "duration": 2.82}, {"text": "we get the corollary whereby\nyou have this picture,", "start": 2835.03, "duration": 4.99}, {"text": "you have this partition.", "start": 2840.02, "duration": 1.59}, {"text": "I don't even require\nthe Vi's to be regular.", "start": 2841.61, "duration": 2.58}, {"text": "That doesn't matter anymore.", "start": 2844.19, "duration": 1.45}, {"text": "All that matters is that between\nthe Wi's they are very regular,", "start": 2845.64, "duration": 3.59}, {"text": "and that there are no irregular\nparts between these Wi's.", "start": 2849.23, "duration": 5.22}, {"text": "And now we'll be able to go back\nto the induced graph removal", "start": 2854.45, "duration": 7.16}, {"text": "lemma where previously we had\nan issue with the existence", "start": 2861.61, "duration": 5.31}, {"text": "of irregular pairs in the use of\nSzemeredi regularity partition,", "start": 2866.92, "duration": 4.96}, {"text": "and now we have a tool\nto get around that.", "start": 2871.88, "duration": 3.37}, {"text": "So next we will see how\nto execute this proof,", "start": 2875.25, "duration": 5.05}, {"text": "but at this point hopefully\nyou already see an outline.", "start": 2880.3, "duration": 3.54}, {"text": "Because you no longer need to\nworry about this thing here.", "start": 2883.84, "duration": 6.838}, {"text": "Let's take a quick break.", "start": 2890.678, "duration": 1.042}, {"text": "Any questions so far?", "start": 2894.76, "duration": 1.07}, {"text": "Yes?", "start": 2900.6, "duration": 0.88}, {"text": "AUDIENCE: Why are we\nable to [INAUDIBLE]", "start": 2901.48, "duration": 10.06}, {"text": "YUFEI ZHAO: OK, so\nthe question was,", "start": 2911.54, "duration": 1.5}, {"text": "there was a step where we were\nlooking at some expectations", "start": 2913.04, "duration": 4.13}, {"text": "of squares.", "start": 2917.17, "duration": 2.13}, {"text": "And so why was\nthat identity true?", "start": 2919.3, "duration": 4.37}, {"text": "So if you look back to the\nproof of Szemeredi's regularity", "start": 2923.67, "duration": 2.58}, {"text": "lemma, we already saw an\ninstance of that inequality", "start": 2926.25, "duration": 2.682}, {"text": "in the computation\nof the variance.", "start": 2928.932, "duration": 1.458}, {"text": "So you know that the\nvariance of x, on one", "start": 2937.86, "duration": 3.41}, {"text": "hand it is equal to where\nmu is the mean of x.", "start": 2941.27, "duration": 9.2}, {"text": "And on the other hand, it\nis equal to this quantity.", "start": 2950.47, "duration": 5.2}, {"text": "So you agree with this formula?", "start": 2960.41, "duration": 2.95}, {"text": "And you can expand it to\nprove it, and the thing that--", "start": 2963.36, "duration": 5.0}, {"text": "the question that you\nraised basically you", "start": 2968.36, "duration": 2.63}, {"text": "can prove by looking at\nthis formula part by part.", "start": 2970.99, "duration": 3.69}, {"text": "Any more questions?", "start": 2979.25, "duration": 1.352}, {"text": "So let's now prove the\ninduced graph removal lemma.", "start": 2989.76, "duration": 4.59}, {"text": "And we'll follow the\nregularity partition,", "start": 2994.35, "duration": 2.76}, {"text": "but with a small\ntwist that Instead", "start": 2997.11, "duration": 2.4}, {"text": "of using Szemeredi's\nregularity lemma,", "start": 2999.51, "duration": 2.34}, {"text": "we will use that\ncorollary up there.", "start": 3001.85, "duration": 1.89}, {"text": "So let's prove the induced\ngraph removal lemma.", "start": 3011.56, "duration": 3.32}, {"text": "So the three steps.", "start": 3020.82, "duration": 0.98}, {"text": "First, we do partition.", "start": 3021.8, "duration": 1.651}, {"text": "So let's suppose you have a--", "start": 3030.05, "duration": 3.32}, {"text": "so we suppose g is like above.", "start": 3036.85, "duration": 2.25}, {"text": "You have very few\ninduced copies of H.", "start": 3039.1, "duration": 6.1}, {"text": "Let's apply the corollary to get\na partition of the vertex set", "start": 3045.2, "duration": 5.97}, {"text": "of g into k parts.", "start": 3051.17, "duration": 6.49}, {"text": "And inside each part\nI have a W. Satisfying", "start": 3057.66, "duration": 7.03}, {"text": "the following properties\nthat each Wi Wj", "start": 3064.69, "duration": 7.26}, {"text": "is regular with the\nfollowing parameter which", "start": 3071.95, "duration": 6.567}, {"text": "will come out of later when we\nneed to use the counting lemma.", "start": 3078.517, "duration": 2.583}, {"text": "But it's some number, but\ndon't worry too much about it.", "start": 3081.1, "duration": 2.64}, {"text": "So here I'm going to--", "start": 3087.05, "duration": 3.26}, {"text": "so let's say H has\nlittle H vertices.", "start": 3090.31, "duration": 5.375}, {"text": "So between Wi Wj\nit is this regular.", "start": 3105.405, "duration": 2.655}, {"text": "So we actually have not\nyet used the full strength", "start": 3108.06, "duration": 2.67}, {"text": "of the corollary where I can\nmake the regularity even depend", "start": 3110.73, "duration": 8.01}, {"text": "on k.", "start": 3118.74, "duration": 0.78}, {"text": "So we will not need\nthat here, but we'll", "start": 3119.52, "duration": 2.13}, {"text": "need it in a later application.", "start": 3121.65, "duration": 2.44}, {"text": "So the exponent is little H.", "start": 3124.09, "duration": 7.03}, {"text": "OK, so other properties are that\nthe densities between the Vi's", "start": 3131.12, "duration": 7.77}, {"text": "and the Wi's do not differ\nby more than epsilon over 2", "start": 3138.89, "duration": 10.02}, {"text": "for all but a small fraction--", "start": 3148.91, "duration": 4.79}, {"text": "so epsilon k squared over 2--", "start": 3153.7, "duration": 2.78}, {"text": "pairs.", "start": 3156.48, "duration": 0.5}, {"text": "And finally, the sizes of the\nWi's are at least delta 0 times", "start": 3165.15, "duration": 7.86}, {"text": "n where delta 0 depends\nonly on epsilon.", "start": 3173.01, "duration": 4.0}, {"text": "Epsilon and H.", "start": 3184.31, "duration": 3.29}, {"text": "This is the partition step,\nso now let's do the cleaning.", "start": 3201.21, "duration": 4.11}, {"text": "In the cleaning step,\nbasically we're not going to--", "start": 3208.21, "duration": 6.62}, {"text": "I mean, there is no longer an\nissue of irregular pairs if we", "start": 3214.83, "duration": 2.79}, {"text": "only look at the Wi's.", "start": 3217.62, "duration": 2.48}, {"text": "So we just need to think\nabout the low density pairs", "start": 3220.1, "duration": 3.46}, {"text": "or whatever the\ncorresponding analog is.", "start": 3223.56, "duration": 3.15}, {"text": "And what happens here is\nthat for every i less than j,", "start": 3226.71, "duration": 5.49}, {"text": "and crucially including\nwhen i equals to j,", "start": 3232.2, "duration": 5.59}, {"text": "if the edge densities\nbetween the W's is too small", "start": 3237.79, "duration": 8.54}, {"text": "then we remove all\nedges between Vi and Vj.", "start": 3246.33, "duration": 12.46}, {"text": "And if the edge density\nbetween the Wi's is too big,", "start": 3263.07, "duration": 8.74}, {"text": "then we remove all edges.", "start": 3271.81, "duration": 3.585}, {"text": "So we add all edges\nbetween Vi and Vj.", "start": 3278.28, "duration": 3.28}, {"text": "How many edges do we end\nup adding or removing?", "start": 3300.9, "duration": 2.07}, {"text": "So the total number of edges\nadded or removed from g is--", "start": 3306.56, "duration": 14.9}, {"text": "in this case, so if\nthe edges density", "start": 3321.46, "duration": 5.22}, {"text": "in g between the Vi's and\nVj's is also very small,", "start": 3326.68, "duration": 5.48}, {"text": "then you do not remove\nvery many edges.", "start": 3332.16, "duration": 3.95}, {"text": "But most pairs of Vi and\nVj have that property.", "start": 3336.11, "duration": 5.08}, {"text": "So you tidy up\nwhat kind of errors", "start": 3341.19, "duration": 2.46}, {"text": "you can get from here\nand there, and you", "start": 3343.65, "duration": 4.49}, {"text": "find that the total number of\nedges that are added or removed", "start": 3348.14, "duration": 3.75}, {"text": "from g is less than, let's\nsay, epsilon n squared.", "start": 3351.89, "duration": 7.26}, {"text": "Maybe even get an\nextra factor of 2,", "start": 3359.15, "duration": 1.68}, {"text": "but you know, upon changing\nsome constant factors,", "start": 3360.83, "duration": 3.48}, {"text": "it's less than\nepsilon n squared.", "start": 3364.31, "duration": 3.87}, {"text": "So this is some small\ndetails you can work out.", "start": 3368.18, "duration": 5.29}, {"text": "Here we're using--\nasking, how is", "start": 3373.47, "duration": 2.31}, {"text": "the density between Vi and\nVj related to Wi and Wj?", "start": 3375.78, "duration": 3.63}, {"text": "Well, for most pairs of i\nand j they're very similar.", "start": 3379.41, "duration": 4.13}, {"text": "And there's a small fraction\nof them that are not similar,", "start": 3383.54, "duration": 2.64}, {"text": "but then you lump everything\nin to this bound over here.", "start": 3386.18, "duration": 6.13}, {"text": "So maybe I need to--", "start": 3400.29, "duration": 2.922}, {"text": "let me just put a 2\nhere just to be safe.", "start": 3403.212, "duration": 1.708}, {"text": "All right.", "start": 3408.69, "duration": 2.09}, {"text": "So we deleted a very\nsmall number of edges,", "start": 3410.78, "duration": 4.81}, {"text": "and now we want to show\nthat the graph that", "start": 3415.59, "duration": 2.16}, {"text": "has resulted from\nthis modification", "start": 3417.75, "duration": 3.99}, {"text": "does not have any\ninduced H sub-graphs.", "start": 3421.74, "duration": 3.51}, {"text": "And the final step\nis the counting step.", "start": 3431.48, "duration": 3.63}, {"text": "So suppose there\nwere any induced", "start": 3435.11, "duration": 5.85}, {"text": "H left after the modification.", "start": 3440.96, "duration": 5.9}, {"text": "So I want to show that, in fact,\nthere must be a lot of H's--", "start": 3446.86, "duration": 3.16}, {"text": "induced H's originally\nin the graph,", "start": 3450.02, "duration": 2.14}, {"text": "thereby contradicting\nthe hypothesis.", "start": 3452.16, "duration": 2.176}, {"text": "So where does this\ninduced H sit?", "start": 3461.69, "duration": 3.52}, {"text": "Well, you have the V's,\nand inside the V's you have", "start": 3465.21, "duration": 9.86}, {"text": "the W's.", "start": 3475.07, "duration": 0.5}, {"text": "So suppose my H is that\ngraph for illustration.", "start": 3484.17, "duration": 9.03}, {"text": "And in particular,\nI have a non-edge.", "start": 3493.2, "duration": 3.57}, {"text": "So I have an edge, and\nI also have a non-edge.", "start": 3496.77, "duration": 3.6}, {"text": "So between these two,\nthat's the non-edge.", "start": 3500.37, "duration": 2.525}, {"text": "So suppose you find a copy\nof H in the cleaned-up graph.", "start": 3507.95, "duration": 6.64}, {"text": "Where can that cleaned up--", "start": 3514.59, "duration": 1.52}, {"text": "this copy of H sit?", "start": 3516.11, "duration": 1.83}, {"text": "Suppose you find it here.", "start": 3517.94, "duration": 1.85}, {"text": "The claim now is that if this\ncopy of H existed here, then", "start": 3523.44, "duration": 8.69}, {"text": "I must be able to find\nmany such copies of H", "start": 3532.13, "duration": 4.92}, {"text": "in the corresponding\nyellow parts.", "start": 3537.05, "duration": 2.04}, {"text": "Because between the yellow\nparts you have regularity,", "start": 3541.94, "duration": 8.11}, {"text": "and you also have the\nright kinds of densities.", "start": 3550.05, "duration": 5.4}, {"text": "Because if they didn't have\nthe right kind of density,", "start": 3555.45, "duration": 2.26}, {"text": "we would have cleaned\nit up already.", "start": 3557.71, "duration": 1.5}, {"text": "So that's the ideal.", "start": 3562.9, "duration": 3.1}, {"text": "If you had a copy\nof this H somewhere,", "start": 3566.0, "duration": 3.72}, {"text": "then I zoom into\nthe yellow parts,", "start": 3569.72, "duration": 2.1}, {"text": "zoom into these W's, and I find\nlots of copies of H in between", "start": 3571.82, "duration": 5.34}, {"text": "the W's.", "start": 3577.16, "duration": 2.27}, {"text": "So suppose-- let\nme write this down.", "start": 3579.43, "duration": 1.5}, {"text": "So suppose the little V's, so\nthe vertices, lies in the--", "start": 3580.93, "duration": 16.76}, {"text": "so I'm just indexing\nwhere a little v lies.", "start": 3597.69, "duration": 2.85}, {"text": "The little v lies\nin big V sub phi", "start": 3600.54, "duration": 2.685}, {"text": "V for some phi which since the\nvertices of H2 went through k.", "start": 3603.225, "duration": 11.375}, {"text": "So now we apply counting lemma\nto embed induced copies of H", "start": 3614.6, "duration": 20.05}, {"text": "in g where the vertex\nV in H is mapped", "start": 3634.65, "duration": 11.06}, {"text": "to a vertex in the\ncorresponding W.", "start": 3645.71, "duration": 8.745}, {"text": "And we would like to know that\nthere are lots of such copies.", "start": 3660.63, "duration": 4.81}, {"text": "And the counting Lemma--", "start": 3665.44, "duration": 1.22}, {"text": "or rather, some variant, but I\nshould read the counting lemma", "start": 3666.66, "duration": 5.07}, {"text": "that we did last time and view\nit as a multi-partite version.", "start": 3671.73, "duration": 5.21}, {"text": "Apply this so far part to part.", "start": 3676.94, "duration": 4.5}, {"text": "So we find that the number\nof such induced copies", "start": 3681.44, "duration": 8.9}, {"text": "is within a small error.", "start": 3690.34, "duration": 1.84}, {"text": "So that regularity parameter\nmultiplied by the number", "start": 3696.63, "duration": 11.07}, {"text": "of edges of H, which we\nalready canceled out,", "start": 3707.7, "duration": 3.99}, {"text": "multiplied by the\nproduct of these Wi's.", "start": 3711.69, "duration": 9.325}, {"text": "So it's within\nthis error of what", "start": 3724.49, "duration": 4.17}, {"text": "you would suspect if you\nnaively multiply the edge", "start": 3728.66, "duration": 4.59}, {"text": "densities together along\nwith the vertex densities.", "start": 3733.25, "duration": 3.703}, {"text": "So these factors are for the\nedges that you want to embed,", "start": 3749.28, "duration": 6.51}, {"text": "and then I also need to\nmultiply the densities", "start": 3755.79, "duration": 3.67}, {"text": "for the long edges.", "start": 3759.46, "duration": 1.05}, {"text": "So 1 minus these edge densities.", "start": 3771.378, "duration": 3.164}, {"text": "So one way you can think\nof it is just consider", "start": 3774.542, "duration": 1.958}, {"text": "the complement in g.", "start": 3776.5, "duration": 2.01}, {"text": "So consider the complement of\ng to get this version here.", "start": 3778.51, "duration": 3.99}, {"text": "And then finally, the product\nof the vertex set sizes.", "start": 3782.5, "duration": 3.74}, {"text": "And the point is that this\nis not a small number.", "start": 3798.0, "duration": 4.5}, {"text": "So hence the number of\ninduced copies of H in g", "start": 3802.5, "duration": 13.37}, {"text": "is at least on the order of--", "start": 3815.87, "duration": 5.58}, {"text": "well, OK?", "start": 3821.45, "duration": 0.92}, {"text": "So it's at least some\nnumber, which is basically", "start": 3824.91, "duration": 5.68}, {"text": "this guy over here.", "start": 3830.59, "duration": 1.29}, {"text": "So epsilon over 4 raised to--", "start": 3831.88, "duration": 3.94}, {"text": "all of these are constants,\nso that's the point.", "start": 3835.82, "duration": 2.0}, {"text": "All of these guys are\nconstants, minus--", "start": 3837.82, "duration": 1.92}, {"text": "so here is the main term,\nand then the error term.", "start": 3845.05, "duration": 3.053}, {"text": "And then the product of\nthese vertex set sizes,", "start": 3853.79, "duration": 3.42}, {"text": "and we saw that each vertex\nset is not too small.", "start": 3857.21, "duration": 2.47}, {"text": "So you have lots of\ninduced copies of H in g.", "start": 3865.84, "duration": 4.195}, {"text": "Yep?", "start": 3870.035, "duration": 1.395}, {"text": "AUDIENCE: How do you\ndo in the case where", "start": 3871.43, "duration": 3.17}, {"text": "the density between [INAUDIBLE]", "start": 3874.6, "duration": 10.14}, {"text": "YUFEI ZHAO: OK, so can\nyou repeat your question?", "start": 3884.74, "duration": 2.62}, {"text": "AUDIENCE: How are you\ndealing with the [INAUDIBLE]", "start": 3887.36, "duration": 5.685}, {"text": "YUFEI ZHAO: OK.", "start": 3893.045, "duration": 0.625}, {"text": "So question, how do we deal\nwith the all but epsilon", "start": 3893.67, "duration": 2.19}, {"text": "over two pairs?", "start": 3895.86, "duration": 1.22}, {"text": "So that comes up in\nthe cleaning step", "start": 3897.08, "duration": 2.295}, {"text": "in what I wrote\nin red in dealing", "start": 3899.375, "duration": 2.385}, {"text": "with the number of total edges\nthat are added or removed.", "start": 3901.76, "duration": 6.02}, {"text": "So think about how many\nedges are added or removed.", "start": 3907.78, "duration": 2.55}, {"text": "In these non-exceptional pairs,\nthe number of edges that are", "start": 3910.33, "duration": 5.11}, {"text": "added or removed--", "start": 3915.44, "duration": 0.87}, {"text": "let's just think\nabout added edges.", "start": 3926.47, "duration": 2.2}, {"text": "So if the density of V is\ncontrolled by that of W,", "start": 3928.67, "duration": 17.26}, {"text": "then the number of edges added--", "start": 3945.93, "duration": 2.98}, {"text": "or removed, in that case--", "start": 3948.91, "duration": 1.82}, {"text": "from all such pairs along with--", "start": 3950.73, "duration": 5.5}, {"text": "yeah.", "start": 3956.23, "duration": 0.5}, {"text": "So you have epsilon n\nsquared edges changed.", "start": 3956.73, "duration": 4.68}, {"text": "On the other hand, if this is\nnot true then you only have", "start": 3966.54, "duration": 11.24}, {"text": "epsilon k squared such pairs ij\nfor which this cannot be true.", "start": 3977.78, "duration": 5.22}, {"text": "So you also only have at\nmost epsilon n squared edges", "start": 3983.0, "duration": 3.38}, {"text": "added or removed in such cases.", "start": 3986.38, "duration": 3.47}, {"text": "That answers your question?", "start": 3989.85, "duration": 2.792}, {"text": "Yes?", "start": 3992.642, "duration": 1.265}, {"text": "AUDIENCE: Is that number 0?", "start": 3993.907, "duration": 1.125}, {"text": "YUFEI ZHAO: Is which number 0?", "start": 3997.755, "duration": 1.869}, {"text": "AUDIENCE: The number of induced\nedges for the [INAUDIBLE]", "start": 3999.624, "duration": 5.696}, {"text": "YUFEI ZHAO: The--", "start": 4005.32, "duration": 1.2}, {"text": "AUDIENCE: Yeah, the top board.", "start": 4006.52, "duration": 1.431}, {"text": "YUFEI ZHAO: Top board?", "start": 4007.951, "duration": 0.917}, {"text": "Good.", "start": 4018.84, "duration": 0.56}, {"text": "So asking about this number.", "start": 4019.4, "duration": 2.295}, {"text": "So that should have been 2.", "start": 4021.695, "duration": 1.125}, {"text": "Yes?", "start": 4028.58, "duration": 1.44}, {"text": "AUDIENCE: I don't\nsee k anywhere.", "start": 4030.02, "duration": 2.153}, {"text": "YUFEI ZHAO: OK, so question, you\ndon't see k appearing anywhere.", "start": 4032.173, "duration": 2.667}, {"text": "So the k in the\ncorollary, do you mean?", "start": 4034.84, "duration": 2.053}, {"text": "AUDIENCE: Yeah.", "start": 4036.893, "duration": 0.927}, {"text": "YUFEI ZHAO: So that\nhasn't come up yet.", "start": 4037.82, "duration": 1.71}, {"text": "So it comes up implicitly\nbecause we need to lower bound", "start": 4039.53, "duration": 4.65}, {"text": "the sizes of these W's.", "start": 4044.18, "duration": 2.535}, {"text": "So this is partly why we need\na bound on the number of parts,", "start": 4051.82, "duration": 3.06}, {"text": "but it is true that we do\nnot need epsilon k to depend", "start": 4054.88, "duration": 3.27}, {"text": "on k in this application yet.", "start": 4058.15, "duration": 1.71}, {"text": "I will mention a different\napplication in the second", "start": 4059.86, "duration": 2.28}, {"text": "where you do need that k.", "start": 4062.14, "duration": 1.09}, {"text": "OK, so the number of induced H\nin g is at least this amount.", "start": 4068.81, "duration": 4.11}, {"text": "And that's a small lie.", "start": 4072.92, "duration": 1.16}, {"text": "You need to maybe consider this\nis the number of homomorphic.", "start": 4074.08, "duration": 5.7}, {"text": "Well, actually, no, we're OK.", "start": 4079.78, "duration": 1.95}, {"text": "Never mind.", "start": 4081.73, "duration": 0.784}, {"text": "So you can set delta to\nbe this quantity here,", "start": 4091.12, "duration": 8.489}, {"text": "and then that\nfinishes the proof.", "start": 4099.609, "duration": 1.601}, {"text": "So you have lots of\ninduced copies of H", "start": 4101.21, "duration": 2.29}, {"text": "in your graph which\ncontradicts the hypothesis.", "start": 4103.5, "duration": 4.265}, {"text": "So that finishes the proof\nof the induced removal lemma,", "start": 4107.765, "duration": 2.835}, {"text": "and basically the proof is\nthe same as the usual graph", "start": 4110.6, "duration": 3.509}, {"text": "removal lemma except\nthat now we need", "start": 4114.109, "duration": 2.401}, {"text": "some strengthened\nregularity lemma which", "start": 4116.51, "duration": 3.75}, {"text": "allows us to get rid\nof irregular parts", "start": 4120.26, "duration": 3.03}, {"text": "but in a more\nrestricted setting.", "start": 4123.29, "duration": 1.6}, {"text": "Because we saw you cannot\ncompletely get rid of irregular", "start": 4124.89, "duration": 2.839}, {"text": "parts.", "start": 4127.729, "duration": 0.5}, {"text": "Any questions?", "start": 4131.72, "duration": 0.78}, {"text": "Yes?", "start": 4136.109, "duration": 0.74}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4136.849, "duration": 4.624}, {"text": "YUFEI ZHAO: So I want to\naddress the question of why", "start": 4141.473, "duration": 2.167}, {"text": "did I state this\ncorollary in this more", "start": 4143.64, "duration": 2.31}, {"text": "general form of a decreasing\nsequence of epsilons?", "start": 4145.95, "duration": 3.57}, {"text": "So first of all, with\nstrong regularity lemmas,", "start": 4149.52, "duration": 2.25}, {"text": "the strength is sometimes\nalways nice to--", "start": 4151.77, "duration": 3.419}, {"text": "it's always nice to state\nit with this extra strength.", "start": 4155.189, "duration": 2.25}, {"text": "Because it's the\nright way to think", "start": 4157.439, "duration": 2.641}, {"text": "about these types of theorems.", "start": 4160.08, "duration": 2.69}, {"text": "That the regularity\non the parts depends--", "start": 4162.77, "duration": 2.56}, {"text": "you can make it depend\non the number of parts", "start": 4165.33, "duration": 3.449}, {"text": "so that you get much stronger\ncontrol on the regularity.", "start": 4168.779, "duration": 3.391}, {"text": "But there are also\nsome applications.", "start": 4172.17, "duration": 1.57}, {"text": "For example, whether\nI will state next,", "start": 4173.74, "duration": 3.23}, {"text": "an application where you do\nneed that kind of strength.", "start": 4176.97, "duration": 3.24}, {"text": "So here's what's known as\nthe infinite removal lemma.", "start": 4180.21, "duration": 3.689}, {"text": "Here we have not\njust a single pattern", "start": 4187.26, "duration": 2.429}, {"text": "or a finite number of patterns\nwe want to get rid of.", "start": 4189.689, "duration": 2.971}, {"text": "For now we have\ninfinitely many patterns.", "start": 4192.66, "duration": 2.67}, {"text": "So for every curly H, which\nis a possibly infinite set", "start": 4195.33, "duration": 13.55}, {"text": "of graphs.", "start": 4208.88, "duration": 2.16}, {"text": "The graphs themselves\nare always finite,", "start": 4211.04, "duration": 2.05}, {"text": "but this may be\nan infinite list.", "start": 4213.09, "duration": 2.39}, {"text": "And an epsilon parameter.", "start": 4215.48, "duration": 4.35}, {"text": "There exists an H0 and a\ndelta positive parameter", "start": 4219.83, "duration": 6.52}, {"text": "such that every n vertex\ngraph with at most delta--", "start": 4226.35, "duration": 11.88}, {"text": "so less than delta--", "start": 4238.23, "duration": 2.95}, {"text": "V to the H induced\ncopies of H for every H", "start": 4241.18, "duration": 11.4}, {"text": "in this family with\nfewer than H0 vertices.", "start": 4252.58, "duration": 7.625}, {"text": "So every graph\nwith this property", "start": 4263.67, "duration": 4.0}, {"text": "can be made curly H free.", "start": 4267.67, "duration": 7.24}, {"text": "So it means free of--", "start": 4274.91, "duration": 2.67}, {"text": "induced curly H free by\nadding or removing fewer", "start": 4277.58, "duration": 14.81}, {"text": "than epsilon n squared edges.", "start": 4292.39, "duration": 1.99}, {"text": "So now instead of\na single pattern", "start": 4298.23, "duration": 1.43}, {"text": "you have a possibly infinite\nset of induced patterns and a", "start": 4299.66, "duration": 3.71}, {"text": "want to make your\ngraph curly H free--", "start": 4303.37, "duration": 6.33}, {"text": "induced curly H free.", "start": 4309.7, "duration": 2.23}, {"text": "And the theorem is\nthat if there exists", "start": 4311.93, "duration": 3.98}, {"text": "some finite bound, H0, such\nthat if you have few copies--", "start": 4315.91, "duration": 7.41}, {"text": "so for all the patterns\nup to that point--", "start": 4323.32, "duration": 3.14}, {"text": "then you can do\nwhat you need to do.", "start": 4326.46, "duration": 1.59}, {"text": "So take some time to even\ndigest this statement,", "start": 4331.05, "duration": 2.34}, {"text": "but it's somehow infinite\nversions-- the correct infinite", "start": 4333.39, "duration": 2.61}, {"text": "version of the\nremoval lemma if you", "start": 4336.0, "duration": 2.22}, {"text": "have infinitely many patterns\nthat you need to remove.", "start": 4338.22, "duration": 3.127}, {"text": "And I claim that the\nproof is actually", "start": 4341.347, "duration": 1.583}, {"text": "more or less the same proof\nas the one that we did here,", "start": 4342.93, "duration": 2.71}, {"text": "except now you need\nto take your epsilon", "start": 4345.64, "duration": 2.12}, {"text": "case, as in this\ncorollary, to depend on k.", "start": 4347.76, "duration": 4.14}, {"text": "You need to in some way look\nahead in this infinite pattern.", "start": 4351.9, "duration": 4.77}, {"text": "So here in proof, this epsilon\nk from corollary depends on k.", "start": 4356.67, "duration": 13.49}, {"text": "And also it depends on\nyour family of patterns H.", "start": 4370.16, "duration": 12.63}, {"text": "Finally, I want to\nmention a perspective--", "start": 4382.79, "duration": 2.55}, {"text": "a computer science\nperspective on these removal", "start": 4385.34, "duration": 3.682}, {"text": "lemmas that we've been\ndiscussing so far.", "start": 4389.022, "duration": 1.708}, {"text": "And that's in the\ncontext of something", "start": 4394.75, "duration": 1.76}, {"text": "called property testing.", "start": 4396.51, "duration": 1.08}, {"text": "And basically, we would\nlike an efficient--", "start": 4417.83, "duration": 5.52}, {"text": "efficient meaning fast--\nrandomized algorithm", "start": 4423.35, "duration": 8.55}, {"text": "to distinguish graphs that\nare triangle-free from those", "start": 4431.9, "duration": 19.92}, {"text": "that are epsilon far\nfrom triangle-free.", "start": 4451.82, "duration": 3.927}, {"text": "Where being epsilon far\nfrom triangle-free means", "start": 4459.33, "duration": 3.04}, {"text": "that you need to change more\nthan epsilon n squared edges", "start": 4462.37, "duration": 10.19}, {"text": "here. n is, as usual, the number\nof vertices to make the graph", "start": 4472.56, "duration": 12.75}, {"text": "triangle-free.", "start": 4485.31, "duration": 0.63}, {"text": "So the distance, the\n[INAUDIBLE] distance", "start": 4485.94, "duration": 2.1}, {"text": "is more than epsilon away\nfrom being triangle-free.", "start": 4488.04, "duration": 4.71}, {"text": "So somebody gives you\na very large graphing.", "start": 4492.75, "duration": 2.7}, {"text": "n is very large.", "start": 4495.45, "duration": 1.38}, {"text": "You cannot search through\nevery triple vertices.", "start": 4496.83, "duration": 3.57}, {"text": "That's too expensive.", "start": 4500.4, "duration": 1.2}, {"text": "But you want some way to test\nif a graph is triangle-free", "start": 4501.6, "duration": 4.68}, {"text": "versus very far away\nfrom being triangle-free.", "start": 4506.28, "duration": 3.271}, {"text": "So there's a very simple\nrandomized algorithm", "start": 4514.27, "duration": 2.4}, {"text": "to do this, which is\nto just try randomly", "start": 4516.67, "duration": 7.33}, {"text": "sample a random\ntriple of vertices", "start": 4524.0, "duration": 6.85}, {"text": "and check if it's a triangle.", "start": 4530.85, "duration": 2.24}, {"text": "So you do this.", "start": 4541.86, "duration": 1.85}, {"text": "And just to make our\nlife a bit more secure,", "start": 4543.71, "duration": 5.62}, {"text": "let's try it some\nlarger number of times.", "start": 4549.33, "duration": 3.99}, {"text": "So some c of epsilon some\nconstant number of times.", "start": 4553.32, "duration": 5.84}, {"text": "And if you find a triangle--", "start": 4559.16, "duration": 3.73}, {"text": "so if you don't find\na triangle, then we", "start": 4562.89, "duration": 5.88}, {"text": "return that it's triangle-free.", "start": 4568.77, "duration": 5.314}, {"text": "Otherwise we return that it is\nepsilon far from triangle-free.", "start": 4578.35, "duration": 5.094}, {"text": "So that's the algorithm.", "start": 4591.98, "duration": 1.316}, {"text": "So it's a very\nintuitive algorithm,", "start": 4596.56, "duration": 2.91}, {"text": "but why does it work?", "start": 4599.47, "duration": 2.71}, {"text": "So we want to know that,\nindeed, somebody gives you", "start": 4602.18, "duration": 2.87}, {"text": "one of these two possibilities.", "start": 4605.05, "duration": 1.32}, {"text": "You run that algorithm, you can\nsucceed with high probability.", "start": 4606.37, "duration": 3.97}, {"text": "Question?", "start": 4610.34, "duration": 1.204}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4611.544, "duration": 2.836}, {"text": "YUFEI ZHAO: So let's talk\nabout why this works.", "start": 4614.38, "duration": 4.12}, {"text": "So theorem, for\nevery epsilon, there", "start": 4618.5, "duration": 3.84}, {"text": "exists a c such that\nalgorithm succeeds", "start": 4622.34, "duration": 5.984}, {"text": "with probability bigger than\n2/3, and 2/3 can be any number.", "start": 4628.324, "duration": 9.436}, {"text": "So any number that you\nlike because you can always", "start": 4637.76, "duration": 2.24}, {"text": "repeat it to boost that\nconstant probability.", "start": 4640.0, "duration": 2.901}, {"text": "So there are two cases.", "start": 4646.2, "duration": 2.12}, {"text": "If g is triangle-free,\nthen it always succeeds.", "start": 4648.32, "duration": 6.75}, {"text": "You'll never find\nthis triangle, and it", "start": 4655.07, "duration": 1.65}, {"text": "would return triangle-free.", "start": 4656.72, "duration": 1.715}, {"text": "On the other hand, if g is\nepsilon far from triangle-free,", "start": 4664.26, "duration": 11.08}, {"text": "then triangle removal\nlemma tells us", "start": 4675.34, "duration": 4.89}, {"text": "that g has lots of triangles.", "start": 4680.23, "duration": 3.683}, {"text": "Delta n cubed triangles.", "start": 4687.23, "duration": 1.62}, {"text": "So if we sample c being, let's\nsay, 1 over delta times--", "start": 4692.1, "duration": 11.61}, {"text": "delta here is a function of\nepsilon from the triangle", "start": 4703.71, "duration": 3.06}, {"text": "removal lemma.", "start": 4706.77, "duration": 1.87}, {"text": "So we find that the probability\nthat the algorithm fails", "start": 4708.64, "duration": 6.32}, {"text": "is at most--", "start": 4714.96, "duration": 1.83}, {"text": "so you have a lot of triangles.", "start": 4731.71, "duration": 2.11}, {"text": "So very likely you will\nhit one of these triangles.", "start": 4733.82, "duration": 2.76}, {"text": "So the probability that the\nalgorithm fails is at most 1", "start": 4736.58, "duration": 3.44}, {"text": "minus delta n cubed divided\nby total number of triples", "start": 4740.02, "duration": 5.76}, {"text": "raised to 1 over delta.", "start": 4745.78, "duration": 2.46}, {"text": "And this is 1 minus at\nmost 1 minus 6 delta raised", "start": 4748.24, "duration": 4.85}, {"text": "to 1 over delta, and it's\nat most e to the minus 6.", "start": 4753.09, "duration": 4.81}, {"text": "So less than 1/3 in particular.", "start": 4757.9, "duration": 3.99}, {"text": "So this algorithm succeeds\nwith high probability.", "start": 4761.89, "duration": 3.15}, {"text": "Now, how big of a c do you need?", "start": 4765.04, "duration": 1.81}, {"text": "Well, that depends on the\ntriangle removal lemma.", "start": 4766.85, "duration": 3.24}, {"text": "So it's a constant.", "start": 4770.09, "duration": 2.2}, {"text": "So it's a constant,\ndoes not depend", "start": 4772.29, "duration": 2.12}, {"text": "on the size of the graph.", "start": 4774.41, "duration": 3.11}, {"text": "But it's a large\nconstant, because we", "start": 4777.52, "duration": 1.84}, {"text": "saw in the proof\nof regularity lemma", "start": 4779.36, "duration": 2.2}, {"text": "that it can be very large.", "start": 4781.56, "duration": 1.13}, {"text": "But you know, this\ntheorem here is basically", "start": 4786.8, "duration": 2.7}, {"text": "the same as a triangle\nremoval lemma.", "start": 4789.5, "duration": 3.73}, {"text": "So it's highly\nnon-trivial if it's true.", "start": 4793.23, "duration": 2.4}, {"text": "Even though the algorithm is\nextremely naive and simple.", "start": 4795.63, "duration": 3.84}, {"text": "I just want to finish\noff with one more thing.", "start": 4799.47, "duration": 1.95}, {"text": "Instead of testing\nfor triangle-freeness,", "start": 4801.42, "duration": 1.8}, {"text": "you can ask what other\nproperties can you test?", "start": 4803.22, "duration": 2.88}, {"text": "So which graph\nproperties are testable", "start": 4806.1, "duration": 6.49}, {"text": "in default in that sense?", "start": 4812.59, "duration": 1.18}, {"text": "So distinguishing\nsomething which", "start": 4816.95, "duration": 2.09}, {"text": "has the property, so P versus\nepsilon far from this property", "start": 4819.04, "duration": 8.03}, {"text": "P.", "start": 4827.07, "duration": 5.05}, {"text": "And you have this\ntester which is you", "start": 4832.12, "duration": 1.94}, {"text": "sample some number of vertices.", "start": 4834.06, "duration": 2.96}, {"text": "So this is called\nthe oblivious tester.", "start": 4837.02, "duration": 1.78}, {"text": "So you sample k\nvertices, and you try", "start": 4842.12, "duration": 6.64}, {"text": "to see if it has that property.", "start": 4848.76, "duration": 3.95}, {"text": "So there's a class of\nproperties called hereditary.", "start": 4852.71, "duration": 3.927}, {"text": "So hereditary properties\nare properties", "start": 4860.05, "duration": 2.51}, {"text": "that are closed under\nvertex deletion.", "start": 4862.56, "duration": 3.15}, {"text": "And these properties are--", "start": 4871.32, "duration": 2.41}, {"text": "lots of properties that you're\nseeing are of this form.", "start": 4873.73, "duration": 2.93}, {"text": "So for example, being H3 is this\nform being planar so this one", "start": 4876.66, "duration": 8.12}, {"text": "being induced H3, so this\none being three-colorable,", "start": 4884.78, "duration": 6.926}, {"text": "being perfect,\nthey're all examples", "start": 4891.706, "duration": 2.244}, {"text": "of hereditary properties.", "start": 4893.95, "duration": 1.65}, {"text": "Properties that if your\ngraph is three-colorable,", "start": 4895.6, "duration": 2.61}, {"text": "you take out some vertices,\nit's still three-colorable.", "start": 4898.21, "duration": 3.48}, {"text": "And all the\ndiscussions that we've", "start": 4901.69, "duration": 2.43}, {"text": "done so far, in particular\nthe infinite removal lemma.", "start": 4904.12, "duration": 3.84}, {"text": "If you phrase it in the form\nof property testing given", "start": 4907.96, "duration": 4.05}, {"text": "the above discussion, it implies\nthat every hereditary property", "start": 4912.01, "duration": 11.05}, {"text": "is testable.", "start": 4923.06, "duration": 0.57}, {"text": "In fact, it's testable\nin the above sense", "start": 4926.86, "duration": 4.11}, {"text": "with a one-sided error\nusing an oblivious tester.", "start": 4930.97, "duration": 5.14}, {"text": "One-sided error means that up\nthere if it's triangle-free,", "start": 4936.11, "duration": 3.72}, {"text": "then it always succeeds.", "start": 4939.83, "duration": 1.43}, {"text": "So here one of the cases\nthat always succeeds.", "start": 4941.26, "duration": 4.85}, {"text": "And the reason is that\nyou can characterize", "start": 4946.11, "duration": 2.04}, {"text": "a hereditary property\nby a curly H induced H3", "start": 4948.15, "duration": 9.2}, {"text": "for some curly H. Namely,\nyou're putting everything", "start": 4957.35, "duration": 4.44}, {"text": "into H that do not\nhave this property.", "start": 4961.79, "duration": 4.01}, {"text": "This is a possibly\ninfinite set of graphs,", "start": 4973.97, "duration": 4.61}, {"text": "and that completely\ncharacterizes", "start": 4978.58, "duration": 1.92}, {"text": "this hereditary property.", "start": 4980.5, "duration": 2.2}, {"text": "And if you read out the\ninfinite removal lemma,", "start": 4982.7, "duration": 2.76}, {"text": "it says precisely, using\nabove this interpretation,", "start": 4985.46, "duration": 4.49}, {"text": "that you have a property\ntesting algorithm.", "start": 4989.95, "duration": 4.4}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.464}, {"text": "[RUSTLING]", "start": 1.464, "duration": 2.928}, {"text": "[CLICKING]", "start": 4.392, "duration": 4.392}, {"text": "PROFESSOR: We started off\ntalking about the two aspects", "start": 12.2, "duration": 3.18}, {"text": "of image formation,\nwhere and how bright.", "start": 15.38, "duration": 3.78}, {"text": "And where we talked about\nperspective projections.", "start": 19.16, "duration": 5.55}, {"text": "And in a camera-centric\ncoordinate system,", "start": 24.71, "duration": 2.94}, {"text": "it's very easy to just get with\nthat, and the extent of that", "start": 27.65, "duration": 6.27}, {"text": "to be able to talk about motion.", "start": 33.92, "duration": 2.8}, {"text": "And so we just\ndifferentiated that.", "start": 36.72, "duration": 1.985}, {"text": "And we had a slightly\ndifferent version", "start": 57.07, "duration": 2.94}, {"text": "of this where we made use of the\nperspective projection equation", "start": 60.01, "duration": 8.52}, {"text": "in order to write it in.", "start": 68.53, "duration": 2.55}, {"text": "Then we introduced the idea\nof the focus of expansion.", "start": 71.08, "duration": 4.98}, {"text": "That is the place where u is 0.", "start": 76.06, "duration": 3.09}, {"text": "And clearly, that's\nwhere this part is 0.", "start": 79.15, "duration": 3.45}, {"text": "And so if you solve for\nx, we get x over there.", "start": 82.6, "duration": 4.38}, {"text": "It's u/w.", "start": 86.98, "duration": 2.07}, {"text": "So the focus of the\nexpansion is the point", "start": 95.68, "duration": 3.06}, {"text": "in the image towards\nwhich you're moving.", "start": 98.74, "duration": 4.26}, {"text": "And then we introduce\nthe [INAUDIBLE]", "start": 103.0, "duration": 6.12}, {"text": "and talked about various\nways of estimating that.", "start": 109.12, "duration": 3.72}, {"text": "Then from a somewhat\ndifferent point of view,", "start": 115.63, "duration": 8.07}, {"text": "we looked at the image solid.", "start": 123.7, "duration": 3.89}, {"text": "So we're thinking\nabout an image as--", "start": 127.59, "duration": 4.17}, {"text": "brightness as a\nfunction of x and y,", "start": 131.76, "duration": 3.57}, {"text": "and sometimes x and y and t.", "start": 135.33, "duration": 3.99}, {"text": "And so there's an\nimage solid video.", "start": 139.32, "duration": 10.08}, {"text": "And in this case, we\nlooked at the possibility", "start": 149.4, "duration": 6.82}, {"text": "that the brightness of\nan image of some point", "start": 156.22, "duration": 4.74}, {"text": "in the environment\ndoesn't change with time.", "start": 160.96, "duration": 3.1}, {"text": "So we introduced the constant\nbrightness assumption.", "start": 164.06, "duration": 4.7}, {"text": "So as we follow some point and\nits image in successive frames,", "start": 168.76, "duration": 11.28}, {"text": "we are saying that in\nmany circumstances,", "start": 180.04, "duration": 2.913}, {"text": "the brightness won't change.", "start": 182.953, "duration": 1.167}, {"text": "And we can exploit that.", "start": 184.12, "duration": 2.2}, {"text": "So if we-- it's quite\ninteresting to look", "start": 186.32, "duration": 3.29}, {"text": "at this image solid and slice\nit in different directions.", "start": 189.61, "duration": 4.15}, {"text": "And you'll see kind of a\nvery streaky nature because", "start": 193.76, "duration": 5.15}, {"text": "of this phenomenon.", "start": 198.91, "duration": 1.42}, {"text": "So the slices, of course,\nare not independent.", "start": 200.33, "duration": 3.83}, {"text": "And we see that\nthings are streaky,", "start": 204.16, "duration": 4.14}, {"text": "like extruding toothpaste with\nmultiple different colors in it", "start": 208.3, "duration": 6.46}, {"text": "as things move in the image.", "start": 214.76, "duration": 2.79}, {"text": "And then from this, we got the\nbrightness change constraint", "start": 217.55, "duration": 6.63}, {"text": "equation, which gives\nus a relationship", "start": 224.18, "duration": 5.09}, {"text": "between the movement\nin the image", "start": 229.27, "duration": 2.46}, {"text": "and the brightness\ngradient and the time", "start": 231.73, "duration": 3.18}, {"text": "rate of change of brightness.", "start": 234.91, "duration": 2.07}, {"text": "And we then\naddressed the problem", "start": 236.98, "duration": 5.43}, {"text": "that this is not giving us\nthe ability to solve locally", "start": 242.41, "duration": 4.95}, {"text": "for velocity, because this is\na linear equation in u and v.", "start": 247.36, "duration": 6.66}, {"text": "So it just defines a\nline in velocity space.", "start": 254.02, "duration": 4.27}, {"text": "So looking at a single pixel,\nwe can't recover the motion,", "start": 258.29, "duration": 10.97}, {"text": "unlike the 1D case,\nwhere we could.", "start": 269.26, "duration": 3.46}, {"text": "And so we need more constraints.", "start": 272.72, "duration": 3.41}, {"text": "Well, a very extreme\nform of constraint", "start": 276.13, "duration": 3.51}, {"text": "is where everything is\nmoving at the same speed.", "start": 279.64, "duration": 4.77}, {"text": "And so as I announced, there's a\npaper under Materials on Stella", "start": 289.15, "duration": 10.38}, {"text": "that goes into that.", "start": 299.53, "duration": 2.37}, {"text": "And it's doing the last part of\nthe previous homework problem.", "start": 301.9, "duration": 7.53}, {"text": "And what it does is\nminimize some errors.", "start": 309.43, "duration": 5.2}, {"text": "So if this applies\nat every pixel", "start": 314.63, "duration": 7.04}, {"text": "and we have a constant u\nand v for the whole image,", "start": 321.67, "duration": 4.03}, {"text": "as in the optical\nmouse case, then we", "start": 325.7, "duration": 2.66}, {"text": "can write the problem this way.", "start": 328.36, "duration": 2.64}, {"text": "And again, that integral\nshould be small,", "start": 333.53, "duration": 2.58}, {"text": "or it should be 0 if there\nwas no error in u and v,", "start": 336.11, "duration": 4.02}, {"text": "and if there was no noise.", "start": 340.13, "duration": 2.31}, {"text": "But we're satisfied\njust to minimize that.", "start": 342.44, "duration": 4.74}, {"text": "And that's going to be our\nbest estimate of u and v.", "start": 347.18, "duration": 3.87}, {"text": "And it's highly overconstrained.", "start": 351.05, "duration": 3.45}, {"text": "We've got one of these\nequations for every pixel.", "start": 354.5, "duration": 3.55}, {"text": "And we're only looking\nfor two unknowns.", "start": 358.05, "duration": 1.71}, {"text": "So this is a case where we\nhave millions of equations.", "start": 359.76, "duration": 3.26}, {"text": "And we've only got two unknowns.", "start": 363.02, "duration": 1.54}, {"text": "So that's very favorable.", "start": 364.56, "duration": 1.61}, {"text": "That means that\nthe result is going", "start": 366.17, "duration": 2.37}, {"text": "to be much more accurate\nand reliable than it", "start": 368.54, "duration": 3.06}, {"text": "would otherwise be.", "start": 371.6, "duration": 1.84}, {"text": "So doing that, we obtain\nthe linear equation", "start": 373.44, "duration": 6.98}, {"text": "in the unknowns with a symmetric\n2 by 2 coefficient matrix.", "start": 380.42, "duration": 11.0}, {"text": "So we just run\nthrough the image,", "start": 396.0, "duration": 3.45}, {"text": "and we estimate\nthe gradient Ex Ey.", "start": 399.45, "duration": 4.05}, {"text": "We estimate the rate of\nchange of brightness, Et.", "start": 403.5, "duration": 2.85}, {"text": "And then we just\naccumulate these totals.", "start": 406.35, "duration": 4.05}, {"text": "And when we're\ndone doing that, we", "start": 410.4, "duration": 2.7}, {"text": "have two linear\nequations in u and v.", "start": 413.1, "duration": 2.52}, {"text": "And we all know how to\nsolve linear equations,", "start": 415.62, "duration": 3.0}, {"text": "particularly if there\nare only two of them.", "start": 418.62, "duration": 3.32}, {"text": "Now, as usual, we need to\nlook at when that fails.", "start": 421.94, "duration": 5.2}, {"text": "And so we did that.", "start": 427.14, "duration": 1.19}, {"text": "We said that, well, it\ndepends on the determinant.", "start": 428.33, "duration": 6.71}, {"text": "So the problem is when that\ncoefficient matrix is singular.", "start": 435.04, "duration": 7.13}, {"text": "So we have a problem if that is\n0, or if that's equal to that.", "start": 442.17, "duration": 12.52}, {"text": "And we looked at various\nconditions, like e equals 0.", "start": 454.69, "duration": 4.77}, {"text": "Of course, if you have a black\nimage, then that won't work.", "start": 459.46, "duration": 5.19}, {"text": "And also, if Ex is 0\nor Ey is 0 as well.", "start": 464.65, "duration": 4.71}, {"text": "And just let's look at one more.", "start": 469.36, "duration": 2.46}, {"text": "Suppose that we have\nan image like this.", "start": 478.24, "duration": 2.45}, {"text": "And what we're trying\nto do is figure out", "start": 480.69, "duration": 2.16}, {"text": "whether this motion\nrecovery is going to work.", "start": 482.85, "duration": 4.42}, {"text": "So how can we attack that?", "start": 487.27, "duration": 3.41}, {"text": "Well, in two ways, the one is\nwhat type of an image is that.", "start": 490.68, "duration": 4.47}, {"text": "Can we intuitively\nsee why that's", "start": 495.15, "duration": 3.27}, {"text": "going to work or not work?", "start": 498.42, "duration": 1.77}, {"text": "And the other one is just\nto break down and compute", "start": 500.19, "duration": 4.68}, {"text": "the derivatives.", "start": 504.87, "duration": 1.59}, {"text": "So e sub x is going to be\nthe derivative of this thing", "start": 509.02, "duration": 7.289}, {"text": "plus the derivative of\nthe argument with respect", "start": 516.309, "duration": 3.571}, {"text": "to x many times.", "start": 519.88, "duration": 2.159}, {"text": "And so the derivative of this\nwith respect to x, of course,", "start": 522.039, "duration": 2.971}, {"text": "is just a.", "start": 525.01, "duration": 0.78}, {"text": "And take out the x so it doesn't\nlook confusingly like a times.", "start": 528.47, "duration": 5.91}, {"text": "And then I can look\nat the y derivative.", "start": 534.38, "duration": 3.322}, {"text": "So this is a very\nparticular type of image.", "start": 541.85, "duration": 3.58}, {"text": "And in this case,\nI have Ex and Ey.", "start": 545.43, "duration": 5.33}, {"text": "f may be some\ncomplicated function.", "start": 550.76, "duration": 2.01}, {"text": "But the important thing is that\nEx and Ey are in the same ratio", "start": 552.77, "duration": 4.62}, {"text": "everywhere.", "start": 557.39, "duration": 0.9}, {"text": "And so in this integration,\nI can replace Ey", "start": 558.29, "duration": 5.61}, {"text": "by b of a times Ex.", "start": 563.9, "duration": 2.97}, {"text": "And so this is going to be true.", "start": 566.87, "duration": 2.73}, {"text": "This condition will be\ntrue, and it'll fail.", "start": 569.6, "duration": 3.96}, {"text": "So this is another way of\nsaying the condition under which", "start": 573.56, "duration": 3.78}, {"text": "this method won't work.", "start": 577.34, "duration": 1.69}, {"text": "And then we can look at what\nkind of an image is that.", "start": 579.03, "duration": 4.52}, {"text": "Well, as usual, I can't draw\ngray levels on the blackboard,", "start": 583.55, "duration": 5.63}, {"text": "and not draw gradients.", "start": 589.18, "duration": 2.55}, {"text": "But I can draw contours of\nconstant brightness, isophotes,", "start": 591.73, "duration": 3.9}, {"text": "which are perpendicular\nto the gradient.", "start": 595.63, "duration": 3.06}, {"text": "And so what are the isophotes?", "start": 598.69, "duration": 1.98}, {"text": "Well, the isophotes are\nwhere E x, y is constant.", "start": 600.67, "duration": 3.24}, {"text": "That means where f of\nax plus by is constant.", "start": 603.91, "duration": 4.17}, {"text": "That means where ax\nplus by is a constant.", "start": 608.08, "duration": 3.045}, {"text": "And that's the equation of what?", "start": 618.06, "duration": 4.8}, {"text": "It's a straight line, right?", "start": 622.86, "duration": 1.2}, {"text": "So the isophotes\nare straight lines.", "start": 624.06, "duration": 3.21}, {"text": "Also, they're all\nparallel straight lines.", "start": 627.27, "duration": 2.86}, {"text": "They only differ in C. a and\nb are fixed ahead of time.", "start": 630.13, "duration": 6.1}, {"text": "So this is the kind of\nimage that gives us trouble.", "start": 641.04, "duration": 3.6}, {"text": "Yeah, we know that, right?", "start": 644.64, "duration": 1.29}, {"text": "Because if it slides\nin this direction,", "start": 645.93, "duration": 2.76}, {"text": "we can't measure that.", "start": 648.69, "duration": 2.13}, {"text": "There's no change in the image.", "start": 650.82, "duration": 2.16}, {"text": "If it slides in that\ndirection, we can.", "start": 652.98, "duration": 2.16}, {"text": "But it doesn't allow us to\ndetermine the other part of it.", "start": 655.14, "duration": 5.41}, {"text": "So then that's the\noptical mouse problem.", "start": 663.89, "duration": 3.78}, {"text": "So from that we went\nto time to contact.", "start": 671.8, "duration": 3.8}, {"text": "And we looked at--", "start": 675.6, "duration": 1.47}, {"text": "so we had this.", "start": 682.02, "duration": 0.995}, {"text": "There are various ways\nof rewriting that.", "start": 691.52, "duration": 2.5}, {"text": "Let's see.", "start": 694.02, "duration": 0.5}, {"text": "Which way around do\nI want to do this?", "start": 694.52, "duration": 2.19}, {"text": "So w is the z component of\nthe motion in the world.", "start": 707.15, "duration": 3.66}, {"text": "So that's dZ dt.", "start": 710.81, "duration": 2.77}, {"text": "And I don't know.", "start": 721.1, "duration": 0.93}, {"text": "That may or may not ring a bell.", "start": 722.03, "duration": 2.91}, {"text": "But that's a\nderivative of log of z.", "start": 724.94, "duration": 9.62}, {"text": "So if I plot things on\na logarithmic scale,", "start": 734.56, "duration": 3.42}, {"text": "this is just the\nslope of the graph", "start": 737.98, "duration": 3.84}, {"text": "on that logarithmic scale.", "start": 741.82, "duration": 3.15}, {"text": "So that's interesting.", "start": 744.97, "duration": 1.36}, {"text": "So it's all dependent on\nratios, fractional parts,", "start": 746.33, "duration": 5.88}, {"text": "rather than absolute values.", "start": 752.21, "duration": 1.9}, {"text": "So what's important is by what\nfractional part does z change", "start": 754.11, "duration": 4.43}, {"text": "in a certain time interval?", "start": 758.54, "duration": 1.23}, {"text": "Not by how many meters.", "start": 759.77, "duration": 2.16}, {"text": "And that's one reason\nwhy we could do this", "start": 761.93, "duration": 3.0}, {"text": "without calibration.", "start": 764.93, "duration": 1.17}, {"text": "We didn't have to know what\nthe focal length of the camera", "start": 766.1, "duration": 3.42}, {"text": "is, for example,\nbecause it's only", "start": 769.52, "duration": 2.4}, {"text": "the ratio, the fractional\npart that matters.", "start": 771.92, "duration": 4.68}, {"text": "And now another way to\nthink about time to contact", "start": 776.6, "duration": 6.78}, {"text": "is in terms of image size.", "start": 783.38, "duration": 6.48}, {"text": "So suppose here is some\nobject in the world of size S,", "start": 789.86, "duration": 5.55}, {"text": "and here's its image\nof size little s.", "start": 795.41, "duration": 2.97}, {"text": "Then I can write an equation\nrelating those quantities", "start": 803.42, "duration": 3.45}, {"text": "based on the triangle,\nsimilar triangles,", "start": 806.87, "duration": 3.99}, {"text": "this triangle on the\noutside, and this triangle", "start": 810.86, "duration": 3.84}, {"text": "in the camera.", "start": 814.7, "duration": 1.05}, {"text": "So I've got s/f\nis S/Z. It's just", "start": 815.75, "duration": 9.72}, {"text": "the lateral magnification of\nthe camera, which in this case", "start": 825.47, "duration": 3.54}, {"text": "is much smaller than 1.", "start": 829.01, "duration": 2.66}, {"text": "The image is much\nsmaller than the object.", "start": 831.67, "duration": 1.97}, {"text": "But we call it\nmagnification anyway.", "start": 833.64, "duration": 4.94}, {"text": "Well, I can cross multiply.", "start": 838.58, "duration": 1.755}, {"text": "So I have that relationship.", "start": 846.14, "duration": 1.41}, {"text": "And why do I do that?", "start": 847.55, "duration": 1.27}, {"text": "Well, because now I'm going\nto differentiate that and see", "start": 848.82, "duration": 3.62}, {"text": "how it changes with time.", "start": 852.44, "duration": 2.89}, {"text": "And so s is changing.", "start": 855.33, "duration": 2.3}, {"text": "If we're approaching the object,\nthen s will be increasing.", "start": 857.63, "duration": 3.25}, {"text": "So s will be changing.", "start": 860.88, "duration": 1.23}, {"text": "So we're going to have Z ds dt.", "start": 862.11, "duration": 3.62}, {"text": "And it's a product.", "start": 865.73, "duration": 0.9}, {"text": "So we also get Z.\nGet the other one.", "start": 866.63, "duration": 6.3}, {"text": "We're going to\nget s times dZ dt.", "start": 872.93, "duration": 3.345}, {"text": "And then we need the\nderivative of this product.", "start": 882.28, "duration": 3.69}, {"text": "Well, the size of the object,\npresumably, is constant.", "start": 885.97, "duration": 4.17}, {"text": "We aren't changing the\nimaging parameters.", "start": 890.14, "duration": 2.92}, {"text": "So this is the\nderivative of that is 0.", "start": 893.06, "duration": 2.87}, {"text": "And the derivative of\n0, of course, is 0.", "start": 895.93, "duration": 2.43}, {"text": "So we get this relationship.", "start": 898.36, "duration": 2.11}, {"text": "And so this tells us that--", "start": 900.47, "duration": 2.87}, {"text": "which way around did\nwe use it over here?", "start": 903.34, "duration": 1.905}, {"text": "S ds dt over S is Z\nover dZ dt over Z.", "start": 912.47, "duration": 9.95}, {"text": "So the change in image size, in\nfractional change in image size", "start": 922.42, "duration": 6.03}, {"text": "is exactly the fractional\nchange in distance.", "start": 928.45, "duration": 5.28}, {"text": "And so for example, if the\npicture of the image of the bus", "start": 933.73, "duration": 5.88}, {"text": "increases by 1% as\nyou go from one frame", "start": 939.61, "duration": 4.08}, {"text": "to the next in your\nvideo sequence,", "start": 943.69, "duration": 3.39}, {"text": "then that implies\nthat the TTC is 100.", "start": 947.08, "duration": 9.56}, {"text": "And so that's-- at\n20 frames a second,", "start": 956.64, "duration": 6.37}, {"text": "that means it's\nonly 5 seconds away.", "start": 963.01, "duration": 4.43}, {"text": "So one conclusion\nis that in a lot", "start": 967.44, "duration": 2.55}, {"text": "of important practical\ncases, the time to contact", "start": 969.99, "duration": 4.2}, {"text": "is not tens of frames,\nbut hundreds of thousands", "start": 974.19, "duration": 4.92}, {"text": "of frames.", "start": 979.11, "duration": 0.84}, {"text": "Otherwise, you'd have a problem.", "start": 979.95, "duration": 3.0}, {"text": "You'd probably be just about\nready to crash into something", "start": 982.95, "duration": 4.59}, {"text": "and may have trouble\ncompensating.", "start": 987.54, "duration": 2.16}, {"text": "So if the time to contact\nin many cases is thousands,", "start": 989.7, "duration": 3.6}, {"text": "that means that the\nfractional change per frame", "start": 993.3, "duration": 2.91}, {"text": "is 1 over thousands.", "start": 996.21, "duration": 3.39}, {"text": "And so the fractional change in\nthe image from frame to frame", "start": 999.6, "duration": 4.17}, {"text": "is relatively small.", "start": 1003.77, "duration": 2.23}, {"text": "And so that means if we\nwere to use a method that's", "start": 1006.0, "duration": 2.78}, {"text": "dependent on actually\nmeasuring the image size,", "start": 1008.78, "duration": 4.14}, {"text": "estimating how big the picture\nof the bus is in your image,", "start": 1012.92, "duration": 4.03}, {"text": "it better be really\naccurate, like", "start": 1016.95, "duration": 2.69}, {"text": "one part in several thousand.", "start": 1019.64, "duration": 2.19}, {"text": "And that means it's going\nto need subpixel accuracy,", "start": 1021.83, "duration": 3.9}, {"text": "that it won't be good\nenough to simply measure", "start": 1025.73, "duration": 4.44}, {"text": "where the front and the back\nof the bus is in the image.", "start": 1030.17, "duration": 3.5}, {"text": "And that's why that turns out\nto be not a good way to estimate", "start": 1033.67, "duration": 4.88}, {"text": "the time to contact, as\nopposed to the method", "start": 1038.55, "duration": 3.9}, {"text": "that we described.", "start": 1042.45, "duration": 3.058}, {"text": "So that's one thing I\nwanted to get across,", "start": 1045.508, "duration": 1.792}, {"text": "this very simple\nrelationship that if there's", "start": 1047.3, "duration": 3.03}, {"text": "a certain percentage change\nin size between frames,", "start": 1050.33, "duration": 3.48}, {"text": "that translates directly\ninto a certain percentage", "start": 1053.81, "duration": 2.49}, {"text": "change in the distance.", "start": 1056.3, "duration": 1.92}, {"text": "And that directly translates\ninto time to contact.", "start": 1058.22, "duration": 3.89}, {"text": "So it's a very easy\nway to understand that.", "start": 1062.11, "duration": 4.75}, {"text": "Now, when we did\nthis, or you did it,", "start": 1066.86, "duration": 7.2}, {"text": "we had a very simple situation.", "start": 1074.06, "duration": 2.55}, {"text": "We started off moving\ndirectly towards a wall", "start": 1076.61, "duration": 5.28}, {"text": "so that we had constraints on\nboth the direction of motion", "start": 1081.89, "duration": 4.38}, {"text": "and on the surface\nwe're looking at.", "start": 1086.27, "duration": 2.83}, {"text": "So the very-- you may\nremember the very first thing", "start": 1089.1, "duration": 3.11}, {"text": "we calculated was C, which\nwas the component in the Z", "start": 1092.21, "duration": 7.52}, {"text": "direction.", "start": 1099.73, "duration": 2.29}, {"text": "And we had some simple\nratio of two integrals.", "start": 1102.02, "duration": 3.172}, {"text": "And that's the case where\nwe're moving straight", "start": 1105.192, "duration": 1.958}, {"text": "towards the wall, the wall\nis-- what does it mean?", "start": 1107.15, "duration": 5.76}, {"text": "The optical axis is\nperpendicular to the wall.", "start": 1112.91, "duration": 3.18}, {"text": "Z is constant on the wall.", "start": 1116.09, "duration": 2.56}, {"text": "It doesn't vary as\nwe go left and right.", "start": 1118.65, "duration": 3.27}, {"text": "So that's a very simple case.", "start": 1121.92, "duration": 1.44}, {"text": "So then we said, well, let's\nbe slightly more general.", "start": 1123.36, "duration": 4.41}, {"text": "Let's assume that we could\nalso be moving sideways", "start": 1127.77, "duration": 3.44}, {"text": "as we're going along.", "start": 1131.21, "duration": 1.45}, {"text": "And then we added the motion\nin x and the motion in y.", "start": 1132.66, "duration": 3.56}, {"text": "And we had the slightly\nmore interesting problem", "start": 1136.22, "duration": 2.43}, {"text": "where we were looking for\nthree unknowns, A, B, and C.", "start": 1138.65, "duration": 5.49}, {"text": "And we ended up with three\nlinear equations and three", "start": 1144.14, "duration": 5.1}, {"text": "unknowns.", "start": 1149.24, "duration": 1.318}, {"text": "And right now I remember\nwhat I was going to say.", "start": 1150.558, "duration": 2.042}, {"text": "Again, this is all\nspelled out in the paper", "start": 1152.6, "duration": 6.9}, {"text": "that's on the website\non time to contact.", "start": 1159.5, "duration": 4.72}, {"text": "I guess the full title\nis \"The Time to Contract", "start": 1164.22, "duration": 2.33}, {"text": "Relative to a Planar Surface.\"", "start": 1166.55, "duration": 3.82}, {"text": "And now the paper discusses\nsome other things as well.", "start": 1170.37, "duration": 3.42}, {"text": "It's just like the other paper.", "start": 1173.79, "duration": 2.14}, {"text": "The first half is exactly\nwhat we did in class,", "start": 1175.93, "duration": 2.69}, {"text": "and then it goes off into\nsome other directions.", "start": 1178.62, "duration": 2.49}, {"text": "Same here.", "start": 1181.11, "duration": 1.02}, {"text": "So is this the most\ngeneral we can get?", "start": 1182.13, "duration": 2.85}, {"text": "Well, we're still making an\nassumption that Z is constant.", "start": 1184.98, "duration": 5.085}, {"text": "So we're approaching the\nwall, and the optical axis", "start": 1195.46, "duration": 5.51}, {"text": "is perpendicular to the wall.", "start": 1200.97, "duration": 1.56}, {"text": "Well, what if our\ncamera is tilted,", "start": 1202.53, "duration": 2.97}, {"text": "or conversely, we're\napproaching a wall that that's", "start": 1205.5, "duration": 2.91}, {"text": "tilted in the world?", "start": 1208.41, "duration": 1.05}, {"text": "So a different\ngeneralization has", "start": 1209.46, "duration": 6.79}, {"text": "Z be a tilted plane so that\nit's no longer the case", "start": 1216.25, "duration": 9.41}, {"text": "that the depth is constant\nas I scan left and right", "start": 1225.66, "duration": 3.99}, {"text": "or up and down in the image.", "start": 1229.65, "duration": 1.77}, {"text": "And well, what's the\nequation of a plane?", "start": 1231.42, "duration": 2.43}, {"text": "Well, it's going to be some\nlinear equation in x and y.", "start": 1233.85, "duration": 5.83}, {"text": "So one way I could write\nit is in that form.", "start": 1239.68, "duration": 10.54}, {"text": "So this could be a more\ncomplicated model to look at.", "start": 1250.22, "duration": 5.73}, {"text": "And well, you might expect at\nsome point the equations get", "start": 1255.95, "duration": 5.24}, {"text": "pretty complicated.", "start": 1261.19, "duration": 1.36}, {"text": "And in fact, there might not\nbe a closed form solution.", "start": 1262.55, "duration": 2.93}, {"text": "And that's fine.", "start": 1265.48, "duration": 2.26}, {"text": "You can do it numerically.", "start": 1267.74, "duration": 1.25}, {"text": "But in terms of\nunderstanding what's going on", "start": 1268.99, "duration": 3.21}, {"text": "and the noise effect,\nit's nice to focus first", "start": 1272.2, "duration": 4.77}, {"text": "on cases where there is\na closed form solution.", "start": 1276.97, "duration": 2.77}, {"text": "So what you can do,\nactually, is say, fine.", "start": 1279.74, "duration": 4.11}, {"text": "So now we will generalize\nit by allowing the plane", "start": 1283.85, "duration": 2.57}, {"text": "to be tilted.", "start": 1286.42, "duration": 0.84}, {"text": "But let's go back to the case\nwhere we were moving straight", "start": 1287.26, "duration": 3.6}, {"text": "down the barrel, straight\ndown the optical axis.", "start": 1290.86, "duration": 2.94}, {"text": "And in that case, then we'll\nonly have these three unknowns.", "start": 1293.8, "duration": 4.72}, {"text": "So instead of having A,\nB, and C be the unknowns,", "start": 1298.52, "duration": 3.89}, {"text": "we have these three or\nsome function of them.", "start": 1302.41, "duration": 4.05}, {"text": "And so we want to\ndo that because it's", "start": 1306.46, "duration": 2.94}, {"text": "pretty straightforward,\nmore messy algebra.", "start": 1309.4, "duration": 4.21}, {"text": "We end up with three linear\nequations and three unknowns.", "start": 1313.61, "duration": 3.12}, {"text": "And we can solve for that.", "start": 1316.73, "duration": 1.53}, {"text": "So we can do the time\nto contact in the case", "start": 1318.26, "duration": 4.61}, {"text": "where the surface is tilted.", "start": 1322.87, "duration": 2.7}, {"text": "So we're no longer\nmaking the assumption", "start": 1325.57, "duration": 2.07}, {"text": "that we're driving into\nthe side of the truck", "start": 1327.64, "duration": 3.57}, {"text": "coming out of a parking lot.", "start": 1331.21, "duration": 1.47}, {"text": "But we could be\ncoming at an angle.", "start": 1332.68, "duration": 3.69}, {"text": "So that's an interesting\ncase to consider.", "start": 1336.37, "duration": 4.29}, {"text": "What if we do both?", "start": 1340.66, "duration": 1.66}, {"text": "What if we allow the\nsurface to be tilted", "start": 1342.32, "duration": 3.2}, {"text": "as well as our\nmotion to be general?", "start": 1345.52, "duration": 2.7}, {"text": "Well, we can formulate\nthat problem pretty easily.", "start": 1348.22, "duration": 3.28}, {"text": "And we end up with six unknowns.", "start": 1351.5, "duration": 2.45}, {"text": "Unfortunately, they are no\nlonger linear equations.", "start": 1353.95, "duration": 3.24}, {"text": "And so from the\npoint of view of pain", "start": 1357.19, "duration": 3.51}, {"text": "and agony, they're not\nmuch fun to write down.", "start": 1360.7, "duration": 3.36}, {"text": "And also, it's unsatisfying\nbecause we end up", "start": 1364.06, "duration": 2.94}, {"text": "with this mixed\nset of equations.", "start": 1367.0, "duration": 2.63}, {"text": "Some of them are linear.", "start": 1369.63, "duration": 1.0}, {"text": "Some of them are quadratic.", "start": 1370.63, "duration": 1.53}, {"text": "And it's very hard to say\nanything general about them.", "start": 1372.16, "duration": 4.24}, {"text": "Whereas in these\nspecial cases, we", "start": 1376.4, "duration": 2.42}, {"text": "can do a full analysis\nof noise and so on.", "start": 1378.82, "duration": 5.41}, {"text": "So we're not going to do that.", "start": 1384.23, "duration": 3.15}, {"text": "Just you know that it's there.", "start": 1387.38, "duration": 2.97}, {"text": "Then we get to why is\nthe surface planar?", "start": 1390.35, "duration": 3.68}, {"text": "Well, the surface is\nplanar because it's going", "start": 1394.03, "duration": 2.1}, {"text": "to give us linear equations.", "start": 1396.13, "duration": 1.68}, {"text": "So we start with\na planar surface.", "start": 1397.81, "duration": 2.31}, {"text": "Now, real surfaces\nmay not be planar.", "start": 1400.12, "duration": 3.66}, {"text": "And then what?", "start": 1403.78, "duration": 1.77}, {"text": "Well, we can approximate\nthem by polynomials,", "start": 1405.55, "duration": 3.87}, {"text": "some locally quadratic surface.", "start": 1409.42, "duration": 2.94}, {"text": "And we go through\nthe same process.", "start": 1412.36, "duration": 2.11}, {"text": "We set up a least\nsquares problem.", "start": 1414.47, "duration": 2.91}, {"text": "And we, unfortunately, won't\nfind closed form solutions.", "start": 1417.38, "duration": 5.03}, {"text": "But we can set it up so that\nsome numerical process gives us", "start": 1422.41, "duration": 6.36}, {"text": "a solution.", "start": 1428.77, "duration": 1.76}, {"text": "Now, the reason\nwe're not doing that", "start": 1430.53, "duration": 1.92}, {"text": "is mostly because it actually\ndoesn't buy you anything.", "start": 1432.45, "duration": 3.09}, {"text": "So in practice when\nyou implement this,", "start": 1435.54, "duration": 2.5}, {"text": "you find that modeling\nthe surface as planar", "start": 1438.04, "duration": 4.88}, {"text": "gives you a very good estimate\nof the time to contact.", "start": 1442.92, "duration": 6.07}, {"text": "And if you model it as\nsomething more complicated,", "start": 1448.99, "duration": 3.08}, {"text": "now you have more unknowns,\nwhich is good in a way,", "start": 1452.07, "duration": 4.02}, {"text": "because it allows you to model\nthe world more accurately.", "start": 1456.09, "duration": 3.16}, {"text": "But at the same time, you\nlose that overconstraintness.", "start": 1459.25, "duration": 4.25}, {"text": "Every time you introduce\nmore variables,", "start": 1463.5, "duration": 2.22}, {"text": "there is an opportunity for\nthe solution to squiggle off", "start": 1465.72, "duration": 4.77}, {"text": "in another direction.", "start": 1470.49, "duration": 3.27}, {"text": "So there are some\npluses and minuses.", "start": 1473.76, "duration": 1.95}, {"text": "And overall, the only time you\nwant to even think about that", "start": 1475.71, "duration": 5.22}, {"text": "is if the object\nhas a shape in depth", "start": 1480.93, "duration": 4.29}, {"text": "where the depth change is\nsimilar to the distance", "start": 1485.22, "duration": 4.73}, {"text": "from the object.", "start": 1489.95, "duration": 1.03}, {"text": "So if the truck is over there--", "start": 1490.98, "duration": 2.05}, {"text": "I'm 50 meters away\nfrom the truck,", "start": 1493.03, "duration": 2.23}, {"text": "and the side of the\ntruck is-- one side", "start": 1495.26, "duration": 2.4}, {"text": "is maybe 2 meters closer\nto me than the other,", "start": 1497.66, "duration": 2.43}, {"text": "it makes no difference.", "start": 1500.09, "duration": 1.08}, {"text": "I mean, it's a 4%\nchange in distance.", "start": 1501.17, "duration": 3.18}, {"text": "And that won't affect anything.", "start": 1504.35, "duration": 2.25}, {"text": "If I am right in front of\nthe truck, I'm 2 meters away", "start": 1506.6, "duration": 4.41}, {"text": "and one side is 1 meter and\nthe other one is 4 meters,", "start": 1511.01, "duration": 2.82}, {"text": "then yes, then\nyou may need this.", "start": 1513.83, "duration": 2.43}, {"text": "But we found in practice that\nwe don't need that extra level", "start": 1516.26, "duration": 4.02}, {"text": "of sophistication.", "start": 1520.28, "duration": 1.59}, {"text": "These two things are\nsufficient in practice.", "start": 1521.87, "duration": 3.69}, {"text": "Then let me just briefly\ntalk about multi-scale.", "start": 1532.37, "duration": 11.33}, {"text": "So when I showed you\nthe implementation, when", "start": 1543.7, "duration": 4.62}, {"text": "you got really close to impact,\nthings kind of just fell apart.", "start": 1548.32, "duration": 4.57}, {"text": "So the graph of time\nto contact estimated", "start": 1552.89, "duration": 3.68}, {"text": "was quite similar to the\nactual time to contact.", "start": 1556.57, "duration": 4.92}, {"text": "So this was a\ncontrived situation", "start": 1561.49, "duration": 6.13}, {"text": "with constant velocity\nso that the time", "start": 1567.62, "duration": 5.16}, {"text": "to contact decreased\nlinearly as time", "start": 1572.78, "duration": 2.43}, {"text": "went on, because we got closer\nand closer to the surface.", "start": 1575.21, "duration": 3.12}, {"text": "And then when we looked\nat the computed results,", "start": 1578.33, "duration": 3.0}, {"text": "they were something\nlike that, noisy.", "start": 1581.33, "duration": 4.8}, {"text": "And that's partly because the\nmeasurement of the position", "start": 1586.13, "duration": 4.77}, {"text": "was not very accurate.", "start": 1590.9, "duration": 1.35}, {"text": "It was eyeballing down\non the measuring tape.", "start": 1592.25, "duration": 4.62}, {"text": "There was an interesting offset\nvertically, so there's a bias.", "start": 1596.87, "duration": 3.55}, {"text": "So it's not just noise.", "start": 1600.42, "duration": 1.37}, {"text": "Actually, the estimated\ntime to contact", "start": 1601.79, "duration": 3.15}, {"text": "was overestimated, which\nin itself isn't good,", "start": 1604.94, "duration": 3.42}, {"text": "because if you're about\nto crash into something,", "start": 1608.36, "duration": 3.0}, {"text": "you don't want to be\ntold that actually it'll", "start": 1611.36, "duration": 3.39}, {"text": "take longer than the true time.", "start": 1614.75, "duration": 3.25}, {"text": "On the other hand, since\nit's a systematic fixed bias,", "start": 1618.0, "duration": 3.47}, {"text": "you can compensate for it.", "start": 1621.47, "duration": 2.14}, {"text": "It doesn't mean that you\nshouldn't try and figure out", "start": 1623.61, "duration": 2.21}, {"text": "where it comes from.", "start": 1625.82, "duration": 1.11}, {"text": "But it's pretty simple to just\nfit a different slope to this.", "start": 1626.93, "duration": 7.17}, {"text": "But then at the end\nhere, we had some spikes.", "start": 1634.1, "duration": 5.34}, {"text": "And basically, the\nresults were not reliable.", "start": 1639.44, "duration": 3.57}, {"text": "And we already mentioned\nsome reasons for that.", "start": 1643.01, "duration": 3.22}, {"text": "And one of them is that\nthe image motion is large.", "start": 1646.23, "duration": 3.65}, {"text": "So earlier we said that\nwhen the bus is far away,", "start": 1649.88, "duration": 3.69}, {"text": "the image motion is very small.", "start": 1653.57, "duration": 3.36}, {"text": "The image of the bus will tend\nto expand and contract and move", "start": 1656.93, "duration": 4.56}, {"text": "by a fraction of a pixel.", "start": 1661.49, "duration": 2.8}, {"text": "And that's where these\nmethods really excel.", "start": 1664.29, "duration": 5.27}, {"text": "As we go along, we've been\nmaking some assumptions", "start": 1669.56, "duration": 3.18}, {"text": "that certain distances,\nthe epsilons are small.", "start": 1672.74, "duration": 3.06}, {"text": "When we estimate E sub x, E\nsub y, E sub t, for example,", "start": 1675.8, "duration": 3.61}, {"text": "we're taking a finite\ndifference and saying,", "start": 1679.41, "duration": 2.55}, {"text": "oh, this is almost a derivative,\nbecause epsilon is small.", "start": 1681.96, "duration": 3.23}, {"text": "Well, that won't work if we\nhave a large jump in x, y, or t.", "start": 1685.19, "duration": 4.95}, {"text": "And so that's one reason\nthat this falls apart.", "start": 1690.14, "duration": 3.867}, {"text": "I mean, there are other reasons.", "start": 1694.007, "duration": 1.333}, {"text": "One of them was that the\ncamera went out of focus.", "start": 1695.34, "duration": 2.61}, {"text": "And so you didn't have a clear\npicture of the object anymore.", "start": 1697.95, "duration": 3.26}, {"text": "But this first part\nis easy to deal with.", "start": 1701.21, "duration": 3.96}, {"text": "As I already mentioned\nbefore, I just", "start": 1705.17, "duration": 2.4}, {"text": "want to reiterate\nthat if we have", "start": 1707.57, "duration": 3.57}, {"text": "an image with less resolution--", "start": 1711.14, "duration": 2.22}, {"text": "say we have half\nthe number of rows", "start": 1713.36, "duration": 2.16}, {"text": "and half the number of\ncolumns in the image--", "start": 1715.52, "duration": 2.88}, {"text": "well, then the motion in\nterms of pixels per frame", "start": 1718.4, "duration": 4.29}, {"text": "is half what it was before.", "start": 1722.69, "duration": 2.47}, {"text": "And so what was a large motion\nin the original raw image", "start": 1725.16, "duration": 5.36}, {"text": "is now half of that.", "start": 1730.52, "duration": 2.2}, {"text": "And so that means that you'll\nstill have it falling apart,", "start": 1732.72, "duration": 3.62}, {"text": "but it will fall apart later.", "start": 1736.34, "duration": 2.88}, {"text": "So this part will still be OK.", "start": 1739.22, "duration": 2.28}, {"text": "And then it'll fall\napart down there.", "start": 1741.5, "duration": 2.22}, {"text": "And of course, then you\ncan repeat that process,", "start": 1743.72, "duration": 2.13}, {"text": "and say, OK, so now\nin that image suddenly", "start": 1745.85, "duration": 2.88}, {"text": "the motion has gotten to be\nmore than a pixel per frame.", "start": 1748.73, "duration": 2.62}, {"text": "So let's, again, subsample,\naverage and subsample.", "start": 1751.35, "duration": 4.57}, {"text": "And then we can continue it.", "start": 1755.92, "duration": 1.93}, {"text": "And so multi-scale\njust means that we", "start": 1757.85, "duration": 2.37}, {"text": "work in that set of images that\nbecome smaller and smaller.", "start": 1760.22, "duration": 5.44}, {"text": "And we can handle motions\nthat become quite large.", "start": 1765.66, "duration": 4.04}, {"text": "And also, I mentioned that\nif we do the simple 2 by 2", "start": 1769.7, "duration": 5.04}, {"text": "block averaging, that means\nthe second image is only", "start": 1774.74, "duration": 2.86}, {"text": "a quarter of the size\nof the first one.", "start": 1777.6, "duration": 1.95}, {"text": "So the amount of work is 1 plus\n1/4 times what it would have", "start": 1779.55, "duration": 4.46}, {"text": "taken just on the raw image.", "start": 1784.01, "duration": 2.43}, {"text": "And then we do it again, so\nthat's going to be a 16th.", "start": 1786.44, "duration": 2.78}, {"text": "And so the total\namount of work--", "start": 1792.05, "duration": 2.85}, {"text": "well, writing the\ncode, of course,", "start": 1794.9, "duration": 3.07}, {"text": "takes a bit more effort.", "start": 1797.97, "duration": 1.65}, {"text": "But in terms of the time,\nit's not a big penalty", "start": 1799.62, "duration": 3.2}, {"text": "to work at multiple scales.", "start": 1802.82, "duration": 1.89}, {"text": "And you get hugely\nimproved results.", "start": 1804.71, "duration": 4.94}, {"text": "And we'll talk a little\nbit later about how", "start": 1809.65, "duration": 2.64}, {"text": "to do the subsampling.", "start": 1812.29, "duration": 2.97}, {"text": "Those of you who've\ntaken 6003, of course,", "start": 1815.26, "duration": 2.64}, {"text": "realize that you can't\nsample without getting", "start": 1817.9, "duration": 4.05}, {"text": "aliasing unless you've\nlow pass filtered first.", "start": 1821.95, "duration": 3.7}, {"text": "So actually, what you want to\ndo is low pass filter, and then", "start": 1825.65, "duration": 5.0}, {"text": "subsample.", "start": 1830.65, "duration": 1.05}, {"text": "And you don't necessarily need\nto subsample on the scale in x", "start": 1831.7, "duration": 4.38}, {"text": "by 2 and y by 2.", "start": 1836.08, "duration": 1.62}, {"text": "You could subsample by--", "start": 1837.7, "duration": 1.76}, {"text": "I don't know-- square root of\n2, which is less aggressive", "start": 1839.46, "duration": 2.8}, {"text": "and introduces fewer artifacts.", "start": 1842.26, "duration": 2.1}, {"text": "But for the moment we'll\nignore that and just", "start": 1844.36, "duration": 3.66}, {"text": "take the very simple idea of\n2 by 2 block averaging, which", "start": 1848.02, "duration": 4.08}, {"text": "is a crude form of\nlow pass filtering.", "start": 1852.1, "duration": 2.64}, {"text": "And it doesn't do exactly\nwhat you need to do,", "start": 1854.74, "duration": 3.09}, {"text": "but it removes--", "start": 1857.83, "duration": 1.65}, {"text": "it suppresses some of the\nhigh frequency content.", "start": 1859.48, "duration": 2.47}, {"text": "And while there will\nbe aliasing artifacts,", "start": 1861.95, "duration": 2.51}, {"text": "they'll be greatly reduced.", "start": 1864.46, "duration": 2.14}, {"text": "And that's such a simple\nmethod to implement.", "start": 1866.6, "duration": 3.86}, {"text": "And it works pretty well.", "start": 1870.46, "duration": 3.95}, {"text": "Well, let's talk a little\nbit about what to do--", "start": 1874.41, "duration": 2.55}, {"text": "what do I do with\ntime to contact?", "start": 1876.96, "duration": 2.87}, {"text": "So there's a number of\ninteresting applications.", "start": 1879.83, "duration": 4.82}, {"text": "Every year there are\nseveral incidents", "start": 1884.65, "duration": 2.96}, {"text": "with airplanes on the runway\nwhere wingtips are taken off.", "start": 1887.61, "duration": 8.87}, {"text": "So these planes have\nvery long wings,", "start": 1896.48, "duration": 3.68}, {"text": "and they're\ntypically swept back.", "start": 1900.16, "duration": 2.37}, {"text": "So they're not terribly visible.", "start": 1902.53, "duration": 2.28}, {"text": "And so there's an opportunity\nto bang them into a building", "start": 1904.81, "duration": 5.46}, {"text": "or into another plane.", "start": 1910.27, "duration": 1.47}, {"text": "And that's a really\nexpensive thing to deal with.", "start": 1911.74, "duration": 3.64}, {"text": "It's not life threatening\nin most cases,", "start": 1915.38, "duration": 4.34}, {"text": "but it's something\nthat you try and avoid.", "start": 1919.72, "duration": 2.58}, {"text": "And as you approach the place\nthat you get on the plane,", "start": 1922.3, "duration": 6.9}, {"text": "there's often some person down\nthere with some red lighted", "start": 1929.2, "duration": 3.9}, {"text": "stick.", "start": 1933.1, "duration": 0.99}, {"text": "And they're called wingmen.", "start": 1934.09, "duration": 1.65}, {"text": "And the reason is they walk\nunder the tip of the wing", "start": 1935.74, "duration": 3.31}, {"text": "so that the pilot\ncan look back and see", "start": 1939.05, "duration": 3.41}, {"text": "where's the ground\nprojection of the wing.", "start": 1942.46, "duration": 2.01}, {"text": "And I'll try not to hit that\nstaircase with the wing.", "start": 1944.47, "duration": 3.78}, {"text": "So it looks like you could\nimplement time to contract.", "start": 1948.25, "duration": 5.89}, {"text": "I mean, you can implement it\neasily on Android, for example.", "start": 1954.14, "duration": 3.81}, {"text": "So you could build a\nreally cheap little box.", "start": 1957.95, "duration": 2.39}, {"text": "The only purpose\nin life for it is", "start": 1960.34, "duration": 3.12}, {"text": "to look out and see if something\nis rapidly approaching,", "start": 1963.46, "duration": 3.25}, {"text": "and then give you a warning.", "start": 1966.71, "duration": 1.64}, {"text": "And so we've thought\nabout suggesting that", "start": 1968.35, "duration": 4.47}, {"text": "to airplane\nmanufacturers and such.", "start": 1972.82, "duration": 3.39}, {"text": "And it didn't get anywhere.", "start": 1976.21, "duration": 3.56}, {"text": "But Boeing took the\nidea, and they came up", "start": 1979.77, "duration": 3.21}, {"text": "with a $150,000 radar solution.", "start": 1982.98, "duration": 3.21}, {"text": "And that's obviously\ngoing to be much more", "start": 1986.19, "duration": 3.57}, {"text": "fun for the corporation to\nimplement than something", "start": 1989.76, "duration": 3.27}, {"text": "as silly as this.", "start": 1993.03, "duration": 1.07}, {"text": "So anyway, sour grapes.", "start": 1994.1, "duration": 5.095}, {"text": "The next project is\nNASA landing on Europa.", "start": 1999.195, "duration": 6.225}, {"text": "So Europa is a long way away.", "start": 2005.42, "duration": 3.9}, {"text": "And we have some idea of what's\non there, but not a whole lot.", "start": 2009.32, "duration": 3.28}, {"text": "So it's not like\nwe have detailed", "start": 2012.6, "duration": 1.94}, {"text": "topographic maps and imagery.", "start": 2014.54, "duration": 2.7}, {"text": "And so they want something\nthat reliably brings down", "start": 2017.24, "duration": 4.62}, {"text": "a spacecraft.", "start": 2021.86, "duration": 1.14}, {"text": "And so one idea is to use\ntime to contact in control.", "start": 2023.0, "duration": 6.4}, {"text": "So let's look at how we do that.", "start": 2029.4, "duration": 4.82}, {"text": "So we have a typical\ncontrol system.", "start": 2034.22, "duration": 10.17}, {"text": "We input some desired\ntime to contact.", "start": 2044.39, "duration": 4.41}, {"text": "Then we have an\nactual estimated,", "start": 2048.8, "duration": 10.62}, {"text": "and we subtract the two.", "start": 2059.42, "duration": 1.83}, {"text": "And that gives us some\nkind of error signal.", "start": 2061.25, "duration": 2.34}, {"text": "And we multiply that\nby a gain, and we", "start": 2063.59, "duration": 2.97}, {"text": "use that to control the jet,\nthe rocket engine to change", "start": 2066.56, "duration": 6.119}, {"text": "the acceleration.", "start": 2072.679, "duration": 2.601}, {"text": "And then there's a\ndynamical system,", "start": 2075.28, "duration": 3.93}, {"text": "which is second\norder in the sense", "start": 2079.21, "duration": 4.33}, {"text": "that we're controlling\nacceleration, not", "start": 2083.54, "duration": 5.639}, {"text": "height directly.", "start": 2089.179, "duration": 2.341}, {"text": "Height is two integrals\ndown from the part", "start": 2091.52, "duration": 2.88}, {"text": "that we can control.", "start": 2094.4, "duration": 1.739}, {"text": "And then there's\nan imaging system.", "start": 2096.139, "duration": 2.986}, {"text": "And so this system does\nsomething very simple,", "start": 2105.72, "duration": 2.28}, {"text": "which may not be\nthe best you can do,", "start": 2108.0, "duration": 2.64}, {"text": "but it's easy to analyze,\nwhich is to try and maintain", "start": 2110.64, "duration": 4.73}, {"text": "the time to contact the same.", "start": 2115.37, "duration": 3.225}, {"text": "So if your measurement says that\nat the current rate of descent", "start": 2122.46, "duration": 9.4}, {"text": "you're going to have a shorter\ntime to contact than desired,", "start": 2131.86, "duration": 5.16}, {"text": "then it'll add some more\nforce to the engine.", "start": 2137.02, "duration": 6.12}, {"text": "And conversely, if\nit looks like you're", "start": 2143.14, "duration": 4.53}, {"text": "kind of hovering too much,\nyou should be dropping down,", "start": 2147.67, "duration": 3.87}, {"text": "then the time to contact\nwill appear large.", "start": 2151.54, "duration": 3.48}, {"text": "And then the error\nsignal will cause you", "start": 2155.02, "duration": 4.29}, {"text": "to reduce the engine output.", "start": 2159.31, "duration": 3.1}, {"text": "So a very simple system.", "start": 2162.41, "duration": 2.49}, {"text": "And we saw that time to contact\nis very easy to implement.", "start": 2164.9, "duration": 5.39}, {"text": "And it doesn't care what the\nimagery is to a large extent.", "start": 2170.29, "duration": 4.8}, {"text": "So we don't really know\nwhat the surface of Europa", "start": 2175.09, "duration": 3.18}, {"text": "looks like, except\nfrom far away.", "start": 2178.27, "duration": 3.24}, {"text": "But we're not depending on\nsome particular texture,", "start": 2181.51, "duration": 3.87}, {"text": "or calibration, or\ntopographic map of the surface", "start": 2185.38, "duration": 4.92}, {"text": "or something.", "start": 2190.3, "duration": 1.32}, {"text": "This method works\nwith any texture.", "start": 2191.62, "duration": 3.15}, {"text": "Well, except we saw that there\nwere certain special textures", "start": 2194.77, "duration": 3.75}, {"text": "where it would fail.", "start": 2198.52, "duration": 1.38}, {"text": "But presumably,\nEuropa hasn't been", "start": 2199.9, "duration": 3.57}, {"text": "painted in one of these\nunique stripy patterns.", "start": 2203.47, "duration": 3.105}, {"text": "What are the dynamics of this?", "start": 2214.1, "duration": 2.58}, {"text": "Because this idea of\ntime to contact control", "start": 2216.68, "duration": 3.06}, {"text": "can be used in other situations\nas well, such as in autonomous", "start": 2219.74, "duration": 4.2}, {"text": "cars.", "start": 2223.94, "duration": 1.47}, {"text": "But let's focus on\nthe descent here.", "start": 2225.41, "duration": 3.78}, {"text": "Now, why constant\ntime to contact?", "start": 2234.5, "duration": 2.37}, {"text": "Well, we don't really know\nhow to accurately, reliably,", "start": 2236.87, "duration": 7.08}, {"text": "easily compute height from\na monocular camera image,", "start": 2243.95, "duration": 5.31}, {"text": "unless we have some target,\nlike there's a Walmart,", "start": 2249.26, "duration": 3.18}, {"text": "and we know what\nsize Walmarts are.", "start": 2252.44, "duration": 1.68}, {"text": "So we can compute\nhow high we are.", "start": 2254.12, "duration": 3.0}, {"text": "Well, there aren't\nany on Europa.", "start": 2257.12, "duration": 2.31}, {"text": "I hope so.", "start": 2259.43, "duration": 0.93}, {"text": "That won't work for us.", "start": 2260.36, "duration": 2.65}, {"text": "So if we could separately\ncompute height and speed,", "start": 2263.01, "duration": 6.01}, {"text": "then we could do much\nmore sophisticated things.", "start": 2269.02, "duration": 3.39}, {"text": "But we know that we can very\nrobustly get their ratio", "start": 2272.41, "duration": 3.96}, {"text": "in a very simple way.", "start": 2276.37, "duration": 1.58}, {"text": "So that's the attraction there.", "start": 2277.95, "duration": 2.8}, {"text": "So we've got Z/w is\nT. And now we are", "start": 2280.75, "duration": 5.1}, {"text": "assuming that T is constant.", "start": 2285.85, "duration": 2.58}, {"text": "It's very curious\nthat when DARPA", "start": 2288.43, "duration": 3.98}, {"text": "had the grand\nchallenge, of course,", "start": 2292.41, "duration": 1.56}, {"text": "MIT was involved in that.", "start": 2293.97, "duration": 1.63}, {"text": "And we instrumented a car.", "start": 2295.6, "duration": 2.09}, {"text": "And there was one\nsequence that we", "start": 2297.69, "duration": 3.15}, {"text": "thought would be interesting\nto compute after the fact.", "start": 2300.84, "duration": 5.05}, {"text": "They've recorded all this video.", "start": 2305.89, "duration": 1.64}, {"text": "Let's do something with it.", "start": 2307.53, "duration": 1.68}, {"text": "Let's compute time to contact.", "start": 2309.21, "duration": 1.71}, {"text": "And so there's the vehicle\ncoming out of a parking lot,", "start": 2310.92, "duration": 4.11}, {"text": "and it's approaching the\nMIT transport little bus.", "start": 2315.03, "duration": 4.68}, {"text": "And if you plot the time to\ncontact, it's almost constant.", "start": 2319.71, "duration": 5.38}, {"text": "So the vehicle is slowing down.", "start": 2325.09, "duration": 2.96}, {"text": "The closer it gets to the\nbus, the more it slows down.", "start": 2328.05, "duration": 3.06}, {"text": "And so I have no idea\nwhat in the control", "start": 2331.11, "duration": 4.59}, {"text": "algorithm of that\nautonomous vehicle did that,", "start": 2335.7, "duration": 3.87}, {"text": "but it was\ninteresting to observe", "start": 2339.57, "duration": 2.61}, {"text": "that it used a constant\ntime to contact control", "start": 2342.18, "duration": 3.63}, {"text": "to approach the bus\nwithout running into it.", "start": 2345.81, "duration": 4.2}, {"text": "Well, here's an equation\nthat we can solve.", "start": 2350.01, "duration": 3.7}, {"text": "So it goes Z over dZ dt is\nT. And so dZ dt is 1/T Z.", "start": 2353.71, "duration": 11.84}, {"text": "And well, there's a ordinary\ndifferential equation", "start": 2365.55, "duration": 5.97}, {"text": "that you should know the\nsolution for, keeping", "start": 2371.52, "duration": 4.34}, {"text": "in mind that T is a constant.", "start": 2375.86, "duration": 2.99}, {"text": "So dZ dt is proportional\nto Z. What sort of function", "start": 2378.85, "duration": 5.33}, {"text": "does that?", "start": 2384.18, "duration": 0.75}, {"text": "Quadratic?", "start": 2391.23, "duration": 0.81}, {"text": "Exponential?", "start": 2398.18, "duration": 0.78}, {"text": "Anyone?", "start": 2398.96, "duration": 1.89}, {"text": "OK.", "start": 2400.85, "duration": 0.72}, {"text": "So we get Z is e to the minus\nt over T, something like that.", "start": 2401.57, "duration": 7.13}, {"text": "We differentiate that,\nand the derivative", "start": 2408.7, "duration": 2.04}, {"text": "is proportional to\nthe function itself.", "start": 2410.74, "duration": 3.52}, {"text": "And so if we implement\nthis constant time", "start": 2414.26, "duration": 5.81}, {"text": "to contact control\nsystem, what we'll find", "start": 2420.07, "duration": 3.42}, {"text": "is that we're going to get a\ndescent that looks like this.", "start": 2423.49, "duration": 8.8}, {"text": "So here's our Z0.", "start": 2432.29, "duration": 1.73}, {"text": "So it's going to be nice\nand gradual and smooth,", "start": 2437.67, "duration": 3.09}, {"text": "and it will never get there.", "start": 2440.76, "duration": 2.83}, {"text": "So that's the downside.", "start": 2443.59, "duration": 3.29}, {"text": "So what do you do there?", "start": 2446.88, "duration": 1.75}, {"text": "Well, we can do what flies do.", "start": 2448.63, "duration": 3.53}, {"text": "They use constant\ntime to contact", "start": 2452.16, "duration": 2.31}, {"text": "when landing on the ceiling.", "start": 2454.47, "duration": 2.08}, {"text": "And when their legs touch\nthe ceiling, they stop.", "start": 2456.55, "duration": 4.07}, {"text": "So we can have wire hanging\ndown from our spacecraft,", "start": 2460.62, "duration": 5.07}, {"text": "and when it touches the ground,\nwe shut off the engines.", "start": 2465.69, "duration": 2.46}, {"text": "And then it'll just fall\nthose last meter or 2.", "start": 2468.15, "duration": 3.0}, {"text": "And that method, of\ncourse, has been used", "start": 2471.15, "duration": 2.01}, {"text": "in planetary spacecraft before.", "start": 2473.16, "duration": 2.28}, {"text": "But we can just combine it\nhere with the time to contact.", "start": 2475.44, "duration": 3.39}, {"text": "So at a certain point, we\ndo have a distance measurer,", "start": 2478.83, "duration": 4.23}, {"text": "an actual wire, and\nthen it just drops", "start": 2483.06, "duration": 3.84}, {"text": "under gravitational control\nuntil it hits the surface,", "start": 2486.9, "duration": 4.02}, {"text": "I guess.", "start": 2490.92, "duration": 2.59}, {"text": "So that's one aspect of this.", "start": 2493.51, "duration": 2.91}, {"text": "And we can go into\nan error analysis", "start": 2496.42, "duration": 2.61}, {"text": "of what will happen there.", "start": 2499.03, "duration": 6.1}, {"text": "Just for fun we can\ncompare this with a more", "start": 2505.13, "duration": 3.39}, {"text": "traditional approach.", "start": 2508.52, "duration": 1.51}, {"text": "So a more traditional\napproach would", "start": 2510.03, "duration": 2.54}, {"text": "be we run the engine\nat its rate of speed.", "start": 2512.57, "duration": 4.92}, {"text": "And we decelerate.", "start": 2517.49, "duration": 1.68}, {"text": "And we only turn\nit on at the time", "start": 2519.17, "duration": 4.14}, {"text": "where we need to\nturn it on so that we", "start": 2523.31, "duration": 3.33}, {"text": "don't crash into the surface.", "start": 2526.64, "duration": 1.84}, {"text": "So now that method\nrequires that we", "start": 2528.48, "duration": 4.97}, {"text": "know the distance to the surface\nand we know the velocity.", "start": 2533.45, "duration": 2.95}, {"text": "So we have to know\na lot of stuff,", "start": 2536.4, "duration": 1.88}, {"text": "where with the time to\ncontact control, we don't.", "start": 2538.28, "duration": 3.48}, {"text": "You just keep the time\nto contact constant.", "start": 2541.76, "duration": 2.28}, {"text": "So one advantage of\nthis alternate method", "start": 2552.28, "duration": 3.54}, {"text": "is it's more energy efficient.", "start": 2555.82, "duration": 1.96}, {"text": "So here we'll be kind of going\nalmost into a hovering mode.", "start": 2557.78, "duration": 5.24}, {"text": "So we're kind of\nwasting fuel in a way.", "start": 2563.02, "duration": 2.8}, {"text": "So there's a trade-off.", "start": 2565.82, "duration": 1.31}, {"text": "So we're ignoring the fact\nthat the spacecraft is getting", "start": 2578.27, "duration": 4.43}, {"text": "lighter as it's using fuel,\nand so the acceleration will", "start": 2582.7, "duration": 2.88}, {"text": "change.", "start": 2585.58, "duration": 0.5}, {"text": "We'll just assume\nthat it's constant.", "start": 2586.08, "duration": 1.78}, {"text": "And so we integrate\nthat once, and we", "start": 2587.86, "duration": 2.55}, {"text": "get a constant of integration.", "start": 2590.41, "duration": 6.81}, {"text": "And we can apply the\nboundary conditions,", "start": 2597.22, "duration": 3.34}, {"text": "which are that at some\npoint we reach the surface.", "start": 2600.56, "duration": 2.795}, {"text": "And then we integrate\na second time.", "start": 2614.84, "duration": 2.64}, {"text": "We integrate that,\nand we get Z is 1/2", "start": 2617.48, "duration": 3.84}, {"text": "a t squared plus some other\nconstant of integration.", "start": 2621.32, "duration": 5.67}, {"text": "And again, we use the boundary\ncondition, and we end up with z", "start": 2626.99, "duration": 4.29}, {"text": "is 1/2 a.", "start": 2631.28, "duration": 2.1}, {"text": "Of course, you can do\nthis the other way around.", "start": 2637.53, "duration": 2.24}, {"text": "It might be easier to\nstart off with that,", "start": 2639.77, "duration": 2.94}, {"text": "and then just\ndifferentiate to get", "start": 2642.71, "duration": 1.68}, {"text": "to the constant acceleration.", "start": 2644.39, "duration": 2.67}, {"text": "So why did I even\nbother doing this?", "start": 2651.26, "duration": 2.58}, {"text": "Well, because it's\ninteresting to ask,", "start": 2653.84, "duration": 2.64}, {"text": "under that type of control,\nwhat is the time to contact?", "start": 2656.48, "duration": 3.78}, {"text": "And so how do we compute that?", "start": 2660.26, "duration": 1.6}, {"text": "Well, we need Z and dZ dt.", "start": 2661.86, "duration": 3.08}, {"text": "So we just take the\nratio of these two.", "start": 2664.94, "duration": 4.23}, {"text": "So T is-- and so\nthat's going to be 1/2.", "start": 2669.17, "duration": 8.87}, {"text": "So that's saying what\nthe time to contact", "start": 2682.75, "duration": 3.54}, {"text": "is during any part\nof this maneuver.", "start": 2686.29, "duration": 3.42}, {"text": "And it's fascinating that it's a\nhalf of what you get over here.", "start": 2689.71, "duration": 6.45}, {"text": "Over here, of course, the time\nto contact would be T minus T0.", "start": 2699.34, "duration": 4.59}, {"text": "But because of this constant\nacceleration control,", "start": 2703.93, "duration": 3.3}, {"text": "we get that result. Anyway,\nit's just a way of comparing", "start": 2707.23, "duration": 7.38}, {"text": "constant time to contact\ncontrol with a more traditional", "start": 2714.61, "duration": 7.15}, {"text": "approach.", "start": 2721.76, "duration": 1.8}, {"text": "The more traditional approach\nis somewhat more fuel efficient.", "start": 2723.56, "duration": 4.65}, {"text": "But it's much\nharder to implement.", "start": 2728.21, "duration": 1.71}, {"text": "It requires accurate estimations\nof distance and velocities.", "start": 2729.92, "duration": 4.74}, {"text": "Anyway, apparently, NASA\ndecided they can accurately", "start": 2734.66, "duration": 3.45}, {"text": "estimate distance and velocity.", "start": 2738.11, "duration": 1.6}, {"text": "So these crazy machine\nvision programs,", "start": 2739.71, "duration": 4.5}, {"text": "who knows whether they'll work?", "start": 2744.21, "duration": 1.34}, {"text": "So they're not going to do that.", "start": 2745.55, "duration": 2.82}, {"text": "But you can imagine\nthat there are", "start": 2748.37, "duration": 3.3}, {"text": "other applications for this.", "start": 2751.67, "duration": 1.35}, {"text": "Because this is a sensor\nthat's really dumb.", "start": 2753.02, "duration": 3.21}, {"text": "I mean, it's simply a\nmatter of brute force", "start": 2756.23, "duration": 5.31}, {"text": "estimating gradients\nand accumulating totals,", "start": 2761.54, "duration": 3.99}, {"text": "multiplying, and then\nsolving a bunch of equations.", "start": 2765.53, "duration": 3.4}, {"text": "So it's very straightforward.", "start": 2768.93, "duration": 2.46}, {"text": "Now, before we go\non to another topic,", "start": 2771.39, "duration": 2.57}, {"text": "I want to point out\nanother generalization", "start": 2773.96, "duration": 3.27}, {"text": "that we'll take up later,\nand that's optical flow.", "start": 2777.23, "duration": 3.42}, {"text": "So the paper on Stella that\ntalks about the optical mouse", "start": 2783.83, "duration": 4.95}, {"text": "problem primarily is--", "start": 2788.78, "duration": 3.57}, {"text": "what's the title?", "start": 2792.35, "duration": 2.04}, {"text": "\"Computational Fixed Flow,\nDetermining Fixed Flow.\"", "start": 2794.39, "duration": 3.06}, {"text": "Fixed flow, what does that mean?", "start": 2797.45, "duration": 1.6}, {"text": "Well, it means that the motion\nof all parts of the image", "start": 2799.05, "duration": 4.19}, {"text": "are the same.", "start": 2803.24, "duration": 1.24}, {"text": "And as I explained,\nfor an optical mouse,", "start": 2804.48, "duration": 2.69}, {"text": "that's a very good model.", "start": 2807.17, "duration": 1.2}, {"text": "That's very accurate.", "start": 2808.37, "duration": 1.08}, {"text": "But as I'm walking\naround the room,", "start": 2809.45, "duration": 2.85}, {"text": "the motion of different\nparts of the image", "start": 2812.3, "duration": 1.95}, {"text": "are not the same because\nyou're at different distances.", "start": 2814.25, "duration": 3.07}, {"text": "And we saw how we can get that\nout of a perspective projection", "start": 2817.32, "duration": 4.85}, {"text": "equation by differentiating.", "start": 2822.17, "duration": 1.53}, {"text": "And we get some terms that\nare affected by division by z,", "start": 2823.7, "duration": 4.71}, {"text": "and so on.", "start": 2828.41, "duration": 1.92}, {"text": "And then, also, some of\nyou may be moving around,", "start": 2830.33, "duration": 2.58}, {"text": "independent motion.", "start": 2832.91, "duration": 1.2}, {"text": "It's not that.", "start": 2834.11, "duration": 1.23}, {"text": "So these problems\nare particularly", "start": 2835.34, "duration": 2.13}, {"text": "easy to solve when there\nare only a few parameters.", "start": 2837.47, "duration": 3.4}, {"text": "So for the optical mouse there\nare two-- motion in x, motion", "start": 2840.87, "duration": 2.93}, {"text": "and y.", "start": 2843.8, "duration": 1.94}, {"text": "Well, you might be\nturning the mouse.", "start": 2845.74, "duration": 2.46}, {"text": "So it could be three.", "start": 2848.2, "duration": 1.44}, {"text": "And we'll probably take that\nup in a homework problem.", "start": 2849.64, "duration": 3.79}, {"text": "So it'll be a slight\ngeneralization", "start": 2853.43, "duration": 2.12}, {"text": "of what we did with\nthe added feature", "start": 2855.55, "duration": 2.73}, {"text": "that you're not only tracking\nthe position of the mouse,", "start": 2858.28, "duration": 3.15}, {"text": "but if the user is turning it,\nyou also want to recover that.", "start": 2861.43, "duration": 4.8}, {"text": "Maybe not because that's an\ninteresting input to your GUI,", "start": 2866.23, "duration": 3.18}, {"text": "but because it might screw up\nthe estimation of the x and y", "start": 2869.41, "duration": 4.32}, {"text": "motion if you do rotate.", "start": 2873.73, "duration": 2.7}, {"text": "Anyway, so those\nare all cases where", "start": 2876.43, "duration": 2.25}, {"text": "we have a fairly small\nnumber of unknowns,", "start": 2878.68, "duration": 3.63}, {"text": "and we have a hugely\noverdetermined system.", "start": 2882.31, "duration": 2.25}, {"text": "We have some measurement\nat every pixel.", "start": 2884.56, "duration": 3.0}, {"text": "What if we don't have that?", "start": 2887.56, "duration": 1.77}, {"text": "Well, that's going to be a\nproblem, because at every pixel", "start": 2889.33, "duration": 11.15}, {"text": "we have an equation like that.", "start": 2900.48, "duration": 2.38}, {"text": "So we have a constraint.", "start": 2902.86, "duration": 1.32}, {"text": "So if we have 10\nmillion pixels, we've", "start": 2904.18, "duration": 2.06}, {"text": "got 10 million constraints.", "start": 2906.24, "duration": 1.8}, {"text": "Great.", "start": 2908.04, "duration": 0.6}, {"text": "Except at every pixel now, we\nalso have an unknown velocity.", "start": 2908.64, "duration": 5.4}, {"text": "Whoa!", "start": 2916.83, "duration": 0.88}, {"text": "Cheap chalk.", "start": 2917.71, "duration": 2.36}, {"text": "So that means that we have\ntwice as many unknowns", "start": 2920.07, "duration": 5.19}, {"text": "as there are equations.", "start": 2925.26, "duration": 1.47}, {"text": "Well, that's a\nprescription for disaster.", "start": 2926.73, "duration": 4.4}, {"text": "So highly underconstrained,\nand it's an ill-posed problem.", "start": 2931.13, "duration": 9.585}, {"text": "And in this case, it's\nill posed in the sense", "start": 2946.15, "duration": 2.27}, {"text": "that there's an infinite\nnumber of solutions.", "start": 2948.42, "duration": 3.21}, {"text": "And in fact, if you\ngive me a solution,", "start": 2951.63, "duration": 2.4}, {"text": "I can easily construct\nanother solution,", "start": 2954.03, "duration": 3.57}, {"text": "because all I need to\ndo is at every pixel I", "start": 2957.6, "duration": 2.49}, {"text": "need to obey this constraint.", "start": 2960.09, "duration": 2.1}, {"text": "So at every pixel, I'm\nsomewhere along this line.", "start": 2962.19, "duration": 6.21}, {"text": "And now you give me the,\nquote, \"correct solution\"", "start": 2968.4, "duration": 2.79}, {"text": "that says here for that pixel.", "start": 2971.19, "duration": 2.67}, {"text": "Well, the thing is\nthat I can go there.", "start": 2973.86, "duration": 4.45}, {"text": "It doesn't change anything.", "start": 2978.31, "duration": 2.46}, {"text": "And so that's pretty dramatic.", "start": 2980.77, "duration": 4.57}, {"text": "That means that I\ncan systematically", "start": 2985.34, "duration": 2.1}, {"text": "go through the image,\nand at every pixel", "start": 2987.44, "duration": 1.8}, {"text": "I can give you an infinite\nnumber of other values", "start": 2989.24, "duration": 2.91}, {"text": "that will work.", "start": 2992.15, "duration": 1.87}, {"text": "So we'll need some\nheavy constraint.", "start": 2994.02, "duration": 3.05}, {"text": "And one constraint that we\ncan use and will use later", "start": 2997.07, "duration": 4.29}, {"text": "is that neighboring\npoints in the image", "start": 3001.36, "duration": 2.85}, {"text": "do not move independently.", "start": 3004.21, "duration": 1.83}, {"text": "They may not move at\nthe same velocity,", "start": 3006.04, "duration": 2.25}, {"text": "but they tend to move\nat a similar velocity.", "start": 3008.29, "duration": 4.08}, {"text": "So that's a good\nthing and a bad thing.", "start": 3012.37, "duration": 2.13}, {"text": "I mean, it's good in\nthat, oh, here we've", "start": 3014.5, "duration": 1.89}, {"text": "got some sort of constraint.", "start": 3016.39, "duration": 1.71}, {"text": "And it's a bad thing,\nbecause it's not", "start": 3018.1, "duration": 2.19}, {"text": "like an equation that says u\nplus 3v is 15 or something.", "start": 3020.29, "duration": 4.63}, {"text": "It's more vague.", "start": 3024.92, "duration": 1.1}, {"text": "It's like, oh, it's\nvarying smoothly.", "start": 3026.02, "duration": 2.43}, {"text": "What does that mean?", "start": 3028.45, "duration": 1.29}, {"text": "What's smoothly?", "start": 3029.74, "duration": 1.26}, {"text": "What epsilon change\ncan you allow?", "start": 3031.0, "duration": 3.27}, {"text": "So that makes that problem very\ninteresting and non-trivial.", "start": 3034.27, "duration": 7.11}, {"text": "We'll get to that later.", "start": 3041.38, "duration": 1.38}, {"text": "We don't have the tools\nat this point to do that,", "start": 3042.76, "duration": 2.94}, {"text": "but it's just to\nalert you to the fact", "start": 3045.7, "duration": 2.55}, {"text": "that the fixed flow isn't\nthe be all and end all.", "start": 3048.25, "duration": 5.07}, {"text": "There's more to come.", "start": 3053.32, "duration": 2.14}, {"text": "Now, suppose that you don't\nhave the tools to solve", "start": 3055.46, "duration": 4.73}, {"text": "that problem.", "start": 3060.19, "duration": 1.69}, {"text": "Well, you can do\nsomething, which", "start": 3061.88, "duration": 2.6}, {"text": "is divide the image\nup into pieces,", "start": 3064.48, "duration": 4.05}, {"text": "and then apply fix\nflow to each piece.", "start": 3068.53, "duration": 10.005}, {"text": "And the idea is\nthat, well, if we", "start": 3082.82, "duration": 2.25}, {"text": "make the pieces\nsmall enough, there", "start": 3085.07, "duration": 2.07}, {"text": "won't be much variation in the\nvelocity within that piece.", "start": 3087.14, "duration": 4.0}, {"text": "And so the assumption\nthat u and v", "start": 3091.14, "duration": 3.14}, {"text": "are constant in that little\narea isn't such a bad one.", "start": 3094.28, "duration": 5.04}, {"text": "And so now there are\nall kinds of trade-offs,", "start": 3099.32, "duration": 2.67}, {"text": "because if we make\nthese boxes very large,", "start": 3101.99, "duration": 4.5}, {"text": "we get only a very\ncoarse image of the flow.", "start": 3106.49, "duration": 3.24}, {"text": "We only have a flow vector\nfor each of these boxes.", "start": 3109.73, "duration": 5.99}, {"text": "On the other hand, if we make\nthe subimage areas very small,", "start": 3115.72, "duration": 5.94}, {"text": "we have much less constraint.", "start": 3121.66, "duration": 1.86}, {"text": "And we have much less of that\nwonderful noise suppression", "start": 3123.52, "duration": 4.95}, {"text": "property of an\noverdetermined system.", "start": 3128.47, "duration": 3.12}, {"text": "And also, when we look at\nsmall areas of an image,", "start": 3131.59, "duration": 5.61}, {"text": "they are much more likely to\nbe similar to the type of image", "start": 3137.2, "duration": 4.02}, {"text": "that we talked about\nthat doesn't work.", "start": 3141.22, "duration": 2.61}, {"text": "If I look at a very\nsmall area of the image", "start": 3143.83, "duration": 3.48}, {"text": "and it just has this\nedge in it, well, that's", "start": 3147.31, "duration": 2.31}, {"text": "exactly the kind of thing where\nthe aperture problem comes in.", "start": 3149.62, "duration": 3.39}, {"text": "And I can't determine what the\nmotion is in that direction.", "start": 3153.01, "duration": 3.62}, {"text": "So yes, you can do this.", "start": 3156.63, "duration": 1.7}, {"text": "You can use what we\nhave-- the fixed flow", "start": 3158.33, "duration": 2.51}, {"text": "method on a grid of\na chopped up image.", "start": 3160.84, "duration": 4.83}, {"text": "But there are trade-offs, and\nthey're somewhat unpleasant.", "start": 3165.67, "duration": 3.45}, {"text": "If you make these areas\nfairly small, some of them", "start": 3169.12, "duration": 3.03}, {"text": "may be even more or less\nuniform in brightness.", "start": 3172.15, "duration": 3.21}, {"text": "If I'm looking at\nthat gray wall,", "start": 3175.36, "duration": 1.8}, {"text": "it's uniform in brightness.", "start": 3177.16, "duration": 1.5}, {"text": "And if it moves, I can't tell.", "start": 3178.66, "duration": 2.64}, {"text": "It's just the same.", "start": 3181.3, "duration": 1.39}, {"text": "So anyway, that's something\nthat has been done and works,", "start": 3182.69, "duration": 6.56}, {"text": "but it's not the solution\nthat we'll be looking for.", "start": 3189.25, "duration": 5.88}, {"text": "We're moving towards talking\nabout brightness more", "start": 3199.43, "duration": 3.33}, {"text": "than perspective projection.", "start": 3202.76, "duration": 2.25}, {"text": "But I want to just\ndo one more thing", "start": 3205.01, "duration": 5.22}, {"text": "with perspective projection.", "start": 3210.23, "duration": 2.49}, {"text": "And that has to do\nwith vanishing points.", "start": 3212.72, "duration": 2.55}, {"text": "And these play a role in\ncamera calibration or sometimes", "start": 3219.0, "duration": 11.55}, {"text": "finding the relative orientation\nof two coordinate systems.", "start": 3230.55, "duration": 4.72}, {"text": "And just to make that\nsound less mysterious,", "start": 3235.27, "duration": 2.96}, {"text": "if we have man-made\nobjects, they often", "start": 3238.23, "duration": 4.5}, {"text": "have planar surfaces.", "start": 3242.73, "duration": 1.32}, {"text": "And they often have right angles\nbetween their planar surfaces,", "start": 3244.05, "duration": 4.41}, {"text": "unless you go over\nto start there.", "start": 3248.46, "duration": 2.34}, {"text": "And so when we\nlook in the images,", "start": 3250.8, "duration": 2.31}, {"text": "we're going to find a lot\nof straight edges often.", "start": 3253.11, "duration": 3.84}, {"text": "And often, a lot of\nthem are parallel.", "start": 3256.95, "duration": 3.045}, {"text": "And so we can\nactually exploit that.", "start": 3264.06, "duration": 4.27}, {"text": "So if, for example, you're\nhovering above some building,", "start": 3268.33, "duration": 4.01}, {"text": "like the main buildings at MIT\nis all on a rectangular grid,", "start": 3272.34, "duration": 4.26}, {"text": "you can determine from the\nimage certain vanishing points.", "start": 3276.6, "duration": 3.33}, {"text": "And from that, you can\ndetermine your rotation", "start": 3279.93, "duration": 3.84}, {"text": "relative to the\ncoordinate system", "start": 3283.77, "duration": 2.07}, {"text": "of that rectangular block.", "start": 3285.84, "duration": 2.43}, {"text": "And so that's something there.", "start": 3288.27, "duration": 3.24}, {"text": "Or if you look at a cube or\nsome other calibration object,", "start": 3291.51, "duration": 6.12}, {"text": "you may be able to recover\nparameters of the imaging", "start": 3297.63, "duration": 3.42}, {"text": "system.", "start": 3301.05, "duration": 0.52}, {"text": "So it's important in\nthe camera calibration,", "start": 3301.57, "duration": 2.88}, {"text": "which is, of course,\nimportant in robotics", "start": 3304.45, "duration": 2.06}, {"text": "and other applications.", "start": 3306.51, "duration": 1.66}, {"text": "So let's just see\nwhat this is about.", "start": 3308.17, "duration": 3.69}, {"text": "So in the first\nhomework problem,", "start": 3311.86, "duration": 2.42}, {"text": "one of the questions\nyou were asked", "start": 3314.28, "duration": 1.5}, {"text": "is, what's the\nprediction of a line?", "start": 3315.78, "duration": 3.18}, {"text": "And there are various ways of\napproaching that algebraically", "start": 3318.96, "duration": 3.33}, {"text": "or geometrically.", "start": 3322.29, "duration": 1.23}, {"text": "One geometric way is just\nto say, here's my line.", "start": 3323.52, "duration": 4.71}, {"text": "I'm going to connect it to\nthe center of projection.", "start": 3328.23, "duration": 5.01}, {"text": "And what do I get?", "start": 3333.24, "duration": 1.36}, {"text": "Well, I get a plane.", "start": 3334.6, "duration": 1.67}, {"text": "If I connect-- if I look at\nthe locus of all those lines", "start": 3336.27, "duration": 4.83}, {"text": "that connect that point to\nthe line, it forms a plane.", "start": 3341.1, "duration": 3.45}, {"text": "And then what is the\nimage of it going to be?", "start": 3344.55, "duration": 1.98}, {"text": "Well, I'm going to intersect\nthat with the image plane.", "start": 3346.53, "duration": 3.37}, {"text": "So what's the intersection of\none plane with another plane?", "start": 3349.9, "duration": 4.52}, {"text": "It's a straight line.", "start": 3354.42, "duration": 1.78}, {"text": "So there's a simple way\nof seeing that line in 3D", "start": 3356.2, "duration": 4.13}, {"text": "projected into a line in 2D.", "start": 3360.33, "duration": 2.1}, {"text": "It's a funny projection\nin that if you", "start": 3362.43, "duration": 3.63}, {"text": "were to mark this\nlike a measuring tape", "start": 3366.06, "duration": 5.16}, {"text": "with equal intervals,\nand then you", "start": 3371.22, "duration": 2.01}, {"text": "look at the projection\nof those marks,", "start": 3373.23, "duration": 2.67}, {"text": "they won't be equally spaced,\nbecause the part where", "start": 3375.9, "duration": 3.24}, {"text": "the measuring tape\nis close to you", "start": 3379.14, "duration": 2.97}, {"text": "will image with\nlarger magnification", "start": 3382.11, "duration": 2.25}, {"text": "so the marks are\nfurther apart then.", "start": 3384.36, "duration": 5.01}, {"text": "So the fact that a\nline goes to a line", "start": 3389.37, "duration": 1.95}, {"text": "is a little bit overconfident.", "start": 3391.32, "duration": 4.46}, {"text": "It's making us think that we\nunderstand the problem very", "start": 3395.78, "duration": 3.19}, {"text": "well, when actually\nit's a little subtle.", "start": 3398.97, "duration": 2.73}, {"text": "So the other way is algebraic.", "start": 3401.7, "duration": 2.13}, {"text": "And so one way we can do this\nis to say that a line in 3D", "start": 3403.83, "duration": 10.12}, {"text": "can be defined in various ways.", "start": 3413.95, "duration": 1.63}, {"text": "One of them is we have\na point on the line,", "start": 3415.58, "duration": 3.53}, {"text": "and then we have a direction.", "start": 3419.11, "duration": 2.29}, {"text": "And we might as well use a unit\nvector to define the direction.", "start": 3421.4, "duration": 4.25}, {"text": "So that's one way of\ntalking about a line in 3D.", "start": 3425.65, "duration": 4.89}, {"text": "What are other ways?", "start": 3430.54, "duration": 1.5}, {"text": "Can you think of\nsome other ways?", "start": 3432.04, "duration": 3.66}, {"text": "We can do a parametric\nrepresentation", "start": 3435.7, "duration": 1.89}, {"text": "where we have, for example, x is\nsome function of some parameter", "start": 3437.59, "duration": 6.15}, {"text": "T, and y is some\nfunction of parameter T,", "start": 3443.74, "duration": 2.91}, {"text": "and z is some function\nof parameter T,", "start": 3446.65, "duration": 3.03}, {"text": "or we can have some\nimplicit representation,", "start": 3449.68, "duration": 3.3}, {"text": "or we can intersect two planes.", "start": 3452.98, "duration": 4.23}, {"text": "And why is that convenient?", "start": 3457.21, "duration": 1.77}, {"text": "Well, the equation of a\nplane is a linear equation.", "start": 3458.98, "duration": 3.25}, {"text": "And so when you\nintersect two planes,", "start": 3462.23, "duration": 2.15}, {"text": "we're dealing with two\nlinear equations then.", "start": 3464.38, "duration": 2.16}, {"text": "We've already seen that having\nlinear equations can be a plus.", "start": 3466.54, "duration": 4.35}, {"text": "But let's stay with this.", "start": 3470.89, "duration": 1.2}, {"text": "And in component\nform, of course,", "start": 3472.09, "duration": 2.26}, {"text": "that just means it's x0 plus s.", "start": 3474.35, "duration": 3.41}, {"text": "What did I call it,\nalpha or something?", "start": 3477.76, "duration": 2.554}, {"text": "Alpha s.", "start": 3483.22, "duration": 0.705}, {"text": "So then we're going\nto now project that", "start": 3492.12, "duration": 3.81}, {"text": "into the image using\nperspective projection.", "start": 3495.93, "duration": 7.05}, {"text": "And we can, of course,\nuse the component form", "start": 3502.98, "duration": 3.21}, {"text": "that we used up there, or\nwe can use the vector form.", "start": 3506.19, "duration": 4.44}, {"text": "And so we get--", "start": 3510.63, "duration": 1.41}, {"text": "so unfortunately,\nthis doesn't lead", "start": 3533.53, "duration": 3.84}, {"text": "to some very\nelegant, nice result.", "start": 3537.37, "duration": 5.52}, {"text": "Or rather, it doesn't without--", "start": 3542.89, "duration": 2.67}, {"text": "sorry.", "start": 3545.56, "duration": 0.54}, {"text": "I guess Z is dependent on gamma.", "start": 3546.1, "duration": 4.59}, {"text": "Unless we go quite a\nlong way further than", "start": 3550.69, "duration": 2.31}, {"text": "I want to when it becomes\nnice and elegant again.", "start": 3553.0, "duration": 5.97}, {"text": "So that's our transformation.", "start": 3558.97, "duration": 3.13}, {"text": "And so s is a parameter\nthat varies along the line.", "start": 3562.1, "duration": 5.57}, {"text": "So different points on the line\nhave different values of s.", "start": 3567.67, "duration": 3.99}, {"text": "And if that's a\nunit vector, then s", "start": 3571.66, "duration": 2.16}, {"text": "is actually a measure\nof length along there.", "start": 3573.82, "duration": 3.06}, {"text": "Because of that division\nby Z, it's kind of messy.", "start": 3579.67, "duration": 2.79}, {"text": "But one thing that's\ninteresting to do", "start": 3582.46, "duration": 2.1}, {"text": "is to look at what happens when\nwe go very far along the line.", "start": 3584.56, "duration": 4.275}, {"text": "So we go there.", "start": 3594.6, "duration": 1.03}, {"text": "So we make s very big.", "start": 3595.63, "duration": 1.52}, {"text": "Well, that means that\nwe can ignore s0,", "start": 3597.15, "duration": 2.46}, {"text": "and we can ignore z0.", "start": 3599.61, "duration": 1.86}, {"text": "And we get alpha over gamma.", "start": 3601.47, "duration": 2.31}, {"text": "Gamma, not beta.", "start": 3611.32, "duration": 1.25}, {"text": "And that is called\nthe vanishing point.", "start": 3618.56, "duration": 2.175}, {"text": "So as you move\nalong this line, you", "start": 3624.03, "duration": 7.19}, {"text": "start to go more and\nmore slowly in the image.", "start": 3631.22, "duration": 2.55}, {"text": "And you approach, but\nnever reach this point.", "start": 3633.77, "duration": 4.18}, {"text": "And so actually the image\nof an infinitely long line", "start": 3637.95, "duration": 4.04}, {"text": "is not an infinitely long\nline in the image plane.", "start": 3641.99, "duration": 2.67}, {"text": "It starts somewhere, and\nthis is where it starts.", "start": 3644.66, "duration": 4.86}, {"text": "Then as we move\nalong the line in 3D,", "start": 3649.52, "duration": 4.52}, {"text": "we don't move along the\nline in 2D in a uniform way,", "start": 3654.04, "duration": 5.73}, {"text": "because when we're very far out,\nwe can move a long way in 3D.", "start": 3659.77, "duration": 5.16}, {"text": "And it only has a tiny\neffect in the image.", "start": 3664.93, "duration": 2.06}, {"text": "So that's what makes\nit kind of awkward.", "start": 3666.99, "duration": 2.935}, {"text": "Now, one thing that we\nshould immediately recognize", "start": 3672.72, "duration": 3.45}, {"text": "is that parallel lines\nhave the same vanishing", "start": 3676.17, "duration": 4.48}, {"text": "point, because the offset x0,\ny0, Z0, the origin of our line,", "start": 3680.65, "duration": 15.37}, {"text": "they don't come\ninto this equation.", "start": 3696.02, "duration": 2.22}, {"text": "It's only the\ndirection that matters.", "start": 3698.24, "duration": 3.04}, {"text": "And so that's\ninteresting, because that", "start": 3701.28, "duration": 2.18}, {"text": "means that if we have a bunch\nof parallel lines in 3D,", "start": 3703.46, "duration": 3.93}, {"text": "they are all going to give rise\nto the same vanishing point.", "start": 3707.39, "duration": 3.97}, {"text": "So if we're looking at\na rectangular building,", "start": 3711.36, "duration": 4.73}, {"text": "there are three sets of edges,\neach containing parallel lines.", "start": 3716.09, "duration": 7.68}, {"text": "And so we expect to see\nthree vanishing points.", "start": 3723.77, "duration": 4.56}, {"text": "So let's see if I can do this.", "start": 3728.33, "duration": 2.18}, {"text": "This might be--", "start": 3730.51, "duration": 0.87}, {"text": "Now, this is a bit extreme\nbecause I picked the vanishing", "start": 3749.59, "duration": 2.49}, {"text": "points pretty close.", "start": 3752.08, "duration": 4.17}, {"text": "So here's a cube.", "start": 3756.25, "duration": 1.575}, {"text": "Well, not that good.", "start": 3770.48, "duration": 3.03}, {"text": "But anyway, if it\nwas for real, there", "start": 3773.51, "duration": 3.0}, {"text": "would be three sets of parallel\nlines, which each give rise", "start": 3776.51, "duration": 4.83}, {"text": "to a vanishing point.", "start": 3781.34, "duration": 1.74}, {"text": "And so what?", "start": 3785.93, "duration": 2.87}, {"text": "Well, the point is that if\nI can find those vanishing", "start": 3788.8, "duration": 3.15}, {"text": "points in the image, I can\nuse them to my advantage", "start": 3791.95, "duration": 3.72}, {"text": "to learn something about the\ngeometry of the image taking", "start": 3795.67, "duration": 3.6}, {"text": "situation.", "start": 3799.27, "duration": 2.25}, {"text": "And just to let\nyou know that this", "start": 3801.52, "duration": 4.32}, {"text": "isn't some vague theoretical\nthing that nobody cares about,", "start": 3805.84, "duration": 5.58}, {"text": "here's an application.", "start": 3811.42, "duration": 1.36}, {"text": "So every year a few people are\nkilled on the side of the road", "start": 3812.78, "duration": 5.09}, {"text": "because of distracted\ndrivers, even before texting.", "start": 3817.87, "duration": 5.31}, {"text": "And so there's an\ninterest in trying", "start": 3823.18, "duration": 3.93}, {"text": "to warn whoever's stopped\nthere-- police officer,", "start": 3827.11, "duration": 2.79}, {"text": "construction worker,\nwhatever-- that there", "start": 3829.9, "duration": 2.73}, {"text": "is a car on a trajectory\nthat may impact them.", "start": 3832.63, "duration": 4.18}, {"text": "So how do you do that?", "start": 3836.81, "duration": 2.58}, {"text": "Well, you can stick a camera,\nmaybe an Android phone,", "start": 3839.39, "duration": 3.56}, {"text": "in the window of the cruiser.", "start": 3842.95, "duration": 2.34}, {"text": "And it's watching-- this\nis mostly nighttime--", "start": 3845.29, "duration": 3.52}, {"text": "it's watching\nheadlights going by.", "start": 3848.81, "duration": 1.82}, {"text": "And it's monocular, so it\ndoesn't have depth information.", "start": 3850.63, "duration": 4.32}, {"text": "But it can figure out whether\nthe trajectory is possibly", "start": 3854.95, "duration": 5.67}, {"text": "dangerous or not.", "start": 3860.62, "duration": 0.96}, {"text": "But one of the\nthings it needs to do", "start": 3861.58, "duration": 1.56}, {"text": "is to figure out the geometry\nof its coordinate system", "start": 3863.14, "duration": 3.66}, {"text": "and the road's\ncoordinate system.", "start": 3866.8, "duration": 2.118}, {"text": "You don't want the\nperson who's using", "start": 3868.918, "duration": 1.542}, {"text": "it to have to come out\nwith surveying equipment", "start": 3870.46, "duration": 2.67}, {"text": "and measure the\nangles and so on.", "start": 3873.13, "duration": 3.3}, {"text": "So the camera has\nto, on its own,", "start": 3876.43, "duration": 3.55}, {"text": "try and determine the\nrotation of its camera-centric", "start": 3879.98, "duration": 5.15}, {"text": "coordinate system\nrelative to the line,", "start": 3885.13, "duration": 4.14}, {"text": "to the road, x, y, and z.", "start": 3889.27, "duration": 2.25}, {"text": "And so one way to do that is\nto look for a vanishing point.", "start": 3891.52, "duration": 4.7}, {"text": "So in the case that the\nroad section is straight,", "start": 3896.22, "duration": 4.93}, {"text": "you can use image processing\nmethods to find those lines.", "start": 3901.15, "duration": 3.52}, {"text": "And then you can intersect them\nto find the vanishing points.", "start": 3904.67, "duration": 2.87}, {"text": "And then you can use those to\nrecover at least two parameters", "start": 3907.54, "duration": 4.53}, {"text": "of the transformation.", "start": 3912.07, "duration": 1.29}, {"text": "One is how much is the\ncamera turned relative", "start": 3913.36, "duration": 2.91}, {"text": "to the direction of the\nroad, and the other one", "start": 3916.27, "duration": 2.97}, {"text": "is how much is the camera\nturned relative to the line", "start": 3919.24, "duration": 3.18}, {"text": "to the horizon.", "start": 3922.42, "duration": 1.11}, {"text": "So we've got pan\nand tilt. And we", "start": 3923.53, "duration": 2.1}, {"text": "can get pan and tilt\nusing vanishing points.", "start": 3925.63, "duration": 2.655}, {"text": "Ugh, I don't want to do that.", "start": 3934.504, "duration": 2.376}, {"text": "So let's think about using\nthis in camera calibration,", "start": 3936.88, "duration": 5.79}, {"text": "another application.", "start": 3942.67, "duration": 3.15}, {"text": "So in calibrating\na camera, there", "start": 3945.82, "duration": 6.53}, {"text": "are several parameters\nyou're looking for.", "start": 3952.35, "duration": 3.06}, {"text": "The main ones are the\ncenter of projection.", "start": 3955.41, "duration": 6.27}, {"text": "So you say, well, yeah,\nthe center of projection", "start": 3961.68, "duration": 2.67}, {"text": "is where the lens is.", "start": 3964.35, "duration": 1.33}, {"text": "Yeah.", "start": 3965.68, "duration": 0.5}, {"text": "But where's the lens?", "start": 3966.18, "duration": 1.59}, {"text": "And relative to what?", "start": 3967.77, "duration": 2.1}, {"text": "So here's our integrated\ncircuit sensor.", "start": 3969.87, "duration": 4.56}, {"text": "And up here is the lens\nor pinhole for the moment.", "start": 3974.43, "duration": 5.43}, {"text": "And presumably, whoever\nbuilt this thing", "start": 3979.86, "duration": 4.38}, {"text": "tries to put the\ncenter of projection", "start": 3984.24, "duration": 5.85}, {"text": "above the middle of the chip.", "start": 3990.09, "duration": 1.38}, {"text": "But that's not necessarily\ngoing to be accurately done.", "start": 3991.47, "duration": 3.75}, {"text": "I mean, these things are\nmicroscopic in some cases,", "start": 3995.22, "duration": 4.8}, {"text": "like this thing.", "start": 4000.02, "duration": 1.68}, {"text": "It had a focal length\nof 4 millimeters.", "start": 4001.7, "duration": 3.04}, {"text": "And so we're dealing with\nvery small quantities.", "start": 4004.74, "duration": 3.89}, {"text": "Plus, the pixels here may be 10\nmicrons, or in the cell phone", "start": 4008.63, "duration": 4.44}, {"text": "maybe only 5.", "start": 4013.07, "duration": 1.23}, {"text": "So it's very unlikely\nthat you would", "start": 4014.3, "duration": 3.54}, {"text": "be able to position\nthe lens in such a way", "start": 4017.84, "duration": 2.31}, {"text": "that it was accurate\nto one sensor position.", "start": 4020.15, "duration": 3.54}, {"text": "So we need to recover\nthat position.", "start": 4023.69, "duration": 3.36}, {"text": "And we also need to recover the\nheight of the center projection", "start": 4027.05, "duration": 4.71}, {"text": "above the image plane.", "start": 4031.76, "duration": 3.27}, {"text": "And ultimately, we'll be using\na camera-centric system that's", "start": 4035.03, "duration": 4.53}, {"text": "origin at the center\nof projection.", "start": 4039.56, "duration": 2.04}, {"text": "But to do that, we\nneed to understand", "start": 4041.6, "duration": 2.31}, {"text": "how row and column in the image\nsensor translate into x and y", "start": 4043.91, "duration": 5.61}, {"text": "in that camera-centric\ncoordinate system.", "start": 4049.52, "duration": 3.12}, {"text": "So the short answer\nis if you give me", "start": 4052.64, "duration": 4.41}, {"text": "a coordinate system in the chip,\nwhich is a, let's say, column", "start": 4057.05, "duration": 6.0}, {"text": "and row count, I want to\nknow where that point is.", "start": 4063.05, "duration": 6.09}, {"text": "And typically, the\nrow and column count", "start": 4069.14, "duration": 2.52}, {"text": "won't be taken from\nthe center of the chip,", "start": 4071.66, "duration": 2.13}, {"text": "but from one of the corners.", "start": 4073.79, "duration": 2.59}, {"text": "And when you give\nme the position", "start": 4076.38, "duration": 2.57}, {"text": "of the center of projection,\nwhat units do I want?", "start": 4078.95, "duration": 4.05}, {"text": "The size of the pixel.", "start": 4083.0, "duration": 2.42}, {"text": "It'd be nice to\nhave it in microns.", "start": 4085.42, "duration": 1.5}, {"text": "But if you don't know\nthe size of the pixels,", "start": 4086.92, "duration": 3.69}, {"text": "you can't do that.", "start": 4090.61, "duration": 1.02}, {"text": "And conversely, you don't\nneed to know the size", "start": 4091.63, "duration": 2.85}, {"text": "of the pixels for projection.", "start": 4094.48, "duration": 1.68}, {"text": "We can express that.", "start": 4096.16, "duration": 3.313}, {"text": "Like the focal length,\nwe can express it", "start": 4099.473, "duration": 1.667}, {"text": "in terms of pixel\nsize, particularly easy", "start": 4101.14, "duration": 3.0}, {"text": "if the pixel is square.", "start": 4104.14, "duration": 1.049}, {"text": "I mean, otherwise, you've\ngot to deal with the fact", "start": 4105.189, "duration": 2.641}, {"text": "that the x and y dimensions\naren't on the same scale.", "start": 4107.83, "duration": 4.17}, {"text": "So that's the task.", "start": 4112.0, "duration": 1.729}, {"text": "Tell me where that point is.", "start": 4113.729, "duration": 2.201}, {"text": "And it may need to be\nrepeated, particularly if it's", "start": 4115.93, "duration": 2.37}, {"text": "a camera that has\nzoom capability,", "start": 4118.3, "duration": 3.21}, {"text": "because then all of\nthat's going to change", "start": 4121.51, "duration": 2.01}, {"text": "as you zoom in and out.", "start": 4123.52, "duration": 1.5}, {"text": "And you'd want to perform this\nkind of calibration again.", "start": 4125.02, "duration": 4.78}, {"text": "So there are various\nways of doing this.", "start": 4129.8, "duration": 2.28}, {"text": "One is-- and we'll talk\nabout this some more later.", "start": 4132.08, "duration": 3.32}, {"text": "But here's a very simple one.", "start": 4137.96, "duration": 3.06}, {"text": "We use a calibration object.", "start": 4141.02, "duration": 1.754}, {"text": "And so a calibration object is\nsomething with a known shape.", "start": 4149.52, "duration": 3.9}, {"text": "And we already talked\nabout that when", "start": 4153.42, "duration": 1.74}, {"text": "I was showing the slides,\nwhere we used the sphere", "start": 4155.16, "duration": 2.369}, {"text": "as a calibration object.", "start": 4157.529, "duration": 2.04}, {"text": "So would a sphere be a useful\ncalibration object here?", "start": 4159.569, "duration": 8.821}, {"text": "So the image of the sphere,\nas you saw in homework problem", "start": 4168.39, "duration": 2.719}, {"text": "one, is a conic section.", "start": 4171.109, "duration": 2.521}, {"text": "And so for example, if the\nsphere was directly above", "start": 4180.09, "duration": 5.82}, {"text": "on this line, its projection\nwould be a circle.", "start": 4185.91, "duration": 3.869}, {"text": "The sphere is up here.", "start": 4189.779, "duration": 0.961}, {"text": "And how do I know that?", "start": 4190.74, "duration": 1.119}, {"text": "Well, because I\nconnect the sphere", "start": 4191.859, "duration": 2.361}, {"text": "to the center of projection.", "start": 4194.22, "duration": 1.86}, {"text": "And I get a right circular cone.", "start": 4196.08, "duration": 2.31}, {"text": "And I extend that down here and\nintersect it with this plane,", "start": 4198.39, "duration": 3.39}, {"text": "and intersect the right circular\ncone with a plane perpendicular", "start": 4201.78, "duration": 3.75}, {"text": "to its axis.", "start": 4205.53, "duration": 2.1}, {"text": "And you get a circle.", "start": 4207.63, "duration": 1.56}, {"text": "But when I move the\nsphere to the side,", "start": 4209.19, "duration": 2.82}, {"text": "it's going to become elliptical.", "start": 4212.01, "duration": 1.723}, {"text": "It's going to become--", "start": 4213.733, "duration": 0.917}, {"text": "imagine-- take an extreme case\nwhere this is way down here.", "start": 4214.65, "duration": 4.09}, {"text": "And now you project\nit into the image,", "start": 4218.74, "duration": 1.82}, {"text": "it becomes a very\nelongated ellipse.", "start": 4220.56, "duration": 2.8}, {"text": "And if you move it down far\nenough, it'll be a hyperbola.", "start": 4223.36, "duration": 5.25}, {"text": "So yeah, you can do that.", "start": 4228.61, "duration": 1.26}, {"text": "But it would then require\nthat you accurately", "start": 4229.87, "duration": 2.43}, {"text": "determine the position\nof that figure,", "start": 4232.3, "duration": 2.97}, {"text": "whether it's an ellipse,\nor hyperbola, or circle,", "start": 4235.27, "duration": 2.67}, {"text": "or parabola, and its parameters.", "start": 4237.94, "duration": 4.87}, {"text": "So that can be done.", "start": 4242.81, "duration": 0.9}, {"text": "But the noise gain is high.", "start": 4243.71, "duration": 2.78}, {"text": "It's not a very good method.", "start": 4246.49, "duration": 2.31}, {"text": "The big advantage\nof this is a sphere", "start": 4248.8, "duration": 2.07}, {"text": "is easy to make, easy to obtain.", "start": 4250.87, "duration": 3.87}, {"text": "A cube isn't.", "start": 4254.74, "duration": 0.97}, {"text": "So let's try a cube.", "start": 4255.71, "duration": 3.25}, {"text": "I know that a cube isn't easy\nbecause when my father got", "start": 4258.96, "duration": 4.83}, {"text": "his master's in operating\nequipment to make objects,", "start": 4263.79, "duration": 8.22}, {"text": "his task was to make\na 1 centimeter cube.", "start": 4272.01, "duration": 3.75}, {"text": "And it had to be\naccurate to a micron.", "start": 4275.76, "duration": 2.52}, {"text": "And it apparently\ntook him quite a while", "start": 4278.28, "duration": 2.22}, {"text": "to do it because it had to\nbe accurate to a micron,", "start": 4280.5, "duration": 3.48}, {"text": "and the sides had to be at\nright angles, and so on.", "start": 4283.98, "duration": 3.87}, {"text": "So making a sphere as\na calibration object", "start": 4287.85, "duration": 2.4}, {"text": "is somewhat easier\nthan making a cube.", "start": 4290.25, "duration": 2.73}, {"text": "But the cube has\nsome huge advantages.", "start": 4292.98, "duration": 3.12}, {"text": "And one way of exploiting\nit is this diagram.", "start": 4296.1, "duration": 3.82}, {"text": "So if we take an image of the\ncube, we can detect the edges.", "start": 4299.92, "duration": 6.08}, {"text": "We'll talk about that later.", "start": 4306.0, "duration": 1.84}, {"text": "And then we can extend them\nto find the vanishing point.", "start": 4307.84, "duration": 3.36}, {"text": "And by the way, the\nvanishing points", "start": 4311.2, "duration": 1.61}, {"text": "don't have to be in the image.", "start": 4312.81, "duration": 1.53}, {"text": "It could be that the image you\nactually see is this thing.", "start": 4314.34, "duration": 4.86}, {"text": "The vanishing points are in that\nplane, but they, in many cases,", "start": 4319.2, "duration": 5.4}, {"text": "are not in the image.", "start": 4324.6, "duration": 1.48}, {"text": "And that's why I\nstruggle in part.", "start": 4326.08, "duration": 3.35}, {"text": "Aside from having\nno drawing ability,", "start": 4329.43, "duration": 2.46}, {"text": "I struggled with that diagram\nbecause in the real situation,", "start": 4331.89, "duration": 3.33}, {"text": "they tend to be further out.", "start": 4335.22, "duration": 1.71}, {"text": "And so the perspective\ndistortion, as it's called,", "start": 4336.93, "duration": 4.8}, {"text": "wouldn't be as extreme.", "start": 4341.73, "duration": 3.21}, {"text": "So what?", "start": 4344.94, "duration": 0.56}, {"text": "So I have a calibration\nobject that's a cube.", "start": 4345.5, "duration": 3.59}, {"text": "And then I take a picture of it.", "start": 4349.09, "duration": 1.79}, {"text": "And I find the vanishing points.", "start": 4350.88, "duration": 2.37}, {"text": "What then?", "start": 4353.25, "duration": 1.15}, {"text": "Well, one thing I know\nis that the cube has", "start": 4354.4, "duration": 4.85}, {"text": "three sets of parallel line.", "start": 4359.25, "duration": 1.665}, {"text": "And those are at right\nangles to each other.", "start": 4364.0, "duration": 4.53}, {"text": "If they weren't, then it\nwould be a parallelepiped, not", "start": 4368.53, "duration": 3.24}, {"text": "a cube.", "start": 4371.77, "duration": 1.41}, {"text": "So they're at right\nangles to each other.", "start": 4373.18, "duration": 2.89}, {"text": "And so that's very important\nbecause it brings me", "start": 4376.07, "duration": 3.44}, {"text": "to the equations for\nthe vanishing points.", "start": 4379.51, "duration": 3.69}, {"text": "It means that the directions\nto the vanishing points", "start": 4383.2, "duration": 3.36}, {"text": "are at right angles\nto each other.", "start": 4386.56, "duration": 2.41}, {"text": "So here's my center\nof projection,", "start": 4388.97, "duration": 2.69}, {"text": "and then I have three\nvectors corresponding", "start": 4391.66, "duration": 3.15}, {"text": "to the three sets of lines.", "start": 4394.81, "duration": 1.74}, {"text": "So there's one that's\ngoing up and down,", "start": 4396.55, "duration": 2.76}, {"text": "and one from that side,\nand one from that side.", "start": 4399.31, "duration": 2.64}, {"text": "And I can draw them through\nthe center of projection.", "start": 4401.95, "duration": 3.27}, {"text": "So here's one, here's another\none, and here's a third one.", "start": 4405.22, "duration": 4.54}, {"text": "And so what are those lines?", "start": 4409.76, "duration": 2.61}, {"text": "Well, those are lines in the\ndirection of the 3D lines,", "start": 4412.37, "duration": 8.14}, {"text": "which I guess we've lost now.", "start": 4420.51, "duration": 2.79}, {"text": "So we said that all of the\nlines in this parallel bundle", "start": 4423.3, "duration": 7.42}, {"text": "project into the\nsame vanishing point.", "start": 4430.72, "duration": 2.82}, {"text": "But there's one\nthat's special, which", "start": 4433.54, "duration": 2.61}, {"text": "is the one that goes through\nthe center of projection.", "start": 4436.15, "duration": 2.25}, {"text": "So think of this whole\nslew of parallel lines.", "start": 4438.4, "duration": 3.51}, {"text": "And they all end up at\nthe same vanishing point.", "start": 4441.91, "duration": 4.41}, {"text": "But they can be represented\nby a single line.", "start": 4446.32, "duration": 2.91}, {"text": "We can just pick one.", "start": 4449.23, "duration": 1.017}, {"text": "We pick the one that\ngoes through the center", "start": 4450.247, "duration": 1.833}, {"text": "of projection.", "start": 4452.08, "duration": 1.87}, {"text": "And so that's what this is.", "start": 4453.95, "duration": 1.155}, {"text": "So this is-- and then because\nof the way our projection works,", "start": 4455.105, "duration": 10.605}, {"text": "there's a point down\nhere and a point down", "start": 4465.71, "duration": 2.79}, {"text": "here in the image plane.", "start": 4468.5, "duration": 1.95}, {"text": "So if you tell me the\nthree vectors that", "start": 4474.3, "duration": 4.59}, {"text": "point in 3D along the\nlines, I can tell you", "start": 4478.89, "duration": 4.08}, {"text": "where they will be imaged\njust by this construction,", "start": 4482.97, "duration": 3.51}, {"text": "because here's the direction\nthat's going along one--", "start": 4486.48, "duration": 4.17}, {"text": "here all these parallel lines.", "start": 4490.65, "duration": 1.57}, {"text": "They all going in\nthat direction.", "start": 4492.22, "duration": 1.67}, {"text": "And all I need to do is follow\nthis backward into the image", "start": 4493.89, "duration": 3.36}, {"text": "plane, and that's going\nto be its vanishing point.", "start": 4497.25, "duration": 2.47}, {"text": "So that's vanishing point\n1, vanishing point 2.", "start": 4499.72, "duration": 2.75}, {"text": "I called them something else.", "start": 4502.47, "duration": 1.46}, {"text": "Sorry.", "start": 4503.93, "duration": 1.27}, {"text": "I guess I called\nthem a, b, and c.", "start": 4505.2, "duration": 1.74}, {"text": "Now, the neat thing is I\nknow that if my calibration", "start": 4513.61, "duration": 4.71}, {"text": "objects is a cube, that these\nthree vectors up here aren't", "start": 4518.32, "duration": 3.0}, {"text": "just any old three vectors,\nbut they are all at right", "start": 4521.32, "duration": 2.67}, {"text": "angles to one another.", "start": 4523.99, "duration": 1.77}, {"text": "Hard to draw that, but there\nare three relationships", "start": 4525.76, "duration": 3.3}, {"text": "between them.", "start": 4529.06, "duration": 0.94}, {"text": "So let's call the unknown\ncenter of projection p.", "start": 4530.0, "duration": 4.81}, {"text": "That's our task.", "start": 4534.81, "duration": 1.38}, {"text": "Find p, given a, b, and c.", "start": 4536.19, "duration": 3.36}, {"text": "Well, then I can say this.", "start": 4539.55, "duration": 2.01}, {"text": "So why is that?", "start": 4559.99, "duration": 1.38}, {"text": "Well, p minus a is the\nvector along this line.", "start": 4561.37, "duration": 4.07}, {"text": "And p minus b is the\nvector along that line.", "start": 4565.44, "duration": 2.4}, {"text": "And those are the same\nvectors as these two.", "start": 4567.84, "duration": 3.06}, {"text": "And we know they're\nat right angles.", "start": 4570.9, "duration": 1.74}, {"text": "And the dot product\nof two vectors", "start": 4572.64, "duration": 2.28}, {"text": "that are at right angles is 0.", "start": 4574.92, "duration": 4.88}, {"text": "So we get the\ncalibration, obviously.", "start": 4579.8, "duration": 3.282}, {"text": "We take an image.", "start": 4583.082, "duration": 0.708}, {"text": "We find the vanishing points.", "start": 4583.79, "duration": 1.83}, {"text": "And then we have\nthose three equations,", "start": 4585.62, "duration": 2.76}, {"text": "and we have three unknowns,\nnamely the components", "start": 4588.38, "duration": 4.32}, {"text": "of p, the center of projection.", "start": 4592.7, "duration": 3.3}, {"text": "Or another way of looking at it\nis we need to know this height.", "start": 4596.0, "duration": 4.5}, {"text": "Call it f.", "start": 4600.5, "duration": 1.23}, {"text": "And we need to know where\nthis is on the image sensor.", "start": 4601.73, "duration": 2.522}, {"text": "So there are two\ndegrees of freedom here,", "start": 4604.252, "duration": 1.708}, {"text": "one degree of freedom\nthere, three total.", "start": 4605.96, "duration": 2.19}, {"text": "But simply speaking, we're\ntrying to find where this is.", "start": 4608.15, "duration": 4.17}, {"text": "And that's a vector in 3D, so\nit has three degrees of freedom.", "start": 4612.32, "duration": 3.18}, {"text": "We've got three equations.", "start": 4615.5, "duration": 1.53}, {"text": "Great.", "start": 4617.03, "duration": 1.95}, {"text": "Well, if you look\nat them, you'll", "start": 4618.98, "duration": 2.01}, {"text": "see that they're\nsecond order in p.", "start": 4620.99, "duration": 2.4}, {"text": "p is the unknown.", "start": 4623.39, "duration": 1.8}, {"text": "And they're second order.", "start": 4625.19, "duration": 1.05}, {"text": "They're quadratic.", "start": 4626.24, "duration": 1.98}, {"text": "So there's a finite\nnumber of solutions,", "start": 4628.22, "duration": 3.28}, {"text": "except for pathological cases.", "start": 4631.5, "duration": 2.22}, {"text": "But what is the\nnumber of solutions?", "start": 4633.72, "duration": 4.24}, {"text": "So with a single\nquadratic, we know", "start": 4637.96, "duration": 1.71}, {"text": "that there are possibly two.", "start": 4639.67, "duration": 2.47}, {"text": "So maybe there are\nmore solutions.", "start": 4642.14, "duration": 2.25}, {"text": "So there's a thing here\ncalled B\u00e9zout's theorem,", "start": 4644.39, "duration": 8.25}, {"text": "which we'll use quite a bit.", "start": 4652.64, "duration": 1.98}, {"text": "And it says that the\nmaximum number of solutions", "start": 4654.62, "duration": 8.38}, {"text": "is the product of the\norder of the equations.", "start": 4663.0, "duration": 6.51}, {"text": "So for example, if I\nhave two quadratics,", "start": 4669.51, "duration": 2.69}, {"text": "it is possible there might\nbe four solutions, 2 times 2.", "start": 4672.2, "duration": 3.81}, {"text": "Here I've got three\nquadratics, so it's", "start": 4676.01, "duration": 2.52}, {"text": "possible there could\nbe eight solutions.", "start": 4678.53, "duration": 2.79}, {"text": "So that's unpleasant, so we want\nto talk some more about that.", "start": 4681.32, "duration": 4.17}, {"text": "By the way, it's called\nB\u00e9zout's theorem after B\u00e9zout,", "start": 4685.49, "duration": 3.39}, {"text": "who wrote this up, and actually\nNewton used this result in his", "start": 4688.88, "duration": 8.67}, {"text": "Principia.", "start": 4697.55, "duration": 2.28}, {"text": "But he didn't\nreally formalize it.", "start": 4699.83, "duration": 2.76}, {"text": "He just used it like\nanyone would know", "start": 4702.59, "duration": 3.48}, {"text": "this, that kind of thing.", "start": 4706.07, "duration": 1.96}, {"text": "And when B\u00e9zout wrote it up,\nhe didn't actually rigorously", "start": 4708.03, "duration": 3.95}, {"text": "prove it.", "start": 4711.98, "duration": 0.63}, {"text": "So there's a whole lot of--", "start": 4712.61, "duration": 1.755}, {"text": "it's as usual.", "start": 4714.365, "duration": 0.855}, {"text": "Someone ends up with\ntheir name on something,", "start": 4715.22, "duration": 2.22}, {"text": "and there's a whole interesting\nstory behind it, like, OK,", "start": 4717.44, "duration": 3.332}, {"text": "he didn't-- he wasn't\nactually the first,", "start": 4720.772, "duration": 1.708}, {"text": "or he didn't actually get\nit right, or something.", "start": 4722.48, "duration": 2.23}, {"text": "Anyway, it's an\nimportant theorem for us.", "start": 4724.71, "duration": 2.54}, {"text": "Now, with linear equations,\nthe product is always 1, right?", "start": 4727.25, "duration": 3.87}, {"text": "1 to the whatever power is 1.", "start": 4731.12, "duration": 1.86}, {"text": "So with linear\nequations, as long", "start": 4732.98, "duration": 1.68}, {"text": "as we can match constraints\nwith unknowns, we're done.", "start": 4734.66, "duration": 4.68}, {"text": "Unfortunately, in other cases\nit's not quite that simple.", "start": 4739.34, "duration": 4.53}, {"text": "But we can do something,\nwhich is notice", "start": 4743.87, "duration": 5.22}, {"text": "that these aren't just any\nold quadratic equations.", "start": 4749.09, "duration": 2.59}, {"text": "They have a very\nspecial structure.", "start": 4751.68, "duration": 1.52}, {"text": "And we can subtract\nthem pairwise to get rid", "start": 4753.2, "duration": 2.85}, {"text": "of the second order term.", "start": 4756.05, "duration": 1.92}, {"text": "So we can get--", "start": 4757.97, "duration": 1.32}, {"text": "so let's see.", "start": 4773.12, "duration": 0.68}, {"text": "If we subtract the first and\nthe second, we end up with this.", "start": 4773.8, "duration": 4.56}, {"text": "This is 0.", "start": 4778.36, "duration": 1.05}, {"text": "And then we can get a few more.", "start": 4779.41, "duration": 3.6}, {"text": "So terrific.", "start": 4797.28, "duration": 1.44}, {"text": "We've reduced it to\nthree linear equations.", "start": 4798.72, "duration": 2.04}, {"text": "And we know that they\nhave only one solution.", "start": 4800.76, "duration": 3.63}, {"text": "Well, not so fast.", "start": 4807.18, "duration": 2.32}, {"text": "Are those three linear\nequations linearly independent?", "start": 4809.5, "duration": 5.36}, {"text": "We have to worry\nabout that edge case", "start": 4814.86, "duration": 2.43}, {"text": "where the matrix is\nsingular, and so on.", "start": 4817.29, "duration": 2.22}, {"text": "Well, the truth is that\nif we add two of these,", "start": 4819.51, "duration": 5.38}, {"text": "we get the third one.", "start": 4824.89, "duration": 2.0}, {"text": "So they're not\nindependent equations.", "start": 4826.89, "duration": 2.18}, {"text": "So actually, when we get to\nthe third one, we should stop.", "start": 4829.07, "duration": 3.8}, {"text": "So yes, we can reduce it\nto two linear equations.", "start": 4832.87, "duration": 4.15}, {"text": "But we're still left\nwith one quadratic.", "start": 4837.02, "duration": 2.09}, {"text": "And so the answer is that\nthere are two solutions.", "start": 4839.11, "duration": 3.21}, {"text": "And we won't actually\ndo the algebra,", "start": 4850.55, "duration": 2.15}, {"text": "but it's pretty straightforward.", "start": 4852.7, "duration": 2.77}, {"text": "I'm not quite done with this.", "start": 4863.86, "duration": 1.8}, {"text": "I wanted to say something more,\nbut we're sort out of time.", "start": 4865.66, "duration": 4.12}, {"text": "So one thing that I\nwanted to still say", "start": 4869.78, "duration": 2.48}, {"text": "is that those linear\nequations, what", "start": 4872.26, "duration": 3.21}, {"text": "do they define in 3D space?", "start": 4875.47, "duration": 2.76}, {"text": "Planes.", "start": 4878.23, "duration": 1.05}, {"text": "So each of them defines a plane.", "start": 4879.28, "duration": 2.67}, {"text": "And what we're\nreally doing is we're", "start": 4881.95, "duration": 1.56}, {"text": "intersecting those planes.", "start": 4883.51, "duration": 1.95}, {"text": "And it turns out that two\nplanes intersect in a line.", "start": 4885.46, "duration": 6.85}, {"text": "And it turns out in\nthis case that that line", "start": 4892.31, "duration": 1.85}, {"text": "contains the third plane.", "start": 4894.16, "duration": 1.14}, {"text": "So the third plane\ndoesn't get you anything.", "start": 4895.3, "duration": 3.52}, {"text": "And then just to summarize\nhow this works, and we'll", "start": 4898.82, "duration": 6.68}, {"text": "finish this next time,\noften, we are in need", "start": 4905.5, "duration": 4.26}, {"text": "of calibrating a camera.", "start": 4909.76, "duration": 1.86}, {"text": "Time to contact is one of the\nfew places where we didn't", "start": 4911.62, "duration": 2.73}, {"text": "need a calibrated camera.", "start": 4914.35, "duration": 2.16}, {"text": "And to calibrate a camera, we\noften use calibration objects.", "start": 4916.51, "duration": 3.78}, {"text": "I mean, it doesn't\nhave to be a cube.", "start": 4920.29, "duration": 1.56}, {"text": "It could be, for example,\nthe corner of a room,", "start": 4921.85, "duration": 2.16}, {"text": "as long as you know\nthe geometry of it.", "start": 4924.01, "duration": 3.81}, {"text": "And then in that case, often\nvanishing points are helpful.", "start": 4927.82, "duration": 5.64}, {"text": "And we can work out the geometry\nof the vanishing points, which", "start": 4933.46, "duration": 3.27}, {"text": "lead us to a set of equations.", "start": 4936.73, "duration": 3.04}, {"text": "And when we solve them,\nwe find the position", "start": 4939.77, "duration": 2.93}, {"text": "of the center of projection.", "start": 4942.7, "duration": 1.81}, {"text": "Now, if lenses were\nperfect, that would be it.", "start": 4944.51, "duration": 3.42}, {"text": "So this would be it\nfor camera calibration.", "start": 4947.93, "duration": 2.99}, {"text": "And we'll talk more about\ncamera calibration later.", "start": 4950.92, "duration": 3.315}, {"text": "Our lenses have\nradial distortion,", "start": 4954.235, "duration": 3.045}, {"text": "and there are reasons why\npeople don't completely", "start": 4957.28, "duration": 2.88}, {"text": "get rid of that.", "start": 4960.16, "duration": 1.06}, {"text": "So actually in practice\nwhen you do real robotics", "start": 4961.22, "duration": 3.05}, {"text": "camera calibration, it's this\nplus the radial distortion", "start": 4964.27, "duration": 4.2}, {"text": "parameter.", "start": 4968.47, "duration": 0.69}, {"text": "So OK.", "start": 4969.16, "duration": 2.04}, {"text": "That's it for today.", "start": 4971.2, "duration": 2.3}]
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+[{"text": "[SQUEAKING]\n[RUSTLING] [CLICKING]", "start": 0.0, "duration": 5.434}, {"text": "PROFESSOR: OK, why\ndon't I get started?", "start": 25.51, "duration": 2.59}, {"text": "So OK, what have we been doing?", "start": 28.1, "duration": 6.68}, {"text": "So last time, we\nconsidered a bunch", "start": 34.78, "duration": 2.16}, {"text": "of procedures for testing\nproperties of various automata", "start": 36.94, "duration": 4.77}, {"text": "and grammars, the acceptance\nproblem for DFAs, for NFAs,", "start": 41.71, "duration": 8.75}, {"text": "the acceptance problem,\nwhich is really", "start": 50.46, "duration": 2.04}, {"text": "degeneration problem for\ncontext-free grammars,", "start": 52.5, "duration": 3.03}, {"text": "and emptiness problems for\nDFAs and context-free grammars.", "start": 55.53, "duration": 4.89}, {"text": "And also, we showed that\nA,TM is Turing-recognizable.", "start": 60.42, "duration": 6.138}, {"text": "There's a question here in\nthe chat already about that.", "start": 66.558, "duration": 2.292}, {"text": "Yes, we did show that.", "start": 68.85, "duration": 1.32}, {"text": "That was the universal\nTuring machine", "start": 70.17, "duration": 1.56}, {"text": "that we presented at the end.", "start": 71.73, "duration": 1.27}, {"text": "That's what shows that A,TM\nis Turing-recognizable.", "start": 73.0, "duration": 4.01}, {"text": "We mentioned that\nA,TM is not decidable,", "start": 77.01, "duration": 4.57}, {"text": "which we promised\nwe will prove today.", "start": 81.58, "duration": 1.88}, {"text": "And we will do so.", "start": 83.46, "duration": 1.98}, {"text": "OK, so that is the plan--", "start": 85.44, "duration": 2.64}, {"text": "proving A,TM is undecidable.", "start": 88.08, "duration": 2.1}, {"text": "And we'll introduce the\nmethod for doing that called", "start": 90.18, "duration": 2.28}, {"text": "the diagonalization method.", "start": 92.46, "duration": 2.01}, {"text": "I will also show the\ncomplement of A,TM is", "start": 94.47, "duration": 4.2}, {"text": "Turing-unrecognizable.", "start": 98.67, "duration": 2.46}, {"text": "Even though A,TM\nitself is recognizable,", "start": 101.13, "duration": 2.49}, {"text": "the complement is not.", "start": 103.62, "duration": 2.04}, {"text": "And then we will introduce\nanother method called", "start": 105.66, "duration": 3.81}, {"text": "the reducibility method for\nshowing other problems are not", "start": 109.47, "duration": 3.45}, {"text": "decidable and give one example\nof another problem, which", "start": 112.92, "duration": 3.892}, {"text": "is not decidable, assuming\nwe have time to get to it.", "start": 116.812, "duration": 2.208}, {"text": "If not, we will delay that part\nuntil next Tuesday's lecture.", "start": 119.02, "duration": 6.47}, {"text": "All right, acceptance\nproblem for Turing Machines.", "start": 125.49, "duration": 3.25}, {"text": "So just as I mentioned,\nwe showed that A,TM,", "start": 128.74, "duration": 4.82}, {"text": "which is the language of Turing\nmachines and inputs where", "start": 133.56, "duration": 3.34}, {"text": "the machine accepts the input.", "start": 136.9, "duration": 2.9}, {"text": "We showed that was recognizable.", "start": 139.8, "duration": 1.68}, {"text": "We claimed it was decidable.", "start": 141.48, "duration": 1.23}, {"text": "Today, we're going to\nprove it's not decidable.", "start": 142.71, "duration": 2.52}, {"text": "All right, now the method\nthat we're going to use,", "start": 145.23, "duration": 5.29}, {"text": "which is really the\nonly method out there", "start": 150.52, "duration": 2.42}, {"text": "for proving a problem\nas undecidable", "start": 152.94, "duration": 6.3}, {"text": "is called the\ndiagonalization method.", "start": 159.24, "duration": 2.175}, {"text": "I mean, ultimately, we're going\nto show the reducibility method", "start": 161.415, "duration": 2.625}, {"text": "as well.", "start": 164.04, "duration": 0.85}, {"text": "But it really depends\non having already", "start": 164.89, "duration": 2.18}, {"text": "shown some other\nproblem undecidable", "start": 167.07, "duration": 2.22}, {"text": "via the diagonalization method.", "start": 169.29, "duration": 3.76}, {"text": "So ultimately, everything hinges\non the diagonalization method,", "start": 173.05, "duration": 2.9}, {"text": "which is really what we have.", "start": 175.95, "duration": 2.89}, {"text": "And so to introduce the\ndiagonalization method,", "start": 178.84, "duration": 6.98}, {"text": "I'm going to make a\nbit of a digression", "start": 185.82, "duration": 3.72}, {"text": "into a branch of mathematics\ncalled set theory", "start": 189.54, "duration": 3.84}, {"text": "or it's a part of\nmathematical logic, where", "start": 193.38, "duration": 3.48}, {"text": "the method of\ndiagonalization was first", "start": 196.86, "duration": 3.18}, {"text": "conceived of back in the late\n19th century by a mathematician", "start": 200.04, "duration": 5.28}, {"text": "called Georg Cantor.", "start": 205.32, "duration": 2.37}, {"text": "And Cantor was considering\nthe problem of,", "start": 207.69, "duration": 3.45}, {"text": "how do you compare the relative\nsizes of infinite sets?", "start": 211.14, "duration": 5.39}, {"text": "For finite sets, the problem\nof comparing-- somebody", "start": 216.53, "duration": 6.96}, {"text": "said that Cantor went crazy.", "start": 223.49, "duration": 1.89}, {"text": "That is true.", "start": 225.38, "duration": 2.07}, {"text": "And maybe I don't know\nwhy he went crazy.", "start": 227.45, "duration": 3.18}, {"text": "But he did go--", "start": 230.63, "duration": 3.33}, {"text": "he had some mental\nproblems, unfortunately.", "start": 233.96, "duration": 2.82}, {"text": "And so how do we compare the\nsizes of sets in general?", "start": 240.56, "duration": 2.91}, {"text": "If they're finite sets,\nwe can just count them up.", "start": 243.47, "duration": 2.78}, {"text": "We can say, whoa, this\nset has 11 elements,", "start": 246.25, "duration": 3.49}, {"text": "and the other set\nhas 10 elements.", "start": 249.74, "duration": 2.88}, {"text": "So the one with 11 is bigger.", "start": 252.62, "duration": 2.01}, {"text": "Or if they both have 11,\nthey're the same size.", "start": 254.63, "duration": 1.99}, {"text": "Well, that's not going\nto work for infinite sets", "start": 256.62, "duration": 2.0}, {"text": "because you can't count them up.", "start": 258.62, "duration": 2.49}, {"text": "And so he had--", "start": 261.11, "duration": 1.74}, {"text": "Cantor had the following\nidea for comparing", "start": 262.85, "duration": 2.07}, {"text": "the sizes of infinite sets.", "start": 264.92, "duration": 2.52}, {"text": "And that was, basically,\nto see whether you", "start": 267.44, "duration": 4.5}, {"text": "can have a function\nthat would map", "start": 271.94, "duration": 3.37}, {"text": "from one set to the other\nset with certain properties.", "start": 275.31, "duration": 4.26}, {"text": "And those properties are\ncalled, traditionally, well,", "start": 279.57, "duration": 4.34}, {"text": "I mean, in the past, have\nbeen called the one-to-one", "start": 283.91, "duration": 3.4}, {"text": "and onto properties\nfor the function.", "start": 287.31, "duration": 2.1}, {"text": "I'll tell you what that means.", "start": 289.41, "duration": 1.89}, {"text": "But the concept is very simple.", "start": 291.3, "duration": 2.88}, {"text": "So a one-to-one\nfunction is a function", "start": 294.18, "duration": 2.64}, {"text": "that's mapping from A to B.\nThose are the two sets whose", "start": 296.82, "duration": 3.42}, {"text": "sizes we're trying to compare.", "start": 300.24, "duration": 3.03}, {"text": "And the function\nbeing one-to-one just", "start": 303.27, "duration": 3.54}, {"text": "means that there\nare no collisions.", "start": 306.81, "duration": 1.62}, {"text": "If you have two\ndifferent elements of A,", "start": 308.43, "duration": 2.31}, {"text": "they're never going to map\nonto the same element of B.", "start": 310.74, "duration": 2.79}, {"text": "So two different\nelements of A always", "start": 313.53, "duration": 1.68}, {"text": "map onto two different\nelements of B.", "start": 315.21, "duration": 2.07}, {"text": "So that's the\none-to-one property.", "start": 317.28, "duration": 2.44}, {"text": "It's also called injective.", "start": 319.72, "duration": 2.69}, {"text": "And the other property is\ncalled onto or surjective,", "start": 322.41, "duration": 6.55}, {"text": "which is that the range\nof f has to be all of B.", "start": 328.96, "duration": 2.398}, {"text": "So you're not allowed\nto miss any elements,", "start": 331.358, "duration": 1.792}, {"text": "but you have to hit everything.", "start": 333.15, "duration": 2.52}, {"text": "And when you have both\nof those properties,", "start": 335.67, "duration": 2.85}, {"text": "the function is called a\none-to-one correspondence", "start": 338.52, "duration": 3.06}, {"text": "or a bijection also, OK?", "start": 341.58, "duration": 4.26}, {"text": "Now another way\nof looking at it--", "start": 345.84, "duration": 2.67}, {"text": "I don't want to make this\nmore complicated than it", "start": 348.51, "duration": 2.22}, {"text": "needs to be.", "start": 350.73, "duration": 0.75}, {"text": "It just simply\nmeans that two sets", "start": 351.48, "duration": 2.37}, {"text": "are considered to be the\nsame size if we can match up", "start": 353.85, "duration": 3.39}, {"text": "the elements with one set with\nelements of the other set.", "start": 357.24, "duration": 2.82}, {"text": "You just pair them up.", "start": 360.06, "duration": 2.01}, {"text": "For example, well, if you\nhave finite sets, that idea,", "start": 362.07, "duration": 6.69}, {"text": "that informal idea just works\nexactly as you would expect.", "start": 368.76, "duration": 3.15}, {"text": "For example, if we have two\nsets-- here's a set of puppies.", "start": 371.91, "duration": 3.72}, {"text": "Here's a set of kittens.", "start": 375.63, "duration": 2.85}, {"text": "Now we want to show that those\ntwo sets have the same size.", "start": 378.48, "duration": 4.82}, {"text": "We could count them up, as I\nmentioned, and see that there", "start": 383.3, "duration": 2.82}, {"text": "are six elements in both.", "start": 386.12, "duration": 1.92}, {"text": "But counting up does not\nwork for infinite sets.", "start": 388.04, "duration": 3.7}, {"text": "So we can just match up\nthe elements of the puppies", "start": 391.74, "duration": 5.42}, {"text": "with the kittens,\nand then we know", "start": 397.16, "duration": 2.63}, {"text": "we have the same number\nof puppies as kittens.", "start": 399.79, "duration": 2.82}, {"text": "OK, now that has the\nadvantage of it making sense", "start": 402.61, "duration": 4.53}, {"text": "when you have infinite sets.", "start": 407.14, "duration": 1.57}, {"text": "So we're just going\nto extend that idea", "start": 408.71, "duration": 1.813}, {"text": "and apply it to\ninfinite sets too.", "start": 410.523, "duration": 1.417}, {"text": "And then we'll have\na notion of what", "start": 411.94, "duration": 1.56}, {"text": "it means for two infinite\nsets to have the same size.", "start": 413.5, "duration": 3.78}, {"text": "And you might wonder,\nwhat do you get?", "start": 417.28, "duration": 1.74}, {"text": "Are all infinite\nsets of the same size", "start": 419.02, "duration": 2.61}, {"text": "when you use this notion or not?", "start": 421.63, "duration": 2.6}, {"text": "What happens?", "start": 424.23, "duration": 1.63}, {"text": "Well, some strange\nthings do happen.", "start": 425.86, "duration": 2.31}, {"text": "But there actually are quite\nsome interesting structure", "start": 428.17, "duration": 4.62}, {"text": "there that emerges.", "start": 432.79, "duration": 1.87}, {"text": "So anyway, I don't\nwant to rush on.", "start": 434.66, "duration": 5.0}, {"text": "Questions on any of this?", "start": 439.66, "duration": 1.14}, {"text": "If you want to--", "start": 440.8, "duration": 1.62}, {"text": "quick question.", "start": 442.42, "duration": 0.66}, {"text": "This, hopefully, was not too\nhard, but I want to make sure", "start": 443.08, "duration": 2.417}, {"text": "everybody's together with\nme on it, so we can pop in--", "start": 445.497, "duration": 3.373}, {"text": "I'll give a few seconds for a\nchat if you have any questions.", "start": 448.87, "duration": 3.66}, {"text": "The range of the set\nis all of the elements", "start": 458.58, "duration": 2.64}, {"text": "that you hit as you look at\nthe different possible elements", "start": 461.22, "duration": 3.39}, {"text": "of A. So all of the things that\nf hits, the standard notion", "start": 464.61, "duration": 2.64}, {"text": "of a range of a function.", "start": 467.25, "duration": 1.17}, {"text": "So the range of f\nhas to be equal to B.", "start": 471.22, "duration": 2.15}, {"text": "You have to hit everything.", "start": 473.37, "duration": 1.478}, {"text": "All right, can you think of\na one-to-one correspondence", "start": 478.06, "duration": 4.12}, {"text": "as a relabeling?", "start": 482.18, "duration": 0.923}, {"text": "Yeah, I'm not sure\nthat's helpful.", "start": 483.103, "duration": 1.417}, {"text": "But, yes, you can think of as\na relabeling of the elements", "start": 484.52, "duration": 3.06}, {"text": "in a sense, but yeah.", "start": 487.58, "duration": 2.2}, {"text": "I just think of it\nas a matching up.", "start": 489.78, "duration": 3.1}, {"text": "All right, so let's move on.", "start": 492.88, "duration": 2.44}, {"text": "So coming out of\nthis notion of sets", "start": 495.32, "duration": 4.8}, {"text": "being of the same\nsize with this notion", "start": 500.12, "duration": 2.55}, {"text": "of countable sets, as\nwe'll see in a minute,", "start": 502.67, "duration": 2.89}, {"text": "so let's do an example.", "start": 505.56, "duration": 2.84}, {"text": "Let's take the set\nof natural numbers--", "start": 508.4, "duration": 2.6}, {"text": "1, 2, 3, 4, dot, dot,\ndot, dot, and the set", "start": 511.0, "duration": 2.429}, {"text": "of integers, which includes\nthe natural numbers", "start": 513.429, "duration": 3.48}, {"text": "but also the negative\nnumbers and zero.", "start": 516.909, "duration": 2.461}, {"text": "So the natural\nnumbers are typically", "start": 522.159, "duration": 2.611}, {"text": "referred to as N. The integers\nare typically referred to as Z.", "start": 524.77, "duration": 4.74}, {"text": "And what do we think of the\nrelative sizes of N and Z?", "start": 529.51, "duration": 8.7}, {"text": "Well, N is a subset of Z.\nIt's a proper subset of Z.", "start": 538.21, "duration": 3.39}, {"text": "So you might, at first glance,\nthink that Z is larger,", "start": 541.6, "duration": 2.88}, {"text": "and they're not really going\nto be of the same size.", "start": 544.48, "duration": 2.76}, {"text": "But actually, it turns out that\nthere's a very simple way--", "start": 547.24, "duration": 3.72}, {"text": "the arithmetic and the\nproperties of infinite sets", "start": 550.96, "duration": 3.63}, {"text": "can be a little bit surprising.", "start": 554.59, "duration": 1.41}, {"text": "And there is a way of matching\nup all of the elements of Z", "start": 556.0, "duration": 3.66}, {"text": "with their own elements\nof N. And so you", "start": 559.66, "duration": 3.93}, {"text": "can show that following that\ndefinition, that these two sets", "start": 563.59, "duration": 4.89}, {"text": "are, in fact, of the same size.", "start": 568.48, "duration": 1.54}, {"text": "So let's just quickly go\nmake sure you see that.", "start": 570.02, "duration": 4.86}, {"text": "So here is N. Here\nis Z I'm going", "start": 574.88, "duration": 2.57}, {"text": "to write down a table which\nshows how they match up.", "start": 577.45, "duration": 3.06}, {"text": "Here is the function f of n\nthat I'm going to be describing.", "start": 580.51, "duration": 2.91}, {"text": "That's the one-to-one\ncorrespondence.", "start": 583.42, "duration": 3.63}, {"text": "And so here are the\nnatural numbers--", "start": 587.05, "duration": 1.83}, {"text": "dot, dot, dot, 1 through\n7, dot, dot, dot.", "start": 588.88, "duration": 3.15}, {"text": "And here are the\nelements of Z that I'm", "start": 592.03, "duration": 1.64}, {"text": "going to be matching up.", "start": 593.67, "duration": 1.0}, {"text": "This is how the\nfunction is working.", "start": 594.67, "duration": 1.63}, {"text": "So one, I'm going to--", "start": 596.3, "duration": 1.55}, {"text": "f of 1 is going to be 0.", "start": 597.85, "duration": 1.71}, {"text": "F of 2 is going to be minus 1.", "start": 599.56, "duration": 2.28}, {"text": "F of 3 is going to be 1.", "start": 601.84, "duration": 3.33}, {"text": "And I'm just giving\nyou a way to match up", "start": 605.17, "duration": 3.57}, {"text": "each of the natural\nnumbers with integers", "start": 608.74, "duration": 3.97}, {"text": "so that every single integer has\nits own natural number and vice", "start": 612.71, "duration": 4.2}, {"text": "versa.", "start": 616.91, "duration": 0.5}, {"text": "So 4 goes to minus 2.", "start": 619.99, "duration": 1.505}, {"text": "5 goes to 2.", "start": 621.495, "duration": 1.23}, {"text": "6 goes to minus 3.", "start": 622.725, "duration": 1.575}, {"text": "7 goes to 3, and then minus\n4, and then 4, and minus 5,", "start": 624.3, "duration": 3.44}, {"text": "and then 5, and so on.", "start": 627.74, "duration": 1.96}, {"text": "You're clearly\ngoing to cover all", "start": 629.7, "duration": 1.44}, {"text": "of the integers in this way.", "start": 631.14, "duration": 1.5}, {"text": "And each of the\nnatural numbers is", "start": 632.64, "duration": 1.47}, {"text": "going to have its own integer.", "start": 634.11, "duration": 1.275}, {"text": "And there's never going\nto be any collisions.", "start": 635.385, "duration": 1.875}, {"text": "There's never going to be\ntwo natural numbers assigned", "start": 637.26, "duration": 1.83}, {"text": "to the same integer.", "start": 639.09, "duration": 1.18}, {"text": "So this meets the conditions\nof a one-to-one correspondence", "start": 640.27, "duration": 4.91}, {"text": "and shows that the natural\nnumbers and the integers", "start": 645.18, "duration": 4.23}, {"text": "have the same size\nfollowing this definition.", "start": 649.41, "duration": 5.99}, {"text": "OK, let's do one that's slightly\nmore complicated and, perhaps,", "start": 655.4, "duration": 6.63}, {"text": "slightly more surprising,\nwhich is that if you consider", "start": 662.03, "duration": 4.2}, {"text": "all of the rational numbers,\nand then they have the same--", "start": 666.23, "duration": 5.485}, {"text": "that is a collection.", "start": 671.715, "duration": 0.875}, {"text": "Even though the\nrational numbers seem", "start": 672.59, "duration": 2.4}, {"text": "to be much richer and more\nnumerous than the integers,", "start": 674.99, "duration": 4.2}, {"text": "from this perspective,\nthey have the same size.", "start": 679.19, "duration": 2.31}, {"text": "And for the simplicity\nof my presentation,", "start": 681.5, "duration": 3.61}, {"text": "I'm going to consider only\nthe positive rational numbers,", "start": 685.11, "duration": 2.61}, {"text": "which I'm going to write as Q+.", "start": 687.72, "duration": 2.36}, {"text": "So those are all of the\npositive rational numbers", "start": 690.08, "duration": 2.85}, {"text": "that can be expressed as a\nratio of two natural numbers.", "start": 692.93, "duration": 3.6}, {"text": "And I'm going to show that there\nis a one-to-one correspondence", "start": 696.53, "duration": 4.47}, {"text": "between these positive\nrational numbers", "start": 701.0, "duration": 3.18}, {"text": "and the natural numbers.", "start": 704.18, "duration": 2.64}, {"text": "OK, so here, I'm\ngoing to, again,", "start": 706.82, "duration": 3.21}, {"text": "make a table, just\nas I did up above--", "start": 710.03, "duration": 3.48}, {"text": "so comparing the\nnatural numbers and", "start": 713.51, "duration": 2.01}, {"text": "the positive rational numbers.", "start": 715.52, "duration": 2.01}, {"text": "And to do that, I'm going\nto write down over here", "start": 717.53, "duration": 3.48}, {"text": "on the side, just\nto help you see", "start": 721.01, "duration": 1.98}, {"text": "how I'm getting this table,\na separate table that", "start": 722.99, "duration": 5.19}, {"text": "has all of the positive\nrational numbers appearing", "start": 728.18, "duration": 3.63}, {"text": "in a nicely organized way.", "start": 731.81, "duration": 3.36}, {"text": "Here are all of the\nrational numbers", "start": 735.17, "duration": 2.28}, {"text": "here that have 1 as a numerator,\nthat have 2 as a numerator,", "start": 737.45, "duration": 3.51}, {"text": "and so on, and going\nthrough across the columns,", "start": 740.96, "duration": 3.18}, {"text": "the different denominators.", "start": 744.14, "duration": 2.17}, {"text": "So the numbers\ninside here represent", "start": 746.31, "duration": 3.057}, {"text": "all of the different\nrational numbers.", "start": 749.367, "duration": 1.583}, {"text": "And so whatever rational\nnumber you have,", "start": 750.95, "duration": 1.95}, {"text": "m over n, that's\ngoing to appear down", "start": 752.9, "duration": 3.87}, {"text": "the nth row in the nth column.", "start": 756.77, "duration": 2.248}, {"text": "That number is going to appear.", "start": 759.018, "duration": 1.292}, {"text": "So they're all going to show up.", "start": 760.31, "duration": 1.89}, {"text": "And I'm going to use this table\nhere to fill out this function.", "start": 762.2, "duration": 6.87}, {"text": "So here are all the\nnatural numbers.", "start": 769.07, "duration": 3.29}, {"text": "And the way I'm going to assign\nthe rational numbers to appear", "start": 772.36, "duration": 4.59}, {"text": "over here is I'm just going to\nwork my way in from the corner.", "start": 776.95, "duration": 5.73}, {"text": "And I'm going to do\nthat by doing layers.", "start": 782.68, "duration": 3.52}, {"text": "So first, I'll take\nthe 1 in this number", "start": 786.2, "duration": 3.17}, {"text": "here in this corner.", "start": 789.37, "duration": 0.96}, {"text": "Then, I'll do these\nthree that surrounded it,", "start": 790.33, "duration": 2.82}, {"text": "and then these guys\nthat surround that,", "start": 793.15, "duration": 2.4}, {"text": "and these guys sort of in shells\ngoing around the previous ones", "start": 795.55, "duration": 3.36}, {"text": "that I've already covered.", "start": 798.91, "duration": 1.92}, {"text": "OK, so let me illustrate that.", "start": 800.83, "duration": 2.86}, {"text": "So here's 1 over 1, my\nfirst rational number", "start": 803.69, "duration": 2.84}, {"text": "that I'm going to\nenter into the table,", "start": 806.53, "duration": 2.04}, {"text": "appearing right over there.", "start": 808.57, "duration": 1.35}, {"text": "So next, I'm going\nto go 2 over 1.", "start": 809.92, "duration": 2.64}, {"text": "That's going to appear\nin the table over there.", "start": 812.56, "duration": 2.71}, {"text": "Now, we have 2 over 2.", "start": 815.27, "duration": 1.41}, {"text": "Now that's actually a little\nbit problematic because 2 over 2", "start": 816.68, "duration": 4.53}, {"text": "has already been done.", "start": 821.21, "duration": 2.32}, {"text": "And if we put that in--", "start": 823.53, "duration": 1.88}, {"text": "because 2 over 2\nequals 1 over 1.", "start": 825.41, "duration": 1.65}, {"text": "They're both the equal\nto the rational number 1.", "start": 827.06, "duration": 3.24}, {"text": "So if we put 2 over 2\nin this table over here,", "start": 830.3, "duration": 2.61}, {"text": "then we would no longer\nhave the one-to-one property", "start": 832.91, "duration": 2.67}, {"text": "because both 1 and 3 would\nbe mapping to the same point.", "start": 835.58, "duration": 4.27}, {"text": "So we're just going to\nsimply skip over 2 over 2.", "start": 839.85, "duration": 5.0}, {"text": "I'll show that as kind\nof graying it out.", "start": 844.85, "duration": 2.08}, {"text": "So we're not going to add\nthat one on to the table", "start": 846.93, "duration": 3.08}, {"text": "onto my function.", "start": 850.01, "duration": 2.64}, {"text": "But so we'll skip over that.", "start": 852.65, "duration": 1.62}, {"text": "We'll go to 1 over 2, which\nhas not been seen before.", "start": 854.27, "duration": 4.262}, {"text": "And then we're just going to\ncontinue doing the same thing,", "start": 858.532, "duration": 2.458}, {"text": "now going to this\nnext shell out here.", "start": 860.99, "duration": 2.61}, {"text": "3 over 1, 3 over 2, 3 over 3--", "start": 863.6, "duration": 5.16}, {"text": "same thing, we're going\nto skip over that one--", "start": 868.76, "duration": 3.08}, {"text": "2 over 3, 1 over 3.", "start": 871.84, "duration": 2.76}, {"text": "I hope you're getting the idea.", "start": 874.6, "duration": 2.08}, {"text": "So I'm not going\nto fill this table.", "start": 876.68, "duration": 1.5}, {"text": "I ran out of room to fill\nout this table some more.", "start": 878.18, "duration": 3.23}, {"text": "But just to look at how the\nprocess is going to continue", "start": 881.41, "duration": 2.73}, {"text": "here, we get 4 over 1.", "start": 884.14, "duration": 1.44}, {"text": "Now 4 over 2, again, is a\nnumber we previously seen", "start": 885.58, "duration": 4.05}, {"text": "because that's the\nrational number 2.", "start": 889.63, "duration": 2.67}, {"text": "We saw that up here\nwhen we had 2 over 1,", "start": 892.3, "duration": 2.1}, {"text": "so we're going to\nhave to skip that one.", "start": 894.4, "duration": 1.77}, {"text": "4 over 3, 4 over 4--", "start": 896.17, "duration": 2.31}, {"text": "that was going to skip.", "start": 898.48, "duration": 1.74}, {"text": "3 over 4, and so on.", "start": 900.22, "duration": 2.54}, {"text": "OK?", "start": 902.76, "duration": 0.5}, {"text": "So by following\nthis procedure, I'm", "start": 903.26, "duration": 3.78}, {"text": "going to be able to\ndefine this function.", "start": 907.04, "duration": 1.938}, {"text": "Now this function\nis not particularly", "start": 908.978, "duration": 1.542}, {"text": "nice in terms of having\nan elegant, closed form.", "start": 910.52, "duration": 3.6}, {"text": "But it is a totally\nlegitimate function", "start": 914.12, "duration": 2.7}, {"text": "in the sense of being a\nmapping from natural numbers", "start": 916.82, "duration": 3.18}, {"text": "to the positive\nrational numbers.", "start": 920.0, "duration": 3.63}, {"text": "And it has the one-to-one\ncorrespondence property.", "start": 923.63, "duration": 3.9}, {"text": "So it pairs up each\nof the natural numbers", "start": 927.53, "duration": 3.81}, {"text": "with each of the positive\nrational numbers.", "start": 931.34, "duration": 5.4}, {"text": "They each get their\nown mate, in a sense.", "start": 936.74, "duration": 3.477}, {"text": "And so that shows that\nthe rational numbers,", "start": 940.217, "duration": 1.833}, {"text": "despite the fact\nthat they're dense,", "start": 942.05, "duration": 2.1}, {"text": "and they have all sorts of\nvery more much bigger seeming,", "start": 944.15, "duration": 3.87}, {"text": "they really, from this\nperspective of the sizes", "start": 948.02, "duration": 3.09}, {"text": "of the sets, they have the same\nsize as the natural numbers do.", "start": 951.11, "duration": 5.1}, {"text": "And so with that, it suggests\nthat the following definition", "start": 956.21, "duration": 3.81}, {"text": "that a set is\ncountable if it has", "start": 960.02, "duration": 2.58}, {"text": "the same size as the natural\nnumbers or it's finite.", "start": 962.6, "duration": 3.983}, {"text": "From this perspective,\nwe're going", "start": 966.583, "duration": 1.417}, {"text": "to be focusing on infinite sets.", "start": 968.0, "duration": 2.22}, {"text": "But yeah, countable or countably\ninfinite, sometimes people say,", "start": 970.22, "duration": 3.72}, {"text": "if it has the same size\nas the natural numbers.", "start": 973.94, "duration": 2.008}, {"text": "Or otherwise, you have to\ninclude the finite sets", "start": 975.948, "duration": 2.042}, {"text": "as well.", "start": 977.99, "duration": 0.66}, {"text": "And countable means you can\njust go through the elements", "start": 978.65, "duration": 4.8}, {"text": "of the set as a list.", "start": 983.45, "duration": 3.93}, {"text": "So you can count them-- the\nfirst one, the second one,", "start": 987.38, "duration": 2.25}, {"text": "the third one, the fourth\none, dot, dot, dot.", "start": 989.63, "duration": 2.576}, {"text": "And once you can do\nthat, and that counting", "start": 992.206, "duration": 2.784}, {"text": "is going to hit everything,\nthen you know can match them--", "start": 994.99, "duration": 3.61}, {"text": "you can pair them up\nwith the natural numbers.", "start": 998.6, "duration": 1.97}, {"text": "And so therefore, you\nhave a countable set.", "start": 1000.57, "duration": 2.19}, {"text": "OK.", "start": 1002.76, "duration": 2.43}, {"text": "So as we've shown,\nboth Z, the integers,", "start": 1005.19, "duration": 4.56}, {"text": "and the positive rational\nnumbers are countable sets.", "start": 1009.75, "duration": 3.94}, {"text": "OK?", "start": 1013.69, "duration": 0.5}, {"text": "Now you might think\nthat, well, since we're", "start": 1014.19, "duration": 3.65}, {"text": "allowing ourselves\nto do something", "start": 1017.84, "duration": 2.88}, {"text": "as arbitrary, in a way,\nas this kind of a function", "start": 1020.72, "duration": 5.82}, {"text": "to match up the natural numbers\nwith whatever set you're trying", "start": 1026.54, "duration": 4.2}, {"text": "to measure, that every set\nis going to be countable,", "start": 1030.74, "duration": 4.832}, {"text": "if you think about it that way\nbecause it seems like you're", "start": 1035.572, "duration": 2.458}, {"text": "allowing too many possibilities.", "start": 1038.03, "duration": 2.422}, {"text": "And then all the\ninfinite sets are", "start": 1040.452, "duration": 1.417}, {"text": "going to end up being the same\nsize as the natural numbers.", "start": 1041.869, "duration": 2.73}, {"text": "Well, that is, in\nfact, is not true.", "start": 1044.599, "duration": 3.401}, {"text": "And I don't know.", "start": 1048.0, "duration": 1.97}, {"text": "Cantor, is the one\nwho discovered that.", "start": 1049.97, "duration": 2.49}, {"text": "I don't know if that\nwas surprising or not.", "start": 1052.46, "duration": 3.04}, {"text": "But it is interesting,\nI think, that there are", "start": 1055.5, "duration": 3.95}, {"text": "different sizes of infinities.", "start": 1059.45, "duration": 2.49}, {"text": "And so we're going to now\ntake a look and see that.", "start": 1061.94, "duration": 4.93}, {"text": "But I want to, again,\nI want to stop and make", "start": 1066.87, "duration": 4.79}, {"text": "sure we're all together.", "start": 1071.66, "duration": 1.32}, {"text": "Can we always find\na closed formula", "start": 1072.98, "duration": 1.71}, {"text": "for f, somebody's asking me.", "start": 1074.69, "duration": 2.16}, {"text": "I don't know.", "start": 1076.85, "duration": 1.35}, {"text": "For this particular\nf, you probably could,", "start": 1078.2, "duration": 5.26}, {"text": "but it would probably\nbe very messy.", "start": 1083.46, "duration": 4.14}, {"text": "But in general, that's\nnot a requirement,", "start": 1087.6, "duration": 2.34}, {"text": "having a closed form for\nthe mapping function.", "start": 1089.94, "duration": 3.87}, {"text": "Any function is allowed as long\nas a one-to-one correspondence.", "start": 1093.81, "duration": 3.51}, {"text": "Are we all together on this?", "start": 1100.53, "duration": 1.59}, {"text": "Are we comfortable\nwith the notion", "start": 1102.12, "duration": 1.8}, {"text": "of some infinite sets\nhaving the same size", "start": 1103.92, "duration": 4.007}, {"text": "as the natural numbers,\nand therefore, we're going", "start": 1107.927, "duration": 2.083}, {"text": "to call them countable sets?", "start": 1110.01, "duration": 1.41}, {"text": "And we're going to show\nsome other sets are", "start": 1111.42, "duration": 2.34}, {"text": "going to have more elements.", "start": 1113.76, "duration": 2.76}, {"text": "They're going to be uncountable.", "start": 1116.52, "duration": 1.68}, {"text": "They're going to be beyond--", "start": 1118.2, "duration": 1.35}, {"text": "strictly speaking, strictly\nlarger sets in the sense", "start": 1119.55, "duration": 3.75}, {"text": "that we won't be\nable to put them", "start": 1123.3, "duration": 1.44}, {"text": "into a one-to-one correspondence\nwith the integers.", "start": 1124.74, "duration": 3.49}, {"text": "So is N the smallest infinity?", "start": 1128.23, "duration": 1.31}, {"text": "Yes, N is the smallest one.", "start": 1129.54, "duration": 3.27}, {"text": "So any infinity\nis going to have--", "start": 1132.81, "duration": 4.11}, {"text": "you're going to always--", "start": 1136.92, "duration": 1.187}, {"text": "I don't think you even need it--", "start": 1138.107, "duration": 1.333}, {"text": "you need a special--", "start": 1139.44, "duration": 3.18}, {"text": "whenever you have an\ninfinite collection,", "start": 1142.62, "duration": 1.98}, {"text": "you can always\nfind a subset which", "start": 1144.6, "duration": 2.28}, {"text": "is going to be a\ncountable subset", "start": 1146.88, "duration": 5.567}, {"text": "and is going to be the\nsmallest of the infinities,", "start": 1152.447, "duration": 2.083}, {"text": "but there are bigger ones.", "start": 1154.53, "duration": 2.117}, {"text": "All right, why don't we move on?", "start": 1156.647, "duration": 1.333}, {"text": "OK, so the example of a set that\nwe will show is not countable--", "start": 1160.68, "duration": 6.6}, {"text": "an uncountable set,\nas we call it--", "start": 1167.28, "duration": 4.02}, {"text": "is a set of real numbers, which\nwe all know what these are,", "start": 1171.3, "duration": 6.61}, {"text": "I hope.", "start": 1177.91, "duration": 0.77}, {"text": "These are all of\nthe numbers that you", "start": 1178.68, "duration": 2.31}, {"text": "can express by possibly\ninfinite decimal representations", "start": 1180.99, "duration": 3.63}, {"text": "like pi, or E squared of 2, or\nany of the other familiar ones.", "start": 1184.62, "duration": 6.27}, {"text": "Rational numbers are also\nmembers of or also count", "start": 1190.89, "duration": 5.7}, {"text": "as real numbers\nand integers too.", "start": 1196.59, "duration": 2.82}, {"text": "And so but there are\nthese additional numbers", "start": 1199.41, "duration": 4.98}, {"text": "that you can get by the\ndecimal expansions which", "start": 1204.39, "duration": 2.85}, {"text": "may not be rational.", "start": 1207.24, "duration": 2.28}, {"text": "And that collection, even\nthough, in some ways,", "start": 1209.52, "duration": 2.58}, {"text": "it looks somewhat similar\nto the rational numbers,", "start": 1212.1, "duration": 3.96}, {"text": "the real numbers--", "start": 1216.06, "duration": 1.268}, {"text": "I hope I said that right.", "start": 1217.328, "duration": 1.042}, {"text": "The real numbers,\nwhich is the set", "start": 1218.37, "duration": 4.53}, {"text": "I'm considering here, the\nones with the infinite decimal", "start": 1222.9, "duration": 2.73}, {"text": "expansions, they\nactually are much larger.", "start": 1225.63, "duration": 4.57}, {"text": "So the theorem is-- and this\nwas discovered by Cantor--", "start": 1230.2, "duration": 6.45}, {"text": "that R is an uncountable set.", "start": 1236.65, "duration": 3.07}, {"text": "And the reason why\nI'm introducing", "start": 1239.72, "duration": 2.39}, {"text": "this is, besides that I think\nit's interesting and has", "start": 1242.11, "duration": 5.67}, {"text": "some relation to the kinds\nof things we're doing,", "start": 1247.78, "duration": 3.58}, {"text": "but it's really for\nthe purposes right now,", "start": 1251.36, "duration": 2.27}, {"text": "is to introduce this method\ncalled diagonalization.", "start": 1253.63, "duration": 2.42}, {"text": "OK, that's what we're going\nto use later on again.", "start": 1259.13, "duration": 2.97}, {"text": "But this is the first\ntime it appeared.", "start": 1262.1, "duration": 2.43}, {"text": "So we're going to use a proof\nby contradiction in order", "start": 1264.53, "duration": 3.66}, {"text": "to show that R, the\ncollection of real numbers,", "start": 1268.19, "duration": 3.87}, {"text": "is uncountable.", "start": 1272.06, "duration": 1.68}, {"text": "And we'll assume,\nfor contradiction,", "start": 1273.74, "duration": 2.1}, {"text": "that R countable.", "start": 1275.84, "duration": 2.07}, {"text": "OK?", "start": 1277.91, "duration": 2.34}, {"text": "So if we assume\nthat R is countable,", "start": 1280.25, "duration": 3.09}, {"text": "it means we have, by definition,\na one-to-one correspondence", "start": 1283.34, "duration": 3.3}, {"text": "from the natural numbers\nto the real numbers.", "start": 1286.64, "duration": 2.89}, {"text": "OK, so we can match up\nall of the natural numbers", "start": 1289.53, "duration": 3.03}, {"text": "with the real numbers in a\none-to-one and onto fashion.", "start": 1292.56, "duration": 4.96}, {"text": "So we can pair up the natural\nnumbers with the real numbers.", "start": 1297.52, "duration": 3.12}, {"text": "And we will cover all of the\nreal numbers by doing that.", "start": 1300.64, "duration": 3.6}, {"text": "And we can make a table,\njust like I did before.", "start": 1304.24, "duration": 3.6}, {"text": "Here it is.", "start": 1307.84, "duration": 2.93}, {"text": "And you can fill this out\nwith all of the real numbers.", "start": 1310.77, "duration": 3.93}, {"text": "And that was what\nthe assumption means.", "start": 1314.7, "duration": 3.24}, {"text": "And I'm going to show you\nthat that's impossible.", "start": 1317.94, "duration": 2.19}, {"text": "Something is going to go\nterribly wrong if you do that.", "start": 1320.13, "duration": 4.57}, {"text": "Now you might disagree.", "start": 1324.7, "duration": 2.71}, {"text": "You might be surprised.", "start": 1327.41, "duration": 1.17}, {"text": "You might think,\nwell, Professor Sipser", "start": 1328.58, "duration": 4.62}, {"text": "is wrong, that I'm going\nto work on this overnight", "start": 1333.2, "duration": 4.44}, {"text": "and forget the\nrest of my classes,", "start": 1337.64, "duration": 1.44}, {"text": "and I'm going to come up with\na list of all the real numbers.", "start": 1339.08, "duration": 4.96}, {"text": "I'm going to fill\nthem out here and show", "start": 1344.04, "duration": 2.24}, {"text": "that that's impossible.", "start": 1346.28, "duration": 1.74}, {"text": "So let's say, hypothetically,\njust for my example's sake,", "start": 1348.02, "duration": 3.72}, {"text": "here is the list that\nyou came up with.", "start": 1351.74, "duration": 3.54}, {"text": "So you have to match up\nsomething with the 1.", "start": 1355.28, "duration": 1.92}, {"text": "Let's say, E. That\nwas a special case,", "start": 1357.2, "duration": 2.28}, {"text": "so you're going to\nstick that with 1.", "start": 1359.48, "duration": 2.07}, {"text": "And then pi came\nout to be the number", "start": 1361.55, "duration": 1.77}, {"text": "that you connected up with 2.", "start": 1363.32, "duration": 2.662}, {"text": "You understand what\nI'm doing here?", "start": 1365.982, "duration": 1.458}, {"text": "I'm making a list.", "start": 1367.44, "duration": 0.89}, {"text": "I'm trying to make my\ncorrespondence-- my matching up", "start": 1368.33, "duration": 3.33}, {"text": "between the natural\nnumbers and my real numbers", "start": 1371.66, "duration": 3.21}, {"text": "that I'm hypothesizing to\nexist for a contradiction.", "start": 1374.87, "duration": 4.57}, {"text": "So 3, I don't know, 3\nis gets connected to 0.", "start": 1379.44, "duration": 3.56}, {"text": "I'm making this up, obviously--", "start": 1383.0, "duration": 2.82}, {"text": "not on the spot.", "start": 1385.82, "duration": 0.84}, {"text": "I wrote the slide,\nyou know, yesterday.", "start": 1386.66, "duration": 2.55}, {"text": "But here is the square root of 2\nshowing up for whatever reason.", "start": 1389.21, "duration": 4.11}, {"text": "Here is 1/7.", "start": 1393.32, "duration": 2.64}, {"text": "Here is some other number,\nwhich, I'll be interested", "start": 1395.96, "duration": 2.7}, {"text": "if you recognize that one.", "start": 1398.66, "duration": 1.747}, {"text": "That's a subtle one.", "start": 1400.407, "duration": 0.833}, {"text": "This is 1.234-- yeah, some\nfamiliar looking sequence here.", "start": 1403.99, "duration": 5.94}, {"text": "And whatever it is--", "start": 1409.93, "duration": 1.68}, {"text": "whatever it is, this is\nwhat you came up with.", "start": 1411.61, "duration": 2.16}, {"text": "You claim that this\nis going to work as--", "start": 1413.77, "duration": 3.39}, {"text": "very good.", "start": 1417.16, "duration": 0.78}, {"text": "Somebody got it.", "start": 1417.94, "duration": 1.17}, {"text": "It's i to the ith power.", "start": 1419.11, "duration": 1.53}, {"text": "But let's not get hung\nup on that, please.", "start": 1420.64, "duration": 4.0}, {"text": "I to the ith power,\noddly enough,", "start": 1424.64, "duration": 1.46}, {"text": "can be seen as a\nreal number under--", "start": 1426.1, "duration": 2.13}, {"text": "if you define the imaginary\nexponentiation, which is weird.", "start": 1428.23, "duration": 7.33}, {"text": "But anyway, let's not\nget too distracted.", "start": 1435.56, "duration": 4.34}, {"text": "So here's my list of\nnumbers, my real numbers", "start": 1439.9, "duration": 3.33}, {"text": "that I've matched up in my table\nhere with the natural numbers.", "start": 1443.23, "duration": 4.72}, {"text": "Now I claim\nsomething goes wrong.", "start": 1447.95, "duration": 1.76}, {"text": "What goes wrong?", "start": 1449.71, "duration": 0.9}, {"text": "I'm going to show you\nthat you actually did not", "start": 1450.61, "duration": 5.22}, {"text": "do as you claimed,\nthat there's actually", "start": 1455.83, "duration": 3.57}, {"text": "at least one number that's\nmissing from this list.", "start": 1459.4, "duration": 3.622}, {"text": "And I'll exhibit that number.", "start": 1463.022, "duration": 1.208}, {"text": "I'm going to show you\nwhat that number is.", "start": 1464.23, "duration": 1.75}, {"text": "I'm going to explicitly\ncome up with a number", "start": 1465.98, "duration": 1.96}, {"text": "and show you that\nthere's that number it's", "start": 1467.94, "duration": 1.75}, {"text": "missing from the list.", "start": 1469.69, "duration": 1.81}, {"text": "So here, it's going\nto be a number x.", "start": 1471.5, "duration": 3.41}, {"text": "X is the one that's missing.", "start": 1474.91, "duration": 1.93}, {"text": "So how am I going to get x?", "start": 1476.84, "duration": 1.58}, {"text": "So x, well, I'm going to\nstart it off with 0 point,", "start": 1478.42, "duration": 2.88}, {"text": "and then I'm going to fill\nout the rest of the places.", "start": 1481.3, "duration": 2.25}, {"text": "And how am I going\nto get those places?", "start": 1483.55, "duration": 1.44}, {"text": "I'm going to look\nat the table here.", "start": 1484.99, "duration": 1.5}, {"text": "So I want to look at--", "start": 1488.94, "duration": 1.22}, {"text": "to get my first digit after\nthe decimal point of x,", "start": 1490.16, "duration": 3.45}, {"text": "I'm going to look\nat the first digit", "start": 1493.61, "duration": 1.5}, {"text": "after the decimal point\nof the very first number.", "start": 1495.11, "duration": 4.28}, {"text": "So I take the first number,\nlook at the first digit", "start": 1499.39, "duration": 2.15}, {"text": "after the decimal point,\nwhich happens to be a 7.", "start": 1501.54, "duration": 3.87}, {"text": "And the number I'm\ngoing to put in for x", "start": 1505.41, "duration": 2.1}, {"text": "It's not going to be 7.", "start": 1507.51, "duration": 1.44}, {"text": "It's going to be\nanything except 7.", "start": 1508.95, "duration": 2.94}, {"text": "Let say, 8.", "start": 1511.89, "duration": 0.57}, {"text": "For my next digit of x,\nI'm going to look at--", "start": 1515.41, "duration": 3.31}, {"text": "so my second digit\nof x, I'm going to--", "start": 1518.72, "duration": 2.05}, {"text": "everything's going to be\nup to the decimal point", "start": 1520.77, "duration": 2.0}, {"text": "now, so I'm not going\nto keep saying that.", "start": 1522.77, "duration": 2.09}, {"text": "I'm going to look\nat the second digit", "start": 1524.86, "duration": 1.65}, {"text": "of the second number, which is\na 4 after the decimal point.", "start": 1526.51, "duration": 5.37}, {"text": "There it is.", "start": 1534.43, "duration": 1.83}, {"text": "And for the second\ndigit of x, I'm", "start": 1536.26, "duration": 2.04}, {"text": "going to use something which\nis anything besides 4--", "start": 1538.3, "duration": 3.99}, {"text": "5.", "start": 1542.29, "duration": 1.86}, {"text": "I have some flexibility here.", "start": 1544.15, "duration": 2.342}, {"text": "So I could have used 6.", "start": 1546.492, "duration": 0.958}, {"text": "I could have used 7.", "start": 1547.45, "duration": 2.37}, {"text": "For those of you who\nhave seen this before,", "start": 1549.82, "duration": 2.04}, {"text": "who are going to\nnitpick on me, I'm", "start": 1551.86, "duration": 2.58}, {"text": "going to stay away from 9\nand 0 just because there", "start": 1554.44, "duration": 3.6}, {"text": "is some little edge cases that\narise there, which I don't want", "start": 1558.04, "duration": 3.127}, {"text": "to get into because\nI don't think it's", "start": 1561.167, "duration": 1.583}, {"text": "interesting for this argument.", "start": 1562.75, "duration": 2.16}, {"text": "But since I have\nsome flexibility,", "start": 1564.91, "duration": 1.65}, {"text": "I'm going to avoid\nzeros and nines--", "start": 1566.56, "duration": 1.71}, {"text": "probably just nines\nis all I really need.", "start": 1568.27, "duration": 1.87}, {"text": "And then the argument is\njust going to work fine, OK?", "start": 1570.14, "duration": 5.66}, {"text": "So the next digit is a 0.", "start": 1575.8, "duration": 4.49}, {"text": "The third digit, or the\nthird number is a 0.", "start": 1580.29, "duration": 2.61}, {"text": "The third digit of x is going\nto be anything except for 0.", "start": 1582.9, "duration": 2.685}, {"text": "It could be a 1.", "start": 1585.585, "duration": 1.785}, {"text": "Then I have a 2 here.", "start": 1587.37, "duration": 3.39}, {"text": "Anything except a 2, 6.", "start": 1590.76, "duration": 5.35}, {"text": "Then a 5-- anything\nexcept a 5, a 1.", "start": 1596.11, "duration": 3.0}, {"text": "A 9-- anything except\na 9, an 8, and so on.", "start": 1599.11, "duration": 4.56}, {"text": "There's an 8.", "start": 1603.67, "duration": 1.8}, {"text": "There's a 2, and dot, dot, dot.", "start": 1605.47, "duration": 1.8}, {"text": "I'm just going to\nkeep doing that.", "start": 1607.27, "duration": 2.0}, {"text": "And I'm going to say you missed\nthat number, whatever it is.", "start": 1609.27, "duration": 5.06}, {"text": "But that number,\nthat's a number.", "start": 1614.33, "duration": 1.64}, {"text": "After I'm all done,\nit's going to be", "start": 1615.97, "duration": 1.8}, {"text": "the decimal representation\nof something.", "start": 1617.77, "duration": 2.43}, {"text": "And that number, I claim,\nis absent from the table.", "start": 1620.2, "duration": 6.28}, {"text": "And you might say,\nwell, it's really there.", "start": 1626.48, "duration": 6.09}, {"text": "It's just on the 23rd row.", "start": 1632.57, "duration": 4.68}, {"text": "You just didn't get\nto it and your slide.", "start": 1637.25, "duration": 2.79}, {"text": "But it's there.", "start": 1640.04, "duration": 1.14}, {"text": "Well, I'm going to say I\nknow it's not in the 23rd row", "start": 1641.18, "duration": 3.18}, {"text": "because it differs from\nthe number in the 23rd row", "start": 1644.36, "duration": 2.91}, {"text": "at the 23rd digit because\nI constructed it that way.", "start": 1647.27, "duration": 4.65}, {"text": "This number is\ndesigned explicitly", "start": 1651.92, "duration": 2.82}, {"text": "to be different from each of\nthe numbers that's on the list.", "start": 1654.74, "duration": 2.94}, {"text": "So it can't be on\nthe list because it's", "start": 1661.255, "duration": 1.625}, {"text": "been constructed to be\ndifferent from each of them", "start": 1662.88, "duration": 1.8}, {"text": "in at least one place.", "start": 1664.68, "duration": 0.917}, {"text": "So I think this is a\nbeautiful argument,", "start": 1668.29, "duration": 2.12}, {"text": "and it shows that\nno matter how you", "start": 1670.41, "duration": 3.09}, {"text": "try to come up with a\none-to-one correspondence,", "start": 1673.5, "duration": 4.08}, {"text": "you're going to fail.", "start": 1677.58, "duration": 1.41}, {"text": "You might say, oh,\nlike, just one number?", "start": 1678.99, "duration": 4.79}, {"text": "I did so much hard work.", "start": 1683.78, "duration": 1.003}, {"text": "I'm missing just one number.", "start": 1684.783, "duration": 1.167}, {"text": "Can't I get partial credit\nand put this one on the list", "start": 1685.95, "duration": 3.695}, {"text": "now I fixed it?", "start": 1689.645, "duration": 0.625}, {"text": "No.", "start": 1690.27, "duration": 0.36}, {"text": "Obviously, there are many,\nmany numbers that are missing.", "start": 1690.63, "duration": 2.1}, {"text": "If you put this\none on the list, I", "start": 1692.73, "duration": 1.425}, {"text": "was going to construct another\nnumber that was missing.", "start": 1694.155, "duration": 2.415}, {"text": "So there's just not no\npossibility of fixing this.", "start": 1696.57, "duration": 7.74}, {"text": "And in fact, the real\nnumbers are uncountable--", "start": 1704.31, "duration": 5.013}, {"text": "cannot be matched up\nwith the natural numbers.", "start": 1709.323, "duration": 1.917}, {"text": "And there's nothing.", "start": 1711.24, "duration": 1.77}, {"text": "It doesn't even come close.", "start": 1713.01, "duration": 1.125}, {"text": "So here, a summary\nof what I just said.", "start": 1716.65, "duration": 4.4}, {"text": "F is not a one-to-one\ncorrespondence", "start": 1721.05, "duration": 1.582}, {"text": "no matter what you try to do.", "start": 1722.632, "duration": 1.208}, {"text": "You can't come up with a\none-to-one correspondence.", "start": 1723.84, "duration": 2.125}, {"text": "That's the contradiction.", "start": 1725.965, "duration": 2.935}, {"text": "So that proves that\nR is uncountable.", "start": 1728.9, "duration": 4.41}, {"text": "And that's why, by the way,\nwe call this a diagonalization", "start": 1733.31, "duration": 3.45}, {"text": "because we're going\ndown this diagonal here", "start": 1736.76, "duration": 2.19}, {"text": "that's where the term-- that's\nwhere the name is come from.", "start": 1738.95, "duration": 4.04}, {"text": "OK, so I'm happy to--", "start": 1742.99, "duration": 5.73}, {"text": "[CHUCKLES] OK, that's a--", "start": 1748.72, "duration": 2.52}, {"text": "somebody's asking me--\n[CHUCKLES] I'm actually--", "start": 1754.26, "duration": 3.0}, {"text": "I have a-- is it here?", "start": 1757.26, "duration": 3.31}, {"text": "I can't remember if it's here.", "start": 1760.57, "duration": 1.25}, {"text": "I have a check-in\ncoming about this.", "start": 1761.82, "duration": 3.27}, {"text": "And somebody is\nanticipating that", "start": 1765.09, "duration": 2.55}, {"text": "by asking the actually rather\nfamous question about there", "start": 1767.64, "duration": 3.81}, {"text": "being a possible infinity in\nbetween the natural numbers", "start": 1771.45, "duration": 5.1}, {"text": "and the real numbers.", "start": 1776.55, "duration": 1.435}, {"text": "We know the real\nnumbers now are bigger", "start": 1777.985, "duration": 1.625}, {"text": "than the natural numbers.", "start": 1779.61, "duration": 1.047}, {"text": "But is there something\nthat's an in between?", "start": 1780.657, "duration": 1.833}, {"text": "I mean, this is a very,\nvery famous problem,", "start": 1782.49, "duration": 3.51}, {"text": "which I'll talk about when\nwe get to our check-in, which", "start": 1786.0, "duration": 3.09}, {"text": "is coming up.", "start": 1789.09, "duration": 0.72}, {"text": "Somebody is objecting\njust the way", "start": 1795.02, "duration": 1.92}, {"text": "I've defined x using\nthis procedure that", "start": 1796.94, "duration": 2.76}, {"text": "really can't, in a sense, state,\nyou know-- but x is a number.", "start": 1799.7, "duration": 4.0}, {"text": "X is the result of\nwhat this procedure is.", "start": 1803.7, "duration": 4.28}, {"text": "Following this procedure,\nwe're converging", "start": 1807.98, "duration": 1.75}, {"text": "on some particular value.", "start": 1809.73, "duration": 1.53}, {"text": "And so that is a value.", "start": 1811.26, "duration": 2.43}, {"text": "If you want, we can make a more\nprecise way of determining.", "start": 1813.69, "duration": 4.682}, {"text": "We don't have the\nflexibility of choosing", "start": 1818.372, "duration": 1.708}, {"text": "the way I did in my example.", "start": 1820.08, "duration": 1.54}, {"text": "We can make a precise\nprocedure for coming up", "start": 1821.62, "duration": 3.23}, {"text": "with these digits.", "start": 1824.85, "duration": 0.97}, {"text": "But I don't think there's\nanybody thinks there's anything", "start": 1825.82, "duration": 3.255}, {"text": "that's--", "start": 1829.075, "duration": 0.5}, {"text": "there's any shortcoming\nin this argument in terms", "start": 1832.46, "duration": 3.24}, {"text": "of the way we're defining x.", "start": 1835.7, "duration": 1.77}, {"text": "I think it's worth understanding\nthis because it's really going", "start": 1837.47, "duration": 3.39}, {"text": "to set the groundwork for our\nproof that A,TM is undecidable,", "start": 1840.86, "duration": 6.57}, {"text": "which is a little,\nI think, perhaps,", "start": 1847.43, "duration": 1.59}, {"text": "slightly more abstract in a\nway in the way it sort of comes", "start": 1849.02, "duration": 3.33}, {"text": "across.", "start": 1852.35, "duration": 0.87}, {"text": "I'm going to try\nto connect the two.", "start": 1853.22, "duration": 3.03}, {"text": "But I think it's\nhelpful to understand", "start": 1856.25, "duration": 2.07}, {"text": "at least this argument\nbecause this argument is", "start": 1858.32, "duration": 2.22}, {"text": "diagonalization in\nits most raw form.", "start": 1860.54, "duration": 3.93}, {"text": "All right, I think we're good.", "start": 1869.6, "duration": 1.69}, {"text": "So why don't we continue, then?", "start": 1871.29, "duration": 2.93}, {"text": "So there are a\nnumber of corollaries", "start": 1874.22, "duration": 2.34}, {"text": "that follow from the statement\nthat the real numbers is", "start": 1876.56, "duration": 3.12}, {"text": "uncountable.", "start": 1879.68, "duration": 0.81}, {"text": "First of all, if\nyou let script L", "start": 1883.91, "duration": 3.27}, {"text": "be the collection\nof all languages,", "start": 1887.18, "duration": 2.305}, {"text": "if you want to consider it\nover some particular alphabet,", "start": 1889.485, "duration": 2.375}, {"text": "that's fine.", "start": 1891.86, "duration": 0.51}, {"text": "But that's not going to be\nreally important for this point", "start": 1892.37, "duration": 6.64}, {"text": "that I'm going to make.", "start": 1899.01, "duration": 1.59}, {"text": "So script L is the\ncollection of all languages.", "start": 1900.6, "duration": 5.94}, {"text": "So every subset of sigma star--", "start": 1906.54, "duration": 3.74}, {"text": "every subset of sigma\nstar is a language.", "start": 1910.28, "duration": 2.97}, {"text": "So look at all those\npossible subsets.", "start": 1913.25, "duration": 3.51}, {"text": "So that includes 0\nto the k, 1 to the k,", "start": 1916.76, "duration": 2.28}, {"text": "plus every other language you\ncan ever think of and more--", "start": 1919.04, "duration": 2.82}, {"text": "all possible languages.", "start": 1921.86, "duration": 2.87}, {"text": "So the collection of all\nlanguages is uncountable.", "start": 1924.73, "duration": 4.38}, {"text": "There's uncountably many\ndifferent languages out there.", "start": 1929.11, "duration": 3.0}, {"text": "I don't want to\nbelabor this point.", "start": 1932.11, "duration": 1.832}, {"text": "You can just take this\nif you don't quite", "start": 1933.942, "duration": 1.708}, {"text": "follow the quick argument\nI'm going to make here.", "start": 1935.65, "duration": 2.88}, {"text": "But you can make a\none-to-one correspondence", "start": 1938.53, "duration": 4.89}, {"text": "from all languages to the\nreals so that each language", "start": 1943.42, "duration": 4.23}, {"text": "gets its own real number.", "start": 1947.65, "duration": 2.678}, {"text": "And the way I'm going to\nthink about that-- let's", "start": 1950.328, "duration": 2.042}, {"text": "put the real numbers\ninto binary form.", "start": 1952.37, "duration": 2.85}, {"text": "And if you imagine\nhere being sigma star,", "start": 1955.22, "duration": 2.37}, {"text": "all of the possible\nstrings of sigma", "start": 1957.59, "duration": 1.68}, {"text": "star written out in\ntheir standard order.", "start": 1959.27, "duration": 4.29}, {"text": "And now if you have\na language here, A,", "start": 1963.56, "duration": 1.94}, {"text": "it's just some\narbitrary language.", "start": 1965.5, "duration": 2.35}, {"text": "So that's going to have some\nof the strings of sigma star", "start": 1967.85, "duration": 4.36}, {"text": "appearing.", "start": 1972.21, "duration": 0.5}, {"text": "Like 0 is appearing,\nbut 1 is not appearing.", "start": 1972.71, "duration": 2.64}, {"text": "00 is appearing and 01,\nbut not these three.", "start": 1975.35, "duration": 3.24}, {"text": "And I'm going to associate\nto A, my language,", "start": 1981.27, "duration": 3.33}, {"text": "some real number in binary by\nputting in a 0 in the decimal", "start": 1984.6, "duration": 6.84}, {"text": "representation-- well,\nthe binary representation,", "start": 1991.44, "duration": 2.46}, {"text": "I should say--", "start": 1993.9, "duration": 1.71}, {"text": "for that string if it's not\nthere and a 1 if it is there.", "start": 1995.61, "duration": 5.16}, {"text": "And so a real number--\nbecause there's infinitely", "start": 2004.45, "duration": 3.41}, {"text": "many yes/no choices in\nthe binary representation", "start": 2007.86, "duration": 4.02}, {"text": "can represent a\nlanguage because of each", "start": 2011.88, "duration": 3.21}, {"text": "of the yes/no choices of a\nstring being present or not.", "start": 2015.09, "duration": 3.15}, {"text": "I'm going to put a 1 for\nwhen the string is present,", "start": 2018.24, "duration": 2.21}, {"text": "a 0 when it's not present.", "start": 2020.45, "duration": 1.3}, {"text": "So each language has\nits own real number,", "start": 2021.75, "duration": 3.072}, {"text": "and each real number\nis going to be", "start": 2024.822, "duration": 1.458}, {"text": "associated to its own language.", "start": 2026.28, "duration": 2.22}, {"text": "Here, I'm restricting myself to\nreal numbers between 0 and 1.", "start": 2028.5, "duration": 3.92}, {"text": "That's not going to\nbe an essential point.", "start": 2032.42, "duration": 1.75}, {"text": "So let's not get\nhung up on that.", "start": 2034.17, "duration": 1.71}, {"text": "So the fact that the\nlanguages can be putting it", "start": 2040.05, "duration": 10.629}, {"text": "into a one-to-one correspondence\nwith the real numbers", "start": 2050.679, "duration": 3.75}, {"text": "shows that the collection of all\nlanguages is also uncountable.", "start": 2054.429, "duration": 4.801}, {"text": "Now another observation here--", "start": 2059.23, "duration": 2.67}, {"text": "another point worth noting is\nthat if you look at sigma star", "start": 2061.9, "duration": 3.15}, {"text": "itself, the strings,\nall possible strings,", "start": 2065.05, "duration": 5.41}, {"text": "that's a countable set.", "start": 2070.46, "duration": 2.42}, {"text": "The collection of all possible\nlanguages is uncountable.", "start": 2072.88, "duration": 2.46}, {"text": "But the collection of all\npossible finite strings", "start": 2075.34, "duration": 3.0}, {"text": "is countable because\nI can just list them.", "start": 2078.34, "duration": 2.93}, {"text": "Here's my list of all\npossible strings, which", "start": 2081.27, "duration": 2.1}, {"text": "you can put into a\ntable if you like", "start": 2083.37, "duration": 1.5}, {"text": "to think of it matching up\nwith the natural numbers", "start": 2084.87, "duration": 2.125}, {"text": "in that way.", "start": 2086.995, "duration": 2.605}, {"text": "Now I'm trying to\nmake a point here,", "start": 2089.6, "duration": 2.41}, {"text": "which is that if you take M,\nwhich is all possible Turing", "start": 2092.01, "duration": 3.62}, {"text": "machines-- script M\nis all possible Turing", "start": 2095.63, "duration": 2.4}, {"text": "machines-- the collection of\nall possible Turing machines", "start": 2098.03, "duration": 2.82}, {"text": "is countable.", "start": 2100.85, "duration": 1.52}, {"text": "There are only countably many\ndifferent Turing machines.", "start": 2102.37, "duration": 4.14}, {"text": "And you can argue that in all\nsorts of messy different ways.", "start": 2106.51, "duration": 2.707}, {"text": "But I think the most\nsimple way to see", "start": 2109.217, "duration": 1.583}, {"text": "that is to think about\neach Turing machine", "start": 2110.8, "duration": 3.3}, {"text": "as having a description,\nwhich is a string.", "start": 2114.1, "duration": 5.13}, {"text": "So the collection of all\ndescriptions of Turing machines", "start": 2119.23, "duration": 3.3}, {"text": "is just a subset of sigma\nstar, which we already", "start": 2122.53, "duration": 2.91}, {"text": "know is countable.", "start": 2125.44, "duration": 1.29}, {"text": "And the subset of any countable\nset is going to be countable.", "start": 2126.73, "duration": 5.48}, {"text": "So anyway, I think\nit's worth remembering", "start": 2132.21, "duration": 9.04}, {"text": "that the collection of old\nTuring machines is countable.", "start": 2141.25, "duration": 5.64}, {"text": "Whereas the collection of\nall languages is uncountable.", "start": 2146.89, "duration": 2.4}, {"text": "And that tells you right there\nthat some language is not", "start": 2149.29, "duration": 3.6}, {"text": "decided because there are more\nlanguages than Turing machines.", "start": 2152.89, "duration": 6.94}, {"text": "We've unaccountably\nmany language, only", "start": 2159.83, "duration": 2.27}, {"text": "countably many Turing machines,\nso that's fewer Turing machines", "start": 2162.1, "duration": 3.37}, {"text": "than languages.", "start": 2165.47, "duration": 1.02}, {"text": "There's no way to map all the\nlanguages onto Turing machines.", "start": 2166.49, "duration": 2.908}, {"text": "So there's going to always\nbe some languages that", "start": 2169.398, "duration": 2.042}, {"text": "got unmapped.", "start": 2171.44, "duration": 1.89}, {"text": "And so, in particular,\nthere are going", "start": 2173.33, "duration": 1.988}, {"text": "to be some languages\nwhich are undecidable.", "start": 2175.318, "duration": 1.792}, {"text": "There are going to be\nsome languages which", "start": 2177.11, "duration": 1.75}, {"text": "are not Turing-recognizable.", "start": 2178.86, "duration": 1.22}, {"text": "And anything based on some\nautomata kind of a definition", "start": 2180.08, "duration": 5.37}, {"text": "process is going to be some\nlanguages that they're not", "start": 2185.45, "duration": 3.277}, {"text": "going to be defined.", "start": 2188.727, "duration": 0.833}, {"text": "OK, now what this\ncorollary shows you", "start": 2192.16, "duration": 2.58}, {"text": "that there is some language out\nthere, which is not decidable.", "start": 2194.74, "duration": 3.21}, {"text": "What we're going to\nshow next is that there", "start": 2197.95, "duration": 2.25}, {"text": "is a specific language--", "start": 2200.2, "duration": 1.41}, {"text": "A,TM-- which is not decidable.", "start": 2201.61, "duration": 3.08}, {"text": "And but first, I think we\nhave a check-in coming up.", "start": 2204.69, "duration": 3.24}, {"text": "And let me give you a\nlittle bit of background", "start": 2207.93, "duration": 2.643}, {"text": "here because this is\nrelevant to this question", "start": 2210.573, "duration": 1.917}, {"text": "that I got about\nintermediate size sets.", "start": 2212.49, "duration": 3.06}, {"text": "So the question of\nwhether there is", "start": 2215.55, "duration": 2.55}, {"text": "a set of size between\nthe natural numbers", "start": 2218.1, "duration": 3.27}, {"text": "and the real numbers\nstrictly in between--", "start": 2221.37, "duration": 3.21}, {"text": "so bigger than the natural\nnumbers, not the same size", "start": 2224.58, "duration": 2.52}, {"text": "as the natural numbers,\nbut not the same size", "start": 2227.1, "duration": 2.22}, {"text": "as the real numbers either,\nbut in between in size.", "start": 2229.32, "duration": 5.67}, {"text": "That was Hilbert's question\nnumber 1 out of his list of 23", "start": 2234.99, "duration": 3.51}, {"text": "that I talked about\na few lectures back.", "start": 2238.5, "duration": 3.277}, {"text": "It's interesting that he put\nit as number 1 in that very", "start": 2241.777, "duration": 2.333}, {"text": "privileged special place because\nI know Hilbert was very--", "start": 2244.11, "duration": 4.86}, {"text": "he felt that the\nunderstanding infinity", "start": 2248.97, "duration": 1.95}, {"text": "was a really central\nissue in mathematics.", "start": 2250.92, "duration": 2.248}, {"text": "And that if we can't answer\na question like this,", "start": 2253.168, "duration": 2.042}, {"text": "we don't really\nunderstand infinity.", "start": 2255.21, "duration": 3.198}, {"text": "You want to understand what\nkind of sizes of infinities", "start": 2258.408, "duration": 2.292}, {"text": "are there.", "start": 2260.7, "duration": 0.752}, {"text": "We know there's the\nreal number is bigger", "start": 2261.452, "duration": 1.708}, {"text": "than the natural numbers.", "start": 2263.16, "duration": 1.8}, {"text": "Is there something in between?", "start": 2264.96, "duration": 1.38}, {"text": "So fundamental, really.", "start": 2266.34, "duration": 2.46}, {"text": "But it was shown during the\ncourse of the 20th century,", "start": 2268.8, "duration": 3.45}, {"text": "really, in two separate steps--\none in the 1930s by Godel,", "start": 2272.25, "duration": 2.73}, {"text": "one in the early\n1970s by Cohen--", "start": 2274.98, "duration": 2.76}, {"text": "that we can't\nanswer this question", "start": 2277.74, "duration": 2.1}, {"text": "by using the standard\naxioms of mathematics.", "start": 2279.84, "duration": 4.6}, {"text": "The answer can go either way.", "start": 2284.44, "duration": 3.31}, {"text": "And both of them are consistent\nwith the axes mathematics.", "start": 2287.75, "duration": 3.57}, {"text": "So you're never going\nto be able to prove", "start": 2291.32, "duration": 1.94}, {"text": "that there is a set\nwhose size is in between", "start": 2293.26, "duration": 5.4}, {"text": "or that there is no such set.", "start": 2298.66, "duration": 1.68}, {"text": "It's just impossible to\nprove either way using", "start": 2300.34, "duration": 3.545}, {"text": "the standard axiom of\nmathematics, which, actually,", "start": 2303.885, "duration": 2.125}, {"text": "is kind of remarkable.", "start": 2306.01, "duration": 3.137}, {"text": "And so my question for you\nis-- and this is really", "start": 2309.147, "duration": 2.083}, {"text": "a philosophical question,\nnot one that is directly you", "start": 2311.23, "duration": 4.07}, {"text": "need to know about\nmaterial in the course.", "start": 2315.3, "duration": 1.75}, {"text": "I think it's just a matter\nof your own interest.", "start": 2317.05, "duration": 2.488}, {"text": "I hope you find it interesting.", "start": 2319.538, "duration": 1.292}, {"text": "If you don't, you can\njust answer it randomly.", "start": 2320.83, "duration": 3.96}, {"text": "But what's going on here\nthat we can't answer", "start": 2324.79, "duration": 5.47}, {"text": "that question\nabout whether there", "start": 2330.26, "duration": 1.89}, {"text": "is a set of intermediate size?", "start": 2332.15, "duration": 1.89}, {"text": "Is it because our axioms for\nmathematics are inadequate?", "start": 2334.04, "duration": 3.93}, {"text": "Or maybe there is no such thing\nas a mathematical reality.", "start": 2337.97, "duration": 4.5}, {"text": "You can talk about\nwhat's real here?", "start": 2342.47, "duration": 2.95}, {"text": "What's the reality?", "start": 2345.42, "duration": 1.7}, {"text": "Either there is a set\nin between or not.", "start": 2347.12, "duration": 2.785}, {"text": "If you can imagine,\nall of these things", "start": 2349.905, "duration": 1.625}, {"text": "have their own reality\nto them, well, then,", "start": 2351.53, "duration": 2.67}, {"text": "there's going to be an answer.", "start": 2354.2, "duration": 1.267}, {"text": "And then you would\nexpect, well, maybe", "start": 2355.467, "duration": 1.583}, {"text": "we can find better axioms,\nwhich will actually", "start": 2357.05, "duration": 1.917}, {"text": "give us that answer.", "start": 2358.967, "duration": 0.873}, {"text": "Or you can say, well,\nthere is no reality.", "start": 2359.84, "duration": 2.7}, {"text": "And infinite sets are\nkind of human constructs", "start": 2362.54, "duration": 4.68}, {"text": "anyway, so we can make them kind\nof play out any way we like.", "start": 2367.22, "duration": 2.91}, {"text": "Mathematicians argue\nabout that to this day.", "start": 2370.13, "duration": 4.44}, {"text": "And it is, as I say, really,\nit's a philosophical question.", "start": 2374.57, "duration": 3.72}, {"text": "But just out of curiosity,\nlet's see how you guys end up", "start": 2378.29, "duration": 3.87}, {"text": "deciding on that one.", "start": 2382.16, "duration": 2.11}, {"text": "So here is the poll.", "start": 2384.27, "duration": 2.04}, {"text": "5 seconds to go.", "start": 2386.31, "duration": 1.14}, {"text": "Please vote.", "start": 2387.45, "duration": 1.48}, {"text": "And we're going to end\nthe polling, 1, 2, 3, now.", "start": 2388.93, "duration": 3.44}, {"text": "All right, here we go.", "start": 2395.2, "duration": 1.87}, {"text": "So there's no right answer.", "start": 2397.07, "duration": 3.15}, {"text": "I think if most mathematicians\nwere to, I think,", "start": 2400.22, "duration": 5.0}, {"text": "the instinct of most\nlogicians, especially, I'm", "start": 2405.22, "duration": 2.61}, {"text": "not sure if general\nmathematicians really even care", "start": 2407.83, "duration": 2.4}, {"text": "about this question, but\nlogicians would probably", "start": 2410.23, "duration": 3.27}, {"text": "have an instinct that, probably,\nthere are sets in between.", "start": 2413.5, "duration": 3.55}, {"text": "There's no reason that\nthere shouldn't be.", "start": 2417.05, "duration": 3.02}, {"text": "It seems kind of\nstrange that there", "start": 2420.07, "duration": 1.77}, {"text": "should be this sort of jump\nfrom the natural numbers", "start": 2421.84, "duration": 4.44}, {"text": "to the real numbers and\nwhy nothing in between?", "start": 2426.28, "duration": 4.81}, {"text": "But I don't think that\nquestion is really settled.", "start": 2431.09, "duration": 5.505}, {"text": "All right, let's continue on.", "start": 2439.962, "duration": 1.208}, {"text": "I think we are--", "start": 2441.17, "duration": 2.46}, {"text": "OK, so we're going to--", "start": 2443.63, "duration": 1.08}, {"text": "our coffee break is coming,\nin case you're wondering.", "start": 2447.872, "duration": 2.208}, {"text": "So this is my last\nslide before then.", "start": 2450.08, "duration": 1.71}, {"text": "But this is an important\nslide, so please hold out.", "start": 2451.79, "duration": 6.09}, {"text": "So here is our promised\ntheorem of the day.", "start": 2457.88, "duration": 4.29}, {"text": "I'm going to show that\nA,TM is not decidable,", "start": 2462.17, "duration": 2.34}, {"text": "the acceptance problem\nfor Turing machines.", "start": 2464.51, "duration": 2.77}, {"text": "And it's all going to be\ncontained on this one slide.", "start": 2467.28, "duration": 2.877}, {"text": "We're going to give a\nproof by contradiction", "start": 2470.157, "duration": 1.833}, {"text": "using diagonalization.", "start": 2471.99, "duration": 3.0}, {"text": "And we're going to assume\nsome Turing machine, H,", "start": 2474.99, "duration": 3.63}, {"text": "decides A,TM.", "start": 2478.62, "duration": 2.74}, {"text": "And we're going to\nget a contradiction.", "start": 2481.36, "duration": 2.94}, {"text": "So let's, first of\nall, make sure we", "start": 2484.3, "duration": 1.5}, {"text": "understand what H is doing.", "start": 2485.8, "duration": 3.1}, {"text": "So H gets an input--", "start": 2488.9, "duration": 1.44}, {"text": "a Turing machine and an input.", "start": 2490.34, "duration": 3.57}, {"text": "And H is going to be a\ndecider, so it always", "start": 2493.91, "duration": 3.27}, {"text": "halts with an\naccept or a reject.", "start": 2497.18, "duration": 3.65}, {"text": "It's supposed to accept if\nM accepts w and reject if it", "start": 2500.83, "duration": 5.0}, {"text": "doesn't.", "start": 2505.83, "duration": 0.91}, {"text": "So in other words,\nit's going to reject", "start": 2506.74, "duration": 1.88}, {"text": "if M rejects w either by\nhalting or by looping.", "start": 2508.62, "duration": 4.71}, {"text": "That's the job of H. And\nwe're assuming we can do that.", "start": 2516.34, "duration": 6.19}, {"text": "But we will see a\ncontradiction occur.", "start": 2522.53, "duration": 1.61}, {"text": "So the way we're going to do\nthat is really kind of just one", "start": 2526.9, "duration": 4.55}, {"text": "step here in a way.", "start": 2531.45, "duration": 1.77}, {"text": "And we're going to use H\nto construct another Turing", "start": 2533.22, "duration": 3.69}, {"text": "machine D. H is going to be a\nsubroutine to D. We've already", "start": 2536.91, "duration": 3.93}, {"text": "seen us doing that in the past.", "start": 2540.84, "duration": 1.65}, {"text": "D is going to do something\na little strange,", "start": 2545.17, "duration": 2.66}, {"text": "just to warn you.", "start": 2547.83, "duration": 3.22}, {"text": "D's input is just\na Turing machine--", "start": 2551.05, "duration": 2.3}, {"text": "no w.", "start": 2553.35, "duration": 2.82}, {"text": "And what D is going to\ndo using its subroutine", "start": 2556.17, "duration": 5.46}, {"text": "H is going to simulate H on\ninput M, comma, the description", "start": 2561.63, "duration": 6.59}, {"text": "of M. Now what is that?", "start": 2568.22, "duration": 3.64}, {"text": "Well, the description of\nM is just some string.", "start": 2571.86, "duration": 3.45}, {"text": "So what H is trying--", "start": 2575.31, "duration": 1.61}, {"text": "what it's asking H to\ntell, to answer is,", "start": 2576.92, "duration": 4.08}, {"text": "does M accept the\nstring representing", "start": 2581.0, "duration": 6.01}, {"text": "M's own description?", "start": 2587.01, "duration": 3.55}, {"text": "It's as if we're\nfeeding M into itself,", "start": 2590.56, "duration": 3.58}, {"text": "which seems like a totally\ntwisted thing to do,", "start": 2594.14, "duration": 6.67}, {"text": "you might say.", "start": 2600.81, "duration": 0.71}, {"text": "Why would you ever feed\na program into itself?", "start": 2605.12, "duration": 2.64}, {"text": "Somebody has written\ncannibalism here--", "start": 2610.37, "duration": 2.34}, {"text": "yeah, kind of.", "start": 2612.71, "duration": 1.77}, {"text": "I'd say it's worse\n[LAUGHS] because it's not", "start": 2614.48, "duration": 3.57}, {"text": "eating somebody else.", "start": 2618.05, "duration": 0.96}, {"text": "It's eating yourself.", "start": 2619.01, "duration": 2.89}, {"text": "OK, but I claim that there are\nactual cases in practice where", "start": 2621.9, "duration": 7.86}, {"text": "we do this.", "start": 2629.76, "duration": 2.18}, {"text": "We feed programs\ninto themselves.", "start": 2631.94, "duration": 4.56}, {"text": "And the example that I\nknow of where this is done", "start": 2636.5, "duration": 4.2}, {"text": "is when you're\nmaking a compiler.", "start": 2640.7, "duration": 3.33}, {"text": "You might want to\nmake a compiler", "start": 2644.03, "duration": 1.98}, {"text": "and then written in the same\nlanguage that it's compiling.", "start": 2646.01, "duration": 3.27}, {"text": "And then you feed the\ncompiler into itself.", "start": 2649.28, "duration": 3.66}, {"text": "You may say, why even\nbother because it's already,", "start": 2652.94, "duration": 2.43}, {"text": "obviously, if it,\nonce it's running,", "start": 2655.37, "duration": 1.63}, {"text": "you don't need to\ncompile it again.", "start": 2657.0, "duration": 4.84}, {"text": "But actually, an example\nwhere this was really used", "start": 2661.84, "duration": 3.42}, {"text": "was when there was an\noptimizing compiler, I think,", "start": 2665.26, "duration": 2.7}, {"text": "for C written on\nearly Unix machines.", "start": 2667.96, "duration": 3.98}, {"text": "And the optimizing compiler\nfor C was written in C.", "start": 2671.94, "duration": 5.08}, {"text": "So you would feed the\noptimizing compiler", "start": 2677.02, "duration": 4.26}, {"text": "into the regular\ncompiler, first of all.", "start": 2681.28, "duration": 2.67}, {"text": "Now, you had the\ncompiler running,", "start": 2683.95, "duration": 5.02}, {"text": "but it was an optimized.", "start": 2688.97, "duration": 2.37}, {"text": "So but now that it's the\noptimizing compiler is running,", "start": 2691.34, "duration": 3.12}, {"text": "you can feed the\noptimizing compiler", "start": 2694.46, "duration": 1.83}, {"text": "into that, which is itself.", "start": 2696.29, "duration": 1.75}, {"text": "Now you have an optimized\noptimizing compiler.", "start": 2698.04, "duration": 3.25}, {"text": "So it really makes some--", "start": 2701.29, "duration": 2.07}, {"text": "there is at least one case\nwhere this has actually", "start": 2703.36, "duration": 2.97}, {"text": "been done in practice.", "start": 2706.33, "duration": 3.29}, {"text": "Not that we really care.", "start": 2709.62, "duration": 1.11}, {"text": "This is a theory class-- but\njust for fun to observe that.", "start": 2710.73, "duration": 4.17}, {"text": "So here, H is trying to\nsay, well, does in a M end", "start": 2714.9, "duration": 3.98}, {"text": "up accepting when it's fed\nthe description of itself?", "start": 2718.88, "duration": 4.287}, {"text": "You know, at least,\nmathematically speaking,", "start": 2723.167, "duration": 1.833}, {"text": "that's a reasonable\nthing to ask.", "start": 2725.0, "duration": 2.61}, {"text": "And then what D is going to do\nwhen it gets the answer back", "start": 2727.61, "duration": 3.72}, {"text": "from H--", "start": 2731.33, "duration": 1.11}, {"text": "H is a decider, don't forget--", "start": 2732.44, "duration": 1.8}, {"text": "is D's going to do the\nopposite of whatever H does.", "start": 2734.24, "duration": 2.74}, {"text": "It's going to\naccept if H rejects", "start": 2736.98, "duration": 1.49}, {"text": "and reject if H accepts.", "start": 2738.47, "duration": 3.56}, {"text": "So let's, in summary,\nlet's pull this together,", "start": 2742.03, "duration": 3.02}, {"text": "so it's easy to understand,\nin the end, what is D doing?", "start": 2745.05, "duration": 6.18}, {"text": "D is going to accept.", "start": 2751.23, "duration": 2.01}, {"text": "D is also going to be\ndecider, by the way.", "start": 2753.24, "duration": 1.77}, {"text": "So D is always going to\neither accept or reject--", "start": 2755.01, "duration": 2.74}, {"text": "Just.", "start": 2757.75, "duration": 0.5}, {"text": "The opposite of what\nH tells it to do.", "start": 2758.25, "duration": 1.9}, {"text": "So D is going to accept M\nexactly when M doesn't accept M", "start": 2760.15, "duration": 6.21}, {"text": "because when M doesn't accept\nM, H is going to reject,", "start": 2766.36, "duration": 6.07}, {"text": "and so then D is\ngoing to accept.", "start": 2772.43, "duration": 1.92}, {"text": "So D accepts M if and\nonly if M doesn't accept", "start": 2774.35, "duration": 3.14}, {"text": "M. That's exactly the\ncondition in which D accepts", "start": 2777.49, "duration": 2.64}, {"text": "M. I think it's important to\njust step back and make sure", "start": 2780.13, "duration": 4.12}, {"text": "you understand this line\nbecause we have only one line", "start": 2784.25, "duration": 2.43}, {"text": "left to get our contradiction.", "start": 2786.68, "duration": 4.98}, {"text": "Right?", "start": 2791.66, "duration": 0.5}, {"text": "Are we together?", "start": 2792.16, "duration": 0.69}, {"text": "D accepts M if and\nonly if M doesn't", "start": 2792.85, "duration": 2.22}, {"text": "accept M. That's just by the\nway we've defined setup D.", "start": 2795.07, "duration": 3.7}, {"text": "Now what we're going to do is\nfeed in, instead of M to D,", "start": 2798.77, "duration": 5.02}, {"text": "and not some arbitrary feed,\nwe're going to use feed in D", "start": 2803.79, "duration": 3.11}, {"text": "into D. And that is going\nto be our contradiction", "start": 2806.9, "duration": 3.86}, {"text": "because D is now\ngoing to accept D if", "start": 2810.76, "duration": 2.49}, {"text": "and only if D doesn't\naccept D, and that's", "start": 2813.25, "duration": 2.01}, {"text": "certainly impossible.", "start": 2815.26, "duration": 1.415}, {"text": "That's our contradiction which\nproves that H cannot exist.", "start": 2819.52, "duration": 3.93}, {"text": "And therefore, A,TM\nis undecidable.", "start": 2823.45, "duration": 3.82}, {"text": "OK, so we're done,\nexcept for the one", "start": 2827.27, "duration": 2.79}, {"text": "point, which is that why\nis this a diagonalization?", "start": 2830.06, "duration": 6.03}, {"text": "And I think you can get that\nfrom the following picture.", "start": 2836.09, "duration": 4.71}, {"text": "If you imagine here writing\ndown all possible times--", "start": 2840.8, "duration": 3.48}, {"text": "I'm going to make a table here.", "start": 2844.28, "duration": 1.33}, {"text": "Here is the list of\nall Turing machines,", "start": 2845.61, "duration": 4.88}, {"text": "including D, which\nis a machine which", "start": 2850.49, "duration": 2.37}, {"text": "I built under the\nassumption that H exists.", "start": 2852.86, "duration": 5.46}, {"text": "So D appears here somewhere.", "start": 2858.32, "duration": 1.47}, {"text": "But here are all the\nother Turing machines.", "start": 2859.79, "duration": 1.8}, {"text": "And here are all of these\ndescriptions of the Turing", "start": 2861.59, "duration": 2.167}, {"text": "machines along the labeling\nall of the columns.", "start": 2863.757, "duration": 4.103}, {"text": "OK, so these are\nthe rows labeled.", "start": 2867.86, "duration": 1.53}, {"text": "These are the column labels.", "start": 2869.39, "duration": 1.32}, {"text": "And inside, I'm\ngoing to tell you", "start": 2870.71, "duration": 3.39}, {"text": "the answer for whether a given\nmachine accepts a given input.", "start": 2874.1, "duration": 7.02}, {"text": "So for example, M1 accepts\nits own description", "start": 2881.12, "duration": 3.51}, {"text": "but rejects the\ndescription of M2,", "start": 2884.63, "duration": 2.37}, {"text": "but accepts the\ndescription of M3.", "start": 2887.0, "duration": 1.92}, {"text": "I don't you know.", "start": 2888.92, "duration": 0.84}, {"text": "I'm obviously I'm\nmaking this up.", "start": 2889.76, "duration": 1.2}, {"text": "I don't know what M1 is.", "start": 2890.96, "duration": 1.0}, {"text": "But just hypothetically, that's\nwhat the machine M1 does.", "start": 2891.96, "duration": 4.152}, {"text": "So I'm just filling\nout this table.", "start": 2896.112, "duration": 1.458}, {"text": "H could get the answer to any\nof the elements in this table", "start": 2901.632, "duration": 2.868}, {"text": "because it can test whether M4\naccepts the description of M3.", "start": 2904.5, "duration": 5.94}, {"text": "So H could fill out this table.", "start": 2910.44, "duration": 2.58}, {"text": "So maybe M2 is a machine\nthat always rejects.", "start": 2913.02, "duration": 2.7}, {"text": "It's a very unfriendly,\nrejecting machine.", "start": 2915.72, "duration": 2.85}, {"text": "M3 is a very friendly machine.", "start": 2918.57, "duration": 1.48}, {"text": "It accepts all inputs.", "start": 2920.05, "duration": 1.85}, {"text": "M4 rejects some and accepts\nothers, dot, dot, dot.", "start": 2921.9, "duration": 4.495}, {"text": "Now, I want to look and\nsee, what does D do?", "start": 2926.395, "duration": 4.715}, {"text": "Now based on the information\nthat I've already given you,", "start": 2931.11, "duration": 2.73}, {"text": "we can understand what D does.", "start": 2933.84, "duration": 3.4}, {"text": "So for example, what\ndoes D do when I", "start": 2937.24, "duration": 2.19}, {"text": "feed it the description of M1?", "start": 2939.43, "duration": 4.51}, {"text": "What does D do?", "start": 2943.94, "duration": 1.66}, {"text": "Well, we can look here.", "start": 2945.6, "duration": 1.01}, {"text": "D accepts M if and only\nif M doesn't accept M. So", "start": 2946.61, "duration": 3.6}, {"text": "D is going to accept M1 if and\nonly if M1 does not accept M1.", "start": 2950.21, "duration": 7.88}, {"text": "Well, M1 does accept M1.", "start": 2958.09, "duration": 2.4}, {"text": "So D does the opposite.", "start": 2960.49, "duration": 2.49}, {"text": "D rejects.", "start": 2962.98, "duration": 1.26}, {"text": "So OK, I'm highlighting here.", "start": 2964.24, "duration": 2.01}, {"text": "D rejects because\nD is going to do", "start": 2966.25, "duration": 3.0}, {"text": "the opposite of what the machine\ndoes on its own it on input.", "start": 2969.25, "duration": 3.54}, {"text": "So D on M2, you have to\nlook what M2 does on M2.", "start": 2975.37, "duration": 3.78}, {"text": "It rejects, so D does\nthe opposite of that.", "start": 2979.15, "duration": 2.41}, {"text": "It accepts.", "start": 2981.56, "duration": 1.66}, {"text": "And similarly, each\none of these things--", "start": 2983.22, "duration": 5.88}, {"text": "D's answer is going to\nbe the opposite of what", "start": 2989.1, "duration": 2.96}, {"text": "the machine does on\nits own description,", "start": 2992.06, "duration": 2.76}, {"text": "just by virtue of the\ndefinition of D. OK, and so on--", "start": 2994.82, "duration": 5.23}, {"text": "so far, so good.", "start": 3000.05, "duration": 1.49}, {"text": "But the problem is, what\nhappens when D is fed itself?", "start": 3001.54, "duration": 4.86}, {"text": "Because, as you can see,\nwe're heading for trouble", "start": 3006.4, "duration": 5.19}, {"text": "because this is a\ndiagonal down here.", "start": 3011.59, "duration": 2.4}, {"text": "D is just one of the rows.", "start": 3013.99, "duration": 1.35}, {"text": "That diagonal is going\nto intersect that row", "start": 3015.34, "duration": 2.55}, {"text": "at this point.", "start": 3017.89, "duration": 1.41}, {"text": "And D is defined to be going to\nbe doing the opposite of what", "start": 3019.3, "duration": 3.472}, {"text": "that element is, but it can't\nbe the opposite of itself.", "start": 3022.772, "duration": 2.333}, {"text": "And so that's the contradiction.", "start": 3027.98, "duration": 3.32}, {"text": "So I think we're--", "start": 3031.3, "duration": 3.44}, {"text": "I'm going to call us, give\nus a little break here.", "start": 3034.74, "duration": 4.45}, {"text": "And then you can also\ntext me in the meantime.", "start": 3039.19, "duration": 2.01}, {"text": "I'll be happy to answer\nsome questions during that.", "start": 3041.2, "duration": 2.66}, {"text": "A little over 4 minutes\nto go-- so let's see.", "start": 3043.86, "duration": 2.31}, {"text": "Let me see if I can\nanswer your questions.", "start": 3046.17, "duration": 3.6}, {"text": "OK, what's so special about\nA,TM that enables us to do this?", "start": 3049.77, "duration": 3.04}, {"text": "Why can't we do this\non ADFA, for example?", "start": 3052.81, "duration": 4.21}, {"text": "That's a good question.", "start": 3057.02, "duration": 2.47}, {"text": "And the answer is that, in a\nsense, we can do this on DFA.", "start": 3059.49, "duration": 15.4}, {"text": "I mean, I think this is,\nperhaps, a bit of a stretch.", "start": 3074.89, "duration": 3.03}, {"text": "But DFAs could not answer ADFA.", "start": 3077.92, "duration": 4.44}, {"text": "I mean, we could prove that in\nother ways as well by just--", "start": 3082.36, "duration": 4.338}, {"text": "we could use things\nlike the pumping lemma,", "start": 3086.698, "duration": 1.792}, {"text": "and it's not clear, even\nhow you'd formulate ADFA.", "start": 3088.49, "duration": 2.72}, {"text": "But what's important\nhere is that it's really", "start": 3091.21, "duration": 5.73}, {"text": "the model talking about\nitself that really", "start": 3096.94, "duration": 3.33}, {"text": "is where the problem comes up.", "start": 3100.27, "duration": 2.44}, {"text": "So if you try to push\nthis argument through", "start": 3102.71, "duration": 2.78}, {"text": "to show that ADFA is not\ndecidable by Turing machines,", "start": 3105.49, "duration": 3.9}, {"text": "you're going to fail\nbecause we're starting off", "start": 3109.39, "duration": 5.3}, {"text": "with a Turing machine.", "start": 3114.69, "duration": 1.44}, {"text": "And I think I'm going\nto confuse myself", "start": 3116.13, "duration": 3.93}, {"text": "if I try to just repeat it.", "start": 3120.06, "duration": 1.51}, {"text": "But you won't get\na contradiction", "start": 3121.57, "duration": 2.78}, {"text": "because the Turing machine\nis not a finite automaton.", "start": 3124.35, "duration": 2.758}, {"text": "OK.", "start": 3130.245, "duration": 0.5}, {"text": "Will this argument\nget into self-loops?", "start": 3133.87, "duration": 2.01}, {"text": "I don't see why it would--\nthere is some self-reference,", "start": 3135.88, "duration": 3.18}, {"text": "perhaps.", "start": 3139.06, "duration": 0.633}, {"text": "We're going to talk about\nthat a little later.", "start": 3139.693, "duration": 1.917}, {"text": "So we're going to come back and\nrevisit this argument in a week", "start": 3141.61, "duration": 5.19}, {"text": "or so when we talk about\nthe recursion theorem which", "start": 3146.8, "duration": 2.37}, {"text": "talks about machines that\ncan refer to themselves.", "start": 3149.17, "duration": 3.57}, {"text": "But this is a little\nbit of a head--", "start": 3152.74, "duration": 2.635}, {"text": "getting ahead of ourselves.", "start": 3155.375, "duration": 1.125}, {"text": "So somebody's commenting\non this reminding them", "start": 3156.5, "duration": 4.01}, {"text": "of the barber paradox,\nif you remember that,", "start": 3160.51, "duration": 2.64}, {"text": "which has some similarity.", "start": 3163.15, "duration": 4.972}, {"text": "There is a town\nin which there was", "start": 3168.122, "duration": 2.758}, {"text": "a barber which shaves every man\nwho doesn't shave themselves.", "start": 3170.88, "duration": 3.7}, {"text": "It seems he's a\nvery good barber.", "start": 3174.58, "duration": 1.79}, {"text": "So there are some people\nwho shave themselves.", "start": 3176.37, "duration": 2.34}, {"text": "And all the rest,\nthe barber shaves.", "start": 3178.71, "duration": 3.24}, {"text": "The question is, does\nthe barber shave himself?", "start": 3181.95, "duration": 2.61}, {"text": "Because he shaves only those\nmen who don't shave themselves.", "start": 3184.56, "duration": 3.09}, {"text": "So you've got a same\nkind of a contradiction.", "start": 3187.65, "duration": 2.24}, {"text": "There is a relationship there.", "start": 3189.89, "duration": 1.69}, {"text": "So someone wants to know, where\ndid we use the decidability?", "start": 3194.56, "duration": 2.84}, {"text": "So we used the decidability\nto come up with H.", "start": 3197.4, "duration": 5.81}, {"text": "Once we know that\nA,TM is decidable,", "start": 3203.21, "duration": 2.01}, {"text": "then we have that H function,\nand then we can build D.", "start": 3205.22, "duration": 4.38}, {"text": "So that's the chain of reason.", "start": 3209.6, "duration": 5.95}, {"text": "So you assume A,TM is decidable.", "start": 3215.55, "duration": 1.82}, {"text": "Then you have the\ndecider called H,", "start": 3217.37, "duration": 3.21}, {"text": "and then you can build\nD. Somebody wants", "start": 3220.58, "duration": 3.67}, {"text": "to see the previous slide.", "start": 3224.25, "duration": 3.1}, {"text": "What part of the\nslide do you want?", "start": 3227.35, "duration": 1.8}, {"text": "So I'll leave that up there.", "start": 3232.88, "duration": 2.348}, {"text": "Why can we apply the proof\nthat all Turing machines are", "start": 3235.228, "duration": 2.292}, {"text": "accountable to all languages?", "start": 3237.52, "duration": 1.5}, {"text": "Well, because Turing\nmachines have descriptions.", "start": 3239.02, "duration": 3.18}, {"text": "General languages don't\nhave descriptions.", "start": 3242.2, "duration": 2.64}, {"text": "And so that's why.", "start": 3244.84, "duration": 1.8}, {"text": "OK, the candle has\nburnt to the bottom,", "start": 3246.64, "duration": 3.21}, {"text": "and it's time to move on.", "start": 3249.85, "duration": 1.62}, {"text": "So now, let's look at\nthe acceptance problem", "start": 3254.2, "duration": 3.17}, {"text": "for queue automata.", "start": 3257.37, "duration": 3.01}, {"text": "I'll give you a queue automaton\non input, and I want to know,", "start": 3260.38, "duration": 3.66}, {"text": "does it accept the input?", "start": 3264.04, "duration": 1.41}, {"text": "Is that going to be decidable?", "start": 3265.45, "duration": 2.52}, {"text": "And you have your choices.", "start": 3267.97, "duration": 1.125}, {"text": "It's either yes, it is\ndecidable because these", "start": 3269.095, "duration": 3.735}, {"text": "are similar to pushdown\nautomata and APDA is decidable,", "start": 3272.83, "duration": 2.37}, {"text": "or no because yes\ncontradicts results", "start": 3275.2, "duration": 5.53}, {"text": "that we know at\nthis point, or we", "start": 3280.73, "duration": 1.83}, {"text": "don't have enough information\nto answer the question.", "start": 3282.56, "duration": 2.76}, {"text": "OK, let's put that up.", "start": 3285.32, "duration": 1.2}, {"text": "One second-- [LAUGHS]\nall right, that's it.", "start": 3289.1, "duration": 6.02}, {"text": "Ready, going, gone.", "start": 3295.12, "duration": 0.99}, {"text": "So yes, the answer is, well, no.", "start": 3300.18, "duration": 4.08}, {"text": "[LAUGHS] The answer\nis, indeed, the answer", "start": 3304.26, "duration": 2.64}, {"text": "is B. True, that\nqueue automata are", "start": 3306.9, "duration": 5.663}, {"text": "similar to pushdown automata,\nbut all these automata", "start": 3312.563, "duration": 2.167}, {"text": "are similar to each\nother, and that's not", "start": 3314.73, "duration": 2.01}, {"text": "going to be good enough.", "start": 3316.74, "duration": 1.0}, {"text": "What the homework\nhas asked you to do", "start": 3320.67, "duration": 1.88}, {"text": "is to show that you\ncan simulate Turing", "start": 3322.55, "duration": 1.71}, {"text": "machines with queue automata.", "start": 3324.26, "duration": 2.07}, {"text": "So if you can\nanswer the question", "start": 3326.33, "duration": 1.47}, {"text": "about whether the queue automata\nwill accept their input,", "start": 3327.8, "duration": 3.51}, {"text": "that would allow you to be\nable to answer questions", "start": 3331.31, "duration": 2.16}, {"text": "about whether Turing\nmachines accept their input.", "start": 3333.47, "duration": 2.34}, {"text": "And we just proved\nthat's not possible.", "start": 3335.81, "duration": 2.91}, {"text": "So it would be a contradiction\nif we could answer--", "start": 3338.72, "duration": 8.4}, {"text": "if we could decide A, queue, A.", "start": 3347.12, "duration": 3.36}, {"text": "Now, we have an example of\nan undecidable language.", "start": 3350.48, "duration": 2.34}, {"text": "Let's look at an example of\nan unrecognizable language.", "start": 3352.82, "duration": 3.39}, {"text": "Now A,TM is not going to serve\nthat purpose because A,TM is", "start": 3356.21, "duration": 12.35}, {"text": "Turing-recognizable, as we\npointed out by the universal", "start": 3368.56, "duration": 2.34}, {"text": "Turing machine.", "start": 3370.9, "duration": 1.57}, {"text": "So A,TM is undecidable, however.", "start": 3372.47, "duration": 2.87}, {"text": "How about an\nunrecognizable language?", "start": 3375.34, "duration": 3.18}, {"text": "For that, we will see that the\ncomplement of A,TM will serve.", "start": 3378.52, "duration": 5.5}, {"text": "So the complement of A,TM is\nneither decidable nor even", "start": 3384.02, "duration": 4.61}, {"text": "recognizable.", "start": 3388.63, "duration": 2.07}, {"text": "Now it's not\nTuring-recognizable.", "start": 3390.7, "duration": 2.13}, {"text": "And that's going to follow from\na pretty basic theorem that", "start": 3392.83, "duration": 3.0}, {"text": "connects recognizability and\ndecidability that I've put up", "start": 3395.83, "duration": 3.3}, {"text": "here on the screen,\nwhich is that if you have", "start": 3399.13, "duration": 2.49}, {"text": "a language where it\nand its complement", "start": 3401.62, "duration": 2.55}, {"text": "are both recognizable, then\nthe language turnout turns out", "start": 3404.17, "duration": 3.3}, {"text": "to be decidable.", "start": 3407.47, "duration": 0.75}, {"text": "In fact, a language and its\ncomplement are decidable.", "start": 3408.22, "duration": 2.24}, {"text": "But being decidable is\nclosed under complement,", "start": 3410.46, "duration": 2.56}, {"text": "so that's something\nyou should be aware.", "start": 3413.02, "duration": 3.2}, {"text": "But being-- OK.", "start": 3416.22, "duration": 3.5}, {"text": "We'll get to that in a minute.", "start": 3419.72, "duration": 1.25}, {"text": "But if-- so anyway, so\nif you have a language", "start": 3420.97, "duration": 6.63}, {"text": "and it's complement\nboth recognizable,", "start": 3427.6, "duration": 1.95}, {"text": "how do we know the\nlanguage is decidable?", "start": 3429.55, "duration": 2.91}, {"text": "So first of all, let's take\nthe two Turing machines,", "start": 3432.46, "duration": 2.43}, {"text": "M1 and M2 that recognizes\nA and A-complement.", "start": 3434.89, "duration": 5.49}, {"text": "And we're going to\nput those together", "start": 3440.38, "duration": 1.89}, {"text": "to get a decider for A. And\nthat's going to work like this.", "start": 3442.27, "duration": 6.31}, {"text": "It's going to be\ncalled T. So T says,", "start": 3448.58, "duration": 3.16}, {"text": "on input w, what\nit's going to do,", "start": 3451.74, "duration": 2.28}, {"text": "it's going to feed w\ninto M1 and M2 both.", "start": 3454.02, "duration": 3.36}, {"text": "A is the language,\nby the way, yes.", "start": 3460.582, "duration": 1.458}, {"text": "A is-- when I say it's\nTuring-recognizable,", "start": 3462.04, "duration": 3.24}, {"text": "you know, Turing-recognizable\nonly applies to languages.", "start": 3465.28, "duration": 2.91}, {"text": "So yes, A is often this symbol\nI'm going to use for languages,", "start": 3468.19, "duration": 4.11}, {"text": "sometimes for an automaton.", "start": 3472.3, "duration": 1.35}, {"text": "But A is typically\ngoing to be a language.", "start": 3473.65, "duration": 3.88}, {"text": "So now, I'm trying to\nmake T be a decider for A", "start": 3477.53, "duration": 9.448}, {"text": "from the recognizers\nfor A and A-complement.", "start": 3486.978, "duration": 3.252}, {"text": "So I'm going to\ntake an input to T", "start": 3490.23, "duration": 3.69}, {"text": "and feed it into both\nrecognizers, M1 and M2.", "start": 3493.92, "duration": 3.245}, {"text": "OK, I'm going to run\nthem in parallel.", "start": 3500.96, "duration": 3.27}, {"text": "What's nice is that\nbecause M2 recognizes", "start": 3504.23, "duration": 7.71}, {"text": "the complement of\nwhat M1 recognizes,", "start": 3511.94, "duration": 2.76}, {"text": "every string is going to be\naccepted either by M1 or by M2", "start": 3514.7, "duration": 5.37}, {"text": "because every string is either\nan A or an A-complement.", "start": 3520.07, "duration": 3.81}, {"text": "So if I run M1 and M2 on w until\none of the halts or one of them", "start": 3523.88, "duration": 4.91}, {"text": "accepts, I know I'm not\ngoing to run forever", "start": 3528.79, "duration": 2.61}, {"text": "because, eventually, one or\nthe other one have to accept.", "start": 3531.4, "duration": 4.46}, {"text": "So and then I got my answer\nbecause if M1 accepts,", "start": 3535.86, "duration": 2.747}, {"text": "then I know I'm in the language.", "start": 3538.607, "duration": 1.333}, {"text": "But if M2 accepts, I know I'm in\nthe complement of the language,", "start": 3539.94, "duration": 3.36}, {"text": "so I'm out of the language.", "start": 3543.3, "duration": 1.42}, {"text": "So if M1 accepts,\nthen T should accept.", "start": 3544.72, "duration": 2.42}, {"text": "But if M2 accepts,\nthen T should reject. ,", "start": 3547.14, "duration": 7.5}, {"text": "So that proves that nice little\ntheorem written at the top", "start": 3554.64, "duration": 5.7}, {"text": "in blue.", "start": 3560.34, "duration": 2.24}, {"text": "So I got my decider\nfor A built out", "start": 3562.58, "duration": 3.05}, {"text": "of the recognizers for\nA and A-complement.", "start": 3565.63, "duration": 3.27}, {"text": "Now immediately, it follows that\nthe complement of A,TM is not", "start": 3568.9, "duration": 5.31}, {"text": "Turing-recognizable because\nwe know that A,TM itself is", "start": 3574.21, "duration": 7.44}, {"text": "recognizable, but\nit's undecidable.", "start": 3581.65, "duration": 2.81}, {"text": "If the complement was\nalso recognizable,", "start": 3587.41, "duration": 2.82}, {"text": "then A,TM would be\ndecidable, but it isn't.", "start": 3590.23, "duration": 4.02}, {"text": "So when something is decidable,\neither it or its complement", "start": 3594.25, "duration": 3.99}, {"text": "have to be unrecognizable.", "start": 3598.24, "duration": 1.443}, {"text": "And in the case for A,TM, it has\nto be the complement because we", "start": 3599.683, "duration": 2.667}, {"text": "already showed that it is\nitself is recognizable.", "start": 3602.35, "duration": 3.18}, {"text": "So that's the proof of that.", "start": 3609.13, "duration": 1.48}, {"text": "So here is a little\npicture of the way", "start": 3610.61, "duration": 1.73}, {"text": "the world looks right now if\nyou have here, in the middle are", "start": 3612.34, "duration": 2.55}, {"text": "the decidable languages--\nso these are all", "start": 3614.89, "duration": 2.34}, {"text": "languages, this Venn\ndiagram of languages.", "start": 3617.23, "duration": 2.58}, {"text": "We showed earlier, the regular,\nthe context-free, decidable,", "start": 3619.81, "duration": 3.93}, {"text": "recognizable.", "start": 3623.74, "duration": 2.34}, {"text": "Here, I've got the recognizable\nand what I'm calling", "start": 3626.08, "duration": 3.09}, {"text": "the co-Turing recognizable.", "start": 3629.17, "duration": 4.12}, {"text": "This is the collection\nof all complements", "start": 3633.29, "duration": 3.06}, {"text": "of recognizable languages.", "start": 3636.35, "duration": 1.59}, {"text": "So A,TM bar, A,TM\ncomplement is the complement", "start": 3637.94, "duration": 3.6}, {"text": "of a recognizable language.", "start": 3641.54, "duration": 1.59}, {"text": "This region here are\nall the complements", "start": 3643.13, "duration": 5.16}, {"text": "of the recognizable languages\nor the so-called co-Turing", "start": 3648.29, "duration": 4.74}, {"text": "recognizable languages--\ncomplement of.", "start": 3653.03, "duration": 4.08}, {"text": "So A,TM is on this side.", "start": 3657.11, "duration": 1.77}, {"text": "A,TM-complement is on that side.", "start": 3658.88, "duration": 2.07}, {"text": "But if something's in both, by\nvirtue of this theorem here,", "start": 3660.95, "duration": 3.66}, {"text": "then it's decidable.", "start": 3664.61, "duration": 1.315}, {"text": "OK, last check-in for the day.", "start": 3668.6, "duration": 3.45}, {"text": "From what we learned so far,\nwhich closure properties", "start": 3672.05, "duration": 3.9}, {"text": "can we prove for the\nclass of deterring", "start": 3675.95, "duration": 2.25}, {"text": "recognizable languages?", "start": 3678.2, "duration": 2.52}, {"text": "Choose all that apply.", "start": 3680.72, "duration": 0.99}, {"text": "Well, as I say, you don't\nhave to get it right.", "start": 3684.73, "duration": 3.35}, {"text": "Let's not spend too\nmuch more time on this", "start": 3688.08, "duration": 2.17}, {"text": "because we'll talk a\nlittle bit about it.", "start": 3690.25, "duration": 4.49}, {"text": "Almost all-- its closed\nunder almost all of them,", "start": 3694.74, "duration": 2.257}, {"text": "but not all of them.", "start": 3696.997, "duration": 0.833}, {"text": "Because-- are we done here?", "start": 3705.38, "duration": 3.81}, {"text": "I think we're done--", "start": 3709.19, "duration": 2.24}, {"text": "5 seconds.", "start": 3711.43, "duration": 0.525}, {"text": "OK, here we go, ending polling.", "start": 3714.7, "duration": 1.425}, {"text": "I'm not sure what the meaning\nof [LAUGHS] deleting your answer", "start": 3720.16, "duration": 3.78}, {"text": "is here.", "start": 3723.94, "duration": 1.38}, {"text": "Everybody likes union, I guess.", "start": 3725.32, "duration": 1.92}, {"text": "They're closed under\nall of these operations", "start": 3727.24, "duration": 1.89}, {"text": "except complement.", "start": 3729.13, "duration": 1.36}, {"text": "But we just proved it's not\nclosed under complement,", "start": 3733.753, "duration": 2.167}, {"text": "so I'm a little puzzled by\nwhy we have so many votes", "start": 3735.92, "duration": 4.84}, {"text": "for closure under complement.", "start": 3740.76, "duration": 2.73}, {"text": "We have here, A,TM is\nTuring-recognizable,", "start": 3743.49, "duration": 3.6}, {"text": "but A,TM-complement is\nnot Turing-recognizable.", "start": 3747.09, "duration": 1.965}, {"text": "it's right here on the slide.", "start": 3749.055, "duration": 3.215}, {"text": "I'm not trying to\nmake you feel bad,", "start": 3752.27, "duration": 1.5}, {"text": "but I'm trying to just point\nout that you think, please.", "start": 3753.77, "duration": 8.05}, {"text": "So now closure under union\nand intersection, I mean,", "start": 3761.82, "duration": 6.2}, {"text": "you could kind of\nget those answers", "start": 3768.02, "duration": 1.56}, {"text": "just by running things\nin parallel the way", "start": 3769.58, "duration": 2.13}, {"text": "we did the proof here.", "start": 3771.71, "duration": 1.17}, {"text": "You just run both machines.", "start": 3772.88, "duration": 3.36}, {"text": "And if they both give--", "start": 3776.24, "duration": 5.803}, {"text": "I mean, it's a little\ntricky, I suppose.", "start": 3782.043, "duration": 1.667}, {"text": "If either one of them\naccept, then you can accept.", "start": 3783.71, "duration": 5.06}, {"text": "Or if they both\naccept, you just wait", "start": 3788.77, "duration": 1.59}, {"text": "until they both have accepted.", "start": 3790.36, "duration": 1.25}, {"text": "Otherwise, you\njust keep running.", "start": 3791.61, "duration": 1.85}, {"text": "So the first two are\npretty straightforward.", "start": 3793.46, "duration": 2.503}, {"text": "Closure under\nconcatenation-- this", "start": 3795.963, "duration": 1.417}, {"text": "is also going to be similar.", "start": 3797.38, "duration": 1.21}, {"text": "You just try every possible\nway of cutting the string up", "start": 3798.59, "duration": 3.23}, {"text": "into two pieces and\nrun in parallel on.", "start": 3801.82, "duration": 2.62}, {"text": "And if you ever find a\nway of cutting it up,", "start": 3804.44, "duration": 2.48}, {"text": "and you run those two, and put\nthose two sides in parallel,", "start": 3806.92, "duration": 2.62}, {"text": "and if they both accept,\nthen you can accept.", "start": 3809.54, "duration": 4.97}, {"text": "And star is, again,\nvery similar.", "start": 3814.51, "duration": 2.26}, {"text": "So these are not too bad.", "start": 3816.77, "duration": 2.57}, {"text": "But I admit, you know, it's\nnot a whole lot of time", "start": 3819.34, "duration": 2.46}, {"text": "to have to contend with\nsomething that you're just", "start": 3821.8, "duration": 2.94}, {"text": "getting used to.", "start": 3824.74, "duration": 2.25}, {"text": "So let's talk about the very\nlast topic of the day, which", "start": 3826.99, "duration": 6.28}, {"text": "is really going to be setting\nourselves up for Tuesday's", "start": 3833.27, "duration": 3.78}, {"text": "lecture next week.", "start": 3837.05, "duration": 1.86}, {"text": "And that's how we are going to\nbe showing other languages are", "start": 3838.91, "duration": 4.32}, {"text": "undecidable, which is something\nthat I'm going to be expecting", "start": 3843.23, "duration": 4.26}, {"text": "you guys to be able to do.", "start": 3847.49, "duration": 3.39}, {"text": "This is the standard\nprocedure for showing", "start": 3850.88, "duration": 5.07}, {"text": "languages are\nundecidable using what's", "start": 3855.95, "duration": 2.67}, {"text": "called the reducibility method.", "start": 3858.62, "duration": 2.77}, {"text": "And what that does is it\ntakes, as a starting point,", "start": 3861.39, "duration": 3.86}, {"text": "a language that we already\nknow is undecidable--", "start": 3865.25, "duration": 3.84}, {"text": "typically, A,TM-- or it\ncould be another one that", "start": 3869.09, "duration": 3.54}, {"text": "you've previously shown\nto be undecidable--", "start": 3872.63, "duration": 2.13}, {"text": "and leverages that information\nto show other languages are", "start": 3874.76, "duration": 3.3}, {"text": "undecidable.", "start": 3878.06, "duration": 1.98}, {"text": "And it's using what's\ncalled reducibility.", "start": 3880.04, "duration": 4.69}, {"text": "We're going to go into this\nmore carefully next time.", "start": 3884.73, "duration": 3.84}, {"text": "But basically,\nreducibility is a way", "start": 3888.57, "duration": 2.25}, {"text": "of using one problem to\nsolve another problem.", "start": 3890.82, "duration": 3.93}, {"text": "And so we are going to\nshow, for example, let's", "start": 3894.75, "duration": 3.38}, {"text": "take a look at\nthe problem called", "start": 3898.13, "duration": 2.25}, {"text": "the halting problem, which\nis like the famous problem", "start": 3900.38, "duration": 2.22}, {"text": "for Turing machines.", "start": 3902.6, "duration": 2.97}, {"text": "You just want to know whether\nit halts, not necessarily", "start": 3905.57, "duration": 2.67}, {"text": "whether it accepts.", "start": 3908.24, "duration": 1.5}, {"text": "So it's very similar,\nbut not exactly the same.", "start": 3909.74, "duration": 2.1}, {"text": "And we're going to show\nthat this halting problem is", "start": 3914.64, "duration": 4.04}, {"text": "similarly undecidable.", "start": 3918.68, "duration": 1.41}, {"text": "Now we could go back and do\nthe whole diagonalization,", "start": 3920.09, "duration": 2.43}, {"text": "but that seems like--", "start": 3922.52, "duration": 1.44}, {"text": "well, that's more work than\nnecessary now that we already", "start": 3923.96, "duration": 2.58}, {"text": "know A,TM is undecidable because\nwe're going to show that we can", "start": 3926.54, "duration": 4.29}, {"text": "reduce the A,TM problem\nto the halting problem.", "start": 3930.83, "duration": 6.0}, {"text": "And we'll explain what\nthat means again later.", "start": 3936.83, "duration": 2.68}, {"text": "But the idea is-- and as\nwe'll show in an illustration", "start": 3939.51, "duration": 4.55}, {"text": "shortly--", "start": 3944.06, "duration": 1.44}, {"text": "that by proving by contradiction\nif the if HALT,TM were", "start": 3945.5, "duration": 8.2}, {"text": "decidable, then A,TM\nwould be decided.", "start": 3953.7, "duration": 3.79}, {"text": "And we know A,TM\nis not decidable.", "start": 3957.49, "duration": 1.96}, {"text": "And so that's our contradiction.", "start": 3959.45, "duration": 5.16}, {"text": "Now the way we're going to show\nthat if HALT,TM is decidable,", "start": 3964.61, "duration": 7.98}, {"text": "then A,TM is decidable is use\na decider for HALT,TM to decide", "start": 3972.59, "duration": 5.7}, {"text": "A,TM with a suitable\nmodification.", "start": 3978.29, "duration": 10.63}, {"text": "So basically, we want to turn\na HALT,TM decider into an A,TM", "start": 3988.92, "duration": 6.7}, {"text": "decider.", "start": 3995.62, "duration": 1.02}, {"text": "And that's how we're going to\nreduce the problem of solving", "start": 3996.64, "duration": 4.38}, {"text": "A,TM to the problem\nof solving HALT,TM.", "start": 4001.02, "duration": 3.12}, {"text": "Let's just do an example.", "start": 4004.14, "duration": 1.832}, {"text": "If you've seen it\nbefore, obviously, this", "start": 4005.972, "duration": 1.708}, {"text": "is not going to be hard.", "start": 4007.68, "duration": 1.36}, {"text": "But for the many of you who\nhave not seen it before,", "start": 4009.04, "duration": 3.91}, {"text": "I'm partly doing it this time\njust so we can do it again", "start": 4012.95, "duration": 2.52}, {"text": "next time.", "start": 4015.47, "duration": 0.85}, {"text": "And maybe it'll sink in\nby virtue of repetition.", "start": 4016.32, "duration": 2.66}, {"text": "So again, so as I just\nsaid, we're going to assume", "start": 4023.52, "duration": 2.52}, {"text": "the HALT,TM problem is decidable\nand use that to show that A,TM", "start": 4026.04, "duration": 3.15}, {"text": "is decidable, which\nwe know is false.", "start": 4029.19, "duration": 1.98}, {"text": "We showed it just\nearlier that it's not.", "start": 4031.17, "duration": 3.29}, {"text": "So assume we have a\ndecider for HALT,TM.", "start": 4034.46, "duration": 2.02}, {"text": "We'll call it R. And we're going\nto construct from R a decider", "start": 4036.48, "duration": 7.52}, {"text": "for A,TM we'll call S. OK?", "start": 4044.0, "duration": 4.43}, {"text": "So we're, again, typical\nproof by contradiction.", "start": 4048.43, "duration": 2.22}, {"text": "We're assuming the opposite\nof what we're trying to prove.", "start": 4050.65, "duration": 3.45}, {"text": "And then we're going\nto get something crazy.", "start": 4054.1, "duration": 3.54}, {"text": "OK, so here, my job now,\nis I'm assuming I have R,", "start": 4057.64, "duration": 4.29}, {"text": "which is a HALT,TM decider.", "start": 4061.93, "duration": 1.42}, {"text": "So now, I'm assuming\nI know how to decide", "start": 4063.35, "duration": 6.32}, {"text": "if a Turing machine and an\ninput eventually halts--", "start": 4069.67, "duration": 4.33}, {"text": "Not.", "start": 4074.0, "duration": 0.5}, {"text": "Necessarily would it accept,\njust whether it halts.", "start": 4074.5, "duration": 3.89}, {"text": "It's conceivable.", "start": 4078.39, "duration": 1.07}, {"text": "You have to bear with me here.", "start": 4079.46, "duration": 1.86}, {"text": "It's conceivable that\nyou could find a way", "start": 4081.32, "duration": 2.34}, {"text": "to test whether Turing\nmachines halt on their input,", "start": 4083.66, "duration": 3.78}, {"text": "even though we now know that\ntesting whether they accept", "start": 4087.44, "duration": 2.61}, {"text": "their input is not decidable.", "start": 4090.05, "duration": 3.034}, {"text": "So you have to be open-minded\nto the possibility", "start": 4095.87, "duration": 2.55}, {"text": "that the HALT\nproblem is decidable,", "start": 4098.42, "duration": 3.42}, {"text": "and we're going to show\nthat that's can't be.", "start": 4101.84, "duration": 1.979}, {"text": "So we're going to show that\nif we could decide the halting", "start": 4103.819, "duration": 3.301}, {"text": "problem, then we can use that to\ndecide the acceptance problem.", "start": 4107.12, "duration": 5.359}, {"text": "OK, so how are we\ngoing to do that?", "start": 4112.479, "duration": 2.111}, {"text": "So imagine how we can\nsolve the halting problem.", "start": 4114.59, "duration": 2.49}, {"text": "So to solve the A,TM, which\nis what my job is to do,", "start": 4117.08, "duration": 6.26}, {"text": "so S is supposed to solve A,TM.", "start": 4123.34, "duration": 2.9}, {"text": "I'm constructing a Turing\nmachine as decide A,TM.", "start": 4126.24, "duration": 3.6}, {"text": "I'm going to use first--", "start": 4129.84, "duration": 1.229}, {"text": "I'm giving it M and w.", "start": 4131.069, "duration": 1.321}, {"text": "I'm going to feed it into R\nsince that's really all I got.", "start": 4132.39, "duration": 3.44}, {"text": "See if R tells me what happens.", "start": 4135.83, "duration": 4.98}, {"text": "Does M on w at least halt?", "start": 4140.81, "duration": 3.87}, {"text": "Well, if R says,\nno, it doesn't halt,", "start": 4144.68, "duration": 3.719}, {"text": "well then I'm actually done\nbecause if M doesn't even", "start": 4148.399, "duration": 3.721}, {"text": "halt on w, then it\ncouldn't be accepting w.", "start": 4152.12, "duration": 2.25}, {"text": "So at that point, I know\nthat M doesn't accept w,", "start": 4154.37, "duration": 3.029}, {"text": "and I can reject right off.", "start": 4157.399, "duration": 3.441}, {"text": "So R, you can see how it\ncould potentially be helpful.", "start": 4160.84, "duration": 3.059}, {"text": "But it's going to be\nhelpful in either way", "start": 4163.899, "duration": 1.83}, {"text": "because if R says M\ndoes hold, well, then,", "start": 4165.729, "duration": 5.071}, {"text": "I'm also good because I\ndon't know the answer yet,", "start": 4170.8, "duration": 3.22}, {"text": "but what I do know is I\ncan now simulate M on w", "start": 4174.02, "duration": 4.669}, {"text": "until it halts because\nR has told me it halts.", "start": 4178.689, "duration": 3.451}, {"text": "So I don't have to worry\nabout getting into a loop.", "start": 4182.14, "duration": 5.02}, {"text": "So S can be confident in being\na decider for whatever it's", "start": 4187.16, "duration": 3.47}, {"text": "doing because I'm running\nnow M on w with a guarantee", "start": 4190.63, "duration": 6.64}, {"text": "that it halts.", "start": 4197.27, "duration": 3.11}, {"text": "And now, that's going to\ntell me-- now eventually,", "start": 4200.38, "duration": 2.58}, {"text": "the simulation of M on w is\ngoing to end up at an accept", "start": 4202.96, "duration": 2.76}, {"text": "or reject.", "start": 4205.72, "duration": 0.5}, {"text": "And that's going to\nbe the answer I need.", "start": 4206.22, "duration": 1.708}, {"text": "So if M is accepted,\nthen accept.", "start": 4207.928, "duration": 1.392}, {"text": "And if M is rejected,\nthen reject.", "start": 4209.32, "duration": 3.78}, {"text": "And that's how S solves A,TM\nusing R, which solves HALT,TM.", "start": 4213.1, "duration": 6.89}, {"text": "But S can't exist.", "start": 4219.99, "duration": 2.55}, {"text": "And so therefore, R can't exist.", "start": 4222.54, "duration": 1.59}, {"text": "And therefore, HALT,TM\ncan't be decidable.", "start": 4224.13, "duration": 4.33}, {"text": "OK?", "start": 4228.46, "duration": 0.71}, {"text": "So that quickly--", "start": 4229.17, "duration": 1.125}, {"text": "OK, I'm not sure which\ndiagram you wanted me to show.", "start": 4235.63, "duration": 4.24}, {"text": "But anyway, maybe\nwe can do that.", "start": 4239.87, "duration": 1.62}, {"text": "We're basically at the end\nof the hour or end of the 90", "start": 4241.49, "duration": 2.82}, {"text": "minutes.", "start": 4244.31, "duration": 0.61}, {"text": "So let's do a quick review.", "start": 4244.92, "duration": 1.7}, {"text": "And if you stick around, I'm\nhappy to go back and look", "start": 4246.62, "duration": 2.295}, {"text": "at any of the other slides that\nyou might have missed something", "start": 4248.915, "duration": 2.625}, {"text": "on.", "start": 4251.54, "duration": 0.95}, {"text": "OK, so just to recap, we\nshowed that the natural numbers", "start": 4252.49, "duration": 5.46}, {"text": "and the real numbers are not the\nsame size using that definition", "start": 4257.95, "duration": 3.0}, {"text": "of one-to-one correspondence to\nintroduce the diagonalization", "start": 4260.95, "duration": 2.79}, {"text": "method.", "start": 4263.74, "duration": 0.75}, {"text": "We used the diagonalization\nmethod to show that A,TM is", "start": 4264.49, "duration": 2.46}, {"text": "undecidable.", "start": 4266.95, "duration": 1.29}, {"text": "We also showed\nthat little theorem", "start": 4268.24, "duration": 2.065}, {"text": "that if the language\nand its complement", "start": 4270.305, "duration": 1.625}, {"text": "are recognizable, then\nthe language is decidable.", "start": 4271.93, "duration": 3.36}, {"text": "And from that, we concluded\nthat A,TM complement is not", "start": 4275.29, "duration": 3.66}, {"text": "recognizable.", "start": 4278.95, "duration": 1.26}, {"text": "And then we showed, at least\nby virtue of an introduction", "start": 4280.21, "duration": 3.18}, {"text": "to the method, the reducibility\nmethod to show that HALT,TM is", "start": 4283.39, "duration": 3.0}, {"text": "undecidable.", "start": 4286.39, "duration": 1.38}, {"text": "And that was today's lecture.", "start": 4287.77, "duration": 1.89}, {"text": "And we're and we're at\nthe end of the hour.", "start": 4289.66, "duration": 3.22}, {"text": "So why don't I--", "start": 4292.88, "duration": 3.02}, {"text": "we are finished.", "start": 4295.9, "duration": 0.99}, {"text": "You can log out.", "start": 4296.89, "duration": 2.37}, {"text": "And if you want, I\nwill stick around.", "start": 4299.26, "duration": 4.04}, {"text": "OK, OK, this is kind of\na good question here.", "start": 4303.3, "duration": 3.21}, {"text": "So I'm getting a question about\nthe A,TM-complement, which is--", "start": 4310.13, "duration": 10.66}, {"text": "since we have a\nrecognizer for A,TM,", "start": 4320.79, "duration": 6.17}, {"text": "if I'm doing justice\nto this question,", "start": 4326.96, "duration": 5.19}, {"text": "we have a recogniser for A,TM,\nso why can't we just invert", "start": 4332.15, "duration": 2.79}, {"text": "the answer?", "start": 4334.94, "duration": 3.01}, {"text": "Flip the answer around, and\nnow, we have a recognizer", "start": 4337.95, "duration": 5.36}, {"text": "for the complement of\nA,TM, A,TM-complement.", "start": 4343.31, "duration": 4.59}, {"text": "So why doesn't that work?", "start": 4347.9, "duration": 2.63}, {"text": "Well, the reason that doesn't\nwork is because the recognizer", "start": 4350.53, "duration": 5.64}, {"text": "for A,TM might be rejecting\nsome things by looping.", "start": 4356.17, "duration": 5.91}, {"text": "And now, if you just flip\nthe accepting and rejecting,", "start": 4362.08, "duration": 6.39}, {"text": "when it hits one of\nthose halting states,", "start": 4368.47, "duration": 2.94}, {"text": "it's going to give\nthe reverse answer.", "start": 4371.41, "duration": 2.25}, {"text": "But when it rejects\nby looping, it'll", "start": 4373.66, "duration": 4.47}, {"text": "continue to reject by looping.", "start": 4378.13, "duration": 1.41}, {"text": "So you won't get the\ncomplementary language", "start": 4379.54, "duration": 2.49}, {"text": "coming out.", "start": 4382.03, "duration": 0.57}, {"text": "So if it would be helpful, I\ncan go back to that slide here,", "start": 4386.56, "duration": 9.22}, {"text": "which proves that\nA,TM-complement is", "start": 4395.78, "duration": 2.45}, {"text": "unrecognizable because maybe we\nshould start with the bottom.", "start": 4398.23, "duration": 7.9}, {"text": "We know that A,TM is\nrecognizable and undecidable,", "start": 4406.13, "duration": 7.04}, {"text": "right?", "start": 4413.17, "duration": 0.5}, {"text": "We already proved\nthose two facts.", "start": 4413.67, "duration": 1.56}, {"text": "A,TM is recognizable from\nthe universal Turing machine,", "start": 4415.23, "duration": 5.79}, {"text": "and it's undecidable by the\ndiagonalization argument.", "start": 4421.02, "duration": 4.34}, {"text": "Those two things\ntogether tell us", "start": 4425.36, "duration": 2.7}, {"text": "that the complement has\nto be unrecognizable", "start": 4428.06, "duration": 4.14}, {"text": "because if a language\nand its complement", "start": 4432.2, "duration": 3.15}, {"text": "are both recognizable-- and\nwe already know the language", "start": 4435.35, "duration": 2.4}, {"text": "itself is recognizable.", "start": 4437.75, "duration": 1.74}, {"text": "So now, if the complement\nis also recognizable,", "start": 4439.49, "duration": 2.207}, {"text": "the language is going to be\ndecidable by the upper theorem.", "start": 4441.697, "duration": 2.458}, {"text": "So it must be the case had\neither the language itself", "start": 4450.67, "duration": 2.31}, {"text": "is unrecognizable, or its\ncomplement is unrecognizable.", "start": 4452.98, "duration": 3.968}, {"text": "We know the language\nis recognizable.", "start": 4456.948, "duration": 1.542}, {"text": "That's what the universal\nTuring machine told us.", "start": 4458.49, "duration": 2.07}, {"text": "So the only thing left\nis for the complement", "start": 4460.56, "duration": 1.98}, {"text": "to be unrecognizable.", "start": 4462.54, "duration": 2.76}, {"text": "You should review that\nif you didn't get it", "start": 4465.3, "duration": 3.39}, {"text": "because this is the\nkind of reasoning", "start": 4468.69, "duration": 3.87}, {"text": "we're going to be building\non things like that.", "start": 4472.56, "duration": 3.37}, {"text": "So I think it's good to\nmake sure you understand.", "start": 4475.93, "duration": 4.58}, {"text": "OK.", "start": 4480.51, "duration": 0.5}, {"text": "OK, the diagram on\nthe right-- so this", "start": 4484.147, "duration": 1.583}, {"text": "is just a Venn diagram here.", "start": 4485.73, "duration": 1.62}, {"text": "I threw this in at\nthe last minute here.", "start": 4487.35, "duration": 2.07}, {"text": "I was worried about\nit being confusing.", "start": 4489.42, "duration": 4.22}, {"text": "That part is--", "start": 4493.64, "duration": 1.39}, {"text": "I'm trying to show that the\nthree classes that we've", "start": 4500.57, "duration": 2.67}, {"text": "already talked about--", "start": 4503.24, "duration": 1.35}, {"text": "the languages which\nare decidable,", "start": 4504.59, "duration": 2.19}, {"text": "the languages which are\nTuring-recognizable,", "start": 4506.78, "duration": 2.43}, {"text": "and the languages\nwhose complements", "start": 4509.21, "duration": 1.95}, {"text": "are Turing-recognizable.", "start": 4511.16, "duration": 1.62}, {"text": "Those are three separate\nclasses of languages.", "start": 4512.78, "duration": 4.51}, {"text": "And those come up here\nin those three regions.", "start": 4517.29, "duration": 5.34}, {"text": "These are the decidable ones.", "start": 4522.63, "duration": 1.82}, {"text": "Here are the recognizable ones.", "start": 4524.45, "duration": 2.79}, {"text": "And here are the ones whose\ncomplements are recognizable.", "start": 4527.24, "duration": 4.69}, {"text": "Now if a language is in\nboth the recognizable,", "start": 4531.93, "duration": 4.85}, {"text": "and its complement\nis recognizable--", "start": 4536.78, "duration": 1.53}, {"text": "so it's in both of these\nbigger regions here--", "start": 4538.31, "duration": 3.15}, {"text": "then this theorem tells\nyou it's decidable.", "start": 4541.46, "duration": 4.52}, {"text": "So that's why the intersection\nof these two regions", "start": 4545.98, "duration": 3.62}, {"text": "is marked as being\ndecidable because that", "start": 4549.6, "duration": 2.34}, {"text": "means you're in both.", "start": 4551.94, "duration": 0.93}, {"text": "OK?", "start": 4557.51, "duration": 2.07}, {"text": "But we know that A,TM is\nsitting out here as recognizable", "start": 4559.58, "duration": 3.51}, {"text": "but not decidable.", "start": 4563.09, "duration": 1.08}, {"text": "So A,TM is in the\nrecognizable side,", "start": 4564.17, "duration": 2.55}, {"text": "but it's not on the complement\nof recognizable, A,TM itself.", "start": 4566.72, "duration": 5.73}, {"text": "The complement of A,TM is the\ncomplement of a recognizable", "start": 4572.45, "duration": 3.39}, {"text": "but itself is not recognizable\nand not decidable.", "start": 4575.84, "duration": 6.28}, {"text": "So you got this side\nof nice, you know--", "start": 4582.12, "duration": 4.06}, {"text": "I hope you think\nit's nice, but it's", "start": 4586.18, "duration": 2.16}, {"text": "sort of a try to summarize\nthings in this little Venn", "start": 4588.34, "duration": 3.37}, {"text": "diagram.", "start": 4591.71, "duration": 0.5}, {"text": "So I think I'm going\nto then sign off.", "start": 4595.2, "duration": 5.41}, {"text": "And I'll see you all on Tuesday.", "start": 4600.61, "duration": 5.08}, {"text": "And have a good weekend.", "start": 4605.69, "duration": 1.41}, {"text": "Bye bye.", "start": 4607.1, "duration": 1.67}]
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+[{"text": "The following content is\nprovided by MIT OpenCourseWare", "start": 1.0, "duration": 2.0}, {"text": "under a Creative\nCommons license.", "start": 3.0, "duration": 2.0}, {"text": "Additional information\nabout our license and MIT", "start": 5.0, "duration": 4.0}, {"text": "OpenCourseWare in general is\navailable at OCW.mit.edu.", "start": 9.0, "duration": 10.0}, {"text": "PROFESSOR: Good afternoon.", "start": 19.0, "duration": 2.0}, {"text": "When we parted last time, I\nwas -- you just did that demo", "start": 24.0, "duration": 6.0}, {"text": "with Sam, who was either\ncollecting stamps or lady's", "start": 30.0, "duration": 6.0}, {"text": "undergarments, depending.", "start": 36.0, "duration": 2.0}, {"text": "And the point there was to\ndescribe the fact that any", "start": 38.0, "duration": 9.0}, {"text": "behavior is going to be\ndistributed across the", "start": 47.0, "duration": 5.0}, {"text": "population in some fashion.", "start": 52.0, "duration": 2.0}, {"text": "It may well be that the extreme\nof the population is abnormal", "start": 54.0, "duration": 6.0}, {"text": "in some meaningful sense, maybe\neven pathological in some", "start": 60.0, "duration": 7.0}, {"text": "sense, but that the border\nbetween what is normal and what", "start": 67.0, "duration": 5.0}, {"text": "is abnormal is going to be\nnecessarily ambiguous.", "start": 72.0, "duration": 6.0}, {"text": "There's not going to be some\nnice, neat line that can", "start": 78.0, "duration": 3.0}, {"text": "be drawn in all cases.", "start": 81.0, "duration": 4.0}, {"text": "I was arguing that something\nlike schizophrenia is a bit", "start": 85.0, "duration": 6.0}, {"text": "more like that, where the\nabnormal state really does look", "start": 91.0, "duration": 3.0}, {"text": "quite different from the normal\nstate and less like that", "start": 94.0, "duration": 6.0}, {"text": "it's on a continuum.", "start": 100.0, "duration": 2.0}, {"text": "You will notice on your handout\nthat it says Lecture 20.", "start": 102.0, "duration": 4.0}, {"text": "And those of you who are\nparticularly observant", "start": 106.0, "duration": 3.0}, {"text": "will say, last one was\ncalled Lecture 20.", "start": 109.0, "duration": 4.0}, {"text": "And that's true.", "start": 113.0, "duration": 3.0}, {"text": "I just liked 20.", "start": 116.0, "duration": 3.0}, {"text": "No, this is really 21.", "start": 119.0, "duration": 3.0}, {"text": "And with a bit of luck, I'll\nlabel the next one 22.", "start": 122.0, "duration": 4.0}, {"text": "Otherwise it'll just turn out\nthat there's 20A and 20B", "start": 126.0, "duration": 2.0}, {"text": "or something like that.", "start": 128.0, "duration": 1.0}, {"text": "Anyway, it really is\nthe right handout.", "start": 129.0, "duration": 3.0}, {"text": "You'll discover that it is\nclosely related to the later", "start": 132.0, "duration": 8.0}, {"text": "pages of the last handout that\nwe didn't get to last time.", "start": 140.0, "duration": 5.0}, {"text": "Yeah, it's kind of the same\nis what people are noting.", "start": 145.0, "duration": 3.0}, {"text": "But I didn't have any faith\nthat people would remember", "start": 148.0, "duration": 2.0}, {"text": "to bring the real\nLecture 20 handout.", "start": 150.0, "duration": 2.0}, {"text": "Anyway, what I want to talk\nabout, at least initially here,", "start": 152.0, "duration": 8.0}, {"text": "is to talk a bit about how you\nwould end up in this abnormal", "start": 160.0, "duration": 4.0}, {"text": "bin of schizophrenia.", "start": 164.0, "duration": 4.0}, {"text": "And one reasonable\nquestion to ask is, well,", "start": 168.0, "duration": 3.0}, {"text": "it's on the handout.\nIt says, is there evidence\nfor a genetic component?", "start": 171.0, "duration": 0.0}, {"text": "And the answer is yes.", "start": 175.0, "duration": 2.0}, {"text": "And the way you get one of the\nimportant sources of that", "start": 177.0, "duration": 4.0}, {"text": "information is similar to the\ndata that we were talking about", "start": 181.0, "duration": 4.0}, {"text": "in intelligence testing.", "start": 185.0, "duration": 2.0}, {"text": "Take a look at people who vary\nin the amount that they are", "start": 187.0, "duration": 6.0}, {"text": "genetically related\nto each other.", "start": 193.0, "duration": 1.0}, {"text": "Notably here, MZ stands for\nmonozygotic or identical", "start": 194.0, "duration": 7.0}, {"text": "single-egg twins.", "start": 201.0, "duration": 1.0}, {"text": "And DZ stands for dizygotic\ntwo-egg twins who are no", "start": 202.0, "duration": 6.0}, {"text": "more similar than siblings.", "start": 208.0, "duration": 2.0}, {"text": "Concordance means what the\nchance is of Twin Two having", "start": 210.0, "duration": 8.0}, {"text": "the disease if Twin One has it.", "start": 218.0, "duration": 3.0}, {"text": "And so what you can see is that\nfor monozygotic twins, if one", "start": 221.0, "duration": 4.0}, {"text": "of a pair of identical twins\nbecomes schizophrenic, there's", "start": 225.0, "duration": 4.0}, {"text": "a 50% chance that the\nother one will, too.", "start": 229.0, "duration": 4.0}, {"text": "That tells you two things.", "start": 233.0, "duration": 2.0}, {"text": "Well, it only tells you\ntwo things if you look", "start": 235.0, "duration": 2.0}, {"text": "at the dizygotic.", "start": 237.0, "duration": 1.0}, {"text": "The dizygotic twins have\na much lower concordance", "start": 238.0, "duration": 3.0}, {"text": "rate of about 15%.", "start": 241.0, "duration": 3.0}, {"text": "So that tells you first of all\nthat there's a probable genetic", "start": 244.0, "duration": 4.0}, {"text": "component there, and second of\nall, that it's not absolute.", "start": 248.0, "duration": 4.0}, {"text": "If you have the genetic\nmutation that makes you", "start": 252.0, "duration": 5.0}, {"text": "color-blind or color anomalous,\nyou'll be color anomalous.", "start": 257.0, "duration": 5.0}, {"text": "There's no big mystery at\nthis point about that.", "start": 262.0, "duration": 3.0}, {"text": "If you have whatever the\ngenetic predisposition is for", "start": 265.0, "duration": 5.0}, {"text": "schizophrenia, something else\nhas to happen before you would", "start": 270.0, "duration": 6.0}, {"text": "end up showing the disorder.", "start": 276.0, "duration": 2.0}, {"text": "Now, these twin studies run\ninto the same problem that the", "start": 278.0, "duration": 4.0}, {"text": "intelligence testing twin\nstudies did, which is that", "start": 282.0, "duration": 3.0}, {"text": "monozygotic twins are simply\nmore similar on all", "start": 285.0, "duration": 3.0}, {"text": "sorts of things.", "start": 288.0, "duration": 1.0}, {"text": "You know, they're treated\nmore similarly and so on.", "start": 289.0, "duration": 2.0}, {"text": "One way to look at whether or\nnot there is a, you know,", "start": 291.0, "duration": 5.0}, {"text": "to try parceling this out,\nis this third line here.", "start": 296.0, "duration": 5.0}, {"text": "This was a population of\ndizygotic twins who thought", "start": 301.0, "duration": 3.0}, {"text": "they were identical.", "start": 304.0, "duration": 1.0}, {"text": "You know, they looked alike.", "start": 305.0, "duration": 1.0}, {"text": "Presumably they're the same\nsex and stuff like that.", "start": 306.0, "duration": 3.0}, {"text": "Thought they were identical.", "start": 309.0, "duration": 2.0}, {"text": "You'll see that their\nconcordance rate was less", "start": 311.0, "duration": 2.0}, {"text": "than the 50% that the true\nmonozygotic twins had.", "start": 313.0, "duration": 5.0}, {"text": "So there does seem to be\nsomething to being really", "start": 318.0, "duration": 2.0}, {"text": "genetically identical.", "start": 320.0, "duration": 1.0}, {"text": "You can also do twins\nreared apart things.", "start": 321.0, "duration": 4.0}, {"text": "But look, if you have a\nset of -- twins reared", "start": 325.0, "duration": 3.0}, {"text": "apart -- not common.", "start": 328.0, "duration": 2.0}, {"text": "But all those twins have IQs.", "start": 330.0, "duration": 2.0}, {"text": "You can always\nmeasure their IQs.", "start": 332.0, "duration": 3.0}, {"text": "If you take twins reared apart\nand then take the cases where", "start": 335.0, "duration": 5.0}, {"text": "one of them has schizophrenia\nand ask what the concordance", "start": 340.0, "duration": 7.0}, {"text": "rate is, the answer is\nit's quite elevated.", "start": 347.0, "duration": 2.0}, {"text": "But, you know, it's a really\nsmall population of people.", "start": 349.0, "duration": 3.0}, {"text": "You know, twin reared\napart and schizophrenic,", "start": 352.0, "duration": 2.0}, {"text": "it's not a big crowd.", "start": 354.0, "duration": 4.0}, {"text": "Now, when you go look for the\ngenetic marker, since the late", "start": 358.0, "duration": 7.0}, {"text": "'80s, there have been a slew of\npapers on genetic markers", "start": 365.0, "duration": 4.0}, {"text": "for schizophrenia.", "start": 369.0, "duration": 1.0}, {"text": "The way you look for this --\none of the typical ways to look", "start": 370.0, "duration": 2.0}, {"text": "for this is that schizophrenia\nruns in families.", "start": 372.0, "duration": 4.0}, {"text": "And if you go and analyze the\ngenetics of families, you can", "start": 376.0, "duration": 5.0}, {"text": "find specific loci that seem\nto be abnormal in the", "start": 381.0, "duration": 5.0}, {"text": "schizophrenic members\nof the family.", "start": 386.0, "duration": 3.0}, {"text": "The difficulty or the\ninteresting aspect of this", "start": 389.0, "duration": 3.0}, {"text": "genetic story is that the story\nthat works for this family", "start": 392.0, "duration": 4.0}, {"text": "doesn't necessarily\nwork for this family.", "start": 396.0, "duration": 4.0}, {"text": "In the early days of this,\nthere'd be some big article in", "start": 400.0, "duration": 3.0}, {"text": "Science or Nature or something\nsaying gene locus on chromosome", "start": 403.0, "duration": 4.0}, {"text": "eight for schizophrenia\nor whatever.", "start": 407.0, "duration": 5.0}, {"text": "I'm making it up.", "start": 412.0, "duration": 1.0}, {"text": "And then, you know, either in\nthe same issue or in the, you", "start": 413.0, "duration": 4.0}, {"text": "know, next week, there'd\nbe another thing saying,", "start": 417.0, "duration": 2.0}, {"text": "but not in this family.", "start": 419.0, "duration": 2.0}, {"text": "Clearly schizophrenic but not\nclearly having the same defect.", "start": 421.0, "duration": 3.0}, {"text": "It suggests that there are\nmultiple roots, genetic", "start": 424.0, "duration": 6.0}, {"text": "predispositions,\nto schizophrenia.", "start": 430.0, "duration": 2.0}, {"text": "It's also possible that\nyou need more than", "start": 432.0, "duration": 2.0}, {"text": "one genetic insult.", "start": 434.0, "duration": 3.0}, {"text": "That's jargon -- you don't\nsay, you got an ugly gene.", "start": 437.0, "duration": 4.0}, {"text": "You need to have perhaps more\nthan one defect in order to", "start": 441.0, "duration": 4.0}, {"text": "have the susceptibility\nto schizophrenia.", "start": 445.0, "duration": 5.0}, {"text": "One of the curious little\nwrinkles that I dug up in my", "start": 450.0, "duration": 4.0}, {"text": "reading on this -- and I've\nonly read this in a", "start": 454.0, "duration": 3.0}, {"text": "secondary source.\nI have been unsuccessful\nin tracking down", "start": 457.0, "duration": 0.0}, {"text": "the primary source.", "start": 459.0, "duration": 1.0}, {"text": "But I'll tell you anyway -- is\na study -- it turns out that", "start": 460.0, "duration": 5.0}, {"text": "there are two types\nof identical twins.", "start": 465.0, "duration": 2.0}, {"text": "There are, sort of, plain\nvanilla identical twins.", "start": 467.0, "duration": 4.0}, {"text": "You know, Twin One\nis right-handed.", "start": 471.0, "duration": 2.0}, {"text": "Twin Two is right-handed\nand so on.", "start": 473.0, "duration": 2.0}, {"text": "And then there are\nso-called mirror twins.", "start": 475.0, "duration": 2.0}, {"text": "They're genetically identical,\nbut the phenotype, the actual", "start": 477.0, "duration": 5.0}, {"text": "organism, is mirrored\nrather than identical or", "start": 482.0, "duration": 7.0}, {"text": "something like that.", "start": 489.0, "duration": 1.0}, {"text": "So if one's right-handed,\nthe other is left-handed.", "start": 490.0, "duration": 2.0}, {"text": "You know, swirl on the top\nof your head, if it swirls", "start": 492.0, "duration": 4.0}, {"text": "clockwise for one twin, it\nswirls the other way for", "start": 496.0, "duration": 4.0}, {"text": "the other twin and so on.", "start": 500.0, "duration": 2.0}, {"text": "And the curious finding\nreported in this one relatively", "start": 502.0, "duration": 3.0}, {"text": "small study, I think, is that\nthe concordance rates for", "start": 505.0, "duration": 5.0}, {"text": "identical identical twins, the\nright hand, right hand", "start": 510.0, "duration": 3.0}, {"text": "identical twins, very high in\nthis study, like over 90%.", "start": 513.0, "duration": 4.0}, {"text": "If one twin was schizophrenic,\nthe other was schizophrenic.", "start": 517.0, "duration": 4.0}, {"text": "The mirrored twins, the left,\nright ones, were concordance", "start": 521.0, "duration": 6.0}, {"text": "rate down at about 25%.", "start": 527.0, "duration": 3.0}, {"text": "Both of these are genetically\nidentical pairs of twins.", "start": 530.0, "duration": 4.0}, {"text": "It's abundantly unclear what it\nis that makes these two groups", "start": 534.0, "duration": 5.0}, {"text": "different, if indeed that turns\nout to be a reliable result.", "start": 539.0, "duration": 4.0}, {"text": "I went hunting in the\ndatabases, and I think I", "start": 543.0, "duration": 2.0}, {"text": "found the guy who did it.", "start": 545.0, "duration": 2.0}, {"text": "So I sent him an email, but he\ndidn't get back to me in time.", "start": 547.0, "duration": 5.0}, {"text": "Oh, that reminds me.", "start": 552.0, "duration": 1.0}, {"text": "It's a little late in the day\nto tell you this, but if you", "start": 553.0, "duration": 3.0}, {"text": "discover that something that\nyou're looking for in primary", "start": 556.0, "duration": 4.0}, {"text": "source land, you know, you're\nlooking for the Journal of", "start": 560.0, "duration": 3.0}, {"text": "Hoozy Phoozy Results or\nwhatever, and oh my god, MIT", "start": 563.0, "duration": 3.0}, {"text": "doesn't carry it so you don't\nhave access to it, it's often", "start": 566.0, "duration": 4.0}, {"text": "very useful to go and see if\nyou can find the website for", "start": 570.0, "duration": 3.0}, {"text": "the lab where the\nwork was done.", "start": 573.0, "duration": 1.0}, {"text": "Because many, many of us post\nall of our publications, or as", "start": 574.0, "duration": 5.0}, {"text": "many as we have PDFs for, on\nthe website to be downloaded.", "start": 579.0, "duration": 3.0}, {"text": "And so you can dig things up.", "start": 582.0, "duration": 4.0}, {"text": "You can dig things up that way.", "start": 586.0, "duration": 2.0}, {"text": "So anyway, there's pretty\nstrong evidence for", "start": 588.0, "duration": 3.0}, {"text": "a genetic component.", "start": 591.0, "duration": 2.0}, {"text": "And then there's pretty\nstrong evidence that that", "start": 593.0, "duration": 3.0}, {"text": "by itself is not enough.", "start": 596.0, "duration": 2.0}, {"text": "Unlike a variety of other\nneurological disorders, there", "start": 598.0, "duration": 3.0}, {"text": "are plenty of neurological\ndisorders where if you've got", "start": 601.0, "duration": 3.0}, {"text": "this problem with your genome,\nit's going to munch up your", "start": 604.0, "duration": 4.0}, {"text": "brain in the following\nfashion, you're going", "start": 608.0, "duration": 2.0}, {"text": "to have this problem.\nAnd fortunately most of\nthese are very rare.", "start": 610.0, "duration": 0.0}, {"text": "But they're straightforward\ngenetic stories.", "start": 614.0, "duration": 3.0}, {"text": "In schizophrenia, something\nabout the environment seems to", "start": 617.0, "duration": 4.0}, {"text": "be important to trip it off.", "start": 621.0, "duration": 1.0}, {"text": "The leading notion is stress.", "start": 622.0, "duration": 3.0}, {"text": "So, actually, does\nanybody remember?", "start": 625.0, "duration": 2.0}, {"text": "The book used to go on at vast\nlengths about the stress", "start": 627.0, "duration": 6.0}, {"text": "diathesis model of\nschizophrenia.", "start": 633.0, "duration": 3.0}, {"text": "Does this sound\nfamiliar to anybody?", "start": 636.0, "duration": 3.0}, {"text": "Has anybody looked at the\nrelevant parts of the book yet?", "start": 639.0, "duration": 4.0}, {"text": "Nobody knows.", "start": 643.0, "duration": 1.0}, {"text": "All right, well anyway, one of\nthe leading notions about what", "start": 644.0, "duration": 6.0}, {"text": "it is that actually produces\nthe florid disease, is that you", "start": 650.0, "duration": 5.0}, {"text": "need to have some genetic\npredisposition and then you", "start": 655.0, "duration": 2.0}, {"text": "need something like stress to\ndrop-kick you into pathology.", "start": 657.0, "duration": 5.0}, {"text": "Now, this is an interesting\n-- this raises interesting", "start": 662.0, "duration": 5.0}, {"text": "problems for public policy.", "start": 667.0, "duration": 2.0}, {"text": "I think we talked last time\nabout, you know, when is it", "start": 669.0, "duration": 3.0}, {"text": "OK to force somebody to\nbe medicated, right?", "start": 672.0, "duration": 5.0}, {"text": "This is a similar\nsort of problem.", "start": 677.0, "duration": 2.0}, {"text": "Suppose you are applying\nto MIT this year.", "start": 685.0, "duration": 4.0}, {"text": "Should I be able to -- should I\ngo and suggest to the head of", "start": 689.0, "duration": 4.0}, {"text": "admissions that we really\nshould get little tubes", "start": 693.0, "duration": 3.0}, {"text": "of blood from everybody?", "start": 696.0, "duration": 2.0}, {"text": "Because if we got little tubes\nblood from everybody, we could", "start": 698.0, "duration": 2.0}, {"text": "genetically screen them.", "start": 700.0, "duration": 2.0}, {"text": "And we know where -- we don't\nknow exactly which loci are", "start": 702.0, "duration": 5.0}, {"text": "critical, but we know a bunch\nof loci that seem to be", "start": 707.0, "duration": 3.0}, {"text": "related to family histories\nof schizophrenia.", "start": 710.0, "duration": 3.0}, {"text": "And anyway, there's all sorts\nof other interesting genetic", "start": 713.0, "duration": 2.0}, {"text": "markers out there\nat this point.", "start": 715.0, "duration": 1.0}, {"text": "We could screen the incoming\npopulation or the population of", "start": 716.0, "duration": 3.0}, {"text": "applicants and systematically\ndecide not to admit people who", "start": 719.0, "duration": 8.0}, {"text": "had the genetic marker for\nschizophrenia or for some other", "start": 727.0, "duration": 4.0}, {"text": "-- well, schizophrenia\nis a good example.", "start": 731.0, "duration": 1.0}, {"text": "Why in the world\nwould we do this?", "start": 732.0, "duration": 2.0}, {"text": "Well, is there anybody\ncurrently present who believes", "start": 734.0, "duration": 4.0}, {"text": "that MIT is a at least modestly\nstressful environment?", "start": 738.0, "duration": 5.0}, {"text": "All right.", "start": 743.0, "duration": 1.0}, {"text": "Short of Guantanamo Bay\nor something, you know,", "start": 746.0, "duration": 3.0}, {"text": "it's right up there.", "start": 749.0, "duration": 1.0}, {"text": "All right.", "start": 753.0, "duration": 2.0}, {"text": "The state of the art is that\nwe know that stress is a", "start": 755.0, "duration": 5.0}, {"text": "contributing factor to\na variety of mental", "start": 760.0, "duration": 2.0}, {"text": "illnesses, notably in this\nexample schizophrenia.", "start": 762.0, "duration": 3.0}, {"text": "If we admit people to an\nenvironment that we know is", "start": 765.0, "duration": 6.0}, {"text": "highly stressful, we are asking\nfor a certain number of", "start": 771.0, "duration": 7.0}, {"text": "psychiatric problems.", "start": 778.0, "duration": 3.0}, {"text": "Isn't it our responsibility to\nprevent that from happening?", "start": 781.0, "duration": 5.0}, {"text": "Well, now, typically the -- I\nwon't take a poll, but the", "start": 786.0, "duration": 4.0}, {"text": "typical answer is, no,\nthat doesn't sound right.", "start": 790.0, "duration": 3.0}, {"text": "You know, that somehow\nthat sounds a little too", "start": 793.0, "duration": 4.0}, {"text": "paternalistic, too invasive for\nme to be screening your genes.", "start": 797.0, "duration": 4.0}, {"text": "And, you know, who knows?\nDown the line, we take a look\nat this hunk of the genome and", "start": 801.0, "duration": 0.0}, {"text": "we say, you know, sorry, you're\njust never passing 18.03.", "start": 804.0, "duration": 6.0}, {"text": "You know, what would we ever do\nwith information like that?", "start": 810.0, "duration": 4.0}, {"text": "But the disease case,\nit doesn't feel right", "start": 814.0, "duration": 4.0}, {"text": "typically to people.", "start": 818.0, "duration": 2.0}, {"text": "But on the other hand, we\nspend a lot of time worrying,", "start": 820.0, "duration": 4.0}, {"text": "believe it or not, about\nyour mental health.", "start": 824.0, "duration": 4.0}, {"text": "The dean's office has\nsubstantial branches devoted to", "start": 828.0, "duration": 6.0}, {"text": "mental health issues as does\nthe medical department.", "start": 834.0, "duration": 3.0}, {"text": "We know that university\nenvironments kick up a certain", "start": 837.0, "duration": 3.0}, {"text": "amount of psychiatric problems.", "start": 840.0, "duration": 4.0}, {"text": "And we know that that can\nbe catastrophically bad", "start": 844.0, "duration": 3.0}, {"text": "for the person and for\npeople around them.", "start": 847.0, "duration": 4.0}, {"text": "Wouldn't it be our\nresponsibility to do", "start": 851.0, "duration": 2.0}, {"text": "something about that?", "start": 853.0, "duration": 1.0}, {"text": "Well, look, I'm not going to\ngive you an answer to that, and", "start": 854.0, "duration": 2.0}, {"text": "I promise not to ask on the\nexam, you know, should we get", "start": 856.0, "duration": 3.0}, {"text": "blood samples from everybody\nand, you know, the choices are", "start": 859.0, "duration": 3.0}, {"text": "yes, no, all of the above\nor something like that.", "start": 862.0, "duration": 6.0}, {"text": "I raise that as an\nissue to think about.", "start": 868.0, "duration": 6.0}, {"text": "When you take a look at the\nbrains of schizophrenics, by", "start": 874.0, "duration": 3.0}, {"text": "the way, they don't look like\nthe brains of healthy,", "start": 877.0, "duration": 7.0}, {"text": "normal individuals.", "start": 884.0, "duration": 1.0}, {"text": "So you get things like\nshrinkage of grey matter.", "start": 885.0, "duration": 4.0}, {"text": "You get enlargement\nof the ventricles.", "start": 889.0, "duration": 4.0}, {"text": "The ventricles are those\nnice, empty fluid-filled", "start": 893.0, "duration": 2.0}, {"text": "spaces in your brain.", "start": 895.0, "duration": 2.0}, {"text": "Great answer for a -- if you're\nlooking at the multiple-choice", "start": 897.0, "duration": 3.0}, {"text": "question on the final, and\nyou're thinking, I'm going to", "start": 900.0, "duration": 4.0}, {"text": "go for, you know, the third\nventricle as the answer,", "start": 904.0, "duration": 4.0}, {"text": "you're probably getting\nsuckered here, right?", "start": 908.0, "duration": 3.0}, {"text": "Because the ventricles are\nempty fluid-filled spaces.", "start": 911.0, "duration": 3.0}, {"text": "It's not where any of the more\nimportant mental functions are", "start": 914.0, "duration": 5.0}, {"text": "thought to be localized, at\nleast not since the Middle", "start": 919.0, "duration": 3.0}, {"text": "Ages, where people did think\nthat memories were stored in", "start": 922.0, "duration": 3.0}, {"text": "the ventricles, because\nafter all they looked", "start": 925.0, "duration": 1.0}, {"text": "like store rooms.", "start": 926.0, "duration": 2.0}, {"text": "Anyway, the ventricles\nget bigger.", "start": 928.0, "duration": 1.0}, {"text": "That's presumably not a good\nthing because it's reflecting", "start": 929.0, "duration": 2.0}, {"text": "loss of brain tissue.", "start": 931.0, "duration": 2.0}, {"text": "What's not absolutely clear is\nwhether or not abnormalities", "start": 933.0, "duration": 4.0}, {"text": "in brain structure\nprecede disease.", "start": 937.0, "duration": 5.0}, {"text": "You know, are they there\nsomehow from birth?", "start": 942.0, "duration": 2.0}, {"text": "Is part of what the gene is\ndoing somehow changing the", "start": 944.0, "duration": 3.0}, {"text": "structure of the brain in\nsuch a way that it makes it", "start": 947.0, "duration": 3.0}, {"text": "vulnerable, or is it that\nhaving the disease itself", "start": 950.0, "duration": 3.0}, {"text": "is bad for the brain?", "start": 953.0, "duration": 4.0}, {"text": "In any case, the point to take\naway here is there are lots of", "start": 957.0, "duration": 7.0}, {"text": "different routes into the\nkingdom of schizophrenia.", "start": 964.0, "duration": 6.0}, {"text": "It's not a nice, clean simple\ndiagnosis where you say, you", "start": 970.0, "duration": 3.0}, {"text": "get this bacterium, you get\nthis disease, we give you this", "start": 973.0, "duration": 5.0}, {"text": "antibiotic, and you're OK.", "start": 978.0, "duration": 2.0}, {"text": "Multiple routes in and\ntreatment options are,", "start": 980.0, "duration": 5.0}, {"text": "you know, getting better\nbut remain difficult.", "start": 985.0, "duration": 5.0}, {"text": "Let's see here.\nOh yes.", "start": 990.0, "duration": 0.0}, {"text": "What I think I will do is\nswitch gears and talk a", "start": 991.0, "duration": 5.0}, {"text": "bit about depression.", "start": 996.0, "duration": 2.0}, {"text": "But in order to talk about\ndepression, what I want you to", "start": 998.0, "duration": 4.0}, {"text": "do is to decide how you want to\ntreat my three invented", "start": 1002.0, "duration": 5.0}, {"text": "patients on the handout.", "start": 1007.0, "duration": 3.0}, {"text": "The third one is on\nthe back of the page.", "start": 1010.0, "duration": 3.0}, {"text": "So play with that for a second.", "start": 1013.0, "duration": 1.0}, {"text": "Kristen, can you do me a favor?", "start": 1014.0, "duration": 4.0}, {"text": "Go find me a bottle of water.", "start": 1018.0, "duration": 1.0}, {"text": "I'm going to expire\ntoday otherwise.", "start": 1019.0, "duration": 2.0}, {"text": "AUDIENCE: I have some.", "start": 1021.0, "duration": 1.0}, {"text": "Do you want some?", "start": 1022.0, "duration": 1.0}, {"text": "PROFESSOR: I don't know.\nDo you got any\ninteresting diseases?", "start": 1023.0, "duration": 0.0}, {"text": "AUDIENCE: No.", "start": 1024.0, "duration": 2.0}, {"text": "PROFESSOR: I don't\nwant to steal yours.", "start": 1026.0, "duration": 4.0}, {"text": "Find me something somewhere.", "start": 1030.0, "duration": 1.0}, {"text": "Thank you.", "start": 1031.0, "duration": 1.0}, {"text": "I'm recovering from a cold\nstill, and I can feel that I'm", "start": 1037.0, "duration": 4.0}, {"text": "going to run out of moisture.", "start": 1041.0, "duration": 3.0}, {"text": "And my tongue is going to\nget all big and like a", "start": 1044.0, "duration": 2.0}, {"text": "parrot or something.\nI won't be able to talk.", "start": 1046.0, "duration": 0.0}, {"text": "All right, have you\nmanaged to do this?", "start": 1048.0, "duration": 3.0}, {"text": "Still working on it.\nAll right.", "start": 1051.0, "duration": 0.0}, {"text": "Don't cheat off your neighbors.", "start": 1052.0, "duration": 2.0}, {"text": "But I promise you this time,\nnone of these guys are dealing", "start": 1054.0, "duration": 4.0}, {"text": "in lady's undergarments.", "start": 1058.0, "duration": 0.0}, {"text": "Here.\nLet's collect some.", "start": 1062.0, "duration": 0.0}, {"text": "All right.\nLet's collect us some data.", "start": 1071.0, "duration": 0.0}, {"text": "OK.", "start": 1083.0, "duration": 2.0}, {"text": "Everybody pretty\nmuch done here?", "start": 1085.0, "duration": 4.0}, {"text": "Make assenting noises\nor something.", "start": 1089.0, "duration": 3.0}, {"text": "OK, that's good.", "start": 1092.0, "duration": 1.0}, {"text": "That sounded very assenting.", "start": 1093.0, "duration": 2.0}, {"text": "OK, so Sarah had a bad day.", "start": 1095.0, "duration": 4.0}, {"text": "How many people would, let's\nsee, so that -- slow numbers", "start": 1099.0, "duration": 6.0}, {"text": "are the \"no way, we're not\ngoing to medicate this", "start": 1105.0, "duration": 3.0}, {"text": "depression.\" How many people\n-- oh, that was quick.", "start": 1108.0, "duration": 3.0}, {"text": "That was good.", "start": 1111.0, "duration": 1.0}, {"text": "Thank you.", "start": 1112.0, "duration": 2.0}, {"text": "How many people are going\nto give her no meds?", "start": 1114.0, "duration": 3.0}, {"text": "Oh, OK.", "start": 1117.0, "duration": 1.0}, {"text": "So the answer is\neverybody, more or less.", "start": 1118.0, "duration": 5.0}, {"text": "Don't worry if you said, I'll\ngive her a little bit of med.", "start": 1123.0, "duration": 2.0}, {"text": "That's OK, too.", "start": 1125.0, "duration": 1.0}, {"text": "But I won't bother\nasking about it.", "start": 1126.0, "duration": 3.0}, {"text": "These really are all\nthe same, by the way.", "start": 1129.0, "duration": 2.0}, {"text": "There's no fifty-fifty split.", "start": 1131.0, "duration": 2.0}, {"text": "This is just straight\nup, normal.", "start": 1133.0, "duration": 2.0}, {"text": "I'm not tricking you this time.", "start": 1135.0, "duration": 2.0}, {"text": "OK.", "start": 1137.0, "duration": 3.0}, {"text": "And by contrast if we look at\nSam, Sam's depressed, no", "start": 1140.0, "duration": 4.0}, {"text": "particular reason,\njust happens.", "start": 1144.0, "duration": 2.0}, {"text": "And he oscillates between\nmanic and depressed states.", "start": 1146.0, "duration": 4.0}, {"text": "How many people think no\ntreatment or unlikely", "start": 1150.0, "duration": 5.0}, {"text": "to medicate?", "start": 1155.0, "duration": 3.0}, {"text": "How many moderately like,\nyou know, somewhere in the", "start": 1158.0, "duration": 2.0}, {"text": "four to seven department?", "start": 1160.0, "duration": 1.0}, {"text": "Well, a few people in there.", "start": 1161.0, "duration": 3.0}, {"text": "And you have all embodied\nthe ethos of the", "start": 1164.0, "duration": 3.0}, {"text": "yeah, yeah, OK, good.", "start": 1167.0, "duration": 2.0}, {"text": "I mean, I don't know if it's\ngood or not, but it's clearly", "start": 1169.0, "duration": 5.0}, {"text": "where medical science, I\nsuppose, is these days, which", "start": 1174.0, "duration": 5.0}, {"text": "is that he would be a candidate\nfor an antidepressant in", "start": 1179.0, "duration": 3.0}, {"text": "a way that she wouldn't.", "start": 1182.0, "duration": 2.0}, {"text": "Why not?", "start": 1184.0, "duration": 1.0}, {"text": "Why wouldn't you give\nher an antidepressant?", "start": 1185.0, "duration": 2.0}, {"text": "She's depressed.", "start": 1187.0, "duration": 1.0}, {"text": "AUDIENCE: It's normal for\nher to be depressed.", "start": 1193.0, "duration": 3.0}, {"text": "Like, anyone could be depressed\nin that situation, but if", "start": 1196.0, "duration": 3.0}, {"text": "you're depressed for no reason,\nthen that [UNINTELLIGIBLE]", "start": 1199.0, "duration": 5.0}, {"text": "problem in the brain that could\nbe solved by medication,", "start": 1204.0, "duration": 4.0}, {"text": "whereas with her thing, all\nthat needs to happen is the", "start": 1208.0, "duration": 3.0}, {"text": "problem's [? cured. ?]", "start": 1211.0, "duration": 1.0}, {"text": "PROFESSOR: There's a couple\nof things that are worth", "start": 1212.0, "duration": 3.0}, {"text": "picking up on here.", "start": 1215.0, "duration": 2.0}, {"text": "One is, I mentioned last time\nthat the exact mapping between", "start": 1217.0, "duration": 6.0}, {"text": "cause and treatment shouldn't\nbe seen as one to one.", "start": 1223.0, "duration": 5.0}, {"text": "So even if we take as correct\nfor present purposes that Sam's", "start": 1228.0, "duration": 7.0}, {"text": "got something biochemical wrong\nwith him, it wouldn't", "start": 1235.0, "duration": 3.0}, {"text": "necessarily be the case that\nthe only way to deal with this", "start": 1238.0, "duration": 3.0}, {"text": "would be by a biochemical\nkind of treatment.", "start": 1241.0, "duration": 4.0}, {"text": "There isn't that necessary\none-to-one mapping.", "start": 1245.0, "duration": 2.0}, {"text": "But it's not an\nunreasonable thought.", "start": 1247.0, "duration": 3.0}, {"text": "And the other part of that\nthought was, you know, she's", "start": 1250.0, "duration": 3.0}, {"text": "depressed for a reason.", "start": 1253.0, "duration": 2.0}, {"text": "And we don't want to shield\nher necessarily from", "start": 1255.0, "duration": 6.0}, {"text": "that depression.", "start": 1261.0, "duration": 1.0}, {"text": "Though this gets raised\nas an issue too now.", "start": 1262.0, "duration": 7.0}, {"text": "I talked last time about\ntreatments for post-traumatic", "start": 1269.0, "duration": 3.0}, {"text": "stress disorder.", "start": 1272.0, "duration": 2.0}, {"text": "One of the notions is that you\ncould give people medications", "start": 1274.0, "duration": 8.0}, {"text": "that would in a sense prevent\nthem from feeling as bad about", "start": 1282.0, "duration": 4.0}, {"text": "something horrible as\nthey normally would.", "start": 1286.0, "duration": 6.0}, {"text": "I mean, this is a real\nsomething horrible", "start": 1292.0, "duration": 2.0}, {"text": "now, you understand.", "start": 1294.0, "duration": 1.0}, {"text": "But we're going to get you --\nsomething horrible has happened", "start": 1295.0, "duration": 3.0}, {"text": "-- we're going to give you a\npill that is going to decrease,", "start": 1298.0, "duration": 5.0}, {"text": "we hope, the chance of you\nhaving a post-traumatic stress", "start": 1303.0, "duration": 2.0}, {"text": "disorder, but it's going to\ndo that by blunting your", "start": 1305.0, "duration": 3.0}, {"text": "emotional response and your\nmemory for that event.", "start": 1308.0, "duration": 6.0}, {"text": "Is that something that\nwe want to get into?", "start": 1314.0, "duration": 3.0}, {"text": "Now, Sam I described as having\nthis -- if this is now, oh,", "start": 1317.0, "duration": 9.0}, {"text": "I suppose, mood -- Sam I\ndescribed as having one of", "start": 1326.0, "duration": 4.0}, {"text": "these oscillatory or bipolar\nconditions where he bounces", "start": 1330.0, "duration": 4.0}, {"text": "back and forth between -- well,\nlet's see, which end is this?", "start": 1334.0, "duration": 4.0}, {"text": "This can be the manic end\nand the depressed end.", "start": 1338.0, "duration": 8.0}, {"text": "You sometimes think that it\nmight kind of be worth it,", "start": 1352.0, "duration": 4.0}, {"text": "right, because you have to put\nup with the depression, but the", "start": 1356.0, "duration": 4.0}, {"text": "manic energy thing\nwould be good.", "start": 1360.0, "duration": 2.0}, {"text": "Well, the manic energy thing\nis kind of good here, maybe.", "start": 1362.0, "duration": 3.0}, {"text": "You know, you get all your\nproblem sets done in ten", "start": 1365.0, "duration": 3.0}, {"text": "minutes or something.", "start": 1368.0, "duration": 2.0}, {"text": "But by the time you get out\nhere, you are just as abnormal,", "start": 1370.0, "duration": 6.0}, {"text": "if you like, or just as crazy\nif we want to be colloquial", "start": 1376.0, "duration": 3.0}, {"text": "about this, out here\nas you are down here.", "start": 1379.0, "duration": 5.0}, {"text": "And you can be pretty hard on\nyour friends and neighbors", "start": 1384.0, "duration": 3.0}, {"text": "and yourself, in fact.", "start": 1387.0, "duration": 4.0}, {"text": "I don't need -- I mean, this\nis very MIT, right -- I", "start": 1391.0, "duration": 2.0}, {"text": "don't need to sleep anymore.", "start": 1393.0, "duration": 1.0}, {"text": "I can talk all night.", "start": 1394.0, "duration": 3.0}, {"text": "You don't want to listen to me?", "start": 1397.0, "duration": 1.0}, {"text": "Well, I'll talk anyway.", "start": 1398.0, "duration": 1.0}, {"text": "I remember reading a memoir by\nthe child of a manic depressive", "start": 1402.0, "duration": 6.0}, {"text": "mother, who as I recall comes\nhome -- the child comes home", "start": 1408.0, "duration": 5.0}, {"text": "from school one day, discovers\nmom has decided we're going to", "start": 1413.0, "duration": 3.0}, {"text": "have a great old-fashioned\nChristmas this year.", "start": 1416.0, "duration": 4.0}, {"text": "So she went out and bought like\nthirty-five Christmas trees.", "start": 1420.0, "duration": 4.0}, {"text": "And you walk into the living\nroom and it's just, you", "start": 1424.0, "duration": 3.0}, {"text": "know, forest in there.", "start": 1427.0, "duration": 1.0}, {"text": "She's stuffed the Christmas\ntrees all over the -- and, you", "start": 1428.0, "duration": 3.0}, {"text": "know, this is, I'm sorry, I'm\nglad you're feeling really", "start": 1431.0, "duration": 3.0}, {"text": "up, but this is nuts too.", "start": 1434.0, "duration": 4.0}, {"text": "It's not working.", "start": 1438.0, "duration": 1.0}, {"text": "It's an interesting\nobservation.", "start": 1445.0, "duration": 4.0}, {"text": "There are interesting data\nsuggesting that this sort of", "start": 1449.0, "duration": 5.0}, {"text": "bipolar disorder, this\noscillation between deep", "start": 1454.0, "duration": 3.0}, {"text": "depression and this wild mania,\nthat that's overrepresented in", "start": 1457.0, "duration": 7.0}, {"text": "at least some creative\npopulations.", "start": 1464.0, "duration": 3.0}, {"text": "The notable one is poets.", "start": 1467.0, "duration": 4.0}, {"text": "It's notable because a woman\nnamed -- what is her full name?", "start": 1471.0, "duration": 4.0}, {"text": "-- well, anyway, Jamison\nis her last name.", "start": 1475.0, "duration": 3.0}, {"text": "I think it's spelled like this.", "start": 1481.0, "duration": 2.0}, {"text": "Anyway, she wrote a book called\nTouched by Fire where what she", "start": 1483.0, "duration": 3.0}, {"text": "did was she went and looked\nat the biographies of, in", "start": 1486.0, "duration": 3.0}, {"text": "particular, sort of the run\nof famous English poets.", "start": 1489.0, "duration": 4.0}, {"text": "And over and over in their\nbiographies you get these", "start": 1493.0, "duration": 3.0}, {"text": "descriptions that -- you know,\nthey didn't have the diagnosis", "start": 1496.0, "duration": 4.0}, {"text": "in 18th century England, but it\nsure sounds like a manic", "start": 1500.0, "duration": 4.0}, {"text": "depressive disorder.", "start": 1504.0, "duration": 1.0}, {"text": "You know, Shelley or Keats or\nsomebody writes eight million", "start": 1505.0, "duration": 3.0}, {"text": "poems and then lies\nin bed for a month.", "start": 1508.0, "duration": 5.0}, {"text": "It's that sort of thing.", "start": 1513.0, "duration": 1.0}, {"text": "Now, great, you know.", "start": 1514.0, "duration": 2.0}, {"text": "I can be a famous poet.", "start": 1516.0, "duration": 1.0}, {"text": "All I have to do is\nput up with this.", "start": 1517.0, "duration": 1.0}, {"text": "The problem -- well, there are\na number of problems with this.", "start": 1518.0, "duration": 3.0}, {"text": "First of all, you become a\nlittle intolerable to your", "start": 1521.0, "duration": 3.0}, {"text": "immediate surroundings.", "start": 1524.0, "duration": 1.0}, {"text": "The other thing is that a\nvery serious consequence", "start": 1525.0, "duration": 4.0}, {"text": "of deep depression is\nthe threat of suicide.", "start": 1529.0, "duration": 4.0}, {"text": "Interestingly, you would think\nthat this was a continuum", "start": 1533.0, "duration": 5.0}, {"text": "thing, right, that you go way,\nway down here and if you get", "start": 1538.0, "duration": 3.0}, {"text": "this far down into depression,\nthat's when people", "start": 1541.0, "duration": 4.0}, {"text": "commit suicide.", "start": 1545.0, "duration": 1.0}, {"text": "Turns out not to be the case.", "start": 1546.0, "duration": 2.0}, {"text": "When people describe their\nreally deep -- there's", "start": 1548.0, "duration": 2.0}, {"text": "a huge genre here.", "start": 1550.0, "duration": 2.0}, {"text": "It's a very popular\ngenre at the moment.", "start": 1552.0, "duration": 2.0}, {"text": "If you're into depression,\nyour, you know, Christmas", "start": 1554.0, "duration": 5.0}, {"text": "reading list can be all set\nout because there's all", "start": 1559.0, "duration": 2.0}, {"text": "sorts of people who\nare happy to describe", "start": 1561.0, "duration": 3.0}, {"text": "-- happy to describe their\ndepression? -- anyway, more", "start": 1564.0, "duration": 4.0}, {"text": "than willing to describe\ntheir depression in", "start": 1568.0, "duration": 4.0}, {"text": "volumes thin or thick.", "start": 1572.0, "duration": 2.0}, {"text": "Jamison actually has a volume\nof her -- she got interested in", "start": 1574.0, "duration": 2.0}, {"text": "this because she was a manic\ndepressive and trained", "start": 1576.0, "duration": 5.0}, {"text": "in psychiatry.", "start": 1581.0, "duration": 1.0}, {"text": "So she's coming at it\nfrom every which way.", "start": 1582.0, "duration": 2.0}, {"text": "Anyway, she has a memoir -- I\ndon't remember the title of it", "start": 1584.0, "duration": 4.0}, {"text": "-- about her own depression\nthat's actually nice and slim.", "start": 1588.0, "duration": 6.0}, {"text": "It's not a bad read.", "start": 1594.0, "duration": 2.0}, {"text": "But what the descriptions sound\nlike is that when you're", "start": 1596.0, "duration": 4.0}, {"text": "really, really deeply\ndepressed, you just", "start": 1600.0, "duration": 3.0}, {"text": "don't do anything.", "start": 1603.0, "duration": 1.0}, {"text": "You might in some sense want\nto be dead, but that's just", "start": 1604.0, "duration": 4.0}, {"text": "too much effort to do\nanything about that.", "start": 1608.0, "duration": 5.0}, {"text": "The danger for suicide in\nbipolar disorders turns out to", "start": 1613.0, "duration": 6.0}, {"text": "be -- well, let's get rid of\nthis -- turns out to be when", "start": 1619.0, "duration": 4.0}, {"text": "you're on your way back out.", "start": 1623.0, "duration": 3.0}, {"text": "Still depressed, but now you're\nactivated enough that you can", "start": 1626.0, "duration": 6.0}, {"text": "do stuff, but you're not\nconvinced you're ever really", "start": 1632.0, "duration": 2.0}, {"text": "going to get better.", "start": 1634.0, "duration": 2.0}, {"text": "I mean, look, most of us have\nnot been really clinically", "start": 1636.0, "duration": 3.0}, {"text": "depressed, but many of us can\ntap into this, into this aspect", "start": 1639.0, "duration": 6.0}, {"text": "in the sense of have you had\nthe flu or some, you know,", "start": 1645.0, "duration": 5.0}, {"text": "relatively disgusting disorder\nof some variety where you're", "start": 1650.0, "duration": 3.0}, {"text": "sitting there thinking, \"I know\nrationally that I'm going to", "start": 1653.0, "duration": 4.0}, {"text": "get better, but am I really\ngoing to get better, or am I", "start": 1657.0, "duration": 4.0}, {"text": "just going to be barfing\nforever?\" So you're coming on", "start": 1661.0, "duration": 6.0}, {"text": "your way out, and that's where\nthe suicide risk is high.", "start": 1667.0, "duration": 4.0}, {"text": "Now, that phenomenon may be\nrelated to something that hit", "start": 1671.0, "duration": 6.0}, {"text": "the news a lot this year, which\nwas concerns about giving", "start": 1677.0, "duration": 8.0}, {"text": "antidepressants to\nchildren and adolescents.", "start": 1685.0, "duration": 5.0}, {"text": "Because there are data out\nthere that say that the suicide", "start": 1690.0, "duration": 3.0}, {"text": "risk in depressed adolescents\ntaking antidepressants", "start": 1693.0, "duration": 5.0}, {"text": "is elevated.", "start": 1698.0, "duration": 1.0}, {"text": "Exactly what you don't want\nto have happen, right?", "start": 1699.0, "duration": 2.0}, {"text": "What you really want to not\nhave happen is people", "start": 1701.0, "duration": 3.0}, {"text": "committing suicide when\nthey're depressed.", "start": 1704.0, "duration": 2.0}, {"text": "What is the cause of this?", "start": 1706.0, "duration": 2.0}, {"text": "Well, we don't actually\nknow, I don't think.", "start": 1708.0, "duration": 2.0}, {"text": "At least I haven't seen\nanything definitive.", "start": 1710.0, "duration": 1.0}, {"text": "But there are a number -- one\ntheory is that antidepressants", "start": 1711.0, "duration": 4.0}, {"text": "work differently in young\nbrains than in older brains.", "start": 1715.0, "duration": 3.0}, {"text": "That's one possibility.", "start": 1718.0, "duration": 1.0}, {"text": "But the other possibility is\nthat what the antidepressant", "start": 1719.0, "duration": 3.0}, {"text": "did was it moved the patient\nalong to a point where they", "start": 1722.0, "duration": 7.0}, {"text": "weren't so paralyzed by the\ndepression that suicide", "start": 1729.0, "duration": 2.0}, {"text": "became an option.", "start": 1731.0, "duration": 2.0}, {"text": "It sounds weird and disturbing,\nbut that is one possibility for", "start": 1733.0, "duration": 4.0}, {"text": "where this elevated rate of\nsuicide in antidepressant", "start": 1737.0, "duration": 6.0}, {"text": "treated young\npatients came from.", "start": 1743.0, "duration": 4.0}, {"text": "Let's see, what else do I want\nto say about Sam and Emma here?", "start": 1750.0, "duration": 10.0}, {"text": "Oh, Emma's the one on the back.", "start": 1760.0, "duration": 2.0}, {"text": "All right, so how about Emma?", "start": 1762.0, "duration": 2.0}, {"text": "We need to collect\nsome data on Emma.", "start": 1764.0, "duration": 6.0}, {"text": "Did I describe Emma\nas dysphoric?", "start": 1770.0, "duration": 2.0}, {"text": "Yes.\nEmma is a dysphoric.", "start": 1772.0, "duration": 0.0}, {"text": "That's the opposite\nof euphoric.", "start": 1774.0, "duration": 2.0}, {"text": "So it's not depressed.", "start": 1776.0, "duration": 2.0}, {"text": "It would be sort of lying\naround here somewhere.", "start": 1778.0, "duration": 3.0}, {"text": "Just kind of flat.", "start": 1781.0, "duration": 2.0}, {"text": "All right.", "start": 1783.0, "duration": 2.0}, {"text": "So how many people voted\nthat we'll leave her be?", "start": 1785.0, "duration": 10.0}, {"text": "OK.\nHow many people voted maybe?", "start": 1795.0, "duration": 0.0}, {"text": "And how many people voted sure?", "start": 1799.0, "duration": 3.0}, {"text": "Well, OK, we got a normal\ncurve out of that.", "start": 1802.0, "duration": 3.0}, {"text": "Well, I could have gone -- it\nlooked sort of like this to me.", "start": 1805.0, "duration": 5.0}, {"text": "So people are sort of\nunsure about -- oops.", "start": 1814.0, "duration": 3.0}, {"text": "Well, I guess it's\ngoing over there now.", "start": 1817.0, "duration": 2.0}, {"text": "People are sort of\nunsure about it.", "start": 1819.0, "duration": 3.0}, {"text": "So what are the issues here?", "start": 1822.0, "duration": 2.0}, {"text": "Why wouldn't you\ngive it to her?", "start": 1824.0, "duration": 3.0}, {"text": "Yeah?\nAUDIENCE: If she\ndoesn't want it.", "start": 1827.0, "duration": 0.0}, {"text": "PROFESSOR: Oh, yes, yes.", "start": 1829.0, "duration": 1.0}, {"text": "Well, that's a separate issue.\nDid I say anything about it?", "start": 1830.0, "duration": 0.0}, {"text": "No, no, no, this is just\n-- well, actually, we'll", "start": 1834.0, "duration": 2.0}, {"text": "come back to that.", "start": 1836.0, "duration": 1.0}, {"text": "That's an interesting problem.", "start": 1837.0, "duration": 2.0}, {"text": "But yes, I was not suggesting\nthat we jam it down her throat,", "start": 1839.0, "duration": 3.0}, {"text": "which is by the way not\nthe problem with Prozac.", "start": 1842.0, "duration": 4.0}, {"text": "Let's imagine that the\nantidepressant is Prozac here,", "start": 1850.0, "duration": 4.0}, {"text": "or one of its newer friends.", "start": 1854.0, "duration": 3.0}, {"text": "Prozac gets a lot of play\nin the public sphere.", "start": 1857.0, "duration": 8.0}, {"text": "Whoops.", "start": 1865.0, "duration": 1.0}, {"text": "Well, I'll put a P there now.", "start": 1866.0, "duration": 3.0}, {"text": "Uh oh.\nC or K?", "start": 1869.0, "duration": 0.0}, {"text": "AUDIENCE: C.", "start": 1871.0, "duration": 1.0}, {"text": "Yes.\nPROFESSOR: C.\nThank you.", "start": 1872.0, "duration": 0.0}, {"text": "OK.", "start": 1873.0, "duration": 1.0}, {"text": "Prozac is a serotonin -- that's\na neurotransmitter -- selective", "start": 1874.0, "duration": 11.0}, {"text": "-- thank you, where\nwas that coming --", "start": 1885.0, "duration": 2.0}, {"text": "AUDIENCE: It's first.\nPROFESSOR: Oh, it's a\nselective serotonin, not", "start": 1887.0, "duration": 0.0}, {"text": "serotonin selective.", "start": 1889.0, "duration": 1.0}, {"text": "It's SS.", "start": 1890.0, "duration": 1.0}, {"text": "All right.", "start": 1891.0, "duration": 2.0}, {"text": "All right.\nIt's a serotonin selective --\nreverse -- uptake, reuptake", "start": 1893.0, "duration": 0.0}, {"text": "-- can I do reuptake?", "start": 1901.0, "duration": 2.0}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1903.0, "duration": 1.0}, {"text": "Yeah.\nPROFESSOR: Yeah.\nOK.", "start": 1904.0, "duration": 0.0}, {"text": "Reuptake inhibitor.", "start": 1906.0, "duration": 8.0}, {"text": "Or an SSRI, which makes it\nunderstandable how I would have", "start": 1918.0, "duration": 4.0}, {"text": "thought it might have been\nan SSRI rather than an SSRI.", "start": 1922.0, "duration": 4.0}, {"text": "But let me explain what\nthis is doing actually.", "start": 1929.0, "duration": 5.0}, {"text": "So remember that in\nschizophrenia, the first big", "start": 1934.0, "duration": 4.0}, {"text": "psychopharmacological\nbreakthrough was the discovery", "start": 1938.0, "duration": 3.0}, {"text": "there's too much dopamine\nin bits of the brain.", "start": 1941.0, "duration": 1.0}, {"text": "If we block some dopamine\nreceptors, we reduce", "start": 1942.0, "duration": 7.0}, {"text": "the symptoms.", "start": 1949.0, "duration": 1.0}, {"text": "In the case of at least some\nforms of depression, the", "start": 1950.0, "duration": 5.0}, {"text": "problem seems to be too little\nserotonin -- or a problem.", "start": 1955.0, "duration": 3.0}, {"text": "Seems to be too little\nserotonin in some", "start": 1958.0, "duration": 2.0}, {"text": "parts of the brain.", "start": 1960.0, "duration": 2.0}, {"text": "And so you've got a synapse.", "start": 1962.0, "duration": 3.0}, {"text": "And serotonin is being\nreleased here and binding", "start": 1970.0, "duration": 4.0}, {"text": "to the other side.", "start": 1974.0, "duration": 3.0}, {"text": "But now, in order to have this\nsynapse be reusable, once", "start": 1977.0, "duration": 5.0}, {"text": "you've released some serotonin,\nyou've got to get rid of it.", "start": 1982.0, "duration": 3.0}, {"text": "You've got to get it out of\nthe synapse so you can do it", "start": 1985.0, "duration": 2.0}, {"text": "again and again and again.", "start": 1987.0, "duration": 1.0}, {"text": "One of the techniques is\nto take the molecules and", "start": 1988.0, "duration": 4.0}, {"text": "suck them back into the\noriginating neuron.", "start": 1992.0, "duration": 6.0}, {"text": "That's called reuptake.", "start": 1998.0, "duration": 2.0}, {"text": "Now, if you don't have enough\nserotonin here to do the job,", "start": 2000.0, "duration": 3.0}, {"text": "one thing to do is to slow\ndown this reuptake so that", "start": 2003.0, "duration": 5.0}, {"text": "the serotonin hangs\naround here longer.", "start": 2008.0, "duration": 2.0}, {"text": "And that way you get more bang\nfor your molecular buck.", "start": 2010.0, "duration": 6.0}, {"text": "And so that's what\nProzac is doing.", "start": 2016.0, "duration": 4.0}, {"text": "The reason I put Emma on here\nis that Prozac seemed to do", "start": 2020.0, "duration": 5.0}, {"text": "good things for dysphoric\npatients, patients who did not", "start": 2025.0, "duration": 5.0}, {"text": "meet a clinical criterion for\ndepression but who found -- I", "start": 2030.0, "duration": 7.0}, {"text": "think in part because the drug\nmanufacturer gave the docs", "start": 2037.0, "duration": 6.0}, {"text": "piles of free Prozac.", "start": 2043.0, "duration": 2.0}, {"text": "You know, patient comes through\nand says, \"I feel kind", "start": 2045.0, "duration": 3.0}, {"text": "of down.\" So, \"Oh yeah.", "start": 2048.0, "duration": 2.0}, {"text": "Try this.", "start": 2050.0, "duration": 1.0}, {"text": "This is new.\" You\nknow, \"All right.", "start": 2051.0, "duration": 3.0}, {"text": "Hey!\nI feel better.", "start": 2054.0, "duration": 0.0}, {"text": "I feel a bunch better.", "start": 2056.0, "duration": 1.0}, {"text": "I'm not clinically depressed,\nbut I really like this stuff.", "start": 2057.0, "duration": 5.0}, {"text": "And not only that, if I\ngo off it, I go back", "start": 2064.0, "duration": 4.0}, {"text": "to my dysphoric state.", "start": 2068.0, "duration": 2.0}, {"text": "I go back to -- \"", "start": 2070.0, "duration": 2.0}, {"text": "The example says something\nto the effect of, that's", "start": 2072.0, "duration": 2.0}, {"text": "just the way she is.", "start": 2074.0, "duration": 3.0}, {"text": "If she goes off Prozac, there\nare lots of reports even in the", "start": 2077.0, "duration": 6.0}, {"text": "popular literature of this, of\npeople who said, you know, if", "start": 2083.0, "duration": 3.0}, {"text": "I'm off Prozac, I'm just, ughh.", "start": 2086.0, "duration": 2.0}, {"text": "But if I'm on Prozac,\nI'm just a better me.", "start": 2088.0, "duration": 4.0}, {"text": "Well, do you give\nthem the drug?", "start": 2092.0, "duration": 2.0}, {"text": "Do you give them the drug?", "start": 2094.0, "duration": 1.0}, {"text": "Do you allow them to continue\ntaking the drug for the rest", "start": 2095.0, "duration": 2.0}, {"text": "of their natural born days,\nparticularly since we have no", "start": 2097.0, "duration": 3.0}, {"text": "idea since it's a new drug --\nwell, now it's over", "start": 2100.0, "duration": 3.0}, {"text": "a decade old.", "start": 2103.0, "duration": 1.0}, {"text": "But, you know, we don't know\nwhat happens if you take this", "start": 2104.0, "duration": 1.0}, {"text": "for twenty, thirty,\nforty years.", "start": 2105.0, "duration": 3.0}, {"text": "Who should pay for it?", "start": 2108.0, "duration": 2.0}, {"text": "You know, if you think that\nthis drug makes you feel", "start": 2110.0, "duration": 4.0}, {"text": "better, that's lovely.", "start": 2114.0, "duration": 2.0}, {"text": "Should your insurance\ncompany pay for it on", "start": 2116.0, "duration": 3.0}, {"text": "a continuing basis?", "start": 2119.0, "duration": 5.0}, {"text": "So those are the\nEmma issues here.", "start": 2124.0, "duration": 4.0}, {"text": "The issues about whether or not\nit's OK to make somebody better", "start": 2128.0, "duration": 6.0}, {"text": "than they, in some sense,\nbetter than they were.", "start": 2134.0, "duration": 4.0}, {"text": "Are you the same person?", "start": 2138.0, "duration": 3.0}, {"text": "Is this, you know, is this\nthe real Emma, or is this", "start": 2141.0, "duration": 3.0}, {"text": "some medicated Emma?", "start": 2144.0, "duration": 3.0}, {"text": "And, well, all right, now let's\nlook back to the comment", "start": 2147.0, "duration": 5.0}, {"text": "about forcing them.", "start": 2152.0, "duration": 2.0}, {"text": "Well, you know what?", "start": 2154.0, "duration": 1.0}, {"text": "It works on kids, too.", "start": 2155.0, "duration": 4.0}, {"text": "And you know that there's a\nfairly substantial industry in", "start": 2159.0, "duration": 7.0}, {"text": "feeding psychiatric drugs to\nkids for various and", "start": 2166.0, "duration": 5.0}, {"text": "sundry problems.", "start": 2171.0, "duration": 2.0}, {"text": "Suppose, well, we know\nthat shy -- how did I", "start": 2173.0, "duration": 5.0}, {"text": "describe old Emma here?", "start": 2178.0, "duration": 2.0}, {"text": "Is she shy and withdrawn?", "start": 2180.0, "duration": 2.0}, {"text": "No, that was what's his\nname collecting the", "start": 2182.0, "duration": 1.0}, {"text": "underwear, wasn't it?", "start": 2183.0, "duration": 2.0}, {"text": "Oh well.", "start": 2185.0, "duration": 1.0}, {"text": "I could have described\nEmma as shy and quiet.", "start": 2190.0, "duration": 3.0}, {"text": "We know that the kid who's shy\nand quiet in first grade", "start": 2193.0, "duration": 4.0}, {"text": "doesn't get the same amount\nof attention that the", "start": 2197.0, "duration": 3.0}, {"text": "bouncy, active kid gets.", "start": 2200.0, "duration": 3.0}, {"text": "And in fact, there's some\nevidence that if you feed", "start": 2203.0, "duration": 6.0}, {"text": "something like Prozac to this\nkid, the kid will move from", "start": 2209.0, "duration": 6.0}, {"text": "here in the -- well, we've got\nto change the axis again.", "start": 2215.0, "duration": 4.0}, {"text": "You know, I don't know,\nwhat's the axis here?", "start": 2219.0, "duration": 1.0}, {"text": "Bounciness?", "start": 2220.0, "duration": 2.0}, {"text": "Technical term.", "start": 2222.0, "duration": 3.0}, {"text": "You know.\nSo the kid's going to move from\nbeing unbouncy to, you know,", "start": 2225.0, "duration": 0.0}, {"text": "Tigger is up here somewhere.", "start": 2230.0, "duration": 2.0}, {"text": "As are several -- couple of\npeople out there halfway up the", "start": 2237.0, "duration": 4.0}, {"text": "-- so there's Tigger, I guess.", "start": 2241.0, "duration": 7.0}, {"text": "But, you know, move them\nup here, let's say.", "start": 2248.0, "duration": 2.0}, {"text": "Get them above average and\nthe teacher's going to pay", "start": 2250.0, "duration": 2.0}, {"text": "more attention to them.", "start": 2252.0, "duration": 2.0}, {"text": "Is it OK to medicate your kid?", "start": 2254.0, "duration": 1.0}, {"text": "AUDIENCE: No.", "start": 2255.0, "duration": 2.0}, {"text": "PROFESSOR: If it's -- all\nright, it's not OK to", "start": 2257.0, "duration": 3.0}, {"text": "medicate your kid.\nI'm not going to\nmedicate my kid.", "start": 2260.0, "duration": 0.0}, {"text": "Uh oh.", "start": 2262.0, "duration": 2.0}, {"text": "The neighbors.", "start": 2264.0, "duration": 2.0}, {"text": "They're medicating their kids.", "start": 2266.0, "duration": 3.0}, {"text": "So what they've done --\nmy kid was right here.", "start": 2269.0, "duration": 2.0}, {"text": "He was average, right.", "start": 2271.0, "duration": 3.0}, {"text": "All right, now what the\nneighbors and the population as", "start": 2274.0, "duration": 3.0}, {"text": "a whole has done is they moved\nthe whole distribution over.", "start": 2277.0, "duration": 4.0}, {"text": "Because they're all handing\nout Prozac in the lunch box.", "start": 2281.0, "duration": 5.0}, {"text": "Now is it fair to my kid --\nthis is a hypothetical my kid.", "start": 2286.0, "duration": 4.0}, {"text": "This is not a real issue\non my street in case", "start": 2290.0, "duration": 2.0}, {"text": "you're wondering.", "start": 2292.0, "duration": 1.0}, {"text": "But is it fair to my kid\nto not medicate him?", "start": 2293.0, "duration": 4.0}, {"text": "He's going to fall behind.", "start": 2297.0, "duration": 3.0}, {"text": "Is this systematically\ndifferent, you know, is this", "start": 2300.0, "duration": 4.0}, {"text": "sort of morally or ethically\ndifferent than the Kaplan", "start": 2304.0, "duration": 6.0}, {"text": "or Princeton Review\napproach to SAT tests?", "start": 2310.0, "duration": 4.0}, {"text": "What Princeton Review and stuff\ndoes is it takes the population", "start": 2317.0, "duration": 4.0}, {"text": "and it shoves it on --\neverybody gets to gain those", "start": 2321.0, "duration": 3.0}, {"text": "hundred points or whatever.", "start": 2324.0, "duration": 2.0}, {"text": "So is it OK for you to say, \"My\nkid doesn't need to do that.", "start": 2326.0, "duration": 4.0}, {"text": "I didn't do that when I was a\nkid, and no kid of mine's going", "start": 2330.0, "duration": 5.0}, {"text": "to go off and get tutored.", "start": 2335.0, "duration": 1.0}, {"text": "He'll do it on his own brains.", "start": 2336.0, "duration": 2.0}, {"text": "It's an aptitude test\nafter all.\" Right.", "start": 2338.0, "duration": 3.0}, {"text": "You know, is there a difference\nbetween everybody being signed", "start": 2341.0, "duration": 4.0}, {"text": "up for Princeton Review versus\neverybody being signed up, you", "start": 2345.0, "duration": 5.0}, {"text": "know, going down to the\nnurse's office for the", "start": 2350.0, "duration": 1.0}, {"text": "daily Prozac dose?", "start": 2351.0, "duration": 3.0}, {"text": "Or is there a difference\nbetween just sitting there", "start": 2354.0, "duration": 2.0}, {"text": "saying, \"I'm not going to go\nand make myself into a better", "start": 2356.0, "duration": 3.0}, {"text": "me by popping Prozac\nall the time.", "start": 2359.0, "duration": 7.0}, {"text": "I'll stick with --\" What\nis that, Mountain Dew?", "start": 2366.0, "duration": 4.0}, {"text": "You know, twice the caffeine\nof whatever, right?", "start": 2370.0, "duration": 4.0}, {"text": "AUDIENCE: Late\nnight last night.", "start": 2374.0, "duration": 1.0}, {"text": "PROFESSOR: Yeah.", "start": 2375.0, "duration": 1.0}, {"text": "OK, well, that's good.", "start": 2376.0, "duration": 1.0}, {"text": "You're vertical.", "start": 2377.0, "duration": 1.0}, {"text": "That's encouraging.", "start": 2378.0, "duration": 2.0}, {"text": "Give some to the guy\nnext to you there.", "start": 2380.0, "duration": 1.0}, {"text": "He's gone.", "start": 2381.0, "duration": 1.0}, {"text": "[LAUGHTER FROM AUDIENCE]", "start": 2382.0, "duration": 3.0}, {"text": "I shouldn't have said that.", "start": 2385.0, "duration": 1.0}, {"text": "Anyway, we do this\nall the time, right?", "start": 2389.0, "duration": 3.0}, {"text": "We self-medicate.", "start": 2392.0, "duration": 3.0}, {"text": "We self-medicate,\nparticularly with caffeine.", "start": 2395.0, "duration": 4.0}, {"text": "But perhaps with a\nvariety of other things.", "start": 2399.0, "duration": 2.0}, {"text": "The use of alcohol as an\nantidepressant is probably a", "start": 2401.0, "duration": 3.0}, {"text": "mistake, but is not uncommon.", "start": 2404.0, "duration": 5.0}, {"text": "So when is this a sort of an\nunwarranted medicalization of", "start": 2409.0, "duration": 8.0}, {"text": "your life, and when is it, you\nknow, a lifestyle choice?", "start": 2417.0, "duration": 4.0}, {"text": "And again, there's not going to\nbe a question on the final that", "start": 2421.0, "duration": 3.0}, {"text": "says, \"It's OK to drink\nMountain Dew: yes, no, only if", "start": 2424.0, "duration": 6.0}, {"text": "it was a late night.\" But\nyou can see that there are", "start": 2430.0, "duration": 7.0}, {"text": "issues to wrestle with.", "start": 2437.0, "duration": 2.0}, {"text": "And the doctors ended up with\nor have ended up with a serious", "start": 2439.0, "duration": 6.0}, {"text": "problem, which is what do you\ndo with these patients who you", "start": 2445.0, "duration": 3.0}, {"text": "cannot in good conscience give\na clinical diagnosis of", "start": 2448.0, "duration": 6.0}, {"text": "clinical depression to, but who\nsay, you know, if you don't", "start": 2454.0, "duration": 4.0}, {"text": "give me my Prozac, I'm just\ngoing to be so depressed, who", "start": 2458.0, "duration": 5.0}, {"text": "really need that or who think\nthat they really need that.", "start": 2463.0, "duration": 4.0}, {"text": "Oh, by the way,\nOK, what's this?", "start": 2467.0, "duration": 5.0}, {"text": "Want to make sure that\nI do what it says.", "start": 2472.0, "duration": 3.0}, {"text": "Well, OK.\nOh.\nLet's say something about\nhow antidepressants work.", "start": 2475.0, "duration": 0.0}, {"text": "Here's a mystery for you.", "start": 2484.0, "duration": 4.0}, {"text": "Take Prozac.", "start": 2488.0, "duration": 2.0}, {"text": "It blocks the reuptake\npathway within hours.", "start": 2490.0, "duration": 6.0}, {"text": "It doesn't take\nmuch time at all.", "start": 2496.0, "duration": 2.0}, {"text": "OK.\nSo you are down here,\nclinically depressed.", "start": 2498.0, "duration": 0.0}, {"text": "You come into the\ndoctor's office.", "start": 2504.0, "duration": 1.0}, {"text": "He says, here's your Prozac.", "start": 2505.0, "duration": 2.0}, {"text": "You take the Prozac.", "start": 2507.0, "duration": 1.0}, {"text": "A few hours later,\nmore serotonin at", "start": 2508.0, "duration": 4.0}, {"text": "all those synapses.", "start": 2512.0, "duration": 1.0}, {"text": "How do you feel?", "start": 2513.0, "duration": 2.0}, {"text": "Well, you feel\ndepressed, actually.", "start": 2515.0, "duration": 3.0}, {"text": "It takes typically at least\ndays, more like several weeks,", "start": 2518.0, "duration": 6.0}, {"text": "before an antidepressant of\nthis sort has an effect, beyond", "start": 2524.0, "duration": 6.0}, {"text": "perhaps placebo effects.", "start": 2530.0, "duration": 1.0}, {"text": "There are placebo effects where\nyou can take any old damn thing", "start": 2531.0, "duration": 3.0}, {"text": "and you feel a little better if\nyou're convinced that", "start": 2534.0, "duration": 2.0}, {"text": "it's going to work.", "start": 2536.0, "duration": 1.0}, {"text": "But the main effect of\nantidepressants seems", "start": 2537.0, "duration": 4.0}, {"text": "to take a long time.", "start": 2541.0, "duration": 2.0}, {"text": "That's a mystery.", "start": 2543.0, "duration": 1.0}, {"text": "At least as far as I know,\nthere's no neat, clean answer", "start": 2544.0, "duration": 3.0}, {"text": "to why it should be the case\nthat the pharmacological effect", "start": 2547.0, "duration": 6.0}, {"text": "is there instantly almost\nand the psychological effect", "start": 2553.0, "duration": 4.0}, {"text": "takes a vastly longer time.", "start": 2557.0, "duration": 3.0}, {"text": "The reference that I put on\nthe handout is a theory.", "start": 2560.0, "duration": 3.0}, {"text": "It's not proven.", "start": 2563.0, "duration": 1.0}, {"text": "But it's an interesting theory\nabout what might be going on.", "start": 2564.0, "duration": 4.0}, {"text": "As I think I mentioned earlier\nin the course, one of the", "start": 2568.0, "duration": 3.0}, {"text": "interesting new findings in\nneuroscience is that", "start": 2571.0, "duration": 4.0}, {"text": "we grow new neurons.", "start": 2575.0, "duration": 1.0}, {"text": "We didn't used to think\nwe grew new neurons.", "start": 2576.0, "duration": 2.0}, {"text": "But now it's pretty clear\nthat you grow new neurons.", "start": 2578.0, "duration": 6.0}, {"text": "And there's a pretty strong\nsuggestion that this", "start": 2584.0, "duration": 4.0}, {"text": "neurogenesis, as it's called,\nis depressed in depression.", "start": 2588.0, "duration": 5.0}, {"text": "You're not making\nthose new neurons.", "start": 2593.0, "duration": 2.0}, {"text": "And one theory is that what an\nantidepressant is doing is", "start": 2595.0, "duration": 6.0}, {"text": "jump-starting the neurogenesis,\nthat this is the beginning of a", "start": 2601.0, "duration": 3.0}, {"text": "cascade of events that leads\neventually to the birth of", "start": 2604.0, "duration": 5.0}, {"text": "new cells, new neurons.", "start": 2609.0, "duration": 2.0}, {"text": "And only when you manage to\nsort of grow yourself a new bit", "start": 2611.0, "duration": 2.0}, {"text": "of brain, in a sense, does it\nhelp you to break out", "start": 2613.0, "duration": 7.0}, {"text": "of the depression.", "start": 2620.0, "duration": 4.0}, {"text": "The data on how well these\nthings work is a little", "start": 2624.0, "duration": 2.0}, {"text": "depressing in its own right.", "start": 2626.0, "duration": 1.0}, {"text": "Antidepressants, like a lot\nof these -- antidepressants", "start": 2632.0, "duration": 3.0}, {"text": "don't work as well once\nthey go off patent.", "start": 2635.0, "duration": 3.0}, {"text": "It's a mysterious thing.", "start": 2638.0, "duration": 4.0}, {"text": "You want to worry about this.", "start": 2642.0, "duration": 2.0}, {"text": "Over and over again you get\nsome cool new drug like Prozac.", "start": 2644.0, "duration": 3.0}, {"text": "It's got no after effects.", "start": 2647.0, "duration": 2.0}, {"text": "It cures the disease like that.", "start": 2649.0, "duration": 2.0}, {"text": "And everybody is better,\nand it's a miracle drug.", "start": 2651.0, "duration": 5.0}, {"text": "Amazingly, by the time, you\nknow, Eli Lilly or whoever's", "start": 2656.0, "duration": 3.0}, {"text": "patent has worn off, it now has\nside effects, doesn't work all", "start": 2659.0, "duration": 3.0}, {"text": "that well, but you want to try\nmy new amazing wonder drug.", "start": 2662.0, "duration": 5.0}, {"text": "So the last few reviews I've\nread of the effectiveness of", "start": 2667.0, "duration": 3.0}, {"text": "antidepressants have been,\nwell, they've been sort of", "start": 2670.0, "duration": 3.0}, {"text": "depressing, actually, that\nthey're not magic bullets.", "start": 2673.0, "duration": 5.0}, {"text": "Now, there are several\nways to treat depression.", "start": 2678.0, "duration": 3.0}, {"text": "And how you treat it depends\n-- there are also several", "start": 2681.0, "duration": 4.0}, {"text": "flavors of depression.", "start": 2685.0, "duration": 3.0}, {"text": "Not all depressions -- well,\ncertainly not all are bipolar.", "start": 2688.0, "duration": 3.0}, {"text": "And there's evidence that they\ndiffer both in their symptoms", "start": 2691.0, "duration": 5.0}, {"text": "and in their neurochemistry.", "start": 2696.0, "duration": 3.0}, {"text": "So for instance, say, I think\nit says on the handout --", "start": 2699.0, "duration": 3.0}, {"text": "yeah, typical versus\natypical depression.", "start": 2702.0, "duration": 3.0}, {"text": "I'm sure if I rummaged around\nI'd remember which was which.", "start": 2705.0, "duration": 4.0}, {"text": "But in some forms of\ndepression, people sleep", "start": 2709.0, "duration": 6.0}, {"text": "too much and eat too much.", "start": 2715.0, "duration": 2.0}, {"text": "In other forms of depression,\nthey sleep too little", "start": 2717.0, "duration": 2.0}, {"text": "and eat too little.", "start": 2719.0, "duration": 3.0}, {"text": "They're both depressions in\nterms of the mood, but they", "start": 2722.0, "duration": 5.0}, {"text": "are clinically distinct and\npsychopharmacologically", "start": 2727.0, "duration": 4.0}, {"text": "distinct.", "start": 2731.0, "duration": 1.0}, {"text": "Actually, bipolar disorders,\nthe treatment of choice for", "start": 2732.0, "duration": 10.0}, {"text": "long before Prozac came\non the scene was of all", "start": 2742.0, "duration": 3.0}, {"text": "things lithium chloride.", "start": 2745.0, "duration": 1.0}, {"text": "It's just the salt of lithium.", "start": 2746.0, "duration": 3.0}, {"text": "You know, just move right\nup from sodium chloride.", "start": 2749.0, "duration": 2.0}, {"text": "Jamison credits lithium with\nkeeping her alive, that if she", "start": 2754.0, "duration": 4.0}, {"text": "had not been put on lithium as\na treatment for her bipolar", "start": 2758.0, "duration": 5.0}, {"text": "disorder, that she thinks she\nprobably would have ended", "start": 2763.0, "duration": 2.0}, {"text": "up committing suicide.", "start": 2765.0, "duration": 2.0}, {"text": "Anybody an expert on\nhow lithium works?", "start": 2767.0, "duration": 4.0}, {"text": "No.\nI think I don't know\nthe answer to this.", "start": 2771.0, "duration": 0.0}, {"text": "I'm not sure it's known.", "start": 2773.0, "duration": 1.0}, {"text": "The last time I checked on it,\nwe didn't know how it worked.", "start": 2774.0, "duration": 2.0}, {"text": "It was -- how was\nit discovered?", "start": 2776.0, "duration": 3.0}, {"text": "It was discovered in\nsome bizarro fashion.", "start": 2779.0, "duration": 3.0}, {"text": "You know, where do\nyou find lithium?", "start": 2782.0, "duration": 4.0}, {"text": "Like a salt -- I'm\nremembering some odd", "start": 2786.0, "duration": 4.0}, {"text": "story about, you know --", "start": 2790.0, "duration": 1.0}, {"text": "AUDIENCE: Batteries?", "start": 2791.0, "duration": 1.0}, {"text": "PROFESSOR: Fine.\nBatteries?", "start": 2792.0, "duration": 0.0}, {"text": "That people -- that's --", "start": 2794.0, "duration": 2.0}, {"text": "AUDIENCE: 7 Up.", "start": 2796.0, "duration": 2.0}, {"text": "PROFESSOR: 7 Up.", "start": 2798.0, "duration": 1.0}, {"text": "OK, if you dissolve your\nbattery in 7 Up, I don't know", "start": 2799.0, "duration": 4.0}, {"text": "what happens but I don't\nimagine it's good because the", "start": 2803.0, "duration": 2.0}, {"text": "mercury and the rest of it\nprobably isn't really", "start": 2805.0, "duration": 1.0}, {"text": "good for you.", "start": 2806.0, "duration": 1.0}, {"text": "The other treatment for -- now,\nsadly not all depressions are", "start": 2810.0, "duration": 10.0}, {"text": "amenable to pharmacology.", "start": 2820.0, "duration": 2.0}, {"text": "Oh, first of all, the big\nmistake, which I think the", "start": 2822.0, "duration": 7.0}, {"text": "insurance people are growing\nout of, was the notion, OK, now", "start": 2829.0, "duration": 5.0}, {"text": "that we've got these cool\npills, we'll pay for the", "start": 2834.0, "duration": 3.0}, {"text": "pills, but that's it.", "start": 2837.0, "duration": 2.0}, {"text": "So if it's going to take you\nseveral weeks for the medicine", "start": 2839.0, "duration": 7.0}, {"text": "to work, it turns out to be\nvery helpful if you're actually", "start": 2846.0, "duration": 3.0}, {"text": "talking to somebody during this\ntime, if there's some", "start": 2849.0, "duration": 3.0}, {"text": "psychotherapy of\nsome sort going on.", "start": 2852.0, "duration": 4.0}, {"text": "Because if you are down here in\nthe depths of the depression", "start": 2856.0, "duration": 2.0}, {"text": "and some genius hands you a\npill and says, \"Go away.", "start": 2858.0, "duration": 3.0}, {"text": "Don't bother me no more.\" You\nknow, if it's true that as", "start": 2861.0, "duration": 4.0}, {"text": "you're slowly coming out of the\ndepression, that's when the", "start": 2865.0, "duration": 2.0}, {"text": "suicides take place, you know,\nthis is a recipe for disaster.", "start": 2867.0, "duration": 4.0}, {"text": "And if it takes a long time to\nwork -- you know, if you take a", "start": 2871.0, "duration": 3.0}, {"text": "medicine and nothing happens\nfor weeks, what do you do?", "start": 2874.0, "duration": 3.0}, {"text": "You stop taking the medicine.", "start": 2877.0, "duration": 2.0}, {"text": "And so what you really need\ntypically as part of a sensible", "start": 2879.0, "duration": 5.0}, {"text": "treatment for a depression is\nnot only somebody who will give", "start": 2884.0, "duration": 4.0}, {"text": "you the medicine, but\nsomebody who will talk", "start": 2888.0, "duration": 1.0}, {"text": "to you about it too.", "start": 2889.0, "duration": 2.0}, {"text": "But even so there are\ndepressions that are not", "start": 2891.0, "duration": 3.0}, {"text": "amenable -- or don't seem\nto respond well to any", "start": 2894.0, "duration": 4.0}, {"text": "of the medicines that\nwe have at the moment.", "start": 2898.0, "duration": 2.0}, {"text": "And under the heading of even\nmore unlikely treatments that", "start": 2900.0, "duration": 4.0}, {"text": "really turn out to work, more\nunlikely than feeding them", "start": 2904.0, "duration": 5.0}, {"text": "lithium salts, is what's\nknown as ECT for", "start": 2909.0, "duration": 4.0}, {"text": "electroconvulsive therapy.", "start": 2913.0, "duration": 2.0}, {"text": "I talked about this a bit when\nwe were talking about memory.", "start": 2915.0, "duration": 3.0}, {"text": "Remember this is little rats.", "start": 2918.0, "duration": 2.0}, {"text": "They step down.", "start": 2920.0, "duration": 1.0}, {"text": "You run electrical current\nthrough their heads.", "start": 2921.0, "duration": 3.0}, {"text": "You shock their little feet.", "start": 2924.0, "duration": 1.0}, {"text": "You run electrical current\nthrough their brains.", "start": 2925.0, "duration": 2.0}, {"text": "They don't remember that you\nshocked their feet, so they", "start": 2927.0, "duration": 1.0}, {"text": "step down again, you know.", "start": 2928.0, "duration": 2.0}, {"text": "Sound familiar?", "start": 2930.0, "duration": 1.0}, {"text": "OK, good.", "start": 2931.0, "duration": 3.0}, {"text": "Well, this is a treatment\nfor depression.", "start": 2934.0, "duration": 3.0}, {"text": "Not abundantly clear why it\nworks, but in my circle of", "start": 2937.0, "duration": 7.0}, {"text": "friends, I have a friend who\nactually went back to --", "start": 2944.0, "duration": 7.0}, {"text": "graduated college, went off,\ndid a whole bunch of stuff,", "start": 2951.0, "duration": 2.0}, {"text": "then went back to med school,\nthen became desperately", "start": 2953.0, "duration": 5.0}, {"text": "clinically depressed and\nhad to be hospitalized.", "start": 2958.0, "duration": 5.0}, {"text": "And what got her through it was\nelectroconvulsive therapy.", "start": 2963.0, "duration": 6.0}, {"text": "Not an entirely\nbenign procedure.", "start": 2969.0, "duration": 4.0}, {"text": "It does have memory\nside effects.", "start": 2973.0, "duration": 3.0}, {"text": "But it used to be that nobody\nin an intro psych class thought", "start": 2976.0, "duration": 3.0}, {"text": "this was a good idea at all\nbecause everybody had seen One", "start": 2979.0, "duration": 2.0}, {"text": "Flew Over the Cuckoo's Nest.", "start": 2981.0, "duration": 2.0}, {"text": "How many people have\nseen that movie?", "start": 2983.0, "duration": 2.0}, {"text": "Oh, so still a fair number\npeople have seen it.", "start": 2985.0, "duration": 2.0}, {"text": "That's a movie that does\nnothing good for the reputation", "start": 2987.0, "duration": 2.0}, {"text": "of electroconvulsive therapy.", "start": 2989.0, "duration": 2.0}, {"text": "Electroconvulsive therapy\nthese days is, you know, you", "start": 2991.0, "duration": 4.0}, {"text": "give somebody a sedative.", "start": 2995.0, "duration": 1.0}, {"text": "They don't thrash around.", "start": 2996.0, "duration": 2.0}, {"text": "They don't hurt themselves.", "start": 2998.0, "duration": 1.0}, {"text": "It still has memory\nconsequences, consolidation of", "start": 2999.0, "duration": 3.0}, {"text": "memory consequences, but it\nreally does seem to", "start": 3002.0, "duration": 2.0}, {"text": "mysteriously break\nup depressions.", "start": 3004.0, "duration": 5.0}, {"text": "Now the latest wrinkle on this,\nyou know, what boils down", "start": 3009.0, "duration": 5.0}, {"text": "to smack-them-up-th\ne-side-of-the-head treatments", "start": 3014.0, "duration": 3.0}, {"text": "of depression is the use of,\nvery new, is the use of", "start": 3017.0, "duration": 4.0}, {"text": "transcranial magnetic\nstimulation, which I think I", "start": 3021.0, "duration": 4.0}, {"text": "also talked about earlier.", "start": 3025.0, "duration": 1.0}, {"text": "But basically what you do is\nyou put a giant electromagnet", "start": 3026.0, "duration": 3.0}, {"text": "or strong electromagnet\nnext to the skull.", "start": 3029.0, "duration": 3.0}, {"text": "You fire a big pulse of -- a\nbig magnetic field that induces", "start": 3032.0, "duration": 5.0}, {"text": "an electrical field locally and\nknocks out neural", "start": 3037.0, "duration": 7.0}, {"text": "activity locally.", "start": 3044.0, "duration": 3.0}, {"text": "And there's some evidence that\nproperly applied, that this is", "start": 3047.0, "duration": 3.0}, {"text": "a sort of a kinder, gentler\nversion of ECT, that it acts", "start": 3050.0, "duration": 6.0}, {"text": "to break up depressions.", "start": 3056.0, "duration": 1.0}, {"text": "I don't -- anybody know if\nthere's a brilliant theory", "start": 3057.0, "duration": 2.0}, {"text": "for how that works?", "start": 3059.0, "duration": 2.0}, {"text": "Uh, who knows?", "start": 3061.0, "duration": 1.0}, {"text": "But it's very new.", "start": 3062.0, "duration": 4.0}, {"text": "But I expect that in a few\nyears, I'll be lecturing", "start": 3066.0, "duration": 4.0}, {"text": "more about that.", "start": 3070.0, "duration": 1.0}, {"text": "Because it, at least initially,\nsounds rather promising.", "start": 3071.0, "duration": 7.0}, {"text": "All right.\nI think this would be a\ngood time to take a break.", "start": 3078.0, "duration": 0.0}, {"text": "Let's take -- unless you're\ntoo depressed to get", "start": 3086.0, "duration": 4.0}, {"text": "up, take a break.", "start": 3090.0, "duration": 1.0}, {"text": "AUDIENCE: I read\nJamison's book.", "start": 3102.0, "duration": 5.0}, {"text": "PROFESSOR: Uh huh.\nWhich one?", "start": 3107.0, "duration": 0.0}, {"text": "AUDIENCE: Prozac Nation.", "start": 3108.0, "duration": 1.0}, {"text": "PROFESSOR: No.", "start": 3109.0, "duration": 1.0}, {"text": "Prozac Nation is\nsomebody else's book.", "start": 3110.0, "duration": 1.0}, {"text": "AUDIENCE: Not Jamison?", "start": 3111.0, "duration": 1.0}, {"text": "PROFESSOR: No, that's\nsomebody else.", "start": 3112.0, "duration": 1.0}, {"text": "I can't remember who wrote\nit, but yes, that's", "start": 3113.0, "duration": 3.0}, {"text": "a cool book, too.", "start": 3116.0, "duration": 1.0}, {"text": "AUDIENCE: Yes.\nThat's what I thought\nyou were talking about.", "start": 3117.0, "duration": 0.0}, {"text": "PROFESSOR: Nope.", "start": 3118.0, "duration": 1.0}, {"text": "Nope.", "start": 3119.0, "duration": 1.0}, {"text": "But you'll come back and\ntell me who wrote it.", "start": 3120.0, "duration": 2.0}, {"text": "Because we're both\nforgetting who wrote it.", "start": 3122.0, "duration": 3.0}, {"text": "AUDIENCE: Have they ever done,\nwhat is it, using sugar pill", "start": 3125.0, "duration": 3.0}, {"text": "and Prozac and hand them out to\npatients and just seeing", "start": 3128.0, "duration": 2.0}, {"text": "if the sugar pill --", "start": 3130.0, "duration": 1.0}, {"text": "PROFESSOR: It's a big problem\nin mental illness in general", "start": 3131.0, "duration": 5.0}, {"text": "and certainly in depression,\nwhich is, particularly if", "start": 3136.0, "duration": 3.0}, {"text": "you've got a cycling\ndepression, who's", "start": 3139.0, "duration": 2.0}, {"text": "going to get better?", "start": 3141.0, "duration": 1.0}, {"text": "Right?\nAnd, yeah, the difference\nbetween placebos and Prozac is,", "start": 3142.0, "duration": 0.0}, {"text": "at least in some of the studies\nthat I've read, a lot less", "start": 3150.0, "duration": 3.0}, {"text": "dramatic than you would think.", "start": 3153.0, "duration": 3.0}, {"text": "And the problem with a\npopulation like us is that", "start": 3156.0, "duration": 5.0}, {"text": "we're too well informed.", "start": 3161.0, "duration": 3.0}, {"text": "Placebos are great.", "start": 3164.0, "duration": 1.0}, {"text": "The side effects are\nreally limited.", "start": 3165.0, "duration": 3.0}, {"text": "In the good old days, your\ndoctor would come around, have", "start": 3168.0, "duration": 3.0}, {"text": "no clue, you know, how to treat\nyou, but give you, you know,", "start": 3171.0, "duration": 4.0}, {"text": "Dr. Hoozy's magic elixir,\nand you'd feel better.", "start": 3175.0, "duration": 6.0}, {"text": "And it's a great pity that now\nif I fed you Dr. Hoozy's", "start": 3181.0, "duration": 3.0}, {"text": "elixir, the first thing you'd\ndo is Google it and discover", "start": 3184.0, "duration": 3.0}, {"text": "that it's snake oil, and\nfeel worse and sue me.", "start": 3187.0, "duration": 3.0}, {"text": "So, yeah, if you turn out to be\nparticularly interested, send", "start": 3190.0, "duration": 7.0}, {"text": "me an email and I can send you\na couple of the references of", "start": 3197.0, "duration": 3.0}, {"text": "things that depressed\nme when I read them.", "start": 3200.0, "duration": 2.0}, {"text": "Because they weren't\nthat much good.", "start": 3202.0, "duration": 3.0}, {"text": "On the other hand, my\nmother absolutely", "start": 3205.0, "duration": 3.0}, {"text": "swears by this stuff.", "start": 3208.0, "duration": 3.0}, {"text": "She's had her own issues\nwith depression and thinks", "start": 3211.0, "duration": 3.0}, {"text": "that Prozac is wonderful.", "start": 3214.0, "duration": 1.0}, {"text": "[PRIVATE CONVERSATION]", "start": 3215.0, "duration": 118.0}, {"text": "PROFESSOR: I want to talk about\na couple of other disease, you", "start": 3333.0, "duration": 5.0}, {"text": "know, mental illness states, in\npart as a way of illustrating", "start": 3338.0, "duration": 8.0}, {"text": "-- I guess what I really want\nto illustrate in the last bit", "start": 3346.0, "duration": 4.0}, {"text": "of this lecture is the, sort\nof, mind and brain links.", "start": 3350.0, "duration": 5.0}, {"text": "We tend to like to make\nup theories that are", "start": 3355.0, "duration": 4.0}, {"text": "one or the other.", "start": 3359.0, "duration": 1.0}, {"text": "And the current popular trend\nis towards brain explanations.", "start": 3360.0, "duration": 4.0}, {"text": "Oh, you're depressed because\nyou don't have enough", "start": 3364.0, "duration": 4.0}, {"text": "serotonin happening for you.", "start": 3368.0, "duration": 2.0}, {"text": "We'll boost up your serotonin.", "start": 3370.0, "duration": 1.0}, {"text": "You'll be fine.", "start": 3371.0, "duration": 1.0}, {"text": "It's a very brain\nkind of thing.", "start": 3372.0, "duration": 2.0}, {"text": "Freudian theories were very\nmind kinds of things.", "start": 3374.0, "duration": 3.0}, {"text": "But there's a number of cases\nthat really illustrate, I", "start": 3377.0, "duration": 5.0}, {"text": "think, well, what you sort\nof know intuitively, right?", "start": 3382.0, "duration": 6.0}, {"text": "The brain isn't here\nand the mind is here.", "start": 3388.0, "duration": 3.0}, {"text": "It's, you know, waves\nand particles.", "start": 3391.0, "duration": 2.0}, {"text": "They're two manifestations\nof the same thing.", "start": 3393.0, "duration": 3.0}, {"text": "And brain stuff and mind\nstuff bounce back and", "start": 3396.0, "duration": 3.0}, {"text": "forth here all the time.", "start": 3399.0, "duration": 2.0}, {"text": "So let's think, for\nexample, of panic attacks.", "start": 3401.0, "duration": 5.0}, {"text": "Which I didn't put on the\nhandout at all, I see, but I", "start": 3406.0, "duration": 3.0}, {"text": "suddenly developed a need to\ntalk about because I", "start": 3409.0, "duration": 3.0}, {"text": "was feeling really\nanxious and -- no.", "start": 3412.0, "duration": 6.0}, {"text": "So panic attack is this feeling\nof anxiety out of the blue.", "start": 3418.0, "duration": 6.0}, {"text": "People report that they just\nsuddenly feel very, very,", "start": 3428.0, "duration": 2.0}, {"text": "very fearful and anxious.", "start": 3430.0, "duration": 3.0}, {"text": "And it's scary and it's\nunpleasant and so on.", "start": 3433.0, "duration": 4.0}, {"text": "You may recall that Freud and\nhis followers had a perfectly", "start": 3437.0, "duration": 4.0}, {"text": "nice notion about this, which\nwas that anxiety was warning", "start": 3441.0, "duration": 4.0}, {"text": "you that you were about to\ntread on the super ego.", "start": 3445.0, "duration": 5.0}, {"text": "And it was the warning sign\nof the ego that was saying,", "start": 3450.0, "duration": 4.0}, {"text": "don't go and do that.", "start": 3454.0, "duration": 1.0}, {"text": "But that hasn't\nworked that well.", "start": 3455.0, "duration": 4.0}, {"text": "More modern notions tend to\nfocus on the idea that it's", "start": 3459.0, "duration": 5.0}, {"text": "essentially neurochemical.", "start": 3464.0, "duration": 2.0}, {"text": "You get too much of some\njuice, some neurotransmitter.", "start": 3469.0, "duration": 5.0}, {"text": "It fires off the bits of your\nbrain that are responsible for", "start": 3474.0, "duration": 3.0}, {"text": "the experience of anxiety.", "start": 3477.0, "duration": 2.0}, {"text": "And you feel this anxiety.", "start": 3479.0, "duration": 3.0}, {"text": "And this is a lovely case\nof looping back to a prior", "start": 3482.0, "duration": 5.0}, {"text": "mode of understanding.", "start": 3487.0, "duration": 3.0}, {"text": "The notion that you feel too\nanxious because you have too", "start": 3490.0, "duration": 3.0}, {"text": "much of this fluid, it's an\nawful lot like the notion that", "start": 3493.0, "duration": 3.0}, {"text": "you feel melancholic because\nyou have too much black bile.", "start": 3496.0, "duration": 4.0}, {"text": "The difference of course is\nthat we think we've got", "start": 3500.0, "duration": 2.0}, {"text": "a better scientific\ngrounding than we had.", "start": 3502.0, "duration": 1.0}, {"text": "But the form of the argument\nis rather similar.", "start": 3503.0, "duration": 6.0}, {"text": "So is it the case that panic\nattacks, the clinical condition", "start": 3509.0, "duration": 4.0}, {"text": "of a panic attack, is just\ntoo much of some juice.", "start": 3513.0, "duration": 6.0}, {"text": "It's possible to think about\nit as being somewhat more", "start": 3519.0, "duration": 4.0}, {"text": "complicated than that.", "start": 3523.0, "duration": 2.0}, {"text": "And, well, I didn't put that\nreference on the handout,", "start": 3525.0, "duration": 2.0}, {"text": "because I didn't.", "start": 3527.0, "duration": 1.0}, {"text": "But I'm stealing a story from\n-- who am I stealing it from?", "start": 3528.0, "duration": 6.0}, {"text": "Oh, Dave Barlow,\nwho's over at BU.", "start": 3534.0, "duration": 6.0}, {"text": "This is a three-step\nroute into panic attack.", "start": 3540.0, "duration": 5.0}, {"text": "And the first part of it is\nthat you feel the visible", "start": 3545.0, "duration": 7.0}, {"text": "symptoms of anxiety.", "start": 3552.0, "duration": 3.0}, {"text": "Your heart starts -- remember\nthe shaky bridge experiment", "start": 3555.0, "duration": 7.0}, {"text": "all about misattribution\nof arousal?", "start": 3562.0, "duration": 3.0}, {"text": "You're feeling \"ooh-ooh-ooh\"\nand you see her, and you just", "start": 3565.0, "duration": 3.0}, {"text": "think you're feeling\n\"aah.\" Right?", "start": 3568.0, "duration": 3.0}, {"text": "So that can work in\nall sorts of ways.", "start": 3571.0, "duration": 3.0}, {"text": "Suppose that your heart is\ngoing through -- there are a", "start": 3574.0, "duration": 4.0}, {"text": "variety of things that cause\nyour heart to go pitter-pat.", "start": 3578.0, "duration": 3.0}, {"text": "Suppose that you get these sort\nof symptoms and you don't", "start": 3581.0, "duration": 5.0}, {"text": "interpret it as love, you\ninterpret it as \"I feel", "start": 3586.0, "duration": 4.0}, {"text": "nervous about something.", "start": 3590.0, "duration": 2.0}, {"text": "I can't quite tell\nexactly what it is.", "start": 3592.0, "duration": 3.0}, {"text": "But I don't --\"", "start": 3595.0, "duration": 1.0}, {"text": "People don't have panic\nattacks, by the way,", "start": 3596.0, "duration": 2.0}, {"text": "typically, when they're\nexercising vigorously.", "start": 3598.0, "duration": 4.0}, {"text": "Because they've got a good\naccount of where that", "start": 3602.0, "duration": 2.0}, {"text": "symptom is coming from.", "start": 3604.0, "duration": 1.0}, {"text": "Your heart's pounding, you're\nsweating, and stuff like that.", "start": 3605.0, "duration": 3.0}, {"text": "Yeah, all right, fine.", "start": 3608.0, "duration": 1.0}, {"text": "If you're walking down the\nstreet and your heart is", "start": 3609.0, "duration": 2.0}, {"text": "pounding and you're sweating,\nyou need a different", "start": 3611.0, "duration": 4.0}, {"text": "interpretation.", "start": 3615.0, "duration": 1.0}, {"text": "Now, this is unpleasant.", "start": 3616.0, "duration": 3.0}, {"text": "So you develop, flipping back\nto an earlier piece of the", "start": 3619.0, "duration": 4.0}, {"text": "course, you develop a\nconditioned fear of", "start": 3623.0, "duration": 4.0}, {"text": "these symptoms.", "start": 3627.0, "duration": 2.0}, {"text": "So you start avoiding\nsituations that would produce", "start": 3629.0, "duration": 9.0}, {"text": "the symptoms, or that you think\nmight produce these symptoms.", "start": 3638.0, "duration": 5.0}, {"text": "And this can be quite\nunconscious, right?", "start": 3643.0, "duration": 3.0}, {"text": "This is good classical\nassociation learning or", "start": 3646.0, "duration": 3.0}, {"text": "something of that sort.", "start": 3649.0, "duration": 3.0}, {"text": "And that in turn -- that's sort\nof step two, is sort of a", "start": 3652.0, "duration": 3.0}, {"text": "learning story that is going to\ncause you to start -- you're", "start": 3655.0, "duration": 9.0}, {"text": "going to act to avoid\nsituations that make", "start": 3664.0, "duration": 3.0}, {"text": "you feel nervous.", "start": 3667.0, "duration": 3.0}, {"text": "But, all right,\nremember Pavlov?", "start": 3670.0, "duration": 5.0}, {"text": "Bell, tone.", "start": 3675.0, "duration": 1.0}, {"text": "Bell, tone.", "start": 3676.0, "duration": 1.0}, {"text": "Bell, tone.", "start": 3677.0, "duration": 1.0}, {"text": "Now I ring the bell by itself.", "start": 3678.0, "duration": 1.0}, {"text": "No.", "start": 3679.0, "duration": 1.0}, {"text": "Bell, tone.\nThat's stupid.", "start": 3680.0, "duration": 0.0}, {"text": "I'm not supposed to be the one\nwho notices that first, guys.", "start": 3683.0, "duration": 3.0}, {"text": "You're supposed to --\n\"What's he talking about?\"", "start": 3686.0, "duration": 1.0}, {"text": "Anyway, bell, food.", "start": 3687.0, "duration": 1.0}, {"text": "Bell, food.", "start": 3688.0, "duration": 1.0}, {"text": "Bell, food.", "start": 3689.0, "duration": 1.0}, {"text": "Eventually the bell by\nitself produces salivation.", "start": 3690.0, "duration": 2.0}, {"text": "So you make this association\nin your own mind.", "start": 3692.0, "duration": 5.0}, {"text": "So when did this happen to me?", "start": 3697.0, "duration": 3.0}, {"text": "I was outside.", "start": 3700.0, "duration": 2.0}, {"text": "OK.", "start": 3702.0, "duration": 1.0}, {"text": "So now I'm outside, it\ndoesn't happen to me.", "start": 3703.0, "duration": 4.0}, {"text": "But I feel -- I get the\nconditioned response in effect.", "start": 3707.0, "duration": 4.0}, {"text": "So now something else acts\nas a trigger for the panic.", "start": 3711.0, "duration": 4.0}, {"text": "The initial feeling of panic\nmight have been, I don't", "start": 3715.0, "duration": 3.0}, {"text": "know, too many bottles\nof Mountain Dew, right.", "start": 3718.0, "duration": 5.0}, {"text": "You drink enough caffeine,\nand you'll get b-b-b-b.", "start": 3723.0, "duration": 3.0}, {"text": "Forget that you drank -- your\nbrain doesn't remember the", "start": 3726.0, "duration": 2.0}, {"text": "caffeine part of the story.", "start": 3728.0, "duration": 2.0}, {"text": "And you're going b-b-b-b.", "start": 3730.0, "duration": 1.0}, {"text": "And you say, \"Oh!", "start": 3731.0, "duration": 1.0}, {"text": "I'm having a panic attack.\"\nThen you don't want that --", "start": 3732.0, "duration": 5.0}, {"text": "this is an aversive event.", "start": 3737.0, "duration": 3.0}, {"text": "It's just like the business of\nthe rat stepping down, right?", "start": 3740.0, "duration": 3.0}, {"text": "The rat steps down\n-- oh, all right.", "start": 3743.0, "duration": 4.0}, {"text": "Rat's up here, rat steps down,\ngets his little feet shocked.", "start": 3747.0, "duration": 4.0}, {"text": "That's unpleasant.", "start": 3751.0, "duration": 1.0}, {"text": "Rat's put back up here.", "start": 3752.0, "duration": 2.0}, {"text": "Does the rat step down again?", "start": 3754.0, "duration": 1.0}, {"text": "No.", "start": 3755.0, "duration": 1.0}, {"text": "Why?\nBecause he's got this\nanticipatory fear.", "start": 3756.0, "duration": 0.0}, {"text": "You can actually measure\nthe fear physiologically.", "start": 3758.0, "duration": 3.0}, {"text": "All right, so you caffeine\noverdose or whatever.", "start": 3761.0, "duration": 4.0}, {"text": "You have this\nunpleasant experience.", "start": 3765.0, "duration": 2.0}, {"text": "Now you're in that environment\nagain sometime later and you", "start": 3767.0, "duration": 3.0}, {"text": "have the experience again\nbecause it's a conditioned", "start": 3770.0, "duration": 3.0}, {"text": "response now, no\ncaffeine involved.", "start": 3773.0, "duration": 3.0}, {"text": "You come to the reasonable, if\nperhaps unconscious, conclusion", "start": 3776.0, "duration": 5.0}, {"text": "that what makes me nervous is\nbeing outside in public", "start": 3781.0, "duration": 7.0}, {"text": "or being on shaky\nbridges or whatever.", "start": 3788.0, "duration": 2.0}, {"text": "Then you get step three, which\nis again learning theory kind", "start": 3790.0, "duration": 3.0}, {"text": "of stuff like Thorndike's\nLaw of Effect.", "start": 3793.0, "duration": 2.0}, {"text": "You start doing things to\navoid this punishment, right.", "start": 3795.0, "duration": 7.0}, {"text": "You're going to avoid\nthe aversive stimulus.", "start": 3802.0, "duration": 3.0}, {"text": "So you can get secondary\nsymptoms to the panic, like a", "start": 3805.0, "duration": 4.0}, {"text": "fear of open spaces, let's say,\nbecause you've now, perhaps", "start": 3809.0, "duration": 7.0}, {"text": "completely unconsciously,\nconcluded, \"If I go out in", "start": 3816.0, "duration": 3.0}, {"text": "public, the sky is so big.", "start": 3819.0, "duration": 2.0}, {"text": "I feel so small.", "start": 3821.0, "duration": 1.0}, {"text": "I get panicky.", "start": 3822.0, "duration": 2.0}, {"text": "And so now I'm not\ngoing to go outside.\"", "start": 3824.0, "duration": 2.0}, {"text": "And so what you end up with is\nthe possibility that the", "start": 3826.0, "duration": 4.0}, {"text": "clinical thing that you see,\nwhat you get in your office if", "start": 3830.0, "duration": 3.0}, {"text": "you're the clinician, is\nsomebody who says, \"I have, you", "start": 3833.0, "duration": 4.0}, {"text": "know, I have uncontrollable\npanic when I'm outdoors.", "start": 3837.0, "duration": 3.0}, {"text": "This is crippling my life\nbecause I don't go out", "start": 3840.0, "duration": 3.0}, {"text": "anymore.\" And what this may be\nis a cascade of events coming", "start": 3843.0, "duration": 4.0}, {"text": "from some sort of an initial\nphysiological issue that you", "start": 3847.0, "duration": 4.0}, {"text": "then learned about, if you\nlike, using the laws of animal", "start": 3851.0, "duration": 4.0}, {"text": "learning, in ways that\nthat don't work well.", "start": 3855.0, "duration": 5.0}, {"text": "Well, what are you\ngoing to do about it?", "start": 3860.0, "duration": 2.0}, {"text": "Well, one thing you might do\nabout it if you believed that", "start": 3862.0, "duration": 2.0}, {"text": "there was a significant\nlearning component here is to", "start": 3864.0, "duration": 4.0}, {"text": "use learning theory kinds\nof things to treat it.", "start": 3868.0, "duration": 4.0}, {"text": "Now if it turns out that there\nreally is a chemical imbalance", "start": 3872.0, "duration": 4.0}, {"text": "and every time the chemicals\ngo out of whack, you feel", "start": 3876.0, "duration": 3.0}, {"text": "panicked, you might want to do\nsomething about the chemicals.", "start": 3879.0, "duration": 2.0}, {"text": "But if you've got one of these\nsituations where the person has", "start": 3881.0, "duration": 3.0}, {"text": "basically scared themselves\ninto maladaptive behavior,", "start": 3884.0, "duration": 5.0}, {"text": "you've now got to\nun-scare them.", "start": 3889.0, "duration": 3.0}, {"text": "So what are you going to do?", "start": 3892.0, "duration": 1.0}, {"text": "One of the standard techniques\nfor these sort of disorders", "start": 3893.0, "duration": 3.0}, {"text": "would be desensitization\nmethods.", "start": 3896.0, "duration": 3.0}, {"text": "Is it Barlow who\nwas doing this?", "start": 3899.0, "duration": 2.0}, {"text": "So one of the versions --\nyou can imagine -- I did a", "start": 3904.0, "duration": 3.0}, {"text": "version where you became\nscared of the outside.", "start": 3907.0, "duration": 2.0}, {"text": "Another version is you have a\npanic attack in an enclosed", "start": 3909.0, "duration": 4.0}, {"text": "space and you become very\nnervous about enclosed spaces.", "start": 3913.0, "duration": 2.0}, {"text": "You won't go into elevators\nand stuff like that.", "start": 3915.0, "duration": 3.0}, {"text": "I can't remember if it was\nBarlow -- I got a feeling it", "start": 3918.0, "duration": 4.0}, {"text": "was -- whose technique for --\nthere are a variety of ways of", "start": 3922.0, "duration": 5.0}, {"text": "using learning theory\nto get around this.", "start": 3927.0, "duration": 3.0}, {"text": "One is the kinder, gentler one.", "start": 3930.0, "duration": 2.0}, {"text": "So you come to me.", "start": 3932.0, "duration": 2.0}, {"text": "You say, \"I'm really afraid of\nbeing in enclosed spaces.\"", "start": 3934.0, "duration": 3.0}, {"text": "You say, \"OK\" -- the first cure\nout in this field that you've", "start": 3937.0, "duration": 6.0}, {"text": "come to, that I'm using for my\ndoctor's office at the", "start": 3943.0, "duration": 3.0}, {"text": "moment -- \"Imagine that\nyou're in a space.", "start": 3946.0, "duration": 3.0}, {"text": "Can you deal with that?\"", "start": 3949.0, "duration": 1.0}, {"text": "\"Oh, it's making me nervous,\nbut, yeah, OK, I can", "start": 3950.0, "duration": 2.0}, {"text": "deal with that.\"", "start": 3952.0, "duration": 1.0}, {"text": "\"OK, now we'll go to 10-250.", "start": 3953.0, "duration": 2.0}, {"text": "It's a big enclosed space.", "start": 3955.0, "duration": 2.0}, {"text": "And then we'll go to a smaller\nroom and a smaller room.", "start": 3957.0, "duration": 2.0}, {"text": "And eventually we'll put you\nin a closet for a while.", "start": 3959.0, "duration": 5.0}, {"text": "And you'll discover -- what\nyou'll do is un-learn", "start": 3964.0, "duration": 2.0}, {"text": "the response, in effect.", "start": 3966.0, "duration": 2.0}, {"text": "You'll learn nothing\nbad happened to me.\"", "start": 3968.0, "duration": 4.0}, {"text": "And this behaviorist sort of\ntherapy does work to break up", "start": 3972.0, "duration": 6.0}, {"text": "these sorts of behaviors\nin many cases.", "start": 3978.0, "duration": 3.0}, {"text": "I think it's Barlow who has\nbeen advocating a much less", "start": 3981.0, "duration": 4.0}, {"text": "kinder, gentler version,\nwhich is to shut", "start": 3985.0, "duration": 2.0}, {"text": "people in car trunks.", "start": 3987.0, "duration": 2.0}, {"text": "So none of this business\nof doing it gradually.", "start": 3992.0, "duration": 2.0}, {"text": "This is known in the\ntrade as flooding.", "start": 3994.0, "duration": 3.0}, {"text": "You just take the -- the guy\nsays, \"You know, I think if", "start": 3997.0, "duration": 4.0}, {"text": "I'm in an enclosed space,\nI'm going to die.\"", "start": 4001.0, "duration": 4.0}, {"text": "\"All right.", "start": 4005.0, "duration": 1.0}, {"text": "Boom.\nYou dead yet?", "start": 4006.0, "duration": 0.0}, {"text": "No.\nOK.", "start": 4008.0, "duration": 0.0}, {"text": "You're cured.", "start": 4009.0, "duration": 1.0}, {"text": "Out.\"\nGood.\nWell, it's not quite that\nsimple, but the basic idea is", "start": 4010.0, "duration": 0.0}, {"text": "that if you have a patient who\ncan actually deal with this,", "start": 4013.0, "duration": 5.0}, {"text": "that you can basically speed up\nthe therapy rather dramatically", "start": 4018.0, "duration": 4.0}, {"text": "by not moving gradually to --\nthis is used for all", "start": 4022.0, "duration": 4.0}, {"text": "sorts of phobias.", "start": 4026.0, "duration": 2.0}, {"text": "So, scared of snakes, you\nknow, you're pathologically", "start": 4028.0, "duration": 5.0}, {"text": "scared of snakes.", "start": 4033.0, "duration": 1.0}, {"text": "OK, what we'll do is first\nwe'll show you -- so the two", "start": 4034.0, "duration": 5.0}, {"text": "versions are desensitization\nand flooding.", "start": 4039.0, "duration": 2.0}, {"text": "The desensitization\nstory would be:", "start": 4041.0, "duration": 3.0}, {"text": "\"We'll show you\npictures of snakes.\"", "start": 4044.0, "duration": 1.0}, {"text": "\"Ooh, I hate it.", "start": 4045.0, "duration": 2.0}, {"text": "\"No.\"\n\"Are you dead?\"\nI hate it.\"\n\"Oh, OK.\" So now we'll go\nto the zoo. \"And see that", "start": 4047.0, "duration": 0.0}, {"text": "snake cage way over there?", "start": 4053.0, "duration": 1.0}, {"text": "Are you dead yet?\"\n\"No.\"", "start": 4054.0, "duration": 0.0}, {"text": "\"OK, let's get closer.", "start": 4055.0, "duration": 1.0}, {"text": "OK, that's a snake, right.", "start": 4056.0, "duration": 1.0}, {"text": "OK, now you're going\nto get in with him.", "start": 4057.0, "duration": 1.0}, {"text": "Yeah.\"", "start": 4058.0, "duration": 1.0}, {"text": "\"Aah.\"\nAll right.", "start": 4059.0, "duration": 0.0}, {"text": "\"But I'm not dead.\"", "start": 4060.0, "duration": 2.0}, {"text": "And the flooding technique is\n\"You're afraid of snakes?", "start": 4062.0, "duration": 3.0}, {"text": "Boom.", "start": 4065.0, "duration": 2.0}, {"text": "See those boas?", "start": 4067.0, "duration": 2.0}, {"text": "Are you dead?\"\n\"Yes, actually.\"", "start": 4069.0, "duration": 0.0}, {"text": "[LAUGHTER FROM AUDIENCE]", "start": 4070.0, "duration": 4.0}, {"text": "So, anyway, the point from the\npanic attack example is that", "start": 4074.0, "duration": 8.0}, {"text": "it's possible that what you're\nseeing as the clinical entity", "start": 4082.0, "duration": 4.0}, {"text": "is a dance between physiology\nand learning, in effect, and", "start": 4086.0, "duration": 7.0}, {"text": "that what you learn -- and\nthat a mode of treatment", "start": 4093.0, "duration": 3.0}, {"text": "would be to unlearn.", "start": 4096.0, "duration": 3.0}, {"text": "Now, let's take another example\nwhich I did put on the", "start": 4099.0, "duration": 3.0}, {"text": "handout, which is obsessive\ncompulsive disorders.", "start": 4102.0, "duration": 2.0}, {"text": "Obsessive compulsive disorders\nare, well, there's the", "start": 4107.0, "duration": 5.0}, {"text": "obsessive part and there's\nthe compulsive part.", "start": 4112.0, "duration": 5.0}, {"text": "The obsessive part refers\nto obsessive thoughts.", "start": 4117.0, "duration": 5.0}, {"text": "What gets you into treatment\nis not some sort of obsessive", "start": 4122.0, "duration": 6.0}, {"text": "thought that \"I love him.", "start": 4128.0, "duration": 3.0}, {"text": "I really love him.", "start": 4131.0, "duration": 1.0}, {"text": "Oh, I love him a lot.", "start": 4132.0, "duration": 1.0}, {"text": "Oh yeah, yeah, yeah.", "start": 4133.0, "duration": 1.0}, {"text": "I can't help but think about\nhim.\" Yeah, it's a little", "start": 4134.0, "duration": 2.0}, {"text": "obsessive, but tough.", "start": 4136.0, "duration": 2.0}, {"text": "It's \"Every time I look at him,\nI want to rip his guts out.", "start": 4138.0, "duration": 5.0}, {"text": "I'm imagining the knife.\"\nYou know, or something.", "start": 4143.0, "duration": 4.0}, {"text": "It's disturbing thoughts\nthat somehow won't get", "start": 4147.0, "duration": 3.0}, {"text": "out of your brain.", "start": 4150.0, "duration": 1.0}, {"text": "That's the sort of obsession\nthat people seek treatment for.", "start": 4151.0, "duration": 5.0}, {"text": "And compulsive behaviors are\nbehaviors where -- everybody", "start": 4156.0, "duration": 6.0}, {"text": "has some degree of this.", "start": 4162.0, "duration": 1.0}, {"text": "How many people here have left\ntheir room, gotten halfway down", "start": 4163.0, "duration": 6.0}, {"text": "the hall, said \"Did I really\nlock it?\", and gone", "start": 4169.0, "duration": 4.0}, {"text": "back to check?", "start": 4173.0, "duration": 2.0}, {"text": "Everybody does that sometime.", "start": 4175.0, "duration": 2.0}, {"text": "Or did I turn the stove off\nor something like that.", "start": 4177.0, "duration": 4.0}, {"text": "That's normal on\ncompulsion land.", "start": 4181.0, "duration": 4.0}, {"text": "And almost always you\nhave locked it, right?", "start": 4185.0, "duration": 3.0}, {"text": "Because the time you didn't\nlock it is the time you don't", "start": 4188.0, "duration": 3.0}, {"text": "go back to check, and somebody\nsteals all your stuff.", "start": 4191.0, "duration": 4.0}, {"text": "Very annoying.", "start": 4195.0, "duration": 1.0}, {"text": "I donated a laptop to\nthe criminal elements", "start": 4196.0, "duration": 3.0}, {"text": "doing exactly that.", "start": 4199.0, "duration": 1.0}, {"text": "Very annoying.", "start": 4200.0, "duration": 1.0}, {"text": "But anyway, if you have to\ngo and, you know, get down", "start": 4201.0, "duration": 8.0}, {"text": "the hall, \"Did I lock it?", "start": 4209.0, "duration": 3.0}, {"text": "Yep, it's locked.", "start": 4212.0, "duration": 2.0}, {"text": "Did I lock it?\" You've got to\ndo that forty or fifty times", "start": 4214.0, "duration": 5.0}, {"text": "and you can't get on with\nyour life, literally.", "start": 4219.0, "duration": 3.0}, {"text": "You can't get to the next\nevent in your life.", "start": 4222.0, "duration": 3.0}, {"text": "That's a compulsion that is\nlikely to lead you to want", "start": 4225.0, "duration": 4.0}, {"text": "to do something about it.", "start": 4229.0, "duration": 2.0}, {"text": "It's interesting that these are\ncompulsions -- rather like", "start": 4231.0, "duration": 5.0}, {"text": "there are similarities in\npeople's narrative dreams --", "start": 4236.0, "duration": 3.0}, {"text": "that compulsions seem to be\ndrawn from a limited vocabulary", "start": 4239.0, "duration": 7.0}, {"text": "of candidate compulsions.", "start": 4246.0, "duration": 1.0}, {"text": "I mean, I'm sure there's one\nof everything out there,", "start": 4247.0, "duration": 2.0}, {"text": "but there's lots of\nhand washers, right.", "start": 4249.0, "duration": 5.0}, {"text": "Actually, I can see my\nhands are covered in", "start": 4254.0, "duration": 2.0}, {"text": "chalk at the moment.", "start": 4256.0, "duration": 1.0}, {"text": "I should go wash them.", "start": 4257.0, "duration": 1.0}, {"text": "But, you know, why do\nyou wash your hands?", "start": 4258.0, "duration": 1.0}, {"text": "Because your mother said\nso, right, and because", "start": 4263.0, "duration": 2.0}, {"text": "there's germs on them.", "start": 4265.0, "duration": 1.0}, {"text": "Can you see the germs?", "start": 4266.0, "duration": 3.0}, {"text": "No.", "start": 4269.0, "duration": 1.0}, {"text": "So you got to do the act\nand convince yourself", "start": 4270.0, "duration": 3.0}, {"text": "that you've done it.", "start": 4273.0, "duration": 1.0}, {"text": "OK, hands are clean.", "start": 4277.0, "duration": 1.0}, {"text": "Are they really clean?", "start": 4278.0, "duration": 3.0}, {"text": "I can't tell because there\nmight be germs there.", "start": 4281.0, "duration": 3.0}, {"text": "I'm going to get sick.\nI'll wash them again.", "start": 4284.0, "duration": 0.0}, {"text": "If you have to do this so often\nthat your hands are getting", "start": 4285.0, "duration": 3.0}, {"text": "red and raw, that's a\ncompulsion of some sort.", "start": 4288.0, "duration": 8.0}, {"text": "Now, you can treat OCD, as\nit's known in the trade, in", "start": 4296.0, "duration": 5.0}, {"text": "a number of different ways.", "start": 4301.0, "duration": 1.0}, {"text": "It turns out, for example,\nthat Prozac is good against", "start": 4302.0, "duration": 6.0}, {"text": "obsessive compulsive disorders.", "start": 4308.0, "duration": 1.0}, {"text": "It breaks up the obsession, you\nknow, the obsessive quality", "start": 4309.0, "duration": 4.0}, {"text": "here of this sort of thought\nthat doesn't quite", "start": 4313.0, "duration": 4.0}, {"text": "work for you.", "start": 4317.0, "duration": 1.0}, {"text": "You can imagine that you've got\nsome little circuit in the", "start": 4318.0, "duration": 3.0}, {"text": "brain somewhere that's\na little checker.", "start": 4321.0, "duration": 4.0}, {"text": "You know, did I do what\nI was supposed to do?", "start": 4325.0, "duration": 3.0}, {"text": "And if that goes a little wacko\non you, that that's got too", "start": 4328.0, "duration": 3.0}, {"text": "much serotonin or too little\nserotonin, I suppose, or", "start": 4331.0, "duration": 3.0}, {"text": "whatever, you know, you might\nend up in a sort of an infinite", "start": 4334.0, "duration": 3.0}, {"text": "loop where, \"Got to check.", "start": 4337.0, "duration": 1.0}, {"text": "Got to check.", "start": 4338.0, "duration": 1.0}, {"text": "Got to check.", "start": 4339.0, "duration": 1.0}, {"text": "Got to check.\" And something\nchemical that gives", "start": 4340.0, "duration": 3.0}, {"text": "it a kick will help.", "start": 4343.0, "duration": 3.0}, {"text": "OK.", "start": 4346.0, "duration": 1.0}, {"text": "You can treat it that way.", "start": 4347.0, "duration": 1.0}, {"text": "You can also treat it using\nthe same sort of behavioral", "start": 4348.0, "duration": 4.0}, {"text": "techniques that I was just\ntalking about for phobias.", "start": 4352.0, "duration": 3.0}, {"text": "So let's do it for\nhand washing.", "start": 4355.0, "duration": 3.0}, {"text": "All right, Patient So and So,\nwhy do you have to wash? \"Well,", "start": 4358.0, "duration": 3.0}, {"text": "I'm just really concerned\nthat my hands are dirty.", "start": 4361.0, "duration": 4.0}, {"text": "When I get dirt on my hands,\nI get all excited and", "start": 4368.0, "duration": 4.0}, {"text": "[NERVOUS SOUND].\" Right.", "start": 4372.0, "duration": 2.0}, {"text": "All right.\nSo we can do the densitization\nbusiness or we can do", "start": 4374.0, "duration": 0.0}, {"text": "the flooding business.", "start": 4377.0, "duration": 1.0}, {"text": "In the interests of time,\nwe'll do flooding.", "start": 4378.0, "duration": 2.0}, {"text": "\"All right.", "start": 4380.0, "duration": 1.0}, {"text": "See this?\nThis is dirt.", "start": 4381.0, "duration": 0.0}, {"text": "Put your hands in it.\"\nRight. \"Are you dead yet?\"", "start": 4382.0, "duration": 4.0}, {"text": "\"No.\"", "start": 4386.0, "duration": 1.0}, {"text": "\"All right.\nHow long can you\nleave them there?\"", "start": 4387.0, "duration": 0.0}, {"text": "And you can basically\ndesensitize this feeling", "start": 4391.0, "duration": 4.0}, {"text": "of deep anxiety about\nnot cleaning your hands.", "start": 4395.0, "duration": 5.0}, {"text": "All right.\nSo that's mildly interesting.", "start": 4400.0, "duration": 0.0}, {"text": "What's interesting, the reason\nfor raising this question or", "start": 4403.0, "duration": 7.0}, {"text": "this example, comes from this\nnice article, now more than", "start": 4410.0, "duration": 5.0}, {"text": "a decade old, by Baxter.", "start": 4415.0, "duration": 2.0}, {"text": "You can see obsessive\ncompulsive states", "start": 4417.0, "duration": 7.0}, {"text": "in brain imaging.", "start": 4424.0, "duration": 3.0}, {"text": "There are little bits of brain\nspecifically in the caudate.", "start": 4427.0, "duration": 3.0}, {"text": "It doesn't particularly\nmatter for present purposes", "start": 4430.0, "duration": 3.0}, {"text": "where that might be.", "start": 4433.0, "duration": 1.0}, {"text": "But it's overactive.", "start": 4434.0, "duration": 3.0}, {"text": "You look at the brain of an\nobsessive compulsive sort, and", "start": 4437.0, "duration": 3.0}, {"text": "this little chunk of brain\nis busy, you know,", "start": 4440.0, "duration": 3.0}, {"text": "just going nuts.", "start": 4443.0, "duration": 2.0}, {"text": "If you give the patients\nProzac, that chunk of brain now", "start": 4445.0, "duration": 5.0}, {"text": "doesn't look weird anymore.", "start": 4450.0, "duration": 3.0}, {"text": "It comes into the normal range.", "start": 4453.0, "duration": 2.0}, {"text": "If you'd go and do behavioral\ntherapy on a patient with the", "start": 4455.0, "duration": 5.0}, {"text": "same story, the same piece of\nbrain comes to look normal.", "start": 4460.0, "duration": 5.0}, {"text": "The point here is that you can\nreach this chunk of the brain,", "start": 4465.0, "duration": 4.0}, {"text": "if you like, either through the\nbrain sort of neurochemical", "start": 4469.0, "duration": 3.0}, {"text": "route, or through the\npsych behavioral route.", "start": 4472.0, "duration": 4.0}, {"text": "They're not necessarily either\nmutually exclusive or, you", "start": 4476.0, "duration": 4.0}, {"text": "know, one works and the other\ndoesn't or something like that.", "start": 4480.0, "duration": 4.0}, {"text": "This is a case where you can\nget to the source of the", "start": 4484.0, "duration": 3.0}, {"text": "problem, at least in a\nneurolocalization", "start": 4487.0, "duration": 4.0}, {"text": "kind of a way.", "start": 4491.0, "duration": 1.0}, {"text": "You can get to the source\nof the problem through", "start": 4492.0, "duration": 2.0}, {"text": "either of these routes.", "start": 4494.0, "duration": 3.0}, {"text": "And I suppose the bottom line\nhere is that in disorder after", "start": 4500.0, "duration": 6.0}, {"text": "disorder, what you find is that\nthere isn't just one way of", "start": 4506.0, "duration": 6.0}, {"text": "treating -- one problem is\nthat in most mental illness", "start": 4512.0, "duration": 5.0}, {"text": "situations, there isn't one\nmagic bullet treatment that", "start": 4517.0, "duration": 4.0}, {"text": "automatically works for you.", "start": 4521.0, "duration": 2.0}, {"text": "And then in many of these\ncases, there are both brain", "start": 4523.0, "duration": 4.0}, {"text": "and mind routes to therapy.", "start": 4527.0, "duration": 4.0}, {"text": "So when you're asking -- when\nyou have like these patients we", "start": 4531.0, "duration": 5.0}, {"text": "were cooking up, when you have\na particular patient, there's a", "start": 4536.0, "duration": 6.0}, {"text": "spectrum of choices that might\npotentially be of some use.", "start": 4542.0, "duration": 6.0}, {"text": "It says on the handout, \"What\nhappens when drugs make us", "start": 4548.0, "duration": 3.0}, {"text": "better than we ever were?\" That\nwas the example I was talking", "start": 4551.0, "duration": 3.0}, {"text": "about before of Emma, who feels\nbetter on Prozac even though", "start": 4554.0, "duration": 7.0}, {"text": "she wasn't technically --\ndidn't have a reasonable", "start": 4561.0, "duration": 7.0}, {"text": "diagnosis of something\nbeing wrong with her.", "start": 4568.0, "duration": 3.0}, {"text": "So we've already\ntalked about that.", "start": 4571.0, "duration": 2.0}, {"text": "So I think I'll quit.", "start": 4573.0, "duration": 5.0}, {"text": "See you next week.", "start": 4578.0, "duration": 2.0}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.43}, {"text": "[RUSTLING]", "start": 2.43, "duration": 1.944}, {"text": "[CLICKING]", "start": 4.374, "duration": 1.458}, {"text": "DAVID HSU: My name is David Hsu.", "start": 10.197, "duration": 1.333}, {"text": "Welcome to another installment\nof my lecture series", "start": 11.53, "duration": 2.46}, {"text": "on urban energy\nsystems and policy.", "start": 13.99, "duration": 2.55}, {"text": "This is a class taught by the\nDepartment of Urban Studies", "start": 16.54, "duration": 2.43}, {"text": "and Planning at MIT.", "start": 18.97, "duration": 2.023}, {"text": "And what we're going\nto talk about today", "start": 20.993, "duration": 1.667}, {"text": "is the next installment of\ntalking about renewables", "start": 22.66, "duration": 3.48}, {"text": "and renewable energy.", "start": 26.14, "duration": 1.54}, {"text": "We're going to talk\nabout solar today.", "start": 27.68, "duration": 1.64}, {"text": "And this, again, is a\nfundamental building block", "start": 29.32, "duration": 2.64}, {"text": "for how we are going\nto decarbonize cities.", "start": 31.96, "duration": 3.39}, {"text": "The readings for today\nare on the syllabus.", "start": 35.35, "duration": 2.02}, {"text": "If you have the PDF\nhard copies, you", "start": 37.37, "duration": 1.58}, {"text": "can click through to the\nreadings in the pink links", "start": 38.95, "duration": 2.91}, {"text": "here on this page.", "start": 41.86, "duration": 2.7}, {"text": "I'll just recap what I\nsaid in the last lecture.", "start": 44.56, "duration": 2.91}, {"text": "You have a renewable toolbox.", "start": 47.47, "duration": 2.19}, {"text": "The exciting thing is\nthat our building blocks,", "start": 49.66, "duration": 2.34}, {"text": "like solar, wind, storage,\ngeothermal, electrolysis,", "start": 52.0, "duration": 3.93}, {"text": "are all becoming\ncheaper quickly.", "start": 55.93, "duration": 2.19}, {"text": "They're all cleaner\ntechnologies.", "start": 58.12, "duration": 1.71}, {"text": "But they are fundamentally\ndifferent technologies", "start": 59.83, "duration": 2.43}, {"text": "than the fossil fuel\nsystem that we've", "start": 62.26, "duration": 1.74}, {"text": "built our civilization on.", "start": 64.0, "duration": 2.83}, {"text": "So we need to build about 47\ntimes more solar, about 28", "start": 66.83, "duration": 3.8}, {"text": "times more wind than we've\nbuilt in the last 40 years,", "start": 70.63, "duration": 3.27}, {"text": "to basically provide enough\nenergy to decarbonize", "start": 73.9, "duration": 3.03}, {"text": "our energy system.", "start": 76.93, "duration": 1.68}, {"text": "That gives you a very\nlengthy to do list,", "start": 78.61, "duration": 2.58}, {"text": "but an exciting to do\nlist for your careers.", "start": 81.19, "duration": 2.7}, {"text": "Your to do list includes\nfinancing, generation,", "start": 83.89, "duration": 2.7}, {"text": "transmission, distributing\npower, balancing power,", "start": 86.59, "duration": 2.71}, {"text": "making sure that\npower is reliable,", "start": 89.3, "duration": 1.52}, {"text": "making sure that the energy\nsystems are resilient,", "start": 90.82, "duration": 2.13}, {"text": "and siting these\nenergy resources.", "start": 92.95, "duration": 3.15}, {"text": "Last time we talked\nabout wind basics.", "start": 96.1, "duration": 2.26}, {"text": "We talked about capacity\nfactors as a key concept", "start": 98.36, "duration": 2.93}, {"text": "to understand intermittency.", "start": 101.29, "duration": 2.805}, {"text": "Today we're going to\ntalk about solar basics.", "start": 104.095, "duration": 1.875}, {"text": "And we're going to\nuse solar technologies", "start": 105.97, "duration": 1.708}, {"text": "as an example of adoption\ncosts, or learning curves,", "start": 107.678, "duration": 3.152}, {"text": "and siting issues.", "start": 110.83, "duration": 1.5}, {"text": "And the next lecture, we'll talk\nabout storage and geothermal.", "start": 112.33, "duration": 3.06}, {"text": "Those are technologies that\nare developing new niches", "start": 115.39, "duration": 2.46}, {"text": "in the energy system, and may be\ncritical building blocks going", "start": 117.85, "duration": 3.96}, {"text": "forward, but haven't\nquite developed", "start": 121.81, "duration": 1.92}, {"text": "into the same kind of\ncompetitive technology", "start": 123.73, "duration": 4.559}, {"text": "that solar and wind have become.", "start": 128.289, "duration": 2.5}, {"text": "So just to review\nbasically, here's", "start": 130.789, "duration": 2.371}, {"text": "a diagram from MacKay's book.", "start": 133.16, "duration": 1.77}, {"text": "This is a solar, basically\nconverts incident", "start": 134.93, "duration": 3.03}, {"text": "light on the Earth into energy.", "start": 137.96, "duration": 2.25}, {"text": "Of course, you have\nto capture the portion", "start": 140.21, "duration": 3.06}, {"text": "of the electromagnetic\nenergy in the ray.", "start": 143.27, "duration": 3.04}, {"text": "And so this diagram simply\nshows that at the equator,", "start": 146.31, "duration": 2.81}, {"text": "you capture the full amount of\nthe energy landing in Nairobi", "start": 149.12, "duration": 4.2}, {"text": "with a horizontally-mounted\nground panel,", "start": 153.32, "duration": 2.88}, {"text": "a panel simply lying\nflat on the ground.", "start": 156.2, "duration": 2.55}, {"text": "Whereas at 52 degrees latitude,\nCambridge, United Kingdom,", "start": 158.75, "duration": 4.59}, {"text": "or Cambridge,\nMassachusetts, are the same,", "start": 163.34, "duration": 2.16}, {"text": "you actually only capture\nabout 60% of the energy", "start": 165.5, "duration": 3.81}, {"text": "because a 52 degree angle\ndoesn't capture the full ray", "start": 169.31, "duration": 3.66}, {"text": "energy of the\nelectromagnetic energy,", "start": 172.97, "duration": 3.06}, {"text": "or the sunlight\nfalling on the Earth.", "start": 176.03, "duration": 2.37}, {"text": "Helpfully, however, as\nthis last line points out,", "start": 178.4, "duration": 3.0}, {"text": "52 degrees is about the\npitch of a roof angle.", "start": 181.4, "duration": 3.0}, {"text": "So if you lay solar panels\nflat on a roof in Cambridge,", "start": 184.4, "duration": 3.88}, {"text": "Massachusetts, and\nthose are pointed", "start": 188.28, "duration": 2.24}, {"text": "in the direction of the sun,\npredominantly South, coming", "start": 190.52, "duration": 3.09}, {"text": "from the South in the\nnorthern hemisphere,", "start": 193.61, "duration": 1.8}, {"text": "then you can capture the full\namount of the solar energy", "start": 195.41, "duration": 3.24}, {"text": "falling on the roof.", "start": 198.65, "duration": 2.49}, {"text": "This is why we have different\nmaps for solar resources.", "start": 201.14, "duration": 3.52}, {"text": "This is a map of the global\nhorizontal irradiation.", "start": 204.66, "duration": 3.293}, {"text": "This is the amount of\nenergy you would capture", "start": 207.953, "duration": 1.917}, {"text": "if you laid a solar panel\nsimply down on the ground flat", "start": 209.87, "duration": 3.51}, {"text": "facing up at the sky.", "start": 213.38, "duration": 1.92}, {"text": "As you can see,\naround the equator,", "start": 215.3, "duration": 2.34}, {"text": "there are relatively\nhigh amounts", "start": 217.64, "duration": 2.01}, {"text": "of global horizontal radiation.", "start": 219.65, "duration": 2.13}, {"text": "And, of course, slightly\noff the equator,", "start": 221.78, "duration": 3.15}, {"text": "you also get a lot of\nglobal horizontal radiation", "start": 224.93, "duration": 3.75}, {"text": "probably due to climate.", "start": 228.68, "duration": 1.32}, {"text": "This map probably incorporates\nnot only climate, but also", "start": 230.0, "duration": 4.29}, {"text": "the level of radiation that's\nmeasured in these places.", "start": 234.29, "duration": 4.23}, {"text": "For the direct,\nnormal irradiation,", "start": 238.52, "duration": 2.13}, {"text": "this is how much\nenergy you'd capture", "start": 240.65, "duration": 2.37}, {"text": "if you laid a solar panel\nat the precise angle", "start": 243.02, "duration": 3.69}, {"text": "to capture the maximum\namount of irradiation.", "start": 246.71, "duration": 3.66}, {"text": "And you can see that it's\na much more balanced view.", "start": 250.37, "duration": 2.65}, {"text": "This probably includes\nclimate, probably includes", "start": 253.02, "duration": 2.93}, {"text": "weather conditions,\nbut actually is based", "start": 255.95, "duration": 2.67}, {"text": "on empirical measurements.", "start": 258.62, "duration": 1.11}, {"text": "And you can see that\nthere, solar is actually", "start": 259.73, "duration": 3.0}, {"text": "a resource that's spread\nfairly well around the world,", "start": 262.73, "duration": 3.22}, {"text": "especially closer\nto the equator.", "start": 265.95, "duration": 2.9}, {"text": "The northern, southern\nhemispheres also", "start": 268.85, "duration": 1.71}, {"text": "have abundant solar potential.", "start": 270.56, "duration": 3.68}, {"text": "So if you look at the total\nphotovoltaic power potential,", "start": 274.24, "duration": 3.17}, {"text": "again, a good\nmessage from this map", "start": 277.41, "duration": 2.79}, {"text": "is that photovoltaic power is\nevenly spread across the world.", "start": 280.2, "duration": 4.68}, {"text": "It can be accessed\nin many countries.", "start": 284.88, "duration": 2.67}, {"text": "Quite importantly, it can be\naccessed in parts of countries,", "start": 287.55, "duration": 2.79}, {"text": "depending on climate, depending\non incident solar radiation.", "start": 290.34, "duration": 5.35}, {"text": "And, of course, we can also\nuse solar tracking devices", "start": 295.69, "duration": 3.51}, {"text": "because the sun\ntends to come low", "start": 299.2, "duration": 2.52}, {"text": "from the south in the\nnorthern hemisphere,", "start": 301.72, "duration": 2.85}, {"text": "you might have a\nhouse that's not", "start": 304.57, "duration": 3.93}, {"text": "pointed in the right direction.", "start": 308.5, "duration": 1.31}, {"text": "It may not be pointed East West.", "start": 309.81, "duration": 2.53}, {"text": "You may want a rooftop facing\nto the South where the sun is.", "start": 312.34, "duration": 4.05}, {"text": "As the sun comes over\nat different portions", "start": 316.39, "duration": 2.61}, {"text": "of the year-- it's higher in\nthe sky in the summer and lower", "start": 319.0, "duration": 3.21}, {"text": "in the sky in the winter--", "start": 322.21, "duration": 1.45}, {"text": "you may want a\nsolar collector that", "start": 323.66, "duration": 1.73}, {"text": "actually has different\nangles, angles", "start": 325.39, "duration": 1.86}, {"text": "that can tilt to capture\nthis seasonal variation", "start": 327.25, "duration": 2.61}, {"text": "between summer and winter, and\nmay even tilt as the sun moves", "start": 329.86, "duration": 4.29}, {"text": "throughout the sky.", "start": 334.15, "duration": 1.9}, {"text": "So that's a two axis\nsolar tracking panel.", "start": 336.05, "duration": 3.74}, {"text": "Another technology that could\nbe used to capture solar energy", "start": 339.79, "duration": 4.29}, {"text": "is called concentrated\nsolar power.", "start": 344.08, "duration": 2.67}, {"text": "This is a CSP plant, or\na solar thermal tower.", "start": 346.75, "duration": 3.78}, {"text": "This is Crescent Dunes\nin the American West.", "start": 350.53, "duration": 3.69}, {"text": "This is actually\n10,000 heliostats.", "start": 354.22, "duration": 2.58}, {"text": "These are those tracking\nmirrors I showed you.", "start": 356.8, "duration": 2.62}, {"text": "But instead of tracking\nthe sun directly,", "start": 359.42, "duration": 2.27}, {"text": "what these mirrors are doing\nare actually tracking the sun,", "start": 361.69, "duration": 3.33}, {"text": "reflecting the sun\nto this one point,", "start": 365.02, "duration": 2.4}, {"text": "and super heating\nup a fluid here", "start": 367.42, "duration": 2.97}, {"text": "that's used to drive\na steam turbine.", "start": 370.39, "duration": 2.05}, {"text": "So these 10,000 mirrors\nare moving in concert,", "start": 372.44, "duration": 3.29}, {"text": "are all moving differently,\nall concentrating the sun", "start": 375.73, "duration": 2.88}, {"text": "on this one point to\nsuperheat the site", "start": 378.61, "duration": 2.7}, {"text": "and create superheated liquid\nor steam to drive a turbine", "start": 381.31, "duration": 3.69}, {"text": "to create energy.", "start": 385.0, "duration": 1.53}, {"text": "Of course, what we're going\nto talk about mostly today", "start": 386.53, "duration": 2.25}, {"text": "is much humbler,\nsmaller technology.", "start": 388.78, "duration": 2.49}, {"text": "It's the solar\nphotovoltaic panel.", "start": 391.27, "duration": 2.46}, {"text": "A utility-scale solar\narray is composed", "start": 393.73, "duration": 3.39}, {"text": "of many of these\nmodules, a rooftop", "start": 397.12, "duration": 2.79}, {"text": "on a residential installation,\nor in a, let's say,", "start": 399.91, "duration": 3.57}, {"text": "camping cabin would probably\nbe based on one standard panel.", "start": 403.48, "duration": 3.45}, {"text": "This is a solar\npanel installation", "start": 406.93, "duration": 2.01}, {"text": "on top of a big box store.", "start": 408.94, "duration": 1.95}, {"text": "But solar panels are\nfundamentally modular.", "start": 410.89, "duration": 3.25}, {"text": "They can be deployed\nin different ways.", "start": 414.14, "duration": 1.788}, {"text": "And we're going to spend most\nof our time talking today", "start": 415.928, "duration": 2.292}, {"text": "about why solar photovoltaics,\nthat modular technology,", "start": 418.22, "duration": 3.95}, {"text": "has gotten cheap much faster\nthan other technologies.", "start": 422.17, "duration": 4.14}, {"text": "And so if you look at the\nfundamental cell efficiency,", "start": 426.31, "duration": 3.7}, {"text": "this is how efficiently a solar\ncell converts incident energy", "start": 430.01, "duration": 5.27}, {"text": "to electricity.", "start": 435.28, "duration": 1.48}, {"text": "This is what's called the\nchampion graph that NREL does.", "start": 436.76, "duration": 2.6}, {"text": "Every year, they\nupdate this graph.", "start": 439.36, "duration": 2.08}, {"text": "And you can see\nsteadily, there are", "start": 441.44, "duration": 1.61}, {"text": "these different trajectories\nof different technologies.", "start": 443.05, "duration": 2.91}, {"text": "The technologies are\nall in upper left.", "start": 445.96, "duration": 2.52}, {"text": "They range from\nmulti junction cells", "start": 448.48, "duration": 1.92}, {"text": "to crystalline silicon\ncells, to emerging", "start": 450.4, "duration": 3.27}, {"text": "photovoltaic technologies.", "start": 453.67, "duration": 1.56}, {"text": "You can see these technologies\nhave all developed over time", "start": 455.23, "duration": 3.0}, {"text": "and gotten better.", "start": 458.23, "duration": 2.0}, {"text": "The best research\ncell efficiency", "start": 460.23, "duration": 2.07}, {"text": "is 47% conversion of incident\nsunlight into electricity.", "start": 462.3, "duration": 5.41}, {"text": "But your average\nsolar panel that's", "start": 467.71, "duration": 2.66}, {"text": "deployed on most solar arrays\nranges from 20% to 25%.", "start": 470.37, "duration": 5.365}, {"text": "What MacKay says in\nhis book, that he'd", "start": 475.735, "duration": 1.625}, {"text": "be shocked if there's better\nresearch cell, or better", "start": 477.36, "duration": 3.57}, {"text": "efficiencies.", "start": 480.93, "duration": 0.93}, {"text": "Efficiencies have\ngone up over time.", "start": 481.86, "duration": 2.7}, {"text": "But that's not the key story\nI want to focus on today.", "start": 484.56, "duration": 2.49}, {"text": "It's the fact that solar\npanels have gotten much cheaper", "start": 487.05, "duration": 3.15}, {"text": "much more quickly, even\nthough the research", "start": 490.2, "duration": 2.4}, {"text": "efficiency, or the efficiency\nof most solar panels", "start": 492.6, "duration": 2.82}, {"text": "sold has stayed relatively\nconstant, around 20%.", "start": 495.42, "duration": 5.14}, {"text": "So if you look at-- this\ngraph from the BP Statistical", "start": 500.56, "duration": 4.04}, {"text": "Review of World Energy.", "start": 504.6, "duration": 1.77}, {"text": "It shows the share of global\nelectricity generation by fuel.", "start": 506.37, "duration": 3.66}, {"text": "And you can see that oil and\ncoal and hydroelectricity", "start": 510.03, "duration": 4.62}, {"text": "are all relatively flat.", "start": 514.65, "duration": 2.07}, {"text": "Natural gas has trended up.", "start": 516.72, "duration": 1.959}, {"text": "But the one that's quite\nremarkably trending up", "start": 518.679, "duration": 2.24}, {"text": "is renewables.", "start": 520.919, "duration": 1.051}, {"text": "And renewables is\ntrending up both in terms", "start": 521.97, "duration": 1.92}, {"text": "of wind and solar.", "start": 523.89, "duration": 1.367}, {"text": "If you look on the right-hand\ngraph and renewables", "start": 525.257, "duration": 2.083}, {"text": "as a share of power\ngeneration by region,", "start": 527.34, "duration": 2.22}, {"text": "in every single\nregion of the world,", "start": 529.56, "duration": 1.65}, {"text": "renewables seem to be on this\nvery steep, increasing curve.", "start": 531.21, "duration": 4.74}, {"text": "That curve is\nreminiscent of this", "start": 535.95, "duration": 2.13}, {"text": "putting of what's called\na cumulative distribution", "start": 538.08, "duration": 2.25}, {"text": "function.", "start": 540.33, "duration": 0.78}, {"text": "And this is basically simply\na sum of a bell curve.", "start": 541.11, "duration": 4.96}, {"text": "And you get this S curve by\nsumming up the bell curve.", "start": 546.07, "duration": 2.79}, {"text": "So using different\nparameters for the mean", "start": 548.86, "duration": 2.42}, {"text": "or the standard deviation,\nyou get different steepness", "start": 551.28, "duration": 2.97}, {"text": "of S curves between this\nmustard-colored curve", "start": 554.25, "duration": 2.55}, {"text": "and this green curve.", "start": 556.8, "duration": 2.4}, {"text": "And so just to point out how\nthat is the sum of these bell", "start": 559.2, "duration": 2.81}, {"text": "curves, those\nS-shaped curves come", "start": 562.01, "duration": 2.52}, {"text": "from these green, and mustard,\nand blue, and red bell curves.", "start": 564.53, "duration": 4.5}, {"text": "The reason why this is\nimportant is because this", "start": 569.03, "duration": 2.97}, {"text": "is an idea about how\ninnovations diffuse,", "start": 572.0, "duration": 3.39}, {"text": "that you may have\nseen this famous curve", "start": 575.39, "duration": 3.0}, {"text": "called the diffusion\nof innovations", "start": 578.39, "duration": 1.56}, {"text": "curve that was coined\nby Everett Rogers.", "start": 579.95, "duration": 2.58}, {"text": "And you may have heard\nthis phrase, \"innovators", "start": 582.53, "duration": 2.04}, {"text": "and early adopters.\"", "start": 584.57, "duration": 1.41}, {"text": "And he adopts this idea of a\nbell curve of different people", "start": 585.98, "duration": 4.38}, {"text": "or different organizations\nwilling to adopt technologies", "start": 590.36, "duration": 2.94}, {"text": "in different ways.", "start": 593.3, "duration": 1.12}, {"text": "There's innovators and early\nadopters who are first.", "start": 594.42, "duration": 2.72}, {"text": "There's an early majority, late\nmajority, and there's laggers.", "start": 597.14, "duration": 2.61}, {"text": "And if you take this bell curve\nof behaviors and add it up,", "start": 599.75, "duration": 3.63}, {"text": "you get this distribution,\nthis S-shaped distribution", "start": 603.38, "duration": 3.09}, {"text": "of adoption.", "start": 606.47, "duration": 1.14}, {"text": "And that's really what we\nwant to talk about today", "start": 607.61, "duration": 2.64}, {"text": "because if you look at\nthis S-shaped curve,", "start": 610.25, "duration": 2.61}, {"text": "this is a curve from\na New York Times", "start": 612.86, "duration": 2.94}, {"text": "article by Nicholas Felton.", "start": 615.8, "duration": 2.61}, {"text": "And you can see\nthat our adoption", "start": 618.41, "duration": 1.68}, {"text": "of different technologies\nover the last century", "start": 620.09, "duration": 2.4}, {"text": "have essentially followed\nthis S-shaped curve.", "start": 622.49, "duration": 3.03}, {"text": "We have electricity which has a\nkind of bump here in the 1920s,", "start": 625.52, "duration": 3.69}, {"text": "but looks roughly S-shaped.", "start": 629.21, "duration": 1.74}, {"text": "You see rapid adoption\nof refrigerators.", "start": 630.95, "duration": 2.76}, {"text": "You see rapid\nadoption of color TVs.", "start": 633.71, "duration": 2.34}, {"text": "And the point of this\ncolumn by Nicholas Felton", "start": 636.05, "duration": 2.43}, {"text": "a number of years ago\nwas that these curves get", "start": 638.48, "duration": 2.19}, {"text": "increasingly steep over time.", "start": 640.67, "duration": 2.19}, {"text": "Of course, we can't assume\nthat this is a causal process,", "start": 642.86, "duration": 3.15}, {"text": "or this is a inevitable\nor ineluctable process.", "start": 646.01, "duration": 3.318}, {"text": "Obviously, some of\nthese technologies", "start": 649.328, "duration": 1.542}, {"text": "like clothes, dryers,\nmicrowaves, color TVs, cell", "start": 650.87, "duration": 2.76}, {"text": "phones, computers,\nVCRs, could only", "start": 653.63, "duration": 2.55}, {"text": "exist if electricity\nexisted beforehand.", "start": 656.18, "duration": 2.82}, {"text": "You see the track\nof the telephone", "start": 659.0, "duration": 3.09}, {"text": "has a much more mixed,\nnot S-shaped curve.", "start": 662.09, "duration": 4.0}, {"text": "So we shouldn't assume\nthat a S-shaped curve is", "start": 666.09, "duration": 2.63}, {"text": "inevitable or\nineluctable, we obviously", "start": 668.72, "duration": 2.34}, {"text": "have to do things to\nadopt these technologies.", "start": 671.06, "duration": 3.0}, {"text": "The progress of our\ntechnologies may not", "start": 674.06, "duration": 2.13}, {"text": "be completely\npredictable or linear.", "start": 676.19, "duration": 3.63}, {"text": "But the point I want to\nmake about solar power", "start": 679.82, "duration": 2.66}, {"text": "is that solar power has\ndeclined by price by about 90%", "start": 682.48, "duration": 3.75}, {"text": "in the last 10 years.", "start": 686.23, "duration": 1.26}, {"text": "This is, again, that graph\nfrom Our World in Data.", "start": 687.49, "duration": 2.52}, {"text": "And the key point of this being\npart of your renewable toolbox", "start": 690.01, "duration": 3.51}, {"text": "is that you want to\nwork with technologies", "start": 693.52, "duration": 2.1}, {"text": "that are getting cheaper and\nalso happen to be cleaner.", "start": 695.62, "duration": 3.12}, {"text": "So if you look at all\nthe energy or electricity", "start": 698.74, "duration": 2.73}, {"text": "generating technologies\non this graph,", "start": 701.47, "duration": 2.13}, {"text": "again, nuclear's\ngotten more expensive.", "start": 703.6, "duration": 2.43}, {"text": "Coal stayed relatively flat.", "start": 706.03, "duration": 1.68}, {"text": "Gas has gotten cheaper, but not\nas quickly as solar power has", "start": 707.71, "duration": 3.93}, {"text": "gotten cheaper.", "start": 711.64, "duration": 0.84}, {"text": "Solar thermal towers, the\nconcentrating solar technology", "start": 712.48, "duration": 3.51}, {"text": "I showed you a few\nslides ago, that kind", "start": 715.99, "duration": 2.61}, {"text": "of awesome installation\nin the desert,", "start": 718.6, "duration": 2.73}, {"text": "though it's awesome\nin how it looks,", "start": 721.33, "duration": 1.95}, {"text": "it has not necessarily\ngone cheap as quick", "start": 723.28, "duration": 3.54}, {"text": "as the humble solar panel.", "start": 726.82, "duration": 2.93}, {"text": "And, also, of\ncourse, onshore wind", "start": 729.75, "duration": 2.37}, {"text": "has declined rapidly over time.", "start": 732.12, "duration": 3.16}, {"text": "And, again, if you\nlook at these curves,", "start": 735.28, "duration": 2.43}, {"text": "you can see that lithium\nion batteries since 1992", "start": 737.71, "duration": 3.45}, {"text": "are also steeply\ndecreasing in price.", "start": 741.16, "duration": 2.65}, {"text": "And I think I said\nin the last lecture", "start": 743.81, "duration": 1.61}, {"text": "that this is called\nthe learning rate.", "start": 745.42, "duration": 2.34}, {"text": "For every doubling in\ncumulative capacity,", "start": 747.76, "duration": 1.98}, {"text": "price has declined\nan average of 18.9%.", "start": 749.74, "duration": 3.96}, {"text": "Solar technologies,\nelectrolyzers,", "start": 753.7, "duration": 2.37}, {"text": "are also following\na very rapid curve.", "start": 756.07, "duration": 4.3}, {"text": "And, again, the key\npoint is that, yes,", "start": 760.37, "duration": 3.51}, {"text": "coal is a dirty fuel.", "start": 763.88, "duration": 3.12}, {"text": "But nuclear is also a low\ncarbon or clean resource.", "start": 767.0, "duration": 4.98}, {"text": "I would argue that\nnuclear will probably", "start": 771.98, "duration": 2.67}, {"text": "be a critical or important\nfirm resource for the future.", "start": 774.65, "duration": 4.38}, {"text": "But the problem is, our existing\nways of building nuclear power", "start": 779.03, "duration": 3.03}, {"text": "plants have only gotten\nmore expensive over time.", "start": 782.06, "duration": 2.52}, {"text": "They've not demonstrated\nany learning rate,", "start": 784.58, "duration": 2.67}, {"text": "whereas solar photovoltaics\nhave a learning rate of 36%.", "start": 787.25, "duration": 4.86}, {"text": "Offshore wind has a\nlearning rate of 10%.", "start": 792.11, "duration": 2.64}, {"text": "Onshore wind has a\nlearning rate of 23%.", "start": 794.75, "duration": 2.85}, {"text": "And lithium ion\nbatteries, which are", "start": 797.6, "duration": 2.61}, {"text": "crucial to electrifying\nvehicles and all", "start": 800.21, "duration": 3.0}, {"text": "of our electronic devices,\nhave a learning rate of 19%.", "start": 803.21, "duration": 4.14}, {"text": "You can perhaps,\nif not count on it,", "start": 807.35, "duration": 3.84}, {"text": "assume that some of\nthese learning rates", "start": 811.19, "duration": 2.22}, {"text": "will continue in the near\nfuture that will only", "start": 813.41, "duration": 2.52}, {"text": "make these technologies more\ncompetitive in the near future.", "start": 815.93, "duration": 4.58}, {"text": "And so a key question is, why\nhave the solar prices declined?", "start": 820.51, "duration": 3.78}, {"text": "This is a topic that\nmy colleague Jessika", "start": 824.29, "duration": 2.63}, {"text": "Trancik at MIT has studied.", "start": 826.92, "duration": 2.4}, {"text": "And she studied in a 2016\npaper all the various factors", "start": 829.32, "duration": 4.77}, {"text": "leading to these\ndeclines in solar prices,", "start": 834.09, "duration": 3.27}, {"text": "or this learning rate.", "start": 837.36, "duration": 1.08}, {"text": "And it's also\nimportant to point out", "start": 838.44, "duration": 1.5}, {"text": "that, as the\nNicholas Felton graph", "start": 839.94, "duration": 2.61}, {"text": "I showed you a few\nslides ago, it's", "start": 842.55, "duration": 2.28}, {"text": "not necessarily\nineluctable, or inevitable,", "start": 844.83, "duration": 3.12}, {"text": "or fated for all these\nthings to happen.", "start": 847.95, "duration": 3.43}, {"text": "But it is a little strange,\nand it is a little weirdly", "start": 851.38, "duration": 3.08}, {"text": "wonderful how they follow a\nfairly consistent pattern,", "start": 854.46, "duration": 3.39}, {"text": "even if different factors\nare leading to these price", "start": 857.85, "duration": 3.06}, {"text": "declines.", "start": 860.91, "duration": 1.23}, {"text": "For example, in\nJessika Trancik's paper", "start": 862.14, "duration": 2.13}, {"text": "she decomposes the\nsources of price decline", "start": 864.27, "duration": 3.54}, {"text": "from 1980 to 2001, from 2001 to\n2012, and the overall effect.", "start": 867.81, "duration": 6.52}, {"text": "And so she finds that the\noverall effect, the biggest", "start": 874.33, "duration": 3.47}, {"text": "contribution to solar prices\ndeclining is the efficiency.", "start": 877.8, "duration": 4.95}, {"text": "Nonsilicon material\ncosts have also improved.", "start": 882.75, "duration": 3.87}, {"text": "Silicon prices\nthemselves have improved.", "start": 886.62, "duration": 3.12}, {"text": "The usage of silicon\nhas improved.", "start": 889.74, "duration": 1.89}, {"text": "The wafer areas have improved.", "start": 891.63, "duration": 1.41}, {"text": "Plant sizes have gotten bigger.", "start": 893.04, "duration": 1.84}, {"text": "The yields have gotten better.", "start": 894.88, "duration": 1.29}, {"text": "And there's been\nslight impact on price.", "start": 896.17, "duration": 2.99}, {"text": "But you can see\nfrom 1980 to 2001,", "start": 899.16, "duration": 2.46}, {"text": "and 2001, 2012, a lot of\nthese different factors", "start": 901.62, "duration": 3.84}, {"text": "play in at different times.", "start": 905.46, "duration": 1.69}, {"text": "In other words,\nfor some reason, we", "start": 907.15, "duration": 2.21}, {"text": "have these fairly steady\ndeclines in solar,", "start": 909.36, "duration": 2.34}, {"text": "though they're not\ncompletely linear when", "start": 911.7, "duration": 1.77}, {"text": "graphed on a logarithmic graph.", "start": 913.47, "duration": 2.01}, {"text": "But it's also weirdly wonderful\nhow all these different factors", "start": 915.48, "duration": 3.24}, {"text": "play together.", "start": 918.72, "duration": 1.08}, {"text": "And when one part\nof the industry", "start": 919.8, "duration": 1.77}, {"text": "improved in one part\nof the technology,", "start": 921.57, "duration": 2.73}, {"text": "other parts of industry were\nthen able to, let's say,", "start": 924.3, "duration": 3.21}, {"text": "improve others.", "start": 927.51, "duration": 1.15}, {"text": "For example, Germany\nwas a pioneer in solar", "start": 928.66, "duration": 2.87}, {"text": "until China pioneered\nlarge-scale manufacturing", "start": 931.53, "duration": 3.24}, {"text": "of solar panels.", "start": 934.77, "duration": 2.37}, {"text": "If we break down\nsome of these changes", "start": 937.14, "duration": 3.28}, {"text": "and attribute them\nto larger categories,", "start": 940.42, "duration": 3.65}, {"text": "you can see that there's\nan overall effect", "start": 944.07, "duration": 2.04}, {"text": "of public and private research\nand development funding.", "start": 946.11, "duration": 3.21}, {"text": "There are some effects\nof learning by doing.", "start": 949.32, "duration": 2.01}, {"text": "The more you do something, the\nbetter you learn how to do it.", "start": 951.33, "duration": 2.85}, {"text": "Economies of scale--\nthe more of something", "start": 954.18, "duration": 2.19}, {"text": "you build, it\nactually gets cheaper", "start": 956.37, "duration": 2.16}, {"text": "if you build it in large\nvolumes, and other factors.", "start": 958.53, "duration": 2.99}, {"text": "But, again, between 1980\nand 2001, and 2001, 2012,", "start": 961.52, "duration": 3.94}, {"text": "you actually see the really\ndifferent contributions", "start": 965.46, "duration": 2.37}, {"text": "from these different factors.", "start": 967.83, "duration": 3.37}, {"text": "And so another question\nis, will solar prices", "start": 971.2, "duration": 1.91}, {"text": "continue to decline?", "start": 973.11, "duration": 1.695}, {"text": "And this is that\nlearning rate graph", "start": 974.805, "duration": 2.025}, {"text": "showing solar actual\nasset costs by year.", "start": 976.83, "duration": 4.53}, {"text": "This is from a recent paper by\nWay, Ives, Mealy and Farmer.", "start": 981.36, "duration": 4.05}, {"text": "And what's really entertaining\nabout this graph to me", "start": 985.41, "duration": 2.685}, {"text": "is that you can see the\ndifferent projections", "start": 988.095, "duration": 1.875}, {"text": "for solar costs.", "start": 989.97, "duration": 1.033}, {"text": "And the important\nthing about this graph", "start": 991.003, "duration": 1.667}, {"text": "is that, in every single\ncase, the empirically-observed", "start": 992.67, "duration": 3.69}, {"text": "capacity cost has been lower\nthan the projected costs.", "start": 996.36, "duration": 3.45}, {"text": "In fact, for some reason, a lot\nof integrated assessment models", "start": 999.81, "duration": 3.57}, {"text": "keep on projecting\nthat solar is not", "start": 1003.38, "duration": 1.92}, {"text": "going to get cheaper faster.", "start": 1005.3, "duration": 1.33}, {"text": "They have a shallower curve.", "start": 1006.63, "duration": 2.58}, {"text": "But in reality, solar\nhas gotten much cheaper", "start": 1009.21, "duration": 2.6}, {"text": "much more quickly than\nanyone ever projected", "start": 1011.81, "duration": 2.295}, {"text": "in the first place.", "start": 1014.105, "duration": 2.545}, {"text": "The authors of this\npaper argue and forecast", "start": 1016.65, "duration": 4.05}, {"text": "that solar prices will\ncontinue to get cheaper", "start": 1020.7, "duration": 2.31}, {"text": "because they look at\nother empirical cost", "start": 1023.01, "duration": 2.52}, {"text": "declines over time.", "start": 1025.53, "duration": 1.92}, {"text": "If you look at wind, wind has\nbeen on a similar trajectory", "start": 1027.45, "duration": 4.139}, {"text": "of decline.", "start": 1031.589, "duration": 0.99}, {"text": "And in all of these\ncases, many models", "start": 1032.579, "duration": 2.581}, {"text": "keep on predicting that\nwind is going to cost", "start": 1035.16, "duration": 2.37}, {"text": "more than it actually has.", "start": 1037.53, "duration": 1.589}, {"text": "So this leads to the question,\nif solar and wind continue", "start": 1039.119, "duration": 2.881}, {"text": "to get cheaper more\nquickly than we expect,", "start": 1042.0, "duration": 2.609}, {"text": "what might happen in\nthe energy transition?", "start": 1044.609, "duration": 2.581}, {"text": "The authors of\nthis paper actually", "start": 1047.19, "duration": 1.44}, {"text": "argue that there could be a fast\ntransition between clean energy", "start": 1048.63, "duration": 3.27}, {"text": "and fossil fuels, a slow\ntransition, or no transition", "start": 1051.9, "duration": 3.48}, {"text": "at all, where fossil fuels\nremain in our energy system.", "start": 1055.38, "duration": 4.17}, {"text": "And clean energy\nsimply adds to it.", "start": 1059.55, "duration": 2.05}, {"text": "But they actually\nargue that based", "start": 1061.6, "duration": 1.91}, {"text": "on the probability of technical\nand technological process,", "start": 1063.51, "duration": 2.68}, {"text": "which could be low,\nmedium, or high,", "start": 1066.19, "duration": 2.66}, {"text": "we'd actually save\nquite a bit of energy", "start": 1068.85, "duration": 2.04}, {"text": "if we had a fast\ntransition to renewables.", "start": 1070.89, "duration": 2.94}, {"text": "That would actually result in\nless costs in this scenario", "start": 1073.83, "duration": 3.96}, {"text": "than it would if we continue\nto use fossil fuels.", "start": 1077.79, "duration": 2.58}, {"text": "And that's assuming\nthat solar and wind", "start": 1080.37, "duration": 1.74}, {"text": "prices continue to get cheaper.", "start": 1082.11, "duration": 1.98}, {"text": "If we have a slower,\nmedium transition,", "start": 1084.09, "duration": 2.52}, {"text": "then we will still save money\nover a no transition scenario.", "start": 1086.61, "duration": 3.42}, {"text": "It just won't be as much.", "start": 1090.03, "duration": 1.65}, {"text": "And it won't be as fast.", "start": 1091.68, "duration": 3.16}, {"text": "If you look at some of\nthe price breakdowns", "start": 1094.84, "duration": 2.03}, {"text": "of solar installation\ncosts, this", "start": 1096.87, "duration": 1.86}, {"text": "is, again, the cost to actually\ninstall and get solar running,", "start": 1098.73, "duration": 5.07}, {"text": "you can see that NREL\ndid a study in 2015", "start": 1103.8, "duration": 2.82}, {"text": "looking at benchmark prices\nand price breakdowns.", "start": 1106.62, "duration": 3.09}, {"text": "And you can see in a\nlot of these cases,", "start": 1109.71, "duration": 1.89}, {"text": "that residential, small\ninstallations are much more", "start": 1111.6, "duration": 3.24}, {"text": "expensive than commercial\nlarge installations,", "start": 1114.84, "duration": 2.4}, {"text": "or utility-scale installations.", "start": 1117.24, "duration": 2.25}, {"text": "But when I point out to you\nis that the actual hardware,", "start": 1119.49, "duration": 3.09}, {"text": "the solar module, the inverter,\nthe rack, and the balance", "start": 1122.58, "duration": 2.46}, {"text": "of system, are actually\nnot much different", "start": 1125.04, "duration": 2.52}, {"text": "between residential\nand commercial", "start": 1127.56, "duration": 1.65}, {"text": "and utility-scale installations.", "start": 1129.21, "duration": 2.01}, {"text": "The panels are basically\nthe same panel.", "start": 1131.22, "duration": 2.68}, {"text": "It might cost different amounts\nto mount them and put them", "start": 1133.9, "duration": 3.83}, {"text": "in a rack.", "start": 1137.73, "duration": 0.78}, {"text": "But the costs are\nnot very different", "start": 1138.51, "duration": 1.62}, {"text": "between even a single solar\npanel on a residential house", "start": 1140.13, "duration": 3.36}, {"text": "versus utility-scale solar.", "start": 1143.49, "duration": 2.04}, {"text": "The big difference is\nbetween the soft costs.", "start": 1145.53, "duration": 2.95}, {"text": "The labor is slightly higher to\ninstall on a residential house,", "start": 1148.48, "duration": 3.59}, {"text": "probably because we\nhaven't achieved economies", "start": 1152.07, "duration": 2.16}, {"text": "of scale or large volumes.", "start": 1154.23, "duration": 2.02}, {"text": "But the soft costs\nare a big difference.", "start": 1156.25, "duration": 2.9}, {"text": "Why residential?", "start": 1159.15, "duration": 1.2}, {"text": "Rooftop solar is\nmuch more expensive", "start": 1160.35, "duration": 1.98}, {"text": "than utility-scale solar.", "start": 1162.33, "duration": 2.07}, {"text": "And so if I had to urge\nurban planners in cities", "start": 1164.4, "duration": 3.06}, {"text": "to work on one problem, I would\nargue that if we were to--", "start": 1167.46, "duration": 3.91}, {"text": "if we were able to decrease\nthe soft cost of installation,", "start": 1171.37, "duration": 3.29}, {"text": "then rooftop solar could be\ncompetitive with utility-scale", "start": 1174.66, "duration": 3.51}, {"text": "solar installations.", "start": 1178.17, "duration": 2.69}, {"text": "And so NREL also\ndid a study in 2018,", "start": 1180.86, "duration": 2.85}, {"text": "showing a road map to achieving\ncheaper solar electricity.", "start": 1183.71, "duration": 4.92}, {"text": "This shows the 2017\nreal levelized cost", "start": 1188.63, "duration": 3.185}, {"text": "of energy, something\nwe've talked", "start": 1191.815, "duration": 1.375}, {"text": "about in this class before.", "start": 1193.19, "duration": 1.84}, {"text": "This shows what the goal\nis, $0.05 per kilowatt hour", "start": 1195.03, "duration": 4.25}, {"text": "for a residential PV system.", "start": 1199.28, "duration": 2.4}, {"text": "And it shows that the\nroadmap for cheaper rooftop", "start": 1201.68, "duration": 4.05}, {"text": "or residential\nsolar goes entirely", "start": 1205.73, "duration": 2.22}, {"text": "through soft cost reduction.", "start": 1207.95, "duration": 1.39}, {"text": "This is a waterfall\ndiagram again.", "start": 1209.34, "duration": 2.19}, {"text": "You can see all the things\nyou can do to get to the goal.", "start": 1211.53, "duration": 2.9}, {"text": "But, obviously, the\nbulk of the savings", "start": 1214.43, "duration": 2.37}, {"text": "comes from reducing soft cost.", "start": 1216.8, "duration": 1.98}, {"text": "That's reducing permitting.", "start": 1218.78, "duration": 1.44}, {"text": "That's reducing design costs.", "start": 1220.22, "duration": 1.32}, {"text": "That's reducing\ndesign complexity.", "start": 1221.54, "duration": 2.43}, {"text": "It's making permitting\neasier at city hall.", "start": 1223.97, "duration": 2.76}, {"text": "If urban planners\nand policy makers", "start": 1226.73, "duration": 2.73}, {"text": "were to focus their\nattention on this,", "start": 1229.46, "duration": 1.62}, {"text": "we could have equally\ncheap rooftop solar.", "start": 1231.08, "duration": 3.27}, {"text": "And that would probably\nnot have the same land-use", "start": 1234.35, "duration": 2.43}, {"text": "impacts as utility-scale solar.", "start": 1236.78, "duration": 1.995}, {"text": "Now, let's go to\nthe MacKay graphs", "start": 1241.42, "duration": 1.86}, {"text": "for a second, MacKay\npapers for a second,", "start": 1243.28, "duration": 2.16}, {"text": "because I think they\nusually show points", "start": 1245.44, "duration": 2.16}, {"text": "about the energy density\nper area required", "start": 1247.6, "duration": 2.61}, {"text": "for renewable technologies.", "start": 1250.21, "duration": 1.41}, {"text": "This brings us into\ntalking about siting.", "start": 1251.62, "duration": 3.12}, {"text": "This is a graph of a vertical\naxis and energy consumption", "start": 1254.74, "duration": 3.81}, {"text": "per person the population\ndensity of people", "start": 1258.55, "duration": 2.82}, {"text": "per square kilometer.", "start": 1261.37, "duration": 1.56}, {"text": "And you can see, the\nworld has generally", "start": 1262.93, "duration": 2.01}, {"text": "in the last two centuries,\nboth consumed more energy", "start": 1264.94, "duration": 3.0}, {"text": "and gotten more dense.", "start": 1267.94, "duration": 1.77}, {"text": "The United States had\nhigher energy consumption", "start": 1269.71, "duration": 2.22}, {"text": "at the beginning and\nlower population densities", "start": 1271.93, "duration": 3.75}, {"text": "than the world.", "start": 1275.68, "duration": 1.175}, {"text": "Developing countries\ntend to have", "start": 1276.855, "duration": 1.375}, {"text": "lower energy consumption and\nhigher population densities.", "start": 1278.23, "duration": 3.66}, {"text": "England, over the\nlast four centuries,", "start": 1281.89, "duration": 3.06}, {"text": "has gotten to very high\nenergy consumption per person,", "start": 1284.95, "duration": 2.73}, {"text": "though not as high as\nthe US, but much higher", "start": 1287.68, "duration": 2.37}, {"text": "population densities\nthan the US.", "start": 1290.05, "duration": 3.53}, {"text": "And what MacKay does is graph\nsimply where we are currently.", "start": 1293.58, "duration": 4.35}, {"text": "This is the United States.", "start": 1297.93, "duration": 1.41}, {"text": "And he uses this graph to\nshow that if you multiply", "start": 1299.34, "duration": 3.66}, {"text": "these factors together, you can\nget these kind of isoclines,", "start": 1303.0, "duration": 3.06}, {"text": "or these gradient lines.", "start": 1306.06, "duration": 2.25}, {"text": "And you can see that the\nenergy consumption of the US", "start": 1308.31, "duration": 2.61}, {"text": "and the size of the circle is\nthe population of the country", "start": 1310.92, "duration": 2.88}, {"text": "is basically approaching what\ncan be provided by energy", "start": 1313.8, "duration": 2.67}, {"text": "crops, which is to\nsay, given this energy", "start": 1316.47, "duration": 2.37}, {"text": "consumption per\nperson for the US,", "start": 1318.84, "duration": 1.53}, {"text": "and given this\npopulation density,", "start": 1320.37, "duration": 2.1}, {"text": "we could supply all of our\nenergy needs with energy crops,", "start": 1322.47, "duration": 3.66}, {"text": "assuming we use the entire\nUnited States for energy crops.", "start": 1326.13, "duration": 3.9}, {"text": "If we add other\npossible technologies,", "start": 1330.03, "duration": 2.73}, {"text": "you can see the limit for\nwind power is further out.", "start": 1332.76, "duration": 3.87}, {"text": "Of course, that would require\nus to use much of the US", "start": 1336.63, "duration": 2.64}, {"text": "for wind power.", "start": 1339.27, "duration": 1.11}, {"text": "And the US has enough\nenergy density.", "start": 1340.38, "duration": 3.01}, {"text": "So we would have to use the\nentire country for wind power.", "start": 1343.39, "duration": 2.72}, {"text": "But you can see\ncountries like Germany,", "start": 1346.11, "duration": 1.99}, {"text": "the United Kingdom,\nand Japan, are already", "start": 1348.1, "duration": 1.97}, {"text": "at the limit for what\nwind power can provide.", "start": 1350.07, "duration": 2.28}, {"text": "South Korea does\nnot have enough land", "start": 1352.35, "duration": 2.16}, {"text": "to provide all of its\nenergy through wind power.", "start": 1354.51, "duration": 3.825}, {"text": "If you look at these\nother technologies", "start": 1358.335, "duration": 1.625}, {"text": "that MacKay discusses,\nsolar PV parks", "start": 1359.96, "duration": 3.82}, {"text": "in sunny locations\nor northern Europe", "start": 1363.78, "duration": 2.52}, {"text": "are concentrating solar power.", "start": 1366.3, "duration": 1.71}, {"text": "You can see that they\nhave lower energy--", "start": 1368.01, "duration": 2.13}, {"text": "the higher energy densities\nor lower land take.", "start": 1370.14, "duration": 2.61}, {"text": "So the frontier gets\npushed further out.", "start": 1372.75, "duration": 3.61}, {"text": "So for one of the\nstudents from Singapore,", "start": 1376.36, "duration": 2.63}, {"text": "he asked how much,\nwhat technologies could", "start": 1378.99, "duration": 2.76}, {"text": "we use to supply Singapore?", "start": 1381.75, "duration": 2.49}, {"text": "You can see that it's\npossible to use the UK", "start": 1384.24, "duration": 3.81}, {"text": "sun before conversion--", "start": 1388.05, "duration": 2.04}, {"text": "sorry, and the desert\nsun before conversion.", "start": 1390.09, "duration": 2.55}, {"text": "Those are things that\nthe population and energy", "start": 1392.64, "duration": 3.24}, {"text": "consumption of Singapore\nwould fit into.", "start": 1395.88, "duration": 2.16}, {"text": "Obviously, it's not\nentirely possible to convert", "start": 1398.04, "duration": 2.82}, {"text": "all of Singapore into\nenergy production.", "start": 1400.86, "duration": 2.4}, {"text": "But this gives you a back\nof the envelope estimate", "start": 1403.26, "duration": 2.79}, {"text": "of how much energy,\nor how much land you", "start": 1406.05, "duration": 2.22}, {"text": "need to provide that energy.", "start": 1408.27, "duration": 3.08}, {"text": "And so this brings\nme to the paper", "start": 1411.35, "duration": 1.67}, {"text": "by Carley et al 2020,\nwhich focuses on energy", "start": 1413.02, "duration": 3.75}, {"text": "infrastructure and NIMBY-ism.", "start": 1416.77, "duration": 2.44}, {"text": "And let's just start with what\nis a systematic literature", "start": 1419.21, "duration": 2.4}, {"text": "review.", "start": 1421.61, "duration": 0.84}, {"text": "A systematic\nliterature review is", "start": 1422.45, "duration": 1.59}, {"text": "a paper where you set particular\nsearch terms and parameters.", "start": 1424.04, "duration": 4.53}, {"text": "You extract the relevant\nacademic literature.", "start": 1428.57, "duration": 2.243}, {"text": "The reason why you do this\nkind of literature search", "start": 1430.813, "duration": 2.167}, {"text": "is that there's just too\nmuch literature to read.", "start": 1432.98, "duration": 2.22}, {"text": "So we occasionally write\npapers to summarize", "start": 1435.2, "duration": 2.34}, {"text": "what's been written.", "start": 1437.54, "duration": 1.65}, {"text": "And then you code and\nanalyze and summarize", "start": 1439.19, "duration": 2.25}, {"text": "all the papers you find.", "start": 1441.44, "duration": 1.38}, {"text": "And you categorize the\nvital data they use,", "start": 1442.82, "duration": 2.7}, {"text": "what kind of methods and\nfindings they come to.", "start": 1445.52, "duration": 3.35}, {"text": "And so the findings of\nthis particular systematic", "start": 1448.87, "duration": 2.32}, {"text": "literature review is\nthat on page 1 they say,", "start": 1451.19, "duration": 3.27}, {"text": "knowledge, trust, and\npositive perceptions", "start": 1454.46, "duration": 2.37}, {"text": "of the benefits of\nprojects are positively", "start": 1456.83, "duration": 2.4}, {"text": "correlated with support\nfor projects with variation", "start": 1459.23, "duration": 2.22}, {"text": "across energy types.", "start": 1461.45, "duration": 1.5}, {"text": "They actually say that we don't\nfocus on the positive aspects", "start": 1462.95, "duration": 3.09}, {"text": "of energy projects enough.", "start": 1466.04, "duration": 1.59}, {"text": "And our study of energy\ninfrastructure and often", "start": 1467.63, "duration": 2.73}, {"text": "NIMBY-ism were often focused\non some of the drawbacks", "start": 1470.36, "duration": 3.0}, {"text": "of these policies.", "start": 1473.36, "duration": 0.96}, {"text": "And people ask, or asked\nin survey literature,", "start": 1474.32, "duration": 2.94}, {"text": "much more about the drawbacks.", "start": 1477.26, "duration": 2.74}, {"text": "And so, and also they\nfind in this paper", "start": 1480.0, "duration": 2.6}, {"text": "that in our assessment,\nit's not clear that NIMBY--", "start": 1482.6, "duration": 3.0}, {"text": "which stands for \"Not\nIn My Backyard\"--", "start": 1485.6, "duration": 2.76}, {"text": "traditionally defined is\noften being evaluated.", "start": 1488.36, "duration": 2.97}, {"text": "At best, we have a set of\ninconsistent findings regarding", "start": 1491.33, "duration": 2.58}, {"text": "the weight that people give\nto the proximity of energy", "start": 1493.91, "duration": 2.67}, {"text": "infrastructure.", "start": 1496.58, "duration": 1.89}, {"text": "And, finally, they say on page\n13 the high rates of support", "start": 1498.47, "duration": 3.02}, {"text": "or found literature\nmay seem to contradict", "start": 1501.49, "duration": 2.43}, {"text": "what is often portrayed\nas significant opposition.", "start": 1503.92, "duration": 3.25}, {"text": "And so this leads us to the\nquestion, how much opposition", "start": 1507.17, "duration": 3.14}, {"text": "is there really to\nenergy infrastructure?", "start": 1510.31, "duration": 2.58}, {"text": "Do we actually have\nsignificant opposition", "start": 1512.89, "duration": 2.37}, {"text": "to energy infrastructure?", "start": 1515.26, "duration": 1.17}, {"text": "We have a million anecdotes\nabout this happening", "start": 1516.43, "duration": 2.34}, {"text": "in many places.", "start": 1518.77, "duration": 1.23}, {"text": "But this paper is trying to\nget at the existing survey", "start": 1520.0, "duration": 2.94}, {"text": "literature, summarizing\na lot of papers,", "start": 1522.94, "duration": 2.43}, {"text": "trying to understand, what\nis the actual opposition?", "start": 1525.37, "duration": 3.0}, {"text": "Does it actually fit\ninto our definition", "start": 1528.37, "duration": 2.79}, {"text": "of \"not in my\nbackyard\" sentiments?", "start": 1531.16, "duration": 3.56}, {"text": "And so I like this graph.", "start": 1534.72, "duration": 1.44}, {"text": "Actually it's in this\npaper quite a bit.", "start": 1536.16, "duration": 1.75}, {"text": "It's a way of\nsummarizing the papers.", "start": 1537.91, "duration": 2.18}, {"text": "They look at these\nindependent variables,", "start": 1540.09, "duration": 2.55}, {"text": "whether or not\nthey're considered", "start": 1542.64, "duration": 2.4}, {"text": "in the literature,\nterms of knowledge,", "start": 1545.04, "duration": 2.4}, {"text": "gender, trust,\nbenefits of energy,", "start": 1547.44, "duration": 3.18}, {"text": "and drawbacks of\nenergy infrastructure.", "start": 1550.62, "duration": 2.16}, {"text": "And they look at the total\nportfolio of energy types.", "start": 1552.78, "duration": 2.85}, {"text": "Total portfolio--\nand then that's", "start": 1555.63, "duration": 1.47}, {"text": "composed of wind, solar, nuclear\npower plants, fossil fuels,", "start": 1557.1, "duration": 4.14}, {"text": "and transmission and\ndistribution lines.", "start": 1561.24, "duration": 1.98}, {"text": "And the red, yellow,\nand blue columns", "start": 1563.22, "duration": 2.79}, {"text": "represent percent of papers\nthat include this factor,", "start": 1566.01, "duration": 4.29}, {"text": "the percent of papers that\nfind it to be statistically", "start": 1570.3, "duration": 2.52}, {"text": "significant, and the\npercent of papers that find", "start": 1572.82, "duration": 2.22}, {"text": "it to have a positive effect.", "start": 1575.04, "duration": 2.008}, {"text": "So what's important to\nnote from this graph, what", "start": 1577.048, "duration": 2.042}, {"text": "I want to point out,\nis that wind, solar,", "start": 1579.09, "duration": 2.85}, {"text": "nuclear, fossil fuels,\nand transmission lines", "start": 1581.94, "duration": 2.1}, {"text": "have very different profiles\nin terms of who supports it.", "start": 1584.04, "duration": 5.02}, {"text": "Not many researchers\nhave considered", "start": 1589.06, "duration": 2.45}, {"text": "asking people about their actual\nknowledge of wind projects.", "start": 1591.51, "duration": 3.7}, {"text": "But if you include\na gender variable,", "start": 1595.21, "duration": 2.27}, {"text": "you'll often find that one\ngender, I'm guessing female,", "start": 1597.48, "duration": 3.75}, {"text": "is actually quite\nsupportive of wind projects.", "start": 1601.23, "duration": 3.493}, {"text": "Not all the papers find this\nas statistically significant.", "start": 1604.723, "duration": 2.417}, {"text": "But almost all the papers\nfind this support of gender", "start": 1607.14, "duration": 3.24}, {"text": "to be a very strong factor\nin supporting wind power.", "start": 1610.38, "duration": 4.03}, {"text": "If you look at a\ndifferent technology,", "start": 1614.41, "duration": 1.64}, {"text": "let's say, nuclear technology,\nonly about half of the papers", "start": 1616.05, "duration": 4.44}, {"text": "asked people their actual\nknowledge of nuclear power.", "start": 1620.49, "duration": 3.27}, {"text": "Only about 50% of\npapers find it to be", "start": 1623.76, "duration": 1.83}, {"text": "statistically significant.", "start": 1625.59, "duration": 1.27}, {"text": "And, actually, they find that\nknowledge of nuclear power", "start": 1626.86, "duration": 3.53}, {"text": "is quite positively correlated\nwith support for nuclear power.", "start": 1630.39, "duration": 5.13}, {"text": "At the same, time if you\ninclude gender, almost 100%", "start": 1635.52, "duration": 3.21}, {"text": "of the papers include gender.", "start": 1638.73, "duration": 1.65}, {"text": "2/3 of them find to be\nstatistically significant.", "start": 1640.38, "duration": 2.41}, {"text": "And they don't find a strong\npositive effect of gender", "start": 1642.79, "duration": 3.59}, {"text": "sentiment about nuclear power.", "start": 1646.38, "duration": 2.28}, {"text": "What I'm trying to\npoint out this graph", "start": 1648.66, "duration": 1.92}, {"text": "is that all of these factors,\nknowledge, gender, trust,", "start": 1650.58, "duration": 3.63}, {"text": "benefits, and drawbacks,\nhave different profiles.", "start": 1654.21, "duration": 3.85}, {"text": "Some of these\ntechnologies like solar", "start": 1658.06, "duration": 1.88}, {"text": "have extremely\npositive correlations", "start": 1659.94, "duration": 3.06}, {"text": "with the benefits\nof solar power,", "start": 1663.0, "duration": 2.97}, {"text": "whereas the drawbacks are\nquite often asked about", "start": 1665.97, "duration": 2.28}, {"text": "and have very little\ndifference in how", "start": 1668.25, "duration": 2.13}, {"text": "people feel about solar power.", "start": 1670.38, "duration": 1.83}, {"text": "What I encourage you to do\nis just look at this graph.", "start": 1672.21, "duration": 2.5}, {"text": "Look at these different\nfactors on the top.", "start": 1674.71, "duration": 2.25}, {"text": "Look at the energy technologies.", "start": 1676.96, "duration": 1.4}, {"text": "And think about how you might\nappeal to different people", "start": 1678.36, "duration": 3.27}, {"text": "to support different\ntechnologies.", "start": 1681.63, "duration": 1.86}, {"text": "Obviously, the profile\nfor fossil fuels", "start": 1683.49, "duration": 5.01}, {"text": "is quite different than the\nprofile for transmission", "start": 1688.5, "duration": 2.55}, {"text": "and distribution lines.", "start": 1691.05, "duration": 1.36}, {"text": "And so we should think\nabout this research,", "start": 1692.41, "duration": 2.9}, {"text": "and think about how\nto use it to get", "start": 1695.31, "duration": 1.62}, {"text": "people to support these\ndifferent technologies that we", "start": 1696.93, "duration": 2.49}, {"text": "do need.", "start": 1699.42, "duration": 1.7}, {"text": "So another paper I\nwant to talk about", "start": 1701.12, "duration": 1.94}, {"text": "is written by my colleague\nLarry Susskind at MIT.", "start": 1703.06, "duration": 3.21}, {"text": "It's just written this year\nabout sources of opposition", "start": 1706.27, "duration": 2.82}, {"text": "to renewable energy.", "start": 1709.09, "duration": 1.56}, {"text": "And to summarize this\npaper, a team of students--", "start": 1710.65, "duration": 3.23}, {"text": "many students I know\nfrom our department--", "start": 1713.88, "duration": 1.75}, {"text": "helped build this\ndatabase of opposition", "start": 1715.63, "duration": 2.01}, {"text": "to renewable energy projects.", "start": 1717.64, "duration": 2.54}, {"text": "And they did this by reviewing\nopen access media reports", "start": 1720.18, "duration": 3.69}, {"text": "and published scholarship\nto identify instances", "start": 1723.87, "duration": 2.94}, {"text": "in which conflict or\nopposition paused,", "start": 1726.81, "duration": 2.1}, {"text": "delayed, or canceled a\nutility-scale renewable energy", "start": 1728.91, "duration": 2.79}, {"text": "project.", "start": 1731.7, "duration": 0.99}, {"text": "There were media\nreports on projects", "start": 1732.69, "duration": 1.77}, {"text": "that had been defeated,\nincluding some concerns", "start": 1734.46, "duration": 2.79}, {"text": "about these projects that did\nnot lead to stoppage or delay.", "start": 1737.25, "duration": 3.15}, {"text": "They did not include\nthese in their study.", "start": 1740.4, "duration": 2.35}, {"text": "So essentially what\nthey did is they", "start": 1742.75, "duration": 1.82}, {"text": "went and looked\nat media reports,", "start": 1744.57, "duration": 1.56}, {"text": "and looked for projects\nin which there actually", "start": 1746.13, "duration": 2.28}, {"text": "had been delays or opposition.", "start": 1748.41, "duration": 3.49}, {"text": "What they find in\nthis database, they", "start": 1751.9, "duration": 1.89}, {"text": "find 53 projects equivalent\nto 9,586 megawatts", "start": 1753.79, "duration": 5.19}, {"text": "that were affected.", "start": 1758.98, "duration": 1.39}, {"text": "They find that 34% of the\nprojects were delayed.", "start": 1760.37, "duration": 2.72}, {"text": "50% of the projects were\ncanceled permanently.", "start": 1763.09, "duration": 2.49}, {"text": "And 26% of the\nprojects were resumed", "start": 1765.58, "duration": 3.36}, {"text": "after being stopped for\nseveral months or years.", "start": 1768.94, "duration": 3.09}, {"text": "In terms of the\nenergy transition,", "start": 1772.03, "duration": 1.83}, {"text": "this is a very\nconcerning finding", "start": 1773.86, "duration": 2.1}, {"text": "because we know we need to\nbuild solar and wind much more", "start": 1775.96, "duration": 3.0}, {"text": "rapidly than in the past to\nachieve our decarbonization", "start": 1778.96, "duration": 3.06}, {"text": "goals.", "start": 1782.02, "duration": 2.13}, {"text": "And they have seven\ndistinct hypotheses", "start": 1784.15, "duration": 1.92}, {"text": "regarding the sources of\nopposition and barriers", "start": 1786.07, "duration": 2.58}, {"text": "to renewable energy development.", "start": 1788.65, "duration": 2.19}, {"text": "First, communities could\nbe expressing concerns", "start": 1790.84, "duration": 3.33}, {"text": "about possible\nenvironmental impacts,", "start": 1794.17, "duration": 1.6}, {"text": "including impacts on wildlife.", "start": 1795.77, "duration": 2.64}, {"text": "There could be challenges to\nproject financing and revenue", "start": 1798.41, "duration": 2.52}, {"text": "generation.", "start": 1800.93, "duration": 1.62}, {"text": "There could be\npublic perceptions", "start": 1802.55, "duration": 1.38}, {"text": "of unfair\nparticipation processes", "start": 1803.93, "duration": 2.04}, {"text": "or inadequate inclusion in light\nof regulatory requirements.", "start": 1805.97, "duration": 3.94}, {"text": "There could be a\nfailure to respect", "start": 1809.91, "duration": 1.55}, {"text": "tribal rights, including\nthe right to consultation.", "start": 1811.46, "duration": 3.18}, {"text": "There could be health\nand safety concerns.", "start": 1814.64, "duration": 2.37}, {"text": "The intergovernmental disputes.", "start": 1817.01, "duration": 2.37}, {"text": "And there could be potential\nimpacts on land and property", "start": 1819.38, "duration": 2.64}, {"text": "value.", "start": 1822.02, "duration": 1.52}, {"text": "In the paper, one of the\nnotable findings, I think,", "start": 1823.54, "duration": 2.55}, {"text": "is that they find that\nmost opposition to projects", "start": 1826.09, "duration": 2.97}, {"text": "is not composed of a single\nsource of opposition.", "start": 1829.06, "duration": 3.87}, {"text": "As they characterize\nit, only 20%", "start": 1832.93, "duration": 2.4}, {"text": "of the sources of opposition\nhave one rationale", "start": 1835.33, "duration": 5.52}, {"text": "or one basis for opposition.", "start": 1840.85, "duration": 2.01}, {"text": "Most projects represent multiple\nconcerns or multiple sources", "start": 1842.86, "duration": 4.65}, {"text": "of opposition, or a\ncollision of different groups", "start": 1847.51, "duration": 2.58}, {"text": "that may be opposed\nto the project.", "start": 1850.09, "duration": 2.74}, {"text": "Now, this is a very\nconcerning finding", "start": 1852.83, "duration": 2.18}, {"text": "in terms of what\nwe are going to be", "start": 1855.01, "duration": 1.74}, {"text": "able to site in terms of\nour future renewable energy", "start": 1856.75, "duration": 2.97}, {"text": "projects.", "start": 1859.72, "duration": 1.21}, {"text": "But one thing I actually\nnoticed about this paper", "start": 1860.93, "duration": 2.06}, {"text": "is that I actually thought back\nto other studies I've seen.", "start": 1862.99, "duration": 3.72}, {"text": "This is a graph from the\nUS Energy Information", "start": 1866.71, "duration": 3.09}, {"text": "Administration.", "start": 1869.8, "duration": 0.93}, {"text": "And this actually shows how\nmuch generation capacity we've", "start": 1870.73, "duration": 2.67}, {"text": "added over the last 22 years.", "start": 1873.4, "duration": 3.03}, {"text": "In 1990, you can see that our\nenergy, our renewable energy", "start": 1876.43, "duration": 4.02}, {"text": "generation is actually dominated\nby hydroconventional and", "start": 1880.45, "duration": 4.17}, {"text": "hydropumped storage.", "start": 1884.62, "duration": 1.62}, {"text": "Even by 2005, we had very little\nwind and very little solar.", "start": 1886.24, "duration": 3.93}, {"text": "And by 2021, 16 years\nlater, we basically", "start": 1890.17, "duration": 3.48}, {"text": "had this massive\nexplosion of wind,", "start": 1893.65, "duration": 1.68}, {"text": "and this very rapid explosion\nof solar that is probably", "start": 1895.33, "duration": 3.69}, {"text": "only increasing this year also.", "start": 1899.02, "duration": 2.79}, {"text": "But what I realized\nwhen I calculated", "start": 1901.81, "duration": 1.96}, {"text": "this is that you\nhad this question", "start": 1903.77, "duration": 3.47}, {"text": "about whether the findings of\nthis paper are generalizable.", "start": 1907.24, "duration": 3.21}, {"text": "The Susskind et al\npaper finds 53 projects", "start": 1910.45, "duration": 3.09}, {"text": "over the years 2008 to 2021.", "start": 1913.54, "duration": 2.52}, {"text": "And that basically\nis 9,586 megawatts,", "start": 1916.06, "duration": 4.66}, {"text": "which is 9.6 gigawatts.", "start": 1920.72, "duration": 2.15}, {"text": "But from that graph\nI just showed you,", "start": 1922.87, "duration": 1.86}, {"text": "the Energy Information\nAdministration", "start": 1924.73, "duration": 1.83}, {"text": "finds roughly over the same\nperiod of time 2005 to 2021,", "start": 1926.56, "duration": 3.78}, {"text": "that we added 185 gigawatts.", "start": 1930.34, "duration": 3.0}, {"text": "So if you calculate\nthe percentage,", "start": 1933.34, "duration": 2.28}, {"text": "essentially the\nSusskind paper is", "start": 1935.62, "duration": 1.44}, {"text": "looking at 5% of the projects.", "start": 1937.06, "duration": 2.52}, {"text": "And so there's three\nperhaps stupid questions", "start": 1939.58, "duration": 2.73}, {"text": "that we need to ask about\nthis question of permitting", "start": 1942.31, "duration": 3.36}, {"text": "and sources of opposition\nto renewable energy.", "start": 1945.67, "duration": 2.79}, {"text": "First, how big is the\nproblem of permitting?", "start": 1948.46, "duration": 2.34}, {"text": "If these opposition sources\nare expressing themselves", "start": 1950.8, "duration": 3.27}, {"text": "through denying\npermits for projects,", "start": 1954.07, "duration": 2.04}, {"text": "we can find 5% of the projects\nhave been blocked or opposed,", "start": 1956.11, "duration": 4.05}, {"text": "does that mean that our other\n185 gigawatts of projects that", "start": 1960.16, "duration": 3.81}, {"text": "were built, could we have\nhad another 185 gigawatts", "start": 1963.97, "duration": 3.39}, {"text": "of projects if 50% of the\nprojects were canceled?", "start": 1967.36, "duration": 3.42}, {"text": "Or do we find in this\ncase the projects that", "start": 1970.78, "duration": 3.96}, {"text": "were canceled or opposed, and\nthe vast majority of projects", "start": 1974.74, "duration": 3.33}, {"text": "are actually built without\nas much controversy?", "start": 1978.07, "duration": 5.1}, {"text": "And so this brings me to the\nquestion of permitting reform,", "start": 1983.17, "duration": 2.833}, {"text": "which we started the class,\nwhich is discussed quite a bit", "start": 1986.003, "duration": 2.417}, {"text": "in Congress, and we in class.", "start": 1988.42, "duration": 1.56}, {"text": "How pervasive is this problem?", "start": 1989.98, "duration": 2.26}, {"text": "And, finally, are\nthe future problems", "start": 1992.24, "duration": 1.95}, {"text": "we're going to have around\nsources of opposition", "start": 1994.19, "duration": 2.0}, {"text": "or permitting similar to\nthe past problems that have", "start": 1996.19, "duration": 3.39}, {"text": "been found in this database?", "start": 1999.58, "duration": 1.71}, {"text": "Those are all open\nquestions for us", "start": 2001.29, "duration": 1.5}, {"text": "to consider in class discussion.", "start": 2002.79, "duration": 1.83}, {"text": "I look forward to seeing\nyou in class tomorrow.", "start": 2004.62, "duration": 4.43}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.946}, {"text": "[RUSTLING]", "start": 2.946, "duration": 1.473}, {"text": "[CLICKING]", "start": 4.419, "duration": 1.473}, {"text": "ROBERT TOWNSEND:\nOK, so let me say", "start": 11.31, "duration": 2.14}, {"text": "a couple of words about where\nwe are in the reading list.", "start": 13.45, "duration": 2.91}, {"text": "We're going to start today.", "start": 16.36, "duration": 1.68}, {"text": "We're done with the segment on\ncontracts and mechanism design,", "start": 18.04, "duration": 4.83}, {"text": "theory and applications.", "start": 22.87, "duration": 1.2}, {"text": "And we start today, Walrasian\nGeneral Equilibrium,", "start": 24.07, "duration": 3.61}, {"text": "which you've seen a\nbit before already.", "start": 27.68, "duration": 2.3}, {"text": "But we'll review and give\nthe proper definitions", "start": 29.98, "duration": 3.03}, {"text": "for the first 20%\nof the lecture.", "start": 33.01, "duration": 2.22}, {"text": "And then the rest\nof the lecture is", "start": 35.23, "duration": 1.92}, {"text": "devoted to an\nimportant application", "start": 37.15, "duration": 3.42}, {"text": "of General Equilibrium theory.", "start": 40.57, "duration": 1.98}, {"text": "And in particular, it\nhas to do with trade.", "start": 42.55, "duration": 3.18}, {"text": "So this lecture\ntoday is the theory,", "start": 45.73, "duration": 3.42}, {"text": "with some really startling\nand interesting propositions.", "start": 49.15, "duration": 3.39}, {"text": "And then with\ntrade on our minds,", "start": 52.54, "duration": 2.31}, {"text": "we'll go back to the Thai\ndata, and take a look", "start": 54.85, "duration": 2.61}, {"text": "at trade flows and\nfinancial flows that", "start": 57.46, "duration": 3.03}, {"text": "have changed over time\nas the country became", "start": 60.49, "duration": 2.13}, {"text": "more liberalized, or\nmore open internally.", "start": 62.62, "duration": 3.75}, {"text": "And then we're going to go to\na parallel lecture on the US", "start": 66.37, "duration": 4.71}, {"text": "that's going to look at\ntrade flows and potentially", "start": 71.08, "duration": 3.18}, {"text": "financial flows across\nstates in the US,", "start": 74.26, "duration": 3.06}, {"text": "where we'll be analyzing\nthe impact of tariffs,", "start": 77.32, "duration": 3.54}, {"text": "and/or China shocks--", "start": 80.86, "duration": 1.83}, {"text": "China imports.", "start": 82.69, "duration": 1.5}, {"text": "So these, dare I say it, it\nmay or may not be on your mind.", "start": 84.19, "duration": 5.28}, {"text": "If it's on your mind\nalready, the motivation", "start": 89.47, "duration": 3.24}, {"text": "here is a US policy decision\nwhich is very much in the news,", "start": 92.71, "duration": 5.16}, {"text": "and in some respects, a big\npart of the upcoming election.", "start": 97.87, "duration": 3.57}, {"text": "So I don't know if the timing of\nthese lectures are good or bad.", "start": 101.44, "duration": 3.36}, {"text": "But anyway, we'll be talking\nabout US trade policy", "start": 104.8, "duration": 5.82}, {"text": "within two lectures.", "start": 110.62, "duration": 2.11}, {"text": "So that's what's coming up.", "start": 112.73, "duration": 1.79}, {"text": "And today's lecture has got\ntwo start readings, the Kreps", "start": 114.52, "duration": 4.98}, {"text": "book on section 6.1, and\nthis Mas-Colell, Whinston,", "start": 119.5, "duration": 4.54}, {"text": "and Green.", "start": 124.04, "duration": 0.5}, {"text": "I rarely assign this book.", "start": 124.54, "duration": 1.92}, {"text": "But on the other\nhand, the lecture", "start": 126.46, "duration": 1.86}, {"text": "is based very closely\non that chapter.", "start": 128.32, "duration": 3.45}, {"text": "So I went ahead and just\nlisted it, MWG chapter 15 D,", "start": 131.77, "duration": 5.34}, {"text": "although it's quite\na famous model.", "start": 137.11, "duration": 2.55}, {"text": "We've been using MWG in\nthe theorems and so on.", "start": 139.66, "duration": 3.01}, {"text": "But I've never really\nfeatured it so heavily.", "start": 142.67, "duration": 3.77}, {"text": "In terms of the overall--", "start": 146.44, "duration": 2.4}, {"text": "just to see it in one\nspot, again, we're", "start": 148.84, "duration": 2.61}, {"text": "going to do Walrasian\nequilibrium, and then", "start": 151.45, "duration": 3.15}, {"text": "two applications of trade\nin Thailand and the US.", "start": 154.6, "duration": 3.48}, {"text": "That's actually\ngoing to complete--", "start": 158.08, "duration": 1.98}, {"text": "lecture 15 completes the\ncurrent segment of lectures", "start": 160.06, "duration": 3.3}, {"text": "before the second exam.", "start": 163.36, "duration": 2.2}, {"text": "So problem set 4, which was\nreleased last-- the last thing", "start": 165.56, "duration": 3.95}, {"text": "I want to do before\ngetting to the lecture", "start": 169.51, "duration": 2.7}, {"text": "is to review a bit of\nwhat we did last time.", "start": 172.21, "duration": 4.23}, {"text": "I deliberately didn't pick\nout very many questions here.", "start": 176.44, "duration": 3.45}, {"text": "Allow risk aversion on\nthe part of the borrower.", "start": 179.89, "duration": 2.7}, {"text": "There are several\nadvantages to writing down", "start": 182.59, "duration": 2.61}, {"text": "programs in lotteries.", "start": 185.2, "duration": 2.25}, {"text": "List two of them and explain.", "start": 187.45, "duration": 2.83}, {"text": "So let's see if I can get some--", "start": 190.28, "duration": 3.74}, {"text": "Charles, do you want to\ntake a crack at that?", "start": 194.02, "duration": 3.91}, {"text": "AUDIENCE: I think I can guess\none, definitely at least one", "start": 197.93, "duration": 2.64}, {"text": "of them, which, if I\nremember correctly,", "start": 200.57, "duration": 2.05}, {"text": "is that it allows you\nto make an incentive.", "start": 202.62, "duration": 3.98}, {"text": "You may select between\npeople with high income", "start": 206.6, "duration": 4.44}, {"text": "and low income, if you don't\nknow the income already.", "start": 211.04, "duration": 2.61}, {"text": "So like, if you're risk\naverse in the correct manner,", "start": 213.65, "duration": 4.41}, {"text": "then if you have a lottery,\nthen someone with low income", "start": 218.06, "duration": 6.54}, {"text": "might prefer a lottery with\nsomething like-- you might", "start": 224.6, "duration": 6.3}, {"text": "prefer the different risk return\ntrade off at different incomes.", "start": 230.9, "duration": 7.95}, {"text": "There's a dislike\nbetween various things,", "start": 238.85, "duration": 2.67}, {"text": "and help with some\nof the constraints.", "start": 241.52, "duration": 2.49}, {"text": "The other one, I don't\nremember the exact details.", "start": 244.01, "duration": 4.68}, {"text": "I haven't quite got them yet.", "start": 248.69, "duration": 3.33}, {"text": "ROBERT TOWNSEND: The\nfirst one is good.", "start": 252.02, "duration": 2.73}, {"text": "AUDIENCE: I'm going to\nguess something like,", "start": 254.75, "duration": 8.73}, {"text": "maybe making people not\nas willing to borrow", "start": 263.48, "duration": 3.112}, {"text": "or something like that.", "start": 266.592, "duration": 0.958}, {"text": "But I'm not exactly sure.", "start": 267.55, "duration": 3.38}, {"text": "ROBERT TOWNSEND: Let's see.", "start": 270.93, "duration": 2.48}, {"text": "Kerry, can you get\none more of them?", "start": 273.41, "duration": 3.21}, {"text": "AUDIENCE: Is it, like,\nincentive constraints", "start": 281.41, "duration": 2.58}, {"text": "could be non-convex.", "start": 283.99, "duration": 2.76}, {"text": "So it might be hard to solve.", "start": 286.75, "duration": 3.21}, {"text": "ROBERT TOWNSEND: Yeah, good.", "start": 289.96, "duration": 1.59}, {"text": "So there's various\nsources of non-convexity.", "start": 291.55, "duration": 2.66}, {"text": "So those incentive\nconstraints, when", "start": 294.21, "duration": 1.81}, {"text": "written without the lotteries,\nlike first order conditions", "start": 296.02, "duration": 4.97}, {"text": "of the borrower's\nchoice of effort.", "start": 300.99, "duration": 3.12}, {"text": "Those things can lead\nto non-convexity.", "start": 304.11, "duration": 3.28}, {"text": "So by doing it in lotteries,\nwe get that problem solved.", "start": 307.39, "duration": 4.4}, {"text": "And also, if there is\nsome indivisibilities,", "start": 311.79, "duration": 4.05}, {"text": "that would be solved.", "start": 315.84, "duration": 1.15}, {"text": "There are two indivisibilities\nin this problem.", "start": 316.99, "duration": 3.66}, {"text": "One has to do with\noccupation choice.", "start": 320.65, "duration": 2.93}, {"text": "You're either a wage\nearner or an entrepreneur.", "start": 323.58, "duration": 2.46}, {"text": "That's a binary choice.", "start": 326.04, "duration": 3.13}, {"text": "So the lotteries kind\nof smooth that over", "start": 329.17, "duration": 2.72}, {"text": "because you can effectively\nchoose the probability.", "start": 331.89, "duration": 4.57}, {"text": "And secondly, there could\nbe individual abilities", "start": 336.46, "duration": 4.01}, {"text": "in the discreteness\nof the capital grid.", "start": 340.47, "duration": 2.19}, {"text": "Like, you're going to capitalize\na high amount or a low amount.", "start": 342.66, "duration": 5.16}, {"text": "And again, lotteries help\nwith that indivisibility.", "start": 347.82, "duration": 4.57}, {"text": "OK, so the next one is really\na summary of what we did.", "start": 352.39, "duration": 7.73}, {"text": "But let me read it out.", "start": 360.12, "duration": 2.64}, {"text": "Sketch out how one can take\nthe model with the lotteries", "start": 362.76, "duration": 3.45}, {"text": "to the data on\noccupation choice,", "start": 366.21, "duration": 3.9}, {"text": "and estimate parameters.", "start": 370.11, "duration": 3.28}, {"text": "So can anyone attempt a\nsummary of what we did", "start": 373.39, "duration": 2.76}, {"text": "last time on that dimension?", "start": 376.15, "duration": 2.16}, {"text": "Pablo?", "start": 388.375, "duration": 0.5}, {"text": "AUDIENCE: Sure, I can\ntake a stab at this.", "start": 391.88, "duration": 1.75}, {"text": "So I think the way\nthat we did it was we--", "start": 393.63, "duration": 4.52}, {"text": "given these different parameters\nthat we had, of ability,", "start": 398.15, "duration": 3.75}, {"text": "education, and wealth, we solved\nfor this optimal contract,", "start": 401.9, "duration": 4.5}, {"text": "theoretically.", "start": 406.4, "duration": 1.23}, {"text": "And then we made a\nlikelihood function to--", "start": 407.63, "duration": 3.63}, {"text": "given these solutions,\nto see which one of these", "start": 411.26, "duration": 2.94}, {"text": "is like going to be like\nthe best, essentially.", "start": 414.2, "duration": 3.93}, {"text": "ROBERT TOWNSEND: Do you remember\nhow we did, quote, \"the best?\"", "start": 418.13, "duration": 3.528}, {"text": "The best in terms of what?", "start": 421.658, "duration": 2.592}, {"text": "AUDIENCE: Just kind of, like,\nthe likelihood function,", "start": 424.25, "duration": 2.55}, {"text": "trying to maximize that.", "start": 426.8, "duration": 1.05}, {"text": "ROBERT TOWNSEND: Yeah, OK.", "start": 427.85, "duration": 1.89}, {"text": "Yeah, so the likelihood\nfunction tells us", "start": 429.74, "duration": 5.22}, {"text": "the probability of what\nwe are seeing in the data", "start": 434.96, "duration": 5.98}, {"text": "if the model were true.", "start": 440.94, "duration": 2.25}, {"text": "So we're choosing parameters\nto make that probability", "start": 443.19, "duration": 2.99}, {"text": "as high as possible.", "start": 446.18, "duration": 1.26}, {"text": "OK, that's good.", "start": 451.39, "duration": 2.45}, {"text": "Any other questions\nabout that lecture?", "start": 453.84, "duration": 4.38}, {"text": "All the other questions\nat the beginning", "start": 458.22, "duration": 1.8}, {"text": "here were basically, write\nit down the way we did it", "start": 460.02, "duration": 3.78}, {"text": "in class, et cetera, et cetera.", "start": 463.8, "duration": 1.68}, {"text": "So it's not exactly\nconducive to asking you", "start": 465.48, "duration": 4.44}, {"text": "these questions in class.", "start": 469.92, "duration": 1.26}, {"text": "But it is important to\nbe reviewing these review", "start": 471.18, "duration": 4.83}, {"text": "questions.", "start": 476.01, "duration": 2.71}, {"text": "All right, so then we\ncome to the lecture today.", "start": 478.72, "duration": 5.28}, {"text": "This is Walrasian equilibria\nwith an application to trade.", "start": 484.0, "duration": 4.86}, {"text": "And we're going to consider\ntrade, for the most part,", "start": 488.86, "duration": 3.03}, {"text": "in a small open economy.", "start": 491.89, "duration": 2.1}, {"text": "Although we'll say a little bit\nabout putting the world pieces", "start": 493.99, "duration": 2.91}, {"text": "together at the very end.", "start": 496.9, "duration": 2.17}, {"text": "So here's the notation,\nwhich is largely", "start": 499.07, "duration": 3.08}, {"text": "a review because you have\nseen almost all of it before.", "start": 502.15, "duration": 3.75}, {"text": "When we write down an economy,\nwe mean the commodity space,", "start": 505.9, "duration": 3.27}, {"text": "in this case, capital L, a\nfinite number of commodities.", "start": 509.17, "duration": 3.3}, {"text": "I is the number of consumers.", "start": 512.47, "duration": 2.22}, {"text": "J is the number of firms--", "start": 514.69, "duration": 1.77}, {"text": "finite for each.", "start": 516.46, "duration": 1.38}, {"text": "Household or consumer,\nI, has a consumption set.", "start": 517.84, "duration": 3.839}, {"text": "And preferences over bundles\nin the consumption set, as for,", "start": 521.679, "duration": 4.381}, {"text": "example, represented\nby a utility function.", "start": 526.06, "duration": 2.79}, {"text": "Each firm, J, has a technology\nproduction possibility", "start": 528.85, "duration": 3.63}, {"text": "set in the same L\ndimensional space.", "start": 532.48, "duration": 2.8}, {"text": "And the economy has\nexogenously given endowments,", "start": 535.28, "duration": 4.25}, {"text": "according to this L\ndimensional endowment vector,", "start": 539.53, "duration": 3.24}, {"text": "with the bars being\nthe aggregates.", "start": 542.77, "duration": 3.29}, {"text": "So that's the economy.", "start": 546.06, "duration": 2.43}, {"text": "Now, in, say, a private\nownership economy, we", "start": 548.49, "duration": 3.09}, {"text": "have to specify, in\naddition, who owns what.", "start": 551.58, "duration": 3.46}, {"text": "So we imagine that consumer\nI has an endowment vector, L", "start": 555.04, "duration": 5.03}, {"text": "dimensional, subscript\nI, for consumer, I.", "start": 560.07, "duration": 3.72}, {"text": "And it is the sum of\nthese endowments over all", "start": 563.79, "duration": 3.3}, {"text": "the household that adds\nup to the omega bar L", "start": 567.09, "duration": 3.75}, {"text": "dimensional endowment vector\non the previous slide.", "start": 570.84, "duration": 2.88}, {"text": "Aggregates naturally come from\nthe individual's ownership.", "start": 573.72, "duration": 4.11}, {"text": "Each consumer, in addition\nto having endowments,", "start": 577.83, "duration": 3.27}, {"text": "has some share of\nthe profits of firms.", "start": 581.1, "duration": 3.55}, {"text": "So theta, IJ, being the\nshare that household, I, has,", "start": 584.65, "duration": 5.21}, {"text": "of J's profits.", "start": 589.86, "duration": 1.53}, {"text": "So these are meant to be\na division of the profit.", "start": 591.39, "duration": 3.28}, {"text": "So the sum of the shares\nover households, I,", "start": 594.67, "duration": 3.95}, {"text": "for a given firm,\nJ, add up to 1.", "start": 598.62, "duration": 2.67}, {"text": "Everything gets distributed.", "start": 601.29, "duration": 1.68}, {"text": "And household I is getting theta\nIJ of pi J, for firm, J. Now,", "start": 602.97, "duration": 4.83}, {"text": "pi J is obviously an\nendogenous object.", "start": 607.8, "duration": 2.83}, {"text": "It could be 0 if there were\nconstant returns to scale.", "start": 610.63, "duration": 3.53}, {"text": "It could be positive if\nthere are diminishing returns", "start": 614.16, "duration": 3.21}, {"text": "to scale.", "start": 617.37, "duration": 0.75}, {"text": "And also, when we did risk and\nreturn in village economies,", "start": 618.12, "duration": 4.89}, {"text": "we kind of naturally had\nan interesting and relevant", "start": 623.01, "duration": 3.93}, {"text": "special case that household\nI gets all the profits", "start": 626.94, "duration": 3.96}, {"text": "from the activities\nthat it undertakes.", "start": 630.9, "duration": 2.49}, {"text": "In that case, there was a\nhousehold, I, and a firm,", "start": 633.39, "duration": 2.94}, {"text": "I. It was the same entity.", "start": 636.33, "duration": 2.46}, {"text": "And household I was\ngetting theta IJ", "start": 638.79, "duration": 2.4}, {"text": "equal to 1 of its own\nprofits, as a special case.", "start": 641.19, "duration": 4.83}, {"text": "But general equilibrium\ntheory usually", "start": 646.02, "duration": 2.82}, {"text": "allows something more general.", "start": 648.84, "duration": 1.86}, {"text": "And you could think of\nthis literally as a market", "start": 650.7, "duration": 2.82}, {"text": "economy, where the shares are\nequity shares being traded.", "start": 653.52, "duration": 3.33}, {"text": "And all of the\ndividends are claimed", "start": 656.85, "duration": 2.79}, {"text": "by the ownership of shares.", "start": 659.64, "duration": 1.74}, {"text": "OK, so a private\nownership economy", "start": 661.38, "duration": 3.0}, {"text": "has a summary of\nthe consumption,", "start": 664.38, "duration": 2.52}, {"text": "set preferences,\nendowments of consumer", "start": 666.9, "duration": 2.31}, {"text": "I, the production sets of\nall the house firms, J,", "start": 669.21, "duration": 3.75}, {"text": "and the shares, theta IJ.", "start": 672.96, "duration": 3.1}, {"text": "Now we get to the\nbig definition here.", "start": 676.06, "duration": 3.02}, {"text": "In this L dimensional\ncommodity space,", "start": 679.08, "duration": 2.97}, {"text": "a price vector, p, is the price\nof all the commodities, inputs,", "start": 682.05, "duration": 4.74}, {"text": "and outputs, and everything.", "start": 686.79, "duration": 1.53}, {"text": "And a Walrasian equilibrium,\nor competitive equilibrium", "start": 688.32, "duration": 3.6}, {"text": "for short, for this\nprivate ownership economy,", "start": 691.92, "duration": 3.03}, {"text": "is a specification of\nallocations with stars on them,", "start": 694.95, "duration": 4.8}, {"text": "x and y star, for\nconsumers and firms--", "start": 699.75, "duration": 3.15}, {"text": "and a price vector star here\nbecause it's a special price.", "start": 702.9, "duration": 6.12}, {"text": "Allocations and prices have\nthe special properties.", "start": 709.02, "duration": 3.18}, {"text": "Each firm, J, has y\nstar J as the maximum", "start": 712.2, "duration": 3.69}, {"text": "of the firm's problem, which\nis to maximize profits.", "start": 715.89, "duration": 3.66}, {"text": "Hence, at y star, the valuation\nof outputs less inputs", "start": 719.55, "duration": 4.11}, {"text": "is weakly greater than it\nwould be for any other choice", "start": 723.66, "duration": 3.33}, {"text": "of production vector.", "start": 726.99, "duration": 1.38}, {"text": "Each consumer, i, is maximizing\nrelative to the preference", "start": 728.37, "duration": 4.02}, {"text": "ordering on bundles in the\nconsumption set, but also", "start": 732.39, "duration": 4.02}, {"text": "subject to the\nbudget constraint,", "start": 736.41, "duration": 1.5}, {"text": "that expenditures at price\np star, for any xi that", "start": 737.91, "duration": 3.81}, {"text": "could potentially be chosen--", "start": 741.72, "duration": 2.04}, {"text": "cannot exceed the\nright hand side,", "start": 743.76, "duration": 3.25}, {"text": "which is the private\nownership part.", "start": 747.01, "duration": 1.91}, {"text": "So omega i, being the\nendowments of consumer,", "start": 748.92, "duration": 3.57}, {"text": "i, evaluated at price p star,\nthat dot is inner product.", "start": 752.49, "duration": 4.38}, {"text": "And again, household i's claim\non the profits of firm, J.", "start": 756.87, "duration": 5.19}, {"text": "And the final property\nis that the allocation", "start": 762.06, "duration": 2.55}, {"text": "has to be feasible.", "start": 764.61, "duration": 0.885}, {"text": "And you can just read this as\ndemand cannot exceed supply,", "start": 765.495, "duration": 4.305}, {"text": "where supply includes both\nthe aggregated endowment", "start": 769.8, "duration": 2.7}, {"text": "and production.", "start": 772.5, "duration": 2.04}, {"text": "So we worked a lot with\nfeasibility before.", "start": 774.54, "duration": 3.05}, {"text": "We did that when we\ndefined Pareto optimality.", "start": 777.59, "duration": 3.12}, {"text": "The difference here\nin general equilibrium", "start": 780.71, "duration": 2.22}, {"text": "or Walrasian\nequilibrium is we've", "start": 782.93, "duration": 2.22}, {"text": "added this price vector\nexplicitly, and rewritten", "start": 785.15, "duration": 3.54}, {"text": "consumer maximization\nproblem, on which we've", "start": 788.69, "duration": 2.58}, {"text": "had several lectures.", "start": 791.27, "duration": 1.14}, {"text": "And firms-- sorry, I\nreversed the order--", "start": 792.41, "duration": 2.58}, {"text": "firms max and\nconsumers max problems.", "start": 794.99, "duration": 4.06}, {"text": "So everything's in one spot.", "start": 799.05, "duration": 3.856}, {"text": "OK, so a classic example\nis the Edgeworth Box.", "start": 802.906, "duration": 4.414}, {"text": "We previously defined\nPareto optimal allocations", "start": 807.32, "duration": 3.42}, {"text": "in this box, as\ncharacterized by tangencies", "start": 810.74, "duration": 3.51}, {"text": "of indifference curves.", "start": 814.25, "duration": 1.47}, {"text": "Here we add one more\ningredient, that if they", "start": 815.72, "duration": 2.7}, {"text": "start with this endowment,\nand we draw a price line", "start": 818.42, "duration": 3.81}, {"text": "through the endowment, then\neach consumer is maximizing", "start": 822.23, "duration": 4.56}, {"text": "utility, subject to its budget.", "start": 826.79, "duration": 2.89}, {"text": "So consumer 1 here has the\nnormal-looking budget line.", "start": 829.68, "duration": 6.87}, {"text": "And coming from the endowment\nand the tangency at x star", "start": 836.55, "duration": 4.58}, {"text": "would be the maximum.", "start": 841.13, "duration": 1.35}, {"text": "You may remember consumer\n2 up here on the northeast", "start": 842.48, "duration": 4.02}, {"text": "is moving to the southwest in\nterms of increased utility,", "start": 846.5, "duration": 3.42}, {"text": "and is also maximizing\nutility, which", "start": 849.92, "duration": 2.67}, {"text": "is achieved by a tangency on\nthat consumer's budget line.", "start": 852.59, "duration": 3.19}, {"text": "So this line here is\ndoing double duty.", "start": 855.78, "duration": 2.78}, {"text": "It's a budget line\nfor each household.", "start": 858.56, "duration": 2.4}, {"text": "But the perspective is\nat or below consumer 1,", "start": 860.96, "duration": 4.05}, {"text": "at or above the\nline for consumer 2.", "start": 865.01, "duration": 3.51}, {"text": "And here you're seeing the\nstar allocations, which", "start": 868.52, "duration": 3.33}, {"text": "are a competitive equilibrium.", "start": 871.85, "duration": 2.16}, {"text": "Everything in the box adds up to\nthe aggregates by construction.", "start": 874.01, "duration": 3.69}, {"text": "There is no production.", "start": 877.7, "duration": 1.47}, {"text": "They're all maximizing utility.", "start": 879.17, "duration": 2.19}, {"text": "And the price vector is\ncharacterized by the slope", "start": 881.36, "duration": 4.32}, {"text": "of this budget line.", "start": 885.68, "duration": 1.62}, {"text": "Now, we could go on with\na lot more interesting,", "start": 887.3, "duration": 3.6}, {"text": "and some nonstandard pictures,\nof the Edgeworth Box.", "start": 890.9, "duration": 3.81}, {"text": "But we're going to save a lot\nof that for another lecture.", "start": 894.71, "duration": 3.45}, {"text": "Here, I defined\nWalrasian equilibrium.", "start": 898.16, "duration": 2.58}, {"text": "I wanted to find something\nsimilar but not identical.", "start": 900.74, "duration": 3.93}, {"text": "It's a price equilibrium\nwith transfers.", "start": 904.67, "duration": 3.36}, {"text": "So here, the idea is\nthat the right hand", "start": 908.03, "duration": 3.03}, {"text": "side is a wealth assignment.", "start": 911.06, "duration": 2.97}, {"text": "Household, i, has\nwealth, w sub i.", "start": 914.03, "duration": 2.7}, {"text": "So the rest is similar.", "start": 916.73, "duration": 2.173}, {"text": "We're going to have an\nallocation with stars--", "start": 918.903, "duration": 1.917}, {"text": "a price vector, p, which\nshould have had stars on it", "start": 920.82, "duration": 3.02}, {"text": "because it's a special one--", "start": 923.84, "duration": 1.71}, {"text": "with the property,\nand an assignment", "start": 925.55, "duration": 2.94}, {"text": "of these wealth levels, such\nthat firms maximize profits.", "start": 928.49, "duration": 3.85}, {"text": "That's the same as before.", "start": 932.34, "duration": 1.46}, {"text": "Households maximize utility.", "start": 933.8, "duration": 2.35}, {"text": "But the right hand side of the\nbudget is this wealth object.", "start": 936.15, "duration": 4.01}, {"text": "And again, when we did partial\nequilibrium consumer problem,", "start": 940.16, "duration": 3.63}, {"text": "we talked about\nprices and wealth.", "start": 943.79, "duration": 1.71}, {"text": "We had income expansion\npaths as wealth varied.", "start": 945.5, "duration": 3.24}, {"text": "So this formulation\nof the problem", "start": 948.74, "duration": 2.34}, {"text": "is consistent with that.", "start": 951.08, "duration": 1.62}, {"text": "Although in partial\nequilibrium, we", "start": 952.7, "duration": 1.98}, {"text": "didn't ask where that\nwealth was coming from.", "start": 954.68, "duration": 2.49}, {"text": "An allocation is feasible.", "start": 957.17, "duration": 1.71}, {"text": "Again, demand cannot be greater\nthan the two sources of supply.", "start": 958.88, "duration": 4.48}, {"text": "Now the wealth assignments\nhave to be feasible.", "start": 963.36, "duration": 2.9}, {"text": "And here's where we\ncan say something", "start": 966.26, "duration": 2.01}, {"text": "about where wealth\nis coming from,", "start": 968.27, "duration": 1.65}, {"text": "namely, the sum of the\nwealths, whatever they are,", "start": 969.92, "duration": 2.79}, {"text": "have to equal the valuation of\nthe aggregated endowment vector", "start": 972.71, "duration": 4.98}, {"text": "plus the profits\nof all the firms.", "start": 977.69, "duration": 3.735}, {"text": "So somehow, this stuff\non the right hand side", "start": 981.425, "duration": 1.875}, {"text": "gets distributed across the\nhouseholds, each household, i,", "start": 983.3, "duration": 3.33}, {"text": "getting wealth, wi.", "start": 986.63, "duration": 1.77}, {"text": "And when we add it\nup, therefore, it", "start": 988.4, "duration": 2.4}, {"text": "sums up to the right hand side.", "start": 990.8, "duration": 2.56}, {"text": "Now note that at the bottom\nhere, a particular wealth", "start": 993.36, "duration": 4.61}, {"text": "assignment that works is what\nwe had on the previous slide,", "start": 997.97, "duration": 3.81}, {"text": "namely, give household, i, the\nvaluation of its endowment,", "start": 1001.78, "duration": 4.59}, {"text": "plus its share of the profits\nof the firms that it owns.", "start": 1006.37, "duration": 3.91}, {"text": "So in that sense, a price\nequilibrium with transfers", "start": 1010.28, "duration": 4.4}, {"text": "is more general, but includes\nthe valuation equilibrium.", "start": 1014.68, "duration": 4.56}, {"text": "That said, the word\ntransfers may catch your eye.", "start": 1019.24, "duration": 4.5}, {"text": "And the idea here is that\na Walrasian equilibrium", "start": 1023.74, "duration": 3.869}, {"text": "with ownership specifies\none level of wealth.", "start": 1027.609, "duration": 3.121}, {"text": "But we could, in principle,\nredistribute that wealth", "start": 1030.73, "duration": 2.879}, {"text": "by the government\nwith lump sum taxes", "start": 1033.609, "duration": 2.191}, {"text": "and transfers, and then look\nfor a new priced equilibrium.", "start": 1035.8, "duration": 4.92}, {"text": "And we will-- I think it's\non the next slide, yeah.", "start": 1040.72, "duration": 2.369}, {"text": "We will get to why\nwe're doing this.", "start": 1043.089, "duration": 2.671}, {"text": "Namely, any Walrasian\nequilibrium is Pareto-optimal.", "start": 1045.76, "duration": 4.8}, {"text": "But it's also true that any\nPareto-optimal allocation", "start": 1050.56, "duration": 4.32}, {"text": "can be supported as\na price equilibrium", "start": 1054.88, "duration": 2.28}, {"text": "with transfers, as\nin this definition.", "start": 1057.16, "duration": 2.88}, {"text": "However, to achieve the\nfact that any optimum can", "start": 1060.04, "duration": 2.97}, {"text": "be supported, it's\nkind of intuitive.", "start": 1063.01, "duration": 2.97}, {"text": "We may have to\nredistribute wealth.", "start": 1065.98, "duration": 3.59}, {"text": "And again, I have a series\nof lectures on this.", "start": 1069.57, "duration": 3.54}, {"text": "But if we're back in\nthe Edgeworth Box,", "start": 1073.11, "duration": 2.67}, {"text": "the competitive\nequilibrium has picked", "start": 1075.78, "duration": 2.07}, {"text": "out one particular\nPareto-optimal allocation.", "start": 1077.85, "duration": 3.63}, {"text": "But as there are many\noptimal allocations--", "start": 1081.48, "duration": 4.05}, {"text": "and to get to those,\nwe're going to have", "start": 1085.53, "duration": 1.77}, {"text": "to move this budget\nline up or down, hence,", "start": 1087.3, "duration": 3.3}, {"text": "redistributing the wealth.", "start": 1090.6, "duration": 1.215}, {"text": "OK, so now that we've got\nthe concept of the Walrasian", "start": 1094.55, "duration": 3.96}, {"text": "equilibrium in hand,\nI want to focus", "start": 1098.51, "duration": 2.49}, {"text": "on the primary application\ntoday, which is production", "start": 1101.0, "duration": 3.6}, {"text": "in a small open economy.", "start": 1104.6, "duration": 2.4}, {"text": "We have to shift gears\njust a little bit.", "start": 1107.0, "duration": 2.61}, {"text": "It's definitely going to\nbe general equilibrium.", "start": 1109.61, "duration": 2.64}, {"text": "We're going to have J firms.", "start": 1112.25, "duration": 2.04}, {"text": "And firms are producing goods.", "start": 1114.29, "duration": 2.37}, {"text": "So they're J goods\nbecause we have J firms.", "start": 1116.66, "duration": 3.48}, {"text": "Firm J produces good, qJ.", "start": 1120.14, "duration": 2.31}, {"text": "And there are L\nfactors of production,", "start": 1122.45, "duration": 2.46}, {"text": "labeled, in this\ncase, Z. So Z1J is", "start": 1124.91, "duration": 4.17}, {"text": "the input of the first\nfactor by firm, J, and so on.", "start": 1129.08, "duration": 4.42}, {"text": "And each firm, J, has a strictly\nconcave production function,", "start": 1133.5, "duration": 3.95}, {"text": "indicated here by f sub J.\nOutput of consumer good, qJ,", "start": 1137.45, "duration": 5.07}, {"text": "is a function of the\ninput vector, ZJ.", "start": 1142.52, "duration": 3.18}, {"text": "So now we specify endowments.", "start": 1145.7, "duration": 2.82}, {"text": "The endowments are going to\nbe given of the factor inputs.", "start": 1148.52, "duration": 4.8}, {"text": "They're owned by households.", "start": 1153.32, "duration": 1.74}, {"text": "And for the sake of\nargument, let's say they're", "start": 1155.06, "duration": 2.61}, {"text": "supplied in-elastically.", "start": 1157.67, "duration": 1.44}, {"text": "And they're not\ngoing to be consumed.", "start": 1159.11, "duration": 2.23}, {"text": "What we're going to try to\ndo is find the factor prices", "start": 1161.34, "duration": 3.95}, {"text": "that's consistent\nwith an equilibrium", "start": 1165.29, "duration": 2.34}, {"text": "within this small open economy.", "start": 1167.63, "duration": 2.35}, {"text": "However, we're going to take the\nprices of the goods as fixed.", "start": 1169.98, "duration": 4.17}, {"text": "So in that sense, it's\nstill partial equilibrium.", "start": 1174.15, "duration": 2.51}, {"text": "Think of it as a village,\nas a small open economy", "start": 1176.66, "duration": 3.33}, {"text": "or a country, that\nis small relative", "start": 1179.99, "duration": 2.43}, {"text": "to the rest of the world so that\nthese price vectors are fixed.", "start": 1182.42, "duration": 4.77}, {"text": "They're not going to be\nthe focus of our attention.", "start": 1187.19, "duration": 2.67}, {"text": "We are going to,\nhowever, try to find", "start": 1189.86, "duration": 2.94}, {"text": "the allocation of the inputs\nacross all the firms, how", "start": 1192.8, "duration": 3.6}, {"text": "those endowments of\nfactors get used,", "start": 1196.4, "duration": 3.21}, {"text": "as well as the Walrasian\nequilibrium price vector.", "start": 1199.61, "duration": 3.78}, {"text": "So firm j producing good qj\nwill maximize the difference", "start": 1203.39, "duration": 6.45}, {"text": "between revenues and costs.", "start": 1209.84, "duration": 2.74}, {"text": "So if w star, say, is a\ncandidate equilibrium price", "start": 1212.58, "duration": 4.43}, {"text": "vector, the firm would\nchoose its input vectors, Zj,", "start": 1217.01, "duration": 4.71}, {"text": "to maximize revenue minus costs\nat that guessed equilibrium", "start": 1221.72, "duration": 5.46}, {"text": "price vector, w star.", "start": 1227.18, "duration": 2.43}, {"text": "p is, again, a given-- pj,\nthe price of quantity, j,", "start": 1229.61, "duration": 5.04}, {"text": "is externally specified.", "start": 1234.65, "duration": 3.6}, {"text": "So Z star j is the solution to\nfirm j's maximization problem.", "start": 1238.25, "duration": 6.37}, {"text": "And if we're finding\nan equilibrium,", "start": 1244.62, "duration": 2.15}, {"text": "each firm will be\nmaximizing profits", "start": 1246.77, "duration": 2.76}, {"text": "and the sum of\nthe input demands,", "start": 1249.53, "duration": 2.76}, {"text": "in this case, the demand for\nthe L-th input from firm,", "start": 1252.29, "duration": 4.32}, {"text": "j, summing over all the\nfirms j, and in particular", "start": 1256.61, "duration": 3.06}, {"text": "the stars, which are\nalready profit-maximizing,", "start": 1259.67, "duration": 3.27}, {"text": "add up to the economy's\nendowment of the factor, Z bar,", "start": 1262.94, "duration": 5.04}, {"text": "for the L-th factor.", "start": 1267.98, "duration": 1.59}, {"text": "And this is true for all,\neach and every, factor,", "start": 1269.57, "duration": 3.06}, {"text": "L. This one is true for\neach and every firm, j.", "start": 1272.63, "duration": 4.17}, {"text": "So this is what we're looking\nfor, the Walrasian equilibrium", "start": 1276.8, "duration": 3.81}, {"text": "in the factor markets, taking\nexternal prices as given.", "start": 1280.61, "duration": 4.26}, {"text": "All right, you already know\nsomething about the solutions", "start": 1284.87, "duration": 3.69}, {"text": "to the profit\nmaximization problem.", "start": 1288.56, "duration": 2.58}, {"text": "Namely, the value of\nthe marginal product", "start": 1291.14, "duration": 3.48}, {"text": "should be equal to--\nof the L factor,", "start": 1294.62, "duration": 3.3}, {"text": "should be equal to its cost.", "start": 1297.92, "duration": 1.98}, {"text": "Just differentiate this\nthing on the previous slide.", "start": 1299.9, "duration": 3.9}, {"text": "With respect to zj, you'll get\na derivative in the F function,", "start": 1303.8, "duration": 3.9}, {"text": "and will get the factor\ninput price on the cost side.", "start": 1307.7, "duration": 5.13}, {"text": "That's what this says.", "start": 1312.83, "duration": 1.08}, {"text": "Factor input price--\nhere's the derivative of F,", "start": 1313.91, "duration": 3.54}, {"text": "with respect to the L factor.", "start": 1317.45, "duration": 1.65}, {"text": "And that p is, of course, part\nof the exogenously-given price", "start": 1319.1, "duration": 4.44}, {"text": "vector.", "start": 1323.54, "duration": 0.99}, {"text": "How many equations\nare there like this?", "start": 1324.53, "duration": 3.46}, {"text": "Well, we have to specify here.", "start": 1327.99, "duration": 3.08}, {"text": "It's the L factor.", "start": 1331.07, "duration": 1.8}, {"text": "And we have L--", "start": 1332.87, "duration": 2.28}, {"text": "capital L factors all together.", "start": 1335.15, "duration": 2.37}, {"text": "And this is for the j firm.", "start": 1337.52, "duration": 2.61}, {"text": "But we have capital J firms.", "start": 1340.13, "duration": 3.55}, {"text": "So we have L times\nJ equations here.", "start": 1343.68, "duration": 4.94}, {"text": "And we have another\nset of equations", "start": 1348.62, "duration": 1.86}, {"text": "which are the equilibrium,\nthat the demand for the factors", "start": 1350.48, "duration": 3.45}, {"text": "adds up to the total.", "start": 1353.93, "duration": 1.44}, {"text": "But again, this is true for\neach and every L-th factor.", "start": 1355.37, "duration": 3.34}, {"text": "So there are L of these guys.", "start": 1358.71, "duration": 2.1}, {"text": "So we have L times\nJ equations here.", "start": 1360.81, "duration": 3.68}, {"text": "And we have L equations here.", "start": 1364.49, "duration": 3.16}, {"text": "So the number of equations\nis equal to the number", "start": 1367.65, "duration": 3.2}, {"text": "of variables.", "start": 1370.85, "duration": 1.39}, {"text": "So in principle, we\nshould be able to solve", "start": 1372.24, "duration": 2.09}, {"text": "this system of equations to\ndetermine the equilibrium", "start": 1374.33, "duration": 3.09}, {"text": "factor prices.", "start": 1377.42, "duration": 1.47}, {"text": "It's tedious and\nboring to keep counting", "start": 1378.89, "duration": 2.21}, {"text": "the number of variables.", "start": 1381.1, "duration": 1.0}, {"text": "But it is actually useful to\nsee if we have fully specified,", "start": 1382.1, "duration": 4.62}, {"text": "and we potentially\nhave a solution.", "start": 1386.72, "duration": 2.62}, {"text": "So now, we've already\nsolved in lecture 4,", "start": 1389.34, "duration": 3.74}, {"text": "which was about production,\na cost minimization problem.", "start": 1393.08, "duration": 3.94}, {"text": "So we defined there\nthe cost for firm J", "start": 1397.02, "duration": 4.01}, {"text": "of producing the quantity, qj,\nwhen the input vector was w.", "start": 1401.03, "duration": 6.09}, {"text": "I must say, even I\nwent back this morning", "start": 1407.12, "duration": 3.3}, {"text": "in reviewing this lecture to\ntake a look at the earlier", "start": 1410.42, "duration": 3.12}, {"text": "lecture.", "start": 1413.54, "duration": 1.05}, {"text": "Today there's kind of an uneasy\ntension because I'm partially", "start": 1414.59, "duration": 3.69}, {"text": "telling you things that you've\nhad before, on the other hand,", "start": 1418.28, "duration": 3.3}, {"text": "aware that you may not remember\nexactly what we had before.", "start": 1421.58, "duration": 4.44}, {"text": "If you go back and look,\nit'll all come back to you.", "start": 1426.02, "duration": 2.61}, {"text": "And some of these\nslides are actually", "start": 1428.63, "duration": 2.19}, {"text": "repeats of what\nwas in lecture 4.", "start": 1430.82, "duration": 3.0}, {"text": "Anyway, when we\nderived the least cost", "start": 1433.82, "duration": 3.72}, {"text": "way of producing\nan output, qj, we", "start": 1437.54, "duration": 3.12}, {"text": "got that marginal cost\nwas equal to price.", "start": 1440.66, "duration": 3.67}, {"text": "It's equal.", "start": 1444.33, "duration": 0.5}, {"text": "Marginal cost is from your very\nfirst economics micro course,", "start": 1444.83, "duration": 4.83}, {"text": "probably.", "start": 1449.66, "duration": 0.9}, {"text": "Now, this second\nequation is the equation", "start": 1450.56, "duration": 3.75}, {"text": "that the demands for the\nfactors adds up to the total.", "start": 1454.31, "duration": 3.66}, {"text": "But it's written\nin an interesting", "start": 1457.97, "duration": 1.83}, {"text": "and a bit unconventional way.", "start": 1459.8, "duration": 2.19}, {"text": "The aggregate amount of factor\nl that's available is z bar l.", "start": 1461.99, "duration": 4.98}, {"text": "And we want the demands of\nthese firms for producing.", "start": 1466.97, "duration": 3.6}, {"text": "But instead, we use\nthe Shephard's lemma,", "start": 1470.57, "duration": 3.21}, {"text": "the derivative of\nthe cost of firm j,", "start": 1473.78, "duration": 3.27}, {"text": "with respect to the\nprice of the l-th factor,", "start": 1477.05, "duration": 3.51}, {"text": "we derived as the amount of\nthe l-th factor to be used.", "start": 1480.56, "duration": 5.26}, {"text": "And again, you may or may\nnot remember that that's", "start": 1485.82, "duration": 2.69}, {"text": "the Shephard's lemma.", "start": 1488.51, "duration": 2.1}, {"text": "Here it is, written\ndown here at the bottom.", "start": 1490.61, "duration": 3.16}, {"text": "So we just substitute\nwhat was written as zlj,", "start": 1493.77, "duration": 3.89}, {"text": "summation over j equal to z\nbar, we substitute in the result", "start": 1497.66, "duration": 5.04}, {"text": "from Shephard's lemma\nto get this equation", "start": 1502.7, "duration": 2.85}, {"text": "OK, special case, 2 by 2.", "start": 1505.55, "duration": 3.12}, {"text": "And there'll be another\ntwo coming later.", "start": 1508.67, "duration": 3.25}, {"text": "But for now, two types\nof firms, J equals 1, 2--", "start": 1511.92, "duration": 5.84}, {"text": "two inputs.", "start": 1517.76, "duration": 1.47}, {"text": "Now, it's useful to think of\nthe inputs as labor and capital.", "start": 1519.23, "duration": 4.18}, {"text": "And that, in fact, will\nanticipate the trade", "start": 1523.41, "duration": 2.63}, {"text": "applications.", "start": 1526.04, "duration": 1.145}, {"text": "Are we reproducing\ngoods with machines?", "start": 1527.185, "duration": 1.625}, {"text": "Are we producing\ngoods with labor?", "start": 1528.81, "duration": 2.63}, {"text": "What happens to the\nlabor when we have", "start": 1531.44, "duration": 3.3}, {"text": "a decline in manufacturing?", "start": 1534.74, "duration": 1.98}, {"text": "It comes from\nhaving more inputs.", "start": 1536.72, "duration": 1.89}, {"text": "So these are the kind of\ningredients, labor and capital", "start": 1538.61, "duration": 3.03}, {"text": "being kind of obvious labels\nfor us, in the case of this two", "start": 1541.64, "duration": 4.68}, {"text": "factor model.", "start": 1546.32, "duration": 1.41}, {"text": "Production functions,\njust to write out", "start": 1547.73, "duration": 1.86}, {"text": "the notation, production\nfunction for good 1, as it", "start": 1549.59, "duration": 4.47}, {"text": "inputs, the second\nsubscript denotes the firm,", "start": 1554.06, "duration": 4.2}, {"text": "the first one, the input.", "start": 1558.26, "duration": 1.39}, {"text": "So this is the first\ninput in firm 1,", "start": 1559.65, "duration": 2.39}, {"text": "the second input in firm 1.", "start": 1562.04, "duration": 2.595}, {"text": "f2 is output of\nfirm 2 as a function", "start": 1564.635, "duration": 3.225}, {"text": "of the first input\nin for firm 2,", "start": 1567.86, "duration": 2.19}, {"text": "and the second input for firm 2.", "start": 1570.05, "duration": 2.37}, {"text": "And we're going to\nassume, in this special 2", "start": 1572.42, "duration": 2.04}, {"text": "by 2 model, that these\nproduction functions, each", "start": 1574.46, "duration": 2.94}, {"text": "of them, are constant\nreturns to scale.", "start": 1577.4, "duration": 2.86}, {"text": "So it's homogeneity of degree 1.", "start": 1580.26, "duration": 2.72}, {"text": "So if we're given a\nvector of input prices", "start": 1582.98, "duration": 3.39}, {"text": "for capital and\nlabor, we can define", "start": 1586.37, "duration": 3.3}, {"text": "the cost of producing\none unit of good, j.", "start": 1589.67, "duration": 4.65}, {"text": "This is called the unit cost--", "start": 1594.32, "duration": 3.69}, {"text": "or you may want to review that\nthe cost of producing arbitrary", "start": 1598.01, "duration": 4.62}, {"text": "levels just scales\nup or down depending", "start": 1602.63, "duration": 2.79}, {"text": "on whether that\nother target level is", "start": 1605.42, "duration": 2.7}, {"text": "higher or lower than 1.", "start": 1608.12, "duration": 2.28}, {"text": "So once we have the cost\nof producing one unit,", "start": 1610.4, "duration": 3.51}, {"text": "we can get the cost of\nproducing any number of units.", "start": 1613.91, "duration": 3.42}, {"text": "And what inputs solve\nthat minimum cost problem?", "start": 1617.33, "duration": 3.51}, {"text": "They're denoted with a's.", "start": 1620.84, "duration": 2.1}, {"text": "So for firm j, a1j\nand a2j are the way", "start": 1622.94, "duration": 4.95}, {"text": "to achieve the least cost\nwhen the input vector is w.", "start": 1627.89, "duration": 4.71}, {"text": "Input price vector\nis w So here I", "start": 1632.6, "duration": 4.59}, {"text": "belabor a little bit\nwhat you've seen before.", "start": 1637.19, "duration": 3.16}, {"text": "It's constant returns to scale.", "start": 1640.35, "duration": 2.19}, {"text": "So the cost function is linear.", "start": 1642.54, "duration": 2.64}, {"text": "Constant returns to scale\nis this linear production", "start": 1645.18, "duration": 2.45}, {"text": "possibilities frontier.", "start": 1647.63, "duration": 1.59}, {"text": "Cost function is linear.", "start": 1649.22, "duration": 1.51}, {"text": "Marginal cost\nequals average cost.", "start": 1650.73, "duration": 2.06}, {"text": "If price of a good,\nsay good j, is", "start": 1652.79, "duration": 2.28}, {"text": "less than marginal and average\ncost, nothing gets produced.", "start": 1655.07, "duration": 3.49}, {"text": "And when price is equal to\nmarginal and average cost,", "start": 1658.56, "duration": 3.38}, {"text": "then they're happy\nto produce anything.", "start": 1661.94, "duration": 1.68}, {"text": "Although profits are 0.", "start": 1663.62, "duration": 1.23}, {"text": "And price cannot be higher\nbecause they would go bananas.", "start": 1664.85, "duration": 4.08}, {"text": "And then the assertion, which\nI've already said twice,", "start": 1668.93, "duration": 3.24}, {"text": "profits must be zero.", "start": 1672.17, "duration": 1.68}, {"text": "And that's just, again, a\nreview slide from before.", "start": 1673.85, "duration": 3.01}, {"text": "So price equals cost.", "start": 1676.86, "duration": 2.75}, {"text": "This is the unit cost.", "start": 1679.61, "duration": 1.44}, {"text": "Price is the price of a unit.", "start": 1681.05, "duration": 1.95}, {"text": "So we have cost equal to prices.", "start": 1683.0, "duration": 3.03}, {"text": "OK, so another review.", "start": 1686.03, "duration": 2.85}, {"text": "We did this before, too.", "start": 1688.88, "duration": 1.62}, {"text": "What's special about\nconstant returns", "start": 1690.5, "duration": 1.95}, {"text": "to scale is we can solve\nthe problem for the one", "start": 1692.45, "duration": 5.17}, {"text": "unit of output,\nminimize the cost", "start": 1697.62, "duration": 2.97}, {"text": "of achieving one unit of output.", "start": 1700.59, "duration": 2.52}, {"text": "And that's going to give us--", "start": 1703.11, "duration": 1.68}, {"text": "I guess I just\nsaid this, the cost", "start": 1704.79, "duration": 1.92}, {"text": "for any other level of output,\njust by scaling up and down", "start": 1706.71, "duration": 3.78}, {"text": "the solution.", "start": 1710.49, "duration": 0.93}, {"text": "And the ratios of input\nuse will not be changing.", "start": 1711.42, "duration": 4.32}, {"text": "I think in the previous\nlecture, I actually", "start": 1715.74, "duration": 2.7}, {"text": "said I wasn't terribly\npleased with how", "start": 1718.44, "duration": 2.67}, {"text": "cryptically-worded it was.", "start": 1721.11, "duration": 1.59}, {"text": "And I gave you as an\ninformal homework assignment", "start": 1722.7, "duration": 3.15}, {"text": "to do a proof by contradiction\nto prove that the input use", "start": 1725.85, "duration": 4.92}, {"text": "ratio is going to\nbe entirely dictated", "start": 1730.77, "duration": 2.82}, {"text": "by the input prices,\nregardless of the scale.", "start": 1733.59, "duration": 4.2}, {"text": "That is to say, this input\nratio will remain constant.", "start": 1737.79, "duration": 3.36}, {"text": "And again, please, I apologize\nbecause I'm throwing at you", "start": 1741.15, "duration": 3.81}, {"text": "things from a previous lecture.", "start": 1744.96, "duration": 1.62}, {"text": "It was lecture 4.", "start": 1746.58, "duration": 0.99}, {"text": "So that was some time ago.", "start": 1747.57, "duration": 1.8}, {"text": "But I don't want\nto belabor it today", "start": 1749.37, "duration": 1.5}, {"text": "or we won't get\nto something new.", "start": 1750.87, "duration": 1.87}, {"text": "So for now, we'll just\naccept this as a fact.", "start": 1752.74, "duration": 3.2}, {"text": "Then we come to a key definition\nabout factor intensity.", "start": 1755.94, "duration": 3.66}, {"text": "Say good 1 is more intensive\nin factor 1 than good 2.", "start": 1759.6, "duration": 5.58}, {"text": "Then the production of\ngood 2, if naturally,", "start": 1765.18, "duration": 2.76}, {"text": "firm producing good 1 uses\nrelatively more of input 1--", "start": 1767.94, "duration": 5.4}, {"text": "input 1 relative to input\n2, then does firm 2.", "start": 1773.34, "duration": 4.26}, {"text": "So the definition, to say\ngood 1 is relatively more", "start": 1777.6, "duration": 3.6}, {"text": "intensive than factor 1, means\nthat the ratio of factor 1", "start": 1781.2, "duration": 3.75}, {"text": "to factor 2 in firm 1 is\nhigher than it is in firm 2.", "start": 1784.95, "duration": 4.2}, {"text": "So it's a pretty\nnatural definition.", "start": 1789.15, "duration": 2.49}, {"text": "Of course, it can move around.", "start": 1791.64, "duration": 1.98}, {"text": "But the inequality\nremains the same.", "start": 1793.62, "duration": 3.46}, {"text": "It's intense.", "start": 1797.08, "duration": 0.8}, {"text": "No matter what the\ninput price ratio is,", "start": 1797.88, "duration": 3.63}, {"text": "the optimizing choice\nof inputs will always", "start": 1801.51, "duration": 3.45}, {"text": "satisfy this inequality when\ncomparing firm 1 to firm 2.", "start": 1804.96, "duration": 4.65}, {"text": "So now something a bit new\nthat was not in lecture 4,", "start": 1809.61, "duration": 4.23}, {"text": "although it's not hard.", "start": 1813.84, "duration": 1.5}, {"text": "We're going to plot the cost of\nproducing one unit of a good.", "start": 1815.34, "duration": 5.43}, {"text": "We're going to plot that\ncost curve as a function", "start": 1820.77, "duration": 3.0}, {"text": "of the input prices, w1 and w2.", "start": 1823.77, "duration": 3.9}, {"text": "So in particular, if, say,\nfor a given w1 and w2 bar,", "start": 1827.67, "duration": 4.71}, {"text": "your assertion is we're\non this cost curve,", "start": 1832.38, "duration": 3.27}, {"text": "then if we increase the price\nof the first input to w prime 1", "start": 1835.65, "duration": 5.91}, {"text": "and we're supposed\nto be on an isocost,", "start": 1841.56, "duration": 2.49}, {"text": "meaning same cost\ncurve, the increase", "start": 1844.05, "duration": 2.43}, {"text": "in the first factor price would\nmean the cost would be higher.", "start": 1846.48, "duration": 3.52}, {"text": "So we have to lower the\nprice of the second factor", "start": 1850.0, "duration": 3.53}, {"text": "in order to compensate.", "start": 1853.53, "duration": 1.78}, {"text": "So that on net, after\nwe make this move,", "start": 1855.31, "duration": 3.65}, {"text": "total costs are the same\nbecause it is the isocost curve.", "start": 1858.96, "duration": 3.82}, {"text": "So this down-sloping nature\nof the isocost curve,", "start": 1862.78, "duration": 4.31}, {"text": "plotted against various input\nprices, makes a lot of sense.", "start": 1867.09, "duration": 4.48}, {"text": "The other thing is\nthis concave shape.", "start": 1871.57, "duration": 2.69}, {"text": "This comes from a property\nof the minimized cost.", "start": 1874.26, "duration": 4.8}, {"text": "In particular, this set of input\nprices at or above the cost", "start": 1879.06, "duration": 5.13}, {"text": "line is a convex set.", "start": 1884.19, "duration": 1.59}, {"text": "But we did this a\nlot with respect", "start": 1885.78, "duration": 1.95}, {"text": "to the consumer\noptimization problem.", "start": 1887.73, "duration": 2.82}, {"text": "We defined quasi-concave utility\nfunctions and the associated", "start": 1890.55, "duration": 3.84}, {"text": "concave indifference curves.", "start": 1894.39, "duration": 1.53}, {"text": "And we had the\nweak upper contour", "start": 1895.92, "duration": 2.04}, {"text": "set as being strictly convex.", "start": 1897.96, "duration": 2.13}, {"text": "So these are analogs here.", "start": 1900.09, "duration": 1.56}, {"text": "Now, the assertion is that\nthis cost function is, in fact,", "start": 1901.65, "duration": 3.66}, {"text": "concave.", "start": 1905.31, "duration": 1.02}, {"text": "And again, as a review--", "start": 1906.33, "duration": 2.52}, {"text": "but who remembers?", "start": 1908.85, "duration": 2.0}, {"text": "We already had\nderived in lecture 4", "start": 1910.85, "duration": 3.69}, {"text": "that the cost function is\nconcave in the input prices.", "start": 1914.54, "duration": 3.49}, {"text": "So I just pasted in\nthe slide to remind us.", "start": 1918.03, "duration": 3.11}, {"text": "So now we have\ndown-sloping concave.", "start": 1921.14, "duration": 3.03}, {"text": "And the other thing\nthat's going on here", "start": 1924.17, "duration": 1.71}, {"text": "is, at these particular\ninput prices,", "start": 1925.88, "duration": 3.45}, {"text": "if we go back to\nShephard's lemma,", "start": 1929.33, "duration": 1.98}, {"text": "the derivative of\nthe minimized cost,", "start": 1931.31, "duration": 3.27}, {"text": "with respect to, say, the\nprice of the first factor,", "start": 1934.58, "duration": 3.18}, {"text": "is the level input\nof the first factor,", "start": 1937.76, "duration": 3.03}, {"text": "and similarly, for the level\ninput of the second factor.", "start": 1940.79, "duration": 3.25}, {"text": "So the ratio, the slope\nof this line, which", "start": 1944.04, "duration": 3.44}, {"text": "is the ratio of the\nderivatives of the cost", "start": 1947.48, "duration": 2.37}, {"text": "curve at an optimum,\nmust, by Shephard's lemma,", "start": 1949.85, "duration": 3.78}, {"text": "be equal to the ratio of\nthe optimizing inputs.", "start": 1953.63, "duration": 4.0}, {"text": "And again, logically, if you\nincreased the input price", "start": 1957.63, "duration": 5.24}, {"text": "of factor 1, keeping\ncost constant,", "start": 1962.87, "duration": 3.6}, {"text": "you would move along\nthis isocost line.", "start": 1966.47, "duration": 2.7}, {"text": "And you would increase\nthe amount of good 2", "start": 1969.17, "duration": 3.93}, {"text": "and factor 2, and decrease\nthe amount of factor 1.", "start": 1973.1, "duration": 4.77}, {"text": "You substitute away\nfrom the factor, which", "start": 1977.87, "duration": 1.83}, {"text": "has now increased in price.", "start": 1979.7, "duration": 1.6}, {"text": "So in the earlier slide, lecture\n4, I didn't replicate it.", "start": 1981.3, "duration": 3.05}, {"text": "We had a Walt Disney example\nabout machinery versus humans.", "start": 1984.35, "duration": 5.07}, {"text": "Now I'll just warn\nyou, it is very hard", "start": 1989.42, "duration": 3.18}, {"text": "to remember what's\ndivided by what.", "start": 1992.6, "duration": 2.19}, {"text": "But anyway, the fact that this\nperpendicular becomes steeper", "start": 1994.79, "duration": 3.51}, {"text": "is consistent with\nthe input of factor 1", "start": 1998.3, "duration": 3.42}, {"text": "going down because\nit's the inverse ratio.", "start": 2001.72, "duration": 3.84}, {"text": "All right, did that.", "start": 2005.56, "duration": 2.77}, {"text": "So now, how do we solve for\nequilibrium factor prices?", "start": 2008.33, "duration": 3.98}, {"text": "This is just a picture\nof a particular firm", "start": 2012.31, "duration": 2.79}, {"text": "and what it would do, firm j--", "start": 2015.1, "duration": 2.28}, {"text": "what it would do as we\nvary the input prices?", "start": 2017.38, "duration": 2.43}, {"text": "And we want to find\nparticular input prices,", "start": 2019.81, "duration": 2.4}, {"text": "such that both firms\nare minimizing costs,", "start": 2022.21, "duration": 3.75}, {"text": "and all the factors\nget utilized.", "start": 2025.96, "duration": 2.43}, {"text": "So remember, because we have\nconstant returns to scale", "start": 2028.39, "duration": 3.42}, {"text": "and because we've taken the\nright hand side prices as", "start": 2031.81, "duration": 3.24}, {"text": "arbitrary and given,\ncoming from nowhere,", "start": 2035.05, "duration": 2.94}, {"text": "say, but certainly known\nto the firms, as part", "start": 2037.99, "duration": 3.81}, {"text": "of the solution,\nthe unit cost has", "start": 2041.8, "duration": 2.97}, {"text": "to equal to the price\nfor both firms 1 and 2.", "start": 2044.77, "duration": 3.9}, {"text": "So we have, from this, two\nequations and two unknowns,", "start": 2048.67, "duration": 4.66}, {"text": "namely the factor prices, w1 and\nw2, that we want to solve for.", "start": 2053.33, "duration": 4.98}, {"text": "So visually, we can actually\nput both firm 1's and firm 2's", "start": 2058.31, "duration": 4.97}, {"text": "isocost lines on\nthe same diagram.", "start": 2063.28, "duration": 2.939}, {"text": "In other words,\nI've gone from here,", "start": 2066.219, "duration": 1.931}, {"text": "which was firm j, and firm\nj's particular isocost line--", "start": 2068.15, "duration": 5.9}, {"text": "talking about how it\nvaries with w1 and w2,", "start": 2074.05, "duration": 2.82}, {"text": "to this diagram, in which\nwe have not only firm 1--", "start": 2076.87, "duration": 3.39}, {"text": "excuse me, but also firm two.", "start": 2080.26, "duration": 3.06}, {"text": "And if we're going to\nfind an equilibrium,", "start": 2083.32, "duration": 3.149}, {"text": "we're going to find price for\nfactor 1 and a price for factor", "start": 2086.469, "duration": 3.841}, {"text": "2, each.", "start": 2090.31, "duration": 1.23}, {"text": "So each firm, in an\nequilibrium, is going", "start": 2091.54, "duration": 2.61}, {"text": "to face the same factor prices.", "start": 2094.15, "duration": 2.52}, {"text": "And each firm must lie\non its own unit cost", "start": 2096.67, "duration": 4.14}, {"text": "curve equal to the price\nfrom this equation.", "start": 2100.81, "duration": 3.13}, {"text": "So you can see the unit cost\nfor firm 1 equal to p 2,", "start": 2103.94, "duration": 6.17}, {"text": "the unit cost of\nfirm 2 equal to p2.", "start": 2110.11, "duration": 2.82}, {"text": "These are particular\nisocost curves for firm 1", "start": 2112.93, "duration": 3.3}, {"text": "and firm 2 that are associated\nwith two of the equilibrium", "start": 2116.23, "duration": 3.69}, {"text": "equations.", "start": 2119.92, "duration": 0.79}, {"text": "And if we're going to find\ncommon factor prices faced", "start": 2120.71, "duration": 2.87}, {"text": "by both of the\nfirms, we only want", "start": 2123.58, "duration": 2.76}, {"text": "one factor price for\nthe first factor,", "start": 2126.34, "duration": 2.55}, {"text": "and one factor price\nfor the second one.", "start": 2128.89, "duration": 2.26}, {"text": "So where can that\nhappen in this diagram?", "start": 2131.15, "duration": 2.09}, {"text": "Only one spot, and that's where\nthese isocost curves cross.", "start": 2133.24, "duration": 4.87}, {"text": "So this is kind of\ndisplaying the equilibrium.", "start": 2138.11, "duration": 2.82}, {"text": "Let me say one more word about\nwhy they're shaped in this way.", "start": 2140.93, "duration": 4.34}, {"text": "Remember, firm 1 is\nintensive in factor 1.", "start": 2145.27, "duration": 3.81}, {"text": "So if we did move\nalong its curve,", "start": 2149.08, "duration": 2.82}, {"text": "lowering w2 and increasing w1--", "start": 2151.9, "duration": 3.27}, {"text": "because it's\nintensive in factor 1,", "start": 2155.17, "duration": 2.67}, {"text": "it tends to use a\nlot of factor 1.", "start": 2157.84, "duration": 1.89}, {"text": "So increasing the\nprice of factor 1", "start": 2159.73, "duration": 2.43}, {"text": "is kind over big\nburden for firm 1.", "start": 2162.16, "duration": 2.58}, {"text": "And to compensate,\nwe have to lower", "start": 2164.74, "duration": 2.52}, {"text": "the price of the second\nfactor quite a lot,", "start": 2167.26, "duration": 2.88}, {"text": "relative to the compensation\nwe would have to offer firm 2.", "start": 2170.14, "duration": 4.86}, {"text": "For the same increase in w1,\nthe corresponding decrease in w2", "start": 2175.0, "duration": 4.95}, {"text": "is less for firm 2 than firm\n1 because, again, firm 1", "start": 2179.95, "duration": 4.68}, {"text": "is intensive in factor 1.", "start": 2184.63, "duration": 2.16}, {"text": "So this factor\nintensity, which I", "start": 2186.79, "duration": 2.31}, {"text": "said was a very\nnatural definition,", "start": 2189.1, "duration": 2.37}, {"text": "is true everywhere\nby definition.", "start": 2191.47, "duration": 3.39}, {"text": "Hence, the curve for firm 1\nhas to be steeper everywhere", "start": 2194.86, "duration": 3.87}, {"text": "than the curve for firm 2.", "start": 2198.73, "duration": 1.62}, {"text": "And that's why\nthey have to cross.", "start": 2200.35, "duration": 2.55}, {"text": "Questions?", "start": 2202.9, "duration": 2.25}, {"text": "OK, so again, just\nto review this slide,", "start": 2205.15, "duration": 3.22}, {"text": "we're looking for\nan equilibrium.", "start": 2208.37, "duration": 1.76}, {"text": "The claim is we found\nit now because we", "start": 2210.13, "duration": 3.03}, {"text": "have found the factor prices\nfor the first and second factor,", "start": 2213.16, "duration": 4.32}, {"text": "such that each firm is\nminimizing its unit costs", "start": 2217.48, "duration": 4.05}, {"text": "associated with the cost--", "start": 2221.53, "duration": 2.34}, {"text": "the unit cost being\nequal to price.", "start": 2223.87, "duration": 2.72}, {"text": "So these must be the\nequilibrium quantities", "start": 2226.59, "duration": 2.87}, {"text": "of the factors being utilized\nin each of the two firms.", "start": 2229.46, "duration": 4.47}, {"text": "All right, so we're kind\nof doing an algorithm here.", "start": 2233.93, "duration": 4.5}, {"text": "The algorithm was define\nWalrasian equilibrium.", "start": 2238.43, "duration": 5.1}, {"text": "And do that for\nthis 2 by 2 model.", "start": 2243.53, "duration": 3.12}, {"text": "And without telling you\nthat I was going to do this,", "start": 2246.65, "duration": 2.85}, {"text": "we're doing it iteratively.", "start": 2249.5, "duration": 1.92}, {"text": "The very first thing we do is\nsolve for the factor prices.", "start": 2251.42, "duration": 4.98}, {"text": "And now we're going to get\nthe quantities this way.", "start": 2256.4, "duration": 3.22}, {"text": "So the quantities,\nnaturally, are", "start": 2259.62, "duration": 1.85}, {"text": "going to come from a diagram\nwhere we have isoquants.", "start": 2261.47, "duration": 3.69}, {"text": "So here we have the\ninput of factor 1,", "start": 2265.16, "duration": 2.19}, {"text": "the input of factor 2.", "start": 2267.35, "duration": 1.5}, {"text": "For firm j, this is an\nisoquant equal production,", "start": 2268.85, "duration": 3.42}, {"text": "as you move along\nthat isoquant curve.", "start": 2272.27, "duration": 3.07}, {"text": "And again, you may\nremember, or not,", "start": 2275.34, "duration": 3.32}, {"text": "that to minimize the cost\nof producing one unit,", "start": 2278.66, "duration": 6.24}, {"text": "we find the tangency,\nwhere the isoquant", "start": 2284.9, "duration": 3.27}, {"text": "is tangent to the isocost line.", "start": 2288.17, "duration": 3.48}, {"text": "Now again, it's a bit\ndizzying because what's", "start": 2291.65, "duration": 2.58}, {"text": "an isocost line in one space\nis a different-looking cost", "start": 2294.23, "duration": 4.65}, {"text": "line in another.", "start": 2298.88, "duration": 0.99}, {"text": "In this space,\nthe isocost curves", "start": 2299.87, "duration": 2.28}, {"text": "are concave, as I was saying.", "start": 2302.15, "duration": 3.15}, {"text": "That's in the space\nof factor inputs.", "start": 2305.3, "duration": 2.37}, {"text": "W1 and W2 prices.", "start": 2307.67, "duration": 2.28}, {"text": "w1 and w2 here,\nthe isocost line is", "start": 2309.95, "duration": 4.26}, {"text": "linear, in the space of\ninput quantities, z1 and z2.", "start": 2314.21, "duration": 5.67}, {"text": "So again, the minimized cost\nof producing one unit of output", "start": 2319.88, "duration": 4.59}, {"text": "here at these factor\nprices, w, is this tangency.", "start": 2324.47, "duration": 5.31}, {"text": "And it's associated with the\ninputs, a1 and a2, to firm, j.", "start": 2329.78, "duration": 5.34}, {"text": "And again, the\nreason is something", "start": 2335.12, "duration": 3.12}, {"text": "we reviewed before,\nthat when you take", "start": 2338.24, "duration": 2.58}, {"text": "the derivative of the isoquant,\nwe're getting dz2, dz1,", "start": 2340.82, "duration": 6.69}, {"text": "the quantity is\nstaying the same.", "start": 2347.51, "duration": 1.78}, {"text": "So we solve for the solution.", "start": 2349.29, "duration": 2.24}, {"text": "And we're getting a relationship\nbetween the derivative", "start": 2351.53, "duration": 2.85}, {"text": "of the isocost and the inputs.", "start": 2354.38, "duration": 3.34}, {"text": "OK, so now we want to solve,\nnot only for quantities,", "start": 2357.72, "duration": 4.44}, {"text": "but the equilibrium amounts.", "start": 2362.16, "duration": 3.0}, {"text": "Now remember, again, here\nwe were playing around", "start": 2365.16, "duration": 4.38}, {"text": "with unit costs.", "start": 2369.54, "duration": 1.44}, {"text": "But we don't know the level\nof the quantities yet.", "start": 2370.98, "duration": 3.3}, {"text": "And likewise, hence, we don't\nknow the levels of the inputs.", "start": 2374.28, "duration": 3.99}, {"text": "Although we do know\nsomething about the ratios", "start": 2378.27, "duration": 2.25}, {"text": "of the inputs one once we find\nthe equilibrium factor prices.", "start": 2380.52, "duration": 4.74}, {"text": "So having found the\nequilibrium factor prices,", "start": 2385.26, "duration": 2.73}, {"text": "we now turn to\ndetermining the inputs.", "start": 2387.99, "duration": 3.96}, {"text": "But it almost looks\nlike a review.", "start": 2391.95, "duration": 2.52}, {"text": "The input ratio\nfor firm 1 must be", "start": 2394.47, "duration": 3.27}, {"text": "those a coefficients,\nthe solution to the cost", "start": 2397.74, "duration": 3.63}, {"text": "minimization problem\nin the quantity", "start": 2401.37, "duration": 2.43}, {"text": "space at the equilibrium\nfactor prices, w star.", "start": 2403.8, "duration": 4.47}, {"text": "This is true for firm 1.", "start": 2408.27, "duration": 1.29}, {"text": "It's also true for firm 2.", "start": 2409.56, "duration": 1.93}, {"text": "So the ratios of\ninputs being used", "start": 2411.49, "duration": 3.05}, {"text": "must be consistent with\nthe optimized ratio", "start": 2414.54, "duration": 3.45}, {"text": "of inputs being used at the\nequilibrium factor prices.", "start": 2417.99, "duration": 3.9}, {"text": "There are two equations there.", "start": 2421.89, "duration": 1.47}, {"text": "There's another equation,\nnamely that the inputs being", "start": 2423.36, "duration": 4.53}, {"text": "used by the firm, in this case,\ninput 1, and the second, input", "start": 2427.89, "duration": 3.57}, {"text": "2--", "start": 2431.46, "duration": 0.6}, {"text": "input 1 in firm 1,\ninput 1 in firm 2,", "start": 2432.06, "duration": 2.73}, {"text": "must sum up to the\naggregate endowments.", "start": 2434.79, "duration": 2.68}, {"text": "So finally, another\ningredient of the economy,", "start": 2437.47, "duration": 4.22}, {"text": "the level of the\ninput endowments,", "start": 2441.69, "duration": 2.67}, {"text": "is here on the right hand side.", "start": 2444.36, "duration": 2.14}, {"text": "And when we found an\nequilibrium in input use,", "start": 2446.5, "duration": 3.14}, {"text": "it has to satisfy this\nsystem of equations.", "start": 2449.64, "duration": 4.09}, {"text": "Now I can show you\na picture of it.", "start": 2453.73, "duration": 2.57}, {"text": "You may remember that\nwhen we did production,", "start": 2456.3, "duration": 2.85}, {"text": "we talked about the\nproduction box--", "start": 2459.15, "duration": 2.5}, {"text": "not the Edgeworth Box\nof the consumer theory,", "start": 2461.65, "duration": 3.05}, {"text": "but the production box\nof production theory.", "start": 2464.7, "duration": 3.33}, {"text": "We had, again,\nlike the isoquants,", "start": 2468.03, "duration": 2.58}, {"text": "input 1 and input 2\non the x and y-axis,", "start": 2470.61, "duration": 3.33}, {"text": "firm 1 is oriented around 01.", "start": 2473.94, "duration": 3.33}, {"text": "And we have\nisoquants for firm 1.", "start": 2477.27, "duration": 3.09}, {"text": "And this ratio, the\nslope of this line,", "start": 2480.36, "duration": 3.72}, {"text": "is the optimizing\nratio of inputs.", "start": 2484.08, "duration": 3.64}, {"text": "And again, that\noptimizing ratio of inputs", "start": 2487.72, "duration": 3.05}, {"text": "is entirely pinned down\nby the equilibrium factor", "start": 2490.77, "duration": 2.64}, {"text": "prices, which we already found.", "start": 2493.41, "duration": 1.99}, {"text": "So they have to lie on\nthis line somewhere.", "start": 2495.4, "duration": 3.2}, {"text": "Why here?", "start": 2498.6, "duration": 1.11}, {"text": "Because when we go up to firm\n2, the same thing is true,", "start": 2499.71, "duration": 4.32}, {"text": "that the optimizing input ratio\nof factor 2 to factor 1 must", "start": 2504.03, "duration": 5.01}, {"text": "lie on this line coming\nout of the 02 origin.", "start": 2509.04, "duration": 4.51}, {"text": "So input ratio for\nfirm 1 is fixed.", "start": 2513.55, "duration": 3.26}, {"text": "Input ratio for firm 2 is fixed.", "start": 2516.81, "duration": 2.537}, {"text": "Fixed at what?", "start": 2519.347, "duration": 0.583}, {"text": "Fixed at these levels, as\nin the earlier diagrams.", "start": 2519.93, "duration": 3.48}, {"text": "Hence, in an equilibrium, to be\nconsistent with each of them,", "start": 2523.41, "duration": 4.02}, {"text": "it must be where\nthese lines cross.", "start": 2527.43, "duration": 2.76}, {"text": "So this finally\ndetermines output", "start": 2530.19, "duration": 2.46}, {"text": "because we have isoquants here.", "start": 2532.65, "duration": 2.19}, {"text": "So firm 1 is producing\non this isoquant.", "start": 2534.84, "duration": 3.66}, {"text": "Firm 2 is producing\non this isoquant.", "start": 2538.5, "duration": 2.37}, {"text": "So now we've got\nboth, the equilibrium", "start": 2540.87, "duration": 3.33}, {"text": "level of the inputs--", "start": 2544.2, "duration": 2.04}, {"text": "which is boom boom and\nboom boom, as well as", "start": 2546.24, "duration": 2.97}, {"text": "the outputs associated\nwith these isoquants.", "start": 2549.21, "duration": 3.35}, {"text": "OK, are there questions so far?", "start": 2552.56, "duration": 4.27}, {"text": "Well, let me just\nsay, when you review,", "start": 2556.83, "duration": 2.57}, {"text": "there is a lot of\ncontent in this lecture.", "start": 2559.4, "duration": 2.34}, {"text": "Some of it's review, as I've\nalready been apologizing.", "start": 2561.74, "duration": 3.39}, {"text": "Go back to lecture 4.", "start": 2565.13, "duration": 1.62}, {"text": "But also, it's kind of\nstacked, in the sense", "start": 2566.75, "duration": 2.37}, {"text": "that each segment builds\non the subsequent segments.", "start": 2569.12, "duration": 4.65}, {"text": "And it's very hard\nto take it in when", "start": 2573.77, "duration": 1.68}, {"text": "I go through these slides\nfor the first time.", "start": 2575.45, "duration": 2.65}, {"text": "But I think if you review\nit the second round,", "start": 2578.1, "duration": 3.0}, {"text": "you'll see how the ingredients\nare coming together.", "start": 2581.1, "duration": 2.72}, {"text": "Anyway, where are\nwe at this point?", "start": 2583.82, "duration": 2.94}, {"text": "We had a country,\nsay, an economy,", "start": 2586.76, "duration": 2.7}, {"text": "with two types of\nfirms, j, equal 1, 2.", "start": 2589.46, "duration": 3.51}, {"text": "We have two factors,\nsay labor and capital.", "start": 2592.97, "duration": 3.42}, {"text": "We had this economy facing\nexternally-given arbitrary", "start": 2596.39, "duration": 4.35}, {"text": "prices, p1 and p2,\nfor the firms 1 and 2.", "start": 2600.74, "duration": 4.59}, {"text": "And we have now solved for the\nmarket clearing factor prices", "start": 2605.33, "duration": 5.04}, {"text": "in the input markets for the\nlevel of the inputs being used", "start": 2610.37, "duration": 4.77}, {"text": "and the equilibrium\nquantities being produced.", "start": 2615.14, "duration": 3.37}, {"text": "That's how far we got already.", "start": 2618.51, "duration": 2.05}, {"text": "OK, so now I want to\nget to the trade part.", "start": 2620.56, "duration": 3.68}, {"text": "And I'm going to\nadd the other two.", "start": 2624.24, "duration": 1.68}, {"text": "So this is two firms, two\nfactors, and two countries.", "start": 2625.92, "duration": 3.71}, {"text": "And the two countries\nare denoted A and B.", "start": 2629.63, "duration": 2.76}, {"text": "So each country has\nthe same technologies.", "start": 2632.39, "duration": 3.87}, {"text": "Each country can produce\ngood 1 and produce", "start": 2636.26, "duration": 3.09}, {"text": "good 2 with these factors, the\ntwo factors, labor and capital.", "start": 2639.35, "duration": 5.1}, {"text": "We could have imagined\ndifferent technologies", "start": 2644.45, "duration": 2.64}, {"text": "in the different\ncountries, and in a minute,", "start": 2647.09, "duration": 2.49}, {"text": "different preferences.", "start": 2649.58, "duration": 1.5}, {"text": "You haven't seen the\nconsumer side of it yet.", "start": 2651.08, "duration": 2.16}, {"text": "But the famous 2 by 2 by 2\nmodel with some amazingly cool", "start": 2653.24, "duration": 5.16}, {"text": "theorems assumes\nidentical technologies", "start": 2658.4, "duration": 3.03}, {"text": "and identical preferences\nin the two countries.", "start": 2661.43, "duration": 2.97}, {"text": "What's different across\nthe two countries", "start": 2664.4, "duration": 2.16}, {"text": "are the factor endowments.", "start": 2666.56, "duration": 1.68}, {"text": "Namely, one country\nis capital abundant.", "start": 2668.24, "duration": 2.76}, {"text": "The other is labor abundant.", "start": 2671.0, "duration": 1.89}, {"text": "So you might, for\nexample, have thought--", "start": 2672.89, "duration": 2.7}, {"text": "although this is\nno longer as true", "start": 2675.59, "duration": 2.07}, {"text": "as it once was for reasons\nof the theorem we're", "start": 2677.66, "duration": 2.76}, {"text": "about to see--", "start": 2680.42, "duration": 1.14}, {"text": "that countries like\nMexico or China", "start": 2681.56, "duration": 3.48}, {"text": "are relatively\nwell-endowed with labor.", "start": 2685.04, "duration": 2.49}, {"text": "The US, being quite\nindustrialized,", "start": 2687.53, "duration": 2.67}, {"text": "is relatively\nwell-endowed with capital.", "start": 2690.2, "duration": 3.03}, {"text": "So the US, as\ndistinct from Mexico,", "start": 2693.23, "duration": 3.78}, {"text": "is a capital-abundant country.", "start": 2697.01, "duration": 3.0}, {"text": "And Mexico is a\nlabor-abundant country.", "start": 2700.01, "duration": 2.82}, {"text": "I choose the example carefully\nbecause, again, with NAFTA,", "start": 2702.83, "duration": 3.69}, {"text": "there's all kinds\nof controversies", "start": 2706.52, "duration": 2.01}, {"text": "about what happened to the\nwages of US domestic workers", "start": 2708.53, "duration": 4.11}, {"text": "when the US increased\nits trade with Mexico.", "start": 2712.64, "duration": 3.48}, {"text": "We now have a theorem\nthat's going to tell us", "start": 2716.12, "duration": 2.55}, {"text": "something about that.", "start": 2718.67, "duration": 1.41}, {"text": "Oh, anyway, here, two countries,\nA and B, with different factor", "start": 2720.08, "duration": 3.39}, {"text": "endowments-- one being\ncapital abundant,", "start": 2723.47, "duration": 2.31}, {"text": "and the other labor abundant.", "start": 2725.78, "duration": 1.35}, {"text": "Now, what if there's\nno trade at all?", "start": 2727.13, "duration": 2.04}, {"text": "We're in autarky.", "start": 2729.17, "duration": 1.41}, {"text": "What's going to determine the\nprice of the consumption goods?", "start": 2730.58, "duration": 3.6}, {"text": "Well, that's where we\nneed the consumer part.", "start": 2734.18, "duration": 2.4}, {"text": "We're going to need the\nrepresentative consumer", "start": 2736.58, "duration": 2.16}, {"text": "in a given country\nmaximizing utility,", "start": 2738.74, "duration": 2.7}, {"text": "given its ownership of factors,\nand potentially shares.", "start": 2741.44, "duration": 5.14}, {"text": "Although in this constant\nreturns to scale world,", "start": 2746.58, "duration": 2.54}, {"text": "there are no profits anyway.", "start": 2749.12, "duration": 1.83}, {"text": "So we have an entirely\ndomestic market,", "start": 2750.95, "duration": 2.73}, {"text": "like China completely closed\nto the rest of the world.", "start": 2753.68, "duration": 3.3}, {"text": "Now we jump all the\nway to free trade.", "start": 2756.98, "duration": 3.03}, {"text": "And if there's no cost\nof shipping goods around,", "start": 2760.01, "duration": 2.4}, {"text": "there's an abstraction.", "start": 2762.41, "duration": 1.23}, {"text": "The price of the\ntwo goods now have", "start": 2763.64, "duration": 1.68}, {"text": "to be the same in each\ncountry because if there's", "start": 2765.32, "duration": 4.08}, {"text": "no cost to shipping goods\naround, if the price of a good", "start": 2769.4, "duration": 3.78}, {"text": "were lower in one country\nthan another, then", "start": 2773.18, "duration": 4.65}, {"text": "they would basically\nbe exporting", "start": 2777.83, "duration": 2.46}, {"text": "a lot of that good\nat a low price", "start": 2780.29, "duration": 1.98}, {"text": "to the other country\nthat's willing to buy it", "start": 2782.27, "duration": 2.16}, {"text": "at a high price.", "start": 2784.43, "duration": 0.91}, {"text": "So those prices\ncan't be different", "start": 2785.34, "duration": 1.7}, {"text": "when there's no cost to\nshipping goods around.", "start": 2787.04, "duration": 2.49}, {"text": "Now exactly where\nthe prices are,", "start": 2789.53, "duration": 3.33}, {"text": "I will show you in a minute.", "start": 2792.86, "duration": 2.05}, {"text": "But first, let me give\nyou the theorem called", "start": 2794.91, "duration": 4.0}, {"text": "Heckscher-Ohlin theorem.", "start": 2798.91, "duration": 1.73}, {"text": "Suppose initially,\nwe're in autarky.", "start": 2800.64, "duration": 2.0}, {"text": "And neither country is trading.", "start": 2802.64, "duration": 2.1}, {"text": "And the price of the\ncapital-intensive good", "start": 2804.74, "duration": 2.73}, {"text": "in the capital-abundant country\nwill be relatively low--", "start": 2807.47, "duration": 4.68}, {"text": "relative to the price of\nthat capital-intensive good", "start": 2812.15, "duration": 3.63}, {"text": "in the other country.", "start": 2815.78, "duration": 1.77}, {"text": "This is intuitive in\nterms of the economics.", "start": 2817.55, "duration": 3.09}, {"text": "You have a country that has a\nlot of capital and relatively", "start": 2820.64, "duration": 4.59}, {"text": "little labor.", "start": 2825.23, "duration": 1.14}, {"text": "That's abundant capital.", "start": 2826.37, "duration": 1.65}, {"text": "That should drive down\nthe price of the capital", "start": 2828.02, "duration": 2.55}, {"text": "input, relative to the\nwage of the labor input--", "start": 2830.57, "duration": 4.38}, {"text": "relative also to\nthe other country,", "start": 2834.95, "duration": 3.45}, {"text": "which is abundant in\nlabor, and should have,", "start": 2838.4, "duration": 3.3}, {"text": "because there's a lot of labor\naround, a relatively low wage.", "start": 2841.7, "duration": 5.37}, {"text": "So those are the two\nstatements, the price", "start": 2847.07, "duration": 1.95}, {"text": "of the capital-intensive good\nin the capital-abundant country", "start": 2849.02, "duration": 3.06}, {"text": "will be lower,\nrelative to the price", "start": 2852.08, "duration": 3.63}, {"text": "of that capital-intensive\ngood in the other country.", "start": 2855.71, "duration": 2.79}, {"text": "And vise versa for labor.", "start": 2858.5, "duration": 1.95}, {"text": "The price of the labor-intensive\ngood in the labor-abundant", "start": 2860.45, "duration": 3.45}, {"text": "country will be lower,\nrelative to the price of that", "start": 2863.9, "duration": 4.59}, {"text": "labor-intensive good\nin the other country--", "start": 2868.49, "duration": 2.25}, {"text": "or in some, when an input is\nabundant, it has a low price.", "start": 2870.74, "duration": 4.45}, {"text": "Now we go to trade.", "start": 2875.19, "duration": 2.03}, {"text": "We don't allow the\ninputs to migrate.", "start": 2877.22, "duration": 2.73}, {"text": "But we do allow\ntrade in the goods.", "start": 2879.95, "duration": 2.79}, {"text": "Think about that first line.", "start": 2882.74, "duration": 1.47}, {"text": "The price of the\ncapital-intensive good", "start": 2884.21, "duration": 2.22}, {"text": "is low, relative to the price\nof the capital-intensive", "start": 2886.43, "duration": 4.2}, {"text": "good in the other country.", "start": 2890.63, "duration": 1.6}, {"text": "So because it has\na low price, it", "start": 2892.23, "duration": 3.14}, {"text": "should be a, quote,\n\"competitive export.\"", "start": 2895.37, "duration": 2.61}, {"text": "So the capital-abundant\ncountry will be exporting", "start": 2897.98, "duration": 4.32}, {"text": "the capital-intensive good.", "start": 2902.3, "duration": 1.92}, {"text": "The labor-abundant\ncountry will be exporting", "start": 2904.22, "duration": 3.12}, {"text": "the labor-intensive good.", "start": 2907.34, "duration": 2.25}, {"text": "And we're going to find\nan equilibrium where", "start": 2909.59, "duration": 2.7}, {"text": "this kind of arbitrage is\nno longer profitable, where", "start": 2912.29, "duration": 4.02}, {"text": "the prices will be the same.", "start": 2916.31, "duration": 3.15}, {"text": "But the adjustment mechanism\nis coming from the possibility", "start": 2919.46, "duration": 4.41}, {"text": "of exports and imports.", "start": 2923.87, "duration": 1.6}, {"text": "So let me show you\nan example picture.", "start": 2925.47, "duration": 2.75}, {"text": "Suppose we have country B\nhere with this production", "start": 2928.22, "duration": 4.08}, {"text": "possibilities set in the\ntwo goods, G1 and G2.", "start": 2932.3, "duration": 4.05}, {"text": "Now, I'm not telling you\nexactly why it looks like this.", "start": 2936.35, "duration": 3.55}, {"text": "But it has to do with the fact\nthat country B is relatively", "start": 2939.9, "duration": 6.8}, {"text": "abundant in one of the factors.", "start": 2946.7, "duration": 2.34}, {"text": "You can see, relative\nto country A,", "start": 2949.04, "duration": 2.67}, {"text": "this country can\nproduce a lot of good 2,", "start": 2951.71, "duration": 2.49}, {"text": "and relatively little of good 1.", "start": 2954.2, "duration": 2.22}, {"text": "And that's because of the\ndifferent factor intensities.", "start": 2956.42, "duration": 2.61}, {"text": "The flip side of\nthat is country A", "start": 2959.03, "duration": 2.07}, {"text": "over here with its production\npossibility frontier.", "start": 2961.1, "duration": 3.06}, {"text": "And it can produce relatively\nmore of good 1 than good 2,", "start": 2964.16, "duration": 5.22}, {"text": "in the sense of enumerating\nall the possibilities.", "start": 2969.38, "duration": 2.58}, {"text": "If you're in autarky--", "start": 2971.96, "duration": 1.47}, {"text": "now, you remember the\nRobinson Crusoe economy", "start": 2973.43, "duration": 2.58}, {"text": "where we had Robinson\nCrusoe producing two goods?", "start": 2976.01, "duration": 2.97}, {"text": "No trade-- we had, in autarky\ntherefore, on the island,", "start": 2978.98, "duration": 4.65}, {"text": "Robinson Crusoe's\nindifference curve", "start": 2983.63, "duration": 2.49}, {"text": "would be tangent to his\nproduction possibility set.", "start": 2986.12, "duration": 3.43}, {"text": "So this would be the autarky\nallocation in country B.", "start": 2989.55, "duration": 4.94}, {"text": "Likewise, country A, with\na different technology,", "start": 2994.49, "duration": 3.77}, {"text": "a different island, so to speak,\nwould have another tangency", "start": 2998.26, "duration": 3.88}, {"text": "of its preference\nindifference curve,", "start": 3002.14, "duration": 3.24}, {"text": "with a production\npossibility set.", "start": 3005.38, "duration": 2.13}, {"text": "Now, it's kind of easier to\ndraw with common preferences,", "start": 3007.51, "duration": 4.5}, {"text": "having the same indifference\ncurve tangent in both.", "start": 3012.01, "duration": 3.33}, {"text": "But that's not a necessary\npart of the argument.", "start": 3015.34, "duration": 3.42}, {"text": "All we care about is\ntangency for country B", "start": 3018.76, "duration": 3.39}, {"text": "relative to its\nindifference curves,", "start": 3022.15, "duration": 1.92}, {"text": "and tangency for\ncountry A in autarky,", "start": 3024.07, "duration": 3.12}, {"text": "relative to its\nindifference curves.", "start": 3027.19, "duration": 1.635}, {"text": "It just happens to be the\nsame indifference curve.", "start": 3028.825, "duration": 2.715}, {"text": "Now finally, we go from\nautarky to free trade.", "start": 3031.54, "duration": 3.15}, {"text": "What must be the solution?", "start": 3034.69, "duration": 2.01}, {"text": "Each country-- B over here\nwill separate its consumption", "start": 3036.7, "duration": 5.76}, {"text": "and production problems.", "start": 3042.46, "duration": 1.29}, {"text": "It will maximize\nprofits by finding", "start": 3043.75, "duration": 2.67}, {"text": "the point on its production\npossibility frontier", "start": 3046.42, "duration": 3.15}, {"text": "which gives it the\nhighest level of profits,", "start": 3049.57, "duration": 3.39}, {"text": "as captured by this\nbudget line, really--", "start": 3052.96, "duration": 4.26}, {"text": "trade line, that emanates\nfrom the new change production", "start": 3057.22, "duration": 4.27}, {"text": "point.", "start": 3061.49, "duration": 0.5}, {"text": "And I know the old\nproduction point was autarky", "start": 3061.99, "duration": 2.85}, {"text": "for country B. It's now shifted\nto be giving up some of good 1,", "start": 3064.84, "duration": 5.34}, {"text": "and producing more of good\n2, and then exporting good 2", "start": 3070.18, "duration": 5.43}, {"text": "and getting more of good 1 back.", "start": 3075.61, "duration": 2.16}, {"text": "So it specializes\nmore in production.", "start": 3077.77, "duration": 3.48}, {"text": "And then achieves\nbalance in consumption", "start": 3081.25, "duration": 2.31}, {"text": "by imports and exports.", "start": 3083.56, "duration": 2.28}, {"text": "And country A down here\nis doing the opposite.", "start": 3085.84, "duration": 3.22}, {"text": "It specialized\nmore in production", "start": 3089.06, "duration": 1.91}, {"text": "in the other direction,\nmore of good 1,", "start": 3090.97, "duration": 3.0}, {"text": "and then trades in the world\neconomy, giving up good 1", "start": 3093.97, "duration": 4.29}, {"text": "and getting good 2.", "start": 3098.26, "duration": 1.68}, {"text": "And although it's not drawn\nhere, the exports of good 1", "start": 3099.94, "duration": 4.2}, {"text": "for country A are exactly\nequal to the imports of good 1", "start": 3104.14, "duration": 4.68}, {"text": "for country B. So the prices\nof the goods associated", "start": 3108.82, "duration": 4.47}, {"text": "with this external\nprice line are", "start": 3113.29, "duration": 2.4}, {"text": "the same for both\ncountries, and have", "start": 3115.69, "duration": 2.07}, {"text": "the property that, finally,\nwe have an equilibrium", "start": 3117.76, "duration": 2.64}, {"text": "in the goods markets.", "start": 3120.4, "duration": 1.05}, {"text": "In sum, we've now made\nthe prices endogenous.", "start": 3121.45, "duration": 3.09}, {"text": "P1 and 2, which were given\nthroughout 3/4 of the lecture,", "start": 3124.54, "duration": 3.72}, {"text": "are now determined\ninternationally by free trade.", "start": 3128.26, "duration": 3.78}, {"text": "All right, so we\ndid Heckscher-Ohlin.", "start": 3132.04, "duration": 2.55}, {"text": "Now we have another theorem,\nStopler-Samuelson theorem.", "start": 3134.59, "duration": 3.54}, {"text": "In this 2 by 2 by 2 model\nwith these varying factor", "start": 3138.13, "duration": 3.96}, {"text": "intensities, if the price\nof good i increases,", "start": 3142.09, "duration": 5.17}, {"text": "then the equilibrium\nprice of the factor", "start": 3147.26, "duration": 2.42}, {"text": "that's used more\nintensively in good i", "start": 3149.68, "duration": 2.68}, {"text": "also increases, while the price\nof the other factor decreases.", "start": 3152.36, "duration": 4.23}, {"text": "So let me say it again.", "start": 3156.59, "duration": 2.49}, {"text": "And let me give the\nmotivation here.", "start": 3159.08, "duration": 2.49}, {"text": "We're going from autarky\nin each country one", "start": 3161.57, "duration": 3.75}, {"text": "at a time, with its\ninternal domestic prices,", "start": 3165.32, "duration": 3.96}, {"text": "to an equilibrium\nin the world economy", "start": 3169.28, "duration": 3.0}, {"text": "with free trade at\ndifferent prices.", "start": 3172.28, "duration": 3.4}, {"text": "So for country b\nhere, P1 over P2", "start": 3175.68, "duration": 4.31}, {"text": "is going down, relative to what\nit will be in the free trade", "start": 3179.99, "duration": 4.62}, {"text": "equilibrium.", "start": 3184.61, "duration": 0.84}, {"text": "And the reverse is\ntrue for country A.", "start": 3185.45, "duration": 2.04}, {"text": "So when we go from\nautarky to trade,", "start": 3187.49, "duration": 2.73}, {"text": "we're moving the price\nratio in both countries--", "start": 3190.22, "duration": 3.33}, {"text": "in different directions,\nbut we're moving it.", "start": 3193.55, "duration": 2.14}, {"text": "So let's say, what is the\nimpact now of moving a price?", "start": 3195.69, "duration": 3.5}, {"text": "If we increase the price of good\ni relative to the other good,", "start": 3199.19, "duration": 4.2}, {"text": "the equilibrium\nprice of the factor", "start": 3203.39, "duration": 2.4}, {"text": "that was used more intensively\nin the production of good i", "start": 3205.79, "duration": 3.54}, {"text": "will increase, while the\nprice of the other factor", "start": 3209.33, "duration": 2.88}, {"text": "will decrease.", "start": 3212.21, "duration": 1.72}, {"text": "OK, so let's go back to a proof\nof this in the earlier diagram,", "start": 3213.93, "duration": 4.28}, {"text": "setting aside the two countries,\nkind of not asking for a minute", "start": 3218.21, "duration": 3.99}, {"text": "where the price comes from--\nexcept that where previously we", "start": 3222.2, "duration": 3.66}, {"text": "had these isocost\nlines crossing,", "start": 3225.86, "duration": 2.67}, {"text": "the cost lines associated\nwith P1 and P2--", "start": 3228.53, "duration": 3.06}, {"text": "we now increase the\nprice of good 1.", "start": 3231.59, "duration": 3.03}, {"text": "So C1 equal to P1 is here.", "start": 3234.62, "duration": 4.47}, {"text": "C1 equal to P prime\n1 lies further out.", "start": 3239.09, "duration": 4.59}, {"text": "It kind of stands\nto reason that it", "start": 3243.68, "duration": 1.62}, {"text": "should lie further out because\nwe've increased the price.", "start": 3245.3, "duration": 2.85}, {"text": "And we want cost equal to price.", "start": 3248.15, "duration": 2.05}, {"text": "So if price is higher,\ncost can be higher.", "start": 3250.2, "duration": 2.45}, {"text": "And cost can be higher by having\nhigher levels of w1 and w2", "start": 3252.65, "duration": 4.68}, {"text": "as the input prices.", "start": 3257.33, "duration": 1.45}, {"text": "So the isocost\nline for the price", "start": 3258.78, "duration": 2.84}, {"text": "when the price increases,\nin this case, good 1's price", "start": 3261.62, "duration": 2.82}, {"text": "increases, shifts outward.", "start": 3264.44, "duration": 2.28}, {"text": "We haven't done anything to\nthe price of the other good.", "start": 3266.72, "duration": 3.66}, {"text": "The C2-- where is it?", "start": 3270.38, "duration": 1.77}, {"text": "The C2 line is staying constant.", "start": 3272.15, "duration": 2.88}, {"text": "The C2 isocost line of price\nB2 is staying constant.", "start": 3275.03, "duration": 4.14}, {"text": "However, we need a crossing--\nthat an equilibrium", "start": 3279.17, "duration": 2.97}, {"text": "is described by where\nthe lines cross.", "start": 3282.14, "duration": 2.04}, {"text": "So we would move from\nthis initial crossing", "start": 3284.18, "duration": 2.52}, {"text": "to this second crossing.", "start": 3286.7, "duration": 2.25}, {"text": "And you can see,\nas a consequence", "start": 3288.95, "duration": 2.55}, {"text": "of the increase in price in P1,\nthat the price of factor 1--", "start": 3291.5, "duration": 4.89}, {"text": "good 1 is intensive in factor 1.", "start": 3296.39, "duration": 3.09}, {"text": "That's the definition that we\nwere given at the beginning.", "start": 3299.48, "duration": 3.18}, {"text": "The price of good 1 increases.", "start": 3302.66, "duration": 2.67}, {"text": "Therefore, the\ninput, which is used", "start": 3305.33, "duration": 2.13}, {"text": "intensively in good 1, namely\nfactor 1, should increase.", "start": 3307.46, "duration": 4.21}, {"text": "And the other one decreases.", "start": 3311.67, "duration": 1.65}, {"text": "So this diagram illustrates\nthe Stopler-Samuelson theorem.", "start": 3313.32, "duration": 4.07}, {"text": "But again, in the\ncontext of free trade,", "start": 3317.39, "duration": 2.55}, {"text": "those price movements\ncome about for a reason.", "start": 3319.94, "duration": 2.49}, {"text": "Namely, we've gone from\nautarky to free trade.", "start": 3322.43, "duration": 3.21}, {"text": "So you could see earlier which\nway the price was moving,", "start": 3325.64, "duration": 3.36}, {"text": "depending on the initial\ncountry and the autarky.", "start": 3329.0, "duration": 3.87}, {"text": "Now, although we\nknow, again, to repeat", "start": 3332.87, "duration": 2.85}, {"text": "the steps of the\nalgorithm, we now", "start": 3335.72, "duration": 1.8}, {"text": "know what happens\nto the factor prices", "start": 3337.52, "duration": 2.01}, {"text": "from this diagram, what happens\nto the levels of the inputs,", "start": 3339.53, "duration": 3.51}, {"text": "and what happens to output.", "start": 3343.04, "duration": 1.8}, {"text": "Well, we have this,\nagain, box for production.", "start": 3344.84, "duration": 3.21}, {"text": "We had the initial allocation\nratio of the factors", "start": 3348.05, "duration": 3.84}, {"text": "as quantities crossed.", "start": 3351.89, "duration": 1.86}, {"text": "That is to say, the line for\ngood 1 and the line for good 2", "start": 3353.75, "duration": 3.87}, {"text": "crossed.", "start": 3357.62, "duration": 1.11}, {"text": "And they crossed here.", "start": 3358.73, "duration": 1.89}, {"text": "But now those factor\nprices have changed.", "start": 3360.62, "duration": 3.21}, {"text": "As a consequence of\nthe price change,", "start": 3363.83, "duration": 2.37}, {"text": "the quantity of the\nfirst factor will go down", "start": 3366.2, "duration": 4.2}, {"text": "because its price has gone up\nfrom country 1's point of view.", "start": 3370.4, "duration": 4.35}, {"text": "That produces a somewhat\nsteeper sloped line.", "start": 3374.75, "duration": 4.26}, {"text": "And the opposite is\ngoing on with country 2.", "start": 3379.01, "duration": 2.76}, {"text": "So the new equilibrium is\nwhere these now-changed slope", "start": 3381.77, "duration": 4.44}, {"text": "lines cross.", "start": 3386.21, "duration": 1.62}, {"text": "And you can actually\nsee, in this case,", "start": 3387.83, "duration": 2.43}, {"text": "that firm 1 is producing more\nbecause its isoquant will", "start": 3390.26, "duration": 4.08}, {"text": "be higher.", "start": 3394.34, "duration": 0.51}, {"text": "And it's using a higher\nlevel of both inputs.", "start": 3394.85, "duration": 2.91}, {"text": "And likewise, the production\nof good 2 will contract.", "start": 3397.76, "duration": 5.73}, {"text": "So again, this factor price\nequalization theorem is,", "start": 3403.49, "duration": 4.14}, {"text": "just to restate it, in the\n2 by 2 and 2-country model,", "start": 3407.63, "duration": 4.92}, {"text": "as long as we have this factor\nintensity assumption holding", "start": 3412.55, "duration": 3.84}, {"text": "and the countries are not\ncompletely specialized,", "start": 3416.39, "duration": 2.91}, {"text": "the equilibrium price\nof factors, inputs,", "start": 3419.3, "duration": 3.81}, {"text": "only depends on the technologies\nand on the output prices--", "start": 3423.11, "duration": 4.68}, {"text": "determined as it may\nbe, in such a way", "start": 3427.79, "duration": 2.85}, {"text": "that the prices of the outputs\nequals the input costs.", "start": 3430.64, "duration": 4.67}, {"text": "But now, look, if both\ncountries face the same prices", "start": 3435.31, "duration": 3.45}, {"text": "because they trade in\ngoods, and otherwise there", "start": 3438.76, "duration": 2.13}, {"text": "would be arbitrage, then\nsince the prices are", "start": 3440.89, "duration": 2.85}, {"text": "the same in both countries, we\ncan zero inside each country,", "start": 3443.74, "duration": 4.47}, {"text": "and look at the factor prices,\nwhich are clearing the factor", "start": 3448.21, "duration": 3.81}, {"text": "markets in each country.", "start": 3452.02, "duration": 2.23}, {"text": "And since each country\nhas the same technology,", "start": 3454.25, "duration": 3.11}, {"text": "these equations across the two\ngoods in each country hold.", "start": 3457.36, "duration": 4.74}, {"text": "If the prices are the\nsame on the right hand", "start": 3462.1, "duration": 2.19}, {"text": "side as a consequence\nof free trade,", "start": 3464.29, "duration": 3.0}, {"text": "then the solution\nto the input prices", "start": 3467.29, "duration": 3.09}, {"text": "has to be the same on\nthe left hand side.", "start": 3470.38, "duration": 2.8}, {"text": "So in short, remarkably, we have\nnot allowed trade in factors--", "start": 3473.18, "duration": 5.18}, {"text": "no migration.", "start": 3478.36, "duration": 1.71}, {"text": "But we've managed to equalize\nfactor prices without migration", "start": 3480.07, "duration": 3.96}, {"text": "simply by having trade in goods.", "start": 3484.03, "duration": 3.25}, {"text": "So that's the famous factor\nprice equalization theorem.", "start": 3487.28, "duration": 3.98}, {"text": "So vis a vis, the US and Mexico,\nallowing the NAFTA, free trade", "start": 3491.26, "duration": 6.3}, {"text": "in goods, even with\na wall, if I dare", "start": 3497.56, "duration": 2.55}, {"text": "say, prohibiting\nMexican migration,", "start": 3500.11, "duration": 3.96}, {"text": "the theorem says that the wages\nin Mexico should rise in Mexico", "start": 3504.07, "duration": 5.61}, {"text": "and fall to the US, to the point\nthat the wages are the same.", "start": 3509.68, "duration": 3.94}, {"text": "So the factors\nbear consequences.", "start": 3513.62, "duration": 2.99}, {"text": "It's not necessarily a good\nthing that wages of labor", "start": 3516.61, "duration": 3.66}, {"text": "are falling in the US--", "start": 3520.27, "duration": 1.92}, {"text": "not good for those firms.", "start": 3522.19, "duration": 1.5}, {"text": "We have to come back\nto those households.", "start": 3523.69, "duration": 2.85}, {"text": "We have to come back\nto the welfare theorems", "start": 3526.54, "duration": 2.07}, {"text": "to think about the winners\nand losers from trade.", "start": 3528.61, "duration": 3.52}, {"text": "The point here only is that you\ncan see why there is sometimes", "start": 3532.13, "duration": 4.31}, {"text": "resistance to trade because\ntrade does have consequences", "start": 3536.44, "duration": 4.05}, {"text": "for factor prices.", "start": 3540.49, "duration": 1.42}, {"text": "Hence, for the welfare of the\nproviders of those factors,", "start": 3541.91, "duration": 3.53}, {"text": "depending on whether they're\ncapitalists that own wealth,", "start": 3545.44, "duration": 3.66}, {"text": "capital that's used in\nmachinery and so on,", "start": 3549.1, "duration": 3.06}, {"text": "versus laborers that have\nonly their labor endowment.", "start": 3552.16, "duration": 4.94}, {"text": "OK, so next time we're going\nto go with this kind of theorem", "start": 3557.1, "duration": 3.3}, {"text": "back to the Thai villages.", "start": 3560.4, "duration": 2.16}, {"text": "And then we're going to go,\nin the subsequent lecture,", "start": 3562.56, "duration": 2.91}, {"text": "to the US, and\nexplore these ideas.", "start": 3565.47, "duration": 3.43}, {"text": "OK, that's all I have for today.", "start": 3568.9, "duration": 2.0}, {"text": "OK, thank you very much.", "start": 3570.9, "duration": 2.57}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.936}, {"text": "[RUSTLING]", "start": 1.936, "duration": 2.42}, {"text": "[CLICKING]", "start": 4.356, "duration": 0.968}, {"text": "MATTHEW VANDER HEIDEN:\nHello, everybody.", "start": 10.66, "duration": 1.71}, {"text": "Last time, I introduced\nthe idea of the TCA cycle,", "start": 12.37, "duration": 5.01}, {"text": "tricarboxylic acid cycle.", "start": 17.38, "duration": 2.2}, {"text": "Also known as the citric acid\ncycle, because citric acid", "start": 19.58, "duration": 2.99}, {"text": "is a tricarboxylic acid,\nas you'll see later today.", "start": 22.57, "duration": 3.12}, {"text": "Also known as the\nKrebs cycle, named", "start": 25.69, "duration": 2.01}, {"text": "after Hans Krebs,\nwho discovered it", "start": 27.7, "duration": 4.11}, {"text": "in the early part\nof the last century.", "start": 31.81, "duration": 3.73}, {"text": "The TCA cycle is the\nseries of reactions", "start": 35.54, "duration": 2.79}, {"text": "that occurs in the\nmitochondrial matrix", "start": 38.33, "duration": 2.1}, {"text": "and it allows the complete\noxidation of two carbon", "start": 40.43, "duration": 3.12}, {"text": "units, derived from many things,\nincluding pyruvate, derived", "start": 43.55, "duration": 3.54}, {"text": "from glucose and glycolysis and\nenables the complete oxidation", "start": 47.09, "duration": 5.82}, {"text": "of that carbon to CO2.", "start": 52.91, "duration": 2.61}, {"text": "Now, it's a cycle\nbecause those two carbon", "start": 55.52, "duration": 2.55}, {"text": "units from pyruvate or other\nsources enter the cycle,", "start": 58.07, "duration": 4.98}, {"text": "combine with 4-carbon\noxaloacetate,", "start": 63.05, "duration": 2.88}, {"text": "and combine to make\n6-carbon citrate.", "start": 65.93, "duration": 2.31}, {"text": "Hence the citric\nacid cycle, or TCA", "start": 68.24, "duration": 3.3}, {"text": "cycle, that is then oxidized\nback to 4 carbon units,", "start": 71.54, "duration": 4.26}, {"text": "forming a cycle\nthat allows cells", "start": 75.8, "duration": 5.76}, {"text": "to release lots of energy.", "start": 81.56, "duration": 1.71}, {"text": "Complete oxygen\nenables, ultimately,", "start": 83.27, "duration": 2.1}, {"text": "complete oxidation\nof glucose to CO2.", "start": 85.37, "duration": 2.64}, {"text": "We've talked many times\nhow this releases energy.", "start": 88.01, "duration": 2.55}, {"text": "And it also generates\nlots of intermediates", "start": 90.56, "duration": 2.19}, {"text": "for the cell that can be\nused to make other stuff.", "start": 92.75, "duration": 3.51}, {"text": "Last time, I alluded to the\nfact that citrate can be", "start": 96.26, "duration": 3.03}, {"text": "used, say, to make fatty acids.", "start": 99.29, "duration": 3.09}, {"text": "Today, what I want to\ndo is I want to dive", "start": 102.38, "duration": 1.98}, {"text": "into the details of how\nthis TCA cycle occurs", "start": 104.36, "duration": 4.65}, {"text": "and the consequences\nof the way it works,", "start": 109.01, "duration": 2.97}, {"text": "and how that affects other\naspects of metabolism.", "start": 111.98, "duration": 3.66}, {"text": "You'll see that it\nactually affects", "start": 115.64, "duration": 2.28}, {"text": "the ability of\ndifferent organisms,", "start": 117.92, "duration": 3.52}, {"text": "whether or not they\ncan make things", "start": 121.44, "duration": 1.61}, {"text": "from intermediates\nin this cycle,", "start": 123.05, "duration": 2.88}, {"text": "because of how the cycle works.", "start": 125.93, "duration": 1.735}, {"text": "Now, to start.", "start": 137.75, "duration": 0.645}, {"text": "Of course, if we're going\nto start from pyruvate.", "start": 141.15, "duration": 3.83}, {"text": "Pyruvate, of course,\nhas three carbons.", "start": 147.87, "duration": 3.34}, {"text": "And so if we're going to\ngenerate a two-carbon acetate", "start": 151.21, "duration": 4.55}, {"text": "group, we have to lose CO2.", "start": 155.76, "duration": 2.13}, {"text": "And as I described a\ncouple lectures ago,", "start": 164.22, "duration": 3.06}, {"text": "acetate is also\nthe thing that we", "start": 167.28, "duration": 2.46}, {"text": "can derive from\nmetabolism of ethanol,", "start": 169.74, "duration": 2.97}, {"text": "showing us two things--", "start": 172.71, "duration": 2.01}, {"text": "metabolized glucose to\npyruvate or ethanol itself--", "start": 174.72, "duration": 3.03}, {"text": "can both be turned into acetate.", "start": 177.75, "duration": 2.07}, {"text": "But really, the donor is\nthis molecule, acetyl-CoA.", "start": 179.82, "duration": 6.12}, {"text": "Which is basically also a\ncarboxylic acid, but rather", "start": 185.94, "duration": 3.3}, {"text": "than being a carboxylic\nacid, instead makes this", "start": 189.24, "duration": 2.94}, {"text": "a thioester bond, which\nactivates this carbon", "start": 192.18, "duration": 3.7}, {"text": "as a leaving group, such that it\ncan combine with oxaloacetate,", "start": 195.88, "duration": 19.88}, {"text": "which you'll remember\nfrom gluconeogenesis,", "start": 215.76, "duration": 5.37}, {"text": "releasing that S-CoA molecule\nto generate six-carbon citric.", "start": 221.13, "duration": 11.63}, {"text": "So, this is citric.", "start": 255.73, "duration": 0.96}, {"text": "You can see that we've made\na bond from this carbon", "start": 256.69, "duration": 3.42}, {"text": "on the acetate, losing this\nS-CoA group to this carbon", "start": 260.11, "duration": 5.59}, {"text": "oxaloacetate to make this\nsix-carbon citrate molecule,", "start": 265.7, "duration": 4.59}, {"text": "which is a one, two, three--", "start": 270.29, "duration": 1.88}, {"text": "three-carboxylic acid,\nor tricarboxylic acid.", "start": 272.17, "duration": 4.29}, {"text": "Hence the name\ncitric acid cycle,", "start": 276.46, "duration": 2.82}, {"text": "tricarboxylic acid cycle.", "start": 279.28, "duration": 2.17}, {"text": "Now, these six\ncarbons can then--", "start": 281.45, "duration": 3.14}, {"text": "or this six-carbon\ncitrate molecule", "start": 284.59, "duration": 2.31}, {"text": "can then be oxidized, generating\ntwo CO2 molecules that", "start": 286.9, "duration": 6.84}, {"text": "are released, and\nultimately reforming", "start": 293.74, "duration": 2.66}, {"text": "oxaloacetate that can pick up\nanother two-carbon acetyl-CoA", "start": 296.4, "duration": 5.38}, {"text": "to generate another citrate,\nand around and around the cycle", "start": 301.78, "duration": 3.33}, {"text": "goes, allowing in\nthe end the net entry", "start": 305.11, "duration": 4.92}, {"text": "of two carbons,\neffectively from acetate,", "start": 310.03, "duration": 3.81}, {"text": "and release of two\ncarbons as CO2.", "start": 313.84, "duration": 4.8}, {"text": "Now, as I alluded to, this\ncan come from pyruvate.", "start": 318.64, "duration": 5.55}, {"text": "It can come from\nacetate itself, vinegar.", "start": 324.19, "duration": 3.48}, {"text": "It can come from alcohol.", "start": 327.67, "duration": 1.53}, {"text": "It turns out that when\nyou break down fat,", "start": 329.2, "duration": 1.8}, {"text": "you also break it\ninto two carbon units.", "start": 331.0, "duration": 4.18}, {"text": "And so this cycle becomes\nvery useful for cells,", "start": 335.18, "duration": 3.5}, {"text": "because it allows the oxidation\nof many different molecules", "start": 338.68, "duration": 4.92}, {"text": "to completely turn\nthat carbon into CO2.", "start": 343.6, "duration": 5.2}, {"text": "Now, if we're going to\ndo this from glucose,", "start": 348.8, "duration": 4.57}, {"text": "however, you'll remember that\npyruvate has three carbons.", "start": 353.37, "duration": 12.38}, {"text": "And so if we're going\nto turn pyruvate", "start": 365.75, "duration": 1.94}, {"text": "into acetate, or acetyl-CoA, we\nhave to lose a carbon of CO2.", "start": 367.69, "duration": 6.75}, {"text": "We have to lose\nthis carbon as CO2.", "start": 374.44, "duration": 3.49}, {"text": "Now, we saw this before,\nthat we can do this via--", "start": 377.93, "duration": 3.77}, {"text": "this is exactly how\nwe generated ethanol", "start": 381.7, "duration": 5.1}, {"text": "when we did fermentation\nof pyruvate to ethanol,", "start": 386.8, "duration": 6.03}, {"text": "but that molecule\ndidn't generate acetate,", "start": 392.83, "duration": 3.3}, {"text": "It generated acetaldehyde.", "start": 396.13, "duration": 2.4}, {"text": "The difference, of course, being\nwhether or not this carbon gets", "start": 398.53, "duration": 3.66}, {"text": "oxidized in the case\nof acetate to the acid,", "start": 402.19, "duration": 2.64}, {"text": "or in acetaldehyde in\nethanol metabolism,", "start": 404.83, "duration": 2.37}, {"text": "where it remains an aldehyde.", "start": 407.2, "duration": 2.37}, {"text": "Now obviously, you can\nmake ethanol and then", "start": 409.57, "duration": 2.76}, {"text": "turn that ethanol into acetate.", "start": 412.33, "duration": 2.25}, {"text": "And that's a pathway that I\nguess certainly would work.", "start": 414.58, "duration": 3.22}, {"text": "However, that's not the way\nit happens in most organisms.", "start": 417.8, "duration": 3.62}, {"text": "Most organisms actually\ndirectly produce", "start": 421.42, "duration": 5.76}, {"text": "acetate, or more correctly,\nacetyl-CoA from pyruvate.", "start": 427.18, "duration": 4.69}, {"text": "So let's take a look\nat that reaction.", "start": 431.87, "duration": 2.33}, {"text": "So here once again is pyruvate.", "start": 438.5, "duration": 1.87}, {"text": "And if we turn\nthat pyruvate into", "start": 444.49, "duration": 3.42}, {"text": "this two-carbon\nacetyl-CoA, let's", "start": 447.91, "duration": 6.68}, {"text": "look here what has to happen.", "start": 454.59, "duration": 2.8}, {"text": "Well, the first\nthing is that we have", "start": 457.39, "duration": 4.67}, {"text": "to decarboxylate this molecule.", "start": 462.06, "duration": 5.99}, {"text": "And so that generates a CO2.", "start": 468.05, "duration": 3.56}, {"text": "We have to lose that one carbon.", "start": 471.61, "duration": 3.81}, {"text": "Also, as I pointed\nout, if we do this", "start": 475.42, "duration": 4.59}, {"text": "as if we did it in\nethanol metabolism,", "start": 480.01, "duration": 2.31}, {"text": "we'd be left with an aldehyde.", "start": 482.32, "duration": 2.38}, {"text": "But this is an acid, and so this\ncarbon also has to be oxidized.", "start": 484.7, "duration": 6.23}, {"text": "We know how to do that.", "start": 490.93, "duration": 1.11}, {"text": "We can donate those electrons\nto something like NAD,", "start": 492.04, "duration": 7.2}, {"text": "so the NAD is reduced to NADH.", "start": 499.24, "duration": 3.81}, {"text": "And we had to add this\nS-CoA molecule, which", "start": 503.05, "duration": 7.72}, {"text": "I'll come to in a minute.", "start": 510.77, "duration": 2.68}, {"text": "And so each of\nthese steps ends up", "start": 513.45, "duration": 6.28}, {"text": "making a fairly\ncomplicated reaction.", "start": 519.73, "duration": 3.99}, {"text": "Obviously, several co-factors\nare going to be involved.", "start": 523.72, "duration": 3.078}, {"text": "You should be able to guess\nthat just by looking at it.", "start": 526.798, "duration": 2.292}, {"text": "Obviously, I already\ndrew up there NAD.", "start": 529.09, "duration": 2.31}, {"text": "If we're going to\ndecarboxylate, remember", "start": 531.4, "duration": 3.06}, {"text": "this is a alpha\ncarboxylic, an alpha", "start": 534.46, "duration": 9.29}, {"text": "ketoacid-- the ketone group is\nalpha to the carboxylic acid.", "start": 543.75, "duration": 4.42}, {"text": "And so if we're doing\nalpha decarboxylation,", "start": 548.17, "duration": 3.02}, {"text": "as you might guess,\nwe need a co-factor.", "start": 551.19, "duration": 2.31}, {"text": "That co-factor, as\nI told you before,", "start": 553.5, "duration": 1.71}, {"text": "is the co-factor factor\nthiamine pyrophosphate.", "start": 555.21, "duration": 2.64}, {"text": "And finally, there's\nthis S-CoA group.", "start": 557.85, "duration": 4.09}, {"text": "We need to describe\nwhat that is.", "start": 561.94, "duration": 3.38}, {"text": "However, before delving\ninto those, and there's", "start": 565.32, "duration": 3.87}, {"text": "actually a couple other factors\nthat are needed as well,", "start": 569.19, "duration": 2.97}, {"text": "I want to mention\none other issue", "start": 572.16, "duration": 3.99}, {"text": "about this reaction, in\nthat this reaction happens", "start": 576.15, "duration": 4.83}, {"text": "in the mitochondria,\nbecause that's also", "start": 580.98, "duration": 3.84}, {"text": "where the TCA cycle happens.", "start": 584.82, "duration": 1.95}, {"text": "So, recall that if we divide\nthe cell into two compartments", "start": 586.77, "duration": 4.05}, {"text": "like an eukaryotic cell,\nhere we have the cytosol", "start": 590.82, "duration": 3.06}, {"text": "and the mitochondria\nin a eukaryotic cell.", "start": 593.88, "duration": 2.76}, {"text": "As we've already talked about,\nhaving different compartments", "start": 596.64, "duration": 3.0}, {"text": "helps facilitate different\nmetabolic reactions,", "start": 599.64, "duration": 2.753}, {"text": "because you can have different\nconditions in the two", "start": 602.393, "duration": 2.167}, {"text": "compartments.", "start": 604.56, "duration": 1.3}, {"text": "And so as we said, glycolysis\noccurs in the cytosol.", "start": 605.86, "duration": 9.38}, {"text": "Glucose to pyruvate.", "start": 615.24, "duration": 1.85}, {"text": "And last time I\nmentioned, the TCA cycle", "start": 617.09, "duration": 9.63}, {"text": "occurs in the mitochondria.", "start": 626.72, "duration": 4.62}, {"text": "And so that means if we're\ngoing to fully oxidize", "start": 631.34, "duration": 3.36}, {"text": "the pyruvate carbon\nto CO2 using the TCA", "start": 634.7, "duration": 4.2}, {"text": "cycle in the mitochondria,\nthat pyruvate", "start": 638.9, "duration": 2.61}, {"text": "has to get from the cytosol to\nthe mitochondria, or at least", "start": 641.51, "duration": 3.33}, {"text": "carbons from the pyruvate\nhave to get there.", "start": 644.84, "duration": 2.568}, {"text": "It turns out, you'll\nsee in a minute,", "start": 647.408, "duration": 1.542}, {"text": "acetyl-CoA is a\nvery large group.", "start": 648.95, "duration": 1.92}, {"text": "And so pyruvate\nitself is transported", "start": 650.87, "duration": 2.88}, {"text": "into the mitochondria.", "start": 653.75, "duration": 1.89}, {"text": "And that's where\nthe reaction occurs", "start": 655.64, "duration": 1.62}, {"text": "to turn it into acetyl-CoA that\ncan then enter the TCA cycle", "start": 657.26, "duration": 3.36}, {"text": "and oxidize.", "start": 660.62, "duration": 1.92}, {"text": "However, what this means is\nthat a transporter is actually", "start": 662.54, "duration": 4.83}, {"text": "needed to get this across\nthe mitochondrial membranes", "start": 667.37, "duration": 3.24}, {"text": "and into the matrix of the\nmitochondria where the TCA", "start": 670.61, "duration": 2.61}, {"text": "cycle happens.", "start": 673.22, "duration": 1.942}, {"text": "And I like to mention\nthis because it turns out", "start": 675.162, "duration": 1.958}, {"text": "the pyruvate carrier--", "start": 677.12, "duration": 1.17}, {"text": "that is, the\ntransporter-- the way", "start": 678.29, "duration": 1.5}, {"text": "that it actually gets that\npyruvate from the cytosol", "start": 679.79, "duration": 3.03}, {"text": "into the mitochondria\nactually was", "start": 682.82, "duration": 2.4}, {"text": "an unknown thing\nabout metabolism", "start": 685.22, "duration": 1.83}, {"text": "until 2012, so\nnot that long ago.", "start": 687.05, "duration": 3.33}, {"text": "Sometimes one can be\nleft with the feeling,", "start": 690.38, "duration": 4.77}, {"text": "listening to these metabolism\nclasses or reading a textbook,", "start": 695.15, "duration": 3.54}, {"text": "that everything about metabolism\nhas been known forever,", "start": 698.69, "duration": 3.66}, {"text": "but it's actually not true.", "start": 702.35, "duration": 1.59}, {"text": "Here's a very key, central\npart of the pathway that", "start": 703.94, "duration": 3.57}, {"text": "was actually just\ndiscovered, at least", "start": 707.51, "duration": 2.25}, {"text": "at the time of this lecture,\nless than 10 years ago.", "start": 709.76, "duration": 2.46}, {"text": "It also illustrates that not\nall metabolism is completely", "start": 715.04, "duration": 4.3}, {"text": "understood.", "start": 719.34, "duration": 3.17}, {"text": "Now, let's get back to this\nreaction, how you turn pyruvate", "start": 722.51, "duration": 4.47}, {"text": "into acetyl-CoA.", "start": 726.98, "duration": 2.61}, {"text": "And I want to go through\nnow and point out", "start": 729.59, "duration": 2.31}, {"text": "that several\nco-factors are needed.", "start": 731.9, "duration": 3.1}, {"text": "And so I already mentioned\none of them, S-CoA,", "start": 735.0, "duration": 4.46}, {"text": "which is shorthand\nfor coenzyme A. So,", "start": 739.46, "duration": 7.03}, {"text": "I need to tell you what that is.", "start": 746.49, "duration": 3.38}, {"text": "You hopefully are already\nfamiliar with TPP plus,", "start": 749.87, "duration": 4.98}, {"text": "thiamine pyrophosphate.", "start": 754.85, "duration": 1.32}, {"text": "We talked about\nthat when we talked", "start": 756.17, "duration": 3.12}, {"text": "about how you do alpha\ndecarboxylation to generate", "start": 759.29, "duration": 3.6}, {"text": "ethanol from pyruvate,\nalso used here", "start": 762.89, "duration": 2.55}, {"text": "for the alpha\ndecarboxylation reaction.", "start": 765.44, "duration": 3.18}, {"text": "Redox reaction\nhappens, and so we", "start": 768.62, "duration": 2.58}, {"text": "needed NAD plus to get\nconverted into NADH.", "start": 771.2, "duration": 6.56}, {"text": "We talked a lot about how that\nserves as an electron carrier,", "start": 777.76, "duration": 3.36}, {"text": "but it turns out that there's\ntwo additional electron", "start": 781.12, "duration": 3.0}, {"text": "carriers that are\ninvolved in this reaction.", "start": 784.12, "duration": 3.27}, {"text": "One of them is called\nFAD and the other one", "start": 787.39, "duration": 4.56}, {"text": "is called lipoic acid.", "start": 791.95, "duration": 2.205}, {"text": "Now you might say,\nwhy do we need", "start": 798.12, "duration": 1.58}, {"text": "all these electron carriers?", "start": 799.7, "duration": 2.37}, {"text": "Well, these are just\ndifferent molecules", "start": 802.07, "duration": 2.19}, {"text": "that can carry two\nelectrons, similar to NADH.", "start": 804.26, "duration": 6.34}, {"text": "And effectively, what these can\ndo by having multiple electron", "start": 810.6, "duration": 3.83}, {"text": "carriers--", "start": 814.43, "duration": 1.05}, {"text": "one can build chains of\noxidation and reduction", "start": 815.48, "duration": 4.2}, {"text": "reactions.", "start": 819.68, "duration": 1.26}, {"text": "And it turns out these chains\nof oxidation reduction reactions", "start": 820.94, "duration": 3.18}, {"text": "really become central to\nenergy transfers in biology,", "start": 824.12, "duration": 4.08}, {"text": "because building\nthese chains allows", "start": 828.2, "duration": 2.49}, {"text": "more easy stepwise\nrelease of energy", "start": 830.69, "duration": 3.33}, {"text": "as one moves across these\noxidation reduction reactions.", "start": 834.02, "duration": 3.64}, {"text": "Which remember, as I\nalluded to earlier, really", "start": 837.66, "duration": 2.51}, {"text": "are at the core of bioenergetics\nand a lot of what allows energy", "start": 840.17, "duration": 6.72}, {"text": "release from these pathways.", "start": 846.89, "duration": 3.09}, {"text": "What I mean by this\nwill be more explicit", "start": 849.98, "duration": 3.51}, {"text": "as we go through what some of\nthese co-factors look like.", "start": 853.49, "duration": 4.86}, {"text": "So, I'm not going to draw TPP\nplus or NAD again, but let's", "start": 858.35, "duration": 7.2}, {"text": "define what some of these\nother cofactors look like.", "start": 865.55, "duration": 4.54}, {"text": "So, let's start with coenzyme\nA. So, coenzyme A, it turns out,", "start": 870.09, "duration": 9.32}, {"text": "is useful.", "start": 879.41, "duration": 1.8}, {"text": "It's actually involved in\nlots of acylation reactions.", "start": 881.21, "duration": 5.15}, {"text": "What's an acylation reaction?", "start": 886.36, "duration": 1.71}, {"text": "Well, that's basically if you're\nmaking a carbon-carbon bond", "start": 888.07, "duration": 4.68}, {"text": "by adding a molecule of greater\nthan one carbon, so two carbons", "start": 892.75, "duration": 3.45}, {"text": "or greater, to something else.", "start": 896.2, "duration": 1.83}, {"text": "That's an acylation\nreaction, as we", "start": 898.03, "duration": 2.04}, {"text": "did with adding the two-carbon\nacetate to oxaloacetate", "start": 900.07, "duration": 4.74}, {"text": "to make citrate.", "start": 904.81, "duration": 1.65}, {"text": "And you'll actually see\ncoenzyme A will come up", "start": 906.46, "duration": 2.22}, {"text": "in this in many, many\nlectures throughout the rest", "start": 908.68, "duration": 2.43}, {"text": "of the course.", "start": 911.11, "duration": 1.29}, {"text": "Why this becomes useful\nis because it activates", "start": 912.4, "duration": 4.35}, {"text": "this basically carbon to\nthe left of, in this case,", "start": 916.75, "duration": 8.78}, {"text": "the ketone.", "start": 925.53, "duration": 0.92}, {"text": "Because, by having\nthat thioester there,", "start": 926.45, "duration": 2.88}, {"text": "ends up activating that carbon\nand allows it to carry out", "start": 929.33, "duration": 4.29}, {"text": "these acylation reactions.", "start": 933.62, "duration": 3.45}, {"text": "Coenzyme A itself is\nderived from a vitamin", "start": 937.07, "duration": 3.93}, {"text": "called pantothenic acid.", "start": 941.0, "duration": 3.285}, {"text": "And as a vitamin,\nthis is something", "start": 948.67, "duration": 4.05}, {"text": "that you have to\nget from the diet.", "start": 952.72, "duration": 2.65}, {"text": "Now, when we\nabbreviate coenzyme A,", "start": 955.37, "duration": 3.32}, {"text": "which is often\nabbreviated S-CoA,", "start": 958.69, "duration": 3.75}, {"text": "you get the sense that it's\nthis little tiny molecule", "start": 962.44, "duration": 2.52}, {"text": "that's just stuck on sulfur--", "start": 964.96, "duration": 1.74}, {"text": "stuck on to the end to\nmake this thioester bond.", "start": 966.7, "duration": 2.91}, {"text": "But it turns out coenzyme A is\nactually a giant molecule, one", "start": 969.61, "duration": 3.12}, {"text": "of the reasons why you\nactually synthesize acetyl-CoA", "start": 972.73, "duration": 6.66}, {"text": "in the mitochondria,\nbecause it's", "start": 979.39, "duration": 1.41}, {"text": "hard to transport\nthis giant molecule.", "start": 980.8, "duration": 3.37}, {"text": "And so this is what\npantothenic acid looks like.", "start": 984.17, "duration": 4.82}, {"text": "So, if I put an acid group here\nand a hydroxyl group there,", "start": 1007.92, "duration": 5.48}, {"text": "that would be pantothenic\nacid, the thing", "start": 1013.4, "duration": 2.13}, {"text": "that's in your cereal, on\nthe side of your cereal box.", "start": 1015.53, "duration": 4.545}, {"text": "Then there's these\nadditional pieces.", "start": 1025.47, "duration": 2.22}, {"text": "This is the active\nend of the molecule,", "start": 1027.69, "duration": 9.69}, {"text": "that's that sulfur\nfrom the S-CoA,", "start": 1037.38, "duration": 2.459}, {"text": "and then this side of the\nmolecule is esterified to two", "start": 1039.839, "duration": 5.341}, {"text": "phosphates, which\nare esterified to--", "start": 1045.18, "duration": 3.63}, {"text": "I'm not going to\ndraw it out, but this", "start": 1051.477, "duration": 1.583}, {"text": "would have an adenine base\nand a phosphate there.", "start": 1053.06, "duration": 6.14}, {"text": "So basically, this is\nADP, with a phosphate", "start": 1059.2, "duration": 8.34}, {"text": "added to the 3 prime\nposition of the ADP molecule,", "start": 1067.54, "duration": 4.2}, {"text": "added to pantothenic acid,\nadded to this short chain", "start": 1071.74, "duration": 4.26}, {"text": "with the sulfur on the end.", "start": 1076.0, "duration": 1.56}, {"text": "And this whole molecule\ntogether is coenzyme A.", "start": 1077.56, "duration": 3.99}, {"text": "And so when we say\nacetyl-CoA, it's", "start": 1081.55, "duration": 1.98}, {"text": "this giant molecule,\nS-thioester to the carbonyl,", "start": 1083.53, "duration": 9.1}, {"text": "the acid on acetate, to CH3.", "start": 1092.63, "duration": 4.32}, {"text": "And so that would be,\nbasically, acetyl-CoA.", "start": 1096.95, "duration": 3.73}, {"text": "And so one convenient\nthing about this", "start": 1100.68, "duration": 3.35}, {"text": "is it's much easier than\ndrawing that big molecule,", "start": 1104.03, "duration": 2.58}, {"text": "but it is a little bit\nmisleading in terms", "start": 1106.61, "duration": 4.32}, {"text": "of its size.", "start": 1110.93, "duration": 1.74}, {"text": "So, that's coenzyme A.", "start": 1112.67, "duration": 3.3}, {"text": "Next one I want to\ntalk about is FAD", "start": 1115.97, "duration": 6.27}, {"text": "which stands for flavin\nadenine dinucleotide.", "start": 1122.24, "duration": 8.88}, {"text": "So, flavin adenine dinucleotide\nis an electron carrier,", "start": 1134.6, "duration": 3.51}, {"text": "just like NAD plus.", "start": 1138.11, "duration": 1.725}, {"text": "And it's derived from\nthe vitamin riboflavin,", "start": 1145.33, "duration": 6.15}, {"text": "also referred to as vitamin B2.", "start": 1151.48, "duration": 3.0}, {"text": "Another thing from the side of\nyour cereal box, and basically", "start": 1157.24, "duration": 4.17}, {"text": "looks like this.", "start": 1161.41, "duration": 2.03}, {"text": "So, like NAD, it's\na dinucleotide.", "start": 1163.44, "duration": 8.23}, {"text": "And so here's ADP, just\nlike we do for CoA, or just", "start": 1180.14, "duration": 5.13}, {"text": "like one end of NAD.", "start": 1185.27, "duration": 2.16}, {"text": "One difference is that the\nother nucleotide down here", "start": 1187.43, "duration": 3.9}, {"text": "actually isn't\ntechnically a sugar.", "start": 1191.33, "duration": 2.68}, {"text": "It's ribitol instead of ribose.", "start": 1194.01, "duration": 3.23}, {"text": "What does that mean?", "start": 1197.24, "duration": 1.0}, {"text": "It doesn't have an aldehyde.", "start": 1198.24, "duration": 1.7}, {"text": "Instead, it is just\na five-carbon chain", "start": 1199.94, "duration": 4.77}, {"text": "where all of the\ncarbons are alcohols.", "start": 1204.71, "duration": 3.3}, {"text": "And so since\nthere's no aldehyde,", "start": 1214.45, "duration": 1.8}, {"text": "it doesn't form a ring.", "start": 1216.25, "duration": 1.95}, {"text": "And the base on this\nend, as a nicotinamide,", "start": 1245.15, "duration": 4.53}, {"text": "is this flavin group,\nwhich looks like this.", "start": 1249.68, "duration": 17.5}, {"text": "And so this is FAD, which\nis in the oxidized form.", "start": 1267.18, "duration": 8.56}, {"text": "Turns out, in the\noxidized form, FAD", "start": 1275.74, "duration": 3.51}, {"text": "is yellow, hence riboflavin--\n\"flavin\", yellow.", "start": 1279.25, "duration": 6.27}, {"text": "And the reason it's\nyellow-- you see", "start": 1285.52, "duration": 1.89}, {"text": "there's a conjugated double\nbond here across this part.", "start": 1287.41, "duration": 3.36}, {"text": "It turns out this is the\nactive part of the molecule,", "start": 1290.77, "duration": 3.69}, {"text": "and it works as follows.", "start": 1294.46, "duration": 1.44}, {"text": "And so if you have\na hydride ion,", "start": 1295.9, "duration": 2.64}, {"text": "remember the way we can\ntransfer two electrons.", "start": 1298.54, "duration": 3.06}, {"text": "Can transfer the two\nelectrons that way,", "start": 1306.39, "duration": 2.88}, {"text": "and that allows it to generate.", "start": 1309.27, "duration": 1.65}, {"text": "And I'll just draw\nthe middle, here.", "start": 1310.92, "duration": 2.7}, {"text": "Active part of the molecule.", "start": 1313.62, "duration": 2.7}, {"text": "So, that would be\nthese two nitrogens.", "start": 1331.18, "duration": 2.33}, {"text": "We've added two electrons to it.", "start": 1333.51, "duration": 1.84}, {"text": "And so this is\nabbreviated FADH2,", "start": 1335.35, "duration": 5.24}, {"text": "or the reduced form of FAD.", "start": 1340.59, "duration": 4.11}, {"text": "And it is colorless,\nbecause now you no longer", "start": 1344.7, "duration": 4.36}, {"text": "have that conjugated double\nbond system, loses its color.", "start": 1349.06, "duration": 3.75}, {"text": "And so you can follow whether\nFAD is oxidized or reduced", "start": 1352.81, "duration": 3.78}, {"text": "by just looking at color change.", "start": 1356.59, "duration": 3.96}, {"text": "So, that's FAD.", "start": 1360.55, "duration": 1.95}, {"text": "It's an electron carrier,\ncarries electrons", "start": 1362.5, "duration": 3.39}, {"text": "by a hydride transfer,\nvery similarly", "start": 1365.89, "duration": 3.24}, {"text": "to what we described\nfor NAD, but obviously", "start": 1369.13, "duration": 3.24}, {"text": "a different molecule.", "start": 1372.37, "duration": 2.52}, {"text": "And the last molecule,\nthe last co-factor", "start": 1374.89, "duration": 4.11}, {"text": "that we need for this\nreaction, is lipoic acid.", "start": 1379.0, "duration": 6.91}, {"text": "Which, unlike most\nthings in metabolism,", "start": 1385.91, "duration": 2.31}, {"text": "doesn't have an abbreviation\nand also functions", "start": 1388.22, "duration": 4.62}, {"text": "as an electron carrier.", "start": 1392.84, "duration": 1.86}, {"text": "And so lipoic acid\nlooks like this.", "start": 1394.7, "duration": 2.34}, {"text": "So, that is lipoic acid.", "start": 1417.57, "duration": 3.24}, {"text": "This is in the oxidized form.", "start": 1420.81, "duration": 4.38}, {"text": "And so where it's\noxidized is here", "start": 1425.19, "duration": 2.91}, {"text": "at this sulfur-sulfur bond.", "start": 1428.1, "duration": 1.56}, {"text": "So, you can think of this as\nthe same as a disulfide bond", "start": 1429.66, "duration": 3.72}, {"text": "that you learned about from\nProfessor Yaffe in proteins.", "start": 1433.38, "duration": 3.73}, {"text": "And so this is the oxidized\nform of the disulfide bond.", "start": 1437.11, "duration": 4.28}, {"text": "If I take this hydride, transfer\ntwo electrons across that bond,", "start": 1441.39, "duration": 7.84}, {"text": "then it goes to-- and I'll\njust draw here the active end.", "start": 1449.23, "duration": 4.445}, {"text": "Then we go here to the\nreduced form of lipoic acid,", "start": 1459.37, "duration": 5.74}, {"text": "and there's no\nabbreviation for oxidized", "start": 1465.11, "duration": 2.91}, {"text": "or reduced lipoic acid.", "start": 1468.02, "duration": 1.68}, {"text": "It's just lipoic acid,\noxidized lipoic acid, reduced.", "start": 1469.7, "duration": 4.26}, {"text": "And how they're\noxidized and reduced", "start": 1473.96, "duration": 2.25}, {"text": "is basically very similar\nto the disulfide bonds", "start": 1476.21, "duration": 5.34}, {"text": "that you saw in proteins being\noxidized, disulfide bond being", "start": 1481.55, "duration": 5.22}, {"text": "oxidized, or it can be reduced\nto not be a disulfide bond.", "start": 1486.77, "duration": 5.58}, {"text": "Now, it turns out that these\ncofactors, our TPP, FAD,", "start": 1492.35, "duration": 10.41}, {"text": "and lipoic acid, are\nall stably associated", "start": 1502.76, "duration": 4.92}, {"text": "with different subunits\nof a multi-protein complex", "start": 1507.68, "duration": 6.38}, {"text": "that assembles to catalyze that\nreaction to convert pyruvate", "start": 1514.06, "duration": 6.24}, {"text": "to acetyl-CoA.", "start": 1520.3, "duration": 3.03}, {"text": "The enzyme or\nenzyme complex that", "start": 1523.33, "duration": 2.28}, {"text": "carries this out is\nreferred to as PDH,", "start": 1525.61, "duration": 3.6}, {"text": "sometimes abbreviated\nPDC, which stands", "start": 1529.21, "duration": 3.42}, {"text": "for the pyruvate\ndehydrogenase complex.", "start": 1532.63, "duration": 13.48}, {"text": "So, pyruvate dehydrogenase, PDH,\npyruvate dehydrogenase complex,", "start": 1546.11, "duration": 4.08}, {"text": "PDC.", "start": 1550.19, "duration": 1.6}, {"text": "This complex is basically\nthree different polypeptides", "start": 1551.79, "duration": 4.67}, {"text": "that come together\nto form a complex", "start": 1556.46, "duration": 2.19}, {"text": "and catalyze that reaction.", "start": 1558.65, "duration": 2.31}, {"text": "Now, where this complex sits--", "start": 1560.96, "duration": 2.65}, {"text": "so, this is the mitochondria.", "start": 1563.61, "duration": 2.03}, {"text": "This is the matrix.", "start": 1565.64, "duration": 2.13}, {"text": "That's where this pyruvate\ndehydrogenase reaction occurs.", "start": 1567.77, "duration": 2.76}, {"text": "That's where the\nTCA cycle occurs.", "start": 1570.53, "duration": 2.64}, {"text": "And this PDH\ncomplex is basically", "start": 1573.17, "duration": 2.46}, {"text": "sitting here at the\nmembrane on the matrix side", "start": 1575.63, "duration": 3.96}, {"text": "of the membrane.", "start": 1579.59, "duration": 2.86}, {"text": "Now, the three\ndifferent polypeptides", "start": 1582.45, "duration": 2.27}, {"text": "that come together\nto form this complex", "start": 1584.72, "duration": 2.25}, {"text": "are creatively named\nE1, E2, and E3, four.", "start": 1586.97, "duration": 8.04}, {"text": "Enzyme one, two, and three.", "start": 1595.01, "duration": 2.67}, {"text": "And each of these,\nas I alluded to,", "start": 1597.68, "duration": 3.33}, {"text": "is associated with a\ndifferent co-factor.", "start": 1601.01, "duration": 3.557}, {"text": "And so E1 is associated\nwith thymine pyrophosphate.", "start": 1609.71, "duration": 7.05}, {"text": "E2 is associated\nwith lipoic acid.", "start": 1616.76, "duration": 10.75}, {"text": "And E3 is associated with FAD.", "start": 1627.51, "duration": 5.165}, {"text": "Now, let's go\nthrough the mechanism", "start": 1637.09, "duration": 3.03}, {"text": "for how this pyruvate\ndehydrogenase reaction works.", "start": 1640.12, "duration": 5.225}, {"text": "So remember, this is the\nactive part of TBP plus.", "start": 1702.47, "duration": 5.48}, {"text": "It is bound in the\nactive site of E1.", "start": 1707.95, "duration": 4.5}, {"text": "And it reacts with pyruvate to\ncatalyze alpha decarboxylation,", "start": 1712.45, "duration": 11.15}, {"text": "just like we described\nfor conversion of pyruvate", "start": 1723.6, "duration": 4.95}, {"text": "to alcohol.", "start": 1728.55, "duration": 1.56}, {"text": "So, you're going to see\nexactly the same mechanism", "start": 1730.11, "duration": 3.69}, {"text": "that we drew before.", "start": 1733.8, "duration": 2.69}, {"text": "So, that decarboxylates\nthe alpha-keto acid,", "start": 1755.98, "duration": 4.47}, {"text": "just like we saw to\ngenerate acetaldehyde.", "start": 1760.45, "duration": 6.99}, {"text": "The difference is rather\nthan resolve this such", "start": 1773.39, "duration": 3.9}, {"text": "that this carbon has\nthe same oxidation state", "start": 1777.29, "duration": 2.49}, {"text": "and make acetaldehyde, instead\nthe next step of this reaction", "start": 1779.78, "duration": 4.74}, {"text": "is going to be oxidized\nby reducing lipoic acid.", "start": 1784.52, "duration": 11.71}, {"text": "So, the active\npart of lipoic acid", "start": 1796.23, "duration": 2.81}, {"text": "that is in the active\nsite of the E2 subunit.", "start": 1799.04, "duration": 5.49}, {"text": "So this will now regenerate\nE1, but what we're left with,", "start": 1880.75, "duration": 6.42}, {"text": "then, is this.", "start": 1887.17, "duration": 3.65}, {"text": "Now, this intermediate\nbound to E2.", "start": 1890.82, "duration": 3.99}, {"text": "Here's where coenzyme\nA can come in, which", "start": 1905.13, "duration": 9.04}, {"text": "will then generate acetyl-CoA.", "start": 1914.17, "duration": 10.09}, {"text": "But now we are left with\nE2 in the reduced state,", "start": 1927.65, "duration": 12.24}, {"text": "rather than being in\nthe oxidized state.", "start": 1939.89, "duration": 3.06}, {"text": "So E2 has to be re-oxidized\nin order for this complex", "start": 1942.95, "duration": 5.04}, {"text": "to carry out the next\ncatalytic cycle, and the way", "start": 1947.99, "duration": 4.83}, {"text": "that works is as follows.", "start": 1952.82, "duration": 2.31}, {"text": "So you have FAD bound on E3.", "start": 1955.13, "duration": 6.0}, {"text": "And so you have a hydride\nion from the oxidation of E3", "start": 1961.13, "duration": 13.42}, {"text": "that can be transferred to FAD.", "start": 1974.55, "duration": 3.57}, {"text": "That will generate FAD from the\noxidized to the reduced form.", "start": 1978.12, "duration": 9.38}, {"text": "So re-oxidize lipoic acid\non E2, reduce FAD to FADH2,", "start": 1987.5, "duration": 8.7}, {"text": "and then that FADH2\ncan be re-oxidized back", "start": 1996.2, "duration": 3.81}, {"text": "to FAD via transferring\nthose electrons to NAD", "start": 2000.01, "duration": 6.41}, {"text": "plus to generate NADH.", "start": 2006.42, "duration": 5.3}, {"text": "So in this case, FADH2\nre-oxidized the FAD, NAD", "start": 2011.72, "duration": 5.46}, {"text": "plus reduced to NADH.", "start": 2017.18, "duration": 3.9}, {"text": "And so, effectively,\nwhat this happens", "start": 2021.08, "duration": 3.33}, {"text": "is that enzyme E1\nand E2 cooperate", "start": 2024.41, "duration": 4.68}, {"text": "to call what's referred to as\noxidative alpha decarboxylation", "start": 2029.09, "duration": 13.74}, {"text": "of pyruvate, while\nadding -CoA, so that's", "start": 2042.83, "duration": 4.26}, {"text": "where you get acetyl-CoA, with\nreduction of lipoic acid in E2,", "start": 2047.09, "duration": 8.0}, {"text": "and then E3 re-oxidizes\nthe lipoic acid in E2", "start": 2055.09, "duration": 5.28}, {"text": "while generating NADH.", "start": 2060.37, "duration": 4.039}, {"text": "This NADH, once it's\ngenerated, of course", "start": 2064.409, "duration": 2.268}, {"text": "those electrons have\nto go somewhere,", "start": 2066.677, "duration": 1.542}, {"text": "so they, like in glycolysis--", "start": 2068.219, "duration": 2.19}, {"text": "it also needs to regenerate\nto NAD at some point.", "start": 2070.409, "duration": 3.48}, {"text": "This is ultimately the\nelectrons that end up on oxygen,", "start": 2073.889, "duration": 4.231}, {"text": "and it's really this series\nof electron transfers,", "start": 2078.12, "duration": 4.47}, {"text": "with oxygen being a good\nelectron acceptor, that", "start": 2082.59, "duration": 2.91}, {"text": "ultimately allows controlled\nenergy release during carbon", "start": 2085.5, "duration": 5.07}, {"text": "oxidation.", "start": 2090.57, "duration": 1.169}, {"text": "And cells, you'll see, can\nuse that to make ATP or do", "start": 2091.739, "duration": 3.331}, {"text": "other kinds of work.", "start": 2095.07, "duration": 3.87}, {"text": "So, the net reaction\nand/or another way", "start": 2098.94, "duration": 3.78}, {"text": "to draw the pyruvate\ndehydrogenase reaction", "start": 2102.72, "duration": 4.44}, {"text": "would be as follows, and that's\ntaking pyruvate to acetyl-CoA.", "start": 2107.16, "duration": 8.23}, {"text": "And so we're going to take\ncoenzyme A and release CO2.", "start": 2118.89, "duration": 9.09}, {"text": "This is done by TPP\nplus, as part of E1.", "start": 2127.98, "duration": 14.52}, {"text": "That involves converting\nthe lipoic acid in E2", "start": 2142.5, "duration": 10.16}, {"text": "from the oxidized to\nthe reduced state.", "start": 2152.66, "duration": 3.42}, {"text": "That lipoic acid then\nhas to be re-oxidized.", "start": 2156.08, "duration": 4.05}, {"text": "If something's\noxidized, something else", "start": 2160.13, "duration": 2.13}, {"text": "has to be reduced.", "start": 2162.26, "duration": 1.53}, {"text": "That's FAD on E3,\nwhich also then cycles", "start": 2163.79, "duration": 6.3}, {"text": "between the oxidized\nand reduce state.", "start": 2170.09, "duration": 3.93}, {"text": "And ultimately, those\nelectrons ended up", "start": 2174.02, "duration": 3.42}, {"text": "being transferred to NAD\nplus to generate NADH.", "start": 2177.44, "duration": 6.57}, {"text": "And so the PDH complex\nis basically a chain", "start": 2184.01, "duration": 8.37}, {"text": "of electron transfer reactions.", "start": 2192.38, "duration": 8.63}, {"text": "And it's the first example of\na chain of electron transfer", "start": 2201.01, "duration": 4.68}, {"text": "reactions.", "start": 2205.69, "duration": 0.54}, {"text": "We're going to see that there\nis the electron transport", "start": 2206.23, "duration": 2.4}, {"text": "chain in the mitochondria,\neffectively does", "start": 2208.63, "duration": 3.27}, {"text": "the same thing.", "start": 2211.9, "duration": 0.97}, {"text": "And by coupling oxidation\nand reduction reactions", "start": 2212.87, "duration": 3.53}, {"text": "across chains of molecules like\nthis, effectively as a preview,", "start": 2216.4, "duration": 4.08}, {"text": "allows the stepwise energy\nrelease of these oxidation", "start": 2220.48, "duration": 3.45}, {"text": "reactions to occur.", "start": 2223.93, "duration": 4.24}, {"text": "So remember, if we burn glucose,\ncompletely oxidize it in one", "start": 2228.17, "duration": 3.38}, {"text": "step, where those electrons\nare directly transferred", "start": 2231.55, "duration": 2.2}, {"text": "to oxygen in combustion.", "start": 2233.75, "duration": 1.76}, {"text": "Lots of energy released,\nbut all in one step.", "start": 2235.51, "duration": 3.21}, {"text": "By doing these stepwise\nelectron transfers,", "start": 2238.72, "duration": 2.49}, {"text": "we can then basically break\nup that energy release", "start": 2241.21, "duration": 3.9}, {"text": "in a way that can be\ncaptured by cells to do work.", "start": 2245.11, "duration": 4.08}, {"text": "Here, the way\nenergy is captured,", "start": 2249.19, "duration": 1.86}, {"text": "it's not so obvious in this\nelectron transport reaction.", "start": 2251.05, "duration": 3.81}, {"text": "But effectively,\nyou're using oxidation", "start": 2254.86, "duration": 3.72}, {"text": "of the ketone on pyruvate, with\ndecarboxylation to the acid", "start": 2258.58, "duration": 8.19}, {"text": "to generate, rather than just\nthe acid, a thioester bond.", "start": 2266.77, "duration": 3.63}, {"text": "And that's that thioester bond--", "start": 2270.4, "duration": 2.07}, {"text": "as well as NADH, that's\nenergy as well-- but it's", "start": 2272.47, "duration": 2.64}, {"text": "really that thioester bond that\nthen can be recaptured later", "start": 2275.11, "duration": 3.51}, {"text": "to drive synthesis of\ncitrate in the TCA cycle.", "start": 2278.62, "duration": 4.8}, {"text": "Now, next what I want to do is\nI want to discuss the TCA cycle", "start": 2286.48, "duration": 5.49}, {"text": "reactions.", "start": 2291.97, "duration": 0.63}, {"text": "Now that you see how you\ncan get acetyl-CoA, at least", "start": 2292.6, "duration": 2.82}, {"text": "from pyruvate, I want to\ndiscuss how you can now", "start": 2295.42, "duration": 3.03}, {"text": "use that acetyl-CoA and\noxidize it back to combine it", "start": 2298.45, "duration": 5.46}, {"text": "with oxaloacetate,\nand oxidize it back", "start": 2303.91, "duration": 4.05}, {"text": "to make citrate, and then\noxidize it back to oxaloacetate", "start": 2307.96, "duration": 3.39}, {"text": "to run the TCA cycle.", "start": 2311.35, "duration": 4.14}, {"text": "OK, great.", "start": 2315.49, "duration": 2.47}, {"text": "So, the first reaction\nof the TCA cycle.", "start": 2317.96, "duration": 16.16}, {"text": "Here's acetyl-CoA.", "start": 2334.12, "duration": 5.97}, {"text": "It will combine\nwith oxaloacetate.", "start": 2340.09, "duration": 13.44}, {"text": "This reaction is catalyzed by an\nenzyme called citrate synthase,", "start": 2366.42, "duration": 31.71}, {"text": "and generates the six-carbon\ntricarboxylic acid citrate.", "start": 2398.13, "duration": 7.35}, {"text": "So, how does this reaction work?", "start": 2405.48, "duration": 3.86}, {"text": "Here's drawing acetyl-CoA\nin a slightly different way.", "start": 2447.99, "duration": 4.93}, {"text": "If I redraw this\nas the enol, this", "start": 2452.92, "duration": 32.7}, {"text": "will generate citrate via,\neffectively, that mechanism.", "start": 2485.62, "duration": 60.72}, {"text": "Next, citrate is\nconverted by adding water", "start": 2549.61, "duration": 12.99}, {"text": "across this carbon-carbon,\nor by removing water", "start": 2562.6, "duration": 5.85}, {"text": "across this carbon-carbon\nbond, to generate", "start": 2568.45, "duration": 8.34}, {"text": "this intermediate\ncalled cis-aconitate.", "start": 2576.79, "duration": 2.47}, {"text": "So this intermediate is\ncalled cis-aconitate.", "start": 2611.989, "duration": 2.671}, {"text": "so all I did was\ndehydrate across that bond", "start": 2618.26, "duration": 3.18}, {"text": "so there's a double bond there.", "start": 2621.44, "duration": 1.9}, {"text": "And then if I re-add\nwater across that bond,", "start": 2623.34, "duration": 12.84}, {"text": "I generate this molecule\ncalled isocitrate.", "start": 2636.18, "duration": 23.46}, {"text": "So effectively, to convert\ncitrate to isocitrate,", "start": 2662.24, "duration": 4.26}, {"text": "I'm moving the hydroxyl\ngroup from that carbon", "start": 2666.5, "duration": 3.48}, {"text": "to this carbon.", "start": 2669.98, "duration": 1.65}, {"text": "To do that, I basically\ndehydrate, make a double bond,", "start": 2671.63, "duration": 4.13}, {"text": "remove water, re-add\nwater across that bond", "start": 2675.76, "duration": 2.95}, {"text": "in the opposite direction\nto generate this molecule,", "start": 2678.71, "duration": 3.24}, {"text": "isocitrate.", "start": 2681.95, "duration": 1.6}, {"text": "This reaction is carried out\nby an enzyme called aconitase,", "start": 2683.55, "duration": 16.66}, {"text": "and converts citrate\nto isocitrate.", "start": 2700.21, "duration": 5.3}, {"text": "I think it's a little\neasier to see this reaction", "start": 2705.51, "duration": 5.31}, {"text": "if I draw it a\nslightly different way.", "start": 2710.82, "duration": 2.27}, {"text": "So, this here is\njust drawing citrate", "start": 2772.59, "duration": 2.3}, {"text": "by just slightly rotating the\nmolecule to look like that.", "start": 2774.89, "duration": 6.67}, {"text": "And so I'm basically\nremoving water here.", "start": 2781.56, "duration": 2.93}, {"text": "And then I'm now just\nadding water back", "start": 2811.04, "duration": 6.06}, {"text": "in the opposite orientation\nto generate isocitrate.", "start": 2817.1, "duration": 23.75}, {"text": "Now, you'll notice\nwhen I drew this--", "start": 2848.83, "duration": 4.47}, {"text": "if you look at citrate, this\nis actually a symmetrical", "start": 2853.3, "duration": 3.6}, {"text": "molecule, so the top half and\nthe bottom half of citrate", "start": 2856.9, "duration": 6.48}, {"text": "are identical.", "start": 2863.38, "duration": 2.32}, {"text": "And so what's interesting\nabout nature is", "start": 2865.7, "duration": 3.71}, {"text": "that it treats these carbons--", "start": 2869.41, "duration": 2.1}, {"text": "the green carbons that\ncame from acetyl-CoA--", "start": 2871.51, "duration": 2.55}, {"text": "different from the side\nof the molecule that", "start": 2874.06, "duration": 3.21}, {"text": "comes from oxaloacetate.", "start": 2877.27, "duration": 2.94}, {"text": "And effectively, nature always\nmoves the hydroxyl group", "start": 2880.21, "duration": 5.16}, {"text": "to this carbon that\ncame from oxaloacetate,", "start": 2885.37, "duration": 3.45}, {"text": "and never moves\nit to this carbon", "start": 2888.82, "duration": 2.85}, {"text": "that came from acetyl-CoA.", "start": 2891.67, "duration": 3.6}, {"text": "This is an example\nwhere enzymes--", "start": 2895.27, "duration": 2.97}, {"text": "nature treats a symmetrical\nmolecule like citrate", "start": 2898.24, "duration": 4.71}, {"text": "in an asymmetrical way.", "start": 2902.95, "duration": 2.13}, {"text": "And this has consequences for\nhow carbon is actually traced", "start": 2905.08, "duration": 4.83}, {"text": "through the entire TCA cycle.", "start": 2909.91, "duration": 2.49}, {"text": "Because even though you\nmight think things could get", "start": 2912.4, "duration": 2.19}, {"text": "scrambled at citrate,\nthey never do.", "start": 2914.59, "duration": 2.64}, {"text": "Meaning an isocitrate-- it's\nalways these green carbons", "start": 2917.23, "duration": 4.35}, {"text": "that came from acetyl-CoA.", "start": 2921.58, "duration": 1.74}, {"text": "You never get\nthose green carbons", "start": 2923.32, "duration": 1.86}, {"text": "on the other side of isocitrate.", "start": 2925.18, "duration": 3.78}, {"text": "And so when we go\nthrough the TCA cycle,", "start": 2928.96, "duration": 2.01}, {"text": "I'll keep these carbons\ngreen until the point where", "start": 2930.97, "duration": 3.06}, {"text": "you can no longer distinguish\nwhich carbon came from", "start": 2934.03, "duration": 4.26}, {"text": "came from which reaction.", "start": 2938.29, "duration": 1.295}, {"text": "The next reaction is\nwe're going to oxidize", "start": 2942.16, "duration": 5.58}, {"text": "this carbon of isocitrate.", "start": 2947.74, "duration": 4.29}, {"text": "So if we're going to\noxidize that carbon,", "start": 2952.03, "duration": 2.52}, {"text": "those electrons have\nto go somewhere.", "start": 2954.55, "duration": 2.82}, {"text": "And so if we oxidize\nthe carbon, we", "start": 2976.31, "duration": 3.84}, {"text": "can use NAD plus as an electron\nacceptor, reduce it to NADH.", "start": 2980.15, "duration": 9.09}, {"text": "That generates\nthis intermediate.", "start": 2989.24, "duration": 9.01}, {"text": "So hopefully this is clear\nto everybody at this point,", "start": 3020.46, "duration": 3.48}, {"text": "but just in case.", "start": 3023.94, "duration": 2.21}, {"text": "So, this carbon\nhere and isocitrate.", "start": 3029.23, "duration": 5.33}, {"text": "If I oxidize that\nalcohol to the ketone,", "start": 3034.56, "duration": 15.01}, {"text": "now I generate a hydride ion.", "start": 3049.57, "duration": 2.04}, {"text": "Those two electrons and the\nhydrogen can go to NAD plus", "start": 3051.61, "duration": 2.67}, {"text": "and reduce it to NADH.", "start": 3054.28, "duration": 2.79}, {"text": "That generates\nthis intermediate.", "start": 3057.07, "duration": 2.52}, {"text": "It's called oxalosuccinate.", "start": 3062.43, "duration": 3.79}, {"text": "Which then, if you\nnotice, the oxalosuccinate", "start": 3066.22, "duration": 5.64}, {"text": "is now a beta keto acid.", "start": 3071.86, "duration": 4.56}, {"text": "So alpha, beta.", "start": 3076.42, "duration": 6.0}, {"text": "The acid group is\nbeta to the ketone,", "start": 3082.42, "duration": 3.31}, {"text": "so it's a beta keto acid.", "start": 3085.73, "duration": 1.95}, {"text": "Remember, beta\ndecarboxylation is favorable,", "start": 3087.68, "duration": 4.59}, {"text": "and so I can lose that CO2.", "start": 3092.27, "duration": 3.59}, {"text": "And what I'm left with\nis this molecule, which", "start": 3095.86, "duration": 19.31}, {"text": "is called alpha keto glutarate.", "start": 3115.17, "duration": 10.93}, {"text": "So this whole reaction\nhere, the oxidation", "start": 3126.1, "duration": 8.27}, {"text": "of the alcohol to\nthe ketone, followed", "start": 3134.37, "duration": 2.22}, {"text": "by beta decarboxylation\nof oxalosuccinate", "start": 3136.59, "duration": 3.42}, {"text": "to alpha ketoglutarate,\nis carried out", "start": 3140.01, "duration": 2.55}, {"text": "by an enzyme called\nisocitrate dehydrogenase.", "start": 3142.56, "duration": 6.12}, {"text": "And of course,\njust to remind you,", "start": 3154.31, "duration": 16.352}, {"text": "here's that beta keto\nacid in oxalosuccinate.", "start": 3170.662, "duration": 7.998}, {"text": "And so that can decarboxylate,\nleading this enol.", "start": 3184.51, "duration": 16.06}, {"text": "Which can, of course, rearrange\nback to the ketone that we see,", "start": 3200.57, "duration": 15.23}, {"text": "an alpha ketoglutarate.", "start": 3215.8, "duration": 6.45}, {"text": "Now, if you look at\nalpha ketoglutarate,", "start": 3222.25, "duration": 7.46}, {"text": "you'll notice that-- and\nI will redraw over here.", "start": 3229.71, "duration": 7.155}, {"text": "So, this here is just me\nredrawing alpha ketoglutarate,", "start": 3251.94, "duration": 6.69}, {"text": "which is often\nabbreviated alpha kG.", "start": 3258.63, "duration": 5.33}, {"text": "Just drew it as a straight line.", "start": 3263.96, "duration": 2.41}, {"text": "Now, if you'll notice,\nalpha keto glutarate", "start": 3266.37, "duration": 2.93}, {"text": "is a alpha ketoacid.", "start": 3269.3, "duration": 3.45}, {"text": "And so here the acid group\nis alpha to the ketone.", "start": 3272.75, "duration": 4.87}, {"text": "So, an alpha keto acid.", "start": 3277.62, "duration": 2.0}, {"text": "It's effectively\njust like pyruvate,", "start": 3279.62, "duration": 2.55}, {"text": "but has this additional\npieces on it.", "start": 3282.17, "duration": 2.94}, {"text": "And it turns out the next\nstep in the TCA cycle", "start": 3285.11, "duration": 3.63}, {"text": "is the exact\nreaction that we saw", "start": 3288.74, "duration": 4.08}, {"text": "with pyruvate dehydrogenase.", "start": 3292.82, "duration": 3.42}, {"text": "It's alpha decarboxylation,\noxidative alpha", "start": 3296.24, "duration": 5.01}, {"text": "keto acid decarboxylation,\nas follows.", "start": 3301.25, "duration": 21.03}, {"text": "So, we carry out.", "start": 3322.28, "duration": 2.81}, {"text": "This is a molecule\ncalled succinyl-CoA.", "start": 3357.15, "duration": 7.56}, {"text": "And so, you'll see what happened\nthere is decarboxylated here,", "start": 3364.71, "duration": 6.12}, {"text": "this carbon, while oxidizing\nthis ketone to the acid", "start": 3370.83, "duration": 7.2}, {"text": "and adding -CoA.", "start": 3378.03, "duration": 1.77}, {"text": "That's a redox reaction.", "start": 3379.8, "duration": 1.6}, {"text": "So NAD, NADH, it turns out this\nis exactly the same mechanism--", "start": 3381.4, "duration": 7.43}, {"text": "so I don't need\nto draw it again--", "start": 3388.83, "duration": 1.53}, {"text": "that I just showed you for\npyruvate dehydrogenase.", "start": 3390.36, "duration": 4.38}, {"text": "So it needs all the\nsame cofactors--", "start": 3394.74, "duration": 1.98}, {"text": "TPP plus, lipoic acid, FAD.", "start": 3396.72, "duration": 4.05}, {"text": "And in fact, it even shares some\nof the same enzyme complexes,", "start": 3400.77, "duration": 6.24}, {"text": "subunits, as pyruvate\ndehydrogenase.", "start": 3407.01, "duration": 4.71}, {"text": "And so this is a reaction\nthat's catalyzed by alpha", "start": 3411.72, "duration": 5.61}, {"text": "ketoglutarate dehydrogenase.", "start": 3417.33, "duration": 2.13}, {"text": "Like pyruvate dehydrogenase,\nthis is a complex,", "start": 3422.52, "duration": 3.69}, {"text": "and so it has a unique\nE1, which makes sense.", "start": 3426.21, "duration": 3.44}, {"text": "Remember, E1 of\npyruvate dehydrogenase", "start": 3429.65, "duration": 2.35}, {"text": "was actually the subunit\nthat bound the pyruvate.", "start": 3432.0, "duration": 3.03}, {"text": "E1 of alpha ketoglutarate\ndehydrogenase is unique.", "start": 3435.03, "duration": 2.79}, {"text": "It binds alpha ketoglutarate\ninstead of pyruvate.", "start": 3437.82, "duration": 2.58}, {"text": "However, they share\nthe same E2 and E3s,", "start": 3440.4, "duration": 4.35}, {"text": "and so the E2s and\nE3s would carry out", "start": 3444.75, "duration": 3.39}, {"text": "exactly the same reaction\nand play the same part", "start": 3448.14, "duration": 4.2}, {"text": "in the mechanism of how you\ndo this alpha oxidative alpha", "start": 3452.34, "duration": 6.06}, {"text": "decarboxylation to turn\nalpha ketoglutarate", "start": 3458.4, "duration": 2.7}, {"text": "into succinyl-CoA.", "start": 3461.1, "duration": 4.23}, {"text": "Now, remember in\npyruvate dehydrogenase,", "start": 3465.33, "duration": 2.01}, {"text": "once we got that\nacetyl-CoA, we then", "start": 3467.34, "duration": 1.77}, {"text": "use this CoA group to drive\ncondensation with citrate.", "start": 3469.11, "duration": 3.57}, {"text": "Well, in this case,\nwhat happens is", "start": 3472.68, "duration": 1.86}, {"text": "you don't want to combine\ncondensation here.", "start": 3474.54, "duration": 3.57}, {"text": "Instead, what is\ngoing to happen is", "start": 3478.11, "duration": 2.58}, {"text": "you want to use this CoA\ngroup to now generate ATP.", "start": 3480.69, "duration": 7.47}, {"text": "And so this is going to\ncouple release of the CoA", "start": 3488.16, "duration": 7.05}, {"text": "to generate an ATP equivalent.", "start": 3495.21, "duration": 2.22}, {"text": "It's actually GTP that's\ngenerated by the TCA cycle.", "start": 3497.43, "duration": 5.32}, {"text": "And so, this is\ngoing to generate", "start": 3502.75, "duration": 11.88}, {"text": "this molecule, succinate.", "start": 3514.63, "duration": 4.86}, {"text": "And the enzyme that does this\nis called succinic bio-kinase.", "start": 3519.49, "duration": 8.3}, {"text": "So, let's go through over\nhere how this enzyme works.", "start": 3536.93, "duration": 4.275}, {"text": "So here's succinyl-CoA,\nbasically using favorable loss", "start": 3552.8, "duration": 12.15}, {"text": "of the CoA breaking the\nthioester bond to generate", "start": 3564.95, "duration": 15.97}, {"text": "this acid anhydride.", "start": 3580.92, "duration": 1.83}, {"text": "We saw an acid anhydride\nbefore in glycolysis.", "start": 3582.75, "duration": 5.4}, {"text": "Remember, we made\n1-3-bisphosphoglycerate,", "start": 3588.15, "duration": 2.91}, {"text": "so that's a good\nphosphate donor.", "start": 3591.06, "duration": 3.12}, {"text": "And then that can be used\nto generate succinate,", "start": 3594.18, "duration": 4.93}, {"text": "and transferring that\nphosphate to GDP to make GTP,", "start": 3599.11, "duration": 6.45}, {"text": "just like\n1-3-bisphosphoglycerate,", "start": 3605.56, "duration": 3.06}, {"text": "was able to transfer\nthe phosphate", "start": 3608.62, "duration": 1.8}, {"text": "from the acid anhydride to\nADP to make ATP in glycolysis.", "start": 3610.42, "duration": 7.95}, {"text": "So, the next step is to\noxidize this carbon-carbon bond", "start": 3620.95, "duration": 13.54}, {"text": "in succinate.", "start": 3634.49, "duration": 2.91}, {"text": "So if we're going to oxidize\na carbon-carbon bond,", "start": 3637.4, "duration": 4.29}, {"text": "those electrons have\nto go somewhere.", "start": 3641.69, "duration": 2.4}, {"text": "So there's our\ncarbon-carbon bond.", "start": 3650.67, "duration": 3.12}, {"text": "And so if we\ngenerate hydride ion", "start": 3661.67, "duration": 11.53}, {"text": "just like we did in other\noxidation reactions,", "start": 3673.2, "duration": 5.07}, {"text": "but this hydride ion is\ntransferred not to NAD,", "start": 3678.27, "duration": 5.61}, {"text": "but instead to FAD, a\ndifferent electron carrier,", "start": 3683.88, "duration": 6.63}, {"text": "to generate if FADH2.", "start": 3690.51, "duration": 4.17}, {"text": "Now, I should point out\nsuccinate, like citrate, is", "start": 3694.68, "duration": 3.69}, {"text": "a symmetrical molecule.", "start": 3698.37, "duration": 1.68}, {"text": "But at this point, nature\ndoesn't tell the difference.", "start": 3700.05, "duration": 3.63}, {"text": "Once it generates\nsuccinate, this molecule", "start": 3703.68, "duration": 3.76}, {"text": "now gets scrambled.", "start": 3707.44, "duration": 1.31}, {"text": "And so everything\ndownstream of succinate,", "start": 3708.75, "duration": 2.58}, {"text": "you no longer know which\ncarbons came from acetyl-CoA.", "start": 3711.33, "duration": 3.42}, {"text": "This generates this\nmolecule called fumarate,", "start": 3725.77, "duration": 4.77}, {"text": "and this reaction is carried\nout by an enzyme called", "start": 3730.54, "duration": 8.48}, {"text": "succinate dehydrogenase,\noften abbreviated SDH", "start": 3739.02, "duration": 13.0}, {"text": "for succinate dehydrogenase.", "start": 3752.02, "duration": 2.55}, {"text": "Now, the next reaction\nis, we're going", "start": 3757.85, "duration": 7.05}, {"text": "to add water across this\ndouble bond of fumarate.", "start": 3764.9, "duration": 5.62}, {"text": "And that generates this\nintermediate, malate.", "start": 3808.27, "duration": 5.425}, {"text": "This reaction is\ncarried out by an enzyme", "start": 3817.95, "duration": 4.68}, {"text": "called fumarate hydratase.", "start": 3822.63, "duration": 9.3}, {"text": "And it's simply adding\na water molecule", "start": 3831.93, "duration": 3.39}, {"text": "across that double bond.", "start": 3835.32, "duration": 3.15}, {"text": "Once we have malate,\nif you look what's", "start": 3838.47, "duration": 3.24}, {"text": "the difference between\nmalate and oxaloacetate,", "start": 3841.71, "duration": 4.74}, {"text": "the difference is that in\noxaloacetate, this carbon", "start": 3846.45, "duration": 5.1}, {"text": "is a ketone.", "start": 3851.55, "duration": 1.41}, {"text": "Whereas in malate,\nit's an alcohol.", "start": 3852.96, "duration": 2.43}, {"text": "And so if we want to turn\nthis carbon from the alcohol", "start": 3855.39, "duration": 2.76}, {"text": "into the ketone, that is, of\ncourse, a oxidation reaction,", "start": 3858.15, "duration": 6.34}, {"text": "and so those electrons\nhave to go somewhere.", "start": 3864.49, "duration": 7.98}, {"text": "Don't need to draw\nthe mechanism again.", "start": 3872.47, "duration": 4.32}, {"text": "It's basically just\nthe hydride transfer", "start": 3876.79, "duration": 4.29}, {"text": "to oxidize this to an\nalcohol, to the ketone.", "start": 3881.08, "duration": 4.64}, {"text": "That oxidation couples to a\nreduction of NAD plus to NADH.", "start": 3885.72, "duration": 5.46}, {"text": "This is carried out by an enzyme\ncalled malate dehydrogenase.", "start": 3891.18, "duration": 6.913}, {"text": "And doing this\ncompletes the TCA cycle,", "start": 3907.19, "duration": 5.79}, {"text": "regenerating oxaloacetate,\nthat can then", "start": 3912.98, "duration": 3.18}, {"text": "recombine with\nanother acetyl-CoA", "start": 3916.16, "duration": 2.52}, {"text": "to go through another\nround of the cycle.", "start": 3918.68, "duration": 5.52}, {"text": "You'll notice that going\nthrough this cycle,", "start": 3924.2, "duration": 4.5}, {"text": "there's two CO2s lost.", "start": 3928.7, "duration": 3.39}, {"text": "One of them is lost here\nat the isocitrate to alpha", "start": 3932.09, "duration": 6.93}, {"text": "ketoglutarate reaction.", "start": 3939.02, "duration": 1.84}, {"text": "So, this decarboxylation\nfrom oxaloacetate", "start": 3940.86, "duration": 4.555}, {"text": "to alpha ketoglutarate.", "start": 3945.415, "duration": 1.255}, {"text": "That beta decarboxylation,\nthat's the first CO2.", "start": 3946.67, "duration": 3.33}, {"text": "The other one is lost here\nat the alpha ketoglutarate.", "start": 3950.0, "duration": 3.405}, {"text": "The alpha ketoglutarate\ndehydrogenase step,", "start": 3957.37, "duration": 2.73}, {"text": "where you have this\nalpha decarboxylation", "start": 3960.1, "duration": 3.87}, {"text": "to take alpha ketoglutarate\nto succinyl-CoA", "start": 3963.97, "duration": 3.57}, {"text": "oxidative alpha decarboxylation.", "start": 3967.54, "duration": 4.74}, {"text": "Now, what's cool about\nthis, as you noticed,", "start": 3972.28, "duration": 3.39}, {"text": "we just discussed all the\nreactions of the TCA cycle.", "start": 3975.67, "duration": 5.1}, {"text": "And I showed you, reminded\nyou, of some chemistry", "start": 3980.77, "duration": 2.69}, {"text": "that you've already\nseen, but unless you", "start": 3983.46, "duration": 2.55}, {"text": "count the chemistry we showed\nyou earlier for how the PDH", "start": 3986.01, "duration": 3.465}, {"text": "and alpha ketoglutarate\ndehydrogenase", "start": 3989.475, "duration": 1.875}, {"text": "reactions work with E1, E2\nand E3, with lipoic acid, FAD.", "start": 3991.35, "duration": 4.26}, {"text": "That was obviously\nnew for today.", "start": 3995.61, "duration": 1.69}, {"text": "But other than that,\neverything else", "start": 3997.3, "duration": 2.3}, {"text": "was chemistry that\nyou've already seen.", "start": 3999.6, "duration": 2.64}, {"text": "And this really\npoints out the point", "start": 4002.24, "duration": 1.65}, {"text": "that I made earlier, that\nmetabolism is really variations", "start": 4003.89, "duration": 3.57}, {"text": "on relatively few reactions.", "start": 4007.46, "duration": 1.77}, {"text": "We've just repurposed some of\nthe same tricks, if you will,", "start": 4009.23, "duration": 3.4}, {"text": "that we're used in\nglycolysis, and allowed", "start": 4012.63, "duration": 3.07}, {"text": "it to now do an entire different\npathway, the TCA cycle.", "start": 4015.7, "duration": 4.39}, {"text": "It also points out how Hans\nKrebs was-- well, is still--", "start": 4020.09, "duration": 2.78}, {"text": "remarkable, able to figure\nout from chemistry alone,", "start": 4022.87, "duration": 3.66}, {"text": "because there's actually quite\na bit of logic to the way", "start": 4026.53, "duration": 2.88}, {"text": "metabolism works.", "start": 4029.41, "duration": 2.62}, {"text": "Now, I want to say this again.", "start": 4032.03, "duration": 1.25}, {"text": "Note there were two carbons\nthat entered acetyl-CoA,", "start": 4033.28, "duration": 3.0}, {"text": "and two carbons that\nwere lost to CO2.", "start": 4036.28, "duration": 3.77}, {"text": "But if you look,\nthe green carbons", "start": 4040.05, "duration": 2.64}, {"text": "remain in the same places\nuntil they get to succinate.", "start": 4042.69, "duration": 4.5}, {"text": "and so the two\ncarbons that enter", "start": 4047.19, "duration": 2.13}, {"text": "are not lost on the\nfirst turn of the cycle.", "start": 4049.32, "duration": 3.03}, {"text": "It's actually two carbons\nthat came from oxaloacetate", "start": 4052.35, "duration": 5.46}, {"text": "that are converted to CO2\nas that acetyl-CoA goes", "start": 4057.81, "duration": 4.41}, {"text": "through the cycle.", "start": 4062.22, "duration": 1.12}, {"text": "And so to oxidize the exact\ncarbons from acetyl-CoA to CO2", "start": 4063.34, "duration": 4.58}, {"text": "requires more than\none turn of the cycle.", "start": 4067.92, "duration": 5.3}, {"text": "You'll also notice that\nthe cycle is oxidation.", "start": 4073.22, "duration": 4.44}, {"text": "And so oxidation reactions,\nof course, release energy.", "start": 4077.66, "duration": 4.01}, {"text": "We've talked about that.", "start": 4081.67, "duration": 1.0}, {"text": "And so it's favorable.", "start": 4082.67, "duration": 2.4}, {"text": "And the products, if you will,\nare three NADH molecules.", "start": 4085.07, "duration": 6.965}, {"text": "You can say plus one more NADH\nif we're going all the way", "start": 4092.035, "duration": 4.465}, {"text": "from glucose or from pyruvate.", "start": 4096.5, "duration": 4.529}, {"text": "Glucose derived pyruvate because\nthe pyruvate dehydrogenase", "start": 4101.029, "duration": 3.091}, {"text": "reaction also generates an\nNADH to make that a acetyl-CoA.", "start": 4104.12, "duration": 5.529}, {"text": "One FADH2, as well\nas one GTP molecule.", "start": 4109.649, "duration": 8.71}, {"text": "And so lots of\noxidation going on here.", "start": 4118.359, "duration": 3.21}, {"text": "We completely oxidized\ntwo carbons to CO2,", "start": 4121.569, "duration": 2.781}, {"text": "so that's energy release.", "start": 4124.35, "duration": 2.879}, {"text": "But you notice you only get\none GTP from the molecule.", "start": 4127.229, "duration": 5.05}, {"text": "Now, this GTP, of\ncourse-- that reaction,", "start": 4132.279, "duration": 3.231}, {"text": "the succinic\nthiokinase reaction,", "start": 4135.51, "duration": 2.429}, {"text": "like the reactions\nwe saw on glycolysis,", "start": 4137.939, "duration": 2.071}, {"text": "is such that it can generate\nGTP at a high DGP-GDP", "start": 4140.01, "duration": 4.53}, {"text": "ratio, or ATP-ADP ratio.", "start": 4144.54, "duration": 1.678}, {"text": "Remember, those are equivalent.", "start": 4146.218, "duration": 1.292}, {"text": "Those energy charge are similar,\nand so that makes sense.", "start": 4147.51, "duration": 3.389}, {"text": "But most of the energy\nreleased is actually", "start": 4150.899, "duration": 4.351}, {"text": "reducing NAD and FAD\nto NADH and FADH2.", "start": 4155.25, "duration": 4.71}, {"text": "And of course, these need\nto transfer their electrons", "start": 4159.96, "duration": 5.34}, {"text": "somewhere else, and\nthat's the role of oxygen.", "start": 4165.3, "duration": 3.12}, {"text": "Oxygen, remember, is a\nvery good electron donor,", "start": 4168.42, "duration": 2.83}, {"text": "and so it's the ultimate\ntransfer of those electrons", "start": 4171.25, "duration": 3.229}, {"text": "from these molecules to oxygen\nthat also provide energy", "start": 4174.479, "duration": 6.271}, {"text": "that the cell can use to do\nwork, but it does so, in a way,", "start": 4180.75, "duration": 3.99}, {"text": "by charging up different\nratios in the cell.", "start": 4184.74, "duration": 5.17}, {"text": "So the NAD-NADH or\nthe FADH2-FAD ratios.", "start": 4189.91, "duration": 6.92}, {"text": "And just like we talked about,\nthe ratio or the energy of ATP", "start": 4196.83, "duration": 5.19}, {"text": "is in the interconversion\nbetween ATP and ADP.", "start": 4202.02, "duration": 3.15}, {"text": "It's the ratio that drives\nthe free energy change.", "start": 4205.17, "duration": 4.02}, {"text": "The same thing exists for an\nNADH and NAD, FADH2 and FAD.", "start": 4209.19, "duration": 4.59}, {"text": "And so charging up these ratios\nwhile passing through the TCA", "start": 4213.78, "duration": 3.21}, {"text": "cycle, and the ultimate\ndownstream transfer", "start": 4216.99, "duration": 2.82}, {"text": "of those electrons\nto oxygen, really", "start": 4219.81, "duration": 2.73}, {"text": "is where most of the energy\nis captured as carbon", "start": 4222.54, "duration": 4.11}, {"text": "is oxidized through\nthe TCA cycle.", "start": 4226.65, "duration": 3.57}, {"text": "And exactly how that works and\nhow it can be related to ATP", "start": 4230.22, "duration": 4.86}, {"text": "will be something that'll be\nmore explicit in the coming", "start": 4235.08, "duration": 2.67}, {"text": "lectures.", "start": 4237.75, "duration": 1.55}, {"text": "Now, I want to point out\napart from the oxidation,", "start": 4239.3, "duration": 3.9}, {"text": "there's actually lots of\nintermediates made here.", "start": 4243.2, "duration": 3.16}, {"text": "And it turns out, a bunch\nof these intermediates", "start": 4246.36, "duration": 2.09}, {"text": "are useful for\ncells to make stuff.", "start": 4248.45, "duration": 3.16}, {"text": "So we talked about\ngluconeogenesis.", "start": 4251.61, "duration": 1.64}, {"text": "Gluconeogenesis needs\nelectron balance.", "start": 4253.25, "duration": 1.92}, {"text": "We get NADH from the\nTCA cycle, and so you", "start": 4255.17, "duration": 2.97}, {"text": "can think of gluconeogenesis\nas an alternative", "start": 4258.14, "duration": 3.15}, {"text": "to fermentation to\ndispose of electrons.", "start": 4261.29, "duration": 2.15}, {"text": "Well, you can use the\nNADH from the TCA cycle", "start": 4263.44, "duration": 2.56}, {"text": "to run gluconeogenesis as well.", "start": 4266.0, "duration": 2.98}, {"text": "But beyond the cofactors,\nthe carbon itself.", "start": 4268.98, "duration": 2.64}, {"text": "So citrate, I've alluded\nto now a few times,", "start": 4271.62, "duration": 2.84}, {"text": "is important as a\nprecursor to make fat.", "start": 4274.46, "duration": 2.67}, {"text": "We'll discuss that in\nlater lectures, too.", "start": 4277.13, "duration": 2.49}, {"text": "But other intermediates\nin this pathway", "start": 4279.62, "duration": 3.09}, {"text": "are useful for various amino\nacids and nucleic acids.", "start": 4282.71, "duration": 4.0}, {"text": "And so there's\nlots of things that", "start": 4286.71, "duration": 2.63}, {"text": "can come from the\nTCA cycle that cells", "start": 4289.34, "duration": 3.15}, {"text": "can find useful to do,\nnot just catabolism,", "start": 4292.49, "duration": 5.35}, {"text": "but also anabolic processes.", "start": 4297.84, "duration": 4.04}, {"text": "Now, the way the TCA\ncycle works, though,", "start": 4301.88, "duration": 4.21}, {"text": "is that there's\nactually an issue", "start": 4306.09, "duration": 2.57}, {"text": "if you want to use the\nintermediates from the TCA", "start": 4308.66, "duration": 3.48}, {"text": "cycle to make stuff.", "start": 4312.14, "duration": 2.98}, {"text": "And so what is that issue?", "start": 4315.12, "duration": 4.77}, {"text": "Well, the TCA cycle functions\nat a site as a cycle.", "start": 4319.89, "duration": 5.528}, {"text": "And so, if we're going to\ntake things in and out of it,", "start": 4325.418, "duration": 2.292}, {"text": "that has consequences\nfor how the cycle runs.", "start": 4327.71, "duration": 4.02}, {"text": "Now there's a couple\nwords for this", "start": 4331.73, "duration": 3.01}, {"text": "that I want to just\nintroduce to you.", "start": 4334.74, "duration": 2.46}, {"text": "The first one is cataplerosis\nand the second one", "start": 4337.2, "duration": 3.17}, {"text": "is anaplerosis.", "start": 4340.37, "duration": 2.83}, {"text": "And so cataplerosis is\nthe act of removing stuff", "start": 4343.2, "duration": 9.48}, {"text": "from a metabolic cycle.", "start": 4352.68, "duration": 1.545}, {"text": "So, we're going\nto remove citrate", "start": 4358.03, "duration": 1.65}, {"text": "from the cycle to make fat.", "start": 4359.68, "duration": 1.44}, {"text": "That's cataplerosis.", "start": 4361.12, "duration": 1.74}, {"text": "And anaplerosis is adding\nstuff back to a metabolic cycle", "start": 4362.86, "duration": 14.68}, {"text": "so it can continue to function.", "start": 4377.54, "duration": 3.84}, {"text": "Viewing this is really evident\nif you think of the TCA cycle", "start": 4381.38, "duration": 3.75}, {"text": "as a chicken and egg problem.", "start": 4385.13, "duration": 2.2}, {"text": "So, the very first\ntime acetyl-CoA", "start": 4387.33, "duration": 2.34}, {"text": "was generated, how\ndo you start the TCA", "start": 4389.67, "duration": 3.05}, {"text": "cycle in the first place?", "start": 4392.72, "duration": 1.77}, {"text": "You can't add it\nto the TCA cycle", "start": 4394.49, "duration": 2.31}, {"text": "unless you have\noxaloacetate to combine", "start": 4396.8, "duration": 3.12}, {"text": "with the acetyl-CoA,\nwhich can then", "start": 4399.92, "duration": 2.13}, {"text": "generate another oxaloacetate.", "start": 4402.05, "duration": 3.12}, {"text": "So where does the first\noxaloacetate come from?", "start": 4405.17, "duration": 4.33}, {"text": "Well, we already talked\nabout one reaction.", "start": 4409.5, "duration": 2.06}, {"text": "We talked about it in the\ncontext of gluconeogenesis.", "start": 4411.56, "duration": 3.48}, {"text": "That can solve this problem.", "start": 4415.04, "duration": 1.36}, {"text": "And so we have pyruvate.", "start": 4416.4, "duration": 1.82}, {"text": "And so we talked\nearlier today how", "start": 4418.22, "duration": 2.16}, {"text": "we can do oxidative\ndecarboxylation of pyruvate", "start": 4420.38, "duration": 5.34}, {"text": "to give acetyl-CoA.", "start": 4425.72, "duration": 2.73}, {"text": "But we talked to in\nthe gluconeogenesis", "start": 4428.45, "duration": 1.71}, {"text": "lecture how we can add a\nCO2 pyruvate to generate", "start": 4430.16, "duration": 5.31}, {"text": "oxaloacetate.", "start": 4435.47, "duration": 1.8}, {"text": "So if I do those\ntwo reactions, now I", "start": 4437.27, "duration": 2.64}, {"text": "have all the carbon I\nneed to generate a citrate", "start": 4439.91, "duration": 6.49}, {"text": "and start off the TCA cycle.", "start": 4446.4, "duration": 4.79}, {"text": "Now obviously, if\nI do cataplerosis", "start": 4451.19, "duration": 4.94}, {"text": "and I remove that citrate\nI made to make fat,", "start": 4456.13, "duration": 3.09}, {"text": "well, now I need\ntwo pyruvate again", "start": 4459.22, "duration": 1.98}, {"text": "to generate the next citrate\nif I'm using this pathway,", "start": 4461.2, "duration": 4.74}, {"text": "because every time I bring\nan acetyl-CoA into the cycle,", "start": 4465.94, "duration": 3.48}, {"text": "I need an oxaloacetate\nto combine it with.", "start": 4469.42, "duration": 3.24}, {"text": "And so if I remove something,\nI have to add something back.", "start": 4472.66, "duration": 3.18}, {"text": "And so pyruvate to oxaloacetate,\nthe pyruvate carboxylase", "start": 4475.84, "duration": 3.9}, {"text": "reaction is an example of\nan anaplerotic reaction.", "start": 4479.74, "duration": 6.11}, {"text": "Now what this means,\nthough, is that in order", "start": 4485.85, "duration": 4.05}, {"text": "to do an anaplerosis,\nyou have to be", "start": 4489.9, "duration": 2.7}, {"text": "able to generate\nfour-carbon oxaloacetate,", "start": 4492.6, "duration": 4.35}, {"text": "or a four-carbon molecule.", "start": 4496.95, "duration": 2.83}, {"text": "Now, pyruvate carboxylase,\npyruvate to oxaloacetate,", "start": 4499.78, "duration": 2.81}, {"text": "allows you to do that.", "start": 4502.59, "duration": 1.212}, {"text": "We can take a\nthree-carbon molecule", "start": 4503.802, "duration": 1.458}, {"text": "and generate four-carbon\noxaloacetate.", "start": 4505.26, "duration": 2.82}, {"text": "However, if we start from\na two-carbon molecule", "start": 4508.08, "duration": 4.86}, {"text": "like acetate or acetyl-CoA\nthat enters the cycle,", "start": 4512.94, "duration": 7.27}, {"text": "it's actually not so simple to\ntake that two-carbon molecule", "start": 4520.21, "duration": 4.2}, {"text": "and turn it into\nfour-carbon oxaloacetate.", "start": 4524.41, "duration": 2.94}, {"text": "And in fact, humans\nlack any enzymes", "start": 4527.35, "duration": 3.72}, {"text": "that allow them to\ntake a two-carbon unit,", "start": 4531.07, "duration": 2.37}, {"text": "to take acetate or\nacetyl-CoA, and turn it", "start": 4533.44, "duration": 3.24}, {"text": "into anything that's\nlonger than net-- turn", "start": 4536.68, "duration": 4.32}, {"text": "it into anything that's\nlonger than two carbons.", "start": 4541.0, "duration": 3.27}, {"text": "And this has\nimportant implications", "start": 4544.27, "duration": 1.83}, {"text": "for human physiology,\nbecause what it says", "start": 4546.1, "duration": 2.97}, {"text": "is that we can't make\nglucose from anything", "start": 4549.07, "duration": 3.3}, {"text": "that starts with something\nless than three carbons long.", "start": 4552.37, "duration": 4.21}, {"text": "So if you drink alcohol and\nyou metabolize that alcohol", "start": 4556.58, "duration": 3.17}, {"text": "to acetate, it turns\nout you take fat", "start": 4559.75, "duration": 2.76}, {"text": "and you break down fat\nalso to acetyl-CoA,", "start": 4562.51, "duration": 2.82}, {"text": "to acetate two carbons long.", "start": 4565.33, "duration": 2.19}, {"text": "There is no way to turn\nthose molecules into glucose,", "start": 4567.52, "duration": 5.94}, {"text": "because you cannot generate\nthe oxaloacetate to do", "start": 4573.46, "duration": 3.15}, {"text": "the anaplerosis that's\nnecessary to get it there.", "start": 4576.61, "duration": 4.87}, {"text": "What this means is\nthat our body can only", "start": 4584.23, "duration": 5.79}, {"text": "store calories that come\nfrom two carbon units,", "start": 4590.02, "duration": 3.18}, {"text": "fat or alcohol, as fat.", "start": 4593.2, "duration": 2.4}, {"text": "We can never turn them back\ninto glucose or make glycogen.", "start": 4595.6, "duration": 5.602}, {"text": "And this is very relevant\nfor those of you that", "start": 4601.202, "duration": 1.958}, {"text": "go to medical\nschool, because it's", "start": 4603.16, "duration": 1.417}, {"text": "relevant to our physiology.", "start": 4604.577, "duration": 2.093}, {"text": "And that is, when\nour bodies exhaust", "start": 4606.67, "duration": 2.04}, {"text": "all of our stores of\nglucose, what happens?", "start": 4608.71, "duration": 2.61}, {"text": "Our liver can no longer\ndo gluconeogenesis.", "start": 4611.32, "duration": 2.82}, {"text": "And so what happens?", "start": 4614.14, "duration": 0.99}, {"text": "Now it has to switch over\nto doing something else.", "start": 4615.13, "duration": 2.32}, {"text": "It has to work with\ntwo carbon units.", "start": 4617.45, "duration": 1.92}, {"text": "And ultimately, this is\nketone metabolism, which we'll", "start": 4619.37, "duration": 2.78}, {"text": "talk about in a few lectures.", "start": 4622.15, "duration": 3.45}, {"text": "It also said that the body--", "start": 4625.6, "duration": 2.055}, {"text": "that this is also the basis\nof a very old adage that's", "start": 4631.31, "duration": 3.75}, {"text": "out there that some of\nyou may have heard--", "start": 4635.06, "duration": 2.22}, {"text": "that you need to have\nsome other fuel if you're", "start": 4637.28, "duration": 2.94}, {"text": "going to burn fat.", "start": 4640.22, "duration": 2.04}, {"text": "The basis for that is that\nfat is turned into two carbon", "start": 4642.26, "duration": 3.48}, {"text": "units, acetyl-CoA units.", "start": 4645.74, "duration": 2.1}, {"text": "And so if you're going to\ntake those acetyl-CoA units", "start": 4647.84, "duration": 2.34}, {"text": "and ultimately burn them\naway, turn them into CO2,", "start": 4650.18, "duration": 2.91}, {"text": "you need a source\nof oxaloacetate,", "start": 4653.09, "duration": 2.1}, {"text": "or your TCA cycle won't work.", "start": 4655.19, "duration": 2.4}, {"text": "And you don't need a lot of\nsomething, but it is true.", "start": 4657.59, "duration": 2.7}, {"text": "You can't start just with\nacetyl-CoA as a human and turn", "start": 4660.29, "duration": 4.71}, {"text": "it into CO2, so you need some--", "start": 4665.0, "duration": 1.86}, {"text": "at least a little\nbit of oxaloacetate", "start": 4666.86, "duration": 2.34}, {"text": "to get your TCA cycle started.", "start": 4669.2, "duration": 3.21}, {"text": "Now, that's a problem that we as\nhumans and other mammals face,", "start": 4672.41, "duration": 4.925}, {"text": "but it turns out there's\nlots of microbes out there", "start": 4677.335, "duration": 2.125}, {"text": "that grow just fine on\nacetate or on alcohol,", "start": 4679.46, "duration": 3.42}, {"text": "even if it's only carbon source.", "start": 4682.88, "duration": 2.1}, {"text": "And so those organisms\nmust have some way", "start": 4684.98, "duration": 3.57}, {"text": "to build stuff from\ntwo carbon units.", "start": 4688.55, "duration": 2.28}, {"text": "That is a way to use two carbon\nunits and do an anaplerosis.", "start": 4690.83, "duration": 4.45}, {"text": "And it turns out the way\nthey do this is via something", "start": 4695.28, "duration": 2.33}, {"text": "called the glyoxylate cycle.", "start": 4697.61, "duration": 2.8}, {"text": "And so the glyoxylate cycle\nis an alternative version", "start": 4703.05, "duration": 3.17}, {"text": "of the TCA cycle that\neffectively uses two enzymes", "start": 4706.22, "duration": 3.39}, {"text": "that we lack as mammals.", "start": 4709.61, "duration": 2.4}, {"text": "And so I'll quickly\ntell you about it here.", "start": 4712.01, "duration": 2.22}, {"text": "So, this is isocitrate\nfrom the TCA cycle.", "start": 4727.92, "duration": 9.5}, {"text": "And some microbes have an\nenzyme called isocitrate lyase.", "start": 4737.42, "duration": 10.85}, {"text": "And what isocitrate lyase does\nis basically splits citrate", "start": 4748.27, "duration": 10.16}, {"text": "in half, such that the top\nportion of the molecule", "start": 4758.43, "duration": 4.83}, {"text": "is another TCA cycle\nintermediate, succinate.", "start": 4763.26, "duration": 6.93}, {"text": "And the bottom\nportion of a molecule", "start": 4770.19, "duration": 3.96}, {"text": "is this two carbon\naldehyde called glyoxylate.", "start": 4774.15, "duration": 8.7}, {"text": "Glyoxylate can react with\nacetyl-CoA by another enzyme", "start": 4782.85, "duration": 18.04}, {"text": "that we lack as humans\ncalled malate synthase.", "start": 4800.89, "duration": 7.5}, {"text": "And I don't have time to\nshow the mechanism again,", "start": 4811.03, "duration": 3.85}, {"text": "but malate synthase basically\nadds the two carbons", "start": 4814.88, "duration": 4.28}, {"text": "from acetyl-CoA to the\naldehyde, the carbonyl,", "start": 4819.16, "duration": 7.02}, {"text": "the aldehyde carbonyl of\nglyoxylate in a reaction that", "start": 4826.18, "duration": 3.72}, {"text": "is, for all intents and\npurposes, exactly what happens", "start": 4829.9, "duration": 3.72}, {"text": "in citrate synthase.", "start": 4833.62, "duration": 2.43}, {"text": "That will generate this\nmolecule, which is malate, also", "start": 4836.05, "duration": 15.88}, {"text": "in the TCA cycle.", "start": 4851.93, "duration": 2.44}, {"text": "And so having these two extra\nreactions, isocitrate lyase", "start": 4854.37, "duration": 3.62}, {"text": "and malate synthase,\ngives microbes", "start": 4857.99, "duration": 3.93}, {"text": "the ability to have\nacetyl-CoA be anaplerotic.", "start": 4861.92, "duration": 6.12}, {"text": "And so how does that work?", "start": 4868.04, "duration": 1.41}, {"text": "Well, that's because if we start\nwith one oxaloacetate, four", "start": 4869.45, "duration": 6.39}, {"text": "carbons, and acetyl-CoA, two\ncarbons, can run the TCA cycle", "start": 4875.84, "duration": 10.56}, {"text": "and make citrate, six carbons.", "start": 4886.4, "duration": 4.71}, {"text": "Turn that citrate\ninto isocitrate.", "start": 4891.11, "duration": 2.774}, {"text": "Use isocitrate lyase to generate\nglyoxylate, two carbons.", "start": 4897.95, "duration": 11.14}, {"text": "Plus succinate.", "start": 4909.09, "duration": 2.46}, {"text": "That succinate can run through\nsuccinate dehydrogenase", "start": 4915.31, "duration": 6.76}, {"text": "to generate malate,\nwhich you can", "start": 4922.07, "duration": 1.98}, {"text": "go through malate dehydrogenase\nto generate oxaloacetate.", "start": 4924.05, "duration": 4.14}, {"text": "This glyoxylate can start\nwith a second acetyl-CoA.", "start": 4928.19, "duration": 7.74}, {"text": "Two carbons come\ntogether, generate malate.", "start": 4935.93, "duration": 3.96}, {"text": "That generates a\nsecond malate molecule,", "start": 4939.89, "duration": 2.88}, {"text": "which can then exit the cycle\nas malate or oxaloacetate", "start": 4942.77, "duration": 7.41}, {"text": "or whatever you want.", "start": 4950.18, "duration": 1.95}, {"text": "And so basically, it allows\ntwo acetyl-CoAs to net", "start": 4952.13, "duration": 4.29}, {"text": "generate an oxaloacetate,\nand so net generates a way", "start": 4956.42, "duration": 4.62}, {"text": "to do an anaplerosis\nfrom two carbon units", "start": 4961.04, "duration": 4.05}, {"text": "by having this malate\nsynthase reaction", "start": 4965.09, "duration": 6.07}, {"text": "and this isocitrate\nlyase reaction", "start": 4971.16, "duration": 6.2}, {"text": "and run this alternative\nversion of the TCA cycle,", "start": 4977.36, "duration": 3.57}, {"text": "called the glyoxylate cycle.", "start": 4980.93, "duration": 3.06}, {"text": "And it's a nice way how life--\nagain, no new chemistry here,", "start": 4983.99, "duration": 4.11}, {"text": "just variations on what\nwe've already shown--", "start": 4988.1, "duration": 2.64}, {"text": "repurposed the\nsimilar chemistries", "start": 4990.74, "duration": 1.95}, {"text": "that it's already using\nas a way to live off", "start": 4992.69, "duration": 3.93}, {"text": "of carbon sources that contain\nonly two carbons, like ethanol", "start": 4996.62, "duration": 7.92}, {"text": "or acetate.", "start": 5004.54, "duration": 2.81}, {"text": "So in closing today,\nthe last thing", "start": 5007.35, "duration": 4.05}, {"text": "I want to talk\nabout, very briefly,", "start": 5011.4, "duration": 3.03}, {"text": "is how the TCA\ncycle is regulated.", "start": 5014.43, "duration": 6.18}, {"text": "And we don't need to\nspend a ton of time", "start": 5020.61, "duration": 2.01}, {"text": "on this, because it really\nfollows principles that", "start": 5022.62, "duration": 6.09}, {"text": "make sense, particularly when\nwe think about things that we've", "start": 5028.71, "duration": 5.63}, {"text": "already talk about.", "start": 5034.34, "duration": 1.48}, {"text": "And so, regulation of the TCA\ncycles is of course important,", "start": 5035.82, "duration": 3.98}, {"text": "and it's really a critical hub,\nboth for anabolic and catabolic", "start": 5039.8, "duration": 3.63}, {"text": "pathways.", "start": 5043.43, "duration": 0.52}, {"text": "So, you needed to get energy\nto fully oxidize carbon,", "start": 5043.95, "duration": 2.99}, {"text": "but it's also a useful\nplace to get stuff.", "start": 5046.94, "duration": 3.312}, {"text": "And before I talk\nabout regulation,", "start": 5050.252, "duration": 1.458}, {"text": "I just want to point out that\nmany of the enzymes in the TCA", "start": 5051.71, "duration": 2.88}, {"text": "cycle, even though we talk\nabout it in the mitochondria", "start": 5054.59, "duration": 3.06}, {"text": "and we're about to talk\nabout regulation in terms", "start": 5057.65, "duration": 2.34}, {"text": "of catabolism--\nthat is oxidation,", "start": 5059.99, "duration": 2.67}, {"text": "ways to release energy--", "start": 5062.66, "duration": 2.4}, {"text": "many of these enzymes are\nalso in other locations", "start": 5065.06, "duration": 2.64}, {"text": "in the cell, because there's\nfunctions for them in making", "start": 5067.7, "duration": 4.47}, {"text": "stuff that is very different\nthan what goes on in the TCA", "start": 5072.17, "duration": 2.85}, {"text": "cycle.", "start": 5075.02, "duration": 0.99}, {"text": "And the regulation that\nI'll tell you about,", "start": 5076.01, "duration": 3.45}, {"text": "and that comes up on\nMCAT exams and stuff", "start": 5079.46, "duration": 2.82}, {"text": "like that, usually\ntalks about this pathway", "start": 5082.28, "duration": 3.18}, {"text": "as a catabolic pathway, as a\nway to make CO2, to make ATP.", "start": 5085.46, "duration": 4.48}, {"text": "However, recognize\nthat there's also", "start": 5089.94, "duration": 3.44}, {"text": "variations on this pathway that\ncan use in anabolic things,", "start": 5093.38, "duration": 4.23}, {"text": "making stuff.", "start": 5097.61, "duration": 1.11}, {"text": "And that regulation is something\nthat really is not necessarily", "start": 5098.72, "duration": 4.98}, {"text": "what we're going\nto talk about here", "start": 5103.7, "duration": 1.89}, {"text": "and is a little bit\nless well-understood.", "start": 5105.59, "duration": 4.2}, {"text": "But at least the\nregulation, in terms", "start": 5109.79, "duration": 1.74}, {"text": "of catabolism, if we put it in\ncontext of glucose metabolism--", "start": 5111.53, "duration": 7.39}, {"text": "so here's glycolysis, turning\nglucose into pyruvate.", "start": 5118.92, "duration": 6.97}, {"text": "And then that\npyruvate can operate", "start": 5132.34, "duration": 3.21}, {"text": "through the pyruvate\ndehydrogenase reaction", "start": 5135.55, "duration": 4.74}, {"text": "to generate acetyl-CoA.", "start": 5140.29, "duration": 4.14}, {"text": "That acetyl-CoA can\ncombine with oxaloacetate", "start": 5144.43, "duration": 5.76}, {"text": "to generate citrate.", "start": 5150.19, "duration": 3.592}, {"text": "That citrate, of course,\ncan be used to generate fat,", "start": 5153.782, "duration": 3.748}, {"text": "as we've talked about.", "start": 5157.53, "duration": 2.87}, {"text": "That can go to isocitrate.", "start": 5160.4, "duration": 1.68}, {"text": "Isocitrate to alpha\nketoglutarate.", "start": 5164.94, "duration": 4.33}, {"text": "That's catalyzed by\nisocitrate dehydrogenase,", "start": 5169.27, "duration": 4.23}, {"text": "which I will abbreviate IDH.", "start": 5173.5, "duration": 2.13}, {"text": "Alpha ketoglutarate\nto succinate.", "start": 5175.63, "duration": 4.12}, {"text": "More correctly, to succinyl-CoA\nby alpha ketoglutarate", "start": 5179.75, "duration": 11.08}, {"text": "dehydrogenase, Alpha KGDH.", "start": 5190.83, "duration": 4.41}, {"text": "And then this back\nto oxaloacetate.", "start": 5195.24, "duration": 2.91}, {"text": "And so the main enzymes\nthat are typically", "start": 5198.15, "duration": 3.06}, {"text": "discussed as being regulated\nare alpha ketoglutarate", "start": 5201.21, "duration": 3.92}, {"text": "dehydrogenase,\nisocitrate dehydrogenase,", "start": 5205.13, "duration": 2.98}, {"text": "and pyruvate dehydrogenase.", "start": 5208.11, "duration": 2.07}, {"text": "I also drew glycolysis.", "start": 5210.18, "duration": 3.01}, {"text": "And I'll just write over\nhere, gluconeogenesis up here,", "start": 5213.19, "duration": 5.07}, {"text": "because we can now see\nmore fully how this plays", "start": 5218.26, "duration": 6.31}, {"text": "in with citrate acting\nas a positive regulator", "start": 5224.57, "duration": 5.19}, {"text": "with gluconeogenesis and\nan inhibitor of glycolysis.", "start": 5229.76, "duration": 6.07}, {"text": "Again, we're full in citrate,\nstop running glycolysis,", "start": 5235.83, "duration": 5.58}, {"text": "start running gluconeogenesis.", "start": 5241.41, "duration": 3.54}, {"text": "Now, the other regulation.", "start": 5244.95, "duration": 1.74}, {"text": "If you have a lot of\nacetyl-CoA, stop making it", "start": 5246.69, "duration": 3.39}, {"text": "from pyruvate. acetyl-CoA is\na negative regulator of PDH.", "start": 5250.08, "duration": 4.74}, {"text": "This is carbon oxidation.", "start": 5254.82, "duration": 2.73}, {"text": "Releases a lot of energy,\ngenerates a lot of ATP,", "start": 5257.55, "duration": 3.48}, {"text": "generates a lot of NADH.", "start": 5261.03, "duration": 3.12}, {"text": "If you have lots\nof those things,", "start": 5264.15, "duration": 1.86}, {"text": "no reason to keep\nsending carbon into", "start": 5266.01, "duration": 3.38}, {"text": "acetyl-CoA to go\ninto the TCA cycle.", "start": 5269.39, "duration": 3.57}, {"text": "Ultimately, we have to send\nthose electrons somewhere.", "start": 5272.96, "duration": 3.773}, {"text": "So if there's\nnowhere to put them,", "start": 5276.733, "duration": 1.417}, {"text": "low oxygen also inhibits\npyruvate dehydrogenase.", "start": 5278.15, "duration": 4.35}, {"text": "And of course, if you need\nmore energy, if ADP is high,", "start": 5282.5, "duration": 4.17}, {"text": "that activates\npyruvate dehydrogenase.", "start": 5286.67, "duration": 3.33}, {"text": "So at least in terms of glucose,\ncomplete glucose oxidation,", "start": 5290.0, "duration": 4.32}, {"text": "a lot of regulation happens\nat pyruvate dehydrogenase.", "start": 5294.32, "duration": 3.96}, {"text": "And a lot of it\nreally makes sense.", "start": 5298.28, "duration": 3.77}, {"text": "High levels of ATP,\nhigh levels of NADH,", "start": 5302.05, "duration": 5.4}, {"text": "also inhibit isocitrate\ndehydrogenase and alpha", "start": 5307.45, "duration": 6.72}, {"text": "ketoglutarate dehydrogenase.", "start": 5314.17, "duration": 4.52}, {"text": "Makes sense.", "start": 5318.69, "duration": 1.15}, {"text": "Succinol-CoA high, inhibit alpha\nketoglutarate dehydrogenase.", "start": 5319.84, "duration": 5.15}, {"text": "High levels of ADP, need\nto release more energy,", "start": 5324.99, "duration": 7.23}, {"text": "activate alpha\nketoglutarate dehydrogenase.", "start": 5332.22, "duration": 4.08}, {"text": "Again, these are the feedbacks\nthat people talk about", "start": 5339.18, "duration": 2.85}, {"text": "on board exams.", "start": 5342.03, "duration": 1.56}, {"text": "Good to know, but you can\nalmost guess what they", "start": 5343.59, "duration": 2.64}, {"text": "would be from first principles.", "start": 5346.23, "duration": 1.98}, {"text": "Because remember,\nthis is a pathway", "start": 5348.21, "duration": 1.59}, {"text": "that releases a lot of energy.", "start": 5349.8, "duration": 1.86}, {"text": "High energy high\nATP, high NADH--", "start": 5351.66, "duration": 3.21}, {"text": "don't run the cycle, don't\nenter carbon in the cycle.", "start": 5354.87, "duration": 3.3}, {"text": "Low energy, high ADP,\nput carbon in the cycle,", "start": 5358.17, "duration": 5.73}, {"text": "run the cycle faster.", "start": 5363.9, "duration": 1.86}, {"text": "Makes sense.", "start": 5365.76, "duration": 1.14}, {"text": "Also makes sense of the\nreciprocal regulation", "start": 5366.9, "duration": 2.58}, {"text": "of glycolysis and\ngluconeogenesis.", "start": 5369.48, "duration": 3.58}, {"text": "Great.", "start": 5373.06, "duration": 0.5}, {"text": "Next time, we will\ntalk more about", "start": 5373.56, "duration": 4.56}, {"text": "how we can oxidize fatty acids,\nfat, by accessing acetyl-CoA", "start": 5378.12, "duration": 8.64}, {"text": "and entering it into the cycle.", "start": 5386.76, "duration": 1.62}, {"text": "Thanks.", "start": 5388.38, "duration": 1.55}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.44}, {"text": "[RUSTLING]", "start": 2.44, "duration": 1.952}, {"text": "[CLICKING]", "start": 4.392, "duration": 0.976}, {"text": "DAVID HSU: Hi, everyone,\nand welcome back to the MIT", "start": 10.74, "duration": 3.0}, {"text": "class on urban energy systems.", "start": 13.74, "duration": 2.23}, {"text": "Wherever you're seeing this\nlecture, please subscribe.", "start": 15.97, "duration": 3.21}, {"text": "You can either find\nit on the web page", "start": 19.18, "duration": 2.0}, {"text": "where you found this video\nor ask the instructor.", "start": 21.18, "duration": 4.48}, {"text": "So let's get back to\nthe topic for today,", "start": 25.66, "duration": 3.96}, {"text": "which is going to be\ncities and decarbonization.", "start": 29.62, "duration": 3.23}, {"text": "What is the role of cities?", "start": 32.85, "duration": 2.22}, {"text": "Again, I'm David\nHsu, and if you're", "start": 35.07, "duration": 2.94}, {"text": "thinking about how\ncities can take action", "start": 38.01, "duration": 3.33}, {"text": "or what their role is\nin decarbonization,", "start": 41.34, "duration": 2.01}, {"text": "you have found the right\nplace and your people.", "start": 43.35, "duration": 3.75}, {"text": "So I want to cover just\nbriefly how you're going", "start": 47.1, "duration": 2.67}, {"text": "to prepare for class this week.", "start": 49.77, "duration": 1.38}, {"text": "This is our second class.", "start": 51.15, "duration": 1.27}, {"text": "I want to make sure that\neveryone's caught up.", "start": 52.42, "duration": 2.75}, {"text": "First, the introductory\nreading from last week", "start": 55.17, "duration": 2.52}, {"text": "is fairly short and scalable.", "start": 57.69, "duration": 1.93}, {"text": "So it's easy to catch up,\nbut you should catch up.", "start": 59.62, "duration": 3.03}, {"text": "And it's particularly important\nto look at MacKay chapter 2.", "start": 62.65, "duration": 4.46}, {"text": "Again, it's MacKay chapter 2.", "start": 67.11, "duration": 2.962}, {"text": "There's the initial problem\nset due Monday night.", "start": 70.072, "duration": 3.128}, {"text": "You can just access\nthe problem set", "start": 73.2, "duration": 2.28}, {"text": "by going directly to this Google\nform, the link on the screen.", "start": 75.48, "duration": 4.585}, {"text": "You should do the\nreading for this week", "start": 80.065, "duration": 1.625}, {"text": "that's on the syllabus.", "start": 81.69, "duration": 1.14}, {"text": "I also show the reading for\nthis week on the next page.", "start": 82.83, "duration": 3.51}, {"text": "And then you should watch the\nrest of this video lecture.", "start": 86.34, "duration": 2.97}, {"text": "And during the reading and while\nwatching the video lecture,", "start": 89.31, "duration": 2.957}, {"text": "it's important for you to\nwrite down the questions", "start": 92.267, "duration": 2.083}, {"text": "that you have for discussion.", "start": 94.35, "duration": 1.443}, {"text": "And then I want you to\nfeel free to share them", "start": 95.793, "duration": 1.917}, {"text": "on Slack, whenever,\nasynchronously, or in our class", "start": 97.71, "duration": 3.51}, {"text": "meeting on Tuesday.", "start": 101.22, "duration": 3.05}, {"text": "So the material for today--", "start": 104.27, "duration": 1.44}, {"text": "again, I won't go over them.", "start": 105.71, "duration": 1.17}, {"text": "These are all in your syllabus.", "start": 106.88, "duration": 1.26}, {"text": "But these will also\nbe in the slides,", "start": 108.14, "duration": 1.542}, {"text": "so you can follow the links.", "start": 109.682, "duration": 1.478}, {"text": "The first four readings\nare the required readings,", "start": 111.16, "duration": 4.716}, {"text": "a kind of gathering of\nvery different readings.", "start": 115.876, "duration": 3.774}, {"text": "And the last two readings\nare optional readings", "start": 119.65, "duration": 2.4}, {"text": "that give additional information\nto the articles above.", "start": 122.05, "duration": 5.65}, {"text": "So what I want to start\nwith is MacKay chapter 2,", "start": 127.7, "duration": 2.719}, {"text": "what he calls the\nbalance sheet, and it's", "start": 130.419, "duration": 2.216}, {"text": "an important set\nof concepts simply", "start": 132.635, "duration": 2.255}, {"text": "so we can think about\nthe energy system.", "start": 134.89, "duration": 2.61}, {"text": "And very simply, what MacKay\nis trying to do in his book", "start": 137.5, "duration": 3.36}, {"text": "is contrast these\nred and green bars.", "start": 140.86, "duration": 3.51}, {"text": "Energy consumption is\non the left and red,", "start": 144.37, "duration": 3.06}, {"text": "and energy production is\non the right in green.", "start": 147.43, "duration": 2.71}, {"text": "And so when MacKay\ntitles his book", "start": 150.14, "duration": 2.42}, {"text": "Sustainable Energy--\nwithout the hot air, what", "start": 152.56, "duration": 2.37}, {"text": "we're trying to do is\nreplace our current level", "start": 154.93, "duration": 2.76}, {"text": "of consumption with entirely\nrenewable resources,", "start": 157.69, "duration": 3.253}, {"text": "and that's how we're going to\nachieve a sustainable energy", "start": 160.943, "duration": 2.417}, {"text": "system.", "start": 163.36, "duration": 1.12}, {"text": "And so a sustainable\nenergy system", "start": 164.48, "duration": 3.02}, {"text": "would be if our total\nconceivable sustainable", "start": 167.5, "duration": 2.76}, {"text": "production sources,\non the right,", "start": 170.26, "duration": 2.01}, {"text": "are greater than our\ntotal consumption.", "start": 172.27, "duration": 2.52}, {"text": "And an unsustainable\nenergy system", "start": 174.79, "duration": 2.07}, {"text": "would be where our total\nconsumption of energy", "start": 176.86, "duration": 2.61}, {"text": "is larger than our total\nconceivable sustainable", "start": 179.47, "duration": 2.52}, {"text": "production.", "start": 181.99, "duration": 0.79}, {"text": "And, of course, these\ntwo bars will change over", "start": 182.78, "duration": 2.27}, {"text": "time as our expectations\naround consumption change", "start": 185.05, "duration": 4.05}, {"text": "and our technologies\nand our institutions", "start": 189.1, "duration": 3.54}, {"text": "and our markets for\nsustainable production change.", "start": 192.64, "duration": 2.25}, {"text": "But that's the challenge.", "start": 194.89, "duration": 1.29}, {"text": "The challenge is to try to\nput these two in balance", "start": 196.18, "duration": 2.67}, {"text": "and at least have total\nsustainable production that", "start": 198.85, "duration": 2.7}, {"text": "is enough to meet all\nof our societal needs,", "start": 201.55, "duration": 3.24}, {"text": "or our global societal needs,\nfor energy consumption.", "start": 204.79, "duration": 3.93}, {"text": "And so what that might look like\nis the key forms of consumption", "start": 208.72, "duration": 3.9}, {"text": "on the left-hand stack in red--", "start": 212.62, "duration": 2.4}, {"text": "that is the energy we need\nfor transportation, including", "start": 215.02, "duration": 3.09}, {"text": "cars, planes, and freight.", "start": 218.11, "duration": 2.25}, {"text": "It's the energy we\nneed to heat and cool", "start": 220.36, "duration": 1.95}, {"text": "the spaces that we live in.", "start": 222.31, "duration": 1.53}, {"text": "That can wildly differ\nacross countries.", "start": 223.84, "duration": 2.58}, {"text": "It's a basic need for lighting\nso we can see at night.", "start": 226.42, "duration": 3.72}, {"text": "It's a growing need for\nenergy for information systems", "start": 230.14, "duration": 3.39}, {"text": "and our other gadgets.", "start": 233.53, "duration": 2.64}, {"text": "The fifth point, food--", "start": 236.17, "duration": 1.83}, {"text": "a tremendous amount\nof energy goes", "start": 238.0, "duration": 1.83}, {"text": "into growing and transporting\nand keeping our food cold.", "start": 239.83, "duration": 5.7}, {"text": "And, finally, the\nmanufacturing--", "start": 245.53, "duration": 2.04}, {"text": "for all the technologies\nor all the gadgets", "start": 247.57, "duration": 2.49}, {"text": "we need to do transportation\nor heating and cooling,", "start": 250.06, "duration": 3.09}, {"text": "like information\nsystems and food,", "start": 253.15, "duration": 1.68}, {"text": "we have to make these\nthings in the first place,", "start": 254.83, "duration": 2.324}, {"text": "and that requires a\ntremendous amount of energy.", "start": 257.154, "duration": 2.925}, {"text": "On the right-hand side, our\nsustainable production stack", "start": 260.079, "duration": 3.151}, {"text": "has a number of categories.", "start": 263.23, "duration": 1.63}, {"text": "The good thing is-- and I'll try\nto emphasize this in the class", "start": 264.86, "duration": 2.9}, {"text": "repeatedly-- is that we have\nmany sustainable technologies", "start": 267.76, "duration": 4.32}, {"text": "that can produce energy.", "start": 272.08, "duration": 1.87}, {"text": "We have wind and solar.", "start": 273.95, "duration": 2.21}, {"text": "Solar energy can be\nharnessed in the form", "start": 276.16, "duration": 2.07}, {"text": "of photovoltaic or solar cells\nthat produce electricity.", "start": 278.23, "duration": 4.2}, {"text": "We can harness solar energy\nthrough thermal energy,", "start": 282.43, "duration": 3.255}, {"text": "and we can also harness\nsolar energy through biomass,", "start": 285.685, "duration": 3.195}, {"text": "by harvesting the\npotential of the Earth", "start": 288.88, "duration": 2.58}, {"text": "to engage in\nphotosynthesis, create crops", "start": 291.46, "duration": 2.52}, {"text": "that we then can use\nfor other things,", "start": 293.98, "duration": 2.53}, {"text": "including burning in engines.", "start": 296.51, "duration": 3.38}, {"text": "Hydroelectric power is producing\nelectricity directly from--", "start": 299.89, "duration": 4.02}, {"text": "or mechanical storage\ndirectly from-- hydropower.", "start": 303.91, "duration": 4.14}, {"text": "Wave energy and tide energy\nare two sources of energy", "start": 308.05, "duration": 3.54}, {"text": "that come from the Earth\non a regular basis.", "start": 311.59, "duration": 4.41}, {"text": "Geothermal energy also\ncomes from the Earth.", "start": 316.0, "duration": 2.91}, {"text": "The heat inside the Earth can\nbe harnessed to produce energy.", "start": 318.91, "duration": 3.15}, {"text": "And finally, nuclear, And MacKay\nputs it with a question mark", "start": 322.06, "duration": 3.708}, {"text": "because it's not\nclear whether or not", "start": 325.768, "duration": 1.542}, {"text": "nuclear energy or nuclear\npower counts as sustainable.", "start": 327.31, "duration": 2.94}, {"text": "It is low carbon, but as I\nsaid in an earlier class,", "start": 330.25, "duration": 3.99}, {"text": "we have questions\nabout how do we handle", "start": 334.24, "duration": 2.79}, {"text": "the fuel for nuclear\npower plants,", "start": 337.03, "duration": 3.01}, {"text": "how do we handle the waste\nfrom nuclear power plants,", "start": 340.04, "duration": 2.21}, {"text": "and whether or not\nthat will be fully", "start": 342.25, "duration": 1.65}, {"text": "sustainable in the long run.", "start": 343.9, "duration": 3.06}, {"text": "And so I want to cover two\nphysical concepts from MacKay", "start": 346.96, "duration": 2.6}, {"text": "chapter 2 that I\nthink are basically", "start": 349.56, "duration": 2.31}, {"text": "going to be the most important\nphysical concepts you", "start": 351.87, "duration": 2.79}, {"text": "need to understand this class.", "start": 354.66, "duration": 2.28}, {"text": "And the first one,\nquite simply, is energy.", "start": 356.94, "duration": 2.85}, {"text": "It's the quantitative\nproperty of doing work.", "start": 359.79, "duration": 3.97}, {"text": "Energy can be neither\ndestroyed nor created,", "start": 363.76, "duration": 2.97}, {"text": "one of our fundamental\nlaws of thermodynamics.", "start": 366.73, "duration": 3.75}, {"text": "Energy can be transformed into\nlight, heat, or mass, hence", "start": 370.48, "duration": 4.74}, {"text": "the famous equation by\nEinstein, E equals mc squared,", "start": 375.22, "duration": 4.65}, {"text": "energy equals mass times\nof speed of light squared.", "start": 379.87, "duration": 3.63}, {"text": "This is a fundamental\nfinding out of relativity.", "start": 383.5, "duration": 3.61}, {"text": "And, of course, energy can\ntake many different forms.", "start": 387.11, "duration": 3.07}, {"text": "And we use it in many different\nforms in our energy system.", "start": 390.18, "duration": 2.9}, {"text": "Energy can be kinetic.", "start": 393.08, "duration": 1.68}, {"text": "It can be chemical.", "start": 394.76, "duration": 1.68}, {"text": "We can have potential energy.", "start": 396.44, "duration": 1.65}, {"text": "We have mechanical\nenergy, let's say,", "start": 398.09, "duration": 1.74}, {"text": "stored in the elastic\nproperties of materials", "start": 399.83, "duration": 2.49}, {"text": "and, of course, biological\nenergy, which is fundamentally", "start": 402.32, "duration": 3.21}, {"text": "chemical energy, but\nwe have different modes", "start": 405.53, "duration": 2.46}, {"text": "of perhaps using that chemical\nenergy in our muscles,", "start": 407.99, "duration": 2.88}, {"text": "in animals, in ecosystems.", "start": 410.87, "duration": 2.96}, {"text": "And we're going to\nmeasure energy in terms", "start": 413.83, "duration": 1.75}, {"text": "of units of kilowatt-hours.", "start": 415.58, "duration": 1.98}, {"text": "You'll see energy referred to in\nterms of British Thermal Units,", "start": 417.56, "duration": 3.66}, {"text": "BTUs, something only used\nin the US and America", "start": 421.22, "duration": 3.87}, {"text": "or the United States.", "start": 425.09, "duration": 1.32}, {"text": "Therms, joules, calories,\nare all units for energy.", "start": 426.41, "duration": 3.99}, {"text": "They can all be converted\nto kilowatt-hours.", "start": 430.4, "duration": 2.82}, {"text": "A specific category I just\nwant to highlight below", "start": 433.22, "duration": 2.79}, {"text": "is fossil fuels are sometimes\nmeasured in barrels of oil,", "start": 436.01, "duration": 4.26}, {"text": "short tons of coal, cubic\nfeet of natural gas.", "start": 440.27, "duration": 3.21}, {"text": "That's because\nthat's how we measure", "start": 443.48, "duration": 1.5}, {"text": "the things we trade\nin commodity markets", "start": 444.98, "duration": 2.28}, {"text": "for commoditized fossil fuels.", "start": 447.26, "duration": 2.16}, {"text": "But, again, the amount of\nenergy in a barrel of oil", "start": 449.42, "duration": 3.06}, {"text": "and a short ton of coal and\ncubic foot of natural gas", "start": 452.48, "duration": 3.48}, {"text": "can be converted\nto kilowatt-hours.", "start": 455.96, "duration": 3.08}, {"text": "So just to give you a\nfew examples, example 1,", "start": 459.04, "duration": 2.75}, {"text": "you may have had the\nfrustrating experience", "start": 461.79, "duration": 2.25}, {"text": "of having gone to\nthe gym, foolishly", "start": 464.04, "duration": 3.15}, {"text": "counting your calories,\nrealizing you worked out", "start": 467.19, "duration": 2.7}, {"text": "for an hour on a\nrunning treadmill,", "start": 469.89, "duration": 1.85}, {"text": "and it's only equivalent\nto three Oreos.", "start": 471.74, "duration": 2.8}, {"text": "You can also look at example 2.", "start": 474.54, "duration": 1.98}, {"text": "The average American household\nuses per year about 11,000", "start": 476.52, "duration": 3.72}, {"text": "kilowatt hours in electricity.", "start": 480.24, "duration": 2.31}, {"text": "Each person uses 300\nmillion BTUs total", "start": 482.55, "duration": 4.5}, {"text": "per year, which is approximately\n2.3 gallons of oil,", "start": 487.05, "duration": 4.35}, {"text": "7.89 pounds of coal,\nand 252 cubic feet", "start": 491.4, "duration": 3.9}, {"text": "of natural gas per day.", "start": 495.3, "duration": 2.195}, {"text": "Now, it's just\nworth pointing out", "start": 497.495, "duration": 1.375}, {"text": "that the first example, in\nterms of the American household,", "start": 498.87, "duration": 3.06}, {"text": "is in kilowatt-hours but\nonly counts for electricity.", "start": 501.93, "duration": 3.6}, {"text": "That's for the whole\nhousehold per year.", "start": 505.53, "duration": 2.35}, {"text": "The second sentence\nmeasures each person", "start": 507.88, "duration": 2.33}, {"text": "on a per-capita basis but then\nbreaks the millions of BTUs", "start": 510.21, "duration": 5.04}, {"text": "into different units because\nof the different sources", "start": 515.25, "duration": 3.0}, {"text": "of energy.", "start": 518.25, "duration": 0.909}, {"text": "And this is to say that,\nwhen we do these comparisons,", "start": 519.159, "duration": 2.811}, {"text": "we want to be careful\nabout the units we use,", "start": 521.97, "duration": 2.43}, {"text": "the averaging over time,\nand the sources of energy,", "start": 524.4, "duration": 3.21}, {"text": "because the original\nsource of energy", "start": 527.61, "duration": 2.22}, {"text": "may not actually be how much\nenergy we use in the end.", "start": 529.83, "duration": 2.95}, {"text": "And we'll talk about that\nmore in a few slides.", "start": 532.78, "duration": 4.07}, {"text": "Another key physical concept\nwe have to talk about", "start": 536.85, "duration": 2.42}, {"text": "or will be very useful\nis power, and that's", "start": 539.27, "duration": 3.27}, {"text": "the quantitative\nrate of doing work.", "start": 542.54, "duration": 2.7}, {"text": "That is power is\nenergy per time.", "start": 545.24, "duration": 4.41}, {"text": "It's a rate.", "start": 549.65, "duration": 1.35}, {"text": "The units we use\nof that are watts,", "start": 551.0, "duration": 2.7}, {"text": "or equal to joules per second.", "start": 553.7, "duration": 2.64}, {"text": "Other forms of power that\nyou might be familiar with", "start": 556.34, "duration": 3.81}, {"text": "are ergs, amperes in terms of\nelectrical current, horsepower", "start": 560.15, "duration": 4.71}, {"text": "in terms of the engine in\nyour car or other motors,", "start": 564.86, "duration": 4.36}, {"text": "and lumens are the amount\nof energy passed off", "start": 569.22, "duration": 4.86}, {"text": "per second from\nan LED light bulb", "start": 574.08, "duration": 2.82}, {"text": "but measured over a sphere\naround a light bulb.", "start": 576.9, "duration": 2.462}, {"text": "So it's actually weighted by\nthe area around the light bulb", "start": 579.362, "duration": 2.458}, {"text": "or what degree of area is\nputting out how much energy.", "start": 581.82, "duration": 6.77}, {"text": "So to just use the same\nexample as the previous slide,", "start": 588.59, "duration": 4.2}, {"text": "you could say, I\nworked out for an hour,", "start": 592.79, "duration": 2.0}, {"text": "and I only worked off the\nequivalent of three Oreos.", "start": 594.79, "duration": 2.85}, {"text": "But maybe it sounds\nperhaps more impressive", "start": 597.64, "duration": 2.34}, {"text": "if you say, \"My workout\nmaintained a steady power", "start": 599.98, "duration": 2.79}, {"text": "output of three Oreos per hour!\"", "start": 602.77, "duration": 4.45}, {"text": "Another key concept\nwe have to cover", "start": 607.22, "duration": 2.06}, {"text": "that links energy and climate\nis emissions intensity.", "start": 609.28, "duration": 3.36}, {"text": "And emissions are measured\nin terms of greenhouse gases,", "start": 612.64, "duration": 3.66}, {"text": "usually measured in metric-ton\ncarbon dioxide equivalent,", "start": 616.3, "duration": 3.67}, {"text": "which is abbreviated MTCDE,\nor mt-CO2-e, and so on.", "start": 619.97, "duration": 6.183}, {"text": "And the reason why\nwe have to measure it", "start": 626.153, "duration": 1.667}, {"text": "in terms of metric-ton\ncarbon dioxide equivalent", "start": 627.82, "duration": 3.57}, {"text": "is that there's a lot of\ndifferent greenhouse gases,", "start": 631.39, "duration": 2.37}, {"text": "and some of them, for\nexample, methane, CH4,", "start": 633.76, "duration": 3.42}, {"text": "has much more global warming\npotential than carbon dioxide.", "start": 637.18, "duration": 3.46}, {"text": "So a single ton of\nmethane has about 84 times", "start": 640.64, "duration": 4.52}, {"text": "the global warming potential\nof a ton of carbon dioxide", "start": 645.16, "duration": 4.26}, {"text": "early in its life.", "start": 649.42, "duration": 1.02}, {"text": "That declines over time\nto about 20 metric tons", "start": 650.44, "duration": 3.54}, {"text": "of carbon dioxide equivalent.", "start": 653.98, "duration": 1.44}, {"text": "So this is just to say that,\nif we have different greenhouse", "start": 655.42, "duration": 3.33}, {"text": "gases, we measure\nthem or make them", "start": 658.75, "duration": 2.28}, {"text": "all equivalent to a\nmetric ton of carbon", "start": 661.03, "duration": 2.04}, {"text": "dioxide equivalent\nduring their lifetime.", "start": 663.07, "duration": 3.47}, {"text": "We can also measure emissions\nintensity by the type of gas,", "start": 666.54, "duration": 4.2}, {"text": "as the example I just gave\nyou in terms of methane,", "start": 670.74, "duration": 3.09}, {"text": "also nitrous oxide and\nfluorohexane, I think,", "start": 673.83, "duration": 3.36}, {"text": "are another greenhouse gas.", "start": 677.19, "duration": 1.83}, {"text": "You can measure in emissions\nintensity per unit of energy.", "start": 679.02, "duration": 3.3}, {"text": "This much greenhouse\ngas is created", "start": 682.32, "duration": 2.01}, {"text": "in terms of this much energy.", "start": 684.33, "duration": 2.4}, {"text": "You can measure greenhouse\ngases per activity,", "start": 686.73, "duration": 2.85}, {"text": "per dollar of GDP, or by region.", "start": 689.58, "duration": 2.16}, {"text": "People use lots of\ndifferent intensities.", "start": 691.74, "duration": 2.07}, {"text": "And the reason why\nI want to focus", "start": 693.81, "duration": 1.417}, {"text": "on this key concept\nof intensity is", "start": 695.227, "duration": 1.973}, {"text": "that, as we look at different\nparts of the system,", "start": 697.2, "duration": 2.26}, {"text": "we're going to look\nat the intensity", "start": 699.46, "duration": 1.16}, {"text": "of the different\nparts of the system", "start": 700.62, "duration": 1.5}, {"text": "to get a whole picture of where\ngreenhouse gases are coming", "start": 702.12, "duration": 2.97}, {"text": "from, just like we're going\nto look at energy intensity", "start": 705.09, "duration": 2.82}, {"text": "in terms of how much\nenergy do you need", "start": 707.91, "duration": 1.71}, {"text": "for different activities,\nhow much energy do", "start": 709.62, "duration": 2.49}, {"text": "different regions\nof the world use.", "start": 712.11, "duration": 2.35}, {"text": "And so to give you a few\nexamples of the Conference", "start": 714.46, "duration": 3.35}, {"text": "of the Parties, the COP\nmeetings that the UN Framework", "start": 717.81, "duration": 3.33}, {"text": "Convention on Climate\nChange runs every year--", "start": 721.14, "duration": 4.56}, {"text": "they have reporting inventory.", "start": 725.7, "duration": 1.53}, {"text": "And when every country which\nis party to the Paris Agreement", "start": 727.23, "duration": 4.23}, {"text": "has to report its greenhouse\ngas emissions and, frankly,", "start": 731.46, "duration": 2.713}, {"text": "the actions that they're taking\nto reduce their greenhouse", "start": 734.173, "duration": 2.417}, {"text": "gases.", "start": 736.59, "duration": 0.82}, {"text": "They have to measure or report\ntheir greenhouse gases in terms", "start": 737.41, "duration": 3.11}, {"text": "of a specific inventory format.", "start": 740.52, "duration": 1.86}, {"text": "So I have linked to that here.", "start": 742.38, "duration": 1.66}, {"text": "You can click on\nit, and you can see", "start": 744.04, "duration": 1.88}, {"text": "how countries report different\nkinds of greenhouse gases.", "start": 745.92, "duration": 3.75}, {"text": "It's because\ncountries can only see", "start": 749.67, "duration": 2.34}, {"text": "the source of the activities\nthat create greenhouse gases.", "start": 752.01, "duration": 4.09}, {"text": "So it's easier for us to\nmeasure how many barrels of oil", "start": 756.1, "duration": 2.93}, {"text": "we burned or how many short\ntons of coal we burned or, let's", "start": 759.03, "duration": 3.96}, {"text": "say, how much land\nuse conversion has", "start": 762.99, "duration": 1.77}, {"text": "led to how much methane or\nhow much carbon dioxide.", "start": 764.76, "duration": 3.24}, {"text": "We can also measure, let's say,\nour greenhouse gas emissions", "start": 768.0, "duration": 4.2}, {"text": "per unit of electricity because\nelectricity comes from a grid.", "start": 772.2, "duration": 4.45}, {"text": "The grid is a technology\nwe'll talk about a lot", "start": 776.65, "duration": 1.99}, {"text": "in in this class that mixes\ndifferent sources of energy", "start": 778.64, "duration": 2.98}, {"text": "together.", "start": 781.62, "duration": 0.72}, {"text": "And so we try to get an average\nintensity of greenhouse gas", "start": 782.34, "duration": 3.9}, {"text": "emissions per unit\nof electricity", "start": 786.24, "duration": 2.04}, {"text": "in different regions.", "start": 788.28, "duration": 1.77}, {"text": "Another emissions\nintensity factor", "start": 790.05, "duration": 1.98}, {"text": "that people look at quite\noften is air quality.", "start": 792.03, "duration": 2.35}, {"text": "You can look at how many\ngreenhouse gases or how", "start": 794.38, "duration": 2.72}, {"text": "much particulate matter is\nproduced by certain activities,", "start": 797.1, "duration": 4.05}, {"text": "like vehicle miles traveled\nor number of cars on the road.", "start": 801.15, "duration": 4.87}, {"text": "So just to give you an example\nof what carbon emission", "start": 806.02, "duration": 2.25}, {"text": "intensity looks like, this is\nthe carbon emission intensity", "start": 808.27, "duration": 3.63}, {"text": "of economies in 2018, and this\nis from Our World in Data.", "start": 811.9, "duration": 4.26}, {"text": "And you can see,\nactually, it's measured,", "start": 816.16, "duration": 2.04}, {"text": "on the bottom legend here, in\nterms of amount of kilograms", "start": 818.2, "duration": 4.74}, {"text": "of carbon dioxide equivalent,\nthe carbon dioxide intensity,", "start": 822.94, "duration": 4.59}, {"text": "per dollar of GDP measured\nin international 2011 prices.", "start": 827.53, "duration": 5.02}, {"text": "And you can see, by\nthat measure, actually,", "start": 832.55, "duration": 2.51}, {"text": "a lot of the developed world,\nsuch as Australia, Europe,", "start": 835.06, "duration": 3.9}, {"text": "North America, and\nparts of Latin America", "start": 838.96, "duration": 2.91}, {"text": "don't look very intense,\nif only because they", "start": 841.87, "duration": 2.7}, {"text": "don't produce that\nmany greenhouse", "start": 844.57, "duration": 1.74}, {"text": "gases per dollar of GDP output.", "start": 846.31, "duration": 3.36}, {"text": "Now, like we talked\nabout in the last class", "start": 849.67, "duration": 2.76}, {"text": "in terms of population,\nwhat does this hide?", "start": 852.43, "duration": 3.513}, {"text": "Well, there's a couple\nof things with the map.", "start": 855.943, "duration": 1.917}, {"text": "Sometimes the area of the\nmap distorts the actual area", "start": 857.86, "duration": 3.6}, {"text": "or total emissions.", "start": 861.46, "duration": 1.26}, {"text": "Small places don't look like\nthey have as much impact", "start": 862.72, "duration": 2.58}, {"text": "as big places, even\nthough that really has", "start": 865.3, "duration": 2.01}, {"text": "nothing to do with the average.", "start": 867.31, "duration": 1.65}, {"text": "But the more important\npoint from a map like this", "start": 868.96, "duration": 2.76}, {"text": "is that it hides the fact\nthat the rich countries,", "start": 871.72, "duration": 2.97}, {"text": "like Australia, Europe,\nNorth America, and parts", "start": 874.69, "duration": 3.81}, {"text": "of Latin America, simply\nhave much larger GDPs.", "start": 878.5, "duration": 3.21}, {"text": "So it looks like the carbon\ndioxide output per GDP is low.", "start": 881.71, "duration": 5.74}, {"text": "But if we look at the\nper-capita CO2 emissions,", "start": 887.45, "duration": 2.48}, {"text": "like the point at\nour last class,", "start": 889.93, "duration": 1.552}, {"text": "you can see that, for a\nrelatively small number", "start": 891.482, "duration": 1.958}, {"text": "of people in those rich,\ndeveloped countries,", "start": 893.44, "duration": 2.25}, {"text": "they have very high CO2\nemissions per capita.", "start": 895.69, "duration": 3.06}, {"text": "And so your map basically\nchanges diametrically.", "start": 898.75, "duration": 2.988}, {"text": "And you can see the difference\nbetween richer countries", "start": 901.738, "duration": 2.292}, {"text": "and poor countries.", "start": 904.03, "duration": 1.05}, {"text": "And overwhelmingly,\nthe richer countries", "start": 905.08, "duration": 2.22}, {"text": "are more responsible for\ncarbon dioxide emissions.", "start": 907.3, "duration": 4.48}, {"text": "If we look at this\nsimilarly in a scatterplot,", "start": 911.78, "duration": 3.54}, {"text": "you can, again,\nsee that it looks", "start": 915.32, "duration": 2.07}, {"text": "like, on an emission\nintensity basis,", "start": 917.39, "duration": 2.165}, {"text": "India and the United States\nare not that different.", "start": 919.555, "duration": 2.125}, {"text": "Of course, the\ndifference is, in terms", "start": 921.68, "duration": 2.22}, {"text": "of the output of the economy\non a per-capita basis,", "start": 923.9, "duration": 3.09}, {"text": "the average person\nin the United States", "start": 926.99, "duration": 2.37}, {"text": "produces much more and\ninevitably consumes much more", "start": 929.36, "duration": 3.36}, {"text": "than your average person\nin India or Pakistan.", "start": 932.72, "duration": 2.22}, {"text": "So even though we have\nequivalent emissions intensity", "start": 934.94, "duration": 3.87}, {"text": "per dollar, we simply\nproduce and consume", "start": 938.81, "duration": 2.91}, {"text": "much more in the\nricher countries.", "start": 941.72, "duration": 1.98}, {"text": "And I make this point because,\nafter the Kyoto Protocol", "start": 943.7, "duration": 4.02}, {"text": "and after the George\nW. Bush administration", "start": 947.72, "duration": 3.03}, {"text": "chose to leave the\nKyoto Protocol,", "start": 950.75, "duration": 1.95}, {"text": "one of their arguments\nwas that the US actually", "start": 952.7, "duration": 2.94}, {"text": "had a lower carbon emission\nintensity, or at least", "start": 955.64, "duration": 3.54}, {"text": "a comparable carbon\nemission intensity,", "start": 959.18, "duration": 2.43}, {"text": "to some developing countries.", "start": 961.61, "duration": 1.77}, {"text": "Of course, this hid the\nfact that the United States", "start": 963.38, "duration": 3.39}, {"text": "is both richer and consumes much\nmore and produces much more.", "start": 966.77, "duration": 4.63}, {"text": "So that's just a way to talk\nabout what intensities may tell", "start": 971.4, "duration": 3.65}, {"text": "us and what they may hide also.", "start": 975.05, "duration": 3.05}, {"text": "Now I'll get to a\nreally key diagram", "start": 978.1, "duration": 2.04}, {"text": "that I rather love\nin this class.", "start": 980.14, "duration": 1.96}, {"text": "So I'll start off this class by\ntalking about Sankey diagrams.", "start": 982.1, "duration": 3.77}, {"text": "And you can find a\nSankey diagram for the US", "start": 985.87, "duration": 2.22}, {"text": "and every state at this web\nlink at part of the bottom", "start": 988.09, "duration": 3.09}, {"text": "from Lawrence Livermore\nNational Laboratory.", "start": 991.18, "duration": 2.91}, {"text": "What a Sankey diagram is\nis basically a flow chart,", "start": 994.09, "duration": 3.18}, {"text": "and it's a flow chart between\nthe sources on the left.", "start": 997.27, "duration": 2.368}, {"text": "And you can see all of\nour energy sources, solar,", "start": 999.638, "duration": 2.042}, {"text": "nuclear, hydro, wind,\ngeothermal, natural gas, coal,", "start": 1001.68, "duration": 3.24}, {"text": "biomass, and petroleum.", "start": 1004.92, "duration": 1.56}, {"text": "And you can see all of the\nultimate uses on the right.", "start": 1006.48, "duration": 3.6}, {"text": "And the final--", "start": 1010.08, "duration": 1.63}, {"text": "I guess what we'd call\nfinal consumption is", "start": 1011.71, "duration": 2.0}, {"text": "in residential buildings,\ncommercial buildings,", "start": 1013.71, "duration": 1.96}, {"text": "industrial buildings,\nand transportation.", "start": 1015.67, "duration": 2.24}, {"text": "Of course, this\nfinal category here", "start": 1017.91, "duration": 2.55}, {"text": "is also a kind of a statement\nabout where does the energy go", "start": 1020.46, "duration": 3.12}, {"text": "in the first place.", "start": 1023.58, "duration": 1.32}, {"text": "Only about 50% of the energy\nor less that we actually", "start": 1024.9, "duration": 4.35}, {"text": "burn from the original\nsources goes into these uses", "start": 1029.25, "duration": 5.16}, {"text": "in these sectors.", "start": 1034.41, "duration": 1.53}, {"text": "About, actually, looks like\none third of the energy", "start": 1035.94, "duration": 3.12}, {"text": "goes to what we call\nenergy services.", "start": 1039.06, "duration": 2.64}, {"text": "And rejected energy\nis the byproduct", "start": 1041.7, "duration": 2.79}, {"text": "of that combustion, usually,\nthat we don't capture", "start": 1044.49, "duration": 3.57}, {"text": "for actual energy services.", "start": 1048.06, "duration": 1.35}, {"text": "So to give you an\nexample, you can see how--", "start": 1049.41, "duration": 2.79}, {"text": "I said before, the electric\ngrid mixes many different types", "start": 1052.2, "duration": 3.72}, {"text": "of energy sources--", "start": 1055.92, "duration": 1.71}, {"text": "solar, nuclear, hydro, wind,\nall these, natural gas, and coal", "start": 1057.63, "duration": 4.89}, {"text": "all feed into the electric grid.", "start": 1062.52, "duration": 1.95}, {"text": "But when we feed that energy\ninto the electric grid,", "start": 1064.47, "duration": 2.46}, {"text": "into power plants, we basically\nonly take a fraction of it.", "start": 1066.93, "duration": 3.12}, {"text": "It looks like about one\nthird of the electricity,", "start": 1070.05, "duration": 2.7}, {"text": "one third of the energy\nin those energy sources,", "start": 1072.75, "duration": 2.16}, {"text": "actually goes to things like\nresidential, commercial,", "start": 1074.91, "duration": 3.07}, {"text": "and industrial.", "start": 1077.98, "duration": 0.77}, {"text": "But about 2/3 of\nit gets rejected,", "start": 1078.75, "duration": 2.26}, {"text": "which means that it's\nheat energy going out", "start": 1081.01, "duration": 2.54}, {"text": "of the chimney of a\ncoal-fired power plant,", "start": 1083.55, "duration": 2.64}, {"text": "or might be energy lost in\nthe electric grid that's", "start": 1086.19, "duration": 2.52}, {"text": "simply lost because\nof the resistance", "start": 1088.71, "duration": 1.86}, {"text": "of the electrical wires.", "start": 1090.57, "duration": 2.01}, {"text": "And so this kind of\ngraph, I actually", "start": 1092.58, "duration": 2.25}, {"text": "find tremendously\nuseful to summarize", "start": 1094.83, "duration": 2.55}, {"text": "what the sources\non the left are,", "start": 1097.38, "duration": 2.4}, {"text": "the ultimate uses of the\nenergy are on the right,", "start": 1099.78, "duration": 3.03}, {"text": "and also some of the\ninterim steps where", "start": 1102.81, "duration": 2.103}, {"text": "we might be able to\ncapture some of the energy", "start": 1104.913, "duration": 1.917}, {"text": "back in terms of energy\nefficiency or at least", "start": 1106.83, "duration": 2.49}, {"text": "think about how our\nintermediate technologies,", "start": 1109.32, "duration": 2.25}, {"text": "like the electric grid,\nactually use energy", "start": 1111.57, "duration": 2.61}, {"text": "and how much of the intrinsic\nenergy in the fuel source", "start": 1114.18, "duration": 3.06}, {"text": "are we using.", "start": 1117.24, "duration": 1.53}, {"text": "To take one example\nfrom this graph,", "start": 1118.77, "duration": 2.52}, {"text": "I think it does a really\ngood job of showing you,", "start": 1121.29, "duration": 2.17}, {"text": "for example, that\nelectricity overwhelmingly", "start": 1123.46, "duration": 2.06}, {"text": "goes into residential\nbuildings, commercial buildings,", "start": 1125.52, "duration": 2.34}, {"text": "and industrial buildings\nor industrial activities,", "start": 1127.86, "duration": 3.325}, {"text": "but you can see that there is\nno link between electricity", "start": 1131.185, "duration": 2.375}, {"text": "generation and transportation,\nso a very small orange line", "start": 1133.56, "duration": 3.03}, {"text": "here, 0.02 quads.", "start": 1136.59, "duration": 3.572}, {"text": "And once again, I\nshould have pointed out", "start": 1140.162, "duration": 1.708}, {"text": "is that the total US\nenergy consumption in 2021", "start": 1141.87, "duration": 2.7}, {"text": "was at 97 quads.", "start": 1144.57, "duration": 1.83}, {"text": "It's pretty easy mentally to\nround that up to about 100.", "start": 1146.4, "duration": 3.18}, {"text": "So this is actually\n0.02%, roughly,", "start": 1149.58, "duration": 3.66}, {"text": "of all the energy in\nthe US or electricity", "start": 1153.24, "duration": 3.06}, {"text": "is used for transportation.", "start": 1156.3, "duration": 1.41}, {"text": "You can see, overwhelmingly,\nthat the majority of energy", "start": 1157.71, "duration": 3.03}, {"text": "for transportation, 24.3 quads,\nor about 24% going to the US,", "start": 1160.74, "duration": 5.7}, {"text": "comes from petroleum.", "start": 1166.44, "duration": 1.35}, {"text": "And originally, that came from\nabout 35 quads of-- or 35%", "start": 1167.79, "duration": 5.25}, {"text": "of our initial energy sources.", "start": 1173.04, "duration": 2.46}, {"text": "And you can see some\nportion goes off", "start": 1175.5, "duration": 1.77}, {"text": "to industrial activities.", "start": 1177.27, "duration": 1.38}, {"text": "But the vast majority\nof the energy", "start": 1178.65, "duration": 1.8}, {"text": "that drives our transportation\nsystem is petroleum.", "start": 1180.45, "duration": 3.24}, {"text": "And you can see that, when\nwe burn petroleum or gasoline", "start": 1183.69, "duration": 4.05}, {"text": "in our internal\ncombustion engines,", "start": 1187.74, "duration": 2.16}, {"text": "a very small fraction-- it\nlooks like about 20% of it--", "start": 1189.9, "duration": 3.27}, {"text": "is actually used for\nmoving the car forward.", "start": 1193.17, "duration": 3.36}, {"text": "About 80% of the energy actually\ngoes out of the tailpipe", "start": 1196.53, "duration": 3.42}, {"text": "either in the form of heat out\nof the tailpipe or else air", "start": 1199.95, "duration": 3.84}, {"text": "resistance.", "start": 1203.79, "duration": 0.57}, {"text": "That is not really what\nwe are trying to do.", "start": 1204.36, "duration": 2.17}, {"text": "We're trying to move goods and\nservices and people around.", "start": 1206.53, "duration": 3.91}, {"text": "And so this is\njust, again, a way", "start": 1210.44, "duration": 1.817}, {"text": "of saying that there's lots\nof different kinds of Sankey", "start": 1212.257, "duration": 2.333}, {"text": "diagrams.", "start": 1214.59, "duration": 0.63}, {"text": "This is a nice one that\nit has proportional flows", "start": 1215.22, "duration": 2.82}, {"text": "between sources, intermediate,\ntransforming technologies,", "start": 1218.04, "duration": 3.78}, {"text": "and usages.", "start": 1221.82, "duration": 1.14}, {"text": "It also shows you\nwhat efficiency level", "start": 1222.96, "duration": 2.58}, {"text": "is being achieved in\nthese different sectors.", "start": 1225.54, "duration": 2.34}, {"text": "This is essentially an\naccounting exercise,", "start": 1227.88, "duration": 2.29}, {"text": "but if you can find a\nSankey diagram for a given", "start": 1230.17, "duration": 2.36}, {"text": "region or a city\nor a country, it", "start": 1232.53, "duration": 2.263}, {"text": "gives you a really\ngood picture of where", "start": 1234.793, "duration": 1.667}, {"text": "the energy is coming from and\nwhere the energy is going to.", "start": 1236.46, "duration": 3.7}, {"text": "So we want to use\nthese Sankey diagrams", "start": 1240.16, "duration": 1.86}, {"text": "to think about what our pathways\nare to deep decarbonization.", "start": 1242.02, "duration": 3.48}, {"text": "Deep decarbonization-- I\nthink I've said before,", "start": 1245.5, "duration": 2.59}, {"text": "if I haven't said it before--", "start": 1248.09, "duration": 1.52}, {"text": "it is both a goal and a process.", "start": 1249.61, "duration": 2.53}, {"text": "We know that climate\nscience tells us--", "start": 1252.14, "duration": 2.66}, {"text": "the IPCC has told us through an\nexhaustive scientific process", "start": 1254.8, "duration": 3.93}, {"text": "that we need to achieve net-zero\nanthropogenic greenhouse gas", "start": 1258.73, "duration": 3.69}, {"text": "emissions by 2050.", "start": 1262.42, "duration": 1.71}, {"text": "Deep decarbonization\nis both the goal", "start": 1264.13, "duration": 2.49}, {"text": "of getting to net-zero\nemissions by 2050,", "start": 1266.62, "duration": 3.06}, {"text": "and also, it's this process.", "start": 1269.68, "duration": 1.44}, {"text": "We're decarbonizing\nfor the next 28 years", "start": 1271.12, "duration": 2.76}, {"text": "to lessen the effects\nof climate change.", "start": 1273.88, "duration": 3.16}, {"text": "And so the first deep\ndecarbonization plan", "start": 1277.04, "duration": 2.75}, {"text": "started in 2015.", "start": 1279.79, "duration": 2.25}, {"text": "The Deep Decarbonization\nPathways Project", "start": 1282.04, "duration": 2.7}, {"text": "started 2015 for a\nnumber of countries", "start": 1284.74, "duration": 1.86}, {"text": "to try to think about\nwhat analytical or policy", "start": 1286.6, "duration": 3.03}, {"text": "or technology\npathways we needed.", "start": 1289.63, "duration": 1.83}, {"text": "It was updated in\nthis paper in 2020", "start": 1291.46, "duration": 2.04}, {"text": "that you read for this class.", "start": 1293.5, "duration": 1.77}, {"text": "That was quickly followed by\nthe White House Mid-Century", "start": 1295.27, "duration": 2.91}, {"text": "Strategy, which was the Obama\nadministration's commitment", "start": 1298.18, "duration": 2.82}, {"text": "to the Paris Agreement to reduce\ngreenhouse gas emissions by 80%", "start": 1301.0, "duration": 3.39}, {"text": "by 2050.", "start": 1304.39, "duration": 1.17}, {"text": "But just four years later,\nyou have a series of reports", "start": 1305.56, "duration": 2.67}, {"text": "from academics and\nNGOs looking at ways", "start": 1308.23, "duration": 3.78}, {"text": "to get to 100%\nreduction by 2050,", "start": 1312.01, "duration": 2.74}, {"text": "which is what the IPCC\nsays we need to do by 2050.", "start": 1314.75, "duration": 4.56}, {"text": "And so the key thing I\nwant to say in this class", "start": 1319.31, "duration": 2.93}, {"text": "but also in the paper I\nreferred to last time last week,", "start": 1322.24, "duration": 4.625}, {"text": "the paper on deep\ndecarbonization", "start": 1326.865, "duration": 1.375}, {"text": "that I wrote recently, is\nthat many of these plans", "start": 1328.24, "duration": 2.73}, {"text": "agree what the\ntechnology pathways are.", "start": 1330.97, "duration": 2.2}, {"text": "So we should focus as\nurban policy analysts", "start": 1333.17, "duration": 4.67}, {"text": "and urban planners\nand people who work", "start": 1337.84, "duration": 1.68}, {"text": "in cities on implementation.", "start": 1339.52, "duration": 2.28}, {"text": "We should focus on geography.", "start": 1341.8, "duration": 1.53}, {"text": "We should focus on\nthe politics of it.", "start": 1343.33, "duration": 1.77}, {"text": "And, frankly, as planners, we\nshould look at the land use", "start": 1345.1, "duration": 3.12}, {"text": "and built environment\nimplications", "start": 1348.22, "duration": 2.01}, {"text": "of deep decarbonization.", "start": 1350.23, "duration": 3.19}, {"text": "So look at the Sankey diagram\nfrom Williams et al., 2020.", "start": 1353.42, "duration": 3.63}, {"text": "They look at the reference\ncase for energy use", "start": 1357.05, "duration": 5.725}, {"text": "in the United States.", "start": 1362.775, "duration": 0.875}, {"text": "And this is a reference case\nI think the Energy Information", "start": 1363.65, "duration": 2.73}, {"text": "Administration puts\nout every year.", "start": 1366.38, "duration": 2.88}, {"text": "You can see on\nthe left-hand side", "start": 1369.26, "duration": 1.44}, {"text": "that, overwhelmingly,\nthe reference case, which", "start": 1370.7, "duration": 2.55}, {"text": "is usually fairly\nconservative, shows", "start": 1373.25, "duration": 2.07}, {"text": "that we will get\nmost of our energy", "start": 1375.32, "duration": 2.22}, {"text": "from-- we get most of our energy\ncurrently from uranium, coal,", "start": 1377.54, "duration": 3.31}, {"text": "natural gas, a little\nbit from biomass,", "start": 1380.85, "duration": 2.21}, {"text": "and a large portion\nfrom petroleum.", "start": 1383.06, "duration": 2.4}, {"text": "You can see renewables\nhere are relatively small--", "start": 1385.46, "duration": 2.7}, {"text": "geothermal, solar,\nwind, and hydro.", "start": 1388.16, "duration": 2.7}, {"text": "And all the energy goes through\nthe intermediate steps--", "start": 1390.86, "duration": 3.03}, {"text": "electricity generation,\npipeline gas, petroleum refining", "start": 1393.89, "duration": 3.48}, {"text": "outputs, or liquid fuels.", "start": 1397.37, "duration": 1.98}, {"text": "It gets transmitted\nthrough the electric grid,", "start": 1399.35, "duration": 1.95}, {"text": "and it ultimately\ngoes to buildings,", "start": 1401.3, "duration": 1.92}, {"text": "which are residential and\ncommercial buildings together.", "start": 1403.22, "duration": 2.52}, {"text": "It goes to industry, and\nit goes to transportation.", "start": 1405.74, "duration": 2.76}, {"text": "Again, you can see\nhere from buildings", "start": 1408.5, "duration": 2.19}, {"text": "that, overwhelmingly,\nabout half of the energy", "start": 1410.69, "duration": 2.4}, {"text": "comes from the grid, and\nhalf the energy comes", "start": 1413.09, "duration": 1.92}, {"text": "from pipeline gas.", "start": 1415.01, "duration": 1.44}, {"text": "Transportation, almost all\nthe energy we currently use", "start": 1416.45, "duration": 3.15}, {"text": "comes from petroleum.", "start": 1419.6, "duration": 3.12}, {"text": "And industry uses a variety of\nenergy technologies and fuels.", "start": 1422.72, "duration": 4.35}, {"text": "Now let's contrast that with\nthe Williams paper on what", "start": 1427.07, "duration": 3.6}, {"text": "a 100%-renewable-energy\nfuture would look like.", "start": 1430.67, "duration": 3.31}, {"text": "There's a couple of\nthings to notice here.", "start": 1433.98, "duration": 1.98}, {"text": "First, all of our renewables,\nthe 100% renewable sources", "start": 1435.96, "duration": 3.14}, {"text": "we are going to need, have taken\nover completely-- geothermal,", "start": 1439.1, "duration": 3.84}, {"text": "solar, wind, hydro, and biomass.", "start": 1442.94, "duration": 2.26}, {"text": "There's no coal, no natural\ngas, and no petroleum.", "start": 1445.2, "duration": 3.8}, {"text": "Overwhelmingly, about\n2/3 of the energy", "start": 1449.0, "duration": 1.98}, {"text": "will go through\nthe electric grid.", "start": 1450.98, "duration": 1.9}, {"text": "It will be generated\nas electricity,", "start": 1452.88, "duration": 2.36}, {"text": "either goes through\nthe grid or be", "start": 1455.24, "duration": 2.0}, {"text": "used to produce\nhydrogen. Hydrogen will", "start": 1457.24, "duration": 2.35}, {"text": "produce various liquid\nand gaseous fuels.", "start": 1459.59, "duration": 3.76}, {"text": "And if you look at what the\nfuture looks like in 2050", "start": 1463.35, "duration": 2.54}, {"text": "according to this paper or\nthis technology pathway,", "start": 1465.89, "duration": 3.282}, {"text": "you can see that buildings\nhave to overwhelmingly get", "start": 1469.172, "duration": 2.208}, {"text": "their energy from electricity.", "start": 1471.38, "duration": 1.83}, {"text": "Industry will still use\na variety of inputs,", "start": 1473.21, "duration": 2.1}, {"text": "but all those inputs will be\nfrom intermediate steps that", "start": 1475.31, "duration": 3.57}, {"text": "have transformed our renewable\nenergy into the kinds of fuels", "start": 1478.88, "duration": 3.82}, {"text": "we need to drive\nindustrial processes.", "start": 1482.7, "duration": 1.88}, {"text": "And you can see\nthat transportation", "start": 1484.58, "duration": 2.19}, {"text": "is going to come\noverwhelmingly from electric.", "start": 1486.77, "duration": 3.03}, {"text": "About 50% of our energy\nin transportation", "start": 1489.8, "duration": 2.39}, {"text": "will come from electric.", "start": 1492.19, "duration": 1.0}, {"text": "Some of it will come from,\nI think, liquid fuels,", "start": 1493.19, "duration": 3.15}, {"text": "and some will come\nfrom compressed gases,", "start": 1496.34, "duration": 3.63}, {"text": "such as hydrogen and\nmaybe natural gas", "start": 1499.97, "duration": 2.7}, {"text": "or methane produced from\nrenewable resources.", "start": 1502.67, "duration": 5.04}, {"text": "And let's just look at the\nimplications from this,", "start": 1507.71, "duration": 2.16}, {"text": "and this is to read the numbers\noff those previous two graphs.", "start": 1509.87, "duration": 3.42}, {"text": "And then you look\nat the power sector.", "start": 1513.29, "duration": 2.34}, {"text": "You can see that petroleum,\nnatural gas, and coal,", "start": 1515.63, "duration": 2.49}, {"text": "as I said, have to be\neliminated completely, 100%.", "start": 1518.12, "duration": 4.17}, {"text": "Biomass has to grow\nby 3 and 1/2 times.", "start": 1522.29, "duration": 3.66}, {"text": "Nuclear power, in the\n100% renewable case,", "start": 1525.95, "duration": 2.85}, {"text": "is actually\neliminated completely", "start": 1528.8, "duration": 1.56}, {"text": "because I think Williams et\nal. do not define nuclear", "start": 1530.36, "duration": 2.88}, {"text": "as a renewable energy source.", "start": 1533.24, "duration": 1.74}, {"text": "But the key things,\nthe most dire, I think,", "start": 1534.98, "duration": 3.09}, {"text": "or most challenging things\nwe have to deal with", "start": 1538.07, "duration": 3.18}, {"text": "are growing our solar energy\nshare by about a factor of 46.", "start": 1541.25, "duration": 4.86}, {"text": "We have to grow our share\nfrom wind by a factor of 27.", "start": 1546.11, "duration": 3.75}, {"text": "Hydro and geothermal are going\nto be relatively small players", "start": 1549.86, "duration": 3.06}, {"text": "in this forecast.", "start": 1552.92, "duration": 1.23}, {"text": "And that's just for the\nelectric power sector.", "start": 1554.15, "duration": 2.83}, {"text": "If you look at buildings,\nresidential/commercial,", "start": 1556.98, "duration": 2.24}, {"text": "you can see two things.", "start": 1559.22, "duration": 1.63}, {"text": "Not only does electricity\nhave to decline in total use,", "start": 1560.85, "duration": 4.76}, {"text": "but we have to completely\neliminate natural gas.", "start": 1565.61, "duration": 2.82}, {"text": "And we have to increase our\nuse of biomass just slightly.", "start": 1568.43, "duration": 4.59}, {"text": "Now, the key thing\nis that the reason", "start": 1573.02, "duration": 1.95}, {"text": "why we're declining our\ntotal use of electricity", "start": 1574.97, "duration": 2.7}, {"text": "is that it's more efficient.", "start": 1577.67, "duration": 1.218}, {"text": "But at the same\ntime, the electricity", "start": 1578.888, "duration": 1.542}, {"text": "we do use is going to\nbe used to do things", "start": 1580.43, "duration": 2.52}, {"text": "that natural gas\ncurrently does, like we're", "start": 1582.95, "duration": 2.22}, {"text": "going to get heating and cooling\nfrom electricity rather than", "start": 1585.17, "duration": 3.42}, {"text": "from natural gas as we do now.", "start": 1588.59, "duration": 2.17}, {"text": "And so this is one\nimportant point", "start": 1590.76, "duration": 1.492}, {"text": "I want to highlight\nfrom Sankey diagrams.", "start": 1592.252, "duration": 1.708}, {"text": "If you look at the total\nprimary energy in buildings,", "start": 1593.96, "duration": 2.73}, {"text": "it actually has to\ngo down by about 50%.", "start": 1596.69, "duration": 2.738}, {"text": "And this is the point I think\nI made in the last class, which", "start": 1599.428, "duration": 2.542}, {"text": "is, if you look back here,\nthe total amount of energy--", "start": 1601.97, "duration": 4.2}, {"text": "it looks like, I think,\nroughly 100 quads,", "start": 1606.17, "duration": 2.01}, {"text": "also 100 exajoules I think is\nhow this paper measures it.", "start": 1608.18, "duration": 3.28}, {"text": "And if you look\nat the next slide,", "start": 1611.46, "duration": 1.68}, {"text": "you can see that the\nwidth of these flows", "start": 1613.14, "duration": 2.12}, {"text": "have gone down quite a bit,\nwhich is just to make the point", "start": 1615.26, "duration": 3.42}, {"text": "that I think I said to\nyou last week, which", "start": 1618.68, "duration": 1.83}, {"text": "is that not only do our uses\nhave to become more efficient,", "start": 1620.51, "duration": 3.94}, {"text": "we also have to simply reduce\nthe total amount we're using.", "start": 1624.45, "duration": 4.07}, {"text": "And the remaining 50%\nhave to become renewable.", "start": 1628.52, "duration": 2.37}, {"text": "So we actually need a\ncomplete transformation", "start": 1630.89, "duration": 1.92}, {"text": "of our energy system both\non the consumption side", "start": 1632.81, "duration": 2.7}, {"text": "and the production side.", "start": 1635.51, "duration": 2.18}, {"text": "If you look at the\nTong paper, this", "start": 1637.69, "duration": 3.39}, {"text": "is going to shift a little bit\nto this question of existing", "start": 1641.08, "duration": 3.42}, {"text": "energy infrastructure.", "start": 1644.5, "duration": 1.56}, {"text": "This is a paper written\nin 2019 in Nature.", "start": 1646.06, "duration": 3.78}, {"text": "And in this paper,\nthey say our estimates", "start": 1649.84, "duration": 2.1}, {"text": "suggest that little or no new\nCO2-emitting infrastructure", "start": 1651.94, "duration": 4.17}, {"text": "can be commissioned, and that\nexisting infrastructure may", "start": 1656.11, "duration": 2.88}, {"text": "need to be retired early or be\nretrofitted with carbon capture", "start": 1658.99, "duration": 3.54}, {"text": "and storage technology in order\nto meet the Paris Agreement", "start": 1662.53, "duration": 3.0}, {"text": "climate goals.", "start": 1665.53, "duration": 1.15}, {"text": "So this paper is basically\ngoing to show us that we have", "start": 1666.68, "duration": 2.96}, {"text": "existing infrastructure--\nobviously,", "start": 1669.64, "duration": 1.74}, {"text": "the energy infrastructure\nthat we use every day--", "start": 1671.38, "duration": 2.327}, {"text": "and if we want to meet our\nParis Agreement climate", "start": 1673.707, "duration": 2.083}, {"text": "goals, which is\nkeeping, preferably,", "start": 1675.79, "duration": 2.13}, {"text": "global average temperatures less\nthan 1.5 degrees Celsius higher", "start": 1677.92, "duration": 4.35}, {"text": "than pre-Industrial\nera, we actually", "start": 1682.27, "duration": 2.37}, {"text": "need to build no more fossil\nfuel infrastructure, which", "start": 1684.64, "duration": 3.99}, {"text": "is CO2-emitting infrastructure.", "start": 1688.63, "duration": 1.65}, {"text": "And we may have to retire some\nof the energy infrastructure", "start": 1690.28, "duration": 2.64}, {"text": "that we have early before\nit's planned lifetime.", "start": 1692.92, "duration": 3.48}, {"text": "This is part of the struggle.", "start": 1696.4, "duration": 2.16}, {"text": "This is why you have\nactivists trying", "start": 1698.56, "duration": 1.71}, {"text": "to retire coal-fired\npower plants", "start": 1700.27, "duration": 3.27}, {"text": "and avoid building new\npipelines and natural gas plants", "start": 1703.54, "duration": 3.45}, {"text": "or having, let's say, gas bans\nfor new appliances in parts", "start": 1706.99, "duration": 4.35}, {"text": "of Massachusetts and\nCalifornia and other states.", "start": 1711.34, "duration": 3.012}, {"text": "So just to show\nyou what this looks", "start": 1714.352, "duration": 1.458}, {"text": "like, all these categories\nin the legend here--", "start": 1715.81, "duration": 2.907}, {"text": "commercial buildings,\nresidential buildings,", "start": 1718.717, "duration": 1.833}, {"text": "international transport,\nroad transport, industry,", "start": 1720.55, "duration": 2.083}, {"text": "electricity-- these\nkinds of technologies", "start": 1722.633, "duration": 2.357}, {"text": "have a natural lifetime\nin terms of they", "start": 1724.99, "duration": 3.51}, {"text": "have a committed CO2\nemission from existing", "start": 1728.5, "duration": 3.3}, {"text": "and proposed infrastructure.", "start": 1731.8, "duration": 1.66}, {"text": "And you can see that our\nexisting infrastructure", "start": 1733.46, "duration": 2.24}, {"text": "is overwhelmingly dominated\nby industry and electricity.", "start": 1735.7, "duration": 3.15}, {"text": "And road transport\nis this blue wedge,", "start": 1738.85, "duration": 2.22}, {"text": "and buildings are\nactually relatively small.", "start": 1741.07, "duration": 2.255}, {"text": "And those are all\nthings that are", "start": 1743.325, "duration": 1.375}, {"text": "going to phase out\nnaturally over time", "start": 1744.7, "duration": 2.22}, {"text": "because infrastructure gets old.", "start": 1746.92, "duration": 1.66}, {"text": "If you don't maintain it,\nand you don't rebuild it,", "start": 1748.58, "duration": 2.63}, {"text": "then it wears out, and\nyou can't use it anymore.", "start": 1751.21, "duration": 2.95}, {"text": "We've had more proposed\ninfrastructure,", "start": 1754.16, "duration": 2.18}, {"text": "but that proposed infrastructure\ncannot be built if we need", "start": 1756.34, "duration": 4.17}, {"text": "to try to meet our\nParis Climate goals.", "start": 1760.51, "duration": 2.58}, {"text": "At the same time, in\nthe B panel here, we", "start": 1763.09, "duration": 3.93}, {"text": "have the committed emissions\nfrom different countries.", "start": 1767.02, "duration": 3.1}, {"text": "And you can see the\nlifetime of infrastructure", "start": 1770.12, "duration": 2.09}, {"text": "in China is relatively\nlong and a large portion", "start": 1772.21, "duration": 4.23}, {"text": "of the future problem\nbecause so much of it", "start": 1776.44, "duration": 2.67}, {"text": "has been built fairly recently.", "start": 1779.11, "duration": 1.89}, {"text": "You can see the\nrest of the world", "start": 1781.0, "duration": 1.53}, {"text": "is actually only about 2/3 of\nthe problem that China poses.", "start": 1782.53, "duration": 4.53}, {"text": "And, actually, the US has\na relatively small future", "start": 1787.06, "duration": 2.67}, {"text": "committed emissions because\nthe nature of our technology.", "start": 1789.73, "duration": 3.34}, {"text": "Of course, there's been\nmany more proposed projects,", "start": 1793.07, "duration": 2.99}, {"text": "but the point of this paper is\nthat we cannot actually build", "start": 1796.06, "duration": 4.112}, {"text": "the proposed infrastructure,\nand we may have to retire some", "start": 1800.172, "duration": 2.458}, {"text": "of those existing infrastructure\nearly to avoid going over", "start": 1802.63, "duration": 3.36}, {"text": "our climate limits.", "start": 1805.99, "duration": 2.02}, {"text": "So another kind of interesting\ngraph in this paper which", "start": 1808.01, "duration": 2.69}, {"text": "I like quite a bit is\na population pyramid,", "start": 1810.7, "duration": 2.22}, {"text": "but it's a population\npyramid showing", "start": 1812.92, "duration": 2.91}, {"text": "the proportions of the\npopulation of people by age.", "start": 1815.83, "duration": 3.69}, {"text": "It actually shows\nthe age structure", "start": 1819.52, "duration": 1.77}, {"text": "of our global\nelectricity-generating", "start": 1821.29, "duration": 2.19}, {"text": "capacity.", "start": 1823.48, "duration": 1.02}, {"text": "And I want to simply\nmake a point about what", "start": 1824.5, "duration": 2.43}, {"text": "the different nature of the\nproblem in China and the US", "start": 1826.93, "duration": 3.36}, {"text": "are.", "start": 1830.29, "duration": 0.6}, {"text": "You can see on the\nleft-hand side--", "start": 1830.89, "duration": 2.49}, {"text": "this is the rest of the\nworld, in some ways,", "start": 1833.38, "duration": 2.34}, {"text": "dominated by the US.", "start": 1835.72, "duration": 1.03}, {"text": "You can see around\n15 or 17 years ago,", "start": 1836.75, "duration": 2.42}, {"text": "we've built quite a bit\nof natural gas or oil", "start": 1839.17, "duration": 2.85}, {"text": "infrastructure.", "start": 1842.02, "duration": 1.445}, {"text": "You can see the\nrest of the world", "start": 1843.465, "duration": 1.375}, {"text": "has more recently been\nbuilding gas and oil", "start": 1844.84, "duration": 2.61}, {"text": "infrastructure,\nthese yellow bars.", "start": 1847.45, "duration": 1.843}, {"text": "And you can see on\nthe right-hand side--", "start": 1849.293, "duration": 1.667}, {"text": "this is electricity\ngeneration from coal,", "start": 1850.96, "duration": 3.27}, {"text": "and that is overwhelmingly\ndominated by coal-fired power", "start": 1854.23, "duration": 2.85}, {"text": "plants built in China mostly\nin the last 12 or 14 years.", "start": 1857.08, "duration": 4.48}, {"text": "The reason why we\nuse this graph is", "start": 1861.56, "duration": 1.52}, {"text": "to look at the\nnature of the problem", "start": 1863.08, "duration": 1.5}, {"text": "and what particular sectors\nwe're going to have to tackle", "start": 1864.58, "duration": 2.863}, {"text": "or which particular\npower plants we have", "start": 1867.443, "duration": 1.667}, {"text": "to tackle to avoid creating more\ngreenhouse gas emissions that,", "start": 1869.11, "duration": 4.2}, {"text": "again, will put us beyond our\nParis Agreement targets, that", "start": 1873.31, "duration": 3.03}, {"text": "will then finally jeopardize\nthe climate of the planet.", "start": 1876.34, "duration": 6.89}, {"text": "So this brings me to\ncities, which is--", "start": 1883.23, "duration": 3.41}, {"text": "numerous recent studies show\nthat most US greenhouse gas", "start": 1886.64, "duration": 3.06}, {"text": "emissions or global\ngreenhouse gas", "start": 1889.7, "duration": 1.74}, {"text": "emissions in some of these\nstudies are from cities.", "start": 1891.44, "duration": 2.7}, {"text": "But the key point of this\nliterature I want to highlight", "start": 1894.14, "duration": 2.52}, {"text": "is that the exact\nproportion depends", "start": 1896.66, "duration": 1.86}, {"text": "on how and where you count.", "start": 1898.52, "duration": 2.75}, {"text": "The Jones et al.", "start": 1901.27, "duration": 1.11}, {"text": "2018 paper and the\nGoldstein et al 2020 paper", "start": 1902.38, "duration": 3.36}, {"text": "both find that higher incomes\nand lower population densities", "start": 1905.74, "duration": 3.36}, {"text": "are highly correlated\nwith higher carbon", "start": 1909.1, "duration": 2.01}, {"text": "footprints and energy use.", "start": 1911.11, "duration": 3.03}, {"text": "The Gurney et al 2018, 2020,\nand 2021 reports and papers", "start": 1914.14, "duration": 5.07}, {"text": "find that a majority\nof road and fossil fuel", "start": 1919.21, "duration": 2.7}, {"text": "infrastructure or use can\nbe associated with cities.", "start": 1921.91, "duration": 4.068}, {"text": "The Moran paper is\nquite interesting,", "start": 1925.978, "duration": 1.542}, {"text": "and it finds that, both\nin China and the US,", "start": 1927.52, "duration": 3.9}, {"text": "the largest 10 cities\nplus 5%, or the top 5%--", "start": 1931.42, "duration": 4.26}, {"text": "of suburban residents\nby income are", "start": 1935.68, "duration": 2.4}, {"text": "responsible for more than a\nmajority of the greenhouse", "start": 1938.08, "duration": 2.49}, {"text": "gas emissions from both\ncountries, China and the US,", "start": 1940.57, "duration": 3.39}, {"text": "which is to say that, if we\nfocused just on the largest 10", "start": 1943.96, "duration": 3.57}, {"text": "cities and the most\ncarbon-intensive suburbs, now", "start": 1947.53, "duration": 3.742}, {"text": "we could actually make\na significant difference", "start": 1951.272, "duration": 1.958}, {"text": "in the greenhouse gas\nemissions of the countries.", "start": 1953.23, "duration": 2.22}, {"text": "It is also kind of\nrecapping the moral argument", "start": 1955.45, "duration": 2.46}, {"text": "I made to you in the last\nclass, which is that the richest", "start": 1957.91, "duration": 3.69}, {"text": "people in both countries have a\ndisproportionate responsibility", "start": 1961.6, "duration": 4.65}, {"text": "to lower the greenhouse gas\nemissions just in the same way", "start": 1966.25, "duration": 2.61}, {"text": "that the US has a\ndisproportionate responsibility", "start": 1968.86, "duration": 2.28}, {"text": "to lower its greenhouse gas\nemissions relative to the rest", "start": 1971.14, "duration": 2.61}, {"text": "of the world.", "start": 1973.75, "duration": 1.17}, {"text": "Finally, the Seto in the\n2021 and the Wiedmann et al.", "start": 1974.92, "duration": 3.9}, {"text": "papers, 2021, show different\nresearch and planning", "start": 1978.82, "duration": 3.553}, {"text": "frameworks for how do we really\ncount these greenhouse gas", "start": 1982.373, "duration": 2.417}, {"text": "emissions.", "start": 1984.79, "duration": 0.5}, {"text": "And so there's debate\nabout how you count it,", "start": 1985.29, "duration": 2.23}, {"text": "but there's this emerging\nconsensus in the literature", "start": 1987.52, "duration": 3.06}, {"text": "that cities are responsible\nfor a large proportion", "start": 1990.58, "duration": 2.82}, {"text": "of greenhouse gas emissions\nin many countries,", "start": 1993.4, "duration": 2.98}, {"text": "including China and the US.", "start": 1996.38, "duration": 2.45}, {"text": "Just to highlight a\nfew of the key issues", "start": 1998.83, "duration": 1.8}, {"text": "why it's hard to get\nan exact proportion,", "start": 2000.63, "duration": 2.34}, {"text": "depends on different\ndefinitions of cities", "start": 2002.97, "duration": 2.16}, {"text": "or what an urban area is.", "start": 2005.13, "duration": 1.83}, {"text": "It depends which emissions\nyou count, upstream emissions,", "start": 2006.96, "duration": 3.24}, {"text": "like things that you import\nin the form of fuels or goods;", "start": 2010.2, "duration": 4.41}, {"text": "downstream emissions, the things\nthat you export out of the city", "start": 2014.61, "duration": 2.88}, {"text": "or waste energy or\nwaste products that", "start": 2017.49, "duration": 2.43}, {"text": "go outside of the city;\nand goods and services.", "start": 2019.92, "duration": 2.25}, {"text": "There's all different ways\nto count the emissions", "start": 2022.17, "duration": 1.56}, {"text": "from all of these things.", "start": 2023.73, "duration": 1.042}, {"text": "The C40 annual report that\nI assigned in the reading", "start": 2024.772, "duration": 3.668}, {"text": "gets to some of these issues.", "start": 2028.44, "duration": 2.77}, {"text": "Finally, some\ninteresting questions", "start": 2031.21, "duration": 1.88}, {"text": "that are not always\naccounted for-- cities", "start": 2033.09, "duration": 2.13}, {"text": "clearly shape local\nmicroclimates.", "start": 2035.22, "duration": 1.58}, {"text": "Do we count that as\npart of climate change,", "start": 2036.8, "duration": 2.57}, {"text": "because that actually changes\nhow people subsequently", "start": 2039.37, "duration": 2.27}, {"text": "use energy in cities?", "start": 2041.64, "duration": 1.222}, {"text": "And there's this kind of\nfundamental question--", "start": 2042.862, "duration": 1.958}, {"text": "how do you measure affluence?", "start": 2044.82, "duration": 1.56}, {"text": "Do you measure in terms\nof wealth or income?", "start": 2046.38, "duration": 2.25}, {"text": "I suspect if we measured\nthese in different ways,", "start": 2048.63, "duration": 2.819}, {"text": "you'd find different\nplaces responsible", "start": 2051.449, "duration": 2.551}, {"text": "for different levels of\ngreenhouse gas emissions.", "start": 2054.0, "duration": 2.699}, {"text": "Just again, to kind\nof make this argument", "start": 2056.699, "duration": 1.77}, {"text": "about how we measure\nthings matters", "start": 2058.469, "duration": 2.52}, {"text": "and also how intensity may\nshow us a different picture,", "start": 2060.989, "duration": 3.281}, {"text": "this is from the Gurney et al.", "start": 2064.27, "duration": 1.25}, {"text": "2020 paper.", "start": 2065.52, "duration": 1.44}, {"text": "The left-hand panel\nshows absolute emissions.", "start": 2066.96, "duration": 2.83}, {"text": "You can see the\nabsolute emissions", "start": 2069.79, "duration": 2.119}, {"text": "in this country basically\nalmost identically", "start": 2071.909, "duration": 3.0}, {"text": "mimics the spatial or\nurban spatial structure", "start": 2074.909, "duration": 3.031}, {"text": "of the country, where all the\nred areas and the left coast", "start": 2077.94, "duration": 5.07}, {"text": "are high concentrations\nof absolute emissions.", "start": 2083.01, "duration": 3.39}, {"text": "Of course, if you measure\non a per-capita basis,", "start": 2086.4, "duration": 2.1}, {"text": "you might say, OK,\nout West, people", "start": 2088.5, "duration": 1.83}, {"text": "are relatively inefficient.", "start": 2090.33, "duration": 1.758}, {"text": "But we should also\nhighlight the fact", "start": 2092.088, "duration": 1.542}, {"text": "that there's these\ninterrelationships", "start": 2093.63, "duration": 1.56}, {"text": "between these two areas.", "start": 2095.19, "duration": 1.87}, {"text": "Places out here in the West\nis a high concentration", "start": 2097.06, "duration": 3.08}, {"text": "of fossil fuel\nproduction/generation.", "start": 2100.14, "duration": 2.37}, {"text": "But where is that energy going?", "start": 2102.51, "duration": 2.19}, {"text": "That energy is going to cities.", "start": 2104.7, "duration": 1.68}, {"text": "And so we think back to MacKay's\nleft-hand bar of consumption.", "start": 2106.38, "duration": 4.71}, {"text": "I would argue to all the\nurban planners in the room--", "start": 2111.09, "duration": 2.68}, {"text": "and I've said this to my\ncolleagues in city government--", "start": 2113.77, "duration": 2.96}, {"text": "that we should not be\ncomplacent about the fact", "start": 2116.73, "duration": 2.19}, {"text": "that we think we have relatively\nlow per-capita emissions", "start": 2118.92, "duration": 3.72}, {"text": "in cities.", "start": 2122.64, "duration": 0.78}, {"text": "We have to be\nresponsible for the fact", "start": 2123.42, "duration": 2.04}, {"text": "that energy is being\nused elsewhere,", "start": 2125.46, "duration": 1.95}, {"text": "that we consume in the\nform of fuels, goods", "start": 2127.41, "duration": 3.27}, {"text": "and services, food, and\nwe export our waste also.", "start": 2130.68, "duration": 3.6}, {"text": "So that is the\nplace where cities", "start": 2134.28, "duration": 1.89}, {"text": "can have a big impact on\ngreenhouse gas emissions.", "start": 2136.17, "duration": 2.58}, {"text": "But it may be a different\nkind of efficiency.", "start": 2138.75, "duration": 2.01}, {"text": "We might have to think\nabout how much we consume,", "start": 2140.76, "duration": 2.94}, {"text": "why we consume energy, and how\ndo we do it more efficiently,", "start": 2143.7, "duration": 3.45}, {"text": "and, hopefully, ultimately\nreduce our consumption to meet", "start": 2147.15, "duration": 2.85}, {"text": "our decarbonization goals.", "start": 2150.0, "duration": 2.665}, {"text": "Finally, I'll just flash\nthrough the readings", "start": 2152.665, "duration": 1.875}, {"text": "quickly because we'll talk\nabout them more in class.", "start": 2154.54, "duration": 3.12}, {"text": "The Hsu et al 2019 paper--\nthis is actually not my paper.", "start": 2157.66, "duration": 3.12}, {"text": "It's written by a\ncolleague, Angel Hsu", "start": 2160.78, "duration": 2.7}, {"text": "at University of North Carolina.", "start": 2163.48, "duration": 1.77}, {"text": "It is a research roadmap for\nhow do we spend more time", "start": 2165.25, "duration": 2.94}, {"text": "or how do we spend more thinking\nabout quantifying the climate", "start": 2168.19, "duration": 3.96}, {"text": "mitigation actions that nonstate\nor subnational governments", "start": 2172.15, "duration": 4.68}, {"text": "could take.", "start": 2176.83, "duration": 0.69}, {"text": "And this is getting at\nthat measurement question.", "start": 2177.52, "duration": 2.38}, {"text": "How are we going to measure\ngreenhouse gas emissions?", "start": 2179.9, "duration": 2.42}, {"text": "And how are we going\nto measure what", "start": 2182.32, "duration": 1.5}, {"text": "action those entities take?", "start": 2183.82, "duration": 1.993}, {"text": "And just to give you\nan example, there's", "start": 2185.813, "duration": 1.667}, {"text": "different ways to count how\ncities take climate action", "start": 2187.48, "duration": 4.08}, {"text": "in comparison to state targets.", "start": 2191.56, "duration": 1.77}, {"text": "And those targets may\nbe different still", "start": 2193.33, "duration": 2.28}, {"text": "than national-level targets.", "start": 2195.61, "duration": 2.01}, {"text": "And so there's a question--\nare we going to double count?", "start": 2197.62, "duration": 2.91}, {"text": "In some cases, or,\nactually, most cases,", "start": 2200.53, "duration": 3.13}, {"text": "cities are more ambitious\nthan their states.", "start": 2203.66, "duration": 2.9}, {"text": "Cities are often more ambitious\nthan national governments.", "start": 2206.56, "duration": 3.53}, {"text": "We want to avoid\ndouble counting.", "start": 2210.09, "duration": 2.2}, {"text": "We want to assume--", "start": 2212.29, "duration": 1.23}, {"text": "we want to count\ncities considering", "start": 2213.52, "duration": 3.72}, {"text": "how those cities are going\nto act relative to cities", "start": 2217.24, "duration": 2.76}, {"text": "without targets.", "start": 2220.0, "duration": 1.27}, {"text": "So this paper will get at that.", "start": 2221.27, "duration": 1.97}, {"text": "We'll just talk\nabout more in class.", "start": 2223.24, "duration": 2.04}, {"text": "And this brings me to\nthis optional reading", "start": 2225.28, "duration": 2.73}, {"text": "by Markolf et al., which\nis \"Pledges and Progress.\"", "start": 2228.01, "duration": 3.93}, {"text": "This is a Brookings\nInstitution report.", "start": 2231.94, "duration": 1.98}, {"text": "It looks at the 100 largest\ncities across nine states.", "start": 2233.92, "duration": 3.21}, {"text": "They find that number of\ncities, these 100 cities,", "start": 2237.13, "duration": 3.3}, {"text": "have all set fairly ambitious\ngoals, everything on the blue", "start": 2240.43, "duration": 4.77}, {"text": "here on the right.", "start": 2245.2, "duration": 1.74}, {"text": "The parentheses shows you\nwhen they set the goal.", "start": 2246.94, "duration": 2.64}, {"text": "And you can see\nBoston, where we are--", "start": 2249.58, "duration": 2.85}, {"text": "actually, Cambridge is also\nin the graph somewhere.", "start": 2252.43, "duration": 2.61}, {"text": "But Boston,\nMassachusetts, in 2005--", "start": 2255.04, "duration": 2.19}, {"text": "so they're going to have\nan 80% reduction by 2050,", "start": 2257.23, "duration": 3.18}, {"text": "as all of these cities did,\nalso meeting the White House's", "start": 2260.41, "duration": 6.21}, {"text": "targets in 2016.", "start": 2266.62, "duration": 2.52}, {"text": "It's commensurate with the\nnational targets in 2016.", "start": 2269.14, "duration": 2.31}, {"text": "You can see a number\nof these cities", "start": 2271.45, "duration": 1.5}, {"text": "here in the left have set\nless ambitious targets--", "start": 2272.95, "duration": 2.79}, {"text": "50% reduction, let's\nsay 40% reduction.", "start": 2275.74, "duration": 3.15}, {"text": "But they may have\nmore closer targets.", "start": 2278.89, "duration": 3.31}, {"text": "So this might be an\ninterim goal on the way", "start": 2282.2, "duration": 2.09}, {"text": "to a more ambitious\ntarget down the road.", "start": 2284.29, "duration": 3.42}, {"text": "But the take-home from\nthis Markolf report--", "start": 2287.71, "duration": 2.7}, {"text": "and I'll let you\nlook at your leisure", "start": 2290.41, "duration": 1.602}, {"text": "because I think\nsome of you will be", "start": 2292.012, "duration": 1.458}, {"text": "quite interested in\nparticular cities--", "start": 2293.47, "duration": 2.033}, {"text": "you can see what\nthe difference is", "start": 2295.503, "duration": 1.417}, {"text": "between their current emissions\ninventory and their target", "start": 2296.92, "duration": 2.417}, {"text": "emissions.", "start": 2299.337, "duration": 0.733}, {"text": "And you can see in the\ncase of Chicago, Illinois,", "start": 2300.07, "duration": 3.24}, {"text": "they set a 2015-- they had a\n2015 greenhouse gas inventory.", "start": 2303.31, "duration": 4.8}, {"text": "They had a target emission in\nthe year of that inventory,", "start": 2308.11, "duration": 2.508}, {"text": "and it looks like\nChicago is emitting", "start": 2310.618, "duration": 1.542}, {"text": "about 50% more emissions\nthan they targeted in 2015.", "start": 2312.16, "duration": 4.08}, {"text": "I actually find this\nreport quite hopeful", "start": 2316.24, "duration": 2.1}, {"text": "because it takes a serious look\nat all these cities and says,", "start": 2318.34, "duration": 2.92}, {"text": "well, we should take\ncities seriously", "start": 2321.26, "duration": 2.27}, {"text": "in terms of the climate\naction goals we're studying.", "start": 2323.53, "duration": 2.4}, {"text": "But in order to\ntake them seriously,", "start": 2325.93, "duration": 1.87}, {"text": "we also have to hold them\naccording to the plans", "start": 2327.8, "duration": 2.51}, {"text": "that they're setting.", "start": 2330.31, "duration": 0.97}, {"text": "So it looks like\nBoston is closer", "start": 2331.28, "duration": 2.69}, {"text": "to its target of 10%\nhigher inventory emissions", "start": 2333.97, "duration": 3.63}, {"text": "than it had planned for in 2016.", "start": 2337.6, "duration": 3.21}, {"text": "That 10% hopefully gives us--\nor that inventory difference", "start": 2340.81, "duration": 4.08}, {"text": "gives us a good place\nto target our actions.", "start": 2344.89, "duration": 2.37}, {"text": "Other places, let's\nsay, Los Angeles--", "start": 2347.26, "duration": 1.86}, {"text": "looks like it's actually\nahead of its goals.", "start": 2349.12, "duration": 1.833}, {"text": "It's actually 10% less in terms\nof greenhouse gas emissions", "start": 2350.953, "duration": 3.237}, {"text": "than they planned for in 2013.", "start": 2354.19, "duration": 1.92}, {"text": "So cities-- looks like almost\noverwhelmingly temperate cities", "start": 2356.11, "duration": 3.72}, {"text": "except for Minneapolis,\nbut all of these fairly", "start": 2359.83, "duration": 2.97}, {"text": "temperate-region\ncities are doing", "start": 2362.8, "duration": 1.62}, {"text": "better than they expected.", "start": 2364.42, "duration": 1.41}, {"text": "Some of these cities here--", "start": 2365.83, "duration": 1.98}, {"text": "I guess Chicago is\na cold climate city,", "start": 2367.81, "duration": 2.46}, {"text": "and Tucson is the opposite.", "start": 2370.27, "duration": 1.59}, {"text": "But for different reasons,\nTucson and Chicago", "start": 2371.86, "duration": 2.7}, {"text": "are wildly over the goals\nthey set in 2014 and 2015.", "start": 2374.56, "duration": 5.22}, {"text": "And so I'll just stop here,\nand I will talk more in class", "start": 2379.78, "duration": 3.75}, {"text": "this week.", "start": 2383.53, "duration": 0.75}, {"text": "We'll talk the results\nof our carbon calculators", "start": 2384.28, "duration": 2.22}, {"text": "that you did for homework.", "start": 2386.5, "duration": 1.89}, {"text": "We will put some questions\nfor discussion on the board,", "start": 2388.39, "duration": 2.49}, {"text": "and we'll just start\nour discussion.", "start": 2390.88, "duration": 1.89}, {"text": "And we'll have some news\nitems to talk about in class.", "start": 2392.77, "duration": 2.92}, {"text": "Thank you very much.", "start": 2395.69, "duration": 1.05}, {"text": "I hope you guys have a\ngreat rest of your weekend--", "start": 2396.74, "duration": 3.77}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 0.995, "duration": 2.325}, {"text": "Commons license.", "start": 3.32, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.71, "duration": 2.21}, {"text": "continue to offer high quality\neducational resources for free.", "start": 6.92, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 11.01, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.58, "duration": 3.96}, {"text": "at ocw.mit.edu.", "start": 17.54, "duration": 0.88}, {"text": "MICHAEL SHORT: Hey guys, hope\nyou enjoyed the brief break", "start": 22.505, "duration": 3.095}, {"text": "from the heavy technical stuff.", "start": 25.6, "duration": 1.61}, {"text": "Because we're going to\nget right back into it", "start": 27.21, "duration": 1.875}, {"text": "and develop the neutron\ntransport equation today,", "start": 29.085, "duration": 2.137}, {"text": "the one that you\nsee on everybody's", "start": 31.222, "duration": 1.458}, {"text": "t-shirts here in the department.", "start": 32.68, "duration": 1.79}, {"text": "So I think multiple\nyears folks have", "start": 34.47, "duration": 2.08}, {"text": "used this equation on the\nback of t-shirts just be like,", "start": 36.55, "duration": 3.39}, {"text": "we're awesome.", "start": 39.94, "duration": 0.6}, {"text": "And we do difficult math.", "start": 40.54, "duration": 2.4}, {"text": "Well, this is what you're\ngoing to start to do it.", "start": 42.94, "duration": 2.623}, {"text": "In fact, it's big\nenough and hard enough", "start": 45.563, "duration": 1.667}, {"text": "that we're going to spend\nall day today developing it,", "start": 47.23, "duration": 3.54}, {"text": "like actually writing out\nthe terms of the equation", "start": 50.77, "duration": 2.31}, {"text": "and understanding what\nit actually means.", "start": 53.08, "duration": 2.31}, {"text": "Before, on Thursday\nand Friday, we're", "start": 55.39, "duration": 2.1}, {"text": "going to reduce it down to\na much simpler equation,", "start": 57.49, "duration": 3.09}, {"text": "something that you can\nactually solve and do", "start": 60.58, "duration": 2.1}, {"text": "some simple reactor\ncalculations with.", "start": 62.68, "duration": 2.4}, {"text": "We started off the whole idea of\nthe neutron transport equation", "start": 65.08, "duration": 4.02}, {"text": "as a way to track some\npopulation of neutrons.", "start": 69.1, "duration": 4.61}, {"text": "Let's see, I'm going to have\nour variable list up here.", "start": 73.71, "duration": 4.06}, {"text": "What I'll probably do is\non Thursday and Friday", "start": 77.77, "duration": 1.993}, {"text": "I'll just have it\nback up on the screens", "start": 79.763, "duration": 1.667}, {"text": "so that we don't have\nto write it twice.", "start": 81.43, "duration": 1.667}, {"text": "But there's going to be a lot\nof variables in this equation.", "start": 83.097, "duration": 2.888}, {"text": "I'm going to do my\nbest, again, to make", "start": 85.985, "duration": 1.625}, {"text": "the difference between V and nu\nvery obvious, and anything else", "start": 87.61, "duration": 3.63}, {"text": "like that.", "start": 91.24, "duration": 0.99}, {"text": "But the goal is to track\nsome population of neutrons,", "start": 92.23, "duration": 4.71}, {"text": "at some position,\nat some energy,", "start": 96.94, "duration": 3.39}, {"text": "traveling in some direction\nomega, as a function of time.", "start": 100.33, "duration": 4.78}, {"text": "And the 3D representation of\nwhat we're looking at here", "start": 105.11, "duration": 3.95}, {"text": "is let's say we had some\nsmall volume element, which", "start": 109.06, "duration": 5.19}, {"text": "we'll call that our dV.", "start": 114.25, "duration": 3.12}, {"text": "That's got normal vectors\nsticking out of it.", "start": 117.37, "duration": 2.73}, {"text": "We'll call those n-hats\nin all directions.", "start": 120.1, "duration": 3.45}, {"text": "And inside there, let's say\nif this is our energy scale,", "start": 123.55, "duration": 4.98}, {"text": "we're tracking the\npopulation of neutrons", "start": 128.53, "duration": 4.32}, {"text": "that occupies some\nsmall energy group dE,", "start": 132.85, "duration": 5.69}, {"text": "and is also traveling\nin some small direction", "start": 138.54, "duration": 5.16}, {"text": "that we designate as d-omega.", "start": 143.7, "duration": 1.392}, {"text": "So that's the goal of\nthis whole equation", "start": 147.93, "duration": 1.73}, {"text": "is to track the number of\nneutrons at any given position.", "start": 149.66, "duration": 3.31}, {"text": "So let's call this\ndistance, or the vector r.", "start": 152.97, "duration": 4.76}, {"text": "In this little volume, traveling\nin some direction omega,", "start": 157.73, "duration": 3.66}, {"text": "with some infinitesimally\nsmall energy group d.", "start": 161.39, "duration": 5.16}, {"text": "That's going to be the\ngoal of the whole thing.", "start": 166.55, "duration": 2.55}, {"text": "And what we'll do\nis write this to say", "start": 169.1, "duration": 2.8}, {"text": "the change in the population of\nneutrons at a given distance,", "start": 171.9, "duration": 4.32}, {"text": "energy, angle, and\ntime, over time", "start": 176.22, "duration": 7.69}, {"text": "is just going to be a sum\nof gain and loss terms.", "start": 183.91, "duration": 2.53}, {"text": "And what I think we'll\ntake all day today to do", "start": 191.11, "duration": 2.08}, {"text": "is to figure out what are\nthe actual physical things", "start": 193.19, "duration": 2.25}, {"text": "that neutrons can do in\nand out of this volume,", "start": 195.44, "duration": 3.36}, {"text": "and how do we turn those\ninto math, something", "start": 198.8, "duration": 2.19}, {"text": "that we can abstract and solve?", "start": 200.99, "duration": 2.99}, {"text": "There's a couple\nother terms that we're", "start": 203.98, "duration": 2.04}, {"text": "going to put up here.", "start": 206.02, "duration": 1.69}, {"text": "We'll say that the flux of\nneutrons, which is usually", "start": 207.71, "duration": 3.5}, {"text": "the variable that\nwe actually track,", "start": 211.21, "duration": 3.75}, {"text": "is just the velocity times\nthe neutron population.", "start": 214.96, "duration": 5.16}, {"text": "And also let's define some\nangularly independent terms.", "start": 220.12, "duration": 6.42}, {"text": "Because in the end\nwe've been talking", "start": 230.608, "duration": 1.542}, {"text": "about what's the\nprobability of some neutron", "start": 232.15, "duration": 3.33}, {"text": "or particle interacting\nwith some electron going out", "start": 235.48, "duration": 2.52}, {"text": "at some angle.", "start": 238.0, "duration": 1.23}, {"text": "But as we're interested in\nhow many neutrons are there", "start": 239.23, "duration": 2.61}, {"text": "in the reactor, we usually\ndon't care in which direction", "start": 241.84, "duration": 2.85}, {"text": "they're traveling.", "start": 244.69, "duration": 0.75}, {"text": "So the first simplification\nthat we will do", "start": 245.44, "duration": 2.91}, {"text": "is get rid of any sort\nof angular dependence,", "start": 248.35, "duration": 2.462}, {"text": "getting rid of two of\nthe seven variables", "start": 250.812, "duration": 1.708}, {"text": "that we're dealing with here.", "start": 252.52, "duration": 1.475}, {"text": "So all these\nvariables right here", "start": 253.995, "duration": 1.375}, {"text": "will be dependent on angle.", "start": 255.37, "duration": 1.8}, {"text": "And all these\nvariables right here", "start": 257.17, "duration": 1.5}, {"text": "will be angularly independent.", "start": 258.67, "duration": 6.26}, {"text": "So there'll be some\ncorresponding capital", "start": 269.46, "duration": 2.13}, {"text": "N, or number of neutrons as\na function of r, E, and t.", "start": 271.59, "duration": 4.67}, {"text": "We'll call this Flux.", "start": 278.97, "duration": 2.35}, {"text": "We'll call this Number.", "start": 281.32, "duration": 1.02}, {"text": "There's going to be a\nnumber of cross sections", "start": 285.813, "duration": 1.917}, {"text": "that we need to worry about.", "start": 287.73, "duration": 1.167}, {"text": "So we'll refer to little\nsigma as a function of energy,", "start": 288.897, "duration": 4.923}, {"text": "as our micro-cross-section,\nand big sigma of E", "start": 293.82, "duration": 9.57}, {"text": "as a macroscopic cross-section.", "start": 303.39, "duration": 1.83}, {"text": "Then you want to remember the\nrelation between these two.", "start": 311.69, "duration": 4.665}, {"text": "AUDIENCE: Solid angle?", "start": 316.355, "duration": 1.485}, {"text": "MICHAEL SHORT: The\nsolid angle, not quite.", "start": 317.84, "duration": 2.82}, {"text": "That's, let's see.", "start": 320.66, "duration": 1.938}, {"text": "There's a difference\nbetween-- and so", "start": 322.598, "duration": 1.542}, {"text": "what these physically\nmean is little sigma", "start": 324.14, "duration": 1.89}, {"text": "means the probability of\ninteraction with one particle.", "start": 326.03, "duration": 2.947}, {"text": "And this is just the\ntotal probability", "start": 328.977, "duration": 1.583}, {"text": "of interaction with all the\nparticles that may be there.", "start": 330.56, "duration": 2.333}, {"text": "So yeah, Chris?", "start": 332.893, "duration": 0.855}, {"text": "AUDIENCE: Number density?", "start": 333.748, "duration": 1.042}, {"text": "MICHAEL SHORT: There's\nnumber density.", "start": 334.79, "duration": 2.76}, {"text": "Already we have another\nvariable conflict.", "start": 337.55, "duration": 2.22}, {"text": "How do we want to resolve this?", "start": 339.77, "duration": 3.16}, {"text": "Let's see.", "start": 342.93, "duration": 0.51}, {"text": "We'll have to change\nthe symbol somehow.", "start": 346.46, "duration": 2.502}, {"text": "Let's make it cursive.", "start": 348.962, "duration": 3.233}, {"text": "Don't know what else to do.", "start": 352.195, "duration": 1.125}, {"text": "I don't want to give it\na number other than n", "start": 353.32, "duration": 1.875}, {"text": "since we're talking\nabout neutrons,", "start": 355.195, "duration": 1.835}, {"text": "or that right here it's\ngoing to be number density.", "start": 357.03, "duration": 2.125}, {"text": "And in the end, we're worried\nabout some sort of reaction", "start": 363.75, "duration": 2.6}, {"text": "rate, which is always\ngoing to equal some flux,", "start": 366.35, "duration": 4.8}, {"text": "or let's just stick with some\nangularly dependent flux,", "start": 371.15, "duration": 4.32}, {"text": "that r, E omega t,\ntimes some cross-section", "start": 375.47, "duration": 7.86}, {"text": "as a function of energy.", "start": 383.33, "duration": 1.47}, {"text": "And it's these\nreaction rates that", "start": 384.8, "duration": 1.66}, {"text": "are the rates of gains\nand losses of neutrons", "start": 386.46, "duration": 4.23}, {"text": "out of this volume, out\nof this little angle,", "start": 390.69, "duration": 2.61}, {"text": "out of this energy group,\nand out of that space,", "start": 393.3, "duration": 2.67}, {"text": "or into that volume\nenergy group and space.", "start": 395.97, "duration": 3.63}, {"text": "So let's see, other terms\nthat we'll want to define", "start": 399.6, "duration": 3.18}, {"text": "include nu, like last time.", "start": 402.78, "duration": 5.22}, {"text": "We'll call this\nneutron multiplication.", "start": 408.0, "duration": 2.28}, {"text": "In other words,\nthis is the number", "start": 416.523, "duration": 1.417}, {"text": "of neutrons made on average\nduring each fission event.", "start": 417.94, "duration": 3.75}, {"text": "And we give it energy\ndependence because as we", "start": 421.69, "duration": 2.1}, {"text": "saw on the Janis libraries\non Friday, I think it was.", "start": 423.79, "duration": 4.38}, {"text": "What's today, Tuesday?", "start": 428.17, "duration": 1.15}, {"text": "I don't even know anymore.", "start": 429.32, "duration": 1.37}, {"text": "I think as we saw on Friday,\nthat depends on energy", "start": 430.69, "duration": 3.27}, {"text": "for the higher energy levels.", "start": 433.96, "duration": 1.655}, {"text": "And there's also\ngoing to be some Kai", "start": 435.615, "duration": 3.935}, {"text": "spectrum, or some\nneutron birth spectrum,", "start": 439.55, "duration": 10.46}, {"text": "which tells you the average\nenergy at which neutrons", "start": 450.01, "duration": 3.12}, {"text": "are born from fission.", "start": 453.13, "duration": 1.05}, {"text": "So regardless of what energy\ngoes in to cause the fission,", "start": 454.18, "duration": 4.8}, {"text": "there's some\nprobability distribution", "start": 458.98, "duration": 3.49}, {"text": "of a neutron being born\nat a certain energy.", "start": 462.47, "duration": 3.81}, {"text": "And it looks something like\nthis, where that's about 1 MeV.", "start": 466.28, "duration": 7.63}, {"text": "That's about 10 MeV.", "start": 473.91, "duration": 2.25}, {"text": "And that average right\nthere is around 2 MeV.", "start": 476.16, "duration": 3.998}, {"text": "And so it's important\nto note that neutrons", "start": 480.158, "duration": 1.792}, {"text": "are born at different energies.", "start": 481.95, "duration": 1.41}, {"text": "Because we want to track\nevery single possible dE", "start": 483.36, "duration": 2.49}, {"text": "throughout this\ncontrol volume, which", "start": 485.85, "duration": 2.49}, {"text": "we'll also call a reactor.", "start": 488.34, "duration": 2.06}, {"text": "Let's see, what other\nterms will we need to know?", "start": 490.4, "duration": 2.53}, {"text": "The different types\nof cross sections,", "start": 492.93, "duration": 1.59}, {"text": "or the different\ninteractions that neutrons", "start": 494.52, "duration": 1.8}, {"text": "can have with matter.", "start": 496.32, "duration": 1.2}, {"text": "What are some of the ones\nthat we had talked about?", "start": 497.52, "duration": 2.125}, {"text": "What can neutrons do\nwhen they run into stuff?", "start": 503.44, "duration": 2.15}, {"text": "AUDIENCE: Scatter.", "start": 505.59, "duration": 0.76}, {"text": "MICHAEL SHORT: They can scatter.", "start": 506.35, "duration": 1.333}, {"text": "So there's going to be some\nscattering cross-section.", "start": 507.683, "duration": 3.428}, {"text": "And when they scatter,\nthe important part", "start": 513.701, "duration": 1.708}, {"text": "here is they're going\nto change in energy.", "start": 515.409, "duration": 1.75}, {"text": "What else can they do?", "start": 522.82, "duration": 1.79}, {"text": "Yeah?", "start": 524.61, "duration": 0.5}, {"text": "AUDIENCE: Absorbed.", "start": 525.11, "duration": 0.71}, {"text": "MICHAEL SHORT: They\ncan be absorbed.", "start": 525.82, "duration": 1.0}, {"text": "So we'll have some\nsigma absorption.", "start": 526.82, "duration": 1.82}, {"text": "What are some of the various\nthings that can happen", "start": 535.08, "duration": 2.13}, {"text": "when a neutron is absorbed?", "start": 537.21, "duration": 1.185}, {"text": "AUDIENCE: Fission.", "start": 542.196, "duration": 1.004}, {"text": "MICHAEL SHORT: Yeah, so\none of them is fission.", "start": 543.2, "duration": 2.61}, {"text": "What are some of the other ones?", "start": 551.68, "duration": 2.976}, {"text": "AUDIENCE: Capture.", "start": 554.656, "duration": 0.75}, {"text": "MICHAEL SHORT: Yep, capture.", "start": 555.406, "duration": 1.184}, {"text": "What were some of the\nones that we talked about", "start": 563.232, "duration": 1.958}, {"text": "during the Chadwick paper?", "start": 565.19, "duration": 2.55}, {"text": "AUDIENCE: Neutron [INAUDIBLE].", "start": 567.74, "duration": 1.44}, {"text": "MICHAEL SHORT: Yep,\nso there can be some--", "start": 569.18, "duration": 3.08}, {"text": "we'll call it n,in, which means\none neutron goes in, i neutrons", "start": 572.26, "duration": 6.45}, {"text": "come out, so 1 to\ni neutrons, sure.", "start": 578.71, "duration": 8.71}, {"text": "Anything else?", "start": 587.42, "duration": 0.68}, {"text": "Encompassed in absorption?", "start": 591.32, "duration": 1.615}, {"text": "Well when we refer to scatter\nhere, what type of scattering", "start": 598.98, "duration": 3.405}, {"text": "are we talking about?", "start": 602.385, "duration": 0.875}, {"text": "AUDIENCE: Compton's scatter?", "start": 607.688, "duration": 1.972}, {"text": "MICHAEL SHORT:\nCompton's for photons.", "start": 609.66, "duration": 1.725}, {"text": "It's OK.", "start": 611.385, "duration": 1.875}, {"text": "Was it elastic or\ninelastic scattering?", "start": 613.26, "duration": 2.16}, {"text": "AUDIENCE: Elastic.", "start": 615.42, "duration": 0.75}, {"text": "MICHAEL SHORT:\nElastic scattering.", "start": 616.17, "duration": 1.47}, {"text": "So another thing you could call\nan absorption event, depending", "start": 617.64, "duration": 2.79}, {"text": "on what bin you put things\nin, is inelastic scattering,", "start": 620.43, "duration": 9.72}, {"text": "which is that kind of--", "start": 630.15, "duration": 1.44}, {"text": "we call it scattering\nbecause one neutron goes in,", "start": 631.59, "duration": 2.52}, {"text": "one neutron comes out.", "start": 634.11, "duration": 1.5}, {"text": "But in reality, you have\na compound nucleus forming", "start": 635.61, "duration": 2.9}, {"text": "and a neutron emitted from\na different energy level.", "start": 638.51, "duration": 2.41}, {"text": "So it doesn't follow the\nsimple ballistic laws of,", "start": 640.92, "duration": 3.84}, {"text": "and kinematic laws of\ninelastic scattering.", "start": 644.76, "duration": 3.09}, {"text": "What else can neutrons do?", "start": 647.85, "duration": 1.2}, {"text": "Now we're getting into\nthe real esoteric stuff.", "start": 652.092, "duration": 1.958}, {"text": "But I want to see if\nyou guys have any idea.", "start": 654.05, "duration": 1.833}, {"text": "Did you know that\nneutrons can decay?", "start": 658.77, "duration": 3.87}, {"text": "A low neutron is actually\nnot a stable particle.", "start": 665.41, "duration": 2.67}, {"text": "If you look up on the\nKyrie table of nuclides,", "start": 668.08, "duration": 3.05}, {"text": "it's got a half\nlife of 12 minutes.", "start": 671.13, "duration": 2.33}, {"text": "So if you happen\nto be able to have", "start": 673.46, "duration": 1.71}, {"text": "neutrons in a bottle or\nsomething, which we actually", "start": 675.17, "duration": 2.4}, {"text": "can do.", "start": 677.57, "duration": 1.07}, {"text": "There's centers for\nultra-cold neutrons and atoms.", "start": 678.64, "duration": 2.68}, {"text": "There's one at North Carolina\nState where they actually cool", "start": 681.32, "duration": 3.613}, {"text": "down neutrons to cryogenic\ntemperatures to the point where", "start": 684.933, "duration": 2.417}, {"text": "they can actually confine them.", "start": 687.35, "duration": 1.8}, {"text": "They only live on\naverage 12 minutes.", "start": 689.15, "duration": 3.39}, {"text": "And then there would\nalso be what we call", "start": 697.212, "duration": 1.708}, {"text": "a neutron-neutron interactions.", "start": 698.92, "duration": 1.89}, {"text": "There is a finite,\nnon-zero but very small", "start": 704.18, "duration": 3.15}, {"text": "probability that neutrons\ncan hit other neutrons.", "start": 707.33, "duration": 3.54}, {"text": "But the mean-free path for\nthese is on the order of 10", "start": 710.87, "duration": 5.1}, {"text": "to the 8th centimeters.", "start": 715.97, "duration": 3.525}, {"text": "So this is not something\nwe have to consider.", "start": 719.495, "duration": 1.875}, {"text": "But it's interesting to\nknow that yes, neutrons", "start": 721.37, "duration": 1.98}, {"text": "can run into other neutrons.", "start": 723.35, "duration": 1.74}, {"text": "And these sorts of things\nhave been measured.", "start": 725.09, "duration": 2.19}, {"text": "We won't have to\nworry about this.", "start": 727.28, "duration": 2.4}, {"text": "We won't have to worry\nabout neutron decay.", "start": 729.68, "duration": 2.13}, {"text": "But it's interesting to note\nthat a low neutron is not", "start": 731.81, "duration": 2.25}, {"text": "a stable particle.", "start": 734.06, "duration": 1.4}, {"text": "It will spontaneously\nundergo beta decay,", "start": 735.46, "duration": 4.54}, {"text": "into a proton and an electron.", "start": 740.0, "duration": 2.52}, {"text": "Pretty neat, huh?", "start": 742.52, "duration": 1.99}, {"text": "Anyway, if we sum up all\nthese possible interactions,", "start": 744.51, "duration": 5.71}, {"text": "we have one other\ncross-section, which", "start": 750.22, "duration": 3.12}, {"text": "we're going to call the total\ncross-section, the probability", "start": 753.34, "duration": 3.99}, {"text": "of absolutely any\ninteraction occurring at all.", "start": 757.33, "duration": 3.27}, {"text": "Because any sort of\ninteraction of that neutron", "start": 760.6, "duration": 3.66}, {"text": "is going to cause removal from\nthis group of energy position,", "start": 764.26, "duration": 5.26}, {"text": "angle, location, whatever.", "start": 769.52, "duration": 2.93}, {"text": "Whether it's absorption, or\nfission, or elastic scattering,", "start": 772.45, "duration": 3.12}, {"text": "or inelastic scattering,\nany sort of event--", "start": 775.57, "duration": 2.73}, {"text": "except for forward scattering,\nwhich means nothing happens--", "start": 778.3, "duration": 3.57}, {"text": "is going to result in this\nneutron either leaving", "start": 781.87, "duration": 3.66}, {"text": "the volume.", "start": 785.53, "duration": 0.63}, {"text": "So it might scatter out\nof our little volume.", "start": 786.16, "duration": 2.94}, {"text": "Or it might change direction,\nscatter out of our d-omega.", "start": 789.1, "duration": 4.08}, {"text": "Or it will lose\nsome energy, or gain", "start": 793.18, "duration": 3.9}, {"text": "some energy, in some cases,\nleaving our little dE, which", "start": 797.08, "duration": 3.84}, {"text": "is what we're trying to track.", "start": 800.92, "duration": 2.137}, {"text": "Because we're actually\ntracking what's", "start": 803.057, "duration": 1.583}, {"text": "the population of neutrons\nin this little dE,", "start": 804.64, "duration": 2.94}, {"text": "in this direction, in this\nposition, at this time.", "start": 807.58, "duration": 3.63}, {"text": "And supposedly if we\nknow this term fully,", "start": 811.21, "duration": 2.55}, {"text": "we can solve for\nall the neutrons", "start": 813.76, "duration": 1.44}, {"text": "everywhere, anywhere in the\nreactor with full information.", "start": 815.2, "duration": 3.208}, {"text": "So what we'll spend\nthe rest of today doing", "start": 818.408, "duration": 1.792}, {"text": "is figuring out what are all the\npossible gain and loss terms.", "start": 820.2, "duration": 4.1}, {"text": "So let's start just putting them\nout physically, or in words.", "start": 824.3, "duration": 4.64}, {"text": "And then we'll put them to math.", "start": 828.94, "duration": 1.8}, {"text": "So what are some of the\nways in which neutrons", "start": 830.74, "duration": 3.42}, {"text": "can enter our little group\nof volume, angle, and energy?", "start": 834.16, "duration": 4.47}, {"text": "How are neutrons created?", "start": 841.414, "duration": 3.526}, {"text": "Yeah, Luke?", "start": 844.94, "duration": 0.64}, {"text": "AUDIENCE: From fission,\nor a neutron emission.", "start": 845.58, "duration": 3.25}, {"text": "MICHAEL SHORT: From fission,\nyeah, so that's one big source.", "start": 848.83, "duration": 3.18}, {"text": "So we'll call this a gains.", "start": 852.01, "duration": 2.64}, {"text": "This is a losses.", "start": 854.65, "duration": 2.9}, {"text": "And you said a neutron source.", "start": 857.55, "duration": 1.35}, {"text": "Can you be more specific?", "start": 858.9, "duration": 1.042}, {"text": "AUDIENCE: A neutron\nemission, like [INAUDIBLE]..", "start": 859.942, "duration": 2.318}, {"text": "MICHAEL SHORT: OK, so we'll\nsay n,in reactions, right?", "start": 862.26, "duration": 6.93}, {"text": "OK, cool.", "start": 869.19, "duration": 1.98}, {"text": "How else can we gain neutrons?", "start": 871.17, "duration": 1.335}, {"text": "AUDIENCE: Fusion?", "start": 877.164, "duration": 1.436}, {"text": "MICHAEL SHORT: Fusion?", "start": 878.6, "duration": 1.2}, {"text": "OK.", "start": 879.8, "duration": 1.59}, {"text": "That is true.", "start": 881.39, "duration": 1.62}, {"text": "Although fusion\nreactors don't really", "start": 883.01, "duration": 1.68}, {"text": "operate on the principle of\nneutron criticality, or neutron", "start": 884.69, "duration": 3.69}, {"text": "balance.", "start": 888.38, "duration": 0.932}, {"text": "So this discussion\nfor now is going", "start": 889.312, "duration": 1.458}, {"text": "to be limited to\nfission reactors.", "start": 890.77, "duration": 1.54}, {"text": "But yeah, good point.", "start": 892.31, "duration": 1.38}, {"text": "Fusion does make neutrons.", "start": 893.69, "duration": 2.85}, {"text": "What else?", "start": 896.54, "duration": 0.54}, {"text": "Yeah?", "start": 902.21, "duration": 0.5}, {"text": "AUDIENCE: They could enter from\none of the adjacent volume?", "start": 902.71, "duration": 4.515}, {"text": "MICHAEL SHORT: Yeah, they\ncould come from somewhere else,", "start": 907.225, "duration": 2.375}, {"text": "right?", "start": 909.6, "duration": 1.02}, {"text": "Let's just call that\nan external source.", "start": 910.62, "duration": 1.795}, {"text": "In the books and\nin your reading,", "start": 915.76, "duration": 1.54}, {"text": "you'll just see them\ntreat this external source", "start": 917.3, "duration": 2.45}, {"text": "as some variable s\nof r, E, omega, t.", "start": 919.75, "duration": 9.15}, {"text": "So you'll just see this\ntreated as s, a source,", "start": 933.6, "duration": 2.1}, {"text": "with no further explanation.", "start": 935.7, "duration": 1.29}, {"text": "It's like, oh, math\nsays that there", "start": 936.99, "duration": 1.5}, {"text": "could be external sources.", "start": 938.49, "duration": 1.355}, {"text": "But I want to tell you\nwhere they really come from.", "start": 939.845, "duration": 2.125}, {"text": "Most reactors\nnowadays don't just", "start": 941.97, "duration": 2.22}, {"text": "start up when you throw a\nbunch of uranium into a pool", "start": 944.19, "duration": 2.67}, {"text": "and pull out the control rods.", "start": 946.86, "duration": 1.65}, {"text": "You actually have to stick in--", "start": 948.51, "duration": 2.07}, {"text": "if this is your little\nreactor right here--", "start": 950.58, "duration": 2.95}, {"text": "you actually have to stick in\na little piece of californium--", "start": 953.53, "duration": 4.1}, {"text": "I think the isotope is 252--", "start": 957.63, "duration": 3.0}, {"text": "as what we call a\nkickstarter source.", "start": 960.63, "duration": 2.45}, {"text": "So californium is made mostly\nin the HFIR, or the High Flux", "start": 963.08, "duration": 6.04}, {"text": "Isotope Reactor, at the Oakridge\nNational Lab in Tennessee,", "start": 969.12, "duration": 4.86}, {"text": "where they have a really,\nreally high power reactor.", "start": 973.98, "duration": 3.0}, {"text": "It's 85 megawatts.", "start": 976.98, "duration": 1.8}, {"text": "It's about that big\naround and this tall.", "start": 978.78, "duration": 3.27}, {"text": "It's really, really small.", "start": 982.05, "duration": 1.44}, {"text": "For reference, that's about\nthe size of the MIT reactor,", "start": 983.49, "duration": 3.09}, {"text": "except our reactor's\n6 megawatts.", "start": 986.58, "duration": 1.95}, {"text": "Theirs is 85 megawatts.", "start": 988.53, "duration": 1.98}, {"text": "And it's designed to be\nan incredibly high flux,", "start": 990.51, "duration": 3.18}, {"text": "to go by neutron capture, and\nneutron capture reactions,", "start": 993.69, "duration": 2.94}, {"text": "to build up californium\n252, which is spontaneously", "start": 996.63, "duration": 4.8}, {"text": "giving off neutrons like crazy.", "start": 1001.43, "duration": 2.68}, {"text": "And this right here, that's\nyour external source.", "start": 1004.11, "duration": 4.69}, {"text": "And this helps get\nreactors going.", "start": 1008.8, "duration": 1.99}, {"text": "Because you can\neither very slowly", "start": 1010.79, "duration": 1.77}, {"text": "wait for the fission\nreaction to build up", "start": 1012.56, "duration": 2.13}, {"text": "in a controlled manner.", "start": 1014.69, "duration": 1.26}, {"text": "Or you can give it a kick in\nthe pants and get it going.", "start": 1015.95, "duration": 2.67}, {"text": "This HFIR reactor\nis pretty cool.", "start": 1018.62, "duration": 2.34}, {"text": "Like I said, it's 85 megawatts.", "start": 1020.96, "duration": 2.79}, {"text": "And it's about as\ndense as it can get.", "start": 1023.75, "duration": 2.19}, {"text": "The fuel is actually made by\nexplosively bonding sheets", "start": 1025.94, "duration": 2.94}, {"text": "of uranium in a certain sort of\nsemi-cylindrical configuration.", "start": 1028.88, "duration": 5.31}, {"text": "And it produces so much\ndecay heat in so little space", "start": 1034.19, "duration": 3.179}, {"text": "that if it were to lose\ncooling, the reactor", "start": 1037.369, "duration": 1.861}, {"text": "would melt in 8 seconds.", "start": 1039.23, "duration": 1.976}, {"text": "You usually have\ndays or so before", "start": 1041.206, "duration": 2.324}, {"text": "that happens in a\nconventional reactor", "start": 1043.53, "duration": 2.67}, {"text": "because the power density\njust isn't that high.", "start": 1046.2, "duration": 2.64}, {"text": "So you can actually\nsee down to the tank", "start": 1048.84, "duration": 2.13}, {"text": "that contains HFIR if you go\nfor a tour at Oakridge National", "start": 1050.97, "duration": 3.12}, {"text": "Lab.", "start": 1054.09, "duration": 0.78}, {"text": "And it's way down below this\ngigantic like, not quite", "start": 1054.87, "duration": 2.76}, {"text": "Olympic, but getting\nthere sized pool of water,", "start": 1057.63, "duration": 3.253}, {"text": "just to make sure\nthat there is adequate", "start": 1060.883, "duration": 1.667}, {"text": "cooling for this thing.", "start": 1062.55, "duration": 1.36}, {"text": "It's intense.", "start": 1063.91, "duration": 1.34}, {"text": "But that's just a notice\nthat these external sources,", "start": 1065.25, "duration": 3.13}, {"text": "these are real things that\nwe use in power reactors", "start": 1068.38, "duration": 3.14}, {"text": "to get them going.", "start": 1071.52, "duration": 2.44}, {"text": "What are some other ways\nthat one could make neutrons,", "start": 1073.96, "duration": 2.79}, {"text": "or that neutrons could\nenter into our energy group?", "start": 1076.75, "duration": 3.42}, {"text": "And the silence is expected\nbecause this is usually", "start": 1084.515, "duration": 2.125}, {"text": "the hardest part of\ndeveloping this equation.", "start": 1086.64, "duration": 2.85}, {"text": "And I want to introduce it.", "start": 1089.49, "duration": 1.23}, {"text": "Yeah, Luke?", "start": 1090.72, "duration": 0.746}, {"text": "AUDIENCE: [INAUDIBLE]\nscattering, too.", "start": 1091.466, "duration": 1.624}, {"text": "MICHAEL SHORT:\nThat's exactly it.", "start": 1093.09, "duration": 1.375}, {"text": "They can scatter in.", "start": 1094.465, "duration": 1.115}, {"text": "So when we develop this\nneutron transport equation,", "start": 1095.58, "duration": 3.33}, {"text": "we're not just\ntracking the neutrons", "start": 1098.91, "duration": 2.46}, {"text": "in this little energy group dE,\ndirection, d-omega, and volume", "start": 1101.37, "duration": 4.08}, {"text": "dV.", "start": 1105.45, "duration": 0.84}, {"text": "You actually have to know what's\nthe population of neutrons", "start": 1106.29, "duration": 3.03}, {"text": "in every single group.", "start": 1109.32, "duration": 1.71}, {"text": "Because you might have a neutron\nat a higher energy level that", "start": 1111.03, "duration": 3.18}, {"text": "undergoes scattering from\nsome different energy,", "start": 1114.21, "duration": 6.035}, {"text": "E-prime into our energy group.", "start": 1120.245, "duration": 3.405}, {"text": "So continuing with our\ngigantic list of variables,", "start": 1123.65, "duration": 5.38}, {"text": "we're going to call E\nis, we'll say r energy.", "start": 1129.03, "duration": 2.7}, {"text": "And this vector omega\nis our direction,", "start": 1135.29, "duration": 2.118}, {"text": "the one that we're tracking.", "start": 1137.408, "duration": 1.167}, {"text": "And E-prime is going to\nbe some other energy.", "start": 1143.1, "duration": 2.4}, {"text": "And omega-vector-prime is\ngoing to be some coming", "start": 1149.78, "duration": 3.48}, {"text": "from some other direction.", "start": 1153.26, "duration": 1.41}, {"text": "And like Luke said,\nthis is what we", "start": 1158.35, "duration": 1.66}, {"text": "would refer to as in-scattering,\nwhich means some neutron comes,", "start": 1160.01, "duration": 10.73}, {"text": "that was going in a\ndifferent direction, that", "start": 1170.74, "duration": 2.22}, {"text": "did have a different\nenergy, and has now", "start": 1172.96, "duration": 2.04}, {"text": "entered into the single\ngroup that we're tracking.", "start": 1175.0, "duration": 2.832}, {"text": "Eventually we're going to\nintegrate over all energies", "start": 1177.832, "duration": 2.208}, {"text": "to track all energy groups.", "start": 1180.04, "duration": 2.23}, {"text": "So that's where we're going.", "start": 1182.27, "duration": 2.69}, {"text": "And there's one more term that\nI want to introduce right now.", "start": 1184.96, "duration": 3.57}, {"text": "It's what's called\nthe scattering kernel.", "start": 1188.53, "duration": 1.8}, {"text": "Don't ask me why\nit's called kernel.", "start": 1195.88, "duration": 1.56}, {"text": "But this is just the terminology\nI want you guys to get used to.", "start": 1197.44, "duration": 3.96}, {"text": "And there's going to be some\nsort of probability function", "start": 1201.4, "duration": 2.97}, {"text": "where a neutron starts off at\na different energy, E-prime,", "start": 1204.37, "duration": 3.84}, {"text": "and in a different\ndirection, omega-prime.", "start": 1208.21, "duration": 1.96}, {"text": "And it enters into our group\nenergy E and direction omega.", "start": 1210.17, "duration": 7.75}, {"text": "Right now we'll leave it as\na highly general function.", "start": 1217.92, "duration": 2.51}, {"text": "What we're going to find\nlater is there's just", "start": 1220.43, "duration": 2.56}, {"text": "some sort of simple line to it.", "start": 1222.99, "duration": 3.45}, {"text": "If you guys remember, if\nsome neutron starts off,", "start": 1226.44, "duration": 4.7}, {"text": "let's see, probability of\nentering into some energy", "start": 1231.14, "duration": 6.03}, {"text": "group.", "start": 1237.17, "duration": 1.02}, {"text": "If you notice, if you\nremember from last time,", "start": 1238.19, "duration": 1.92}, {"text": "the neutron, when it undergoes\nany sort of scattering", "start": 1240.11, "duration": 3.54}, {"text": "reaction, can end\nup with any energy", "start": 1243.65, "duration": 3.81}, {"text": "between its original energy\nfor the case of theta equals 0,", "start": 1247.46, "duration": 5.82}, {"text": "and this parameter, alpha\nenergy, for the case theta", "start": 1253.28, "duration": 2.43}, {"text": "equals pi, where\nalpha is A minus 1,", "start": 1255.71, "duration": 5.51}, {"text": "over A plus 1 squared,\nwhere A is the atomic mass.", "start": 1261.22, "duration": 4.65}, {"text": "You guys remember this\nfrom back in the Q equation", "start": 1269.927, "duration": 2.083}, {"text": "days, when we were\nfinding out what's", "start": 1272.01, "duration": 2.31}, {"text": "the probability that a neutron\ncoming in with energy E", "start": 1274.32, "duration": 3.0}, {"text": "ends up at any energy E-prime?", "start": 1277.32, "duration": 1.26}, {"text": "Actually I'll just write this\nas the scattering kernel.", "start": 1281.18, "duration": 3.3}, {"text": "What it ends up looking\nlike, in most cases,", "start": 1284.48, "duration": 2.64}, {"text": "is just a flat line.", "start": 1287.12, "duration": 1.14}, {"text": "There's an equal probability of\nthe neutron ending up anywhere", "start": 1288.26, "duration": 4.29}, {"text": "between energy E and\nanywhere between energy", "start": 1292.55, "duration": 4.52}, {"text": "alpha-E. It's actually a\npretty simple function.", "start": 1297.07, "duration": 2.89}, {"text": "It's just a constant value\nhere and 0 everywhere else.", "start": 1299.96, "duration": 4.557}, {"text": "What that means is\nthat if, let's say,", "start": 1304.517, "duration": 1.583}, {"text": "a neutron hits a uranium\natom, there is no way in hell", "start": 1306.1, "duration": 2.79}, {"text": "that it can transfer\nall of its energy", "start": 1308.89, "duration": 2.16}, {"text": "to a uranium atom because\nof conservation of energy", "start": 1311.05, "duration": 5.67}, {"text": "and momentum, like we've\nbeen harping on for kind", "start": 1316.72, "duration": 3.53}, {"text": "of this whole class.", "start": 1320.25, "duration": 1.9}, {"text": "What's the only time that\nthis alpha-E could actually", "start": 1322.15, "duration": 2.79}, {"text": "extend all the way to 0?", "start": 1324.94, "duration": 4.17}, {"text": "What case would that be?", "start": 1329.11, "duration": 2.68}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 1331.79, "duration": 1.34}, {"text": "AUDIENCE: You're\nhitting another neutron.", "start": 1333.13, "duration": 1.708}, {"text": "MICHAEL SHORT: You're hitting\nanother neutron, which,", "start": 1334.838, "duration": 2.209}, {"text": "as we said, is a\nvery rare event.", "start": 1337.047, "duration": 1.613}, {"text": "That is true.", "start": 1338.66, "duration": 1.11}, {"text": "Or what else could\nyou be hitting?", "start": 1339.77, "duration": 1.542}, {"text": "AUDIENCE: A proton?", "start": 1341.312, "duration": 1.478}, {"text": "MICHAEL SHORT: A proton,\nhydrogen. That's right.", "start": 1342.79, "duration": 2.14}, {"text": "So it can only be,\nlet's say you can only", "start": 1344.93, "duration": 3.18}, {"text": "have the probability of\nthe neutron ending up", "start": 1348.11, "duration": 2.58}, {"text": "with any energy for the case\nof hydrogen. Incidentally,", "start": 1350.69, "duration": 8.44}, {"text": "this is why we fill\nlight water reactors", "start": 1359.13, "duration": 2.13}, {"text": "with hydrogen.\nThe goal is to get", "start": 1361.26, "duration": 2.16}, {"text": "the neutrons as slow as\npossible as quick as possible.", "start": 1363.42, "duration": 3.66}, {"text": "Interesting sentence\nto say there, right?", "start": 1367.08, "duration": 1.98}, {"text": "We want the neutrons to be\nas low energy as possible", "start": 1369.06, "duration": 3.36}, {"text": "as rapidly as possible.", "start": 1372.42, "duration": 1.92}, {"text": "And the best way to do\nthat is to fill the reactor", "start": 1374.34, "duration": 2.43}, {"text": "with hydrogen because then any\ncollision could, in theory, get", "start": 1376.77, "duration": 3.3}, {"text": "the neutron down to zero energy.", "start": 1380.07, "duration": 2.19}, {"text": "Without water, or something\nwith the same mass as a neutron,", "start": 1382.26, "duration": 3.42}, {"text": "like another neutron,\nthere is no way", "start": 1385.68, "duration": 3.92}, {"text": "that that neutron can\nslow down by very much.", "start": 1389.6, "duration": 2.088}, {"text": "So even though we're\ngoing to keep it", "start": 1391.688, "duration": 1.542}, {"text": "as this generalized function,\nnote that in reality it's", "start": 1393.23, "duration": 3.03}, {"text": "this pretty simple function.", "start": 1396.26, "duration": 2.01}, {"text": "It changes a little\nbit, as there", "start": 1398.27, "duration": 1.92}, {"text": "can be a forward scattering\nbias for some neutron reactions.", "start": 1400.19, "duration": 3.84}, {"text": "But we are not going to\ndeal with that this year.", "start": 1404.03, "duration": 2.97}, {"text": "You will deal with that\nnext year in 22.05.", "start": 1407.0, "duration": 3.89}, {"text": "So I've been saying a\nlot, oh, well, we're", "start": 1410.89, "duration": 1.95}, {"text": "not going to go into this topic\nbecause you're going to see it", "start": 1412.84, "duration": 2.583}, {"text": "in 22.02, which is quantum.", "start": 1415.423, "duration": 1.797}, {"text": "Now I switched\ngears to say, we're", "start": 1417.22, "duration": 1.83}, {"text": "not going to go into the\nway this function changes", "start": 1419.05, "duration": 2.58}, {"text": "because you'll see it\nnext year in 22.05,", "start": 1421.63, "duration": 2.31}, {"text": "which is neutron physics.", "start": 1423.94, "duration": 1.56}, {"text": "But for now I want you\nto be prepared for 22.05.", "start": 1425.5, "duration": 3.99}, {"text": "So we'll put on in-scattering\nas one of our gains.", "start": 1429.49, "duration": 3.825}, {"text": "There's a last one I want\nto make you aware of.", "start": 1436.702, "duration": 1.958}, {"text": "We very briefly touched upon it.", "start": 1438.66, "duration": 1.483}, {"text": "But I wouldn't be surprised\nif no one remembers because it", "start": 1440.143, "duration": 2.417}, {"text": "was for like 10 seconds.", "start": 1442.56, "duration": 2.375}, {"text": "It's what's called\nphoto fission.", "start": 1444.935, "duration": 1.375}, {"text": "What this means is you have some\nreaction that would, in comes", "start": 1450.617, "duration": 2.583}, {"text": "a gamma, and out goes fission.", "start": 1453.2, "duration": 4.99}, {"text": "This actually does start to\nhappen around 3 or 4 MeV,", "start": 1458.19, "duration": 4.12}, {"text": "for isotopes like uranium 235.", "start": 1462.31, "duration": 2.72}, {"text": "And in our reactor, whatever\nshape we decide it is,", "start": 1465.03, "duration": 4.77}, {"text": "there are tons of gamma rays\nflying about in all directions", "start": 1469.8, "duration": 3.15}, {"text": "at very high energy.", "start": 1472.95, "duration": 1.07}, {"text": "Does anyone remember\nwhere they come from?", "start": 1474.02, "duration": 1.75}, {"text": "Anyone remember the\nfission timeline", "start": 1482.82, "duration": 3.11}, {"text": "that we drew on Friday?", "start": 1485.93, "duration": 2.83}, {"text": "So what we said\nthere was right away,", "start": 1488.76, "duration": 2.48}, {"text": "let's say fission happens.", "start": 1491.24, "duration": 2.2}, {"text": "And almost instantly, you\nget your fission product one", "start": 1493.44, "duration": 5.08}, {"text": "and fission product two.", "start": 1498.52, "duration": 2.23}, {"text": "And they move around\nfor a little while.", "start": 1500.75, "duration": 2.35}, {"text": "And then some of them\nwill emit some neutrons.", "start": 1503.1, "duration": 2.825}, {"text": "And then some of them will\nstart to emit gamma rays, betas,", "start": 1509.27, "duration": 3.84}, {"text": "and whatever else they're\ngoing to do until they finally", "start": 1513.11, "duration": 6.05}, {"text": "lose all their kinetic energy\nand stop in the surrounding", "start": 1519.16, "duration": 3.21}, {"text": "fuel, creating the heat that\nactually powers the turbine", "start": 1522.37, "duration": 3.96}, {"text": "and make steam to\nmake electricity.", "start": 1526.33, "duration": 2.88}, {"text": "And so it's from these\ngammas, as well as", "start": 1529.21, "duration": 2.19}, {"text": "any of the gammas from the\ndecay products of the fission", "start": 1531.4, "duration": 3.75}, {"text": "products that lead to a huge\nflux of gamma rays firing out", "start": 1535.15, "duration": 3.84}, {"text": "from all sides in the reactor.", "start": 1538.99, "duration": 1.65}, {"text": "That's one of the main\nthings that you actually have", "start": 1540.64, "duration": 2.167}, {"text": "to shield in a nuclear reactor.", "start": 1542.807, "duration": 1.943}, {"text": "Since we talked about all\nsorts of different shielding,", "start": 1544.75, "duration": 2.82}, {"text": "and all sorts of ways that\nyou have to shield things,", "start": 1547.57, "duration": 2.88}, {"text": "you know from seeing the MIT\nreactor-- which you all did--", "start": 1550.45, "duration": 3.18}, {"text": "that there's like six\nfeet of lead and concrete", "start": 1553.63, "duration": 2.64}, {"text": "shielding around the reactor.", "start": 1556.27, "duration": 1.83}, {"text": "It's not there to shield\nthe alphas and the betas,", "start": 1558.1, "duration": 2.37}, {"text": "because those don't really\nmake it out of the water.", "start": 1560.47, "duration": 2.62}, {"text": "It's not there to shield\nthe soft X-rays that betas", "start": 1563.09, "duration": 2.66}, {"text": "make from bremsstrahlung.", "start": 1565.75, "duration": 2.37}, {"text": "It's also not there\nto shield the neutrons", "start": 1568.12, "duration": 2.51}, {"text": "because the neutrons\ndon't really get out.", "start": 1570.63, "duration": 1.75}, {"text": "They bounce around, or\nget absorbed in the water,", "start": 1572.38, "duration": 2.92}, {"text": "or the fuel, the reflector.", "start": 1575.3, "duration": 1.54}, {"text": "It's there to shield the\nhigh-energy gamma rays.", "start": 1576.84, "duration": 2.98}, {"text": "Because the only\nthing that stops", "start": 1579.82, "duration": 1.38}, {"text": "high energy gamma\nrays is lots of mass", "start": 1581.2, "duration": 2.55}, {"text": "in between the source and you.", "start": 1583.75, "duration": 2.73}, {"text": "So we know there's tons\nof gammas all about.", "start": 1586.48, "duration": 2.87}, {"text": "So let's say there's also going\nto be some gamma ray flux.", "start": 1589.35, "duration": 6.67}, {"text": "There'll be some\ngamma ray energy.", "start": 1596.02, "duration": 2.49}, {"text": "And there'll be some\ncross-section for photo fission", "start": 1598.51, "duration": 4.23}, {"text": "as a function of the incoming\ngamma ray energy spectrum.", "start": 1602.74, "duration": 5.5}, {"text": "Now I'm adding terms to the ones\nthat you'll see in the reading", "start": 1608.24, "duration": 3.42}, {"text": "because drawing them out in math\nis actually fairly instructive.", "start": 1611.66, "duration": 3.69}, {"text": "They all follow\nthe same pattern.", "start": 1615.35, "duration": 1.46}, {"text": "So instead of just\nshowing you one of each", "start": 1616.81, "duration": 1.75}, {"text": "and saying memorize, we'll\ndevelop a whole lot of these.", "start": 1618.56, "duration": 3.155}, {"text": "And you'll find\nout that they all", "start": 1621.715, "duration": 1.375}, {"text": "actually look almost the same.", "start": 1623.09, "duration": 1.57}, {"text": "Can anyone else think of any\npossible gains of neutrons?", "start": 1627.22, "duration": 4.037}, {"text": "Where else could they come from?", "start": 1631.257, "duration": 1.333}, {"text": "Yeah?", "start": 1635.7, "duration": 0.64}, {"text": "AUDIENCE: Neutron birth\nspectrum, is that?", "start": 1636.34, "duration": 2.067}, {"text": "MICHAEL SHORT: So the\nneutron birth spectrum", "start": 1638.407, "duration": 1.833}, {"text": "is included in fission.", "start": 1640.24, "duration": 2.04}, {"text": "So our nu is in there.", "start": 1642.28, "duration": 2.67}, {"text": "Our chi of E is in there.", "start": 1644.95, "duration": 1.53}, {"text": "And that's a nu of E.\nThat's all accounted", "start": 1646.48, "duration": 2.82}, {"text": "for in the fission term.", "start": 1649.3, "duration": 1.14}, {"text": "And we'll see how we put\nthat together to math.", "start": 1650.44, "duration": 2.373}, {"text": "And if no one else has\nany ideas, that's good.", "start": 1652.813, "duration": 1.917}, {"text": "Because neither do I.", "start": 1654.73, "duration": 1.8}, {"text": "Now what about the lost terms?", "start": 1656.53, "duration": 2.1}, {"text": "There aren't too many\nof these, as long", "start": 1658.63, "duration": 2.07}, {"text": "as you lump them correctly.", "start": 1660.7, "duration": 2.56}, {"text": "So what sort of\nways could neutrons", "start": 1663.26, "duration": 1.91}, {"text": "be lost from our energy group?", "start": 1665.17, "duration": 3.438}, {"text": "Yep?", "start": 1668.608, "duration": 0.872}, {"text": "AUDIENCE: Scatter out.", "start": 1669.48, "duration": 1.43}, {"text": "MICHAEL SHORT: Scatter out, yep.", "start": 1670.91, "duration": 2.202}, {"text": "They can undergo any kind\nof scattering reaction.", "start": 1676.57, "duration": 2.13}, {"text": "And they will probably\nchange direction and energy.", "start": 1678.7, "duration": 2.52}, {"text": "What else?", "start": 1681.22, "duration": 2.7}, {"text": "Well, we've got to list up on\nthe board right there, right?", "start": 1683.92, "duration": 4.16}, {"text": "Capture, fission,\nbecause in order", "start": 1688.08, "duration": 5.85}, {"text": "to undergo a vision you\nactually have to lose a neutron,", "start": 1693.93, "duration": 5.41}, {"text": "and so on, and so on, and so on.", "start": 1699.34, "duration": 1.47}, {"text": "What I want to do to\nsimplify things is this.", "start": 1700.81, "duration": 4.55}, {"text": "It's a lot simpler just to\ntrack the total cross-section,", "start": 1708.75, "duration": 4.38}, {"text": "the probability\nof any interaction", "start": 1713.13, "duration": 1.8}, {"text": "at all whatsoever,\nbecause any interaction", "start": 1714.93, "duration": 2.64}, {"text": "will cause the neutron to\neither change energy and angle,", "start": 1717.57, "duration": 3.69}, {"text": "or disappear, even if it\nmakes some other ones.", "start": 1721.26, "duration": 3.6}, {"text": "So we can simplify this to just\nthe total cross-section term.", "start": 1724.86, "duration": 4.97}, {"text": "And there's only one\nother way that neutrons", "start": 1729.83, "duration": 2.02}, {"text": "can leave our energy\nangle and volume group.", "start": 1731.85, "duration": 4.578}, {"text": "What would that be?", "start": 1736.428, "duration": 0.792}, {"text": "So any reaction takes\ncare of energy and angle.", "start": 1741.27, "duration": 3.42}, {"text": "What about volume?", "start": 1744.69, "duration": 2.212}, {"text": "How do neutrons leave\nthe control volume?", "start": 1746.902, "duration": 1.708}, {"text": "It's simpler than it may sound.", "start": 1752.47, "duration": 2.27}, {"text": "They just go.", "start": 1754.74, "duration": 1.08}, {"text": "They just move.", "start": 1755.82, "duration": 1.23}, {"text": "The neutrons are\nalways moving, right?", "start": 1757.05, "duration": 1.94}, {"text": "We'll call that leakage.", "start": 1758.99, "duration": 1.0}, {"text": "Because every neutron's got a\nspeed, like we showed up here,", "start": 1763.65, "duration": 6.73}, {"text": "where the flux of\nneutrons, the number", "start": 1770.38, "duration": 2.34}, {"text": "of neutrons moving through\nsome surface per second,", "start": 1772.72, "duration": 3.48}, {"text": "is just their velocity times\nthe number that are there.", "start": 1776.2, "duration": 3.18}, {"text": "For there to be a\nneutron flux there", "start": 1779.38, "duration": 1.5}, {"text": "has to be a velocity, which\nmeans the neutrons are moving.", "start": 1780.88, "duration": 2.91}, {"text": "So the neutrons, even without\nundergoing any reaction,", "start": 1783.79, "duration": 2.88}, {"text": "could just move out\nof our control volume.", "start": 1786.67, "duration": 2.683}, {"text": "And then they're gone.", "start": 1789.353, "duration": 0.917}, {"text": "And that's all there is\nfor gain and loss terms.", "start": 1793.49, "duration": 2.56}, {"text": "So let's see if we can\ndo this all on one board.", "start": 1796.05, "duration": 4.16}, {"text": "I want to start putting this\ntable right here into math", "start": 1800.21, "duration": 4.5}, {"text": "that we'll be able to abstract,\nsimplify, and then solve,", "start": 1804.71, "duration": 3.38}, {"text": "but not today, not solve today.", "start": 1808.09, "duration": 2.5}, {"text": "So if we want to\ntrack the change", "start": 1810.59, "duration": 1.71}, {"text": "in the number of neutrons\nas a function of time,", "start": 1812.3, "duration": 8.97}, {"text": "let's start writing\ndown the gain terms.", "start": 1821.27, "duration": 2.97}, {"text": "So how do we describe\nthe number of neutrons", "start": 1824.24, "duration": 2.25}, {"text": "produced from fission?", "start": 1826.49, "duration": 3.522}, {"text": "What sort of terms do\nwe have to include?", "start": 1830.012, "duration": 1.708}, {"text": "And Jared started kicking us\noff, so what would you say?", "start": 1835.027, "duration": 2.333}, {"text": "AUDIENCE: Neutron birth?", "start": 1839.94, "duration": 1.0}, {"text": "MICHAEL SHORT: Yep, so the\nneutron birth spectrum,", "start": 1840.94, "duration": 2.09}, {"text": "there's going to be some\nprobability that a neutron is", "start": 1843.03, "duration": 3.48}, {"text": "born in our energy\ngroup E. Because we're", "start": 1846.51, "duration": 3.33}, {"text": "tracking how many neutrons are\nin our little dE energy group.", "start": 1849.84, "duration": 4.74}, {"text": "What else matters\nin terms of fission?", "start": 1854.58, "duration": 4.74}, {"text": "AUDIENCE: Number of fissions?", "start": 1862.645, "duration": 1.905}, {"text": "MICHAEL SHORT: Yep,\nnumber of fissions.", "start": 1864.55, "duration": 1.72}, {"text": "So if we want to write\nnumber of fissions,", "start": 1866.27, "duration": 1.75}, {"text": "we have to write that\nas a reaction rate.", "start": 1868.02, "duration": 2.91}, {"text": "So let's take those\ntwo terms right there.", "start": 1870.93, "duration": 2.98}, {"text": "So we'll have sigma fission.", "start": 1873.91, "duration": 4.32}, {"text": "In this case, we're going\nto write E-prime times flux", "start": 1878.23, "duration": 4.38}, {"text": "of r E-prime, omega-prime, t.", "start": 1882.61, "duration": 6.98}, {"text": "Why did I write E\nand omega prime here?", "start": 1889.59, "duration": 2.22}, {"text": "Just from a physical reason.", "start": 1895.64, "duration": 1.29}, {"text": "Yeah?", "start": 1896.93, "duration": 0.18}, {"text": "AUDIENCE: So you're going to\nbe coming from another energy", "start": 1897.11, "duration": 1.84}, {"text": "group.", "start": 1898.95, "duration": 0.92}, {"text": "MICHAEL SHORT: Precisely.", "start": 1899.87, "duration": 1.47}, {"text": "That's right.", "start": 1901.34, "duration": 0.57}, {"text": "So the neutrons are going to be\nproduced from some other energy", "start": 1901.91, "duration": 3.84}, {"text": "group.", "start": 1905.75, "duration": 0.75}, {"text": "For example, the fission\nbirth spectrum right here", "start": 1906.5, "duration": 2.88}, {"text": "starts out--", "start": 1909.38, "duration": 1.223}, {"text": "where did it go?", "start": 1910.603, "duration": 0.667}, {"text": "I knew I drew it\nsomewhere-- at one MeV.", "start": 1911.27, "duration": 2.88}, {"text": "But most of the neutrons\nthat cause fission to happen", "start": 1914.15, "duration": 3.27}, {"text": "are way down below 1 eV.", "start": 1917.42, "duration": 2.79}, {"text": "So it's different\nenergy neutrons", "start": 1920.21, "duration": 2.19}, {"text": "that cause neutrons to be\nborn in our energy group.", "start": 1922.4, "duration": 3.12}, {"text": "That's why we're using\nE-prime and not E.", "start": 1925.52, "duration": 2.16}, {"text": "It's some other energy group.", "start": 1927.68, "duration": 3.48}, {"text": "And so we also have to account\nfor all possible other energy", "start": 1931.16, "duration": 5.65}, {"text": "groups.", "start": 1936.81, "duration": 0.692}, {"text": "So if we want to write\nthis, right, we'll", "start": 1937.502, "duration": 1.708}, {"text": "say this could be as low as\n0 eV, to our maximum energy.", "start": 1939.21, "duration": 8.8}, {"text": "And there's going to be some\nd-omega-prime, dE-prime, dV.", "start": 1948.01, "duration": 7.97}, {"text": "We'll also have to account\nfor all possible angles", "start": 1955.98, "duration": 5.94}, {"text": "and integrate over\nour entire volume.", "start": 1961.92, "duration": 5.85}, {"text": "It's going to look ugly\nquick, but it's all", "start": 1967.77, "duration": 1.93}, {"text": "going to be understandable.", "start": 1969.7, "duration": 2.16}, {"text": "So what this says\nis that we have", "start": 1971.86, "duration": 1.5}, {"text": "to account for the\nreaction rate of fission", "start": 1973.36, "duration": 3.0}, {"text": "from all other energy\nneutrons inside our volume", "start": 1976.36, "duration": 4.29}, {"text": "from other energies\nand other angles,", "start": 1980.65, "duration": 2.01}, {"text": "and account for every\nother possible energy.", "start": 1982.66, "duration": 2.82}, {"text": "Because they can all\nmake fission happen.", "start": 1985.48, "duration": 3.15}, {"text": "What else is missing in terms\nof describing the number", "start": 1988.63, "duration": 2.37}, {"text": "of neutrons made from fission?", "start": 1991.0, "duration": 3.051}, {"text": "AUDIENCE: Neutron\nmultiplication.", "start": 1994.051, "duration": 1.375}, {"text": "MICHAEL SHORT: Yep,\nthere's the number", "start": 1995.426, "duration": 1.583}, {"text": "of neutrons made per fission.", "start": 1997.009, "duration": 1.931}, {"text": "So we have to put in our\nneutron multiplication factor.", "start": 1998.94, "duration": 4.75}, {"text": "And in this case, normalize--", "start": 2003.69, "duration": 2.35}, {"text": "I think someone had mentioned\nsolid angle-- we normalize over", "start": 2006.04, "duration": 2.87}, {"text": "all possible angles with\nan over 4 pi in there.", "start": 2008.91, "duration": 3.66}, {"text": "And this right here\nis the fission term.", "start": 2012.57, "duration": 2.89}, {"text": "So this tells us the\nnumber of neutrons", "start": 2015.46, "duration": 2.03}, {"text": "gained in terms of\na reaction rate,", "start": 2017.49, "duration": 2.97}, {"text": "times the number of neutrons\nfor each of those reactions,", "start": 2020.46, "duration": 4.29}, {"text": "times the probability\nthat there just", "start": 2024.75, "duration": 1.68}, {"text": "happened to be born\nin the energy group", "start": 2026.43, "duration": 1.71}, {"text": "that we're tracking.", "start": 2028.14, "duration": 2.76}, {"text": "So is there any term here\nthat's unclear to folks?", "start": 2030.9, "duration": 3.48}, {"text": "Yeah?", "start": 2034.38, "duration": 0.63}, {"text": "AUDIENCE: So what's the lower\nbound on the first integral?", "start": 2035.01, "duration": 2.1}, {"text": "MICHAEL SHORT: On\nthe first integral?", "start": 2037.11, "duration": 1.542}, {"text": "That 0 electron volts.", "start": 2038.652, "duration": 0.918}, {"text": "AUDIENCE: Oh, OK.", "start": 2039.57, "duration": 0.738}, {"text": "MICHAEL SHORT:\nBecause supposedly you", "start": 2040.308, "duration": 1.542}, {"text": "could have a neutron\nat 0 eV, which", "start": 2041.85, "duration": 2.64}, {"text": "has a very high cross-section.", "start": 2044.49, "duration": 1.89}, {"text": "So it should probably\ninduce fission.", "start": 2046.38, "duration": 2.37}, {"text": "In reality, there might be some\nactual minimum temperature.", "start": 2048.75, "duration": 3.179}, {"text": "But there is a\nnon-zero probability", "start": 2051.929, "duration": 2.701}, {"text": "that you could have\na neutron at rest.", "start": 2054.63, "duration": 2.078}, {"text": "It's just not very large.", "start": 2056.708, "duration": 1.042}, {"text": "AUDIENCE: And the top bound?", "start": 2057.75, "duration": 1.02}, {"text": "MICHAEL SHORT: The top\nbound as E max, whatever", "start": 2058.77, "duration": 1.958}, {"text": "your maximum neutron energy is.", "start": 2060.728, "duration": 2.032}, {"text": "This is usually around 10 MeV,\nfor most fission reactors.", "start": 2062.76, "duration": 5.91}, {"text": "That E max is going to be this\npoint right here, the highest", "start": 2068.67, "duration": 4.93}, {"text": "energy at which neutrons\ncan be born by any process.", "start": 2073.6, "duration": 5.15}, {"text": "And so this term\nright here is going", "start": 2078.75, "duration": 2.4}, {"text": "to serve as a template for all\nthe other gain and loss terms.", "start": 2081.15, "duration": 4.612}, {"text": "So I think this is the\nhardest one that we had", "start": 2085.762, "duration": 1.917}, {"text": "to develop from the beginning.", "start": 2087.679, "duration": 1.951}, {"text": "Now let's develop the\nterm for, let's just", "start": 2089.63, "duration": 4.6}, {"text": "go with external\nsources, pretty easy.", "start": 2094.23, "duration": 2.8}, {"text": "There's going to be some\nsource making neutrons.", "start": 2097.03, "duration": 3.035}, {"text": "It's something that\nyou would just impose.", "start": 2105.5, "duration": 2.4}, {"text": "Like say, all right, I have a\ncalifornium source giving off", "start": 2107.9, "duration": 2.76}, {"text": "this many neutrons.", "start": 2110.66, "duration": 1.242}, {"text": "Well then you know how many\nneutrons it's giving off.", "start": 2111.902, "duration": 2.208}, {"text": "And that one's done.", "start": 2114.11, "duration": 0.96}, {"text": "That's easy.", "start": 2115.07, "duration": 1.57}, {"text": "So we've done fission.", "start": 2116.64, "duration": 2.85}, {"text": "We've done external.", "start": 2119.49, "duration": 0.97}, {"text": "Now that we've done fission\nlet's tackle photo fission.", "start": 2123.69, "duration": 4.5}, {"text": "So what would be photo fission\ncross-section look like?", "start": 2128.19, "duration": 2.6}, {"text": "It's going to look\nawfully similar.", "start": 2139.84, "duration": 2.453}, {"text": "So what sort of\nthings do you need", "start": 2142.293, "duration": 1.417}, {"text": "to know if it's a\nfission reaction?", "start": 2143.71, "duration": 1.458}, {"text": "Well, what do we have up here?", "start": 2150.46, "duration": 1.25}, {"text": "Just start reading things off.", "start": 2151.71, "duration": 1.25}, {"text": "I heard a murmur.", "start": 2156.392, "duration": 0.708}, {"text": "What was that?", "start": 2157.1, "duration": 0.71}, {"text": "AUDIENCE: [INAUDIBLE] flux.", "start": 2157.81, "duration": 1.45}, {"text": "MICHAEL SHORT: Yeah,\nso you're going", "start": 2159.26, "duration": 1.5}, {"text": "to have to have some flux.", "start": 2160.76, "duration": 2.14}, {"text": "In this case, we want to know\nwhat's the flux of gamma rays", "start": 2162.9, "duration": 4.41}, {"text": "because photo fission\nstarts off with a gamma,", "start": 2167.31, "duration": 2.39}, {"text": "then ends up with a fission.", "start": 2169.7, "duration": 1.69}, {"text": "And it's also going\nto be in our volume.", "start": 2171.39, "duration": 3.21}, {"text": "It's going to matter what the\nenergy of those gammas is.", "start": 2174.6, "duration": 3.51}, {"text": "They'll all be traveling in\nsome direction at some time.", "start": 2178.11, "duration": 4.14}, {"text": "What else do we need?", "start": 2182.25, "duration": 3.08}, {"text": "AUDIENCE: [INAUDIBLE]\nthe 4 pi [INAUDIBLE]..", "start": 2185.33, "duration": 2.122}, {"text": "MICHAEL SHORT:\nYeah, if we're going", "start": 2187.452, "duration": 1.458}, {"text": "to be going over all\nangles, you need the 4 pi.", "start": 2188.91, "duration": 5.1}, {"text": "What else?", "start": 2194.01, "duration": 0.54}, {"text": "Do we have a reaction rate yet?", "start": 2198.23, "duration": 2.944}, {"text": "AUDIENCE: No.", "start": 2201.174, "duration": 0.846}, {"text": "MICHAEL SHORT: No,\nwell what's missing?", "start": 2202.02, "duration": 2.432}, {"text": "AUDIENCE: The cross-section.", "start": 2204.452, "duration": 1.871}, {"text": "MICHAEL SHORT: That's right.", "start": 2206.323, "duration": 1.167}, {"text": "We need a cross-section.", "start": 2207.49, "duration": 1.79}, {"text": "And in this case,\ninstead of just fission,", "start": 2209.28, "duration": 1.84}, {"text": "or neutron fission, we'll\nput in the gamma fission", "start": 2211.12, "duration": 3.63}, {"text": "cross-section.", "start": 2214.75, "duration": 2.81}, {"text": "And so now we have a reaction\nrate for a single reaction.", "start": 2217.56, "duration": 3.54}, {"text": "We've got to integrate\nover all of our gamma ray", "start": 2221.1, "duration": 3.57}, {"text": "energies, over all\nangles, over our volume.", "start": 2224.67, "duration": 6.04}, {"text": "What else is missing besides\nour d-omega, dE gamma, d-Volume.", "start": 2230.71, "duration": 16.07}, {"text": "It should look awfully similar\nbecause the terms are basically", "start": 2246.78, "duration": 2.64}, {"text": "exactly the same, with just\ndifferent cross sections", "start": 2249.42, "duration": 2.323}, {"text": "and energies in there.", "start": 2251.743, "duration": 0.917}, {"text": "So what's missing between the\nphoto fission and the neutron", "start": 2252.66, "duration": 2.94}, {"text": "fission one?", "start": 2255.6, "duration": 1.406}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2257.006, "duration": 1.691}, {"text": "MICHAEL SHORT: Sure, there\nmight be some different birth", "start": 2258.697, "duration": 2.333}, {"text": "spectrum for gammas.", "start": 2261.03, "duration": 2.706}, {"text": "And there might be some\ndifferent multiplication", "start": 2263.736, "duration": 2.064}, {"text": "factor for gammas between\nneutron fission and photo", "start": 2265.8, "duration": 3.77}, {"text": "fission.", "start": 2269.57, "duration": 0.68}, {"text": "But these terms should\nlook exactly the same", "start": 2270.25, "duration": 2.07}, {"text": "because in every case you're\nlooking at some reaction", "start": 2272.32, "duration": 3.03}, {"text": "rate between either the neutrons\nand fission or the gamma", "start": 2275.35, "duration": 3.42}, {"text": "and fission.", "start": 2278.77, "duration": 1.38}, {"text": "And you need to know at\nwhat energy they're born,", "start": 2280.15, "duration": 2.52}, {"text": "how many are made,\nall the angles,", "start": 2282.67, "duration": 2.97}, {"text": "and integrate overall the\nvariables that we care about.", "start": 2285.64, "duration": 2.96}, {"text": "And this is part of why I'm\nadding these extra terms", "start": 2288.6, "duration": 2.32}, {"text": "because they end up looking\nall exactly the same.", "start": 2290.92, "duration": 2.88}, {"text": "It's the integral of a\nreaction rate times some stuff.", "start": 2293.8, "duration": 4.48}, {"text": "That's all that every single one\nof these terms is going to be.", "start": 2298.28, "duration": 2.95}, {"text": "So we've got photo fission.", "start": 2301.23, "duration": 1.82}, {"text": "Now let's tackle in-scattering.", "start": 2303.05, "duration": 3.86}, {"text": "So how do we\nrepresent scattering?", "start": 2306.91, "duration": 1.92}, {"text": "In the same way that we\nrepresented fission, what do we", "start": 2311.58, "duration": 3.58}, {"text": "start with inside the integral?", "start": 2315.16, "duration": 2.97}, {"text": "AUDIENCE: Reaction rate?", "start": 2318.13, "duration": 1.0}, {"text": "MICHAEL SHORT:\nReaction rate, yes.", "start": 2319.13, "duration": 1.77}, {"text": "So we're going to have some\nscattering cross-section.", "start": 2320.9, "duration": 3.945}, {"text": "And if it's in\nthe scattering, it", "start": 2324.845, "duration": 1.375}, {"text": "means it's coming from a\ndifferent energy, hence", "start": 2326.22, "duration": 2.49}, {"text": "the prime.", "start": 2328.71, "duration": 1.467}, {"text": "We'll have our flux.", "start": 2330.177, "duration": 0.833}, {"text": "And here's where we're going to\nbring in our scattering kernel.", "start": 2337.84, "duration": 3.99}, {"text": "Because there's some\nprobability that the neutron", "start": 2341.83, "duration": 2.88}, {"text": "scatters in from\na different group.", "start": 2344.71, "duration": 2.49}, {"text": "And then we'll have our\nd-omega, dE-prime, dV.", "start": 2355.18, "duration": 6.325}, {"text": "Is this complete yet?", "start": 2361.505, "duration": 0.875}, {"text": "We've now accounted for\none other energy, E-prime.", "start": 2368.63, "duration": 4.07}, {"text": "Now how do we account for\nall possible other energies", "start": 2372.7, "duration": 2.6}, {"text": "scattering into\nour energy group?", "start": 2375.3, "duration": 1.913}, {"text": "AUDIENCE: Integrals.", "start": 2377.213, "duration": 0.927}, {"text": "MICHAEL SHORT: Yep,\nagain, same integrals.", "start": 2378.14, "duration": 2.54}, {"text": "We integrate over all\npossible energies,", "start": 2380.68, "duration": 4.79}, {"text": "over all possible angles,\nand over our volume.", "start": 2385.47, "duration": 5.72}, {"text": "Hopefully these terms\nare looking very similar.", "start": 2391.19, "duration": 2.16}, {"text": "In every case it's a volume,\nangle, energy integral", "start": 2393.35, "duration": 4.47}, {"text": "of a reaction rate.", "start": 2397.82, "duration": 1.545}, {"text": "And all that's saying is there's\nsome rate that these reactions", "start": 2399.365, "duration": 2.625}, {"text": "are occurring, which is either\na gain rate or a loss rate.", "start": 2401.99, "duration": 3.78}, {"text": "We integrate over whatever\nvolume, energy, and angle", "start": 2405.77, "duration": 2.31}, {"text": "we're tracking.", "start": 2408.08, "duration": 0.72}, {"text": "And that's all there is to it.", "start": 2408.8, "duration": 2.04}, {"text": "So we've got in-scattering.", "start": 2410.84, "duration": 1.623}, {"text": "Now let's tackle\nthe n,in reactions.", "start": 2416.54, "duration": 4.182}, {"text": "There's only going to be\none little difference.", "start": 2420.722, "duration": 1.958}, {"text": "But I want you guys to\ntell me what sort of things", "start": 2422.68, "duration": 2.083}, {"text": "are going to be the same\nas all the other terms", "start": 2424.763, "duration": 2.267}, {"text": "that we have here.", "start": 2427.03, "duration": 0.75}, {"text": "So what do we start off\nwith inside the integral?", "start": 2431.66, "duration": 3.1}, {"text": "AUDIENCE: Reaction rate.", "start": 2434.76, "duration": 1.0}, {"text": "MICHAEL SHORT: A reaction rate.", "start": 2435.76, "duration": 1.292}, {"text": "And how do we write that?", "start": 2437.052, "duration": 1.558}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 2438.61, "duration": 1.0}, {"text": "MICHAEL SHORT: Yep,\na cross-section,", "start": 2443.11, "duration": 2.395}, {"text": "there's going to be\nsome cross-section,", "start": 2445.505, "duration": 1.625}, {"text": "for, let's call it n,in reaction\nas a function of energy,", "start": 2447.13, "duration": 5.87}, {"text": "times a flux.", "start": 2453.0, "duration": 0.71}, {"text": "There'll be our normal\nintegrated over all angles,", "start": 2458.29, "duration": 4.68}, {"text": "all energies, and our volume.", "start": 2462.97, "duration": 3.97}, {"text": "So we have a reaction rate.", "start": 2466.94, "duration": 1.26}, {"text": "What do we have to then\nintegrate that reaction right", "start": 2468.2, "duration": 3.09}, {"text": "over to get all the neutrons in?", "start": 2471.29, "duration": 1.62}, {"text": "AUDIENCE: [INAUDIBLE]\nsame things.", "start": 2476.375, "duration": 3.475}, {"text": "MICHAEL SHORT: Same things\nas everything else, exactly.", "start": 2479.85, "duration": 2.55}, {"text": "Integrate over all\npossible energies,", "start": 2482.4, "duration": 3.65}, {"text": "integrate over all\npossible angles,", "start": 2486.05, "duration": 1.83}, {"text": "integrate over our volume,\nlooks quite similar.", "start": 2487.88, "duration": 3.75}, {"text": "The only thing we haven't dealt\nwith is this i term right here.", "start": 2491.63, "duration": 4.63}, {"text": "Because there can be, there are\nactually n,2n reactions, n,3n,", "start": 2496.26, "duration": 9.53}, {"text": "n,4n, and so on.", "start": 2505.79, "duration": 3.77}, {"text": "So there are probabilities\nthat, let's say", "start": 2509.56, "duration": 2.51}, {"text": "you, in goes 1 neutron,\nout comes 3 neutrons.", "start": 2512.07, "duration": 3.06}, {"text": "But no fission\nactually happened.", "start": 2515.13, "duration": 1.68}, {"text": "You just blast a\nfew of them out.", "start": 2516.81, "duration": 1.95}, {"text": "So I think all we'd really have\nto do is sum over i equals 1.", "start": 2518.76, "duration": 6.015}, {"text": "Oh, I'm sorry, i equals\n2, because a neutron", "start": 2524.775, "duration": 2.94}, {"text": "going in and then the\nsame neutron going out,", "start": 2527.715, "duration": 1.875}, {"text": "that's just scattering.", "start": 2529.59, "duration": 1.41}, {"text": "And what would be the maximum?", "start": 2531.0, "duration": 4.05}, {"text": "Probably 4.", "start": 2535.05, "duration": 2.39}, {"text": "Because the probability\nof an increasing i", "start": 2537.44, "duration": 2.43}, {"text": "or more neutrons coming out\ngets lower and lower as you go.", "start": 2539.87, "duration": 4.53}, {"text": "In fact, these reactions\ndon't even turn on until--", "start": 2544.4, "duration": 3.24}, {"text": "the n,2n reaction turns\non and around like 1 MeV.", "start": 2547.64, "duration": 4.62}, {"text": "This one turns on and\naround like 5 MeV.", "start": 2552.26, "duration": 3.81}, {"text": "This one turns on\nat like 12 MeV.", "start": 2556.07, "duration": 1.86}, {"text": "I was just looking up these\ncross-sections before class.", "start": 2557.93, "duration": 4.48}, {"text": "So if you have a reaction\nthat doesn't happen", "start": 2562.41, "duration": 2.6}, {"text": "beyond your highest\nneutron energy,", "start": 2565.01, "duration": 2.4}, {"text": "you probably don't\nneed to worry about it.", "start": 2567.41, "duration": 2.245}, {"text": "But the reason I had us write\nall these extra equations--", "start": 2569.655, "duration": 2.375}, {"text": "and I think that the t-shirt\nfor this department needs some", "start": 2572.03, "duration": 3.48}, {"text": "updating to include\nthese extra terms--", "start": 2575.51, "duration": 2.32}, {"text": "is because they're\nall the same term.", "start": 2577.83, "duration": 2.27}, {"text": "It is in every case,\nit's an integral", "start": 2580.1, "duration": 2.88}, {"text": "over all of our stuff\nof a reaction rate,", "start": 2582.98, "duration": 10.88}, {"text": "d-stuff, times a multiplier.", "start": 2593.86, "duration": 4.23}, {"text": "Every single term\nin this equation", "start": 2601.59, "duration": 2.31}, {"text": "follows the exact same pattern.", "start": 2603.9, "duration": 3.46}, {"text": "So what I hope, and I would\nexpect out of you guys,", "start": 2607.36, "duration": 3.51}, {"text": "is that if I were to\ngive you this table", "start": 2610.87, "duration": 1.92}, {"text": "of possible reactions,\nyou would be", "start": 2612.79, "duration": 2.46}, {"text": "able to recreate this neutron\ntransport equation using", "start": 2615.25, "duration": 4.26}, {"text": "this template to know that\nevery single reaction is just", "start": 2619.51, "duration": 2.52}, {"text": "multiplier, times integral\nof stuff of a reaction rate,", "start": 2622.03, "duration": 3.42}, {"text": "d-stuff, where the reaction rate\nis just a cross-section times", "start": 2625.45, "duration": 4.44}, {"text": "a flux.", "start": 2629.89, "duration": 1.56}, {"text": "That's all there is to it.", "start": 2631.45, "duration": 3.05}, {"text": "Not bad when you see\nthat everything follows", "start": 2634.5, "duration": 1.95}, {"text": "the same pattern, right?", "start": 2636.45, "duration": 2.29}, {"text": "That's the basis behind most\nof the hideous equations", "start": 2638.74, "duration": 2.34}, {"text": "that you see in all\nof physics everywhere,", "start": 2641.08, "duration": 1.86}, {"text": "is if there are additive\nor subtractive terms,", "start": 2642.94, "duration": 2.76}, {"text": "they'd better be\nin the same units.", "start": 2645.7, "duration": 1.663}, {"text": "And so they're going\nto follow some sort", "start": 2647.363, "duration": 1.667}, {"text": "of a similar template.", "start": 2649.03, "duration": 2.4}, {"text": "Not too scary when you\nthink of it that way.", "start": 2651.43, "duration": 2.95}, {"text": "So let's now come up\nwith the loss terms.", "start": 2654.38, "duration": 1.955}, {"text": "I should have planned\nthese boards better.", "start": 2660.27, "duration": 2.38}, {"text": "Keep these ones here\nso we keep a template.", "start": 2662.65, "duration": 2.7}, {"text": "And we'll have a\nminus, well, how", "start": 2665.35, "duration": 3.54}, {"text": "do we write the anything\nreaction using this template?", "start": 2668.89, "duration": 6.88}, {"text": "How many neutrons\nundergo a reaction", "start": 2681.16, "duration": 2.09}, {"text": "when one neutron\nundergoes a reaction?", "start": 2683.25, "duration": 1.75}, {"text": "Yeah, 1.", "start": 2688.25, "duration": 0.732}, {"text": "So our multiplier is 1.", "start": 2688.982, "duration": 0.958}, {"text": "We don't have to worry about it.", "start": 2689.94, "duration": 1.69}, {"text": "We have our integral of stuff.", "start": 2691.63, "duration": 1.81}, {"text": "So we'll have to integrate over\nall possible volumes, angles,", "start": 2693.44, "duration": 4.75}, {"text": "and energy.", "start": 2698.19, "duration": 1.35}, {"text": "And what's on the inside?", "start": 2699.54, "duration": 2.945}, {"text": "AUDIENCE: [INAUDIBLE]\ntotal cross-section.", "start": 2702.485, "duration": 2.815}, {"text": "MICHAEL SHORT: Yep,\ntotal cross-section", "start": 2705.3, "duration": 3.92}, {"text": "as a function of energy times\nthe flux, d-stuff to save time.", "start": 2709.22, "duration": 13.24}, {"text": "So don't worry, even though\nthe boards are laid out funny,", "start": 2722.46, "duration": 2.64}, {"text": "on the pictures of the\nblackboard that we'll", "start": 2725.1, "duration": 1.833}, {"text": "put on the Stellar site, I'll\nPhotoshop these and arrange", "start": 2726.933, "duration": 2.375}, {"text": "them so that they're\nall in sequence.", "start": 2729.308, "duration": 1.542}, {"text": "And you can see everything.", "start": 2730.85, "duration": 1.33}, {"text": "And then there's the\nlast term to account for.", "start": 2732.18, "duration": 3.21}, {"text": "That's the leakage term.", "start": 2735.39, "duration": 2.15}, {"text": "This one is a little different.", "start": 2737.54, "duration": 1.66}, {"text": "It's the only one that's\na little different.", "start": 2739.2, "duration": 3.77}, {"text": "And in this case, we're going\nto say that our little volume", "start": 2742.97, "duration": 3.78}, {"text": "element also has\na surface to it.", "start": 2746.75, "duration": 6.39}, {"text": "And if the neutrons\nleave the surface,", "start": 2753.14, "duration": 4.34}, {"text": "then they leave the volume.", "start": 2757.48, "duration": 1.99}, {"text": "So in this case, we'll have a\nsurface integral of our neutron", "start": 2759.47, "duration": 6.3}, {"text": "flux, say our neutron flux dS.", "start": 2765.77, "duration": 5.09}, {"text": "Because there's no reaction\nhappening when neutrons just", "start": 2770.86, "duration": 3.3}, {"text": "move, right.", "start": 2774.16, "duration": 1.68}, {"text": "They just go.", "start": 2775.84, "duration": 1.68}, {"text": "And so, well, we'd also have to\nmultiply by our normal vector.", "start": 2777.52, "duration": 6.132}, {"text": "Because every flux\nis going to have", "start": 2783.652, "duration": 1.458}, {"text": "a certain number of neutrons\nmoving in a certain direction.", "start": 2785.11, "duration": 3.1}, {"text": "Let's say we were tracking\nthe flow of neutrons", "start": 2788.21, "duration": 3.65}, {"text": "through this surface right here.", "start": 2791.86, "duration": 2.45}, {"text": "And if we had a flux going\nin exactly this direction,", "start": 2794.31, "duration": 8.52}, {"text": "through this surface, and\nthis is the normal vector,", "start": 2802.83, "duration": 4.77}, {"text": "in this case, flux,\nwhich is a vector", "start": 2807.6, "duration": 5.2}, {"text": "dotted with the normal\nvector, is just the flux.", "start": 2812.8, "duration": 3.15}, {"text": "Which is to say that if the\nflux and the normal vector", "start": 2815.95, "duration": 2.25}, {"text": "are aligned in the same way,\nthen every neutron going", "start": 2818.2, "duration": 2.88}, {"text": "through the surface is tracked\nas going through the surface.", "start": 2821.08, "duration": 3.66}, {"text": "To take the opposite example,\nwhat about the situation where", "start": 2824.74, "duration": 4.02}, {"text": "you have a surface here and you\nhave a mono-directional flux", "start": 2828.76, "duration": 6.36}, {"text": "of neutrons in this direction.", "start": 2835.12, "duration": 3.22}, {"text": "And that is your surface normal.", "start": 2838.34, "duration": 1.98}, {"text": "What does the flux dotted\nwith the surface normal vector", "start": 2845.67, "duration": 2.84}, {"text": "equal?", "start": 2848.51, "duration": 1.77}, {"text": "0, it's just a dot product\nbetween the direction", "start": 2850.28, "duration": 5.56}, {"text": "that your neutrons are moving\nand the normal vector saying,", "start": 2855.84, "duration": 3.57}, {"text": "does it go out of\nthe surface at all?", "start": 2859.41, "duration": 1.98}, {"text": "So for these two limiting cases,\nin this case, the fluxes just", "start": 2861.39, "duration": 4.6}, {"text": "let's say, what\nis it, the number", "start": 2865.99, "duration": 1.55}, {"text": "of neutrons leaving the\nsurface is the flux.", "start": 2867.54, "duration": 2.28}, {"text": "In this case, no neutrons\nleave the surface", "start": 2869.82, "duration": 2.01}, {"text": "because they're not actually\ngoing through the surface.", "start": 2871.83, "duration": 2.85}, {"text": "It's a good time to mention,\nagain, that these units of flux", "start": 2874.68, "duration": 4.14}, {"text": "are in neutrons per centimeter\nsquared per second, which", "start": 2878.82, "duration": 4.77}, {"text": "is to say the number\nof particles traveling", "start": 2883.59, "duration": 2.1}, {"text": "through this area in centimeter\nsquared every second.", "start": 2885.69, "duration": 3.965}, {"text": "I know we've gone\nover it before,", "start": 2889.655, "duration": 1.375}, {"text": "but I want you to keep\nthese units in mind.", "start": 2891.03, "duration": 2.592}, {"text": "Because now they actually\nhave a little more physical", "start": 2893.622, "duration": 2.208}, {"text": "significance.", "start": 2895.83, "duration": 2.18}, {"text": "And that's why we have this\nflux times normal vector dS.", "start": 2898.01, "duration": 4.58}, {"text": "That describes the\nnumber of neutrons", "start": 2902.59, "duration": 1.62}, {"text": "that get through the surface.", "start": 2904.21, "duration": 1.84}, {"text": "The last thing we'll do, because\neverything else is a volume", "start": 2906.05, "duration": 4.68}, {"text": "integral, we want this to be a\nvolume integral because we're", "start": 2910.73, "duration": 3.12}, {"text": "going to simplify this\nin terms of getting", "start": 2913.85, "duration": 1.86}, {"text": "rid of all the volume stuff.", "start": 2915.71, "duration": 1.447}, {"text": "We're going to use what's\ncalled the divergence theorem.", "start": 2917.157, "duration": 2.333}, {"text": "I hear some snickering.", "start": 2922.17, "duration": 2.64}, {"text": "Because I remember\nthis is probably", "start": 2924.81, "duration": 1.53}, {"text": "something where you were told\nin 1801 or 1802, this exists.", "start": 2926.34, "duration": 3.74}, {"text": "Use it in a few problems.", "start": 2930.08, "duration": 1.15}, {"text": "Moving on.", "start": 2931.23, "duration": 0.96}, {"text": "That sound about right?", "start": 2932.19, "duration": 1.775}, {"text": "This is when you\nactually use it.", "start": 2933.965, "duration": 1.375}, {"text": "So the divergence theorem\nsays that the integral", "start": 2938.82, "duration": 3.29}, {"text": "of some variable F dS, through\nsome volume element of surface,", "start": 2942.11, "duration": 5.2}, {"text": "is the same as the\nvolume integral of--", "start": 2947.31, "duration": 4.66}, {"text": "how does this go--", "start": 2951.97, "duration": 0.83}, {"text": "del dot F dV.", "start": 2956.81, "duration": 2.35}, {"text": "And this is going to be\nquite important because one,", "start": 2959.16, "duration": 2.9}, {"text": "it gives us a volume integral.", "start": 2962.06, "duration": 3.31}, {"text": "So this is, it will be a volume\nintegral of our del dot flux", "start": 2965.37, "duration": 8.26}, {"text": "dV, so now everything's\nin the same units.", "start": 2973.63, "duration": 3.31}, {"text": "And if we were to say forget\nabout our little volume", "start": 2976.94, "duration": 3.39}, {"text": "element.", "start": 2980.33, "duration": 0.5}, {"text": "Let's just assume\nan infinite reactor.", "start": 2980.83, "duration": 2.4}, {"text": "Every single volume integral in\nterm just instantly disappears.", "start": 2983.23, "duration": 3.84}, {"text": "Because we wrote\nthese equations to be", "start": 2987.07, "duration": 2.58}, {"text": "identical for any dV\nanywhere inside this reactor.", "start": 2989.65, "duration": 5.43}, {"text": "If the reactor is then infinite,\nthen all of those volume terms", "start": 2995.08, "duration": 4.26}, {"text": "disappear.", "start": 2999.34, "duration": 0.612}, {"text": "And that's the\nfirst simplification", "start": 2999.952, "duration": 1.458}, {"text": "that we'll make\nin the next class.", "start": 3001.41, "duration": 3.62}, {"text": "But right here on\nthese five boards,", "start": 3005.03, "duration": 4.35}, {"text": "we've developed the\nneutron transport equation,", "start": 3009.38, "duration": 2.23}, {"text": "which is the absolute, most\ngeneral, highest escalated", "start": 3011.61, "duration": 3.53}, {"text": "form of how do\nyou track neutrons", "start": 3015.14, "duration": 2.25}, {"text": "through any volume, any\ndirection, any energy,", "start": 3017.39, "duration": 4.17}, {"text": "at any time.", "start": 3021.56, "duration": 1.5}, {"text": "And we'll spend Thursday\nand Friday simplifying this", "start": 3023.06, "duration": 2.79}, {"text": "to something that we can solve.", "start": 3025.85, "duration": 2.34}, {"text": "The other reason that we\nuse this divergence theorem", "start": 3028.19, "duration": 3.85}, {"text": "is because we're going\nto make an approximation.", "start": 3032.04, "duration": 2.0}, {"text": "This crazy looking\nthing right here,", "start": 3034.04, "duration": 2.4}, {"text": "we will make an approximation\ncalled the diffusion", "start": 3036.44, "duration": 2.13}, {"text": "approximation where we\nassume that neutrons", "start": 3038.57, "duration": 2.37}, {"text": "are like a gas that just\ndiffuse away from each other.", "start": 3040.94, "duration": 2.64}, {"text": "And that's going to make solving\nthis really, really easy.", "start": 3043.58, "duration": 3.33}, {"text": "It's going to go from\nsome second order", "start": 3046.91, "duration": 1.74}, {"text": "differential or differential\nintegral equation", "start": 3048.65, "duration": 3.09}, {"text": "to just the equation that\nyou can solve with algebra.", "start": 3051.74, "duration": 3.35}, {"text": "Yep?", "start": 3055.09, "duration": 1.1}, {"text": "AUDIENCE: Do you need the dE\nd-omega for the last term?", "start": 3056.19, "duration": 3.28}, {"text": "MICHAEL SHORT: Probably, yeah,\nover all E, over all omega.", "start": 3059.47, "duration": 6.0}, {"text": "And that flux is going\nto be of r, E omega, t.", "start": 3065.47, "duration": 6.81}, {"text": "Absolutely.", "start": 3075.19, "duration": 1.565}, {"text": "Just to make sure, everything\nis in the same units,", "start": 3076.755, "duration": 2.125}, {"text": "every term has a fairly\nsimilar template.", "start": 3078.88, "duration": 2.73}, {"text": "The only difference is leakage,\nthere's no reaction here.", "start": 3081.61, "duration": 4.65}, {"text": "Every single other term\nconstitutes a reaction.", "start": 3089.79, "duration": 3.15}, {"text": "And they all follow\nthis template.", "start": 3092.94, "duration": 1.71}, {"text": "So I will stop here\nbecause it is five of.", "start": 3097.28, "duration": 2.47}, {"text": "See if anyone has\nany quick questions", "start": 3099.75, "duration": 1.6}, {"text": "on what you've got here.", "start": 3101.35, "duration": 1.63}, {"text": "I'll make sure to get all\nof this on the board images", "start": 3102.98, "duration": 3.2}, {"text": "so you guys can\ntake a look at it.", "start": 3106.18, "duration": 1.77}, {"text": "And I'll projected\nup on the screen", "start": 3107.95, "duration": 1.5}, {"text": "so that we can make some\nsimplifications based on what", "start": 3109.45, "duration": 2.25}, {"text": "we see here on Thursday.", "start": 3111.7, "duration": 2.74}, {"text": "Yeah?", "start": 3114.44, "duration": 0.63}, {"text": "AUDIENCE: What is the\nneutron birth spectrum?", "start": 3115.07, "duration": 2.512}, {"text": "MICHAEL SHORT: The\nneutron birth spectrum", "start": 3117.582, "duration": 1.708}, {"text": "says that if you have any\nold fission event, what's", "start": 3119.29, "duration": 2.61}, {"text": "the probability of\nthose neutrons being", "start": 3121.9, "duration": 2.1}, {"text": "born at different energies?", "start": 3124.0, "duration": 2.08}, {"text": "What this says is that they're\nborn between 1 and 10 MeV,", "start": 3126.08, "duration": 3.17}, {"text": "with a peak at around 2 MeV.", "start": 3129.25, "duration": 2.092}, {"text": "But if you want to track\nthe number of neutrons", "start": 3131.342, "duration": 1.958}, {"text": "in every energy group, you\nneed to know where they begin.", "start": 3133.3, "duration": 2.375}, {"text": "Good question.", "start": 3139.02, "duration": 0.6}, {"text": "So if any of the terms here are\nunclear what they physically", "start": 3139.62, "duration": 3.203}, {"text": "mean, because that's what\nI'm most interested in you", "start": 3142.823, "duration": 2.167}, {"text": "guys knowing, please do\nask either on Piazza,", "start": 3144.99, "duration": 3.03}, {"text": "on email, on Thursday.", "start": 3148.02, "duration": 1.6}, {"text": "Yeah?", "start": 3149.62, "duration": 0.5}, {"text": "AUDIENCE: What's the\ndifference between the big N", "start": 3150.12, "duration": 0.69}, {"text": "and the little n again?", "start": 3150.81, "duration": 1.8}, {"text": "MICHAEL SHORT: The big N\nand the little n, which one?", "start": 3152.61, "duration": 2.88}, {"text": "The cursive one, or this one?", "start": 3155.49, "duration": 2.564}, {"text": "AUDIENCE: The little n\nup top there and then", "start": 3158.054, "duration": 2.296}, {"text": "the non-cursive one.", "start": 3160.35, "duration": 0.99}, {"text": "MICHAEL SHORT: OK, the little\nn and the non-cursive one.", "start": 3161.34, "duration": 2.88}, {"text": "The little n is the number\nof neutrons in a volume,", "start": 3164.22, "duration": 3.48}, {"text": "at a certain energy, going in\na direction, at a certain time.", "start": 3167.7, "duration": 3.59}, {"text": "Big N right here is just\nnumber density, number", "start": 3171.29, "duration": 2.98}, {"text": "of atoms per centimeter cubed.", "start": 3174.27, "duration": 6.76}, {"text": "Cursive n is the number\nof neutrons at an energy,", "start": 3181.03, "duration": 3.18}, {"text": "in a volume.", "start": 3184.21, "duration": 0.81}, {"text": "We don't care where\nthey're going.", "start": 3185.02, "duration": 2.25}, {"text": "And the reason I write\nthese terms up here is we", "start": 3187.27, "duration": 3.6}, {"text": "are going to switch from\nlowercase to capital,", "start": 3190.87, "duration": 2.88}, {"text": "or angularly-dependent\nto angularly-independent", "start": 3193.75, "duration": 2.73}, {"text": "by making a simple\napproximation to say,", "start": 3196.48, "duration": 1.81}, {"text": "we don't care what\ndirection they're going.", "start": 3198.29, "duration": 1.792}, {"text": "We just care if they're there.", "start": 3200.082, "duration": 2.478}, {"text": "But in real complex\nneutron physics problems,", "start": 3202.56, "duration": 2.467}, {"text": "like the one solved at the\ncomputational reactor physics", "start": 3205.027, "duration": 2.333}, {"text": "group, you need to\nknow all the angles.", "start": 3207.36, "duration": 2.31}, {"text": "And you need to\nknow the probability", "start": 3209.67, "duration": 1.5}, {"text": "or the cross-section that a\nneutron coming in at this angle", "start": 3211.17, "duration": 2.79}, {"text": "leaves at that angle and\nimparts a certain energy.", "start": 3213.96, "duration": 2.27}, {"text": "Because they're all different.", "start": 3216.23, "duration": 1.25}, {"text": "For the purposes of\nthis class, I just", "start": 3217.48, "duration": 1.97}, {"text": "want you to know\nthat they exist.", "start": 3219.45, "duration": 1.802}, {"text": "And the first thing we will\ndo is simplify them away.", "start": 3221.252, "duration": 2.208}, {"text": "But this way, you'll\nbe fully prepared", "start": 3225.717, "duration": 1.583}, {"text": "for 22.05 and a lifetime\nof reactor physics,", "start": 3227.3, "duration": 2.43}, {"text": "if you so choose.", "start": 3229.73, "duration": 0.81}, {"text": "Who here is done a year op\nin the computational reactor", "start": 3233.23, "duration": 2.35}, {"text": "physics group?", "start": 3235.58, "duration": 1.11}, {"text": "Just one, OK.", "start": 3236.69, "duration": 1.496}, {"text": "I recommend more.", "start": 3238.186, "duration": 0.847}, {"text": "They tend to be the biggest\ngroup in the department.", "start": 3239.033, "duration": 2.167}, {"text": "They've got like\n20 grad students", "start": 3241.2, "duration": 1.73}, {"text": "and probably more\nyear ops than that.", "start": 3242.93, "duration": 2.95}, {"text": "So try it out.", "start": 3245.88, "duration": 1.43}, {"text": "It's what makes us\nus, us nukes, right,", "start": 3247.31, "duration": 3.12}, {"text": "is neutrons and tracking them\nto ridiculous proportions.", "start": 3250.43, "duration": 5.97}, {"text": "OK, definitely want to let\nyou guys go it's one of.", "start": 3256.4, "duration": 2.95}, {"text": "So I'll see you all on Thursday.", "start": 3259.35, "duration": 2.111}]
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+[{"text": "[SQUEAKING]\n[RUSTLING] [CLICKING]", "start": 0.0, "duration": 13.05}, {"text": "CASEY RODRIGUEZ:\nOK, so last time, we", "start": 13.05, "duration": 3.93}, {"text": "were talking about sequences,\nand I introduced the notion", "start": 16.98, "duration": 5.4}, {"text": "of a limit of a sequence.", "start": 22.38, "duration": 3.16}, {"text": "So we say that x n converges to\nx if for all epsilon positive", "start": 25.54, "duration": 4.04}, {"text": "there exists an M,\na natural number,", "start": 29.58, "duration": 1.68}, {"text": "such that for all little n\nbigger than or equal to capital", "start": 31.26, "duration": 2.7}, {"text": "M we have x sub n minus\nx is less than epsilon.", "start": 33.96, "duration": 3.76}, {"text": "So what this definition\nsays is that given", "start": 37.72, "duration": 5.83}, {"text": "any little bit of tolerance,\nas long as I go far enough", "start": 43.55, "duration": 3.03}, {"text": "out in the sequence,\nthe entries are getting", "start": 46.58, "duration": 2.58}, {"text": "within that tolerance to x.", "start": 49.16, "duration": 2.46}, {"text": "And when x then\nconverges to x, we'll", "start": 51.62, "duration": 3.06}, {"text": "write x is equal to the limit as\nn goes to infinity of x sub n,", "start": 54.68, "duration": 3.63}, {"text": "or using this notation,\nx sub n arrow x.", "start": 58.31, "duration": 6.25}, {"text": "And so I've said\nbefore that if you ever", "start": 64.56, "duration": 3.97}, {"text": "have a reasonably complicated\nor interesting definition,", "start": 68.53, "duration": 5.1}, {"text": "you should try to come up\nwith examples and negate it.", "start": 73.63, "duration": 3.64}, {"text": "So the end of last time,\nwe saw a few examples of--", "start": 77.27, "duration": 6.98}, {"text": "at least one example of--\na convergent sequence.", "start": 84.25, "duration": 2.88}, {"text": "Let's negate this definition\nbecause then we'll", "start": 87.13, "duration": 2.7}, {"text": "also come up with an\nexample of a sequence which", "start": 89.83, "duration": 2.13}, {"text": "does not converge.", "start": 91.96, "duration": 1.36}, {"text": "And so the negation\nof this definition", "start": 93.32, "duration": 5.24}, {"text": "is that x n does\nnot converge to x.", "start": 98.56, "duration": 10.48}, {"text": "What does this mean?", "start": 109.04, "duration": 0.94}, {"text": "So this is the\nactual negation part.", "start": 109.98, "duration": 1.97}, {"text": "If there exists an\nepsilon positive-- so", "start": 111.95, "duration": 6.03}, {"text": "whenever we negate a \"for all,\"\nit becomes \"there exists,\"", "start": 117.98, "duration": 3.45}, {"text": "and whenever we negate\na \"there exists,\"", "start": 121.43, "duration": 1.92}, {"text": "it becomes a \"for all.\"", "start": 123.35, "duration": 1.53}, {"text": "So there exists some bad\nepsilon 0 positive such", "start": 124.88, "duration": 5.64}, {"text": "that for all natural numbers\nN, there exists an n bigger", "start": 130.52, "duration": 8.22}, {"text": "than or equal to M\nsuch that x n minus", "start": 138.74, "duration": 6.54}, {"text": "x is bigger than or equal to\nthis bad epsilon 0 in distance.", "start": 145.28, "duration": 7.14}, {"text": "So we have a picture that\ngoes along with convergence.", "start": 152.42, "duration": 2.61}, {"text": "We can have a picture that\ngoes along with a sequence not", "start": 155.03, "duration": 3.3}, {"text": "converging to x.", "start": 158.33, "duration": 0.81}, {"text": "So this means if I go out\nwithin this bad epsilon 0,", "start": 159.14, "duration": 7.38}, {"text": "and if I go arbitrarily\nout in the sequence,", "start": 166.52, "duration": 4.26}, {"text": "I can always find an\nelement x sub n which", "start": 170.78, "duration": 3.21}, {"text": "is not in that interval.", "start": 173.99, "duration": 4.605}, {"text": "And we use this negation\nto prove a certain sequence", "start": 181.33, "duration": 2.7}, {"text": "does not converge to x.", "start": 184.03, "duration": 3.09}, {"text": "But let's go back\ndo another example", "start": 187.12, "duration": 2.76}, {"text": "of a sequence which\ndoes converge, so--", "start": 189.88, "duration": 3.585}, {"text": "equals 0.", "start": 205.31, "duration": 0.6}, {"text": "So again, how does the proof go?", "start": 208.78, "duration": 2.13}, {"text": "You have to verify the\ndefinition of the limit.", "start": 210.91, "duration": 3.6}, {"text": "I mean, there's nothing else\nthat we have to use right now.", "start": 214.51, "duration": 4.26}, {"text": "So let epsilon be positive.", "start": 218.77, "duration": 3.492}, {"text": "And now, off to\nthe side over here,", "start": 222.262, "duration": 1.458}, {"text": "I'm going to do a\nlittle bit of work", "start": 223.72, "duration": 4.38}, {"text": "to show you how\nexactly in practice one", "start": 228.1, "duration": 3.54}, {"text": "would find such a capital M\nor choose a capital M to get", "start": 231.64, "duration": 3.54}, {"text": "that 1 over n squared plus\n30n plus 1 would be less", "start": 235.18, "duration": 4.29}, {"text": "than epsilon for n bigger\nthan or equal to capital M.", "start": 239.47, "duration": 4.91}, {"text": "So typically how this works\nis, unlike in calculus", "start": 244.38, "duration": 4.26}, {"text": "where you have some inequality\nthat you want to get", "start": 248.64, "duration": 3.39}, {"text": "and then you solve for\nn, in analysis what's", "start": 252.03, "duration": 4.619}, {"text": "great is that you can\nreplace that thing", "start": 256.649, "duration": 2.851}, {"text": "you want to make small\nby something simpler,", "start": 259.5, "duration": 2.55}, {"text": "and then solve that inequality.", "start": 262.05, "duration": 1.44}, {"text": "What do I mean?", "start": 263.49, "duration": 1.53}, {"text": "So what I want to do,\nI want to find M so", "start": 265.02, "duration": 8.43}, {"text": "that if n it is bigger\nthan or equal to M, then--", "start": 273.45, "duration": 4.8}, {"text": "so I'm saying the limit is\n0, so I want to show 1 over n", "start": 278.25, "duration": 5.5}, {"text": "squared plus 30n plus\n1 is less than epsilon.", "start": 283.75, "duration": 6.94}, {"text": "Now, I could try to solve\nthis inequality for n,", "start": 290.69, "duration": 3.3}, {"text": "but this is a quadratic function\nand imagine I put 20 there,", "start": 293.99, "duration": 6.03}, {"text": "so I can't exactly solve\nexactly for n to guarantee this.", "start": 300.02, "duration": 4.92}, {"text": "But what's great about\nanalysis is that I", "start": 304.94, "duration": 4.73}, {"text": "don't have to work that hard.", "start": 309.67, "duration": 3.96}, {"text": "I could start with\nthis thing which", "start": 313.63, "duration": 2.13}, {"text": "I want to bound by epsilon,\nreplace it by something bigger,", "start": 315.76, "duration": 4.62}, {"text": "and then find capital\nM so that that bigger", "start": 320.38, "duration": 2.88}, {"text": "thing is less than epsilon.", "start": 323.26, "duration": 1.3}, {"text": "So what do I mean?", "start": 324.56, "duration": 0.9}, {"text": "So let's start with this thing--", "start": 325.46, "duration": 1.67}, {"text": "1 over n squared\nplus 30n plus 1.", "start": 327.13, "duration": 6.47}, {"text": "So this one is only\nmaking things bigger.", "start": 333.6, "duration": 2.42}, {"text": "I'm going to do\nthis very slowly.", "start": 336.02, "duration": 1.375}, {"text": "So this is less than\nor equal to this", "start": 342.52, "duration": 4.08}, {"text": "because for this, I've just\nadded 1 to the denominator.", "start": 346.6, "duration": 5.28}, {"text": "And 1 over n squared plus 30n--", "start": 351.88, "duration": 2.582}, {"text": "this certainly looks\na little bit simpler", "start": 354.462, "duration": 1.708}, {"text": "to solve for n\nless than epsilon.", "start": 356.17, "duration": 2.11}, {"text": "But I can make it even simpler\nby dropping the n squared,", "start": 358.28, "duration": 2.78}, {"text": "because n squared is\npositive, so that's", "start": 361.06, "duration": 1.68}, {"text": "only making the bottom bigger.", "start": 362.74, "duration": 1.25}, {"text": "So I've 1 over 30n,\nand this is certainly", "start": 367.46, "duration": 3.24}, {"text": "less than or equal to 1 over n.", "start": 370.7, "duration": 3.54}, {"text": "So what does this\ncomputation show?", "start": 374.24, "duration": 4.95}, {"text": "This shows that if 1 over\nn is less than epsilon,", "start": 379.19, "duration": 5.49}, {"text": "then this implies that 1 over\nn squared plus 30n plus 1 is", "start": 384.68, "duration": 5.82}, {"text": "less than epsilon.", "start": 390.5, "duration": 0.75}, {"text": "If this thing is\nless than epsilon,", "start": 395.38, "duration": 1.56}, {"text": "then by this string\nof inequalities,", "start": 396.94, "duration": 1.89}, {"text": "this thing will be\nless than epsilon.", "start": 398.83, "duration": 1.6}, {"text": "So we choose capital\nM so that we get this.", "start": 400.43, "duration": 5.487}, {"text": "Now, when we actually\nwrite the proof,", "start": 405.917, "duration": 1.583}, {"text": "it'll look something like this.", "start": 407.5, "duration": 1.292}, {"text": "But the actual\nstyle of the proof", "start": 408.792, "duration": 2.668}, {"text": "is a little bit different.", "start": 411.46, "duration": 3.062}, {"text": "And if you didn't see\nthis, it would just", "start": 414.522, "duration": 1.708}, {"text": "seem like I pulled this\ncapital M out of nowhere,", "start": 416.23, "duration": 4.345}, {"text": "but this is the thinking\nthat goes behind it.", "start": 420.575, "duration": 1.875}, {"text": "So let epsilon be positive.", "start": 422.45, "duration": 1.89}, {"text": "Now I'll tell you how to\nchoose capital M. Choose", "start": 424.34, "duration": 5.39}, {"text": "M a natural number so\nthat-- so we want it", "start": 429.73, "duration": 4.68}, {"text": "for all n bigger than or\nequal to capital M, 1 over n", "start": 434.41, "duration": 2.55}, {"text": "is less than epsilon.", "start": 436.96, "duration": 1.45}, {"text": "So this will\ncertainly be true if n", "start": 438.41, "duration": 2.99}, {"text": "is bigger than or\nequal to capital M", "start": 441.4, "duration": 2.34}, {"text": "so that 1 over capital\nM is less than epsilon.", "start": 443.74, "duration": 2.07}, {"text": "And the reason we\ncan choose capital", "start": 449.985, "duration": 1.5}, {"text": "M like this-- again,\nwhere is this coming from?", "start": 451.485, "duration": 2.425}, {"text": "It's coming from the Archimedean\nproperty of the real numbers.", "start": 453.91, "duration": 3.605}, {"text": "So we've chosen\ncapital M. Now we", "start": 460.71, "duration": 2.55}, {"text": "need to show that\nthis capital M works.", "start": 463.26, "duration": 1.665}, {"text": "Then for all n bigger than\nor equal to capital M,", "start": 468.03, "duration": 5.16}, {"text": "if I look at 1 over n\nsquared plus 30n plus 1", "start": 473.19, "duration": 6.0}, {"text": "minus 0, my proposed\nlimit, this is equal to 1", "start": 479.19, "duration": 3.9}, {"text": "over n squared plus 1.", "start": 483.09, "duration": 4.8}, {"text": "And this is less\nthan or equal to,", "start": 487.89, "duration": 1.5}, {"text": "if I drop n squared\nand 1, 30n, which", "start": 489.39, "duration": 3.6}, {"text": "is less than or equal to 1\nover n, which is less than", "start": 492.99, "duration": 3.12}, {"text": "or equal to 1 over capital M,\nwhich is less than epsilon.", "start": 496.11, "duration": 2.73}, {"text": "So something of a non-example--", "start": 517.03, "duration": 5.94}, {"text": "let's show that the sequence\nminus 1 to the n DNC", "start": 522.97, "duration": 6.99}, {"text": "does not converge--", "start": 529.96, "duration": 1.35}, {"text": "not Democratic\nNational Committee--", "start": 531.31, "duration": 1.86}, {"text": "does not converge.", "start": 536.13, "duration": 1.44}, {"text": "So this is just a\nsequence minus 1,", "start": 537.57, "duration": 4.43}, {"text": "1, minus 1, 1,\nminus 1, and so on.", "start": 542.0, "duration": 4.87}, {"text": "So we have to show\nit does not converge,", "start": 546.87, "duration": 2.31}, {"text": "meaning for every\nx in R, we'll show", "start": 549.18, "duration": 2.4}, {"text": "that x n does not converge\nto x using the negation", "start": 551.58, "duration": 3.6}, {"text": "of the definition--", "start": 555.18, "duration": 2.13}, {"text": "so proof.", "start": 557.31, "duration": 3.285}, {"text": "Let x be in R. And what\ndo we want to show?", "start": 574.64, "duration": 1.905}, {"text": "Minus 1 to the n-th\ndoes not converge to x.", "start": 581.2, "duration": 11.82}, {"text": "And we'll use this definition.", "start": 595.7, "duration": 1.42}, {"text": "So this definition means we\nneed to find a bad epsilon 0.", "start": 597.12, "duration": 5.54}, {"text": "And here's the kind of thinking\nthat goes along with this--", "start": 606.78, "duration": 4.69}, {"text": "there's 1, there's minus 1.", "start": 611.47, "duration": 2.46}, {"text": "This sequence just keeps\nalternating, so intuitively", "start": 613.93, "duration": 3.72}, {"text": "there's no way that every\nelement of the sequence", "start": 617.65, "duration": 3.63}, {"text": "can be getting--", "start": 621.28, "duration": 0.93}, {"text": "or every entry in the\nsequence can be getting--", "start": 622.21, "duration": 1.98}, {"text": "close to some single x.", "start": 624.19, "duration": 1.83}, {"text": "So what's the idea?", "start": 626.02, "duration": 1.36}, {"text": "The idea is that the distance\nbetween these two guys", "start": 627.38, "duration": 4.4}, {"text": "is always 2.", "start": 631.78, "duration": 0.84}, {"text": "So somehow, the distance\nbetween every entry,", "start": 635.21, "duration": 9.01}, {"text": "or basically, some entry\nhas to be within distance--", "start": 644.22, "duration": 4.11}, {"text": "if this is within distance\n1, say, to a given x,", "start": 648.33, "duration": 4.5}, {"text": "then this will be greater than\nor equal to 1 in distance to x.", "start": 652.83, "duration": 5.37}, {"text": "So you can imagine\nx is over here.", "start": 658.2, "duration": 1.89}, {"text": "Minus 1 is within\ndistance 1 to x,", "start": 660.09, "duration": 2.97}, {"text": "but then 1 would be greater\nthan distance 1 to x.", "start": 663.06, "duration": 6.06}, {"text": "So our bad epsilon 0 was\ngoing to be 1, as we'll see.", "start": 669.12, "duration": 4.17}, {"text": "Let epsilon 0 equals 1.", "start": 677.01, "duration": 1.29}, {"text": "That's our bad epsilon.", "start": 678.3, "duration": 1.33}, {"text": "So now we have to\nshow for all capital", "start": 679.63, "duration": 1.67}, {"text": "M in the natural numbers,\nthere exists a little n", "start": 681.3, "duration": 1.89}, {"text": "bigger than or\nequal to capital M", "start": 683.19, "duration": 1.375}, {"text": "so that we have that inequality.", "start": 684.565, "duration": 3.645}, {"text": "So let M be a natural number.", "start": 688.21, "duration": 3.365}, {"text": "Then what do we see?", "start": 702.02, "duration": 1.425}, {"text": "So then it says, they're\nexists an n greater than", "start": 706.33, "duration": 2.97}, {"text": "or equal to capital\nM. And I will", "start": 709.3, "duration": 4.88}, {"text": "show that n is, in fact,\neither capital M or capital", "start": 714.18, "duration": 3.15}, {"text": "M plus 1, then 2, which is\nthe distance between minus 1", "start": 717.33, "duration": 11.4}, {"text": "to the M and minus\n1 to the M plus 1 is", "start": 728.73, "duration": 6.04}, {"text": "less than or equal to-- now\nusing the triangle inequality,", "start": 734.77, "duration": 2.67}, {"text": "I add and subtract x and then\nuse the triangle inequality.", "start": 737.44, "duration": 3.57}, {"text": "So I have the sum of two numbers\nis bigger than or equal to 2.", "start": 751.32, "duration": 5.9}, {"text": "And the only way that can happen\nis if one of these numbers", "start": 757.22, "duration": 2.58}, {"text": "is bigger than or equal to 1.", "start": 759.8, "duration": 1.47}, {"text": "If both of these\nnumbers are less than 1,", "start": 761.27, "duration": 2.13}, {"text": "then the sum is less than 2, and\nI would have 2 is less than 2.", "start": 763.4, "duration": 3.18}, {"text": "That's not possible.", "start": 766.58, "duration": 1.21}, {"text": "So one of these numbers has to\nbe bigger than or equal to 1.", "start": 767.79, "duration": 2.99}, {"text": "And therefore, I could\ntake n equal to capital M", "start": 789.14, "duration": 3.0}, {"text": "if this is bigger\nthan or equal to 1,", "start": 792.14, "duration": 1.8}, {"text": "or if this is bigger\nthan or equal to 1,", "start": 793.94, "duration": 2.34}, {"text": "I take little n to\nbe capital M plus 1.", "start": 796.28, "duration": 2.31}, {"text": "So that's the end of that.", "start": 798.59, "duration": 2.44}, {"text": "So that's good for\nexamples for now.", "start": 808.08, "duration": 5.79}, {"text": "Let's prove a general theorem\nabout convergent sequences--", "start": 813.87, "duration": 3.69}, {"text": "namely, that if I have a\nconvergent sequence, then", "start": 817.56, "duration": 2.67}, {"text": "it's bounded.", "start": 820.23, "duration": 0.63}, {"text": "And let me just give\nyou a quick reminder", "start": 837.69, "duration": 6.54}, {"text": "about what being bounded\nmeans for a sequence, i.e.,", "start": 844.23, "duration": 6.66}, {"text": "there exists some number\nsuch that for all n,", "start": 850.89, "duration": 5.7}, {"text": "x n is less than or\nequal to capital B. Now,", "start": 856.59, "duration": 5.84}, {"text": "as beginning students of\nmath, what types of questions", "start": 862.43, "duration": 8.08}, {"text": "should we start\nasking ourselves?", "start": 870.51, "duration": 1.62}, {"text": "So one of the types,\nor a type of question", "start": 877.22, "duration": 3.29}, {"text": "that we should ask when we\ncome across the theorem that", "start": 880.51, "duration": 3.54}, {"text": "is a one-way street,\nmeaning if something", "start": 884.05, "duration": 3.78}, {"text": "happens then something\nelse happens,", "start": 887.83, "duration": 2.73}, {"text": "is does the converse hold?", "start": 890.56, "duration": 1.38}, {"text": "Namely, if I assume x sub\nn is a bounded sequence,", "start": 891.94, "duration": 3.51}, {"text": "does this imply that\nx n is convergent?", "start": 895.45, "duration": 2.94}, {"text": "So if you ever hear the words,\n\"does the converse hold,\"", "start": 901.09, "duration": 2.58}, {"text": "that's what they mean.", "start": 903.67, "duration": 1.83}, {"text": "Now, for this statement,\nthis is false.", "start": 905.5, "duration": 2.48}, {"text": "If x n is bounded implies\nx n is convergent,", "start": 907.98, "duration": 2.92}, {"text": "that's false because we\nhave an example right", "start": 910.9, "duration": 2.09}, {"text": "there of a bounded sequence.", "start": 912.99, "duration": 1.71}, {"text": "This sequence here,\nminus 1 to the n,", "start": 914.7, "duration": 1.86}, {"text": "is bounded since the\nsequence in absolute value", "start": 916.56, "duration": 6.03}, {"text": "equals 1 for all n, so\nwe could take B equals 1.", "start": 922.59, "duration": 3.51}, {"text": "So minus 1 to the n\nis a bounded sequence,", "start": 926.1, "duration": 1.95}, {"text": "which is not convergent.", "start": 928.05, "duration": 1.06}, {"text": "So the converse does not hold.", "start": 929.11, "duration": 2.68}, {"text": "So let's prove the theorem.", "start": 931.79, "duration": 3.46}, {"text": "And let me draw a little\npicture to go along", "start": 935.25, "duration": 4.37}, {"text": "with it of what's going on.", "start": 939.62, "duration": 3.74}, {"text": "So here is 0, let's imagine.", "start": 943.36, "duration": 4.08}, {"text": "Let me make this picture\na little bit bigger", "start": 947.44, "duration": 5.22}, {"text": "before I go into the proof.", "start": 952.66, "duration": 1.29}, {"text": "So let x be the limit.", "start": 959.91, "duration": 1.725}, {"text": "So this is not the proof yet.", "start": 964.69, "duration": 1.31}, {"text": "This is just more discussion.", "start": 966.0, "duration": 5.2}, {"text": "So if this x sub n\nis converging to x,", "start": 971.2, "duration": 3.41}, {"text": "then let's say I go\nout distance 1 to x.", "start": 974.61, "duration": 7.17}, {"text": "Then all of the x\nsub n's eventually", "start": 981.78, "duration": 2.25}, {"text": "have to land in this strip here.", "start": 984.03, "duration": 3.18}, {"text": "So x sub n, n bigger than\nor equal to some capital M.", "start": 990.88, "duration": 8.46}, {"text": "So I know that they're all\nwithin distance 1 to x.", "start": 999.34, "duration": 2.49}, {"text": "So in absolute value,\nthey'd be bounded by,", "start": 1001.83, "duration": 3.9}, {"text": "let's say for this\npicture, it'd be x plus 1.", "start": 1005.73, "duration": 2.13}, {"text": "But if this was\nover there, capital,", "start": 1007.86, "duration": 3.66}, {"text": "it would be the absolute\nvalue of x plus 1.", "start": 1011.52, "duration": 3.3}, {"text": "So that takes care of all x\nsub n's with n bigger than", "start": 1014.82, "duration": 2.79}, {"text": "or equal to M. And then\nthere's only finitely many guys", "start": 1017.61, "duration": 6.32}, {"text": "to deal with.", "start": 1023.93, "duration": 1.35}, {"text": "Maybe there's a bigger one\nout here, x sub n minus 1", "start": 1025.28, "duration": 4.799}, {"text": "to deal with, and that's\nhow we define our number,", "start": 1030.079, "duration": 4.02}, {"text": "is by the absolute\nvalue of x plus 1", "start": 1034.099, "duration": 4.47}, {"text": "plus the absolute value\nof these finitely many.", "start": 1038.569, "duration": 3.266}, {"text": "And then that would\nbe something that's", "start": 1041.835, "duration": 1.625}, {"text": "bigger than or equal to every\nelement in the sequence.", "start": 1043.46, "duration": 2.25}, {"text": "That's the picture\nthat goes with it.", "start": 1048.298, "duration": 1.542}, {"text": "How do we take that\npicture to proof?", "start": 1053.83, "duration": 1.8}, {"text": "So suppose x n converges to\nx-- that's our assumption,", "start": 1060.24, "duration": 10.26}, {"text": "and there exists a\nnatural number M such", "start": 1070.5, "duration": 4.53}, {"text": "that for all n bigger than\nor equal to capital m, x sub", "start": 1075.03, "duration": 7.95}, {"text": "n minus x is within distance 1,\nor x sub n is within distance 1", "start": 1082.98, "duration": 4.79}, {"text": "to x, then for all n bigger\nthan or equal to capital M,", "start": 1087.77, "duration": 6.64}, {"text": "if we look at the\nabsolute value of x sub n,", "start": 1094.41, "duration": 5.75}, {"text": "add and subtract x, and now\nuse the triangle inequality,", "start": 1100.16, "duration": 3.81}, {"text": "this is less than or equal\nto absolute value of x sub", "start": 1103.97, "duration": 2.82}, {"text": "n minus x plus the absolute\nvalue of x equals 1 plus x.", "start": 1106.79, "duration": 6.27}, {"text": "So for all entries in the\nsequence past this point", "start": 1113.06, "duration": 4.81}, {"text": "capital M, they're bounded in\nabsolute value by 1 plus x.", "start": 1117.87, "duration": 4.36}, {"text": "That's just a number.", "start": 1122.23, "duration": 0.875}, {"text": "So then, we just have\nto take care of the 1", "start": 1126.3, "duration": 6.36}, {"text": "up to capital M minus 1 guys.", "start": 1132.66, "duration": 2.1}, {"text": "We just have to\nfind a number bigger", "start": 1134.76, "duration": 1.5}, {"text": "than those guys and\nthis number, and we'll", "start": 1136.26, "duration": 3.18}, {"text": "have found a B.\nSo then let's take", "start": 1139.44, "duration": 2.97}, {"text": "B to be x sub 1 plus x\nsub 2 plus x sub capital", "start": 1142.41, "duration": 9.26}, {"text": "M minus 1 plus this.", "start": 1151.67, "duration": 7.2}, {"text": "Then for all n a natural number,\nthe absolute value of x of n", "start": 1169.53, "duration": 8.66}, {"text": "is less than or equal\nto B. Because if n", "start": 1178.19, "duration": 2.4}, {"text": "is less than capital M,\nthen its absolute value", "start": 1180.59, "duration": 3.87}, {"text": "is bounded by one of these.", "start": 1184.46, "duration": 1.36}, {"text": "Its absolute value is\nequal to 1 over these,", "start": 1185.82, "duration": 2.09}, {"text": "and therefore, less than\nor equal to one of these", "start": 1187.91, "duration": 3.0}, {"text": "plus some non-negative numbers.", "start": 1190.91, "duration": 3.11}, {"text": "And if n is bigger than\nor equal to capital M,", "start": 1194.02, "duration": 2.82}, {"text": "then we have this\nbound that we use.", "start": 1196.84, "duration": 3.39}, {"text": "And this number is\ncertainly less than", "start": 1200.23, "duration": 1.74}, {"text": "or equal to capital\nB, again, because it's", "start": 1201.97, "duration": 2.7}, {"text": "this number plus a sum\nof non-negative numbers.", "start": 1204.67, "duration": 2.13}, {"text": "Now in general, there's no\neasily checkable criterion", "start": 1224.23, "duration": 5.64}, {"text": "for a sequence to converge.", "start": 1229.87, "duration": 2.85}, {"text": "All we can do is\nverify the definition.", "start": 1232.72, "duration": 2.22}, {"text": "But there are some sequences\nwhich you can easily", "start": 1238.69, "duration": 2.81}, {"text": "check or figure out\nif they converge just", "start": 1241.5, "duration": 3.54}, {"text": "by telling if they're bounded.", "start": 1245.04, "duration": 3.15}, {"text": "Those are what are called\n\"monotone sequences.\"", "start": 1248.19, "duration": 2.21}, {"text": "So this is, in some\nsense, the class", "start": 1255.71, "duration": 2.04}, {"text": "of sequences that\ndoes kind of satisfy", "start": 1257.75, "duration": 2.28}, {"text": "the converse of that theorem\nI stated a minute ago.", "start": 1260.03, "duration": 4.41}, {"text": "So sequence x sub n\nis monotone increasing", "start": 1264.44, "duration": 18.29}, {"text": "if for all natural numbers\nlittle n, x sub n is less than", "start": 1282.73, "duration": 9.79}, {"text": "or equal to x sub n plus 1.", "start": 1292.52, "duration": 1.83}, {"text": "So this means that\nx sub 1 is less", "start": 1294.35, "duration": 4.53}, {"text": "than or equal to x sub 2 is\nless than or equal to x to 3,", "start": 1298.88, "duration": 4.14}, {"text": "and so on.", "start": 1303.02, "duration": 0.72}, {"text": "Sequence is monotone\ndecreasing if we", "start": 1314.58, "duration": 8.47}, {"text": "have the other inequality.", "start": 1323.05, "duration": 1.45}, {"text": "So things are getting\nsmaller, so x sub n", "start": 1324.5, "duration": 4.58}, {"text": "is bigger than or equal\nto x sub n plus 1.", "start": 1329.08, "duration": 2.205}, {"text": "And if we have a sequence\nwhich is monotone increasing", "start": 1352.24, "duration": 7.59}, {"text": "or monotone decreasing--", "start": 1359.83, "duration": 1.68}, {"text": "so it's one or the other--", "start": 1364.85, "duration": 2.34}, {"text": "we say x n is\nmonotone or monotonic.", "start": 1367.19, "duration": 8.25}, {"text": "So it's simple enough to come\nup with examples of sequences", "start": 1380.14, "duration": 6.12}, {"text": "which are monotone\nincreasing, monotone", "start": 1386.26, "duration": 3.36}, {"text": "decreasing, or neither.", "start": 1389.62, "duration": 1.87}, {"text": "So 1 over n--", "start": 1391.49, "duration": 5.45}, {"text": "this is just 1, 1/2, 1/3, 1/4--", "start": 1396.94, "duration": 5.82}, {"text": "this is monotone decreasing.", "start": 1402.76, "duration": 5.01}, {"text": "And if I take\nminus the sequence,", "start": 1407.77, "duration": 5.01}, {"text": "then that reverses basically\nall of the inequalities,", "start": 1412.78, "duration": 3.48}, {"text": "and I get a monotone\nincreasing one.", "start": 1416.26, "duration": 1.87}, {"text": "So then this is minus\n1, minus 1/2, minus 1/3,", "start": 1418.13, "duration": 3.95}, {"text": "minus 1/4, monotone increasing.", "start": 1422.08, "duration": 4.71}, {"text": "And then something\nthat's not is-- we've", "start": 1426.79, "duration": 1.68}, {"text": "already come across that--\nminus 1 to the n, and so on.", "start": 1428.47, "duration": 8.84}, {"text": "And so the theorem\nabout monotone sequences", "start": 1444.06, "duration": 3.48}, {"text": "is that there is a simpler\ncriterion than the definition", "start": 1447.54, "duration": 5.28}, {"text": "for determining when\nthey're convergent,", "start": 1452.82, "duration": 2.58}, {"text": "or if you like, they satisfy\nthe converse of this theorem up", "start": 1455.4, "duration": 3.6}, {"text": "here.", "start": 1459.0, "duration": 1.18}, {"text": "So a monotonic sequence\nis convergent if and only", "start": 1460.18, "duration": 18.48}, {"text": "if it is bounded.", "start": 1478.66, "duration": 6.19}, {"text": "So we proved a minute ago\nthat convergent sequences", "start": 1484.85, "duration": 2.57}, {"text": "are bounded, so for monotonic\nsequences, the converse holds.", "start": 1487.42, "duration": 3.555}, {"text": "So let's do the proof of this.", "start": 1494.51, "duration": 1.25}, {"text": "I'm going to do the proof for\nmonotone increasing sequences,", "start": 1495.76, "duration": 4.44}, {"text": "and as an exercise,\nI'll leave it to you", "start": 1500.2, "duration": 2.52}, {"text": "to do the proof for monotone\ndecreasing sequences.", "start": 1502.72, "duration": 5.37}, {"text": "So suppose x sub n is a\nmonotone increasing sequence.", "start": 1508.09, "duration": 11.07}, {"text": "So there's two directions to\nprove convergence if and only", "start": 1523.08, "duration": 5.27}, {"text": "if bounded.", "start": 1528.35, "duration": 1.21}, {"text": "So we have one\ndirection, meaning", "start": 1529.56, "duration": 3.71}, {"text": "convergence implies bounded.", "start": 1533.27, "duration": 1.89}, {"text": "This is just the\nprevious theorem,", "start": 1535.16, "duration": 5.41}, {"text": "where we proved that every\nconvergent sequence is bounded,", "start": 1540.57, "duration": 2.58}, {"text": "not just monotonic sequences.", "start": 1543.15, "duration": 3.07}, {"text": "So the meat is in proving\nthe converse direction.", "start": 1546.22, "duration": 3.8}, {"text": "And in fact, we'll be\nable to pick out what", "start": 1550.02, "duration": 3.03}, {"text": "the limit is of this sequence.", "start": 1553.05, "duration": 1.635}, {"text": "So suppose x sub n is bounded.", "start": 1557.2, "duration": 11.41}, {"text": "Then if I look at\nthe set of entries--", "start": 1574.06, "duration": 2.41}, {"text": "so not the sequence but if\nI look at the set of values", "start": 1576.47, "duration": 5.66}, {"text": "that this sequence takes-- so x\nsub n is just a natural number,", "start": 1582.13, "duration": 4.98}, {"text": "this is now a subset\nof the real numbers.", "start": 1587.11, "duration": 3.615}, {"text": "This is a bounded set, meaning\nit's bounded above and below", "start": 1594.88, "duration": 16.18}, {"text": "because there exists some\ncapital B so that x sub", "start": 1611.06, "duration": 2.7}, {"text": "n is, in absolute\nvalue, less than", "start": 1613.76, "duration": 3.63}, {"text": "or equal to capital B for all n.", "start": 1617.39, "duration": 1.53}, {"text": "So that means x sub n is\nbetween B and minus B.", "start": 1618.92, "duration": 7.68}, {"text": "All right, so what's the picture\nagain that goes with this?", "start": 1626.6, "duration": 3.76}, {"text": "So we have these x sub n's,\nx sub 1, x sub 2, x sub 3.", "start": 1630.36, "duration": 5.64}, {"text": "We know that they cannot\ngo past a certain B,", "start": 1636.0, "duration": 5.1}, {"text": "and they're steadily increasing,\nbut they can't keep strictly--", "start": 1641.1, "duration": 7.89}, {"text": "they can't increase\nwithout bound.", "start": 1648.99, "duration": 2.07}, {"text": "Not only that, they're\nbounded by some number", "start": 1654.16, "duration": 8.0}, {"text": "x, which I'll define to be\nthe supremum of this set.", "start": 1662.16, "duration": 4.47}, {"text": "And these guys are just\ngetting, in essence--", "start": 1666.63, "duration": 2.88}, {"text": "so this is a picture,\njust me trying", "start": 1669.51, "duration": 3.06}, {"text": "to explain to you\nwhat's going on.", "start": 1672.57, "duration": 1.68}, {"text": "If x is the sup of this\nset of entries, then", "start": 1674.25, "duration": 8.37}, {"text": "what do I know about x sub n?", "start": 1682.62, "duration": 2.93}, {"text": "I mean x is that if I go a\nlittle bit to the left of x--", "start": 1685.55, "duration": 4.33}, {"text": "so let me draw this again.", "start": 1689.88, "duration": 3.31}, {"text": "So let me back up a minute here.", "start": 1693.19, "duration": 3.71}, {"text": "So since this set is bounded\nin R, it has a supremum in R.", "start": 1701.07, "duration": 12.72}, {"text": "And what I claim is that\nthis supremum is, in fact,", "start": 1713.79, "duration": 2.92}, {"text": "the limit of this sequence.", "start": 1716.71, "duration": 1.88}, {"text": "This is a supremum of a set.", "start": 1718.59, "duration": 2.58}, {"text": "I'm saying it's the\nlimit of the sequence.", "start": 1721.17, "duration": 2.55}, {"text": "So what's the thinking here?", "start": 1723.72, "duration": 3.49}, {"text": "So x is the supremum of\nall the entries in x sub n,", "start": 1727.21, "duration": 2.99}, {"text": "so nothing's ever\ngoing to be bigger", "start": 1730.2, "duration": 1.5}, {"text": "than some tolerance\nx plus epsilon.", "start": 1731.7, "duration": 4.6}, {"text": "So we just need to worry about\nwhat's to the left of it.", "start": 1736.3, "duration": 3.66}, {"text": "And we need to find\na capital number", "start": 1739.96, "duration": 1.5}, {"text": "M so that all the x sub\nn's are in this interval", "start": 1741.46, "duration": 5.1}, {"text": "here, because we're trying\nto show that the x sub", "start": 1746.56, "duration": 17.175}, {"text": "n's converge to x, the\nsupremum of this guy.", "start": 1763.735, "duration": 2.945}, {"text": "So let's walk through\nthis by this picture.", "start": 1766.68, "duration": 4.35}, {"text": "So x is the supremum.", "start": 1771.03, "duration": 2.34}, {"text": "Nothing's bigger than x,\nso all of the x sub n's", "start": 1773.37, "duration": 3.63}, {"text": "are to the left\nof x plus epsilon.", "start": 1777.0, "duration": 2.14}, {"text": "So now we just need to\nworry about x minus epsilon.", "start": 1779.14, "duration": 2.94}, {"text": "Now, since x is the supremum\nof this set, x minus epsilon", "start": 1782.08, "duration": 4.04}, {"text": "can't be an upper bound for\nthe set of entries of x sub n.", "start": 1786.12, "duration": 4.32}, {"text": "So that means there has to\nexist some x sub M so that it's", "start": 1790.44, "duration": 6.39}, {"text": "bigger than x minus epsilon.", "start": 1796.83, "duration": 3.3}, {"text": "But now, this is where we\nuse the fact that this is", "start": 1800.13, "duration": 2.64}, {"text": "a monotone increasing sequence.", "start": 1802.77, "duration": 3.33}, {"text": "Because then, if n is bigger\nthan or equal to capital M,", "start": 1806.1, "duration": 3.03}, {"text": "then x sub n is strictly\nto the right of x sub M,", "start": 1809.13, "duration": 4.23}, {"text": "or it's equal to x sub M\nand still less than or equal", "start": 1813.36, "duration": 6.7}, {"text": "to x because x is the\nsupremum of all the entries.", "start": 1820.06, "duration": 3.31}, {"text": "So then, for n bigger than\nor equal to capital M,", "start": 1823.37, "duration": 2.45}, {"text": "they all have to lie\nin this interval.", "start": 1825.82, "duration": 2.01}, {"text": "And that's why the\nsequence converges", "start": 1827.83, "duration": 2.25}, {"text": "to the supremum of this set.", "start": 1830.08, "duration": 2.13}, {"text": "So we're using,\nin a crucial way,", "start": 1832.21, "duration": 3.63}, {"text": "the fact that this sequence\nis monotonic increasing.", "start": 1835.84, "duration": 5.73}, {"text": "I'll prove this claim.", "start": 1841.57, "duration": 1.18}, {"text": "Let epsilon be positive.", "start": 1842.75, "duration": 3.09}, {"text": "Then since x minus\nepsilon is not", "start": 1845.84, "duration": 11.27}, {"text": "an upper bound for\nthis set, x sub n,", "start": 1857.11, "duration": 7.59}, {"text": "there exists an\nM0, natural number,", "start": 1864.7, "duration": 4.17}, {"text": "so that x sub n minus\nepsilon is less than x", "start": 1868.87, "duration": 5.1}, {"text": "sub M0 is less\nthan or equal to x.", "start": 1873.97, "duration": 3.855}, {"text": "And we'll choose\nM to be this M0.", "start": 1880.38, "duration": 4.26}, {"text": "Then for all n bigger\nthan or equal to M,", "start": 1888.76, "duration": 3.5}, {"text": "we have x sub n minus epsilon,\nwhich is less than x sub M0.", "start": 1892.26, "duration": 6.03}, {"text": "And because n is bigger\nthan or equal to capital M,", "start": 1898.29, "duration": 2.52}, {"text": "and this is a monotone\nincreasing sequence,", "start": 1900.81, "duration": 2.7}, {"text": "x sub M0 is less than\nor equal to x sub n.", "start": 1903.51, "duration": 2.91}, {"text": "And because x is a\nsupremum of the set", "start": 1906.42, "duration": 6.06}, {"text": "of all entries of\nthis sequence, this", "start": 1912.48, "duration": 1.74}, {"text": "is less than or equal to\nx, which is less than x", "start": 1914.22, "duration": 4.35}, {"text": "plus epsilon.", "start": 1918.57, "duration": 1.95}, {"text": "Or to summarize--\nso this should not", "start": 1920.52, "duration": 1.59}, {"text": "be x sub n, that should\nbe x minus epsilon.", "start": 1922.11, "duration": 2.61}, {"text": "Or x minus epsilon is less\nthan x sub n is less than x", "start": 1924.72, "duration": 5.52}, {"text": "plus epsilon.", "start": 1930.24, "duration": 0.72}, {"text": "And that's the same as showing\nthe absolute value of x sub", "start": 1930.96, "duration": 2.76}, {"text": "n minus x is less than epsilon.", "start": 1933.72, "duration": 1.68}, {"text": "Now, what's the change\nfor monotone decreasing", "start": 1939.53, "duration": 2.64}, {"text": "is that we'll be\nable to identify", "start": 1942.17, "duration": 2.79}, {"text": "the limit of the\nsequence as being", "start": 1944.96, "duration": 3.18}, {"text": "the imf, the\ninfimum of this set.", "start": 1948.14, "duration": 4.85}, {"text": "But I'll leave that\nto you as an exercise.", "start": 1952.99, "duration": 1.94}, {"text": "So let's use this real quick to\nprove the limit of a little bit", "start": 1977.86, "duration": 4.55}, {"text": "more interesting sequence\nthan 1 over this one,", "start": 1982.41, "duration": 4.62}, {"text": "which is reasonably\ninteresting, I guess.", "start": 1987.03, "duration": 4.08}, {"text": "But typically in math, we\njust don't prove theorems", "start": 1991.11, "duration": 15.38}, {"text": "for the sake of\nproving theorems.", "start": 2006.49, "duration": 2.22}, {"text": "Typically, there's some\nconcrete reason we do things.", "start": 2008.71, "duration": 6.46}, {"text": "There's some concrete\nsequence we're", "start": 2015.17, "duration": 1.55}, {"text": "trying to prove converges,\nor has a certain property,", "start": 2016.72, "duration": 4.17}, {"text": "or doesn't have a\ncertain property.", "start": 2020.89, "duration": 2.56}, {"text": "And so the basic one is if\nyou like a geometric sequence.", "start": 2023.45, "duration": 9.75}, {"text": "So if c is a positive\nnumber between 0 and 1,", "start": 2033.2, "duration": 11.09}, {"text": "then we'll prove that\nthis sequence c to the n", "start": 2044.29, "duration": 7.349}, {"text": "is convergent and\nit converges to 0.", "start": 2051.639, "duration": 1.891}, {"text": "And we'll prove if\nc is bigger than 1,", "start": 2057.969, "duration": 8.121}, {"text": "then the sequence c\nto the n is unbounded.", "start": 2066.09, "duration": 5.884}, {"text": "In particular, it\ncan't converge.", "start": 2071.974, "duration": 1.375}, {"text": "So let's go in reverse order.", "start": 2080.65, "duration": 3.63}, {"text": "Let's prove that if\nc is bigger than 1,", "start": 2084.28, "duration": 3.129}, {"text": "then this thing is unbounded.", "start": 2087.409, "duration": 1.83}, {"text": "It doesn't require 1,\nbut it's shorter than 1,", "start": 2089.239, "duration": 2.451}, {"text": "and we can go ahead and do it.", "start": 2091.69, "duration": 1.87}, {"text": "And we'll use this\nfact that we proved,", "start": 2093.56, "duration": 2.54}, {"text": "I think, in the first or\nsecond lecture using induction.", "start": 2096.1, "duration": 6.82}, {"text": "So what does it mean to\nshow something is unbounded?", "start": 2102.92, "duration": 3.74}, {"text": "Again, we get to use\nour negation skills.", "start": 2106.66, "duration": 2.76}, {"text": "It means that-- what\ndo we want to show--", "start": 2109.42, "duration": 2.415}, {"text": "for all B bigger\nthan or equal to 0,", "start": 2115.29, "duration": 5.01}, {"text": "there exists an n, a natural\nnumber, so that c to the n", "start": 2120.3, "duration": 5.82}, {"text": "is bigger than B. Now, how\nare we going to find this n?", "start": 2126.12, "duration": 17.86}, {"text": "This seems like a\ncomplicated thing.", "start": 2143.98, "duration": 1.605}, {"text": "So let's replace it\nby something simpler.", "start": 2149.41, "duration": 3.38}, {"text": "Again, this is analysis, which\nmeans we get to use our wits,", "start": 2152.79, "duration": 5.34}, {"text": "and try to replace complicated\nthings by simpler things,", "start": 2158.13, "duration": 2.39}, {"text": "and work with the\nsimpler things.", "start": 2160.52, "duration": 1.375}, {"text": "So let me do a little bit of--", "start": 2164.46, "duration": 1.58}, {"text": "again, this is off\nto the side, how", "start": 2166.04, "duration": 2.82}, {"text": "would one think through this.", "start": 2168.86, "duration": 2.79}, {"text": "If you look at c to\nthe n, remember we", "start": 2171.65, "duration": 1.71}, {"text": "have this inequality\nfrom infinite time", "start": 2173.36, "duration": 3.21}, {"text": "ago that as long as x is bigger\nthan or equal to minus 1,", "start": 2176.57, "duration": 8.19}, {"text": "then I get 1 plus x to\nthe n is bigger than 1", "start": 2184.76, "duration": 3.09}, {"text": "plus n times x for\nall natural numbers n.", "start": 2187.85, "duration": 5.0}, {"text": "So that means c to the n, which\nis equal to 1 plus c minus 1", "start": 2198.45, "duration": 8.6}, {"text": "to the n-- so this is my x--", "start": 2207.05, "duration": 1.8}, {"text": "is bigger than or\nequal to 1 plus n times", "start": 2208.85, "duration": 4.02}, {"text": "c minus 1, which is bigger than\nor equal to n times c minus 1.", "start": 2212.87, "duration": 7.57}, {"text": "You see?", "start": 2220.44, "duration": 0.63}, {"text": "So if I want to make this big,\nit suffices to make this big.", "start": 2221.07, "duration": 7.46}, {"text": "So that's what I'll do.", "start": 2228.53, "duration": 2.25}, {"text": "So let n be a natural\nnumber such that n is", "start": 2230.78, "duration": 11.1}, {"text": "bigger than B over c minus 1.", "start": 2241.88, "duration": 3.24}, {"text": "Then now this we did off\nto the side we'll just", "start": 2255.92, "duration": 2.73}, {"text": "put in the proof now.", "start": 2258.65, "duration": 1.32}, {"text": "And c to the n equals 1\nplus 1 minus c to the n", "start": 2262.51, "duration": 5.34}, {"text": "is bigger than or\nequal to 1 plus n times", "start": 2267.85, "duration": 3.21}, {"text": "c minus 1, which is bigger\nthan or equal to n times", "start": 2271.06, "duration": 3.47}, {"text": "c minus 1, which is bigger\nthan B over c minus 1 times c", "start": 2274.53, "duration": 6.04}, {"text": "minus 1 equals B. So now\nlet's prove the first claim,", "start": 2280.57, "duration": 10.36}, {"text": "that if c is between 0\nand 1, then the limit as n", "start": 2290.93, "duration": 2.94}, {"text": "goes to infinity of\nc to the n equals 0.", "start": 2293.87, "duration": 3.84}, {"text": "So first, I want to prove\nthe following claim--", "start": 2297.71, "duration": 2.76}, {"text": "that we, in fact, have a\ndecreasing sequence, which", "start": 2300.47, "duration": 3.57}, {"text": "is bounded below by 0.", "start": 2304.04, "duration": 4.56}, {"text": "So claim for all n, 0\nis less than c to the n", "start": 2308.6, "duration": 10.61}, {"text": "is less than, I should say, c\nto the n plus 1 is less than c", "start": 2319.21, "duration": 6.3}, {"text": "to the n.", "start": 2325.51, "duration": 0.51}, {"text": "So the proof of this claim is a\nvery simple induction argument,", "start": 2333.72, "duration": 4.27}, {"text": "so we'll do this by induction.", "start": 2337.99, "duration": 1.92}, {"text": "So we have the base\ncase n equals 1.", "start": 2339.91, "duration": 6.11}, {"text": "So we are assuming that\nc is between 0 and 1.", "start": 2346.02, "duration": 11.39}, {"text": "And if I multiply\nthrough by c, I", "start": 2357.41, "duration": 2.28}, {"text": "conclude that 0 is less than\nc squared is less than c.", "start": 2359.69, "duration": 4.52}, {"text": "And that's the n equals 1 case.", "start": 2364.21, "duration": 2.58}, {"text": "And the inductive step is\nessentially the same proof.", "start": 2366.79, "duration": 5.995}, {"text": "Suppose 0 is less than c to\nthe m plus 1 is less than c", "start": 2375.5, "duration": 6.95}, {"text": "to the m.", "start": 2382.45, "duration": 0.64}, {"text": "Then multiplying through by c,\nwe get that 0 is less than c", "start": 2386.17, "duration": 5.11}, {"text": "to the m plus 2 is\nless than c to the m", "start": 2391.28, "duration": 3.74}, {"text": "plus 1, which is\nn equals m plus 1.", "start": 2395.02, "duration": 3.86}, {"text": "Here, we're using\nthis fact here--", "start": 2398.88, "duration": 2.91}, {"text": "that c is positive so it\ndoesn't flip the inequalities,", "start": 2401.79, "duration": 3.61}, {"text": "so I can multiply it through\nand preserve the inequalities.", "start": 2405.4, "duration": 4.61}, {"text": "So this shows that this\nsequence is monotone decreasing", "start": 2410.01, "duration": 10.73}, {"text": "and it's bounded below by\n0, and in fact bounded,", "start": 2420.74, "duration": 4.8}, {"text": "because c to the n and absolute\nvalue, these are all positive,", "start": 2425.54, "duration": 14.99}, {"text": "is equal to c to the n.", "start": 2440.53, "duration": 1.59}, {"text": "And c to the n is less\nthan c to the n minus 1,", "start": 2442.12, "duration": 4.68}, {"text": "which is less than c to the\nn minus 2, so on, and so on,", "start": 2446.8, "duration": 3.84}, {"text": "which is less than c.", "start": 2450.64, "duration": 2.16}, {"text": "So it's bounded.", "start": 2452.8, "duration": 3.54}, {"text": "I guess I could have built\nthat into this inequality", "start": 2456.34, "duration": 6.0}, {"text": "and proved that as\nwell, but that's OK.", "start": 2462.34, "duration": 4.28}, {"text": "So it has a limit.", "start": 2466.62, "duration": 2.13}, {"text": "So by the previous theorem, has\na limit, and I'll call it L.", "start": 2468.75, "duration": 16.34}, {"text": "And now what I want to\nshow is that L is 0.", "start": 2485.09, "duration": 2.145}, {"text": "And how we'll do that is one of\nthese analysis tricks, where--", "start": 2494.35, "duration": 5.55}, {"text": "not really tricks-- but\nrather than show with L", "start": 2499.9, "duration": 2.85}, {"text": "is directly equal\nto 0, we'll show", "start": 2502.75, "duration": 2.22}, {"text": "that the absolute value\nof L is less than epsilon", "start": 2504.97, "duration": 2.79}, {"text": "for every epsilon\npositive, and therefore", "start": 2507.76, "duration": 1.74}, {"text": "it has to be 0 because\nit's just a fixed number.", "start": 2509.5, "duration": 2.0}, {"text": "So let epsilon be positive.", "start": 2518.01, "duration": 1.16}, {"text": "Again, we're going to show that\nthe absolute value of L, which", "start": 2519.17, "duration": 2.583}, {"text": "is just a fixed number,\nis less than epsilon.", "start": 2521.753, "duration": 3.037}, {"text": "And therefore,\ncapital L has to be 0.", "start": 2524.79, "duration": 2.51}, {"text": "Then there exists, since this\nsequence converges, an M,", "start": 2532.43, "duration": 6.06}, {"text": "a natural number, such\nthat for all n bigger", "start": 2538.49, "duration": 5.19}, {"text": "than or equal to capital\nM, c to the n minus L", "start": 2543.68, "duration": 4.11}, {"text": "is less than 1 minus c\ntimes epsilon over 2.", "start": 2547.79, "duration": 8.08}, {"text": "Now, maybe you're wondering why\ndidn't I just use epsilon here?", "start": 2555.87, "duration": 6.61}, {"text": "Well, in the end,\nit's just going", "start": 2562.48, "duration": 3.08}, {"text": "to come out to this being less\nthan epsilon in absolute value.", "start": 2565.56, "duration": 3.818}, {"text": "Otherwise, I would have come\nout with less than epsilon times", "start": 2569.378, "duration": 2.542}, {"text": "some number, and I did\naway with that number", "start": 2571.92, "duration": 2.19}, {"text": "by choosing a\ndifferent number here.", "start": 2574.11, "duration": 3.1}, {"text": "So now we compute that\nif I look at 1 minus c", "start": 2577.21, "duration": 7.61}, {"text": "times the absolute\nvalue of L, this", "start": 2584.82, "duration": 2.28}, {"text": "is equal to L minus\nc times L. And this", "start": 2587.1, "duration": 5.42}, {"text": "is less than or equal to L\nminus c to the capital M plus--", "start": 2592.52, "duration": 8.98}, {"text": "let's put a plus 1, plus c to\nthe M plus 1 minus c to the L.", "start": 2604.89, "duration": 5.1}, {"text": "And by the triangle\ninequality, this", "start": 2609.99, "duration": 2.43}, {"text": "is less than or equal to L\nminus c to the M plus 1 plus--", "start": 2612.42, "duration": 5.46}, {"text": "now c to the M plus\n1 minus c to the L,", "start": 2617.88, "duration": 2.85}, {"text": "so I can pull out a c which\nis positive, so I can get L.", "start": 2620.73, "duration": 7.13}, {"text": "Now, M plus 1 is\nbigger than M. So it", "start": 2627.86, "duration": 4.53}, {"text": "satisfies this inequality,\nand so does this one.", "start": 2632.39, "duration": 5.43}, {"text": "And therefore, this is less\nthan epsilon over 2 times", "start": 2637.82, "duration": 3.75}, {"text": "1 minus c plus c times epsilon\nover 2 times 1 minus c.", "start": 2641.57, "duration": 6.63}, {"text": "And C is less than 1,\nso this whole thing", "start": 2648.2, "duration": 2.94}, {"text": "is less than\nepsilon over 2 times", "start": 2651.14, "duration": 1.83}, {"text": "1 minus c plus another\nepsilon over 2.", "start": 2652.97, "duration": 2.64}, {"text": "So I get epsilon over\n2 times 1 minus c.", "start": 2655.61, "duration": 5.24}, {"text": "And thus, the absolute value\nof L is less than epsilon.", "start": 2666.66, "duration": 8.3}, {"text": "And since epsilon was\narbitrary, that implies", "start": 2674.96, "duration": 2.39}, {"text": "the absolute value of L is equal\nto 0, i.e., L is equal to 0.", "start": 2677.35, "duration": 4.92}, {"text": "So that's a very\nconcrete application", "start": 2691.56, "duration": 4.44}, {"text": "of some of these theorems we've\nbeen proving, which is really--", "start": 2696.0, "duration": 4.98}, {"text": "I think the only real\nreason one proves", "start": 2700.98, "duration": 2.07}, {"text": "theorems is you typically have\na concrete example of something", "start": 2703.05, "duration": 7.163}, {"text": "in mind that you want to study.", "start": 2710.213, "duration": 1.292}, {"text": "But in order to\nstudy it, it often", "start": 2714.3, "duration": 2.06}, {"text": "requires some general\nmachinery, i.e., theorems.", "start": 2716.36, "duration": 6.575}, {"text": "So now we'll talk a\nlittle bit about sequences", "start": 2735.68, "duration": 3.15}, {"text": "obtained from other sequences.", "start": 2738.83, "duration": 3.72}, {"text": "So these are called\nsubsequences,", "start": 2742.55, "duration": 6.39}, {"text": "or sequences obtained\nfrom a single sequence.", "start": 2748.94, "duration": 7.177}, {"text": "So what do I mean by this?", "start": 2756.117, "duration": 1.083}, {"text": "Let me give you the\nprecise definition.", "start": 2757.2, "duration": 2.19}, {"text": "So we started off with a\nsequence and an increasing", "start": 2767.2, "duration": 9.18}, {"text": "sequence of integers, n sub k.", "start": 2776.38, "duration": 6.87}, {"text": "So let me just say what this\nmeans rather than write out", "start": 2791.91, "duration": 3.91}, {"text": "the word and then\nsay what it means.", "start": 2795.82, "duration": 2.29}, {"text": "So this is the sequence\nof natural numbers, which", "start": 2798.11, "duration": 13.82}, {"text": "are strictly increasing.\nn sub 1 is less", "start": 2811.93, "duration": 2.4}, {"text": "than n sub 2 is less\nthan n sub 3, and so on.", "start": 2814.33, "duration": 3.81}, {"text": "The new sequence, x sub n sub\nk-- so now the index is not n,", "start": 2825.62, "duration": 8.51}, {"text": "but the index is k--", "start": 2834.13, "duration": 1.22}, {"text": "is called a subsequence of\nthe original sequence x sub n.", "start": 2840.6, "duration": 12.87}, {"text": "So how should you view\nsubsequences of a sequence?", "start": 2857.4, "duration": 4.92}, {"text": "You should think that I line\nup all the entries of x,", "start": 2862.32, "duration": 5.46}, {"text": "of my original sequence\nx sub n, and then", "start": 2867.78, "duration": 4.05}, {"text": "I just start picking\nentries out of the sequence.", "start": 2871.83, "duration": 5.94}, {"text": "But every time I make a choice,\nI have to move to the right", "start": 2877.77, "duration": 3.48}, {"text": "and make another choice.", "start": 2881.25, "duration": 2.16}, {"text": "That's what I was just saying\nthere, expresses this condition", "start": 2883.41, "duration": 3.57}, {"text": "that this sequence of natural\nnumbers is increasing.", "start": 2886.98, "duration": 3.76}, {"text": "So I pick an entry\nin the sequence.", "start": 2890.74, "duration": 2.69}, {"text": "That's going to be my first\nguy, the first element", "start": 2893.43, "duration": 3.27}, {"text": "of my new subsequence.", "start": 2896.7, "duration": 1.5}, {"text": "And then I move to the right,\nand maybe I pick the next one,", "start": 2898.2, "duration": 4.44}, {"text": "maybe I pick one three down.", "start": 2902.64, "duration": 1.68}, {"text": "I pick that one.", "start": 2904.32, "duration": 1.18}, {"text": "And then I move to the right\nof that one and pick a new one.", "start": 2905.5, "duration": 4.9}, {"text": "And then I move to the right of\nthat one and pick another one.", "start": 2910.4, "duration": 2.91}, {"text": "So if you want to\ngenerate a subsequence", "start": 2913.31, "duration": 2.97}, {"text": "from an original sequence,\nhow do you think about this?", "start": 2916.28, "duration": 4.2}, {"text": "Again, line them all up,\nstart picking entries,", "start": 2920.48, "duration": 2.585}, {"text": "but every time\nyou pick an entry,", "start": 2923.065, "duration": 1.375}, {"text": "you have to move to the right in\norder to pick your next entry.", "start": 2924.44, "duration": 3.435}, {"text": "So let me give you some\nexamples and non-examples.", "start": 2932.6, "duration": 3.58}, {"text": "So for example, if our original\nsequence is 1, 2, 3, 4, 5, 6,", "start": 2936.18, "duration": 10.55}, {"text": "and so on, what would be\nexamples of some subsequences?", "start": 2946.73, "duration": 6.15}, {"text": "The odd numbers 1,\n3, 5, 7, 9 and so on.", "start": 2952.88, "duration": 6.28}, {"text": "You see how I'm taking\nthe original sequence,", "start": 2959.16, "duration": 2.4}, {"text": "so this is x sub n.", "start": 2961.56, "duration": 4.003}, {"text": "I'm just picking entries\nfrom the original sequence,", "start": 2965.563, "duration": 2.167}, {"text": "but every time I pick an\nentry, I move to the right", "start": 2967.73, "duration": 2.208}, {"text": "and pick a new one.", "start": 2969.938, "duration": 0.792}, {"text": "So I picked 1, now I\nget to choose anything", "start": 2970.73, "duration": 2.34}, {"text": "to the right of that.", "start": 2973.07, "duration": 1.24}, {"text": "I pick 3, now I can choose\nanything to the right of that.", "start": 2974.31, "duration": 3.75}, {"text": "So in the language\nof this definition,", "start": 2978.06, "duration": 2.42}, {"text": "the increasing\nsequence of integers", "start": 2980.48, "duration": 3.9}, {"text": "is just the odd\nintegers, so 2k minus 1.", "start": 2984.38, "duration": 3.87}, {"text": "So here, x sub n\nis equal to just n.", "start": 2988.25, "duration": 3.84}, {"text": "I could pick another\nsubsequence would be", "start": 2997.42, "duration": 3.39}, {"text": "the sequence of even numbers--", "start": 3000.81, "duration": 2.07}, {"text": "2, 4, 6, 8, 10.", "start": 3002.88, "duration": 4.74}, {"text": "This is a subsequence of\nthis original sequence.", "start": 3007.62, "duration": 2.43}, {"text": "Here, the increasing\nsequence of integers is 2k.", "start": 3010.05, "duration": 3.54}, {"text": "I could pick the\nsubsequence could be", "start": 3020.16, "duration": 3.09}, {"text": "the sequence of prime numbers--", "start": 3023.25, "duration": 2.79}, {"text": "2, 3, 5, 7, 11, 13.", "start": 3026.04, "duration": 4.5}, {"text": "And the increasing--\nso I don't have", "start": 3034.0, "duration": 4.51}, {"text": "a general formula for that.", "start": 3038.51, "duration": 2.22}, {"text": "Good luck finding\none, but we'll just", "start": 3040.73, "duration": 2.49}, {"text": "write this as k-th prime number.", "start": 3043.22, "duration": 5.905}, {"text": "Now, what would\nnot be an example?", "start": 3057.79, "duration": 2.62}, {"text": "So these are examples\nof subsequences.", "start": 3060.41, "duration": 2.48}, {"text": "Not examples of\nsubsequences would", "start": 3065.65, "duration": 2.13}, {"text": "be, for example, the\nsequence 1, 1, 1, 1, 1.", "start": 3067.78, "duration": 4.5}, {"text": "This is not a subsequence\nof this original sequence.", "start": 3072.28, "duration": 3.84}, {"text": "Remember, I have a\nsequence of natural numbers", "start": 3076.12, "duration": 2.41}, {"text": "which is increasing.", "start": 3078.53, "duration": 1.49}, {"text": "And x sub n sub k means\nthat this new sequence is", "start": 3080.02, "duration": 7.05}, {"text": "obtained from the old\none by picking entries--", "start": 3087.07, "duration": 3.09}, {"text": "by picking an entry,\nmoving to the right,", "start": 3090.16, "duration": 2.067}, {"text": "picking the next entry,\nmoving to the right,", "start": 3092.227, "duration": 1.833}, {"text": "and picking the next entry.", "start": 3094.06, "duration": 1.65}, {"text": "Here, in order to get this\nsequence from this one,", "start": 3095.71, "duration": 3.345}, {"text": "I just stay on the first\nentry and keep picking it.", "start": 3099.055, "duration": 3.585}, {"text": "But that's not how a\nsubsequence is defined.", "start": 3102.64, "duration": 3.945}, {"text": "So here, if you like, this would\nmean n sub k is equal to 1.", "start": 3109.43, "duration": 7.07}, {"text": "And this is not a strictly\nincreasing sequence", "start": 3116.5, "duration": 2.163}, {"text": "of natural numbers.", "start": 3118.663, "duration": 0.792}, {"text": "Or 1, 1 3, 3, 5, 5, and\nso on-- that's also not.", "start": 3123.04, "duration": 6.79}, {"text": "So these are not subsequences\nof the original sequence", "start": 3129.83, "duration": 10.22}, {"text": "given here.", "start": 3140.05, "duration": 0.75}, {"text": "So I hope that's clear.", "start": 3147.527, "duration": 0.958}, {"text": "Now, I want to emphasize this--", "start": 3154.0, "duration": 6.04}, {"text": "I'm not saying that the\nnumber you pick each time", "start": 3160.04, "duration": 6.39}, {"text": "has to be different from the\nnumber you picked before,", "start": 3166.43, "duration": 3.48}, {"text": "meaning the value.", "start": 3169.91, "duration": 2.31}, {"text": "You couldn't have 1, 1, 1, 1\nas a subsequence of this guy", "start": 3172.22, "duration": 4.53}, {"text": "because 1 is only\nin the first entry.", "start": 3176.75, "duration": 2.49}, {"text": "You can't keep\npicking one entry.", "start": 3179.24, "duration": 2.16}, {"text": "You have to pick\nan entry and move", "start": 3181.4, "duration": 1.71}, {"text": "to the next entry or\nthe one after that", "start": 3183.11, "duration": 2.97}, {"text": "and pick that entry to\nobtain your sequence.", "start": 3186.08, "duration": 3.72}, {"text": "But that doesn't\nnecessarily mean", "start": 3189.8, "duration": 1.77}, {"text": "that those actual\nnumbers in those entries", "start": 3191.57, "duration": 4.56}, {"text": "have to be different.", "start": 3196.13, "duration": 1.12}, {"text": "So for example, if I look\nat the sequence minus 1,", "start": 3197.25, "duration": 6.86}, {"text": "1, 1, minus 1, 1, one meaning\nx sub n is equal to minus 1", "start": 3204.11, "duration": 7.16}, {"text": "to the n-th then a perfectly\ngood subsequence is given", "start": 3211.27, "duration": 5.58}, {"text": "by minus 1, minus\n1, minus 1, minus 1,", "start": 3216.85, "duration": 5.22}, {"text": "where it looks like I'm just\npicking one of the entries,", "start": 3222.07, "duration": 3.06}, {"text": "but really I'm not.", "start": 3225.13, "duration": 0.99}, {"text": "Here, the increasing\nsequence-- so", "start": 3226.12, "duration": 2.91}, {"text": "what I'm doing here to\nget this new sequence,", "start": 3229.03, "duration": 2.43}, {"text": "I picked the first entry,\nthen I picked the third,", "start": 3231.46, "duration": 2.7}, {"text": "then I picked the fifth,\nthen I picked the seventh.", "start": 3234.16, "duration": 2.25}, {"text": "So n sub k equals 2k minus 1.", "start": 3236.41, "duration": 5.1}, {"text": "So all the actual numbers\nappearing in the sequence", "start": 3241.51, "duration": 3.09}, {"text": "are the same, but I'm actually\npicking different entries", "start": 3244.6, "duration": 5.37}, {"text": "from the original sequence,\nwhere they appear.", "start": 3249.97, "duration": 4.25}, {"text": "So this is also fine.", "start": 3254.22, "duration": 1.41}, {"text": "So is 1, 1, 1, 1, 1.", "start": 3255.63, "duration": 2.795}, {"text": "This is n k equals 2 times k.", "start": 3262.08, "duration": 2.35}, {"text": "So these are all\ngood subsequences.", "start": 3264.43, "duration": 3.0}, {"text": "So these were subsequences\nof the original sequence.", "start": 3267.43, "duration": 6.76}, {"text": "These are subsequences\nof this sequence.", "start": 3274.19, "duration": 2.88}, {"text": "So from a given sequence,\nwe can obtain new sequences", "start": 3309.12, "duration": 5.58}, {"text": "from this original\nsequence in this way.", "start": 3314.7, "duration": 4.91}, {"text": "So a natural question\nis to ask, how", "start": 3319.61, "duration": 2.45}, {"text": "does going from a\nsequence to a subsequence", "start": 3322.06, "duration": 11.29}, {"text": "behave with respect to limits?", "start": 3333.35, "duration": 2.22}, {"text": "If the original sequence\nconverges to a limit,", "start": 3335.57, "duration": 2.76}, {"text": "does a subsequence or\ndoes every subsequence", "start": 3338.33, "duration": 2.73}, {"text": "converge to that limit as well?", "start": 3341.06, "duration": 2.38}, {"text": "And this shouldn't come as\na surprise that it does.", "start": 3343.44, "duration": 2.48}, {"text": "Because all of the elements of\nthe sequence are getting close,", "start": 3345.92, "duration": 4.728}, {"text": "all the entries of the\nsequence are getting", "start": 3350.648, "duration": 1.792}, {"text": "close to a given number.", "start": 3352.44, "duration": 1.5}, {"text": "And a subsequence is just, if\nyou like, picking certain ones", "start": 3353.94, "duration": 3.57}, {"text": "along the way.", "start": 3357.51, "duration": 1.12}, {"text": "So certainly if I'm\nin a subsequence,", "start": 3358.63, "duration": 2.99}, {"text": "then as long as I'm far\nenough out in the subsequence,", "start": 3361.62, "duration": 2.85}, {"text": "I'll be close to\nthat limit as well.", "start": 3364.47, "duration": 2.07}, {"text": "So if you didn't get\nall that rambling,", "start": 3366.54, "duration": 3.0}, {"text": "I'll go ahead and state\nthe theorem and prove it.", "start": 3369.54, "duration": 3.87}, {"text": "x n is a sequence\nwhich converges to x.", "start": 3389.27, "duration": 4.305}, {"text": "And x sub n sub k is a\nsubsequence of x sub n.", "start": 3403.15, "duration": 15.37}, {"text": "Then the subsequence\nconverges to x, as well.", "start": 3418.52, "duration": 4.33}, {"text": "Limit as k goes to infinity\nof x sub n sub k equals x.", "start": 3427.2, "duration": 5.31}, {"text": "So let me just start off by\nmaking a simple observation", "start": 3454.25, "duration": 4.44}, {"text": "based on the fact that\nthis increasing sequence--", "start": 3458.69, "duration": 3.3}, {"text": "that the n sub k's\nare an increasing", "start": 3461.99, "duration": 1.728}, {"text": "sequence of natural numbers.", "start": 3463.718, "duration": 1.167}, {"text": "Since n sub 1 is bigger than\nor equal to 1 is less than n", "start": 3467.42, "duration": 8.02}, {"text": "sub 2 is less than\nn sub 3 and so on,", "start": 3475.44, "duration": 4.56}, {"text": "this implies that for\nall k, a natural number,", "start": 3480.0, "duration": 5.37}, {"text": "n sub k is bigger\nthan or equal to k.", "start": 3485.37, "duration": 2.82}, {"text": "So this is not so hard to\nbelieve because n sub 1 has", "start": 3493.92, "duration": 2.67}, {"text": "to be at least bigger than 1.", "start": 3496.59, "duration": 1.56}, {"text": "And n sub 2 has to be at\nleast bigger than n sub 1,", "start": 3498.15, "duration": 2.73}, {"text": "so it's either n sub\n1 plus 1 or bigger.", "start": 3500.88, "duration": 3.39}, {"text": "And therefore, by a\nsimple induction argument,", "start": 3504.27, "duration": 3.787}, {"text": "which I'll leave to\nyou, you can prove", "start": 3508.057, "duration": 1.583}, {"text": "that for all k,\na natural number,", "start": 3509.64, "duration": 1.485}, {"text": "n sub k is bigger than or\nequal to k, induct on k.", "start": 3511.125, "duration": 4.58}, {"text": "So we want to prove that\nthis sequence converges to x.", "start": 3521.34, "duration": 3.6}, {"text": "And we're going to do that\nusing the only means we have.", "start": 3524.94, "duration": 2.55}, {"text": "So this is just some arbitrary\nsubsequence of x sub n.", "start": 3527.49, "duration": 4.29}, {"text": "All we have is the\ndefinition to use.", "start": 3531.78, "duration": 1.695}, {"text": "So we're going to\nnow prove this.", "start": 3536.22, "duration": 1.43}, {"text": "So we have to show\nfor all epsilon", "start": 3537.65, "duration": 1.68}, {"text": "positive, blah, blah, blah, so\nthe first thing we have to do", "start": 3539.33, "duration": 3.12}, {"text": "is let epsilon be positive.", "start": 3542.45, "duration": 2.14}, {"text": "Now we'll use the fact that\nx sub n converges to x.", "start": 3544.59, "duration": 2.54}, {"text": "So x sub n converges to x.", "start": 3550.655, "duration": 3.855}, {"text": "There exists a natural\nnumber M0 such that", "start": 3554.51, "duration": 5.28}, {"text": "for all n bigger than\nor equal to M0, x", "start": 3559.79, "duration": 10.57}, {"text": "sub n minus x absolute\nvalue is less than epsilon.", "start": 3570.36, "duration": 5.36}, {"text": "This M sub 0 we'll choose\nfor our subsequence.", "start": 3575.72, "duration": 2.691}, {"text": "Choose M to equal\nM sub 0, so now we", "start": 3581.06, "duration": 4.64}, {"text": "need to show that this capital\nM works for our subsequence,", "start": 3585.7, "duration": 2.55}, {"text": "meaning if k is bigger\nthan or equal to capital M,", "start": 3588.25, "duration": 2.82}, {"text": "then x sub n sub k minus x\nis an absolute value less", "start": 3591.07, "duration": 5.28}, {"text": "than epsilon.", "start": 3596.35, "duration": 0.82}, {"text": "But this just follows\nfrom this fact.", "start": 3597.17, "duration": 4.67}, {"text": "And if k is bigger than or\nequal to M, this implies,", "start": 3601.84, "duration": 4.95}, {"text": "by this inequality, n\nsub k is bigger than", "start": 3606.79, "duration": 5.07}, {"text": "or equal to M, which\nremember, is equal to M sub 0.", "start": 3611.86, "duration": 3.33}, {"text": "So n sub k is some\ninteger, so natural number", "start": 3615.19, "duration": 3.18}, {"text": "bigger than or equal to M sub 0.", "start": 3618.37, "duration": 3.12}, {"text": "So that implies\nby this inequality", "start": 3621.49, "duration": 2.22}, {"text": "that x sub n sub k minus\nx in absolute value", "start": 3623.71, "duration": 4.38}, {"text": "is less than epsilon.", "start": 3628.09, "duration": 2.015}]
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+[{"text": "Last week we talked about--", "start": 16.933, "duration": 1.402}, {"text": "we went quantum.", "start": 18.335, "duration": 0.7}, {"text": "We had Dr. Quantum\nshow us the way.", "start": 19.035, "duration": 3.203}, {"text": "And this week, we're going to\ngo quantum for electrons, right?", "start": 22.238, "duration": 4.705}, {"text": "That's what we're\ngoing to do this week.", "start": 26.943, "duration": 2.803}, {"text": "These are my two favorite\nquantum mechanicists", "start": 29.746, "duration": 2.903}, {"text": "of all time.", "start": 32.649, "duration": 1.601}, {"text": "I believe that\nthis sign is meant", "start": 34.25, "duration": 1.736}, {"text": "to teach us something about\nthe double slit experiment.", "start": 35.986, "duration": 4.07}, {"text": "And just as you're\nleaving the lot,", "start": 40.056, "duration": 2.403}, {"text": "knowing that there\nis some chance", "start": 42.459, "duration": 2.702}, {"text": "that your one car could\nactually split into two,", "start": 45.161, "duration": 3.504}, {"text": "go through both\nexits, and recombine.", "start": 48.665, "duration": 2.302}, {"text": "Just like an electron\ndoes through two slits.", "start": 50.967, "duration": 2.369}, {"text": "And in fact, we know\nthat that's possible now.", "start": 53.336, "duration": 2.202}, {"text": "And if we wanted to, you could\nwrite down-- from de Broglie--", "start": 58.108, "duration": 4.404}, {"text": "you could write down like the\nwavelength of a car, right?", "start": 62.512, "duration": 3.504}, {"text": "So like in a car--", "start": 66.016, "duration": 1.968}, {"text": "I don't know, your\nlambda of the car", "start": 67.984, "duration": 2.569}, {"text": "would be equal to h over mv.", "start": 70.553, "duration": 4.538}, {"text": "And if you plus some\nnumbers in, this", "start": 75.091, "duration": 1.769}, {"text": "is going to be something\nlike oh, you know,", "start": 76.86, "duration": 1.935}, {"text": "maybe 10 to the\nminus 37th meters.", "start": 78.795, "duration": 3.237}, {"text": "It's small, but it's a wave.", "start": 82.032, "duration": 3.336}, {"text": "Your car is a wave, you know?", "start": 85.368, "duration": 2.802}, {"text": "The baseball is a wave.", "start": 88.17, "duration": 3.204}, {"text": "The electron-- we are all waves.", "start": 91.374, "duration": 3.003}, {"text": "And I know, and that's what--\nso the electron is a wave.", "start": 94.377, "duration": 3.504}, {"text": "And I know-- hashtag,\nwe are all waves.", "start": 97.881, "duration": 3.235}, {"text": "Because it's a thing.", "start": 101.116, "duration": 1.903}, {"text": "It's really a thing.", "start": 103.019, "duration": 1.234}, {"text": "Because it's true.", "start": 104.253, "duration": 2.369}, {"text": "I am a wave.", "start": 106.622, "duration": 1.869}, {"text": "You are a wave.", "start": 108.491, "duration": 1.035}, {"text": "We are all waves.", "start": 109.526, "duration": 1.368}, {"text": "It's just-- our wavelengths\nare pretty small,", "start": 110.894, "duration": 1.868}, {"text": "but they're not zero.", "start": 112.762, "duration": 1.568}, {"text": "And so the next time\nyou get-- oh, we're", "start": 114.33, "duration": 2.103}, {"text": "on the same wavelength.", "start": 116.433, "duration": 1.167}, {"text": "You really are.", "start": 117.6, "duration": 2.236}, {"text": "It's true.", "start": 119.836, "duration": 1.201}, {"text": "We are-- right?", "start": 121.037, "duration": 1.135}, {"text": "That's deep.", "start": 122.172, "duration": 1.468}, {"text": "We are waves.", "start": 123.64, "duration": 1.968}, {"text": "All of us.", "start": 125.608, "duration": 0.935}, {"text": "And so, the wavelength--", "start": 126.543, "duration": 2.569}, {"text": "OK, the wavelength for an\nelectron was something like 10", "start": 129.112, "duration": 2.336}, {"text": "to the minus 10th meters.", "start": 131.448, "duration": 2.469}, {"text": "Which made it a really nice\nway to interrogate images.", "start": 133.917, "duration": 4.704}, {"text": "And that was my \"why this\nmatters\" last week, right?", "start": 138.621, "duration": 2.436}, {"text": "On Friday.", "start": 141.057, "duration": 0.801}, {"text": "So you can take advantage of\nthat wavelength to do things.", "start": 141.858, "duration": 5.005}, {"text": "Like see electron\nmicroscopy, right?", "start": 146.863, "duration": 4.171}, {"text": "But everyone's awake.", "start": 151.034, "duration": 1.501}, {"text": "That's what quantum\nmechanics told us.", "start": 152.535, "duration": 3.704}, {"text": "But what we want\nto do now is know", "start": 156.239, "duration": 1.702}, {"text": "how to represent this wave.", "start": 157.941, "duration": 3.904}, {"text": "So everything's waving.", "start": 161.845, "duration": 1.601}, {"text": "We've got that.", "start": 163.446, "duration": 1.001}, {"text": "But how do I describe it?", "start": 164.447, "duration": 2.236}, {"text": "Right?", "start": 166.683, "duration": 0.533}, {"text": "And that's where we left off.", "start": 167.216, "duration": 2.37}, {"text": "And we left off\nby me telling you", "start": 169.586, "duration": 1.767}, {"text": "that it all led to Schrodinger,\nwho came up with the wave", "start": 171.353, "duration": 4.305}, {"text": "equation for quantum mechanics.", "start": 175.658, "duration": 1.802}, {"text": "And the wave equation\nof Schrodinger", "start": 177.527, "duration": 3.103}, {"text": "is really pretty\nincredible, because--", "start": 180.63, "duration": 4.137}, {"text": "so I'm not going to\nwrite out Schrodinger.", "start": 184.767, "duration": 2.336}, {"text": "That would take me forever.", "start": 187.103, "duration": 1.502}, {"text": "So I'm going to\nwrite S. Eq., right?", "start": 188.605, "duration": 4.471}, {"text": "The Schrodinger equation, right?", "start": 193.076, "duration": 2.936}, {"text": "And here-- so what he had is he\nhad the sort of wave behavior", "start": 196.012, "duration": 7.875}, {"text": "that was captured.", "start": 203.887, "duration": 1.901}, {"text": "And it was captured\nautomatically.", "start": 205.788, "duration": 1.902}, {"text": "And it gave us also\nallowed energies, you see?", "start": 207.69, "duration": 4.004}, {"text": "So, allowed energies.", "start": 211.694, "duration": 2.97}, {"text": "And this is also\nthe quantization.", "start": 214.664, "duration": 5.539}, {"text": "Ah-- I ran out of room.", "start": 220.203, "duration": 1.735}, {"text": "Right.", "start": 221.938, "duration": 0.5}, {"text": "But now, If you go\nback to classical--", "start": 222.438, "duration": 2.503}, {"text": "so if you think about\nclassical physics, what", "start": 224.941, "duration": 4.104}, {"text": "you would have is something\nlike maybe F equals ma.", "start": 229.045, "duration": 2.569}, {"text": "But what that gives you--", "start": 231.614, "duration": 2.903}, {"text": "well, it doesn't give\nyou wave behavior,", "start": 234.517, "duration": 2.336}, {"text": "but it gives you\ncontinuous energies.", "start": 236.853, "duration": 4.304}, {"text": "Continuous energies.", "start": 241.157, "duration": 4.204}, {"text": "So the powerful point here\nis that from that equation--", "start": 245.361, "duration": 5.105}, {"text": "and we don't need to\nknow this equation.", "start": 250.466, "duration": 2.77}, {"text": "We're not going to derive it.", "start": 253.236, "duration": 1.401}, {"text": "Right?", "start": 254.637, "duration": 0.501}, {"text": "Today I'm going to tell\nyou how it's solved,", "start": 255.138, "duration": 1.835}, {"text": "but you don't need to\nknow how to solve it.", "start": 256.973, "duration": 1.268}, {"text": "But you need to know\nwhat the solutions mean.", "start": 258.241, "duration": 2.302}, {"text": "That's what we're\ntalking about today.", "start": 260.543, "duration": 1.969}, {"text": "But that equation-- what it\ndoes is it sets up the energies", "start": 262.512, "duration": 6.54}, {"text": "as a function of the wave.", "start": 269.052, "duration": 1.935}, {"text": "Psi-- that function, psi--\nis the wave function, OK?", "start": 270.987, "duration": 5.205}, {"text": "And so you get waves by default,\nbecause that's what you're", "start": 276.192, "duration": 2.936}, {"text": "solving for-- these waves.", "start": 279.128, "duration": 1.769}, {"text": "And then you have\na minus second--", "start": 280.897, "duration": 1.768}, {"text": "oh, there's an h bar.", "start": 282.665, "duration": 2.036}, {"text": "That's an h over 2 pi.", "start": 284.701, "duration": 2.102}, {"text": "Right?", "start": 289.239, "duration": 0.5}, {"text": "But it's like the same\nPlanck's constant.", "start": 289.739, "duration": 2.903}, {"text": "OK.", "start": 292.642, "duration": 0.5}, {"text": "But the wave\nbehavior gives you--", "start": 293.142, "duration": 3.037}, {"text": "because there's only\ncertain energies that", "start": 296.179, "duration": 2.569}, {"text": "solve that equation.", "start": 298.748, "duration": 1.034}, {"text": "So quantization\nfalls out naturally.", "start": 299.782, "duration": 3.938}, {"text": "You don't have to\nput it in anymore.", "start": 303.72, "duration": 1.935}, {"text": "It is a direct result of\nsolving this equation.", "start": 305.655, "duration": 4.004}, {"text": "If I take a wave--", "start": 309.659, "duration": 2.169}, {"text": "think about this, right.", "start": 311.828, "duration": 1.034}, {"text": "If you take a wave and\nyou put it in a box,", "start": 312.862, "duration": 3.404}, {"text": "then it can only have\ncertain solutions.", "start": 316.266, "duration": 3.303}, {"text": "Once you define the box,\nif you throw a wave in it,", "start": 319.569, "duration": 3.937}, {"text": "well, that's where those\nthings are on the right are.", "start": 323.506, "duration": 3.537}, {"text": "Maybe it's a standing wave.", "start": 327.043, "duration": 1.468}, {"text": "And so it's going to look--", "start": 328.511, "duration": 2.402}, {"text": "no-- it's going to be like this.", "start": 330.913, "duration": 4.839}, {"text": "One solution.", "start": 335.752, "duration": 2.002}, {"text": "And some energy.", "start": 337.754, "duration": 3.87}, {"text": "Or maybe it's going to look--", "start": 341.624, "duration": 2.569}, {"text": "I didn't leave myself any room--", "start": 344.193, "duration": 1.969}, {"text": "like this.", "start": 346.162, "duration": 2.302}, {"text": "And it's going to have\nsome other energy, right?", "start": 348.464, "duration": 3.037}, {"text": "1, 2.", "start": 351.501, "duration": 1.401}, {"text": "That's it.", "start": 352.902, "duration": 0.501}, {"text": "If you throw a wave\nin a box-- like,", "start": 353.403, "duration": 1.534}, {"text": "here's the first\none, second one.", "start": 354.937, "duration": 1.602}, {"text": "But there are only certain\nones that are going to work.", "start": 356.539, "duration": 3.103}, {"text": "All right, and you\ncan get that sense.", "start": 359.642, "duration": 2.202}, {"text": "Because otherwise it's not\ngoing to line up and then", "start": 361.844, "duration": 2.169}, {"text": "be able to wave and keep going.", "start": 364.013, "duration": 2.603}, {"text": "It's not going to\nbe a standing wave.", "start": 366.616, "duration": 2.035}, {"text": "Right?", "start": 368.651, "duration": 0.901}, {"text": "So you get this sense\nright away of quantization.", "start": 369.552, "duration": 2.87}, {"text": "Only certain waves, and\nonly certain energies,", "start": 372.422, "duration": 2.936}, {"text": "will solve this equation.", "start": 375.358, "duration": 1.201}, {"text": "Now, here's the key, is this--", "start": 376.559, "duration": 4.271}, {"text": "we're going to throw an electron\ninto this equation, right?", "start": 380.83, "duration": 3.57}, {"text": "But we're going to throw it\ninto the right potential.", "start": 384.4, "duration": 3.237}, {"text": "And that is the potential that\nwe know it sits in, in an atom.", "start": 387.637, "duration": 3.57}, {"text": "Which is simply a\nCoulomb potential.", "start": 391.207, "duration": 3.17}, {"text": "So this is how we\nget there, right?", "start": 394.377, "duration": 1.868}, {"text": "We take Schrodinger's\nequation of quantum mechanics.", "start": 396.245, "duration": 3.304}, {"text": "And we solve it for an\nelectron waving in the presence", "start": 399.549, "duration": 6.306}, {"text": "of the potential of the atom.", "start": 405.855, "duration": 3.37}, {"text": "Which is a positive potential.", "start": 409.225, "duration": 2.302}, {"text": "And you can see, this is a--", "start": 411.527, "duration": 1.168}, {"text": "OK, V is a potential.", "start": 412.695, "duration": 1.802}, {"text": "And that's an attractive\npotential, right?", "start": 414.497, "duration": 2.502}, {"text": "That's an attractive potential.", "start": 416.999, "duration": 1.736}, {"text": "So what happens when we do that?", "start": 418.735, "duration": 1.334}, {"text": "So that's what\nwe're going to do.", "start": 420.069, "duration": 1.368}, {"text": "I'm going to leave this for--", "start": 421.437, "duration": 1.635}, {"text": "so.", "start": 423.072, "duration": 0.834}, {"text": "What happens?", "start": 423.906, "duration": 0.534}, {"text": "So if we take a hydrogen atom--", "start": 424.44, "duration": 3.37}, {"text": "or as I've written it here, a\n\"Hatom,\" then you would have--", "start": 427.81, "duration": 6.707}, {"text": "Let's see.", "start": 434.517, "duration": 0.5}, {"text": "What do you get from this?", "start": 435.017, "duration": 1.068}, {"text": "Well, you get that the potential\nis going to be minus 1 over r.", "start": 436.085, "duration": 4.672}, {"text": "Yeah.", "start": 440.757, "duration": 0.5}, {"text": "It goes as minus 1--", "start": 441.257, "duration": 1.368}, {"text": "an e and an over-permittivity\nof space and stuff like that.", "start": 442.625, "duration": 3.47}, {"text": "But it goes as minus 1 over r.", "start": 446.095, "duration": 2.803}, {"text": "That's the Coulomb potential.", "start": 448.898, "duration": 2.236}, {"text": "Right?", "start": 451.134, "duration": 1.034}, {"text": "A plus charge is sitting\noutside of a minus charge.", "start": 452.168, "duration": 7.074}, {"text": "Ah!", "start": 459.242, "duration": 2.102}, {"text": "That was a close call.", "start": 461.344, "duration": 1.435}, {"text": "The electron is sitting out\nhere, and there's the nucleus.", "start": 462.779, "duration": 4.237}, {"text": "And the potential feels\nis a Coulomb potential.", "start": 467.016, "duration": 2.136}, {"text": "OK, so that's point 1.", "start": 469.152, "duration": 1.334}, {"text": "Point 2 is that we're\ngoing to apply the--", "start": 470.486, "duration": 6.072}, {"text": "oh, I'm saving\nmyself so much time.", "start": 476.558, "duration": 3.104}, {"text": "I love it, when you're\nefficient like that--", "start": 479.662, "duration": 2.402}, {"text": "S. Eq.", "start": 482.064, "duration": 0.768}, {"text": "Schrodinger equation.", "start": 482.832, "duration": 1.969}, {"text": "The Schrodinger equation.", "start": 484.801, "duration": 1.768}, {"text": "But the way that we're going\nto do this is in spherical", "start": 486.569, "duration": 3.403}, {"text": "coordinates.", "start": 489.972, "duration": 3.137}, {"text": "Spherical coords.", "start": 493.109, "duration": 4.571}, {"text": "And all that means\nis that I'm going", "start": 497.68, "duration": 2.603}, {"text": "to write psi as a function\nof r, theta, and phi.", "start": 500.283, "duration": 8.808}, {"text": "And the last thing\nthat I'm going to do", "start": 512.462, "duration": 2.802}, {"text": "is I'm going to\nseparate the variables.", "start": 515.264, "duration": 4.371}, {"text": "And that's just a\nstandard way to solve", "start": 519.635, "duration": 3.137}, {"text": "mathematical equations.", "start": 522.772, "duration": 1.168}, {"text": "So I'm going to\nseparate the variables.", "start": 523.94, "duration": 1.635}, {"text": "So separate.", "start": 525.575, "duration": 1.501}, {"text": "And so what that means is\nthat psi can be written as one", "start": 527.076, "duration": 7.241}, {"text": "function-- let's call it r--", "start": 534.317, "duration": 2.602}, {"text": "of the radius, times another\nfunction, p, of the theta,", "start": 536.919, "duration": 6.807}, {"text": "times another function f of phi.", "start": 543.726, "duration": 2.536}, {"text": "So that's my separation\nof variables, OK?", "start": 546.262, "duration": 3.67}, {"text": "Again, I'm not all\nabout having you know", "start": 549.932, "duration": 3.771}, {"text": "how to solve this equation.", "start": 553.703, "duration": 3.003}, {"text": "OK?", "start": 556.706, "duration": 0.834}, {"text": "That you can learn\nin quantum mechanics.", "start": 557.54, "duration": 2.402}, {"text": "But what I'm all about is what\nthat quantum mechanics solution", "start": 559.942, "duration": 3.837}, {"text": "means for us here in chemistry.", "start": 563.779, "duration": 2.636}, {"text": "And this is deep.", "start": 566.415, "duration": 1.936}, {"text": "This is deep, because--", "start": 568.351, "duration": 1.234}, {"text": "why?", "start": 569.585, "duration": 0.734}, {"text": "Because this whole thing\nis quantized, right?", "start": 570.319, "duration": 4.738}, {"text": "So just like before, there's\nonly certain allowed values", "start": 575.057, "duration": 8.142}, {"text": "for the wave function.", "start": 583.199, "duration": 1.301}, {"text": "There's only certain allowed\nvalues for these variables.", "start": 584.5, "duration": 5.973}, {"text": "Each one of them is quantized.", "start": 590.473, "duration": 2.769}, {"text": "Each one of them.", "start": 593.242, "duration": 1.902}, {"text": "OK?", "start": 595.144, "duration": 0.934}, {"text": "And that's what we need\nto learn about today,", "start": 596.078, "duration": 2.269}, {"text": "is what that means\nfor chemistry.", "start": 598.347, "duration": 2.369}, {"text": "All right.", "start": 600.716, "duration": 1.235}, {"text": "So now we're going to go\nthrough the quantum numbers", "start": 601.951, "duration": 6.406}, {"text": "and see what they mean.", "start": 608.357, "duration": 0.968}, {"text": "And we're going to start\nwith this first one,", "start": 609.325, "duration": 2.97}, {"text": "the radial function.", "start": 612.295, "duration": 2.702}, {"text": "So radial, and then\ntwo angular functions.", "start": 614.997, "duration": 4.405}, {"text": "OK.", "start": 619.402, "duration": 0.667}, {"text": "Now the radial--\nso what do we get?", "start": 620.069, "duration": 2.369}, {"text": "Well, the radial function--", "start": 622.438, "duration": 3.637}, {"text": "I'm using a word here,\nI got to tell you why.", "start": 626.075, "duration": 2.469}, {"text": "Orbital of hydrogen, right?", "start": 628.544, "duration": 3.003}, {"text": "So I've solved this now.", "start": 631.547, "duration": 1.135}, {"text": "I've solved this equation,\nand I'm plotting this orbital", "start": 632.682, "duration": 6.006}, {"text": "for first quantization--\nn equals 1, n equals 2,", "start": 638.688, "duration": 4.137}, {"text": "n equals 3.", "start": 642.825, "duration": 0.934}, {"text": "We've got to talk\nabout this, right?", "start": 643.759, "duration": 1.969}, {"text": "But I'm just plotting what\nthat function looks like.", "start": 645.728, "duration": 4.104}, {"text": "Well, let's compare.", "start": 649.832, "duration": 1.401}, {"text": "Because if I'm Bohr,\nthen what I have is this.", "start": 651.233, "duration": 5.106}, {"text": "Remember this?", "start": 656.339, "duration": 0.567}, {"text": "I've got like this--", "start": 656.906, "duration": 1.501}, {"text": "OK, there's 1, and\nit's going around,", "start": 658.407, "duration": 3.337}, {"text": "and it's very happy in an orbit.", "start": 661.744, "duration": 2.603}, {"text": "But see, we don't call\nthese orbits anymore.", "start": 668.784, "duration": 3.571}, {"text": "And it's going to be clear as\nwe talk about this picture,", "start": 672.355, "duration": 2.369}, {"text": "because these aren't\ndistinct orbits, right?", "start": 674.724, "duration": 4.004}, {"text": "So now in quantum\nwhat you have--", "start": 678.728, "duration": 7.34}, {"text": "I'm just going to take\nthat n equals 1 solution.", "start": 686.068, "duration": 3.17}, {"text": "That's the first solution\nto the radial part, right?", "start": 689.238, "duration": 5.205}, {"text": "That's not a fixed distance.", "start": 694.443, "duration": 2.436}, {"text": "That's not a fixed\ndistance, right?", "start": 696.879, "duration": 2.035}, {"text": "So now I'm just looking\nat the radial distribution", "start": 698.914, "duration": 5.239}, {"text": "of the probability.", "start": 704.153, "duration": 2.302}, {"text": "The probability of\nfinding the electron.", "start": 706.455, "duration": 3.304}, {"text": "That's how we speak\nwhen we speak quantum.", "start": 709.759, "duration": 3.37}, {"text": "We don't say it's here, right?", "start": 713.129, "duration": 2.869}, {"text": "We say it could be here.", "start": 715.998, "duration": 2.036}, {"text": "I don't know.", "start": 718.034, "duration": 0.533}, {"text": "But there's a probability\nthat it's there.", "start": 718.567, "duration": 1.769}, {"text": "So now it sort of has\na probability cloud.", "start": 720.336, "duration": 5.639}, {"text": "Now it looks like it\ngets a little less--", "start": 725.975, "duration": 3.27}, {"text": "why am I drawing spirals?", "start": 729.245, "duration": 1.968}, {"text": "It looks like it gets\na little less probable", "start": 731.213, "duration": 2.336}, {"text": "as you go further out, right?", "start": 733.549, "duration": 2.002}, {"text": "So maybe the density of\nprobability-- because look,", "start": 735.551, "duration": 2.202}, {"text": "right?", "start": 737.753, "duration": 0.501}, {"text": "It's got a peak there.", "start": 738.254, "duration": 1.635}, {"text": "But even if I just plot\nthat first orbital,", "start": 739.889, "duration": 5.372}, {"text": "even as I go all the way out\nto here, it is non-0, right?", "start": 745.261, "duration": 4.971}, {"text": "So this is probability.", "start": 750.232, "duration": 2.236}, {"text": "And this would be n equals 1.", "start": 757.139, "duration": 2.102}, {"text": "So it's a totally\ndifferent story.", "start": 759.241, "duration": 2.736}, {"text": "That electron isn't in\none place, but it is.", "start": 761.977, "duration": 4.972}, {"text": "But it's not.", "start": 766.949, "duration": 1.502}, {"text": "It could be anywhere.", "start": 768.451, "duration": 1.134}, {"text": "It could be-- if\nI'm a hydrogen atom,", "start": 769.585, "duration": 2.269}, {"text": "my electron could literally\nbe across the room.", "start": 771.854, "duration": 2.603}, {"text": "There is a finite\nprobability that that's true.", "start": 774.457, "duration": 3.236}, {"text": "And we know that since\nwe are all waves,", "start": 777.693, "duration": 3.737}, {"text": "and we can all be defined\nby the equations of quantum", "start": 781.43, "duration": 3.137}, {"text": "mechanics-- and in fact, that\nis the way to define the world--", "start": 784.567, "duration": 3.57}, {"text": "that we also have probabilities.", "start": 788.137, "duration": 2.903}, {"text": "They're small, you know.", "start": 791.04, "duration": 2.335}, {"text": "But I could be over\nthere right now.", "start": 793.375, "duration": 2.803}, {"text": "There's a chance.", "start": 796.178, "duration": 1.168}, {"text": "My weight function\nis not exactly 0", "start": 797.346, "duration": 2.87}, {"text": "all the way over there.", "start": 800.216, "duration": 1.101}, {"text": "It's close.", "start": 801.317, "duration": 1.134}, {"text": "But it's not exact, right?", "start": 802.451, "duration": 3.704}, {"text": "That is a very different picture\nof an electron in an orbit--", "start": 806.155, "duration": 4.638}, {"text": "in fact, it's not an orbit.", "start": 810.793, "duration": 1.468}, {"text": "It's an orbital.", "start": 812.261, "duration": 1.902}, {"text": "And that's where we say orbital.", "start": 814.163, "duration": 4.871}, {"text": "That's why we stay it.", "start": 819.034, "duration": 0.901}, {"text": "OK, but-- we're listing\nquantum numbers.", "start": 819.935, "duration": 2.503}, {"text": "These are the quantum numbers.", "start": 822.438, "duration": 2.269}, {"text": "Oh, oh- I'm going all caps.", "start": 824.707, "duration": 4.738}, {"text": "Didn't even know I\nwas going to do that.", "start": 829.445, "duration": 3.136}, {"text": "So we have n, which is\ncalled the principle--", "start": 832.581, "duration": 3.037}, {"text": "principle quantum number.", "start": 838.754, "duration": 5.906}, {"text": "And this is going to be related\nto the main energy, kind", "start": 844.66, "duration": 5.472}, {"text": "of e, 1, 1, right?", "start": 850.132, "duration": 2.169}, {"text": "E, 2, 2.", "start": 852.301, "duration": 0.834}, {"text": "So this is going to be related\nto the main energy level.", "start": 853.135, "duration": 3.704}, {"text": "Main energy level, right?", "start": 856.839, "duration": 5.772}, {"text": "And it's also related\nto the radial distance.", "start": 862.611, "duration": 4.104}, {"text": "Radial distance.", "start": 866.715, "duration": 1.602}, {"text": "And sometimes we\ncall this the shell.", "start": 871.62, "duration": 3.237}, {"text": "So sometimes the\nprincipal quantum number,", "start": 874.857, "duration": 1.969}, {"text": "this is the shell, right?", "start": 876.826, "duration": 1.968}, {"text": "It's the first shell,\nor the second shell.", "start": 878.794, "duration": 3.237}, {"text": "So we can call this the shell.", "start": 882.031, "duration": 3.17}, {"text": "Come back to that later.", "start": 885.201, "duration": 2.335}, {"text": "And you can see right there.", "start": 887.536, "duration": 1.769}, {"text": "OK, we'll talk about n\nequals 2 and 3 in a second.", "start": 889.305, "duration": 2.602}, {"text": "But you know-- oh,\nlet's talk about it now.", "start": 891.907, "duration": 3.437}, {"text": "You can see right there--", "start": 895.344, "duration": 1.435}, {"text": "it I go from n equals 1 to n\nequals 2, then I'm further out.", "start": 896.779, "duration": 6.573}, {"text": "Yeah, I still got non-0.", "start": 903.352, "duration": 1.668}, {"text": "Doesn't quite go to 0\nlike I just said there.", "start": 905.02, "duration": 2.903}, {"text": "But it's further out,\nit's shifted out, right?", "start": 907.923, "duration": 2.67}, {"text": "So with increasing n--", "start": 910.593, "duration": 3.203}, {"text": "so another thing\nwe can say about n", "start": 913.796, "duration": 1.968}, {"text": "is that with increasing n, you\nget higher energies and larger", "start": 915.764, "duration": 18.986}, {"text": "distances.", "start": 934.75, "duration": 0.901}, {"text": "larger r, a [? hole. ?]", "start": 935.651, "duration": 2.869}, {"text": "But you get something else.", "start": 938.52, "duration": 2.169}, {"text": "You get something else,\nand you can see it there.", "start": 940.689, "duration": 2.469}, {"text": "And I've been avoiding it, but\nI got to address it right now.", "start": 943.158, "duration": 2.636}, {"text": "Because those higher\nend functions go to 0.", "start": 945.794, "duration": 3.938}, {"text": "So they have nodes.", "start": 949.732, "duration": 1.968}, {"text": "With increasing n,\nyou get more nodes.", "start": 951.7, "duration": 3.871}, {"text": "What's a node?", "start": 955.571, "duration": 0.634}, {"text": "A node is when it goes to 0.", "start": 956.205, "duration": 2.736}, {"text": "And there's more of them.", "start": 958.941, "duration": 1.601}, {"text": "Now that's also\nreally important.", "start": 960.542, "duration": 2.269}, {"text": "So what that means is in\nBohr, my orbit was r, e.", "start": 965.948, "duration": 7.874}, {"text": "Heisenberg said no way.", "start": 973.822, "duration": 2.837}, {"text": "Can't have them both.", "start": 976.659, "duration": 1.001}, {"text": "But I had a r,\nwhich was one value.", "start": 977.66, "duration": 3.403}, {"text": "And remember-- it\ncould only then", "start": 981.063, "duration": 1.768}, {"text": "be the r of the next\nvalue, the next n.", "start": 982.831, "duration": 4.138}, {"text": "Now I'm basically\nsaying the opposite.", "start": 986.969, "duration": 2.202}, {"text": "I'm saying, well actually,\nr can be anything.", "start": 989.171, "duration": 2.869}, {"text": "There's a probability\ncloud, so this electron", "start": 992.04, "duration": 2.603}, {"text": "could be anywhere with certain\nprobability, except not here.", "start": 994.643, "duration": 6.874}, {"text": "In this one place.", "start": 1001.517, "duration": 1.768}, {"text": "This node.", "start": 1003.285, "duration": 1.201}, {"text": "It's 0.", "start": 1004.486, "duration": 0.868}, {"text": "It's literally 0.", "start": 1005.354, "duration": 1.401}, {"text": "The probability of finding\nthe electron there is 0.", "start": 1006.755, "duration": 2.736}, {"text": "It cannot exist there.", "start": 1009.491, "duration": 1.235}, {"text": "But how bizarre is that?", "start": 1010.726, "duration": 2.236}, {"text": "The electron can exist\nwith probability out here,", "start": 1012.962, "duration": 5.005}, {"text": "and probability in here, but\nit can't exist in between.", "start": 1017.967, "duration": 4.17}, {"text": "It's the same electron.", "start": 1022.137, "duration": 3.203}, {"text": "Try explaining how it\ngoes back and forth.", "start": 1025.34, "duration": 2.702}, {"text": "It skips over a zero\nprobability part, r.", "start": 1028.042, "duration": 5.473}, {"text": "Right?", "start": 1033.515, "duration": 0.501}, {"text": "But these nodes\nare very important.", "start": 1034.016, "duration": 1.668}, {"text": "And just to give you a\nsense of what this means,", "start": 1035.684, "duration": 2.502}, {"text": "I found a very fancy\nanimation, because I", "start": 1038.186, "duration": 2.202}, {"text": "want to make sure\nyou guys understand.", "start": 1040.388, "duration": 1.569}, {"text": "So here's the electron.", "start": 1041.957, "duration": 1.668}, {"text": "It's doing this, it's\ndoing its waving thing.", "start": 1043.625, "duration": 2.103}, {"text": "But look at what\nhappens with the nodes.", "start": 1045.728, "duration": 1.935}, {"text": "Uh uh.", "start": 1047.663, "duration": 1.034}, {"text": "The probability\nthere is always 0.", "start": 1048.697, "duration": 2.036}, {"text": "You see that?", "start": 1050.733, "duration": 0.967}, {"text": "Can't go-- no.", "start": 1051.7, "duration": 1.268}, {"text": "Not gonna exist there.", "start": 1052.968, "duration": 2.202}, {"text": "Right?", "start": 1055.17, "duration": 2.336}, {"text": "That is super deep.", "start": 1057.506, "duration": 1.568}, {"text": "Because there's no classical\nanalog to these things.", "start": 1059.074, "duration": 4.305}, {"text": "There's no classical analog.", "start": 1063.379, "duration": 1.768}, {"text": "But this is what\nelectrons do in an atom.", "start": 1065.147, "duration": 4.771}, {"text": "Now, this is what the\nclouds look like--", "start": 1069.918, "duration": 1.969}, {"text": "a little better\ndrawn than mine--", "start": 1071.887, "duration": 1.935}, {"text": "for n equals 1, n equals\n2, and n equals 3.", "start": 1073.822, "duration": 3.337}, {"text": "So again, you can see--", "start": 1077.159, "duration": 1.101}, {"text": "this is one electron.", "start": 1078.26, "duration": 1.935}, {"text": "It's colored differently,\njust to contrast it,", "start": 1080.195, "duration": 1.902}, {"text": "but this is one electron.", "start": 1082.097, "duration": 1.835}, {"text": "Right?", "start": 1083.932, "duration": 0.501}, {"text": "And", "start": 1084.433, "duration": 0.5}, {"text": "These are plus and\nminus of this, right?", "start": 1084.933, "duration": 2.536}, {"text": "So it'd be like a wavy\nwave, and you're just", "start": 1087.469, "duration": 1.902}, {"text": "showing plus and minus\nwith the yellow and blue.", "start": 1089.371, "duration": 2.569}, {"text": "But that note in between\nis where it can never be.", "start": 1091.94, "duration": 2.67}, {"text": "But it's one electron.", "start": 1094.61, "duration": 1.134}, {"text": "It's not many, it's one.", "start": 1095.744, "duration": 1.535}, {"text": "And this is its\nprobability distribution.", "start": 1097.279, "duration": 3.403}, {"text": "Now I want to make one\nreally important point, which", "start": 1100.682, "duration": 2.169}, {"text": "is that--", "start": 1102.851, "duration": 1.835}, {"text": "look at what I'm plotting here.", "start": 1104.686, "duration": 1.635}, {"text": "Maybe something-- that's\nsize squared, right?", "start": 1106.321, "duration": 3.137}, {"text": "So it's only the square\nof the wave function", "start": 1109.458, "duration": 4.571}, {"text": "that we can relate any\nphysical meaning to.", "start": 1114.029, "duration": 4.738}, {"text": "The physical meaning\nI just related to you", "start": 1118.767, "duration": 2.569}, {"text": "is the probability\nof being somewhere.", "start": 1121.336, "duration": 2.737}, {"text": "That's what size squared\ngives us-- the probability", "start": 1124.073, "duration": 2.469}, {"text": "of being somewhere.", "start": 1126.542, "duration": 1.668}, {"text": "But ask your teacher--", "start": 1128.21, "duration": 1.735}, {"text": "not me, your quantum teacher.", "start": 1129.945, "duration": 3.07}, {"text": "Ask what psi means.", "start": 1133.015, "duration": 2.035}, {"text": "And they're going to have a--", "start": 1135.05, "duration": 1.335}, {"text": "it's going to be an\ninteresting class.", "start": 1136.385, "duration": 2.569}, {"text": "Force the issue.", "start": 1138.954, "duration": 0.834}, {"text": "Don't let them go\nuntil they answer.", "start": 1139.788, "duration": 3.937}, {"text": "We still don't know.", "start": 1143.725, "duration": 1.402}, {"text": "We still don't know\nwhat the actual wave", "start": 1145.127, "duration": 2.035}, {"text": "function means physically.", "start": 1147.162, "duration": 2.603}, {"text": "We cannot attribute a\nphysical meaning to it,", "start": 1149.765, "duration": 1.968}, {"text": "only to its square.", "start": 1151.733, "duration": 2.269}, {"text": "So we go about our business\nfor the last 100 years", "start": 1154.002, "duration": 2.136}, {"text": "squaring it and saying, OK,\nwell it describes nature.", "start": 1156.138, "duration": 2.202}, {"text": "That's great.", "start": 1158.34, "duration": 0.567}, {"text": "But no one, still, knows what\nit means without the square.", "start": 1158.907, "duration": 4.805}, {"text": "I find that incredible.", "start": 1163.712, "duration": 1.201}, {"text": "And it led Bohr to say all\nsorts of really cool things.", "start": 1164.913, "duration": 3.671}, {"text": "He said, \"We must be clear\nthat when it comes to atoms,", "start": 1168.584, "duration": 3.069}, {"text": "language can be used\nonly as in poetry.", "start": 1171.653, "duration": 4.572}, {"text": "The poet, too, is not\nnearly so concerned", "start": 1176.225, "duration": 2.535}, {"text": "with describing facts\nas with creating images", "start": 1178.76, "duration": 3.037}, {"text": "and establishing\nmental connections.\"", "start": 1181.797, "duration": 2.502}, {"text": "That's Bohr like\ndeep in it, trying", "start": 1184.299, "duration": 1.502}, {"text": "to figure out what psi means.", "start": 1185.801, "duration": 2.769}, {"text": "He's like, I don't know.", "start": 1188.57, "duration": 1.302}, {"text": "It's poetry.", "start": 1189.872, "duration": 2.869}, {"text": "OK, that's cool.", "start": 1192.741, "duration": 2.269}, {"text": "That's cool.", "start": 1195.01, "duration": 1.869}, {"text": "V squared means\nsomething, v doesn't.", "start": 1196.879, "duration": 1.668}, {"text": "Really?", "start": 1198.547, "duration": 1.068}, {"text": "No.", "start": 1199.615, "duration": 0.934}, {"text": "Classically, we've got nothing.", "start": 1200.549, "duration": 2.402}, {"text": "Right?", "start": 1202.951, "duration": 0.834}, {"text": "Quantum mechanics.", "start": 1203.785, "duration": 1.102}, {"text": "Oh, it's a beautiful thing.", "start": 1204.887, "duration": 1.501}, {"text": "Why does this matter?", "start": 1206.388, "duration": 0.901}, {"text": "I'm going to give you a\nbrief \"why this matters.\"", "start": 1207.289, "duration": 2.035}, {"text": "And we've been talking about\nthe quantum nature of things,", "start": 1209.324, "duration": 3.237}, {"text": "right?", "start": 1212.561, "duration": 0.767}, {"text": "Quantum is this.", "start": 1213.328, "duration": 1.502}, {"text": "Quantum are these differences.", "start": 1214.83, "duration": 1.702}, {"text": "It's this probability.", "start": 1216.532, "duration": 1.401}, {"text": "It's quantization of energies.", "start": 1217.933, "duration": 2.736}, {"text": "What does that mean, right?", "start": 1220.669, "duration": 1.702}, {"text": "Well, last time I told\nyou that by electrons", "start": 1222.371, "duration": 3.403}, {"text": "being quantum, and having\nwave-like character--", "start": 1225.774, "duration": 2.469}, {"text": "we're able to use\nthem to see things,", "start": 1228.243, "duration": 2.202}, {"text": "and it started the\nnanotechnology revolution", "start": 1230.445, "duration": 2.369}, {"text": "about 30 years ago.", "start": 1232.814, "duration": 1.302}, {"text": "And today I want to give\nyou an example of that", "start": 1234.116, "duration": 2.135}, {"text": "in my \"why this matters.\"", "start": 1236.251, "duration": 2.703}, {"text": "And it has to do with quantum\ndomination, which should be", "start": 1238.954, "duration": 3.737}, {"text": "the title of a movie or a book.", "start": 1242.691, "duration": 3.804}, {"text": "And here's the example-- take\na piece of bulk material.", "start": 1246.495, "duration": 2.569}, {"text": "Take a piece of silicon, OK?", "start": 1249.064, "duration": 1.935}, {"text": "And if you look at\nthe silicon, it's", "start": 1250.999, "duration": 1.669}, {"text": "kind of boring to\nlook at optically.", "start": 1252.668, "duration": 1.635}, {"text": "It's not very interesting.", "start": 1254.303, "duration": 1.401}, {"text": "You know, don't tell\nthat to your iPhone,", "start": 1255.704, "duration": 1.702}, {"text": "which has a lot of it in\nthere, but it's boring.", "start": 1257.406, "duration": 3.537}, {"text": "But now, take out your little\nnano ice cream scooper,", "start": 1260.943, "duration": 3.67}, {"text": "which you all have.", "start": 1264.613, "duration": 0.901}, {"text": "And you take a little\ntiny piece of it.", "start": 1265.514, "duration": 1.968}, {"text": "We call that a quantum dot.", "start": 1267.482, "duration": 2.57}, {"text": "Why?", "start": 1270.052, "duration": 0.7}, {"text": "We call it a quantum dot\nbecause it kind of looks", "start": 1270.752, "duration": 2.57}, {"text": "like a dot-- its smallish.", "start": 1273.322, "duration": 2.636}, {"text": "But we call it that\nbecause quantum mechanics", "start": 1275.958, "duration": 2.602}, {"text": "takes over the properties.", "start": 1278.56, "duration": 1.802}, {"text": "Here's an example-- shine\nlight on this thing,", "start": 1280.362, "duration": 3.37}, {"text": "or have it glow, and\nall of a sudden instead", "start": 1283.732, "duration": 2.102}, {"text": "of being boring it can\nbe any color you want.", "start": 1285.834, "duration": 3.971}, {"text": "Why?", "start": 1289.805, "duration": 0.767}, {"text": "Because if I shine\nlight-- and here is", "start": 1290.572, "duration": 1.735}, {"text": "a very sophisticated picture\nof a laser, which you can tell", "start": 1292.307, "duration": 3.704}, {"text": "I had trouble\nmaking transparent.", "start": 1296.011, "duration": 2.436}, {"text": "And so you shine a\nlaser on this piece--", "start": 1298.447, "duration": 3.303}, {"text": "we know already, light\nexcites charge in an atom.", "start": 1301.75, "duration": 4.538}, {"text": "It does the same in solids.", "start": 1306.288, "duration": 1.335}, {"text": "So here's my piece of\nsilicon, and what that does", "start": 1307.623, "duration": 3.103}, {"text": "is it sends an electron\nup in energy levels.", "start": 1310.726, "duration": 3.136}, {"text": "But the electron is\nup in an energy level,", "start": 1313.862, "duration": 1.769}, {"text": "and it left behind a hole.", "start": 1315.631, "duration": 1.801}, {"text": "Which is something we'll\ntalk about later when", "start": 1317.432, "duration": 1.902}, {"text": "we talk about semiconductors.", "start": 1319.334, "duration": 1.902}, {"text": "A hole is just a\npositive charge.", "start": 1321.236, "duration": 2.836}, {"text": "And it turns out that that\nelectron and that hole", "start": 1324.072, "duration": 2.803}, {"text": "are attracted to each other, but\nnot-- they can't get too close.", "start": 1326.875, "duration": 4.438}, {"text": "But they want to kind of hang\nout at a certain distance.", "start": 1331.313, "duration": 2.569}, {"text": "Where?", "start": 1333.882, "duration": 0.501}, {"text": "How far?", "start": 1334.383, "duration": 1.201}, {"text": "Yeah-- quantum mechanics.", "start": 1335.584, "duration": 2.569}, {"text": "N 2, 3, 4 tells us.", "start": 1338.153, "duration": 2.97}, {"text": "It tells us how far, right?", "start": 1341.123, "duration": 3.503}, {"text": "They want to hang out--", "start": 1344.626, "duration": 0.968}, {"text": "and now all of a sudden,\nI've nano-scooped them out,", "start": 1345.594, "duration": 2.469}, {"text": "and I've made a quantum dot.", "start": 1348.063, "duration": 1.168}, {"text": "But if I try to do\nthe same thing there,", "start": 1349.231, "duration": 1.868}, {"text": "that's how far\nthey wanted to be.", "start": 1351.099, "duration": 1.902}, {"text": "And they can't be.", "start": 1353.001, "duration": 0.934}, {"text": "They literally ran\nout of real estate.", "start": 1353.935, "duration": 3.037}, {"text": "They ran out of atoms.", "start": 1356.972, "duration": 1.968}, {"text": "They cannot be out here, because\nthere's no stuff out here.", "start": 1358.94, "duration": 2.803}, {"text": "So they get squeezed.", "start": 1361.743, "duration": 2.002}, {"text": "I am squeezing these\nquantum mechanical objects,", "start": 1363.745, "duration": 2.67}, {"text": "this electron and this hole.", "start": 1366.415, "duration": 1.701}, {"text": "And by squeezing them,\nI'm changing the way", "start": 1368.116, "duration": 4.371}, {"text": "they interact with light.", "start": 1372.487, "duration": 1.368}, {"text": "I'm changing the color, right?", "start": 1373.855, "duration": 3.804}, {"text": "Oh.", "start": 1377.659, "duration": 0.901}, {"text": "It's all stuff we've\nlearned that explains", "start": 1378.56, "duration": 2.603}, {"text": "something revolutionary.", "start": 1381.163, "duration": 2.602}, {"text": "By the way, if you buy a QLED\nTV, is it as good as OLED?", "start": 1383.765, "duration": 3.337}, {"text": "No.", "start": 1387.102, "duration": 0.934}, {"text": "But is it better than LED?", "start": 1388.036, "duration": 1.769}, {"text": "Yeah, a little bit.", "start": 1389.805, "duration": 1.134}, {"text": "That's what they-- QLED--", "start": 1390.939, "duration": 1.101}, {"text": "quantum is quantum dots.", "start": 1392.04, "duration": 2.102}, {"text": "They have coated the LED\nemitters with quantum dots", "start": 1394.142, "duration": 3.771}, {"text": "to give you better color.", "start": 1397.913, "duration": 2.436}, {"text": "Now what this means,\nwhy this matters,", "start": 1400.349, "duration": 4.037}, {"text": "is nothing less than the\nperiodic table itself.", "start": 1404.386, "duration": 2.703}, {"text": "Because I think I\nshowed you this--", "start": 1407.089, "duration": 2.569}, {"text": "we're living in these\ndifferent ages, which I love.", "start": 1409.658, "duration": 2.235}, {"text": "We have the periodic\ntable that has--", "start": 1411.893, "duration": 2.102}, {"text": "the ability to work with\nit is what's brought us", "start": 1413.995, "duration": 2.503}, {"text": "to the age of materials design.", "start": 1416.498, "duration": 3.136}, {"text": "But see, now I've literally\njust told you that by changing", "start": 1419.634, "duration": 5.072}, {"text": "the size-- nothing\nmore than the size--", "start": 1424.706, "duration": 2.336}, {"text": "I can tune a property\nbecause of quantum mechanics.", "start": 1427.042, "duration": 3.003}, {"text": "Because I'm changing its\nquantum mechanical interactions.", "start": 1430.045, "duration": 2.703}, {"text": "It would be like saying, I can\ntake a piece of this table--", "start": 1432.748, "duration": 3.47}, {"text": "I can break a piece\nof this table,", "start": 1436.218, "duration": 1.468}, {"text": "and it's now going to be red.", "start": 1437.686, "duration": 2.402}, {"text": "That's exactly what we're\ndoing, but at a very tiny size.", "start": 1440.088, "duration": 3.337}, {"text": "That is as if we are\ntaking this periodic table", "start": 1443.425, "duration": 3.37}, {"text": "and giving it a whole\nother dimension.", "start": 1446.795, "duration": 3.003}, {"text": "Every element can do more\nthings than we thought possible", "start": 1449.798, "duration": 4.438}, {"text": "because we can tune\nthese properties related", "start": 1454.236, "duration": 3.136}, {"text": "to quantum mechanics.", "start": 1457.372, "duration": 2.036}, {"text": "So that's a big deal.", "start": 1459.408, "duration": 1.468}, {"text": "That's a very big deal.", "start": 1460.876, "duration": 1.601}, {"text": "OK.", "start": 1462.477, "duration": 0.501}, {"text": "Now back to our solution to\nthe Schrodinger equation.", "start": 1462.978, "duration": 3.87}, {"text": "For an electron in an atom.", "start": 1466.848, "duration": 2.303}, {"text": "Because now we move on and\nwe solve for the next one,", "start": 1469.151, "duration": 7.307}, {"text": "which is--", "start": 1476.458, "duration": 1.034}, {"text": "OK, so we did r.", "start": 1477.492, "duration": 2.002}, {"text": "Now we're going to do theta.", "start": 1479.494, "duration": 2.536}, {"text": "And what happens\nwith theta is, you", "start": 1482.03, "duration": 2.269}, {"text": "get another quantization\nof that variable.", "start": 1484.299, "duration": 4.438}, {"text": "And that's the second\nquantum number.", "start": 1488.737, "duration": 1.902}, {"text": "So we're going to put it here.", "start": 1490.639, "duration": 1.268}, {"text": "N-- I'll number them\nso we don't lose track.", "start": 1491.907, "duration": 4.337}, {"text": "Who knows how many they'll be?", "start": 1496.244, "duration": 3.304}, {"text": "OK.", "start": 1499.548, "duration": 1.534}, {"text": "Not three.", "start": 1501.082, "duration": 2.336}, {"text": "OK, so the second one is l.", "start": 1503.418, "duration": 3.904}, {"text": "And it's the angular\nquantum number.", "start": 1507.322, "duration": 4.771}, {"text": "And it has also\nquantization 0, 1, 2, 3.", "start": 1515.163, "duration": 8.108}, {"text": "OK?", "start": 1523.271, "duration": 0.501}, {"text": "So l can be--", "start": 1523.772, "duration": 2.869}, {"text": "Oh, I need to put that up there.", "start": 1526.641, "duration": 2.436}, {"text": "I meant to put that right here.", "start": 1529.077, "duration": 2.169}, {"text": "This is just like what we\nlearned for Bohr, right?", "start": 1531.246, "duration": 4.137}, {"text": "And l can be 0, 1, 2, all\nthe way up to l minus 1.", "start": 1538.753, "duration": 8.008}, {"text": "OK?", "start": 1546.761, "duration": 2.069}, {"text": "I'm going too fast,\nthat's n minus 1.", "start": 1548.83, "duration": 3.704}, {"text": "L goes from 0 to n minus 1.", "start": 1552.534, "duration": 2.602}, {"text": "OK, so what that\nmeans right away--", "start": 1557.939, "duration": 3.938}, {"text": "what you can see-- if it\nonly goes to n minus 1,", "start": 1561.877, "duration": 2.002}, {"text": "then for example for n\nequals 1 then l equals 0.", "start": 1563.879, "duration": 7.107}, {"text": "That's it.", "start": 1570.986, "duration": 1.568}, {"text": "There's no other options.", "start": 1572.554, "duration": 1.535}, {"text": "It stops, right?", "start": 1574.089, "duration": 2.002}, {"text": "And we have a name for this.", "start": 1576.091, "duration": 1.535}, {"text": "We call this s, the s orbital.", "start": 1577.626, "duration": 1.801}, {"text": "And for n equals 2, l\ncan be 0, or l can be 1.", "start": 1583.198, "duration": 8.275}, {"text": "And this one is called--", "start": 1591.473, "duration": 2.636}, {"text": "this one is the p orbital.", "start": 1594.109, "duration": 2.102}, {"text": "This is the p orbital, OK?", "start": 1596.211, "duration": 6.173}, {"text": "Those have names.", "start": 1602.384, "duration": 0.8}, {"text": "And so on and so on.", "start": 1603.184, "duration": 2.169}, {"text": "d, f--", "start": 1605.353, "duration": 3.103}, {"text": "This is old notation that\nwe cannot get rid of.", "start": 1608.456, "duration": 4.805}, {"text": "This is called\nspectroscopic notation,", "start": 1613.261, "duration": 1.802}, {"text": "because it comes\nfrom spectroscopists.", "start": 1615.063, "duration": 1.802}, {"text": "And remember, I told you-- never\nmake a spectroscopist angry.", "start": 1616.865, "duration": 3.57}, {"text": "Don't do it.", "start": 1620.435, "duration": 1.535}, {"text": "Don't do it.", "start": 1621.97, "duration": 1.168}, {"text": "And so we use their\nnotation still.", "start": 1623.138, "duration": 2.202}, {"text": "s was sharp.", "start": 1625.34, "duration": 1.401}, {"text": "Spherically symmetric.", "start": 1626.741, "duration": 1.836}, {"text": "p was principle,\nbecause it sort of", "start": 1628.577, "duration": 1.468}, {"text": "dominated in some experiments.\nd was more diffuse.", "start": 1630.045, "duration": 2.369}, {"text": "f fundamental, because it looked\nkind of like the hydrogen atom", "start": 1632.414, "duration": 2.636}, {"text": "sometimes.", "start": 1635.05, "duration": 1.468}, {"text": "These shouldn't be the names,\nbut they are because they still", "start": 1636.518, "duration": 2.536}, {"text": "stay with us.", "start": 1639.054, "duration": 1.368}, {"text": "Spectroscopic\nnotation-- s, p, d, f.", "start": 1640.422, "duration": 3.036}, {"text": "What they really do\nis just correspond--", "start": 1643.458, "duration": 3.036}, {"text": "that looks like \"porbital.\"", "start": 1646.494, "duration": 1.435}, {"text": "Let's put a little\nmore space there.", "start": 1650.565, "duration": 2.002}, {"text": "P orbital.", "start": 1652.567, "duration": 1.769}, {"text": "Right?", "start": 1654.336, "duration": 0.834}, {"text": "Because what they really\nmean is nothing more", "start": 1655.17, "duration": 3.17}, {"text": "than a quantum number for the\nsecond quantum number, which", "start": 1658.34, "duration": 2.636}, {"text": "is the angular quantum number.", "start": 1660.976, "duration": 2.469}, {"text": "These are also sometimes\ncalled subshells, right?", "start": 1663.445, "duration": 3.436}, {"text": "Because they're\nunderneath the shell.", "start": 1666.881, "duration": 3.938}, {"text": "And as you can see\nfrom this picture,", "start": 1670.819, "duration": 2.269}, {"text": "it describes the angular shape.", "start": 1673.088, "duration": 4.971}, {"text": "The angular shape\nof the orbital.", "start": 1678.059, "duration": 3.904}, {"text": "The shape, right?", "start": 1681.963, "duration": 1.201}, {"text": "So it gives us a shape.", "start": 1683.164, "duration": 0.935}, {"text": "Now-- if we think about it, and\nwe think about that p orbital,", "start": 1688.069, "duration": 8.609}, {"text": "that has a different shape\nthan the [INAUDIBLE]..", "start": 1696.678, "duration": 2.97}, {"text": "Then you think, well,\nthis could be aligned", "start": 1699.648, "duration": 2.802}, {"text": "in different directions, right?", "start": 1702.45, "duration": 2.369}, {"text": "So if I think about\nthat p orbital-- well,", "start": 1704.819, "duration": 1.769}, {"text": "I could align it in\nthree different ways.", "start": 1706.588, "duration": 2.469}, {"text": "It could go along this axis,\nthis axis, or that one, right?", "start": 1709.057, "duration": 4.404}, {"text": "And so those are p\norbitals in hydrogen", "start": 1713.461, "duration": 3.103}, {"text": "that have three\npossible orientations,", "start": 1716.564, "duration": 2.803}, {"text": "and that automatically gets\nus to another quantum number.", "start": 1719.367, "duration": 4.004}, {"text": "In fact, it's the last\none, and it makes sense", "start": 1723.371, "duration": 3.07}, {"text": "just physically--\nthat's phi, right?", "start": 1726.441, "duration": 3.17}, {"text": "So the last one--", "start": 1729.611, "duration": 2.602}, {"text": "or is it the last one--", "start": 1732.213, "duration": 1.702}, {"text": "is m.", "start": 1733.915, "duration": 1.034}, {"text": "And we call it m sub l, which\nis the magnetic quantum number.", "start": 1734.949, "duration": 7.508}, {"text": "And this one can have\nquantization equal to minus l,", "start": 1745.26, "duration": 6.54}, {"text": "right?", "start": 1751.8, "duration": 0.5}, {"text": "All the way up to plus l.", "start": 1752.3, "duration": 3.637}, {"text": "So the number of orientations\nthat the orbital can have--", "start": 1755.937, "duration": 7.04}, {"text": "if I'm a-- n equals\n2, l equals 1,", "start": 1762.977, "duration": 9.009}, {"text": "then m sub l equals\nminus 1, 0, 1.", "start": 1771.986, "duration": 6.34}, {"text": "Three orientations.", "start": 1778.326, "duration": 1.935}, {"text": "Right?", "start": 1780.261, "duration": 0.501}, {"text": "It's got three orientations--\nthree possible magnetic quantum", "start": 1780.762, "duration": 3.737}, {"text": "numbers.", "start": 1784.499, "duration": 0.5}, {"text": "Why is it called the\nmagnetic quantum number?", "start": 1784.999, "duration": 1.836}, {"text": "Because those are\nthe experiments.", "start": 1786.835, "duration": 4.137}, {"text": "We're done using magnetization--", "start": 1790.972, "duration": 3.003}, {"text": "magnetic fields--\nto discover these", "start": 1793.975, "duration": 4.271}, {"text": "orientations, to\nsort through it.", "start": 1798.246, "duration": 2.302}, {"text": "To see it.", "start": 1800.548, "duration": 1.769}, {"text": "OK.", "start": 1802.317, "duration": 0.7}, {"text": "So if I had l equals--", "start": 1803.017, "duration": 1.936}, {"text": "all right, so if I had,\nfor example l equals 2.", "start": 1804.953, "duration": 5.338}, {"text": "Then m sub l would\nhave five values.", "start": 1810.291, "duration": 3.204}, {"text": "Five possible values, right?", "start": 1813.495, "duration": 2.535}, {"text": "I should put a plus\nthere, just to be sure we", "start": 1818.733, "duration": 2.169}, {"text": "keep track of minus and plus.", "start": 1820.902, "duration": 1.735}, {"text": "These are quantum numbers.", "start": 1822.637, "duration": 2.836}, {"text": "That means they're\nintegers, right?", "start": 1825.473, "duration": 1.602}, {"text": "But they can have these ranges\nand these rules, and again--", "start": 1827.075, "duration": 5.872}, {"text": "you may think, why did\nthis come out like this?", "start": 1832.947, "duration": 2.403}, {"text": "Well, it comes out from\nsolving this equation--", "start": 1835.35, "duration": 4.004}, {"text": "separation of variables--", "start": 1839.354, "duration": 2.369}, {"text": "with that potential.", "start": 1841.723, "duration": 1.101}, {"text": "That's it, right?", "start": 1842.824, "duration": 1.969}, {"text": "That's it.", "start": 1844.793, "duration": 0.5}, {"text": "You get these allowed values of\nthese three variables, quantum", "start": 1845.293, "duration": 4.638}, {"text": "numbers.", "start": 1849.931, "duration": 0.767}, {"text": "OK?", "start": 1850.698, "duration": 0.801}, {"text": "All right.", "start": 1851.499, "duration": 0.467}, {"text": "Now-- and there's the d.", "start": 1856.137, "duration": 1.068}, {"text": "These are called d--", "start": 1857.205, "duration": 1.935}, {"text": "So if n equals 2--", "start": 1859.14, "duration": 4.071}, {"text": "OK.", "start": 1863.211, "duration": 0.5}, {"text": "So did I mess up here?", "start": 1863.711, "duration": 3.437}, {"text": "No, I didn't, because n would\nhave to be 3 here, right?", "start": 1867.148, "duration": 5.172}, {"text": "For l to be 2.", "start": 1872.32, "duration": 1.668}, {"text": "Because l can't be equal to\nn, because I wrote it there", "start": 1873.988, "duration": 3.17}, {"text": "as the list of allowed quantum\nnumbers that l can have.", "start": 1877.158, "duration": 4.138}, {"text": "And there it is\nfor the d orbitals.", "start": 1881.296, "duration": 3.403}, {"text": "And so there's five d orbitals.", "start": 1884.699, "duration": 2.202}, {"text": "Five d orbitals.", "start": 1886.901, "duration": 0.801}, {"text": "And you can do f on your own,\nand it's an extremely fun thing", "start": 1887.702, "duration": 4.204}, {"text": "to do at night.", "start": 1891.906, "duration": 1.235}, {"text": "Late at night.", "start": 1893.141, "duration": 1.334}, {"text": "Now, this gives\nyou the orbitals.", "start": 1894.475, "duration": 4.138}, {"text": "You get them all.", "start": 1898.613, "duration": 1.034}, {"text": "These are the orbitals.", "start": 1899.647, "duration": 1.569}, {"text": "These are the beautiful,\nbeautiful orbitals", "start": 1901.216, "duration": 2.669}, {"text": "that we have from\nquantum mechanics", "start": 1903.885, "duration": 2.669}, {"text": "describing an\nelectron in an atom.", "start": 1906.554, "duration": 2.202}, {"text": "Which tells you everything about\nwhere that electron can be,", "start": 1908.756, "duration": 6.44}, {"text": "how it behaves, what\nits energies are,", "start": 1915.196, "duration": 4.638}, {"text": "and therefore literally why\natoms are what they are.", "start": 1919.834, "duration": 3.504}, {"text": "That's what it tells us, right?", "start": 1923.338, "duration": 1.902}, {"text": "Because the next thing we need\nto do is fill up our atoms.", "start": 1925.24, "duration": 4.738}, {"text": "And know how electrons fill\natoms using these quantum", "start": 1929.978, "duration": 3.67}, {"text": "numbers.", "start": 1933.648, "duration": 1.401}, {"text": "And then relate\nthat to chemistry,", "start": 1935.049, "duration": 1.635}, {"text": "and to the differences\nbetween one atom and another,", "start": 1936.684, "duration": 2.57}, {"text": "and explaining why\natoms are different.", "start": 1939.254, "duration": 2.435}, {"text": "Remember, that was our goal.", "start": 1941.689, "duration": 2.87}, {"text": "We needed to go\nquantum to answer that.", "start": 1944.559, "duration": 1.668}, {"text": "So we're getting closer,\nbut we're still not there.", "start": 1949.264, "duration": 3.103}, {"text": "And one of the reasons is there\nis a fourth quantum number.", "start": 1952.367, "duration": 4.371}, {"text": "And this came out\nof experiments--", "start": 1956.738, "duration": 1.501}, {"text": "I thought that I\nwould just show you", "start": 1958.239, "duration": 1.802}, {"text": "a very quick video, because it's\neasier to see this in action.", "start": 1960.041, "duration": 5.873}, {"text": "And so these are\nexperiments that", "start": 1965.914, "duration": 1.735}, {"text": "were done by Stern\nand Gerlach that", "start": 1967.649, "duration": 3.536}, {"text": "showed something very\npeculiar about atoms", "start": 1971.185, "duration": 2.67}, {"text": "and their electrons.", "start": 1973.855, "duration": 1.368}, {"text": "OK, so here I'm just\ngoing to play it.", "start": 1975.223, "duration": 2.402}, {"text": "It's got a really nice--", "start": 1977.625, "duration": 1.302}, {"text": "oh, that's loud.", "start": 1978.927, "duration": 0.734}, {"text": "Yeah?", "start": 1982.597, "duration": 1.068}, {"text": "I don't mind that.", "start": 1983.665, "duration": 0.767}, {"text": "That's good.", "start": 1984.432, "duration": 0.501}, {"text": "So you can read the text here.", "start": 1984.933, "duration": 1.468}, {"text": "OK, so they've got a magnet.", "start": 1986.401, "duration": 1.234}, {"text": "A very strong magnet, right?", "start": 1987.635, "duration": 2.403}, {"text": "Magnetic fields.", "start": 1990.038, "duration": 1.468}, {"text": "And they're going to\nshoot a classical magnet.", "start": 1991.506, "duration": 2.202}, {"text": "There's a classical magnet.", "start": 1993.708, "duration": 1.134}, {"text": "And you see it's going to\nreact to the magnetic field,", "start": 1994.842, "duration": 3.003}, {"text": "and be pushed up.", "start": 1997.845, "duration": 2.77}, {"text": "That magnetic could've\nbeen oriented differently.", "start": 2000.615, "duration": 2.235}, {"text": "Like sideways, right?", "start": 2002.85, "duration": 0.935}, {"text": "In which case it\ndoesn't feel this.", "start": 2003.785, "duration": 1.868}, {"text": "And you could throw\na bunch of them", "start": 2005.653, "duration": 1.468}, {"text": "randomly, with\nrandom orientations,", "start": 2007.121, "duration": 3.37}, {"text": "and that's what you would see.", "start": 2010.491, "duration": 1.735}, {"text": "[JAZZY MUSIC]", "start": 2012.226, "duration": 1.736}, {"text": "It's good music, too.", "start": 2013.962, "duration": 1.301}, {"text": "But now-- watch this.", "start": 2015.263, "duration": 1.134}, {"text": "I love the animation here.", "start": 2016.397, "duration": 1.569}, {"text": "Look at this.", "start": 2017.966, "duration": 2.235}, {"text": "And the bass, right?", "start": 2020.201, "duration": 3.437}, {"text": "Those are what happens\nto atoms with electrons.", "start": 2023.638, "duration": 2.736}, {"text": "You'd shoot them\nthrough a high field,", "start": 2026.374, "duration": 2.002}, {"text": "and you don't get anything.", "start": 2028.376, "duration": 2.769}, {"text": "You get two things.", "start": 2031.145, "duration": 1.535}, {"text": "Only two.", "start": 2032.68, "duration": 1.468}, {"text": "[JAZZY MUSIC]", "start": 2034.148, "duration": 2.803}, {"text": "I'm just playing it because\nI really want to groove out", "start": 2047.795, "duration": 2.303}, {"text": "and I'm debating--", "start": 2050.098, "duration": 3.436}, {"text": "OK.", "start": 2053.534, "duration": 1.569}, {"text": "All done.", "start": 2055.103, "duration": 2.134}, {"text": "I was debating how\nembarrassing it would be", "start": 2057.237, "duration": 1.803}, {"text": "if I just started grooving out.", "start": 2059.04, "duration": 1.501}, {"text": "So this was Sterin and Gerlach,\nwho discovered, essentially,", "start": 2063.844, "duration": 3.203}, {"text": "a fourth quantum number that\ncan have only two values.", "start": 2067.047, "duration": 4.906}, {"text": "So they showed that this thing\nthat the atoms were doing", "start": 2071.953, "duration": 3.27}, {"text": "was because of the electrons.", "start": 2075.223, "duration": 2.002}, {"text": "And that the only\nway you could explain", "start": 2077.225, "duration": 2.903}, {"text": "what these electrons\nwere doing is if there", "start": 2080.128, "duration": 2.836}, {"text": "was this thing called spin.", "start": 2082.964, "duration": 2.135}, {"text": "And if you really need\nto think classically--", "start": 2085.099, "duration": 1.935}, {"text": "and it's dangerous to do\nso, because then you'd", "start": 2087.034, "duration": 3.404}, {"text": "forget that I could be all\nthe way over there, right?", "start": 2090.438, "duration": 2.636}, {"text": "Right now.", "start": 2093.074, "duration": 1.034}, {"text": "But if you really need\nto think classically,", "start": 2094.108, "duration": 1.835}, {"text": "you can think of\na charge spinning.", "start": 2095.943, "duration": 1.702}, {"text": "It could be spinning\nthis way or that way.", "start": 2097.645, "duration": 2.836}, {"text": "In a way, it helps\nour classical needs.", "start": 2100.481, "duration": 2.803}, {"text": "But it's so not\nwhat's happening.", "start": 2103.284, "duration": 2.169}, {"text": "But it does help our\nclassical desires, right?", "start": 2105.453, "duration": 4.304}, {"text": "And that would give\nyou the two fields.", "start": 2109.757, "duration": 2.236}, {"text": "Right?", "start": 2111.993, "duration": 0.967}, {"text": "But I would advise you just\nto think about spin as simply", "start": 2112.96, "duration": 3.137}, {"text": "a fourth quantum number.", "start": 2116.097, "duration": 2.703}, {"text": "And so we call\nthat one number 4.", "start": 2118.8, "duration": 3.503}, {"text": "Not from that equation.", "start": 2122.303, "duration": 1.802}, {"text": "Separate from those experiments.", "start": 2124.105, "duration": 2.569}, {"text": "And that is-- we call\nthat the spin M sub", "start": 2126.674, "duration": 4.705}, {"text": "s is the spin quantum number.", "start": 2131.379, "duration": 3.904}, {"text": "And it's the fourth\none in our series.", "start": 2135.283, "duration": 3.904}, {"text": "The fourth quantum number.", "start": 2139.187, "duration": 2.168}, {"text": "And it has only two values--", "start": 2141.355, "duration": 1.836}, {"text": "up or down.", "start": 2143.191, "duration": 2.969}, {"text": "Or if you like, you could write\nit as plus 1/2 or minus 1/2.", "start": 2146.16, "duration": 5.539}, {"text": "Or you could write it\nas up or down arrows.", "start": 2151.699, "duration": 4.204}, {"text": "So many ways to distinguish\ntwo things that are opposite.", "start": 2155.903, "duration": 4.905}, {"text": "Spin up, spin down.", "start": 2160.808, "duration": 1.335}, {"text": "Two values that this can have.", "start": 2162.143, "duration": 2.302}, {"text": "So we're not ready yet.", "start": 2167.982, "duration": 0.968}, {"text": "We're still not ready.", "start": 2168.95, "duration": 0.901}, {"text": "We're so close, but we're\nstill not there, right?", "start": 2169.851, "duration": 5.405}, {"text": "Because we still don't\nknow, well-- can't I just--?", "start": 2175.256, "duration": 2.269}, {"text": "How do I--?", "start": 2177.525, "duration": 0.534}, {"text": "What are the rules\nhere going to be?", "start": 2178.059, "duration": 4.337}, {"text": "For populating atoms.", "start": 2182.396, "duration": 2.236}, {"text": "And this is where Pauli said\nsomething very important,", "start": 2184.632, "duration": 3.604}, {"text": "and made this incredibly\nimportant statement.", "start": 2188.236, "duration": 5.105}, {"text": "Which is that-- no particles\nin the same system--", "start": 2193.341, "duration": 3.17}, {"text": "read that as, no electrons\nin the same atom--", "start": 2196.511, "duration": 4.304}, {"text": "can have the same\nquantum numbers.", "start": 2200.815, "duration": 3.236}, {"text": "No electrons in the same atom\ncan have the same quantum", "start": 2204.051, "duration": 3.604}, {"text": "numbers.", "start": 2207.655, "duration": 1.068}, {"text": "And that immediately tells you--", "start": 2208.723, "duration": 3.069}, {"text": "again, this has to do with the\nnature of quantum mechanics--", "start": 2211.792, "duration": 3.471}, {"text": "what that immediately tells\nyou is that two electrons--", "start": 2215.263, "duration": 5.805}, {"text": "ho-ho, this is big!", "start": 2221.068, "duration": 3.27}, {"text": "Two electrons-- I'm gonna write,\ntwo electrons, and watch this--", "start": 2224.338, "duration": 3.871}, {"text": "I'm going all caps--", "start": 2228.209, "duration": 1.268}, {"text": "only two electrons\ncan occupy an orbital.", "start": 2229.477, "duration": 7.34}, {"text": "An orbital.", "start": 2240.955, "duration": 0.534}, {"text": "Or- bi- tal.", "start": 2245.86, "duration": 2.069}, {"text": "That called the Pauli\nexclusion principle.", "start": 2250.565, "duration": 4.938}, {"text": "OK.", "start": 2255.503, "duration": 0.5}, {"text": "So we're going to use\nall of this information", "start": 2259.24, "duration": 1.902}, {"text": "to fill stuff up, but I\ndon't want to do that yet.", "start": 2261.142, "duration": 4.371}, {"text": "On Wednesday, we're\nfilling up the table,", "start": 2265.513, "duration": 2.769}, {"text": "and we're making\nour first solid.", "start": 2268.282, "duration": 1.368}, {"text": "I figure it's our\nthree week anniversary.", "start": 2269.65, "duration": 1.769}, {"text": "I know you've all been\nlooking forward to it.", "start": 2271.419, "duration": 2.536}, {"text": "I've been thinking\nabout it a lot.", "start": 2273.955, "duration": 1.501}, {"text": "And I think-- that makes\nme want to throw t-shirts.", "start": 2275.456, "duration": 4.004}, {"text": "[STUDENTS CHEERING]", "start": 2279.46, "duration": 1.034}, {"text": "I got to do this.", "start": 2280.494, "duration": 2.77}, {"text": "All right, all right.", "start": 2283.264, "duration": 1.335}, {"text": "I got to go--", "start": 2284.599, "duration": 1.167}, {"text": "I know.", "start": 2285.766, "duration": 0.701}, {"text": "I got to go backwards here.", "start": 2286.467, "duration": 1.468}, {"text": "OK, OK, hold on, hold on.", "start": 2290.538, "duration": 1.568}, {"text": "I'm missing there\nand there, I know.", "start": 2294.709, "duration": 1.635}, {"text": "I got to work on my arm.", "start": 2296.344, "duration": 1.501}, {"text": "Yeah.", "start": 2297.845, "duration": 0.868}, {"text": "Show you love over there.", "start": 2298.713, "duration": 1.034}, {"text": "OK, all right.", "start": 2299.747, "duration": 1.768}, {"text": "I'll have more on Wednesday,\nand the reason is--", "start": 2301.515, "duration": 4.004}, {"text": "we're making our first solid.", "start": 2305.519, "duration": 1.969}, {"text": "I almost wanted to\nleave it a surprise,", "start": 2307.488, "duration": 1.635}, {"text": "but I couldn't help myself.", "start": 2309.123, "duration": 2.269}, {"text": "It's extremely exciting.", "start": 2311.392, "duration": 1.468}, {"text": "This is, after all,\nsolid-state chemistry,", "start": 2312.86, "duration": 2.469}, {"text": "and Wednesday we're\nmaking a solid.", "start": 2315.329, "duration": 2.069}, {"text": "Literally.", "start": 2317.398, "duration": 0.5}, {"text": "We are not only making a bond,\nbut we're making a solid,", "start": 2317.898, "duration": 3.07}, {"text": "and talking about solids.", "start": 2320.968, "duration": 1.035}, {"text": "So that's going to\nbe very exciting.", "start": 2322.003, "duration": 1.768}, {"text": "And we're going to start\nby filling elements.", "start": 2323.771, "duration": 2.669}, {"text": "But before we do that, I\nwant to explain something", "start": 2326.44, "duration": 4.338}, {"text": "very important, which is--", "start": 2330.778, "duration": 3.604}, {"text": "what's happening with energy?", "start": 2334.382, "duration": 2.569}, {"text": "Right?", "start": 2336.951, "duration": 0.567}, {"text": "We did just see\nsomething dramatic.", "start": 2337.518, "duration": 3.57}, {"text": "As you go from Bohr to quantum,\nsomething very dramatic", "start": 2341.088, "duration": 3.27}, {"text": "happens with where, right?", "start": 2344.358, "duration": 4.705}, {"text": "And we know something\nelse very dramatic", "start": 2349.063, "duration": 2.569}, {"text": "happens, which is right here.", "start": 2351.632, "duration": 3.404}, {"text": "You know, that's Bohr over\nthere- n equals 1, [INAUDIBLE]..", "start": 2355.036, "duration": 3.403}, {"text": "Bohr is 1, 2, 3, right?", "start": 2358.439, "duration": 4.638}, {"text": "Now it's like-- oh no,\nwait, it's 1 and with 1s.", "start": 2363.077, "duration": 3.337}, {"text": "2-- I can put two electrons\nin there, thanks to Pauli.", "start": 2366.414, "duration": 3.136}, {"text": "I know I can put two, because\nI have all the quantum", "start": 2369.55, "duration": 2.302}, {"text": "numbers in here the\nsame except spin, which", "start": 2371.852, "duration": 2.169}, {"text": "could be up or down, right?", "start": 2374.021, "duration": 2.436}, {"text": "N equals 1, l equals 0, m sub\nl equals 0, spin is up or down.", "start": 2376.457, "duration": 4.271}, {"text": "Two electrons.", "start": 2380.728, "duration": 0.834}, {"text": "But look, I'm now\nhere at n equals 2,", "start": 2381.562, "duration": 3.47}, {"text": "going from the Bohr\nmodel to quantum.", "start": 2385.032, "duration": 2.002}, {"text": "I've got this and I've\ngot three p orbitals.", "start": 2387.034, "duration": 5.072}, {"text": "So now all of a sudden\nI've got eight electrons", "start": 2392.106, "duration": 2.536}, {"text": "that can go into\nthat quantum number.", "start": 2394.642, "duration": 2.803}, {"text": "That's very different\nthan Bohr, right?", "start": 2397.445, "duration": 4.471}, {"text": "And that's called degeneracy,\nbecause you're taking something", "start": 2401.916, "duration": 3.203}, {"text": "and you're saying, there\nare multiple variations", "start": 2405.119, "duration": 2.269}, {"text": "that have the same n.", "start": 2407.388, "duration": 1.868}, {"text": "But there's\nsomething else that I", "start": 2409.256, "duration": 1.735}, {"text": "want to explain right now\nthat is can be understood very", "start": 2410.991, "duration": 3.537}, {"text": "physically and intuitively.", "start": 2414.528, "duration": 2.036}, {"text": "And that is that\nthe motivation-- one", "start": 2416.564, "duration": 2.769}, {"text": "of the big motivations\nof this was that we", "start": 2419.333, "duration": 2.369}, {"text": "needed more than one electron.", "start": 2421.702, "duration": 2.67}, {"text": "Our atoms are not all\nhydrogen and ionized atoms.", "start": 2424.372, "duration": 3.737}, {"text": "They are just neutral atoms\ngoing up above hydrogen.", "start": 2428.109, "duration": 2.902}, {"text": "So what happens when\nwe go multi electron?", "start": 2431.011, "duration": 3.871}, {"text": "And there's two effects\nthat I want to explain.", "start": 2434.882, "duration": 2.102}, {"text": "Here's what happens\nto this picture.", "start": 2436.984, "duration": 2.169}, {"text": "Those are the one\nelectron levels, right?", "start": 2439.153, "duration": 1.702}, {"text": "There's Bohr over there.", "start": 2440.855, "duration": 1.801}, {"text": "This is what you really\nget in terms of energy.", "start": 2442.656, "duration": 3.704}, {"text": "Right?", "start": 2446.36, "duration": 0.501}, {"text": "This is energy along\nthe vertical axis.", "start": 2446.861, "duration": 1.902}, {"text": "And there's two reasons,\ntwo very important reasons,", "start": 2448.763, "duration": 3.47}, {"text": "why these are so different.", "start": 2452.233, "duration": 1.835}, {"text": "One is called\nshielding, and the other", "start": 2454.068, "duration": 2.035}, {"text": "is called orbital penetration.", "start": 2456.103, "duration": 1.235}, {"text": "And I want to talk\nabout both of them", "start": 2457.338, "duration": 1.868}, {"text": "in the last seven\nminutes of class.", "start": 2459.206, "duration": 4.305}, {"text": "I'm going over here.", "start": 2463.511, "duration": 1.501}, {"text": "All right, so let's talk about--", "start": 2468.983, "duration": 2.669}, {"text": "let's do shielding first.", "start": 2471.652, "duration": 1.068}, {"text": "Shielding is something\nthat you can kind of", "start": 2475.723, "duration": 4.204}, {"text": "get a very good sense for it\nif you just look at what's", "start": 2479.927, "duration": 3.57}, {"text": "happening in these atoms.", "start": 2483.497, "duration": 1.635}, {"text": "So in shielding--\nlet's take an example.", "start": 2488.102, "duration": 7.474}, {"text": "I'm going to give you an\natom with 15 protons and 15", "start": 2495.576, "duration": 4.738}, {"text": "electrons.", "start": 2500.314, "duration": 1.435}, {"text": "What atom is it?", "start": 2501.749, "duration": 2.169}, {"text": "Anybody know?", "start": 2503.918, "duration": 2.335}, {"text": "Phosphorus.", "start": 2506.253, "duration": 1.168}, {"text": "OK, so I'm going to take an\nexample of the phosphorus atom,", "start": 2507.421, "duration": 3.037}, {"text": "OK?", "start": 2510.458, "duration": 2.569}, {"text": "And I've got 15 positive\ncharges in the nucleus.", "start": 2513.027, "duration": 6.706}, {"text": "15.", "start": 2519.733, "duration": 1.135}, {"text": "Right?", "start": 2520.868, "duration": 2.569}, {"text": "Now, 15 protons.", "start": 2523.437, "duration": 2.436}, {"text": "Now I've got my\nlevels, and it gets", "start": 2525.873, "duration": 3.637}, {"text": "very difficult to draw levels\nas probability distributions.", "start": 2529.51, "duration": 4.871}, {"text": "So I'm going to draw them\nas rings, even though we", "start": 2534.381, "duration": 2.103}, {"text": "know they're not, right?", "start": 2536.484, "duration": 1.434}, {"text": "These are my orbitals.", "start": 2537.918, "duration": 1.068}, {"text": "But I've got like an electron\nhere, OK, an electron there.", "start": 2538.986, "duration": 4.304}, {"text": "All right.", "start": 2543.29, "duration": 0.501}, {"text": "So I've got two electrons\nin the n equals 1--", "start": 2543.791, "duration": 4.004}, {"text": "n equals 1 orbital.", "start": 2547.795, "duration": 1.968}, {"text": "So that's the 1s orbital,\nright there on the bottom.", "start": 2549.763, "duration": 4.438}, {"text": "But if I go out--", "start": 2554.201, "duration": 1.902}, {"text": "OK, so I'm going to go out now.", "start": 2556.103, "duration": 3.837}, {"text": "To n equals 2.", "start": 2559.94, "duration": 2.836}, {"text": "Well, now I've got\n1, 2, 3, 4, and--", "start": 2562.776, "duration": 7.675}, {"text": "oh boy-- put one here.", "start": 2570.451, "duration": 2.302}, {"text": "5, 6, 7, 8.", "start": 2572.753, "duration": 4.438}, {"text": "Because here-- remember, I've\ngot l equals 0 and l equals 1,", "start": 2577.191, "duration": 4.404}, {"text": "and as we just said, because\nn sub s can be up or down,", "start": 2581.595, "duration": 3.17}, {"text": "I've got eight electrons here.", "start": 2584.765, "duration": 2.569}, {"text": "So here, I've got n equals\n1, here I've got n equals 2.", "start": 2587.334, "duration": 3.103}, {"text": "That's eight electrons.", "start": 2590.437, "duration": 1.335}, {"text": "And then out here--", "start": 2591.772, "duration": 1.668}, {"text": "oh, now it gets really\ninteresting-- because for n", "start": 2593.44, "duration": 2.87}, {"text": "equals 3, how many\nelectrons do I have left?", "start": 2596.31, "duration": 2.636}, {"text": "1, 2, 3, 4, 5.", "start": 2598.946, "duration": 4.771}, {"text": "And you can already\nsee what's happening.", "start": 2603.717, "duration": 2.102}, {"text": "So remember, Rutherford\ntold us this.", "start": 2605.819, "duration": 2.036}, {"text": "All this charge is in a\ntiny little point here.", "start": 2607.855, "duration": 3.303}, {"text": "You wouldn't even see it if\nwe were drawing this to scale.", "start": 2611.158, "duration": 4.905}, {"text": "But what are these\nelectrons seeing?", "start": 2616.063, "duration": 3.37}, {"text": "What are the electrons seeing?", "start": 2619.433, "duration": 1.301}, {"text": "Well, these inner two\nelectrons are just", "start": 2620.734, "duration": 2.803}, {"text": "seeing this huge\namount of charge.", "start": 2623.537, "duration": 1.802}, {"text": "They are happy.", "start": 2625.339, "duration": 2.135}, {"text": "Low energy.", "start": 2627.474, "duration": 1.902}, {"text": "Right?", "start": 2629.376, "duration": 0.668}, {"text": "The lower your\nenergy, the happier.", "start": 2630.044, "duration": 1.668}, {"text": "You're in a lower\nenergy, ground state.", "start": 2631.712, "duration": 1.935}, {"text": "Remember-- more lower\nenergy, more happiness.", "start": 2633.647, "duration": 4.204}, {"text": "More bound.", "start": 2637.851, "duration": 1.302}, {"text": "Right?", "start": 2639.153, "duration": 1.501}, {"text": "So those electrons down\nthere are enjoying.", "start": 2640.654, "duration": 5.139}, {"text": "But these out here--", "start": 2645.793, "duration": 2.068}, {"text": "you see?", "start": 2647.861, "duration": 0.568}, {"text": "These electrons.", "start": 2648.429, "duration": 2.302}, {"text": "Those electrons in here--", "start": 2650.731, "duration": 2.035}, {"text": "these shield the outer\nelectrons, these shield", "start": 2652.766, "duration": 5.039}, {"text": "outer electrons\nby two electrons.", "start": 2657.805, "duration": 5.939}, {"text": "Right?", "start": 2663.744, "duration": 0.667}, {"text": "Because they're\nkind of in the way.", "start": 2664.411, "duration": 3.07}, {"text": "It's like you've got this\nnegative charge that's", "start": 2667.481, "duration": 2.636}, {"text": "in between me and the\npositive charge, right?", "start": 2670.117, "duration": 2.936}, {"text": "And so if I'm out\nhere at n equals 2,", "start": 2673.053, "duration": 2.403}, {"text": "I don't see 15 positive\ncharges there anymore.", "start": 2675.456, "duration": 6.706}, {"text": "I see 13-- ish.", "start": 2682.162, "duration": 2.703}, {"text": "That's shielding.", "start": 2684.865, "duration": 2.035}, {"text": "But now this one--", "start": 2686.9, "duration": 1.469}, {"text": "this has the 2s and\nthe 2p electrons.", "start": 2688.369, "duration": 4.938}, {"text": "It's got eight electrons\nthere, and those", "start": 2693.307, "duration": 2.669}, {"text": "are shielding another eight.", "start": 2695.976, "duration": 2.803}, {"text": "Those are shielding\nanother eight protons.", "start": 2698.779, "duration": 4.872}, {"text": "To things outside\nof them, right?", "start": 2707.388, "duration": 2.235}, {"text": "Shielding doesn't work going in.", "start": 2709.623, "duration": 1.602}, {"text": "If I'm this electron and I look\nout, all I see are repulsive--", "start": 2711.225, "duration": 6.74}, {"text": "I see repulsiveness.", "start": 2717.965, "duration": 2.002}, {"text": "In a good way--", "start": 2719.967, "duration": 0.634}, {"text": "I'm sure they're friends.", "start": 2720.601, "duration": 1.268}, {"text": "But two negative charges, right?", "start": 2721.869, "duration": 4.337}, {"text": "So I'm only looking in.", "start": 2726.206, "duration": 1.635}, {"text": "Looking in, shielded.", "start": 2727.841, "duration": 2.603}, {"text": "Looking in, shielded.", "start": 2730.444, "duration": 2.536}, {"text": "So these ones have\nsort of an effective--", "start": 2732.98, "duration": 3.336}, {"text": "z effective.", "start": 2736.316, "duration": 1.802}, {"text": "You know, that could\nbe something like five.", "start": 2738.118, "duration": 3.671}, {"text": "This is not the z of\nthe atom, but it's", "start": 2741.789, "duration": 2.469}, {"text": "sort of like those very\nouter electrons don't", "start": 2744.258, "duration": 2.502}, {"text": "see the whole proton cloud.", "start": 2746.76, "duration": 2.303}, {"text": "They get shielded.", "start": 2749.063, "duration": 0.767}, {"text": "And that's a very\nimportant part of what", "start": 2749.83, "duration": 2.769}, {"text": "happens to orbitals when you\nput a lot of electrons in them.", "start": 2752.599, "duration": 3.504}, {"text": "And there's one more\nthing that happens,", "start": 2756.103, "duration": 2.402}, {"text": "and it goes back to this plot\nthat I showed you before,", "start": 2758.505, "duration": 4.838}, {"text": "which is that the\norbitals themselves", "start": 2763.343, "duration": 5.106}, {"text": "are very different than just\nlike a straight line from Bohr.", "start": 2768.449, "duration": 6.106}, {"text": "They have these\nshapes to them, right?", "start": 2774.555, "duration": 2.536}, {"text": "So the second thing that happens\nis that if I have that same s--", "start": 2777.091, "duration": 8.441}, {"text": "this is s, so this\nwould now be the 1s.", "start": 2785.532, "duration": 3.304}, {"text": "And now I'm going to put--", "start": 2788.836, "duration": 1.167}, {"text": "remember that 2s\nlooked like this.", "start": 2790.003, "duration": 3.504}, {"text": "And it had the node there.", "start": 2793.507, "duration": 1.235}, {"text": "Remember that?", "start": 2794.742, "duration": 0.6}, {"text": "Ho-ho.", "start": 2795.342, "duration": 1.602}, {"text": "That was 2s.", "start": 2796.944, "duration": 2.636}, {"text": "But now we're going\nto put the 2p there.", "start": 2799.58, "duration": 4.604}, {"text": "May not be drawn to scale.", "start": 2804.184, "duration": 3.304}, {"text": "OK, here's the 2p.", "start": 2807.488, "duration": 1.601}, {"text": "Something very, very\ninteresting is happening here.", "start": 2813.093, "duration": 3.003}, {"text": "And again, it has to do with\nwhat electrons are seeing.", "start": 2816.096, "duration": 2.836}, {"text": "Because the 2s electron\nhas a probability--", "start": 2818.932, "duration": 3.337}, {"text": "remember, this is the\nprobability normalized,", "start": 2822.269, "duration": 2.97}, {"text": "so we put in r-squared\nthere, right?", "start": 2825.239, "duration": 3.403}, {"text": "That probability-- all that\nmeans is if I integrate over", "start": 2828.642, "duration": 3.303}, {"text": "everything, it's 1.", "start": 2831.945, "duration": 1.135}, {"text": "It's got to be somewhere.", "start": 2833.08, "duration": 1.468}, {"text": "But look, the 2s electron can be\nreally deep inside the shells.", "start": 2834.548, "duration": 5.138}, {"text": "It can be in there.", "start": 2839.686, "duration": 3.003}, {"text": "Literally-- look, it's\neven inside the 1s.", "start": 2842.689, "duration": 3.804}, {"text": "So it gets some of that\n15-proton action, right?", "start": 2846.493, "duration": 5.306}, {"text": "Orbital penetration\nleads to massive changes.", "start": 2851.799, "duration": 3.303}, {"text": "Orbital penetration is\nwhat this is called,", "start": 2855.102, "duration": 2.302}, {"text": "and it allows some of the--", "start": 2857.404, "duration": 3.337}, {"text": "but the p doesn't have that.", "start": 2860.741, "duration": 2.069}, {"text": "It goes in a little,\nbut the p doesn't", "start": 2862.81, "duration": 1.568}, {"text": "have that peak, all\nthe way in there,", "start": 2864.378, "duration": 1.802}, {"text": "where it can see all\nthat positive charge.", "start": 2866.18, "duration": 2.002}, {"text": "And that is why these\ntwo things are different.", "start": 2868.182, "duration": 4.704}, {"text": "You see?", "start": 2872.886, "duration": 0.668}, {"text": "Because the 2s now,\ncan be closer sometimes", "start": 2873.554, "duration": 4.004}, {"text": "to those 15 protons, right?", "start": 2877.558, "duration": 2.569}, {"text": "And so it lowers the\nenergy, making it happier.", "start": 2880.127, "duration": 3.203}, {"text": "It finds a lower happy place.", "start": 2883.33, "duration": 2.202}, {"text": "OK?", "start": 2885.532, "duration": 0.501}, {"text": "So we're going to use this,\nand on Wednesday, we're", "start": 2886.033, "duration": 5.739}, {"text": "going to take these things and\nwe're going to fill them up,", "start": 2891.772, "duration": 2.536}, {"text": "and we're going to\nmake our first solid.", "start": 2894.308, "duration": 2.569}, {"text": "Have a very good\nrest of your day.", "start": 2896.877, "duration": 2.936}]
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@@ -0,0 +1 @@
+[{"text": "[SQUEAKING]", "start": 0.5, "duration": 0.961}, {"text": "[RUSTLING]", "start": 1.461, "duration": 2.435}, {"text": "[CLICKING]", "start": 3.896, "duration": 1.948}, {"text": "GARY GENSLER: We're going to go\nthrough payment systems, what", "start": 10.898, "duration": 2.542}, {"text": "is a payment system, in fact,\nsome trends around the payment", "start": 13.44, "duration": 3.45}, {"text": "system, which is a little\nbit of a statistical review,", "start": 16.89, "duration": 3.03}, {"text": "and then critically think\nabout the pain points, a list", "start": 19.92, "duration": 4.05}, {"text": "that I've been keeping\nas I teach FinTech", "start": 23.97, "duration": 2.88}, {"text": "and also as I think\nabout cryptocurrencies", "start": 26.85, "duration": 2.49}, {"text": "and how they might insert\nthemselves in this space.", "start": 29.34, "duration": 3.57}, {"text": "Some trends around\nthe globe with nations", "start": 32.91, "duration": 3.0}, {"text": "trying to move forward with\nreal-time gross settlement,", "start": 35.91, "duration": 3.12}, {"text": "the idea that you could\nsettle payment transactions", "start": 39.03, "duration": 4.17}, {"text": "instantaneously, 24 hours\na day, 7 days a week,", "start": 43.2, "duration": 4.51}, {"text": "which many nations don't do yet.", "start": 47.71, "duration": 1.94}, {"text": "Some do.", "start": 49.65, "duration": 0.63}, {"text": "We'll get into that.", "start": 50.28, "duration": 1.63}, {"text": "And then the landscape itself.", "start": 51.91, "duration": 1.39}, {"text": "What are the companies\ndoing and so forth?", "start": 53.3, "duration": 3.68}, {"text": "Harkening back to\nlast discussion,", "start": 56.98, "duration": 3.16}, {"text": "what are we seeing in the crypto\nprojects and tokenization?", "start": 60.14, "duration": 3.65}, {"text": "And then close out\non Facebook Libra", "start": 63.79, "duration": 2.58}, {"text": "and China's Digital Currency\nElectronic Payment project.", "start": 66.37, "duration": 4.14}, {"text": "So a lot to cover.", "start": 70.51, "duration": 1.08}, {"text": "But please, as I had\nsaid, video's on.", "start": 71.59, "duration": 4.23}, {"text": "So we can keep this sense\nof community and audio off.", "start": 75.82, "duration": 3.34}, {"text": "But anytime you have a\nquestion, raise the blue hand", "start": 79.16, "duration": 2.64}, {"text": "in the participant area.", "start": 81.8, "duration": 1.85}, {"text": "Engage in the chat room\namongst yourselves,", "start": 83.65, "duration": 3.48}, {"text": "or Romain would be\ngood enough just", "start": 87.13, "duration": 2.46}, {"text": "to interrupt me when\nhe sees something", "start": 89.59, "duration": 1.68}, {"text": "interesting in the chat.", "start": 91.27, "duration": 1.98}, {"text": "Or for that matter,\neven if you're a student", "start": 93.25, "duration": 2.445}, {"text": "and you see something\ninteresting in the chat", "start": 95.695, "duration": 1.875}, {"text": "that Romain's not raising, you\ncan raise your hand and say,", "start": 97.57, "duration": 3.04}, {"text": "I see three things\nin the chat room,", "start": 100.61, "duration": 1.82}, {"text": "and I want to capture that\nfor the class and so forth.", "start": 102.43, "duration": 5.86}, {"text": "So the readings\ntoday, I thought it", "start": 108.29, "duration": 2.66}, {"text": "was interesting to take a\nspeech by Lael Brainard.", "start": 110.95, "duration": 3.36}, {"text": "Lael is on the US\nFederal Reserve Board.", "start": 114.31, "duration": 3.9}, {"text": "And as they do in many\ncommissions and boards", "start": 118.21, "duration": 6.41}, {"text": "of central banks\naround the globe,", "start": 124.62, "duration": 2.42}, {"text": "they allocate\ndifferent projects.", "start": 127.04, "duration": 1.56}, {"text": "Now, Lael is part of the\nFederal Open Market Committee", "start": 128.6, "duration": 6.44}, {"text": "and helps set interest\nrates, but she also", "start": 135.04, "duration": 2.04}, {"text": "is that key player on the\nReserve Board around payments.", "start": 137.08, "duration": 5.49}, {"text": "So she gave a speech\nabout the updating", "start": 142.57, "duration": 2.31}, {"text": "and where we stand, and I\nhope you found that helpful.", "start": 144.88, "duration": 5.04}, {"text": "Along with Neha Narula, we did\na cryptocurrency online course", "start": 149.92, "duration": 5.28}, {"text": "last summer.", "start": 155.2, "duration": 1.07}, {"text": "And the payment system\nspace was something", "start": 156.27, "duration": 1.9}, {"text": "we wrote just as a background,\nas a primer in this area,", "start": 158.17, "duration": 4.17}, {"text": "and then some payment\ninnovations in the FinTech", "start": 162.34, "duration": 3.03}, {"text": "space, and a little map\nabout nine payment track.", "start": 165.37, "duration": 4.86}, {"text": "So I hope that was helpful.", "start": 170.23, "duration": 1.93}, {"text": "If you haven't dug into it, I\ndo think that Lael's speech is", "start": 172.16, "duration": 3.32}, {"text": "a good update as to where we\nare and particularly as the US", "start": 175.48, "duration": 4.95}, {"text": "Federal Reserve is thinking\nabout things like Facebook's", "start": 180.43, "duration": 2.73}, {"text": "Libra, thinking about going\nto real-time gross settlement", "start": 183.16, "duration": 4.89}, {"text": "in something called FedNow\nthat won't be rolled out now", "start": 188.05, "duration": 3.48}, {"text": "for three or four years.", "start": 191.53, "duration": 1.89}, {"text": "But I think Lael gives a good\nsense of where things are.", "start": 193.42, "duration": 2.82}, {"text": "So just if we can have a little\nbit of conversation here,", "start": 199.3, "duration": 4.08}, {"text": "and Romain will help facilitate.", "start": 203.38, "duration": 2.1}, {"text": "But what are the key\nchallenges and opportunities", "start": 205.48, "duration": 2.61}, {"text": "in the current system, just\nfrom your own perspective?", "start": 208.09, "duration": 3.66}, {"text": "In essence, what do\nyou think I will later", "start": 211.75, "duration": 2.58}, {"text": "have on that list\nof pain points,", "start": 214.33, "duration": 1.71}, {"text": "if you've not yet\ndownloaded the slides?", "start": 216.04, "duration": 4.34}, {"text": "But Romain.", "start": 220.38, "duration": 2.206}, {"text": "ROMAIN: Let's see who will be\nthe first volunteer for today.", "start": 222.586, "duration": 3.986}, {"text": "GARY GENSLER: Just to get\nit a little bit interesting.", "start": 226.572, "duration": 4.75}, {"text": "ROMAIN: Still waiting\nfor a blue hand.", "start": 231.322, "duration": 2.028}, {"text": "Hassan.", "start": 238.718, "duration": 0.5}, {"text": "GARY GENSLER: [INAUDIBLE] page.", "start": 239.218, "duration": 1.292}, {"text": "You might have to get one.", "start": 240.51, "duration": 1.31}, {"text": "What did you have, Romain?", "start": 241.82, "duration": 1.13}, {"text": "ROMAIN: Hassan,\nthe floor is yours.", "start": 242.95, "duration": 2.25}, {"text": "AUDIENCE: Thank you.", "start": 245.2, "duration": 1.12}, {"text": "Yeah, about the\npayment system, I've", "start": 246.32, "duration": 2.67}, {"text": "noticed that there is kind of\na monopoly, especially here", "start": 248.99, "duration": 5.04}, {"text": "in the Middle East.", "start": 254.03, "duration": 0.9}, {"text": "All the payments\nare, or I would say", "start": 254.93, "duration": 2.76}, {"text": "almost all payments are through\nVisa, and Mastercard, and AMEX.", "start": 257.69, "duration": 5.76}, {"text": "And if you can see\nthat, these companies", "start": 263.45, "duration": 2.67}, {"text": "take a percentage\nof the merchants.", "start": 266.12, "duration": 3.55}, {"text": "And I don't if you guys\nhave this in the States,", "start": 269.67, "duration": 2.0}, {"text": "but sometimes, for instance,\nin my country in Bahrain,", "start": 271.67, "duration": 4.83}, {"text": "if I would go and buy something,\nif I know the owner person,", "start": 276.5, "duration": 4.23}, {"text": "he would say, hey, listen,\nif you would pay me in cash,", "start": 280.73, "duration": 3.54}, {"text": "I could give you a discount.", "start": 284.27, "duration": 2.29}, {"text": "So I think that there are many\nopportunities for companies", "start": 286.56, "duration": 4.28}, {"text": "that could maybe take less money\nand exploit this opportunity.", "start": 290.84, "duration": 9.73}, {"text": "GARY GENSLER: So this\ncaptured two themes", "start": 300.57, "duration": 2.52}, {"text": "that you picked up there,\nand there were many others.", "start": 303.09, "duration": 2.8}, {"text": "And I see Andrea's hand up.", "start": 305.89, "duration": 1.65}, {"text": "So we'll have some\nother good discussions.", "start": 307.54, "duration": 2.09}, {"text": "Cost, you're saying that\nthe current payment rails--", "start": 309.63, "duration": 3.9}, {"text": "my word-- that the\ncurrent payment rails", "start": 313.53, "duration": 2.22}, {"text": "have a significant cost.", "start": 315.75, "duration": 1.95}, {"text": "And you also mentioned\nthe concentration.", "start": 317.7, "duration": 3.33}, {"text": "You said monopoly.", "start": 321.03, "duration": 1.83}, {"text": "Some might say oligopolies,\nbut there's a concentration", "start": 322.86, "duration": 3.63}, {"text": "usually in the payment systems.", "start": 326.49, "duration": 1.89}, {"text": "And this comes by\nand large not only", "start": 328.38, "duration": 3.36}, {"text": "because of the\nhistory of payments", "start": 331.74, "duration": 1.53}, {"text": "but also the significant\nnetwork effects,", "start": 333.27, "duration": 3.15}, {"text": "that if you have one central\npayment mechanism, whether it's", "start": 336.42, "duration": 4.08}, {"text": "a clearing house in days of\nold or, in the last 40 years,", "start": 340.5, "duration": 4.76}, {"text": "the credit card companies became\nvery significant in the payment", "start": 345.26, "duration": 4.99}, {"text": "space.", "start": 350.25, "duration": 0.93}, {"text": "They had network\neffects, scale, bringing", "start": 351.18, "duration": 2.73}, {"text": "merchants on the one side, the\nstore owners on the one side,", "start": 353.91, "duration": 3.9}, {"text": "and the consumers on\nthe other side together.", "start": 357.81, "duration": 2.59}, {"text": "And the platform economics\ncreate a significant network", "start": 360.4, "duration": 3.53}, {"text": "effect.", "start": 363.93, "duration": 0.52}, {"text": "So there's a lot\nof concentration.", "start": 364.45, "duration": 1.91}, {"text": "But Andrea or others?", "start": 366.36, "duration": 1.915}, {"text": "ROMAIN: Andrea?", "start": 368.275, "duration": 1.491}, {"text": "AUDIENCE: Yeah.", "start": 369.766, "duration": 1.064}, {"text": "So I'm not fully sure\nif this is related", "start": 370.83, "duration": 3.15}, {"text": "or if you count it\nalso as payment.", "start": 373.98, "duration": 1.67}, {"text": "But I think one of the\nbiggest opportunities", "start": 375.65, "duration": 2.24}, {"text": "and also challenges\nis still to resolve", "start": 377.89, "duration": 1.97}, {"text": "the international\npayments, so basically", "start": 379.86, "duration": 2.55}, {"text": "how you send the money\nacross the borders.", "start": 382.41, "duration": 2.13}, {"text": "There are many startups, like\neveryone knows TransferWise", "start": 384.54, "duration": 3.54}, {"text": "who are doing a great job.", "start": 388.08, "duration": 1.74}, {"text": "But when you think\nabout it, it's still--", "start": 389.82, "duration": 1.98}, {"text": "the way their business\nmodel or how it works,", "start": 391.8, "duration": 2.89}, {"text": "it's still not basically\ninstant sending of money,", "start": 394.69, "duration": 3.6}, {"text": "and there are a\ncouple of limitations.", "start": 398.29, "duration": 1.86}, {"text": "For example, you\nalso need to do it--", "start": 400.15, "duration": 3.57}, {"text": "you also need to\nor you're allowed", "start": 403.72, "duration": 2.12}, {"text": "to send the money\ninternationally", "start": 405.84, "duration": 1.71}, {"text": "if you have a bank account.", "start": 407.55, "duration": 1.51}, {"text": "But I, for example, know I\nwas working in the Middle East", "start": 409.06, "duration": 3.18}, {"text": "where, for example,\nthere is a lot of people,", "start": 412.24, "duration": 3.23}, {"text": "a lot of international people\ncoming and working there.", "start": 415.47, "duration": 3.81}, {"text": "And they are sending\na lot of money", "start": 419.28, "duration": 2.97}, {"text": "back to their families home.", "start": 422.25, "duration": 2.79}, {"text": "And, for example, a lot of them\ndon't have a banking account.", "start": 425.04, "duration": 2.82}, {"text": "So they're using services\nsuch as Western Union.", "start": 427.86, "duration": 2.855}, {"text": "GARY GENSLER: So let's--", "start": 430.715, "duration": 1.375}, {"text": "AUDIENCE: And [INAUDIBLE].", "start": 432.09, "duration": 1.14}, {"text": "GARY GENSLER: I think\nAndrea was good.", "start": 433.23, "duration": 1.583}, {"text": "She raised three\npoints in there.", "start": 434.813, "duration": 1.957}, {"text": "I see Ivy's hand,\nand then we'll close.", "start": 436.77, "duration": 1.96}, {"text": "But the three points I heard,\ncross-border, sending payments", "start": 438.73, "duration": 3.71}, {"text": "from one nation to another.", "start": 442.44, "duration": 2.65}, {"text": "Now that could be because\nit's moving from one currency", "start": 445.09, "duration": 4.25}, {"text": "to another, or even if\nit's in the same currency,", "start": 449.34, "duration": 3.33}, {"text": "if you're using US dollars\nand sending it cross-border", "start": 452.67, "duration": 2.74}, {"text": "or using Euro or yen and\nsending it cross-border,", "start": 455.41, "duration": 3.82}, {"text": "you're jumping between two\ndifferent payment systems, two", "start": 459.23, "duration": 3.28}, {"text": "different banking systems.", "start": 462.51, "duration": 2.23}, {"text": "And so cross-border same\ncurrency or cross-border", "start": 464.74, "duration": 3.62}, {"text": "cross currency, there's\na significant amount", "start": 468.36, "duration": 2.61}, {"text": "of cost embedded in that.", "start": 470.97, "duration": 3.19}, {"text": "There is time delays that\nAndrea mentioned until you", "start": 474.16, "duration": 4.22}, {"text": "can have settled money.", "start": 478.38, "duration": 3.0}, {"text": "Final settled money means\nthat you can actually use it", "start": 481.38, "duration": 3.54}, {"text": "in your commercial daily lives.", "start": 484.92, "duration": 3.69}, {"text": "And then thirdly, I think\nAndrea raised inclusion,", "start": 488.61, "duration": 2.88}, {"text": "whether everybody has\naccess to that system.", "start": 491.49, "duration": 3.19}, {"text": "So I thank you.", "start": 494.68, "duration": 0.89}, {"text": "And then Ivy, and\nthen we'll move on.", "start": 495.57, "duration": 2.582}, {"text": "AUDIENCE: Sorry.", "start": 498.152, "duration": 0.74}, {"text": "I actually had some\nearlier points.", "start": 498.892, "duration": 1.458}, {"text": "But I think just building up\noff of that, things like Plaid,", "start": 500.35, "duration": 4.81}, {"text": "I think, are quite interesting\nbecause you really need this--", "start": 505.16, "duration": 4.3}, {"text": "I guess I think about it as the\nplumbing of the payment system,", "start": 509.46, "duration": 5.01}, {"text": "if you will, because\nthey really need", "start": 514.47, "duration": 1.97}, {"text": "to plug into so many different\ntypes, the payment systems, all", "start": 516.44, "duration": 4.26}, {"text": "these different\nfinancial institutions.", "start": 520.7, "duration": 1.83}, {"text": "And just even thinking about\ninclusion and consumer--", "start": 522.53, "duration": 4.74}, {"text": "customer behavior and\nconsumer credit behavior", "start": 527.27, "duration": 2.85}, {"text": "or cross-countries,\nit's entirely different.", "start": 530.12, "duration": 2.7}, {"text": "Like people in the UK don't,\nor in Europe in general,", "start": 532.82, "duration": 3.7}, {"text": "I don't think, use credit\ncards as much as Americans do.", "start": 536.52, "duration": 4.82}, {"text": "People in Asia are really\nused to using Alipay, WeChat.", "start": 541.34, "duration": 3.48}, {"text": "QR codes have\nbecome a big thing.", "start": 544.82, "duration": 3.45}, {"text": "And in Canada, people\npay down their debt", "start": 548.27, "duration": 4.38}, {"text": "much faster than we do.", "start": 552.65, "duration": 1.775}, {"text": "So just trying to\nthink about how", "start": 554.425, "duration": 1.375}, {"text": "all these different players,\nboth on the consumer side", "start": 555.8, "duration": 3.15}, {"text": "as well as on the supply\nside, if you will,", "start": 558.95, "duration": 4.08}, {"text": "will fit into the entire\nsystem in the future.", "start": 563.03, "duration": 2.29}, {"text": "GARY GENSLER: So Ivy's\nmentioned a bunch", "start": 565.32, "duration": 2.36}, {"text": "of cultural and\ngeographic differences.", "start": 567.68, "duration": 3.7}, {"text": "Country by country,\nwe have differences", "start": 571.38, "duration": 1.91}, {"text": "in our payment systems.", "start": 573.29, "duration": 1.89}, {"text": "We have different cultural\nbehaviors about paying down", "start": 575.18, "duration": 2.34}, {"text": "our debt and so forth.", "start": 577.52, "duration": 1.89}, {"text": "And you mentioned one company,\nPlaid, that helps the plumbing.", "start": 579.41, "duration": 4.11}, {"text": "And what's interesting is\nthat the word \"plumbing\"", "start": 583.52, "duration": 5.13}, {"text": "in banking or plumbing and\npayment is an age old thought.", "start": 588.65, "duration": 5.52}, {"text": "Actually, when\nAlexander Hamilton,", "start": 594.17, "duration": 2.34}, {"text": "our nation's first\nSecretary of the Treasury,", "start": 596.51, "duration": 4.08}, {"text": "helped found one of the\nfirst banks in the nation,", "start": 600.59, "duration": 3.27}, {"text": "the Bank of New York-- it still\nis part of the Bank of New York", "start": 603.86, "duration": 3.3}, {"text": "Mellon-- this was in the 1780s,\nthey took as their logo--", "start": 607.16, "duration": 4.95}, {"text": "logo is a modern word.", "start": 612.11, "duration": 1.53}, {"text": "But they took as\ntheir symbol something", "start": 613.64, "duration": 2.73}, {"text": "that looked like\nplumbing, literally", "start": 616.37, "duration": 2.79}, {"text": "that they thought of\nbanking as like waterworks", "start": 619.16, "duration": 3.46}, {"text": "or a central utility, sending\nmoney around rather than", "start": 622.62, "duration": 4.19}, {"text": "sending water around.", "start": 626.81, "duration": 2.28}, {"text": "So I thank you for that.", "start": 629.09, "duration": 1.25}, {"text": "But yes, Plaid is\npart of that plumbing.", "start": 630.34, "duration": 2.23}, {"text": "And as Andrea said,\nTransferWise is", "start": 632.57, "duration": 2.01}, {"text": "trying to find a gap\nin the cross-border.", "start": 634.58, "duration": 2.91}, {"text": "They're not alone.", "start": 637.49, "duration": 0.95}, {"text": "There's Remitly and WorldRemit,\nand many other companies also.", "start": 638.44, "duration": 5.17}, {"text": "And so this is a long question.", "start": 643.61, "duration": 2.34}, {"text": "But just anybody want to\nsay, what lessons can you", "start": 645.95, "duration": 2.28}, {"text": "take from Big Tech in\nthis space, Alipay,", "start": 648.23, "duration": 3.93}, {"text": "WeChat Pay, M-Pesa, et\ncetera, just Big Tech?", "start": 652.16, "duration": 3.51}, {"text": "And secondly, any lessons\nfrom all the startups.", "start": 655.67, "duration": 4.12}, {"text": "So it's two buckets,\nbut it's what can you", "start": 659.79, "duration": 3.53}, {"text": "take from the competitive\nlandscape, either Big", "start": 663.32, "duration": 2.46}, {"text": "Tech or the disruptors?", "start": 665.78, "duration": 1.68}, {"text": "ROMAIN: Anyone?", "start": 672.564, "duration": 0.946}, {"text": "GARY GENSLER: I'm sure that\nsome of you use these companies,", "start": 677.956, "duration": 2.934}, {"text": "whether you're from Asia, and\nyou use many of the Big Tech", "start": 680.89, "duration": 3.59}, {"text": "ones, or even in\nthe US if you do,", "start": 684.48, "duration": 2.01}, {"text": "or you're bound to use Venmo,\nwhich is owned by PayPal,", "start": 686.49, "duration": 6.15}, {"text": "or something.", "start": 692.64, "duration": 1.3}, {"text": "ROMAIN: So we have\nLuke and then Yi.", "start": 693.94, "duration": 3.8}, {"text": "AUDIENCE: So one of the--", "start": 697.74, "duration": 1.3}, {"text": "GARY GENSLER: Which side\nare you [INAUDIBLE],,", "start": 699.04, "duration": 1.917}, {"text": "Big Tech or disruptors?", "start": 700.957, "duration": 1.508}, {"text": "AUDIENCE: I'm sorry.", "start": 702.465, "duration": 0.85}, {"text": "Say that again.", "start": 703.315, "duration": 0.625}, {"text": "Say that again now.", "start": 703.94, "duration": 0.792}, {"text": "GARY GENSLER: Are you addressing\nBig Tech or the disruptors?", "start": 704.732, "duration": 4.604}, {"text": "AUDIENCE: So let's\ngo with Big Tech,", "start": 709.336, "duration": 2.074}, {"text": "but I guess it's not to\neasy when I talk about,", "start": 711.41, "duration": 2.5}, {"text": "for example, KakaoPay, which\nis the payment platform made", "start": 713.91, "duration": 4.4}, {"text": "by Kakao Group, which\nis the largest--", "start": 718.31, "duration": 3.54}, {"text": "the tech company in Korea.", "start": 721.85, "duration": 2.88}, {"text": "And basically, it's\nWhatsApp of Korea.", "start": 724.73, "duration": 2.95}, {"text": "So whether it be KakaoPay, or\nWeChat Pay, Alipay, Apple Pay,", "start": 727.68, "duration": 4.52}, {"text": "the key thing is it's very,\nvery easy compared to the bank.", "start": 732.2, "duration": 5.01}, {"text": "Now, the banks are trying to\ncatch up with the API Open", "start": 737.21, "duration": 2.4}, {"text": "Banking system and all that.", "start": 739.61, "duration": 1.71}, {"text": "But basically, the\nUI user interface", "start": 741.32, "duration": 2.93}, {"text": "is pretty easy to use.", "start": 744.25, "duration": 2.78}, {"text": "And if you have a problem, if\nyou contact customer service,", "start": 747.03, "duration": 2.72}, {"text": "they'll contact you\nright away, versus banks", "start": 749.75, "duration": 4.39}, {"text": "make you wait 20 minutes,\nblah, blah, blah.", "start": 754.14, "duration": 2.0}, {"text": "Sad to say it as a banker,\nbut it is what it is.", "start": 756.14, "duration": 2.9}, {"text": "GARY GENSLER: So I think that\nthe key lesson you're saying", "start": 759.04, "duration": 2.417}, {"text": "is it's easier, it's\ngot a user interface", "start": 761.457, "duration": 2.783}, {"text": "that's quite convenient.", "start": 764.24, "duration": 1.48}, {"text": "And while you didn't use the\nword, it's also ubiquitous.", "start": 765.72, "duration": 2.63}, {"text": "And so KakaoPay in Korea,\nLINE Pay in Japan and Taiwan,", "start": 768.35, "duration": 8.45}, {"text": "WeChat Pay, Alipay,\nM-Pesa really", "start": 776.8, "duration": 3.19}, {"text": "leapfrog the banking system.", "start": 779.99, "duration": 1.86}, {"text": "But there is a very established\nbanking system in Korea.", "start": 781.85, "duration": 2.88}, {"text": "And yet still,\nKakaoPay leaped over.", "start": 784.73, "duration": 4.23}, {"text": "Not as much so in the US.", "start": 788.96, "duration": 2.13}, {"text": "I mean, yes, Google\nWallet is there.", "start": 791.09, "duration": 1.77}, {"text": "Yes, Apple Pay is there,\nand they're significant.", "start": 792.86, "duration": 2.79}, {"text": "Less so for Facebook actually.", "start": 795.65, "duration": 1.802}, {"text": "AUDIENCE: I think\nthat's because of the--", "start": 797.452, "duration": 1.708}, {"text": "GARY GENSLER:\n[INAUDIBLE] we're weaker,", "start": 799.16, "duration": 1.89}, {"text": "in a sense, adoption, Google,\nApple, Facebook in the US,", "start": 801.05, "duration": 5.16}, {"text": "than we find in Korea or China.", "start": 806.21, "duration": 4.385}, {"text": "AUDIENCE: But I\nthink that's more", "start": 810.595, "duration": 1.375}, {"text": "because of-- not\nbecause of overbanking", "start": 811.97, "duration": 1.85}, {"text": "or the power of bank.", "start": 813.82, "duration": 2.26}, {"text": "It's more because of\nthe telecom services,", "start": 816.08, "duration": 3.12}, {"text": "how reachable,\napproachable you are", "start": 819.2, "duration": 2.75}, {"text": "with the LTE speed or\n3G speed you have here", "start": 821.95, "duration": 3.92}, {"text": "in big land of America.", "start": 825.87, "duration": 1.855}, {"text": "GARY GENSLER: So\nwhat Luke's raising", "start": 827.725, "duration": 2.065}, {"text": "is there's also facts on the\nground about how developed", "start": 829.79, "duration": 3.81}, {"text": "the technology is, whether\nit was already at 3G or 4G", "start": 833.6, "duration": 3.18}, {"text": "or how developed the\ntechnology was on the ground.", "start": 836.78, "duration": 3.88}, {"text": "So it's not just about\nhow developed the banking", "start": 840.66, "duration": 2.15}, {"text": "system is but also technology.", "start": 842.81, "duration": 2.24}, {"text": "Romain, we had\nsomebody else that", "start": 845.05, "duration": 1.96}, {"text": "might take the disrupter side.", "start": 847.01, "duration": 1.77}, {"text": "Thank you, Luke.", "start": 848.78, "duration": 0.7}, {"text": "ROMAIN: Yes.", "start": 849.48, "duration": 0.4}, {"text": "GARY GENSLER: Good.", "start": 849.88, "duration": 0.792}, {"text": "ROMAIN: Yi, go ahead.", "start": 850.672, "duration": 0.922}, {"text": "AUDIENCE: Yeah.", "start": 851.594, "duration": 0.926}, {"text": "I just want to raise a trend,\nthe loss of the payments", "start": 852.52, "duration": 3.85}, {"text": "this time.", "start": 856.37, "duration": 0.53}, {"text": "GARY GENSLER: And then,\nYi, do we have a video?", "start": 856.9, "duration": 3.06}, {"text": "Do we have your face?", "start": 859.96, "duration": 1.315}, {"text": "AUDIENCE: Yeah.", "start": 861.275, "duration": 0.895}, {"text": "I'm just very ugly\nthis morning, but--", "start": 862.17, "duration": 2.2}, {"text": "GARY GENSLER: Oh, I'm\nsure you look fine.", "start": 864.37, "duration": 2.361}, {"text": "You look great.", "start": 866.731, "duration": 0.625}, {"text": "AUDIENCE: Yeah.", "start": 867.356, "duration": 1.064}, {"text": "So I just feel like there's\na key trend between the--", "start": 868.42, "duration": 5.82}, {"text": "even including the Big Tech\npayment firms as well as like", "start": 874.24, "duration": 4.15}, {"text": "the FinTech firm\nis social media.", "start": 878.39, "duration": 3.14}, {"text": "People want to pay\nvia the social media.", "start": 881.53, "duration": 3.09}, {"text": "This happened between\nthe Alipay, WeChat Pay,", "start": 884.62, "duration": 2.6}, {"text": "the KakaoPay, and\nalso the Venmo.", "start": 887.22, "duration": 2.77}, {"text": "You can connect with friends.", "start": 889.99, "duration": 1.48}, {"text": "You can send stickers.", "start": 891.47, "duration": 2.33}, {"text": "You can send--\nexpress your emotions.", "start": 893.8, "duration": 2.52}, {"text": "You can make your\ntransactions available", "start": 896.32, "duration": 2.91}, {"text": "to your social network.", "start": 899.23, "duration": 1.59}, {"text": "And I think there's also\nsimilar to M-Pesa in Kenya.", "start": 900.82, "duration": 3.88}, {"text": "So I feel like this\nis a huge trend", "start": 904.7, "duration": 1.76}, {"text": "that people don't\nwant to only make", "start": 906.46, "duration": 4.57}, {"text": "the transaction\nwith banks, which is", "start": 911.03, "duration": 3.02}, {"text": "very separate and individual.", "start": 914.05, "duration": 2.83}, {"text": "They want to make transactions\nwith their social network.", "start": 916.88, "duration": 4.23}, {"text": "GARY GENSLER: Yeah.", "start": 921.11, "duration": 0.92}, {"text": "I think that's right.", "start": 922.03, "duration": 0.93}, {"text": "I think that's probably a\nlarger factor with regard", "start": 922.96, "duration": 3.9}, {"text": "to the Big Tech companies,\nbut it is also true", "start": 926.86, "duration": 2.79}, {"text": "that it's a factor\nwith the startups.", "start": 929.65, "duration": 4.74}, {"text": "And then lastly, a\nquestion is, do you", "start": 934.39, "duration": 4.41}, {"text": "think stable value\ncoins, tokenized assets,", "start": 938.8, "duration": 2.94}, {"text": "even the initiative of Libra--", "start": 941.74, "duration": 4.29}, {"text": "what will that do on\nthis payment space?", "start": 946.03, "duration": 3.33}, {"text": "In essence, are they\nhype or a passing fad,", "start": 949.36, "duration": 2.475}, {"text": "or are they going to\ndo something here?", "start": 951.835, "duration": 1.625}, {"text": "Romain?", "start": 958.41, "duration": 0.5}, {"text": "ROMAIN: Any opinions on this?", "start": 958.91, "duration": 1.36}, {"text": "I'm still waiting.", "start": 964.68, "duration": 1.07}, {"text": "GARY GENSLER: We're\ngoing to help out.", "start": 965.75, "duration": 0.84}, {"text": "We're going to help out.", "start": 966.59, "duration": 1.0}, {"text": "We have a poll.", "start": 967.59, "duration": 0.69}, {"text": "This is exactly when we can\nask a poll to tease this out.", "start": 968.28, "duration": 4.47}, {"text": "You've done terrific, but no one\nanswer, because now, Romain's", "start": 972.75, "duration": 3.41}, {"text": "going to pull up a poll.", "start": 976.16, "duration": 2.03}, {"text": "And this is more broadly-- this\nis about blockchain technology,", "start": 978.19, "duration": 3.24}, {"text": "but curious what\neveryone thinks here.", "start": 981.43, "duration": 4.0}, {"text": "ROMAIN: So you\nshould now see a poll", "start": 985.43, "duration": 1.813}, {"text": "with three different\nquestions on your screen.", "start": 987.243, "duration": 1.917}, {"text": "GARY GENSLER: This is a\nlittle bit more broadly as", "start": 992.088, "duration": 2.522}, {"text": "to whether financial\nfirms will incorporate", "start": 994.61, "duration": 2.55}, {"text": "blockchain technology into\ntheir business models.", "start": 997.16, "duration": 3.57}, {"text": "As they've already incorporated\nAI and machine learning,", "start": 1000.73, "duration": 4.05}, {"text": "as they've been\nincorporating open API,", "start": 1004.78, "duration": 3.03}, {"text": "will this be a fundamental\nfeature in the next 2,", "start": 1007.81, "duration": 3.57}, {"text": "5, or 10 years, or not at all?", "start": 1011.38, "duration": 2.1}, {"text": "ROMAIN: 20% of the\nclass voted so far.", "start": 1017.304, "duration": 2.916}, {"text": "Please check the\nwindow and vote.", "start": 1020.22, "duration": 1.59}, {"text": "GARY GENSLER: Romain,\nI like your ability", "start": 1027.39, "duration": 2.929}, {"text": "to pull in the votes.", "start": 1030.319, "duration": 1.29}, {"text": "You might have a job\nto do come November", "start": 1031.609, "duration": 4.891}, {"text": "in our next general\nelection here.", "start": 1036.5, "duration": 2.28}, {"text": "ROMAIN: Are you confident\nit's going to take place?", "start": 1043.091, "duration": 3.069}, {"text": "GARY GENSLER: Yes.", "start": 1046.16, "duration": 0.87}, {"text": "I am confident under our\nconstitutional system", "start": 1047.03, "duration": 3.18}, {"text": "that we will have an election.", "start": 1050.21, "duration": 1.605}, {"text": "ROMAIN: Excellent.", "start": 1051.815, "duration": 2.195}, {"text": "OK.", "start": 1054.01, "duration": 0.52}, {"text": "We have 70% of the\nclass that has voted.", "start": 1054.53, "duration": 2.64}, {"text": "I'm going to let\n5 more seconds--", "start": 1057.17, "duration": 2.64}, {"text": "GARY GENSLER:\n[INAUDIBLE] 10 seconds.", "start": 1059.81, "duration": 1.71}, {"text": "ROMAIN: Yeah.", "start": 1061.52, "duration": 0.94}, {"text": "And we reached 80%.", "start": 1067.64, "duration": 2.04}, {"text": "Thank you, everyone, for\nsharing your thoughts.", "start": 1069.68, "duration": 2.525}, {"text": "I'm sharing the\nresults with you.", "start": 1072.205, "duration": 1.375}, {"text": "You should now be\nable to see them.", "start": 1073.58, "duration": 2.21}, {"text": "GARY GENSLER: So let's\nsee, that the class tends", "start": 1075.79, "duration": 3.33}, {"text": "to be optimistic that blockchain\ntechnology will be incorporated", "start": 1079.12, "duration": 5.03}, {"text": "in, even though it might\ntake 5 to 10 years.", "start": 1084.15, "duration": 3.16}, {"text": "It looks like the mode is\n5 years or 5 or 10 years.", "start": 1087.31, "duration": 7.94}, {"text": "In terms of, what\nwill it have will be--", "start": 1095.25, "duration": 5.56}, {"text": "beyond speculative digital\nstore valuable Bitcoin", "start": 1100.81, "duration": 3.75}, {"text": "become the currency of choice\nin some part of the economy,", "start": 1104.56, "duration": 4.156}, {"text": "that generally 60-some% say no.", "start": 1108.716, "duration": 4.424}, {"text": "And then, who is\nSatoshi Nakamoto?", "start": 1113.14, "duration": 2.13}, {"text": "Well, that was just\nmy one little question", "start": 1115.27, "duration": 4.17}, {"text": "because, of course, we don't\nknow who Satoshi Nakamoto is,", "start": 1119.44, "duration": 3.42}, {"text": "this woman or man who wrote\nthe eight-page white paper", "start": 1122.86, "duration": 5.04}, {"text": "and put it out on the\ninternet 12 years ago.", "start": 1127.9, "duration": 1.99}, {"text": "But it looks like\na third of you said", "start": 1129.89, "duration": 1.64}, {"text": "maybe it was a\nforeign state actor,", "start": 1131.53, "duration": 2.37}, {"text": "or 20% said US intelligence.", "start": 1133.9, "duration": 2.31}, {"text": "OK.", "start": 1139.55, "duration": 0.5}, {"text": "So let's get back to payments,\nI like this thought there.", "start": 1140.05, "duration": 5.04}, {"text": "If you want to take that\nwindow, you have to, I think,", "start": 1145.09, "duration": 2.91}, {"text": "get rid of the\npoll individually,", "start": 1148.0, "duration": 2.41}, {"text": "which I'm about to do now--", "start": 1150.41, "duration": 1.72}, {"text": "ROMAIN: Yes, thank you.", "start": 1152.13, "duration": 1.56}, {"text": "GARY GENSLER: --as well.", "start": 1153.69, "duration": 2.84}, {"text": "So what is a payment system?", "start": 1156.53, "duration": 3.51}, {"text": "Let's just dive in and\ntalk about what it is.", "start": 1160.04, "duration": 3.41}, {"text": "And it's been around a century.", "start": 1163.45, "duration": 3.31}, {"text": "So it's not a new thing.", "start": 1166.76, "duration": 2.07}, {"text": "But in a digital world,\nin a ledger-based world,", "start": 1168.83, "duration": 3.93}, {"text": "it's a method to\nchange a ledger.", "start": 1172.76, "duration": 4.41}, {"text": "Now, this isn't an\naccounting class.", "start": 1177.17, "duration": 1.5}, {"text": "I'm not going to bore\nyou with accounting.", "start": 1178.67, "duration": 1.75}, {"text": "But basically, if I'm\nmoving money to you,", "start": 1180.42, "duration": 2.06}, {"text": "somebody has to lower my\naccount, credit my account.", "start": 1182.48, "duration": 5.43}, {"text": "Remember assets or debits.", "start": 1187.91, "duration": 2.77}, {"text": "So credit means it's\ngoing down, a little bit", "start": 1190.68, "duration": 3.29}, {"text": "of accounting here.", "start": 1193.97, "duration": 1.71}, {"text": "And then somebody else's\naccount has to be debited.", "start": 1195.68, "duration": 3.36}, {"text": "So one debit, one credit.", "start": 1199.04, "duration": 2.31}, {"text": "One account goes down,\none account goes up.", "start": 1201.35, "duration": 3.24}, {"text": "It's also about authorizing\nthose movements and then", "start": 1204.59, "duration": 5.04}, {"text": "what's called clearing\nand final settlement.", "start": 1209.63, "duration": 2.64}, {"text": "And earlier we discussed that--", "start": 1212.27, "duration": 1.78}, {"text": "and sometimes final\nsettlement doesn't", "start": 1214.05, "duration": 1.91}, {"text": "happen for a couple of days.", "start": 1215.96, "duration": 2.12}, {"text": "And a long time ago, if\nyou wrote a physical check,", "start": 1218.08, "duration": 3.58}, {"text": "you might not have\nit settled, meaning", "start": 1221.66, "duration": 1.95}, {"text": "having money in your account\nfor five days or longer even.", "start": 1223.61, "duration": 5.7}, {"text": "Now it's closer to two days.", "start": 1229.31, "duration": 2.96}, {"text": "But it's basically amending\nand recording those ledgers.", "start": 1232.27, "duration": 3.73}, {"text": "That's what it is in\nan accounting system.", "start": 1236.0, "duration": 2.92}, {"text": "And so how did we do this?", "start": 1238.92, "duration": 1.86}, {"text": "This is just some\nfun background,", "start": 1240.78, "duration": 2.77}, {"text": "but Thomas Jefferson, the\nwriter of the Declaration", "start": 1243.55, "duration": 2.68}, {"text": "of Independence, actually\nyou can find online a check", "start": 1246.23, "duration": 3.45}, {"text": "he wrote to himself.", "start": 1249.68, "duration": 1.21}, {"text": "I'm not quite sure why he did.", "start": 1250.89, "duration": 2.48}, {"text": "This would have been the\nyear after he was president,", "start": 1253.37, "duration": 3.05}, {"text": "but he wrote a check to himself.", "start": 1256.42, "duration": 1.81}, {"text": "So physical personal checks\nhave been around a long time,", "start": 1258.23, "duration": 3.79}, {"text": "but they are basically\nan instruction", "start": 1262.02, "duration": 2.52}, {"text": "called negotiable\norders of withdrawal,", "start": 1264.54, "duration": 2.39}, {"text": "but an instruction to a\nbank to amend the ledger.", "start": 1266.93, "duration": 3.25}, {"text": "Lower my ledger, and\ngive me maybe paper cash,", "start": 1270.18, "duration": 3.41}, {"text": "or lower my ledger,\nraise somebody else's.", "start": 1273.59, "duration": 2.73}, {"text": "All of the sudden, the\ntelegraph comes along.", "start": 1278.925, "duration": 1.875}, {"text": "And a company, Western\nUnion, which still exists--", "start": 1280.8, "duration": 2.91}, {"text": "Western Union comes along,\nand it's a telegram company.", "start": 1283.71, "duration": 4.5}, {"text": "But they figure out how to\nsend money by telegraph,", "start": 1288.21, "duration": 4.05}, {"text": "the FinTech of its time.", "start": 1292.26, "duration": 2.19}, {"text": "And yes, there were\nmachines that looked", "start": 1294.45, "duration": 2.52}, {"text": "like this, telex machines.", "start": 1296.97, "duration": 1.74}, {"text": "These were ubiquitous across\nfinancial firms in the 1950s", "start": 1298.71, "duration": 4.29}, {"text": "to the 1970s.", "start": 1303.0, "duration": 1.59}, {"text": "I will admit I saw one or two of\nthese when I was on Wall Street", "start": 1304.59, "duration": 3.24}, {"text": "still in the 1980s.", "start": 1307.83, "duration": 2.19}, {"text": "But a telex machine\nexisted basically", "start": 1310.02, "duration": 3.69}, {"text": "to send instructions on\npayments around to another bank.", "start": 1313.71, "duration": 5.502}, {"text": "But what's it look like today?", "start": 1319.212, "duration": 2.468}, {"text": "Well, first, the\nimportant thing is", "start": 1321.68, "duration": 2.49}, {"text": "central banks sit in the\nmiddle of payment systems.", "start": 1324.17, "duration": 3.84}, {"text": "This was not as true\nin terms of the--", "start": 1328.01, "duration": 4.17}, {"text": "I'm just trying to move\na window out of the way.", "start": 1332.18, "duration": 3.72}, {"text": "This was not as true in the\nphysical coin and currency", "start": 1335.9, "duration": 5.37}, {"text": "world.", "start": 1341.27, "duration": 0.9}, {"text": "But here, this little chart puts\nthe central bank at the top.", "start": 1342.17, "duration": 3.66}, {"text": "And we have central banks around\nthe globe, 180 different Fiat", "start": 1345.83, "duration": 3.54}, {"text": "currencies.", "start": 1349.37, "duration": 1.41}, {"text": "The central banks are\ncentral to commercial banks.", "start": 1350.78, "duration": 4.95}, {"text": "And what's important to\nremember is our money system", "start": 1355.73, "duration": 5.76}, {"text": "has moved on from being\npaper money to basically", "start": 1361.49, "duration": 6.18}, {"text": "digital money.", "start": 1367.67, "duration": 1.38}, {"text": "And so today in the\nUS, if you think", "start": 1369.05, "duration": 2.31}, {"text": "about the total\nstock of currency,", "start": 1371.36, "duration": 3.09}, {"text": "the total stock\nof paper currency", "start": 1374.45, "duration": 3.24}, {"text": "prior to this coronavirus\ncrisis was about $1.8 trillion.", "start": 1377.69, "duration": 4.41}, {"text": "It's actually gone\nup in the last month.", "start": 1382.1, "duration": 3.51}, {"text": "It seems that there are people\nthat want to take cash out", "start": 1385.61, "duration": 2.7}, {"text": "of the bank, out of the\nATM as a store of value", "start": 1388.31, "duration": 4.99}, {"text": "around the globe.", "start": 1393.3, "duration": 0.9}, {"text": "We're not using it.", "start": 1394.2, "duration": 1.44}, {"text": "It's a disease vector, but\nit seems that the growth--", "start": 1395.64, "duration": 3.8}, {"text": "and it might be\nnow $1.9 trillion.", "start": 1399.44, "duration": 3.02}, {"text": "So it's gone up $100\nbillion or approximately.", "start": 1402.46, "duration": 4.61}, {"text": "But the digital money, all the\npeople's bank accounts, bank", "start": 1407.07, "duration": 3.78}, {"text": "deposits, money market funds\nis multiples of that, $15", "start": 1410.85, "duration": 4.14}, {"text": "or so trillion.", "start": 1414.99, "duration": 2.31}, {"text": "So about 90% of the\nmoney in the US,", "start": 1417.3, "duration": 4.05}, {"text": "depending upon your definition\nof money, is digital.", "start": 1421.35, "duration": 3.33}, {"text": "And most of that digital money\nis commercial bank money.", "start": 1424.68, "duration": 3.27}, {"text": "You and I, when we\ngo into Starbucks,", "start": 1427.95, "duration": 1.92}, {"text": "we're basically spending Bank\nAmerica dollars, or Citibank", "start": 1429.87, "duration": 5.4}, {"text": "dollars, or Wells Fargo\ndollars, or SunTrust dollars,", "start": 1435.27, "duration": 3.39}, {"text": "or Community Bank dollar.", "start": 1438.66, "duration": 1.92}, {"text": "That's what we're spending\nwhen we walk into Starbucks.", "start": 1440.58, "duration": 3.16}, {"text": "It might have some implicit\nor explicit guarantee", "start": 1443.74, "duration": 3.27}, {"text": "of a government here in the US,\ndeposit insurance and the like.", "start": 1447.01, "duration": 4.43}, {"text": "But we're in essence saying\nto Bank of America, please", "start": 1451.44, "duration": 2.7}, {"text": "change my ledger\nbalance and move", "start": 1454.14, "duration": 2.97}, {"text": "something to somebody\nelse's ledger balance,", "start": 1457.11, "duration": 2.46}, {"text": "maybe a Community Bank\nfor that local Starbucks.", "start": 1459.57, "duration": 4.89}, {"text": "So in between has to be\nsome electronic means,", "start": 1464.46, "duration": 3.09}, {"text": "some payments system, a\ndeferred net settlement system.", "start": 1467.55, "duration": 3.66}, {"text": "And this chart lists\nthe number of them.", "start": 1471.21, "duration": 3.18}, {"text": "These payment systems are\nthe domain of central banks.", "start": 1474.39, "duration": 6.44}, {"text": "Some central banks\nactually run them,", "start": 1480.83, "duration": 2.37}, {"text": "like the US Federal Reserve runs\nsomething called the Fedwire.", "start": 1483.2, "duration": 4.44}, {"text": "But some are run by a consortium\nof the commercial banks.", "start": 1487.64, "duration": 7.54}, {"text": "Some are private.", "start": 1495.18, "duration": 1.91}, {"text": "And in some countries, they\ncan even be for-profit.", "start": 1497.09, "duration": 2.83}, {"text": "But all of them\nhave some regulation", "start": 1499.92, "duration": 3.12}, {"text": "from the central bank.", "start": 1503.04, "duration": 1.12}, {"text": "So either the central bank\nowns them or the central bank", "start": 1504.16, "duration": 2.99}, {"text": "oversees them.", "start": 1507.15, "duration": 1.75}, {"text": "And usually then\nthe commercial banks", "start": 1508.9, "duration": 1.64}, {"text": "might run these\nsingle purpose payment", "start": 1510.54, "duration": 4.11}, {"text": "systems around the globe.", "start": 1514.65, "duration": 1.56}, {"text": "Some countries have\nmultiple systems.", "start": 1516.21, "duration": 1.89}, {"text": "The US, we have the\nFed system, and we also", "start": 1518.1, "duration": 3.24}, {"text": "have something called the\nautomated clearing house.", "start": 1521.34, "duration": 3.07}, {"text": "The clearing house was\nfounded in the 1850s", "start": 1524.41, "duration": 3.41}, {"text": "to give you a sense of its\nhistory, a long history.", "start": 1527.82, "duration": 3.63}, {"text": "Questions, Romain, any?", "start": 1531.45, "duration": 3.218}, {"text": "ROMAIN: None so far, Gary.", "start": 1534.668, "duration": 1.302}, {"text": "GARY GENSLER: All right.", "start": 1535.97, "duration": 0.34}, {"text": "So you'll see how\nthis fits together.", "start": 1536.31, "duration": 1.72}, {"text": "But let me say what the modern\npayment system looks like when", "start": 1538.03, "duration": 6.27}, {"text": "I think of it in terms\nof you go into Starbucks,", "start": 1544.3, "duration": 4.95}, {"text": "and you want to make a payment.", "start": 1549.25, "duration": 3.03}, {"text": "You're the consumer.", "start": 1552.28, "duration": 1.42}, {"text": "We're going to go across.", "start": 1553.7, "duration": 1.22}, {"text": "You have an issuing bank.", "start": 1554.92, "duration": 1.32}, {"text": "Let's use Bank of\nAmerica just to say.", "start": 1556.24, "duration": 2.47}, {"text": "And you're giving that\nbank, Bank of America,", "start": 1558.71, "duration": 2.63}, {"text": "a payment instruction.", "start": 1561.34, "duration": 2.81}, {"text": "Now, in an earlier day, you\ncould write a physical check,", "start": 1564.15, "duration": 2.55}, {"text": "like Thomas Jefferson's check.", "start": 1566.7, "duration": 1.73}, {"text": "You could use a credit card, a\ndebit card, some prepaid card.", "start": 1568.43, "duration": 5.35}, {"text": "But you have to give\nsome payment instruction.", "start": 1573.78, "duration": 3.24}, {"text": "Even that QR code\nthat you pass--", "start": 1577.02, "duration": 2.265}, {"text": "and we'll get to Alipay and\nWeChat Pay in a moment--", "start": 1579.285, "duration": 4.575}, {"text": "there is a payment\ninstruction somewhere,", "start": 1583.86, "duration": 2.43}, {"text": "digital payment instruction.", "start": 1586.29, "duration": 2.42}, {"text": "And then at the heart in\nthe middle is a network.", "start": 1588.71, "duration": 3.13}, {"text": "Now, these payment\nservice providers, PSPs,", "start": 1591.84, "duration": 3.45}, {"text": "in the middle or networks could\nbe associated with a credit", "start": 1595.29, "duration": 3.6}, {"text": "card company, the Visa\ncredit card network", "start": 1598.89, "duration": 3.48}, {"text": "founded in the late\n1950s by Bank of America,", "start": 1602.37, "duration": 3.495}, {"text": "a California bank at the time.", "start": 1605.865, "duration": 1.935}, {"text": "And it became ubiquitous\nby the late 1960s.", "start": 1607.8, "duration": 3.9}, {"text": "Visa, Mastercard,\nUnionPay in China", "start": 1611.7, "duration": 5.22}, {"text": "can both be credit\ncards and networks,", "start": 1616.92, "duration": 3.39}, {"text": "or there could be a network\nthat services the credit cards.", "start": 1620.31, "duration": 3.3}, {"text": "But you need something\nin the middle", "start": 1623.61, "duration": 3.64}, {"text": "because on the other side,\nthere's tens of thousands", "start": 1627.25, "duration": 2.64}, {"text": "of merchants or millions of\nmerchants if you go to China.", "start": 1629.89, "duration": 5.01}, {"text": "And on their side,\nthey have another bank.", "start": 1634.9, "duration": 3.23}, {"text": "But they need some way to access\nthis network, a point of sale--", "start": 1638.13, "duration": 4.74}, {"text": "POS is point of sale--", "start": 1642.87, "duration": 1.98}, {"text": "or by phone or by some\nmodern mechanism to access", "start": 1644.85, "duration": 3.72}, {"text": "that network.", "start": 1648.57, "duration": 1.78}, {"text": "And then the merchant\non the other side.", "start": 1650.35, "duration": 4.08}, {"text": "So you have consumer\nall the way to merchant.", "start": 1654.43, "duration": 4.4}, {"text": "You have banks,\nthe issuing bank.", "start": 1658.83, "duration": 2.91}, {"text": "The issuing bank is that\nparty that says, all right,", "start": 1661.74, "duration": 3.14}, {"text": "I'm going to take a\npayment instruction.", "start": 1664.88, "duration": 3.37}, {"text": "And you have the merchant\nbank on the other side", "start": 1668.25, "duration": 2.4}, {"text": "or acquire a bank,\nsometimes it's called.", "start": 1670.65, "duration": 2.66}, {"text": "But in the middle,\nthere's some network.", "start": 1673.31, "duration": 3.55}, {"text": "And it leads to a\nlot of concentration", "start": 1676.86, "duration": 2.97}, {"text": "because there's such\nsignificant economic and network", "start": 1679.83, "duration": 2.88}, {"text": "effects in a modern\ndigital payment system.", "start": 1682.71, "duration": 5.14}, {"text": "Questions.", "start": 1687.85, "duration": 0.5}, {"text": "ROMAIN: Yes.", "start": 1688.35, "duration": 0.45}, {"text": "We have questions from\nCarlos and then Jose.", "start": 1688.8, "duration": 1.833}, {"text": "GARY GENSLER: Please.", "start": 1690.633, "duration": 1.907}, {"text": "AUDIENCE: Hi.", "start": 1692.54, "duration": 0.92}, {"text": "So I wanted to ask, I know in\na lot of developing markets", "start": 1693.46, "duration": 3.64}, {"text": "now making the-- since\nyou mentioned the ACH,", "start": 1697.1, "duration": 2.91}, {"text": "making it real-time\nis a big focus", "start": 1700.01, "duration": 2.61}, {"text": "and using different\ntechnologies, right?", "start": 1702.62, "duration": 2.16}, {"text": "So could you explain, I guess,\nthe magnitude of difference", "start": 1704.78, "duration": 4.38}, {"text": "that having a real-time ACH\nsystem versus not makes?", "start": 1709.16, "duration": 3.96}, {"text": "GARY GENSLER: We're going to\ndive into this in about a half", "start": 1713.12, "duration": 3.78}, {"text": "an hour, but let me try\nit very quickly, Carlos.", "start": 1716.9, "duration": 2.34}, {"text": "And then remind me\nas we get back to it.", "start": 1719.24, "duration": 2.337}, {"text": "As a merchant, there's\na value to getting", "start": 1724.44, "duration": 4.56}, {"text": "final settlement when\nyou sell your coffee", "start": 1729.0, "duration": 4.83}, {"text": "or sell your produce or\na big machine, whatever", "start": 1733.83, "duration": 3.69}, {"text": "you're selling.", "start": 1737.52, "duration": 2.14}, {"text": "And there's the value\nbecause there's certainty,", "start": 1739.66, "duration": 3.66}, {"text": "and there's also timing.", "start": 1743.32, "duration": 1.47}, {"text": "So if you can get your cash on\nMonday rather than Wednesday,", "start": 1744.79, "duration": 2.85}, {"text": "there's a value to it.", "start": 1747.64, "duration": 1.5}, {"text": "Payment systems around\nthe globe historically", "start": 1749.14, "duration": 3.69}, {"text": "could give you final settlement\nif you used physical cash.", "start": 1752.83, "duration": 3.84}, {"text": "And physical cash under the\nlaws of the developed world", "start": 1756.67, "duration": 4.05}, {"text": "became final settlement\nfrom the earliest days.", "start": 1760.72, "duration": 4.26}, {"text": "There's a famous lawsuit\nfrom the Crawford case,", "start": 1764.98, "duration": 2.76}, {"text": "if you ever want to look it up,\nabout final settlement using", "start": 1767.74, "duration": 3.03}, {"text": "physical cash.", "start": 1770.77, "duration": 0.9}, {"text": "It's from the days of\nKing George II, I think.", "start": 1771.67, "duration": 5.13}, {"text": "But digitally, it was harder\nto get final settlement,", "start": 1776.8, "duration": 4.89}, {"text": "and we still have delays.", "start": 1781.69, "duration": 2.14}, {"text": "So what's happened\nin the last 25", "start": 1783.83, "duration": 2.93}, {"text": "years is many nations\nhave said, can we", "start": 1786.76, "duration": 2.34}, {"text": "get to real-time\nsettlement rather", "start": 1789.1, "duration": 3.69}, {"text": "than delayed settlement\nof one day, two days,", "start": 1792.79, "duration": 2.97}, {"text": "or, in the old days, five days?", "start": 1795.76, "duration": 2.07}, {"text": "And trying to get to\nthat real-time settlement", "start": 1797.83, "duration": 2.28}, {"text": "has been a challenge.", "start": 1800.11, "duration": 1.02}, {"text": "And we'll go through different\ncountries in about a half", "start": 1801.13, "duration": 2.53}, {"text": "an hour.", "start": 1803.66, "duration": 0.5}, {"text": "Let me hold that.", "start": 1804.16, "duration": 1.29}, {"text": "But a lot of countries,\ncentral banks around the globe", "start": 1805.45, "duration": 2.49}, {"text": "are trying to get to\nreal-time settlement.", "start": 1807.94, "duration": 2.19}, {"text": "But the value is to the merchant\nthat they have finality,", "start": 1810.13, "duration": 4.68}, {"text": "that they can then use\nthose funds in some way.", "start": 1814.81, "duration": 3.31}, {"text": "And I can tell you, even when I\nwas the chief financial officer", "start": 1818.12, "duration": 3.09}, {"text": "of the Hillary Clinton\ncampaign in 2016,", "start": 1821.21, "duration": 3.32}, {"text": "we had to deal with it.", "start": 1824.53, "duration": 0.96}, {"text": "We were the merchant\non the right-hand side.", "start": 1825.49, "duration": 3.27}, {"text": "We might get a donation.", "start": 1828.76, "duration": 1.92}, {"text": "But until that donation\nactually settled,", "start": 1830.68, "duration": 4.01}, {"text": "sometimes several days later,\nsometimes a day later--", "start": 1834.69, "duration": 3.15}, {"text": "it was different\nsettlement cycles--", "start": 1837.84, "duration": 2.28}, {"text": "but until that settled,\nwe couldn't actually", "start": 1840.12, "duration": 2.37}, {"text": "use it to buy advertisements\non, let's say,", "start": 1842.49, "duration": 4.14}, {"text": "Facebook or Google Ads.", "start": 1846.63, "duration": 2.22}, {"text": "So we needed-- even\nin that instance,", "start": 1848.85, "duration": 2.94}, {"text": "particularly when you get down\nto the last six or 10 days", "start": 1851.79, "duration": 2.79}, {"text": "before election time,\nthose days matter.", "start": 1854.58, "duration": 3.57}, {"text": "So I lived this as a--", "start": 1858.15, "duration": 2.43}, {"text": "other questions?", "start": 1860.58, "duration": 1.716}, {"text": "ROMAIN: Yes, Jose?", "start": 1862.296, "duration": 2.599}, {"text": "AUDIENCE: Yeah.", "start": 1864.895, "duration": 0.875}, {"text": "So I'm not sure if this is a bit\nout of the scope of the class,", "start": 1865.77, "duration": 2.63}, {"text": "but I've always been\nvery curious on,", "start": 1868.4, "duration": 2.16}, {"text": "why are checks so\nprevalent in the US?", "start": 1870.56, "duration": 3.98}, {"text": "So, for example, in Spain, I've\nnever used a check in my life.", "start": 1874.54, "duration": 3.265}, {"text": "And I think it\ndoesn't seem to be", "start": 1877.805, "duration": 1.875}, {"text": "a very efficient\nway of transferring", "start": 1879.68, "duration": 1.5}, {"text": "money versus, for\nexample, a wire transfer.", "start": 1881.18, "duration": 2.18}, {"text": "But in the US, it seems like\nbanks sometimes charge more", "start": 1883.36, "duration": 2.47}, {"text": "for wire transfers, and\nthey require more security,", "start": 1885.83, "duration": 3.685}, {"text": "passwords and things for a\nwire transfer than for checks.", "start": 1889.515, "duration": 2.375}, {"text": "GARY GENSLER: So it's--", "start": 1891.89, "duration": 0.33}, {"text": "AUDIENCE: And I don't\nreally understand why.", "start": 1892.22, "duration": 1.2}, {"text": "GARY GENSLER: --very much part--\nit's part of the pain points,", "start": 1893.42, "duration": 2.64}, {"text": "and each country has a little\nbit different heritage.", "start": 1896.06, "duration": 4.71}, {"text": "Of course, through the\n1960s, physical checks", "start": 1900.77, "duration": 2.94}, {"text": "were very a important dominant\npart of many payment systems.", "start": 1903.71, "duration": 4.53}, {"text": "It was only in the 1990s\nthat the US government", "start": 1908.24, "duration": 4.02}, {"text": "said by an Act of Congress\nthat the US government should", "start": 1912.26, "duration": 4.65}, {"text": "move to electronic\npayment of social security", "start": 1916.91, "duration": 5.49}, {"text": "and other important parts\nthat government pays money.", "start": 1922.4, "duration": 3.79}, {"text": "But even then, the\nadoption was supposed", "start": 1926.19, "duration": 2.36}, {"text": "to be by the late 1990s, and\nthere was various exemptions", "start": 1928.55, "duration": 3.84}, {"text": "and so forth installed.", "start": 1932.39, "duration": 1.89}, {"text": "And so we even see\nnow, in the middle", "start": 1934.28, "duration": 1.8}, {"text": "of the corona crisis, that you\ncan read in today's newspapers", "start": 1936.08, "duration": 4.35}, {"text": "that the $1,200\nthat's moving out", "start": 1940.43, "duration": 2.97}, {"text": "of our tax authority, the IRS,\nto individuals, while the bulk", "start": 1943.4, "duration": 5.58}, {"text": "of that's electronic--", "start": 1948.98, "duration": 1.29}, {"text": "80 or 90 million\nof those will be", "start": 1950.27, "duration": 1.8}, {"text": "electronic-- it's estimated\nthat there's still", "start": 1952.07, "duration": 1.98}, {"text": "millions of people that will\nget physical checks in the US.", "start": 1954.05, "duration": 5.1}, {"text": "So we still have this\nlegacy that's probably", "start": 1959.15, "duration": 3.09}, {"text": "a little bit more dominant.", "start": 1962.24, "duration": 1.26}, {"text": "I'm going to show\nsome statistics", "start": 1963.5, "duration": 1.39}, {"text": "on check uses in a moment.", "start": 1964.89, "duration": 3.44}, {"text": "Some of it's cultural.", "start": 1968.33, "duration": 1.44}, {"text": "Some of it's\nactually commercial.", "start": 1969.77, "duration": 2.55}, {"text": "At the middle of\nall this are banks.", "start": 1972.32, "duration": 2.57}, {"text": "And in the middle is these\nnetworks in the middle.", "start": 1974.89, "duration": 4.0}, {"text": "So it's not only\ncultural, but it's", "start": 1978.89, "duration": 2.37}, {"text": "also sometimes hard\nfor a merchant to say,", "start": 1981.26, "duration": 4.53}, {"text": "I want to pay--", "start": 1985.79, "duration": 1.5}, {"text": "the merchant, remember,\nhas to pay the 2 and 1/2%", "start": 1987.29, "duration": 4.15}, {"text": "cost if you're going\nto be accepting Visa.", "start": 1991.44, "duration": 2.99}, {"text": "So the cost of interchange\nfees, the cost the credit card", "start": 1994.43, "duration": 4.68}, {"text": "companies are taking here in the\nUS average around 2 and 3/4%,", "start": 1999.11, "duration": 5.394}, {"text": "2.75%.", "start": 2004.504, "duration": 2.076}, {"text": "So a lot of merchants\nstill would prefer", "start": 2006.58, "duration": 2.13}, {"text": "to take a check than that 2.75.", "start": 2008.71, "duration": 3.79}, {"text": "You go over to China,\nand you say, well,", "start": 2012.5, "duration": 2.27}, {"text": "within the Alipay,\nWeChat Pay systems,", "start": 2014.77, "duration": 2.52}, {"text": "the costs are\nsignificantly lower.", "start": 2017.29, "duration": 3.25}, {"text": "In fact, if you're all within\nservice, within system,", "start": 2020.54, "duration": 4.61}, {"text": "it's 0%.", "start": 2025.15, "duration": 1.8}, {"text": "In India, I think it's\naround 10 basis points.", "start": 2026.95, "duration": 2.74}, {"text": "So there's a lot of\nreasons a merchant might", "start": 2029.69, "duration": 3.11}, {"text": "say, all right, I might\nprefer if you can give me", "start": 2032.8, "duration": 2.58}, {"text": "an ACH or a check.", "start": 2035.38, "duration": 2.47}, {"text": "So gives you a\nlittle background.", "start": 2037.85, "duration": 2.78}, {"text": "But layered on\ntop of this system", "start": 2040.63, "duration": 2.67}, {"text": "is all these digital\nwallets, an invention really", "start": 2043.3, "duration": 3.18}, {"text": "just of the last 20 years.", "start": 2046.48, "duration": 1.44}, {"text": "And whether it's here in the\nUS or overseas, a lot of these", "start": 2050.929, "duration": 4.201}, {"text": "are related to Big\nTech, not only,", "start": 2055.13, "duration": 2.64}, {"text": "but a lot are\nrelated to Big Tech.", "start": 2057.77, "duration": 1.949}, {"text": "And then the question is, will\ncryptocurrency play some role?", "start": 2059.719, "duration": 4.831}, {"text": "Can crypto skip some of these\ninefficiencies and play a role?", "start": 2064.55, "duration": 6.629}, {"text": "And so with that, some of the\ntrends, just a quick look.", "start": 2071.179, "duration": 3.661}, {"text": "And this goes to the--\nthis is from a report.", "start": 2074.84, "duration": 2.79}, {"text": "Worldpay, which is a\nbig payment company,", "start": 2077.63, "duration": 3.299}, {"text": "puts out an annual\nreport each year.", "start": 2080.929, "duration": 2.761}, {"text": "And this is their most\nrecent report that", "start": 2083.69, "duration": 2.88}, {"text": "came out in February of 2020.", "start": 2086.57, "duration": 3.39}, {"text": "But around the\nglobe, mobile wallets", "start": 2089.96, "duration": 2.37}, {"text": "are estimated to already be\n42% of global e-commerce.", "start": 2092.33, "duration": 4.292}, {"text": "Now, this is important.", "start": 2096.622, "duration": 0.958}, {"text": "This is e-commerce.", "start": 2097.58, "duration": 1.5}, {"text": "If you go off to the\nbig wholesale payments", "start": 2099.08, "duration": 2.37}, {"text": "or large value payments,\ndifferent story.", "start": 2101.45, "duration": 2.77}, {"text": "But this is electronic payments\nin the e-commerce space", "start": 2104.22, "duration": 4.19}, {"text": "and then point of sale payments.", "start": 2108.41, "duration": 2.55}, {"text": "Cash is still a pretty big\npiece of the worldwide global", "start": 2110.96, "duration": 4.41}, {"text": "environment for point of\nsale, whereas e-commerce,", "start": 2115.37, "duration": 3.87}, {"text": "basically online using your\nmobile phone or your laptop--", "start": 2119.24, "duration": 3.93}, {"text": "can't really use cash much--", "start": 2123.17, "duration": 2.16}, {"text": "cash on delivery is still 4 and\n1/2%, though, interestingly.", "start": 2125.33, "duration": 4.23}, {"text": "That's Worldpay's\noverall view, but they", "start": 2129.56, "duration": 2.88}, {"text": "say credit card will\ndecline, debit cards", "start": 2132.44, "duration": 4.07}, {"text": "decline, bank\ntransfers about even.", "start": 2136.51, "duration": 4.47}, {"text": "And so what's increasing?", "start": 2140.98, "duration": 1.59}, {"text": "Digital mobile wallets.", "start": 2142.57, "duration": 1.5}, {"text": "And then, of course, at point\nof sale, cash declining.", "start": 2144.07, "duration": 3.27}, {"text": "And there you will see\nincreases in their estimation.", "start": 2147.34, "duration": 4.11}, {"text": "But the US is a\nlittle different.", "start": 2151.45, "duration": 2.2}, {"text": "The US or North America,\nwhich is the best statistics", "start": 2153.65, "duration": 3.56}, {"text": "I can grab off the\nWorldpay, we still", "start": 2157.21, "duration": 2.85}, {"text": "have a significant\namount of credit card.", "start": 2160.06, "duration": 2.61}, {"text": "Look at that.", "start": 2162.67, "duration": 1.02}, {"text": "Credit card's still a third.", "start": 2163.69, "duration": 2.34}, {"text": "Digital mobile wallet's 23%.", "start": 2166.03, "duration": 3.01}, {"text": "And from a merchant's\npoint of view,", "start": 2169.04, "duration": 1.65}, {"text": "they would prefer actually\nto have something that", "start": 2170.69, "duration": 2.87}, {"text": "takes the less bite out of it.", "start": 2173.56, "duration": 2.61}, {"text": "Here in the US,\ndebit cards by an Act", "start": 2176.17, "duration": 3.24}, {"text": "of Congress after\nthe 2008 crisis--", "start": 2179.41, "duration": 4.57}, {"text": "Carl Levin, a Senator\nfrom Illinois,", "start": 2183.98, "duration": 1.98}, {"text": "said, we should make sure\nthat debit cards do not--", "start": 2185.96, "duration": 4.05}, {"text": "and banks issuing debit cards\ncan't charge more than the cost", "start": 2190.01, "duration": 5.22}, {"text": "of actually issuing\nthat debit card.", "start": 2195.23, "duration": 1.86}, {"text": "And after a series\nof rule makings", "start": 2197.09, "duration": 1.98}, {"text": "by the central bank, the Federal\nReserve, that settled out.", "start": 2199.07, "duration": 3.27}, {"text": "But debit cards are\na little less costly", "start": 2202.34, "duration": 2.34}, {"text": "than credit cards for the banks.", "start": 2204.68, "duration": 4.77}, {"text": "And in terms of trends just\nin the US specifically,", "start": 2209.45, "duration": 3.33}, {"text": "this is from the Federal Reserve\nin December of this past year.", "start": 2212.78, "duration": 3.75}, {"text": "But this just gives you\na sense, 20 year history.", "start": 2216.53, "duration": 5.02}, {"text": "And this is overall\npayment trends.", "start": 2221.55, "duration": 2.06}, {"text": "This is not just e-commerce.", "start": 2223.61, "duration": 1.48}, {"text": "Checks were 45% 20 years ago.", "start": 2225.09, "duration": 3.07}, {"text": "And you can see that line just\ndecline, decline, decline.", "start": 2228.16, "duration": 2.57}, {"text": "So to Jose's point, we're\nnot quite there yet.", "start": 2230.73, "duration": 2.52}, {"text": "Spain might be down to 5%\non checks or something,", "start": 2233.25, "duration": 4.08}, {"text": "but you can see where we are.", "start": 2237.33, "duration": 2.41}, {"text": "And this is the number\nof payment instructions.", "start": 2239.74, "duration": 3.95}, {"text": "This is dollar amounts.", "start": 2243.69, "duration": 2.08}, {"text": "So in terms of dollars,\nchecks only went--", "start": 2245.77, "duration": 3.38}, {"text": "lost this parade\neight years ago.", "start": 2251.69, "duration": 4.95}, {"text": "So one is volume of payments.", "start": 2256.64, "duration": 1.64}, {"text": "One is the actual\nchecks and so forth.", "start": 2258.28, "duration": 3.33}, {"text": "And large value payments\nare included here.", "start": 2261.61, "duration": 2.88}, {"text": "The other charts did not.", "start": 2264.49, "duration": 2.52}, {"text": "And just one last thing in terms\nof the e-commerce side of it", "start": 2267.01, "duration": 3.57}, {"text": "and card payments,\nthis just gives you", "start": 2270.58, "duration": 2.28}, {"text": "a sense of remote\nand in-person, that I", "start": 2272.86, "duration": 4.26}, {"text": "like this right-hand chart.", "start": 2277.12, "duration": 2.46}, {"text": "But the trillions\nof dollars we move,", "start": 2279.58, "duration": 2.58}, {"text": "we are moving on\nour physical cards", "start": 2282.16, "duration": 3.36}, {"text": "more remote than\nwe are in person.", "start": 2285.52, "duration": 3.51}, {"text": "This gives an\nopportunity to startups.", "start": 2289.03, "duration": 2.0}, {"text": "Startups can say, wait, Visa,\nMastercard in many countries", "start": 2291.03, "duration": 6.15}, {"text": "has this 2 and 3/4%.", "start": 2297.18, "duration": 2.875}, {"text": "Maybe we can get\ninside that pricing.", "start": 2300.055, "duration": 2.685}, {"text": "Maybe we can get\ninside especially", "start": 2302.74, "duration": 2.28}, {"text": "as we move from in-person\nto remote payments", "start": 2305.02, "duration": 3.27}, {"text": "as an opportunity.", "start": 2308.29, "duration": 3.19}, {"text": "So that brings us to\na list of pain points.", "start": 2311.48, "duration": 3.753}, {"text": "What point are--", "start": 2315.233, "duration": 0.667}, {"text": "ROMAIN: Gary?", "start": 2315.9, "duration": 0.35}, {"text": "GARY GENSLER:\n--these pain points?", "start": 2316.25, "duration": 1.417}, {"text": "ROMAIN: Perhaps--", "start": 2317.667, "duration": 0.754}, {"text": "GARY GENSLER: Please, Romain.", "start": 2318.421, "duration": 1.209}, {"text": "ROMAIN: Actually,\nbefore we move there,", "start": 2319.63, "duration": 1.44}, {"text": "I think Hassan had a question.", "start": 2321.07, "duration": 1.14}, {"text": "GARY GENSLER: Please, Hassan.", "start": 2322.21, "duration": 1.26}, {"text": "Hassan, you might need\nto take your mute off.", "start": 2328.64, "duration": 2.832}, {"text": "AUDIENCE: Yeah.", "start": 2331.472, "duration": 2.628}, {"text": "About payments,\nso, for instance,", "start": 2334.1, "duration": 2.71}, {"text": "you could see we have the\nbank transfers and e-wallets.", "start": 2336.81, "duration": 4.94}, {"text": "So my question is,\nfor instance, I", "start": 2341.75, "duration": 3.45}, {"text": "was trying to pay my landlord\nwhile I was in Bahrain,", "start": 2345.2, "duration": 3.66}, {"text": "because I still have my\napartment in Cambridge.", "start": 2348.86, "duration": 3.39}, {"text": "And if the amount\nexceeds a certain number,", "start": 2352.25, "duration": 4.14}, {"text": "they have to send me a\nmessage, which can be annoying", "start": 2356.39, "duration": 4.66}, {"text": "because if my mobile\nisn't working,", "start": 2361.05, "duration": 3.69}, {"text": "they would not send me an email.", "start": 2364.74, "duration": 2.13}, {"text": "So is it like the\nsystem, the whole system,", "start": 2366.87, "duration": 4.53}, {"text": "the whole payment system\nsupports bank transfers", "start": 2371.4, "duration": 4.26}, {"text": "when it comes to big\npayments and small transfers", "start": 2375.66, "duration": 3.39}, {"text": "when it comes to e-wallets\nand mobile payments?", "start": 2379.05, "duration": 5.606}, {"text": "GARY GENSLER: Well, I'm\nnot sure of your question.", "start": 2384.656, "duration": 3.944}, {"text": "It is true that ultimately\nsitting in the midst of this,", "start": 2388.6, "duration": 5.64}, {"text": "with the risk of going\nback a bunch of slides,", "start": 2394.24, "duration": 2.76}, {"text": "there has to be something--", "start": 2397.0, "duration": 2.37}, {"text": "well, I'll just stay here.", "start": 2399.37, "duration": 1.77}, {"text": "There has to be an instruction\nthat moves it from an issuing", "start": 2401.14, "duration": 5.34}, {"text": "bank to an acquiring bank.", "start": 2406.48, "duration": 1.69}, {"text": "So your landlord would\nbe the merchant here.", "start": 2408.17, "duration": 3.26}, {"text": "Your landlord's bank has to\nget an instruction somehow.", "start": 2411.43, "duration": 4.65}, {"text": "So even if it's in this orange\nbox, the digital wallets", "start": 2416.08, "duration": 3.295}, {"text": "at the top, you have to send\nan instruction somewhere", "start": 2419.375, "duration": 5.065}, {"text": "that takes funds from your\nbank, which is called an issuing", "start": 2424.44, "duration": 4.65}, {"text": "bank, and somehow moves those\nfunds to the landlord's bank.", "start": 2429.09, "duration": 5.97}, {"text": "And what you're finding\nis that your merchant", "start": 2435.06, "duration": 5.97}, {"text": "bank, the acquiring bank\non behalf of your landlord,", "start": 2441.03, "duration": 3.87}, {"text": "is saying, listen, if it's\ngreater than a certain dollar", "start": 2444.9, "duration": 2.64}, {"text": "amount, we need a\nsecond security check.", "start": 2447.54, "duration": 3.96}, {"text": "And the mobile wallet companies\nbasically inserted that check,", "start": 2451.5, "duration": 6.67}, {"text": "I think is what\nyou're telling me.", "start": 2458.17, "duration": 2.135}, {"text": "You could have that\nsame similar thing.", "start": 2460.305, "duration": 1.625}, {"text": "Venmo has a limit.", "start": 2461.93, "duration": 1.19}, {"text": "I don't think you could move $1\nmillion on Venmo, for instance.", "start": 2463.12, "duration": 3.21}, {"text": "Venmo is a PayPal subsidiary,\nand Venmo is actually--", "start": 2466.33, "duration": 5.31}, {"text": "avoids those credit card fees.", "start": 2471.64, "duration": 1.98}, {"text": "Venmo is a form of\naccount to account", "start": 2473.62, "duration": 2.91}, {"text": "transfer, your\naccount at your bank", "start": 2476.53, "duration": 3.27}, {"text": "to somebody else's account.", "start": 2479.8, "duration": 1.35}, {"text": "And account to account transfers\nare a very important feature", "start": 2481.15, "duration": 4.02}, {"text": "of the competition.", "start": 2485.17, "duration": 1.56}, {"text": "But still, Venmo is not\ngoing to move $1 million", "start": 2486.73, "duration": 2.25}, {"text": "without having additional\nsecurity checks.", "start": 2488.98, "duration": 4.09}, {"text": "So that's probably what's\nhappening here, I fear to say.", "start": 2493.07, "duration": 4.585}, {"text": "AUDIENCE: Yeah.", "start": 2497.655, "duration": 0.775}, {"text": "I, mean my point is it's a\nbit annoying because I would--", "start": 2498.43, "duration": 5.19}, {"text": "for instance, because my\nmobile is a prepaid mobile.", "start": 2503.62, "duration": 3.96}, {"text": "So I could not receive\na message from my bank.", "start": 2507.58, "duration": 2.73}, {"text": "GARY GENSLER: Oh, well, I\ncan't solve that for you here,", "start": 2510.31, "duration": 4.05}, {"text": "but I think that's part\nof what you're saying.", "start": 2514.36, "duration": 2.67}, {"text": "That's part of these pain\npoints is that fraud.", "start": 2517.03, "duration": 5.82}, {"text": "Basically, when you think\nof all the pain points,", "start": 2522.85, "duration": 4.41}, {"text": "you and I, as users, we want\nsomething that's easy to use,", "start": 2527.26, "duration": 6.99}, {"text": "nearly costless.", "start": 2534.25, "duration": 1.29}, {"text": "We're willing to\nspend something,", "start": 2535.54, "duration": 1.71}, {"text": "but we'd prefer not to spend\n2% to 3% of our purchases", "start": 2537.25, "duration": 3.42}, {"text": "on the payment system.", "start": 2540.67, "duration": 1.98}, {"text": "And we want it not\nto have complexity,", "start": 2542.65, "duration": 3.66}, {"text": "the cross-border payments\nthat we talked about earlier.", "start": 2546.31, "duration": 3.9}, {"text": "We kind of know that\nthey're tracking us,", "start": 2550.21, "duration": 2.67}, {"text": "they're getting our data,\nbut we're a little concerned", "start": 2552.88, "duration": 2.25}, {"text": "about data privacy.", "start": 2555.13, "duration": 1.81}, {"text": "And so you're capturing one of\nthe pain points around fraud.", "start": 2556.94, "duration": 4.43}, {"text": "And that's from\nthe merchant side.", "start": 2561.37, "duration": 2.14}, {"text": "The merchant doesn't\nwant the fraud,", "start": 2563.51, "duration": 1.64}, {"text": "but also you don't want it.", "start": 2565.15, "duration": 1.35}, {"text": "You don't want somebody to be\nable to tap into your account", "start": 2566.5, "duration": 3.96}, {"text": "and move your money out.", "start": 2570.46, "duration": 1.65}, {"text": "And the pain point sounds\nlike the fraud detection", "start": 2572.11, "duration": 2.97}, {"text": "system that your bank is using\nis requiring your mobile phone", "start": 2575.08, "duration": 3.99}, {"text": "in a way that's friction.", "start": 2579.07, "duration": 3.15}, {"text": "It's frankly friction.", "start": 2582.22, "duration": 2.43}, {"text": "It's similar to a pain point--", "start": 2584.65, "duration": 1.92}, {"text": "it used to be until\nvery recently,", "start": 2586.57, "duration": 3.24}, {"text": "if you traveled overseas, you\nwere better to tell your bank", "start": 2589.81, "duration": 5.97}, {"text": "that you were going to be using\nyour credit card in Spain,", "start": 2595.78, "duration": 3.84}, {"text": "or France, or Asia, or Bahrain.", "start": 2599.62, "duration": 4.17}, {"text": "But now no longer\nbecause now they have--", "start": 2603.79, "duration": 4.1}, {"text": "they use our mobile\nphones to say--", "start": 2607.89, "duration": 2.38}, {"text": "they track us.", "start": 2610.27, "duration": 1.23}, {"text": "They know that we're in Spain,\nor France, or Asia, or Bahrain.", "start": 2611.5, "duration": 3.84}, {"text": "That's part of the reason we\ndon't need to call any longer,", "start": 2615.34, "duration": 4.06}, {"text": "but that's part of their\nfraud detection programs.", "start": 2619.4, "duration": 3.32}, {"text": "Let me keep moving on if I can.", "start": 2622.72, "duration": 3.99}, {"text": "So there's a series\nof pain points.", "start": 2626.71, "duration": 1.92}, {"text": "And I don't necessarily have all\nof them, but these are also--", "start": 2628.63, "duration": 3.36}, {"text": "you can think of them\nas opportunities.", "start": 2631.99, "duration": 3.28}, {"text": "These are opportunities\nfor disruptors to say,", "start": 2635.27, "duration": 3.08}, {"text": "maybe we can provide\na better service.", "start": 2638.35, "duration": 2.88}, {"text": "Maybe we can provide\nsomething at a lower", "start": 2641.23, "duration": 5.25}, {"text": "cost and more inclusive.", "start": 2646.48, "duration": 4.89}, {"text": "These are the possibilities\nfor any startup in a sense.", "start": 2651.37, "duration": 4.72}, {"text": "So I talked a little\nabout the cost.", "start": 2656.09, "duration": 3.72}, {"text": "This is a couple of years ago,\nbut this Bloomberg article", "start": 2659.81, "duration": 3.98}, {"text": "broke down the cost, and\nI find it very helpful.", "start": 2663.79, "duration": 4.18}, {"text": "Often in the US and\nin Europe, we think,", "start": 2667.97, "duration": 2.28}, {"text": "all right, I pay\n$100 for something.", "start": 2670.25, "duration": 3.63}, {"text": "You think you paid $100 for it.", "start": 2673.88, "duration": 1.83}, {"text": "Well, actually you paid\n$97 roughly for it,", "start": 2675.71, "duration": 4.14}, {"text": "and $2.75 went to\nthe payment system.", "start": 2679.85, "duration": 3.81}, {"text": "And that $2.75 that went to\nthe payment system, most of it", "start": 2683.66, "duration": 3.69}, {"text": "goes to what's called\nthe issuing bank.", "start": 2687.35, "duration": 2.32}, {"text": "And again, the issuing\nbank is the purchaser.", "start": 2689.67, "duration": 4.43}, {"text": "The acquiring bank\nis the merchant.", "start": 2694.1, "duration": 3.29}, {"text": "So that merchant bank is\nonly getting $0.19 on average", "start": 2697.39, "duration": 4.58}, {"text": "two years ago, the acquiring\nbank, Bank of America,", "start": 2701.97, "duration": 4.91}, {"text": "or whomever issued\nthe credit card.", "start": 2706.88, "duration": 2.67}, {"text": "So the dominant part\nof the economics", "start": 2709.55, "duration": 2.55}, {"text": "here is on the credit card side.", "start": 2712.1, "duration": 2.56}, {"text": "There's seven big companies\nin America being the big four", "start": 2714.66, "duration": 4.43}, {"text": "banks of Bank of America,\nand Wells Fargo, and Citi,", "start": 2719.09, "duration": 4.05}, {"text": "and Chase.", "start": 2723.14, "duration": 2.04}, {"text": "But then Cap One is a\nvery big credit card bank.", "start": 2725.18, "duration": 3.96}, {"text": "And then, of course,\nAmerican Express and Discover", "start": 2729.14, "duration": 3.0}, {"text": "and the like.", "start": 2732.14, "duration": 1.53}, {"text": "Those seven big banks are\nthe big issuing banks.", "start": 2733.67, "duration": 3.54}, {"text": "But community banks, even\nsmaller banks across the land,", "start": 2737.21, "duration": 5.46}, {"text": "will issue credit cards,\nand they get that roughly $2", "start": 2742.67, "duration": 4.77}, {"text": "out of $100 purchase.", "start": 2747.44, "duration": 3.102}, {"text": "Now, what do they do with it?", "start": 2750.542, "duration": 1.208}, {"text": "Part of it is the\nrewards program.", "start": 2751.75, "duration": 2.93}, {"text": "And wrapped up inside of all\nthis is an incentive system", "start": 2754.68, "duration": 3.99}, {"text": "that issuing banks are using\npart of that $2.20 on average,", "start": 2758.67, "duration": 5.76}, {"text": "on average about $1--", "start": 2764.43, "duration": 2.73}, {"text": "I think the national\naverage recently was $1.06.", "start": 2767.16, "duration": 3.33}, {"text": "If you take all the\ndifferent rewards programs,", "start": 2770.49, "duration": 3.06}, {"text": "they come back.", "start": 2773.55, "duration": 1.88}, {"text": "So you buy something for $100.", "start": 2775.43, "duration": 2.08}, {"text": "$2.20 goes to your issuing bank.", "start": 2777.51, "duration": 3.61}, {"text": "$1 might come back\nto you as a reward.", "start": 2781.12, "duration": 4.25}, {"text": "And it makes behavioral\nsciences important", "start": 2785.37, "duration": 2.57}, {"text": "and makes this stuff sticky.", "start": 2787.94, "duration": 2.07}, {"text": "It makes us loyal to our cards\nin a way that pure economics,", "start": 2790.01, "duration": 5.53}, {"text": "you would think, that\nit would be easier", "start": 2795.54, "duration": 1.97}, {"text": "to disrupt this space.", "start": 2797.51, "duration": 1.95}, {"text": "So I wouldn't put aside some\nof these reward programs", "start": 2799.46, "duration": 2.66}, {"text": "when you're thinking\nabout, all right, I'm", "start": 2802.12, "duration": 1.75}, {"text": "going to be a disrupter.", "start": 2803.87, "duration": 1.05}, {"text": "I'm going to break\ninto the payment space.", "start": 2804.92, "duration": 2.94}, {"text": "The credit card companies, they\nhave a point of view on this,", "start": 2807.86, "duration": 4.78}, {"text": "too.", "start": 2812.64, "duration": 0.5}, {"text": "And they're going to want to\nprotect their market share.", "start": 2813.14, "duration": 3.63}, {"text": "Questions, Romain?", "start": 2816.77, "duration": 1.865}, {"text": "Anything there?", "start": 2818.635, "duration": 0.625}, {"text": "ROMAIN: Let's give\nit a few seconds", "start": 2819.26, "duration": 1.622}, {"text": "just in case someone\nwants to raise their hand.", "start": 2820.882, "duration": 1.958}, {"text": "Yeah.", "start": 2825.44, "duration": 0.5}, {"text": "GARY GENSLER: I'm going to--", "start": 2825.94, "duration": 0.29}, {"text": "ROMAIN: We have Luno.", "start": 2826.23, "duration": 1.27}, {"text": "Luno has a question.", "start": 2827.5, "duration": 1.27}, {"text": "GARY GENSLER: Sure.", "start": 2828.77, "duration": 1.18}, {"text": "And then I'm going to do\nan overview of the cost.", "start": 2829.95, "duration": 2.985}, {"text": "Luno?", "start": 2832.935, "duration": 0.5}, {"text": "AUDIENCE: It's actually\nnot a question.", "start": 2833.435, "duration": 2.545}, {"text": "It's just in Europe,\nit's a bit different.", "start": 2835.98, "duration": 3.03}, {"text": "The interchange fee\nis actually capped", "start": 2839.01, "duration": 2.94}, {"text": "to 0.3% if it's a credit card\nand 0.2% if it's a debit card.", "start": 2841.95, "duration": 5.34}, {"text": "I'm not sure about the numbers.", "start": 2847.29, "duration": 2.23}, {"text": "And so I think this has\ninteresting spillovers in terms", "start": 2849.52, "duration": 2.96}, {"text": "of rewards programs in\nEurope are definitely not", "start": 2852.48, "duration": 3.69}, {"text": "as good as in the US.", "start": 2856.17, "duration": 1.71}, {"text": "And then you can also\nsee that the credit card", "start": 2857.88, "duration": 2.54}, {"text": "usage is much smaller.", "start": 2860.42, "duration": 3.13}, {"text": "And that might be one\nof the reasons why.", "start": 2863.55, "duration": 1.96}, {"text": "GARY GENSLER: No.", "start": 2865.51, "duration": 0.708}, {"text": "It's a very good point\nbecause around the globe,", "start": 2866.218, "duration": 4.252}, {"text": "the official sector inserts\nthem self from time to time.", "start": 2870.47, "duration": 3.54}, {"text": "And because of the\nnatural network effects--", "start": 2874.01, "duration": 4.59}, {"text": "remember that chart--\nright in the middle,", "start": 2878.6, "duration": 2.04}, {"text": "there's powerful,\npowerful economics", "start": 2880.64, "duration": 2.22}, {"text": "around network effects.", "start": 2882.86, "duration": 1.76}, {"text": "Think of plumbing again.", "start": 2884.62, "duration": 1.18}, {"text": "We only have one--", "start": 2885.8, "duration": 2.55}, {"text": "we usually only have\none electric company,", "start": 2888.35, "duration": 2.28}, {"text": "one waterworks company\nper city because", "start": 2890.63, "duration": 3.24}, {"text": "of that incredible network\neffect of the plumbing.", "start": 2893.87, "duration": 2.76}, {"text": "Similar here.", "start": 2896.63, "duration": 1.72}, {"text": "And so what some official\nsectors have said", "start": 2898.35, "duration": 2.09}, {"text": "is, so now we have to put a\nlimit on what can be charged.", "start": 2900.44, "duration": 4.02}, {"text": "In the US we did do that.", "start": 2904.46, "duration": 2.31}, {"text": "Senator-- did I say Levin?", "start": 2906.77, "duration": 4.93}, {"text": "It was Senator Durbin\nactually of Illinois.", "start": 2911.7, "duration": 2.4}, {"text": "I'm sorry.", "start": 2914.1, "duration": 1.02}, {"text": "But Senator Durbin, the\nDurbin Amendment, we", "start": 2915.12, "duration": 3.87}, {"text": "did that in debit cards.", "start": 2918.99, "duration": 1.47}, {"text": "But credit cards, not the case.", "start": 2920.46, "duration": 3.06}, {"text": "And then in other\ncountries, like", "start": 2923.52, "duration": 1.62}, {"text": "in Asia, which really Alipay\nand WeChat Pay and others", "start": 2925.14, "duration": 4.74}, {"text": "leapfrogged.", "start": 2929.88, "duration": 0.84}, {"text": "And then the official sector\nis involved in a different way.", "start": 2930.72, "duration": 2.8}, {"text": "So you're absolutely right.", "start": 2933.52, "duration": 1.73}, {"text": "So rewards programs\nwould be lower.", "start": 2935.25, "duration": 2.13}, {"text": "Credit card users\nmight be lower.", "start": 2937.38, "duration": 2.55}, {"text": "If you're going to be\nstarting something,", "start": 2939.93, "duration": 2.28}, {"text": "you have to think of those\nseparate dynamics country", "start": 2942.21, "duration": 3.27}, {"text": "by country, very much so.", "start": 2945.48, "duration": 2.97}, {"text": "The worldwide-- an\ninteresting report, and this", "start": 2948.45, "duration": 4.8}, {"text": "is from a McKinsey report\nfrom September of last year.", "start": 2953.25, "duration": 5.16}, {"text": "McKinsey puts out an\nannual report of payments.", "start": 2958.41, "duration": 5.16}, {"text": "If you're interested\nin the area,", "start": 2963.57, "duration": 1.62}, {"text": "I didn't assign it as a reading.", "start": 2965.19, "duration": 1.35}, {"text": "It's a remarkable\nreport once a year.", "start": 2966.54, "duration": 2.88}, {"text": "But this is one chart that\nI pulled from this McKinsey", "start": 2969.42, "duration": 3.36}, {"text": "report.", "start": 2972.78, "duration": 0.96}, {"text": "The worldwide revenues\nin the payment system", "start": 2973.74, "duration": 3.21}, {"text": "add up to about $1.8\ntrillion, $1.9 trillion.", "start": 2976.95, "duration": 4.875}, {"text": "Now, I should caution,\nMcKinsey includes what they", "start": 2981.825, "duration": 4.305}, {"text": "call account-related liquidity.", "start": 2986.13, "duration": 2.91}, {"text": "And this quote,\n\"account-related liquidity,\"", "start": 2989.04, "duration": 4.23}, {"text": "is earning interest for the\nbanks on your credit card", "start": 2993.27, "duration": 5.74}, {"text": "balances.", "start": 2999.01, "duration": 1.29}, {"text": "Earlier World Bank statistics\nwould say the payment system", "start": 3000.3, "duration": 3.72}, {"text": "around the globe takes\nabout a 1/2 a percent", "start": 3004.02, "duration": 2.28}, {"text": "to 1% of the economy.", "start": 3006.3, "duration": 1.98}, {"text": "The worldwide economy\nbefore the corona crisis", "start": 3008.28, "duration": 3.03}, {"text": "was hovering just\nshort of $100 trillion,", "start": 3011.31, "duration": 2.31}, {"text": "the US economy\nabout $22 trillion,", "start": 3013.62, "duration": 3.15}, {"text": "the world economy\nabout $95 trillion.", "start": 3016.77, "duration": 3.49}, {"text": "But of that $95 trillion,\nwe've probably been spending,", "start": 3020.26, "duration": 4.49}, {"text": "McKinsey would say, nearly\n2% on our payment system.", "start": 3024.75, "duration": 5.62}, {"text": "World Bank would say this--", "start": 3030.37, "duration": 1.46}, {"text": "the figure is more like a\nquarter to a half of that", "start": 3031.83, "duration": 3.1}, {"text": "because McKinsey includes\nall the interest that we're", "start": 3034.93, "duration": 3.48}, {"text": "paying on our balances.", "start": 3038.41, "duration": 1.84}, {"text": "So this is the opportunity.", "start": 3040.25, "duration": 1.89}, {"text": "This is the opportunity.", "start": 3042.14, "duration": 1.13}, {"text": "If you're saying, aha, what did\nStripe, what did TransferWise,", "start": 3043.27, "duration": 3.33}, {"text": "what did Plaid see?", "start": 3046.6, "duration": 2.31}, {"text": "This is anywhere from a half a\ntrillion dollars at the low end", "start": 3048.91, "duration": 4.26}, {"text": "to $2 trillion at the high end.", "start": 3053.17, "duration": 3.02}, {"text": "1/2% to 2% of the\nworld economy relates", "start": 3056.19, "duration": 3.34}, {"text": "to just moving these digital\npayments back and forth", "start": 3059.53, "duration": 4.71}, {"text": "plus the\naccount-related activity", "start": 3064.24, "duration": 2.79}, {"text": "liquidity, the\nstarting, the lending", "start": 3067.03, "duration": 3.6}, {"text": "balances on top of that.", "start": 3070.63, "duration": 2.81}, {"text": "Romain, I see the\nchat room seems", "start": 3073.44, "duration": 2.17}, {"text": "to be lighting up quite a bit.", "start": 3075.61, "duration": 2.33}, {"text": "Are there questions\nthere, or do I keep going?", "start": 3077.94, "duration": 2.275}, {"text": "ROMAIN: You can keep going.", "start": 3080.215, "duration": 1.125}, {"text": "It's mainly students sharing\nadditional resources.", "start": 3081.34, "duration": 2.76}, {"text": "GARY GENSLER: All right, great.", "start": 3084.1, "duration": 2.13}, {"text": "So I was asked earlier--", "start": 3086.23, "duration": 2.23}, {"text": "I'm sorry, I can't\nremember now who asked it.", "start": 3088.46, "duration": 3.86}, {"text": "Was it Carlos?", "start": 3092.32, "duration": 0.84}, {"text": "But I apologize-- about\nreal-time gross settlements.", "start": 3093.16, "duration": 4.53}, {"text": "Real-time gross settlements\nis this conceptual framework", "start": 3097.69, "duration": 4.2}, {"text": "that we are all familiar\nwith in one way or the other.", "start": 3101.89, "duration": 2.51}, {"text": "Can I move a digital\ninstruction to move money", "start": 3104.4, "duration": 8.78}, {"text": "and to have the settlement\nbe relatively fast,", "start": 3113.18, "duration": 5.22}, {"text": "real-time gross settlement?", "start": 3118.4, "duration": 3.33}, {"text": "What's the word \"gross\" mean?", "start": 3121.73, "duration": 1.36}, {"text": "It means that we're\nnot net settling.", "start": 3123.09, "duration": 2.66}, {"text": "If you run a settlement system\nwith millions of checks coming", "start": 3125.75, "duration": 3.54}, {"text": "into a warehouse-- and that's\nliterally how the system", "start": 3129.29, "duration": 4.38}, {"text": "of check clearing used to\nwork in New York and elsewhere", "start": 3133.67, "duration": 4.41}, {"text": "in this country--", "start": 3138.08, "duration": 2.76}, {"text": "you can actually net settle.", "start": 3140.84, "duration": 1.81}, {"text": "You can say, well, there's\nthese checks coming in", "start": 3142.65, "duration": 3.29}, {"text": "from Bank of America to\nWells Fargo and these checks", "start": 3145.94, "duration": 3.6}, {"text": "from Wells Fargo\nto Bank of America.", "start": 3149.54, "duration": 2.1}, {"text": "Let's net these settlements\noff against each other.", "start": 3151.64, "duration": 4.05}, {"text": "But if you do\nsomething in real-time,", "start": 3155.69, "duration": 2.01}, {"text": "if you do it almost\ninstantaneous,", "start": 3157.7, "duration": 1.98}, {"text": "it has to be gross.", "start": 3159.68, "duration": 0.99}, {"text": "You can't net the\npayment instructions", "start": 3160.67, "duration": 2.64}, {"text": "between the various banks.", "start": 3163.31, "duration": 2.16}, {"text": "Real-time gross settlement is\nused for large value payments", "start": 3165.47, "duration": 3.96}, {"text": "and has been used\nfor large value", "start": 3169.43, "duration": 1.65}, {"text": "payments for quite some time.", "start": 3171.08, "duration": 1.7}, {"text": "In fact, the early large value\nmodel is the Fedwire, 1970.", "start": 3172.78, "duration": 5.92}, {"text": "That's 50 years of\ntechnology that we've", "start": 3178.7, "duration": 3.12}, {"text": "had the Fedwire,\nmeaning I can do", "start": 3181.82, "duration": 2.76}, {"text": "what's called a\nwire instruction.", "start": 3184.58, "duration": 2.18}, {"text": "But in the United\nKingdom, we had CHAPS.", "start": 3186.76, "duration": 3.19}, {"text": "And in China--", "start": 3189.95, "duration": 3.75}, {"text": "I'm going to mispronounce\nit, but C-N-A-P-S high-value", "start": 3193.7, "duration": 6.0}, {"text": "payment system, the\nEurozone TARGET.", "start": 3199.7, "duration": 2.55}, {"text": "2002 is actually when\nthe Eurozone was created.", "start": 3202.25, "duration": 4.05}, {"text": "So we've had large value models.", "start": 3206.3, "duration": 2.82}, {"text": "Coupled with that is\nsomething called SWIFT.", "start": 3209.12, "duration": 2.61}, {"text": "SWIFT is just a\nmessaging company.", "start": 3211.73, "duration": 2.67}, {"text": "SWIFT, the Society for\nWorldwide Interbank Financial", "start": 3214.4, "duration": 3.81}, {"text": "Telecommunications,\nI think, it's", "start": 3218.21, "duration": 3.42}, {"text": "basically to send messages to\nfacilitate these interbank.", "start": 3221.63, "duration": 5.1}, {"text": "The question in the\nlast 10 to 15 years", "start": 3226.73, "duration": 2.58}, {"text": "is, can we move from\nlarge value to just", "start": 3229.31, "duration": 3.735}, {"text": "you and me, in essence, what we\nthink we're doing with Venmo?", "start": 3233.045, "duration": 5.595}, {"text": "Can I move you money\nrapidly instantaneously?", "start": 3238.64, "duration": 4.68}, {"text": "And some countries have\nactually moved forward.", "start": 3243.32, "duration": 2.655}, {"text": "It's called real-time retail.", "start": 3248.66, "duration": 2.35}, {"text": "And the important thing is\nit's retail instant payments.", "start": 3251.01, "duration": 3.44}, {"text": "Now, a lot of people don't call\nit real-time retail instant.", "start": 3254.45, "duration": 4.16}, {"text": "A lot of people would just\ncall it 24 hours a day,", "start": 3258.61, "duration": 2.54}, {"text": "7 days a week, or some\npeople might call it RTGS.", "start": 3261.15, "duration": 4.28}, {"text": "But fundamentally, the\nquestion is, can we", "start": 3265.43, "duration": 2.31}, {"text": "do what the Fed the Reserve\nof the US did 50 years ago", "start": 3267.74, "duration": 6.92}, {"text": "and the United Kingdom\ndid nearly 40 years ago?", "start": 3274.66, "duration": 4.38}, {"text": "Can we do that for\nthe retail public,", "start": 3279.04, "duration": 2.86}, {"text": "and can we do it 24\nhours a day, 7 days", "start": 3281.9, "duration": 2.63}, {"text": "a week, every day of the year?", "start": 3284.53, "duration": 2.41}, {"text": "And the answer is yes,\nthe technology exists.", "start": 3286.94, "duration": 2.78}, {"text": "I'm listing here seven\nor eight countries", "start": 3289.72, "duration": 2.73}, {"text": "that either have\ninstantaneous payment", "start": 3292.45, "duration": 3.66}, {"text": "systems or near instantaneous.", "start": 3296.11, "duration": 2.89}, {"text": "Some of these are not\nliterally instantaneous.", "start": 3299.0, "duration": 2.84}, {"text": "A couple of them are\nthree cycles a day", "start": 3301.84, "duration": 4.12}, {"text": "where they do this\nthree times a day.", "start": 3305.96, "duration": 2.54}, {"text": "And I can't remember\neach country,", "start": 3308.5, "duration": 2.1}, {"text": "but you can see it's\nrelatively recent.", "start": 3310.6, "duration": 2.82}, {"text": "And then the US.", "start": 3313.42, "duration": 1.87}, {"text": "With the US projects, we\nhave this split system.", "start": 3315.29, "duration": 3.92}, {"text": "The clearing house is owned\nby 24 major banks in the US,", "start": 3319.21, "duration": 5.13}, {"text": "and it's been around\nsince the 1850s.", "start": 3324.34, "duration": 4.04}, {"text": "The clearing house\nby 2017 said, we", "start": 3328.38, "duration": 2.92}, {"text": "want to provide a\nreal-time payment network.", "start": 3331.3, "duration": 3.45}, {"text": "But it's really buying\namongst these 24 major banks,", "start": 3334.75, "duration": 3.81}, {"text": "all the big banks in the US.", "start": 3338.56, "duration": 3.0}, {"text": "The Federal Reserve at first\nseemed comfortable with that.", "start": 3341.56, "duration": 4.71}, {"text": "And then frankly, the rest\nof the banking community,", "start": 3346.27, "duration": 3.42}, {"text": "the banks that weren't the\ntop 24 said, no, not really.", "start": 3349.69, "duration": 5.05}, {"text": "And they went to Congress.", "start": 3354.74, "duration": 1.43}, {"text": "They went to the US Congress,\nand many members of Congress", "start": 3356.17, "duration": 4.02}, {"text": "got involved on behalf\nof community banks.", "start": 3360.19, "duration": 3.3}, {"text": "There's 5,000 or\n6,000 banks that", "start": 3363.49, "duration": 1.95}, {"text": "are not direct members\nof the clearinghouse.", "start": 3365.44, "duration": 3.36}, {"text": "And so now the Federal Reserve\nis standing up FedNow service.", "start": 3368.8, "duration": 4.77}, {"text": "And you can see this in\nLael Brainard's speech.", "start": 3373.57, "duration": 2.5}, {"text": "Now, FedNow service\nis also meant", "start": 3376.07, "duration": 3.76}, {"text": "to be like a public\nutility rather than", "start": 3379.83, "duration": 2.73}, {"text": "controlled by these 24 banks.", "start": 3382.56, "duration": 2.49}, {"text": "And so there's some interesting\ndynamics back and forth", "start": 3385.05, "duration": 2.76}, {"text": "in the competition.", "start": 3387.81, "duration": 1.33}, {"text": "The clearinghouse real-time\npayment network probably", "start": 3389.14, "duration": 2.72}, {"text": "will up its game, and FedNow\nwill come along as well.", "start": 3391.86, "duration": 4.56}, {"text": "Some said that the announcement\nlast year by the Federal", "start": 3396.42, "duration": 3.0}, {"text": "Reserve was in reaction\nto Facebook Libra,", "start": 3399.42, "duration": 2.55}, {"text": "and maybe that spurred\nthis a little bit,", "start": 3401.97, "duration": 3.15}, {"text": "that the official\nsector was then", "start": 3405.12, "duration": 1.47}, {"text": "competing with Facebook\nbecause the announcement came", "start": 3406.59, "duration": 2.97}, {"text": "just weeks after.", "start": 3409.56, "duration": 1.59}, {"text": "Now, I would imagine the Federal\nReserve was working on it", "start": 3411.15, "duration": 3.33}, {"text": "a long time beforehand.", "start": 3414.48, "duration": 1.83}, {"text": "And we'll close out\nthis lecture today", "start": 3416.31, "duration": 1.96}, {"text": "on when China's digital currency\nelectronic payments program.", "start": 3418.27, "duration": 5.51}, {"text": "China and the Federal\nReserve in the US", "start": 3423.78, "duration": 2.34}, {"text": "both had major announcements\nright after Facebook Libra.", "start": 3426.12, "duration": 4.23}, {"text": "This project, FedNow, and\nChina's, both had been--", "start": 3430.35, "duration": 4.59}, {"text": "work had been done, but it\nfeels like the announcements", "start": 3434.94, "duration": 3.39}, {"text": "were accelerated and\nin reaction a bit.", "start": 3438.33, "duration": 3.81}, {"text": "We don't know for\nsure, of course.", "start": 3442.14, "duration": 3.15}, {"text": "Questions, Romain?", "start": 3445.29, "duration": 2.196}, {"text": "ROMAIN: None so far, Gary.", "start": 3447.486, "duration": 1.399}, {"text": "GARY GENSLER: All right.", "start": 3448.885, "duration": 1.155}, {"text": "So what's the payment landscape?", "start": 3450.04, "duration": 1.77}, {"text": "Who are the companies?", "start": 3451.81, "duration": 1.2}, {"text": "Well, we've talked\nabout Big Tech.", "start": 3453.01, "duration": 1.68}, {"text": "And I'm glad, Luke,\nI think I have", "start": 3454.69, "duration": 3.98}, {"text": "KakaoPay on there thankfully.", "start": 3458.67, "duration": 3.25}, {"text": "I should have had\nLINE Pay as well.", "start": 3461.92, "duration": 2.4}, {"text": "But Big Tech, OK, we've chatted\na little bit about that.", "start": 3464.32, "duration": 4.17}, {"text": "And then there's, of course,\na bunch of unicorn startups.", "start": 3468.49, "duration": 4.43}, {"text": "I could have put another\nhalf dozen to a dozen,", "start": 3472.92, "duration": 2.64}, {"text": "unicorn being $1 billion\nof value or more.", "start": 3475.56, "duration": 4.69}, {"text": "But each of these startups\nhave a little bit different way", "start": 3480.25, "duration": 3.24}, {"text": "that they've broken\ninto this space.", "start": 3483.49, "duration": 2.73}, {"text": "Plaid, which we've chatted\na little bit about,", "start": 3486.22, "duration": 4.06}, {"text": "Plaid is in this space because\nthey came in through open APIs", "start": 3490.28, "duration": 4.58}, {"text": "and facilitating the\nsoftware in the system.", "start": 3494.86, "duration": 3.81}, {"text": "Ripple is a cryptocurrency\ntype company.", "start": 3498.67, "duration": 4.69}, {"text": "One97 is in India.", "start": 3503.36, "duration": 2.54}, {"text": "It's really-- I could even\nhave put that in the Big Tech", "start": 3505.9, "duration": 2.64}, {"text": "because they started,\nI think, Paytm.", "start": 3508.54, "duration": 2.67}, {"text": "NewBank addressed it a little\nbit from being a challenger", "start": 3511.21, "duration": 4.64}, {"text": "bank, and we're going\nto be talking about that", "start": 3515.85, "duration": 1.95}, {"text": "in a couple of lectures.", "start": 3517.8, "duration": 1.0}, {"text": "Toast picks a sector,\nand they really", "start": 3518.8, "duration": 3.57}, {"text": "dominate the restaurant sector.", "start": 3522.37, "duration": 3.17}, {"text": "But they initially were\ngetting into payments", "start": 3525.54, "duration": 2.74}, {"text": "because they were into tablets.", "start": 3528.28, "duration": 1.38}, {"text": "So each has a bit of\na different story.", "start": 3529.66, "duration": 4.23}, {"text": "Brex was about startups\nand facilitating", "start": 3533.89, "duration": 2.76}, {"text": "credit for startups.", "start": 3536.65, "duration": 1.17}, {"text": "TransferWise was cross-border,\nas we talked about earlier.", "start": 3537.82, "duration": 4.48}, {"text": "So they each found a\nstrategy to build themselves", "start": 3542.3, "duration": 3.74}, {"text": "into this place.", "start": 3546.04, "duration": 1.52}, {"text": "But let's just talk about Alipay\nand WeChat Pay for a moment.", "start": 3547.56, "duration": 4.6}, {"text": "This is even dated because\nthis is nearly a year old,", "start": 3552.16, "duration": 2.91}, {"text": "but this is their user base\nin the last seven years,", "start": 3555.07, "duration": 3.99}, {"text": "this remarkable growth\nof usage between Alipay", "start": 3559.06, "duration": 4.14}, {"text": "and WeChat Pay in China,\nboth with approximately", "start": 3563.2, "duration": 4.2}, {"text": "a billion users.", "start": 3567.4, "duration": 1.59}, {"text": "It's thought that WeChat\nPay and Alipay now", "start": 3568.99, "duration": 2.19}, {"text": "have 92% of the retail\npayment space in China.", "start": 3571.18, "duration": 6.13}, {"text": "And one of their\nstrategic approaches", "start": 3577.31, "duration": 4.08}, {"text": "is that if you have a store\nof value on an Alipay wallet", "start": 3581.39, "duration": 4.71}, {"text": "and you move it to somebody\nelse within the Alipay system,", "start": 3586.1, "duration": 4.77}, {"text": "as I understand it,\nit's still 0 cost.", "start": 3590.87, "duration": 2.37}, {"text": "If you jump out of service,\nout of system, 10 basis points.", "start": 3593.24, "duration": 4.74}, {"text": "But this conceptual framework--\nand their pricing model", "start": 3597.98, "duration": 3.6}, {"text": "could change at any time,\nbut their pricing model", "start": 3601.58, "duration": 3.12}, {"text": "has been historically, if you\nstay within the Alipay wallet", "start": 3604.7, "duration": 3.6}, {"text": "system, heck of a\nbenefit in cost.", "start": 3608.3, "duration": 4.39}, {"text": "So merchants then start to\nwant to pay their vendors.", "start": 3612.69, "duration": 3.88}, {"text": "And merchants and customers\nwant to stay within those wallet", "start": 3616.57, "duration": 4.05}, {"text": "systems to keep\nthose costs down,", "start": 3620.62, "duration": 3.3}, {"text": "significant network effects.", "start": 3623.92, "duration": 2.64}, {"text": "Romain?", "start": 3626.56, "duration": 0.785}, {"text": "ROMAIN: Sijin has her hand up.", "start": 3627.345, "duration": 2.495}, {"text": "GARY GENSLER: Please.", "start": 3629.84, "duration": 1.015}, {"text": "AUDIENCE: Yeah.", "start": 3630.855, "duration": 0.915}, {"text": "Hi.", "start": 3631.77, "duration": 0.85}, {"text": "Just want to add one point.", "start": 3632.62, "duration": 2.13}, {"text": "I think the social platform\nbase is really important,", "start": 3634.75, "duration": 3.37}, {"text": "but another thing that\nAlipay is so successful", "start": 3638.12, "duration": 3.41}, {"text": "because it's working\nclosely with the government.", "start": 3641.53, "duration": 2.73}, {"text": "For example, right now in China,\nwe can use a QR code in Alipay", "start": 3644.26, "duration": 5.91}, {"text": "when we try to get\non the shuttle bus", "start": 3650.17, "duration": 3.74}, {"text": "or we want to get a phone.", "start": 3653.91, "duration": 2.08}, {"text": "We can use the Alipay\nto pay that bill.", "start": 3655.99, "duration": 2.7}, {"text": "So actually, the government is\nencouraging all of the citizens", "start": 3658.69, "duration": 3.78}, {"text": "to use this Alipay\nand WeChat Pay.", "start": 3662.47, "duration": 3.288}, {"text": "GARY GENSLER: Yeah.", "start": 3665.758, "duration": 0.792}, {"text": "So there's incredible\ncollaboration,", "start": 3666.55, "duration": 3.18}, {"text": "what you're talking\nabout, between government", "start": 3669.73, "duration": 3.72}, {"text": "and these payments systems.", "start": 3673.45, "duration": 2.61}, {"text": "And we've seen this\nin India as well.", "start": 3676.06, "duration": 2.08}, {"text": "India really\nencouraged the uptake.", "start": 3678.14, "duration": 2.9}, {"text": "And I could have put various\nstatistics in for India.", "start": 3681.04, "duration": 3.66}, {"text": "They're a couple or\nfew years behind.", "start": 3684.7, "duration": 1.89}, {"text": "They're not as robust\nand developed in India.", "start": 3686.59, "duration": 4.86}, {"text": "But this encouragement by the\nofficial sector or the banking", "start": 3691.45, "duration": 4.56}, {"text": "sector--", "start": 3696.01, "duration": 0.66}, {"text": "sometimes in other countries,\nit can be by the banking sector.", "start": 3696.67, "duration": 3.21}, {"text": "But what's interesting in China,\nand we'll close out on this,", "start": 3699.88, "duration": 3.45}, {"text": "is now the Chinese\ngovernment is offering", "start": 3703.33, "duration": 3.97}, {"text": "what one might say is a\ncomplement or a competitor", "start": 3707.3, "duration": 3.47}, {"text": "to WeChat and Alipay through\nthe Chinese digital currency", "start": 3710.77, "duration": 3.96}, {"text": "electronic payment\nproject or DCEP.", "start": 3714.73, "duration": 2.97}, {"text": "And so they've facilitated the\nramp up of Alipay and WeChat", "start": 3717.7, "duration": 4.53}, {"text": "Pay, but now they're going to\nhave an alternative as well.", "start": 3722.23, "duration": 5.05}, {"text": "So it's very interesting.", "start": 3727.28, "duration": 1.22}, {"text": "And I think in part,\nthis is to facilitate", "start": 3728.5, "duration": 2.73}, {"text": "the commercial banks were\nlosing a significant market", "start": 3731.23, "duration": 3.33}, {"text": "share to Alipay and WeChat Pay,\nthat the Chinese government", "start": 3734.56, "duration": 3.51}, {"text": "may well have been encouraged\nto build their own--", "start": 3738.07, "duration": 4.38}, {"text": "they call it the central\nbank digital currency--", "start": 3742.45, "duration": 2.4}, {"text": "but their own wallet\nsystem, digital wallet,", "start": 3744.85, "duration": 4.26}, {"text": "digital yuan that will look\na lot like Alipay and WeChat", "start": 3749.11, "duration": 7.14}, {"text": "wallets.", "start": 3756.25, "duration": 0.81}, {"text": "And in fact, this is all\nbeing rolled out in 2020.", "start": 3757.06, "duration": 3.69}, {"text": "But in fact, the\ninitial pronouncements", "start": 3760.75, "duration": 3.81}, {"text": "say that it must be\naccepted, so just", "start": 3764.56, "duration": 3.81}, {"text": "as we have had multiple\ncenturies of laws that", "start": 3768.37, "duration": 3.6}, {"text": "are called legal tender laws.", "start": 3771.97, "duration": 1.83}, {"text": "And the legal tender\nlaws go all the way", "start": 3773.8, "duration": 2.79}, {"text": "back to Genghis\nKhan in China, where", "start": 3776.59, "duration": 3.45}, {"text": "under the coercive\npower of the state,", "start": 3780.04, "duration": 3.31}, {"text": "you must accept in those\ndays the paper bark", "start": 3783.35, "duration": 3.71}, {"text": "currency of Genghis\nKhan, or in the US,", "start": 3787.06, "duration": 3.0}, {"text": "you must accept the US\ndollar for all debts", "start": 3790.06, "duration": 3.01}, {"text": "public and private.", "start": 3793.07, "duration": 1.37}, {"text": "Those are called\nlegal tender laws.", "start": 3794.44, "duration": 1.92}, {"text": "Something similar is\nhappening right now in China", "start": 3796.36, "duration": 2.61}, {"text": "that this DCEP will\nhave to be accepted,", "start": 3798.97, "duration": 3.51}, {"text": "at first in certain cities.", "start": 3802.48, "duration": 1.57}, {"text": "They're going to start,\nI think, in two cities,", "start": 3804.05, "duration": 2.828}, {"text": "and then they're\ngoing to roll it out", "start": 3806.878, "duration": 1.542}, {"text": "over time in other places.", "start": 3808.42, "duration": 3.46}, {"text": "So now let's look\nhere in the US.", "start": 3811.88, "duration": 2.39}, {"text": "And I picked\nFacebook because they", "start": 3814.27, "duration": 2.4}, {"text": "haven't been as successful.", "start": 3816.67, "duration": 2.04}, {"text": "This remarkable platform,\nFacebook is so ubiquitous,", "start": 3818.71, "duration": 6.06}, {"text": "over 2 billion members\naround the globe.", "start": 3824.77, "duration": 2.7}, {"text": "They've tried multiple\ntimes to get into payments", "start": 3827.47, "duration": 2.66}, {"text": "starting 11 years ago.", "start": 3830.13, "duration": 2.5}, {"text": "Virtual currency\nin 15 currencies", "start": 3832.63, "duration": 2.22}, {"text": "terminated in four\nyears, Facebook credit.", "start": 3834.85, "duration": 3.48}, {"text": "They came about in 2015\nFacebook Messenger.", "start": 3838.33, "duration": 3.96}, {"text": "They started in the\nUS, UK, and France.", "start": 3842.29, "duration": 2.49}, {"text": "By 2019, they rolled out\nof France and the UK.", "start": 3844.78, "duration": 4.45}, {"text": "They, in India, had a pilot\nthat for the longest time", "start": 3849.23, "duration": 4.17}, {"text": "was in pilot\npurgatory, in a sense.", "start": 3853.4, "duration": 6.3}, {"text": "Facebook could not\nget the approval", "start": 3859.7, "duration": 1.86}, {"text": "of the Indian government to go\nbeyond one million accounts.", "start": 3861.56, "duration": 2.94}, {"text": "They only recently in the early\nspring of 2020, late winter,", "start": 3864.5, "duration": 5.55}, {"text": "got approval that they\ncould move up to 10 million", "start": 3870.05, "duration": 2.73}, {"text": "and so forth.", "start": 3872.78, "duration": 1.6}, {"text": "But it's pending further\ndata standardization,", "start": 3874.38, "duration": 4.79}, {"text": "and it's conditional on\ndata standardization.", "start": 3879.17, "duration": 3.51}, {"text": "And then last November,\nthey announced Facebook Pay.", "start": 3882.68, "duration": 3.06}, {"text": "Now, that puts aside\nFacebook Libra.", "start": 3885.74, "duration": 2.43}, {"text": "I'm just saying their\nefforts to do Facebook Pay,", "start": 3888.17, "duration": 3.57}, {"text": "bringing together\nFacebook Messenger,", "start": 3891.74, "duration": 2.34}, {"text": "Instagram, WhatsApp\nis their new effort.", "start": 3894.08, "duration": 5.0}, {"text": "You can decide whether you\nthink they'll be successful.", "start": 3899.08, "duration": 2.44}, {"text": "But it's interesting that\nin some circumstances,", "start": 3901.52, "duration": 2.78}, {"text": "Facebook has been very\nsuccessful, but not so much", "start": 3904.3, "duration": 2.64}, {"text": "in the payment space.", "start": 3906.94, "duration": 1.2}, {"text": "And even Google Wallet and\nGoogle Pay has more adoption,", "start": 3908.14, "duration": 5.04}, {"text": "and Apple Pay has more adoption\nthan we've seen in Facebook,", "start": 3913.18, "duration": 3.96}, {"text": "as I understand it.", "start": 3917.14, "duration": 1.42}, {"text": "It's hard to get\nall the statistics.", "start": 3918.56, "duration": 3.0}, {"text": "So it gives you a little bit\nof a sense of these challenges.", "start": 3921.56, "duration": 3.98}, {"text": "What's the landscape?", "start": 3925.54, "duration": 1.95}, {"text": "Going to do it a little\nquickly, but this", "start": 3927.49, "duration": 2.23}, {"text": "is to give you that landscape.", "start": 3929.72, "duration": 1.25}, {"text": "First, commercial banks and\nthe bank-owned networks.", "start": 3930.97, "duration": 3.69}, {"text": "I put here thousands of banks.", "start": 3934.66, "duration": 2.31}, {"text": "They've been around since 1784.", "start": 3936.97, "duration": 1.8}, {"text": "I like taking 1784\nbecause that's", "start": 3938.77, "duration": 1.89}, {"text": "the Bank of New York here in the\nUS, Alexander Hamilton's bank.", "start": 3940.66, "duration": 4.23}, {"text": "But the clearinghouse\nliterally has been around", "start": 3944.89, "duration": 2.4}, {"text": "since the 1850s.", "start": 3947.29, "duration": 1.53}, {"text": "It was a place where people\ntook physical checks,", "start": 3948.82, "duration": 3.06}, {"text": "negotiable orders\nof withdraw, and had", "start": 3951.88, "duration": 1.98}, {"text": "to take them into a\nwarehouse and clear them.", "start": 3953.86, "duration": 3.43}, {"text": "But even UnionPay\nin China, which", "start": 3957.29, "duration": 2.57}, {"text": "was formed amongst\n85 banks initially--", "start": 3959.86, "duration": 3.15}, {"text": "and some say maybe the\nPeople's Bank of China", "start": 3963.01, "duration": 2.7}, {"text": "owns something of it, too--\nbut UnionPay, these bank", "start": 3965.71, "duration": 3.75}, {"text": "consortium.", "start": 3969.46, "duration": 2.66}, {"text": "Next in this architecture\nof the payment landscape,", "start": 3972.12, "duration": 3.87}, {"text": "the card companies.", "start": 3975.99, "duration": 1.47}, {"text": "I would note that\nVisa was a consortium.", "start": 3977.46, "duration": 2.59}, {"text": "Bank of America was\na California bank.", "start": 3980.05, "duration": 2.33}, {"text": "It was not a national\nbank at the time.", "start": 3982.38, "duration": 2.43}, {"text": "And Bank of America wanted to\noffer its California credit", "start": 3984.81, "duration": 3.42}, {"text": "card across the country\nand formed a consortium.", "start": 3988.23, "duration": 3.48}, {"text": "It later became an\nindependent company.", "start": 3991.71, "duration": 2.31}, {"text": "It later went public.", "start": 3994.02, "duration": 1.68}, {"text": "And it's got a $373 billion\nmarket value as of last Friday.", "start": 3995.7, "duration": 5.62}, {"text": "Now, we sometimes talk about the\nBig Tech firms, the big four,", "start": 4001.32, "duration": 4.55}, {"text": "Microsoft, and Google,\nand Amazon, and Apple.", "start": 4005.87, "duration": 3.39}, {"text": "They all have market\nvalues above this.", "start": 4009.26, "duration": 2.34}, {"text": "But Visa is one of the\n10 highest market cap", "start": 4011.6, "duration": 3.33}, {"text": "companies in the country,\nmaybe in the world.", "start": 4014.93, "duration": 4.54}, {"text": "And then, of course, Mastercard\nand so forth, Discover", "start": 4019.47, "duration": 2.66}, {"text": "and the Dow.", "start": 4022.13, "duration": 0.87}, {"text": "So that's the base\nlayer, but then there's", "start": 4023.0, "duration": 2.85}, {"text": "something that you and I\ndon't think a lot about,", "start": 4025.85, "duration": 2.64}, {"text": "is payments service providers.", "start": 4028.49, "duration": 2.55}, {"text": "And these companies have gone\nthrough a significant wave", "start": 4031.04, "duration": 3.72}, {"text": "of consolidation.", "start": 4034.76, "duration": 1.41}, {"text": "These were data\ncompanies basically,", "start": 4036.17, "duration": 2.1}, {"text": "expounded around 20 years ago.", "start": 4038.27, "duration": 2.43}, {"text": "Fiserv is an agglomeration\nof three or four", "start": 4040.7, "duration": 3.33}, {"text": "different companies\nthat have come together", "start": 4044.03, "duration": 2.07}, {"text": "over the last few years.", "start": 4046.1, "duration": 1.23}, {"text": "But these dominant\ncompanies here in the US", "start": 4047.33, "duration": 4.23}, {"text": "are the backbones of\nthe payment network", "start": 4051.56, "duration": 2.94}, {"text": "right in the middle of\nthat earlier chart that we", "start": 4054.5, "duration": 2.61}, {"text": "talked about, $45 billion to\n$80 billion market value each.", "start": 4057.11, "duration": 4.65}, {"text": "And now we get to the\nstartups starting with PayPal", "start": 4061.76, "duration": 6.41}, {"text": "at $124 billion of value, and\nSquare, and then some companies", "start": 4068.17, "duration": 5.57}, {"text": "you might not be\nas familiar with.", "start": 4073.74, "duration": 2.22}, {"text": "But each one of these companies\nfounded usually in the 20-year", "start": 4075.96, "duration": 4.42}, {"text": "timeframe--", "start": 4080.38, "duration": 0.5}, {"text": "I'll put Western\nUnion to the side.", "start": 4080.88, "duration": 2.22}, {"text": "Western Union was that company\nthat started in the 1850s.", "start": 4083.1, "duration": 5.52}, {"text": "These are publicly\ntraded companies.", "start": 4088.62, "duration": 3.97}, {"text": "You can look at\ntheir financials.", "start": 4092.59, "duration": 1.45}, {"text": "If you were actually going to\ngo and compete in this space,", "start": 4094.04, "duration": 3.46}, {"text": "I'd largely recommend you've\ngot to pull these financials,", "start": 4097.5, "duration": 2.58}, {"text": "read their public statements,\nsee how they make their money.", "start": 4100.08, "duration": 3.87}, {"text": "But then there's the\nprivate companies.", "start": 4103.95, "duration": 2.369}, {"text": "And all I could do to\nvalue these companies that", "start": 4106.319, "duration": 2.531}, {"text": "go to Forbes and Crunchbase\nand some other sources to say,", "start": 4108.85, "duration": 3.799}, {"text": "what was their\nlast funding round?", "start": 4112.649, "duration": 2.79}, {"text": "Stripe has not gone public yet.", "start": 4115.439, "duration": 2.63}, {"text": "Paytm in India has\nnot gone public yet,", "start": 4118.069, "duration": 3.37}, {"text": "but these are their\nlast funding rounds.", "start": 4121.439, "duration": 1.771}, {"text": "Plaid was purchased for\n$5.3 billion by Visa.", "start": 4123.21, "duration": 6.67}, {"text": "But it gives you that\nsense, putting aside", "start": 4129.88, "duration": 3.24}, {"text": "whether these values\nwill persist or not.", "start": 4133.12, "duration": 2.67}, {"text": "And there's hundreds,\nthousands of other companies", "start": 4135.79, "duration": 2.73}, {"text": "in this space competing.", "start": 4138.52, "duration": 3.9}, {"text": "As I said, there's a\nlot of consolidation.", "start": 4142.42, "duration": 3.059}, {"text": "And one of the consolidations\nis around payment service", "start": 4145.479, "duration": 3.481}, {"text": "providers.", "start": 4148.96, "duration": 0.87}, {"text": "Just in the last 18\nmonths, four big mergers,", "start": 4149.83, "duration": 3.48}, {"text": "one in Europe, three\nin the US, basically", "start": 4153.31, "duration": 3.509}, {"text": "consolidation in the\nmiddle of this technology.", "start": 4156.819, "duration": 4.351}, {"text": "First Data, which was one of\nthe biggest companies, that", "start": 4161.17, "duration": 3.21}, {"text": "basically was on\nthe merchant side,", "start": 4164.38, "duration": 3.45}, {"text": "helping merchants with\ntheir point of sale,", "start": 4167.83, "duration": 2.01}, {"text": "Worldpay that does this annual\nreport that I talked about,", "start": 4169.84, "duration": 4.4}, {"text": "and Total Systems Services all\nbought in the last 15 months.", "start": 4174.24, "duration": 4.239}, {"text": "And then in Europe, Worldline\nbought Ingenico, which", "start": 4178.479, "duration": 4.681}, {"text": "was like a cross-Europe merger.", "start": 4183.16, "duration": 3.21}, {"text": "But we're seeing\na lot of mergers", "start": 4186.37, "duration": 1.44}, {"text": "also in the data\naggregator side.", "start": 4187.81, "duration": 2.549}, {"text": "Visa bought Plaid,\nas we talked about.", "start": 4190.359, "duration": 1.771}, {"text": "And SoFi recently announced for\nover $1 billion buying Galileo.", "start": 4192.13, "duration": 4.17}, {"text": "Galileo is a smaller\ncompetitor of Plaid", "start": 4196.3, "duration": 3.05}, {"text": "that is in this API\ndata aggregators", "start": 4199.35, "duration": 3.54}, {"text": "space, a really important\nspace in payments.", "start": 4202.89, "duration": 3.31}, {"text": "SoFi, which we'll talk about\nin our next couple of classes,", "start": 4206.2, "duration": 3.69}, {"text": "started as a credit provider,\nnot in the payment side.", "start": 4209.89, "duration": 5.92}, {"text": "But here it's interesting that\nSoFi is going back and saying,", "start": 4215.81, "duration": 3.29}, {"text": "we want to get to\nthat payment side.", "start": 4219.1, "duration": 1.83}, {"text": "We want to acquire\nGalileo and the API side.", "start": 4220.93, "duration": 5.69}, {"text": "And so a little talk, and we've\nonly got a few minutes left.", "start": 4226.62, "duration": 3.54}, {"text": "We already talked\nabout crypto projects,", "start": 4230.16, "duration": 2.26}, {"text": "but the crypto land is here.", "start": 4232.42, "duration": 2.72}, {"text": "And they're saying\nmaybe a digital token", "start": 4235.14, "duration": 4.77}, {"text": "backed by US dollars\nor backed by Euro", "start": 4239.91, "duration": 2.8}, {"text": "or yen would be the way to\naddress these pain points.", "start": 4242.71, "duration": 4.46}, {"text": "Some are retail projects.", "start": 4247.17, "duration": 2.07}, {"text": "Mostly tether and others\non the retail side", "start": 4249.24, "duration": 2.52}, {"text": "are about cryptocurrency\nexchanges.", "start": 4251.76, "duration": 2.52}, {"text": "But the wholesale\nprojects are interesting.", "start": 4254.28, "duration": 2.46}, {"text": "14 large banks\nhave come together", "start": 4256.74, "duration": 2.34}, {"text": "and formed this\nthing called Fnality", "start": 4259.08, "duration": 2.31}, {"text": "without an I. It's F-nality.", "start": 4261.39, "duration": 3.03}, {"text": "JP Morgan has said\nJP Morgan Coin.", "start": 4264.42, "duration": 2.88}, {"text": "These are trying to use digital\ntokens representing Fiat money", "start": 4267.3, "duration": 6.25}, {"text": "to smooth out pain points.", "start": 4273.55, "duration": 2.07}, {"text": "And then the messaging\ncompanies, Telegram,", "start": 4275.62, "duration": 2.28}, {"text": "the world's largest secure or\nencrypted messaging company", "start": 4277.9, "duration": 4.26}, {"text": "with 400 million\nmembers or customers,", "start": 4282.16, "duration": 3.51}, {"text": "they're trying to have a token\ncalled GRAM, even though it's", "start": 4285.67, "duration": 2.82}, {"text": "held up in the\nsecurities law case", "start": 4288.49, "duration": 2.16}, {"text": "that they have with the\nSecurities and Exchange", "start": 4290.65, "duration": 2.04}, {"text": "Commission here in the US.", "start": 4292.69, "duration": 2.22}, {"text": "And that sets the stage--", "start": 4294.91, "duration": 1.51}, {"text": "I'm going to skip over--", "start": 4296.42, "duration": 1.78}, {"text": "that Bitcoin and all of these\npayment tokens are out there", "start": 4298.2, "duration": 4.03}, {"text": "and talk about the goals\nthey're trying to do.", "start": 4302.23, "duration": 2.13}, {"text": "The goals they are trying\nto do are the same things--", "start": 4304.36, "duration": 3.45}, {"text": "addressing pain points,\nextending settlement", "start": 4307.81, "duration": 2.43}, {"text": "to 24 hours a day, 7 days\na week, and lowering costs.", "start": 4310.24, "duration": 4.65}, {"text": "That's why JP Morgan\nhas JP Morgan Coin.", "start": 4314.89, "duration": 4.11}, {"text": "It might be a\nlittle bit of hype,", "start": 4319.0, "duration": 2.1}, {"text": "but there's some\nreality, too, that they", "start": 4321.1, "duration": 1.83}, {"text": "think that between their project\nand this competitive project", "start": 4322.93, "duration": 4.32}, {"text": "Fnality at the\nwholesale payment space,", "start": 4327.25, "duration": 2.37}, {"text": "they can lower cost in\nthe cross-border space.", "start": 4329.62, "duration": 4.65}, {"text": "So Facebook comes along, and\nFacebook says, well, maybe we", "start": 4334.27, "duration": 3.12}, {"text": "can do it.", "start": 4337.39, "duration": 1.44}, {"text": "Maybe we can do it with\na worldwide currency.", "start": 4338.83, "duration": 3.21}, {"text": "They announced it was--", "start": 4342.04, "duration": 1.96}, {"text": "it didn't lack ambition.", "start": 4344.0, "duration": 1.715}, {"text": "Mark Zuckerberg and Facebook\nannounced a new global currency", "start": 4345.715, "duration": 5.145}, {"text": "to meet the needs of\nbillions of people.", "start": 4350.86, "duration": 2.22}, {"text": "They talked about\nfinancial inclusion.", "start": 4353.08, "duration": 2.19}, {"text": "They talked about\ncross-border pain points.", "start": 4355.27, "duration": 2.64}, {"text": "And they said, this is\nthe wave of the future.", "start": 4357.91, "duration": 3.33}, {"text": "It's run into a lot of central\nbank concerns around the globe.", "start": 4361.24, "duration": 4.12}, {"text": "It's run into\nsignificant public sector", "start": 4365.36, "duration": 3.23}, {"text": "concerns around the globe.", "start": 4368.59, "duration": 2.17}, {"text": "It's still uncertain\nwhether it will take off,", "start": 4370.76, "duration": 3.14}, {"text": "but it's a significant\nfeature of this payment space", "start": 4373.9, "duration": 3.03}, {"text": "that one needs to\nunderstand, even if it's just", "start": 4376.93, "duration": 3.36}, {"text": "a catalyst for change.", "start": 4380.29, "duration": 1.77}, {"text": "Both China and the US reacted\nquickly with the FedNow project", "start": 4382.06, "duration": 4.44}, {"text": "here in the US and the\ncentral bank digital currency", "start": 4386.5, "duration": 3.99}, {"text": "project in China.", "start": 4390.49, "duration": 2.25}, {"text": "So I'm going to close on\njust a little chart that", "start": 4392.74, "duration": 2.31}, {"text": "shows Libra versus central\nbank digital currency", "start": 4395.05, "duration": 2.955}, {"text": "and just say something\nabout China's project.", "start": 4398.005, "duration": 3.225}, {"text": "China's project, not yet\nlived, digital currency", "start": 4401.23, "duration": 4.08}, {"text": "electronic payment\nprogram, the issuer", "start": 4405.31, "duration": 3.6}, {"text": "is the People's Bank of China.", "start": 4408.91, "duration": 1.74}, {"text": "And this is a really\nimportant question that", "start": 4410.65, "duration": 3.15}, {"text": "is on a lot of people's mind.", "start": 4413.8, "duration": 2.61}, {"text": "If a central bank issues a\ndigital representation of money", "start": 4416.41, "duration": 4.11}, {"text": "directly, what's the role\nof the commercial banks?", "start": 4420.52, "duration": 6.1}, {"text": "Commercial banks\nin most countries", "start": 4426.62, "duration": 1.86}, {"text": "are the issuer of digital money.", "start": 4428.48, "duration": 2.82}, {"text": "I know we think about central\nbanks in the 180 countries", "start": 4431.3, "duration": 3.18}, {"text": "that have money, and\nthey're really important.", "start": 4434.48, "duration": 2.85}, {"text": "But it's commercial banks\nthat keep those ledgers.", "start": 4437.33, "duration": 3.03}, {"text": "The commercial banks with some\nbacking of their governments,", "start": 4440.36, "duration": 3.72}, {"text": "either implicit or explicit\nwith deposit insurance,", "start": 4444.08, "duration": 3.66}, {"text": "you and I have a liability to\nour banks, to Bank America,", "start": 4447.74, "duration": 4.2}, {"text": "to Barclays, to\nsome bank in Asia.", "start": 4451.94, "duration": 3.71}, {"text": "The People's Bank\nof China is saying,", "start": 4455.65, "duration": 1.9}, {"text": "no, we will issue this\ndirectly, but we'll", "start": 4457.55, "duration": 3.18}, {"text": "have the commercial\nbanks involved.", "start": 4460.73, "duration": 3.15}, {"text": "And the commercial banks,\nyou'll get your digital wallet", "start": 4463.88, "duration": 2.7}, {"text": "from the commercial banks.", "start": 4466.58, "duration": 1.2}, {"text": "There were announcements\nas of early April 2020", "start": 4467.78, "duration": 3.27}, {"text": "that update us, but we don't\nyet have the full picture.", "start": 4471.05, "duration": 5.28}, {"text": "It looks like it's basically a\ncentralized private network run", "start": 4476.33, "duration": 3.69}, {"text": "by the PBOC.", "start": 4480.02, "duration": 1.65}, {"text": "It does look like\nAlipay and WeChat Pay", "start": 4481.67, "duration": 2.88}, {"text": "will have to use this system.", "start": 4484.55, "duration": 2.29}, {"text": "So some question is, how\ndifferent will it really be?", "start": 4486.84, "duration": 3.89}, {"text": "It looks like by government Fiat\nrolled out by city and region", "start": 4490.73, "duration": 5.34}, {"text": "that merchants will\nhave to accept DCEP.", "start": 4496.07, "duration": 3.18}, {"text": "So the QR system\non those buses will", "start": 4499.25, "duration": 2.37}, {"text": "have to have DCEP,\nAlipay, and WeChat Pay.", "start": 4501.62, "duration": 4.62}, {"text": "Alipay has taken out\na bunch of patents", "start": 4506.24, "duration": 2.46}, {"text": "already on how to\ninterface with DCEP.", "start": 4508.7, "duration": 3.51}, {"text": "So it's a work in\nprogress, but it's", "start": 4512.21, "duration": 2.16}, {"text": "an important feature of this.", "start": 4514.37, "duration": 1.61}, {"text": "And if you're thinking\nabout payments,", "start": 4515.98, "duration": 2.65}, {"text": "this is really important.", "start": 4518.63, "duration": 1.08}, {"text": "And what's fascinating is\ncentral banks around the globe", "start": 4519.71, "duration": 2.73}, {"text": "are then looking to\nsee what China's done.", "start": 4522.44, "duration": 2.93}, {"text": "Sweden was already looking at an\nelectronic digital central bank", "start": 4525.37, "duration": 5.35}, {"text": "currency, the E-krona.", "start": 4530.72, "duration": 2.58}, {"text": "And they were at the forefront.", "start": 4533.3, "duration": 2.22}, {"text": "But now you can go central\nbank around central bank.", "start": 4535.52, "duration": 2.67}, {"text": "France has made announcements.", "start": 4538.19, "duration": 1.59}, {"text": "The United Kingdom has\nmade announcements in 2020,", "start": 4539.78, "duration": 3.24}, {"text": "all in this milieu of, how\ndo we address pain points?", "start": 4543.02, "duration": 5.16}, {"text": "Do we as a central bank have a\nresponsibility to our citizens", "start": 4548.18, "duration": 3.21}, {"text": "to continue to offer a digital\ncurrency when the paper", "start": 4551.39, "duration": 3.9}, {"text": "currency is going away?", "start": 4555.29, "duration": 1.77}, {"text": "And important public\npolicy questions of,", "start": 4557.06, "duration": 2.07}, {"text": "what does this do?", "start": 4559.13, "duration": 0.96}, {"text": "Does it destabilize\ncommercial banks?", "start": 4560.09, "duration": 2.86}, {"text": "So I think that's\na bit of a wrap.", "start": 4562.95, "duration": 4.28}]
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+[{"text": "YUFEI ZHAO: Last\ntime, we started", "start": 18.955, "duration": 1.375}, {"text": "discussing the extremal\nproblem for bipartide graphs.", "start": 20.33, "duration": 4.62}, {"text": "And in particular, we saw\nthe Kovari-Sos-Turan theorem,", "start": 24.95, "duration": 4.02}, {"text": "which tells us that if you\nforbid your graph from having", "start": 28.97, "duration": 3.84}, {"text": "a complete bipartide\ngraph, Kst, then", "start": 32.81, "duration": 3.51}, {"text": "you have this upper bound on the\nnumber of edges in your graph.", "start": 36.32, "duration": 6.35}, {"text": "So we gave a proof.", "start": 42.67, "duration": 0.81}, {"text": "It was fairly short, used\nthe double counting argument,", "start": 43.48, "duration": 4.2}, {"text": "and it give you this bound.", "start": 47.68, "duration": 2.07}, {"text": "And the next question is\nhow tight is this bound?", "start": 49.75, "duration": 3.3}, {"text": "Is there a lower bound\nthat is off by, let's say,", "start": 53.05, "duration": 4.71}, {"text": "at most a constant factor?", "start": 57.76, "duration": 2.37}, {"text": "And that's a major open problem.", "start": 60.13, "duration": 2.13}, {"text": "It's a conjecture that\nthis bound is tight", "start": 62.26, "duration": 5.42}, {"text": "up to constant factors.", "start": 67.68, "duration": 2.15}, {"text": "But that conjecture is known\nfor only a very small number", "start": 69.83, "duration": 3.13}, {"text": "of graphs.", "start": 72.96, "duration": 1.05}, {"text": "And we saw a couple\nof examples last time.", "start": 74.01, "duration": 3.58}, {"text": "So last time we saw\nconstruction that", "start": 77.59, "duration": 2.81}, {"text": "shows that for S equals\nto 2, this bound is tight.", "start": 80.4, "duration": 7.65}, {"text": "So the extremal number for k\nthrough 2 is on the order of n", "start": 91.67, "duration": 4.44}, {"text": "to the 3/2.", "start": 96.11, "duration": 1.56}, {"text": "So this theta means I'm\nhiding constant factors.", "start": 97.67, "duration": 4.63}, {"text": "And our construction\nused this polarity graph,", "start": 102.3, "duration": 2.79}, {"text": "which is essentially\nthe point line incidence", "start": 105.09, "duration": 2.31}, {"text": "graph of a projective plane.", "start": 107.4, "duration": 2.19}, {"text": "And a basic algebraic or\ngeometric fact, if you will,", "start": 109.59, "duration": 4.11}, {"text": "that two lines intersecting\nat most one point.", "start": 113.7, "duration": 4.01}, {"text": "We also sketched a\nconstruction that", "start": 117.71, "duration": 5.3}, {"text": "showed that for S equals to\n3, this bound is also tight.", "start": 123.01, "duration": 5.57}, {"text": "And this construction\nhere involved", "start": 131.37, "duration": 1.69}, {"text": "using spheres, again, in some\nspace over a finite field.", "start": 133.06, "duration": 8.01}, {"text": "So both these constructions\nare in some sense", "start": 141.07, "duration": 1.89}, {"text": "algebraic geometric.", "start": 142.96, "duration": 1.53}, {"text": "And you can ask, is\nthere a way to extend", "start": 144.49, "duration": 2.1}, {"text": "these ideas to construct other\nexamples of Kst free graphs", "start": 146.59, "duration": 4.95}, {"text": "with the right number of\nedges using some ingredients", "start": 151.54, "duration": 4.5}, {"text": "from algebraic geometry?", "start": 156.04, "duration": 1.83}, {"text": "And today, I want to show\nyou two different ways", "start": 157.87, "duration": 2.16}, {"text": "of doing that.", "start": 160.03, "duration": 0.63}, {"text": "So the state of the art,\nwhich I mentioned last time,", "start": 164.87, "duration": 6.35}, {"text": "let me remind you what is\nknown about constructions", "start": 171.22, "duration": 4.43}, {"text": "that achieve the right\nexponent up there.", "start": 175.65, "duration": 4.59}, {"text": "So in a series of two\npapers by [INAUDIBLE]", "start": 180.24, "duration": 7.32}, {"text": "it is shown that if\nthe constants t and s,", "start": 187.56, "duration": 3.9}, {"text": "such that t is large\nenough compared to s,", "start": 191.46, "duration": 3.84}, {"text": "in particular t is bigger\nthan s minus 1 factorial,", "start": 195.3, "duration": 5.23}, {"text": "then the extremal\nnumber of Kst's is", "start": 200.53, "duration": 6.95}, {"text": "of the order, same\norder, as given", "start": 207.48, "duration": 3.51}, {"text": "in the upper bound of the\nKovari-Sos-Turan theorem.", "start": 210.99, "duration": 3.99}, {"text": "In particular, these range of\nparameters allows you to do", "start": 214.98, "duration": 5.8}, {"text": "(2, 2), (3, 3), which we\nalready know how to do.", "start": 220.78, "duration": 5.88}, {"text": "But the next case is 4, 7.", "start": 226.66, "duration": 2.74}, {"text": "And it is still\nopen how to do 4, 6.", "start": 229.4, "duration": 3.17}, {"text": "So I want to show you\nthis construction.", "start": 238.94, "duration": 1.893}, {"text": "And I will tell you\nexactly what the graph is.", "start": 240.833, "duration": 1.917}, {"text": "I'll give you an\nexplicit description", "start": 242.75, "duration": 2.34}, {"text": "of this graph, which is Kst\nfree and has lots of edges.", "start": 245.09, "duration": 4.29}, {"text": "And as I mentioned earlier, it\nis an algebraic construction.", "start": 251.99, "duration": 3.87}, {"text": "So as before, we\nstart with p prime.", "start": 255.86, "duration": 6.24}, {"text": "And we will take n to be\na p raised to the power s.", "start": 262.1, "duration": 8.58}, {"text": "And let's restrict s to\nbe integer at least 2.", "start": 270.68, "duration": 3.492}, {"text": "And, of course, that's\nsame as last time,", "start": 274.172, "duration": 1.708}, {"text": "if you have other values\nof n, take a prime close", "start": 275.88, "duration": 3.51}, {"text": "to the desired value and\nthen take it from there.", "start": 279.39, "duration": 3.1}, {"text": "To describe the construction,\nlet me remind you,", "start": 285.18, "duration": 4.98}, {"text": "the norm map, if you have a\nfield extension, in this case,", "start": 290.16, "duration": 5.04}, {"text": "specifically I am looking\nat the field extension,", "start": 295.2, "duration": 3.95}, {"text": "this Fp to the s, I can\ndefine a norm map as follows.", "start": 299.15, "duration": 9.55}, {"text": "Sending x to be the product\nof all the conjugates,", "start": 308.7, "duration": 6.36}, {"text": "or the Galois conjugates of\nx, in this field extension.", "start": 315.06, "duration": 4.68}, {"text": "So explicitly written out\nis just that expression,", "start": 319.74, "duration": 3.76}, {"text": "which I can clean and collect\nand write it down like this.", "start": 323.5, "duration": 3.74}, {"text": "So I wrote that the\nimage of this norm map", "start": 332.09, "duration": 1.87}, {"text": "lies in the base field Fp.", "start": 333.96, "duration": 2.35}, {"text": "And that is because--", "start": 336.31, "duration": 0.875}, {"text": "well, one of the many\nreasons why this is the case,", "start": 341.388, "duration": 2.892}, {"text": "is that if you look at--", "start": 344.28, "duration": 3.03}, {"text": "so I'll denote this\nnorm map by N--", "start": 347.31, "duration": 2.43}, {"text": "if you look at N of x,\nit raised to power p,", "start": 349.74, "duration": 8.25}, {"text": "leaves this value unchanged.", "start": 357.99, "duration": 2.43}, {"text": "And the base field\nis the field where it", "start": 360.42, "duration": 4.08}, {"text": "is invariant under power by p.", "start": 364.5, "duration": 2.61}, {"text": "So here's the graph,\nwhich I'll denote the norm", "start": 369.93, "duration": 5.62}, {"text": "graph with parameters p and s.", "start": 375.55, "duration": 4.63}, {"text": "So the norm graph will have\nas vertices just the elements", "start": 380.18, "duration": 10.46}, {"text": "of this field extension.", "start": 390.64, "duration": 11.05}, {"text": "And the edges will be the set\nof all pairs of vertices, not", "start": 401.69, "duration": 12.61}, {"text": "equal, of course, such that a\nnorm of their sum equals to 1.", "start": 414.3, "duration": 5.88}, {"text": "So that's the graph.", "start": 424.547, "duration": 0.833}, {"text": "This is an explicit description\nof what the vertices", "start": 425.38, "duration": 2.532}, {"text": "and what the edges are.", "start": 427.912, "duration": 0.958}, {"text": "So now, we need to verify\na couple of things.", "start": 431.43, "duration": 3.33}, {"text": "One is that this graph has\nthe desired number of edges.", "start": 434.76, "duration": 5.28}, {"text": "It has lots of edges.", "start": 440.04, "duration": 1.94}, {"text": "And two is that this\ngraph is Kst free.", "start": 441.98, "duration": 4.19}, {"text": "So let's do both\nof those things.", "start": 446.17, "duration": 2.81}, {"text": "So the first is let's check it\nhas the right number of edges.", "start": 448.98, "duration": 4.37}, {"text": "So that's a\nrelatively easy task.", "start": 453.35, "duration": 3.42}, {"text": "What we need to do is\nto count for every a", "start": 456.77, "duration": 5.81}, {"text": "how many choices of b are\nthere in this field extension", "start": 462.58, "duration": 5.28}, {"text": "such that a plus b\nhas norm exactly 1?", "start": 467.86, "duration": 5.79}, {"text": "And I claim that that number--", "start": 473.65, "duration": 2.78}, {"text": "well, so here's a\nbasic algebra fact,", "start": 476.43, "duration": 4.68}, {"text": "that the number of elements in\nthis field extension with norm", "start": 481.11, "duration": 6.6}, {"text": "exactly 1 is precisely\np to the s minus 1", "start": 487.71, "duration": 7.41}, {"text": "divided by p to the s.", "start": 495.12, "duration": 2.73}, {"text": "And this is because\nreally we're looking", "start": 503.646, "duration": 3.654}, {"text": "in the multiplicative subgroup.", "start": 507.3, "duration": 3.85}, {"text": "So the multiplicative\ngroup in this Fp to the s.", "start": 511.15, "duration": 5.49}, {"text": "And it has a cyclical--", "start": 516.64, "duration": 1.618}, {"text": "so there's a generator--", "start": 522.162, "duration": 1.968}, {"text": "the order of the cyclic\ngroup is p to the s minus 1.", "start": 524.13, "duration": 7.82}, {"text": "So you're asking,\nhow many elements", "start": 531.95, "duration": 5.98}, {"text": "when raised to this power\nhere ends up at the identity?", "start": 537.93, "duration": 10.427}, {"text": "So that's the answer.", "start": 550.985, "duration": 0.875}, {"text": "So that's one aspect.", "start": 555.97, "duration": 1.46}, {"text": "And so as a result, every\nvertex is adjacent to, well,", "start": 557.43, "duration": 9.8}, {"text": "how many vertices?", "start": 567.23, "duration": 2.1}, {"text": "For every given a I\nneed to solve for b.", "start": 569.33, "duration": 3.8}, {"text": "And basically, this\nmany solutions,", "start": 573.13, "duration": 2.14}, {"text": "I have to be just\nslightly careful because I", "start": 575.27, "duration": 2.73}, {"text": "don't want loops in my graph.", "start": 578.0, "duration": 2.43}, {"text": "So I may need to subtract 1.", "start": 580.43, "duration": 1.86}, {"text": "So it's adjacent to at least\nthis number up here minus 1", "start": 582.29, "duration": 7.8}, {"text": "to account for possible\nloops, which is pretty large,", "start": 590.09, "duration": 10.65}, {"text": "p to the s minus 1,\nwhich in other words", "start": 600.74, "duration": 4.33}, {"text": "is n raised to 1 minus 1\nover s, that many vertices,", "start": 605.07, "duration": 7.07}, {"text": "and you see that this gives\nyou the right number of edges.", "start": 612.14, "duration": 2.7}, {"text": "So this is a graph\nwith lots of edges.", "start": 628.62, "duration": 2.2}, {"text": "So that part wasn't so hard.", "start": 630.82, "duration": 2.35}, {"text": "The next part,\nit's much trickier,", "start": 633.17, "duration": 2.87}, {"text": "which is we want to check\nthat this graph has no Kst's.", "start": 636.04, "duration": 5.02}, {"text": "So previously in our\nalgebraic construction,", "start": 641.06, "duration": 2.04}, {"text": "we used some geometric\nfacts, such as no two lines", "start": 643.1, "duration": 3.42}, {"text": "intersect in more than one point\nto show that there's no k to 2", "start": 646.52, "duration": 4.71}, {"text": "in the polarity graph.", "start": 651.23, "duration": 1.89}, {"text": "So there's going to be\nsomething like that here.", "start": 653.12, "duration": 2.43}, {"text": "So the claim is that this\nconstruction, this norm graph,", "start": 655.55, "duration": 9.86}, {"text": "is Ks, s factorial plus 1 free.", "start": 665.41, "duration": 7.47}, {"text": "So it's not quite\nthe bound I claimed.", "start": 675.78, "duration": 2.11}, {"text": "So it's a little bit weaker.", "start": 677.89, "duration": 1.29}, {"text": "But it is in the spirit\nof what I am claiming,", "start": 679.18, "duration": 2.25}, {"text": "namely that for t large\nenough, this graph is Kst free.", "start": 681.43, "duration": 5.63}, {"text": "So for t a large enough\ncomes constant here", "start": 687.06, "duration": 2.51}, {"text": "will show s factorial plus 1.", "start": 689.57, "duration": 3.9}, {"text": "And as a result, it would follow\nthat the extremal number 4s", "start": 693.47, "duration": 7.88}, {"text": "sub s factorial plus\n1 is at least 1/2", "start": 701.35, "duration": 12.71}, {"text": "minus little 1 of the constant--", "start": 714.06, "duration": 2.22}, {"text": "I don't already worry\nabout that much,", "start": 716.28, "duration": 2.73}, {"text": "but it's on the order of\nn to the 2 minus 1 over s.", "start": 719.01, "duration": 4.558}, {"text": "OK, everyone with me?", "start": 723.568, "duration": 3.292}, {"text": "So we need to verify this\ngraph here has no Kst.", "start": 726.86, "duration": 3.63}, {"text": "Yes, question?", "start": 730.49, "duration": 0.921}, {"text": "AUDIENCE: Should that t be an s?", "start": 731.411, "duration": 3.227}, {"text": "YUFEI ZHAO: Yes,\nthat should be an s.", "start": 734.638, "duration": 1.542}, {"text": "Thank you.", "start": 736.18, "duration": 0.5}, {"text": "Any more questions?", "start": 741.48, "duration": 1.672}, {"text": "AUDIENCE: Should that\nbe s minus 1 factorial?", "start": 743.152, "duration": 3.808}, {"text": "YUFEI ZHAO: So we\nwill show later", "start": 746.96, "duration": 2.1}, {"text": "on a better result using\ns minus 1 factorial,", "start": 749.06, "duration": 3.39}, {"text": "but for now I'll show you the\nslightly weaker result, which", "start": 752.45, "duration": 2.97}, {"text": "is still in the same spirit.", "start": 755.42, "duration": 1.39}, {"text": "Yep.", "start": 756.81, "duration": 0.5}, {"text": "AUDIENCE: Is the stronger\nresult using the same graph?", "start": 757.31, "duration": 2.643}, {"text": "YUFEI ZHAO: We'll change\nto a different graph.", "start": 759.953, "duration": 1.917}, {"text": "For the stronger result, we will\nchange to a different graph.", "start": 761.87, "duration": 2.542}, {"text": "OK, so now let's show that\nthis graph here is Kst free.", "start": 770.0, "duration": 5.26}, {"text": "And for that claim, we need to\ninvoke an algebraic fact, which", "start": 775.26, "duration": 3.393}, {"text": "let me write down now.", "start": 778.653, "duration": 0.917}, {"text": "So suppose we have a field f.", "start": 782.77, "duration": 2.98}, {"text": "Any field will work\nwith a finite field.", "start": 790.28, "duration": 3.81}, {"text": "Any field is fine.", "start": 794.09, "duration": 1.2}, {"text": "And I have a bunch of\nelements from the field,", "start": 795.29, "duration": 7.23}, {"text": "such that a sub ij is\ndifferent from a sub", "start": 802.52, "duration": 8.8}, {"text": "rj for all i not the same as r.", "start": 811.32, "duration": 5.8}, {"text": "Then the system of equations--", "start": 820.24, "duration": 2.96}, {"text": "and I'll write down the system.", "start": 827.468, "duration": 1.292}, {"text": "So x minus 1--", "start": 828.76, "duration": 1.69}, {"text": "x1 minus a 1, 1, x2\nminus a 1, 2, and so on.", "start": 830.45, "duration": 9.01}, {"text": "xs minus a1x equals to b1.", "start": 839.46, "duration": 4.826}, {"text": "That's the first equation.", "start": 844.286, "duration": 1.784}, {"text": "Second equation,\nx1 minus a 2, 1.", "start": 846.07, "duration": 3.17}, {"text": "It almost looks like the usual\nsystem of linear equations.", "start": 849.24, "duration": 4.39}, {"text": "But I'm taking products.", "start": 853.63, "duration": 2.16}, {"text": "And so on.", "start": 861.17, "duration": 1.3}, {"text": "So the last one being x1 minus\na s1 x2 minus a s2, dot dot dot,", "start": 862.47, "duration": 12.44}, {"text": "xs minus a ss equals to b sub s.", "start": 874.91, "duration": 5.55}, {"text": "The system has at most s\nfactorial solutions, where", "start": 880.46, "duration": 13.94}, {"text": "I'm working inside this field.", "start": 894.4, "duration": 1.92}, {"text": "So that's the claim.", "start": 899.78, "duration": 1.59}, {"text": "So let me just give you some\nintuition for this claim.", "start": 901.37, "duration": 2.412}, {"text": "Suppose the right side\nvector is 0, all zeroes.", "start": 908.71, "duration": 8.13}, {"text": "Then I claim that\nthis is trivial.", "start": 916.84, "duration": 2.89}, {"text": "So what is the saying?", "start": 919.73, "duration": 1.55}, {"text": "I need to select x1 to be one\nof the a's from the first row", "start": 921.28, "duration": 7.46}, {"text": "and x2 be one of the a's from\nthe second row, and so on.", "start": 928.74, "duration": 3.37}, {"text": "But each column\nof a is distinct.", "start": 932.11, "duration": 2.88}, {"text": "So that's the hypothesis.", "start": 934.99, "duration": 1.68}, {"text": "You have all the a's in the\nfirst column are distinct.", "start": 936.67, "duration": 3.99}, {"text": "So no two of the x's can--", "start": 940.66, "duration": 5.28}, {"text": "so I need to set one\nof the xi's to be one", "start": 949.15, "duration": 4.2}, {"text": "of the a's from the first row.", "start": 953.35, "duration": 1.98}, {"text": "But you see that you\ncannot set x1 to be a 1, 1,", "start": 955.33, "duration": 5.88}, {"text": "and x1 to be a s1\nat the same time.", "start": 961.21, "duration": 4.21}, {"text": "So the solution just\ncounts permutations,", "start": 965.42, "duration": 3.03}, {"text": "which is exactly s factorial.", "start": 968.45, "duration": 1.889}, {"text": "So this algebraic\nfact plays a key role", "start": 981.59, "duration": 3.32}, {"text": "in the proof of the theorem\nthat the lower bound", "start": 984.91, "duration": 4.64}, {"text": "that we're stating up there,\nif you look at the paper,", "start": 989.55, "duration": 5.17}, {"text": "they give a proof\nof this result.", "start": 994.72, "duration": 1.44}, {"text": "And it's not a long proof.", "start": 996.16, "duration": 1.65}, {"text": "But it uses some commutative\nalgebra and algebraic geometry.", "start": 997.81, "duration": 4.17}, {"text": "And usually in a class,\nif the instructor", "start": 1001.98, "duration": 3.51}, {"text": "doesn't present the proof, it's\nfor one of several reasons.", "start": 1005.49, "duration": 3.3}, {"text": "Maybe the proof is too short.", "start": 1008.79, "duration": 2.16}, {"text": "It doesn't need to be presented.", "start": 1010.95, "duration": 1.41}, {"text": "Maybe it's too long or\ntoo difficult. Maybe", "start": 1012.36, "duration": 2.34}, {"text": "it's not instructive\nto the class.", "start": 1014.7, "duration": 3.09}, {"text": "And the last reason,\nwhich is the case here,", "start": 1017.79, "duration": 2.13}, {"text": "is that I don't actually\nunderstand the proof.", "start": 1019.92, "duration": 2.01}, {"text": "As in I can follow\nit line by line,", "start": 1021.93, "duration": 2.85}, {"text": "but I don't understand\nwhy it is true.", "start": 1024.78, "duration": 3.299}, {"text": "And if one of you wants to\ncome up with a different proof", "start": 1028.079, "duration": 4.561}, {"text": "or try to explain to\nme how this seemingly", "start": 1032.64, "duration": 4.05}, {"text": "elementary algebraic fact is\nproved, I would appreciate it.", "start": 1036.69, "duration": 7.139}, {"text": "For small values of x,\nyou can check it by hand.", "start": 1043.829, "duration": 2.881}, {"text": "So x equals to 2,\nyou're solving a system", "start": 1046.71, "duration": 2.4}, {"text": "of two quadratic equations.", "start": 1049.11, "duration": 2.28}, {"text": "And that you can check by hand.", "start": 1051.39, "duration": 1.5}, {"text": "And three maybe you can\ndo it with some work.", "start": 1052.89, "duration": 2.16}, {"text": "But even with 4 it's not\nso clear how to do it.", "start": 1055.05, "duration": 5.22}, {"text": "And also, one of the geometric\nintuition is that if b is o0,", "start": 1060.27, "duration": 7.14}, {"text": "then you have exactly\ns factorial solutions.", "start": 1067.41, "duration": 2.91}, {"text": "And the geometric\nintuition is somehow", "start": 1070.32, "duration": 1.77}, {"text": "that if you move b\naround, then the fiber,", "start": 1072.09, "duration": 4.2}, {"text": "the sides of the fiber,\nthe number of solutions x", "start": 1076.29, "duration": 2.79}, {"text": "can only go down.", "start": 1079.08, "duration": 1.03}, {"text": "It can not go up.", "start": 1080.11, "duration": 0.83}, {"text": "And this corresponds to some\nalgebraic geometry phenomenon.", "start": 1080.94, "duration": 4.23}, {"text": "And that's all I will say about\nthis algebraic fact, which", "start": 1085.17, "duration": 3.27}, {"text": "we'll now use as a black box.", "start": 1088.44, "duration": 1.23}, {"text": "Great.", "start": 1097.33, "duration": 2.19}, {"text": "So now we have that as\nour algebraic input,", "start": 1099.52, "duration": 3.27}, {"text": "let us show that a\nnorm graph is Kst free.", "start": 1102.79, "duration": 5.16}, {"text": "It's actually not\nso hard once you", "start": 1107.95, "duration": 2.13}, {"text": "assume that theorem up there.", "start": 1110.08, "duration": 2.23}, {"text": "So let's show at a norm graph\nis Ks, s factorial plus 1 free.", "start": 1116.48, "duration": 10.92}, {"text": "Well, what does it\nmean to have a Kst?", "start": 1130.07, "duration": 5.1}, {"text": "It means that if you\nhave distinct vertices,", "start": 1135.17, "duration": 3.99}, {"text": "which then correspond\nto elements,", "start": 1139.16, "duration": 6.17}, {"text": "s elements, y1 through\nys, of this field,", "start": 1145.33, "duration": 7.25}, {"text": "then the common neighbors\nof these elements", "start": 1152.58, "duration": 5.0}, {"text": "correspond to solutions of\nthis system of equations", "start": 1157.58, "duration": 11.22}, {"text": "where I set all of\nthese values to be 1.", "start": 1168.8, "duration": 3.76}, {"text": "But I can write l exactly\nwhat these guys are", "start": 1172.56, "duration": 2.76}, {"text": "because I have this form,\nthat representation there", "start": 1175.32, "duration": 4.16}, {"text": "for the norm map, so\nI can write it out.", "start": 1179.48, "duration": 5.21}, {"text": "And now remember\nthis fact that when", "start": 1184.69, "duration": 3.87}, {"text": "you are in characteristic p, x\nplus y raised to the power p,", "start": 1188.56, "duration": 4.52}, {"text": "is the same as x to the p\nplus yp and characteristic p.", "start": 1193.08, "duration": 7.42}, {"text": "So I can expand the remaining\nparenthesis like that.", "start": 1200.5, "duration": 4.22}, {"text": "So I want the first line\nto equal to 1, and so on.", "start": 1213.34, "duration": 2.71}, {"text": "And each of the lines\nhas that equal to 1.", "start": 1216.05, "duration": 3.9}, {"text": "How many solutions in x does\nthis system of equations have?", "start": 1231.56, "duration": 4.23}, {"text": "So even if I treat each\nof x and x to the p", "start": 1235.79, "duration": 3.72}, {"text": "and so on as separate\nvariables, that theorem", "start": 1239.51, "duration": 2.82}, {"text": "appear tells me that there are\nat most s factorial solutions", "start": 1242.33, "duration": 6.87}, {"text": "in x.", "start": 1249.2, "duration": 1.05}, {"text": "Satisfies all the hypotheses\nof that theorem up there.", "start": 1253.31, "duration": 4.19}, {"text": "Therefore, the graph is Ks\nsub s factorial plus 1 free.", "start": 1257.5, "duration": 6.75}, {"text": "You do not have more than\ns plus 1 different values", "start": 1264.25, "duration": 3.36}, {"text": "of x satisfying this\nsystem of equations.", "start": 1267.61, "duration": 3.75}, {"text": "And that's the proof that\nthis norm graph is Kst free.", "start": 1271.36, "duration": 3.927}, {"text": "Yes, question?", "start": 1275.287, "duration": 0.583}, {"text": "AUDIENCE: Why can't\npowers of like [INAUDIBLE]", "start": 1275.87, "duration": 6.962}, {"text": "YUFEI ZHAO: Sorry, can\nyou repeat the question?", "start": 1282.832, "duration": 1.958}, {"text": "AUDIENCE: Why cannot the\npowers of the y's be the same?", "start": 1284.79, "duration": 4.555}, {"text": "YUFEI ZHAO: The question is why\ncannot the powers of the p's be", "start": 1289.345, "duration": 2.625}, {"text": "the same?", "start": 1291.97, "duration": 1.39}, {"text": "So you are asking,\ndown the second column,", "start": 1293.36, "duration": 2.85}, {"text": "let's say, why are all\nthese y's different?", "start": 1296.21, "duration": 3.12}, {"text": "Because you're working\ninside a field.", "start": 1299.33, "duration": 3.07}, {"text": "And raising to a p in\nthis field is a bijection.", "start": 1302.4, "duration": 4.97}, {"text": "So think about the order\nof the cyclic group.", "start": 1311.37, "duration": 2.67}, {"text": "It has co-prime to p.", "start": 1314.04, "duration": 3.8}, {"text": "But great question.", "start": 1317.84, "duration": 2.2}, {"text": "Anything else?", "start": 1320.04, "duration": 2.6}, {"text": "OK, so this gives\nyou a construction", "start": 1322.64, "duration": 1.7}, {"text": "that gives you Kst free for t\nbigger than s plus s factorial.", "start": 1324.34, "duration": 7.53}, {"text": "Now, let me show you how to\nimprove this construction", "start": 1331.87, "duration": 2.76}, {"text": "to do a little bit better,\nto get s minus 1 factorial.", "start": 1334.63, "duration": 4.65}, {"text": "And the idea is\nto take a variant", "start": 1339.28, "duration": 1.8}, {"text": "of this norm graph, which we'll\ncall the projective norm graph.", "start": 1341.08, "duration": 3.71}, {"text": "And the projective norm\ngraph will define it", "start": 1351.67, "duration": 2.76}, {"text": "for s at least 3\nis rather similar.", "start": 1354.43, "duration": 4.67}, {"text": "But there's a twist.", "start": 1359.1, "duration": 2.06}, {"text": "I have as the vertex set, not\njust the field extension--", "start": 1361.16, "duration": 5.25}, {"text": "OK, so now I take field\nextension, but one level less.", "start": 1366.41, "duration": 4.08}, {"text": "And I take a second\ncoordinate, which consists", "start": 1370.49, "duration": 3.72}, {"text": "of non-zero elements from Fp.", "start": 1374.21, "duration": 2.85}, {"text": "The edges are formed by putting\nan edge between these two", "start": 1381.34, "duration": 8.31}, {"text": "elements, if and\nonly if, the norm", "start": 1389.65, "duration": 4.08}, {"text": "of the sum of the\nfirst coordinates", "start": 1393.73, "duration": 3.34}, {"text": "equals to the product of\nthe second coordinates.", "start": 1397.07, "duration": 3.27}, {"text": "So now, you can run through\na similar calculation that", "start": 1404.48, "duration": 3.28}, {"text": "tells you the number of edges.", "start": 1407.76, "duration": 1.53}, {"text": "So first of all, the\nnumber of vertices", "start": 1409.29, "duration": 2.28}, {"text": "is p to the s minus\n1 times p minus 1,", "start": 1411.57, "duration": 3.87}, {"text": "so basically the same as p to s.", "start": 1415.44, "duration": 4.16}, {"text": "And additionally, every\nvertex has degree exactly", "start": 1419.6, "duration": 9.6}, {"text": "p raised to s minus 1 minus 1.", "start": 1429.2, "duration": 5.49}, {"text": "And the reason is that if I tell\nyou the values of x little x", "start": 1434.69, "duration": 9.77}, {"text": "and big y, which\ncannot equal minus x,", "start": 1444.46, "duration": 3.93}, {"text": "or else you will\nnever form an edge,", "start": 1448.39, "duration": 1.95}, {"text": "then they together uniquely\ndetermine little y.", "start": 1450.34, "duration": 4.068}, {"text": "So for every value of\nbig X and little x,", "start": 1458.16, "duration": 2.36}, {"text": "I just need to run through\nall the values of big Y other", "start": 1460.52, "duration": 3.36}, {"text": "than minus x.", "start": 1463.88, "duration": 0.81}, {"text": "So the number of edges\nthen equals to 1/2 times", "start": 1469.11, "duration": 5.76}, {"text": "the number of vertices times the\ndegree of every vertex, which,", "start": 1474.87, "duration": 4.25}, {"text": "as before, is the\nclaimed asymptotic.", "start": 1479.12, "duration": 9.4}, {"text": "And the remaining thing to show\nis that this projective norm", "start": 1488.52, "duration": 2.93}, {"text": "graph is Kst free.", "start": 1491.45, "duration": 1.28}, {"text": "So it's K sub s, s minus\n1 factorial plus 1 free.", "start": 1505.82, "duration": 5.565}, {"text": "It's a similar calculation\nas the one before,", "start": 1516.84, "duration": 2.17}, {"text": "but we need to take into\naccount the small variant", "start": 1519.01, "duration": 3.23}, {"text": "in the construction.", "start": 1522.24, "duration": 1.28}, {"text": "So suppose we fix s vertices,\nlabeled by this big Y's, little", "start": 1527.12, "duration": 9.4}, {"text": "y's.", "start": 1536.52, "duration": 0.5}, {"text": "And now we need to\nsolve for uppercase X,", "start": 1543.04, "duration": 6.06}, {"text": "lowercase x in this\nsystem of equations,", "start": 1549.1, "duration": 16.7}, {"text": "so asking how many different\npairs, big X, little", "start": 1565.8, "duration": 3.43}, {"text": "x, can appear as a solution\nto this system of equations?", "start": 1569.23, "duration": 4.48}, {"text": "Well, first of all, if some\npairs of the first coordinates,", "start": 1573.71, "duration": 7.32}, {"text": "big I is equal to big J,\nthen if you have a solution,", "start": 1581.03, "duration": 10.58}, {"text": "then that forces little y\nto be the same as little j.", "start": 1591.61, "duration": 5.79}, {"text": "And so the y's wouldn't have\nbeen distinct to begin with.", "start": 1597.4, "duration": 3.49}, {"text": "So this is not possible.", "start": 1600.89, "duration": 3.6}, {"text": "So all the big Y's are distinct.", "start": 1604.49, "duration": 4.2}, {"text": "Well, now, let's\ndivide these equations", "start": 1615.99, "duration": 7.33}, {"text": "by the final equation.", "start": 1623.32, "duration": 1.44}, {"text": "And we get that\nthe i-th equation", "start": 1630.04, "duration": 3.0}, {"text": "becomes like that,\nwhich you can rewrite", "start": 1633.04, "duration": 13.93}, {"text": "by dividing by the coordinate\nof the norm of big Y i", "start": 1646.97, "duration": 10.88}, {"text": "minus big Y s.", "start": 1657.85, "duration": 1.95}, {"text": "This is non-zero because we\njust showed that all the big Y", "start": 1659.8, "duration": 3.35}, {"text": "i's are distinct.", "start": 1663.15, "duration": 1.98}, {"text": "If you divide by this norm here\nand rearrange appropriately,", "start": 1665.13, "duration": 4.65}, {"text": "we find that the equations\nbecome like this.", "start": 1669.78, "duration": 4.08}, {"text": "So after doing some\nrearranging-- so", "start": 1695.87, "duration": 1.7}, {"text": "this is the equation the set\nof new questions that we get.", "start": 1697.57, "duration": 2.97}, {"text": "And you see that if you\nuse new variables, x prime,", "start": 1700.54, "duration": 8.67}, {"text": "do a substitution,\nthis being x prime,", "start": 1709.21, "duration": 4.09}, {"text": "then it has basically\nthe same form as the one", "start": 1713.3, "duration": 3.72}, {"text": "that we just saw with a\ndifferent set of constants.", "start": 1717.02, "duration": 4.18}, {"text": "And in particular\nfrom what we just saw,", "start": 1721.2, "duration": 3.44}, {"text": "we see that you cannot have\nmore than s minus 1 factorial", "start": 1724.64, "duration": 5.34}, {"text": "solutions in x.", "start": 1729.98, "duration": 3.27}, {"text": "Now, they're s\nminus 1 equations.", "start": 1733.25, "duration": 3.66}, {"text": "And the field extension\nworking as the x minus 1", "start": 1736.91, "duration": 3.47}, {"text": "field extension.", "start": 1740.38, "duration": 3.5}, {"text": "So we saved an equation by\nusing this projectivization.", "start": 1743.88, "duration": 4.81}, {"text": "And that's it.", "start": 1748.69, "duration": 2.37}, {"text": "So this shows you the\nclaim of constructing", "start": 1751.06, "duration": 3.45}, {"text": "a Kst free graph for t bigger\nthan s minus 1 factorial, which", "start": 1754.51, "duration": 5.6}, {"text": "has the desired number of edges.", "start": 1760.11, "duration": 2.59}, {"text": "Yes, question?", "start": 1762.7, "duration": 0.883}, {"text": "AUDIENCE: Why do you\nhave the if some capital", "start": 1763.583, "duration": 2.489}, {"text": "Y equals capital IJ?", "start": 1766.072, "duration": 2.968}, {"text": "YUFEI ZHAO: OK, so the question\nis why do I say this part?", "start": 1769.04, "duration": 6.25}, {"text": "So I'm maybe\nskipping a sentence.", "start": 1775.29, "duration": 2.04}, {"text": "I'm saying, if there is\na solution to this system", "start": 1777.33, "duration": 2.34}, {"text": "of equations x, if\nthese vertices have", "start": 1779.67, "duration": 2.97}, {"text": "a common neighbor, then if\nyou have some x satisfying", "start": 1782.64, "duration": 5.13}, {"text": "this system of equations, then\nhaving two different big Y's", "start": 1787.77, "duration": 4.2}, {"text": "being the same forces you\nto have the two smaller y's", "start": 1791.97, "duration": 4.67}, {"text": "being the same.", "start": 1796.64, "duration": 0.906}, {"text": "AUDIENCE: OK.", "start": 1797.546, "duration": 0.794}, {"text": "YUFEI ZHAO: Right.", "start": 1798.34, "duration": 0.75}, {"text": "And then the Y's will\nhave been distinct.", "start": 1799.09, "duration": 3.29}, {"text": "So for them to have\nsome common neighbors,", "start": 1802.38, "duration": 1.77}, {"text": "you better have these\nbig Y's being distinct.", "start": 1804.15, "duration": 3.85}, {"text": "Any more questions?", "start": 1808.0, "duration": 2.62}, {"text": "Great.", "start": 1810.62, "duration": 1.413}, {"text": "So as I mentioned,\nit is an open problem", "start": 1812.033, "duration": 1.667}, {"text": "to determine whether what is the\nextremal number for K44, K45,", "start": 1813.7, "duration": 7.39}, {"text": "K46.", "start": 1821.09, "duration": 1.79}, {"text": "And you may ask, well, we\nhave this nice construction--", "start": 1822.88, "duration": 3.706}, {"text": "it maybe somewhat mysterious\nbecause of that, but explicit.", "start": 1826.586, "duration": 5.014}, {"text": "And you can write\nthis graph down.", "start": 1831.6, "duration": 1.98}, {"text": "And you can ask is\nthis graph K46 free?", "start": 1833.58, "duration": 3.6}, {"text": "So do we gain one\nextra number for free,", "start": 1837.18, "duration": 3.3}, {"text": "maybe because we didn't\nanalyze things properly?", "start": 1840.48, "duration": 3.93}, {"text": "And it turns out\nthat's not the case.", "start": 1844.41, "duration": 2.17}, {"text": "So there was a very recent\npaper just released last month", "start": 1846.58, "duration": 3.62}, {"text": "showing that this graph here\nfor s equals to 4 actually does", "start": 1850.2, "duration": 4.65}, {"text": "contain some K46's.", "start": 1854.85, "duration": 1.86}, {"text": "So if you want to prove a\ncorresponding lower bound", "start": 1860.01, "duration": 5.13}, {"text": "for K46, you better come up\nwith a different construction.", "start": 1865.14, "duration": 5.61}, {"text": "And that's I think an\ninteresting direction", "start": 1870.75, "duration": 2.28}, {"text": "to explore.", "start": 1873.03, "duration": 0.65}, {"text": "Any questions?", "start": 1877.19, "duration": 1.11}, {"text": "Yes.", "start": 1878.3, "duration": 0.5}, {"text": "AUDIENCE: Do we know\nof any similar results", "start": 1878.8, "duration": 2.445}, {"text": "about this construction\nnot working for larger s?", "start": 1881.245, "duration": 2.178}, {"text": "YUFEI ZHAO: The\nquestion is, do we", "start": 1883.423, "duration": 1.417}, {"text": "know any similar result of\nabout does this graph contain", "start": 1884.84, "duration": 5.97}, {"text": "Kst for other values\nof s and t less", "start": 1890.81, "duration": 5.25}, {"text": "than the claimed threshold?", "start": 1896.06, "duration": 2.01}, {"text": "It is unclear.", "start": 1898.07, "duration": 1.18}, {"text": "So the paper that\nwas uploaded, it", "start": 1899.25, "duration": 3.38}, {"text": "doesn't address the\nissue of s bigger than 4.", "start": 1902.63, "duration": 2.856}, {"text": "Yeah.", "start": 1905.486, "duration": 0.5}, {"text": "AUDIENCE: Why Fp to the power s?", "start": 1905.986, "duration": 4.884}, {"text": "YUFEI ZHAO: So question is\nwhy Fp to the power of s?", "start": 1910.87, "duration": 2.66}, {"text": "So let's go back to the\nnorm graph construction.", "start": 1913.53, "duration": 2.16}, {"text": "So where do we use\nFp to the power of s?", "start": 1915.69, "duration": 2.97}, {"text": "Well, certainly we needed it\nto have the right edge count.", "start": 1918.66, "duration": 7.35}, {"text": "So that comes up\nin the edge count.", "start": 1926.01, "duration": 2.35}, {"text": "And also in the\nnorm expression, you", "start": 1928.36, "duration": 4.14}, {"text": "have the correct\nnumber of factors.", "start": 1932.5, "duration": 2.34}, {"text": "So I encourage you\nto try for if you", "start": 1940.96, "duration": 1.73}, {"text": "use a smaller or\nbigger value of s,", "start": 1942.69, "duration": 2.19}, {"text": "you either don't get\nsomething which is Kst free", "start": 1944.88, "duration": 2.58}, {"text": "or you have the wrong\nnumber of edges.", "start": 1947.46, "duration": 3.67}, {"text": "Any more questions?", "start": 1951.13, "duration": 3.7}, {"text": "So later, I will show you\na different construction", "start": 1954.83, "duration": 2.82}, {"text": "of Kst free graphs, again,\nfor t large compared to s", "start": 1957.65, "duration": 4.2}, {"text": "that will not do as\nwell as this one.", "start": 1961.85, "duration": 2.94}, {"text": "But it is a genuinely\ndifferent construction.", "start": 1964.79, "duration": 2.34}, {"text": "And it uses the idea\nof randomized algebraic", "start": 1967.13, "duration": 3.21}, {"text": "construction, which is\nsomething that actually was only", "start": 1970.34, "duration": 3.87}, {"text": "developed a few years ago.", "start": 1974.21, "duration": 1.39}, {"text": "It's a very recent development.", "start": 1975.6, "duration": 2.347}, {"text": "And it's quite nice.", "start": 1977.947, "duration": 0.833}, {"text": "So it combines some of the\nthings we've talked about", "start": 1978.78, "duration": 2.48}, {"text": "with constructing using\nrandom graphs to construct", "start": 1981.26, "duration": 2.6}, {"text": "H free graphs on one hand,\nand on the other hand,", "start": 1983.86, "duration": 2.87}, {"text": "some of the algebraic ideas.", "start": 1986.73, "duration": 1.52}, {"text": "In particular, we're not going\nto use that theorem up there,", "start": 1988.25, "duration": 3.0}, {"text": "but we'll use some other\nalgebraic geometry fact.", "start": 1991.25, "duration": 3.527}, {"text": "OK, so let's take a quick break.", "start": 1994.777, "duration": 1.333}, {"text": "So what I want to discuss\nnow is a relatively new idea", "start": 1999.5, "duration": 4.32}, {"text": "called a randomized\nalgebraic construction, which", "start": 2003.82, "duration": 4.92}, {"text": "combines some ideas from both\nthe randomized construction", "start": 2008.74, "duration": 5.19}, {"text": "and also the algebraic\nconstruction that we just saw.", "start": 2013.93, "duration": 2.24}, {"text": "So this idea is due to Boris\nBukh just a few years ago.", "start": 2019.97, "duration": 3.65}, {"text": "And the goal is to give an\nalternative construction", "start": 2027.66, "duration": 6.24}, {"text": "of a Kst free graph\nwith lots of edges", "start": 2033.9, "duration": 15.72}, {"text": "provided that as before, t\nis much larger compared to s.", "start": 2049.62, "duration": 9.99}, {"text": "So this band here will\nnot be as good as the one", "start": 2063.659, "duration": 2.391}, {"text": "that we just saw.", "start": 2066.05, "duration": 1.109}, {"text": "And I will even\ntell you what it is.", "start": 2067.159, "duration": 2.121}, {"text": "But it's some constant.", "start": 2069.28, "duration": 1.24}, {"text": "So for every s there\nis some t, such", "start": 2070.52, "duration": 2.13}, {"text": "that this construction works.", "start": 2072.65, "duration": 1.22}, {"text": "As before, we working inside\nsome finite field geometry.", "start": 2077.63, "duration": 6.609}, {"text": "So let's start with\na, a prime power.", "start": 2084.239, "duration": 2.823}, {"text": "You can think of\nprime if you like.", "start": 2087.062, "duration": 1.458}, {"text": "It doesn't make so\nmuch difference.", "start": 2088.52, "duration": 1.29}, {"text": "So we're working\ninside a finite field.", "start": 2089.81, "duration": 1.74}, {"text": "And let's assume s is\nfixed and at least 4.", "start": 2094.389, "duration": 4.791}, {"text": "Let me write down\nsome parameters.", "start": 2103.513, "duration": 1.417}, {"text": "Don't worry about them for now.", "start": 2104.93, "duration": 1.39}, {"text": "Just think of them as\nsufficiently large constants.", "start": 2106.32, "duration": 2.41}, {"text": "So d is this quantity here.", "start": 2108.73, "duration": 2.74}, {"text": "So we'll come back to it\nlater when it comes up.", "start": 2111.47, "duration": 3.61}, {"text": "OK, so what's the idea?", "start": 2115.08, "duration": 3.92}, {"text": "When we looked at the\nrandomized construction,", "start": 2119.0, "duration": 2.43}, {"text": "we took a random graph.", "start": 2121.43, "duration": 1.26}, {"text": "We took an Erdos Renyi graph.", "start": 2122.69, "duration": 2.28}, {"text": "Every edge appeared\nindependently.", "start": 2124.97, "duration": 2.31}, {"text": "And saw that it\nhas lots of edges,", "start": 2127.28, "duration": 2.73}, {"text": "if you choose p property\nand not so many copies of h.", "start": 2130.01, "duration": 3.72}, {"text": "So you can remove\nall the copies of h", "start": 2133.73, "duration": 2.43}, {"text": "to get a graph with lots\nof edges that is h free.", "start": 2136.16, "duration": 5.25}, {"text": "What we're going to\ndo now is instead", "start": 2141.41, "duration": 1.9}, {"text": "of taking the edges\nrandomly, we're", "start": 2143.31, "duration": 2.07}, {"text": "going to take a\nrandom polynomial.", "start": 2145.38, "duration": 2.825}, {"text": "F will be a random\npolynomial chosen uniformly", "start": 2154.03, "duration": 13.66}, {"text": "among all polynomials with--", "start": 2167.69, "duration": 12.03}, {"text": "so I wrote uppercase Y and\nuppercase X and Y. Actually, X", "start": 2179.72, "duration": 4.79}, {"text": "and Y, they're not\nsingle variants.", "start": 2184.51, "duration": 1.83}, {"text": "They are-- so each of them\nis a vector of s variables.", "start": 2186.34, "duration": 12.94}, {"text": "So in other words, x1\nthrough xs are the variables", "start": 2201.87, "duration": 4.68}, {"text": "in the polynomial.", "start": 2206.55, "duration": 1.02}, {"text": "And then y1 through ys.", "start": 2207.57, "duration": 4.23}, {"text": "So it's a 2s\nvariable polynomial.", "start": 2211.8, "duration": 2.258}, {"text": "So among all polynomials\nwith degree, at most d--", "start": 2218.18, "duration": 7.87}, {"text": "d being the number up here--", "start": 2226.05, "duration": 1.74}, {"text": "in each of x and y\nsets of variables.", "start": 2227.79, "duration": 6.05}, {"text": "So you look at it\nas xs variables,", "start": 2233.84, "duration": 2.86}, {"text": "each monominal has\ntheir exponents sum", "start": 2236.7, "duration": 4.05}, {"text": "to our most d, and likewise\nwith each monomial for the y", "start": 2240.75, "duration": 3.42}, {"text": "variables.", "start": 2244.17, "duration": 1.62}, {"text": "So this is the random object.", "start": 2245.79, "duration": 3.47}, {"text": "It's a random polynomial\nin 2s variables.", "start": 2249.26, "duration": 3.04}, {"text": "And the degree is bounded.", "start": 2252.3, "duration": 1.15}, {"text": "So you only have a finite\nnumber of possibilities,", "start": 2253.45, "duration": 2.54}, {"text": "and I choose one of them\nuniformly at random.", "start": 2255.99, "duration": 2.13}, {"text": "And now, what's my graph?", "start": 2264.75, "duration": 2.28}, {"text": "We're going to construct\na bipartide graph", "start": 2267.03, "duration": 2.09}, {"text": "G. The bipartideness,\nit's not so crucial.", "start": 2269.12, "duration": 3.69}, {"text": "But it'll make our\nlife somewhat easier.", "start": 2272.81, "duration": 1.88}, {"text": "So it's a bipartide graph.", "start": 2278.87, "duration": 1.46}, {"text": "So it hs two vertex parts, which\nI will label left and right,", "start": 2280.33, "duration": 3.49}, {"text": "L and R. And they are both\nthe s dimensional vector", "start": 2283.82, "duration": 5.5}, {"text": "space over f cube.", "start": 2289.32, "duration": 2.28}, {"text": "And we'll put an edge\nbetween two vertices,", "start": 2291.6, "duration": 6.93}, {"text": "if and only if that\npolynomial up there", "start": 2298.53, "duration": 2.67}, {"text": "f evaluates to 0\non these values.", "start": 2301.2, "duration": 6.76}, {"text": "That's the graph.", "start": 2307.96, "duration": 1.24}, {"text": "So I give you a\nrandom polynomial f.", "start": 2309.2, "duration": 2.89}, {"text": "And then you put in edges\naccording to when f vanishes.", "start": 2312.09, "duration": 6.63}, {"text": "So f, if you view the bipartide\ngraph as a subset of Fq", "start": 2318.72, "duration": 5.7}, {"text": "to s cross F to the s,\nthen this is the zero set.", "start": 2324.42, "duration": 4.79}, {"text": "The edge set is the zero set.", "start": 2329.21, "duration": 3.76}, {"text": "Just like in random graphs,\nwith the construction", "start": 2332.97, "duration": 3.51}, {"text": "with random graphs, we'll need\nto show a couple of things.", "start": 2336.48, "duration": 2.47}, {"text": "One is that has lots of edges,\nwhich will not be hard to show.", "start": 2338.95, "duration": 3.38}, {"text": "And second, that it will\nhave typically a small number", "start": 2342.33, "duration": 3.72}, {"text": "of copies of Kst.", "start": 2346.05, "duration": 3.6}, {"text": "And that will have\nsome ingredients which", "start": 2349.65, "duration": 3.35}, {"text": "are similar to the random\ngraphs case we saw before,", "start": 2353.0, "duration": 3.66}, {"text": "but it will have some new ideas\ncoming from algebraic geometry.", "start": 2356.66, "duration": 6.16}, {"text": "First, let's show that this\ngraph has lots of edges.", "start": 2362.82, "duration": 4.54}, {"text": "And that's a simple calculation,\nbecause for every pair", "start": 2367.36, "duration": 7.17}, {"text": "of points of vertices, I\nclaim that the probability--", "start": 2374.53, "duration": 10.09}, {"text": "so here f is the random object--", "start": 2384.62, "duration": 2.32}, {"text": "the probability that f evaluates\nto 0 on this pair is exactly q.", "start": 2386.94, "duration": 6.85}, {"text": "So exactly 1 over q, 1\nover the size of the field.", "start": 2393.79, "duration": 5.18}, {"text": "So this is not too hard.", "start": 2398.97, "duration": 2.96}, {"text": "And the reason is that\nthe distribution of f", "start": 2401.93, "duration": 4.92}, {"text": "is identical to if you are an\nextra random constant on f,", "start": 2406.85, "duration": 25.36}, {"text": "chosen uniformly at random.", "start": 2432.21, "duration": 1.86}, {"text": "So I took a random polynomial.", "start": 2434.07, "duration": 1.77}, {"text": "I shifted by a random constant.", "start": 2435.84, "duration": 1.59}, {"text": "It's still uniformly\nrandom polynomial,", "start": 2437.43, "duration": 1.89}, {"text": "according to that distribution.", "start": 2439.32, "duration": 1.86}, {"text": "But now, you see\nthat this, whatever f", "start": 2441.18, "duration": 5.49}, {"text": "evaluated to, if I shift\nby a random constant,", "start": 2446.67, "duration": 3.14}, {"text": "you will end up with a\nuniform distribution.", "start": 2449.81, "duration": 3.89}, {"text": "So it tells you that that guy\nup there is uniform distribution", "start": 2453.7, "duration": 9.94}, {"text": "on every fixed point\nu, v. So in particular,", "start": 2463.64, "duration": 8.96}, {"text": "it hits 0 with probability\nexactly 1 over q.", "start": 2472.6, "duration": 5.62}, {"text": "And as a result, the number of\nedges of g in the expectation", "start": 2478.22, "duration": 7.09}, {"text": "is exactly n squared\nover q, where", "start": 2485.31, "duration": 6.31}, {"text": "n is the number of vertices.", "start": 2491.62, "duration": 2.65}, {"text": "So n is actually not\nthe number of vertices,", "start": 2494.27, "duration": 3.14}, {"text": "but the size of each vertex\npart, namely q to the s.", "start": 2497.41, "duration": 6.245}, {"text": "So you see that it gives you\nthe right number of edges, so n", "start": 2503.655, "duration": 5.115}, {"text": "to the 2 minus 1 over s.", "start": 2508.77, "duration": 2.52}, {"text": "So we have the right\nnumber of edges.", "start": 2511.29, "duration": 1.99}, {"text": "And now, we want to show that\nthis graph here typically does", "start": 2513.28, "duration": 5.0}, {"text": "not have too many\ncopies of Kst's.", "start": 2518.28, "duration": 3.41}, {"text": "It might have some\ncopies of Kst's.", "start": 2521.69, "duration": 1.81}, {"text": "Somehow that is unavoidable.", "start": 2523.5, "duration": 2.12}, {"text": "Just as in the random case, you\ndo have some copies of Kst's.", "start": 2525.62, "duration": 4.03}, {"text": "But if they are not\ntoo many copies,", "start": 2529.65, "duration": 1.71}, {"text": "I can remove them and\nobtain a Kst free graph.", "start": 2531.36, "duration": 2.94}, {"text": "OK, so what is the intuition?", "start": 2537.83, "duration": 2.24}, {"text": "How does it compare\nto the case when", "start": 2540.07, "duration": 2.52}, {"text": "you have a genuine\nErdos-Renyi random graph?", "start": 2542.59, "duration": 4.67}, {"text": "Well, what is the expected\nnumber of common neighbors?", "start": 2547.26, "duration": 5.343}, {"text": "So if you fix some\nu with let's say", "start": 2556.05, "duration": 7.07}, {"text": "on the left side with\nexactly s vertices,", "start": 2563.12, "duration": 6.48}, {"text": "I want to understand, how many\ncommon neighbors does u have?", "start": 2569.6, "duration": 12.7}, {"text": "But because the\ncommon neighbors,", "start": 2589.845, "duration": 1.375}, {"text": "if he has too many common\nneighbors, then that's a Kst.", "start": 2591.22, "duration": 2.85}, {"text": "It is not hard to\ncalculate the expectation", "start": 2596.82, "duration": 3.25}, {"text": "of this quantity, both\nin the random graph case", "start": 2600.07, "duration": 2.69}, {"text": "as well as in this case.", "start": 2602.76, "duration": 2.02}, {"text": "And you can calculate if you\npretend every edge occurs", "start": 2604.78, "duration": 3.0}, {"text": "independently, the expected\nnumber of common neighbors", "start": 2607.78, "duration": 4.79}, {"text": "is exactly n to the\nq to the minus s.", "start": 2612.57, "duration": 6.64}, {"text": "So there are s elements\nof u, which is exactly 1.", "start": 2619.21, "duration": 3.66}, {"text": "And you know that for a binomial\ndistribution with expectation 1", "start": 2625.98, "duration": 4.62}, {"text": "and a large number of\nvariables, the distribution", "start": 2630.6, "duration": 3.12}, {"text": "is approximately Poissonian.", "start": 2633.72, "duration": 1.854}, {"text": "Ah, but that's in the case when\nit's independently distributed,", "start": 2643.802, "duration": 7.838}, {"text": "which is the case\nin the case of GMP.", "start": 2651.64, "duration": 3.12}, {"text": "But it turns out for\nthe algebraic setting", "start": 2654.76, "duration": 3.0}, {"text": "we're doing here, things\ndon't behave independently.", "start": 2657.76, "duration": 4.48}, {"text": "It's not that you're doing coin\nflops for every possible edge.", "start": 2662.24, "duration": 3.93}, {"text": "We're doing some randomized\nalgebraic construction.", "start": 2666.17, "duration": 2.63}, {"text": "And for algebraic\ngeometry reasons,", "start": 2668.8, "duration": 2.31}, {"text": "you will see that the\ndistribution is very much not", "start": 2671.11, "duration": 2.56}, {"text": "like Poissonian.", "start": 2673.67, "duration": 1.99}, {"text": "It will turn out that either\nthe number of common neighbors", "start": 2675.66, "duration": 4.38}, {"text": "is bounded or it is very large.", "start": 2680.04, "duration": 3.66}, {"text": "And that means that we can show\nusing some Markov inequality", "start": 2686.81, "duration": 6.81}, {"text": "that the probability that it\nis very large is quite small.", "start": 2693.62, "duration": 3.51}, {"text": "So typically, it will not\nhave many common neighbors?", "start": 2697.13, "duration": 5.17}, {"text": "And that's the intuition, and so\nlet's work out this intuition.", "start": 2702.3, "duration": 4.44}, {"text": "Any questions so far?", "start": 2706.74, "duration": 0.88}, {"text": "So how do we do\nthis calculation?", "start": 2712.22, "duration": 1.43}, {"text": "So first, let's start\nwith something that's", "start": 2713.65, "duration": 2.42}, {"text": "actually fairly elementary.", "start": 2716.07, "duration": 1.17}, {"text": "So suppose you have some\nparameters, r and s.", "start": 2717.24, "duration": 7.82}, {"text": "So I think of r and s--", "start": 2725.06, "duration": 2.1}, {"text": "so I have some\nparameters r and s.", "start": 2727.16, "duration": 2.82}, {"text": "And thick of them as constants.", "start": 2729.98, "duration": 4.18}, {"text": "Have some restrictions,\nbut don't worry too much", "start": 2734.16, "duration": 2.0}, {"text": "about them.", "start": 2736.16, "duration": 2.47}, {"text": "Suppose I have two bounded\nsubsets of the finite field,", "start": 2738.63, "duration": 8.97}, {"text": "where you have size\ns and v has size r.", "start": 2747.6, "duration": 6.99}, {"text": "Then the claim is\nthat the probability", "start": 2754.59, "duration": 3.72}, {"text": "that f vanishes on the Cartesian\nproduct of u and v. OK,", "start": 2758.31, "duration": 10.93}, {"text": "so what do you expect it to be?", "start": 2769.24, "duration": 3.6}, {"text": "So I have s r elements, and I\nwant f, this random polynomial,", "start": 2772.84, "duration": 4.47}, {"text": "to vanish on the entire product.", "start": 2777.31, "duration": 1.93}, {"text": "Well, if s, its value behaved\nindependently for every point,", "start": 2779.24, "duration": 4.13}, {"text": "you should expect that\nthe probability is exactly", "start": 2783.37, "duration": 2.66}, {"text": "q to the power minus s r.", "start": 2786.03, "duration": 4.03}, {"text": "And it turns out\nthat is the case.", "start": 2790.06, "duration": 2.65}, {"text": "So this is true.", "start": 2792.71, "duration": 0.77}, {"text": "This is an exact statement.", "start": 2793.48, "duration": 1.817}, {"text": "OK, so why is this true?", "start": 2798.57, "duration": 1.16}, {"text": "So this is in some\nsense a generalization", "start": 2799.73, "duration": 2.37}, {"text": "of this claim over here.", "start": 2802.1, "duration": 2.15}, {"text": "And you have to do a\nlittle bit more work.", "start": 2804.25, "duration": 1.79}, {"text": "But it's not too difficult.", "start": 2806.04, "duration": 2.48}, {"text": "So let's first\nconsider this lemma", "start": 2808.52, "duration": 6.56}, {"text": "in a somewhat simpler case,\nwhere all the first coordinates", "start": 2815.08, "duration": 16.87}, {"text": "of x are distinct--", "start": 2831.95, "duration": 2.13}, {"text": "of u are distinct.", "start": 2834.08, "duration": 2.29}, {"text": "And all the first coordinates\nof v are distinct.", "start": 2839.44, "duration": 4.28}, {"text": "Suppose u and v have that form.", "start": 2843.72, "duration": 1.94}, {"text": "So I write down the\nlist of points for u", "start": 2845.66, "duration": 3.48}, {"text": "and first coordinates\nare all distinct.", "start": 2849.14, "duration": 2.13}, {"text": "What I want to do is to\ngive you a random shift,", "start": 2853.99, "duration": 5.01}, {"text": "to do a uniform random shift.", "start": 2859.0, "duration": 4.47}, {"text": "And I will shift it by\na polynomial g, which", "start": 2863.47, "duration": 3.81}, {"text": "is a bivariate polynomial.", "start": 2867.28, "duration": 1.68}, {"text": "So these are not vectors.", "start": 2868.96, "duration": 1.64}, {"text": "They are just single variables.", "start": 2870.6, "duration": 4.58}, {"text": "And I look at all\npossible sum of monomials,", "start": 2875.18, "duration": 8.59}, {"text": "where the degree in i is less\nthan s, and the degree in j", "start": 2883.77, "duration": 8.79}, {"text": "is less than r.", "start": 2892.56, "duration": 1.32}, {"text": "And these a's are chosen\nuniformly independently", "start": 2896.64, "duration": 7.72}, {"text": "at random from the\nground field fq.", "start": 2904.36, "duration": 7.97}, {"text": "And as before, we see\nthat f and f plus g", "start": 2914.91, "duration": 4.89}, {"text": "have the same distribution, the\nsame probability distribution.", "start": 2919.8, "duration": 6.09}, {"text": "And so all it remains to show\nthat is whatever f comes out", "start": 2925.89, "duration": 3.77}, {"text": "to be, if I tack on\nthis extra random g,", "start": 2929.66, "duration": 3.87}, {"text": "it creates a uniform\ndistribution on the values", "start": 2933.53, "duration": 3.15}, {"text": "on the entire u cross\nv. But, actually, see,", "start": 2936.68, "duration": 7.59}, {"text": "I have sr choices exactly\nfor these coefficients.", "start": 2944.27, "duration": 5.08}, {"text": "And I have sr values that\nI'm trying to control.", "start": 2949.35, "duration": 5.62}, {"text": "So really it's a\ncounting problem.", "start": 2954.97, "duration": 2.45}, {"text": "And it suffices to show\na bijection, namely", "start": 2957.42, "duration": 9.79}, {"text": "that for every possible\nvector of values,", "start": 2967.21, "duration": 10.19}, {"text": "there exists a choice\nof coefficients,", "start": 2977.4, "duration": 3.23}, {"text": "as above, such that g evaluates\nto the prescribed values", "start": 2980.63, "duration": 9.6}, {"text": "with the given coefficients.", "start": 2990.23, "duration": 2.314}, {"text": "And that uniformity will follow\njust because you have the exact", "start": 3002.71, "duration": 4.68}, {"text": "if you just do a counting.", "start": 3007.39, "duration": 3.02}, {"text": "And the one-dimensional\nversion of this claim,", "start": 3010.41, "duration": 3.253}, {"text": "so let's think\nabout what that is.", "start": 3013.663, "duration": 1.417}, {"text": "So if I have, let's say,\nthree points on the line", "start": 3015.08, "duration": 3.92}, {"text": "and a degree 2 polynomial,\nwhat I am saying", "start": 3019.0, "duration": 3.33}, {"text": "is that if you give me the\nvalues you want on these three", "start": 3022.33, "duration": 4.53}, {"text": "points, I can produce for\nyou a unique polynomial that", "start": 3026.86, "duration": 4.23}, {"text": "evaluates to the prescribed\nvalues on these three points.", "start": 3031.09, "duration": 4.37}, {"text": "And that you should all know\nas Lagrange interpolation.", "start": 3035.46, "duration": 3.79}, {"text": "So it tells you\nexactly how to do that.", "start": 3039.25, "duration": 3.47}, {"text": "And that works for many reasons.", "start": 3042.72, "duration": 2.67}, {"text": "One of them is that the random\nindeterminate is invertible.", "start": 3045.39, "duration": 5.85}, {"text": "Here, we have multi-variables.", "start": 3051.24, "duration": 3.01}, {"text": "So let's do Lagrange\ninterpolation twice, once", "start": 3054.25, "duration": 4.04}, {"text": "for each variable.", "start": 3058.29, "duration": 3.63}, {"text": "So we'll apply Lagrange\ninterpolation twice.", "start": 3061.92, "duration": 14.11}, {"text": "So the first time, we'll see\nthat for all values of u,", "start": 3076.03, "duration": 7.33}, {"text": "there exists a single\nvariate polynomial", "start": 3083.36, "duration": 6.53}, {"text": "in the y variable with\ndegree at most r minus 1 that", "start": 3089.89, "duration": 8.96}, {"text": "evaluates to the correct\nvalues on the fixed little u.", "start": 3098.85, "duration": 8.09}, {"text": "So do it for one\nvariable at a time.", "start": 3114.28, "duration": 1.81}, {"text": "For fixed u, do\nLagrange interpolation", "start": 3116.09, "duration": 3.51}, {"text": "on the y variable.", "start": 3119.6, "duration": 2.6}, {"text": "And now, once we have\nthose things there,", "start": 3122.2, "duration": 4.29}, {"text": "viewing the g that we want\nto find as a polynomial whose", "start": 3126.49, "duration": 10.09}, {"text": "coefficients are polynomials in\nthe x variables, but is itself", "start": 3136.58, "duration": 6.26}, {"text": "is a polynomial\nin the y variable,", "start": 3142.84, "duration": 7.73}, {"text": "we find that again using\nLagrange interpolation,", "start": 3150.57, "duration": 3.93}, {"text": "there exists these values\nfor these coefficients", "start": 3154.5, "duration": 5.81}, {"text": "here, such that each\ncoefficient of if you plug", "start": 3160.31, "duration": 11.2}, {"text": "in the first entry into little\nu agrees with the coefficients", "start": 3171.51, "duration": 13.14}, {"text": "of the g that we just found.", "start": 3184.65, "duration": 4.81}, {"text": "And that should be the\ncase for every little u.", "start": 3189.46, "duration": 2.08}, {"text": "So once you find\nthese polynomials", "start": 3194.91, "duration": 2.41}, {"text": "and now you have a\nbonafide polynomial in g.", "start": 3197.32, "duration": 2.96}, {"text": "And that's the claim above.", "start": 3200.28, "duration": 3.33}, {"text": "So using Lagrange interpolation\ntwice, once for each variable.", "start": 3203.61, "duration": 3.38}, {"text": "So this is-- if you're\nconfused, just think about it.", "start": 3206.99, "duration": 4.38}, {"text": "There is nothing deep here.", "start": 3211.37, "duration": 3.22}, {"text": "So that finishes the\nclaim in the case", "start": 3214.59, "duration": 3.3}, {"text": "when the first coordinates\nare all distinct.", "start": 3217.89, "duration": 4.27}, {"text": "So we use that fact crucially\nin doing this Lagrange", "start": 3222.16, "duration": 3.02}, {"text": "interpolation.", "start": 3225.18, "duration": 2.02}, {"text": "Now, for general\nu and v, where we", "start": 3227.2, "duration": 5.15}, {"text": "don't have this\nassumption of having", "start": 3232.35, "duration": 1.56}, {"text": "distinct first\ncoordinates, well,", "start": 3233.91, "duration": 3.18}, {"text": "let's make them to have\ndistinct first coordinates", "start": 3237.09, "duration": 3.75}, {"text": "by considering a random\nlinear transformation,", "start": 3240.84, "duration": 3.51}, {"text": "so using a probabilistic method.", "start": 3244.35, "duration": 3.63}, {"text": "So we suffice as to find\ninvertible linear maps, p", "start": 3247.98, "duration": 12.9}, {"text": "and s, on this vector space,\nsuch that TU and SV have", "start": 3260.88, "duration": 13.29}, {"text": "the above properties.", "start": 3274.17, "duration": 1.542}, {"text": "So let me show you\nhow to do it for u.", "start": 3280.91, "duration": 2.24}, {"text": "So I need to find you\na invertible linear", "start": 3283.15, "duration": 2.02}, {"text": "transformation t.", "start": 3285.17, "duration": 2.89}, {"text": "Well, it's just the first\ncoordinate that matters.", "start": 3288.06, "duration": 2.11}, {"text": "So it suffices to\nfind just a linear map", "start": 3290.17, "duration": 5.74}, {"text": "corresponding to the\nfirst coordinate that", "start": 3295.91, "duration": 7.69}, {"text": "is injective of u.", "start": 3303.6, "duration": 2.286}, {"text": "Whatever linear map you have,\neven if it's zero, that's fine,", "start": 3308.84, "duration": 3.18}, {"text": "I can extend it to the\nremaining coordinates.", "start": 3312.02, "duration": 6.825}, {"text": "Actually, if it's\nzero, then it's", "start": 3318.845, "duration": 1.375}, {"text": "not going to be injective of u.", "start": 3320.22, "duration": 1.365}, {"text": "So it better not be zero.", "start": 3321.585, "duration": 3.405}, {"text": "OK, well, let's find\nthis map randomly.", "start": 3324.99, "duration": 2.73}, {"text": "So pick t uniform via random\namong all linear maps.", "start": 3327.72, "duration": 12.8}, {"text": "And I want to understand\nwhat is the probability", "start": 3346.31, "duration": 2.0}, {"text": "of collision, bad event,\nif two elements of u", "start": 3348.31, "duration": 5.13}, {"text": "end up getting mapped\nto the same point.", "start": 3353.44, "duration": 3.02}, {"text": "Well, that's not too hard.", "start": 3356.46, "duration": 2.25}, {"text": "So for every distinct pair\nof points in fq to the s", "start": 3358.71, "duration": 8.44}, {"text": "the probability\nthat they collide,", "start": 3367.15, "duration": 15.95}, {"text": "think about why this is true.", "start": 3383.1, "duration": 1.5}, {"text": "It's exactly 1 over q.", "start": 3384.6, "duration": 2.612}, {"text": "If x and x prime, they're\ndiffering at least one", "start": 3390.99, "duration": 2.76}, {"text": "coordinate, then even just\nalong that coordinate,", "start": 3393.75, "duration": 2.17}, {"text": "I can make them distinct.", "start": 3395.92, "duration": 2.73}, {"text": "So this is the case\nfor every pair.", "start": 3398.65, "duration": 2.82}, {"text": "So now by union\nbound, the probability", "start": 3401.47, "duration": 5.7}, {"text": "that t1 is injective on u\nis at least 1 minus the size", "start": 3407.17, "duration": 8.73}, {"text": "if u choose 2 times 1 over q.", "start": 3415.9, "duration": 5.47}, {"text": "And that's why we chose\nq to be large enough.", "start": 3421.37, "duration": 5.78}, {"text": "So q is at least r squared, s\nSo this number here is positive.", "start": 3427.15, "duration": 6.39}, {"text": "So such a t exists.", "start": 3433.54, "duration": 3.19}, {"text": "And so we can transform this u\nand v, two configurations where", "start": 3436.73, "duration": 4.62}, {"text": "the first coordinates\nare all distinct,", "start": 3441.35, "duration": 1.77}, {"text": "and then run the\nargument as before.", "start": 3443.12, "duration": 3.67}, {"text": "OK, great.", "start": 3446.79, "duration": 1.102}, {"text": "So what we've shown so far is\nthat if you look at these Ksr", "start": 3450.66, "duration": 6.12}, {"text": "structures, they appear\nwith probability exactly--", "start": 3456.78, "duration": 4.84}, {"text": "well, with expectation\nexactly what", "start": 3461.62, "duration": 2.96}, {"text": "you might expect as in\nindependent random case.", "start": 3464.58, "duration": 4.74}, {"text": "But what we really\nwant to understand", "start": 3469.32, "duration": 1.89}, {"text": "is the distribution of the\nnumber of common neighbors.", "start": 3471.21, "duration": 4.4}, {"text": "In particular, we want to\nupper bound the probability", "start": 3475.61, "duration": 4.44}, {"text": "that there are too\nmany common neighbors.", "start": 3480.05, "duration": 2.31}, {"text": "We want to understand some\nkind of tail probabilities.", "start": 3482.36, "duration": 5.8}, {"text": "And to do that, one way\nto do tail probabilities", "start": 3488.16, "duration": 3.44}, {"text": "is to consider moments.", "start": 3491.6, "duration": 1.555}, {"text": "Yes, question?", "start": 3493.155, "duration": 2.467}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3495.622, "duration": 6.298}, {"text": "YUFEI ZHAO: Sorry, can\nyou repeat the question?", "start": 3501.92, "duration": 3.565}, {"text": "AUDIENCE: How do you\nhave the equality right", "start": 3505.485, "duration": 2.415}, {"text": "before the lemma?", "start": 3507.9, "duration": 1.932}, {"text": "YUFEI ZHAO: Question, how\ndo I have the equality right", "start": 3509.832, "duration": 2.958}, {"text": "before the lemma?", "start": 3512.79, "duration": 2.01}, {"text": "So there, I'm actually saying\nfor the Erdos-Renyi random", "start": 3514.8, "duration": 8.67}, {"text": "graph case--", "start": 3523.47, "duration": 1.39}, {"text": "that's the case-- in\nErdos-Renyi random graph,", "start": 3524.86, "duration": 2.96}, {"text": "each edge, if you have the same\nedge probability, is 1 over q.", "start": 3527.82, "duration": 4.86}, {"text": "And then that's the\nnumber of common neighbors", "start": 3532.68, "duration": 3.252}, {"text": "you would expect.", "start": 3535.932, "duration": 0.708}, {"text": "So that's a heuristic for the\nErdos-Renyi random graph case.", "start": 3540.2, "duration": 4.95}, {"text": "OK, so now let's\ntry to understand", "start": 3545.15, "duration": 2.07}, {"text": "the distribution of the\nnumber of common neighbors.", "start": 3547.22, "duration": 3.46}, {"text": "So let's fix a u subset of Fp to\nthe s with exactly s elements.", "start": 3550.68, "duration": 9.17}, {"text": "And I want to understand how\nmany common neighbors it has.", "start": 3559.85, "duration": 2.94}, {"text": "So let's consider the number\nof common neighbors of u", "start": 3562.79, "duration": 13.54}, {"text": "and the d-th moment of\nthis random variable.", "start": 3576.33, "duration": 3.81}, {"text": "So this is a common way\nto do upper tail bounds.", "start": 3580.14, "duration": 4.33}, {"text": "And one way to\nanalyze such moments", "start": 3584.47, "duration": 3.12}, {"text": "is to decompose this count\nas a sum of indicator", "start": 3587.59, "duration": 4.08}, {"text": "random variables.", "start": 3591.67, "duration": 1.33}, {"text": "So let me write I of v to be the\nquantity which is 1 if f of uv", "start": 3593.0, "duration": 10.67}, {"text": "is 0 for all with ou\nand big U. In the words,", "start": 3603.67, "duration": 5.1}, {"text": "it's a common neighbor.", "start": 3608.77, "duration": 1.96}, {"text": "It's 1 if v is a common\nneighbor for u, and 0 otherwise.", "start": 3610.73, "duration": 6.007}, {"text": "So then the number\nof common neighbors", "start": 3620.22, "duration": 2.19}, {"text": "would simply be the sum of\nthis indicator as v ranges", "start": 3622.41, "duration": 8.79}, {"text": "over the entire vertex set.", "start": 3631.2, "duration": 1.88}, {"text": "And I can expand the sum.", "start": 3636.59, "duration": 2.58}, {"text": "Then all of these\nare standard things", "start": 3639.17, "duration": 2.61}, {"text": "to do when you're trying\nto calculate moments.", "start": 3641.78, "duration": 2.145}, {"text": "OK, so I can bring\nthis expectation inside", "start": 3656.15, "duration": 10.09}, {"text": "and try to understand what is\nthe expectation of this object", "start": 3666.24, "duration": 3.93}, {"text": "inside.", "start": 3670.17, "duration": 0.5}, {"text": "Well, if all the\nv's are distinct,", "start": 3674.1, "duration": 3.32}, {"text": "then this is simply the\nexpected number of Kst's.", "start": 3677.42, "duration": 4.625}, {"text": "But the v's might\nnot be distinct.", "start": 3690.09, "duration": 2.0}, {"text": "So we need to be a\nlittle bit careful.", "start": 3692.09, "duration": 2.13}, {"text": "But that's not too\nhard to handle.", "start": 3694.22, "duration": 2.07}, {"text": "So let me write M sub\nr to be the number", "start": 3696.29, "duration": 3.15}, {"text": "of subjective functions from\nd element set to an r elements", "start": 3699.44, "duration": 6.2}, {"text": "set, an M to be sum of these\nM sub r's for r up to d.", "start": 3705.64, "duration": 7.46}, {"text": "Then, let's consider how many\ndistinct v values are there.", "start": 3713.1, "duration": 5.29}, {"text": "If there are distinct\nv values, then they", "start": 3718.39, "duration": 5.43}, {"text": "take on that many\npossible values.", "start": 3723.82, "duration": 3.75}, {"text": "And Mr for the number\nof subjections,", "start": 3727.57, "duration": 2.97}, {"text": "and for each possible\nr, the exact number", "start": 3730.54, "duration": 5.7}, {"text": "for the exact value\nof this expectation", "start": 3736.24, "duration": 2.4}, {"text": "is q to the minus rs.", "start": 3738.64, "duration": 1.74}, {"text": "And that's exactly\nwhat we showed.", "start": 3740.38, "duration": 1.83}, {"text": "So this comes from\nthe lemma just now.", "start": 3742.21, "duration": 3.76}, {"text": "But we chose-- I\nmean, look, this", "start": 3749.77, "duration": 1.94}, {"text": "is that binomial coefficient.", "start": 3751.71, "duration": 2.71}, {"text": "And you have this number here.", "start": 3754.42, "duration": 1.25}, {"text": "So they multiply\nit to at most 1.", "start": 3755.67, "duration": 1.86}, {"text": "So we have this number,\nthis quantity there,", "start": 3762.28, "duration": 3.3}, {"text": "which I think of as a constant.", "start": 3765.58, "duration": 1.51}, {"text": "So this is a constant.", "start": 3767.09, "duration": 2.43}, {"text": "So the d-th moment is bounded.", "start": 3769.52, "duration": 2.07}, {"text": "And one way to get tail bounds\nonce you have the moments", "start": 3777.9, "duration": 4.36}, {"text": "is that we can use\nMarkov's inequality.", "start": 3782.26, "duration": 5.026}, {"text": "It tells us that the number\nof common neighbors of u,", "start": 3787.286, "duration": 5.564}, {"text": "the probability that u has too\nmany common neighbors, more", "start": 3792.85, "duration": 5.61}, {"text": "than lambda common neighbors.", "start": 3798.46, "duration": 4.13}, {"text": "I can rewrite this\ninequality here", "start": 3802.59, "duration": 7.1}, {"text": "by raising both\nsides to the power d.", "start": 3809.69, "duration": 5.04}, {"text": "And then, using Markov\ninequality, take expectation.", "start": 3814.73, "duration": 7.62}, {"text": "So all of these are\nstandard techniques", "start": 3831.95, "duration": 2.06}, {"text": "for upper tail estimation.", "start": 3834.01, "duration": 2.73}, {"text": "You want to understand the\nupper tails on random variable,", "start": 3836.74, "duration": 3.06}, {"text": "understand its moments and\nuse Markov on its moments.", "start": 3839.8, "duration": 3.87}, {"text": "But now, we know we have some\nbound for the d-th moment,", "start": 3846.71, "duration": 6.21}, {"text": "right?", "start": 3852.92, "duration": 1.68}, {"text": "Which is M as we just showed.", "start": 3854.6, "duration": 2.28}, {"text": "So there is this bound here.", "start": 3856.88, "duration": 1.68}, {"text": "So far you can run\nthe same argument", "start": 3861.32, "duration": 2.1}, {"text": "in the random graphs case.", "start": 3863.42, "duration": 1.68}, {"text": "And you wouldn't really\ndo much different.", "start": 3865.1, "duration": 2.45}, {"text": "I mean everything is\nmore or less the same", "start": 3867.55, "duration": 1.75}, {"text": "what I've said so\nfar, although we", "start": 3869.3, "duration": 1.71}, {"text": "had to do a special\ncalculation algebraically that", "start": 3871.01, "duration": 2.13}, {"text": "didn't really make sense--", "start": 3873.14, "duration": 1.15}, {"text": "I mean, that you have to show\nsome kind of near independence.", "start": 3874.29, "duration": 3.62}, {"text": "Question?", "start": 3877.91, "duration": 0.795}, {"text": "AUDIENCE: Is that less\nthan or equal to, right?", "start": 3878.705, "duration": 4.75}, {"text": "The Markov inequality.", "start": 3883.455, "duration": 0.938}, {"text": "YUFEI ZHAO: Ah, thank you.", "start": 3884.393, "duration": 1.457}, {"text": "So this is less\nthan or equal to.", "start": 3885.85, "duration": 1.62}, {"text": "Thank you.", "start": 3887.47, "duration": 2.56}, {"text": "But now is where the\nalgebra comes in,", "start": 3890.03, "duration": 2.92}, {"text": "so the algebraic geometry nature\nof this argument comes in.", "start": 3892.95, "duration": 3.23}, {"text": "It turns out that\nthis quantity here--", "start": 3896.18, "duration": 2.76}, {"text": "previously, we said,\nat least heuristically,", "start": 3902.99, "duration": 2.64}, {"text": "in the random graphs case,\nit behaves like a qua Poisson", "start": 3905.63, "duration": 3.09}, {"text": "random variable.", "start": 3908.72, "duration": 1.42}, {"text": "So it's fairly uniform\nin a Poisson sense.", "start": 3910.14, "duration": 3.76}, {"text": "It turns out because\nof the algebraic nature", "start": 3913.9, "duration": 2.04}, {"text": "of the construction,\nthis random variable", "start": 3915.94, "duration": 1.92}, {"text": "behaves nothing like a Poisson.", "start": 3917.86, "duration": 2.16}, {"text": "So it turns out it's highly\nconstrained due to reasons", "start": 3920.02, "duration": 11.57}, {"text": "using algebraic geometry.", "start": 3931.59, "duration": 1.2}, {"text": "And I'll tell you exactly why.", "start": 3932.79, "duration": 2.61}, {"text": "So that the number\nof common neighbors", "start": 3935.4, "duration": 1.92}, {"text": "is either very\nsmall or very large.", "start": 3937.32, "duration": 3.3}, {"text": "And here is the claim\nthat for every s and d,", "start": 3940.62, "duration": 9.93}, {"text": "there exists some\nc, such that if I", "start": 3950.55, "duration": 4.11}, {"text": "have a bunch of polynomials\non fq to the s of degree", "start": 3954.66, "duration": 12.38}, {"text": "o at most d, then if you\nlook at the number of zeros,", "start": 3967.04, "duration": 7.22}, {"text": "common zeros, of the f's, how\nmany common zeros can you have?", "start": 3974.26, "duration": 15.6}, {"text": "It turns out it cannot just\nbe some arbitrary number.", "start": 3989.86, "duration": 2.37}, {"text": "So this set has size\neither bounded at most c.", "start": 3992.23, "duration": 10.17}, {"text": "Or it is at least q minus\nsomething very small.", "start": 4002.4, "duration": 6.2}, {"text": "And I'll explain\njust a little bit", "start": 4011.52, "duration": 1.47}, {"text": "why this is the case, although\nI will not give a proof.", "start": 4012.99, "duration": 2.8}, {"text": "So either somehow\nyou are working", "start": 4015.79, "duration": 3.14}, {"text": "in a zero dimensional case, or\nif this algebraic variety that", "start": 4018.93, "duration": 7.96}, {"text": "comes with it has\npositive dimension,", "start": 4026.89, "duration": 3.78}, {"text": "then you should have\na lot more points.", "start": 4030.67, "duration": 1.93}, {"text": "And the reason\nfor this dichotomy", "start": 4046.36, "duration": 2.94}, {"text": "has to do with how\nmany points are there", "start": 4049.3, "duration": 4.44}, {"text": "on the algebraic variety\nover a finite field?", "start": 4053.74, "duration": 5.32}, {"text": "So I will not give a\nproof, although if you", "start": 4059.06, "duration": 2.302}, {"text": "look on the course website\nfor a link to a reference,", "start": 4061.362, "duration": 2.208}, {"text": "that does have a proof.", "start": 4063.57, "duration": 1.61}, {"text": "But I will tell you what\nthe key algebraic geometric", "start": 4065.18, "duration": 2.49}, {"text": "input is to that claim up here.", "start": 4067.67, "duration": 3.28}, {"text": "And this is a important\nand famous theorem", "start": 4070.95, "duration": 3.96}, {"text": "called a Lang Weil bound.", "start": 4074.91, "duration": 1.42}, {"text": "So the Lang Weil bound\ntells you that if you", "start": 4081.18, "duration": 3.79}, {"text": "have an algebraic variety, v.\nAnd for now, it is important", "start": 4084.97, "duration": 8.28}, {"text": "in order to say this properly to\nwork in the algebraic closure,", "start": 4093.25, "duration": 6.51}, {"text": "so Fq bar as the\nalgebraic closure,", "start": 4099.76, "duration": 7.3}, {"text": "it's the smallest field\nextension where I can", "start": 4107.06, "duration": 2.5}, {"text": "solve all polynomial equations.", "start": 4109.56, "duration": 3.95}, {"text": "Then, the variety cut out\nby a set of polynomials--", "start": 4113.51, "duration": 7.701}, {"text": "so v is this variety.", "start": 4125.45, "duration": 1.26}, {"text": "So if it is irreducible, it\ncannot be written as a union", "start": 4126.71, "duration": 6.71}, {"text": "of finite number of\nsmaller varieties,", "start": 4133.42, "duration": 3.88}, {"text": "irreducible over Fq bar.", "start": 4137.3, "duration": 5.19}, {"text": "And all of these polynomials\nhave degree bounded.", "start": 4142.49, "duration": 7.08}, {"text": "Then the question is, if\nI take these polynomials", "start": 4152.24, "duration": 5.98}, {"text": "and I look at how many\nFq points does it have?", "start": 4158.22, "duration": 4.61}, {"text": "So in other words,\nnow I leave the field.", "start": 4162.83, "duration": 2.56}, {"text": "I come back down to Earth,\nto the base field and ask,", "start": 4165.39, "duration": 4.259}, {"text": "what's the number\nof solutions where", "start": 4169.649, "duration": 3.571}, {"text": "the coordinates are in Fq?", "start": 4173.22, "duration": 1.24}, {"text": "OK, so how many\npoints do we expect?", "start": 4179.04, "duration": 1.75}, {"text": "Well, the simplest example\nof an algebraic variety", "start": 4180.79, "duration": 2.23}, {"text": "is that of a subspace.", "start": 4183.02, "duration": 2.169}, {"text": "If you have a d-dimensional\nsubspace over Fq,", "start": 4185.189, "duration": 3.451}, {"text": "you have q to the\nd points exactly.", "start": 4188.64, "duration": 3.21}, {"text": "So you expect something like\nq raised to the dimension", "start": 4191.85, "duration": 5.61}, {"text": "of the variety.", "start": 4197.46, "duration": 1.55}, {"text": "Now the dimensions is actually\na somewhat subtle concept.", "start": 4199.01, "duration": 2.92}, {"text": "I won't define.", "start": 4201.93, "duration": 0.82}, {"text": "But there are many definitions\nin algebraic geometry.", "start": 4202.75, "duration": 3.32}, {"text": "It turns out it's not\nalways exactly as nice", "start": 4206.07, "duration": 2.31}, {"text": "as in the case of\nlinear subspaces.", "start": 4208.38, "duration": 1.98}, {"text": "But the Lang Weil bound tells\nus that is not too far off.", "start": 4210.36, "duration": 3.27}, {"text": "You have a deviation\nthat is at most", "start": 4213.63, "duration": 5.7}, {"text": "on the order of q 1\nover root q, where", "start": 4219.33, "duration": 3.03}, {"text": "there are some hidden\nconstants depending", "start": 4222.36, "duration": 2.7}, {"text": "on the description of\nyour variety in terms", "start": 4225.06, "duration": 3.63}, {"text": "of the degrees of the\npolynomial with the dimension", "start": 4228.69, "duration": 2.25}, {"text": "and the number of polynomials.", "start": 4230.94, "duration": 1.47}, {"text": "But the point is that the\nnumber of points on this variety", "start": 4232.41, "duration": 3.83}, {"text": "is basically should be\naround the same as the model", "start": 4236.24, "duration": 4.06}, {"text": "case, namely that of a subspace.", "start": 4240.3, "duration": 1.365}, {"text": "And that brings\nus some intuition", "start": 4244.54, "duration": 2.1}, {"text": "to why this lemma is true.", "start": 4246.64, "duration": 1.59}, {"text": "So you have those\npolynomials up there.", "start": 4248.23, "duration": 2.592}, {"text": "So there are some\nsubtle points one", "start": 4250.822, "duration": 1.458}, {"text": "needs to verify about\nyour disability,", "start": 4252.28, "duration": 1.92}, {"text": "but the punchline\nis that either you", "start": 4254.2, "duration": 2.79}, {"text": "are in the zero-dimensional\ncase, in which case", "start": 4256.99, "duration": 2.477}, {"text": "you have something like\n[INAUDIBLE] theorem,", "start": 4259.467, "duration": 1.833}, {"text": "and that tells you that a\nnumber of solutions is bounded.", "start": 4261.3, "duration": 4.29}, {"text": "Or you're in the positive\ndimensional case, in which case", "start": 4265.59, "duration": 2.495}, {"text": "the Lang Weil term\ntells you, you", "start": 4268.085, "duration": 1.375}, {"text": "must have lots of solutions.", "start": 4269.46, "duration": 1.98}, {"text": "And there is no middle ground.", "start": 4271.44, "duration": 1.74}, {"text": "And now, we're ready to finish\noff Boris Bukh's construction.", "start": 4276.17, "duration": 4.466}, {"text": "So we see that applying this\nlemma up there with this, what", "start": 4286.1, "duration": 9.48}, {"text": "should be my polynomials be?", "start": 4295.58, "duration": 2.11}, {"text": "I'm going to use my polynomials\nf sub u of y to be--", "start": 4297.69, "duration": 8.39}, {"text": "well, I have a random\npolynomial up there.", "start": 4306.08, "duration": 3.22}, {"text": "So I'm trying to find\ncommon neighbors.", "start": 4309.3, "duration": 4.34}, {"text": "I'm trying to find\ncommon solutions.", "start": 4313.64, "duration": 2.37}, {"text": "So these are my polynomial\nas u ranges over big U.", "start": 4319.97, "duration": 8.48}, {"text": "So for q large enough,\nwe find that the number", "start": 4328.45, "duration": 9.39}, {"text": "of common neighbors of u, the\nprobability that it is bigger", "start": 4337.84, "duration": 6.48}, {"text": "than c, where c is\nsupplied by that lemma,", "start": 4344.32, "duration": 6.28}, {"text": "is equal to the probability that\na number of common neighbors", "start": 4350.6, "duration": 4.4}, {"text": "of u exceeds q over 2, where\nq over w is this quantity", "start": 4355.0, "duration": 6.43}, {"text": "rounded--", "start": 4361.43, "duration": 1.35}, {"text": "smaller than that\nquantity up there.", "start": 4362.78, "duration": 2.63}, {"text": "So if it has more\nthan c solutions,", "start": 4365.41, "duration": 1.81}, {"text": "that automatically has\na lot of solutions.", "start": 4367.22, "duration": 1.95}, {"text": "And now, we can apply the\nMarkov inequality up there,", "start": 4372.23, "duration": 3.66}, {"text": "the tail bound on the moments to\ndeduce that this probability is", "start": 4375.89, "duration": 4.44}, {"text": "at most M divided by q over\n2 raised to the power d.", "start": 4380.33, "duration": 5.07}, {"text": "And the moral of it\nis that we should", "start": 4388.58, "duration": 1.98}, {"text": "have a very small number--", "start": 4390.56, "duration": 2.34}, {"text": "I mean, this should occur\nwith very small probability.", "start": 4392.9, "duration": 3.13}, {"text": "So let's call u being a subset\nof v bad if u has r elements, u", "start": 4396.03, "duration": 13.11}, {"text": "is contained entirely on the\nleft side or the right side", "start": 4409.14, "duration": 3.64}, {"text": "of the original bipartition.", "start": 4412.78, "duration": 2.7}, {"text": "And most importantly, u has\na lot, namely more than c,", "start": 4415.48, "duration": 5.76}, {"text": "common neighbors in j.", "start": 4421.24, "duration": 7.87}, {"text": "So how many bad\nsets do we expect?", "start": 4433.086, "duration": 3.564}, {"text": "Basically, a very small number.", "start": 4436.65, "duration": 2.29}, {"text": "So the number of\nbad sets, bad use,", "start": 4438.94, "duration": 8.38}, {"text": "is upper bounded by-- well,\nfor each choice of s elements,", "start": 4447.32, "duration": 4.86}, {"text": "the probability that\nsomething is bad", "start": 4452.18, "duration": 1.95}, {"text": "is this quantity up here,\nwhich we chose d to be a large", "start": 4454.13, "duration": 8.68}, {"text": "enough constant depending on s.", "start": 4462.81, "duration": 1.89}, {"text": "If you look at the\nchoice of d up there,", "start": 4464.7, "duration": 3.18}, {"text": "see that this quantity\nhere is quite a bit smaller", "start": 4467.88, "duration": 4.47}, {"text": "than the number of vertices.", "start": 4472.35, "duration": 2.19}, {"text": "And now, the last step is\nthe same as our randomized", "start": 4480.73, "duration": 11.34}, {"text": "construction using\nErdos-Renyi random graphs,", "start": 4492.07, "duration": 3.9}, {"text": "where we remove--", "start": 4495.97, "duration": 3.21}, {"text": "well, it's almost\nthe same, but now", "start": 4499.18, "duration": 1.7}, {"text": "we remove one vertex\nfrom every bad set.", "start": 4500.88, "duration": 5.76}, {"text": "And we get some graph g prime.", "start": 4517.36, "duration": 5.16}, {"text": "And we just need to check that\ng prime has lots of edges.", "start": 4522.52, "duration": 4.02}, {"text": "We know got rid of\nall the bad sets.", "start": 4526.54, "duration": 2.46}, {"text": "So g prime is now K\nsub sc plus 1 free.", "start": 4529.0, "duration": 9.18}, {"text": "We got rid of all possibilities\nfor s points having", "start": 4542.39, "duration": 3.72}, {"text": "more than c common neighbors.", "start": 4546.11, "duration": 2.93}, {"text": "Now, we just need to check\nthat g prime has lots of edges.", "start": 4549.04, "duration": 3.68}, {"text": "Well, the expected number\nof edges in g prime", "start": 4552.72, "duration": 4.15}, {"text": "is at least the x--", "start": 4556.87, "duration": 4.31}, {"text": "what we removed one\nvertex for every bad u.", "start": 4561.18, "duration": 8.57}, {"text": "And each bad u carries\nwith it at most n edges,", "start": 4569.75, "duration": 5.46}, {"text": "because there are only n edge\non each side of the bipartition.", "start": 4575.21, "duration": 3.824}, {"text": "And, well, the\nnumber of edges of g", "start": 4586.95, "duration": 2.86}, {"text": "has expectations exactly\nn squared over q.", "start": 4589.81, "duration": 3.72}, {"text": "And the number of bad u's we\nsaw up there is not very large.", "start": 4596.36, "duration": 10.42}, {"text": "So in particular, this\nquantity, the second term", "start": 4606.78, "duration": 5.13}, {"text": "is dominated by the first term.", "start": 4611.91, "duration": 2.98}, {"text": "And so we obtain the\nclaimed number of edges.", "start": 4614.89, "duration": 6.75}, {"text": "Also, the graph has\nat most 2n vertices.", "start": 4629.3, "duration": 7.25}, {"text": "So we may have gotten\ngot rid of some.", "start": 4636.55, "duration": 2.08}, {"text": "But actually, fewer\nvertices, the better.", "start": 4638.63, "duration": 2.67}, {"text": "At most, 2n vertices,\nand it is a case of s--", "start": 4641.3, "duration": 7.49}, {"text": "So it's Kst free\nfor t large enough.", "start": 4648.79, "duration": 2.4}, {"text": "So this gives you\nanother construction", "start": 4654.32, "duration": 2.19}, {"text": "of Kst free graphs.", "start": 4656.51, "duration": 2.67}, {"text": "And so today, we saw two\ndifferent constructions", "start": 4659.18, "duration": 2.0}, {"text": "of Kst free graphs for constants\ns and t, but in both cases,", "start": 4661.18, "duration": 3.84}, {"text": "t is substantially\nlarger than s.", "start": 4665.02, "duration": 2.67}, {"text": "But the most important thing\nis that they both match", "start": 4667.69, "duration": 2.58}, {"text": "the Kovari-Sos-Turan bound.", "start": 4670.27, "duration": 4.11}, {"text": "So it gives you some\nevidence that maybe", "start": 4674.38, "duration": 3.46}, {"text": "the Kovari-Sos-Turan\nconjecture, the theorem,", "start": 4677.84, "duration": 3.45}, {"text": "is tight up to at most a\nconstant factor, although that", "start": 4681.29, "duration": 3.42}, {"text": "is a major open problem.", "start": 4684.71, "duration": 1.86}, {"text": "And it remains a very difficult\nit seems open problem, but one", "start": 4686.57, "duration": 4.86}, {"text": "that is of central importance\nin extremal graph theory", "start": 4691.43, "duration": 3.93}, {"text": "to try to come up perhaps\nwith other constructions", "start": 4695.36, "duration": 5.14}, {"text": "that can do better.", "start": 4700.5, "duration": 1.7}, {"text": "Maybe they will have\nsome algebraic input.", "start": 4702.2, "duration": 2.85}, {"text": "But maybe they will have\nsome input from other ideas.", "start": 4705.05, "duration": 3.07}, {"text": "We do not know.", "start": 4708.12, "duration": 1.1}, {"text": "Question?", "start": 4709.22, "duration": 0.806}, {"text": "AUDIENCE: So is this q defined?", "start": 4710.026, "duration": 2.38}, {"text": "Because I remember\nq as a prime power,", "start": 4712.406, "duration": 2.023}, {"text": "but it doesn't say there.", "start": 4714.429, "duration": 1.321}, {"text": "YUFEI ZHAO: So question\nis, is q defined?", "start": 4715.75, "duration": 1.76}, {"text": "So just like in the proofs of\npolarity graphs and what not--", "start": 4717.51, "duration": 3.39}, {"text": "so you have some n.", "start": 4720.9, "duration": 2.85}, {"text": "You rounded down to the\nnearest prime powers.", "start": 4723.75, "duration": 3.39}, {"text": "So s is a constant.", "start": 4727.14, "duration": 1.23}, {"text": "So n is basically q to the s.", "start": 4728.37, "duration": 3.78}, {"text": "So take large n, round it down\nto the nearest prime power.", "start": 4732.15, "duration": 4.05}, {"text": "q could be a prime,\nfor instance.", "start": 4736.2, "duration": 1.512}, {"text": "It could be a prime.", "start": 4737.712, "duration": 0.833}, {"text": "It could be a prime power.", "start": 4738.545, "duration": 1.595}, {"text": "Think q to be a prime.", "start": 4740.14, "duration": 1.16}, {"text": "So I'm saying for every q,\nthere is a construction.", "start": 4744.05, "duration": 3.37}, {"text": "And for every n, you can round\ndown to the nearest q to the s", "start": 4747.42, "duration": 5.37}, {"text": "and then run this construction.", "start": 4752.79, "duration": 4.61}, {"text": "Any more questions?", "start": 4757.4, "duration": 2.55}, {"text": "Great.", "start": 4759.95, "duration": 0.5}, {"text": "So next time I will begin by\ntelling you a few more things", "start": 4760.45, "duration": 3.78}, {"text": "about why people really\nlike this construction", "start": 4764.23, "duration": 3.54}, {"text": "and some conjectures that\nwere solved using this idea", "start": 4767.77, "duration": 3.428}, {"text": "and some conjectures\nthat still remain open", "start": 4771.198, "duration": 1.792}, {"text": "along the same lines.", "start": 4772.99, "duration": 1.66}, {"text": "And we'll also go beyond Kst,\nso other bipartide graphs", "start": 4774.65, "duration": 4.88}, {"text": "and show you how\nto do upper bounds", "start": 4779.53, "duration": 1.53}, {"text": "for those bipartide graphs.", "start": 4781.06, "duration": 2.33}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.98}, {"text": "[RUSTLING]", "start": 1.98, "duration": 1.98}, {"text": "[CLICKING]", "start": 3.96, "duration": 1.98}, {"text": "MICHAEL SIPSER: All right,\nwhy don't we get started?", "start": 25.323, "duration": 2.167}, {"text": "It's 2:35, time to begin.", "start": 27.49, "duration": 5.33}, {"text": "So everyone, welcome back--", "start": 32.82, "duration": 2.43}, {"text": "good to see you all.", "start": 35.25, "duration": 2.99}, {"text": "Well, at least a few of you--", "start": 38.24, "duration": 2.513}, {"text": "glad that you're here.", "start": 40.753, "duration": 0.917}, {"text": "So let's see.", "start": 44.32, "duration": 3.85}, {"text": "Why don't I get a layout, as I\nusually do, where we have been,", "start": 48.17, "duration": 5.14}, {"text": "where we're going today.", "start": 53.31, "duration": 1.14}, {"text": "I'll talk a little tiny\nbit about the homework,", "start": 54.45, "duration": 1.958}, {"text": "because I've gotten a\ncouple of questions on that.", "start": 56.408, "duration": 2.302}, {"text": "And then we'll jump in.", "start": 58.71, "duration": 2.7}, {"text": "So we have been talking\nabout Turing machines, which", "start": 61.41, "duration": 5.4}, {"text": "is going to be our\npreferred model for the rest", "start": 66.81, "duration": 3.78}, {"text": "of the semester, since Turing\nmachines are the model which", "start": 70.59, "duration": 4.74}, {"text": "we use to capture general\npurpose computing.", "start": 75.33, "duration": 4.74}, {"text": "And we looked at Turing\nmachines in various variations", "start": 80.07, "duration": 7.73}, {"text": "on Turing machines--\nmulti-tapes, non-deterministic,", "start": 87.8, "duration": 3.21}, {"text": "and so on.", "start": 91.01, "duration": 2.64}, {"text": "It's a bit recapping the history\nof the subject, when people", "start": 93.65, "duration": 3.78}, {"text": "looked at a variety of\ndifferent ways of formalizing", "start": 97.43, "duration": 4.23}, {"text": "the notion of algorithm.", "start": 101.66, "duration": 1.53}, {"text": "And they showed that all of\nthose different formalizations", "start": 103.19, "duration": 5.46}, {"text": "were equivalent to one another,\nwhich led to the Church-Turing", "start": 108.65, "duration": 3.24}, {"text": "thesis that all\nof these models--", "start": 111.89, "duration": 3.18}, {"text": "each of these models really\ncapture our intuitive idea", "start": 115.07, "duration": 3.36}, {"text": "of what we mean by a procedure\nor an algorithm for--", "start": 118.43, "duration": 8.22}, {"text": "at least for addressing things\nlike mathematical problems", "start": 126.65, "duration": 4.59}, {"text": "and precise problems\nof that kind.", "start": 131.24, "duration": 3.96}, {"text": "So we talked about the\nChurch-Turing thesis.", "start": 135.2, "duration": 2.31}, {"text": "We also talked about a notation\nfor encodings and Turing", "start": 137.51, "duration": 2.92}, {"text": "machines.", "start": 140.43, "duration": 0.5}, {"text": "We'll review that briefly.", "start": 140.93, "duration": 3.3}, {"text": "So today we're going to give\na bunch of examples of Turing", "start": 144.23, "duration": 4.38}, {"text": "machine algorithms for solving\na variety of different problems.", "start": 148.61, "duration": 3.078}, {"text": "I should just say\nalgorithms really--", "start": 151.688, "duration": 1.542}, {"text": "nothing special about\nTuring machines.", "start": 153.23, "duration": 1.65}, {"text": "Turing machines are just going\nto be our formal counterpart.", "start": 154.88, "duration": 3.42}, {"text": "But from now on, we're going\nto use our Church-Turing thesis", "start": 158.3, "duration": 4.83}, {"text": "in a way to just talk about\nalgorithms in general,", "start": 163.13, "duration": 2.13}, {"text": "because that's\nreally our interest.", "start": 165.26, "duration": 1.56}, {"text": "Turing machines is just our\nway of reasoning about them", "start": 166.82, "duration": 4.44}, {"text": "mathematically, but\nwe're really ultimately", "start": 171.26, "duration": 1.89}, {"text": "interested in\nunderstanding algorithms.", "start": 173.15, "duration": 1.625}, {"text": "In terms of the format\nof today's class,", "start": 177.82, "duration": 2.1}, {"text": "I'm going to try a\nlittle experiment.", "start": 179.92, "duration": 3.07}, {"text": "We're going to have little\nbreaks along the way,", "start": 182.99, "duration": 3.11}, {"text": "as well as the big coffee\nbreak in the middle.", "start": 186.1, "duration": 2.64}, {"text": "We're going to have a little\nmini breaks, because I", "start": 188.74, "duration": 2.49}, {"text": "sometimes feel that there really\nisn't enough time for people", "start": 191.23, "duration": 2.94}, {"text": "to be writing chat--", "start": 194.17, "duration": 2.73}, {"text": "questions in the chat, because\nthings just are racing on.", "start": 196.9, "duration": 4.01}, {"text": "And so this way we'll have\na little break after the--", "start": 200.91, "duration": 2.98}, {"text": "pretty much after each slide.", "start": 203.89, "duration": 1.32}, {"text": "Some of them are going to be\na little longer than others.", "start": 205.21, "duration": 2.49}, {"text": "In case you have questions,\nyou can pose them", "start": 207.7, "duration": 2.1}, {"text": "to me or to the TAs, and\nwe'll try to get back to you", "start": 209.8, "duration": 3.0}, {"text": "on those.", "start": 212.8, "duration": 1.45}, {"text": "So moving on then, so today,\njust as a quick review,", "start": 214.25, "duration": 6.15}, {"text": "Turing machines, as we\nset them up, they have--", "start": 220.4, "duration": 4.65}, {"text": "on any input w, they have\nthree possible outcomes.", "start": 225.05, "duration": 4.05}, {"text": "The Turing machine\ncan halt and accept w,", "start": 229.1, "duration": 3.03}, {"text": "can halt and reject w,\nor it can go forever", "start": 232.13, "duration": 3.84}, {"text": "on w, which is rejecting\nby looping in our language.", "start": 235.97, "duration": 3.96}, {"text": "A Turing machine can recognize\na language, the collection", "start": 242.65, "duration": 3.78}, {"text": "of old strings that it accepts.", "start": 246.43, "duration": 2.1}, {"text": "And if the Turing\nmachine always halts,", "start": 248.53, "duration": 2.25}, {"text": "we say it decides the\nlanguage, and it's a decider,", "start": 250.78, "duration": 2.79}, {"text": "and so therefore, that language\nis a decided language, a Turing", "start": 253.57, "duration": 3.3}, {"text": "decider.", "start": 256.87, "duration": 0.742}, {"text": "Often we just say decidable,\nbecause we don't really", "start": 257.612, "duration": 2.167}, {"text": "have a notion of\ndeciding in other models,", "start": 259.779, "duration": 3.631}, {"text": "so we often talk about\nTuring-recognizable", "start": 263.41, "duration": 2.64}, {"text": "or just decidable.", "start": 266.05, "duration": 0.91}, {"text": "Or we'll sometimes\njust say recognizable,", "start": 266.96, "duration": 1.79}, {"text": "when we understand that we're\ntalking about Turing machines.", "start": 268.75, "duration": 4.71}, {"text": "We briefly talked\nabout encodings.", "start": 273.46, "duration": 3.93}, {"text": "When you write it inside\nbrackets, some objects--", "start": 277.39, "duration": 2.7}, {"text": "whatever they are-- could be\nstrings, could be machines,", "start": 280.09, "duration": 2.64}, {"text": "could be graphs,\ncould be polynomials--", "start": 282.73, "duration": 3.48}, {"text": "we're representing\nthem as strings,", "start": 286.21, "duration": 3.27}, {"text": "and maybe a\ncollection of objects", "start": 289.48, "duration": 1.41}, {"text": "together represented\nas a string in order", "start": 290.89, "duration": 2.52}, {"text": "so that we can present\nthat information", "start": 293.41, "duration": 1.83}, {"text": "as an input to a machine.", "start": 295.24, "duration": 2.28}, {"text": "And we talk about--", "start": 297.52, "duration": 1.29}, {"text": "our languages our\ncollections of strings.", "start": 298.81, "duration": 3.93}, {"text": "And a notation for\nwriting a Turing machine", "start": 302.74, "duration": 2.1}, {"text": "is going to be simply that\nEnglish description put", "start": 304.84, "duration": 4.47}, {"text": "inside quotation\nmarks to represent", "start": 309.31, "duration": 2.25}, {"text": "our informal way of talking\nabout the formal object", "start": 311.56, "duration": 3.3}, {"text": "that we could produce,\nif we wanted to.", "start": 314.86, "duration": 1.77}, {"text": "But we're never going\nto ask you to do that.", "start": 316.63, "duration": 3.33}, {"text": "OK, so now let me see.", "start": 319.96, "duration": 8.605}, {"text": "Let's just take a quick\nbreak, as I promised.", "start": 331.695, "duration": 1.875}, {"text": "If there's any quick\nquestions here, you can ask.", "start": 340.518, "duration": 2.042}, {"text": "Let's see-- got a lot\nof questions here.", "start": 372.04, "duration": 2.49}, {"text": "All right, why don't we move on?", "start": 378.18, "duration": 1.53}, {"text": "And some of these things\nare good questions.", "start": 379.71, "duration": 4.53}, {"text": "Somebody asked, can\nyou-- how do you", "start": 384.24, "duration": 1.83}, {"text": "tell if the machine is looping\nor if it's really just taking", "start": 386.07, "duration": 3.57}, {"text": "a very long time?", "start": 389.64, "duration": 2.46}, {"text": "You can't.", "start": 392.1, "duration": 1.61}, {"text": "That's what we're going to\nprove not in today's lecture,", "start": 393.71, "duration": 2.56}, {"text": "but going to prove\nthat on Thursday.", "start": 396.27, "duration": 1.5}, {"text": "You just can't tell.", "start": 400.73, "duration": 1.35}, {"text": "So if that's in\nreference to problem 5,", "start": 402.08, "duration": 2.04}, {"text": "you're going to have to find\nsome other way of doing--", "start": 404.12, "duration": 2.25}, {"text": "solving that problem without\nknowing whether the machine is", "start": 406.37, "duration": 2.61}, {"text": "actually ever going to halt.", "start": 408.98, "duration": 5.57}, {"text": "And somebody asked,\nhow can we tell", "start": 414.55, "duration": 2.61}, {"text": "if an English description is\npossible for a Turing machine?", "start": 417.16, "duration": 2.79}, {"text": "Well, you can always write\ndown an English description", "start": 419.95, "duration": 6.15}, {"text": "for any machine.", "start": 426.1, "duration": 1.65}, {"text": "It's-- might be very\ntechnical looking,", "start": 427.75, "duration": 4.18}, {"text": "but if you can write it down\nin a formal way as states", "start": 431.93, "duration": 2.84}, {"text": "and transitions, then you can\nsimply write down an English", "start": 434.77, "duration": 2.52}, {"text": "description, which would\njust be, follow those states.", "start": 437.29, "duration": 5.46}, {"text": "OK, let's move on.", "start": 442.75, "duration": 1.41}, {"text": "OK, this is going to\nbe our first example", "start": 449.3, "duration": 3.18}, {"text": "of a algorithm that's\ngoing to answer", "start": 452.48, "duration": 4.78}, {"text": "a question about automata.", "start": 457.26, "duration": 4.13}, {"text": "And it's a very simple problem.", "start": 461.39, "duration": 1.48}, {"text": "It's a very simple\nproblem to solve,", "start": 462.87, "duration": 3.8}, {"text": "because we want\nto start out easy.", "start": 466.67, "duration": 1.485}, {"text": "The name of the problem\nis the acceptance problem", "start": 471.14, "duration": 2.64}, {"text": "for deterministic\nfinite automata,", "start": 473.78, "duration": 2.7}, {"text": "acceptance problem for DFAs.", "start": 476.48, "duration": 3.08}, {"text": "And I'm going to express it,\nas I always do, as a language.", "start": 479.56, "duration": 4.67}, {"text": "So with this language here,\nI'm calling it a ADFA--", "start": 484.23, "duration": 3.11}, {"text": "which stands for the\nacceptance problem for DFAs--", "start": 487.34, "duration": 3.36}, {"text": "is the collection of pairs.", "start": 490.7, "duration": 3.57}, {"text": "B and w--", "start": 494.27, "duration": 1.05}, {"text": "B is a DFA.", "start": 495.32, "duration": 2.25}, {"text": "w is considered to be\nsome other string, which", "start": 497.57, "duration": 4.2}, {"text": "will be an input to B.\nWe're going to be thinking", "start": 501.77, "duration": 2.67}, {"text": "of it as an input to B.\nI put the two of them", "start": 504.44, "duration": 2.67}, {"text": "in brackets to represent\nthe pair of them", "start": 507.11, "duration": 2.61}, {"text": "as a single string.", "start": 509.72, "duration": 2.84}, {"text": "We're not going to make explicit\nwhat the form of the encoding", "start": 512.56, "duration": 2.78}, {"text": "is.", "start": 515.34, "duration": 0.5}, {"text": "The only important thing\nis that the encoding should", "start": 515.84, "duration": 2.579}, {"text": "be something simple, but\nthat the Turing machine", "start": 518.419, "duration": 3.721}, {"text": "can decode back into the DFA and\nthis input string to that DFA.", "start": 522.14, "duration": 6.78}, {"text": "So anything reasonable is going\nto be a satisfactory encoding", "start": 528.92, "duration": 4.08}, {"text": "from us-- for us.", "start": 533.0, "duration": 2.18}, {"text": "So this is an encoding of the\ntwo of them into a string,", "start": 535.18, "duration": 3.05}, {"text": "and where B is a\nDFA, and B accepts w.", "start": 538.23, "duration": 3.3}, {"text": "So now, if you want to test if\nsomething's a member of ADFA,", "start": 541.53, "duration": 6.51}, {"text": "then, first of all,\nyou want to make sure", "start": 548.04, "duration": 2.46}, {"text": "that the string itself\nthat you're getting really", "start": 550.5, "duration": 3.45}, {"text": "encodes a DFA and a string.", "start": 553.95, "duration": 3.96}, {"text": "So it has to be the right form.", "start": 557.91, "duration": 2.32}, {"text": "And once you know that,\nthen you have the DFA,", "start": 560.23, "duration": 4.28}, {"text": "you have the string\nw, and you're then", "start": 564.51, "duration": 2.37}, {"text": "going to do the\nobvious thing, which", "start": 566.88, "duration": 1.86}, {"text": "would be to simulate\nB on w and see", "start": 568.74, "duration": 2.97}, {"text": "if it's actually accepting w.", "start": 571.71, "duration": 3.78}, {"text": "So that's what the\ncontent of this slide is.", "start": 575.49, "duration": 2.89}, {"text": "I'm just going to\nwrite it down for you.", "start": 578.38, "duration": 2.237}, {"text": "So I'm going to give a\nTuring machine, which", "start": 580.617, "duration": 1.833}, {"text": "I'm going to call--", "start": 582.45, "duration": 1.2}, {"text": "the name of that Turing\nmachine is going to be D A DFA.", "start": 583.65, "duration": 2.92}, {"text": "To help you remember the\nfunction of this machine.", "start": 589.26, "duration": 3.07}, {"text": "This is a decider\nfor the language", "start": 592.33, "duration": 2.78}, {"text": "below, the ADFA language.", "start": 595.11, "duration": 2.4}, {"text": "This is just a name, but-- so\nnothing fancy going on here,", "start": 597.51, "duration": 2.73}, {"text": "but just to help us\nremember, because I'm", "start": 600.24, "duration": 2.1}, {"text": "going to refer to some of\nthese Turing machines later on.", "start": 602.34, "duration": 4.66}, {"text": "So this is the decider for ADFA.", "start": 607.0, "duration": 2.54}, {"text": "And I'm going to describe\nthat machine for you,", "start": 609.54, "duration": 2.01}, {"text": "and that machine decides\nthe ADFA language.", "start": 611.55, "duration": 4.94}, {"text": "So what does that mean?", "start": 616.49, "duration": 1.2}, {"text": "So that machine--", "start": 617.69, "duration": 1.2}, {"text": "I'm describing it now in\nEnglish, as I promised.", "start": 618.89, "duration": 3.41}, {"text": "We're going to take\nan input string s,", "start": 622.3, "duration": 3.69}, {"text": "and first, it's going to check\nthat s has the right form, as I", "start": 625.99, "duration": 4.53}, {"text": "mentioned-- has\nthe form which is", "start": 630.52, "duration": 2.25}, {"text": "the encoding of a DFA and a w.", "start": 632.77, "duration": 4.21}, {"text": "If it's not of that\nform, the Turing machine", "start": 636.98, "duration": 2.28}, {"text": "should reject that\ninput right away.", "start": 639.26, "duration": 2.735}, {"text": "Now, I'm not going to go through\nthe details of how that Turing", "start": 641.995, "duration": 2.625}, {"text": "machine is going to work, though\nI'll say a little bit more", "start": 644.62, "duration": 3.02}, {"text": "this time only just to give\nyou a sense of how it actually", "start": 647.64, "duration": 4.05}, {"text": "might carry that out.", "start": 651.69, "duration": 3.012}, {"text": "If you don't believe that\nyou can do it with a Turing", "start": 654.702, "duration": 2.208}, {"text": "machine, believe you could do it\nwith your favorite programming", "start": 656.91, "duration": 1.95}, {"text": "language.", "start": 658.86, "duration": 0.33}, {"text": "That's good enough,\nbecause that's", "start": 659.19, "duration": 1.417}, {"text": "going to be-- that's\nequivalent to a Turing machine.", "start": 660.607, "duration": 3.101}, {"text": "So first, you check that the\ninput's of the right form.", "start": 663.708, "duration": 2.292}, {"text": "Then you're going to simulate\nthe computation of B on w.", "start": 666.0, "duration": 2.93}, {"text": "And then, if B ends\nup in an accept state,", "start": 668.93, "duration": 2.72}, {"text": "then we know B is accepting the\ninput, and we should accept,", "start": 671.65, "duration": 2.5}, {"text": "and we do.", "start": 674.15, "duration": 1.23}, {"text": "If B does not end up in an\naccept state at the end of w,", "start": 675.38, "duration": 5.01}, {"text": "then we should reject,\nbecause B is not accepting w.", "start": 680.39, "duration": 3.61}, {"text": "OK?", "start": 684.0, "duration": 0.5}, {"text": "That's my description\nof this machine.", "start": 684.5, "duration": 4.44}, {"text": "Let's just turn to a\nlittle bit of details", "start": 688.94, "duration": 2.27}, {"text": "just to make sure we're\ncomfortable with this.", "start": 691.21, "duration": 2.86}, {"text": "So here is our Turing machine--", "start": 694.07, "duration": 3.32}, {"text": "D, the decider for ADFA.", "start": 697.39, "duration": 3.548}, {"text": "The input to that Turing\nmachine, as I mentioned,", "start": 700.938, "duration": 2.042}, {"text": "is going to be B and w,\nprovided it's of the right form.", "start": 702.98, "duration": 4.52}, {"text": "So that's what this string S\nis supposed to be of that form.", "start": 707.5, "duration": 3.31}, {"text": "And what does that mean?", "start": 710.81, "duration": 1.16}, {"text": "It's just an encoding of the\nmachine w and the string--", "start": 711.97, "duration": 3.66}, {"text": "the machine B and the string w.", "start": 715.63, "duration": 4.527}, {"text": "Let me just write it down.", "start": 720.157, "duration": 1.083}, {"text": "Here is B written down in some\njust completely explicit way,", "start": 721.24, "duration": 4.23}, {"text": "where you're just listing the\nstates of B, the alphabet of B,", "start": 725.47, "duration": 3.81}, {"text": "the transition function as\na table, the start state,", "start": 729.28, "duration": 3.21}, {"text": "and the set of\naccepting states--", "start": 732.49, "duration": 2.43}, {"text": "just writing it down\nexplicitly, as you might do it", "start": 734.92, "duration": 2.49}, {"text": "if you would just\nwant to describe", "start": 737.41, "duration": 1.5}, {"text": "that machine in a\ncompletely formal way,", "start": 738.91, "duration": 2.04}, {"text": "and then writing down\nwith the string is--", "start": 740.95, "duration": 3.48}, {"text": "whatever it is.", "start": 744.43, "duration": 2.2}, {"text": "Once DADFA has\nthat as its input,", "start": 746.63, "duration": 3.88}, {"text": "it can then go ahead\nand do that computation.", "start": 750.51, "duration": 2.6}, {"text": "And just to try to make it\na little bit more explicit,", "start": 753.11, "duration": 4.41}, {"text": "I'm going to capture\nthat here by saying,", "start": 757.52, "duration": 1.98}, {"text": "let's give that Turing\nmachine an extra tape,", "start": 759.5, "duration": 3.75}, {"text": "because we already know that the\nmulti-tape model is equivalent", "start": 763.25, "duration": 2.637}, {"text": "to the single tape model--", "start": 765.887, "duration": 1.083}, {"text": "make our life perhaps\na little easier.", "start": 766.97, "duration": 2.31}, {"text": "And in the course of doing\nthat simulation, what", "start": 769.28, "duration": 2.16}, {"text": "do we want to keep track of?", "start": 771.44, "duration": 1.29}, {"text": "Well, what is the current\nstate of B, the DFA,", "start": 772.73, "duration": 5.07}, {"text": "as we're reading\nthe symbols of w?", "start": 777.8, "duration": 3.18}, {"text": "And where in w are\nwe at right now?", "start": 780.98, "duration": 2.41}, {"text": "So I'll call that k, which is\nthe input head location on w.", "start": 783.39, "duration": 5.24}, {"text": "How many symbols\nof w have we read?", "start": 788.63, "duration": 3.71}, {"text": "OK?", "start": 792.34, "duration": 0.6}, {"text": "And that's all I'm going to say\nabout what this Turing machine", "start": 792.94, "duration": 4.95}, {"text": "D looks like.", "start": 797.89, "duration": 1.14}, {"text": "Oh, there's one more thing\nI do want to say for the--", "start": 802.6, "duration": 2.31}, {"text": "that's coming up, because pretty\nmuch all of the Turing machines", "start": 804.91, "duration": 6.24}, {"text": "that we're going to talk\nabout today and going forward", "start": 811.15, "duration": 2.94}, {"text": "are going to often want to\ncheck that their input is", "start": 814.09, "duration": 2.76}, {"text": "of the correct form.", "start": 816.85, "duration": 0.99}, {"text": "I don't want to repeat this\nevery time, because that's", "start": 817.84, "duration": 2.25}, {"text": "going to be assumed.", "start": 820.09, "duration": 1.41}, {"text": "So my shorthand for that is\nto say my input is of the form", "start": 821.5, "duration": 3.99}, {"text": "I'm looking for, and\nthat has built into it", "start": 825.49, "duration": 3.15}, {"text": "the check that the string--", "start": 828.64, "duration": 1.8}, {"text": "the input string\nis of that form,", "start": 830.44, "duration": 1.77}, {"text": "and we're going to\nreject if it is not.", "start": 832.21, "duration": 3.27}, {"text": "So all of our\nTuring machines are", "start": 835.48, "duration": 2.01}, {"text": "going to start out, on\ninput, the string is", "start": 837.49, "duration": 3.81}, {"text": "of a certain form, and then go\nout and do something with it.", "start": 841.3, "duration": 3.86}, {"text": "OK?", "start": 845.16, "duration": 0.5}, {"text": "OK, so let me try to answer\na few of the questions", "start": 853.37, "duration": 3.5}, {"text": "that I've gotten here, because\nI think this is important", "start": 856.87, "duration": 5.81}, {"text": "as a way of getting\nus all started.", "start": 862.68, "duration": 3.013}, {"text": "Now, somebody asked me, can\nwe use arguments of this form?", "start": 865.693, "duration": 2.417}, {"text": "Somebody asking, can we use--", "start": 871.85, "duration": 1.86}, {"text": "can we give our\ndescription of a procedure,", "start": 873.71, "duration": 4.7}, {"text": "if I'm understanding\nthis correctly,", "start": 878.41, "duration": 1.5}, {"text": "as using some other\nprogramming language?", "start": 879.91, "duration": 3.4}, {"text": "Well, typically, you just want\nto make sure you're understood.", "start": 883.31, "duration": 2.66}, {"text": "If you want to do\nthat on a homework,", "start": 885.97, "duration": 1.59}, {"text": "I wouldn't advocate writing\nyour algorithm in Java,", "start": 887.56, "duration": 4.607}, {"text": "because it's going\nto be hard to read.", "start": 892.167, "duration": 1.583}, {"text": "But write it down in some\npseudo programming language", "start": 893.75, "duration": 3.11}, {"text": "if you want, just to\nmake sure it's clear", "start": 896.86, "duration": 1.71}, {"text": "that-- what you're doing.", "start": 898.57, "duration": 1.422}, {"text": "Probably English is going\nto be the easiest for you--", "start": 899.992, "duration": 2.208}, {"text": "even though this person says--", "start": 906.42, "duration": 1.465}, {"text": "feels it would be\neasier to do it", "start": 907.885, "duration": 1.375}, {"text": "in terms of a formal language.", "start": 909.26, "duration": 2.13}, {"text": "Well, whatever's easier-- as\nlong as we can understand it.", "start": 911.39, "duration": 5.25}, {"text": "This is a good question\nhere I got to ask.", "start": 916.64, "duration": 2.04}, {"text": "What if B-- here's our\nB-- gets into a loop on w?", "start": 918.68, "duration": 7.61}, {"text": "Well, that's not\ngoing to happen.", "start": 926.29, "duration": 1.77}, {"text": "B is a DFA.", "start": 928.06, "duration": 1.02}, {"text": "DFAs-- they move from state\nto state every time they", "start": 929.08, "duration": 5.97}, {"text": "read a symbol of w.", "start": 935.05, "duration": 1.5}, {"text": "When they get to the end of\nw, it's the end of the story.", "start": 936.55, "duration": 2.52}, {"text": "There's no more\ncomputation to be done.", "start": 939.07, "duration": 2.07}, {"text": "So we know in exactly\nhow many steps", "start": 941.14, "duration": 2.22}, {"text": "B is ever going to\ntake on-- it's going", "start": 943.36, "duration": 2.13}, {"text": "to take the same number of steps\nas the length of the input.", "start": 945.49, "duration": 2.79}, {"text": "That's how many moves\nit gets to make.", "start": 948.28, "duration": 2.52}, {"text": "B as a DFA never loops.", "start": 950.8, "duration": 2.67}, {"text": "So that would be a problem if\nit did loop, but it doesn't.", "start": 953.47, "duration": 3.46}, {"text": "That input never does loop.", "start": 956.93, "duration": 3.93}, {"text": "So have we verified\nthat D is a decider?", "start": 960.86, "duration": 2.4}, {"text": "Well, I think I just did.", "start": 963.26, "duration": 1.62}, {"text": "From my standpoint, we've\nsaid enough to be sure", "start": 969.83, "duration": 3.6}, {"text": "that D is a decider.", "start": 973.43, "duration": 3.09}, {"text": "There's never any\nreason for D to be--", "start": 976.52, "duration": 2.49}, {"text": "for that DADFA Turing machine\nto be getting into a loop.", "start": 979.01, "duration": 5.565}, {"text": "The input head location\nis referring to where", "start": 984.575, "duration": 1.875}, {"text": "we are on the string w?", "start": 986.45, "duration": 1.45}, {"text": "Yes.", "start": 987.9, "duration": 0.5}, {"text": "And somebody's asking\nme, is this the level", "start": 994.278, "duration": 1.792}, {"text": "of detail for the homework?", "start": 996.07, "duration": 1.14}, {"text": "Yes.", "start": 997.21, "duration": 0.87}, {"text": "That's all I want.", "start": 998.08, "duration": 0.75}, {"text": "It's all I'm looking for.", "start": 998.83, "duration": 2.515}, {"text": "OK?", "start": 1001.345, "duration": 0.5}, {"text": "Let us move on.", "start": 1004.48, "duration": 2.67}, {"text": "I'm going to have to--", "start": 1007.15, "duration": 1.842}, {"text": "otherwise we'll\nnever get anywhere.", "start": 1008.992, "duration": 1.458}, {"text": "There are a lot\nof questions here.", "start": 1010.45, "duration": 1.417}, {"text": "They're good questions.", "start": 1011.867, "duration": 1.383}, {"text": "So why don't we go on?", "start": 1013.25, "duration": 1.91}, {"text": "Some of these may\nget resolved as we're", "start": 1015.16, "duration": 1.698}, {"text": "going to look at\nadditional examples,", "start": 1016.858, "duration": 1.542}, {"text": "because that's all of today\nis pretty much examples.", "start": 1018.4, "duration": 3.43}, {"text": "Let's talk about the similar\nproblem, the acceptance", "start": 1021.83, "duration": 2.827}, {"text": "problem, but now for NFAs.", "start": 1024.657, "duration": 1.083}, {"text": "So now, actually,\nNFAs can loop, so we", "start": 1029.39, "duration": 2.88}, {"text": "have to think about what\nthat possibly could look at.", "start": 1032.27, "duration": 2.68}, {"text": "But before we get ahead\nof ourselves-- so now", "start": 1034.95, "duration": 2.69}, {"text": "the acceptance problems for\nNFAs looked very similar,", "start": 1037.64, "duration": 2.679}, {"text": "except B is going to be an NFA.", "start": 1040.319, "duration": 3.78}, {"text": "That's going to be a\ndecidable language too.", "start": 1044.099, "duration": 3.331}, {"text": "And now we have\nTuring machine A--", "start": 1047.43, "duration": 2.31}, {"text": "DANFA, the decider for\nANFA that decides ANFA.", "start": 1049.74, "duration": 5.21}, {"text": "OK?", "start": 1054.95, "duration": 0.5}, {"text": "So now, as promised,\nhere's our new form", "start": 1055.45, "duration": 2.848}, {"text": "for writing our Turing machine.", "start": 1058.298, "duration": 1.292}, {"text": "On input B, w, we're\nassuming that B--", "start": 1059.59, "duration": 5.436}, {"text": "based on the context,\nsometimes you", "start": 1065.026, "duration": 2.004}, {"text": "may want to say at this\npoint, what B and w are.", "start": 1067.03, "duration": 2.217}, {"text": "But from the context,\nwe know what they are.", "start": 1069.247, "duration": 1.833}, {"text": "They're going to be an NFA\nand an input w for that NFA.", "start": 1071.08, "duration": 2.805}, {"text": "I do want to jump\ninto the solution.", "start": 1078.2, "duration": 3.31}, {"text": "First, before we actually look\nat the solution of this, we--", "start": 1081.51, "duration": 5.425}, {"text": "the Turing machine could\nsimulate the NFA on input w.", "start": 1086.935, "duration": 4.045}, {"text": "And you have to be\ncareful on that simulation", "start": 1090.98, "duration": 2.07}, {"text": "that you don't end up\nlooping, because don't forget,", "start": 1093.05, "duration": 4.47}, {"text": "an NFA could have epsilon\nmoves, and could be", "start": 1097.52, "duration": 4.71}, {"text": "looping on those epsilon moves.", "start": 1102.23, "duration": 2.31}, {"text": "And so that would be a problem,\nif you're not careful about how", "start": 1104.54, "duration": 4.38}, {"text": "you do that simulation.", "start": 1108.92, "duration": 1.14}, {"text": "Now, I think, if you were\ngoing to simulate an NFA,", "start": 1113.51, "duration": 4.38}, {"text": "you would be--", "start": 1117.89, "duration": 2.46}, {"text": "wouldn't follow loop\naround loops forever.", "start": 1120.35, "duration": 4.77}, {"text": "And I think you can--", "start": 1125.12, "duration": 1.818}, {"text": "without getting--\nbecause this is not", "start": 1126.938, "duration": 1.542}, {"text": "the way I'm going to\nsolve the problem--", "start": 1128.48, "duration": 1.667}, {"text": "you could find a way\nto avoid getting caught", "start": 1130.147, "duration": 2.773}, {"text": "and getting stuck\nin loops for an NFA.", "start": 1132.92, "duration": 5.31}, {"text": "So even though that looks like\nit could be a problem, in terms", "start": 1138.23, "duration": 6.21}, {"text": "of looping forever, it turns\nout that it won't be a problem--", "start": 1144.44, "duration": 3.96}, {"text": "it wouldn't be a problem\nif you're careful.", "start": 1148.4, "duration": 2.13}, {"text": "But I'm not going\nto solve it that way", "start": 1150.53, "duration": 1.59}, {"text": "anyway, because I'm going to\nillustrate a different method", "start": 1152.12, "duration": 2.55}, {"text": "for solving this problem.", "start": 1154.67, "duration": 1.2}, {"text": "And that is we have exhibited\nbefore a way of converting NFAs", "start": 1155.87, "duration": 5.755}, {"text": "to DFAs.", "start": 1161.625, "duration": 0.5}, {"text": "So my Turing machine is going\nto solve the ANFA problem", "start": 1165.02, "duration": 5.16}, {"text": "by converting its\ninput, which is an NFA,", "start": 1170.18, "duration": 2.76}, {"text": "to an equivalent DFA.", "start": 1172.94, "duration": 1.89}, {"text": "I'm calling the\nNFA B and the DFA", "start": 1174.83, "duration": 2.07}, {"text": "that I got-- converting\nit into B prime.", "start": 1176.9, "duration": 3.55}, {"text": "And what's nice about that\nis that, first of all,", "start": 1180.45, "duration": 3.01}, {"text": "we already know how to do\nthat conversion, because we", "start": 1183.46, "duration": 3.86}, {"text": "essentially went over that in\nlecture a few lectures back,", "start": 1187.32, "duration": 3.42}, {"text": "and it's spelled out in\nfull detail in the textbook.", "start": 1190.74, "duration": 3.31}, {"text": "So that is a conversion\nwe know how to do--", "start": 1194.05, "duration": 1.97}, {"text": "we'll assume we know how to do.", "start": 1196.02, "duration": 2.6}, {"text": "And we can implement that\nTuring-- that conversion", "start": 1198.62, "duration": 3.27}, {"text": "on a Turing machine.", "start": 1201.89, "duration": 2.39}, {"text": "Then, once we have\nthe equivalent DFA,", "start": 1204.28, "duration": 3.54}, {"text": "what do we do with that?", "start": 1207.82, "duration": 2.4}, {"text": "In the previous\nslide, we showed how", "start": 1210.22, "duration": 1.92}, {"text": "to solve the problem for DFAs.", "start": 1212.14, "duration": 3.05}, {"text": "So if we can convert\nthe NFA to a DFA,", "start": 1215.19, "duration": 2.37}, {"text": "and then we already know how\nto solve the problem for DFAs,", "start": 1217.56, "duration": 2.61}, {"text": "then we're done.", "start": 1220.17, "duration": 1.528}, {"text": "So that's how I'm going to say.", "start": 1221.698, "duration": 1.292}, {"text": "We're going to convert\nthe NFA to a DFA,", "start": 1222.99, "duration": 2.52}, {"text": "and then I'm going\nto run that DADFA", "start": 1225.51, "duration": 4.53}, {"text": "problem on the new\nmachine that I produced.", "start": 1230.04, "duration": 3.61}, {"text": "So remember that the--", "start": 1233.65, "duration": 1.44}, {"text": "this machine here\ndecides the ADFA problem.", "start": 1235.09, "duration": 4.81}, {"text": "And now I'm going to accept,\nif that new machine--", "start": 1239.9, "duration": 3.72}, {"text": "if that previous Turing machine\naccepts the DADFA problem", "start": 1243.62, "duration": 8.1}, {"text": "the machine accepts, and\nI'm going to basically do", "start": 1251.72, "duration": 3.96}, {"text": "whatever it does.", "start": 1255.68, "duration": 0.75}, {"text": "If it accepts, I'll accept.", "start": 1256.43, "duration": 1.98}, {"text": "If it rejects, then I'll reject.", "start": 1258.41, "duration": 1.77}, {"text": "So I guess the thing\nthat this illustrates", "start": 1271.1, "duration": 3.6}, {"text": "is this idea of using a\nconversion construction", "start": 1274.7, "duration": 3.6}, {"text": "inside a Turing\nmachine, and then", "start": 1278.3, "duration": 2.01}, {"text": "a previously constructed\nTuring machine", "start": 1280.31, "duration": 1.98}, {"text": "basically as a subroutine.", "start": 1282.29, "duration": 3.85}, {"text": "All this is perfectly legal,\nand it's the kind of thing", "start": 1286.14, "duration": 2.94}, {"text": "we're going to be\ndoing a lot of,", "start": 1289.08, "duration": 1.44}, {"text": "and that you should\nbe used to doing", "start": 1290.52, "duration": 1.35}, {"text": "that-- get ready to be doing\nthat on your homework too.", "start": 1291.87, "duration": 2.292}, {"text": "And in fact, I'll give you\nanother a little extra hint", "start": 1298.65, "duration": 3.24}, {"text": "that problem 6 can be\nsolved in this way.", "start": 1301.89, "duration": 3.51}, {"text": "OK.", "start": 1308.91, "duration": 2.28}, {"text": "All right, so here,\nlet's pause briefly.", "start": 1311.19, "duration": 2.67}, {"text": "OK, got some interesting\nquestions here coming up--", "start": 1321.55, "duration": 4.17}, {"text": "somebody asked me,\ndo we need to be", "start": 1330.85, "duration": 1.71}, {"text": "explicit about how\nwe're going to simulate", "start": 1332.56, "duration": 2.01}, {"text": "that NFA or the DFA?", "start": 1334.57, "duration": 2.565}, {"text": "Because we don't know\nhow many states it has.", "start": 1337.135, "duration": 1.875}, {"text": "You do know how\nmany states it has.", "start": 1341.82, "duration": 1.78}, {"text": "Once it's presented\nto you on the input,", "start": 1343.6, "duration": 2.79}, {"text": "you can see, oh, this is a\nmachine that has 12 states--", "start": 1346.39, "duration": 3.6}, {"text": "because you're given\nthe machine, and then", "start": 1349.99, "duration": 2.37}, {"text": "you can do the simulation.", "start": 1352.36, "duration": 1.14}, {"text": "Let's see.", "start": 1360.27, "duration": 0.555}, {"text": "And someone's asking me about\nlimits on the simulation", "start": 1364.37, "duration": 3.15}, {"text": "power of a Turing machine.", "start": 1367.52, "duration": 2.34}, {"text": "That's a question that I'm\ngoing to postpone to later,", "start": 1369.86, "duration": 2.61}, {"text": "because you're\nasking if a Turing", "start": 1372.47, "duration": 1.42}, {"text": "machine can simulate itself.", "start": 1373.89, "duration": 1.377}, {"text": "And we'll talk about\nthings like that,", "start": 1375.267, "duration": 1.583}, {"text": "but that's in a\nfew weeks from now,", "start": 1376.85, "duration": 3.04}, {"text": "so I'll hold off on that one.", "start": 1379.89, "duration": 2.45}, {"text": "Decidable languages--\nsomebody's asking me", "start": 1385.56, "duration": 3.04}, {"text": "a good question about closure\nproperties of the class", "start": 1388.6, "duration": 3.06}, {"text": "of decidable languages.", "start": 1391.66, "duration": 1.74}, {"text": "Are they closed under\nintersection, union, and so on?", "start": 1393.4, "duration": 3.36}, {"text": "Yes.", "start": 1396.76, "duration": 2.7}, {"text": "And the decidable languages are\nalso closed under complement.", "start": 1399.46, "duration": 4.2}, {"text": "That should be something\nyou should think about.", "start": 1403.66, "duration": 2.19}, {"text": "But yes, that is true.", "start": 1405.85, "duration": 2.16}, {"text": "The recognizable\nlanguages, however,", "start": 1408.01, "duration": 2.46}, {"text": "are closed under union\nand intersection,", "start": 1410.47, "duration": 2.58}, {"text": "but they are not closed\nunder complement.", "start": 1413.05, "duration": 3.54}, {"text": "So that we will prove\non Thursday's lecture.", "start": 1416.59, "duration": 2.91}, {"text": "So another question is, could we\nhave just run B on w in this--", "start": 1425.83, "duration": 3.375}, {"text": "in solving this problem,\ninstead of using reduced--", "start": 1429.205, "duration": 2.655}, {"text": "converting it to a\nnew Turing machine--", "start": 1431.86, "duration": 3.39}, {"text": "the B prime?", "start": 1435.25, "duration": 1.44}, {"text": "Well, yes, we could\nhave just done that.", "start": 1436.69, "duration": 5.25}, {"text": "OK.", "start": 1441.94, "duration": 1.11}, {"text": "I think we better move on.", "start": 1443.05, "duration": 1.29}, {"text": "I don't want to get\ntoo bogged down here--", "start": 1444.34, "duration": 2.94}, {"text": "got a lot of questions\nthere, so sorry", "start": 1447.28, "duration": 1.74}, {"text": "if I'm not getting to\nall of the questions.", "start": 1449.02, "duration": 3.93}, {"text": "OK.", "start": 1452.95, "duration": 2.41}, {"text": "Or you can write to\nthe TAs too, obviously.", "start": 1455.36, "duration": 1.95}, {"text": "I'm sure you are.", "start": 1457.31, "duration": 1.41}, {"text": "OK, so let's talk about\na different problem--", "start": 1458.72, "duration": 2.61}, {"text": "emptiness problem for DFAs.", "start": 1461.33, "duration": 1.47}, {"text": "I'm going to give you now a--", "start": 1469.74, "duration": 2.67}, {"text": "just a DFA--", "start": 1472.41, "duration": 2.82}, {"text": "B-- and no input.", "start": 1475.23, "duration": 3.42}, {"text": "And I'm going to ask, is\nthe language of that DFA", "start": 1478.65, "duration": 3.39}, {"text": "the empty set, the\nempty language?", "start": 1482.04, "duration": 4.052}, {"text": "You understand the\nproblem, first of all?", "start": 1486.092, "duration": 1.708}, {"text": "I'm just handing you in a\nDFA, and I want to know,", "start": 1487.8, "duration": 3.38}, {"text": "does this DFA accept\nany strings at all,", "start": 1491.18, "duration": 2.34}, {"text": "or is it just some dumb DFA--", "start": 1493.52, "duration": 3.24}, {"text": "it's just always\nvery negative DFA,", "start": 1496.76, "duration": 2.35}, {"text": "it just rejects everything--", "start": 1499.11, "duration": 3.01}, {"text": "and it has the empty language?", "start": 1502.12, "duration": 2.43}, {"text": "How do you tell?", "start": 1504.55, "duration": 2.25}, {"text": "Not super hard, if\nyou think about how", "start": 1506.8, "duration": 2.27}, {"text": "you would write a\nprogram to do that", "start": 1509.07, "duration": 2.6}, {"text": "or how you would\ndo it yourself--", "start": 1511.67, "duration": 2.8}, {"text": "so that's a decidable\nlanguage again.", "start": 1514.47, "duration": 2.65}, {"text": "So we're going to give\nnow a Turing machine", "start": 1517.12, "duration": 2.23}, {"text": "decider for that language.", "start": 1519.35, "duration": 2.94}, {"text": "That decider says, well,\nI'm giving that DFA--", "start": 1522.29, "duration": 5.25}, {"text": "I want to know if its\nlanguage is empty.", "start": 1527.54, "duration": 2.22}, {"text": "And the idea is just\nwhat you would think.", "start": 1529.76, "duration": 2.67}, {"text": "I'm going to see, is there\na path from the start state", "start": 1532.43, "duration": 3.06}, {"text": "of that DFA to the-- an\naccept state of the DFA?", "start": 1535.49, "duration": 2.55}, {"text": "If there is such a\npath, then that DFA", "start": 1538.04, "duration": 2.55}, {"text": "is going to have an input\nwhich goes along that path,", "start": 1540.59, "duration": 2.68}, {"text": "and will be accepted.", "start": 1543.27, "duration": 1.8}, {"text": "And so the language\nwon't be empty.", "start": 1545.07, "duration": 1.77}, {"text": "If there's no such path,\nthen clearly, this DFA", "start": 1546.84, "duration": 3.19}, {"text": "can never accept anything, and\nso this language will be empty.", "start": 1550.03, "duration": 4.14}, {"text": "OK.", "start": 1554.17, "duration": 0.69}, {"text": "Now, there are many\ndifferent path algorithms.", "start": 1554.86, "duration": 6.61}, {"text": "I think it would be a little\nbit sparse of me just--", "start": 1561.47, "duration": 6.06}, {"text": "some of you know algorithms.", "start": 1567.53, "duration": 1.18}, {"text": "Some of you don't know\npath checking algorithms.", "start": 1568.71, "duration": 2.52}, {"text": "I would like you to just\nto-- if you were giving", "start": 1571.23, "duration": 2.0}, {"text": "this kind of an\nanswer on a homework,", "start": 1573.23, "duration": 1.56}, {"text": "to give me some sense\nof how that algorithm is", "start": 1574.79, "duration": 2.25}, {"text": "going to work.", "start": 1577.04, "duration": 2.07}, {"text": "Don't be too high\nlevel about it.", "start": 1579.11, "duration": 3.59}, {"text": "So the one I have in mind\nis the breadth research,", "start": 1582.7, "duration": 4.61}, {"text": "if you've heard of that.", "start": 1587.31, "duration": 1.0}, {"text": "But it's very simple algorithm.", "start": 1588.31, "duration": 2.31}, {"text": "What I'm going to use is\nkind of a marking procedure.", "start": 1590.62, "duration": 2.89}, {"text": "So I'm going to start\nby coloring the--", "start": 1593.51, "duration": 2.93}, {"text": "here is this-- I should have\nindicated-- this is my DFAB.", "start": 1596.44, "duration": 5.51}, {"text": "This is B over here.", "start": 1601.95, "duration": 3.51}, {"text": "Should I try taking a chance\nof writing on this thing--", "start": 1605.46, "duration": 4.32}, {"text": "oops.", "start": 1609.78, "duration": 1.96}, {"text": "This is B. Oh, great--", "start": 1611.74, "duration": 4.73}, {"text": "that didn't help.", "start": 1616.47, "duration": 2.67}, {"text": "So this is B here.", "start": 1619.14, "duration": 1.71}, {"text": "And the way I'm going to\ntest if it has a path--", "start": 1620.85, "duration": 3.3}, {"text": "if it accepts an\ninput is by seeing", "start": 1624.15, "duration": 2.46}, {"text": "if there's a path from\nthe start state to any one", "start": 1626.61, "duration": 2.1}, {"text": "of the accept states.", "start": 1628.71, "duration": 1.14}, {"text": "And I'm going to start it\nby marking the start state,", "start": 1629.85, "duration": 3.36}, {"text": "and then marking\nall states that I", "start": 1633.21, "duration": 1.95}, {"text": "can get to from\npreviously marked states,", "start": 1635.16, "duration": 2.37}, {"text": "and keep doing that until I\ncan't get to anything new.", "start": 1637.53, "duration": 2.67}, {"text": "There's going to be a series\nof iterations here marking", "start": 1643.2, "duration": 3.06}, {"text": "more and more states until\nthere's nothing new to mark,", "start": 1646.26, "duration": 3.24}, {"text": "and then I say, did I\nmark any accept states?", "start": 1649.5, "duration": 2.37}, {"text": "OK, so let's just see how I\nwrite that down in English.", "start": 1654.8, "duration": 4.23}, {"text": "So I started marking\nthe start state.", "start": 1659.03, "duration": 2.94}, {"text": "I repeat until no\nnew state is marked.", "start": 1661.97, "duration": 2.19}, {"text": "I'm going to say,\nmark every state that", "start": 1666.885, "duration": 1.625}, {"text": "has an incoming arrow from\na previously marked state.", "start": 1668.51, "duration": 4.62}, {"text": "Accept-- then, once I'm done\nwith, that repeat loop--", "start": 1673.13, "duration": 2.94}, {"text": "accept if no accept state is\nmarked, because that means--", "start": 1676.07, "duration": 4.123}, {"text": "don't forget, it's a\nlittle bit inverted", "start": 1680.193, "duration": 1.667}, {"text": "from what you might think.", "start": 1681.86, "duration": 1.083}, {"text": "I'm going to accept if there's\nno marked accept state,", "start": 1682.943, "duration": 3.957}, {"text": "because that means there's\nno path to an accept state", "start": 1686.9, "duration": 3.27}, {"text": "from the start state, which\nmeans the language is empty.", "start": 1690.17, "duration": 3.03}, {"text": "And EDFA is the DFAs\nthat have empty language,", "start": 1693.2, "duration": 4.41}, {"text": "so I should be accepting those.", "start": 1697.61, "duration": 2.78}, {"text": "If there's no way to\nget to an accept state,", "start": 1700.39, "duration": 3.15}, {"text": "no accept state is marked.", "start": 1703.54, "duration": 1.38}, {"text": "And reject if some accept\nstate earmark, because then", "start": 1704.92, "duration": 2.64}, {"text": "the language is not empty.", "start": 1707.56, "duration": 2.79}, {"text": "OK, so that's all I\nwanted to say about that.", "start": 1710.35, "duration": 2.34}, {"text": "Somebody's asking,\ncan you just say", "start": 1715.262, "duration": 1.458}, {"text": "something like breadth\nversus [AUDIO OUT]..", "start": 1716.72, "duration": 3.55}, {"text": "The sketchier you\nare, the more chances", "start": 1720.27, "duration": 2.78}, {"text": "that you're going to get\ncaught by the grader, who's", "start": 1723.05, "duration": 2.91}, {"text": "not going--", "start": 1725.96, "duration": 2.565}, {"text": "we have an army of people\ngrading these problems,", "start": 1728.525, "duration": 2.805}, {"text": "and just to stay on the--", "start": 1731.33, "duration": 1.92}, {"text": "be on the safe\nside of sketchiness", "start": 1733.25, "duration": 2.73}, {"text": "and, say, don't cut\ntoo many corners,", "start": 1735.98, "duration": 2.13}, {"text": "because you might\nmiss something.", "start": 1738.11, "duration": 2.437}, {"text": "Chances are it would be OK\njust to say breadth research,", "start": 1740.547, "duration": 2.333}, {"text": "but I would prefer if--", "start": 1742.88, "duration": 1.65}, {"text": "you'd be safer if you said\na little bit more than that.", "start": 1744.53, "duration": 2.73}, {"text": "OK.", "start": 1747.26, "duration": 1.73}, {"text": "Oh, this is a good\nquestion here.", "start": 1748.99, "duration": 5.11}, {"text": "Somebody asked, can we just\nrun the DFA on all short--", "start": 1754.1, "duration": 4.57}, {"text": "on all strings?", "start": 1758.67, "duration": 0.85}, {"text": "Well, first of all, one thing--", "start": 1759.52, "duration": 3.99}, {"text": "to say something bad\nwould be, well, just", "start": 1763.51, "duration": 2.85}, {"text": "feed in all possible\nstrings into the DFA,", "start": 1766.36, "duration": 3.84}, {"text": "and if any one of them--", "start": 1770.2, "duration": 1.77}, {"text": "if it accepts any\none of them, then we", "start": 1771.97, "duration": 1.8}, {"text": "know its language is not empty.", "start": 1773.77, "duration": 2.82}, {"text": "Well, that's not\na good algorithm,", "start": 1776.59, "duration": 1.83}, {"text": "because that's going to\npotentially run forever,", "start": 1778.42, "duration": 4.14}, {"text": "because there's lots of strings.", "start": 1782.56, "duration": 1.68}, {"text": "There's infinitely many\nstrings to feed in to that DFA.", "start": 1784.24, "duration": 3.9}, {"text": "And so a Turing machine, if\nit's trying to be a decider,", "start": 1788.14, "duration": 3.99}, {"text": "had better not do any infinite\noperations that are potentially", "start": 1792.13, "duration": 3.082}, {"text": "going to go forever.", "start": 1795.212, "duration": 0.833}, {"text": "To be fair to the proposer\nhere, the questioner here--", "start": 1799.29, "duration": 3.12}, {"text": "didn't ask that-- says, well,\ncan we feed in all strings", "start": 1802.41, "duration": 3.6}, {"text": "up to some bound, which\nwould be the number of states", "start": 1806.01, "duration": 4.46}, {"text": "of the machine in this case?", "start": 1810.47, "duration": 1.26}, {"text": "And yes, that would\nwork, but then you", "start": 1811.73, "duration": 1.62}, {"text": "would have to argue\nthat that's enough.", "start": 1813.35, "duration": 3.96}, {"text": "And yes, it is enough, but it\nwouldn't-- would not be enough", "start": 1817.31, "duration": 3.75}, {"text": "in answering the\nproblem just to say,", "start": 1821.06, "duration": 1.86}, {"text": "feed it in that number\nof them, and we're done.", "start": 1822.92, "duration": 2.787}, {"text": "You would have to say why.", "start": 1825.707, "duration": 1.083}, {"text": "OK.", "start": 1832.365, "duration": 0.5}, {"text": "Lot of questions here--", "start": 1840.55, "duration": 1.015}, {"text": "I'm going to move on.", "start": 1841.565, "duration": 0.875}, {"text": "Let's see.", "start": 1845.72, "duration": 0.62}, {"text": "Equivalence problem for DFAs--", "start": 1846.34, "duration": 2.43}, {"text": "now we're going to take things\nto the next level-- ask,", "start": 1848.77, "duration": 3.09}, {"text": "are there two--", "start": 1851.86, "duration": 3.63}, {"text": "I'm going to give you two DFAs.", "start": 1855.49, "duration": 3.68}, {"text": "And I want to know, do they\ndescribe the same language--", "start": 1859.17, "duration": 2.64}, {"text": "do they recognize\nthe same language?", "start": 1861.81, "duration": 3.33}, {"text": "OK?", "start": 1865.14, "duration": 2.76}, {"text": "So how are we going to do that?", "start": 1867.9, "duration": 1.72}, {"text": "So that's a decidable language.", "start": 1869.62, "duration": 2.528}, {"text": "Here's the decider.", "start": 1872.148, "duration": 0.792}, {"text": "My input now is going\nto be two DFAs--", "start": 1876.16, "duration": 3.4}, {"text": "again, represented as a\nstring, because that's", "start": 1879.56, "duration": 2.22}, {"text": "what Turing machines deal\nwith as their inputs.", "start": 1881.78, "duration": 2.49}, {"text": "But they can unpack that\nstring into two DFAs.", "start": 1884.27, "duration": 4.02}, {"text": "And there are several different\nways to do this problem,", "start": 1888.29, "duration": 3.75}, {"text": "and I'm sure I'm going to get\nsuggestions with other ways", "start": 1892.04, "duration": 3.1}, {"text": "to go.", "start": 1895.14, "duration": 0.5}, {"text": "One thing you could do is\njust to feed in strings", "start": 1895.64, "duration": 6.27}, {"text": "up to a certain length.", "start": 1901.91, "duration": 3.35}, {"text": "Just like before, you can't\nfeed in all possible strings", "start": 1905.26, "duration": 2.91}, {"text": "and see if the machines\never behave differently", "start": 1908.17, "duration": 2.07}, {"text": "on any of them, because\nthat's an infinite operation,", "start": 1910.24, "duration": 4.92}, {"text": "and we already decided\nwe can't do that.", "start": 1915.16, "duration": 1.77}, {"text": "Now, if you want\nto talk about this", "start": 1916.93, "duration": 2.52}, {"text": "being a recognizer,\ninstead of a decider,", "start": 1919.45, "duration": 3.12}, {"text": "then you might be able\nto do something like that", "start": 1922.57, "duration": 2.16}, {"text": "just to make sure your--", "start": 1924.73, "duration": 1.89}, {"text": "you have to be just careful.", "start": 1926.62, "duration": 2.737}, {"text": "Let me not say more\non that right now.", "start": 1929.357, "duration": 1.583}, {"text": "But certainly, for a decider,\nyou can't go forever.", "start": 1930.94, "duration": 4.6}, {"text": "You can't have\ninfinite operations.", "start": 1935.54, "duration": 3.41}, {"text": "So you would have\nto have a cut-off.", "start": 1938.95, "duration": 4.55}, {"text": "So you can feed in all possible\nstrings up to some length,", "start": 1943.5, "duration": 3.21}, {"text": "say, into A and B, and see\nif there's any difference.", "start": 1946.71, "duration": 3.09}, {"text": "Now, we actually had a problem\non that in the problem set", "start": 1949.8, "duration": 2.61}, {"text": "1, which said, if two DFAs\nhave unequal languages,", "start": 1952.41, "duration": 6.75}, {"text": "then they're going\nto see a difference.", "start": 1959.16, "duration": 2.407}, {"text": "Then there's going to be a\nstring which acts differently", "start": 1961.567, "duration": 2.333}, {"text": "on them, which is\nof length, at most,", "start": 1963.9, "duration": 2.61}, {"text": "the product of the number of\nstates of those two machines.", "start": 1966.51, "duration": 3.15}, {"text": "So you can either\nreference that problem--", "start": 1969.66, "duration": 4.38}, {"text": "that would be an adequate\nsolution-- or reprove it", "start": 1974.04, "duration": 2.8}, {"text": "or whatever.", "start": 1976.84, "duration": 0.5}, {"text": "That would be fine.", "start": 1977.34, "duration": 1.06}, {"text": "In fact, you can do\neven better than that,", "start": 1978.4, "duration": 1.76}, {"text": "as the optional problem showed.", "start": 1980.16, "duration": 1.47}, {"text": "You only have to go up to the\nsum of the number of states,", "start": 1981.63, "duration": 2.52}, {"text": "not up to the product.", "start": 1984.15, "duration": 1.29}, {"text": "But that's actually\nvery difficult to show.", "start": 1985.44, "duration": 4.07}, {"text": "I'm not going to\nprove it that way.", "start": 1989.51, "duration": 1.745}, {"text": "I'm going to prove it in an\nentirely different way, which", "start": 1991.255, "duration": 2.375}, {"text": "doesn't require any\nanalysis at all--", "start": 1993.63, "duration": 2.52}, {"text": "no proving something\nabout balance.", "start": 1996.15, "duration": 3.36}, {"text": "I'm going to take advantage of\nsomething we've already shown,", "start": 1999.51, "duration": 4.71}, {"text": "which is I'm going to make\na new finite automaton,", "start": 2004.22, "duration": 3.6}, {"text": "a new DFAC built out\nof A and B, which", "start": 2007.82, "duration": 4.35}, {"text": "accepts all the strings\non which A and B disagree.", "start": 2012.17, "duration": 4.077}, {"text": "And I'll show you how to--", "start": 2016.247, "duration": 1.083}, {"text": "that's easy to do.", "start": 2017.33, "duration": 1.852}, {"text": "So first of all, let's--\nin terms of a picture,", "start": 2019.182, "duration": 1.958}, {"text": "let's understand what this is.", "start": 2021.14, "duration": 1.28}, {"text": "So here we have--", "start": 2022.42, "duration": 1.54}, {"text": "this is the language of\nA, this is the language", "start": 2023.96, "duration": 2.55}, {"text": "of B written as a Venn diagram.", "start": 2026.51, "duration": 3.08}, {"text": "And where are those places\nwhere they disagree?", "start": 2029.59, "duration": 3.84}, {"text": "Well, they're either in\nA, but not in B, or in B,", "start": 2033.43, "duration": 3.42}, {"text": "but not in A. I'm\nshowing it to you here", "start": 2036.85, "duration": 1.74}, {"text": "in terms of the blue region.", "start": 2038.59, "duration": 3.45}, {"text": "That actually has a name\ncalled the symmetric difference", "start": 2042.04, "duration": 3.09}, {"text": "of these two sets.", "start": 2045.13, "duration": 2.7}, {"text": "These are the--\nall of the members", "start": 2047.83, "duration": 2.29}, {"text": "which are in exactly one out\nof the two, but not both.", "start": 2050.12, "duration": 2.9}, {"text": "If you can make a machine C that\nwould accept all of the strings", "start": 2055.87, "duration": 5.419}, {"text": "in the blue region, then what\ndo we do with that machine?", "start": 2061.289, "duration": 2.375}, {"text": "We test of its length\nlanguage is empty,", "start": 2066.61, "duration": 2.46}, {"text": "which is what we've\nalready shown how to do--", "start": 2069.07, "duration": 2.31}, {"text": "because of the blue region is\nempty, that means that L of A", "start": 2071.38, "duration": 3.299}, {"text": "equals L of B.", "start": 2074.679, "duration": 4.46}, {"text": "So I'm going to make a machine,\na DFAC where the language of C", "start": 2079.139, "duration": 4.861}, {"text": "is exactly that\nsymmetric difference.", "start": 2084.0, "duration": 1.98}, {"text": "It's all the strings in A\nintersected with the strings", "start": 2085.98, "duration": 2.909}, {"text": "that are not in B-- so in A and\nnot in B-- or in B and not--", "start": 2088.889, "duration": 4.261}, {"text": "then not an A--", "start": 2093.15, "duration": 0.9}, {"text": "take the union of\nthose two parts.", "start": 2094.05, "duration": 2.129}, {"text": "And how do we know\nwe can make C?", "start": 2096.179, "duration": 1.921}, {"text": "Well, we have those\nclosure constructions,", "start": 2098.1, "duration": 4.59}, {"text": "which we showed\nseveral lectures back.", "start": 2102.69, "duration": 1.74}, {"text": "Those closure instructions\ncan be implemented", "start": 2104.43, "duration": 2.25}, {"text": "on a Turing machine.", "start": 2106.68, "duration": 2.88}, {"text": "So a Turing machine\ncan build the DFAC,", "start": 2109.56, "duration": 2.96}, {"text": "and then use that test\nfrom a few slides back,", "start": 2112.52, "duration": 6.33}, {"text": "the emptiness-- the last\nslide-- the emptiness tester", "start": 2118.85, "duration": 3.03}, {"text": "for DFAs on C to see whether\nits language is empty.", "start": 2121.88, "duration": 4.09}, {"text": "And now, if C's\nlanguage is empty,", "start": 2125.97, "duration": 2.073}, {"text": "then we know we can\naccept, because that", "start": 2128.043, "duration": 1.667}, {"text": "means the two-- that L of\nA equals L of B. Otherwise,", "start": 2129.71, "duration": 3.6}, {"text": "we can reject.", "start": 2133.31, "duration": 2.3}, {"text": "OK?", "start": 2135.61, "duration": 0.72}, {"text": "So here's a note--", "start": 2136.33, "duration": 1.02}, {"text": "I'm going to ask you a check-in.", "start": 2137.35, "duration": 3.08}, {"text": "You can also use that time to\nsend me a few more questions,", "start": 2140.43, "duration": 3.2}, {"text": "if you want.", "start": 2143.63, "duration": 1.19}, {"text": "OK, here's my check-in.", "start": 2144.82, "duration": 1.75}, {"text": "OK, now, instead of testing\nequivalence of finite--", "start": 2146.57, "duration": 3.18}, {"text": "of DFAs, I want to\ntest equivalence", "start": 2149.75, "duration": 2.13}, {"text": "of regular expressions.", "start": 2151.88, "duration": 1.35}, {"text": "So here are R1, R2.", "start": 2156.44, "duration": 1.85}, {"text": "Regular expressions are called\nthe EQ regular expressions", "start": 2158.29, "duration": 2.55}, {"text": "problem--", "start": 2160.84, "duration": 0.9}, {"text": "equivalents of\nregular expressions.", "start": 2161.74, "duration": 1.56}, {"text": "Can we now conclude that this\nproblem is also decidable,", "start": 2163.3, "duration": 4.61}, {"text": "either immediately from\nstuff we've already shown;", "start": 2167.91, "duration": 3.03}, {"text": "or yes, but would take some\nsignificant extra work; or no,", "start": 2170.94, "duration": 3.84}, {"text": "because intersection is\nnot a regular operation?", "start": 2174.78, "duration": 2.22}, {"text": "So let's see if I can pull that\nout here-- launch the polling.", "start": 2177.0, "duration": 2.64}, {"text": "Here we go.", "start": 2182.83, "duration": 0.63}, {"text": "OK, I think we're\njust about done here.", "start": 2186.51, "duration": 1.695}, {"text": "Five seconds more--", "start": 2192.823, "duration": 1.087}, {"text": "OK, ready, set, end.", "start": 2197.0, "duration": 1.905}, {"text": "All right.", "start": 2202.79, "duration": 0.57}, {"text": "Yes, the correct answer is A.\nWe have basically already shown", "start": 2207.58, "duration": 4.05}, {"text": "this fact, because--", "start": 2211.63, "duration": 3.27}, {"text": "why is that?", "start": 2214.9, "duration": 0.69}, {"text": "Because we have shown\nthat we can convert--", "start": 2215.59, "duration": 4.14}, {"text": "if you're given two\nregular expressions,", "start": 2219.73, "duration": 1.96}, {"text": "and we want to test\nwhether they're equivalent,", "start": 2221.69, "duration": 2.21}, {"text": "they generate the\nsame language, we", "start": 2223.9, "duration": 1.86}, {"text": "can convert them both\nto find out automata.", "start": 2225.76, "duration": 5.22}, {"text": "We can convert them to NFAs,\nand then the NFAs to DFAs.", "start": 2230.98, "duration": 4.64}, {"text": "And then we can\napply what we've just", "start": 2235.62, "duration": 3.15}, {"text": "showed about testing\nequivalence of DFAs.", "start": 2238.77, "duration": 3.87}, {"text": "So yes, it really follows\nimmediately from stuff", "start": 2242.64, "duration": 2.37}, {"text": "we've already shown-- the\nconversion, number one,", "start": 2245.01, "duration": 2.58}, {"text": "and then the testing of\nequivalence for DFAs.", "start": 2247.59, "duration": 3.96}, {"text": "So there's not really\nany work to do here.", "start": 2251.55, "duration": 2.04}, {"text": "And in fact, what I'm trying to\nillustrate with this check-in--", "start": 2253.59, "duration": 4.41}, {"text": "that, once you've shown\nhow to do some kind", "start": 2258.0, "duration": 3.24}, {"text": "of a test for one model, it--", "start": 2261.24, "duration": 2.77}, {"text": "going to apply for all\nof the equivalent models", "start": 2264.01, "duration": 2.51}, {"text": "that we've shown to be\nequivalent, because the Turing", "start": 2266.52, "duration": 2.34}, {"text": "machine can do the constructions\nwhich show the equivalence.", "start": 2268.86, "duration": 5.71}, {"text": "OK, so let's move on.", "start": 2274.57, "duration": 2.31}, {"text": "Somebody didn't get the poll.", "start": 2279.45, "duration": 1.8}, {"text": "Did most people\nnot get the poll?", "start": 2281.25, "duration": 2.46}, {"text": "Well, I think most of\nyou have gotten it.", "start": 2283.71, "duration": 3.1}, {"text": "Did you?", "start": 2286.81, "duration": 1.982}, {"text": "I'm not seeing a\nlot of complaints.", "start": 2288.792, "duration": 1.458}, {"text": "So if you didn't get\nthe poll, something", "start": 2290.25, "duration": 2.1}, {"text": "is wrong with your\nsetup, and you're", "start": 2292.35, "duration": 2.16}, {"text": "going to have to take the\nrecorded check-ins that", "start": 2294.51, "duration": 5.55}, {"text": "are going to launch right\nafter this lecture's over.", "start": 2300.06, "duration": 2.66}, {"text": "Sorry.", "start": 2302.72, "duration": 1.432}, {"text": "But you should figure out\nwhat's wrong with the setup", "start": 2304.152, "duration": 2.208}, {"text": "there, because I think most\npeople are getting these.", "start": 2306.36, "duration": 2.37}, {"text": "OK, and with that, we're\ngoing to take a little break,", "start": 2308.73, "duration": 2.79}, {"text": "and then we'll\ncontinue on afterward.", "start": 2311.52, "duration": 2.72}, {"text": "Let me know how this is--", "start": 2314.24, "duration": 3.01}, {"text": "should I be speed\na little speedier", "start": 2317.25, "duration": 2.73}, {"text": "about the little mini\nbreaks that we're taking,", "start": 2319.98, "duration": 4.62}, {"text": "or is this good for you?", "start": 2324.6, "duration": 2.93}, {"text": "Feedback is always--", "start": 2327.53, "duration": 1.39}, {"text": "I'm trying to make this as\ngood as I can for all of you.", "start": 2328.92, "duration": 3.84}, {"text": "OK, I think there's a mixture\nof between people saying", "start": 2332.76, "duration": 3.12}, {"text": "that these breaks are good.", "start": 2335.88, "duration": 1.33}, {"text": "Someone says they're\na little overlong,", "start": 2337.21, "duration": 1.97}, {"text": "so I'll try to tighten\nthem up a little.", "start": 2339.18, "duration": 3.27}, {"text": "Some folks are saying what--", "start": 2342.45, "duration": 2.49}, {"text": "more people should\nbe asking the TAs.", "start": 2344.94, "duration": 4.35}, {"text": "I don't know how the TAs are\ndoing, in terms of their--", "start": 2349.29, "duration": 2.34}, {"text": "I'll check with them\nafterward-- how well", "start": 2351.63, "duration": 1.86}, {"text": "this is going for them,\nin terms of the questions.", "start": 2353.49, "duration": 3.05}, {"text": "But I think some amount of\nbreak is good so that we don't--", "start": 2356.54, "duration": 4.4}, {"text": "so there's time to\nbe asking questions.", "start": 2360.94, "duration": 2.372}, {"text": "Otherwise, what's the point\nof having a live lecture?", "start": 2363.312, "duration": 2.208}, {"text": "So we will start promptly\nwhen this timer runs down.", "start": 2370.47, "duration": 4.95}, {"text": "So be ready to go in\n55 seconds from now.", "start": 2375.42, "duration": 7.58}, {"text": "Just to confirm, to show the\ndecidability of the equivalence", "start": 2390.17, "duration": 3.245}, {"text": "of two regular\nexpressions, do we", "start": 2393.415, "duration": 1.375}, {"text": "need to show that we can use a\nTuring machine to convert them", "start": 2394.79, "duration": 2.542}, {"text": "to two DFAs first?", "start": 2397.332, "duration": 1.013}, {"text": "If you want to test whether\ntwo regular expressions are", "start": 2403.77, "duration": 2.91}, {"text": "equivalent, you can\ngive any procedure", "start": 2406.68, "duration": 4.29}, {"text": "for doing that\ndeciding you want.", "start": 2410.97, "duration": 3.4}, {"text": "I'm just offering one\nsimple way to do it", "start": 2414.37, "duration": 2.48}, {"text": "that takes advantage of\nstuff we've already shown.", "start": 2416.85, "duration": 2.65}, {"text": "But if you want\nto dig down and do", "start": 2419.5, "duration": 1.67}, {"text": "some analysis of those\nregular expressions", "start": 2421.17, "duration": 2.73}, {"text": "to show that they describe\nthe same language,", "start": 2423.9, "duration": 2.7}, {"text": "they generate the same\nlanguage, be my guest.", "start": 2426.6, "duration": 2.34}, {"text": "I think that's-- actually would\nbe complicated to do that that", "start": 2428.94, "duration": 3.12}, {"text": "way.", "start": 2432.06, "duration": 0.54}, {"text": "OK, so we're just about ready\nto go here, so let's continue.", "start": 2432.6, "duration": 4.65}, {"text": "And let me take\nthis timer off here.", "start": 2441.83, "duration": 2.16}, {"text": "All right.", "start": 2447.56, "duration": 1.11}, {"text": "Now, we are going\nto talk a little", "start": 2448.67, "duration": 2.79}, {"text": "about context-free grammars.", "start": 2451.46, "duration": 2.2}, {"text": "So we talked about decision\nproblems for finite automata.", "start": 2453.66, "duration": 3.06}, {"text": "Let's talk about\nsome for grammars.", "start": 2456.72, "duration": 1.685}, {"text": "OK, now I'm going to give\nus an analogous problem.", "start": 2461.137, "duration": 2.083}, {"text": "I'm going to give you a--", "start": 2463.22, "duration": 1.89}, {"text": "I'm calling it the\nacceptance problem,", "start": 2465.11, "duration": 1.62}, {"text": "but-- just for consistency\nwith everything else,", "start": 2466.73, "duration": 2.37}, {"text": "but it's really the\ngenerating problem.", "start": 2469.1, "duration": 1.93}, {"text": "So I'm giving you a grammar--", "start": 2471.03, "duration": 2.84}, {"text": "context-free grammar G and\na string that's in a string.", "start": 2473.87, "duration": 4.522}, {"text": "And I want to know, is\nit in the language of G?", "start": 2478.392, "duration": 1.958}, {"text": "So does G generate w?", "start": 2480.35, "duration": 3.07}, {"text": "I'm calling that\nthe ACFG problem.", "start": 2483.42, "duration": 3.45}, {"text": "So that's going to\nbe a decidable again.", "start": 2486.87, "duration": 1.7}, {"text": "These are getting slightly\nharder as we're moving along,", "start": 2491.63, "duration": 2.82}, {"text": "so I'm giving you a grammar and\na string, and I want to know,", "start": 2494.45, "duration": 8.71}, {"text": "does the grammar\ngenerate that string?", "start": 2503.16, "duration": 2.09}, {"text": "Well, it's not totally\ntrivial to solve that.", "start": 2509.79, "duration": 4.95}, {"text": "One thing you might try doing is\nlooking at all possible things,", "start": 2514.74, "duration": 4.83}, {"text": "all possible derivations\nfrom that grammar", "start": 2519.57, "duration": 4.24}, {"text": "and see if any one\nof them leads to w--", "start": 2523.81, "duration": 3.72}, {"text": "leads you to generate w.", "start": 2527.53, "duration": 3.22}, {"text": "Well, you have to be careful,\nbecause as I've-- as we've", "start": 2530.75, "duration": 4.99}, {"text": "shown in some of our examples,\nyou actually could have--", "start": 2535.74, "duration": 5.46}, {"text": "because you're allowed\nto have variables", "start": 2541.2, "duration": 2.76}, {"text": "that can get converted\nto empty string,", "start": 2543.96, "duration": 2.99}, {"text": "you might have very long\nintermediate strings being", "start": 2546.95, "duration": 4.08}, {"text": "generated from a, grammar\nwhich then ultimately give you", "start": 2551.03, "duration": 3.63}, {"text": "a small string of terminals\nthat get generated,", "start": 2554.66, "duration": 4.412}, {"text": "a small string in the\nlanguage that gets produced.", "start": 2559.072, "duration": 2.083}, {"text": "You certainly don't want to\ntry every possible derivation,", "start": 2566.13, "duration": 3.15}, {"text": "because there's infinitely\nmany different derivations--", "start": 2569.28, "duration": 2.94}, {"text": "most of them\ngenerating, of course,", "start": 2572.22, "duration": 1.71}, {"text": "things that are irrelevant\nto the string w.", "start": 2573.93, "duration": 2.94}, {"text": "But you have to know\nhow to cut things off,", "start": 2576.87, "duration": 3.447}, {"text": "and it's not immediately\nobvious how you do that--", "start": 2580.317, "duration": 2.083}, {"text": "unless you have done the\nhomework problems that I asked", "start": 2584.93, "duration": 6.923}, {"text": "you to do, which I'm sure very\nmany of you have not done--", "start": 2591.853, "duration": 2.417}, {"text": "the zero point X problems,\nbecause they're--", "start": 2594.27, "duration": 3.21}, {"text": "that's going to come\nin handy right now.", "start": 2597.48, "duration": 2.7}, {"text": "And so I'll help\nyou through that.", "start": 2600.18, "duration": 1.65}, {"text": "Remember-- you should remember,\nbut you may not have looked", "start": 2604.82, "duration": 4.08}, {"text": "at it--", "start": 2608.9, "duration": 1.26}, {"text": "something called\nChomsky normal form,", "start": 2610.16, "duration": 4.05}, {"text": "which is for\ncontext-free grammars,", "start": 2614.21, "duration": 2.39}, {"text": "but only allows the rules\nto be of a special kind.", "start": 2616.6, "duration": 3.76}, {"text": "And they have to look like this.", "start": 2620.36, "duration": 1.93}, {"text": "They can be a variable\nthat goes to two variables,", "start": 2622.29, "duration": 3.448}, {"text": "on the right-hand\nside, or a variable", "start": 2625.738, "duration": 1.542}, {"text": "that goes to a terminal.", "start": 2627.28, "duration": 1.62}, {"text": "Those are the only kinds of\nrules that you're allowed.", "start": 2628.9, "duration": 2.307}, {"text": "This is a special case\nfor the empty string,", "start": 2631.207, "duration": 1.833}, {"text": "but let's ignore that for--", "start": 2633.04, "duration": 3.0}, {"text": "the start variable can also\nwork to the empty string,", "start": 2636.04, "duration": 2.43}, {"text": "if you want to have a-- the\nempty string in a language.", "start": 2638.47, "duration": 2.85}, {"text": "But that's a special case.", "start": 2641.32, "duration": 1.74}, {"text": "Let's ignore that.", "start": 2643.06, "duration": 2.79}, {"text": "These are the only\ntwo kinds of rules", "start": 2645.85, "duration": 1.92}, {"text": "that you can have in a\nChomsky normal form grammar.", "start": 2647.77, "duration": 4.32}, {"text": "Once you have a Chomsky\nnormal form grammar--", "start": 2652.09, "duration": 4.145}, {"text": "well, first of all,\nthere's two things.", "start": 2656.235, "duration": 1.625}, {"text": "First of all, you\ncan always convert", "start": 2657.86, "duration": 1.5}, {"text": "any context-free grammar\ninto Chomsky normal form.", "start": 2659.36, "duration": 4.13}, {"text": "So that's given in the textbook.", "start": 2663.49, "duration": 2.82}, {"text": "You do the obvious thing.", "start": 2666.31, "duration": 2.34}, {"text": "I'm not going to\nspend time on it.", "start": 2668.65, "duration": 2.05}, {"text": "And you don't have to know it.", "start": 2670.7, "duration": 1.25}, {"text": "It's just a little bit tedious,\nbut it's straightforward", "start": 2671.95, "duration": 5.16}, {"text": "and it's there,\nif you're curious.", "start": 2677.11, "duration": 4.075}, {"text": "But the second lemma's\nthe thing that's", "start": 2681.185, "duration": 1.625}, {"text": "important to us, which is that,\nif you have a grammar which", "start": 2682.81, "duration": 5.96}, {"text": "is in Chomsky normal form and\na string that's generated,", "start": 2688.77, "duration": 4.56}, {"text": "every derivation of that\nstring has exactly 2 times", "start": 2693.33, "duration": 6.54}, {"text": "the length of the\nstring minus 1 steps.", "start": 2699.87, "duration": 2.235}, {"text": "If you think about it, this is\na lemma-- very easy to prove.", "start": 2704.85, "duration": 3.42}, {"text": "I think the homework\nproblem asks", "start": 2708.27, "duration": 2.16}, {"text": "you to prove that in\nthe 0.2 or whatever", "start": 2710.43, "duration": 2.97}, {"text": "it was in problem set 1--", "start": 2713.4, "duration": 2.22}, {"text": "or problem set 2--", "start": 2715.62, "duration": 0.75}, {"text": "I don't remember.", "start": 2716.37, "duration": 0.708}, {"text": "Rules of this kind allow you\nto make the string one longer,", "start": 2723.5, "duration": 3.13}, {"text": "and rules of this kind allow\nyou to produce a new terminal", "start": 2726.63, "duration": 4.24}, {"text": "symbol.", "start": 2730.87, "duration": 0.5}, {"text": "If the length w is n, you're\ngoing to have n minus 1", "start": 2736.266, "duration": 3.594}, {"text": "of these and n of.", "start": 2739.86, "duration": 0.96}, {"text": "Those that's why you\nget 2n minus 1 steps.", "start": 2740.82, "duration": 5.62}, {"text": "But the point is that I don't\nreally care exactly how many.", "start": 2746.44, "duration": 2.85}, {"text": "It's just that we have a bound.", "start": 2749.29, "duration": 1.77}, {"text": "And once you have\nthat bound, life", "start": 2751.06, "duration": 2.19}, {"text": "is good from the point\nof view of giving", "start": 2753.25, "duration": 4.02}, {"text": "a Turing machine which is\ngoing to decide this language--", "start": 2757.27, "duration": 5.51}, {"text": "because here's the\nTuring machine.", "start": 2762.78, "duration": 1.51}, {"text": "What it's going to do--", "start": 2764.29, "duration": 0.958}, {"text": "the first thing is\nit's going to convert G", "start": 2765.248, "duration": 1.772}, {"text": "into Chomsky normal form.", "start": 2767.02, "duration": 3.31}, {"text": "That we assume we\nknow how to do.", "start": 2770.33, "duration": 2.36}, {"text": "Now, we're going to try all\nderivations, but only those", "start": 2772.69, "duration": 3.06}, {"text": "of length 2--", "start": 2775.75, "duration": 3.57}, {"text": "twice the length of\nthe string minus 1,", "start": 2779.32, "duration": 5.55}, {"text": "because if any derivation\nis going to generate w,", "start": 2784.87, "duration": 3.57}, {"text": "it has to be this many steps,\nnow that we know the grammar", "start": 2788.44, "duration": 5.55}, {"text": "is in Chomsky normal form.", "start": 2793.99, "duration": 2.78}, {"text": "OK, so we have\nconverted this problem", "start": 2796.77, "duration": 5.01}, {"text": "of one that might be a very\nunboundedly lengthy problem", "start": 2801.78, "duration": 4.2}, {"text": "and to one where it's going\nto terminate after some fixed", "start": 2805.98, "duration": 2.73}, {"text": "number of steps.", "start": 2808.71, "duration": 1.64}, {"text": "And so therefore, we can\naccept, if any of those", "start": 2810.35, "duration": 3.81}, {"text": "generate w, and reject if not.", "start": 2814.16, "duration": 2.84}, {"text": "OK?", "start": 2817.0, "duration": 2.7}, {"text": "Before moving on, so this\nanswers the problem--", "start": 2819.7, "duration": 4.14}, {"text": "shows that this language is\ndecidable, the ACFG language.", "start": 2823.84, "duration": 5.78}, {"text": "So that's something that--", "start": 2829.62, "duration": 1.47}, {"text": "make sure you understand.", "start": 2831.09, "duration": 2.108}, {"text": "We're basically trying\nold derivations of up to--", "start": 2835.95, "duration": 3.12}, {"text": "of a certain length,\nbecause that's", "start": 2839.07, "duration": 1.98}, {"text": "all that's needed when the\ngrammar is in that form.", "start": 2841.05, "duration": 3.28}, {"text": "Now we're going to use that\nto prove a corollary, which", "start": 2844.33, "duration": 5.67}, {"text": "is important for understanding\nhow everything fits together.", "start": 2850.0, "duration": 3.39}, {"text": "And that corollary states that\nevery context-free language", "start": 2853.39, "duration": 5.85}, {"text": "is a decidable language.", "start": 2859.24, "duration": 2.33}, {"text": "Every context-free\nlanguage is decidable.", "start": 2861.57, "duration": 1.92}, {"text": "Now, why does that\nfollow from this?", "start": 2863.49, "duration": 2.5}, {"text": "Well, suppose you have\na context-free language.", "start": 2865.99, "duration": 6.56}, {"text": "We know that\nlanguage is generated", "start": 2872.55, "duration": 2.37}, {"text": "by some context-free grammar\nG. That's what it means.", "start": 2874.92, "duration": 7.58}, {"text": "So then you can take that\ngrammar G and you can build it", "start": 2882.5, "duration": 5.0}, {"text": "into a Turing machine.", "start": 2887.5, "duration": 1.18}, {"text": "So there's going to be a term\nmachine which is constructed", "start": 2888.68, "duration": 7.91}, {"text": "with the knowledge of G.", "start": 2896.59, "duration": 4.35}, {"text": "And that Turing machine\nis going to take its w", "start": 2900.94, "duration": 3.99}, {"text": "and run the ACFG algorithm\nwith w combined with a G that's", "start": 2904.93, "duration": 6.96}, {"text": "already built into it.", "start": 2911.89, "duration": 1.69}, {"text": "So it's just going to stick\nthat grammar G in front of w,", "start": 2913.58, "duration": 3.23}, {"text": "and now we run the ACFG decider.", "start": 2916.81, "duration": 4.09}, {"text": "It's going to say,\ndoes degenerate w?", "start": 2920.9, "duration": 2.7}, {"text": "Well, that's going to be\nyes every time w is in A.", "start": 2923.6, "duration": 6.27}, {"text": "And so this machine here\nnow is going to end up", "start": 2929.87, "duration": 3.27}, {"text": "accepting every\nstring that's in A,", "start": 2933.14, "duration": 3.81}, {"text": "because it's every\nstring that G generates.", "start": 2936.95, "duration": 3.81}, {"text": "So that is, I think, what\nI wanted to say about this.", "start": 2940.76, "duration": 6.13}, {"text": "Now, I feel that this\ncorollary here throws", "start": 2946.89, "duration": 5.23}, {"text": "a little bit of a curveball.", "start": 2952.12, "duration": 2.61}, {"text": "And we can just\npause for a moment", "start": 2954.73, "duration": 3.48}, {"text": "here just to make sure\nyou're understanding this.", "start": 2958.21, "duration": 4.44}, {"text": "The tricky thing about\nthis corollary is--", "start": 2968.91, "duration": 5.64}, {"text": "that I often get--", "start": 2974.55, "duration": 1.98}, {"text": "a question I often get where--", "start": 2976.53, "duration": 1.89}, {"text": "is when we start off with\na context-free language,", "start": 2978.42, "duration": 4.77}, {"text": "who gives--", "start": 2983.19, "duration": 1.8}, {"text": "how do we get G?", "start": 2984.99, "duration": 1.23}, {"text": "Because we need G to build\na Turing machine M sub G. So", "start": 2988.83, "duration": 5.928}, {"text": "we know A is a\ncontext-free language,", "start": 2994.758, "duration": 1.542}, {"text": "but how do we know what G is?", "start": 2996.3, "duration": 2.67}, {"text": "Well, the point is that\nwe may not know what G is,", "start": 2998.97, "duration": 7.83}, {"text": "but we know G exists, because\nthat's a definition of A", "start": 3006.8, "duration": 4.41}, {"text": "being a context-free language.", "start": 3011.21, "duration": 3.33}, {"text": "It must have a context-free\ngrammar, by definition.", "start": 3014.54, "duration": 4.71}, {"text": "And so because G exists, I now\nknow my Turing machine, M sub", "start": 3019.25, "duration": 3.82}, {"text": "G, exists.", "start": 3023.07, "duration": 1.96}, {"text": "And that's enough to\nknow that A is decidable,", "start": 3025.03, "duration": 4.05}, {"text": "because it has a\ndecider that exists.", "start": 3029.08, "duration": 3.11}, {"text": "Now, if you're not going to\ntell me the grammar for G,", "start": 3032.19, "duration": 3.24}, {"text": "I'm not going to tell you the\nTuring machine which decides A.", "start": 3035.43, "duration": 6.95}, {"text": "But both of them exist.", "start": 3042.38, "duration": 2.28}, {"text": "So if you tell me G, then I can\ntell you the Turing machine.", "start": 3044.66, "duration": 2.84}, {"text": "So it's a subtle,\ntricky issue there.", "start": 3050.24, "duration": 2.55}, {"text": "A certain little element\nmaybe of-- sometimes people", "start": 3052.79, "duration": 2.43}, {"text": "call it non-constructive,\nbecause we're just, in a sense,", "start": 3055.22, "duration": 1.95}, {"text": "showing just that\nsomething is existing.", "start": 3057.17, "duration": 1.667}, {"text": "It does the job for\nus, because it shows", "start": 3062.25, "duration": 2.02}, {"text": "that A is a decidable language.", "start": 3064.27, "duration": 2.71}, {"text": "OK, so not so many questions\nhere-- maybe the TAs", "start": 3066.98, "duration": 2.422}, {"text": "are getting them.", "start": 3069.402, "duration": 0.708}, {"text": "So let's move on.", "start": 3070.11, "duration": 1.71}, {"text": "Here's another check-in.", "start": 3071.82, "duration": 3.44}, {"text": "So now, can we conclude that A--", "start": 3075.26, "duration": 3.02}, {"text": "instead of ACFG,\nAPDA is decidable?", "start": 3078.28, "duration": 3.45}, {"text": "People are getting\nthis one pretty fast.", "start": 3096.608, "duration": 1.667}, {"text": "Another 10 seconds--\nthree seconds--", "start": 3102.89, "duration": 11.1}, {"text": "OK, going to shut it down--", "start": 3113.99, "duration": 1.29}, {"text": "end polling, share results.", "start": 3117.88, "duration": 4.53}, {"text": "Yeah.", "start": 3122.41, "duration": 0.5}, {"text": "So this problem here\nis APDA is decidable.", "start": 3128.01, "duration": 6.637}, {"text": "I was almost wondering whether\nor not to give this poll,", "start": 3134.647, "duration": 2.333}, {"text": "because it has-- it's true for\nthe same reason as poll number", "start": 3136.98, "duration": 3.18}, {"text": "1, because we know\nhow to convert PDAs--", "start": 3140.16, "duration": 3.675}, {"text": "or we stated we can\nconvert PDAs to CFGs.", "start": 3143.835, "duration": 6.015}, {"text": "And that conversion\nhas given in the book.", "start": 3149.85, "duration": 1.992}, {"text": "We didn't do in\nlecture, but I just", "start": 3151.842, "duration": 1.458}, {"text": "stated you have\nto know that fact,", "start": 3153.3, "duration": 1.47}, {"text": "but not necessarily\nknow how to do it.", "start": 3154.77, "duration": 1.96}, {"text": "That's OK.", "start": 3156.73, "duration": 0.86}, {"text": "But the fact is true.", "start": 3157.59, "duration": 2.418}, {"text": "The conversion is\nin the book, and it", "start": 3160.008, "duration": 1.542}, {"text": "could be implemented\non a Turing machine.", "start": 3161.55, "duration": 1.87}, {"text": "So if you want to know whether\na PDA's language is empty,", "start": 3163.42, "duration": 4.16}, {"text": "you convert it to a context-free\ngrammar and then use this", "start": 3167.58, "duration": 2.67}, {"text": "procedure here to test\nwhether it's a language--", "start": 3170.25, "duration": 2.31}, {"text": "oh, not empty-- I'm sorry.", "start": 3175.71, "duration": 3.0}, {"text": "The acceptance problem--", "start": 3178.71, "duration": 2.46}, {"text": "I just want to know, does\nthe PDA accept some input?", "start": 3181.17, "duration": 4.2}, {"text": "I'm saying it wrong.", "start": 3185.37, "duration": 1.12}, {"text": "So I want to know, does\nthe PDA accept some input?", "start": 3186.49, "duration": 2.63}, {"text": "I convert that PDA to\na grammar, and then I", "start": 3189.12, "duration": 3.87}, {"text": "see if the grammar generates\nthat input, because it's", "start": 3192.99, "duration": 2.34}, {"text": "an equivalent grammar.", "start": 3195.33, "duration": 2.65}, {"text": "So again, this is using the\nfact that grammars and PDAs are", "start": 3197.98, "duration": 4.05}, {"text": "equivalent and convertible\nfrom one to another,", "start": 3202.03, "duration": 3.61}, {"text": "just like regular\nexpressions and DFAs", "start": 3205.64, "duration": 1.82}, {"text": "from the previous poll.", "start": 3207.46, "duration": 2.33}, {"text": "So you need to be\ncomfortable with that,", "start": 3209.79, "duration": 2.36}, {"text": "because we're going to not\neven talk about it anymore.", "start": 3212.15, "duration": 2.25}, {"text": "We're just going to be\ntreating those things--", "start": 3214.4, "duration": 1.917}, {"text": "going back and forth between\nthem without sometimes", "start": 3216.317, "duration": 2.863}, {"text": "even any comment.", "start": 3219.18, "duration": 2.31}, {"text": "OK.", "start": 3221.49, "duration": 2.36}, {"text": "So let's move on.", "start": 3223.85, "duration": 3.28}, {"text": "Emptiness problem for CFGs--", "start": 3227.13, "duration": 2.31}, {"text": "hopefully you're\ngetting comfortable", "start": 3229.44, "duration": 1.5}, {"text": "with the terminology I'm using.", "start": 3230.94, "duration": 2.85}, {"text": "So now the emptiness problem\nfor context-free grammars--", "start": 3233.79, "duration": 4.02}, {"text": "I'm just going to\ngive you a grammar,", "start": 3237.81, "duration": 1.71}, {"text": "and I want to know if\nits language is empty.", "start": 3239.52, "duration": 3.91}, {"text": "OK, so remember, we did\nthis for finite automata", "start": 3243.43, "duration": 2.76}, {"text": "by testing a path.", "start": 3246.19, "duration": 2.34}, {"text": "We don't really have paths here.", "start": 3248.53, "duration": 2.07}, {"text": "You might think testing\npaths and pushed automata.", "start": 3250.6, "duration": 2.21}, {"text": "That's not going to really work,\nbecause the stack is there.", "start": 3252.81, "duration": 2.5}, {"text": "So how are we going\nto do that test?", "start": 3255.31, "duration": 1.8}, {"text": "Well, there's something\nsort of like testing a path,", "start": 3257.11, "duration": 3.36}, {"text": "just working with\nthe grammar itself,", "start": 3260.47, "duration": 3.61}, {"text": "kind of working backwards\nfrom the terminals now.", "start": 3264.08, "duration": 3.66}, {"text": "I'll illustrate that here.", "start": 3267.74, "duration": 4.17}, {"text": "Here's a very simple\ngrammar, and I want to know,", "start": 3271.91, "duration": 5.4}, {"text": "does it generate any strings?", "start": 3277.31, "duration": 3.15}, {"text": "Obviously, only care about\nstrings of terminals,", "start": 3280.46, "duration": 2.46}, {"text": "because those are the things\nthat are in the language--", "start": 3282.92, "duration": 2.93}, {"text": "so does this grammar generate\nany strings of terminals?", "start": 3285.85, "duration": 5.31}, {"text": "So way we're going to answer\nthat is by a marking procedure,", "start": 3291.16, "duration": 4.08}, {"text": "but in a sense, we're going\nto start from the terminals", "start": 3295.24, "duration": 3.45}, {"text": "and work backwards to see if we\ncan get to the start variable.", "start": 3298.69, "duration": 4.12}, {"text": "So first, we're going to mark\nall the terminal symbols,", "start": 3302.81, "duration": 3.56}, {"text": "and then we're going\nto mark anything", "start": 3306.37, "duration": 2.79}, {"text": "that goes to a string of\ncompletely marked symbols,", "start": 3309.16, "duration": 7.21}, {"text": "either terminals or variables--", "start": 3316.37, "duration": 2.85}, {"text": "because anything that's\nmarked, we know, can derive", "start": 3319.22, "duration": 3.12}, {"text": "a string of terminals.", "start": 3322.34, "duration": 1.08}, {"text": "That's what it means.", "start": 3323.42, "duration": 1.14}, {"text": "Anything that's blue can derive\na string of just terminals.", "start": 3324.56, "duration": 4.02}, {"text": "And so now, if you\nhave a collection", "start": 3328.58, "duration": 1.59}, {"text": "of those that are all\nmarked, they together", "start": 3330.17, "duration": 3.96}, {"text": "can generate some string\nof terminals together.", "start": 3334.13, "duration": 5.05}, {"text": "And so then you can mark\nthe associated variable.", "start": 3339.18, "duration": 2.43}, {"text": "So T goes to a.", "start": 3341.61, "duration": 1.7}, {"text": "So that may be\noversimple, but we're", "start": 3343.31, "duration": 2.55}, {"text": "going to mark T here\neverywhere in the grammar.", "start": 3345.86, "duration": 3.45}, {"text": "So all these T's are\ngoing to get marked,", "start": 3349.31, "duration": 1.74}, {"text": "because we know that T can\ngenerate a string of terminals.", "start": 3351.05, "duration": 5.38}, {"text": "Now let's take a\nlook at R. R is going", "start": 3356.43, "duration": 3.21}, {"text": "to a string of symbols\nthat are all marked,", "start": 3359.64, "duration": 3.9}, {"text": "and that means those symbols\ncan, in turn, generate", "start": 3363.54, "duration": 3.025}, {"text": "strings of terminals.", "start": 3366.565, "duration": 0.875}, {"text": "So we're going to mark R2.", "start": 3367.44, "duration": 1.83}, {"text": "We can't yet mark S,\nbecause we don't know yet", "start": 3369.27, "duration": 2.88}, {"text": "whether S has some unmarked\nthing that it goes to.", "start": 3372.15, "duration": 3.0}, {"text": "So we don't know\nyet whether S can", "start": 3375.15, "duration": 1.68}, {"text": "generate a string of terminals.", "start": 3376.83, "duration": 1.32}, {"text": "But R we know right now,\nso we're going to mark R.", "start": 3378.15, "duration": 3.24}, {"text": "But then now that gets\nus to mark this R,", "start": 3381.39, "duration": 2.43}, {"text": "and so then we can go\nbackwards and we can mark S.", "start": 3383.82, "duration": 3.68}, {"text": "And we keep doing that until\nthere's nothing new to mark.", "start": 3387.5, "duration": 3.695}, {"text": "And here we've\nmarked everything,", "start": 3391.195, "duration": 1.375}, {"text": "so clearly there's\nnothing more you can mark.", "start": 3392.57, "duration": 1.92}, {"text": "But you might stop before\nyou've marked everything.", "start": 3394.49, "duration": 2.97}, {"text": "And then you see whether you've\nmarked the start variable", "start": 3397.46, "duration": 5.43}, {"text": "or not.", "start": 3402.89, "duration": 0.85}, {"text": "And if you have, you know\nthe language is not empty.", "start": 3403.74, "duration": 4.96}, {"text": "OK, so let's just go\nthrough this in text.", "start": 3408.7, "duration": 4.77}, {"text": "Mark all occurrences\nof terminals in G, then", "start": 3413.47, "duration": 3.21}, {"text": "repeat until no new\nvariables are marked.", "start": 3416.68, "duration": 2.01}, {"text": "We mark all occurrences\nof variables A,", "start": 3418.69, "duration": 3.93}, {"text": "if A goes to a\nstring of symbols,", "start": 3422.62, "duration": 2.79}, {"text": "and all of those symbols\nwere already marked,", "start": 3425.41, "duration": 3.345}, {"text": "because those are\nthe things that", "start": 3428.755, "duration": 1.375}, {"text": "already have been shown to\ngenerate a string of terminals.", "start": 3430.13, "duration": 4.7}, {"text": "And so now we're going to\nreject if the start date--", "start": 3434.83, "duration": 2.46}, {"text": "start variable's marked--\nbecause that means that", "start": 3437.29, "duration": 2.25}, {"text": "the language is not empty--", "start": 3439.54, "duration": 1.59}, {"text": "and accept if it's not.", "start": 3441.13, "duration": 2.89}, {"text": "OK?", "start": 3444.02, "duration": 0.5}, {"text": "I'll take a couple of\nquick questions here.", "start": 3454.21, "duration": 2.35}, {"text": "OK, somebody asked whether--", "start": 3464.35, "duration": 6.82}, {"text": "if I understand-- are the\nregular languages also", "start": 3471.17, "duration": 2.31}, {"text": "decidable?", "start": 3473.48, "duration": 0.648}, {"text": "Well, remember, the\nregular languages", "start": 3474.128, "duration": 1.542}, {"text": "are context-free languages,\nand the context-free languages", "start": 3475.67, "duration": 2.7}, {"text": "are decidable, so yes,\nthe regular languages", "start": 3478.37, "duration": 2.28}, {"text": "are decidable.", "start": 3480.65, "duration": 1.177}, {"text": "Some of those are going\nto be too long to answer,", "start": 3492.268, "duration": 2.042}, {"text": "and they're trying to come up\nwith alternative solutions.", "start": 3494.31, "duration": 3.25}, {"text": "So I think we're\ngoing to move on.", "start": 3497.56, "duration": 3.32}, {"text": "All right.", "start": 3500.88, "duration": 0.54}, {"text": "Just like we did for\nthe finite automata,", "start": 3503.94, "duration": 3.19}, {"text": "we talked about acceptance,\nwe talked about emptiness,", "start": 3507.13, "duration": 3.0}, {"text": "we talked about equivalence.", "start": 3510.13, "duration": 3.27}, {"text": "So how about the equivalence\nproblem for context-free", "start": 3513.4, "duration": 3.03}, {"text": "grammars?", "start": 3516.43, "duration": 1.62}, {"text": "I'm going to give you now\ntwo context-free grammars,", "start": 3518.05, "duration": 3.81}, {"text": "and I'd like to know, are\nthose two context-free grammars", "start": 3521.86, "duration": 4.53}, {"text": "generating the same language?", "start": 3526.39, "duration": 3.68}, {"text": "OK, so how might you\nthink about that?", "start": 3530.07, "duration": 4.48}, {"text": "Well, one thing-- following some\nof the ideas that we've already", "start": 3534.55, "duration": 3.84}, {"text": "had, you could try feeding\nstrings into those grammars.", "start": 3538.39, "duration": 5.34}, {"text": "You know how to test whether\nthose individual grammars can", "start": 3543.73, "duration": 3.54}, {"text": "generate those strings,\nso you can just", "start": 3547.27, "duration": 1.68}, {"text": "try feeding strings\nin to G and to H,", "start": 3548.95, "duration": 4.35}, {"text": "and seeing whether those\ngrammars ever disagree", "start": 3553.3, "duration": 3.57}, {"text": "or whether they\ngenerate some string.", "start": 3556.87, "duration": 1.68}, {"text": "Find some string that say\nG generates, but H does not", "start": 3558.55, "duration": 2.85}, {"text": "generate.", "start": 3561.4, "duration": 0.72}, {"text": "And we can test that\nstring by string.", "start": 3562.12, "duration": 3.12}, {"text": "Unfortunately, we got a\nlot of strings to test.", "start": 3565.24, "duration": 4.52}, {"text": "We would need to give\nsome bound if we were", "start": 3569.76, "duration": 3.18}, {"text": "going to use that procedure--", "start": 3572.94, "duration": 2.61}, {"text": "not clear what the bound is.", "start": 3575.55, "duration": 1.53}, {"text": "Another idea might be to\nuse the closure construction", "start": 3579.88, "duration": 8.64}, {"text": "that we had from before.", "start": 3588.52, "duration": 2.34}, {"text": "So let's mull that over--", "start": 3590.86, "duration": 2.43}, {"text": "whether that might work.", "start": 3593.29, "duration": 2.07}, {"text": "But in fact, let me give\naway the answer here.", "start": 3595.36, "duration": 9.59}, {"text": "This language is not decidable.", "start": 3604.95, "duration": 2.79}, {"text": "There's no algorithm out\nthere-- no Turing machine,", "start": 3607.74, "duration": 3.15}, {"text": "but therefore no algorithm--", "start": 3610.89, "duration": 1.87}, {"text": "which can take two grammars\nand test whether they generate", "start": 3612.76, "duration": 4.16}, {"text": "the same language or not--", "start": 3616.92, "duration": 3.09}, {"text": "seems, at first, glance\nkind of surprising.", "start": 3620.01, "duration": 3.4}, {"text": "Such simple things as\ncontext-free grammars can", "start": 3623.41, "duration": 3.06}, {"text": "nonetheless be so complicated\nthat there's no procedure out", "start": 3626.47, "duration": 3.78}, {"text": "there which can tell\nwhether the two--", "start": 3630.25, "duration": 2.913}, {"text": "those two grammars\ngenerate the same language.", "start": 3633.163, "duration": 1.917}, {"text": "We will show that next week.", "start": 3635.08, "duration": 2.7}, {"text": "A related problem, which is\nrelated to your homework--", "start": 3640.94, "duration": 3.48}, {"text": "this that's due on Thursday--", "start": 3644.42, "duration": 4.53}, {"text": "is testing whether a\ngrammar is ambiguous.", "start": 3648.95, "duration": 4.87}, {"text": "So given a grammar,\nI'd like to know,", "start": 3653.82, "duration": 1.73}, {"text": "is that grammar an\nambiguous grammar or not?", "start": 3655.55, "duration": 4.53}, {"text": "Does it generate some\nstring in the language", "start": 3660.08, "duration": 4.62}, {"text": "of that grammar in two\npossibly different ways, two", "start": 3664.7, "duration": 2.67}, {"text": "or more different ways?", "start": 3667.37, "duration": 1.63}, {"text": "So is there some string\nthat can be generated", "start": 3669.0, "duration": 3.78}, {"text": "with two different parts.", "start": 3672.78, "duration": 3.61}, {"text": "So the problem with testing\nwhether grammar is ambiguous--", "start": 3676.39, "duration": 4.07}, {"text": "not decidable.", "start": 3680.46, "duration": 2.03}, {"text": "So I'm asking you to\ndo something hard,", "start": 3682.49, "duration": 3.12}, {"text": "when you have to produce that\ngrammar which is unambiguous", "start": 3685.61, "duration": 5.07}, {"text": "for that language.", "start": 3690.68, "duration": 1.47}, {"text": "In general, testing\nwhether a grammar is", "start": 3692.15, "duration": 2.91}, {"text": "ambiguous or is not\na decidable problem.", "start": 3695.06, "duration": 2.82}, {"text": "Now, hopefully the grammar that\nyou'll produce to show that--", "start": 3697.88, "duration": 7.05}, {"text": "that unambiguous grammar\nfor that language", "start": 3704.93, "duration": 3.03}, {"text": "that I'm asking you\nto produce is not", "start": 3707.96, "duration": 1.8}, {"text": "going to require our graders to\nsolve some decidable problem,", "start": 3709.76, "duration": 4.14}, {"text": "but it'll be clear based the\nconstruction of that grammar", "start": 3713.9, "duration": 2.97}, {"text": "why it's not ambiguous.", "start": 3716.87, "duration": 2.19}, {"text": "So you'll have to hopefully\nsay some explanation", "start": 3719.06, "duration": 3.06}, {"text": "of your thinking there.", "start": 3722.12, "duration": 1.56}, {"text": "OK.", "start": 3726.505, "duration": 0.5}, {"text": "And we will prove that the\nproblem of testing ambiguity", "start": 3729.84, "duration": 4.05}, {"text": "is not decidable.", "start": 3733.89, "duration": 1.17}, {"text": "That's going to be a homework\nproblem in problem set 3.", "start": 3735.06, "duration": 4.45}, {"text": "OK.", "start": 3739.51, "duration": 1.88}, {"text": "Last check-in here--\nsomething that I alluded", "start": 3741.39, "duration": 3.09}, {"text": "to, but didn't quite--", "start": 3744.48, "duration": 1.56}, {"text": "didn't want to give away.", "start": 3746.04, "duration": 2.01}, {"text": "Why not use the same\ntechnique that we", "start": 3748.05, "duration": 3.12}, {"text": "use to show equivalence\nof DFAs is decidable,", "start": 3751.17, "duration": 3.63}, {"text": "to show that equivalence\nof context-free grammars", "start": 3754.8, "duration": 2.16}, {"text": "is desirable?", "start": 3756.96, "duration": 0.66}, {"text": "Obviously, something goes wrong\nbecause EQCFG is not decidable.", "start": 3757.62, "duration": 5.25}, {"text": "Why doesn't that same\ntechnique just work?", "start": 3762.87, "duration": 3.81}, {"text": "Well, what's the answer?", "start": 3766.68, "duration": 5.495}, {"text": "Got a real race here--", "start": 3784.68, "duration": 1.23}, {"text": "another 15 seconds-- this\none gives you something", "start": 3791.74, "duration": 4.35}, {"text": "to mull over.", "start": 3796.09, "duration": 0.72}, {"text": "All right.", "start": 3804.43, "duration": 0.78}, {"text": "Let's end it.", "start": 3805.21, "duration": 1.32}, {"text": "OK, you're good to go.", "start": 3806.53, "duration": 1.68}, {"text": "At least click something.", "start": 3808.21, "duration": 2.29}, {"text": "OK, ending polling,\nsharing results--", "start": 3810.5, "duration": 7.015}, {"text": "OK, bunch of you have thought,\nwell, CFGs are generators", "start": 3817.515, "duration": 4.095}, {"text": "and DFAs are recognizers,\nand that's the issue.", "start": 3821.61, "duration": 2.7}, {"text": "Well, not really,\nbecause we could test", "start": 3824.31, "duration": 8.1}, {"text": "equivalence of\nregular expressions--", "start": 3832.41, "duration": 2.67}, {"text": "those are generators.", "start": 3835.08, "duration": 0.96}, {"text": "It's nothing to do\nwith being a generator", "start": 3836.04, "duration": 1.89}, {"text": "or not, because we can convert\nregular expressions to DFAs", "start": 3837.93, "duration": 6.62}, {"text": "and then test\nequivalence for the DFAs,", "start": 3844.55, "duration": 2.58}, {"text": "so that-- it's not really a\nmatter of being generated.", "start": 3847.13, "duration": 2.88}, {"text": "That's not the issue.", "start": 3850.01, "duration": 2.14}, {"text": "The issue is that we can't\nfollow the same construction", "start": 3852.15, "duration": 3.44}, {"text": "that we did to show\nEQDFA is decidable,", "start": 3855.59, "duration": 2.85}, {"text": "because the context-free\nlanguages are not closed under", "start": 3858.44, "duration": 3.87}, {"text": "those operations we needed to\nmake that symmetric difference", "start": 3862.31, "duration": 3.39}, {"text": "machine--", "start": 3865.7, "duration": 1.37}, {"text": "if you remember how that worked.", "start": 3867.07, "duration": 2.77}, {"text": "So they're not closed\nunder implementation", "start": 3869.84, "duration": 1.75}, {"text": "and not closed\nunder intersection.", "start": 3871.59, "duration": 1.417}, {"text": "We needed both in order\nto build that machine", "start": 3873.007, "duration": 2.723}, {"text": "C, which accepted\nall the strings that", "start": 3875.73, "duration": 3.39}, {"text": "are in the difference.", "start": 3879.12, "duration": 3.13}, {"text": "OK?", "start": 3882.25, "duration": 1.35}, {"text": "So let's continue on.", "start": 3883.6, "duration": 2.8}, {"text": "Let's move now to\nTuring machines.", "start": 3886.4, "duration": 2.492}, {"text": "This is where stuff\nis really going", "start": 3888.892, "duration": 1.458}, {"text": "to start to get interesting--\nhope it's been interesting", "start": 3890.35, "duration": 3.09}, {"text": "all along, but maybe\neven more interesting.", "start": 3893.44, "duration": 3.88}, {"text": "So let's talk about\nthe acceptance problem", "start": 3897.32, "duration": 3.02}, {"text": "for Turing machines, ATM.", "start": 3900.34, "duration": 3.12}, {"text": "This language is going\nto become an old friend,", "start": 3903.46, "duration": 3.09}, {"text": "but we're just\ngetting to know it.", "start": 3906.55, "duration": 3.332}, {"text": "So this is the problem.", "start": 3909.882, "duration": 0.958}, {"text": "You're given a Turing\nmachine now, and an input,", "start": 3910.84, "duration": 3.15}, {"text": "and I want to know, does\nM accept that input?", "start": 3913.99, "duration": 4.82}, {"text": "Does that Turing machine\naccept its input?", "start": 3918.81, "duration": 1.8}, {"text": "OK, so that's going to not be\na decidable problem either.", "start": 3923.27, "duration": 4.12}, {"text": "So we've shifted gears from\na bunch of decidable things", "start": 3927.39, "duration": 2.39}, {"text": "to a bunch of\nundecidable things.", "start": 3929.78, "duration": 3.04}, {"text": "So this is not a\ndecidable language.", "start": 3932.82, "duration": 1.91}, {"text": "We will prove that on Thursday.", "start": 3934.73, "duration": 2.587}, {"text": "That's going to be the whole\npoint of Thursday's lecture", "start": 3937.317, "duration": 2.333}, {"text": "is proving the ATM is decidable.", "start": 3939.65, "duration": 2.88}, {"text": "And that's going to be\nreally a jumping off point", "start": 3942.53, "duration": 2.07}, {"text": "for showing other\nproblems are decidable.", "start": 3944.6, "duration": 3.64}, {"text": "So that's going to be our\nfirst proof of decidability.", "start": 3948.24, "duration": 3.3}, {"text": "But we do know that\nATM is recognizable,", "start": 3954.24, "duration": 4.62}, {"text": "and that's worth understanding--", "start": 3958.86, "duration": 5.37}, {"text": "for multiple reasons,\nbut for one thing,", "start": 3964.23, "duration": 2.31}, {"text": "it's going to give us an\nexample of a problem which", "start": 3966.54, "duration": 2.46}, {"text": "we know is recognizable,\nbut not decidable,", "start": 3969.0, "duration": 2.46}, {"text": "as we'll prove undecidability.", "start": 3971.46, "duration": 2.55}, {"text": "But it's also, I think,\nof historical importance,", "start": 3974.01, "duration": 9.6}, {"text": "this algorithm for showing--", "start": 3983.61, "duration": 2.49}, {"text": "recognizable.", "start": 3986.1, "duration": 0.732}, {"text": "So let's go through\nthat algorithm.", "start": 3986.832, "duration": 1.458}, {"text": "It's very simple, sort of\ndoing the obvious thing.", "start": 3988.29, "duration": 4.18}, {"text": "The following Turing machine--", "start": 3992.47, "duration": 1.25}, {"text": "I'm going to call it U, for\na reason that I'll make clear", "start": 3993.72, "duration": 4.2}, {"text": "in a second.", "start": 3997.92, "duration": 0.96}, {"text": "That's going to be a\nrecognizer for ATM.", "start": 3998.88, "duration": 3.03}, {"text": "So it takes as\ninput an M and a w,", "start": 4001.91, "duration": 5.08}, {"text": "and it's just going to simulate\nM on w, pretty much the way", "start": 4006.99, "duration": 3.84}, {"text": "the algorithm the\ndecider for ADFA work.", "start": 4010.83, "duration": 6.75}, {"text": "But now the machine--", "start": 4017.58, "duration": 2.58}, {"text": "instead of being a DFA,\nit's a Turing machine,", "start": 4020.16, "duration": 2.25}, {"text": "and the Turing machine\nmight go forever.", "start": 4022.41, "duration": 3.06}, {"text": "And so the simulation\nmay not stop.", "start": 4025.47, "duration": 3.05}, {"text": "And that's the key difference,\nwhich makes it from a decider", "start": 4028.52, "duration": 2.58}, {"text": "into a recognizer.", "start": 4031.1, "duration": 1.11}, {"text": "So you're going to\nbe simulating, just", "start": 4035.457, "duration": 1.583}, {"text": "keeping track of the tape of M,\nthe current state of M, where--", "start": 4037.04, "duration": 5.61}, {"text": "and proceeding to modify\nthe tape as M modifies it.", "start": 4042.65, "duration": 5.76}, {"text": "And then, if M enters\nan accept state,", "start": 4048.41, "duration": 4.57}, {"text": "then you know M has\naccepted its input,", "start": 4052.98, "duration": 1.71}, {"text": "so U also will enter\nan accept state.", "start": 4054.69, "duration": 1.71}, {"text": "So the machine U\nenters the accept state", "start": 4056.4, "duration": 3.12}, {"text": "if M observes during\nthe simulation", "start": 4059.52, "duration": 2.25}, {"text": "that M enters an accept state.", "start": 4061.77, "duration": 3.25}, {"text": "Furthermore, if an M\nenters a reject state,", "start": 4065.02, "duration": 4.78}, {"text": "then U also enters\na reject state.", "start": 4069.8, "duration": 4.7}, {"text": "OK?", "start": 4074.5, "duration": 1.17}, {"text": "Now I'm going to say\nsomething beyond that, which", "start": 4075.67, "duration": 2.25}, {"text": "I want you to pay attention to,\nwhich is the kind of thing I", "start": 4077.92, "duration": 9.11}, {"text": "do see sometimes people saying.", "start": 4087.03, "duration": 3.61}, {"text": "We want U to reject\nif M never halts.", "start": 4090.64, "duration": 3.18}, {"text": "That's also-- seems\nlike what we want,", "start": 4096.569, "duration": 3.54}, {"text": "because if it never halts,\nthen M is rejecting by looping,", "start": 4100.109, "duration": 3.721}, {"text": "so you should also reject.", "start": 4103.83, "duration": 2.949}, {"text": "But I don't like that.", "start": 4106.779, "duration": 2.281}, {"text": "I don't like that line here,\nstep 4 of the Turing machine,", "start": 4109.06, "duration": 4.71}, {"text": "because there's no way for a\nTuring machine to determine--", "start": 4113.77, "duration": 3.24}, {"text": "or at least as we--\nno obvious way--", "start": 4117.01, "duration": 3.13}, {"text": "and in fact, there\nwill not be any way,", "start": 4120.14, "duration": 1.79}, {"text": "but certainly, at this\npoint, no obvious way for M", "start": 4121.93, "duration": 2.849}, {"text": "to even tell--", "start": 4124.779, "duration": 1.691}, {"text": "for U you to tell whether\nM is halting or not.", "start": 4126.47, "duration": 4.257}, {"text": "Well, certainly you\ncan tell that it's", "start": 4130.727, "duration": 1.583}, {"text": "to say it never halts.", "start": 4132.31, "duration": 1.049}, {"text": "How can you make\nthat determination?", "start": 4133.359, "duration": 3.21}, {"text": "If I saw this on a\nsolution, either on an exam", "start": 4136.569, "duration": 4.891}, {"text": "or a homework, I\nwould mark you off.", "start": 4141.46, "duration": 2.85}, {"text": "This is no good.", "start": 4144.31, "duration": 1.469}, {"text": "It's not illegal to\nTuring machine action.", "start": 4145.779, "duration": 3.37}, {"text": "If M does not hold on w,\nthen you should reject.", "start": 4149.149, "duration": 8.151}, {"text": "That is correct.", "start": 4157.3, "duration": 1.2}, {"text": "And you can make that reasoning\nexternal to the algorithm of U,", "start": 4158.5, "duration": 5.25}, {"text": "but U is going to end up\nrejecting, because it never", "start": 4163.75, "duration": 2.819}, {"text": "holds either.", "start": 4166.569, "duration": 2.0}, {"text": "It never actually knows that\nM is rejecting w in that case,", "start": 4168.569, "duration": 4.83}, {"text": "if M is rejecting by looping.", "start": 4173.399, "duration": 1.5}, {"text": "It's just blindly going along\nand doing the simulation of M", "start": 4174.899, "duration": 3.031}, {"text": "on w--", "start": 4177.93, "duration": 2.27}, {"text": "and will end up halting--", "start": 4180.2, "duration": 1.05}, {"text": "rejecting by looping, if\nM is rejecting by looping.", "start": 4181.25, "duration": 2.675}, {"text": "But that's something\nthat you can", "start": 4183.925, "duration": 1.375}, {"text": "argue if you need\nto make a proof", "start": 4185.3, "duration": 3.309}, {"text": "or make some sort of\nreasoning about the machine,", "start": 4188.609, "duration": 2.201}, {"text": "but it's not part of the\nalgorithm of the machine.", "start": 4190.81, "duration": 2.083}, {"text": "OK.", "start": 4196.31, "duration": 0.54}, {"text": "Now, what's, I think, from\na historical standpoint,", "start": 4196.85, "duration": 2.76}, {"text": "that's interesting\nabout this machine U", "start": 4199.61, "duration": 1.71}, {"text": "and why I'm calling it U\nis because this appeared--", "start": 4201.32, "duration": 3.42}, {"text": "this machine U appeared\nin Turing's original paper", "start": 4204.74, "duration": 4.71}, {"text": "where he laid out\nTuring machines.", "start": 4209.45, "duration": 1.68}, {"text": "He didn't call them Turing\nmachines, by the way.", "start": 4211.13, "duration": 1.47}, {"text": "He called them\ncomputing machines.", "start": 4212.6, "duration": 1.51}, {"text": "People afterward called\nthem Turing machines.", "start": 4214.11, "duration": 3.59}, {"text": "But Turing called this the\nuniversal computing machine.", "start": 4217.7, "duration": 3.857}, {"text": "That's his language.", "start": 4221.557, "duration": 0.833}, {"text": "Actually, I just\nlooked at the paper", "start": 4222.39, "duration": 1.5}, {"text": "yesterday just to\nrefresh my memory of it.", "start": 4223.89, "duration": 3.47}, {"text": "And he gives the description\nof the operation of U", "start": 4227.36, "duration": 3.09}, {"text": "in gory detail, with all of\nthe transitions and the states.", "start": 4230.45, "duration": 3.798}, {"text": "He nails the whole\nthing down-- takes", "start": 4234.248, "duration": 1.542}, {"text": "pages, and pages, and pages.", "start": 4235.79, "duration": 2.99}, {"text": "So he it gives it there.", "start": 4238.78, "duration": 3.48}, {"text": "So this is the original\nuniversal computing machine,", "start": 4242.26, "duration": 4.62}, {"text": "universal Turing machine.", "start": 4246.88, "duration": 2.61}, {"text": "It's more than just\nan idle curiosity", "start": 4249.49, "duration": 2.28}, {"text": "that this appeared\nin Turing's paper,", "start": 4251.77, "duration": 1.77}, {"text": "because this actually\nturned out to be profoundly", "start": 4253.54, "duration": 2.64}, {"text": "influential in computer\nscience, because it really", "start": 4256.18, "duration": 4.89}, {"text": "was the first example of\na machine that operated", "start": 4261.07, "duration": 3.36}, {"text": "based on a stored program.", "start": 4264.43, "duration": 3.8}, {"text": "It really was a\nrevolutionary idea.", "start": 4268.23, "duration": 2.16}, {"text": "In those days, if\nyou wanted to make", "start": 4270.39, "duration": 1.98}, {"text": "a machine that did\nsomething different,", "start": 4272.37, "duration": 2.11}, {"text": "you had to wire the--", "start": 4274.48, "duration": 0.98}, {"text": "rewire the machine.", "start": 4275.46, "duration": 2.27}, {"text": "But here's a machine that\noperated based on instructions.", "start": 4277.73, "duration": 5.13}, {"text": "And instructions, in a sense,\nare no different than the data.", "start": 4282.86, "duration": 4.25}, {"text": "So this is what's been--", "start": 4287.11, "duration": 2.63}, {"text": "come to be known as the\nvon Neumann architecture,", "start": 4289.74, "duration": 2.31}, {"text": "but von Neumann himself gave\ncredit to Turing machine", "start": 4292.05, "duration": 3.21}, {"text": "for having inspired\nhim to think of this.", "start": 4295.26, "duration": 3.21}, {"text": "And some people argue\nthat it's really--", "start": 4298.47, "duration": 2.01}, {"text": "calling it the von Neumann--", "start": 4300.48, "duration": 1.32}, {"text": "bunch of people came\nup with this concept", "start": 4301.8, "duration": 2.1}, {"text": "around the same time,\nmaybe other people too.", "start": 4303.9, "duration": 2.46}, {"text": "There's Babbage and so\non, and others who--", "start": 4306.36, "duration": 3.72}, {"text": "Ada Lovelace-- also who came\nup with notions of programming,", "start": 4310.08, "duration": 4.11}, {"text": "but I think it's a little\ndifferent than this,", "start": 4314.19, "duration": 3.51}, {"text": "in concept.", "start": 4317.7, "duration": 1.2}, {"text": "But anyway, this nevertheless\nplayed an important role", "start": 4318.9, "duration": 3.78}, {"text": "in the history of the subject.", "start": 4322.68, "duration": 1.8}, {"text": "So with that, I think\nwe're out of time.", "start": 4324.48, "duration": 1.77}, {"text": "I'm going to quickly\nreview where we've been.", "start": 4326.25, "duration": 4.56}, {"text": "So we just showed\nthe decidability", "start": 4330.81, "duration": 1.68}, {"text": "of various problems.", "start": 4332.49, "duration": 2.47}, {"text": "These are all languages that\nwe showed are decidable.", "start": 4334.96, "duration": 4.22}, {"text": "We showed that ATM is\nTuring-recognizable,", "start": 4339.18, "duration": 2.79}, {"text": "and I think that was\nall we had for today.", "start": 4341.97, "duration": 3.49}, {"text": "So I will stop right here.", "start": 4345.46, "duration": 5.69}, {"text": "I will stick around and\ntake a few questions,", "start": 4351.15, "duration": 1.95}, {"text": "and our TAs can take a few\nquestions, if you want,", "start": 4353.1, "duration": 2.55}, {"text": "by chat.", "start": 4355.65, "duration": 2.1}, {"text": "And then I also have\nmy office hours,", "start": 4357.75, "duration": 1.87}, {"text": "which will start in\nlike five minutes or so,", "start": 4359.62, "duration": 1.845}, {"text": "once I get everything\nset up on my end.", "start": 4361.465, "duration": 1.625}, {"text": "OK, somebody wanted me to\nreview this point here,", "start": 4366.01, "duration": 5.39}, {"text": "which I'm happy to do.", "start": 4371.4, "duration": 1.04}, {"text": "This code here that I'm\ndescribing in English", "start": 4379.118, "duration": 4.462}, {"text": "needs to be something\nthat you can", "start": 4383.58, "duration": 2.61}, {"text": "implement on a Turing machine.", "start": 4386.19, "duration": 5.61}, {"text": "We're never going to go\nthrough the effort of building", "start": 4391.8, "duration": 4.11}, {"text": "the transition functions,\nand the states, and so on,", "start": 4395.91, "duration": 3.42}, {"text": "but we need to be sure that\nwe could, if we had to.", "start": 4399.33, "duration": 4.17}, {"text": "And how could you make a\nTuring machine do the test", "start": 4403.5, "duration": 7.62}, {"text": "that M doesn't halt?", "start": 4411.12, "duration": 2.49}, {"text": "That's something we\ndon't know how to do.", "start": 4413.61, "duration": 2.74}, {"text": "I can see if M halts.", "start": 4416.35, "duration": 2.9}, {"text": "During the simulation,\nI can see that M", "start": 4419.25, "duration": 2.29}, {"text": "has entered the Q reject\nstate or the Q accept state,", "start": 4421.54, "duration": 3.86}, {"text": "so I can tell while I'm\nsimulating that it has halted.", "start": 4425.4, "duration": 4.83}, {"text": "But how would the\nmachine, or how", "start": 4430.23, "duration": 3.24}, {"text": "would you know that M is now--", "start": 4433.47, "duration": 3.4}, {"text": "someone says, well,\ndo x if M never holds.", "start": 4436.87, "duration": 4.61}, {"text": "Well, how do you know M--\nhow can you do the test", "start": 4441.48, "duration": 3.45}, {"text": "that M is not halting?", "start": 4444.93, "duration": 1.11}, {"text": "There's no obvious\nway to do that.", "start": 4449.57, "duration": 1.73}, {"text": "In fact, there is\nno way to do that.", "start": 4451.3, "duration": 1.87}, {"text": "But as it stands\nright now, the proof", "start": 4453.17, "duration": 2.19}, {"text": "would be on you to show how to\nimplement that on a machine,", "start": 4455.36, "duration": 6.16}, {"text": "and there's just no\nobvious way to do that.", "start": 4461.52, "duration": 2.22}, {"text": "So I think that's why you\nshould only put down things", "start": 4463.74, "duration": 3.23}, {"text": "here which you're sure\nyou could implement,", "start": 4466.97, "duration": 3.54}, {"text": "even if it might\ntake a long time.", "start": 4470.51, "duration": 1.66}, {"text": "So you don't have to worry\nabout how long it would take,", "start": 4472.17, "duration": 2.72}, {"text": "but you have to put\nthings down that you", "start": 4474.89, "duration": 2.7}, {"text": "are sure you could at least\nimplement in principle.", "start": 4477.59, "duration": 4.45}, {"text": "OK, so someone has asked me\nabout the equivalence problem", "start": 4482.04, "duration": 6.28}, {"text": "for context-free grammars\nbeing unsolvable.", "start": 4488.32, "duration": 4.38}, {"text": "Why couldn't the machine be\na human level system of logic", "start": 4492.7, "duration": 4.12}, {"text": "so that the computer could\nlogically deduce whether or not", "start": 4496.82, "duration": 4.28}, {"text": "it was decidable?", "start": 4501.1, "duration": 1.138}, {"text": "We're taking a turn\ninto the subject", "start": 4508.95, "duration": 3.0}, {"text": "of mathematical logic, which is\nsupposed to formalize reasoning", "start": 4511.95, "duration": 4.95}, {"text": "in a way.", "start": 4516.9, "duration": 0.66}, {"text": "In the end, what it\nreally has come down to--", "start": 4521.63, "duration": 2.7}, {"text": "that there are\ncertain grammars which", "start": 4524.33, "duration": 5.58}, {"text": "are equivalent to one\nanother, but there's not", "start": 4529.91, "duration": 8.12}, {"text": "going to be any way\nto prove that they're", "start": 4538.03, "duration": 2.37}, {"text": "equivalent in any\nreasonable system.", "start": 4540.4, "duration": 1.77}, {"text": "Inequivalence you\ncan always prove.", "start": 4545.87, "duration": 2.43}, {"text": "You can exhibit a\nstring that one-- you", "start": 4548.3, "duration": 2.55}, {"text": "can show that this\ngrammar's generating it,", "start": 4550.85, "duration": 2.52}, {"text": "this grammar's not generating.", "start": 4553.37, "duration": 2.04}, {"text": "This other one is not.", "start": 4555.41, "duration": 1.27}, {"text": "So inequivalence you can\nalways prove, but equivalence--", "start": 4556.68, "duration": 4.112}, {"text": "there are going to be certain\npairs of grammars which", "start": 4560.792, "duration": 2.208}, {"text": "are going to be\nbeyond the capability", "start": 4563.0, "duration": 2.82}, {"text": "of any reasonable\nformal system to be", "start": 4565.82, "duration": 1.98}, {"text": "able to prove that\nthey're equivalent,", "start": 4567.8, "duration": 1.95}, {"text": "because you can even convert--", "start": 4569.75, "duration": 1.59}, {"text": "make those grammars\ninto something", "start": 4571.34, "duration": 1.89}, {"text": "which talk about the\nsystem itself, ultimately.", "start": 4573.23, "duration": 3.4}, {"text": "You're going to end up with a\nRussell paradox kind of thing.", "start": 4576.63, "duration": 2.85}, {"text": "That's maybe going beyond\nmore than you want to know,", "start": 4579.48, "duration": 2.79}, {"text": "and I'm happy to talk\nabout it offline.", "start": 4582.27, "duration": 2.25}, {"text": "But there's just no way to make\na Turing machine which is going", "start": 4584.52, "duration": 4.02}, {"text": "to implement human reasoning,\nand then get the right answer", "start": 4588.54, "duration": 3.39}, {"text": "on all pairs of grammars--\njust cannot be done.", "start": 4591.93, "duration": 2.77}, {"text": "Goodbye.", "start": 4594.7, "duration": 0.5}, {"text": "I'm going to shut\ndown the meeting now.", "start": 4595.2, "duration": 4.19}]
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+[{"text": "The following\ncontent is provided", "start": 0.57, "duration": 1.8}, {"text": "by MIT OpenCourseWare under\na Creative Commons license.", "start": 2.37, "duration": 3.96}, {"text": "Additional information\nabout our license,", "start": 6.33, "duration": 2.1}, {"text": "and MIT OpenCourseWare\nin general,", "start": 8.43, "duration": 2.37}, {"text": "is available at ocw.mit.edu.", "start": 10.8, "duration": 1.96}, {"text": "TAFT BROOME: OK.", "start": 15.48, "duration": 1.83}, {"text": "Now, this should be the\nmost interesting class", "start": 17.31, "duration": 6.15}, {"text": "of the semester.", "start": 23.46, "duration": 2.4}, {"text": "Parzival-- what do\ny'all think of Parzival?", "start": 25.86, "duration": 5.1}, {"text": "[INAUDIBLE]", "start": 30.96, "duration": 1.205}, {"text": "AUDIENCE: We were\ndiscussing earlier,", "start": 32.165, "duration": 1.82}, {"text": "and we can't wait to\nhear why [INAUDIBLE]", "start": 33.985, "duration": 3.902}, {"text": "TAFT BROOME: Why?", "start": 37.887, "duration": 0.708}, {"text": "Well, let's go-- let's\ndo the facts, first.", "start": 38.595, "duration": 1.965}, {"text": "Let's tell the story.", "start": 40.56, "duration": 2.58}, {"text": "Let's just go back and\nforth, round and round,", "start": 43.14, "duration": 3.12}, {"text": "until we get it done.", "start": 46.26, "duration": 1.24}, {"text": "[INAUDIBLE]", "start": 47.5, "duration": 0.5}, {"text": "AUDIENCE: Yeah, but we were\nstarting in the beginning.", "start": 48.0, "duration": 2.25}, {"text": "And we were both\nstruck by the fact", "start": 50.25, "duration": 1.59}, {"text": "that [INAUDIBLE] we still\nhaven't met Parzival yet.", "start": 51.84, "duration": 4.588}, {"text": "TAFT BROOME: Right.", "start": 56.428, "duration": 0.792}, {"text": "[LAUGHTER]", "start": 57.22, "duration": 1.936}, {"text": "AUDIENCE: So I thought that was\ninteresting [INAUDIBLE] right?", "start": 59.156, "duration": 7.329}, {"text": "TAFT BROOME: Uh.", "start": 66.485, "duration": 0.667}, {"text": "AUDIENCE: I don't\nthink it's a big deal.", "start": 67.152, "duration": 1.964}, {"text": "[INAUDIBLE]", "start": 69.116, "duration": 2.946}, {"text": "TAFT BROOME: Well, I\nthink what the author", "start": 72.062, "duration": 2.028}, {"text": "is doing there is emphasizing\nthat the first principle", "start": 74.09, "duration": 6.45}, {"text": "of moral behavior is family.", "start": 80.54, "duration": 2.4}, {"text": "It's kinship.", "start": 82.94, "duration": 2.88}, {"text": "And that we have to know his\nlineage before we can know him.", "start": 85.82, "duration": 6.81}, {"text": "And whatever he does, I\nthink there's another--", "start": 92.63, "duration": 2.91}, {"text": "and that's a big difference\nbetween Parzival and Mallory.", "start": 95.54, "duration": 13.63}, {"text": "This is your-- this is\nyour King Arthur's legend", "start": 109.17, "duration": 4.14}, {"text": "in the first form, OK?", "start": 113.31, "duration": 3.42}, {"text": "This one here.", "start": 116.73, "duration": 2.175}, {"text": "That is that there's\na lot of attention", "start": 118.905, "duration": 2.385}, {"text": "given to the morality\nof being a knight.", "start": 121.29, "duration": 5.58}, {"text": "But the first principle is--", "start": 126.87, "duration": 2.139}, {"text": "first principle, I\nthink, is kinship.", "start": 129.009, "duration": 2.361}, {"text": "And an interesting\nprinciple is that it's", "start": 131.37, "duration": 3.18}, {"text": "immoral to mistreat a kinship--", "start": 134.55, "duration": 4.74}, {"text": "a relative, even\nif you don't know", "start": 139.29, "duration": 1.89}, {"text": "that this person is a relative.", "start": 141.18, "duration": 3.84}, {"text": "Remember that?", "start": 145.02, "duration": 0.85}, {"text": "You're not supposed--", "start": 145.87, "duration": 0.875}, {"text": "AUDIENCE: Right, I\nmean, first of all,", "start": 146.745, "duration": 1.788}, {"text": "there's all this time\nspent on who his father is.", "start": 148.533, "duration": 3.222}, {"text": "TAFT BROOME: That's right.", "start": 151.755, "duration": 1.083}, {"text": "AUDIENCE: We know\nwho his father is.", "start": 152.838, "duration": 1.632}, {"text": "TAFT BROOME: That's right.", "start": 154.47, "duration": 1.31}, {"text": "And there's this big to do about\nall of these relationships.", "start": 159.31, "duration": 5.45}, {"text": "And you don't discover\nthem immediately.", "start": 164.76, "duration": 1.98}, {"text": "You find out later.", "start": 166.74, "duration": 3.39}, {"text": "So Parzival's father\ngoes out, gets married,", "start": 170.13, "duration": 12.18}, {"text": "does a heroic deed,\nmarries a queen", "start": 182.31, "duration": 4.32}, {"text": "as a result of it, thanks,\ngets tired of being a king,", "start": 186.63, "duration": 6.72}, {"text": "and goes back out on\nthe road, so to speak.", "start": 193.35, "duration": 3.78}, {"text": "Marries again, finds no\nlegal or moral problem", "start": 197.13, "duration": 4.26}, {"text": "in doing that because one wife\nwas a pagan and the other one", "start": 201.39, "duration": 4.02}, {"text": "was a Christian.", "start": 205.41, "duration": 3.39}, {"text": "Well, keep going.", "start": 208.8, "duration": 0.93}, {"text": "Y'all get in there.", "start": 209.73, "duration": 0.81}, {"text": "I want to hear more\nabout these stories.", "start": 210.54, "duration": 1.77}, {"text": "You can and you can\ndo it bullet-wise.", "start": 212.31, "duration": 1.583}, {"text": "Just, you don't have to go\nfrom the beginning to the end.", "start": 213.893, "duration": 2.444}, {"text": "What were some of the things\nthat struck you about this?", "start": 216.337, "duration": 2.333}, {"text": "Then we're going to tie\nit all in at the end,", "start": 218.67, "duration": 2.69}, {"text": "make sure we get the\nfacts straight first.", "start": 221.36, "duration": 1.75}, {"text": "Name some of the things he did.", "start": 225.87, "duration": 2.938}, {"text": "AUDIENCE: Gahmuret\nmarries again.", "start": 228.808, "duration": 3.902}, {"text": "Herzeloyde.", "start": 236.034, "duration": 2.236}, {"text": "TAFT BROOME: Herzeloyde.", "start": 238.27, "duration": 1.0}, {"text": "AUDIENCE: Herzeloyde.", "start": 239.27, "duration": 0.891}, {"text": "And I guess Gahmuret is gone\nby the time Parzival was born,", "start": 244.88, "duration": 8.39}, {"text": "he's dead.", "start": 253.27, "duration": 1.75}, {"text": "TAFT BROOME: Yeah.", "start": 255.02, "duration": 0.75}, {"text": "AUDIENCE: He dies in Baghdad\n[INAUDIBLE] and dies.", "start": 255.77, "duration": 8.6}, {"text": "TAFT BROOME: And dies.", "start": 264.37, "duration": 1.728}, {"text": "AUDIENCE: --a valiant death.", "start": 266.098, "duration": 1.984}, {"text": "His mother goes off [INAUDIBLE].", "start": 271.07, "duration": 2.43}, {"text": "TAFT BROOME: Yeah, they are\nafraid that some other person", "start": 273.5, "duration": 4.92}, {"text": "might take over his property and\ndo her and her child some harm.", "start": 278.42, "duration": 6.9}, {"text": "AUDIENCE: And she doesn't want\nhim to know about Gahmuret.", "start": 285.32, "duration": 2.797}, {"text": "TAFT BROOME: She doesn't want\nhim to be like his father.", "start": 288.117, "duration": 2.333}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 295.91, "duration": 4.275}, {"text": "TAFT BROOME: Said,\nthat's for me.", "start": 300.185, "duration": 1.375}, {"text": "OK.", "start": 304.39, "duration": 0.5}, {"text": "AUDIENCE: And his father dies.", "start": 307.73, "duration": 2.507}, {"text": "AUDIENCE: After he leaves.", "start": 310.237, "duration": 1.083}, {"text": "AUDIENCE: After he leaves.", "start": 311.32, "duration": 3.7}, {"text": "TAFT BROOME: Yeah, I\ndidn't remember that.", "start": 315.02, "duration": 2.52}, {"text": "But I--", "start": 317.54, "duration": 0.597}, {"text": "AUDIENCE: We know they're\nnot totally there.", "start": 318.137, "duration": 1.833}, {"text": "TAFT BROOME: Yes.", "start": 319.97, "duration": 0.75}, {"text": "Towards the end.", "start": 320.72, "duration": 0.36}, {"text": "AUDIENCE: Parzival\ndoesn't know about it", "start": 321.08, "duration": 1.76}, {"text": "until he meets with\nhis uncle, the brother", "start": 322.84, "duration": 6.46}, {"text": "of a king of the Grail.", "start": 329.3, "duration": 2.35}, {"text": "TAFT BROOME: The\nFisher King, now", "start": 331.65, "duration": 1.83}, {"text": "let's talk about\nthe Fisher King.", "start": 333.48, "duration": 1.95}, {"text": "Let's go into the Fisher\nKing in some detail.", "start": 335.43, "duration": 1.965}, {"text": "When does he encounter\nthe Fisher King?", "start": 340.74, "duration": 3.89}, {"text": "AUDIENCE: I was looking\nfor adventure again", "start": 344.63, "duration": 3.242}, {"text": "and needed a place to stay.", "start": 347.872, "duration": 2.274}, {"text": "Maybe referencing both of them.", "start": 350.146, "duration": 3.984}, {"text": "[INAUDIBLE] Five.", "start": 354.13, "duration": 7.968}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 362.098, "duration": 4.992}, {"text": "TAFT BROOME: This is the\nGrail, the Grail King.", "start": 367.09, "duration": 3.24}, {"text": "And he doesn't know he's\nthe Grail King at first.", "start": 370.33, "duration": 2.58}, {"text": "All he sees is the\nman out in a boat.", "start": 372.91, "duration": 2.46}, {"text": "AUDIENCE: Right, it's Book Five.", "start": 375.37, "duration": 2.751}, {"text": "TAFT BROOME: You can read\nquick portions of it.", "start": 378.121, "duration": 3.419}, {"text": "That's legitimate.", "start": 381.54, "duration": 2.28}, {"text": "AUDIENCE: It was something\nlike, He was wandering around", "start": 383.82, "duration": 3.15}, {"text": "[INAUDIBLE] and he runs\ninto this Fisher King, which", "start": 386.97, "duration": 4.053}, {"text": "is in the middle of nowhere.", "start": 391.023, "duration": 1.167}, {"text": "TAFT BROOME: Right,", "start": 392.19, "duration": 0.788}, {"text": "AUDIENCE: And he's looking\nfor a place to stay.", "start": 392.978, "duration": 1.958}, {"text": "And he uses the point--", "start": 394.936, "duration": 3.414}, {"text": "here is this fortress.", "start": 398.35, "duration": 1.68}, {"text": "Go up to the wall [INAUDIBLE].", "start": 400.03, "duration": 3.19}, {"text": "TAFT BROOME: Right.", "start": 403.22, "duration": 1.575}, {"text": "AUDIENCE: And he didn't know\nhe was the king at the time.", "start": 404.795, "duration": 2.375}, {"text": "He just thought he\nwas a fisherman.", "start": 407.17, "duration": 1.984}, {"text": "So he goes--", "start": 412.63, "duration": 2.931}, {"text": "AUDIENCE: [INAUDIBLE]\nthere's this big deal.", "start": 415.561, "duration": 5.189}, {"text": "TAFT BROOME: Yes,\nthat's what I'm getting.", "start": 420.75, "duration": 2.66}, {"text": "AUDIENCE: It seems\nlike everybody", "start": 423.41, "duration": 1.75}, {"text": "knows about [INAUDIBLE].", "start": 425.16, "duration": 1.2}, {"text": "AUDIENCE: Right.", "start": 426.36, "duration": 1.26}, {"text": "AUDIENCE: But the other thing\nis, people come and they", "start": 427.62, "duration": 2.58}, {"text": "fault the king of the Grail.", "start": 430.2, "duration": 1.45}, {"text": "And I think in today's\nsociety, you would say,", "start": 431.65, "duration": 3.258}, {"text": "you could claim innocence\nbecause, I didn't know.", "start": 434.908, "duration": 2.042}, {"text": "I didn't know why\nyou were there.", "start": 436.95, "duration": 1.75}, {"text": "He sort of feels\nlike, he feels guilty.", "start": 438.7, "duration": 3.87}, {"text": "He goes, I should have\nasked the question.", "start": 442.57, "duration": 1.75}, {"text": "And it's a little strange and I\nknow it's cultural [INAUDIBLE]..", "start": 444.32, "duration": 3.275}, {"text": "TAFT BROOME: Yeah,\nI think the second.", "start": 454.88, "duration": 2.465}, {"text": "The way I look at it, the\nfirst principles of morality", "start": 457.345, "duration": 3.075}, {"text": "for him are kinship.", "start": 460.42, "duration": 1.29}, {"text": "And a second set\nof principles are", "start": 461.71, "duration": 2.79}, {"text": "chivalry, which are\nconnected to it in some way.", "start": 464.5, "duration": 4.92}, {"text": "But, yeah, I want to\ndelve into this question.", "start": 469.42, "duration": 3.87}, {"text": "AUDIENCE: Yeah, the notion\nof admitting wrongdoing", "start": 473.29, "duration": 4.44}, {"text": "and wanting to atone\nfor it, atonement", "start": 477.73, "duration": 3.3}, {"text": "is a major theme in\nthis book that, to me,", "start": 481.03, "duration": 6.04}, {"text": "the mistake or the\nsin seems trivial.", "start": 487.07, "duration": 5.21}, {"text": "Not asking a question\nout of politeness", "start": 492.28, "duration": 5.21}, {"text": "is not a compelling sin to\nme or compelling wrongdoing.", "start": 497.49, "duration": 3.39}, {"text": "But it's what's\nused in the story.", "start": 500.88, "duration": 2.68}, {"text": "And Parzival feels\nvery guilty about it", "start": 503.56, "duration": 3.256}, {"text": "and wants to atone for it,\nlike, makes it his mission", "start": 506.816, "duration": 3.154}, {"text": "to make his way back\nto the [INAUDIBLE]..", "start": 509.97, "duration": 4.87}, {"text": "TAFT BROOME: OK, now,\nI don't know if you all", "start": 514.84, "duration": 1.98}, {"text": "read Joseph Campbell.", "start": 516.82, "duration": 2.333}, {"text": "AUDIENCE: I never have.", "start": 519.153, "duration": 1.497}, {"text": "TAFT BROOME: OK, the only\nreason I haven't assigned", "start": 520.65, "duration": 2.913}, {"text": "Joseph Campbell yet is\nthat I can't figure out", "start": 523.563, "duration": 1.917}, {"text": "which one to assign because\nI'd have you reading", "start": 525.48, "duration": 3.84}, {"text": "four or five of them and\nwatching this TV program", "start": 529.32, "duration": 6.15}, {"text": "where Bill Moyers, he does\none with Bill Moyers called", "start": 535.47, "duration": 5.43}, {"text": "The Power of Myth.", "start": 540.9, "duration": 1.98}, {"text": "And he's a spectacular lecturer.", "start": 542.88, "duration": 2.04}, {"text": "And I've got some videotapes\nof his in his classes.", "start": 544.92, "duration": 3.885}, {"text": "Well, for me, Joseph Campbell\nis one of my maybe top five,", "start": 553.9, "duration": 4.22}, {"text": "if you want to put it\nthat way, scholars.", "start": 558.12, "duration": 3.47}, {"text": "Now, here's the big issue\nthat Joseph Campbell makes out", "start": 561.59, "duration": 3.51}, {"text": "of the question.", "start": 565.1, "duration": 0.765}, {"text": "Campbell starts off with a\npoet by the name of T.S. Eliot.", "start": 570.08, "duration": 10.24}, {"text": "He got a Nobel Prize\nfor literature.", "start": 580.32, "duration": 3.71}, {"text": "And one of Eliot's pieces\nis called \"The Wasteland.\"", "start": 584.03, "duration": 5.64}, {"text": "And in \"The Wasteland,\"\nthe wasteland", "start": 594.02, "duration": 5.79}, {"text": "is a place where everybody does\nwhat everybody else expects", "start": 599.81, "duration": 5.01}, {"text": "you to do.", "start": 604.82, "duration": 0.66}, {"text": "So you never break out and find\nyour individual, what he calls", "start": 609.89, "duration": 3.99}, {"text": "bliss, what I call destiny.", "start": 613.88, "duration": 3.45}, {"text": "You never break out of that.", "start": 617.33, "duration": 1.38}, {"text": "You're always, come in.", "start": 618.71, "duration": 1.98}, {"text": "You learn the rules.", "start": 620.69, "duration": 1.11}, {"text": "And you follow them, which\nis good 99% of the time.", "start": 621.8, "duration": 7.33}, {"text": "The question is, when\ndo you break out?", "start": 629.13, "duration": 2.42}, {"text": "And by what reason\ndo you break out?", "start": 631.55, "duration": 1.95}, {"text": "Parzival really wants\nto be a good knight,", "start": 636.28, "duration": 3.03}, {"text": "I'm sorry, a competent knight.", "start": 639.31, "duration": 8.39}, {"text": "Just playing with words\nright now, good night, OK.", "start": 647.7, "duration": 3.53}, {"text": "And he's been taught very well.", "start": 651.23, "duration": 2.04}, {"text": "You remember his teacher?", "start": 653.27, "duration": 2.79}, {"text": "And the teacher\ntold him, virtually,", "start": 656.06, "duration": 4.557}, {"text": "when you go to somebody's house,\nyou don't start quizzing them", "start": 660.617, "duration": 2.583}, {"text": "when you ask them questions.", "start": 663.2, "duration": 2.8}, {"text": "That's one of the\nrules of chivalry.", "start": 666.0, "duration": 1.92}, {"text": "And Parzival wants to be true\nto all of the rules of chivalry.", "start": 667.92, "duration": 7.11}, {"text": "But he's sitting there\ntalking to his host,", "start": 675.03, "duration": 4.83}, {"text": "and his host is in pain.", "start": 679.86, "duration": 2.4}, {"text": "And the authors\nhave made it clear", "start": 682.26, "duration": 2.023}, {"text": "that this is the worst kind\nof pain that a man can endure.", "start": 684.283, "duration": 2.417}, {"text": "Now, actually, the\nworst kind of pain,", "start": 689.25, "duration": 1.98}, {"text": "I've had six physicians tell\nme that kidney stones are", "start": 691.23, "duration": 5.17}, {"text": "the worst kind of\npain a man can endure.", "start": 696.4, "duration": 2.42}, {"text": "It's man's equivalent\nof a woman's childbirth,", "start": 698.82, "duration": 4.8}, {"text": "natural childbirth.", "start": 703.62, "duration": 1.61}, {"text": "Worse than pains in the arm.", "start": 705.23, "duration": 3.97}, {"text": "I've had them.", "start": 709.2, "duration": 0.62}, {"text": "I know.", "start": 709.82, "duration": 2.04}, {"text": "But there is nothing fearful\nattached to kidney stones.", "start": 711.86, "duration": 7.69}, {"text": "I have not lost my manhood\nwhen I pass a kidney stone.", "start": 723.05, "duration": 4.32}, {"text": "This man lost his manhood.", "start": 727.37, "duration": 2.46}, {"text": "And not only that,\nbut the tip of that", "start": 729.83, "duration": 2.04}, {"text": "thing is still stuck in him.", "start": 731.87, "duration": 1.99}, {"text": "So then you ask\nyourself, if Parzival", "start": 733.86, "duration": 2.82}, {"text": "is going to lift himself\nup above the rules,", "start": 736.68, "duration": 5.19}, {"text": "now's the time to do it.", "start": 741.87, "duration": 2.213}, {"text": "You've got a colleague\nsitting there suffering", "start": 744.083, "duration": 1.917}, {"text": "the worst pain they\ncould ever suffer, and is", "start": 746.0, "duration": 1.875}, {"text": "going to die of it.", "start": 747.875, "duration": 1.973}, {"text": "The least you could do\nis say, oh my God, I", "start": 749.848, "duration": 1.792}, {"text": "feel sorry for you.", "start": 751.64, "duration": 2.8}, {"text": "Parzival didn't do it.", "start": 754.44, "duration": 2.64}, {"text": "Now, there's another\ngame that everybody", "start": 757.08, "duration": 2.01}, {"text": "plays, particularly parents.", "start": 759.09, "duration": 3.63}, {"text": "There are some lessons you\ncannot teach a child by giving", "start": 762.72, "duration": 4.44}, {"text": "them the answer first.", "start": 767.16, "duration": 2.97}, {"text": "You got to put the\nchild in the situation.", "start": 770.13, "duration": 3.63}, {"text": "Everybody does it.", "start": 773.76, "duration": 0.87}, {"text": "There are certain\nsituations you get", "start": 774.63, "duration": 1.5}, {"text": "in where you just can't tell.", "start": 776.13, "duration": 4.662}, {"text": "If you're going to give a\nperson some kind of a test,", "start": 780.792, "duration": 2.208}, {"text": "you can't tell them\ncertain things.", "start": 783.0, "duration": 4.89}, {"text": "Like for example, when I had\nmy first test on the job,", "start": 787.89, "duration": 2.82}, {"text": "they couldn't tell me,\noh, we got that covered", "start": 790.71, "duration": 2.43}, {"text": "in case you mess up.", "start": 793.14, "duration": 1.74}, {"text": "I had to believe\nthat this was it.", "start": 794.88, "duration": 4.18}, {"text": "So they couldn't tell\nhim to ask that question", "start": 799.06, "duration": 3.662}, {"text": "and that the result would be\nthat he would become the Grail", "start": 802.722, "duration": 2.458}, {"text": "King.", "start": 805.18, "duration": 1.14}, {"text": "He had to break out of the rule\nand show that he was worthy.", "start": 806.32, "duration": 4.44}, {"text": "So there's that big issue\nnow with the Grail King.", "start": 813.89, "duration": 3.9}, {"text": "And Parzival felt bad\nthat he missed a chance.", "start": 817.79, "duration": 7.98}, {"text": "He felt bad that he should have\nshown some compassion, at least", "start": 825.77, "duration": 5.08}, {"text": "verbally.", "start": 830.85, "duration": 0.5}, {"text": "But the real issue is that this\ntest was one of his fitness", "start": 834.29, "duration": 6.93}, {"text": "to be the Grail King.", "start": 841.22, "duration": 2.07}, {"text": "And the fitness was not\nmeasured in terms of obedience", "start": 843.29, "duration": 4.41}, {"text": "to the rules.", "start": 847.7, "duration": 0.66}, {"text": "The fitness was\nmeasured in terms", "start": 848.36, "duration": 2.19}, {"text": "of being quote unquote\n\"above the rules.\"", "start": 850.55, "duration": 2.86}, {"text": "There's a film called\nThe Cincinnati Kid.", "start": 857.41, "duration": 11.44}, {"text": "It's the same theme\nas The Hustler,", "start": 868.85, "duration": 2.31}, {"text": "except that The Hustler was\nabout pool, professional pool", "start": 871.16, "duration": 4.56}, {"text": "players.", "start": 875.72, "duration": 1.08}, {"text": "And The Cincinnati Kid was\nabout professional card player.", "start": 876.8, "duration": 6.1}, {"text": "And the film ends, I'm\nassuming that you all", "start": 882.9, "duration": 2.987}, {"text": "are going to watch the\nfilm, won't be disappointed", "start": 885.887, "duration": 2.083}, {"text": "by me telling you the end.", "start": 887.97, "duration": 3.35}, {"text": "No, y'all won't watch it\nbecause it's in black and white.", "start": 891.32, "duration": 2.837}, {"text": "I think it's in black and white.", "start": 894.157, "duration": 1.333}, {"text": "It might be color.", "start": 895.49, "duration": 1.29}, {"text": "Might be color.", "start": 896.78, "duration": 0.9}, {"text": "But anyway, the film ends\nwhere the main character", "start": 897.68, "duration": 3.33}, {"text": "loses this card game.", "start": 901.01, "duration": 1.517}, {"text": "And he loses it\nto the old master.", "start": 905.8, "duration": 1.88}, {"text": "He's beating him up\nuntil the very end.", "start": 907.68, "duration": 2.3}, {"text": "And he loses all his money.", "start": 909.98, "duration": 2.45}, {"text": "And he comes up to the master\nat the end and he says to him,", "start": 912.43, "duration": 3.54}, {"text": "says, why did you\ngive up that game?", "start": 915.97, "duration": 6.51}, {"text": "He said that was against all\nof the rules of probability.", "start": 925.841, "duration": 7.819}, {"text": "Everybody knows it.", "start": 933.66, "duration": 1.53}, {"text": "And the old man\nsaid, the question", "start": 935.19, "duration": 3.54}, {"text": "is not about making mistakes.", "start": 938.73, "duration": 1.97}, {"text": "The question about\nwhen to make it.", "start": 940.7, "duration": 3.71}, {"text": "In other words, he threw the guy\noff by throwing away that game.", "start": 944.41, "duration": 6.25}, {"text": "So once, when the time comes\nfor you to break the rule,", "start": 950.66, "duration": 6.86}, {"text": "you got to know that\nthis is the time", "start": 957.52, "duration": 3.51}, {"text": "and be prepared to\nsuffer the consequences.", "start": 961.03, "duration": 3.05}, {"text": "And Parzival wasn't\nwilling to do that.", "start": 964.08, "duration": 1.75}, {"text": "And Parzival had to mature.", "start": 965.83, "duration": 1.69}, {"text": "How long was it?", "start": 967.52, "duration": 1.26}, {"text": "How many years passed\nbetween the time", "start": 968.78, "duration": 3.57}, {"text": "that he missed his\nchance at the time", "start": 972.35, "duration": 5.79}, {"text": "that he came back and\nbecame Grail King?", "start": 978.14, "duration": 2.08}, {"text": "And he's looking for\nthis thing all along.", "start": 983.16, "duration": 2.46}, {"text": "The castle disappears.", "start": 985.62, "duration": 1.74}, {"text": "Remember, he gets\nup the next morning", "start": 987.36, "duration": 2.76}, {"text": "and he hears the\nknights thundering out", "start": 990.12, "duration": 2.97}, {"text": "of the castle on their\nway away someplace.", "start": 993.09, "duration": 2.1}, {"text": "And he gets all dressed up\nand goes out to follow them.", "start": 995.19, "duration": 3.1}, {"text": "He can't find them.", "start": 998.29, "duration": 0.89}, {"text": "He turns around to go back\nand the castle is gone.", "start": 999.18, "duration": 2.43}, {"text": "And he spends the\nnext x amount of time", "start": 1005.7, "duration": 3.9}, {"text": "to go back and find the castle.", "start": 1009.6, "duration": 1.65}, {"text": "My calculation was 20 years.", "start": 1014.07, "duration": 1.59}, {"text": "I want you to take\nsome time, if you", "start": 1019.45, "duration": 2.55}, {"text": "dispute that, whether to\ngive that some thought,", "start": 1022.0, "duration": 3.99}, {"text": "maybe look through the\nbook a little bit more.", "start": 1025.99, "duration": 2.43}, {"text": "He was out there\nfor quite a while.", "start": 1028.42, "duration": 1.56}, {"text": "And after he has all\nof these exploits,", "start": 1037.839, "duration": 3.631}, {"text": "then he has proved\nhimself worthy.", "start": 1041.47, "duration": 1.77}, {"text": "AUDIENCE: I was trying to think\nof how old his sons were when", "start": 1065.2, "duration": 3.665}, {"text": "they were reunited at the end.", "start": 1068.865, "duration": 2.717}, {"text": "That would be a way to check.", "start": 1071.582, "duration": 1.208}, {"text": "But I don't remember it saying.", "start": 1072.79, "duration": 1.56}, {"text": "TAFT BROOME: They\nnever say exactly.", "start": 1074.35, "duration": 2.367}, {"text": "And I didn't want to go get one\nof the Cliff Notes or anything", "start": 1076.717, "duration": 2.583}, {"text": "like that to look it up.", "start": 1079.3, "duration": 1.0}, {"text": "I just did not want to do that.", "start": 1080.3, "duration": 1.74}, {"text": "And so I went back and reading\nand taking the little pieces.", "start": 1082.04, "duration": 3.65}, {"text": "And like I said, there\nis a good answer to that.", "start": 1085.69, "duration": 3.58}, {"text": "If you go to the\nHumanities Department,", "start": 1089.27, "duration": 2.06}, {"text": "they'll all know the number.", "start": 1091.33, "duration": 1.635}, {"text": "But I didn't want to do it.", "start": 1092.965, "duration": 1.125}, {"text": "I wanted to have fun\ndoing it on my own.", "start": 1094.09, "duration": 1.8}, {"text": "And I want to leave\nthat to you all.", "start": 1095.89, "duration": 2.34}, {"text": "But my calculation was 20 years.", "start": 1098.23, "duration": 2.04}, {"text": "AUDIENCE: If it was 20\nyears, he didn't necessarily", "start": 1112.102, "duration": 4.088}, {"text": "have any [INAUDIBLE]\nall the sudden.", "start": 1116.19, "duration": 2.72}, {"text": "Oh, I should have--", "start": 1118.91, "duration": 2.05}, {"text": "I feel so awful.", "start": 1120.96, "duration": 1.41}, {"text": "I should have asked\nmore about this.", "start": 1122.37, "duration": 2.68}, {"text": "I feel bad.", "start": 1125.05, "duration": 0.5}, {"text": "I need to go back.", "start": 1125.55, "duration": 0.93}, {"text": "AUDIENCE: Like, other people\ntold him that he messed up.", "start": 1126.48, "duration": 3.49}, {"text": "Which is an interesting take\non confession in terms of,", "start": 1129.97, "duration": 8.396}, {"text": "he didn't have a\nself realization.", "start": 1138.366, "duration": 2.974}, {"text": "He did internalize\nit eventually.", "start": 1141.34, "duration": 2.1}, {"text": "TAFT BROOME: Yeah.", "start": 1143.44, "duration": 0.75}, {"text": "AUDIENCE: But he didn't come\nto the realization [INAUDIBLE]", "start": 1144.19, "duration": 3.227}, {"text": "told that he did wrong.", "start": 1147.417, "duration": 1.383}, {"text": "TAFT BROOME: Yeah, now,\nthis is another trait", "start": 1148.8, "duration": 3.21}, {"text": "of many mythic heroes.", "start": 1152.01, "duration": 4.26}, {"text": "And that is, they all have at\nleast one fatal character flaw,", "start": 1156.27, "duration": 9.42}, {"text": "fatal.", "start": 1165.69, "duration": 2.07}, {"text": "You read Oedipus.", "start": 1167.76, "duration": 2.66}, {"text": "You go back to the Trojan Wars.", "start": 1170.42, "duration": 3.03}, {"text": "No matter who they are,\nthey all have some very bad,", "start": 1173.45, "duration": 5.04}, {"text": "bad is not the word,\nfatal is the word.", "start": 1178.49, "duration": 3.21}, {"text": "Even if it doesn't kill\nthem, it kills their careers.", "start": 1181.7, "duration": 2.34}, {"text": "It does all of these\nterrible things.", "start": 1184.04, "duration": 2.82}, {"text": "And is there a lesson\nin all of that?", "start": 1186.86, "duration": 4.605}, {"text": "Well I think one lesson\nis that if you're", "start": 1198.37, "duration": 2.36}, {"text": "going to look for\nsomebody to pattern", "start": 1200.73, "duration": 3.57}, {"text": "your life after in any\nway, in any particular way,", "start": 1204.3, "duration": 3.81}, {"text": "or if you're going to\nadvise your children to be", "start": 1208.11, "duration": 3.24}, {"text": "like somebody else,\nyou're not going", "start": 1211.35, "duration": 2.19}, {"text": "to find anybody that's\nperfect unless you", "start": 1213.54, "duration": 5.01}, {"text": "got a religious bent.", "start": 1218.55, "duration": 1.32}, {"text": "But you're going to find\npeople who make mistakes.", "start": 1219.87, "duration": 5.13}, {"text": "And the heroes, at least all\nof the ones that I have read,", "start": 1225.0, "duration": 4.44}, {"text": "are the ones who not\nonly do great deeds,", "start": 1229.44, "duration": 2.55}, {"text": "but make big mistakes.", "start": 1231.99, "duration": 1.29}, {"text": "I mean, when they\nmake a mistake,", "start": 1233.28, "duration": 1.77}, {"text": "it is big, terrible to\nthem, terrible to everybody", "start": 1235.05, "duration": 5.22}, {"text": "around them.", "start": 1240.27, "duration": 2.1}, {"text": "And I think that's\nthe way it is.", "start": 1242.37, "duration": 1.44}, {"text": "If you play in the big\ngame, you make big mistakes.", "start": 1243.81, "duration": 3.6}, {"text": "You make big gains\nwhen you make them.", "start": 1247.41, "duration": 1.98}, {"text": "But you make big mistakes too.", "start": 1249.39, "duration": 1.38}, {"text": "Yeah, let's talk about\nhis character some more.", "start": 1255.56, "duration": 3.0}, {"text": "Did he did his character\nchange as he got older?", "start": 1258.56, "duration": 3.72}, {"text": "Yeah, I think he did.", "start": 1262.28, "duration": 1.53}, {"text": "AUDIENCE: I mean,\nwhat frustrates", "start": 1263.81, "duration": 6.69}, {"text": "me is the way he\nbecame a knight was", "start": 1270.5, "duration": 2.22}, {"text": "by killing another knight in\norder to get his clothing.", "start": 1272.72, "duration": 3.36}, {"text": "TAFT BROOME: Yeah.", "start": 1276.08, "duration": 0.75}, {"text": "AUDIENCE: And I know that\nthe trajectory in the book", "start": 1279.41, "duration": 4.29}, {"text": "is that he is\nfoolish, he's young,", "start": 1283.7, "duration": 2.31}, {"text": "he doesn't know\nabout knighthood.", "start": 1286.01, "duration": 1.453}, {"text": "He thinks he needs to go to\nthe knight to get the clothes.", "start": 1287.463, "duration": 2.417}, {"text": "And then he matures.", "start": 1289.88, "duration": 2.18}, {"text": "But the author doesn't\nthink that murder", "start": 1292.06, "duration": 5.69}, {"text": "to be the major flaw\nof Parzival's life.", "start": 1297.75, "duration": 4.65}, {"text": "The major mistake is not\na question of the king.", "start": 1302.4, "duration": 3.75}, {"text": "TAFT BROOME: Right.", "start": 1306.15, "duration": 2.282}, {"text": "AUDIENCE: I don't know.", "start": 1308.432, "duration": 0.958}, {"text": "I don't know what we're\nsupposed to do with that,", "start": 1309.39, "duration": 2.46}, {"text": "just accept that he\nhad to kill the knight?", "start": 1311.85, "duration": 4.245}, {"text": "AUDIENCE: It wasn't\na heroic deed", "start": 1316.095, "duration": 1.375}, {"text": "that made him become a knight,\nunless maybe it is somehow", "start": 1317.47, "duration": 4.0}, {"text": "heroic and I'm missing it.", "start": 1321.47, "duration": 2.7}, {"text": "TAFT BROOME: No, I\nwouldn't call that heroic", "start": 1324.17, "duration": 4.86}, {"text": "because there was nobody\nelse's interest at stake", "start": 1329.03, "duration": 5.19}, {"text": "that he was protecting.", "start": 1334.22, "duration": 1.17}, {"text": "There's a scene, I'm trying\nto think of it, in the film,", "start": 1339.78, "duration": 3.51}, {"text": "this is one of my\nfavorite films.", "start": 1343.29, "duration": 3.352}, {"text": "I'm trying to think of what--", "start": 1346.642, "duration": 1.208}, {"text": "I think it was Robin Hood,\none of the Robin Hood movies", "start": 1347.85, "duration": 3.99}, {"text": "where Robin Hood gets into the\nsword fight with this knight.", "start": 1351.84, "duration": 4.29}, {"text": "And he doesn't\nknow it's Richard.", "start": 1356.13, "duration": 5.45}, {"text": "And they're fighting.", "start": 1364.29, "duration": 2.97}, {"text": "And Richard goes with a lunge.", "start": 1367.26, "duration": 4.5}, {"text": "And Robin Hood steps\nout of the way.", "start": 1371.76, "duration": 2.46}, {"text": "And Richard gets his\nsword stuck into a tree.", "start": 1374.22, "duration": 5.483}, {"text": "Now they're fighting\nto the death.", "start": 1379.703, "duration": 1.417}, {"text": "This is serious.", "start": 1381.12, "duration": 1.68}, {"text": "And Robin Hood, I think it is,\nputs down his sword and goes", "start": 1382.8, "duration": 4.11}, {"text": "helps him pull it\nout of the tree.", "start": 1386.91, "duration": 3.347}, {"text": "He got an opportunity to\nstab the man in the back.", "start": 1390.257, "duration": 2.083}, {"text": "But chivalry says,\nyou don't do that.", "start": 1392.34, "duration": 4.05}, {"text": "So they got these\nrules of chivalry.", "start": 1396.39, "duration": 2.79}, {"text": "Well, I think if you follow\nthe rules of chivalry,", "start": 1399.18, "duration": 3.9}, {"text": "there's something about it\nthat is hero-making in it.", "start": 1403.08, "duration": 6.33}, {"text": "It helps you get there.", "start": 1409.41, "duration": 3.008}, {"text": "I don't think that\nthere was a heroic deed.", "start": 1412.418, "duration": 1.792}, {"text": "But it gets you into a\nmindset that there's something", "start": 1414.21, "duration": 3.54}, {"text": "that's higher than you.", "start": 1417.75, "duration": 1.23}, {"text": "I mean, if you're\ngoing to kill a man,", "start": 1422.64, "duration": 2.213}, {"text": "you don't kill him\nby stabbing him", "start": 1424.853, "duration": 1.417}, {"text": "in the back or certain\nkind of things.", "start": 1426.27, "duration": 1.65}, {"text": "You just don't do these things.", "start": 1427.92, "duration": 1.33}, {"text": "What about his half brother?", "start": 1434.689, "duration": 1.761}, {"text": "You see any point to the story\nof him and his half brother?", "start": 1440.88, "duration": 5.525}, {"text": "Fee or fees, that's\nthe best pronunciation", "start": 1455.03, "duration": 2.02}, {"text": "I can get out of it.", "start": 1457.05, "duration": 3.25}, {"text": "AUDIENCE: Well,\nhe certainly seems", "start": 1460.3, "duration": 2.52}, {"text": "essential to Parzival's eventual\nsaving of the Grail Castle", "start": 1462.82, "duration": 9.075}, {"text": "and of the Fisher King.", "start": 1471.895, "duration": 1.419}, {"text": "They go there\ntogether in the end.", "start": 1473.314, "duration": 4.291}, {"text": "And you could probably argue\nthat if he hadn't met up", "start": 1477.605, "duration": 3.305}, {"text": "with Feirefiz, he\nwouldn't have gone.", "start": 1480.91, "duration": 3.661}, {"text": "[INAUDIBLE]", "start": 1488.515, "duration": 3.173}, {"text": "the importance of family.", "start": 1491.688, "duration": 3.182}, {"text": "TAFT BROOME: Why do you\nthink the author made", "start": 1494.87, "duration": 3.33}, {"text": "this bizarre\ncharacterization of Fierefiz", "start": 1498.2, "duration": 5.37}, {"text": "as being patched black,\nlike a Pinto horse.", "start": 1503.57, "duration": 8.68}, {"text": "That's sort of bizarre.", "start": 1514.562, "duration": 0.958}, {"text": "Why would an author\njust do that?", "start": 1515.52, "duration": 5.04}, {"text": "I mean, why would\nan author do that?", "start": 1520.56, "duration": 2.65}, {"text": "That was not [INAUDIBLE].", "start": 1523.21, "duration": 4.46}, {"text": "But why would the\nauthor do that?", "start": 1527.67, "duration": 1.49}, {"text": "Well, I tell you what I think.", "start": 1533.84, "duration": 1.25}, {"text": "Well, I'll tell you what\nJoseph Campbell says.", "start": 1535.09, "duration": 2.28}, {"text": "And then I'll tell\nyou what I think,", "start": 1537.37, "duration": 1.5}, {"text": "which is almost the same thing.", "start": 1538.87, "duration": 1.5}, {"text": "This author wants to\nreconcile the pagans.", "start": 1544.24, "duration": 6.81}, {"text": "And the only thing that's going\nto impress Parzival, in terms", "start": 1555.49, "duration": 2.76}, {"text": "of reconciliation, is kinship.", "start": 1558.25, "duration": 3.173}, {"text": "So I think what\nhe's trying to say", "start": 1561.423, "duration": 1.417}, {"text": "is that Fierefiz is half black,\nhalf white, which he was.", "start": 1562.84, "duration": 5.514}, {"text": "AUDIENCE: Half pagan,\nhalf Christian.", "start": 1568.354, "duration": 1.656}, {"text": "TAFT BROOME: But the key issue\nwas, pagan versus Christian,", "start": 1570.01, "duration": 6.69}, {"text": "and that the two of them became\nthe best of friends at the end.", "start": 1576.7, "duration": 5.97}, {"text": "So I think the author\nwas trying to say", "start": 1582.67, "duration": 1.95}, {"text": "that these are the early\nMiddle Ages and the Dark Ages,", "start": 1584.62, "duration": 8.34}, {"text": "that all of this hatred between\nChristians and pagans gotta go.", "start": 1592.96, "duration": 4.89}, {"text": "And he tries to do it in\nthe most compelling way", "start": 1600.91, "duration": 3.58}, {"text": "with somebody like\nParzival make [INAUDIBLE]..", "start": 1604.49, "duration": 2.988}, {"text": "AUDIENCE: So Parzival\naccepted Feirefiz", "start": 1615.71, "duration": 2.13}, {"text": "as he was, black and\nwhite, half pagan,", "start": 1617.84, "duration": 2.784}, {"text": "half Christian, but actually\nall pagan in practice.", "start": 1620.624, "duration": 4.139}, {"text": "TAFT BROOME: In practice.", "start": 1624.763, "duration": 1.042}, {"text": "AUDIENCE: He accepted\nhim as his brother.", "start": 1628.59, "duration": 2.73}, {"text": "But in the end, for\nFeirefiz to have the wife", "start": 1631.32, "duration": 3.99}, {"text": "that he wanted, to lead\nthe life that he wanted,", "start": 1635.31, "duration": 2.53}, {"text": "he had to be baptized and\nrenounce the paganism.", "start": 1637.84, "duration": 2.0}, {"text": "TAFT BROOME: That's right.", "start": 1639.84, "duration": 1.47}, {"text": "He still had to be baptized.", "start": 1641.31, "duration": 1.59}, {"text": "AUDIENCE: So they reconciled as\nbrothers and as friends but--", "start": 1642.9, "duration": 4.91}, {"text": "TAFT BROOME: Now--", "start": 1647.81, "duration": 1.296}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1649.106, "duration": 7.984}, {"text": "TAFT BROOME: Well,\nlet's dig into that one.", "start": 1657.09, "duration": 3.15}, {"text": "At the time civilizations\nwere created", "start": 1666.95, "duration": 3.63}, {"text": "around the world\nindependently of one another,", "start": 1670.58, "duration": 10.21}, {"text": "it was motivated by two things.", "start": 1680.79, "duration": 3.15}, {"text": "Number one, well, it was\nmotivated by the weather.", "start": 1683.94, "duration": 4.02}, {"text": "Yeah, I mean, it was\na time when there", "start": 1687.96, "duration": 3.63}, {"text": "were these grasses that could\nsustain a large population.", "start": 1691.59, "duration": 6.75}, {"text": "And we have the wheat cultures\nin the Middle East, the rice", "start": 1701.22, "duration": 6.0}, {"text": "cultures in the East, the\ncorn cultures in the Western,", "start": 1707.22, "duration": 5.94}, {"text": "in the Americas, in\nthe Western Americas.", "start": 1713.16, "duration": 3.03}, {"text": "They could sustain\nlarge cultures.", "start": 1716.19, "duration": 1.98}, {"text": "And the cultures did not have\nto be nomadic or semi-nomadic.", "start": 1718.17, "duration": 3.63}, {"text": "They could stay in one place.", "start": 1721.8, "duration": 3.66}, {"text": "The other thing was\nthat around that time", "start": 1725.46, "duration": 1.94}, {"text": "was that human beings\nhad figured out how", "start": 1727.4, "duration": 4.95}, {"text": "to herd animals.", "start": 1732.35, "duration": 3.27}, {"text": "So instead of going out\nhoping you see one one day", "start": 1735.62, "duration": 2.43}, {"text": "and killing it and hoping\nit doesn't kill you.", "start": 1738.05, "duration": 3.18}, {"text": "You can just herd the\nanimals right along", "start": 1741.23, "duration": 2.94}, {"text": "and take one whenever\nyou get ready.", "start": 1744.17, "duration": 3.8}, {"text": "So you have two\nkinds of cultures.", "start": 1747.97, "duration": 2.1}, {"text": "You have the herding culture.", "start": 1750.07, "duration": 2.55}, {"text": "And you have the\nagrarian culture.", "start": 1752.62, "duration": 4.56}, {"text": "Herding is still moving around.", "start": 1757.18, "duration": 1.41}, {"text": "The agrarian is separate.", "start": 1758.59, "duration": 2.268}, {"text": "The herding cultures\nare kinships societies.", "start": 1768.23, "duration": 5.6}, {"text": "Civilization was made up by\ndifferent kinship groups.", "start": 1776.62, "duration": 3.49}, {"text": "It was a multicultural society.", "start": 1780.11, "duration": 1.475}, {"text": "So the rules of social order\nfor a poor civilization we're", "start": 1785.85, "duration": 10.71}, {"text": "more strict, or\nstricter, or social order", "start": 1796.56, "duration": 5.61}, {"text": "was more problematic\nfor culture,", "start": 1802.17, "duration": 2.25}, {"text": "for civilized cultures, than it\nwas for nomadic herders herding", "start": 1804.42, "duration": 6.09}, {"text": "cultures because\nall you did was obey", "start": 1810.51, "duration": 2.28}, {"text": "your father and your father\nobey your grandfather.", "start": 1812.79, "duration": 3.75}, {"text": "You obeyed your mother.", "start": 1816.54, "duration": 1.53}, {"text": "And mother obeyed\nher grandmother.", "start": 1818.07, "duration": 3.01}, {"text": "But when you've got\ndifferent families living", "start": 1821.08, "duration": 3.86}, {"text": "in the same place, how do\nyou keep them in order?", "start": 1824.94, "duration": 5.17}, {"text": "And here's how they\ndid it, religion.", "start": 1830.11, "duration": 3.96}, {"text": "So they invented\ngreat priesthoods.", "start": 1837.31, "duration": 2.67}, {"text": "And the great priesthoods\nfound it increasingly difficult", "start": 1839.98, "duration": 5.01}, {"text": "to keep the social order.", "start": 1844.99, "duration": 2.86}, {"text": "So what they did was\nthey had to find ways", "start": 1847.85, "duration": 3.14}, {"text": "of keeping people\nanchored to an idea that", "start": 1850.99, "duration": 6.72}, {"text": "was compelling on them and\nthe shaman, with his insights", "start": 1857.71, "duration": 8.1}, {"text": "into unconscious, just became\nnot very compelling any longer", "start": 1865.81, "duration": 7.8}, {"text": "because people did not\nshare the same unconscious.", "start": 1873.61, "duration": 3.27}, {"text": "They were different\nfrom different groups,", "start": 1876.88, "duration": 1.99}, {"text": "different families.", "start": 1878.87, "duration": 1.43}, {"text": "So what happened in the end was\nthat a priesthood developed,", "start": 1880.3, "duration": 7.02}, {"text": "probably not out of the\nshamans because a shaman has", "start": 1887.32, "duration": 6.13}, {"text": "a personality that\nrequires a discussion.", "start": 1893.45, "duration": 5.15}, {"text": "So I don't see three or four\nshaman getting down and saying,", "start": 1898.6, "duration": 3.68}, {"text": "let's start a priesthood and\nwork together in a hierarchy.", "start": 1902.28, "duration": 5.88}, {"text": "I don't see that.", "start": 1908.16, "duration": 2.508}, {"text": "A shaman becomes a shaman\nby virtue of having--", "start": 1910.668, "duration": 4.655}, {"text": "I hope you all can tolerate\nsome of these diversions", "start": 1915.323, "duration": 2.167}, {"text": "because they're just\ntoo interesting.", "start": 1917.49, "duration": 1.74}, {"text": "A shaman becomes\na shaman by virtue", "start": 1919.23, "duration": 2.13}, {"text": "of having had a traumatic\nexperience in childhood.", "start": 1921.36, "duration": 5.41}, {"text": "AUDIENCE: I'm sorry, the\nword shaman describes a--", "start": 1926.77, "duration": 3.9}, {"text": "TAFT BROOME: Witch doctor.", "start": 1930.67, "duration": 2.21}, {"text": "AUDIENCE: In very early\nprehistoric times?", "start": 1932.88, "duration": 2.49}, {"text": "TAFT BROOME: Yes.", "start": 1935.37, "duration": 1.52}, {"text": "Yes.", "start": 1936.89, "duration": 2.88}, {"text": "But you can find\npeople who do not", "start": 1939.77, "duration": 1.89}, {"text": "have the function of a\nshaman in society today.", "start": 1941.66, "duration": 6.3}, {"text": "One very good\nexample of a person", "start": 1947.96, "duration": 4.62}, {"text": "who has the same\npersonality as a shaman", "start": 1952.58, "duration": 3.78}, {"text": "is this mathematician\nnamed Ramanujan.", "start": 1956.36, "duration": 2.16}, {"text": "He's an Indian.", "start": 1961.7, "duration": 1.71}, {"text": "And the story is that\nwhen he was a child,", "start": 1963.41, "duration": 3.64}, {"text": "his parents would get into\nthese violent arguments.", "start": 1967.05, "duration": 4.22}, {"text": "And he would crawl under the\nbed with a pencil and paper", "start": 1971.27, "duration": 4.8}, {"text": "and try to do math problems\nto keep it out of his head.", "start": 1976.07, "duration": 2.46}, {"text": "What happened in the\nend was that he became", "start": 1982.0, "duration": 2.67}, {"text": "a very great mathematician.", "start": 1984.67, "duration": 2.58}, {"text": "But they call him an\nintuitive mathematician.", "start": 1987.25, "duration": 2.11}, {"text": "He could not prove to\nyou any of his results.", "start": 1989.36, "duration": 3.89}, {"text": "But his results worked.", "start": 1993.25, "duration": 1.44}, {"text": "One of the things\nhe did was, here's", "start": 1994.69, "duration": 3.96}, {"text": "something for you to\nlook up in the details.", "start": 1998.65, "duration": 2.26}, {"text": "I'm going to recite from memory.", "start": 2000.91, "duration": 2.6}, {"text": "Ramanujan found a way to discern\nwhether a 20-digit number was", "start": 2003.51, "duration": 10.43}, {"text": "a prime number or not.", "start": 2013.94, "duration": 2.43}, {"text": "And he figured it out by hand.", "start": 2016.37, "duration": 3.86}, {"text": "There's a hand method\nwhere you could figure out", "start": 2020.23, "duration": 5.04}, {"text": "whether it's prime or not.", "start": 2025.27, "duration": 2.2}, {"text": "And somebody used that method\nto frustrate the US military", "start": 2027.47, "duration": 11.37}, {"text": "because the military\nhad its ICBMs,", "start": 2038.84, "duration": 9.91}, {"text": "its intercontinental ballistic\nmissiles, their orders", "start": 2048.75, "duration": 5.79}, {"text": "were coded in prime numbers.", "start": 2054.54, "duration": 3.46}, {"text": "You can break the code by hand.", "start": 2058.0, "duration": 1.687}, {"text": "The idea is, you could still\nbreak the code by computer.", "start": 2059.687, "duration": 2.333}, {"text": "But you'd have to run\na computer for a month.", "start": 2062.02, "duration": 3.63}, {"text": "By that time, they\nwould change the codes.", "start": 2065.65, "duration": 3.538}, {"text": "But if you could come in\nthere and do it by hand,", "start": 2069.188, "duration": 2.042}, {"text": "you could knock it out.", "start": 2071.23, "duration": 1.38}, {"text": "The story is that they had to\nreconfigure the whole thing.", "start": 2072.61, "duration": 2.894}, {"text": "Ramanujan was\n[? brilliant. ?] So we're", "start": 2075.504, "duration": 2.506}, {"text": "talking about a\nperson who really", "start": 2078.01, "duration": 2.28}, {"text": "is an outsider, a\nperson who really", "start": 2080.29, "duration": 4.199}, {"text": "lives in another state of mind.", "start": 2084.489, "duration": 5.19}, {"text": "I saw a program on\ntelevision, a documentary,", "start": 2095.4, "duration": 4.05}, {"text": "who talked about savants and\nother types of people that have", "start": 2099.45, "duration": 4.41}, {"text": "the shamanistic personality.", "start": 2103.86, "duration": 1.68}, {"text": "They all had these traumatic\nchildhood experiences", "start": 2105.54, "duration": 2.73}, {"text": "where they tried to get\naway from the world.", "start": 2108.27, "duration": 3.81}, {"text": "And they showed this one guy.", "start": 2112.08, "duration": 3.73}, {"text": "This one I'm telling you now\nis good scientific stuff.", "start": 2115.81, "duration": 3.44}, {"text": "We're not talking about\nalien visitations.", "start": 2119.25, "duration": 4.76}, {"text": "This is very well-documented.", "start": 2124.01, "duration": 1.62}, {"text": "These people have been\nstudied in college lab", "start": 2125.63, "duration": 2.46}, {"text": "researchers and stuff.", "start": 2128.09, "duration": 2.45}, {"text": "They had this one\nman who was about,", "start": 2130.54, "duration": 2.7}, {"text": "when he was 50 years\nold, he could tell you", "start": 2133.24, "duration": 4.03}, {"text": "the weather of every\nday of his life,", "start": 2137.27, "duration": 3.54}, {"text": "well, after three or four.", "start": 2140.81, "duration": 1.8}, {"text": "You say, well, what was the\nweather like November 6, 1942.", "start": 2142.61, "duration": 4.62}, {"text": "Oh, it rained that day.", "start": 2147.23, "duration": 1.042}, {"text": "And they'd go back and check.", "start": 2150.832, "duration": 1.208}, {"text": "And sure enough, it was.", "start": 2152.04, "duration": 1.89}, {"text": "Now, how do you explain that?", "start": 2153.93, "duration": 1.42}, {"text": "Well, it turns out, basically,\nhe knew nothing else.", "start": 2155.35, "duration": 6.09}, {"text": "But he memorized those things\nto keep whatever problem he", "start": 2161.44, "duration": 3.12}, {"text": "had as a child out of his mind.", "start": 2164.56, "duration": 3.81}, {"text": "And so they tried\nto rehabilitate him.", "start": 2168.37, "duration": 3.09}, {"text": "And they showed a scene\nwhere he goes to the street", "start": 2171.46, "duration": 5.1}, {"text": "to cross the street.", "start": 2176.56, "duration": 1.53}, {"text": "And the sign is saying go.", "start": 2178.09, "duration": 3.6}, {"text": "And he gets out in the\nmiddle of the street", "start": 2181.69, "duration": 2.04}, {"text": "and the sign says stop.", "start": 2183.73, "duration": 1.47}, {"text": "And he stops.", "start": 2185.2, "duration": 0.63}, {"text": "I think his mother kept him\nclose to her all his life.", "start": 2190.79, "duration": 3.84}, {"text": "He just didn't\nknow those things.", "start": 2194.63, "duration": 1.56}, {"text": "The more he got into\nsociety, he got a job.", "start": 2196.19, "duration": 5.04}, {"text": "He could only hold a job for\nsomething like one hour a day", "start": 2201.23, "duration": 3.18}, {"text": "at first, bussing\ntables in a restaurant.", "start": 2204.41, "duration": 4.57}, {"text": "The more he got\nsocialized, the more", "start": 2208.98, "duration": 3.59}, {"text": "he began to lose that skill.", "start": 2212.57, "duration": 1.44}, {"text": "They say that the\nbards back in 400 BC--", "start": 2219.23, "duration": 13.34}, {"text": "when's the world going around\ntalking about former and all", "start": 2232.57, "duration": 3.0}, {"text": "that--", "start": 2235.57, "duration": 0.87}, {"text": "they said that they could\ntell, they had memorized--", "start": 2236.44, "duration": 2.73}, {"text": "I read some place\nwhere these people", "start": 2239.17, "duration": 2.73}, {"text": "had memorized something like a\nmillion lines of verse before.", "start": 2241.9, "duration": 5.74}, {"text": "Now, a million lines of verse.", "start": 2247.64, "duration": 2.35}, {"text": "So I sat down one day\nand I did a calculation.", "start": 2249.99, "duration": 2.34}, {"text": "I know how long the lines are,\nabout the same length of a line", "start": 2252.33, "duration": 3.18}, {"text": "in Shakespeare.", "start": 2255.51, "duration": 1.86}, {"text": "So I did back of the hand\nkind of a calculation,", "start": 2257.37, "duration": 4.89}, {"text": "10 volumes of Shakespeare.", "start": 2262.26, "duration": 3.04}, {"text": "Now, I concluded from\nthat television program", "start": 2265.3, "duration": 6.03}, {"text": "I saw, that these people\nprobably didn't do", "start": 2271.33, "duration": 3.55}, {"text": "a whole lot of anything else.", "start": 2274.88, "duration": 3.06}, {"text": "One other program\nthat I saw was one", "start": 2277.94, "duration": 3.93}, {"text": "where they were talking about\nthese professional Scrabble", "start": 2281.87, "duration": 4.29}, {"text": "players.", "start": 2286.16, "duration": 2.18}, {"text": "Actually, I think\nthey play for money.", "start": 2288.34, "duration": 4.84}, {"text": "And they talked\nabout how many words", "start": 2293.18, "duration": 2.68}, {"text": "these people have memorized.", "start": 2295.86, "duration": 2.39}, {"text": "And not only that,\nbut they had a skill", "start": 2298.25, "duration": 3.99}, {"text": "to take the words on their\npalate, I mean, the letters,", "start": 2302.24, "duration": 7.68}, {"text": "and be able to turn them\naround in their minds", "start": 2309.92, "duration": 4.02}, {"text": "to see the patterns\nbefore they put them down.", "start": 2313.94, "duration": 2.88}, {"text": "I try to do that.", "start": 2316.82, "duration": 1.14}, {"text": "If it's obvious, I can do it.", "start": 2317.96, "duration": 1.41}, {"text": "I can do it with three\nletters if there's one.", "start": 2319.37, "duration": 2.13}, {"text": "But seven, it takes an effort.", "start": 2321.5, "duration": 2.903}, {"text": "These people just\ndo it like that.", "start": 2324.403, "duration": 1.417}, {"text": "[CLICKING FINGERS] And they\nhad all of these interviews", "start": 2325.82, "duration": 5.07}, {"text": "with the winners.", "start": 2330.89, "duration": 2.37}, {"text": "It turns out in the end\nthat the winners know", "start": 2333.26, "duration": 3.96}, {"text": "the meanings of very few words.", "start": 2337.22, "duration": 3.69}, {"text": "But they word from a nonword.", "start": 2340.91, "duration": 2.37}, {"text": "And they interviewed\nsome of them at home.", "start": 2349.26, "duration": 3.05}, {"text": "And these people had\nshamanic personalities.", "start": 2352.31, "duration": 3.79}, {"text": "I mean, you just don't see two\nof them sitting down for long,", "start": 2356.1, "duration": 5.72}, {"text": "organizing together.", "start": 2361.82, "duration": 3.64}, {"text": "So in my mind, I\ndon't see shaman.", "start": 2365.46, "duration": 4.14}, {"text": "Oh, I tell you where else\nyou can find a shaman.", "start": 2369.6, "duration": 3.86}, {"text": "I knew a person who\nwas not a shaman.", "start": 2373.46, "duration": 2.07}, {"text": "But she said she was\ntaught by shaman.", "start": 2375.53, "duration": 1.65}, {"text": "So she knows some of\nthe shaman skills.", "start": 2377.18, "duration": 2.4}, {"text": "Native Americans, you can\nstill find a shaman out there.", "start": 2379.58, "duration": 8.17}, {"text": "So what happened was,\ngoing back to civilization,", "start": 2387.75, "duration": 6.64}, {"text": "the priests were\nable to find cycles", "start": 2394.39, "duration": 6.05}, {"text": "that were connected\nfirst with the moon,", "start": 2400.44, "duration": 1.74}, {"text": "then with the sun, by which they\nwere able to organize everybody", "start": 2402.18, "duration": 5.19}, {"text": "to plant and to reap.", "start": 2407.37, "duration": 2.47}, {"text": "And so therefore, it's\nvery easy to understand", "start": 2412.41, "duration": 2.82}, {"text": "from that who invented\nmathematics and astronomy,", "start": 2415.23, "duration": 5.8}, {"text": "these priests, right?", "start": 2421.03, "duration": 3.84}, {"text": "Now I'm getting to my point.", "start": 2424.87, "duration": 1.74}, {"text": "Now I'm getting to my point.", "start": 2426.61, "duration": 1.38}, {"text": "Joseph Campbell\nmakes the big point", "start": 2432.34, "duration": 5.16}, {"text": "that in primitive society,\nno, in the transition", "start": 2437.5, "duration": 9.57}, {"text": "from small primitive\nsocieties to big.", "start": 2447.07, "duration": 4.56}, {"text": "OK, instead of having six or\nseven people in a family group,", "start": 2451.63, "duration": 4.95}, {"text": "now you're talking\nabout hundreds.", "start": 2456.58, "duration": 2.94}, {"text": "And they're herding\nthese reindeer or cattle.", "start": 2459.52, "duration": 7.125}, {"text": "Here's what happens.", "start": 2469.27, "duration": 1.56}, {"text": "Joseph Campbell, I think,\nis right about this.", "start": 2470.83, "duration": 2.25}, {"text": "He does a lot of\ncultural anthropology.", "start": 2473.08, "duration": 3.478}, {"text": "This is germane to all of this.", "start": 2476.558, "duration": 1.292}, {"text": "And I'll make all of this makes\nsense before the class is out.", "start": 2477.85, "duration": 5.973}, {"text": "I don't ask you to trust me.", "start": 2483.823, "duration": 1.167}, {"text": "But that's a promise.", "start": 2484.99, "duration": 2.28}, {"text": "Joseph Campbell says that once\nyou have a successful society,", "start": 2487.27, "duration": 5.31}, {"text": "successful in terms of holding\npeople together and feeding", "start": 2492.58, "duration": 2.51}, {"text": "everybody, you will find that\nyour biggest problem it's not", "start": 2495.09, "duration": 9.53}, {"text": "family.", "start": 2504.62, "duration": 2.31}, {"text": "Biggest problem is not disease.", "start": 2506.93, "duration": 3.323}, {"text": "He says, you want\nto guess what he", "start": 2510.253, "duration": 1.417}, {"text": "says your biggest problem is?", "start": 2511.67, "duration": 1.29}, {"text": "Men with free time because\nyou get a bad combination.", "start": 2517.15, "duration": 6.66}, {"text": "The women don't have free time.", "start": 2523.81, "duration": 1.61}, {"text": "They've got kids.", "start": 2525.42, "duration": 2.48}, {"text": "That's 24 hours a day.", "start": 2527.9, "duration": 3.39}, {"text": "Men with free time, here's\nthe bad combination.", "start": 2531.29, "duration": 3.78}, {"text": "What they do?", "start": 2539.51, "duration": 1.404}, {"text": "If they want a sheep, they\njust go out and get one.", "start": 2540.914, "duration": 2.906}, {"text": "They got free time.", "start": 2543.82, "duration": 0.84}, {"text": "Men with free time, here's\nthe bad combination.", "start": 2544.66, "duration": 4.2}, {"text": "Free time and\ninclination to organize", "start": 2548.86, "duration": 6.86}, {"text": "in hierarchical\ngroups, and guess", "start": 2555.72, "duration": 5.41}, {"text": "what the last\npiece of the puzzle", "start": 2561.13, "duration": 1.53}, {"text": "is, high levels of testosterone,\nhigh levels of testosterone.", "start": 2562.66, "duration": 8.38}, {"text": "That's a bad combination, free\ntime, men, men with free time.", "start": 2571.04, "duration": 5.982}, {"text": "So what happens is that,\nto let out that energy,", "start": 2579.94, "duration": 9.04}, {"text": "one of the things\nthat men learned to do", "start": 2588.98, "duration": 4.3}, {"text": "was to hunt other men.", "start": 2593.28, "duration": 1.02}, {"text": "That is the root of\nthe heroic story.", "start": 2599.09, "duration": 2.775}, {"text": "And these ancient herding\nsocieties, anthropologists call", "start": 2606.47, "duration": 7.09}, {"text": "warrior herding societies,\nthey were warriors.", "start": 2613.56, "duration": 3.405}, {"text": "Civilization was\npriests and farmers.", "start": 2620.9, "duration": 4.065}, {"text": "Now, here's the last\npiece of this puzzle.", "start": 2632.29, "duration": 1.83}, {"text": "As civilization got more\ncomplicated, get more people,", "start": 2636.64, "duration": 5.49}, {"text": "got bigger problems, the priest\ncan't keep everybody together", "start": 2642.13, "duration": 4.71}, {"text": "just on holidays and Sundays,\nif you want to put it like that.", "start": 2646.84, "duration": 7.65}, {"text": "You have to have a\nprinciple of force.", "start": 2654.49, "duration": 3.72}, {"text": "So what happened was that the\nwarrior herders, the young men,", "start": 2658.21, "duration": 6.743}, {"text": "would get out and\nsay, well, look,", "start": 2664.953, "duration": 1.417}, {"text": "we've got to prove our manhood.", "start": 2666.37, "duration": 2.04}, {"text": "So they'd run out to\nsome civilization,", "start": 2668.41, "duration": 4.65}, {"text": "kill someone, steal some women.", "start": 2673.06, "duration": 3.54}, {"text": "Then the civilization\nstarted building walls", "start": 2679.94, "duration": 2.31}, {"text": "to keep them out.", "start": 2682.25, "duration": 2.68}, {"text": "And then what happened\nwas, the priest", "start": 2684.93, "duration": 2.3}, {"text": "started hiring them\nas mercenaries.", "start": 2687.23, "duration": 4.17}, {"text": "The priests started hiring\nthem as, first of all,", "start": 2691.4, "duration": 2.73}, {"text": "mercenaries, whenever one\ncivilized group thought", "start": 2694.13, "duration": 7.44}, {"text": "that they needed something\nfrom another civilized group.", "start": 2701.57, "duration": 2.395}, {"text": "Some bugs got in and ate\nall of the wheat over here.", "start": 2706.64, "duration": 4.32}, {"text": "These people got\nwheat over there.", "start": 2710.96, "duration": 1.637}, {"text": "They're not going to give\nyou any wheat over here.", "start": 2712.597, "duration": 2.083}, {"text": "So you hire some of\nthese mercenaries", "start": 2714.68, "duration": 1.575}, {"text": "to go beat up on a couple of\nthem and bring some wheat back.", "start": 2716.255, "duration": 5.085}, {"text": "Then you have all of these\nproblems within the culture.", "start": 2721.34, "duration": 4.057}, {"text": "People are fighting.", "start": 2725.397, "duration": 0.833}, {"text": "So then you hire these\npeople, not as mercenaries,", "start": 2728.94, "duration": 2.343}, {"text": "but you hire them as police.", "start": 2731.283, "duration": 1.167}, {"text": "You see it?", "start": 2735.37, "duration": 0.916}, {"text": "The invention of the king.", "start": 2736.286, "duration": 1.428}, {"text": "You already got the high priest.", "start": 2741.05, "duration": 1.5}, {"text": "The king is really an outsider.", "start": 2742.55, "duration": 2.97}, {"text": "That's what happened\nto the Roman Empire.", "start": 2745.52, "duration": 2.44}, {"text": "The Romans came in.", "start": 2747.96, "duration": 0.96}, {"text": "They just didn't subdue\neverybody and beat everybody", "start": 2748.92, "duration": 2.37}, {"text": "up.", "start": 2751.29, "duration": 0.5}, {"text": "They just came in and\nbecame the police.", "start": 2751.79, "duration": 2.758}, {"text": "They left a lot of the\nhigh priests in control.", "start": 2757.88, "duration": 4.45}, {"text": "So what I'm saying now is\nthat the religion in warrior", "start": 2762.33, "duration": 6.29}, {"text": "societies is based on kinship.", "start": 2768.62, "duration": 2.265}, {"text": "And they don't believe\nthat they lose anything", "start": 2773.97, "duration": 7.04}, {"text": "by adopting your religion.", "start": 2781.01, "duration": 4.81}, {"text": "You can't adopt theirs\nbecause you're not", "start": 2785.82, "duration": 1.92}, {"text": "a member of the family.", "start": 2787.74, "duration": 2.6}, {"text": "So warrior herding societies\nare not like civilized society.", "start": 2790.34, "duration": 4.19}, {"text": "Civilized societies compete\nto the death over religion.", "start": 2794.53, "duration": 4.528}, {"text": "Warrior herding societies,\nit doesn't matter that", "start": 2799.058, "duration": 2.042}, {"text": "much to them.", "start": 2801.1, "duration": 0.542}, {"text": "The pagans that we're\ntalking about in Parzival", "start": 2804.27, "duration": 3.66}, {"text": "were warrior herding Arabs.", "start": 2807.93, "duration": 1.32}, {"text": "So Feirefiz really wasn't\ngiven up a whole lot", "start": 2814.84, "duration": 2.54}, {"text": "to become a Christian,\nnot a whole lot.", "start": 2817.38, "duration": 7.7}, {"text": "Even when Muhammad invented\nIslam, he did it as an attempt", "start": 2825.08, "duration": 9.44}, {"text": "to synthesize their own\nreligions with Christianity", "start": 2834.52, "duration": 4.98}, {"text": "and Judaism and one other\none, Zoroastrianism.", "start": 2839.5, "duration": 6.8}, {"text": "So any person who comes in here\nwho says that I am a Muslim", "start": 2846.3, "duration": 5.73}, {"text": "will say that I have very\nfew arguments with you", "start": 2852.03, "duration": 2.61}, {"text": "about religion.", "start": 2854.64, "duration": 3.15}, {"text": "You will say, I have a\nlot of arguments with you", "start": 2857.79, "duration": 2.077}, {"text": "about religion.", "start": 2859.867, "duration": 0.931}, {"text": "But they will say, I\ndon't have a whole lot", "start": 2860.798, "duration": 1.792}, {"text": "of arguments with\nyou about religion", "start": 2862.59, "duration": 1.5}, {"text": "because part of my religion is\nalready built in Christianity.", "start": 2864.09, "duration": 5.67}, {"text": "So Feirefiz wasn't giving\nup a whole lot by doing it.", "start": 2869.76, "duration": 3.39}, {"text": "It meant almost\neverything to Parzival.", "start": 2873.15, "duration": 2.31}, {"text": "So I thought I'd go\nthrough that long spiel", "start": 2879.98, "duration": 3.03}, {"text": "because it's built\ninto the story here.", "start": 2883.01, "duration": 5.357}, {"text": "These things are\nbuilt into the story.", "start": 2888.367, "duration": 1.583}, {"text": "What had just happened was,\nwhat created the knights", "start": 2893.59, "duration": 3.39}, {"text": "and what made them\nwho they were was", "start": 2896.98, "duration": 2.52}, {"text": "that there was this big\nvoid in the Western world", "start": 2899.5, "duration": 3.72}, {"text": "after the Roman\nEmpire collapsed.", "start": 2903.22, "duration": 3.9}, {"text": "And any time some\nbig power collapses,", "start": 2907.12, "duration": 3.812}, {"text": "there are a whole lot of people\nrushing in to fill the void", "start": 2910.932, "duration": 2.458}, {"text": "and get the piece of the action.", "start": 2913.39, "duration": 2.31}, {"text": "Then came Islam.", "start": 2915.7, "duration": 2.28}, {"text": "That lasted for a\nwhile, went back.", "start": 2917.98, "duration": 2.37}, {"text": "And now you have the Dark Ages.", "start": 2920.35, "duration": 1.8}, {"text": "And then when everything\ncomes back together,", "start": 2922.15, "duration": 2.22}, {"text": "you start having\nthe Middle Ages.", "start": 2924.37, "duration": 2.04}, {"text": "And when did you start\nhaving the Middle Ages?", "start": 2926.41, "duration": 2.43}, {"text": "When Charlemagne started\norganizing all of these Dukes", "start": 2928.84, "duration": 6.39}, {"text": "under one king.", "start": 2935.23, "duration": 0.9}, {"text": "Some people would\nsay it was Otto I who", "start": 2939.53, "duration": 5.26}, {"text": "came after Charlemagne,\nbut nevertheless.", "start": 2944.79, "duration": 3.12}, {"text": "So we're talking\nabout a time now", "start": 2947.91, "duration": 1.77}, {"text": "when the West was ruled\nby Arabs who left.", "start": 2949.68, "duration": 7.74}, {"text": "And you got this big void.", "start": 2957.42, "duration": 1.38}, {"text": "And you have a feudal system.", "start": 2958.8, "duration": 3.78}, {"text": "And the knights\nserve a feudal lord.", "start": 2962.58, "duration": 6.88}, {"text": "And there is this something\nabout some of these knights", "start": 2969.46, "duration": 2.85}, {"text": "that say, well,\nlook, yeah, we're", "start": 2972.31, "duration": 2.7}, {"text": "ravaging the land\nand all of that.", "start": 2975.01, "duration": 2.55}, {"text": "But there's got\nto be principles.", "start": 2977.56, "duration": 2.79}, {"text": "And some of these knights\nreally did bring chivalry", "start": 2980.35, "duration": 4.29}, {"text": "to a high peak level.", "start": 2984.64, "duration": 1.74}, {"text": "And some of them even\ncalled themselves priests", "start": 2989.11, "duration": 2.67}, {"text": "like the Knights Templar.", "start": 2991.78, "duration": 2.14}, {"text": "They thought of\nthemselves as priests.", "start": 2993.92, "duration": 2.82}, {"text": "So that's where we\nare with all of this.", "start": 2996.74, "duration": 2.1}, {"text": "And that one thing that isn't\nemphasized in here like it", "start": 2998.84, "duration": 11.25}, {"text": "is other places,\nkilling of the dragons,", "start": 3010.09, "duration": 6.5}, {"text": "is that the purpose of mythology\nis to hold a society together.", "start": 3016.59, "duration": 11.01}, {"text": "And one of its functions\nis to organize the men", "start": 3032.2, "duration": 4.49}, {"text": "with the free time\nand say now, if you're", "start": 3036.69, "duration": 2.302}, {"text": "going to kill somebody,\nthey've got to be [INAUDIBLE]..", "start": 3038.992, "duration": 2.292}, {"text": "And why have these\nthings lasted so long?", "start": 3045.36, "duration": 4.84}, {"text": "Well, what we find\nout is that they've", "start": 3050.2, "duration": 2.06}, {"text": "lasted a long time\nbecause they become", "start": 3052.26, "duration": 3.36}, {"text": "metaphors for\neverybody's problems,", "start": 3055.62, "duration": 3.06}, {"text": "your big problems in your life.", "start": 3058.68, "duration": 2.71}, {"text": "And one that I like to talk\nabout, make mention here, let's", "start": 3061.39, "duration": 6.41}, {"text": "entertain a problem.", "start": 3067.8, "duration": 3.39}, {"text": "You've just graduated.", "start": 3071.19, "duration": 1.89}, {"text": "No, you haven't just graduated.", "start": 3073.08, "duration": 1.59}, {"text": "You've graduated\nand you're working.", "start": 3074.67, "duration": 1.71}, {"text": "And you have sacrificed a lot.", "start": 3076.38, "duration": 4.53}, {"text": "And you've progressed\nin your company.", "start": 3080.91, "duration": 2.58}, {"text": "And your company is competing\nfor a contract, let's say,", "start": 3089.28, "duration": 10.332}, {"text": "with the Germans.", "start": 3099.612, "duration": 0.708}, {"text": "And the company is going to\nmake its pitch Monday morning.", "start": 3102.99, "duration": 10.27}, {"text": "And you have to leave.", "start": 3113.26, "duration": 1.72}, {"text": "Sunday night, you get a call\nfrom your husband's mother", "start": 3122.41, "duration": 10.23}, {"text": "in Arizona.", "start": 3132.64, "duration": 2.922}, {"text": "The kids are out visiting.", "start": 3135.562, "duration": 1.083}, {"text": "Your husband says, one of\nthe kids got hit by a car.", "start": 3139.81, "duration": 3.93}, {"text": "The doctor says, we\ndon't if the kid's", "start": 3147.64, "duration": 2.27}, {"text": "going to last another two days.", "start": 3149.91, "duration": 3.0}, {"text": "Now, do you go to that\nmeeting on Monday?", "start": 3152.91, "duration": 2.86}, {"text": "Or do you go to Arizona?", "start": 3155.77, "duration": 1.457}, {"text": "AUDIENCE: I'd go to Arizona.", "start": 3161.44, "duration": 2.78}, {"text": "TAFT BROOME: Well,\nlet me tell you", "start": 3164.22, "duration": 4.59}, {"text": "how this heroic story is going\nto help you with that decision.", "start": 3168.81, "duration": 4.68}, {"text": "The heroic story says that\nyour conscious mind does not", "start": 3173.49, "duration": 10.63}, {"text": "possess all of the knowledge\nthat your mind possessed.", "start": 3184.12, "duration": 4.75}, {"text": "Your unconscious mind, and\nI'm not talking about memories", "start": 3188.87, "duration": 2.85}, {"text": "right now.", "start": 3191.72, "duration": 1.02}, {"text": "I'm talking about parts of\nyour conscious mind that", "start": 3192.74, "duration": 3.15}, {"text": "are virtually permanent.", "start": 3195.89, "duration": 3.07}, {"text": "There are truths that are\nhidden down in your unconscious.", "start": 3198.96, "duration": 2.66}, {"text": "And if you are able to get\ninto a mythic state of mind,", "start": 3206.06, "duration": 5.36}, {"text": "then what you will\nbe able to do is", "start": 3211.42, "duration": 3.38}, {"text": "to go down in your\nunconscious and find out", "start": 3214.8, "duration": 2.52}, {"text": "if one of those monsters down\nthere needs to be killed.", "start": 3217.32, "duration": 4.655}, {"text": "Now what kind of monster\nwould be down there?", "start": 3224.415, "duration": 1.875}, {"text": "Well, I'll tell you one kind\nthat would be down there,", "start": 3226.29, "duration": 2.25}, {"text": "your ambition\nbecause your ambition", "start": 3228.54, "duration": 4.57}, {"text": "is competing with that child.", "start": 3233.11, "duration": 3.29}, {"text": "That was unfair because\nI made you all mothers.", "start": 3236.4, "duration": 2.49}, {"text": "But suppose it was\nsome people that", "start": 3238.89, "duration": 7.2}, {"text": "are going to die if\nyou don't go help", "start": 3246.09, "duration": 1.83}, {"text": "them as opposed to going then.", "start": 3247.92, "duration": 6.45}, {"text": "Then you got to face that\ndemon down there that's", "start": 3254.37, "duration": 3.06}, {"text": "your ambition.", "start": 3257.43, "duration": 2.65}, {"text": "And what you have got to do\nis to say that I would rather", "start": 3260.08, "duration": 5.34}, {"text": "be dead than to continue to live\na life not being able to deal", "start": 3265.42, "duration": 4.65}, {"text": "with these decisions.", "start": 3270.07, "duration": 1.71}, {"text": "I got to deal with this.", "start": 3271.78, "duration": 1.0}, {"text": "Maybe my ambition\nis good for me.", "start": 3272.78, "duration": 3.863}, {"text": "Maybe it's got to be killed.", "start": 3276.643, "duration": 1.167}, {"text": "But whatever it is, I've\ngot to face the demon.", "start": 3277.81, "duration": 2.73}, {"text": "And I am ready to die because\nthat unconscious demon is", "start": 3280.54, "duration": 5.82}, {"text": "lethal in the real world.", "start": 3286.36, "duration": 2.51}, {"text": "So if you decide that on\nsomebody else's behalf,", "start": 3291.5, "duration": 4.13}, {"text": "you are willing\nto kill the demon", "start": 3295.63, "duration": 1.59}, {"text": "and to bring the truth back\nto your conscious mind, that's", "start": 3297.22, "duration": 5.41}, {"text": "the best way to\nhandle the problem.", "start": 3302.63, "duration": 1.695}, {"text": "Whatever decision you\ncome up with after that", "start": 3304.325, "duration": 1.875}, {"text": "is the best you can do.", "start": 3306.2, "duration": 1.98}, {"text": "And the metaphor is\nin the heroic story.", "start": 3308.18, "duration": 5.68}, {"text": "So if you can get into\nthe story to the point", "start": 3313.86, "duration": 2.57}, {"text": "where you can get\ninto Parzival's place", "start": 3316.43, "duration": 2.28}, {"text": "and actually feel\nwhat Parzival feels,", "start": 3318.71, "duration": 3.15}, {"text": "and then get into some\nof these other stories", "start": 3321.86, "duration": 2.22}, {"text": "where they're really killing\ndragons, then what it does,", "start": 3324.08, "duration": 4.53}, {"text": "what we know now\n1,000 years later,", "start": 3328.61, "duration": 5.79}, {"text": "is that if you embrace\nthose things seriously.", "start": 3334.4, "duration": 2.67}, {"text": "And if you really feel that\nyou are Parzival in there,", "start": 3337.07, "duration": 6.11}, {"text": "then the wiring in\nyour brain will change.", "start": 3343.18, "duration": 3.45}, {"text": "And your 12-year-old\nwill start looking", "start": 3349.83, "duration": 4.41}, {"text": "like a 14-year-old,\nnot somebody who's", "start": 3354.24, "duration": 3.81}, {"text": "going to be 18-year-old still\nlooking like a 12-year-old,", "start": 3358.05, "duration": 3.48}, {"text": "that your physiology, if you're\nyoung enough, will change.", "start": 3361.53, "duration": 3.66}, {"text": "You will grow up.", "start": 3365.19, "duration": 1.11}, {"text": "Now, ancient people and medieval\npeople and early modern people", "start": 3370.49, "duration": 8.22}, {"text": "do all of this before the\nscience could prove any of it.", "start": 3378.71, "duration": 4.51}, {"text": "Better stated,\nbetter stated, they", "start": 3383.22, "duration": 3.39}, {"text": "were willing to commit to it\nregardless of the consequences.", "start": 3386.61, "duration": 4.39}, {"text": "So when they had their\nyoung kids coming along,", "start": 3391.0, "duration": 4.32}, {"text": "particularly if they were\nafraid that the boys we're", "start": 3395.32, "duration": 3.2}, {"text": "going to have some free time--", "start": 3398.52, "duration": 2.33}, {"text": "Oh, I mean, it's a nightmare\nif you got a 16-year-old", "start": 3400.85, "duration": 4.66}, {"text": "on a Saturday night.", "start": 3405.51, "duration": 1.81}, {"text": "I don't care how\nmuch you put into it.", "start": 3407.32, "duration": 3.24}, {"text": "That can be a bad night for you.", "start": 3410.56, "duration": 3.02}, {"text": "I know, I was 16 years old once.", "start": 3413.58, "duration": 3.9}, {"text": "But if you read these\nstories to them,", "start": 3417.48, "duration": 4.2}, {"text": "and if they can embrace\nthem, then that's a big help.", "start": 3421.68, "duration": 4.47}, {"text": "It's a big help.", "start": 3426.15, "duration": 1.8}, {"text": "Some people have\nsaid that Freud,", "start": 3427.95, "duration": 2.43}, {"text": "no matter what\nothers say, that he", "start": 3430.38, "duration": 3.06}, {"text": "brought the scientific method\nto the study of the mind.", "start": 3433.44, "duration": 3.57}, {"text": "What they really say is\nthat Freud was actually", "start": 3437.01, "duration": 2.28}, {"text": "a mythologist because\nwhat he said was the best", "start": 3439.29, "duration": 4.86}, {"text": "solution to your problem.", "start": 3444.15, "duration": 1.59}, {"text": "Freud went one other step.", "start": 3445.74, "duration": 2.13}, {"text": "This is very significant.", "start": 3447.87, "duration": 1.11}, {"text": "And see if you can find it\nin any of these stories.", "start": 3448.98, "duration": 2.91}, {"text": "Freud said that if you are\nan amateur fooling around", "start": 3451.89, "duration": 6.18}, {"text": "with the unconscious,\nyou're unconscious", "start": 3458.07, "duration": 2.55}, {"text": "or anybody else's, you\nmay release the demon.", "start": 3460.62, "duration": 5.32}, {"text": "But unless you make\nthe demon morally", "start": 3465.94, "duration": 3.42}, {"text": "acceptable to your\nconscious mind,", "start": 3469.36, "duration": 2.728}, {"text": "the demon will get up there and\nrun you to the insane asylum.", "start": 3472.088, "duration": 2.542}, {"text": "And Freud talked about that\nin terms of the competition", "start": 3479.57, "duration": 8.1}, {"text": "that boys have with the father\nand wanting to kill the father", "start": 3487.67, "duration": 5.52}, {"text": "and take the father's\nplace with the mother.", "start": 3493.19, "duration": 2.265}, {"text": "And Mary Shelley made a big deal\nout of it with Frankenstein.", "start": 3499.28, "duration": 4.41}, {"text": "Because what did\nFrankenstein want to do?", "start": 3503.69, "duration": 1.98}, {"text": "To kill his maker?", "start": 3505.67, "duration": 0.93}, {"text": "It's wired down in the brain.", "start": 3509.48, "duration": 3.45}, {"text": "Freud said if that's the\ntruth, then that's a hard thing", "start": 3512.93, "duration": 3.6}, {"text": "to justify morally.", "start": 3516.53, "duration": 2.25}, {"text": "So it's best left down there\nunless you can find a way", "start": 3518.78, "duration": 2.91}, {"text": "to bring it up morally.", "start": 3521.69, "duration": 3.59}, {"text": "So mythology is\nsupposed to do all that.", "start": 3525.28, "duration": 2.15}, {"text": "Now, let's talk about how this\nthing fits into this class.", "start": 3527.43, "duration": 3.915}, {"text": "If you want to solve\nan ethical problem", "start": 3538.74, "duration": 3.63}, {"text": "and you want to solve it by\nusing the method of virtues,", "start": 3542.37, "duration": 5.73}, {"text": "but you don't want\nthe list of virtues", "start": 3548.1, "duration": 3.84}, {"text": "that Plato or any of\nthose people have,", "start": 3551.94, "duration": 2.55}, {"text": "but you want to find a character\nlike I did with my first day", "start": 3554.49, "duration": 5.34}, {"text": "on an engineering job, put\nthat character in your place.", "start": 3559.83, "duration": 2.94}, {"text": "Work the character through it.", "start": 3562.77, "duration": 1.44}, {"text": "And then imitate, to some\nextent, that character.", "start": 3564.21, "duration": 3.17}, {"text": "The question is, what\ncharacter to choose.", "start": 3567.38, "duration": 1.75}, {"text": "It's not simply a matter of\nchoosing a good person because", "start": 3572.31, "duration": 5.34}, {"text": "in the end, what you want\nis to still have your job.", "start": 3577.65, "duration": 3.99}, {"text": "You have to be\nprepared to lose it.", "start": 3587.44, "duration": 3.33}, {"text": "But what you want in the end is\nto have somebody on your side.", "start": 3590.77, "duration": 6.51}, {"text": "Now the idea of the mythic\nstory is that the mythic story", "start": 3597.28, "duration": 4.71}, {"text": "provides a hero that is\nnot only a hero to you,", "start": 3601.99, "duration": 4.57}, {"text": "but is a hero to people.", "start": 3606.56, "duration": 1.04}, {"text": "And why is that?", "start": 3610.3, "duration": 1.11}, {"text": "Because of the long\nstory I just gave.", "start": 3611.41, "duration": 4.62}, {"text": "It's another thing that's\nwired into the brain.", "start": 3616.03, "duration": 2.52}, {"text": "After a while, people began\nto see from these stories", "start": 3618.55, "duration": 6.69}, {"text": "that there's something\nof me in these heroes.", "start": 3625.24, "duration": 9.12}, {"text": "Why isn't that?", "start": 3634.36, "duration": 0.66}, {"text": "All right, this is\nthis word, gestalt.", "start": 3641.75, "duration": 9.95}, {"text": "And let's take the\nNecker cube again.", "start": 3651.7, "duration": 1.83}, {"text": "What your brain actually sees\nis a three-dimensional figure.", "start": 3656.05, "duration": 4.44}, {"text": "What's up there is 12\nlines on a flat board.", "start": 3660.49, "duration": 4.08}, {"text": "When you are sitting\naround with your family,", "start": 3669.48, "duration": 5.0}, {"text": "is there one person that gets\nup to represent your family.", "start": 3674.48, "duration": 5.48}, {"text": "Is there such a thing\nas an MIT person?", "start": 3679.96, "duration": 4.525}, {"text": "Can you go to the\nairport and, say there", "start": 3687.86, "duration": 5.773}, {"text": "are 400 students out here.", "start": 3693.633, "duration": 1.467}, {"text": "But that one is\nprobably from MIT.", "start": 3695.1, "duration": 2.2}, {"text": "Can you do that?", "start": 3697.3, "duration": 1.22}, {"text": "Probably.", "start": 3698.52, "duration": 0.84}, {"text": "Doesn't matter if\nyou're right or wrong.", "start": 3699.36, "duration": 1.667}, {"text": "The point is that you've\ngot a picture in your mind.", "start": 3701.027, "duration": 2.923}, {"text": "Did I ever tell you a story\nabout the old blues at Yale?", "start": 3703.95, "duration": 5.49}, {"text": "Yeah, I was chair of\nthe Faculty Senate.", "start": 3709.44, "duration": 3.15}, {"text": "We had just gotten a\nconstitution approved", "start": 3712.59, "duration": 2.49}, {"text": "where we could get\nfaculty members", "start": 3715.08, "duration": 1.98}, {"text": "on the board of trustees.", "start": 3717.06, "duration": 2.19}, {"text": "The question was, what kind\nof faculty member do we want?", "start": 3719.25, "duration": 3.39}, {"text": "You get somebody that's quote\nunquote \"too scholarly,\"", "start": 3722.64, "duration": 2.25}, {"text": "the board won't understand them.", "start": 3724.89, "duration": 4.26}, {"text": "You get somebody who's\ntoo businesslike,", "start": 3729.15, "duration": 1.668}, {"text": "and he won't reflect\nthe rest, or she", "start": 3730.818, "duration": 1.542}, {"text": "won't reflect the rest of us.", "start": 3732.36, "duration": 1.87}, {"text": "So what do you do?", "start": 3734.23, "duration": 0.86}, {"text": "How do you deal\nwith that problem?", "start": 3735.09, "duration": 1.2}, {"text": "There was one\nfaculty member there", "start": 3736.29, "duration": 1.417}, {"text": "who got his law\ndegree from Yale.", "start": 3737.707, "duration": 2.376}, {"text": "And he said, look,\nwhy don't you call up", "start": 3740.083, "duration": 1.667}, {"text": "to the President's Office\nand ask for the person who", "start": 3741.75, "duration": 5.55}, {"text": "staffs the trustees.", "start": 3747.3, "duration": 2.192}, {"text": "And when you get the\nperson on the phone,", "start": 3749.492, "duration": 1.708}, {"text": "ask them what an old blue is.", "start": 3751.2, "duration": 1.23}, {"text": "I said, what's an old blue?", "start": 3752.43, "duration": 0.9}, {"text": "He said, you ask this person.", "start": 3753.33, "duration": 0.946}, {"text": "I said OK.", "start": 3754.276, "duration": 0.734}, {"text": "So I called up there.", "start": 3755.01, "duration": 1.593}, {"text": "They gave me the staff\nperson for the trustee board.", "start": 3756.603, "duration": 2.167}, {"text": "And I said, what's an old blue?", "start": 3758.77, "duration": 1.76}, {"text": "And she said, an\nold blue is a member", "start": 3760.53, "duration": 2.382}, {"text": "of the faculty who\nlooks like Yale.", "start": 3762.912, "duration": 1.458}, {"text": "I understood that.", "start": 3767.8, "duration": 0.75}, {"text": "I mean, it was abstract.", "start": 3768.55, "duration": 1.895}, {"text": "Yeah, OK.", "start": 3770.445, "duration": 1.825}, {"text": "And we concluded in\nthe end, they said,", "start": 3772.27, "duration": 2.07}, {"text": "they come into board meetings.", "start": 3774.34, "duration": 1.32}, {"text": "The board, by some\nYale tradition,", "start": 3775.66, "duration": 5.46}, {"text": "is able to pick out\nwho the old blues are.", "start": 3781.12, "duration": 3.21}, {"text": "And the board brings them\ninto the board meeting.", "start": 3784.33, "duration": 2.64}, {"text": "And here's what really\nhappens according", "start": 3786.97, "duration": 2.13}, {"text": "to that conversation, that\n95% of the time, the board", "start": 3789.1, "duration": 3.96}, {"text": "is talking about\nwhat Yale lives for.", "start": 3793.06, "duration": 3.528}, {"text": "But when they want to\nmake a decision where", "start": 3796.588, "duration": 1.792}, {"text": "they can gain a\nlot, maybe they want", "start": 3798.38, "duration": 2.88}, {"text": "to know what Yale is\nwilling to die for.", "start": 3801.26, "duration": 2.738}, {"text": "Then they turn to the old blue.", "start": 3803.998, "duration": 1.292}, {"text": "Should we take this\ntake on this project?", "start": 3805.29, "duration": 3.74}, {"text": "Should we have a course\nin here on Islam?", "start": 3809.03, "duration": 5.46}, {"text": "Should we have Jerry\nFalwell on the faculty?", "start": 3814.49, "duration": 6.53}, {"text": "They look to the old blues.", "start": 3821.02, "duration": 1.338}, {"text": "And the answer is\nnot right or wrong.", "start": 3822.358, "duration": 1.542}, {"text": "The answer's is this\nhere, if we do this,", "start": 3823.9, "duration": 3.0}, {"text": "will we have Yale at the end?", "start": 3826.9, "duration": 4.07}, {"text": "Well, that's a gestalt of Yale.", "start": 3830.97, "duration": 4.41}, {"text": "And this tradition I'm talking\nabout is Yale's mythology.", "start": 3835.38, "duration": 4.94}, {"text": "Mythology will give you these\nold blues for a culture.", "start": 3840.32, "duration": 5.07}, {"text": "And if an old blue is\nrepresentative of the whole,", "start": 3845.39, "duration": 3.96}, {"text": "then the old blue has a part\nof each of us in him or her.", "start": 3849.35, "duration": 7.41}, {"text": "And once she has done\nwhatever she has done,", "start": 3856.76, "duration": 2.77}, {"text": "no matter how bad it is, we all\nhave a tendency to say, well,", "start": 3859.53, "duration": 4.908}, {"text": "maybe she needs to be punished.", "start": 3864.438, "duration": 1.292}, {"text": "But let's not be too harsh.", "start": 3865.73, "duration": 2.7}, {"text": "I mean, I might have done that.", "start": 3868.43, "duration": 2.91}, {"text": "Or we are decent people here.", "start": 3871.34, "duration": 2.98}, {"text": "But this is the best it\ngets with our family.", "start": 3874.32, "duration": 2.27}, {"text": "So if you pull out\na cultural hero", "start": 3880.12, "duration": 2.33}, {"text": "and imitate a cultural\nhero, my argument has been,", "start": 3882.45, "duration": 3.99}, {"text": "and I'm not alone in this, that\nwhatever you do in the end,", "start": 3886.44, "duration": 5.37}, {"text": "and no matter whether they\nwant to punish you for it,", "start": 3891.81, "duration": 5.37}, {"text": "there will be a tendency\nfor them to side with", "start": 3897.18, "duration": 3.87}, {"text": "or to forgive you or to see\nthe point of what you did", "start": 3901.05, "duration": 3.15}, {"text": "or something.", "start": 3904.2, "duration": 1.08}, {"text": "AUDIENCE: Did I hear you using\nthe words cultural heroes?", "start": 3909.96, "duration": 3.154}, {"text": "TAFT BROOME: Yes.", "start": 3913.114, "duration": 1.491}, {"text": "AUDIENCE: And it's hard\nfor me to see knights--", "start": 3914.605, "duration": 4.97}, {"text": "our theory of knights\nas cultural heroes.", "start": 3919.575, "duration": 3.485}, {"text": "TAFT BROOME: Yes.", "start": 3923.06, "duration": 0.72}, {"text": "AUDIENCE: So I'm trying really\nhard to think metaphorically", "start": 3923.78, "duration": 2.458}, {"text": "and to see Parzival\nor characters like him", "start": 3926.238, "duration": 2.762}, {"text": "as heroes that could\nhelp make decisions.", "start": 3929.0, "duration": 3.04}, {"text": "But it's really\ntough because all", "start": 3932.04, "duration": 1.62}, {"text": "of the activities that\nthese knights engage in", "start": 3933.66, "duration": 4.02}, {"text": "are not relevant.", "start": 3937.68, "duration": 0.99}, {"text": "So now you're using\ncultural hero.", "start": 3943.96, "duration": 1.835}, {"text": "And I wonder if\nthat's different.", "start": 3945.795, "duration": 1.375}, {"text": "Like, a cultural\nhero to me would", "start": 3947.17, "duration": 1.83}, {"text": "be someone who has faced\ndecisions that we can relate to", "start": 3949.0, "duration": 5.59}, {"text": "or has lived in the time that\nwe relate to or has distractions", "start": 3954.59, "duration": 4.429}, {"text": "that we also have to deal with.", "start": 3959.019, "duration": 1.292}, {"text": "So someone like Martin Luther\nKing, Jr. or Ghandi or John", "start": 3960.311, "duration": 5.796}, {"text": "Kennedy or whoever, why\nwouldn't those types of people", "start": 3966.107, "duration": 3.943}, {"text": "be perhaps more helpful than\ndead heroes from the past.", "start": 3970.05, "duration": 6.68}, {"text": "TAFT BROOME: OK,\nfirst of all, you", "start": 3976.73, "duration": 2.67}, {"text": "hit a very, very,\nvery important nerve.", "start": 3979.4, "duration": 3.45}, {"text": "And that is that there's some\ngenerational differences.", "start": 3982.85, "duration": 4.69}, {"text": "And so the question\nis, why is it", "start": 3987.54, "duration": 3.53}, {"text": "that Parzival meant\nso much to me?", "start": 3991.07, "duration": 3.24}, {"text": "I was not in his generation.", "start": 3994.31, "duration": 1.47}, {"text": "And the key word in\nthe end is metaphor.", "start": 3999.25, "duration": 9.68}, {"text": "Now, listen to me\ncarefully because I", "start": 4012.5, "duration": 1.92}, {"text": "want to choose my words properly\nhere because if I mess up,", "start": 4014.42, "duration": 3.42}, {"text": "I could really\nthrow everybody off.", "start": 4017.84, "duration": 1.86}, {"text": "When I had to make that decision\non my first day as an engineer,", "start": 4024.27, "duration": 6.745}, {"text": "I didn't see any difference\nbetween Parzival and my uncle", "start": 4031.015, "duration": 2.375}, {"text": "Roy.", "start": 4033.39, "duration": 0.5}, {"text": "Campbell says that the\nhero's journey has this path.", "start": 4044.81, "duration": 4.98}, {"text": "We just went through it.", "start": 4049.79, "duration": 1.33}, {"text": "First of all, you hear a call.", "start": 4051.12, "duration": 1.79}, {"text": "That's really your unconscious\ntrying to say, look,", "start": 4057.165, "duration": 2.125}, {"text": "you better get down here.", "start": 4059.29, "duration": 3.42}, {"text": "You hear a call.", "start": 4062.71, "duration": 0.903}, {"text": "You don't really want to do\nit because somehow you know", "start": 4063.613, "duration": 2.292}, {"text": "that this thing can be lethal.", "start": 4065.905, "duration": 3.615}, {"text": "But somebody else makes the\ncase that if you don't go,", "start": 4069.52, "duration": 4.17}, {"text": "somebody else is\ngoing to suffer.", "start": 4073.69, "duration": 1.66}, {"text": "So you got to go.", "start": 4075.35, "duration": 3.12}, {"text": "So the first thing\nis to hear the call.", "start": 4078.47, "duration": 2.06}, {"text": "The second thing\nis the separation.", "start": 4080.53, "duration": 2.25}, {"text": "You have got to go away\nfrom the comfort zone", "start": 4082.78, "duration": 4.62}, {"text": "and into the unknown\nand the fabulous.", "start": 4087.4, "duration": 4.47}, {"text": "That's very important,\nfabulous, fabulous,", "start": 4091.87, "duration": 2.82}, {"text": "Not fabulous in terms\nof peacock feathers,", "start": 4094.69, "duration": 5.52}, {"text": "fabulous in terms\nof fable, that there", "start": 4100.21, "duration": 3.39}, {"text": "are things that you are going\nto encounter that are not", "start": 4103.6, "duration": 2.31}, {"text": "of this conscious Earth.", "start": 4105.91, "duration": 1.497}, {"text": "They are the demons\nin your unconscious.", "start": 4107.407, "duration": 1.667}, {"text": "You've got to slay a\ndragon because that's", "start": 4109.074, "duration": 2.745}, {"text": "a real thing in\nyour unconscious.", "start": 4111.819, "duration": 2.221}, {"text": "And then when you\nslayed the dragon,", "start": 4114.04, "duration": 2.189}, {"text": "you have to bring back\nsomething, like the truth.", "start": 4116.229, "duration": 3.871}, {"text": "That's the Holy Grail.", "start": 4120.1, "duration": 2.07}, {"text": "You've got to bring\nthe Grail back.", "start": 4122.17, "duration": 1.763}, {"text": "And what do you do with the\nGrail when you get back?", "start": 4123.933, "duration": 2.167}, {"text": "You share it with everybody.", "start": 4126.1, "duration": 1.679}, {"text": "OK, so that's the pattern\nof the hero's journey.", "start": 4132.35, "duration": 3.39}, {"text": "Look at Roy.", "start": 4135.74, "duration": 0.81}, {"text": "Why was Roy a hero?", "start": 4136.55, "duration": 2.729}, {"text": "Well, when they\ngot back home, they", "start": 4139.279, "duration": 6.241}, {"text": "found out that all\nthe parents were dead,", "start": 4145.52, "duration": 4.31}, {"text": "then they heard a call to do\nsomething for the children.", "start": 4149.83, "duration": 7.406}, {"text": "But it wasn't staying\nthere working.", "start": 4157.236, "duration": 2.964}, {"text": "So they had to go out.", "start": 4160.2, "duration": 1.289}, {"text": "When they got down\nto Oberlin, that", "start": 4164.279, "duration": 2.04}, {"text": "was just like being in\na dream world for them.", "start": 4166.319, "duration": 2.551}, {"text": "I've heard them talk about it.", "start": 4168.87, "duration": 2.76}, {"text": "And when they got\ntheir degrees, what", "start": 4171.63, "duration": 2.78}, {"text": "did they do with the degree?", "start": 4174.41, "duration": 1.47}, {"text": "They didn't go out\nand get a big job.", "start": 4175.88, "duration": 2.46}, {"text": "They brought the\ndegree back home", "start": 4178.34, "duration": 2.91}, {"text": "to help the others get out.", "start": 4181.25, "duration": 1.979}, {"text": "That was their Holy Grail.", "start": 4183.229, "duration": 1.441}, {"text": "It's the same thing.", "start": 4184.67, "duration": 1.5}, {"text": "So what you've got to\ndo is to look around", "start": 4189.01, "duration": 5.42}, {"text": "you and find somebody you know.", "start": 4194.43, "duration": 2.49}, {"text": "You don't have to\nknow them personally.", "start": 4196.92, "duration": 2.43}, {"text": "But find somebody you know who\nhas had that same experience.", "start": 4199.35, "duration": 4.458}, {"text": "They don't have to\nbe perfect people.", "start": 4203.808, "duration": 1.542}, {"text": "But if they have\nhad that experience,", "start": 4208.53, "duration": 3.39}, {"text": "and they are heroes in\nthe sense that they are--", "start": 4211.92, "duration": 2.94}, {"text": "The beautiful thing\nabout these things", "start": 4214.86, "duration": 1.65}, {"text": "is, they don't hide,\nas we just discussed,", "start": 4216.51, "duration": 2.52}, {"text": "the negative sides of\nthese people's characters.", "start": 4219.03, "duration": 2.92}, {"text": "I mean, when you\nfind out what is", "start": 4221.95, "duration": 1.58}, {"text": "relevant in them\nthat's heroic, put them", "start": 4223.53, "duration": 3.45}, {"text": "in one of those situations.", "start": 4226.98, "duration": 2.42}, {"text": "Do your best or\ndo what you think", "start": 4229.4, "duration": 1.53}, {"text": "is right in terms of how\nmuch you can follow them.", "start": 4230.93, "duration": 4.12}, {"text": "Then once you have done\nit, everybody else,", "start": 4235.05, "duration": 3.24}, {"text": "even if it's only on\nan unconscious level,", "start": 4238.29, "duration": 2.72}, {"text": "we'll see some sense in it and\nhave some compassion for you,", "start": 4241.01, "duration": 3.33}, {"text": "why you did it.", "start": 4244.34, "duration": 1.05}, {"text": "And we'll be inclined\nto say, well,", "start": 4245.39, "duration": 3.54}, {"text": "that's as good as\nit gets with us.", "start": 4248.93, "duration": 2.34}, {"text": "And you'll be the kind that,\nif they sent to prison,", "start": 4256.06, "duration": 4.36}, {"text": "you get your old job\nback when you get out.", "start": 4260.42, "duration": 2.14}, {"text": "You see what I'm saying?", "start": 4262.56, "duration": 1.0}, {"text": "You'll be like John\nBrown at rugby.", "start": 4267.25, "duration": 4.47}, {"text": "Was it rugby?", "start": 4271.72, "duration": 1.83}, {"text": "John Brown's School\nDays, was that rugby?", "start": 4273.55, "duration": 2.55}, {"text": "I'm talking about this\nstory about this American", "start": 4276.1, "duration": 3.84}, {"text": "that goes to one of\nthe British schools.", "start": 4279.94, "duration": 4.03}, {"text": "And he does something\nvery heroic.", "start": 4283.97, "duration": 1.46}, {"text": "But he gets sent down\nfor it, gets kicked out", "start": 4285.43, "duration": 3.87}, {"text": "of school for it.", "start": 4289.3, "duration": 0.75}, {"text": "It's Oxford.", "start": 4293.44, "duration": 2.58}, {"text": "It's John Brown at\nOxford is the name of it.", "start": 4296.02, "duration": 3.3}, {"text": "Well, anyway, what happens\nis he gets sent down for it.", "start": 4299.32, "duration": 3.27}, {"text": "But when he's in the\ncarriage leaving Oxford,", "start": 4302.59, "duration": 2.64}, {"text": "on the way to the port\nwhere he gets the boat home,", "start": 4305.23, "duration": 6.09}, {"text": "all of the Oxford students\nare out there cheering him on.", "start": 4311.32, "duration": 2.49}, {"text": "That's the kind of\nhero I'm talking about.", "start": 4315.69, "duration": 1.75}, {"text": "If you've got to go, they still\nwill treat you like a hero", "start": 4317.44, "duration": 4.05}, {"text": "or think of what you did\nwas as good as it gets.", "start": 4321.49, "duration": 4.2}, {"text": "All right, so my\npoint is that we", "start": 4325.69, "duration": 3.66}, {"text": "can bring virtue ethics back.", "start": 4329.35, "duration": 4.908}, {"text": "But mythology is the way to go.", "start": 4334.258, "duration": 5.012}, {"text": "And if you do mythology\nright, and this", "start": 4339.27, "duration": 2.768}, {"text": "is another one of the things\nthat Joseph Campbell takes", "start": 4342.038, "duration": 2.292}, {"text": "credit for.", "start": 4344.33, "duration": 0.72}, {"text": "As a matter of fact, this is\nreally the source of his fame,", "start": 4345.05, "duration": 4.02}, {"text": "that what he found out was\nthat if you look at mythologies", "start": 4349.07, "duration": 4.95}, {"text": "of all cultures, you'll find a\nwhole lot of things in common.", "start": 4354.02, "duration": 4.86}, {"text": "And the hero's journey\nis one of them.", "start": 4358.88, "duration": 2.126}, {"text": "And there are different\nkinds of hero's journeys", "start": 4367.71, "duration": 3.0}, {"text": "and all of that.", "start": 4370.71, "duration": 0.78}, {"text": "Your challenge then is to\nfind somebody that you,", "start": 4375.85, "duration": 3.48}, {"text": "like I said, that you know.", "start": 4379.33, "duration": 1.375}, {"text": "You don't have to\nknow them personally.", "start": 4380.705, "duration": 1.625}, {"text": "They don't even\nhave to be alive.", "start": 4382.33, "duration": 1.375}, {"text": "You can read them out of books,\nand say, I know that person", "start": 4383.705, "duration": 3.405}, {"text": "and say that, uh huh, that\nperson fits the pattern.", "start": 4387.11, "duration": 4.69}, {"text": "And if I really\nget in some trouble", "start": 4391.8, "duration": 1.46}, {"text": "and do what I think\nthat person will do,", "start": 4393.26, "duration": 2.25}, {"text": "it may not be the right thing.", "start": 4395.51, "duration": 2.92}, {"text": "But somehow or another, I\nwill still fit in the culture", "start": 4398.43, "duration": 2.91}, {"text": "when it's done.", "start": 4401.34, "duration": 0.66}, {"text": "It will be probably\nthe best you can do.", "start": 4406.42, "duration": 2.31}, {"text": "And the only reason I was hoping\nthat this would be a bigger", "start": 4408.73, "duration": 9.14}, {"text": "class, the only\nreason, is that I", "start": 4417.87, "duration": 2.602}, {"text": "was hoping that we'd have\na whole lot of people", "start": 4420.472, "duration": 1.958}, {"text": "in here saying, well,\nyou know, where I'm from,", "start": 4422.43, "duration": 3.25}, {"text": "we got another story.", "start": 4425.68, "duration": 2.1}, {"text": "And the hero didn't go\nout and kill a dragon.", "start": 4427.78, "duration": 5.09}, {"text": "The hero went out and\nkilled something else,", "start": 4432.87, "duration": 6.78}, {"text": "might be just as bad.", "start": 4439.65, "duration": 2.13}, {"text": "I've heard some stories\nfrom South Americans", "start": 4441.78, "duration": 2.43}, {"text": "where the person goes out and\nkills something in the forest.", "start": 4444.21, "duration": 2.764}, {"text": "Well, even anthropologists\nwho study Oedipus", "start": 4450.57, "duration": 2.91}, {"text": "say that he did not kill, it\nwas a Sphinx that he killed,", "start": 4453.48, "duration": 6.27}, {"text": "a lion with a person's head that\nwas terrorizing the populace.", "start": 4459.75, "duration": 6.44}, {"text": "They did find something.", "start": 4466.19, "duration": 1.622}, {"text": "And I don't know how they did\nit, but they found something.", "start": 4467.812, "duration": 2.458}, {"text": "They said around that\nplace at around that time", "start": 4470.27, "duration": 2.79}, {"text": "there was a\npestilence, a disease.", "start": 4473.06, "duration": 4.115}, {"text": "And somehow or another, this\nman came in from outside", "start": 4477.175, "duration": 2.775}, {"text": "and walked among the people\nand helped cure them.", "start": 4479.95, "duration": 3.03}, {"text": "Well, how does it work\n12 generations later", "start": 4482.98, "duration": 3.72}, {"text": "when it gets down in the\nunconscious into a story.", "start": 4486.7, "duration": 3.54}, {"text": "You kill dragons.", "start": 4490.24, "duration": 1.0}, {"text": "So now, what I want\nyou to do since you", "start": 4499.12, "duration": 3.87}, {"text": "all got all of this\nfree time is to take", "start": 4502.99, "duration": 4.89}, {"text": "this last paper that I've\ngiven you back and resubmit it.", "start": 4507.88, "duration": 5.04}, {"text": "But you can change\nit if you want to.", "start": 4512.92, "duration": 3.582}, {"text": "These were good papers.", "start": 4516.502, "duration": 0.958}, {"text": "But what I want you to\ndo is take the character", "start": 4517.46, "duration": 4.55}, {"text": "that you analyzed, and\nsubstitute Parzival in there.", "start": 4522.01, "duration": 4.05}, {"text": "And if that doesn't work, then\nsubstitute some kind of hero", "start": 4529.152, "duration": 2.458}, {"text": "in there and see what\nthat person would", "start": 4531.61, "duration": 3.54}, {"text": "have done in that situation.", "start": 4535.15, "duration": 2.687}, {"text": "And what would have been the\nconsequences to that person", "start": 4537.837, "duration": 2.333}, {"text": "after?", "start": 4540.17, "duration": 2.785}, {"text": "AUDIENCE: So we can\ndo a different hero,", "start": 4542.955, "duration": 1.94}, {"text": "well, any heroic figure?", "start": 4544.895, "duration": 2.132}, {"text": "TAFT BROOME: What I\nwould like for you to do", "start": 4547.027, "duration": 1.833}, {"text": "is to try Parzival first.", "start": 4548.86, "duration": 3.34}, {"text": "If it does not work for you,\nthen choose another one.", "start": 4552.2, "duration": 3.0}, {"text": "But justify why that person is\na mythic hero, a mythic hero", "start": 4555.2, "duration": 6.43}, {"text": "of some sort or another.", "start": 4561.63, "duration": 1.62}, {"text": "Like my Uncle Roy and those,\nthey followed the pattern.", "start": 4563.25, "duration": 6.738}, {"text": "The heard the call.", "start": 4569.988, "duration": 0.792}, {"text": "They went out for\na higher cause.", "start": 4570.78, "duration": 2.39}, {"text": "They had this\nfabulous experience.", "start": 4573.17, "duration": 3.07}, {"text": "They killed the dragon.", "start": 4576.24, "duration": 1.2}, {"text": "They brought the Grail home\nand shared it with everybody.", "start": 4577.44, "duration": 5.19}, {"text": "There's a pattern.", "start": 4582.63, "duration": 0.75}, {"text": "If that doesn't work, then\npick another case, the A7D", "start": 4586.99, "duration": 6.03}, {"text": "or some other case that\nyou've already studied.", "start": 4593.02, "duration": 2.01}, {"text": "I don't want to, as we all\nknow, none of these methods", "start": 4598.54, "duration": 3.18}, {"text": "will work every\ntime for everybody.", "start": 4601.72, "duration": 4.56}, {"text": "But so but I'd like for you\nto try Parzival on Chernobyl.", "start": 4606.28, "duration": 6.92}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.976}, {"text": "[RUSTLING]", "start": 1.976, "duration": 1.976}, {"text": "[CLICKING]", "start": 3.952, "duration": 0.988}, {"text": "SCOTT HUGHES: So let me\njust do a quick recap", "start": 10.975, "duration": 1.875}, {"text": "of what we did last time.", "start": 12.85, "duration": 2.71}, {"text": "So today, we're going\nto move into things that", "start": 15.56, "duration": 1.92}, {"text": "are a little bit more physics.", "start": 17.48, "duration": 1.25}, {"text": "Last time we were really\ndoing some things that", "start": 18.73, "duration": 2.22}, {"text": "allows us to establish some\nof the critical mathematical", "start": 20.95, "duration": 2.94}, {"text": "concepts we need to\nstudy the tensors that", "start": 23.89, "duration": 4.26}, {"text": "are going to be used for\nphysics on a curved manifold.", "start": 28.15, "duration": 3.6}, {"text": "So one of the things\nthat we saw is", "start": 31.75, "duration": 2.46}, {"text": "that if I wanted to formulate\ndifferential equations", "start": 34.21, "duration": 2.46}, {"text": "on a curved manifold, if I just\ndefined my derivative the most", "start": 36.67, "duration": 3.84}, {"text": "naive way you\nmight think of, you", "start": 40.51, "duration": 2.73}, {"text": "end up with objects\nthat are not tensorial.", "start": 43.24, "duration": 2.7}, {"text": "And so mathematically you\nmight say, well, that's fine.", "start": 45.94, "duration": 2.668}, {"text": "It's just not a tensor anymore.", "start": 48.608, "duration": 1.292}, {"text": "But we really want\ntensors for our physics", "start": 49.9, "duration": 2.88}, {"text": "because we want to be\nworking with quantities", "start": 52.78, "duration": 2.61}, {"text": "that have frame-independent\ngeometric meaning to them.", "start": 55.39, "duration": 2.71}, {"text": "So that notion of a derivative--\nif I just do it the naive way--", "start": 58.1, "duration": 2.78}, {"text": "isn't the best.", "start": 60.88, "duration": 1.675}, {"text": "And so I argued that\nwhat we need to do", "start": 62.555, "duration": 1.625}, {"text": "is to find some kind of\na transport operation", "start": 64.18, "duration": 2.76}, {"text": "in which there is a linear\nmapping between things", "start": 66.94, "duration": 5.31}, {"text": "like my vector\nfield or my tensor", "start": 72.25, "duration": 1.41}, {"text": "field and the displacement,\nwhich allows me to cancel out", "start": 73.66, "duration": 4.29}, {"text": "the bits of the partial\nderivative transformation", "start": 77.95, "duration": 2.43}, {"text": "laws that are non tensorial.", "start": 80.38, "duration": 2.75}, {"text": "There's a lot of\nfreedom to do that.", "start": 83.13, "duration": 1.56}, {"text": "One of the ways I suggest we do\nthat is by demanding that when", "start": 84.69, "duration": 2.79}, {"text": "I do this, that derivative--\nwhen applied to the metric--", "start": 87.48, "duration": 2.97}, {"text": "give me 0.", "start": 90.45, "duration": 0.94}, {"text": "And if we do that,\nwe see right away", "start": 91.39, "duration": 2.09}, {"text": "that the transport\nlaw that emerges", "start": 93.48, "duration": 1.993}, {"text": "gives me the covariant\nderivative as one", "start": 95.473, "duration": 1.667}, {"text": "of my examples.", "start": 97.14, "duration": 0.79}, {"text": "Now this shouldn't\nbe a surprise.", "start": 97.93, "duration": 1.375}, {"text": "We introduced the\ncovariant derivative", "start": 99.305, "duration": 1.675}, {"text": "by thinking about flat\nspacetime operations,", "start": 100.98, "duration": 3.36}, {"text": "but with all my basis\nobjects being functionals.", "start": 104.34, "duration": 2.76}, {"text": "And this in some way is sort of\na continuation of that notion.", "start": 107.1, "duration": 4.988}, {"text": "The other thing which I talked\nabout is telling you we're not", "start": 112.088, "duration": 2.542}, {"text": "going to use a tremendous amount\nhere except to motivate one", "start": 114.63, "duration": 2.55}, {"text": "very important result. And\nthat is if I define transport", "start": 117.18, "duration": 3.9}, {"text": "by basically imagining that\nI slide my vectors in order", "start": 121.08, "duration": 2.67}, {"text": "to make the comparison-- along\nsome specified vector field--", "start": 123.75, "duration": 3.27}, {"text": "I get what's known as\nthe Lie derivative.", "start": 127.02, "duration": 1.86}, {"text": "And so this is an example of\nthe Lie derivative of a vector.", "start": 128.88, "duration": 5.73}, {"text": "And you get this form that\nlooks like a commutator", "start": 134.61, "duration": 3.18}, {"text": "between the vector field\nyou're sliding along", "start": 137.79, "duration": 1.95}, {"text": "and the vector field\nyou are differentiating.", "start": 139.74, "duration": 2.19}, {"text": "Similar forms--\nwhich are not really", "start": 141.93, "duration": 2.067}, {"text": "the form of a commutator--\nbut similar forms", "start": 143.997, "duration": 1.833}, {"text": "can be written down\nfor general tensors.", "start": 145.83, "duration": 3.69}, {"text": "The key thing that\nyou should be aware of", "start": 149.52, "duration": 3.96}, {"text": "is that it's got a similar form\nto the covariant derivative,", "start": 153.48, "duration": 3.24}, {"text": "in that you have\none term-- let's", "start": 156.72, "duration": 1.38}, {"text": "focus on the top\nline for the second--", "start": 158.1, "duration": 1.42}, {"text": "you have one term\nthat looks just", "start": 159.52, "duration": 1.375}, {"text": "like the ordinary\nvector contracted", "start": 160.895, "duration": 2.845}, {"text": "onto a partial\nderivative of your field.", "start": 163.74, "duration": 3.09}, {"text": "And then you have terms which\ncorrect every free index", "start": 166.83, "duration": 3.15}, {"text": "of your field--", "start": 169.98, "duration": 0.75}, {"text": "one free index if it's\na vector, one free index", "start": 170.73, "duration": 2.97}, {"text": "if it's a one form, and\ncorrections for an end index", "start": 173.7, "duration": 4.44}, {"text": "tensor--", "start": 178.14, "duration": 0.99}, {"text": "with the sign doing something\nopposite to the sign", "start": 179.13, "duration": 3.12}, {"text": "that appears in the\ncovariant derivative.", "start": 182.25, "duration": 2.61}, {"text": "What's interesting about\nthis is that so defined,", "start": 184.86, "duration": 3.368}, {"text": "the Lie derivative is\nonly written in terms", "start": 188.228, "duration": 1.792}, {"text": "of partial derivatives.", "start": 190.02, "duration": 1.77}, {"text": "But if you just\nimagine-- you promote", "start": 191.79, "duration": 2.873}, {"text": "those partial derivatives\nto covariant derivatives--", "start": 194.663, "duration": 2.167}, {"text": "you find the exact\nsame result holds", "start": 196.83, "duration": 2.28}, {"text": "because all of your Christoffel\nsymbols-- or connections", "start": 199.11, "duration": 2.652}, {"text": "as we like to think of them\nwhen we're using parallel", "start": 201.762, "duration": 2.208}, {"text": "transport-- all the connective\nobjects cancel each other out.", "start": 203.97, "duration": 3.767}, {"text": "And this is nice\nbecause this tells me", "start": 207.737, "duration": 1.583}, {"text": "that even though this\nobject, strictly speaking,", "start": 209.32, "duration": 2.85}, {"text": "only involves partial\nderivatives, what emerges out", "start": 212.17, "duration": 3.06}, {"text": "of it is in fact tensorial.", "start": 215.23, "duration": 1.55}, {"text": "And it's an object that I\ncan use for a lot of things", "start": 216.78, "duration": 3.33}, {"text": "I want to do in physics.", "start": 220.11, "duration": 1.0}, {"text": "In particular where we're\ngoing to use it the most--", "start": 221.11, "duration": 2.292}, {"text": "and I said you're going\nto do this on the PSET,", "start": 223.402, "duration": 1.958}, {"text": "but I was wrong-- you're going\nto do something related to one", "start": 225.36, "duration": 1.67}, {"text": "of the PSETs--", "start": 227.03, "duration": 0.583}, {"text": "but I'm going to actually--\nif all goes well--", "start": 227.613, "duration": 2.389}, {"text": "derive an important result\ninvolving these symmetries", "start": 230.002, "duration": 2.208}, {"text": "in today's lecture.", "start": 232.21, "duration": 1.83}, {"text": "We can use this to\nunderstand things", "start": 234.04, "duration": 1.5}, {"text": "that are related to conserved\nquantities in your space time.", "start": 235.54, "duration": 2.715}, {"text": "And where this comes\nfrom is that there", "start": 238.255, "duration": 1.625}, {"text": "is a definition of an object we\ncall the Killing vector, which", "start": 239.88, "duration": 3.04}, {"text": "is an object where if your\nmetric is Lie transported", "start": 242.92, "duration": 4.56}, {"text": "along some field C, we\ncall C a Killing vector.", "start": 247.48, "duration": 4.14}, {"text": "And from the fact that the\ncovariant derivative the metric", "start": 251.62, "duration": 4.899}, {"text": "is 0, you can turn\nthe equation governing", "start": 256.519, "duration": 5.25}, {"text": "the Lie derivative along C into\nwhat I wrote down just there.", "start": 261.769, "duration": 2.824}, {"text": "And I should write its name.", "start": 264.593, "duration": 1.167}, {"text": "There's the result known\nas Killing's Equation.", "start": 269.81, "duration": 2.11}, {"text": "If a vector has a\nKilling vector--", "start": 283.27, "duration": 3.69}, {"text": "if a metric has a\nKilling vector--", "start": 286.96, "duration": 1.95}, {"text": "then you know that\nyour metric is", "start": 288.91, "duration": 1.92}, {"text": "independent of some\nkind of a parameter that", "start": 290.83, "duration": 2.25}, {"text": "characterizes that spacetime.", "start": 293.08, "duration": 1.71}, {"text": "The converse also holds.", "start": 294.79, "duration": 1.5}, {"text": "If your metric is\nindependent of something--", "start": 296.29, "duration": 1.98}, {"text": "like say the time\ncoordinate-- you", "start": 298.27, "duration": 1.71}, {"text": "know that there is a\nKilling vector corresponding", "start": 299.98, "duration": 2.64}, {"text": "to that independent thing.", "start": 302.62, "duration": 1.61}, {"text": "And so you'll often see this\ndescribed as a differing", "start": 304.23, "duration": 2.452}, {"text": "amorphism of the\nspacetime-- if you", "start": 306.682, "duration": 1.458}, {"text": "want to dig into some of\nthe more advanced textbooks", "start": 308.14, "duration": 2.167}, {"text": "on the subject.", "start": 310.307, "duration": 0.863}, {"text": "We'll come back to that in a few\nmore details hopefully shortly", "start": 311.17, "duration": 2.94}, {"text": "before the end of\ntoday's lecture.", "start": 314.11, "duration": 1.78}, {"text": "So where I concluded\nlast time, was we", "start": 315.89, "duration": 1.697}, {"text": "started talking about\nthese quantities known", "start": 317.587, "duration": 1.833}, {"text": "as tensor densities,\nwhich are given", "start": 319.42, "duration": 1.95}, {"text": "the less-than-helpful\ndefinition-- quantities", "start": 321.37, "duration": 3.39}, {"text": "that are like tensors,\nbut not quite.", "start": 324.76, "duration": 2.97}, {"text": "The example I gave of this--\nwhere we were starting--", "start": 327.73, "duration": 2.55}, {"text": "was the Levi-Civita symbol.", "start": 330.28, "duration": 2.88}, {"text": "So let me just write down\nagain what resulted from that.", "start": 333.16, "duration": 4.02}, {"text": "So if I have Levi-Civita--\nand the tilde here is going", "start": 337.18, "duration": 3.77}, {"text": "to reflect the fact that\nthis is not really a tensor--", "start": 340.95, "duration": 3.73}, {"text": "this guy in some\nprime coordinates", "start": 347.58, "duration": 6.49}, {"text": "is related to this guy in\nthe unprime coordinates", "start": 354.07, "duration": 6.95}, {"text": "via the following--", "start": 361.02, "duration": 1.32}, {"text": "let's get the primes\nin the right place--", "start": 370.452, "duration": 1.708}, {"text": "the following mess\nof quantities.", "start": 376.44, "duration": 2.87}, {"text": "So I'm not going to\ngo through this again.", "start": 381.87, "duration": 1.75}, {"text": "This is basically a\ntheorem from linear algebra", "start": 383.62, "duration": 2.01}, {"text": "that relates the\ndeterminant of a matrix--", "start": 385.63, "duration": 3.39}, {"text": "not metric, but matrix--", "start": 389.02, "duration": 2.64}, {"text": "to what you get when you\ncontract a bunch of matrices", "start": 391.66, "duration": 2.7}, {"text": "onto the Levi-Civita symbol.", "start": 394.36, "duration": 2.732}, {"text": "And so the key thing to note\nis that if this were not here,", "start": 397.092, "duration": 2.458}, {"text": "this would look just like\na tensor transformation.", "start": 399.55, "duration": 2.3}, {"text": "But that is there.", "start": 401.85, "duration": 1.04}, {"text": "So it's not.", "start": 402.89, "duration": 1.76}, {"text": "And so we call this a\ntensor density of weight 1.", "start": 404.65, "duration": 3.36}, {"text": "So the other one-- which I\nhinted at the end of the last", "start": 416.29, "duration": 2.52}, {"text": "lecture, but did not\nhave time to get into--", "start": 418.81, "duration": 3.72}, {"text": "is suppose we look\nat the metric.", "start": 422.53, "duration": 2.53}, {"text": "Now, the metric-- no ifs,\nands, or buts about it--", "start": 425.06, "duration": 3.367}, {"text": "it's a tensor.", "start": 428.427, "duration": 0.583}, {"text": "And it's actually\nthe first tensor", "start": 435.081, "duration": 2.789}, {"text": "we've started talking\nabout back in our toddler", "start": 437.87, "duration": 5.02}, {"text": "years of studying flat\nspacetime, which by the way,", "start": 442.89, "duration": 3.58}, {"text": "was about three weeks ago.", "start": 446.47, "duration": 2.897}, {"text": "Obviously that's a tensor.", "start": 449.367, "duration": 1.083}, {"text": "It's a simple\ntensor relationship.", "start": 450.45, "duration": 1.65}, {"text": "Let's take the determinant\nof both sides of this.", "start": 452.1, "duration": 2.13}, {"text": "You might look at this and go,\nwhy do you want to do that?", "start": 467.293, "duration": 2.417}, {"text": "Well when I do this,\nI'm going to call", "start": 469.71, "duration": 3.02}, {"text": "the determinant of the metric\nin the primed representation.", "start": 472.73, "duration": 2.98}, {"text": "Let's call that G prime.", "start": 475.71, "duration": 2.99}, {"text": "I get 2 powers--", "start": 478.7, "duration": 1.35}, {"text": "2 powers of this Jacobian\nmatrix is determinant.", "start": 483.53, "duration": 3.67}, {"text": "And I get the determinant in\nmy original representation.", "start": 491.81, "duration": 4.38}, {"text": "Now I want to write\nthis in a way that's", "start": 496.19, "duration": 1.89}, {"text": "similar to the way I\nwrote it over here.", "start": 498.08, "duration": 1.667}, {"text": "Notice I have all\nmy primed objects", "start": 499.747, "duration": 1.753}, {"text": "over here on the left-hand side.", "start": 501.5, "duration": 1.38}, {"text": "And my factor of this\ndeterminant relates--", "start": 502.88, "duration": 4.02}, {"text": "it's got primed indices in the\nupstairs position, unprimed", "start": 506.9, "duration": 2.46}, {"text": "in the downstairs.", "start": 509.36, "duration": 1.47}, {"text": "But the determinant of 1\nover a metric is just 1", "start": 510.83, "duration": 4.02}, {"text": "over the determinant of--", "start": 514.85, "duration": 1.439}, {"text": "the determinant of the\ninverse of a matrix is just 1", "start": 516.289, "duration": 3.51}, {"text": "over the determinant\nof that matrix.", "start": 519.799, "duration": 2.281}, {"text": "And so I can really simply\njust say this looks like so.", "start": 522.08, "duration": 10.71}, {"text": "So the determinant of the\nmetric is a tensor density", "start": 532.79, "duration": 7.65}, {"text": "of weight minus 2.", "start": 540.44, "duration": 1.35}, {"text": "What this basically tells us is\nI now have two of these things.", "start": 563.55, "duration": 4.62}, {"text": "I've been arguing basically\nthis entire course", "start": 568.17, "duration": 1.95}, {"text": "that we want to use\ntensors because of the fact", "start": 570.12, "duration": 2.55}, {"text": "that they give me a\ncovariant way of encoding", "start": 572.67, "duration": 4.92}, {"text": "geometric concepts.", "start": 577.59, "duration": 2.52}, {"text": "I've got these two things\nthat are not quite tensors.", "start": 580.11, "duration": 3.24}, {"text": "I can put them together and\nget a tensor out of this.", "start": 583.35, "duration": 3.21}, {"text": "So what this tells me now is I\ncan convert any tensor density", "start": 586.56, "duration": 5.88}, {"text": "into a proper tensor.", "start": 592.44, "duration": 1.185}, {"text": "So suppose I have a\ntensor density of weight", "start": 596.54, "duration": 2.28}, {"text": "W. I can convert this\ninto a proper tensor", "start": 598.82, "duration": 12.34}, {"text": "by multiplying by a power\nof that G. So multiply it", "start": 611.16, "duration": 10.27}, {"text": "by G to the W over 2.", "start": 621.43, "duration": 5.51}, {"text": "One slight subtlety here,\nwhen we work in spacetime--", "start": 626.94, "duration": 4.2}, {"text": "let's just stop for a second and\nthink about special relativity.", "start": 631.14, "duration": 4.48}, {"text": "In special relativity in an\ninertial reference frame,", "start": 635.62, "duration": 5.4}, {"text": "my metric is minus 1\n1 1 1 on the diagonal.", "start": 641.02, "duration": 3.39}, {"text": "So its determinant\nis negative 1.", "start": 644.41, "duration": 2.47}, {"text": "And when I take negative 1\nto some power that involves", "start": 646.88, "duration": 4.73}, {"text": "a square root, I get sad.", "start": 651.61, "duration": 2.58}, {"text": "We all know how to work\nwith complex numbers.", "start": 654.19, "duration": 2.29}, {"text": "You might think that's all OK.", "start": 656.48, "duration": 1.85}, {"text": "It's not in this case.", "start": 658.33, "duration": 0.93}, {"text": "But the way I can fix that\nis that equation's still true", "start": 659.26, "duration": 4.11}, {"text": "if I multiply both\nsides by minus 1.", "start": 663.37, "duration": 2.983}, {"text": "I want this to be a\npositive number when", "start": 666.353, "duration": 1.667}, {"text": "I take the square root.", "start": 668.02, "duration": 0.958}, {"text": "So I'm allowed just to\ntake the absolute value.", "start": 668.978, "duration": 4.262}, {"text": "So we take the absolute\nvalue to clear out the fact", "start": 673.24, "duration": 3.0}, {"text": "that in spacetime, we tend to\nhave an indeterminate metric,", "start": 676.24, "duration": 3.58}, {"text": "where the sign depends\non the interval.", "start": 679.82, "duration": 2.39}, {"text": "So remember the only\nreason we're doing this--", "start": 693.753, "duration": 1.917}, {"text": "this is just a--", "start": 695.67, "duration": 0.85}, {"text": "I don't want to\nsay it's a trick.", "start": 696.52, "duration": 2.12}, {"text": "But it's not that\nfar off from a trick.", "start": 698.64, "duration": 3.68}, {"text": "I'm just combining two\ntensor densities in order", "start": 702.32, "duration": 2.49}, {"text": "to get a tensor out of it.", "start": 704.81, "duration": 1.44}, {"text": "And minus a tensor density\nis still a tensor density.", "start": 706.25, "duration": 3.69}, {"text": "So I'm OK to do that.", "start": 709.94, "duration": 1.05}, {"text": "And I'm just doing this\nso that my square root", "start": 710.99, "duration": 1.917}, {"text": "doesn't go haywire on me.", "start": 712.907, "duration": 2.403}, {"text": "So a particular example--", "start": 715.31, "duration": 1.32}, {"text": "in fact the one that in my\ncareer has come up the most--", "start": 716.63, "duration": 3.33}, {"text": "is making a proper\nvolume element", "start": 722.85, "duration": 5.7}, {"text": "converting my Levi-Civita\nsymbol into a tensor that", "start": 728.55, "duration": 8.127}, {"text": "gives me a volume element.", "start": 736.677, "duration": 1.083}, {"text": "So my Levi-Civita symbol has\na tensor density of weight 1.", "start": 742.57, "duration": 3.36}, {"text": "If I want to make that\ninto a proper tensor,", "start": 745.93, "duration": 2.7}, {"text": "I multiply by the square root of\nthe determinant of the metric.", "start": 748.63, "duration": 4.38}, {"text": "So now I will no\nlonger have that tilde", "start": 753.01, "duration": 3.03}, {"text": "on there, which was meant\nto be a signpost that this", "start": 756.04, "duration": 2.22}, {"text": "as a quantity is a\nlittle bit goofy.", "start": 758.26, "duration": 1.5}, {"text": "You wind up with\nsomething like this.", "start": 766.99, "duration": 2.58}, {"text": "When you go-- and by\nthe way, sometimes", "start": 769.57, "duration": 2.1}, {"text": "when you're working\nwith this, you", "start": 771.67, "duration": 0.84}, {"text": "need to have this thing\nwith indices in the upstairs", "start": 772.51, "duration": 1.86}, {"text": "position.", "start": 774.37, "duration": 0.78}, {"text": "You have to be a\nlittle bit careful.", "start": 775.15, "duration": 1.11}, {"text": "But I'll just give\nyou one example.", "start": 776.26, "duration": 1.458}, {"text": "If you raise all four\nof the indices, what", "start": 777.718, "duration": 4.722}, {"text": "you find when\neverything goes through,", "start": 782.44, "duration": 1.585}, {"text": "this one is not that hard to\nsee because you're basically", "start": 784.025, "duration": 2.375}, {"text": "playing with a similar\nrelationship to the one", "start": 786.4, "duration": 1.917}, {"text": "that I wrote down over here--", "start": 788.317, "duration": 1.533}, {"text": "just a short homework\nexercise to demonstrate this.", "start": 789.85, "duration": 3.158}, {"text": "And then you end up\nwith the tensor density", "start": 793.008, "duration": 1.792}, {"text": "of the opposite sign.", "start": 794.8, "duration": 1.46}, {"text": "Weight minus 1, you wind up\nwith a 1 over square root there.", "start": 796.26, "duration": 2.5}, {"text": "So like I said\none of the reasons", "start": 803.43, "duration": 1.59}, {"text": "why this is an important example\nis that we use it to form", "start": 805.02, "duration": 5.01}, {"text": "covariant volume operators.", "start": 810.03, "duration": 2.058}, {"text": "So in four-dimensional space--", "start": 835.52, "duration": 3.92}, {"text": "so imagine here's my basis\ndirection for spatial direction", "start": 839.44, "duration": 7.42}, {"text": "1, spatial direction 2,\nspatial direction 3--", "start": 846.86, "duration": 3.75}, {"text": "you guys can figure out how\nto write spatial direction", "start": 850.61, "duration": 2.25}, {"text": "0 on your own time--", "start": 852.86, "duration": 4.2}, {"text": "I would define a\ncovariant 4 volume--", "start": 857.06, "duration": 3.73}, {"text": "4 volume element from this.", "start": 860.79, "duration": 1.64}, {"text": "It'll look like this.", "start": 874.755, "duration": 1.495}, {"text": "And if this is an\northogonal basis,", "start": 876.25, "duration": 3.83}, {"text": "this simply turns\ninto something like--", "start": 880.08, "duration": 12.85}, {"text": "these are meant\nto be superscripts", "start": 895.745, "duration": 1.905}, {"text": "because these are coordinates.", "start": 897.65, "duration": 2.615}, {"text": "So it just turns into\nsomething like this", "start": 900.265, "duration": 2.215}, {"text": "if I'm working in\nan orthogonal basis.", "start": 902.48, "duration": 1.73}, {"text": "And again for intuition,\nI suggest go down", "start": 909.21, "duration": 3.26}, {"text": "to 3-dimensional\nspherical coordinates.", "start": 912.47, "duration": 4.215}, {"text": "And I wrote this last time.", "start": 916.685, "duration": 1.125}, {"text": "But let me just\nquickly write it up.", "start": 917.81, "duration": 1.68}, {"text": "I mean everything I did here,\nI tend to-- since this is", "start": 919.49, "duration": 4.26}, {"text": "a course on spacetime--", "start": 923.75, "duration": 1.92}, {"text": "by default I write\ndown all my formulas", "start": 925.67, "duration": 2.58}, {"text": "for three space dimensions,\none time dimension.", "start": 928.25, "duration": 4.165}, {"text": "But it's perfectly good\nin 3 spatial dimensions,", "start": 932.415, "duration": 2.765}, {"text": "2 spatial dimensions, 17 spatial\ndimensions-- whatever crazy", "start": 935.18, "duration": 4.523}, {"text": "spacetime your physics want\nyou to put yourself in--", "start": 939.703, "duration": 2.167}, {"text": "or space your physics\nwants to put you in.", "start": 941.87, "duration": 1.75}, {"text": "So I'll just remind you--", "start": 948.46, "duration": 1.16}, {"text": "that when you do this,\nyou've got yourself", "start": 963.61, "duration": 1.75}, {"text": "a metric across\nthe diagonal of 1 r", "start": 965.36, "duration": 7.29}, {"text": "squared r squared\nsine squared theta.", "start": 972.65, "duration": 5.04}, {"text": "And just to be consistent--", "start": 977.69, "duration": 1.87}, {"text": "I usually use Latin letters\nfor only spatial things.", "start": 979.56, "duration": 5.012}, {"text": "So let's do that.", "start": 984.572, "duration": 0.708}, {"text": "This would be how I would\nthen write my volume element.", "start": 995.64, "duration": 4.045}, {"text": "Did I miss something?", "start": 999.685, "duration": 0.875}, {"text": "AUDIENCE: Yeah.", "start": 1000.56, "duration": 0.625}, {"text": "[INAUDIBLE]", "start": 1001.185, "duration": 1.085}, {"text": "SCOTT HUGHES: Absolutely.", "start": 1002.27, "duration": 1.07}, {"text": "Yeah.", "start": 1003.34, "duration": 2.38}, {"text": "Thank you.", "start": 1005.72, "duration": 1.047}, {"text": "I'm writing quickly.", "start": 1006.767, "duration": 0.833}, {"text": "Yeah?", "start": 1007.6, "duration": 0.5}, {"text": "AUDIENCE: Is there [INAUDIBLE]?", "start": 1008.1, "duration": 3.727}, {"text": "SCOTT HUGHES: This is dx--", "start": 1011.827, "duration": 1.083}, {"text": "oh, bugger.", "start": 1012.91, "duration": 1.03}, {"text": "Yep.", "start": 1013.94, "duration": 1.972}, {"text": "I'm trying to get\nto something new.", "start": 1015.912, "duration": 1.458}, {"text": "And I'm afraid I'm\nrushing a little bit.", "start": 1017.37, "duration": 1.667}, {"text": "So thank you for catching this.", "start": 1019.037, "duration": 2.016}, {"text": "And so with this, take the\ndeterminer of this thing.", "start": 1021.053, "duration": 2.167}, {"text": "And sure enough you get r\nsquared sine theta d r d theta", "start": 1023.22, "duration": 5.91}, {"text": "d phi.", "start": 1029.13, "duration": 2.04}, {"text": "So this is the\nmain thing that we", "start": 1031.17, "duration": 1.47}, {"text": "are going to use this result\nfor-- this thing with tensor", "start": 1032.64, "duration": 2.82}, {"text": "densities.", "start": 1035.46, "duration": 1.02}, {"text": "I want to go on a\nbrief aside, which", "start": 1036.48, "duration": 2.28}, {"text": "is relevant to the\nproblem that I delayed on", "start": 1038.76, "duration": 3.03}, {"text": "this week's problem 7.", "start": 1041.79, "duration": 1.1}, {"text": "So there are three\nparts of problem 7", "start": 1046.64, "duration": 2.73}, {"text": "that I moved from PSET 3 to PSET\n4 because they rely on a result", "start": 1049.37, "duration": 12.57}, {"text": "that I want to talk about now.", "start": 1061.94, "duration": 1.29}, {"text": "So the main thing that we use\nthe determinant of the metric", "start": 1066.01, "duration": 2.99}, {"text": "for in a formal way is\nthis-- that it's a tensor", "start": 1069.0, "duration": 2.88}, {"text": "density of weight minus 2.", "start": 1071.88, "duration": 2.07}, {"text": "And so it's a really\nuseful quantity", "start": 1073.95, "duration": 1.8}, {"text": "for converting tensor\ndensities into proper tensors.", "start": 1075.75, "duration": 3.273}, {"text": "And really the most\ncommon application of this", "start": 1079.023, "duration": 1.917}, {"text": "tends to be to volume elements.", "start": 1080.94, "duration": 1.902}, {"text": "But it turns out\nthat it's actually", "start": 1082.842, "duration": 1.458}, {"text": "really useful for what a\nformer professor of mine", "start": 1084.3, "duration": 3.63}, {"text": "used to like to\ncall party tricks.", "start": 1087.93, "duration": 2.52}, {"text": "There's some really-- it\noffers a really nice shortcut", "start": 1090.45, "duration": 5.31}, {"text": "to computing certain\nChristoffel symbols.", "start": 1095.76, "duration": 2.85}, {"text": "So in honor of Saul Teukolsky\nlet's call this a party trick.", "start": 1098.61, "duration": 2.58}, {"text": "So we're using the\ndeterminant of the metric", "start": 1106.48, "duration": 10.18}, {"text": "to compute certain Christoffels.", "start": 1116.66, "duration": 1.81}, {"text": "So this is going to\nrely on the following.", "start": 1127.59, "duration": 1.75}, {"text": "So suppose I calculate\nthe Christoffel symbol,", "start": 1129.34, "duration": 5.76}, {"text": "but I'm going to sum\non the raised index.", "start": 1135.1, "duration": 3.143}, {"text": "And bearing in mind it's\nsymmetric in the lower one,", "start": 1138.243, "duration": 2.167}, {"text": "I'm going to do a contraction\nof the raised index with one", "start": 1140.41, "duration": 2.22}, {"text": "of the lower indices.", "start": 1142.63, "duration": 0.875}, {"text": "So let's just throw in\na couple of definitions.", "start": 1146.26, "duration": 4.37}, {"text": "This is equivalent\nto the following.", "start": 1150.63, "duration": 6.65}, {"text": "And so throwing in the\ndefinition of the Christoffel", "start": 1157.28, "duration": 3.87}, {"text": "with all the indices in\nthe downstairs position--", "start": 1161.15, "duration": 2.267}, {"text": "this formula, by the\nway, is something", "start": 1183.82, "duration": 1.65}, {"text": "that I've been writing down\nnow for about 27 years.", "start": 1185.47, "duration": 4.77}, {"text": "And I have to look\nit up every time.", "start": 1190.24, "duration": 1.59}, {"text": "Usually by the end of a\nsemester of teaching 8.962,", "start": 1191.83, "duration": 2.617}, {"text": "I have it memorized.", "start": 1194.447, "duration": 0.833}, {"text": "But it decays by then.", "start": 1195.28, "duration": 1.38}, {"text": "So if you're wondering how\nto go from here to here--", "start": 1196.66, "duration": 2.475}, {"text": "this is the kind of thing--", "start": 1199.135, "duration": 1.125}, {"text": "just look it up.", "start": 1200.26, "duration": 2.08}, {"text": "So let's pause for a second.", "start": 1202.34, "duration": 1.98}, {"text": "Remember that the metric is--", "start": 1204.32, "duration": 3.77}, {"text": "it's itself symmetric.", "start": 1208.09, "duration": 2.31}, {"text": "So in keeping with\nthat, I'm going", "start": 1210.4, "duration": 2.24}, {"text": "to flip the indices on this last\nterm, which-- hang on a second.", "start": 1212.64, "duration": 7.22}, {"text": "That was stupid.", "start": 1219.86, "duration": 1.56}, {"text": "Wait.", "start": 1221.42, "duration": 0.5}, {"text": "Pardon me.", "start": 1224.96, "duration": 0.5}, {"text": "This is the term I want\nto switch indices on.", "start": 1232.055, "duration": 1.875}, {"text": "My apologies.", "start": 1233.93, "duration": 2.763}, {"text": "So the reason I\ndid that is I want", "start": 1236.693, "duration": 1.417}, {"text": "to have both of\nthese guys ending", "start": 1238.11, "duration": 1.5}, {"text": "with the alpha because\nnotice this and this--", "start": 1239.61, "duration": 3.702}, {"text": "they're the same.", "start": 1243.312, "duration": 0.708}, {"text": "But I have interchanged\nthe beta and the mu.", "start": 1244.02, "duration": 4.47}, {"text": "So these two terms--", "start": 1248.49, "duration": 1.36}, {"text": "the first term and\nthe third term--", "start": 1249.85, "duration": 2.12}, {"text": "are anti symmetric upon\nexchange of beta and mu.", "start": 1251.97, "duration": 5.0}, {"text": "They are contracted\nwith the metric,", "start": 1256.97, "duration": 1.72}, {"text": "which is symmetric upon\nexchange of beta and mu.", "start": 1258.69, "duration": 3.69}, {"text": "Question?", "start": 1262.38, "duration": 0.5}, {"text": "AUDIENCE: Does the metric\nhave to be symmetric?", "start": 1262.88, "duration": 2.2}, {"text": "SCOTT HUGHES: The metric\nhas to be symmetric.", "start": 1265.08, "duration": 2.402}, {"text": "[LAUGHS] I don't want to get\ninto that right now, but yes", "start": 1267.482, "duration": 8.848}, {"text": "[LAUGHS].", "start": 1276.33, "duration": 1.29}, {"text": "So these guys are\nanti symmetric.", "start": 1277.62, "duration": 2.16}, {"text": "This guy is symmetric.", "start": 1279.78, "duration": 1.3}, {"text": "And remember the rule.", "start": 1281.08, "duration": 1.97}, {"text": "Whenever you contract some\nkind of a symmetric object", "start": 1283.05, "duration": 2.67}, {"text": "with an anti\nsymmetric m you get 0.", "start": 1285.72, "duration": 3.18}, {"text": "So that means this\nterm and this term die.", "start": 1288.9, "duration": 3.15}, {"text": "And what we are left\nwith is gamma mu", "start": 1307.751, "duration": 3.839}, {"text": "mu alpha is 1/2 g u beta, and\nthe alpha derivative of g u", "start": 1311.59, "duration": 10.93}, {"text": "beta.", "start": 1322.52, "duration": 2.44}, {"text": "There is the way\nit is contracting", "start": 1324.96, "duration": 2.28}, {"text": "the indices in the 2\nmetric with the other one.", "start": 1327.24, "duration": 2.22}, {"text": "Well here's a theorem that I'm\ngoing to prove in a second--", "start": 1329.46, "duration": 2.458}, {"text": "or at least motivate-- that\nit's going to rely on a result", "start": 1331.918, "duration": 4.182}, {"text": "that I will pull\nout of thin air,", "start": 1336.1, "duration": 1.58}, {"text": "but can be found in most\nlinear algebra textbooks.", "start": 1337.68, "duration": 4.64}, {"text": "It's not too hard to show that\nthis can be further written", "start": 1342.32, "duration": 4.5}, {"text": "as 1 over square root of the\ndeterminant times the partial", "start": 1346.82, "duration": 7.57}, {"text": "derivative of the square\nroot of the determinant,", "start": 1354.39, "duration": 10.01}, {"text": "which is sometimes-- depending\non your applications--", "start": 1364.4, "duration": 2.69}, {"text": "this can be written very\nnicely as the derivative", "start": 1367.09, "duration": 3.61}, {"text": "of the logarithm of the\nabsolute value of the--", "start": 1370.7, "duration": 3.33}, {"text": "the square root of the absolute\nvalue of the determinant.", "start": 1374.03, "duration": 2.459}, {"text": "So before I go on and\nactually demonstrate this,", "start": 1381.65, "duration": 3.85}, {"text": "you can see why this\nis actually a pretty--", "start": 1385.5, "duration": 3.27}, {"text": "so this actually comes up.", "start": 1388.77, "duration": 1.38}, {"text": "I'm going to show\na few applications", "start": 1390.15, "duration": 1.5}, {"text": "as to why this particular\ncombination of Christoffel", "start": 1391.65, "duration": 2.23}, {"text": "symbols shows up more\noften than you might guess.", "start": 1393.88, "duration": 2.6}, {"text": "It's really important for\ncertain important calculations.", "start": 1396.48, "duration": 2.71}, {"text": "And this is telling\nme that I can get it", "start": 1399.19, "duration": 1.73}, {"text": "by just taking one partial\nderivative of a scalar", "start": 1400.92, "duration": 2.46}, {"text": "function.", "start": 1403.38, "duration": 1.52}, {"text": "And if you know your\nmetric, that's easy.", "start": 1404.9, "duration": 3.016}, {"text": "So this becomes really\neasy thing to calculate.", "start": 1407.916, "duration": 3.084}, {"text": "So let's prove it.", "start": 1411.0, "duration": 0.75}, {"text": "So the proof of this\nrelies on a few results", "start": 1421.17, "duration": 3.937}, {"text": "from linear algebra.", "start": 1425.107, "duration": 0.833}, {"text": "So let's not think about\ntensors for a second.", "start": 1443.37, "duration": 2.28}, {"text": "And let's just think\nabout matrices.", "start": 1445.65, "duration": 1.5}, {"text": "So imagine I've\ngot some matrix m.", "start": 1447.15, "duration": 2.7}, {"text": "I'm going to be agnostic about\nthe dimensions of this thing.", "start": 1452.91, "duration": 2.5}, {"text": "And suppose I look at\nthe following variation", "start": 1458.86, "duration": 2.18}, {"text": "of this matrix.", "start": 1461.04, "duration": 0.625}, {"text": "So suppose I imagine\ndoing a little variation.", "start": 1471.24, "duration": 3.1}, {"text": "So suppose every element\nof m is a function.", "start": 1474.34, "duration": 2.87}, {"text": "And I look at a little variation\nof the log of the determinant", "start": 1477.21, "duration": 6.18}, {"text": "of that matrix.", "start": 1483.39, "duration": 2.36}, {"text": "Well this can be written\nas log is basically", "start": 1485.75, "duration": 12.53}, {"text": "a definition of this.", "start": 1498.28, "duration": 7.97}, {"text": "Now, if I exploit\nproperties of logarithms,", "start": 1508.85, "duration": 4.41}, {"text": "this can be written as the\nlog of the determinant--", "start": 1513.26, "duration": 7.18}, {"text": "m plus delta m--", "start": 1520.44, "duration": 2.8}, {"text": "divided by the determinant of m.", "start": 1523.24, "duration": 2.77}, {"text": "Now I'm going to\nuse the fact that 1", "start": 1533.06, "duration": 1.86}, {"text": "over the determinant\nof m is the determinant", "start": 1534.92, "duration": 3.397}, {"text": "of the inverse of m.", "start": 1538.317, "duration": 0.833}, {"text": "So taking advantage of that,\nI can further write this guy", "start": 1560.85, "duration": 3.85}, {"text": "as something like this.", "start": 1564.7, "duration": 15.3}, {"text": "Now I'm going to invoke\nan identity, which", "start": 1580.0, "duration": 3.495}, {"text": "I believe you can find proven in\nmany linear algebra textbooks.", "start": 1583.495, "duration": 2.625}, {"text": "It just occurred to me as\nI'm thinking about this,", "start": 1586.12, "duration": 1.65}, {"text": "I don't know if I've ever seen\nit explicitly proven myself.", "start": 1587.77, "duration": 2.85}, {"text": "But it's something that's\nvery easy to demonstrate", "start": 1590.62, "duration": 2.25}, {"text": "with just a quick calculation.", "start": 1592.87, "duration": 2.33}, {"text": "You can just do--", "start": 1595.2, "duration": 1.263}, {"text": "I'm a physicist.", "start": 1596.463, "duration": 0.667}, {"text": "So for me I'll use Mathematica.", "start": 1597.13, "duration": 1.15}, {"text": "I'll look at six or\nseven examples and go,", "start": 1598.28, "duration": 1.78}, {"text": "it seems right.", "start": 1600.06, "duration": 1.07}, {"text": "And so I've\ndefinitely done that.", "start": 1601.13, "duration": 1.76}, {"text": "But I believe this\nis something that you", "start": 1602.89, "duration": 1.667}, {"text": "can find proven explicitly--", "start": 1604.557, "duration": 1.543}, {"text": "like I said-- in most books.", "start": 1606.1, "duration": 1.83}, {"text": "So remember these\nare all matrices.", "start": 1607.93, "duration": 1.99}, {"text": "So this isn't the number 1.", "start": 1609.92, "duration": 1.44}, {"text": "We want to think of this\nas the identity matrix.", "start": 1611.36, "duration": 2.0}, {"text": "Oh and I'm also going\nto regard this variation", "start": 1619.9, "duration": 2.19}, {"text": "as a small quantity.", "start": 1622.09, "duration": 2.49}, {"text": "So if I regard epsilon\nas a small matrix--", "start": 1624.58, "duration": 10.82}, {"text": "this can be made formal\nby defining something", "start": 1635.4, "duration": 1.89}, {"text": "like condition number\nassociated with the matrix", "start": 1637.29, "duration": 2.0}, {"text": "or something like that.", "start": 1639.29, "duration": 0.79}, {"text": "But generally what\nI want to mean", "start": 1640.08, "duration": 1.4}, {"text": "by that is if I\ntake this epsilon", "start": 1641.48, "duration": 1.74}, {"text": "and I add it to 1, all of this--", "start": 1643.22, "duration": 3.42}, {"text": "so my identity is\n1 on the diagonal--", "start": 1646.64, "duration": 2.37}, {"text": "0s everywhere else--\nall the things", "start": 1649.01, "duration": 2.37}, {"text": "that are put into the\nsum of 1 plus epsilon", "start": 1651.38, "duration": 2.1}, {"text": "are much, much smaller than\nthat 1 that's on the diagonal.", "start": 1653.48, "duration": 2.91}, {"text": "That will be sufficient.", "start": 1656.39, "duration": 1.87}, {"text": "So if epsilon is a small\nmatrix, then the determinant", "start": 1658.26, "duration": 7.97}, {"text": "of 1 plus epsilon is\napproximately equal to 1", "start": 1666.23, "duration": 9.31}, {"text": "plus the trace of epsilon.", "start": 1675.54, "duration": 3.59}, {"text": "What that approximately\nrefers to is-- of course", "start": 1685.84, "duration": 2.16}, {"text": "you can take that further.", "start": 1688.0, "duration": 1.18}, {"text": "And you'll get\nadditional corrections", "start": 1689.18, "duration": 1.19}, {"text": "that involve epsilon times\nepsilon, epsilon times epsilon,", "start": 1690.37, "duration": 2.49}, {"text": "times epsilon.", "start": 1692.86, "duration": 1.71}, {"text": "I believe when you do\nthat, the coefficient is", "start": 1694.57, "duration": 2.58}, {"text": "no longer universal.", "start": 1697.15, "duration": 0.87}, {"text": "But it depends upon the\ndimensions of the matrix.", "start": 1698.02, "duration": 2.97}, {"text": "But leading order it's\nindependent of dimensions", "start": 1700.99, "duration": 2.01}, {"text": "of the matrix.", "start": 1703.0, "duration": 0.6}, {"text": "And that's something\nthat you can", "start": 1703.6, "duration": 0.9}, {"text": "you can play with a\nlittle bit yourself.", "start": 1704.5, "duration": 1.96}, {"text": "Like I said, this is sufficient\nfor what we want to do here.", "start": 1706.46, "duration": 2.5}, {"text": "So I'm going to think\nof my small matrix", "start": 1715.07, "duration": 7.39}, {"text": "as the matrix of inverse\nm times a variation of m.", "start": 1722.46, "duration": 7.89}, {"text": "This is our epsilon.", "start": 1730.35, "duration": 1.59}, {"text": "So we're going to apply it to\nthe line that I have up here.", "start": 1735.01, "duration": 3.48}, {"text": "And this tells me that my delta\non the log of the derivative", "start": 1738.49, "duration": 5.69}, {"text": "of m is the log of 1 plus\nthe trace of m to the minus 1", "start": 1744.18, "duration": 13.51}, {"text": "on the matrix m.", "start": 1757.69, "duration": 2.69}, {"text": "Log of 1 plus a small\nnumber is that small number.", "start": 1760.38, "duration": 2.75}, {"text": "Now the application.", "start": 1773.0, "duration": 1.44}, {"text": "So this is-- like I said,\nthis the theorem that you", "start": 1774.44, "duration": 2.46}, {"text": "can find in books that I don't\nknow about but truly exist.", "start": 1776.9, "duration": 4.83}, {"text": "This is something I've seen\ndocumented in a lot of places.", "start": 1781.73, "duration": 3.96}, {"text": "Let's treat our m as\nthe metric of spacetime.", "start": 1785.69, "duration": 4.425}, {"text": "So my m will be g alpha beta.", "start": 1795.7, "duration": 2.6}, {"text": "My m inverse will be g\nin the upstairs position.", "start": 1798.3, "duration": 2.71}, {"text": "And I will write this\nsomething like so.", "start": 1806.03, "duration": 3.04}, {"text": "And I'm going to\napply this by looking", "start": 1809.07, "duration": 3.53}, {"text": "at variations in my metric.", "start": 1812.6, "duration": 1.47}, {"text": "So delta log--", "start": 1850.51, "duration": 3.56}, {"text": "I'm going to throw my\nabsolute values in here.", "start": 1854.07, "duration": 2.26}, {"text": "That's perfectly allowed to go\nahead and put that into there.", "start": 1856.33, "duration": 3.99}, {"text": "Applying this to\nwhat I've got, this", "start": 1860.32, "duration": 3.03}, {"text": "is going to be the trace of g\nmu beta times the variation of g", "start": 1863.35, "duration": 11.988}, {"text": "beta gamma.", "start": 1875.338, "duration": 1.597}, {"text": "And I forgot to say, how do\nI take the trace of a matrix?", "start": 1876.935, "duration": 2.375}, {"text": "So the trace that\nwe're going to use-- we", "start": 1893.482, "duration": 1.708}, {"text": "want it to be something\nthat has geometric meaning", "start": 1895.19, "duration": 2.52}, {"text": "and has a tensorial\nmeaning to it.", "start": 1897.71, "duration": 2.53}, {"text": "So we're going to call the\ntrace of this thing g alpha", "start": 1900.24, "duration": 7.96}, {"text": "beta epsilon alpha beta.", "start": 1908.2, "duration": 2.16}, {"text": "If you think about\nwhat this is doing,", "start": 1913.217, "duration": 1.583}, {"text": "you're essentially\ngoing to take your--", "start": 1914.8, "duration": 2.58}, {"text": "let's say I apply this\nto the metric itself.", "start": 1917.38, "duration": 2.535}, {"text": "I put one index in the\nupstairs position, one", "start": 1919.915, "duration": 1.875}, {"text": "the downstairs position,\nand then I am summing along", "start": 1921.79, "duration": 3.33}, {"text": "the diagonal when I do this.", "start": 1925.12, "duration": 3.27}, {"text": "You will sometimes see this\nwritten as something like that.", "start": 1928.39, "duration": 7.6}, {"text": "So in this case, when I'm taking\nthe trace of this guy here,", "start": 1941.3, "duration": 4.49}, {"text": "that is going to force me to--", "start": 1945.79, "duration": 3.02}, {"text": "let's see.", "start": 1948.81, "duration": 3.0}, {"text": "So this gives me\na quantity where", "start": 1951.81, "duration": 1.75}, {"text": "I'm summing over my betas.", "start": 1953.56, "duration": 2.35}, {"text": "And then I'm just going to\nsum over the diagonal indices.", "start": 1955.91, "duration": 2.72}, {"text": "I'm forcing my two remaining\nindices to be the same.", "start": 1958.63, "duration": 4.15}, {"text": "So putting this\ntogether, this tells me--", "start": 1962.78, "duration": 4.1}, {"text": "so now what I'm\ngoing to do is say,", "start": 1979.16, "duration": 3.47}, {"text": "I basically have part of\na partial derivative here.", "start": 1982.63, "duration": 3.44}, {"text": "All I need to do is now divide\nby a variation in my coordinate", "start": 1986.07, "duration": 11.98}, {"text": "and take the limit.", "start": 1998.05, "duration": 0.96}, {"text": "So it comes out of this as\nthe partial derivative--", "start": 2019.34, "duration": 4.293}, {"text": "looks like this.", "start": 2033.31, "duration": 1.36}, {"text": "Now let's trace it back\nto our Christoffel symbol.", "start": 2034.67, "duration": 2.27}, {"text": "My Christoffel\nsymbol-- the thing", "start": 2042.06, "duration": 3.21}, {"text": "which I'm trying to\ncompute-- is one half", "start": 2045.27, "duration": 1.83}, {"text": "of this right-hand side.", "start": 2047.1, "duration": 1.01}, {"text": "So it's one half of\nthe left-hand side.", "start": 2055.63, "duration": 2.292}, {"text": "And I can take that one half,\nmarch it through my derivative,", "start": 2057.922, "duration": 2.542}, {"text": "and use the fact\nthat 1/2 the log of x", "start": 2060.464, "duration": 2.836}, {"text": "is the log of the\nsquare root of x.", "start": 2063.3, "duration": 1.53}, {"text": "Check.", "start": 2080.909, "duration": 2.351}, {"text": "So like I said, this is\nwhat an old mentor of mine", "start": 2083.26, "duration": 3.6}, {"text": "used to like to\ncall a party trick.", "start": 2086.86, "duration": 1.71}, {"text": "It is a really useful party\ntrick for certain calculations.", "start": 2088.57, "duration": 3.87}, {"text": "So I want to make sure you\nsaw where that comes from.", "start": 2092.44, "duration": 2.509}, {"text": "This is something you will\nnow use on the problem", "start": 2094.949, "duration": 2.411}, {"text": "that I just moved\nfrom PSET 3 to PSET 4.", "start": 2097.36, "duration": 2.727}, {"text": "It's useful for you to\nknow where this comes from.", "start": 2100.087, "duration": 2.083}, {"text": "You're certainly not going\nto need to go through this", "start": 2102.17, "duration": 1.46}, {"text": "yourself.", "start": 2103.63, "duration": 0.5}, {"text": "But this is a good\ntype of calculation", "start": 2104.13, "duration": 2.59}, {"text": "to be comfortable with.", "start": 2106.72, "duration": 3.72}, {"text": "Those of you who are more\nrigorous in your math than me,", "start": 2110.44, "duration": 2.52}, {"text": "you might want to\nrun off and verify", "start": 2112.96, "duration": 2.7}, {"text": "a couple of these\nidentities that I used.", "start": 2115.66, "duration": 2.25}, {"text": "But this is very nice\nfor physics level rigor--", "start": 2117.91, "duration": 6.69}, {"text": "at least astrophysicists\nlevel rigor.", "start": 2124.6, "duration": 2.13}, {"text": "So let me talk about one\nof the places where this", "start": 2126.73, "duration": 2.34}, {"text": "shows up and is quite useful.", "start": 2129.07, "duration": 3.48}, {"text": "So a place where I've\nseen this show up the most", "start": 2139.31, "duration": 2.69}, {"text": "is when you're looking at\nthe spacetime divergence", "start": 2142.0, "duration": 2.19}, {"text": "of a vector field.", "start": 2144.19, "duration": 0.78}, {"text": "So when you're calculating\nthe covariant derivative", "start": 2155.32, "duration": 3.23}, {"text": "of alpha contracting\non the indices--", "start": 2158.55, "duration": 2.43}, {"text": "let's just throw in--", "start": 2160.98, "duration": 0.96}, {"text": "expand out the full\ndefinition of things--", "start": 2165.14, "duration": 1.89}, {"text": "all you've gotta do\nis correct one index.", "start": 2173.92, "duration": 2.16}, {"text": "And voila, this is exactly\nthe things that change--", "start": 2176.08, "duration": 5.01}, {"text": "where is it-- change my\nalpha to a mu-- that's", "start": 2181.09, "duration": 2.1}, {"text": "exactly what I've got before.", "start": 2183.19, "duration": 3.42}, {"text": "And so-- hang on\njust one moment.", "start": 2186.61, "duration": 6.07}, {"text": "I know what I'm doing.", "start": 2192.68, "duration": 1.76}, {"text": "These are all dummy indices.", "start": 2194.44, "duration": 2.31}, {"text": "So in order to keep things\nfrom getting crossed,", "start": 2196.75, "duration": 2.86}, {"text": "I'm going to relabel\nthese over here.", "start": 2199.61, "duration": 1.69}, {"text": "So I can take advantage of\nthis identity and write this.", "start": 2207.66, "duration": 3.68}, {"text": "So stare at this for a second.", "start": 2228.15, "duration": 9.11}, {"text": "And you'll see that the\nwhole thing can be rewritten", "start": 2237.26, "duration": 3.94}, {"text": "in a very simple form.", "start": 2241.2, "duration": 1.36}, {"text": "Ta-da.", "start": 2267.56, "duration": 2.1}, {"text": "You haven't done as much work\nwith covariant in your lives", "start": 2269.66, "duration": 2.7}, {"text": "as I have.", "start": 2272.36, "duration": 0.99}, {"text": "So let me just emphasize\nthat ordinarily when", "start": 2273.35, "duration": 2.855}, {"text": "you see an expression\nlike you've", "start": 2276.205, "duration": 1.375}, {"text": "got up there on the top\nline, you look at that,", "start": 2277.58, "duration": 2.37}, {"text": "and you kind of go [GROANS]\nbecause you look at that,", "start": 2279.95, "duration": 2.438}, {"text": "and the first thing\nthat comes to your mind", "start": 2282.388, "duration": 1.792}, {"text": "is you've got to work out\nevery one of those Christoffel", "start": 2284.18, "duration": 3.18}, {"text": "symbols and sum it up\nto get those things.", "start": 2287.36, "duration": 3.11}, {"text": "And in a general spacetime,\nthere will be 40 of them.", "start": 2290.47, "duration": 3.4}, {"text": "And before Odin\ngave us Mathematica,", "start": 2293.87, "duration": 3.09}, {"text": "that was a fair amount of labor.", "start": 2296.96, "duration": 1.35}, {"text": "Even with Mathematica it's\nnot necessarily trivial", "start": 2298.31, "duration": 2.56}, {"text": "because it's really\neasy to screw things up.", "start": 2300.87, "duration": 2.65}, {"text": "With this you calculate the\ndeterminant of the metric,", "start": 2303.52, "duration": 2.83}, {"text": "you take its square root,\nyou multiply your guy,", "start": 2306.35, "duration": 2.64}, {"text": "and you take a partial\nderivative, and you divide.", "start": 2308.99, "duration": 2.34}, {"text": "That is something\nthat most of us", "start": 2311.33, "duration": 2.25}, {"text": "learned how to do\nquite a long time ago.", "start": 2313.58, "duration": 1.83}, {"text": "It cleans the hell\nout of this up.", "start": 2315.41, "duration": 3.482}, {"text": "So the fact that this gives us\nsomething that only involves", "start": 2318.892, "duration": 2.458}, {"text": "partial derivatives is awesome.", "start": 2321.35, "duration": 2.444}, {"text": "This also-- it turns out-- so\nwhen you have things like this,", "start": 2335.66, "duration": 3.93}, {"text": "it gives us a nice way to\nexpress Gauss's theorem", "start": 2339.59, "duration": 4.14}, {"text": "in a curved manifold.", "start": 2343.73, "duration": 1.01}, {"text": "So Gauss's theorem-- if I\njust look at the integrals", "start": 2348.83, "duration": 2.395}, {"text": "that-- or rather the integral\nfor Gauss's theorem-- let's", "start": 2351.225, "duration": 2.375}, {"text": "put it that way.", "start": 2353.6, "duration": 1.47}, {"text": "Let's say a\nGauss's-type integral.", "start": 2355.07, "duration": 2.49}, {"text": "So go back to when\nyou're talking", "start": 2363.33, "duration": 2.19}, {"text": "about conservation laws.", "start": 2365.52, "duration": 1.23}, {"text": "If I imagine I'm integrating the\ndivergence of some vector field", "start": 2370.21, "duration": 8.19}, {"text": "over a four-dimensional\nvolume, look at that,", "start": 2378.4, "duration": 2.73}, {"text": "I get a nice cancellation.", "start": 2381.13, "duration": 3.69}, {"text": "So this turns into an integral\nof that nice, clean derivative", "start": 2384.82, "duration": 12.36}, {"text": "over my four coordinates.", "start": 2397.18, "duration": 3.6}, {"text": "And then you can take\nadvantage of the actual content", "start": 2400.78, "duration": 2.79}, {"text": "of Gauss's Theorem to\nturn that into an integral", "start": 2403.57, "duration": 2.407}, {"text": "over the three-dimensional\nsurface that bounds that four", "start": 2405.977, "duration": 2.333}, {"text": "volume.", "start": 2408.31, "duration": 0.5}, {"text": "It's a good point--", "start": 2413.33, "duration": 0.99}, {"text": "so you're emboldened by this.", "start": 2414.32, "duration": 1.505}, {"text": "You say, yay, look at that.", "start": 2415.825, "duration": 1.125}, {"text": "We can do all this awesome\nstuff with this identity.", "start": 2416.95, "duration": 2.28}, {"text": "It gives me a great\nway to express some", "start": 2419.23, "duration": 1.645}, {"text": "of these conservation laws.", "start": 2420.875, "duration": 2.525}, {"text": "You might think to yourself--", "start": 2423.4, "duration": 1.367}, {"text": "and I realized as I was\nlooking over these notes--", "start": 2424.767, "duration": 2.083}, {"text": "I'm about to I think give away\na part of one of the problems", "start": 2426.85, "duration": 3.54}, {"text": "on the PSET-- but c'est la vie.", "start": 2430.39, "duration": 2.12}, {"text": "It's an important point.", "start": 2432.51, "duration": 3.0}, {"text": "Can we do something\nsimilar for tensors?", "start": 2435.51, "duration": 2.922}, {"text": "So this is great that you\nhave this form for vectors.", "start": 2438.432, "duration": 2.208}, {"text": "The divergence of a vector\nis a mathematical notion that", "start": 2443.22, "duration": 3.067}, {"text": "comes up in various contexts.", "start": 2446.287, "duration": 1.208}, {"text": "So this is important.", "start": 2447.495, "duration": 1.825}, {"text": "But we've already\ntalked about the fact", "start": 2449.32, "duration": 2.09}, {"text": "that things like\nenergy and momentum", "start": 2451.41, "duration": 1.74}, {"text": "are described by a\nstress energy tensor.", "start": 2453.15, "duration": 2.52}, {"text": "So can we do this for tensors?", "start": 2455.67, "duration": 1.41}, {"text": "Well the answer\nturns out to be no,", "start": 2465.19, "duration": 3.81}, {"text": "except in a handful of cases.", "start": 2469.0, "duration": 1.245}, {"text": "And I have a comment about\nthose handful of cases.", "start": 2473.07, "duration": 4.19}, {"text": "So suppose I take this--", "start": 2477.26, "duration": 2.25}, {"text": "and I'm taking the\ndivergence on say", "start": 2479.51, "duration": 1.53}, {"text": "the first index of this guy--", "start": 2481.04, "duration": 1.32}, {"text": "so there's the bit involves\nmy partial derivative--", "start": 2487.15, "duration": 4.39}, {"text": "I'm going to have\na bit that involves", "start": 2491.54, "duration": 4.91}, {"text": "correcting the first index.", "start": 2496.45, "duration": 2.19}, {"text": "So the first correction\nis it's of a form that", "start": 2511.6, "duration": 6.56}, {"text": "does in fact involve\nthis guy we just", "start": 2518.16, "duration": 1.56}, {"text": "worked out this identity for.", "start": 2519.72, "duration": 1.243}, {"text": "And in principle we\ncould take advantage", "start": 2520.963, "duration": 1.667}, {"text": "of that to massage this\nand use this identity.", "start": 2522.63, "duration": 2.85}, {"text": "But the second one there's\nnothing to do with that.", "start": 2525.48, "duration": 3.028}, {"text": "This you just have\nto go and work out", "start": 2528.508, "duration": 1.542}, {"text": "all of your 40 different\nChristoffel symbols", "start": 2530.05, "duration": 2.79}, {"text": "and sit down and\nslog through it.", "start": 2532.84, "duration": 1.47}, {"text": "This spoils your\nability to do anything", "start": 2534.31, "duration": 1.625}, {"text": "with it, with one exception.", "start": 2535.935, "duration": 5.335}, {"text": "What if a is an\nanti-symmetric tensor?", "start": 2541.27, "duration": 3.832}, {"text": "If a is an\nanti-symmetric tensor,", "start": 2545.102, "duration": 1.528}, {"text": "you've got symmetry, anti\nsymmetry, and it dies.", "start": 2546.63, "duration": 3.24}, {"text": "So that is one example of where\nyou can actually apply it.", "start": 2549.87, "duration": 2.55}, {"text": "And I had you guys play with\nthat a little bit on the PSET.", "start": 2552.42, "duration": 3.42}, {"text": "It's worth noting though that\nthe main reason why one often", "start": 2555.84, "duration": 2.94}, {"text": "finds this to be a\nuseful thing to do", "start": 2558.78, "duration": 2.52}, {"text": "is that when you take the\ndivergence of something", "start": 2561.3, "duration": 3.51}, {"text": "like a vector, you\nget a scalar out.", "start": 2564.81, "duration": 2.76}, {"text": "You get a quantity that is--", "start": 2567.57, "duration": 3.0}, {"text": "really its\ntransformation properties", "start": 2570.57, "duration": 1.92}, {"text": "between different inertial\nframes or freely-falling frames", "start": 2572.49, "duration": 2.91}, {"text": "is simple.", "start": 2575.4, "duration": 0.54}, {"text": "So even when you can do this and\ntake advantage of this thing,", "start": 2586.23, "duration": 3.06}, {"text": "working with the\ndivergence of a tensor--", "start": 2589.29, "duration": 3.738}, {"text": "exploiting a trick like this\nturns out to generally not", "start": 2593.028, "duration": 2.292}, {"text": "be all that useful.", "start": 2595.32, "duration": 0.92}, {"text": "And I'll use the example of\nthe stress energy tensor.", "start": 2596.24, "duration": 3.76}, {"text": "So conservation of stress\nenergy in special relativity--", "start": 2600.0, "duration": 4.39}, {"text": "it was the partial derivative--", "start": 2604.39, "duration": 3.412}, {"text": "the divergence of\nthe stress energy", "start": 2607.802, "duration": 1.458}, {"text": "tensor expressed with\nthe partial derivative", "start": 2609.26, "duration": 1.833}, {"text": "was equal to 0.", "start": 2611.093, "duration": 1.107}, {"text": "We're going to take this\nover to covariant derivative", "start": 2612.2, "duration": 2.355}, {"text": "of the stress energy\ntensor being equal to 0.", "start": 2614.555, "duration": 1.875}, {"text": "That's what the equivalence\nprinciple tells us", "start": 2616.43, "duration": 1.38}, {"text": "that we can do.", "start": 2617.81, "duration": 0.625}, {"text": "Now when I take the divergence\nof something like the stress", "start": 2620.96, "duration": 2.64}, {"text": "energy tensor, I get a 4 vector.", "start": 2623.6, "duration": 2.22}, {"text": "Every 4 vector\nalways has implicitly", "start": 2628.58, "duration": 2.55}, {"text": "a set of basis objects\nattached to it.", "start": 2631.13, "duration": 3.008}, {"text": "When I've got basis\nobjects attached to it,", "start": 2634.138, "duration": 1.792}, {"text": "those are defined with\nrespect to the tangent space", "start": 2635.93, "duration": 3.078}, {"text": "at a particular\npoint in the manifold", "start": 2639.008, "duration": 1.542}, {"text": "where you are currently working.", "start": 2640.55, "duration": 1.71}, {"text": "And so if I want to try to do\nsomething like an integral like", "start": 2642.26, "duration": 3.42}, {"text": "this-- where I add up the\nfour vector I get by taking", "start": 2645.68, "duration": 3.51}, {"text": "the divergence of stress\nenergy and integrate it over", "start": 2649.19, "duration": 3.03}, {"text": "a volume--", "start": 2652.22, "duration": 1.11}, {"text": "I'm going to get nonsense\nbecause what's going on", "start": 2653.33, "duration": 2.85}, {"text": "is I'm combining vector\nfields that are defined", "start": 2656.18, "duration": 2.7}, {"text": "in different tangent spaces\nthat can't be properly compared", "start": 2658.88, "duration": 3.18}, {"text": "to one another.", "start": 2662.06, "duration": 1.65}, {"text": "In order to do that\nkind of comparison,", "start": 2663.71, "duration": 1.69}, {"text": "you have to introduce\na transport law.", "start": 2665.4, "duration": 3.12}, {"text": "And when you start\ndoing transports", "start": 2668.52, "duration": 1.64}, {"text": "over macroscopic regions,\nyou run into trouble.", "start": 2670.16, "duration": 3.9}, {"text": "They turn out to\nbe path dependent.", "start": 2674.06, "duration": 2.31}, {"text": "And this is where we\nrun into ambiguities", "start": 2676.37, "duration": 2.06}, {"text": "that have to do with\nthe curvature content", "start": 2678.43, "duration": 1.75}, {"text": "of your manifold.", "start": 2680.18, "duration": 1.38}, {"text": "We'll discuss where that\ncomes into our calculations", "start": 2681.56, "duration": 2.88}, {"text": "a little bit later.", "start": 2684.44, "duration": 1.17}, {"text": "But what it basically\nboils down to is", "start": 2685.61, "duration": 3.66}, {"text": "if I use a stress energy\ntensor as an example,", "start": 2689.27, "duration": 2.58}, {"text": "this equation tells me\nabout local conservation", "start": 2691.85, "duration": 4.2}, {"text": "of energy and momentum.", "start": 2696.05, "duration": 3.47}, {"text": "In general relativity I cannot\ntake the local conservation", "start": 2699.52, "duration": 4.2}, {"text": "of energy and momentum\nand promote it to a global", "start": 2703.72, "duration": 2.4}, {"text": "conservation of\nenergy and momentum.", "start": 2706.12, "duration": 2.01}, {"text": "It's ambiguous.", "start": 2708.13, "duration": 2.38}, {"text": "We'll deal with that and\nthe conceptual difficulties", "start": 2710.51, "duration": 5.4}, {"text": "that that presents a little\nbit later in the course.", "start": 2715.91, "duration": 2.19}, {"text": "But it's a good see the\nplant at this point.", "start": 2718.1, "duration": 3.75}, {"text": "So let's switch gears.", "start": 2721.85, "duration": 1.5}, {"text": "We have a new set of\nmathematical tools.", "start": 2723.35, "duration": 2.22}, {"text": "I want to take a detour away\nfrom thinking about some more", "start": 2730.34, "duration": 5.52}, {"text": "abstract mathematical notions\nand start thinking about how", "start": 2735.86, "duration": 3.21}, {"text": "we actually do some physics.", "start": 2739.07, "duration": 2.23}, {"text": "So what I want to do\nis talk today about how", "start": 2741.3, "duration": 2.9}, {"text": "do we formulate the\nkinematics of a body", "start": 2744.2, "duration": 3.78}, {"text": "moving in curved spacetime?", "start": 2747.98, "duration": 1.718}, {"text": "So I've already\nhinted at this in some", "start": 2768.427, "duration": 1.583}, {"text": "of my previous lectures.", "start": 2770.01, "duration": 0.99}, {"text": "And what I want\nto do now is just", "start": 2771.0, "duration": 1.375}, {"text": "basically fill in\nsome of the gaps.", "start": 2772.375, "duration": 2.615}, {"text": "The way that we do\nthis really just", "start": 2774.99, "duration": 3.48}, {"text": "builds on Einstein's\ninsight about what", "start": 2778.47, "duration": 3.47}, {"text": "the weak equivalence\nprinciple means.", "start": 2781.94, "duration": 2.56}, {"text": "So go into a freely\nfalling frame.", "start": 2784.5, "duration": 2.82}, {"text": "Go in that freely-falling frame.", "start": 2794.91, "duration": 1.96}, {"text": "Put things into locally\nLorentz coordinates.", "start": 2796.87, "duration": 5.29}, {"text": "In other words perform\nthat little calculation", "start": 2802.16, "duration": 2.378}, {"text": "that make spacetime\nlook like the spacetime", "start": 2804.538, "duration": 1.792}, {"text": "of special relativity of\nthe curvature corrections.", "start": 2806.33, "duration": 2.889}, {"text": "And to start with, let's\nconsider what we always", "start": 2819.21, "duration": 2.28}, {"text": "do in physics, is we'll look\nat the simplest body first.", "start": 2821.49, "duration": 2.95}, {"text": "We're going to look at\nwhat we call a test body.", "start": 2824.44, "duration": 2.0}, {"text": "So this is the body that has\nno charge, no spatial extent,", "start": 2835.41, "duration": 6.74}, {"text": "it's of zero dimensional\npoint, no spin--", "start": 2842.15, "duration": 7.77}, {"text": "nothing interesting,\nexcept a mass.", "start": 2849.92, "duration": 3.66}, {"text": "So if you want to\nthink about this--", "start": 2862.35, "duration": 2.01}, {"text": "I use a way that I find\nto think about this", "start": 2864.36, "duration": 2.07}, {"text": "is all these various aspects to\nit, you're adding additional--", "start": 2866.43, "duration": 4.77}, {"text": "either charges to it or\nadditional multipolar structure", "start": 2871.2, "duration": 3.6}, {"text": "to this body.", "start": 2874.8, "duration": 1.29}, {"text": "I'm thinking of this-- this is\nsort of like a pure monopole.", "start": 2876.09, "duration": 3.0}, {"text": "It's nothing but\nmass concentrated", "start": 2879.09, "duration": 1.83}, {"text": "in a single zero size point.", "start": 2880.92, "duration": 2.76}, {"text": "Obviously it's an idealization.", "start": 2883.68, "duration": 1.619}, {"text": "But you've got to\nstart somewhere.", "start": 2885.299, "duration": 1.417}, {"text": "So since it's got no\ncharge, no spatial extent,", "start": 2894.81, "duration": 4.11}, {"text": "it's got nothing\nbut mass, nothing's", "start": 2898.92, "duration": 3.883}, {"text": "going to couple to it.", "start": 2902.803, "duration": 0.917}, {"text": "It's not going to basically\ndo anything but freefall.", "start": 2903.72, "duration": 2.965}, {"text": "In this frame the body moves on\na purely inertial trajectory.", "start": 2917.04, "duration": 12.866}, {"text": "And what does a purely\ninertial trajectory look like?", "start": 2944.262, "duration": 2.208}, {"text": "Well you take whatever your\ninitial conditions are.", "start": 2946.47, "duration": 4.89}, {"text": "And you move in a\nstraight line with respect", "start": 2955.33, "duration": 2.16}, {"text": "to time as measured\non your own clock.", "start": 2957.49, "duration": 3.07}, {"text": "Simplest, stupidest possible\nmotion that you can.", "start": 2960.56, "duration": 3.11}, {"text": "So we would obviously call that\na straight line with respect", "start": 2977.32, "duration": 2.57}, {"text": "to the parameterization\nthat's being", "start": 2979.89, "duration": 1.5}, {"text": "used in this representation.", "start": 2981.39, "duration": 2.35}, {"text": "So what does that mean\nin a more general sense", "start": 2983.74, "duration": 2.9}, {"text": "of the representation?", "start": 2986.64, "duration": 1.09}, {"text": "So if we think about this a\nlittle bit more geometrically,", "start": 2987.73, "duration": 2.57}, {"text": "when a body is moving in a\nstraight line, that basically", "start": 2990.3, "duration": 3.48}, {"text": "means that whatever the tangent\nvector to its world line is,", "start": 2993.78, "duration": 4.47}, {"text": "it's essentially moving such\nthat the tangent vector at time", "start": 2998.25, "duration": 4.29}, {"text": "T1 is parallel to the tangent\nvector at T1 plus delta T1,", "start": 3002.54, "duration": 6.01}, {"text": "provided that's\nactually small enough", "start": 3008.55, "duration": 1.61}, {"text": "that they're sort of within\nthe same local Lorentz frame.", "start": 3010.16, "duration": 2.85}, {"text": "So a more geometric way of\nthinking about this motion", "start": 3016.95, "duration": 3.17}, {"text": "is that it's parallel\ntransporting its tangent", "start": 3020.12, "duration": 1.99}, {"text": "vector.", "start": 3022.11, "duration": 0.5}, {"text": "Let's make this a little\nbit more rigorous.", "start": 3073.858, "duration": 1.792}, {"text": "So let's imagine\nthis body's moving", "start": 3075.65, "duration": 1.5}, {"text": "on a particular trajectory\nthrough spacetime.", "start": 3077.15, "duration": 2.833}, {"text": "So it's a trajectory\nparameterized.", "start": 3085.78, "duration": 3.06}, {"text": "I will define its\nparameterization a little bit", "start": 3088.84, "duration": 4.41}, {"text": "more carefully very soon.", "start": 3093.25, "duration": 1.19}, {"text": "So for now, just think of lambda\nas some kind of a quantity.", "start": 3098.66, "duration": 3.43}, {"text": "It's a scale that just\naccumulates uniformly as it", "start": 3102.09, "duration": 2.33}, {"text": "moves along the world line.", "start": 3104.42, "duration": 3.58}, {"text": "So I'm going to say\nthe small body has", "start": 3108.0, "duration": 2.62}, {"text": "a path through spacetime,\ngiven by u x of lambda.", "start": 3110.62, "duration": 5.28}, {"text": "Its tangent is given by this.", "start": 3115.9, "duration": 12.29}, {"text": "And if it is parallel\ntransporting its own tangent", "start": 3128.19, "duration": 2.4}, {"text": "vector, that is--", "start": 3130.59, "duration": 14.163}, {"text": "I'll remind you\nthat the condition", "start": 3144.753, "duration": 1.417}, {"text": "for parallel\ntransport was that you", "start": 3146.17, "duration": 5.78}, {"text": "take the covariant\nderivative your field.", "start": 3151.95, "duration": 2.13}, {"text": "And as you are moving\nalong, you contract it", "start": 3154.08, "duration": 4.59}, {"text": "along the tangent vector of the\ntrajectory you're moving on.", "start": 3158.67, "duration": 2.7}, {"text": "And you get 0.", "start": 3161.37, "duration": 1.89}, {"text": "So in my notes, there's a\ncouple of equivalent ways", "start": 3163.26, "duration": 5.34}, {"text": "of writing this.", "start": 3168.6, "duration": 0.68}, {"text": "So you will sometimes\nsee this written", "start": 3169.28, "duration": 1.72}, {"text": "as the gradient along u of u.", "start": 3171.0, "duration": 4.32}, {"text": "And you'll sometimes see\nthis written as capital u", "start": 3179.09, "duration": 7.88}, {"text": "u lambda equals 0.", "start": 3186.97, "duration": 1.138}, {"text": "So these are just--", "start": 3188.108, "duration": 0.792}, {"text": "I just throw that\nout because these", "start": 3188.9, "duration": 0.89}, {"text": "are different forms that\nare common in the notation", "start": 3189.79, "duration": 2.125}, {"text": "that you will see.", "start": 3191.915, "duration": 0.927}, {"text": "So let's expand this guy out.", "start": 3192.842, "duration": 1.208}, {"text": "It's something like this.", "start": 3219.018, "duration": 1.042}, {"text": "So what we're going to do-- so\nremember this is dx d lambda.", "start": 3220.06, "duration": 3.81}, {"text": "This is d by dx.", "start": 3223.87, "duration": 2.568}, {"text": "That's a total derivative\nwith respect to the parameter", "start": 3226.438, "duration": 2.292}, {"text": "lambda.", "start": 3228.73, "duration": 0.5}, {"text": "So this becomes--", "start": 3231.712, "duration": 0.708}, {"text": "I'm going to write\nit in two forms.", "start": 3245.5, "duration": 2.09}, {"text": "This is often written expanding\nout the u into a second order", "start": 3247.59, "duration": 3.48}, {"text": "form.", "start": 3251.07, "duration": 0.5}, {"text": "This is obvious but\nsufficiently important.", "start": 3258.89, "duration": 2.34}, {"text": "It's worth calling it out.", "start": 3261.23, "duration": 5.67}, {"text": "And this has earned\nitself a box.", "start": 3266.9, "duration": 3.51}, {"text": "This result is known as\nthe geodesic equation.", "start": 3279.57, "duration": 3.36}, {"text": "The trajectories which\nsolve these equations", "start": 3303.02, "duration": 2.02}, {"text": "are known as geodesics.", "start": 3305.04, "duration": 1.48}, {"text": "One of the reasons why I\nhighlight this is it's--", "start": 3322.083, "duration": 3.497}, {"text": "I'm trying to keep a straight\nface with the comment I", "start": 3329.79, "duration": 2.82}, {"text": "want to make.", "start": 3332.61, "duration": 0.99}, {"text": "A tremendous amount of\nresearch in general relativity", "start": 3333.6, "duration": 3.75}, {"text": "is based around doing\nsolutions of this equation", "start": 3337.35, "duration": 4.32}, {"text": "for various spacetimes that\ngo in to make the Christoffel", "start": 3341.67, "duration": 3.39}, {"text": "symbols.", "start": 3345.06, "duration": 2.31}, {"text": "My career-- [LAUGHS] it's\nprobably not false to say that", "start": 3347.37, "duration": 6.87}, {"text": "about 65% of my papers have\nthis equation at its centerpiece", "start": 3354.24, "duration": 6.48}, {"text": "at some point with the\nthing that goes into making", "start": 3360.72, "duration": 2.82}, {"text": "my gammas--", "start": 3363.54, "duration": 1.32}, {"text": "things related to\nblack hole spacetimes.", "start": 3364.86, "duration": 3.33}, {"text": "This is really important\nbecause this gives me the motion", "start": 3368.19, "duration": 4.26}, {"text": "of a freely-falling frame.", "start": 3372.45, "duration": 1.81}, {"text": "What does a freely-falling\nframe describe?", "start": 3374.26, "duration": 2.12}, {"text": "Somebody who's\nmoving under gravity.", "start": 3376.38, "duration": 2.23}, {"text": "So when you're doing things like\ndescribing orbits, for example,", "start": 3378.61, "duration": 2.81}, {"text": "this is your tool.", "start": 3381.42, "duration": 2.28}, {"text": "A tremendous number\nof applications", "start": 3383.7, "duration": 1.65}, {"text": "where if what you care\nabout is the motion", "start": 3385.35, "duration": 2.49}, {"text": "of a body due to\nrelativistic gravity,", "start": 3387.84, "duration": 2.61}, {"text": "this gives you a\nleading solution.", "start": 3390.45, "duration": 2.13}, {"text": "Now bear in mind\nwhen I did this,", "start": 3392.58, "duration": 2.61}, {"text": "this is the motion\nof a test body.", "start": 3395.19, "duration": 1.71}, {"text": "This is an object\nwith no charge,", "start": 3396.9, "duration": 1.98}, {"text": "no spatial extent, no spin--", "start": 3398.88, "duration": 2.85}, {"text": "that describes no object.", "start": 3401.73, "duration": 3.84}, {"text": "So it should be borne\nin mind that this is", "start": 3405.57, "duration": 3.51}, {"text": "the leading solution to things.", "start": 3409.08, "duration": 3.03}, {"text": "Suppose the body is charged.", "start": 3412.11, "duration": 2.06}, {"text": "And there is an\nelectromagnetic field", "start": 3414.17, "duration": 1.96}, {"text": "that this body is\ninteracting with.", "start": 3416.13, "duration": 2.28}, {"text": "Then what you do is\nyou are no longer going", "start": 3418.41, "duration": 2.76}, {"text": "to be parallel transporting\nthis tangent factor.", "start": 3421.17, "duration": 2.73}, {"text": "It will be pushed\naway-- we like to say--", "start": 3423.9, "duration": 1.833}, {"text": "from the parallel transport.", "start": 3425.733, "duration": 1.167}, {"text": "And you'll replace the\n0 on the right hand side", "start": 3426.9, "duration": 2.28}, {"text": "here with a\nproperly-constructed force", "start": 3429.18, "duration": 2.37}, {"text": "that describes the\ninteractions of those charges", "start": 3431.55, "duration": 3.18}, {"text": "with the fields.", "start": 3434.73, "duration": 2.55}, {"text": "Suppose the body has some size.", "start": 3437.28, "duration": 2.49}, {"text": "Well then what ends up happening\nis that the body actually", "start": 3439.77, "duration": 2.88}, {"text": "doesn't just couple to a\nsingle-- remember what's", "start": 3442.65, "duration": 2.37}, {"text": "going on here is that in\nthe freely falling frame,", "start": 3445.02, "duration": 4.17}, {"text": "I'm imagining that spacetime\nis flat at some point.", "start": 3449.19, "duration": 3.3}, {"text": "And in a decent enough\nvicinity of that point,", "start": 3452.49, "duration": 2.693}, {"text": "the first order\ncorrections are 0.", "start": 3455.183, "duration": 1.417}, {"text": "But there might be\nsecond order corrections.", "start": 3456.6, "duration": 2.01}, {"text": "Well imagine a body is\nso big that it fills", "start": 3458.61, "duration": 2.43}, {"text": "that freely-falling frame.", "start": 3461.04, "duration": 1.76}, {"text": "And it actually tastes those\nsecond order corrections.", "start": 3462.8, "duration": 3.568}, {"text": "Then what's going\nto happen is you're", "start": 3466.368, "duration": 1.542}, {"text": "going to get additional\nterms on this equation, which", "start": 3467.91, "duration": 2.41}, {"text": "have to do with the coupling of\nthe spatial extent of that body", "start": 3470.32, "duration": 2.88}, {"text": "to the curvature\nof the spacetime.", "start": 3473.2, "duration": 2.58}, {"text": "That is where-- so for people\nwho study astrophysical systems", "start": 3475.78, "duration": 4.8}, {"text": "involving binaries, when\nyou have spinning bodies,", "start": 3480.58, "duration": 3.39}, {"text": "that ends up actually--\nyou cannot describe a body", "start": 3483.97, "duration": 2.43}, {"text": "that's spinning without it\nhaving some spatial extent.", "start": 3486.4, "duration": 2.55}, {"text": "And you find terms here that\ninvolve coupling of those", "start": 3488.95, "duration": 2.88}, {"text": "spins to the curvature\nof the spacetime.", "start": 3491.83, "duration": 2.89}, {"text": "So this is the leading piece\nof the motion of a body moving", "start": 3494.72, "duration": 4.19}, {"text": "in the current spacetime.", "start": 3498.91, "duration": 1.77}, {"text": "And it's enough to do\na tremendous amount.", "start": 3500.68, "duration": 1.78}, {"text": "Basically because gravity is\njust so bloody strong that all", "start": 3502.46, "duration": 5.01}, {"text": "of these various things--", "start": 3507.47, "duration": 1.322}, {"text": "it's the weakest\nfundamental force.", "start": 3508.792, "duration": 1.458}, {"text": "But it adds up because\nit's only got one sine.", "start": 3510.25, "duration": 3.09}, {"text": "And when you're dealing\nwith some of these things,", "start": 3513.34, "duration": 2.85}, {"text": "it really ends up being the\ncoupling to the monopole--", "start": 3516.19, "duration": 2.58}, {"text": "the most important thing.", "start": 3518.77, "duration": 1.77}, {"text": "So all these other terms\nthat come in and correct this", "start": 3520.54, "duration": 2.67}, {"text": "are small enough that\nwe can add them in.", "start": 3523.21, "duration": 2.22}, {"text": "And that, to be blunt,\nis modern research.", "start": 3525.43, "duration": 3.18}, {"text": "So let me make a couple\nof comments about this.", "start": 3528.61, "duration": 2.76}, {"text": "A more general form--", "start": 3534.75, "duration": 1.395}, {"text": "this will help to clarify what\nthe meaning of that lambda", "start": 3539.3, "duration": 3.63}, {"text": "actually is.", "start": 3542.93, "duration": 0.72}, {"text": "Suppose that as my vector is\ntransported along itself--", "start": 3554.94, "duration": 6.76}, {"text": "so one way is recall how we\nderive parallel transport.", "start": 3561.7, "duration": 3.24}, {"text": "We imagine going into\na freely-falling frame", "start": 3564.94, "duration": 3.87}, {"text": "and a Lorentz representation.", "start": 3568.81, "duration": 1.77}, {"text": "And we said, in that\nframe, I'm going", "start": 3570.58, "duration": 2.202}, {"text": "to imagine moving\nthis thing along,", "start": 3572.782, "duration": 1.458}, {"text": "holding all the components\nconstants-- that", "start": 3574.24, "duration": 3.0}, {"text": "defined parallel transport.", "start": 3577.24, "duration": 2.19}, {"text": "Imagine that I don't keep\nthe components constant,", "start": 3579.43, "duration": 4.47}, {"text": "but I hold them all in a\nconstant ratio with respect", "start": 3583.9, "duration": 2.37}, {"text": "to each other, but I allow\nthe overall magnitude", "start": 3586.27, "duration": 2.82}, {"text": "to expand or contract.", "start": 3589.09, "duration": 1.29}, {"text": "So suppose we allow the\nvector's normalization", "start": 3596.05, "duration": 7.37}, {"text": "to change as it slides along.", "start": 3603.42, "duration": 1.8}, {"text": "Well the way I\nwould mathematically", "start": 3618.74, "duration": 1.59}, {"text": "formulate this is I'm going\nto use a notation that", "start": 3620.33, "duration": 4.53}, {"text": "looks like this.", "start": 3624.86, "duration": 0.68}, {"text": "So recall this capital\nD-- it's a shorthand", "start": 3625.54, "duration": 2.38}, {"text": "for this combination\nof the tangent", "start": 3627.92, "duration": 10.71}, {"text": "and the covariant derivative.", "start": 3638.63, "duration": 3.367}, {"text": "I'm going to call\nthe parameterization", "start": 3641.997, "duration": 1.583}, {"text": "I use when I set up\nlike this lambda star,", "start": 3643.58, "duration": 2.07}, {"text": "for reasons that I hope\nwill be clear in just about", "start": 3645.65, "duration": 2.125}, {"text": "two minutes.", "start": 3647.775, "duration": 1.325}, {"text": "So what I'm basically saying\nis that as I move along,", "start": 3649.1, "duration": 2.97}, {"text": "I don't keep the\ncomponents constant.", "start": 3652.07, "duration": 2.028}, {"text": "But I keep them\nproportional to where", "start": 3654.098, "duration": 1.542}, {"text": "they were on the previous step.", "start": 3655.64, "duration": 1.598}, {"text": "But I allow their magnitude to\nchange by some function, which", "start": 3657.238, "duration": 2.542}, {"text": "I'll call a kappa.", "start": 3659.78, "duration": 0.75}, {"text": "So you might look at\nthat and think, you know,", "start": 3668.573, "duration": 1.917}, {"text": "that's a more general\nkind of transport law.", "start": 3670.49, "duration": 2.73}, {"text": "It seems to describe physically\na very similar situation here.", "start": 3673.22, "duration": 3.75}, {"text": "It's kind of annoying that\nthis normalization is changing.", "start": 3676.97, "duration": 3.03}, {"text": "Is there anything\ngoing on with this?", "start": 3680.0, "duration": 2.94}, {"text": "Well what you guys are going\nto do as a homework exercise,", "start": 3682.94, "duration": 6.99}, {"text": "you're going to\nprove that if this", "start": 3689.93, "duration": 2.595}, {"text": "is the situation\nyou're in, you've", "start": 3692.525, "duration": 1.785}, {"text": "chosen a dumb parameterization.", "start": 3694.31, "duration": 1.83}, {"text": "And you can actually\nconvert this", "start": 3696.14, "duration": 2.64}, {"text": "to the normal geodesic\nparameterization", "start": 3698.78, "duration": 2.28}, {"text": "by just relabeling your lambda.", "start": 3701.06, "duration": 2.46}, {"text": "So we can always\nreparameterize this, such", "start": 3711.31, "duration": 8.6}, {"text": "that the right-hand side is 0.", "start": 3719.91, "duration": 3.57}, {"text": "And right-hand side\nbeing 0 corresponds", "start": 3723.48, "duration": 1.98}, {"text": "to the transport vector\nremaining constant", "start": 3725.46, "duration": 2.55}, {"text": "as it moves along.", "start": 3728.01, "duration": 1.66}, {"text": "So I'll just quickly sketch--", "start": 3729.67, "duration": 1.4}, {"text": "so imagine there exists some\ndifferent parameterization,", "start": 3731.07, "duration": 6.98}, {"text": "which I will call lambda.", "start": 3738.05, "duration": 1.74}, {"text": "So imagine something that gives\nme my normal parallel transport", "start": 3749.03, "duration": 3.45}, {"text": "exists.", "start": 3752.48, "duration": 2.7}, {"text": "And I have a different one that\ninvolves the star parameter.", "start": 3755.18, "duration": 5.79}, {"text": "You can actually show that these\ntwo things describe exactly", "start": 3760.97, "duration": 2.73}, {"text": "the same motion, but with lambda\nand the dumb parameterization,", "start": 3763.7, "duration": 6.93}, {"text": "lambda star, related to each\nother by a particular integral.", "start": 3770.63, "duration": 5.46}, {"text": "So what this shows\nus is we can always--", "start": 3784.68, "duration": 3.14}, {"text": "as long as I'm talking about\nmotion where I'm in this", "start": 3787.82, "duration": 2.58}, {"text": "regime-- where there's\nno forces acting--", "start": 3790.4, "duration": 1.86}, {"text": "it's not an extended body--\nit's just a test body--", "start": 3792.26, "duration": 2.25}, {"text": "I can always put\nit into a regime", "start": 3794.51, "duration": 2.047}, {"text": "where it'll [INAUDIBLE]\ngeodesic and the right-hand side", "start": 3796.557, "duration": 2.333}, {"text": "is equal to 0.", "start": 3798.89, "duration": 1.14}, {"text": "If I'm finding\nthat's not the case,", "start": 3800.03, "duration": 1.83}, {"text": "I need to adjust my\nparameterization.", "start": 3801.86, "duration": 3.96}, {"text": "When you are, in fact,\nin a prioritization", "start": 3805.82, "duration": 2.73}, {"text": "such as the\nright-hand side is 0,", "start": 3808.55, "duration": 5.1}, {"text": "you are using what is called\nan affine parameterization.", "start": 3813.65, "duration": 3.172}, {"text": "That's a name that's\nworth knowing about.", "start": 3816.822, "duration": 1.708}, {"text": "So your intuition is that\nthe affine parameterization--", "start": 3837.55, "duration": 4.36}, {"text": "I described this\nin words last time.", "start": 3841.91, "duration": 1.5}, {"text": "And this just helps to make it\na little bit more mathematically", "start": 3843.41, "duration": 2.625}, {"text": "precise what those words mean.", "start": 3846.035, "duration": 1.405}, {"text": "Affine parameters\ncorrespond to the tick marks", "start": 3857.21, "duration": 8.13}, {"text": "on the world line,\nbeing uniformly spaced", "start": 3865.34, "duration": 12.725}, {"text": "in the local Lorentz frame.", "start": 3878.065, "duration": 1.125}, {"text": "If you are working with\ntime-like trajectories--", "start": 3885.55, "duration": 2.12}, {"text": "which if you're a physicist,\nyou will be much of the time--", "start": 3887.67, "duration": 3.75}, {"text": "a really good choice\nof the affine parameter", "start": 3891.42, "duration": 2.61}, {"text": "is the proper time of a body\nmoving through the spacetime.", "start": 3894.03, "duration": 3.99}, {"text": "That is something that\nis uniformly spaced,", "start": 3898.02, "duration": 3.03}, {"text": "assuming that's--", "start": 3901.05, "duration": 0.96}, {"text": "you don't have to\nassume anything.", "start": 3902.01, "duration": 1.02}, {"text": "Just by definition\nit's the thing", "start": 3903.03, "duration": 1.375}, {"text": "that uniformly measures\nthe time as experienced", "start": 3904.405, "duration": 2.675}, {"text": "by that observer.", "start": 3907.08, "duration": 0.915}, {"text": "So this is-- you guys are\ngoing to do on PSET 4--", "start": 3951.13, "duration": 3.0}, {"text": "this is the exercise you\nneed to do to convert", "start": 3954.13, "duration": 2.01}, {"text": "a nonaffine\nparameterized geodesic", "start": 3956.14, "duration": 2.22}, {"text": "to an affine parameterized one.", "start": 3958.36, "duration": 2.91}, {"text": "That kind of\nparameterization is not", "start": 3961.27, "duration": 1.83}, {"text": "too hard to show that if we\nadjust the parameterization", "start": 3963.1, "duration": 6.86}, {"text": "in a linear fashion--", "start": 3969.96, "duration": 0.96}, {"text": "so in other words, let's say I\ngo from lambda to some lambda", "start": 3980.58, "duration": 4.58}, {"text": "prime, which is equal\nto a lambda plus b,", "start": 3985.16, "duration": 4.06}, {"text": "where and b are both constants--", "start": 3989.22, "duration": 2.48}, {"text": "we get a new affine\nparameterization.", "start": 3997.45, "duration": 2.745}, {"text": "But that's the only class\nof reparamterizations", "start": 4003.45, "duration": 2.06}, {"text": "that allows me to do that.", "start": 4005.51, "duration": 1.083}, {"text": "And hopefully that makes sense.", "start": 4009.288, "duration": 1.292}, {"text": "If you imagine that\nyou're using proper time", "start": 4010.58, "duration": 2.52}, {"text": "as your reparameterization,\nthis is basically", "start": 4013.1, "duration": 2.34}, {"text": "saying that you just chose\na different origin for when", "start": 4015.44, "duration": 2.25}, {"text": "you started your clock.", "start": 4017.69, "duration": 0.958}, {"text": "And this means you changed\nthe units in which you", "start": 4018.648, "duration": 2.042}, {"text": "are measuring time.", "start": 4020.69, "duration": 0.87}, {"text": "That's all.", "start": 4021.56, "duration": 0.5}, {"text": "So I'm going to skip a\nbunch of the details.", "start": 4028.21, "duration": 3.57}, {"text": "But I'm going to scan\nand put up the notes", "start": 4031.78, "duration": 2.16}, {"text": "corresponding to one\nother route to getting", "start": 4033.94, "duration": 2.64}, {"text": "to the geodesic equation, which\nI think it's definitely worth", "start": 4036.58, "duration": 3.647}, {"text": "knowing about.", "start": 4040.227, "duration": 0.583}, {"text": "It connects very nicely to other\nwork in classical mechanics.", "start": 4048.88, "duration": 7.448}, {"text": "So it's a bit of a shame we're\ngoing to need to skip over it.", "start": 4056.328, "duration": 2.542}, {"text": "But we're a little\nbit behind pace.", "start": 4058.87, "duration": 2.16}, {"text": "And this is\nstraightforward enough", "start": 4061.03, "duration": 1.56}, {"text": "that I feel OK posting the\nnotes that you can read it.", "start": 4062.59, "duration": 3.36}, {"text": "So there is a second\npath to geodesics.", "start": 4065.95, "duration": 4.96}, {"text": "So recall the way that we\nargued how to get the geodesic", "start": 4076.04, "duration": 3.34}, {"text": "equation, which we\nsaid we're going to go", "start": 4079.38, "duration": 2.825}, {"text": "into-- it's actually in\nthe board right above where", "start": 4082.205, "duration": 2.125}, {"text": "I'm writing right now--", "start": 4084.33, "duration": 1.08}, {"text": "go into the\nfreely-falling frame.", "start": 4085.41, "duration": 1.71}, {"text": "I have a body that isn't\ncoupling to anything", "start": 4087.12, "duration": 1.95}, {"text": "but gravity.", "start": 4089.07, "duration": 1.2}, {"text": "Therefore in the\nfreely-falling frame,", "start": 4090.27, "duration": 1.6}, {"text": "it just maintains its momentum.", "start": 4091.87, "duration": 1.4}, {"text": "It's going to go\nin a straight line.", "start": 4093.27, "duration": 1.92}, {"text": "Straight means parallel\ntransporting tangent vector--", "start": 4095.19, "duration": 2.4}, {"text": "math, math, math-- and\nthat's how we get all that.", "start": 4097.59, "duration": 3.24}, {"text": "So what this boiled\ndown to is I was", "start": 4100.83, "duration": 1.739}, {"text": "trying to make rigorous in a\ngeometric sense what straight", "start": 4102.569, "duration": 3.54}, {"text": "meant.", "start": 4106.109, "duration": 2.511}, {"text": "There's another\nnotion of straight", "start": 4108.62, "duration": 1.602}, {"text": "that one can imagine\napplying when you're", "start": 4110.222, "duration": 1.708}, {"text": "working in a curved space.", "start": 4111.93, "duration": 1.083}, {"text": "So your intuition for--", "start": 4115.85, "duration": 1.89}, {"text": "if you're talking about how\ndo I make a straight line", "start": 4117.74, "duration": 2.789}, {"text": "between two points on a globe--", "start": 4120.529, "duration": 2.431}, {"text": "your intuition is you say,\noh, well the straightest line", "start": 4122.96, "duration": 2.729}, {"text": "that I can make is the\npath that is shortest.", "start": 4125.689, "duration": 2.641}, {"text": "We're going to\nformulate-- and I'll", "start": 4159.29, "duration": 2.17}, {"text": "leave the details\nand the calculation", "start": 4161.46, "duration": 1.705}, {"text": "to the notes-- we're\ngoing to formulate", "start": 4163.165, "duration": 1.625}, {"text": "how one can apply\na similar thing", "start": 4164.79, "duration": 2.13}, {"text": "to the notion of geodesics.", "start": 4166.92, "duration": 1.68}, {"text": "So imagine I've got an event\np here and event q up here.", "start": 4168.6, "duration": 8.16}, {"text": "And I ask myself, what is\nthe accumulated proper time", "start": 4176.76, "duration": 6.99}, {"text": "experienced by all\npossible paths that take me", "start": 4183.75, "duration": 5.189}, {"text": "from event p to event q?", "start": 4188.939, "duration": 1.429}, {"text": "I'm going to need\nto restrict myself.", "start": 4190.368, "duration": 1.542}, {"text": "I want it to be something that\nan observer can physically", "start": 4191.91, "duration": 2.375}, {"text": "ride-- so all the\ntime-like trajectories that", "start": 4194.285, "duration": 2.445}, {"text": "connect event p to event q.", "start": 4196.73, "duration": 2.32}, {"text": "So I've got one a path\nthat goes like this,", "start": 4199.05, "duration": 2.61}, {"text": "got a path that goes like this,\npath that goes like this, path", "start": 4201.66, "duration": 3.075}, {"text": "goes like this, path\ngoes like-- some of them", "start": 4204.735, "duration": 1.875}, {"text": "might have just become\nsomewhat space like,", "start": 4206.61, "duration": 1.66}, {"text": "so I should rule them out.", "start": 4208.27, "duration": 1.19}, {"text": "But you get the idea.", "start": 4209.46, "duration": 0.92}, {"text": "Imagine I take all the\npossible time-like paths", "start": 4210.38, "duration": 2.5}, {"text": "that connect p and q.", "start": 4212.88, "duration": 1.35}, {"text": "Some of those paths will\ninvolve strong accelerations.", "start": 4218.01, "duration": 4.59}, {"text": "So they will not be\nthe freefall path.", "start": 4222.6, "duration": 3.09}, {"text": "Among them there will be\none that corresponds exactly", "start": 4225.69, "duration": 2.57}, {"text": "to freefall.", "start": 4228.26, "duration": 0.5}, {"text": "So if I were talking about--\nimagine I was trying to--", "start": 4243.29, "duration": 2.25}, {"text": "and this is something that\nMuslim astronomers worked out", "start": 4245.54, "duration": 3.02}, {"text": "long, long ago-- they wanted\nto know the shortest path", "start": 4248.56, "duration": 2.25}, {"text": "from some point on\nearth towards Mecca.", "start": 4250.81, "duration": 2.85}, {"text": "And so you need to find what\nthe shortest distance was", "start": 4253.66, "duration": 3.02}, {"text": "for something like that.", "start": 4256.68, "duration": 1.0}, {"text": "And when you're doing this\non the surface of a sphere,", "start": 4257.68, "duration": 2.61}, {"text": "that's complicated.", "start": 4260.29, "duration": 1.847}, {"text": "And that's where the\nqibla arose from,", "start": 4262.137, "duration": 1.583}, {"text": "was working out the mathematics\nto know how to do this.", "start": 4263.72, "duration": 2.49}, {"text": "This is a similar\nkind of concept.", "start": 4266.21, "duration": 1.52}, {"text": "I'm trying to define--", "start": 4267.73, "duration": 2.13}, {"text": "in this case, it's going to turn\nout it's not the shortest path,", "start": 4269.86, "duration": 3.88}, {"text": "but it's the path on which an\nobserver ages the most because", "start": 4273.74, "duration": 3.86}, {"text": "as soon as you\naccelerate someone--", "start": 4277.6, "duration": 1.8}, {"text": "it's not hard.", "start": 4279.4, "duration": 0.6}, {"text": "Go back to some of\nthose problem sets", "start": 4280.0, "duration": 1.542}, {"text": "you guys did where you look\nat accelerated observers.", "start": 4281.542, "duration": 2.298}, {"text": "Acceleration tends to decrease\nthe amount of aging you have", "start": 4283.84, "duration": 2.88}, {"text": "as you move through some\ninterval of spacetime.", "start": 4286.72, "duration": 2.65}, {"text": "So the path that has\nno acceleration on it,", "start": 4289.37, "duration": 4.55}, {"text": "this is going to be the one on\nwhich an observer is maximally", "start": 4293.92, "duration": 2.56}, {"text": "aged.", "start": 4296.48, "duration": 0.5}, {"text": "Why maximum instead\nof a minimum?", "start": 4307.065, "duration": 1.375}, {"text": "Well it comes down to\nthe bloody minus sign", "start": 4308.44, "duration": 2.37}, {"text": "that enters into the\ntimepiece of an interval", "start": 4310.81, "duration": 2.97}, {"text": "that we have in relativity.", "start": 4313.78, "duration": 1.272}, {"text": "And that's all I'll\nsay about that,", "start": 4315.052, "duration": 1.458}, {"text": "is just boils down to that.", "start": 4316.51, "duration": 2.46}, {"text": "So what we want to do\nis say, well along all", "start": 4318.97, "duration": 4.38}, {"text": "of these trajectories,\nthe amount", "start": 4323.35, "duration": 3.03}, {"text": "of proper time that's\naccumulated-- so let's", "start": 4326.38, "duration": 3.268}, {"text": "just say that every one\nof these is parameterized", "start": 4329.648, "duration": 2.042}, {"text": "by some lambda that describes\nthe motion along these things.", "start": 4331.69, "duration": 3.75}, {"text": "This is the amount\nof proper time", "start": 4354.48, "duration": 1.41}, {"text": "that someone accumulates\nas they move from point p--", "start": 4355.89, "duration": 3.51}, {"text": "which is at-- let's say this\nis defined as lambda equals 0--", "start": 4359.4, "duration": 3.288}, {"text": "and it's indeterminate what\nthat top lambda is actually", "start": 4362.688, "duration": 2.292}, {"text": "going to be.", "start": 4364.98, "duration": 0.5}, {"text": "It's whatever it takes when\nyou get up to lambda of q.", "start": 4365.48, "duration": 2.38}, {"text": "So what the notes\nI'm going to post do,", "start": 4373.82, "duration": 4.2}, {"text": "is they define an\naction principle that", "start": 4378.02, "duration": 3.51}, {"text": "can be applied to understand\nwhat the trajectory is", "start": 4381.53, "duration": 3.915}, {"text": "that allows you to do this.", "start": 4385.445, "duration": 1.125}, {"text": "So I'll just hit the highlights.", "start": 4403.79, "duration": 1.97}, {"text": "So in notes to be posted,\nI show that this delta t--", "start": 4405.76, "duration": 11.3}, {"text": "this delta tau rather--", "start": 4417.06, "duration": 1.09}, {"text": "this can be used to\ndefine an action.", "start": 4423.41, "duration": 2.17}, {"text": "It looks like this.", "start": 4451.6, "duration": 0.81}, {"text": "And then if you\nvary the action--", "start": 4457.37, "duration": 2.45}, {"text": "or rather you do a variation\nof your trajectory--", "start": 4466.97, "duration": 2.79}, {"text": "where you require that the\naction remain stationary under", "start": 4469.76, "duration": 3.87}, {"text": "that variation-- in other words\nI require delta i equals 0 as x", "start": 4473.63, "duration": 8.98}, {"text": "goes over to such--", "start": 4482.61, "duration": 0.81}, {"text": "so-- what you wind up with--", "start": 4497.82, "duration": 11.02}, {"text": "is delta i equals--", "start": 4520.87, "duration": 4.845}, {"text": "Notice what I've got in here.", "start": 4570.04, "duration": 4.3}, {"text": "This is just a\nChristoffel symbol.", "start": 4574.34, "duration": 1.45}, {"text": "So when I do this\nvariation, what I find--", "start": 4581.29, "duration": 4.425}, {"text": "and by the way going from\nessentially that board", "start": 4585.715, "duration": 3.235}, {"text": "to that board, it's about\n2/3 a page of algebra.", "start": 4588.95, "duration": 4.13}, {"text": "Going down to this\none, there's a bunch", "start": 4593.08, "duration": 1.77}, {"text": "of straightforward but\nfairly tedious stuff.", "start": 4594.85, "duration": 1.833}, {"text": "It's one reasons why I'm\nskipping over the details.", "start": 4596.683, "duration": 2.302}, {"text": "We've got enough G\nmu nus on the board.", "start": 4598.985, "duration": 1.625}, {"text": "So the key point is I am going\nto require that my action be", "start": 4620.72, "duration": 7.53}, {"text": "stationary, independent of\nthe nature of the variation", "start": 4628.25, "duration": 3.6}, {"text": "that I make.", "start": 4631.85, "duration": 1.3}, {"text": "For that to be true,\nthe quantity in braces", "start": 4633.15, "duration": 2.96}, {"text": "here must be equal to 0.", "start": 4636.11, "duration": 3.947}, {"text": "Let me just write\nthat down over here.", "start": 4640.057, "duration": 1.583}, {"text": "This is a good place to\nconclude today's lecture.", "start": 4641.64, "duration": 2.042}, {"text": "So we require this to\nbe 0 for any variation.", "start": 4662.63, "duration": 2.76}, {"text": "Yet the bracketed term\nbeing equal to 0, pull that", "start": 4673.04, "duration": 6.98}, {"text": "out, and clear out that factor\nof the metric with an inverse,", "start": 4680.02, "duration": 7.37}, {"text": "you've got your\ngeodesic equation back.", "start": 4687.39, "duration": 2.47}, {"text": "So we just quickly wrap this up.", "start": 4689.86, "duration": 1.73}, {"text": "So it's worth looking\nover these notes.", "start": 4691.59, "duration": 3.49}, {"text": "It's not worth going\nthrough them in gory detail", "start": 4695.08, "duration": 2.0}, {"text": "on the board, which\nis why I'm skipping", "start": 4697.08, "duration": 1.625}, {"text": "a few pages of these things.", "start": 4698.705, "duration": 1.315}, {"text": "But what this demonstrates\nis that geodesics--", "start": 4700.02, "duration": 3.48}, {"text": "our original\ndefinition is that they", "start": 4708.07, "duration": 1.71}, {"text": "carry the notion of a straight\nline in a straightforward way", "start": 4709.78, "duration": 3.6}, {"text": "from where they are obvious\nin a locally Lorentz frame", "start": 4713.38, "duration": 6.09}, {"text": "to a more covariant\nformulation of that--", "start": 4719.47, "duration": 1.77}, {"text": "so a generalized straight\nline to a curved spacetime.", "start": 4728.17, "duration": 7.0}, {"text": "And they give the trajectory of\nextremal aging in other words", "start": 4735.17, "duration": 13.33}, {"text": "a trajectory along which\nbetween two points in spacetime,", "start": 4748.5, "duration": 4.35}, {"text": "an observer moving from\none to the other will", "start": 4752.85, "duration": 2.67}, {"text": "accumulate the most proper time.", "start": 4755.52, "duration": 1.54}, {"text": "So I'm going to stop here.", "start": 4760.35, "duration": 6.03}, {"text": "There's a bit more,\nwhich I would like to do,", "start": 4766.38, "duration": 2.368}, {"text": "but I just don't have the time.", "start": 4768.748, "duration": 1.292}, {"text": "But I'll tell you the key\nthings that I want to say next.", "start": 4770.04, "duration": 3.9}, {"text": "Everything that I've\ndone here so far", "start": 4773.94, "duration": 3.12}, {"text": "is I've really fixated on\ntime-like trajectories.", "start": 4777.06, "duration": 4.307}, {"text": "I've imagined there's a\nbody with some finite rest", "start": 4781.367, "duration": 2.083}, {"text": "mass where I can make a\nsensible notion of proper time.", "start": 4783.45, "duration": 4.05}, {"text": "We are also going\nto want to talk", "start": 4787.5, "duration": 1.5}, {"text": "about the behavior of light.", "start": 4789.0, "duration": 1.75}, {"text": "Light moves on\nnull trajectories.", "start": 4790.75, "duration": 2.84}, {"text": "I cannot sensibly define proper\ntime on long such a trajectory.", "start": 4793.59, "duration": 5.07}, {"text": "They are massless.", "start": 4798.66, "duration": 0.84}, {"text": "There's all sorts of\nproperties associated with them", "start": 4799.5, "duration": 2.167}, {"text": "that just make this analysis.", "start": 4801.667, "duration": 1.583}, {"text": "The way I've done\nit so far, I'll", "start": 4803.25, "duration": 2.01}, {"text": "need to tweak things a little\nbit in order for it to work.", "start": 4805.26, "duration": 2.928}, {"text": "We will do that tweaking.", "start": 4808.188, "duration": 1.042}, {"text": "It's actually quite\nstraightforward", "start": 4809.23, "duration": 2.06}, {"text": "and allows us to also bring\nin a bit more intuition", "start": 4811.29, "duration": 2.82}, {"text": "about what affine parameters\nmean when we do that.", "start": 4814.11, "duration": 2.1}, {"text": "So that'll be the\none thing we do.", "start": 4816.21, "duration": 1.47}, {"text": "The other-- it's unfortunate\nI wasn't able to get to it", "start": 4817.68, "duration": 2.1}, {"text": "today-- but it's a\nstraightforward saying,", "start": 4819.78, "duration": 1.84}, {"text": "which I think I may include\nin the notes that I post--", "start": 4821.62, "duration": 2.48}, {"text": "is including what happens,\nif your spacetime--", "start": 4824.1, "duration": 4.32}, {"text": "so if the metric you use to\ngenerate these Christoffels has", "start": 4828.42, "duration": 3.15}, {"text": "a Killing factor\nassociated with it,", "start": 4831.57, "duration": 2.29}, {"text": "you can combine\nKilling's equation", "start": 4833.86, "duration": 1.91}, {"text": "with the geodesic\nequation to prove", "start": 4835.77, "duration": 1.59}, {"text": "the existence of conserved\nquantities associated", "start": 4837.36, "duration": 3.21}, {"text": "with that motion.", "start": 4840.57, "duration": 0.773}, {"text": "And that's where\nwe start to begin", "start": 4841.343, "duration": 1.417}, {"text": "to see that if I\nhave a spacetime that", "start": 4842.76, "duration": 3.39}, {"text": "is independent of time, there's\na notion of conserved energy", "start": 4846.15, "duration": 2.7}, {"text": "associated with it.", "start": 4848.85, "duration": 1.17}, {"text": "So we will do that on Tuesday.", "start": 4850.02, "duration": 2.39}]
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+[{"text": "MARKUS KLUTE: Welcome back\nto 8.20, Special Relativity.", "start": 13.24, "duration": 3.34}, {"text": "So if there is a\ntime dilation effect", "start": 16.58, "duration": 2.87}, {"text": "due to gravitational\nfields, then there's", "start": 19.45, "duration": 3.03}, {"text": "also a redshift which is\nof gravitational fields.", "start": 22.48, "duration": 3.45}, {"text": "So a consequence\nof time dilation", "start": 25.93, "duration": 1.83}, {"text": "is a change in the\nlight frequency.", "start": 27.76, "duration": 2.31}, {"text": "And I asked you to estimate\nthe magnitude of this effect.", "start": 30.07, "duration": 3.72}, {"text": "And the example you want to\nuse is the one shown here.", "start": 33.79, "duration": 3.58}, {"text": "So you have a tower just--", "start": 37.37, "duration": 2.65}, {"text": "not randomly, but 22\nand 1/2 meters tall.", "start": 40.02, "duration": 3.78}, {"text": "And a light beam is sent down.", "start": 43.8, "duration": 3.06}, {"text": "Basically, the tower is\nbuilt on this planet,", "start": 46.86, "duration": 2.16}, {"text": "and there's gravity\nthat's acting.", "start": 49.02, "duration": 3.09}, {"text": "So this is basically an\naccelerating reference frame.", "start": 52.11, "duration": 5.07}, {"text": "The length of the tower\nis, again, 22 meters.", "start": 57.18, "duration": 2.34}, {"text": "And I would like you\nto just get a feeling.", "start": 59.52, "duration": 2.46}, {"text": "How big can this effect be,\nthe effect of redshift here?", "start": 61.98, "duration": 4.54}, {"text": "So please, try to work this out.", "start": 66.52, "duration": 3.23}, {"text": "The way to think about\nthis is first to say, OK,", "start": 69.75, "duration": 2.82}, {"text": "now the light--", "start": 72.57, "duration": 1.455}, {"text": "the delta t equals\nthe light to travel--", "start": 74.025, "duration": 2.985}, {"text": "is l divided by c.", "start": 77.01, "duration": 1.57}, {"text": "The speed of light is c.", "start": 78.58, "duration": 1.31}, {"text": "The length is l.", "start": 79.89, "duration": 1.74}, {"text": "The change in velocity\nis g, acceleration,", "start": 81.63, "duration": 4.95}, {"text": "times l divided by c.", "start": 86.58, "duration": 2.49}, {"text": "So the Doppler shift then is the\nfrequency, the new frequency,", "start": 89.07, "duration": 3.39}, {"text": "divided by the\ninitial frequency.", "start": 92.46, "duration": 2.52}, {"text": "And that can be approximated\nby 1 plus delta v over c.", "start": 94.98, "duration": 5.31}, {"text": "So we find that it's 1 plus\ng times l over c square.", "start": 100.29, "duration": 4.23}, {"text": "Now the speed of\nlight is pretty fast,", "start": 104.52, "duration": 3.36}, {"text": "3 times 10 to the\n9 meter per second.", "start": 107.88, "duration": 3.99}, {"text": "And this distance is\nonly 22 and 1/2 meters.", "start": 111.87, "duration": 3.27}, {"text": "So we find that this is a\ntiny, tiny, tiny effect.", "start": 115.14, "duration": 3.12}, {"text": "But nevertheless,\nexperimentalists at Harvard", "start": 118.26, "duration": 6.47}, {"text": "tested this effect.", "start": 124.73, "duration": 1.05}, {"text": "So Pound, Rebka, and Snider\nin the 1950s and '60s", "start": 125.78, "duration": 5.13}, {"text": "were able to show\nthis very tiny effect.", "start": 130.91, "duration": 4.65}, {"text": "You want to know\nmore about this,", "start": 135.56, "duration": 1.78}, {"text": "you can, for example, look up a\nsmall description in Wikipedia", "start": 137.34, "duration": 3.71}, {"text": "here.", "start": 141.05, "duration": 1.62}, {"text": "But there's quite\nsome literature", "start": 142.67, "duration": 2.19}, {"text": "on those experimental\ntests [INAUDIBLE]", "start": 144.86, "duration": 3.38}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.98}, {"text": "[RUSTLING]", "start": 1.98, "duration": 1.98}, {"text": "[CLICKING]", "start": 3.96, "duration": 2.97}, {"text": "MICHAEL SIPSER: Let's get\nback to space complexity.", "start": 24.76, "duration": 5.8}, {"text": "So just to review\nwhat we've been doing", "start": 30.56, "duration": 4.07}, {"text": "from last lecture, which\nfeels like a long time ago", "start": 34.63, "duration": 3.21}, {"text": "but it was only two\ndays ago, we were", "start": 37.84, "duration": 5.19}, {"text": "looking at those three\ntheorems, which all", "start": 43.03, "duration": 5.7}, {"text": "had basically the same proof.", "start": 48.73, "duration": 3.03}, {"text": "One was about the\nladder problem,", "start": 51.76, "duration": 3.45}, {"text": "where you're trying to see if\nyou can get from one string", "start": 55.21, "duration": 3.78}, {"text": "to another string changing\none symbol at a time.", "start": 58.99, "duration": 4.02}, {"text": "And all of the strings\nwere in the language", "start": 63.01, "duration": 3.06}, {"text": "of some finite automaton, or\nyou had some reasonable rule", "start": 66.07, "duration": 2.94}, {"text": "for saying which are the\nvalid strings, which are not.", "start": 69.01, "duration": 4.08}, {"text": "And then we built on that idea.", "start": 73.09, "duration": 3.57}, {"text": "We showed Savitch's\ntheorem, that", "start": 76.66, "duration": 1.77}, {"text": "going from any\nnondeterministic machine", "start": 78.43, "duration": 2.61}, {"text": "to a deterministic machine only\nsquares the amount of space.", "start": 81.04, "duration": 3.12}, {"text": "And then we finally\nproved that TQBF,", "start": 84.16, "duration": 7.05}, {"text": "this problem about\nquantified Boolean formulas,", "start": 91.21, "duration": 3.18}, {"text": "testing whether they are\ntrue, that that problem is", "start": 94.39, "duration": 3.0}, {"text": "complete for PSPACE.", "start": 97.39, "duration": 2.98}, {"text": "So we're going to build\noff of that last theorem", "start": 100.37, "duration": 2.72}, {"text": "today, and talk about one\nother complete problem,", "start": 103.09, "duration": 7.02}, {"text": "and also show a\nconnection between PSPACE", "start": 110.11, "duration": 4.62}, {"text": "and testing which side can\nwin in certain kinds of games.", "start": 114.73, "duration": 5.745}, {"text": "And then at the end of the\nlecture, the second half", "start": 124.3, "duration": 2.7}, {"text": "of the lecture, we'll\ntalk about diving deeper", "start": 127.0, "duration": 3.419}, {"text": "into space complexity.", "start": 130.419, "duration": 1.231}, {"text": "We're going to talk about a\ndifferent part of the parameter", "start": 131.65, "duration": 3.48}, {"text": "space where instead of\nlooking at polynomial space,", "start": 135.13, "duration": 2.627}, {"text": "we're going to talk about\nwhat happens if you have", "start": 137.757, "duration": 2.083}, {"text": "logarithmic space, which is\nanother natural point to look", "start": 139.84, "duration": 3.96}, {"text": "at for space complexity.", "start": 143.8, "duration": 2.76}, {"text": "But we'll get to\nthat after the break.", "start": 146.56, "duration": 2.73}, {"text": "Talk about game\ncomplexity and games--", "start": 153.07, "duration": 3.84}, {"text": "so when I was little, we used\nto play, me and my sisters,", "start": 156.91, "duration": 5.19}, {"text": "would play a game\ncalled Geography.", "start": 162.1, "duration": 1.92}, {"text": "I don't know how many\nof you have heard it", "start": 164.02, "duration": 1.98}, {"text": "or maybe it goes under\na different name.", "start": 166.0, "duration": 3.33}, {"text": "But it was a game basically\nabout words and places.", "start": 169.33, "duration": 4.92}, {"text": "And it has a very\nsimple set of rules.", "start": 174.25, "duration": 3.9}, {"text": "Let's say there were two people.", "start": 178.15, "duration": 1.41}, {"text": "You take turns picking\nnames of places.", "start": 179.56, "duration": 3.3}, {"text": "And then each person has\nto pick a place which", "start": 185.91, "duration": 4.53}, {"text": "starts with the letter that the\nprevious person's place ended", "start": 190.44, "duration": 5.01}, {"text": "with.", "start": 195.45, "duration": 2.53}, {"text": "So for example, you\nhave two people playing.", "start": 197.98, "duration": 4.41}, {"text": "Perhaps you agree on\nsome starting place", "start": 202.39, "duration": 3.06}, {"text": "like a major city\nnearby, like Boston.", "start": 205.45, "duration": 3.45}, {"text": "So one player, the first\nplayer, picks Boston.", "start": 208.9, "duration": 3.48}, {"text": "And then after that,\nthe next player", "start": 212.38, "duration": 1.71}, {"text": "has to pick a place that starts\nwith N, because Boston ends", "start": 214.09, "duration": 4.74}, {"text": "with N. And so maybe\nNebraska would be", "start": 218.83, "duration": 4.97}, {"text": "a possible response to Boston.", "start": 223.8, "duration": 2.47}, {"text": "And then the first\nplayer would have", "start": 226.27, "duration": 1.55}, {"text": "to respond to that with a\nplace that starts with an A,", "start": 227.82, "duration": 2.52}, {"text": "because Nebraska\nends with an A, maybe", "start": 230.34, "duration": 2.22}, {"text": "Alaska, which also starts\nwith A, ends with A.", "start": 232.56, "duration": 4.78}, {"text": "So then Arkansas,\nmaybe, would be", "start": 237.34, "duration": 3.14}, {"text": "a reasonable response to that.", "start": 240.48, "duration": 1.99}, {"text": "And then that ends with\nS, so San Francisco,", "start": 242.47, "duration": 4.52}, {"text": "and then so on, and so on.", "start": 246.99, "duration": 2.22}, {"text": "And of course, you\nwant to forbid people", "start": 249.21, "duration": 5.07}, {"text": "from reusing names because then\nyou'll just get into a loop.", "start": 254.28, "duration": 4.739}, {"text": "Saying, \"Alaska,\"\n\"Alaska,\" \"Alaska,\"", "start": 259.019, "duration": 2.25}, {"text": "won't make the game\nvery interesting,", "start": 261.269, "duration": 1.801}, {"text": "so you have to forbid\nthat possibility.", "start": 263.07, "duration": 3.66}, {"text": "Names cannot be reused.", "start": 266.73, "duration": 1.51}, {"text": "They can be used at most once.", "start": 268.24, "duration": 1.88}, {"text": "And then, eventually,\none side or the other", "start": 270.12, "duration": 4.11}, {"text": "is going to run out of\nnames and not have--", "start": 274.23, "duration": 3.15}, {"text": "either because of the lack of\ntheir geographical knowledge", "start": 277.38, "duration": 3.42}, {"text": "or maybe you've just exhausted\nall the possibilities--", "start": 280.8, "duration": 2.52}, {"text": "and will not have\na good response.", "start": 283.32, "duration": 2.61}, {"text": "And that person will be stuck.", "start": 285.93, "duration": 1.47}, {"text": "And that person is the loser.", "start": 287.4, "duration": 1.92}, {"text": "The other person\nhas won the game.", "start": 289.32, "duration": 1.87}, {"text": "So the objective is to try\nto avoid getting stuck.", "start": 291.19, "duration": 3.03}, {"text": "So let's just take a look.", "start": 294.22, "duration": 1.97}, {"text": "I'm going to think about\nthat game in a slightly more", "start": 296.19, "duration": 4.14}, {"text": "abstracted, formalized way.", "start": 300.33, "duration": 2.46}, {"text": "So you write down all of\nthe legitimate places.", "start": 302.79, "duration": 2.91}, {"text": "They become nodes of a graph\nsuch as I've shown here.", "start": 305.7, "duration": 3.45}, {"text": "And then you draw an edge\nfrom one node to another", "start": 309.15, "duration": 4.71}, {"text": "if that corresponds to a legal\nmove in the game, a legal step", "start": 313.86, "duration": 7.09}, {"text": "of the game.", "start": 320.95, "duration": 0.58}, {"text": "So Boston connects to\nplaces that start with N,", "start": 321.53, "duration": 3.5}, {"text": "like New York and Nebraska.", "start": 325.03, "duration": 2.43}, {"text": "So the first person\nmight pick Boston.", "start": 327.46, "duration": 1.77}, {"text": "The second person might\npick either of these two,", "start": 329.23, "duration": 2.573}, {"text": "and then back to\nthe first person.", "start": 331.803, "duration": 1.417}, {"text": "If they picked Nebraska,\nthey could pick Arkansas.", "start": 333.22, "duration": 2.083}, {"text": "They can pick Alaska, and\nso on, just as I described.", "start": 335.303, "duration": 4.327}, {"text": "Believe it or not, we\nactually played this game.", "start": 339.63, "duration": 2.97}, {"text": "I can remember playing\nthis game when I was a kid.", "start": 342.6, "duration": 2.16}, {"text": "That was, of course, before\nwe had \"League of Legends\"", "start": 344.76, "duration": 5.58}, {"text": "and other fun stuff, but\nthis is what kids used to do.", "start": 350.34, "duration": 4.02}, {"text": "So anyway, just to get it down\non the slide, the rules are--", "start": 354.36, "duration": 9.85}, {"text": "assuming we have\ntwo players, we'll", "start": 364.21, "duration": 2.73}, {"text": "call them Player\nI and Player II.", "start": 366.94, "duration": 1.98}, {"text": "Player I goes first.", "start": 368.92, "duration": 2.34}, {"text": "And they take turns\npicking places", "start": 371.26, "duration": 1.71}, {"text": "that start with the letter\nwhich ended the previous place,", "start": 372.97, "duration": 3.36}, {"text": "no repeats allowed.", "start": 376.33, "duration": 1.32}, {"text": "And the first player stuck\nloses, the person who", "start": 377.65, "duration": 5.67}, {"text": "doesn't have a move to make.", "start": 383.32, "duration": 3.61}, {"text": "So what we're going\nto look at today", "start": 386.93, "duration": 2.57}, {"text": "is a generalized version\nof that, where we're just", "start": 389.5, "duration": 3.99}, {"text": "going to take away\nthe names, but just", "start": 393.49, "duration": 2.25}, {"text": "leave the underlying graph.", "start": 395.74, "duration": 2.62}, {"text": "And we call it going to call\nthat \"generalized geography.\"", "start": 398.36, "duration": 3.69}, {"text": "So here, that can be played\non any directed graph.", "start": 402.05, "duration": 3.51}, {"text": "You take away the\nnames of the nodes.", "start": 405.56, "duration": 3.6}, {"text": "Now you just have\nsome arbitrary graph.", "start": 409.16, "duration": 3.99}, {"text": "You're going to designate\na particular node", "start": 413.15, "duration": 1.86}, {"text": "as the starting node.", "start": 415.01, "duration": 1.23}, {"text": "And then the players take\nturns following those edges.", "start": 416.24, "duration": 3.435}, {"text": "And because you're going to\nforbid having any loops reusing", "start": 422.18, "duration": 7.62}, {"text": "any nodes, what you end up\ndoing is, working together,", "start": 429.8, "duration": 5.71}, {"text": "you're going to be constructing\na simple path in that graph.", "start": 435.51, "duration": 4.61}, {"text": "Simple path just\nfollows those edges", "start": 440.12, "duration": 2.67}, {"text": "and never intersects itself.", "start": 442.79, "duration": 3.99}, {"text": "And the first player to\nbe stuck is the loser.", "start": 446.78, "duration": 3.09}, {"text": "So the other one is the winner.", "start": 449.87, "duration": 1.86}, {"text": "So we're going to call that\n\"generalized geography.\"", "start": 451.73, "duration": 3.9}, {"text": "And we're going to look at\nthe computational complexity", "start": 455.63, "duration": 2.67}, {"text": "of deciding, for a\ngiven graph and starting", "start": 458.3, "duration": 2.7}, {"text": "point, which side would win if\nboth players played optimally,", "start": 461.0, "duration": 8.73}, {"text": "the best possible.", "start": 469.73, "duration": 1.96}, {"text": "And we'll name that\nproblem GG, or look", "start": 471.69, "duration": 3.47}, {"text": "at its associated language.", "start": 475.16, "duration": 1.6}, {"text": "So here is a graph\nand the starting node.", "start": 476.76, "duration": 3.41}, {"text": "And you want to say that\npair is in the language GG", "start": 480.17, "duration": 6.66}, {"text": "if the first player, Player I,\nwho must play at that node A", "start": 486.83, "duration": 6.39}, {"text": "to start off with\nhas a forced win", "start": 493.22, "duration": 6.04}, {"text": "in that generalized geography\ngame on that graph starting", "start": 499.26, "duration": 3.66}, {"text": "at A. Again, what I\nmean by a forced win--", "start": 502.92, "duration": 3.187}, {"text": "I'm not going to\ndefine this formally,", "start": 506.107, "duration": 1.583}, {"text": "though we could do that--", "start": 507.69, "duration": 1.05}, {"text": "it's not hard to do.", "start": 508.74, "duration": 1.08}, {"text": "But a forced win is also\ncalled a \"winning strategy.\"", "start": 509.82, "duration": 4.05}, {"text": "That just means that if\nboth sides play optimally,", "start": 513.87, "duration": 3.419}, {"text": "they play the best possible--", "start": 517.289, "duration": 2.431}, {"text": "not of their capability,\nI mean absolutely", "start": 519.72, "duration": 2.43}, {"text": "the best possible play--", "start": 522.15, "duration": 2.25}, {"text": "then that Player\nI would still win.", "start": 524.4, "duration": 5.49}, {"text": "There's nothing\nthat Player II can", "start": 529.89, "duration": 1.74}, {"text": "do to prevent Player\nI from winning", "start": 531.63, "duration": 3.75}, {"text": "if Player I has a winning\nstrategy or a forced win.", "start": 535.38, "duration": 3.75}, {"text": "You may have seen, for example--", "start": 539.13, "duration": 3.03}, {"text": "there are examples\nof this that--", "start": 542.16, "duration": 1.623}, {"text": "I mean, I don't even\nknow if they still exist,", "start": 543.783, "duration": 1.917}, {"text": "but it used to be\nin the newspaper.", "start": 545.7, "duration": 1.83}, {"text": "There used to be\nexamples of chess boards", "start": 547.53, "duration": 2.37}, {"text": "and they would start\nfrom a certain position.", "start": 549.9, "duration": 3.15}, {"text": "And they would say,\n\"White to win in three.\"", "start": 553.05, "duration": 2.85}, {"text": "And so that means\nwhite has a forced win.", "start": 555.9, "duration": 2.28}, {"text": "No matter what black does, white\nis going to end up winning.", "start": 558.18, "duration": 2.68}, {"text": "But you have to think\nof what the strategy is.", "start": 560.86, "duration": 1.917}, {"text": "It may not be so\nobvious to think", "start": 562.777, "duration": 1.463}, {"text": "through what are the right\nmoves that white makes.", "start": 564.24, "duration": 2.85}, {"text": "But the point is that no\nmatter what black would do,", "start": 567.09, "duration": 3.06}, {"text": "white would end up winning.", "start": 570.15, "duration": 2.52}, {"text": "And what you can show--", "start": 572.67, "duration": 1.26}, {"text": "we're not going to do that--\nbut for a class of games that", "start": 573.93, "duration": 3.84}, {"text": "includes this\ngeneralized geography,", "start": 577.77, "duration": 3.12}, {"text": "either one side or\nthe other is going", "start": 580.89, "duration": 2.49}, {"text": "to be guaranteed to\nhave a forced win.", "start": 583.38, "duration": 2.67}, {"text": "That's not necessarily true for\nall possible games, obviously,", "start": 586.05, "duration": 3.51}, {"text": "but for a large class of\ngames, one side or the other", "start": 589.56, "duration": 4.2}, {"text": "is guaranteed to have a winning\nstrategy or a forced win.", "start": 593.76, "duration": 5.73}, {"text": "So let's just review\nthat, because this", "start": 599.49, "duration": 1.68}, {"text": "is going to be essential for\nthe first half of the lecture--", "start": 601.17, "duration": 4.2}, {"text": "to understand what\nwe mean by a game", "start": 605.37, "duration": 2.35}, {"text": "and what we mean by one side or\nthe other to have a forced win.", "start": 607.72, "duration": 3.92}, {"text": "And what we're going to show\nis that GG is PSPACE complete,", "start": 614.37, "duration": 3.35}, {"text": "that the problem of\ngiven one of these graphs", "start": 617.72, "duration": 2.16}, {"text": "and a starting\npoint, figuring out", "start": 619.88, "duration": 2.25}, {"text": "does Player I have a forced\nwin or is it Player II that", "start": 622.13, "duration": 2.34}, {"text": "has a forced win?", "start": 624.47, "duration": 2.94}, {"text": "Which side is guaranteed\nto win under optimal play?", "start": 627.41, "duration": 3.09}, {"text": "That's a PSPACE\ncomplete problem.", "start": 630.5, "duration": 3.19}, {"text": "And so let's do a\nlittle checking on that.", "start": 633.69, "duration": 2.85}, {"text": "And so I'm going to give\nyou a very small example", "start": 636.54, "duration": 2.96}, {"text": "of a generalized geography game.", "start": 639.5, "duration": 1.77}, {"text": "You have to figure out whether\nit's Player I or Player II that", "start": 644.13, "duration": 3.93}, {"text": "has the forced win, the\nwinning strategy, or maybe", "start": 648.06, "duration": 3.39}, {"text": "neither, or both.", "start": 651.45, "duration": 1.35}, {"text": "Those are the four options.", "start": 652.8, "duration": 1.65}, {"text": "And you understand Player\nI has to play here,", "start": 654.45, "duration": 2.58}, {"text": "because that's\nthe starting place", "start": 657.03, "duration": 1.542}, {"text": "of this generalized\ngeography game.", "start": 658.572, "duration": 1.458}, {"text": "So then it's up to\nPlayer II to continue on.", "start": 660.03, "duration": 3.13}, {"text": "All right, so let's\nlaunch that poll.", "start": 663.16, "duration": 4.07}, {"text": "You'll have to think\nabout it a little bit,", "start": 667.23, "duration": 3.55}, {"text": "and let me know what you think.", "start": 670.78, "duration": 4.62}, {"text": "Which side has a forced win?", "start": 675.4, "duration": 3.92}, {"text": "Which player makes\nthe first move?", "start": 679.32, "duration": 1.53}, {"text": "It's Player I makes the first\nmove, and Player I plays,", "start": 680.85, "duration": 3.21}, {"text": "as I showed you here, this\nis Player I playing at A.", "start": 684.06, "duration": 3.96}, {"text": "So Player I picks A,\nand then Player II", "start": 688.02, "duration": 2.812}, {"text": "has to pick one of these two.", "start": 690.832, "duration": 1.208}, {"text": "All right, I think we're\nthe end of the poll.", "start": 696.43, "duration": 2.17}, {"text": "Everybody's in?", "start": 698.6, "duration": 1.67}, {"text": "Pick something.", "start": 700.27, "duration": 0.84}, {"text": "You guys did not do\nwell on this poll.", "start": 710.09, "duration": 4.8}, {"text": "At least not too\nmany of you picked", "start": 714.89, "duration": 2.01}, {"text": "D. That's a little\nreassuring because you", "start": 716.9, "duration": 4.2}, {"text": "can't have both players\nhaving a forced win.", "start": 721.1, "duration": 2.31}, {"text": "I did say that in games of this\nkind, one side or the other", "start": 723.41, "duration": 3.21}, {"text": "is going to have a\nforced win, so C is not", "start": 726.62, "duration": 2.04}, {"text": "a very good choice, either.", "start": 728.66, "duration": 2.34}, {"text": "So maybe you should spend\nless time reading your email", "start": 731.0, "duration": 3.745}, {"text": "and more time listening\nto the lecture.", "start": 734.745, "duration": 1.625}, {"text": "The actual correct answer is B.", "start": 740.73, "duration": 2.46}, {"text": "Player II, which obviously\nis a minority position here--", "start": 743.19, "duration": 4.89}, {"text": "Player II has the forced win.", "start": 748.08, "duration": 1.56}, {"text": "Let's understand why.", "start": 749.64, "duration": 2.25}, {"text": "So Player I plays here.", "start": 751.89, "duration": 3.63}, {"text": "As I said, that's\nthe first move.", "start": 755.52, "duration": 2.22}, {"text": "Player II can either take the\nupper node or the lower node.", "start": 757.74, "duration": 3.6}, {"text": "Player II takes the\nupper node, then", "start": 764.05, "duration": 2.55}, {"text": "Player I has no choice but\nto take the right-most node,", "start": 766.6, "duration": 4.26}, {"text": "and now there's no more\nmove for Player II.", "start": 770.86, "duration": 4.52}, {"text": "So Player II will lose if\nPlayer II takes the upper node,", "start": 775.38, "duration": 5.22}, {"text": "the upper choice there.", "start": 780.6, "duration": 1.74}, {"text": "Because Player II will go\nhere, Player I will go there,", "start": 782.34, "duration": 3.84}, {"text": "and it'll be game over.", "start": 786.18, "duration": 2.04}, {"text": "And Player I will have won\nbecause Player II was stuck.", "start": 788.22, "duration": 3.45}, {"text": "However, Player II\nhad another choice.", "start": 791.67, "duration": 2.64}, {"text": "Player II could have\nalso gone down here.", "start": 801.8, "duration": 3.91}, {"text": "So Player II, if it\nplayed down here,", "start": 805.71, "duration": 4.503}, {"text": "things are looking a lot\nbetter for Player II.", "start": 810.213, "duration": 1.917}, {"text": "If Player II goes here, Player\nI's move is forced, goes here.", "start": 812.13, "duration": 3.66}, {"text": "But now, there's another move\nleft that Player II could make.", "start": 815.79, "duration": 3.54}, {"text": "So Player II goes here, I goes\nthere, Player II goes up there.", "start": 819.33, "duration": 6.05}, {"text": "And now Player I is stuck.", "start": 825.38, "duration": 1.68}, {"text": "So it's Player II's\nchoice, Player II", "start": 827.06, "duration": 4.42}, {"text": "can make a move\nwhich will end up", "start": 831.48, "duration": 2.91}, {"text": "causing Player I to get\nstuck, because that's", "start": 834.39, "duration": 4.83}, {"text": "the nature of what we mean\nby having a winning strategy.", "start": 839.22, "duration": 2.73}, {"text": "There is some way to guarantee\nif you're playing optimally,", "start": 841.95, "duration": 3.175}, {"text": "and you're certainly\nplaying optimally,", "start": 845.125, "duration": 1.625}, {"text": "means you'll take\nthat lower move.", "start": 846.75, "duration": 3.45}, {"text": "Then you will take that.", "start": 850.2, "duration": 3.1}, {"text": "So under optimal play,\nPlayer II will win this game,", "start": 853.3, "duration": 6.69}, {"text": "and so Player II has\na winning strategy.", "start": 859.99, "duration": 2.1}, {"text": "It has a forced win.", "start": 862.09, "duration": 2.94}, {"text": "So I see.", "start": 865.03, "duration": 1.02}, {"text": "So I'm not going to define\n\"playing optimally.\"", "start": 866.05, "duration": 4.49}, {"text": "There's some questions\nhere about that.", "start": 870.54, "duration": 3.66}, {"text": "I'm going to-- I'm going to\nleave it somewhat informal,", "start": 879.18, "duration": 7.35}, {"text": "but we could make\nthat all precise.", "start": 886.53, "duration": 2.31}, {"text": "I don't think it\nwould be clarifying", "start": 888.84, "duration": 2.13}, {"text": "to go through a precise\ndefinition of that.", "start": 890.97, "duration": 2.7}, {"text": "We don't even have\nto think about it", "start": 898.92, "duration": 1.56}, {"text": "in terms of optimal play.", "start": 900.48, "duration": 1.38}, {"text": "You can say that a\nplayer has a forced", "start": 901.86, "duration": 13.04}, {"text": "win if they have moves\nthat they could make", "start": 914.9, "duration": 5.07}, {"text": "in response to every possible\nmove the opponent could make", "start": 919.97, "duration": 4.4}, {"text": "that will guarantee that\nthey will end up winning.", "start": 924.37, "duration": 3.2}, {"text": "So you don't even have to\ntalk about optimality here.", "start": 927.57, "duration": 2.76}, {"text": "Just talk about every\npossible opponent.", "start": 930.33, "duration": 3.18}, {"text": "Every possible opponent\nis going to lose", "start": 933.51, "duration": 2.4}, {"text": "to somebody who has\na winning strategy", "start": 935.91, "duration": 7.96}, {"text": "and follows that strategy.", "start": 943.87, "duration": 1.47}, {"text": "I can see there was\nsome confusion about who", "start": 949.37, "duration": 2.13}, {"text": "was going first and so on.", "start": 951.5, "duration": 1.14}, {"text": "I'm glad.", "start": 952.64, "duration": 0.51}, {"text": "That was part of the reason\nI gave this check, just", "start": 953.15, "duration": 2.125}, {"text": "to hopefully to clear\nup some of those points.", "start": 955.275, "duration": 2.805}, {"text": "So Player I plays here\nthen Player II goes.", "start": 958.08, "duration": 3.83}, {"text": "And I got some comments\nthat some people", "start": 961.91, "duration": 2.01}, {"text": "were confused about\nwhat does it mean where", "start": 963.92, "duration": 5.22}, {"text": "does the first person move.", "start": 969.14, "duration": 1.95}, {"text": "Hopefully, that's clearer.", "start": 971.09, "duration": 3.84}, {"text": "All right, so let's\nmove on because we're", "start": 974.93, "duration": 2.67}, {"text": "going to be spending a\nwhile proving something", "start": 977.6, "duration": 4.77}, {"text": "about generalized\ngeography in these graphs.", "start": 982.37, "duration": 2.64}, {"text": "So let's continue.", "start": 988.42, "duration": 2.76}, {"text": "So in order to make the\nconnection between games", "start": 991.18, "duration": 6.22}, {"text": "and complexity,\nwe're going to need", "start": 997.4, "duration": 2.82}, {"text": "to talk about a problem,\none related to one", "start": 1000.22, "duration": 5.73}, {"text": "that we've already seen,\nwhere we can reformulate", "start": 1005.95, "duration": 2.58}, {"text": "that problem as a game.", "start": 1008.53, "duration": 1.87}, {"text": "And that's going to be a problem\non quantified Boolean formulas", "start": 1010.4, "duration": 3.51}, {"text": "called the \"Formula Game.\"", "start": 1013.91, "duration": 2.94}, {"text": "So this is a different game\nnow, not one that you're", "start": 1016.85, "duration": 5.0}, {"text": "likely to end up playing.", "start": 1021.85, "duration": 1.29}, {"text": "But in a sense in\nwhich you'll see,", "start": 1023.14, "duration": 3.179}, {"text": "this is still a reasonable\ngame where two players", "start": 1026.319, "duration": 2.881}, {"text": "can play against one another.", "start": 1029.2, "duration": 1.419}, {"text": "And one of them is going to\nend up winning and one of them", "start": 1030.619, "duration": 2.45}, {"text": "is going to end up having--", "start": 1033.069, "duration": 2.461}, {"text": "one or the other will\nhave a winning strategy.", "start": 1035.53, "duration": 2.92}, {"text": "So let's understand\nwhat the game is.", "start": 1038.45, "duration": 3.03}, {"text": "The game is played on a formula.", "start": 1041.48, "duration": 7.83}, {"text": "So you write down a\nquantified Boolean formula.", "start": 1049.31, "duration": 2.81}, {"text": "Remember, we talked about\nthat for several lectures now.", "start": 1052.12, "duration": 4.41}, {"text": "It's a bunch of quanti--\nvariables with quantifiers.", "start": 1056.53, "duration": 3.96}, {"text": "And then there's a part that\nhas no quantifiers, which", "start": 1060.49, "duration": 6.36}, {"text": "you can always put into\nconjunctive normal form", "start": 1066.85, "duration": 3.36}, {"text": "if you want.", "start": 1070.21, "duration": 0.55}, {"text": "But for the purposes of\nthis discussion so far,", "start": 1070.76, "duration": 2.93}, {"text": "it doesn't matter.", "start": 1073.69, "duration": 0.75}, {"text": "Later on, we'll actually\nwant it to be in CNF.", "start": 1074.44, "duration": 4.56}, {"text": "But for now, we just\nhave some formula.", "start": 1079.0, "duration": 4.85}, {"text": "And associated to\nthat formula there", "start": 1083.85, "duration": 3.27}, {"text": "is a game, in a\nvery natural sense.", "start": 1087.12, "duration": 2.08}, {"text": "So first of all, there are\ngoing to be two players.", "start": 1089.2, "duration": 3.33}, {"text": "But now the names\nof those players", "start": 1092.53, "duration": 1.52}, {"text": "are going to be Player\nExist and Player For All.", "start": 1094.05, "duration": 2.31}, {"text": "And this is how the game goes--", "start": 1100.8, "duration": 2.07}, {"text": "both players are going to be\npicking values for variables.", "start": 1108.63, "duration": 3.72}, {"text": "They're going to say variable x1\nis true, variable x2 is false,", "start": 1112.35, "duration": 5.49}, {"text": "variable x3 is false,\nvariable x4 is true.", "start": 1117.84, "duration": 3.45}, {"text": "And that's how the\nmoves of the game go.", "start": 1121.29, "duration": 4.59}, {"text": "They're just assigning values\nto variables so that in the end,", "start": 1125.88, "duration": 3.87}, {"text": "all of the variables have\nbeen assigned a Boolean value.", "start": 1129.75, "duration": 3.42}, {"text": "And so we end up\nwith an assignment.", "start": 1133.17, "duration": 1.95}, {"text": "But before we get to\nthat stage, which players", "start": 1135.12, "duration": 5.41}, {"text": "get to pick which variables?", "start": 1140.53, "duration": 2.58}, {"text": "And the way it works\nis the Exist player", "start": 1143.11, "duration": 2.22}, {"text": "is going to assign values\nto the Exist variables.", "start": 1145.33, "duration": 3.52}, {"text": "So Exist will pick x1 and\nx3 and assign them values.", "start": 1148.85, "duration": 5.57}, {"text": "The For All player is\ngoing to assign values", "start": 1154.42, "duration": 3.96}, {"text": "to the variables that have a\nFor All quantifier attached.", "start": 1158.38, "duration": 3.04}, {"text": "So in this case,\nthe For All player", "start": 1161.42, "duration": 6.56}, {"text": "will pick the value\nfor the x2 variable.", "start": 1167.98, "duration": 4.5}, {"text": "Fading out here.", "start": 1172.48, "duration": 0.84}, {"text": "And the order of\nplay is according", "start": 1179.36, "duration": 2.58}, {"text": "to the order of the\nappearance of the qualifiers", "start": 1181.94, "duration": 3.63}, {"text": "in the formula.", "start": 1185.57, "duration": 2.04}, {"text": "So the way I have it written\nout in this particular formula,", "start": 1187.61, "duration": 2.96}, {"text": "it's Exist x1--", "start": 1190.57, "duration": 1.26}, {"text": "so Exist will pick\nthe value for x1.", "start": 1191.83, "duration": 2.79}, {"text": "Then For All's turn.", "start": 1194.62, "duration": 1.5}, {"text": "For All will pick\nthe value of x2.", "start": 1196.12, "duration": 2.13}, {"text": "Then it's going to be Exist\npicking the value for x3,", "start": 1198.25, "duration": 5.56}, {"text": "and so on, until they get to the\nend, and all of the variables", "start": 1203.81, "duration": 4.05}, {"text": "have been assigned to value\nby one side or the other.", "start": 1207.86, "duration": 3.81}, {"text": "And now the game is over.", "start": 1211.67, "duration": 3.74}, {"text": "So what's left is to understand\nwho has won at that point.", "start": 1215.41, "duration": 8.505}, {"text": "And the way we say who has won\nis Exist wins if in the end,", "start": 1226.98, "duration": 10.25}, {"text": "this part psi, which is the\npart without quantifiers,", "start": 1237.23, "duration": 4.23}, {"text": "ended up being satisfied\nby that assignment", "start": 1241.46, "duration": 5.31}, {"text": "that the two players\ntogether ended up picking.", "start": 1246.77, "duration": 3.39}, {"text": "And then For All will win\nif that part of the formula", "start": 1250.16, "duration": 6.81}, {"text": "is not satisfied.", "start": 1256.97, "duration": 1.8}, {"text": "So let me just write\nthat down here.", "start": 1258.77, "duration": 1.5}, {"text": "After the variables have\nbeen assigned values,", "start": 1260.27, "duration": 2.19}, {"text": "we determine the winner.", "start": 1262.46, "duration": 1.44}, {"text": "Exist wins if the assignment\nthat built cooperatively", "start": 1263.9, "duration": 5.07}, {"text": "together satisfied psi,\nand otherwise For All,", "start": 1268.97, "duration": 4.77}, {"text": "if it doesn't satisfy psi.", "start": 1273.74, "duration": 2.87}, {"text": "So think about it this way--", "start": 1276.61, "duration": 3.18}, {"text": "Exist is picking the\nvalues of those variables.", "start": 1279.79, "duration": 2.58}, {"text": "He's trying to make this part\nof the formula satisfied,", "start": 1282.37, "duration": 5.91}, {"text": "trying to satisfy this\npart of the formula.", "start": 1288.28, "duration": 1.89}, {"text": "For All is picking\nvalues, but she's", "start": 1290.17, "duration": 3.51}, {"text": "trying to make this part\nof the formula unsatisfied.", "start": 1293.68, "duration": 3.21}, {"text": "So they're in opposition\nto one another.", "start": 1296.89, "duration": 5.2}, {"text": "And in the end, one of them\nis going to have succeeded", "start": 1302.09, "duration": 4.64}, {"text": "and the other one\nwill have failed.", "start": 1306.73, "duration": 2.7}, {"text": "And now, thinking\nabout it as a game,", "start": 1309.43, "duration": 3.0}, {"text": "depending upon the formula,\none side or the other", "start": 1312.43, "duration": 3.0}, {"text": "is going to have the ability\nto dominate the other one", "start": 1315.43, "duration": 2.76}, {"text": "and always win.", "start": 1318.19, "duration": 0.9}, {"text": "And so the question\nis, which side", "start": 1321.93, "duration": 4.43}, {"text": "has that ability to always win?", "start": 1326.36, "duration": 3.09}, {"text": "Which side has the\nwinning strategy?", "start": 1329.45, "duration": 2.522}, {"text": "Of course, it'll depend\nupon the formula.", "start": 1331.972, "duration": 1.708}, {"text": "Some formulas, it'll\nbe the Exist player", "start": 1333.68, "duration": 1.762}, {"text": "who has the winning strategy.", "start": 1335.442, "duration": 1.208}, {"text": "And other formulas, it\nwill be the For All player", "start": 1336.65, "duration": 2.042}, {"text": "who has the winning strategy.", "start": 1338.692, "duration": 1.318}, {"text": "And computationally, we'd like\nto make that determination.", "start": 1340.01, "duration": 3.25}, {"text": "Which side is going to\nwin for a given formula?", "start": 1343.26, "duration": 5.93}, {"text": "And there's a very, very\nnice, and actually very easy", "start": 1349.19, "duration": 5.19}, {"text": "and simple way to understand\nthat because we've already", "start": 1354.38, "duration": 3.58}, {"text": "run into that problem before.", "start": 1357.96, "duration": 2.7}, {"text": "The problem of determining\nwhich side has a forced win", "start": 1360.66, "duration": 4.02}, {"text": "is exactly the same\nthing as determining", "start": 1364.68, "duration": 1.98}, {"text": "whether this quantified\nBoolean formula is true", "start": 1366.66, "duration": 4.1}, {"text": "because the Exist player has a\nforced win when that formula--", "start": 1370.76, "duration": 5.1}, {"text": "let me say it again--", "start": 1381.46, "duration": 0.93}, {"text": "the Exist player has a forced\nwin when that formula is true.", "start": 1382.39, "duration": 2.94}, {"text": "So if this quantified Boolean\nformula were a true quantified", "start": 1388.57, "duration": 4.16}, {"text": "Boolean formula, then\nExist is guaranteed", "start": 1392.73, "duration": 2.76}, {"text": "to be able to win that game\nif it plays its hand right.", "start": 1395.49, "duration": 6.05}, {"text": "If this is a false\nformula, the For All player", "start": 1401.54, "duration": 3.75}, {"text": "will always be able to win\nif it plays its hand right.", "start": 1405.29, "duration": 5.47}, {"text": "So why is that?", "start": 1410.76, "duration": 2.22}, {"text": "It really follows kind of almost\nwithout doing any work at all.", "start": 1416.07, "duration": 5.89}, {"text": "This proof, even though\nit looks superficially", "start": 1421.96, "duration": 3.75}, {"text": "like it might be not\nso easy to prove,", "start": 1425.71, "duration": 2.79}, {"text": "it follows for a\nvery simple reason", "start": 1428.5, "duration": 2.19}, {"text": "because the meaning of what\nit means for Exist to have", "start": 1430.69, "duration": 5.52}, {"text": "a winning strategy is exactly\ncaptured by the semantics", "start": 1436.21, "duration": 4.32}, {"text": "of the quantifiers.", "start": 1440.53, "duration": 1.8}, {"text": "Let's see what that means.", "start": 1442.33, "duration": 1.36}, {"text": "What does it mean that\nExist has a forced", "start": 1443.69, "duration": 2.45}, {"text": "win, let's say up here?", "start": 1446.14, "duration": 4.28}, {"text": "That means that Exist has\na move that it could make,", "start": 1450.42, "duration": 3.91}, {"text": "that Exist can pick some value\nfor x1-- so there was some way", "start": 1454.33, "duration": 7.59}, {"text": "to assign x1 so that no\nmatter what the opponent does,", "start": 1461.92, "duration": 4.77}, {"text": "no matter what For\nAll does, there's", "start": 1466.69, "duration": 2.77}, {"text": "going to be a response\nthat Exist can make,", "start": 1469.46, "duration": 3.52}, {"text": "some assignment to x3, so that\nno matter what For All does,", "start": 1472.98, "duration": 7.345}, {"text": "there's going to\nbe an assignment", "start": 1480.325, "duration": 1.375}, {"text": "to the next variable,\nand so on and so on,", "start": 1481.7, "duration": 4.84}, {"text": "so that this thing\nends up being true.", "start": 1486.54, "duration": 2.137}, {"text": "So let me just say\nthat again somehow.", "start": 1488.677, "duration": 1.583}, {"text": "I didn't feel it\ncame out very clear.", "start": 1490.26, "duration": 2.3}, {"text": "So Exist has a winning\nstrategy exactly when", "start": 1492.56, "duration": 4.02}, {"text": "there is some assignment\nto x1 that Exist", "start": 1496.58, "duration": 2.49}, {"text": "can make such that no\nmatter what assignment", "start": 1499.07, "duration": 2.55}, {"text": "that For All makes to x2,\nthere is some assignment", "start": 1501.62, "duration": 3.57}, {"text": "x3 such that no matter what\nassignment that For All", "start": 1505.19, "duration": 4.59}, {"text": "makes to x4 and so on,\nmakes this thing true.", "start": 1509.78, "duration": 5.08}, {"text": "That's what it means for Exist\nto have a winning strategy.", "start": 1514.86, "duration": 4.17}, {"text": "That's exactly what\nthe quantifiers", "start": 1519.03, "duration": 2.04}, {"text": "are saying in the first place.", "start": 1521.07, "duration": 1.69}, {"text": "So even really without\ndoing anything,", "start": 1522.76, "duration": 2.51}, {"text": "you can see that \"Exist\nhas a winning strategy\"", "start": 1525.27, "duration": 3.51}, {"text": "means exactly the same thing\nas the quantified Boolean", "start": 1528.78, "duration": 3.63}, {"text": "formula being true.", "start": 1532.41, "duration": 1.6}, {"text": "So making the test of which\nside has a winning strategy", "start": 1534.01, "duration": 5.0}, {"text": "is the same as testing\nwhether the formula is true.", "start": 1539.01, "duration": 2.34}, {"text": "So let me try to\nturn to the chat", "start": 1545.55, "duration": 2.97}, {"text": "before we move on\nto anything else.", "start": 1548.52, "duration": 1.92}, {"text": "Here we go.", "start": 1557.84, "duration": 0.63}, {"text": "So I'm getting some questions\nabout the order of play", "start": 1570.26, "duration": 2.7}, {"text": "and about the alternation\nof the quantifiers here.", "start": 1572.96, "duration": 2.74}, {"text": "So the way I'm showing it is\nthat the quantifiers always", "start": 1575.7, "duration": 3.2}, {"text": "alternate--", "start": 1578.9, "duration": 1.02}, {"text": "Exist, For All, Exist, For All.", "start": 1579.92, "duration": 1.98}, {"text": "That doesn't really matter.", "start": 1581.9, "duration": 3.24}, {"text": "You can have several\nExists in a row,", "start": 1585.14, "duration": 1.98}, {"text": "and that would\ncorrespond to Exist", "start": 1587.12, "duration": 1.5}, {"text": "making several moves\nin a row before turning", "start": 1588.62, "duration": 2.91}, {"text": "it over to For All.", "start": 1591.53, "duration": 1.83}, {"text": "But alternatively, we could\njust add extra variables which", "start": 1593.36, "duration": 6.29}, {"text": "don't play any role in psi.", "start": 1599.65, "duration": 3.31}, {"text": "And they're just kind\nof dummy variables", "start": 1602.96, "duration": 2.76}, {"text": "that serve as spacers so if\nyou have two Exists in a row", "start": 1605.72, "duration": 3.21}, {"text": "and you don't like\nthat, you can just add a", "start": 1608.93, "duration": 2.19}, {"text": "For All of some variables that\nyou never see again in between.", "start": 1611.12, "duration": 4.35}, {"text": "So you can always get it to\nbe alternating if you want.", "start": 1615.47, "duration": 2.31}, {"text": "OK, also question-- the\ndifference between phi and psi.", "start": 1625.94, "duration": 6.66}, {"text": "So psi is the part here that\ndoes not have any quantifiers.", "start": 1632.6, "duration": 3.91}, {"text": "So the way we always\nwrite down our QBFs", "start": 1636.51, "duration": 2.9}, {"text": "is they're leading quantifiers\nwith the variables,", "start": 1639.41, "duration": 4.2}, {"text": "and all variables have to\nbe within the scope of one", "start": 1643.61, "duration": 2.7}, {"text": "of the quantified variables.", "start": 1646.31, "duration": 2.83}, {"text": "So there are no\nfree variables that", "start": 1649.14, "duration": 2.45}, {"text": "are unquantified in our QBFs.", "start": 1651.59, "duration": 2.245}, {"text": "And so all of these\nQBFs have a run", "start": 1656.57, "duration": 3.54}, {"text": "of quantifiers and then a\npart without quantifiers, so", "start": 1660.11, "duration": 2.85}, {"text": "the Boolean logic part.", "start": 1662.96, "duration": 1.86}, {"text": "Psi here is the\nBoolean logic part.", "start": 1664.82, "duration": 3.19}, {"text": "And phi is the whole thing\ntogether with the quantifiers.", "start": 1668.01, "duration": 2.895}, {"text": "So I'm not sure I\nunderstand some of these--", "start": 1673.58, "duration": 7.47}, {"text": "why not have the For All\nplayer have a forced win?", "start": 1681.05, "duration": 2.2}, {"text": "The For All player\nmight have a forced win.", "start": 1683.25, "duration": 3.8}, {"text": "One side or the\nother is guaranteed", "start": 1687.05, "duration": 1.92}, {"text": "to have a forced win.", "start": 1688.97, "duration": 1.27}, {"text": "So if Exist does not\nhave a forced win,", "start": 1690.24, "duration": 1.94}, {"text": "then For All will\nhave a forced win.", "start": 1692.18, "duration": 2.58}, {"text": "I'm not going to prove that.", "start": 1694.76, "duration": 1.95}, {"text": "That's a fairly simple\nproof by induction, which", "start": 1696.71, "duration": 2.553}, {"text": "I'm not going to go through.", "start": 1699.263, "duration": 1.167}, {"text": "Just take it as a fact.", "start": 1700.43, "duration": 2.86}, {"text": "Somebody is asking, why does\nFor All want to not satisfy", "start": 1703.29, "duration": 4.65}, {"text": "this expression, the psi part?", "start": 1707.94, "duration": 4.53}, {"text": "Well, that's the way\nwe set up the game.", "start": 1712.47, "duration": 2.67}, {"text": "In order to make this\ncorrespond to TQBF,", "start": 1715.14, "duration": 4.92}, {"text": "just the truth of\nthis expression,", "start": 1720.06, "duration": 4.21}, {"text": "we want to make Exist\ntry to satisfy this part", "start": 1724.27, "duration": 4.56}, {"text": "and For All try to make it\nnot satisfied because that's", "start": 1728.83, "duration": 7.7}, {"text": "what works.", "start": 1736.53, "duration": 0.69}, {"text": "I'm not sure what else, what\nother why I can answer there.", "start": 1737.22, "duration": 5.13}, {"text": "I'm going to answer some of\nthe most basic questions here.", "start": 1742.35, "duration": 2.95}, {"text": "Somebody is asking, how do we\nknow how many variables to use?", "start": 1745.3, "duration": 3.69}, {"text": "So the variables are the\nvariables of the formula.", "start": 1748.99, "duration": 4.2}, {"text": "So somebody is going\nto hand you a formula.", "start": 1753.19, "duration": 2.3}, {"text": "That's going to have x1 to\nx10, whatever that formula has,", "start": 1755.49, "duration": 3.54}, {"text": "some number of variables.", "start": 1759.03, "duration": 1.32}, {"text": "And so that game is\ngoing to have 10 moves.", "start": 1760.35, "duration": 3.63}, {"text": "If the quantifiers alternate,\nthen the moves will alternate,", "start": 1763.98, "duration": 4.14}, {"text": "but whatever the pattern\nof the quantifiers", "start": 1768.12, "duration": 2.43}, {"text": "is going to be the\npattern of the moves.", "start": 1770.55, "duration": 1.71}, {"text": "So Exist is going to follow\nthe places where the Exist", "start": 1772.26, "duration": 5.73}, {"text": "quantifier occurs,\nand For All is", "start": 1777.99, "duration": 2.245}, {"text": "going to follow the places where\nthe For All quantifier occurs.", "start": 1780.235, "duration": 2.625}, {"text": "So if you have Exist, For\nAll, Exist, For All, Exist", "start": 1782.86, "duration": 3.123}, {"text": "will move first, then\nFor All will move,", "start": 1785.983, "duration": 1.667}, {"text": "then Exist will move,\nthen For All will move.", "start": 1787.65, "duration": 1.875}, {"text": "Together, they're picking values\nto their respective variables", "start": 1789.525, "duration": 3.115}, {"text": "with their opposing goals.", "start": 1792.64, "duration": 2.09}, {"text": "Exist is trying to make\nthe psi part satisfied.", "start": 1794.73, "duration": 4.98}, {"text": "For All is trying to\navoid making it satisfied,", "start": 1799.71, "duration": 3.26}, {"text": "to make the assignment\nnot satisfy that part.", "start": 1802.97, "duration": 4.4}, {"text": "And if you think about\nwhat that means, just", "start": 1807.37, "duration": 3.32}, {"text": "in terms of the\nmeaning of that, it's", "start": 1810.69, "duration": 2.85}, {"text": "going to mean exactly\nthe same thing,", "start": 1813.54, "duration": 1.74}, {"text": "that the formula is true.", "start": 1815.28, "duration": 1.08}, {"text": "So anyway, if you don't--", "start": 1820.6, "duration": 4.24}, {"text": "let's see.", "start": 1824.84, "duration": 0.87}, {"text": "I don't know if there's\nany more questions", "start": 1825.71, "duration": 1.75}, {"text": "that I can try to answer here.", "start": 1827.46, "duration": 1.31}, {"text": "It's still about the\nnumbers of variables.", "start": 1837.89, "duration": 2.055}, {"text": "Each formula is going to\ndefine a different game.", "start": 1843.26, "duration": 3.48}, {"text": "You see the formula.", "start": 1846.74, "duration": 2.76}, {"text": "So the formula, however big--\nit may have 50 variables,", "start": 1849.5, "duration": 2.81}, {"text": "it may have two variables.", "start": 1852.31, "duration": 1.347}, {"text": "Well, we'll do an example.", "start": 1853.657, "duration": 1.083}, {"text": "Maybe that'll help.", "start": 1854.74, "duration": 2.94}, {"text": "The next check in, which\nis coming up pretty soon--", "start": 1857.68, "duration": 2.29}, {"text": "might actually be now--", "start": 1859.97, "duration": 1.52}, {"text": "we'll give you an example.", "start": 1861.49, "duration": 2.05}, {"text": "So we'll see who is\nunderstanding and who is not.", "start": 1863.54, "duration": 4.64}, {"text": "So let's continue here.", "start": 1868.18, "duration": 1.08}, {"text": "So therefore, the\nproblem of determining", "start": 1872.04, "duration": 3.67}, {"text": "does Exist have a forced win\nis exactly the TQBF problem,", "start": 1875.71, "duration": 3.75}, {"text": "because Exist has a forced win\nexactly when the formula is", "start": 1879.46, "duration": 2.85}, {"text": "true.", "start": 1882.31, "duration": 2.51}, {"text": "And what we're going to show is\nthat TQBF is a polynomial time", "start": 1884.82, "duration": 5.58}, {"text": "reducible to\ngeneralized geography,", "start": 1890.4, "duration": 2.7}, {"text": "but conceptually, we're going to\nthink about TQBF now as a game", "start": 1893.1, "duration": 4.11}, {"text": "because that's how generalized\ngeography is set up.", "start": 1897.21, "duration": 3.39}, {"text": "So given a formula\nlike this, we're", "start": 1900.6, "duration": 3.06}, {"text": "going to construct an instance\nof generalized geography.", "start": 1903.66, "duration": 2.7}, {"text": "We're going to construct a\ngraph where play on that graph", "start": 1906.36, "duration": 4.37}, {"text": "is going to mimic play\nin the formula game.", "start": 1910.73, "duration": 4.42}, {"text": "So making the\nmoves in that graph", "start": 1915.15, "duration": 1.65}, {"text": "are going to correspond\nto setting variables", "start": 1916.8, "duration": 2.67}, {"text": "true and false\nbecause the graph is", "start": 1919.47, "duration": 1.83}, {"text": "going to be specially designed\nto force that behavior.", "start": 1921.3, "duration": 3.015}, {"text": "So I think we have a\ncheck-in coming in.", "start": 1926.85, "duration": 1.97}, {"text": "Yeah, so let's just see how--", "start": 1928.82, "duration": 2.43}, {"text": "I suggest you pay\nattention to this check-in,", "start": 1931.25, "duration": 2.36}, {"text": "really try to think\nabout it and solve it,", "start": 1933.61, "duration": 1.75}, {"text": "because I think\nthat'll help you make", "start": 1935.36, "duration": 1.542}, {"text": "the connection between\nthe truth of the formula", "start": 1936.902, "duration": 4.488}, {"text": "and Exist having a\nwinning strategy.", "start": 1941.39, "duration": 2.895}, {"text": "So if you take\nthis formula here--", "start": 1948.87, "duration": 2.52}, {"text": "this is some particular\nformula, Exist x for all y,", "start": 1951.39, "duration": 2.88}, {"text": "blah, blah, blah.", "start": 1954.27, "duration": 2.25}, {"text": "There's going to be associated\nto that formula, a formula", "start": 1956.52, "duration": 2.49}, {"text": "game where first\nExist moves, assigns", "start": 1959.01, "duration": 3.18}, {"text": "a value for x, and\ndepending upon that value,", "start": 1962.19, "duration": 2.67}, {"text": "For All is going to move and is\ngoing to assign a value for y.", "start": 1964.86, "duration": 3.18}, {"text": "And after that's\ndone, this part here", "start": 1968.04, "duration": 2.28}, {"text": "is either going to\nbe true or false,", "start": 1970.32, "duration": 1.5}, {"text": "is either going to be\nsatisfied or unsatisfied.", "start": 1971.82, "duration": 3.09}, {"text": "And I want to know,\ncan Exist always find", "start": 1974.91, "duration": 2.64}, {"text": "a way to guarantee that this\npart is going to be satisfied,", "start": 1977.55, "duration": 4.38}, {"text": "or can For All always find a way\nto guarantee that this part is", "start": 1981.93, "duration": 3.57}, {"text": "not satisfied?", "start": 1985.5, "duration": 2.17}, {"text": "So you have to look\nat this formula", "start": 1987.67, "duration": 5.22}, {"text": "to understand which side is\ngoing to end up succeeding.", "start": 1992.89, "duration": 5.78}, {"text": "So if you're not clear on\nthe rules, look back here.", "start": 1998.67, "duration": 3.2}, {"text": "Exist is trying to make\nthis part satisfied.", "start": 2001.87, "duration": 2.61}, {"text": "For All is trying to make\nthis part unsatisfied.", "start": 2004.48, "duration": 2.49}, {"text": "But they neither of them\nhas the totally upper hand,", "start": 2006.97, "duration": 2.82}, {"text": "because Exist is picking\none of the variables,", "start": 2009.79, "duration": 2.67}, {"text": "For All is picking\nthe other variable.", "start": 2012.46, "duration": 1.89}, {"text": "But they're doing it\nin a certain order.", "start": 2014.35, "duration": 4.07}, {"text": "First Exist is going to pick,\nthen For All is going to pick.", "start": 2018.42, "duration": 2.82}, {"text": "So that's the way\nthe game works--", "start": 2024.15, "duration": 2.03}, {"text": "Exist picks a value, then\nFor All picks a value,", "start": 2026.18, "duration": 2.53}, {"text": "and then you see who wins.", "start": 2028.71, "duration": 2.82}, {"text": "So who wins?", "start": 2031.53, "duration": 1.46}, {"text": "Who's guaranteed to win?", "start": 2032.99, "duration": 2.58}, {"text": "Can we make sure\nthat Exists always", "start": 2035.57, "duration": 2.4}, {"text": "wins or can we make sure\nthat For All always wins", "start": 2037.97, "duration": 2.64}, {"text": "for this particular formula?", "start": 2040.61, "duration": 1.63}, {"text": "So there's just\ntwo variables here.", "start": 2042.24, "duration": 2.885}, {"text": "You can think about this in\neither of two ways-- strictly", "start": 2045.125, "duration": 2.375}, {"text": "speaking, purely as a\ngame, or you can look at,", "start": 2047.5, "duration": 3.42}, {"text": "understand whether that\nformula is true or not.", "start": 2050.92, "duration": 2.489}, {"text": "They're equivalent ways\nof looking at the problem.", "start": 2060.11, "duration": 3.79}, {"text": "In fact, in a certain\nsense, it's the same.", "start": 2063.9, "duration": 2.279}, {"text": "That's what I'm\ntrying to get across.", "start": 2066.179, "duration": 2.642}, {"text": "Thinking about this as a\ngame or thinking about it", "start": 2068.821, "duration": 2.083}, {"text": "in terms of quantifiers-- it\ndoesn't make any difference.", "start": 2070.904, "duration": 2.821}, {"text": "Almost done here.", "start": 2077.79, "duration": 1.72}, {"text": "So all right, last call.", "start": 2079.51, "duration": 5.0}, {"text": "Closing the poll.", "start": 2084.51, "duration": 0.93}, {"text": "I think this one you got.", "start": 2089.01, "duration": 1.979}, {"text": "You did pretty well on.", "start": 2090.989, "duration": 1.621}, {"text": "So the correct answer\nis the For All player", "start": 2092.61, "duration": 2.97}, {"text": "has a winning strategy,\nhas a forced win.", "start": 2095.58, "duration": 5.4}, {"text": "And also, similarly, the\nexpression, phi is false.", "start": 2100.98, "duration": 8.1}, {"text": "Because if you try to\nfind some x such that", "start": 2109.08, "duration": 3.9}, {"text": "no matter what y you pick,\nthis is going to be true,", "start": 2112.98, "duration": 4.307}, {"text": "this is going to be\nsatisfied, you're out of luck.", "start": 2117.287, "duration": 2.083}, {"text": "Because if you make\nx true, well, then--", "start": 2119.37, "duration": 4.215}, {"text": "now I'm confused.", "start": 2132.332, "duration": 0.708}, {"text": "What is going on.", "start": 2137.972, "duration": 0.708}, {"text": "If you make x true,\nthen x bar is false,", "start": 2138.68, "duration": 10.26}, {"text": "so y bar has to be true.", "start": 2148.94, "duration": 1.355}, {"text": "Now I'm completely confused.", "start": 2155.85, "duration": 1.26}, {"text": "Oh, no.", "start": 2157.11, "duration": 2.6}, {"text": "If you make x true, you\nhave to work For All y.", "start": 2159.71, "duration": 2.23}, {"text": "So this thing is clearly false.", "start": 2161.94, "duration": 1.32}, {"text": "If you make x true, then this\nx bar is going to be false,", "start": 2163.26, "duration": 7.05}, {"text": "and it's not the case that\nfor every y, setting for y--", "start": 2170.31, "duration": 4.77}, {"text": "because y is forced here. y\nis going to have to be true.", "start": 2175.08, "duration": 2.703}, {"text": "y bar is going to\nhave to be true,", "start": 2177.783, "duration": 1.417}, {"text": "so y is going to\nhave to be false.", "start": 2179.2, "duration": 1.417}, {"text": "So if you try again\nto make x false--", "start": 2180.617, "duration": 8.773}, {"text": "maybe that's one to think about\nfirst-- if you make x false,", "start": 2189.39, "duration": 4.887}, {"text": "you're going to be stuck\non the first clause", "start": 2194.277, "duration": 1.833}, {"text": "because it has to work\nfor both settings of y.", "start": 2196.11, "duration": 3.48}, {"text": "But maybe thinking about\nit as a game is better.", "start": 2199.59, "duration": 4.68}, {"text": "No matter what x\ndoes, y is going", "start": 2204.27, "duration": 2.94}, {"text": "to have a way of making one of\nthose two clauses unsatisfied.", "start": 2207.21, "duration": 5.04}, {"text": "So if x is true, we can set\ny to make the second clause", "start": 2212.25, "duration": 10.1}, {"text": "unsatisfied, and\nif x is false, y", "start": 2222.35, "duration": 3.3}, {"text": "can be assigned to make the\nfirst clause unsatisfied.", "start": 2225.65, "duration": 3.9}, {"text": "So anyway, the right answer\nis the For All player", "start": 2229.55, "duration": 5.56}, {"text": "has the winning strategy here.", "start": 2235.11, "duration": 1.41}, {"text": "And at the end of the\nday, it's not critical", "start": 2236.52, "duration": 2.4}, {"text": "that you understand\nthis correspondence,", "start": 2238.92, "duration": 1.68}, {"text": "but you have to then,\nif you don't quite", "start": 2240.6, "duration": 2.898}, {"text": "understand that,\nyou're going to have", "start": 2243.498, "duration": 1.542}, {"text": "to take on faith that the\nformula game is the same as", "start": 2245.04, "duration": 3.96}, {"text": "TQBF because that's\nwhat we're going to use.", "start": 2249.0, "duration": 2.55}, {"text": "And by the way, I would\nlike to also mention here", "start": 2251.55, "duration": 2.28}, {"text": "that this correspondence\nbetween games and quantifiers", "start": 2253.83, "duration": 6.6}, {"text": "is something that\nmathematicians use all the time.", "start": 2260.43, "duration": 4.0}, {"text": "Because if you have\nsome expression which", "start": 2264.43, "duration": 2.96}, {"text": "comes up often in\nmathematics, where there", "start": 2267.39, "duration": 2.25}, {"text": "are a whole run of quantifiers\nin front of some statement,", "start": 2269.64, "duration": 7.53}, {"text": "it's really kind\nof hard for anybody", "start": 2277.17, "duration": 3.24}, {"text": "to really get a feeling\nfor what that means.", "start": 2280.41, "duration": 4.14}, {"text": "If you have six alternating\nquantifiers, which", "start": 2284.55, "duration": 3.21}, {"text": "happens often in\nmathematics-- you're", "start": 2287.76, "duration": 1.717}, {"text": "going to have statements that\nhave a lot of alternations", "start": 2289.477, "duration": 2.333}, {"text": "with quantifiers--\nvery hard to get", "start": 2291.81, "duration": 1.5}, {"text": "a feeling for what that means.", "start": 2293.31, "duration": 1.39}, {"text": "But if you think about it as a\ngame, it's much more intuitive.", "start": 2294.7, "duration": 3.29}, {"text": "And it's completely equivalent\nto think about quantifiers.", "start": 2297.99, "duration": 3.24}, {"text": "Go back and forth between\nquantifiers and games.", "start": 2301.23, "duration": 3.84}, {"text": "Anyway, let's look\nat the reduction,", "start": 2305.07, "duration": 4.92}, {"text": "the construction that\nshows generalized geography", "start": 2309.99, "duration": 2.79}, {"text": "is complete.", "start": 2312.78, "duration": 1.56}, {"text": "A little longer than I thought--", "start": 2314.34, "duration": 1.96}, {"text": "I just want to make sure\neverybody is with me on this.", "start": 2316.3, "duration": 2.28}, {"text": "So why don't we call the break\nnow, and then we'll come back", "start": 2318.58, "duration": 4.76}, {"text": "and we'll look at the\nconstruction after that.", "start": 2323.34, "duration": 2.633}, {"text": "Because the\nconstruction itself is", "start": 2325.973, "duration": 1.417}, {"text": "going to take about 10 minutes\nto work through to, figure out", "start": 2327.39, "duration": 3.3}, {"text": "how to reduce TQBF\nand build a graph that", "start": 2330.69, "duration": 5.45}, {"text": "simulates the formula.", "start": 2336.14, "duration": 2.34}, {"text": "So I'm going to move\nright on to the--", "start": 2338.48, "duration": 3.795}, {"text": "and we'll come back.", "start": 2345.58, "duration": 2.07}, {"text": "So feel free to ask some\nquestions and get ready for us", "start": 2347.65, "duration": 6.78}, {"text": "diving in to a construction\nfor the reduction of TQBF", "start": 2354.43, "duration": 6.93}, {"text": "to generalized geography.", "start": 2361.36, "duration": 2.23}, {"text": "So it is an interesting\nquestion about what's", "start": 2363.59, "duration": 4.67}, {"text": "the relationship\nbetween a formula", "start": 2368.26, "duration": 3.52}, {"text": "and when you swap the\norder of the quantifiers.", "start": 2371.78, "duration": 2.69}, {"text": "The questioner is asking, does\nthat somehow relate to negating", "start": 2377.66, "duration": 4.89}, {"text": "the quantifier-free part, the\npart without the quantifiers?", "start": 2382.55, "duration": 5.46}, {"text": "And I don't think that that's\nthe right correspondence.", "start": 2388.01, "duration": 3.06}, {"text": "There actually is\nsome relationship.", "start": 2391.07, "duration": 3.09}, {"text": "When you say \"there\nexists for all,\"", "start": 2394.16, "duration": 5.1}, {"text": "it's actually a\nstronger statement", "start": 2399.26, "duration": 1.65}, {"text": "than saying that \"for\nall there exists.\"", "start": 2400.91, "duration": 2.31}, {"text": "And in general, that\nactually implies--", "start": 2403.22, "duration": 3.57}, {"text": "exist x for a y implies\nfor a y there exists an x,", "start": 2406.79, "duration": 7.65}, {"text": "because what you're saying\nis that if there exists an x", "start": 2414.44, "duration": 7.62}, {"text": "for a y, there is one x that\nworks for every one of the y's.", "start": 2422.06, "duration": 3.48}, {"text": "If you're saying for\na y there exists an x,", "start": 2425.54, "duration": 2.37}, {"text": "the choice of that x\ncan depend on the y.", "start": 2427.91, "duration": 4.03}, {"text": "So there is a\nconnection, but you", "start": 2431.94, "duration": 3.51}, {"text": "have to think through\nwhat it means in order", "start": 2435.45, "duration": 1.95}, {"text": "to understand that connection.", "start": 2437.4, "duration": 3.3}, {"text": "You won't need to\nknow that in order", "start": 2440.7, "duration": 2.37}, {"text": "to process what we're\ngoing to be doing,", "start": 2443.07, "duration": 1.87}, {"text": "but maybe it just helps\nyou think about it.", "start": 2444.94, "duration": 1.792}, {"text": "Other questions here.", "start": 2449.67, "duration": 1.08}, {"text": "I think we're out of time here.", "start": 2459.98, "duration": 3.63}, {"text": "So let's return to our lecture.", "start": 2466.39, "duration": 5.055}, {"text": "So I'm going to go back.", "start": 2475.02, "duration": 2.7}, {"text": "Hopefully that won't\ncrash everything.", "start": 2477.72, "duration": 3.0}, {"text": "There we go.", "start": 2484.25, "duration": 2.43}, {"text": "So now we're going\nto be reducing TQBF", "start": 2486.68, "duration": 3.18}, {"text": "to generalized geography.", "start": 2489.86, "duration": 1.4}, {"text": "Are we all together now?", "start": 2491.26, "duration": 1.0}, {"text": "OK.", "start": 2496.4, "duration": 1.14}, {"text": "So I'm going to illustrate this\nconstruction, which is a very", "start": 2497.54, "duration": 3.81}, {"text": "nice construction, by the way.", "start": 2501.35, "duration": 1.47}, {"text": "I'm going to illustrate\nthis construction just", "start": 2502.82, "duration": 1.917}, {"text": "by doing an example,\nor a partial example,", "start": 2504.737, "duration": 3.433}, {"text": "but I think it'll\ngive you the idea.", "start": 2508.17, "duration": 2.45}, {"text": "So you understand what\nI'm trying to do here,", "start": 2510.62, "duration": 2.15}, {"text": "is I'm starting off with a\nquantified Boolean formula.", "start": 2512.77, "duration": 5.97}, {"text": "So here it is.", "start": 2518.74, "duration": 2.12}, {"text": "I'm going to assume it's in\nconjunctive normal form, which", "start": 2520.86, "duration": 4.59}, {"text": "I can always convert\nit into that form,", "start": 2525.45, "duration": 2.97}, {"text": "maybe by adding some\nadditional variables,", "start": 2528.42, "duration": 2.43}, {"text": "but without doing anything\ntoo drastic to it.", "start": 2530.85, "duration": 7.36}, {"text": "And so now, starting\nfrom that formula,", "start": 2538.21, "duration": 5.37}, {"text": "I'm going to now build a graph,\nwhere playing the geography", "start": 2543.58, "duration": 3.99}, {"text": "game on that graph-- which\nis, remember, taking turns,", "start": 2547.57, "duration": 2.94}, {"text": "picking nodes\nwhich form a path--", "start": 2550.51, "duration": 3.3}, {"text": "is going to correspond to\nplaying the formula game, which", "start": 2553.81, "duration": 4.77}, {"text": "is picking the variables\nof that formula.", "start": 2558.58, "duration": 2.67}, {"text": "And then you want--", "start": 2561.25, "duration": 3.396}, {"text": "if the Exist player\nwins in the formula,", "start": 2564.646, "duration": 2.514}, {"text": "then Player I is supposed to\nwin in the geography game.", "start": 2567.16, "duration": 4.2}, {"text": "So here is how the\ngraph is going to look.", "start": 2574.24, "duration": 2.31}, {"text": "So try to follow this.", "start": 2579.2, "duration": 2.31}, {"text": "So there's going to\nbe kind of two parts,", "start": 2581.51, "duration": 4.0}, {"text": "one that's going to\ncorrespond to the variables,", "start": 2585.51, "duration": 2.9}, {"text": "and the other part that's going\nto correspond to the clauses.", "start": 2588.41, "duration": 4.35}, {"text": "And so for each\nvariable, I'm going", "start": 2592.76, "duration": 2.22}, {"text": "to have a diamond\nstructure here.", "start": 2594.98, "duration": 1.883}, {"text": "So there's a little\nstarting thing", "start": 2596.863, "duration": 1.417}, {"text": "that's going to be unique\nto the first variable.", "start": 2598.28, "duration": 2.8}, {"text": "But then every variable is\ngoing to have a little diamond", "start": 2601.08, "duration": 2.72}, {"text": "structure here.", "start": 2603.8, "duration": 2.16}, {"text": "And they're going to be\nattached one to the next.", "start": 2605.96, "duration": 3.56}, {"text": "And we'll understand what this\nmeans when we play geography", "start": 2609.52, "duration": 7.35}, {"text": "on this piece of the\ngraph, but let's just", "start": 2616.87, "duration": 3.383}, {"text": "understand the structure first.", "start": 2620.253, "duration": 1.292}, {"text": "So this is the start node.", "start": 2624.34, "duration": 2.4}, {"text": "And now, here Player I is going\nto play the role of Exist.", "start": 2626.74, "duration": 4.8}, {"text": "Player II is going to\nplay the role of For All.", "start": 2631.54, "duration": 2.25}, {"text": "And in fact, I'm going\nto identify that.", "start": 2633.79, "duration": 2.5}, {"text": "So I'm going to\ncall-- because it's", "start": 2636.29, "duration": 1.82}, {"text": "going to be helpful just\nto think about Player I", "start": 2638.11, "duration": 5.28}, {"text": "as being the Exist player.", "start": 2643.39, "duration": 1.47}, {"text": "So the Exist player is going\nto be playing on this graph.", "start": 2644.86, "duration": 3.665}, {"text": "The Exist and the\nFor All players", "start": 2648.525, "duration": 1.375}, {"text": "are going to be\nplaying on the graph.", "start": 2649.9, "duration": 1.542}, {"text": "It's really just\nPlayers I and II.", "start": 2651.442, "duration": 1.458}, {"text": "So the Exist player,\nPlayer I, by the rules,", "start": 2652.9, "duration": 6.93}, {"text": "has to pick the start node.", "start": 2659.83, "duration": 2.81}, {"text": "And now it's Player II's move,\nthe For All player's move.", "start": 2662.64, "duration": 3.92}, {"text": "Now, if you're with\nme on this graph,", "start": 2666.56, "duration": 6.82}, {"text": "the For All player's move\nis now not very interesting", "start": 2673.38, "duration": 3.39}, {"text": "because it's forced.", "start": 2676.77, "duration": 1.71}, {"text": "It has to go to here,\nbecause again, they're", "start": 2678.48, "duration": 2.61}, {"text": "just picking the nodes of a\nsimple path in this graph.", "start": 2681.09, "duration": 7.67}, {"text": "So the For All, Player\nII, the For All player,", "start": 2688.76, "duration": 3.95}, {"text": "has to go here if Exist\nstarted over there.", "start": 2692.71, "duration": 3.6}, {"text": "Now it's the Exist\nplayer's turn.", "start": 2696.31, "duration": 4.41}, {"text": "And now something\ninteresting happens.", "start": 2700.72, "duration": 2.91}, {"text": "The Exist player has a choice--", "start": 2703.63, "duration": 1.92}, {"text": "it can either go left or right.", "start": 2705.55, "duration": 3.02}, {"text": "There are two possibilities.", "start": 2708.57, "duration": 2.97}, {"text": "And then after that,\nthe For All player's", "start": 2711.54, "duration": 3.47}, {"text": "turn, who is,\nagain, just forced.", "start": 2715.01, "duration": 3.24}, {"text": "So far, For All has not\nhad much interesting stuff", "start": 2718.25, "duration": 2.43}, {"text": "to do in this, has\nnot had to think hard.", "start": 2720.68, "duration": 5.77}, {"text": "So no matter whether\nExist went left or right,", "start": 2726.45, "duration": 4.1}, {"text": "the For All player's move is\nforced and ends up over here.", "start": 2730.55, "duration": 4.27}, {"text": "And now it's this player's turn.", "start": 2734.82, "duration": 1.62}, {"text": "And again, this is\nkind of an easy one.", "start": 2736.44, "duration": 2.21}, {"text": "Oh, before I do that, let's just\nlook at how that play could go.", "start": 2738.65, "duration": 6.03}, {"text": "So the first two moves, as\nkind of I was suggesting,", "start": 2744.68, "duration": 2.9}, {"text": "Exist goes here and\nthen For All goes there.", "start": 2747.58, "duration": 4.57}, {"text": "I'm going to illustrate possible\nplays through this graph", "start": 2752.15, "duration": 4.53}, {"text": "by tracing them out in green.", "start": 2756.68, "duration": 1.92}, {"text": "So now Exist goes here,\nFor All goes there.", "start": 2761.57, "duration": 2.39}, {"text": "Those were forced.", "start": 2763.96, "duration": 1.23}, {"text": "But now, the Exist player\ngoes, could either go this way", "start": 2765.19, "duration": 3.45}, {"text": "or could go that way.", "start": 2768.64, "duration": 2.16}, {"text": "So those are two\npossible different ways", "start": 2775.12, "duration": 3.63}, {"text": "of playing the game\nthat we're building.", "start": 2778.75, "duration": 4.59}, {"text": "And now, whose turn is it here?", "start": 2783.34, "duration": 6.62}, {"text": "This was the For All\nplayer picked this one,", "start": 2792.547, "duration": 1.833}, {"text": "so the next turn is the Exist\nplayer, and that's forced.", "start": 2794.38, "duration": 6.03}, {"text": "But now notice-- now\nfor the first time,", "start": 2800.41, "duration": 3.33}, {"text": "the For All player has to think,\nbecause the For All player", "start": 2803.74, "duration": 3.3}, {"text": "can either go left or right,\nso could either go left,", "start": 2807.04, "duration": 9.445}, {"text": "or it could go right.", "start": 2816.485, "duration": 0.875}, {"text": "And so then there's going to\nbe a sequence of these diamond", "start": 2820.98, "duration": 4.94}, {"text": "structures, where they're\nconstructed so that alternately", "start": 2825.92, "duration": 4.92}, {"text": "either the Exist\nhas a choice or the", "start": 2830.84, "duration": 2.19}, {"text": "For All player has a choice,\nuntil you get all the way down", "start": 2833.03, "duration": 3.407}, {"text": "to the bottom.", "start": 2836.437, "duration": 0.583}, {"text": "That is the graph\nwe've built so far.", "start": 2841.38, "duration": 2.28}, {"text": "Now, if we stopped here, then\nwhoever ended up at this point,", "start": 2843.66, "duration": 8.31}, {"text": "whether it was Exist or For\nAll, would be the winner", "start": 2851.97, "duration": 2.25}, {"text": "because there's nowhere\nfor the opponent to go.", "start": 2854.22, "duration": 4.17}, {"text": "Of course, that wouldn't\nbe very interesting.", "start": 2858.39, "duration": 2.62}, {"text": "So there's going to be more\nstuff we're going to add on,", "start": 2861.01, "duration": 2.93}, {"text": "which are going to\ncorrespond to the clauses.", "start": 2863.94, "duration": 3.31}, {"text": "Now, how to think about\nwhat's happened so far?", "start": 2867.25, "duration": 5.09}, {"text": "Maybe some of you\nmight be guessing", "start": 2872.34, "duration": 3.47}, {"text": "that when the Exist player\nover here has a choice,", "start": 2875.81, "duration": 3.467}, {"text": "could have either gone\nleft or right, that's going", "start": 2879.277, "duration": 2.083}, {"text": "to correspond-- because this\nis supposed to be mimicking", "start": 2881.36, "duration": 3.99}, {"text": "the formula game-- that's going\nto correspond to the Exist", "start": 2885.35, "duration": 4.62}, {"text": "player in the formula\npicking the variable", "start": 2889.97, "duration": 3.48}, {"text": "either true or false.", "start": 2893.45, "duration": 1.93}, {"text": "So to the left or right is going\nto correspond to true or false.", "start": 2895.38, "duration": 3.99}, {"text": "And so let's just\narbitrarily say", "start": 2899.37, "duration": 2.82}, {"text": "left is going to correspond\nto picking it true and right", "start": 2902.19, "duration": 3.358}, {"text": "is going to correspond\nto picking false.", "start": 2905.548, "duration": 1.667}, {"text": "So the way I've set it\nso far is Exist ended up", "start": 2910.3, "duration": 5.67}, {"text": "picking the first\nvariable false,", "start": 2915.97, "duration": 2.37}, {"text": "then For All picked the\nsecond variable false.", "start": 2918.34, "duration": 3.57}, {"text": "And the nth variable\nalso got set false.", "start": 2921.91, "duration": 2.25}, {"text": "Everything got set false so far.", "start": 2924.16, "duration": 1.383}, {"text": "Who knows what happened\nover here, of course--", "start": 2925.543, "duration": 1.917}, {"text": "so just to understand\nwhat we've done so far.", "start": 2931.5, "duration": 3.19}, {"text": "Now I'm going to show you how\nto build the rest of the graph.", "start": 2934.69, "duration": 3.51}, {"text": "So let's take away\nthe green part.", "start": 2938.2, "duration": 4.08}, {"text": "And now we're just back\nto the construction.", "start": 2942.28, "duration": 3.06}, {"text": "The green part is actually\nhow you use that construction.", "start": 2945.34, "duration": 2.38}, {"text": "So back to the\nconstruction here-- now,", "start": 2947.72, "duration": 1.85}, {"text": "what do we want to achieve?", "start": 2949.57, "duration": 2.64}, {"text": "By the time the players on the\ngraph have got down to here,", "start": 2952.21, "duration": 5.97}, {"text": "they've effectively made an\nassignment to the variables", "start": 2958.18, "duration": 3.21}, {"text": "by going either left or right\nat each one of these diamonds.", "start": 2961.39, "duration": 3.18}, {"text": "So the assignment is done.", "start": 2964.57, "duration": 2.43}, {"text": "From the perspective of the\nformula game, the game is over,", "start": 2967.0, "duration": 4.14}, {"text": "and now one side or\nthe other has won.", "start": 2971.14, "duration": 3.68}, {"text": "Here, we want to build\nsome extra structure here", "start": 2974.82, "duration": 3.78}, {"text": "as a kind of an endgame, to make\nsure that the For All player", "start": 2978.6, "duration": 5.69}, {"text": "gets stuck if the\nExist player has", "start": 2984.29, "duration": 3.15}, {"text": "made an assignment\nwhich satisfies", "start": 2987.44, "duration": 3.13}, {"text": "this part of the formula.", "start": 2990.57, "duration": 1.37}, {"text": "And the Exist player should get\nstuck if the For All player,", "start": 2991.94, "duration": 4.69}, {"text": "if the assignment that they made\ndoes not satisfy the formula.", "start": 2996.63, "duration": 5.44}, {"text": "So let's see how we're\ngoing to achieve that", "start": 3002.07, "duration": 2.01}, {"text": "with some additional structure.", "start": 3004.08, "duration": 2.23}, {"text": "So there's going to be\nsome extra node over here.", "start": 3006.31, "duration": 3.153}, {"text": "Let me just tell you what the\nstructure is, and then we'll", "start": 3009.463, "duration": 2.417}, {"text": "argue why it works.", "start": 3011.88, "duration": 1.41}, {"text": "So going from this\nbottom node, we're", "start": 3013.29, "duration": 3.18}, {"text": "going to start the\nsecond part of the graph.", "start": 3016.47, "duration": 4.83}, {"text": "There's going to be\na node which fans out", "start": 3021.3, "duration": 3.09}, {"text": "to a node for each\none of the clauses.", "start": 3024.39, "duration": 1.86}, {"text": "And each one of those\nclauses, in turn,", "start": 3029.31, "duration": 1.68}, {"text": "fans out to a node for\neach one of its literals.", "start": 3030.99, "duration": 5.01}, {"text": "So you see we have\nclause c1, and it", "start": 3036.0, "duration": 3.03}, {"text": "has the literals x1, x2\nbar, x3, x1, x2 bar, x3.", "start": 3039.03, "duration": 4.92}, {"text": "So there's a node for each\nof the literals in clause c1,", "start": 3043.95, "duration": 3.33}, {"text": "same for clause c2, and so on.", "start": 3047.28, "duration": 2.37}, {"text": "Now we're almost done.", "start": 3052.34, "duration": 1.43}, {"text": "Now I'm going to tell you how to\nconnect up these literal nodes.", "start": 3053.77, "duration": 4.38}, {"text": "So x1, each node is\ngoing to correspond back", "start": 3058.15, "duration": 4.98}, {"text": "to its own diamond.", "start": 3063.13, "duration": 2.37}, {"text": "So now we're going\nto tie it back", "start": 3065.5, "duration": 1.47}, {"text": "to the first part, where\nwe made the assignment", "start": 3066.97, "duration": 3.15}, {"text": "part of the graph.", "start": 3070.12, "duration": 1.23}, {"text": "x1 is going to connect\nback to the true part", "start": 3071.35, "duration": 3.69}, {"text": "of the x1 diamond.", "start": 3075.04, "duration": 3.23}, {"text": "And x2 because, it's\nnegated, is going", "start": 3078.27, "duration": 2.19}, {"text": "to tie back to the false\npart of the x2 diamond", "start": 3080.46, "duration": 4.46}, {"text": "because it's an x2 variable.", "start": 3084.92, "duration": 3.24}, {"text": "Similarly, x1 bar--\nbecause x1 bar--", "start": 3088.16, "duration": 7.88}, {"text": "here's x1 bar in clause 2--", "start": 3096.04, "duration": 3.31}, {"text": "x1 bar is going\nto connect up now", "start": 3099.35, "duration": 3.66}, {"text": "to the false side\nof the x1 diamond.", "start": 3103.01, "duration": 5.09}, {"text": "And x2 bar is\ngoing to connect up", "start": 3108.1, "duration": 2.25}, {"text": "to the false side of the\nx2 diamond, and so on.", "start": 3110.35, "duration": 4.79}, {"text": "I don't have the\nother diamonds here,", "start": 3115.14, "duration": 1.83}, {"text": "but the x4 would connect\nup to the true side", "start": 3116.97, "duration": 4.08}, {"text": "of the x4 diamond, for example.", "start": 3121.05, "duration": 4.5}, {"text": "That's the whole construction.", "start": 3125.55, "duration": 1.26}, {"text": "Let's understand why it works.", "start": 3126.81, "duration": 2.81}, {"text": "So the endgame here\nis we want Exist", "start": 3129.62, "duration": 2.25}, {"text": "to win if the assignment\nsatisfied all the clauses.", "start": 3131.87, "duration": 6.47}, {"text": "And For All should win if there\nwas some unsatisfied clauses.", "start": 3138.34, "duration": 4.06}, {"text": "So why does this happen?", "start": 3142.4, "duration": 1.51}, {"text": "So let's put back an\nassignment here that was made.", "start": 3143.91, "duration": 2.46}, {"text": "So the one I'm putting\nback, the assignment", "start": 3146.37, "duration": 5.66}, {"text": "that they cooperatively\nbuilt had x1 being true,", "start": 3152.03, "duration": 4.41}, {"text": "x2 being false, and\nsome other stuff.", "start": 3156.44, "duration": 4.26}, {"text": "Now, why does this work?", "start": 3160.7, "duration": 1.15}, {"text": "So what we want to\nhave happen now--", "start": 3161.85, "duration": 2.81}, {"text": "so now, the move\nproceeds over to here,", "start": 3164.66, "duration": 2.91}, {"text": "and you need to arrange\nit so that Exist", "start": 3167.57, "duration": 5.25}, {"text": "is the one who picks that node.", "start": 3172.82, "duration": 1.83}, {"text": "If this would have been For\nAll, just add an extra node", "start": 3180.73, "duration": 2.64}, {"text": "to switch whose turn it is.", "start": 3183.37, "duration": 3.49}, {"text": "But you want Exist\nto be up here.", "start": 3186.86, "duration": 1.56}, {"text": "And what you want is for For All\nto be picking the clause node.", "start": 3188.42, "duration": 5.34}, {"text": "Now, here is the part to\nunderstand what's going on--", "start": 3193.76, "duration": 4.32}, {"text": "we want For All to win\nif this is not satisfied.", "start": 3202.24, "duration": 5.92}, {"text": "So For All is going\nto make a claim.", "start": 3208.16, "duration": 3.91}, {"text": "If it is not satisfied,\nthere is some clause", "start": 3212.07, "duration": 1.98}, {"text": "which is not satisfied.", "start": 3214.05, "duration": 1.14}, {"text": "There's some clause\nwhich ended up", "start": 3215.19, "duration": 1.68}, {"text": "being false in the assignment.", "start": 3216.87, "duration": 1.54}, {"text": "So the For All player going\nto say, \"I think I won.", "start": 3218.41, "duration": 4.12}, {"text": "And I won because clause\nnumber 1 is unsatisfied.\"", "start": 3222.53, "duration": 4.97}, {"text": "So it's going to pick\nclause number one.", "start": 3227.5, "duration": 3.147}, {"text": "So here's the For All\nplayer's [INAUDIBLE]..", "start": 3230.647, "duration": 1.833}, {"text": "Here's Exist player.", "start": 3232.48, "duration": 1.44}, {"text": "And so the For All player picks\nthe clause claimed unsatisfied.", "start": 3233.92, "duration": 5.19}, {"text": "So over here, For All player\nsays, clause c1 is unsatisfied.", "start": 3239.11, "duration": 4.02}, {"text": "I'm going to move here.", "start": 3243.13, "duration": 3.04}, {"text": "Exist player says, \"Uh-uh,\nI don't agree with you.", "start": 3246.17, "duration": 3.88}, {"text": "The assignment, your line--", "start": 3250.05, "duration": 2.79}, {"text": "the assignment actually\nmakes one of the literals", "start": 3255.66, "duration": 4.44}, {"text": "true in clause c1.", "start": 3260.1, "duration": 3.5}, {"text": "Let's say you made x1 was\ntrue, as in fact, it is here--", "start": 3263.6, "duration": 4.59}, {"text": "x1, in fact, is true.", "start": 3268.19, "duration": 1.39}, {"text": "So Exist is now going to pick\nthe literal that was true", "start": 3269.58, "duration": 7.76}, {"text": "in the assignment in that\nclause, that the For All player", "start": 3277.34, "duration": 3.48}, {"text": "is claiming is unsatisfied.", "start": 3280.82, "duration": 2.27}, {"text": "One of them is\nlying at this point.", "start": 3283.09, "duration": 3.66}, {"text": "This is either now true in here,\nwhich means the For All player", "start": 3286.75, "duration": 2.88}, {"text": "did not pick an\nunsatisfied clause,", "start": 3289.63, "duration": 1.89}, {"text": "or the Exist player\npicked the false literal,", "start": 3291.52, "duration": 2.89}, {"text": "which is the Exist player picked\nthe false literal so the Exist", "start": 3294.41, "duration": 4.37}, {"text": "player is lying.", "start": 3298.78, "duration": 1.29}, {"text": "Now, the moment of truth\nbecause let's see--", "start": 3300.07, "duration": 6.44}, {"text": "if Exist picked here, now it's\nthe For All player's turn.", "start": 3306.51, "duration": 6.08}, {"text": "It's connected back to the\ntrue side of the diamond.", "start": 3312.59, "duration": 2.415}, {"text": "So that node was already used.", "start": 3318.53, "duration": 2.04}, {"text": "That's the only place that\nFor All could possibly go.", "start": 3320.57, "duration": 2.82}, {"text": "For All is stuck,\nand Exist has won", "start": 3323.39, "duration": 2.64}, {"text": "the game, which is what you\nwant because For All's claims", "start": 3326.03, "duration": 5.16}, {"text": "are false and the Exist\nwas correct in saying", "start": 3331.19, "duration": 4.92}, {"text": "that x1 satisfied clause c1.", "start": 3336.11, "duration": 3.3}, {"text": "So x1 is true, so there's\nnowhere for For All to go.", "start": 3339.41, "duration": 4.08}, {"text": "But compare that\nwith the situation", "start": 3343.49, "duration": 2.34}, {"text": "if the assignment, on\nthis part of the graph,", "start": 3345.83, "duration": 3.3}, {"text": "had gone through the\nfalse, had assigned x1", "start": 3349.13, "duration": 3.42}, {"text": "to be false, so the path\nhad gone through the", "start": 3352.55, "duration": 3.16}, {"text": "For All side of the diamond.", "start": 3355.71, "duration": 2.18}, {"text": "Now this node would\nstill be unoccupied,", "start": 3357.89, "duration": 2.76}, {"text": "would still be available.", "start": 3360.65, "duration": 4.21}, {"text": "So now the For All\nplay-- so if Exist", "start": 3364.86, "duration": 3.35}, {"text": "was claiming that x1 was\ntrue and it really was false,", "start": 3368.21, "duration": 5.71}, {"text": "the For All player would be\nable to move onto that node.", "start": 3373.92, "duration": 2.688}, {"text": "And now it's the\nExist player's turn,", "start": 3376.608, "duration": 1.542}, {"text": "and the Exist would be stuck\nbecause this node down here is", "start": 3378.15, "duration": 3.84}, {"text": "guaranteed to have been used.", "start": 3381.99, "duration": 1.23}, {"text": "So that is the idea.", "start": 3385.78, "duration": 3.68}, {"text": "It's really very beautiful, and\nactually not that complicated.", "start": 3389.46, "duration": 4.71}, {"text": "You have to stare at it a bit.", "start": 3394.17, "duration": 1.84}, {"text": "So let's just see what\nhappens, for example,", "start": 3396.01, "duration": 2.37}, {"text": "if I had one other case-- maybe\nit's not necessary at this", "start": 3398.38, "duration": 3.8}, {"text": "point, but if the For All player\nclaimed it's the second clause", "start": 3402.18, "duration": 6.9}, {"text": "which is unsatisfied in the\nmutually selected assignment,", "start": 3409.08, "duration": 4.63}, {"text": "then--", "start": 3413.71, "duration": 0.5}, {"text": "so this is sort of the case\nwhere the For All player", "start": 3417.93, "duration": 2.83}, {"text": "is correct, in that if\nthe Exist player now says,", "start": 3420.76, "duration": 4.74}, {"text": "well, I think x1 bar\nsatisfied that second clause,", "start": 3425.5, "duration": 6.02}, {"text": "but this assignment made x1\ntrue, so x1 bar is false.", "start": 3431.52, "duration": 5.76}, {"text": "And so the Exist\nplayer's lying this time.", "start": 3437.28, "duration": 2.89}, {"text": "And so now the For All player\ncan take this last edge", "start": 3440.17, "duration": 3.08}, {"text": "and go here, and has\none last move to make.", "start": 3443.25, "duration": 4.54}, {"text": "And then the Exist\nplayer's stuck.", "start": 3447.79, "duration": 1.58}, {"text": "So the For All will\nwin in that case.", "start": 3449.37, "duration": 1.96}, {"text": "So let's turn now,\nshifting gears entirely", "start": 3451.33, "duration": 3.92}, {"text": "to a different part\nof space complexity.", "start": 3455.25, "duration": 7.23}, {"text": "Instead of looking at polynomial\nspace, which is very powerful,", "start": 3462.48, "duration": 3.73}, {"text": "we're going to look at log\nspace, which is comparatively", "start": 3466.21, "duration": 2.78}, {"text": "speaking much, much weaker.", "start": 3468.99, "duration": 1.65}, {"text": "So log space are the things\nthat you can do when you only", "start": 3470.64, "duration": 3.54}, {"text": "have enough space to\nwrite down, essentially,", "start": 3474.18, "duration": 3.42}, {"text": "a pointer or some fixed number\nof pointers into the input.", "start": 3477.6, "duration": 3.21}, {"text": "That's what you get when\nyou have logarithmic space,", "start": 3480.81, "duration": 7.2}, {"text": "because log space is\nenough to write down", "start": 3488.01, "duration": 2.42}, {"text": "an index of something.", "start": 3490.43, "duration": 1.56}, {"text": "So this is what you can do\nwith a bunch of pointers.", "start": 3491.99, "duration": 3.84}, {"text": "And in order to\nmake sense of this,", "start": 3495.83, "duration": 4.38}, {"text": "we have to change the\nmodel of computation.", "start": 3500.21, "duration": 2.16}, {"text": "Because if we use the ordinary\none-tape Turing machine, just", "start": 3502.37, "duration": 3.75}, {"text": "scanning across the input,\njust reading the input the way", "start": 3506.12, "duration": 5.85}, {"text": "we've defined it,\nwould cost space n.", "start": 3511.97, "duration": 2.61}, {"text": "And so you can't\neven read the input", "start": 3514.58, "duration": 2.07}, {"text": "if you have less than n space\navailable, like log space.", "start": 3516.65, "duration": 3.46}, {"text": "So we're going to introduce\na different model just", "start": 3520.11, "duration": 3.25}, {"text": "to allow us to define this.", "start": 3523.36, "duration": 1.5}, {"text": "And that's a model\nwhere it's going", "start": 3524.86, "duration": 2.01}, {"text": "to have two tapes, where the\npart that contains the input", "start": 3526.87, "duration": 4.84}, {"text": "doesn't count.", "start": 3531.71, "duration": 1.235}, {"text": "And in order to make sure\nit's not being cheated,", "start": 3532.945, "duration": 4.275}, {"text": "the input tape is\ngoing to be read only,", "start": 3537.22, "duration": 3.848}, {"text": "but it doesn't count\ntoward the space used.", "start": 3541.068, "duration": 1.792}, {"text": "Only the work tape, which\nnow can be written or read,", "start": 3542.86, "duration": 7.232}, {"text": "is going to count\ntoward the space bound.", "start": 3550.092, "duration": 1.708}, {"text": "So now what we're\ngoing to define is,", "start": 3554.72, "duration": 3.06}, {"text": "using this definition\nfor our space complexity,", "start": 3557.78, "duration": 6.84}, {"text": "we'll define SPACE\nlog n, the things", "start": 3564.62, "duration": 3.93}, {"text": "that you can do if you have\nonly a log amount of space", "start": 3568.55, "duration": 2.25}, {"text": "here, on the work tape.", "start": 3570.8, "duration": 3.9}, {"text": "So the length of the input is n.", "start": 3574.7, "duration": 2.16}, {"text": "The length of the work\ntape is order log n.", "start": 3576.86, "duration": 7.39}, {"text": "So we have the deterministic\nand nondeterministic associated", "start": 3584.25, "duration": 4.86}, {"text": "classes--", "start": 3589.11, "duration": 1.5}, {"text": "SPACE log n and NSPACE log n.", "start": 3590.61, "duration": 2.31}, {"text": "We're calling it L and NL--", "start": 3592.92, "duration": 2.34}, {"text": "log space and\nnondeterministic log space.", "start": 3595.26, "duration": 4.17}, {"text": "And as I said, that's\njust enough space", "start": 3599.43, "duration": 1.71}, {"text": "to write down some\npointers into the input.", "start": 3601.14, "duration": 2.1}, {"text": "And let's do some\nquick examples.", "start": 3603.24, "duration": 1.455}, {"text": "So if you take the language of\npalindromes, essentially, or ww", "start": 3608.09, "duration": 3.95}, {"text": "reverse, that's in log space.", "start": 3612.04, "duration": 5.89}, {"text": "So here is a string.", "start": 3617.93, "duration": 1.88}, {"text": "Here's a string\nthat's in ww reverse.", "start": 3619.81, "duration": 3.84}, {"text": "And the ordinary\nway you might use", "start": 3623.65, "duration": 4.95}, {"text": "to test whether a string is\nof this form in ww reverse", "start": 3628.6, "duration": 3.99}, {"text": "might be to cross off\ncorresponding locations here.", "start": 3632.59, "duration": 3.073}, {"text": "But you can't do that.", "start": 3635.663, "duration": 0.917}, {"text": "It's a read-only input tape.", "start": 3636.58, "duration": 1.81}, {"text": "So you have to somehow avoid\nwriting on the input tape,", "start": 3638.39, "duration": 3.11}, {"text": "but still testing whether\nyou're in this language.", "start": 3641.5, "duration": 2.61}, {"text": "It's not hard to do.", "start": 3644.11, "duration": 1.35}, {"text": "You can use the work tape\njust to keep track of where", "start": 3645.46, "duration": 3.75}, {"text": "your pointers would be.", "start": 3649.21, "duration": 2.49}, {"text": "And in so doing,\nyou can just make", "start": 3651.7, "duration": 4.56}, {"text": "sure you're matching off\ncorresponding locations", "start": 3656.26, "duration": 4.38}, {"text": "with each other in the input.", "start": 3660.64, "duration": 2.8}, {"text": "So log space, because\nof its ability", "start": 3663.44, "duration": 2.15}, {"text": "to store some fixed\nnumber of pointers,", "start": 3665.59, "duration": 2.79}, {"text": "gives you enough to test\nmembership in this language.", "start": 3668.38, "duration": 3.86}, {"text": "So this is in\nsolvable in log space.", "start": 3672.24, "duration": 4.67}, {"text": "The path problem, which\nwe've seen before--", "start": 3676.91, "duration": 2.64}, {"text": "you're given a graph, and a\nstart node, and an ending node,", "start": 3679.55, "duration": 3.66}, {"text": "or a start and a target.", "start": 3683.21, "duration": 1.5}, {"text": "You're given a graph\nof an s and t--", "start": 3684.71, "duration": 2.87}, {"text": "it's a directed a graph--", "start": 3687.58, "duration": 1.2}, {"text": "and can I know, can\nI get from s to t?", "start": 3688.78, "duration": 3.42}, {"text": "So that problem is solvable\nin nondeterministic log space", "start": 3692.2, "duration": 5.58}, {"text": "because the way we would do\nthat, not writing this down", "start": 3697.78, "duration": 6.42}, {"text": "in any detail,\nbut what you would", "start": 3704.2, "duration": 3.27}, {"text": "do in your nondeterministic\nlog space machine--", "start": 3707.47, "duration": 4.8}, {"text": "you have your input graph\nwritten here in the input,", "start": 3712.27, "duration": 4.02}, {"text": "and you're just going to guess\nthe sequence of nodes one", "start": 3716.29, "duration": 6.36}, {"text": "by one, which takes you from the\nstart node to the target node.", "start": 3722.65, "duration": 6.69}, {"text": "You're not going to write down\nthat whole sequence in advance", "start": 3729.34, "duration": 2.7}, {"text": "because that cost you way\ntoo much space to write down.", "start": 3732.04, "duration": 3.93}, {"text": "The only space that\nyou're going to use", "start": 3735.97, "duration": 1.68}, {"text": "is to remember the current\nlocation where you're sitting.", "start": 3737.65, "duration": 2.94}, {"text": "So you start out, you\nwrite down on the work tape", "start": 3740.59, "duration": 2.73}, {"text": "the start node.", "start": 3743.32, "duration": 1.26}, {"text": "Then you're going to\nnondeterministically pick", "start": 3744.58, "duration": 2.34}, {"text": "one of the outgoing\nedges from the start node", "start": 3746.92, "duration": 2.73}, {"text": "and look at its associated node,\nand replace that on your work", "start": 3749.65, "duration": 4.02}, {"text": "tape, and keep repeating that.", "start": 3753.67, "duration": 3.12}, {"text": "If you ever get to the node\nt, then you can accept.", "start": 3756.79, "duration": 5.4}, {"text": "And you also have to\nbe a little careful--", "start": 3762.19, "duration": 1.75}, {"text": "I don't have this on the slide.", "start": 3763.94, "duration": 2.3}, {"text": "You also have to make sure that\nif the graph has a loop in it,", "start": 3766.24, "duration": 7.03}, {"text": "because that's not allowed\nin space complexity,", "start": 3773.27, "duration": 3.1}, {"text": "so you're going to need\nalso a counter to make sure", "start": 3776.37, "duration": 2.36}, {"text": "that if you count up to--", "start": 3778.73, "duration": 4.82}, {"text": "you've gone through\na number of nodes", "start": 3783.55, "duration": 1.96}, {"text": "which exceeds the total\nnumber of nodes in the graph,", "start": 3785.51, "duration": 2.97}, {"text": "then you can shut down that\nbranch of the nondeterministic,", "start": 3788.48, "duration": 3.03}, {"text": "because it's just\ngoing in a loop.", "start": 3791.51, "duration": 8.05}, {"text": "If there's any path\nthat connects s to t,", "start": 3799.56, "duration": 2.46}, {"text": "there's certainly\ngoing to be a path that", "start": 3802.02, "duration": 1.728}, {"text": "has the most of the number\nof nodes of the graph in it.", "start": 3803.748, "duration": 2.292}, {"text": "So path is in NL.", "start": 3808.73, "duration": 1.65}, {"text": "This language here\nis in L. What's", "start": 3810.38, "duration": 3.87}, {"text": "the relationship\nbetween L and NL?", "start": 3814.25, "duration": 2.22}, {"text": "Well, certainly the\ndeterministic class", "start": 3816.47, "duration": 2.31}, {"text": "is contained in the\nnondeterministic class.", "start": 3818.78, "duration": 2.37}, {"text": "That's all that's known.", "start": 3821.15, "duration": 2.17}, {"text": "Whether these two collapse down\nto be the same is unsolved.", "start": 3823.32, "duration": 4.08}, {"text": "And so we're going to spend\na little time next lecture", "start": 3827.4, "duration": 2.4}, {"text": "exploring this.", "start": 3829.8, "duration": 2.55}, {"text": "But let's first look at some\nof the basic facts about log", "start": 3832.35, "duration": 6.33}, {"text": "space, sort of setting\nourselves up for next lecture.", "start": 3838.68, "duration": 3.915}, {"text": "So first of all,\nanything that you", "start": 3846.71, "duration": 2.21}, {"text": "can do in log space you\ncan do in polynomial time--", "start": 3848.92, "duration": 3.21}, {"text": "in a sense kind of\ntrivially, and in a sense", "start": 3852.13, "duration": 3.24}, {"text": "we almost kind of really\nproved this already.", "start": 3855.37, "duration": 2.76}, {"text": "Because if you remember,\nwe said that anything", "start": 3858.13, "duration": 3.48}, {"text": "that you can do in a\ncertain amount of space", "start": 3861.61, "duration": 2.19}, {"text": "you can do in time that's\nexponential in the amount", "start": 3863.8, "duration": 10.17}, {"text": "of space, in the\ncorresponding amount of space.", "start": 3873.97, "duration": 2.46}, {"text": "So going from space to time\nblows you up exponentially.", "start": 3876.43, "duration": 4.24}, {"text": "And the exponential of\norder log n is polynomial.", "start": 3880.67, "duration": 5.24}, {"text": "So the way we're\ngoing to prove this--", "start": 3885.91, "duration": 2.55}, {"text": "and again, we kind of\nproved this already", "start": 3888.46, "duration": 2.19}, {"text": "but let's just go through it\nagain, specific to log space.", "start": 3890.65, "duration": 5.19}, {"text": "We'll say-- and this is going\nto be a useful definition for us", "start": 3895.84, "duration": 2.76}, {"text": "anyway--", "start": 3898.6, "duration": 1.53}, {"text": "a configuration for M on w.", "start": 3900.13, "duration": 2.73}, {"text": "So we also already talked\nabout the configuration", "start": 3902.86, "duration": 2.97}, {"text": "of the Turing machine\nM, which is just", "start": 3905.83, "duration": 2.13}, {"text": "a snapshot, which is the\ntape, the state, and the head", "start": 3907.96, "duration": 4.71}, {"text": "position.", "start": 3912.67, "duration": 1.74}, {"text": "When we have an\ninput, which is sort", "start": 3914.41, "duration": 3.57}, {"text": "of a read-only\ninput, which is not", "start": 3917.98, "duration": 2.67}, {"text": "being counted\ntoward the space, we", "start": 3920.65, "duration": 1.86}, {"text": "don't include that\nin the configuration.", "start": 3922.51, "duration": 3.66}, {"text": "We just say it's a configuration\nof M on that particular input,", "start": 3926.17, "duration": 4.08}, {"text": "but we're going to be\ncounting configurations.", "start": 3930.25, "duration": 2.37}, {"text": "And I don't want to count all\nthe different inputs as well.", "start": 3932.62, "duration": 2.7}, {"text": "I'm going to fix\nthe input and count", "start": 3935.32, "duration": 1.65}, {"text": "all of the configurations\nrelative to that input.", "start": 3936.97, "duration": 2.415}, {"text": "And so the number of\nsuch configurations", "start": 3942.72, "duration": 3.06}, {"text": "is just simply going to\nbe the number of states", "start": 3945.78, "duration": 3.75}, {"text": "times the number of head\npositions for the two heads", "start": 3949.53, "duration": 3.33}, {"text": "now, times the number of\npossible tape contents, which", "start": 3952.86, "duration": 3.72}, {"text": "is, as I mentioned,\nhere is a number", "start": 3956.58, "duration": 2.04}, {"text": "of different possible\ntape contents.", "start": 3958.62, "duration": 2.17}, {"text": "It's d, which is the tape\nalphabet, to the order log n.", "start": 3960.79, "duration": 4.4}, {"text": "And that's just going to\nbe n to the k for some k.", "start": 3965.19, "duration": 2.34}, {"text": "So it's going to be polynomial.", "start": 3967.53, "duration": 1.59}, {"text": "So that tells us that\nbecause the total number", "start": 3969.12, "duration": 3.15}, {"text": "of configurations for\nM on w is polynomial,", "start": 3972.27, "duration": 5.49}, {"text": "this machine can only be\nrunning for a polynomial number", "start": 3977.76, "duration": 3.75}, {"text": "of steps.", "start": 3981.51, "duration": 0.773}, {"text": "Otherwise, it'll be looping.", "start": 3982.283, "duration": 1.167}, {"text": "It'll be repeating\na configuration.", "start": 3983.45, "duration": 1.93}, {"text": "And so therefore, that\nmachine has to run itself", "start": 3985.38, "duration": 3.06}, {"text": "in polynomial time.", "start": 3988.44, "duration": 1.21}, {"text": "So you don't really, in a\nsense, have to do any work.", "start": 3989.65, "duration": 2.54}, {"text": "If a machine is\ndeterministically", "start": 3992.19, "duration": 2.49}, {"text": "deciding a language\nin log space,", "start": 3994.68, "duration": 2.34}, {"text": "it's also deterministically\ndeciding the language", "start": 3997.02, "duration": 3.065}, {"text": "in polynomial time\nbecause that's", "start": 4000.085, "duration": 1.375}, {"text": "all the time you\ncan use when you", "start": 4001.46, "duration": 1.62}, {"text": "have log space, unless you're\nlooping, which is not allowed.", "start": 4003.08, "duration": 3.81}, {"text": "So therefore, the\nsame machine shows", "start": 4006.89, "duration": 2.64}, {"text": "that you're also in P. I'll\nget to that in a second.", "start": 4009.53, "duration": 4.175}, {"text": "One thing I forgot to\nmention on the previous slide", "start": 4013.705, "duration": 2.125}, {"text": "when I'm talking about\nthe model is by the way,", "start": 4015.83, "duration": 1.958}, {"text": "this model is not\nso unreasonable,", "start": 4017.788, "duration": 3.232}, {"text": "where you have kind\nof-- imagine having", "start": 4021.02, "duration": 2.25}, {"text": "a very large, read-only\ninput and your local storage", "start": 4023.27, "duration": 5.44}, {"text": "is much smaller.", "start": 4028.71, "duration": 0.85}, {"text": "It's much too small to\npull in the entire input.", "start": 4029.56, "duration": 4.2}, {"text": "The way I used to\nexplain this years ago", "start": 4033.76, "duration": 2.79}, {"text": "was your input as a CD-ROM,\nwhich you guys probably barely", "start": 4036.55, "duration": 4.24}, {"text": "even know what it\nis anymore, but you", "start": 4040.79, "duration": 1.88}, {"text": "used to distribute\nsoftware that way.", "start": 4042.67, "duration": 1.86}, {"text": "So the ROM was on a\nDVD or a CD, which", "start": 4044.53, "duration": 4.44}, {"text": "contained whatever you're trying\nto-- like your software you're", "start": 4048.97, "duration": 4.05}, {"text": "trying to distribute.", "start": 4053.02, "duration": 1.44}, {"text": "It was some large\nthing, relatively,", "start": 4054.46, "duration": 3.09}, {"text": "and so you imagine having\na smaller amount of memory", "start": 4057.55, "duration": 4.8}, {"text": "relative to that.", "start": 4062.35, "duration": 0.708}, {"text": "So you didn't want\nto necessarily copy", "start": 4063.058, "duration": 1.584}, {"text": "that whole thing\ninto your storage.", "start": 4064.642, "duration": 1.608}, {"text": "Maybe even a better example\nnow is you think of the input", "start": 4066.25, "duration": 2.88}, {"text": "as being the entire internet.", "start": 4069.13, "duration": 2.88}, {"text": "Obviously, unless\nyou're Google, you", "start": 4072.01, "duration": 2.07}, {"text": "can't download\nthe whole internet", "start": 4074.08, "duration": 3.27}, {"text": "into your own local\nmemory, but you", "start": 4077.35, "duration": 3.26}, {"text": "can have references,\npointers into the input", "start": 4080.61, "duration": 2.61}, {"text": "into different places.", "start": 4083.22, "duration": 1.2}, {"text": "That's perhaps more analogous\nto this sort of read-only input", "start": 4084.42, "duration": 3.24}, {"text": "Turing machine model\nthat I'm describing.", "start": 4087.66, "duration": 2.58}, {"text": "And there's another fact\nthat I want to mention,", "start": 4096.12, "duration": 2.04}, {"text": "is that anything that you can\ndo in nondeterministic log", "start": 4098.16, "duration": 6.39}, {"text": "space you can do in\ndeterministic space,", "start": 4104.55, "duration": 3.66}, {"text": "but now with the squaring.", "start": 4108.21, "duration": 2.13}, {"text": "And that's using the same proof.", "start": 4110.34, "duration": 2.04}, {"text": "That's using Savitch's theorem,\nwhich you have to check also", "start": 4112.38, "duration": 3.24}, {"text": "works down to log space--", "start": 4115.62, "duration": 2.19}, {"text": "same proof.", "start": 4117.81, "duration": 0.629}, {"text": "So anything that you\ndo nondeterministically", "start": 4121.89, "duration": 2.19}, {"text": "in log n space you can use\ndeterministically in log", "start": 4124.08, "duration": 3.09}, {"text": "squared n space.", "start": 4127.17, "duration": 1.984}, {"text": "So let me just see if\nthere's a couple of questions", "start": 4129.154, "duration": 2.125}, {"text": "I want to answer here.", "start": 4131.279, "duration": 0.917}, {"text": "The relationship between L and\nNL is not known to be strict.", "start": 4135.359, "duration": 6.681}, {"text": "Nobody knows of an example.", "start": 4142.04, "duration": 1.47}, {"text": "No one knows whether\nthey're equal.", "start": 4143.51, "duration": 3.28}, {"text": "And have people looked at\nsublinear time classes?", "start": 4146.79, "duration": 9.71}, {"text": "Yes, generally when you\nhave nondeterministic", "start": 4156.5, "duration": 3.42}, {"text": "or probabilistic-- which\nwe haven't defined yet,", "start": 4159.92, "duration": 2.859}, {"text": "but we will--", "start": 4162.779, "duration": 1.071}, {"text": "people have looked at those\nsublinear time classes as well.", "start": 4163.85, "duration": 3.969}, {"text": "Deterministically, it\ndoesn't make so much sense", "start": 4167.819, "duration": 2.0}, {"text": "because then you can't even\ntalk about the whole input.", "start": 4169.819, "duration": 3.451}, {"text": "OK, let me move on.", "start": 4179.029, "duration": 1.861}, {"text": "This is my last slide.", "start": 4183.95, "duration": 1.119}, {"text": "Let me see if we can do\nthis before we break.", "start": 4185.069, "duration": 3.29}, {"text": "Not only is L\ncontained within P,", "start": 4188.359, "duration": 2.521}, {"text": "but the much\nstronger statement is", "start": 4190.88, "duration": 1.95}, {"text": "that NL is contained\nwithin P. And for that", "start": 4192.83, "duration": 4.41}, {"text": "you'll have to do some\nwork because converting", "start": 4197.24, "duration": 2.34}, {"text": "your nondeterministic\nlog space machine", "start": 4199.58, "duration": 2.1}, {"text": "to a deterministic machine--", "start": 4201.68, "duration": 3.99}, {"text": "obviously, you're going to\nhave to change the machine.", "start": 4205.67, "duration": 4.08}, {"text": "And so we'll introduce\na new method here.", "start": 4209.75, "duration": 1.95}, {"text": "Maybe we'll quickly go\nover this at the beginning", "start": 4211.7, "duration": 2.97}, {"text": "of the next lecture.", "start": 4214.67, "duration": 2.325}, {"text": "I don't like rushing\nthrough things at the end.", "start": 4216.995, "duration": 2.955}, {"text": "But for this, if I'm given a\nnondeterministic machine that", "start": 4219.95, "duration": 8.0}, {"text": "runs in log space, I want\nto make a new machine that", "start": 4227.95, "duration": 3.39}, {"text": "runs in polynomial\ntime deterministically", "start": 4231.34, "duration": 2.1}, {"text": "for the same language.", "start": 4233.44, "duration": 1.38}, {"text": "And I'm going to\ndefine something", "start": 4234.82, "duration": 1.5}, {"text": "called the \"configuration\ngraph\" for M on an input w.", "start": 4236.32, "duration": 5.38}, {"text": "And that's just you\ntake M and w, its input,", "start": 4241.7, "duration": 7.08}, {"text": "and you look at all of the\nconfigurations for M on w--", "start": 4248.78, "duration": 6.34}, {"text": "actually, configuration--", "start": 4255.12, "duration": 1.71}, {"text": "actually, that should be\ncalled the \"computation graph.\"", "start": 4256.83, "duration": 3.27}, {"text": "That's what it's called in\nthe book, but it's a typo.", "start": 4260.1, "duration": 2.7}, {"text": "Yeah, I'll fix that next time.", "start": 4262.8, "duration": 2.16}, {"text": "It doesn't matter.", "start": 4264.96, "duration": 1.08}, {"text": "Computation graph, configuration\ngraph, all the same.", "start": 4266.04, "duration": 4.212}, {"text": "Basically, you're going to take\nall of the configurations of M", "start": 4270.252, "duration": 2.583}, {"text": "on w, of which we\nalready observed", "start": 4272.835, "duration": 4.155}, {"text": "are only polynomial in number.", "start": 4276.99, "duration": 2.58}, {"text": "And they become the\nnodes of a graph.", "start": 4279.57, "duration": 3.75}, {"text": "And the edges connect\ntwo configurations", "start": 4283.32, "duration": 3.15}, {"text": "if one follows another according\nto the rules of the machine.", "start": 4286.47, "duration": 4.49}, {"text": "So here's a picture.", "start": 4290.96, "duration": 1.26}, {"text": "This is some graph.", "start": 4292.22, "duration": 2.49}, {"text": "The nodes of this graph are\nthe configurations of M on w.", "start": 4294.71, "duration": 5.86}, {"text": "So each node here\ncorresponds to a snapshot", "start": 4300.57, "duration": 4.29}, {"text": "of the machine, a tape contents,\nhead position, and state.", "start": 4304.86, "duration": 7.87}, {"text": "So writing down all those\ndifferent configurations,", "start": 4312.73, "duration": 2.34}, {"text": "I connect one to\nthe other, if I can", "start": 4315.07, "duration": 1.8}, {"text": "get to C j from C i in one\nstep legally on the machine.", "start": 4316.87, "duration": 5.74}, {"text": "And then, the\nnondeterministic machine M", "start": 4322.61, "duration": 4.67}, {"text": "accepts w exactly when\nthere's a path from the start", "start": 4327.28, "duration": 4.48}, {"text": "configuration to an\naccept configuration.", "start": 4331.76, "duration": 3.42}, {"text": "Let's assume we have just a\nsingle accept configuration,", "start": 4335.18, "duration": 3.09}, {"text": "as we argued we can do\none or two lectures back,", "start": 4338.27, "duration": 5.14}, {"text": "if we clean up the tapes.", "start": 4343.41, "duration": 1.44}, {"text": "So testing whether you can get\nfrom the start to the accept", "start": 4344.85, "duration": 7.05}, {"text": "is the same as testing whether\nthe machine accepts its input.", "start": 4351.9, "duration": 4.84}, {"text": "And so because we can\ntest whether there's", "start": 4356.74, "duration": 4.17}, {"text": "a path in a graph connecting\ntwo nodes in polynomial time,", "start": 4360.91, "duration": 4.17}, {"text": "we can solve this problem on\nthis computation/configuration", "start": 4365.08, "duration": 3.15}, {"text": "graph in polynomial time.", "start": 4368.23, "duration": 1.81}, {"text": "And so we can figure out whether\nthe nondeterministic machine", "start": 4370.04, "duration": 2.69}, {"text": "accepts its input.", "start": 4372.73, "duration": 1.415}, {"text": "Sorry, that came a little\nfaster than I like to do,", "start": 4374.145, "duration": 2.125}, {"text": "so we'll see it again.", "start": 4376.27, "duration": 2.8}, {"text": "So here's the polynomial\ntime algorithm.", "start": 4379.07, "duration": 2.15}, {"text": "You construct the\ngraph, you accept", "start": 4381.22, "duration": 2.602}, {"text": "if there's a path from\nthe start to the accept,", "start": 4383.822, "duration": 1.958}, {"text": "and you reject if there is not.", "start": 4385.78, "duration": 1.292}, {"text": "And so that tells us that not\nonly is L contained within NL,", "start": 4389.8, "duration": 5.03}, {"text": "but NL itself is also\ncontained within P.", "start": 4394.83, "duration": 2.88}, {"text": "So here's a kind of a nice\nhierarchy of languages.", "start": 4397.71, "duration": 5.43}, {"text": "Not only do we not know\nwhether L equals NL,", "start": 4403.14, "duration": 2.73}, {"text": "we don't know\nwhether L equals P.", "start": 4405.87, "duration": 2.82}, {"text": "It's possible that anything\nyou can do in polynomial time,", "start": 4408.69, "duration": 2.79}, {"text": "you can do deterministically\nin log space,", "start": 4411.48, "duration": 2.31}, {"text": "shocking as that\nmight be, because this", "start": 4413.79, "duration": 1.74}, {"text": "is a pretty weak class.", "start": 4415.53, "duration": 2.55}, {"text": "But we don't know how\nto prove that there's", "start": 4418.08, "duration": 2.1}, {"text": "anything different, anything\nin P that's not in here.", "start": 4420.18, "duration": 4.8}, {"text": "Last check in.", "start": 4424.98, "duration": 2.17}, {"text": "So we showed that PATH is in NL.", "start": 4427.15, "duration": 1.97}, {"text": "What's the best thing we can do\nabout the deterministic space", "start": 4429.12, "duration": 2.73}, {"text": "complexity of PATH?", "start": 4431.85, "duration": 1.14}, {"text": "So deterministic.", "start": 4432.99, "duration": 1.12}, {"text": "So this is\nnondeterministic log space.", "start": 4434.11, "duration": 1.94}, {"text": "What can we say\ndeterministically about PATH?", "start": 4436.05, "duration": 4.59}, {"text": "Hint-- this should not be\nhard if you think back to what", "start": 4440.64, "duration": 5.01}, {"text": "we've shown very recently.", "start": 4445.65, "duration": 2.55}, {"text": "Get your check in points.", "start": 4453.36, "duration": 1.53}, {"text": "Closing up.", "start": 4454.89, "duration": 1.11}, {"text": "Closing shop here.", "start": 4456.0, "duration": 1.68}, {"text": "All set, 1, 2, 3.", "start": 4457.68, "duration": 1.095}, {"text": "Yeah, so the correct answer\nis log squared space,", "start": 4461.55, "duration": 2.79}, {"text": "because this is just\nSavitch's theorem.", "start": 4464.34, "duration": 2.84}, {"text": "We can do it in log space\nnondeterministically,", "start": 4467.18, "duration": 2.29}, {"text": "so you can do it in log squared\nspace deterministically.", "start": 4469.47, "duration": 3.23}, {"text": "So this is what we did today.", "start": 4472.7, "duration": 2.73}, {"text": "And as I mentioned,\nI will do this again", "start": 4478.9, "duration": 6.68}, {"text": "on Tuesday's lecture,\njust to recap that.", "start": 4485.58, "duration": 3.21}, {"text": "All right, so I'll stick around\na little bit for questions.", "start": 4488.79, "duration": 2.97}, {"text": "And someone's asking me\nabout the nomenclature.", "start": 4491.76, "duration": 4.71}, {"text": "Why is it L and not L space?", "start": 4496.47, "duration": 1.85}, {"text": "Because people don't\nusually talk about L time.", "start": 4503.16, "duration": 3.12}, {"text": "So L is sort of--", "start": 4506.28, "duration": 1.61}, {"text": "everybody knows the only\nreasonable option is space,", "start": 4507.89, "duration": 3.12}, {"text": "so people just say L and NL.", "start": 4511.01, "duration": 3.54}, {"text": "I mean, some of these names have\na little bit evolved over time.", "start": 4514.55, "duration": 9.18}, {"text": "And even now, some\npeople talk about--", "start": 4523.73, "duration": 2.385}, {"text": "I call \"time classes,\" some\npeople call \"detime classes.\"", "start": 4529.21, "duration": 3.42}, {"text": "You can make different\nchoices there.", "start": 4538.16, "duration": 3.73}, {"text": "Let's see.", "start": 4541.89, "duration": 0.5}, {"text": "Good.", "start": 4544.775, "duration": 0.5}, {"text": "Why does Savitch's\ntheorem work for log n?", "start": 4547.78, "duration": 3.12}, {"text": "You have to look back\nand see what you needed.", "start": 4550.9, "duration": 3.36}, {"text": "And all you needed\nto be able to do", "start": 4554.26, "duration": 2.1}, {"text": "was to write down\nthe configurations.", "start": 4556.36, "duration": 7.36}, {"text": "And if you look back at\nhow Savitch's film works,", "start": 4563.72, "duration": 3.333}, {"text": "you're just needing to write\ndown the configuration.", "start": 4567.053, "duration": 2.167}, {"text": "So the deterministic\nmachine can write down", "start": 4569.22, "duration": 2.323}, {"text": "the configurations for the\nnondeterministic machine.", "start": 4571.543, "duration": 2.167}, {"text": "They take exactly the same size.", "start": 4573.71, "duration": 2.74}, {"text": "And then you look\nat the recursion.", "start": 4576.45, "duration": 1.91}, {"text": "And the depth of\nthe recursion is", "start": 4578.36, "duration": 2.55}, {"text": "going to be exponential in the\nsize of the configurations.", "start": 4580.91, "duration": 4.773}, {"text": "And so you're going to end\nup with a squaring again.", "start": 4585.683, "duration": 2.167}, {"text": "You have to go back and\njust rethink that proof.", "start": 4587.85, "duration": 3.29}, {"text": "And you'll see nowhere did it\nneed a linear amount of space.", "start": 4591.14, "duration": 3.27}, {"text": "It works down to--", "start": 4594.41, "duration": 1.32}, {"text": "it actually does not\nwork for less than log n.", "start": 4595.73, "duration": 2.37}, {"text": "Log n is sort of the\nlower threshold there.", "start": 4598.1, "duration": 3.58}, {"text": "And the reason for that\nis because you also", "start": 4601.68, "duration": 3.05}, {"text": "need to store the\ninput location,", "start": 4604.73, "duration": 3.78}, {"text": "and that already\ntakes log space.", "start": 4608.51, "duration": 1.53}, {"text": "The tape heads-- the\ntape heads already kind", "start": 4613.92, "duration": 2.54}, {"text": "have kind of a log\nspace aspect to them.", "start": 4616.46, "duration": 4.93}, {"text": "And so if you're going to\nuse less than log space,", "start": 4621.39, "duration": 3.35}, {"text": "then funky things happen\nwith storing the tape heads.", "start": 4624.74, "duration": 3.81}, {"text": "And so less than\nlog space usually", "start": 4628.55, "duration": 2.67}, {"text": "turns out not to be\ninteresting, very", "start": 4631.22, "duration": 3.33}, {"text": "specific to Turing machines\nand not general models.", "start": 4634.55, "duration": 3.39}, {"text": "Yeah, so somebody's asking,\nsuppose in the reduction", "start": 4641.17, "duration": 5.37}, {"text": "to generalized\ngeography from TQBF,", "start": 4646.54, "duration": 2.88}, {"text": "if the formula had\ntwo Exists in a row,", "start": 4649.42, "duration": 3.325}, {"text": "then you would do kind of the\nnatural thing in the graph.", "start": 4652.745, "duration": 2.375}, {"text": "Instead of having that spacer\nedge between the two diamonds,", "start": 4655.12, "duration": 3.03}, {"text": "you could just have one\ndiamond connecting directly", "start": 4658.15, "duration": 2.49}, {"text": "to the other diamond\nwithout a spacer edge.", "start": 4660.64, "duration": 2.61}, {"text": "And that would give you\nthe effect of not switching", "start": 4663.25, "duration": 5.31}, {"text": "whose turn it is.", "start": 4668.56, "duration": 2.26}, {"text": "Somebody is asking me\njust a general question,", "start": 4670.82, "duration": 3.54}, {"text": "are people thinking about\nthese open problems?", "start": 4674.36, "duration": 3.06}, {"text": "I don't know.", "start": 4682.63, "duration": 2.9}, {"text": "People don't say.", "start": 4685.53, "duration": 4.23}, {"text": "There was a lot of work\non problems related,", "start": 4689.76, "duration": 3.36}, {"text": "that seemed to be related to\nthose many open questions,", "start": 4693.12, "duration": 4.41}, {"text": "like P versus NP, L versus\nNL or L versus P and so on,", "start": 4697.53, "duration": 4.68}, {"text": "P versus PSPACE.", "start": 4702.21, "duration": 1.99}, {"text": "We'll talk a little bit\nmore about some of that.", "start": 4704.2, "duration": 2.0}, {"text": "There's some very\ninteresting things", "start": 4706.2, "duration": 1.23}, {"text": "that have been developed.", "start": 4707.43, "duration": 1.12}, {"text": "I think there's a sense\nwithin the community", "start": 4708.55, "duration": 2.21}, {"text": "that people are\nstuck, and you're", "start": 4710.76, "duration": 3.39}, {"text": "going to need some\nsort of major new idea", "start": 4714.15, "duration": 3.6}, {"text": "in order to push\nthe thing forward.", "start": 4717.75, "duration": 1.78}, {"text": "So I don't know how many people\nare still thinking about them.", "start": 4719.53, "duration": 4.665}, {"text": "I hope people are\nbecause I would", "start": 4724.195, "duration": 1.375}, {"text": "like to see the answer at\nsome point, or get the answer.", "start": 4725.57, "duration": 4.56}, {"text": "I think about them\nsometimes myself,", "start": 4730.13, "duration": 1.68}, {"text": "but one has to acknowledge\nchances of success", "start": 4731.81, "duration": 5.55}, {"text": "are not high.", "start": 4737.36, "duration": 0.63}, {"text": "So we're a little after past\nthe end of the hour here.", "start": 4743.79, "duration": 4.53}, {"text": "Unless there's any\nother questions,", "start": 4748.32, "duration": 1.5}, {"text": "if I didn't answer your\nquestion, I may have missed it,", "start": 4749.82, "duration": 2.292}, {"text": "so you can ask again.", "start": 4752.112, "duration": 2.938}, {"text": "But otherwise, I'm going to\nclose this, close the session", "start": 4755.05, "duration": 3.95}, {"text": "here.", "start": 4759.0, "duration": 1.08}, {"text": "OK, bye-bye all.", "start": 4760.08, "duration": 1.86}, {"text": "Have a good weekend.", "start": 4761.94, "duration": 1.0}, {"text": "See you next week.", "start": 4762.94, "duration": 1.62}, {"text": "Take care.", "start": 4764.56, "duration": 1.6}]
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+[{"text": "MICHALE FEE: So who\nremembers what that's called?", "start": 13.53, "duration": 2.76}, {"text": "A spectrograph.", "start": 16.29, "duration": 1.66}, {"text": "Good.", "start": 17.95, "duration": 1.65}, {"text": "And it's a spectrogram of me.", "start": 19.6, "duration": 2.925}, {"text": "Good morning, class.", "start": 26.47, "duration": 1.58}, {"text": "OK.", "start": 28.05, "duration": 0.61}, {"text": "So it's a spectrogram of speech.", "start": 28.66, "duration": 3.12}, {"text": "And so we are going\nto continue today", "start": 31.78, "duration": 4.92}, {"text": "on the topic of understanding--", "start": 36.7, "duration": 2.89}, {"text": "developing methods\nfor understanding", "start": 39.59, "duration": 2.0}, {"text": "how to characterize\nand understand", "start": 41.59, "duration": 4.44}, {"text": "temporally structured signals.", "start": 46.03, "duration": 1.43}, {"text": "So that is the\nmicrophone recording", "start": 47.46, "duration": 2.08}, {"text": "of my voice saying\n\"good morning, class.\"", "start": 49.54, "duration": 3.27}, {"text": "And then this is a spectrogram\nof that signal where", "start": 52.81, "duration": 3.21}, {"text": "at each moment in\ntime, you can actually", "start": 56.02, "duration": 2.1}, {"text": "extract the spectral\nstructure of that signal.", "start": 58.12, "duration": 3.1}, {"text": "And you can see that the\ninformation in speech signals", "start": 61.22, "duration": 3.769}, {"text": "is actually carried in parts of\nthe signal in the way the power", "start": 64.989, "duration": 7.981}, {"text": "in the signal at different\nfrequencies changes over time.", "start": 72.97, "duration": 3.88}, {"text": "And your ears detect\nthese changes in frequency", "start": 76.85, "duration": 3.56}, {"text": "and translate that\ninto information", "start": 80.41, "duration": 2.07}, {"text": "about what I'm saying.", "start": 82.48, "duration": 2.55}, {"text": "And so we're going to\ntoday start on a-- well,", "start": 85.03, "duration": 6.39}, {"text": "we sort of started last\ntime, but we're really", "start": 91.42, "duration": 2.13}, {"text": "going to get going on this\nin the next three lectures.", "start": 93.55, "duration": 4.32}, {"text": "We're going to develop\na powerful set of tools", "start": 97.87, "duration": 3.66}, {"text": "for characterizing\nand understanding", "start": 101.53, "duration": 2.7}, {"text": "the temporal\nstructure of signals.", "start": 104.23, "duration": 2.55}, {"text": "So this is the game plan\nfor the next three lectures.", "start": 106.78, "duration": 5.61}, {"text": "Today we're going to\ncover Fourier series--", "start": 112.39, "duration": 3.03}, {"text": "complex Fourier series.", "start": 115.42, "duration": 1.29}, {"text": "We're going to extend that\nto the idea of the Fourier", "start": 116.71, "duration": 2.91}, {"text": "transform.", "start": 119.62, "duration": 1.14}, {"text": "And then so the\nFourier transform", "start": 120.76, "duration": 1.7}, {"text": "is sort of a very general\nmathematical approach", "start": 122.46, "duration": 4.48}, {"text": "to understanding the temporal\nstructure of signals.", "start": 126.94, "duration": 3.21}, {"text": "That's more of a--", "start": 130.15, "duration": 2.19}, {"text": "you think of that\nmore in terms of doing", "start": 132.34, "duration": 3.48}, {"text": "analytical calculations or sort\nof conceptual understanding", "start": 135.82, "duration": 6.54}, {"text": "of what Fourier\ndecomposition is.", "start": 142.36, "duration": 5.02}, {"text": "But then there's a\nvery concrete algorithm", "start": 147.38, "duration": 5.78}, {"text": "for characterizing spectral\nstructure of signals called", "start": 153.16, "duration": 3.86}, {"text": "the fast Fourier transform.", "start": 157.02, "duration": 1.27}, {"text": "And that's one class of methods\nwhere you sample signals", "start": 158.29, "duration": 5.19}, {"text": "discretely in time and\nget back discrete power", "start": 163.48, "duration": 4.23}, {"text": "at discrete frequencies.", "start": 167.71, "duration": 1.41}, {"text": "So that's called a\ndiscrete Fourier transform.", "start": 169.12, "duration": 2.46}, {"text": "And most often that's\nused to compute", "start": 171.58, "duration": 2.19}, {"text": "the power spectrum of signals.", "start": 173.77, "duration": 2.4}, {"text": "And so that's what we're\ngoing to cover today.", "start": 176.17, "duration": 3.4}, {"text": "And then in the\nnext lecture, we're", "start": 179.57, "duration": 2.83}, {"text": "going to cover a number\nof topics leading up", "start": 182.4, "duration": 2.59}, {"text": "to spectral estimation.", "start": 184.99, "duration": 1.267}, {"text": "We're going to start with the\nconvolution theorem, which", "start": 186.257, "duration": 2.333}, {"text": "is a really powerful\nway of understanding", "start": 188.59, "duration": 3.06}, {"text": "the relationship\nbetween convolution", "start": 191.65, "duration": 3.9}, {"text": "in the time domain and\nmultiplication of things", "start": 195.55, "duration": 2.61}, {"text": "in the frequency domain.", "start": 198.16, "duration": 1.53}, {"text": "And the convolution\ntheorem is really powerful,", "start": 199.69, "duration": 2.76}, {"text": "allowing you to kind of\nthink about, intuitively", "start": 202.45, "duration": 2.55}, {"text": "understand the spectral\nstructure of different kinds", "start": 205.0, "duration": 2.55}, {"text": "of signals that you can build\nby convolving different sort", "start": 207.55, "duration": 4.132}, {"text": "of basic elements.", "start": 211.682, "duration": 2.118}, {"text": "So if you understand the Fourier\ndecomposition of a square pulse", "start": 213.8, "duration": 5.21}, {"text": "and a train of\npulses or a Gaussian,", "start": 219.01, "duration": 4.78}, {"text": "you can basically just by\nkind of thinking about it", "start": 223.79, "duration": 4.13}, {"text": "figure out the\nspectral structure", "start": 227.92, "duration": 1.41}, {"text": "of a lot of different signals\nby just combining those things", "start": 229.33, "duration": 3.27}, {"text": "sort of like LEGO blocks.", "start": 232.6, "duration": 1.11}, {"text": "It's super cool.", "start": 233.71, "duration": 1.35}, {"text": "We're going to talk about\nnoise and filtering.", "start": 235.06, "duration": 3.06}, {"text": "We're going to talk about\nthe Shannon-Nyquist sampling", "start": 238.12, "duration": 2.73}, {"text": "theorem, which tells\nyou how fast you", "start": 240.85, "duration": 2.19}, {"text": "have to sample a signal in order\nto perfectly reconstruct it.", "start": 243.04, "duration": 3.36}, {"text": "It turns out it's\nreally amazing.", "start": 246.4, "duration": 1.7}, {"text": "If you have a\nsignal in time, you", "start": 248.1, "duration": 2.08}, {"text": "can sample that signal\nat regular intervals", "start": 250.18, "duration": 2.73}, {"text": "and perfectly\nreconstruct the signal", "start": 252.91, "duration": 3.0}, {"text": "if that signal doesn't have\nfrequency components that", "start": 255.91, "duration": 4.32}, {"text": "are too high.", "start": 260.23, "duration": 0.9}, {"text": "And so that's captured in\nthis Shannon-Nyquist sampling", "start": 261.13, "duration": 2.52}, {"text": "theorem.", "start": 263.65, "duration": 0.54}, {"text": "That turns out to actually\nbe a topic of current debate.", "start": 264.19, "duration": 4.03}, {"text": "There was a paper\npublished recently", "start": 268.22, "duration": 2.93}, {"text": "by somebody claiming to be\nable to get around the sampling", "start": 271.15, "duration": 3.78}, {"text": "theorem and record neural\nsignals without having", "start": 274.93, "duration": 3.87}, {"text": "to guarantee the\nconditions under which", "start": 278.8, "duration": 3.03}, {"text": "the Shannon-Nyquist\nsampling theorem claims.", "start": 281.83, "duration": 3.99}, {"text": "And Markus Meister wrote\na scathing rebuttal", "start": 285.82, "duration": 4.53}, {"text": "to that basically claiming\nthat they're full of baloney.", "start": 290.35, "duration": 3.3}, {"text": "And so those folks who\nwrote that paper maybe", "start": 293.65, "duration": 4.71}, {"text": "should have taken this class.", "start": 298.36, "duration": 2.34}, {"text": "So anyway, you don't want\nto be on the wrong end", "start": 300.7, "duration": 2.21}, {"text": "of Markus Meister's blog post.", "start": 302.91, "duration": 3.61}, {"text": "So pay attention.", "start": 306.52, "duration": 2.81}, {"text": "So then we're going to get\ninto spectral estimation.", "start": 309.33, "duration": 2.418}, {"text": "Then in the last\nlecture, we're going", "start": 311.748, "duration": 1.542}, {"text": "to talk about spectrograms.", "start": 313.29, "duration": 1.65}, {"text": "We're going to talk about\nhow to compute spectrograms", "start": 314.94, "duration": 2.4}, {"text": "and understand really\nhow to take the data", "start": 317.34, "duration": 2.94}, {"text": "and break it into\nsamples called windowing,", "start": 320.28, "duration": 2.55}, {"text": "how to multiply those samples\nby what's called a taper", "start": 322.83, "duration": 3.45}, {"text": "to avoid contaminating\nthe signal with lots", "start": 326.28, "duration": 2.82}, {"text": "of noise that's unnecessary.", "start": 329.1, "duration": 1.818}, {"text": "We're going to understand the\nidea of time bandwidth product.", "start": 330.918, "duration": 2.542}, {"text": "How do you choose the\nwidth of that window", "start": 333.46, "duration": 1.76}, {"text": "to emphasize different\nparts of the data?", "start": 335.22, "duration": 2.25}, {"text": "And then we're going to end\nwith some advanced filtering", "start": 337.47, "duration": 3.99}, {"text": "methods that are commonly used\nto control different frequency", "start": 341.46, "duration": 7.23}, {"text": "components of\nsignals in your data.", "start": 348.69, "duration": 2.7}, {"text": "So a bunch of really\npowerful things.", "start": 351.39, "duration": 2.44}, {"text": "Here's what we're going\nto talk about today.", "start": 353.83, "duration": 3.17}, {"text": "We're going to continue\nwith this Fourier series.", "start": 357.0, "duration": 2.25}, {"text": "We started with symmetric\nfunctions last time.", "start": 359.25, "duration": 2.443}, {"text": "We're going to finish\nthat and then talk", "start": 361.693, "duration": 1.667}, {"text": "about asymmetric functions.", "start": 363.36, "duration": 1.74}, {"text": "We're going to extend that\nto complex Fourier series,", "start": 365.1, "duration": 3.51}, {"text": "introduce the Fourier transform\nand the discrete Fourier", "start": 368.61, "duration": 2.34}, {"text": "transform and this algorithm\nand the fast Fourier transform,", "start": 370.95, "duration": 3.03}, {"text": "and then I'm going to show you\nhow to compute power spectrum.", "start": 373.98, "duration": 3.96}, {"text": "So just to make it\nclear, all of this stuff", "start": 377.94, "duration": 4.83}, {"text": "is basically going\nto be to teach you", "start": 382.77, "duration": 2.34}, {"text": "how to use one line of MATLAB.", "start": 385.11, "duration": 2.88}, {"text": "One function, FFT.", "start": 387.99, "duration": 2.73}, {"text": "Now, the problem is it's\nreally easy to do this wrong.", "start": 390.72, "duration": 6.45}, {"text": "It's really easy\nto use this but not", "start": 397.17, "duration": 2.61}, {"text": "understand what you're doing and\ncome up with the wrong answer.", "start": 399.78, "duration": 4.56}, {"text": "So all of these things that\nwe're going to talk about today", "start": 404.34, "duration": 3.24}, {"text": "are just the kind\nof basics that you", "start": 407.58, "duration": 2.34}, {"text": "need to understand in order to\nuse this very powerful function", "start": 409.92, "duration": 3.76}, {"text": "in MATLAB.", "start": 413.68, "duration": 0.5}, {"text": "All right.", "start": 416.76, "duration": 2.07}, {"text": "So let's get started.", "start": 418.83, "duration": 1.06}, {"text": "So last time, we introduced\nthe idea of a Fourier series.", "start": 419.89, "duration": 3.775}, {"text": "We talked about\nthe idea that you", "start": 423.665, "duration": 1.375}, {"text": "can approximate any\nperiodic function.", "start": 425.04, "duration": 2.29}, {"text": "So here I'm just taking a\nsquare wave that alternates", "start": 427.33, "duration": 3.35}, {"text": "between positive and negative.", "start": 430.68, "duration": 2.31}, {"text": "It's periodic with\na period capital T.", "start": 432.99, "duration": 2.31}, {"text": "So it's a function of time.", "start": 435.3, "duration": 1.57}, {"text": "It's a even function or\na symmetric function,", "start": 436.87, "duration": 4.28}, {"text": "because you can see that\nit's basically mirror", "start": 441.15, "duration": 2.82}, {"text": "symmetry around the y-axis.", "start": 443.97, "duration": 3.07}, {"text": "It's even because\neven polynomials also", "start": 447.04, "duration": 2.93}, {"text": "have that property\nof being symmetric.", "start": 449.97, "duration": 3.09}, {"text": "We can approximate\nthis periodic function", "start": 453.06, "duration": 3.63}, {"text": "T as a sum of sine waves or\ncosine waves, in this case.", "start": 456.69, "duration": 4.8}, {"text": "We can approximate that as a\ncosine wave of the same period", "start": 461.49, "duration": 5.82}, {"text": "and the same amplitude.", "start": 467.31, "duration": 1.81}, {"text": "So we can approximate as a\ncoefficient times cosine 2 pi", "start": 469.12, "duration": 4.64}, {"text": "f0 t where f0 is just\n1 over the period.", "start": 473.76, "duration": 4.45}, {"text": "So if the period is one\nsecond, then the frequency", "start": 478.21, "duration": 2.73}, {"text": "is 1 hertz, 1 over 1 second.", "start": 480.94, "duration": 2.67}, {"text": "We often use this\ndifferent representation", "start": 483.61, "duration": 5.13}, {"text": "of frequency, which is\nusually called omega,", "start": 488.74, "duration": 3.43}, {"text": "which is angular frequency.", "start": 492.17, "duration": 3.23}, {"text": "And it's just 2 pi times\nthis oscillation frequency.", "start": 495.4, "duration": 4.52}, {"text": "And it has units of\nradians per second.", "start": 499.92, "duration": 3.7}, {"text": "So we talked about\nthe fact that you", "start": 503.62, "duration": 2.85}, {"text": "can approximate this periodic\nfunction as a sum of cosines.", "start": 506.47, "duration": 5.01}, {"text": "We talked about the\nidea that you only", "start": 511.48, "duration": 2.04}, {"text": "need to consider cosines that\nare integer multiples of omega", "start": 513.52, "duration": 3.09}, {"text": "0, because those are the\nonly cosine functions,", "start": 516.61, "duration": 3.99}, {"text": "those are the only\nfunctions, that also are", "start": 520.6, "duration": 3.18}, {"text": "periodic at frequency omega 0.", "start": 523.78, "duration": 3.42}, {"text": "So a function cosine\n3 omega 0 t is also", "start": 527.2, "duration": 4.17}, {"text": "periodic at frequency omega 0.", "start": 531.37, "duration": 3.02}, {"text": "Does that make sense?", "start": 534.39, "duration": 2.35}, {"text": "So now we can approximate\nany periodic function.", "start": 536.74, "duration": 4.77}, {"text": "In this case, any even\nor symmetric periodic", "start": 541.51, "duration": 3.21}, {"text": "function as a sum of cosines\nof frequencies that are", "start": 544.72, "duration": 7.62}, {"text": "integer multiples of omega 0.", "start": 552.34, "duration": 1.793}, {"text": "And each one of\nthose cosines will", "start": 554.133, "duration": 1.417}, {"text": "have a different coefficient.", "start": 555.55, "duration": 1.77}, {"text": "So here's an example where I'm\napproximating this square wave", "start": 557.32, "duration": 5.73}, {"text": "here as a sum of cosines of\nthese different frequencies.", "start": 563.05, "duration": 4.182}, {"text": "And it turns out\nfor a square wave,", "start": 567.232, "duration": 1.458}, {"text": "you only need the odd\nmultiples of omega 0.", "start": 568.69, "duration": 4.77}, {"text": "So here's what\nthis approximation", "start": 573.46, "duration": 2.46}, {"text": "looks like for the case where\nyou only have a single cosine", "start": 575.92, "duration": 2.88}, {"text": "function.", "start": 578.8, "duration": 0.93}, {"text": "You can add another\ncosine of 3 omega 0 t", "start": 579.73, "duration": 3.358}, {"text": "and you can see that that\nfunction starts getting", "start": 583.088, "duration": 2.042}, {"text": "a little bit more square.", "start": 585.13, "duration": 1.83}, {"text": "You can add a\ncosine 5 omega 0 t.", "start": 586.96, "duration": 2.76}, {"text": "And as you keep\nadding those things,", "start": 589.72, "duration": 1.59}, {"text": "again, with the correct\ncoefficients in front of these,", "start": 591.31, "duration": 3.16}, {"text": "you can see that the\nfunction more and more", "start": 594.47, "duration": 2.18}, {"text": "closely approximates the square\nwave that we're trying to--", "start": 596.65, "duration": 4.3}, {"text": "yes, Habiba", "start": 600.95, "duration": 0.64}, {"text": "AUDIENCE: Why do we only\nneed the odd multiples?", "start": 601.59, "duration": 2.73}, {"text": "MICHALE FEE: It\njust, in general, you", "start": 604.32, "duration": 1.99}, {"text": "need all the multiples.", "start": 606.31, "duration": 1.74}, {"text": "But for this\nparticular function,", "start": 608.05, "duration": 1.635}, {"text": "you only need the odd ones.", "start": 609.685, "duration": 1.125}, {"text": "Here's another example.", "start": 622.21, "duration": 1.02}, {"text": "So in this case, we are summing\ntogether cosine functions", "start": 623.23, "duration": 5.54}, {"text": "to approximate a\ntrain of pulses.", "start": 628.77, "duration": 5.1}, {"text": "So the signal we're\ntrying to approximate here", "start": 633.87, "duration": 2.46}, {"text": "just has a pulse every one\nunit of time, one period.", "start": 636.33, "duration": 5.8}, {"text": "And you can see that\nto approximate this,", "start": 642.13, "duration": 1.97}, {"text": "we can basically just\nsum up all the cosines", "start": 644.1, "duration": 3.27}, {"text": "of all frequencies n omega 0.", "start": 647.37, "duration": 3.0}, {"text": "And you can see that at time\n0, all of those functions", "start": 650.37, "duration": 4.98}, {"text": "are positive.", "start": 655.35, "duration": 1.47}, {"text": "And so all of those positive\ncontributions to that sum", "start": 656.82, "duration": 5.58}, {"text": "all add up.", "start": 662.4, "duration": 1.22}, {"text": "And as you add them\nup, you get a big peak.", "start": 663.62, "duration": 2.41}, {"text": "That's called\nconstructive interference.", "start": 666.03, "duration": 2.16}, {"text": "So all those peaks add up.", "start": 668.19, "duration": 3.51}, {"text": "And you also get those peaks\nall adding up one period away.", "start": 671.7, "duration": 4.95}, {"text": "One period of cosine omega 0.", "start": 676.65, "duration": 4.26}, {"text": "You can see they add up again.", "start": 680.91, "duration": 1.47}, {"text": "So you can see this is\na periodic function.", "start": 682.38, "duration": 1.92}, {"text": "In this time window\nbetween those peaks,", "start": 684.3, "duration": 3.24}, {"text": "you can see that you have\npositive peaks of some", "start": 687.54, "duration": 2.37}, {"text": "of those cosines, negative\npeaks, positive, negative.", "start": 689.91, "duration": 3.45}, {"text": "They just sort of all add up.", "start": 693.36, "duration": 1.86}, {"text": "They interfere with\neach other destructively", "start": 695.22, "duration": 3.21}, {"text": "to give you a 0 in the\nintervals between the peaks.", "start": 698.43, "duration": 3.42}, {"text": "Does that make sense?", "start": 701.85, "duration": 1.24}, {"text": "And so basically, by\nchoosing the amplitude", "start": 703.09, "duration": 3.17}, {"text": "of these different\ncosine functions,", "start": 706.26, "duration": 1.53}, {"text": "you can basically build any\narbitrary periodic function", "start": 707.79, "duration": 4.35}, {"text": "down here.", "start": 712.14, "duration": 0.84}, {"text": "Does that makes sense?", "start": 712.98, "duration": 3.48}, {"text": "All right.", "start": 716.46, "duration": 0.57}, {"text": "There's one more\nelement that we need", "start": 717.03, "duration": 2.22}, {"text": "to add here for our Fourier\nseries for even functions.", "start": 719.25, "duration": 4.02}, {"text": "Anybody have any\nidea what that is?", "start": 723.27, "duration": 2.46}, {"text": "Notice here I've shifted this\nfunction up a little bit.", "start": 725.73, "duration": 4.29}, {"text": "So it's not centered at 0.", "start": 730.02, "duration": 2.61}, {"text": "A constant term.", "start": 732.63, "duration": 1.1}, {"text": "What's called a DC term.", "start": 733.73, "duration": 2.17}, {"text": "We basically take the\naverage of that function.", "start": 735.9, "duration": 2.88}, {"text": "We add it here.", "start": 738.78, "duration": 1.05}, {"text": "That's called a DC term.", "start": 739.83, "duration": 2.93}, {"text": "a 0 over 2 is\nessentially the average", "start": 742.76, "duration": 2.62}, {"text": "of the function we're\ntrying to approximate.", "start": 745.38, "duration": 2.95}, {"text": "All right.", "start": 748.33, "duration": 0.5}, {"text": "Good.", "start": 748.83, "duration": 1.23}, {"text": "We can now write that as a sum.", "start": 750.06, "duration": 2.19}, {"text": "y even of t equals\na0 over 2 plus a sum", "start": 752.25, "duration": 4.56}, {"text": "over all these different\nn's of a sub n,", "start": 756.81, "duration": 4.28}, {"text": "which is a coefficient,\ntimes cosine n omega 0 t.", "start": 761.09, "duration": 3.92}, {"text": "Omega 0 is 1 over--", "start": 765.01, "duration": 2.45}, {"text": "is 2 pi over this time\ninterval here, the periodicity.", "start": 767.46, "duration": 5.11}, {"text": "All right.", "start": 775.16, "duration": 0.5}, {"text": "Good.", "start": 775.66, "duration": 0.97}, {"text": "How do we find\nthose coefficients?", "start": 776.63, "duration": 3.04}, {"text": "So I just told you that the\nfirst coefficient, the a 0", "start": 779.67, "duration": 3.02}, {"text": "over 2, is just the\naverage of our function t", "start": 782.69, "duration": 2.85}, {"text": "over one time window from minus\nt over 2 to plus t over 2.", "start": 785.54, "duration": 4.7}, {"text": "It's just the integral\nof that function", "start": 790.24, "duration": 2.2}, {"text": "over one period divided by t.", "start": 792.44, "duration": 1.53}, {"text": "And that gives you the\naverage, which is a 0 over 2.", "start": 793.97, "duration": 2.37}, {"text": "All right, any\nquestions about that?", "start": 799.35, "duration": 1.5}, {"text": "It's pretty straightforward.", "start": 800.85, "duration": 1.3}, {"text": "What about this next\ncoefficient, a1?", "start": 802.15, "duration": 2.78}, {"text": "So the a1 coefficient is just\nthe overlap of our function", "start": 804.93, "duration": 3.54}, {"text": "y of t with this cosine.", "start": 808.47, "duration": 2.34}, {"text": "We're just multiplying y0\ntimes cosine of omega 0 t", "start": 815.83, "duration": 5.45}, {"text": "integrating over time and\nthen multiplying by 2 over t.", "start": 821.28, "duration": 8.4}, {"text": "So that's the answer.", "start": 829.68, "duration": 2.1}, {"text": "And I'm going to\nexplain why that is.", "start": 831.78, "duration": 2.74}, {"text": "That is just a correlation.", "start": 838.52, "duration": 3.03}, {"text": "It's just like asking how much--", "start": 841.55, "duration": 3.59}, {"text": "let's say we had a neuron with a\nreceptive field of cosine omega", "start": 845.14, "duration": 5.58}, {"text": "0 t.", "start": 850.72, "duration": 0.93}, {"text": "We're asking how well\ndoes our signal overlap", "start": 851.65, "duration": 3.66}, {"text": "with that receptive field.", "start": 855.31, "duration": 1.855}, {"text": "Does that make sense?", "start": 857.165, "duration": 0.875}, {"text": "We're just\ncorrelating our signal", "start": 858.04, "duration": 3.62}, {"text": "with some basis function,\nwith some receptive field.", "start": 861.66, "duration": 5.4}, {"text": "And we're asking how\nmuch overlap is there.", "start": 867.06, "duration": 5.54}, {"text": "The a2 coefficient is just\nthe overlap of the function", "start": 872.6, "duration": 2.91}, {"text": "y with cosine 2 omega 0 t.", "start": 875.51, "duration": 3.79}, {"text": "And the a sub n\ncoefficient is just", "start": 879.3, "duration": 2.22}, {"text": "the overlap with\ncosine n omega 0 t.", "start": 881.52, "duration": 2.38}, {"text": "Just like that.", "start": 886.455, "duration": 0.625}, {"text": "And you can see that this\naverage that we took up here", "start": 889.74, "duration": 3.56}, {"text": "just is the\ngeneralization of this", "start": 893.3, "duration": 2.16}, {"text": "to the overlap of our function\nto cosine 0 omega 0 t.", "start": 895.46, "duration": 5.37}, {"text": "Cosine 0 omega 0 t is just 1.", "start": 900.83, "duration": 4.01}, {"text": "And so this coefficient a0\njust looks the same as this.", "start": 904.84, "duration": 6.182}, {"text": "It's just that in this\ncase, it turns out", "start": 911.022, "duration": 1.708}, {"text": "to be the average\nof the function.", "start": 912.73, "duration": 3.04}, {"text": "Any questions about that?", "start": 915.77, "duration": 3.46}, {"text": "So that is, in general, how you\ncalculate those coefficients.", "start": 919.23, "duration": 3.88}, {"text": "So you would literally\njust take your function,", "start": 923.11, "duration": 2.69}, {"text": "multiply it by a cosine of\nsome frequency, integrate it,", "start": 925.8, "duration": 4.903}, {"text": "and that's the answer.", "start": 930.703, "duration": 0.917}, {"text": "Let's just take a look at what\nsome of these coefficients", "start": 935.86, "duration": 3.39}, {"text": "are for some really\nsimple functions.", "start": 939.25, "duration": 2.97}, {"text": "So there I've rewritten what\neach of those coefficients", "start": 942.22, "duration": 3.72}, {"text": "is as an integral.", "start": 945.94, "duration": 2.22}, {"text": "And now let's consider\nthe following function.", "start": 948.16, "duration": 2.44}, {"text": "So let's say our function is 1.", "start": 950.6, "duration": 2.12}, {"text": "It's just a constant at 1.", "start": 952.72, "duration": 2.25}, {"text": "So you can see that this\nintegral from minus t over 2", "start": 954.97, "duration": 5.82}, {"text": "to t over 2, that integral is\njust t multiplied by 2 over t", "start": 960.79, "duration": 5.01}, {"text": "gives that\ncoefficient as just 2.", "start": 965.8, "duration": 3.99}, {"text": "If our function is\ncosine omega 0 t,", "start": 969.79, "duration": 3.57}, {"text": "you can see that if you put a\ncosine in here, that averages", "start": 973.36, "duration": 3.96}, {"text": "to 0.", "start": 977.32, "duration": 1.29}, {"text": "If you put a cosine in here,\nyou get cosine squared.", "start": 978.61, "duration": 3.66}, {"text": "The integral of cosine\nsquared is just half", "start": 982.27, "duration": 7.32}, {"text": "of basically the full range.", "start": 989.59, "duration": 2.38}, {"text": "So that's just t over 2.", "start": 991.97, "duration": 1.49}, {"text": "When you multiply by\n2 over t, you get 1.", "start": 993.46, "duration": 2.01}, {"text": "And the coefficient a2 for\na function cosine omega t", "start": 998.01, "duration": 4.02}, {"text": "is 0, because the integral\nof cosine omega 0 t times", "start": 1002.03, "duration": 3.66}, {"text": "cosine 2 omega 0 t is 0.", "start": 1005.69, "duration": 1.86}, {"text": "All right.", "start": 1010.17, "duration": 0.63}, {"text": "If we have a function\ncosine 2 omega 0 t,", "start": 1010.8, "duration": 2.58}, {"text": "then these coefficients are\n0, and that coefficient is 1.", "start": 1013.38, "duration": 3.796}, {"text": "You can see that you have\nthis interesting thing here.", "start": 1017.176, "duration": 3.284}, {"text": "If your function is\ncosine omega 0 t,", "start": 1020.46, "duration": 3.45}, {"text": "then the only coefficient\nthat's non-zero", "start": 1023.91, "duration": 3.54}, {"text": "is the one that you're\noverlapping with cosine omega 0", "start": 1027.45, "duration": 2.8}, {"text": "t.", "start": 1030.25, "duration": 0.5}, {"text": "It's only this first\ncoefficient that's non-zero.", "start": 1030.75, "duration": 3.42}, {"text": "If your function has a\nfrequency 2 omega 0 t,", "start": 1034.17, "duration": 3.899}, {"text": "then the only coefficient\nthat's non-zero is the a2.", "start": 1038.069, "duration": 2.956}, {"text": "So what that means is\nthat if the function has", "start": 1044.52, "duration": 3.829}, {"text": "maximal overlap, if it overlaps\none of those cosines, then", "start": 1048.349, "duration": 3.871}, {"text": "it has 0 overlap\nwith all the others.", "start": 1052.22, "duration": 2.27}, {"text": "And we can say that set\nof cosine functions,", "start": 1057.45, "duration": 3.12}, {"text": "cosine omega 0 t,\ncosine 2 omega 0 t,", "start": 1060.57, "duration": 3.8}, {"text": "forms what's called an\northogonal basis set.", "start": 1064.37, "duration": 2.47}, {"text": "We're going to spend a lot of\ntime talking about basis set", "start": 1066.84, "duration": 3.77}, {"text": "later, but I'm just going\nto throw this word out", "start": 1070.61, "duration": 2.28}, {"text": "to you so that\nyou've heard it when", "start": 1072.89, "duration": 2.49}, {"text": "I come back to the idea\nof basis sets later.", "start": 1075.38, "duration": 2.82}, {"text": "You're going to see\nthis connection.", "start": 1078.2, "duration": 3.49}, {"text": "So the basic idea is\nthat what we're doing", "start": 1081.69, "duration": 2.91}, {"text": "is we're taking our\nsignal, which is a vector.", "start": 1084.6, "duration": 4.03}, {"text": "It's a set of points in time.", "start": 1088.63, "duration": 2.79}, {"text": "We can think of that as a vector\nin a high dimensional space.", "start": 1091.42, "duration": 3.77}, {"text": "And we're simply expressing it\nin a new basis set of cosines", "start": 1095.19, "duration": 5.76}, {"text": "of different frequencies.", "start": 1100.95, "duration": 1.42}, {"text": "So each of those functions,\ncosine n omega t,", "start": 1102.37, "duration": 3.38}, {"text": "is like a vector in a basis set.", "start": 1105.75, "duration": 3.39}, {"text": "Our signal like a vector.", "start": 1109.14, "duration": 2.82}, {"text": "And what we're doing is when\nwe're doing these projections,", "start": 1111.96, "duration": 4.17}, {"text": "we're simply computing\nthe projection", "start": 1116.13, "duration": 2.19}, {"text": "of that vector, our signal,\nonto these different basis", "start": 1118.32, "duration": 4.35}, {"text": "functions, these\ndifferent basis vectors.", "start": 1122.67, "duration": 3.27}, {"text": "So we're just finding\nthe coefficient", "start": 1125.94, "duration": 5.85}, {"text": "so that we can\nexpress our signal", "start": 1131.79, "duration": 3.42}, {"text": "as a sum of a coefficient\ntimes a basis vector", "start": 1135.21, "duration": 3.21}, {"text": "plus another coefficient times\nanother basis vector and so on.", "start": 1138.42, "duration": 4.27}, {"text": "So for example, in the\nsimple standard basis", "start": 1142.69, "duration": 2.72}, {"text": "where this vector is 0 1\nand that vector is 1 0,", "start": 1145.41, "duration": 4.68}, {"text": "you can write down\nan arbitrary vector", "start": 1150.09, "duration": 2.46}, {"text": "as a coefficient times this plus\nanother coefficient times that.", "start": 1152.55, "duration": 5.46}, {"text": "That make sense?", "start": 1158.01, "duration": 2.74}, {"text": "And how do we find\nthose coefficients?", "start": 1160.75, "duration": 1.62}, {"text": "We just take our\nvector and dot it", "start": 1162.37, "duration": 2.97}, {"text": "onto each one of these\nbasis vectors, x2.", "start": 1165.34, "duration": 3.45}, {"text": "Does that make sense?", "start": 1168.79, "duration": 1.08}, {"text": "You don't need to know\nthis for this section,", "start": 1172.71, "duration": 3.52}, {"text": "but we're going to\ncome back to this.", "start": 1176.23, "duration": 1.98}, {"text": "I would like you to\neventually kind of combine", "start": 1178.21, "duration": 2.66}, {"text": "these views of taking signals\nand looking at projections", "start": 1180.87, "duration": 6.24}, {"text": "of those into new basis sets.", "start": 1187.11, "duration": 3.06}, {"text": "And as you know, how\nyou see things depends", "start": 1190.17, "duration": 4.58}, {"text": "on how you're looking at\nthem, the direction that you", "start": 1194.75, "duration": 3.39}, {"text": "look at them.", "start": 1198.14, "duration": 0.7}, {"text": "That's what we're doing.", "start": 1198.84, "duration": 1.0}, {"text": "When we take a signal and we\nproject it onto a function,", "start": 1199.84, "duration": 3.38}, {"text": "we're taking a particular\nview of that function.", "start": 1203.22, "duration": 2.84}, {"text": "So as you know, the view\nyou have on something", "start": 1209.96, "duration": 12.8}, {"text": "has a big impact\non what you see.", "start": 1222.76, "duration": 3.37}, {"text": "Right?", "start": 1226.13, "duration": 0.5}, {"text": "So that's all we're doing\nis we're taking functions", "start": 1234.24, "duration": 3.57}, {"text": "and finding the\nprojection on which we", "start": 1237.81, "duration": 3.78}, {"text": "can see something interesting.", "start": 1241.59, "duration": 3.42}, {"text": "That's it.", "start": 1245.01, "duration": 0.99}, {"text": "That's all spectral analysis is.", "start": 1246.0, "duration": 2.28}, {"text": "And the particular\nviews we're looking at", "start": 1248.28, "duration": 2.91}, {"text": "are projections onto\ndifferent periodic functions.", "start": 1251.19, "duration": 4.32}, {"text": "Cosines of different\nfrequencies.", "start": 1255.51, "duration": 2.19}, {"text": "All right?", "start": 1257.7, "duration": 0.57}, {"text": "And what you find is that\nfor periodic signals,", "start": 1258.27, "duration": 2.71}, {"text": "there are certain views where\nsomething magically pops out", "start": 1260.98, "duration": 3.47}, {"text": "and you see what's there that\nyou can't see when you just", "start": 1264.45, "duration": 3.57}, {"text": "look at the time domain.", "start": 1268.02, "duration": 3.32}, {"text": "All right.", "start": 1271.34, "duration": 2.68}, {"text": "So we looked at even functions\nor symmetric functions.", "start": 1274.02, "duration": 3.94}, {"text": "Now let's take a\nlook at odd functions", "start": 1277.96, "duration": 2.78}, {"text": "are antisymmetric functions.", "start": 1280.74, "duration": 1.41}, {"text": "These are called odd because\nthe odd polynomials like x cubed", "start": 1282.15, "duration": 4.95}, {"text": "looks like this.", "start": 1287.1, "duration": 1.0}, {"text": "If it's negative\non one side, it's", "start": 1288.1, "duration": 1.82}, {"text": "positive on the other side.", "start": 1289.92, "duration": 1.15}, {"text": "Same here.", "start": 1291.07, "duration": 0.5}, {"text": "If it's negative here,\nthen it's positive there.", "start": 1291.57, "duration": 3.06}, {"text": "So we can now write down Fourier\nseries for odd or antisymmetric", "start": 1294.63, "duration": 6.18}, {"text": "functions.", "start": 1300.81, "duration": 0.79}, {"text": "What do you think\nwe're going to use?", "start": 1301.6, "duration": 1.542}, {"text": "Instead of cosines, we're going\nto use sines, because sines", "start": 1303.142, "duration": 3.558}, {"text": "are symmetric around--", "start": 1306.7, "duration": 4.16}, {"text": "antisymmetric around the origin.", "start": 1310.86, "duration": 1.9}, {"text": "And we're still going to\nconsider functions that", "start": 1312.76, "duration": 2.0}, {"text": "are periodic with period t.", "start": 1314.76, "duration": 1.98}, {"text": "We can take any\nantisymmetric function", "start": 1316.74, "duration": 2.43}, {"text": "and approximate it as a sum\nof sine waves of frequency 2", "start": 1319.17, "duration": 5.85}, {"text": "pi over t or, again, omega 0.", "start": 1325.02, "duration": 3.75}, {"text": "And integer multiples\nof that omega 0.", "start": 1328.77, "duration": 2.88}, {"text": "All right.", "start": 1334.74, "duration": 0.5}, {"text": "So again, our odd functions\ncan be approximated", "start": 1335.24, "duration": 3.6}, {"text": "as a sum of components,\ncontributions", "start": 1338.84, "duration": 4.97}, {"text": "of different frequencies\nwith a coefficient times", "start": 1343.81, "duration": 4.34}, {"text": "sine of omega 0 t plus\nanother coefficient times", "start": 1348.15, "duration": 2.86}, {"text": "sine of 2 omega 0 t and so on.", "start": 1351.01, "duration": 3.12}, {"text": "And we can write that as a\nsum that looks like this.", "start": 1354.13, "duration": 2.51}, {"text": "So a sum over n from 1 to\ninfinity of coefficient b", "start": 1356.64, "duration": 4.35}, {"text": "sub n times sine of n omega 0 t.", "start": 1360.99, "duration": 5.39}, {"text": "And why is there\nno DC term here?", "start": 1366.38, "duration": 1.74}, {"text": "Good.", "start": 1371.018, "duration": 0.972}, {"text": "Because an antisymmetric\nfunction can't have a DC", "start": 1371.99, "duration": 3.4}, {"text": "offset.", "start": 1375.39, "duration": 0.5}, {"text": "So for arbitrary functions, you\ncan write down any arbitrary", "start": 1379.55, "duration": 6.21}, {"text": "periodic function as the\nsum of a symmetric part", "start": 1385.76, "duration": 4.76}, {"text": "and an antisymmetric part.", "start": 1390.52, "duration": 1.48}, {"text": "So we can write\ndown an arbitrary", "start": 1392.0, "duration": 1.62}, {"text": "function as a sum\nof these cosines", "start": 1393.62, "duration": 6.36}, {"text": "plus a sum of sine waves.", "start": 1399.98, "duration": 1.77}, {"text": "So that's Fourier series.", "start": 1406.28, "duration": 1.41}, {"text": "Any questions about that?", "start": 1407.69, "duration": 1.05}, {"text": "So this is kind of messy.", "start": 1413.01, "duration": 2.64}, {"text": "And it turns out that there's a\nmuch simpler way of writing out", "start": 1415.65, "duration": 5.52}, {"text": "functions as sums of\nperiodic functions.", "start": 1421.17, "duration": 5.53}, {"text": "So rather than using\ncosines and sines,", "start": 1426.7, "duration": 2.16}, {"text": "we're going to use\ncomplex exponentials.", "start": 1428.86, "duration": 2.97}, {"text": "And that is what complex\nFourier series does.", "start": 1431.83, "duration": 4.44}, {"text": "All right, so let's do that.", "start": 1436.27, "duration": 1.32}, {"text": "So you probably recall\nthat you can write down", "start": 1437.59, "duration": 5.07}, {"text": "a complex exponential e to the\ni omega t as a cosine omega", "start": 1442.66, "duration": 7.54}, {"text": "t plus i sine omega t.", "start": 1450.2, "duration": 3.74}, {"text": "So e to the i omega t\nis just a generalization", "start": 1453.94, "duration": 3.82}, {"text": "of sines and cosines.", "start": 1457.76, "duration": 2.13}, {"text": "So the way to\nthink about this is", "start": 1459.89, "duration": 2.06}, {"text": "e to the i omega t\nis a complex number.", "start": 1461.95, "duration": 3.02}, {"text": "If we plot it in a\ncomplex plane where", "start": 1464.97, "duration": 2.15}, {"text": "we look at the real\npart along this axis,", "start": 1467.12, "duration": 2.79}, {"text": "the imaginary part along\nthat axis, e to the i omega", "start": 1469.91, "duration": 3.93}, {"text": "t just lives on this circle.", "start": 1473.84, "duration": 2.22}, {"text": "No matter what omega t is,\ne to the i omega t just", "start": 1476.06, "duration": 4.81}, {"text": "sits on this circle in the\ncomplex plane, the unit", "start": 1480.87, "duration": 3.0}, {"text": "circle in the complex plane.", "start": 1483.87, "duration": 3.8}, {"text": "e to the i omega t is\na function of time.", "start": 1487.67, "duration": 5.53}, {"text": "It simply has a real part\nthat looks like cosine.", "start": 1493.2, "duration": 5.2}, {"text": "So the real part of this as you\nincrease t or the phase omega t", "start": 1498.4, "duration": 7.56}, {"text": "is the real part just oscillates\nsinusoidally back and forth", "start": 1505.96, "duration": 5.37}, {"text": "like this as a cosine.", "start": 1511.33, "duration": 2.76}, {"text": "The imaginary part just\noscillates back and forth", "start": 1514.09, "duration": 4.12}, {"text": "as a sine.", "start": 1518.21, "duration": 2.49}, {"text": "And when you put them\ntogether, something", "start": 1520.7, "duration": 2.19}, {"text": "that goes back and forth\nthis way as a cosine", "start": 1522.89, "duration": 2.88}, {"text": "and up and down that way as a\nsine just traces out a circle.", "start": 1525.77, "duration": 4.2}, {"text": "So e to the i omega traces out\na circle in this direction,", "start": 1529.97, "duration": 3.88}, {"text": "and as time increases, it\njust goes around and around", "start": 1533.85, "duration": 3.17}, {"text": "like this.", "start": 1537.02, "duration": 0.93}, {"text": "E to the minus i omega t\njust goes the other way.", "start": 1537.95, "duration": 3.63}, {"text": "That make sense?", "start": 1544.11, "duration": 2.02}, {"text": "Got the real part that's going\nlike this, the imaginary part", "start": 1546.13, "duration": 4.5}, {"text": "that's going like this.", "start": 1550.63, "duration": 3.18}, {"text": "And you put those\ntogether and they just", "start": 1553.81, "duration": 2.1}, {"text": "go around in a circle.", "start": 1555.91, "duration": 2.62}, {"text": "So you can see it's a\nway of combining cosine", "start": 1558.53, "duration": 4.48}, {"text": "and sine together\nin one function.", "start": 1563.01, "duration": 1.63}, {"text": "So what we're going\nto do is we're", "start": 1567.003, "duration": 1.417}, {"text": "going to rewrite our Fourier\nseries as instead of sines", "start": 1568.42, "duration": 5.4}, {"text": "and cosines, we're\ngoing to stick", "start": 1573.82, "duration": 1.5}, {"text": "in e to the-- we're going\nto replace the sines", "start": 1575.32, "duration": 2.43}, {"text": "and cosines with e to the i\nomega t and e to the minus i", "start": 1577.75, "duration": 4.6}, {"text": "omega t.", "start": 1582.35, "duration": 0.59}, {"text": "So we're just going to solve\nthese two functions for cosine", "start": 1582.94, "duration": 6.92}, {"text": "and sine, and we're going\nto take this and plug it", "start": 1589.86, "duration": 2.79}, {"text": "into our Fourier series\nand see what we get.", "start": 1592.65, "duration": 3.732}, {"text": "So let's do that.", "start": 1596.382, "duration": 0.708}, {"text": "And remember, 1 over\ni is just minus i.", "start": 1597.09, "duration": 3.51}, {"text": "So here's our Fourier\nseries with our sum", "start": 1604.57, "duration": 2.46}, {"text": "of cosines, our sum of sines.", "start": 1607.03, "duration": 1.693}, {"text": "We're just going to\nreplace those things", "start": 1608.723, "duration": 1.667}, {"text": "with the e to the i omega\nt plus e to the minus", "start": 1610.39, "duration": 3.12}, {"text": "i omega t and so on.", "start": 1613.51, "duration": 1.75}, {"text": "So there we go.", "start": 1615.26, "duration": 0.89}, {"text": "Just replacing that.", "start": 1616.15, "duration": 1.05}, {"text": "There's a 1/2 there.", "start": 1617.2, "duration": 2.81}, {"text": "And now we're just going\nto do some algebra.", "start": 1620.01, "duration": 2.93}, {"text": "And we're going to collect\neither the i omega t's and e to", "start": 1622.94, "duration": 3.75}, {"text": "the minus i omega t's together.", "start": 1626.69, "duration": 2.968}, {"text": "And this is what it looks like.", "start": 1629.658, "duration": 1.292}, {"text": "So you can see that\nwhat we're doing", "start": 1633.95, "duration": 4.17}, {"text": "is collecting this\ninto a bunch of terms", "start": 1638.12, "duration": 3.15}, {"text": "that have e to the\npositive in omega", "start": 1641.27, "duration": 3.33}, {"text": "t here and e to the\nminus in omega 0 t there.", "start": 1644.6, "duration": 6.48}, {"text": "And now we have still\na sum of three things.", "start": 1651.08, "duration": 3.45}, {"text": "So it doesn't really look like\nwe've really gotten anywhere.", "start": 1654.53, "duration": 5.53}, {"text": "But notice something.", "start": 1660.06, "duration": 2.79}, {"text": "If we just put the\nminus sign into the n,", "start": 1662.85, "duration": 4.842}, {"text": "then we can combine\nthese two into one sum.", "start": 1667.692, "duration": 3.438}, {"text": "And this, if n is 0, what\nis e to the in omega t?", "start": 1671.13, "duration": 7.17}, {"text": "It's just 1.", "start": 1678.3, "duration": 1.62}, {"text": "So we can also write this as\nsomething e to the in omega t", "start": 1679.92, "duration": 4.08}, {"text": "as long as n is 0.", "start": 1684.0, "duration": 2.82}, {"text": "So that's what we do.", "start": 1686.82, "duration": 1.17}, {"text": "Oh, and by the way,\nthese coefficients here", "start": 1687.99, "duration": 2.88}, {"text": "we can just rewrite as sums of\nthose coefficients up there.", "start": 1690.87, "duration": 5.78}, {"text": "Don't worry.", "start": 1696.65, "duration": 1.03}, {"text": "This all looks\nreally complicated.", "start": 1697.68, "duration": 1.47}, {"text": "By the end, it's just boiled\ndown to one simple thing.", "start": 1699.15, "duration": 2.55}, {"text": "That's why we're doing this.", "start": 1701.7, "duration": 1.35}, {"text": "We're simplifying things.", "start": 1703.05, "duration": 1.17}, {"text": "So when you do this,\nwhen you rewrite this,", "start": 1706.82, "duration": 4.08}, {"text": "this looks like a\nsum over n equals 0.", "start": 1710.9, "duration": 3.3}, {"text": "This is a sum over positive\nn, n equals 1 to infinity.", "start": 1714.2, "duration": 3.9}, {"text": "This is a sum over negative\nn, minus 1 to minus infinity.", "start": 1718.1, "duration": 4.26}, {"text": "And all those\ncombine into one sum.", "start": 1722.36, "duration": 4.77}, {"text": "So now we can write\ndown any function y of t", "start": 1727.13, "duration": 3.27}, {"text": "as a sum over n\nequals minus infinity", "start": 1730.4, "duration": 3.36}, {"text": "to infinity of a coefficient a\nsub n times e to the in omega.", "start": 1733.76, "duration": 5.55}, {"text": "So we went from having this\ncomplicated thing, this sum", "start": 1741.96, "duration": 4.77}, {"text": "over our constant terms,\nsines, and cosines,", "start": 1746.73, "duration": 3.63}, {"text": "and we boiled it\ndown to a single sum.", "start": 1750.36, "duration": 4.7}, {"text": "That's why these complex\nexponentials are useful.", "start": 1755.06, "duration": 5.85}, {"text": "Because we don't\nhave to carry around", "start": 1760.91, "duration": 1.77}, {"text": "a bunch of different functions,\ndifferent basis functions", "start": 1762.68, "duration": 3.87}, {"text": "to describe an\narbitrary signal y.", "start": 1766.55, "duration": 5.48}, {"text": "But remember, this is\njust a mathematical trick", "start": 1772.03, "duration": 3.24}, {"text": "to hide sines and cosines.", "start": 1775.27, "duration": 1.11}, {"text": "A very powerful trick,\nbut that's all it's doing.", "start": 1780.3, "duration": 4.225}, {"text": "It's hiding sines and cosines.", "start": 1784.525, "duration": 1.25}, {"text": "All right.", "start": 1788.42, "duration": 1.41}, {"text": "So we've replaced our sums\nover coastlines and signs", "start": 1789.83, "duration": 3.66}, {"text": "with a sum of\ncomplex exponentials.", "start": 1793.49, "duration": 3.08}, {"text": "All right.", "start": 1796.57, "duration": 1.17}, {"text": "Remember what we're doing here.", "start": 1797.74, "duration": 2.53}, {"text": "We're finding a new way\nof writing down functions.", "start": 1800.27, "duration": 7.28}, {"text": "So what's cool\nabout this, what's", "start": 1807.55, "duration": 2.25}, {"text": "really interesting about this,\nis that for some functions--", "start": 1809.8, "duration": 3.88}, {"text": "so what we're doing is we\nhave an arbitrary function y.", "start": 1813.68, "duration": 2.75}, {"text": "And we're writing a down with\njust some numbers a sub n.", "start": 1816.43, "duration": 5.25}, {"text": "And what's cool about this\nis that for some functions y,", "start": 1821.68, "duration": 4.85}, {"text": "you can describe that\nfunction with just a few", "start": 1826.53, "duration": 2.85}, {"text": "of these coefficients a.", "start": 1829.38, "duration": 3.705}, {"text": "Does that make sense?", "start": 1833.085, "duration": 1.455}, {"text": "So let me just\nshow you an example", "start": 1834.54, "duration": 1.62}, {"text": "of some functions\nthat look really,", "start": 1836.16, "duration": 2.44}, {"text": "really simple when\nyou rewrite them", "start": 1838.6, "duration": 3.14}, {"text": "using these coefficients a.", "start": 1841.74, "duration": 2.58}, {"text": "So here's an example.", "start": 1844.32, "duration": 1.93}, {"text": "So here's a function of\nn that has three numbers.", "start": 1846.25, "duration": 6.85}, {"text": "a sub minus 1, n equals\nminus 1 is 1/2, a sub 0 is 0,", "start": 1853.1, "duration": 5.28}, {"text": "and a sub 1 is 1/2.", "start": 1858.38, "duration": 2.1}, {"text": "And all the rest of them are 0.", "start": 1860.48, "duration": 1.47}, {"text": "So really, we only have two\nnon-zero entries in this sum.", "start": 1861.95, "duration": 5.66}, {"text": "So what function is that?", "start": 1867.61, "duration": 2.92}, {"text": "It's just a cosine.", "start": 1870.53, "duration": 1.95}, {"text": "So we have-- let's\nwrite this out.", "start": 1872.48, "duration": 3.15}, {"text": "Y equals a sum over\nall of these things.", "start": 1875.63, "duration": 2.92}, {"text": "1/2 e to the minus--", "start": 1878.55, "duration": 3.38}, {"text": "the first n is minus 1. e to\nthe minus i omega 0 t plus 1/2 e", "start": 1881.93, "duration": 5.8}, {"text": "to the plus i omega 0 t.", "start": 1887.73, "duration": 2.12}, {"text": "We're just writing out that sum.", "start": 1889.85, "duration": 2.31}, {"text": "And that is just--", "start": 1892.16, "duration": 1.167}, {"text": "sorry, I didn't tell you\nwhat that equation was.", "start": 1897.66, "duration": 3.99}, {"text": "That's Euler's equation.", "start": 1901.65, "duration": 4.68}, {"text": "That's just cosine\nminus i sine omega t.", "start": 1906.33, "duration": 2.82}, {"text": "That is just cosine\nplus i sine omega t.", "start": 1909.15, "duration": 2.76}, {"text": "The sines cancel.", "start": 1911.91, "duration": 1.035}, {"text": "And you're left with\ncosine omega 0 t.", "start": 1915.63, "duration": 2.3}, {"text": "So here's this function of\ntime that goes on infinitely.", "start": 1920.89, "duration": 5.31}, {"text": "If you wanted to write down all\nthe values of cosine omega 0 t,", "start": 1926.2, "duration": 4.77}, {"text": "you'd have to write down\nan awful lot of numbers.", "start": 1930.97, "duration": 3.16}, {"text": "And here we can write down that\nsame function with two numbers.", "start": 1934.13, "duration": 3.605}, {"text": "So this is a very compact\nview of that function of time.", "start": 1943.7, "duration": 6.93}, {"text": "Here's another function.", "start": 1956.15, "duration": 1.74}, {"text": "What function do\nyou think that is?", "start": 1957.89, "duration": 2.12}, {"text": "What would be the time\ndomain equivalent of this set", "start": 1962.7, "duration": 6.08}, {"text": "of Fourier coefficients?", "start": 1968.78, "duration": 5.27}, {"text": "Good.", "start": 1974.05, "duration": 0.54}, {"text": "So we're going to\ndo the same thing.", "start": 1974.59, "duration": 1.5}, {"text": "Just write it out.", "start": 1976.09, "duration": 1.54}, {"text": "All these sums are 0.", "start": 1977.63, "duration": 1.74}, {"text": "All these components are\n0 except for two of them.", "start": 1979.37, "duration": 3.03}, {"text": "n equals minus 2\nand n equals plus 2.", "start": 1982.4, "duration": 3.585}, {"text": "You just put those\nin there as 1/2", "start": 1985.985, "duration": 2.025}, {"text": "e to the minus 2 omega 0 t plus\n1/2 e to the plus 2 omega 0 t.", "start": 1988.01, "duration": 10.55}, {"text": "And that is just if you write\nthat out, those sines cancel,", "start": 1998.56, "duration": 3.93}, {"text": "and you have cosine 2 omega 0 t.", "start": 2002.49, "duration": 2.28}, {"text": "Pretty simple, right?", "start": 2004.77, "duration": 2.73}, {"text": "How about this one?", "start": 2007.5, "duration": 2.74}, {"text": "This is the-- remember, the\na's are complex numbers.", "start": 2010.24, "duration": 3.83}, {"text": "The ones we were looking at\nhere had two real numbers.", "start": 2014.07, "duration": 3.95}, {"text": "Here's an example where\nthe a's are imaginary.", "start": 2018.02, "duration": 4.9}, {"text": "One is i over 2.", "start": 2022.92, "duration": 1.65}, {"text": "One is minus i over 2.", "start": 2024.57, "duration": 3.35}, {"text": "That's what the complex\nFourier representation", "start": 2027.92, "duration": 5.31}, {"text": "looks like of this function.", "start": 2033.23, "duration": 3.3}, {"text": "We can just plug it in here.", "start": 2036.53, "duration": 2.56}, {"text": "You solve that, you can\nsee that in this case,", "start": 2039.09, "duration": 4.32}, {"text": "the cosines cancel,\nbecause this is i over 2", "start": 2043.41, "duration": 2.94}, {"text": "cosine 2 omega t minus i\nover 2 cosine 2 omega t.", "start": 2046.35, "duration": 4.079}, {"text": "Those cancel and you're\nleft with sine 2 omega 0 t.", "start": 2050.429, "duration": 4.741}, {"text": "So that is what Fourier\nrepresentation of sine 2 omega", "start": 2055.17, "duration": 5.43}, {"text": "t looks like.", "start": 2060.6, "duration": 2.34}, {"text": "So the functions that\nhave higher frequencies", "start": 2062.94, "duration": 3.14}, {"text": "will have non-zero elements\nthat are further out in n.", "start": 2066.08, "duration": 6.329}, {"text": "Any questions about that?", "start": 2077.639, "duration": 1.171}, {"text": "So again, this set of\nfunctions e to the in omega 0 t", "start": 2085.37, "duration": 5.269}, {"text": "form an orthogonal, orthonormal\nbasis set over that [INAUDIBLE]", "start": 2090.639, "duration": 7.091}, {"text": "over that interval.", "start": 2097.73, "duration": 1.523}, {"text": "The a0 coefficient is\njust the projection", "start": 2099.253, "duration": 4.577}, {"text": "of our function onto e to the 0.", "start": 2103.83, "duration": 4.23}, {"text": "n equals 0.", "start": 2108.06, "duration": 1.47}, {"text": "And that's just the average.", "start": 2109.53, "duration": 1.23}, {"text": "The a1 coefficient is just\nthe projection of our function", "start": 2113.69, "duration": 3.86}, {"text": "e to the minus i omega 0 t.", "start": 2117.55, "duration": 4.22}, {"text": "And in general, the\nm-th coefficient", "start": 2121.77, "duration": 2.77}, {"text": "is just the projection\nof our function onto e", "start": 2124.54, "duration": 3.71}, {"text": "to the minus im omega 0 t.", "start": 2128.25, "duration": 2.52}, {"text": "And we can take\nthose coefficients,", "start": 2136.31, "duration": 3.6}, {"text": "plug them into this sum,\nand reconstruct an arbitrary", "start": 2139.91, "duration": 5.31}, {"text": "periodic function, this y of t.", "start": 2145.22, "duration": 4.2}, {"text": "So we have a way of\ntaking a function", "start": 2149.42, "duration": 2.55}, {"text": "and getting these complex\nFourier coefficients.", "start": 2151.97, "duration": 4.29}, {"text": "And we have a way of\ntaking those coefficients", "start": 2156.26, "duration": 3.33}, {"text": "and reconstructing our function.", "start": 2159.59, "duration": 3.64}, {"text": "This is just a bunch of\ndifferent views function y.", "start": 2163.23, "duration": 6.86}, {"text": "And from all of those\ndifferent views,", "start": 2170.09, "duration": 2.04}, {"text": "we can reconstruct our function.", "start": 2172.13, "duration": 3.87}, {"text": "That's all it is.", "start": 2176.0, "duration": 1.96}, {"text": "So in general, when we\ndo Fourier decomposition", "start": 2177.96, "duration": 6.87}, {"text": "in a computer in\nMATLAB on real signals", "start": 2184.83, "duration": 4.05}, {"text": "that you've sampled\nin time, it's", "start": 2188.88, "duration": 2.85}, {"text": "always done in this kind\nof discrete representation.", "start": 2191.73, "duration": 6.05}, {"text": "You've got, in this case,\ndiscrete frequencies.", "start": 2197.78, "duration": 3.36}, {"text": "When you sample\nsignals, you've got", "start": 2201.14, "duration": 1.83}, {"text": "functions that are discrete in\ntime, and this becomes a sum.", "start": 2202.97, "duration": 4.5}, {"text": "But before we go to\nthe discrete case,", "start": 2207.47, "duration": 2.13}, {"text": "I just want to\nshow you what this", "start": 2209.6, "duration": 1.47}, {"text": "looks like when we go to the\ncase of arbitrary functions.", "start": 2211.07, "duration": 4.15}, {"text": "Remember, this thing\nwas about representing", "start": 2215.22, "duration": 2.57}, {"text": "periodic functions.", "start": 2217.79, "duration": 1.47}, {"text": "You can only represent\nperiodic functions", "start": 2219.26, "duration": 2.37}, {"text": "using these Fourier series.", "start": 2221.63, "duration": 3.51}, {"text": "But before we go on to the\nFourier transform algorithm", "start": 2225.14, "duration": 3.69}, {"text": "and discrete Fourier\ntransforms, I just", "start": 2228.83, "duration": 2.01}, {"text": "want to show you what this looks\nlike for the case of arbitrary", "start": 2230.84, "duration": 3.12}, {"text": "functions.", "start": 2233.96, "duration": 1.97}, {"text": "And I'm just\nshowing this to you.", "start": 2235.93, "duration": 2.34}, {"text": "I don't expect you to be able\nto reproduce any of this.", "start": 2238.27, "duration": 2.89}, {"text": "But you should see what it\nlooks like, for those of you who", "start": 2241.16, "duration": 3.06}, {"text": "haven't seen it already.", "start": 2244.22, "duration": 3.02}, {"text": "So what we're going to\ndo is go from the case", "start": 2247.24, "duration": 2.46}, {"text": "of periodic functions to\nnon-periodic functions.", "start": 2249.7, "duration": 2.833}, {"text": "And the simplest way\nto think about that", "start": 2252.533, "duration": 1.667}, {"text": "is a periodic function\ndoes something here,", "start": 2254.2, "duration": 2.64}, {"text": "and then it just does\nthe same thing here,", "start": 2256.84, "duration": 2.4}, {"text": "and then it just does\nthe same thing here.", "start": 2259.24, "duration": 2.82}, {"text": "So how do we go from this\nto an arbitrary function?", "start": 2262.06, "duration": 6.1}, {"text": "Well, we're just going to let\nthe period go to infinity.", "start": 2268.16, "duration": 4.924}, {"text": "Does that make sense?", "start": 2273.084, "duration": 2.356}, {"text": "That's actually pretty easy.", "start": 2275.44, "duration": 1.65}, {"text": "We're going to let t\ngo to infinity, which", "start": 2277.09, "duration": 2.52}, {"text": "means the frequencies, which\nare 2 pi omega 0 or 2 pi over t,", "start": 2279.61, "duration": 7.38}, {"text": "that's going to go to 0.", "start": 2286.99, "duration": 2.49}, {"text": "So our steps.", "start": 2289.48, "duration": 2.43}, {"text": "Remember when we had this\ndiscrete Fourier transform", "start": 2291.91, "duration": 2.31}, {"text": "here, we had these steps in\nfrequency as a function of n.", "start": 2294.22, "duration": 6.09}, {"text": "Those steps are just going to\nget infinitely close together,", "start": 2300.31, "duration": 3.79}, {"text": "the different frequency bins.", "start": 2304.1, "duration": 2.68}, {"text": "So that's what we're\ngoing to do now.", "start": 2306.78, "duration": 1.96}, {"text": "You're just going to let\nthose frequency steps go to 0.", "start": 2308.74, "duration": 3.13}, {"text": "And now frequency,\nin discrete case,", "start": 2311.87, "duration": 4.26}, {"text": "the frequency is just that\nnumber, that n times omega 0.", "start": 2316.13, "duration": 6.6}, {"text": "m times omega 0.", "start": 2322.73, "duration": 1.56}, {"text": "Well, omega 0 is going to 0, but\nthe m's are getting really big.", "start": 2324.29, "duration": 4.89}, {"text": "So we can just change--", "start": 2329.18, "duration": 1.89}, {"text": "we're just going\nto call that omega.", "start": 2331.07, "duration": 1.5}, {"text": "The omega 0's are\ngoing to 0, so the m's", "start": 2337.35, "duration": 2.055}, {"text": "are getting infinitely big.", "start": 2339.405, "duration": 1.125}, {"text": "So we can't really\nuse m anymore or n", "start": 2340.53, "duration": 2.97}, {"text": "to label our frequency steps.", "start": 2343.5, "duration": 2.135}, {"text": "So we're just\ngoing to use omega.", "start": 2345.635, "duration": 1.375}, {"text": "We used to call\nour coefficients,", "start": 2350.16, "duration": 2.16}, {"text": "our Fourier coefficients, we\nused to label them with m.", "start": 2352.32, "duration": 4.05}, {"text": "We can't use m anymore, because\nm is getting infinitely big.", "start": 2356.37, "duration": 3.66}, {"text": "So we use this new label omega.", "start": 2360.03, "duration": 2.52}, {"text": "So a sub m becomes a new\nvariable, our Fourier", "start": 2362.55, "duration": 4.65}, {"text": "transform, labeled by\nthe frequency omega.", "start": 2367.2, "duration": 6.13}, {"text": "And we're just going\nto basically just make", "start": 2373.33, "duration": 4.89}, {"text": "those replacements in here.", "start": 2378.22, "duration": 1.38}, {"text": "So the coefficients become\na function of frequency.", "start": 2379.6, "duration": 4.69}, {"text": "That's just an integral.", "start": 2384.29, "duration": 1.34}, {"text": "Remember, t is going\nto infinity now.", "start": 2385.63, "duration": 2.28}, {"text": "So this has to go\nfrom minus infinity", "start": 2387.91, "duration": 2.16}, {"text": "to infinity of our function\ny times our basis function.", "start": 2390.07, "duration": 6.87}, {"text": "And instead of e to\nthe im omega 0 t,", "start": 2396.94, "duration": 2.7}, {"text": "we just replace m\nomega 0 with omega.", "start": 2399.64, "duration": 3.33}, {"text": "So e to the minus i omega t.", "start": 2402.97, "duration": 3.09}, {"text": "And that is the\nFourier transform.", "start": 2406.06, "duration": 4.36}, {"text": "And we're just going to do\nthe same replacement here,", "start": 2410.42, "duration": 3.46}, {"text": "but instead of summing over\nn going from minus infinity", "start": 2413.88, "duration": 6.11}, {"text": "to infinity, we have to write\nthis as an integral as well.", "start": 2419.99, "duration": 3.06}, {"text": "And so that we can\nreconstruct our function", "start": 2423.05, "duration": 2.64}, {"text": "y of t as an integral of\nour Fourier coefficients", "start": 2425.69, "duration": 6.09}, {"text": "times the e to the i omega t.", "start": 2431.78, "duration": 4.41}, {"text": "See that?", "start": 2436.19, "duration": 1.4}, {"text": "It's essentially the same thing.", "start": 2437.59, "duration": 1.368}, {"text": "It's just that we're turning\nthis sum into an integral.", "start": 2438.958, "duration": 2.292}, {"text": "All right.", "start": 2446.24, "duration": 0.5}, {"text": "So that's called a\nFourier transform.", "start": 2446.74, "duration": 2.5}, {"text": "And that's the inverse Fourier\ntransform, this [INAUDIBLE]", "start": 2449.24, "duration": 2.46}, {"text": "from a function to\nFourier coefficients.", "start": 2451.7, "duration": 3.15}, {"text": "And this takes your\nFourier coefficients", "start": 2454.85, "duration": 1.83}, {"text": "and goes back to your function.", "start": 2456.68, "duration": 1.32}, {"text": "All right, good.", "start": 2462.88, "duration": 1.86}, {"text": "Let me just show you\na few simple examples.", "start": 2464.74, "duration": 3.13}, {"text": "So let's start with the\nfunction y of t equals 1.", "start": 2467.87, "duration": 4.38}, {"text": "So it's just a constant.", "start": 2472.25, "duration": 2.48}, {"text": "What is the Fourier transform?", "start": 2474.73, "duration": 1.32}, {"text": "So let's plug this into here.", "start": 2476.05, "duration": 2.01}, {"text": "Does anyone know what\nthat integral looks", "start": 2480.73, "duration": 3.39}, {"text": "like of the integral from\nminus infinity to infinity", "start": 2484.12, "duration": 5.45}, {"text": "of e the minus i omega t\ndt integrating over time.", "start": 2489.57, "duration": 7.555}, {"text": "It's a delta function.", "start": 2497.125, "duration": 2.325}, {"text": "There's only one value of omega\nfor which that function is not", "start": 2499.45, "duration": 6.9}, {"text": "0.", "start": 2506.35, "duration": 0.5}, {"text": "Remember, so let's say omega\nequals 1, 1-- you know,", "start": 2506.85, "duration": 4.942}, {"text": "1 hertz.", "start": 2511.792, "duration": 1.548}, {"text": "This is just a bunch\nof sines and cosines.", "start": 2513.34, "duration": 2.04}, {"text": "So when you integrate over\nsines and cosines, you get 0.", "start": 2515.38, "duration": 5.49}, {"text": "Integral over time\nof cosine is just 0.", "start": 2520.87, "duration": 3.9}, {"text": "But if omega is 0, then\nwhat is e to the i omega t?", "start": 2524.77, "duration": 4.07}, {"text": "e to the i 0 is 1.", "start": 2532.85, "duration": 3.0}, {"text": "And so we're integrating\nover 1 times dt.", "start": 2535.85, "duration": 5.01}, {"text": "And that becomes infinity\nat omega equals 0.", "start": 2540.86, "duration": 3.815}, {"text": "And that's a delta\nfunction, it's", "start": 2544.675, "duration": 1.375}, {"text": "0 everywhere except 4 at 0.", "start": 2546.05, "duration": 5.69}, {"text": "So that becomes\na delta function.", "start": 2551.74, "duration": 2.31}, {"text": "This Fourier transform of a\nconstant is a delta function.", "start": 2554.05, "duration": 5.94}, {"text": "And that's a really--", "start": 2559.99, "duration": 1.72}, {"text": "it's a really good one to know.", "start": 2561.71, "duration": 2.37}, {"text": "The Fourier transform of a\nconstant is a delta function.", "start": 2564.08, "duration": 3.42}, {"text": "That's called a\nFourier transform pair.", "start": 2567.5, "duration": 2.46}, {"text": "You have a function\nand another function.", "start": 2569.96, "duration": 3.51}, {"text": "One function is the\nFourier transform", "start": 2573.47, "duration": 1.682}, {"text": "of the other function\nthat's called", "start": 2575.152, "duration": 1.458}, {"text": "a Fourier transform pair.", "start": 2576.61, "duration": 3.49}, {"text": "So the Fourier\ntransform of a constant", "start": 2580.1, "duration": 2.76}, {"text": "is just a delta function at 0.", "start": 2582.86, "duration": 2.96}, {"text": "You can invert that.", "start": 2585.82, "duration": 2.04}, {"text": "If you integrate, let's just\nplug that delta function", "start": 2587.86, "duration": 3.51}, {"text": "into here.", "start": 2591.37, "duration": 0.63}, {"text": "If you integrate delta function\ntimes e to the i omega t,", "start": 2592.0, "duration": 5.55}, {"text": "you just get e to the\ni 0t, which is just 1.", "start": 2597.55, "duration": 4.26}, {"text": "So we can take the\nFourier transform of 1,", "start": 2604.68, "duration": 3.12}, {"text": "get a delta function,\n[INAUDIBLE] inverse Fourier", "start": 2607.8, "duration": 2.43}, {"text": "transform the delta\nfunction, and get back 1.", "start": 2610.23, "duration": 2.25}, {"text": "How about this\nfunction right here?", "start": 2615.01, "duration": 2.65}, {"text": "This function is e\nto the i omega 1.", "start": 2617.66, "duration": 2.77}, {"text": "It's a sine wave and a\ncosine wave, a complex sine", "start": 2620.43, "duration": 4.12}, {"text": "and cosine, at\nfrequency omega 1.", "start": 2624.55, "duration": 3.57}, {"text": "Anybody know what the\nFourier transform of that is?", "start": 2628.12, "duration": 3.388}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2631.508, "duration": 2.112}, {"text": "MICHALE FEE: Yeah.", "start": 2633.62, "duration": 0.75}, {"text": "So it's basically--\nyou can think of this--", "start": 2634.37, "duration": 9.36}, {"text": "that's the right answer.", "start": 2643.73, "duration": 1.06}, {"text": "Rather than try to explain\nit, I'll just show you.", "start": 2644.79, "duration": 2.58}, {"text": "So the Fourier transform of\nthis is just a peak at omega 1.", "start": 2647.37, "duration": 4.08}, {"text": "And we can inverse Fourier\ntransform that and recover", "start": 2654.52, "duration": 2.7}, {"text": "our original function.", "start": 2657.22, "duration": 1.68}, {"text": "So those last few slides are\nmore for the aficionados.", "start": 2658.9, "duration": 3.33}, {"text": "You don't have to know that.", "start": 2662.23, "duration": 1.685}, {"text": "We're going to\nspend time looking", "start": 2663.915, "duration": 1.375}, {"text": "at the discrete versions\nof these things.", "start": 2665.29, "duration": 6.0}, {"text": "How about this case?", "start": 2671.29, "duration": 1.54}, {"text": "This is a simple\ncase where you have", "start": 2672.83, "duration": 2.57}, {"text": "a function that the\nFourier transform", "start": 2675.4, "duration": 3.54}, {"text": "of which has a peak at omega\n1 and a peak at minus omega 1.", "start": 2678.94, "duration": 5.06}, {"text": "The Fourier transform of the\ninverse Fourier transform", "start": 2684.0, "duration": 3.16}, {"text": "of that is just cosine omega 1t.", "start": 2687.16, "duration": 3.81}, {"text": "So a function, a cosine\nfunction with frequency omega 1,", "start": 2690.97, "duration": 4.17}, {"text": "has two peaks, one\nat frequency omega 1", "start": 2695.14, "duration": 4.2}, {"text": "and another one at\nfrequency minus omega 1.", "start": 2699.34, "duration": 4.97}, {"text": "So that looks a\nlot like the case", "start": 2704.31, "duration": 2.35}, {"text": "we just talked about where\nwe had this complex Fourier", "start": 2706.66, "duration": 3.51}, {"text": "series.", "start": 2710.17, "duration": 0.87}, {"text": "And we had a peak at n equals\n2 and another peak at n", "start": 2711.04, "duration": 5.1}, {"text": "equals minus 2.", "start": 2716.14, "duration": 1.95}, {"text": "And that function that gave\nus that complex Fourier", "start": 2718.09, "duration": 3.57}, {"text": "series was cosine 2 omega t.", "start": 2721.66, "duration": 2.765}, {"text": "So that's just\nwhat we have here.", "start": 2724.425, "duration": 1.375}, {"text": "We have a peak in the\nspectrum at omega 1,", "start": 2725.8, "duration": 3.21}, {"text": "peak at minus omega\n1, and that is", "start": 2729.01, "duration": 2.85}, {"text": "the Fourier decomposition\nof a function that", "start": 2731.86, "duration": 2.49}, {"text": "is cosine omega 1t.", "start": 2734.35, "duration": 2.58}, {"text": "So it's just like\nwhat we saw before", "start": 2736.93, "duration": 2.12}, {"text": "for the case of the\ncomplex Fourier series.", "start": 2739.05, "duration": 4.28}, {"text": "So that was Fourier transform.", "start": 2746.04, "duration": 2.45}, {"text": "And now let's talk about the\ndiscrete Fourier transform", "start": 2748.49, "duration": 6.28}, {"text": "and the associated\nalgorithm for computing", "start": 2754.77, "duration": 2.52}, {"text": "that very quickly called the\nFast Fourier Transform, or FFT.", "start": 2757.29, "duration": 4.92}, {"text": "So you can see computing\nthese Fourier transforms,", "start": 2762.21, "duration": 4.41}, {"text": "if you were to actually try\nto compute Fourier transforms", "start": 2766.62, "duration": 3.33}, {"text": "by taking a function,\nmultiplying it", "start": 2769.95, "duration": 3.45}, {"text": "by these complex exponentials\nlike writing down", "start": 2773.4, "duration": 4.02}, {"text": "the value of e to the i omega t\nat a bunch of different omegas", "start": 2777.42, "duration": 5.09}, {"text": "and a bunch of different\nt's and then integrating", "start": 2782.51, "duration": 2.76}, {"text": "that numerically, that would\ntake forever computationally.", "start": 2785.27, "duration": 7.66}, {"text": "But it turns out that there's--", "start": 2792.93, "duration": 2.91}, {"text": "so you have to\ncompute that integral", "start": 2795.84, "duration": 2.25}, {"text": "over time for every omega\nthat you're interested in.", "start": 2798.09, "duration": 4.5}, {"text": "It turns out really, really\nfast algorithm that you", "start": 2802.59, "duration": 4.08}, {"text": "can use for the\ncase where you've", "start": 2806.67, "duration": 1.5}, {"text": "got functions that\nare sampled in time", "start": 2808.17, "duration": 4.4}, {"text": "and you want to extract the\nfrequencies of that signal", "start": 2812.57, "duration": 4.32}, {"text": "at a discrete set\nof frequencies.", "start": 2816.89, "duration": 2.46}, {"text": "I'm going to switch\nfrom using omega, which", "start": 2823.89, "duration": 2.55}, {"text": "is very commonly\nused when you're", "start": 2826.44, "duration": 1.47}, {"text": "talking about\nFourier transforms,", "start": 2827.91, "duration": 1.47}, {"text": "to just using f, the frequency.", "start": 2829.38, "duration": 2.29}, {"text": "So it's just f is just 2 pi.", "start": 2831.67, "duration": 3.56}, {"text": "So omega is 2 pi f.", "start": 2835.23, "duration": 3.18}, {"text": "So here I'm just rewriting\nthe Fourier transform", "start": 2838.41, "duration": 8.2}, {"text": "and the inverse\nFourier transform", "start": 2846.61, "duration": 1.5}, {"text": "with f rather than omega.", "start": 2848.11, "duration": 1.62}, {"text": "So we're going to\nstart using f's now", "start": 2849.73, "duration": 1.86}, {"text": "for the discrete\nFourier transform case.", "start": 2851.59, "duration": 3.42}, {"text": "And we're going to\nconsider the case where", "start": 2855.01, "duration": 1.75}, {"text": "we have signals that are sampled\nat regular intervals delta t.", "start": 2856.76, "duration": 3.62}, {"text": "So here we have a\nfunction of time y of t.", "start": 2860.38, "duration": 4.01}, {"text": "And we're going to sample that\nsignal at regular intervals", "start": 2864.39, "duration": 4.21}, {"text": "delta t.", "start": 2868.6, "duration": 0.66}, {"text": "So this is delta t right here.", "start": 2869.26, "duration": 2.61}, {"text": "That time interval there.", "start": 2871.87, "duration": 1.95}, {"text": "So the sampling rate, the\nsampling frequency, is just 1", "start": 2873.82, "duration": 4.68}, {"text": "over delta t.", "start": 2878.5, "duration": 0.81}, {"text": "So the way this works in\nthe fast Fourier transform", "start": 2884.92, "duration": 5.38}, {"text": "algorithm is you just\ntake those samples", "start": 2890.3, "duration": 2.85}, {"text": "and you put them into a\nvector in MATLAB, just", "start": 2893.15, "duration": 4.82}, {"text": "some one-dimensional array.", "start": 2897.97, "duration": 3.18}, {"text": "And we're going to imagine\nthat our samples are", "start": 2903.95, "duration": 5.7}, {"text": "acquired at different times.", "start": 2909.65, "duration": 2.67}, {"text": "And let's [INAUDIBLE] minus\ntime step 8, minus 7, minus 6.", "start": 2912.32, "duration": 5.37}, {"text": "Time step 0 is in the\nmiddle up to time step 7.", "start": 2917.69, "duration": 3.24}, {"text": "And we're going to say\nthat N is an even number.", "start": 2920.93, "duration": 2.45}, {"text": "The fast Fourier\ntransform works much,", "start": 2923.38, "duration": 2.42}, {"text": "much faster when N\nis an even number,", "start": 2925.8, "duration": 2.42}, {"text": "and it works even faster when\nN is a multiple, a power of 2.", "start": 2928.22, "duration": 5.37}, {"text": "So in this case,\nwe have 16 samples.", "start": 2933.59, "duration": 1.94}, {"text": "It's 2 to the 4.", "start": 2935.53, "duration": 1.42}, {"text": "Should usually try to make\nyour samples be a power of 2.", "start": 2936.95, "duration": 8.55}, {"text": "The number of samples.", "start": 2945.5, "duration": 3.15}, {"text": "So there is our function of time\nsampled at regular intervals t.", "start": 2948.65, "duration": 5.46}, {"text": "So you can see that the\nt min, the minimum time,", "start": 2959.24, "duration": 4.47}, {"text": "in this vector of sample\npoints in our function", "start": 2963.71, "duration": 4.14}, {"text": "is minus N over 2 delta t.", "start": 2967.85, "duration": 3.57}, {"text": "And that [INAUDIBLE] time is N\nover 2 minus 1 times delta t.", "start": 2971.42, "duration": 5.38}, {"text": "And that's what the\nMATLAB code would", "start": 2982.65, "duration": 2.64}, {"text": "look like to generate\nan array of time values.", "start": 2985.29, "duration": 6.334}, {"text": "Does that make sense?", "start": 2991.624, "duration": 1.186}, {"text": "The FFT algorithm returns\nthe Fourier components", "start": 2996.26, "duration": 5.77}, {"text": "of that function of time.", "start": 3002.03, "duration": 4.22}, {"text": "And it returns the\nFourier components", "start": 3006.25, "duration": 2.82}, {"text": "in a vector that has the\nnegative frequencies on one", "start": 3009.07, "duration": 5.43}, {"text": "side and the\npositive frequencies", "start": 3014.5, "duration": 2.28}, {"text": "on the other side\nand the constant term", "start": 3016.78, "duration": 3.74}, {"text": "here in the middle.", "start": 3020.52, "duration": 1.65}, {"text": "The minimum frequency is N\nover 2 times delta F. Oh,", "start": 3026.64, "duration": 3.99}, {"text": "I should say it returns the\nFourier components in steps", "start": 3030.63, "duration": 4.26}, {"text": "of delta f where delta F is\nthe sampling rate divided", "start": 3034.89, "duration": 3.15}, {"text": "by the number of time\nsteps that you put into it.", "start": 3038.04, "duration": 2.46}, {"text": "Don't panic.", "start": 3043.68, "duration": 1.79}, {"text": "This is just reference.", "start": 3045.47, "duration": 1.81}, {"text": "I'm showing you how\nyou put the data in", "start": 3047.28, "duration": 4.7}, {"text": "and how you get the data out.", "start": 3051.98, "duration": 3.36}, {"text": "When you put data into\nthe Fourier transform", "start": 3055.34, "duration": 2.43}, {"text": "algorithm, the\nFFT algorithm, you", "start": 3057.77, "duration": 3.07}, {"text": "put in data that's\nsampled at times,", "start": 3060.84, "duration": 2.79}, {"text": "and you have to know\nwhat those times are.", "start": 3063.63, "duration": 3.51}, {"text": "If you want to make\na plot of the data,", "start": 3067.14, "duration": 2.37}, {"text": "you need to make an\narray of time values.", "start": 3069.51, "duration": 4.15}, {"text": "And they just go from\na t min to a t max.", "start": 3073.66, "duration": 4.132}, {"text": "And there's a little\npiece of MATLAB code", "start": 3077.792, "duration": 1.708}, {"text": "that produces that\narray of times for you.", "start": 3079.5, "duration": 3.65}, {"text": "What you get back from\nthe Fourier transform,", "start": 3085.66, "duration": 2.25}, {"text": "the FFT, an array of not\nvalues of the function of time,", "start": 3087.91, "duration": 6.01}, {"text": "but rather an array of\nFourier coefficients.", "start": 3093.92, "duration": 4.7}, {"text": "Just like we stuck in into our--", "start": 3098.62, "duration": 3.39}, {"text": "when we did the\ncomplex Fourier series,", "start": 3102.01, "duration": 3.75}, {"text": "we stuck in a function of time.", "start": 3105.76, "duration": 1.95}, {"text": "And we get out a list\nof Fourier coefficients.", "start": 3107.71, "duration": 3.45}, {"text": "Same thing here.", "start": 3111.16, "duration": 1.3}, {"text": "We put in a function\nof time, and we get out", "start": 3112.46, "duration": 5.82}, {"text": "Fourier coefficients.", "start": 3118.28, "duration": 1.11}, {"text": "And the Fourier coefficients\nare complex numbers associated", "start": 3119.39, "duration": 5.16}, {"text": "with different frequencies.", "start": 3124.55, "duration": 3.36}, {"text": "So let's say the\nmiddle coefficient", "start": 3127.91, "duration": 3.03}, {"text": "that you get will\nbe the coefficient", "start": 3130.94, "duration": 2.34}, {"text": "for the constant term.", "start": 3133.28, "duration": 2.25}, {"text": "This coefficient down here\nwill be the coefficient", "start": 3135.53, "duration": 2.34}, {"text": "for the minimum frequency,\nand that coefficient", "start": 3137.87, "duration": 2.97}, {"text": "will be the coefficient for\nthe maximum frequency, the most", "start": 3140.84, "duration": 2.64}, {"text": "positive frequency.", "start": 3143.48, "duration": 1.378}, {"text": "Does that make sense?", "start": 3149.47, "duration": 0.875}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3154.504, "duration": 3.416}, {"text": "MICHALE FEE: Ah, OK.", "start": 3157.92, "duration": 2.09}, {"text": "So I was hoping to just kind\nof skip over that for now.", "start": 3160.01, "duration": 4.31}, {"text": "But when you do a discrete\nFourier transform,", "start": 3164.32, "duration": 3.43}, {"text": "turns out that the coefficient\nfor the most negative frequency", "start": 3167.75, "duration": 3.63}, {"text": "is always exactly the same as\nthe coefficient for the most", "start": 3171.38, "duration": 2.79}, {"text": "positive frequency.", "start": 3174.17, "duration": 3.96}, {"text": "And so they're\njust given in one--", "start": 3178.13, "duration": 2.97}, {"text": "they're both given in\none element of the array.", "start": 3181.1, "duration": 2.85}, {"text": "You could replicate\nthat up here,", "start": 3186.49, "duration": 4.12}, {"text": "but it would be pointless.", "start": 3190.61, "duration": 1.44}, {"text": "And the length of the array\nwould have to be n plus 1.", "start": 3192.05, "duration": 2.73}, {"text": "Yes?", "start": 3199.73, "duration": 1.485}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3201.215, "duration": 2.985}, {"text": "MICHALE FEE: OK.", "start": 3204.2, "duration": 1.21}, {"text": "Good.", "start": 3205.41, "duration": 0.6}, {"text": "That question always comes\nup, and it's a great question.", "start": 3206.01, "duration": 3.66}, {"text": "What we're trying\nto do is to come up", "start": 3212.53, "duration": 1.71}, {"text": "with a way of representing\narbitrary functions.", "start": 3214.24, "duration": 5.17}, {"text": "So we can represent\nsymmetric functions", "start": 3224.98, "duration": 4.55}, {"text": "by summing together\na bunch of cosines.", "start": 3229.53, "duration": 3.69}, {"text": "We can represent\nantisymmetric functions", "start": 3233.22, "duration": 2.67}, {"text": "by summing together\na bunch of sines.", "start": 3235.89, "duration": 2.56}, {"text": "But if we want to represent\nan arbitrary function,", "start": 3238.45, "duration": 2.84}, {"text": "we have to use both\ncosines and sines.", "start": 3241.29, "duration": 2.34}, {"text": "So we have this trick,\nthough, where we can,", "start": 3250.08, "duration": 3.24}, {"text": "instead of using\nsines and cosines,", "start": 3253.32, "duration": 2.55}, {"text": "using these two\nseparate functions,", "start": 3255.87, "duration": 2.04}, {"text": "we can use a single function\nwhich is a complex exponential", "start": 3257.91, "duration": 4.71}, {"text": "to represent things that can be\nrepresented by sums of cosines", "start": 3262.62, "duration": 4.83}, {"text": "as well as things that can be\nrepresented as sums of signs.", "start": 3267.45, "duration": 3.63}, {"text": "It's an arbitrary function.", "start": 3271.08, "duration": 2.76}, {"text": "And the reason is because\nthe complex exponential has", "start": 3273.84, "duration": 3.72}, {"text": "both a cosine in it and a sine.", "start": 3277.56, "duration": 2.64}, {"text": "So we can represent a cosine\nas a complex exponential", "start": 3285.59, "duration": 5.37}, {"text": "with a positive\nfrequency, meaning", "start": 3290.96, "duration": 2.22}, {"text": "that it's a complex\nnumber that goes", "start": 3293.18, "duration": 3.12}, {"text": "around this direction\nplus another function", "start": 3296.3, "duration": 6.41}, {"text": "where the complex number is\ngoing around in this direction.", "start": 3302.71, "duration": 3.73}, {"text": "So positive frequencies\nmean as time increases,", "start": 3306.44, "duration": 6.36}, {"text": "this complex number is\ngoing around the unit", "start": 3312.8, "duration": 1.98}, {"text": "circle in this direction.", "start": 3314.78, "duration": 1.32}, {"text": "Negative frequencies\nmean the complex number's", "start": 3316.1, "duration": 2.88}, {"text": "going around in this direction.", "start": 3318.98, "duration": 1.36}, {"text": "And you can see that in\norder to represent a cosine,", "start": 3320.34, "duration": 6.07}, {"text": "I need to have--", "start": 3326.41, "duration": 1.67}, {"text": "so let's see if I can do this.", "start": 3328.08, "duration": 1.6}, {"text": "Here's my e to the-- here's\nmy plus frequency going", "start": 3329.68, "duration": 3.99}, {"text": "around this way.", "start": 3333.67, "duration": 1.87}, {"text": "Here's my minus frequency\ngoing around this way.", "start": 3335.54, "duration": 3.26}, {"text": "And you can see\nthat I can represent", "start": 3338.8, "duration": 1.71}, {"text": "a cosine if I can make the\nimaginary parts cancel.", "start": 3340.51, "duration": 7.02}, {"text": "So if I have one function\nthat's going around like this,", "start": 3347.53, "duration": 3.09}, {"text": "another function that's\ngoing around like this.", "start": 3350.62, "duration": 2.13}, {"text": "If I add them, then the\nimaginary part cancels.", "start": 3352.75, "duration": 7.49}, {"text": "The sine cancels.", "start": 3360.24, "duration": 1.54}, {"text": "This plus this is\ncosine plus cosine.", "start": 3361.78, "duration": 3.63}, {"text": "i sine minus i sine.", "start": 3365.41, "duration": 1.98}, {"text": "So the sines can--\nthe sine cancels.", "start": 3367.39, "duration": 2.8}, {"text": "And what I'm left\nwith is a sine.", "start": 3370.19, "duration": 1.64}, {"text": "So represent a cosine as\na sum of a function that", "start": 3371.83, "duration": 4.05}, {"text": "has a positive frequency\nand a negative frequency.", "start": 3375.88, "duration": 5.82}, {"text": "You can see that\nthe y component,", "start": 3381.7, "duration": 2.37}, {"text": "the imaginary component,\ncancels and all", "start": 3384.07, "duration": 2.13}, {"text": "I'm left with is the cosine\nthat's going across like this.", "start": 3386.2, "duration": 3.75}, {"text": "So it's just a\nmathematical trick.", "start": 3389.95, "duration": 3.67}, {"text": "Positive and\nnegative frequencies", "start": 3393.62, "duration": 1.65}, {"text": "are just a mathematical trick to\nmake either the symmetric part", "start": 3395.27, "duration": 7.94}, {"text": "of the function or antisymmetric\npart of the function cancel.", "start": 3403.21, "duration": 4.05}, {"text": "So I can just use these positive\nand negative frequencies", "start": 3407.26, "duration": 5.58}, {"text": "to represent any function.", "start": 3412.84, "duration": 1.56}, {"text": "If I only had\npositive frequencies,", "start": 3414.4, "duration": 2.73}, {"text": "I wouldn't be able to\nrepresent arbitrary functions.", "start": 3417.13, "duration": 2.49}, {"text": "So just one more\nlittle thing that you", "start": 3423.72, "duration": 2.64}, {"text": "need to know about\nthe FFT algorithm.", "start": 3426.36, "duration": 5.1}, {"text": "So remember we talked about if\nyou have a function of time,", "start": 3431.46, "duration": 4.04}, {"text": "negative times are over here,\npositive times are over here.", "start": 3435.5, "duration": 4.7}, {"text": "You can put-- you can\nsample your function", "start": 3440.2, "duration": 3.03}, {"text": "at different times and put\nthose different samples", "start": 3443.23, "duration": 2.88}, {"text": "into an array.", "start": 3446.11, "duration": 1.32}, {"text": "Before you send this\narray of time samples", "start": 3447.43, "duration": 3.45}, {"text": "to the FFT algorithm,\nyou just need", "start": 3450.88, "duration": 2.49}, {"text": "to swap the right\nhalf of the array", "start": 3453.37, "duration": 2.82}, {"text": "with the left half of the\narray using a function called", "start": 3456.19, "duration": 2.52}, {"text": "time shifted arrays.", "start": 3458.71, "duration": 1.85}, {"text": "Don't worry about it.", "start": 3463.37, "duration": 0.94}, {"text": "It's just the guts\nof the FFT algorithm", "start": 3464.31, "duration": 2.78}, {"text": "wants to have the positive\ntimes in the first half", "start": 3467.09, "duration": 2.67}, {"text": "and the negative times\nin the second half.", "start": 3469.76, "duration": 3.09}, {"text": "So you just do this.", "start": 3472.85, "duration": 4.55}, {"text": "Then you run the FFT function\non this time shifted array.", "start": 3477.4, "duration": 7.57}, {"text": "And what it spits\nback is an array", "start": 3484.97, "duration": 2.72}, {"text": "with the positive\nfrequencies in the first half", "start": 3487.69, "duration": 3.06}, {"text": "and the negative frequencies\nin the second half.", "start": 3490.75, "duration": 2.94}, {"text": "And you can just swap those\nback using the circshift again.", "start": 3493.69, "duration": 5.43}, {"text": "That is your spectrum.", "start": 3499.12, "duration": 4.65}, {"text": "Your spectral coefficients.", "start": 3503.77, "duration": 1.65}, {"text": "Your Fourier coefficients\nof this function.", "start": 3505.42, "duration": 2.73}, {"text": "Just MATLAB guts.", "start": 3511.98, "duration": 1.705}, {"text": "Don't worry about it.", "start": 3513.685, "duration": 0.875}, {"text": "So here's a piece of code\nthat computes the Fourier", "start": 3519.12, "duration": 3.31}, {"text": "coefficients of a function.", "start": 3522.43, "duration": 3.03}, {"text": "So the first thing\nwe're going to do", "start": 3525.46, "duration": 1.95}, {"text": "is define the number of points\nthat we have in our array.", "start": 3527.41, "duration": 4.39}, {"text": "2048.", "start": 3531.8, "duration": 1.34}, {"text": "So it's a power of 2.", "start": 3533.14, "duration": 1.84}, {"text": "So the FFT algorithm runs fast.", "start": 3534.98, "duration": 2.51}, {"text": "We're figuring out-- we're\ngoing to write down a delta t.", "start": 3537.49, "duration": 4.45}, {"text": "In this case, it's\none millisecond.", "start": 3541.94, "duration": 3.53}, {"text": "The sampling rate, the\nsampling frequency is just 1", "start": 3545.47, "duration": 5.29}, {"text": "over delta t.", "start": 3550.76, "duration": 0.96}, {"text": "So 1 kilohertz.", "start": 3551.72, "duration": 3.03}, {"text": "The array of times at\nwhich the function sampled", "start": 3554.75, "duration": 4.98}, {"text": "is just going from\nminus n over 2", "start": 3559.73, "duration": 2.75}, {"text": "to plus n over 2\nminus 1 times delta t.", "start": 3562.48, "duration": 3.91}, {"text": "I'm defining the\nfrequency of a sine wave.", "start": 3569.87, "duration": 3.19}, {"text": "And we're now getting the\nvalues of that cosine function", "start": 3573.06, "duration": 4.2}, {"text": "at those different times.", "start": 3577.26, "duration": 2.61}, {"text": "Does that make sense?", "start": 3579.87, "duration": 2.29}, {"text": "We're taking that\nfunction of time", "start": 3582.16, "duration": 2.79}, {"text": "and circularly shifting\nit by half the array.", "start": 3584.95, "duration": 3.96}, {"text": "So that's the circularly\nshifted, the swapped values", "start": 3588.91, "duration": 6.3}, {"text": "of our function y.", "start": 3595.21, "duration": 1.29}, {"text": "We stick that into\nthe FFT function.", "start": 3596.5, "duration": 1.815}, {"text": "It gives you back the\nFourier coefficients.", "start": 3600.87, "duration": 2.7}, {"text": "You just swap it again.", "start": 3603.57, "duration": 2.07}, {"text": "And that is the spectrum, the\nFourier transform [INAUDIBLE]", "start": 3608.51, "duration": 3.78}, {"text": "signal.", "start": 3612.29, "duration": 0.5}, {"text": "And now you can\nwrite down a vector", "start": 3615.46, "duration": 1.79}, {"text": "of frequencies of each one of\nthose Fourier coefficients.", "start": 3617.25, "duration": 5.213}, {"text": "Each one of those segments\nin that vector y--", "start": 3630.36, "duration": 4.41}, {"text": "remember, there are 2,000\nof them now, 2,048 of them--", "start": 3634.77, "duration": 4.08}, {"text": "each one of those is\nthe Fourier coefficient", "start": 3638.85, "duration": 3.55}, {"text": "of the function we\nput in at each one", "start": 3642.4, "duration": 3.75}, {"text": "of those different frequencies.", "start": 3646.15, "duration": 1.41}, {"text": "Does that make sense?", "start": 3652.12, "duration": 2.58}, {"text": "Now let's take a look\nat a few examples", "start": 3654.7, "duration": 2.1}, {"text": "of what that looks like.", "start": 3656.8, "duration": 2.77}, {"text": "So here is a function y of t.", "start": 3659.57, "duration": 3.43}, {"text": "It's cosine 2 pi f 0 t\nwhere f 0 is 20 hertz.", "start": 3663.0, "duration": 6.23}, {"text": "So it's just a cosine wave.", "start": 3669.23, "duration": 3.81}, {"text": "You run this code on it.", "start": 3673.04, "duration": 4.97}, {"text": "And what you get back is an\narray of complex numbers.", "start": 3678.01, "duration": 5.27}, {"text": "It has a real and imaginary\npart as a function of frequency.", "start": 3683.28, "duration": 8.15}, {"text": "And you get this\ncosine function.", "start": 3691.43, "duration": 3.315}, {"text": "It has two peaks, as promised.", "start": 3694.745, "duration": 4.125}, {"text": "It has a peak at plus 20 hertz\nand a peak at minus 20 hertz.", "start": 3698.87, "duration": 5.22}, {"text": "One of those peaks\ngives you an e", "start": 3706.63, "duration": 4.61}, {"text": "to the i omega t that\ngoes this way at 20 hertz.", "start": 3711.24, "duration": 3.55}, {"text": "The other one gives you\nan e of the i omega t", "start": 3714.79, "duration": 2.58}, {"text": "that goes this way at 20 hertz.", "start": 3717.37, "duration": 2.28}, {"text": "And when you add them\ntogether, if I can do that,", "start": 3719.65, "duration": 5.05}, {"text": "it gives you a cosine.", "start": 3724.7, "duration": 1.73}, {"text": "It goes back and\nforth at 20 hertz.", "start": 3726.43, "duration": 2.543}, {"text": "That one.", "start": 3728.973, "duration": 0.986}, {"text": "Here's a sine wave.", "start": 3738.84, "duration": 1.26}, {"text": "y equals sine 2 pi f\n0 t again at 20 hertz.", "start": 3740.1, "duration": 4.67}, {"text": "You run that code on it.", "start": 3744.77, "duration": 1.95}, {"text": "It gives you this.", "start": 3746.72, "duration": 2.67}, {"text": "Notice that-- OK, sorry.", "start": 3749.39, "duration": 1.59}, {"text": "Let me just point\nout one more thing.", "start": 3750.98, "duration": 1.62}, {"text": "In this case, the peaks\nare in the real part of y.", "start": 3752.6, "duration": 4.8}, {"text": "For the sine function,\nthe real part is 0", "start": 3757.4, "duration": 4.23}, {"text": "and the peaks are in\nthe imaginary part.", "start": 3761.63, "duration": 1.68}, {"text": "There's a plus i at\nminus 20 i over 2,", "start": 3763.31, "duration": 5.16}, {"text": "actually, at minus 20 hertz,\na minus i at plus 20 hertz.", "start": 3768.47, "duration": 7.76}, {"text": "And what that does is when you\nmultiply that coefficient times", "start": 3776.23, "duration": 4.47}, {"text": "e to the i omega t and that\ncoefficient times whichever", "start": 3780.7, "duration": 5.35}, {"text": "the opposite one is.", "start": 3786.05, "duration": 1.5}, {"text": "One going this way, the\nother one going this way.", "start": 3787.55, "duration": 3.01}, {"text": "You can see that the\nreal part now cancels.", "start": 3790.56, "duration": 3.02}, {"text": "And what you're left with is the\nsine part that doesn't cancel.", "start": 3793.58, "duration": 5.175}, {"text": "And that is this\nfunction sine omega t.", "start": 3801.46, "duration": 3.37}, {"text": "Any questions about that?", "start": 3811.508, "duration": 3.652}, {"text": "That's kind of boring.", "start": 3815.16, "duration": 1.182}, {"text": "We're going to put more\ninteresting functions in here", "start": 3816.342, "duration": 2.208}, {"text": "soon.", "start": 3818.55, "duration": 1.06}, {"text": "But I just wanted you to\nsee what this algorithm does", "start": 3819.61, "duration": 3.5}, {"text": "on the things that we've\nbeen talking about all along.", "start": 3823.11, "duration": 4.612}, {"text": "And it gives you\nexactly what you expect.", "start": 3827.722, "duration": 1.708}, {"text": "Remember, we can write\ndown any arbitrary function", "start": 3832.33, "duration": 5.52}, {"text": "as a sum of sines and cosines.", "start": 3837.85, "duration": 4.6}, {"text": "Which means we can write\ndown any arbitrary function", "start": 3844.97, "duration": 4.69}, {"text": "as a sum of these little\npeaks and these peaks", "start": 3849.66, "duration": 12.21}, {"text": "at different frequencies.", "start": 3861.87, "duration": 3.71}, {"text": "Does that make sense?", "start": 3865.58, "duration": 1.26}, {"text": "So all we have to do is\nfind these coefficients,", "start": 3866.84, "duration": 5.48}, {"text": "these peaks, what values\nof these different peaks", "start": 3872.32, "duration": 2.64}, {"text": "to stick in to reconstruct\nany arbitrary function.", "start": 3874.96, "duration": 4.93}, {"text": "And we're going to do a lot\nof that in the next lecture.", "start": 3879.89, "duration": 3.91}, {"text": "We're going to look at what\ndifferent functions here look", "start": 3883.8, "duration": 3.41}, {"text": "like in the Fourier domain.", "start": 3887.21, "duration": 3.36}, {"text": "We're going to do that for some\nsegments like a square pulse,", "start": 3890.57, "duration": 3.57}, {"text": "for trains of\npulses, for Gaussian,", "start": 3894.14, "duration": 6.52}, {"text": "for all kinds of\ndifferent functions.", "start": 3900.66, "duration": 1.59}, {"text": "And then using the\nconvolution theorem,", "start": 3902.25, "duration": 2.13}, {"text": "you can actually just\npredict in your own mind", "start": 3904.38, "duration": 2.61}, {"text": "what different combinations of\nthose functions will look like.", "start": 3906.99, "duration": 4.62}, {"text": "So I want to end by talking\nabout one other really", "start": 3911.61, "duration": 3.15}, {"text": "critical concept called\nthe power spectrum.", "start": 3914.76, "duration": 3.735}, {"text": "And it's basically\nusually what you", "start": 3918.495, "duration": 3.525}, {"text": "do when you compute the\nFourier transform of a function", "start": 3922.02, "duration": 6.45}, {"text": "is to figure out what\nthe power spectrum is.", "start": 3928.47, "duration": 4.32}, {"text": "The simple answer\nis that all you do", "start": 3932.79, "duration": 2.1}, {"text": "is you square this thing.", "start": 3934.89, "duration": 2.25}, {"text": "Take the magnitude squared.", "start": 3937.14, "duration": 2.37}, {"text": "But I'm going to build\nup to that a little bit.", "start": 3939.51, "duration": 2.16}, {"text": "So it's called the\npower spectrum.", "start": 3944.25, "duration": 1.47}, {"text": "But first we need to understand\nwhat we mean by power.", "start": 3945.72, "duration": 4.613}, {"text": "So we're going to\nthink about this", "start": 3950.333, "duration": 1.417}, {"text": "in the context of a\nsimple electrical circuit.", "start": 3951.75, "duration": 3.3}, {"text": "Let's imagine that this\nfunction that we're", "start": 3955.05, "duration": 2.88}, {"text": "computing the Fourier\ntransform of, imagine", "start": 3957.93, "duration": 2.88}, {"text": "this function is voltage.", "start": 3960.81, "duration": 2.16}, {"text": "That's where this\nidea comes from.", "start": 3962.97, "duration": 2.16}, {"text": "Imagine that this\nfunction is the voltage", "start": 3965.13, "duration": 2.22}, {"text": "that you've measured\nsomewhere in a circuit.", "start": 3967.35, "duration": 2.19}, {"text": "Let's say in this\ncircuit right here.", "start": 3969.54, "duration": 1.74}, {"text": "Or current, either way.", "start": 3971.28, "duration": 3.29}, {"text": "So when you have current\nflowing through this circuit,", "start": 3974.57, "duration": 5.1}, {"text": "you can see that sinusoid--\nthat some oscillatory", "start": 3979.67, "duration": 3.39}, {"text": "current, some\ncosine, that drives", "start": 3983.06, "duration": 2.61}, {"text": "current through this resistor.", "start": 3985.67, "duration": 2.16}, {"text": "And when current flows to a\nresistor, it dissipates power.", "start": 3987.83, "duration": 5.64}, {"text": "And the power\ndissipated in a resistor", "start": 3993.47, "duration": 2.22}, {"text": "is just the current\ntimes the voltage drop", "start": 3995.69, "duration": 3.42}, {"text": "across that resistor.", "start": 3999.11, "duration": 2.93}, {"text": "That means that the power--", "start": 4002.04, "duration": 1.74}, {"text": "now, remember,\nOhm's law tells you", "start": 4003.78, "duration": 1.65}, {"text": "that current is just voltage\ndivided by resistance.", "start": 4005.43, "duration": 3.66}, {"text": "So this is v divided by r.", "start": 4009.09, "duration": 1.83}, {"text": "So the power is just v\nsquared divided by r.", "start": 4010.92, "duration": 6.17}, {"text": "So if the voltage is just a\nsine wave at frequency omega,", "start": 4017.09, "duration": 5.01}, {"text": "then v is some coefficient,\nsome amplitude at that", "start": 4022.1, "duration": 6.79}, {"text": "frequency times cosine omega t.", "start": 4028.89, "duration": 2.6}, {"text": "We can write that voltage\nusing Euler's equation as 1/2 e", "start": 4031.49, "duration": 7.33}, {"text": "to the minus i omega t plus\n1/2 e to the plus i omega t.", "start": 4038.82, "duration": 3.75}, {"text": "And let's calculate the power\nassociated with that voltage.", "start": 4046.11, "duration": 3.83}, {"text": "Well, we have to average over\none cycle of that oscillation.", "start": 4049.94, "duration": 7.33}, {"text": "So the average\npower is just given", "start": 4057.27, "duration": 2.51}, {"text": "by the square magnitude of the\nFourier transform [INAUDIBLE]..", "start": 4059.78, "duration": 4.03}, {"text": "So let's just plug\nthis into here.", "start": 4063.81, "duration": 2.45}, {"text": "And what you see is that the\npower at a given frequency", "start": 4066.26, "duration": 3.87}, {"text": "omega is just that coefficient\nmagnitude squared over", "start": 4070.13, "duration": 4.56}, {"text": "resistance times 1/2 e to\nthe minus i omega t magnitude", "start": 4074.69, "duration": 8.59}, {"text": "squared plus 1/2 e\nto the plus i over i", "start": 4083.28, "duration": 3.09}, {"text": "omega t magnitude squared.", "start": 4086.37, "duration": 2.95}, {"text": "And that's just\nequal to 1 over r.", "start": 4089.32, "duration": 4.9}, {"text": "That coefficient\nmagnitude squared over 2.", "start": 4094.22, "duration": 4.759}, {"text": "So you can see that\nthe power dissipated", "start": 4098.979, "duration": 3.981}, {"text": "by this sinusoidal\nvoltage is just", "start": 4102.96, "duration": 6.99}, {"text": "that magnitude squared over 2.", "start": 4109.95, "duration": 2.64}, {"text": "So we can calculate the power\ndissipated in any resistor", "start": 4116.79, "duration": 4.71}, {"text": "simply by summing up the\n[INAUDIBLE] magnitude", "start": 4121.5, "duration": 2.609}, {"text": "of those coefficients.", "start": 4124.109, "duration": 2.87}, {"text": "So let's look at that\nin a little more detail.", "start": 4126.979, "duration": 3.951}, {"text": "So let's think for a moment\nabout the energy that", "start": 4130.93, "duration": 4.139}, {"text": "is dissipated by a signal.", "start": 4135.069, "duration": 5.511}, {"text": "So energy is just the\nintegral over time.", "start": 4140.58, "duration": 3.359}, {"text": "Power is per unit time.", "start": 4143.939, "duration": 1.801}, {"text": "Total energy is\njust the integral", "start": 4145.74, "duration": 1.89}, {"text": "of the power over time.", "start": 4147.63, "duration": 2.67}, {"text": "So power is just equal\nto v squared over r.", "start": 4150.3, "duration": 4.2}, {"text": "So I'm just going to\nsubstitute that in there.", "start": 4154.5, "duration": 1.939}, {"text": "So the energy of\na signal is just 1", "start": 4156.439, "duration": 2.29}, {"text": "over r times the integral\nof v squared over time.", "start": 4158.729, "duration": 4.471}, {"text": "Now, there's an\nimportant theorem", "start": 4168.85, "duration": 3.29}, {"text": "in complex analysis\ncalled Parseval's theorem", "start": 4172.14, "duration": 2.58}, {"text": "that says that the integral over\nthe square of the coefficients", "start": 4174.72, "duration": 6.84}, {"text": "in time is just\nequal to the integral", "start": 4181.56, "duration": 4.99}, {"text": "of the square magnitude\ncoefficients in frequency.", "start": 4186.55, "duration": 3.44}, {"text": "So what that's\nsaying is that it's", "start": 4194.31, "duration": 2.34}, {"text": "just the same as the\ntotal power in the signal", "start": 4196.65, "duration": 2.85}, {"text": "or the total energy in a signal\nif you represent it in the time", "start": 4199.5, "duration": 4.02}, {"text": "domain is just the same as\nthe total energy in the signal", "start": 4203.52, "duration": 4.67}, {"text": "if you look at it in\nthe frequency domain.", "start": 4208.19, "duration": 3.4}, {"text": "And what that's saying is\nthat the sum of all the", "start": 4211.59, "duration": 3.81}, {"text": "squared temporal\ncomponents is just", "start": 4215.4, "duration": 6.25}, {"text": "this equal to the sum of all the\nsquared frequency components.", "start": 4221.65, "duration": 6.06}, {"text": "And what that means\nis that you can", "start": 4227.71, "duration": 3.33}, {"text": "see that each of these frequency\ncomponents, each component", "start": 4231.04, "duration": 4.17}, {"text": "in frequency contributes\nindependently", "start": 4235.21, "duration": 2.49}, {"text": "to the power in the signal.", "start": 4237.7, "duration": 3.24}, {"text": "What that means is\nthat you can think--", "start": 4240.94, "duration": 3.27}, {"text": "so you can think\nof the total energy", "start": 4244.21, "duration": 2.73}, {"text": "in the signal as just the\nintegral over all frequencies", "start": 4246.94, "duration": 3.93}, {"text": "of this quantity here that\nwe call the power spectrum.", "start": 4250.87, "duration": 3.03}, {"text": "And so we'll often\ntake a signal,", "start": 4258.4, "duration": 1.83}, {"text": "calculate the\nFourier components,", "start": 4260.23, "duration": 2.01}, {"text": "and plot the area of\nthe Fourier transform,", "start": 4262.24, "duration": 3.83}, {"text": "the square magnitude of\nthe Fourier transform.", "start": 4266.07, "duration": 2.818}, {"text": "And that's called\nthe power spectrum.", "start": 4268.888, "duration": 1.542}, {"text": "And I've already said the total\nvariance of the signal in time", "start": 4273.55, "duration": 3.92}, {"text": "is the same as the total\nvariance of the signal", "start": 4277.47, "duration": 2.47}, {"text": "in the frequency domain.", "start": 4279.94, "duration": 2.08}, {"text": "So mathy people talk about\nthe variant of a signal.", "start": 4282.02, "duration": 4.15}, {"text": "The more engineering people talk\nabout the power in the signal.", "start": 4286.17, "duration": 2.95}, {"text": "But they're really talking\nabout the same thing.", "start": 4289.12, "duration": 2.0}, {"text": "So let's take this example\nthat we just looked at", "start": 4296.83, "duration": 2.233}, {"text": "and look at the power spectrum.", "start": 4299.063, "duration": 1.292}, {"text": "So that's a cosine function.", "start": 4303.83, "duration": 2.32}, {"text": "It has these two peaks.", "start": 4306.15, "duration": 1.025}, {"text": "Let me just point out\none more important thing.", "start": 4312.86, "duration": 3.45}, {"text": "For real functions,\nso in this class,", "start": 4316.31, "duration": 3.64}, {"text": "we're only going to be talking\nabout real functions of time.", "start": 4319.95, "duration": 3.35}, {"text": "For real functions, the square\nmagnitude of the Fourier", "start": 4323.3, "duration": 3.96}, {"text": "transform is symmetric.", "start": 4327.26, "duration": 4.58}, {"text": "So you can see here\nif there is a peak", "start": 4331.84, "duration": 3.25}, {"text": "in the positive\nfrequencies, there's", "start": 4335.09, "duration": 2.36}, {"text": "an equivalent peak in\nthe negative frequencies.", "start": 4337.45, "duration": 3.73}, {"text": "So when we plot the power\nspectrum of a signal,", "start": 4341.18, "duration": 4.36}, {"text": "we always just plot\nthe positive side.", "start": 4345.54, "duration": 4.14}, {"text": "And so here's what\nthat looks like.", "start": 4349.68, "duration": 1.69}, {"text": "Here is the power spectrum\nof a cosine signal.", "start": 4351.37, "duration": 5.44}, {"text": "And it's just a single peak.", "start": 4356.81, "duration": 2.7}, {"text": "So in that case, it was\na cosine at 20 hertz.", "start": 4359.51, "duration": 3.23}, {"text": "You get a single\npeak at 20 hertz.", "start": 4362.74, "duration": 3.121}, {"text": "What does it look like\nfor a sine function?", "start": 4369.75, "duration": 4.55}, {"text": "What is the power spectrum\nof a sine function?", "start": 4374.3, "duration": 2.03}, {"text": "Remember, in that case,\nit was the real part was 0", "start": 4376.33, "duration": 3.39}, {"text": "and the imaginary part\nhad a plus peak here", "start": 4379.72, "duration": 2.46}, {"text": "and a minus peak here.", "start": 4382.18, "duration": 1.47}, {"text": "What does the spectrum\nof that look like?", "start": 4383.65, "duration": 2.34}, {"text": "Right.", "start": 4388.67, "duration": 0.55}, {"text": "The square magnitude\nof i is just 1.", "start": 4389.22, "duration": 6.03}, {"text": "Magnitude squared\nof i is just 1.", "start": 4395.25, "duration": 2.64}, {"text": "So the power spectrum\nof a sine function", "start": 4401.55, "duration": 3.32}, {"text": "looks exactly like this.", "start": 4404.87, "duration": 2.65}, {"text": "Same as a cosine.", "start": 4407.52, "duration": 1.68}, {"text": "Makes a lot of sense.", "start": 4409.2, "duration": 0.93}, {"text": "Sine and cosine are\nexactly the same function.", "start": 4410.13, "duration": 2.52}, {"text": "One's just shifted\nby a quarter period.", "start": 4412.65, "duration": 5.63}, {"text": "So it has to have the\nsame power spectrum.", "start": 4421.02, "duration": 2.25}, {"text": "It has to have the same power.", "start": 4423.27, "duration": 3.29}, {"text": "Let's take a look at a\ndifferent function of time.", "start": 4426.56, "duration": 2.52}, {"text": "Here's a train of\ndelta functions.", "start": 4429.08, "duration": 1.59}, {"text": "So we just have a bunch\nof peaks spaced regularly", "start": 4430.67, "duration": 3.99}, {"text": "at some period.", "start": 4434.66, "duration": 1.05}, {"text": "I think it was--", "start": 4435.71, "duration": 0.69}, {"text": "I forget the exact number here.", "start": 4436.4, "duration": 1.74}, {"text": "But it's around 10-ish hertz.", "start": 4438.14, "duration": 3.48}, {"text": "Fourier transform of a\ntrain of delta functions", "start": 4444.82, "duration": 3.26}, {"text": "is another train\nof delta functions.", "start": 4448.08, "duration": 3.47}, {"text": "Pretty cool.", "start": 4451.55, "duration": 2.71}, {"text": "The period in the time\ndomain is delta t.", "start": 4454.26, "duration": 4.27}, {"text": "The period in the Fourier\ndomain is 1 over delta t.", "start": 4458.53, "duration": 4.8}, {"text": "That's another really important\nFourier transform pair for you", "start": 4463.33, "duration": 3.92}, {"text": "to know.", "start": 4467.25, "duration": 0.5}, {"text": "So the first Fourier transform\npair that you need to know", "start": 4467.75, "duration": 3.08}, {"text": "is that a constant in the time\ndomain is a delta function", "start": 4470.83, "duration": 4.21}, {"text": "in the frequency domain.", "start": 4475.04, "duration": 1.29}, {"text": "A delta function\nin the time domain", "start": 4476.33, "duration": 2.57}, {"text": "is a constant in the\nfrequency domain.", "start": 4478.9, "duration": 3.77}, {"text": "A train of delta functions\nin the time domain", "start": 4482.67, "duration": 2.86}, {"text": "is a train of functions in\nthe frequency domain and vice", "start": 4485.53, "duration": 3.36}, {"text": "versa.", "start": 4488.89, "duration": 1.83}, {"text": "And there's a very\nsimple relation", "start": 4490.72, "duration": 1.47}, {"text": "between the period\nin the time domain", "start": 4492.19, "duration": 2.08}, {"text": "and the period in\nthe frequency domain.", "start": 4494.27, "duration": 2.21}, {"text": "What does the power spectrum of\nthis train of delta functions", "start": 4496.48, "duration": 4.54}, {"text": "look like?", "start": 4501.02, "duration": 0.5}, {"text": "It's just the square\nmagnitude of this.", "start": 4509.16, "duration": 3.275}, {"text": "So it just looks like\na bunch of peaks.", "start": 4512.435, "duration": 1.625}, {"text": "So here's another function.", "start": 4517.62, "duration": 2.61}, {"text": "A square wave.", "start": 4520.23, "duration": 1.38}, {"text": "This is exactly the same\nfunction that we started with.", "start": 4521.61, "duration": 5.5}, {"text": "If you look at the\nFourier transform", "start": 4527.11, "duration": 1.59}, {"text": "of the imaginary part of 0,\nthe real part has these peaks.", "start": 4528.7, "duration": 7.11}, {"text": "So the Fourier transform-- so\nthese are now the coefficients", "start": 4535.81, "duration": 4.37}, {"text": "that you would put in front\nof your different cosines", "start": 4540.18, "duration": 3.72}, {"text": "at different frequencies to\nrepresent the square wave.", "start": 4543.9, "duration": 5.2}, {"text": "But what it looks like is\npositive peak for the lowest", "start": 4549.1, "duration": 4.32}, {"text": "frequency, negative peak for the\nnext harmonic, positive peak,", "start": 4553.42, "duration": 7.61}, {"text": "and gradually\ndecreasing amplitudes.", "start": 4561.03, "duration": 3.72}, {"text": "The power spectrum of this--", "start": 4564.75, "duration": 2.74}, {"text": "oh, and one more point is that\nif you look at the Fourier", "start": 4567.49, "duration": 5.16}, {"text": "transform of a higher\nfrequency square wave,", "start": 4572.65, "duration": 4.92}, {"text": "you can see that those\npeaks move apart.", "start": 4577.57, "duration": 4.58}, {"text": "So you can transform.", "start": 4582.15, "duration": 1.91}, {"text": "So higher frequencies in the\ntime domain, stuff happening", "start": 4584.06, "duration": 3.78}, {"text": "faster in the time\ndomain, is associated", "start": 4587.84, "duration": 4.89}, {"text": "with things moving out to higher\nfrequencies in the frequency", "start": 4592.73, "duration": 4.81}, {"text": "domain.", "start": 4597.54, "duration": 1.21}, {"text": "You can see that the same\nfunction higher frequencies", "start": 4598.75, "duration": 3.44}, {"text": "has the same Fourier transform\nbut with the components spread", "start": 4602.19, "duration": 4.23}, {"text": "out to higher frequencies.", "start": 4606.42, "duration": 2.52}, {"text": "And the power spectrum\nlooks like this.", "start": 4608.94, "duration": 2.98}, {"text": "And notice that one\nmore final point here", "start": 4611.92, "duration": 4.58}, {"text": "is that when you look at\npower spectra, often signals", "start": 4616.5, "duration": 3.69}, {"text": "can have frequency\ncomponents that", "start": 4620.19, "duration": 4.86}, {"text": "are very small so that it's hard\nto see them on a linear scale.", "start": 4625.05, "duration": 4.69}, {"text": "And so we actually plot\nthem in this method.", "start": 4629.74, "duration": 3.11}, {"text": "You plot them in\nunits of decibels.", "start": 4632.85, "duration": 2.19}, {"text": "And I'll explain what\nthose are the next time.", "start": 4635.04, "duration": 2.33}, {"text": "But that's another\nrepresentation of the power", "start": 4637.37, "duration": 2.83}, {"text": "spectrum of a signal.", "start": 4640.2, "duration": 3.0}, {"text": "OK, so that's what\nwe've covered.", "start": 4643.2, "duration": 2.35}, {"text": "And we're going to continue\nwith the game plan next time.", "start": 4645.55, "duration": 4.39}]
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+[{"text": "[SQUEAKING]\n[RUSTLING] [CLICKING]", "start": 0.0, "duration": 6.986}, {"text": "JASON KU: Hi, everybody.", "start": 18.49, "duration": 1.21}, {"text": "Welcome to the last\nlecture of 6.006.", "start": 19.7, "duration": 3.17}, {"text": "Last lecture, we talked\nabout summing up this class", "start": 22.87, "duration": 4.54}, {"text": "and talking about future\ncourses in the department that", "start": 27.41, "duration": 2.99}, {"text": "use this material.", "start": 30.4, "duration": 3.12}, {"text": "Just as a pointer to\nsome of those classes,", "start": 33.52, "duration": 3.12}, {"text": "I have a little slide\nhere I didn't get to", "start": 36.64, "duration": 2.04}, {"text": "at the last lecture,\ntalking about what", "start": 38.68, "duration": 2.717}, {"text": "I was talking about at the\nend of the last lecture", "start": 41.397, "duration": 2.083}, {"text": "about different models--", "start": 43.48, "duration": 2.82}, {"text": "different specialized classes\non different aspects of 006", "start": 46.3, "duration": 4.38}, {"text": "material--", "start": 50.68, "duration": 1.35}, {"text": "for example, more graph\nstuff, different models", "start": 52.03, "duration": 3.66}, {"text": "of computation,\nrandomness, complexity.", "start": 55.69, "duration": 3.54}, {"text": "All of these things have\ntheir own specialized classes", "start": 59.23, "duration": 2.82}, {"text": "in the department, as well\nas a lot of applications", "start": 62.05, "duration": 3.81}, {"text": "for this material in subjects\nlike biology, cryptography,", "start": 65.86, "duration": 3.9}, {"text": "and in particular, for\nyour instructors, the realm", "start": 69.76, "duration": 5.1}, {"text": "of graphics and geometry.", "start": 74.86, "duration": 2.58}, {"text": "All of your\ninstructors this term", "start": 77.44, "duration": 1.95}, {"text": "happened to be geometers\nand be interested", "start": 79.39, "duration": 3.6}, {"text": "in geometry-related problems.", "start": 82.99, "duration": 3.21}, {"text": "Me in particular, I didn't\nstart out in computer science.", "start": 86.2, "duration": 3.24}, {"text": "I started out in\nmechanical engineering.", "start": 89.44, "duration": 3.06}, {"text": "And the thing that was my\npassion coming into MIT", "start": 92.5, "duration": 4.71}, {"text": "was origami.", "start": 97.21, "duration": 2.16}, {"text": "Here's a couple of\npieces that I designed--", "start": 99.37, "duration": 5.19}, {"text": "origami pieces, one square\nsheet of paper without cutting.", "start": 104.56, "duration": 2.76}, {"text": "Here's a lobster, and here's\na copyrighted dinosaur", "start": 107.32, "duration": 6.87}, {"text": "from a particular movie of\nthe year that I designed it.", "start": 114.19, "duration": 2.85}, {"text": "When I was young,\nin high school,", "start": 121.79, "duration": 1.74}, {"text": "I started designing\nmy own origami models.", "start": 123.53, "duration": 3.3}, {"text": "And what I didn't realize\nwas, the procedures", "start": 126.83, "duration": 3.24}, {"text": "that I went about\ndesigning these models", "start": 130.07, "duration": 2.94}, {"text": "was actually algorithms.", "start": 133.01, "duration": 2.01}, {"text": "And I just didn't have\nthe mathematical language", "start": 135.02, "duration": 2.37}, {"text": "to understand exactly\nwhat I was doing,", "start": 137.39, "duration": 3.6}, {"text": "but I could gain some\nintuition as an origami artist", "start": 140.99, "duration": 3.24}, {"text": "and design these\nthings by using some", "start": 144.23, "duration": 2.717}, {"text": "of those algorithmic techniques.", "start": 146.947, "duration": 1.333}, {"text": "It wasn't until grad school,\nas a mechanical engineer,", "start": 148.28, "duration": 3.93}, {"text": "that I started talking with\nour other instructor here,", "start": 152.21, "duration": 6.78}, {"text": "Professor Demaine, about using\nalgorithms and computer science", "start": 158.99, "duration": 4.11}, {"text": "to design not just\norigami, which we both do,", "start": 163.1, "duration": 5.49}, {"text": "but also folded structures\nthat can be used for mechanical", "start": 168.59, "duration": 4.8}, {"text": "applications like space flight,\ndeployable bridges in times", "start": 173.39, "duration": 8.07}, {"text": "when you can't--", "start": 181.46, "duration": 2.7}, {"text": "you need a temporary bridge or\nshelter or something like that.", "start": 184.16, "duration": 3.48}, {"text": "Deployable structures\nwhere you might", "start": 187.64, "duration": 2.64}, {"text": "need to make folded structures--\ntransformable structures that", "start": 190.28, "duration": 3.6}, {"text": "can have different applications\nfor different purposes--", "start": 193.88, "duration": 4.41}, {"text": "need to reconfigure.", "start": 198.29, "duration": 1.38}, {"text": "The dream being that, we\nhave these powerful devices", "start": 199.67, "duration": 3.21}, {"text": "in our pockets right\nnow-- cell phones--", "start": 202.88, "duration": 3.37}, {"text": "which are really powerful\nbecause we can reconfigure", "start": 206.25, "duration": 3.47}, {"text": "the bits in them\nto make software", "start": 209.72, "duration": 1.77}, {"text": "of all different kinds, right?", "start": 211.49, "duration": 1.74}, {"text": "There's an exponential\nnumber of different programs", "start": 213.23, "duration": 3.57}, {"text": "that we can write.", "start": 216.8, "duration": 0.81}, {"text": "And that's part of\nwhy you're here,", "start": 217.61, "duration": 1.98}, {"text": "is to write the next best one.", "start": 219.59, "duration": 1.62}, {"text": "Right?", "start": 221.21, "duration": 0.81}, {"text": "So that's how to make\nkind of a universal device", "start": 222.02, "duration": 5.94}, {"text": "at the electronic level.", "start": 227.96, "duration": 1.56}, {"text": "What if we could do that\nfrom a material standpoint?", "start": 229.52, "duration": 4.47}, {"text": "What if I could reprogram the\nmatter in my phone so that,", "start": 233.99, "duration": 3.63}, {"text": "not only could I reprogram\nthe app that's on your phone,", "start": 237.62, "duration": 4.41}, {"text": "but instead of having, say, the\niPhone 10 or whatever that you", "start": 242.03, "duration": 4.59}, {"text": "have, and you want to\ngo by the iPhone 11,", "start": 246.62, "duration": 2.43}, {"text": "instead, you download a software\napp that then reconfigures", "start": 249.05, "duration": 4.89}, {"text": "the matter in your phone--", "start": 253.94, "duration": 1.5}, {"text": "it folds or reconfigures into\nthe next generation iPhone.", "start": 255.44, "duration": 5.339}, {"text": "You don't have to throw\naway that old one.", "start": 260.779, "duration": 2.281}, {"text": "You can essentially\nrecycle the material", "start": 263.06, "duration": 1.8}, {"text": "that you have to potentially\nsave material, save", "start": 264.86, "duration": 4.59}, {"text": "cost, and be better for the\nenvironment, potentially.", "start": 269.45, "duration": 3.55}, {"text": "So I started moving\ninto computer science", "start": 273.0, "duration": 4.13}, {"text": "because I found that it\nwas a really good way", "start": 277.13, "duration": 3.03}, {"text": "to model the world\nand solve some really", "start": 280.16, "duration": 2.61}, {"text": "interesting problems about\nfolding that I really enjoyed.", "start": 282.77, "duration": 5.73}, {"text": "The three of us today\nare going to spend", "start": 288.5, "duration": 3.36}, {"text": "some time talking a\nlittle bit about how", "start": 291.86, "duration": 2.19}, {"text": "we can use algorithms--", "start": 294.05, "duration": 1.83}, {"text": "6.006 material and beyond--", "start": 295.88, "duration": 2.67}, {"text": "in our own research.", "start": 298.55, "duration": 1.71}, {"text": "And we're going to start\noff with Professor Demaine,", "start": 300.26, "duration": 3.39}, {"text": "and then Professor Solomon.", "start": 303.65, "duration": 1.14}, {"text": "ERIK DEMAINE: Thanks.", "start": 307.532, "duration": 1.378}, {"text": "So let me just jump in here\nto computational origami", "start": 308.91, "duration": 3.98}, {"text": "and geometric\nfolding algorithms,", "start": 312.89, "duration": 2.7}, {"text": "sort of a broader umbrella for\nfolding-related things, which", "start": 315.59, "duration": 3.21}, {"text": "is encapsulated by\nthis class, 6.849,", "start": 318.8, "duration": 3.54}, {"text": "which is happening next fall.", "start": 322.34, "duration": 1.29}, {"text": "So you should all take it.", "start": 323.63, "duration": 2.31}, {"text": "006 should be a\nreasonable background.", "start": 325.94, "duration": 3.96}, {"text": "And in general, we're interested\nin two kinds of problems.", "start": 329.9, "duration": 3.52}, {"text": "One-- the big one\nis origami design,", "start": 333.42, "duration": 2.39}, {"text": "or in general,\nfolding design, where", "start": 335.81, "duration": 1.8}, {"text": "you have some specifications of\nwhat you would like to build.", "start": 337.61, "duration": 2.7}, {"text": "In this case I wanted to\nmake a logo for 6.849.", "start": 340.31, "duration": 4.23}, {"text": "And I imagined extruding that\ntext into third dimension.", "start": 344.54, "duration": 5.79}, {"text": "And then I wanted an\nalgorithm to tell me", "start": 350.33, "duration": 2.97}, {"text": "how to fold that structure.", "start": 353.3, "duration": 1.332}, {"text": "And so there is an\nalgorithm, which", "start": 354.632, "duration": 1.458}, {"text": "I'll talk about\nin a moment, that", "start": 356.09, "duration": 1.05}, {"text": "gives you a crease pattern.", "start": 357.14, "duration": 1.125}, {"text": "And then, currently,\nyou fold it by hand.", "start": 358.265, "duration": 1.845}, {"text": "The dream is, we'll eventually\nhave folding machines that", "start": 360.11, "duration": 2.4}, {"text": "do it all for us.", "start": 362.51, "duration": 2.86}, {"text": "And so that's the\norigami design,", "start": 365.37, "duration": 1.4}, {"text": "where you go from\nthe target shape", "start": 366.77, "duration": 2.67}, {"text": "back to the crease pattern.", "start": 369.44, "duration": 4.53}, {"text": "The reverse direction\nis sort of foldability.", "start": 373.97, "duration": 1.89}, {"text": "If I gave you a structure like\nthis and I wanted to know,", "start": 375.86, "duration": 3.15}, {"text": "does it fold?", "start": 379.01, "duration": 1.86}, {"text": "That's the problem\nwe call foldability--", "start": 380.87, "duration": 2.67}, {"text": "in general, class of problems.", "start": 383.54, "duration": 2.07}, {"text": "And sadly, most of those\nproblems are NP-hard.", "start": 385.61, "duration": 2.28}, {"text": "Jason and I proved\nthat foldability", "start": 387.89, "duration": 3.45}, {"text": "is hard for a general-- given\na crease pattern like that,", "start": 391.34, "duration": 2.76}, {"text": "telling you whether\nfolds into anything,", "start": 394.1, "duration": 1.71}, {"text": "it turns out to be NP-hard.", "start": 395.81, "duration": 1.34}, {"text": "So that's bad news.", "start": 397.15, "duration": 2.12}, {"text": "So we focus a lot on\nthe design problem,", "start": 399.27, "duration": 2.3}, {"text": "because that actually\ntends to be easier.", "start": 401.57, "duration": 1.81}, {"text": "We can solve it with algorithms\nlike that one you're seeing.", "start": 403.38, "duration": 2.96}, {"text": "A long time ago, we proved\nthat you can fold everything.", "start": 409.04, "duration": 3.93}, {"text": "If I give you a\nsquare piece of paper", "start": 412.97, "duration": 1.95}, {"text": "and you take any polygon\nyou want to make--", "start": 414.92, "duration": 3.092}, {"text": "or maybe the paper's white on\none side, black on the other,", "start": 418.012, "duration": 2.458}, {"text": "you want to fold some two-color\npattern, like a zebra,", "start": 420.47, "duration": 2.73}, {"text": "or in general, some\nthree-dimensional surface,", "start": 423.2, "duration": 2.64}, {"text": "like these guys, there\nis a way to fold it", "start": 425.84, "duration": 2.55}, {"text": "from a large enough\nsquare of paper.", "start": 428.39, "duration": 2.487}, {"text": "And it's actually really easy\nto prove that with an algorithm.", "start": 430.877, "duration": 2.583}, {"text": "I have the sketch of\nthe two pages of proof", "start": 433.46, "duration": 3.33}, {"text": "that we go over in\n6.849, but I'll just", "start": 436.79, "duration": 2.43}, {"text": "hand-wave a little bit.", "start": 439.22, "duration": 1.44}, {"text": "If you take a piece of\npaper, like my lecture notes", "start": 440.66, "duration": 2.61}, {"text": "here, the first thing\nyou do is fold it down", "start": 443.27, "duration": 3.3}, {"text": "into a very long, narrow strip--", "start": 446.57, "duration": 2.16}, {"text": "much longer and\nnarrower than this one--", "start": 448.73, "duration": 2.01}, {"text": "wasting most of the material.", "start": 450.74, "duration": 1.74}, {"text": "And then you take your strip,\nand you just figure out", "start": 452.48, "duration": 2.55}, {"text": "how to turn it in\nsome general way,", "start": 455.03, "duration": 2.61}, {"text": "and then you just sort\nof zigzag back and forth", "start": 457.64, "duration": 2.16}, {"text": "along the surface.", "start": 459.8, "duration": 1.33}, {"text": "So it's very cool in that you\ncan prove with an algorithm,", "start": 461.13, "duration": 2.6}, {"text": "and in a very short\namount of time,", "start": 463.73, "duration": 1.947}, {"text": "to someone you can\nactually fold everything.", "start": 465.677, "duration": 1.833}, {"text": "Of course, it's a\nterrible folding,", "start": 467.51, "duration": 1.32}, {"text": "because in the\nvery first step, we", "start": 468.83, "duration": 1.417}, {"text": "throw away all but\nepsilon of the material.", "start": 470.247, "duration": 3.893}, {"text": "But it's a starting point.", "start": 474.14, "duration": 1.5}, {"text": "That was back in the '90s--", "start": 475.64, "duration": 1.23}, {"text": "late '90s-- one of\nthe first results", "start": 476.87, "duration": 2.19}, {"text": "in computational origami.", "start": 479.06, "duration": 1.68}, {"text": "And in modern times, we\nlook for better algorithms", "start": 480.74, "duration": 3.39}, {"text": "that are more efficient, that\ntry to minimize the scale", "start": 484.13, "duration": 3.15}, {"text": "factor from, how big\nof a piece of paper", "start": 487.28, "duration": 1.92}, {"text": "do I start from to, how\nbig of a model do I get?", "start": 489.2, "duration": 3.87}, {"text": "And one of the cool\nways these days, which", "start": 493.07, "duration": 2.58}, {"text": "was invented by\nTomohiro Tachi and then", "start": 495.65, "duration": 2.07}, {"text": "analyzed by the two of us--", "start": 497.72, "duration": 1.922}, {"text": "it's called Origamizer.", "start": 499.642, "duration": 0.958}, {"text": "It's free software.", "start": 500.6, "duration": 1.05}, {"text": "You take a 3D\nmodel and you can--", "start": 501.65, "duration": 3.54}, {"text": "it makes it into a pattern\nthat you fold from a square.", "start": 505.19, "duration": 2.64}, {"text": "In this case, it uses 22% of\nthe area, which is pretty good--", "start": 507.83, "duration": 4.5}, {"text": "similar to these guys\nin terms of efficiency.", "start": 512.33, "duration": 4.29}, {"text": "But very, very different\nkind of folding", "start": 516.62, "duration": 2.76}, {"text": "than what you would get from\nmore traditional origami", "start": 519.38, "duration": 3.543}, {"text": "design, which uses\ndifferent algorithms, which", "start": 522.923, "duration": 1.917}, {"text": "I'm not going to talk about.", "start": 524.84, "duration": 0.81}, {"text": "But you should take the class.", "start": 525.65, "duration": 0.87}, {"text": "Jason gives a\nlecture in the class,", "start": 526.52, "duration": 1.458}, {"text": "so you can learn from him.", "start": 527.978, "duration": 2.962}, {"text": "But the vision is, we can take\nany sheet of material that", "start": 530.94, "duration": 3.62}, {"text": "can hold a crease, like\nthis sheet of steel", "start": 534.56, "duration": 2.97}, {"text": "that Tomohiro is folding.", "start": 537.53, "duration": 1.08}, {"text": "It was cut by a big\nlaser cutter at MIT.", "start": 538.61, "duration": 3.88}, {"text": "And this is him in\nthis Data Center", "start": 542.49, "duration": 1.52}, {"text": "several years ago, folding\nit into a steel bunny.", "start": 544.01, "duration": 4.44}, {"text": "And so this is a totally new\nway to manufacture 3D objects.", "start": 548.45, "duration": 4.65}, {"text": "And you can make particularly\ninteresting objects", "start": 553.1, "duration": 3.27}, {"text": "that either collapse flat for\ntransportation or transform,", "start": 556.37, "duration": 5.41}, {"text": "like Jason was talking about.", "start": 561.78, "duration": 2.48}, {"text": "But I'm just giving\nyou a flavor.", "start": 564.26, "duration": 2.16}, {"text": "I think the first paper we wrote\ntogether was on maze folding.", "start": 566.42, "duration": 3.81}, {"text": "So this is an example\nof folding a maze", "start": 570.23, "duration": 2.73}, {"text": "from a rectangle of paper.", "start": 572.96, "duration": 1.9}, {"text": "And you can all try this out.", "start": 574.86, "duration": 3.65}, {"text": "You just google for\nour Maze Folder.", "start": 578.51, "duration": 3.15}, {"text": "You can generate a random maze.", "start": 581.66, "duration": 1.74}, {"text": "And this 3D structure\ncan be folded", "start": 583.4, "duration": 3.54}, {"text": "from this crease pattern.", "start": 586.94, "duration": 2.55}, {"text": "That's a really hard one, so\nmaybe try something smaller.", "start": 589.49, "duration": 3.52}, {"text": "You can also write your favorite\nmessage and fold this maze--", "start": 593.01, "duration": 5.87}, {"text": "extruded graph-- from\nthis crease pattern.", "start": 598.88, "duration": 4.178}, {"text": "Might want to start\nwith something smaller,", "start": 603.058, "duration": 1.792}, {"text": "but that's the general idea.", "start": 604.85, "duration": 2.34}, {"text": "And it's actually quite easy\nto prove this algorithmically,", "start": 607.19, "duration": 2.67}, {"text": "if you have a really\ngood origamist", "start": 609.86, "duration": 1.74}, {"text": "like Jason on your team.", "start": 611.6, "duration": 1.62}, {"text": "What you do is design how\nto fold each type of vertex.", "start": 613.22, "duration": 3.91}, {"text": "This is just a graph on a grid.", "start": 617.13, "duration": 2.39}, {"text": "There are some constant\nnumber of different ways", "start": 619.52, "duration": 2.55}, {"text": "that each vertex could look.", "start": 622.07, "duration": 1.23}, {"text": "It could be degree 4.", "start": 623.3, "duration": 0.96}, {"text": "It could be degree 3, as\na T. It could be degree", "start": 624.26, "duration": 3.66}, {"text": "2, either a turn or a straight.", "start": 627.92, "duration": 1.71}, {"text": "And you design little gadgets,\nlittle crease patterns,", "start": 629.63, "duration": 3.18}, {"text": "that fold into each of\nthose little structures.", "start": 632.81, "duration": 2.028}, {"text": "And if you can do it in a\nway that these boundaries are", "start": 634.838, "duration": 2.292}, {"text": "compatible, then to\nfold the whole thing,", "start": 637.13, "duration": 1.98}, {"text": "you just sort of gluon\ntogether those crease patterns.", "start": 639.11, "duration": 2.25}, {"text": "And that's how that\nsoftware works.", "start": 641.36, "duration": 3.57}, {"text": "This was particularly\ninteresting,", "start": 644.93, "duration": 1.92}, {"text": "because you can fold an\narbitrarily complicated graph--", "start": 646.85, "duration": 3.36}, {"text": "arbitrarily complicated\nmaze, n by n,", "start": 650.21, "duration": 2.43}, {"text": "with a constant scale factor.", "start": 652.64, "duration": 1.415}, {"text": "As long as the\nheight that you're", "start": 654.055, "duration": 1.375}, {"text": "extruding that maze\nis constant, then", "start": 655.43, "duration": 2.91}, {"text": "this is one family of shapes we\nknow how to fold really well.", "start": 658.34, "duration": 2.61}, {"text": "In general, we're\ntrying to understand,", "start": 660.95, "duration": 1.77}, {"text": "what makes this lobster\na nice shape in that it", "start": 662.72, "duration": 3.69}, {"text": "can be represented with a\nnot-too-large piece of paper.", "start": 666.41, "duration": 3.12}, {"text": "And we don't have general\nanswers to that problem.", "start": 669.53, "duration": 4.43}, {"text": "I think that was a whirlwind\ntour of computational origami.", "start": 673.96, "duration": 3.84}, {"text": "I also play a lot in\nalgorithmic sculpture.", "start": 677.8, "duration": 3.87}, {"text": "One of the leading edges\nin origami and origami math", "start": 681.67, "duration": 3.87}, {"text": "is understanding how\ncurved creases work.", "start": 685.54, "duration": 3.01}, {"text": "And one of our\nfavorite models is", "start": 688.55, "duration": 1.97}, {"text": "this one, where you fold\nconcentric circles alternating", "start": 690.52, "duration": 2.82}, {"text": "mountain and valley,\ncut a circular hole out,", "start": 693.34, "duration": 2.4}, {"text": "and it folds into this\nkind of Pringle shape", "start": 695.74, "duration": 3.15}, {"text": "as a nice physics\nequilibrium thing.", "start": 698.89, "duration": 3.93}, {"text": "And then you can turn it into\nfun sculptures like this.", "start": 702.82, "duration": 3.78}, {"text": "These are done with my dad,\nMartin Demaine, who's also here", "start": 706.6, "duration": 2.97}, {"text": "at MIT, or this guy.", "start": 709.57, "duration": 2.19}, {"text": "This paper has been\nprinted with a pattern", "start": 711.76, "duration": 2.79}, {"text": "according to getting\nburned by glass.", "start": 714.55, "duration": 2.19}, {"text": "And then it gets folded and\nthen put inside glass, also.", "start": 716.74, "duration": 3.75}, {"text": "Made here at MIT.", "start": 720.49, "duration": 2.85}, {"text": "We use sculpture to try\nto explore and understand", "start": 723.34, "duration": 2.37}, {"text": "intuitively how\ncurved creases work,", "start": 725.71, "duration": 1.53}, {"text": "and then we get better\nand better understanding", "start": 727.24, "duration": 2.31}, {"text": "of the mathematics of even--", "start": 729.55, "duration": 2.42}, {"text": "we don't even know whether this\nsurface exists, whether it's", "start": 731.97, "duration": 2.5}, {"text": "possible to fold in this\nway, although getting", "start": 734.47, "duration": 2.617}, {"text": "close to proving it.", "start": 737.087, "duration": 0.833}, {"text": "That was sort of in the top\nlevel of this hierarchy.", "start": 740.59, "duration": 5.79}, {"text": "Computational geometry\nis a bigger umbrella,", "start": 746.38, "duration": 2.97}, {"text": "which is represented by\nanother class, 6.850,", "start": 749.35, "duration": 2.28}, {"text": "that's being taught this term.", "start": 751.63, "duration": 1.8}, {"text": "And then I talked\nabout geometric folding", "start": 753.43, "duration": 2.4}, {"text": "within that branch.", "start": 755.83, "duration": 1.32}, {"text": "Let me briefly tell\nyou about another world", "start": 757.15, "duration": 2.01}, {"text": "of geometry-- very different in\nterms of model of computation.", "start": 759.16, "duration": 3.84}, {"text": "Oh, I jumped ahead a little bit.", "start": 763.0, "duration": 2.67}, {"text": "Rewind.", "start": 765.67, "duration": 0.96}, {"text": "Let me show you\none more fun demo,", "start": 766.63, "duration": 2.11}, {"text": "which-- if I find my scissors.", "start": 768.74, "duration": 2.18}, {"text": "If I take a rectangle of\npaper, and I fold it flat", "start": 774.58, "duration": 4.17}, {"text": "and make one straight cut,\nwhat shapes can I get?", "start": 778.75, "duration": 4.68}, {"text": "It's called the\nfolding cut problem.", "start": 783.43, "duration": 2.45}, {"text": "It's hundreds of years old.", "start": 785.88, "duration": 3.52}, {"text": "Here, for example, I get a swan.", "start": 789.4, "duration": 6.15}, {"text": "Here, I get-- one straight cut.", "start": 795.55, "duration": 10.985}, {"text": "I unfold and get angelfish.", "start": 806.535, "duration": 5.535}, {"text": "Tough audience today.", "start": 812.07, "duration": 1.85}, {"text": "I've got to keep going.", "start": 813.92, "duration": 0.97}, {"text": "You've seen all of these before.", "start": 814.89, "duration": 1.6}, {"text": "This is this one is a\nparticularly difficult one", "start": 816.49, "duration": 3.55}, {"text": "to fold--", "start": 820.04, "duration": 0.785}, {"text": "to only fold.", "start": 820.825, "duration": 1.655}, {"text": "And to cut, yeah.", "start": 822.48, "duration": 2.95}, {"text": "OK.", "start": 825.43, "duration": 1.16}, {"text": "That works well.", "start": 826.59, "duration": 0.94}, {"text": "This is the MIT logo.", "start": 830.71, "duration": 5.54}, {"text": "Ooh, ah.", "start": 836.25, "duration": 1.568}, {"text": "AUDIENCE: Ooh, aah.", "start": 837.818, "duration": 0.996}, {"text": "MIT, yeah!", "start": 838.814, "duration": 0.894}, {"text": "ERIK DEMAINE: Yeah.", "start": 839.708, "duration": 0.792}, {"text": "Go, MIT.", "start": 840.5, "duration": 1.53}, {"text": "All right.", "start": 842.03, "duration": 1.68}, {"text": "That's actually\nthe first problem", "start": 843.71, "duration": 1.62}, {"text": "I worked on in\ncomputational origami.", "start": 845.33, "duration": 1.71}, {"text": "It's a lot of fun.", "start": 847.04, "duration": 0.91}, {"text": "And there's a really interesting\nalgorithm here, also,", "start": 847.95, "duration": 2.51}, {"text": "for computing the\ncrease pattern,", "start": 850.46, "duration": 1.8}, {"text": "how to fold your piece\nof paper to align--", "start": 852.26, "duration": 2.67}, {"text": "in fact, any graph you\ndraw on a piece of paper,", "start": 854.93, "duration": 3.057}, {"text": "you can align all of those\nedges and nothing else.", "start": 857.987, "duration": 2.083}, {"text": "So you cut along the line and\nyou get exactly what you want.", "start": 860.07, "duration": 3.66}, {"text": "Cool.", "start": 863.73, "duration": 0.84}, {"text": "All right.", "start": 864.57, "duration": 0.63}, {"text": "Now, I want to talk about\nsomething completely different,", "start": 865.2, "duration": 2.53}, {"text": "which is self-assembly.", "start": 867.73, "duration": 1.43}, {"text": "A fun thing you can do with\nDNA, which we all have.", "start": 869.16, "duration": 4.11}, {"text": "Just pick out some\ncool DNA strands", "start": 873.27, "duration": 2.37}, {"text": "and design them in a clever\nway so they fit together", "start": 875.64, "duration": 2.88}, {"text": "to form a kind of square\nwith dangling ends, which", "start": 878.52, "duration": 3.57}, {"text": "I'll call glues and each\nof those dangling ends", "start": 882.09, "duration": 2.55}, {"text": "can have a very\nparticular pattern,", "start": 884.64, "duration": 1.53}, {"text": "and only identical or\ncomplementary patterns", "start": 886.17, "duration": 3.27}, {"text": "will attach to each other.", "start": 889.44, "duration": 2.53}, {"text": "And so you can\nuse this to design", "start": 891.97, "duration": 1.7}, {"text": "your own self-assembling\nsystem, like biology", "start": 893.67, "duration": 2.97}, {"text": "does, but engineered, for\nexample, to build a computer.", "start": 896.64, "duration": 3.46}, {"text": "This is an example of taking\na bunch of these square tiles", "start": 900.1, "duration": 3.56}, {"text": "and building a binary counter.", "start": 903.66, "duration": 1.71}, {"text": "This thing is roughly counting\nin binary along the diagonal.", "start": 905.37, "duration": 3.18}, {"text": "It's a little skewed,\nso it's hard to see.", "start": 908.55, "duration": 1.84}, {"text": "But the general model\nis, you have squares--", "start": 910.39, "duration": 8.78}, {"text": "this is sort of the\ncomputational model--", "start": 919.17, "duration": 3.6}, {"text": "with four different glues.", "start": 922.77, "duration": 1.35}, {"text": "And you can build\nany square you want,", "start": 924.12, "duration": 2.11}, {"text": "but you don't have very many of\nthese different glues, ideally.", "start": 926.23, "duration": 3.44}, {"text": "And then, if you have two\ntiles with complementary glues,", "start": 929.67, "duration": 5.52}, {"text": "they will want to\nmatch together.", "start": 935.19, "duration": 2.34}, {"text": "But it depends how strong this\nglue is, how much affinity", "start": 937.53, "duration": 3.63}, {"text": "there is for how long those\nDNA dangling ends are,", "start": 941.16, "duration": 3.372}, {"text": "and also, the temperature\nof your system.", "start": 944.532, "duration": 1.708}, {"text": "If you have really high\ntemperature, nothing.", "start": 946.24, "duration": 1.22}, {"text": "Will stick together\nlow temperature,", "start": 947.46, "duration": 1.69}, {"text": "things will stick together even\nif they're not supposed to.", "start": 949.15, "duration": 4.01}, {"text": "If you tune your\nsystem really well,", "start": 953.16, "duration": 2.55}, {"text": "you can design a system so that\nmaybe these guys-- these glues", "start": 955.71, "duration": 4.47}, {"text": "are really strong.", "start": 960.18, "duration": 1.51}, {"text": "And so let's, I don't\nknow, write \"E\" here--", "start": 961.69, "duration": 3.41}, {"text": "Erik.", "start": 965.1, "duration": 1.2}, {"text": "And so these tiles will\nalways glue together,", "start": 966.3, "duration": 2.98}, {"text": "but only when all three of\nthese are glued together", "start": 969.28, "duration": 2.6}, {"text": "can this tile--", "start": 971.88, "duration": 1.02}, {"text": "which has C complement\nand F complement.", "start": 972.9, "duration": 4.74}, {"text": "Then it will, if you set\nthe temperatures just right,", "start": 977.64, "duration": 2.61}, {"text": "only because both of\nthese edges match will", "start": 980.25, "duration": 2.37}, {"text": "this dial be able to come in.", "start": 982.62, "duration": 1.38}, {"text": "And that's the basis for\nbuilding that binary counter.", "start": 984.0, "duration": 3.3}, {"text": "This is a very different\nmodel of computation", "start": 987.3, "duration": 2.43}, {"text": "from what we're used\nto in this class,", "start": 989.73, "duration": 1.8}, {"text": "where you think of instructions,\nand they run one at a time.", "start": 991.53, "duration": 2.73}, {"text": "Here the, model of\ncomputation is geometric.", "start": 994.26, "duration": 3.18}, {"text": "It's these squares that are\njust floating around and gluing", "start": 997.44, "duration": 2.79}, {"text": "together.", "start": 1000.23, "duration": 0.52}, {"text": "And so your program,\nat any moment,", "start": 1000.75, "duration": 2.0}, {"text": "is some conglomerate of squares.", "start": 1002.75, "duration": 3.523}, {"text": "I just wanted to\nmention it because it's", "start": 1006.273, "duration": 1.667}, {"text": "a really fun model.", "start": 1007.94, "duration": 0.943}, {"text": "You can prove cool\nthings in this model,", "start": 1008.883, "duration": 1.667}, {"text": "like how to build any shape\nby a sequence of pores", "start": 1010.55, "duration": 4.74}, {"text": "mixing between tiles that\nyou can execute in parallel.", "start": 1015.29, "duration": 3.61}, {"text": "And so it only\ntakes log and time", "start": 1018.9, "duration": 2.3}, {"text": "of parallel steps, a linear\nnumber of different mix", "start": 1021.2, "duration": 3.3}, {"text": "operations, to make\nan arbitrary shape--", "start": 1024.5, "duration": 2.28}, {"text": "even using a constant number of\ndifferent glues, which is cool,", "start": 1026.78, "duration": 4.77}, {"text": "and maybe practical.", "start": 1031.55, "duration": 2.44}, {"text": "You can also use it to\nbuild a replicator, where", "start": 1033.99, "duration": 2.0}, {"text": "you're given an object\nlike this that you", "start": 1035.99, "duration": 2.79}, {"text": "don't know the shape of--", "start": 1038.78, "duration": 1.723}, {"text": "like, we don't know\nwhether this exists,", "start": 1040.503, "duration": 1.667}, {"text": "and we can't model it\nmathematically very well,", "start": 1042.17, "duration": 2.52}, {"text": "and you stick it in a vat,\nand all of these tiles", "start": 1044.69, "duration": 2.37}, {"text": "would attach and\nbasically build a mold,", "start": 1047.06, "duration": 2.04}, {"text": "and then start photocopying,\nin 3D, that mold.", "start": 1049.1, "duration": 2.97}, {"text": "And you can build that with\na system with only two steps,", "start": 1052.07, "duration": 3.72}, {"text": "I believe, and a constant\nnumber of tile types.", "start": 1055.79, "duration": 3.15}, {"text": "And it does all of that, in\nthis model, in constant time.", "start": 1058.94, "duration": 3.18}, {"text": "In reality, you would\nhave to feed this machine", "start": 1062.12, "duration": 2.08}, {"text": "and wait for it to print\nout all of these things,", "start": 1064.2, "duration": 2.36}, {"text": "and these experiments take\nhours, if not days, to run.", "start": 1066.56, "duration": 3.51}, {"text": "But in theory, it's really cool.", "start": 1070.07, "duration": 1.373}, {"text": "And you get some\nreally fun models", "start": 1071.443, "duration": 1.417}, {"text": "and very general results.", "start": 1072.86, "duration": 1.45}, {"text": "You can also use it to build\na miniaturizer or a magnifier", "start": 1074.31, "duration": 2.81}, {"text": "and other fun stuff.", "start": 1077.12, "duration": 1.7}, {"text": "That was a brief tour of\ncomputational geometry.", "start": 1081.67, "duration": 2.4}, {"text": "I work mostly in four different\nareas of algorithms-- geometry,", "start": 1084.07, "duration": 3.96}, {"text": "data structures, graph\nalgorithms, and what", "start": 1088.03, "duration": 1.86}, {"text": "I call recreational algorithms.", "start": 1089.89, "duration": 1.92}, {"text": "I think I made up that term.", "start": 1091.81, "duration": 2.39}, {"text": "And let's go into\ndata structures,", "start": 1094.2, "duration": 2.9}, {"text": "which is represented\nby this class, 6.851.", "start": 1097.1, "duration": 3.62}, {"text": "All of the classes I mentioned\nhave online video lectures,", "start": 1100.72, "duration": 3.55}, {"text": "especially for those watching\nat home on OpenCourseWare.", "start": 1104.27, "duration": 3.83}, {"text": "Most of these classes are on\nOpenCourseWare, and if not,", "start": 1108.1, "duration": 2.73}, {"text": "they're on my webpage.", "start": 1110.83, "duration": 2.7}, {"text": "6.851, Advanced Data Structures,\nis an extension of the sorts", "start": 1113.53, "duration": 3.36}, {"text": "of data structures\nyou've seen here,", "start": 1116.89, "duration": 2.1}, {"text": "in 006 and the ones\nyou will see in 6.046.", "start": 1118.99, "duration": 3.72}, {"text": "I thought I would\ngive you a flavor", "start": 1122.71, "duration": 1.83}, {"text": "of one such result,\nwhich is a problem we've", "start": 1124.54, "duration": 10.41}, {"text": "seen in this class done better.", "start": 1134.95, "duration": 5.31}, {"text": "Suppose you want to store\na dynamic ordered set.", "start": 1140.26, "duration": 3.48}, {"text": "This is the set interface.", "start": 1147.49, "duration": 2.55}, {"text": "Dynamic in the sense that\nI have insert and delete,", "start": 1150.04, "duration": 7.11}, {"text": "and ordered in the sense that\nI want to support find-next", "start": 1157.15, "duration": 3.3}, {"text": "and find-previous.", "start": 1160.45, "duration": 1.11}, {"text": "Exactly which subset\nof the set interface", "start": 1167.29, "duration": 2.79}, {"text": "you choose influences what\ndata structure you've seen.", "start": 1170.08, "duration": 3.0}, {"text": "We've seen, for dynamic sets,\nyou want to use hashing.", "start": 1173.08, "duration": 3.36}, {"text": "If you don't care\nabout find-next,", "start": 1176.44, "duration": 1.47}, {"text": "if you just care about\nfind, then hashing", "start": 1177.91, "duration": 2.16}, {"text": "is great-- constant expected.", "start": 1180.07, "duration": 1.83}, {"text": "You can prove stronger\nthings about hashing.", "start": 1181.9, "duration": 2.12}, {"text": "And we do in that class.", "start": 1184.02, "duration": 2.35}, {"text": "But if you want\ndynamic and ordered,", "start": 1186.37, "duration": 3.24}, {"text": "you cannot do constant\ntime per operation.", "start": 1189.61, "duration": 2.46}, {"text": "You can prove that,\nwhich is cool.", "start": 1192.07, "duration": 3.84}, {"text": "What data structure have we seen\nthat solves this problem pretty", "start": 1195.91, "duration": 2.73}, {"text": "well?", "start": 1198.64, "duration": 1.14}, {"text": "Set AVL trees, which\nsolve everything in log n.", "start": 1199.78, "duration": 3.93}, {"text": "So log n is one competitor.", "start": 1203.71, "duration": 3.27}, {"text": "Yeah.", "start": 1213.29, "duration": 1.18}, {"text": "I'm interested in\nthe word RAM model,", "start": 1214.47, "duration": 6.26}, {"text": "which is the only model\nwe've seen in this class.", "start": 1220.73, "duration": 2.24}, {"text": "This happens to work\nin a stronger model.", "start": 1222.97, "duration": 2.58}, {"text": "And we can do better than\nlog n in the following--", "start": 1225.55, "duration": 6.697}, {"text": "it will take me a while\nbefore I get better,", "start": 1232.247, "duration": 1.833}, {"text": "but here's, at least, a\ndifferent bound we can get--", "start": 1234.08, "duration": 2.45}, {"text": "log w.", "start": 1236.53, "duration": 3.06}, {"text": "This is via a structure called\nvan Emde Boas, who is a person.", "start": 1239.59, "duration": 6.06}, {"text": "AVL is two people.", "start": 1245.65, "duration": 1.59}, {"text": "van Emde Boas,\nI've actually met.", "start": 1247.24, "duration": 2.82}, {"text": "Log w-- remember,\nw is our word size.", "start": 1250.06, "duration": 2.882}, {"text": "So this is a bit of\na weird running time.", "start": 1252.942, "duration": 1.708}, {"text": "It's great if w is log n,\nthen this is log log n.", "start": 1254.65, "duration": 3.72}, {"text": "And we know w is at least log\nn, but it could be bigger.", "start": 1258.37, "duration": 3.533}, {"text": "We don't really have a sense\nof how big w could get.", "start": 1261.903, "duration": 2.167}, {"text": "Maybe it's even n.", "start": 1264.07, "duration": 1.08}, {"text": "Maybe it's big-- and\nthen these are the same.", "start": 1265.15, "duration": 2.13}, {"text": "Maybe it's bigger than n,\nand then this is maybe worse.", "start": 1267.28, "duration": 3.19}, {"text": "But for most ws, this is\nactually pretty good--", "start": 1270.47, "duration": 2.93}, {"text": "and indeed, optimal.", "start": 1273.4, "duration": 1.545}, {"text": "But it's not strictly\nbetter, in any sense, yet.", "start": 1277.84, "duration": 2.85}, {"text": "On the other hand, there's\nanother data structure which", "start": 1280.69, "duration": 3.48}, {"text": "runs in log n divided by log w.", "start": 1284.17, "duration": 3.66}, {"text": "This is called fusion trees.", "start": 1287.83, "duration": 2.49}, {"text": "This was invented\naround the time", "start": 1290.32, "duration": 1.59}, {"text": "that cold fusion\nwas in the news,", "start": 1291.91, "duration": 1.69}, {"text": "and so they wanted data\nstructures to represent.", "start": 1293.6, "duration": 3.915}, {"text": "We can achieve this bound or\nwe can achieve this bound.", "start": 1300.19, "duration": 2.76}, {"text": "And this bound is\ngood is if w is large.", "start": 1302.95, "duration": 3.48}, {"text": "This band as good if w is small.", "start": 1306.43, "duration": 2.82}, {"text": "You can always take the min of\nthe two, whatever is better.", "start": 1309.25, "duration": 4.23}, {"text": "And in particular, the min of\nthose two things is at most--", "start": 1313.48, "duration": 11.55}, {"text": "I think it's square root\nlog n over log log n.", "start": 1325.03, "duration": 4.95}, {"text": "If you want to bound\njust in terms of n,", "start": 1329.98, "duration": 3.87}, {"text": "then the crossover point\nbetween these two is this place.", "start": 1333.85, "duration": 3.03}, {"text": "And so you're always,\nat most, this,", "start": 1336.88, "duration": 1.5}, {"text": "which is quite a bit better\nthan the log n of AVL.", "start": 1338.38, "duration": 2.94}, {"text": "We've got a square\nroot and we've", "start": 1341.32, "duration": 1.375}, {"text": "got a slight thing\nin the denominator.", "start": 1342.695, "duration": 2.765}, {"text": "Pretty tiny.", "start": 1345.46, "duration": 0.858}, {"text": "But the big thing\nis the square root.", "start": 1346.318, "duration": 1.542}, {"text": "And that's kind of cool.", "start": 1347.86, "duration": 1.14}, {"text": "And it turns out, that's\npretty much optimal.", "start": 1349.0, "duration": 2.01}, {"text": "In terms of an n\nbound, this is optimal.", "start": 1351.01, "duration": 2.01}, {"text": "The min of these\ntwo, in general,", "start": 1353.02, "duration": 2.19}, {"text": "is roughly optimal\nup to log log terms.", "start": 1355.21, "duration": 3.72}, {"text": "For fun, I threw up\nthe actual formula", "start": 1358.93, "duration": 2.97}, {"text": "for the right-bound,\nwhich is tight", "start": 1361.9, "duration": 3.18}, {"text": "up to constant factors of\nmatching upper and lower", "start": 1365.08, "duration": 2.37}, {"text": "bounds, which we talk about.", "start": 1367.45, "duration": 1.8}, {"text": "It's min of three things--", "start": 1369.25, "duration": 3.31}, {"text": "four things, including log of\nw over a divided by log of log", "start": 1372.56, "duration": 4.22}, {"text": "w over a log of log n over a.", "start": 1376.78, "duration": 3.02}, {"text": "That's the last term\nthat I just read.", "start": 1379.8, "duration": 1.9}, {"text": "This was messy.", "start": 1381.7, "duration": 1.68}, {"text": "Surprisingly, that\nis the right answer", "start": 1383.38, "duration": 1.83}, {"text": "for this very\nparticular problem--", "start": 1385.21, "duration": 1.892}, {"text": "a very natural problem.", "start": 1387.102, "duration": 0.958}, {"text": "AUDIENCE: What is a?", "start": 1388.06, "duration": 1.53}, {"text": "ERIK DEMAINE: A is the log\nof the space you're using.", "start": 1389.59, "duration": 3.01}, {"text": "So it's the address size.", "start": 1392.6, "duration": 2.36}, {"text": "Good question.", "start": 1394.96, "duration": 2.04}, {"text": "If you throw it-- so it depends.", "start": 1397.0, "duration": 1.7}, {"text": "If you have a polynomial space\ndata structure, then basically,", "start": 1398.7, "duration": 3.04}, {"text": "these are optimal.", "start": 1401.74, "duration": 1.51}, {"text": "And this is generalizing\nto beyond that.", "start": 1403.25, "duration": 3.35}, {"text": "Maybe you have a little bit\nmore than polynomial space.", "start": 1406.6, "duration": 3.61}, {"text": "Cool.", "start": 1410.21, "duration": 1.35}, {"text": "So that's data structures.", "start": 1411.56, "duration": 2.16}, {"text": "I'm going to jump ahead to\ngraph algorithms, which,", "start": 1413.72, "duration": 5.43}, {"text": "if you want to take this class,\nI recommend a time travel", "start": 1419.15, "duration": 2.52}, {"text": "device.", "start": 1421.67, "duration": 0.6}, {"text": "Go back to fall 2011.", "start": 1422.27, "duration": 2.13}, {"text": "It may never get taught again.", "start": 1424.4, "duration": 1.38}, {"text": "But it has video,\nso you can watch--", "start": 1425.78, "duration": 2.55}, {"text": "instead of time\ntraveling, if you", "start": 1428.33, "duration": 1.712}, {"text": "don't want to watch\nit live, you can just", "start": 1430.042, "duration": 1.708}, {"text": "watch the recorded version.", "start": 1431.75, "duration": 1.53}, {"text": "It was taught by a bunch\nof postdocs that were here,", "start": 1433.28, "duration": 2.7}, {"text": "and a bit myself.", "start": 1435.98, "duration": 3.12}, {"text": "What I like to do with graphs\nis the world of planar graphs,", "start": 1439.1, "duration": 4.08}, {"text": "or near-planar graphs.", "start": 1443.18, "duration": 1.695}, {"text": "We've talked a lot\nabout, this class,", "start": 1448.538, "duration": 1.542}, {"text": "algorithms that work\nfor arbitrary graphs.", "start": 1450.08, "duration": 2.138}, {"text": "And the algorithms\nwe've seen in this class", "start": 1452.218, "duration": 1.792}, {"text": "are pretty much the best we\nknow for a lot of problems", "start": 1454.01, "duration": 2.73}, {"text": "for arbitrary graphs.", "start": 1456.74, "duration": 2.208}, {"text": "But if your graph\nhas some structure,", "start": 1458.948, "duration": 1.542}, {"text": "like it's a road network\nand there aren't too", "start": 1460.49, "duration": 2.1}, {"text": "many overpasses, you can usually\ndraw these graphs in the plane", "start": 1462.59, "duration": 3.72}, {"text": "without crossings.", "start": 1466.31, "duration": 0.93}, {"text": "That's the meaning of planar.", "start": 1467.24, "duration": 1.35}, {"text": "Maybe not exactly.", "start": 1468.59, "duration": 0.96}, {"text": "Maybe just a few crossings.", "start": 1469.55, "duration": 1.44}, {"text": "There's a generalization of\nthis, which I won't get into.", "start": 1470.99, "duration": 2.462}, {"text": "But let's just think\nabout planar graphs.", "start": 1473.452, "duration": 1.708}, {"text": "Planar graphs have\nsome nice features,", "start": 1475.16, "duration": 1.583}, {"text": "like they always have a\nlinear number of edges.", "start": 1476.743, "duration": 3.155}, {"text": "They're always sparse.", "start": 1479.898, "duration": 0.917}, {"text": "So you can immediately plug\nthat into our existing bounds.", "start": 1483.51, "duration": 2.87}, {"text": "But even so, Dijkstra, in such a\ngraph, would take v log v time.", "start": 1486.38, "duration": 6.72}, {"text": "For planar graphs, you can do\nthe equivalent of Dijkstra,", "start": 1493.1, "duration": 3.42}, {"text": "meaning, I can compute\nsingle-source shortest paths", "start": 1496.52, "duration": 2.39}, {"text": "with negative edge\nweights in linear time.", "start": 1498.91, "duration": 2.83}, {"text": "No log.", "start": 1507.26, "duration": 2.56}, {"text": "Not that impressive,\nbut remove a log.", "start": 1509.82, "duration": 2.49}, {"text": "More impressive is, we can do\nthe equivalent of Bellman-Ford,", "start": 1512.31, "duration": 4.2}, {"text": "which is a single-source\nshortest paths with arbitrary", "start": 1516.51, "duration": 2.25}, {"text": "edge weights in a planar\ngraph in some time--", "start": 1518.76, "duration": 7.11}, {"text": "almost linear time.", "start": 1525.87, "duration": 1.02}, {"text": "The log squared v\nover log log v. So", "start": 1529.77, "duration": 5.43}, {"text": "there's a couple\nof factors here--", "start": 1535.2, "duration": 2.07}, {"text": "but for almost linear\ntime, whereas Bellman-Ford", "start": 1537.27, "duration": 2.4}, {"text": "would take v squared time.", "start": 1539.67, "duration": 1.27}, {"text": "So this is a huge\nimprovement over what", "start": 1540.94, "duration": 2.27}, {"text": "we've seen in the class.", "start": 1543.21, "duration": 1.11}, {"text": "These are quite\ncomplicated algorithms,", "start": 1544.32, "duration": 1.35}, {"text": "but they're covered\nin that class,", "start": 1545.67, "duration": 1.417}, {"text": "if you're interested in them.", "start": 1547.087, "duration": 2.153}, {"text": "Then the area I work in a lot\nis approximation algorithms", "start": 1549.24, "duration": 4.17}, {"text": "for planar graphs.", "start": 1553.41, "duration": 3.42}, {"text": "And let me just give you a fun\nflavor using something we know,", "start": 1556.83, "duration": 4.62}, {"text": "which is breadth-first search.", "start": 1561.45, "duration": 4.205}, {"text": "Breath-first search\nyou can think", "start": 1565.655, "duration": 1.375}, {"text": "of as building sort of rings\naround a single root node.", "start": 1567.03, "duration": 6.35}, {"text": "And there's this\ngeneral approach--", "start": 1573.38, "duration": 1.77}, {"text": "this was introduced\nby Baker in 1994,", "start": 1575.15, "duration": 2.47}, {"text": "we've used for lots\nof different problems.", "start": 1577.62, "duration": 2.27}, {"text": "We want to solve some\nNP-hard problem on a graph.", "start": 1579.89, "duration": 3.46}, {"text": "So just run breadth-first\nsearch from an arbitrary vertex", "start": 1583.35, "duration": 3.41}, {"text": "and decompose your\ngraph into these layers.", "start": 1586.76, "duration": 2.402}, {"text": "You could number them--", "start": 1589.162, "duration": 0.958}, {"text": "0, 1, 2, 3.", "start": 1590.12, "duration": 2.43}, {"text": "These are levels.", "start": 1592.55, "duration": 2.82}, {"text": "And let's just, like,\ndelete some of those layers.", "start": 1595.37, "duration": 3.39}, {"text": "Let's say, let's delete\nevery fourth layer.", "start": 1598.76, "duration": 2.92}, {"text": "So maybe I delete this one.", "start": 1601.68, "duration": 1.388}, {"text": "I delete all of the\nvertices in that layer.", "start": 1603.068, "duration": 1.792}, {"text": "And then I delete all\nof the things in layer", "start": 1604.86, "duration": 1.833}, {"text": "8, and layer 12, and so on.", "start": 1606.693, "duration": 3.977}, {"text": "Guessing-- I don't know which\none to start with, but from--", "start": 1610.67, "duration": 3.51}, {"text": "I'll just try them all.", "start": 1614.18, "duration": 1.08}, {"text": "And then I delete every\nfourth layer after that.", "start": 1615.26, "duration": 3.12}, {"text": "So I've deleted, on average,\nabout a quarter of the graph.", "start": 1618.38, "duration": 4.14}, {"text": "And it turns out, for a lot of\nproblems that you care about,", "start": 1622.52, "duration": 4.14}, {"text": "like choosing where to place\nfire stations in this graph", "start": 1626.66, "duration": 3.33}, {"text": "to minimize travel\ntime for if there's", "start": 1629.99, "duration": 2.97}, {"text": "a fire somewhere in the graph--", "start": 1632.96, "duration": 1.712}, {"text": "this happens, you know?", "start": 1634.672, "duration": 0.958}, {"text": "Fires and graphs.", "start": 1635.63, "duration": 1.98}, {"text": "Then this will only hurt\nyour solution by, like,", "start": 1637.61, "duration": 3.51}, {"text": "a factor of 1 plus a quarter.", "start": 1641.12, "duration": 5.49}, {"text": "So you will get\na solution that's", "start": 1646.61, "duration": 2.64}, {"text": "within 25% of the optimal,\nfor a lot of problems.", "start": 1649.25, "duration": 6.1}, {"text": "And that works for any value 4.", "start": 1655.35, "duration": 3.12}, {"text": "So I could do it\nfor 10, and then I", "start": 1658.47, "duration": 2.13}, {"text": "would get within 10% of\nthe optimal solution.", "start": 1660.6, "duration": 3.36}, {"text": "OK, but how do I actually\nsolve the problem once I", "start": 1663.96, "duration": 2.43}, {"text": "delete every fourth layer?", "start": 1666.39, "duration": 1.65}, {"text": "Well, then your graph has\nthis extra special structure,", "start": 1668.04, "duration": 2.85}, {"text": "which is a constant number\nof layers, let's say.", "start": 1670.89, "duration": 2.29}, {"text": "A constant number of\nbreadth-first search layers.", "start": 1673.18, "duration": 1.43}, {"text": "If you just look\nat this portion,", "start": 1674.61, "duration": 1.65}, {"text": "this connected component,\nor this connected component", "start": 1676.26, "duration": 2.5}, {"text": "in here, you can--", "start": 1678.76, "duration": 1.67}, {"text": "your graph is\nalmost like a cycle.", "start": 1680.43, "duration": 3.36}, {"text": "It's like four cycles\nstacked up together", "start": 1683.79, "duration": 2.31}, {"text": "with some connections\nbetween them.", "start": 1686.1, "duration": 1.463}, {"text": "And it turns out,\nthat's something", "start": 1687.563, "duration": 1.417}, {"text": "you can solve with very\nfancy dynamic programming,", "start": 1688.98, "duration": 3.39}, {"text": "like the stuff we've\nseen in this class, which", "start": 1692.37, "duration": 2.43}, {"text": "focuses on just a single\npath or a single cycle.", "start": 1694.8, "duration": 2.325}, {"text": "If you just have a\nconstant number of cycles,", "start": 1697.125, "duration": 1.875}, {"text": "with more work, you can still do\neverything in polynomial time.", "start": 1699.0, "duration": 3.6}, {"text": "This is a very general approach\nfor getting arbitrarily", "start": 1702.6, "duration": 3.55}, {"text": "good approximation algorithms.", "start": 1706.15, "duration": 1.25}, {"text": "We call these 1 plus epsilon\napproximation for any epsilon.", "start": 1707.4, "duration": 4.53}, {"text": "But the larger the epsilon,\nthe more time you take.", "start": 1711.93, "duration": 2.28}, {"text": "It's something like 2 to the\norder 1 over epsilon times", "start": 1714.21, "duration": 5.4}, {"text": "polynomial n.", "start": 1719.61, "duration": 1.86}, {"text": "So as long as\nepsilon is constant,", "start": 1721.47, "duration": 1.5}, {"text": "this is polynomial time.", "start": 1722.97, "duration": 1.803}, {"text": "This is called a PTAS.", "start": 1724.773, "duration": 0.917}, {"text": "Anyway, that was\ngraph algorithms.", "start": 1729.09, "duration": 2.22}, {"text": "Last topic is recreational\nalgorithms, which is maybe", "start": 1731.31, "duration": 3.99}, {"text": "best encompassed by this class.", "start": 1735.3, "duration": 1.53}, {"text": "6.892 is its latest name.", "start": 1736.83, "duration": 2.01}, {"text": "It changes names\nevery once in a while.", "start": 1738.84, "duration": 2.1}, {"text": "And I mentioned it in the\nhardness complexity lecture,", "start": 1740.94, "duration": 3.24}, {"text": "because this class is all\nabout hardness proofs,", "start": 1744.18, "duration": 2.28}, {"text": "analyzing fun games and puzzles.", "start": 1746.46, "duration": 1.95}, {"text": "We saw the Tetris\nNP-hardness in that lecture.", "start": 1748.41, "duration": 3.75}, {"text": "But you can also prove Super\nMario Brothers is hard,", "start": 1752.16, "duration": 3.33}, {"text": "or Portal is hard, or\nMario Kart is hard,", "start": 1755.49, "duration": 2.58}, {"text": "or The Witness, a modern\nvideo game, is hard.", "start": 1758.07, "duration": 3.27}, {"text": "Or, one of our latest\nresults is that Recurse--", "start": 1761.34, "duration": 2.73}, {"text": "that game in the top\nright-- is undecidable.", "start": 1764.07, "duration": 2.67}, {"text": "There's no algorithm to\nplay that game perfectly.", "start": 1766.74, "duration": 6.0}, {"text": "And you can even\ndownload the level--", "start": 1772.74, "duration": 2.05}, {"text": "an example of the level\nand play it, if you dare.", "start": 1774.79, "duration": 5.28}, {"text": "So that's a lot of--", "start": 1780.07, "duration": 1.73}, {"text": "we have a lot of fun in\nthat world of hardness", "start": 1781.8, "duration": 3.15}, {"text": "of different games and puzzles.", "start": 1784.95, "duration": 2.36}, {"text": "Where do I want to go next?", "start": 1787.31, "duration": 3.02}, {"text": "OK.", "start": 1790.33, "duration": 0.5}, {"text": "Next topic is balloon twisting.", "start": 1790.83, "duration": 1.59}, {"text": "Totally different.", "start": 1792.42, "duration": 1.2}, {"text": "This is recreational,\nbut not about hardness.", "start": 1793.62, "duration": 2.73}, {"text": "This is an octahedron\ntwisted from one balloon.", "start": 1796.35, "duration": 4.92}, {"text": "I made another one on a stick.", "start": 1801.27, "duration": 2.647}, {"text": "Each of these is\nmade for one balloon.", "start": 1803.917, "duration": 1.583}, {"text": "What graphs can you\nmake for one balloon?", "start": 1805.5, "duration": 3.36}, {"text": "Well, you should read our paper.", "start": 1808.86, "duration": 1.563}, {"text": "And you can characterize\nhow many balloons you", "start": 1810.423, "duration": 1.917}, {"text": "need to make each polyhedron.", "start": 1812.34, "duration": 2.88}, {"text": "And some of these problems are\nNP-hard, and it's a lot of fun.", "start": 1815.22, "duration": 5.95}, {"text": "Cool.", "start": 1821.17, "duration": 0.5}, {"text": "I think that's the\nend of the slides.", "start": 1821.67, "duration": 2.31}, {"text": "The last thing I\nwanted to show you", "start": 1823.98, "duration": 1.71}, {"text": "is a problem, a\npuzzle/magic trick--", "start": 1825.69, "duration": 7.2}, {"text": "it comes from the puzzle world--", "start": 1832.89, "duration": 1.59}, {"text": "called the picture\nhanging problem.", "start": 1834.48, "duration": 1.51}, {"text": "So imagine you have a picture.", "start": 1835.99, "duration": 1.76}, {"text": "You want to hang it on a wall.", "start": 1837.75, "duration": 1.48}, {"text": "So you invested\nin some nice rope,", "start": 1839.23, "duration": 1.73}, {"text": "and you hang it on a nail.", "start": 1840.96, "duration": 3.18}, {"text": "If the nail falls out, the\npicture falls, and you're sad.", "start": 1844.14, "duration": 3.24}, {"text": "So you invest in two\nnails, like I have here,", "start": 1847.38, "duration": 3.21}, {"text": "and maybe you hang your\npicture on both those nails.", "start": 1850.59, "duration": 2.91}, {"text": "Now, if one of the\nnails falls out,", "start": 1853.5, "duration": 2.37}, {"text": "you still have a\ncrookedly hung picture.", "start": 1855.87, "duration": 2.7}, {"text": "If the other nail falls\nout, OK, it's gone.", "start": 1858.57, "duration": 2.97}, {"text": "I want to hang a\npicture on two nails", "start": 1861.54, "duration": 2.94}, {"text": "such that, if I remove either\nnail, the picture falls.", "start": 1864.48, "duration": 3.66}, {"text": "So, Jason, pick a\nnail, left or right.", "start": 1868.14, "duration": 2.93}, {"text": "Left, we remove.", "start": 1871.07, "duration": 1.94}, {"text": "Make sure this\ndoesn't fall off--", "start": 1873.01, "duration": 1.77}, {"text": "and, boom, the picture falls.", "start": 1874.78, "duration": 1.65}, {"text": "Same wrapping.", "start": 1876.43, "duration": 0.992}, {"text": "You can check-- you\ncan rewind the video,", "start": 1877.422, "duration": 1.708}, {"text": "make sure I did\nthe same wrapping.", "start": 1879.13, "duration": 1.32}, {"text": "JASON KU: And take\nout the right.", "start": 1880.45, "duration": 1.23}, {"text": "ERIK DEMAINE: Then\ntake out the right one.", "start": 1881.68, "duration": 1.75}, {"text": "Good choice.", "start": 1883.43, "duration": 1.22}, {"text": "Then, also, the picture falls.", "start": 1884.65, "duration": 1.95}, {"text": "This is a classic puzzle,\nbut you can generalize it.", "start": 1889.15, "duration": 2.35}, {"text": "So let me do it for three\nnails, which is all I have here.", "start": 1891.5, "duration": 4.75}, {"text": "This nail is sagging\na little bit.", "start": 1896.25, "duration": 2.86}, {"text": "y, x-- y inverse, x inverse.", "start": 1899.11, "duration": 3.32}, {"text": "I think that's right.", "start": 1902.43, "duration": 1.51}, {"text": "So this is one way to hang\na picture on three nails", "start": 1903.94, "duration": 2.46}, {"text": "such that, if I remove any of\nthe nails, the picture falls.", "start": 1906.4, "duration": 3.21}, {"text": "Justin, 1, 2, or 3?", "start": 1909.61, "duration": 3.81}, {"text": "2.", "start": 1913.42, "duration": 0.87}, {"text": "OK.", "start": 1914.29, "duration": 1.59}, {"text": "Yeah, I want to\nget out of the way", "start": 1915.88, "duration": 1.56}, {"text": "and make sure I don't\ngo over the edge here.", "start": 1917.44, "duration": 2.7}, {"text": "Yeah.", "start": 1924.38, "duration": 1.02}, {"text": "It's a lot easier to\nmake this one work.", "start": 1925.4, "duration": 2.38}, {"text": "But you can see, boom,\npicture falls there.", "start": 1927.78, "duration": 3.44}, {"text": "And of course, imagine\ninfinite gravity.", "start": 1931.22, "duration": 2.58}, {"text": "And the picture falls.", "start": 1933.8, "duration": 1.13}, {"text": "Ta-da!", "start": 1934.93, "duration": 1.78}, {"text": "You can generalize this\nto do essentially any--", "start": 1936.71, "duration": 3.27}, {"text": "what's called a monotone Boolean\nfunction-- on any set of nails.", "start": 1939.98, "duration": 3.18}, {"text": "I mean, you can make\nany subset of the nails", "start": 1943.16, "duration": 2.25}, {"text": "cause the picture to fall\nand any collection of subsets", "start": 1945.41, "duration": 2.318}, {"text": "of nails to make it fall.", "start": 1947.728, "duration": 1.042}, {"text": "Of course, if you\nremove more nails,", "start": 1948.77, "duration": 1.11}, {"text": "it's still going to fall.", "start": 1949.88, "duration": 1.32}, {"text": "That's the monotone sense.", "start": 1951.2, "duration": 1.83}, {"text": "But otherwise, you can\ndo an arbitrary pattern,", "start": 1953.03, "duration": 3.428}, {"text": "which is fun.", "start": 1956.458, "duration": 0.542}, {"text": "That's actually a\nresult with Ron Rivest", "start": 1957.0, "duration": 2.12}, {"text": "and a bunch of other people.", "start": 1959.12, "duration": 3.88}, {"text": "I think I'm\napproximately on time.", "start": 1963.0, "duration": 3.37}, {"text": "So that was a quick tour.", "start": 1966.37, "duration": 2.12}, {"text": "And there are obviously various\nclasses here you can take.", "start": 1968.49, "duration": 3.54}, {"text": "6.892, the hardness class, was\njust offered last semester,", "start": 1972.03, "duration": 3.36}, {"text": "so it probably won't\nbe for a while.", "start": 1975.39, "duration": 1.5}, {"text": "But all of these\nclasses are online.", "start": 1976.89, "duration": 1.5}, {"text": "Watch the videos, feel\nfree to ask me questions.", "start": 1978.39, "duration": 2.88}, {"text": "And now we have Justin.", "start": 1981.27, "duration": 1.83}, {"text": "I left you space here\nfor your outline.", "start": 1983.1, "duration": 2.565}, {"text": "You don't have to, but\nI'll put your name.", "start": 1988.39, "duration": 3.517}, {"text": "JUSTIN SOLOMON: Thank you.", "start": 1991.907, "duration": 1.083}, {"text": "JASON KU: So Justin\nis also a geometer.", "start": 1998.17, "duration": 2.138}, {"text": "ERIK DEMAINE: Yeah, we've got\na lot of geometry people in 006", "start": 2000.308, "duration": 2.542}, {"text": "this semester.", "start": 2002.85, "duration": 1.65}, {"text": "JUSTIN SOLOMON: Thank you.", "start": 2004.5, "duration": 1.1}, {"text": "OK.", "start": 2005.6, "duration": 1.98}, {"text": "I can't help but share that,\non our instructor chat,", "start": 2007.58, "duration": 3.36}, {"text": "Erik was texting that\nhe was going to be--", "start": 2010.94, "duration": 2.158}, {"text": "he was somehow nervous\nthat the applied guy would", "start": 2013.098, "duration": 2.042}, {"text": "have all of the cool\nstuff to show off,", "start": 2015.14, "duration": 1.77}, {"text": "and now I feel totally boring.", "start": 2016.91, "duration": 2.772}, {"text": "[LAUGHING] Right.", "start": 2019.682, "duration": 3.408}, {"text": "Yeah.", "start": 2023.09, "duration": 1.11}, {"text": "We have three different geometry\ninstructors in this class.", "start": 2024.2, "duration": 3.75}, {"text": "In this class, I think we\nhave many different flavors", "start": 2027.95, "duration": 3.09}, {"text": "of geometry that are\nkind of represented", "start": 2031.04, "duration": 1.77}, {"text": "in this room here, from\nmechanical engineering,", "start": 2032.81, "duration": 2.04}, {"text": "to theory plus lots\nof other cool stuff,", "start": 2034.85, "duration": 2.61}, {"text": "to whatever it is that I do.", "start": 2037.46, "duration": 3.0}, {"text": "I'm a professor, also, in\nCSAIL, and lead a group", "start": 2040.46, "duration": 3.27}, {"text": "that studies slightly more\napplied geometry problems,", "start": 2043.73, "duration": 3.66}, {"text": "in some sense, and in\nCSAIL, we kind of cross", "start": 2047.39, "duration": 3.96}, {"text": "a lot of boundaries-- actually,\ncloser to the math department", "start": 2051.35, "duration": 3.869}, {"text": "than to the theory group\nand computer science,", "start": 2055.219, "duration": 2.681}, {"text": "which I would argue is largely\na historical artifact rather", "start": 2057.9, "duration": 2.6}, {"text": "than anything interesting\nabout computer science or math.", "start": 2060.5, "duration": 5.219}, {"text": "Continuing in our whirlwind tour\nof interesting geometry classes", "start": 2065.719, "duration": 3.451}, {"text": "here at MIT, I have some more\nfun things to add to the list.", "start": 2069.17, "duration": 4.057}, {"text": "And we'll introduce some of\nthe ideas in the next couple", "start": 2073.227, "duration": 2.333}, {"text": "of slides here.", "start": 2075.56, "duration": 1.96}, {"text": "So normally, every\nfall, I teach 6.837,", "start": 2077.52, "duration": 3.86}, {"text": "which is the introduction\nto computer graphics course.", "start": 2081.38, "duration": 2.25}, {"text": "In fact, my background was\nworking in an animation studio", "start": 2083.63, "duration": 3.48}, {"text": "for a little bit of time, and\ngot one movie credit out of it", "start": 2087.11, "duration": 3.779}, {"text": "until they changed the\nstandards for movie credits,", "start": 2090.889, "duration": 2.161}, {"text": "and then that stopped happening.", "start": 2093.05, "duration": 2.439}, {"text": "But in any event, if you\nwatch-- what's that movie--", "start": 2095.489, "duration": 2.211}, {"text": "Up, with the old man.", "start": 2097.7, "duration": 1.16}, {"text": "If you hit pause at\njust the right moment,", "start": 2098.86, "duration": 1.75}, {"text": "you can find me right above\nthe list of babies that", "start": 2100.61, "duration": 2.22}, {"text": "were born during production.", "start": 2102.83, "duration": 2.97}, {"text": "But in any event--", "start": 2105.8, "duration": 1.35}, {"text": "although computer\ngraphics might not", "start": 2107.15, "duration": 1.5}, {"text": "sound like an\nalgorithmic discipline,", "start": 2108.65, "duration": 1.542}, {"text": "I'll try to convince you\nguys that, in some sense,", "start": 2110.192, "duration": 2.771}, {"text": "you could take just about\nanybody in our department,", "start": 2112.963, "duration": 2.167}, {"text": "have them teach 6.006, and\ngive a similar talk that,", "start": 2115.13, "duration": 2.58}, {"text": "like, the material that you've\nencountered in this course", "start": 2117.71, "duration": 2.49}, {"text": "is going to be\nrelevant to your life.", "start": 2120.2, "duration": 2.95}, {"text": "The other course that I teach\nthat might be of interest--", "start": 2123.15, "duration": 2.66}, {"text": "and actually, is a little\nmore theoretically flavored--", "start": 2125.81, "duration": 2.85}, {"text": "that I teach is 6.838.", "start": 2128.66, "duration": 2.46}, {"text": "So since Erik so kindly put\nmy name on the board here,", "start": 2131.12, "duration": 3.03}, {"text": "I guess I can draw\nThe So the main object", "start": 2134.15, "duration": 2.58}, {"text": "of interest in 6.838\nis a particular thing", "start": 2136.73, "duration": 3.03}, {"text": "called the simplicial complex.", "start": 2139.76, "duration": 1.65}, {"text": "Usually, in 6.006,\nwe spend a lot", "start": 2147.6, "duration": 2.73}, {"text": "of time thinking about graphs.", "start": 2150.33, "duration": 1.77}, {"text": "Let me draw you a graph.", "start": 2152.1, "duration": 1.83}, {"text": "So I'm going to take a\nsquare and subdivide it.", "start": 2153.93, "duration": 3.96}, {"text": "And now, let's say I put\nedges diagonally like that.", "start": 2157.89, "duration": 6.2}, {"text": "Now, in 6.006, this\nthing is just a bunch", "start": 2164.09, "duration": 4.3}, {"text": "of nodes connected by edges.", "start": 2168.39, "duration": 1.5}, {"text": "In fact, if I took this edge and\nI moved it down or something,", "start": 2169.89, "duration": 2.76}, {"text": "it would be the same graph.", "start": 2172.65, "duration": 1.65}, {"text": "But of course, in a lot of\ncomputer graphics applications,", "start": 2174.3, "duration": 3.12}, {"text": "this thing also looks an\nawful lot like a square.", "start": 2177.42, "duration": 3.0}, {"text": "And the reason is\nthat, of course,", "start": 2180.42, "duration": 2.47}, {"text": "the graph here contains\ntriangles inside of it.", "start": 2182.89, "duration": 2.91}, {"text": "And so for instance,\nmaybe I think of my graph", "start": 2185.8, "duration": 3.92}, {"text": "as a collection of vertices,\na collection of edges.", "start": 2189.72, "duration": 2.31}, {"text": "This is the sort of\nnotation we've seen before.", "start": 2192.03, "duration": 1.96}, {"text": "And then I add a third\nthing to my description,", "start": 2193.99, "duration": 4.08}, {"text": "which is a set of triplets.", "start": 2198.07, "duration": 1.37}, {"text": "That's a set of triangles here.", "start": 2199.44, "duration": 2.125}, {"text": "And we can take a\nlot of the algorithms", "start": 2201.565, "duration": 1.625}, {"text": "that we've talked\nabout in this class", "start": 2203.19, "duration": 1.39}, {"text": "and extend it to this case.", "start": 2204.58, "duration": 1.125}, {"text": "For example, here's a\ndeceptively annoying one.", "start": 2205.705, "duration": 4.805}, {"text": "Let's say that I want the\nshortest path between two", "start": 2210.51, "duration": 2.37}, {"text": "vertices of my graph.", "start": 2212.88, "duration": 1.83}, {"text": "We certainly have learned\nDijkstra's algorithm.", "start": 2214.71, "duration": 3.18}, {"text": "That's one technique to do that.", "start": 2217.89, "duration": 1.54}, {"text": "And indeed, common practice\nin computer graphics,", "start": 2219.43, "duration": 2.69}, {"text": "which is shameful, is\non your triangle mesh,", "start": 2222.12, "duration": 2.64}, {"text": "if you want the shortest path\nbetween two vertices, run", "start": 2224.76, "duration": 3.33}, {"text": "Dijkstra's algorithm\non the edges.", "start": 2228.09, "duration": 2.702}, {"text": "And let's see if that\nworks really quick.", "start": 2230.792, "duration": 1.708}, {"text": "Let's say that I want the\nshortest path between--", "start": 2232.5, "duration": 2.162}, {"text": "and, by the way, I'm going to\nassume the length of my edges", "start": 2234.662, "duration": 2.458}, {"text": "are the lengths as I've\ndrawn them on the board here.", "start": 2237.12, "duration": 2.208}, {"text": "So it's like 1, 1,\nsquare root of 2.", "start": 2239.328, "duration": 3.312}, {"text": "OK.", "start": 2242.64, "duration": 0.54}, {"text": "So let's say I want the shortest\npath between the bottom left", "start": 2243.18, "duration": 2.1}, {"text": "and the upper right.", "start": 2245.28, "duration": 0.93}, {"text": "If I run Dijkstra's algorithm,\nwe're in good shape, right?", "start": 2246.21, "duration": 2.417}, {"text": "We get-- I'll let you do\nthe computations at home.", "start": 2248.627, "duration": 2.903}, {"text": "You'll get the path\nthat is these two edges.", "start": 2251.53, "duration": 4.31}, {"text": "But here's a really\nannoying thing.", "start": 2255.84, "duration": 2.16}, {"text": "Let's say, instead, I\nwanted the shortest path", "start": 2258.0, "duration": 2.79}, {"text": "from the upper left\nto the lower right.", "start": 2260.79, "duration": 4.05}, {"text": "If I run Dijkstra's algorithm\non this triangulated square,", "start": 2264.84, "duration": 4.44}, {"text": "what's going to be\nthe shortest path?", "start": 2269.28, "duration": 2.54}, {"text": "Yeah.", "start": 2271.82, "duration": 0.5}, {"text": "In fact, there's\na bunch of them.", "start": 2272.32, "duration": 1.462}, {"text": "One of them might go all\nthe way down, and then", "start": 2273.782, "duration": 1.958}, {"text": "all the way to the right.", "start": 2275.74, "duration": 1.498}, {"text": "What's the length of this path?", "start": 2277.238, "duration": 1.292}, {"text": "1, 2, 3, 4.", "start": 2278.53, "duration": 2.43}, {"text": "Is that the length\nof the shortest path?", "start": 2280.96, "duration": 1.74}, {"text": "Well, probably not.", "start": 2282.7, "duration": 1.38}, {"text": "Well, we would like our shortest\npath to do something like that.", "start": 2284.08, "duration": 4.06}, {"text": "But graphs don't know\nhow to talk to triangles.", "start": 2288.14, "duration": 3.15}, {"text": "And this is going\nto be a problem.", "start": 2291.29, "duration": 1.92}, {"text": "In fact, it wasn't until\nfairly recently [INAUDIBLE]", "start": 2293.21, "duration": 3.03}, {"text": "history terms that we were\nable to kind of work out", "start": 2296.24, "duration": 2.39}, {"text": "the correct algorithm\nfor the shortest", "start": 2298.63, "duration": 2.01}, {"text": "path in a triangulated\ndomain like this.", "start": 2300.64, "duration": 2.227}, {"text": "And that's the runtime\nthat we would expect.", "start": 2302.867, "duration": 1.833}, {"text": "This is called MMP.", "start": 2304.7, "duration": 2.36}, {"text": "I'm guessing Erik and\nJason could do a better", "start": 2307.06, "duration": 2.88}, {"text": "job describing it than I can.", "start": 2309.94, "duration": 2.1}, {"text": "But the basic idea\nof the MMP algorithm", "start": 2312.04, "duration": 2.25}, {"text": "actually is a really--", "start": 2314.29, "duration": 0.93}, {"text": "happens to be a nice\nextension of the way", "start": 2315.22, "duration": 1.708}, {"text": "that we taught Dijkstra's\nalgorithm in 6.006,", "start": 2316.928, "duration": 3.032}, {"text": "because they really do\nkeep track of these level", "start": 2319.96, "duration": 2.2}, {"text": "sets of the distance function.", "start": 2322.16, "duration": 1.55}, {"text": "But now, the level\nsets have to--", "start": 2323.71, "duration": 2.34}, {"text": "oops-- have to window\nand edge like that", "start": 2326.05, "duration": 2.82}, {"text": "when I compute shortest path,\nwhich is a giant headache.", "start": 2328.87, "duration": 2.7}, {"text": "This is one of these\nalgorithms that", "start": 2331.57, "duration": 1.5}, {"text": "was known in theory about 10\nyears before anybody bothered", "start": 2333.07, "duration": 2.85}, {"text": "to implement it in a way that\nthey could convince themselves", "start": 2335.92, "duration": 3.21}, {"text": "it ran in n log n time.", "start": 2339.13, "duration": 2.04}, {"text": "And nowadays, there's a cottage\nindustry in computer graphics", "start": 2341.17, "duration": 2.88}, {"text": "research papers to\nimplement this and then", "start": 2344.05, "duration": 2.05}, {"text": "speed it up in different ways.", "start": 2346.1, "duration": 1.25}, {"text": "And sadly, the reality is that\na different algorithm that we", "start": 2347.35, "duration": 3.04}, {"text": "cover in 6.838 called\nfast marching--", "start": 2350.39, "duration": 1.627}, {"text": "which doesn't actually\ngive you the shortest path,", "start": 2352.017, "duration": 2.083}, {"text": "but some approximation thereof--", "start": 2354.1, "duration": 1.95}, {"text": "is faster, easier to use, and\nbasically indistinguishable.", "start": 2356.05, "duration": 4.77}, {"text": "In any event, in\n6.838, we kind of", "start": 2360.82, "duration": 4.02}, {"text": "have an interesting\ndual-mindset.", "start": 2364.84, "duration": 3.57}, {"text": "We'll talk about a\nlot of algorithms", "start": 2368.41, "duration": 1.53}, {"text": "that look like what we've done\nin whatever this class is--", "start": 2369.94, "duration": 3.36}, {"text": "6.006.", "start": 2373.3, "duration": 1.88}, {"text": "But at the same time, start to\nhave a more geometric flavor,", "start": 2375.18, "duration": 2.5}, {"text": "and we don't worry quite\nas much about [INAUDIBLE]..", "start": 2377.68, "duration": 3.333}, {"text": "So in our computation\nmodel, oftentimes, we're", "start": 2381.013, "duration": 1.917}, {"text": "kind of OK with real\nnumbers, because that's not", "start": 2382.93, "duration": 2.0}, {"text": "where the headache is.", "start": 2384.93, "duration": 0.917}, {"text": "And of course, when you\nwrite code in this class,", "start": 2385.847, "duration": 2.041}, {"text": "you use double-precision\nfloating-point.", "start": 2387.888, "duration": 1.762}, {"text": "If you're more responsible, like\nin Jason's previous lecture,", "start": 2389.65, "duration": 3.04}, {"text": "you should probably keep track\nof the number of operations", "start": 2392.69, "duration": 2.42}, {"text": "to make sure that\nyour error is counted.", "start": 2395.11, "duration": 1.667}, {"text": "But I'm not sure that we\nreally bother with that.", "start": 2396.777, "duration": 3.613}, {"text": "In any event, this allows us\nto have two different mindsets.", "start": 2400.39, "duration": 4.35}, {"text": "There's one mindset,\nwhich is discrete.", "start": 2404.74, "duration": 2.1}, {"text": "There's another mindset,\nwhich is smooth.", "start": 2406.84, "duration": 2.38}, {"text": "We think about understanding\ngeometry, like these triangular", "start": 2409.22, "duration": 3.05}, {"text": "domains, as an approximation\nof a smooth surface.", "start": 2412.27, "duration": 2.705}, {"text": "And then we might want to do\nstuff like compute curvature", "start": 2414.975, "duration": 2.375}, {"text": "and so on, which is really\nassociated with computing", "start": 2417.35, "duration": 2.24}, {"text": "derivatives, which\nof course, we'll", "start": 2419.59, "duration": 1.47}, {"text": "have on these kinds\nof simplicial objects.", "start": 2421.06, "duration": 2.34}, {"text": "And that leads to this really\nfun area of math and computer", "start": 2423.4, "duration": 2.76}, {"text": "science, whatever, called\ndiscrete differential", "start": 2426.16, "duration": 2.73}, {"text": "geometry, which sounds like\na contradiction in terms.", "start": 2428.89, "duration": 3.27}, {"text": "And it's something that we\ncovered in quite some detail", "start": 2432.16, "duration": 2.475}, {"text": "in this course.", "start": 2434.635, "duration": 0.835}, {"text": "So we build up, all of calculus,\nthat the only calculations", "start": 2435.47, "duration": 3.35}, {"text": "you're left to do\nare on the vertices", "start": 2438.82, "duration": 1.71}, {"text": "and edges and triangles\nof a triangle mesh.", "start": 2440.53, "duration": 2.88}, {"text": "And get pretty far, including\nsome constructions of topology,", "start": 2443.41, "duration": 3.42}, {"text": "like the Duran\ncomplex, and so on.", "start": 2446.83, "duration": 2.16}, {"text": "I would argue, actually, if\nyou take our course and then", "start": 2448.99, "duration": 3.0}, {"text": "the differential\ngeometry courses", "start": 2451.99, "duration": 1.51}, {"text": "in that department,\nsomehow, some of the indices", "start": 2453.5, "duration": 3.283}, {"text": "and headaches that you often\nencounter in that world", "start": 2456.783, "duration": 2.167}, {"text": "are much more\nconcrete when you try", "start": 2458.95, "duration": 1.68}, {"text": "to make them work on a mesh.", "start": 2460.63, "duration": 1.357}, {"text": "In any event, I think I've\nalready spent all of my time.", "start": 2461.987, "duration": 2.333}, {"text": "I can tell you a little bit\nabout research in our group.", "start": 2464.32, "duration": 4.75}, {"text": "I really lead kind of a weird,\nextremely [INAUDIBLE] group,", "start": 2469.07, "duration": 3.18}, {"text": "where some of our students are\nessentially theory students--", "start": 2472.25, "duration": 2.96}, {"text": "touch your keyboard.", "start": 2475.21, "duration": 1.84}, {"text": "I'm sorry.", "start": 2477.05, "duration": 0.51}, {"text": "It was a reflex.", "start": 2477.56, "duration": 2.38}, {"text": "But it was fast.", "start": 2479.94, "duration": 1.11}, {"text": "All right.", "start": 2481.05, "duration": 0.5}, {"text": "So we have some students\nwhose background", "start": 2481.55, "duration": 2.1}, {"text": "is in math, other\nones that we're", "start": 2483.65, "duration": 1.67}, {"text": "in autonomous driving\nindustry and decided", "start": 2485.32, "duration": 1.75}, {"text": "to come back and\nwork in research.", "start": 2487.07, "duration": 4.498}, {"text": "Because of that, we have\nthis extremely broad set", "start": 2491.568, "duration": 2.042}, {"text": "of research problems,\neverything from the sort", "start": 2493.61, "duration": 2.04}, {"text": "of classic machine learning\nproblems you might encounter", "start": 2495.65, "duration": 3.18}, {"text": "in geometry world-- like if\nI have a self-driving car", "start": 2498.83, "duration": 2.82}, {"text": "and I want to identify\npedestrians and other cars", "start": 2501.65, "duration": 3.3}, {"text": "on the road in an efficient\nand accurate fashion.", "start": 2504.95, "duration": 3.6}, {"text": "By the way, part of\nthat is machine learning", "start": 2508.55, "duration": 2.46}, {"text": "and deep whatever, but\nthere's another part,", "start": 2511.01, "duration": 1.837}, {"text": "which is algorithms.", "start": 2512.847, "duration": 0.833}, {"text": "Because actually, what comes\ninto your LiDAR scanner", "start": 2513.68, "duration": 2.88}, {"text": "is on the order of\n[INAUDIBLE] with points", "start": 2516.56, "duration": 2.55}, {"text": "and some minuscule\nfraction of time.", "start": 2519.11, "duration": 2.28}, {"text": "And time complexity of\nyour learning algorithm", "start": 2521.39, "duration": 2.73}, {"text": "actually is really\ncritical to get it right,", "start": 2524.12, "duration": 2.007}, {"text": "and something that there are a\nlot of open problems right now,", "start": 2526.127, "duration": 2.583}, {"text": "because it's really not\ncompatible with the hardware", "start": 2528.71, "duration": 2.85}, {"text": "architecture that\nthese cars often use.", "start": 2531.56, "duration": 3.57}, {"text": "We also look at [INAUDIBLE]\ngeometry problems,", "start": 2535.13, "duration": 2.3}, {"text": "like if I give you data, can\nI find a geometric structure?", "start": 2537.43, "duration": 4.16}, {"text": "So it's a classic example of\nnatural language processing.", "start": 2541.59, "duration": 2.96}, {"text": "When we use words like near\nand far, in terms of semantics", "start": 2544.55, "duration": 3.99}, {"text": "and meaning, all the time.", "start": 2548.54, "duration": 1.39}, {"text": "The question is, can we actually\nfind an embedded of our word", "start": 2549.93, "duration": 4.25}, {"text": "data into a geometric\nspace to facilitate", "start": 2554.18, "duration": 2.64}, {"text": "the statistical algorithms\nthat we care about?", "start": 2556.82, "duration": 3.09}, {"text": "And of course, we apply geometry\nto lots of practical problems,", "start": 2559.91, "duration": 2.91}, {"text": "everything from meshing\nand scientific computing,", "start": 2562.82, "duration": 2.49}, {"text": "which I think is sort\nof a classic one--", "start": 2565.31, "duration": 2.61}, {"text": "in fact, I think we're the first\ngroup that sort of enumerated", "start": 2567.92, "duration": 2.64}, {"text": "all of the cool things that may\nhappen to decahedral meshes,", "start": 2570.56, "duration": 3.61}, {"text": "which is this\nbottom figure here.", "start": 2574.17, "duration": 1.4}, {"text": "I should show this to people.", "start": 2575.57, "duration": 1.208}, {"text": "There's some fun things\nto look at there.", "start": 2576.778, "duration": 2.416}, {"text": "To other practical\nproblems, like taking--", "start": 2579.194, "duration": 2.406}, {"text": "Erik took a zebra and folded it.", "start": 2581.6, "duration": 2.58}, {"text": "We can take a zebra and move its\ntexture onto a cat or a pig--", "start": 2584.18, "duration": 3.87}, {"text": "or, actually, off the\nside of the screen.", "start": 2588.05, "duration": 1.9}, {"text": "But if we don't move the paper,\n[INAUDIBLE] for the 3D scan", "start": 2589.95, "duration": 2.458}, {"text": "of what it might [INAUDIBLE].", "start": 2592.408, "duration": 2.752}, {"text": "In any event, in my five\nminutes remaining here,", "start": 2595.16, "duration": 3.45}, {"text": "I thought I would dig into a\nlittle bit of detail of two--", "start": 2598.61, "duration": 3.938}, {"text": "or maybe one application,\ndepending on when", "start": 2602.548, "duration": 1.792}, {"text": "Jason and Erik get bored.", "start": 2604.34, "duration": 2.43}, {"text": "And essentially, my\nmessage for you guys", "start": 2606.77, "duration": 2.43}, {"text": "is, of course, [INAUDIBLE].", "start": 2609.2, "duration": 2.34}, {"text": "I'm not really a\ncentral CS theory group", "start": 2611.54, "duration": 3.12}, {"text": "member here at MIT.", "start": 2614.66, "duration": 2.01}, {"text": "But unfortunately for you\nguys, 6.006 is unavoidable.", "start": 2616.67, "duration": 3.3}, {"text": "Even if you want to go into\ndeep learning, statistics,", "start": 2619.97, "duration": 2.28}, {"text": "whatever-- data science--", "start": 2622.25, "duration": 1.042}, {"text": "you're going to encounter\nthe material that you've", "start": 2623.292, "duration": 2.083}, {"text": "seen in this course.", "start": 2625.375, "duration": 0.865}, {"text": "And in fact, it's really\nthe bread and butter", "start": 2626.24, "duration": 2.43}, {"text": "of just about everything\neverybody does here", "start": 2628.67, "duration": 2.88}, {"text": "in this Data Center.", "start": 2631.55, "duration": 1.45}, {"text": "So then, I'll give you two\nquick examples, one of which", "start": 2633.0, "duration": 2.78}, {"text": "lifted from my teaching,\none from my research.", "start": 2635.78, "duration": 3.75}, {"text": "If you continue\nwith me next fall,", "start": 2639.53, "duration": 2.49}, {"text": "we'll teach 6.837, which is\nthe Intro to Computer Graphics", "start": 2642.02, "duration": 3.21}, {"text": "course.", "start": 2645.23, "duration": 0.608}, {"text": "One thing that's always\namazing to students", "start": 2645.838, "duration": 1.792}, {"text": "is, these, algorithms\nthat produce", "start": 2647.63, "duration": 1.417}, {"text": "these really beautiful\nimages, can fit in about 10,", "start": 2649.047, "duration": 2.633}, {"text": "20 lines of code.", "start": 2651.68, "duration": 1.84}, {"text": "So really, this is\ntotally facetious,", "start": 2653.52, "duration": 2.11}, {"text": "because if you want\nthose beautiful images", "start": 2655.63, "duration": 1.75}, {"text": "and you use those\n20 lines of code,", "start": 2657.38, "duration": 1.468}, {"text": "you'll be waiting until\nthe death of the universe", "start": 2658.848, "duration": 2.042}, {"text": "to actually compute\nthese things.", "start": 2660.89, "duration": 2.85}, {"text": "But in any event, one nice\none for rendering-- so", "start": 2663.74, "duration": 2.575}, {"text": "drawing a bunch of\nshapes [INAUDIBLE],,", "start": 2666.315, "duration": 1.625}, {"text": "something called ray casting,\nor its better known cousin,", "start": 2667.94, "duration": 4.35}, {"text": "ray tracing.", "start": 2672.29, "duration": 1.02}, {"text": "Typically, the difference\nis whether your rays", "start": 2673.31, "duration": 2.28}, {"text": "can bounce off of the surface\nand have a secondary thing.", "start": 2675.59, "duration": 3.24}, {"text": "Right.", "start": 2678.83, "duration": 0.885}, {"text": "Here's the ray\ncasting algorithm.", "start": 2679.715, "duration": 1.375}, {"text": "Let's say I have a scene built\nout of spheres and cubes.", "start": 2681.09, "duration": 3.47}, {"text": "I'm going to have a for\nloop over every pixel", "start": 2684.56, "duration": 1.92}, {"text": "on the computer screen.", "start": 2686.48, "duration": 1.44}, {"text": "For every pixel,\nI've got to discover", "start": 2687.92, "duration": 1.65}, {"text": "what color that should be.", "start": 2689.57, "duration": 1.38}, {"text": "So I shoot a ray from my\neyeball through that pixel", "start": 2690.95, "duration": 3.21}, {"text": "and find the first\nobject that it runs into.", "start": 2694.16, "duration": 3.17}, {"text": "It's not so hard to\nintersect a line of a sphere", "start": 2697.33, "duration": 2.0}, {"text": "or a line of a cube.", "start": 2699.33, "duration": 1.76}, {"text": "So what is that algorithm?", "start": 2701.09, "duration": 1.28}, {"text": "I've given it to you\non the screen here.", "start": 2702.37, "duration": 1.88}, {"text": "Not too bad to think about.", "start": 2704.25, "duration": 1.79}, {"text": "And I think you guys\nare all extremely well", "start": 2706.04, "duration": 2.25}, {"text": "equipped to analyze\nthe runtime of this,", "start": 2708.29, "duration": 2.56}, {"text": "which is roughly\nthe number of pixels", "start": 2710.85, "duration": 2.36}, {"text": "times the number of objects.", "start": 2713.21, "duration": 1.2}, {"text": "Because for every\npixel, I've got", "start": 2714.41, "duration": 1.41}, {"text": "to decide what object the ray\nout of my eyeball hits first.", "start": 2715.82, "duration": 3.62}, {"text": "So I need a for loop\nover [INAUDIBLE]..", "start": 2719.44, "duration": 2.22}, {"text": "Make sense?", "start": 2721.66, "duration": 1.7}, {"text": "Cool.", "start": 2723.36, "duration": 0.5}, {"text": "So let's look at a\nbasic rendering problem.", "start": 2723.86, "duration": 3.73}, {"text": "In fact, Erik already secretly\nsnuck this one in here.", "start": 2727.59, "duration": 3.49}, {"text": "There's a very famous 3D model\ncalled the Stanford bunny.", "start": 2731.08, "duration": 3.82}, {"text": "The Stanford bunny is\nactually a great example", "start": 2734.9, "duration": 2.16}, {"text": "of a simplicial complex--", "start": 2737.06, "duration": 1.57}, {"text": "in fact, a manifold one,\ntriangulated surface.", "start": 2738.63, "duration": 3.56}, {"text": "Actually, I'm not sure it's\nmanifold in its original form.", "start": 2742.19, "duration": 3.24}, {"text": "But usually, it is.", "start": 2745.43, "duration": 1.57}, {"text": "And this innocent-looking,\nextremely famous 3D model", "start": 2747.0, "duration": 3.54}, {"text": "is actually quite pernicious.", "start": 2750.54, "duration": 1.74}, {"text": "It's composed of\n69,000 triangles.", "start": 2752.28, "duration": 4.2}, {"text": "And if I wanted\n1080p-- like a high def", "start": 2756.48, "duration": 4.11}, {"text": "rendering of my triangle--\nthen, of course,", "start": 2760.59, "duration": 2.04}, {"text": "there's two million\npixels on the screen.", "start": 2762.63, "duration": 2.29}, {"text": "So if we look at our\nbig O expression,", "start": 2764.92, "duration": 1.94}, {"text": "roughly, our\ncomputation time scales", "start": 2766.86, "duration": 1.5}, {"text": "like the product of\nthose two big numbers.", "start": 2768.36, "duration": 2.38}, {"text": "So just to render\nthis ugly gray bunny", "start": 2770.74, "duration": 2.33}, {"text": "takes me a pretty\nlarge amount of time.", "start": 2773.07, "duration": 2.74}, {"text": "And in fact, the reality--\nby the way, the bunny", "start": 2775.81, "duration": 2.0}, {"text": "is this famous test case\nin computer graphics,", "start": 2777.81, "duration": 1.95}, {"text": "so if you take my class, you'll\nbe rendering buddies all day.", "start": 2779.76, "duration": 3.42}, {"text": "The reality is,\nwe don't want just", "start": 2783.18, "duration": 1.62}, {"text": "grayed, flat-shaded bunnies.", "start": 2784.8, "duration": 1.29}, {"text": "We want bunnies that are\ntransparent, and reflecting", "start": 2786.09, "duration": 3.48}, {"text": "stuff, and I shoot my\nbunny with a bullet", "start": 2789.57, "duration": 2.37}, {"text": "and shatters into a\nmillion pieces, and all", "start": 2791.94, "duration": 1.89}, {"text": "of these cool things.", "start": 2793.83, "duration": 1.54}, {"text": "So of course that,\nray casting algorithm,", "start": 2795.37, "duration": 2.1}, {"text": "with each one of these new\ngraphics features I add,", "start": 2797.47, "duration": 2.84}, {"text": "only adds to the time\ncomplexity of the technique", "start": 2800.31, "duration": 3.39}, {"text": "that I implement.", "start": 2803.7, "duration": 1.075}, {"text": "So pretty quickly-- and indeed,\nif you write your own ray", "start": 2804.775, "duration": 2.375}, {"text": "tracer at home, which I\nstrongly encourage you to do--", "start": 2807.15, "duration": 2.82}, {"text": "what you will discover\nis that a [INAUDIBLE]", "start": 2809.97, "duration": 2.61}, {"text": "would be the technical phrase.", "start": 2812.58, "duration": 2.503}, {"text": "What is our way out of this?", "start": 2815.083, "duration": 1.167}, {"text": "Well, if you take\nit 837, you'll see", "start": 2816.25, "duration": 2.99}, {"text": "that our way out\nof these problems,", "start": 2819.24, "duration": 1.53}, {"text": "in graphics, is data\nstructures and algorithms.", "start": 2820.77, "duration": 2.31}, {"text": "It's completely unavoidable.", "start": 2823.08, "duration": 2.16}, {"text": "For instance, obviously, we\nspent quite a bit of time", "start": 2825.24, "duration": 2.34}, {"text": "in this course talking\nabout AVL trees.", "start": 2827.58, "duration": 3.09}, {"text": "In 837, we'll spend a big\nchunk of our tours talking", "start": 2830.67, "duration": 3.3}, {"text": "about space partitioning trees.", "start": 2833.97, "duration": 2.82}, {"text": "Here-- I actually forgot\nwhat kind of tree this is.", "start": 2836.79, "duration": 3.54}, {"text": "I think it's a KD tree.", "start": 2840.33, "duration": 2.85}, {"text": "Doesn't matter.", "start": 2843.18, "duration": 1.47}, {"text": "In any event, one\nthing I could do", "start": 2844.65, "duration": 1.8}, {"text": "is take all of the\ntriangles of my bunny,", "start": 2846.45, "duration": 3.36}, {"text": "and I could put the entire\nbunny in a giant cube", "start": 2849.81, "duration": 3.42}, {"text": "with the property that the\ncube is outside the bunny.", "start": 2853.23, "duration": 2.55}, {"text": "Let's say I cast a ray and the\nray doesn't touch the cube.", "start": 2855.78, "duration": 4.03}, {"text": "Can the ray touch the bunny?", "start": 2859.81, "duration": 1.96}, {"text": "No, right?", "start": 2861.77, "duration": 0.5}, {"text": "It zings right past it.", "start": 2862.27, "duration": 1.93}, {"text": "So suddenly, I just saved myself\na lot of computation time,", "start": 2864.2, "duration": 2.48}, {"text": "right?", "start": 2866.68, "duration": 0.5}, {"text": "I don't have to iterate over\nall the triangles inside", "start": 2867.18, "duration": 2.44}, {"text": "of the body to see whether\nthey hit the ray or not,", "start": 2869.62, "duration": 2.322}, {"text": "because I already\nconvinced myself,", "start": 2871.942, "duration": 1.458}, {"text": "by this conservative\ntest, that I", "start": 2873.4, "duration": 2.19}, {"text": "didn't hit even the bounding\nbox of the whole bunny.", "start": 2875.59, "duration": 4.24}, {"text": "Well, that's sort of a\nnice order 1 speed-up.", "start": 2879.83, "duration": 2.29}, {"text": "But depending on\nhow big the bunny", "start": 2882.12, "duration": 1.52}, {"text": "is relative to the size\nof my rendered image,", "start": 2883.64, "duration": 2.01}, {"text": "that might not be a super\nuseful efficiency test.", "start": 2885.65, "duration": 3.7}, {"text": "But of course, what could I do?", "start": 2889.35, "duration": 1.41}, {"text": "I could take the box\ncontaining the bunny,", "start": 2890.76, "duration": 1.94}, {"text": "I could slice it in half,\nand now it's saying,", "start": 2892.7, "duration": 2.855}, {"text": "does my ray hit the front\nor the back of the bunny?", "start": 2895.555, "duration": 2.125}, {"text": "Or maybe both.", "start": 2897.68, "duration": 0.63}, {"text": "That's where you've got to--\nthat's where things get gnarly.", "start": 2898.31, "duration": 3.22}, {"text": "And so on.", "start": 2901.53, "duration": 1.075}, {"text": "So now you have this nice\nrecursive tree structure,", "start": 2902.605, "duration": 2.125}, {"text": "where I keep taking the\nbox containing my bunny", "start": 2904.73, "duration": 2.01}, {"text": "and chopping it in\nhalf and placing--", "start": 2906.74, "duration": 2.88}, {"text": "in some sense, usually,\nthe triangles--", "start": 2909.62, "duration": 3.13}, {"text": "maybe not the leaves of my\ntree, but [INAUDIBLE] that's", "start": 2912.75, "duration": 2.34}, {"text": "probably good enough.", "start": 2915.09, "duration": 1.42}, {"text": "You get a structure like what\nyou see on the screen here.", "start": 2916.51, "duration": 3.28}, {"text": "And why should you do that?", "start": 2919.79, "duration": 1.33}, {"text": "Well, remember, it takes pn time\nto render my image of my bunny", "start": 2921.12, "duration": 3.59}, {"text": "normally.", "start": 2924.71, "duration": 1.14}, {"text": "Well, now, the\npicture is actually", "start": 2925.85, "duration": 3.0}, {"text": "misleadingly suggestive.", "start": 2928.85, "duration": 1.86}, {"text": "But you might think that,\nmaybe, it takes roughly--", "start": 2930.71, "duration": 2.46}, {"text": "remember, n is the number\nof objects in my scene--", "start": 2933.17, "duration": 2.88}, {"text": "p log n time to\nrender my bunny now,", "start": 2936.05, "duration": 2.7}, {"text": "because I can kind of\ntraverse the tree of objects", "start": 2938.75, "duration": 2.85}, {"text": "in my scene.", "start": 2941.6, "duration": 1.33}, {"text": "Of course, notice, I put\na question mark here.", "start": 2942.93, "duration": 2.57}, {"text": "And the devil's in\nthe details here.", "start": 2945.5, "duration": 2.632}, {"text": "In fact, I think computer\ngraphics people often", "start": 2948.132, "duration": 1.958}, {"text": "believe that their rendering\nalgorithm takes p log n time.", "start": 2950.09, "duration": 3.49}, {"text": "That's often not\npossible, although kind", "start": 2953.58, "duration": 3.05}, {"text": "of an interesting\nquestion, which", "start": 2956.63, "duration": 1.44}, {"text": "is, the heuristics they use for\nbuilding these sorts of trees", "start": 2958.07, "duration": 3.3}, {"text": "often do, on average,\ngive them log n time.", "start": 2961.37, "duration": 2.68}, {"text": "And so there's\nsomething about the data", "start": 2964.05, "duration": 1.7}, {"text": "that's making this problem\neasier than it might seem.", "start": 2965.75, "duration": 2.983}, {"text": "So we'll dig into that a little\nbit in the graphics class.", "start": 2968.733, "duration": 2.417}, {"text": "Of course, you're not going\nto proof as many bounds", "start": 2971.15, "duration": 2.125}, {"text": "as you might in a theory course.", "start": 2973.275, "duration": 1.64}, {"text": "But we're certainly\nbuilding on the intuition", "start": 2974.915, "duration": 1.875}, {"text": "that we've seen in this class\nto build on practical data", "start": 2976.79, "duration": 2.58}, {"text": "structures.", "start": 2979.37, "duration": 0.653}, {"text": "And these data structures\nappear everywhere", "start": 2980.023, "duration": 1.792}, {"text": "in computer graphics.", "start": 2981.815, "duration": 1.335}, {"text": "For instance, directed\nacyclic graphs", "start": 2983.15, "duration": 4.47}, {"text": "appear all over the place in\ncomputer graphics literature", "start": 2987.62, "duration": 3.03}, {"text": "to describe 3D scenes.", "start": 2990.65, "duration": 1.65}, {"text": "For example, this classroom\nis a stark reminder", "start": 2992.3, "duration": 3.15}, {"text": "of why we need DAGs\nand computer graphics,", "start": 2995.45, "duration": 3.18}, {"text": "because we have all of\nthese empty seats here,", "start": 2998.63, "duration": 1.95}, {"text": "and they're all\ncopies of one another.", "start": 3000.58, "duration": 2.41}, {"text": "So would it make sense for\nme to store however many,", "start": 3002.99, "duration": 3.32}, {"text": "like, 100 3D molds\nof the same chair?", "start": 3006.31, "duration": 2.61}, {"text": "Probably not.", "start": 3008.92, "duration": 1.87}, {"text": "So instead, what do I do?", "start": 3010.79, "duration": 1.32}, {"text": "I store one instance of a chair,\nand then some instructions", "start": 3012.11, "duration": 3.11}, {"text": "on how to tile it\ninto my entire scene.", "start": 3015.22, "duration": 3.62}, {"text": "One way that I can\ndo that is to think", "start": 3018.84, "duration": 1.89}, {"text": "of there being a\nnode in a graph which", "start": 3020.73, "duration": 2.16}, {"text": "knows how to draw one chair.", "start": 3022.89, "duration": 2.4}, {"text": "And now, I can have a\nbunch of different nodes", "start": 3025.29, "duration": 1.92}, {"text": "in my scene for all of\nthe instances of the chair", "start": 3027.21, "duration": 2.042}, {"text": "and then store a different\ntransformation for each one.", "start": 3029.252, "duration": 2.78}, {"text": "So if you think about\nthe graph structure here,", "start": 3032.032, "duration": 1.958}, {"text": "each of those ones is going to\npoint into the same 3D model", "start": 3033.99, "duration": 3.09}, {"text": "of the chair for rendering.", "start": 3037.08, "duration": 1.75}, {"text": "And that makes a directed\nacyclic graph structure", "start": 3038.83, "duration": 2.692}, {"text": "called a scene graph, which\nwe'll spend quite a bit of time", "start": 3041.522, "duration": 2.458}, {"text": "talking about in 837, how\nto traverse and construct", "start": 3043.98, "duration": 2.91}, {"text": "all that good stuff.", "start": 3046.89, "duration": 3.06}, {"text": "And there are lots of\ndifferent models of computation", "start": 3049.95, "duration": 2.43}, {"text": "in that universe, as well.", "start": 3052.38, "duration": 1.74}, {"text": "Your graphics card is\na very specific kind", "start": 3054.12, "duration": 4.38}, {"text": "of parallel processor\nthat's kind of like Lucille", "start": 3058.5, "duration": 2.43}, {"text": "Ball on the conveyor belt,\nhammering at the same object", "start": 3060.93, "duration": 3.03}, {"text": "over and over again.", "start": 3063.96, "duration": 1.12}, {"text": "But if you ask it to do\nanything other than the one", "start": 3065.08, "duration": 2.125}, {"text": "thing it knows how to do to\na bunch of data at a time,", "start": 3067.205, "duration": 2.285}, {"text": "then all of your computation\ngrinds to a halt.", "start": 3069.49, "duration": 2.16}, {"text": "This is called Single\nInstruction Multiple Data", "start": 3071.65, "duration": 2.66}, {"text": "parallelism, SIMD.", "start": 3074.31, "duration": 2.04}, {"text": "Numerical algorithms\nmatter a lot", "start": 3076.35, "duration": 1.59}, {"text": "for things like\nfluid simulation.", "start": 3077.94, "duration": 2.25}, {"text": "And approximation algorithms\nare quite critical, too.", "start": 3080.19, "duration": 4.23}, {"text": "In computer graphics,\nthe complexity", "start": 3084.42, "duration": 2.07}, {"text": "is kind of interesting,\nbecause of course, your eyeball", "start": 3086.49, "duration": 3.12}, {"text": "is sensitive to\nabout 29.97 frames", "start": 3089.61, "duration": 3.12}, {"text": "per second worth of material.", "start": 3092.73, "duration": 3.15}, {"text": "You can choose that time to\ndo really well-rendering one", "start": 3095.88, "duration": 3.278}, {"text": "object, but then you take out\nof the time rendering something", "start": 3099.158, "duration": 2.542}, {"text": "else.", "start": 3101.7, "duration": 1.26}, {"text": "There's kind of an\ninteresting conservation law", "start": 3102.96, "duration": 2.13}, {"text": "that you have to\nbalance when you solve", "start": 3105.09, "duration": 1.625}, {"text": "these kinds of problems, which\nis an interesting balance, now,", "start": 3106.715, "duration": 2.965}, {"text": "between complexity and\nruntime of your algorithm", "start": 3109.68, "duration": 3.24}, {"text": "and perception.", "start": 3112.92, "duration": 1.26}, {"text": "What things can you get away\nwith when you draw a scene?", "start": 3114.18, "duration": 2.79}, {"text": "And maybe I can do tons\nof extra computation", "start": 3116.97, "duration": 2.522}, {"text": "to get that extra shadow,\nbut it's just not worth it.", "start": 3119.492, "duration": 2.208}, {"text": "I'll quickly sketch out\nanother completely different", "start": 3124.31, "duration": 2.46}, {"text": "application of the\nmaterial that we've covered", "start": 3126.77, "duration": 3.19}, {"text": "in 6.006 from my own research.", "start": 3129.96, "duration": 2.49}, {"text": "Again, just like Erik--", "start": 3132.45, "duration": 1.07}, {"text": "I guess, in a funny way,\nboth of our groups, I think,", "start": 3133.52, "duration": 2.208}, {"text": "are kind of broad in terms of\nsubject material, rather than--", "start": 3135.728, "duration": 2.892}, {"text": "some of our colleagues\nhave really laser focus", "start": 3138.62, "duration": 2.1}, {"text": "on one topic or another.", "start": 3140.72, "duration": 3.06}, {"text": "Another Research area that\nI have sort of backed into", "start": 3143.78, "duration": 3.5}, {"text": "is the area of\npolitical redistricting.", "start": 3147.28, "duration": 2.5}, {"text": "This is relevant in\nthe United States.", "start": 3149.78, "duration": 2.125}, {"text": "Recently, I've been\nreading this great proposal", "start": 3151.905, "duration": 1.235}, {"text": "about other countries, which\nis really interesting, how", "start": 3153.14, "duration": 2.292}, {"text": "they do this stuff.", "start": 3155.432, "duration": 2.118}, {"text": "In the US, when we vote\nfor people in Congress--", "start": 3157.55, "duration": 3.15}, {"text": "by the way, not\nnecessarily for presidents.", "start": 3160.7, "duration": 2.2}, {"text": "This is a common misconception.", "start": 3162.9, "duration": 1.97}, {"text": "But certainly for\nCongress, your state", "start": 3164.87, "duration": 3.6}, {"text": "is divided into little\nregions, each of which", "start": 3168.47, "duration": 1.95}, {"text": "elects one member of the House.", "start": 3170.42, "duration": 2.62}, {"text": "And there's sort of a\nsubtle problem if you're not", "start": 3173.04, "duration": 3.935}, {"text": "used to thinking\nabout it, or one", "start": 3176.975, "duration": 1.375}, {"text": "that's staring you in the\nface and screaming, depending", "start": 3178.35, "duration": 2.292}, {"text": "on how often you read\nthe news and politics.", "start": 3180.642, "duration": 3.181}, {"text": "There is an issue\ncalled gerrymandering,", "start": 3183.823, "duration": 1.667}, {"text": "where your legislature draws the\nlines for what area on the map", "start": 3185.49, "duration": 3.54}, {"text": "elects a member of Congress.", "start": 3189.03, "duration": 2.61}, {"text": "And depending on how\nyou draw the lines,", "start": 3191.64, "duration": 2.22}, {"text": "you can engineer\ndifferent results", "start": 3193.86, "duration": 1.56}, {"text": "for who's likely to get elected.", "start": 3195.42, "duration": 1.8}, {"text": "So for instance, maybe\nthere's some minority.", "start": 3197.22, "duration": 1.92}, {"text": "I can cluster them all together\ninto one voting district.", "start": 3199.14, "duration": 2.55}, {"text": "Then they will only\nget the opportunity", "start": 3201.69, "duration": 1.77}, {"text": "to elect one person.", "start": 3203.46, "duration": 1.23}, {"text": "But maybe, if I divide the\nspace where they live into two,", "start": 3204.69, "duration": 4.08}, {"text": "I managed to engineer\ntwo districts", "start": 3208.77, "duration": 2.01}, {"text": "with a high probability\nof electing somebody", "start": 3210.78, "duration": 2.28}, {"text": "with their political\ninterests in mind.", "start": 3213.06, "duration": 3.21}, {"text": "It turns out that\npolitical redistricting,", "start": 3216.27, "duration": 2.49}, {"text": "in a broad sense, is a great\nproblem, computationally.", "start": 3218.76, "duration": 2.67}, {"text": "Even if you're a totally\nheartless theorist,", "start": 3221.43, "duration": 1.84}, {"text": "there are some really\nfun problems here.", "start": 3223.27, "duration": 2.012}, {"text": "So for example,\nthe state of Iowa--", "start": 3225.282, "duration": 1.458}, {"text": "we all pick on Iowa because\nit has a unique law, which", "start": 3226.74, "duration": 3.27}, {"text": "is that districts have to be\nbuilt out of counties, which", "start": 3230.01, "duration": 2.52}, {"text": "are much larger than\nthe typical census unit,", "start": 3232.53, "duration": 2.26}, {"text": "so it computationally is easier.", "start": 3234.79, "duration": 1.92}, {"text": "But even in Iowa,\nwhich is a giant grid--", "start": 3236.71, "duration": 3.103}, {"text": "with the exception of one\nshift in the middle, which", "start": 3239.813, "duration": 2.167}, {"text": "is fascinating to me--", "start": 3241.98, "duration": 2.82}, {"text": "I know [INAUDIBLE], fun fact.", "start": 3244.8, "duration": 2.07}, {"text": "Literally, people were\nmaking the map of Iowa,", "start": 3246.87, "duration": 2.01}, {"text": "and they worked from the\nbottom up and the top down,", "start": 3248.88, "duration": 1.8}, {"text": "and it meets in the middle\nand their grids were shifted,", "start": 3250.68, "duration": 2.58}, {"text": "and now we're stuck with that.", "start": 3253.26, "duration": 1.53}, {"text": "And it has an interesting effect\non the topology of the graph,", "start": 3254.79, "duration": 2.16}, {"text": "because it looks like\nsquares, but then there's", "start": 3256.95, "duration": 1.958}, {"text": "triangles in the middle.", "start": 3258.908, "duration": 1.552}, {"text": "But in any event,\neven though there's", "start": 3260.46, "duration": 3.21}, {"text": "only 99 counties\nin four districts,", "start": 3263.67, "duration": 1.86}, {"text": "there's approximately\nquintillions of possible ways", "start": 3265.53, "duration": 3.0}, {"text": "you can divide that state into\nfour contiguous districts that", "start": 3268.53, "duration": 3.09}, {"text": "satisfy the rules as they were--", "start": 3271.62, "duration": 2.01}, {"text": "at least, if you read the\ncode literally in the law.", "start": 3273.63, "duration": 4.842}, {"text": "It seems like\ncomputers are useful,", "start": 3278.472, "duration": 1.458}, {"text": "but unfortunately, it's\na little subtle how.", "start": 3279.93, "duration": 2.31}, {"text": "For instance, there's no\nsingle \"best\" districting", "start": 3282.24, "duration": 2.49}, {"text": "plan out there.", "start": 3284.73, "duration": 1.345}, {"text": "I can't think of a single\nstate with a law that gives you", "start": 3286.075, "duration": 2.375}, {"text": "an objective function, similar\nto whatever cute characters", "start": 3288.45, "duration": 5.61}, {"text": "that we've had in 6.006.", "start": 3294.06, "duration": 1.47}, {"text": "They often have very\nclear objectives in life,", "start": 3295.53, "duration": 2.43}, {"text": "but unfortunately,\nredistricting, that's", "start": 3297.96, "duration": 2.1}, {"text": "very rarely the case.", "start": 3300.06, "duration": 0.99}, {"text": "You have to balance\ncontiguity, population balance,", "start": 3301.05, "duration": 2.52}, {"text": "compactness, all of\nthese different things.", "start": 3303.57, "duration": 3.51}, {"text": "Reality check number two\nis that, even if somebody", "start": 3307.08, "duration": 2.4}, {"text": "did give you an\nobjective function,", "start": 3309.48, "duration": 2.19}, {"text": "for just about any interesting\nobjective function,", "start": 3311.67, "duration": 2.2}, {"text": "it's very obvious that\ngenerating the best possible", "start": 3313.87, "duration": 3.14}, {"text": "districting plan is NP-hard.", "start": 3317.01, "duration": 3.18}, {"text": "And by the way, it\ndoesn't even matter,", "start": 3320.19, "duration": 1.65}, {"text": "because the law doesn't\nsay that computers have", "start": 3321.84, "duration": 2.73}, {"text": "to draw the best districts.", "start": 3324.57, "duration": 1.77}, {"text": "Even if P equals NP\nreally could extract", "start": 3326.34, "duration": 2.43}, {"text": "the best possible districting\nplan using an algorithm,", "start": 3328.77, "duration": 3.683}, {"text": "it doesn't mean you have\nto use it, at least the way", "start": 3332.453, "duration": 2.167}, {"text": "the law's written now.", "start": 3334.62, "duration": 1.71}, {"text": "Interestingly, this is not true\nin certain parts of Mexico,", "start": 3336.33, "duration": 2.53}, {"text": "where they actually make\nyou compare your districting", "start": 3338.86, "duration": 2.208}, {"text": "plan against a\ncomputer-generated one, which", "start": 3341.068, "duration": 1.839}, {"text": "is philosophically\nreally interesting,", "start": 3342.907, "duration": 1.583}, {"text": "although in practice, it\ndoesn't work terribly well.", "start": 3344.49, "duration": 2.256}, {"text": "Our researchers studied analysis\nof districting plans instead.", "start": 3349.35, "duration": 2.883}, {"text": "So instead of running a\npiece of software that", "start": 3352.233, "duration": 1.917}, {"text": "takes in your state,\ndraws your districts,", "start": 3354.15, "duration": 2.13}, {"text": "and then you're done--", "start": 3356.28, "duration": 1.26}, {"text": "instead, we ask\nstatistical questions", "start": 3357.54, "duration": 1.92}, {"text": "about, I propose a\ndistricting plan,", "start": 3359.46, "duration": 2.31}, {"text": "what does it look like\nrelative to the space", "start": 3361.77, "duration": 2.1}, {"text": "of the possibilities?", "start": 3363.87, "duration": 3.517}, {"text": "So that, of course,\nbegs the question,", "start": 3367.387, "duration": 1.583}, {"text": "what are the possibilities?", "start": 3368.97, "duration": 1.6}, {"text": "So these are the connected\ngraph partitions.", "start": 3370.57, "duration": 2.45}, {"text": "Meaning, you have a graph,\nand you take the vertices", "start": 3373.02, "duration": 2.97}, {"text": "and you cluster them together\nin a way where they're", "start": 3375.99, "duration": 2.168}, {"text": "connected to one another.", "start": 3378.158, "duration": 1.042}, {"text": "The one thing that we all agree\non-- actually, philosophically,", "start": 3379.2, "duration": 3.21}, {"text": "it's questionable why--", "start": 3382.41, "duration": 1.452}, {"text": "is that you should\nbe able to start", "start": 3383.862, "duration": 1.458}, {"text": "at any point in your district\nand walk to any other one", "start": 3385.32, "duration": 2.46}, {"text": "without leaving.", "start": 3387.78, "duration": 1.497}, {"text": "These days, with\nthe internet, it's", "start": 3389.277, "duration": 1.458}, {"text": "not clear that that's\nactually the best criterion.", "start": 3390.735, "duration": 2.535}, {"text": "But that's a law that,\nI think, is never", "start": 3393.27, "duration": 1.71}, {"text": "going to get passed\nin the near future.", "start": 3394.98, "duration": 4.848}, {"text": "Anyway, I think I'm\nout of time, so I", "start": 3399.828, "duration": 1.542}, {"text": "don't think I'll walk you\nguys through the theory here.", "start": 3401.37, "duration": 3.173}, {"text": "Maybe I'll leave\nit in the slides.", "start": 3404.543, "duration": 1.417}, {"text": "There's a sort of\nvery simple proof", "start": 3405.96, "duration": 2.43}, {"text": "that can show that, at least the\nvery simplest thing you might", "start": 3408.39, "duration": 2.64}, {"text": "think of for analyzing\nyour districting plan,", "start": 3411.03, "duration": 1.875}, {"text": "which is to say,\nyou propose a plan,", "start": 3412.905, "duration": 2.385}, {"text": "and now, I want your\nplan to be at least as", "start": 3415.29, "duration": 2.52}, {"text": "good, under some axis, as\nit's a randomly drawn one", "start": 3417.81, "duration": 3.54}, {"text": "from the space of all possible\nconnected partitions--", "start": 3421.35, "duration": 2.46}, {"text": "all of the possible ways\nI could draw the lines.", "start": 3423.81, "duration": 2.587}, {"text": "Well, then, it might\nbe useful to have", "start": 3426.397, "duration": 1.583}, {"text": "a piece of software that\ncould just randomly draw", "start": 3427.98, "duration": 2.53}, {"text": "such a thing.", "start": 3430.51, "duration": 1.25}, {"text": "So in other words,\nto draw something", "start": 3431.76, "duration": 1.5}, {"text": "where the probability\nof any one partition", "start": 3433.26, "duration": 2.04}, {"text": "is 1 over the number\nof partitions.", "start": 3435.3, "duration": 2.76}, {"text": "This seems innocent.", "start": 3438.06, "duration": 1.393}, {"text": "In fact, there's a\nnumber of papers that", "start": 3439.453, "duration": 1.667}, {"text": "claim to do things like this.", "start": 3441.12, "duration": 1.89}, {"text": "But it turns out that it's\ncomputationally difficult,", "start": 3443.01, "duration": 4.56}, {"text": "assuming that you believe\nthat P doesn't equal NP.", "start": 3447.57, "duration": 2.4}, {"text": "So I'll maybe leave\nsome suggestive pictures", "start": 3449.97, "duration": 2.58}, {"text": "in the slide that we can--", "start": 3452.55, "duration": 1.89}, {"text": "if you guys text me, or if we\nhave a professor-student chat,", "start": 3454.44, "duration": 4.32}, {"text": "I'm happy to sketch\nit out to you then.", "start": 3458.76, "duration": 2.4}, {"text": "There's a very nice,\neasy proof that", "start": 3461.16, "duration": 2.01}, {"text": "reduces this to\nHamiltonian cycle,", "start": 3463.17, "duration": 2.67}, {"text": "and shows you that maybe you\nshouldn't trust these tools,", "start": 3465.84, "duration": 2.633}, {"text": "as much as they're\nargued about, literally,", "start": 3468.473, "duration": 1.792}, {"text": "in the Supreme Court a\ncouple of months ago.", "start": 3470.265, "duration": 2.115}, {"text": "By the way, it was pretty fun.", "start": 3472.38, "duration": 1.47}, {"text": "Our expert report was referenced\nin the defense of the case", "start": 3473.85, "duration": 3.57}, {"text": "last summer.", "start": 3477.42, "duration": 1.145}, {"text": "And when you read\nthe discussion,", "start": 3478.565, "duration": 1.375}, {"text": "you can see the\njudges trying to talk", "start": 3479.94, "duration": 1.38}, {"text": "their way around complexity.", "start": 3481.32, "duration": 1.23}, {"text": "And it's an interesting,\nif somewhat dry, read.", "start": 3482.55, "duration": 5.127}, {"text": "In any event, that's\njust the starting point", "start": 3487.677, "duration": 1.833}, {"text": "for our research, which\nsays that, of course,", "start": 3489.51, "duration": 1.875}, {"text": "these sampling problems\nare really hard.", "start": 3491.385, "duration": 1.695}, {"text": "The questions is,\nwhat can you do?", "start": 3493.08, "duration": 1.8}, {"text": "[INAUDIBLE] or not.", "start": 3494.88, "duration": 3.03}, {"text": "But the real message\nhere is, of course,", "start": 3497.91, "duration": 2.89}, {"text": "that this course is unavoidable.", "start": 3500.8, "duration": 1.64}, {"text": "Even in these extremely\napplied problems", "start": 3502.44, "duration": 1.92}, {"text": "showing up in court cases or on\nyour graphics card, you still--", "start": 3504.36, "duration": 3.63}, {"text": "complexity and algorithms\nand data structures", "start": 3507.99, "duration": 2.55}, {"text": "are going to come back to play.", "start": 3510.54, "duration": 2.69}, {"text": "So with that, our\nother two instructors", "start": 3513.23, "duration": 2.86}, {"text": "up here for our final farewell--\nsuitably distance ourselves.", "start": 3516.09, "duration": 4.68}, {"text": "ERIK DEMAINE: So\nalgorithms are everywhere.", "start": 3520.77, "duration": 1.89}, {"text": "I hope you enjoyed this class.", "start": 3522.66, "duration": 1.965}, {"text": "It's been a lot of fun teaching\nyou and having you as students.", "start": 3524.625, "duration": 2.625}, {"text": "Even though you're not here\nphysically in the room,", "start": 3527.25, "duration": 1.8}, {"text": "we still feel your presence.", "start": 3529.05, "duration": 1.41}, {"text": "And I look forward to\nseeing you all soon.", "start": 3530.46, "duration": 3.22}, {"text": "Thanks for being a\npart of this fun thing.", "start": 3533.68, "duration": 3.36}, {"text": "I want to thank our two--", "start": 3537.04, "duration": 2.57}, {"text": "my two co-instructors for an\nawesome time this semester.", "start": 3539.61, "duration": 3.76}, {"text": "It's been a lot of fun\nteaching to you guys.", "start": 3543.37, "duration": 2.96}, {"text": "JASON KU: Thanks for spending\n006 with us this term.", "start": 3546.33, "duration": 2.245}, {"text": "JUSTIN SOLOMON: Yeah.", "start": 3548.575, "duration": 0.875}, {"text": "Thank you.", "start": 3549.45, "duration": 0.4}, {"text": "And hopefully we'll\nsee you again soon.", "start": 3549.85, "duration": 1.41}, {"text": "ERIK DEMAINE: Bye.", "start": 3551.26, "duration": 0.75}, {"text": "JASON KU: Bye.", "start": 3552.01, "duration": 1.26}]
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+[{"text": "[SQUEAKING]", "start": 0.964, "duration": 1.446}, {"text": "[RUSTLING]", "start": 2.41, "duration": 0.964}, {"text": "[CLICKING]", "start": 3.374, "duration": 2.41}, {"text": "NORVIN RICHARDS: All right.", "start": 12.215, "duration": 1.125}, {"text": "Let's progress, then.", "start": 13.34, "duration": 2.985}, {"text": "So last time we got started\ndrawing trees for sentences.", "start": 19.34, "duration": 4.41}, {"text": "I spent a lot of time\nwith verb phrases", "start": 23.75, "duration": 3.21}, {"text": "drawing trees for more and\nmore elaborate verb phrases", "start": 26.96, "duration": 3.54}, {"text": "and ignoring repeated requests\nthat I go ahead and diagram", "start": 30.5, "duration": 3.87}, {"text": "the rest of the sentence\nalready, and I finally did.", "start": 34.37, "duration": 4.24}, {"text": "So we had sentences like--", "start": 38.61, "duration": 1.792}, {"text": "I think this was not one of\nthem, but this is like the ones", "start": 40.402, "duration": 2.458}, {"text": "we were talking about--", "start": 42.86, "duration": 0.958}, {"text": "\"She will tickle the child.\"", "start": 43.818, "duration": 1.882}, {"text": "I said we're going to do the\nconstruction of sentences", "start": 45.7, "duration": 4.165}, {"text": "the same way we did the\nconstruction of words", "start": 49.865, "duration": 1.875}, {"text": "back when we were\ndoing morphology.", "start": 51.74, "duration": 1.62}, {"text": "We're going to use\nthis operation \"merge\"", "start": 53.36, "duration": 1.74}, {"text": "which takes pairs of things\nand puts them together", "start": 55.1, "duration": 2.19}, {"text": "to make new things.", "start": 57.29, "duration": 1.18}, {"text": "So we'll merge \"the\" and \"child\"\nand get a new thing, which", "start": 58.47, "duration": 4.13}, {"text": "we'll name a noun\nphrase after the fact", "start": 62.6, "duration": 2.13}, {"text": "that it crucially\ncontains a noun.", "start": 64.73, "duration": 2.58}, {"text": "And we'll merge that\nnoun phrase with the verb", "start": 67.31, "duration": 3.03}, {"text": "\"tickle\" and that's how\nwe get the verb phrase.", "start": 70.34, "duration": 2.07}, {"text": "And then we have\nthese two other words", "start": 72.41, "duration": 1.66}, {"text": "in here, \"she\" and \"will.\"", "start": 74.07, "duration": 2.18}, {"text": "And \"she\" is a noun, a\nspecial kind of noun.", "start": 76.25, "duration": 3.12}, {"text": "It's a pronoun.", "start": 79.37, "duration": 0.95}, {"text": "And \"will,\" I made\nup a name for \"will.\"", "start": 80.32, "duration": 4.42}, {"text": "I called it a \"T.\"", "start": 84.74, "duration": 1.44}, {"text": "T for tense.", "start": 86.18, "duration": 1.753}, {"text": "Actually, that gives\nme too much credit.", "start": 87.933, "duration": 1.667}, {"text": "Other people gave it\nthat name, I'm just", "start": 89.6, "duration": 1.89}, {"text": "transmitting to you that name.", "start": 91.49, "duration": 1.84}, {"text": "Yeah.", "start": 93.33, "duration": 0.5}, {"text": "And then we said,\nif we want to make", "start": 93.83, "duration": 2.43}, {"text": "a tree for the whole\nsentence, what we'll do", "start": 96.26, "duration": 2.1}, {"text": "is first we'll merge T\nwith the verb phrase.", "start": 98.36, "duration": 3.94}, {"text": "So we'll merge those\ntwo things and we'll", "start": 102.3, "duration": 1.88}, {"text": "give the resulting\nobject the label T.", "start": 104.18, "duration": 3.21}, {"text": "And then we'll merge that\nnew object that we've", "start": 107.39, "duration": 3.15}, {"text": "created with the noun.", "start": 110.54, "duration": 3.3}, {"text": "And since, maybe you\nremember, \"phrase\" is just", "start": 113.84, "duration": 3.72}, {"text": "a name for the largest\nthing with a given label,", "start": 117.56, "duration": 4.11}, {"text": "that daughter of TP that\nwe've got there, \"she\"--", "start": 121.67, "duration": 4.53}, {"text": "yeah, it's a noun, but\nit's now also a noun phrase", "start": 126.2, "duration": 2.88}, {"text": "because it's the highest\nthing with its label.", "start": 129.08, "duration": 3.72}, {"text": "That noun phrase and\nits sister, that T bar,", "start": 132.8, "duration": 3.75}, {"text": "become the daughters of this\nnew node that we've created, TP.", "start": 136.55, "duration": 3.63}, {"text": "I said that's the way we're\ngoing to build sentences.", "start": 140.18, "duration": 3.39}, {"text": "Immediately several\nof you objected.", "start": 143.57, "duration": 2.16}, {"text": "Kateryna here, for\nexample, ruthlessly", "start": 145.73, "duration": 2.31}, {"text": "demanded that I explain\nwhy we were doing it", "start": 148.04, "duration": 3.39}, {"text": "in that order and not,\nfor example, like this.", "start": 151.43, "duration": 3.84}, {"text": "We've got \"tickle the child\"\njust like before, but this time", "start": 155.27, "duration": 2.91}, {"text": "we'll merge \"she\"\nwith \"will\" first.", "start": 158.18, "duration": 3.21}, {"text": "It'd be a projecting T. And then\nwe'll merge the result of that", "start": 161.39, "duration": 3.69}, {"text": "with \"tickle the child,\"\ngiving you a TP again--", "start": 165.08, "duration": 3.25}, {"text": "[COUGHS]", "start": 168.33, "duration": 0.68}, {"text": "Excuse me.", "start": 169.01, "duration": 0.96}, {"text": "Giving you a TP again--", "start": 169.97, "duration": 1.26}, {"text": "that didn't help at all, did it?", "start": 171.23, "duration": 2.61}, {"text": "But with a different\nconstituent structure.", "start": 173.84, "duration": 2.725}, {"text": "Several of you wanted to know,\nwhy are we not doing that?", "start": 176.565, "duration": 2.375}, {"text": "Yeah.", "start": 178.94, "duration": 0.81}, {"text": "And I attempted to\nconvince you not", "start": 179.75, "duration": 3.78}, {"text": "to do that with the tools\nthat we have available,", "start": 183.53, "duration": 3.57}, {"text": "the constituent structure\ntests that we've", "start": 187.1, "duration": 4.26}, {"text": "developed in like a day\nand a half of syntax.", "start": 191.36, "duration": 2.37}, {"text": "And I was not able to do\nthat because I had not", "start": 193.73, "duration": 2.82}, {"text": "shown you sufficiently\nsophisticated constituency", "start": 196.55, "duration": 2.19}, {"text": "tests.", "start": 198.74, "duration": 1.38}, {"text": "So I began on the board showing\nyou another constituency test,", "start": 200.12, "duration": 4.95}, {"text": "and I promised you that\ntoday I would use that test", "start": 205.07, "duration": 3.51}, {"text": "to demonstrate that we\nneed the tree on the left", "start": 208.58, "duration": 2.19}, {"text": "and not the tree on\nthe right, and that", "start": 210.77, "duration": 2.01}, {"text": "was a dramatic\ncliffhanger last time.", "start": 212.78, "duration": 2.05}, {"text": "And then I attempted\nto distract you", "start": 214.83, "duration": 1.683}, {"text": "from this by talking about\nother stuff for a little while.", "start": 216.513, "duration": 2.417}, {"text": "That's more or less\nwhere we were last time.", "start": 218.93, "duration": 1.95}, {"text": "Yeah?", "start": 220.88, "duration": 1.5}, {"text": "OK.", "start": 222.38, "duration": 0.5}, {"text": "So now let me attempt\nto distinctly show you", "start": 222.88, "duration": 3.103}, {"text": "that we should have\nthe tree on the left", "start": 225.983, "duration": 1.667}, {"text": "and the tree on the right.", "start": 227.65, "duration": 0.66}, {"text": "And I should tell\nyou that although I'm", "start": 228.31, "duration": 1.625}, {"text": "going to give you a piece\nof evidence for that today,", "start": 229.935, "duration": 3.805}, {"text": "the evidence is going\nto come in in bits", "start": 233.74, "duration": 3.69}, {"text": "over our discussion\nof syntax, which is", "start": 237.43, "duration": 2.58}, {"text": "going to last a little while.", "start": 240.01, "duration": 1.89}, {"text": "So I'll show you one\npiece of evidence now", "start": 241.9, "duration": 2.59}, {"text": "and if you don't like that piece\nof evidence, well, just wait.", "start": 244.49, "duration": 2.69}, {"text": "There will be more.", "start": 247.18, "duration": 1.54}, {"text": "But what I'm going to do\ntoday, thanks to Kateryna,", "start": 248.72, "duration": 2.59}, {"text": "is rush something that I was\nplanning to tell you about much", "start": 251.31, "duration": 2.5}, {"text": "later.", "start": 253.81, "duration": 1.92}, {"text": "So if you don't like what\nI'm about to do, blame her.", "start": 255.73, "duration": 2.87}, {"text": "This was all her idea.", "start": 258.6, "duration": 1.54}, {"text": "OK?", "start": 260.14, "duration": 1.08}, {"text": "Yeah?", "start": 261.22, "duration": 1.23}, {"text": "OK.", "start": 262.45, "duration": 2.33}, {"text": "So here are some data that\nwe talked about last time.", "start": 264.78, "duration": 3.87}, {"text": "Different sentences, I think,\nbut the same general idea.", "start": 268.65, "duration": 4.26}, {"text": "Observation.", "start": 272.91, "duration": 0.67}, {"text": "These are both grammatical\nEnglish sentences:", "start": 273.58, "duration": 1.875}, {"text": "\"She would recognize Mary\"\nand \"Anyone who knows", "start": 275.455, "duration": 3.125}, {"text": "her would recognize Mary.\"", "start": 278.58, "duration": 1.14}, {"text": "They're both English sentences.", "start": 279.72, "duration": 1.68}, {"text": "But there's an interesting\ndifference between them.", "start": 281.4, "duration": 2.94}, {"text": "They both contain pronouns and\nthey contain the name Mary,", "start": 284.34, "duration": 4.71}, {"text": "but they differ in that\nthe first sentence, \"she\"", "start": 289.05, "duration": 3.57}, {"text": "cannot be Mary.", "start": 292.62, "duration": 2.1}, {"text": "It has to be some other\nperson in that first sentence.", "start": 294.72, "duration": 3.33}, {"text": "So that first sentence has to\ninvolve two different people--", "start": 298.05, "duration": 5.68}, {"text": "one of them female, and Mary\nis probably also female, though", "start": 303.73, "duration": 3.15}, {"text": "who knows.", "start": 306.88, "duration": 0.5}, {"text": "Maybe not.", "start": 307.38, "duration": 0.63}, {"text": "Yeah?", "start": 308.01, "duration": 2.84}, {"text": "On the other hand, in\nthe second sentence,", "start": 310.85, "duration": 2.46}, {"text": "\"Anyone who knows her\nwould recognize Mary,\"", "start": 313.31, "duration": 1.95}, {"text": "it's possible that\n\"her\" refers to Mary.", "start": 315.26, "duration": 3.285}, {"text": "Those were the data\nthat we collectively", "start": 318.545, "duration": 2.687}, {"text": "decided on last time\nwhen we were talking", "start": 321.232, "duration": 1.708}, {"text": "about examples like this.", "start": 322.94, "duration": 1.12}, {"text": "And I showed you the second\nkind of example partly--", "start": 324.06, "duration": 3.26}, {"text": "I think somebody\nhopefully offered me", "start": 327.32, "duration": 4.32}, {"text": "a theory of why the\nfirst one was bad.", "start": 331.64, "duration": 1.843}, {"text": "It was the theory I was hoping\nthey would offer where they", "start": 333.483, "duration": 2.417}, {"text": "said, yeah, maybe what's wrong\nwith \"She would recognize", "start": 335.9, "duration": 2.453}, {"text": "Mary\"-- what's wrong with\nhaving \"She\" refer to Mary", "start": 338.353, "duration": 2.167}, {"text": "is that Mary is later\nin the sentence.", "start": 340.52, "duration": 2.94}, {"text": "Pronouns refer to\nother people, but they", "start": 343.46, "duration": 2.13}, {"text": "have to be people who we've\nalready been talking about", "start": 345.59, "duration": 2.25}, {"text": "or something like that.", "start": 347.84, "duration": 0.958}, {"text": "Totally sensible,\nreasonable theory.", "start": 348.798, "duration": 2.822}, {"text": "You might expect it to work\nthat way, and it doesn't.", "start": 351.62, "duration": 3.36}, {"text": "The second sentence shows that\nit's possible for pronouns", "start": 354.98, "duration": 2.73}, {"text": "to refer to things that\nare later in the sentence.", "start": 357.71, "duration": 2.13}, {"text": "Yeah?", "start": 359.84, "duration": 1.2}, {"text": "Cool.", "start": 361.04, "duration": 0.87}, {"text": "So how are we going to\ndistinguish these two theories", "start": 361.91, "duration": 2.363}, {"text": "from each other?", "start": 364.273, "duration": 0.667}, {"text": "That was the\ncliffhanger last time.", "start": 364.94, "duration": 1.458}, {"text": "I said we can distinguish these\ntheories or these examples.", "start": 366.398, "duration": 6.78}, {"text": "So that's just the data\nI just ran through.", "start": 373.178, "duration": 1.792}, {"text": "\"She\" is not Mary in\nthe first sentence,", "start": 374.97, "duration": 1.79}, {"text": "but \"she\" can be Mary\nin the second sentence.", "start": 376.76, "duration": 1.7}, {"text": "It doesn't have\nto be, but it can.", "start": 378.46, "duration": 1.417}, {"text": "All right.", "start": 382.1, "duration": 0.75}, {"text": "Now, I'm going to show\nyou how we'll distinguish", "start": 382.85, "duration": 3.78}, {"text": "those kinds of examples using\nthe tree that I was hoping", "start": 386.63, "duration": 5.34}, {"text": "you would just unthinkingly\naccept when I built it for you.", "start": 391.97, "duration": 4.74}, {"text": "And then what I'll\ndo is show you", "start": 396.71, "duration": 2.76}, {"text": "that the theory that\nI'm going to show you", "start": 399.47, "duration": 2.19}, {"text": "for this pair of sentences\nwouldn't work if we had", "start": 401.66, "duration": 2.52}, {"text": "the other kind of structure.", "start": 404.18, "duration": 1.26}, {"text": "And then if you\nwant, we can talk", "start": 405.44, "duration": 1.68}, {"text": "some about whether\nthere is another way", "start": 407.12, "duration": 1.98}, {"text": "to talk about the other\nkind of structure.", "start": 409.1, "duration": 1.75}, {"text": "Now, my abilities as\na graphic designer--", "start": 410.85, "duration": 3.92}, {"text": "you may have picked up on\nthis seeing my slides--", "start": 414.77, "duration": 2.79}, {"text": "are limited.", "start": 417.56, "duration": 2.91}, {"text": "So I was not able to\ncome up with a way", "start": 420.47, "duration": 2.31}, {"text": "to put all of the trees\nthat you might like", "start": 422.78, "duration": 2.34}, {"text": "to be able to look at all\nat once on a single slide,", "start": 425.12, "duration": 3.19}, {"text": "so I'm going to put some of them\nup here on the board instead.", "start": 428.31, "duration": 4.88}, {"text": "We'll see if we can\nmake reference to them.", "start": 433.19, "duration": 6.28}, {"text": "So she would-- here's\nthe tree that people were", "start": 439.47, "duration": 5.63}, {"text": "offering as an alternative.", "start": 445.1, "duration": 1.74}, {"text": "Yeah.", "start": 450.8, "duration": 0.54}, {"text": "This is the kind of\ntree that people were", "start": 451.34, "duration": 1.23}, {"text": "offering as an alternative.", "start": 452.57, "duration": 0.97}, {"text": "So the tree that's on\nthe slide is the tree", "start": 453.54, "duration": 1.4}, {"text": "that I want you to believe in.", "start": 454.94, "duration": 1.56}, {"text": "The tree that's on\nthe board is the tree", "start": 456.5, "duration": 1.26}, {"text": "that people said, \"Hey, why\nare we not doing it that way?\"", "start": 457.76, "duration": 2.29}, {"text": "Right?", "start": 460.05, "duration": 0.5}, {"text": "I always feel nervous when\nI write things on the board", "start": 464.29, "duration": 2.67}, {"text": "that I want you not to believe.", "start": 466.96, "duration": 2.38}, {"text": "So just so we're\nclear, this is wrong.", "start": 469.34, "duration": 7.1}, {"text": "Not the right tree.", "start": 476.44, "duration": 1.89}, {"text": "That's the right tree, yeah?", "start": 478.33, "duration": 1.2}, {"text": "But I'm now going to try\nto convince you of that.", "start": 479.53, "duration": 2.26}, {"text": "So the reason it\nmakes me nervous", "start": 481.79, "duration": 1.79}, {"text": "is that I know it's\nmorning, loosely construed.", "start": 483.58, "duration": 4.632}, {"text": "It's late enough in the\nsemester that you're probably", "start": 488.212, "duration": 2.208}, {"text": "sleep deprived.", "start": 490.42, "duration": 0.785}, {"text": "It's easy to think, well,\nif the professor wrote it", "start": 491.205, "duration": 2.125}, {"text": "on the board it\nmust be true, yeah?", "start": 493.33, "duration": 1.59}, {"text": "This is not true.", "start": 494.92, "duration": 2.003}, {"text": "At least, I don't\nthink it's true.", "start": 496.923, "duration": 1.417}, {"text": "I'll try to convince you.", "start": 498.34, "duration": 1.042}, {"text": "OK, so that tree up there.", "start": 499.382, "duration": 2.978}, {"text": "If we use that tree\nup there, we can", "start": 502.36, "duration": 5.52}, {"text": "account for the contrast\nbetween the two sentences", "start": 507.88, "duration": 2.46}, {"text": "on the slide--", "start": 510.34, "duration": 1.29}, {"text": "[COUGH]", "start": 511.63, "duration": 0.96}, {"text": "My gracious.", "start": 512.59, "duration": 1.65}, {"text": "We can account for the contrast\nbetween the two sentences", "start": 514.24, "duration": 2.819}, {"text": "on the slide with the\nfollowing principle.", "start": 517.059, "duration": 2.431}, {"text": "It goes like this.", "start": 519.49, "duration": 1.5}, {"text": "If you have an NP like \"she\"\nthat merges with another node--", "start": 520.99, "duration": 4.89}, {"text": "let's call it alpha--", "start": 525.88, "duration": 1.8}, {"text": "the NP can't refer to any of\nthe names that are inside alpha,", "start": 527.68, "duration": 4.83}, {"text": "any of the names that\nare dominated by alpha.", "start": 532.51, "duration": 3.04}, {"text": "I'll keep it specific\nto names for now.", "start": 535.55, "duration": 3.56}, {"text": "We're going to talk much more\nabout principles like this", "start": 539.11, "duration": 2.68}, {"text": "later.", "start": 541.79, "duration": 0.5}, {"text": "We're going to develop a\ntheory of what kinds of things", "start": 542.29, "duration": 2.85}, {"text": "pronouns can refer to and what\nkinds of things they can't.", "start": 545.14, "duration": 3.18}, {"text": "But this works for the pair\nof examples that we have here.", "start": 548.32, "duration": 4.36}, {"text": "So what's wrong\nwith this example--", "start": 552.68, "duration": 2.93}, {"text": "why can't \"she\" refer\nto Mary in this example?", "start": 555.61, "duration": 2.93}, {"text": "The theory would be it's because\nyou merge \"she\" with that T bar", "start": 558.54, "duration": 4.63}, {"text": "there, and that T\nbar dominates \"Mary.\"", "start": 563.17, "duration": 3.74}, {"text": "And therefore,\nthis principle says", "start": 566.91, "duration": 2.38}, {"text": "\"she\" can't refer\nto anything that's", "start": 569.29, "duration": 1.59}, {"text": "inside that T bar and\n\"Mary\" is inside that T bar.", "start": 570.88, "duration": 3.39}, {"text": "That's what this\nprinciple is meant to do.", "start": 574.27, "duration": 3.048}, {"text": "Let me show you that that\ndistinguishes between the two", "start": 577.318, "duration": 2.292}, {"text": "examples.", "start": 579.61, "duration": 1.0}, {"text": "So if instead we had\n\"anyone who knows her\"--", "start": 580.61, "duration": 5.36}, {"text": "if we had \"anyone who\nknows her\" as the subject,", "start": 585.97, "duration": 2.31}, {"text": "\"Anyone who knows her\nwould recognize Mary\"--", "start": 588.28, "duration": 1.98}, {"text": "well, I'm going to try to get\naway without actually telling", "start": 590.26, "duration": 3.87}, {"text": "you how we're going to diagram\nall of \"anyone who knows her.\"", "start": 594.13, "duration": 3.72}, {"text": "But \"anyone\" is the noun\nin \"anyone who knows her,\"", "start": 597.85, "duration": 3.54}, {"text": "and it's a noun that's\nmodified by what's", "start": 601.39, "duration": 2.19}, {"text": "called a relative clause.", "start": 603.58, "duration": 1.68}, {"text": "So \"who knows her\" is a kind\nof clause that modifies nouns.", "start": 605.26, "duration": 4.44}, {"text": "And I have given it the label\nquestion mark, question mark", "start": 609.7, "duration": 2.863}, {"text": "because someday we'll talk\nabout relative clauses", "start": 612.563, "duration": 2.042}, {"text": "and talk about what\nlabel they ought to have", "start": 614.605, "duration": 1.725}, {"text": "and all that good stuff.", "start": 616.33, "duration": 1.06}, {"text": "But for now, it's a thing.", "start": 617.39, "duration": 2.18}, {"text": "Yeah.", "start": 619.57, "duration": 0.78}, {"text": "And what's inside\nit is that pronoun,", "start": 620.35, "duration": 2.79}, {"text": "\"her,\" which got merged.", "start": 623.14, "duration": 3.27}, {"text": "Somewhere inside that relative\nclause is a verb phrase,", "start": 626.41, "duration": 3.21}, {"text": "\"knows,\" and the\nnoun phrase, \"her.\"", "start": 629.62, "duration": 3.84}, {"text": "So if we ask, what was this\nnoun first merged with?", "start": 633.46, "duration": 3.57}, {"text": "Well, it definitely\nwasn't merged with T bar.", "start": 637.03, "duration": 2.61}, {"text": "It was merged with something\ninside the relative clause.", "start": 639.64, "duration": 2.61}, {"text": "It was merged with this verb.", "start": 642.25, "duration": 1.63}, {"text": "Yeah.", "start": 643.88, "duration": 1.08}, {"text": "Yeah?", "start": 644.96, "duration": 0.99}, {"text": "So this principle that says,\nif a noun phrase merges", "start": 645.95, "duration": 3.24}, {"text": "with another node,\nalpha, the noun phrase", "start": 649.19, "duration": 2.28}, {"text": "can't refer to any names\nthat alpha dominates.", "start": 651.47, "duration": 3.27}, {"text": "That distinguishes between \"She\nwould recognize Mary,\" where", "start": 654.74, "duration": 4.05}, {"text": "\"she\" is merged with something\nthat contains \"Mary,\"", "start": 658.79, "duration": 3.27}, {"text": "and \"Anyone who knows\nher would recognize", "start": 662.06, "duration": 2.37}, {"text": "Mary,\" where \"her\" is\nnot merged with something", "start": 664.43, "duration": 2.94}, {"text": "that contains \"Mary.\"", "start": 667.37, "duration": 2.55}, {"text": "Do people see that this\nprinciple draws the distinction", "start": 669.92, "duration": 2.52}, {"text": "that we wanted to draw?", "start": 672.44, "duration": 3.43}, {"text": "OK.", "start": 675.87, "duration": 0.93}, {"text": "Giray?", "start": 676.8, "duration": 0.9}, {"text": "AUDIENCE: [INAUDIBLE]\nsomewhere in the subtree", "start": 677.7, "duration": 3.0}, {"text": "or does it have [INAUDIBLE]?", "start": 680.7, "duration": 1.248}, {"text": "NORVIN RICHARDS: No, that's\nmore or less what it means.", "start": 681.948, "duration": 2.292}, {"text": "So trees-- you think of\nthe basic relation in trees", "start": 684.24, "duration": 4.58}, {"text": "as \"immediately dominate,\"\nso a node immediately", "start": 688.82, "duration": 2.28}, {"text": "dominates the nodes that\nwere merged to create it.", "start": 691.1, "duration": 2.67}, {"text": "And dominate is the\ntransitive closure", "start": 693.77, "duration": 2.1}, {"text": "of immediately dominate.", "start": 695.87, "duration": 1.18}, {"text": "So you dominate the things\nyou immediately dominate", "start": 697.05, "duration": 2.128}, {"text": "and the things those things\nimmediately dominate,", "start": 699.178, "duration": 2.042}, {"text": "and so on until you run out of\nimmediate domination relations.", "start": 701.22, "duration": 2.583}, {"text": "That's what \"dominate\" means.", "start": 703.803, "duration": 1.937}, {"text": "To put it more\ngraphically, you dominate", "start": 705.74, "duration": 1.92}, {"text": "the things that are related\nto you by lines pointing down.", "start": 707.66, "duration": 4.65}, {"text": "That's what this means.", "start": 712.31, "duration": 1.95}, {"text": "Raquel?", "start": 714.26, "duration": 0.63}, {"text": "AUDIENCE: So did we agree\nthat the \"her\" in this thing", "start": 714.89, "duration": 3.42}, {"text": "can refer to Mary potentially or\nare we saying specifically not?", "start": 718.31, "duration": 3.5}, {"text": "NORVIN RICHARDS: I\nasserted that it could.", "start": 721.81, "duration": 1.75}, {"text": "AUDIENCE: So it's that the\nNP contains \"who knows her\"", "start": 723.56, "duration": 3.63}, {"text": "and it's merging with the T bar.", "start": 727.19, "duration": 1.8}, {"text": "The T bar dominates \"Mary.\"", "start": 728.99, "duration": 1.93}, {"text": "Then does that not contradict\nthe new rule we just learned,", "start": 730.92, "duration": 4.66}, {"text": "or is it like the who knows\npart that combined with?", "start": 735.58, "duration": 2.203}, {"text": "NORVIN RICHARDS: Yeah.", "start": 737.783, "duration": 0.917}, {"text": "So here, let me draw\n\"anyone who knows her\"", "start": 738.7, "duration": 3.18}, {"text": "a little more carefully.", "start": 741.88, "duration": 1.06}, {"text": "So here's \"anyone.\"", "start": 742.94, "duration": 3.98}, {"text": "Here's the relative\nclauses that I'm", "start": 746.92, "duration": 1.86}, {"text": "going to continue possibly\nfoolishly not to label,", "start": 748.78, "duration": 3.16}, {"text": "so there's some stuff in here.", "start": 751.94, "duration": 1.4}, {"text": "And then, \"who\nknows her,\" there's", "start": 753.34, "duration": 3.63}, {"text": "maybe a TP down in there\ncontaining a T bar and a T.", "start": 756.97, "duration": 4.92}, {"text": "And who knows, maybe the\nsubject of it is \"who.\"", "start": 761.89, "duration": 2.35}, {"text": "Right?", "start": 764.24, "duration": 0.5}, {"text": "So somewhere inside--\nso there's \"anyone\"", "start": 764.74, "duration": 1.92}, {"text": "and then there's this\nrelative clause which contains", "start": 766.66, "duration": 2.49}, {"text": "a sentence, \"who knows her.\"", "start": 769.15, "duration": 2.13}, {"text": "That's what relative\nclauses are.", "start": 771.28, "duration": 1.8}, {"text": "They're a special\nkind of sentence", "start": 773.08, "duration": 1.68}, {"text": "that acts as a\nmodifier for nouns.", "start": 774.76, "duration": 2.55}, {"text": "So you're right.", "start": 777.31, "duration": 2.16}, {"text": "And then this thing is\nbecoming part of a larger TP.", "start": 779.47, "duration": 5.58}, {"text": "\"Would\"-- so now\nI'm just drawing", "start": 785.05, "duration": 2.43}, {"text": "what's on the slide with\na little more detail--", "start": 787.48, "duration": 4.77}, {"text": "\"recognize\"-- bless you--", "start": 792.25, "duration": 4.11}, {"text": "\"Mary.\"", "start": 796.36, "duration": 2.4}, {"text": "So now there are--", "start": 798.76, "duration": 3.022}, {"text": "apart from \"Mary\"-- well, OK.", "start": 801.782, "duration": 1.208}, {"text": "There are three noun\nphrases in this sentence.", "start": 802.99, "duration": 1.917}, {"text": "There's \"Mary,\"\nthere's this thing,", "start": 804.907, "duration": 3.153}, {"text": "and there's this pronoun, \"her.\"", "start": 808.06, "duration": 2.1}, {"text": "Yeah?", "start": 810.16, "duration": 1.32}, {"text": "And claim, a noun\nphrase can't refer", "start": 811.48, "duration": 5.97}, {"text": "to something that is contained\nin the alpha with which", "start": 817.45, "duration": 3.99}, {"text": "the noun phrase merges.", "start": 821.44, "duration": 2.25}, {"text": "So that's a claim\nthat says when we ask,", "start": 823.69, "duration": 3.42}, {"text": "who does \"her\" refer to here?", "start": 827.11, "duration": 2.1}, {"text": "Can it refer to Mary?", "start": 829.21, "duration": 1.77}, {"text": "The answer is, yeah, because\nthis was merged with \"knows.\"", "start": 830.98, "duration": 4.275}, {"text": "\"Knows\" doesn't contain\n\"Mary\" and so we're all set.", "start": 835.255, "duration": 3.705}, {"text": "AUDIENCE: So your ancestors\nmerging doesn't impact that?", "start": 838.96, "duration": 2.335}, {"text": "NORVIN RICHARDS: Yes.", "start": 841.295, "duration": 0.875}, {"text": "No, you're not responsible for\nthe crimes of your ancestors.", "start": 842.17, "duration": 2.5}, {"text": "That's right.", "start": 844.67, "duration": 1.1}, {"text": "So this noun phrase shouldn't\nbe able to refer to Mary.", "start": 845.77, "duration": 6.08}, {"text": "Yeah?", "start": 851.85, "duration": 0.88}, {"text": "And that might be true.", "start": 852.73, "duration": 1.51}, {"text": "Yeah.", "start": 854.24, "duration": 1.74}, {"text": "Yeah.", "start": 855.98, "duration": 1.29}, {"text": "Yeah?", "start": 857.27, "duration": 1.36}, {"text": "OK, so this has been an attempt\nat an argument form, argument", "start": 858.63, "duration": 4.12}, {"text": "by successful account.", "start": 862.75, "duration": 2.11}, {"text": "So I've shown you how, with\nthis principle and these trees,", "start": 864.86, "duration": 6.41}, {"text": "the trees that I\nhad on the slide,", "start": 871.27, "duration": 2.07}, {"text": "this kind of tree where a\nTP contains three things.", "start": 873.34, "duration": 5.01}, {"text": "There's a T, the sister of\nthe T is the verb phrase,", "start": 878.35, "duration": 3.36}, {"text": "and then the\ndaughter of the TP is", "start": 881.71, "duration": 3.54}, {"text": "the subject of the whole thing.", "start": 885.25, "duration": 1.292}, {"text": "That's the kind of tree\nthat I was drawing you.", "start": 886.542, "duration": 1.958}, {"text": "Or to say that in another\nway, when you're assembling", "start": 888.5, "duration": 2.24}, {"text": "a sentence out of those three\nthings, what you're doing", "start": 890.74, "duration": 2.292}, {"text": "is you're first merging\nT with the verb phrase", "start": 893.032, "duration": 2.118}, {"text": "and then you're merging the\nresult of that with a noun", "start": 895.15, "duration": 2.37}, {"text": "phrase.", "start": 897.52, "duration": 0.78}, {"text": "That was the order in which\nI wanted to do things.", "start": 898.3, "duration": 2.49}, {"text": "I said, what I've tried to show\nyou is that if we do things", "start": 900.79, "duration": 2.64}, {"text": "in that order we can\nhave an account using", "start": 903.43, "duration": 2.64}, {"text": "this principle that\nI've just invoked", "start": 906.07, "duration": 3.36}, {"text": "for this contrast between\nthese two sentences, the fact", "start": 909.43, "duration": 2.322}, {"text": "that \"she\" can't refer to\nMary in the first sentence,", "start": 911.752, "duration": 2.208}, {"text": "but that \"her\" can refer to\nMary in the second sentence.", "start": 913.96, "duration": 4.29}, {"text": "So this is, as I said,\nargument form, argument", "start": 918.25, "duration": 2.52}, {"text": "by successful account.", "start": 920.77, "duration": 1.215}, {"text": "If you buy these\ntrees then, hey,", "start": 921.985, "duration": 2.325}, {"text": "we get this account\nof this contrast", "start": 924.31, "duration": 1.56}, {"text": "between these sentences.", "start": 925.87, "duration": 1.2}, {"text": "Yeah?", "start": 927.07, "duration": 0.51}, {"text": "Now suppose we were instead\nto do this kind of tree.", "start": 927.58, "duration": 5.43}, {"text": "Well, good.", "start": 933.01, "duration": 2.76}, {"text": "But notice at least the\nprinciple that I posited here", "start": 935.77, "duration": 4.23}, {"text": "wouldn't work for\nthis kind of tree.", "start": 940.0, "duration": 3.1}, {"text": "So the principle that\nI've posited here", "start": 943.1, "duration": 1.73}, {"text": "says if a noun phrase is\nmerged with some alpha the noun", "start": 944.83, "duration": 3.97}, {"text": "phrase can't refer to\nanything inside the alpha.", "start": 948.8, "duration": 2.0}, {"text": "Well, this noun phrase, \"she\"\nhas just been merged with the T", "start": 950.8, "duration": 3.15}, {"text": "\"would.\"", "start": 953.95, "duration": 1.59}, {"text": "So that principle at least\nwould not draw this distinction.", "start": 955.54, "duration": 4.38}, {"text": "Possible response\ncould be, yeah, but now", "start": 959.92, "duration": 1.77}, {"text": "we need another principle.", "start": 961.69, "duration": 2.37}, {"text": "To which the response is,\nyeah, well, what principle?", "start": 964.06, "duration": 4.08}, {"text": "Show it to me.", "start": 968.14, "duration": 1.43}, {"text": "So what we're going to do\nis we'll have this tree", "start": 969.57, "duration": 2.44}, {"text": "and we're comparing\nthis tree with--", "start": 972.01, "duration": 2.617}, {"text": "I'll draw it again--", "start": 974.627, "duration": 0.833}, {"text": "\"Mary,\" \"recognize,\"\n\"would,\" and now we're", "start": 978.64, "duration": 7.08}, {"text": "going to have \"anyone,\"\nblah, blah, blah, \"her.\"", "start": 985.72, "duration": 8.16}, {"text": "So we want this \"her\" to\nbe able to refer to Mary", "start": 993.88, "duration": 2.94}, {"text": "but we want this \"she\" not\nto be able to refer to Mary.", "start": 996.82, "duration": 3.075}, {"text": "So there.", "start": 1003.28, "duration": 2.88}, {"text": "That's part of an\nargument, anyway,", "start": 1006.16, "duration": 2.37}, {"text": "that you should buy\nthe kinds of trees,", "start": 1008.53, "duration": 2.85}, {"text": "do the mergers in the order\nthat I wanted you to do them in.", "start": 1011.38, "duration": 4.02}, {"text": "We have a name for\nthis relation that", "start": 1015.4, "duration": 2.7}, {"text": "holds between \"she\" and\n\"Mary\" in this kind of tree.", "start": 1018.1, "duration": 6.749}, {"text": "The relation that holds\nbetween a node like the she--", "start": 1024.849, "duration": 3.391}, {"text": "the noun phrase \"she\" in this\ntree and another node like", "start": 1028.24, "duration": 5.07}, {"text": "the noun phrase \"Mary\" in this\ntree, which is contained--", "start": 1033.31, "duration": 4.2}, {"text": "I'm sorry.", "start": 1037.51, "duration": 0.89}, {"text": "This is too complicated.", "start": 1038.4, "duration": 1.0}, {"text": "Let me introduce some variables.", "start": 1039.4, "duration": 1.495}, {"text": "We have a name for\nthe kind of relation", "start": 1040.895, "duration": 1.625}, {"text": "that holds between a node\nlike the noun phrase \"she\"--", "start": 1042.52, "duration": 4.38}, {"text": "let's call that node x--", "start": 1046.9, "duration": 1.65}, {"text": "and another node that is\ncontained in something", "start": 1048.55, "duration": 4.02}, {"text": "that x was merged with.", "start": 1052.57, "duration": 2.34}, {"text": "So the relation that holds\nbetween \"she\" and \"Mary.\"", "start": 1054.91, "duration": 2.41}, {"text": "Yeah.", "start": 1057.32, "duration": 0.5}, {"text": "Or for that matter, between\n\"she\" and the verb phrase", "start": 1057.82, "duration": 2.79}, {"text": "or between \"she\" and \"would.\"", "start": 1060.61, "duration": 1.33}, {"text": "Yeah?", "start": 1061.94, "duration": 0.5}, {"text": "So the relationship that holds\nbetween a node x and everything", "start": 1062.44, "duration": 5.43}, {"text": "that's inside the node with\nwhich that x was merged.", "start": 1067.87, "duration": 4.36}, {"text": "Yeah.", "start": 1072.23, "duration": 0.5}, {"text": "That relation is\ncalled C command.", "start": 1072.73, "duration": 1.695}, {"text": "We're now not going to\ntalk about C command", "start": 1078.97, "duration": 1.89}, {"text": "for a little while\nbecause, as I said,", "start": 1080.86, "duration": 2.16}, {"text": "you're experiencing a\nmoment of anachronism.", "start": 1083.02, "duration": 2.04}, {"text": "I'm telling you things that\nI was planning to tell you", "start": 1085.06, "duration": 2.25}, {"text": "in a few weeks but\nbecause you demanded it,", "start": 1087.31, "duration": 3.57}, {"text": "I'm offering you an argument\nfor this particular way", "start": 1090.88, "duration": 2.19}, {"text": "of assembling trees.", "start": 1093.07, "duration": 1.14}, {"text": "Yeah.", "start": 1094.21, "duration": 1.232}, {"text": "OK?", "start": 1095.442, "duration": 1.948}, {"text": "All right.", "start": 1097.39, "duration": 1.908}, {"text": "All right, good.", "start": 1099.298, "duration": 0.667}, {"text": "Yes.", "start": 1103.85, "duration": 0.51}, {"text": "Alternative way of\ndrawing trees wouldn't", "start": 1104.36, "duration": 1.14}, {"text": "let us use this explanation.", "start": 1105.5, "duration": 1.32}, {"text": "You would need a\ndifferent one, and then", "start": 1106.82, "duration": 2.01}, {"text": "if you like that alternative\nway of drawing trees,", "start": 1108.83, "duration": 2.403}, {"text": "it's your job to come\nup with a different one.", "start": 1111.233, "duration": 1.917}, {"text": "Kateryna, yes, has\nalready come up with one.", "start": 1113.15, "duration": 3.125}, {"text": "AUDIENCE: I just\nwant to clarify.", "start": 1116.275, "duration": 1.375}, {"text": "Does C command refer\nto that principle", "start": 1117.65, "duration": 1.935}, {"text": "that we were talking about?", "start": 1119.585, "duration": 1.125}, {"text": "NORVIN RICHARDS: No, I'm sorry.", "start": 1120.71, "duration": 1.292}, {"text": "Let me say it better.", "start": 1122.002, "duration": 2.668}, {"text": "There's a definition\nfor C command.", "start": 1124.67, "duration": 2.55}, {"text": "AUDIENCE: C command\nis the relationship?", "start": 1127.22, "duration": 0.08}, {"text": "NORVIN RICHARDS: C command\nis the relationship.", "start": 1127.3, "duration": 1.958}, {"text": "So you say \"x C commands y.\"", "start": 1129.258, "duration": 6.092}, {"text": "There are various ways to define\nC command, but one of them--", "start": 1135.35, "duration": 2.61}, {"text": "here, I'll show you one and then\nwe can talk about another one.", "start": 1137.96, "duration": 2.625}, {"text": "You can say \"x C commands y\nif every node that dominates", "start": 1140.585, "duration": 6.315}, {"text": "x dominates y,\" and\npeople usually add", "start": 1146.9, "duration": 9.77}, {"text": "\"and x does not dominate y.\"", "start": 1156.67, "duration": 2.76}, {"text": "So this is one way to\ndefine it formally.", "start": 1163.75, "duration": 1.98}, {"text": "What does that do?", "start": 1165.73, "duration": 0.87}, {"text": "It says if you look\nat the noun phrase", "start": 1166.6, "duration": 2.25}, {"text": "\"she,\" what the noun phrase\nC commands is everything that", "start": 1168.85, "duration": 5.22}, {"text": "is dominated by everything\nthat dominates \"she,\"", "start": 1174.07, "duration": 3.06}, {"text": "the noun phrase \"she.\"", "start": 1177.13, "duration": 1.2}, {"text": "So what dominates the\nnoun phrase \"she\"?", "start": 1178.33, "duration": 1.95}, {"text": "Well, it's just the node TP.", "start": 1180.28, "duration": 3.15}, {"text": "And so \"she\" C commands\neverything that's", "start": 1183.43, "duration": 2.46}, {"text": "dominated by the node\nTP, which is basically", "start": 1185.89, "duration": 3.0}, {"text": "everything except for TP.", "start": 1188.89, "duration": 1.29}, {"text": "So T bar and T and\nthe verb phrase.", "start": 1190.18, "duration": 2.97}, {"text": "The T would C commands\nthe verb phrase", "start": 1193.15, "duration": 4.23}, {"text": "and also the verb and\nthe noun phrase \"Mary.\"", "start": 1197.38, "duration": 2.73}, {"text": "Yeah.", "start": 1200.11, "duration": 0.96}, {"text": "To put it yet another\nway, you C command", "start": 1201.07, "duration": 1.95}, {"text": "your sister and everything\nyour sister dominates.", "start": 1203.02, "duration": 3.33}, {"text": "That's what C command is.", "start": 1206.35, "duration": 2.46}, {"text": "Lots and lots of syntax\nmakes reference to C command,", "start": 1208.81, "duration": 2.64}, {"text": "and so we will keep\ncoming back to it.", "start": 1211.45, "duration": 2.08}, {"text": "It's a thing that\nwill come up again.", "start": 1213.53, "duration": 3.33}, {"text": "OK?", "start": 1216.86, "duration": 1.26}, {"text": "So again, this is all dramatic\nforeshadowing or anachronism", "start": 1218.12, "duration": 3.45}, {"text": "or whatever you want to say--", "start": 1221.57, "duration": 1.35}, {"text": "whatever you want to call it.", "start": 1222.92, "duration": 1.47}, {"text": "These are things I was\nplanning to teach you", "start": 1224.39, "duration": 1.89}, {"text": "a little bit in the\nfuture, and so now you", "start": 1226.28, "duration": 3.06}, {"text": "have a jump on in life.", "start": 1229.34, "duration": 2.49}, {"text": "Later on some things will\nsuddenly become familiar.", "start": 1231.83, "duration": 3.03}, {"text": "Yeah.", "start": 1234.86, "duration": 0.75}, {"text": "Yep.", "start": 1235.61, "duration": 2.65}, {"text": "All right, good.", "start": 1238.26, "duration": 0.69}, {"text": "I have been teasing you\nfor making me do this", "start": 1241.84, "duration": 2.538}, {"text": "but I really appreciate\nit, actually.", "start": 1244.378, "duration": 1.542}, {"text": "It's a real pleasure\nteaching people who", "start": 1245.92, "duration": 2.7}, {"text": "disagree with me all the time.", "start": 1248.62, "duration": 1.755}, {"text": "When I'm on airplanes and I\ncan't avoid telling the person", "start": 1258.743, "duration": 2.417}, {"text": "next to me what I do for\na living and I tell them", "start": 1261.16, "duration": 1.68}, {"text": "I teach linguistics\nat MIT, they're like,", "start": 1262.84, "duration": 1.65}, {"text": "oh-- sometimes they\nsay, \"Oh, I didn't know", "start": 1264.49, "duration": 1.83}, {"text": "they had linguistics at MIT.\"", "start": 1266.32, "duration": 1.208}, {"text": "I'm like, \"Yes, yes!\"", "start": 1267.528, "duration": 1.852}, {"text": "And then they say, \"So what's\nit like teaching MIT undergrads", "start": 1269.38, "duration": 4.05}, {"text": "linguistics?\"", "start": 1273.43, "duration": 0.66}, {"text": "And I say, \"It's\ngreat because they all", "start": 1274.09, "duration": 1.625}, {"text": "have these math and\nscience backgrounds so they", "start": 1275.715, "duration": 1.975}, {"text": "don't believe a word I say.", "start": 1277.69, "duration": 1.32}, {"text": "It's terrific.", "start": 1279.01, "duration": 1.56}, {"text": "So I go in there and\nI tell them things", "start": 1280.57, "duration": 2.01}, {"text": "and they're like, well,\nno, show me some proof.", "start": 1282.58, "duration": 2.63}, {"text": "I go, well, OK.", "start": 1285.21, "duration": 2.368}, {"text": "In another university\nI think I would", "start": 1287.578, "duration": 1.542}, {"text": "be able to get away with\njust the authority of having", "start": 1289.12, "duration": 2.4}, {"text": "a beard this length.", "start": 1291.52, "duration": 1.74}, {"text": "People would just\nbelieve me, but no.", "start": 1293.26, "duration": 3.51}, {"text": "It's great.\"", "start": 1296.77, "duration": 0.96}, {"text": "OK.", "start": 1297.73, "duration": 1.29}, {"text": "This is a slide we saw before.", "start": 1299.02, "duration": 1.51}, {"text": "This is just to remind you\nof a bunch of terminology.", "start": 1300.53, "duration": 2.91}, {"text": "Some of it I've been using\nas we've been talking.", "start": 1303.44, "duration": 2.39}, {"text": "So just to remind you, when\nwe're talking about trees,", "start": 1305.83, "duration": 5.13}, {"text": "standardly use\nfeminine kinship terms", "start": 1310.96, "duration": 1.71}, {"text": "to talk about relations\nbetween parts of trees.", "start": 1312.67, "duration": 2.1}, {"text": "So we talk about sisters, which\nare two things that are both--", "start": 1314.77, "duration": 4.02}, {"text": "two things that were\nmerged to form a node.", "start": 1318.79, "duration": 2.58}, {"text": "So for example, the\nD, \"the,\" and the N,", "start": 1321.37, "duration": 3.21}, {"text": "\"child,\" those are sisters.", "start": 1324.58, "duration": 1.98}, {"text": "The V, \"tickle,\"\nand the noun phrase,", "start": 1326.56, "duration": 1.98}, {"text": "\"the child,\" those are\nsisters in this tree.", "start": 1328.54, "duration": 3.81}, {"text": "We talk about mothers.", "start": 1332.35, "duration": 1.05}, {"text": "So the noun phrase \"the child\"\nis the mother of D and N,", "start": 1333.4, "duration": 4.26}, {"text": "\"the\" and \"child.\"", "start": 1337.66, "duration": 2.2}, {"text": "We also talk about daughters.", "start": 1339.86, "duration": 1.74}, {"text": "So \"the\" and \"child\" are the\ndaughters of the noun phrase.", "start": 1341.6, "duration": 3.75}, {"text": "And I think I said\nlast time that's it,", "start": 1345.35, "duration": 1.727}, {"text": "so we don't talk about\ngrandmothers or aunts", "start": 1347.077, "duration": 1.833}, {"text": "or anything else.", "start": 1348.91, "duration": 1.78}, {"text": "And then and this came up when\nGiday asked a question earlier.", "start": 1350.69, "duration": 3.95}, {"text": "The basic relation that's\nreflected in these trees", "start": 1354.64, "duration": 3.75}, {"text": "is the relation of\nimmediate domination.", "start": 1358.39, "duration": 2.67}, {"text": "That's the relation that's\ncreated by the operation", "start": 1361.06, "duration": 2.2}, {"text": "\"merge.\"", "start": 1363.26, "duration": 0.5}, {"text": "So when you merge\ntwo things, you", "start": 1363.76, "duration": 3.3}, {"text": "create a new thing that\nimmediately dominates the two", "start": 1367.06, "duration": 2.52}, {"text": "things that you merged.", "start": 1369.58, "duration": 0.99}, {"text": "That's just our name for\nthat relation in the tree.", "start": 1370.57, "duration": 3.66}, {"text": "And then there is\nanother notion, dominate,", "start": 1374.23, "duration": 3.6}, {"text": "which is the transitive closure\nof immediately dominate.", "start": 1377.83, "duration": 2.95}, {"text": "So you dominate the things\nthat you immediately dominate", "start": 1380.78, "duration": 2.573}, {"text": "and the things that those things\nimmediately dominate and so on,", "start": 1383.353, "duration": 2.667}, {"text": "all the way down to the tree.", "start": 1386.02, "duration": 2.56}, {"text": "And then we said there's this\nword \"constituent,\" which we've", "start": 1388.58, "duration": 3.09}, {"text": "been using for some\ntime, and all of you", "start": 1391.67, "duration": 3.882}, {"text": "seem to have a\nhandle on it anyway.", "start": 1395.552, "duration": 1.458}, {"text": "But just to give it\na formal definition,", "start": 1397.01, "duration": 2.07}, {"text": "we'll say that something\nis a constituent", "start": 1399.08, "duration": 1.98}, {"text": "if there's a single\nnode that dominates", "start": 1401.06, "duration": 3.0}, {"text": "all the words in alpha.", "start": 1404.06, "duration": 2.83}, {"text": "So \"the child\" is a\nconstituent because there's", "start": 1406.89, "duration": 3.17}, {"text": "a node that dominates just\nthose words, the noun phrase.", "start": 1410.06, "duration": 3.6}, {"text": "\"Tickle the child\"\nis a constituent", "start": 1413.66, "duration": 2.37}, {"text": "because there's a verb phrase\ndominating just those words.", "start": 1416.03, "duration": 3.9}, {"text": "\"Will tickle the\"\nis not a constituent", "start": 1419.93, "duration": 2.55}, {"text": "because there's no node\ndominating just those words.", "start": 1422.48, "duration": 3.74}, {"text": "Is that clear?", "start": 1426.22, "duration": 1.97}, {"text": "This is all just\nterminology, and I'm", "start": 1428.19, "duration": 2.96}, {"text": "telling you about it because\nyou're going to hear me use it.", "start": 1431.15, "duration": 2.5}, {"text": "In fact, you already have.", "start": 1433.65, "duration": 2.5}, {"text": "OK.", "start": 1436.15, "duration": 0.72}, {"text": "All right?", "start": 1436.87, "duration": 0.78}, {"text": "So the way we've been talking,\nthen, we take pairs of things,", "start": 1437.65, "duration": 5.02}, {"text": "we merge them to\ncreate new things.", "start": 1442.67, "duration": 3.09}, {"text": "And we haven't said very much.", "start": 1445.76, "duration": 2.56}, {"text": "In fact, we haven't\nsaid anything at all", "start": 1448.32, "duration": 1.88}, {"text": "about why you pick\nthe particular things", "start": 1450.2, "duration": 4.23}, {"text": "that you pick.", "start": 1454.43, "duration": 1.72}, {"text": "So I want to talk about\nthat a little bit.", "start": 1456.15, "duration": 2.51}, {"text": "Here are some sentences mostly\ninvolving ants, I guess,", "start": 1458.66, "duration": 4.77}, {"text": "and anteaters, And they're\nall grammatical sentences", "start": 1463.43, "duration": 4.17}, {"text": "of English, I think.", "start": 1467.6, "duration": 1.59}, {"text": "\"The ants thrived\" and\n\"The anteater arrived\"--", "start": 1469.19, "duration": 2.4}, {"text": "this is kind of a\nlittle dramatic story", "start": 1471.59, "duration": 2.76}, {"text": "about some ants and\ntheir difficult lives!--", "start": 1474.35, "duration": 2.988}, {"text": "\"The ants thrived.\"", "start": 1477.338, "duration": 0.792}, {"text": "\"The anteater arrived.\"", "start": 1478.13, "duration": 0.9}, {"text": "\"The anteater\ndevoured the ants.\"", "start": 1479.03, "duration": 1.41}, {"text": "And \"Mary slapped the anteater.\"", "start": 1480.44, "duration": 1.333}, {"text": "A little sad story about\nants, or a happy story", "start": 1481.773, "duration": 2.147}, {"text": "about an anteater.", "start": 1483.92, "duration": 0.75}, {"text": "It depends on whose\nside you're on, I guess.", "start": 1484.67, "duration": 2.11}, {"text": "Yeah?", "start": 1486.78, "duration": 0.5}, {"text": "Observation, old observation.", "start": 1490.92, "duration": 2.61}, {"text": "Verbs, in lots of languages,\nmaybe all languages,", "start": 1493.53, "duration": 5.68}, {"text": "can be fruitfully thought of as\ncoming in at least two types.", "start": 1499.21, "duration": 4.06}, {"text": "There are verbs like\n\"thrive\" and \"arrive\"", "start": 1503.27, "duration": 3.14}, {"text": "which need to not have objects.", "start": 1506.41, "duration": 3.45}, {"text": "So you can say \"The ants\nthrived\" or \"The anteater", "start": 1509.86, "duration": 2.25}, {"text": "arrived.\"", "start": 1512.11, "duration": 0.72}, {"text": "You cannot say \"The ants\nthrived the ant farm\"", "start": 1512.83, "duration": 2.34}, {"text": "or \"The anteater\narrived the anthill.\"", "start": 1515.17, "duration": 2.16}, {"text": "You can't put an object\nafter those kinds of verbs.", "start": 1517.33, "duration": 3.89}, {"text": "And then there are other verbs,\nlike \"devour\" and \"slap,\"", "start": 1521.22, "duration": 3.21}, {"text": "that are the opposite.", "start": 1524.43, "duration": 1.38}, {"text": "You can say \"The anteater\ndevoured the ants.\"", "start": 1525.81, "duration": 1.92}, {"text": "You can't very well say\n\"The anteater devoured.\"", "start": 1527.73, "duration": 2.0}, {"text": "That sentence is not finished.", "start": 1529.73, "duration": 1.7}, {"text": "Yeah.", "start": 1531.43, "duration": 0.71}, {"text": "So really \"Mary\nslapped the anteater.\"", "start": 1532.14, "duration": 2.22}, {"text": "You can't say \"Mary slapped.\"", "start": 1534.36, "duration": 2.37}, {"text": "Did I hear noises\nof disagreement?", "start": 1536.73, "duration": 2.34}, {"text": "Facial expressions\nof disagreement?", "start": 1539.07, "duration": 2.342}, {"text": "AUDIENCE: \"Mary slaps.\"", "start": 1541.412, "duration": 1.268}, {"text": "NORVIN RICHARDS: Sorry?", "start": 1542.68, "duration": 2.4}, {"text": "Apart from the\ntechnical term, yeah.", "start": 1545.08, "duration": 3.18}, {"text": "Apart from that.", "start": 1548.26, "duration": 1.29}, {"text": "Yeah?", "start": 1549.55, "duration": 2.21}, {"text": "OK.", "start": 1551.76, "duration": 1.26}, {"text": "So there are verbs that\nseem to want to have objects", "start": 1553.02, "duration": 2.773}, {"text": "and there are verbs that seem\nto want to not have objects.", "start": 1555.793, "duration": 2.417}, {"text": "Classic observation.", "start": 1558.21, "duration": 1.02}, {"text": "The name for that\nclassic observation", "start": 1559.23, "duration": 1.56}, {"text": "is that there are verbs that\nare what's called transitive.", "start": 1560.79, "duration": 2.73}, {"text": "Those are the verbs that\nwant to have objects,", "start": 1563.52, "duration": 1.92}, {"text": "verbs like \"devour\" and \"slap.\"", "start": 1565.44, "duration": 1.5}, {"text": "There are other verbs\nthat are intransitive.", "start": 1566.94, "duration": 1.833}, {"text": "Those are verbs like\n\"thrive\" and \"arrive.\"", "start": 1568.773, "duration": 2.577}, {"text": "I picked these verbs\nfairly carefully.", "start": 1571.35, "duration": 2.1}, {"text": "There are many, many--", "start": 1573.45, "duration": 2.34}, {"text": "possibly most verbs--\nthat can be either one.", "start": 1575.79, "duration": 3.39}, {"text": "So for example, you can say\n\"The anteater ate the ants\"", "start": 1579.18, "duration": 4.14}, {"text": "and you can also say\n\"The anteater ate.\"", "start": 1583.32, "duration": 2.34}, {"text": "It's fine.", "start": 1585.66, "duration": 0.78}, {"text": "Yeah?", "start": 1586.44, "duration": 2.22}, {"text": "So some verbs are transitive,\nothers are intransitive.", "start": 1588.66, "duration": 3.69}, {"text": "Maybe there are also other\nverbs that are indecisive.", "start": 1592.35, "duration": 2.98}, {"text": "Yeah?", "start": 1595.33, "duration": 0.5}, {"text": "AUDIENCE: In that\ncontext, how is \"ate\"", "start": 1595.83, "duration": 1.41}, {"text": "different from \"devoured\"?", "start": 1597.24, "duration": 1.11}, {"text": "NORVIN RICHARDS: Good question.", "start": 1598.35, "duration": 0.75}, {"text": "Yeah.", "start": 1599.1, "duration": 0.5}, {"text": "But I think the fact, the facts\nare as I just described them,", "start": 1599.6, "duration": 2.87}, {"text": "right?", "start": 1602.47, "duration": 0.5}, {"text": "That \"The anteater devoured\"\nis not a complete sentence,", "start": 1602.97, "duration": 2.95}, {"text": "but \"The anteater ate\" is.", "start": 1605.92, "duration": 1.91}, {"text": "\"Devoured\" and \"ate\" mean\nslightly different things.", "start": 1607.83, "duration": 2.79}, {"text": "You have to be louder and\nmessier and more violent", "start": 1610.62, "duration": 4.045}, {"text": "if you're devouring,\nI guess, and \"eat\"", "start": 1614.665, "duration": 1.625}, {"text": "is a more plain vanilla verb.", "start": 1616.29, "duration": 1.622}, {"text": "Why that means that one of\nthese verbs has to be transitive", "start": 1617.912, "duration": 2.458}, {"text": "and the other doesn't is\na really good question.", "start": 1620.37, "duration": 2.0}, {"text": "Yeah.", "start": 1622.37, "duration": 1.34}, {"text": "Yeah.", "start": 1623.71, "duration": 1.17}, {"text": "Other questions?", "start": 1624.88, "duration": 2.5}, {"text": "To which I may, again,\nonly be able to say, yeah,", "start": 1627.38, "duration": 2.28}, {"text": "that's a good question.", "start": 1629.66, "duration": 1.57}, {"text": "Yeah?", "start": 1631.23, "duration": 0.5}, {"text": "AUDIENCE: I was just going\nto follow up and then say,", "start": 1631.73, "duration": 2.508}, {"text": "are we going to\nanswer that question?", "start": 1634.238, "duration": 1.542}, {"text": "NORVIN RICHARDS: No.", "start": 1635.78, "duration": 0.833}, {"text": "No, no, no.", "start": 1636.613, "duration": 0.787}, {"text": "No.", "start": 1637.4, "duration": 0.78}, {"text": "No.", "start": 1638.18, "duration": 0.96}, {"text": "No, we are not.", "start": 1639.14, "duration": 1.26}, {"text": "Other questions?", "start": 1640.4, "duration": 1.32}, {"text": "I enjoy listening\nto your questions", "start": 1641.72, "duration": 1.59}, {"text": "even if I can't answer them.", "start": 1643.31, "duration": 3.51}, {"text": "OK, so some verbs\nare transitive,", "start": 1646.82, "duration": 1.5}, {"text": "others are intransitive.", "start": 1648.32, "duration": 2.55}, {"text": "So that's a classic observation.", "start": 1650.87, "duration": 1.605}, {"text": "People have been saying\nthat since the Romans", "start": 1652.475, "duration": 1.875}, {"text": "and the Greeks.", "start": 1654.35, "duration": 1.86}, {"text": "Less classic observation\nis that there", "start": 1656.21, "duration": 1.98}, {"text": "are other kinds of verbs\nthat not only need an object", "start": 1658.19, "duration": 3.63}, {"text": "but also need a\nprepositional phrase.", "start": 1661.82, "duration": 1.89}, {"text": "Actually, there\nare verbs that just", "start": 1663.71, "duration": 1.11}, {"text": "need a prepositional phrase.", "start": 1664.82, "duration": 1.167}, {"text": "We'll talk about\nthat maybe later,", "start": 1665.987, "duration": 1.813}, {"text": "but let's talk for now\nabout a verb like \"put.\"", "start": 1667.8, "duration": 3.056}, {"text": "\"Put\" absolutely has\nto have an object,", "start": 1670.856, "duration": 3.424}, {"text": "so it's transitive\nin that sense.", "start": 1674.28, "duration": 1.43}, {"text": "But it also has to have\na prepositional phrase.", "start": 1675.71, "duration": 2.92}, {"text": "So you can say \"The anteater\nput the ants onto a plate.\"", "start": 1678.63, "duration": 3.48}, {"text": "This is a comparatively\ncivilized anteater.", "start": 1682.11, "duration": 3.38}, {"text": "But you can't leave\nout either the object", "start": 1685.49, "duration": 2.433}, {"text": "or the prepositional phrase.", "start": 1687.923, "duration": 1.167}, {"text": "You can't say \"The\nanteater put the ants.\"", "start": 1689.09, "duration": 2.25}, {"text": "That's not a sentence.", "start": 1691.34, "duration": 1.05}, {"text": "And you also cannot say \"The\nanteater put onto a plate.\"", "start": 1692.39, "duration": 3.48}, {"text": "Also not a sentence.", "start": 1695.87, "duration": 1.35}, {"text": "So \"put\" needs to combine\nwith both an object", "start": 1697.22, "duration": 3.75}, {"text": "and a preposition.", "start": 1700.97, "duration": 2.88}, {"text": "So apparently, in--", "start": 1703.85, "duration": 2.367}, {"text": "I hope this is what I\nsay on the next slide.", "start": 1706.217, "duration": 1.833}, {"text": "Yeah.", "start": 1708.05, "duration": 2.473}, {"text": "Remember when we were\ntalking about what", "start": 1710.523, "duration": 1.667}, {"text": "we would need to state in\nour lexicon about each word", "start": 1712.19, "duration": 4.32}, {"text": "or about each morpheme,\nif we're putting morphemes", "start": 1716.51, "duration": 2.4}, {"text": "in our lexicon, which we were\nsaying probably we should?", "start": 1718.91, "duration": 3.885}, {"text": "We were saying, yeah, When you\nlist an entry in your lexicon", "start": 1722.795, "duration": 4.468}, {"text": "you're going to need\nto say whether it's", "start": 1727.263, "duration": 1.667}, {"text": "a free morpheme or\na bound morpheme", "start": 1728.93, "duration": 1.86}, {"text": "and whether it's a prefix\nor a suffix or an infix", "start": 1730.79, "duration": 2.34}, {"text": "or whatever all else,\nand how it's pronounced.", "start": 1733.13, "duration": 3.33}, {"text": "And we spend some time doing\nphonology and convincing", "start": 1736.46, "duration": 3.06}, {"text": "ourselves that saying how\nsomething is pronounced", "start": 1739.52, "duration": 2.31}, {"text": "might be more complicated\nthan it looks.", "start": 1741.83, "duration": 2.49}, {"text": "Here's something else that\nwe're going to have to state.", "start": 1744.32, "duration": 3.21}, {"text": "When we list a verb we're going\nto need to state something", "start": 1747.53, "duration": 5.67}, {"text": "about-- this is\ncalled selection.", "start": 1753.2, "duration": 1.48}, {"text": "So we need to say\nverbs, for example,", "start": 1754.68, "duration": 2.73}, {"text": "select for the kinds of things\nthat they want to combine with.", "start": 1757.41, "duration": 3.77}, {"text": "So our list, our lexical\nentry for a verb like \"devour\"", "start": 1761.18, "duration": 4.272}, {"text": "has to say, oh\nyeah, this is a verb", "start": 1765.452, "duration": 1.458}, {"text": "that needs to have an object.", "start": 1766.91, "duration": 1.208}, {"text": "I think we need to say that.", "start": 1770.5, "duration": 1.23}, {"text": "This gets back to your question\nof a second ago, right?", "start": 1771.73, "duration": 2.73}, {"text": "Can we derive it\nfrom anything else", "start": 1774.46, "duration": 2.16}, {"text": "about the meaning of \"devour\"\nthat it has to have an object?", "start": 1776.62, "duration": 2.73}, {"text": "Can we make that\nfollow from something?", "start": 1779.35, "duration": 2.19}, {"text": "Rather than just having to\nsay next to \"devour,\" oh yeah,", "start": 1781.54, "duration": 2.49}, {"text": "this one needs an object.", "start": 1784.03, "duration": 1.47}, {"text": "Can that be a general property\nof certain classes of verbs?", "start": 1785.5, "duration": 2.5}, {"text": "That's an ongoing project.", "start": 1788.0, "duration": 0.95}, {"text": "There are linguists trying\nto figure out the answers", "start": 1788.95, "duration": 2.167}, {"text": "to questions like that.", "start": 1791.117, "duration": 2.343}, {"text": "But yeah, for 24.900 we'll\njust state for every verb,", "start": 1793.46, "duration": 3.28}, {"text": "this verb needs an object.", "start": 1796.74, "duration": 1.76}, {"text": "This is kind of like--", "start": 1798.5, "duration": 1.44}, {"text": "and it should look\na little familiar--", "start": 1799.94, "duration": 2.31}, {"text": "when we were doing \"unlockable\"\nand other polymorphemic words", "start": 1802.25, "duration": 5.58}, {"text": "like that we were saying, yeah,\nthere are affixes that say,", "start": 1807.83, "duration": 2.82}, {"text": "\"I want to combine with\na verb,\" let's say,", "start": 1810.65, "duration": 3.15}, {"text": "and \"I'll give you an\nadjective as a result.\"", "start": 1813.8, "duration": 3.88}, {"text": "Similarly, verbs have to\nspecify what they merge with.", "start": 1817.68, "duration": 2.81}, {"text": "So the verb \"put\" is\npronounced \"put\"--", "start": 1820.49, "duration": 3.84}, {"text": "I should really have\ndone that in IPA.", "start": 1824.33, "duration": 2.22}, {"text": "It's pronounced whatever.", "start": 1826.55, "duration": 1.89}, {"text": "\"Put.\"", "start": 1828.44, "duration": 1.38}, {"text": "And it means something.", "start": 1829.82, "duration": 2.77}, {"text": "It means to cause\nsomething to be in a place,", "start": 1832.59, "duration": 1.97}, {"text": "whatever, however we're\ngoing to state its meaning,", "start": 1834.56, "duration": 2.125}, {"text": "and it selects for a noun phrase\nand a prepositional phrase.", "start": 1836.685, "duration": 2.565}, {"text": "That's the way we'll say that.", "start": 1839.25, "duration": 1.25}, {"text": "So the verb put needs to\nmerge with those things.", "start": 1840.5, "duration": 3.65}, {"text": "OK?", "start": 1844.15, "duration": 0.5}, {"text": "Actually, be a\nlittle more specific", "start": 1848.06, "duration": 1.77}, {"text": "about how selection\nworks exactly.", "start": 1849.83, "duration": 2.7}, {"text": "So I just said-- yeah, is\nthis much clearer so far?", "start": 1852.53, "duration": 4.098}, {"text": "So let's be a little more\nspecific about what selection", "start": 1856.628, "duration": 2.292}, {"text": "is and what exactly\nyou're selecting for.", "start": 1858.92, "duration": 4.08}, {"text": "I just said there are\nverbs like \"put\" that", "start": 1863.0, "duration": 2.52}, {"text": "select for an object and\nalso a prepositional phrase.", "start": 1865.52, "duration": 2.52}, {"text": "There are also verbs\nthat only select", "start": 1868.04, "duration": 1.77}, {"text": "for a prepositional phrase.", "start": 1869.81, "duration": 1.29}, {"text": "\"Depend\" is one of those.", "start": 1871.1, "duration": 2.28}, {"text": "So \"depend\" can combine--", "start": 1873.38, "duration": 4.75}, {"text": "kind of needs to combine,\nit depends, but at least can", "start": 1878.13, "duration": 6.12}, {"text": "combine with a\nprepositional phrase,", "start": 1884.25, "duration": 2.34}, {"text": "but not just any\nprepositional phrase.", "start": 1886.59, "duration": 1.807}, {"text": "It needs to combine with a\nprepositional phrase in which", "start": 1888.397, "duration": 2.333}, {"text": "the preposition is \"on.\"", "start": 1890.73, "duration": 2.73}, {"text": "You can depend on things.", "start": 1893.46, "duration": 2.34}, {"text": "You cannot depend from things\nor at things or near things", "start": 1895.8, "duration": 3.39}, {"text": "or by things.", "start": 1899.19, "duration": 0.96}, {"text": "You can't depend near something.", "start": 1900.15, "duration": 1.59}, {"text": "That's not how you\nuse the word \"depend.\"", "start": 1901.74, "duration": 3.57}, {"text": "If you learn other\nlanguages-- especially", "start": 1905.31, "duration": 2.46}, {"text": "if you learn other\nIndo-European languages", "start": 1907.77, "duration": 1.8}, {"text": "because Indo-European\nlanguages seem", "start": 1909.57, "duration": 1.5}, {"text": "to be especially fond of\nprepositions, I don't know,", "start": 1911.07, "duration": 5.51}, {"text": "Indo-European languages, the\nlanguage family that English is", "start": 1916.58, "duration": 2.99}, {"text": "part of, we have more\nprepositions than languages", "start": 1919.57, "duration": 3.9}, {"text": "really should--", "start": 1923.47, "duration": 0.82}, {"text": "And if you learn a\nnew language, there's", "start": 1924.29, "duration": 2.54}, {"text": "this weird mapping from\none language to the next", "start": 1926.83, "duration": 2.52}, {"text": "where you just need to\nlearn which prepositions.", "start": 1929.35, "duration": 2.13}, {"text": "It's not simple.", "start": 1931.48, "duration": 0.93}, {"text": "You don't get to learn \"This\npreposition is the translation", "start": 1932.41, "duration": 1.86}, {"text": "for that preposition.\"", "start": 1934.27, "duration": 0.99}, {"text": "You learn things like, \"This\nis the preposition that", "start": 1935.26, "duration": 2.22}, {"text": "means 'at' for cities and large\nislands but for small islands", "start": 1937.48, "duration": 4.2}, {"text": "you should use this other\npreposition instead.\"", "start": 1941.68, "duration": 2.25}, {"text": "Not to scare you or\nanything, but if you", "start": 1943.93, "duration": 1.35}, {"text": "want to learn other\nIndo-European languages you", "start": 1945.28, "duration": 1.958}, {"text": "should brace yourself\nfor things like that.", "start": 1947.238, "duration": 2.394}, {"text": "If you don't want to\ndo things like that,", "start": 1949.632, "duration": 1.708}, {"text": "learn a language that's\nnot Indo-European,", "start": 1951.34, "duration": 1.56}, {"text": "because outside Indo-European\nit's mostly like,", "start": 1952.9, "duration": 2.13}, {"text": "\"Here is our\nlocative preposition.", "start": 1955.03, "duration": 1.44}, {"text": "Please use responsibly.\"", "start": 1956.47, "duration": 2.892}, {"text": "But English is an\nIndo-European language,", "start": 1959.362, "duration": 1.708}, {"text": "and so we have stuff like this,\nverbs like \"depend\" that say,", "start": 1961.07, "duration": 2.57}, {"text": "\"I want a prepositional phrase\nand I want the preposition", "start": 1963.64, "duration": 2.85}, {"text": "to be 'on.'", "start": 1966.49, "duration": 1.7}, {"text": "Can't be anything else.\"", "start": 1968.19, "duration": 1.0}, {"text": "So apparently it's possible, at\nleast in some kinds of cases,", "start": 1972.28, "duration": 3.08}, {"text": "for a verb to select not\njust a prepositional phrase,", "start": 1975.36, "duration": 3.31}, {"text": "but a prepositional phrase\nwith a particular head.", "start": 1978.67, "duration": 2.21}, {"text": "Where by head I mean the\npreposition-- the thing", "start": 1980.88, "duration": 2.49}, {"text": "that the prepositional\nphrase is named after,", "start": 1983.37, "duration": 2.625}, {"text": "the smallest thing\nwith the label P.", "start": 1985.995, "duration": 6.635}, {"text": "So that's the kind\nof selection you get.", "start": 1992.63, "duration": 2.46}, {"text": "There are other imaginable\nkinds of selection", "start": 1995.09, "duration": 2.82}, {"text": "that you don't ever get.", "start": 1997.91, "duration": 1.71}, {"text": "So prepositional phrases\ncan be modified by adverbs.", "start": 1999.62, "duration": 4.275}, {"text": "So you can say \"She put\nthem under the tree.\"", "start": 2003.895, "duration": 1.875}, {"text": "You can also say \"She put\nthem right under the tree,\"", "start": 2005.77, "duration": 2.31}, {"text": "\"She put them directly under the\ntree,\" where those adverbs are", "start": 2008.08, "duration": 3.51}, {"text": "modifying the prepositional\nphrase \"under the tree,\"", "start": 2011.59, "duration": 3.75}, {"text": "saying something about\nthe spatial relation", "start": 2015.34, "duration": 1.83}, {"text": "between those\nthings and the tree.", "start": 2017.17, "duration": 1.42}, {"text": "Yeah?", "start": 2018.59, "duration": 0.5}, {"text": "But we're never going to\nfind a verb that selects", "start": 2022.72, "duration": 4.66}, {"text": "for a prepositional phrase.", "start": 2027.38, "duration": 1.23}, {"text": "So there are verbs like\n\"depend\" that select", "start": 2031.097, "duration": 1.833}, {"text": "for a prepositional phrase\nwhere the preposition has", "start": 2032.93, "duration": 2.167}, {"text": "to be something, like\n\"depend\" needs \"on\" We're", "start": 2035.097, "duration": 2.423}, {"text": "never going to find\na verb that selects", "start": 2037.52, "duration": 1.77}, {"text": "for a prepositional\nphrase and it", "start": 2039.29, "duration": 1.41}, {"text": "needs to be modified by a\ncertain kind of modifier.", "start": 2040.7, "duration": 3.24}, {"text": "We'll never find a--", "start": 2043.94, "duration": 1.14}, {"text": "I made up a verb, \"glorf.\"", "start": 2045.08, "duration": 1.65}, {"text": "Yeah.", "start": 2046.73, "duration": 0.54}, {"text": "And \"glorf\" says, \"I need\na prepositional phrase.", "start": 2047.27, "duration": 2.73}, {"text": "I don't care what\nthe preposition is.", "start": 2050.0, "duration": 2.01}, {"text": "You can say 'She\nglorfed them right under", "start": 2052.01, "duration": 2.669}, {"text": "the tree,' 'She glorfed\nthem right through", "start": 2054.679, "duration": 1.77}, {"text": "the tree,' 'She glorfed them\nright beside the tree,' I", "start": 2056.449, "duration": 2.25}, {"text": "don't care what\nthe preposition is,", "start": 2058.699, "duration": 1.201}, {"text": "but we need 'right' at the\nbeginning of the prepositional", "start": 2059.9, "duration": 2.56}, {"text": "phrase.\"", "start": 2062.46, "duration": 0.5}, {"text": "There are no verbs like\nthat in any language.", "start": 2062.96, "duration": 3.27}, {"text": "Selection doesn't work that way.", "start": 2066.23, "duration": 2.28}, {"text": "How does selection work?", "start": 2068.51, "duration": 1.169}, {"text": "If you're selecting for\na prepositional phrase,", "start": 2069.679, "duration": 2.04}, {"text": "you're selecting if you\nhave any restrictions", "start": 2071.719, "duration": 2.011}, {"text": "on the kind of prepositional\nphrase you want.", "start": 2073.73, "duration": 1.719}, {"text": "They are restrictions of\nthe form \"I would like", "start": 2075.449, "duration": 1.958}, {"text": "the preposition to be (this).\"", "start": 2077.407, "duration": 1.881}, {"text": "Sometimes they are\nrestrictions of the form", "start": 2079.288, "duration": 1.792}, {"text": "\"I would like the\npreposition to be", "start": 2081.08, "duration": 1.458}, {"text": "(this class of prepositions).\"", "start": 2082.538, "duration": 1.422}, {"text": "So I might have a slide\nabout this later too.", "start": 2083.96, "duration": 2.429}, {"text": "\"Put\" can combine with a bunch\nof different prepositional", "start": 2086.389, "duration": 3.181}, {"text": "phrases.", "start": 2089.57, "duration": 1.44}, {"text": "The preposition can be \"under\"\nor \"on,\" \"beside,\" whatever,", "start": 2091.01, "duration": 4.8}, {"text": "but you can't say things like\n\"She put them during the party\"", "start": 2095.81, "duration": 4.62}, {"text": "or \"She put them\ndespite the rain.\"", "start": 2100.43, "duration": 2.58}, {"text": "So there are a bunch\nof prepositions", "start": 2103.01, "duration": 1.5}, {"text": "that don't go well with \"put.\"", "start": 2104.51, "duration": 1.71}, {"text": "It's basically \"put\" needs\na prepositional phrase that", "start": 2106.22, "duration": 2.25}, {"text": "is a location.", "start": 2108.47, "duration": 1.98}, {"text": "So that's a class\nof prepositions", "start": 2110.45, "duration": 2.46}, {"text": "but it's not every\nimaginable preposition.", "start": 2112.91, "duration": 5.04}, {"text": "But there are no verbs--\nthere's no \"glorf,\"", "start": 2117.95, "duration": 2.33}, {"text": "there are no verbs that say,\n\"I want a prepositional phrase.", "start": 2120.28, "duration": 2.5}, {"text": "I don't care what\nthe preposition is,", "start": 2122.78, "duration": 1.542}, {"text": "but I want it to be modified by\n'right,'\" or \"I want it to be", "start": 2124.322, "duration": 2.838}, {"text": "modified by 'directly,'\" or\neven just \"I want it to be", "start": 2127.16, "duration": 2.25}, {"text": "modified.\"", "start": 2129.41, "duration": 0.91}, {"text": "There aren't verbs like that.", "start": 2130.32, "duration": 3.54}, {"text": "So it looks as though\nheads, like verbs,", "start": 2133.86, "duration": 3.96}, {"text": "get to select for\nphrases, and they-- this", "start": 2137.82, "duration": 2.67}, {"text": "is an old observation of Noam\nChomsky's in a '65 book of his.", "start": 2140.49, "duration": 5.135}, {"text": "He said, looks like there\nare all these cases where", "start": 2145.625, "duration": 2.125}, {"text": "a verb is not only selecting\nfor a certain kind of phrase,", "start": 2147.75, "duration": 3.652}, {"text": "but it's selecting for\na certain kind of phrase", "start": 2151.402, "duration": 1.958}, {"text": "with a particular head or with\nthe head of a particular class", "start": 2153.36, "duration": 3.24}, {"text": "like locative.", "start": 2156.6, "duration": 0.98}, {"text": "I want a locative\npreposition like \"put.\"", "start": 2157.58, "duration": 3.82}, {"text": "Yeah?", "start": 2161.4, "duration": 1.17}, {"text": "Sound great?", "start": 2162.57, "duration": 2.0}, {"text": "OK.", "start": 2164.57, "duration": 0.91}, {"text": "Cool.", "start": 2165.48, "duration": 0.5}, {"text": "So once we believe this, once\nwe recognize that this is true,", "start": 2168.85, "duration": 5.16}, {"text": "that this is how\nselection works,", "start": 2174.01, "duration": 1.86}, {"text": "that verbs get to\nselect for things", "start": 2175.87, "duration": 2.16}, {"text": "they want to merge with--\nnot just verbs, we'll see.", "start": 2178.03, "duration": 2.397}, {"text": "All kinds of things get\nto select for things", "start": 2180.427, "duration": 1.833}, {"text": "that they want to merge with.", "start": 2182.26, "duration": 2.76}, {"text": "And if they are picky about\nthe nature of the thing", "start": 2185.02, "duration": 5.04}, {"text": "that they merge with,\nwhat they are picky about", "start": 2190.06, "duration": 2.61}, {"text": "is the head of the thing\nthat they merge with,", "start": 2192.67, "duration": 3.82}, {"text": "the thing that the\nphrase is named after.", "start": 2196.49, "duration": 2.69}, {"text": "So the preposition, in the\ncase of a prepositional phrase.", "start": 2199.18, "duration": 4.11}, {"text": "So once we recognize that that's\na thing of the \"depend on\"", "start": 2203.29, "duration": 3.06}, {"text": "phenomenon, then we\ncan start using it", "start": 2206.35, "duration": 3.57}, {"text": "as a way of looking\naround for other heads", "start": 2209.92, "duration": 2.37}, {"text": "when we see that kind of\nrelation of pickiness.", "start": 2212.29, "duration": 3.152}, {"text": "If you have this verb\nthen you had better", "start": 2215.442, "duration": 1.708}, {"text": "have this kind of word here.", "start": 2217.15, "duration": 2.82}, {"text": "Then we get to suspect that\nthere's a selection relation", "start": 2219.97, "duration": 2.958}, {"text": "there because now\nwe know that that's", "start": 2222.928, "duration": 1.542}, {"text": "how selection relations work.", "start": 2224.47, "duration": 3.04}, {"text": "So here's another\nexample of the same kind.", "start": 2227.51, "duration": 3.08}, {"text": "\"I think that I have\nwon the lottery.\"", "start": 2230.59, "duration": 1.98}, {"text": "Fine.", "start": 2232.57, "duration": 1.71}, {"text": "That's actually kind of\npleasant to think about.", "start": 2234.28, "duration": 3.03}, {"text": "\"I wonder whether I\nhave won the lottery.\"", "start": 2237.31, "duration": 2.36}, {"text": "Also fine.", "start": 2239.67, "duration": 1.67}, {"text": "But \"I think whether I\nhave won the lottery.\"", "start": 2241.34, "duration": 3.35}, {"text": "No.", "start": 2244.69, "duration": 0.81}, {"text": "I cannot say that.", "start": 2245.5, "duration": 1.84}, {"text": "And also \"I wonder that\nI have won the lottery.\"", "start": 2247.34, "duration": 3.05}, {"text": "Cannot say in modern English.", "start": 2250.39, "duration": 2.187}, {"text": "There are older versions\nof English in which", "start": 2252.577, "duration": 1.833}, {"text": "you could say things like this.", "start": 2254.41, "duration": 1.292}, {"text": "It meant \"I am surprised\nthat I have won the lottery.\"", "start": 2255.702, "duration": 3.598}, {"text": "But in modern English the\nfirst two sentences are OK,", "start": 2259.3, "duration": 3.15}, {"text": "the second two\nsentences are bad.", "start": 2262.45, "duration": 2.1}, {"text": "Do people agree?", "start": 2264.55, "duration": 0.99}, {"text": "Don't let me run roughshod\nover your English judgments,", "start": 2265.54, "duration": 2.58}, {"text": "but I think this is true.", "start": 2268.12, "duration": 2.08}, {"text": "So here's another\nplace where there's", "start": 2270.2, "duration": 1.64}, {"text": "this relationship of pickiness.", "start": 2271.84, "duration": 2.34}, {"text": "So we know that if\nyou have a \"depends,\"", "start": 2274.18, "duration": 2.34}, {"text": "you must have a\nprepositional phrase", "start": 2276.52, "duration": 1.5}, {"text": "and the head of the\nprepositional phrase", "start": 2278.02, "duration": 1.667}, {"text": "must be \"on.\"", "start": 2279.687, "duration": 1.153}, {"text": "Here we seem to be\nseeing that with \"think\"", "start": 2280.84, "duration": 2.49}, {"text": "there can be a clause after it,\nand then there's a particular", "start": 2283.33, "duration": 5.22}, {"text": "word that starts that\nclause which must be \"that\"", "start": 2288.55, "duration": 2.79}, {"text": "and cannot be \"whether.\"", "start": 2291.34, "duration": 3.09}, {"text": "And we're seeing\nthat \"wonder\" seems", "start": 2294.43, "duration": 3.72}, {"text": "to be selecting for the\nclause that comes after it,", "start": 2298.15, "duration": 3.07}, {"text": "and it's picky about the\nproperties of the first word", "start": 2301.22, "duration": 3.89}, {"text": "in that clause.", "start": 2305.11, "duration": 0.73}, {"text": "It can be \"whether\" but\nit cannot be \"that.\"", "start": 2305.84, "duration": 1.833}, {"text": "So here we get to make the\nmove that I foreshadowed.", "start": 2309.98, "duration": 3.38}, {"text": "Is that going to go--", "start": 2313.36, "duration": 0.94}, {"text": "we can say maybe this is\nlike \"depend\" and \"on.\"", "start": 2314.3, "duration": 2.09}, {"text": "Maybe \"think\" is\nselecting for that clause", "start": 2316.39, "duration": 2.64}, {"text": "and maybe that is\nlike \"on,\" so \"on\"", "start": 2319.03, "duration": 2.653}, {"text": "is the head of the\nprepositional phrase.", "start": 2321.683, "duration": 1.667}, {"text": "The prepositional phrase\nis named after \"on.\"", "start": 2323.35, "duration": 2.055}, {"text": "\"On\" is a preposition.", "start": 2325.405, "duration": 1.395}, {"text": "Similarly, we're going\nto say this clause has,", "start": 2326.8, "duration": 2.25}, {"text": "as its head, words like\n\"that\" and \"whether.\"", "start": 2329.05, "duration": 2.4}, {"text": "We have a name for words\nlike \"that\" and \"whether.\"", "start": 2335.22, "duration": 3.18}, {"text": "We call them\n\"complementizers,\" which--", "start": 2338.4, "duration": 5.508}, {"text": "I feel as though I've done\na lot of apologizing already", "start": 2343.908, "duration": 2.292}, {"text": "for terminology in this class\nso maybe I'll just stop.", "start": 2346.2, "duration": 2.678}, {"text": "That's what we call them.", "start": 2348.878, "duration": 1.042}, {"text": "We call them complementizers.", "start": 2349.92, "duration": 1.5}, {"text": "Deal.", "start": 2351.42, "duration": 2.68}, {"text": "You may have heard them\ncalled other things", "start": 2354.1, "duration": 2.93}, {"text": "in English classes.", "start": 2357.03, "duration": 1.32}, {"text": "\"Subordinating conjunctions,\"\nthey're sometimes called.", "start": 2358.35, "duration": 3.36}, {"text": "Try not to get too\nhung up on that.", "start": 2361.71, "duration": 1.53}, {"text": "In this class they are\ncalled complementizers.", "start": 2363.24, "duration": 3.33}, {"text": "And they have the\nhandy abbreviation C.", "start": 2366.57, "duration": 5.04}, {"text": "So what we'll say is that a verb\nlike \"think\" selects for CP.", "start": 2371.61, "duration": 7.95}, {"text": "So the name we're going to\ngive to this clause that", "start": 2379.56, "duration": 3.84}, {"text": "comes after \"think,\" \"that\nI have won the lottery,\"", "start": 2383.4, "duration": 4.12}, {"text": "we're going to call that a CP.", "start": 2387.52, "duration": 1.35}, {"text": "Why?", "start": 2388.87, "duration": 0.5}, {"text": "Well, because we've seen that\nthis relationship of pickiness", "start": 2389.37, "duration": 2.622}, {"text": "holds between \"think\" and\n\"that\" and between \"wonder\"", "start": 2391.992, "duration": 2.208}, {"text": "and \"whether,\" and that\nentitles us to believe", "start": 2394.2, "duration": 3.0}, {"text": "\"that\" and \"whether\" are\nthe heads of the phrases", "start": 2397.2, "duration": 3.387}, {"text": "that \"think\" and \"wonder\"\nare selecting for.", "start": 2400.587, "duration": 1.833}, {"text": "They're like the\n\"on\" in \"depend on.\"", "start": 2402.42, "duration": 2.1}, {"text": "Yeah.", "start": 2404.52, "duration": 0.75}, {"text": "So that's the reason to\ndraw the trees this way.", "start": 2405.27, "duration": 2.89}, {"text": "So we'll say, when you have a\nclause like \"that I have won", "start": 2408.16, "duration": 4.518}, {"text": "the lottery\" or \"whether\nI have won the lottery,\"", "start": 2412.678, "duration": 2.042}, {"text": "that thing is a CP.", "start": 2414.72, "duration": 1.41}, {"text": "\"That\" or \"whether\" is\nits head, and those things", "start": 2416.13, "duration": 2.19}, {"text": "are being selected by verbs\nlike \"think\" or \"wonder.\"", "start": 2418.32, "duration": 2.22}, {"text": "Yeah.", "start": 2420.54, "duration": 0.5}, {"text": "OK?", "start": 2423.75, "duration": 1.86}, {"text": "All right.", "start": 2425.61, "duration": 0.6}, {"text": "Those are all complementizers.", "start": 2426.21, "duration": 3.41}, {"text": "OK.", "start": 2429.62, "duration": 0.5}, {"text": "So are we done with syntax?", "start": 2430.12, "duration": 1.125}, {"text": "We now have this\nbelief in selection", "start": 2435.79, "duration": 1.87}, {"text": "which is allowing us to explain\nwhy certain pairs of things", "start": 2437.66, "duration": 5.21}, {"text": "are merging in the\nway that they are.", "start": 2442.87, "duration": 1.81}, {"text": "So in this example, \"I will\ntickle the child,\" when", "start": 2444.68, "duration": 4.01}, {"text": "we ask why did\nyou merge \"tickle\"", "start": 2448.69, "duration": 3.21}, {"text": "together with the noun\nphrase \"the child,\"", "start": 2451.9, "duration": 2.46}, {"text": "we now have an answer.", "start": 2454.36, "duration": 1.59}, {"text": "We get to say, yeah, we\ndid that because \"tickle\"", "start": 2455.95, "duration": 4.23}, {"text": "is a transitive verb.", "start": 2460.18, "duration": 1.78}, {"text": "So if we look up\n\"tickle\" in the lexicon", "start": 2461.96, "duration": 1.88}, {"text": "the lexicon will\ntell us, yeah, this", "start": 2463.84, "duration": 1.68}, {"text": "is a verb that at least\nhas a use in which it", "start": 2465.52, "duration": 4.77}, {"text": "wants to combine with\na noun phrase object.", "start": 2470.29, "duration": 2.95}, {"text": "So that's why you merged\nthe verb with the noun", "start": 2473.24, "duration": 3.8}, {"text": "phrase \"the child.\"", "start": 2477.04, "duration": 1.89}, {"text": "And similarly, we\nmight say, yeah,", "start": 2478.93, "duration": 1.89}, {"text": "why did we merge the verb phrase\ntogether with the T \"will\"?", "start": 2480.82, "duration": 3.5}, {"text": "And we can say\nsomething similar.", "start": 2484.32, "duration": 1.66}, {"text": "The T \"will\" is selecting\nfor a verb phrase.", "start": 2485.98, "duration": 2.61}, {"text": "It needs a verb phrase as\nits sister, and so there.", "start": 2488.59, "duration": 4.163}, {"text": "That's why we're merging these\ntwo things with each other.", "start": 2492.753, "duration": 2.417}, {"text": "So we have beginners of\nexplanations or answers", "start": 2495.17, "duration": 3.56}, {"text": "to questions like,\nwhy did you merge", "start": 2498.73, "duration": 2.625}, {"text": "those things in that order?", "start": 2501.355, "duration": 1.125}, {"text": "Why did you merge those\ntwo things together?", "start": 2502.48, "duration": 2.28}, {"text": "The answer is going\nto sometimes be,", "start": 2504.76, "duration": 1.505}, {"text": "well, because\nthere's a selection", "start": 2506.265, "duration": 1.375}, {"text": "relation between those things.", "start": 2507.64, "duration": 2.86}, {"text": "OK?", "start": 2510.5, "duration": 1.89}, {"text": "But here's the problem.", "start": 2512.39, "duration": 2.6}, {"text": "You can do anything\nwith a feather.", "start": 2514.99, "duration": 3.08}, {"text": "So I spent some time\ntelling you there", "start": 2518.07, "duration": 2.272}, {"text": "are verbs that need\nobjects and there are verbs", "start": 2520.342, "duration": 1.958}, {"text": "that need to not have objects.", "start": 2522.3, "duration": 1.29}, {"text": "There are transitive verbs,\nthere are intransitive verbs,", "start": 2523.59, "duration": 1.83}, {"text": "and OK, there are verbs\nthat can be either one.", "start": 2525.42, "duration": 1.958}, {"text": "And I tried to move us quickly\npast that class of verbs,", "start": 2527.378, "duration": 3.892}, {"text": "but they exist.", "start": 2531.27, "duration": 2.71}, {"text": "So yeah, the child, we know\nwhy the child is in there", "start": 2533.98, "duration": 3.38}, {"text": "and we think that the\nrelationship between \"tickle\"", "start": 2537.36, "duration": 2.43}, {"text": "and \"the child\" is a\nrelation of pickiness.", "start": 2539.79, "duration": 3.18}, {"text": "There are some verbs that can\nmerge together with an object", "start": 2542.97, "duration": 2.97}, {"text": "like that and there are\nother verbs that can't.", "start": 2545.94, "duration": 4.0}, {"text": "But \"with a feather\"\nis not like that.", "start": 2549.94, "duration": 2.61}, {"text": "You can tickle a\nchild with a feather.", "start": 2552.55, "duration": 1.71}, {"text": "You can walk down the\nstreet with a feather.", "start": 2554.26, "duration": 3.69}, {"text": "You can stand with a feather.", "start": 2557.95, "duration": 1.222}, {"text": "You can dance with a feather.", "start": 2559.172, "duration": 1.208}, {"text": "You can do anything\nwith a feather.", "start": 2560.38, "duration": 2.1}, {"text": "Prepositional phrase\n\"with a feather\"--", "start": 2562.48, "duration": 1.953}, {"text": "you can write your\ndissertation with a feather", "start": 2564.433, "duration": 1.917}, {"text": "if you work hard at it.", "start": 2566.35, "duration": 1.838}, {"text": "Prepositional phrase\nlike \"with a feather,\"", "start": 2568.188, "duration": 1.792}, {"text": "there's no pickiness involved.", "start": 2569.98, "duration": 2.4}, {"text": "It can just combine\nwith anything.", "start": 2572.38, "duration": 1.83}, {"text": "So this does not fall\nunder our generalizations", "start": 2577.06, "duration": 4.52}, {"text": "about how selection works.", "start": 2581.58, "duration": 2.67}, {"text": "We don't seem to have\nthe kind of relation", "start": 2584.25, "duration": 2.04}, {"text": "that we have between\nthe verb and the object.", "start": 2586.29, "duration": 2.49}, {"text": "Yeah, there are verbs that\nwant objects and verbs that", "start": 2588.78, "duration": 2.25}, {"text": "don't want objects,\nbut we're not", "start": 2591.03, "duration": 1.375}, {"text": "going to find a verb that\nneeds \"with the feather\"", "start": 2592.405, "duration": 2.885}, {"text": "in this sense, using a feather.", "start": 2595.29, "duration": 3.0}, {"text": "Yeah?", "start": 2598.29, "duration": 0.748}, {"text": "AUDIENCE: Could you\nalmost look at it", "start": 2599.038, "duration": 1.542}, {"text": "from a perspective\nof agency, the fact", "start": 2600.58, "duration": 2.5}, {"text": "that you could say \"with a\nfeather\" but not \"with a dog.\"", "start": 2603.08, "duration": 2.97}, {"text": "The dog is able to--", "start": 2606.05, "duration": 2.48}, {"text": "you can't tickle a\nchild with a dog.", "start": 2608.53, "duration": 2.51}, {"text": "NORVIN RICHARDS: Yeah.", "start": 2611.04, "duration": 1.47}, {"text": "Well, it's complicated, right?", "start": 2612.51, "duration": 2.52}, {"text": "You can tickle a child with\na dog-- well, let's see.", "start": 2615.03, "duration": 2.7}, {"text": "The fact that you cannot\ntickle a child with a dog,", "start": 2617.73, "duration": 2.91}, {"text": "if it's a fact, I think is\nprobably a fact about dogs.", "start": 2620.64, "duration": 4.08}, {"text": "Right?", "start": 2624.72, "duration": 0.84}, {"text": "I mean, so we're in \"colorless\ngreen ideas\" territory here.", "start": 2625.56, "duration": 5.52}, {"text": "I was about to do the thing that\neverybody always does when I", "start": 2631.08, "duration": 2.58}, {"text": "show them colorless green\nideas where they say, \"Well,", "start": 2633.66, "duration": 3.52}, {"text": "but if 'colorless' and 'green'\nmeant different things then", "start": 2637.18, "duration": 2.87}, {"text": "the sentence would be OK.\"", "start": 2640.05, "duration": 1.71}, {"text": "And I think tickling\na child with a dog,", "start": 2641.76, "duration": 2.25}, {"text": "I find myself saying,\nwell, but what if it's", "start": 2644.01, "duration": 1.98}, {"text": "a particularly hairy dog?", "start": 2645.99, "duration": 2.1}, {"text": "And you grab it and\nrub it on the child", "start": 2648.09, "duration": 4.317}, {"text": "in just the right way, you could\nimagine maybe being able to--", "start": 2652.407, "duration": 2.583}, {"text": "but yeah.", "start": 2654.99, "duration": 0.93}, {"text": "\"I will tickle the\nchild with the hammer.\"", "start": 2655.92, "duration": 3.1}, {"text": "Probably you could never\ntickle the child with a hammer,", "start": 2659.02, "duration": 2.63}, {"text": "but this is 24.900 and we\ndon't have to care about that.", "start": 2661.65, "duration": 4.83}, {"text": "So some things are better\ntickling instruments", "start": 2666.48, "duration": 3.81}, {"text": "than others, but\nthankfully I am not here", "start": 2670.29, "duration": 4.41}, {"text": "to educate you about\ntickling instruments.", "start": 2674.7, "duration": 2.94}, {"text": "That'll be somebody\nelse's job, if anybody.", "start": 2677.64, "duration": 2.88}, {"text": "Yeah.", "start": 2680.52, "duration": 1.96}, {"text": "Not that I'm\npromising that there", "start": 2682.48, "duration": 1.47}, {"text": "is an MIT class\nwhere you can learn", "start": 2683.95, "duration": 1.755}, {"text": "about tickling instruments.", "start": 2685.705, "duration": 1.125}, {"text": "I mean, I suppose\nthere could be,", "start": 2686.83, "duration": 1.08}, {"text": "but it's definitely\nnot this one.", "start": 2687.91, "duration": 1.38}, {"text": "Yeah.", "start": 2689.29, "duration": 0.9}, {"text": "Yeah?", "start": 2690.19, "duration": 1.18}, {"text": "Good.", "start": 2691.37, "duration": 0.5}, {"text": "All right.", "start": 2691.87, "duration": 1.41}, {"text": "OK.", "start": 2693.28, "duration": 2.16}, {"text": "So \"with the feather\" is\nanother kind of thing.", "start": 2695.44, "duration": 4.41}, {"text": "Yeah.", "start": 2699.85, "duration": 0.5}, {"text": "This is just saying\nwhat I just said.", "start": 2700.35, "duration": 1.542}, {"text": "Doesn't seem right to say that\n\"child\" or \"tickle\" selects", "start": 2701.892, "duration": 2.658}, {"text": "\"with a feather\" because you\ncan do anything with a feather", "start": 2704.55, "duration": 4.11}, {"text": "and, uh--", "start": 2708.66, "duration": 1.63}, {"text": "there.", "start": 2710.29, "duration": 0.5}, {"text": "Yeah.", "start": 2710.79, "duration": 0.3}, {"text": "So \"I will tickle the\nchild with the feather.\"", "start": 2711.09, "duration": 1.917}, {"text": "\"I will devour the\nchild with the feather.\"", "start": 2713.007, "duration": 2.116}, {"text": "\"I will write a novel\nwith the feather.\"", "start": 2715.123, "duration": 1.667}, {"text": "\"I will thrive\nwith the feather.\"", "start": 2716.79, "duration": 1.375}, {"text": "You can do anything\nwith the feather.", "start": 2718.165, "duration": 2.075}, {"text": "Some of these things are more\nor less plausible than others,", "start": 2720.24, "duration": 2.65}, {"text": "but they're all grammatical.", "start": 2722.89, "duration": 1.97}, {"text": "Yeah?", "start": 2724.86, "duration": 0.603}, {"text": "Does that sound right?", "start": 2725.463, "duration": 0.917}, {"text": "I don't know why\nI used \"devour.\"", "start": 2728.845, "duration": 1.375}, {"text": "So we said there are verbs\nlike \"tickle\" and \"devour\" and", "start": 2735.56, "duration": 3.16}, {"text": "\"write\" that need\nto have objects,", "start": 2738.72, "duration": 5.04}, {"text": "or at least can have objects.", "start": 2743.76, "duration": 1.33}, {"text": "And there are other verbs\nlike \"thrive\" that pickily", "start": 2745.09, "duration": 1.88}, {"text": "can't have objects.\nso not every verb", "start": 2746.97, "duration": 1.56}, {"text": "can be followed by the child.", "start": 2748.53, "duration": 1.11}, {"text": "I can \"tickle the child.\"", "start": 2749.64, "duration": 1.042}, {"text": "I can \"devour the child.\"", "start": 2750.682, "duration": 1.358}, {"text": "I can \"write the child.\"", "start": 2752.04, "duration": 3.24}, {"text": "But I cannot \"thrive the child\"\nno matter how hard I try.", "start": 2755.28, "duration": 3.98}, {"text": "Yeah?", "start": 2759.26, "duration": 0.615}, {"text": "AUDIENCE: In the\nprevious slide--", "start": 2759.875, "duration": 1.375}, {"text": "NORVIN RICHARDS: Yeah?", "start": 2761.25, "duration": 0.39}, {"text": "AUDIENCE: The fact that\nwith something a little bit", "start": 2761.64, "duration": 2.125}, {"text": "better [INAUDIBLE] verb.", "start": 2763.765, "duration": 1.115}, {"text": "How does that relate to what\nyou said earlier about how", "start": 2764.88, "duration": 2.292}, {"text": "verbs select the preposition?", "start": 2767.172, "duration": 1.968}, {"text": "NORVIN RICHARDS: So yeah, good.", "start": 2769.14, "duration": 1.41}, {"text": "Nice point", "start": 2770.55, "duration": 1.02}, {"text": "AUDIENCE: [INAUDIBLE]\ndoesn't work.", "start": 2771.57, "duration": 1.693}, {"text": "NORVIN RICHARDS: Yeah.", "start": 2773.263, "duration": 0.917}, {"text": "Yeah, Yeah, yeah.", "start": 2774.18, "duration": 0.708}, {"text": "That's a good point.", "start": 2774.888, "duration": 1.162}, {"text": "So maybe this is\na way to say it.", "start": 2776.05, "duration": 1.97}, {"text": "If you have a verb and you give\nthat verb everything it needs--", "start": 2778.02, "duration": 5.1}, {"text": "everything it selects,\nyou can always then", "start": 2783.12, "duration": 2.64}, {"text": "add \"with a feather.\"", "start": 2785.76, "duration": 1.95}, {"text": "So \"I will depend on the child\nwith the feather\" is fine.", "start": 2787.71, "duration": 5.22}, {"text": "You gave \"depend\" its\nprepositional phrase", "start": 2792.93, "duration": 2.37}, {"text": "that it wanted, \"on\nthe child,\" and then", "start": 2795.3, "duration": 3.443}, {"text": "you get to add\n\"with the feather.\"", "start": 2798.743, "duration": 1.417}, {"text": "\"With the feather\" is desert.", "start": 2800.16, "duration": 1.65}, {"text": "You never need\n\"with the feather,\"", "start": 2801.81, "duration": 1.47}, {"text": "but you can always have it.", "start": 2803.28, "duration": 1.92}, {"text": "That's right.", "start": 2805.2, "duration": 0.66}, {"text": "And then yes, you're\nabsolutely right.", "start": 2805.86, "duration": 1.72}, {"text": "You can't say \"I will\ndepend with the feather\"", "start": 2807.58, "duration": 2.15}, {"text": "because that's a case\nwhere \"depend\" needs", "start": 2809.73, "duration": 2.135}, {"text": "a prepositional phrase and\nit needs the preposition", "start": 2811.865, "duration": 2.125}, {"text": "to be \"on.\"", "start": 2813.99, "duration": 0.69}, {"text": "But if you give\n\"depend\" what it needs,", "start": 2814.68, "duration": 1.99}, {"text": "then you may always\nadd \"with the feather.\"", "start": 2816.67, "duration": 2.39}, {"text": "Yeah.", "start": 2819.06, "duration": 1.93}, {"text": "It's an optional extra, always.", "start": 2820.99, "duration": 2.81}, {"text": "Yeah.", "start": 2823.8, "duration": 1.23}, {"text": "Always, modulo-- \"modulo\"!", "start": 2825.03, "duration": 2.88}, {"text": "That's a word I\nlearned in grad school.", "start": 2827.91, "duration": 2.1}, {"text": "It means \"Always\nsetting aside issues", "start": 2830.01, "duration": 4.89}, {"text": "like, wait, what do you\nmean you will devour", "start": 2834.9, "duration": 2.73}, {"text": "the child with the feather?", "start": 2837.63, "duration": 1.2}, {"text": "Like, how are you-- what?", "start": 2838.83, "duration": 1.08}, {"text": "How are you going to do that?\"", "start": 2839.91, "duration": 0.97}, {"text": "So some of these things it's\nnot so clear what exactly--", "start": 2840.88, "duration": 2.333}, {"text": "or \"I will thrive\nwith the feather.\"", "start": 2843.213, "duration": 1.557}, {"text": "Maybe that means something.", "start": 2844.77, "duration": 1.125}, {"text": "I will live a long\nand happy life", "start": 2845.895, "duration": 1.635}, {"text": "as long as I have the feather.", "start": 2847.53, "duration": 1.92}, {"text": "So we're back to \"colorless\ngreen ideas\" territory,", "start": 2849.45, "duration": 5.25}, {"text": "more or less.", "start": 2854.7, "duration": 0.75}, {"text": "We're not in the business of\ntrying to figure out which", "start": 2855.45, "duration": 2.58}, {"text": "of these sentences make sense.", "start": 2858.03, "duration": 1.32}, {"text": "We're in the business\nof trying to figure out", "start": 2859.35, "duration": 1.875}, {"text": "which of them are grammatical,\nand they're all grammatical.", "start": 2861.225, "duration": 2.595}, {"text": "That's all I'm asserting.", "start": 2863.82, "duration": 1.23}, {"text": "Yeah?", "start": 2865.05, "duration": 1.05}, {"text": "AUDIENCE: [INAUDIBLE]\n\"...with this feather.\"", "start": 2866.1, "duration": 4.02}, {"text": "Does \"with this feather\"\nmodify \"the child\" or \"tickle\"?", "start": 2870.12, "duration": 2.425}, {"text": "NORVIN RICHARDS: Yes.", "start": 2872.545, "duration": 0.875}, {"text": "To which the answer is yes.", "start": 2873.42, "duration": 1.168}, {"text": "You're right.", "start": 2874.588, "duration": 0.542}, {"text": "So it's ambiguous.", "start": 2875.13, "duration": 1.507}, {"text": "It can have either\nof those structures", "start": 2876.637, "duration": 1.583}, {"text": "and either of those meanings.", "start": 2878.22, "duration": 1.2}, {"text": "Yeah.", "start": 2879.42, "duration": 0.5}, {"text": "So good point.", "start": 2879.92, "duration": 1.22}, {"text": "So \"I will tickle the child\nwith the feather\" could mean--", "start": 2881.14, "duration": 3.135}, {"text": "I think we talked\nabout this in class--", "start": 2884.275, "duration": 1.625}, {"text": "I will use the feather\nto tickle the child,", "start": 2885.9, "duration": 1.792}, {"text": "or I will tickle, possibly\nwith my fingers, the child who", "start": 2887.692, "duration": 3.655}, {"text": "has a feather.", "start": 2891.347, "duration": 0.583}, {"text": "That's absolutely right.", "start": 2891.93, "duration": 2.25}, {"text": "But \"with the feather\" doesn't--", "start": 2894.18, "duration": 1.95}, {"text": "so \"with the feather,\" yeah,\nit's even more adaptable", "start": 2896.13, "duration": 3.27}, {"text": "than I made it sound.", "start": 2899.4, "duration": 1.08}, {"text": "It can combine with noun\nphrases and with verb phrases,", "start": 2900.48, "duration": 3.42}, {"text": "and it can always combine\nwith noun phrases.", "start": 2903.9, "duration": 3.96}, {"text": "Concentrate on\nthat reading where", "start": 2907.86, "duration": 1.392}, {"text": "it's the child who\nhas the feather,", "start": 2909.252, "duration": 1.458}, {"text": "\"I can tickle a child\nwith a feather.\"", "start": 2910.71, "duration": 1.59}, {"text": "I can tickle an\nadult with a feather,", "start": 2912.3, "duration": 1.553}, {"text": "I can tickle a dog\nwith a feather,", "start": 2913.853, "duration": 1.417}, {"text": "I can tickle an orange\nwith a feather--", "start": 2915.27, "duration": 2.745}, {"text": "would be hard, but\nit's grammatical.", "start": 2918.015, "duration": 3.255}, {"text": "Yeah.", "start": 2921.27, "duration": 0.9}, {"text": "Yeah.", "start": 2922.17, "duration": 0.78}, {"text": "Yeah?", "start": 2922.95, "duration": 0.54}, {"text": "So \"with a feather\"-- anything\ncan have a feather, and you", "start": 2923.49, "duration": 2.417}, {"text": "can always use a\nfeather to do anything.", "start": 2925.907, "duration": 2.033}, {"text": "That's the moral of all this.", "start": 2927.94, "duration": 2.32}, {"text": "OK?", "start": 2930.26, "duration": 0.5}, {"text": "People are leaving.", "start": 2933.678, "duration": 0.792}, {"text": "Was it all the talk\nabout devouring children?", "start": 2934.47, "duration": 2.766}, {"text": "AUDIENCE: People are leaving.", "start": 2937.236, "duration": 1.494}, {"text": "NORVIN RICHARDS: Sorry?", "start": 2938.73, "duration": 1.385}, {"text": "AUDIENCE: I was\ntrying to come up", "start": 2940.115, "duration": 1.375}, {"text": "with something that wouldn't\ndepend on this feather.", "start": 2941.49, "duration": 2.258}, {"text": "NORVIN RICHARDS:\n\"With this feather\"?", "start": 2943.748, "duration": 1.542}, {"text": "No.", "start": 2945.29, "duration": 0.9}, {"text": "So.", "start": 2946.19, "duration": 1.11}, {"text": "\"Who are you with this feather?\"", "start": 2947.3, "duration": 3.51}, {"text": "\"I am far, far more\nimpressive with this feather.\"", "start": 2950.81, "duration": 2.41}, {"text": "Yeah.", "start": 2953.22, "duration": 0.64}, {"text": "Yeah.", "start": 2953.86, "duration": 0.625}, {"text": "Yeah?", "start": 2954.485, "duration": 0.615}, {"text": "OK.", "start": 2955.1, "duration": 0.33}, {"text": "All right.", "start": 2955.43, "duration": 0.5}, {"text": "So you can do anything\nwith the feather.", "start": 2955.93, "duration": 1.87}, {"text": "And conversely, so\n\"with a feather\"", "start": 2957.8, "duration": 2.76}, {"text": "can combine with anything--\nmaybe not conversely.", "start": 2960.56, "duration": 2.37}, {"text": "\"With a feather\" can\ncombine with anything.", "start": 2962.93, "duration": 2.7}, {"text": "Objects can't combine\nwith just anything.", "start": 2965.63, "duration": 2.94}, {"text": "You have to pick a\nverb that is transitive", "start": 2968.57, "duration": 2.3}, {"text": "or at least can be transitive.", "start": 2970.87, "duration": 1.25}, {"text": "So you can \"tickle a child.\"", "start": 2972.12, "duration": 1.258}, {"text": "You can \"devour a child.\"", "start": 2973.378, "duration": 1.042}, {"text": "You can \"write a child.\"", "start": 2974.42, "duration": 2.22}, {"text": "You cannot \"thrive a child.\"", "start": 2976.64, "duration": 1.62}, {"text": "So if you pick an\nintransitive verb then", "start": 2978.26, "duration": 1.74}, {"text": "you can't combine it\nwith a direct object.", "start": 2980.0, "duration": 1.99}, {"text": "So there's a selection\nrelation between the verb", "start": 2981.99, "duration": 2.03}, {"text": "and its object.", "start": 2984.02, "duration": 0.66}, {"text": "That's what we were\njust talking about.", "start": 2984.68, "duration": 1.625}, {"text": "We have to look up verbs\nlike \"tickle\" and \"devour\"", "start": 2986.305, "duration": 2.245}, {"text": "and \"write\" in the\nlexicon and find out", "start": 2988.55, "duration": 1.71}, {"text": "whether they can combine\nwith objects or not,", "start": 2990.26, "duration": 1.93}, {"text": "but we'll never have\nto look anything up", "start": 2992.19, "duration": 1.52}, {"text": "to know whether you can\nadd \"with a feather.\"", "start": 2993.71, "duration": 1.38}, {"text": "You can just always\nadd \"with a feather.\"", "start": 2995.09, "duration": 1.92}, {"text": "Yeah?", "start": 2997.01, "duration": 2.1}, {"text": "So yes, when we're\nbuilding trees", "start": 2999.11, "duration": 2.73}, {"text": "we're going to have selection\nrelations that sometimes tell", "start": 3001.84, "duration": 2.61}, {"text": "us, yeah, if we have,\nsay, this kind of verb,", "start": 3004.45, "duration": 2.34}, {"text": "we'd better have this kind\nof phrase combining with it.", "start": 3006.79, "duration": 2.94}, {"text": "We have \"devour.\"", "start": 3009.73, "duration": 1.608}, {"text": "It had better combine\nwith an object.", "start": 3011.338, "duration": 1.542}, {"text": "Something has to get devoured.", "start": 3012.88, "duration": 1.703}, {"text": "But then there are going\nto be other kinds of things", "start": 3014.583, "duration": 2.167}, {"text": "like \"with a feather\" that\nare just always options.", "start": 3016.75, "duration": 3.04}, {"text": "You can always put them in.", "start": 3019.79, "duration": 2.42}, {"text": "Another terminology break.", "start": 3022.21, "duration": 1.8}, {"text": "We call things that\nare selected arguments.", "start": 3024.01, "duration": 4.0}, {"text": "So \"the child\" is an argument\nof the verb \"tickle,\"", "start": 3028.01, "duration": 5.54}, {"text": "in this example,\nand we call phrases", "start": 3033.55, "duration": 2.768}, {"text": "that don't seem to be\nselected by anything,", "start": 3036.318, "duration": 1.792}, {"text": "we call those adjuncts.", "start": 3038.11, "duration": 1.68}, {"text": "Just the name for those things.", "start": 3039.79, "duration": 1.8}, {"text": "Here we have to be careful.", "start": 3047.43, "duration": 1.57}, {"text": "This is a point where people\nget confused sometimes.", "start": 3049.0, "duration": 3.26}, {"text": "So let me see if I can say this.", "start": 3052.26, "duration": 3.53}, {"text": "Knowing me, I will probably\nsay this several different ways", "start": 3055.79, "duration": 3.57}, {"text": "and we'll just see\nif I manage to say it", "start": 3059.36, "duration": 2.22}, {"text": "in a way that makes it\nmake sense because people", "start": 3061.58, "duration": 2.73}, {"text": "get confused about this.", "start": 3064.31, "duration": 1.83}, {"text": "Arguments.", "start": 3066.14, "duration": 0.748}, {"text": "Here's a way to think about it.", "start": 3066.888, "duration": 1.292}, {"text": "Arguments, like direct\nobjects, arguments", "start": 3068.18, "duration": 2.88}, {"text": "are picky about which heads\nthey can combine with.", "start": 3071.06, "duration": 3.25}, {"text": "So if you're asking, should\nI put in a noun phrase", "start": 3074.31, "duration": 4.55}, {"text": "object for this verb?", "start": 3078.86, "duration": 1.64}, {"text": "Well, you've got to\nknow what the verb is,", "start": 3080.5, "duration": 1.75}, {"text": "whether it's a transitive\nverb or an intransitive verb.", "start": 3082.25, "duration": 3.78}, {"text": "Adjuncts are not.", "start": 3086.03, "duration": 1.29}, {"text": "So adjuncts like\n\"with a feather\"", "start": 3087.32, "duration": 2.79}, {"text": "can combine with anything.", "start": 3090.11, "duration": 3.48}, {"text": "There's no selection, really.", "start": 3093.59, "duration": 1.29}, {"text": "You don't have to\nlook anything up", "start": 3094.88, "duration": 1.32}, {"text": "to find out whether you\ncan merge \"with a feather.\"", "start": 3096.2, "duration": 2.125}, {"text": "The confusion\ncomes in like this.", "start": 3100.95, "duration": 4.22}, {"text": "The problem is there\nare optional arguments.", "start": 3105.17, "duration": 2.86}, {"text": "So I flagged this earlier.", "start": 3108.03, "duration": 1.19}, {"text": "There are verbs\nthat are transitive", "start": 3109.22, "duration": 1.61}, {"text": "and there are verbs\nthat are intransitive,", "start": 3110.83, "duration": 1.75}, {"text": "and in the earlier\nslides where I", "start": 3112.58, "duration": 1.927}, {"text": "was talking about\ntransitivity I tried", "start": 3114.507, "duration": 1.583}, {"text": "to concentrate on\nverbs that were", "start": 3116.09, "duration": 2.11}, {"text": "comfortable in their identity\nas either transitive verbs", "start": 3118.2, "duration": 2.63}, {"text": "or intransitive verbs, but\nthere are many, many verbs", "start": 3120.83, "duration": 2.55}, {"text": "that can be either one.", "start": 3123.38, "duration": 2.085}, {"text": "So you can \"dance\" or you\ncan \"dance a hornpipe.\"", "start": 3125.465, "duration": 3.075}, {"text": "Here's the thing.", "start": 3131.24, "duration": 0.78}, {"text": "So you can \"dance\" or you can\n\"dance a hornpipe,\" but when", "start": 3135.81, "duration": 3.02}, {"text": "you \"dance a\nhornpipe,\" \"a hornpipe\"", "start": 3138.83, "duration": 1.95}, {"text": "is an argument of\n\"dance\" because you", "start": 3140.78, "duration": 2.64}, {"text": "have to know whether the\nverb can be a transitive verb", "start": 3143.42, "duration": 3.84}, {"text": "to know whether there can\nbe a noun phrase there.", "start": 3147.26, "duration": 2.67}, {"text": "The confusion comes in.", "start": 3149.93, "duration": 1.45}, {"text": "People look at sentences\nlike \"I will devour the child", "start": 3151.38, "duration": 8.8}, {"text": "with the feather.\"", "start": 3160.18, "duration": 0.75}, {"text": "Let's make it \"tickle.\"", "start": 3165.33, "duration": 0.96}, {"text": "\"I will tickle the\nchild with the feather.\"", "start": 3168.233, "duration": 1.792}, {"text": "Syntacticians are\nthe kind of people", "start": 3172.65, "duration": 1.5}, {"text": "for whom \"I will devour\nthe child with a feather\"", "start": 3174.15, "duration": 2.04}, {"text": "and \"I will tickle the\nchild with the feather\"", "start": 3176.19, "duration": 1.245}, {"text": "are basically the same sentence.", "start": 3177.435, "duration": 1.695}, {"text": "We're just not interested in\nthe differences between those.", "start": 3179.13, "duration": 4.03}, {"text": "They're basically the same.", "start": 3183.16, "duration": 1.73}, {"text": "People look at\nthat and they go--", "start": 3184.89, "duration": 1.608}, {"text": "well, maybe I want\nit to be \"devour.\"", "start": 3186.498, "duration": 1.542}, {"text": "No, we can stick with \"tickle.\"", "start": 3188.04, "duration": 1.292}, {"text": "So what we say is\nthis is an argument", "start": 3193.48, "duration": 3.32}, {"text": "and this is an adjunct.", "start": 3196.8, "duration": 4.988}, {"text": "To say that this is an argument\nis to say that whether it can", "start": 3201.788, "duration": 2.542}, {"text": "be there or not is\ndetermined by what verb", "start": 3204.33, "duration": 2.19}, {"text": "you've got, whether the\nverb is transitive or not.", "start": 3206.52, "duration": 2.43}, {"text": "To say that this\nis an adjunct is", "start": 3208.95, "duration": 1.375}, {"text": "to say that I don't care what\nthe verb is when I decide", "start": 3210.325, "duration": 2.292}, {"text": "whether to put that in or not.", "start": 3212.617, "duration": 1.343}, {"text": "What people get\nconfused by is this.", "start": 3213.96, "duration": 2.31}, {"text": "Adjuncts are pretty\ntypically optional.", "start": 3216.27, "duration": 2.737}, {"text": "You can tickle a\nchild with a feather.", "start": 3219.007, "duration": 1.583}, {"text": "You don't have to, you\ncan just tickle a child.", "start": 3220.59, "duration": 3.39}, {"text": "There's never a requirement\nthat an adjunct be there.", "start": 3223.98, "duration": 3.31}, {"text": "And so this is one of those\ntests for whether you're", "start": 3227.29, "duration": 4.852}, {"text": "looking at an argument\nor an adjunct that", "start": 3232.142, "duration": 1.708}, {"text": "only works in one direction.", "start": 3233.85, "duration": 2.26}, {"text": "If it's an adjunct it\nhad better be optional.", "start": 3236.11, "duration": 4.89}, {"text": "But if it's optional,\nit could be an adjunct", "start": 3241.0, "duration": 3.36}, {"text": "or it could be a hornpipe.", "start": 3244.36, "duration": 2.1}, {"text": "It could be an object, in\nthese kinds of examples, that's", "start": 3246.46, "duration": 5.1}, {"text": "combining with the\nkind of verb that", "start": 3251.56, "duration": 1.5}, {"text": "can be either transitive\nor intransitive.", "start": 3253.06, "duration": 2.93}, {"text": "So if you're looking at a phrase\nand you're saying to yourself", "start": 3255.99, "duration": 2.82}, {"text": "\"This phrase is\noptional,\" you're", "start": 3258.81, "duration": 1.65}, {"text": "not then entitled to guess that\nit's an adjunct, necessarily.", "start": 3260.46, "duration": 4.043}, {"text": "You only get to\nfind out that it's", "start": 3264.503, "duration": 1.417}, {"text": "an adjunct by asking\nyourself, will it", "start": 3265.92, "duration": 2.55}, {"text": "matter what verb\nI have, let's say?", "start": 3268.47, "duration": 2.95}, {"text": "Or what noun I have,\ndepending on what", "start": 3271.42, "duration": 1.61}, {"text": "you're combining it with.", "start": 3273.03, "duration": 1.85}, {"text": "OK?", "start": 3274.88, "duration": 1.33}, {"text": "Is that clear?", "start": 3276.21, "duration": 1.2}, {"text": "Have I said it in enough\ndifferent ways, Faith?", "start": 3277.41, "duration": 2.34}, {"text": "AUDIENCE: Is this\nat all complicated", "start": 3279.75, "duration": 1.5}, {"text": "if you treat the feather\nas, like, an animate entity?", "start": 3281.25, "duration": 5.28}, {"text": "So if you were to actually\n[INAUDIBLE] a person", "start": 3286.53, "duration": 2.86}, {"text": "and you would say, I\ndanced with the feather.", "start": 3289.39, "duration": 2.486}, {"text": "Would it mean you're dancing--", "start": 3291.876, "duration": 1.786}, {"text": "like, is that [INAUDIBLE]?", "start": 3293.662, "duration": 1.505}, {"text": "NORVIN RICHARDS: Oh.", "start": 3295.167, "duration": 0.833}, {"text": "Oh.", "start": 3296.0, "duration": 0.45}, {"text": "Oh.", "start": 3296.45, "duration": 0.5}, {"text": "Oh.", "start": 3296.95, "duration": 0.85}, {"text": "Oh.", "start": 3297.8, "duration": 0.85}, {"text": "Oh.", "start": 3298.65, "duration": 0.5}, {"text": "Oh, dear.", "start": 3299.15, "duration": 0.75}, {"text": "Well, let's reluctantly put\nfeathers aside for a second", "start": 3304.1, "duration": 4.69}, {"text": "and talk about something that we\nknow is animate, like children.", "start": 3308.79, "duration": 6.51}, {"text": "So you can dance with the child.", "start": 3315.3, "duration": 2.39}, {"text": "You can play games\nwith the child.", "start": 3317.69, "duration": 3.15}, {"text": "You can eat lunch\nwith the child.", "start": 3320.84, "duration": 2.79}, {"text": "\"With the child\"\nis probably still", "start": 3323.63, "duration": 3.27}, {"text": "an adjunct in that\nkind of reading.", "start": 3326.9, "duration": 3.28}, {"text": "So \"with the feather\"--\nyou're raising a good", "start": 3330.18, "duration": 1.98}, {"text": "point that with in English--", "start": 3332.16, "duration": 1.65}, {"text": "I was warning you about\nIndo-European prepositions.", "start": 3333.81, "duration": 3.36}, {"text": "\"With\" can mean two subtly\ndifferent things, right?", "start": 3337.17, "duration": 3.735}, {"text": "So you're pointing out that if\nI tickle a child with a feather,", "start": 3340.905, "duration": 2.625}, {"text": "I'm using the feather as\nan instrument for what", "start": 3343.53, "duration": 2.43}, {"text": "I'm going to do.", "start": 3345.96, "duration": 1.65}, {"text": "If I have lunch with a feather--", "start": 3347.61, "duration": 2.1}, {"text": "if I have lunch with a\nchild, then that \"with\"", "start": 3349.71, "duration": 2.67}, {"text": "is introducing somebody who\nis doing something together", "start": 3352.38, "duration": 2.76}, {"text": "with me, right?", "start": 3355.14, "duration": 1.71}, {"text": "We're both doing the\nactivity in the verb frames.", "start": 3356.85, "duration": 2.34}, {"text": "So those are maybe two different\n\"with\"s, but they're both ad--", "start": 3359.19, "duration": 4.44}, {"text": "those two prepositional phrases,\nthey're probably both adjuncts.", "start": 3363.63, "duration": 3.81}, {"text": "And \"I will dance with\nthe feather,\" I guess,", "start": 3367.44, "duration": 2.89}, {"text": "could have either\nreading in principle.", "start": 3370.33, "duration": 1.95}, {"text": "Yeah.", "start": 3372.28, "duration": 0.5}, {"text": "Yeah.", "start": 3372.78, "duration": 1.26}, {"text": "Yeah.", "start": 3374.04, "duration": 0.72}, {"text": "Yeah?", "start": 3374.76, "duration": 1.49}, {"text": "Cool.", "start": 3376.25, "duration": 0.99}, {"text": "Nice example.", "start": 3377.24, "duration": 3.04}, {"text": "OK.", "start": 3380.28, "duration": 1.8}, {"text": "OK, so that's the distinction\nbetween arguments and adjuncts.", "start": 3382.08, "duration": 2.64}, {"text": "Why are we bothering\nto distinguish", "start": 3387.9, "duration": 1.712}, {"text": "arguments and adjuncts?", "start": 3389.612, "duration": 0.958}, {"text": "Well, there are various places\nwhere they behave differently", "start": 3390.57, "duration": 2.5}, {"text": "in interesting ways.", "start": 3393.07, "duration": 2.04}, {"text": "So take a sentence like\n\"I decided on the boat.\"", "start": 3395.11, "duration": 5.15}, {"text": "That can mean a couple\nof different things.", "start": 3400.26, "duration": 2.01}, {"text": "Somebody tell me something\nthat it can mean.", "start": 3402.27, "duration": 2.142}, {"text": "AUDIENCE: I made the\ndecision on the boat.", "start": 3404.412, "duration": 1.968}, {"text": "NORVIN RICHARDS: Sorry?", "start": 3406.38, "duration": 0.42}, {"text": "AUDIENCE: I made the\ndecision while I was on.", "start": 3406.8, "duration": 1.5}, {"text": "NORVIN RICHARDS: \"I\nmade the decision", "start": 3408.3, "duration": 0.69}, {"text": "while I was on the boat.\"", "start": 3408.99, "duration": 0.63}, {"text": "That's one thing it can mean.", "start": 3409.62, "duration": 0.9}, {"text": "What's the other thing?", "start": 3410.52, "duration": 0.87}, {"text": "AUDIENCE: \"I was a\nboat dealer and I", "start": 3411.39, "duration": 1.092}, {"text": "was picking between\ntwo different boats", "start": 3412.482, "duration": 1.625}, {"text": "and I decided on this one.\"", "start": 3414.107, "duration": 1.323}, {"text": "NORVIN RICHARDS: Yeah.", "start": 3415.43, "duration": 0.37}, {"text": "Yeah, yeah, yeah.", "start": 3415.8, "duration": 0.708}, {"text": "So I was deciding between\na boat and something else.", "start": 3416.508, "duration": 3.152}, {"text": "You know, am I going to buy--", "start": 3419.66, "duration": 2.04}, {"text": "or maybe I was deciding\nbetween two different boats", "start": 3421.7, "duration": 2.22}, {"text": "and I decided on the boat.", "start": 3423.92, "duration": 1.11}, {"text": "I decided on the big\nblack boat instead", "start": 3425.03, "duration": 2.55}, {"text": "of the small white boat.", "start": 3427.58, "duration": 1.11}, {"text": "Yeah.", "start": 3428.69, "duration": 0.5}, {"text": "Whatever.", "start": 3429.19, "duration": 0.53}, {"text": "Yeah.", "start": 3429.72, "duration": 0.5}, {"text": "Or I decided on the boat\nrather than the motorcycle.", "start": 3430.22, "duration": 2.22}, {"text": "I was deciding what to\nspend my lottery money on.", "start": 3432.44, "duration": 2.28}, {"text": "Yeah.", "start": 3434.72, "duration": 0.78}, {"text": "Yeah.", "start": 3435.5, "duration": 0.69}, {"text": "It can mean either\nof those things.", "start": 3436.19, "duration": 1.458}, {"text": "Maybe the next\nslide will do this", "start": 3440.27, "duration": 1.44}, {"text": "and I won't have to mess\nwith the blackboard.", "start": 3441.71, "duration": 3.0}, {"text": "Yes.", "start": 3444.71, "duration": 0.84}, {"text": "So those are the two\nreadings, actually,", "start": 3445.55, "duration": 3.792}, {"text": "in the same order\nthat we got them.", "start": 3449.342, "duration": 1.458}, {"text": "Faith's reading, which\nis the first one,", "start": 3450.8, "duration": 1.44}, {"text": "I made my decision\nwhile I was on the boat.", "start": 3452.24, "duration": 1.95}, {"text": "And then Joseph's\nreading, I chose the boat.", "start": 3454.19, "duration": 2.62}, {"text": "It can mean either\nof those things.", "start": 3456.81, "duration": 3.19}, {"text": "Is \"on the boat\" an\nargument or an adjunct?", "start": 3460.0, "duration": 1.905}, {"text": "Given what we've said about\narguments and adjuncts.", "start": 3464.85, "duration": 3.803}, {"text": "AUDIENCE: It depends on the\nmeaning that you intend.", "start": 3468.653, "duration": 2.167}, {"text": "NORVIN RICHARDS: Yes.", "start": 3470.82, "duration": 1.31}, {"text": "Yes.", "start": 3472.13, "duration": 0.53}, {"text": "The answer to that\nquestion is yes.", "start": 3472.66, "duration": 1.552}, {"text": "Is it an argument or adjunct?", "start": 3474.212, "duration": 1.208}, {"text": "Yes.", "start": 3475.42, "duration": 0.5}, {"text": "Yes, it is.", "start": 3475.92, "duration": 0.73}, {"text": "Yeah.", "start": 3476.65, "duration": 1.86}, {"text": "Suppose we take the first\nreading for \"on the boat.\"", "start": 3478.51, "duration": 3.24}, {"text": "So I made my decision\nwhile I was on the boat.", "start": 3481.75, "duration": 2.49}, {"text": "Is that an argument\nor an adjunct,", "start": 3484.24, "duration": 1.98}, {"text": "that version of on the boat?", "start": 3486.22, "duration": 2.65}, {"text": "AUDIENCE: Adjunct.", "start": 3488.87, "duration": 0.91}, {"text": "NORVIN RICHARDS:\nIt's an adjunct.", "start": 3489.78, "duration": 1.375}, {"text": "You can do anything on a boat.", "start": 3491.155, "duration": 2.386}, {"text": "Sleep on a boat.", "start": 3493.541, "duration": 0.759}, {"text": "Write your\ndissertation on a boat.", "start": 3494.3, "duration": 2.22}, {"text": "Lots of things you\ncan do on a boat.", "start": 3496.52, "duration": 1.98}, {"text": "On a boat can combine\nwith all kinds of things.", "start": 3498.5, "duration": 2.76}, {"text": "But the second reading\nwhere I decided on the boat", "start": 3501.26, "duration": 3.21}, {"text": "ends up meaning \"I\nchose the boat,\" that's", "start": 3504.47, "duration": 3.84}, {"text": "kind of an idiosyncratic fact\nabout \"decide\" and \"on,\" right?", "start": 3508.31, "duration": 3.66}, {"text": "That \"decide\" and \"on\" can\nsquash together to mean", "start": 3511.97, "duration": 3.93}, {"text": "\"choose.\"", "start": 3515.9, "duration": 1.89}, {"text": "Right?", "start": 3517.79, "duration": 2.25}, {"text": "You can't do this even\nwith other expressions that", "start": 3520.04, "duration": 2.82}, {"text": "more or less mean \"decide.\"", "start": 3522.86, "duration": 1.41}, {"text": "You can't say \"I made\nup my mind on the boat\"", "start": 3524.27, "duration": 2.73}, {"text": "and mean \"I chose the\nboat,\" I don't think.", "start": 3527.0, "duration": 3.22}, {"text": "Right?", "start": 3530.22, "duration": 0.5}, {"text": "And you certainly can't\ncombine \"on the boat\"", "start": 3533.81, "duration": 2.01}, {"text": "with any random verb and\nexpect to get a new meaning.", "start": 3535.82, "duration": 2.73}, {"text": "That's not the way life works.", "start": 3538.55, "duration": 3.34}, {"text": "So there's an adjunct\nmeaning of \"on the boat\"", "start": 3541.89, "duration": 3.05}, {"text": "and there's an argument\nmeaning of \"on the boat.\"", "start": 3544.94, "duration": 3.27}, {"text": "OK.", "start": 3548.21, "duration": 0.87}, {"text": "Cool.", "start": 3549.08, "duration": 0.57}, {"text": "Now, yeah, is it an\nargument or adjunct?", "start": 3549.65, "duration": 2.49}, {"text": "Yes.", "start": 3552.14, "duration": 0.78}, {"text": "So the first one is an adjunct,\nthe second one is an argument.", "start": 3552.92, "duration": 2.25}, {"text": "Good.", "start": 3555.17, "duration": 0.5}, {"text": "Consider a sentence like,\n\"I decided on the boat", "start": 3558.07, "duration": 2.04}, {"text": "on the plane.\"", "start": 3560.11, "duration": 1.62}, {"text": "Please, while you're\nconsidering the sentence,", "start": 3561.73, "duration": 2.1}, {"text": "do not think about cases where\nboats are on planes or planes", "start": 3563.83, "duration": 2.73}, {"text": "are on boats.", "start": 3566.56, "duration": 0.84}, {"text": "There are planes\nthat are also boats--", "start": 3567.4, "duration": 1.71}, {"text": "I've been teaching this class\nto MIT undergrads for a while.", "start": 3569.11, "duration": 3.66}, {"text": "I know the kinds\nof moves that you", "start": 3572.77, "duration": 2.19}, {"text": "are thinking about even now.", "start": 3574.96, "duration": 2.19}, {"text": "So just consider cases where--", "start": 3577.15, "duration": 3.36}, {"text": "so the imaginable things that\nit could mean given those", "start": 3580.51, "duration": 2.97}, {"text": "two readings for \"on the boat.\"", "start": 3583.48, "duration": 2.49}, {"text": "I think there are two.", "start": 3585.97, "duration": 1.05}, {"text": "It could mean, \"While I was on\nthe plane I chose the boat,\"", "start": 3587.02, "duration": 5.91}, {"text": "or it could mean \"While I was\non the boat I chose the plane.\"", "start": 3592.93, "duration": 4.87}, {"text": "Yeah?", "start": 3597.8, "duration": 0.84}, {"text": "In principle it ought to be able\nto mean either of those things.", "start": 3598.64, "duration": 3.59}, {"text": "Can it mean both\nof those things?", "start": 3602.23, "duration": 3.605}, {"text": "AUDIENCE: [INAUDIBLE],,\nbut I just--", "start": 3605.835, "duration": 5.445}, {"text": "I decided on the\nboat on the plane.", "start": 3611.28, "duration": 2.8}, {"text": "Like, deciding on the plane on\nthe boat sounds much weirder.", "start": 3614.08, "duration": 4.053}, {"text": "NORVIN RICHARDS: Yeah.", "start": 3618.133, "duration": 0.917}, {"text": "Here, I'll tell you what.", "start": 3619.05, "duration": 0.63}, {"text": "Let me write these\nreadings down just", "start": 3619.68, "duration": 1.542}, {"text": "so we can point at them as we're\ntalking because otherwise I", "start": 3621.222, "duration": 3.696}, {"text": "can tell we're going\nto get confused.", "start": 3624.918, "duration": 1.542}, {"text": "I'm already confused and\nwe've only just started.", "start": 3626.46, "duration": 2.77}, {"text": "So one reading is \"I chose the\nboat while I was on the plane.\"", "start": 3629.23, "duration": 10.754}, {"text": "The other is \"I chose the\nplane while I was on the boat.\"", "start": 3639.984, "duration": 11.956}, {"text": "Is that legible at all?", "start": 3657.78, "duration": 1.68}, {"text": "Can you read that, any of you?", "start": 3659.46, "duration": 1.28}, {"text": "Yes?", "start": 3660.74, "duration": 0.5}, {"text": "Sort of?", "start": 3661.24, "duration": 0.37}, {"text": "Kind of?", "start": 3661.61, "duration": 0.5}, {"text": "OK, good.", "start": 3662.11, "duration": 1.25}, {"text": "So those are the two readings.", "start": 3663.36, "duration": 1.44}, {"text": "Call them reading\none and reading two,", "start": 3664.8, "duration": 1.838}, {"text": "or we could call them\nthe \"choose the boat\"", "start": 3666.638, "duration": 1.792}, {"text": "reading and the \"choose\nthe plane\" reading.", "start": 3668.43, "duration": 1.792}, {"text": "And now we're trying to figure\nout which of those things", "start": 3670.222, "duration": 2.333}, {"text": "can this mean.", "start": 3672.555, "duration": 0.585}, {"text": "Kate?", "start": 3673.14, "duration": 0.5}, {"text": "AUDIENCE: OK.", "start": 3673.64, "duration": 0.542}, {"text": "So instinctively I chose reading\none because the boat just--", "start": 3674.182, "duration": 5.016}, {"text": "I don't know.", "start": 3679.198, "duration": 0.542}, {"text": "That feels like it makes sense.", "start": 3679.74, "duration": 1.98}, {"text": "But then I thought, if you\nwork hard enough to make sense,", "start": 3681.72, "duration": 3.7}, {"text": "especially if you\nwere to replace", "start": 3685.42, "duration": 2.723}, {"text": "the second prepositional\nphrase with something", "start": 3688.143, "duration": 1.917}, {"text": "more simple, like \"at lunch\"--", "start": 3690.06, "duration": 2.49}, {"text": "NORVIN RICHARDS: Oh.", "start": 3692.55, "duration": 0.99}, {"text": "AUDIENCE: In [? formal, ?]\nor yesterday, I guess,", "start": 3693.54, "duration": 3.34}, {"text": "which isn't--", "start": 3696.88, "duration": 0.68}, {"text": "I don't know.", "start": 3697.56, "duration": 0.542}, {"text": "[INAUDIBLE]", "start": 3698.102, "duration": 0.914}, {"text": "But \"I decided on the boat\nat lunch\" makes sense.", "start": 3699.016, "duration": 3.964}, {"text": "You still have essentially\nthe same content.", "start": 3702.98, "duration": 3.085}, {"text": "NORVIN RICHARDS: Yes.", "start": 3706.065, "duration": 0.875}, {"text": "Yes.", "start": 3706.94, "duration": 1.38}, {"text": "So that's a nice point.", "start": 3708.32, "duration": 3.21}, {"text": "Let me react to it by\nattempting to squash it.", "start": 3711.53, "duration": 4.35}, {"text": "So don't change either of\nthe prepositional phrases", "start": 3715.88, "duration": 4.02}, {"text": "into anything else.", "start": 3719.9, "duration": 0.978}, {"text": "But we are going to\nwant to come back", "start": 3720.878, "duration": 1.542}, {"text": "to that because that's a nice\npoint that you're making.", "start": 3722.42, "duration": 3.25}, {"text": "I think if I say \"I decided\non the boat at lunch,\"", "start": 3725.67, "duration": 6.92}, {"text": "that we're back to the\noriginal ambiguity.", "start": 3732.59, "duration": 2.34}, {"text": "Is that your feeling?", "start": 3734.93, "duration": 1.17}, {"text": "That that can mean either\nI chose the boat at lunch", "start": 3736.1, "duration": 2.46}, {"text": "or I decided while I was\non the boat at lunch.", "start": 3738.56, "duration": 5.82}, {"text": "Is that true, do you think?", "start": 3744.38, "duration": 1.53}, {"text": "AUDIENCE: I just got lost.", "start": 3745.91, "duration": 1.083}, {"text": "NORVIN RICHARDS: Me too.", "start": 3746.993, "duration": 1.0}, {"text": "Me too.", "start": 3747.993, "duration": 0.527}, {"text": "So yeah, stick to\nthese prepositions", "start": 3748.52, "duration": 2.16}, {"text": "or these prepositions.", "start": 3750.68, "duration": 1.32}, {"text": "That sentence, we're\ntrying to figure out", "start": 3752.0, "duration": 1.708}, {"text": "what that sentence can mean.", "start": 3753.708, "duration": 1.262}, {"text": "What can that sentence mean?", "start": 3754.97, "duration": 1.0}, {"text": "Yeah?", "start": 3755.97, "duration": 0.5}, {"text": "AUDIENCE: I think\nthe first one would", "start": 3756.47, "duration": 1.587}, {"text": "be more usual in the sense\nthat if you tried to--", "start": 3758.057, "duration": 3.893}, {"text": "I mean, I know you told us\nnot to replace anything, but--", "start": 3761.95, "duration": 2.642}, {"text": "NORVIN RICHARDS: It's all right.", "start": 3764.592, "duration": 1.333}, {"text": "AUDIENCE: If you do try\nto replace \"on the boat\"", "start": 3765.925, "duration": 3.255}, {"text": "with another adjunct, I don't\nknow, like \"the building,\"", "start": 3769.18, "duration": 4.11}, {"text": "it would be a little weird.", "start": 3773.29, "duration": 1.89}, {"text": "It would pass off as something--", "start": 3775.18, "duration": 1.95}, {"text": "I would pass it off as\nsomething that you could say,", "start": 3777.13, "duration": 2.34}, {"text": "but I wouldn't quite say it and\nit sounds super weird to say.", "start": 3779.47, "duration": 2.94}, {"text": "Like, \"I decided in the\nbuilding on the plane\"?", "start": 3782.41, "duration": 3.57}, {"text": "Is this clearly\ndeciding on the plane?", "start": 3785.98, "duration": 3.61}, {"text": "Decide on the plane,\nbut it sounds weird", "start": 3789.59, "duration": 3.44}, {"text": "because \"decided on\"\nshould be kind of better.", "start": 3793.03, "duration": 2.045}, {"text": "NORVIN RICHARDS:\nOK, so now we've", "start": 3795.075, "duration": 1.375}, {"text": "had two votes for changing\nsome of the prepositions,", "start": 3796.45, "duration": 2.25}, {"text": "so I'll stop fighting it.", "start": 3798.7, "duration": 2.08}, {"text": "We could also be thinking about,\n\"I decided in the building", "start": 3800.78, "duration": 10.73}, {"text": "on the boat.\"", "start": 3811.51, "duration": 0.66}, {"text": "Is this grammatical?", "start": 3818.42, "duration": 2.73}, {"text": "Sort of?", "start": 3821.15, "duration": 1.416}, {"text": "Yeah?", "start": 3822.566, "duration": 0.924}, {"text": "Yeah?", "start": 3823.49, "duration": 0.78}, {"text": "And does this mean\nI chose the boat", "start": 3824.27, "duration": 4.327}, {"text": "while it was in the building?", "start": 3828.597, "duration": 1.208}, {"text": "It can.", "start": 3833.01, "duration": 0.75}, {"text": "Yeah.", "start": 3833.76, "duration": 0.81}, {"text": "I guess it's hard for me\nto be both in a building", "start": 3834.57, "duration": 2.46}, {"text": "and on a boat unless the\nbuilding is on the boat", "start": 3837.03, "duration": 3.09}, {"text": "or the boat is on the building.", "start": 3840.12, "duration": 1.31}, {"text": "Yeah.", "start": 3841.43, "duration": 1.06}, {"text": "Many, many hands.", "start": 3842.49, "duration": 1.02}, {"text": "Yes?", "start": 3843.51, "duration": 1.155}, {"text": "AUDIENCE: Yeah.", "start": 3844.665, "duration": 0.625}, {"text": "My thinking was that when\nthe prepositional phrase is", "start": 3848.41, "duration": 4.93}, {"text": "in argument, it's more attached\nto the verb by association.", "start": 3853.34, "duration": 5.67}, {"text": "So it kind of makes less\nsense to split in the middle.", "start": 3859.01, "duration": 6.88}, {"text": "So that sentence that\nyou put below there", "start": 3865.89, "duration": 5.05}, {"text": "doesn't quite go as\nwell, and so that's", "start": 3870.94, "duration": 7.23}, {"text": "why choosing the boat on\nthe plane makes more sense.", "start": 3878.17, "duration": 5.847}, {"text": "NORVIN RICHARDS: OK.", "start": 3884.017, "duration": 0.833}, {"text": "Cool.", "start": 3884.85, "duration": 0.5}, {"text": "So actually, what you just\nsaid and what Faith just said", "start": 3885.35, "duration": 3.1}, {"text": "and what you just\nsaid a second ago,", "start": 3888.45, "duration": 2.07}, {"text": "these dovetail nicely, I think.", "start": 3890.52, "duration": 1.977}, {"text": "Let me now try to\nsummarize something that I", "start": 3892.497, "duration": 1.833}, {"text": "think all three of you said.", "start": 3894.33, "duration": 2.91}, {"text": "Maybe we can say it like this.", "start": 3897.24, "duration": 2.43}, {"text": "When I asked, can this\nmean \"I chose the boat", "start": 3899.67, "duration": 2.16}, {"text": "while it was in the building\"?", "start": 3901.83, "duration": 1.5}, {"text": "Everybody was like, nah.", "start": 3903.33, "duration": 2.82}, {"text": "I think it can, but for\nme I have to pronounce it", "start": 3906.15, "duration": 2.82}, {"text": "in a particular way.", "start": 3908.97, "duration": 1.66}, {"text": "So I can say \"I decided, in\nthe building, on the boat.\"", "start": 3910.63, "duration": 6.8}, {"text": "I think that's the easiest\nway for me to say it and have", "start": 3917.43, "duration": 3.66}, {"text": "it mean that.", "start": 3921.09, "duration": 2.19}, {"text": "So I did something\nfancy with my voice", "start": 3923.28, "duration": 2.73}, {"text": "there that involved trying to\nhide this prepositional phrase.", "start": 3926.01, "duration": 3.24}, {"text": "Yeah.", "start": 3929.25, "duration": 1.56}, {"text": "It's sometimes called\na parenthetical", "start": 3930.81, "duration": 3.39}, {"text": "where you put in these\nthings in strange places.", "start": 3934.2, "duration": 2.58}, {"text": "There's lots of interesting\nwork on parentheticals.", "start": 3936.78, "duration": 3.39}, {"text": "So one thing that all\nof you are teaching us,", "start": 3940.17, "duration": 2.43}, {"text": "maybe, is that it's\ndangerous for me", "start": 3942.6, "duration": 1.65}, {"text": "to just show you these words\non this slide and ask you", "start": 3944.25, "duration": 2.58}, {"text": "what they mean.", "start": 3946.83, "duration": 0.78}, {"text": "What I should really do is\npronounce the sentence at you.", "start": 3947.61, "duration": 2.52}, {"text": "So when you're asking yourself\nhow many things can this mean,", "start": 3950.13, "duration": 3.09}, {"text": "don't ask yourself what\n\"I decided, on the boat,", "start": 3953.22, "duration": 3.99}, {"text": "on the plane\" means.", "start": 3957.21, "duration": 2.07}, {"text": "Ask yourself, what does\n\"I decided on the boat", "start": 3959.28, "duration": 2.88}, {"text": "on the plane\" mean?", "start": 3962.16, "duration": 3.82}, {"text": "Should I do that again?", "start": 3965.98, "duration": 1.73}, {"text": "How many of you think that\nit can mean number one?", "start": 3967.71, "duration": 3.69}, {"text": "\"I decided on the\nboat on the plane.\"", "start": 3971.4, "duration": 2.52}, {"text": "How many of you think that\nit can mean number two?", "start": 3973.92, "duration": 2.998}, {"text": "Is there anybody who thinks\nthat it can mean number two", "start": 3976.918, "duration": 2.292}, {"text": "and cannot mean number one?", "start": 3979.21, "duration": 1.758}, {"text": "Is there anybody who thinks\nthat it can mean number one", "start": 3980.968, "duration": 2.292}, {"text": "and cannot mean number two?", "start": 3983.26, "duration": 2.43}, {"text": "OK.", "start": 3985.69, "duration": 0.87}, {"text": "So through the\npower of democracy", "start": 3986.56, "duration": 2.917}, {"text": "we've come to the conclusion\nthat it can mean number one", "start": 3989.477, "duration": 2.333}, {"text": "and can't mean number two,\nexcept for a couple of you who", "start": 3991.81, "duration": 3.0}, {"text": "feel that it can\nmean either one.", "start": 3994.81, "duration": 1.92}, {"text": "Yeah?", "start": 3996.73, "duration": 0.6}, {"text": "I think the ones who feel\nthat it can mean either one", "start": 3997.33, "duration": 2.46}, {"text": "are ones who maybe have ways\nof doing parentheticals that", "start": 3999.79, "duration": 3.63}, {"text": "are less dramatic than I just\ndid, this process of hiding", "start": 4003.42, "duration": 4.14}, {"text": "a prepositional phrase.", "start": 4007.56, "duration": 1.92}, {"text": "Because I agree that you\ncan say \"I decided\"--", "start": 4009.48, "duration": 2.91}, {"text": "see if you agree--", "start": 4012.39, "duration": 0.99}, {"text": "\"I decided on the\nboat on the plane\"", "start": 4013.38, "duration": 3.87}, {"text": "can mean \"I chose the plane\nwhile I was on the boat.\"", "start": 4017.25, "duration": 2.85}, {"text": "I have to say that\nin a particular way,", "start": 4020.1, "duration": 2.67}, {"text": "play those games with\npitch as I speak.", "start": 4022.77, "duration": 3.118}, {"text": "Lots of interesting\nquestions about what the heck", "start": 4025.888, "duration": 2.042}, {"text": "I am doing when I do that.", "start": 4027.93, "duration": 1.368}, {"text": "Yeah, you had a\nquestion a while ago.", "start": 4029.298, "duration": 1.542}, {"text": "Sorry.", "start": 4030.84, "duration": 0.63}, {"text": "Yep, you.", "start": 4031.47, "duration": 0.5}, {"text": "AUDIENCE: What do you think\nabout the sentence \"I,", "start": 4031.97, "duration": 2.083}, {"text": "in the building,\ndecided on the boat.\"", "start": 4034.053, "duration": 1.647}, {"text": "NORVIN RICHARDS: Whoa.", "start": 4035.7, "duration": 1.02}, {"text": "\"I, in the building,\ndecided on the boat.\"", "start": 4036.72, "duration": 4.28}, {"text": "You asked this question before.", "start": 4041.0, "duration": 1.665}, {"text": "You're the guy who\nlikes to modify pronouns", "start": 4042.665, "duration": 2.505}, {"text": "with prepositional phrases.", "start": 4045.17, "duration": 2.13}, {"text": "What's your name?", "start": 4047.3, "duration": 1.803}, {"text": "AUDIENCE: I'm the guy who\nlikes to modify pronouns--", "start": 4049.103, "duration": 2.167}, {"text": "NORVIN RICHARDS: OK,\nthat's your name.", "start": 4051.27, "duration": 1.583}, {"text": "OK, the guy who likes--", "start": 4052.853, "duration": 1.027}, {"text": "do you have a nickname?", "start": 4053.88, "duration": 1.29}, {"text": "\"Guy.\"", "start": 4055.17, "duration": 0.5}, {"text": "We'll call you \"Guy.\"", "start": 4055.67, "duration": 2.86}, {"text": "Cool.", "start": 4058.53, "duration": 0.5}, {"text": "So I, in the building,\ndecided on the boat.", "start": 4059.03, "duration": 5.64}, {"text": "Hey, you think I could do that?", "start": 4064.67, "duration": 1.6}, {"text": "Yeah?", "start": 4066.27, "duration": 0.5}, {"text": "Then we have the problem\nthat if I'm in the building", "start": 4070.874, "duration": 3.506}, {"text": "I can't also be on a boat unless\nreally unlikely things are", "start": 4074.38, "duration": 4.05}, {"text": "happening.", "start": 4078.43, "duration": 1.26}, {"text": "Right?", "start": 4079.69, "duration": 0.6}, {"text": "Unless there's a\nbuilding on a boat", "start": 4080.29, "duration": 1.26}, {"text": "or a boat on a building\nor something like that.", "start": 4081.55, "duration": 2.05}, {"text": "And so you're kind of biased\nin favor of the reading where", "start": 4083.6, "duration": 2.417}, {"text": "I chose the boat\nbecause we've also", "start": 4086.017, "duration": 1.713}, {"text": "said that I'm in\nthe building, thanks", "start": 4087.73, "duration": 2.28}, {"text": "to the prepositional phrase\nthat you're named after,", "start": 4090.01, "duration": 4.2}, {"text": "the one that\nmodifies the pronoun.", "start": 4094.21, "duration": 2.479}, {"text": "That's a nice example.", "start": 4096.689, "duration": 1.5}, {"text": "Faith?", "start": 4098.189, "duration": 0.5}, {"text": "AUDIENCE: Don't\nwe have something", "start": 4098.689, "duration": 1.375}, {"text": "similar that happens if you say,\n\"I decided to run on the boat?\"", "start": 4100.064, "duration": 3.031}, {"text": "Because either you're\nrunning on the boat", "start": 4103.095, "duration": 1.785}, {"text": "or you're deciding to\nrun for president--", "start": 4104.88, "duration": 3.42}, {"text": "I don't know.", "start": 4108.3, "duration": 0.893}, {"text": "Campaign while\nyou're on the boat.", "start": 4109.193, "duration": 1.507}, {"text": "NORVIN RICHARDS: Yeah.", "start": 4110.7, "duration": 0.315}, {"text": "Yeah.", "start": 4111.015, "duration": 0.315}, {"text": "\"I decided to run on the boat.\"", "start": 4111.33, "duration": 1.292}, {"text": "That's a nice example.", "start": 4112.622, "duration": 1.043}, {"text": "Yeah, so I decided\nto run for president", "start": 4113.665, "duration": 1.625}, {"text": "or I decided to\nbe in the marathon", "start": 4115.29, "duration": 1.83}, {"text": "while I was on the\nboat, or I decided,", "start": 4117.12, "duration": 3.483}, {"text": "\"Here's a fun thing I'll do.", "start": 4120.603, "duration": 1.167}, {"text": "I'll run on the boat.\"", "start": 4121.77, "duration": 0.917}, {"text": "Yeah.", "start": 4122.687, "duration": 1.363}, {"text": "Right.", "start": 4124.05, "duration": 0.54}, {"text": "Those are good examples where--", "start": 4124.59, "duration": 2.243}, {"text": "actually, all of these\nare examples where--", "start": 4126.833, "duration": 1.792}, {"text": "yeah, let me back up.", "start": 4131.46, "duration": 1.45}, {"text": "So \"I decided on the\nboat on the plane.\"", "start": 4132.91, "duration": 1.732}, {"text": "Through the power of democracy\nwe've come to the conclusion", "start": 4134.642, "duration": 2.458}, {"text": "that that means number one.", "start": 4137.1, "duration": 2.28}, {"text": "What that means is\nthere are two places", "start": 4139.38, "duration": 3.45}, {"text": "for on the boat for\nprepositional phrases to be.", "start": 4142.83, "duration": 2.91}, {"text": "There's the place where\nit gets to be an argument", "start": 4145.74, "duration": 2.411}, {"text": "and there's the place where\nit gets to be an adjunct.", "start": 4148.151, "duration": 2.208}, {"text": "Right?", "start": 4150.359, "duration": 1.156}, {"text": "And the place where it\ngets to be an argument", "start": 4151.515, "duration": 1.875}, {"text": "is closer to the verb.", "start": 4153.39, "duration": 1.067}, {"text": "Several of you said this, right?", "start": 4154.457, "duration": 1.333}, {"text": "So if it's right after the\nverb it gets to be an argument,", "start": 4155.79, "duration": 2.417}, {"text": "and if it's not right\nafter the verb then", "start": 4158.207, "duration": 2.293}, {"text": "it needs to be an adjunct.", "start": 4160.5, "duration": 1.47}, {"text": "And in simple sentences,\nlike \"I decided on the boat,\"", "start": 4161.97, "duration": 3.03}, {"text": "you don't know where it is.", "start": 4165.0, "duration": 1.442}, {"text": "So you don't know whether\nit's in the argument", "start": 4166.442, "duration": 1.917}, {"text": "place or the adjunct place, and\nso the example is ambiguous.", "start": 4168.359, "duration": 2.701}, {"text": "It's kind of like the\nambiguity of \"I will tickle", "start": 4171.06, "duration": 2.37}, {"text": "the child with the feather,\"\nwhere you don't know", "start": 4173.43, "duration": 2.152}, {"text": "whether \"with the feather\"\nmodifies \"the child\"", "start": 4175.582, "duration": 1.958}, {"text": "or the verb phrase\n\"tickled the child.\"", "start": 4177.54, "duration": 2.67}, {"text": "Or, and now this\nis why finally I'm", "start": 4180.21, "duration": 3.09}, {"text": "becoming relevant to what\nyou just said, Faith,", "start": 4183.3, "duration": 2.4}, {"text": "that's another example\nwhere \"on the boat,\"", "start": 4185.7, "duration": 2.159}, {"text": "it's ambiguous where you put.", "start": 4187.859, "duration": 1.351}, {"text": "It could be a couple different\nplaces in the structure", "start": 4189.21, "duration": 2.25}, {"text": "and it could modify\ndifferent things.", "start": 4191.46, "duration": 2.64}, {"text": "Yeah.", "start": 4194.1, "duration": 0.54}, {"text": "So we're getting\nthese ambiguities.", "start": 4194.64, "duration": 2.01}, {"text": "And the fact that these\nambiguities disappear", "start": 4196.65, "duration": 1.95}, {"text": "if you pile these\nprepositional phrases up", "start": 4198.6, "duration": 1.98}, {"text": "disappear for most of us.", "start": 4200.58, "duration": 1.29}, {"text": "Some of you are more creative\nwith prepositional phrases.", "start": 4201.87, "duration": 3.757}, {"text": "Kateryna, for example, has\ngreat prepositional phrases--", "start": 4205.627, "duration": 2.333}, {"text": "go ahead.", "start": 4207.96, "duration": 0.63}, {"text": "AUDIENCE: Is there\na reason why we're", "start": 4208.59, "duration": 1.542}, {"text": "ignoring the intonation angle?", "start": 4210.132, "duration": 2.148}, {"text": "Is this like a competence\nversus performance situation?", "start": 4212.28, "duration": 2.377}, {"text": "NORVIN RICHARDS: No.", "start": 4214.657, "duration": 0.833}, {"text": "No.", "start": 4215.49, "duration": 0.84}, {"text": "No.", "start": 4216.33, "duration": 0.57}, {"text": "This is more a let's\nstart with imagining", "start": 4216.9, "duration": 8.28}, {"text": "that there's no wind resistance\nwhen we're doing physics,", "start": 4225.18, "duration": 2.68}, {"text": "right?", "start": 4227.86, "duration": 0.5}, {"text": "This is a, yeah, that's a really\ninteresting complication, which", "start": 4228.36, "duration": 3.87}, {"text": "we need to study what the heck\nis going on with intonation.", "start": 4232.23, "duration": 3.87}, {"text": "But we're going to\nstart by developing", "start": 4236.1, "duration": 2.618}, {"text": "a theory of English sentences\nin which nothing interesting is", "start": 4238.718, "duration": 2.542}, {"text": "happening with intonation.", "start": 4241.26, "duration": 1.59}, {"text": "And then because this is 24.900\nwe will probably never get out", "start": 4242.85, "duration": 2.88}, {"text": "of that.", "start": 4245.73, "duration": 1.47}, {"text": "But intonation is\na fascinating topic", "start": 4247.2, "duration": 3.42}, {"text": "that you then go try\nto add to your model.", "start": 4250.62, "duration": 2.64}, {"text": "Yeah.", "start": 4253.26, "duration": 1.23}, {"text": "Yes?", "start": 4254.49, "duration": 0.75}, {"text": "AUDIENCE: So to correctly\nwrite sentence two", "start": 4255.24, "duration": 2.85}, {"text": "and the sentence below,\nwould you put commas around--", "start": 4258.09, "duration": 4.08}, {"text": "NORVIN RICHARDS: Oh, yeah.", "start": 4262.17, "duration": 1.53}, {"text": "AUDIENCE: --\"on the boat\"?", "start": 4263.7, "duration": 0.6}, {"text": "NORVIN RICHARDS: Oh, I see.", "start": 4264.3, "duration": 1.125}, {"text": "So yes, if we--\nyou mean the string", "start": 4265.425, "duration": 2.163}, {"text": "\"I decided on the\nboat on the plane,\"", "start": 4267.588, "duration": 1.542}, {"text": "if we wanted it to\nhave reading two?", "start": 4269.13, "duration": 2.49}, {"text": "Yeah, commas are\none way that you", "start": 4271.62, "duration": 2.04}, {"text": "indicate the special intonation\nthat makes this possible.", "start": 4273.66, "duration": 3.96}, {"text": "So commas-- no\nlanguage, actually,", "start": 4277.62, "duration": 3.24}, {"text": "has a very good way to\nindicate intonation.", "start": 4280.86, "duration": 3.06}, {"text": "It's not something that\nwe're good at spelling,", "start": 4283.92, "duration": 2.85}, {"text": "but punctuation marks are one\nof the things we do to do that.", "start": 4286.77, "duration": 3.87}, {"text": "Yeah.", "start": 4290.64, "duration": 0.54}, {"text": "Nice point.", "start": 4291.18, "duration": 0.99}, {"text": "Raquel?", "start": 4292.17, "duration": 0.72}, {"text": "AUDIENCE: I was\nthinking that the rule", "start": 4292.89, "duration": 1.77}, {"text": "that you were saying\nabout the number one", "start": 4294.66, "duration": 2.85}, {"text": "being the preferred computation.", "start": 4297.51, "duration": 1.8}, {"text": "It makes a lot of\nsense in that the--", "start": 4299.31, "duration": 2.18}, {"text": "if there was going to\nbe a situation where", "start": 4301.49, "duration": 1.75}, {"text": "a thought two sounded\ncorrect, I think", "start": 4303.24, "duration": 2.43}, {"text": "it would have to be something\nwhere the adjunct sounds", "start": 4305.67, "duration": 2.46}, {"text": "like it needs to come\nreally close to the verb", "start": 4308.13, "duration": 1.917}, {"text": "decide on a whim.", "start": 4310.047, "duration": 1.293}, {"text": "If you said, \"I decided\non a whim on the boat,\"", "start": 4311.34, "duration": 3.12}, {"text": "I feel like I would be more\nlikely to say that made sense", "start": 4314.46, "duration": 2.822}, {"text": "than \"I decided on\nthe boat on the plane\"", "start": 4317.282, "duration": 1.708}, {"text": "because I need to hear\nand decide on a whim.", "start": 4318.99, "duration": 2.31}, {"text": "NORVIN RICHARDS: Yeah.", "start": 4321.3, "duration": 1.14}, {"text": "That's a very nice point\nand a really nice example.", "start": 4322.44, "duration": 3.24}, {"text": "I mean maybe-- so I think\nthe next slide is going", "start": 4325.68, "duration": 2.07}, {"text": "to echo a version of that.", "start": 4327.75, "duration": 1.62}, {"text": "What we're seeing is--", "start": 4329.37, "duration": 2.19}, {"text": "so here I've got an idealized\nversion of the judgments", "start": 4331.56, "duration": 2.61}, {"text": "that we more or less got.", "start": 4334.17, "duration": 2.07}, {"text": "There are some people for whom\nyou can get either reading.", "start": 4336.24, "duration": 3.42}, {"text": "Interestingly, nobody has\nthe opposite judgment,", "start": 4339.66, "duration": 2.16}, {"text": "that \"I decided on the boat on\nthe plane\" preferentially means", "start": 4341.82, "duration": 5.7}, {"text": "\"I chose the plane while\nI was on the boat.\"", "start": 4347.52, "duration": 2.43}, {"text": "And what we're seeing\nthen is that if you have--", "start": 4349.95, "duration": 5.368}, {"text": "so one difference between\narguments and adjuncts,", "start": 4355.318, "duration": 2.042}, {"text": "the reason that I\nintroduced you to them,", "start": 4357.36, "duration": 1.89}, {"text": "is that arguments\nare picky about which", "start": 4359.25, "duration": 1.948}, {"text": "heads they can combine\nwith and adjuncts are not.", "start": 4361.198, "duration": 2.042}, {"text": "You can do anything with\na feather but something", "start": 4363.24, "duration": 2.25}, {"text": "like a direct object,\nyou have to look", "start": 4365.49, "duration": 2.103}, {"text": "at the verb to see whether\nyou have it or not.", "start": 4367.593, "duration": 1.917}, {"text": "And what we're also seeing is\nthat if you have a head that", "start": 4369.51, "duration": 2.49}, {"text": "has both an argument\nand an adjunct,", "start": 4372.0, "duration": 2.64}, {"text": "and that's the \"decide on\nthe boat on the plane\" thing,", "start": 4374.64, "duration": 3.04}, {"text": "then the argument is\ncloser to the head.", "start": 4377.68, "duration": 3.56}, {"text": "So far, yeah?", "start": 4381.24, "duration": 1.2}, {"text": "And this connects with\nRaquel was just saying.", "start": 4382.44, "duration": 3.03}, {"text": "One way to think about\nit, maybe, is to say,", "start": 4385.47, "duration": 1.928}, {"text": "if you have these two\nprepositional phrases", "start": 4387.398, "duration": 1.792}, {"text": "and you have this\nverb and you're", "start": 4389.19, "duration": 1.53}, {"text": "trying to decide, in\nwhat order shall I merge", "start": 4390.72, "duration": 2.04}, {"text": "these things with each other?", "start": 4392.76, "duration": 1.47}, {"text": "Apparently the answer\nis, well, first,", "start": 4394.23, "duration": 2.88}, {"text": "see what the verb\nwould like you to do.", "start": 4397.11, "duration": 2.62}, {"text": "So if the verb needs\nsomething, then", "start": 4399.73, "duration": 3.17}, {"text": "satisfy the needs of the verb\nfirst and then fool around", "start": 4402.9, "duration": 3.36}, {"text": "with adjuncts.", "start": 4406.26, "duration": 0.65}, {"text": "Yes.", "start": 4406.91, "duration": 0.5}, {"text": "You can do adjuncts later.", "start": 4407.41, "duration": 1.55}, {"text": "And Raquel's making the point\nthat there are various things", "start": 4408.96, "duration": 2.73}, {"text": "in life that verbs could need\nand we have to develop a theory", "start": 4411.69, "duration": 3.24}, {"text": "of all of them, and\ntoday we haven't.", "start": 4414.93, "duration": 2.86}, {"text": "Yep.", "start": 4417.79, "duration": 1.45}, {"text": "Any questions about any of this?", "start": 4419.24, "duration": 2.34}, {"text": "I think, if I\nremember right, this", "start": 4421.58, "duration": 2.257}, {"text": "might be a good place\nto pause and see", "start": 4423.837, "duration": 1.583}, {"text": "what I was going to do next.", "start": 4425.42, "duration": 1.62}, {"text": "Yes, no.", "start": 4427.04, "duration": 0.6}, {"text": "So we're about to do\nanother test for arguments", "start": 4427.64, "duration": 2.098}, {"text": "and adjuncts.", "start": 4429.738, "duration": 0.542}, {"text": "And we will do it, but\nwe'll do it next time", "start": 4430.28, "duration": 2.76}, {"text": "where \"next time\" is not next\nweek, but the week after,", "start": 4433.04, "duration": 3.64}, {"text": "right?", "start": 4436.68, "duration": 0.5}, {"text": "Because you guys have\nto go break spring.", "start": 4437.18, "duration": 3.3}, {"text": "So have a great spring\nbreak, everybody.", "start": 4440.48, "duration": 2.04}, {"text": "Go do something relaxing,\nand we will see you again", "start": 4442.52, "duration": 3.39}, {"text": "in a couple weeks.", "start": 4445.91, "duration": 2.42}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.952}, {"text": "[PAPER RUSTLING]", "start": 1.952, "duration": 1.452}, {"text": "[CLICKING]", "start": 3.904, "duration": 0.976}, {"text": "YUFEI ZHAO: Last time we started\ntalking about Roth's theorem,", "start": 18.08, "duration": 2.88}, {"text": "and we showed a Fourier\nanalytic proof of Roth's theorem", "start": 20.96, "duration": 5.46}, {"text": "in the finite field model.", "start": 26.42, "duration": 2.34}, {"text": "So Roth's theorem\nin F3 to the N.", "start": 28.76, "duration": 4.01}, {"text": "And I want to today show\nyou how to modify that proof", "start": 32.77, "duration": 4.9}, {"text": "to work in integers.", "start": 37.67, "duration": 1.98}, {"text": "And this will be basically\nRoth's original proof", "start": 39.65, "duration": 6.48}, {"text": "of his theorem.", "start": 46.13, "duration": 0.69}, {"text": "OK.", "start": 56.44, "duration": 0.97}, {"text": "So what we'll prove\ntoday is the statement", "start": 57.41, "duration": 3.45}, {"text": "that the size of the largest\n3AP-free subset of 1 through N", "start": 60.86, "duration": 9.72}, {"text": "is, at most, N divided\nby log log N. OK,", "start": 70.58, "duration": 10.5}, {"text": "so we'll prove a\nbound of this form.", "start": 81.08, "duration": 1.8}, {"text": "The strategy of this proof\nwill be very similar to the one", "start": 86.45, "duration": 3.15}, {"text": "that we had from last time.", "start": 89.6, "duration": 1.32}, {"text": "So let me review for you\nwhat is the strategy.", "start": 90.92, "duration": 1.917}, {"text": "So from last time, the\nproof had three main steps.", "start": 104.68, "duration": 4.85}, {"text": "In the first step, we\nobserved that if you", "start": 109.53, "duration": 3.39}, {"text": "are in the 3AP-free set then\nthere exists a large Fourier", "start": 112.92, "duration": 9.25}, {"text": "coefficient.", "start": 122.17, "duration": 1.104}, {"text": "From this Fourier\ncoefficient, we", "start": 131.81, "duration": 1.92}, {"text": "were able to extract\na large subspace where", "start": 133.73, "duration": 8.64}, {"text": "there is a density increment.", "start": 142.37, "duration": 2.85}, {"text": "I want to modify that\nstrategy so that we", "start": 145.22, "duration": 3.69}, {"text": "can work in the integers.", "start": 148.91, "duration": 2.67}, {"text": "Unlike an F2 to\nthe N, where things", "start": 151.58, "duration": 2.61}, {"text": "were fairly nice and clean,\nbecause you have subspaces,", "start": 154.19, "duration": 3.42}, {"text": "you can take a\nFourier coefficient,", "start": 157.61, "duration": 1.92}, {"text": "pass it down to a subspace.", "start": 159.53, "duration": 2.37}, {"text": "There is no subspaces, right?", "start": 161.9, "duration": 1.86}, {"text": "There are no subspaces\nin the integers.", "start": 163.76, "duration": 3.22}, {"text": "So we have to do something\nslightly different,", "start": 166.98, "duration": 2.04}, {"text": "but in the same spirit.", "start": 169.02, "duration": 2.1}, {"text": "So you'll find a large\nFourier coefficient.", "start": 171.12, "duration": 2.457}, {"text": "And we will find that there\nis density increment when", "start": 180.4, "duration": 9.97}, {"text": "you restrict not to\nsubspaces, but what", "start": 190.37, "duration": 4.04}, {"text": "could play the role of subspaces\nwhen it comes to the integers?", "start": 194.41, "duration": 2.925}, {"text": "So I want something which\nlooks like a smaller", "start": 199.9, "duration": 3.15}, {"text": "version of the original space.", "start": 203.05, "duration": 3.21}, {"text": "So instead of it\nbeing integers, if we", "start": 206.26, "duration": 3.02}, {"text": "restrict to a subprogression,\nso to a smaller arithmetic", "start": 209.28, "duration": 4.5}, {"text": "progression.", "start": 213.78, "duration": 1.19}, {"text": "I will show that you can\nrestrict to a subprogression", "start": 214.97, "duration": 3.07}, {"text": "where you can obtain\ndensity increment.", "start": 218.04, "duration": 2.657}, {"text": "So we'll restrict integers\nto something smaller.", "start": 225.84, "duration": 4.23}, {"text": "And then, same as last time,\nwe can iterate this increment", "start": 230.07, "duration": 14.61}, {"text": "to obtain the\nconclusion that you", "start": 244.68, "duration": 3.81}, {"text": "have an upper bound on the\nsize of this 3AP-free set.", "start": 248.49, "duration": 6.055}, {"text": "OK, so that's the strategy.", "start": 254.545, "duration": 1.125}, {"text": "So you see the same strategy\nas the one we did last time,", "start": 255.67, "duration": 2.64}, {"text": "and many of the ingredients\nwill have parallels,", "start": 258.31, "duration": 2.519}, {"text": "but the execution will\nbe slightly different,", "start": 260.829, "duration": 3.001}, {"text": "especially in the\nsecond step where,", "start": 263.83, "duration": 2.92}, {"text": "because we no longer\nhave sub spaces, which", "start": 266.75, "duration": 2.69}, {"text": "are nice and clean,\nso that's why", "start": 269.44, "duration": 1.44}, {"text": "we started with a\nfinite fuel model, just", "start": 270.88, "duration": 2.19}, {"text": "to show how things work in\na slightly easier setting.", "start": 273.07, "duration": 2.46}, {"text": "And today, we'll see how to\ndo a same kind of strategy", "start": 275.53, "duration": 4.14}, {"text": "here, where there is going\nto be a bit more work.", "start": 279.67, "duration": 3.22}, {"text": "Not too much more,\nbut a bit more work.", "start": 282.89, "duration": 2.4}, {"text": "OK, so before we\nstart, any questions?", "start": 285.29, "duration": 2.501}, {"text": "All right.", "start": 293.2, "duration": 1.72}, {"text": "So last time I used the\nproof Roth's theorem", "start": 294.92, "duration": 2.37}, {"text": "as an excuse to introduce\nFourier analysis.", "start": 297.29, "duration": 1.955}, {"text": "And we're going to see basically\nthe same kind of Fourier", "start": 299.245, "duration": 2.375}, {"text": "analysis, but it's going to take\non a slightly different form,", "start": 301.62, "duration": 3.8}, {"text": "because we're not working\nat F3 to the N. We're", "start": 305.42, "duration": 2.52}, {"text": "working inside the integers.", "start": 307.94, "duration": 2.55}, {"text": "And there's a general theory of\nFourier analysis on the group,", "start": 310.49, "duration": 3.38}, {"text": "on a billion groups.", "start": 313.87, "duration": 2.602}, {"text": "I don't want to go into that\ntheory, because that's--", "start": 316.472, "duration": 2.208}, {"text": "I want to focus on\nthe specific case,", "start": 318.68, "duration": 1.762}, {"text": "but the point is that\ngiven the billion groups,", "start": 320.442, "duration": 1.958}, {"text": "you always have a dual\ngroup of characters.", "start": 322.4, "duration": 4.82}, {"text": "And they play the role\nof Fourier transform.", "start": 327.22, "duration": 2.58}, {"text": "Specifically in\nthe case of Z, we", "start": 329.8, "duration": 3.99}, {"text": "have the following\nFourier transform.", "start": 333.79, "duration": 2.1}, {"text": "So the dual group of Z\nturns out to be the torus.", "start": 341.39, "duration": 9.72}, {"text": "So real numbers mod one.", "start": 351.11, "duration": 3.43}, {"text": "And the Fourier\ntransform is defined", "start": 354.54, "duration": 8.91}, {"text": "as follows, starting with a\nfunction on the integers, OK.", "start": 363.45, "duration": 11.46}, {"text": "If you'd like, let's say\nit's finitely supported,", "start": 374.91, "duration": 2.1}, {"text": "just to make our\nlives a bit easier.", "start": 377.01, "duration": 1.72}, {"text": "Don't have to deal\nwith technicalities.", "start": 378.73, "duration": 1.95}, {"text": "But in general, the\nfollowing formula holds.", "start": 380.68, "duration": 3.14}, {"text": "We have this Fourier\ntransform defined", "start": 383.82, "duration": 8.46}, {"text": "by setting f hat of theta\nto be the following sum.", "start": 392.28, "duration": 7.34}, {"text": "OK, where this e is actually\nsomewhat standard notation,", "start": 404.922, "duration": 5.108}, {"text": "additive combinatorics.", "start": 410.03, "duration": 2.45}, {"text": "It's e to the 2\npi i t, all right?", "start": 412.48, "duration": 3.92}, {"text": "So it goes a fraction, t,\naround the complex unit circle.", "start": 416.4, "duration": 5.95}, {"text": "OK.", "start": 422.35, "duration": 0.5}, {"text": "So that's the Fourier\ntransform on the integers.", "start": 422.85, "duration": 2.657}, {"text": "OK, so you might have seen this\nbefore under a different name.", "start": 425.507, "duration": 2.583}, {"text": "This is usually\ncalled Fourier series.", "start": 428.09, "duration": 1.68}, {"text": "All right.", "start": 433.79, "duration": 0.5}, {"text": "You know, the notation\nmay be slightly different.", "start": 434.29, "duration": 2.042}, {"text": "OK, so that's what\nwe'll see today.", "start": 436.332, "duration": 2.718}, {"text": "And this Fourier transform plays\nthe same role as the Fourier", "start": 439.05, "duration": 3.71}, {"text": "transform from last time, which\nwas on the group F3 to the N.", "start": 442.76, "duration": 6.63}, {"text": "And just us in--", "start": 449.39, "duration": 3.672}, {"text": "so last time, we had a number\nof important identities,", "start": 453.062, "duration": 3.958}, {"text": "and we'll have the same\nkinds of identities here.", "start": 457.02, "duration": 2.88}, {"text": "So let me remind\nyou what they are.", "start": 459.9, "duration": 2.07}, {"text": "And the proofs are all\nbasically the same,", "start": 461.97, "duration": 1.84}, {"text": "so I won't show you the proofs.", "start": 463.81, "duration": 1.292}, {"text": "f hat of 0 is simply the\nsum of f over the domain.", "start": 474.13, "duration": 7.41}, {"text": "We have this Plancherel Parseval\nidentity, which tells us", "start": 485.22, "duration": 11.25}, {"text": "that if you look at\nthe inner product", "start": 496.47, "duration": 6.15}, {"text": "by linear form in\nthe physical space,", "start": 502.62, "duration": 4.99}, {"text": "it equals to the inner\nproduct in the Fourier space.", "start": 507.61, "duration": 5.84}, {"text": "OK.", "start": 522.62, "duration": 0.5}, {"text": "So in the physical\nspace now, you sum.", "start": 523.12, "duration": 2.13}, {"text": "In the frequency space,\nyou take integral", "start": 525.25, "duration": 2.1}, {"text": "over the torus, or the\ncircle, in this case.", "start": 527.35, "duration": 4.61}, {"text": "It's a one-dimensional torus.", "start": 531.96, "duration": 2.61}, {"text": "There is also the Fourier\ninversion formula,", "start": 534.57, "duration": 3.9}, {"text": "which now says that f of x\nis equal to f hat of theta.", "start": 538.47, "duration": 6.88}, {"text": "E of x theta, you integrate\ntheta from 0 to 1.", "start": 545.35, "duration": 4.43}, {"text": "Again, on the torus,\non the circle.", "start": 549.78, "duration": 4.05}, {"text": "And third-- and finally, there\nwas this identity last time", "start": 553.83, "duration": 4.23}, {"text": "that related three-term\narithmetic progressions", "start": 558.06, "duration": 2.88}, {"text": "to the Fourier transform, OK?", "start": 560.94, "duration": 1.74}, {"text": "So this last one was\nslightly not as--", "start": 562.68, "duration": 3.85}, {"text": "I mean, it's not as standard\nas the first several, which are", "start": 566.53, "duration": 3.02}, {"text": "standard Fourier identities.", "start": 569.55, "duration": 2.01}, {"text": "But this one will\nbe useful to us.", "start": 571.56, "duration": 2.8}, {"text": "So the identity relating the\nFourier transform, the 3AP, now", "start": 574.36, "duration": 3.92}, {"text": "has the following form.", "start": 578.28, "duration": 1.363}, {"text": "OK, so if we define\nlambda of f, g,", "start": 579.643, "duration": 7.455}, {"text": "and h to be the\nfollowing sum, which", "start": 587.098, "duration": 8.692}, {"text": "sums over all 3APs\nin the integers,", "start": 595.79, "duration": 6.81}, {"text": "then one can write\nthis expression", "start": 602.6, "duration": 8.87}, {"text": "in terms of the Fourier\ntransform as follows.", "start": 611.47, "duration": 4.5}, {"text": "OK.", "start": 626.75, "duration": 0.97}, {"text": "All right.", "start": 627.72, "duration": 0.5}, {"text": "So comparing this formula to the\none that we saw from last time,", "start": 628.22, "duration": 3.72}, {"text": "it's the same formula,\nwhere different domains,", "start": 631.94, "duration": 2.55}, {"text": "where you're summing\nor integrating,", "start": 634.49, "duration": 1.5}, {"text": "but it's the same formula.", "start": 635.99, "duration": 1.17}, {"text": "And the proof is the same.", "start": 637.16, "duration": 1.84}, {"text": "So go look at the proof.", "start": 639.0, "duration": 1.07}, {"text": "It's the same proof.", "start": 640.07, "duration": 0.833}, {"text": "OK.", "start": 643.71, "duration": 0.5}, {"text": "So these are the key Fourier\nthings that we'll use.", "start": 644.21, "duration": 3.6}, {"text": "And then we'll try to\nfollow on those with--", "start": 647.81, "duration": 3.17}, {"text": "the same as the proof as last\ntime, and see where we can get.", "start": 650.98, "duration": 4.19}, {"text": "So let me introduce\none more notation.", "start": 655.17, "duration": 2.01}, {"text": "So I'll write lambda sub 3\nof f to be lambda of f, f, f,", "start": 657.18, "duration": 7.31}, {"text": "three times.", "start": 664.49, "duration": 0.54}, {"text": "OK.", "start": 667.509, "duration": 0.5}, {"text": "So at this point, if you\nunderstood the lecture", "start": 668.009, "duration": 1.971}, {"text": "from last time, none of\nanything I've said so far", "start": 669.98, "duration": 3.24}, {"text": "should be surprising.", "start": 673.22, "duration": 1.23}, {"text": "We are working\nintegers, so we should", "start": 674.45, "duration": 1.83}, {"text": "look at the corresponding\nFourier transform in integers.", "start": 676.28, "duration": 2.89}, {"text": "And if you follow your\nnotes, this is all the things", "start": 679.17, "duration": 2.51}, {"text": "that we're going to use.", "start": 681.68, "duration": 1.98}, {"text": "OK, so what was one\nof the first things", "start": 683.66, "duration": 2.31}, {"text": "we mentioned regarding\nthe Fourier transform", "start": 685.97, "duration": 3.3}, {"text": "from last time after this point?", "start": 689.27, "duration": 1.56}, {"text": "OK.", "start": 700.25, "duration": 0.5}, {"text": "AUDIENCE: The counting lemma.", "start": 700.75, "duration": 1.325}, {"text": "YUFEI ZHAO: OK.", "start": 702.075, "duration": 0.625}, {"text": "So let's do a counting lemma.", "start": 702.7, "duration": 1.56}, {"text": "So what should the\ncounting lemma say?", "start": 704.26, "duration": 5.52}, {"text": "Well, the spirit of the counting\nlemma is that if you have two", "start": 709.78, "duration": 2.92}, {"text": "functions that are close to\neach other-- and now, \"close\"", "start": 712.7, "duration": 3.66}, {"text": "means close in Fourier--", "start": 716.36, "duration": 2.58}, {"text": "then their corresponding number\nof 3APs should be similar, OK?", "start": 718.94, "duration": 4.97}, {"text": "So that's what we want to say.", "start": 723.91, "duration": 2.24}, {"text": "And indeed, right, so\nthe counting lemma for us", "start": 726.15, "duration": 8.59}, {"text": "will say that if f and g\nare functions on Z, and--", "start": 734.74, "duration": 10.77}, {"text": "such that their L2 norms are\nboth bounded by this M. OK,", "start": 748.42, "duration": 18.955}, {"text": "the sum of the squared absolute\nvalue entries are both bounded.", "start": 767.375, "duration": 4.565}, {"text": "Then the difference\nof their 3AP counts", "start": 771.94, "duration": 11.77}, {"text": "should not be so different\nfrom each other if f", "start": 783.71, "duration": 4.86}, {"text": "and g are close in Fourier, OK?", "start": 788.57, "duration": 2.22}, {"text": "And that means that if all\nthe Fourier coefficients of f", "start": 790.79, "duration": 11.2}, {"text": "minus g are small,\nthen lambda 3ff,", "start": 801.99, "duration": 6.28}, {"text": "which considers 3AP counts\nin f, is close to that of g.", "start": 808.27, "duration": 4.02}, {"text": "OK.", "start": 815.685, "duration": 2.425}, {"text": "Same kind of 3AP counting\nlemma from last time.", "start": 818.11, "duration": 4.634}, {"text": "OK, so let's prove it, OK?", "start": 822.744, "duration": 2.962}, {"text": "As with the counting\nlemma proofs", "start": 831.52, "duration": 2.1}, {"text": "you've seen several times\nalready in this course,", "start": 833.62, "duration": 2.73}, {"text": "we will prove it by first\nwriting this difference", "start": 836.35, "duration": 3.72}, {"text": "as a telescoping sum.", "start": 840.07, "duration": 1.38}, {"text": "The first term\nbeing f minus g f f,", "start": 847.42, "duration": 5.5}, {"text": "and then g of f minus g f and\nlambda g, g, f, f minus g.", "start": 852.92, "duration": 12.125}, {"text": "OK, and we will like to show\nthat each of these terms", "start": 865.045, "duration": 2.745}, {"text": "is small if f minus g has\nsmall Fourier coefficients.", "start": 867.79, "duration": 6.483}, {"text": "OK.", "start": 879.69, "duration": 0.5}, {"text": "So let's bound the first term.", "start": 880.19, "duration": 1.71}, {"text": "OK, so let me bound this first\nterm using the 3AP identity,", "start": 890.077, "duration": 5.263}, {"text": "relating 3AP to\nFourier coefficients,", "start": 895.34, "duration": 2.61}, {"text": "we can write this lambda\nas the following integral", "start": 897.95, "duration": 7.2}, {"text": "over Fourier coefficients.", "start": 905.15, "duration": 1.968}, {"text": "And now, let me--", "start": 924.07, "duration": 1.66}, {"text": "OK, so what was the\ntrick last time?", "start": 925.73, "duration": 1.82}, {"text": "So we said let's pull\nout one of these guys", "start": 927.55, "duration": 5.05}, {"text": "and then use triangle inequality\non the remaining factors.", "start": 932.6, "duration": 4.645}, {"text": "OK, so we'll do that.", "start": 937.245, "duration": 0.905}, {"text": "So far, so good.", "start": 956.41, "duration": 2.442}, {"text": "And now you see this integral.", "start": 958.852, "duration": 3.443}, {"text": "Apply Cauchy-Schwartz.", "start": 962.295, "duration": 1.478}, {"text": "OK, so apply Cauchy-Schwartz\nto the first factor,", "start": 978.09, "duration": 2.8}, {"text": "you got this l2 sum,\nthis l2 integral.", "start": 980.89, "duration": 4.643}, {"text": "And then you apply\nCauchy-Schwartz", "start": 985.533, "duration": 1.417}, {"text": "to the second factor.", "start": 986.95, "duration": 1.345}, {"text": "You get that integral.", "start": 994.633, "duration": 0.917}, {"text": "OK, now what do we do?", "start": 998.826, "duration": 2.094}, {"text": "Yep?", "start": 1004.912, "duration": 1.497}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1006.409, "duration": 3.571}, {"text": "YUFEI ZHAO: OK, so yeah.", "start": 1009.98, "duration": 1.0}, {"text": "So you see an l2 of Fourier,\nthe first automatic reaction", "start": 1010.98, "duration": 3.72}, {"text": "should be to use a\nPlancherel or Parseval, OK?", "start": 1014.7, "duration": 2.19}, {"text": "So apply Plancherel identity\nto each of these factors.", "start": 1016.89, "duration": 7.699}, {"text": "We find that each\nof those factors", "start": 1024.589, "duration": 8.931}, {"text": "is equal to this l2 sum\nin the physical space.", "start": 1033.52, "duration": 6.52}, {"text": "OK, so this square\nroot, the same thing.", "start": 1043.75, "duration": 1.859}, {"text": "Square root again.", "start": 1045.609, "duration": 2.371}, {"text": "OK.", "start": 1047.98, "duration": 0.54}, {"text": "And then we find\nthat because there", "start": 1048.52, "duration": 6.23}, {"text": "was an hypothesis--\nin the hypothesis,", "start": 1054.75, "duration": 1.97}, {"text": "there was a bound M on\nthis sum of squares.", "start": 1056.72, "duration": 3.71}, {"text": "You have that down there.", "start": 1063.61, "duration": 2.48}, {"text": "And similarly, with\nthe other two terms.", "start": 1066.09, "duration": 1.99}, {"text": "OK.", "start": 1081.526, "duration": 0.524}, {"text": "So that proves the\ncounting lemma.", "start": 1082.05, "duration": 1.461}, {"text": "Question?", "start": 1087.359, "duration": 1.443}, {"text": "AUDIENCE: Last time, the\nterm on the right-hand side", "start": 1088.802, "duration": 3.958}, {"text": "was the maximum over\nnon-zero frequency?", "start": 1092.76, "duration": 3.765}, {"text": "YUFEI ZHAO: OK.", "start": 1096.525, "duration": 1.205}, {"text": "OK.", "start": 1097.73, "duration": 0.5}, {"text": "So the question is, last time\nwe had a counting lemma that", "start": 1098.23, "duration": 4.0}, {"text": "looked slightly different.", "start": 1102.23, "duration": 1.89}, {"text": "But I claimed they're all\nreally the same counting lemma.", "start": 1104.12, "duration": 2.61}, {"text": "They're all the same proofs.", "start": 1106.73, "duration": 1.59}, {"text": "If you run this\nproof, it won't work.", "start": 1108.32, "duration": 2.49}, {"text": "If you take what\nwe did last time,", "start": 1110.81, "duration": 2.34}, {"text": "it's the same kind of proofs.", "start": 1113.15, "duration": 2.11}, {"text": "So last time we had\na counting lemma", "start": 1115.26, "duration": 1.5}, {"text": "where we had the same\nf, f, f essentially.", "start": 1116.76, "duration": 7.36}, {"text": "We know have-- I allow you\nto essentially take three", "start": 1124.12, "duration": 4.54}, {"text": "different things, and--", "start": 1128.66, "duration": 0.98}, {"text": "OK, so both-- in\nboth cases, you're", "start": 1129.64, "duration": 3.34}, {"text": "running through\nthis calculation,", "start": 1132.98, "duration": 1.77}, {"text": "but they look\nslightly different.", "start": 1134.75, "duration": 2.628}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1137.378, "duration": 5.177}, {"text": "YUFEI ZHAO: So, yeah.", "start": 1142.555, "duration": 0.875}, {"text": "So I agree.", "start": 1143.43, "duration": 1.005}, {"text": "It doesn't look\nexactly the same,", "start": 1144.435, "duration": 1.375}, {"text": "but if you think about\nwhat's involved in the proof,", "start": 1145.81, "duration": 1.71}, {"text": "they're the same proofs.", "start": 1147.52, "duration": 1.0}, {"text": "OK.", "start": 1151.232, "duration": 1.398}, {"text": "Any more questions?", "start": 1152.63, "duration": 3.54}, {"text": "All right.", "start": 1156.17, "duration": 2.89}, {"text": "So now, we have\nthis counting lemma,", "start": 1159.06, "duration": 1.61}, {"text": "so let's start our proof of\nRoth's theorem in the integers.", "start": 1160.67, "duration": 4.99}, {"text": "As with last time, there\nwill be three steps,", "start": 1165.66, "duration": 2.16}, {"text": "as mentioned up there, OK?", "start": 1167.82, "duration": 4.355}, {"text": "In the first step, let us\nshow that if you are 3AP-free,", "start": 1172.175, "duration": 5.415}, {"text": "then we can obtain a density--", "start": 1177.59, "duration": 2.54}, {"text": "a large Fourier coefficient.", "start": 1180.13, "duration": 2.068}, {"text": "Yeah, so in this course,\nthis counting lemma,", "start": 1196.64, "duration": 2.56}, {"text": "we actually solved this--", "start": 1199.2, "duration": 2.25}, {"text": "basically this kind of proof\nfor the first time when we", "start": 1201.45, "duration": 2.52}, {"text": "discussed graph counting\nlemma, back in the chapter", "start": 1203.97, "duration": 3.03}, {"text": "on Szemer\u00e9di's regularity lemma.", "start": 1207.0, "duration": 2.81}, {"text": "And sure, they all\nlook literally--", "start": 1209.81, "duration": 2.62}, {"text": "not exactly the same,\nbut they're all really", "start": 1212.43, "duration": 2.31}, {"text": "the same kind of proofs, right?", "start": 1214.74, "duration": 1.66}, {"text": "So I want--", "start": 1216.4, "duration": 0.65}, {"text": "I'm showing you the same thing\nin many different guises.", "start": 1217.05, "duration": 2.49}, {"text": "But they're all the same proofs.", "start": 1219.54, "duration": 1.333}, {"text": "So if you are a set\nthat is 3AP-free--", "start": 1223.69, "duration": 4.85}, {"text": "and as with last time,\nI'm going to call", "start": 1237.63, "duration": 3.85}, {"text": "alpha the density of A now\ninside this progression,", "start": 1241.48, "duration": 5.07}, {"text": "this length N progression.", "start": 1246.55, "duration": 3.27}, {"text": "And suppose N is large enough.", "start": 1249.82, "duration": 4.74}, {"text": "OK, so the conclusion now is\nthat there exists some theta", "start": 1259.46, "duration": 8.12}, {"text": "such that if you look\nat this sum over here", "start": 1267.58, "duration": 11.59}, {"text": "as a sum over both integers--", "start": 1279.17, "duration": 4.76}, {"text": "actually, let me do\nthe sum only from 1", "start": 1283.93, "duration": 2.75}, {"text": "to uppercase N. Claim that--", "start": 1286.68, "duration": 8.36}, {"text": "OK, so-- so it's saying\nwhat this title says.", "start": 1295.04, "duration": 4.47}, {"text": "If you are 3AP-free\nand this N is large", "start": 1299.51, "duration": 3.695}, {"text": "enough relative to the density,\nyou think of this density", "start": 1303.205, "duration": 2.375}, {"text": "alpha is a constant, then\nI can find a large Fourier", "start": 1305.58, "duration": 4.41}, {"text": "coefficient.", "start": 1309.99, "duration": 0.87}, {"text": "Now, there's a small\ndifference, and this", "start": 1310.86, "duration": 3.15}, {"text": "is related to what you\nwere asking earlier,", "start": 1314.01, "duration": 2.13}, {"text": "between how we set things up now\nversus what happened last time.", "start": 1316.14, "duration": 3.57}, {"text": "So last time, we just looked\nfor a Fourier coefficient", "start": 1319.71, "duration": 5.82}, {"text": "corresponding to a non-zero r.", "start": 1325.53, "duration": 4.55}, {"text": "Now, I'm not\nrestricting non-zero,", "start": 1330.08, "duration": 3.26}, {"text": "but I don't start with\nan indicator function.", "start": 1333.34, "duration": 2.36}, {"text": "I start with the demeaned\nindicator function.", "start": 1335.7, "duration": 3.58}, {"text": "I take out the mean so that\nthe zeroth coefficient,", "start": 1339.28, "duration": 5.06}, {"text": "so to speak, which corresponds\nto the mean, is already 0.", "start": 1344.34, "duration": 4.11}, {"text": "So you don't get to use\nthat for your coefficient.", "start": 1348.45, "duration": 4.34}, {"text": "So if you didn't do\nthis, if you just", "start": 1352.79, "duration": 2.05}, {"text": "tried to do this\nlast time, I mean,", "start": 1354.84, "duration": 1.58}, {"text": "you can also do\nexactly the same setup.", "start": 1356.42, "duration": 1.625}, {"text": "But if you don't\ndemean it, then--", "start": 1358.045, "duration": 2.135}, {"text": "if you don't have this\nterm, then this statement", "start": 1360.18, "duration": 2.22}, {"text": "is trivially true, because I\ncan take theta equal to 0, OK?", "start": 1362.4, "duration": 4.56}, {"text": "But I don't want.", "start": 1366.96, "duration": 1.34}, {"text": "I want an actual significant\nFourier improvement.", "start": 1368.3, "duration": 4.6}, {"text": "So I take--", "start": 1372.9, "duration": 1.03}, {"text": "I do this demean, and then\nI consider its Fourier", "start": 1373.93, "duration": 4.61}, {"text": "coefficient.", "start": 1378.54, "duration": 1.043}, {"text": "OK.", "start": 1382.26, "duration": 0.5}, {"text": "Any questions about\nthe statement?", "start": 1382.76, "duration": 3.46}, {"text": "Yeah, so this demeaning is\nreally important, right?", "start": 1386.22, "duration": 3.59}, {"text": "So that's something that's a\nvery common technique whenever", "start": 1389.81, "duration": 2.72}, {"text": "you do these kind of analysis.", "start": 1392.53, "duration": 1.61}, {"text": "So make sure you're--", "start": 1394.14, "duration": 2.37}, {"text": "so that you're-- yeah, so you're\nlooking at functions with mean", "start": 1396.51, "duration": 3.43}, {"text": "0.", "start": 1399.94, "duration": 2.837}, {"text": "Let's see the proof.", "start": 1402.777, "duration": 0.833}, {"text": "We have the\nfollowing information", "start": 1408.19, "duration": 5.1}, {"text": "about all 3AP counts in A.\nBecause A is 3AP-free, OK,", "start": 1413.29, "duration": 6.38}, {"text": "so what is the value of lambda\nsub 3 of the indicator of A?", "start": 1419.67, "duration": 3.65}, {"text": "Lambda of 3, if you\nlook at the expression,", "start": 1426.1, "duration": 3.34}, {"text": "it basically sums over all\n3APs, but A has no 3APs,", "start": 1429.44, "duration": 6.33}, {"text": "except for the trivial ones.", "start": 1435.77, "duration": 2.73}, {"text": "So we'll only consider\nthe trivial 3APs,", "start": 1438.5, "duration": 2.52}, {"text": "which has size exactly\nthe size of A, which", "start": 1441.02, "duration": 5.19}, {"text": "is alpha N from trivial 3APs.", "start": 1446.21, "duration": 4.61}, {"text": "On the other hand, what\ndo we know about lambda 3", "start": 1454.87, "duration": 5.16}, {"text": "of this interval from 1 to N?", "start": 1460.03, "duration": 5.226}, {"text": "OK, so how many 3APs are there?", "start": 1465.256, "duration": 3.154}, {"text": "OK, so roughly, it's going\nto be about N squared over 2.", "start": 1468.41, "duration": 5.23}, {"text": "And in fact, it will be\nat least N squared over 2,", "start": 1473.64, "duration": 4.83}, {"text": "because to generate\na 3AP, I just", "start": 1478.47, "duration": 3.39}, {"text": "have to pick a first\nterm and a third term,", "start": 1481.86, "duration": 7.21}, {"text": "and I'm OK as long as\nthey're the same parity.", "start": 1489.07, "duration": 2.69}, {"text": "And then you have a 3AP.", "start": 1498.195, "duration": 2.215}, {"text": "So the same parity\ncuts you down by half,", "start": 1500.41, "duration": 3.81}, {"text": "so you have at least N squared\nover 2 3APs from 1 through N.", "start": 1504.22, "duration": 6.97}, {"text": "So now, let's look at\nhow to apply the counting", "start": 1511.19, "duration": 3.74}, {"text": "lemma all to the setting.", "start": 1514.93, "duration": 1.55}, {"text": "So we have the counting\nlemma up there,", "start": 1516.48, "duration": 1.94}, {"text": "where I now want to apply it--", "start": 1518.42, "duration": 1.51}, {"text": "so apply counting\nto, on one hand,", "start": 1522.6, "duration": 6.36}, {"text": "the indicator function of A\nso we get the count 3APs in A,", "start": 1528.96, "duration": 5.82}, {"text": "but also compared to\nthe normalized indicator", "start": 1534.78, "duration": 8.99}, {"text": "on the interval.", "start": 1543.77, "duration": 1.482}, {"text": "OK, so maybe this is\na good point for me", "start": 1545.252, "duration": 1.688}, {"text": "to pause and remind you that\nthe spirit of this whole proof", "start": 1546.94, "duration": 3.485}, {"text": "is understanding structure\nversus pseudorandomness, OK?", "start": 1550.425, "duration": 4.525}, {"text": "So as was the case last time.", "start": 1554.95, "duration": 2.73}, {"text": "So we want to understand, in\nwhat ways is A pseudorandom?", "start": 1557.68, "duration": 5.94}, {"text": "And here, \"pseudorandom,\"\njust as with last time,", "start": 1563.62, "duration": 2.4}, {"text": "means having small\nFourier coefficients,", "start": 1566.02, "duration": 2.52}, {"text": "being Fourier uniform.", "start": 1568.54, "duration": 3.316}, {"text": "If A is pseudorandom,\nwhich here, means f and g", "start": 1571.856, "duration": 4.994}, {"text": "are close to each other.", "start": 1576.85, "duration": 1.98}, {"text": "That's what being\npseudorandom means,", "start": 1578.83, "duration": 1.59}, {"text": "then the counting\nlemma will tell us", "start": 1580.42, "duration": 1.5}, {"text": "that f and g should\nhave similar AP counts.", "start": 1581.92, "duration": 3.87}, {"text": "But A has basically no AP\ncount, so they should not", "start": 1585.79, "duration": 5.4}, {"text": "be close to each other.", "start": 1591.19, "duration": 4.78}, {"text": "So that's the strategy, to\nshow that A is not pseudorandom", "start": 1595.97, "duration": 2.64}, {"text": "in this sense, and thereby\nextracting a large Fourier", "start": 1598.61, "duration": 2.88}, {"text": "coefficient.", "start": 1601.49, "duration": 1.75}, {"text": "So we apply counting\nto these two functions,", "start": 1603.24, "duration": 4.25}, {"text": "and we obtain that.", "start": 1607.49, "duration": 1.86}, {"text": "OK.", "start": 1614.86, "duration": 0.5}, {"text": "So this quantity, which\ncorresponds to lambda 3 of g,", "start": 1615.36, "duration": 7.64}, {"text": "minus alpha N. So these were\nlambda 3 of g, lambda 3 of F.", "start": 1623.0, "duration": 14.3}, {"text": "So it is upper-bounded.", "start": 1637.3, "duration": 1.46}, {"text": "The difference is up\nrebounded by the--", "start": 1638.76, "duration": 5.137}, {"text": "using the counting\nlemma, we find", "start": 1648.01, "duration": 1.75}, {"text": "that their difference\nis upper-bounded", "start": 1649.76, "duration": 1.74}, {"text": "by the following quantity.", "start": 1651.5, "duration": 1.17}, {"text": "Namely, you look at the\ndifference between f and g", "start": 1663.76, "duration": 3.09}, {"text": "and evaluate its maximum\nFourier coefficient.", "start": 1666.85, "duration": 5.232}, {"text": "OK.", "start": 1672.082, "duration": 0.928}, {"text": "So if A is pseudorandom,\nmeaning that Fourier uniform--", "start": 1673.01, "duration": 5.75}, {"text": "this l infinity\nnorm is small, then", "start": 1678.76, "duration": 6.08}, {"text": "I should expect lots\nand lots of 3APs in A,", "start": 1684.84, "duration": 5.17}, {"text": "but because that\nis not the case,", "start": 1690.01, "duration": 2.38}, {"text": "we should be able to\nconclude that there is", "start": 1692.39, "duration": 2.12}, {"text": "some large Fourier coefficient.", "start": 1694.51, "duration": 2.235}, {"text": "All right, so thus--", "start": 1700.0, "duration": 1.09}, {"text": "so rearranging the equation\nabove, we have that--", "start": 1713.131, "duration": 3.589}, {"text": "so this should be a square.", "start": 1724.03, "duration": 1.24}, {"text": "OK.", "start": 1731.48, "duration": 0.62}, {"text": "So we have this expression here.", "start": 1732.1, "duration": 2.16}, {"text": "And now we are--", "start": 1734.26, "duration": 2.43}, {"text": "OK, so let me simplify\nthis expression slightly.", "start": 1736.69, "duration": 6.63}, {"text": "And now we're using that N\nis sufficiently large, OK?", "start": 1743.32, "duration": 4.23}, {"text": "So we're using N is\nsufficiently large.", "start": 1747.55, "duration": 4.74}, {"text": "So this quantity is at least\na tenth of alpha squared N.", "start": 1752.29, "duration": 10.912}, {"text": "OK, and that's the\nconclusion, all right?", "start": 1763.202, "duration": 1.708}, {"text": "So that's the conclusion\nof this step here.", "start": 1764.91, "duration": 4.027}, {"text": "What does this mean?", "start": 1768.937, "duration": 0.833}, {"text": "This means there\nexists some theta", "start": 1769.77, "duration": 3.83}, {"text": "so that the Fourier\ncoefficient at theta", "start": 1773.6, "duration": 3.45}, {"text": "is at least the\nclaimed quantity.", "start": 1777.05, "duration": 1.7}, {"text": "Any questions?", "start": 1782.53, "duration": 1.304}, {"text": "All right.", "start": 1791.42, "duration": 0.63}, {"text": "So that finishes step 1.", "start": 1792.05, "duration": 1.91}, {"text": "So now let me go on step 2.", "start": 1793.96, "duration": 3.76}, {"text": "In step 2, we wish to show that\nif you have a large Fourier", "start": 1797.72, "duration": 4.4}, {"text": "coefficient, then one can\nobtain a density increment.", "start": 1802.12, "duration": 9.836}, {"text": "So last time, we were working\nin a finite field vector space.", "start": 1821.2, "duration": 5.52}, {"text": "A Fourier coefficient, OK,\nso which is a dual vector,", "start": 1826.72, "duration": 3.75}, {"text": "corresponds to some hyperplane.", "start": 1830.47, "duration": 3.55}, {"text": "And having a large\nFourier coefficient", "start": 1834.02, "duration": 3.59}, {"text": "then implies that\nthe density of A", "start": 1837.61, "duration": 2.77}, {"text": "on the co-sets of\nthose hyperplanes", "start": 1840.38, "duration": 2.76}, {"text": "must be not all\nclose to each other.", "start": 1843.14, "duration": 3.58}, {"text": "All right, so one\nof the hyperplanes", "start": 1846.72, "duration": 1.85}, {"text": "must have significantly\nhigher density than the rest.", "start": 1848.57, "duration": 4.81}, {"text": "OK, so we want to do\nsomething similar here,", "start": 1853.38, "duration": 1.92}, {"text": "except we run into this\ntechnical difficulty", "start": 1855.3, "duration": 2.28}, {"text": "where there are no\nsubspaces anymore.", "start": 1857.58, "duration": 3.67}, {"text": "So the Fourier character, namely\ncorresponding to this theta,", "start": 1861.25, "duration": 3.993}, {"text": "is just a real number.", "start": 1865.243, "duration": 0.917}, {"text": "It doesn't divide up your space.", "start": 1866.16, "duration": 1.35}, {"text": "It doesn't divide\nup your 1 through N", "start": 1867.51, "duration": 1.56}, {"text": "very nicely into sub chunks.", "start": 1869.07, "duration": 1.98}, {"text": "But we still want to use this\ntheta to chop up 1 through N", "start": 1871.05, "duration": 4.77}, {"text": "into smaller spaces so\nthat we can iterate and do", "start": 1875.82, "duration": 5.04}, {"text": "density increment.", "start": 1880.86, "duration": 3.87}, {"text": "All right.", "start": 1884.73, "duration": 1.18}, {"text": "So let's see what we can do.", "start": 1885.91, "duration": 3.01}, {"text": "So given this theta,\nwhat we would like to do", "start": 1888.92, "duration": 8.06}, {"text": "is to partition this 1 through\nN into subprogressions.", "start": 1896.98, "duration": 13.28}, {"text": "OK, so chop up 1 through\nN into sub APs such that", "start": 1913.564, "duration": 13.466}, {"text": "if you evaluate for--\nso this theta is fixed.", "start": 1927.03, "duration": 5.2}, {"text": "So on each sub AP,\nthis function here", "start": 1932.23, "duration": 5.76}, {"text": "is roughly constant\non each of your parts.", "start": 1937.99, "duration": 10.01}, {"text": "Last time, we had this\nFourier character,", "start": 1951.15, "duration": 2.85}, {"text": "and then we chopped it up\nusing these three hyperplanes.", "start": 1954.0, "duration": 3.12}, {"text": "And each hyperplane,\nthe Fourier character", "start": 1957.12, "duration": 3.27}, {"text": "is literally constant, OK?", "start": 1960.39, "duration": 2.688}, {"text": "So you have-- and so\nthat's what we work with.", "start": 1963.078, "duration": 3.592}, {"text": "And now, you cannot get\nthem to be exactly constant,", "start": 1966.67, "duration": 2.78}, {"text": "but the next best thing we can\nhope for is to get this Fourier", "start": 1969.45, "duration": 3.57}, {"text": "character to be\nroughly constant.", "start": 1973.02, "duration": 3.077}, {"text": "OK, so we're going to do some\npositioning that allows us", "start": 1976.097, "duration": 2.333}, {"text": "to achieve this characteristic.", "start": 1978.43, "duration": 2.43}, {"text": "And let me give\nyou some intuition", "start": 1980.86, "duration": 2.88}, {"text": "about why this is true.", "start": 1983.74, "duration": 1.17}, {"text": "And this is not exactly\na surprising fact.", "start": 1984.91, "duration": 2.66}, {"text": "The intuition is\njust that if you", "start": 1987.57, "duration": 2.47}, {"text": "look at what this\nfunction behaves like--", "start": 1990.04, "duration": 1.86}, {"text": "all right, so what's\ngoing on here?", "start": 1997.444, "duration": 2.506}, {"text": "You are on the unit circle,\nand you are jumping by theta.", "start": 1999.95, "duration": 7.65}, {"text": "OK, so you just keep\njumping by theta and so on.", "start": 2011.288, "duration": 10.792}, {"text": "And I want to show that I\ncan sharp up my progression", "start": 2022.08, "duration": 7.29}, {"text": "into a bunch of almost periodic\npieces, where in each part,", "start": 2029.37, "duration": 8.32}, {"text": "I'm staying inside a small arc.", "start": 2037.69, "duration": 3.68}, {"text": "So in the extreme case of this\nwhere it is very easy to see", "start": 2041.37, "duration": 5.19}, {"text": "is if x is some rational number,\na over b, with b fairly small,", "start": 2046.56, "duration": 11.599}, {"text": "then we can--", "start": 2058.159, "duration": 3.851}, {"text": "so then, this character is\nactually constant on APs", "start": 2062.01, "duration": 12.18}, {"text": "with common difference b.", "start": 2074.19, "duration": 1.469}, {"text": "Yep?", "start": 2083.063, "duration": 0.5}, {"text": "AUDIENCE: Is theta\nsupposed to be [INAUDIBLE]??", "start": 2083.563, "duration": 3.145}, {"text": "YUFEI ZHAO: Ah, so theta,\nyes. so theta-- thank you.", "start": 2086.708, "duration": 2.167}, {"text": "So theta 2 pi.", "start": 2088.875, "duration": 1.395}, {"text": "AUDIENCE: Like, is x\nequal to your theta?", "start": 2094.174, "duration": 3.196}, {"text": "YUFEI ZHAO: Yeah.", "start": 2097.37, "duration": 0.708}, {"text": "Thank you.", "start": 2098.078, "duration": 0.976}, {"text": "So theta equals-- yeah.", "start": 2099.054, "duration": 1.466}, {"text": "So if theta is some rational\nwith some small denominator--", "start": 2100.52, "duration": 5.66}, {"text": "so then you are literally\njumping in periodic steps", "start": 2106.18, "duration": 7.24}, {"text": "on the unit circle.", "start": 2113.42, "duration": 2.27}, {"text": "So if you partition N according\nto the exact same periods,", "start": 2115.69, "duration": 5.54}, {"text": "you have that this character\nis exactly constant in each", "start": 2121.23, "duration": 5.07}, {"text": "of your progressions.", "start": 2126.3, "duration": 1.89}, {"text": "Now, in general, the theta\nyou get out of that proof", "start": 2128.19, "duration": 4.02}, {"text": "might not have this\nvery nice form,", "start": 2132.21, "duration": 3.19}, {"text": "but we can at\nleast approximately", "start": 2135.4, "duration": 2.94}, {"text": "achieve the desired effect.", "start": 2138.34, "duration": 1.5}, {"text": "OK.", "start": 2142.63, "duration": 0.5}, {"text": "Any questions?", "start": 2146.89, "duration": 0.81}, {"text": "OK.", "start": 2175.56, "duration": 0.7}, {"text": "So to achieve approximately the\ndesired effect, what we'll do", "start": 2176.26, "duration": 3.84}, {"text": "is to find something\nso that b times theta", "start": 2180.1, "duration": 5.27}, {"text": "is not quite an integer, but\nvery close to an integer.", "start": 2185.37, "duration": 4.115}, {"text": "OK, so this, probably many\nof you have seen before.", "start": 2189.485, "duration": 2.125}, {"text": "It's a classic\npigeonhole-type result.", "start": 2191.61, "duration": 5.86}, {"text": "It's usually attributed\nto Dirichlet.", "start": 2197.47, "duration": 4.04}, {"text": "So if you have theta, a\nreal number, and a delta,", "start": 2205.02, "duration": 9.97}, {"text": "kind of a tolerance,\nthen there exists", "start": 2214.99, "duration": 5.31}, {"text": "a positive integer d at\nmost 1 over delta such", "start": 2220.3, "duration": 9.05}, {"text": "that d times theta is\nvery close to an integer.", "start": 2229.35, "duration": 9.68}, {"text": "OK, so this norm\nhere is distance", "start": 2239.03, "duration": 4.69}, {"text": "to the closest integer.", "start": 2243.72, "duration": 2.13}, {"text": "All right, so the proof is\nby pigeonhole principle.", "start": 2253.215, "duration": 5.175}, {"text": "So if we let N be 1\nover delta rounded down", "start": 2258.39, "duration": 6.17}, {"text": "and consider the numbers 0,\ntheta, 2 theta, 3 theta, and so", "start": 2264.56, "duration": 7.41}, {"text": "on, to N theta--", "start": 2271.97, "duration": 3.66}, {"text": "so by pigeonhole, there\nexists i theta and j theta, so", "start": 2275.63, "duration": 12.41}, {"text": "two different terms\nof the sequence such", "start": 2288.04, "duration": 4.62}, {"text": "that they differ by\nless than-- at most", "start": 2292.66, "duration": 8.04}, {"text": "delta in their fractional parts.", "start": 2300.7, "duration": 1.89}, {"text": "OK, so now take d to be\ndifference between i and j.", "start": 2310.26, "duration": 6.66}, {"text": "OK, and that works.", "start": 2316.92, "duration": 0.9}, {"text": "OK.", "start": 2328.06, "duration": 0.5}, {"text": "So even though you don't\nhave exactly rational,", "start": 2328.56, "duration": 4.16}, {"text": "you have approximately rational.", "start": 2332.72, "duration": 2.49}, {"text": "So this is a--", "start": 2335.21, "duration": 0.99}, {"text": "it's a simple rational\napproximation statement.", "start": 2336.2, "duration": 2.77}, {"text": "And using this\nrational approximation,", "start": 2338.97, "duration": 1.92}, {"text": "we can now try to do\nthe intuition here,", "start": 2340.89, "duration": 4.77}, {"text": "pretending that we're working\nwith rational numbers, indeed.", "start": 2345.66, "duration": 4.83}, {"text": "OK, so if we take\neta between 0 and 1", "start": 2356.442, "duration": 4.228}, {"text": "and theta irrational and\nsuppose N is large enough--", "start": 2360.67, "duration": 14.18}, {"text": "OK, so here, C\nmeans there exists", "start": 2374.85, "duration": 2.24}, {"text": "some sufficiently large--", "start": 2377.09, "duration": 3.4}, {"text": "some constant C such that\nthe statement is true, OK?", "start": 2380.49, "duration": 4.93}, {"text": "So suppose you think\na million here.", "start": 2385.42, "duration": 4.0}, {"text": "That should be fine.", "start": 2389.42, "duration": 1.74}, {"text": "So then there exists--", "start": 2391.16, "duration": 4.58}, {"text": "so then one can partition\n1 through N into sub-APs,", "start": 2395.74, "duration": 16.59}, {"text": "which we'll call P i.", "start": 2412.33, "duration": 2.63}, {"text": "And each having length\nbetween cube root of N", "start": 2414.96, "duration": 9.29}, {"text": "and twice the cube root of\nN such that this character", "start": 2424.25, "duration": 8.86}, {"text": "that we want to stay\nroughly constant indeed", "start": 2433.11, "duration": 2.59}, {"text": "does not change very much.", "start": 2435.7, "duration": 3.85}, {"text": "If you look at two terms in\nthe same AP, in the sub-AP,", "start": 2439.55, "duration": 8.06}, {"text": "then the value of this\ncharacter on each P sub i", "start": 2447.61, "duration": 13.06}, {"text": "is roughly the same.", "start": 2460.67, "duration": 2.41}, {"text": "So they don't vary by\nmore than eta on each P i.", "start": 2463.08, "duration": 5.84}, {"text": "So here, we're partitioning this\n1 through N into a sub-A piece", "start": 2468.92, "duration": 7.43}, {"text": "so that this guy here\nstays roughly constant.", "start": 2476.35, "duration": 4.005}, {"text": "OK.", "start": 2485.94, "duration": 0.5}, {"text": "Any questions?", "start": 2486.44, "duration": 3.03}, {"text": "All right.", "start": 2489.47, "duration": 0.5}, {"text": "So think about how\nyou might prove this.", "start": 2489.97, "duration": 3.758}, {"text": "Let's take a quick break.", "start": 2493.728, "duration": 1.042}, {"text": "So you see, we are basically\nfollowing the same strategy", "start": 2497.58, "duration": 3.58}, {"text": "as the proof from last\ntime, but this second step,", "start": 2501.16, "duration": 3.61}, {"text": "which we're on right now,\nneeds to be somewhat modified", "start": 2504.77, "duration": 2.6}, {"text": "because you cannot cut this\nspace up into pieces where", "start": 2507.37, "duration": 4.86}, {"text": "your character is constant.", "start": 2512.23, "duration": 2.1}, {"text": "Well, if they're roughly\nconstant then we're go to go,", "start": 2514.33, "duration": 3.81}, {"text": "so that's what we're doing now.", "start": 2518.14, "duration": 3.16}, {"text": "So let's prove the\nstatement up there.", "start": 2521.3, "duration": 1.7}, {"text": "All right.", "start": 2535.35, "duration": 0.51}, {"text": "So let's prove this\nstatement over here.", "start": 2535.86, "duration": 3.09}, {"text": "So using Dirichlet's lemma, we\nfind that there exists some d.", "start": 2538.95, "duration": 18.65}, {"text": "OK, so I'll write down\nsome number for now.", "start": 2557.6, "duration": 2.015}, {"text": "Don't worry about it.", "start": 2559.615, "duration": 0.875}, {"text": "It will come up shortly why I\nwrite this specific quantity.", "start": 2560.49, "duration": 4.6}, {"text": "So there exists some d which is\nnot too big, such that d theta", "start": 2567.67, "duration": 18.66}, {"text": "is very close to an integer.", "start": 2586.33, "duration": 3.5}, {"text": "So now, I'm literally\napplying Dirichlet's lemma.", "start": 2589.83, "duration": 2.71}, {"text": "OK.", "start": 2596.05, "duration": 1.63}, {"text": "So given such d--", "start": 2597.68, "duration": 7.146}, {"text": "so how big is this d?", "start": 2604.826, "duration": 2.814}, {"text": "You see that because I assumed\nthat N is sufficiently large,", "start": 2607.64, "duration": 5.1}, {"text": "if we choose that C large\nenough, d is at most root N. So", "start": 2612.74, "duration": 16.06}, {"text": "given such d, which\nis at most root N,", "start": 2628.8, "duration": 4.77}, {"text": "you can partition 1 through\nN into subprogressions", "start": 2633.57, "duration": 10.61}, {"text": "with common difference d.", "start": 2644.18, "duration": 5.4}, {"text": "Essentially, look at--\nlet's do classes mod d.", "start": 2649.58, "duration": 4.97}, {"text": "So they're all going to have\nlength by basically N over d.", "start": 2654.55, "duration": 4.58}, {"text": "And I chop them up a\nlittle bit further to get--", "start": 2659.13, "duration": 6.01}, {"text": "so a piece of length\nbetween cube root of N", "start": 2665.14, "duration": 8.25}, {"text": "and twice cube root of N.", "start": 2673.39, "duration": 7.6}, {"text": "OK.", "start": 2680.99, "duration": 0.5}, {"text": "So I'm going to make\nsure that all of my APs", "start": 2681.49, "duration": 3.03}, {"text": "are roughly the same length.", "start": 2684.52, "duration": 3.48}, {"text": "And now, inside each\nsubprogression--", "start": 2688.0, "duration": 8.09}, {"text": "let me call this subprogression\nP prime, subprogression P,", "start": 2700.79, "duration": 5.82}, {"text": "let's look at how much\nthis character value can", "start": 2706.61, "duration": 2.82}, {"text": "vary inside this progression.", "start": 2709.43, "duration": 3.689}, {"text": "All right.", "start": 2719.346, "duration": 0.958}, {"text": "OK, so how much can this vary?", "start": 2726.01, "duration": 3.41}, {"text": "Well, because theta is such\nthat d times theta is very close", "start": 2729.42, "duration": 6.91}, {"text": "to an integer and the length\nof each progression is not too", "start": 2736.33, "duration": 5.448}, {"text": "large-- so here's--", "start": 2741.778, "duration": 0.792}, {"text": "I want some control\non the length.", "start": 2742.57, "duration": 2.14}, {"text": "So we find that the\nmaximum variation", "start": 2744.71, "duration": 4.31}, {"text": "is, at most, the size of\nP, the length of P, times--", "start": 2749.02, "duration": 7.675}, {"text": "so this-- that\ndifference over there.", "start": 2759.58, "duration": 4.95}, {"text": "So all of these are exponential,\nso I can shift them.", "start": 2764.53, "duration": 4.39}, {"text": "Well, the length of P is at\nmost twice cube root of N. And--", "start": 2768.92, "duration": 11.075}, {"text": "OK, so what is this quantity?", "start": 2779.995, "duration": 2.165}, {"text": "So the point is that if\nthis fractional part here", "start": 2782.16, "duration": 3.31}, {"text": "is very close to an\ninteger, then e to that,", "start": 2785.47, "duration": 3.61}, {"text": "e to the 2 pi times that\ni times some number should", "start": 2789.08, "duration": 2.48}, {"text": "be very close to 1, because\nwhat is happening here?", "start": 2791.56, "duration": 5.07}, {"text": "This is the distance\nbetween those two points", "start": 2796.63, "duration": 5.42}, {"text": "on the circle, which\nis at most bounded", "start": 2802.05, "duration": 3.18}, {"text": "by the length of the arc.", "start": 2805.23, "duration": 1.26}, {"text": "OK, so cord length,\nat most of the arc.", "start": 2817.46, "duration": 5.07}, {"text": "So now, you put\neverything here together,", "start": 2822.53, "duration": 3.03}, {"text": "and apply the bound\nthat we got on d theta.", "start": 2825.56, "duration": 3.67}, {"text": "So this is the reason for\nchoosing that weird number", "start": 2829.23, "duration": 2.18}, {"text": "up there.", "start": 2831.41, "duration": 2.55}, {"text": "We find that the variation\nwithin each progression", "start": 2833.96, "duration": 16.09}, {"text": "is at most eta, right?", "start": 2850.05, "duration": 1.853}, {"text": "So the variation\nof this character", "start": 2851.903, "duration": 1.417}, {"text": "within each progression\nis not very large, OK?", "start": 2853.32, "duration": 2.855}, {"text": "And that's the claim.", "start": 2856.175, "duration": 0.875}, {"text": "Any questions?", "start": 2859.83, "duration": 1.95}, {"text": "All right, so this is the\nanalogous claim to the one", "start": 2861.78, "duration": 4.14}, {"text": "that we had--", "start": 2865.92, "duration": 0.86}, {"text": "the one that we used\nlast time, where", "start": 2866.78, "duration": 1.72}, {"text": "we said that the character\nis constant on each coset", "start": 2868.5, "duration": 3.45}, {"text": "of the hyperplane.", "start": 2871.95, "duration": 0.965}, {"text": "They're not exactly constant,\nbut almost good enough.", "start": 2872.915, "duration": 2.515}, {"text": "All right.", "start": 2885.61, "duration": 0.69}, {"text": "So the goal of step 2\nis to show an energy--", "start": 2886.3, "duration": 3.72}, {"text": "show a density increment, that\nif you have a large Fourier", "start": 2890.02, "duration": 3.0}, {"text": "coefficient, then\nwe want to claim", "start": 2893.02, "duration": 2.16}, {"text": "that the density\ngoes up significantly", "start": 2895.18, "duration": 3.54}, {"text": "on some subprogression.", "start": 2898.72, "duration": 3.22}, {"text": "And the next part,\nthe next lemma,", "start": 2901.94, "duration": 2.97}, {"text": "will get us to that goal.", "start": 2904.91, "duration": 2.37}, {"text": "And this part is very\nsimilar to the one", "start": 2907.28, "duration": 2.64}, {"text": "that we saw from last time,\nbut with this new partition", "start": 2909.92, "duration": 4.68}, {"text": "in mind, like I said.", "start": 2914.6, "duration": 1.38}, {"text": "If you have A that is\n3AP-free with density alpha,", "start": 2915.98, "duration": 11.88}, {"text": "and N is large\nenough, then there", "start": 2927.86, "duration": 10.13}, {"text": "exists some subprogression\nP. So by subprogression,", "start": 2937.99, "duration": 10.99}, {"text": "I just mean that I'm starting\nwith original progression", "start": 2948.98, "duration": 2.58}, {"text": "1 through N, and I'm zooming\ninto some subprogression,", "start": 2951.56, "duration": 3.78}, {"text": "with the length of P fairly\nlong, so the length of P", "start": 2955.34, "duration": 6.82}, {"text": "is at least cube root\nof N, and such that A,", "start": 2962.16, "duration": 7.27}, {"text": "when restricted to\nthis subprogression,", "start": 2969.43, "duration": 3.33}, {"text": "has a density increment.", "start": 2972.76, "duration": 3.535}, {"text": "OK, so originally, the\ndensity of A is alpha,", "start": 2981.995, "duration": 2.955}, {"text": "so we're zooming into\nsome subprogression P,", "start": 2984.95, "duration": 2.35}, {"text": "which is a pretty\nlong subprogression,", "start": 2987.3, "duration": 1.68}, {"text": "where the density\ngoes up significantly", "start": 2988.98, "duration": 1.89}, {"text": "from A to essentially A--", "start": 2990.87, "duration": 2.49}, {"text": "from alpha to roughly\nalpha plus alpha squared.", "start": 2993.36, "duration": 2.97}, {"text": "OK.", "start": 3000.24, "duration": 0.5}, {"text": "So we start with\nA, a 3AP-free set.", "start": 3007.12, "duration": 3.54}, {"text": "So from step 1, there exists\nsome theta with large--", "start": 3010.66, "duration": 14.45}, {"text": "so that corresponds to a\nlarge Fourier coefficient.", "start": 3025.11, "duration": 2.822}, {"text": "So this sum here is large.", "start": 3031.79, "duration": 14.28}, {"text": "OK, and now we use--", "start": 3048.782, "duration": 5.928}, {"text": "OK, so-- so step 1 obtains us,\nyou know, this consequence.", "start": 3054.71, "duration": 5.8}, {"text": "And from this theta, now we\napply the lemma up there to--", "start": 3060.51, "duration": 14.27}, {"text": "so we apply lemma\nwith, let's say,", "start": 3074.78, "duration": 1.98}, {"text": "eta being alpha squared over 30.", "start": 3076.76, "duration": 4.59}, {"text": "OK, so the exact constants\nare not so important.", "start": 3081.35, "duration": 2.34}, {"text": "But when we apply the\nlemma to partition,", "start": 3083.69, "duration": 7.32}, {"text": "and into a bunch\nof subprogressions,", "start": 3091.01, "duration": 6.71}, {"text": "which we'll call P1 through Pk.", "start": 3097.72, "duration": 2.85}, {"text": "And each of these\nprogressions have", "start": 3103.462, "duration": 4.618}, {"text": "length between cube root of\nN and twice cube root of N.", "start": 3108.08, "duration": 11.67}, {"text": "And I want to understand what\nhappens to the density of A", "start": 3119.75, "duration": 4.32}, {"text": "when restricted to\nthese progressions.", "start": 3124.07, "duration": 3.61}, {"text": "So starting with this\ninequality over here,", "start": 3127.68, "duration": 6.35}, {"text": "which suggests to us that\nthere must be some deviation.", "start": 3134.03, "duration": 3.12}, {"text": "OK, so starting\nwith what we saw.", "start": 3150.191, "duration": 4.509}, {"text": "And now, inside each\nprogression this e x theta", "start": 3154.7, "duration": 6.25}, {"text": "is roughly constant.", "start": 3160.95, "duration": 3.1}, {"text": "So if you pretend them\nas actually constant,", "start": 3164.05, "duration": 2.71}, {"text": "I can break up the sum,\ndepending on where the x's lie.", "start": 3166.76, "duration": 7.47}, {"text": "So i from 1 to k.", "start": 3174.23, "duration": 3.3}, {"text": "And let me sum inside\neach progression.", "start": 3177.53, "duration": 3.962}, {"text": "So by triangle inequality, I\ncan upper bound the first sum", "start": 3193.56, "duration": 4.05}, {"text": "by where I now cut the sum into\nprogression by progression.", "start": 3197.61, "duration": 5.93}, {"text": "And on each progression, this\ncharacter is roughly constant.", "start": 3203.54, "duration": 5.98}, {"text": "So let me take out the\nmaximum possible deviations", "start": 3209.52, "duration": 5.24}, {"text": "from them being constant.", "start": 3214.76, "duration": 1.68}, {"text": "So upper bound-- again, you'll\nfind that we can essentially", "start": 3216.44, "duration": 12.085}, {"text": "pretend--", "start": 3228.525, "duration": 0.5}, {"text": "all right, so if\neach exponential", "start": 3232.19, "duration": 3.22}, {"text": "is constant on each\nsubprogression,", "start": 3235.41, "duration": 2.04}, {"text": "then I might as well\njust have this sum here.", "start": 3237.45, "duration": 3.3}, {"text": "But I lose a little bit, because\nit's not exactly constant.", "start": 3240.75, "duration": 2.76}, {"text": "It's almost constant.", "start": 3243.51, "duration": 1.17}, {"text": "So I loose a little bit.", "start": 3244.68, "duration": 1.46}, {"text": "And that little bit is this eta.", "start": 3246.14, "duration": 5.21}, {"text": "So you lose that\nlittle bit of eta.", "start": 3251.35, "duration": 2.09}, {"text": "And so on each\nprogression, P i, you", "start": 3253.44, "duration": 5.52}, {"text": "lose at most something that's\nessentially of alpha squared", "start": 3258.96, "duration": 3.87}, {"text": "times the length of P i.", "start": 3262.83, "duration": 1.435}, {"text": "OK.", "start": 3267.24, "duration": 1.92}, {"text": "Now, you see, I've chosen\nthe error parameter", "start": 3269.16, "duration": 3.72}, {"text": "so that everything\nI've lost is not", "start": 3272.88, "duration": 4.38}, {"text": "so much more than the\ninitial bound I began with.", "start": 3277.26, "duration": 3.99}, {"text": "So in particular,\nwe see that even", "start": 3281.25, "duration": 5.85}, {"text": "if we had pretended that the\ncharacters were constant,", "start": 3287.1, "duration": 2.7}, {"text": "on each progression we would\nhave still obtained some lower", "start": 3289.8, "duration": 4.29}, {"text": "bound of the total deviation.", "start": 3294.09, "duration": 2.79}, {"text": "OK.", "start": 3308.68, "duration": 1.18}, {"text": "And what is this\nquantity over here?", "start": 3309.86, "duration": 5.27}, {"text": "Oh, you see, I'm\nrestricting each sum", "start": 3315.13, "duration": 3.75}, {"text": "to each subprogression,\nbut the sum", "start": 3318.88, "duration": 4.71}, {"text": "here, even though it's\nthe sum, but it's really", "start": 3323.59, "duration": 2.85}, {"text": "counting how many elements\nof A are in that progression.", "start": 3326.44, "duration": 5.55}, {"text": "So this sum over here\nis the same thing.", "start": 3331.99, "duration": 3.72}, {"text": "OK, so let me write\nit in a new board.", "start": 3335.71, "duration": 2.833}, {"text": "Oh, we don't need\nstep 1 anymore.", "start": 3343.48, "duration": 1.733}, {"text": "All right.", "start": 3349.077, "duration": 2.193}, {"text": "So what we have--", "start": 3351.27, "duration": 1.17}, {"text": "OK, so left-hand side over\nthere is this quantity here,", "start": 3361.386, "duration": 4.045}, {"text": "all right?", "start": 3365.431, "duration": 2.259}, {"text": "We see that the right-hand side,\neven though you have that sum,", "start": 3367.69, "duration": 8.2}, {"text": "it is really just counting\nhow many elements of A", "start": 3375.89, "duration": 3.12}, {"text": "are in each progression versus\nhow many you should expect", "start": 3379.01, "duration": 4.35}, {"text": "based on the overall\ndensity of A. OK,", "start": 3383.36, "duration": 5.39}, {"text": "so that should look similar\nto what we got last time.", "start": 3388.75, "duration": 3.47}, {"text": "I know the intuition\nshould be that, well,", "start": 3392.22, "duration": 3.06}, {"text": "if the average deviation\nis large, then one of them,", "start": 3395.28, "duration": 6.93}, {"text": "one of these terms, should\nhave the density increment.", "start": 3402.21, "duration": 5.237}, {"text": "If you try to do the next\nstep somewhat naively,", "start": 3411.19, "duration": 2.76}, {"text": "you run into an issue,\nbecause it could be--", "start": 3413.95, "duration": 2.89}, {"text": "now, here you have k terms.", "start": 3416.84, "duration": 2.45}, {"text": "It could be that you have all\nthe densities except for one", "start": 3419.29, "duration": 7.98}, {"text": "going up only slightly, and one\ndensity dropping dramatically,", "start": 3427.27, "duration": 5.37}, {"text": "in which case you may not\nhave a significant density", "start": 3432.64, "duration": 2.94}, {"text": "increment, all right?", "start": 3435.58, "duration": 2.63}, {"text": "So we want to show that\non some progression", "start": 3438.21, "duration": 2.63}, {"text": "the density increases\nsignificantly.", "start": 3440.84, "duration": 3.51}, {"text": "So far, from this\ninequality, we just", "start": 3444.35, "duration": 2.52}, {"text": "know that there is some\nsubprogression where", "start": 3446.87, "duration": 2.85}, {"text": "the density changes\nsignificantly.", "start": 3449.72, "duration": 2.73}, {"text": "But of course, the overall\ndensity, the average density,", "start": 3452.45, "duration": 2.4}, {"text": "should remain constant.", "start": 3454.85, "duration": 1.27}, {"text": "So if some goes up,\nothers must go down.", "start": 3456.12, "duration": 2.83}, {"text": "But if you just try to\ndo an averaging argument,", "start": 3458.95, "duration": 2.23}, {"text": "you have to be careful, OK?", "start": 3461.18, "duration": 1.71}, {"text": "So there was a trick last\ntime, which we didn't really", "start": 3462.89, "duration": 2.4}, {"text": "need last time, but now,\nit's much more useful, where", "start": 3465.29, "duration": 4.62}, {"text": "I want to show\nthat if this holds,", "start": 3469.91, "duration": 2.31}, {"text": "then some P i sees\na large energy--", "start": 3472.22, "duration": 3.63}, {"text": "sees a large density increment.", "start": 3475.85, "duration": 2.67}, {"text": "And to do that, let me rewrite\nthe sum as the following,", "start": 3478.52, "duration": 10.47}, {"text": "so I keep the same expression.", "start": 3488.99, "duration": 2.67}, {"text": "And I add a term, which\nis the same thing,", "start": 3494.88, "duration": 4.1}, {"text": "but without the absolute value.", "start": 3498.98, "duration": 1.58}, {"text": "OK, so you see these\nguys, they total to 0,", "start": 3509.434, "duration": 5.566}, {"text": "so adding that term doesn't\nchange my expression.", "start": 3515.0, "duration": 5.35}, {"text": "But now, the summand\nis always non-negative.", "start": 3520.35, "duration": 5.11}, {"text": "So it's either 0 or\ntwice this number,", "start": 3525.46, "duration": 3.92}, {"text": "depending on the\nsign of that number.", "start": 3529.38, "duration": 2.12}, {"text": "OK.", "start": 3534.61, "duration": 0.5}, {"text": "So comparing left-hand\nside and right-hand side,", "start": 3535.11, "duration": 2.49}, {"text": "we see that there\nmust be some i.", "start": 3537.6, "duration": 3.19}, {"text": "So hence, there exists some eye\nsuch that the left-hand side--", "start": 3540.79, "duration": 7.94}, {"text": "the i-th term on\nthe left hand side", "start": 3553.41, "duration": 1.86}, {"text": "is less than or equal\nto the i-th term", "start": 3555.27, "duration": 3.002}, {"text": "on the right-hand side.", "start": 3558.272, "duration": 0.958}, {"text": "And in particular, that\nterm should be positive,", "start": 3564.94, "duration": 3.7}, {"text": "so it implies--", "start": 3568.64, "duration": 2.82}, {"text": "OK, so how can you\nget this inequality?", "start": 3571.46, "duration": 4.28}, {"text": "It implies simply that the\nrestriction of a to this P i", "start": 3575.74, "duration": 4.8}, {"text": "is at least alpha plus alpha\nsquared over 40 times P i.", "start": 3580.54, "duration": 10.27}, {"text": "So this claim here just says\nthat on the i-th progression,", "start": 3590.81, "duration": 3.51}, {"text": "there's a significant\nenergy increment.", "start": 3594.32, "duration": 4.25}, {"text": "If it's more decrement,\nthat term would have been 0.", "start": 3598.57, "duration": 3.772}, {"text": "So remember that.", "start": 3602.342, "duration": 2.268}, {"text": "OK.", "start": 3616.04, "duration": 1.24}, {"text": "So this achieves what we\nwere looking for in step 2,", "start": 3617.28, "duration": 3.33}, {"text": "namely to find that there\nis a density increment", "start": 3620.61, "duration": 4.11}, {"text": "on some long subprogression.", "start": 3624.72, "duration": 3.321}, {"text": "OK, so now we can go to\nstep 3, which is basically", "start": 3628.041, "duration": 2.589}, {"text": "the same as what we saw\nlast time, where now we", "start": 3630.63, "duration": 4.83}, {"text": "want to iterate this\ndensity increment.", "start": 3635.46, "duration": 3.469}, {"text": "OK, so it's basically the\nsame argument as last time,", "start": 3647.911, "duration": 7.989}, {"text": "but you start with\ndensity alpha,", "start": 3655.9, "duration": 4.4}, {"text": "and each step in the\niteration, the density", "start": 3660.3, "duration": 3.84}, {"text": "goes up quite a bit.", "start": 3664.14, "duration": 1.46}, {"text": "And we want to control\nthe total number of steps,", "start": 3669.74, "duration": 4.29}, {"text": "knowing that the final\ndensity is at most 1, always.", "start": 3674.03, "duration": 6.674}, {"text": "OK.", "start": 3680.704, "duration": 2.666}, {"text": "So how many steps can you take?", "start": 3683.37, "duration": 1.65}, {"text": "Right, so this was the same\nargument that we saw last time.", "start": 3685.02, "duration": 3.06}, {"text": "We see that starting with\nalpha, alpha 0 being alpha,", "start": 3688.08, "duration": 10.37}, {"text": "it doubles after a certain\nnumber of steps, right?", "start": 3698.45, "duration": 3.36}, {"text": "So we double after--", "start": 3701.81, "duration": 3.78}, {"text": "OK, so how many\nsteps do you need?", "start": 3705.59, "duration": 3.12}, {"text": "Well, I want to get\nfrom alpha to 2 alpha.", "start": 3708.71, "duration": 4.72}, {"text": "So I need at most\nalpha over 40 steps.", "start": 3713.43, "duration": 7.53}, {"text": "OK, so last time I\nwas slightly sloppy.", "start": 3720.96, "duration": 2.81}, {"text": "And so there's basically a\nfloor, upper floor down--", "start": 3723.77, "duration": 5.86}, {"text": "rounding up or down situation.", "start": 3729.63, "duration": 1.43}, {"text": "But I should add a plus 1.", "start": 3731.06, "duration": 2.56}, {"text": "Yeah.", "start": 3733.62, "duration": 0.5}, {"text": "AUDIENCE: Shouldn't\nit be 40 over alpha?", "start": 3734.12, "duration": 2.0}, {"text": "YUFEI ZHAO: 40-- thank you.", "start": 3736.12, "duration": 1.22}, {"text": "40 over alpha, yeah.", "start": 3737.34, "duration": 2.59}, {"text": "So you double after at\nmost that many steps.", "start": 3739.93, "duration": 5.15}, {"text": "And then now, you add\ndensity at least 2 alpha.", "start": 3745.08, "duration": 6.48}, {"text": "So we double after at most 20\nover alpha steps, and so on.", "start": 3751.56, "duration": 8.32}, {"text": "And we double at most--", "start": 3759.88, "duration": 4.81}, {"text": "well, basically, log sub\n2 of 1 over alpha times.", "start": 3764.69, "duration": 7.0}, {"text": "OK, so anyway, putting\neverything together,", "start": 3775.658, "duration": 2.942}, {"text": "we see that the\ntotal number of steps", "start": 3778.6, "duration": 5.75}, {"text": "is at most on the\norder of 1 over alpha.", "start": 3784.35, "duration": 4.44}, {"text": "When you stop, you can\nonly stop for one reason,", "start": 3792.34, "duration": 3.15}, {"text": "because in the--", "start": 3795.49, "duration": 2.72}, {"text": "yeah.", "start": 3798.21, "duration": 0.5}, {"text": "So, yeah.", "start": 3798.71, "duration": 1.17}, {"text": "So in step 1,\nremember, the iteration", "start": 3799.88, "duration": 4.91}, {"text": "said that the\nprocess terminates.", "start": 3804.79, "duration": 3.972}, {"text": "The process can always go\non, and then terminates", "start": 3808.762, "duration": 8.827}, {"text": "if the length--", "start": 3817.589, "duration": 5.581}, {"text": "so you're now at\nstep i, so let N i be", "start": 3823.17, "duration": 2.42}, {"text": "the length of the progression,\nthat step i is at most C times", "start": 3825.59, "duration": 8.99}, {"text": "alpha i to the minus 12th.", "start": 3834.58, "duration": 2.41}, {"text": "So we have a--", "start": 3836.99, "duration": 4.19}, {"text": "right, so provided\nthat N is large enough,", "start": 3841.18, "duration": 3.8}, {"text": "you can always pass\nto a subprogression.", "start": 3844.98, "duration": 2.04}, {"text": "And here, when you pass to\nsubprogression, of course,", "start": 3847.02, "duration": 2.52}, {"text": "you can re-label\nthat subprogression.", "start": 3849.54, "duration": 2.49}, {"text": "And it's now, you\nknow, 1 through N i.", "start": 3852.03, "duration": 3.11}, {"text": "Right, so I can-- it's--", "start": 3855.14, "duration": 1.413}, {"text": "all the progressions\nare basically", "start": 3856.553, "duration": 1.417}, {"text": "the same as the first\nset of positive integers.", "start": 3857.97, "duration": 3.403}, {"text": "I'm sorry, prefix of\nthe positive integers.", "start": 3861.373, "duration": 2.477}, {"text": "So when we stop a\nstep i, you must", "start": 3863.85, "duration": 2.74}, {"text": "have N sub i being at most\nthis quantity over here, which", "start": 3866.59, "duration": 4.7}, {"text": "is at most C times the initial\ndensity raised to this minus", "start": 3871.29, "duration": 5.22}, {"text": "12th.", "start": 3876.51, "duration": 0.94}, {"text": "So therefore, the initial length\nN of the space is bounded by--", "start": 3877.45, "duration": 11.6}, {"text": "well, each time we went\ndown by a cube root at most.", "start": 3889.05, "duration": 6.545}, {"text": "Right, so the fine--", "start": 3895.595, "duration": 1.965}, {"text": "if you stop a step i,\nthen the initial length", "start": 3897.56, "duration": 3.42}, {"text": "is at most N sub i to the\n3 times 3 to the power of i", "start": 3900.98, "duration": 6.69}, {"text": "each time you're\ndoing a cube root.", "start": 3907.67, "duration": 3.252}, {"text": "OK, so you put\neverything together.", "start": 3910.922, "duration": 2.213}, {"text": "At most that many\niterations when you stop", "start": 3920.28, "duration": 2.08}, {"text": "the length is at most this.", "start": 3922.36, "duration": 2.421}, {"text": "So you put them\ntogether, and then you", "start": 3924.781, "duration": 1.899}, {"text": "find that the N must be at\nmost double exponential in 1", "start": 3926.68, "duration": 10.64}, {"text": "over the density.", "start": 3937.32, "duration": 2.82}, {"text": "In other words, the\ndensity is at most 1", "start": 3940.14, "duration": 7.53}, {"text": "over log log N, which is what\nwe claimed in Roth's theorem,", "start": 3947.67, "duration": 7.995}, {"text": "so what we claimed up there.", "start": 3955.665, "duration": 1.395}, {"text": "OK.", "start": 3961.46, "duration": 0.5}, {"text": "So that finishes the proof.", "start": 3961.96, "duration": 1.268}, {"text": "Any questions?", "start": 3972.21, "duration": 1.097}, {"text": "So the message here is that it's\nthe same proof as last time,", "start": 3978.78, "duration": 3.45}, {"text": "but we need to do\na bit more work.", "start": 3982.23, "duration": 2.43}, {"text": "And none of this\nwork is difficult,", "start": 3984.66, "duration": 1.56}, {"text": "but there are more technical.", "start": 3986.22, "duration": 1.56}, {"text": "And that's often\nthe theme that you", "start": 3987.78, "duration": 1.8}, {"text": "see in additive combinatorics.", "start": 3989.58, "duration": 1.92}, {"text": "This is part of the reason\nwhy the finite field model is", "start": 3991.5, "duration": 3.15}, {"text": "a really nice playground,\nbecause there, things", "start": 3994.65, "duration": 3.48}, {"text": "tend to be often cleaner,\nbut the idea's often similar,", "start": 3998.13, "duration": 3.72}, {"text": "or the same ideas.", "start": 4001.85, "duration": 1.29}, {"text": "Not always.", "start": 4003.14, "duration": 0.75}, {"text": "Next lecture, we'll\nsee one technique", "start": 4003.89, "duration": 2.352}, {"text": "where there's a\ndramatic difference", "start": 4006.242, "duration": 1.458}, {"text": "between the finite field vector\nspace and over the integers.", "start": 4007.7, "duration": 3.24}, {"text": "But for many things in\nadditive combinatorics,", "start": 4010.94, "duration": 2.23}, {"text": "the finite field\nvector space is just", "start": 4013.17, "duration": 1.55}, {"text": "a nicer place to be in to try\nall your ideas and techniques.", "start": 4014.72, "duration": 3.452}, {"text": "Let me comment on some analogies\nbetween these two approaches", "start": 4024.44, "duration": 4.65}, {"text": "and compare the bounds.", "start": 4029.09, "duration": 1.11}, {"text": "So on one hand--", "start": 4033.09, "duration": 2.19}, {"text": "OK, so we saw last time\nthis proof in F3 to the N,", "start": 4035.28, "duration": 4.85}, {"text": "and now in the integers\ninside this interval of length", "start": 4040.13, "duration": 6.64}, {"text": "N. So let me write\nuppercase N in both cases", "start": 4046.77, "duration": 6.51}, {"text": "to be the size of the\noverall ambient space.", "start": 4053.28, "duration": 4.925}, {"text": "OK, so what kind of bounds\ndo we get in both situations?", "start": 4058.205, "duration": 5.105}, {"text": "So last time, for--", "start": 4063.31, "duration": 2.74}, {"text": "in F3 to the N, we\ngot a bound which", "start": 4066.05, "duration": 5.67}, {"text": "is of the order N over log N,\nwhereas today, the bound is", "start": 4071.72, "duration": 14.5}, {"text": "somewhat worse.", "start": 4086.22, "duration": 2.34}, {"text": "It's a little bit worse.", "start": 4088.56, "duration": 1.36}, {"text": "Now we lose an extra log.", "start": 4089.92, "duration": 3.77}, {"text": "So where do we lose an\nextra log in this argument?", "start": 4093.69, "duration": 3.12}, {"text": "So where does these\ntwo argument--", "start": 4096.81, "duration": 2.25}, {"text": "where do these two arguments\ndiffer, quantitatively?", "start": 4099.06, "duration": 3.92}, {"text": "Yep?", "start": 4106.24, "duration": 0.5}, {"text": "AUDIENCE: When you're dividing\nby 3 versus [INAUDIBLE]??", "start": 4106.74, "duration": 2.829}, {"text": "YUFEI ZHAO: OK, so\nyou're dividing by--", "start": 4109.569, "duration": 1.991}, {"text": "so here, in each\niteration, over here,", "start": 4111.56, "duration": 10.4}, {"text": "your size of the iteration--", "start": 4121.96, "duration": 4.439}, {"text": "I mean, each iteration\nthe size of the space", "start": 4126.399, "duration": 1.901}, {"text": "goes down by a factor of\n3, whereas over here, it", "start": 4128.3, "duration": 4.979}, {"text": "could go down by a cube root.", "start": 4133.279, "duration": 3.7}, {"text": "And that's precisely right.", "start": 4136.979, "duration": 1.42}, {"text": "So that explains for this\nextra log in the balance.", "start": 4138.399, "duration": 4.021}, {"text": "So while this is\na great analogy,", "start": 4145.63, "duration": 2.86}, {"text": "it's not a perfect analogy.", "start": 4148.49, "duration": 2.27}, {"text": "You see there is this\ndivergence here between the two", "start": 4150.76, "duration": 2.519}, {"text": "situations.", "start": 4153.279, "duration": 1.511}, {"text": "And so then you\nmight ask, is there", "start": 4154.79, "duration": 1.64}, {"text": "some way to avoid the\nloss, this extra log factor", "start": 4156.43, "duration": 4.81}, {"text": "loss over here?", "start": 4161.24, "duration": 1.71}, {"text": "Is there some way to\ncarry out the strategy", "start": 4162.95, "duration": 2.31}, {"text": "that we did last\ntime in a way that", "start": 4165.26, "duration": 3.429}, {"text": "is much more faithful to\nthat strategy of passing down", "start": 4168.689, "duration": 2.611}, {"text": "to subspaces.", "start": 4171.3, "duration": 1.76}, {"text": "So here, we pass\nto progressions.", "start": 4173.06, "duration": 3.03}, {"text": "And because we have to do this\nextra pigeonhole-type argument,", "start": 4176.09, "duration": 4.559}, {"text": "it was somewhat lost--", "start": 4180.649, "duration": 1.321}, {"text": "we lost a power, which\ntranslated into this extra log.", "start": 4181.97, "duration": 6.8}, {"text": "So it turns out there\nis some way to do this.", "start": 4188.77, "duration": 3.14}, {"text": "So let me just\nbriefly mention what's", "start": 4191.91, "duration": 1.69}, {"text": "the idea that is\ninvolved, all right?", "start": 4193.6, "duration": 2.04}, {"text": "So last time, we\nwent down from--", "start": 4195.64, "duration": 4.29}, {"text": "so the main objects\nthat we were passing", "start": 4199.93, "duration": 2.73}, {"text": "would start with a vector\nspace and pass down", "start": 4202.66, "duration": 2.52}, {"text": "to a subspace, which is\nalso a vector space, right?", "start": 4205.18, "duration": 3.13}, {"text": "So you can define subspaces in\nF3 to the N by the following.", "start": 4208.31, "duration": 9.18}, {"text": "So I can start with some set\nof characters U, and I define--", "start": 4217.49, "duration": 6.82}, {"text": "some set of characters\nS, and I define", "start": 4224.31, "duration": 2.32}, {"text": "U sub S to be basically the\northogonal complement of S.", "start": 4226.63, "duration": 14.192}, {"text": "OK, so this is a subspace.", "start": 4240.822, "duration": 2.15}, {"text": "And these were the\nkind of subspace", "start": 4242.972, "duration": 1.458}, {"text": "that we saw last time, because\nthe S's or the R's that", "start": 4244.43, "duration": 3.738}, {"text": "came out of the proof last\ntime, every time we saw one,", "start": 4248.168, "duration": 2.292}, {"text": "we threw it in.", "start": 4250.46, "duration": 0.93}, {"text": "We cut down to a smaller\nsubspace, and we repeat.", "start": 4251.39, "duration": 4.94}, {"text": "But the progressions, they\ndon't really look like this.", "start": 4256.33, "duration": 2.688}, {"text": "So the question is,\nis there some way", "start": 4259.018, "duration": 1.542}, {"text": "to do this argument so that\nyou end up with progressions,", "start": 4260.56, "duration": 2.375}, {"text": "and looked like that?", "start": 4262.935, "duration": 1.075}, {"text": "And it turns out there is a way.", "start": 4264.01, "duration": 2.29}, {"text": "And there are these\nobjects, which", "start": 4266.3, "duration": 1.85}, {"text": "we'll see more later in this\ncourse, called Bohr sets.", "start": 4268.15, "duration": 5.065}, {"text": "OK, so they were\nused by Bourgain", "start": 4273.215, "duration": 4.815}, {"text": "to mimic this Machoulin argument\nthat we saw last time more", "start": 4278.03, "duration": 5.19}, {"text": "faithfully into\nthe integers, where", "start": 4283.22, "duration": 2.79}, {"text": "we're going to come up with some\nset of integers that resemble--", "start": 4286.01, "duration": 4.83}, {"text": "much more closely resemble\nthis notion of subspaces", "start": 4290.84, "duration": 4.11}, {"text": "in the finite field setting.", "start": 4294.95, "duration": 2.34}, {"text": "And for this, it's much\neasier to work inside a group.", "start": 4297.29, "duration": 3.73}, {"text": "So instead of working\nin the integers,", "start": 4301.02, "duration": 1.88}, {"text": "let's work inside and Z mod nZ.", "start": 4302.9, "duration": 2.21}, {"text": "So we can do Fourier\ntransform in Z mod nZ, so", "start": 4305.11, "duration": 2.47}, {"text": "the discrete Fourier\nanalysis here.", "start": 4307.58, "duration": 2.46}, {"text": "So in Z mod nZ, we define--", "start": 4310.04, "duration": 2.295}, {"text": "so given a S, let's\ndefine this Bohr", "start": 4315.51, "duration": 3.75}, {"text": "set to be the set of\nelements of Z mod nZ such", "start": 4319.26, "duration": 14.82}, {"text": "that if you look at what\nreally is supposed to resemble", "start": 4334.08, "duration": 6.39}, {"text": "this thing over here, OK?", "start": 4340.47, "duration": 5.81}, {"text": "If this quantity is\nsmall for all S--", "start": 4346.28, "duration": 8.0}, {"text": "OK, so we put that element\ninto this Bohr set.", "start": 4354.28, "duration": 2.65}, {"text": "OK, so these sets, they function\nmuch more like subspaces.", "start": 4359.67, "duration": 5.2}, {"text": "So there are the\nanalog of subspaces", "start": 4364.87, "duration": 4.02}, {"text": "inside Z mod nZ, which,\nyou know, n is prime,", "start": 4368.89, "duration": 4.53}, {"text": "has no subgroups.", "start": 4373.42, "duration": 1.01}, {"text": "It has no natural\nsubspace structure.", "start": 4374.43, "duration": 2.56}, {"text": "But by looking at\nthese Bohr sets,", "start": 4376.99, "duration": 1.89}, {"text": "they provide a\nnatural way to set up", "start": 4378.88, "duration": 4.14}, {"text": "this argument so that you can--", "start": 4383.02, "duration": 2.31}, {"text": "but with much more\ntechnicalities,", "start": 4385.33, "duration": 2.58}, {"text": "repeat these kind of arguments\nmore similar to last time,", "start": 4387.91, "duration": 5.72}, {"text": "but passing not to\nsubspaces but to Bohr sets.", "start": 4393.63, "duration": 3.59}, {"text": "And then with quite\na bit of extra work,", "start": 4397.22, "duration": 5.05}, {"text": "one can obtain bounds of the\nquantity N over a poly log N.", "start": 4402.27, "duration": 10.1}, {"text": "So the current best bound\nI mentioned last time", "start": 4412.37, "duration": 4.14}, {"text": "is of this type, which is\nthrough further refinements", "start": 4416.51, "duration": 3.57}, {"text": "of this technique.", "start": 4420.08, "duration": 1.267}, {"text": "The last thing I\nwant to mention today", "start": 4430.61, "duration": 1.62}, {"text": "is, so far we've been\ntalking about 3APs.", "start": 4432.23, "duration": 3.81}, {"text": "So what about four term\narithmetic progressions?", "start": 4436.04, "duration": 3.56}, {"text": "OK, do any of the things that we\ntalk about here work for 4APs?", "start": 4439.6, "duration": 5.398}, {"text": "And there's an analogy to be\nmade here compared to what", "start": 4444.998, "duration": 2.292}, {"text": "we discussed with graphs.", "start": 4447.29, "duration": 1.795}, {"text": "So in graphs, we had a triangle\ncounting lemma and a triangle", "start": 4449.085, "duration": 2.685}, {"text": "removal lemma.", "start": 4451.77, "duration": 1.16}, {"text": "And then we said\nthat to prove 4APs,", "start": 4452.93, "duration": 2.28}, {"text": "we would need the hypergraph\nversion, the simplex removal", "start": 4455.21, "duration": 3.18}, {"text": "lemma, hypergraph\nregularity lemma.", "start": 4458.39, "duration": 2.19}, {"text": "And that was much\nmore difficult.", "start": 4460.58, "duration": 1.92}, {"text": "And that analogy\ncarries through,", "start": 4462.5, "duration": 1.67}, {"text": "and the same kind of\ndifficulties that come up.", "start": 4464.17, "duration": 2.87}, {"text": "So it can be done, but\nyou need something more.", "start": 4467.04, "duration": 3.66}, {"text": "And the main message I\nwant you to take away", "start": 4470.7, "duration": 3.89}, {"text": "is that 4APs, while we\nhad a counting lemma that", "start": 4474.59, "duration": 8.35}, {"text": "says that the\nFourier coefficients,", "start": 4482.94, "duration": 3.04}, {"text": "so the Fourier transform,\ncontrols 3AP counts,", "start": 4485.98, "duration": 8.56}, {"text": "it turns out the same\nis not true for 4APs.", "start": 4494.54, "duration": 4.56}, {"text": "So the Fourier does\nnot control 4AP counts.", "start": 4499.1, "duration": 6.1}, {"text": "Let me give you some--", "start": 4510.41, "duration": 1.93}, {"text": "OK.", "start": 4512.34, "duration": 0.5}, {"text": "So in fact, in the\nhomework for this week,", "start": 4512.84, "duration": 2.07}, {"text": "there's a specific example of\na set where it has uniformly", "start": 4514.91, "duration": 4.96}, {"text": "small Fourier coefficients.", "start": 4519.87, "duration": 1.62}, {"text": "But that's the wrong\nnumber of 4APs.", "start": 4521.49, "duration": 1.5}, {"text": "So the following-- it is true--", "start": 4527.13, "duration": 1.37}, {"text": "OK, so it is true that you\nhave Szemer\u00e9di's term in--", "start": 4528.5, "duration": 4.11}, {"text": "let's just talk about\nthe finite field setting,", "start": 4532.61, "duration": 2.16}, {"text": "where things are a\nbit easier to discuss.", "start": 4534.77, "duration": 2.07}, {"text": "So it is true that the size\nof the biggest subset of F5", "start": 4536.84, "duration": 5.67}, {"text": "to the N is a tiny\nfraction-- it's a little, one", "start": 4542.51, "duration": 2.67}, {"text": "fraction of the entire space.", "start": 4545.18, "duration": 1.35}, {"text": "OK, I use F5 here,\nbecause if I set F3,", "start": 4546.53, "duration": 3.93}, {"text": "it doesn't make sense\nto talk about 4APs.", "start": 4550.46, "duration": 3.23}, {"text": "So F5, but it doesn't really\nmatter which specific field.", "start": 4553.69, "duration": 5.3}, {"text": "So you can prove this using\nhypergraph removal, same proof,", "start": 4558.99, "duration": 4.56}, {"text": "verbatim, that we saw earlier,\nif you have hypergraph removal.", "start": 4563.55, "duration": 3.78}, {"text": "But if you want to try to prove\nit using Fourier analysis,", "start": 4567.33, "duration": 3.28}, {"text": "well, it doesn't work quite\nusing the same strategy.", "start": 4570.61, "duration": 5.03}, {"text": "But in fact, there\nis a modification", "start": 4575.64, "duration": 1.95}, {"text": "that would allow\nyou to make it work.", "start": 4577.59, "duration": 3.21}, {"text": "But you need an extension\nof Fourier analysis.", "start": 4580.8, "duration": 2.87}, {"text": "And it is known as higher\norder Fourier analysis, which", "start": 4583.67, "duration": 7.12}, {"text": "was an important development in\nmodern additive combinatorics", "start": 4590.79, "duration": 4.68}, {"text": "that initially arose\nin Gowers' work", "start": 4595.47, "duration": 3.12}, {"text": "where he gave a new proof\nof similarities theorem.", "start": 4598.59, "duration": 2.6}, {"text": "So Gowers didn't\nwork in this setting.", "start": 4601.19, "duration": 1.69}, {"text": "He worked in integers.", "start": 4602.88, "duration": 1.14}, {"text": "But many of the ideas\noriginated from his paper,", "start": 4604.02, "duration": 3.12}, {"text": "and then subsequently\ndeveloped by a lot", "start": 4607.14, "duration": 1.98}, {"text": "of people in various settings.", "start": 4609.12, "duration": 2.13}, {"text": "I just want to give you one\nspecific statement, what", "start": 4611.25, "duration": 2.627}, {"text": "this high-order Fourier\nanalysis looks like.", "start": 4613.877, "duration": 1.833}, {"text": "So it's a fancy term,\nand the statements often", "start": 4615.71, "duration": 2.74}, {"text": "get very technical.", "start": 4618.45, "duration": 1.62}, {"text": "But I just want to give you one\nconcrete thing to take away.", "start": 4620.07, "duration": 4.07}, {"text": "All right, so for\na Fourier piece,", "start": 4624.14, "duration": 1.65}, {"text": "higher-order Fourier\nanalysis, roughly--", "start": 4625.79, "duration": 2.43}, {"text": "OK, so it also goes by the name\nquadratic Fourier analysis.", "start": 4628.22, "duration": 4.264}, {"text": "OK, so let me give you\na very specific instance", "start": 4636.436, "duration": 5.934}, {"text": "of the theorem.", "start": 4642.37, "duration": 1.2}, {"text": "And this can be sometimes\ncalled an inverse theorem", "start": 4647.09, "duration": 4.62}, {"text": "for quadratic Fourier analysis.", "start": 4651.71, "duration": 2.562}, {"text": "OK, so for every delta,\nthere exists some c such", "start": 4660.79, "duration": 7.91}, {"text": "that the following is true.", "start": 4668.7, "duration": 2.79}, {"text": "If A is a subset of a F5 to the\nN with density alpha and such", "start": 4671.49, "duration": 11.9}, {"text": "that it's--", "start": 4683.39, "duration": 1.742}, {"text": "OK, so now lambda\nsub 4, so this is", "start": 4685.132, "duration": 2.618}, {"text": "the 4AP density,\nso similar to 3AP,", "start": 4687.75, "duration": 2.63}, {"text": "but now you write four terms.", "start": 4690.38, "duration": 1.33}, {"text": "The 4AP density of A differs\nfrom alpha to the fourth", "start": 4691.71, "duration": 6.92}, {"text": "by a significant amount.", "start": 4698.63, "duration": 2.912}, {"text": "OK, so for 3APs, then we said\nthat now A has a large Fourier", "start": 4701.542, "duration": 3.508}, {"text": "coefficient, right?", "start": 4705.05, "duration": 1.7}, {"text": "So for-- OK.", "start": 4709.7, "duration": 3.94}, {"text": "For 4APs, that may not be\ntrue, but the following", "start": 4713.64, "duration": 3.89}, {"text": "is true, right?", "start": 4717.53, "duration": 0.845}, {"text": "So then there exists a\nnon-zero quadratic polynomial.", "start": 4718.375, "duration": 10.293}, {"text": "F and N variables over F5\nsuch that the indicator", "start": 4735.5, "duration": 13.12}, {"text": "function of A correlates with\nthis quadratic exponential", "start": 4748.62, "duration": 4.66}, {"text": "face.", "start": 4753.28, "duration": 0.5}, {"text": "So Fourier analysis,\nthe conclusion", "start": 4763.2, "duration": 1.633}, {"text": "that we got from\ncounting lemma is", "start": 4764.833, "duration": 1.417}, {"text": "that you have some\nlinear function", "start": 4766.25, "duration": 2.19}, {"text": "F, such that this\nquantity is large,", "start": 4768.44, "duration": 5.21}, {"text": "this large Fourier coefficient.", "start": 4773.65, "duration": 1.98}, {"text": "OK, so that is not true 4APs.", "start": 4775.63, "duration": 2.35}, {"text": "But what is true\nis that now you can", "start": 4777.98, "duration": 1.89}, {"text": "look at quadratic exponential\nfaces, and then it is true.", "start": 4779.87, "duration": 4.99}, {"text": "So that's the content\nof higher order Fourier.", "start": 4784.86, "duration": 3.86}, {"text": "I mean, that's the example of\nhigher-order Fourier analysis.", "start": 4788.72, "duration": 2.94}, {"text": "And you can imagine with\nthis type of result,", "start": 4791.66, "duration": 4.35}, {"text": "and with quite a\nbit more work, you", "start": 4796.01, "duration": 2.19}, {"text": "can try to follow a\nsimilar density increment", "start": 4798.2, "duration": 3.36}, {"text": "strategy to prove\nsimilarities term for 4APs.", "start": 4801.56, "duration": 5.55}]
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+[{"text": "[SQUEAKING]", "start": 1.485, "duration": 1.485}, {"text": "[RUSTLING]", "start": 2.97, "duration": 1.485}, {"text": "[CLICKING]", "start": 4.455, "duration": 6.245}, {"text": "GARY GENSLER: So we've\ngot a lot to cover,", "start": 10.7, "duration": 1.75}, {"text": "but I'm going to start with\na little background about", "start": 12.45, "duration": 3.07}, {"text": "the internet and the payment\nriddle; something about money,", "start": 15.52, "duration": 3.97}, {"text": "which is at the core, really,\nof all classes on finance but we", "start": 19.49, "duration": 4.19}, {"text": "usually take for\ngranted; and then Satoshi", "start": 23.68, "duration": 3.27}, {"text": "Nakamoto's innovation--\nwho was Satoshi Nakamoto,", "start": 26.95, "duration": 3.33}, {"text": "what is that innovation; a\nbit about crypto markets;", "start": 30.28, "duration": 3.06}, {"text": "the blockchain\ntechnology use cases--", "start": 33.34, "duration": 2.61}, {"text": "and then the core\nreally is, how to think", "start": 35.95, "duration": 2.19}, {"text": "about viability of\nthose use cases;", "start": 38.14, "duration": 2.7}, {"text": "a little touch on central\nbank digital currencies;", "start": 40.84, "duration": 2.34}, {"text": "and ground truths.", "start": 43.18, "duration": 0.75}, {"text": "So, a lot to cover.", "start": 43.93, "duration": 1.62}, {"text": "If we don't get\nthrough it all, we", "start": 45.55, "duration": 1.71}, {"text": "will talk about\nthis again when we", "start": 47.26, "duration": 2.07}, {"text": "talk about payments in class 6.", "start": 49.33, "duration": 4.78}, {"text": "In terms of some\nof the readings,", "start": 54.11, "duration": 1.8}, {"text": "I shared with you two write-ups\nthat were done for a class", "start": 55.91, "duration": 5.34}, {"text": "that Neha Narula and I\nteach, an online class", "start": 61.25, "duration": 3.51}, {"text": "called Cryptocurrency, which\nis available through MIT.", "start": 64.76, "duration": 4.65}, {"text": "And those two write-ups,\nthe \"Economics of Money", "start": 69.41, "duration": 2.4}, {"text": "and Technology\"--", "start": 71.81, "duration": 2.31}, {"text": "I'm sorry, and the\n\"Responses of Big Finance\"", "start": 74.12, "duration": 2.27}, {"text": "sort of give you some\nof the challenges", "start": 76.39, "duration": 2.68}, {"text": "and how to think through\nthese technologies.", "start": 79.07, "duration": 5.46}, {"text": "Also, the Bank of\nInternational Settlement", "start": 84.53, "duration": 2.4}, {"text": "did a review just\nearlier in 2020", "start": 86.93, "duration": 3.93}, {"text": "about the central\nbank digital currency", "start": 90.86, "duration": 2.34}, {"text": "space, because so much\nis going on there.", "start": 93.2, "duration": 2.4}, {"text": "And particularly after Facebook\nannounced their Libra project", "start": 95.6, "duration": 3.9}, {"text": "in June of 2019, many central\nbanks took note and said, wait,", "start": 99.5, "duration": 5.64}, {"text": "maybe there's\nsomething going on here", "start": 105.14, "duration": 1.65}, {"text": "that we too need to do more.", "start": 106.79, "duration": 2.22}, {"text": "Now, before Facebook\nLibra, there", "start": 109.01, "duration": 2.37}, {"text": "were many projects the bank--", "start": 111.38, "duration": 3.75}, {"text": "one of the world's\nlargest central banks,", "start": 115.13, "duration": 2.16}, {"text": "the Riksbank in\nSweden, was already", "start": 117.29, "duration": 2.55}, {"text": "looking at an e-krona project.", "start": 119.84, "duration": 1.65}, {"text": "There were other projects.", "start": 121.49, "duration": 1.5}, {"text": "But all of a sudden, that\nFacebook Libra project kicked", "start": 122.99, "duration": 2.7}, {"text": "into high gear central\nbankers around the globe,", "start": 125.69, "duration": 2.94}, {"text": "and particularly\nChina's look and review", "start": 128.63, "duration": 3.51}, {"text": "and announcements around the\nDigital Currency Electronic", "start": 132.14, "duration": 2.94}, {"text": "Payments Project also\ngot kicked into gear.", "start": 135.08, "duration": 4.2}, {"text": "So regardless of\nwhere you come out,", "start": 139.28, "duration": 1.92}, {"text": "whether blockchain technology,\ncryptocurrencies, are getting", "start": 141.2, "duration": 3.48}, {"text": "rolled into the stack, rolled\ninto the technology stack", "start": 144.68, "duration": 4.04}, {"text": "of big finance.", "start": 148.72, "duration": 1.57}, {"text": "What we can say as of 2020,\nwhat's really the case,", "start": 150.29, "duration": 5.16}, {"text": "is that cryptocurrencies\nand blockchain technology", "start": 155.45, "duration": 2.97}, {"text": "have at least been a\ncatalyst for change,", "start": 158.42, "duration": 2.73}, {"text": "an important catalyst for\nchange pushing upon big finance,", "start": 161.15, "duration": 4.26}, {"text": "pushing upon central\nbanks to reconsider", "start": 165.41, "duration": 2.91}, {"text": "how they do payments, how\nthey do the basics of money.", "start": 168.32, "duration": 3.89}, {"text": "And I laid out a few questions.", "start": 174.85, "duration": 2.31}, {"text": "Again, Romain will\nlook for some hands.", "start": 177.16, "duration": 2.095}, {"text": "We're going to keep this a\nlittle shorter than we usually", "start": 179.255, "duration": 2.375}, {"text": "do, just because we have\nso much to cover, but,", "start": 181.63, "duration": 2.19}, {"text": "how does Bitcoin fit into\nthe history of money?", "start": 183.82, "duration": 2.98}, {"text": "What are the strategic and\ntactical considerations", "start": 186.8, "duration": 3.11}, {"text": "assessing viability\nand value propositions?", "start": 189.91, "duration": 3.63}, {"text": "And how are these\ncentral banks thinking", "start": 193.54, "duration": 1.68}, {"text": "about what they're doing?", "start": 195.22, "duration": 1.23}, {"text": "And Romain, if we can just\nsee if we could get one or two", "start": 196.45, "duration": 3.21}, {"text": "people in kind of each of\nthese three questions--", "start": 199.66, "duration": 3.708}, {"text": "and these are the\nessential questions", "start": 203.368, "duration": 1.542}, {"text": "I'm going to try to cover\nin the next hour or so.", "start": 204.91, "duration": 2.548}, {"text": "AUDIENCE: OK.", "start": 207.458, "duration": 0.542}, {"text": "Sounds good.", "start": 208.0, "duration": 0.725}, {"text": "Who would like to\nget us started?", "start": 208.725, "duration": 1.375}, {"text": "I'm watching for\nyour blue hands.", "start": 214.74, "duration": 1.55}, {"text": "GARY GENSLER: Quiet day today.", "start": 219.3, "duration": 1.25}, {"text": "AUDIENCE: If you wish, Gary,\nI'm also happy to cold call.", "start": 223.89, "duration": 2.52}, {"text": "GARY GENSLER: All right.", "start": 226.41, "duration": 1.0}, {"text": "Well, I'm going to start.", "start": 227.41, "duration": 1.16}, {"text": "I'm going to kind of just go.", "start": 228.57, "duration": 1.71}, {"text": "But I hoped that\neveryone would come in.", "start": 230.28, "duration": 2.7}, {"text": "I start with this scene--", "start": 232.98, "duration": 1.9}, {"text": "and I don't know anyone who\nwants to raise a blue hand", "start": 234.88, "duration": 2.8}, {"text": "and tell me what movie\nthis is from and the era.", "start": 237.68, "duration": 4.16}, {"text": "But this is the opening scene\nof a movie from the mid 1990s,", "start": 241.84, "duration": 6.41}, {"text": "The Net, 1995, Sandra Bullock.", "start": 248.25, "duration": 4.79}, {"text": "Now, I start with this, because\nPizza Net was actually real.", "start": 253.04, "duration": 4.989}, {"text": "Now, this cyber security\nsort of spy thriller", "start": 258.029, "duration": 6.021}, {"text": "with Sandra Bullock sort of\ncracking through the computer", "start": 264.05, "duration": 3.63}, {"text": "network--", "start": 267.68, "duration": 0.6}, {"text": "remember, let's place this.", "start": 268.28, "duration": 1.71}, {"text": "Mid 1990s.", "start": 269.99, "duration": 2.55}, {"text": "It was only the early 1990s\nthat Tim Berners-Lee, associated", "start": 272.54, "duration": 5.88}, {"text": "with MIT, actually came\nup with the protocols that", "start": 278.42, "duration": 5.01}, {"text": "connects the world wide web.", "start": 283.43, "duration": 1.5}, {"text": "The internet had been\naround for some time,", "start": 284.93, "duration": 3.0}, {"text": "coming out of DARPA and\nthe Department of Defense", "start": 287.93, "duration": 2.34}, {"text": "in the US and\nacademic institutions.", "start": 290.27, "duration": 2.53}, {"text": "But by the early\n'90s, it was actually", "start": 292.8, "duration": 2.54}, {"text": "something that those\nof us in the public", "start": 295.34, "duration": 1.86}, {"text": "could use beyond universities,\nbeyond the defense", "start": 297.2, "duration": 2.91}, {"text": "establishment and the like.", "start": 300.11, "duration": 1.92}, {"text": "But what hadn't\nbeen solved, what", "start": 302.03, "duration": 2.58}, {"text": "hadn't been solved\nby 1995, was how", "start": 304.61, "duration": 3.09}, {"text": "to move money on the internet.", "start": 307.7, "duration": 2.45}, {"text": "And Pizza Hut founded something\ncalled Pizza Net, which", "start": 310.15, "duration": 4.57}, {"text": "is thought to be the\nfirst commercial use where", "start": 314.72, "duration": 3.57}, {"text": "you could actually\norder something online--", "start": 318.29, "duration": 2.34}, {"text": "just 25 years ago--\norder something", "start": 320.63, "duration": 2.25}, {"text": "online through Pizza Net.", "start": 322.88, "duration": 2.17}, {"text": "There was only sort\nof one problem.", "start": 325.05, "duration": 2.67}, {"text": "You ordered the\npizza, and guess what?", "start": 327.72, "duration": 2.64}, {"text": "You couldn't pay online.", "start": 330.36, "duration": 1.77}, {"text": "Nobody had figured\nout how to pay online.", "start": 332.13, "duration": 3.63}, {"text": "You had to have the pizza\ndelivery at your door,", "start": 335.76, "duration": 2.91}, {"text": "and you paid.", "start": 338.67, "duration": 0.6}, {"text": "So just think.", "start": 339.27, "duration": 0.93}, {"text": "It's in the middle of\nthe corona lockdown,", "start": 340.2, "duration": 2.52}, {"text": "we're sheltering at home.", "start": 342.72, "duration": 2.13}, {"text": "And if it weren't for these\ninventions of 25 years ago", "start": 344.85, "duration": 2.88}, {"text": "we're about to discuss, you\nwould be paying for that pizza", "start": 347.73, "duration": 3.81}, {"text": "at the door when the\ndelivery truck arrived,", "start": 351.54, "duration": 3.06}, {"text": "or for your groceries, or\nfor any other household", "start": 354.6, "duration": 4.02}, {"text": "goods that you have.", "start": 358.62, "duration": 1.75}, {"text": "So this riddle, what I call the\npayments riddle, what others", "start": 360.37, "duration": 4.91}, {"text": "call the payments\nriddle, was at the core", "start": 365.28, "duration": 3.66}, {"text": "of this new technology,\nthe internet.", "start": 368.94, "duration": 3.19}, {"text": "Now, the internet has been fully\nadopted into the technology", "start": 372.13, "duration": 3.11}, {"text": "stack of finance by now.", "start": 375.24, "duration": 1.57}, {"text": "But in the mid 1990s, it\nwas, in essence, fintech.", "start": 376.81, "duration": 5.58}, {"text": "But the question is how to\nmove value on the internet,", "start": 382.39, "duration": 2.58}, {"text": "to do it securely, efficiently,\nand really importantly,", "start": 384.97, "duration": 5.4}, {"text": "similar to the packets of\ndata that move on the internet", "start": 390.37, "duration": 4.9}, {"text": "as packets of data,\nand thus peer-to-peer.", "start": 395.27, "duration": 3.14}, {"text": "So the internet doesn't\nreally have central control.", "start": 398.41, "duration": 3.28}, {"text": "All the data that we're\nlive streaming right now", "start": 401.69, "duration": 2.55}, {"text": "between and amongst us, between\n78 participants on this Zoom", "start": 404.24, "duration": 6.0}, {"text": "meeting right now,\nis through packets", "start": 410.24, "duration": 3.69}, {"text": "of data that's not through\none central control,", "start": 413.93, "duration": 2.49}, {"text": "even though we think, well, Zoom\nmight be controlling all this.", "start": 416.42, "duration": 4.5}, {"text": "But the challenge really\nwas, how could you", "start": 420.92, "duration": 2.16}, {"text": "prohibit double spending?", "start": 423.08, "duration": 1.26}, {"text": "How could you send a packet\nof data to one person", "start": 424.34, "duration": 2.97}, {"text": "and ensure that\nthat packet of data", "start": 427.31, "duration": 2.67}, {"text": "wasn't also sent to another,\nin essence, double spending?", "start": 429.98, "duration": 4.41}, {"text": "Having some data\nlike an email that we", "start": 434.39, "duration": 2.4}, {"text": "might send to two people--", "start": 436.79, "duration": 1.68}, {"text": "they were both reading\nthe same email,", "start": 438.47, "duration": 2.28}, {"text": "they don't know that each\nare reading the same email.", "start": 440.75, "duration": 3.0}, {"text": "So that was this\npayments riddle--", "start": 443.75, "duration": 1.98}, {"text": "secure, efficient\npackets of data,", "start": 445.73, "duration": 2.71}, {"text": "but avoiding double spending.", "start": 448.44, "duration": 1.91}, {"text": "Lots of challenges,\nlots of attempts.", "start": 450.35, "duration": 3.12}, {"text": "And there were\ndozens of attempts.", "start": 453.47, "duration": 1.92}, {"text": "Somebody even went to\ngo in to get patents", "start": 455.39, "duration": 2.58}, {"text": "and started businesses,\nraised money.", "start": 457.97, "duration": 3.07}, {"text": "Some of them through the\nearlier days of venture capital", "start": 461.04, "duration": 3.23}, {"text": "were backed like\nCyberCash and DigiCash,", "start": 464.27, "duration": 2.76}, {"text": "and E-gold, B-Money,\nall of these failed.", "start": 467.03, "duration": 4.83}, {"text": "All of them, and\ndozens more beyond what", "start": 471.86, "duration": 2.91}, {"text": "I list here in the 1990s,\nand the hurdles were, well,", "start": 474.77, "duration": 4.23}, {"text": "of course the same hurdles\nthat any startup would", "start": 479.0, "duration": 2.52}, {"text": "have around merchant adoption--", "start": 481.52, "duration": 3.63}, {"text": "would the stores\nactually adopt it--", "start": 485.15, "duration": 4.17}, {"text": "but this issue of\ndouble spending.", "start": 489.32, "duration": 2.58}, {"text": "And the only sort of\nsolution to double spending", "start": 491.9, "duration": 2.7}, {"text": "was using centralization.", "start": 494.6, "duration": 1.74}, {"text": "There was one central computer,\none central controller,", "start": 496.34, "duration": 4.47}, {"text": "to avoid the double spending.", "start": 500.81, "duration": 2.28}, {"text": "Or the other side of it,\nhow did you form consensus?", "start": 503.09, "duration": 3.18}, {"text": "If you didn't have a\ncentral controller,", "start": 506.27, "duration": 3.6}, {"text": "how to form consensus on\nthe say of who had the money", "start": 509.87, "duration": 3.66}, {"text": "and who didn't have the money.", "start": 513.53, "duration": 1.66}, {"text": "So this sort of central\npayments riddle,", "start": 515.19, "duration": 3.619}, {"text": "a big issue in the\n1990s, attracted", "start": 518.809, "duration": 3.301}, {"text": "the interest of a\ncryptography group", "start": 522.11, "duration": 3.69}, {"text": "called the cypherpunk community.", "start": 525.8, "duration": 2.31}, {"text": "I kid you not, it's called\ncypherpunk community.", "start": 528.11, "duration": 3.03}, {"text": "It was an email list that\nhad started in the late 1980s", "start": 531.14, "duration": 3.03}, {"text": "and had gone on for some time.", "start": 534.17, "duration": 2.29}, {"text": "And so there were early\ndigital solutions that", "start": 536.46, "duration": 5.75}, {"text": "were a little bit different.", "start": 542.21, "duration": 1.5}, {"text": "And some of the cryptography\nthat was brought to it", "start": 543.71, "duration": 2.76}, {"text": "was not brought from the\ncypherpunk community,", "start": 546.47, "duration": 3.55}, {"text": "it was brought to bear from\ngreat cryptographers, some", "start": 550.02, "duration": 3.78}, {"text": "of them at MIT, some\nelsewhere, that came together", "start": 553.8, "duration": 3.03}, {"text": "by 1996 with a solution.", "start": 556.83, "duration": 2.32}, {"text": "It's this updated today the\nsame solution we use now--", "start": 559.15, "duration": 4.28}, {"text": "secure socket layer and\ntransport layer security.", "start": 563.43, "duration": 3.93}, {"text": "These two protocols, on hop\nof Tim Berners-Lee protocols", "start": 567.36, "duration": 5.25}, {"text": "about the world wide web from\nfour or five years earlier.", "start": 572.61, "duration": 3.84}, {"text": "These are the main protocols--", "start": 576.45, "duration": 2.16}, {"text": "there are many others\nthat were added.", "start": 578.61, "duration": 2.16}, {"text": "But these are the main\nprotocols that allowed", "start": 580.77, "duration": 2.28}, {"text": "us to secure the internet.", "start": 583.05, "duration": 1.8}, {"text": "It's how we do it right now--", "start": 584.85, "duration": 2.3}, {"text": "a transfer of data\nthat's secured", "start": 587.15, "duration": 3.19}, {"text": "by the use of cryptography.", "start": 590.34, "duration": 2.46}, {"text": "And what did that lead to?", "start": 592.8, "duration": 3.09}, {"text": "That led to a lot\nof things where", "start": 595.89, "duration": 2.22}, {"text": "we could accept Visas and\nMasterCard, American Express,", "start": 598.11, "duration": 4.59}, {"text": "by the mid 1990s.", "start": 602.7, "duration": 2.85}, {"text": "Amazon, eBay were\nboth formed in 1995.", "start": 605.55, "duration": 4.2}, {"text": "It's a founder's dream\nto get formed right when", "start": 609.75, "duration": 3.66}, {"text": "a technology is transitioning.", "start": 613.41, "duration": 1.7}, {"text": "If Amazon, if Jeff Bezos\nhad been formed in 1992,", "start": 615.11, "duration": 3.34}, {"text": "would it still have\nbeen around by 1996", "start": 618.45, "duration": 3.27}, {"text": "when the secure socket\nlayer and the cryptography", "start": 621.72, "duration": 4.05}, {"text": "was there for him to get going?", "start": 625.77, "duration": 2.4}, {"text": "If Jeff Bezos had decided\nto form it in 1998 or '99,", "start": 628.17, "duration": 4.26}, {"text": "it might have been too late.", "start": 632.43, "duration": 1.5}, {"text": "Now, there's a lot\nof things that Amazon", "start": 633.93, "duration": 1.94}, {"text": "got right and Visa's got right.", "start": 635.87, "duration": 1.59}, {"text": "But I'm saying timing was\none that was remarkable.", "start": 637.46, "duration": 3.19}, {"text": "PayPal came along in 1998.", "start": 640.65, "duration": 3.1}, {"text": "And interestingly, the\nfirst mobile payments", "start": 643.75, "duration": 2.99}, {"text": "was actually Ericsson teaming\nup with Telenor in 1999.", "start": 646.74, "duration": 4.68}, {"text": "Now, that product is\nnot around today--", "start": 651.42, "duration": 2.642}, {"text": "or maybe somebody will\ncorrect me and say", "start": 654.062, "duration": 1.708}, {"text": "there's still a little bit.", "start": 655.77, "duration": 1.48}, {"text": "But one of the early\nones that really took off", "start": 657.25, "duration": 1.94}, {"text": "was Alipay and then\nM-Pesa in Kenya.", "start": 659.19, "duration": 4.32}, {"text": "Now, All of this still\nleft the payments riddle.", "start": 663.51, "duration": 5.13}, {"text": "That payments riddle\nwas still there", "start": 668.64, "duration": 2.87}, {"text": "to some in that\ncypherpunk community.", "start": 671.51, "duration": 3.62}, {"text": "Now, the internet could\nget commercialized,", "start": 675.13, "duration": 1.85}, {"text": "the internet could move on.", "start": 676.98, "duration": 1.77}, {"text": "We had this way\nthrough cryptography", "start": 678.75, "duration": 2.91}, {"text": "to secure payments.", "start": 681.66, "duration": 2.01}, {"text": "But there was still\nthis question.", "start": 683.67, "duration": 2.74}, {"text": "And it goes to the\nheart of, what is money?", "start": 686.41, "duration": 3.69}, {"text": "And so I'm going to turn a\nlittle bit to chat about money,", "start": 690.1, "duration": 3.21}, {"text": "but just see if Romain\nhas any questions so far.", "start": 693.31, "duration": 3.948}, {"text": "AUDIENCE: Nobody at the moment.", "start": 697.258, "duration": 1.292}, {"text": "GARY GENSLER: OK.", "start": 698.55, "duration": 0.84}, {"text": "So I'd like to go back in time.", "start": 699.39, "duration": 1.86}, {"text": "I'd like to go back 2,300, 2,400\nyears in talking about money.", "start": 701.25, "duration": 6.447}, {"text": "It's not the first time\nmoney was discussed,", "start": 707.697, "duration": 1.833}, {"text": "because money was\nreally an invention", "start": 709.53, "duration": 1.74}, {"text": "of humankind thousands\nof years before that.", "start": 711.27, "duration": 2.94}, {"text": "But I'd like to go back\nto Plato and Aristotle.", "start": 714.21, "duration": 3.3}, {"text": "Plato did not write\nextensively on money.", "start": 717.51, "duration": 2.37}, {"text": "But what he did\nwrite is interesting.", "start": 719.88, "duration": 3.63}, {"text": "It's that money is\na symbol devised", "start": 723.51, "duration": 2.22}, {"text": "for the purpose of exchanges.", "start": 725.73, "duration": 1.56}, {"text": "To think, you and I were\ngoing to exchange something--", "start": 727.29, "duration": 2.43}, {"text": "at the time, maybe it\nwas a goat for wheat,", "start": 729.72, "duration": 3.33}, {"text": "maybe I needed the goat today,\nyou needed the wheat tomorrow--", "start": 733.05, "duration": 3.84}, {"text": "but we can use this\nsymbol, as Plato wrote,", "start": 736.89, "duration": 3.9}, {"text": "as a purpose of that exchange.", "start": 740.79, "duration": 2.37}, {"text": "And interestingly,\nseparately Plato wrote--", "start": 743.16, "duration": 3.54}, {"text": "Plato wasn't in for using\ngold and silver for money.", "start": 746.7, "duration": 3.84}, {"text": "Now, this is\ninteresting in contrast", "start": 750.54, "duration": 1.89}, {"text": "to Plato's student, Aristotle.", "start": 752.43, "duration": 2.12}, {"text": "Now, Aristotle wrote\nextensively about money.", "start": 754.55, "duration": 2.87}, {"text": "It seemed like Aristotle wrote\nextensively about many things,", "start": 757.42, "duration": 3.8}, {"text": "but one of them was money.", "start": 761.22, "duration": 2.43}, {"text": "And Aristotle wrote\nthat it solves", "start": 763.65, "duration": 2.31}, {"text": "the problem of\ncommensurability--", "start": 765.96, "duration": 1.82}, {"text": "the same sort of issue that\nPlato was grappling with,", "start": 767.78, "duration": 3.17}, {"text": "commensurability.", "start": 770.95, "duration": 2.09}, {"text": "You need rice, you need\ngrains, I need goats.", "start": 773.04, "duration": 4.02}, {"text": "How do we have some\ncommensurability between that?", "start": 777.06, "duration": 3.524}, {"text": "Or the second point here,\nmoney is a guarantee", "start": 780.584, "duration": 3.376}, {"text": "that we have what we\nwant in the future.", "start": 783.96, "duration": 3.19}, {"text": "So this is sort of a\ntime commensurability.", "start": 787.15, "duration": 2.75}, {"text": "I need something today, you\nneed something tomorrow.", "start": 789.9, "duration": 3.31}, {"text": "So these two forms of marrying\nup needs and wants and values--", "start": 793.21, "duration": 6.41}, {"text": "Aristotle talked also\nas a philosopher about,", "start": 799.62, "duration": 5.07}, {"text": "what is values?", "start": 804.69, "duration": 2.31}, {"text": "And then talked about\nfour absolute values.", "start": 807.0, "duration": 3.66}, {"text": "Now, I hate to disagree\nwith Aristotle.", "start": 810.66, "duration": 2.28}, {"text": "But, you know, over\ntime, there are", "start": 812.94, "duration": 3.0}, {"text": "many of Aristotle's\ngreat writings that", "start": 815.94, "duration": 2.52}, {"text": "have been challenged--\nabout the Earth and about", "start": 818.46, "duration": 2.43}, {"text": "the solar system, about the\nheavens, the skies, the bodies.", "start": 820.89, "duration": 4.17}, {"text": "So why not say that maybe\nAristotle didn't quite", "start": 825.06, "duration": 3.03}, {"text": "have it right about money?", "start": 828.09, "duration": 1.23}, {"text": "He talked about durability,\nportability, divisibility.", "start": 829.32, "duration": 4.42}, {"text": "I still sort of agree.", "start": 833.74, "duration": 1.17}, {"text": "And most monetary economists\nwould agree on that.", "start": 834.91, "duration": 3.45}, {"text": "It's this fourth point--\ndid it have intrinsic value?", "start": 838.36, "duration": 3.15}, {"text": "I find myself more\nassociated with Plato, who", "start": 841.51, "duration": 2.625}, {"text": "had said it was just a symbol.", "start": 844.135, "duration": 2.595}, {"text": "It's but a symbol.", "start": 846.73, "duration": 2.01}, {"text": "And so today when we\nthink about money,", "start": 848.74, "duration": 3.03}, {"text": "we often think of six\nkey characteristics.", "start": 851.77, "duration": 3.04}, {"text": "Is it durable,\nportable, divisible?", "start": 854.81, "duration": 2.03}, {"text": "These were--\nAristotle seemed to--", "start": 856.84, "duration": 3.21}, {"text": "2,300 years later people\nstill tend to agree.", "start": 860.05, "duration": 3.27}, {"text": "But rather than intrinsic value,\nthat it's uniform, acceptable,", "start": 863.32, "duration": 5.28}, {"text": "and stable we'll talk\na little bit more", "start": 868.6, "duration": 3.33}, {"text": "about that when we get to the\neconomics of cryptocurrencies.", "start": 871.93, "duration": 3.9}, {"text": "But remember, instead\nof intrinsic value,", "start": 875.83, "duration": 2.61}, {"text": "that it's uniform; that it's\nthe same unit of account", "start": 878.44, "duration": 3.45}, {"text": "within some local\nor national economy;", "start": 881.89, "duration": 4.26}, {"text": "that others accept it, because\nif others don't accept it,", "start": 886.15, "duration": 3.28}, {"text": "how can I know that that which I\ntake today I can use tomorrow?;", "start": 889.43, "duration": 6.84}, {"text": "and then its value is stable.", "start": 896.27, "duration": 2.73}, {"text": "And we think over the\nlast 300-plus years", "start": 899.0, "duration": 3.38}, {"text": "about institutions\nthat help ensure", "start": 902.38, "duration": 3.54}, {"text": "that currency value is stable,\nwe call them central banks.", "start": 905.92, "duration": 5.02}, {"text": "So instead of an\nintrinsic value, that we", "start": 910.94, "duration": 2.0}, {"text": "humans create some form of\nacceptability, uniformity,", "start": 912.94, "duration": 4.05}, {"text": "and stability.", "start": 916.99, "duration": 1.95}, {"text": "Questions?", "start": 918.94, "duration": 2.63}, {"text": "AUDIENCE: None so far, but I'll\ngive our students a few seconds", "start": 921.57, "duration": 2.81}, {"text": "to raise their hand\nif they want to.", "start": 924.38, "duration": 2.19}, {"text": "Yes, we have a\nquestion from Hassan.", "start": 926.57, "duration": 2.15}, {"text": "GARY GENSLER: Please, Hassan.", "start": 928.72, "duration": 1.69}, {"text": "AUDIENCE: Hello, professor.", "start": 933.635, "duration": 1.125}, {"text": "Yeah, my question\nis, when you said", "start": 934.76, "duration": 5.34}, {"text": "that people could exchange\nthings for other things", "start": 940.1, "duration": 6.34}, {"text": "as a mean.", "start": 946.44, "duration": 0.5}, {"text": "So I mean, how could\nthe cryptocurrency", "start": 946.94, "duration": 4.94}, {"text": "survive if there is no\nintrinsic value in it", "start": 951.88, "duration": 3.33}, {"text": "and it's so volatile?", "start": 955.21, "duration": 1.98}, {"text": "And when you said that\ncentral banks make", "start": 957.19, "duration": 2.58}, {"text": "sure that these currencies\nare stable, it's because--", "start": 959.77, "duration": 4.73}, {"text": "like for instance, in my\ncountry the central bank", "start": 964.5, "duration": 3.46}, {"text": "has to have gold\nand other currencies", "start": 967.96, "duration": 3.72}, {"text": "to support our currency,\nour local currency.", "start": 971.68, "duration": 7.66}, {"text": "So I'm just baffled to see like\nsomeone speak about, well, you", "start": 979.34, "duration": 5.69}, {"text": "know what, it's only a symbol.", "start": 985.03, "duration": 2.31}, {"text": "OK, I know that it\nis a symbol, but it", "start": 987.34, "duration": 2.85}, {"text": "has to have some value in it.", "start": 990.19, "duration": 2.06}, {"text": "Otherwise, the other\nparty would not", "start": 992.25, "duration": 1.96}, {"text": "accept it as a means of\nexchange, if that makes sense.", "start": 994.21, "duration": 4.18}, {"text": "GARY GENSLER: So Hassan\nis associating himself", "start": 998.39, "duration": 2.94}, {"text": "more with Aristotle\nthan Plato, and I", "start": 1001.33, "duration": 1.98}, {"text": "find myself more associated\nwith Plato than Aristotle.", "start": 1003.31, "duration": 3.94}, {"text": "So this is a worthy\ndebate that's", "start": 1007.25, "duration": 1.49}, {"text": "gone on for well over a\ncouple of thousand years.", "start": 1008.74, "duration": 3.96}, {"text": "But when I say that it\ndoesn't have intrinsic value,", "start": 1012.7, "duration": 3.63}, {"text": "and it's more about uniformity,\nacceptability, instability,", "start": 1016.33, "duration": 3.07}, {"text": "think about--", "start": 1019.4, "duration": 1.4}, {"text": "I'll take the US dollar.", "start": 1020.8, "duration": 1.62}, {"text": "I don't know-- what\nyou're country?", "start": 1022.42, "duration": 3.49}, {"text": "AUDIENCE: I'm from Bahrain.", "start": 1025.91, "duration": 1.929}, {"text": "GARY GENSLER: So\nI'm not as familiar", "start": 1027.839, "duration": 1.5}, {"text": "with your central bank.", "start": 1029.339, "duration": 1.74}, {"text": "But let's take the US\ndollar instead of Bahraini.", "start": 1031.079, "duration": 4.441}, {"text": "If you walk into\nthe Federal Reserve,", "start": 1035.52, "duration": 2.46}, {"text": "the US Federal Reserve, and\nyou have $100 bill-- you know,", "start": 1037.98, "duration": 4.5}, {"text": "paper currency, $100--", "start": 1042.48, "duration": 2.99}, {"text": "what will they give you?", "start": 1045.47, "duration": 1.493}, {"text": "I mean, other than that\nthey would probably send you", "start": 1046.963, "duration": 2.167}, {"text": "on your way and the\nsecurity guard would say,", "start": 1049.13, "duration": 2.85}, {"text": "we're in this\ncoronavirus period,", "start": 1051.98, "duration": 2.19}, {"text": "nobody's allowed\nin the building.", "start": 1054.17, "duration": 1.41}, {"text": "But what would they\ndo if you showed up", "start": 1055.58, "duration": 3.48}, {"text": "at the New York Federal\nReserve or the Richmond Federal", "start": 1059.06, "duration": 4.44}, {"text": "Reserve, and you said, I\nwant something for this $100?", "start": 1063.5, "duration": 5.13}, {"text": "AUDIENCE: I suppose\nthat a few years ago", "start": 1068.63, "duration": 3.86}, {"text": "that they would give you like\ngold, if that makes sense.", "start": 1072.49, "duration": 2.662}, {"text": "GARY GENSLER: OK.", "start": 1075.152, "duration": 0.708}, {"text": "So we got rid of that in 1933.", "start": 1075.86, "duration": 3.04}, {"text": "So \"a few years ago\" would\nbe like at the beginning", "start": 1078.9, "duration": 2.93}, {"text": "of the Great Depression under\nPresident Roosevelt. What", "start": 1081.83, "duration": 3.63}, {"text": "would they give you in 2020?", "start": 1085.46, "duration": 2.67}, {"text": "AUDIENCE: They would give me,\nI think, the government's--", "start": 1088.13, "duration": 4.95}, {"text": "that the government\nbasically would support", "start": 1095.8, "duration": 3.55}, {"text": "this piece of paper, I assume.", "start": 1099.35, "duration": 3.568}, {"text": "GARY GENSLER: So you're\ngetting at the government which", "start": 1102.918, "duration": 2.292}, {"text": "sort of insure, through\nits means and methods,", "start": 1105.21, "duration": 4.03}, {"text": "that it's acceptable\nby other citizens,", "start": 1109.24, "duration": 3.87}, {"text": "and it's acceptable\nby the government.", "start": 1113.11, "duration": 1.77}, {"text": "How do they do that?", "start": 1114.88, "duration": 0.91}, {"text": "They say, well, we'll\ntake it for US taxes.", "start": 1115.79, "duration": 2.48}, {"text": "We'll take it for\nBahranian taxes.", "start": 1118.27, "duration": 2.55}, {"text": "And in most economies,\nthe governments", "start": 1120.82, "duration": 3.0}, {"text": "are anywhere from\na quarter to a half", "start": 1123.82, "duration": 2.07}, {"text": "of the economy in some\nway, so they will accept it", "start": 1125.89, "duration": 3.0}, {"text": "for a government.", "start": 1128.89, "duration": 1.8}, {"text": "They'll ensure that other\npeople accept it through what's", "start": 1130.69, "duration": 2.73}, {"text": "called legal tender laws.", "start": 1133.42, "duration": 1.71}, {"text": "Through the coercive power\nof the state, they will say,", "start": 1135.13, "duration": 4.8}, {"text": "others must accept it.", "start": 1139.93, "duration": 2.17}, {"text": "And this is not a new thing.", "start": 1142.1, "duration": 1.66}, {"text": "Genghis Khan was\ndoing this in China,", "start": 1143.76, "duration": 2.83}, {"text": "and it was pretty coercive.", "start": 1146.59, "duration": 1.41}, {"text": "It was kind of [CLICKS TONGUE]\nthe coercive power", "start": 1148.0, "duration": 2.88}, {"text": "of the state, you must\naccept the official currency.", "start": 1150.88, "duration": 3.48}, {"text": "So acceptability can be\naccepted by the government.", "start": 1154.36, "duration": 3.28}, {"text": "It could be\nacceptability that others", "start": 1157.64, "duration": 2.03}, {"text": "must accept it for all\ndebts, public and private.", "start": 1159.67, "duration": 4.24}, {"text": "And they can work on stability\nand form central banks", "start": 1163.91, "duration": 3.38}, {"text": "to ensure that-- now, what\ndoes it mean by stability?", "start": 1167.29, "duration": 3.2}, {"text": "It means addressing the\nofficial sector to the supply", "start": 1170.49, "duration": 4.66}, {"text": "and pricing of money.", "start": 1175.15, "duration": 1.92}, {"text": "Supply and pricing--\nthe supply we", "start": 1177.07, "duration": 2.85}, {"text": "talk about the monetary\nsupply, the pricing", "start": 1179.92, "duration": 2.82}, {"text": "is through interest rates.", "start": 1182.74, "duration": 1.88}, {"text": "But can you go into\nthe US Central Bank,", "start": 1184.62, "duration": 1.85}, {"text": "can you go into Bahrain\nand actually get gold?", "start": 1186.47, "duration": 2.91}, {"text": "No.", "start": 1189.38, "duration": 0.5}, {"text": "You can go in and\nget a $100 bill,", "start": 1189.88, "duration": 1.98}, {"text": "and they might\ngive you five 20's.", "start": 1191.86, "duration": 2.4}, {"text": "If you really want,\nthey'll give you 100 1's.", "start": 1194.26, "duration": 3.54}, {"text": "But you still have\njust a physical piece", "start": 1197.8, "duration": 2.31}, {"text": "of paper or a digital\nrepresentation", "start": 1200.11, "duration": 3.24}, {"text": "that I would contend--", "start": 1203.35, "duration": 1.86}, {"text": "I'm sort of with Plato--", "start": 1205.21, "duration": 1.56}, {"text": "it's just a symbol.", "start": 1206.77, "duration": 1.56}, {"text": "It's a symbol that\nour society, no matter", "start": 1208.33, "duration": 3.45}, {"text": "whether it's small or\nbig, has come together.", "start": 1211.78, "duration": 3.24}, {"text": "And it represents\na store of value.", "start": 1215.02, "duration": 3.09}, {"text": "It represents a\nmeans of exchange.", "start": 1218.11, "duration": 3.6}, {"text": "But it frankly doesn't have\nintrinsic value the way", "start": 1221.71, "duration": 4.74}, {"text": "Aristotle talked about it.", "start": 1226.45, "duration": 1.47}, {"text": "It has only value because we\nhumans place a value on it.", "start": 1227.92, "duration": 5.62}, {"text": "But Hassan, are you on\nstill on the other side?", "start": 1233.54, "duration": 3.87}, {"text": "You feel gold has\nintrinsic value.", "start": 1237.41, "duration": 3.95}, {"text": "AUDIENCE: Yes.", "start": 1241.36, "duration": 0.99}, {"text": "I think because\nit's a scarce metal.", "start": 1242.35, "duration": 3.81}, {"text": "And I know that prices\ncould go up and down,", "start": 1246.16, "duration": 4.32}, {"text": "but still I know that\nI could sell it one day", "start": 1250.48, "duration": 2.9}, {"text": "and get money or get--", "start": 1253.38, "duration": 1.64}, {"text": "GARY GENSLER: So gold is\nwhat we now call an element.", "start": 1255.02, "duration": 4.9}, {"text": "It's on the periodic table.", "start": 1259.92, "duration": 3.75}, {"text": "It's got great attributes\nbecause it's scarce.", "start": 1263.67, "duration": 3.57}, {"text": "It takes a lot of\nhuman resources", "start": 1267.24, "duration": 2.07}, {"text": "to get it out of the ground.", "start": 1269.31, "duration": 2.17}, {"text": "The other thing about gold,\nit's divisible, it's portable,", "start": 1271.48, "duration": 3.76}, {"text": "it's uniform.", "start": 1275.24, "duration": 0.61}, {"text": "It doesn't oxidize, so it's\na really good base sort", "start": 1275.85, "duration": 3.77}, {"text": "of element in that way as well.", "start": 1279.62, "duration": 3.17}, {"text": "And now we have, give\nor take, 10,000 years", "start": 1282.79, "duration": 3.35}, {"text": "of acceptability, that it's\na human shared narrative.", "start": 1286.14, "duration": 4.44}, {"text": "Some of it not good,\nsome of it about war,", "start": 1290.58, "duration": 2.61}, {"text": "and slavery, and all sorts of\nchallenges in human history.", "start": 1293.19, "duration": 4.87}, {"text": "But gold, and to a\nlesser extent silver,", "start": 1298.06, "duration": 3.02}, {"text": "were very acceptable and stable.", "start": 1301.08, "duration": 3.21}, {"text": "But think about\nthis for a moment.", "start": 1304.29, "duration": 1.71}, {"text": "All the world's gold\nthat's ever been mined,", "start": 1306.0, "duration": 3.78}, {"text": "if you take all of\nthat gold, it can fit", "start": 1309.78, "duration": 3.09}, {"text": "in four Olympic-sized pools.", "start": 1312.87, "duration": 3.22}, {"text": "Four Olympic-sized pools,\nyou. could put all that gold", "start": 1316.09, "duration": 3.21}, {"text": "into one space.", "start": 1319.3, "duration": 1.83}, {"text": "Now, it's spread\naround the world", "start": 1321.13, "duration": 2.6}, {"text": "in jewelry and secure vaults.", "start": 1323.73, "duration": 2.77}, {"text": "But it's only four\nOlympic-sized pools.", "start": 1326.5, "duration": 3.0}, {"text": "I would kind of contend\nthat's just a symbol.", "start": 1329.5, "duration": 4.12}, {"text": "Again, it has some kind of\nfeatures that make it durable,", "start": 1333.62, "duration": 6.01}, {"text": "and it's got 10,000\nyears of human narrative", "start": 1339.63, "duration": 3.93}, {"text": "and acceptability.", "start": 1343.56, "duration": 1.8}, {"text": "And I can assure\nyou that those who", "start": 1345.36, "duration": 4.59}, {"text": "are really in times of\ntrouble would probably", "start": 1349.95, "duration": 3.03}, {"text": "take a piece of gold--", "start": 1352.98, "duration": 1.8}, {"text": "if it was really in\ntimes of war and despair,", "start": 1354.78, "duration": 4.05}, {"text": "take a piece of\ngold over Bitcoin.", "start": 1358.83, "duration": 3.423}, {"text": "But on the other\nhand, we're going", "start": 1362.253, "duration": 1.417}, {"text": "to get into what\nBitcoin is and how", "start": 1363.67, "duration": 1.88}, {"text": "it creates some digital\nscarce store of value.", "start": 1365.55, "duration": 4.06}, {"text": "So Hassan, we could keep\ngoing with a lively debate,", "start": 1369.61, "duration": 3.2}, {"text": "but I hope that helps at least\nframe the sides of this thing.", "start": 1372.81, "duration": 4.18}, {"text": "AUDIENCE: Yeah, I just\nhave one thing to say.", "start": 1376.99, "duration": 2.63}, {"text": "Now, I mean, if the US\nfor some reason collapsed,", "start": 1379.62, "duration": 5.61}, {"text": "what would happen to the\nwhole monetary system?", "start": 1385.23, "duration": 2.91}, {"text": "I mean, it's very dangerous,\nif that makes sense.", "start": 1388.14, "duration": 3.72}, {"text": "Because--", "start": 1391.86, "duration": 0.6}, {"text": "GARY GENSLER: You're asking\nwhat happens if a nation's", "start": 1392.46, "duration": 2.25}, {"text": "currency collapses.", "start": 1394.71, "duration": 1.26}, {"text": "And we have history of that.", "start": 1395.97, "duration": 2.41}, {"text": "We don't have\nrecent history when", "start": 1398.38, "duration": 2.57}, {"text": "a world's dominant\ncurrency collapses,", "start": 1400.95, "duration": 2.82}, {"text": "but we've certainly a\nhistory of many countries'", "start": 1403.77, "duration": 2.67}, {"text": "currencies collapsing.", "start": 1406.44, "duration": 1.05}, {"text": "In fact, right now Venezuela's\ncurrency basically collapses.", "start": 1407.49, "duration": 4.29}, {"text": "And what happens in countries\nthat where the currencies enter", "start": 1411.78, "duration": 3.63}, {"text": "hyperinflation and\nstart to collapse,", "start": 1415.41, "duration": 2.55}, {"text": "you start to see communities\nreach out to another symbol,", "start": 1417.96, "duration": 4.95}, {"text": "some other symbol that is\nacceptable and has stability.", "start": 1422.91, "duration": 5.67}, {"text": "It might be in the common\ntime, in the current time,", "start": 1428.58, "duration": 3.21}, {"text": "that those people will\nreach out to the US dollar.", "start": 1431.79, "duration": 3.19}, {"text": "And your question is, what\nif the dollar collapses?", "start": 1434.98, "duration": 2.15}, {"text": "But in monetary history\nserves that usually", "start": 1437.13, "duration": 3.72}, {"text": "that when a currency goes\nbad, people reach out", "start": 1440.85, "duration": 4.07}, {"text": "to the better currency.", "start": 1444.92, "duration": 1.9}, {"text": "And it could be a\nneighboring country.", "start": 1446.82, "duration": 3.08}, {"text": "It could be a different\nmetal, like when", "start": 1449.9, "duration": 3.09}, {"text": "we had challenges between\ndifferent base metals,", "start": 1452.99, "duration": 3.99}, {"text": "or even earlier\ntimes, when we had", "start": 1456.98, "duration": 3.24}, {"text": "money that looked a little\ndifferent than we currently", "start": 1460.22, "duration": 3.09}, {"text": "looked like.", "start": 1463.31, "duration": 2.94}, {"text": "Let me hold that about what\nhappens to the US dollar", "start": 1466.25, "duration": 2.91}, {"text": "for a moment and\njust say, the role", "start": 1469.16, "duration": 1.98}, {"text": "of money, because\nwe will lose time,", "start": 1471.14, "duration": 1.95}, {"text": "and I want to get going\nas to what cryptocurrency", "start": 1473.09, "duration": 2.41}, {"text": "and blockchain technology is.", "start": 1475.5, "duration": 2.16}, {"text": "So the role of money\nis three things--", "start": 1477.66, "duration": 2.42}, {"text": "a medium of exchange,\nas Plato and Aristotle", "start": 1480.08, "duration": 2.55}, {"text": "talked about; a store of\nvalue, that Aristotle basically", "start": 1482.63, "duration": 3.75}, {"text": "said that I can hold it today\nfor something tomorrow-- that's", "start": 1486.38, "duration": 3.45}, {"text": "a store of value; and it also\nthen becomes a unit of account.", "start": 1489.83, "duration": 5.37}, {"text": "The US dollar is a unit\nof account in the US,", "start": 1495.2, "duration": 2.94}, {"text": "the yen in Japan, the euro\nin Europe, a unit of account.", "start": 1498.14, "duration": 6.03}, {"text": "These three roles of money.", "start": 1504.17, "duration": 2.67}, {"text": "And it's looked very\ndifferent over time.", "start": 1506.84, "duration": 2.04}, {"text": "Cowrie shells in Greece.", "start": 1508.88, "duration": 2.55}, {"text": "But today, I put here\nan Alipay mobile wallet.", "start": 1511.43, "duration": 4.43}, {"text": "That's sort of what we use\ndominantly around the world.", "start": 1515.86, "duration": 5.9}, {"text": "We talked a little bit\nabout fiat currency", "start": 1521.76, "duration": 2.63}, {"text": "when Hassan and I were\ngoing back and forth.", "start": 1524.39, "duration": 3.18}, {"text": "A fiat currency is\na representation", "start": 1527.57, "duration": 3.78}, {"text": "of some central bank liability.", "start": 1531.35, "duration": 3.99}, {"text": "Central banks, an invention\nof the late 17th century", "start": 1535.34, "duration": 4.29}, {"text": "both in England and\nin Sweden, just about", "start": 1539.63, "duration": 3.18}, {"text": "the same decade in\nthe late 17th century,", "start": 1542.81, "duration": 3.6}, {"text": "was a check on the sovereign.", "start": 1546.41, "duration": 1.47}, {"text": "You see the king,\nthe king in England--", "start": 1547.88, "duration": 2.22}, {"text": "using that story for a moment--", "start": 1550.1, "duration": 1.89}, {"text": "the king was at yet\nanother war with France", "start": 1551.99, "duration": 3.45}, {"text": "and wanted to borrow money.", "start": 1555.44, "duration": 3.48}, {"text": "And when the king\nwanted to borrow money,", "start": 1558.92, "duration": 1.83}, {"text": "going to the noble\nlords, the noble lords", "start": 1560.75, "duration": 2.13}, {"text": "said, enough already,\nking, and said, we", "start": 1562.88, "duration": 3.57}, {"text": "need some mechanism to control\nhow much you can borrow.", "start": 1566.45, "duration": 6.04}, {"text": "And how much you can\nborrow is, in essence,", "start": 1572.49, "duration": 2.52}, {"text": "a representation of money.", "start": 1575.01, "duration": 2.25}, {"text": "And they set up the\nBank of England.", "start": 1577.26, "duration": 3.04}, {"text": "And in Sweden it was a\ncheck also on the sovereign", "start": 1580.3, "duration": 2.817}, {"text": "for a little bit different\npolitical reasons", "start": 1583.117, "duration": 1.833}, {"text": "than a war with France.", "start": 1584.95, "duration": 2.2}, {"text": "And there we had the initial\nsort of central banks.", "start": 1587.15, "duration": 3.35}, {"text": "Here in the US we\nwent about it--", "start": 1590.5, "duration": 2.82}, {"text": "Alexander Hamilton thought\nwe should have something.", "start": 1593.32, "duration": 2.64}, {"text": "That was during the 1790s.", "start": 1595.96, "duration": 5.64}, {"text": "By the 1830s,\nAndrew Jackson said,", "start": 1601.6, "duration": 2.7}, {"text": "enough with this sort\nof centralized banking.", "start": 1604.3, "duration": 2.7}, {"text": "And then we went for nearly\n80 years-- about 75 years,", "start": 1607.0, "duration": 4.62}, {"text": "from the 1830s to the 19-teens--", "start": 1611.62, "duration": 2.55}, {"text": "with no central bank.", "start": 1614.17, "duration": 2.55}, {"text": "We had crisis after\ncrisis, and we formed one", "start": 1616.72, "duration": 3.33}, {"text": "during President\nWilson's time, one", "start": 1620.05, "duration": 3.15}, {"text": "of the great progressive\nmovements of the day and just", "start": 1623.2, "duration": 6.18}, {"text": "about a hundred years ago.", "start": 1629.38, "duration": 2.01}, {"text": "But fiat currencies are\nrepresentations of liabilities.", "start": 1631.39, "duration": 3.92}, {"text": "And Hassan would say,\nwell, but don't they", "start": 1635.31, "duration": 1.75}, {"text": "have something behind it?", "start": 1637.06, "duration": 2.43}, {"text": "What they have behind it\nis the government's ability", "start": 1639.49, "duration": 3.93}, {"text": "to, of course, tax, the\ngovernment's ability", "start": 1643.42, "duration": 3.39}, {"text": "to be trusted to keep\nits promises to keep", "start": 1646.81, "duration": 3.72}, {"text": "that currency stable.", "start": 1650.53, "duration": 1.86}, {"text": "But again, just like when\nthat English king was", "start": 1652.39, "duration": 3.12}, {"text": "at war with France, sometimes--", "start": 1655.51, "duration": 2.79}, {"text": "sometimes-- they\noverprint the money.", "start": 1658.3, "duration": 2.97}, {"text": "Sometimes it gets out of control\nand central banks lose control.", "start": 1661.27, "duration": 5.25}, {"text": "But it has very big network\neffects that we talked about.", "start": 1666.52, "duration": 4.5}, {"text": "The acceptance for\ntaxes for legal tender,", "start": 1671.02, "duration": 3.81}, {"text": "it's accepted through\nwhat Mundell would say", "start": 1674.83, "duration": 3.66}, {"text": "was an optimum currency area.", "start": 1678.49, "duration": 2.46}, {"text": "Now, we have 180 currencies\naround the globe.", "start": 1680.95, "duration": 3.36}, {"text": "And some work well and\nsome don't work so well,", "start": 1684.31, "duration": 3.3}, {"text": "like Venezuela right now.", "start": 1687.61, "duration": 2.9}, {"text": "And so in the midst\nof all of that,", "start": 1690.51, "duration": 2.15}, {"text": "the question is, and\nthis a little humorous,", "start": 1692.66, "duration": 2.24}, {"text": "is, what's money's future?", "start": 1694.9, "duration": 2.06}, {"text": "Is it digital currencies?", "start": 1696.96, "duration": 1.71}, {"text": "Or is it like in kind of\nthe fun movie Star Wars,", "start": 1698.67, "duration": 4.98}, {"text": "is it these types of things,\ncredit chips and the like?", "start": 1703.65, "duration": 5.25}, {"text": "Now, I would say if\nyou're a Star Trek", "start": 1708.9, "duration": 1.71}, {"text": "fan, in Star Trek Gene\nRoddenberry didn't", "start": 1710.61, "duration": 2.94}, {"text": "have any currency.", "start": 1713.55, "duration": 1.11}, {"text": "If you go through\nall the original Star", "start": 1714.66, "duration": 2.37}, {"text": "Treks and everything, they\nactually didn't have any money.", "start": 1717.03, "duration": 3.18}, {"text": "That was Gene\nRoddenberry's future.", "start": 1720.21, "duration": 3.73}, {"text": "So he sort of dispensed with\nall this Plato and Aristotle--", "start": 1723.94, "duration": 4.18}, {"text": "Let's now sort of go a\nlittle bit more serious", "start": 1728.12, "duration": 2.23}, {"text": "and then talk about\nSatoshi Nakamoto.", "start": 1730.35, "duration": 2.21}, {"text": "But Romain, any questions?", "start": 1732.56, "duration": 3.88}, {"text": "AUDIENCE: None so far.", "start": 1736.44, "duration": 0.93}, {"text": "Let's give it a few seconds.", "start": 1737.37, "duration": 1.167}, {"text": "No, I think we're good to go.", "start": 1744.25, "duration": 1.36}, {"text": "GARY GENSLER: So\nwith that foundation,", "start": 1745.61, "duration": 1.583}, {"text": "let's go back to\nthe payments riddle.", "start": 1747.193, "duration": 2.577}, {"text": "So we get through the 1990s.", "start": 1749.77, "duration": 2.13}, {"text": "The internet is taking off, we\nfigure out how to secure it,", "start": 1751.9, "duration": 4.89}, {"text": "and the credit card companies\nfind a way to move money.", "start": 1756.79, "duration": 5.04}, {"text": "Some startups happen.", "start": 1761.83, "duration": 1.46}, {"text": "PayPal and the like\nstart up in this area,", "start": 1763.29, "duration": 2.86}, {"text": "the fintech of the late 1990s.", "start": 1766.15, "duration": 2.67}, {"text": "Mobile payments\nstart by the noughts.", "start": 1768.82, "duration": 2.82}, {"text": "We already have Alipay\nand M-Pesa in Africa.", "start": 1771.64, "duration": 7.67}, {"text": "But this payment\nriddle is still there.", "start": 1779.31, "duration": 1.95}, {"text": "And that cypherpunk mailing\nlist is still there.", "start": 1781.26, "duration": 3.51}, {"text": "And on Halloween night in\n2008, an eight-page paper", "start": 1784.77, "duration": 5.23}, {"text": "is written and is put up on\nthe internet on this cypherpunk", "start": 1790.0, "duration": 4.33}, {"text": "punk mailing list-- there\nmight only be a couple people.", "start": 1794.33, "duration": 3.07}, {"text": "\"I've been working on a new\nelectronic cash system.\"", "start": 1797.4, "duration": 3.54}, {"text": "Peer-to-peer, no trusted third\nparty, no central authority.", "start": 1800.94, "duration": 4.58}, {"text": "And what Satoshi Nakamoto wrote\nin that eight-page paper, what", "start": 1805.52, "duration": 4.54}, {"text": "Nakamoto-san wrote was\nBitcoin white paper.", "start": 1810.06, "duration": 6.54}, {"text": "Had never used the word\n\"blockchain technology.\"", "start": 1816.6, "duration": 2.37}, {"text": "We've come to call it\nblockchain technology.", "start": 1818.97, "duration": 2.52}, {"text": "So, what is the\nblockchain technology?", "start": 1821.49, "duration": 2.97}, {"text": "fundamentally, it's a\nshared accounting system--", "start": 1824.46, "duration": 4.38}, {"text": "a shared accounting system\nor a shared database system.", "start": 1828.84, "duration": 4.27}, {"text": "So Satoshi Nakamoto had\ntimestamped ledgers.", "start": 1833.11, "duration": 4.58}, {"text": "And a timestamped ledger with\ncryptography to secure it", "start": 1837.69, "duration": 5.69}, {"text": "was not new.", "start": 1843.38, "duration": 1.32}, {"text": "A timestamped ledger-- my\nlittle illustration here,", "start": 1844.7, "duration": 5.08}, {"text": "Neha Narula and I use this,\nso I want to give her credit", "start": 1849.78, "duration": 3.14}, {"text": "as well--", "start": 1852.92, "duration": 2.28}, {"text": "represents blocks of data.", "start": 1855.2, "duration": 2.4}, {"text": "Blocks of data, and between\nthese blocks of data", "start": 1857.6, "duration": 3.24}, {"text": "a cryptographic hash function.", "start": 1860.84, "duration": 2.19}, {"text": "And a cryptographic\nhash function", "start": 1863.03, "duration": 1.68}, {"text": "we use every day\nof our lives, just", "start": 1864.71, "duration": 2.76}, {"text": "we don't know we're using\nit, somewhere on the internet", "start": 1867.47, "duration": 3.45}, {"text": "to commit to data.", "start": 1870.92, "duration": 2.27}, {"text": "This technology, this idea\nof taking a block of data", "start": 1873.19, "duration": 5.35}, {"text": "and adding another\nblock of data and having", "start": 1878.54, "duration": 2.13}, {"text": "a hash function in\nbetween, was an innovation", "start": 1880.67, "duration": 3.3}, {"text": "of the late 1980s.", "start": 1883.97, "duration": 2.41}, {"text": "Two Bell Labs scientists,\nHaber and Stornetta,", "start": 1886.38, "duration": 3.32}, {"text": "wrote a paper about it,\neven started a company", "start": 1889.7, "duration": 3.06}, {"text": "to notarize legal\ndocuments by 1995,", "start": 1892.76, "duration": 4.41}, {"text": "a little startup called Surety.", "start": 1897.17, "duration": 3.03}, {"text": "That existed.", "start": 1900.2, "duration": 1.74}, {"text": "That existed, but what\nNakamoto-san figured out", "start": 1901.94, "duration": 3.09}, {"text": "was how to have\nmultiple parties.", "start": 1905.03, "duration": 3.27}, {"text": "Nakamoto-san solved\nthe consensus riddle,", "start": 1908.3, "duration": 3.38}, {"text": "or what some people call\nByzantine general's problem.", "start": 1911.68, "duration": 4.18}, {"text": "The problem is, what if I don't\nknow the other people keeping", "start": 1915.86, "duration": 5.02}, {"text": "a ledger?", "start": 1920.88, "duration": 1.07}, {"text": "Again, the Byzantine\ngeneral's problem was not new.", "start": 1921.95, "duration": 3.3}, {"text": "It wasn't even about money.", "start": 1925.25, "duration": 1.17}, {"text": "The Byzantine general's\nproblem had been written", "start": 1926.42, "duration": 2.04}, {"text": "about in the early 1980s.", "start": 1928.46, "duration": 1.74}, {"text": "It was a computer\nsystems problem.", "start": 1930.2, "duration": 2.88}, {"text": "If you tie various computers\ntogether, what if one of them", "start": 1933.08, "duration": 3.69}, {"text": "fails?", "start": 1936.77, "duration": 0.6}, {"text": "Or even in an airplane, what\nif one of the engines fails?", "start": 1937.37, "duration": 3.48}, {"text": "It's the question\nof fault tolerance.", "start": 1940.85, "duration": 2.69}, {"text": "But what Satoshi Nakamoto\ndid was solved it", "start": 1943.54, "duration": 3.58}, {"text": "through something\ncalled proof of work.", "start": 1947.12, "duration": 2.36}, {"text": "And we don't have the time\nto go through that, but what", "start": 1949.48, "duration": 3.76}, {"text": "this provided together was\na decentralized, auditable", "start": 1953.24, "duration": 5.04}, {"text": "database.", "start": 1958.28, "duration": 1.17}, {"text": "Now, in the case of\nBitcoin 10,000 computers", "start": 1959.45, "duration": 3.18}, {"text": "around the globe maintain\nthis auditable database.", "start": 1962.63, "duration": 4.41}, {"text": "And this audible\ndatabase builds a block", "start": 1967.04, "duration": 2.58}, {"text": "of data on top of a block of\ndata on top of a block of data,", "start": 1969.62, "duration": 4.02}, {"text": "but its shared accounting\nsystem maintains it.", "start": 1973.64, "duration": 5.91}, {"text": "There was one other thing that\nwent on in this period time.", "start": 1979.55, "duration": 3.54}, {"text": "In the late 1990s, a\ncomputer scientist Nick Szabo", "start": 1983.09, "duration": 5.46}, {"text": "wrote a paper and coined the\nphrase \"smart contracts.\"", "start": 1988.55, "duration": 3.63}, {"text": "Again, not an original idea.", "start": 1992.18, "duration": 1.77}, {"text": "But what Nick Szabo\nsaid, what if we", "start": 1993.95, "duration": 2.16}, {"text": "could take a set of promises,\nput them in digital form,", "start": 1996.11, "duration": 5.65}, {"text": "and then the parties can\nperform against them?", "start": 2001.76, "duration": 2.84}, {"text": "In essence, what if we\nautomate in computer", "start": 2004.6, "duration": 4.6}, {"text": "code the movement\nof a property right?", "start": 2009.2, "duration": 2.85}, {"text": "Now, I grew up in\nBaltimore, Maryland.", "start": 2012.05, "duration": 1.98}, {"text": "My dad had a vending\nmachine business.", "start": 2014.03, "duration": 2.01}, {"text": "You know, cigarette machines\nand candy machines and the like.", "start": 2016.04, "duration": 7.56}, {"text": "A vending machine\nis a smart contract.", "start": 2023.6, "duration": 2.83}, {"text": "It's a conditional movement\nof property rights.", "start": 2026.43, "duration": 2.46}, {"text": "It's a pack of gum if you put\nsome money in the machine.", "start": 2028.89, "duration": 4.14}, {"text": "So you can think\nof a smart contract", "start": 2033.03, "duration": 2.01}, {"text": "as digitizing, basically,\na vending machine.", "start": 2035.04, "duration": 3.9}, {"text": "They're not necessarily\nsmart, they're not necessarily", "start": 2038.94, "duration": 2.46}, {"text": "legal contracts.", "start": 2041.4, "duration": 0.95}, {"text": "So I'd be cautious about that.", "start": 2042.35, "duration": 2.33}, {"text": "But these two concepts came\ntogether-- smart contracts,", "start": 2044.68, "duration": 3.8}, {"text": "meaning, can I digitize the\nmovement of a property right?", "start": 2048.48, "duration": 4.28}, {"text": "And then this accounting\nsystem of a shared ledger,", "start": 2052.76, "duration": 5.18}, {"text": "that multiple parties\ncan share a ledger", "start": 2057.94, "duration": 3.16}, {"text": "with no central controller.", "start": 2061.1, "duration": 2.76}, {"text": "That's kind of the\nconceptual frame where", "start": 2063.86, "duration": 4.26}, {"text": "I want to pause for\na second, Romain,", "start": 2068.12, "duration": 1.92}, {"text": "and take questions\non what I usually", "start": 2070.04, "duration": 6.3}, {"text": "cover in a lot more time\nthan the few minutes", "start": 2076.34, "duration": 2.399}, {"text": "that I just did.", "start": 2078.739, "duration": 0.931}, {"text": "AUDIENCE: Any questions\nfrom the students?", "start": 2081.83, "duration": 1.75}, {"text": "GARY GENSLER: This\nmust be because we just", "start": 2088.179, "duration": 1.75}, {"text": "went through holiday time and\nwe had our Zoom Easters and Zoom", "start": 2089.929, "duration": 6.729}, {"text": "seders.", "start": 2096.658, "duration": 0.5}, {"text": "AUDIENCE: There are\nno hands raised now.", "start": 2100.365, "duration": 1.667}, {"text": "Ah, we do have one\nquestion from Celi.", "start": 2102.032, "duration": 2.678}, {"text": "GARY GENSLER: Please.", "start": 2104.71, "duration": 2.353}, {"text": "AUDIENCE: So I was\njust wondering,", "start": 2107.063, "duration": 1.417}, {"text": "can you explain a\nlittle more the issues", "start": 2108.48, "duration": 3.93}, {"text": "of the decentralized\naudible database?", "start": 2112.41, "duration": 3.51}, {"text": "You mentioned it very briefly\nthat it first came out", "start": 2115.92, "duration": 3.72}, {"text": "and how [INAUDIBLE] were solved.", "start": 2119.64, "duration": 1.97}, {"text": "But can you-- just to understand\nwhat issues they are solving.", "start": 2121.61, "duration": 3.7}, {"text": "Can you kind of\nexplain a little?", "start": 2125.31, "duration": 1.375}, {"text": "GARY GENSLER: So if I\nunderstand the question,", "start": 2126.685, "duration": 2.975}, {"text": "what Nakamoto-san\nwas trying to solve", "start": 2129.66, "duration": 2.13}, {"text": "was what has been come to\ncalled double spending.", "start": 2131.79, "duration": 5.49}, {"text": "Can you in a digital way move\na representation of value,", "start": 2137.28, "duration": 7.47}, {"text": "in a digital way move\nthat, without having", "start": 2144.75, "duration": 2.07}, {"text": "a central authority?", "start": 2146.82, "duration": 2.07}, {"text": "We move digitally representation\nof values every day.", "start": 2148.89, "duration": 4.32}, {"text": "When you go online and buy\nsomething-- you go to Expedia,", "start": 2153.21, "duration": 3.12}, {"text": "you go to Amazon,\nyou go to Alibaba--", "start": 2156.33, "duration": 5.64}, {"text": "we move digitally\nrepresentation of values.", "start": 2161.97, "duration": 3.36}, {"text": "We no longer have much of\nour economy on physical cash.", "start": 2165.33, "duration": 4.255}, {"text": "But we always have some\ncentral authority-- a bank,", "start": 2169.585, "duration": 4.445}, {"text": "a payments company that\nwe'll talk about in class 6--", "start": 2174.03, "duration": 4.62}, {"text": "some central\nauthority controlling", "start": 2178.65, "duration": 2.25}, {"text": "that to ensure that\nyou actually have", "start": 2180.9, "duration": 3.48}, {"text": "that value, to\nauthenticate and authorize", "start": 2184.38, "duration": 3.24}, {"text": "the movement of that money.", "start": 2187.62, "duration": 2.07}, {"text": "So what Satoshi\nNakamoto was solving", "start": 2189.69, "duration": 2.13}, {"text": "for is, what if there\nwas no central authority?", "start": 2191.82, "duration": 3.39}, {"text": "And it was a shared\ndatabase or ledger,", "start": 2195.21, "duration": 4.26}, {"text": "or what I call a shared\naccounting system.", "start": 2199.47, "duration": 2.58}, {"text": "That would be the core thing.", "start": 2202.05, "duration": 3.12}, {"text": "This kind of riddle\nfrom the 1990s,", "start": 2205.17, "duration": 3.21}, {"text": "we send packets of data\naround the internet", "start": 2208.38, "duration": 2.31}, {"text": "with this out-of-central\nauthority,", "start": 2210.69, "duration": 2.57}, {"text": "maybe you could do that.", "start": 2213.26, "duration": 1.24}, {"text": "And I don't think it's\na surprise this happened", "start": 2214.5, "duration": 1.98}, {"text": "in the middle of a\nfinancial crisis, Halloween", "start": 2216.48, "duration": 2.57}, {"text": "in the middle of a\nfinancial crisis,", "start": 2219.05, "duration": 1.5}, {"text": "when trust in central\nauthorities was quite low,", "start": 2220.55, "duration": 3.55}, {"text": "and especially trust in\nWall Street and banking,", "start": 2224.1, "duration": 3.12}, {"text": "and banks in Europe\nwas quite low.", "start": 2227.22, "duration": 2.61}, {"text": "This burst of innovation\ncame at that time.", "start": 2232.47, "duration": 4.13}, {"text": "I hope that helps.", "start": 2236.6, "duration": 1.29}, {"text": "And I think as we're going\nto chat through today", "start": 2237.89, "duration": 2.37}, {"text": "and in other\nclasses, the question", "start": 2240.26, "duration": 1.47}, {"text": "is, are there\nother applications?", "start": 2241.73, "duration": 2.335}, {"text": "See, this goes to\nthe heart of finance.", "start": 2244.065, "duration": 1.985}, {"text": "It goes to the heart\nof the plumbing.", "start": 2246.05, "duration": 1.77}, {"text": "Satoshi Nakamoto's innovation\nstill survives 12 years later.", "start": 2247.82, "duration": 4.935}, {"text": "In this adversarial sort\nof off-the-grid way,", "start": 2252.755, "duration": 5.815}, {"text": "Bitcoins still survives\n12 years later.", "start": 2258.57, "duration": 3.83}, {"text": "But are there other\napplications in finance,", "start": 2262.4, "duration": 3.45}, {"text": "where a shared database system,\na shared accounting system", "start": 2265.85, "duration": 5.97}, {"text": "is the best way to go?", "start": 2271.82, "duration": 1.9}, {"text": "And we've had\ninventions like this,", "start": 2273.72, "duration": 2.48}, {"text": "infrastructure technologies that\nhave radically changed finance.", "start": 2276.2, "duration": 4.41}, {"text": "And one of them from\nseveral hundred years ago", "start": 2280.61, "duration": 2.0}, {"text": "was the joint stock company.", "start": 2282.61, "duration": 2.29}, {"text": "When I talk about\na technology stack,", "start": 2284.9, "duration": 2.4}, {"text": "one from several\ncenturies ago was,", "start": 2287.3, "duration": 3.24}, {"text": "can we have a shared\nownership of a company?", "start": 2290.54, "duration": 4.68}, {"text": "And when that was\nsort of invented,", "start": 2295.22, "duration": 2.33}, {"text": "I guess some people would have\nsaid, what do we need that for?", "start": 2297.55, "duration": 2.94}, {"text": "This, instead of a shared\ncompany, is a shared database.", "start": 2300.49, "duration": 4.5}, {"text": "And so that's the debate.", "start": 2304.99, "duration": 1.59}, {"text": "Is it really needed?", "start": 2306.58, "duration": 1.95}, {"text": "Will it be useful in the future?", "start": 2308.53, "duration": 2.37}, {"text": "It has led to a crypto\nmarket, about $200 billion", "start": 2310.9, "duration": 3.93}, {"text": "as of yesterday, 2/3 of which\nis Bitcoin, highly volatile.", "start": 2314.83, "duration": 7.48}, {"text": "Hassan would say, but\nwhat's the intrinsic value?", "start": 2322.31, "duration": 3.05}, {"text": "It is a digital\nscarce store of value.", "start": 2325.36, "duration": 4.11}, {"text": "And it only has value because\nsomebody else will move it.", "start": 2329.47, "duration": 3.0}, {"text": "When Bitcoin was\nrolled out in 2009,", "start": 2332.47, "duration": 3.09}, {"text": "nobody saw that it had value.", "start": 2335.56, "duration": 1.98}, {"text": "It was just a kind of\ninteresting project.", "start": 2337.54, "duration": 4.95}, {"text": "But by 2010, one person\nwho was in the community", "start": 2342.49, "duration": 4.56}, {"text": "said, let's see if I could\nget anybody to give me", "start": 2347.05, "duration": 2.79}, {"text": "something commercially.", "start": 2349.84, "duration": 2.61}, {"text": "And it was actually pizza.", "start": 2352.45, "duration": 2.11}, {"text": "It wasn't Pizza Net,\nthe Sandra Bullock", "start": 2354.56, "duration": 4.16}, {"text": "movie we started with in 1995.", "start": 2358.72, "duration": 2.61}, {"text": "But 15 years later in 2010, a\ncrypto enthusiast in Florida", "start": 2361.33, "duration": 6.63}, {"text": "put out-- on an email asked,\nI will give you 10,000 bitcoin", "start": 2367.96, "duration": 4.8}, {"text": "if you send me two pizzas.", "start": 2372.76, "duration": 1.95}, {"text": "Two pizzas, 1,000\nbitcoin in May of 2010.", "start": 2374.71, "duration": 4.56}, {"text": "It took about a week\nbefore anybody responded.", "start": 2379.27, "duration": 2.46}, {"text": "But two pizzas showed\nup at his door,", "start": 2381.73, "duration": 2.25}, {"text": "and sure enough this crypto\nenthusiast in Florida", "start": 2383.98, "duration": 5.64}, {"text": "sent the 10,000 bitcoin.", "start": 2389.62, "duration": 1.57}, {"text": "Now, at the time, there\nwasn't a crypto market.", "start": 2391.19, "duration": 3.933}, {"text": "At the time, it was\nthought that the two", "start": 2395.123, "duration": 1.667}, {"text": "pizzas were worth about $42 that\nhe had paid 10,000 bitcoin for.", "start": 2396.79, "duration": 5.34}, {"text": "That 10,000 bitcoin today would\nbe valued at about $65 million.", "start": 2402.13, "duration": 5.65}, {"text": "So 10 years later,\nyou kind of go, well,", "start": 2407.78, "duration": 3.126}, {"text": "that was kind of an\ninteresting time to do that.", "start": 2410.906, "duration": 4.154}, {"text": "It's led to different sectors.", "start": 2415.06, "duration": 2.7}, {"text": "There's thousands\nof these coins.", "start": 2417.76, "duration": 2.01}, {"text": "The payment or store\nof value tokens", "start": 2419.77, "duration": 2.19}, {"text": "are the dominant, about\n3/4 of the market.", "start": 2421.96, "duration": 3.54}, {"text": "Some of you may have\nheard of Ethereum.", "start": 2425.5, "duration": 1.83}, {"text": "But platform tokens were--", "start": 2427.33, "duration": 2.3}, {"text": "Vitalik Buterin rolled out\nthis thing called Ethereum.", "start": 2429.63, "duration": 4.09}, {"text": "And Ethereum is conceptually\na worldwide shared computer.", "start": 2433.72, "duration": 7.45}, {"text": "It has many attributes\nof operating system.", "start": 2441.17, "duration": 6.87}, {"text": "I wouldn't compare\nit and contrasted", "start": 2448.04, "duration": 2.13}, {"text": "with iOS and Android, but it\ndoes have attributes similar", "start": 2450.17, "duration": 4.26}, {"text": "to a worldwide platform\nlayer operating system,", "start": 2454.43, "duration": 4.62}, {"text": "upon which distributed\napplications or dApps can", "start": 2459.05, "duration": 3.36}, {"text": "be put on top.", "start": 2462.41, "duration": 2.54}, {"text": "So this is this ecosystem.", "start": 2464.95, "duration": 1.92}, {"text": "There's a few dozen payment\nor store value tokens.", "start": 2466.87, "duration": 3.9}, {"text": "There's dozens of\nplatform tokens.", "start": 2470.77, "duration": 2.19}, {"text": "There's 1,000 to 2,000\napplications placed on top.", "start": 2472.96, "duration": 5.26}, {"text": "The conceptual framework\nin these applications", "start": 2478.22, "duration": 3.32}, {"text": "is they're decentralized.", "start": 2481.54, "duration": 2.88}, {"text": "Will anybody use them--\ndifferent questions", "start": 2484.42, "duration": 3.63}, {"text": "along the way.", "start": 2488.05, "duration": 2.02}, {"text": "So, what has this led to?", "start": 2490.07, "duration": 1.73}, {"text": "It's led to blockchain use cases\naround speculative investing.", "start": 2491.8, "duration": 5.51}, {"text": "Crowdfunding through\ninitial coin offerings--", "start": 2497.31, "duration": 2.78}, {"text": "from 2017 to 2019,\nnearly $30 billion", "start": 2500.09, "duration": 5.22}, {"text": "was raised by basically\nselling a token", "start": 2505.31, "duration": 5.47}, {"text": "before you had a business.", "start": 2510.78, "duration": 2.97}, {"text": "You might have a\ngood idea, you might", "start": 2513.75, "duration": 2.19}, {"text": "have the legitimate players, and\nyou raised money off of this.", "start": 2515.94, "duration": 4.44}, {"text": "You weren't selling equity,\nyou were not selling debt,", "start": 2520.38, "duration": 3.06}, {"text": "you were selling a\ntoken that could be used", "start": 2523.44, "duration": 2.64}, {"text": "on some site in the future.", "start": 2526.08, "duration": 2.32}, {"text": "Now, those tokens\nhave largely been--", "start": 2528.4, "duration": 3.28}, {"text": "in 2020 this is--", "start": 2531.68, "duration": 1.84}, {"text": "those tokens are largely\nfor crypto exchanges,", "start": 2533.52, "duration": 4.11}, {"text": "for gaming, for\ngambling, for something", "start": 2537.63, "duration": 2.37}, {"text": "called decentralized\nfinance, and file sharing.", "start": 2540.0, "duration": 4.09}, {"text": "Now, there's something\nthat's consistent", "start": 2544.09, "duration": 2.16}, {"text": "about the first three--\ncrypto exchanges, gaming,", "start": 2546.25, "duration": 2.76}, {"text": "and gambling.", "start": 2549.01, "duration": 1.17}, {"text": "Some of the users of these\ngaming/gambling exchange sites", "start": 2550.18, "duration": 3.92}, {"text": "want a sort of a basis\nof staying off the grid.", "start": 2554.1, "duration": 4.12}, {"text": "They want censorship resistance.", "start": 2558.22, "duration": 2.97}, {"text": "So the thing about\ncryptocurrencies,", "start": 2561.19, "duration": 2.46}, {"text": "the good and the bad sometimes,\nis the official sector,", "start": 2563.65, "duration": 4.27}, {"text": "though they can track some of\nit, they can't track all of it.", "start": 2567.92, "duration": 2.75}, {"text": "That it's some way sometimes\nto stay off the grid.", "start": 2570.67, "duration": 3.99}, {"text": "I'm not advising this.", "start": 2574.66, "duration": 1.35}, {"text": "I'm just saying the economics\nof it, some of that,", "start": 2576.01, "duration": 3.09}, {"text": "is about censorship-resistant.", "start": 2579.1, "duration": 2.46}, {"text": "All of the other uses has been\naround blockchain technology.", "start": 2581.56, "duration": 6.35}, {"text": "And the uses really\nare potential uses.", "start": 2587.91, "duration": 2.67}, {"text": "They haven't taken off.", "start": 2590.58, "duration": 1.02}, {"text": "Can we use it in\npayment systems?", "start": 2591.6, "duration": 1.56}, {"text": "Can we use it in trade finance?", "start": 2593.16, "duration": 1.59}, {"text": "Can we use it in clearing\nsettling and processing?", "start": 2594.75, "duration": 2.67}, {"text": "And there are\nhundreds of projects", "start": 2597.42, "duration": 2.91}, {"text": "that have been in proof of\nconcept or pilot stages, none", "start": 2600.33, "duration": 5.28}, {"text": "that have truly broken out yet.", "start": 2605.61, "duration": 2.62}, {"text": "And this is why I say it hasn't\ncome into the technology stack.", "start": 2608.23, "duration": 4.62}, {"text": "You can, by the way,\nget your MIT diploma", "start": 2612.85, "duration": 2.11}, {"text": "on blockchain technology.", "start": 2614.96, "duration": 1.75}, {"text": "I'm saying that if you\ndo, you can decide also", "start": 2616.71, "duration": 6.06}, {"text": "to get it in paper form.", "start": 2622.77, "duration": 2.01}, {"text": "I thought-- Romain, actually we\nhad a poll just to see how many", "start": 2624.78, "duration": 3.27}, {"text": "people--", "start": 2628.05, "duration": 0.69}, {"text": "there's a poll on use of\ncryptocurrency or something,", "start": 2628.74, "duration": 3.75}, {"text": "the first of those two polls.", "start": 2632.49, "duration": 3.04}, {"text": "If folks don't mind just\ngiving a little flavor for,", "start": 2635.53, "duration": 4.52}, {"text": "have you ever owned\ncrypto, and so forth.", "start": 2640.05, "duration": 3.165}, {"text": "So it looks like a third have\nowned Bitcoin or Ethereum", "start": 2643.215, "duration": 5.565}, {"text": "or AUT Coins.", "start": 2648.78, "duration": 2.28}, {"text": "And we have-- does\nBitcoin exhibit", "start": 2651.06, "duration": 2.73}, {"text": "the three roles of money?", "start": 2653.79, "duration": 3.72}, {"text": "A little over half yes, and\na little less than a half no.", "start": 2657.51, "duration": 4.89}, {"text": "I'm going to ask if somebody--\none person on the yes side, one", "start": 2662.4, "duration": 2.94}, {"text": "person on the no\nside-- just points", "start": 2665.34, "duration": 1.71}, {"text": "to articulate why\nit does not exhibit", "start": 2667.05, "duration": 4.05}, {"text": "the three roles of money--\nthe store of value,", "start": 2671.1, "duration": 2.34}, {"text": "medium of exchange,\nunit of account.", "start": 2673.44, "duration": 2.22}, {"text": "And for this Romain,\nwe'll cold call.", "start": 2679.07, "duration": 2.03}, {"text": "So if somebody wants to take\nthe lead on either side.", "start": 2681.1, "duration": 5.902}, {"text": "AUDIENCE: Any volunteers?", "start": 2687.002, "duration": 1.948}, {"text": "Camilo.", "start": 2688.95, "duration": 0.881}, {"text": "GARY GENSLER: And\nif you can declare", "start": 2692.39, "duration": 1.5}, {"text": "which side you're on so somebody\ncan volunteer on the other side", "start": 2693.89, "duration": 2.97}, {"text": "as well.", "start": 2696.86, "duration": 1.51}, {"text": "AUDIENCE: Yeah, I\nam on the no side.", "start": 2698.37, "duration": 2.12}, {"text": "I mean, I--", "start": 2700.49, "duration": 0.5}, {"text": "GARY GENSLER: All right.", "start": 2700.99, "duration": 1.0}, {"text": "So just for a moment, so\nif somebody on the optimist", "start": 2701.99, "duration": 2.28}, {"text": "positive side please volunteer.", "start": 2704.27, "duration": 1.71}, {"text": "But Camilo.", "start": 2705.98, "duration": 1.608}, {"text": "AUDIENCE: Yeah, no.", "start": 2707.588, "duration": 0.792}, {"text": "I mean, I think that still\nas a medium of exchange,", "start": 2708.38, "duration": 4.78}, {"text": "Bitcoin and the rest\nof the cryptocurrencies", "start": 2713.16, "duration": 3.3}, {"text": "are really limited.", "start": 2716.46, "duration": 1.97}, {"text": "If I want to go to, I\ndon't know, the public", "start": 2718.43, "duration": 2.44}, {"text": "and buy something with\nBitcoin, it would be so hard.", "start": 2720.87, "duration": 3.97}, {"text": "I'll have to find an\napp that translates", "start": 2724.84, "duration": 1.73}, {"text": "my Bitcoin to real money\nand then try to pay.", "start": 2726.57, "duration": 3.39}, {"text": "And there is also a questionable\nthing about the store of value.", "start": 2729.96, "duration": 4.62}, {"text": "You know, Bitcoin at least-- and\nEthereum I think is also true--", "start": 2734.58, "duration": 3.9}, {"text": "had been fluctuating\nso much that you never", "start": 2738.48, "duration": 4.44}, {"text": "know how much value are you're\ngetting for a bitcoin day", "start": 2742.92, "duration": 3.42}, {"text": "to day.", "start": 2746.34, "duration": 0.53}, {"text": "So I think there is still a\nlong way before fulfilling", "start": 2746.87, "duration": 3.46}, {"text": "the essentials of money.", "start": 2750.33, "duration": 2.0}, {"text": "GARY GENSLER: All right.", "start": 2752.33, "duration": 1.0}, {"text": "So I think Camilo is saying,\nI can't go to Publix,", "start": 2753.33, "duration": 4.29}, {"text": "not a medium of exchange\nwhere I want to go.", "start": 2757.62, "duration": 3.27}, {"text": "And it's kind of this\nvolatile store of value.", "start": 2760.89, "duration": 5.53}, {"text": "And you didn't address\na unit of account.", "start": 2766.42, "duration": 2.21}, {"text": "But let's see if\nthere's somebody", "start": 2768.63, "duration": 1.59}, {"text": "on the other side who just\nwants to kind of articulate", "start": 2770.22, "duration": 3.0}, {"text": "the other side of this.", "start": 2773.22, "duration": 1.9}, {"text": "AUDIENCE: We have Devin.", "start": 2775.12, "duration": 1.283}, {"text": "GARY GENSLER: Devin, please.", "start": 2776.403, "duration": 1.167}, {"text": "AUDIENCE: Oof.", "start": 2777.57, "duration": 0.93}, {"text": "I can give the counter,\nat least in my opinion.", "start": 2778.5, "duration": 3.81}, {"text": "I don't think that the\nidea of a store of value", "start": 2782.31, "duration": 2.67}, {"text": "and the medium exchange are\nshortcomings of the currency.", "start": 2784.98, "duration": 3.21}, {"text": "I think they're shortcomings\nof the market in which it", "start": 2788.19, "duration": 2.25}, {"text": "operates.", "start": 2790.44, "duration": 1.96}, {"text": "So you can use it\nto exchange value.", "start": 2792.4, "duration": 2.183}, {"text": "If the infrastructure\nisn't there,", "start": 2794.583, "duration": 1.417}, {"text": "that's not the\ncurrencies fault, that's", "start": 2796.0, "duration": 1.937}, {"text": "sort of the market participants.", "start": 2797.937, "duration": 1.333}, {"text": "And then with the store of\nvalue, it does store a value.", "start": 2799.27, "duration": 3.36}, {"text": "That value does\nfluctuate, that's true.", "start": 2802.63, "duration": 1.92}, {"text": "But again, I think that's\nbecause of the market it's in", "start": 2804.55, "duration": 2.52}, {"text": "and speculation going on\naround these currencies.", "start": 2807.07, "duration": 4.95}, {"text": "GARY GENSLER: Camilo\ndo you want to--", "start": 2812.02, "duration": 1.79}, {"text": "you both are unmuted.", "start": 2813.81, "duration": 1.37}, {"text": "You can cross-- and Devin\ncan stay unmuted, too.", "start": 2815.18, "duration": 4.02}, {"text": "Any reply just for 30 seconds?", "start": 2819.2, "duration": 3.415}, {"text": "AUDIENCE: No, no, no.", "start": 2822.615, "duration": 0.875}, {"text": "I just want to say that,\nalthough it's true that", "start": 2823.49, "duration": 2.31}, {"text": "the value of the Bitcoin, it\nfluctuates with the market,", "start": 2825.8, "duration": 3.21}, {"text": "the point is that if you want\na worldwide accepted medium", "start": 2829.01, "duration": 5.1}, {"text": "of exchange, it cannot\nfluctuate as much as a Bitcoin.", "start": 2834.11, "duration": 3.96}, {"text": "Otherwise, the\nfinancial system--", "start": 2838.07, "duration": 1.65}, {"text": "and even people who have savings\nwouldn't have their savings", "start": 2839.72, "duration": 4.38}, {"text": "in Bitcoin.", "start": 2844.1, "duration": 0.69}, {"text": "I mean, you are not going\nto put your funding,", "start": 2844.79, "duration": 2.18}, {"text": "your savings account\ninto Bitcoin,", "start": 2846.97, "duration": 2.62}, {"text": "because you might get\nlosses overnight, so.", "start": 2849.59, "duration": 3.57}, {"text": "GARY GENSLER: And [Devin.", "start": 2853.16, "duration": 2.31}, {"text": "AUDIENCE: I agree that\nit does fluctuate.", "start": 2855.47, "duration": 2.657}, {"text": "I wouldn't put my savings in it.", "start": 2858.127, "duration": 1.333}, {"text": "I never have, I never will.", "start": 2859.46, "duration": 2.68}, {"text": "But I do think it\nkind of comes down", "start": 2862.14, "duration": 1.61}, {"text": "to what is the exact definition\nof the question you're", "start": 2863.75, "duration": 2.79}, {"text": "trying to answer.", "start": 2866.54, "duration": 0.76}, {"text": "Can you store value in it?", "start": 2867.3, "duration": 1.16}, {"text": "Yes.", "start": 2868.46, "duration": 0.63}, {"text": "Is the value going to\nbe the same tomorrow?", "start": 2869.09, "duration": 1.98}, {"text": "Maybe not.", "start": 2871.07, "duration": 1.5}, {"text": "And that's something that\nmight stabilize over time as--", "start": 2872.57, "duration": 2.65}, {"text": "like, if it gets used more\nfor day-to-day interactions", "start": 2875.22, "duration": 2.81}, {"text": "like going to the\nshop, and it's not", "start": 2878.03, "duration": 2.14}, {"text": "kind of speculation and\nsort of hype around it,", "start": 2880.17, "duration": 2.48}, {"text": "then maybe we can kind\nof converge to a point", "start": 2882.65, "duration": 2.49}, {"text": "where it does satisfy\neverything fully.", "start": 2885.14, "duration": 2.76}, {"text": "GARY GENSLER: And this\ndebate that Devin and Camilo", "start": 2887.9, "duration": 2.79}, {"text": "are helping frame is debate\nthat's a worthy debate.", "start": 2890.69, "duration": 3.75}, {"text": "I will tell you that I'm\nnot a Bitcoin maximalist,", "start": 2894.44, "duration": 3.84}, {"text": "but I actually--", "start": 2898.28, "duration": 1.5}, {"text": "I'm probably a little\ncloser to Devin than Camilo", "start": 2899.78, "duration": 2.64}, {"text": "on this in terms of, it is a\ndigital scarce store of value.", "start": 2902.42, "duration": 5.07}, {"text": "Will it be worth something\n10 years from now?", "start": 2907.49, "duration": 2.46}, {"text": "Maybe not, maybe not.", "start": 2909.95, "duration": 2.01}, {"text": "But it has survived\nkind of in this swamp,", "start": 2911.96, "duration": 3.3}, {"text": "it's this uncertain sort\nof world, for 12 years.", "start": 2915.26, "duration": 4.03}, {"text": "And it has some\nvalue to some folks.", "start": 2919.29, "duration": 6.07}, {"text": "Hassan earlier would say, but\nit doesn't have intrinsic value.", "start": 2925.36, "duration": 3.63}, {"text": "And I would say, well, it's\njust a symbol in any regard.", "start": 2928.99, "duration": 3.74}, {"text": "It can be a medium of\nexchange in certain places.", "start": 2932.73, "duration": 4.12}, {"text": "But it needs an infrastructure.", "start": 2936.85, "duration": 1.4}, {"text": "Camilo is absolutely right.", "start": 2938.25, "duration": 2.88}, {"text": "The state treasurer of Ohio\nin late 2018 had announced--", "start": 2941.13, "duration": 5.3}, {"text": "a state controller, I\nthink it might have been,", "start": 2946.43, "duration": 2.83}, {"text": "in Ohio, an elected office--", "start": 2949.26, "duration": 1.89}, {"text": "that the state of Ohio would\naccept Bitcoin for taxes.", "start": 2951.15, "duration": 3.9}, {"text": "Was it just for\npolitical reasons", "start": 2955.05, "duration": 3.03}, {"text": "that this gentleman\nannounced it,", "start": 2958.08, "duration": 2.88}, {"text": "that he thought he was\nassociating himself", "start": 2960.96, "duration": 2.19}, {"text": "with a new innovation\nin the economy?", "start": 2963.15, "duration": 2.67}, {"text": "But they needed\nan infrastructure", "start": 2965.82, "duration": 1.41}, {"text": "to accept the Bitcoin.", "start": 2967.23, "duration": 1.62}, {"text": "They had to convert it for a\n1% fee to US dollars for sure.", "start": 2968.85, "duration": 6.66}, {"text": "It's not much of\na unit of account.", "start": 2975.51, "duration": 1.92}, {"text": "But sometimes it becomes\na unit of account inside", "start": 2977.43, "duration": 3.6}, {"text": "of these other decentralized\napps inside the ICO space.", "start": 2981.03, "duration": 4.74}, {"text": "So it sort of probably exhibits\none out of the three mostly.", "start": 2985.77, "duration": 3.93}, {"text": "It's a speculative\nstore of value.", "start": 2989.7, "duration": 2.58}, {"text": "It can be a medium of exchange.", "start": 2992.28, "duration": 1.83}, {"text": "It can be a unit of account.", "start": 2994.11, "duration": 2.22}, {"text": "But it hasn't adopted this.", "start": 2996.33, "duration": 2.07}, {"text": "A number of years ago, the\nFinancial Stability Board,", "start": 2998.4, "duration": 5.7}, {"text": "a worldwide organization of\n20-- the G20 finance ministers", "start": 3004.1, "duration": 4.44}, {"text": "and central bankers, decided\nthat they would no longer call", "start": 3008.54, "duration": 4.17}, {"text": "Bitcoin and others\ncryptocurrencies,", "start": 3012.71, "duration": 2.01}, {"text": "and they'd call\nthem crypto assets.", "start": 3014.72, "duration": 2.14}, {"text": "So they were associating\nmore with Camilo's side.", "start": 3016.86, "duration": 2.51}, {"text": "They were saying,\nwe're not going", "start": 3019.37, "duration": 1.375}, {"text": "to give this the kind of\nword to call it a currency.", "start": 3020.745, "duration": 4.055}, {"text": "And yet, the US\nDepartment of Treasury", "start": 3024.8, "duration": 2.85}, {"text": "some seven years ago\nhad to address itself", "start": 3027.65, "duration": 2.88}, {"text": "to the question\nof whether Bitcoin", "start": 3030.53, "duration": 2.31}, {"text": "and other similar digital assets\nwere currency under US Bank", "start": 3032.84, "duration": 5.94}, {"text": "Secrecy Act laws, against\nmoney laundering and the like.", "start": 3038.78, "duration": 4.93}, {"text": "And for that purpose,\nthey said that Bitcoin", "start": 3043.71, "duration": 3.05}, {"text": "was a virtual currency.", "start": 3046.76, "duration": 1.98}, {"text": "So there's the US Department of\nTreasury fitting it into a box.", "start": 3048.74, "duration": 4.08}, {"text": "Now, I dare say they\nneeded to somehow address", "start": 3052.82, "duration": 3.87}, {"text": "this public policy\nissue as to whether it", "start": 3056.69, "duration": 2.19}, {"text": "was going to be regulated\nunder the Bank Secrecy Act.", "start": 3058.88, "duration": 3.09}, {"text": "So somehow they had\nto call it a currency,", "start": 3061.97, "duration": 2.43}, {"text": "call it a virtual currency.", "start": 3064.4, "duration": 2.04}, {"text": "Another part of\nthe US Department", "start": 3066.44, "duration": 1.62}, {"text": "of Treasury about\nthe same time said", "start": 3068.06, "duration": 2.31}, {"text": "it was going to be treated\nas property for tax purposes.", "start": 3070.37, "duration": 3.64}, {"text": "So inside the US\nTreasury Department,", "start": 3074.01, "duration": 3.92}, {"text": "clearly for purposes\nof trying to decide", "start": 3077.93, "duration": 2.67}, {"text": "how it's going to be taxed,\nhow it's going to be treated", "start": 3080.6, "duration": 2.94}, {"text": "for anti-money laundering\nlaws, one part of the Treasury", "start": 3083.54, "duration": 3.87}, {"text": "called a virtual\ncurrency, another part", "start": 3087.41, "duration": 2.04}, {"text": "of the US Treasury called it\nproperty rather than currency.", "start": 3089.45, "duration": 6.06}, {"text": "And that fit into that.", "start": 3095.51, "duration": 1.93}, {"text": "So I think I'll move\non a little bit.", "start": 3097.44, "duration": 2.63}, {"text": "But we can take down\nthe poll, I think.", "start": 3100.07, "duration": 3.96}, {"text": "Or do I do that?", "start": 3104.03, "duration": 2.27}, {"text": "You--", "start": 3106.3, "duration": 0.5}, {"text": "AUDIENCE: So every\nperson should be", "start": 3106.8, "duration": 3.53}, {"text": "able to close that\nlittle polling window.", "start": 3110.33, "duration": 2.19}, {"text": "I do not have control over it.", "start": 3112.52, "duration": 1.88}, {"text": "GARY GENSLER: OK.", "start": 3114.4, "duration": 1.45}, {"text": "Then I need to do that here\nfor a second so that it closes.", "start": 3115.85, "duration": 3.27}, {"text": "OK.", "start": 3119.12, "duration": 0.87}, {"text": "So there's a lot of challenges\nof this shared accounting", "start": 3119.99, "duration": 3.58}, {"text": "system.", "start": 3123.57, "duration": 0.5}, {"text": "Scalability,\nperformance-- you can", "start": 3124.07, "duration": 2.61}, {"text": "move about 7 or 10 transactions\non Bitcoin per second.", "start": 3126.68, "duration": 4.05}, {"text": "You can move 10 to 20\ntransactions a second", "start": 3130.73, "duration": 3.76}, {"text": "on Ethereum.", "start": 3134.49, "duration": 2.58}, {"text": "That's kind of not the shot\nthat we need to this system.", "start": 3137.07, "duration": 3.41}, {"text": "Our shared, centralized\nequity-clearing system here", "start": 3140.48, "duration": 5.37}, {"text": "in the US, the Depository\nTrust, DTCC, needs to move--", "start": 3145.85, "duration": 7.243}, {"text": "the Securities and Exchange\nCommission sort of said,", "start": 3153.093, "duration": 2.167}, {"text": "you need to be able to move\nabout 100 million transactions", "start": 3155.26, "duration": 3.12}, {"text": "a day.", "start": 3158.38, "duration": 1.362}, {"text": "Well, guess what?", "start": 3159.742, "duration": 0.708}, {"text": "In the middle of one of the\nmost volatile time in February,", "start": 3160.45, "duration": 3.78}, {"text": "DTCC was moving 350\nmillion transactions.", "start": 3164.23, "duration": 4.007}, {"text": "And when I say transactions, it\ncould be for a hundred shares,", "start": 3168.237, "duration": 2.583}, {"text": "it could be a thousand shares\nor if the volumes in shares", "start": 3170.82, "duration": 2.68}, {"text": "was higher.", "start": 3173.5, "duration": 0.61}, {"text": "But I'm talking about how\nmany transactions were", "start": 3174.11, "duration": 2.81}, {"text": "moving through that system.", "start": 3176.92, "duration": 1.92}, {"text": "Blockchain technology\nby and large", "start": 3178.84, "duration": 2.4}, {"text": "has a bunch of issues\nstill to sort through,", "start": 3181.24, "duration": 3.39}, {"text": "is the point, from public policy\nissues, commercial use cases,", "start": 3184.63, "duration": 3.69}, {"text": "and the like.", "start": 3188.32, "duration": 1.15}, {"text": "And the question\nis for the 2020,", "start": 3189.47, "duration": 2.18}, {"text": "as these scalability,\nperformance,", "start": 3191.65, "duration": 2.01}, {"text": "and efficiency issues,\nas privacy and security,", "start": 3193.66, "duration": 3.15}, {"text": "as some of these\nare worked through,", "start": 3196.81, "duration": 3.21}, {"text": "is a shared accounting system,\na shared ledger system something", "start": 3200.02, "duration": 3.66}, {"text": "that's going to take off?", "start": 3203.68, "duration": 1.74}, {"text": "And I go back to economic\nwork from the 1930s by Coase.", "start": 3205.42, "duration": 5.22}, {"text": "And i just sort of capture\nit in a little slide here", "start": 3210.64, "duration": 3.06}, {"text": "the trade-offs of centralization\nand decentralization,", "start": 3213.7, "duration": 4.26}, {"text": "and these as a cost curve.", "start": 3217.96, "duration": 1.41}, {"text": "But centralization\ndoes lead to cost,", "start": 3219.37, "duration": 2.65}, {"text": "about a single point of\nfailure, about economic rents,", "start": 3222.02, "duration": 4.34}, {"text": "and about capture.", "start": 3226.36, "duration": 4.81}, {"text": "We all know that we\npay more for something", "start": 3231.17, "duration": 2.97}, {"text": "that's highly centralized.", "start": 3234.14, "duration": 1.32}, {"text": "If you want to build an app\non top of iOS or on top--", "start": 3235.46, "duration": 6.16}, {"text": "Apple's iOS or an app on\ntop of Google's Android,", "start": 3241.62, "duration": 4.01}, {"text": "you're going to pay a\nfee, because they're", "start": 3245.63, "duration": 2.22}, {"text": "the two dominant\npipes if you need", "start": 3247.85, "duration": 3.0}, {"text": "to deal with certain\ncentralized financial systems,", "start": 3250.85, "duration": 4.23}, {"text": "there's more economic rents.", "start": 3255.08, "duration": 1.59}, {"text": "And in fact, the\nfinancial sector in the US", "start": 3256.67, "duration": 3.34}, {"text": "takes about 7 and\n1/2% of our economy.", "start": 3260.01, "duration": 3.06}, {"text": "That's double what\nit took in the 1960s.", "start": 3263.07, "duration": 3.97}, {"text": "Now, it's a bigger economy,\nit's a bigger financial sector.", "start": 3267.04, "duration": 3.95}, {"text": "But does it necessarily need to\ntake 7 and 1/2% of our economy?", "start": 3270.99, "duration": 3.64}, {"text": "So some would say,\nthose are some", "start": 3274.63, "duration": 1.7}, {"text": "of the costs of centralization.", "start": 3276.33, "duration": 3.24}, {"text": "And then there's also\ncost of decentralization--", "start": 3279.57, "duration": 3.3}, {"text": "coordination, governance,\nsecurity, scalability.", "start": 3282.87, "duration": 2.66}, {"text": "Now, Coase was\nwriting in the 1930s", "start": 3285.53, "duration": 3.07}, {"text": "why do you bring together\ncertain attributes inside", "start": 3288.6, "duration": 3.21}, {"text": "of a firm.", "start": 3291.81, "duration": 0.69}, {"text": "It was about the\ntheory of the firm", "start": 3292.5, "duration": 1.8}, {"text": "and why some things\nare inside a firm.", "start": 3294.3, "duration": 3.36}, {"text": "And it was the cost\nof information,", "start": 3297.66, "duration": 3.03}, {"text": "the cost of coordination, that\nyou bring some things inside,", "start": 3300.69, "duration": 3.63}, {"text": "some things are left out.", "start": 3304.32, "duration": 1.74}, {"text": "The question is, will this\nchange this balance somehow?", "start": 3306.06, "duration": 3.94}, {"text": "Vitalik Buterin talked\nabout a trilemma", "start": 3310.0, "duration": 3.2}, {"text": "and said it's hard to\nget all three of these,", "start": 3313.2, "duration": 3.94}, {"text": "to get security,\ndecentralization,", "start": 3317.14, "duration": 2.19}, {"text": "and scalability.", "start": 3319.33, "duration": 1.1}, {"text": "So Buterin is the innovator,\nat 19, of the Ethereum network.", "start": 3320.43, "duration": 4.48}, {"text": "He's now 25, maybe.", "start": 3324.91, "duration": 3.96}, {"text": "But Vitalik Buterin\nsaid, look, you", "start": 3328.87, "duration": 2.82}, {"text": "can get decentralization like\nin Bitcoin and secure it.", "start": 3331.69, "duration": 3.48}, {"text": "It's reasonably secure,\nbut it's not scalable.", "start": 3335.17, "duration": 3.15}, {"text": "You maybe can get\ntowards scalability,", "start": 3338.32, "duration": 2.58}, {"text": "but you're probably\ngoing to tend", "start": 3340.9, "duration": 1.41}, {"text": "towards more centralization.", "start": 3342.31, "duration": 2.58}, {"text": "Now, one of MIT's award-winning\ncomputer scientists,", "start": 3344.89, "duration": 4.18}, {"text": "Silvio Micali, says,\nno, he disagrees.", "start": 3349.07, "duration": 3.15}, {"text": "He says you can\nactually solve for this.", "start": 3352.22, "duration": 2.36}, {"text": "Silvio won the Turing Award.", "start": 3354.58, "duration": 2.91}, {"text": "He's sort of the father--", "start": 3357.49, "duration": 2.783}, {"text": "considered the\nfather of something", "start": 3360.273, "duration": 1.417}, {"text": "called zero-knowledge\nproofs, and said, no, you", "start": 3361.69, "duration": 1.968}, {"text": "can solve for this.", "start": 3363.658, "duration": 0.792}, {"text": "And Silvio actually\ntook a sabbatical", "start": 3364.45, "duration": 2.7}, {"text": "leave to create a cryptocurrency\nand a company around Algorand.", "start": 3367.15, "duration": 4.77}, {"text": "And I'm not sort of\nmarketing for him,", "start": 3371.92, "duration": 2.31}, {"text": "but I'm just commenting,\nthere's this debate.", "start": 3374.23, "duration": 2.97}, {"text": "Can you solve, basically,\nwhat Satoshi Nakamoto wanted--", "start": 3377.2, "duration": 4.45}, {"text": "decentralization in a scalable\nway and have it be secure?", "start": 3381.65, "duration": 6.18}, {"text": "So how does one\nassess use cases?", "start": 3387.83, "duration": 1.94}, {"text": "Because this class\nis ultimately about", "start": 3389.77, "duration": 1.77}, {"text": "sort of sorting through this.", "start": 3391.54, "duration": 1.433}, {"text": "Well, first he\nasked the question,", "start": 3392.973, "duration": 1.417}, {"text": "is the project a project that\nactually uses cryptocurrency,", "start": 3394.39, "duration": 4.26}, {"text": "or it services it?", "start": 3398.65, "duration": 1.16}, {"text": "And I give examples\nof companies that", "start": 3399.81, "duration": 3.08}, {"text": "are in custody, in software, in\nexchange operation, finances,", "start": 3402.89, "duration": 3.84}, {"text": "the crypto exchange.", "start": 3406.73, "duration": 2.33}, {"text": "Coinbase is both an\nexchange and custody.", "start": 3409.06, "duration": 2.55}, {"text": "Fidelity, one of the world's\nlargest asset managers,", "start": 3411.61, "duration": 3.12}, {"text": "said, we'll take custody and\nhold your cryptocurrencies.", "start": 3414.73, "duration": 4.61}, {"text": "So you could be on one\nside of the divide and say,", "start": 3419.34, "duration": 3.03}, {"text": "we're going to be even like\na hardware company BitMain", "start": 3422.37, "duration": 3.54}, {"text": "and create the\nhardware in this space.", "start": 3425.91, "duration": 4.42}, {"text": "Those are kind of used\nclassic strategy analysis", "start": 3430.33, "duration": 5.64}, {"text": "to think about those.", "start": 3435.97, "duration": 1.28}, {"text": "The sort of rougher\nside of this is,", "start": 3437.25, "duration": 3.25}, {"text": "how do you consider what\nare the strategic questions", "start": 3440.5, "duration": 2.52}, {"text": "about actually using\nblockchain technology?", "start": 3443.02, "duration": 3.99}, {"text": "What are the value\ncreation propositions?", "start": 3447.01, "duration": 2.7}, {"text": "And I think it's\nembedded in this--", "start": 3449.71, "duration": 2.01}, {"text": "is it worthwhile to have\ndecentralized computing", "start": 3451.72, "duration": 2.91}, {"text": "versus centralized computing?", "start": 3454.63, "duration": 2.63}, {"text": "Is there an area\nthat you think has", "start": 3457.26, "duration": 2.59}, {"text": "such high economic rents that\na decentralized competitor can", "start": 3459.85, "duration": 4.77}, {"text": "come in?", "start": 3464.62, "duration": 1.68}, {"text": "You could create the case that\nif Uber and Lyft didn't exist", "start": 3466.3, "duration": 3.51}, {"text": "today, that Uber and\nLyft, you could say,", "start": 3469.81, "duration": 2.46}, {"text": "could be created on a\ndecentralized ledger system.", "start": 3472.27, "duration": 5.0}, {"text": "But nobody truly had control\nof the ledger system,", "start": 3477.27, "duration": 2.91}, {"text": "and all the ride sharing could\nbe with drivers and users", "start": 3480.18, "duration": 6.57}, {"text": "using that decentralized app.", "start": 3486.75, "duration": 2.19}, {"text": "But then again, who would\nhave actually gone into city", "start": 3488.94, "duration": 4.97}, {"text": "after city, airport\nafter airport,", "start": 3493.91, "duration": 2.7}, {"text": "and should have done what\nUber and Lyft and others have", "start": 3496.61, "duration": 2.76}, {"text": "done to get into the system?", "start": 3499.37, "duration": 3.42}, {"text": "So I think the basic value\nquestion is centralization", "start": 3502.79, "duration": 3.56}, {"text": "versus decentralization,\nand secondly,", "start": 3506.35, "duration": 2.94}, {"text": "are you filling a gap in\nthe fiat currency system?", "start": 3509.29, "duration": 4.11}, {"text": "Fiat currencies\nwork pretty well.", "start": 3513.4, "duration": 3.28}, {"text": "Now, we're going to talk in\nthe next class about the pain", "start": 3516.68, "duration": 2.93}, {"text": "points.", "start": 3519.61, "duration": 0.84}, {"text": "And there are a lot of pain\npoints in the payment system", "start": 3520.45, "duration": 3.68}, {"text": "that take considerable\nchallenges", "start": 3524.13, "duration": 4.0}, {"text": "and costs to overcome.", "start": 3528.13, "duration": 3.12}, {"text": "Clearly, strategically what\nare the competitors doing--", "start": 3531.25, "duration": 2.31}, {"text": "traditional competitors,\nthose using blockchain.", "start": 3533.56, "duration": 3.03}, {"text": "Why use append-only\nlogs, this invention", "start": 3536.59, "duration": 3.51}, {"text": "of this ledger system?", "start": 3540.1, "duration": 1.23}, {"text": "Why have multiple-party\nconsensus?", "start": 3541.33, "duration": 2.25}, {"text": "Multiple-party\nconsensus is a cost.", "start": 3543.58, "duration": 4.48}, {"text": "So if you're going to\nuse it for trade finance,", "start": 3548.06, "duration": 3.48}, {"text": "you're going to try to\nsolve something and trade", "start": 3551.54, "duration": 2.0}, {"text": "finance for instance, what is\nit solving, what are the costs?", "start": 3553.54, "duration": 5.13}, {"text": "It can lower verification\nand networking cost.", "start": 3558.67, "duration": 3.37}, {"text": "That's the core\nof its economics.", "start": 3562.04, "duration": 2.69}, {"text": "But it comes with some cost.", "start": 3564.73, "duration": 2.76}, {"text": "There are also a series of\ntactical considerations--", "start": 3567.49, "duration": 3.0}, {"text": "literally, what data\nis going to be put in?", "start": 3570.49, "duration": 2.42}, {"text": "Who is the multiple\nstakeholders?", "start": 3572.91, "duration": 3.01}, {"text": "What are the trade-offs?", "start": 3575.92, "duration": 2.13}, {"text": "And I think what we've\nfound by and large", "start": 3578.05, "duration": 2.52}, {"text": "is there are not that many\nprojects that have taken off.", "start": 3580.57, "duration": 4.53}, {"text": "I have here a little\nbit deeper dive.", "start": 3585.1, "duration": 2.08}, {"text": "If you get so close to a project\nthat you think, all right,", "start": 3587.18, "duration": 2.84}, {"text": "now let's think about it--", "start": 3590.02, "duration": 1.56}, {"text": "I come back to this question\nabout multiple-party shared", "start": 3591.58, "duration": 3.15}, {"text": "ledgers.", "start": 3594.73, "duration": 1.89}, {"text": "In Bitcoin, the multiple-party\nshared ledger has worked", "start": 3596.62, "duration": 3.63}, {"text": "in part because there\nwas a desire to have", "start": 3600.25, "duration": 3.3}, {"text": "a censorship-resistant token--", "start": 3603.55, "duration": 2.22}, {"text": "a token that could be global,\ntruly move around the globe,", "start": 3605.77, "duration": 4.17}, {"text": "at times away from what the\nofficial sector might ban,", "start": 3609.94, "duration": 4.23}, {"text": "away from certain money\nlaundering anti-terrorism laws,", "start": 3614.17, "duration": 5.28}, {"text": "that's part of it--", "start": 3619.45, "duration": 1.54}, {"text": "but also that it was,\nat least initially,", "start": 3620.99, "duration": 2.78}, {"text": "hard to track and trace.", "start": 3623.77, "duration": 2.34}, {"text": "It's actually gotten easier\nto track and trace over time.", "start": 3626.11, "duration": 4.57}, {"text": "But really the\nquestion is, if you're", "start": 3630.68, "duration": 1.7}, {"text": "going to think about using\nblockchain technology,", "start": 3632.38, "duration": 2.73}, {"text": "what verification cost\nare you really lowering,", "start": 3635.11, "duration": 3.66}, {"text": "and why have this multiple-party\ndistributed ledger?", "start": 3638.77, "duration": 3.78}, {"text": "A little bit like a\nshared stock company", "start": 3642.55, "duration": 2.67}, {"text": "still has a lot\nof centralization.", "start": 3645.22, "duration": 2.31}, {"text": "You have thousands of people\nthat control a shared stock", "start": 3647.53, "duration": 3.24}, {"text": "company, this invention\nof several centuries ago,", "start": 3650.77, "duration": 3.22}, {"text": "but you still have\nthe management team", "start": 3653.99, "duration": 3.17}, {"text": "that controls it.", "start": 3657.16, "duration": 1.32}, {"text": "How do you deal with that here?", "start": 3658.48, "duration": 2.32}, {"text": "So, what have we found?", "start": 3660.8, "duration": 1.86}, {"text": "We found that the incumbents,\nbig finance, by and large,", "start": 3662.66, "duration": 4.13}, {"text": "have stayed over to the\nleft-hand side of this screen.", "start": 3666.79, "duration": 3.56}, {"text": "They've stayed towards\ntraditional databases.", "start": 3670.35, "duration": 3.22}, {"text": "They haven't gone to\nthe cryptocurrency sort", "start": 3673.57, "duration": 2.93}, {"text": "of side of this screen--", "start": 3676.5, "duration": 1.37}, {"text": "permissionless open protocols.", "start": 3677.87, "duration": 3.38}, {"text": "They're exploring a little\nbit the middle, what's", "start": 3681.25, "duration": 2.53}, {"text": "called private blockchain,\n\"private blockchain\" saying,", "start": 3683.78, "duration": 4.34}, {"text": "20 or 50 companies get together.", "start": 3688.12, "duration": 2.49}, {"text": "Maybe-- like in Australia,\nthere was much fanfare in 2016", "start": 3690.61, "duration": 6.96}, {"text": "into, actually, 2017,\nthere was much fanfare", "start": 3697.57, "duration": 3.6}, {"text": "that the Australian\nStock Exchange", "start": 3701.17, "duration": 2.01}, {"text": "would use a permissioned\nblockchain technology to update", "start": 3703.18, "duration": 4.89}, {"text": "their central clearing.", "start": 3708.07, "duration": 2.37}, {"text": "Now, many people\nwould tell you by 2020", "start": 3710.44, "duration": 2.25}, {"text": "that what the\nAustralians have done", "start": 3712.69, "duration": 2.88}, {"text": "was inspired by\nblockchain technology,", "start": 3715.57, "duration": 2.83}, {"text": "but it no longer looks\nlike blockchain technology.", "start": 3718.4, "duration": 2.45}, {"text": "It's a decentralized,\ndistributed database.", "start": 3720.85, "duration": 4.09}, {"text": "But what the Australian\nregulator said is,", "start": 3724.94, "duration": 2.6}, {"text": "we need somebody\nto control this.", "start": 3727.54, "duration": 2.07}, {"text": "We need a central controller--\nthe complete opposite", "start": 3729.61, "duration": 3.81}, {"text": "of what Satoshi Nakamoto\nwas talking about.", "start": 3733.42, "duration": 2.43}, {"text": "Nakamoto was saying\nno central authority.", "start": 3735.85, "duration": 2.64}, {"text": "But the Australians\nsaid, well this", "start": 3738.49, "duration": 1.68}, {"text": "is the central clearing,\nsort of the plumbing,", "start": 3740.17, "duration": 3.42}, {"text": "the central plumbing, of\nthe Australian stock market.", "start": 3743.59, "duration": 3.23}, {"text": "No, we need somebody who\nhas kind of the overall--", "start": 3746.82, "duration": 5.02}, {"text": "plays the overall referee\nrole, so to speak.", "start": 3751.84, "duration": 4.84}, {"text": "So incumbents by and large are\nusing traditional databases.", "start": 3756.68, "duration": 5.2}, {"text": "They're exploring some of\nthese permissioned databases.", "start": 3761.88, "duration": 2.82}, {"text": "They're not really\noff to the side.", "start": 3764.7, "duration": 3.622}, {"text": "Romain, any questions?", "start": 3768.322, "duration": 3.161}, {"text": "AUDIENCE: None so far.", "start": 3771.483, "duration": 0.917}, {"text": "We have 12 minutes left.", "start": 3772.4, "duration": 1.67}, {"text": "GARY GENSLER: All right.", "start": 3774.07, "duration": 1.0}, {"text": "So let me just say something\nabout central bank initiatives.", "start": 3775.07, "duration": 4.11}, {"text": "Central banks-- and we'll chat\nabout this a little bit more", "start": 3779.18, "duration": 3.42}, {"text": "when we do payments-- central\nbanks have taken note of this.", "start": 3782.6, "duration": 3.18}, {"text": "And they've thought both, can\nI use the blockchain technology", "start": 3785.78, "duration": 4.69}, {"text": "for our payment systems--", "start": 3790.47, "duration": 1.44}, {"text": "because central banks\nin most countries", "start": 3791.91, "duration": 2.22}, {"text": "control those payment systems--", "start": 3794.13, "duration": 3.37}, {"text": "or can we actually create\na digital currency?", "start": 3797.5, "duration": 3.24}, {"text": "At first, I mean,\nBitcoin was not", "start": 3800.74, "duration": 2.76}, {"text": "really on the radar\nof central bankers.", "start": 3803.5, "duration": 2.58}, {"text": "By 2018, it became on the\nradar because the market had", "start": 3806.08, "duration": 5.04}, {"text": "taken off and it was,\nfor a brief moment,", "start": 3811.12, "duration": 2.79}, {"text": "worth almost $1 trillion.", "start": 3813.91, "duration": 2.26}, {"text": "It's back down to $200 billion,\nnow but they took note.", "start": 3816.17, "duration": 4.58}, {"text": "And in some countries\nlike Sweden,", "start": 3820.75, "duration": 1.92}, {"text": "they really said, maybe we\nshould be doing something here.", "start": 3822.67, "duration": 3.69}, {"text": "We should be creating a crypto\nequivalent, a digital currency.", "start": 3826.36, "duration": 6.27}, {"text": "And one of the readings\nwas a Bank of International", "start": 3832.63, "duration": 3.09}, {"text": "Settlement reading, which\nshowed three different ways", "start": 3835.72, "duration": 3.03}, {"text": "that a central bank could\ndo a digital currency.", "start": 3838.75, "duration": 2.37}, {"text": "And this is just\nfor your reference", "start": 3841.12, "duration": 1.5}, {"text": "to remind you that it\nwas in the reading.", "start": 3842.62, "duration": 3.9}, {"text": "But going back to these\nprojects a little bit,", "start": 3846.52, "duration": 4.14}, {"text": "some of the projects\nare just papers.", "start": 3850.66, "duration": 5.22}, {"text": "Ecuador tried to do\na project, actually--", "start": 3855.88, "duration": 2.63}, {"text": "a dollar-denominated\ncryptocurrency.", "start": 3858.51, "duration": 4.57}, {"text": "And it failed because nobody\nin Ecuador wanted to use it.", "start": 3863.08, "duration": 4.23}, {"text": "Ecuador was already dollarized.", "start": 3867.31, "duration": 2.64}, {"text": "But the one to watch\nmost closely, China,", "start": 3869.95, "duration": 3.75}, {"text": "which might be a hybrid--\nand I'll go back to the chart", "start": 3873.7, "duration": 2.82}, {"text": "in a second--", "start": 3876.52, "duration": 1.08}, {"text": "China has announced they're\ndoing a digital currency", "start": 3877.6, "duration": 3.3}, {"text": "electronic payment.", "start": 3880.9, "duration": 1.71}, {"text": "It will be fully backed\nby the central bank.", "start": 3882.61, "duration": 3.51}, {"text": "It will be fully a\nrenminbi or digital block.", "start": 3886.12, "duration": 4.48}, {"text": "And in a sense, it may be as\nmuch a reaction to Bitcoin", "start": 3890.6, "duration": 5.61}, {"text": "as it's a reaction\nto Alipay and WeChat", "start": 3896.21, "duration": 3.33}, {"text": "Pay being dominant in the\nretail payment system in China.", "start": 3899.54, "duration": 5.09}, {"text": "And it's also a\nreaction to Facebook", "start": 3904.63, "duration": 2.3}, {"text": "that was starting something\ncalled the Libra project.", "start": 3906.93, "duration": 4.04}, {"text": "So this, again,\nis a central tenet", "start": 3910.97, "duration": 3.45}, {"text": "where I am, where I think of\nthis as that the central banks", "start": 3914.42, "duration": 4.5}, {"text": "are reacting in part because\nbig tech has been reacting", "start": 3918.92, "duration": 6.23}, {"text": "and startups are there.", "start": 3925.15, "duration": 1.98}, {"text": "And they're saying, maybe\nwe can do something better.", "start": 3927.13, "duration": 3.06}, {"text": "The opportunities that they\nsee, the opportunities is", "start": 3930.19, "duration": 3.31}, {"text": "that they say,\nwell, maybe we can", "start": 3933.5, "duration": 1.4}, {"text": "stay in the means of payment.", "start": 3934.9, "duration": 1.65}, {"text": "We can promote\ngreater competition,", "start": 3936.55, "duration": 2.55}, {"text": "and we can address\nsome pain points.", "start": 3939.1, "duration": 2.44}, {"text": "But on the other side,\nthey're really worried.", "start": 3941.54, "duration": 3.35}, {"text": "They're deeply\nworried that if they", "start": 3944.89, "duration": 2.76}, {"text": "offer the public a digital\nrepresentation of central bank", "start": 3947.65, "duration": 6.92}, {"text": "money, that they\nmight disintermediate", "start": 3954.57, "duration": 3.75}, {"text": "the commercial banks.", "start": 3958.32, "duration": 2.48}, {"text": "The central strategic\nquestion for central banks", "start": 3960.8, "duration": 3.04}, {"text": "is, can we offer the public\na digital representation", "start": 3963.84, "duration": 4.41}, {"text": "of that which is paper?", "start": 3968.25, "duration": 3.13}, {"text": "So I've covered central bank\ndigital currencies too quickly.", "start": 3971.38, "duration": 4.082}, {"text": "I'm going to come back\nto it when we talk", "start": 3975.462, "duration": 1.708}, {"text": "about payment systems as well.", "start": 3977.17, "duration": 3.51}, {"text": "But Romain, we only\nhave a few minutes", "start": 3980.68, "duration": 2.24}, {"text": "so I'm going to take questions.", "start": 3982.92, "duration": 3.2}, {"text": "AUDIENCE: Yeah, we have\na question from Victor.", "start": 3986.12, "duration": 2.9}, {"text": "AUDIENCE: Hi, professor.", "start": 3989.02, "duration": 1.55}, {"text": "I want to come back to this\npoint about handling databases", "start": 3990.57, "duration": 3.29}, {"text": "through a private\nblockchain network,", "start": 3993.86, "duration": 2.223}, {"text": "because I didn't fully\nunderstand how it would work.", "start": 3996.083, "duration": 2.167}, {"text": "Could you give me some\nmore guidance on it?", "start": 3998.25, "duration": 3.21}, {"text": "GARY GENSLER: So Satoshi\nNakamoto's concept", "start": 4001.46, "duration": 3.87}, {"text": "is that you could have\nhundreds or thousands of folks'", "start": 4005.33, "duration": 4.53}, {"text": "computers sharing a\ndatabase, and it's", "start": 4009.86, "duration": 3.06}, {"text": "an open database, and\nthat that database can", "start": 4012.92, "duration": 4.92}, {"text": "secure the ledger through this\nconcept of a log structure--", "start": 4017.84, "duration": 5.39}, {"text": "block of data,\nblock of data, block", "start": 4023.23, "duration": 1.99}, {"text": "of data with cryptography.", "start": 4025.22, "duration": 3.39}, {"text": "The commercial banks\nand the financial firms", "start": 4028.61, "duration": 3.18}, {"text": "said, we're not comfortable of\nhaving hundreds or thousands", "start": 4031.79, "duration": 4.83}, {"text": "of people share a database.", "start": 4036.62, "duration": 2.17}, {"text": "In fact, we can't.", "start": 4038.79, "duration": 0.86}, {"text": "Under various guidelines of\nprivacy, of data protection,", "start": 4039.65, "duration": 5.67}, {"text": "we can't have hundreds of\npeople share that database.", "start": 4045.32, "duration": 3.21}, {"text": "But they're looking\nat, maybe we can", "start": 4048.53, "duration": 3.48}, {"text": "have a shared form\nof cooperation,", "start": 4052.01, "duration": 4.11}, {"text": "or what somebody might\ncall coopetition.", "start": 4056.12, "duration": 2.67}, {"text": "We'll cooperate around the\ntrade finance platform,", "start": 4058.79, "duration": 5.31}, {"text": "and then we'll\ncompete on top of it", "start": 4064.1, "duration": 1.77}, {"text": "for the provision of lines of\ncredit, and trade financing,", "start": 4065.87, "duration": 6.22}, {"text": "and so on.", "start": 4072.09, "duration": 2.07}, {"text": "So they've come\ntogether and said,", "start": 4074.16, "duration": 1.62}, {"text": "maybe we can have a\nshared closed system", "start": 4075.78, "duration": 3.27}, {"text": "amongst 20 banks, 16 banks,\n30 banks, and the like.", "start": 4079.05, "duration": 4.14}, {"text": "And so there's five\nor six big consortiums", "start": 4083.19, "duration": 2.25}, {"text": "trying to put together a trade\nfinance private shared ledger.", "start": 4085.44, "duration": 5.21}, {"text": "Now, once you have\nthat, once you say,", "start": 4090.65, "duration": 3.43}, {"text": "it's only these 18\nfirms will share it--", "start": 4094.08, "duration": 4.22}, {"text": "this form of cooperating\non a shared database", "start": 4098.3, "duration": 3.479}, {"text": "but competing on top of it,\nthat form of coopetition--", "start": 4101.779, "duration": 4.051}, {"text": "you don't necessarily\nneed a token.", "start": 4105.83, "duration": 2.199}, {"text": "So there's no cryptocurrency,\nit's just a shared blockchain", "start": 4108.029, "duration": 3.2}, {"text": "technology database.", "start": 4111.229, "duration": 1.92}, {"text": "Some call it a Digital\nLedger Technology, DTP,", "start": 4113.149, "duration": 5.601}, {"text": "to contrast it with\ncryptocurrencies.", "start": 4118.75, "duration": 3.115}, {"text": "I'm a little bit looser in\nthe vocabulary, admittedly.", "start": 4121.865, "duration": 3.675}, {"text": "But that's how-- that's the\nconceptual framework for it,", "start": 4125.54, "duration": 4.14}, {"text": "if that helps.", "start": 4129.68, "duration": 1.29}, {"text": "AUDIENCE: Yeah, thank you.", "start": 4130.97, "duration": 1.117}, {"text": "GARY GENSLER: Let\nme just say a couple", "start": 4132.087, "duration": 1.583}, {"text": "of ground truths in close.", "start": 4133.67, "duration": 2.85}, {"text": "I really do think--", "start": 4136.52, "duration": 1.709}, {"text": "and I don't know which\nside to end up on,", "start": 4138.229, "duration": 2.161}, {"text": "Devin or Camilo's side,\nin terms of, is it money?", "start": 4140.39, "duration": 3.7}, {"text": "But I think Nakamoto\nsolved the payment riddle--", "start": 4144.09, "duration": 2.809}, {"text": "avoiding double spending.", "start": 4146.899, "duration": 1.321}, {"text": "It's lasted 12 years.", "start": 4148.22, "duration": 2.58}, {"text": "Whether you like it, whether\nyou love it, hate it, two is--", "start": 4150.8, "duration": 4.559}, {"text": "I'm sorry, Hassan--\nI'm kind of--", "start": 4155.359, "duration": 2.071}, {"text": "money is but a social\nand economic construct.", "start": 4157.43, "duration": 3.0}, {"text": "I'm deeply with\nPlato on that one.", "start": 4160.43, "duration": 3.509}, {"text": "But I respect those\nthat believe otherwise.", "start": 4163.939, "duration": 3.0}, {"text": "I mean, there's a\ngood debate that's", "start": 4166.939, "duration": 1.561}, {"text": "gone on a couple\nof thousand years.", "start": 4168.5, "duration": 2.22}, {"text": "We already live in an\nage of digital money.", "start": 4170.72, "duration": 2.7}, {"text": "And in fact, the corona\ncrisis will accelerate that.", "start": 4173.42, "duration": 4.915}, {"text": "We will still have\nphysical paper money,", "start": 4178.335, "duration": 2.655}, {"text": "but we'll use it less\nand less in transaction.", "start": 4180.99, "duration": 3.25}, {"text": "And physical paper money is more\nand more just a store of value.", "start": 4184.24, "duration": 5.119}, {"text": "We're not using\nphysical paper money", "start": 4189.359, "duration": 1.981}, {"text": "much as a medium of\nexchange right now.", "start": 4191.34, "duration": 3.73}, {"text": "Append-only logs and\nmulti-party consensus", "start": 4195.07, "duration": 2.42}, {"text": "actually does provide\nan alternative,", "start": 4197.49, "duration": 2.37}, {"text": "but it doesn't mean it's\neverybody's alternative.", "start": 4199.86, "duration": 2.4}, {"text": "It can address\nverification costs,", "start": 4202.26, "duration": 3.0}, {"text": "but it doesn't make sense to\nadopt it unless there's really", "start": 4205.26, "duration": 2.8}, {"text": "some viability and a value\nproposition of that shared", "start": 4208.06, "duration": 3.93}, {"text": "ledger system.", "start": 4211.99, "duration": 2.26}, {"text": "We didn't talk much about it,\nbut I will say one ground truth", "start": 4214.25, "duration": 3.14}, {"text": "is that the crypto markets--\nthat $200 billion market--", "start": 4217.39, "duration": 4.0}, {"text": "it's ripe with scams and frauds.", "start": 4221.39, "duration": 2.34}, {"text": "It just is.", "start": 4223.73, "duration": 2.23}, {"text": "And so what's happened by\n2020 is cryptocurrencies", "start": 4225.96, "duration": 3.44}, {"text": "have evolved to be a speculative\nasset class, generally", "start": 4229.4, "duration": 3.48}, {"text": "not that correlated\nwith equities and bonds.", "start": 4232.88, "duration": 2.82}, {"text": "And I'll give you one statistic.", "start": 4235.7, "duration": 1.53}, {"text": "The worldwide stock\nof gold, that gold", "start": 4237.23, "duration": 1.96}, {"text": "that could be in four\nOlympic-sized pools,", "start": 4239.19, "duration": 4.17}, {"text": "collectively is worth\n$9 or $10 trillion,", "start": 4243.36, "duration": 2.49}, {"text": "roughly, collectively.", "start": 4245.85, "duration": 2.71}, {"text": "So some people would say a\nspeculative store of value", "start": 4248.56, "duration": 2.54}, {"text": "that's only worth 2%\nof that, $200 billion,", "start": 4251.1, "duration": 4.14}, {"text": "might be worthwhile in a\nbig portfolio of a family", "start": 4255.24, "duration": 4.47}, {"text": "office or a hedge fund.", "start": 4259.71, "duration": 3.19}, {"text": "The ICO boom and bust\nraised about $30 billion.", "start": 4262.9, "duration": 4.16}, {"text": "Not much is being\nraised there now,", "start": 4267.06, "duration": 1.96}, {"text": "but it's worthwhile\nto take note of.", "start": 4269.02, "duration": 3.04}, {"text": "Most of this is\nlightly regulated,", "start": 4272.06, "duration": 2.19}, {"text": "and so retail investors are\nnot getting much protection.", "start": 4274.25, "duration": 3.54}, {"text": "I think that's unfortunate.", "start": 4277.79, "duration": 2.94}, {"text": "But I still come back\nto the last point.", "start": 4280.73, "duration": 1.82}, {"text": "I think it's been a\ncatalyst for change.", "start": 4282.55, "duration": 2.11}, {"text": "I think it might be one of\nthese technologies we look back", "start": 4284.66, "duration": 2.65}, {"text": "in decades and say, it was a\nremarkable catalyst for change", "start": 4287.31, "duration": 4.45}, {"text": "for central bankers,\nand to think through", "start": 4291.76, "duration": 2.73}, {"text": "whether it's trade finance\nor other areas in finance,", "start": 4294.49, "duration": 2.88}, {"text": "was their way to\nform some cooperation", "start": 4297.37, "duration": 3.39}, {"text": "and compete on top of\nit-- so coopetition?", "start": 4300.76, "duration": 4.02}, {"text": "But just like we didn't\nknow that the internet", "start": 4304.78, "duration": 3.36}, {"text": "and geolocation devices would\nlead to disruption in rides--", "start": 4308.14, "duration": 6.75}, {"text": "you know, Uber and Lyft, we\ncouldn't predict in the 1990s", "start": 4314.89, "duration": 4.32}, {"text": "that the taxicab\nbusiness in New York", "start": 4319.21, "duration": 1.98}, {"text": "was going to be\ncompletely disrupted.", "start": 4321.19, "duration": 3.0}, {"text": "We don't know what blockchain\ntechnology and cryptocurrencies", "start": 4324.19, "duration": 3.9}, {"text": "will disrupt later in the\n2020s or in the 2030s.", "start": 4328.09, "duration": 4.83}, {"text": "So that's kind of my wrap on it.", "start": 4332.92, "duration": 3.3}, {"text": "You can sort of\nget a sense of why", "start": 4336.22, "duration": 2.61}, {"text": "I'm not going to say I'm\na maximalist in this area.", "start": 4338.83, "duration": 4.29}, {"text": "But I'm also not all\nthe way a minimalist.", "start": 4343.12, "duration": 2.21}, {"text": "The minimalist would say, no,\nnone of these ground truths", "start": 4345.33, "duration": 2.98}, {"text": "matter.", "start": 4348.31, "duration": 0.96}, {"text": "I think it's a really important\ntechnology, if nothing else,", "start": 4349.27, "duration": 3.27}, {"text": "because it's been a\nremarkable catalyst for change", "start": 4352.54, "duration": 2.85}, {"text": "on how central banks and others\nthink about payment systems,", "start": 4355.39, "duration": 3.78}, {"text": "which we'll take up in our next", "start": 4359.17, "duration": 2.96}]
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+[{"text": "MICHALE FEE: So for\nthe next few lectures,", "start": 16.467, "duration": 1.933}, {"text": "we're going to be looking at\ndeveloping methods of studying", "start": 18.4, "duration": 5.63}, {"text": "the computational properties\nof networks of neurons.", "start": 24.03, "duration": 2.973}, {"text": "This is the outline for\nthe next few lectures.", "start": 27.003, "duration": 1.917}, {"text": "Today we are going to introduce\na method of studying networks", "start": 28.92, "duration": 5.61}, {"text": "called a rate model where\nwe basically replace", "start": 34.53, "duration": 5.97}, {"text": "spike trains with\nfiring rates in order", "start": 40.5, "duration": 2.49}, {"text": "to develop simple\nmathematical descriptions", "start": 42.99, "duration": 2.79}, {"text": "of neural networks.", "start": 45.78, "duration": 1.6}, {"text": "And we're going to start by\nintroducing that technique", "start": 47.38, "duration": 4.28}, {"text": "to the problem of studying\nfeed-forward neural networks.", "start": 51.66, "duration": 3.9}, {"text": "And we'll introduce the\nidea of perceptrons trance", "start": 55.56, "duration": 2.52}, {"text": "as a method of\ndeveloping networks that", "start": 58.08, "duration": 3.63}, {"text": "can classify their inputs.", "start": 61.71, "duration": 2.999}, {"text": "Then in the next\nlecture, we're going", "start": 64.709, "duration": 1.651}, {"text": "to turn to largely describing\nmathematical tools based", "start": 66.36, "duration": 6.93}, {"text": "on matrix operations and\nthe idea of basis sets.", "start": 73.29, "duration": 5.16}, {"text": "Matrix operations are very\nimportant for studying", "start": 78.45, "duration": 3.0}, {"text": "neural networks.", "start": 81.45, "duration": 0.81}, {"text": "But they're also\na fundamental tool", "start": 82.26, "duration": 2.76}, {"text": "for analyzing data\nand doing things", "start": 85.02, "duration": 2.76}, {"text": "like reducing the dimensionality\nof high dimensional data sets,", "start": 87.78, "duration": 4.0}, {"text": "including methods such as\nprincipal components analysis.", "start": 91.78, "duration": 4.82}, {"text": "So it's a very\npowerful set of methods", "start": 96.6, "duration": 4.08}, {"text": "that apply both to\nstudying the brain", "start": 100.68, "duration": 3.0}, {"text": "and to analyzing the data that\nwe get when we study the brain.", "start": 103.68, "duration": 5.85}, {"text": "And then finally we'll turn\nto a few lectures that focus", "start": 109.53, "duration": 4.83}, {"text": "on recurrent neural networks.", "start": 114.36, "duration": 1.32}, {"text": "These are networks where\nthe neurons connect", "start": 115.68, "duration": 3.93}, {"text": "to each other densely\nin a recurrent way,", "start": 119.61, "duration": 3.45}, {"text": "meaning a neuron will\nconnect to another neuron.", "start": 123.06, "duration": 2.22}, {"text": "And that neuron will connect\nback to the first neuron.", "start": 125.28, "duration": 2.37}, {"text": "And networks that\nhave that property", "start": 127.65, "duration": 2.4}, {"text": "have very interesting\ncomputational abilities.", "start": 130.05, "duration": 3.78}, {"text": "And we're going to study\nthat in the context of line", "start": 133.83, "duration": 2.43}, {"text": "attractors and short-term\nmemory and hopfield networks.", "start": 136.26, "duration": 7.02}, {"text": "So for today, the plan is\nto develop the rate model.", "start": 143.28, "duration": 6.06}, {"text": "We're going to show how we\ncan build receptive fields", "start": 149.34, "duration": 4.32}, {"text": "with feed forward\nnetworks that we've", "start": 153.66, "duration": 3.18}, {"text": "described with the rate model.", "start": 156.84, "duration": 1.74}, {"text": "We're going to take\na little detour", "start": 158.58, "duration": 3.51}, {"text": "and describe vector notation\nand vector algebra, which", "start": 162.09, "duration": 2.76}, {"text": "is very important for these\nmodels, and also for building", "start": 164.85, "duration": 4.47}, {"text": "up to the matrix\nmethods that we'll", "start": 169.32, "duration": 2.61}, {"text": "talk about in the next lecture.", "start": 171.93, "duration": 2.79}, {"text": "Again, we'll talk about neural\nnetworks for classification", "start": 174.72, "duration": 2.67}, {"text": "and introduce the\nidea of a perceptron.", "start": 177.39, "duration": 2.35}, {"text": "So that's for today.", "start": 179.74, "duration": 2.75}, {"text": "So I've already talked\nabout most of this.", "start": 182.49, "duration": 4.35}, {"text": "Why is it that we want\nto develop a simplified", "start": 186.84, "duration": 2.64}, {"text": "mathematical model of neurons\nthat we can study analytically?", "start": 189.48, "duration": 3.45}, {"text": "Well, the reason is that we can\nreally develop our intuition", "start": 192.93, "duration": 4.2}, {"text": "about how networks work.", "start": 197.13, "duration": 2.58}, {"text": "And that intuition\napplies not just", "start": 199.71, "duration": 2.79}, {"text": "to the very simplified\nmathematical model that we're", "start": 202.5, "duration": 2.76}, {"text": "developing, but also\napplies more broadly", "start": 205.26, "duration": 2.16}, {"text": "to real networks\nwith real neurons", "start": 207.42, "duration": 2.76}, {"text": "that actually generate spikes\nand interact with each other", "start": 210.18, "duration": 3.03}, {"text": "by the more complex\nbiophysical mechanisms that", "start": 213.21, "duration": 3.24}, {"text": "are going on in the brain.", "start": 216.45, "duration": 1.51}, {"text": "So a good example\nof this is how we", "start": 217.96, "duration": 2.0}, {"text": "simplified the detailed\nspiking neurons", "start": 219.96, "duration": 2.755}, {"text": "of the Hodgkin-Huxley\nmodel and approximate that", "start": 222.715, "duration": 4.025}, {"text": "as an integrate and\nfire model, which", "start": 226.74, "duration": 1.98}, {"text": "captures a lot of the\nproperties of real neurons.", "start": 228.72, "duration": 3.78}, {"text": "Simplifies it enough to\ndevelop an intuition,", "start": 232.5, "duration": 3.18}, {"text": "but captures a lot of\nthe important properties", "start": 235.68, "duration": 3.63}, {"text": "of real neural circuits.", "start": 239.31, "duration": 3.9}, {"text": "All right, so let's\nstart by developing", "start": 243.21, "duration": 3.65}, {"text": "the basic idea of a rate model.", "start": 246.86, "duration": 2.372}, {"text": "Let's start with two neurons.", "start": 249.232, "duration": 1.208}, {"text": "We have an input neuron\nand an output neuron.", "start": 250.44, "duration": 2.67}, {"text": "The input neuron has some\nfiring rate given by u.", "start": 253.11, "duration": 5.219}, {"text": "And the output neuron has\nsome firing rate given by v.", "start": 258.329, "duration": 3.75}, {"text": "So we're going to essentially\nignore the times of the spikes", "start": 262.079, "duration": 5.251}, {"text": "and describe the inputs\nand outputs of this network", "start": 267.33, "duration": 3.42}, {"text": "just with firing rates.", "start": 270.75, "duration": 2.4}, {"text": "You can think of the rate\nas just having units have", "start": 273.15, "duration": 2.61}, {"text": "spikes per second, for example.", "start": 275.76, "duration": 2.67}, {"text": "Those neurons, the input\nneuron and the output neuron,", "start": 278.43, "duration": 2.43}, {"text": "are connected to each\nother by a synapse.", "start": 280.86, "duration": 2.43}, {"text": "And we're going to replace\nall of the complex structure", "start": 283.29, "duration": 4.08}, {"text": "of synapses, vesicle release,\nneurotransmitter receptors,", "start": 287.37, "duration": 8.28}, {"text": "long-term depression\nand paired spike", "start": 295.65, "duration": 5.1}, {"text": "facilitation and\ndepression, all that stuff", "start": 300.75, "duration": 2.19}, {"text": "we're just going to ignore.", "start": 302.94, "duration": 1.59}, {"text": "And we're going to replace that\nsynapse with a synaptic weight", "start": 304.53, "duration": 3.93}, {"text": "w.", "start": 308.46, "duration": 0.5}, {"text": "Just to give you the simplest\nintuition of how a rate", "start": 313.38, "duration": 3.09}, {"text": "model works, there are\nmodels where we can just", "start": 316.47, "duration": 3.63}, {"text": "treat the firing rate\nof the output neuron,", "start": 320.1, "duration": 2.79}, {"text": "for example, as\nlinear in its input.", "start": 322.89, "duration": 3.61}, {"text": "And we can simplify\nthis even to the point", "start": 326.5, "duration": 3.68}, {"text": "where we can describe the\nfiring rate of the output neuron", "start": 330.18, "duration": 3.45}, {"text": "as the synaptic weight w times\nthe firing rate of the input", "start": 333.63, "duration": 4.65}, {"text": "neuron.", "start": 338.28, "duration": 0.88}, {"text": "So that's just to give you a\nflavor of where we're heading.", "start": 339.16, "duration": 4.53}, {"text": "And I'm going to justify\nhow we can do this", "start": 343.69, "duration": 4.13}, {"text": "and/or why we can do this.", "start": 347.82, "duration": 2.49}, {"text": "And then we're going\nto build this up", "start": 350.31, "duration": 1.98}, {"text": "from the case of one input\nneuron and one output neuron", "start": 352.29, "duration": 3.93}, {"text": "to the case where we can\nhave many input neurons", "start": 356.22, "duration": 2.19}, {"text": "and many output neurons.", "start": 358.41, "duration": 1.22}, {"text": "So how do we justify going\nfrom spikes to firing rates?", "start": 363.05, "duration": 4.23}, {"text": "So remember that the response\nof a real output neuron,", "start": 367.28, "duration": 5.58}, {"text": "a real neuron, to a\nsingle spike at its input,", "start": 372.86, "duration": 3.99}, {"text": "is some change in the\npostsynaptic conductance that", "start": 376.85, "duration": 2.76}, {"text": "follows an input spike.", "start": 379.61, "duration": 1.35}, {"text": "And in our model\nof a synapse, we", "start": 380.96, "duration": 2.52}, {"text": "described that the input spike\nproduces a transient increase", "start": 383.48, "duration": 5.94}, {"text": "in the synaptic conductance.", "start": 389.42, "duration": 2.31}, {"text": "And that synaptic\nconductance we modeled", "start": 391.73, "duration": 2.37}, {"text": "as a simple step increase\nin the conductance", "start": 394.1, "duration": 3.84}, {"text": "followed by an exponential\ndecay as the neurotransmitter", "start": 397.94, "duration": 4.41}, {"text": "gradually unbinds from the\nneurotransmitter receptors.", "start": 402.35, "duration": 5.1}, {"text": "So we have a transient change\nin the synaptic conductance.", "start": 407.45, "duration": 3.81}, {"text": "That's just a\nmaximum conductance", "start": 411.26, "duration": 1.92}, {"text": "times an exponential decay.", "start": 413.18, "duration": 3.81}, {"text": "Now remember that we wrote\ndown the postsynaptic--", "start": 416.99, "duration": 2.94}, {"text": "we can write down the\npostsynaptic current that", "start": 419.93, "duration": 2.73}, {"text": "results from this synaptic input\nas the synaptic conductance", "start": 422.66, "duration": 4.44}, {"text": "times v minus e synapse, the\nsynaptic reversal potential.", "start": 427.1, "duration": 5.58}, {"text": "In moving forward\nin this model, we're", "start": 437.53, "duration": 2.32}, {"text": "not going to worry about\nsynaptic saturation.", "start": 439.85, "duration": 3.76}, {"text": "So we're just going to imagine\nthat the synaptic current is", "start": 443.61, "duration": 2.93}, {"text": "just proportional to the\nsynaptic conductance.", "start": 446.54, "duration": 6.9}, {"text": "So now we can write\nthe conductance", "start": 453.44, "duration": 2.04}, {"text": "as just some weight times\na kernel that is just", "start": 455.48, "duration": 7.59}, {"text": "some kernel of unit area.", "start": 463.07, "duration": 2.2}, {"text": "So what we've done here is we've\njust taken the synaptic current", "start": 465.27, "duration": 3.41}, {"text": "and we've written\nit as a constant,", "start": 468.68, "duration": 2.4}, {"text": "a synaptic weight, times\nan exponentially decaying", "start": 471.08, "duration": 3.9}, {"text": "kernel of area, area 1.", "start": 474.98, "duration": 2.06}, {"text": "So now if we have a train of\nspikes at the input instead", "start": 481.17, "duration": 3.87}, {"text": "of a single spike,\nwe can write down", "start": 485.04, "duration": 2.58}, {"text": "that train of spikes,\nthe spike train,", "start": 487.62, "duration": 2.19}, {"text": "as a sum of delta\nfunctions where", "start": 489.81, "duration": 1.8}, {"text": "the spike times are t sub i.", "start": 491.61, "duration": 2.82}, {"text": "And if you want to plot\nthe synaptic current", "start": 494.43, "duration": 3.75}, {"text": "as a function of\ntime, you would just", "start": 498.18, "duration": 1.92}, {"text": "take that spike train\ninput and do what", "start": 500.1, "duration": 3.39}, {"text": "with that linear kernel?", "start": 503.49, "duration": 1.56}, {"text": "We would convolve it, right?", "start": 505.05, "duration": 1.56}, {"text": "So we would take\nthat spike train,", "start": 506.61, "duration": 1.73}, {"text": "convolve it with that\nlittle exponential kernel.", "start": 508.34, "duration": 3.699}, {"text": "And that would give us\nthe synaptic current that", "start": 512.039, "duration": 2.431}, {"text": "results from that spike train.", "start": 514.47, "duration": 2.459}, {"text": "So let's think for\na moment about what", "start": 519.96, "duration": 2.849}, {"text": "this quantity is right here.", "start": 522.809, "duration": 1.35}, {"text": "What is k, this k which\nis a little kernel that", "start": 524.159, "duration": 5.341}, {"text": "has an exponential step, and\nthen an exponential decay?", "start": 529.5, "duration": 3.69}, {"text": "What do you get\nwhen you convolve", "start": 533.19, "duration": 2.34}, {"text": "that kind of smooth kernel\nwith this spike train here?", "start": 535.53, "duration": 6.548}, {"text": "What does that look like?", "start": 542.078, "duration": 1.042}, {"text": "We did that at one point\nwhen we were in class", "start": 543.12, "duration": 3.02}, {"text": "when we were talking about how\nyou would estimate something", "start": 546.14, "duration": 3.42}, {"text": "from a spike train.", "start": 549.56, "duration": 2.65}, {"text": "What is that?", "start": 552.21, "duration": 0.99}, {"text": "What is that\nquantity right there?", "start": 553.2, "duration": 1.99}, {"text": "It's sort of a smoothed\nversion of a spike train,", "start": 555.19, "duration": 3.44}, {"text": "which is how you would\ncalculate what, Habiba?", "start": 558.63, "duration": 2.88}, {"text": "AUDIENCE: Is it a window\nfor the spike train?", "start": 561.51, "duration": 3.101}, {"text": "MICHALE FEE: Yeah.", "start": 564.611, "duration": 1.199}, {"text": "It's windowed, but what is\nit that you are calculating", "start": 565.81, "duration": 3.06}, {"text": "when you take a spike\ntrain and you convolve it", "start": 568.87, "duration": 2.49}, {"text": "with some smooth window?", "start": 571.36, "duration": 2.22}, {"text": "AUDIENCE: Low-pass window?", "start": 573.58, "duration": 1.191}, {"text": "MICHALE FEE: It's like\na low-pass version", "start": 574.771, "duration": 2.529}, {"text": "of the spike train.", "start": 577.3, "duration": 0.93}, {"text": "And remember in the\nlecture on firing rates,", "start": 578.23, "duration": 5.67}, {"text": "we talked about how\nthat's a good way", "start": 583.9, "duration": 1.74}, {"text": "to get a time-dependent estimate\nof the firing rate of a neuron.", "start": 585.64, "duration": 5.23}, {"text": "We take the spike train\nand just convolve it", "start": 590.87, "duration": 2.63}, {"text": "with a smooth window.", "start": 593.5, "duration": 1.89}, {"text": "And if the area of that\nsmooth window is 1,", "start": 595.39, "duration": 3.24}, {"text": "then what we're doing\nis we're estimating", "start": 598.63, "duration": 1.71}, {"text": "the firing rate of the\nneuron as a function of time.", "start": 600.34, "duration": 4.99}, {"text": "Does that make sense?", "start": 605.33, "duration": 0.88}, {"text": "Yes?", "start": 606.21, "duration": 0.5}, {"text": "AUDIENCE: So k is just a kernel?", "start": 606.71, "duration": 2.8}, {"text": "MICHALE FEE: k is just is\nsmooth kernel that happens", "start": 609.51, "duration": 3.03}, {"text": "to have this exponential shape.", "start": 612.54, "duration": 2.021}, {"text": "AUDIENCE: Is it like [INAUDIBLE]", "start": 614.561, "duration": 4.149}, {"text": "MICHALE FEE: Well, that's\nour model for how a synapse--", "start": 618.71, "duration": 4.82}, {"text": "basically, what I'm\nsaying is that when", "start": 623.53, "duration": 2.55}, {"text": "you take a spike train and\nput it through a synapse, what", "start": 626.08, "duration": 2.49}, {"text": "comes out the other end\nis a smoothed version", "start": 628.57, "duration": 2.268}, {"text": "of the spike train.", "start": 630.838, "duration": 0.792}, {"text": "AUDIENCE: OK.", "start": 631.63, "duration": 0.542}, {"text": "MICHALE FEE: That's\nall this is saying.", "start": 632.172, "duration": 1.828}, {"text": "AUDIENCE: OK.", "start": 634.0, "duration": 1.09}, {"text": "[INAUDIBLE] they have\nthis area or quantity?", "start": 635.09, "duration": 4.38}, {"text": "MICHALE FEE: Yep.", "start": 639.47, "duration": 1.09}, {"text": "If k has-- you remember that\nif k has an area 1, then when", "start": 640.56, "duration": 6.97}, {"text": "you convolve evolve that\nkernel with the spike train,", "start": 647.53, "duration": 2.98}, {"text": "you get a number that has\nunits of spikes per second.", "start": 650.51, "duration": 7.65}, {"text": "And that quantity is an\nestimate of the local firing", "start": 658.16, "duration": 5.88}, {"text": "rate of the neuron.", "start": 664.04, "duration": 2.645}, {"text": "Does that make sense?", "start": 666.685, "duration": 0.875}, {"text": "So basically, we can\ntake this spike train,", "start": 671.78, "duration": 2.5}, {"text": "and by convolve it\nwith a smooth window,", "start": 674.28, "duration": 1.99}, {"text": "we can estimate the\nnumber of spikes", "start": 676.27, "duration": 2.82}, {"text": "per second in that window.", "start": 679.09, "duration": 3.88}, {"text": "So what do we have here?", "start": 682.97, "duration": 1.41}, {"text": "We have that the current\nis just a constant times", "start": 684.38, "duration": 3.74}, {"text": "an estimate of the\nfiring rate at that time.", "start": 688.12, "duration": 4.75}, {"text": "If k is a kernel, a\nsmooth kernel with an area", "start": 692.87, "duration": 3.39}, {"text": "normalized to 1, then\nthis quantity is just", "start": 696.26, "duration": 3.54}, {"text": "an estimate of the firing rate.", "start": 699.8, "duration": 2.16}, {"text": "So let's take a look at that.", "start": 701.96, "duration": 2.5}, {"text": "So here I have just made\na sample spike train", "start": 704.46, "duration": 3.56}, {"text": "with a bunch of spikes\nthat look like they're", "start": 708.02, "duration": 3.48}, {"text": "increasing in firing rate and\ndecreasing in firing rate.", "start": 711.5, "duration": 2.91}, {"text": "If we take that spike train and\nconvolve it with this kernel,", "start": 714.41, "duration": 3.54}, {"text": "you can see that you get\nthis sort of broad bump", "start": 717.95, "duration": 3.15}, {"text": "that looks like it gets higher\nin the middle where the firing", "start": 721.1, "duration": 3.21}, {"text": "rate is higher.", "start": 724.31, "duration": 0.66}, {"text": "And it's lower at the edges\nwhere the firing rate is lower.", "start": 724.97, "duration": 2.46}, {"text": "So the point is that you\ncan take a spike train", "start": 732.08, "duration": 4.1}, {"text": "and put it into a neuron.", "start": 736.18, "duration": 1.62}, {"text": "The response of the neuron\nis a smooth low-pass version", "start": 737.8, "duration": 6.3}, {"text": "of the rate of this\ninput spike train.", "start": 744.1, "duration": 4.48}, {"text": "And so you can think about\nwriting down the input", "start": 748.58, "duration": 4.59}, {"text": "to this neuron as a weight times\nthe firing rate of the input.", "start": 753.17, "duration": 6.37}, {"text": "So that was a way of writing\ndown the input to this output", "start": 759.54, "duration": 7.02}, {"text": "neuron from the input\nneuron, the current input.", "start": 766.56, "duration": 6.34}, {"text": "Now what is the firing rate of\nthe output neuron in response", "start": 772.9, "duration": 4.98}, {"text": "to that current injection?", "start": 777.88, "duration": 3.09}, {"text": "So that's what we're\ngoing to ask next.", "start": 780.97, "duration": 1.71}, {"text": "And you can remember that when\nwe talked about the integrate", "start": 782.68, "duration": 3.72}, {"text": "and fire model, we\nsaw that neurons", "start": 786.4, "duration": 7.24}, {"text": "in the approximation\nof large inputs", "start": 793.64, "duration": 2.67}, {"text": "have firing rate as\na function of current", "start": 796.31, "duration": 3.03}, {"text": "that looks like this.", "start": 799.34, "duration": 0.89}, {"text": "It's zero for inputs below\nthe threshold current.", "start": 800.23, "duration": 4.3}, {"text": "For input currents that\naren't large enough", "start": 804.53, "duration": 2.94}, {"text": "to drive the neuron\nto threshold,", "start": 807.47, "duration": 1.8}, {"text": "the neuron doesn't spike at all.", "start": 809.27, "duration": 2.28}, {"text": "And then above some\nthreshold, the neuron", "start": 811.55, "duration": 2.64}, {"text": "fires approximately linearly\nat higher input currents.", "start": 814.19, "duration": 5.28}, {"text": "So the way that we\nthink about this", "start": 822.49, "duration": 2.28}, {"text": "is that the input on is\nspiking at some rate.", "start": 824.77, "duration": 4.11}, {"text": "It goes through a synapse.", "start": 828.88, "duration": 1.86}, {"text": "That synapse smooths the input\nand produces some current", "start": 830.74, "duration": 4.32}, {"text": "in the postsynaptic\nneuron that's", "start": 835.06, "duration": 2.01}, {"text": "proportional approximately to\nthe firing rate of the input", "start": 837.07, "duration": 2.82}, {"text": "neuron.", "start": 839.89, "duration": 1.05}, {"text": "And the output neuron has\nsome output firing rate", "start": 840.94, "duration": 3.81}, {"text": "that's some function\nof the input current.", "start": 844.75, "duration": 2.085}, {"text": "So we can write down the firing\nrate of our output neuron,", "start": 850.05, "duration": 3.27}, {"text": "v. It's just equal to\nsome function of the input", "start": 853.32, "duration": 4.95}, {"text": "current, which is just some\nfunction of w times the firing", "start": 858.27, "duration": 5.11}, {"text": "rate of the input neuron.", "start": 863.38, "duration": 2.99}, {"text": "And that right there\nis the basic equation", "start": 866.37, "duration": 4.32}, {"text": "of the rate model.", "start": 870.69, "duration": 2.6}, {"text": "The output firing\nrate is some function", "start": 873.29, "duration": 4.65}, {"text": "of a weight times the firing\nrate of the input neuron.", "start": 877.94, "duration": 4.5}, {"text": "And everything else\nabout the rate model", "start": 887.61, "duration": 3.1}, {"text": "is just different rate models\nhave different numbers of input", "start": 890.71, "duration": 6.03}, {"text": "neurons where we have more than\none contribution to the input", "start": 896.74, "duration": 3.36}, {"text": "current.", "start": 900.1, "duration": 1.29}, {"text": "They can have many\noutput neurons.", "start": 901.39, "duration": 2.25}, {"text": "They can have different FI\ncurves for the output neurons.", "start": 903.64, "duration": 3.66}, {"text": "Some of them are\nnon-linear like this.", "start": 907.3, "duration": 2.64}, {"text": "Some of them are linear.", "start": 909.94, "duration": 1.0}, {"text": "And we're going to\ncome back and talk", "start": 910.94, "duration": 2.15}, {"text": "about the function of\ndifferent FI curves", "start": 913.09, "duration": 5.22}, {"text": "and why different FYI\ncurves are useful.", "start": 918.31, "duration": 2.618}, {"text": "Any questions about this?", "start": 920.928, "duration": 1.042}, {"text": "That's the basic idea.", "start": 921.97, "duration": 1.22}, {"text": "All right, good.", "start": 925.76, "duration": 2.47}, {"text": "So let's take one\nparticularly simple version", "start": 928.23, "duration": 6.78}, {"text": "of the rate model called\na linear rate model.", "start": 935.01, "duration": 2.82}, {"text": "And the linear rate model\nhas a particular FI curve.", "start": 937.83, "duration": 4.74}, {"text": "That FI curve says that the\nfiring rate of the neuron", "start": 942.57, "duration": 5.52}, {"text": "is linear in the input current.", "start": 948.09, "duration": 2.7}, {"text": "Now why is this a really\nweird model of a neuron?", "start": 950.79, "duration": 5.85}, {"text": "What's fundamentally\nnon-biological about this?", "start": 956.64, "duration": 5.82}, {"text": "AUDIENCE: Negative firing rate.", "start": 962.46, "duration": 1.85}, {"text": "MICHALE FEE: I'm hearing\na bunch of right answers", "start": 964.31, "duration": 2.05}, {"text": "at the same time.", "start": 966.36, "duration": 0.78}, {"text": "AUDIENCE: Negative firing rate.", "start": 967.14, "duration": 1.292}, {"text": "MICHALE FEE: This\nneuron is allowed", "start": 968.432, "duration": 4.368}, {"text": "to fire at a\nnegative firing rate", "start": 972.8, "duration": 2.91}, {"text": "if the input\ncurrent is negative.", "start": 975.71, "duration": 2.592}, {"text": "That's a pretty\ncrazy thing to do.", "start": 982.0, "duration": 2.68}, {"text": "Why do you think we\nwould want to do that?", "start": 984.68, "duration": 1.75}, {"text": "AUDIENCE: [INAUDIBLE]?", "start": 990.786, "duration": 2.42}, {"text": "MICHALE FEE: Well,\nno actually we do.", "start": 993.206, "duration": 2.374}, {"text": "So you can have\ninhibitory inputs", "start": 995.58, "duration": 5.82}, {"text": "that produce outward currents\nthat hyperpolarize the neuron.", "start": 1001.4, "duration": 4.08}, {"text": "Any thoughts about that?", "start": 1005.48, "duration": 3.9}, {"text": "It turns out that as soon as\nyou have your output neurons", "start": 1009.38, "duration": 4.5}, {"text": "have this kind of FI\ncurve, a linear FI curve,", "start": 1013.88, "duration": 4.32}, {"text": "then the math\nbecomes super simple.", "start": 1018.2, "duration": 3.43}, {"text": "You can write down very\ncomplex networks of neurons", "start": 1021.63, "duration": 4.07}, {"text": "with a bunch of linear\ndifferential equations.", "start": 1025.7, "duration": 4.08}, {"text": "And it becomes very\neasy to write down", "start": 1029.78, "duration": 2.94}, {"text": "what the solution is to\nhow a network behaves", "start": 1032.72, "duration": 5.34}, {"text": "as a function of its inputs.", "start": 1038.06, "duration": 2.68}, {"text": "And we're going to spend\na lot of time working", "start": 1040.74, "duration": 4.079}, {"text": "with network models that have\nlinear FI curves because you", "start": 1044.819, "duration": 5.961}, {"text": "can develop a lot of intuition\nabout how networks behave", "start": 1050.78, "duration": 3.18}, {"text": "by using models like this.", "start": 1053.96, "duration": 1.83}, {"text": "As soon as you have\nmodels like this,", "start": 1055.79, "duration": 2.52}, {"text": "you can't solve the behavior\nof the network analytically.", "start": 1058.31, "duration": 4.44}, {"text": "You have to do everything\non the computer.", "start": 1062.75, "duration": 2.07}, {"text": "And it becomes very hard\nto derive general solutions", "start": 1064.82, "duration": 4.5}, {"text": "for how things behave.", "start": 1069.32, "duration": 2.24}, {"text": "So we're going to\nuse this model a lot.", "start": 1071.56, "duration": 4.3}, {"text": "And in this case again, for the\ncase of this two-neuron network", "start": 1081.45, "duration": 4.68}, {"text": "where we have one output neuron\nthat receives a synaptic input", "start": 1086.13, "duration": 4.17}, {"text": "from an input neuron, the\nfiring rate of the output neuron", "start": 1090.3, "duration": 2.64}, {"text": "is just w, the synaptic\nweight times the firing rate", "start": 1092.94, "duration": 2.91}, {"text": "of the input neuron.", "start": 1095.85, "duration": 1.001}, {"text": "And we're going to come\nback to non-linear neurons", "start": 1100.04, "duration": 3.69}, {"text": "because that\nnon-linearity actually", "start": 1103.73, "duration": 2.28}, {"text": "does really important things.", "start": 1106.01, "duration": 1.38}, {"text": "And we're going to talk\nabout what that does.", "start": 1107.39, "duration": 4.38}, {"text": "So now let's look at the\ncase where our output neuron", "start": 1111.77, "duration": 3.06}, {"text": "has not just one\ninput but actually", "start": 1114.83, "duration": 2.73}, {"text": "many inputs from a\nbunch of input neurons.", "start": 1117.56, "duration": 2.88}, {"text": "So here we have what\nwe call an input layer,", "start": 1120.44, "duration": 4.401}, {"text": "a layer of neurons\nin the input layer.", "start": 1124.841, "duration": 3.489}, {"text": "Each one of those neurons\nhas a firing rate--", "start": 1128.33, "duration": 2.91}, {"text": "u1, u2, u3, u4, u5.", "start": 1131.24, "duration": 2.67}, {"text": "Each of those neurons sends a\nsynapse onto our output neuron.", "start": 1138.05, "duration": 3.66}, {"text": "Each one of those synapses\nhas a synaptic weight.", "start": 1141.71, "duration": 3.43}, {"text": "This weight is w1.", "start": 1145.14, "duration": 2.48}, {"text": "And that's w2, w3, w4, and w5.", "start": 1147.62, "duration": 2.825}, {"text": "Now you can see that the total\ninput, the total current,", "start": 1153.36, "duration": 4.82}, {"text": "to this output\nneuron is just going", "start": 1158.18, "duration": 1.83}, {"text": "to be a sum of the inputs from\neach of the input neurons.", "start": 1160.01, "duration": 6.55}, {"text": "The total input is just\na sum of the inputs", "start": 1166.56, "duration": 3.08}, {"text": "from each of the input neuron.", "start": 1169.64, "duration": 1.4}, {"text": "So the synaptic current--", "start": 1171.04, "duration": 2.86}, {"text": "total synaptic current\ninto this neuron", "start": 1173.9, "duration": 1.71}, {"text": "is w1 times u1, plus w2\ntimes u2, plus w3 times u3,", "start": 1175.61, "duration": 9.25}, {"text": "plus all the rest.", "start": 1184.86, "duration": 2.24}, {"text": "So the response of\nour linear neuron,", "start": 1187.1, "duration": 7.41}, {"text": "the firing rate of\nour linear neuron,", "start": 1194.51, "duration": 2.25}, {"text": "is just a sum over\nall of those inputs.", "start": 1196.76, "duration": 5.78}, {"text": "So again, in this\ncase, we're going", "start": 1202.54, "duration": 2.37}, {"text": "to say that the total input\ncurrent to this neuron", "start": 1204.91, "duration": 3.15}, {"text": "is the sum over this.", "start": 1208.06, "duration": 1.98}, {"text": "But then because this\nis a linear neuron,", "start": 1210.04, "duration": 3.96}, {"text": "the firing rate is just\nequal to that current input.", "start": 1214.0, "duration": 4.465}, {"text": "Does that make sense?", "start": 1218.465, "duration": 0.875}, {"text": "So you can see that this\ndescription of the firing", "start": 1222.66, "duration": 3.36}, {"text": "rate of the output\nneuron is a sum over all", "start": 1226.02, "duration": 3.99}, {"text": "of those contributions.", "start": 1230.01, "duration": 1.11}, {"text": "It turns out that\nthis actually can", "start": 1231.12, "duration": 4.26}, {"text": "be written in a much more\ncompact way in vector notation.", "start": 1235.38, "duration": 3.608}, {"text": "What does that look like?", "start": 1238.988, "duration": 1.042}, {"text": "Does anyone know in vector\nnotation what that looks like?", "start": 1240.03, "duration": 2.6}, {"text": "AUDIENCE: Dot product.", "start": 1242.63, "duration": 1.07}, {"text": "MICHALE FEE: That's\na dot product.", "start": 1243.7, "duration": 1.417}, {"text": "That's right.", "start": 1245.117, "duration": 1.003}, {"text": "So in general, it's much\neasier to write these responses", "start": 1246.12, "duration": 4.92}, {"text": "in vector notation.", "start": 1251.04, "duration": 0.792}, {"text": "And so I'm just\ngoing to walk you", "start": 1251.832, "duration": 1.375}, {"text": "through some basics\nof vector notation", "start": 1253.207, "duration": 1.703}, {"text": "for those of you who might\nneed a few minutes of reminder.", "start": 1254.91, "duration": 2.655}, {"text": "Actually before we get\nto the vector notation,", "start": 1260.51, "duration": 1.98}, {"text": "I just want to\ndescribe how we can", "start": 1262.49, "duration": 3.06}, {"text": "use a simple network like this\nto build a receptive field.", "start": 1265.55, "duration": 4.42}, {"text": "So you remember that\nwhen we were talking", "start": 1269.97, "duration": 2.27}, {"text": "about receptive\nfields of neurons,", "start": 1272.24, "duration": 2.05}, {"text": "we described how\na neuron can have", "start": 1274.29, "duration": 3.65}, {"text": "a maximal response to a\nparticular pattern of input.", "start": 1277.94, "duration": 4.36}, {"text": "So let's say we\nhave a neuron that's", "start": 1282.3, "duration": 1.79}, {"text": "sensitive to visual inputs.", "start": 1284.09, "duration": 2.05}, {"text": "And as a function\nof one dimension,", "start": 1286.14, "duration": 1.76}, {"text": "let's say along the\nretina, this neuron", "start": 1287.9, "duration": 1.98}, {"text": "has a big response if light\ncomes in central field,", "start": 1289.88, "duration": 4.23}, {"text": "some inhibitory responsive\nlight comes in outside", "start": 1294.11, "duration": 3.15}, {"text": "of that central lobe.", "start": 1297.26, "duration": 2.73}, {"text": "Well, it turns out\nthat a very simple way", "start": 1299.99, "duration": 2.73}, {"text": "to build neurons that have\nreceptive fields like this,", "start": 1302.72, "duration": 5.43}, {"text": "for example, is to have\nan input layer that", "start": 1308.15, "duration": 5.05}, {"text": "projects to this neuron that\nhas this receptive field", "start": 1313.2, "duration": 4.95}, {"text": "and has a pattern\nof synaptic inputs", "start": 1318.15, "duration": 2.76}, {"text": "that corresponds to that\npattern in the field.", "start": 1320.91, "duration": 4.71}, {"text": "So you can see that\nif this neuron--", "start": 1325.62, "duration": 2.5}, {"text": "so let's say these are\nneurons in the retina,", "start": 1328.12, "duration": 2.18}, {"text": "let's say retinal\nganglion cells,", "start": 1330.3, "duration": 2.44}, {"text": "and this neuron is\nin the thalamus,", "start": 1332.74, "duration": 2.58}, {"text": "we can build a\nthalamic neuron that", "start": 1335.32, "duration": 2.07}, {"text": "has a center-surround\nreceptive field like this", "start": 1337.39, "duration": 4.5}, {"text": "by having let's\nsay this neuron has", "start": 1341.89, "duration": 4.53}, {"text": "a strong positive excitatory\nsynaptic weight onto our output", "start": 1346.42, "duration": 4.31}, {"text": "neuron.", "start": 1350.73, "duration": 0.5}, {"text": "So you can see that\nif you have light here", "start": 1351.23, "duration": 4.1}, {"text": "that corresponds to this neuron\nhaving a high firing rate,", "start": 1355.33, "duration": 3.48}, {"text": "that neuron is very effective\nat driving the output neuron.", "start": 1358.81, "duration": 3.76}, {"text": "And so the output neuron\nhas a positive component", "start": 1362.57, "duration": 3.35}, {"text": "of its receptor field\nright there in the middle.", "start": 1365.92, "duration": 2.71}, {"text": "Now if this neuron here, which\nis in this part of the retina,", "start": 1368.63, "duration": 4.28}, {"text": "if that neuron has a negative\nweight onto the output neuron,", "start": 1372.91, "duration": 3.24}, {"text": "then light coming in here\ndriving this neuron will", "start": 1376.15, "duration": 4.83}, {"text": "inhibit the output neuron.", "start": 1380.98, "duration": 2.98}, {"text": "So if you have a pattern of\nweights that looks like this,", "start": 1383.96, "duration": 4.17}, {"text": "0 minus 1, 2 minus 1,\n0, that this neuron", "start": 1388.13, "duration": 4.09}, {"text": "will have a receptive\nfield that looks like that", "start": 1392.22, "duration": 4.24}, {"text": "as a function of its inputs.", "start": 1396.46, "duration": 1.23}, {"text": "So that's a\non-dimensional example.", "start": 1400.87, "duration": 3.722}, {"text": "And you can see\nthat you write down", "start": 1404.592, "duration": 1.458}, {"text": "the output here\nas a weighted sum", "start": 1406.05, "duration": 2.94}, {"text": "of each one of those inputs.", "start": 1408.99, "duration": 1.86}, {"text": "This also works for two\ndimensional receptive fields.", "start": 1410.85, "duration": 3.34}, {"text": "For example, if we have\ninput from the retina that", "start": 1414.19, "duration": 2.87}, {"text": "looks like this where we have--", "start": 1417.06, "duration": 2.16}, {"text": "I guess this was excitatory\nhere in the center,", "start": 1419.22, "duration": 3.93}, {"text": "inhibitory around, you\ncan make a neuron that", "start": 1423.15, "duration": 3.36}, {"text": "has a two-dimensional\nreceptor field like this", "start": 1426.51, "duration": 3.24}, {"text": "by having inputs to\nthis neuron from all", "start": 1429.75, "duration": 3.75}, {"text": "of those different regions\nof the visual field that", "start": 1433.5, "duration": 4.68}, {"text": "have different weights\ncorresponding to positive", "start": 1438.18, "duration": 3.6}, {"text": "in the center.", "start": 1441.78, "duration": 1.08}, {"text": "So neurons in the\npositive synaptic weights", "start": 1442.86, "duration": 3.63}, {"text": "under the output neuron.", "start": 1446.49, "duration": 1.2}, {"text": "And neurons around the edges\nhave negative synaptic weights.", "start": 1447.69, "duration": 5.58}, {"text": "So we can build any receptive\nfield we want into a neuron", "start": 1453.27, "duration": 5.16}, {"text": "by just plugging in-- by\nputting in the right set", "start": 1458.43, "duration": 3.99}, {"text": "of synaptic weights.", "start": 1462.42, "duration": 2.9}, {"text": "Yes?", "start": 1465.32, "duration": 0.63}, {"text": "AUDIENCE: So would you\nrule out [INAUDIBLE]", "start": 1465.95, "duration": 12.454}, {"text": "MICHALE FEE: So in real life,\nI assume you mean in the brain?", "start": 1478.404, "duration": 3.076}, {"text": "AUDIENCE: Yeah.", "start": 1481.48, "duration": 0.906}, {"text": "MICHALE FEE: So in the\nbrain, we don't really", "start": 1482.386, "duration": 3.434}, {"text": "know how these\nweights are built.", "start": 1485.82, "duration": 2.83}, {"text": "So one idea is that\nthere are rules that", "start": 1488.65, "duration": 6.14}, {"text": "control the development\nof these circuits,", "start": 1494.79, "duration": 3.75}, {"text": "let's say, connections\nof bipolar cells", "start": 1498.54, "duration": 6.47}, {"text": "in the retina to\nretinal ganglion cells", "start": 1505.01, "duration": 1.95}, {"text": "that control how these\nweights are determined", "start": 1506.96, "duration": 4.05}, {"text": "to be positive or negative.", "start": 1511.01, "duration": 1.26}, {"text": "Negative weights are implemented\nby bipolar cells connected", "start": 1512.27, "duration": 4.98}, {"text": "to amacrine cells,\nwhich are inhibitory,", "start": 1517.25, "duration": 3.57}, {"text": "and then connect to\nthe retinal ganglion.", "start": 1520.82, "duration": 3.43}, {"text": "So there's a whole\ncircuit that gets", "start": 1524.25, "duration": 2.48}, {"text": "built in the retina that\ncontrols whether these weights", "start": 1526.73, "duration": 2.67}, {"text": "are positive or negative.", "start": 1529.4, "duration": 1.38}, {"text": "And those can be programmed by\ngenetic developmental programs.", "start": 1530.78, "duration": 5.67}, {"text": "They can also be controlled by\nexperience with visual stimuli.", "start": 1536.45, "duration": 8.11}, {"text": "So there's a lot\nwe don't understand", "start": 1544.56, "duration": 2.87}, {"text": "about how these\nweights are controlled", "start": 1547.43, "duration": 3.87}, {"text": "or set up or programmed.", "start": 1551.3, "duration": 3.0}, {"text": "But the way we think\nabout how receptive fields", "start": 1554.3, "duration": 3.99}, {"text": "of these neurons emerge is\nby controlling the weight", "start": 1558.29, "duration": 4.11}, {"text": "of those synaptic input.", "start": 1562.4, "duration": 2.1}, {"text": "That's the message here--", "start": 1564.5, "duration": 2.07}, {"text": "that receptive fields\nemerge from the pattern", "start": 1566.57, "duration": 5.88}, {"text": "of weights from an input\nlayer onto an output layer.", "start": 1572.45, "duration": 3.51}, {"text": "AUDIENCE: [INAUDIBLE]\nhow many [INAUDIBLE]", "start": 1578.93, "duration": 8.91}, {"text": "MICHALE FEE: If you're\ngoing to build a model,", "start": 1587.84, "duration": 2.02}, {"text": "let's say, of the retina.", "start": 1589.86, "duration": 2.57}, {"text": "So it just depends on how\nrealistic you want it to be.", "start": 1592.43, "duration": 3.35}, {"text": "If you wanted to make a model\nof a retinal ganglion cell,", "start": 1599.1, "duration": 2.62}, {"text": "you could try to build a\nmodel that has as many bipolar", "start": 1601.72, "duration": 4.05}, {"text": "neurons as are actually\nin the receptive field", "start": 1605.77, "duration": 6.27}, {"text": "of that retinal ganglion cell.", "start": 1612.04, "duration": 3.15}, {"text": "Or you could make a\nsimplified model that", "start": 1615.19, "duration": 3.27}, {"text": "only has 10 or 100 neurons.", "start": 1618.46, "duration": 3.3}, {"text": "Depends on what\nyou want to study.", "start": 1621.76, "duration": 3.54}, {"text": "All right any other questions?", "start": 1625.3, "duration": 1.695}, {"text": "And again, even for these\nmore complex models,", "start": 1632.32, "duration": 4.92}, {"text": "you can still write\ndown a simple rate model", "start": 1637.24, "duration": 2.91}, {"text": "formulation of the firing\nrate of the output neuron.", "start": 1640.15, "duration": 2.34}, {"text": "It's just a weighted sum\nof the input firing rate.", "start": 1642.49, "duration": 3.91}, {"text": "So each neuron in the input\nlayer fires at some rate.", "start": 1646.4, "duration": 5.61}, {"text": "It has a weight w.", "start": 1652.01, "duration": 1.415}, {"text": "To get the contribution\nof this neuron", "start": 1656.97, "duration": 2.033}, {"text": "to the firing rate\nof the output neuron,", "start": 1659.003, "duration": 1.667}, {"text": "you just take that input firing\nrate times the synaptic weight,", "start": 1660.67, "duration": 4.05}, {"text": "and add that up then for\nall the input layer neurons.", "start": 1664.72, "duration": 3.32}, {"text": "So as I said, we've\nbeen describing", "start": 1673.36, "duration": 2.4}, {"text": "the response of our linear\nneuron as this weighted sum.", "start": 1675.76, "duration": 3.0}, {"text": "And that's a little bit\ncumbersome to carry around.", "start": 1678.76, "duration": 4.27}, {"text": "So we're going to start using\nvector notation and matrix", "start": 1683.03, "duration": 3.23}, {"text": "notation to describe networks.", "start": 1686.26, "duration": 2.58}, {"text": "It's just much more compact.", "start": 1688.84, "duration": 3.24}, {"text": "So we're going to take a little\ndetour, talk about vectors.", "start": 1692.08, "duration": 3.96}, {"text": "So a vector is just a\ncollection of numbers.", "start": 1696.04, "duration": 2.88}, {"text": "The number of numbers is\ncalled the dimensionality", "start": 1698.92, "duration": 2.462}, {"text": "of the vector.", "start": 1701.382, "duration": 0.583}, {"text": "If a vector has\nonly two numbers,", "start": 1705.13, "duration": 2.58}, {"text": "then we can just plot\nthat vector in a plane.", "start": 1707.71, "duration": 4.725}, {"text": "So for a 2D vector, if that\nvector has two components, x1", "start": 1715.0, "duration": 5.1}, {"text": "and x2, then we can\nplot that vector", "start": 1720.1, "duration": 1.65}, {"text": "in that space of x1 and\nx2, put the origin at zero.", "start": 1721.75, "duration": 5.58}, {"text": "In this case, the vector\nhas two vector components", "start": 1727.33, "duration": 2.52}, {"text": "or elements, x1 and x2.", "start": 1729.85, "duration": 2.97}, {"text": "And in two dimensions we\ndescribe that as spaces,", "start": 1732.82, "duration": 4.68}, {"text": "as R2, the space of\ntwo real numbers.", "start": 1737.5, "duration": 3.42}, {"text": "We can write down that vector\nas a row in row vector notation.", "start": 1740.92, "duration": 5.7}, {"text": "So x is x1, x2.", "start": 1746.62, "duration": 4.39}, {"text": "We can write it as a\ncolumn vector, x1, x2,", "start": 1751.01, "duration": 4.07}, {"text": "organized on top of\neach other, like this.", "start": 1755.08, "duration": 2.94}, {"text": "Vector sums are very simple.", "start": 1758.02, "duration": 3.61}, {"text": "So if you have two\nvectors, x and y,", "start": 1761.63, "duration": 3.23}, {"text": "you can write down the sum\nof x and y is x plus y.", "start": 1764.86, "duration": 5.01}, {"text": "That's called the resultant.", "start": 1769.87, "duration": 1.59}, {"text": "X plus y it can be written like\nthis in column vector notation.", "start": 1771.46, "duration": 4.85}, {"text": "You can see that\nthe sum of x and y", "start": 1776.31, "duration": 2.65}, {"text": "is just an element by element\nsum of the vector elements.", "start": 1778.96, "duration": 6.26}, {"text": "It's called element\nby element addition.", "start": 1785.22, "duration": 2.83}, {"text": "Let's look at vector product.", "start": 1788.05, "duration": 1.39}, {"text": "So there are multiple\nways of taking", "start": 1789.44, "duration": 2.6}, {"text": "the product of two vectors.", "start": 1792.04, "duration": 2.64}, {"text": "There's an element by element\nproduct, an inner product,", "start": 1794.68, "duration": 3.66}, {"text": "an outer product that we'll\ncover in later lectures.", "start": 1798.34, "duration": 4.98}, {"text": "And also, something\ncalled the cross product", "start": 1803.32, "duration": 2.76}, {"text": "that's very common in physics.", "start": 1806.08, "duration": 1.71}, {"text": "But I have not yet seen the\napplication of a cross product", "start": 1807.79, "duration": 5.31}, {"text": "to neuroscience.", "start": 1813.1, "duration": 1.36}, {"text": "If anybody can find one of\nthose, I'll give extra credit.", "start": 1814.46, "duration": 5.69}, {"text": "Element by element product\nis called a Hadamard product.", "start": 1822.86, "duration": 3.69}, {"text": "So x times y is just the\nelement-by-element product", "start": 1826.55, "duration": 4.23}, {"text": "of the elements in\nthe two vectors.", "start": 1830.78, "duration": 5.108}, {"text": "In Matlab, that\nelement-by-element product", "start": 1835.888, "duration": 3.092}, {"text": "you compute by x dot star y.", "start": 1838.98, "duration": 3.63}, {"text": "Inner product or dot\nproduct looks like this.", "start": 1848.36, "duration": 2.92}, {"text": "So if we have two\ncolumn vectors,", "start": 1851.28, "duration": 2.75}, {"text": "the dot product of\nx and y is the sum", "start": 1854.03, "duration": 3.6}, {"text": "of the element-by-element\nproducts.", "start": 1857.63, "duration": 4.08}, {"text": "So x dot y is just x1\ntimes y1 plus x2 times y2,", "start": 1861.71, "duration": 6.24}, {"text": "and so on, plus xn times yn.", "start": 1867.95, "duration": 3.69}, {"text": "And that's that sum that we\nsaw earlier in our feed forward", "start": 1871.64, "duration": 8.15}, {"text": "network.", "start": 1879.79, "duration": 0.92}, {"text": "OK.", "start": 1880.71, "duration": 0.5}, {"text": "So notice that the dot\nproduct is a scalar.", "start": 1881.21, "duration": 3.66}, {"text": "It's a single number.", "start": 1884.87, "duration": 1.38}, {"text": "It's no longer a vector.", "start": 1886.25, "duration": 3.51}, {"text": "Products have some\nnice properties.", "start": 1889.76, "duration": 2.167}, {"text": "They're commutative.", "start": 1891.927, "duration": 0.833}, {"text": "So x.y is equal to y.x.", "start": 1892.76, "duration": 3.4}, {"text": "They're distributive\nso that vector w dotted", "start": 1896.16, "duration": 3.53}, {"text": "into the sum of two vectors\nis just the sum of the two", "start": 1899.69, "duration": 4.83}, {"text": "separate dot products.", "start": 1904.52, "duration": 1.8}, {"text": "So w dot x plus y\nis just w.x, w.y.", "start": 1906.32, "duration": 4.73}, {"text": "And it's also linear.", "start": 1911.05, "duration": 1.96}, {"text": "So if you have a x dot y\nthat is equal to a times", "start": 1913.01, "duration": 6.99}, {"text": "the quantity x.y.", "start": 1920.0, "duration": 0.87}, {"text": "So if you have vector x and\ny dotted into each other,", "start": 1923.47, "duration": 3.87}, {"text": "if you make one of those\nvectors twice as long,", "start": 1927.34, "duration": 2.34}, {"text": "then the dot product\nis just twice as big.", "start": 1929.68, "duration": 1.95}, {"text": "A little bit more\nabout inner products.", "start": 1934.79, "duration": 2.24}, {"text": "So we can also write\ndown the inner product", "start": 1937.03, "duration": 2.67}, {"text": "in matrix notation.", "start": 1939.7, "duration": 1.44}, {"text": "So x.y is a matrix\nproduct of a row vector.", "start": 1941.14, "duration": 6.93}, {"text": "Column vector, you remember\nhow to multiply two matrices.", "start": 1948.07, "duration": 3.75}, {"text": "You multiply the elements of\neach row times the elements", "start": 1951.82, "duration": 6.24}, {"text": "of each column.", "start": 1958.06, "duration": 1.18}, {"text": "So you can see that\nthis in matrix notation", "start": 1959.24, "duration": 2.33}, {"text": "is just the dot product\nof those two vectors.", "start": 1961.57, "duration": 3.26}, {"text": "In matrix notation,\nthis is a 1 by n matrix.", "start": 1964.83, "duration": 3.84}, {"text": "This is an n by 1.", "start": 1968.67, "duration": 1.53}, {"text": "So 1 row by n columns,\ntimes n rows by 1 column.", "start": 1970.2, "duration": 8.4}, {"text": "And that is equal to a 1 by 1\nmatrix, which is just a scalar.", "start": 1978.6, "duration": 5.43}, {"text": "All right, in\nMatlab, let me just", "start": 1984.03, "duration": 2.16}, {"text": "show you how to write\ndown these components.", "start": 1986.19, "duration": 3.4}, {"text": "So in this case, x is a column\nvector, a 1 by 3 column vector.", "start": 1989.59, "duration": 6.02}, {"text": "y is a 1 by 3 column vector.", "start": 1995.61, "duration": 2.31}, {"text": "You can calculate those\nvectors like this.", "start": 1997.92, "duration": 3.0}, {"text": "And z is x transpose times y.", "start": 2000.92, "duration": 5.76}, {"text": "And so that's how\nyou can write down", "start": 2006.68, "duration": 2.25}, {"text": "the dot product of two vectors.", "start": 2008.93, "duration": 4.59}, {"text": "What is the dot product\nof a vector with itself?", "start": 2020.14, "duration": 4.24}, {"text": "It's the square\nmagnitude of the vector.", "start": 2024.38, "duration": 5.03}, {"text": "So x is just the norm or\nmagnitude of the vector.", "start": 2029.41, "duration": 5.48}, {"text": "And you can see that the\nnorm of the vector is just--", "start": 2034.89, "duration": 4.11}, {"text": "you can think\nabout this as being", "start": 2039.0, "duration": 1.77}, {"text": "analogous to the\nPythagorean theorem.", "start": 2040.77, "duration": 5.73}, {"text": "The length of one\nside of a triangle", "start": 2046.5, "duration": 4.65}, {"text": "is just the sum of the\nsquares of all the sides,", "start": 2051.15, "duration": 6.46}, {"text": "the square root of that.", "start": 2057.61, "duration": 1.01}, {"text": "So a unit vector is a\nvector that has length 1.", "start": 2062.51, "duration": 4.5}, {"text": "So a unit vector\nby definition has", "start": 2067.01, "duration": 3.36}, {"text": "a magnitude of 1,\nwhich means its dot", "start": 2070.37, "duration": 2.34}, {"text": "product with itself is 1.", "start": 2072.71, "duration": 2.25}, {"text": "We can turn any vector\ninto a unit vector", "start": 2074.96, "duration": 2.19}, {"text": "by just taking that vector,\ndividing by its norm.", "start": 2077.15, "duration": 4.14}, {"text": "I'm going to always use this\nnotation with this little caret", "start": 2081.29, "duration": 3.99}, {"text": "symbol to represent\na unit vector.", "start": 2085.28, "duration": 2.59}, {"text": "So if you see a vector\nwith that little hat on it,", "start": 2087.87, "duration": 2.96}, {"text": "that means it's a unit vector.", "start": 2090.83, "duration": 3.409}, {"text": "You can express any vector as a\nproduct of a scalar, a length,", "start": 2094.239, "duration": 6.361}, {"text": "times a unit vector\nin that direction.", "start": 2100.6, "duration": 4.061}, {"text": "We can find the projection\nor component of any vector", "start": 2107.43, "duration": 4.35}, {"text": "in the direction of this\nunit vector as follows.", "start": 2111.78, "duration": 3.61}, {"text": "So if we have a\nunit vector x, we", "start": 2115.39, "duration": 2.87}, {"text": "can find the projection\nof a vector y", "start": 2118.26, "duration": 5.34}, {"text": "onto that unit vector x.", "start": 2123.6, "duration": 1.53}, {"text": "How do we do that?", "start": 2125.13, "duration": 0.88}, {"text": "We just find the normal\nprojection of that vector.", "start": 2126.01, "duration": 5.54}, {"text": "That distance right there\nis called the scalar", "start": 2131.55, "duration": 4.02}, {"text": "projection of y onto x.", "start": 2135.57, "duration": 2.445}, {"text": "If you write down the\nlength of the vector y,", "start": 2142.47, "duration": 2.91}, {"text": "the norm of the vector y in\nthe angle between y and x,", "start": 2145.38, "duration": 3.9}, {"text": "then the dot product y.x is\njust equal to the magnitude", "start": 2149.28, "duration": 4.89}, {"text": "of y times the cosine of the\nangle between the two vectors.", "start": 2154.17, "duration": 4.5}, {"text": "Just simple trigonometry.", "start": 2158.67, "duration": 4.82}, {"text": "We can also define what's called\nthe vector projection of y", "start": 2163.49, "duration": 3.77}, {"text": "onto x as follows.", "start": 2167.26, "duration": 2.44}, {"text": "So we just draw\nthat same picture.", "start": 2169.7, "duration": 2.67}, {"text": "So we can find the\nprojection of y onto x", "start": 2172.37, "duration": 3.77}, {"text": "and add that as a vector.", "start": 2176.14, "duration": 2.7}, {"text": "And that's just this\nscalar projection of y", "start": 2178.84, "duration": 3.99}, {"text": "onto x times a unit\nvector in the x direction.", "start": 2182.83, "duration": 5.13}, {"text": "So x actually is a unit\nvector in this example.", "start": 2187.96, "duration": 3.22}, {"text": "So this vector projection\nof y to x is just", "start": 2191.18, "duration": 3.95}, {"text": "defined as y dot x times x.", "start": 2195.13, "duration": 3.9}, {"text": "Any questions about that?", "start": 2199.03, "duration": 3.21}, {"text": "I'm guessing most of you have\nseen all of this stuff already.", "start": 2202.24, "duration": 3.49}, {"text": "But we're going to be\nusing these things a lot.", "start": 2205.73, "duration": 3.14}, {"text": "So I just want to make sure\nthat we're all on the same page.", "start": 2208.87, "duration": 2.5}, {"text": "And that's just a scalar\ntimes a unit vector.", "start": 2214.93, "duration": 2.74}, {"text": "Let me just give you a\nlittle bit of intuition", "start": 2221.07, "duration": 2.73}, {"text": "about dot products here.", "start": 2223.8, "duration": 1.75}, {"text": "So a dot product is\nrelated to the cosine", "start": 2225.55, "duration": 3.26}, {"text": "of the angle\nbetween two vectors,", "start": 2228.81, "duration": 1.56}, {"text": "as we talked about before.", "start": 2230.37, "duration": 1.96}, {"text": "The dot product\nis just magnitude", "start": 2232.33, "duration": 1.61}, {"text": "of x times the magnitude\nof y times the cosine", "start": 2233.94, "duration": 2.49}, {"text": "of the angle between them.", "start": 2236.43, "duration": 1.87}, {"text": "So the cosine of the\nangle between two vectors", "start": 2238.3, "duration": 3.85}, {"text": "is just the dot product divided\nby the product of the magnitude", "start": 2242.15, "duration": 6.42}, {"text": "of each of the two vectors.", "start": 2248.57, "duration": 1.9}, {"text": "So if x and y are unit\nvectors, the cosine", "start": 2250.47, "duration": 3.11}, {"text": "of the angle between them\nis just the dot product", "start": 2253.58, "duration": 2.43}, {"text": "of the unit vectors.", "start": 2256.01, "duration": 3.1}, {"text": "So again, if x and\ny are unit vectors,", "start": 2259.11, "duration": 2.0}, {"text": "then that dot product is\njust the cosine of the angle.", "start": 2261.11, "duration": 4.56}, {"text": "Orthogonality.", "start": 2265.67, "duration": 0.61}, {"text": "So two vectors are orthogonal,\nare perpendicular, if", "start": 2266.28, "duration": 4.4}, {"text": "and only if their\ndot product is 0.", "start": 2270.68, "duration": 1.96}, {"text": "So if we have two\nvectors x and y,", "start": 2272.64, "duration": 3.33}, {"text": "they are orthogonal if the angle\nbetween them is 90 degrees.", "start": 2275.97, "duration": 3.38}, {"text": "x.y is just proportional\nto the cosine of the angle.", "start": 2279.35, "duration": 3.97}, {"text": "Cosine of 90 degrees is zero.", "start": 2283.32, "duration": 2.42}, {"text": "So if two vectors\nare orthogonal,", "start": 2285.74, "duration": 3.15}, {"text": "then their dot\nproduct will be zero.", "start": 2288.89, "duration": 2.1}, {"text": "If their dot product\nis zero, then they're", "start": 2290.99, "duration": 2.17}, {"text": "orthogonal with each other.", "start": 2293.16, "duration": 3.33}, {"text": "And using the notation\nwe just developed,", "start": 2296.49, "duration": 3.12}, {"text": "the vector projection\nof y along x", "start": 2299.61, "duration": 3.06}, {"text": "is the zero vector, if those\ntwo vectors are orthogonal.", "start": 2302.67, "duration": 4.83}, {"text": "There is an intuition\nthat one can", "start": 2307.5, "duration": 3.12}, {"text": "think about in terms of the\nrelation between dot product", "start": 2310.62, "duration": 4.14}, {"text": "and correlation.", "start": 2314.76, "duration": 1.57}, {"text": "So the dot product is related\nto the statistical correlation", "start": 2316.33, "duration": 3.5}, {"text": "between the elements\nof those two vectors.", "start": 2319.83, "duration": 2.38}, {"text": "So if you have a\nvector x and y, you", "start": 2322.21, "duration": 4.53}, {"text": "can write down the cosine of\nthe angle between those two", "start": 2326.74, "duration": 2.73}, {"text": "vectors, again, as x.y over\nthe product of the norms.", "start": 2329.47, "duration": 4.07}, {"text": "And if you write\nthat out as sums,", "start": 2333.54, "duration": 2.71}, {"text": "you can see that\nthis is just the sum", "start": 2336.25, "duration": 1.83}, {"text": "of the element-by-element\nproducts--", "start": 2338.08, "duration": 2.26}, {"text": "that's the dot product--", "start": 2340.34, "duration": 1.4}, {"text": "divided by the norm of\nx and the norm of y.", "start": 2341.74, "duration": 4.2}, {"text": "And if you have taken\na statistics class,", "start": 2345.94, "duration": 3.25}, {"text": "you will recognize that\nas just the Pearson", "start": 2349.19, "duration": 3.29}, {"text": "correlation of a set of numbers\nx and a set of numbers y.", "start": 2352.48, "duration": 5.85}, {"text": "The dot product\nis closely related", "start": 2358.33, "duration": 2.88}, {"text": "to the correlation between\ntwo sets of numbers.", "start": 2361.21, "duration": 4.71}, {"text": "One other thing that\nI want to point out", "start": 2369.25, "duration": 3.78}, {"text": "coming back to the\nidea of using this feed", "start": 2373.03, "duration": 3.3}, {"text": "forward network as a\nway of receptive field,", "start": 2376.33, "duration": 3.63}, {"text": "you can see that the response\nof a neuron in this model", "start": 2379.96, "duration": 5.01}, {"text": "is just the dot product\nof the stimulus vector u.", "start": 2384.97, "duration": 5.54}, {"text": "The vector of input firing\nrates represents the stimulus,", "start": 2390.51, "duration": 5.11}, {"text": "the dot product of\nthe stimulus vector u", "start": 2395.62, "duration": 2.04}, {"text": "with the weight vector w.", "start": 2397.66, "duration": 1.74}, {"text": "So the firing rate of the\noutput neuron is just w.u.", "start": 2399.4, "duration": 4.49}, {"text": "So you can see that\nwhat this means is", "start": 2408.19, "duration": 2.64}, {"text": "that the firing rate\nof the output neuron", "start": 2410.83, "duration": 4.19}, {"text": "will be high if there is\na high degree of overlap", "start": 2415.02, "duration": 5.73}, {"text": "between the input, the\npattern of the input,", "start": 2420.75, "duration": 3.66}, {"text": "and the pattern of synaptic\nweights from the input layer", "start": 2424.41, "duration": 3.81}, {"text": "to the output neuron.", "start": 2428.22, "duration": 3.53}, {"text": "We can see that w.u is big\nwhen w and u are parallel,", "start": 2431.75, "duration": 6.58}, {"text": "are highly correlated, which\nmeans a neuron fires a lot when", "start": 2438.33, "duration": 5.73}, {"text": "the stimulus matches the pattern\nof those synaptic weights.", "start": 2444.06, "duration": 3.93}, {"text": "Now, so you can see\nthat for a given amount", "start": 2451.19, "duration": 3.09}, {"text": "of power in the stimulus--", "start": 2454.28, "duration": 2.61}, {"text": "so the power is just the\nsquare magnitude of u--", "start": 2456.89, "duration": 4.29}, {"text": "the stimulus that has the best\noverlap with the receptive", "start": 2461.18, "duration": 2.97}, {"text": "field, where cosine\nof that angle is 1,", "start": 2464.15, "duration": 4.17}, {"text": "produces the largest response.", "start": 2468.32, "duration": 1.56}, {"text": "And so we now have\nactually a definition", "start": 2472.96, "duration": 2.93}, {"text": "of the optimal stimulus\nof a neuron in terms", "start": 2475.89, "duration": 3.87}, {"text": "of the pattern of\nsynaptic weights.", "start": 2479.76, "duration": 2.61}, {"text": "In other words, the\noptimal stimulus", "start": 2482.37, "duration": 3.21}, {"text": "is one that's essentially\nproportional to the weight", "start": 2485.58, "duration": 3.45}, {"text": "matrix.", "start": 2489.03, "duration": 2.03}, {"text": "Any questions so far?", "start": 2491.06, "duration": 2.15}, {"text": "All right, so now let's\nturn to the question of how", "start": 2493.21, "duration": 4.21}, {"text": "we use neural networks to do\nsome interesting computation.", "start": 2497.42, "duration": 7.02}, {"text": "So classification is a\nvery important computation", "start": 2504.44, "duration": 5.52}, {"text": "that neural networks\ndo in the brain", "start": 2509.96, "duration": 4.92}, {"text": "and actually in the\napplication of neural networks", "start": 2514.88, "duration": 2.82}, {"text": "for technology.", "start": 2517.7, "duration": 2.46}, {"text": "So what does\nclassification mean?", "start": 2522.81, "duration": 2.0}, {"text": "So how does the brain--", "start": 2524.81, "duration": 2.32}, {"text": "how does a neural circuit\ndecide how a particular input--", "start": 2527.13, "duration": 8.13}, {"text": "let's say that it looks\nlike you might eat it.", "start": 2535.26, "duration": 4.91}, {"text": "How do we decide--", "start": 2540.17, "duration": 1.17}, {"text": "how do the neural\ncircuits in our brain", "start": 2541.34, "duration": 2.25}, {"text": "decide whether that\nthing that we're seeing", "start": 2543.59, "duration": 2.1}, {"text": "is something edible or\nsomething that will make us sick", "start": 2545.69, "duration": 5.28}, {"text": "based on past experience?", "start": 2550.97, "duration": 1.83}, {"text": "If we see something that\nlooks like an animal or a dog,", "start": 2552.8, "duration": 3.21}, {"text": "how do we know whether that's a\nfriendly puppy or a or a wolf?", "start": 2556.01, "duration": 6.06}, {"text": "So these are\nclassification problems.", "start": 2562.07, "duration": 3.85}, {"text": "And feed forward\ncircuits actually", "start": 2565.92, "duration": 2.03}, {"text": "can be very good\nat classification.", "start": 2567.95, "duration": 2.22}, {"text": "In fact, recent advances\nin training neural networks", "start": 2570.17, "duration": 5.43}, {"text": "have actually resulted in feed\nforward neural networks that", "start": 2575.6, "duration": 4.26}, {"text": "actually approach human\nperformance in terms", "start": 2579.86, "duration": 3.0}, {"text": "of their ability to make\ndecisions like this.", "start": 2582.86, "duration": 4.26}, {"text": "All right.", "start": 2590.93, "duration": 0.75}, {"text": "So basically, a\nfeed forward circuit", "start": 2591.68, "duration": 5.88}, {"text": "that does\nclassification like this", "start": 2597.56, "duration": 1.68}, {"text": "typically has an input layer.", "start": 2599.24, "duration": 2.65}, {"text": "It has a bunch of inputs that\nrepresent sensory stimulus.", "start": 2601.89, "duration": 4.43}, {"text": "And a bunch of output\nneurons that represent", "start": 2606.32, "duration": 3.36}, {"text": "different categorizations\nof that input stimulus.", "start": 2609.68, "duration": 4.74}, {"text": "So you can have a\nretinal input here.", "start": 2614.42, "duration": 2.88}, {"text": "Going to other\nlayers of a network.", "start": 2617.3, "duration": 2.91}, {"text": "And then at the end\nof that, you can", "start": 2620.21, "duration": 1.5}, {"text": "have a network that starts\nfiring when that input was", "start": 2621.71, "duration": 3.6}, {"text": "a dog, or starts firing\nanother neuron that", "start": 2625.31, "duration": 2.34}, {"text": "starts firing when that input\nwas a cat, or something else.", "start": 2627.65, "duration": 5.13}, {"text": "Now in general,\nclassification networks", "start": 2632.78, "duration": 4.03}, {"text": "that have one input layer\nand one output layer", "start": 2636.81, "duration": 3.0}, {"text": "can't do this problem.", "start": 2639.81, "duration": 2.01}, {"text": "You can't take a visual\ninput and have connections", "start": 2641.82, "duration": 5.22}, {"text": "to another layer of\nneurons that just light up", "start": 2647.04, "duration": 3.33}, {"text": "when the picture that the\nnetwork is seeing is a dog.", "start": 2650.37, "duration": 3.39}, {"text": "Another neuron lights\nup when it's a cat.", "start": 2653.76, "duration": 2.71}, {"text": "Generally, there are many\nlayers of neurons in between.", "start": 2656.47, "duration": 6.5}, {"text": "But today, we're going to\ntalk about a very simplified", "start": 2662.97, "duration": 4.5}, {"text": "version of the\nclassification problem", "start": 2667.47, "duration": 2.78}, {"text": "and build up to the sorts of\nnetworks that can actually", "start": 2670.25, "duration": 3.46}, {"text": "do those more complex problems.", "start": 2673.71, "duration": 3.27}, {"text": "So I just want to point out\nthat the obviously our brains", "start": 2676.98, "duration": 7.11}, {"text": "are very good at\nrecognizing things.", "start": 2684.09, "duration": 2.31}, {"text": "We do this all the time.", "start": 2686.4, "duration": 2.25}, {"text": "There are hundreds of objects\nin every visual scene.", "start": 2688.65, "duration": 3.0}, {"text": "And we're able to recognize\nevery one of those objects.", "start": 2691.65, "duration": 3.31}, {"text": "But it turns out that there\nare individual neurons--", "start": 2694.96, "duration": 3.35}, {"text": "so in this case, I\nalluded to the idea", "start": 2698.31, "duration": 3.18}, {"text": "that there are individual\nnones in this network that", "start": 2701.49, "duration": 3.0}, {"text": "light up when the\nsensory input is a dog", "start": 2704.49, "duration": 2.7}, {"text": "or light up when the\ninput is an elephant.", "start": 2707.19, "duration": 3.73}, {"text": "And it turns out that that's\nactually true in the brain.", "start": 2710.92, "duration": 3.92}, {"text": "So there have\nrecently been studies", "start": 2714.84, "duration": 3.9}, {"text": "where it's been\npossible to record", "start": 2718.74, "duration": 3.34}, {"text": "in parts of the human brain in\npatients that are undergoing", "start": 2722.08, "duration": 3.6}, {"text": "brain surgery for the\ntreatment of epilepsy", "start": 2725.68, "duration": 3.87}, {"text": "or tumors or things like\nthat where you have to go in", "start": 2729.55, "duration": 5.69}, {"text": "and find parts of the\nbrain that are defective,", "start": 2735.24, "duration": 4.42}, {"text": "find parts of the\nbrain that are healthy.", "start": 2739.66, "duration": 1.9}, {"text": "So when you do a\nsurgery, you can", "start": 2741.56, "duration": 1.97}, {"text": "be very careful to just\ndo surgery on the damaged", "start": 2743.53, "duration": 4.23}, {"text": "parts of the brain\nand not impact parts", "start": 2747.76, "duration": 2.79}, {"text": "of the brain that are healthy.", "start": 2750.55, "duration": 1.54}, {"text": "So there are cases now,\nmore and more commonly,", "start": 2752.09, "duration": 3.83}, {"text": "where neuroscientists can\nwork with neurosurgeons", "start": 2755.92, "duration": 3.0}, {"text": "to actually record from\nneurons in the brain", "start": 2758.92, "duration": 3.66}, {"text": "in these patients who are\nin preparation for surgery.", "start": 2762.58, "duration": 6.42}, {"text": "And so it's been\npossible to record", "start": 2769.0, "duration": 1.53}, {"text": "from neurons in the brain.", "start": 2770.53, "duration": 1.68}, {"text": "This was a study from\nItzhak Frieds lab at UCLA.", "start": 2772.21, "duration": 7.13}, {"text": "And this shows recording in\nthe right anterior hippocampus.", "start": 2779.34, "duration": 3.37}, {"text": "And what this lab did\nwas to find neurons.", "start": 2782.71, "duration": 6.01}, {"text": "So these were electrodes\nimplanted in the brain.", "start": 2788.72, "duration": 2.0}, {"text": "And then they basically\ntake these patients", "start": 2790.72, "duration": 2.43}, {"text": "and they show them thousands\nof pictures and look", "start": 2793.15, "duration": 3.3}, {"text": "at how their brains respond\nto different visual inputs.", "start": 2796.45, "duration": 3.682}, {"text": "So let me just show you\nwhat you're looking at.", "start": 2800.132, "duration": 1.958}, {"text": "These are just different\npictures of celebrities.", "start": 2802.09, "duration": 4.23}, {"text": "There's Luke Skywalker, Mother\nTeresa, and some others.", "start": 2806.32, "duration": 8.475}, {"text": "This paper is getting old\nenough that you may not", "start": 2817.508, "duration": 2.042}, {"text": "recognize most of these people.", "start": 2819.55, "duration": 2.31}, {"text": "But if you record from\nneurons in the brain,", "start": 2821.86, "duration": 3.78}, {"text": "you can see that--", "start": 2825.64, "duration": 1.31}, {"text": "so what do you see here?", "start": 2826.95, "duration": 3.295}, {"text": "I think that's Oprah.", "start": 2830.245, "duration": 0.875}, {"text": "The image is flashed up on\nthe screen for about a second.", "start": 2831.12, "duration": 3.7}, {"text": "You record this neuron spiking.", "start": 2834.82, "duration": 2.61}, {"text": "Here you see a couple spikes.", "start": 2837.43, "duration": 2.47}, {"text": "Here's when the image\nwas actually presented.", "start": 2839.9, "duration": 2.33}, {"text": "And here's where the\nimage was turned off.", "start": 2842.23, "duration": 2.07}, {"text": "You can see different trials.", "start": 2844.3, "duration": 1.753}, {"text": "So this neuron actually\nhad a little bit", "start": 2846.053, "duration": 1.667}, {"text": "of a response\nright there shortly", "start": 2847.72, "duration": 1.83}, {"text": "after the stimulus\nwas turned on.", "start": 2849.55, "duration": 3.58}, {"text": "But you can see there's not that\nmuch response in these neurons.", "start": 2853.13, "duration": 5.13}, {"text": "But when they flashed\na different stimulus--", "start": 2858.26, "duration": 3.54}, {"text": "anybody know who that is?", "start": 2861.8, "duration": 3.26}, {"text": "That's Halle Berry.", "start": 2865.06, "duration": 0.96}, {"text": "Look at this neuron.", "start": 2868.66, "duration": 2.82}, {"text": "Every time you\nshow this picture,", "start": 2871.48, "duration": 1.41}, {"text": "that neuron fires off a\ncouple spikes very precisely.", "start": 2872.89, "duration": 4.54}, {"text": "If you look at the\nhistogram, these", "start": 2877.43, "duration": 2.3}, {"text": "are histograms underneath\nshowing as a function of time", "start": 2879.73, "duration": 4.47}, {"text": "relative to the onset\nof the stimulus,", "start": 2884.2, "duration": 1.89}, {"text": "you could see that this\nneuron very reliably spikes.", "start": 2886.09, "duration": 2.58}, {"text": "There's a different\npicture of Halle Berry.", "start": 2888.67, "duration": 2.34}, {"text": "Neuron spikes.", "start": 2891.01, "duration": 1.29}, {"text": "Different picture,\nneuron spikes.", "start": 2892.3, "duration": 2.19}, {"text": "Another picture, neuron spikes.", "start": 2894.49, "duration": 1.96}, {"text": "A line drawing of Halle\nBerry, the neuron spikes.", "start": 2899.89, "duration": 5.15}, {"text": "Catwoman, the neuron spikes.", "start": 2905.04, "duration": 5.34}, {"text": "The text, Halle Berry,\nthe neuron spikes.", "start": 2910.38, "duration": 3.38}, {"text": "It's amazing.", "start": 2918.903, "duration": 0.542}, {"text": "So this group got a\nlot of press for this", "start": 2923.43, "duration": 5.28}, {"text": "because they also found\nJennifer Aniston neurons.", "start": 2928.71, "duration": 5.34}, {"text": "They found other celebrities.", "start": 2934.05, "duration": 3.44}, {"text": "This is like some celebrity\npart of the brain.", "start": 2937.49, "duration": 3.08}, {"text": "No, it's actually\na part of the brain", "start": 2940.57, "duration": 1.73}, {"text": "where you have neurons that\nhave very sparse responses", "start": 2942.3, "duration": 3.3}, {"text": "to a wide range of things.", "start": 2945.6, "duration": 2.58}, {"text": "But they're extremely\nspecific to particular people", "start": 2948.18, "duration": 6.06}, {"text": "or categories or objects.", "start": 2954.24, "duration": 4.27}, {"text": "And it actually is consistent\nwith this old notion of what's", "start": 2958.51, "duration": 6.35}, {"text": "called the grandmother cell.", "start": 2964.86, "duration": 2.1}, {"text": "So back before people\nwere able to record", "start": 2966.96, "duration": 3.72}, {"text": "in the human brain like\nthis, there was speculation", "start": 2970.68, "duration": 3.51}, {"text": "that there might be\nneurons in the brain that", "start": 2974.19, "duration": 2.07}, {"text": "are so specific for\nparticular things,", "start": 2976.26, "duration": 2.61}, {"text": "that there might be one\nneuron in your brain", "start": 2978.87, "duration": 2.25}, {"text": "that responds when you\nsee your grandmother.", "start": 2981.12, "duration": 3.12}, {"text": "And so it turns out\nit's actually true.", "start": 2984.24, "duration": 3.0}, {"text": "There are neurons\nin your brain that", "start": 2987.24, "duration": 1.5}, {"text": "respond very specifically to\nparticular concepts or people", "start": 2988.74, "duration": 7.18}, {"text": "or things.", "start": 2995.92, "duration": 2.44}, {"text": "So the question of how\nthese kinds of neurons", "start": 2998.36, "duration": 5.81}, {"text": "acquire their responses is\nreally cool and interesting.", "start": 3004.17, "duration": 3.425}, {"text": "So that leads us to the\nidea of perceptrons.", "start": 3012.01, "duration": 6.48}, {"text": "Perceptron is the simplest\nnotion of how you can have", "start": 3018.49, "duration": 4.65}, {"text": "a neuron that responds to a\nparticular thing that detects", "start": 3023.14, "duration": 4.56}, {"text": "a particular thing and\nresponds when it sees it", "start": 3027.7, "duration": 3.71}, {"text": "and doesn't respond\nwhen it doesn't.", "start": 3031.41, "duration": 1.78}, {"text": "So let's start with the\nsimplest notion of a perceptron.", "start": 3035.72, "duration": 5.43}, {"text": "So how do we make a neuron that\nfires when it sees something--", "start": 3041.15, "duration": 3.38}, {"text": "let's say a dog--", "start": 3044.53, "duration": 2.49}, {"text": "and doesn't fire\nwhen there is no dog?", "start": 3047.02, "duration": 2.06}, {"text": "So in order to think about\nthis a little bit more,", "start": 3053.33, "duration": 2.47}, {"text": "so we can begin thinking\nabout this in the case", "start": 3055.8, "duration": 4.52}, {"text": "where we have a single neuron\ninput and a single output", "start": 3060.32, "duration": 4.23}, {"text": "neuron.", "start": 3064.55, "duration": 0.91}, {"text": "So if we have a single input\nneuron, then what comes in", "start": 3065.46, "duration": 3.29}, {"text": "has to be--", "start": 3068.75, "duration": 0.9}, {"text": "it can't be an image right?", "start": 3069.65, "duration": 1.32}, {"text": "An image is a high\ndimensional thing that", "start": 3070.97, "duration": 2.31}, {"text": "has many thousands of pixels.", "start": 3073.28, "duration": 4.29}, {"text": "So you can't write that\ndown as a simple model", "start": 3077.57, "duration": 4.98}, {"text": "with a single input neuron\nand a single output neuron.", "start": 3082.55, "duration": 3.01}, {"text": "So you need to do this\nclassification problem", "start": 3085.56, "duration": 2.21}, {"text": "in one-dimension.", "start": 3087.77, "duration": 0.98}, {"text": "So we can imagine\nthat we have an input", "start": 3088.75, "duration": 1.69}, {"text": "neuron that comes from, let's\nsay, some set of numbers--", "start": 3090.44, "duration": 6.725}, {"text": "I'll make up a story\nhere-- some set", "start": 3097.165, "duration": 1.975}, {"text": "of neurons that measure\nthe dogginess of an input.", "start": 3099.14, "duration": 4.53}, {"text": "So let's say that we\nhave a single input that", "start": 3103.67, "duration": 3.36}, {"text": "fires like crazy when it sees\nthis cute little guy here.", "start": 3107.03, "duration": 4.29}, {"text": "And fires at a\nnegative rate when", "start": 3111.32, "duration": 4.89}, {"text": "it sees that thing, which\ndoesn't look much like a dog.", "start": 3116.21, "duration": 4.42}, {"text": "So we have a single input\nthat's a measure of dogginess.", "start": 3120.63, "duration": 5.33}, {"text": "And now let's say that we\ntake this dogginess detector", "start": 3125.96, "duration": 3.515}, {"text": "and we point it\naround the world.", "start": 3129.475, "duration": 1.375}, {"text": "And we walk around outside\nwith our dogginess detector", "start": 3130.85, "duration": 2.74}, {"text": "and we make a bunch\nof measurements.", "start": 3133.59, "duration": 3.11}, {"text": "So we're going to see\nsomething that looks like this.", "start": 3136.7, "duration": 2.342}, {"text": "We're going to see a\nlot of measurements,", "start": 3139.042, "duration": 1.708}, {"text": "a lot of observations\ndown here that", "start": 3140.75, "duration": 2.13}, {"text": "are close to zero dogginess.", "start": 3142.88, "duration": 1.98}, {"text": "And we're going to\nsee a bump of things", "start": 3144.86, "duration": 2.7}, {"text": "up here that correspond to dogs.", "start": 3147.56, "duration": 1.74}, {"text": "Whenever we point our\ndogginess detector at a dog,", "start": 3149.3, "duration": 2.577}, {"text": "it's going to give us\na measurement up here.", "start": 3151.877, "duration": 1.833}, {"text": "And we're going to\nget a bunch of those.", "start": 3153.71, "duration": 1.98}, {"text": "And those things\ncorrespond to dogs.", "start": 3155.69, "duration": 2.76}, {"text": "So we need to build\na network that", "start": 3158.45, "duration": 2.82}, {"text": "fires when the input is\nup here and doesn't fire", "start": 3161.27, "duration": 3.63}, {"text": "when the input is down there.", "start": 3164.9, "duration": 1.25}, {"text": "So how do we do that?", "start": 3168.77, "duration": 3.12}, {"text": "So the central feature\nof classification", "start": 3171.89, "duration": 4.2}, {"text": "is this notion of binariness,\nof decision-making.", "start": 3176.09, "duration": 4.38}, {"text": "That it fires when you\nsee a dog and doesn't", "start": 3180.47, "duration": 3.63}, {"text": "fire when you don't see a dog.", "start": 3184.1, "duration": 2.28}, {"text": "So there exists a\nclassification boundary", "start": 3186.38, "duration": 2.79}, {"text": "in this stimulus space.", "start": 3189.17, "duration": 1.32}, {"text": "You can imagine that there's\nsome points along this", "start": 3190.49, "duration": 3.06}, {"text": "dimension above which you'll\nsay that that input is a dog,", "start": 3193.55, "duration": 3.93}, {"text": "below which you\nsay that it isn't.", "start": 3197.48, "duration": 3.12}, {"text": "And we can imagine that\nthat classification boundary", "start": 3200.6, "duration": 3.81}, {"text": "is right here.", "start": 3204.41, "duration": 1.06}, {"text": "It's a particular number.", "start": 3205.47, "duration": 1.59}, {"text": "It's a particular value\nof our dogginess detector,", "start": 3207.06, "duration": 3.5}, {"text": "above which we're\ngoing to call it a dog,", "start": 3210.56, "duration": 1.9}, {"text": "and below which we're going\nto call it something else.", "start": 3212.46, "duration": 4.97}, {"text": "How do we make this\nneuron respond by firing", "start": 3217.43, "duration": 6.01}, {"text": "when there's a dog and not\nfiring when there's no dog?", "start": 3223.44, "duration": 3.18}, {"text": "Can we use a linear neuron?", "start": 3226.62, "duration": 1.44}, {"text": "Can we use one of\nour linear neurons", "start": 3231.7, "duration": 2.64}, {"text": "that we just talked\nabout before?", "start": 3234.34, "duration": 3.09}, {"text": "We can't do that because a\nlinear neuron will always fire", "start": 3237.43, "duration": 4.33}, {"text": "more the bigger the input is.", "start": 3241.76, "duration": 2.69}, {"text": "And it will fire less\nif the dogginess is 0.", "start": 3244.45, "duration": 2.85}, {"text": "And it will even\nfire more negatively", "start": 3247.3, "duration": 1.92}, {"text": "if the dogginess\ninput is negative.", "start": 3249.22, "duration": 2.47}, {"text": "So a linear neuron is\nterrible for actually", "start": 3251.69, "duration": 2.66}, {"text": "making any decisions.", "start": 3254.35, "duration": 1.74}, {"text": "Linear neurons always go,\nah, well, maybe that's a dog.", "start": 3256.09, "duration": 5.58}, {"text": "Not really.", "start": 3261.67, "duration": 1.08}, {"text": "There's no decisions.", "start": 3262.75, "duration": 2.52}, {"text": "So in order to\nhave a decision, we", "start": 3265.27, "duration": 1.95}, {"text": "need to have a particular\nkind of neuron.", "start": 3267.22, "duration": 3.45}, {"text": "And that kind of neuron\nuses something very natural.", "start": 3270.67, "duration": 5.64}, {"text": "In biophysics, it's the\nspike threshold of neurons.", "start": 3276.31, "duration": 3.79}, {"text": "Neurons only fire when the\ninput is above some threshold,", "start": 3280.1, "duration": 5.48}, {"text": "generally.", "start": 3285.58, "duration": 0.6}, {"text": "There are neurons that\nare tonically active.", "start": 3286.18, "duration": 1.833}, {"text": "But let's not worry about those.", "start": 3288.013, "duration": 1.557}, {"text": "So many neurons only\nfire when the input", "start": 3289.57, "duration": 2.4}, {"text": "is above some threshold.", "start": 3291.97, "duration": 1.93}, {"text": "So for decision-making\nand classification,", "start": 3293.9, "duration": 2.87}, {"text": "a commonly used kind of neuron\ntakes this idea to an extreme.", "start": 3296.77, "duration": 6.75}, {"text": "So for perceptrons, we're\ngoing to use a simplified", "start": 3303.52, "duration": 3.24}, {"text": "model of a neuron\nthat's particularly", "start": 3306.76, "duration": 2.25}, {"text": "good at making decisions.", "start": 3309.01, "duration": 1.56}, {"text": "There's no if, ands,\nor buts about it.", "start": 3310.57, "duration": 3.26}, {"text": "It's either off or on.", "start": 3313.83, "duration": 2.71}, {"text": "It's called a binary unit.", "start": 3316.54, "duration": 2.63}, {"text": "And a binary unit uses\nwhat's called a step", "start": 3319.17, "duration": 3.84}, {"text": "function for its FI curve.", "start": 3323.01, "duration": 3.6}, {"text": "That step function is 0--", "start": 3326.61, "duration": 2.56}, {"text": "the output is 0 if the\ninput is zero or below.", "start": 3329.17, "duration": 4.07}, {"text": "And the output is 1 if\nthe input is above 0.", "start": 3333.24, "duration": 5.85}, {"text": "We can use that step\nfunction to create", "start": 3341.96, "duration": 3.54}, {"text": "a neuron that responds\nwhen the input is", "start": 3345.5, "duration": 2.91}, {"text": "above any threshold we want.", "start": 3348.41, "duration": 3.21}, {"text": "So we can write down the output\nfiring rate is this function,", "start": 3351.62, "duration": 6.81}, {"text": "a step function-- that\nfunction of a quantity that's", "start": 3358.43, "duration": 4.62}, {"text": "given by w times u, the synaptic\nweight times the input firing", "start": 3363.05, "duration": 4.65}, {"text": "rate, minus that threshold.", "start": 3367.7, "duration": 2.73}, {"text": "So you can see if\nw times u, which", "start": 3370.43, "duration": 2.61}, {"text": "is the input synaptic current,\nif that synaptic current is", "start": 3373.04, "duration": 4.82}, {"text": "above theta, then this\nargument to this function", "start": 3377.86, "duration": 7.22}, {"text": "is greater than 0,\nthen the neuron spikes.", "start": 3385.08, "duration": 3.12}, {"text": "If this argument is negative,\nthen the neuron doesn't spike.", "start": 3388.2, "duration": 3.77}, {"text": "So by changing theta, we can put\nthat decision boundary anywhere", "start": 3391.97, "duration": 5.98}, {"text": "we want.", "start": 3397.95, "duration": 1.525}, {"text": "Does that make sense?", "start": 3399.475, "duration": 0.875}, {"text": "Usually the way we do\nthis is we pick a theta.", "start": 3409.44, "duration": 5.04}, {"text": "We say our neuron\nhas a theta of 1.", "start": 3414.48, "duration": 3.39}, {"text": "And then we do everything else--", "start": 3417.87, "duration": 2.82}, {"text": "we do everything else\nwe're going to do", "start": 3420.69, "duration": 2.04}, {"text": "with this network with a theta.", "start": 3422.73, "duration": 2.5}, {"text": "So what I'm going to talk\nabout today are just two cases.", "start": 3425.23, "duration": 2.6}, {"text": "Where theta is a fixed\nnumber that's non-zero,", "start": 3427.83, "duration": 3.44}, {"text": "or theta that's a fixed\nnumber that is equal to 0.", "start": 3431.27, "duration": 2.815}, {"text": "So we're going to talk\nabout those two cases.", "start": 3434.085, "duration": 1.875}, {"text": "So the neuron fires\nwhen the input w", "start": 3439.05, "duration": 2.07}, {"text": "u is greater than theta.", "start": 3441.12, "duration": 1.54}, {"text": "And it doesn't fire\nwhen it's less.", "start": 3442.66, "duration": 2.88}, {"text": "So now the output neuron fires\nwhenever the input neuron", "start": 3445.54, "duration": 3.87}, {"text": "has a firing rate greater\nthan this decision boundary.", "start": 3449.41, "duration": 4.51}, {"text": "So the decision boundary,\nthe u threshold,", "start": 3453.92, "duration": 3.8}, {"text": "is equal to theta divided by w.", "start": 3457.72, "duration": 2.25}, {"text": "Does that make sense?", "start": 3459.97, "duration": 1.05}, {"text": "U threshold is the\nneuron fires when", "start": 3461.02, "duration": 3.66}, {"text": "u is greater than\ntheta divided by w.", "start": 3464.68, "duration": 2.61}, {"text": "So the way we learn, the\nway this network learns", "start": 3471.03, "duration": 4.48}, {"text": "to fire when that u is above\nthis classification boundary", "start": 3475.51, "duration": 5.76}, {"text": "is simply by\nchanging the weight.", "start": 3481.27, "duration": 2.67}, {"text": "Does that make sense?", "start": 3483.94, "duration": 1.24}, {"text": "So we're going to\nlearn the weight such", "start": 3485.18, "duration": 3.2}, {"text": "that this network fires whenever\nthe input says there's a dog.", "start": 3488.38, "duration": 3.75}, {"text": "And it doesn't fire whenever\nthe input says there's no dog.", "start": 3492.13, "duration": 2.66}, {"text": "So let's see what happens\nwhen w is really small.", "start": 3498.25, "duration": 4.4}, {"text": "If w is really small,\nthen what happens", "start": 3502.65, "duration": 2.74}, {"text": "is all of these-- remember,\nthis is the input.", "start": 3505.39, "duration": 2.97}, {"text": "That's that the\ndogginess detector.", "start": 3508.36, "duration": 3.81}, {"text": "If w is really small,\nthen all these inputs", "start": 3512.17, "duration": 2.64}, {"text": "get collapsed to a small input\ncurrent into our output neuron.", "start": 3514.81, "duration": 5.97}, {"text": "Does that make sense?", "start": 3520.78, "duration": 3.0}, {"text": "So all those different\ninputs, dogs and non-dogs,", "start": 3523.78, "duration": 3.74}, {"text": "gets multiplied\nby a small number.", "start": 3527.52, "duration": 2.97}, {"text": "And all those inputs\nare close to 0.", "start": 3530.49, "duration": 3.3}, {"text": "And if all those\ninputs are close to 0,", "start": 3533.79, "duration": 2.07}, {"text": "they're all below the threshold\nfor making this neuron spike.", "start": 3535.86, "duration": 4.46}, {"text": "So this network is not\ngood for detecting dogs", "start": 3540.32, "duration": 4.29}, {"text": "because it says it never\nfires, whether the input", "start": 3544.61, "duration": 3.78}, {"text": "is a dog or a non-dog.", "start": 3548.39, "duration": 3.03}, {"text": "Now what happens\nif w is too big?", "start": 3551.42, "duration": 3.15}, {"text": "If w is really big, then this\nrange of dogginess values", "start": 3554.57, "duration": 7.14}, {"text": "gets multiplied by a big number.", "start": 3561.71, "duration": 3.2}, {"text": "And you can see that a bunch of\nnon-dogs make the neuron fire.", "start": 3564.91, "duration": 6.445}, {"text": "Does that make sense?", "start": 3571.355, "duration": 0.875}, {"text": "So now this one fires\nfor dogs plus doggie-ish", "start": 3572.23, "duration": 4.22}, {"text": "looking things,\nwhich, I don't know,", "start": 3576.45, "duration": 1.9}, {"text": "maybe it'll fire\nwhen it sees a cat.", "start": 3578.35, "duration": 2.128}, {"text": "That's terrible.", "start": 3580.478, "duration": 0.667}, {"text": "So you have to choose w to make\nthis classification network", "start": 3583.86, "duration": 5.73}, {"text": "function properly.", "start": 3589.59, "duration": 1.59}, {"text": "Does that make sense?", "start": 3591.18, "duration": 1.08}, {"text": "And if you choose\nw just right, then", "start": 3592.26, "duration": 4.37}, {"text": "that classification\nboundary lands", "start": 3596.63, "duration": 3.73}, {"text": "right on the threshold\nof the neuron.", "start": 3600.36, "duration": 2.86}, {"text": "And now the neuron spikes\nwhenever there is a dog.", "start": 3603.22, "duration": 4.08}, {"text": "And it doesn't spike\nwhenever there's not a dog.", "start": 3607.3, "duration": 3.21}, {"text": "So what's the message here?", "start": 3610.51, "duration": 2.08}, {"text": "The message is we can\nhave a neuron that", "start": 3612.59, "duration": 3.86}, {"text": "has this binary threshold.", "start": 3616.45, "duration": 4.86}, {"text": "And what we can do is simply\nby changing the weight,", "start": 3621.31, "duration": 4.2}, {"text": "we can make that\nthreshold land anywhere", "start": 3625.51, "duration": 3.84}, {"text": "on this space of inputs.", "start": 3629.35, "duration": 1.35}, {"text": "And we can actually use the\nerror to set the weight.", "start": 3634.82, "duration": 3.55}, {"text": "So let's say that\nwe made errors here.", "start": 3638.37, "duration": 2.66}, {"text": "We classify dogs as non-dogs\nbecause the neuron didn't fire.", "start": 3641.03, "duration": 5.25}, {"text": "You can see that this was the\ncase when w was too small.", "start": 3646.28, "duration": 3.91}, {"text": "So if you classify\ndogs as non-dogs,", "start": 3650.19, "duration": 4.1}, {"text": "then you need to make w bigger.", "start": 3654.29, "duration": 3.01}, {"text": "And if you classify\nnon-dogs as dogs,", "start": 3657.3, "duration": 3.8}, {"text": "you need to make w smaller.", "start": 3661.1, "duration": 2.83}, {"text": "And by measuring what\nkind of errors you make,", "start": 3663.93, "duration": 4.38}, {"text": "you can actually fix the weights\nto get to the right answer.", "start": 3668.31, "duration": 6.15}, {"text": "So this is a method\ncalled supervised", "start": 3674.46, "duration": 3.02}, {"text": "learning where you\nset w randomly.", "start": 3677.48, "duration": 4.9}, {"text": "You take a guess.", "start": 3682.38, "duration": 1.83}, {"text": "And then you look at\nthe mistakes you make.", "start": 3684.21, "duration": 2.73}, {"text": "And you use those\nmistakes to fix the w.", "start": 3686.94, "duration": 4.51}, {"text": "In other words, you\njust look at the world", "start": 3691.45, "duration": 5.86}, {"text": "and you say, oh, that's a dog.", "start": 3697.31, "duration": 3.15}, {"text": "And then your mom\nsays, no, that's not", "start": 3700.46, "duration": 1.89}, {"text": "a dog, that's something else.", "start": 3702.35, "duration": 2.62}, {"text": "And you adjust your weights.", "start": 3704.97, "duration": 1.295}, {"text": "I think that was the\nexample I just gave.", "start": 3708.79, "duration": 1.73}, {"text": "You're going to\nmake that w smaller.", "start": 3710.52, "duration": 1.95}, {"text": "In another case, you'll make\nthe other kind of mistake", "start": 3712.47, "duration": 2.25}, {"text": "and you'll fix the weights.", "start": 3714.72, "duration": 1.14}, {"text": "So this is called a perceptron.", "start": 3719.01, "duration": 2.64}, {"text": "And the way you learn the\nweights in a perceptron is you", "start": 3721.65, "duration": 2.94}, {"text": "just classify things and you\nfigure out what kind of mistake", "start": 3724.59, "duration": 4.09}, {"text": "you made and you use that\nto adjust the weights.", "start": 3728.68, "duration": 3.16}, {"text": "So that's the basic idea of\na perceptron and perceptron", "start": 3731.84, "duration": 3.95}, {"text": "learning.", "start": 3735.79, "duration": 0.9}, {"text": "And there's a lot of\nmathematical formalism", "start": 3736.69, "duration": 2.79}, {"text": "that goes into how\nthat learning happens.", "start": 3739.48, "duration": 2.28}, {"text": "And we're going to\nget to that in more", "start": 3741.76, "duration": 4.41}, {"text": "detail in the next lecture.", "start": 3746.17, "duration": 3.25}, {"text": "But before we do that,\nI want to go from having", "start": 3749.42, "duration": 3.92}, {"text": "a one-dimensional case.", "start": 3753.34, "duration": 1.29}, {"text": "So here we had a one-dimensional\nnetwork that was just", "start": 3754.63, "duration": 2.67}, {"text": "operating on dogginess.", "start": 3757.3, "duration": 3.33}, {"text": "And then we have a\nsingle neuron that", "start": 3760.63, "duration": 2.4}, {"text": "says, was that a dog or not.", "start": 3763.03, "duration": 3.14}, {"text": "But in general, you're\nnot classifying things", "start": 3766.17, "duration": 3.12}, {"text": "based on one input.", "start": 3769.29, "duration": 2.13}, {"text": "Like for example when you\nhave to identify a dog,", "start": 3771.42, "duration": 3.42}, {"text": "you have a whole\nimage of something.", "start": 3774.84, "duration": 4.51}, {"text": "And you have to classify\nthat based on an image.", "start": 3779.35, "duration": 2.62}, {"text": "So let's go from the\none-dimensional case", "start": 3781.97, "duration": 1.82}, {"text": "to a two-dimensional case.", "start": 3783.79, "duration": 1.29}, {"text": "So the classification isn't\ndone on one-dimension,", "start": 3785.08, "duration": 3.18}, {"text": "but it's based on many\ndifferent features.", "start": 3788.26, "duration": 3.39}, {"text": "So let's say that we have\ntwo features, furriness", "start": 3791.65, "duration": 4.07}, {"text": "and bad breath.", "start": 3795.72, "duration": 1.78}, {"text": "That dog doesn't really\nlook like it has bad breath.", "start": 3797.5, "duration": 3.66}, {"text": "but mine does.", "start": 3801.16, "duration": 3.63}, {"text": "So you can have two\ndifferent features, furriness", "start": 3804.79, "duration": 2.76}, {"text": "and bad breath.", "start": 3807.55, "duration": 0.67}, {"text": "And dogs are generally,\nlet's say, up here.", "start": 3808.22, "duration": 3.97}, {"text": "Now you can have other animals.", "start": 3812.19, "duration": 2.8}, {"text": "This guy is\ndefinitely not furry.", "start": 3814.99, "duration": 2.97}, {"text": "So he's down here somewhere.", "start": 3817.96, "duration": 1.52}, {"text": "And you can have\nthis guy up here.", "start": 3819.48, "duration": 2.35}, {"text": "He's definitely furry.", "start": 3821.83, "duration": 2.87}, {"text": "So you have these two\ndimensions and a bunch", "start": 3824.7, "duration": 2.61}, {"text": "of observations in\nthose two dimensions,", "start": 3827.31, "duration": 2.49}, {"text": "in those higher dimensions.", "start": 3829.8, "duration": 2.12}, {"text": "And you can see\nthat, in this case,", "start": 3831.92, "duration": 3.55}, {"text": "you can't actually apply that\none-dimensional decision-making", "start": 3835.47, "duration": 6.12}, {"text": "circuit to discriminate dogs\nfrom these other animals.", "start": 3841.59, "duration": 5.08}, {"text": "Why is that?", "start": 3846.67, "duration": 0.96}, {"text": "Because if I apply my\none-dimensional perceptron", "start": 3847.63, "duration": 4.32}, {"text": "to this problem,\nyou can see that I", "start": 3851.95, "duration": 2.1}, {"text": "could put a boundary\nhere and it will", "start": 3854.05, "duration": 4.55}, {"text": "misclassify some of these\nnon-furry animals as dogs.", "start": 3858.6, "duration": 4.88}, {"text": "Or I could put my\nclassifier here", "start": 3863.48, "duration": 2.65}, {"text": "and it will misclassify\nsome of these cats as dogs.", "start": 3866.13, "duration": 4.29}, {"text": "So how would I separate dogs\nfrom these other animals", "start": 3870.42, "duration": 4.69}, {"text": "if I had this\ntwo-dimensional space?", "start": 3875.11, "duration": 2.6}, {"text": "What would I do?", "start": 3877.71, "duration": 2.06}, {"text": "How would I put a\nclassification bound?", "start": 3879.77, "duration": 2.39}, {"text": "If this doesn't work and this\ndoesn't work, what would I do?", "start": 3882.16, "duration": 5.11}, {"text": "You could put a\nboundary right there.", "start": 3887.27, "duration": 2.82}, {"text": "So in this little\ntoy problem, that", "start": 3890.09, "duration": 1.8}, {"text": "would perfectly separate\ndogs from all these non-dogs.", "start": 3891.89, "duration": 3.21}, {"text": "So how do we do that?", "start": 3898.39, "duration": 2.61}, {"text": "Well, what we want is some\nway of projecting these inputs", "start": 3901.0, "duration": 7.29}, {"text": "onto some other\ndirection so that we", "start": 3908.29, "duration": 4.02}, {"text": "can put a classification\nboundary right there.", "start": 3912.31, "duration": 4.16}, {"text": "And it turns out there's a very\nsimple network that does that.", "start": 3916.47, "duration": 3.54}, {"text": "It looks like this.", "start": 3920.01, "duration": 1.413}, {"text": "We take each one of those\ndetectors, a furriness detector", "start": 3921.423, "duration": 4.197}, {"text": "and a bad breath detector,\nand we have those two inputs.", "start": 3925.62, "duration": 5.85}, {"text": "We have those inputs synapse\nonto our output neuron", "start": 3931.47, "duration": 3.03}, {"text": "with some weight w1\nand some weight w2,", "start": 3934.5, "duration": 3.3}, {"text": "and we calculate the\nfiring rate of this neuron.", "start": 3937.8, "duration": 3.4}, {"text": "Now we have this problem of\nhow do we place this decision", "start": 3941.2, "duration": 4.88}, {"text": "boundary correctly.", "start": 3946.08, "duration": 2.65}, {"text": "What's the answer?", "start": 3948.73, "duration": 1.07}, {"text": "Well, in the\none-dimensional example,", "start": 3949.8, "duration": 1.845}, {"text": "what is it that we learned?", "start": 3951.645, "duration": 1.125}, {"text": "What was it that we\nwere actually changing?", "start": 3957.4, "duration": 2.29}, {"text": "We were taking guesses.", "start": 3959.69, "duration": 3.14}, {"text": "And if we were right\nor wrong, we did what?", "start": 3962.83, "duration": 2.7}, {"text": "We changed the weight.", "start": 3965.53, "duration": 2.64}, {"text": "And that's exactly\nwhat we do here.", "start": 3968.17, "duration": 1.71}, {"text": "We're going to learn to\nchange these weights to put", "start": 3969.88, "duration": 4.44}, {"text": "that boundary in\nthe right place.", "start": 3974.32, "duration": 1.83}, {"text": "If we just take a random\nguess for these weights,", "start": 3978.83, "duration": 2.43}, {"text": "that line is just going to\nbe some random position.", "start": 3981.26, "duration": 4.32}, {"text": "But we can learn to\nplace that line exactly", "start": 3985.58, "duration": 2.58}, {"text": "in the right place to\nseparate dogs from non-dogs.", "start": 3988.16, "duration": 4.32}, {"text": "So let's just think\na little bit more", "start": 3992.48, "duration": 1.56}, {"text": "about how that\ndecision boundary looks", "start": 3994.04, "duration": 4.98}, {"text": "as a function of the weight.", "start": 3999.02, "duration": 2.01}, {"text": "So let's look at this case\nwhere we have two inputs.", "start": 4001.03, "duration": 2.61}, {"text": "So now you can see that the\ninput to this neuron is w.u.", "start": 4003.64, "duration": 8.06}, {"text": "So now if we use our binary\nneuron with a threshold,", "start": 4011.7, "duration": 5.25}, {"text": "we can see that the firing\nrate of this output neuron", "start": 4016.95, "duration": 3.42}, {"text": "is this step function\noperating on or acting", "start": 4020.37, "duration": 5.24}, {"text": "on this input, w.u minus theta.", "start": 4025.61, "duration": 2.94}, {"text": "So now what does that look like?", "start": 4032.75, "duration": 1.52}, {"text": "The decision\nboundary happens when", "start": 4034.27, "duration": 1.89}, {"text": "this quantity is pulled to 0.", "start": 4036.16, "duration": 3.94}, {"text": "When this input is greater\nthan 0, the neuron fires.", "start": 4040.1, "duration": 2.52}, {"text": "When this input is less\nthan 0, it doesn't fire.", "start": 4042.62, "duration": 2.85}, {"text": "So what does that look like?", "start": 4045.47, "duration": 2.665}, {"text": "So you can see the\ndecision boundary is", "start": 4048.135, "duration": 1.625}, {"text": "when w.u minus theta equals 0.", "start": 4049.76, "duration": 2.42}, {"text": "Does anyone know what that is?", "start": 4052.18, "duration": 1.66}, {"text": "Remember, u is our input space.", "start": 4057.688, "duration": 2.732}, {"text": "That's what we're asking,\nwhere is this decision", "start": 4060.42, "duration": 3.18}, {"text": "boundary in the input space.", "start": 4063.6, "duration": 2.19}, {"text": "w is some weights that\nare fixed right now,", "start": 4065.79, "duration": 2.82}, {"text": "but we're gradually going\nto change them later.", "start": 4068.61, "duration": 3.25}, {"text": "So what is that an equation for?", "start": 4071.86, "duration": 3.43}, {"text": "It's a line.", "start": 4075.29, "duration": 2.64}, {"text": "That's an equation for a line.", "start": 4077.93, "duration": 1.38}, {"text": "If u is our input, you\ncan see w.u equals theta.", "start": 4079.31, "duration": 8.57}, {"text": "That's an equation\nfor a line, base of u.", "start": 4087.88, "duration": 3.64}, {"text": "The slope and\nposition of that line", "start": 4091.52, "duration": 3.23}, {"text": "are controlled by the weights\nw and the threshold theta.", "start": 4094.75, "duration": 5.359}, {"text": "So you can see this is w1,\nu1, plus w2, u2 equals theta.", "start": 4100.109, "duration": 6.031}, {"text": "In the space of u1 and\nu2, that's just a line.", "start": 4106.14, "duration": 4.74}, {"text": "So let's look at the case\nwhere theta equals 0.", "start": 4110.88, "duration": 3.72}, {"text": "You can see that if you have\nthis input space, u1 and u2,", "start": 4114.6, "duration": 4.81}, {"text": "if you take a particular\ninput u and dot it into w--", "start": 4119.41, "duration": 5.48}, {"text": "so let's just pick a w in\nsome random direction--", "start": 4124.89, "duration": 3.83}, {"text": "the neuron fires when the\nprojection of u along w", "start": 4128.72, "duration": 3.55}, {"text": "is positive.", "start": 4132.27, "duration": 0.7}, {"text": "So you can see here, the\nprojection of u along w", "start": 4132.97, "duration": 3.469}, {"text": "is positive.", "start": 4136.439, "duration": 3.581}, {"text": "So in this case for this\nu the neuron will fire.", "start": 4140.02, "duration": 2.85}, {"text": "So any u that has a\npositive projection along w", "start": 4145.8, "duration": 5.55}, {"text": "will make the neuron spike.", "start": 4151.35, "duration": 2.91}, {"text": "So you can see that\nall of these inputs", "start": 4154.26, "duration": 3.24}, {"text": "will make the neuron spike.", "start": 4157.5, "duration": 2.89}, {"text": "All of these inputs will\nmake the neuron not spike.", "start": 4160.39, "duration": 4.033}, {"text": "Does that make sense?", "start": 4164.423, "duration": 1.877}, {"text": "So you can see that the\ndecision boundary, this boundary", "start": 4166.3, "duration": 4.13}, {"text": "between the inputs\nthat make the neuron", "start": 4170.43, "duration": 2.13}, {"text": "spike and the inputs that\ndon't make the neuron spike,", "start": 4172.56, "duration": 4.83}, {"text": "is a line that's\northogonal to w.", "start": 4177.39, "duration": 4.855}, {"text": "Does that make sense?", "start": 4182.245, "duration": 0.875}, {"text": "Because you can see\nthat any u, any input,", "start": 4187.49, "duration": 3.44}, {"text": "along this line will\nhave zero projection,", "start": 4190.93, "duration": 3.12}, {"text": "will be orthogonal to w.", "start": 4194.05, "duration": 1.85}, {"text": "Will have zero projection.", "start": 4195.9, "duration": 1.66}, {"text": "And that's going to correspond\nto that decision boundary.", "start": 4197.56, "duration": 5.28}, {"text": "So let's just look\nat a couple of cases.", "start": 4206.94, "duration": 5.29}, {"text": "So here a set of points that\ncorrespond to our non-dogs.", "start": 4212.23, "duration": 5.69}, {"text": "Here are a set of points\nthat correspond to our dog.", "start": 4217.92, "duration": 2.65}, {"text": "You can see that if you have\na w in this direction, that", "start": 4220.57, "duration": 3.17}, {"text": "produces a decision boundary\nthat nicely separates", "start": 4223.74, "duration": 2.76}, {"text": "the dogs from the non-dogs.", "start": 4226.5, "duration": 2.48}, {"text": "So what is that w?\nthat w is 1, comma, 0.", "start": 4228.98, "duration": 3.61}, {"text": "And we're going to consider\nthe case where theta is 0.", "start": 4232.59, "duration": 4.2}, {"text": "Let's look at this case here.", "start": 4236.79, "duration": 1.35}, {"text": "So you can see that\nhere are all the dogs.", "start": 4238.14, "duration": 2.07}, {"text": "Here are all the non-dogs.", "start": 4240.21, "duration": 1.38}, {"text": "You can see that if you drew\na line in this direction,", "start": 4241.59, "duration": 2.49}, {"text": "that would be a good\ndecision boundary", "start": 4244.08, "duration": 3.3}, {"text": "for that classification problem.", "start": 4247.38, "duration": 1.95}, {"text": "You can see that\na w corresponding", "start": 4249.33, "duration": 2.61}, {"text": "to solving that problem\nis 1, comma, minus 1,", "start": 4251.94, "duration": 4.26}, {"text": "and theta equals 0.", "start": 4256.2, "duration": 1.22}, {"text": "Let's look at the case\nwhere theta is not 0.", "start": 4262.99, "duration": 3.44}, {"text": "So here we have w.u minus theta.", "start": 4266.43, "duration": 3.3}, {"text": "When theta is not 0, then\nthe decision boundary is w.u", "start": 4269.73, "duration": 3.93}, {"text": "equals some non-zero theta.", "start": 4273.66, "duration": 2.1}, {"text": "That's also a line.", "start": 4275.76, "duration": 1.11}, {"text": "It's a equation for a line.", "start": 4276.87, "duration": 3.28}, {"text": "When theta is 0, that\ndecision boundary", "start": 4280.15, "duration": 2.09}, {"text": "goes through the origin.", "start": 4282.24, "duration": 1.74}, {"text": "When theta is not 0,\nthe decision boundary", "start": 4283.98, "duration": 2.33}, {"text": "is offset from the origin.", "start": 4286.31, "duration": 2.74}, {"text": "So we could see that\nwhen we had theta is 0,", "start": 4289.05, "duration": 2.79}, {"text": "the decision boundary--\nthat network only", "start": 4291.84, "duration": 2.01}, {"text": "works if the decision boundary\nis going through the origin.", "start": 4293.85, "duration": 4.05}, {"text": "In general, though, we can put\nthe decision boundary anywhere", "start": 4297.9, "duration": 2.67}, {"text": "we want by having\nthis non-zero theta.", "start": 4300.57, "duration": 4.17}, {"text": "So here's an example.", "start": 4304.74, "duration": 1.43}, {"text": "Here are a set of points\nthat are the dogs.", "start": 4306.17, "duration": 2.57}, {"text": "Here are a set of points\nthat are the non-dogs.", "start": 4308.74, "duration": 3.65}, {"text": "If we wanted to\ndesign a network that", "start": 4312.39, "duration": 2.64}, {"text": "separates the dogs\nfrom the non-dogs,", "start": 4315.03, "duration": 2.61}, {"text": "we could just draw a line\nthat cleanly separates", "start": 4317.64, "duration": 3.18}, {"text": "the green from the red dots.", "start": 4320.82, "duration": 3.06}, {"text": "And now we can calculate\nw that gives us", "start": 4323.88, "duration": 3.24}, {"text": "that decision boundary.", "start": 4327.12, "duration": 1.62}, {"text": "How do we do that?", "start": 4328.74, "duration": 1.72}, {"text": "So the decision boundary\nis w minus u.theta.", "start": 4330.46, "duration": 2.9}, {"text": "Let's say that we\nwant to calculate", "start": 4333.36, "duration": 1.89}, {"text": "this weight vector w1 and w2.", "start": 4335.25, "duration": 2.48}, {"text": "And let's just say that our\nneuron has a threshold of 1.", "start": 4337.73, "duration": 4.74}, {"text": "So we can see that we have\ntwo points on the decision", "start": 4342.47, "duration": 2.61}, {"text": "boundary.", "start": 4345.08, "duration": 1.17}, {"text": "We have one point here,\na, comma, 0, right there.", "start": 4346.25, "duration": 4.41}, {"text": "We have another point\nhere, 0, comma, b.", "start": 4350.66, "duration": 3.72}, {"text": "And we can calculate\nthe decision boundary", "start": 4354.38, "duration": 2.58}, {"text": "using ua.w equals theta,\nub.w equals theta.", "start": 4356.96, "duration": 6.24}, {"text": "That's two equations and\ntwo unknowns, w1 and w2.", "start": 4363.2, "duration": 6.84}, {"text": "So if I gave you a set of points\nand I said calculate a weight", "start": 4370.04, "duration": 7.05}, {"text": "for this perceptron that will\nseparate one set of points", "start": 4377.09, "duration": 4.95}, {"text": "from another set of\npoints, and I give you", "start": 4382.04, "duration": 4.33}, {"text": "a theta for the output\nneuron, all you have to do", "start": 4386.37, "duration": 3.83}, {"text": "is draw a line that\nseparates them,", "start": 4390.2, "duration": 2.76}, {"text": "and then solve those\ntwo equations to get", "start": 4392.96, "duration": 2.73}, {"text": "w1 and w2 for that network.", "start": 4395.69, "duration": 4.942}, {"text": "It's very easy to do\nthis in two dimensions.", "start": 4400.632, "duration": 3.438}, {"text": "You can just draw a\nline and calculate", "start": 4404.07, "duration": 2.85}, {"text": "the w that corresponds to\nthat decision boundary.", "start": 4406.92, "duration": 5.34}, {"text": "Any questions about that?", "start": 4412.26, "duration": 2.03}, {"text": "Just that, if you\nhave questions,", "start": 4414.29, "duration": 2.57}, {"text": "you should ask because\nthat's going to be", "start": 4416.86, "duration": 3.26}, {"text": "a question you ought to solve.", "start": 4420.12, "duration": 1.33}, {"text": "So you can see in two dimensions\nyou can just look at the data,", "start": 4427.0, "duration": 3.45}, {"text": "decide where's the decision\nboundary, draw a line,", "start": 4430.45, "duration": 2.31}, {"text": "and calculate the weights w.", "start": 4432.76, "duration": 3.03}, {"text": "But in higher dimensions,\nit's a really hard problem.", "start": 4435.79, "duration": 3.36}, {"text": "In high dimensions,\nfirst of all,", "start": 4439.15, "duration": 4.23}, {"text": "remember in high dimensions\nyou've got images.", "start": 4443.38, "duration": 3.81}, {"text": "Each pixel in that image\nis a different dimension", "start": 4447.19, "duration": 3.27}, {"text": "in the classification problem.", "start": 4450.46, "duration": 2.94}, {"text": "So how do you write\ndown a set of weights?", "start": 4453.4, "duration": 4.35}, {"text": "So imagine that's an\nimage, that's an image.", "start": 4457.75, "duration": 4.68}, {"text": "And you want to find\na set of weights", "start": 4462.43, "duration": 2.13}, {"text": "so that this neuron fires\nwhen you have the dog,", "start": 4464.56, "duration": 2.97}, {"text": "but doesn't fire when\nyou have the cat.", "start": 4467.53, "duration": 2.64}, {"text": "That's a really hard problem.", "start": 4470.17, "duration": 1.94}, {"text": "You can't look at\nthose things and decide", "start": 4472.11, "duration": 2.02}, {"text": "what that w should be.", "start": 4474.13, "duration": 1.47}, {"text": "So there's a way of taking\ninputs and taking the answer,", "start": 4478.95, "duration": 9.79}, {"text": "like a 1 for a dog\nand a 0 for non-dogs,", "start": 4488.74, "duration": 3.28}, {"text": "and actually finding a set\nof weights that will properly", "start": 4492.02, "duration": 3.42}, {"text": "classify those inputs.", "start": 4495.44, "duration": 2.07}, {"text": "And that's called the\nperceptron learning rule.", "start": 4497.51, "duration": 2.79}, {"text": "And we're going to talk about\nthat in the next lecture.", "start": 4500.3, "duration": 5.28}, {"text": "So that's what we did today.", "start": 4505.58, "duration": 2.49}, {"text": "And we're going to\ncontinue working", "start": 4508.07, "duration": 2.1}, {"text": "on developing methods\nfor understanding", "start": 4510.17, "duration": 4.71}, {"text": "neural networks next time.", "start": 4514.88, "duration": 3.05}]
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+[{"text": "[SQUEAKING]", "start": 1.948, "duration": 0.961}, {"text": "[RUSTLE]", "start": 2.909, "duration": 0.5}, {"text": "[CLICKING]", "start": 3.409, "duration": 1.461}, {"text": "PROFESSOR: Welcome back to 8.20.", "start": 19.51, "duration": 1.74}, {"text": "In this section, we're going to\ntalk about time, timekeeping,", "start": 21.25, "duration": 4.02}, {"text": "and how to relate time between\ntwo different reference point.", "start": 25.27, "duration": 3.952}, {"text": "Now, let me start with a\nquote by Albert Einstein.", "start": 29.222, "duration": 3.178}, {"text": "\"Everything should be as simple\nas possible, but not simpler.\"", "start": 32.4, "duration": 4.99}, {"text": "So let's start\nwith this in mind.", "start": 37.39, "duration": 1.85}, {"text": "And recall that we\nended the last section", "start": 39.24, "duration": 3.84}, {"text": "by finding that the wave\naether model doesn't really", "start": 43.08, "duration": 3.54}, {"text": "describe electromagnetic\nwaves very well.", "start": 46.62, "duration": 3.54}, {"text": "We see that there is a problem\nbetween the experiments,", "start": 50.16, "duration": 4.08}, {"text": "specifically the one\nby Michelson-Morley,", "start": 54.24, "duration": 3.24}, {"text": "and the theoretical\npicture people had in mind.", "start": 57.48, "duration": 3.94}, {"text": "So Einstein approached\nthis in an interesting way.", "start": 61.42, "duration": 5.74}, {"text": "He simply postulated the things\nhe thought need to be true.", "start": 67.16, "duration": 3.8}, {"text": "He said, \"The same\nlaw of electrodynamics", "start": 70.96, "duration": 2.85}, {"text": "will be valid for\nall reference frames", "start": 73.81, "duration": 2.88}, {"text": "where all laws of\nmechanics hold good.", "start": 76.69, "duration": 3.66}, {"text": "This is the principle\nof relativity.\"", "start": 80.35, "duration": 4.44}, {"text": "The second postulate is that\n\"Light is always propagated", "start": 84.79, "duration": 3.63}, {"text": "in empty space at the velocity\n'c,' independent of the state", "start": 88.42, "duration": 3.39}, {"text": "of motion of the emitting body.\"", "start": 91.81, "duration": 3.21}, {"text": "So with these two\npostulates, we will now", "start": 95.02, "duration": 2.85}, {"text": "derive the theory of\nspecial relativity.", "start": 97.87, "duration": 2.71}, {"text": "And again, we'll start\nby talking about time.", "start": 100.58, "duration": 2.69}, {"text": "So time is suspect.", "start": 105.92, "duration": 1.79}, {"text": "And I alluded to\nthis already when", "start": 107.71, "duration": 1.47}, {"text": "we looked at Galilean\ntransformation,", "start": 109.18, "duration": 1.92}, {"text": "where it simply, out\nof our intuition,", "start": 111.1, "duration": 2.79}, {"text": "assumed that time is invariant.", "start": 113.89, "duration": 3.52}, {"text": "Now, when we now\ntalk about time,", "start": 117.41, "duration": 4.91}, {"text": "the viewpoint I would\nlike you to have", "start": 122.32, "duration": 2.17}, {"text": "is that we want to look at\nclocks from different reference", "start": 124.49, "duration": 2.55}, {"text": "frames.", "start": 127.04, "duration": 0.93}, {"text": "We want to investigate\nwhether or not events", "start": 127.97, "duration": 2.669}, {"text": "happen simultaneously or not.", "start": 130.639, "duration": 2.491}, {"text": "What does it mean?", "start": 133.13, "duration": 1.23}, {"text": "When we make a statement like\na train arrives at 7 o'clock,", "start": 134.36, "duration": 3.63}, {"text": "what we mean is that there\nis a simultaneous-- two", "start": 137.99, "duration": 3.96}, {"text": "simultaneous events happen.", "start": 141.95, "duration": 1.39}, {"text": "One is that this\nlittle clock here shows", "start": 143.34, "duration": 6.43}, {"text": "to point at seven\nand 12, meaning", "start": 149.77, "duration": 2.73}, {"text": "that it indicates to us\nthat-- this event indicates", "start": 152.5, "duration": 3.09}, {"text": "to us that it's 7 o'clock.", "start": 155.59, "duration": 1.89}, {"text": "And the second event is\nthat the train actually", "start": 157.48, "duration": 2.22}, {"text": "arrives at the station.", "start": 159.7, "duration": 1.5}, {"text": "So those two events\nhappen simultaneously.", "start": 161.2, "duration": 3.6}, {"text": "The question now\nis whether or not", "start": 164.8, "duration": 2.13}, {"text": "two observers, one\nstationary and one moving,", "start": 166.93, "duration": 3.63}, {"text": "agree with this observation.", "start": 170.56, "duration": 2.34}, {"text": "And I take it away--\nthe answer is no.", "start": 172.9, "duration": 2.79}, {"text": "There is a relativity\nof simultaneity,", "start": 175.69, "duration": 3.63}, {"text": "meaning that two observers\ncan very much agree", "start": 179.32, "duration": 3.06}, {"text": "on the description\nof two events,", "start": 182.38, "duration": 2.05}, {"text": "but not necessarily\nthat those two", "start": 184.43, "duration": 2.03}, {"text": "events happen simultaneously.", "start": 186.46, "duration": 4.54}, {"text": "So let's investigate.", "start": 191.0, "duration": 0.95}, {"text": "And we use our two friends,\nAlice and Bob, in order", "start": 191.95, "duration": 2.37}, {"text": "to have this discussion.", "start": 194.32, "duration": 2.416}, {"text": "All right, so we\nstart from a situation", "start": 196.736, "duration": 2.704}, {"text": "where Alice and Bob\nare both stationary.", "start": 199.44, "duration": 2.67}, {"text": "Alice is on her\nspacecraft, and she", "start": 202.11, "duration": 2.25}, {"text": "has a device on her spacecraft\nwhich shoots light or paint", "start": 204.36, "duration": 4.035}, {"text": "balls towards two clocks.", "start": 208.395, "duration": 2.145}, {"text": "And each time this happens,\nthe clock ticks, right?", "start": 210.54, "duration": 4.49}, {"text": "And we just look\nat one situation.", "start": 215.03, "duration": 1.72}, {"text": "So she has a clock on the\nleft and a clock on the right.", "start": 216.75, "duration": 3.5}, {"text": "Bob observes Alice's clock.", "start": 220.25, "duration": 2.58}, {"text": "And he can compare this\nobservation of Alice's clock", "start": 222.83, "duration": 3.78}, {"text": "with his own.", "start": 226.61, "duration": 2.92}, {"text": "So in this station,\nas to duration,", "start": 229.53, "duration": 1.76}, {"text": "there's a TA and a TB.", "start": 231.29, "duration": 3.0}, {"text": "Those are the times\nof Alice and Bob.", "start": 234.29, "duration": 2.52}, {"text": "Both are 0.", "start": 236.81, "duration": 0.66}, {"text": "This is when the\nsituation starts.", "start": 237.47, "duration": 2.19}, {"text": "And the capital T indicates\nfor Alice and for Bob", "start": 239.66, "duration": 4.8}, {"text": "when they observe that\nthe clock has been hit.", "start": 244.46, "duration": 3.42}, {"text": "I should add here that when\nwe talk about observation", "start": 250.46, "duration": 3.31}, {"text": "in this entire class, unless I\nmake a very explicit exception", "start": 253.77, "duration": 4.009}, {"text": "to this, we don't consider the\nfact that observing actually", "start": 257.779, "duration": 4.441}, {"text": "means that light has to\nbe emitted from the clock", "start": 262.22, "duration": 3.39}, {"text": "and enters Bob's\neye in order for him", "start": 265.61, "duration": 2.49}, {"text": "to conclude that there\nwas something happening.", "start": 268.1, "duration": 2.67}, {"text": "The observation is like taking\nan instantaneous picture.", "start": 270.77, "duration": 7.15}, {"text": "OK, so we have to\nkeep this in mind.", "start": 277.92, "duration": 1.83}, {"text": "But in this simple\nsituation, nothing is moving.", "start": 279.75, "duration": 3.48}, {"text": "We can hopefully agree\nthat the times being", "start": 283.23, "duration": 4.77}, {"text": "read for Alice and Bob on\nthe left and the right clock", "start": 288.0, "duration": 3.6}, {"text": "are all the same.", "start": 291.6, "duration": 2.86}, {"text": "Now, we go in the\nsecond situation,", "start": 294.46, "duration": 1.73}, {"text": "where we use the same\ndevice but with a paintball.", "start": 296.19, "duration": 3.72}, {"text": "So now, Alice moves and\nBob is observing her.", "start": 299.91, "duration": 3.84}, {"text": "She moves with a\nrelative velocity, v,", "start": 303.75, "duration": 2.85}, {"text": "and shoots off the paint\nballs with a velocity, u.", "start": 306.6, "duration": 3.33}, {"text": "The velocities will add, meaning\nthat the answers to clocks", "start": 309.93, "duration": 6.33}, {"text": "are initially synchronized.", "start": 316.26, "duration": 1.29}, {"text": "So there is a small tA\nequals small tB equals 0.", "start": 317.55, "duration": 6.36}, {"text": "Once the clock hits,\nyou can hopefully", "start": 323.91, "duration": 2.49}, {"text": "agree that Alice\nand Bob will agree", "start": 326.4, "duration": 3.03}, {"text": "that the times when the left\nclock and the right clock hit", "start": 329.43, "duration": 3.72}, {"text": "are the same, right?", "start": 333.15, "duration": 3.12}, {"text": "But now, we want to enter the\nsituation where we use light.", "start": 336.27, "duration": 2.91}, {"text": "So we use a phaser in\norder to do the very same.", "start": 339.18, "duration": 2.77}, {"text": "So Einstein just postulated\nthat the speed of light", "start": 341.95, "duration": 2.9}, {"text": "is constant, is c.", "start": 344.85, "duration": 1.41}, {"text": "And it's the same in\nall reference frames.", "start": 346.26, "duration": 2.04}, {"text": "And it's independent\nof the emitter,", "start": 348.3, "duration": 2.19}, {"text": "which means that we cannot\nadd the velocities anymore.", "start": 350.49, "duration": 3.93}, {"text": "So the velocity, as seen\nby Alice, of light is c.", "start": 354.42, "duration": 4.92}, {"text": "The velocity of the same light\nby the moving observer, Bob,", "start": 359.34, "duration": 5.01}, {"text": "is also c.", "start": 364.35, "duration": 1.27}, {"text": "So here, we can conclude\nthat the times for Alice", "start": 365.62, "duration": 4.67}, {"text": "for where the situation\nis stationary, both clocks", "start": 370.29, "duration": 3.84}, {"text": "will hit at the very same time.", "start": 374.13, "duration": 2.77}, {"text": "Those two events,\nclock one and clock two", "start": 376.9, "duration": 2.76}, {"text": "are hit are simultaneous.", "start": 379.66, "duration": 2.49}, {"text": "Why, for Bob, this is\nclearly not the case.", "start": 382.15, "duration": 3.71}, {"text": "You can see here that\nthis lagging clock", "start": 385.86, "duration": 7.87}, {"text": "is being hit first, while\nthe leading clock is", "start": 393.73, "duration": 3.06}, {"text": "hit a little while after.", "start": 396.79, "duration": 2.92}, {"text": "So if Bob and Alice now meet\nand they discuss whether or not", "start": 399.71, "duration": 4.41}, {"text": "those two events\nhappened simultaneously,", "start": 404.12, "duration": 2.25}, {"text": "they will disagree.", "start": 406.37, "duration": 1.44}, {"text": "For Alice, those two clocks\nwere hit simultaneously--", "start": 407.81, "duration": 3.99}, {"text": "at the same time for her.", "start": 411.8, "duration": 1.53}, {"text": "But for Bob, the first\nclock was hit first", "start": 413.33, "duration": 4.2}, {"text": "and the leading\nclock was hit second.", "start": 417.53, "duration": 4.37}, {"text": "All right, we can\nconclude the two events", "start": 421.9, "duration": 3.9}, {"text": "can be simultaneously\nto one observer", "start": 425.8, "duration": 2.88}, {"text": "but not to another one.", "start": 428.68, "duration": 2.34}, {"text": "This is rather confusing.", "start": 431.02, "duration": 2.34}, {"text": "And we will see\nand use this fact", "start": 433.36, "duration": 2.62}, {"text": "a few times later on when we\ndiscuss the famous paradoxes", "start": 435.98, "duration": 4.13}, {"text": "of special relativity.", "start": 440.11, "duration": 3.46}, {"text": "So let's look at this\nin a concept question", "start": 443.57, "duration": 2.93}, {"text": "to just make sure that\nwe're all on the same page.", "start": 446.5, "duration": 2.31}, {"text": "Again, we discuss\nyour diagram three.", "start": 448.81, "duration": 2.53}, {"text": "Alice move to the right.", "start": 451.34, "duration": 1.64}, {"text": "Bob is the observer.", "start": 452.98, "duration": 1.44}, {"text": "Alice's fires her\nphaser at times equal 0.", "start": 454.42, "duration": 5.73}, {"text": "Then the situation unfolds.", "start": 460.15, "duration": 2.07}, {"text": "At time TA, capital\nTA, Alice observes", "start": 462.22, "duration": 2.73}, {"text": "that both blocks are hit.", "start": 464.95, "duration": 1.77}, {"text": "At time TB1, Bob observes\nthat the left clock is hit.", "start": 466.72, "duration": 3.51}, {"text": "At time TB2, it's\nthe right clock.", "start": 470.23, "duration": 2.97}, {"text": "Which of the following\nanswers is correct?", "start": 473.2, "duration": 2.86}, {"text": "So here, you want\nto stop the video", "start": 476.06, "duration": 1.94}, {"text": "and think about which of\nthe answers is correct.", "start": 478.0, "duration": 3.51}, {"text": "So moving forward,\nthe correct answer", "start": 481.51, "duration": 2.73}, {"text": "is number three,\nwhere TB1 is smaller", "start": 484.24, "duration": 4.05}, {"text": "than TA is smaller than TB2.", "start": 488.29, "duration": 3.09}, {"text": "So again, the\nleading clock lags.", "start": 491.38, "duration": 2.77}, {"text": "The leading clock\nhas a larger TB,", "start": 494.15, "duration": 2.66}, {"text": "which means that clock\nticks a little slower.", "start": 496.81, "duration": 4.93}, {"text": "And again, the two events,\nthey can be simultaneously", "start": 501.74, "duration": 2.88}, {"text": "to one observer--", "start": 504.62, "duration": 0.96}, {"text": "Alice, in this case--\nbut not to another, Bob.", "start": 505.58, "duration": 2.73}, {"text": "All right, let's look at\nclocks a little bit more", "start": 511.16, "duration": 2.22}, {"text": "and design an optical clock.", "start": 513.38, "duration": 3.13}, {"text": "So here, the situation\nis as follows.", "start": 516.51, "duration": 2.919}, {"text": "We have two mirrors in\nwhich we inject light.", "start": 519.429, "duration": 2.811}, {"text": "The light travels\nup and travels down.", "start": 522.24, "duration": 2.67}, {"text": "And that's what\nwe call one clock", "start": 524.91, "duration": 2.22}, {"text": "tick of this optical clock.", "start": 527.13, "duration": 2.31}, {"text": "The length between\nthe two mirrors is L.", "start": 529.44, "duration": 2.49}, {"text": "So for Alice, she has\nthis clock in her hand.", "start": 531.93, "duration": 2.64}, {"text": "And she can happily observe\nthe ticking of the clock.", "start": 534.57, "duration": 5.88}, {"text": "OK, Bob observes Alice's\nclock and compares it", "start": 540.45, "duration": 2.55}, {"text": "with his own identical clock.", "start": 543.0, "duration": 2.43}, {"text": "There's a relative speed\nbetween Alice and Bob,", "start": 545.43, "duration": 2.22}, {"text": "and that's v in x direction.", "start": 547.65, "duration": 3.58}, {"text": "Now, the task for you is to\nrelate the clock ticks which", "start": 551.23, "duration": 3.98}, {"text": "are observed by Bob and\nthe ones which are observed", "start": 555.21, "duration": 3.36}, {"text": "by Alice in Alice's clock.", "start": 558.57, "duration": 2.91}, {"text": "So again, stop the video\nand work out the algebra.", "start": 561.48, "duration": 4.32}, {"text": "The answer is going to\nbe, again, surprising.", "start": 565.8, "duration": 2.58}, {"text": "So if you do this now,\nwe find this picture.", "start": 570.98, "duration": 5.25}, {"text": "So we calculate how long\ndoes a clock tick take.", "start": 576.23, "duration": 2.43}, {"text": "The light has to travel\nto L with a velocity c.", "start": 578.66, "duration": 3.36}, {"text": "So the clock tick is 2L over c.", "start": 582.02, "duration": 2.34}, {"text": "The length can be expressed\nas c times t delta tA over 2.", "start": 584.36, "duration": 5.28}, {"text": "For Bob's, the situation is a\nlittle bit more complicated.", "start": 589.64, "duration": 2.58}, {"text": "And we have to use Pythagoras in\norder to calculate the length.", "start": 592.22, "duration": 5.07}, {"text": "So we define that the length\nthe light has to travel", "start": 597.29, "duration": 2.28}, {"text": "is D, then the delta\ntB as Bob observes", "start": 599.57, "duration": 3.3}, {"text": "this is 2 times D over c.", "start": 602.87, "duration": 3.21}, {"text": "Again, for Bob,\nthe light travels", "start": 606.08, "duration": 2.31}, {"text": "with the speed of light.", "start": 608.39, "duration": 1.35}, {"text": "Einstein just postulated it.", "start": 609.74, "duration": 2.28}, {"text": "And then we find the length\nas expressed to the time", "start": 612.02, "duration": 3.06}, {"text": "as c times delta tB over 2.", "start": 615.08, "duration": 3.35}, {"text": "The length in x is simply given\nby the relative velocity, v,", "start": 618.43, "duration": 4.32}, {"text": "times the time it takes\nfor the clock to tick--", "start": 622.75, "duration": 2.94}, {"text": "v times delta tB.", "start": 625.69, "duration": 1.95}, {"text": "So then we can express D square\nvia L squared plus x squared", "start": 627.64, "duration": 5.37}, {"text": "over 4 and use those\nexpressions here.", "start": 633.01, "duration": 3.37}, {"text": "So we just use this for L,\nthis for D, and this 4x,", "start": 636.38, "duration": 3.99}, {"text": "we find this expression here.", "start": 640.37, "duration": 2.6}, {"text": "All right.", "start": 642.97, "duration": 0.81}, {"text": "And then we solve\nthis for delta tB.", "start": 643.78, "duration": 3.0}, {"text": "And we find the relation\nbetween delta tB and delta tA", "start": 646.78, "duration": 3.96}, {"text": "and can find that it's\n1 over square root", "start": 650.74, "duration": 3.27}, {"text": "1 minus v squared\nover c squared,", "start": 654.01, "duration": 2.46}, {"text": "which is the Lorentz factor.", "start": 656.47, "duration": 2.46}, {"text": "So we just used a simple\nclock and Einstein's postulate", "start": 658.93, "duration": 3.66}, {"text": "derived time dilation.", "start": 662.59, "duration": 2.82}, {"text": "We find that for Bob, Alice's\nmoving clock moves slower.", "start": 665.41, "duration": 5.61}, {"text": "Great.", "start": 674.25, "duration": 0.75}, {"text": "So again, gamma is\n1 over square root 1", "start": 675.0, "duration": 4.23}, {"text": "minus v squared over c squared.", "start": 679.23, "duration": 1.56}, {"text": "We often use, in short, beta\nas a relativistic velocity.", "start": 680.79, "duration": 4.71}, {"text": "It's unitless and\ndefined as v over c.", "start": 685.5, "duration": 4.17}, {"text": "gamma is always\ngreater or equal to 1.", "start": 689.67, "duration": 2.91}, {"text": "And it's mostly\none for everything", "start": 692.58, "duration": 1.68}, {"text": "we observe in nature.", "start": 694.26, "duration": 1.69}, {"text": "So in one of the p\nsets and also here,", "start": 695.95, "duration": 3.65}, {"text": "I invite you to simply\ncalculate values", "start": 699.6, "duration": 3.36}, {"text": "for gamma for things you might\nthink are fast-moving objects.", "start": 702.96, "duration": 4.08}, {"text": "So we start with a fighter jet.", "start": 707.04, "duration": 2.1}, {"text": "We look at the\nInternational Space Station,", "start": 709.14, "duration": 2.34}, {"text": "the Earth around the sun, the\nparticle which almost moves", "start": 711.48, "duration": 3.07}, {"text": "with the speed of light, and\nthe proton at the Large Hadron", "start": 714.55, "duration": 2.93}, {"text": "Collider, which is only 3\nmeters per second slower", "start": 717.48, "duration": 3.18}, {"text": "than the speed of light.", "start": 720.66, "duration": 2.2}, {"text": "So again, stop the video\nand work out those numbers.", "start": 722.86, "duration": 3.5}, {"text": "You will need a\ncalculator for that.", "start": 726.36, "duration": 3.41}, {"text": "So if I do this, I\nfind for this very,", "start": 729.77, "duration": 3.18}, {"text": "very fast F15 fighter jet,\nwhich moves with speeds of 2,680", "start": 732.95, "duration": 4.88}, {"text": "kilometers per hour, that\nthe number for gamma is", "start": 737.83, "duration": 3.3}, {"text": "1.00000000000, which\nis 11 zeros, 3.", "start": 741.13, "duration": 10.08}, {"text": "So we find this very, very\nsmall number or number", "start": 751.21, "duration": 3.45}, {"text": "which is very, very close to 1.", "start": 754.66, "duration": 2.43}, {"text": "The duration for the\nInternational Space Station", "start": 757.09, "duration": 2.37}, {"text": "changes a bit--", "start": 759.46, "duration": 1.02}, {"text": "only 9 zeros.", "start": 760.48, "duration": 1.705}, {"text": "For the Earth around\nthe sun, the Earth", "start": 762.185, "duration": 1.625}, {"text": "is really, really fast,\ntravels a long distance.", "start": 763.81, "duration": 2.4}, {"text": "Every year, we travel\nonce around the sun.", "start": 766.21, "duration": 2.67}, {"text": "And you know, every\nyear you get older.", "start": 768.88, "duration": 2.56}, {"text": "You have a lot of\nmileage on your back.", "start": 771.44, "duration": 2.39}, {"text": "Here, you have eight zeros.", "start": 773.83, "duration": 1.92}, {"text": "Particle which moves with\n0.9 times the speed of light,", "start": 775.75, "duration": 3.21}, {"text": "here the gamma factor is\nvery different from one.", "start": 778.96, "duration": 3.45}, {"text": "It's 2.3.", "start": 782.41, "duration": 1.17}, {"text": "And the protons we\nhave at the LHC,", "start": 783.58, "duration": 2.13}, {"text": "they have a gamma\nfactor of 7,000.", "start": 785.71, "duration": 2.22}, {"text": "So you see, once you get\nclose to the speed of light,", "start": 787.93, "duration": 2.64}, {"text": "the gamma factor\napproaches large numbers.", "start": 790.57, "duration": 3.992}, {"text": "And that's where our\nrelativistic effects really", "start": 794.562, "duration": 2.518}, {"text": "are visible.", "start": 797.08, "duration": 1.67}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 0.82, "duration": 2.37}, {"text": "Commons license.", "start": 3.19, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.58, "duration": 2.21}, {"text": "continue to offer high-quality\neducational resources for free.", "start": 6.79, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 10.88, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.45, "duration": 3.93}, {"text": "at ocw.mit.edu.", "start": 17.38, "duration": 0.906}, {"text": "PROFESSOR: So today, what\nwe're going to be doing is--", "start": 22.53, "duration": 3.61}, {"text": "last week, you gave\nus some feedback what", "start": 26.14, "duration": 2.7}, {"text": "you wanted to do in the class.", "start": 28.84, "duration": 1.78}, {"text": "We're going to go through that\nand talk about the readings.", "start": 30.62, "duration": 2.67}, {"text": "I'm going to do a\nlittle calling on you", "start": 33.29, "duration": 2.03}, {"text": "and helping you take the\nclass through the readings.", "start": 35.32, "duration": 3.27}, {"text": "And then the six or seven\nthings I'm going to do--", "start": 38.59, "duration": 3.4}, {"text": "history of money; ledgers;\nfiat currency, central banks,", "start": 41.99, "duration": 4.16}, {"text": "and credit cards;\nthe role of money;", "start": 46.15, "duration": 3.48}, {"text": "some early digital money.", "start": 49.63, "duration": 2.61}, {"text": "You had the Clark reading as\nto a bunch of failed attempts.", "start": 52.24, "duration": 3.808}, {"text": "All the way through a\nlittle bit of mobile money,", "start": 56.048, "duration": 2.042}, {"text": "all the way up to\nStarbucks and Alipay.", "start": 58.09, "duration": 3.9}, {"text": "And yet, the riddle remains.", "start": 61.99, "duration": 1.89}, {"text": "We're going to get\nreally deep into Bitcoin", "start": 63.88, "duration": 1.92}, {"text": "in the next three classes.", "start": 65.8, "duration": 2.04}, {"text": "But this is to give\nsome foundational", "start": 67.84, "duration": 3.24}, {"text": "bits of money and ledgers and\ncentral banking and technology.", "start": 71.08, "duration": 5.123}, {"text": "And then, of course,\nI always like", "start": 76.203, "duration": 1.417}, {"text": "to finish the class\ntalking a little bit", "start": 77.62, "duration": 1.68}, {"text": "about why we're doing what we're\ndoing between now and then.", "start": 79.3, "duration": 3.93}, {"text": "Even though the\nreadings are required,", "start": 83.23, "duration": 1.59}, {"text": "I know you're all busy.", "start": 84.82, "duration": 0.99}, {"text": "I know that you've all\ngot a bunch of classes.", "start": 85.81, "duration": 1.98}, {"text": "And like good business\nstudents and business people,", "start": 87.79, "duration": 4.29}, {"text": "you optimize.", "start": 92.08, "duration": 0.96}, {"text": "So I'm trying to give you a\nsense of why you might read it,", "start": 93.04, "duration": 2.46}, {"text": "rather than it's required,\nat the end of each class", "start": 95.5, "duration": 2.76}, {"text": "and how it fits into\nthe course narrative.", "start": 98.26, "duration": 4.29}, {"text": "And then we'll do a\nlittle bit of conclusions.", "start": 102.55, "duration": 2.56}, {"text": "So the survey results.", "start": 105.11, "duration": 1.07}, {"text": "What did you want to learn?", "start": 106.18, "duration": 1.14}, {"text": "This is really\nyour class, and I'm", "start": 107.32, "duration": 3.39}, {"text": "going to learn as much from you.", "start": 110.71, "duration": 1.74}, {"text": "But hopefully, we're going\nto cover what you want.", "start": 112.45, "duration": 2.5}, {"text": "So here's a list of those things\nthat were at least written", "start": 114.95, "duration": 2.51}, {"text": "by two of you.", "start": 117.46, "duration": 1.26}, {"text": "First was technical things.", "start": 118.72, "duration": 2.7}, {"text": "18 of you said understanding\nblockchain technology.", "start": 121.42, "duration": 3.18}, {"text": "Hopefully, we get\nto that, but you", "start": 124.6, "duration": 2.76}, {"text": "might find that you'll want\nto do more after this class.", "start": 127.36, "duration": 3.48}, {"text": "The ecosystem and being able\nto have an educated discussion,", "start": 130.84, "duration": 4.05}, {"text": "sort of the dinner party\nconversation around blockchain.", "start": 134.89, "duration": 3.61}, {"text": "I think we'll be successful.", "start": 138.5, "duration": 1.38}, {"text": "But at the end of\nthe semester, we're", "start": 139.88, "duration": 1.67}, {"text": "going to pull these\nslides up again,", "start": 141.55, "duration": 1.5}, {"text": "and we'll see how\nwe did as a group.", "start": 143.05, "duration": 3.03}, {"text": "You all talked a lot\nabout applications.", "start": 146.08, "duration": 3.73}, {"text": "How can you actually apply it,\nlearning in the venture space", "start": 149.81, "duration": 5.18}, {"text": "and thinking about where it\nreally works in the world.", "start": 154.99, "duration": 3.813}, {"text": "And I think we're going\nto spend a lot of time", "start": 158.803, "duration": 1.917}, {"text": "on that in the second half.", "start": 160.72, "duration": 1.41}, {"text": "But all throughout,\nwe're going to be", "start": 162.13, "duration": 1.74}, {"text": "talking about the\neconomics and what's", "start": 163.87, "duration": 2.22}, {"text": "the reality versus the hype.", "start": 166.09, "duration": 4.58}, {"text": "You also wanted to understand\nits impact on people's lives,", "start": 170.67, "duration": 5.76}, {"text": "the regulation.", "start": 176.43, "duration": 1.89}, {"text": "About six of you said\nsomething about regulation.", "start": 178.32, "duration": 3.21}, {"text": "I'm glad, because we're only\ndoing one lecture on that.", "start": 181.53, "duration": 4.19}, {"text": "But we're going\nto spread it out,", "start": 185.72, "duration": 1.57}, {"text": "because as we talked\nabout in our first class--", "start": 187.29, "duration": 3.48}, {"text": "and I'm honored\nLarry's here again--", "start": 190.77, "duration": 1.97}, {"text": "but we're going to always be\nthinking about Larry's four", "start": 192.74, "duration": 4.03}, {"text": "ways.", "start": 196.77, "duration": 1.07}, {"text": "And I see-- is it Jihei?", "start": 197.84, "duration": 2.77}, {"text": "What are Larry Lessig's--", "start": 200.61, "duration": 2.77}, {"text": "you shook your head yes.", "start": 203.38, "duration": 2.12}, {"text": "AUDIENCE: I know-- let's see.", "start": 205.5, "duration": 4.172}, {"text": "It is code and architecture,\nmarket, law, and norms.", "start": 209.672, "duration": 5.248}, {"text": "PROFESSOR: You got it.", "start": 214.92, "duration": 1.417}, {"text": "Does anybody want to say how\nthat relates to blockchain,", "start": 216.337, "duration": 2.333}, {"text": "why we're chatting about that?", "start": 218.67, "duration": 1.31}, {"text": "Oh, my god, I'm going to have\nto cold call fast, right?", "start": 224.7, "duration": 3.42}, {"text": "You're from R3.", "start": 228.12, "duration": 0.75}, {"text": "Joe?", "start": 231.79, "duration": 2.46}, {"text": "AUDIENCE: No, I remember\nwe saw it last class,", "start": 234.25, "duration": 2.1}, {"text": "but I can't relate\nit now to blockchain.", "start": 236.35, "duration": 4.41}, {"text": "PROFESSOR: Can you relate\nit to anything in life?", "start": 240.76, "duration": 3.42}, {"text": "Maybe not.", "start": 244.18, "duration": 0.87}, {"text": "Alan, help your tablemate out.", "start": 245.05, "duration": 2.67}, {"text": "AUDIENCE: I'm waiting\nfor my moment to shine.", "start": 247.72, "duration": 3.428}, {"text": "PROFESSOR: This isn't it.", "start": 251.148, "duration": 1.042}, {"text": "AUDIENCE: This isn't it.", "start": 252.19, "duration": 1.71}, {"text": "PROFESSOR: I'm having fun.", "start": 253.9, "duration": 1.342}, {"text": "This is what I'm going to do.", "start": 255.242, "duration": 1.208}, {"text": "I'm just going to have--", "start": 256.45, "duration": 1.199}, {"text": "don't worry about it.", "start": 257.649, "duration": 2.141}, {"text": "So why do markets, code, law--", "start": 259.79, "duration": 5.25}, {"text": "I can't see your name,\nbut is it [INAUDIBLE]??", "start": 265.04, "duration": 4.29}, {"text": "Yeah, why?", "start": 269.33, "duration": 0.77}, {"text": "Why does that\nrelate to all this?", "start": 270.1, "duration": 2.66}, {"text": "AUDIENCE: Can you\nrepeat the question?", "start": 272.76, "duration": 3.5}, {"text": "PROFESSOR: Jihei, you're\ngoing to repeat the question,", "start": 276.26, "duration": 3.04}, {"text": "because you went through it.", "start": 279.3, "duration": 1.27}, {"text": "AUDIENCE: So how does\nLarry's four forces relate", "start": 280.57, "duration": 5.33}, {"text": "to our topic of blockchain.", "start": 285.9, "duration": 3.755}, {"text": "PROFESSOR: And the four\nforces, again, are market,", "start": 289.655, "duration": 3.025}, {"text": "so business; law;\ncode or architecture,", "start": 292.68, "duration": 5.34}, {"text": "call it technology;\nand social norms.", "start": 298.02, "duration": 4.3}, {"text": "AUDIENCE: So I think\nit's because it", "start": 302.32, "duration": 1.565}, {"text": "brings a new way of\ndoing those things,", "start": 303.885, "duration": 3.375}, {"text": "like a new tool in order to--", "start": 307.26, "duration": 3.68}, {"text": "so what I got from the reading\nis these ledgers already", "start": 310.94, "duration": 4.74}, {"text": "existed, but given that now\nwe have big data, for example,", "start": 315.68, "duration": 4.54}, {"text": "then more things going on helps\nour society roll it out better.", "start": 320.22, "duration": 5.54}, {"text": "PROFESSOR: Good way to say it.", "start": 325.76, "duration": 1.25}, {"text": "Look, it's unfair of me.", "start": 327.01, "duration": 1.38}, {"text": "It wasn't one of the readings.", "start": 328.39, "duration": 1.25}, {"text": "I'm just saying, in\neverything in life,", "start": 329.64, "duration": 2.07}, {"text": "I find these things grind\nup against each other.", "start": 331.71, "duration": 3.55}, {"text": "I spent a lot of time in\nWashington in politics,", "start": 335.26, "duration": 4.37}, {"text": "but the markets and how\nthe commercial enterprise", "start": 339.63, "duration": 3.3}, {"text": "and the economy grinds up\nagainst technology and sort", "start": 342.93, "duration": 4.35}, {"text": "of grinds up against the law--", "start": 347.28, "duration": 3.66}, {"text": "and then, of course, just\nsocial normative behavior.", "start": 350.94, "duration": 2.73}, {"text": "These four forces, in almost\neverything one does in life,", "start": 353.67, "duration": 3.81}, {"text": "you will find.", "start": 357.48, "duration": 1.89}, {"text": "And so I just ask you\nto always, whether it's", "start": 359.37, "duration": 2.7}, {"text": "one reading or another\nreading, bring that", "start": 362.07, "duration": 1.83}, {"text": "into your thought\nprocess of this class.", "start": 363.9, "duration": 2.85}, {"text": "I'm not going to assign\nLarry's assignment.", "start": 366.75, "duration": 1.868}, {"text": "I didn't know he was\neven going to be here.", "start": 368.618, "duration": 1.792}, {"text": "But I've always thought\nit's a good discipline", "start": 370.41, "duration": 3.3}, {"text": "to think, OK, what are\nthe commercial realities,", "start": 373.71, "duration": 2.79}, {"text": "the markets?", "start": 376.5, "duration": 1.68}, {"text": "What's the technology, even\nif it's in an earlier day", "start": 378.18, "duration": 5.1}, {"text": "and it's the technology of\nthe car replacing the horse", "start": 383.28, "duration": 2.803}, {"text": "and carriage?", "start": 386.083, "duration": 0.542}, {"text": "How does government\nor the official sector", "start": 389.44, "duration": 2.89}, {"text": "put it into a set of\nstandards that are required?", "start": 392.33, "duration": 4.665}, {"text": "And then how do\nwe, as a society,", "start": 396.995, "duration": 1.375}, {"text": "even if it's not required,\njust have our behaviors?", "start": 398.37, "duration": 3.05}, {"text": "Those are the four forces.", "start": 401.42, "duration": 1.71}, {"text": "So that's why.", "start": 403.13, "duration": 2.43}, {"text": "I probably just\nfailed Larry's class,", "start": 405.56, "duration": 2.19}, {"text": "but that's how I've\nthought about it.", "start": 407.75, "duration": 2.47}, {"text": "I did, probably, right?", "start": 410.22, "duration": 1.86}, {"text": "No, he's shaking his head.", "start": 412.08, "duration": 1.88}, {"text": "But regulation is just\none of those four forces.", "start": 413.96, "duration": 2.65}, {"text": "And that's why I pause there.", "start": 416.61, "duration": 1.76}, {"text": "And so we'll have it in every\nclass, but only one lecture.", "start": 418.37, "duration": 4.38}, {"text": "Money and markets, that's\none of the other forces.", "start": 422.75, "duration": 2.28}, {"text": "Five of you said you\nwant to make money,", "start": 425.03, "duration": 1.8}, {"text": "and I applaud those who\nsaid that, because own it.", "start": 426.83, "duration": 3.543}, {"text": "You're in a business school.", "start": 430.373, "duration": 1.167}, {"text": "Why not?", "start": 431.54, "duration": 2.49}, {"text": "But investing and trends.", "start": 434.03, "duration": 2.1}, {"text": "Now, there was a bunch of\nother miscellaneous topics.", "start": 436.13, "duration": 2.34}, {"text": "I'm not going to\ngo through them.", "start": 438.47, "duration": 1.375}, {"text": "I kind of thought the last two\nwere interesting-- anecdotes", "start": 439.845, "duration": 3.005}, {"text": "from my past.", "start": 442.85, "duration": 1.5}, {"text": "I'm not sure who said that.", "start": 444.35, "duration": 2.802}, {"text": "I'm not sure what you want\nto know about-- my three", "start": 447.152, "duration": 2.328}, {"text": "daughters, my running, or this\nWall Street stuff and finance.", "start": 449.48, "duration": 4.95}, {"text": "And I'd like to understand\nhyperbitcoinization, as well,", "start": 454.43, "duration": 4.3}, {"text": "but I don't know who\nasked that question.", "start": 458.73, "duration": 2.66}, {"text": "I don't know what\nit is, so I'll try", "start": 461.39, "duration": 1.53}, {"text": "to figure out what\nhyper-- does anyone want", "start": 462.92, "duration": 3.15}, {"text": "to own up to that question?", "start": 466.07, "duration": 1.77}, {"text": "They were anonymous.", "start": 467.84, "duration": 0.87}, {"text": "All right.", "start": 468.71, "duration": 1.24}, {"text": "All right.", "start": 469.95, "duration": 0.5}, {"text": "So today's study questions.", "start": 470.45, "duration": 4.89}, {"text": "What's the role of\nmoney historically", "start": 475.34, "duration": 2.97}, {"text": "and in today's digital economy?", "start": 478.31, "duration": 4.09}, {"text": "And this is when I'm going\nto look for discussion.", "start": 482.4, "duration": 2.27}, {"text": "So does anybody\nwant to tell me what", "start": 484.67, "duration": 1.5}, {"text": "the role of money-- what\nwould be your answer to this?", "start": 486.17, "duration": 5.16}, {"text": "Anton?", "start": 491.33, "duration": 2.905}, {"text": "AUDIENCE: The medium of the\ntransaction, and the unit of--", "start": 494.235, "duration": 5.865}, {"text": "like a counting unit.", "start": 500.1, "duration": 2.08}, {"text": "And also, the\nstate of the value.", "start": 502.18, "duration": 3.48}, {"text": "PROFESSOR: So the three\nclassic rolls of money", "start": 505.66, "duration": 2.79}, {"text": "that people talk about.", "start": 508.45, "duration": 2.37}, {"text": "Kelly, you want to\nrepeat what he just said?", "start": 510.82, "duration": 2.312}, {"text": "AUDIENCE: [INAUDIBLE]\nthe question,", "start": 513.132, "duration": 1.458}, {"text": "but I think historically,\nit was pay off", "start": 514.59, "duration": 2.589}, {"text": "debts, starting and conquering\nvarious lands and wards,", "start": 517.179, "duration": 4.74}, {"text": "and then also funding\ntrade wars, cutting taxes.", "start": 521.919, "duration": 3.311}, {"text": "So a lot of societal things\nthat drove civilization forward.", "start": 525.23, "duration": 5.985}, {"text": "PROFESSOR: And what\nwe'll discuss today", "start": 531.215, "duration": 1.625}, {"text": "and what it is, is that\nmoney is a social construct.", "start": 532.84, "duration": 3.15}, {"text": "It's something that\nsocieties came together--", "start": 535.99, "duration": 2.85}, {"text": "it's hard to tell whether it\nwas 5,000 years ago or 8,000", "start": 538.84, "duration": 3.09}, {"text": "or 10,000 years ago.", "start": 541.93, "duration": 2.85}, {"text": "Really, it's a social\nconsensus mechanism.", "start": 544.78, "duration": 4.98}, {"text": "But we're going to chat about\nthe readings in a minute", "start": 549.76, "duration": 2.91}, {"text": "and come back to that question.", "start": 552.67, "duration": 2.82}, {"text": "What is fiat currency?", "start": 555.49, "duration": 1.033}, {"text": "Does anybody want to--", "start": 556.523, "duration": 0.917}, {"text": "Tom, you want to tell us\nwhat fiat currency is?", "start": 557.44, "duration": 3.99}, {"text": "It's a shame, Tom.", "start": 561.43, "duration": 1.06}, {"text": "See, I recognize you.", "start": 562.49, "duration": 1.95}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 564.44, "duration": 3.29}, {"text": "This is like a\nestablished currency", "start": 567.73, "duration": 2.85}, {"text": "by a central government, by\na government that proposed", "start": 570.58, "duration": 3.56}, {"text": "a market or [INAUDIBLE].", "start": 574.14, "duration": 1.792}, {"text": "PROFESSOR: Right.", "start": 575.932, "duration": 0.708}, {"text": "So you said it's a\ncentral currency,", "start": 576.64, "duration": 2.69}, {"text": "and it's by government.", "start": 579.33, "duration": 1.84}, {"text": "Anybody else want\nto add some things?", "start": 581.17, "duration": 2.61}, {"text": "Is it Kyle?", "start": 583.78, "duration": 1.41}, {"text": "AUDIENCE: I would just\nadd that it's not backed", "start": 585.19, "duration": 2.04}, {"text": "by any physical commodity.", "start": 587.23, "duration": 1.222}, {"text": "PROFESSOR: So it's not backed\nby any physical commodity.", "start": 588.452, "duration": 2.333}, {"text": "AUDIENCE: Yeah.", "start": 590.785, "duration": 0.625}, {"text": "Really just the good faith\nand credit of the nation", "start": 591.41, "duration": 3.05}, {"text": "that issues it.", "start": 594.46, "duration": 1.59}, {"text": "PROFESSOR: Daniel, did\nyou want to add anything?", "start": 596.05, "duration": 2.0}, {"text": "AUDIENCE: I was just\ngoing to say somewhere", "start": 598.05, "duration": 1.792}, {"text": "that it's not gold backed\nor anything like that.", "start": 599.842, "duration": 2.578}, {"text": "PROFESSOR: But was\nit always that way?", "start": 602.42, "duration": 2.113}, {"text": "AUDIENCE: It wasn't\noriginally that way.", "start": 604.533, "duration": 1.667}, {"text": "PROFESSOR: Right.", "start": 606.2, "duration": 0.708}, {"text": "A fiat currency might be\nbacked by something physical.", "start": 606.908, "duration": 3.612}, {"text": "Was there other--\nremind me your name.", "start": 610.52, "duration": 2.64}, {"text": "I'm sorry.", "start": 613.16, "duration": 0.5}, {"text": "AUDIENCE: Josh.", "start": 613.66, "duration": 1.05}, {"text": "PROFESSOR: Josh.", "start": 614.71, "duration": 1.21}, {"text": "AUDIENCE: Specifically\nused to settle", "start": 615.92, "duration": 2.18}, {"text": "debts, specifically those\nto the government, so taxes.", "start": 618.1, "duration": 3.927}, {"text": "PROFESSOR: All right, so\nit can be used for taxes.", "start": 622.027, "duration": 2.083}, {"text": "And remind me of your name,\nbecause I can't see a card.", "start": 624.11, "duration": 2.292}, {"text": "What?", "start": 626.402, "duration": 0.5}, {"text": "AUDIENCE: Sean.", "start": 626.902, "duration": 0.638}, {"text": "PROFESSOR: Sean.", "start": 627.54, "duration": 0.88}, {"text": "AUDIENCE: So, basically,\nthere's no inherent value", "start": 628.42, "duration": 2.59}, {"text": "in fiat currency.", "start": 631.01, "duration": 2.26}, {"text": "So basically, there's\nno one recognize", "start": 633.27, "duration": 3.52}, {"text": "that specific currency itself.", "start": 636.79, "duration": 2.503}, {"text": "There's no government.", "start": 639.293, "duration": 0.917}, {"text": "PROFESSOR: So here's a\nquestion for the class.", "start": 640.21, "duration": 2.49}, {"text": "Is there inherent value\nto non-fiat currencies?", "start": 642.7, "duration": 4.09}, {"text": "Because Sean's saying that maybe\na distinguishing characteristic", "start": 646.79, "duration": 3.29}, {"text": "of fiat is it has\nno inherent value.", "start": 650.08, "duration": 3.25}, {"text": "AUDIENCE: Terry.", "start": 653.33, "duration": 0.733}, {"text": "PROFESSOR: Terry.", "start": 654.063, "duration": 0.787}, {"text": "AUDIENCE: Well,\nactually, the same", "start": 654.85, "duration": 1.47}, {"text": "applies to any commodity\nthat's used to--", "start": 656.32, "duration": 2.28}, {"text": "currency in general.", "start": 662.11, "duration": 1.41}, {"text": "Because it's just the scarcity\nof some specific resource", "start": 663.52, "duration": 4.2}, {"text": "and social common\nagreement that that's", "start": 667.72, "duration": 5.67}, {"text": "going to be the parameter.", "start": 673.39, "duration": 3.43}, {"text": "PROFESSOR: So how many people\nare more in line with Eric or--", "start": 676.82, "duration": 5.33}, {"text": "there's not one\nright answer to this.", "start": 682.15, "duration": 1.89}, {"text": "This is a question\nthat's been debated", "start": 684.04, "duration": 1.89}, {"text": "for decades or centuries.", "start": 685.93, "duration": 3.96}, {"text": "How many are more\nin Sean's camp?", "start": 689.89, "duration": 2.312}, {"text": "AUDIENCE: I think it depends.", "start": 692.202, "duration": 1.208}, {"text": "For example, gold is\ndefinitely a social construct.", "start": 693.41, "duration": 3.25}, {"text": "We decide that, as\na human society,", "start": 696.66, "duration": 2.11}, {"text": "that gold is going to\nbe something valuable.", "start": 698.77, "duration": 2.79}, {"text": "But if it's, like, grains\nthat humans can [INAUDIBLE]", "start": 701.56, "duration": 3.09}, {"text": "and that, I think,\nhas an inherent value.", "start": 704.65, "duration": 2.52}, {"text": "So I think there are\nnon-fiat currencies that", "start": 707.17, "duration": 3.22}, {"text": "does have inherent\nvalues and that", "start": 710.39, "duration": 1.76}, {"text": "does not have inherent values.", "start": 712.15, "duration": 2.085}, {"text": "PROFESSOR: All right,\nanybody-- what's your--", "start": 714.235, "duration": 1.875}, {"text": "Jihi, yeah.", "start": 716.11, "duration": 1.92}, {"text": "Tom?", "start": 718.03, "duration": 0.54}, {"text": "Tomas?", "start": 718.57, "duration": 0.59}, {"text": "AUDIENCE: Tomas.", "start": 719.16, "duration": 0.95}, {"text": "I just want to say\nthat the [INAUDIBLE] is", "start": 720.11, "duration": 2.75}, {"text": "another component which the\nfact that it is a legal tender.", "start": 722.86, "duration": 4.32}, {"text": "So the government\nand some [INAUDIBLE]", "start": 727.18, "duration": 3.45}, {"text": "forced the society to use the\ncurrency, which makes more", "start": 730.63, "duration": 5.83}, {"text": "comfortable for people to use.", "start": 736.46, "duration": 1.885}, {"text": "PROFESSOR: So Tomas is\nsaying that fiat currency is", "start": 738.345, "duration": 3.145}, {"text": "legal tender.", "start": 741.49, "duration": 1.08}, {"text": "So first, we have to discuss,\nwhat is legal tender?", "start": 742.57, "duration": 2.49}, {"text": "Does anybody want to\nknock that one out", "start": 745.06, "duration": 2.49}, {"text": "of the ballpark who hasn't\nraised their hand yet?", "start": 747.55, "duration": 4.15}, {"text": "No?", "start": 751.7, "duration": 1.41}, {"text": "All right.", "start": 753.11, "duration": 1.2}, {"text": "AUDIENCE: I think that's\nmaybe my earlier comment.", "start": 754.31, "duration": 3.855}, {"text": "It can be used to settle\ndebts, and specifically", "start": 758.165, "duration": 5.015}, {"text": "those to the government.", "start": 763.18, "duration": 1.0}, {"text": "So you can use gold as a money.", "start": 764.18, "duration": 2.7}, {"text": "It can be a stored value.", "start": 766.88, "duration": 1.2}, {"text": "It can be a means of exchange.", "start": 768.08, "duration": 2.08}, {"text": "But you can't pay your\ntaxes in gold, right?", "start": 770.16, "duration": 2.33}, {"text": "You have to--", "start": 772.49, "duration": 0.65}, {"text": "PROFESSOR: Is that correct?", "start": 773.14, "duration": 1.21}, {"text": "So 19th century, could you pay\nyour taxes in gold in the US", "start": 774.35, "duration": 4.88}, {"text": "and in Britain and\nother countries that", "start": 779.23, "duration": 2.23}, {"text": "had gold currency?", "start": 781.46, "duration": 1.17}, {"text": "This is just a yes\nor no, but James?", "start": 785.4, "duration": 2.31}, {"text": "AUDIENCE: It's yes, but after\n1970s, the paper currency", "start": 787.71, "duration": 4.395}, {"text": "is attached to\nthe gold standard.", "start": 792.105, "duration": 1.375}, {"text": "So inherently, there\nis an exchange of value", "start": 793.48, "duration": 2.48}, {"text": "that is picked by the\ngovernment or the central bank.", "start": 795.96, "duration": 3.42}, {"text": "So it's almost one of the\nsame thing at that time,", "start": 799.38, "duration": 3.51}, {"text": "until more recent years.", "start": 802.89, "duration": 1.65}, {"text": "PROFESSOR: James is saying you\ncould use gold as legal tender.", "start": 804.54, "duration": 4.11}, {"text": "Legal tender,\nagain, is something", "start": 808.65, "duration": 1.65}, {"text": "that a society comes\ntogether and creates a law--", "start": 810.3, "duration": 4.47}, {"text": "back to the Lessig four.", "start": 814.77, "duration": 2.07}, {"text": "Society together\nsays-- it's not just", "start": 816.84, "duration": 2.31}, {"text": "a social normative behavior.", "start": 819.15, "duration": 2.65}, {"text": "It's a law.", "start": 821.8, "duration": 1.31}, {"text": "One must accept this.", "start": 823.11, "duration": 3.44}, {"text": "And the US and the\nUK and many countries", "start": 826.55, "duration": 2.56}, {"text": "it says for all debts,\npublic and private.", "start": 829.11, "duration": 3.26}, {"text": "So a debt to the government\nor a debt in a store.", "start": 832.37, "duration": 7.03}, {"text": "We're going to get\nto, later, as to when", "start": 839.4, "duration": 2.25}, {"text": "is it true that somebody\nhas to take your cash.", "start": 841.65, "duration": 3.39}, {"text": "But I'm going to hold\noff on that in a minute", "start": 845.04, "duration": 3.57}, {"text": "and talk about it.", "start": 848.61, "duration": 1.48}, {"text": "But I think, also, Jihei said--", "start": 850.09, "duration": 2.345}, {"text": "it was somewhere between Sean\nand Eric, both physically", "start": 852.435, "duration": 4.995}, {"text": "in the class and in terms\nof her articulation--", "start": 857.43, "duration": 2.55}, {"text": "that fiat currency\nmight not have anything", "start": 859.98, "duration": 3.6}, {"text": "inherently behind it.", "start": 863.58, "duration": 2.61}, {"text": "But gold mostly doesn't have\nanything inherently behind it.", "start": 866.19, "duration": 4.56}, {"text": "And then some forms of\ncurrency, like grain, had more.", "start": 870.75, "duration": 5.22}, {"text": "So maybe it's a continuum.", "start": 875.97, "duration": 2.49}, {"text": "Maybe it's not black\nand white, 100% or 0%.", "start": 878.46, "duration": 4.412}, {"text": "And then we're going\nto talk a little bit", "start": 882.872, "duration": 1.708}, {"text": "about how Bitcoin fits into it.", "start": 884.58, "duration": 2.43}, {"text": "And our next three\nclasses are going", "start": 887.01, "duration": 2.17}, {"text": "to be really into the\ntechnology of Bitcoin,", "start": 889.18, "duration": 2.48}, {"text": "but just a little bit\nof teasing out before I", "start": 891.66, "duration": 3.36}, {"text": "go through some lecture slides.", "start": 895.02, "duration": 1.32}, {"text": "Who wants to talk\nabout how Bitcoin might", "start": 896.34, "duration": 2.4}, {"text": "fit into this history of money?", "start": 898.74, "duration": 2.22}, {"text": "And then I'm going to return\nto that question in about", "start": 900.96, "duration": 3.3}, {"text": "45 minutes and ask you again.", "start": 904.26, "duration": 2.91}, {"text": "Does anybody want to\nsay from the readings?", "start": 907.17, "duration": 1.92}, {"text": "And you remind me your name?", "start": 909.09, "duration": 1.542}, {"text": "AUDIENCE: Isabel.", "start": 910.632, "duration": 0.708}, {"text": "PROFESSOR: Isabel.", "start": 911.34, "duration": 0.755}, {"text": "AUDIENCE: So with\nBitcoin, it's kind", "start": 912.095, "duration": 0.93}, {"text": "of the same, where\nthe value is given", "start": 913.025, "duration": 2.065}, {"text": "by society, except\nwith Bitcoin, it's", "start": 915.09, "duration": 2.38}, {"text": "not backed by a central bank.", "start": 917.47, "duration": 1.73}, {"text": "So people don't think that\nthere is an inherent value.", "start": 919.2, "duration": 3.212}, {"text": "But the readings\npointed out that there's", "start": 922.412, "duration": 1.708}, {"text": "sort of that same history,\nexcept it doesn't have", "start": 924.12, "duration": 2.523}, {"text": "[INAUDIBLE].", "start": 926.643, "duration": 0.687}, {"text": "PROFESSOR: So Isabel\nis saying that Bitcoin", "start": 927.33, "duration": 2.01}, {"text": "fits into the history of money\nbecause, like fiat currencies", "start": 929.34, "duration": 4.26}, {"text": "and like Jihei said about\ngold, it doesn't necessarily", "start": 933.6, "duration": 3.3}, {"text": "have any inherent\nmonetary value,", "start": 936.9, "duration": 3.6}, {"text": "but it's a societal set of norms\nthat people are accepting it", "start": 940.5, "duration": 3.81}, {"text": "as having value.", "start": 944.31, "duration": 1.41}, {"text": "But the key distinction\nthat Isabel said", "start": 945.72, "duration": 2.34}, {"text": "was that it's no central.", "start": 948.06, "duration": 1.32}, {"text": "AUDIENCE: It's not backed\nby any kind of central bank.", "start": 949.38, "duration": 2.25}, {"text": "PROFESSOR: It's not\nbacked by a central bank", "start": 951.63, "duration": 1.833}, {"text": "or a central authority.", "start": 953.463, "duration": 1.417}, {"text": "Alan?", "start": 954.88, "duration": 0.86}, {"text": "AUDIENCE: Yes.", "start": 955.74, "duration": 1.11}, {"text": "So Bitcoin, in my\nopinion, is unique,", "start": 956.85, "duration": 2.58}, {"text": "because I think the value of\nBitcoin changes over time, not", "start": 959.43, "duration": 4.53}, {"text": "the fluctuation that we\nsee like $6,000 or $90,000,", "start": 963.96, "duration": 3.39}, {"text": "but in terms of the\nutility of the coin itself.", "start": 967.35, "duration": 5.01}, {"text": "So today, for example, we might\nbe able to buy pizza or coffee", "start": 972.36, "duration": 3.93}, {"text": "or whatever with Bitcoin, so\nthere is an inherent value", "start": 976.29, "duration": 3.68}, {"text": "in terms of medium of exchange.", "start": 979.97, "duration": 1.81}, {"text": "And it will change as society\nadopts it more and more.", "start": 981.78, "duration": 3.22}, {"text": "So I think it's hard to define\nif there is inherent value", "start": 985.0, "duration": 4.25}, {"text": "or not.", "start": 989.25, "duration": 0.91}, {"text": "PROFESSOR: So Alan is\nraising that Bitcoin--", "start": 990.16, "duration": 3.2}, {"text": "if I can put some\nwords in your mouth,", "start": 993.36, "duration": 2.16}, {"text": "and tell me if I'm\ncorrect, that Bitcoin", "start": 995.52, "duration": 2.61}, {"text": "might have some\ndistinguishing features", "start": 998.13, "duration": 1.8}, {"text": "from even fiat currency,\nthat its value is shifting", "start": 999.93, "duration": 3.9}, {"text": "over time with adoption.", "start": 1003.83, "duration": 2.378}, {"text": "Is that-- I mean, you\ndidn't use that word.", "start": 1006.208, "duration": 1.792}, {"text": "Please let me know\nyour name again.", "start": 1011.53, "duration": 2.265}, {"text": "AUDIENCE: Brotish.", "start": 1013.795, "duration": 1.067}, {"text": "PROFESSOR: Right.", "start": 1014.862, "duration": 0.708}, {"text": "Like British, but with an\nO, you told me earlier--", "start": 1015.57, "duration": 2.16}, {"text": "Brotish.", "start": 1017.73, "duration": 0.5}, {"text": "AUDIENCE: Another way I\nwas thinking of [INAUDIBLE]", "start": 1021.05, "duration": 3.37}, {"text": "the evolution of the later\ntechnology like accounting", "start": 1024.42, "duration": 4.1}, {"text": "and the evolution of\nmoney, along with--", "start": 1028.52, "duration": 2.819}, {"text": "so initially, we\nsaw in the reading", "start": 1031.339, "duration": 2.861}, {"text": "how it happened in the\nprehistoric age and then", "start": 1034.2, "duration": 2.43}, {"text": "the advent of the [INAUDIBLE]\nand then [INAUDIBLE]", "start": 1036.63, "duration": 2.729}, {"text": "later, which is kind of one\nof the fundamental blocks", "start": 1039.359, "duration": 3.331}, {"text": "of Bitcoin.", "start": 1042.69, "duration": 1.21}, {"text": "PROFESSOR: Right.", "start": 1043.9, "duration": 0.938}, {"text": "AUDIENCE: So that\nis another way kind", "start": 1044.838, "duration": 1.542}, {"text": "of natural progression\nof how money [INAUDIBLE]..", "start": 1046.38, "duration": 4.658}, {"text": "PROFESSOR: Brotish?", "start": 1051.038, "duration": 0.792}, {"text": "AUDIENCE: Yeah.", "start": 1051.83, "duration": 0.67}, {"text": "PROFESSOR: So what\nBrotish has raised", "start": 1052.5, "duration": 1.542}, {"text": "is also Bitcoin fits into\nthe history of ledgers,", "start": 1054.042, "duration": 2.778}, {"text": "whether it's double entry\nledgers as recognized through T", "start": 1056.82, "duration": 3.66}, {"text": "accounts or other\nforms of ledgers,", "start": 1060.48, "duration": 2.4}, {"text": "that it adds to this whole\nlong history of ledgers.", "start": 1062.88, "duration": 4.65}, {"text": "I agree with that.", "start": 1067.53, "duration": 2.91}, {"text": "And it's a new form\nof keeping ledgers.", "start": 1070.44, "duration": 2.25}, {"text": "Alan?", "start": 1072.69, "duration": 0.98}, {"text": "AUDIENCE: So Bitcoin is\nalso similar to gold.", "start": 1073.67, "duration": 2.43}, {"text": "There is an element of scarcity.", "start": 1076.1, "duration": 2.922}, {"text": "PROFESSOR: Of scarcity.", "start": 1079.022, "duration": 0.958}, {"text": "AUDIENCE: Yeah.", "start": 1079.98, "duration": 0.83}, {"text": "So you cannot generate\nthat many Bitcoin.", "start": 1080.81, "duration": 1.938}, {"text": "PROFESSOR: Correct.", "start": 1082.748, "duration": 0.792}, {"text": "AUDIENCE: You can only generate\n50 bitcoins every 10 minutes,", "start": 1083.54, "duration": 2.542}, {"text": "and it keeps happening\nevery four years.", "start": 1086.082, "duration": 3.378}, {"text": "PROFESSOR: So it seems\nlike scarcity and ledgers", "start": 1089.46, "duration": 3.66}, {"text": "are important components.", "start": 1093.12, "duration": 1.29}, {"text": "Aviva?", "start": 1094.41, "duration": 0.507}, {"text": "AUDIENCE: Yes.", "start": 1094.917, "duration": 0.583}, {"text": "So it does have a fixed demand--", "start": 1095.5, "duration": 2.152}, {"text": "sorry, a fixed supply, like\nyou said, in terms of scarcity.", "start": 1097.652, "duration": 2.458}, {"text": "But the more we\nadopt it, the more", "start": 1100.11, "duration": 1.8}, {"text": "it becomes divisible\nin terms of units.", "start": 1101.91, "duration": 2.83}, {"text": "And so we can increase its use,\nbecause now you can divide them", "start": 1104.74, "duration": 5.66}, {"text": "up to [INAUDIBLE].", "start": 1110.4, "duration": 0.87}, {"text": "PROFESSOR: This is good.", "start": 1111.27, "duration": 1.0}, {"text": "So divisibility is another\ncharacteristic of money,", "start": 1112.27, "duration": 3.62}, {"text": "scarcity, adoption as\nAlan said, ledgers.", "start": 1115.89, "duration": 5.21}, {"text": "Sorry, Tomas?", "start": 1121.1, "duration": 1.01}, {"text": "AUDIENCE: We mention\ndecentralization,", "start": 1122.11, "duration": 1.67}, {"text": "because this implementation\nmake feasible the Bitcoin", "start": 1123.78, "duration": 6.57}, {"text": "and makes feasible to\nimplement this kind of thing", "start": 1130.35, "duration": 2.22}, {"text": "in the decentralized\nenvironment.", "start": 1132.57, "duration": 2.11}, {"text": "So without any central\nauthority to design or dictate", "start": 1134.68, "duration": 5.07}, {"text": "the supply and all the\naspects of the concepts.", "start": 1139.75, "duration": 5.075}, {"text": "PROFESSOR: We'll take\none more, and then I'll", "start": 1144.825, "duration": 1.875}, {"text": "start to talk about the history.", "start": 1146.7, "duration": 1.333}, {"text": "Why don't we go here?", "start": 1148.033, "duration": 1.557}, {"text": "And remind me your name.", "start": 1149.59, "duration": 1.042}, {"text": "AUDIENCE: Alexis.", "start": 1150.632, "duration": 0.708}, {"text": "PROFESSOR: Alexis.", "start": 1151.34, "duration": 0.75}, {"text": "AUDIENCE: [INAUDIBLE]\nof like money", "start": 1152.09, "duration": 1.91}, {"text": "and other forms\nof currency, even", "start": 1154.0, "duration": 3.29}, {"text": "if it's controlled by central\ngovernment or central bank,", "start": 1157.29, "duration": 4.11}, {"text": "there's no fixed exchange rate.", "start": 1161.4, "duration": 3.35}, {"text": "It trades extremely quickly\nwith other types of currency,", "start": 1164.75, "duration": 3.07}, {"text": "so I mean, it's\nstill very different.", "start": 1167.82, "duration": 2.43}, {"text": "PROFESSOR: So, Alexis, if\nI understand Alexis' point,", "start": 1170.25, "duration": 3.39}, {"text": "it's that there's no fixed\nexchange rate about Bitcoin", "start": 1173.64, "duration": 4.65}, {"text": "we're talking about.", "start": 1178.29, "duration": 2.04}, {"text": "But couldn't we really broaden\nthat to all forms of currency?", "start": 1180.33, "duration": 5.12}, {"text": "I mean, what really\nis the exchange", "start": 1185.45, "duration": 2.37}, {"text": "rate between an ounce of\ngold and a bushel of corn?", "start": 1187.82, "duration": 6.295}, {"text": "AUDIENCE: Yes and no.", "start": 1194.115, "duration": 0.875}, {"text": "I mean, yes, that, for example,\nsome states do control exchange", "start": 1194.99, "duration": 4.44}, {"text": "rates with other counties.", "start": 1199.43, "duration": 1.605}, {"text": "PROFESSOR: All\nright, good point.", "start": 1201.035, "duration": 1.375}, {"text": "So Alexis is saying yes and\nno, because some governments", "start": 1202.41, "duration": 3.41}, {"text": "try to fix.", "start": 1205.82, "duration": 1.89}, {"text": "Now back to markets.", "start": 1207.71, "duration": 1.2}, {"text": "How well does that\nwork when governments", "start": 1208.91, "duration": 1.92}, {"text": "try to fix an exchange rate?", "start": 1210.83, "duration": 3.81}, {"text": "I mean, just as a sense of the\nclass, does that work well?", "start": 1214.64, "duration": 4.44}, {"text": "So it sort of might work well\nin temporal, short periods.", "start": 1219.08, "duration": 3.63}, {"text": "Works less well\nfor decades on end.", "start": 1222.71, "duration": 4.255}, {"text": "I'll take one more,\nand then I'm just--", "start": 1226.965, "duration": 1.625}, {"text": "I want to go through a couple--", "start": 1228.59, "duration": 0.96}, {"text": "AUDIENCE: Just one comment.", "start": 1229.55, "duration": 1.125}, {"text": "That way you can\nteach hours of work.", "start": 1230.675, "duration": 1.688}, {"text": "That's how economies define\nit previously, right?", "start": 1232.363, "duration": 4.537}, {"text": "But I just want to\nask, what is a ledger?", "start": 1236.9, "duration": 4.773}, {"text": "PROFESSOR: What is a ledger?", "start": 1241.673, "duration": 1.167}, {"text": "Very good question.", "start": 1242.84, "duration": 2.69}, {"text": "I'm going to be chatting\nabout that in a minute.", "start": 1245.53, "duration": 2.0}, {"text": "But does anybody\nwant to hit that?", "start": 1247.53, "duration": 5.65}, {"text": "I'm sorry.", "start": 1253.18, "duration": 0.79}, {"text": "No, over here.", "start": 1253.97, "duration": 1.405}, {"text": "AUDIENCE: I was going\nto say, it's just", "start": 1255.375, "duration": 1.625}, {"text": "a numerical record of everything\nrecorded, in a fashion.", "start": 1257.0, "duration": 4.08}, {"text": "[INAUDIBLE]", "start": 1261.08, "duration": 0.5}, {"text": "PROFESSOR: A numerical record.", "start": 1261.58, "duration": 1.5}, {"text": "I think that's a good thing.", "start": 1263.08, "duration": 1.23}, {"text": "A ledger is basically a way\nto record economic activity", "start": 1264.31, "duration": 7.35}, {"text": "or social relationships or\nfinancial relationships.", "start": 1271.66, "duration": 4.62}, {"text": "I would say it's both a way\nto record economic activity,", "start": 1276.28, "duration": 4.71}, {"text": "and it's a system of recording\nfinancial relationships.", "start": 1280.99, "duration": 4.77}, {"text": "And while I didn't\nassign these readings,", "start": 1285.76, "duration": 4.17}, {"text": "some very good academic\nresearch suggests", "start": 1289.93, "duration": 4.74}, {"text": "that the first methods of\nwriting and symbols of writing", "start": 1294.67, "duration": 3.84}, {"text": "had to do with numbers and\nhad to do with ledgers, rather", "start": 1298.51, "duration": 2.7}, {"text": "than words and communication.", "start": 1301.21, "duration": 5.19}, {"text": "Because it's so\nfundamental to society", "start": 1306.4, "duration": 2.52}, {"text": "to record various\neconomic transactions", "start": 1308.92, "duration": 4.74}, {"text": "or to record the\nfinancial relationships", "start": 1313.66, "duration": 3.45}, {"text": "amongst and between\nmembers of a community,", "start": 1317.11, "duration": 2.95}, {"text": "whether it was a\nsmall village or when", "start": 1320.06, "duration": 2.24}, {"text": "society burst out of villages\nthousands of years ago.", "start": 1322.3, "duration": 3.285}, {"text": "Does that help?", "start": 1325.585, "duration": 1.975}, {"text": "We'll be back to it.", "start": 1327.56, "duration": 2.74}, {"text": "And better that\nyou ask that here", "start": 1330.3, "duration": 1.45}, {"text": "than in your accounting\nfundamentals class.", "start": 1331.75, "duration": 3.882}, {"text": "I don't know.", "start": 1335.632, "duration": 1.318}, {"text": "So the readings-- we've sort\nof talked about the readings.", "start": 1336.95, "duration": 3.47}, {"text": "How many of you actually watched\nthe little three-minute video?", "start": 1340.42, "duration": 4.8}, {"text": "What'd you think?", "start": 1345.22, "duration": 1.12}, {"text": "I mean, just as a--", "start": 1346.34, "duration": 1.26}, {"text": "I'm sorry, here.", "start": 1347.6, "duration": 1.56}, {"text": "We haven't chatted yet.", "start": 1349.16, "duration": 1.64}, {"text": "AUDIENCE: I think the\nbroad-based message was", "start": 1350.8, "duration": 2.02}, {"text": "that any currency, or\nanything, for that matter,", "start": 1352.82, "duration": 2.58}, {"text": "has value equivalent to what\nthe society assigns it with.", "start": 1355.4, "duration": 3.405}, {"text": "Because the video\nbasically just showed", "start": 1358.805, "duration": 1.625}, {"text": "a guy who created his\nown currency and was just", "start": 1360.43, "duration": 2.05}, {"text": "selling it to the public.", "start": 1362.48, "duration": 1.2}, {"text": "And his whole claim\nwas that it is real", "start": 1363.68, "duration": 2.45}, {"text": "if you believe it is real.", "start": 1366.13, "duration": 1.51}, {"text": "PROFESSOR: So it was just a\nnice little ditty, in a way.", "start": 1367.64, "duration": 2.64}, {"text": "Matthew, I'm sorry?", "start": 1370.28, "duration": 1.045}, {"text": "AUDIENCE: I would have\ngiven him $1 for it.", "start": 1371.325, "duration": 1.505}, {"text": "PROFESSOR: You would\nhave given him $1?", "start": 1372.83, "duration": 1.29}, {"text": "Great.", "start": 1374.12, "duration": 0.68}, {"text": "AUDIENCE: Seeing how\nmuch the pizzas went for.", "start": 1374.8, "duration": 2.957}, {"text": "AUDIENCE: Who knows?", "start": 1377.757, "duration": 0.833}, {"text": "PROFESSOR: Would anybody else\nhave given him $1 for it?", "start": 1378.59, "duration": 3.12}, {"text": "No?", "start": 1381.71, "duration": 0.62}, {"text": "Oh, you would have?", "start": 1382.33, "duration": 2.77}, {"text": "AUDIENCE: Actually, I'm\nworking with local currencies.", "start": 1385.1, "duration": 3.17}, {"text": "And it's kind of the same, but\nyou can use them just locally.", "start": 1388.27, "duration": 5.93}, {"text": "I mean, it keeps the\nmoney inside the community", "start": 1394.2, "duration": 3.36}, {"text": "that decides to use that\nway of transactions.", "start": 1397.56, "duration": 2.787}, {"text": "PROFESSOR: We're going to refer\nback to each of these readings", "start": 1400.347, "duration": 2.583}, {"text": "as we go through\nthe next 45 minutes.", "start": 1402.93, "duration": 2.07}, {"text": "Yeah?", "start": 1405.0, "duration": 0.5}, {"text": "AUDIENCE: I was wondering\nif he was actually", "start": 1405.5, "duration": 1.833}, {"text": "breaking the law by\nlaunching his own competing", "start": 1407.333, "duration": 2.002}, {"text": "currency to the US dollar?", "start": 1409.335, "duration": 1.335}, {"text": "Is that a legitimate--", "start": 1410.67, "duration": 1.91}, {"text": "obviously, it didn't compete\nwith the US dollar, but--", "start": 1412.58, "duration": 2.28}, {"text": "PROFESSOR: You raise\na very good question.", "start": 1414.86, "duration": 1.75}, {"text": "I'm not aware of any\nstatute, federal or state,", "start": 1416.61, "duration": 7.25}, {"text": "that says there's an absolute\nmonopoly on forms of currency", "start": 1423.86, "duration": 6.12}, {"text": "as there is in other\nthings, like you", "start": 1429.98, "duration": 1.95}, {"text": "know that slot in the\ndoor that's called the--", "start": 1431.93, "duration": 3.96}, {"text": "where you can put a letter\nthrough the door or a mailbox?", "start": 1435.89, "duration": 3.57}, {"text": "There's actually a law that says\nthat the US Postal Service has", "start": 1439.46, "duration": 2.94}, {"text": "a monopoly, and\nthat's why UPS is not", "start": 1442.4, "duration": 3.51}, {"text": "allowed to put their boxes\nor anything in there.", "start": 1445.91, "duration": 4.26}, {"text": "There's a government\nfiat monopoly.", "start": 1450.17, "duration": 4.26}, {"text": "But you raise a\nvery good question.", "start": 1454.43, "duration": 3.07}, {"text": "What we've found in the\nlast 10 years with Bitcoin,", "start": 1457.5, "duration": 3.47}, {"text": "with really\noversimplifying, is that it", "start": 1460.97, "duration": 3.63}, {"text": "is legal to create\nyour own form of money,", "start": 1464.6, "duration": 4.37}, {"text": "as Bitcoin is\npossibly this money.", "start": 1468.97, "duration": 5.17}, {"text": "But you have to comply\nwith all the other laws.", "start": 1474.14, "duration": 2.313}, {"text": "And all those other laws\nthat we'll talk about", "start": 1476.453, "duration": 1.917}, {"text": "in other lectures,\nin essence, fall", "start": 1478.37, "duration": 2.31}, {"text": "into buckets of guarding\nagainst illicit activity,", "start": 1480.68, "duration": 2.52}, {"text": "so the Bank Secrecy\nAct and all the laws", "start": 1483.2, "duration": 2.7}, {"text": "related to anti-money\nlaundering and terrorism finance", "start": 1485.9, "duration": 3.03}, {"text": "and so forth.", "start": 1488.93, "duration": 1.35}, {"text": "One still has to pay your taxes\nif you're gaining or losing", "start": 1490.28, "duration": 3.96}, {"text": "on this investment.", "start": 1494.24, "duration": 3.81}, {"text": "The Federal Reserve and other\nauthorities around the globe", "start": 1498.05, "duration": 2.97}, {"text": "still want to insure\nfor financial stability.", "start": 1501.02, "duration": 3.09}, {"text": "The fellow on the streets of--", "start": 1504.11, "duration": 1.845}, {"text": "I don't remember what city.", "start": 1505.955, "duration": 1.125}, {"text": "New York?", "start": 1507.08, "duration": 0.69}, {"text": "Selling his dollars, when\nMatthew bought it for $1", "start": 1507.77, "duration": 3.36}, {"text": "and I think over here--", "start": 1511.13, "duration": 2.71}, {"text": "Brianna?", "start": 1513.84, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1514.34, "duration": 0.875}, {"text": "PROFESSOR: What's that?", "start": 1515.215, "duration": 1.015}, {"text": "AUDIENCE: My name?", "start": 1516.23, "duration": 0.87}, {"text": "PROFESSOR: Yes.", "start": 1517.1, "duration": 0.625}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1517.725, "duration": 1.055}, {"text": "PROFESSOR: Bought it.", "start": 1518.78, "duration": 2.43}, {"text": "The society's still\ngoing to be stable.", "start": 1521.21, "duration": 2.4}, {"text": "It's going to be all right.", "start": 1523.61, "duration": 2.49}, {"text": "But if millions of\npeople were buying it,", "start": 1526.1, "duration": 2.25}, {"text": "then people might worry.", "start": 1528.35, "duration": 1.26}, {"text": "And then there's\nthe third big bucket", "start": 1529.61, "duration": 1.83}, {"text": "that we look at is investor\nand consumer protection.", "start": 1531.44, "duration": 3.12}, {"text": "But I think it's allowed.", "start": 1534.56, "duration": 2.58}, {"text": "So we'll refer to\nthese, Joaquin,", "start": 1537.14, "duration": 1.903}, {"text": "and then I'm going to go on.", "start": 1539.043, "duration": 1.167}, {"text": "AUDIENCE: Can you\nlegally pay, for example,", "start": 1540.21, "duration": 1.792}, {"text": "salaries in bitcoin in the US?", "start": 1542.002, "duration": 3.708}, {"text": "PROFESSOR: Yes.", "start": 1545.71, "duration": 2.26}, {"text": "And why is it that\nyou can legally pay", "start": 1547.97, "duration": 1.92}, {"text": "for wages in bitcoin in the US?", "start": 1549.89, "duration": 4.49}, {"text": "I know it's outside\nof the readings,", "start": 1554.38, "duration": 1.5}, {"text": "but why do you think it is\nallowed in this society?", "start": 1555.88, "duration": 6.08}, {"text": "Is it Kyle?", "start": 1561.96, "duration": 2.23}, {"text": "AUDIENCE: Wouldn't\nthose compensation forms", "start": 1564.19, "duration": 1.82}, {"text": "be allowed under any contract?", "start": 1566.01, "duration": 1.765}, {"text": "PROFESSOR: Most things--\nyou could pay somebody", "start": 1570.47, "duration": 2.76}, {"text": "in these placards.", "start": 1573.23, "duration": 1.74}, {"text": "I doubt, really, that you're\ngoing to value them much.", "start": 1574.97, "duration": 3.03}, {"text": "But you could pay\nsomebody in this.", "start": 1578.0, "duration": 2.1}, {"text": "You could pay somebody\nin gold, euros, bitcoin.", "start": 1580.1, "duration": 4.74}, {"text": "And there are firms\nthat are paying--", "start": 1584.84, "duration": 1.96}, {"text": "usually, they're developing\nblockchain applications.", "start": 1586.8, "duration": 4.97}, {"text": "And interestingly, they have to\ncompute the value of the wages", "start": 1591.77, "duration": 5.77}, {"text": "to do withholding taxes, because\nthe US government will not", "start": 1597.54, "duration": 3.27}, {"text": "accept taxes in bitcoin.", "start": 1600.81, "duration": 3.01}, {"text": "So they figure out the\nfair market value--", "start": 1603.82, "duration": 3.6}, {"text": "and there are companies\nin the US that pay people", "start": 1607.42, "duration": 2.39}, {"text": "in bitcoin who are\ndoing development work", "start": 1609.81, "duration": 2.61}, {"text": "around blockchain applications.", "start": 1612.42, "duration": 1.8}, {"text": "But the taxes need to be\ncomputed and analyzed and then", "start": 1614.22, "duration": 4.08}, {"text": "paid in US dollars.", "start": 1618.3, "duration": 2.64}, {"text": "There was a legislative\ninitiative in Arizona", "start": 1620.94, "duration": 3.06}, {"text": "earlier this year where\na state legislature", "start": 1624.0, "duration": 2.13}, {"text": "wanted to have Arizona be\nthe first state in the land", "start": 1626.13, "duration": 3.24}, {"text": "to accept bitcoin for taxes.", "start": 1629.37, "duration": 2.61}, {"text": "But it failed in committee.", "start": 1631.98, "duration": 1.77}, {"text": "It didn't even get\na full vote of--", "start": 1633.75, "duration": 1.48}, {"text": "I can't remember if it was the\nArizona Senate or the Arizona", "start": 1635.23, "duration": 3.11}, {"text": "House of Delegates.", "start": 1638.34, "duration": 1.54}, {"text": "So just a little walk\nthrough the history.", "start": 1644.09, "duration": 1.95}, {"text": "I was going to do a\nlittle history of money", "start": 1646.04, "duration": 1.792}, {"text": "and have some fun.", "start": 1647.832, "duration": 2.298}, {"text": "So in Ethiopia, people\nput together salt bars.", "start": 1650.13, "duration": 3.17}, {"text": "This is not that long ago.", "start": 1653.3, "duration": 2.91}, {"text": "Salt, as Jihei said earlier,\nis really valuable in society,", "start": 1656.21, "duration": 4.33}, {"text": "and they standardize\nthe shape and size.", "start": 1660.54, "duration": 2.34}, {"text": "And so here's salt bars.", "start": 1662.88, "duration": 3.51}, {"text": "We're going to get to,\na little bit later,", "start": 1666.39, "duration": 2.13}, {"text": "all the characteristics\nof money.", "start": 1668.52, "duration": 2.07}, {"text": "But what else do you think\na salt bar in Ethiopia,", "start": 1670.59, "duration": 2.82}, {"text": "as opposed to maybe\nsome other country--", "start": 1673.41, "duration": 2.82}, {"text": "what did it have, as well, as\nto why people might use that?", "start": 1676.23, "duration": 5.09}, {"text": "AUDIENCE: Oil.", "start": 1681.32, "duration": 0.695}, {"text": "PROFESSOR: What's that?", "start": 1682.015, "duration": 0.958}, {"text": "AUDIENCE: Crude oil.", "start": 1682.973, "duration": 0.833}, {"text": "PROFESSOR: Crude oil.", "start": 1683.806, "duration": 1.334}, {"text": "All right, I hadn't\nthought of that.", "start": 1685.14, "duration": 1.597}, {"text": "I'm going to keep\nthinking about that.", "start": 1686.737, "duration": 1.583}, {"text": "It's not a common\ncharacteristic of money.", "start": 1688.32, "duration": 2.32}, {"text": "But why salt bars?", "start": 1690.64, "duration": 1.26}, {"text": "What else might it\nhave in Ethiopia?", "start": 1691.9, "duration": 2.66}, {"text": "AUDIENCE: Are you\ngoing to say that you", "start": 1696.515, "duration": 1.625}, {"text": "can use salt to preserver food?", "start": 1698.14, "duration": 1.865}, {"text": "PROFESSOR: Well, you\ncan preserve food,", "start": 1700.005, "duration": 1.625}, {"text": "but because it was mined, there\nwas some scarcity, as well.", "start": 1701.63, "duration": 5.43}, {"text": "And a lot of currencies,\na lot of moneys over time,", "start": 1707.06, "duration": 3.2}, {"text": "have that fundamental issue.", "start": 1710.26, "duration": 2.44}, {"text": "Cowrie shells from West Africa.", "start": 1712.7, "duration": 5.05}, {"text": "Does anyone know\nthe history of when", "start": 1717.75, "duration": 1.5}, {"text": "cowrie shells got really\ndebased and stopped", "start": 1719.25, "duration": 3.15}, {"text": "being used, from the readings?", "start": 1722.4, "duration": 2.25}, {"text": "I can't remember if that\nwas in the readings or not.", "start": 1724.65, "duration": 2.64}, {"text": "They got debased when\nEuropeans started", "start": 1729.84, "duration": 2.16}, {"text": "to realize that they\nwere accepted as a value.", "start": 1732.0, "duration": 3.36}, {"text": "And it's a very sad and\nterrible history, too,", "start": 1735.36, "duration": 2.61}, {"text": "because it's related to\nthe whole slave trade.", "start": 1737.97, "duration": 2.67}, {"text": "But that the Europeans\ncould figure out", "start": 1740.64, "duration": 3.12}, {"text": "that societies accepted\nthis as something of value,", "start": 1743.76, "duration": 3.72}, {"text": "but they also\ndebased that currency", "start": 1747.48, "duration": 2.4}, {"text": "and they debased the land and\ncaptured people as slaves.", "start": 1749.88, "duration": 2.79}, {"text": "It was quite a collection of\nnot particularly good things", "start": 1752.67, "duration": 4.98}, {"text": "going on.", "start": 1757.65, "duration": 1.47}, {"text": "Tally sticks in England.", "start": 1759.12, "duration": 1.835}, {"text": "Does anybody, from\nthe readings--", "start": 1760.955, "duration": 1.375}, {"text": "because there was a little\nbit of the debate in the first", "start": 1762.33, "duration": 2.61}, {"text": "reading about the\nhistory of money--", "start": 1764.94, "duration": 3.12}, {"text": "want to chat?", "start": 1768.06, "duration": 1.68}, {"text": "And I'll pull up the\nRai stones from Yap.", "start": 1769.74, "duration": 3.48}, {"text": "How this fits into that first\nreading and the debate between", "start": 1773.22, "duration": 3.93}, {"text": "did money come from\na history of barter,", "start": 1777.15, "duration": 3.12}, {"text": "or did money come from a\nhistory of ledgers and credit,", "start": 1780.27, "duration": 5.14}, {"text": "which is kind of a setup\nof that first reading?", "start": 1785.41, "duration": 4.7}, {"text": "Any thoughts?", "start": 1792.628, "duration": 0.542}, {"text": "Which ones of these four\nbits of money, early money,", "start": 1795.95, "duration": 2.79}, {"text": "are more about maybe barter?", "start": 1798.74, "duration": 1.275}, {"text": "AUDIENCE: There are\ntwo theories, right?", "start": 1803.73, "duration": 4.93}, {"text": "Debt, which corresponds\nto this one.", "start": 1808.66, "duration": 2.51}, {"text": "This was a way to measure debt.", "start": 1811.17, "duration": 2.34}, {"text": "PROFESSOR: Which one?", "start": 1813.51, "duration": 0.88}, {"text": "AUDIENCE: The sticks.", "start": 1814.39, "duration": 1.113}, {"text": "PROFESSOR: The sticks.", "start": 1815.503, "duration": 0.917}, {"text": "The tally sticks, yes, correct.", "start": 1816.42, "duration": 1.71}, {"text": "Which is the second one on\nhere that has to do with debts,", "start": 1818.13, "duration": 2.46}, {"text": "actually, and credits?", "start": 1820.59, "duration": 2.055}, {"text": "AUDIENCE: The stones.", "start": 1822.645, "duration": 0.875}, {"text": "PROFESSOR: The stone,\nthe Rai stones.", "start": 1823.52, "duration": 3.44}, {"text": "So it's remarkable.", "start": 1826.96, "duration": 0.81}, {"text": "The Rai stones were so heavy\nthat on this island of Yap,", "start": 1827.77, "duration": 4.83}, {"text": "they couldn't possibly\nlug it around and use it", "start": 1832.6, "duration": 3.34}, {"text": "in a traditional\nmedium of exchange.", "start": 1835.94, "duration": 2.09}, {"text": "But it was viewed as, well,\nI have 1/6 of this Rai stone.", "start": 1838.03, "duration": 4.32}, {"text": "You have 1/16.", "start": 1842.35, "duration": 1.49}, {"text": "And then if I make an\nexchange, we'd remember.", "start": 1843.84, "duration": 2.89}, {"text": "And the society was small enough\nto keep a form of ledgers, even", "start": 1846.73, "duration": 4.5}, {"text": "to the extent that when a Rai\nstone was lost in a river,", "start": 1851.23, "duration": 4.12}, {"text": "they said, you know,\nthe river Rai stone,", "start": 1855.35, "duration": 2.03}, {"text": "we each have this piece.", "start": 1857.38, "duration": 2.9}, {"text": "So on the island of\nYap, I can assure you,", "start": 1860.28, "duration": 3.57}, {"text": "these stones could not be\nused for anything else.", "start": 1863.85, "duration": 3.8}, {"text": "Does anyone know, because it\nwas outside the readings, what", "start": 1867.65, "duration": 2.94}, {"text": "made these stones so scarce?", "start": 1870.59, "duration": 1.35}, {"text": "So Rai stones were quarried on\nan island about 200 kilometers", "start": 1875.62, "duration": 3.72}, {"text": "away from Yap, so\nwere they exceedingly", "start": 1879.34, "duration": 3.6}, {"text": "hard to get, like gold,\nlike mining of gold.", "start": 1882.94, "duration": 5.03}, {"text": "What else is mined these\ndays that might be a money?", "start": 1887.97, "duration": 3.105}, {"text": "AUDIENCE: Lithium.", "start": 1891.075, "duration": 0.767}, {"text": "PROFESSOR: What's that?", "start": 1891.842, "duration": 0.958}, {"text": "Can I hear everybody?", "start": 1892.8, "duration": 1.374}, {"text": "AUDIENCE: I'm saying lithium.", "start": 1894.174, "duration": 1.388}, {"text": "PROFESSOR: What's that?", "start": 1895.562, "duration": 0.958}, {"text": "AUDIENCE: For batteries.", "start": 1896.52, "duration": 1.05}, {"text": "For batteries.", "start": 1897.57, "duration": 0.6}, {"text": "It's going to be very\ndifficult in the future", "start": 1898.17, "duration": 3.28}, {"text": "for electric\nbatteries and whatnot.", "start": 1901.45, "duration": 1.68}, {"text": "PROFESSOR: But what's\nmined right now that's", "start": 1903.13, "duration": 1.88}, {"text": "at the center of this class?", "start": 1905.01, "duration": 1.32}, {"text": "AUDIENCE: Bitcoin.", "start": 1906.33, "duration": 0.89}, {"text": "PROFESSOR: Bitcoin, right?", "start": 1907.22, "duration": 1.39}, {"text": "The Yap stone was, in essence,\nquarried a couple kilometers", "start": 1908.61, "duration": 3.36}, {"text": "away.", "start": 1911.97, "duration": 1.26}, {"text": "And what debased that currency\nwas when sailors from England", "start": 1913.23, "duration": 4.54}, {"text": "came.", "start": 1917.77, "duration": 0.5}, {"text": "There's a specific sailor--", "start": 1918.27, "duration": 1.26}, {"text": "I think his name was O'Keefe--", "start": 1919.53, "duration": 1.26}, {"text": "in the late 19th century, and\nhe realized that these stones", "start": 1920.79, "duration": 2.76}, {"text": "were valuable.", "start": 1923.55, "duration": 1.63}, {"text": "And he went to the other\nisland, and he started quarrying", "start": 1925.18, "duration": 2.375}, {"text": "and came back and forth.", "start": 1927.555, "duration": 1.825}, {"text": "And within a few years,\nthe whole economic system", "start": 1929.38, "duration": 3.02}, {"text": "collapsed.", "start": 1932.4, "duration": 2.61}, {"text": "We moved to metal money.", "start": 1935.01, "duration": 1.23}, {"text": "At first, it wasn't\nreally stamped.", "start": 1936.24, "duration": 2.13}, {"text": "It was just heavy.", "start": 1938.37, "duration": 0.87}, {"text": "It was hard to quarry.", "start": 1939.24, "duration": 1.98}, {"text": "Bronze in Rome.", "start": 1941.22, "duration": 2.09}, {"text": "There was some China and Sweden.", "start": 1943.31, "duration": 2.29}, {"text": "These were starting to be\nstamped by the official sector.", "start": 1945.6, "duration": 4.18}, {"text": "And then we had minted money\nstarting somewhere around 2,500", "start": 1949.78, "duration": 4.31}, {"text": "years ago.", "start": 1954.09, "duration": 0.93}, {"text": "And there's debates\nas to whether it", "start": 1955.02, "duration": 1.5}, {"text": "started in Greece or in China.", "start": 1956.52, "duration": 4.17}, {"text": "But where an official emblem was\nplaced upon a scarce resource", "start": 1960.69, "duration": 6.78}, {"text": "that was used.", "start": 1967.47, "duration": 0.72}, {"text": "Paper money came along, in\na sense, for what reason?", "start": 1970.71, "duration": 4.5}, {"text": "Why did society first\ntip in to paper money?", "start": 1975.21, "duration": 6.78}, {"text": "AUDIENCE: Because there's not\nenough gold to back it up.", "start": 1981.99, "duration": 2.61}, {"text": "I mean, like because there's--", "start": 1984.6, "duration": 0.91}, {"text": "PROFESSOR: All right.", "start": 1985.51, "duration": 0.875}, {"text": "One reason is not enough gold.", "start": 1986.385, "duration": 2.095}, {"text": "I'm sorry, I haven't--", "start": 1988.48, "duration": 1.73}, {"text": "AUDIENCE: I think\nit's just easy to--", "start": 1990.21, "duration": 2.13}, {"text": "PROFESSOR: Ease of use.", "start": 1992.34, "duration": 1.44}, {"text": "It's kind of heavy, especially\nif there wasn't gold", "start": 1993.78, "duration": 3.51}, {"text": "and if it was copper or bronze.", "start": 1997.29, "duration": 1.71}, {"text": "It was just heavy.", "start": 1999.0, "duration": 1.35}, {"text": "Or if it was wheat, you'd have\nto put it in a storage unit.", "start": 2000.35, "duration": 3.24}, {"text": "So the first paper\nmonies from China", "start": 2003.59, "duration": 3.02}, {"text": "were basically\nwarehouse receipts.", "start": 2006.61, "duration": 2.53}, {"text": "And I spent five years\nrunning something", "start": 2009.14, "duration": 2.16}, {"text": "called a Commodity Futures\nTrading Commission,", "start": 2011.3, "duration": 2.55}, {"text": "and so I guess I learned a\nlot about warehouse receipts,", "start": 2013.85, "duration": 2.46}, {"text": "commodity receipts, where you\nput a commodity in a warehouse.", "start": 2016.31, "duration": 4.265}, {"text": "And then you got\na piece of paper", "start": 2020.575, "duration": 1.375}, {"text": "that said, yes, you have\nthat commodity there.", "start": 2021.95, "duration": 2.49}, {"text": "So the first paper\nmonies were basically", "start": 2024.44, "duration": 2.04}, {"text": "warehouse receipts in China.", "start": 2026.48, "duration": 2.81}, {"text": "Because whatever it\nwas-- grain or gold.", "start": 2029.29, "duration": 5.17}, {"text": "And then you had a piece\nof paper backing it.", "start": 2034.46, "duration": 2.37}, {"text": "These are five pound\nnotes from England", "start": 2036.83, "duration": 1.74}, {"text": "and the continental\nnotes of the US.", "start": 2038.57, "duration": 1.59}, {"text": "But that note in China\nis about 700 years old.", "start": 2040.16, "duration": 4.05}, {"text": "But between that first paper\nmoney and the 18th century,", "start": 2044.21, "duration": 6.08}, {"text": "who do you think we're\nkind of the first bankers", "start": 2050.29, "duration": 3.24}, {"text": "in the late 17th century,\nearly 18th century?", "start": 2053.53, "duration": 4.51}, {"text": "What craft had they been in\nbefore they were in banking?", "start": 2058.04, "duration": 4.369}, {"text": "AUDIENCE: Trading.", "start": 2062.409, "duration": 0.75}, {"text": "AUDIENCE: Trading.", "start": 2063.159, "duration": 0.631}, {"text": "AUDIENCE: Trading.", "start": 2063.79, "duration": 0.82}, {"text": "PROFESSOR: Alpha?", "start": 2064.61, "duration": 0.817}, {"text": "AUDIENCE: International trading.", "start": 2065.427, "duration": 1.333}, {"text": "PROFESSOR: International trade.", "start": 2066.76, "duration": 1.05}, {"text": "They actually did\nsomething more local.", "start": 2067.81, "duration": 1.625}, {"text": "AUDIENCE: I just\ntalked about this.", "start": 2073.87, "duration": 2.69}, {"text": "The ones that have\nlands and all the--", "start": 2076.56, "duration": 2.66}, {"text": "the ones that have lands\nand all the [INAUDIBLE]..", "start": 2079.22, "duration": 3.979}, {"text": "PROFESSOR: Lanes?", "start": 2083.199, "duration": 1.401}, {"text": "AUDIENCE: Lands.", "start": 2084.6, "duration": 0.72}, {"text": "AUDIENCE: Land.", "start": 2085.32, "duration": 0.24}, {"text": "PROFESSOR: Land.", "start": 2085.56, "duration": 0.667}, {"text": "Land.", "start": 2086.227, "duration": 0.773}, {"text": "No, they had something\nelse that they were doing.", "start": 2087.0, "duration": 2.78}, {"text": "Tom?", "start": 2089.78, "duration": 0.826}, {"text": "AUDIENCE: Printmakers.", "start": 2090.606, "duration": 0.934}, {"text": "PROFESSOR: They\nwere printmakers.", "start": 2091.54, "duration": 1.375}, {"text": "I like that.", "start": 2092.915, "duration": 0.744}, {"text": "We're not there yet.", "start": 2093.659, "duration": 2.0}, {"text": "AUDIENCE: Money lenders?", "start": 2095.659, "duration": 1.051}, {"text": "PROFESSOR: What's that?", "start": 2096.71, "duration": 0.958}, {"text": "AUDIENCE: They're\nunderwriting insurance.", "start": 2097.668, "duration": 2.202}, {"text": "PROFESSOR: A little bit later.", "start": 2099.87, "duration": 3.067}, {"text": "AUDIENCE: They were\ndoing agriculture?", "start": 2102.937, "duration": 1.583}, {"text": "PROFESSOR: It's definitely\noutside of the reading.", "start": 2104.52, "duration": 2.11}, {"text": "They were goldsmiths.", "start": 2106.63, "duration": 1.02}, {"text": "Some of the first dominant\nbankers in London,", "start": 2110.87, "duration": 5.24}, {"text": "they were small goldsmiths.", "start": 2116.11, "duration": 1.85}, {"text": "And they took the gold, they\ngave you a piece of paper,", "start": 2117.96, "duration": 2.89}, {"text": "and then they went from there.", "start": 2120.85, "duration": 1.71}, {"text": "And then, all of a sudden, they\nfigured out how to do credit.", "start": 2122.56, "duration": 2.85}, {"text": "Later in the\nsemester, we're going", "start": 2125.41, "duration": 1.417}, {"text": "to talk about Bitcoin credit.", "start": 2126.827, "duration": 2.123}, {"text": "It's not there yet, by the way.", "start": 2128.95, "duration": 2.16}, {"text": "I think in the next\n18 to 36 months,", "start": 2131.11, "duration": 2.22}, {"text": "we're going to start seeing\ncryptolending and cryptofinance", "start": 2133.33, "duration": 5.31}, {"text": "in the form similar to what\nthe goldsmiths were doing", "start": 2138.64, "duration": 2.7}, {"text": "in the early 1700s in England.", "start": 2141.34, "duration": 3.366}, {"text": "Alan?", "start": 2144.706, "duration": 0.816}, {"text": "AUDIENCE: Is that scalable with\na finite number of bitcoins,", "start": 2145.522, "duration": 4.221}, {"text": "in your opinion?", "start": 2149.743, "duration": 0.667}, {"text": "PROFESSOR: It's a\nvery good question.", "start": 2150.41, "duration": 1.542}, {"text": "Is it scalable to lend\nagainst a finite currency?", "start": 2151.952, "duration": 3.173}, {"text": "I think so, but it's\nnot done yet, right?", "start": 2158.69, "duration": 6.39}, {"text": "AUDIENCE: Yeah, because when\nyou lend money to someone,", "start": 2165.08, "duration": 5.35}, {"text": "I guess it could be in\nthe form of bitcoin.", "start": 2170.43, "duration": 2.15}, {"text": "But you lend someone dollars,\nthey could redeem in bitcoin.", "start": 2172.58, "duration": 3.61}, {"text": "You'd be increasing kind\nof the money supply.", "start": 2176.19, "duration": 2.62}, {"text": "So you don't need--", "start": 2178.81, "duration": 1.368}, {"text": "you're not moving money around.", "start": 2180.178, "duration": 1.292}, {"text": "You're actually [INAUDIBLE].", "start": 2181.47, "duration": 0.63}, {"text": "PROFESSOR: So this is\nexactly the central", "start": 2182.1, "duration": 1.71}, {"text": "of commercial banking today.", "start": 2183.81, "duration": 1.29}, {"text": "It's called fractional banking.", "start": 2185.1, "duration": 1.38}, {"text": "We'll be talking\nabout that in a bit.", "start": 2186.48, "duration": 1.542}, {"text": "But yes, you could lend and\nthen have a multiplier effect.", "start": 2188.022, "duration": 7.728}, {"text": "You also had, then,\nbanks come up and started", "start": 2195.75, "duration": 2.39}, {"text": "to issue private bank notes.", "start": 2198.14, "duration": 1.47}, {"text": "Private bank notes effectively\na liability of that bank", "start": 2199.61, "duration": 4.02}, {"text": "and saying it would trade.", "start": 2203.63, "duration": 2.23}, {"text": "And the history of private\nbank notes is usually what?", "start": 2205.86, "duration": 4.97}, {"text": "Good until it's really bad.", "start": 2210.83, "duration": 3.37}, {"text": "And the history of money,\na lot of private banks", "start": 2214.2, "duration": 3.96}, {"text": "went bust in this country\naround the revolutionary period,", "start": 2218.16, "duration": 4.56}, {"text": "again around the Civil War.", "start": 2222.72, "duration": 3.39}, {"text": "And in essence, that's\nwhat we have now", "start": 2226.11, "duration": 2.01}, {"text": "with 1,600 different\ncryptocurrencies.", "start": 2228.12, "duration": 3.42}, {"text": "We have sort of a new\nperiod of a little bit", "start": 2231.54, "duration": 2.43}, {"text": "of private currencies.", "start": 2233.97, "duration": 3.27}, {"text": "And I only ask you to\nremember that as we", "start": 2237.24, "duration": 3.36}, {"text": "start to look at ICOs, Initial\nCoin Offerings, and so forth.", "start": 2240.6, "duration": 3.57}, {"text": "So ledgers-- the earlier\nquestion is, what was a ledger?", "start": 2246.77, "duration": 2.535}, {"text": "You asked it.", "start": 2252.59, "duration": 1.08}, {"text": "Can you remember,\nwhat's a ledger?", "start": 2253.67, "duration": 2.41}, {"text": "AUDIENCE: It's a way to\nrecord economic transaction.", "start": 2256.08, "duration": 3.474}, {"text": "PROFESSOR: There you go.", "start": 2259.554, "duration": 1.356}, {"text": "Principal recordings\nof accounts.", "start": 2260.91, "duration": 3.34}, {"text": "And 5,000 years ago--", "start": 2264.25, "duration": 3.68}, {"text": "you had a little reading on\nthis, just a medium post.", "start": 2267.93, "duration": 3.39}, {"text": "It wasn't meant to be a deep\neconomic, academic paper.", "start": 2271.32, "duration": 3.3}, {"text": "But it was to try to get the\nclass thinking about ledgers.", "start": 2274.62, "duration": 6.48}, {"text": "This is the personal ledger\nof George Washington,", "start": 2281.1, "duration": 3.1}, {"text": "our first president.", "start": 2284.2, "duration": 1.16}, {"text": "He was 15 years old when\nhe kept this ledger.", "start": 2285.36, "duration": 3.26}, {"text": "And he apparently kept\nledgers until his death in--", "start": 2288.62, "duration": 4.94}, {"text": "let's see.", "start": 2293.56, "duration": 1.25}, {"text": "52 years later.", "start": 2294.81, "duration": 1.21}, {"text": "So ledgers could be\nkept just to record", "start": 2299.25, "duration": 2.97}, {"text": "the transactions of the day.", "start": 2302.22, "duration": 2.79}, {"text": "He's got one up there--", "start": 2305.01, "duration": 1.2}, {"text": "Mary Washington.", "start": 2306.21, "duration": 0.757}, {"text": "It must have been a\ncousin, or I can't", "start": 2306.967, "duration": 1.583}, {"text": "remember if it was his mother.", "start": 2308.55, "duration": 3.15}, {"text": "So if they're the principal\nrecordings of accounts--", "start": 2311.7, "duration": 3.122}, {"text": "and I've already sort\nof said this-- they", "start": 2314.822, "duration": 1.708}, {"text": "record economic activity\nand financial relationships.", "start": 2316.53, "duration": 5.25}, {"text": "Economic activity in a\nsense of transactions.", "start": 2321.78, "duration": 3.93}, {"text": "Financial relationships-- what's\na key financial relationship", "start": 2325.71, "duration": 5.06}, {"text": "a ledger might record?", "start": 2330.77, "duration": 2.72}, {"text": "I'm sorry?", "start": 2333.49, "duration": 0.5}, {"text": "AUDIENCE: Debt.", "start": 2333.99, "duration": 0.96}, {"text": "PROFESSOR: Kelly said it-- debt.", "start": 2334.95, "duration": 2.11}, {"text": "And it goes back to the\ndebate you had in the reading.", "start": 2337.06, "duration": 2.49}, {"text": "Is money a history of barter--", "start": 2339.55, "duration": 2.337}, {"text": "did it come out of barter?", "start": 2341.887, "duration": 1.083}, {"text": "Did it come out of\na sense of debts", "start": 2342.97, "duration": 2.67}, {"text": "and credit and store of value?", "start": 2345.64, "duration": 2.73}, {"text": "For this purpose today,\nit doesn't really matter.", "start": 2348.37, "duration": 2.63}, {"text": "It may have come from both.", "start": 2351.0, "duration": 1.87}, {"text": "But know that it has both sides.", "start": 2352.87, "duration": 1.8}, {"text": "And ledgers have\nboth sides, too.", "start": 2354.67, "duration": 1.69}, {"text": "And when we're talking about\nBitcoin, Bitcoin, you will see,", "start": 2356.36, "duration": 3.32}, {"text": "is a mechanism to\nstore transactions.", "start": 2359.68, "duration": 4.65}, {"text": "Some other blockchains, like\nEthereum, stores balances.", "start": 2364.33, "duration": 5.25}, {"text": "So even in the\nblockchain world, you", "start": 2369.58, "duration": 1.83}, {"text": "will see some that are\nbalance ledgers and some", "start": 2371.41, "duration": 3.69}, {"text": "which are transaction\nledgers, not", "start": 2375.1, "duration": 2.86}, {"text": "to lose you and confuse you.", "start": 2377.96, "duration": 2.41}, {"text": "It's an important part\nof what is blockchain.", "start": 2380.37, "duration": 5.45}, {"text": "Some types of ledgers.", "start": 2385.82, "duration": 1.53}, {"text": "I just mentioned one--\ntransactions versus balance.", "start": 2387.35, "duration": 4.75}, {"text": "George Washington's\nledger, by the way,", "start": 2392.1, "duration": 2.58}, {"text": "I think was a\ntransaction ledger.", "start": 2394.68, "duration": 1.71}, {"text": "He was just keeping a list\nof sales and movements.", "start": 2396.39, "duration": 4.74}, {"text": "But I haven't studied President\nGeorge Washington's ledger", "start": 2401.13, "duration": 3.57}, {"text": "close enough.", "start": 2404.7, "duration": 1.78}, {"text": "Does anybody know\nenough accounting", "start": 2406.48, "duration": 2.157}, {"text": "to tell me the difference\nbetween a general ledger", "start": 2408.637, "duration": 2.083}, {"text": "and a subledger or a general\nledger and a supporting ledger?", "start": 2410.72, "duration": 4.46}, {"text": "I mean, I don't want to do\nthe whole lecture myself.", "start": 2415.18, "duration": 3.48}, {"text": "How many of you have\ntaken accounting?", "start": 2418.66, "duration": 4.29}, {"text": "Uh-huh.", "start": 2422.95, "duration": 1.14}, {"text": "I taught undergraduate\naccounting once.", "start": 2424.09, "duration": 3.06}, {"text": "Sorry.", "start": 2427.15, "duration": 1.51}, {"text": "So those of you who just put up\nyour hand who took accounting--", "start": 2428.66, "duration": 3.9}, {"text": "did I see, in the back of the\nroom, did you take accounting?", "start": 2432.56, "duration": 2.6}, {"text": "And that's Aviva.", "start": 2435.16, "duration": 1.217}, {"text": "AUDIENCE: I'm an\naccountant, actually.", "start": 2436.377, "duration": 1.583}, {"text": "PROFESSOR: You're an accountant?", "start": 2437.96, "duration": 1.63}, {"text": "All right, all right.", "start": 2439.59, "duration": 1.89}, {"text": "Did you pass the CPA?", "start": 2441.48, "duration": 2.31}, {"text": "Oh, we have a Certified\nPublic Accountant", "start": 2443.79, "duration": 1.79}, {"text": "who's going to tell\nus the difference", "start": 2445.58, "duration": 0.97}, {"text": "between a general\nledger and a subledger.", "start": 2446.55, "duration": 1.71}, {"text": "AUDIENCE: So a\ngeneral ledger is one", "start": 2448.26, "duration": 1.62}, {"text": "that records all\nkinds of transactions.", "start": 2449.88, "duration": 2.82}, {"text": "Any kind of activity\nthat takes place, you", "start": 2452.7, "duration": 2.52}, {"text": "record in the general ledger.", "start": 2455.22, "duration": 1.41}, {"text": "And subledgers, you can call\nthem as like a specialization.", "start": 2456.63, "duration": 3.28}, {"text": "So let's say if there's\na salary to be paid,", "start": 2459.91, "duration": 3.18}, {"text": "you have your salary subledger.", "start": 2463.09, "duration": 2.2}, {"text": "But it'll also go in\nthe general ledger,", "start": 2465.29, "duration": 1.75}, {"text": "and the other part\nof the transaction's", "start": 2467.04, "duration": 1.73}, {"text": "in the salary ledger.", "start": 2468.77, "duration": 1.06}, {"text": "Or if there's capital or if\nthere's new stuff that you buy,", "start": 2469.83, "duration": 6.99}, {"text": "so all of that goes specifically\nin the general ledger.", "start": 2476.82, "duration": 2.34}, {"text": "And each of them have\ntheir own specific ledgers.", "start": 2479.16, "duration": 2.208}, {"text": "If you want to say\nhow much you spent", "start": 2481.368, "duration": 1.542}, {"text": "on Saturdays for the month, then\nyou go to your Saturday ledger", "start": 2482.91, "duration": 4.24}, {"text": "and see.", "start": 2487.15, "duration": 0.5}, {"text": "But if you want to see, overall,\nhow much money you've spend", "start": 2487.65, "duration": 2.1}, {"text": "and how much has\nmoved around, then you", "start": 2489.75, "duration": 1.625}, {"text": "look at your general ledger.", "start": 2491.375, "duration": 1.845}, {"text": "PROFESSOR: Aviva clearly said\nit better than I could have.", "start": 2493.22, "duration": 3.04}, {"text": "Thank you.", "start": 2496.26, "duration": 1.59}, {"text": "Now we know we have\none CPA in the class.", "start": 2497.85, "duration": 3.64}, {"text": "But the importance-- it's\nnot just a passing note.", "start": 2501.49, "duration": 3.41}, {"text": "The importance of a general\nledger and subledgers", "start": 2504.9, "duration": 3.57}, {"text": "is there is a\nhierarchy, as well.", "start": 2508.47, "duration": 2.37}, {"text": "Subledgers have more detail,\nand maybe the net number", "start": 2510.84, "duration": 3.42}, {"text": "is kept in the general ledger.", "start": 2514.26, "duration": 2.82}, {"text": "That is at the heart of\nour system of banking", "start": 2517.08, "duration": 3.69}, {"text": "and is at the heart of our\nsystem of financial markets,", "start": 2520.77, "duration": 4.54}, {"text": "where the central bank is like\na general ledger for money,", "start": 2525.31, "duration": 4.05}, {"text": "and every commercial bank, all\n9,000 of them or so in the US,", "start": 2529.36, "duration": 5.13}, {"text": "in essence keep a\nsubledger for money.", "start": 2534.49, "duration": 3.04}, {"text": "But they do not\nhave control of what", "start": 2537.53, "duration": 2.27}, {"text": "I will call the master ledger\nor general ledger at the Federal", "start": 2539.8, "duration": 4.88}, {"text": "Reserve.", "start": 2544.68, "duration": 0.5}, {"text": "Then, a third distinction\nabout ledger is a single entry.", "start": 2548.45, "duration": 2.88}, {"text": "A little, young, 15-year-old\nGeorge Washington", "start": 2551.33, "duration": 3.4}, {"text": "was keeping a single\nentry ledger--", "start": 2554.73, "duration": 2.88}, {"text": "just a list of things\nthat was going on.", "start": 2557.61, "duration": 3.0}, {"text": "And I didn't think I was going\nto bore the class with readings", "start": 2560.61, "duration": 3.003}, {"text": "about double-entry\nbookkeeping, because you've", "start": 2563.613, "duration": 1.917}, {"text": "taken accounting.", "start": 2565.53, "duration": 0.725}, {"text": "But does anybody want to\ntell me, other than Aviva,", "start": 2566.255, "duration": 2.125}, {"text": "what double-entry bookkeeping--\nand she'll bail you out.", "start": 2568.38, "duration": 3.82}, {"text": "[INAUDIBLE]?", "start": 2572.2, "duration": 1.44}, {"text": "AUDIENCE: Double-entry\nbookkeeping basically means any", "start": 2573.64, "duration": 2.28}, {"text": "transaction has two\nplaces in the lender--", "start": 2575.92, "duration": 2.21}, {"text": "one on the credit side\nand one on the debt side.", "start": 2578.13, "duration": 2.4}, {"text": "Because every\ntransaction involves", "start": 2580.53, "duration": 1.84}, {"text": "one person lending,\nwhereas the other person", "start": 2582.37, "duration": 2.45}, {"text": "is getting the thing.", "start": 2584.82, "duration": 3.725}, {"text": "PROFESSOR: It works for me.", "start": 2588.545, "duration": 1.125}, {"text": "Anybody else want\na different view?", "start": 2589.67, "duration": 1.67}, {"text": "AUDIENCE: In other\nwords, [INAUDIBLE]", "start": 2594.508, "duration": 1.542}, {"text": "asset and liability [INAUDIBLE]\ntwo sites and then [INAUDIBLE]", "start": 2596.05, "duration": 4.92}, {"text": "to balance each\nother [INAUDIBLE]..", "start": 2600.97, "duration": 2.34}, {"text": "PROFESSOR: So there's a\nbalancing between assets", "start": 2603.31, "duration": 2.19}, {"text": "and liabilities, and\nthen the resulting bit", "start": 2605.5, "duration": 2.52}, {"text": "of capitalism in it is if assets\nare more than liabilities,", "start": 2608.02, "duration": 3.72}, {"text": "the rest is capital.", "start": 2611.74, "duration": 2.22}, {"text": "So at the heart of\ncapitalism, in a sense,", "start": 2613.96, "duration": 2.4}, {"text": "is double-entry bookkeeping.", "start": 2616.36, "duration": 1.83}, {"text": "And in fact, while it\nprobably goes back a little", "start": 2618.19, "duration": 3.51}, {"text": "over 1,000 years, when\nit was truly written up", "start": 2621.7, "duration": 2.88}, {"text": "by the Italians in\nthe 1300s, it started", "start": 2624.58, "duration": 4.32}, {"text": "to help Europe come\nout of the Dark Ages.", "start": 2628.9, "duration": 2.82}, {"text": "I mean, the commercial\nRenaissance of the Middle Ages,", "start": 2631.72, "duration": 4.05}, {"text": "some would say, was in part--", "start": 2635.77, "duration": 1.65}, {"text": "not entirely, but in part--", "start": 2637.42, "duration": 1.76}, {"text": "on the backs of\ndouble-entry bookkeeping.", "start": 2639.18, "duration": 2.36}, {"text": "So ledgers matter is my point.", "start": 2641.54, "duration": 2.715}, {"text": "They're not going to be the\nheart and soul of this class,", "start": 2644.255, "duration": 2.375}, {"text": "but Bitcoin, which is a\ntransaction ledger, Ethereum,", "start": 2646.63, "duration": 3.69}, {"text": "which is a balance ledger,\nour financial system, which", "start": 2650.32, "duration": 4.66}, {"text": "is all set up on ledgers is\na relevant sort of subtext.", "start": 2654.98, "duration": 4.733}, {"text": "You don't have to\nbe afraid of it,", "start": 2659.713, "duration": 1.417}, {"text": "just as you don't have to\nbe afraid of hashing power", "start": 2661.13, "duration": 3.02}, {"text": "that we'll be talking about\non Thursday and cryptography.", "start": 2664.15, "duration": 3.26}, {"text": "You have to have some sort\nof basic sense of where", "start": 2667.41, "duration": 3.11}, {"text": "does Bitcoin fit in,\nin terms of ledgers.", "start": 2670.52, "duration": 2.46}, {"text": "I didn't feel this slide in.", "start": 2676.4, "duration": 1.32}, {"text": "You'll find out it's blank.", "start": 2677.72, "duration": 1.38}, {"text": "Does anybody want\nto tell me what", "start": 2679.1, "duration": 1.375}, {"text": "are some characteristics\nof a good ledger?", "start": 2680.475, "duration": 2.375}, {"text": "Because again, as you start\nto think about your blockchain", "start": 2682.85, "duration": 2.58}, {"text": "projects later in\nthe semester, it's", "start": 2685.43, "duration": 1.59}, {"text": "like, what makes a good ledger?", "start": 2687.02, "duration": 2.58}, {"text": "I don't have any answers here.", "start": 2689.6, "duration": 3.5}, {"text": "AUDIENCE: The bitcoin\nwere immutable.", "start": 2693.1, "duration": 2.16}, {"text": "PROFESSOR: So you want it\nto be immutable, maybe.", "start": 2695.26, "duration": 2.68}, {"text": "Thalita can you do me\na favor and keep these?", "start": 2697.94, "duration": 2.37}, {"text": "We'll put them on the slides.", "start": 2700.31, "duration": 1.69}, {"text": "We'll keep the class's list, and\nwe'll put them in the slides.", "start": 2702.0, "duration": 3.12}, {"text": "Immutable, I like that.", "start": 2705.12, "duration": 2.31}, {"text": "Anybody else want\nto grab something", "start": 2707.43, "duration": 1.73}, {"text": "which is a good ledger?", "start": 2709.16, "duration": 1.512}, {"text": "AUDIENCE: Time stamped.", "start": 2710.672, "duration": 0.958}, {"text": "PROFESSOR: What's that?", "start": 2711.63, "duration": 1.34}, {"text": "Time stamped, all\nright, so that you", "start": 2712.97, "duration": 1.972}, {"text": "know when you made your entry.", "start": 2714.942, "duration": 2.598}, {"text": "Kelly?", "start": 2717.54, "duration": 1.03}, {"text": "AUDIENCE: Ownership.", "start": 2718.57, "duration": 1.09}, {"text": "PROFESSOR: Ownership.", "start": 2719.66, "duration": 0.3}, {"text": "What do you mean by ownership?", "start": 2719.96, "duration": 1.53}, {"text": "AUDIENCE: Essentially, the\nreceiver and the person giving.", "start": 2721.49, "duration": 4.36}, {"text": "So essentially, who's taking\nwhat and who's giving what.", "start": 2725.85, "duration": 2.655}, {"text": "PROFESSOR: So if\nthere's a transaction,", "start": 2728.505, "duration": 1.625}, {"text": "the two counterparties to\nthe transaction, right?", "start": 2730.13, "duration": 3.63}, {"text": "And if it's a balance,\nthen who owns the balance?", "start": 2733.76, "duration": 3.63}, {"text": "I was just adding a little bit.", "start": 2737.39, "duration": 2.43}, {"text": "Let's see if we have\na new name or face.", "start": 2739.82, "duration": 1.87}, {"text": "Back here, on the back table.", "start": 2741.69, "duration": 2.33}, {"text": "I haven't chatted with you yet.", "start": 2744.02, "duration": 1.595}, {"text": "AUDIENCE: Ross.", "start": 2745.615, "duration": 0.625}, {"text": "PROFESSOR: What is that?", "start": 2746.24, "duration": 0.83}, {"text": "AUDIENCE: Ross.", "start": 2747.07, "duration": 0.633}, {"text": "PROFESSOR: Ross.", "start": 2747.703, "duration": 0.667}, {"text": "Thank you, Ross.", "start": 2748.37, "duration": 0.667}, {"text": "Good to meet you.", "start": 2749.037, "duration": 0.93}, {"text": "AUDIENCE: Pleasure\nto meet you, as well.", "start": 2749.967, "duration": 1.667}, {"text": "Accuracy.", "start": 2751.634, "duration": 0.583}, {"text": "PROFESSOR: Accuracy.", "start": 2752.217, "duration": 0.833}, {"text": "So Ross says accuracy.", "start": 2753.05, "duration": 2.12}, {"text": "And can we take one\nor two more, just to--", "start": 2755.17, "duration": 1.75}, {"text": "AUDIENCE: So a description\nof the transaction.", "start": 2756.92, "duration": 2.317}, {"text": "PROFESSOR: Andrew says a\ndescription of the transaction.", "start": 2759.237, "duration": 2.333}, {"text": "And last, Mr. [INAUDIBLE]?", "start": 2761.57, "duration": 3.03}, {"text": "AUDIENCE: Comprehensive.", "start": 2764.6, "duration": 1.0}, {"text": "PROFESSOR: What's that?", "start": 2765.6, "duration": 0.55}, {"text": "AUDIENCE: Comprehensive.", "start": 2766.15, "duration": 0.33}, {"text": "PROFESSOR: Comprehensive.", "start": 2766.48, "duration": 1.33}, {"text": "So all good attributes of a--", "start": 2767.81, "duration": 2.52}, {"text": "characteristics.", "start": 2770.33, "duration": 1.8}, {"text": "Somebody's burning desire\nthat we missed one or two?", "start": 2772.13, "duration": 4.49}, {"text": "Jihei?", "start": 2776.62, "duration": 0.53}, {"text": "All right.", "start": 2777.15, "duration": 0.72}, {"text": "AUDIENCE: I just was curious.", "start": 2777.87, "duration": 1.31}, {"text": "Consistency, maybe?", "start": 2779.18, "duration": 0.983}, {"text": "But I don't know if that's--", "start": 2780.163, "duration": 1.167}, {"text": "PROFESSOR: Consistency.", "start": 2781.33, "duration": 0.958}, {"text": "Well, I think that's inside of\nimmutability, that, in essence,", "start": 2782.288, "duration": 3.212}, {"text": "that it's valid, that\nyou can't change it.", "start": 2785.5, "duration": 4.51}, {"text": "You can't counterfeit\nit and the like.", "start": 2790.01, "duration": 3.21}, {"text": "And what you'll find\nis the characteristics", "start": 2793.22, "duration": 2.39}, {"text": "of a good ledger is\nalso, in some part,", "start": 2795.61, "duration": 2.64}, {"text": "similar to the\ncharacteristics of good money.", "start": 2798.25, "duration": 2.04}, {"text": "They're not identical,\nbut they overlap a lot.", "start": 2800.29, "duration": 3.45}, {"text": "Payment systems-- I'm just\ngoing to say one line about it.", "start": 2803.74, "duration": 3.66}, {"text": "It's a method, basically,\nto amend and record", "start": 2807.4, "duration": 3.51}, {"text": "changes in a ledger for money.", "start": 2810.91, "duration": 2.58}, {"text": "I know it's not what you usually\nthink about a payment system.", "start": 2813.49, "duration": 2.68}, {"text": "But if you go into Starbucks\nand buy a cup of coffee", "start": 2816.17, "duration": 5.41}, {"text": "and use your cell phone,\naren't you really just", "start": 2821.58, "duration": 3.99}, {"text": "amending a set of ledgers?", "start": 2825.57, "duration": 3.0}, {"text": "Starbucks' ledger goes up, and\nyup, your ledger goes down.", "start": 2828.57, "duration": 6.01}, {"text": "Well, your monetary\nledger goes up.", "start": 2834.58, "duration": 3.51}, {"text": "Your utility, your fulfillment\nfrom that latte might go up.", "start": 2838.09, "duration": 5.52}, {"text": "I'm talking about\nthe financial ledger.", "start": 2843.61, "duration": 2.76}, {"text": "So I just wanted to ground--\nwhen we talk about payment", "start": 2846.37, "duration": 3.13}, {"text": "systems, think about it's really\njust a way to amend, usually,", "start": 2849.5, "duration": 4.34}, {"text": "two parties ledgers'-- one\ngoing up, one going down.", "start": 2853.84, "duration": 4.74}, {"text": "Now, in an earlier time, it was\nhanding somebody a bit of gold", "start": 2858.58, "duration": 4.42}, {"text": "or a bit of silver,\nand it was not", "start": 2863.0, "duration": 3.06}, {"text": "recorded on central ledgers.", "start": 2866.06, "duration": 1.83}, {"text": "But we already live in\nan age of electronics,", "start": 2867.89, "duration": 2.39}, {"text": "so this is really what a\npayment system largely is.", "start": 2870.28, "duration": 4.12}, {"text": "It's not entirely.", "start": 2874.4, "duration": 1.17}, {"text": "There's still some other\nways to do finance.", "start": 2875.57, "duration": 4.87}, {"text": "So what were some early\nforms of payment systems", "start": 2880.44, "duration": 3.63}, {"text": "that did just that, that\nmoved and changed ledgers?", "start": 2884.07, "duration": 4.84}, {"text": "They're called\nnegotiable orders.", "start": 2888.91, "duration": 2.31}, {"text": "I would dare say\nthat most of you", "start": 2891.22, "duration": 1.55}, {"text": "probably have not used\nnegotiable orders of withdrawal", "start": 2892.77, "duration": 3.96}, {"text": "that much in the last\nweek or the last month.", "start": 2896.73, "duration": 3.57}, {"text": "Has anybody here\nwritten a personal check", "start": 2900.3, "duration": 3.69}, {"text": "in the last week?", "start": 2903.99, "duration": 1.23}, {"text": "But in an earlier era, it would\nhave been the whole class.", "start": 2908.56, "duration": 4.13}, {"text": "Anybody in the class not\neven have a checkbook?", "start": 2912.69, "duration": 4.56}, {"text": "3/4 of the class.", "start": 2917.25, "duration": 1.63}, {"text": "Larry, how's that make you feel?", "start": 2918.88, "duration": 1.941}, {"text": "AUDIENCE: Old.", "start": 2920.821, "duration": 0.583}, {"text": "PROFESSOR: But a\ncheckbook is, in essence,", "start": 2924.33, "duration": 4.05}, {"text": "with a-- what do\nyou put on a check?", "start": 2928.38, "duration": 3.27}, {"text": "This is all about Bitcoin now.", "start": 2931.65, "duration": 1.74}, {"text": "I'm not doing this\njust as a walk down", "start": 2933.39, "duration": 3.03}, {"text": "memory lane for\nLarry and myself.", "start": 2936.42, "duration": 1.545}, {"text": "What are the important pieces\nof negotiable order, withdraw,", "start": 2940.68, "duration": 2.785}, {"text": "or a check?", "start": 2943.465, "duration": 1.392}, {"text": "AUDIENCE: Signature.", "start": 2944.857, "duration": 0.833}, {"text": "AUDIENCE: Put your\nsignature on it.", "start": 2945.69, "duration": 1.39}, {"text": "PROFESSOR: So\nthere's a signature.", "start": 2947.08, "duration": 1.417}, {"text": "What else is there?", "start": 2948.497, "duration": 1.763}, {"text": "I want to get to people\nI haven't talked to.", "start": 2950.26, "duration": 2.18}, {"text": "In the back.", "start": 2952.44, "duration": 0.74}, {"text": "I can't remember your name.", "start": 2953.18, "duration": 1.294}, {"text": "AUDIENCE: Me?", "start": 2954.474, "duration": 0.542}, {"text": "I'm Dana.", "start": 2955.016, "duration": 0.814}, {"text": "You put who you're paying to,\nhow much, and what it's for.", "start": 2955.83, "duration": 3.602}, {"text": "PROFESSOR: All right,\nso there's a bunch.", "start": 2959.432, "duration": 1.708}, {"text": "So a signature, a payee, how\nmuch, and what it was for.", "start": 2961.14, "duration": 5.91}, {"text": "What else?", "start": 2967.05, "duration": 0.99}, {"text": "AUDIENCE: There's an account\nnumber and routing number.", "start": 2968.04, "duration": 2.52}, {"text": "PROFESSOR: Account numbers\nand routing numbers.", "start": 2970.56, "duration": 2.66}, {"text": "So think about it.", "start": 2973.22, "duration": 0.75}, {"text": "Account numbers and\nrouting numbers is to say,", "start": 2973.97, "duration": 5.75}, {"text": "in essence, what ledger\nis this coming from?", "start": 2979.72, "duration": 4.68}, {"text": "And the payee is the\nledger to whom it's going.", "start": 2984.4, "duration": 4.47}, {"text": "And I'm sorry, Dan?", "start": 2988.87, "duration": 1.67}, {"text": "AUDIENCE: Also a\ndate, and a day.", "start": 2990.54, "duration": 2.08}, {"text": "PROFESSOR: So there's a\ntimestamp, a signature,", "start": 2992.62, "duration": 2.74}, {"text": "a payee, the payor in the\nform of the account number,", "start": 2995.36, "duration": 6.38}, {"text": "and an amount.", "start": 3001.74, "duration": 0.81}, {"text": "Those five are really\ncritical, and you'll", "start": 3002.55, "duration": 2.31}, {"text": "find them all are going to\nbe right in the middle of all", "start": 3004.86, "duration": 2.43}, {"text": "this Bitcoin.", "start": 3007.29, "duration": 2.04}, {"text": "And then the reason why you're--", "start": 3009.33, "duration": 1.74}, {"text": "you know, some\nother information.", "start": 3011.07, "duration": 2.34}, {"text": "I'm sorry, was there\nsomething else?", "start": 3013.41, "duration": 2.401}, {"text": "AUDIENCE: Kyle.", "start": 3015.811, "duration": 0.625}, {"text": "PROFESSOR: Kyle.", "start": 3016.436, "duration": 0.928}, {"text": "AUDIENCE: I just\nhave a question.", "start": 3017.364, "duration": 1.375}, {"text": "Would you consider something\nlike PayPal or Venmo", "start": 3018.739, "duration": 2.596}, {"text": "like a negotiable order?", "start": 3021.335, "duration": 2.447}, {"text": "PROFESSOR: They may be.", "start": 3023.782, "duration": 0.958}, {"text": "They may be new forms.", "start": 3024.74, "duration": 1.81}, {"text": "They're certainly parts\nof the payment system.", "start": 3026.55, "duration": 4.25}, {"text": "They might not be negotiable\norders to withdraw.", "start": 3030.8, "duration": 2.55}, {"text": "They might not be a\ndirect authorization", "start": 3033.35, "duration": 4.11}, {"text": "for a bank with one ledger to\nmove money to another ledger.", "start": 3037.46, "duration": 4.77}, {"text": "They might be moving\nit on their own ledger.", "start": 3042.23, "duration": 2.7}, {"text": "You're asking the\nright question.", "start": 3047.76, "duration": 2.28}, {"text": "So some early money that we\nalready talked about that", "start": 3050.04, "duration": 2.27}, {"text": "was ledger where\nthe tally sticks", "start": 3052.31, "duration": 1.71}, {"text": "in England and the Yap stone.", "start": 3054.02, "duration": 1.59}, {"text": "These were ledger types\nand forms of money", "start": 3055.61, "duration": 3.59}, {"text": "and was kind of interesting.", "start": 3059.2, "duration": 1.31}, {"text": "So ledgers didn't just come\nwith electricity and computers.", "start": 3060.51, "duration": 4.91}, {"text": "So now let's get back to\nfiat currency, the heart", "start": 3065.42, "duration": 2.81}, {"text": "of the earlier question.", "start": 3068.23, "duration": 1.0}, {"text": "We already talked\nabout it, so let's see", "start": 3072.05, "duration": 1.68}, {"text": "how the professor did,\nbecause you already", "start": 3073.73, "duration": 1.92}, {"text": "said some of the things that\nyou said were fiat currency.", "start": 3075.65, "duration": 3.51}, {"text": "One, social and\neconomic consensus.", "start": 3079.16, "duration": 5.05}, {"text": "I'm in the school that it's\njust part of the history.", "start": 3084.21, "duration": 3.53}, {"text": "It's not that different\nthan everything that came,", "start": 3087.74, "duration": 3.54}, {"text": "even though it built on that\npromissory note from China", "start": 3091.28, "duration": 2.82}, {"text": "700 years ago and the private\nbank notes and the goldsmiths", "start": 3094.1, "duration": 4.92}, {"text": "in the 1700s.", "start": 3099.02, "duration": 1.71}, {"text": "But ultimately,\ngovernments took control.", "start": 3100.73, "duration": 4.08}, {"text": "It represents central\nbank liabilities,", "start": 3104.81, "duration": 2.55}, {"text": "and that's important.", "start": 3107.36, "duration": 0.93}, {"text": "It's a liability\nof a central bank.", "start": 3108.29, "duration": 3.6}, {"text": "It's not an asset.", "start": 3111.89, "duration": 1.36}, {"text": "It's their liability side.", "start": 3113.25, "duration": 3.36}, {"text": "But it's also-- guess what?", "start": 3116.61, "duration": 1.64}, {"text": "There's a second form of money.", "start": 3118.25, "duration": 2.62}, {"text": "And that's when\nyou have a deposit", "start": 3120.87, "duration": 3.8}, {"text": "in a bank, that's a liability\nof a commercial bank.", "start": 3124.67, "duration": 4.66}, {"text": "Central bank is the top\ngold standard, in a sense.", "start": 3129.33, "duration": 3.45}, {"text": "Using the word gold,\nbut it's the top ledger.", "start": 3132.78, "duration": 2.76}, {"text": "Commercial banks are like\nsubledgers, in a sense.", "start": 3135.54, "duration": 3.82}, {"text": "Please, Alan?", "start": 3139.36, "duration": 0.84}, {"text": "AUDIENCE: Sure.", "start": 3140.2, "duration": 0.16}, {"text": "I'm not an economist\nor anything,", "start": 3140.36, "duration": 1.375}, {"text": "but what does it mean\nfor a coin or a note", "start": 3141.735, "duration": 3.405}, {"text": "to be a liability\nof the central bank?", "start": 3145.14, "duration": 1.7}, {"text": "What does that actually mean?", "start": 3146.84, "duration": 2.87}, {"text": "PROFESSOR: So before\nI answer, does anybody", "start": 3149.71, "duration": 3.32}, {"text": "want to try to\nanswer what it is?", "start": 3153.03, "duration": 3.57}, {"text": "Eric?", "start": 3156.6, "duration": 0.5}, {"text": "AUDIENCE: Liability is basically\nan obligation to, in this case,", "start": 3157.1, "duration": 4.11}, {"text": "pay someone an amount.", "start": 3161.21, "duration": 2.826}, {"text": "PROFESSOR: So because\nit's a social consensus,", "start": 3164.036, "duration": 2.424}, {"text": "it's a very good question that\nAlan asked, is what does it", "start": 3166.46, "duration": 4.65}, {"text": "mean to be a liability\nof a central bank", "start": 3171.11, "duration": 2.82}, {"text": "when it's just the currency\nin our pocket, right?", "start": 3173.93, "duration": 4.56}, {"text": "This Federal Reserve\nnote, this says", "start": 3178.49, "duration": 2.46}, {"text": "Federal Reserve note on it.", "start": 3180.95, "duration": 1.5}, {"text": "We can pass it around.", "start": 3187.175, "duration": 1.32}, {"text": "I'm not afraid.", "start": 3188.495, "duration": 0.625}, {"text": "It's only $1.", "start": 3189.12, "duration": 1.8}, {"text": "Right?", "start": 3190.92, "duration": 1.48}, {"text": "If you want me to pass around\n20's, then I want them.", "start": 3192.4, "duration": 3.23}, {"text": "But it says Federal\nReserve note, right?", "start": 3195.63, "duration": 3.63}, {"text": "So it's a liability of\nthe commercial bank.", "start": 3199.26, "duration": 2.565}, {"text": "In an earlier day, it\nsaid you could exchange it", "start": 3204.62, "duration": 3.12}, {"text": "for gold or silver.", "start": 3207.74, "duration": 0.845}, {"text": "AUDIENCE: Right, so that's\nwhat I don't understand.", "start": 3208.585, "duration": 2.125}, {"text": "PROFESSOR: By the 1930s,\nfor retail deposits", "start": 3210.71, "duration": 3.42}, {"text": "in the middle of the\nDepression, President Roosevelt", "start": 3214.13, "duration": 3.3}, {"text": "said, no more.", "start": 3217.43, "duration": 1.5}, {"text": "You cannot redeem\ngold and silver.", "start": 3218.93, "duration": 2.19}, {"text": "And then President\nNixon, in the 1970s,", "start": 3221.12, "duration": 2.22}, {"text": "said in the official sector\nthat he was going off of the--", "start": 3223.34, "duration": 4.02}, {"text": "until that point in\ntime, other governments", "start": 3227.36, "duration": 3.09}, {"text": "could redeem in gold.", "start": 3230.45, "duration": 2.97}, {"text": "But when paper money started,\nit was not backed by gold.", "start": 3233.42, "duration": 3.67}, {"text": "We had a period of\nthe gold standard.", "start": 3237.09, "duration": 2.36}, {"text": "We were on and off of it.", "start": 3239.45, "duration": 1.2}, {"text": "We fell off of it during World\nWar I. We went back on it.", "start": 3240.65, "duration": 5.91}, {"text": "It would be a false\nnarrative to say", "start": 3246.56, "duration": 2.13}, {"text": "that we were on the gold\nstandard for our first 140", "start": 3248.69, "duration": 2.7}, {"text": "years.", "start": 3251.39, "duration": 1.8}, {"text": "I just wanted to clear that up.", "start": 3253.19, "duration": 2.19}, {"text": "I mean, we sort of went on the\ngold standard, we went off,", "start": 3255.38, "duration": 2.79}, {"text": "we went back on, and so forth.", "start": 3258.17, "duration": 3.01}, {"text": "But it is a liability on\nthe books and records.", "start": 3261.18, "duration": 2.58}, {"text": "So it is a matter of accounting\nin double-entry bookkeeping.", "start": 3263.76, "duration": 4.11}, {"text": "I will show you in\na minute the balance", "start": 3267.87, "duration": 1.8}, {"text": "sheet of the Federal\nReserve, and I'll", "start": 3269.67, "duration": 1.74}, {"text": "come back to this question.", "start": 3271.41, "duration": 1.2}, {"text": "Is that all right?", "start": 3272.61, "duration": 0.75}, {"text": "AUDIENCE: Can you clarify\nwhat is the bank liable for?", "start": 3273.36, "duration": 2.25}, {"text": "So before, it gave me\n$1, and I could go to $1", "start": 3275.61, "duration": 2.94}, {"text": "and get back the gold, right?", "start": 3278.55, "duration": 1.292}, {"text": "PROFESSOR: Right.", "start": 3279.842, "duration": 0.708}, {"text": "AUDIENCE: Now, what are\nthey liable for now?", "start": 3280.55, "duration": 3.46}, {"text": "PROFESSOR: It is, in\nessence, a social--", "start": 3284.01, "duration": 1.77}, {"text": "it's the first point.", "start": 3285.78, "duration": 2.708}, {"text": "I'm going to separate it.", "start": 3288.488, "duration": 1.042}, {"text": "The central bank is liable that\nthey will move on its ledgers", "start": 3289.53, "duration": 5.46}, {"text": "if you want to move\nthat to somewhere else.", "start": 3294.99, "duration": 2.83}, {"text": "So you could take that\nphysical $1 in and say,", "start": 3297.82, "duration": 2.93}, {"text": "I want to deposit\nthis in a bank.", "start": 3300.75, "duration": 2.31}, {"text": "And they have to record it\non the ledger of that bank.", "start": 3303.06, "duration": 3.24}, {"text": "That is what they are--", "start": 3306.3, "duration": 2.07}, {"text": "and the US government,\nwhich is technically", "start": 3308.37, "duration": 2.97}, {"text": "separate from the central bank--", "start": 3311.34, "duration": 2.19}, {"text": "or the UK government or\nthe Chinese government.", "start": 3313.53, "duration": 2.98}, {"text": "they're all technically\nseparate from their banks--", "start": 3316.51, "duration": 2.93}, {"text": "People's Bank of China\nor the Bank of England.", "start": 3319.44, "duration": 3.35}, {"text": "Their governments are\nsaying they will accept it", "start": 3322.79, "duration": 2.0}, {"text": "for payments against taxes.", "start": 3324.79, "duration": 3.45}, {"text": "So there's a set of\nsocial constructs.", "start": 3328.24, "duration": 2.42}, {"text": "I'm going to just go through\nthis to answer your question.", "start": 3333.273, "duration": 2.417}, {"text": "It relies on a\nsystem of ledgers,", "start": 3335.69, "duration": 3.76}, {"text": "and it's an integration of those\nledgers between the banking", "start": 3339.45, "duration": 3.347}, {"text": "system and the commercial banks.", "start": 3342.797, "duration": 1.333}, {"text": "In the US, we have about\n9,000 commercial banks.", "start": 3344.13, "duration": 4.97}, {"text": "And what the Federal\nReserve is saying--", "start": 3349.1, "duration": 1.77}, {"text": "but it's true about the\nPeople's Bank of China.", "start": 3350.87, "duration": 2.4}, {"text": "It's true about the\nEuropean Central Bank.", "start": 3353.27, "duration": 4.23}, {"text": "Each of these central\nbanks are basically", "start": 3357.5, "duration": 1.83}, {"text": "saying, if you bring\nyour paper money in,", "start": 3359.33, "duration": 4.14}, {"text": "we'll record it on the\nledger of a commercial bank.", "start": 3363.47, "duration": 4.29}, {"text": "And you can pay your\ntaxes to our sister", "start": 3367.76, "duration": 2.27}, {"text": "over here called the government.", "start": 3370.03, "duration": 3.79}, {"text": "I'm sorry to let you down.", "start": 3373.82, "duration": 1.73}, {"text": "It's not more than that.", "start": 3375.55, "duration": 1.3}, {"text": "Sorry, Alan.", "start": 3376.85, "duration": 0.54}, {"text": "AUDIENCE: I have a\npotential answer.", "start": 3377.39, "duration": 1.5}, {"text": "I might be totally wrong.", "start": 3378.89, "duration": 1.042}, {"text": "PROFESSOR: Please, no.", "start": 3379.932, "duration": 0.916}, {"text": "AUDIENCE: I think it's a\nlegal and sustainable way", "start": 3380.848, "duration": 2.092}, {"text": "to conduct a Ponzi scheme with\na proper Ponzi scheme, where", "start": 3382.94, "duration": 8.31}, {"text": "the value will\nincrease by 1% to 3%", "start": 3391.25, "duration": 2.64}, {"text": "if the central bank reaches\nthe goal of inflation.", "start": 3393.89, "duration": 5.4}, {"text": "PROFESSOR: All right, any\nother points of view on that?", "start": 3399.29, "duration": 2.46}, {"text": "I saw-- I'm not\nsure of your name.", "start": 3401.75, "duration": 3.24}, {"text": "Oh, no, you don't\nwant to say anything?", "start": 3404.99, "duration": 1.87}, {"text": "No?", "start": 3406.86, "duration": 0.5}, {"text": "All right.", "start": 3407.36, "duration": 1.467}, {"text": "AUDIENCE: I think I'll\ngo back to point one.", "start": 3408.827, "duration": 1.833}, {"text": "It's a construct that someone\nwould give you something.", "start": 3410.66, "duration": 3.26}, {"text": "So your dollar with the\ncentral bank, the central bank", "start": 3413.92, "duration": 3.09}, {"text": "owes you that dollar's worth\nof whatever you desire.", "start": 3417.01, "duration": 3.69}, {"text": "And someone will\nhappily take that dollar", "start": 3420.7, "duration": 2.1}, {"text": "from the central bank and give\nyou the goods that you want.", "start": 3422.8, "duration": 2.72}, {"text": "So it's a roundabout\nway of-- it's", "start": 3425.52, "duration": 3.25}, {"text": "a way of transacting something,\nwhatever value that dollar has.", "start": 3428.77, "duration": 5.588}, {"text": "AUDIENCE: It's also\ncentral bank liability,", "start": 3434.358, "duration": 1.792}, {"text": "because whenever the\ngovernment has sovereign debt,", "start": 3436.15, "duration": 2.71}, {"text": "it can't just issue new notes.", "start": 3438.86, "duration": 2.34}, {"text": "It's liable.", "start": 3441.2, "duration": 1.103}, {"text": "So that's why it's a\nliability, because you can only", "start": 3442.303, "duration": 2.167}, {"text": "issue notes against a\ncertain amount of reserves", "start": 3444.47, "duration": 2.21}, {"text": "that you carry.", "start": 3446.68, "duration": 1.05}, {"text": "So that's why you refer\nto it as a liability.", "start": 3447.73, "duration": 3.09}, {"text": "Because you can't just issue new\nnotes whenever you need them.", "start": 3450.82, "duration": 3.84}, {"text": "You can't just make new\nmoney out of thin air.", "start": 3454.66, "duration": 2.21}, {"text": "So you're liable\nfor every new note.", "start": 3456.87, "duration": 2.1}, {"text": "PROFESSOR: I'm going to take\none more comment on this", "start": 3458.97, "duration": 2.38}, {"text": "and then give a\ncouple more things.", "start": 3461.35, "duration": 1.52}, {"text": "Eric?", "start": 3462.87, "duration": 1.25}, {"text": "AUDIENCE: The\ncurrency is actually", "start": 3464.12, "duration": 1.94}, {"text": "a small part of the total\nreserves of the Federal Reserve", "start": 3466.06, "duration": 3.33}, {"text": "System.", "start": 3469.39, "duration": 0.93}, {"text": "I think maybe the bank\nreserves are maybe", "start": 3470.32, "duration": 2.91}, {"text": "a more applicable application,\nbecause a bank can actually", "start": 3473.23, "duration": 3.24}, {"text": "require the Fed to print\nmoney by making more loans.", "start": 3476.47, "duration": 4.11}, {"text": "So in that way,\nthere's this mechanism", "start": 3480.58, "duration": 3.33}, {"text": "to ensure that\nliability [INAUDIBLE]..", "start": 3483.91, "duration": 2.14}, {"text": "PROFESSOR: I'm very pleased\nwith this discussion, even", "start": 3486.05, "duration": 2.28}, {"text": "Alan's contributions\nabout the schemes.", "start": 3488.33, "duration": 4.85}, {"text": "This is the debate.", "start": 3493.18, "duration": 1.44}, {"text": "If Jay Powell were\nhere-- how many of you", "start": 3494.62, "duration": 1.92}, {"text": "know who Jay Powell is?", "start": 3496.54, "duration": 3.01}, {"text": "Who's Jay Powell?", "start": 3499.55, "duration": 1.205}, {"text": "AUDIENCE: It's a lab.", "start": 3500.755, "duration": 3.275}, {"text": "PROFESSOR: Jay Powell.", "start": 3504.03, "duration": 1.24}, {"text": "No.", "start": 3505.27, "duration": 0.5}, {"text": "Who's Jay Powell?", "start": 3505.77, "duration": 1.02}, {"text": "AUDIENCE: Head of\nthe Federal Reserve.", "start": 3506.79, "duration": 0.96}, {"text": "PROFESSOR: Head of\nthe Federal Reserve.", "start": 3507.75, "duration": 1.625}, {"text": "Thank you.", "start": 3509.375, "duration": 1.165}, {"text": "Sorry.", "start": 3510.54, "duration": 2.4}, {"text": "But if Jay Powell\nwere here, he'd", "start": 3512.94, "duration": 3.27}, {"text": "have a laugh along with\nwhat Alan just said,", "start": 3516.21, "duration": 3.72}, {"text": "but he would say,\nalso, the liability", "start": 3519.93, "duration": 4.29}, {"text": "is a social liability, as well.", "start": 3524.22, "duration": 2.64}, {"text": "That a central\nbanker, to their core,", "start": 3526.86, "duration": 2.52}, {"text": "believes what they\nare trying to do", "start": 3529.38, "duration": 2.43}, {"text": "is ensure for the stability of\nthis social thing we call money", "start": 3531.81, "duration": 5.82}, {"text": "and to make sure that\nit doesn't get debased", "start": 3537.63, "duration": 2.4}, {"text": "and it has some value.", "start": 3540.03, "duration": 3.3}, {"text": "So it's accepted for\ntaxes, we talked about.", "start": 3543.33, "duration": 3.0}, {"text": "Notes and coins are legal\ntender for all debts,", "start": 3546.33, "duration": 2.44}, {"text": "public and private.", "start": 3548.77, "duration": 2.28}, {"text": "I walk into a Starbucks and I\nsay, I'd like a cup of coffee.", "start": 3551.05, "duration": 5.47}, {"text": "Here's my $5 or whatever\nit costs these days.", "start": 3556.52, "duration": 5.69}, {"text": "Does the person\nbehind the counter", "start": 3562.21, "duration": 1.53}, {"text": "have to brew the coffee?", "start": 3563.74, "duration": 1.51}, {"text": "Is just a yes or no?", "start": 3565.25, "duration": 1.37}, {"text": "Can I see?", "start": 3566.62, "duration": 0.6}, {"text": "Who wants to go for it?", "start": 3570.17, "duration": 2.23}, {"text": "There's a no from Christopher.", "start": 3572.4, "duration": 2.94}, {"text": "What, Chris?", "start": 3575.34, "duration": 1.29}, {"text": "There's a no from Chris.", "start": 3576.63, "duration": 1.08}, {"text": "Who agrees with Chris?", "start": 3577.71, "duration": 2.17}, {"text": "OK.", "start": 3579.88, "duration": 1.67}, {"text": "They brew a cup of coffee.", "start": 3581.55, "duration": 1.5}, {"text": "I go to the other\nside of the counter.", "start": 3583.05, "duration": 1.65}, {"text": "The coffee's sitting there.", "start": 3584.7, "duration": 2.96}, {"text": "Now, do they have to\naccept my $5 at that point?", "start": 3587.66, "duration": 4.14}, {"text": "Yes.", "start": 3591.8, "duration": 1.85}, {"text": "Before they brew the coffee,\nnobody has to take dollars.", "start": 3593.65, "duration": 3.57}, {"text": "But once a debt is established,\nthey've produced the good,", "start": 3597.22, "duration": 5.24}, {"text": "they've provided the service,\nthey have to take it.", "start": 3602.46, "duration": 2.82}, {"text": "Just a small, little thing.", "start": 3605.28, "duration": 1.53}, {"text": "That's what legal tender is.", "start": 3606.81, "duration": 1.8}, {"text": "And so there's\nmany establishments", "start": 3608.61, "duration": 1.74}, {"text": "around the globe\nthat are basically", "start": 3610.35, "duration": 2.73}, {"text": "now putting little signs out,\nwe don't take Swedish krona.", "start": 3613.08, "duration": 4.02}, {"text": "We don't take this.", "start": 3617.1, "duration": 1.11}, {"text": "We don't take that\nin paper form.", "start": 3618.21, "duration": 4.32}, {"text": "They'll still take\nit electronically.", "start": 3622.53, "duration": 1.88}, {"text": "And there's a new little\nbit of definitional thing", "start": 3624.41, "duration": 2.8}, {"text": "going on about legal tender.", "start": 3627.21, "duration": 2.6}, {"text": "There's also some\nunique tax treatments,", "start": 3629.81, "duration": 1.67}, {"text": "but I'm not going to go\nthrough the currency.", "start": 3631.48, "duration": 2.91}, {"text": "So central banking and money\nwe talked about a little bit.", "start": 3634.39, "duration": 2.67}, {"text": "This is a kind of\nchart that I borrowed", "start": 3637.06, "duration": 2.19}, {"text": "from somebody else's paper.", "start": 3639.25, "duration": 3.42}, {"text": "But the central banks at\nthe top is at the center.", "start": 3642.67, "duration": 2.565}, {"text": "And if Alice and Bob-- and we'll\nbe talking about Alice and Bob", "start": 3648.09, "duration": 2.71}, {"text": "in Bitcoin time, so you can\npull this chart down later--", "start": 3650.8, "duration": 3.47}, {"text": "want to transact and they're\nat the same commercial bank,", "start": 3654.27, "duration": 4.06}, {"text": "Bank Number 1, then\ncommercial Bank Number 1", "start": 3658.33, "duration": 2.61}, {"text": "has to change their ledgers,\nmoving money from Alice to Bob.", "start": 3660.94, "duration": 4.08}, {"text": "In essence, if you're both\ntwo people at Bank of America,", "start": 3665.02, "duration": 3.21}, {"text": "you can move your balance\nat Bank of America.", "start": 3668.23, "duration": 4.16}, {"text": "But if you're at Bank of\nAmerica going over to Citicorp,", "start": 3672.39, "duration": 4.19}, {"text": "then something has to go between\ntwo ledgers, Bank of America's", "start": 3676.58, "duration": 6.36}, {"text": "ledger and Citicorp's ledger.", "start": 3682.94, "duration": 1.89}, {"text": "And the only way to transact\nbetween two banks' ledgers", "start": 3684.83, "duration": 5.9}, {"text": "is some balancing\nact has to happen", "start": 3690.73, "duration": 3.53}, {"text": "at the top ledger,\ncalled the central bank.", "start": 3694.26, "duration": 4.39}, {"text": "And later, when we talk about\npayment systems-- and I'm", "start": 3698.65, "duration": 2.513}, {"text": "going to use this slide\nagain later in the semester.", "start": 3701.163, "duration": 2.167}, {"text": "That's why I'm not going to\nspend as much time now on it.", "start": 3703.33, "duration": 2.61}, {"text": "We're going to\ntalk about ledgers.", "start": 3705.94, "duration": 2.78}, {"text": "And when you move money\nbetween two banks,", "start": 3708.72, "duration": 2.26}, {"text": "it's all within\none closed system--", "start": 3710.98, "duration": 2.49}, {"text": "that country's or that society's\ncentral banking system.", "start": 3713.47, "duration": 6.04}, {"text": "But then it gets really\na little bit more iffy", "start": 3719.51, "duration": 2.67}, {"text": "and woolly when you're\nmoving from one currency", "start": 3722.18, "duration": 3.27}, {"text": "to another currency.", "start": 3725.45, "duration": 1.035}, {"text": "Because how do you make two\nclosed ledger systems operable?", "start": 3729.11, "duration": 4.56}, {"text": "Not for today, but\nwe'll go through", "start": 3733.67, "duration": 2.01}, {"text": "that later when we do\npayment systems and the like.", "start": 3735.68, "duration": 6.28}, {"text": "The central bank, the\nUS central bank-- this", "start": 3741.96, "duration": 2.15}, {"text": "was the only good slide I could\nfind, which was about a year", "start": 3744.11, "duration": 2.5}, {"text": "old.", "start": 3746.61, "duration": 0.87}, {"text": "Its liabilities and assets\nare about 4 and 1/4 trillion", "start": 3747.48, "duration": 3.06}, {"text": "dollars, $4.3 trillion.", "start": 3750.54, "duration": 2.34}, {"text": "$1.7 trillion of\nthat is in currency.", "start": 3752.88, "duration": 4.11}, {"text": "Do I get my $1 back, by the way?", "start": 3756.99, "duration": 2.07}, {"text": "I mean, my liability.", "start": 3759.06, "duration": 1.89}, {"text": "So $1.7 trillion of those\ngreenbacks are in circulation.", "start": 3760.95, "duration": 8.31}, {"text": "And remarkably, even\nthough half of you", "start": 3769.26, "duration": 3.39}, {"text": "probably don't use cash\nthat much, you don't even", "start": 3772.65, "duration": 2.37}, {"text": "have checking accounts, the\namount of cash in circulation", "start": 3775.02, "duration": 4.06}, {"text": "is growing faster\nthan the economy", "start": 3779.08, "duration": 1.92}, {"text": "in most developed nations.", "start": 3781.0, "duration": 3.25}, {"text": "Why do you think that is?", "start": 3784.25, "duration": 3.55}, {"text": "What probably one word?", "start": 3787.8, "duration": 2.41}, {"text": "AUDIENCE: The amount of\n2008 crisis [INAUDIBLE]..", "start": 3790.21, "duration": 3.84}, {"text": "PROFESSOR: Oh, that's\nmore than one word.", "start": 3794.05, "duration": 2.014}, {"text": "AUDIENCE: Trust.", "start": 3796.064, "duration": 0.766}, {"text": "PROFESSOR: Drugs.", "start": 3796.83, "duration": 0.708}, {"text": "AUDIENCE: Trust.", "start": 3797.538, "duration": 1.002}, {"text": "PROFESSOR: Oh, trust.", "start": 3798.54, "duration": 1.44}, {"text": "I thought you said drugs.", "start": 3799.98, "duration": 3.15}, {"text": "Trust.", "start": 3803.13, "duration": 0.9}, {"text": "Well, it does have\nto do with trust,", "start": 3804.03, "duration": 1.68}, {"text": "but it also has\nto do with drugs.", "start": 3805.71, "duration": 2.43}, {"text": "Paper currency is\na wonderful method", "start": 3808.14, "duration": 3.27}, {"text": "of money laundering, drug\nrunning, and a store of value.", "start": 3811.41, "duration": 4.45}, {"text": "So there's certain segments\nof our economy and segments", "start": 3815.86, "duration": 2.63}, {"text": "of the worldwide\neconomy that does not", "start": 3818.49, "duration": 2.1}, {"text": "want to be in the\nelectronic banking system.", "start": 3820.59, "duration": 4.64}, {"text": "I'm going to slip\nthrough these quickly,", "start": 3825.23, "duration": 1.87}, {"text": "but there's another piece that\nwe need for this whole class", "start": 3827.1, "duration": 3.42}, {"text": "and for the semester is credit\nand credit intermediation.", "start": 3830.52, "duration": 3.96}, {"text": "But just a little thing--", "start": 3834.48, "duration": 1.68}, {"text": "credit cards started\nonly 60 or 70 years ago,", "start": 3836.16, "duration": 3.78}, {"text": "but they go back to a book\na little over 100 years ago.", "start": 3839.94, "duration": 3.78}, {"text": "The word \"credit\ncard\" is used 18 times", "start": 3843.72, "duration": 2.19}, {"text": "in this book, where a science\nfiction writer in 1887 said,", "start": 3845.91, "duration": 6.45}, {"text": "what would the world be\nlike in the year 2000?", "start": 3852.36, "duration": 2.91}, {"text": "And it was the first use\nof the word \"credit card.\"", "start": 3855.27, "duration": 2.82}, {"text": "And he said that society\nwould have a form of money,", "start": 3858.09, "duration": 3.84}, {"text": "and you would have\ncredit against it.", "start": 3861.93, "duration": 2.19}, {"text": "And it's a fascinating\nthing that somebody", "start": 3864.12, "duration": 1.89}, {"text": "could be that visionary.", "start": 3866.01, "duration": 1.74}, {"text": "But there were merchant\ncards starting,", "start": 3867.75, "duration": 1.98}, {"text": "so maybe he wasn't so visionary.", "start": 3869.73, "duration": 3.09}, {"text": "Oil companies in the 1920s,\ncharge cards were starting,", "start": 3872.82, "duration": 4.62}, {"text": "but they were\nsingle-merchant cards.", "start": 3877.44, "duration": 2.43}, {"text": "You could have credit\nfrom that merchant.", "start": 3879.87, "duration": 3.96}, {"text": "In 1946, in a bank\nin Brooklyn, a guy", "start": 3883.83, "duration": 3.33}, {"text": "named Biggins started with that.", "start": 3887.16, "duration": 2.98}, {"text": "That was the first\nreal charge it.", "start": 3890.14, "duration": 1.83}, {"text": "You could charge things in a\nfew dozen places in Brooklyn,", "start": 3891.97, "duration": 6.56}, {"text": "literally.", "start": 3898.53, "duration": 2.13}, {"text": "And then, all of a\nsudden, it took off.", "start": 3900.66, "duration": 1.92}, {"text": "Diner's Club started\nin the early 1950s.", "start": 3902.58, "duration": 2.498}, {"text": "They found that they could get\na bunch of restaurants to say,", "start": 3905.078, "duration": 2.542}, {"text": "wouldn't you want to extend\ncredit, and we'll back it?", "start": 3907.62, "duration": 3.84}, {"text": "American Express\nin the mid-1950s.", "start": 3911.46, "duration": 2.88}, {"text": "And then, finally,\nin the mid-1960s,", "start": 3914.34, "duration": 2.16}, {"text": "Bank of America, which at that\ntime was a California bank,", "start": 3916.5, "duration": 3.18}, {"text": "figured out they would\ncreate a co-operative", "start": 3919.68, "duration": 3.6}, {"text": "with a bunch of other US\nbanks to extend credit.", "start": 3923.28, "duration": 4.31}, {"text": "And the credit boom took off.", "start": 3927.59, "duration": 2.8}, {"text": "And what was interesting,\nthe laws to regulate all this", "start": 3930.39, "duration": 2.97}, {"text": "didn't come until the\n1970s, at least in the US--", "start": 3933.36, "duration": 3.27}, {"text": "the Fair Credit Reporting\nAct and all the other laws.", "start": 3936.63, "duration": 2.94}, {"text": "There's three big\nones in the 1970s.", "start": 3939.57, "duration": 3.21}, {"text": "I go to conferences sometime and\ntalk about Bitcoin regulation,", "start": 3942.78, "duration": 3.27}, {"text": "and they say, well, why can't\nthe government solve this now?", "start": 3946.05, "duration": 3.09}, {"text": "I sort of remind them that\nit took 15 to 20 years from", "start": 3949.14, "duration": 4.14}, {"text": "the introduction of credit cards\nkind of in the early to mid", "start": 3953.28, "duration": 4.14}, {"text": "1950s and the real\ntake-off in the 1960s--", "start": 3957.42, "duration": 3.69}, {"text": "it was 1974, 1970, '77,\nthe three big credit laws.", "start": 3961.11, "duration": 5.79}, {"text": "So if you're going to be\nan entrepreneur in Bitcoin,", "start": 3966.9, "duration": 3.18}, {"text": "know that it could be\n15 years until there's", "start": 3970.08, "duration": 2.58}, {"text": "some cryptolaws in the future.", "start": 3972.66, "duration": 5.25}, {"text": "That was the processing\nmachine from the 1950s.", "start": 3977.91, "duration": 3.03}, {"text": "I made it too small, sorry.", "start": 3980.94, "duration": 3.11}, {"text": "Visa made it better.", "start": 3984.05, "duration": 2.52}, {"text": "And then, of course, that's\nwhat we all see today,", "start": 3986.57, "duration": 2.73}, {"text": "how your cards get processed.", "start": 3989.3, "duration": 3.25}, {"text": "So the role of money\nwe've talked about.", "start": 3992.55, "duration": 2.48}, {"text": "So I'm going to skip over that.", "start": 3995.03, "duration": 2.19}, {"text": "But now the\ncharacteristics of money.", "start": 3997.22, "duration": 2.37}, {"text": "What makes a good money?", "start": 3999.59, "duration": 2.43}, {"text": "We talked about some\nof this earlier.", "start": 4002.02, "duration": 1.74}, {"text": "It's durable, meaning that that\nsalt cube wasn't the greatest,", "start": 4003.76, "duration": 4.62}, {"text": "because if a lot of rain\ncame, that would wash away.", "start": 4008.38, "duration": 3.27}, {"text": "Gold and silver,\nmetals, are durable.", "start": 4011.65, "duration": 2.81}, {"text": "They're portable.", "start": 4014.46, "duration": 1.21}, {"text": "The heavier it is,\nthe less portable", "start": 4015.67, "duration": 1.83}, {"text": "it is, and that's why gold was\na better money than silver.", "start": 4017.5, "duration": 4.47}, {"text": "You could move it--", "start": 4021.97, "duration": 0.81}, {"text": "and better than\ncopper and bronze.", "start": 4022.78, "duration": 3.02}, {"text": "It was divisible easily.", "start": 4025.8, "duration": 1.66}, {"text": "You could slice things up.", "start": 4027.46, "duration": 3.78}, {"text": "Uniform and fungible.", "start": 4031.24, "duration": 2.04}, {"text": "And anyone who's who down the\nrabbit hole on this stuff,", "start": 4033.28, "duration": 2.71}, {"text": "if you really want\nto learn about money,", "start": 4035.99, "duration": 2.57}, {"text": "read about Crawford\nversus Royal Bank in 1749.", "start": 4038.56, "duration": 5.92}, {"text": "There was a gentleman at the\nearly part of paper money", "start": 4044.48, "duration": 3.69}, {"text": "that mailed two 20-pound notes,\nand he wrote his name on them.", "start": 4048.17, "duration": 6.62}, {"text": "They got lost in the mail,\nand he took the banks to court", "start": 4054.79, "duration": 4.96}, {"text": "to say, those were mine,\nwhen they were found.", "start": 4059.75, "duration": 3.53}, {"text": "And there was no law in Scotland\nor in England at the time", "start": 4063.28, "duration": 4.11}, {"text": "as to what to do about it.", "start": 4067.39, "duration": 1.33}, {"text": "But if you lose or somebody\nstole a piece of art,", "start": 4068.72, "duration": 3.71}, {"text": "you get it back.", "start": 4072.43, "duration": 2.02}, {"text": "And the law was settled\nin 1749 that you actually", "start": 4074.45, "duration": 2.91}, {"text": "don't get your money back.", "start": 4077.36, "duration": 2.37}, {"text": "Does anybody want to guess\nas to why the courts--", "start": 4079.73, "duration": 2.94}, {"text": "it was a matter of\nfirst interpretation.", "start": 4082.67, "duration": 2.27}, {"text": "The courts had no jurisprudence\non this before 1749.", "start": 4084.94, "duration": 5.61}, {"text": "Why did the courts decide\nthat a piece of art", "start": 4090.55, "duration": 4.68}, {"text": "was different than currency?", "start": 4095.23, "duration": 2.249}, {"text": "And it goes to the\nfundamental of what", "start": 4097.479, "duration": 2.401}, {"text": "money is, fiat money is.", "start": 4099.88, "duration": 2.79}, {"text": "Anybody want to take a\nguess as to why the courts--", "start": 4102.67, "duration": 2.82}, {"text": "they could have\ngone the other way.", "start": 4105.49, "duration": 1.581}, {"text": "AUDIENCE: How could you tell\nif someone really owned money?", "start": 4107.071, "duration": 2.458}, {"text": "How could you [INAUDIBLE]?", "start": 4109.529, "duration": 1.083}, {"text": "PROFESSOR: He signed it.", "start": 4110.612, "duration": 1.238}, {"text": "Actually, the facts were clear\nit was the currency he signed.", "start": 4111.85, "duration": 4.39}, {"text": "I'm just helping\nyou out so that--", "start": 4116.24, "duration": 2.369}, {"text": "that's a good point,\nbut he signed it.", "start": 4118.609, "duration": 3.611}, {"text": "AUDIENCE: It can't be used\nas a medium of exchange", "start": 4122.22, "duration": 2.13}, {"text": "if it doesn't belong to\nthe person [INAUDIBLE]..", "start": 4124.35, "duration": 3.142}, {"text": "PROFESSOR: In\nessence, if you were", "start": 4127.492, "duration": 1.417}, {"text": "to go back and read--\nthere's some history on this,", "start": 4128.909, "duration": 2.431}, {"text": "and read the court cases.", "start": 4131.34, "duration": 2.958}, {"text": "This was the point.", "start": 4134.298, "duration": 0.792}, {"text": "The court basically\nsaid, we have", "start": 4135.09, "duration": 1.41}, {"text": "to make this a\nmedium of exchange,", "start": 4136.5, "duration": 3.21}, {"text": "the greater social good.", "start": 4139.71, "duration": 1.29}, {"text": "It has to be fungible.", "start": 4141.0, "duration": 1.77}, {"text": "And the Royal Bank of Scotland\nwas, of course, kind of", "start": 4142.77, "duration": 5.85}, {"text": "closer to the courts than\nthis gentleman, Crawford.", "start": 4148.62, "duration": 3.489}, {"text": "But the banks were also saying,\nwe can't keep track of this.", "start": 4152.109, "duration": 3.608}, {"text": "So it was a mixture of the\ntwo, but it made it fungible.", "start": 4155.717, "duration": 2.333}, {"text": "Eric?", "start": 4158.05, "duration": 1.28}, {"text": "AUDIENCE: Was it\nthose specific notes", "start": 4159.33, "duration": 2.148}, {"text": "that he had signed [INAUDIBLE]?", "start": 4161.478, "duration": 1.292}, {"text": "PROFESSOR: Yeah.", "start": 4162.77, "duration": 0.667}, {"text": "Yeah.", "start": 4163.437, "duration": 0.706}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 4164.143, "duration": 0.917}, {"text": "PROFESSOR: And in 1749,\nthey all had serial numbers,", "start": 4165.06, "duration": 3.0}, {"text": "and they were signed in\na way that not today.", "start": 4168.06, "duration": 2.85}, {"text": "Of course, they're acceptable,\nand they're stable.", "start": 4170.91, "duration": 3.449}, {"text": "And we're going to talk a\nlot about the last point.", "start": 4174.359, "duration": 2.191}, {"text": "They're stable because\nthey're hard to mine,", "start": 4176.55, "duration": 2.19}, {"text": "and Bitcoin has that\nembedded in it, as well.", "start": 4178.74, "duration": 4.0}, {"text": "The design of money is\nreally important, as well.", "start": 4182.74, "duration": 2.579}, {"text": "You can make it a token--", "start": 4185.319, "duration": 1.531}, {"text": "a token is like\nsomething physical--", "start": 4186.85, "duration": 2.73}, {"text": "or account based.", "start": 4189.58, "duration": 2.069}, {"text": "We're of course now living in\na world of account-based money,", "start": 4191.649, "duration": 3.791}, {"text": "and it's digital, not physical.", "start": 4195.44, "duration": 1.34}, {"text": "It can be issued by\nthe private sector,", "start": 4199.445, "duration": 1.625}, {"text": "just like banknotes\nin the 18th century,", "start": 4201.07, "duration": 3.0}, {"text": "or private sector like\nBitcoin, or it can be central.", "start": 4204.07, "duration": 3.97}, {"text": "It can be widely acceptable\nor just wholesale.", "start": 4208.04, "duration": 2.88}, {"text": "There are forms of\nwholesale money.", "start": 4210.92, "duration": 2.528}, {"text": "One of the biggest\nforms of wholesale money", "start": 4213.448, "duration": 1.792}, {"text": "is the central bank's\nreserves are only", "start": 4215.24, "duration": 2.25}, {"text": "available to the\ncommercial banking system.", "start": 4217.49, "duration": 3.56}, {"text": "We're going to study\nthis money flower later,", "start": 4221.05, "duration": 2.04}, {"text": "but I put it in the\nslides because this--", "start": 4223.09, "duration": 3.54}, {"text": "I didn't create this flower.", "start": 4226.63, "duration": 2.25}, {"text": "You have a reading\nlater in the semester", "start": 4228.88, "duration": 1.86}, {"text": "from the Bank of\nInternational Settlement that", "start": 4230.74, "duration": 2.13}, {"text": "has this money flower in it.", "start": 4232.87, "duration": 2.19}, {"text": "But it's basically across\nthese four things--", "start": 4235.06, "duration": 2.58}, {"text": "is it token our account\nbased, physical or digital,", "start": 4237.64, "duration": 2.61}, {"text": "private or central,\nor widely accessible?", "start": 4240.25, "duration": 2.88}, {"text": "And then all monies fall into\none piece of this money flower.", "start": 4243.13, "duration": 3.9}, {"text": "There's a Professor Garrett\nthat came up with this flower,", "start": 4247.03, "duration": 3.39}, {"text": "and there's an optional reading\nlater in the semester from him.", "start": 4250.42, "duration": 3.06}, {"text": "You had a reading from Clark.", "start": 4257.47, "duration": 1.35}, {"text": "There's not enough time,\nbut all this stuff failed.", "start": 4258.82, "duration": 3.74}, {"text": "Does anybody want to\ngive me a flavor for one", "start": 4262.56, "duration": 2.08}, {"text": "or two reasons why a bunch\nof digital cash failed?", "start": 4264.64, "duration": 2.7}, {"text": "Did anybody read\nthe Clark reading,", "start": 4267.34, "duration": 1.56}, {"text": "the history of some DigiCash?", "start": 4268.9, "duration": 1.53}, {"text": "Oh, Alan read it.", "start": 4270.43, "duration": 1.56}, {"text": "Anybody else read it?", "start": 4271.99, "duration": 1.94}, {"text": "Over here.", "start": 4273.93, "duration": 0.5}, {"text": "I can't remember--", "start": 4274.43, "duration": 0.785}, {"text": "AUDIENCE: Zhan.", "start": 4275.215, "duration": 0.625}, {"text": "PROFESSOR: Don.", "start": 4275.84, "duration": 0.39}, {"text": "So what did you--", "start": 4276.23, "duration": 0.735}, {"text": "AUDIENCE: Zhan.", "start": 4276.965, "duration": 0.625}, {"text": "PROFESSOR: What?", "start": 4277.59, "duration": 0.48}, {"text": "AUDIENCE: Zhan.", "start": 4278.07, "duration": 0.62}, {"text": "PROFESSOR: Zhan.", "start": 4278.69, "duration": 0.48}, {"text": "Zhan, what did you\ntake from the reading?", "start": 4279.17, "duration": 1.38}, {"text": "Why did these all fail?", "start": 4280.55, "duration": 1.08}, {"text": "What's the one or two\nbiggest reasons they failed?", "start": 4281.63, "duration": 3.222}, {"text": "AUDIENCE: Most of\nthem still relied", "start": 4284.852, "duration": 1.458}, {"text": "on kind of some form\nof a central authority.", "start": 4286.31, "duration": 2.123}, {"text": "PROFESSOR: All right,\nthey relied on central--", "start": 4288.433, "duration": 1.917}, {"text": "DigiCash certainly did\nit, David Chaum's case,", "start": 4290.35, "duration": 2.35}, {"text": "and some of the others.", "start": 4292.7, "duration": 1.57}, {"text": "Any other big reason?", "start": 4294.27, "duration": 0.98}, {"text": "Alan, did you have--", "start": 4295.25, "duration": 1.883}, {"text": "AUDIENCE: There wasn't\nenough adoption by merchants,", "start": 4297.133, "duration": 2.167}, {"text": "I recall.", "start": 4299.3, "duration": 0.54}, {"text": "PROFESSOR: Definitely not\nadoption by merchants.", "start": 4299.84, "duration": 2.0}, {"text": "Very good.", "start": 4301.84, "duration": 0.73}, {"text": "Third reason why they failed?", "start": 4302.57, "duration": 1.26}, {"text": "One that's at the core\nof what Bitcoin solved.", "start": 4303.83, "duration": 2.175}, {"text": "AUDIENCE: Incentivizing\nlike a decentralized network", "start": 4309.513, "duration": 2.167}, {"text": "to keep that ledger,\nmaintain the ledger.", "start": 4311.68, "duration": 1.952}, {"text": "PROFESSOR: All right,\nincentivizing the ledger.", "start": 4313.632, "duration": 1.958}, {"text": "Behind Eric.", "start": 4315.59, "duration": 1.438}, {"text": "AUDIENCE: They couldn't solve\nthe double spend problem.", "start": 4317.028, "duration": 2.292}, {"text": "PROFESSOR: That's it.", "start": 4319.32, "duration": 0.875}, {"text": "Couldn't spend the\ndouble spend problem.", "start": 4320.195, "duration": 1.995}, {"text": "Could a currency be spent\nnot just once, but twice?", "start": 4322.19, "duration": 2.6}, {"text": "So there's four things\nthat were raised.", "start": 4324.79, "duration": 2.14}, {"text": "Four things about\ncentralization, the double", "start": 4326.93, "duration": 2.73}, {"text": "spend.", "start": 4329.66, "duration": 1.35}, {"text": "They couldn't get\nmerchants to adopt it,", "start": 4331.01, "duration": 2.01}, {"text": "and there was couldn't-- some\nform of consensus as to what", "start": 4333.02, "duration": 3.39}, {"text": "the ledger was.", "start": 4336.41, "duration": 1.153}, {"text": "I'm going to flip\nthrough these quickly,", "start": 4337.563, "duration": 1.667}, {"text": "but digital and mobile\nmoney did happen.", "start": 4339.23, "duration": 1.92}, {"text": "We were asked about\nPayPal earlier.", "start": 4341.15, "duration": 1.47}, {"text": "It was 1998.", "start": 4342.62, "duration": 2.54}, {"text": "In Norway, Ericsson and Telenor\nhad the first mobile app.", "start": 4345.16, "duration": 6.21}, {"text": "And it was to get movies\non your mobile phone.", "start": 4351.37, "duration": 4.23}, {"text": "1999, Alipay comes\nalong that we'll", "start": 4355.6, "duration": 2.85}, {"text": "talk a lot about when\nwe do payments later.", "start": 4358.45, "duration": 2.79}, {"text": "And of course, M-Pesa that we\ntalked about a little last week", "start": 4361.24, "duration": 3.39}, {"text": "in Kenya, where Safaricom\nnoticed that a bunch of money--", "start": 4364.63, "duration": 5.9}, {"text": "near money.", "start": 4370.53, "duration": 0.93}, {"text": "It was mobile minutes that was\nbeing used as money in Kenya,", "start": 4371.46, "duration": 3.87}, {"text": "and now there's 20\nmillion users of that.", "start": 4375.33, "duration": 2.715}, {"text": "And of course, there's\na bunch of regulations", "start": 4378.045, "duration": 1.875}, {"text": "now and so forth.", "start": 4379.92, "duration": 3.03}, {"text": "Starbucks started in 2011.", "start": 4382.95, "duration": 3.05}, {"text": "And then, of course,\nit's now off to the races", "start": 4386.0, "duration": 3.51}, {"text": "in mobile money.", "start": 4389.51, "duration": 1.54}, {"text": "One of the key things\nabout mobile money", "start": 4391.05, "duration": 2.15}, {"text": "we will discuss\nand learn together", "start": 4393.2, "duration": 2.49}, {"text": "is the question\neach one of these", "start": 4395.69, "duration": 1.98}, {"text": "is, where is the stored value?", "start": 4397.67, "duration": 3.84}, {"text": "And I have to tell\nyou, sometimes", "start": 4401.51, "duration": 1.52}, {"text": "I get quite confused when\nI research a new app.", "start": 4403.03, "duration": 3.24}, {"text": "Are they storing the value?", "start": 4406.27, "duration": 2.4}, {"text": "Or are they just a\nprocessing provider to move--", "start": 4408.67, "duration": 5.44}, {"text": "as we said earlier,\npayment systems", "start": 4414.11, "duration": 1.8}, {"text": "move and change and\namend other ledgers.", "start": 4415.91, "duration": 3.46}, {"text": "In a number of these, like\nM-Pesa, initially they", "start": 4419.37, "duration": 3.53}, {"text": "were storing the value.", "start": 4422.9, "duration": 1.48}, {"text": "And mobile apps Starbucks\nstores the value.", "start": 4424.38, "duration": 2.93}, {"text": "But many of them are just\napplications, computer code,", "start": 4427.31, "duration": 4.08}, {"text": "to move the ledger\nsomewhere else.", "start": 4431.39, "duration": 2.99}, {"text": "But the riddle remained.", "start": 4434.38, "duration": 2.81}, {"text": "You remember that riddle--", "start": 4437.19, "duration": 1.77}, {"text": "how to move money peer to peer\nwithout a central authority.", "start": 4438.96, "duration": 4.34}, {"text": "And that's what I'm asking\nfor next class, Thursday,", "start": 4443.3, "duration": 4.59}, {"text": "to actually read.", "start": 4447.89, "duration": 3.49}, {"text": "I wouldn't wing it, and I\nwouldn't be afraid of it.", "start": 4451.38, "duration": 4.76}, {"text": "Satoshi Nakamoto wrote\na paper that everybody", "start": 4456.14, "duration": 3.03}, {"text": "in this class-- if you're\nat MIT, and a few of you", "start": 4459.17, "duration": 2.33}, {"text": "are at Harvard.", "start": 4461.5, "duration": 1.88}, {"text": "I'm telling you,\nyou can read it.", "start": 4463.38, "duration": 2.27}, {"text": "You'll understand\nmaybe 1/2 to 2/3 of it.", "start": 4465.65, "duration": 2.55}, {"text": "It's not deeply technical.", "start": 4468.2, "duration": 1.62}, {"text": "And it's only eight\nor nine pages.", "start": 4472.84, "duration": 2.41}, {"text": "I've also assigned\nNational Institute", "start": 4475.25, "duration": 2.57}, {"text": "of Science Technology, about\n20 pages of reading from NIST.", "start": 4477.82, "duration": 4.9}, {"text": "The question is\nwhether that's Bitcoin.", "start": 4482.72, "duration": 2.193}, {"text": "I'm going to skip through\nthe study questions,", "start": 4484.913, "duration": 1.917}, {"text": "but the study\nquestions are really", "start": 4486.83, "duration": 1.56}, {"text": "about cryptography and how\nappend-only timestamping.", "start": 4488.39, "duration": 3.57}, {"text": "We are going to get into\nthe nitty-gritty over three", "start": 4491.96, "duration": 2.61}, {"text": "lectures.", "start": 4494.57, "duration": 1.05}, {"text": "I couldn't commit the whole\ncourse, the whole semester.", "start": 4495.62, "duration": 3.81}, {"text": "But I think three lectures--", "start": 4499.43, "duration": 1.41}, {"text": "Thursday and the two next week.", "start": 4500.84, "duration": 2.18}, {"text": "Anytime you want\nto come to see me--", "start": 4503.02, "duration": 2.38}, {"text": "Sabrina is somewhere\nhere on the floor, who's", "start": 4505.4, "duration": 3.03}, {"text": "one of our TAs, who's a computer\nscience master's student", "start": 4508.43, "duration": 4.89}, {"text": "and knows more\nabout all of this.", "start": 4513.32, "duration": 2.07}, {"text": "Madores, who was\nhere last week--", "start": 4515.39, "duration": 1.89}, {"text": "I don't know if Madores is\nhere, who's part of the Digital", "start": 4517.28, "duration": 2.58}, {"text": "Currency Initiative.", "start": 4519.86, "duration": 1.89}, {"text": "Over three lectures,\nwe're going to try", "start": 4521.75, "duration": 1.77}, {"text": "to work through what's\nthe cryptography,", "start": 4523.52, "duration": 3.24}, {"text": "and why does that matter?", "start": 4526.76, "duration": 2.41}, {"text": "How does the time\nstamping happen?", "start": 4529.17, "duration": 2.74}, {"text": "How's this look like money, and\nhow are the transactions kept?", "start": 4531.91, "duration": 2.59}, {"text": "Yes?", "start": 4534.5, "duration": 0.5}, {"text": "You get to close it out, almost.", "start": 4535.0, "duration": 1.607}, {"text": "AUDIENCE: Can you just\nanswer the question", "start": 4536.607, "duration": 1.75}, {"text": "posed about the longest\nrunning blockchain?", "start": 4538.357, "duration": 3.083}, {"text": "PROFESSOR: I can answer\nthat, but the assignment", "start": 4541.44, "duration": 2.0}, {"text": "was to answer it\nby Thursday, right?", "start": 4543.44, "duration": 1.614}, {"text": "AUDIENCE: Oh, Thursday.", "start": 4545.054, "duration": 0.958}, {"text": "OK.", "start": 4546.012, "duration": 0.5}, {"text": "PROFESSOR: So by Thursday.", "start": 4546.512, "duration": 2.178}, {"text": "What's your first name?", "start": 4548.69, "duration": 1.11}, {"text": "AUDIENCE: Caroline.", "start": 4549.8, "duration": 0.39}, {"text": "PROFESSOR: Caroline.", "start": 4550.19, "duration": 0.833}, {"text": "Did I say I was going\nto answer it today?", "start": 4551.023, "duration": 2.0}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 4553.023, "duration": 0.917}, {"text": "PROFESSOR: Oh, did I say today?", "start": 4553.94, "duration": 1.8}, {"text": "No, is there a mutable\nrecord of what I said?", "start": 4555.74, "duration": 3.09}, {"text": "I'll answer it now if you want.", "start": 4558.83, "duration": 3.39}, {"text": "Does anyone have the\nanswer in the whole class?", "start": 4562.22, "duration": 3.695}, {"text": "AUDIENCE: Yeah.", "start": 4565.915, "duration": 0.625}, {"text": "It's a service called\nSurety that Gillespie", "start": 4566.54, "duration": 4.18}, {"text": "begun working in\n1995, was a timestamp", "start": 4570.72, "duration": 5.85}, {"text": "service for digital documents.", "start": 4576.57, "duration": 2.87}, {"text": "And the way they did\nit was use a hash", "start": 4579.44, "duration": 2.43}, {"text": "function to create a seal with\na timestamp on the document.", "start": 4581.87, "duration": 6.24}, {"text": "And then present the\nweekly batch of seals.", "start": 4588.11, "duration": 4.17}, {"text": "And they actually published\nit in the New York", "start": 4592.28, "duration": 3.12}, {"text": "Times [INAUDIBLE].", "start": 4595.4, "duration": 1.92}, {"text": "PROFESSOR: So Caroline, it's\ngood to raise the question.", "start": 4597.32, "duration": 3.06}, {"text": "I thought it was for\nThursday, but thank you.", "start": 4600.38, "duration": 2.35}, {"text": "Stewart Haber, a\ncryptographer, and a colleague", "start": 4602.73, "duration": 5.27}, {"text": "at Bell Labs in the\nearly '90s, said,", "start": 4608.0, "duration": 3.33}, {"text": "how do we notarize information,\ndigitally notarize?", "start": 4611.33, "duration": 3.937}, {"text": "And we're going to be talking\nabout this Thursday a lot.", "start": 4615.267, "duration": 2.333}, {"text": "They used a cryptographic\nmethod called hash functions.", "start": 4617.6, "duration": 4.99}, {"text": "And they were just trying\nto notarize information.", "start": 4622.59, "duration": 4.05}, {"text": "And by 1995, they took--", "start": 4626.64, "duration": 2.12}, {"text": "they were entrepreneurs.", "start": 4628.76, "duration": 1.0}, {"text": "They created a\ncompany called Surety.", "start": 4629.76, "duration": 2.49}, {"text": "And once a week, they published,\nin the New York Times--", "start": 4632.25, "duration": 3.39}, {"text": "and they still do it.", "start": 4635.64, "duration": 1.56}, {"text": "You can get a New York Times--", "start": 4637.2, "duration": 1.5}, {"text": "I believe it's on\nSaturday or Sunday.", "start": 4638.7, "duration": 2.1}, {"text": "And they take-- it's in\nthe classifieds section.", "start": 4640.8, "duration": 3.42}, {"text": "And they have the hash function,\nwhich you'll read about", "start": 4644.22, "duration": 2.88}, {"text": "between now and Thursday.", "start": 4647.1, "duration": 1.59}, {"text": "They have the hash of all\nthe pre-existing information.", "start": 4648.69, "duration": 4.84}, {"text": "And so they timestamp it by\nusing the New York Times,", "start": 4653.53, "duration": 3.2}, {"text": "and they use cryptography.", "start": 4656.73, "duration": 2.03}, {"text": "And it's currently\n23 years in running.", "start": 4658.76, "duration": 2.277}, {"text": "AUDIENCE: So that's\nthe longest in terms", "start": 4661.037, "duration": 1.667}, {"text": "of time, not the longest with\nhow many ledgers or how many--", "start": 4662.704, "duration": 4.106}, {"text": "PROFESSOR: Correct,\nbecause Bitcoin", "start": 4666.81, "duration": 2.16}, {"text": "is about 550,000 blocks,\nand this would be", "start": 4668.97, "duration": 3.21}, {"text": "whatever 23 years times 52 is.", "start": 4672.18, "duration": 3.63}, {"text": "Longest in time.", "start": 4675.81, "duration": 1.72}, {"text": "Thank you.", "start": 4677.53, "duration": 0.59}, {"text": "I look forward to seeing you.", "start": 4678.12, "duration": 2.51}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.976}, {"text": "[RUSTLING]", "start": 1.976, "duration": 1.482}, {"text": "[CLICKING]", "start": 3.458, "duration": 1.482}, {"text": "JASON KU: Hi, everyone.", "start": 12.302, "duration": 0.958}, {"text": "Welcome to the 11th\nlecture of 6.006,", "start": 13.26, "duration": 3.815}, {"text": "our first lecture on\nweighted shortest paths.", "start": 17.075, "duration": 4.035}, {"text": "Until now, we've only been\ntalking about graphs that--", "start": 21.11, "duration": 4.83}, {"text": "where we measure distance in\nterms of the number of edges", "start": 25.94, "duration": 3.78}, {"text": "in a path.", "start": 29.72, "duration": 1.67}, {"text": "Today, we're going to\ngeneralize that notion.", "start": 31.39, "duration": 2.017}, {"text": "But I just want to go\nover what we've talked", "start": 33.407, "duration": 1.833}, {"text": "about in the last two lectures.", "start": 35.24, "duration": 2.55}, {"text": "In the last two lectures, we've\ntalked about two algorithms,", "start": 37.79, "duration": 3.03}, {"text": "breadth-first search\nand depth-first search", "start": 40.82, "duration": 2.85}, {"text": "to solve a range of problems.", "start": 43.67, "duration": 1.51}, {"text": "Here's some of the problems\nthat we've been solving.", "start": 45.18, "duration": 2.39}, {"text": "Single-source shortest paths,\nwhere distances are measured", "start": 47.57, "duration": 4.17}, {"text": "in number of edges in a path.", "start": 51.74, "duration": 2.98}, {"text": "And we used BFS to\nsolve this problem,", "start": 54.72, "duration": 4.52}, {"text": "starting from a\nsingle source, usually", "start": 59.24, "duration": 2.35}, {"text": "a vertex s that we call.", "start": 61.59, "duration": 2.96}, {"text": "And we solve that\nin linear time.", "start": 64.55, "duration": 1.95}, {"text": "And we solve that\nin order v plus e.", "start": 66.5, "duration": 6.99}, {"text": "That's what we called\nlinear time for a graph.", "start": 73.49, "duration": 3.09}, {"text": "For the special case of\nsingle-source reachability,", "start": 76.58, "duration": 3.24}, {"text": "here we had to return a shortest\npath distance for every vertex.", "start": 79.82, "duration": 5.6}, {"text": "And there was, at most, E\nthings reachable from a vertex.", "start": 85.42, "duration": 3.84}, {"text": "So this is the bound we got.", "start": 89.26, "duration": 3.95}, {"text": "But in the special case for\nsingle-source reachability,", "start": 93.21, "duration": 2.61}, {"text": "when our output only has\nto list the vertices that", "start": 95.82, "duration": 2.49}, {"text": "are reachable from\nme, the number", "start": 98.31, "duration": 3.87}, {"text": "of things reachable in\nbasically a spanning tree", "start": 102.18, "duration": 3.48}, {"text": "of the connected\ncomponent of my source", "start": 105.66, "duration": 2.61}, {"text": "can almost be of order E. And\nso for all the little singleton", "start": 108.27, "duration": 4.53}, {"text": "vertices in my graph,\nI don't really care.", "start": 112.8, "duration": 4.35}, {"text": "So I can get this in\norder E, but that's", "start": 117.15, "duration": 1.92}, {"text": "kind of a little optimization.", "start": 119.07, "duration": 4.71}, {"text": "The next thing we\ndid was we talked", "start": 123.78, "duration": 1.95}, {"text": "about connected components.", "start": 125.73, "duration": 1.78}, {"text": "And we didn't just reduce\nto using a search algorithm", "start": 127.51, "duration": 3.65}, {"text": "like a single-source\nreachability", "start": 131.16, "duration": 2.55}, {"text": "algorithm like BFS or DFS.", "start": 133.71, "duration": 2.04}, {"text": "We put a for loop around that\nto explore the entire graph", "start": 135.75, "duration": 4.35}, {"text": "by basically saying,\nif I've explored", "start": 140.1, "duration": 1.95}, {"text": "one connected\ncomponent, then I can", "start": 142.05, "duration": 4.76}, {"text": "look at any other\nvertex I haven't seen", "start": 146.81, "duration": 2.58}, {"text": "and explore the next one.", "start": 149.39, "duration": 1.56}, {"text": "And so that actually with some--", "start": 150.95, "duration": 2.88}, {"text": "a little analysis,\nalso got linear time,", "start": 153.83, "duration": 2.67}, {"text": "because I'm at most traversing\nany component of my graph once.", "start": 156.5, "duration": 4.56}, {"text": "That's kind of the idea.", "start": 161.06, "duration": 2.61}, {"text": "And we can use that\nusing BFS or DFS really,", "start": 163.67, "duration": 3.99}, {"text": "because we're just trying\nto get a thing that searches", "start": 167.66, "duration": 2.97}, {"text": "an entire connected component.", "start": 170.63, "duration": 2.52}, {"text": "And then this\ntopological sort we did", "start": 173.15, "duration": 2.13}, {"text": "at the end of the last lecture.", "start": 175.28, "duration": 1.93}, {"text": "We used full DFS\nto give an ordering", "start": 177.21, "duration": 3.26}, {"text": "of the vertices in a DAG--", "start": 180.47, "duration": 4.24}, {"text": "maybe I'll specify clearly\nthat this is only for a DAG--", "start": 184.71, "duration": 5.25}, {"text": "where we have an\nordering of the vertices", "start": 189.96, "duration": 4.06}, {"text": "so all the edges go forward\nin that order, for example.", "start": 194.02, "duration": 4.94}, {"text": "And that we also\ndid in linear time.", "start": 198.96, "duration": 1.5}, {"text": "All right, in this lecture,\nand in actually the next four", "start": 205.71, "duration": 3.09}, {"text": "lectures, what\nwe're going to do is", "start": 208.8, "duration": 4.68}, {"text": "instead of measuring distance\nin terms of the number of edges", "start": 213.48, "duration": 3.27}, {"text": "in a path--", "start": 216.75, "duration": 0.9}, {"text": "so previously, distance\nequaled number of edges--", "start": 217.65, "duration": 8.16}, {"text": "we're going to\ngeneralize that notion.", "start": 225.81, "duration": 1.68}, {"text": "So instead counting\nan edge, we're", "start": 227.49, "duration": 2.7}, {"text": "going to count an integer\nassociated with that edge.", "start": 230.19, "duration": 4.05}, {"text": "It's going to be\ncalled a weight.", "start": 234.24, "duration": 1.77}, {"text": "So here's an example\nof a weighted graph G.", "start": 236.01, "duration": 5.13}, {"text": "And I've labeled,\nin red, weights", "start": 241.14, "duration": 2.72}, {"text": "for each of these edges.", "start": 243.86, "duration": 1.0}, {"text": "This is a directed\ngraph on eight vertices.", "start": 244.86, "duration": 2.99}, {"text": "And I've got an integer\nassociated with each edge.", "start": 247.85, "duration": 2.73}, {"text": "You'll notice, some of them\nare positive, some of them", "start": 250.58, "duration": 2.25}, {"text": "are negative.", "start": 252.83, "duration": 0.542}, {"text": "It's OK to be zero as well.", "start": 253.372, "duration": 1.768}, {"text": "It's just any integer\nedge weight here.", "start": 255.14, "duration": 3.509}, {"text": "So generally we're going to\nbe-- along with our graph", "start": 258.649, "duration": 2.69}, {"text": "G, we're going to be given\na weight function that maps", "start": 261.339, "duration": 8.431}, {"text": "the edges of G to, we're going\nto say, integers, in this class", "start": 269.77, "duration": 8.26}, {"text": "anyway.", "start": 278.03, "duration": 1.83}, {"text": "In other contexts,\nin mathematics,", "start": 279.86, "duration": 1.86}, {"text": "you might have these\nbe real numbers.", "start": 281.72, "duration": 1.66}, {"text": "But in this class, we're\ngoing to deal with integers.", "start": 283.38, "duration": 2.22}, {"text": "So each edge, if\nyou have an edge,", "start": 285.6, "duration": 3.29}, {"text": "we're going to say this\nis the edge weight--", "start": 288.89, "duration": 5.04}, {"text": "the weight of this\nedge e, from e.", "start": 293.93, "duration": 4.17}, {"text": "Sometimes, if this\nedge e is u, v, we", "start": 298.1, "duration": 6.81}, {"text": "might sometimes say\nthe weight from u", "start": 304.91, "duration": 3.93}, {"text": "to v, since we have a simple\ngraph that's unambiguous.", "start": 308.84, "duration": 5.22}, {"text": "All right, so but this is just\ntalking about our notation.", "start": 314.06, "duration": 2.87}, {"text": "So in general, for example,\nthe weight from vertex b", "start": 316.93, "duration": 5.02}, {"text": "to f in this graph is what?", "start": 321.95, "duration": 2.49}, {"text": "Can someone tell me?", "start": 324.44, "duration": 1.63}, {"text": "AUDIENCE: Minus 4.", "start": 326.07, "duration": 0.88}, {"text": "JASON KU: Minus 4, right?", "start": 326.95, "duration": 1.08}, {"text": "It's right here.", "start": 328.03, "duration": 0.667}, {"text": "And I'll be consistent\nwith my coloring,", "start": 328.697, "duration": 4.223}, {"text": "because I've got\ncolored chalk today.", "start": 332.92, "duration": 3.42}, {"text": "Minus 4.", "start": 336.34, "duration": 1.14}, {"text": "Happiness.", "start": 337.48, "duration": 1.2}, {"text": "All right, so why do we\ncare about adding weights", "start": 338.68, "duration": 3.21}, {"text": "to our graph?", "start": 341.89, "duration": 1.44}, {"text": "Well, this comes up a\nlot in many applications.", "start": 343.33, "duration": 3.57}, {"text": "For example, distances\nin a road network.", "start": 346.9, "duration": 3.21}, {"text": "if I have a road from here--", "start": 350.11, "duration": 4.05}, {"text": "so from Mass Ave, front\nof MIT, to Central Square,", "start": 354.16, "duration": 6.75}, {"text": "we might think of\nthat as one road.", "start": 360.91, "duration": 2.43}, {"text": "Maybe you've got each\nroad is a connection", "start": 363.34, "duration": 3.36}, {"text": "between two intersections\nin my road network.", "start": 366.7, "duration": 3.45}, {"text": "But an edge, it takes\nlonger to go from,", "start": 370.15, "duration": 4.24}, {"text": "say, Vassar Street to Amherst.", "start": 374.39, "duration": 3.182}, {"text": "That takes a shorter\namount of time", "start": 377.572, "duration": 1.458}, {"text": "than it does to go from\nMemorial Drive across the river", "start": 379.03, "duration": 3.78}, {"text": "to Beacon Street.", "start": 382.81, "duration": 1.83}, {"text": "So we might want to associate\na larger distance or a weight", "start": 384.64, "duration": 3.93}, {"text": "associated with that edge.", "start": 388.57, "duration": 3.09}, {"text": "Latency in a\nnetwork, for example.", "start": 391.66, "duration": 3.93}, {"text": "Maybe strength of relationships\nin a social network.", "start": 395.59, "duration": 3.48}, {"text": "And you could imagine that\nit's possible maybe you're", "start": 399.07, "duration": 3.54}, {"text": "\"frenemies\" with someone,\nyou don't like them,", "start": 402.61, "duration": 3.52}, {"text": "and so maybe you have a\nnegative weight associated", "start": 406.13, "duration": 2.24}, {"text": "with an edge in\na social network.", "start": 408.37, "duration": 2.68}, {"text": "I'm not sure.", "start": 411.05, "duration": 1.02}, {"text": "Maybe not.", "start": 412.07, "duration": 0.65}, {"text": "But there are lots of\napplications where you might", "start": 412.72, "duration": 2.49}, {"text": "want weights on your edges.", "start": 415.21, "duration": 3.94}, {"text": "So that comes to the\nnext question of,", "start": 419.15, "duration": 3.3}, {"text": "how do I represent--", "start": 422.45, "duration": 1.68}, {"text": "how do I give the\nuser, or the algorithm,", "start": 424.13, "duration": 3.99}, {"text": "these weights in my graph?", "start": 428.12, "duration": 2.49}, {"text": "We had a representation\nfor a graph.", "start": 430.61, "duration": 4.74}, {"text": "Our common way to\nrepresent a graph", "start": 435.35, "duration": 2.19}, {"text": "was store a set data structure\non the vertices mapping", "start": 437.54, "duration": 4.26}, {"text": "to the adjacencies\nof each vertex, which", "start": 441.8, "duration": 3.69}, {"text": "we stored in what we called an\nadjacency list, which really", "start": 445.49, "duration": 2.76}, {"text": "could be any data structure.", "start": 448.25, "duration": 3.96}, {"text": "Commonly, it's just an\narray of the adjacencies.", "start": 452.21, "duration": 3.66}, {"text": "But you could also have that\nbe a set data structure,", "start": 455.87, "duration": 5.01}, {"text": "where you can query in\nconstant time what--", "start": 460.88, "duration": 3.64}, {"text": "if a particular adjacency\nexists in that graph.", "start": 464.52, "duration": 3.48}, {"text": "So there are two common\nways to store these weights.", "start": 468.0, "duration": 5.99}, {"text": "One is just, with\nevery adjacency,", "start": 473.99, "duration": 3.64}, {"text": "I'm going to store its weight.", "start": 477.63, "duration": 1.25}, {"text": "Maybe just in a tuple.", "start": 478.88, "duration": 3.15}, {"text": "With each adjacency, also\nstore weight of the edge", "start": 482.03, "duration": 14.16}, {"text": "that it corresponds\nto, just in any way.", "start": 496.19, "duration": 4.56}, {"text": "A second way, instead of trying\nto modify our graph structure", "start": 500.75, "duration": 4.83}, {"text": "that we gave you\nbefore, let's just", "start": 505.58, "duration": 2.46}, {"text": "have a dictionary of all the\nedges mapping to their weights.", "start": 508.04, "duration": 3.24}, {"text": "And we already know\nhow to do that.", "start": 511.28, "duration": 1.779}, {"text": "Just any set data structure--\nany separate set data structure", "start": 513.059, "duration": 10.311}, {"text": "mapping edges to their,\nI guess, weights.", "start": 523.37, "duration": 8.01}, {"text": "Bad notation, but\nyou get the idea.", "start": 531.38, "duration": 1.74}, {"text": "And it doesn't really\nmatter how we're doing this.", "start": 536.15, "duration": 2.73}, {"text": "The assumption that we're\ngoing to rely on here", "start": 538.88, "duration": 2.22}, {"text": "is that, given an edge,\ngiven this vertex pair,", "start": 541.1, "duration": 6.03}, {"text": "I can query what the weight of\nthat edge is in constant time.", "start": 547.13, "duration": 4.77}, {"text": "And so if I'm\ngoing to do that, I", "start": 551.9, "duration": 1.38}, {"text": "can either store it with maybe\na hash table of hash tables--", "start": 553.28, "duration": 3.93}, {"text": "a hash table mapping the set of\nvertices to their adjacencies,", "start": 557.21, "duration": 5.44}, {"text": "and then each adjacency\nlist stores its adjacencies", "start": 562.65, "duration": 4.25}, {"text": "in a hash table.", "start": 566.9, "duration": 0.84}, {"text": "And that way, in\nconstant time, I", "start": 567.74, "duration": 2.07}, {"text": "can check what the\nweight is there.", "start": 569.81, "duration": 1.8}, {"text": "Or here, I'm just--", "start": 571.61, "duration": 2.22}, {"text": "I could even have\njust a single hash", "start": 573.83, "duration": 1.5}, {"text": "table mapping the pair, the\nedge, the tuple, constant size,", "start": 575.33, "duration": 7.63}, {"text": "to its weight.", "start": 582.96, "duration": 1.36}, {"text": "So either way is fine.", "start": 584.32, "duration": 2.55}, {"text": "We're just going to\nassume that we can query", "start": 586.87, "duration": 2.18}, {"text": "an edge in constant time--", "start": 589.05, "duration": 1.98}, {"text": "the weight of an edge\nin constant time.", "start": 591.03, "duration": 1.64}, {"text": "OK, so this is\nthat graph example.", "start": 592.67, "duration": 5.47}, {"text": "It's a little busy here.", "start": 598.14, "duration": 1.26}, {"text": "I'm probably going to erase\nthat in just a second.", "start": 599.4, "duration": 3.64}, {"text": "But we're going to move on to\nwhat giving these edges weights", "start": 603.04, "duration": 4.64}, {"text": "implies for these problems\nthat we've defined", "start": 607.68, "duration": 6.03}, {"text": "in terms of unweighted graphs.", "start": 613.71, "duration": 2.07}, {"text": "In particular, we are\ngoing to be concentrating", "start": 615.78, "duration": 2.61}, {"text": "on single-source shortest\npaths, again, at least", "start": 618.39, "duration": 3.753}, {"text": "for the next three lectures.", "start": 622.143, "duration": 1.167}, {"text": "We'll generalize that even\nstill in the next lecture--", "start": 623.31, "duration": 5.22}, {"text": "I mean, in the fourth--", "start": 628.53, "duration": 1.92}, {"text": "in three lectures from now.", "start": 630.45, "duration": 3.26}, {"text": "But what we had here was\nthat the distance before", "start": 633.71, "duration": 3.0}, {"text": "in an unweighted graph was the\nnumber of edges in the path.", "start": 636.71, "duration": 3.21}, {"text": "Here, we're going to generalize\nthat notion kind of obviously", "start": 639.92, "duration": 6.48}, {"text": "to weighted paths.", "start": 646.4, "duration": 1.585}, {"text": "And the weight of a path,\nI'm going call it pi.", "start": 652.19, "duration": 7.14}, {"text": "So some weight of\npath pi is just", "start": 659.33, "duration": 8.76}, {"text": "going to be the\nsum of the weights", "start": 668.09, "duration": 2.1}, {"text": "in the edges in the path.", "start": 670.19, "duration": 2.56}, {"text": "So edge in the path, I'm\ngoing to sum their weights.", "start": 672.75, "duration": 7.76}, {"text": "So that's all the\nweight of a path means.", "start": 680.51, "duration": 2.46}, {"text": "It's just I'm going to sum\nall the weights in a path.", "start": 682.97, "duration": 2.5}, {"text": "So if I took a look at the--", "start": 685.47, "duration": 1.55}, {"text": "maybe there's a\nparticular path here.", "start": 687.02, "duration": 2.58}, {"text": "The path from a to b to f\nto g is going to be minus 5,", "start": 689.6, "duration": 6.33}, {"text": "minus 4, 2.", "start": 695.93, "duration": 2.25}, {"text": "It's going to be minus\n9 plus 2 is minus 7.", "start": 698.18, "duration": 5.07}, {"text": "So just as an example.", "start": 703.25, "duration": 1.11}, {"text": "So then what is the\nshortest path then?", "start": 708.77, "duration": 3.69}, {"text": "Well, kind of obviously\namong all paths between two", "start": 712.46, "duration": 3.33}, {"text": "vertices, it's going to be\none with the minimum weight.", "start": 715.79, "duration": 4.38}, {"text": "Yeah, question.", "start": 720.17, "duration": 0.75}, {"text": "AUDIENCE: Can I use the\nsame edge more than once?", "start": 720.92, "duration": 2.19}, {"text": "JASON KU: Can I use the\nsame edge more than once?", "start": 723.11, "duration": 3.6}, {"text": "Right now, you're asking about\nthe distinction in our class", "start": 726.71, "duration": 6.27}, {"text": "which we have between\npaths and simple paths.", "start": 732.98, "duration": 3.0}, {"text": "So here, a weighted\npath doesn't really", "start": 735.98, "duration": 2.58}, {"text": "care if we visit an\nedge more than once.", "start": 738.56, "duration": 3.0}, {"text": "So if an edge appears\nmore than once in pi,", "start": 741.56, "duration": 3.36}, {"text": "we have to count that more\nthan once in the edge weight--", "start": 744.92, "duration": 3.81}, {"text": "in the weight of the path.", "start": 748.73, "duration": 1.38}, {"text": "OK, great question.", "start": 750.11, "duration": 2.52}, {"text": "But what we're going to see\nlater on is shortest paths", "start": 752.63, "duration": 6.49}, {"text": "cannot repeat an edge more\nthan once in certain contexts.", "start": 759.12, "duration": 8.2}, {"text": "So we're going to get\nto the problem there", "start": 767.32, "duration": 3.098}, {"text": "a little later in this lecture.", "start": 770.418, "duration": 1.292}, {"text": "And we're going to solve\nthat in tomorrow's lecture.", "start": 771.71, "duration": 2.7}, {"text": "But if you have--", "start": 774.41, "duration": 2.41}, {"text": "we're getting a little\nahead of ourselves.", "start": 776.82, "duration": 1.75}, {"text": "But when we have negative\nweights in a graph,", "start": 778.57, "duration": 2.76}, {"text": "it's possible that\nthings go wrong.", "start": 781.33, "duration": 1.59}, {"text": "We're going to get there\nin about five lines.", "start": 782.92, "duration": 2.1}, {"text": "OK, great.", "start": 785.02, "duration": 1.83}, {"text": "So a shortest path--", "start": 786.85, "duration": 4.245}, {"text": "and in this case, I'm\ngoing to clarify that this", "start": 797.19, "duration": 2.11}, {"text": "is the weighted shortest path--", "start": 799.3, "duration": 1.38}, {"text": "is a minimum-- min-i-mum--", "start": 803.85, "duration": 5.3}, {"text": "sure-- is a minimum\nweight path from s to t.", "start": 812.8, "duration": 14.34}, {"text": "Nothing too interesting\nhere, but there's actually", "start": 827.14, "duration": 3.12}, {"text": "some subtleties we\nhave to deal with here.", "start": 830.26, "duration": 1.83}, {"text": "We're going to call--", "start": 834.79, "duration": 1.11}, {"text": "just like we did with\nbreadth-first search", "start": 835.9, "duration": 3.03}, {"text": "when we talked about\nshortest paths,", "start": 838.93, "duration": 1.5}, {"text": "we're going to define\nan expression for what", "start": 840.43, "duration": 5.19}, {"text": "the distance or the\nshortest path weight", "start": 845.62, "duration": 5.07}, {"text": "is between two vertices.", "start": 850.69, "duration": 1.53}, {"text": "And I'm going to\nrepresent that by a delta.", "start": 852.22, "duration": 2.61}, {"text": "A delta from a vertex\ns to t is going to be--", "start": 854.83, "duration": 8.4}, {"text": "let's-- I'm going to do\nthe wrong thing first--", "start": 863.23, "duration": 3.12}, {"text": "the minimum over the weight\nof all paths for all paths pi", "start": 866.35, "duration": 10.61}, {"text": "from s to t.", "start": 876.96, "duration": 6.07}, {"text": "OK, so there's a couple\nthings that go wrong here.", "start": 883.03, "duration": 3.9}, {"text": "First thing that goes wrong is\nthe same thing that went wrong", "start": 886.93, "duration": 3.48}, {"text": "with breadth-first search.", "start": 890.41, "duration": 2.88}, {"text": "Anyone remember what could go\nwrong with breadth-first search", "start": 893.29, "duration": 2.79}, {"text": "for this delta definition?", "start": 896.08, "duration": 1.277}, {"text": "AUDIENCE: Maybe there's no path.", "start": 897.357, "duration": 1.333}, {"text": "JASON KU: Maybe\nthere's no path, right.", "start": 898.69, "duration": 2.76}, {"text": "So except if no path.", "start": 901.45, "duration": 4.035}, {"text": "Just by convention,\nwe're setting", "start": 907.99, "duration": 3.63}, {"text": "delta s, t, to equal infinity.", "start": 911.62, "duration": 3.96}, {"text": "But there's one\nadditional problem", "start": 915.58, "duration": 4.9}, {"text": "with weighted shortest paths,\nand it's a little subtle.", "start": 920.48, "duration": 5.84}, {"text": "It's possible that\na finite shortest--", "start": 926.32, "duration": 3.06}, {"text": "finite length shortest\npath doesn't exist.", "start": 929.38, "duration": 4.08}, {"text": "And what do I mean by that?", "start": 933.46, "duration": 1.39}, {"text": "It means I could keep going\nthrough edges in my graph", "start": 934.85, "duration": 6.78}, {"text": "and continually\ngetting a shorter path.", "start": 941.63, "duration": 5.03}, {"text": "So if the shortest-- the\nminimum weight of a path from s", "start": 946.66, "duration": 5.01}, {"text": "to t actually goes through\nan infinite number of edges,", "start": 951.67, "duration": 3.24}, {"text": "then this isn't\nreally well-defined.", "start": 954.91, "duration": 2.64}, {"text": "So I'm going to change\nthis minimum here to--", "start": 957.55, "duration": 4.86}, {"text": "in mathematics we would,\njust to be specific,", "start": 962.41, "duration": 5.46}, {"text": "we call it an infimum.", "start": 967.87, "duration": 2.8}, {"text": "So if in the case where the\nweight of a shortest path", "start": 970.67, "duration": 5.76}, {"text": "can approach arbitrarily\nsmall, then we'll", "start": 976.43, "duration": 4.14}, {"text": "call this thing minus infinity.", "start": 980.57, "duration": 3.57}, {"text": "So when does that occur?", "start": 984.14, "duration": 2.225}, {"text": "When does that occur?", "start": 991.29, "duration": 2.03}, {"text": "When could we have\nour shortest path", "start": 993.32, "duration": 3.37}, {"text": "go through lots and\nlots of vertices?", "start": 996.69, "duration": 1.74}, {"text": "Well, let's actually take a\nlook at this example here.", "start": 998.43, "duration": 3.08}, {"text": "Can someone tell me\nwhat the shortest path", "start": 1001.51, "duration": 1.98}, {"text": "is from a to actually\nany vertex in this graph?", "start": 1003.49, "duration": 6.98}, {"text": "AUDIENCE: b, f, g, c.", "start": 1015.35, "duration": 1.96}, {"text": "JASON KU: Ah, OK.", "start": 1017.31, "duration": 1.48}, {"text": "So well, we could look\nat this path I have to b.", "start": 1018.79, "duration": 4.89}, {"text": "Let's just take a look at b.", "start": 1023.68, "duration": 1.77}, {"text": "I have a path going from\na to b that is minus 5.", "start": 1025.45, "duration": 2.972}, {"text": "OK, that's pretty good.", "start": 1028.422, "duration": 0.958}, {"text": "That's pretty small.", "start": 1029.38, "duration": 1.56}, {"text": "And it seems that if I go around\nthis graph through another way,", "start": 1030.94, "duration": 6.389}, {"text": "it might be bigger.", "start": 1037.329, "duration": 1.301}, {"text": "So I go 7 plus 3\nplus 8-- that's 15--", "start": 1038.63, "duration": 5.39}, {"text": "minus 1-- that's 14.", "start": 1044.02, "duration": 2.28}, {"text": "That's much bigger than minus\n5, so it seems like minus 5", "start": 1046.3, "duration": 4.29}, {"text": "should be good, right?", "start": 1050.59, "duration": 1.44}, {"text": "Anyone have a problem with\nthis path or a problem", "start": 1052.03, "duration": 3.12}, {"text": "with this being\nthe shortest path?", "start": 1055.15, "duration": 2.53}, {"text": "And what your\ncolleague just informed", "start": 1057.68, "duration": 2.3}, {"text": "me was that there is something\ninteresting happening here", "start": 1059.98, "duration": 3.81}, {"text": "in this graph in particular.", "start": 1063.79, "duration": 2.56}, {"text": "We have a cycle from\nb to f to g to c", "start": 1066.35, "duration": 6.27}, {"text": "that has negative\ntotal weight back to b.", "start": 1072.62, "duration": 4.44}, {"text": "This has minus 4 plus\n2 plus 1 minus 1.", "start": 1077.06, "duration": 6.01}, {"text": "So that total cycle has a\ncycle weight of minus 2,", "start": 1083.07, "duration": 6.35}, {"text": "this negative weight cycle.", "start": 1089.42, "duration": 2.29}, {"text": "So if I want to get\nto b, I could go there", "start": 1091.71, "duration": 5.03}, {"text": "via this minus 5 weight edge.", "start": 1096.74, "duration": 3.07}, {"text": "But every time I circled around\nthis cycle, I incur minus 2", "start": 1099.81, "duration": 7.38}, {"text": "to my path weight.", "start": 1107.19, "duration": 2.22}, {"text": "So I just keep going around\nthis cycle over and over", "start": 1109.41, "duration": 3.33}, {"text": "and over and over and\nover and over again,", "start": 1112.74, "duration": 2.8}, {"text": "and I don't have any finite\nlength minimum weight path.", "start": 1115.54, "duration": 5.75}, {"text": "And in such cases, we just say\nthat delta is minus infinity.", "start": 1121.29, "duration": 5.43}, {"text": "So the problem here is that\nwe could have negative weight", "start": 1126.72, "duration": 4.855}, {"text": "cycles--", "start": 1131.575, "duration": 0.5}, {"text": "deserves a capital letter--", "start": 1135.36, "duration": 1.98}, {"text": "Negative weight cycles.", "start": 1137.34, "duration": 5.775}, {"text": "It's a problem.", "start": 1147.39, "duration": 0.88}, {"text": "In particular, if there\nexists a path from s", "start": 1151.69, "duration": 13.54}, {"text": "to some vertex v that\ngoes through a vertex", "start": 1165.23, "duration": 18.4}, {"text": "on a negative\nweight cycle, then I", "start": 1183.63, "duration": 13.21}, {"text": "can take that path to\nthat vertex, circle", "start": 1196.84, "duration": 3.18}, {"text": "around the negative weight\ncycle, and then proceed to v,", "start": 1200.02, "duration": 4.26}, {"text": "and I can take that cycle\nas many times as I want.", "start": 1204.28, "duration": 2.28}, {"text": "Then this delta s,v we're\ngoing to set to minus infinity.", "start": 1206.56, "duration": 7.8}, {"text": "And in such cases, in our\nshortest paths algorithm,", "start": 1214.36, "duration": 3.9}, {"text": "we don't really care about\nwhat the shortest path is.", "start": 1218.26, "duration": 4.78}, {"text": "We're not even going to\ndeal with parent pointers", "start": 1223.04, "duration": 2.6}, {"text": "here, because there is no\nfinite length shortest path.", "start": 1225.64, "duration": 5.035}, {"text": "So I'm just going to kind of\nthrow up my hands in the air", "start": 1230.675, "duration": 2.375}, {"text": "and say, you know what, I can't\nreturn you a shortest path,", "start": 1233.05, "duration": 2.85}, {"text": "but I might want to return to\nyou a negative weight cycle.", "start": 1235.9, "duration": 5.33}, {"text": "If you told me that this\nthing has bad weight,", "start": 1241.23, "duration": 4.14}, {"text": "maybe I want you to\ntell me what a path is", "start": 1245.37, "duration": 2.28}, {"text": "that goes through a negative\nweight cycle to get back to s.", "start": 1247.65, "duration": 4.44}, {"text": "So that's what we're going\nto talk about next lecture.", "start": 1252.09, "duration": 2.25}, {"text": "This lecture, we are not\ngoing to talk about that.", "start": 1254.34, "duration": 3.035}, {"text": "We are going to talk about\nweighted shortest paths,", "start": 1257.375, "duration": 2.125}, {"text": "though.", "start": 1259.5, "duration": 0.63}, {"text": "That's what the remainder\nof this unit on graphs", "start": 1260.13, "duration": 6.39}, {"text": "is really about is\nweighted shortest paths.", "start": 1266.52, "duration": 2.46}, {"text": "OK, so in weighted\nshortest paths,", "start": 1268.98, "duration": 2.91}, {"text": "we actually know an\nalgorithm already", "start": 1271.89, "duration": 2.88}, {"text": "to solve a subset of weighted\nshortest parts, namely BFS,", "start": 1274.77, "duration": 6.87}, {"text": "right?", "start": 1281.64, "duration": 1.58}, {"text": "Now, you're like\nwait, Jason, BFS", "start": 1283.22, "duration": 4.17}, {"text": "doesn't solve weighted\nshortest paths.", "start": 1287.39, "duration": 1.62}, {"text": "We didn't even know about\nweighted graphs then.", "start": 1289.01, "duration": 2.04}, {"text": "How does that solve\nweighted shortest paths?", "start": 1291.05, "duration": 2.79}, {"text": "Well, there's a\ncouple cases where", "start": 1293.84, "duration": 4.02}, {"text": "we might be able to reduce to\nsolving shortest paths using", "start": 1297.86, "duration": 3.99}, {"text": "BFS.", "start": 1301.85, "duration": 0.78}, {"text": "Can anyone think\nof such a scenario?", "start": 1302.63, "duration": 1.59}, {"text": "So let's say, I mean, kind\nof what we did before was we", "start": 1310.11, "duration": 5.04}, {"text": "counted the number of edges.", "start": 1315.15, "duration": 2.76}, {"text": "So if we gave a weight of 1\nto every edge in my graph,", "start": 1317.91, "duration": 5.77}, {"text": "then just that graph,\nthat weighted graph,", "start": 1323.68, "duration": 4.32}, {"text": "corresponds to an unweighted\ngraph using the other distance", "start": 1328.0, "duration": 4.32}, {"text": "metric.", "start": 1332.32, "duration": 1.8}, {"text": "So in that case, BFS\njust solves our problem.", "start": 1334.12, "duration": 3.44}, {"text": "And in fact, we can\ngeneralize further.", "start": 1337.56, "duration": 4.03}, {"text": "What if all of our weights were\npositive, but the same value?", "start": 1341.59, "duration": 5.75}, {"text": "If it was all positive\nand the same value,", "start": 1347.34, "duration": 3.39}, {"text": "then we could just\ndivide by that value.", "start": 1350.73, "duration": 4.95}, {"text": "Now we have an unweighted graph\nwhich we can run BFS, and then", "start": 1355.68, "duration": 5.19}, {"text": "multiply shortest path distances\nby that value later on.", "start": 1360.87, "duration": 3.54}, {"text": "And in fact, there's one further\ngeneralization we can make,", "start": 1364.41, "duration": 4.02}, {"text": "which is a little bit of a\ntricky graph transformation", "start": 1368.43, "duration": 2.88}, {"text": "problem.", "start": 1371.31, "duration": 2.15}, {"text": "But we can also get this\nlinear time algorithm", "start": 1373.46, "duration": 3.48}, {"text": "for weighted single-source\nshortest paths", "start": 1376.94, "duration": 3.54}, {"text": "in contexts where the\nweights aren't that large.", "start": 1380.48, "duration": 6.09}, {"text": "So if I have positive\nedge weights--", "start": 1386.57, "duration": 4.53}, {"text": "if I have a positive\nedge weight, let's say--", "start": 1391.1, "duration": 2.28}, {"text": "using my weight color here--", "start": 1396.15, "duration": 4.02}, {"text": "that's, like,\nweight of 4, that's", "start": 1400.17, "duration": 5.55}, {"text": "kind of problematic, because\nI don't know how to simulate", "start": 1405.72, "duration": 3.18}, {"text": "that using an unweighted graph.", "start": 1408.9, "duration": 1.92}, {"text": "Or do I?", "start": 1410.82, "duration": 1.53}, {"text": "Anyone have an\nidea of how I could", "start": 1412.35, "duration": 1.74}, {"text": "simulate an edge of weight\n4 with an unweighted graph?", "start": 1414.09, "duration": 7.05}, {"text": "Yeah.", "start": 1421.14, "duration": 0.5}, {"text": "AUDIENCE: Have four\nedges of weight 1.", "start": 1421.64, "duration": 2.16}, {"text": "JASON KU: Yeah, I can\njust put four edges", "start": 1423.8, "duration": 1.98}, {"text": "of weight 1 in parallel here--", "start": 1425.78, "duration": 3.18}, {"text": "I'm sorry, in series,\nthe opposite of parallel.", "start": 1428.96, "duration": 4.38}, {"text": "I can just convert this\nhere into 1, 2, 3, 4 edges.", "start": 1433.34, "duration": 9.54}, {"text": "And if I do that for\nevery edge in my graph", "start": 1442.88, "duration": 3.25}, {"text": "and we have positive\nedge weights,", "start": 1446.13, "duration": 2.21}, {"text": "then that\ntransformation can hold.", "start": 1448.34, "duration": 2.1}, {"text": "Now, that's not necessarily a\ngood transformation to make.", "start": 1450.44, "duration": 2.61}, {"text": "Why?", "start": 1453.05, "duration": 1.836}, {"text": "AUDIENCE: The weight\nmight be very big.", "start": 1454.886, "duration": 1.854}, {"text": "JASON KU: Yeah, the\nweights might be very big", "start": 1456.74, "duration": 2.43}, {"text": "compared to the number of\nvertices and edges in my graph.", "start": 1459.17, "duration": 3.69}, {"text": "However, if the sum of\nall weights in my graph", "start": 1462.86, "duration": 3.9}, {"text": "is asymptotically\nless than v plus e,", "start": 1466.76, "duration": 5.64}, {"text": "we can get a linear\ntime algorithm again", "start": 1472.4, "duration": 2.13}, {"text": "by reducing to BFS.", "start": 1474.53, "duration": 1.14}, {"text": "OK, so that's great.", "start": 1475.67, "duration": 0.96}, {"text": "But in general, that gives\nus a linear time algorithm", "start": 1480.65, "duration": 2.65}, {"text": "in these very special cases.", "start": 1483.3, "duration": 3.23}, {"text": "And in general, it's\nan open problem.", "start": 1486.53, "duration": 1.86}, {"text": "We don't know\nwhether we can solve", "start": 1488.39, "duration": 3.78}, {"text": "the single-source\nshortest paths problem", "start": 1492.17, "duration": 4.5}, {"text": "in the weighted context for\ngeneral graphs in linear time.", "start": 1496.67, "duration": 4.29}, {"text": "We don't know how to do it.", "start": 1500.96, "duration": 3.0}, {"text": "But what we do know are some\nalgorithms that do pretty well.", "start": 1503.96, "duration": 4.6}, {"text": "And that's what we\nuse all the time.", "start": 1508.56, "duration": 2.9}, {"text": "But one more special case\nwe're going to go over today", "start": 1511.46, "duration": 3.78}, {"text": "is when we have this\nreally nice structure where", "start": 1515.24, "duration": 3.75}, {"text": "we have a DAG, a\nDirected Acyclic", "start": 1518.99, "duration": 3.36}, {"text": "Graph, like we were talking\nabout in the last lecture.", "start": 1522.35, "duration": 5.68}, {"text": "For any set of edge weights--", "start": 1528.03, "duration": 1.89}, {"text": "remember, with BFS, we needed\nto restrict our edge weights", "start": 1529.92, "duration": 3.66}, {"text": "to be positive and maybe bounded\nto get this good running time?", "start": 1533.58, "duration": 6.13}, {"text": "For any set of edge weights,\nif our graph structure is DAG--", "start": 1539.71, "duration": 3.483}, {"text": "it really has nothing\nto do with the weights--", "start": 1543.193, "duration": 1.917}, {"text": "if the graph structure\nis a DAG, then", "start": 1545.11, "duration": 2.79}, {"text": "we can actually solve this\nsingle-source shortest paths", "start": 1547.9, "duration": 3.42}, {"text": "problem in linear time,\nwhich is pretty awesome.", "start": 1551.32, "duration": 5.31}, {"text": "Now, for general graphs, we're\ngoing to show you in the next", "start": 1556.63, "duration": 6.09}, {"text": "lecture how to, for any\ngraph-- even with cycles,", "start": 1562.72, "duration": 4.26}, {"text": "even with negative\nweight cycles--", "start": 1566.98, "duration": 1.8}, {"text": "we're going to show\nyou how to solve", "start": 1568.78, "duration": 1.5}, {"text": "this single-source\nshortest paths", "start": 1570.28, "duration": 1.41}, {"text": "problem in something like a\nquadratic running time bound.", "start": 1571.69, "duration": 3.22}, {"text": "Now, this isn't the\nbest known, but it's", "start": 1574.91, "duration": 2.18}, {"text": "a really practical algorithm\nand people use it all the time.", "start": 1577.09, "duration": 4.3}, {"text": "And we are going to\nshow Bellman-Ford", "start": 1581.39, "duration": 4.22}, {"text": "in the context of\nthe DAG algorithm", "start": 1585.61, "duration": 3.33}, {"text": "we're going to solve today.", "start": 1588.94, "duration": 3.96}, {"text": "So that's the very\ngeneral case in terms", "start": 1592.9, "duration": 2.13}, {"text": "of restrictions on our graph.", "start": 1595.03, "duration": 2.34}, {"text": "But in reality, most problems\nthat come up in applications", "start": 1597.37, "duration": 5.7}, {"text": "occur with graphs that\nhave positive edge weights.", "start": 1603.07, "duration": 3.87}, {"text": "You can think of a road network.", "start": 1606.94, "duration": 1.44}, {"text": "You've got-- or\nnon-negative ones anyway.", "start": 1608.38, "duration": 2.73}, {"text": "You're traveling along,\nand it's not ever", "start": 1611.11, "duration": 4.89}, {"text": "useful to go back to\nwhere you came from,", "start": 1616.0, "duration": 2.94}, {"text": "because you want to make\nprogress to where you're going.", "start": 1618.94, "duration": 4.53}, {"text": "So in the context where you\ndon't have negative weights,", "start": 1623.47, "duration": 3.403}, {"text": "you don't have this problem\nwhere you have negative weight", "start": 1626.873, "duration": 2.417}, {"text": "cycles.", "start": 1629.29, "duration": 1.29}, {"text": "We can actually do a lot better\nby exploiting that property.", "start": 1630.58, "duration": 4.74}, {"text": "And we get a bound that's\na little bit-- that looks", "start": 1635.32, "duration": 2.58}, {"text": "a little bit more like n log n.", "start": 1637.9, "duration": 3.15}, {"text": "It's pretty close to linear.", "start": 1641.05, "duration": 1.95}, {"text": "You're losing a log factor\non the number of vertices.", "start": 1643.0, "duration": 4.74}, {"text": "But it's pretty good.", "start": 1647.74, "duration": 1.133}, {"text": "This is called\nDijkstra, and we'll", "start": 1648.873, "duration": 1.417}, {"text": "get to that in two lectures.", "start": 1650.29, "duration": 1.98}, {"text": "OK, so that's the\nroadmap of what", "start": 1652.27, "duration": 3.09}, {"text": "we're going to do for at\nleast the next three lectures.", "start": 1655.36, "duration": 3.84}, {"text": "But before we go\non to showing you", "start": 1659.2, "duration": 2.73}, {"text": "how to solve single-source\nshortest paths in a DAG using", "start": 1661.93, "duration": 4.71}, {"text": "this algorithm that I'm\ncalling DAG relaxation here,", "start": 1666.64, "duration": 6.16}, {"text": "I'm going to go back to\na thing that we talked", "start": 1672.8, "duration": 2.91}, {"text": "about in breadth-first\nsearch, where", "start": 1675.71, "duration": 2.198}, {"text": "in breadth-first search when we\nsolved single-source shortest", "start": 1677.908, "duration": 2.542}, {"text": "paths, we output two things.", "start": 1680.45, "duration": 3.6}, {"text": "We output single-source\nshortest paths, these deltas,", "start": 1684.05, "duration": 4.14}, {"text": "for the other definition\nof distance, the weights--", "start": 1688.19, "duration": 4.95}, {"text": "I mean, not the weights,\nthe distances, the shortest", "start": 1693.14, "duration": 3.36}, {"text": "distances.", "start": 1696.5, "duration": 2.1}, {"text": "But we also returned\nparent pointers.", "start": 1698.6, "duration": 2.19}, {"text": "We return parent\npointers back along paths", "start": 1700.79, "duration": 4.2}, {"text": "to the source along\nshortest paths.", "start": 1704.99, "duration": 3.09}, {"text": "We call this the\nshortest paths tree.", "start": 1708.08, "duration": 1.89}, {"text": "So I'm going to revisit this\ntopic of shortest paths tree--", "start": 1709.97, "duration": 3.48}, {"text": "shortest path trees--\nshortest path trees.", "start": 1713.45, "duration": 9.3}, {"text": "And in particular,\nit's kind of going", "start": 1725.39, "duration": 2.16}, {"text": "to be annoying to talk about\nboth of these quantities--", "start": 1727.55, "duration": 4.38}, {"text": "distances and parent pointers--\nas we go through all three", "start": 1731.93, "duration": 4.23}, {"text": "of these algorithms.", "start": 1736.16, "duration": 1.29}, {"text": "It's basically going\nto be bookkeeping to--", "start": 1737.45, "duration": 3.63}, {"text": "distances are actually\nsufficient for us", "start": 1741.08, "duration": 3.03}, {"text": "to reconstruct parent pointers\nif we need them later.", "start": 1744.11, "duration": 3.45}, {"text": "So what I'm going to show\nfor you-- prove to you now", "start": 1747.56, "duration": 2.55}, {"text": "is that, if I give\nyou the shortest path", "start": 1750.11, "duration": 2.34}, {"text": "distances for the subset of\nthe graph reachable from s", "start": 1752.45, "duration": 7.04}, {"text": "that doesn't go through\nnegative weight cycles,", "start": 1759.49, "duration": 4.11}, {"text": "if I'm giving you\nthose distances,", "start": 1763.6, "duration": 1.74}, {"text": "I can reconstruct parent\npointers along shortest paths", "start": 1765.34, "duration": 3.99}, {"text": "in linear time for any\ngraph I might give you", "start": 1769.33, "duration": 5.8}, {"text": "if I give you those\nshortest path distances.", "start": 1775.13, "duration": 2.16}, {"text": "OK, so that's what I'm going\nto try to show to you now.", "start": 1777.29, "duration": 2.91}, {"text": "So here's the algorithm.", "start": 1783.56, "duration": 5.73}, {"text": "For weighted-- there's\nthe caveat here", "start": 1789.29, "duration": 2.39}, {"text": "I'm going to write down.", "start": 1791.68, "duration": 1.0}, {"text": "For weighted shortest paths,\nonly need parent pointers", "start": 1792.68, "duration": 10.32}, {"text": "for v with finite\nshortest path distance--", "start": 1803.0, "duration": 11.71}, {"text": "only finite shortest\npath distance.", "start": 1817.44, "duration": 1.81}, {"text": "We don't care about\nthe infinite ones", "start": 1819.25, "duration": 2.3}, {"text": "or the minus infinite\nones, just the finite ones.", "start": 1821.55, "duration": 2.28}, {"text": "OK, so here's the algorithm.", "start": 1823.83, "duration": 3.27}, {"text": "I can initialize\nall Pv to equal--", "start": 1827.1, "duration": 9.66}, {"text": "sorry, oh, getting\nahead of myself.", "start": 1836.76, "duration": 5.97}, {"text": "I'm writing down DAG.", "start": 1842.73, "duration": 0.946}, {"text": "Init parent pointer data\nstructure to be empty.", "start": 1848.91, "duration": 5.24}, {"text": "At first, I'm not going to\nsort any parent pointers.", "start": 1857.92, "duration": 2.7}, {"text": "But at the beginning, I'm\ngoing to set the parent pointer", "start": 1860.62, "duration": 3.42}, {"text": "of the source to be none.", "start": 1864.04, "duration": 3.78}, {"text": "So that's what we kind of did\nin breadth-first search as well.", "start": 1867.82, "duration": 5.57}, {"text": "Now, what I've given you is--", "start": 1873.39, "duration": 3.21}, {"text": "I'm trying to show that,\ngiven all the shortest path", "start": 1876.6, "duration": 2.37}, {"text": "distances, I can construct\nthese parent pointers correctly.", "start": 1878.97, "duration": 3.13}, {"text": "So what I'm going to do is,\nfor each vertex u in my graph,", "start": 1882.1, "duration": 12.01}, {"text": "where my delta s of u is\nfinite, what am I going to do?", "start": 1894.11, "duration": 13.53}, {"text": "I'm going to say,\nwell, let's take a look", "start": 1907.64, "duration": 3.29}, {"text": "at all my outgoing neighbors.", "start": 1910.93, "duration": 3.45}, {"text": "This is kind of what we do\nin every graph algorithm.", "start": 1914.38, "duration": 3.54}, {"text": "For each v in the adjacency,\nthe outgoing adjacencies of u,", "start": 1917.92, "duration": 12.49}, {"text": "if there is no parent\npointer assigned to this v,", "start": 1930.41, "duration": 7.59}, {"text": "there's the potential\nthat i-- u--", "start": 1938.0, "duration": 2.274}, {"text": "[CHUCKLES] I, you-- this u, this\nvertex u, is the parent of v.", "start": 1940.274, "duration": 4.596}, {"text": "It's possible.", "start": 1944.87, "duration": 0.87}, {"text": "It's some incoming edge to v.", "start": 1945.74, "duration": 4.2}, {"text": "When will it be an\nincoming edge to v?", "start": 1949.94, "duration": 4.5}, {"text": "If v not in P--", "start": 1954.44, "duration": 6.42}, {"text": "I haven't assigned\nit a parent pointer--", "start": 1960.86, "duration": 3.16}, {"text": "and-- so this means\nit could be my parent.", "start": 1964.02, "duration": 7.05}, {"text": "When is it my parent\nalong the shortest path?", "start": 1971.07, "duration": 6.2}, {"text": "Sure.", "start": 1977.27, "duration": 0.705}, {"text": "AUDIENCE: Sum the\ndistance along the edge", "start": 1977.975, "duration": 2.033}, {"text": "to the distance of the other.", "start": 1980.008, "duration": 1.462}, {"text": "JASON KU: Yeah, so we\nhave some edge from u", "start": 1981.47, "duration": 3.165}, {"text": "to v. It has some weight.", "start": 1984.635, "duration": 3.495}, {"text": "If I already know the\nshortest path distance to u,", "start": 1988.13, "duration": 3.27}, {"text": "and I know the shortest\npath distance to v,", "start": 1991.4, "duration": 3.81}, {"text": "if the shortest path\ndistance from s to u--", "start": 1995.21, "duration": 5.71}, {"text": "let's draw a picture here.", "start": 2000.92, "duration": 1.45}, {"text": "We've got s, we've got\nsome path here to u,", "start": 2002.37, "duration": 3.53}, {"text": "and we know we've\ngot an edge from u", "start": 2005.9, "duration": 2.82}, {"text": "to v. If this shortest path\ndistance plus this edge weight", "start": 2008.72, "duration": 8.79}, {"text": "is equal to the shortest\npath distance from s to v,", "start": 2017.51, "duration": 6.06}, {"text": "then it better--", "start": 2023.57, "duration": 0.72}, {"text": "I mean, there may be more\nthan one shortest path,", "start": 2024.29, "duration": 2.5}, {"text": "but this is certainly\na shortest path,", "start": 2026.79, "duration": 1.85}, {"text": "so we can assign a\nparent pointer back to u.", "start": 2028.64, "duration": 3.6}, {"text": "So let's write that\ncondition down.", "start": 2032.24, "duration": 1.86}, {"text": "If the shortest path\ndistance from s to v", "start": 2034.1, "duration": 4.53}, {"text": "equals the shortest path\ndistance from s to u,", "start": 2038.63, "duration": 3.99}, {"text": "and then traversing\nthe edge from u to v,", "start": 2042.62, "duration": 6.91}, {"text": "then exists shortest\npath that uses edge u, v,", "start": 2049.53, "duration": 16.709}, {"text": "in particular this one.", "start": 2066.239, "duration": 2.371}, {"text": "So set the parent of u--", "start": 2071.15, "duration": 5.893}, {"text": "of v to u.", "start": 2077.043, "duration": 3.596}, {"text": "OK, so this is the algorithm.", "start": 2080.639, "duration": 2.261}, {"text": "I'm not going to prove to\nyou that this is correct.", "start": 2082.9, "duration": 3.44}, {"text": "But it kind of intuitively\nmakes sense, right?", "start": 2086.34, "duration": 2.25}, {"text": "If I have these\nshortest path distances,", "start": 2088.59, "duration": 3.629}, {"text": "you can prove by induction\nthat not only does this parent", "start": 2092.219, "duration": 3.48}, {"text": "pointer point to the right place\nalong some shortest path here,", "start": 2095.699, "duration": 5.131}, {"text": "but it also does\nso in linear time,", "start": 2100.83, "duration": 1.65}, {"text": "because I'm looping\nover all the vertices", "start": 2102.48, "duration": 2.34}, {"text": "and looping over its\noutgoing adjacencies once.", "start": 2104.82, "duration": 2.94}, {"text": "Same analysis as we had for\nboth BFS and DFS, essentially.", "start": 2107.76, "duration": 6.55}, {"text": "And then, since we can do this,\nsince we can compute parent", "start": 2114.31, "duration": 4.46}, {"text": "pointers from these\ndistances, we're", "start": 2118.77, "duration": 2.22}, {"text": "going to ignore computing these\nparent pointers from now on.", "start": 2120.99, "duration": 4.832}, {"text": "We're just going to concentrate\non computing the distances,", "start": 2125.822, "duration": 2.458}, {"text": "because we're going to have\nto take linear time anyway", "start": 2128.28, "duration": 4.32}, {"text": "at least.", "start": 2132.6, "duration": 1.44}, {"text": "And all these other\nthings take more time.", "start": 2134.04, "duration": 2.23}, {"text": "So we can compute the\ndistances in more time,", "start": 2136.27, "duration": 2.81}, {"text": "and then compute\nthe parents after.", "start": 2139.08, "duration": 2.4}, {"text": "OK, so that's what\nwe're going to do.", "start": 2141.48, "duration": 2.27}, {"text": "So now, with all that buildup,\nlet's show an algorithm.", "start": 2147.09, "duration": 3.705}, {"text": "[CHUCKLES] How do we compute\nsingle-source shortest paths", "start": 2150.795, "duration": 5.685}, {"text": "in a DAG in linear time?", "start": 2156.48, "duration": 4.67}, {"text": "Well, a DAG-- I mean,\nthis is actually", "start": 2161.15, "duration": 1.71}, {"text": "a super useful, convenient\nthing in algorithms in general.", "start": 2162.86, "duration": 4.53}, {"text": "DAGs are just nice things.", "start": 2167.39, "duration": 2.82}, {"text": "They're kind of\nordered in a way.", "start": 2170.21, "duration": 2.1}, {"text": "There's this\ntopological sort order", "start": 2172.31, "duration": 1.793}, {"text": "that we were talking\nabout before.", "start": 2174.103, "duration": 1.417}, {"text": "This is going to\nplay a key role.", "start": 2175.52, "duration": 2.81}, {"text": "There's a really nice structure\nto DAGs not having cycles,", "start": 2178.33, "duration": 3.16}, {"text": "not having to deal with this\nnegative weight cycle problem.", "start": 2181.49, "duration": 3.51}, {"text": "You can only go in one\ndirection along this graph.", "start": 2185.0, "duration": 5.82}, {"text": "It's a very nice\nstructure to exploit.", "start": 2190.82, "duration": 2.08}, {"text": "And so we're going\nto exploit it.", "start": 2192.9, "duration": 2.9}, {"text": "And here's the idea.", "start": 2195.8, "duration": 2.12}, {"text": "DAG relaxation, what\nit's going to do", "start": 2197.92, "duration": 9.29}, {"text": "is it's going to start out\nwith some estimates of what", "start": 2207.21, "duration": 3.09}, {"text": "these distances should be.", "start": 2210.3, "duration": 2.88}, {"text": "So maintain distance estimates.", "start": 2213.18, "duration": 8.56}, {"text": "And now I'm going to\ntry to be careful here", "start": 2226.02, "duration": 2.85}, {"text": "about how I draw my Ds.", "start": 2228.87, "duration": 2.16}, {"text": "This is a d, this is a delta.", "start": 2234.51, "duration": 5.78}, {"text": "This is shortest paths.", "start": 2240.29, "duration": 1.98}, {"text": "This is a distance estimate.", "start": 2242.27, "duration": 2.7}, {"text": "So that's what I'm\ngoing to be using", "start": 2244.97, "duration": 1.5}, {"text": "for the rest of this time.", "start": 2246.47, "duration": 3.28}, {"text": "So we're going to maintain these\nestimates of distance d, which", "start": 2249.75, "duration": 6.14}, {"text": "are going to start at\ninitially infinite.", "start": 2255.89, "duration": 8.54}, {"text": "I don't know what they are.", "start": 2264.43, "duration": 1.59}, {"text": "I don't know what the\nshortest paths are,", "start": 2266.02, "duration": 1.79}, {"text": "but they better be less than\ninfinite or else I don't care.", "start": 2267.81, "duration": 4.23}, {"text": "So that's the worst\ncase scenario.", "start": 2272.04, "duration": 3.12}, {"text": "It can't be worse than this--", "start": 2275.16, "duration": 1.83}, {"text": "for every vertex.", "start": 2276.99, "duration": 2.14}, {"text": "And we're going to\nmaintain the property that", "start": 2279.13, "duration": 4.52}, {"text": "estimates upper bound--", "start": 2283.65, "duration": 5.19}, {"text": "that should probably\nbe two words--", "start": 2295.1, "duration": 1.89}, {"text": "upper bound delta s, v--", "start": 2296.99, "duration": 3.96}, {"text": "we're going to maintain that\nthey upper-bound this thing", "start": 2305.337, "duration": 2.333}, {"text": "and gradually lower\nuntil they're equal.", "start": 2307.67, "duration": 9.43}, {"text": "So this is the idea.", "start": 2319.82, "duration": 1.0}, {"text": "We start from an over-estimate,\nan upper bound on the distance", "start": 2320.82, "duration": 3.95}, {"text": "estimate.", "start": 2324.77, "duration": 1.14}, {"text": "And then we're repeatedly\ngoing to lower that value", "start": 2325.91, "duration": 3.63}, {"text": "as we gain more information\nabout the graph,", "start": 2329.54, "duration": 3.53}, {"text": "maintaining that we're always\nupper-bounding the distance.", "start": 2333.07, "duration": 3.61}, {"text": "And we're going to keep\ndoing it, keep doing it,", "start": 2336.68, "duration": 2.0}, {"text": "keep doing it, until, as we\nwill try to prove to you,", "start": 2338.68, "duration": 4.2}, {"text": "these estimates reach, actually\nreach down, all the way", "start": 2342.88, "duration": 3.36}, {"text": "to our shortest path distances.", "start": 2346.24, "duration": 3.12}, {"text": "So when do we\nlower these things?", "start": 2349.36, "duration": 1.395}, {"text": "When do we lower these things?", "start": 2353.81, "duration": 2.79}, {"text": "We are going to lower these\ndistance estimates whenever", "start": 2356.6, "duration": 2.61}, {"text": "the distance\nestimates violate what", "start": 2359.21, "duration": 2.1}, {"text": "we're going to call the\ntriangle inequality.", "start": 2361.31, "duration": 2.79}, {"text": "OK, what is the\ntriangle inequality?", "start": 2364.1, "duration": 1.938}, {"text": "Triangle inequality is actually\na pretty intuitive notion.", "start": 2377.0, "duration": 2.565}, {"text": "It's basically saying,\nif I have three points--", "start": 2382.13, "duration": 2.35}, {"text": "thus, triangle-- maybe bigger\nso I can write a letter in them.", "start": 2384.48, "duration": 4.93}, {"text": "It's basically saying that if\nI have a vertex u, a vertex v,", "start": 2392.45, "duration": 5.76}, {"text": "vertex x, for example, the\nshortest path distance--", "start": 2398.21, "duration": 6.25}, {"text": "the shortest path\ndistance delta of u, v--", "start": 2408.95, "duration": 3.36}, {"text": "that's the shortest\ndistance from u to v--", "start": 2412.31, "duration": 3.0}, {"text": "it can't be bigger then a\nshortest path from u to v", "start": 2415.31, "duration": 5.5}, {"text": "that also goes through x.", "start": 2420.81, "duration": 1.47}, {"text": "Of my paths, I'm now\nrestricting the paths", "start": 2425.77, "duration": 2.9}, {"text": "I have to the ones\nthat go through x.", "start": 2428.67, "duration": 2.29}, {"text": "The shortest path\ndistance from u to v", "start": 2436.03, "duration": 1.98}, {"text": "can't be bigger than restricting\npaths that go through", "start": 2438.01, "duration": 3.33}, {"text": "x and taking that\nshortest distance,", "start": 2441.34, "duration": 2.37}, {"text": "getting the shortest\npath distance from here", "start": 2443.71, "duration": 2.16}, {"text": "and adding it to the\nshortest path distance here--", "start": 2445.87, "duration": 3.24}, {"text": "delta u, x, delta x, v.\nThat's just a statement of,", "start": 2449.11, "duration": 11.91}, {"text": "I'm restricting to a\nsubset of the paths.", "start": 2461.02, "duration": 3.96}, {"text": "I can't decrease my\nminimum distance.", "start": 2464.98, "duration": 2.58}, {"text": "So this is the statement\nof the triangle inequality,", "start": 2467.56, "duration": 2.92}, {"text": "that the shortest path\ndistance from u to v", "start": 2470.48, "duration": 4.05}, {"text": "can't be bigger than the\nshortest path distance from u", "start": 2474.53, "duration": 6.03}, {"text": "to x plus the shortest\npath distance from x", "start": 2480.56, "duration": 3.24}, {"text": "to v for any x in my\ngraph that's not u and v.", "start": 2483.8, "duration": 5.61}, {"text": "So that's the\ntriangle inequality.", "start": 2489.41, "duration": 2.85}, {"text": "Pretty intuitive notion, right?", "start": 2492.26, "duration": 1.98}, {"text": "Why is this useful?", "start": 2494.24, "duration": 1.86}, {"text": "OK, well, if I find--", "start": 2496.1, "duration": 0.99}, {"text": "if I find an edge in my graph,\nif there's an edge u, v,", "start": 2499.98, "duration": 6.6}, {"text": "in my graph such that\nthis condition is violated", "start": 2506.58, "duration": 12.98}, {"text": "for the estimates that I have--", "start": 2519.56, "duration": 2.28}, {"text": "it obviously can't be violated\non my shortest path distances,", "start": 2521.84, "duration": 3.21}, {"text": "but if it violates\nit on the estimates--", "start": 2525.05, "duration": 3.18}, {"text": "u, v, is bigger than u, x--", "start": 2528.23, "duration": 5.73}, {"text": "sorry, u-- how am\nI going to do this?", "start": 2533.96, "duration": 3.62}, {"text": "I want this to be s.", "start": 2537.58, "duration": 3.09}, {"text": "I'm calculating shortest\npath distances from s", "start": 2540.67, "duration": 5.18}, {"text": "and shortest path\ndistances from s", "start": 2545.85, "duration": 2.79}, {"text": "to some incoming vertex u\nplus the edge weight from u", "start": 2548.64, "duration": 6.69}, {"text": "to v. All right, so\nwhat is this doing?", "start": 2555.33, "duration": 4.56}, {"text": "I have some edge\nu, v in my graph.", "start": 2559.89, "duration": 4.65}, {"text": "Basically, what I've said\nis that I have some distance", "start": 2564.54, "duration": 3.3}, {"text": "estimate to u, but\ngoing through--", "start": 2567.84, "duration": 4.4}, {"text": "making a path to v\nby going through u,", "start": 2572.24, "duration": 3.42}, {"text": "and then the edge\nfrom u to v is better", "start": 2575.66, "duration": 3.72}, {"text": "than my current estimate,\nmy shortest path", "start": 2579.38, "duration": 4.06}, {"text": "estimate to v.\nThat's bad, right?", "start": 2583.44, "duration": 4.782}, {"text": "That's violating the\ntriangle inequality.", "start": 2588.222, "duration": 1.708}, {"text": "These cannot be\nthe right weights.", "start": 2589.93, "duration": 2.22}, {"text": "These cannot be the\nright distances.", "start": 2592.15, "duration": 2.52}, {"text": "So how we're going\nto do that is lower--", "start": 2594.67, "duration": 3.15}, {"text": "this is what we said, repeatedly\nlower these distance estimates.", "start": 2597.82, "duration": 3.75}, {"text": "I'm going to lower this guy\ndown to equal this thing.", "start": 2601.57, "duration": 3.15}, {"text": "In a sense, this\nconstraint was violated.", "start": 2604.72, "duration": 3.39}, {"text": "But now we're relaxing\nthat constraint", "start": 2608.11, "duration": 2.52}, {"text": "so that this is no\nlonger violated.", "start": 2610.63, "duration": 3.51}, {"text": "So relax is a little\nweird word here.", "start": 2614.14, "duration": 4.23}, {"text": "We're using it for\nhistorical reasons.", "start": 2618.37, "duration": 1.98}, {"text": "But that's what we mean\nby when we say relax.", "start": 2620.35, "duration": 2.4}, {"text": "This thing is a\nviolated constraint.", "start": 2622.75, "duration": 2.64}, {"text": "It's got some pressure\nto be resolved.", "start": 2625.39, "duration": 3.27}, {"text": "And so what we're doing\nis, to resolve it,", "start": 2628.66, "duration": 2.04}, {"text": "we're just setting\nthis guy equal to this,", "start": 2630.7, "duration": 3.002}, {"text": "so it at least resolves,\nlocally, that constraint.", "start": 2633.702, "duration": 2.083}, {"text": "Now, it may violate the triangle\ninequality other places now", "start": 2635.785, "duration": 4.515}, {"text": "that we've done this change.", "start": 2640.3, "duration": 1.35}, {"text": "But at least this constraint\nis now relaxed and satisfied.", "start": 2641.65, "duration": 3.18}, {"text": "OK, so relax edge by lowering\nd of s, v, to this thing.", "start": 2644.83, "duration": 20.21}, {"text": "That's what we're going to\nmean by relaxing an edge.", "start": 2665.04, "duration": 3.27}, {"text": "And relaxing an edge\nis what I'll call safe.", "start": 2668.31, "duration": 7.19}, {"text": "It's safe to do.", "start": 2675.5, "duration": 3.19}, {"text": "What do I mean by\nrelaxation is safe?", "start": 2678.69, "duration": 2.13}, {"text": "It means that as I am computing\nthese shortest path distances,", "start": 2680.82, "duration": 6.39}, {"text": "I'm going to maintain this\nproperty that each one of these", "start": 2687.21, "duration": 5.09}, {"text": "estimates-- sorry,\nthese estimates here--", "start": 2692.3, "duration": 3.0}, {"text": "has the property\nthat it's either", "start": 2695.3, "duration": 1.58}, {"text": "infinite or it is the\nweight of some path to v. So", "start": 2696.88, "duration": 8.92}, {"text": "that's the thing the--", "start": 2705.8, "duration": 1.26}, {"text": "relaxation is safe.", "start": 2707.06, "duration": 1.23}, {"text": "OK, so each distance\nestimate, s, v,", "start": 2717.94, "duration": 10.02}, {"text": "is weight of some path\nfrom s to v or infinite.", "start": 2727.96, "duration": 16.86}, {"text": "And this is a pretty\neasy thing to prove.", "start": 2744.82, "duration": 3.99}, {"text": "If I had the\ninvariant that these", "start": 2748.81, "duration": 3.6}, {"text": "were all weights\nof shortest paths,", "start": 2752.41, "duration": 1.81}, {"text": "let's try to relax an edge.", "start": 2754.22, "duration": 2.87}, {"text": "And we need to show that\nthis property is maintained.", "start": 2757.09, "duration": 3.36}, {"text": "Relax edge u, v, OK?", "start": 2760.45, "duration": 3.69}, {"text": "Now, if I relax edge\nu, v, what do I do?", "start": 2764.14, "duration": 4.82}, {"text": "I set this thing--", "start": 2768.96, "duration": 3.53}, {"text": "or, sorry, I set this thing,\nmy shortest path distance", "start": 2772.49, "duration": 4.05}, {"text": "to v, to be this\nthing plus this thing.", "start": 2776.54, "duration": 3.06}, {"text": "There's a weight of\nan edge from u to v.", "start": 2779.6, "duration": 3.51}, {"text": "Now, by my assumption\nthat we're maintaining", "start": 2783.11, "duration": 3.93}, {"text": "that this is the weight\nof some path in my graph,", "start": 2787.04, "duration": 6.55}, {"text": "if this thing is\nbigger, I'm setting it", "start": 2793.59, "duration": 2.31}, {"text": "to the weight of some\npath on my graph to u,", "start": 2795.9, "duration": 2.43}, {"text": "plus an edge from u to v,\nand so this checks out.", "start": 2798.33, "duration": 4.64}, {"text": "So assign d of s, v,\nto weight of some path.", "start": 2802.97, "duration": 17.395}, {"text": "I'm not going to write down\nall the argument that I just", "start": 2824.77, "duration": 2.37}, {"text": "had here.", "start": 2827.14, "duration": 0.63}, {"text": "But basically, since\nthis distance estimate", "start": 2827.77, "duration": 3.18}, {"text": "was by supposition before the\nweight of some path to v--", "start": 2830.95, "duration": 4.57}, {"text": "to u, then this is, again,\nthe weight of some path to v.", "start": 2835.52, "duration": 4.65}, {"text": "OK, great.", "start": 2840.17, "duration": 1.04}, {"text": "So now we're ready to actually\ngo through this algorithm.", "start": 2841.21, "duration": 3.13}, {"text": "So DAG relaxation,\nfrom over there,", "start": 2848.95, "duration": 6.31}, {"text": "initializes all of our distance\nestimates to equal infinity,", "start": 2855.26, "duration": 7.47}, {"text": "just like we did in BFS.", "start": 2862.73, "duration": 1.305}, {"text": "Then, set my distance\nestimate to myself to be 0.", "start": 2867.47, "duration": 9.87}, {"text": "Now, it's possible that\nthis might be minus infinity", "start": 2877.34, "duration": 3.0}, {"text": "or negative at some point.", "start": 2880.34, "duration": 3.14}, {"text": "But right now, I'm\njust setting it to 0.", "start": 2883.48, "duration": 2.99}, {"text": "And either way, 0 is going to\nupper-bound the distance to s.", "start": 2886.47, "duration": 5.43}, {"text": "So in particular,\nat initialization,", "start": 2891.9, "duration": 6.44}, {"text": "anything not reachable\nfrom s is set correctly.", "start": 2898.34, "duration": 6.24}, {"text": "And s itself is set as an upper\nbound to the shortest path", "start": 2904.58, "duration": 4.56}, {"text": "distance.", "start": 2909.14, "duration": 1.29}, {"text": "Now we're going to process each\nvertex u in a topological sort", "start": 2910.43, "duration": 18.3}, {"text": "order.", "start": 2928.73, "duration": 1.44}, {"text": "So remember, our input to\nDAG relaxation is a DAG.", "start": 2930.17, "duration": 4.08}, {"text": "So this thing has a\ntopological sort order.", "start": 2934.25, "duration": 2.97}, {"text": "We're going to process these\nvertices in that order.", "start": 2937.22, "duration": 3.48}, {"text": "You can imagine we're\nstarting at the top,", "start": 2940.7, "duration": 2.28}, {"text": "and all my vertices are--", "start": 2942.98, "duration": 2.25}, {"text": "all my edges are\npointed away from me.", "start": 2945.23, "duration": 1.83}, {"text": "And I'm just\nprocessing each vertex", "start": 2947.06, "duration": 2.22}, {"text": "down this topological sort line.", "start": 2949.28, "duration": 4.11}, {"text": "And then for each\nof these vertices,", "start": 2953.39, "duration": 2.55}, {"text": "what am I going to do?", "start": 2955.94, "duration": 1.27}, {"text": "I'm going to look at all\nthe outgoing neighbors.", "start": 2957.21, "duration": 2.97}, {"text": "And if the triangle\ninequality is violated,", "start": 2960.18, "duration": 3.17}, {"text": "I'm going to relax that edge.", "start": 2963.35, "duration": 2.76}, {"text": "The algorithm is\nas simple as that.", "start": 2966.11, "duration": 2.4}, {"text": "For each outgoing\nneighbor of v--", "start": 2968.51, "duration": 10.08}, {"text": "sorry, of u--", "start": 2978.59, "duration": 3.24}, {"text": "I always get u and\nv mixed up here.", "start": 2981.83, "duration": 1.76}, {"text": "If my shortest\npath estimate to v", "start": 2987.78, "duration": 6.19}, {"text": "violates the triangle\ninequality for an edge,", "start": 2993.97, "duration": 9.03}, {"text": "for an incoming edge,\nthen I'm going to set--", "start": 3003.0, "duration": 3.12}, {"text": "relax u, v, i.e.", "start": 3006.12, "duration": 7.5}, {"text": "set d, s,v, equal to\nd, s,u, plus w, u,v.", "start": 3013.62, "duration": 11.92}, {"text": "So that's the algorithm.", "start": 3025.54, "duration": 3.32}, {"text": "So if I were to take a look at\nthis example graph over here,", "start": 3028.86, "duration": 6.13}, {"text": "maybe a is my start vertex.", "start": 3034.99, "duration": 2.19}, {"text": "I initialize it to--", "start": 3037.18, "duration": 2.82}, {"text": "AUDIENCE: DAG.", "start": 3040.0, "duration": 1.093}, {"text": "JASON KU: This is not a DAG.", "start": 3041.093, "duration": 1.167}, {"text": "Thank you.", "start": 3042.26, "duration": 1.22}, {"text": "Let's make it a DAG.", "start": 3043.48, "duration": 0.96}, {"text": "I claim to you\nnow this is a DAG.", "start": 3049.71, "duration": 6.03}, {"text": "In particular, a\ntopological sort order", "start": 3055.74, "duration": 2.07}, {"text": "is when there's a path\nthrough all the vertices,", "start": 3057.81, "duration": 4.06}, {"text": "then there's a unique\ntopological sort order--", "start": 3061.87, "duration": 2.48}, {"text": "a, b, e, f, g, h, d, c.", "start": 3064.35, "duration": 5.64}, {"text": "This is a topological order.", "start": 3069.99, "duration": 1.41}, {"text": "You can check all the edges.", "start": 3071.4, "duration": 3.07}, {"text": "So I'm going to start\nby setting the--", "start": 3074.47, "duration": 7.83}, {"text": "actually, let's use e.", "start": 3082.3, "duration": 3.18}, {"text": "Let's use shortest paths from e.", "start": 3085.48, "duration": 1.38}, {"text": "Why not?", "start": 3086.86, "duration": 1.8}, {"text": "Shortest paths from e.", "start": 3088.66, "duration": 1.05}, {"text": "Vertex a actually comes before\ne in the topological order.", "start": 3093.46, "duration": 4.59}, {"text": "So it has no--", "start": 3098.05, "duration": 1.08}, {"text": "I mean, its shortest path\ndistance, when I initialize,", "start": 3099.13, "duration": 3.42}, {"text": "I'm going to\ninitialize this to 0.", "start": 3102.55, "duration": 1.83}, {"text": "I'm going to initialize this to\ninfinite, infinite, infinite,", "start": 3104.38, "duration": 4.91}, {"text": "infinite, all these\nthings to infinite.", "start": 3109.29, "duration": 3.07}, {"text": "These are my estimates.", "start": 3112.36, "duration": 1.75}, {"text": "These are not quite the\nshortest paths yet--", "start": 3114.11, "duration": 2.57}, {"text": "distances.", "start": 3116.68, "duration": 2.22}, {"text": "But when I get here,\nclearly I can't be--", "start": 3118.9, "duration": 3.77}, {"text": "distance to me being\ninfinite can never", "start": 3127.88, "duration": 3.54}, {"text": "violate the triangle inequality\nwith something infinite", "start": 3131.42, "duration": 2.73}, {"text": "or finite.", "start": 3134.15, "duration": 0.78}, {"text": "It doesn't matter, right?", "start": 3134.93, "duration": 1.98}, {"text": "So I don't do anything to a.", "start": 3136.91, "duration": 2.85}, {"text": "Anything before my source\nvertex in the topological order", "start": 3139.76, "duration": 3.66}, {"text": "can't be visited,\nbecause it's before", "start": 3143.42, "duration": 2.508}, {"text": "in the topological order.", "start": 3145.928, "duration": 1.042}, {"text": "That's kind of the point.", "start": 3146.97, "duration": 1.34}, {"text": "There's no path from\nmy source vertex", "start": 3148.31, "duration": 2.31}, {"text": "to anything before it in\nthe topological order.", "start": 3150.62, "duration": 4.68}, {"text": "So same with b.", "start": 3155.3, "duration": 2.58}, {"text": "b is before a in the\ntopological order.", "start": 3157.88, "duration": 3.76}, {"text": "Now, I'm at e, and it's possible\nwe are violating triangle", "start": 3161.64, "duration": 6.51}, {"text": "inequality, in particular here.", "start": 3168.15, "duration": 3.15}, {"text": "I think the shortest path\ndistance to f is infinite.", "start": 3171.3, "duration": 4.14}, {"text": "But actually, if I go to e\nthrough this edge with a weight", "start": 3175.44, "duration": 7.32}, {"text": "3, I know that this is\nviolating triangle inequality.", "start": 3182.76, "duration": 4.62}, {"text": "So actually, this\nthing is wrong,", "start": 3187.38, "duration": 3.88}, {"text": "and I can set it equal to 3.", "start": 3191.26, "duration": 3.8}, {"text": "Now, that might not be the\nshortest path distance.", "start": 3195.06, "duration": 4.99}, {"text": "But right now it's a better\nestimate, so we've set it.", "start": 3200.05, "duration": 4.79}, {"text": "Now, I'm moving on.", "start": 3204.84, "duration": 1.89}, {"text": "I'm done with this guy.", "start": 3206.73, "duration": 1.44}, {"text": "I move to the next vertex\nin my topological order.", "start": 3208.17, "duration": 2.76}, {"text": "And again, I relax\nedges out of f.", "start": 3210.93, "duration": 3.52}, {"text": "OK, so here, looking\nat 8, 3 plus 8", "start": 3214.45, "duration": 3.83}, {"text": "is better than infinite, so\nwe'll say that that's 11.", "start": 3218.28, "duration": 3.27}, {"text": "And 3 plus 2 is better\nthan infinite, so that's 5.", "start": 3224.88, "duration": 5.58}, {"text": "Now, I keep going\nin the topological", "start": 3230.46, "duration": 1.56}, {"text": "order. g is the next.", "start": 3232.02, "duration": 1.98}, {"text": "5 plus 1 is 6.", "start": 3234.0, "duration": 1.86}, {"text": "OK, so we found a\nbetter estimate here.", "start": 3235.86, "duration": 2.61}, {"text": "So this 11 is not as good.", "start": 3238.47, "duration": 2.46}, {"text": "6 is better, so we replace it.", "start": 3240.93, "duration": 3.48}, {"text": "Here, we haven't visited before.", "start": 3244.41, "duration": 2.28}, {"text": "It's still infinite.", "start": 3246.69, "duration": 0.84}, {"text": "So 5 plus minus 2 is 3.", "start": 3247.53, "duration": 2.94}, {"text": "This is the next in\nthe topological order.", "start": 3253.11, "duration": 1.75}, {"text": "3 plus 9 is bigger than 6,\nso that's not a shorter path.", "start": 3254.86, "duration": 5.75}, {"text": "3 plus 4 is certainly\nsmaller than infinite,", "start": 3260.61, "duration": 2.7}, {"text": "so set that equal to 7.", "start": 3263.31, "duration": 2.43}, {"text": "Then, 7 plus 5 is\nalso bigger than 6.", "start": 3265.74, "duration": 3.45}, {"text": "And actually, you can confirm\nthat these are all the shortest", "start": 3269.19, "duration": 3.9}, {"text": "path distances from e.", "start": 3273.09, "duration": 3.53}, {"text": "So this algorithm seems to work.", "start": 3276.62, "duration": 3.21}, {"text": "Does it actually work?", "start": 3279.83, "duration": 3.52}, {"text": "Let's take a look.", "start": 3283.35, "duration": 1.79}, {"text": "The claim to you is that\nat the end of relaxation,", "start": 3285.14, "duration": 7.83}, {"text": "this algorithm, we've set--", "start": 3292.97, "duration": 2.04}, {"text": "claim at end, all the estimates\nequal shortest path distances.", "start": 3298.22, "duration": 14.31}, {"text": "The basic idea here\nis that if I take", "start": 3316.34, "duration": 5.78}, {"text": "the k-th vertex in\nthe topological order,", "start": 3322.12, "duration": 4.53}, {"text": "assuming that these\ndistances are all", "start": 3326.65, "duration": 2.52}, {"text": "equal for the ones before\nme in the topological order,", "start": 3329.17, "duration": 3.93}, {"text": "I can prove by induction.", "start": 3333.1, "duration": 2.22}, {"text": "We can consider a shortest path\nfrom s to v, the k-th vertex,", "start": 3335.32, "duration": 6.41}, {"text": "and look at the vertex preceding\nme along the shortest path.", "start": 3341.73, "duration": 4.31}, {"text": "That vertex better be before\nme in the topological order", "start": 3346.04, "duration": 6.3}, {"text": "or we're not a DAG.", "start": 3352.34, "duration": 2.03}, {"text": "And we've already set its\nshortest path distance", "start": 3354.37, "duration": 2.0}, {"text": "to be equal to the correct\nthing by induction.", "start": 3356.37, "duration": 6.67}, {"text": "So then when we processed u--", "start": 3363.04, "duration": 2.06}, {"text": "s to u to v--", "start": 3368.16, "duration": 4.23}, {"text": "when we processed\nu in DAG relaxation", "start": 3372.39, "duration": 4.29}, {"text": "here, processed the\nvertex and looked at all", "start": 3376.68, "duration": 2.85}, {"text": "its outgoing\nadjacencies, we would", "start": 3379.53, "duration": 2.43}, {"text": "have relaxed this edge to be no\ngreater than that shortest path", "start": 3381.96, "duration": 5.095}, {"text": "distance.", "start": 3387.055, "duration": 0.5}, {"text": "So this is correct.", "start": 3392.32, "duration": 2.72}, {"text": "You can also think of\nit as the DAG relaxation", "start": 3395.04, "duration": 3.38}, {"text": "algorithm for each vertex looks\nall at its incoming neighbors,", "start": 3398.42, "duration": 6.94}, {"text": "assuming that their\nshortest path distances are", "start": 3405.36, "duration": 2.25}, {"text": "computed correctly already.", "start": 3407.61, "duration": 2.38}, {"text": "Any shortest path\ndistance to me needs", "start": 3409.99, "duration": 1.908}, {"text": "to be composed of a shortest\npath distance to one", "start": 3411.898, "duration": 2.042}, {"text": "of my incoming neighbors\nthrough an edge to me,", "start": 3413.94, "duration": 4.86}, {"text": "so I can just check all of them.", "start": 3418.8, "duration": 1.83}, {"text": "That's what DAG relaxation does.", "start": 3420.63, "duration": 3.15}, {"text": "And again, we're looping\nover every vertex", "start": 3423.78, "duration": 2.56}, {"text": "and looking at its adjacencies\ndoing constant work.", "start": 3426.34, "duration": 2.54}, {"text": "This, again, takes linear time.", "start": 3428.88, "duration": 2.28}, {"text": "OK, so that's shortest\npaths and a DAG.", "start": 3431.16, "duration": 4.83}, {"text": "Next time, we'll look\nat, for general graphs,", "start": 3435.99, "duration": 3.57}, {"text": "how we can use kind of the\nsame technique in an algorithm", "start": 3439.56, "duration": 4.17}, {"text": "we call Bellman-Ford.", "start": 3443.73, "duration": 1.11}, {"text": "OK, that's it for today.", "start": 3444.84, "duration": 2.78}]
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+[{"text": "BARBARA IMPERIALI: Now,\nI want to talk today", "start": 16.379, "duration": 2.431}, {"text": "about one small thing before\nwe move on to signaling,", "start": 18.81, "duration": 3.81}, {"text": "because it really\nkind of completes", "start": 22.62, "duration": 1.86}, {"text": "the work that we talked about\nwith respect to trafficking.", "start": 24.48, "duration": 4.42}, {"text": "So I popped this\nquestion up last time,", "start": 28.9, "duration": 3.62}, {"text": "and it seemed like there weren't\nquite enough sort of people", "start": 32.52, "duration": 2.91}, {"text": "leaping to give me an answer.", "start": 35.43, "duration": 1.47}, {"text": "But let's just take a look\nat the big picture of things,", "start": 36.9, "duration": 3.09}, {"text": "as it's always good to do.", "start": 39.99, "duration": 1.68}, {"text": "Because this will also\nget me to one other topic,", "start": 41.67, "duration": 3.27}, {"text": "which is protein misfolding.", "start": 44.94, "duration": 2.97}, {"text": "So at the end of\nthe day, what really", "start": 47.91, "duration": 3.03}, {"text": "defines where a protein\nis, what it does,", "start": 50.94, "duration": 4.16}, {"text": "is defined by its sequence.", "start": 55.1, "duration": 2.77}, {"text": "But you always want to remember\nthat a protein sequence is", "start": 57.87, "duration": 3.12}, {"text": "defined by its messenger.", "start": 60.99, "duration": 2.1}, {"text": "The messenger is defined\nby the pre-messenger.", "start": 63.09, "duration": 3.6}, {"text": "Yes, there may be splicing\nevents that really", "start": 66.69, "duration": 2.82}, {"text": "cause changes in localization.", "start": 69.51, "duration": 3.48}, {"text": "But the pre-messenger\nincludes the content.", "start": 72.99, "duration": 3.42}, {"text": "And then what defines\nthat is the DNA.", "start": 76.41, "duration": 3.07}, {"text": "There's certain\naspects of regulation", "start": 79.48, "duration": 3.07}, {"text": "at the epigenetic level that\nwe don't talk about barely", "start": 82.55, "duration": 3.55}, {"text": "in this course.", "start": 86.1, "duration": 1.12}, {"text": "But I want you to make\nsure that you realize", "start": 87.22, "duration": 2.72}, {"text": "at the end of the day,\nwhat the protein is,", "start": 89.94, "duration": 3.78}, {"text": "how it folds, is\ndefined originally", "start": 93.72, "duration": 3.42}, {"text": "by the sequence of the DNA,\nalthough a long way along here.", "start": 97.14, "duration": 3.42}, {"text": "The post-translational\nmodifications that we started", "start": 100.56, "duration": 3.63}, {"text": "talking about last time\nare defined by the protein", "start": 104.19, "duration": 3.87}, {"text": "sequence, which all the\nway is defined by the DNA--", "start": 108.06, "duration": 4.08}, {"text": "so, so much of protein function.", "start": 112.14, "duration": 2.47}, {"text": "And there's one more\naspect of proteins", "start": 114.61, "duration": 3.05}, {"text": "that's defined by\nthe DNA sequence,", "start": 117.66, "duration": 2.67}, {"text": "and that's whether a protein\nfolds well, or perhaps,", "start": 120.33, "duration": 6.36}, {"text": "in some cases, misfolds.", "start": 126.69, "duration": 1.86}, {"text": "And that's the thing I want to\ntalk about very briefly today.", "start": 128.55, "duration": 2.82}, {"text": "Because I think that this\ncaptures the picture.", "start": 131.37, "duration": 2.94}, {"text": "So let's just go over here\nand write misfolded proteins,", "start": 134.31, "duration": 9.33}, {"text": "which, just like\neverything else,", "start": 143.64, "duration": 2.73}, {"text": "largely end up being\ndictated by the DNA.", "start": 146.37, "duration": 3.9}, {"text": "Because whether a\nprotein folds faithfully", "start": 150.27, "duration": 3.18}, {"text": "into a good\nstructure or misfolds", "start": 153.45, "duration": 2.79}, {"text": "can be a function of\nthe protein sequence.", "start": 156.24, "duration": 2.37}, {"text": "So there could be mutations\nin the protein that ultimately", "start": 158.61, "duration": 6.33}, {"text": "end up that the protein\nmisfolds and forms", "start": 164.94, "duration": 4.02}, {"text": "either a misfolded tertiary\nstructure, or even worse,", "start": 168.96, "duration": 4.26}, {"text": "adopts an aggregated form\nthat causes a lot of damage", "start": 173.22, "duration": 3.6}, {"text": "within cells and\noutsides of cells.", "start": 176.82, "duration": 2.34}, {"text": "So I want to talk just briefly\nabout the processes that we", "start": 179.16, "duration": 3.6}, {"text": "have-- it's just one slide--", "start": 182.76, "duration": 1.98}, {"text": "to deal with misfolded proteins.", "start": 184.74, "duration": 2.83}, {"text": "So when a protein is\ntranslated, it almost", "start": 187.57, "duration": 4.19}, {"text": "starts folding straight away,\nespecially large proteins.", "start": 191.76, "duration": 3.81}, {"text": "A fair amount of a protein\nmay have already emerged", "start": 195.57, "duration": 2.91}, {"text": "from the ribosome and\nstarted folding, even", "start": 198.48, "duration": 3.27}, {"text": "when the whole\nprotein isn't made.", "start": 201.75, "duration": 2.37}, {"text": "The sequence ultimately ends you\nup with a well-folded protein.", "start": 204.12, "duration": 6.99}, {"text": "But if the protein does\nnot fold fast enough,", "start": 211.11, "duration": 3.63}, {"text": "or there is a mistake\nin this, which", "start": 214.74, "duration": 2.19}, {"text": "might be caused intrinsically\nby the primary sequence,", "start": 216.93, "duration": 3.24}, {"text": "if there's a mistake in that--", "start": 220.17, "duration": 1.71}, {"text": "so slow folding or\nincorrect folding--", "start": 221.88, "duration": 6.89}, {"text": "then you will end up with a\nprotein that's partially folded", "start": 236.81, "duration": 3.0}, {"text": "within the context of a cell.", "start": 239.81, "duration": 2.04}, {"text": "We especially encounter\nmisfolded proteins", "start": 241.85, "duration": 3.3}, {"text": "when we are\noverexpressing proteins", "start": 245.15, "duration": 2.46}, {"text": "in cells, because you're just\nmaking one of a type of protein", "start": 247.61, "duration": 3.12}, {"text": "really quickly, and it\ndoesn't have a chance", "start": 250.73, "duration": 2.43}, {"text": "to adopt its faithful structure.", "start": 253.16, "duration": 2.52}, {"text": "So there are proteins\nwithin the cell that", "start": 255.68, "duration": 4.75}, {"text": "helped sort of protect\nthe folding process early", "start": 260.43, "duration": 3.27}, {"text": "on, to allow the protein to have\nenough time in singular, not", "start": 263.7, "duration": 5.31}, {"text": "with a lot of copies of itself\naround that are misfolded,", "start": 269.01, "duration": 3.72}, {"text": "to adopt a folded structure.", "start": 272.73, "duration": 2.01}, {"text": "And these proteins\nare called chaperones.", "start": 274.74, "duration": 2.03}, {"text": "I don't know if you guys\nare familiar with the term", "start": 280.29, "duration": 2.65}, {"text": "chaperone.", "start": 282.94, "duration": 1.08}, {"text": "It was a term that\nwas heavily used", "start": 284.02, "duration": 1.77}, {"text": "in the sort of 18th\nand 19th century.", "start": 285.79, "duration": 3.49}, {"text": "A chaperone used to be\nan aunt or someone who", "start": 289.28, "duration": 4.34}, {"text": "you would send out with your\nbeautiful young daughter", "start": 293.62, "duration": 2.46}, {"text": "to chaperone her, to protect\nher so she didn't get bothered", "start": 296.08, "duration": 3.96}, {"text": "by those mean men out there.", "start": 300.04, "duration": 2.1}, {"text": "So chaperones were-- that\nwas the original definition", "start": 302.14, "duration": 3.78}, {"text": "of the chaperone.", "start": 305.92, "duration": 1.08}, {"text": "And it's kind of interesting\nthat the chaperones are now", "start": 307.0, "duration": 3.61}, {"text": "proteins that help folding or\nprotect against misfolding.", "start": 310.61, "duration": 12.08}, {"text": "How do they do this?", "start": 332.5, "duration": 1.92}, {"text": "Generally, a protein\nwill fold poorly", "start": 334.42, "duration": 3.51}, {"text": "if it's very, very-- if\nit's quite hydrophobic.", "start": 337.93, "duration": 2.85}, {"text": "And hydrophobic patches\nare exposed in aggregate.", "start": 340.78, "duration": 3.72}, {"text": "So let's say, you\nhave a protein,", "start": 344.5, "duration": 2.11}, {"text": "and there's a lot of copies,\nbut they're not folded.", "start": 346.61, "duration": 3.2}, {"text": "If you have things that are\nhydrophobic that would normally", "start": 349.81, "duration": 4.89}, {"text": "end up tucked\ninside the protein,", "start": 354.7, "duration": 3.93}, {"text": "if the protein hasn't\nfolded in its good time,", "start": 358.63, "duration": 3.13}, {"text": "these will just start\nto form aggregates, sort", "start": 361.76, "duration": 4.85}, {"text": "of associating with each other.", "start": 366.61, "duration": 1.99}, {"text": "It's just a physical phenomenon.", "start": 368.6, "duration": 1.64}, {"text": "If you put something that's\ngot a lot of hydrophobic faces", "start": 370.24, "duration": 3.54}, {"text": "on the outside, this\nwill start forming", "start": 373.78, "duration": 3.15}, {"text": "an aggregated bundle, and not\na nicely folded protein at all.", "start": 376.93, "duration": 4.47}, {"text": "What the chaperones\nmay do is in part", "start": 381.4, "duration": 3.93}, {"text": "hold the partially\nfolded protein.", "start": 385.33, "duration": 4.32}, {"text": "So let's just think of this\nbig jelly bean as a chaperone", "start": 389.65, "duration": 3.27}, {"text": "until things start to\nadopt a favorable state.", "start": 392.92, "duration": 3.93}, {"text": "But sometimes it's\njust too much.", "start": 396.85, "duration": 1.86}, {"text": "The chaperone cannot\nhandle the flux of protein.", "start": 398.71, "duration": 3.7}, {"text": "So the protein ends up being\nrecognized as misfolded.", "start": 402.41, "duration": 3.53}, {"text": "And then it gets tagged\nas a misfolded protein,", "start": 405.94, "duration": 3.72}, {"text": "and it gets taken to a place\nin the cell for disposal.", "start": 409.66, "duration": 3.4}, {"text": "So if you are unable to fold,\nthere is a tagging process.", "start": 413.06, "duration": 7.99}, {"text": "And I mentioned it last time.", "start": 421.05, "duration": 1.53}, {"text": "It's a process known\nas ubiquitination.", "start": 422.58, "duration": 2.19}, {"text": "This is also a\npost-translational", "start": 432.17, "duration": 2.91}, {"text": "modification, but\nit's one that occurs", "start": 435.08, "duration": 2.7}, {"text": "on poorly folded proteins.", "start": 437.78, "duration": 2.29}, {"text": "And I'm going to describe\nto you that system,", "start": 440.07, "duration": 2.3}, {"text": "because the ubiquitination\nis the flag, the signal,", "start": 442.37, "duration": 3.63}, {"text": "or the tag, to take this\nprotein to the great shredder,", "start": 446.0, "duration": 4.17}, {"text": "basically.", "start": 450.17, "duration": 1.06}, {"text": "And so what does the--\nwhat's a paper shredder--", "start": 451.23, "duration": 2.93}, {"text": "I like the analogy\nwith a paper shredder.", "start": 454.16, "duration": 2.28}, {"text": "So here's a fellow who's got\ntoo much on in his inbox.", "start": 456.44, "duration": 4.575}, {"text": "So he just sends it\nstraight to the shredder.", "start": 461.015, "duration": 1.875}, {"text": "It's a little bit about too much\nmisfolded protein being made.", "start": 462.89, "duration": 3.69}, {"text": "So instead of sort of waiting\nto deal with the paperwork,", "start": 466.58, "duration": 3.87}, {"text": "you just send it\nstraight to the shredder.", "start": 470.45, "duration": 1.83}, {"text": "And the proteasome is\nthe cellular shredder", "start": 472.28, "duration": 3.66}, {"text": "that actually breaks proteins\nup into small chunks,", "start": 475.94, "duration": 3.63}, {"text": "and then digests them out.", "start": 479.57, "duration": 2.02}, {"text": "So think of the\nproteasome as a shredder,", "start": 481.59, "duration": 15.76}, {"text": "which chops up proteins\ninto small pieces,", "start": 497.35, "duration": 9.82}, {"text": "mostly into short\npeptides that are 8 to 14", "start": 507.17, "duration": 8.07}, {"text": "amino acids in length--", "start": 515.24, "duration": 1.679}, {"text": "fairly small.", "start": 516.919, "duration": 1.561}, {"text": "Short peptides won't cause\na problem in aggregation,", "start": 518.48, "duration": 3.15}, {"text": "and will then be\nfurther digested.", "start": 521.63, "duration": 2.039}, {"text": "Now, if you've got this shredder\nsitting around in the cell,", "start": 523.669, "duration": 2.911}, {"text": "it's like having a paper\nshredder on all the time.", "start": 526.58, "duration": 3.36}, {"text": "You've got a-- there's a risk\nthings may end up in there", "start": 529.94, "duration": 2.46}, {"text": "without meaning to be.", "start": 532.4, "duration": 1.56}, {"text": "So for things to be\ntagged for shredding,", "start": 533.96, "duration": 2.73}, {"text": "they go through what's known\nas the ubiquitin system.", "start": 536.69, "duration": 4.42}, {"text": "So the first thing\nto get into that is--", "start": 541.11, "duration": 3.09}, {"text": "and it's only then\nthat proteins are", "start": 549.39, "duration": 2.28}, {"text": "tagged for shredding up or\nchopping up by the proteasome.", "start": 551.67, "duration": 4.26}, {"text": "So as you can sort\nof tell by its name,", "start": 555.93, "duration": 3.26}, {"text": "it's got protease\nfunction, but it's", "start": 559.19, "duration": 4.42}, {"text": "a large, macromolecular\nprotease,", "start": 563.61, "duration": 3.12}, {"text": "with lots and lots\nof subunits that", "start": 566.73, "duration": 2.55}, {"text": "are important to cut that\npolypeptide into smaller", "start": 569.28, "duration": 3.3}, {"text": "pieces.", "start": 572.58, "duration": 1.31}, {"text": "But because many\nof your proteins", "start": 573.89, "duration": 3.13}, {"text": "may be partially\nfolded or misfolded,", "start": 577.02, "duration": 3.51}, {"text": "they first have to be unfolded.", "start": 580.53, "duration": 2.37}, {"text": "So the ubiquitin is the\nsignal to send proteins", "start": 582.9, "duration": 5.6}, {"text": "to the proteasome, where\nthe second action is", "start": 588.5, "duration": 3.52}, {"text": "protease activity, and the\nfirst action is unfolding.", "start": 592.02, "duration": 3.78}, {"text": "So what I show you\non this picture", "start": 598.96, "duration": 1.88}, {"text": "is the barrel structure\nof a proteasome.", "start": 600.84, "duration": 4.17}, {"text": "Let me explain the\ncomponents of it.", "start": 605.01, "duration": 2.4}, {"text": "The red component\nof the proteasome", "start": 607.41, "duration": 3.12}, {"text": "is a multimeric ring\nthat uses ATP and starts", "start": 610.53, "duration": 4.23}, {"text": "tugging apart the protein\nthat you need to destroy.", "start": 614.76, "duration": 4.53}, {"text": "But it will only do\nthat if the protein", "start": 619.29, "duration": 2.82}, {"text": "becomes labeled for destruction\nby the ubiquitin system.", "start": 622.11, "duration": 4.28}, {"text": "And I am showing you here a\nmassively simplified version.", "start": 626.39, "duration": 3.67}, {"text": "Let's say this is a\nmisfolded protein.", "start": 630.06, "duration": 2.64}, {"text": "It gets tagged with\nanother protein.", "start": 632.7, "duration": 2.7}, {"text": "It's a really little\nprotein known as ubiquitin.", "start": 635.4, "duration": 2.91}, {"text": "I've shown you the\nthree-dimensional structure", "start": 638.31, "duration": 2.1}, {"text": "here.", "start": 640.41, "duration": 0.84}, {"text": "And using ATP, you\nend up managing", "start": 641.25, "duration": 2.97}, {"text": "to put a ubiquitin chain\non the protein that's", "start": 644.22, "duration": 3.09}, {"text": "going to be destroyed.", "start": 647.31, "duration": 1.71}, {"text": "That is a post-translational\nmodification that", "start": 649.02, "duration": 2.85}, {"text": "is a tagging for destruction.", "start": 651.87, "duration": 2.34}, {"text": "If the protein is\nnot tagged, then it's", "start": 654.21, "duration": 2.46}, {"text": "not going to be chewed up.", "start": 656.67, "duration": 1.5}, {"text": "That makes sense.", "start": 658.17, "duration": 0.87}, {"text": "You don't want to be\nchopping up proteins", "start": 659.04, "duration": 2.46}, {"text": "in a cell with wild abandon.", "start": 661.5, "duration": 2.85}, {"text": "Once the ubiquitin\nchain is on here,", "start": 664.35, "duration": 3.06}, {"text": "the protein will bind\nto the unfoldase part", "start": 667.41, "duration": 3.75}, {"text": "of the proteasome,\nand with ATP, it", "start": 671.16, "duration": 2.64}, {"text": "will just stop tugging the rest\nof the residual structure apart", "start": 673.8, "duration": 4.32}, {"text": "to thread the protein down into\nthe blue part of the barrel.", "start": 678.12, "duration": 6.235}, {"text": "It's a little hard\nto see it like this,", "start": 684.355, "duration": 1.625}, {"text": "but it's literally,\nthe proteasome,", "start": 685.98, "duration": 3.03}, {"text": "are four concentric rings.", "start": 689.01, "duration": 2.55}, {"text": "Let me see.", "start": 691.56, "duration": 0.9}, {"text": "I hope my artwork is\ngoing to be good enough.", "start": 692.46, "duration": 2.13}, {"text": "Well, that's an unfoldase.", "start": 698.62, "duration": 1.24}, {"text": "And so is that.", "start": 703.312, "duration": 1.448}, {"text": "And then in the center,\nthere is a protease.", "start": 704.76, "duration": 6.01}, {"text": "And each of these\ncomponents is multimeric,", "start": 710.77, "duration": 2.99}, {"text": "having six or seven subunits.", "start": 713.76, "duration": 3.03}, {"text": "So it's a huge structure.", "start": 716.79, "duration": 3.06}, {"text": "It has a sedimentation\ncoefficient", "start": 719.85, "duration": 3.21}, {"text": "of 20S, that entire structure.", "start": 723.06, "duration": 3.48}, {"text": "I don't know if you remember\nwhen I talked about ribosomes,", "start": 726.54, "duration": 3.06}, {"text": "they were so big we didn't tend\nto talk about them by size.", "start": 729.6, "duration": 3.75}, {"text": "We talked about them by\nsedimentation coefficient.", "start": 733.35, "duration": 3.41}, {"text": "And the large and small\nsubunits of the ribosome,", "start": 736.76, "duration": 3.17}, {"text": "the eukaryotic one, just to\nremind you, were 40S and 60S.", "start": 739.93, "duration": 12.38}, {"text": "So just remember that\nS stands for Svedberg.", "start": 752.31, "duration": 4.38}, {"text": "It's a sedimentation\ncoefficient unit.", "start": 756.69, "duration": 3.46}, {"text": "It describes how fast\napproaching precipitates.", "start": 760.15, "duration": 4.19}, {"text": "So once the protein has\nbeen labeled with ubiquitin,", "start": 764.34, "duration": 2.91}, {"text": "it binds to the unfoldase.", "start": 767.25, "duration": 2.01}, {"text": "And then the single strand feeds\ninto the center core, which", "start": 769.26, "duration": 4.62}, {"text": "is two sections of protease.", "start": 773.88, "duration": 3.48}, {"text": "So it's feeding in here.", "start": 777.36, "duration": 1.92}, {"text": "It sees the protease activity.", "start": 779.28, "duration": 4.57}, {"text": "And then it's just\nshort pieces of protein", "start": 783.85, "duration": 4.34}, {"text": "are spit out of the proteasome.", "start": 788.19, "duration": 2.75}, {"text": "Once these are really\nlittle pieces of peptide,", "start": 794.49, "duration": 3.15}, {"text": "they're readily digested by\nproteases within the cell.", "start": 797.64, "duration": 3.85}, {"text": "And you can recycle\nthe amino acids,", "start": 801.49, "duration": 2.39}, {"text": "or you can do other things with\nthese small pieces of peptide.", "start": 803.88, "duration": 3.72}, {"text": "They actually end up sometimes\nbeing sent for presentation", "start": 807.6, "duration": 3.84}, {"text": "on the surface of the\ncell by the immune system.", "start": 811.44, "duration": 3.15}, {"text": "And you may hear a little\nbit more about that later.", "start": 814.59, "duration": 2.75}, {"text": "So the proteasome--\noh, I apologize--", "start": 817.34, "duration": 2.835}, {"text": "this should have been 26S--", "start": 820.175, "duration": 1.125}, {"text": "has a molecular weight\nthat's very large--", "start": 824.98, "duration": 2.37}, {"text": "2,000 kilodaltons.", "start": 827.35, "duration": 1.89}, {"text": "That's why we refer to it by\nits sedimentation coefficient.", "start": 829.24, "duration": 4.71}, {"text": "So this machinery\nis very important", "start": 833.95, "duration": 2.55}, {"text": "to get rid of misfolded\nor aggregated proteins", "start": 836.5, "duration": 4.8}, {"text": "to destroy them.", "start": 841.3, "duration": 1.17}, {"text": "Now, does-- are people aware of\nthe sorts of diseases that can", "start": 842.47, "duration": 3.39}, {"text": "result from misfolded proteins?", "start": 845.86, "duration": 2.68}, {"text": "Has anyone been\nreading the news much", "start": 848.54, "duration": 1.82}, {"text": "about certain types of diseases,\nparticularly in neurobiology?", "start": 850.36, "duration": 5.16}, {"text": "Anyone aware of those?", "start": 855.52, "duration": 1.62}, {"text": "Yeah.", "start": 857.14, "duration": 0.762}, {"text": "AUDIENCE: Was it\nmad cow disease?", "start": 857.902, "duration": 1.608}, {"text": "BARBARA IMPERIALI: Which one?", "start": 859.51, "duration": 0.3}, {"text": "AUDIENCE: Mad cow.", "start": 859.81, "duration": 0.96}, {"text": "BARBARA IMPERIALI: Yes.", "start": 860.77, "duration": 0.3}, {"text": "Mad cow.", "start": 861.07, "duration": 0.6}, {"text": "So there are a variety of\nneurological disorders,", "start": 861.67, "duration": 3.87}, {"text": "and mad cow is one of them.", "start": 865.54, "duration": 1.53}, {"text": "Creutz U-T-Z feldt-Jakob.", "start": 871.13, "duration": 3.58}, {"text": "But Alzheimer's\ndisease is another one.", "start": 878.53, "duration": 2.3}, {"text": "Pick's disease is another.", "start": 884.17, "duration": 1.98}, {"text": "There are a wide variety\nof neurological disorders", "start": 886.15, "duration": 3.6}, {"text": "that result from misfolded\nproteins, both inside the cell", "start": 889.75, "duration": 4.33}, {"text": "and in the extracellular matrix,\nforming these tangles that", "start": 894.08, "duration": 3.8}, {"text": "are toxic to the neurons,\ncausing them to no longer", "start": 897.88, "duration": 4.02}, {"text": "function, and then\nresulting in many", "start": 901.9, "duration": 2.19}, {"text": "of these neurological disorders.", "start": 904.09, "duration": 2.46}, {"text": "The ones I've described to you,\nI've mentioned to you here.", "start": 906.55, "duration": 3.09}, {"text": "I know many of you are familiar\nwith Alzheimer's disease.", "start": 909.64, "duration": 3.78}, {"text": "Mad cow disease is a variant of\na particular protein misfolding", "start": 913.42, "duration": 5.58}, {"text": "disease that was\nfirst noted in cattle.", "start": 919.0, "duration": 2.81}, {"text": "And they basically just\nfell down, dropped down.", "start": 921.81, "duration": 4.06}, {"text": "And it was in some\ncases ascribed to--", "start": 925.87, "duration": 3.8}, {"text": "the contagion with the disease\nis ascribed not to a virus", "start": 929.67, "duration": 5.26}, {"text": "or to a microorganism,\nbut literally,", "start": 934.93, "duration": 3.03}, {"text": "to misfolded proteins\ncausing the formation", "start": 937.96, "duration": 3.12}, {"text": "of more misfolded proteins.", "start": 941.08, "duration": 2.25}, {"text": "So these are all collectively\ndesignated as prion diseases.", "start": 943.33, "duration": 6.49}, {"text": "I think you'll have\nread that term.", "start": 949.82, "duration": 2.21}, {"text": "And it's a particular\nkind of disease", "start": 952.03, "duration": 2.1}, {"text": "that the infectious agent\nisn't a living system--", "start": 954.13, "duration": 4.89}, {"text": "not a virus, not a\nmicrobe, a fungus,", "start": 959.02, "duration": 2.98}, {"text": "a protozoan, but\nrather a protein,", "start": 962.0, "duration": 3.17}, {"text": "where it's misfolded\nstructure nucleates", "start": 965.17, "duration": 3.69}, {"text": "the formation of more\nmisfolded structure", "start": 968.86, "duration": 2.61}, {"text": "that leads to the disease.", "start": 971.47, "duration": 1.87}, {"text": "So I grew up in England\nduring the years", "start": 973.34, "duration": 2.85}, {"text": "where there was a lot of\nmad cow disease in England.", "start": 976.19, "duration": 2.36}, {"text": "And even though I'm a vegetarian\nin the US for 30 years,", "start": 978.55, "duration": 3.66}, {"text": "I can't give blood in the US,\nbecause I lived in England", "start": 982.21, "duration": 3.21}, {"text": "during the time when there\nwas a lot of mad cow disease.", "start": 985.42, "duration": 3.51}, {"text": "And this can be dormant\nfor a long, long time", "start": 988.93, "duration": 2.76}, {"text": "before it suddenly takes over.", "start": 991.69, "duration": 2.02}, {"text": "So there's restrictions on\nblood donation in certain cases.", "start": 993.71, "duration": 4.52}, {"text": "And it's because\nit's not something", "start": 998.23, "duration": 2.4}, {"text": "you can treat with\nan antibiotic,", "start": 1000.63, "duration": 1.74}, {"text": "you can treat with an antiviral.", "start": 1002.37, "duration": 1.77}, {"text": "It's literally traces\nof badly folded protein", "start": 1004.14, "duration": 4.26}, {"text": "that can nucleate the formation\nof more badly folded protein,", "start": 1008.4, "duration": 3.99}, {"text": "that can lead to the diseases.", "start": 1012.39, "duration": 3.09}, {"text": "These were-- there's\nparticular instances of some", "start": 1015.48, "duration": 4.92}, {"text": "of these diseases in\ntribes where there's", "start": 1020.4, "duration": 4.08}, {"text": "pretty serious\ncannibalism, and eating", "start": 1024.48, "duration": 2.58}, {"text": "your sort of senior\nrelative's brains", "start": 1027.06, "duration": 3.21}, {"text": "was considered to be something--\nan important act of respect.", "start": 1030.27, "duration": 4.68}, {"text": "And there was this\ntransfer of some", "start": 1034.95, "duration": 2.31}, {"text": "of these prion-type diseases\nthrough cannibalism as well.", "start": 1037.26, "duration": 3.72}, {"text": "So eating contaminated\nmeat, be it a cow,", "start": 1040.98, "duration": 4.119}, {"text": "be it your\ngrandparents, whatever,", "start": 1045.099, "duration": 3.388}, {"text": "it's something that\nactually is-- it's", "start": 1048.487, "duration": 1.583}, {"text": "a serious transmissible disease.", "start": 1050.07, "duration": 3.15}, {"text": "And it's really--\nin the situations", "start": 1053.22, "duration": 3.27}, {"text": "where it can be sort of related\nback to contaminated meat are", "start": 1056.49, "duration": 3.9}, {"text": "one thing.", "start": 1060.39, "duration": 0.97}, {"text": "But there are variations in\nthe case of Alzheimer's, where", "start": 1061.36, "duration": 4.34}, {"text": "the sequence of proteins may\ndictate that they don't fold", "start": 1065.7, "duration": 4.92}, {"text": "well, or they're not\npost-translationally modified", "start": 1070.62, "duration": 3.39}, {"text": "properly, so they end up\nas misfolded proteins.", "start": 1074.01, "duration": 3.75}, {"text": "So these are often\ngenetically linked disorders,", "start": 1077.76, "duration": 3.69}, {"text": "some of the things\nlike Alzheimer's.", "start": 1081.45, "duration": 2.07}, {"text": "And once again, remember\nthat goes all the way back", "start": 1083.52, "duration": 2.73}, {"text": "to the DNA, which\nmight, in some cases,", "start": 1086.25, "duration": 3.15}, {"text": "trigger the misfolded disease.", "start": 1089.4, "duration": 1.9}, {"text": "So it's a fascinating area,\nand there's a tremendous amount", "start": 1091.3, "duration": 3.65}, {"text": "to be studied.", "start": 1094.95, "duration": 1.2}, {"text": "Because of the aging population,\nthese diseases are piling up,", "start": 1096.15, "duration": 4.07}, {"text": "and we need to mitigate\nthe causes of the disease,", "start": 1100.22, "duration": 5.14}, {"text": "and find ways, for\nexample, to slow down.", "start": 1105.36, "duration": 3.57}, {"text": "If there are these fibrils of\nprotein that are misfolded,", "start": 1108.93, "duration": 4.14}, {"text": "can we maybe inhibit\nthat formation", "start": 1113.07, "duration": 3.45}, {"text": "with some kind of small\nmolecule inhibitor", "start": 1116.52, "duration": 2.58}, {"text": "to mitigate the\nsymptoms of the disease?", "start": 1119.1, "duration": 3.2}, {"text": "So it's a very,\nvery active area,", "start": 1122.3, "duration": 2.05}, {"text": "because almost every-- many,\nmany neurological disorders", "start": 1124.35, "duration": 4.11}, {"text": "seem to be coming down\nto misfolded proteins.", "start": 1128.46, "duration": 2.295}, {"text": "So let's move on\nnow to signaling.", "start": 1134.14, "duration": 1.91}, {"text": "All right.", "start": 1144.4, "duration": 0.77}, {"text": "So we're going to\nspend two lectures", "start": 1156.77, "duration": 2.01}, {"text": "on-- the remainder of this\nlecture plus the next lecture.", "start": 1158.78, "duration": 3.54}, {"text": "And what I want to\ndo in this lecture", "start": 1162.32, "duration": 2.22}, {"text": "is introduce you to some of the\nparadigms, the nuts and bolts,", "start": 1164.54, "duration": 4.48}, {"text": "the mechanics of\nprotein signaling.", "start": 1169.02, "duration": 2.45}, {"text": "And then in the\nnext lecture, I'm", "start": 1171.47, "duration": 1.91}, {"text": "going to show you\nexamples of how", "start": 1173.38, "duration": 1.93}, {"text": "all the characteristics\nthat we define signaling by", "start": 1175.31, "duration": 3.72}, {"text": "get represented in signaling\npathways within cells.", "start": 1179.03, "duration": 3.67}, {"text": "So I'm going to give you\nall the moving parts,", "start": 1182.7, "duration": 2.24}, {"text": "and then we'll move forward to\nsee how the moving parts might", "start": 1184.94, "duration": 3.24}, {"text": "function in a physiological\naction, such as a response", "start": 1188.18, "duration": 4.89}, {"text": "to something particularly\nscary, or as a trigger to do--", "start": 1193.07, "duration": 4.11}, {"text": "for the cells to do\nsomething different.", "start": 1197.18, "duration": 1.93}, {"text": "So let me take\nyou, first of all,", "start": 1199.11, "duration": 2.39}, {"text": "to a cartoon-like\nimage of a cell.", "start": 1201.5, "duration": 3.01}, {"text": "And we're going to just\ntake from the very simplest", "start": 1204.51, "duration": 3.02}, {"text": "beginning.", "start": 1207.53, "duration": 0.87}, {"text": "But then this topic will get\nquite complex, as you see.", "start": 1208.4, "duration": 3.39}, {"text": "But that's why I think\nit's important to reduce", "start": 1211.79, "duration": 2.85}, {"text": "the process of protein signaling\ndown to simple aspects of it", "start": 1214.64, "duration": 4.98}, {"text": "that we can really\nrecognize, even in much", "start": 1219.62, "duration": 2.79}, {"text": "more complicated pathways.", "start": 1222.41, "duration": 2.35}, {"text": "So in protein\ncellular signaling,", "start": 1224.76, "duration": 2.19}, {"text": "this is a complex\nsystem of communication", "start": 1226.95, "duration": 3.05}, {"text": "that governs all basic\nactivities of the cell.", "start": 1230.0, "duration": 3.31}, {"text": "There are no cells that\ndon't do signaling.", "start": 1233.31, "duration": 2.36}, {"text": "Bacteria and\neukaryotic cells may do", "start": 1235.67, "duration": 2.88}, {"text": "signaling slightly differently.", "start": 1238.55, "duration": 2.43}, {"text": "But they still do have an\nintegrated correlated system", "start": 1240.98, "duration": 5.91}, {"text": "that's responsible\nfor triggering", "start": 1246.89, "duration": 2.49}, {"text": "functions of the cell through\na series of discrete steps.", "start": 1249.38, "duration": 4.53}, {"text": "So protein signaling\ncan be dissected", "start": 1253.91, "duration": 2.61}, {"text": "into three basic steps,\nwhere you, first of all,", "start": 1256.52, "duration": 4.05}, {"text": "receive a signal.", "start": 1260.57, "duration": 0.84}, {"text": "And we're going to talk\nabout what that signal is.", "start": 1266.5, "duration": 3.43}, {"text": "What's the nature\nof that signal,", "start": 1269.93, "duration": 1.85}, {"text": "is it small molecule,\nlarge molecule?", "start": 1271.78, "duration": 1.9}, {"text": "Where is the signal?", "start": 1273.68, "duration": 1.56}, {"text": "Where does it act?", "start": 1275.24, "duration": 1.98}, {"text": "Then the next step is\nto transduce the signal.", "start": 1277.22, "duration": 2.895}, {"text": "And finally, you have an\noutcome, which is a response.", "start": 1286.0, "duration": 2.75}, {"text": "So we're going to talk about\neach of these components", "start": 1292.09, "duration": 2.66}, {"text": "in order to understand flux\nthrough cellular signaling", "start": 1294.75, "duration": 3.57}, {"text": "pathways, and how\nthey work to give you", "start": 1298.32, "duration": 2.61}, {"text": "a rapid response to\na necessary signal.", "start": 1300.93, "duration": 3.23}, {"text": "All right.", "start": 1304.16, "duration": 0.5}, {"text": "So in this cartoon, let's just,\nfor example, think about what", "start": 1304.66, "duration": 4.4}, {"text": "if we want to trigger\ncell division?", "start": 1309.06, "duration": 2.4}, {"text": "We might have a signal, which\nis the yellow molecule--", "start": 1311.46, "duration": 3.75}, {"text": "a small molecule,\nlarge molecule.", "start": 1315.21, "duration": 2.07}, {"text": "We'll get to that later.", "start": 1317.28, "duration": 1.65}, {"text": "There's a cell here, where\non the surface of the cell", "start": 1318.93, "duration": 3.87}, {"text": "is a receptor.", "start": 1322.8, "duration": 2.18}, {"text": "And that would be the entity\nthat receives the signal.", "start": 1324.98, "duration": 3.16}, {"text": "So in the first\nstep in the process,", "start": 1328.14, "duration": 3.01}, {"text": "there's a buildup of a\nconcentration of a signal.", "start": 1331.15, "duration": 2.9}, {"text": "And it occupies the\nreceptors on the surface", "start": 1334.05, "duration": 2.43}, {"text": "of the cell, and in some\ncases, inside the cell.", "start": 1336.48, "duration": 3.03}, {"text": "We'll talk about a\nbifurcation there.", "start": 1339.51, "duration": 2.64}, {"text": "But really, a lot of\ncellular signaling", "start": 1342.15, "duration": 3.06}, {"text": "is dominated by cells\ncoming-- by signals", "start": 1345.21, "duration": 3.24}, {"text": "coming from outside the cell.", "start": 1348.45, "duration": 2.43}, {"text": "What happens upon this binding\nevent is the transduction.", "start": 1350.88, "duration": 5.07}, {"text": "If you bind to something\non the outside of the cell,", "start": 1355.95, "duration": 3.12}, {"text": "as a consequence, you might\nhave a change on that structure.", "start": 1359.07, "duration": 3.6}, {"text": "If it crosses the\nmembrane, you might", "start": 1362.67, "duration": 2.19}, {"text": "have a change on that same\nmolecule structure that's", "start": 1364.86, "duration": 3.45}, {"text": "on the inside of the cell.", "start": 1368.31, "duration": 1.87}, {"text": "So that's why it's\ncalled transduction.", "start": 1370.18, "duration": 2.42}, {"text": "You're transducing\na soluble signal", "start": 1372.6, "duration": 2.25}, {"text": "from outside, binding that\nsignal to the cell surface", "start": 1374.85, "duration": 3.99}, {"text": "receptor.", "start": 1378.84, "duration": 0.87}, {"text": "And the cell surface receptor\nis responding in some way.", "start": 1379.71, "duration": 3.45}, {"text": "And there are two\nprinciple ways in which", "start": 1383.16, "duration": 2.85}, {"text": "we respond to\nextracellular signals,", "start": 1386.01, "duration": 2.46}, {"text": "and we'll cover them both.", "start": 1388.47, "duration": 2.49}, {"text": "The next event that\nmight happen is", "start": 1390.96, "duration": 2.04}, {"text": "through the change that\nhappens to the intracellular", "start": 1393.0, "duration": 3.12}, {"text": "component of the receptor.", "start": 1396.12, "duration": 1.98}, {"text": "There might be a\nchange, a binding event,", "start": 1398.1, "duration": 3.36}, {"text": "another step occur\nwithin the cell.", "start": 1401.46, "duration": 2.86}, {"text": "And as a function of\nthat, you get a response.", "start": 1404.32, "duration": 2.31}, {"text": "All right?", "start": 1406.63, "duration": 0.5}, {"text": "So it's really-- thinking\nit in these three components", "start": 1407.13, "duration": 4.17}, {"text": "is a good way to\nkind of dissect out", "start": 1411.3, "duration": 2.46}, {"text": "the beginnings of\nthe complication.", "start": 1413.76, "duration": 2.165}, {"text": "And then what\nwe'll be able to do", "start": 1415.925, "duration": 1.375}, {"text": "is really start to see what\nkinds of molecules come in?", "start": 1417.3, "duration": 4.5}, {"text": "How are they received?", "start": 1421.8, "duration": 1.59}, {"text": "How is the signal transduced?", "start": 1423.39, "duration": 2.04}, {"text": "And what's the ultimate outcome\nwith respect to a response?", "start": 1425.43, "duration": 4.56}, {"text": "Everyone OK with that?", "start": 1429.99, "duration": 1.85}, {"text": "All right.", "start": 1431.84, "duration": 0.55}, {"text": "Now this is what you\nhave to look forward to.", "start": 1432.39, "duration": 3.07}, {"text": "So we give you something\nwith three moving parts,", "start": 1435.46, "duration": 2.15}, {"text": "and suddenly we show\nyou something with sort", "start": 1437.61, "duration": 2.19}, {"text": "of, you know, 100 moving parts.", "start": 1439.8, "duration": 3.3}, {"text": "And cell biologists\nvery, very frequently", "start": 1443.1, "duration": 2.76}, {"text": "look at these maps\nof cells, where", "start": 1445.86, "duration": 2.51}, {"text": "what they're\nlooking at with each", "start": 1448.37, "duration": 1.75}, {"text": "of these sort of little\nacronyms or names, all of these", "start": 1450.12, "duration": 3.87}, {"text": "are proteins, where they\nhave been mapped out", "start": 1453.99, "duration": 3.63}, {"text": "through cell biology and\ncellular biochemistry", "start": 1457.62, "duration": 3.24}, {"text": "to be existing in certain\ncomponents of the cell.", "start": 1460.86, "duration": 3.29}, {"text": "And what has also been\nmapped out very frequently", "start": 1464.15, "duration": 2.83}, {"text": "is, who talks to who?", "start": 1466.98, "duration": 2.01}, {"text": "So the fact that JAK S\nmight interact with STAT 35", "start": 1468.99, "duration": 4.45}, {"text": "and so on.", "start": 1473.44, "duration": 0.83}, {"text": "So much of this was worked\nout through cell biology", "start": 1474.27, "duration": 3.57}, {"text": "and biochemistry,\nand also by genetics.", "start": 1477.84, "duration": 3.1}, {"text": "So Professor Martin\nhas talked to you", "start": 1480.94, "duration": 1.67}, {"text": "about identifying a player in\na complex system by genetics.", "start": 1482.61, "duration": 4.6}, {"text": "Let's say you have a cell\nthat fails to divide.", "start": 1487.21, "duration": 2.84}, {"text": "You might perhaps screen\nor divides unevenly,", "start": 1490.05, "duration": 3.96}, {"text": "or has some defect\nin cell division.", "start": 1494.01, "duration": 2.38}, {"text": "You might be able to pick\nout a particular player.", "start": 1496.39, "duration": 3.38}, {"text": "Now, the key thing I want to\npoint out to you with this cell", "start": 1499.77, "duration": 4.38}, {"text": "is what's on the\noutside of the cell", "start": 1504.15, "duration": 4.26}, {"text": "and runs across the\nmembrane, and might", "start": 1508.41, "duration": 2.37}, {"text": "have the chance,\nthe opportunity,", "start": 1510.78, "duration": 2.16}, {"text": "to have both an extracellular\nreceptor and an intracellular", "start": 1512.94, "duration": 4.08}, {"text": "function.", "start": 1517.02, "duration": 1.08}, {"text": "And those key proteins are\nthings like receptor tyrosine", "start": 1518.1, "duration": 4.17}, {"text": "kinases.", "start": 1522.27, "duration": 0.57}, {"text": "And we're going to talk about\nall of these in a moment.", "start": 1522.84, "duration": 3.39}, {"text": "G protein-coupled receptors,\nand various other cell surface", "start": 1526.23, "duration": 4.11}, {"text": "receptors--", "start": 1530.34, "duration": 0.93}, {"text": "so all of these--", "start": 1531.27, "duration": 1.29}, {"text": "anything that spans a\nmembrane has the opportunity", "start": 1532.56, "duration": 10.24}, {"text": "to be an important component\nof a signaling pathway.", "start": 1542.8, "duration": 3.165}, {"text": "Because what you're\nroutinely trying to do", "start": 1548.59, "duration": 2.37}, {"text": "is have your signal recognized\non the outside of the cell", "start": 1550.96, "duration": 4.29}, {"text": "by something that\nspans the membrane.", "start": 1555.25, "duration": 2.52}, {"text": "The signal will bind to that.", "start": 1557.77, "duration": 3.57}, {"text": "And then you will have an\nintracellular response.", "start": 1561.34, "duration": 2.76}, {"text": "So that's breaking it down.", "start": 1564.1, "duration": 1.24}, {"text": "That's why proteins\nthat are made", "start": 1565.34, "duration": 2.69}, {"text": "through the secretory\npathway that we talked", "start": 1568.03, "duration": 2.28}, {"text": "about in the last\nlecture, that go", "start": 1570.31, "duration": 2.13}, {"text": "through that\nendomembrane system,", "start": 1572.44, "duration": 2.34}, {"text": "and end up being parked\nin the plasma membrane", "start": 1574.78, "duration": 3.03}, {"text": "are so important.", "start": 1577.81, "duration": 1.74}, {"text": "Other proteins that actually get\nsecreted through that pathway", "start": 1579.55, "duration": 4.17}, {"text": "are also important.", "start": 1583.72, "duration": 0.91}, {"text": "What do you think they\nmay be important for?", "start": 1584.63, "duration": 2.67}, {"text": "Let's say you've made a\nprotein within the cell.", "start": 1587.3, "duration": 2.688}, {"text": "It goes through all the system.", "start": 1589.988, "duration": 1.292}, {"text": "It doesn't stay parked\nin the cell membrane.", "start": 1591.28, "duration": 3.09}, {"text": "It actually gets\nreleased from the cell.", "start": 1594.37, "duration": 2.03}, {"text": "What might that be doing?", "start": 1596.4, "duration": 2.81}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1599.21, "duration": 0.875}, {"text": "BARBARA IMPERIALI: Yeah.", "start": 1600.085, "duration": 1.0}, {"text": "Exactly.", "start": 1601.085, "duration": 0.515}, {"text": "So that endomembrane\nsystem that I", "start": 1601.6, "duration": 2.58}, {"text": "described to you, that pathway\nis great for making receivers.", "start": 1604.18, "duration": 4.17}, {"text": "And it's great for\nmaking signals.", "start": 1608.35, "duration": 2.13}, {"text": "And that's really what can sort\nof fuel the functions of cells.", "start": 1610.48, "duration": 4.97}, {"text": "OK.", "start": 1615.45, "duration": 0.67}, {"text": "So in systems biology, you\nmay have heard this term", "start": 1616.12, "duration": 3.12}, {"text": "quite frequently.", "start": 1619.24, "duration": 1.29}, {"text": "Systems biology is\nresearch that helps", "start": 1620.53, "duration": 4.26}, {"text": "us understand the underlying\nstructure of signaling", "start": 1624.79, "duration": 3.15}, {"text": "networks.", "start": 1627.94, "duration": 1.23}, {"text": "So a lot of people who\nhave common interests", "start": 1629.17, "duration": 2.25}, {"text": "in engineering, computational\nanalysis and cell biology,", "start": 1631.42, "duration": 4.5}, {"text": "might bring in\ndata to allow them", "start": 1635.92, "duration": 3.0}, {"text": "to make models of\ncellular systems,", "start": 1638.92, "duration": 2.52}, {"text": "to understand flux through\nsignaling pathways.", "start": 1641.44, "duration": 3.45}, {"text": "So they may make\nfundamental measurements", "start": 1644.89, "duration": 2.58}, {"text": "about the concentrations of\nsome components within the cell.", "start": 1647.47, "duration": 3.96}, {"text": "And then try to say, OK,\nI know based on everything", "start": 1651.43, "duration": 3.15}, {"text": "I've measured that this is\na dominant pathway for gene", "start": 1654.58, "duration": 4.77}, {"text": "regulation.", "start": 1659.35, "duration": 1.21}, {"text": "And I could control this\npathway by different--", "start": 1660.56, "duration": 3.77}, {"text": "by sort of different\ntypes of interactions.", "start": 1664.33, "duration": 3.81}, {"text": "In this cellular system, I also\nshow you another component,", "start": 1668.14, "duration": 3.49}, {"text": "which is the nucleus.", "start": 1671.63, "duration": 1.72}, {"text": "And when we discuss and\ndescribe specific cell", "start": 1673.35, "duration": 3.31}, {"text": "signaling networks,\nin some cases", "start": 1676.66, "duration": 2.61}, {"text": "the signaling\nnetwork may involve", "start": 1679.27, "duration": 2.76}, {"text": "receiving a signal, undergoing\na variety of changes", "start": 1682.03, "duration": 4.62}, {"text": "in the cytoplasm, but\nthen a change that", "start": 1686.65, "duration": 2.7}, {"text": "eventually results in a\nprotein going to the nucleus.", "start": 1689.35, "duration": 4.71}, {"text": "And oftentimes, those proteins\nthat run into the nucleus", "start": 1694.06, "duration": 3.71}, {"text": "are transcription factors that\nthen trigger DNA replication", "start": 1697.77, "duration": 5.5}, {"text": "or transcription.", "start": 1703.27, "duration": 1.56}, {"text": "And then promote activities.", "start": 1704.83, "duration": 2.35}, {"text": "So this is how you\nthink about it.", "start": 1707.18, "duration": 1.61}, {"text": "When you think of cellular\nsignaling, it's really about,", "start": 1708.79, "duration": 3.36}, {"text": "what does the signal need to do?", "start": 1712.15, "duration": 1.89}, {"text": "And what's the pathway\nthat I follow to get there?", "start": 1714.04, "duration": 5.05}, {"text": "So all of those are\nmembrane proteins.", "start": 1719.09, "duration": 1.74}, {"text": "So now let's look at\nthe canonical aspects", "start": 1720.83, "duration": 3.48}, {"text": "of signal transduction.", "start": 1724.31, "duration": 1.93}, {"text": "So the first-- and I'm going to\nrely on these little cartoons.", "start": 1726.24, "duration": 3.08}, {"text": "But I want, both in this\nlecture and the next,", "start": 1729.32, "duration": 4.11}, {"text": "to really show you where these\nrecur in so many systems.", "start": 1733.43, "duration": 3.77}, {"text": "So to that purpose, I want to\ntalk about the characteristics.", "start": 1737.2, "duration": 4.95}, {"text": "So the first critical\ncharacteristic", "start": 1748.29, "duration": 3.27}, {"text": "is a signal and\nit's specificity.", "start": 1751.56, "duration": 2.88}, {"text": "So a signal will\nbe something that", "start": 1766.15, "duration": 2.0}, {"text": "comes from outside of the cell.", "start": 1768.15, "duration": 1.59}, {"text": "It could be a hormone that's\nproduced in the hypothalamus", "start": 1769.74, "duration": 3.06}, {"text": "and sent to another organ.", "start": 1772.8, "duration": 1.77}, {"text": "But the most important\nthing about the signal", "start": 1774.57, "duration": 3.14}, {"text": "is that that signal, which\nbinds to a receptor in a cell", "start": 1777.71, "duration": 4.48}, {"text": "membrane, is specific for\na particular receptor,", "start": 1782.19, "duration": 5.0}, {"text": "and the different signal won't\nblind to the same receptor.", "start": 1787.19, "duration": 2.89}, {"text": "You have to have faithful\nsignal specificity", "start": 1790.08, "duration": 3.87}, {"text": "to trigger the right function.", "start": 1793.95, "duration": 1.81}, {"text": "So if it's a hormone, it's got\nto be the hormone that you want", "start": 1795.76, "duration": 3.77}, {"text": "to trigger the receptor, not a\nrelated but different-looking", "start": 1799.53, "duration": 3.18}, {"text": "structure.", "start": 1802.71, "duration": 0.93}, {"text": "If it's a small\nprotein, you want", "start": 1803.64, "duration": 1.77}, {"text": "it to be the exact one that\nbinds with high specificity", "start": 1805.41, "duration": 4.187}, {"text": "to a receptor.", "start": 1809.597, "duration": 0.583}, {"text": "So what that means is if\nsomething is binding--", "start": 1816.89, "duration": 4.59}, {"text": "if a small molecule is\nbinding to a protein", "start": 1821.48, "duration": 2.37}, {"text": "on the surface of a cell\nwith high specificity", "start": 1823.85, "duration": 3.3}, {"text": "and high affinity, it means that\neven at a low concentration,", "start": 1827.15, "duration": 4.2}, {"text": "it will make that\nbinding contact.", "start": 1831.35, "duration": 2.79}, {"text": "But all the other small\nmolecules that are around", "start": 1834.14, "duration": 3.75}, {"text": "won't crosstalk into that\ntriggering that interaction.", "start": 1837.89, "duration": 3.33}, {"text": "So we have high specificity,\nand we gain that specificity", "start": 1841.22, "duration": 5.07}, {"text": "through macromolecular\ninteractions,", "start": 1846.29, "duration": 1.89}, {"text": "just like the ones we talked\nabout in biochemistry.", "start": 1848.18, "duration": 3.27}, {"text": "So if we have a small\nmolecule or a protein bind", "start": 1851.45, "duration": 2.52}, {"text": "to the receptor, it's making\nall those hydrogen bonding,", "start": 1853.97, "duration": 4.71}, {"text": "electrostatic, noncovalent\ntypes of interactions", "start": 1858.68, "duration": 3.24}, {"text": "with high specificity, so that a\nlow concentration of the signal", "start": 1861.92, "duration": 5.82}, {"text": "molecule is efficient for\nbinding to the receptor", "start": 1867.74, "duration": 6.69}, {"text": "to trigger the function.", "start": 1874.43, "duration": 1.98}, {"text": "The next characteristic\nis amplification.", "start": 1876.41, "duration": 5.81}, {"text": "Now let's put some lines\nbetween these guys.", "start": 1888.052, "duration": 2.948}, {"text": "Now, with all the\nsignaling pathways", "start": 1895.45, "duration": 2.07}, {"text": "that you're going\nto see, we're going", "start": 1897.52, "duration": 2.04}, {"text": "to be looking where in a\npathway you get amplification.", "start": 1899.56, "duration": 4.17}, {"text": "Very commonly, you\nmight have a response", "start": 1903.73, "duration": 2.67}, {"text": "that's just the result of\na single molecule binding", "start": 1906.4, "duration": 4.34}, {"text": "a single receptor.", "start": 1910.74, "duration": 1.65}, {"text": "But at the end of the day, you\nmight want a large response.", "start": 1912.39, "duration": 2.91}, {"text": "You might want to\nmake a lot of ATP.", "start": 1915.3, "duration": 2.34}, {"text": "Or you might want to\nreplicate all of the genome.", "start": 1917.64, "duration": 3.78}, {"text": "So you need some kind of\namplification where in a sense", "start": 1921.42, "duration": 2.97}, {"text": "you're turning up the\nvolume on your signal.", "start": 1924.39, "duration": 2.52}, {"text": "And you need to do that rapidly.", "start": 1926.91, "duration": 2.01}, {"text": "So frequently in\nsignaling pathways,", "start": 1928.92, "duration": 2.88}, {"text": "you go through a\ncascade of reactions", "start": 1931.8, "duration": 3.24}, {"text": "where the signal might\naffect an enzyme.", "start": 1935.04, "duration": 2.85}, {"text": "But once you make\nthat enzyme active,", "start": 1937.89, "duration": 2.4}, {"text": "it might work on many, many\ncopies of another enzyme.", "start": 1940.29, "duration": 3.3}, {"text": "And then each of those may\nwork on even more copies.", "start": 1943.59, "duration": 3.07}, {"text": "So that's what I mean\nby amplification,", "start": 1946.66, "duration": 2.27}, {"text": "where at some stage\nyou've generated", "start": 1948.93, "duration": 1.74}, {"text": "a molecule that can result\nin the cascade of a reaction.", "start": 1950.67, "duration": 5.71}, {"text": "So we often refer to\nthese as cascades.", "start": 1956.38, "duration": 5.61}, {"text": "So if you're\nSpanish-speaking, cascada.", "start": 1961.99, "duration": 2.46}, {"text": "You want to think about a\nwaterfall coming from just", "start": 1964.45, "duration": 2.82}, {"text": "a single molecule of water.", "start": 1967.27, "duration": 1.89}, {"text": "You're getting a large\nincrease in your signal", "start": 1969.16, "duration": 3.24}, {"text": "as a result of amplification.", "start": 1972.4, "duration": 2.34}, {"text": "The next feature or\ncharacteristic of signaling", "start": 1974.74, "duration": 3.99}, {"text": "is feedback.", "start": 1978.73, "duration": 0.55}, {"text": "At the end of the day,\nif you're signaling,", "start": 1986.29, "duration": 4.47}, {"text": "I got to make some ATP.", "start": 1990.76, "duration": 1.47}, {"text": "I got to run out of the woods.", "start": 1992.23, "duration": 1.98}, {"text": "I'm getting chased.", "start": 1994.21, "duration": 1.2}, {"text": "At a certain stage,\nyou need to stop", "start": 1995.41, "duration": 1.95}, {"text": "all of the process occurring.", "start": 1997.36, "duration": 2.19}, {"text": "So feedback is just a\nnegative feedback loop", "start": 1999.55, "duration": 3.84}, {"text": "that might slow down\nsome of those steps that", "start": 2003.39, "duration": 4.41}, {"text": "are involved in amplification.", "start": 2007.8, "duration": 1.62}, {"text": "So for a pathway, you only\nwant the pathway turned on", "start": 2009.42, "duration": 3.87}, {"text": "for a prescribed amount of time.", "start": 2013.29, "duration": 2.1}, {"text": "And then you want\nto be able to say,", "start": 2015.39, "duration": 2.43}, {"text": "I'm done with that\nwhole pathway.", "start": 2017.82, "duration": 1.73}, {"text": "I don't need to keep churning\nthrough all those enzymes.", "start": 2019.55, "duration": 3.29}, {"text": "It's time to stop that.", "start": 2022.84, "duration": 1.13}, {"text": "And that usually occurs\nthrough negative feedback.", "start": 2023.97, "duration": 3.3}, {"text": "And remember, we talked\nabout negative feedback", "start": 2027.27, "duration": 2.58}, {"text": "when we were talking about\nenzyme catalyzed pathways.", "start": 2029.85, "duration": 3.06}, {"text": "So feedback is very\noften some kind", "start": 2032.91, "duration": 2.94}, {"text": "of negative feedback,\nwhich suppresses", "start": 2035.85, "duration": 6.33}, {"text": "a series of\ntransformations, perhaps", "start": 2042.18, "duration": 2.58}, {"text": "through a product of those\ntransformations acting", "start": 2044.76, "duration": 3.18}, {"text": "as an inhibitor\non an early step.", "start": 2047.94, "duration": 2.43}, {"text": "And then finally,\nthe other component", "start": 2050.37, "duration": 2.88}, {"text": "of a signaling network--", "start": 2053.25, "duration": 1.6}, {"text": "if you think of\nsignaling networks", "start": 2054.85, "duration": 2.0}, {"text": "as electronic structures,\nyou have integration.", "start": 2056.85, "duration": 3.67}, {"text": "So that's the last\ncharacteristic feature.", "start": 2060.52, "duration": 2.975}, {"text": "And let me go back\nto that big circuit", "start": 2071.804, "duration": 7.026}, {"text": "diagram quickly to show you\nan example of integration.", "start": 2078.83, "duration": 4.329}, {"text": "So if you look at this\nsignaling pathway,", "start": 2083.159, "duration": 2.33}, {"text": "all these signaling\nsteps are not single.", "start": 2085.489, "duration": 2.851}, {"text": "You just have a signal\ncome in, and you end up,", "start": 2088.34, "duration": 2.92}, {"text": "for example, in the nucleus.", "start": 2091.26, "duration": 1.729}, {"text": "But rather, other components\nmay have crosstalk", "start": 2092.989, "duration": 3.511}, {"text": "within one pathway,\nand start out", "start": 2096.5, "duration": 2.64}, {"text": "either amplifying\nor turning down", "start": 2099.14, "duration": 2.37}, {"text": "a particular signaling pathway.", "start": 2101.51, "duration": 2.01}, {"text": "So these are networks.", "start": 2103.52, "duration": 1.26}, {"text": "They're not pathways.", "start": 2104.78, "duration": 1.83}, {"text": "They're networks that\ninteract and communicate,", "start": 2106.61, "duration": 3.3}, {"text": "all to amplify signals\nor turn down signals.", "start": 2109.91, "duration": 2.82}, {"text": "So integration is an\nimportant part of signaling,", "start": 2112.73, "duration": 4.14}, {"text": "because you're often dealing\nwith the integrated function", "start": 2116.87, "duration": 3.63}, {"text": "of a number of pathways to\nget a particular response.", "start": 2120.5, "duration": 4.56}, {"text": "And that actually ends up being\none of the situations where", "start": 2125.06, "duration": 3.39}, {"text": "sometimes a\nparticular enzyme may", "start": 2128.45, "duration": 2.55}, {"text": "look like a perfect target\nfor a therapeutic agent.", "start": 2131.0, "duration": 4.51}, {"text": "But if you don't take into\naccount the integration steps,", "start": 2135.51, "duration": 3.32}, {"text": "you may be trying\nto deal with a--", "start": 2138.83, "duration": 1.71}, {"text": "you may think you're dealing\nwith a single pathway,", "start": 2140.54, "duration": 2.61}, {"text": "but you're, rather,\ndealing with crosstalk", "start": 2143.15, "duration": 2.37}, {"text": "with a lot of other pathways.", "start": 2145.52, "duration": 2.22}, {"text": "And what often\nhappens in a cell is", "start": 2147.74, "duration": 2.16}, {"text": "there's compensation\nfrom other pathways.", "start": 2149.9, "duration": 3.01}, {"text": "Is everybody following?", "start": 2152.91, "duration": 1.66}, {"text": "Any questions here about this?", "start": 2154.57, "duration": 2.81}, {"text": "So what I want\nyou to think about", "start": 2157.38, "duration": 1.94}, {"text": "is that it's just amazing\nwhat is orchestrated", "start": 2159.32, "duration": 4.08}, {"text": "to have even the simplest\nfunctions in the cell,", "start": 2163.4, "duration": 2.95}, {"text": "how many interacting\ncomponents there may be.", "start": 2166.35, "duration": 4.16}, {"text": "Specificity, amplification,\nfeedback, and integration--", "start": 2170.51, "duration": 5.37}, {"text": "all right, so let's talk\nbriefly about types of signals", "start": 2175.88, "duration": 3.42}, {"text": "and how we name them, where\nthey come from, in order", "start": 2179.3, "duration": 3.0}, {"text": "to make sure we're all on\nthe same page with respect", "start": 2182.3, "duration": 2.67}, {"text": "to the language that's used.", "start": 2184.97, "duration": 2.58}, {"text": "So now, signals may take\ndifferent molecular forms.", "start": 2187.55, "duration": 11.21}, {"text": "They may be small molecules,\nfor example, an amino acid", "start": 2198.76, "duration": 8.38}, {"text": "or a phospholipid--", "start": 2207.14, "duration": 2.85}, {"text": "just something little.", "start": 2209.99, "duration": 1.38}, {"text": "Alternatively, they\nmay be proteins.", "start": 2211.37, "duration": 2.51}, {"text": "They may be carbohydrates.", "start": 2217.24, "duration": 3.82}, {"text": "They might take\ndifferent forms in terms", "start": 2221.06, "duration": 2.46}, {"text": "of their molecular structure.", "start": 2223.52, "duration": 1.92}, {"text": "But we tend to describe signals\nby where they come from.", "start": 2225.44, "duration": 4.213}, {"text": "So what I've shown\nyou here is a picture", "start": 2229.653, "duration": 1.667}, {"text": "from the book that\njust describes how", "start": 2231.32, "duration": 2.19}, {"text": "we refer to certain signals.", "start": 2233.51, "duration": 3.69}, {"text": "So there are four\ndifferent terms--", "start": 2237.2, "duration": 2.145}, {"text": "autocrine, juxtacrine-- and I'm\ngoing to just give you a little", "start": 2242.78, "duration": 14.14}, {"text": "hint to how to\nremember these terms--", "start": 2256.92, "duration": 4.65}, {"text": "paracrine, endocrine.", "start": 2261.57, "duration": 1.65}, {"text": "OK.", "start": 2267.38, "duration": 1.0}, {"text": "So these don't tell you\nanything about the molecule.", "start": 2268.38, "duration": 4.56}, {"text": "They tell you about\nwhere it's come from.", "start": 2272.94, "duration": 2.82}, {"text": "So an autocrine\nsignal is a signal", "start": 2275.76, "duration": 2.88}, {"text": "that may come from a cell,\nbut it's signaling to itself.", "start": 2278.64, "duration": 4.8}, {"text": "So it may produce a\ncomponent that's released.", "start": 2283.44, "duration": 4.47}, {"text": "And so it's producing this\nthrough a secretory pathway.", "start": 2287.91, "duration": 3.6}, {"text": "It's a release, and it stays\nin the vicinity of the cell.", "start": 2291.51, "duration": 3.34}, {"text": "So the self is self-signaling.", "start": 2294.85, "duration": 2.33}, {"text": "So whenever you\nsee something auto,", "start": 2297.18, "duration": 4.86}, {"text": "you just want to\nsay, oh, that means", "start": 2302.04, "duration": 1.92}, {"text": "it's coming from the same\ncell where the signal occurs.", "start": 2303.96, "duration": 3.94}, {"text": "Let's move to the next\none, which is paracrine.", "start": 2307.9, "duration": 3.89}, {"text": "I'm going to talk about jux--", "start": 2311.79, "duration": 1.59}, {"text": "and that's usually\nfrom a nearby cell,", "start": 2313.38, "duration": 2.64}, {"text": "not a cell that's in contact--", "start": 2316.02, "duration": 2.22}, {"text": "definitely a different cell.", "start": 2318.24, "duration": 1.39}, {"text": "So paracrine is-- we\nwould always call nearby.", "start": 2319.63, "duration": 5.83}, {"text": "And endocrine is completely\nfrom somewhere else, so", "start": 2325.46, "duration": 3.28}, {"text": "perhaps coming through\nthe circulatory system.", "start": 2328.74, "duration": 3.42}, {"text": "One cell may release\nan endocrine signal.", "start": 2332.16, "duration": 4.17}, {"text": "It may weave its way\nthrough the vascular system,", "start": 2336.33, "duration": 3.6}, {"text": "and then target a cell.", "start": 2339.93, "duration": 2.93}, {"text": "So endocrine is always\nfrom a distance.", "start": 2342.86, "duration": 2.125}, {"text": "And juxtacrine is the only\none that's a little odd.", "start": 2348.64, "duration": 2.88}, {"text": "It's really from\ncells that actually", "start": 2351.52, "duration": 2.88}, {"text": "are in contact with each other.", "start": 2354.4, "duration": 2.29}, {"text": "So it's not self-signaling\nwithin a cell.", "start": 2356.69, "duration": 3.15}, {"text": "It's not a cell that's\nnearby but pretty close.", "start": 2359.84, "duration": 3.89}, {"text": "It's actually physically\nmaking a contact.", "start": 2363.73, "duration": 2.86}, {"text": "And so that's the last\nterminology there.", "start": 2366.59, "duration": 2.69}, {"text": "So hopefully, I can get this\ncalcium wave to show you.", "start": 2369.28, "duration": 3.42}, {"text": "This is just a video of\njuxtacrine to signaling.", "start": 2372.7, "duration": 7.61}, {"text": "I just want you to sort\nof keep an eye on things.", "start": 2380.31, "duration": 2.33}, {"text": "It's usually a cell.", "start": 2382.64, "duration": 1.59}, {"text": "What you're observing\nhere is a dye", "start": 2384.23, "duration": 2.73}, {"text": "that lights up in the\npresence of calcium flux.", "start": 2386.96, "duration": 2.85}, {"text": "It's called Fura-2.", "start": 2389.81, "duration": 1.8}, {"text": "And so when you stare at\nthese for long enough, what", "start": 2391.61, "duration": 4.17}, {"text": "you can notice is that\nwhen one signal will often", "start": 2395.78, "duration": 4.02}, {"text": "come from an adjacent\ncell right near it--", "start": 2399.8, "duration": 3.12}, {"text": "so there are long prostheses.", "start": 2402.92, "duration": 1.62}, {"text": "You're not looking\nat the entire cell,", "start": 2404.54, "duration": 2.46}, {"text": "but they're definitely--\nfor example, this little duo", "start": 2407.0, "duration": 2.28}, {"text": "down here, they keep\nsignaling to each other.", "start": 2409.28, "duration": 2.61}, {"text": "And that's just a juxtacrine\nsignaling, because the cells", "start": 2411.89, "duration": 2.79}, {"text": "are in the contact.", "start": 2414.68, "duration": 1.86}, {"text": "So that just shows you\nthe difference there.", "start": 2416.54, "duration": 2.19}, {"text": "If it was autocrine, you just\nhave a single cell responding.", "start": 2418.73, "duration": 3.84}, {"text": "If it's paracrine, they would\nbe at more of a distance", "start": 2422.57, "duration": 2.61}, {"text": "to each other.", "start": 2425.18, "duration": 1.8}, {"text": "I hope that imagery-- this is\nfrom a website in the Smith Lab", "start": 2426.98, "duration": 6.75}, {"text": "at Stanford.", "start": 2433.73, "duration": 2.97}, {"text": "OK.", "start": 2436.7, "duration": 0.75}, {"text": "And then the last thing I\nwant to give you an example,", "start": 2437.45, "duration": 3.3}, {"text": "there are many, many\nhormones in the body that", "start": 2440.75, "duration": 2.85}, {"text": "undergo endocrine signaling,\nand so one example I thought", "start": 2443.6, "duration": 5.58}, {"text": "I would tell you about,\nyou all know that insulin", "start": 2449.18, "duration": 2.49}, {"text": "is made in the pancreas.", "start": 2451.67, "duration": 2.49}, {"text": "It's an important hormone for\nregulating glucose levels.", "start": 2454.16, "duration": 4.14}, {"text": "And it's actually-- functions\nat the muscle level.", "start": 2458.3, "duration": 4.35}, {"text": "So insulin is an example\nof an endocrine signal,", "start": 2462.65, "duration": 3.69}, {"text": "because it travels a\ndistance from where", "start": 2466.34, "duration": 2.49}, {"text": "it's made in the body to where\nit functions in the body.", "start": 2468.83, "duration": 4.335}, {"text": "All right.", "start": 2473.165, "duration": 1.455}, {"text": "Now-- so we've talked\nabout the types of signals.", "start": 2474.62, "duration": 4.9}, {"text": "Let's now move to the\ntypes of receptors.", "start": 2479.52, "duration": 3.57}, {"text": "Now, we cover both\nthe intracellular", "start": 2488.66, "duration": 11.5}, {"text": "and the cell surface receptors.", "start": 2500.16, "duration": 2.04}, {"text": "But we really will focus a lot\non the cell surface receptors.", "start": 2508.2, "duration": 3.93}, {"text": "I just want to give you a\nclue that not all signaling is", "start": 2512.13, "duration": 3.57}, {"text": "cell surface.", "start": 2515.7, "duration": 0.91}, {"text": "So what I've shown\nyou here is a cartoon", "start": 2516.61, "duration": 2.42}, {"text": "where you see signaling,\nwhere a signal", "start": 2519.03, "duration": 2.82}, {"text": "comes from outside the cell.", "start": 2521.85, "duration": 1.98}, {"text": "It goes into the cell\nand triggers a change.", "start": 2523.83, "duration": 3.0}, {"text": "And then the\nmajority of the time", "start": 2526.83, "duration": 2.29}, {"text": "we'll talk about\nthese receptors that", "start": 2529.12, "duration": 1.79}, {"text": "are in the plasma membrane.", "start": 2530.91, "duration": 2.34}, {"text": "And they have an outside\nplace where the signal binds,", "start": 2533.25, "duration": 3.75}, {"text": "and they trigger\na response inside.", "start": 2537.0, "duration": 2.49}, {"text": "And it's only very\nspecific signals", "start": 2539.49, "duration": 2.7}, {"text": "that are able to\nsignal intracellularly,", "start": 2542.19, "duration": 4.8}, {"text": "that is, to cross the membrane\nto get inside the cytoplasm", "start": 2546.99, "duration": 4.5}, {"text": "to do the triggering.", "start": 2551.49, "duration": 1.08}, {"text": "What kinds of molecules can\ncross the membrane easily?", "start": 2552.57, "duration": 3.105}, {"text": "We talked about\nthat before, when", "start": 2558.51, "duration": 1.65}, {"text": "we talked about getting\nacross that barrier.", "start": 2560.16, "duration": 3.275}, {"text": "Yeah?", "start": 2566.15, "duration": 1.47}, {"text": "Nonpolar.", "start": 2567.62, "duration": 0.84}, {"text": "OK.", "start": 2568.46, "duration": 0.6}, {"text": "So you can look at a-- you\ncan stare at a molecule,", "start": 2569.06, "duration": 2.89}, {"text": "and if it's very\npolar or pretty large,", "start": 2571.95, "duration": 3.12}, {"text": "it's not going to be able\nto sneak through a membrane.", "start": 2575.07, "duration": 2.48}, {"text": "So something like\na steroid molecule,", "start": 2577.55, "duration": 3.03}, {"text": "a large, greasy\nmolecule, can definitely", "start": 2580.58, "duration": 2.79}, {"text": "make that transition.", "start": 2583.37, "duration": 1.5}, {"text": "And so those are the only types\nof signals that we can really", "start": 2584.87, "duration": 2.94}, {"text": "do inside the cell, because\nthey can get across the cell.", "start": 2587.81, "duration": 4.78}, {"text": "Many, many other signals\nhave to go through this--", "start": 2592.59, "duration": 3.5}, {"text": "bind to the outside of a\ncell, and transduce a signal", "start": 2596.09, "duration": 2.92}, {"text": "to the inside of the cell.", "start": 2599.01, "duration": 1.7}, {"text": "So one very typical signal that\ncan bind to an intracellular", "start": 2600.71, "duration": 7.35}, {"text": "receptor is a steroid.", "start": 2608.06, "duration": 2.22}, {"text": "So remember when I talked to you\nabout these lipidic molecules,", "start": 2610.28, "duration": 4.53}, {"text": "things like testosterone\nand cortisol.", "start": 2614.81, "duration": 2.67}, {"text": "These are very\nhydrophobic molecules.", "start": 2617.48, "duration": 2.91}, {"text": "So they literally can cross\nfrom the outside of the cell", "start": 2620.39, "duration": 3.72}, {"text": "without a transporter.", "start": 2624.11, "duration": 1.87}, {"text": "So for example, the\nhormone cortisol.", "start": 2625.98, "duration": 2.41}, {"text": "And when that\nfunctions, it just--", "start": 2628.39, "duration": 2.67}, {"text": "an amount of it\nbecomes available,", "start": 2631.06, "duration": 2.66}, {"text": "for example, in the bloodstream.", "start": 2633.72, "duration": 1.73}, {"text": "It crosses the\ncell, and it binds", "start": 2635.45, "duration": 2.52}, {"text": "to an intracellular receptor.", "start": 2637.97, "duration": 3.13}, {"text": "Once it binds to that\nintracellular receptor,", "start": 2641.1, "duration": 2.99}, {"text": "this disengages a different\nkind of chaperone protein", "start": 2644.09, "duration": 4.05}, {"text": "that's keeping it stable.", "start": 2648.14, "duration": 1.89}, {"text": "Once it's found, it can then\ngo into the nucleus and trigger", "start": 2650.03, "duration": 4.89}, {"text": "transcription.", "start": 2654.92, "duration": 1.3}, {"text": "So this is the one example\nof an intracellular receptor", "start": 2656.22, "duration": 3.71}, {"text": "that we'll talk about.", "start": 2659.93, "duration": 1.267}, {"text": "I just wanted to\nshow you a little bit", "start": 2661.197, "duration": 1.583}, {"text": "about the steroid receptors.", "start": 2662.78, "duration": 2.08}, {"text": "These are molecules\nthat are very--", "start": 2664.86, "duration": 3.8}, {"text": "these are macromolecules,\nproteins that are very--", "start": 2668.66, "duration": 4.99}, {"text": "quite a complex structure.", "start": 2673.65, "duration": 1.58}, {"text": "But they can literally-- and\nI'll show you the picture", "start": 2675.23, "duration": 2.25}, {"text": "at the beginning of\nthe talk next time--", "start": 2677.48, "duration": 2.85}, {"text": "they can literally\nengulf these proteins.", "start": 2680.33, "duration": 3.6}, {"text": "So once the steroid\nis bound to that,", "start": 2683.93, "duration": 2.16}, {"text": "it completely changes shape.", "start": 2686.09, "duration": 2.1}, {"text": "And that's what enables\nthe change for it", "start": 2688.19, "duration": 2.31}, {"text": "to be triggered and\nsent to the nucleus.", "start": 2690.5, "duration": 4.27}, {"text": "Now, the key types of receptors\nthat we'll focus on, though,", "start": 2694.77, "duration": 4.04}, {"text": "are the cell surface receptors.", "start": 2698.81, "duration": 2.25}, {"text": "And there are\nthree basic classes", "start": 2701.06, "duration": 2.37}, {"text": "of molecules that occur in\nthe plasma membrane that", "start": 2703.43, "duration": 3.48}, {"text": "are critical for\ncellular signaling.", "start": 2706.91, "duration": 2.22}, {"text": "They are the G\nprotein-coupled receptors,", "start": 2709.13, "duration": 3.36}, {"text": "the receptor tyrosine\nkinases, and then", "start": 2712.49, "duration": 2.52}, {"text": "you will talk in the lecture\n22 about ion channels,", "start": 2715.01, "duration": 4.71}, {"text": "and how they perform\na receptor function.", "start": 2719.72, "duration": 3.0}, {"text": "So the membrane\nproteins, first of all,", "start": 2722.72, "duration": 2.29}, {"text": "I want to underscore\ntheir importance.", "start": 2725.01, "duration": 2.38}, {"text": "50%-- they comprise\n50% of drug targets,", "start": 2727.39, "duration": 5.92}, {"text": "the receptor tyrosine kinases\nand the G protein-coupled", "start": 2733.31, "duration": 3.54}, {"text": "receptors.", "start": 2736.85, "duration": 1.23}, {"text": "The G protein-coupled receptors\nhave this 7 transmembrane helix", "start": 2738.08, "duration": 6.27}, {"text": "structure, which\nspans a membrane.", "start": 2744.35, "duration": 3.82}, {"text": "This would be the\noutside of the cell,", "start": 2748.17, "duration": 5.53}, {"text": "and the inside of the\ncells-- so there's", "start": 2753.7, "duration": 2.73}, {"text": "signals going across there.", "start": 2756.43, "duration": 1.89}, {"text": "The receptor tyrosine kinases\nare another important type", "start": 2758.32, "duration": 3.96}, {"text": "of receptor.", "start": 2762.28, "duration": 1.05}, {"text": "They are dimeric proteins\nthat in the presence", "start": 2763.33, "duration": 2.85}, {"text": "of a ligand dimerize, and then\ncause intracellular signaling.", "start": 2766.18, "duration": 4.14}, {"text": "Once again, they cross\nthe plasma membrane", "start": 2770.32, "duration": 3.48}, {"text": "from the outside to the cytosol.", "start": 2773.8, "duration": 2.1}, {"text": "And then lastly, there are\nthe ion channels, which also", "start": 2775.9, "duration": 3.51}, {"text": "may cross the plasma membrane.", "start": 2779.41, "duration": 1.95}, {"text": "And when you think about\nthese classes of proteins,", "start": 2781.36, "duration": 3.01}, {"text": "there's a tremendous amount\nto be learned with respect", "start": 2784.37, "duration": 2.69}, {"text": "to their functions.", "start": 2787.06, "duration": 1.38}, {"text": "And they are so\nimportant to understand", "start": 2788.44, "duration": 2.16}, {"text": "their physical\nfunctions in the body,", "start": 2790.6, "duration": 3.03}, {"text": "because they really represent\nthe place, the nexus, where", "start": 2793.63, "duration": 4.29}, {"text": "signaling happens in the cell.", "start": 2797.92, "duration": 2.11}, {"text": "So I want to briefly show\nyou a picture of a GPCR.", "start": 2800.03, "duration": 4.49}, {"text": "It's a 7 transmembrane\nhelix structure.", "start": 2804.52, "duration": 3.66}, {"text": "You can see it here.", "start": 2808.18, "duration": 2.07}, {"text": "There are about 30% of\nmodern drugs actually target", "start": 2810.25, "duration": 3.93}, {"text": "the GPCRs.", "start": 2814.18, "duration": 1.53}, {"text": "And here, I'm just going to show\nyou the structure of a GPCR.", "start": 2815.71, "duration": 3.78}, {"text": "Those are the 7\ntransmembrane helices.", "start": 2819.49, "duration": 3.0}, {"text": "If you stretch them out, that's\nabout the width of a membrane.", "start": 2822.49, "duration": 3.81}, {"text": "That's typical of\na signal that would", "start": 2826.3, "duration": 2.1}, {"text": "bind to that kind of receptor.", "start": 2828.4, "duration": 3.22}, {"text": "This is a chemokine.", "start": 2831.62, "duration": 1.71}, {"text": "It's a small protein receptor.", "start": 2833.33, "duration": 2.03}, {"text": "So you can see that\nstructure and how", "start": 2835.36, "duration": 2.16}, {"text": "it would go from one side of\nthe membrane to the other.", "start": 2837.52, "duration": 4.95}, {"text": "In it's bound\nstate, the chemokine", "start": 2842.47, "duration": 4.74}, {"text": "binds to the 7\ntransmembrane helix receptor", "start": 2847.21, "duration": 4.65}, {"text": "through kind of a\nclamping action.", "start": 2851.86, "duration": 1.74}, {"text": "The magenta is the chemokine.", "start": 2853.6, "duration": 2.01}, {"text": "The blue and the green space\nfilled parts are actually", "start": 2855.61, "duration": 5.1}, {"text": "what holds the chemokine.", "start": 2860.71, "duration": 3.48}, {"text": "And if you look at it where\nthe membrane would be,", "start": 2864.19, "duration": 2.43}, {"text": "you can see how\nyou can transduce", "start": 2866.62, "duration": 2.16}, {"text": "a signal from one side of\nthe membrane to the other,", "start": 2868.78, "duration": 3.54}, {"text": "by the binding of\nthe magenta molecule", "start": 2872.32, "duration": 2.64}, {"text": "to the outside of the cell, to\nthose loops outside the cell.", "start": 2874.96, "duration": 4.68}, {"text": "That would have a\nsignificant perturbation", "start": 2879.64, "duration": 2.58}, {"text": "to the biology and chemistry of\nwhat's going on on the inside.", "start": 2882.22, "duration": 4.47}, {"text": "So next class, we'll\ntalk about pathways", "start": 2886.69, "duration": 2.85}, {"text": "that are initiated by these\nG protein-coupled receptors,", "start": 2889.54, "duration": 4.17}, {"text": "and what that terminology means.", "start": 2893.71, "duration": 3.1}, {"text": "OK.", "start": 2896.81, "duration": 1.55}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.895}, {"text": "[RUSTLING]", "start": 2.395, "duration": 1.416}, {"text": "[CLICKING]", "start": 4.311, "duration": 1.437}, {"text": "NORVIN RICHARDS:\nAll right, so one", "start": 11.03, "duration": 4.052}, {"text": "of the things we've\nlearned in this class", "start": 15.082, "duration": 1.708}, {"text": "is that language is complicated.", "start": 16.79, "duration": 1.8}, {"text": "At least, maybe you\nalready knew that,", "start": 18.59, "duration": 2.28}, {"text": "but we've spent a\nsemester looking", "start": 20.87, "duration": 2.19}, {"text": "at various ways in which\nlanguage is more complicated", "start": 23.06, "duration": 3.248}, {"text": "than you might have-- than you\nmight have realized before you", "start": 26.308, "duration": 2.542}, {"text": "came in here and in\nways that maybe you", "start": 28.85, "duration": 1.625}, {"text": "hadn't thought about much.", "start": 30.475, "duration": 2.557}, {"text": "These are a few of\nthe things we've", "start": 33.032, "duration": 1.458}, {"text": "talked about, various special\nproperties of language,", "start": 34.49, "duration": 3.3}, {"text": "fancy things that language does\nthat we've spent the semester", "start": 37.79, "duration": 3.51}, {"text": "puzzling over.", "start": 41.3, "duration": 1.99}, {"text": "And if language has all of\nthese complicated properties,", "start": 43.29, "duration": 4.65}, {"text": "the recurring question, which\nI've raised a couple of times,", "start": 47.94, "duration": 3.24}, {"text": "is how do we acquire this?", "start": 51.18, "duration": 3.09}, {"text": "We're going to talk seriously\nabout language acquisition", "start": 54.27, "duration": 2.58}, {"text": "sometime next week.", "start": 56.85, "duration": 2.35}, {"text": "But a provisional answer to\nthis that people have offered", "start": 59.2, "duration": 4.31}, {"text": "and taken seriously is that\nat least some of this stuff", "start": 63.51, "duration": 3.81}, {"text": "is innate, in the sense that--", "start": 67.32, "duration": 2.19}, {"text": "I think I've said\nit this way before--", "start": 69.51, "duration": 1.71}, {"text": "part of being a\nhuman being is having", "start": 71.22, "duration": 2.25}, {"text": "the kind of mind that constructs\nlanguage in certain ways,", "start": 73.47, "duration": 2.73}, {"text": "but not others.", "start": 76.2, "duration": 0.82}, {"text": "So if we ask questions\nlike, why do languages", "start": 77.02, "duration": 3.62}, {"text": "have binary branching?", "start": 80.64, "duration": 1.47}, {"text": "Why not ternary branching?", "start": 82.11, "duration": 2.01}, {"text": "The answer is, well,\nwe're not equipped", "start": 84.12, "duration": 1.68}, {"text": "with ternary branching.", "start": 85.8, "duration": 1.32}, {"text": "The human brain does it this\nway and not some other way.", "start": 87.12, "duration": 2.73}, {"text": "And that leads to lots of\nother interesting questions,", "start": 89.85, "duration": 3.3}, {"text": "like why?", "start": 93.15, "duration": 0.69}, {"text": "What is it about human minds\nthat are set up this way?", "start": 93.84, "duration": 5.07}, {"text": "Can we get that to follow\nfrom anything else, any deeper", "start": 98.91, "duration": 4.2}, {"text": "conditions?", "start": 103.11, "duration": 0.9}, {"text": "But that's a claim\nthat's out there,", "start": 104.01, "duration": 1.9}, {"text": "which we have referred\nto a couple of times.", "start": 105.91, "duration": 3.98}, {"text": "We don't start\nwith a blank slate.", "start": 109.89, "duration": 1.517}, {"text": "We start with a rich body\nof linguistic knowledge,", "start": 111.407, "duration": 2.083}, {"text": "and learning our actual\nlanguage is a matter", "start": 113.49, "duration": 1.833}, {"text": "of filling in some details.", "start": 115.323, "duration": 1.767}, {"text": "But it's very clear that\nnot everything is innate.", "start": 119.88, "duration": 4.53}, {"text": "For example, here's a cartoon.", "start": 124.41, "duration": 2.4}, {"text": "It has a cat in it.", "start": 126.81, "duration": 2.19}, {"text": "And the fact that animal\nis pronounced \"cat\"", "start": 129.0, "duration": 3.99}, {"text": "is an accident.", "start": 132.99, "duration": 1.86}, {"text": "It could have been\nsomething else.", "start": 134.85, "duration": 2.76}, {"text": "So Saussure famously pointed\nthis out and called it", "start": 137.61, "duration": 2.91}, {"text": "the arbitrariness\nof the sign, that,", "start": 140.52, "duration": 2.79}, {"text": "for the most part, what\nword the language has", "start": 143.31, "duration": 4.47}, {"text": "for a given thing has to do\nwith the phonetic inventory", "start": 147.78, "duration": 3.522}, {"text": "of the language and other\nproperties of the language,", "start": 151.302, "duration": 2.208}, {"text": "but the English word\n\"cat\" refers to cats,", "start": 153.51, "duration": 3.552}, {"text": "but that's kind of a\nhistorical accident.", "start": 157.062, "duration": 1.708}, {"text": "It could have referred to\ndogs or mice or anything else.", "start": 158.77, "duration": 2.87}, {"text": "Just happens to refer to cats.", "start": 161.64, "duration": 1.98}, {"text": "And the fact is that kids, if\nyou're ever around small kids,", "start": 166.25, "duration": 2.85}, {"text": "you'll hear them trying out\ntheories about what words mean", "start": 169.1, "duration": 6.15}, {"text": "and being wrong.", "start": 175.25, "duration": 2.49}, {"text": "I was once around a small\nchild who used the word", "start": 177.74, "duration": 2.43}, {"text": "\"moon\" for every light.", "start": 180.17, "duration": 2.61}, {"text": "So the hall light was a moon,\nand the moon was a moon,", "start": 182.78, "duration": 3.75}, {"text": "and the sun was a moon.", "start": 186.53, "duration": 1.29}, {"text": "Everything was a moon.", "start": 187.82, "duration": 3.09}, {"text": "And sometimes these mistakes\nsurvive to adulthood.", "start": 190.91, "duration": 5.77}, {"text": "So take the word \"livid.\"", "start": 196.68, "duration": 2.828}, {"text": "What do you think\nof the word \"livid\"", "start": 199.508, "duration": 1.542}, {"text": "as meaning, if you're a\nnative speaker of English", "start": 201.05, "duration": 2.88}, {"text": "or even if you're not?", "start": 203.93, "duration": 2.08}, {"text": "Very angry.", "start": 206.01, "duration": 1.14}, {"text": "That's what it often means.", "start": 207.15, "duration": 2.25}, {"text": "It's originally a color term.", "start": 209.4, "duration": 3.51}, {"text": "It meant white.", "start": 212.91, "duration": 1.89}, {"text": "Because there was an idea that\nwhen people got really angry,", "start": 214.8, "duration": 2.67}, {"text": "their faces turned white.", "start": 217.47, "duration": 1.26}, {"text": "They were white with rage.", "start": 218.73, "duration": 2.67}, {"text": "You sometimes see\nthe expression,", "start": 221.4, "duration": 2.22}, {"text": "his face went livid.", "start": 223.62, "duration": 0.87}, {"text": "When I was a kid, I\nthought that meant", "start": 224.49, "duration": 1.583}, {"text": "his face was red because\nI think of people", "start": 226.073, "duration": 2.137}, {"text": "who are angry as being red.", "start": 228.21, "duration": 2.73}, {"text": "But originally, that's\nwhat the word meant.", "start": 230.94, "duration": 2.015}, {"text": "It meant white.", "start": 232.955, "duration": 0.625}, {"text": "And then yes, I think for most\nof us, now it means angry.", "start": 233.58, "duration": 4.65}, {"text": "Or I used to believe in\nthe verb \"misle\" until--", "start": 238.23, "duration": 3.302}, {"text": "I'm embarrassed to say when I\nstopped believing in the word", "start": 241.532, "duration": 2.458}, {"text": "\"misle.\"", "start": 243.99, "duration": 0.63}, {"text": "I was an adult. Did anybody\nelse have the verb \"misle\"?", "start": 244.62, "duration": 3.818}, {"text": "Is there anybody who\nright now is thinking,", "start": 248.438, "duration": 1.792}, {"text": "what are you talking about?", "start": 250.23, "duration": 1.125}, {"text": "Of course, there's\na verb \"misle.\"", "start": 251.355, "duration": 1.845}, {"text": "I believed in the verb\n\"misle\" because I had read it", "start": 253.2, "duration": 2.31}, {"text": "in expressions like this.", "start": 255.51, "duration": 2.61}, {"text": "I had been \"misle-d\"\nwas what I believed.", "start": 258.12, "duration": 5.45}, {"text": "It wasn't-- I think--", "start": 263.57, "duration": 2.11}, {"text": "I don't believe I actually\nused the word in conversation", "start": 265.68, "duration": 3.42}, {"text": "and had somebody correct me.", "start": 269.1, "duration": 1.17}, {"text": "I think this was, like, I\nwas in my 20s or something", "start": 270.27, "duration": 3.12}, {"text": "when I sat down and was\nlike, wait a minute.", "start": 273.39, "duration": 4.18}, {"text": "So stuff like this happens.", "start": 277.57, "duration": 1.28}, {"text": "And sometimes these mistakes\ncatch on, and people--", "start": 281.73, "duration": 3.12}, {"text": "and sort of survive\ninto adulthood.", "start": 284.85, "duration": 1.48}, {"text": "As I say, I was in\nmy 20s, and I still", "start": 286.33, "duration": 1.73}, {"text": "believed that there\nwas a verb \"misle.\"", "start": 288.06, "duration": 2.22}, {"text": "If I were a king\nor something, then", "start": 290.28, "duration": 4.47}, {"text": "if my subjects\ntried to convince me", "start": 294.75, "duration": 1.475}, {"text": "that there wasn't\na verb \"misle,\"", "start": 296.225, "duration": 1.375}, {"text": "I would just have them beheaded.", "start": 297.6, "duration": 1.333}, {"text": "And before we knew\nit, there would", "start": 298.933, "duration": 1.427}, {"text": "be a verb \"misle\" in English.", "start": 300.36, "duration": 4.83}, {"text": "Or if I were somebody else\nwho was hugely, hugely", "start": 305.19, "duration": 3.84}, {"text": "influential, like a linguistics\nprofessor or something.", "start": 309.03, "duration": 4.2}, {"text": "Wait a minute.", "start": 313.23, "duration": 1.95}, {"text": "There are also various\nforms of semantic drift", "start": 315.18, "duration": 2.07}, {"text": "that languages\nundergo, where words", "start": 317.25, "duration": 1.8}, {"text": "change what they refer to.", "start": 319.05, "duration": 3.9}, {"text": "\"Livid\" is maybe\nan example of that.", "start": 322.95, "duration": 1.57}, {"text": "It used to mean white,\nand now it means angry.", "start": 324.52, "duration": 2.03}, {"text": "Here's another example.", "start": 326.55, "duration": 1.21}, {"text": "The modern English word \"bead\"\noriginally meant a prayer.", "start": 327.76, "duration": 4.94}, {"text": "So there's still-- there's\na German verb \"beten.\"", "start": 332.7, "duration": 2.4}, {"text": "That's the verb \"to pray.\"", "start": 335.1, "duration": 1.11}, {"text": "It's related to the\nEnglish word \"bead\"--", "start": 336.21, "duration": 2.76}, {"text": "in Old English, the ancestor of\nthe word \"bead\" meant a prayer.", "start": 338.97, "duration": 4.5}, {"text": "The switch from prayer to bead,\nyou know, small, round object,", "start": 343.47, "duration": 5.19}, {"text": "came via rosaries,\nwhich are devices", "start": 348.66, "duration": 2.73}, {"text": "for counting prayers in\ncertain religious traditions,", "start": 351.39, "duration": 3.7}, {"text": "including Catholicism\nand others.", "start": 355.09, "duration": 2.468}, {"text": "So if you're in a\nreligious tradition", "start": 357.558, "duration": 1.542}, {"text": "where it's important to say\na certain number of prayers,", "start": 359.1, "duration": 2.16}, {"text": "you have this little device\nthat has beads on it.", "start": 361.26, "duration": 2.042}, {"text": "And you're counting the\nprayers using this device.", "start": 363.302, "duration": 3.203}, {"text": "So if you're asked,\nwhat are you doing?", "start": 366.505, "duration": 1.625}, {"text": "Well, you're counting prayers.", "start": 368.13, "duration": 1.14}, {"text": "But there's another\nsense in which", "start": 369.27, "duration": 0.93}, {"text": "you're counting, well, beads,\nlike small, round objects", "start": 370.2, "duration": 2.73}, {"text": "on a wire.", "start": 372.93, "duration": 1.06}, {"text": "And this is thought to be how\nthe word shifted its meaning.", "start": 373.99, "duration": 5.95}, {"text": "Or there are other things like\nthis, words widen or narrow", "start": 379.94, "duration": 5.19}, {"text": "their meanings.", "start": 385.13, "duration": 0.99}, {"text": "In Old English,\n\"steorfan\" meant \"to die.\"", "start": 386.12, "duration": 3.03}, {"text": "It's cognate with\nGerman \"sterben.\"", "start": 389.15, "duration": 2.16}, {"text": "It's the ancestor of\nmodern English \"starve,\"", "start": 391.31, "duration": 2.79}, {"text": "which went through a stage of--", "start": 394.1, "duration": 4.35}, {"text": "sort of originally meant \"die.\"", "start": 398.45, "duration": 1.35}, {"text": "It went through a stage\nof meaning specifically", "start": 399.8, "duration": 1.958}, {"text": "\"die from hunger.\"", "start": 401.758, "duration": 1.342}, {"text": "And today, I think of it\nas basically just meaning,", "start": 403.1, "duration": 3.15}, {"text": "be very hungry.", "start": 406.25, "duration": 1.86}, {"text": "So you can still\nsay \"He starved,\"", "start": 408.11, "duration": 1.95}, {"text": "and have that mean\nhe died, I guess.", "start": 410.06, "duration": 3.15}, {"text": "But I'm a lot more likely\nto use it in an expression", "start": 413.21, "duration": 3.39}, {"text": "like \"I'm starving.", "start": 416.6, "duration": 0.85}, {"text": "Let's have lunch.\"", "start": 417.45, "duration": 2.33}, {"text": "Maybe when I say\nthat, I literally", "start": 419.78, "duration": 1.65}, {"text": "mean I'm dying of\nhunger, or figuratively", "start": 421.43, "duration": 1.98}, {"text": "I mean I'm dying of hunger.", "start": 423.41, "duration": 3.03}, {"text": "Or there's a French word\n\"negre\" which means a Black man.", "start": 426.44, "duration": 4.56}, {"text": "It has a descendant in\nmodern Haitian Creole,", "start": 431.0, "duration": 2.7}, {"text": "\"neg,\" which just means man.", "start": 433.7, "duration": 3.0}, {"text": "So the meaning of\nthat has broadened", "start": 436.7, "duration": 2.85}, {"text": "for reasons that are not\nall that hard to understand.", "start": 439.55, "duration": 2.44}, {"text": "So Haitian Creole speakers,\nwhen they refer to men,", "start": 441.99, "duration": 2.798}, {"text": "they're often\nreferring to Black men,", "start": 444.788, "duration": 1.542}, {"text": "since Haitian Creole\nspeakers tend to be Black.", "start": 446.33, "duration": 5.13}, {"text": "So yeah, in Haitian Creole, I am\na \"neg,\" although in French, I", "start": 451.46, "duration": 3.6}, {"text": "am not a \"negre.\"", "start": 455.06, "duration": 2.7}, {"text": "Or similar\nspecialization of a term,", "start": 457.76, "duration": 4.11}, {"text": "there's the old English\nword \"chniht,\" which", "start": 461.87, "duration": 3.18}, {"text": "meant a servant, and has a\ncognate in modern German,", "start": 465.05, "duration": 3.57}, {"text": "\"knecht,\" which means something\nlike a boy or a servant.", "start": 468.62, "duration": 5.22}, {"text": "It's the ancestor of the\nmodern English word \"knight,\"", "start": 473.84, "duration": 2.79}, {"text": "who was originally specifically\na servant of the king.", "start": 476.63, "duration": 3.902}, {"text": "The reason that the\nEnglish word \"knight\"", "start": 480.532, "duration": 1.708}, {"text": "has all of those\nunpronounced letters in it", "start": 482.24, "duration": 3.51}, {"text": "is that those are there in an\nattempt to pronounce the word", "start": 485.75, "duration": 2.61}, {"text": "or spell the word as\nit was once pronounced.", "start": 488.36, "duration": 3.475}, {"text": "We spell that with\na K at the beginning", "start": 491.835, "duration": 1.625}, {"text": "because it used to be\npronounced \"cniht.\"", "start": 493.46, "duration": 1.74}, {"text": "There used to be a K there.", "start": 495.2, "duration": 1.89}, {"text": "And then English got out of\nthe habit of pronouncing K", "start": 497.09, "duration": 3.69}, {"text": "before N, and so we have\nwords like \"knight\" and \"knee\"", "start": 500.78, "duration": 2.49}, {"text": "where the K is still there\nas a memorial to the times", "start": 503.27, "duration": 5.97}, {"text": "when there was a stop\nthere at the beginning.", "start": 509.24, "duration": 1.98}, {"text": "Same deal with the\nG-H, which spelled", "start": 511.22, "duration": 1.74}, {"text": "a [HISSES IN BACK OF THROAT]\nsound in the middle.", "start": 512.96, "duration": 3.329}, {"text": "Or this is one of my favorites.", "start": 516.289, "duration": 2.791}, {"text": "The old English\nword \"housewife,\"", "start": 519.08, "duration": 1.8}, {"text": "\"huswif,\" which is the ancestor\nof the modern English word", "start": 520.88, "duration": 2.82}, {"text": "\"hussy.\"", "start": 523.7, "duration": 1.17}, {"text": "That's undergone some semantic\nchange over the years,", "start": 524.87, "duration": 3.78}, {"text": "as it's gone down\nthrough the years.", "start": 528.65, "duration": 3.0}, {"text": "There's a disturbing\ntendency for words", "start": 531.65, "duration": 4.56}, {"text": "that refer to women to undergo\npejoration, that is, to become", "start": 536.21, "duration": 5.4}, {"text": "worse in their meaning.", "start": 541.61, "duration": 1.455}, {"text": "There's possibly a\ncorresponding tendency.", "start": 545.63, "duration": 4.17}, {"text": "If you look at\nlots of languages,", "start": 549.8, "duration": 2.49}, {"text": "there are lots of languages in\nwhich the modern word for \"man\"", "start": 552.29, "duration": 3.87}, {"text": "is straightforwardly related\nto earlier words for \"man,\"", "start": 556.16, "duration": 3.24}, {"text": "but in which the\nword for \"woman\"", "start": 559.4, "duration": 1.65}, {"text": "has been replaced by some\nother word for \"woman.\"", "start": 561.05, "duration": 4.08}, {"text": "And I assume it's related\nto this tendency, that words", "start": 565.13, "duration": 2.94}, {"text": "for women tend to become\ninsulting over time", "start": 568.07, "duration": 3.273}, {"text": "in lots of different\ncultures, and so you need", "start": 571.343, "duration": 1.917}, {"text": "to replace them with something.", "start": 573.26, "duration": 2.04}, {"text": "Maybe relatedly, it's not\nuncommon for modern words", "start": 575.3, "duration": 2.52}, {"text": "for women to originally refer\nto queens or noblewomen.", "start": 577.82, "duration": 3.92}, {"text": "That's true, for example,\nboth in German and in Zulu.", "start": 581.74, "duration": 4.075}, {"text": "The modern Zulu word for\n\"woman\" used to mean \"queen.\"", "start": 585.815, "duration": 2.25}, {"text": "It replaced an older word for\na woman that became insulting.", "start": 588.065, "duration": 5.205}, {"text": "Disturbing cross-linguistically\nfairly common tendency.", "start": 593.27, "duration": 5.01}, {"text": "Or-- this is my actual\nfavorite in this list", "start": 598.28, "duration": 2.7}, {"text": "because I wonder\nabout the confusion", "start": 600.98, "duration": 3.3}, {"text": "that it must have\ncaused-- so there's", "start": 604.28, "duration": 1.56}, {"text": "a Proto-Austronesian\nword reconstructed", "start": 605.84, "duration": 2.58}, {"text": "as \"wada,\" which was an\nexistential construction.", "start": 608.42, "duration": 2.95}, {"text": "It meant \"there is.\"", "start": 611.37, "duration": 1.4}, {"text": "It has a nice,\nstraightforward descendant", "start": 612.77, "duration": 2.4}, {"text": "in Tagalog, \"wala,\" which\nmeans \"there is not.\"", "start": 615.17, "duration": 3.0}, {"text": "I don't know how that happened.", "start": 618.17, "duration": 1.68}, {"text": "There's an Arabic\nword, \"wala,\" which", "start": 619.85, "duration": 3.45}, {"text": "means something like \"no.\"", "start": 623.3, "duration": 1.98}, {"text": "If you want to say\nthere are no books,", "start": 625.28, "duration": 1.68}, {"text": "you use \"wala\" to say that.", "start": 626.96, "duration": 1.53}, {"text": "And it's possible that Tagalog\ngot influenced by Arabic.", "start": 628.49, "duration": 2.86}, {"text": "It was in contact with Arabic.", "start": 631.35, "duration": 1.25}, {"text": "It has Arabic borrowings.", "start": 632.6, "duration": 1.857}, {"text": "So maybe that's got\nsomething to do with it.", "start": 634.457, "duration": 1.833}, {"text": "But yes, there's presumably\na fairly weird period", "start": 636.29, "duration": 3.42}, {"text": "in the middle\nthere, where people", "start": 639.71, "duration": 2.16}, {"text": "were having existential crises.", "start": 641.87, "duration": 3.71}, {"text": "I just used a star.", "start": 645.58, "duration": 2.04}, {"text": "You guys are used, by\nnow, to seeing stars", "start": 647.62, "duration": 3.87}, {"text": "on sentences that\nare ungrammatical,", "start": 651.49, "duration": 2.25}, {"text": "and that is how stars\nare used in syntax.", "start": 653.74, "duration": 3.54}, {"text": "But when people are doing\nhistorical linguistics,", "start": 657.28, "duration": 2.34}, {"text": "stars mean something else.", "start": 659.62, "duration": 1.95}, {"text": "They mean, this is a word\nthat we don't actually", "start": 661.57, "duration": 3.24}, {"text": "see in any documents,\nor you can't hear it.", "start": 664.81, "duration": 4.21}, {"text": "It's our theory about\nan ancestral form.", "start": 669.02, "duration": 3.29}, {"text": "So Proto-Austronesian\nis the ancestor", "start": 672.31, "duration": 3.3}, {"text": "of a bunch of languages\nof the Pacific, mostly.", "start": 675.61, "duration": 4.44}, {"text": "So the languages of the\nPhilippines and Indonesia", "start": 680.05, "duration": 2.4}, {"text": "and New Zealand and Hawaii.", "start": 682.45, "duration": 2.49}, {"text": "It's this gigantic geographic\narea that they went over.", "start": 684.94, "duration": 3.24}, {"text": "Plus some who got lost and\nended up in Madagascar.", "start": 688.18, "duration": 3.45}, {"text": "There's an Austronesian language\nover there, too, Malagasy.", "start": 691.63, "duration": 4.65}, {"text": "The ancestor of all\nof those languages,", "start": 696.28, "duration": 2.16}, {"text": "it's called Proto-Austronesian.", "start": 698.44, "duration": 1.56}, {"text": "And that form that I just\nshowed you for \"there is\"", "start": 700.0, "duration": 2.88}, {"text": "is a reconstruction of what\nthey think that word would have", "start": 702.88, "duration": 2.61}, {"text": "been in Proto-Austronesian.", "start": 705.49, "duration": 1.14}, {"text": "We haven't met any\nProto-Austronesians.", "start": 706.63, "duration": 1.77}, {"text": "They didn't leave\nus any documents.", "start": 708.4, "duration": 1.8}, {"text": "It's a hypothesized underlying\nform, given all the forms", "start": 710.2, "duration": 3.27}, {"text": "that we can see.", "start": 713.47, "duration": 1.2}, {"text": "That's what star means in\nhistorical linguistics.", "start": 714.67, "duration": 2.19}, {"text": "So various kinds\nof semantic drift.", "start": 719.42, "duration": 2.71}, {"text": "Recuttings-- so the example of\n\"misle\" is an example of that.", "start": 722.13, "duration": 3.86}, {"text": "I saw the word\n\"misled,\" and I thought", "start": 725.99, "duration": 2.4}, {"text": "that it was the past tense\nor the participle of a verb,", "start": 728.39, "duration": 3.69}, {"text": "\"to misle.\"", "start": 732.08, "duration": 2.25}, {"text": "There are other lots\nof examples of this", "start": 734.33, "duration": 2.13}, {"text": "with the indefinite\narticle in English.", "start": 736.46, "duration": 2.94}, {"text": "So the indefinite article\nin English has two forms.", "start": 739.4, "duration": 3.27}, {"text": "It's \"an\" before a vowel, and\nit's \"a\" before a consonant.", "start": 742.67, "duration": 5.32}, {"text": "So we say \"an apple,\"\nbut we say \"a banana.\"", "start": 747.99, "duration": 5.285}, {"text": "Yes, good.", "start": 756.74, "duration": 0.72}, {"text": "I always worry about when\nto stop spelling banana.", "start": 757.46, "duration": 2.32}, {"text": "It's not easy.", "start": 759.78, "duration": 2.84}, {"text": "A consequence of that is that\nif you hear a sequence like--", "start": 762.62, "duration": 2.82}, {"text": "this is one of the examples\nfor which this happened--", "start": 765.44, "duration": 3.21}, {"text": "you hear a sequence\nlike \"a nickname,\"", "start": 768.65, "duration": 3.18}, {"text": "it's sort of hard to know\nwhether you're hearing", "start": 771.83, "duration": 2.13}, {"text": "\"a nickname\" or \"an ickname.\"", "start": 773.96, "duration": 3.03}, {"text": "So \"nickname\" was originally\n\"ickname,\" \"ekename.\"", "start": 776.99, "duration": 3.75}, {"text": "\"Eke\" is an old word for \"also.\"", "start": 780.74, "duration": 4.38}, {"text": "It has a cognate in\nGerman, which is \"auch.\"", "start": 785.12, "duration": 3.81}, {"text": "It shows up in The\nCanterbury Tales,", "start": 788.93, "duration": 4.843}, {"text": "in the prologue to\nThe Canterbury Tales.", "start": 793.773, "duration": 1.667}, {"text": "If you ever read the prologue\nto The Canterbury Tales,", "start": 795.44, "duration": 2.808}, {"text": "Chaucer says something\nlike \"and Zephyrus", "start": 798.248, "duration": 1.708}, {"text": "eke, with his swete brethe\"--", "start": 799.956, "duration": 1.544}, {"text": "\"And Zephyr also with\nhis sweet breath.\"", "start": 801.5, "duration": 2.04}, {"text": "So that's what that \"eke\" is.", "start": 803.54, "duration": 1.59}, {"text": "It's an \"also name,\" that is, a\nname that you have in addition", "start": 805.13, "duration": 3.03}, {"text": "to your other name.", "start": 808.16, "duration": 2.58}, {"text": "If ordinary sound\nchanges had taken place,", "start": 810.74, "duration": 3.69}, {"text": "the word for \"nickname\"\nwould be \"ickname,\"", "start": 814.43, "duration": 2.64}, {"text": "but it's not, because\nof confusion about where", "start": 817.07, "duration": 2.37}, {"text": "the N went, basically.", "start": 819.44, "duration": 1.61}, {"text": "There are a bunch of words\nlike this in English.", "start": 821.05, "duration": 3.1}, {"text": "This is another example.", "start": 824.15, "duration": 3.31}, {"text": "Middle English had a word\n\"pease\" which was a mass noun.", "start": 827.46, "duration": 3.74}, {"text": "By mass noun, I mean it referred\nto a certain kind of stuff that", "start": 831.2, "duration": 4.44}, {"text": "didn't have a plural.", "start": 835.64, "duration": 0.96}, {"text": "We have a bunch of words\nlike this, words that", "start": 836.6, "duration": 4.65}, {"text": "don't ordinarily have plurals.", "start": 841.25, "duration": 2.01}, {"text": "Words like \"water\" or\n\"ketchup\" or \"flour,\"", "start": 843.26, "duration": 6.51}, {"text": "where if you have\na barrel of flour,", "start": 849.77, "duration": 4.98}, {"text": "you don't talk about it as a\nbarrel of 16 million \"flours.\"", "start": 854.75, "duration": 3.528}, {"text": "That's not what\nyou're talking about.", "start": 858.278, "duration": 1.542}, {"text": "You're talking about\na substance, right?", "start": 859.82, "duration": 1.667}, {"text": "A stuff.", "start": 861.487, "duration": 1.633}, {"text": "Same deal with ketchup or water.", "start": 863.12, "duration": 1.92}, {"text": "You can talk about\ndifferent kinds of flours", "start": 865.04, "duration": 3.09}, {"text": "being different flours.", "start": 868.13, "duration": 1.62}, {"text": "I guess if you were really,\nreally into ketchup,", "start": 869.75, "duration": 2.28}, {"text": "you could do the same\nthing with ketchup, right?", "start": 872.03, "duration": 2.0}, {"text": "I'm fond of the ketchups that\nyou get in Southeast Asia,", "start": 874.03, "duration": 3.91}, {"text": "or whatever.", "start": 877.94, "duration": 2.7}, {"text": "\"Pease\" used to be a\nmass noun like that.", "start": 880.64, "duration": 2.49}, {"text": "It was just a name for this\ngreen stuff that consists", "start": 883.13, "duration": 3.42}, {"text": "of lots of little round things.", "start": 886.55, "duration": 2.58}, {"text": "But because this\nparticular mass, well,", "start": 889.13, "duration": 3.66}, {"text": "can be subdivided into these\nlittle individual, round,", "start": 892.79, "duration": 2.58}, {"text": "green things, and because\nthe word \"pease\" happened", "start": 895.37, "duration": 2.79}, {"text": "to end in a Z sound so\nit looked like a plural,", "start": 898.16, "duration": 2.67}, {"text": "it got reanalyzed as a plural.", "start": 900.83, "duration": 1.77}, {"text": "And so they made up\na singular \"pea,\"", "start": 902.6, "duration": 2.7}, {"text": "which didn't exist before.", "start": 905.3, "duration": 1.868}, {"text": "English has done a lot\nof things like this,", "start": 907.168, "duration": 1.792}, {"text": "sometimes called\nback- formation,", "start": 908.96, "duration": 1.86}, {"text": "where you take a word that looks\npolymorphemic, although it's", "start": 910.82, "duration": 3.36}, {"text": "not, and pretend that it is.", "start": 914.18, "duration": 2.215}, {"text": "Another one, which I don't\nthink I have anywhere in here,", "start": 916.395, "duration": 2.375}, {"text": "is we had for a long\ntime a word, \"beggar.\"", "start": 918.77, "duration": 2.46}, {"text": "That noun was in the\nlanguage for a long time.", "start": 923.75, "duration": 2.73}, {"text": "It ends in a sequence\nthat's pronounced schwa R--", "start": 926.48, "duration": 5.07}, {"text": "I've lost my ability to\nwrite the IPA symbol for R--", "start": 931.55, "duration": 4.02}, {"text": "which sounds like our\nagentive suffix, the \"-er\"", "start": 935.57, "duration": 2.638}, {"text": "that's at the end of \"teacher.\"", "start": 938.208, "duration": 1.292}, {"text": "And so people made\nup a verb, \"beg.\"", "start": 939.5, "duration": 2.43}, {"text": "But it wasn't originally\na polymorphemic word.", "start": 941.93, "duration": 4.02}, {"text": "That's one reason it's not\nspelled \"begger,\" which", "start": 945.95, "duration": 6.387}, {"text": "is what you would have expected\nif you were adding the teacher", "start": 952.337, "duration": 2.583}, {"text": "suffix to \"beg.\"", "start": 954.92, "duration": 2.042}, {"text": "It's spelled like this because,\nwell, this is not the \"-er\"", "start": 956.962, "duration": 2.458}, {"text": "suffix.", "start": 959.42, "duration": 0.5}, {"text": "It's just pronounced like it.", "start": 959.92, "duration": 1.66}, {"text": "So the verb \"to beg\"\ngot back-formed.", "start": 961.58, "duration": 6.12}, {"text": "Another similar\nkind of recutting.", "start": 967.7, "duration": 1.8}, {"text": "Here are three\nOld English words.", "start": 969.5, "duration": 3.27}, {"text": "The positive form,\n\"near,\" which is \"neah.\"", "start": 972.77, "duration": 4.27}, {"text": "Then that has a\ncomparative form,", "start": 977.04, "duration": 1.49}, {"text": "\"nearer,\" which was \"nearra.\"", "start": 978.53, "duration": 1.62}, {"text": "And then there was\na superlative form,", "start": 980.15, "duration": 2.04}, {"text": "\"nearest,\" which was \"neahsta.\"", "start": 982.19, "duration": 2.13}, {"text": "All three of those words have\ndescendants in modern English.", "start": 984.32, "duration": 3.48}, {"text": "\"neah\" is the ancestor of\n\"nigh,\" which we sort of still", "start": 987.8, "duration": 3.75}, {"text": "have in modern English, as a\nsort of archaic-sounding word", "start": 991.55, "duration": 2.61}, {"text": "for \"near.\"", "start": 994.16, "duration": 1.47}, {"text": "Don't use it so much anymore.", "start": 995.63, "duration": 2.01}, {"text": "The comparative, the word\nthat meant \"nearer,\" turned", "start": 997.64, "duration": 2.7}, {"text": "into \"near\" in modern English.", "start": 1000.34, "duration": 2.73}, {"text": "And \"neahsta,\" the\nsuperlative, the nearest,", "start": 1003.07, "duration": 3.12}, {"text": "is the ancestor of the\nmodern English word \"next.\"", "start": 1006.19, "duration": 3.42}, {"text": "Regular sound change applied\nto \"nearra\" to give you \"near\"", "start": 1009.61, "duration": 3.66}, {"text": "and obscured the fact\nthat it was a comparative.", "start": 1013.27, "duration": 3.72}, {"text": "So comparatives normally\nend in a schwa-R sequence.", "start": 1016.99, "duration": 3.36}, {"text": "And because of\nregular sound change,", "start": 1020.35, "duration": 1.77}, {"text": "basically you were adding\nthe comparative suffix", "start": 1022.12, "duration": 2.873}, {"text": "to something that\nended in a vowel", "start": 1024.993, "duration": 1.417}, {"text": "and then an H. The\nconsequence was", "start": 1026.41, "duration": 1.975}, {"text": "that you couldn't hear anymore\nthat it was a comparative,", "start": 1028.385, "duration": 2.375}, {"text": "so it got reanalyzed\nas something", "start": 1030.76, "duration": 1.605}, {"text": "that was not a comparative.", "start": 1032.365, "duration": 1.125}, {"text": "So it's now our word for \"near.\"", "start": 1033.49, "duration": 1.74}, {"text": "It's more or less replaced\n\"nigh\" as our word for \"near.\"", "start": 1035.23, "duration": 3.18}, {"text": "And then we built new\ncomparatives and superlatives", "start": 1038.41, "duration": 4.29}, {"text": "on that.", "start": 1042.7, "duration": 0.54}, {"text": "It was originally comparative.", "start": 1043.24, "duration": 1.807}, {"text": "All kinds of entertaining\nthings happen to languages,", "start": 1047.68, "duration": 4.05}, {"text": "sometimes as a\nmatter of somebody", "start": 1051.73, "duration": 3.42}, {"text": "like me goes through life a\nfairly long time believing", "start": 1055.15, "duration": 3.87}, {"text": "in a verb, \"to misle.\"", "start": 1059.02, "duration": 0.96}, {"text": "And if I had a more forceful\npersonality and more", "start": 1059.98, "duration": 2.64}, {"text": "political clout,\nthen I might have", "start": 1062.62, "duration": 2.52}, {"text": "been able to force\nother people to believe", "start": 1065.14, "duration": 1.8}, {"text": "in the verb \"to misle\" as well.", "start": 1066.94, "duration": 3.66}, {"text": "Some of this presumably\nalso is a matter", "start": 1070.6, "duration": 2.82}, {"text": "of not misunderstandings,\nbut just people deliberately", "start": 1073.42, "duration": 3.27}, {"text": "being weird.", "start": 1076.69, "duration": 0.73}, {"text": "I mean, if you think of things\nthat people do with language", "start": 1077.42, "duration": 2.51}, {"text": "today, they have done this\nall their lives, pretending", "start": 1079.93, "duration": 3.06}, {"text": "that words mean things other\nthan what they mean just", "start": 1082.99, "duration": 2.55}, {"text": "for fun, as a way of\nhaving a good time", "start": 1085.54, "duration": 2.64}, {"text": "or confusing your\nparents or whatever else.", "start": 1088.18, "duration": 3.27}, {"text": "The other big kind of\nsound change, though,", "start": 1091.45, "duration": 2.1}, {"text": "that I mainly want to\ntalk about today are", "start": 1093.55, "duration": 1.75}, {"text": "what are called sound changes.", "start": 1095.3, "duration": 2.54}, {"text": "Here are some numbers from\nvarious languages of Europe.", "start": 1097.84, "duration": 5.317}, {"text": "Are they all Europe?", "start": 1103.157, "duration": 0.833}, {"text": "Yeah, mostly.", "start": 1103.99, "duration": 0.87}, {"text": "Yeah.", "start": 1104.86, "duration": 0.62}, {"text": "Yeah.", "start": 1105.48, "duration": 0.76}, {"text": "Europe, widely-- well, Sanskrit.", "start": 1106.24, "duration": 3.18}, {"text": "That's not in Europe.", "start": 1109.42, "duration": 1.14}, {"text": "So Sanskrit, Greek,\nLatin, Gothic,", "start": 1110.56, "duration": 1.68}, {"text": "which is an ancestor\nof the Germanic.", "start": 1112.24, "duration": 3.508}, {"text": "No, it's not.", "start": 1115.748, "duration": 0.542}, {"text": "It's an old Germanic language.", "start": 1116.29, "duration": 1.68}, {"text": "It was spoken around the Crimea.", "start": 1117.97, "duration": 3.45}, {"text": "Old Irish, Lithuanian,\nOld Church Slavonic,", "start": 1121.42, "duration": 2.55}, {"text": "which is an ancestor of\nthe Slavic languages.", "start": 1123.97, "duration": 3.36}, {"text": "Basque, and Turkish.", "start": 1127.33, "duration": 2.19}, {"text": "If you look at these\nlanguages, I've", "start": 1129.52, "duration": 1.95}, {"text": "highlighted the second\nline because it's", "start": 1131.47, "duration": 2.49}, {"text": "the line in which\nthis is clearest.", "start": 1133.96, "duration": 2.25}, {"text": "You can see a lot of\nthese languages have words", "start": 1136.21, "duration": 4.98}, {"text": "for the number two that look\nkind of similar to each other", "start": 1141.19, "duration": 3.72}, {"text": "except for the last two,\nwhich really, really don't.", "start": 1144.91, "duration": 2.97}, {"text": "So you've got words\nthat have a \"d\"", "start": 1147.88, "duration": 3.78}, {"text": "and then a \"u,\" or\nOK, Gothic has a \"t,\"", "start": 1151.66, "duration": 2.52}, {"text": "the voiceless version of a \"d.\"", "start": 1154.18, "duration": 2.4}, {"text": "And then sometimes\nthere's a \"w.\"", "start": 1156.58, "duration": 2.22}, {"text": "Old Irish lost out on the \"w.\"", "start": 1158.8, "duration": 2.82}, {"text": "And then you get to\nBasque and Turkish,", "start": 1161.62, "duration": 1.8}, {"text": "where there's no \"d\" and no\n\"t\" and nothing rounded at all.", "start": 1163.42, "duration": 3.33}, {"text": "Yeah.", "start": 1166.75, "duration": 0.91}, {"text": "AUDIENCE: What does\nthe colon mean?", "start": 1167.66, "duration": 2.58}, {"text": "NORVIN RICHARDS: Oh, those\nindicate long vowels.", "start": 1170.24, "duration": 2.55}, {"text": "Sorry.", "start": 1172.79, "duration": 1.38}, {"text": "Good question.", "start": 1174.17, "duration": 0.67}, {"text": "I should have said that.", "start": 1174.84, "duration": 1.62}, {"text": "Yeah.", "start": 1176.46, "duration": 2.44}, {"text": "Actually for Latin, I\nshould have used a macron.", "start": 1178.9, "duration": 2.0}, {"text": "I should go in\nthere and fix that.", "start": 1180.9, "duration": 1.417}, {"text": "So a hypothesis that people\ncould entertain, then--", "start": 1185.02, "duration": 3.99}, {"text": "and this was famously\nentertained for the first time", "start": 1189.01, "duration": 4.8}, {"text": "a few centuries ago--", "start": 1193.81, "duration": 1.44}, {"text": "was that it's not just the case\nthat these various European", "start": 1195.25, "duration": 4.98}, {"text": "languages have similar sounding\nwords for one, two, and three,", "start": 1200.23, "duration": 3.51}, {"text": "but that these words are\nsimilar sounding because they're", "start": 1203.74, "duration": 2.61}, {"text": "related to each other.", "start": 1206.35, "duration": 1.11}, {"text": "The word for this is cognates.", "start": 1207.46, "duration": 1.8}, {"text": "These are all descendents\nof a common ancestor.", "start": 1209.26, "duration": 3.45}, {"text": "And that Basque and Turkish\nare not part of this group.", "start": 1212.71, "duration": 4.08}, {"text": "They don't have words that\nare cognate with those.", "start": 1216.79, "duration": 2.5}, {"text": "I don't know why I specifically\nboxed the words for three.", "start": 1219.29, "duration": 3.47}, {"text": "The claim is that the\nwords for one and two", "start": 1222.76, "duration": 2.37}, {"text": "and three in most of those\nlanguages in that table", "start": 1225.13, "duration": 3.18}, {"text": "are cognates with each other,\nand that Basque and Turkish", "start": 1228.31, "duration": 2.91}, {"text": "are the ones that are left out.", "start": 1231.22, "duration": 3.11}, {"text": "So I just said, hey,\nlook, these words look", "start": 1234.33, "duration": 2.84}, {"text": "kind of similar to each other.", "start": 1237.17, "duration": 1.26}, {"text": "And that is indeed often how\nthis kind of thing starts.", "start": 1238.43, "duration": 2.928}, {"text": "You look at two languages\nand say, hmm, these languages", "start": 1241.358, "duration": 2.292}, {"text": "look kind of similar.", "start": 1243.65, "duration": 0.875}, {"text": "I wonder if they're related.", "start": 1244.525, "duration": 1.945}, {"text": "But big discovery from the early\ndays of systematic linguistics", "start": 1246.47, "duration": 6.51}, {"text": "was the observation\nthat it's possible to be", "start": 1252.98, "duration": 2.25}, {"text": "more systematic than this.", "start": 1255.23, "duration": 2.35}, {"text": "So it isn't just a matter\nof saying, oh, look.", "start": 1257.58, "duration": 3.62}, {"text": "These languages look\nsimilar to each other.", "start": 1261.2, "duration": 2.59}, {"text": "We can actually state\nlaws, generalizations,", "start": 1263.79, "duration": 3.02}, {"text": "about which sounds correspond\nto which other sounds.", "start": 1266.81, "duration": 3.708}, {"text": "So we can do better\nthan just saying,", "start": 1270.518, "duration": 1.542}, {"text": "these languages look similar.", "start": 1272.06, "duration": 1.32}, {"text": "We get to say things\nlike, for example, where", "start": 1273.38, "duration": 2.91}, {"text": "Latin and Greek\nhave a \"d,\" English", "start": 1276.29, "duration": 3.03}, {"text": "has a \"t,\" for a\ncertain set of words.", "start": 1279.32, "duration": 3.73}, {"text": "So the Latin and Greek words\nfor \"two\" and \"eat\" and \"ten\"", "start": 1283.05, "duration": 6.41}, {"text": "have \"d\"s in them, which\ncorrespond in English to \"t\"s.", "start": 1289.46, "duration": 4.02}, {"text": "Or the words in\nLatin and Greek that", "start": 1293.48, "duration": 4.08}, {"text": "are related to \"kin\" and\nthat second word means field.", "start": 1297.56, "duration": 4.62}, {"text": "They have a \"k\" as corresponding\n\"k\" sound in English.", "start": 1302.18, "duration": 4.56}, {"text": "These words that\nhave a \"b\" in them--", "start": 1306.74, "duration": 2.61}, {"text": "words that have a \"b\"\nin them are weirdly rare", "start": 1309.35, "duration": 3.03}, {"text": "in Proto-Indo-European,\nthe ancestor", "start": 1312.38, "duration": 2.217}, {"text": "of all of these languages.", "start": 1314.597, "duration": 1.083}, {"text": "There are a couple\nof examples here.", "start": 1315.68, "duration": 1.83}, {"text": "\"Cannabis,\" the\nsecond line there,", "start": 1317.51, "duration": 3.33}, {"text": "is thought to probably\nbe a borrowing", "start": 1320.84, "duration": 2.43}, {"text": "into Proto-Indo-European\nfrom some other language", "start": 1323.27, "duration": 2.55}, {"text": "for several reasons.", "start": 1325.82, "duration": 0.97}, {"text": "One is that it has a\n\"b\" in it, and that's", "start": 1326.79, "duration": 1.75}, {"text": "rare in Proto-Indo-European.", "start": 1328.54, "duration": 1.27}, {"text": "Another is that\nit's weirdly long.", "start": 1329.81, "duration": 2.07}, {"text": "Proto-Indo-European\nwords are mostly not", "start": 1331.88, "duration": 1.77}, {"text": "three syllables long.", "start": 1333.65, "duration": 1.62}, {"text": "So a hypothesis is that\nthe ancestors of the Latins", "start": 1335.27, "duration": 4.89}, {"text": "and the Romans and the Greeks\nand the Sanskrit speakers", "start": 1340.16, "duration": 3.15}, {"text": "and the Gothic speakers,\nthe Proto-Indo-Europeans,", "start": 1343.31, "duration": 3.36}, {"text": "as they were roaming\naround Europe conquering", "start": 1346.67, "duration": 2.37}, {"text": "various people, encountered\nsome people who had discovered", "start": 1349.04, "duration": 2.97}, {"text": "cannabis and were like, cool.", "start": 1352.01, "duration": 1.38}, {"text": "We will take that.", "start": 1353.39, "duration": 1.03}, {"text": "And while we're at it, we\nwill borrow your word for it.", "start": 1354.42, "duration": 4.19}, {"text": "Apparently, something\nlike that happened.", "start": 1358.61, "duration": 2.37}, {"text": "So there's this\ngeneralization-- it's", "start": 1360.98, "duration": 2.61}, {"text": "called Grimm's Law\nbecause it was discovered", "start": 1363.59, "duration": 2.52}, {"text": "by a Dane named Rasmus Rask\nand then discovered again", "start": 1366.11, "duration": 4.17}, {"text": "by Jacob Grimm, who was one of\nthe Grimm brothers of the Grimm", "start": 1370.28, "duration": 4.65}, {"text": "Fairy Tales.", "start": 1374.93, "duration": 0.84}, {"text": "This observation\nabout systematic sound", "start": 1375.77, "duration": 2.97}, {"text": "correspondences between\nthe oldest versions", "start": 1378.74, "duration": 3.03}, {"text": "of these related languages.", "start": 1381.77, "duration": 3.54}, {"text": "You can see with the benefit\nof all of the phonology", "start": 1385.31, "duration": 3.33}, {"text": "that we did at the beginning of\nthis class that what's going on", "start": 1388.64, "duration": 3.33}, {"text": "is that where Latin and\nGreek have voiced stops,", "start": 1391.97, "duration": 3.67}, {"text": "English and other\nGermanic languages tend", "start": 1395.64, "duration": 2.63}, {"text": "to have voiceless stops.", "start": 1398.27, "duration": 1.59}, {"text": "So there was a\ngeneral sound change.", "start": 1399.86, "duration": 2.93}, {"text": "And there's more to\nGrimm's Law than that,", "start": 1402.79, "duration": 1.75}, {"text": "but that's one of\nthe observations", "start": 1404.54, "duration": 1.8}, {"text": "that the Grimm made.", "start": 1406.34, "duration": 3.51}, {"text": "Once we've looked at\na bunch of languages", "start": 1409.85, "duration": 2.46}, {"text": "and figured out all the\nsound laws that we need,", "start": 1412.31, "duration": 3.0}, {"text": "we sort of get to posit\nthese underlying forms.", "start": 1415.31, "duration": 2.67}, {"text": "I was talking about this\nfor Proto-Austronesian.", "start": 1417.98, "duration": 2.64}, {"text": "These, you can think of them as\nbeing like the underlying forms", "start": 1420.62, "duration": 3.57}, {"text": "we talked about when we\ndid phonology, right?", "start": 1424.19, "duration": 2.49}, {"text": "We posit these sound\nchanges, and we", "start": 1426.68, "duration": 2.85}, {"text": "have a sort of point of\norigin for all of these words.", "start": 1429.53, "duration": 3.19}, {"text": "It's the form that undergoes\ndifferent sound changes", "start": 1432.72, "duration": 2.518}, {"text": "in different languages\nwith the consequence", "start": 1435.238, "duration": 1.792}, {"text": "that you have\ndifferent languages.", "start": 1437.03, "duration": 1.74}, {"text": "That underlying\nform, the language", "start": 1438.77, "duration": 2.73}, {"text": "that has those underlying\nforms, is sometimes", "start": 1441.5, "duration": 1.92}, {"text": "called the proto language.", "start": 1443.42, "duration": 1.36}, {"text": "So I've been talking\nabout Proto-Indo-European", "start": 1444.78, "duration": 1.94}, {"text": "and Proto-Austronesian.", "start": 1446.72, "duration": 3.54}, {"text": "Here's one of the examples\nof Grimm's Law at work.", "start": 1450.26, "duration": 3.06}, {"text": "We look at Sanskrit\nand English and Latin.", "start": 1453.32, "duration": 2.61}, {"text": "I don't know why I said\nthem in that order.", "start": 1455.93, "duration": 2.77}, {"text": "And we convince ourselves that\nwhere Sanskrit and Latin have", "start": 1458.7, "duration": 3.59}, {"text": "a \"d,\" English has a \"t.\"", "start": 1462.29, "duration": 2.88}, {"text": "That's part of\nGrimm's Law, so it", "start": 1465.17, "duration": 4.08}, {"text": "has the consequence that voiced\nsounds in Sanskrit and Latin", "start": 1469.25, "duration": 4.92}, {"text": "correlate with voiceless\nstops in English.", "start": 1474.17, "duration": 4.86}, {"text": "If we look at the vowels, so\nwe have an \"a\" in Sanskrit", "start": 1479.03, "duration": 6.21}, {"text": "and an \"e\" in Latin.", "start": 1485.24, "duration": 2.55}, {"text": "And if we look more widely\nat correlating words,", "start": 1487.79, "duration": 4.74}, {"text": "words that look\nlike they might be", "start": 1492.53, "duration": 1.44}, {"text": "related in Sanskrit and Latin--", "start": 1493.97, "duration": 2.01}, {"text": "here are a bunch of examples.", "start": 1495.98, "duration": 3.15}, {"text": "What kind of a\nsound do you think", "start": 1499.13, "duration": 2.19}, {"text": "we should posit as the proto\nsound, a proto vowel for \"eat\"", "start": 1501.32, "duration": 6.03}, {"text": "in both Sanskrit and Latin?", "start": 1507.35, "duration": 2.74}, {"text": "Have a look at those data\nand tell me what you think.", "start": 1510.09, "duration": 3.72}, {"text": "AUDIENCE: [SNEEZE]", "start": 1513.81, "duration": 0.84}, {"text": "NORVIN RICHARDS: Bless you.", "start": 1514.65, "duration": 1.125}, {"text": "Is there a generalization\nthat we can draw of the form", "start": 1519.22, "duration": 2.55}, {"text": "wherever Sanskrit has an\n\"a,\" Latin has an \"e\"?", "start": 1521.77, "duration": 3.48}, {"text": "That's true for\n\"eat\" and \"tooth.\"", "start": 1527.94, "duration": 1.95}, {"text": "And for the first\none in \"field.\"", "start": 1533.11, "duration": 4.55}, {"text": "But we're seeing that\nfor \"sheep\" and \"two\"", "start": 1537.66, "duration": 2.68}, {"text": "and for the second\nvowel in \"field,\"", "start": 1540.34, "duration": 1.97}, {"text": "there are other Latin\nvowels that correspond", "start": 1542.31, "duration": 1.86}, {"text": "with Sanskrit vowels.", "start": 1544.17, "duration": 1.62}, {"text": "So what type of\na vowel should we", "start": 1545.79, "duration": 3.21}, {"text": "posited as the original\nvowel in \"eat\"?", "start": 1549.0, "duration": 2.145}, {"text": "Can we predict the\nSanskrit vowels--", "start": 1555.75, "duration": 1.68}, {"text": "or sorry, the Latin vowels\nfrom the Sanskrit vowels?", "start": 1557.43, "duration": 2.31}, {"text": "No.", "start": 1562.6, "duration": 0.5}, {"text": "Right?", "start": 1563.1, "duration": 0.3}, {"text": "There aren't\ngeneralizations like,", "start": 1563.4, "duration": 1.417}, {"text": "wherever Sanskrit has\nan \"a,\" Latin as an \"e.\"", "start": 1564.817, "duration": 3.423}, {"text": "What should we do?", "start": 1568.24, "duration": 0.75}, {"text": "Yeah.", "start": 1568.99, "duration": 1.16}, {"text": "AUDIENCE: So we [INAUDIBLE].", "start": 1570.15, "duration": 2.443}, {"text": "NORVIN RICHARDS: Yeah.", "start": 1572.593, "duration": 0.917}, {"text": "So if we do it the\nother way around,", "start": 1573.51, "duration": 3.48}, {"text": "if we say the original\nvowels were more", "start": 1576.99, "duration": 4.08}, {"text": "like the Latin\nvowels, and Sanskrit", "start": 1581.07, "duration": 1.68}, {"text": "underwent a bunch of sound\nchanges that squashed many", "start": 1582.75, "duration": 2.67}, {"text": "of the vowels together.", "start": 1585.42, "duration": 0.96}, {"text": "So the original vowels\n\"e\" and \"o\" and also \"a,\"", "start": 1586.38, "duration": 6.33}, {"text": "like the first vowel\nin \"field,\" all three", "start": 1592.71, "duration": 3.39}, {"text": "of those vowels became\n\"a,\" \"ah,\" in Sanskrit.", "start": 1596.1, "duration": 4.65}, {"text": "This is the same\nkind of reasoning", "start": 1600.75, "duration": 1.56}, {"text": "we were using when we were\noriginally doing phonology.", "start": 1602.31, "duration": 2.28}, {"text": "We can't predict the Latin\nvowels from the Sanskrit", "start": 1604.59, "duration": 3.453}, {"text": "vowels, but we can predict\nthe Sanskrit vowels", "start": 1608.043, "duration": 1.917}, {"text": "from the Latin vowels.", "start": 1609.96, "duration": 0.81}, {"text": "Namely, the Latin vowels\nall got squashed together.", "start": 1610.77, "duration": 2.125}, {"text": "So Latin has kept an\nolder vowel system", "start": 1612.895, "duration": 3.635}, {"text": "that Sanskrit has simplified\nto a certain extent.", "start": 1616.53, "duration": 4.41}, {"text": "So we'll posit a\nProto-Indo-European stem, \"ed-\"", "start": 1620.94, "duration": 3.62}, {"text": "for \"eat.\"", "start": 1624.56, "duration": 1.44}, {"text": "Sanskrit undergoes a change,\nwhere the \"eh\" becomes \"ah.\"", "start": 1626.0, "duration": 4.38}, {"text": "English undergoes\nGrimm's Law and also", "start": 1630.38, "duration": 2.01}, {"text": "some changes with the vowels,\nwhich we'll get a chance", "start": 1632.39, "duration": 2.25}, {"text": "to talk about in the second.", "start": 1634.64, "duration": 1.56}, {"text": "And Latin preserves\nat least that much", "start": 1636.2, "duration": 2.97}, {"text": "of the Proto-Indo-European form.", "start": 1639.17, "duration": 2.37}, {"text": "It's worth being careful.", "start": 1641.54, "duration": 1.38}, {"text": "Just like at the beginning\nof this class when", "start": 1642.92, "duration": 3.09}, {"text": "we were doing phonology, we\nstarted off with sound changes,", "start": 1646.01, "duration": 4.92}, {"text": "looking at data sets,\nwhere it was often the case", "start": 1650.93, "duration": 2.79}, {"text": "that you could posit\nan underlying form that", "start": 1653.72, "duration": 3.9}, {"text": "was the same as some form that\nyou could see on the surface.", "start": 1657.62, "duration": 5.07}, {"text": "But I think we saw, back\nwhen we were doing phonology,", "start": 1662.69, "duration": 2.82}, {"text": "that wasn't necessarily true.", "start": 1665.51, "duration": 1.69}, {"text": "There were cases where it was\nuseful to posit an underlying", "start": 1667.2, "duration": 2.69}, {"text": "form that always underwent\nsome kind of change.", "start": 1669.89, "duration": 4.11}, {"text": "It never just surfaced\nin its actual form.", "start": 1674.0, "duration": 2.91}, {"text": "And this also happens when\nwe're positing proto forms.", "start": 1676.91, "duration": 3.09}, {"text": "It hasn't happened in this\nparticular case, so this--", "start": 1680.0, "duration": 2.91}, {"text": "I carefully picked a case\nwhere life was simple,", "start": 1682.91, "duration": 2.67}, {"text": "and Latin has just kept the\nProto-Indo-European form.", "start": 1685.58, "duration": 3.06}, {"text": "But we can't rely on that\nhappening every time.", "start": 1688.64, "duration": 2.02}, {"text": "Sometimes there are cases where\nwe'll want a positive proto", "start": 1690.66, "duration": 2.458}, {"text": "form that just doesn't\nsurvive in its unchanged", "start": 1693.118, "duration": 3.202}, {"text": "form in any case.", "start": 1696.32, "duration": 1.62}, {"text": "Sound changes.", "start": 1700.54, "duration": 2.37}, {"text": "The study of sound changes--", "start": 1702.91, "duration": 1.92}, {"text": "first of all, the discovery\nthat sound changes were regular,", "start": 1704.83, "duration": 3.51}, {"text": "that you could make\nstatements of the form", "start": 1708.34, "duration": 1.83}, {"text": "wherever this\nlanguage has sound X,", "start": 1710.17, "duration": 1.92}, {"text": "this other language\nhas sound Y, that", "start": 1712.09, "duration": 2.73}, {"text": "was a big early discovery in\nlinguistics and the starting", "start": 1714.82, "duration": 4.38}, {"text": "point for a lot of the work\nthat started getting done", "start": 1719.2, "duration": 3.63}, {"text": "in phonology as\npeople started getting", "start": 1722.83, "duration": 3.06}, {"text": "interested in the questions\nof what kinds of sound changes", "start": 1725.89, "duration": 2.55}, {"text": "there were and why some\nkinds of sound changes", "start": 1728.44, "duration": 2.61}, {"text": "were more common than others\nand what motivated them", "start": 1731.05, "duration": 3.15}, {"text": "and why they happened and so on.", "start": 1734.2, "duration": 2.2}, {"text": "Similarly, the\ndiscussion that we", "start": 1736.4, "duration": 2.15}, {"text": "had when we were doing\nphonology rule ordering,", "start": 1738.55, "duration": 2.37}, {"text": "where we decided that it was\nuseful sometimes to posit--", "start": 1740.92, "duration": 4.263}, {"text": "we talked about this for\nLardil, for example--", "start": 1745.183, "duration": 1.917}, {"text": "that it's useful\nsometimes to posit", "start": 1747.1, "duration": 1.53}, {"text": "an original form,\nan underlying form,", "start": 1748.63, "duration": 2.16}, {"text": "and have it undergo sound\nchanges in a particular order.", "start": 1750.79, "duration": 3.36}, {"text": "I think we talked about it as\nbeing like an assembly line,", "start": 1754.15, "duration": 2.71}, {"text": "right?", "start": 1756.86, "duration": 0.5}, {"text": "It first goes to the place where\nit undergoes this sound change,", "start": 1757.36, "duration": 2.98}, {"text": "then it undergoes the sound\nchange, with the consequence", "start": 1760.34, "duration": 2.36}, {"text": "sometimes that the second\nsound change creates something", "start": 1762.7, "duration": 3.39}, {"text": "that would undergo the\nfirst sound change,", "start": 1766.09, "duration": 1.83}, {"text": "but it's too late.", "start": 1767.92, "duration": 0.99}, {"text": "We looked at examples like that.", "start": 1768.91, "duration": 1.56}, {"text": "Way back when we were\ntalking about Lardil,", "start": 1774.55, "duration": 2.94}, {"text": "we had a rule that\nchanged \"u\" to \"a\"", "start": 1777.49, "duration": 4.29}, {"text": "at the ends of\nwords that changed", "start": 1781.78, "duration": 2.73}, {"text": "underlying \"muwu,\" which is the\nunderlying word for \"water,\"", "start": 1784.51, "duration": 2.76}, {"text": "to \"muga.\"", "start": 1787.27, "duration": 4.08}, {"text": "And we had another sound\nchange that got rid of \"k'", "start": 1791.35, "duration": 3.81}, {"text": "at the ends of words.", "start": 1795.16, "duration": 2.143}, {"text": "So if you had a \"k\" at the end\nof the word, it would drop,", "start": 1797.303, "duration": 2.417}, {"text": "which changed\nunderlying \"naluk,\"", "start": 1799.72, "duration": 2.28}, {"text": "which is the word for\n\"story,\" to \"nalu,\"", "start": 1802.0, "duration": 5.492}, {"text": "But it was important that these\nrules applied in this order", "start": 1807.492, "duration": 2.458}, {"text": "because \"nalu\" doesn't\nthen change to \"nala.\"", "start": 1809.95, "duration": 3.05}, {"text": "So that was one of\nthe kinds of cases", "start": 1813.0, "duration": 1.542}, {"text": "we were talking about when we\nwere talking about ordering", "start": 1814.542, "duration": 2.375}, {"text": "rules in a particular order.", "start": 1816.917, "duration": 1.223}, {"text": "All of that talk started in\nwork on historical linguistics,", "start": 1818.14, "duration": 4.17}, {"text": "where it's easy to\nimagine, in fact,", "start": 1822.31, "duration": 3.0}, {"text": "that a bunch of sound\nchanges have taken place,", "start": 1825.31, "duration": 2.13}, {"text": "and they've taken place\nin a particular order.", "start": 1827.44, "duration": 1.92}, {"text": "And people got interested\nin possible relations", "start": 1829.36, "duration": 3.27}, {"text": "between sound changes.", "start": 1832.63, "duration": 2.418}, {"text": "Some kinds of sound\nchanges are cross", "start": 1835.048, "duration": 1.542}, {"text": "linguistically fairly common.", "start": 1836.59, "duration": 1.42}, {"text": "So here's one.", "start": 1838.01, "duration": 1.46}, {"text": "\"w\" changed to \"gwa,\"\nfor example, in Chamorro.", "start": 1839.47, "duration": 4.0}, {"text": "Chamorro is a language\nof Saipan in the Pacific.", "start": 1843.47, "duration": 6.15}, {"text": "It's closely related\nto Tagalog, which is", "start": 1849.62, "duration": 3.405}, {"text": "a language of the Philippines.", "start": 1853.025, "duration": 1.25}, {"text": "They're both\nAustronesian languages.", "start": 1854.275, "duration": 2.258}, {"text": "So for example,\nTagalog has a word", "start": 1856.533, "duration": 1.417}, {"text": "\"asawa,\" which means \"spouse.\"", "start": 1857.95, "duration": 1.84}, {"text": "So Tagalog kinship\nterminology mostly", "start": 1859.79, "duration": 3.53}, {"text": "doesn't indicate the\ngender of the person", "start": 1863.32, "duration": 1.74}, {"text": "you're talking about.", "start": 1865.06, "duration": 0.88}, {"text": "So they don't have words\nfor husband or wife.", "start": 1865.94, "duration": 2.6}, {"text": "They just have this word\n\"asawa,\" which means spouse.", "start": 1868.54, "duration": 3.12}, {"text": "You can say male spouse\nor female spouse,", "start": 1871.66, "duration": 3.15}, {"text": "but you don't, usually.", "start": 1874.81, "duration": 3.72}, {"text": "So Tagalog has a word, \"asawa.\"", "start": 1878.53, "duration": 1.68}, {"text": "In Chamorro, this is \"asagwa.\"", "start": 1880.21, "duration": 1.86}, {"text": "So the \"w\" has become a \"gwa.\"", "start": 1882.07, "duration": 1.56}, {"text": "Tagalog has a number, \"dalawa,\"\nwhich is the number two.", "start": 1883.63, "duration": 3.24}, {"text": "That corresponds to\n\"hugwa\" in Chamorro,", "start": 1886.87, "duration": 3.21}, {"text": "and this \"wala,\" which we\nwere talking about before,", "start": 1890.08, "duration": 2.35}, {"text": "which means \"there\nisn't\" just in Tagalog.", "start": 1892.43, "duration": 2.18}, {"text": "All over Austronesian means\n\"there is,\" and that's", "start": 1894.61, "duration": 3.18}, {"text": "what it means in Chamorro.", "start": 1897.79, "duration": 1.14}, {"text": "But it doesn't start\nwith the \"w\" in Chamorro,", "start": 1898.93, "duration": 1.917}, {"text": "it starts with \"gwa.\"", "start": 1900.847, "duration": 1.893}, {"text": "If you think about\nwhat a \"w\" is,", "start": 1902.74, "duration": 2.37}, {"text": "the fact that a \"w\"\nbecomes a \"gwa\" in Chamorro", "start": 1905.11, "duration": 2.97}, {"text": "is maybe not such a weird fact.", "start": 1908.08, "duration": 3.66}, {"text": "So think about what a \"w\" is.", "start": 1911.74, "duration": 1.29}, {"text": "A \"w\" is a glide that\ncorresponds to the vowel \"u.\"", "start": 1913.03, "duration": 5.32}, {"text": "If you think back, way,\nway back, months ago,", "start": 1918.35, "duration": 3.45}, {"text": "when you were young and carefree\nand knew a lot about phenology", "start": 1921.8, "duration": 4.23}, {"text": "and had not yet encountered\nsyntax and semantics,", "start": 1926.03, "duration": 4.29}, {"text": "maybe you remember that the\nvalue \"u\" has rounding, right?", "start": 1930.32, "duration": 4.05}, {"text": "Your lips are rounding.", "start": 1934.37, "duration": 1.17}, {"text": "But it's also high and back.", "start": 1935.54, "duration": 2.86}, {"text": "What that means is that\nyour tongue is bunched up", "start": 1938.4, "duration": 2.33}, {"text": "toward the top of the\nback of your mouth.", "start": 1940.73, "duration": 2.07}, {"text": "So back then, we were doing\ngroup exercises like saying", "start": 1942.8, "duration": 4.39}, {"text": "\"oo-wee\" over and over again.", "start": 1947.19, "duration": 2.43}, {"text": "And when you did\nthat, you discovered", "start": 1949.62, "duration": 2.927}, {"text": "that your lips were\nrounding and unrounding,", "start": 1952.547, "duration": 1.833}, {"text": "but also that your\ntongue was shifting", "start": 1954.38, "duration": 1.5}, {"text": "from the back of your mouth\nto the front of your mouth.", "start": 1955.88, "duration": 2.292}, {"text": "So \"w\" is a glide that\ncorresponds to the vowel \"u.\"", "start": 1958.172, "duration": 4.428}, {"text": "It's a version of the vowel\n\"u\" said very fast, basically,", "start": 1962.6, "duration": 3.96}, {"text": "in which your tongue\nis bunching up", "start": 1966.56, "duration": 1.855}, {"text": "toward the back of\nyour mouth, reaching", "start": 1968.415, "duration": 1.625}, {"text": "toward the top of the\nback of your mouth,", "start": 1970.04, "duration": 1.708}, {"text": "and your lips are rounding.", "start": 1971.748, "duration": 1.902}, {"text": "So if you think about what you\ndo when you do a \"g,\" a \"guh,\"", "start": 1973.65, "duration": 4.746}, {"text": "a voiced velar stop,\nwell what you're doing", "start": 1978.396, "duration": 2.904}, {"text": "is your tongue is touching\nthe back of your mouth, right?", "start": 1981.3, "duration": 3.18}, {"text": "It's making a velar\nclosure back there.", "start": 1984.48, "duration": 3.04}, {"text": "So the fact that a \"wa\" has\nbecome a \"gwa\" in this language", "start": 1987.52, "duration": 3.74}, {"text": "is sort of understandable.", "start": 1991.26, "duration": 1.31}, {"text": "A \"gwa\" is just a \"w\" that\ngot out of hand, right?", "start": 1992.57, "duration": 3.28}, {"text": "It's your tongue\nnot just bunching up", "start": 1995.85, "duration": 3.03}, {"text": "toward the back of your mouth,\nbut actually colliding with it,", "start": 1998.88, "duration": 3.42}, {"text": "making a closure back there.", "start": 2002.3, "duration": 3.24}, {"text": "And I'm going through all\nthis because this sound change", "start": 2005.54, "duration": 2.61}, {"text": "didn't just happen in Chamorro.", "start": 2008.15, "duration": 2.94}, {"text": "It also happened in Welsh.", "start": 2011.09, "duration": 3.0}, {"text": "So Welsh has a bunch of words.", "start": 2014.09, "duration": 2.43}, {"text": "I've just given you\none, which is \"man.\"", "start": 2016.52, "duration": 2.16}, {"text": "The Welsh word for\n\"man\" is \"gwir.\"", "start": 2018.68, "duration": 1.8}, {"text": "It's related to the Latin word\n\"vir,\" [pronounced \"weer\"],", "start": 2020.48, "duration": 2.417}, {"text": "which we have as \"virile\"\nand English words like that.", "start": 2022.897, "duration": 2.683}, {"text": "The \"vir\" is actually also, I\nthink, related to the \"were\"", "start": 2025.58, "duration": 3.54}, {"text": "in \"werewolf,\" which\nis a man, a man-wolf.", "start": 2029.12, "duration": 2.76}, {"text": "Welsh has another word\nwhich they borrowed from--", "start": 2034.55, "duration": 3.27}, {"text": "borrowed from Latin,\n\"gwin,\" which is \"wine.\"", "start": 2040.46, "duration": 4.5}, {"text": "So they borrowed\nthat from Latin.", "start": 2044.96, "duration": 1.5}, {"text": "They changed the \"w\" sound\nat the beginning to a \"gwa.\"", "start": 2046.46, "duration": 2.64}, {"text": "So Latin underwent--\nWelsh, sorry,", "start": 2049.1, "duration": 2.039}, {"text": "underwent the same sound change.", "start": 2051.139, "duration": 1.913}, {"text": "There are also\nsome words that got", "start": 2053.052, "duration": 1.417}, {"text": "borrowed from Proto-Germanic\ninto late Latin, that", "start": 2054.469, "duration": 4.02}, {"text": "is, Latin right before it was\nabout to break up and turn", "start": 2058.489, "duration": 2.641}, {"text": "into all the Romance languages,\nin which the Proto-Germanic", "start": 2061.13, "duration": 3.509}, {"text": "\"w\" got realized in\nlate Latin as a \"gwa.\"", "start": 2064.639, "duration": 2.941}, {"text": "So the Proto-Germanic word\nfor \"war,\" which was \"werra\"--", "start": 2067.58, "duration": 3.284}, {"text": "it's an ancestor of the\nmodern English, \"war\"--", "start": 2070.864, "duration": 4.006}, {"text": "got borrowed into late\nLatin as \"gwerra.\"", "start": 2074.87, "duration": 4.11}, {"text": "And you now see that in\nEnglish words like guerrilla,", "start": 2078.98, "duration": 4.949}, {"text": "in the sense of a\nperson who fights", "start": 2083.929, "duration": 3.203}, {"text": "a particular type of warfare.", "start": 2087.132, "duration": 1.208}, {"text": "If you study any\nRomance languages,", "start": 2091.25, "duration": 2.76}, {"text": "the old Latin word for\n\"war\" was \"bellum.\"", "start": 2094.01, "duration": 6.72}, {"text": "But that word, I\nbelieve, vanished", "start": 2100.73, "duration": 2.28}, {"text": "from all the Romance languages.", "start": 2103.01, "duration": 1.41}, {"text": "What they all have are\ndescendants of this word.", "start": 2104.42, "duration": 2.95}, {"text": "So if you study Italian\nor French or Spanish,", "start": 2107.37, "duration": 5.39}, {"text": "you need to learn words for\nwar like \"guerre\" and \"guerra.\"", "start": 2112.76, "duration": 3.9}, {"text": "Those are all descendants\nof this Germanic word.", "start": 2116.66, "duration": 2.32}, {"text": "So the late Latins,\nI guess, were really", "start": 2118.98, "duration": 1.91}, {"text": "impressed with the Germanic\nattitude toward war.", "start": 2120.89, "duration": 2.07}, {"text": "They borrowed this word,\nand they completely", "start": 2122.96, "duration": 2.16}, {"text": "replaced their word for \"war\"\nwith it, as far as I can tell.", "start": 2125.12, "duration": 2.553}, {"text": "AUDIENCE: Do we know why\n\"bellum\" disappeared?", "start": 2127.673, "duration": 1.917}, {"text": "NORVIN RICHARDS: No.", "start": 2129.59, "duration": 0.68}, {"text": "At least, I don't.", "start": 2130.27, "duration": 0.69}, {"text": "Yeah.", "start": 2130.96, "duration": 0.5}, {"text": "This just became the\ncool word for war.", "start": 2131.46, "duration": 2.74}, {"text": "So I mean, we have\nit in expressions", "start": 2134.2, "duration": 2.43}, {"text": "that we've borrowed from\nLatin, like \"antebellum.\"", "start": 2136.63, "duration": 2.52}, {"text": "But as far as their\nnormal word for war,", "start": 2139.15, "duration": 4.11}, {"text": "it got replaced with this.", "start": 2143.26, "duration": 2.28}, {"text": "Or we also have words\nin English where", "start": 2145.54, "duration": 2.13}, {"text": "we have both of these words.", "start": 2147.67, "duration": 1.45}, {"text": "So there's the\nProto-Germanic word", "start": 2149.12, "duration": 1.7}, {"text": "for \"guard,\" which was \"ward.\"", "start": 2150.82, "duration": 1.52}, {"text": "We have that as a word,\n\"ward,\" to ward off a threat", "start": 2152.34, "duration": 2.83}, {"text": "or something like that.", "start": 2155.17, "duration": 1.77}, {"text": "It got borrowed into\nlate Latin as \"gward.\"", "start": 2156.94, "duration": 2.67}, {"text": "That's the modern word for\n\"watch\" in lots of languages.", "start": 2159.61, "duration": 4.42}, {"text": "So in Italian, if\nyou want to watch TV,", "start": 2164.03, "duration": 2.63}, {"text": "the verb you use is \"guardare.\"", "start": 2166.66, "duration": 2.34}, {"text": "You guard the TV.", "start": 2169.0, "duration": 1.2}, {"text": "You watch it carefully.", "start": 2170.2, "duration": 1.11}, {"text": "And English has both of these\nwords now, so we have \"ward\"", "start": 2173.98, "duration": 2.94}, {"text": "and we also have \"guard.\"", "start": 2176.92, "duration": 1.29}, {"text": "They both have the same root.", "start": 2178.21, "duration": 2.31}, {"text": "They're both from\nProto-Germanic \"ward,\"", "start": 2180.52, "duration": 2.04}, {"text": "which came to us straight\nin the form of \"ward,\"", "start": 2182.56, "duration": 2.79}, {"text": "and then took a little detour\ninto Latin to become \"guard.\"", "start": 2185.35, "duration": 2.76}, {"text": "And then we borrowed it\nagain in a different form.", "start": 2188.11, "duration": 3.0}, {"text": "Big discovery, then.", "start": 2194.74, "duration": 1.26}, {"text": "Grimm's Law, this\nchange from \"w\"", "start": 2196.0, "duration": 2.01}, {"text": "to \"gwa,\" so lots\nof big discoveries.", "start": 2198.01, "duration": 4.313}, {"text": "But one of the big\ndiscoveries was", "start": 2202.323, "duration": 1.417}, {"text": "that sound change was regular,\nthat you could do better", "start": 2203.74, "duration": 2.292}, {"text": "than just saying these\nwords look kind of similar", "start": 2206.032, "duration": 3.615}, {"text": "to each other.", "start": 2209.647, "duration": 0.583}, {"text": "I bet these languages\nare related.", "start": 2210.23, "duration": 1.46}, {"text": "You could actually\nsay, oh, yeah.", "start": 2211.69, "duration": 1.47}, {"text": "These words are--\nthese languages", "start": 2213.16, "duration": 1.65}, {"text": "are related because there is\nthis general law about how", "start": 2214.81, "duration": 3.99}, {"text": "sounds in language X are\nrelated to sounds in language Y.", "start": 2218.8, "duration": 2.85}, {"text": "This was called the\nNeogrammarian Hypothesis,", "start": 2221.65, "duration": 3.03}, {"text": "and it was one of the\nbig, early discoveries.", "start": 2224.68, "duration": 2.04}, {"text": "It shifts emphasis\naway from looking", "start": 2226.72, "duration": 3.51}, {"text": "at lists of words that\nlook kind of similar.", "start": 2230.23, "duration": 2.522}, {"text": "What we're looking\nfor are lists of words", "start": 2232.752, "duration": 1.708}, {"text": "that can be related by regular\nsound change laws, which is not", "start": 2234.46, "duration": 2.583}, {"text": "the same thing.", "start": 2237.043, "duration": 0.997}, {"text": "There could be lots\nof sound changes.", "start": 2238.04, "duration": 1.63}, {"text": "The sound changes could\nbe really radical.", "start": 2239.67, "duration": 1.75}, {"text": "The result could be\nthat the words don't", "start": 2241.42, "duration": 1.667}, {"text": "look like each other at all.", "start": 2243.087, "duration": 1.343}, {"text": "The point is to\ndiscover that there", "start": 2244.43, "duration": 1.85}, {"text": "are regular correspondences\nbetween the words", "start": 2246.28, "duration": 3.03}, {"text": "and the lists.", "start": 2249.31, "duration": 0.69}, {"text": "Does that make sense?", "start": 2250.0, "duration": 1.12}, {"text": "That's how you discover that\ntwo languages are related.", "start": 2251.12, "duration": 3.72}, {"text": "So just to give you a\ndramatic example of this,", "start": 2254.84, "duration": 2.69}, {"text": "here are three\nwords for the number", "start": 2257.53, "duration": 2.1}, {"text": "two in three languages\nwhose names I have cunningly", "start": 2259.63, "duration": 4.53}, {"text": "hidden from you.", "start": 2264.16, "duration": 2.088}, {"text": "We'll call them language A,\nlanguage B, and language C.", "start": 2266.248, "duration": 2.292}, {"text": "And I will tell you\nthat two of these words", "start": 2268.54, "duration": 1.792}, {"text": "are related to each other\nand the third is not.", "start": 2270.332, "duration": 3.258}, {"text": "You're probably\nsuspecting a trick.", "start": 2273.59, "duration": 2.1}, {"text": "But go ahead,\nsomebody fall for it.", "start": 2275.69, "duration": 2.85}, {"text": "Which of these two\nlanguages do you", "start": 2278.54, "duration": 1.65}, {"text": "think are related to each other?", "start": 2280.19, "duration": 1.69}, {"text": "Yes.", "start": 2281.88, "duration": 0.5}, {"text": "AUDIENCE: B and C.", "start": 2282.38, "duration": 0.78}, {"text": "NORVIN RICHARDS: B and C.\nYes, see, you're right.", "start": 2283.16, "duration": 2.042}, {"text": "But that's because you know\nhow this kind of thing works.", "start": 2285.202, "duration": 3.298}, {"text": "You're supposed to say A and\nB. Would somebody go ahead", "start": 2288.5, "duration": 2.46}, {"text": "and say A and B?", "start": 2290.96, "duration": 0.78}, {"text": "I would feel better.", "start": 2291.74, "duration": 0.99}, {"text": "AUDIENCE: Is it A and B?", "start": 2292.73, "duration": 0.75}, {"text": "NORVIN RICHARDS: Yes, yes, it's\nA and B. Excellent suggestion.", "start": 2293.48, "duration": 2.583}, {"text": "Thank you.", "start": 2296.063, "duration": 1.317}, {"text": "But of course, he's right.", "start": 2297.38, "duration": 2.4}, {"text": "It is B and C. \"Er\" Is\nthe Mandarin word for two.", "start": 2299.78, "duration": 5.55}, {"text": "\"Erku\" is the\nArmenian word for two,", "start": 2305.33, "duration": 1.98}, {"text": "and Greek has \"duo\"\nas it's word for two.", "start": 2307.31, "duration": 3.81}, {"text": "And the way you convince\nyourself of this", "start": 2311.12, "duration": 2.61}, {"text": "is by discovering that\nwherever Greek has a \"dwa,\"", "start": 2313.73, "duration": 3.33}, {"text": "Armenian has an \"erk,\" which is\na pretty radical sound change.", "start": 2317.06, "duration": 3.833}, {"text": "It took people a\nwhile to discover", "start": 2320.893, "duration": 1.417}, {"text": "that Armenian was an\nIndo-European language", "start": 2322.31, "duration": 2.49}, {"text": "because Armenian has had\nreally radical things happen", "start": 2324.8, "duration": 3.282}, {"text": "to it, with the consequence\nthat its words don't look", "start": 2328.082, "duration": 2.208}, {"text": "all that Indo-European anymore.", "start": 2330.29, "duration": 2.04}, {"text": "But it underwent this\ngeneral sound change,", "start": 2332.33, "duration": 2.64}, {"text": "and the point is you discover\nthat the sound change is", "start": 2334.97, "duration": 2.745}, {"text": "general, and that's how\nyou convince yourself", "start": 2337.715, "duration": 1.875}, {"text": "that it belongs to this club.", "start": 2339.59, "duration": 1.92}, {"text": "Yeah.", "start": 2341.51, "duration": 0.54}, {"text": "AUDIENCE: Why?", "start": 2342.05, "duration": 0.75}, {"text": "NORVIN RICHARDS:\nWhy did it do that?", "start": 2342.8, "duration": 2.53}, {"text": "So there isn't any really\ngood answer to that,", "start": 2345.33, "duration": 3.83}, {"text": "but you could think.", "start": 2349.16, "duration": 1.68}, {"text": "If you imagined first\nthat they decided", "start": 2350.84, "duration": 2.58}, {"text": "that it wasn't good to have\nwords start with \"d\" and \"w.\"", "start": 2353.42, "duration": 4.487}, {"text": "Like, that's too many\nconsonants at the beginning.", "start": 2357.907, "duration": 2.083}, {"text": "We don't want that.", "start": 2359.99, "duration": 0.84}, {"text": "We're going to add a vowel.", "start": 2360.83, "duration": 1.77}, {"text": "So they'll add a vowel\nat the beginning.", "start": 2362.6, "duration": 3.15}, {"text": "This alternation\nbetween \"d\" and \"r\"", "start": 2365.75, "duration": 3.21}, {"text": "is not such a\nstrange thing to do.", "start": 2368.96, "duration": 3.46}, {"text": "So an \"r\" is kind of--", "start": 2372.42, "duration": 2.57}, {"text": "it's not unlike the relationship\nbetween \"w\" and \"u\",", "start": 2374.99, "duration": 3.72}, {"text": "that \"d\" is an actual stop,\nan \"ruh,\" it is unlike that.", "start": 2378.71, "duration": 3.99}, {"text": "\"d\" is an actual stop, and\n\"r,\" especially if it's a flap,", "start": 2382.7, "duration": 3.24}, {"text": "is you're just sort of\nwhacking the part of your mouth", "start": 2385.94, "duration": 2.61}, {"text": "that where you\nmake the \"d\" stop.", "start": 2388.55, "duration": 2.13}, {"text": "And then the fact that\n\"w\" became a \"k,\" well,", "start": 2390.68, "duration": 2.76}, {"text": "we've seen \"w\" becoming a\n\"gwa\" in Welsh and in Chamorro.", "start": 2393.44, "duration": 5.88}, {"text": "And a \"k\" has a stop in a\nplace where a \"w\" would just", "start": 2399.32, "duration": 4.44}, {"text": "be an approximant.", "start": 2403.76, "duration": 0.93}, {"text": "So it's maybe not a completely\ncrazy set of sound changes.", "start": 2404.69, "duration": 3.21}, {"text": "I should say, it's not\nalways possible to understand", "start": 2407.9, "duration": 2.64}, {"text": "why a language underwent the\nsound changes that it did.", "start": 2410.54, "duration": 3.06}, {"text": "There's a beautiful example.", "start": 2413.6, "duration": 1.243}, {"text": "I have sometimes used this as\na problem set in this class.", "start": 2414.843, "duration": 2.417}, {"text": "If you were going to\nhave another problem set,", "start": 2417.26, "duration": 1.41}, {"text": "it might have been about this.", "start": 2418.67, "duration": 1.25}, {"text": "There's an Algonquian\nlanguage, Arapaho.", "start": 2419.92, "duration": 5.603}, {"text": "If you look at the\nAlgonquian languages,", "start": 2425.523, "duration": 1.667}, {"text": "the Proto-Algonquian\ncan be reconstructed", "start": 2427.19, "duration": 2.04}, {"text": "to a fair degree of confidence.", "start": 2429.23, "duration": 4.14}, {"text": "There are a bunch of\nAlgonquian languages.", "start": 2433.37, "duration": 1.797}, {"text": "They're very well studied.", "start": 2435.167, "duration": 1.083}, {"text": "There are sound changes.", "start": 2436.25, "duration": 1.0}, {"text": "It's not all that hard to\nrelate them to each other.", "start": 2437.25, "duration": 2.24}, {"text": "Arapaho is an Algonquian\nlanguage, but it has undergone", "start": 2439.49, "duration": 2.82}, {"text": "sound changes like--", "start": 2442.31, "duration": 2.76}, {"text": "I'm trying to remember them\nall. \"p\" has become \"chuh.\"", "start": 2445.07, "duration": 4.44}, {"text": "\"m\" has become--\nwhat has \"m\" become?", "start": 2449.51, "duration": 3.27}, {"text": "\"m\" has become \"b.\"", "start": 2452.78, "duration": 3.54}, {"text": "There's a sound-- so\nwith the consequence", "start": 2456.32, "duration": 2.67}, {"text": "that-- oh, no. \"m\"\nhas become \"chuh.\"", "start": 2458.99, "duration": 2.04}, {"text": "They've both become \"chuh.\"\nthey've blended together.", "start": 2461.03, "duration": 2.88}, {"text": "So the consequence\nis that the word", "start": 2463.91, "duration": 1.98}, {"text": "for \"dog,\" which is the\none that I can remember off", "start": 2465.89, "duration": 2.43}, {"text": "the top of my head.", "start": 2468.32, "duration": 2.07}, {"text": "There's a word for \"dog\"\nthat in Wampanoag, which is", "start": 2470.39, "duration": 4.26}, {"text": "spoken around here, is \"anum.\"", "start": 2474.65, "duration": 2.67}, {"text": "This is a schwa.", "start": 2477.32, "duration": 0.96}, {"text": "And in Passamaquoddy is\n\"alum,\" and in Cree is \"ateem.\"", "start": 2478.28, "duration": 9.13}, {"text": "And so there's an \"m'\nhere that corresponds,", "start": 2487.41, "duration": 3.62}, {"text": "and there are vowels\nhere that have undergone", "start": 2491.03, "duration": 2.25}, {"text": "various kinds of sound changes.", "start": 2493.28, "duration": 1.35}, {"text": "There's a sound here, which\nis kind of mysterious.", "start": 2494.63, "duration": 2.33}, {"text": "It's unclear how to represent\nit in Proto-Algonquian.", "start": 2496.96, "duration": 3.64}, {"text": "But so here's one Wampanoag.", "start": 2500.6, "duration": 2.34}, {"text": "Here's Passamaquoddy.", "start": 2502.94, "duration": 2.97}, {"text": "Here's Cree.", "start": 2505.91, "duration": 2.4}, {"text": "And the Arapaho word\nfor it is \"fench.\"", "start": 2508.31, "duration": 6.6}, {"text": "Yeah.", "start": 2514.91, "duration": 0.54}, {"text": "So you've got \"anum,\" \"alum,\"\n\"ateem\" and then \"fench\"", "start": 2515.45, "duration": 4.86}, {"text": "is the Arapaho word.", "start": 2520.31, "duration": 1.36}, {"text": "So the Arapahos, I don't\nknow what happened to them.", "start": 2521.67, "duration": 3.56}, {"text": "But they underwent sound\nchanges that it's very hard", "start": 2525.23, "duration": 2.82}, {"text": "to justify to yourself.", "start": 2528.05, "duration": 1.65}, {"text": "It's unclear what happened.", "start": 2529.7, "duration": 1.77}, {"text": "I was once talking with\na linguist about this,", "start": 2531.47, "duration": 2.64}, {"text": "and his theory was\nthat what happened", "start": 2534.11, "duration": 2.46}, {"text": "with the Arapaho was that\nthey became a horse culture.", "start": 2536.57, "duration": 4.38}, {"text": "When horses were\nbrought to the US,", "start": 2540.95, "duration": 2.13}, {"text": "the Arapaho got\nreally into horses.", "start": 2543.08, "duration": 2.01}, {"text": "And his theory was\nthere must have", "start": 2545.09, "duration": 2.7}, {"text": "been a generation of Arapaho\nwho just sort of stopped", "start": 2547.79, "duration": 2.76}, {"text": "listening to their parents,\nIt underwent all kinds", "start": 2550.55, "duration": 3.168}, {"text": "of radical sound\nchanges because they", "start": 2553.718, "duration": 1.542}, {"text": "were too busy riding horses.", "start": 2555.26, "duration": 1.56}, {"text": "This is an example where--", "start": 2560.45, "duration": 1.87}, {"text": "thank you.", "start": 2562.32, "duration": 0.5}, {"text": "One of you deliberately fell\nfor the trap that I was setting.", "start": 2562.82, "duration": 6.03}, {"text": "An example where you\nconvince yourself", "start": 2568.85, "duration": 2.49}, {"text": "that these two, the Mandarin\nand the Armenian words,", "start": 2571.34, "duration": 4.47}, {"text": "are not related, despite having\nsome stuff that looks like it's", "start": 2575.81, "duration": 3.12}, {"text": "in common.", "start": 2578.93, "duration": 0.9}, {"text": "It's really the Armenian and the\nGreek words that are related.", "start": 2579.83, "duration": 4.51}, {"text": "Another example where you have\ntwo words that look similar,", "start": 2584.34, "duration": 2.91}, {"text": "but the two languages\nare not related.", "start": 2587.25, "duration": 2.21}, {"text": "There's a beautiful memoir by a\nguy named Dixon, Robert Dixon.", "start": 2589.46, "duration": 7.95}, {"text": "He's a linguist who did--", "start": 2597.41, "duration": 2.77}, {"text": "he wrote a book called\nMemoirs of a Field Worker", "start": 2600.18, "duration": 3.5}, {"text": "which was about his work\nin Aboriginal languages", "start": 2603.68, "duration": 2.94}, {"text": "in Australia in the '60s.", "start": 2606.62, "duration": 2.94}, {"text": "It's a nice book.", "start": 2609.56, "duration": 1.59}, {"text": "And one of the\nthings he talks about", "start": 2611.15, "duration": 1.5}, {"text": "is going-- he was traveling\naround different Aboriginal", "start": 2612.65, "duration": 4.41}, {"text": "areas, talking to\ndifferent speakers", "start": 2617.06, "duration": 2.07}, {"text": "of different languages.", "start": 2619.13, "duration": 1.05}, {"text": "And there was a\nparticular language", "start": 2620.18, "duration": 1.95}, {"text": "that he managed to find possibly\none of the last speakers of,", "start": 2622.13, "duration": 3.075}, {"text": "a language called\nMbabaram, which no longer", "start": 2625.205, "duration": 2.895}, {"text": "has any speakers at all.", "start": 2628.1, "duration": 1.05}, {"text": "This was in the '60s.", "start": 2629.15, "duration": 1.56}, {"text": "And he was very interested\nin this language.", "start": 2630.71, "duration": 1.95}, {"text": "It was supposed to be\nquite different from some", "start": 2632.66, "duration": 1.44}, {"text": "of the languages\nthat were near it.", "start": 2634.1, "duration": 1.458}, {"text": "And he finally\nfound a speaker who", "start": 2635.558, "duration": 1.512}, {"text": "was finally willing to talk to\nhim and sat down with this guy.", "start": 2637.07, "duration": 2.1}, {"text": "And the guy said, OK,\nlet me start teaching", "start": 2639.17, "duration": 1.62}, {"text": "you some Mbabaram words.", "start": 2640.79, "duration": 1.17}, {"text": "Do you know our word for \"dog\"?", "start": 2641.96, "duration": 1.97}, {"text": "And he was like, OK, no.", "start": 2643.93, "duration": 1.0}, {"text": "What's your word for \"dog\"?", "start": 2644.93, "duration": 1.17}, {"text": "And the guy smiled,\nand he said, \"dog.\"", "start": 2646.1, "duration": 3.72}, {"text": "And Dixon was like, OK,\nthis has to be a joke.", "start": 2649.82, "duration": 3.55}, {"text": "But it turned out\nit was not a joke.", "start": 2653.37, "duration": 2.61}, {"text": "Most of the languages\nof the world", "start": 2655.98, "duration": 2.36}, {"text": "probably have a word for \"dog.\"", "start": 2658.34, "duration": 1.53}, {"text": "There are dogs in\nlots of places.", "start": 2659.87, "duration": 2.01}, {"text": "And \"d\" and \"o\" and \"g,\" they're\nnot such uncommon sounds.", "start": 2661.88, "duration": 4.11}, {"text": "And 6,000 whatever languages\nin the world, and yeah,", "start": 2665.99, "duration": 3.93}, {"text": "this kind of thing\nhappens every so often.", "start": 2669.92, "duration": 2.17}, {"text": "So these are completely\nunrelated languages.", "start": 2672.09, "duration": 2.31}, {"text": "Mbabaram \"dog\" can\nbe related to--", "start": 2674.4, "duration": 4.545}, {"text": "what is that, a proto\n[INAUDIBLE] form,", "start": 2678.945, "duration": 2.525}, {"text": "\"gudaga,\" which changed in\nsome related languages to other", "start": 2681.47, "duration": 4.2}, {"text": "sounds.", "start": 2685.67, "duration": 1.02}, {"text": "So you have \"gudaga\" in Yidiny,\nand you have \"guda\" in Dyirbal.", "start": 2686.69, "duration": 3.06}, {"text": "And in Mbabaram, they got\nrid of the first syllable,", "start": 2689.75, "duration": 2.412}, {"text": "and they got rid\nof the last vowel.", "start": 2692.162, "duration": 1.458}, {"text": "And before you knew\nit, you had \"dog.\"", "start": 2693.62, "duration": 1.8}, {"text": "English also has a word \"dog.\"", "start": 2695.42, "duration": 2.25}, {"text": "It's not from Australia.", "start": 2697.67, "duration": 2.712}, {"text": "So we have-- it\noriginally referred", "start": 2700.382, "duration": 1.458}, {"text": "to another kind, a particular\nkind of dog, a mastiff.", "start": 2701.84, "duration": 4.29}, {"text": "And it's taken over\nas our word for \"dog.\"", "start": 2706.13, "duration": 2.19}, {"text": "Our older word for \"dog\" was\n\"hound,\" which we still have.", "start": 2708.32, "duration": 4.188}, {"text": "And this is the kind\nof thing that happens.", "start": 2712.508, "duration": 1.792}, {"text": "So you know, Persian and English\nhave the same word for \"bad.\"", "start": 2714.3, "duration": 3.05}, {"text": "Malay and Greek have very\nsimilar-looking words", "start": 2717.35, "duration": 2.49}, {"text": "for \"eye.\"", "start": 2719.84, "duration": 1.47}, {"text": "And it's just a coincidence.", "start": 2721.31, "duration": 2.43}, {"text": "How do you know whether you're\nlooking at a coincidence?", "start": 2723.74, "duration": 2.61}, {"text": "Well, you ask yourself whether\nyou can posit regular sound", "start": 2726.35, "duration": 2.55}, {"text": "changes.", "start": 2728.9, "duration": 1.11}, {"text": "So English and Kaqchikel\nMayan have words for \"mess\"", "start": 2730.01, "duration": 3.15}, {"text": "that sound more\nor less the same.", "start": 2733.16, "duration": 2.55}, {"text": "That's the kind of\nthing, if I just tell you", "start": 2735.71, "duration": 2.28}, {"text": "in isolation I have\ntwo languages that", "start": 2737.99, "duration": 1.71}, {"text": "have the same word for\n\"mess,\" if you want to know,", "start": 2739.7, "duration": 2.43}, {"text": "are those languages related,\nwell the way you find out", "start": 2742.13, "duration": 2.43}, {"text": "is by trying to\nfind out whether you", "start": 2744.56, "duration": 1.65}, {"text": "can come up with\nsound changes that", "start": 2746.21, "duration": 2.1}, {"text": "apply to more than one word.", "start": 2748.31, "duration": 1.85}, {"text": "Is it generally the case that\nwhere this language has an \"m\"", "start": 2750.16, "duration": 2.5}, {"text": "this other language has an \"m'?", "start": 2752.66, "duration": 1.292}, {"text": "Where this language has an \"s,\"\nthis other language has an \"s\"?", "start": 2753.952, "duration": 3.418}, {"text": "In the case of English and\nKaqchikel, the answer is no.", "start": 2757.37, "duration": 2.68}, {"text": "So here are a bunch of other\nwords with \"m\"s in them,", "start": 2760.05, "duration": 2.42}, {"text": "and they don't have\n\"m\"s in Kaqchikel.", "start": 2762.47, "duration": 2.7}, {"text": "You can't rely on\nit being the case", "start": 2765.17, "duration": 2.73}, {"text": "that every English\nword with an \"m\" in it", "start": 2767.9, "duration": 2.13}, {"text": "would have an \"m\"\nin Kaqchikel, even", "start": 2770.03, "duration": 2.58}, {"text": "if the languages were related.", "start": 2772.61, "duration": 1.54}, {"text": "But you are entitled\nto hope that it'll", "start": 2774.15, "duration": 2.18}, {"text": "happen more than once.", "start": 2776.33, "duration": 2.13}, {"text": "So this looks like\na coincidence.", "start": 2778.46, "duration": 2.37}, {"text": "Any questions about any of this?", "start": 2783.92, "duration": 3.24}, {"text": "Just as an in-class\nexercise, I wanted", "start": 2787.16, "duration": 2.31}, {"text": "to try doing some\nhistorical linguistics,", "start": 2789.47, "duration": 2.1}, {"text": "reconstructing\nsome sound changes.", "start": 2791.57, "duration": 2.31}, {"text": "Here are some\nPolynesian languages.", "start": 2793.88, "duration": 1.93}, {"text": "So they are languages\nfrom the Polynesian branch", "start": 2795.81, "duration": 2.57}, {"text": "of the very large\nAustronesian language family.", "start": 2798.38, "duration": 3.51}, {"text": "Hawaiian, which is spoken\nin Hawaii, and Maori,", "start": 2801.89, "duration": 2.1}, {"text": "which is from New Zealand, and\nTongan, which is from Tonga,", "start": 2803.99, "duration": 3.0}, {"text": "and Samoan, which is from Samoa.", "start": 2806.99, "duration": 3.09}, {"text": "These are all languages spoken\nin islands of the Pacific,", "start": 2810.08, "duration": 3.42}, {"text": "particularly the\neastern Pacific,", "start": 2813.5, "duration": 1.395}, {"text": "or not too far from Hawaii--", "start": 2814.895, "duration": 2.385}, {"text": "between Hawaii and New Zealand.", "start": 2817.28, "duration": 2.4}, {"text": "And these are all words\nthat look pretty related", "start": 2819.68, "duration": 2.61}, {"text": "to each other.", "start": 2822.29, "duration": 0.91}, {"text": "And so let's see if\nwe can figure out", "start": 2823.2, "duration": 1.61}, {"text": "any sound correspondences.", "start": 2824.81, "duration": 1.59}, {"text": "Maybe we can start by\nlooking at the things", "start": 2829.68, "duration": 3.0}, {"text": "that I have made green here.", "start": 2832.68, "duration": 1.245}, {"text": "What do you think?", "start": 2836.46, "duration": 0.93}, {"text": "What sort of proto\nsound should we", "start": 2837.39, "duration": 2.7}, {"text": "posit for the sound that\nis in green in these kinds", "start": 2840.09, "duration": 3.925}, {"text": "of examples?", "start": 2844.015, "duration": 0.5}, {"text": "There are at least two theories\nthat we could take seriously--", "start": 2848.897, "duration": 2.583}, {"text": "hypotheses we could\ntake seriously, right?", "start": 2851.48, "duration": 1.86}, {"text": "There's a third\nkind of hypothesis.", "start": 2853.34, "duration": 2.49}, {"text": "Maybe it's an \"m,\" right?", "start": 2855.83, "duration": 3.45}, {"text": "But let's put that possibility\naside for a second.", "start": 2859.28, "duration": 2.71}, {"text": "We're not going to do that\nunless we're driven to it.", "start": 2861.99, "duration": 2.28}, {"text": "So the two theories that\nwe could take seriously", "start": 2864.27, "duration": 2.0}, {"text": "are maybe it's a \"k\"\nor maybe it's a \"t.\"", "start": 2866.27, "duration": 4.84}, {"text": "Anybody have a theory\nabout what we ought to do?", "start": 2871.11, "duration": 3.81}, {"text": "Joseph?", "start": 2874.92, "duration": 1.47}, {"text": "AUDIENCE: [INAUDIBLE] --that\nmaybe the majority rules", "start": 2876.39, "duration": 6.62}, {"text": "and it's the \"t.\"", "start": 2883.01, "duration": 0.72}, {"text": "NORVIN RICHARDS: Yes, so we\ncould do this democratically", "start": 2883.73, "duration": 2.333}, {"text": "and say, yeah, there are more\n\"t\"s on this slide than there", "start": 2886.063, "duration": 3.337}, {"text": "are \"k\"s.", "start": 2889.4, "duration": 1.74}, {"text": "Majority rules.", "start": 2891.14, "duration": 1.41}, {"text": "Yeah.", "start": 2892.55, "duration": 0.875}, {"text": "AUDIENCE: I would\nalso go with \"t\"", "start": 2893.425, "duration": 1.455}, {"text": "because Hawaii is a more\ngeographically isolated area.", "start": 2894.88, "duration": 5.42}, {"text": "NORVIN RICHARDS: Yeah.", "start": 2900.3, "duration": 0.99}, {"text": "All of these-- I mean,\nthese are all islands.", "start": 2901.29, "duration": 2.97}, {"text": "Amazing story.", "start": 2904.26, "duration": 1.29}, {"text": "These people started--\nthe Proto-Austronesians", "start": 2905.55, "duration": 3.51}, {"text": "are supposed to have\nstarted in Taiwan", "start": 2909.06, "duration": 1.65}, {"text": "and headed out in\noutrigger canoes", "start": 2910.71, "duration": 3.57}, {"text": "and settled all of these\nislands in the Pacific,", "start": 2914.28, "duration": 2.97}, {"text": "tossing consonants overboard\nwhen they got to too heavy,", "start": 2917.25, "duration": 2.85}, {"text": "as far as I can tell.", "start": 2920.1, "duration": 2.262}, {"text": "But you're right.", "start": 2922.362, "duration": 0.708}, {"text": "Hawaiian was near the\nend of their journey.", "start": 2923.07, "duration": 2.79}, {"text": "So they're supposed to\nhave started in Taiwan.", "start": 2925.86, "duration": 2.94}, {"text": "New Zealand and\nTonga and Samoa were", "start": 2928.8, "duration": 2.67}, {"text": "all closer to where they\nstarted than Hawaii.", "start": 2931.47, "duration": 2.74}, {"text": "So maybe Hawaii-- we're\njustified to think", "start": 2934.21, "duration": 3.38}, {"text": "that Hawaiian might\nhave undergone some", "start": 2937.59, "duration": 2.16}, {"text": "of the special sound changes.", "start": 2939.75, "duration": 3.42}, {"text": "I can also tell you something\nspecial about Hawaiian.", "start": 2943.17, "duration": 2.55}, {"text": "I don't know whether\nthis will come up later.", "start": 2945.72, "duration": 2.94}, {"text": "Hawaiian does not have a \"t.\"", "start": 2948.66, "duration": 1.92}, {"text": "It's one of the few languages\nin the world that does not,", "start": 2950.58, "duration": 3.84}, {"text": "which is why, if\nyou've ever heard,", "start": 2954.42, "duration": 2.64}, {"text": "there's a song that is sometimes\nplayed around Christmas", "start": 2957.06, "duration": 4.68}, {"text": "which involves the Hawaiian\nversion of \"Merry Christmas\"--", "start": 2961.74, "duration": 3.81}, {"text": "\"Mele Kalikimaka.\"", "start": 2965.55, "duration": 4.37}, {"text": "\"Mele Kalikimaka\" is\nthe Hawaiian version", "start": 2969.92, "duration": 3.97}, {"text": "of \"Merry Christmas\"\nbecause Hawaiian has no t,\"", "start": 2973.89, "duration": 2.55}, {"text": "and it also has no\n\"s,\" So they need", "start": 2976.44, "duration": 3.39}, {"text": "to replace the \"s\" in\n\"Christmas\" with something,", "start": 2979.83, "duration": 2.43}, {"text": "and what they replace it\nwith is \"k\" because that's", "start": 2982.26, "duration": 2.46}, {"text": "the best they can do.", "start": 2984.72, "duration": 0.94}, {"text": "That's the closest\nthey've got to that.", "start": 2985.66, "duration": 3.32}, {"text": "So yes, Hawaiian has no \"t.\"", "start": 2988.98, "duration": 1.59}, {"text": "So the idea that\nmaybe there was a t,\"", "start": 2990.57, "duration": 2.25}, {"text": "and in Hawaiian,\nit became a \"k,\"", "start": 2992.82, "duration": 2.58}, {"text": "has some initial plausibility.", "start": 2995.4, "duration": 2.46}, {"text": "So yeah, we'll posit a\nsound change in Hawaiian", "start": 2997.86, "duration": 2.07}, {"text": "from \"t\" to \"k.\"", "start": 2999.93, "duration": 2.47}, {"text": "And we'll posit a some\nProto-Polynesian forms", "start": 3002.4, "duration": 3.45}, {"text": "that will have \"t\" in them.", "start": 3005.85, "duration": 1.41}, {"text": "That is, they'll look like\nthe Maori, Tongan, and Samoan", "start": 3007.26, "duration": 2.43}, {"text": "forms, and then we'll\nposit the sound change", "start": 3009.69, "duration": 2.49}, {"text": "in Hawaiian that changes\nthat \"t\" into a \"k.\"", "start": 3012.18, "duration": 4.15}, {"text": "So far, so good.", "start": 3016.33, "duration": 1.65}, {"text": "Here are some more forms.", "start": 3017.98, "duration": 3.64}, {"text": "What should we do with these?", "start": 3021.62, "duration": 1.29}, {"text": "So it's either a \"k\"\nor it's a glottal stop.", "start": 3028.982, "duration": 1.833}, {"text": "Maybe for now we should just sit\non this problem because here,", "start": 3040.63, "duration": 5.37}, {"text": "just this principle of\ndoing this kind of thing", "start": 3046.0, "duration": 2.07}, {"text": "democratically, maybe\nit doesn't help us.", "start": 3048.07, "duration": 2.28}, {"text": "We've got two votes for \"k\"\nand two votes for glottal stop.", "start": 3050.35, "duration": 3.625}, {"text": "This might be a place\nwhere it's easier", "start": 3053.975, "duration": 1.625}, {"text": "to imagine a \"k\"\nbecoming a glottal stop", "start": 3055.6, "duration": 3.09}, {"text": "than it is to imagine a\nglottal stop becoming a \"k.\"", "start": 3058.69, "duration": 3.51}, {"text": "\"k\"s becoming glottal stops,\nthat's a thing that happens", "start": 3062.2, "duration": 2.91}, {"text": "pretty commonly in\nvarious languages.", "start": 3065.11, "duration": 3.87}, {"text": "And in fact, that's what people\nstandardly do in this case.", "start": 3068.98, "duration": 3.49}, {"text": "So in Hawaiian, we posit a\n\"k\" changing to a global stop", "start": 3072.47, "duration": 5.39}, {"text": "in these kinds of examples.", "start": 3077.86, "duration": 2.7}, {"text": "Maori and Tongan\nare the ones that", "start": 3080.56, "duration": 2.07}, {"text": "are being conservative here.", "start": 3082.63, "duration": 1.26}, {"text": "We'll see an additional reason\nto say that in just a second,", "start": 3083.89, "duration": 2.59}, {"text": "I think.", "start": 3086.48, "duration": 0.5}, {"text": "Here's the additional\nreason to say that.", "start": 3091.52, "duration": 2.37}, {"text": "Here are a bunch\nmore words where", "start": 3093.89, "duration": 2.07}, {"text": "Tongan has glottal stops\nin unpredictable places.", "start": 3095.96, "duration": 5.7}, {"text": "So at the beginning\nof the word for \"day\"", "start": 3101.66, "duration": 1.785}, {"text": "and twice in the word for \"love\"\nand in the middle of the words", "start": 3103.445, "duration": 2.625}, {"text": "for \"leg\" and \"voice.\"", "start": 3106.07, "duration": 2.955}, {"text": "And it's not because-- so if you\nwant to learn to speak Tongan,", "start": 3109.025, "duration": 2.625}, {"text": "one of the things\nyou have to learn", "start": 3111.65, "duration": 1.458}, {"text": "is that some words begin\nwith glottal stops,", "start": 3113.108, "duration": 2.502}, {"text": "and others begin with vowels.", "start": 3115.61, "duration": 1.5}, {"text": "So \"dawn\" starts with a\nvowel, and \"day\" starts", "start": 3117.11, "duration": 3.21}, {"text": "with a glottal stop.", "start": 3120.32, "duration": 1.33}, {"text": "And distinguishing these\nfrom each other is tricky.", "start": 3121.65, "duration": 3.65}, {"text": "The fact that Tongan is putting\nthese glottal stops in places", "start": 3125.3, "duration": 2.85}, {"text": "that can't be predicted--", "start": 3128.15, "duration": 1.41}, {"text": "[SNEEZE]", "start": 3129.56, "duration": 0.54}, {"text": "Bless you.", "start": 3130.1, "duration": 0.78}, {"text": "Leads us to think\nthat what's going on", "start": 3133.7, "duration": 2.58}, {"text": "is that those were glottal\nstops in Proto-Polynesian,", "start": 3136.28, "duration": 3.84}, {"text": "and they've been lost in\nall the other languages.", "start": 3140.12, "duration": 2.8}, {"text": "So here's place\nwhere predictability", "start": 3142.92, "duration": 3.56}, {"text": "trumps democracy.", "start": 3146.48, "duration": 2.52}, {"text": "We can't predict where Tongan\nwill have these glottal stops.", "start": 3149.0, "duration": 3.96}, {"text": "We can predict where\nHawaiian, Maori, and Samoan", "start": 3152.96, "duration": 3.72}, {"text": "will have glottal stops.", "start": 3156.68, "duration": 1.2}, {"text": "So Hawaiian and Samoan\nwill have glottal stops", "start": 3157.88, "duration": 3.63}, {"text": "wherever there's a \"k\"\nin Maori and Tongan.", "start": 3161.51, "duration": 3.3}, {"text": "And Maori just won't\nhave glottal stops.", "start": 3164.81, "duration": 3.72}, {"text": "So it's always predictable\nwhere the glottal stops", "start": 3168.53, "duration": 2.43}, {"text": "are in the other languages.", "start": 3170.96, "duration": 1.14}, {"text": "It's not predictable\nwhere they are in Tongan,", "start": 3172.1, "duration": 1.917}, {"text": "so we'll posit them\nfor the proto language.", "start": 3174.017, "duration": 2.263}, {"text": "So Aloha in Hawaiian, which\nliterally means \"love,\"", "start": 3176.28, "duration": 3.89}, {"text": "in Proto-Polynesian is\n\"'alo'ofa\" with two glottal", "start": 3180.17, "duration": 5.43}, {"text": "stops in it.", "start": 3185.6, "duration": 1.23}, {"text": "And you can see, incidentally,\nanother sound change.", "start": 3186.83, "duration": 2.37}, {"text": "The \"f\" became \"h\" in\nHawaiian and also in Maori.", "start": 3189.2, "duration": 5.78}, {"text": "So Hawaiian has\nundergone sound changes,", "start": 3194.98, "duration": 2.25}, {"text": "\"k\" becoming glottal\nstops, \"t\" becoming \"k,\"", "start": 3197.23, "duration": 2.4}, {"text": "and glottal stop vanishing.", "start": 3199.63, "duration": 2.61}, {"text": "This is sometimes-- so I'll\njust do that again dramatically", "start": 3202.24, "duration": 2.76}, {"text": "with a sagittal section here.", "start": 3205.0, "duration": 3.34}, {"text": "So Proto-Polynesian \"ata,\"\n\"dawn,\" has become \"aka.\"", "start": 3208.34, "duration": 4.07}, {"text": "In Hawaiian, \"t\" has become\n\"k,\" with the consequence", "start": 3212.41, "duration": 2.67}, {"text": "that Hawaiian has no \"t.\"", "start": 3215.08, "duration": 2.4}, {"text": "\"k\" has become glottal stop,\nso Proto-Polynesian \"kula,\"", "start": 3217.48, "duration": 3.36}, {"text": "which means \"red,\" has\nbecome \"'ula\" in Hawaiian.", "start": 3220.84, "duration": 3.48}, {"text": "And Proto-Polynesian\nglottal stop has vanished.", "start": 3224.32, "duration": 3.6}, {"text": "This is sometimes\ncalled a chain shift.", "start": 3227.92, "duration": 3.15}, {"text": "And there are different ways\nof thinking about chain shifts,", "start": 3231.07, "duration": 4.23}, {"text": "but they're not--\ncross-linguistically", "start": 3235.3, "duration": 1.59}, {"text": "not uncommon.", "start": 3236.89, "duration": 0.6}, {"text": "I'll show you another\nkind of example of one", "start": 3237.49, "duration": 1.89}, {"text": "in just a second, where you\nhave sound A becoming sound B,", "start": 3239.38, "duration": 4.35}, {"text": "sound B becoming sound C,\nand sound C becoming sound D.", "start": 3243.73, "duration": 4.32}, {"text": "And it's often difficult to\ndetermine the order in which", "start": 3248.05, "duration": 5.37}, {"text": "things like this happen.", "start": 3253.42, "duration": 1.35}, {"text": "One way to think about this\nis the Hawaiians got rid", "start": 3254.77, "duration": 3.21}, {"text": "of Proto-Polynesian\nglottal stop,", "start": 3257.98, "duration": 1.83}, {"text": "and then they were like, now\nthat we have no glottal stop,", "start": 3259.81, "duration": 3.0}, {"text": "we're free to pronounce our\n\"k\" as glottally as we like.", "start": 3262.81, "duration": 3.327}, {"text": "We don't have to worry\nabout the \"k\" getting", "start": 3266.137, "duration": 1.833}, {"text": "confused with the glottal stop.", "start": 3267.97, "duration": 1.74}, {"text": "And so the \"k\" began\ndrifting backwards", "start": 3269.71, "duration": 1.92}, {"text": "and becoming a glottal stop.", "start": 3271.63, "duration": 1.29}, {"text": "And then they were\nlike, wait, wait.", "start": 3272.92, "duration": 1.53}, {"text": "We have no \"k\" anymore.", "start": 3274.45, "duration": 1.27}, {"text": "Our \"k\" is gone.", "start": 3275.72, "duration": 0.74}, {"text": "It's just become a glottal stop.", "start": 3276.46, "duration": 0.99}, {"text": "We miss \"k.\"", "start": 3277.45, "duration": 0.6}, {"text": "We will change our\n\"t\" into a \"k.\"", "start": 3278.05, "duration": 2.46}, {"text": "And then who knows\nwhat would happen,", "start": 3280.51, "duration": 1.89}, {"text": "how they would manage\nto come up with a \"t\"?", "start": 3282.4, "duration": 1.86}, {"text": "Maybe if we keep\nan eye on Hawaiian,", "start": 3284.26, "duration": 1.5}, {"text": "we'll get to see what they do.", "start": 3285.76, "duration": 2.07}, {"text": "It's at least one way to talk\nabout these kinds of chain", "start": 3287.83, "duration": 2.61}, {"text": "shifts.", "start": 3290.44, "duration": 2.555}, {"text": "Another famous\nchain shift, which", "start": 3292.995, "duration": 1.375}, {"text": "is called the Great\nEnglish Vowel Shift--", "start": 3294.37, "duration": 1.89}, {"text": "sorry, the English\nGreat Vowel Shift.", "start": 3296.26, "duration": 2.67}, {"text": "It is the reason that if you\nstudy almost any other language", "start": 3298.93, "duration": 6.3}, {"text": "of Europe, you'll\nlearn vowels that", "start": 3305.23, "duration": 2.73}, {"text": "have a certain set of\nsounds associated with them.", "start": 3307.96, "duration": 3.72}, {"text": "They are the sounds,\nmore or less,", "start": 3311.68, "duration": 1.62}, {"text": "that those symbols\nhave in the IPA.", "start": 3313.3, "duration": 2.25}, {"text": "So in lots of\nlanguages, this symbol", "start": 3315.55, "duration": 2.22}, {"text": "is used for a vowel\nthat's pronounced \"ee.\"", "start": 3317.77, "duration": 2.94}, {"text": "But in English,\nit's pronounced \"I.\"", "start": 3320.71, "duration": 4.65}, {"text": "Or that in lots of languages,\nthis symbol is used for a vowel", "start": 3325.36, "duration": 4.62}, {"text": "that's pronounced \"a,\" but in\nEnglish, it's pronounced \"ee.\"", "start": 3329.98, "duration": 3.96}, {"text": "This is all because of the\nGreat English Vowel Shift.", "start": 3333.94, "duration": 2.425}, {"text": "What was the Great\nEnglish Vowel Shift?", "start": 3336.365, "duration": 1.625}, {"text": "It went like this.", "start": 3337.99, "duration": 1.23}, {"text": "Around the 14th\ncentury, English had", "start": 3339.22, "duration": 2.64}, {"text": "long vowels in these positions.", "start": 3341.86, "duration": 1.8}, {"text": "English also had short vowels.", "start": 3343.66, "duration": 1.65}, {"text": "We'll put those aside.", "start": 3345.31, "duration": 1.11}, {"text": "So there were long vowels,\nthat were just vowels", "start": 3346.42, "duration": 2.0}, {"text": "that were held for a long time.", "start": 3348.42, "duration": 2.02}, {"text": "And they were in those\npositions in the mouth.", "start": 3350.44, "duration": 3.84}, {"text": "So you had an \"ee,\"\nan \"ay,\" an \"aa,\"", "start": 3354.28, "duration": 2.7}, {"text": "and then an \"ah,\"\n\"aw,\" \"oh,\" and \"oo.\"", "start": 3356.98, "duration": 2.61}, {"text": "We had all those long vowels.", "start": 3359.59, "duration": 2.19}, {"text": "And then the \"ee\" and the\n\"oo\" became dipthongs.", "start": 3361.78, "duration": 7.93}, {"text": "If you think about holding\nan \"ee\" for a long time,", "start": 3369.71, "duration": 3.45}, {"text": "your tongue is in a\nposition of maximum tension.", "start": 3373.16, "duration": 3.71}, {"text": "It's front and high,\nand you're supposed", "start": 3376.87, "duration": 2.61}, {"text": "to hold it for a long time.", "start": 3379.48, "duration": 1.413}, {"text": "And you can understand\nhow something like that", "start": 3380.893, "duration": 1.917}, {"text": "might have changed\ninto a dipthong.", "start": 3382.81, "duration": 1.458}, {"text": "So instead of holding\nan \"ee\" for a long time,", "start": 3384.268, "duration": 2.532}, {"text": "you were allowing\nyourself to begin", "start": 3386.8, "duration": 2.55}, {"text": "the vowel with your\ntongue in some more", "start": 3389.35, "duration": 1.95}, {"text": "central position and\nthen just sort of gesture", "start": 3391.3, "duration": 2.19}, {"text": "in the direction of an \"ee.\"", "start": 3393.49, "duration": 1.2}, {"text": "So you went from \"ee\" to\n\"uee\" to \"ayee\" to \"ai.\"", "start": 3394.69, "duration": 4.83}, {"text": "And so \"ee\" and \"oo\"\nbecame \"ai\" and \"ow.\"", "start": 3399.52, "duration": 5.19}, {"text": "And then suddenly,\nEnglish was like, wait.", "start": 3404.71, "duration": 2.22}, {"text": "Didn't we have an\n\"ee\" and an \"oo\"?", "start": 3406.93, "duration": 1.59}, {"text": "Our \"ee\" and \"oo\" are gone.", "start": 3408.52, "duration": 1.29}, {"text": "All we have is \"ai\" and \"ow.\"", "start": 3409.81, "duration": 2.22}, {"text": "And so \"ay\" and \"oh\" changed.", "start": 3412.03, "duration": 3.22}, {"text": "So \"ay\" became \"ee\"\nand \"oh\" became \"oo,\"", "start": 3415.25, "duration": 4.16}, {"text": "filling the gap that the first\npart of the vowel shift left.", "start": 3419.41, "duration": 6.57}, {"text": "And then long \"aa\" and\n\"ah\" both became \"ay.\"", "start": 3425.98, "duration": 3.39}, {"text": "That's why long \"a\" in a word\nlike \"fate\" is pronounced \"ay.\"", "start": 3429.37, "duration": 7.05}, {"text": "It's because, well, the \"ay\"\nwas off becoming an \"ee,\"", "start": 3436.42, "duration": 5.65}, {"text": "and so now we had a space\nwhere there was an \"ay.\"", "start": 3442.07, "duration": 2.27}, {"text": "And so our \"ah\" became an \"ay.\"", "start": 3444.34, "duration": 2.055}, {"text": "And our \"aw\" became an \"oh.\"", "start": 3446.395, "duration": 2.865}, {"text": "So all of our vowels have\nundergone this dance.", "start": 3449.26, "duration": 4.53}, {"text": "And if you look at\nmodern English dialects,", "start": 3453.79, "duration": 4.65}, {"text": "you can see a lot of these\nkinds of sound changes", "start": 3458.44, "duration": 2.31}, {"text": "continuing today.", "start": 3460.75, "duration": 0.91}, {"text": "So I come from a place\nwhere those dipthongs are", "start": 3461.66, "duration": 2.84}, {"text": "getting flattened, where \"ai\"\nhas a tendency to become \"aa.\"", "start": 3464.5, "duration": 6.96}, {"text": "And so the vowels are continuing\nto chase each other around", "start": 3471.46, "duration": 4.41}, {"text": "in the vowel space.", "start": 3475.87, "duration": 1.872}, {"text": "I think I talked\nabout this when we", "start": 3477.742, "duration": 1.458}, {"text": "were talking about\nphonetic inventories,", "start": 3479.2, "duration": 2.01}, {"text": "that there's work on the\nkinds of vowel inventories", "start": 3481.21, "duration": 5.94}, {"text": "that we find.", "start": 3487.15, "duration": 0.9}, {"text": "So there are plenty of\nlanguages out there that", "start": 3488.05, "duration": 2.07}, {"text": "have three vowels, and\nthe three vowels that you", "start": 3490.12, "duration": 2.542}, {"text": "have if you have three vowels\nare \"ee,\" \"oo,\" and \"ah.\"", "start": 3492.662, "duration": 3.668}, {"text": "That is, there's a\nfront high vowel,", "start": 3496.33, "duration": 2.43}, {"text": "there's a back high vowel,\nand there's a low vowel.", "start": 3498.76, "duration": 3.522}, {"text": "That is, you have\nthree vowels that", "start": 3502.282, "duration": 1.458}, {"text": "are kind of as far apart\nfrom each other as possible.", "start": 3503.74, "duration": 2.587}, {"text": "There aren't languages out\nthere that have three vowels,", "start": 3506.327, "duration": 2.333}, {"text": "and the three vowels are\n\"ee,\" \"ey,\" and \"eh.\"", "start": 3508.66, "duration": 4.62}, {"text": "That's not a vowel system.", "start": 3513.28, "duration": 1.597}, {"text": "One of my colleagues,\nEdward Flemming,", "start": 3514.877, "duration": 1.583}, {"text": "has done a lot of work on\ndifferent kinds of vowel", "start": 3516.46, "duration": 2.76}, {"text": "systems and reducing\nthem to this idea", "start": 3519.22, "duration": 2.28}, {"text": "that you're trying to\nkeep your vowels maximally", "start": 3521.5, "duration": 2.97}, {"text": "dispersed from each\nother in the vocal tract.", "start": 3524.47, "duration": 4.24}, {"text": "And that kind of thinking\ncan be one of the ways", "start": 3528.71, "duration": 2.0}, {"text": "to think about why English\nunderwent this vowel shift.", "start": 3530.71, "duration": 3.36}, {"text": "It's like, first the high\nvowels changed into dipthongs,", "start": 3534.07, "duration": 4.56}, {"text": "and then you have this sort\nof unclaimed real estate", "start": 3538.63, "duration": 2.478}, {"text": "at the top of the\nvocal tract, right?", "start": 3541.108, "duration": 1.542}, {"text": "So once you no longer\nhave an \"ee\" or an \"oo,\"", "start": 3542.65, "duration": 2.19}, {"text": "once they've changed\nto \"ay\" and \"ow,\"", "start": 3544.84, "duration": 2.49}, {"text": "there's this desire\nfor dispersion", "start": 3547.33, "duration": 2.52}, {"text": "that's pushing you to get\nsome vowels into that space.", "start": 3549.85, "duration": 4.89}, {"text": "That first change kind of\ntriggers a second change.", "start": 3554.74, "duration": 2.415}, {"text": "If you study languages,\none of the things", "start": 3562.36, "duration": 3.09}, {"text": "that you will\nsometimes be told is", "start": 3565.45, "duration": 2.07}, {"text": "here's a regular rule\nfor how you form, say,", "start": 3567.52, "duration": 2.97}, {"text": "different forms of\na noun, singulars", "start": 3570.49, "duration": 1.95}, {"text": "and plurals or different\ncase forms or whatever.", "start": 3572.44, "duration": 2.53}, {"text": "And then here are\nsome irregular forms.", "start": 3574.97, "duration": 2.51}, {"text": "And sometimes the\nirregular forms", "start": 3577.48, "duration": 2.34}, {"text": "are the consequence\nof sound changes.", "start": 3579.82, "duration": 2.62}, {"text": "So for example,\nwhen I was briefly", "start": 3582.44, "duration": 3.5}, {"text": "attempting to learn\nLatin in high school,", "start": 3585.94, "duration": 2.26}, {"text": "we were taught there\nare certain Latin nouns,", "start": 3588.2, "duration": 4.22}, {"text": "so-called third declension\nnouns, for which you", "start": 3592.42, "duration": 2.7}, {"text": "need to memorize both\nthe nominative singular", "start": 3595.12, "duration": 2.79}, {"text": "form and another form.", "start": 3597.91, "duration": 2.79}, {"text": "We were taught to memorize\nthe genitive singular", "start": 3600.7, "duration": 2.01}, {"text": "form because you can't predict\nfrom the nominative singular", "start": 3602.71, "duration": 6.3}, {"text": "what the other forms will be.", "start": 3609.01, "duration": 1.41}, {"text": "So you get words like\n\"rex,\" which means \"king,\"", "start": 3610.42, "duration": 2.22}, {"text": "and \"nox,\" which means \"night,\"\nand \"vox,\" which means \"voice.\"", "start": 3612.64, "duration": 4.08}, {"text": "But the stems to which\nyou add any other suffix", "start": 3616.72, "duration": 5.67}, {"text": "are unpredictable\nfrom the nominatives.", "start": 3622.39, "duration": 2.17}, {"text": "So king, \"rex,\" the genitive\nand the accusative and all", "start": 3624.56, "duration": 4.49}, {"text": "the other forms are formed off\nof a stem \"reg-\" Or for night,", "start": 3629.05, "duration": 4.23}, {"text": "it's \"noct-,\" and for\na voice, it's \"voc-.\"", "start": 3633.28, "duration": 3.45}, {"text": "Anybody else here study Latin?", "start": 3636.73, "duration": 1.42}, {"text": "This is all stuff that you\nhave to learn if you're", "start": 3638.15, "duration": 2.083}, {"text": "trying to learn Latin.", "start": 3640.233, "duration": 1.117}, {"text": "And what I was\ntaught, at least, was", "start": 3641.35, "duration": 1.5}, {"text": "to think of \"king,\" the word\nfor king as \"rex, regis.\"", "start": 3642.85, "duration": 2.73}, {"text": "We were supposed to just\nsort of cite both of those.", "start": 3645.58, "duration": 3.64}, {"text": "So my old high school\nLatin teacher, Mrs. McNair,", "start": 3649.22, "duration": 2.72}, {"text": "that's what she taught us.", "start": 3651.94, "duration": 1.17}, {"text": "Mrs. McNair could have taught\nus-- she probably knew this,", "start": 3653.11, "duration": 2.417}, {"text": "but she didn't reveal it to us--\nthat although you can't predict", "start": 3655.527, "duration": 4.303}, {"text": "the genitive from\nthe nominative,", "start": 3659.83, "duration": 2.52}, {"text": "you can predict the\nnominative from the genitive.", "start": 3662.35, "duration": 2.58}, {"text": "So what's really happening in\nLatin is that you've got these", "start": 3664.93, "duration": 3.33}, {"text": "stems, which are\n\"reg-,\" \"noct-,\" \"voc-,\"", "start": 3668.26, "duration": 3.18}, {"text": "and that you're forming the\nnominative by adding an \"s\"", "start": 3671.44, "duration": 3.33}, {"text": "and then doing\nsome sound changes.", "start": 3674.77, "duration": 1.96}, {"text": "So you take \"reg-\"\nand you add an \"s.\"", "start": 3676.73, "duration": 3.11}, {"text": "That by itself would\ngive you \"regs.\"", "start": 3679.84, "duration": 1.98}, {"text": "And then Latin doesn't\nallow a sequence", "start": 3681.82, "duration": 2.79}, {"text": "of a \"g\" followed by an \"s.\"", "start": 3684.61, "duration": 1.83}, {"text": "You make them both voiceless.", "start": 3686.44, "duration": 1.4}, {"text": "You change the \"g\"\nso that it's \"k.\"", "start": 3687.84, "duration": 2.08}, {"text": "and Latin spells the\nsequence \"ks\" with an \"x.\"", "start": 3689.92, "duration": 3.72}, {"text": "Or \"nox,\" yeah, that would\nend in two stops followed", "start": 3693.64, "duration": 5.04}, {"text": "by an \"s.\"", "start": 3698.68, "duration": 0.63}, {"text": "A \"k,\" a \"t\"-- a\n\"k\" sound, which", "start": 3699.31, "duration": 1.83}, {"text": "is spelled in Latin with a\n\"c,\" and a \"t\" and then an \"s.\"", "start": 3701.14, "duration": 3.882}, {"text": "And then you simplify\nthat by getting rid", "start": 3705.022, "duration": 2.238}, {"text": "of the \"t\" in between.", "start": 3707.26, "duration": 2.46}, {"text": "Or \"vox,\" which is, well,\nbasically, just \"vocs,\"", "start": 3709.72, "duration": 2.79}, {"text": "just adding \"s\" to the stem.", "start": 3712.51, "duration": 1.65}, {"text": "So Mrs. McNair could\nhave made my life easier", "start": 3714.16, "duration": 3.78}, {"text": "if she had been willing\nto tell me about that.", "start": 3717.94, "duration": 3.155}, {"text": "So there have to\nbe sound changes", "start": 3721.095, "duration": 1.375}, {"text": "that if you're willing to think\nabout the third declension", "start": 3722.47, "duration": 2.52}, {"text": "nouns this way--", "start": 3724.99, "duration": 1.28}, {"text": "[COUGHING] excuse me.", "start": 3726.27, "duration": 1.18}, {"text": "You can think of them as just\nhaving a nominative singular", "start": 3727.45, "duration": 3.42}, {"text": "form \"s\" and some sound\nchanges that obscure", "start": 3730.87, "duration": 3.48}, {"text": "the fact that the nominative\nsingular is really not", "start": 3734.35, "duration": 3.15}, {"text": "so complicated.", "start": 3737.5, "duration": 3.157}, {"text": "She would have had to teach\nus a bunch of sound changes,", "start": 3740.657, "duration": 2.333}, {"text": "but these are some of them.", "start": 3742.99, "duration": 3.12}, {"text": "Or here's another\nexample of this kind.", "start": 3746.11, "duration": 4.02}, {"text": "We had a problem set\nearlier on Inupiaq,", "start": 3750.13, "duration": 1.86}, {"text": "which is one of a\nnumber of languages that", "start": 3751.99, "duration": 2.43}, {"text": "are all related to each other.", "start": 3754.42, "duration": 1.35}, {"text": "They're all members\nof what is still,", "start": 3755.77, "duration": 1.8}, {"text": "for some reason, called the\nEskimo family of languages,", "start": 3757.57, "duration": 2.79}, {"text": "where I say \"still\"\nbecause the word \"Eskimo\"", "start": 3760.36, "duration": 2.79}, {"text": "is not well-regarded among\nthe people to whom it refers.", "start": 3763.15, "duration": 4.83}, {"text": "It's a name for them that\nwas come up with by the Cree.", "start": 3767.98, "duration": 3.81}, {"text": "There are debates\nabout what it means.", "start": 3771.79, "duration": 3.54}, {"text": "But it doesn't\nmatter what it means.", "start": 3775.33, "duration": 1.6}, {"text": "They don't like\nbeing called Eskimos,", "start": 3776.93, "duration": 1.542}, {"text": "so it's unfortunate that\nlinguistics continues", "start": 3778.472, "duration": 3.128}, {"text": "to refer to their\nlanguage family", "start": 3781.6, "duration": 1.56}, {"text": "as the Proto-Eskimo family.", "start": 3783.16, "duration": 2.1}, {"text": "Here are some words in\nthis language family.", "start": 3785.26, "duration": 3.45}, {"text": "These are proto forms,\nand so I should really", "start": 3788.71, "duration": 2.13}, {"text": "have stars on them.", "start": 3790.84, "duration": 1.68}, {"text": "So \"iglu,\" which is a\nword you may have heard,", "start": 3792.52, "duration": 2.28}, {"text": "it's the word for house.", "start": 3794.8, "duration": 2.65}, {"text": "So all of us live in igloos.", "start": 3797.45, "duration": 1.46}, {"text": "We all grew up in igloos, as far\nas the language is concerned,", "start": 3798.91, "duration": 4.29}, {"text": "or \"tuma\" or \"tavsi.\"", "start": 3803.2, "duration": 1.44}, {"text": "Here are some words.", "start": 3804.64, "duration": 1.71}, {"text": "And there's a very\ngeneral plural suffix,", "start": 3806.35, "duration": 2.94}, {"text": "\"t,\" which gets added.", "start": 3809.29, "duration": 4.2}, {"text": "The proto language for\nthis language family had--", "start": 3813.49, "duration": 3.18}, {"text": "let's see now-- four vowels.", "start": 3816.67, "duration": 2.55}, {"text": "So there was \"a,\" \"i,\" and\n\"u,\" and there's also schwa.", "start": 3819.22, "duration": 2.887}, {"text": "You can see there's\na schwa at the end", "start": 3822.107, "duration": 1.583}, {"text": "of the word for \"footprint.\"", "start": 3823.69, "duration": 2.76}, {"text": "And then in the history\nbetween the proto language", "start": 3826.45, "duration": 4.32}, {"text": "and modern Inupiaq, two\nsound changes took place.", "start": 3830.77, "duration": 4.32}, {"text": "First, \"t,\" like the\n\"t\" of the plural,", "start": 3835.09, "duration": 3.402}, {"text": "but not just the\n\"t\" of the plural.", "start": 3838.492, "duration": 1.458}, {"text": "It was a general sound change.", "start": 3839.95, "duration": 1.25}, {"text": "Whenever you had a \"t\" that\nfollowed the vowel \"i,\" the \"t\"", "start": 3841.2, "duration": 4.57}, {"text": "underwent what's\ncalled palatalization,", "start": 3845.77, "duration": 1.633}, {"text": "cross-linguistically\na very common sound", "start": 3847.403, "duration": 1.667}, {"text": "change where a \"t\" becomes\na \"ch\" around a front vowel.", "start": 3849.07, "duration": 5.16}, {"text": "We had something\nlike this happen", "start": 3854.23, "duration": 2.04}, {"text": "in English several times.", "start": 3856.27, "duration": 1.2}, {"text": "It's why our word for cheese\nstarts with a \"ch\" sound.", "start": 3857.47, "duration": 3.255}, {"text": "It comes from Latin caseus,\nwhich started with a \"k\" sound.", "start": 3860.725, "duration": 5.965}, {"text": "So T became \"ch\"\nafter the vowel \"i.\"", "start": 3866.69, "duration": 2.63}, {"text": "That's what you're seeing at\nthe end of the word for \"belts.\"", "start": 3869.32, "duration": 2.97}, {"text": "Regular sound change.", "start": 3872.29, "duration": 1.42}, {"text": "And then another\nsound change, Inupiaq", "start": 3873.71, "duration": 3.568}, {"text": "has a three vowel system.", "start": 3877.278, "duration": 1.042}, {"text": "It only has \"a,\" \"i,\" and \"u.\"", "start": 3878.32, "duration": 1.44}, {"text": "They got rid of schwa.", "start": 3879.76, "duration": 1.38}, {"text": "And in particular, they\nchanged schwa to an \"i.\"", "start": 3881.14, "duration": 2.993}, {"text": "But these sound\nchanges took place", "start": 3884.133, "duration": 1.417}, {"text": "in this order with\nthe consequence", "start": 3885.55, "duration": 2.04}, {"text": "that if you want to learn\nInupiaq now, what you're taught", "start": 3887.59, "duration": 3.24}, {"text": "is, well, the plural suffix is\na \"t,\" except after some nouns,", "start": 3890.83, "duration": 4.5}, {"text": "but not all nouns, that have\nan \"i\" at the end of them,", "start": 3895.33, "duration": 3.93}, {"text": "where the \"t\" becomes a \"ch.\"", "start": 3899.26, "duration": 1.47}, {"text": "And you just have to learn\nwhich nouns that end in \"i\"", "start": 3900.73, "duration": 4.17}, {"text": "change the \"t\" to\na \"ch\" and which", "start": 3904.9, "duration": 1.83}, {"text": "nouns that end in\n\"i\"-- the vowel that's", "start": 3906.73, "duration": 1.89}, {"text": "written with the letter \"i\"--", "start": 3908.62, "duration": 2.13}, {"text": "don't do that.", "start": 3910.75, "duration": 0.66}, {"text": "So \"belt,\" you just\nhave to memorize,", "start": 3911.41, "duration": 3.39}, {"text": "that's the kind of\n\"i\" final noun where", "start": 3914.8, "duration": 1.8}, {"text": "the plural suffix is a \"ch.\"", "start": 3916.6, "duration": 2.01}, {"text": "\"Footprint,\" that's the kind\nof \"i\" final where the plural", "start": 3918.61, "duration": 3.84}, {"text": "suffix is still a \"t.\"", "start": 3922.45, "duration": 3.39}, {"text": "This situation, which is, of\ncourse, distressing to people", "start": 3925.84, "duration": 3.09}, {"text": "who want to learn Inupiaq,\nis the consequence", "start": 3928.93, "duration": 3.333}, {"text": "of these sound changes\noccurring in this order", "start": 3932.263, "duration": 1.917}, {"text": "and creating this\nkind of opacity.", "start": 3934.18, "duration": 1.62}, {"text": "So what's really going\non is, well, there", "start": 3935.8, "duration": 2.4}, {"text": "used to be another vowel.", "start": 3938.2, "duration": 1.68}, {"text": "And we got rid of that\nvowel, but we were already", "start": 3939.88, "duration": 3.72}, {"text": "committed to having \"ch\" in\ncertain places and not others.", "start": 3943.6, "duration": 2.65}, {"text": "I should say there's now dialect\nvariation within Inupiaq.", "start": 3946.25, "duration": 3.47}, {"text": "There are dialects of\nInupiaq that said, no, look,", "start": 3949.72, "duration": 2.28}, {"text": "this is silly.", "start": 3952.0, "duration": 1.11}, {"text": "We're going to change the\n\"ch\" in \"belts\" to a \"t.\"", "start": 3953.11, "duration": 3.36}, {"text": "So they still have \"t\" becoming\n\"ch\" in some other places,", "start": 3956.47, "duration": 2.85}, {"text": "but specifically the plural\nhas gotten regularized", "start": 3959.32, "duration": 2.25}, {"text": "so that it's a \"t\" everywhere.", "start": 3961.57, "duration": 1.69}, {"text": "Consequence of a\nhistory of sound changes", "start": 3967.13, "duration": 1.8}, {"text": "is sometimes opacity.", "start": 3968.93, "duration": 1.41}, {"text": "It's kind of like\nthe Lardil example", "start": 3970.34, "duration": 1.65}, {"text": "that I showed you before.", "start": 3971.99, "duration": 1.26}, {"text": "You have a change\nfrom A to B, and you", "start": 3973.25, "duration": 2.58}, {"text": "have another change from C\nto D. And the consequence", "start": 3975.83, "duration": 3.51}, {"text": "of the change from C to D would\ncreate new environments for A", "start": 3979.34, "duration": 4.35}, {"text": "to B, but A to B has\nalready happened.", "start": 3983.69, "duration": 1.95}, {"text": "It doesn't happen again.", "start": 3985.64, "duration": 2.41}, {"text": "So as you are\nlearning languages,", "start": 3988.05, "duration": 1.79}, {"text": "if you encounter\nfacts like this,", "start": 3989.84, "duration": 2.19}, {"text": "entertain the possibility\nthat what's going on", "start": 3992.03, "duration": 2.07}, {"text": "is opacity because of\nsound change occurring", "start": 3994.1, "duration": 2.4}, {"text": "in a particular order.", "start": 3996.5, "duration": 0.96}, {"text": "I don't know whether\nyou'll consider--", "start": 3997.46, "duration": 1.68}, {"text": "whether you'll have--", "start": 3999.14, "duration": 1.77}, {"text": "whether you'll get any\ncomfort from that thought", "start": 4000.91, "duration": 2.46}, {"text": "or whether it'll just\nannoy you, but that's", "start": 4003.37, "duration": 2.97}, {"text": "sometimes the consequence.", "start": 4006.34, "duration": 2.76}, {"text": "Yeah, Lardil.", "start": 4009.1, "duration": 0.75}, {"text": "We just did Lardil.", "start": 4009.85, "duration": 3.12}, {"text": "Oh, yeah.", "start": 4012.97, "duration": 0.84}, {"text": "Here's another example of\nthe same kind of thing.", "start": 4013.81, "duration": 2.49}, {"text": "Passamaquoddy is an Algonquian\nlanguage spoken up in Maine.", "start": 4016.3, "duration": 4.14}, {"text": "It underwent a sound\nchange that deleted", "start": 4020.44, "duration": 2.43}, {"text": "odd-numbered short\nvowels in words,", "start": 4022.87, "duration": 3.793}, {"text": "depending on the\nconsonants around them.", "start": 4026.663, "duration": 1.667}, {"text": "It's called syncope.", "start": 4028.33, "duration": 2.85}, {"text": "If you started with a word\nthat meant \"I hook a fish,\"", "start": 4031.18, "duration": 3.48}, {"text": "that would have been something\nlike \"nuh-puhteeheek.\"", "start": 4034.66, "duration": 3.21}, {"text": "And what you did was to get rid\nof the first and third vowels", "start": 4037.87, "duration": 4.95}, {"text": "in that word.", "start": 4042.82, "duration": 1.54}, {"text": "So in modern Passamaquoddy,\nthat's now \"npuh-teeg.\"", "start": 4044.36, "duration": 3.142}, {"text": "So you've gotten rid of the\nfirst vowel and the third vowel", "start": 4047.502, "duration": 2.458}, {"text": "in the word.", "start": 4049.96, "duration": 1.29}, {"text": "The \"nuh-\" at the beginning of\nthat is a prefix that agrees", "start": 4051.25, "duration": 3.24}, {"text": "with the subject, \"I.\"", "start": 4054.49, "duration": 2.061}, {"text": "If you get rid of that prefix,\nlike if you want to say he", "start": 4056.551, "duration": 2.674}, {"text": "or she hooks a fish, well then\nyou don't have that prefix", "start": 4059.225, "duration": 2.375}, {"text": "and that changes the count.", "start": 4061.6, "duration": 1.38}, {"text": "So original\n\"puh-tee-hee-geh,\" again,", "start": 4062.98, "duration": 4.02}, {"text": "you've gotten rid of the first\nand third vowels in that.", "start": 4067.0, "duration": 2.47}, {"text": "So in modern Passamaquoddy,\nit's \"tee-gee-geh.\"", "start": 4069.47, "duration": 3.02}, {"text": "So Passamaquoddy\nspeakers, if they", "start": 4072.49, "duration": 2.255}, {"text": "want to learn\nPassamaquoddy, they", "start": 4074.745, "duration": 1.375}, {"text": "have to learn if you add\nthe prefix, you sometimes", "start": 4076.12, "duration": 3.15}, {"text": "change which vowels are where.", "start": 4079.27, "duration": 1.84}, {"text": "So \"I hook a fish\" is \"npu-tig.\"", "start": 4081.11, "duration": 3.32}, {"text": "But \"he or she hooks a\nfish\" is \"tee-hee-guh.\"", "start": 4084.43, "duration": 2.88}, {"text": "There's a vowel between the \"p\"\nand the \"t\" in the \"I\" form,", "start": 4087.31, "duration": 3.18}, {"text": "but not in the \"he or she\" form.", "start": 4090.49, "duration": 1.38}, {"text": "There is a vowel between\nthe \"t\" and the \"h\"", "start": 4091.87, "duration": 2.01}, {"text": "in the \"he or she\" form,\nbut not in the \"I\" form.", "start": 4093.88, "duration": 2.729}, {"text": "If you look at the online\nPassamaquoddy dictionary,", "start": 4096.609, "duration": 2.611}, {"text": "you see lots of examples\nof this kind of thing.", "start": 4099.22, "duration": 2.07}, {"text": "Verbs are listed in\ntheir third-person form,", "start": 4101.29, "duration": 3.239}, {"text": "but then there will be\na listing for each verb.", "start": 4104.529, "duration": 3.299}, {"text": "This is what it looks like\nwhen you add a prefix.", "start": 4107.828, "duration": 2.042}, {"text": "And it's sometimes radically\ndifferent as a consequence", "start": 4109.87, "duration": 2.73}, {"text": "of this sound change.", "start": 4112.6, "duration": 1.54}, {"text": "So for example, here's another\ninstance of the same thing.", "start": 4114.14, "duration": 3.049}, {"text": "\"I'm sorry about\nit\" was originally", "start": 4117.189, "duration": 2.071}, {"text": "\"nuh-muh-zah-kay-in.\"", "start": 4119.26, "duration": 2.79}, {"text": "Getting rid of the first and\nthird vowels in that would have", "start": 4122.05, "duration": 4.29}, {"text": "given you \"nmuh-skey-in,\"\nwhich is the modern way to say", "start": 4126.34, "duration": 4.17}, {"text": "\"I'm sorry about it.\"", "start": 4130.51, "duration": 1.23}, {"text": "If you don't add the \"nuh\"\nprefix, if you want to say", "start": 4131.74, "duration": 3.315}, {"text": "\"he or she is sorry,\"\nyou're going to get rid", "start": 4135.055, "duration": 1.875}, {"text": "of the first and third vowels.", "start": 4136.93, "duration": 1.62}, {"text": "If nothing else happened, that\nwould give you \"sah-key-oo.\"", "start": 4138.55, "duration": 3.809}, {"text": "But in fact, \"n\" next to\n\"s\" tends to become a \"p.\"", "start": 4142.359, "duration": 5.25}, {"text": "So the word for \"I'm sorry\nabout it\" is \"nmuh-skey-in,\"", "start": 4147.609, "duration": 3.721}, {"text": "but \"he or she is\nsorry\" is \"psah-key-oo\"", "start": 4151.33, "duration": 3.182}, {"text": "with the consequence that these\nlook so different from each", "start": 4154.512, "duration": 2.458}, {"text": "other that when I have pointed\nout to Passamaquoddy speakers", "start": 4156.97, "duration": 2.5}, {"text": "that they are the same\nword, they're astonished.", "start": 4159.47, "duration": 2.27}, {"text": "They're like, oh, yeah, right.", "start": 4161.74, "duration": 1.289}, {"text": "I guess they are, even though\nthey don't look all that much", "start": 4163.029, "duration": 2.941}, {"text": "like each other anymore.", "start": 4165.97, "duration": 3.0}, {"text": "Now, the Passamaquoddy\nsystem looks like the result", "start": 4168.97, "duration": 3.69}, {"text": "of a stress system.", "start": 4172.66, "duration": 1.09}, {"text": "So again, the rule is get rid\nof the odd-numbered short vowels", "start": 4173.75, "duration": 5.18}, {"text": "in the sequence.", "start": 4178.93, "duration": 1.143}, {"text": "And that's the kind of rule that\nmakes sense if you think, yeah,", "start": 4180.073, "duration": 2.667}, {"text": "it had a stress\nsystem that stressed", "start": 4182.74, "duration": 2.789}, {"text": "the even-numbered vowels, right?", "start": 4185.529, "duration": 1.441}, {"text": "So \"I hook a fish\" was\n\"nuh-put-tuh-heek.\"", "start": 4186.97, "duration": 4.17}, {"text": "And then they got rid of the\nfirst and the third vowels", "start": 4191.14, "duration": 2.429}, {"text": "because they weren't stressed.", "start": 4193.569, "duration": 1.381}, {"text": "And \"he or she hooks a\nfish\" was \"puh-tee-hee-geh,\"", "start": 4194.95, "duration": 3.12}, {"text": "and you got rid of the schwa\nin the first one because well,", "start": 4198.07, "duration": 3.48}, {"text": "it wasn't stressed.", "start": 4201.55, "duration": 1.62}, {"text": "Whether you get rid\nof vowels or not", "start": 4203.17, "duration": 1.5}, {"text": "depends partly on what\nconsonants are around them.", "start": 4204.67, "duration": 2.16}, {"text": "That's why you're\nnot actually getting", "start": 4206.83, "duration": 1.17}, {"text": "rid of the third\nvowel in this one.", "start": 4208.0, "duration": 1.458}, {"text": "You get \"tee-hee-geh.\"", "start": 4209.458, "duration": 2.952}, {"text": "So if you thought\nof Passamaquoddy", "start": 4212.41, "duration": 2.19}, {"text": "as having stress on its\neven-numbered short vowels,", "start": 4214.6, "duration": 3.87}, {"text": "then you can understand\nwhy it's getting", "start": 4218.47, "duration": 1.74}, {"text": "rid of its odd-numbered\nshort vowels.", "start": 4220.21, "duration": 1.41}, {"text": "It's getting rid of them\nbecause they're not stressed.", "start": 4221.62, "duration": 2.25}, {"text": "And Passamaquoddy\ndoes have relatives", "start": 4223.87, "duration": 1.68}, {"text": "that have stress systems\nlike that, where you stress", "start": 4225.55, "duration": 3.3}, {"text": "the even-numbered vowels.", "start": 4228.85, "duration": 3.0}, {"text": "But that is not Passamaquoddy\nstress system anymore.", "start": 4231.85, "duration": 3.07}, {"text": "So Passamaquoddy underwent all\nof these sound changes because", "start": 4234.92, "duration": 2.957}, {"text": "of the stress system\nthat they used to have,", "start": 4237.877, "duration": 1.833}, {"text": "that they used to share with\nsome of their relatives.", "start": 4239.71, "duration": 2.13}, {"text": "And then they changed\ntheir stress system.", "start": 4241.84, "duration": 1.75}, {"text": "Their modern stress system\ngoes \"Stress the first vowel", "start": 4243.59, "duration": 2.72}, {"text": "and stress every\nother vowel counting", "start": 4246.31, "duration": 1.65}, {"text": "backwards from the end.\"", "start": 4247.96, "duration": 2.16}, {"text": "So you get words\nlike [INAUDIBLE],,", "start": 4250.12, "duration": 2.94}, {"text": "which is \"he or she\ntalks like that,\"", "start": 4253.06, "duration": 1.84}, {"text": "where you're stressing the first\nvowel and the second vowel.", "start": 4254.9, "duration": 2.06}, {"text": "First vowel because you\nalways stress the first vowel,", "start": 4256.96, "duration": 2.25}, {"text": "and the second\nvowel because it's", "start": 4259.21, "duration": 1.44}, {"text": "two vowels back from the end.", "start": 4260.65, "duration": 2.517}, {"text": "So every other vowel,\nstarting from the end.", "start": 4263.167, "duration": 1.833}, {"text": "If you make it one\nsyllable longer,", "start": 4265.0, "duration": 1.62}, {"text": "then you're going to stress\nthe first and the third vowel--", "start": 4266.62, "duration": 2.94}, {"text": "\"wee-guh-west-too,\" \"He or she\ntalks while walking backwards.\"", "start": 4269.56, "duration": 5.19}, {"text": "\"Quiguh-west-too-bin,\"\n\"You and I like talking.\"", "start": 4274.75, "duration": 2.922}, {"text": "So stress is on\nthe first syllable,", "start": 4277.672, "duration": 1.458}, {"text": "and it's on the even-numbered\nsyllables counting backwards", "start": 4279.13, "duration": 2.64}, {"text": "from the end of the word.", "start": 4281.77, "duration": 1.48}, {"text": "So they've innovated\nthis new stress system", "start": 4283.25, "duration": 2.78}, {"text": "after having this older\nstress system which", "start": 4286.03, "duration": 2.46}, {"text": "created all of\nthese alternations", "start": 4288.49, "duration": 2.13}, {"text": "in the positions of vowels.", "start": 4290.62, "duration": 1.182}, {"text": "There's a reason\nthat Passamaquoddy", "start": 4291.802, "duration": 1.458}, {"text": "is difficult to learn.", "start": 4293.26, "duration": 1.357}, {"text": "There are several reasons.", "start": 4294.617, "duration": 1.083}, {"text": "This is one.", "start": 4295.7, "duration": 0.59}, {"text": "So it used to have a different\nstress system, during which", "start": 4299.883, "duration": 2.417}, {"text": "the syncope rule applied.", "start": 4302.3, "duration": 1.05}, {"text": "And now it has the\nsystem it has now.", "start": 4303.35, "duration": 4.41}, {"text": "I want to end today\nbecause I think", "start": 4307.76, "duration": 1.71}, {"text": "we have enough\ntime for me to heap", "start": 4309.47, "duration": 1.74}, {"text": "scorn on a couple of things.", "start": 4311.21, "duration": 3.18}, {"text": "I want to end today\nwith two bad ideas.", "start": 4314.39, "duration": 1.627}, {"text": "So one of the reasons\nthat I'm talking", "start": 4316.017, "duration": 1.583}, {"text": "to you about historical\nlinguistics-- there", "start": 4317.6, "duration": 1.38}, {"text": "are several.", "start": 4318.98, "duration": 0.5}, {"text": "One is that it's fun.", "start": 4319.48, "duration": 1.295}, {"text": "It's kind of interesting to\ntry to trace back these sound", "start": 4320.775, "duration": 2.375}, {"text": "changes.", "start": 4323.15, "duration": 0.57}, {"text": "But another is that\nhistorical linguistics", "start": 4323.72, "duration": 1.98}, {"text": "is the kind of thing that\nis sometimes done badly.", "start": 4325.7, "duration": 2.73}, {"text": "So you'll see in popular\npress people saying things", "start": 4328.43, "duration": 2.832}, {"text": "like, hey, this language is\nrelated to that language,", "start": 4331.262, "duration": 2.208}, {"text": "or this language has borrowed\nthis word from that language.", "start": 4333.47, "duration": 3.39}, {"text": "And if you have any\nskepticism about that,", "start": 4336.86, "duration": 2.85}, {"text": "what you want them\nto do is show you", "start": 4339.71, "duration": 1.5}, {"text": "regular sound correspondences\nor regular rules", "start": 4341.21, "duration": 2.43}, {"text": "for how words are\nrelated to other words.", "start": 4343.64, "duration": 1.83}, {"text": "So there was a popular\nbook for a while that", "start": 4345.47, "duration": 3.54}, {"text": "proposed that the Native\nAmerican languages were all", "start": 4349.01, "duration": 6.93}, {"text": "descended from Chinese, that\nthe Mandarin-- the Chinese", "start": 4355.94, "duration": 4.65}, {"text": "had encountered\nNorth America first,", "start": 4360.59, "duration": 2.4}, {"text": "and that their language had\ntaken over North America,", "start": 4362.99, "duration": 3.42}, {"text": "and that all of the\nmodern languages", "start": 4366.41, "duration": 1.59}, {"text": "were descended from Chinese.", "start": 4368.0, "duration": 1.47}, {"text": "And the examples were things\nlike in modern Mandarin,", "start": 4369.47, "duration": 3.42}, {"text": "there is a greeting, \"nihao.\"", "start": 4372.89, "duration": 3.42}, {"text": "And hey, if you watch\nHollywood movies,", "start": 4376.31, "duration": 2.82}, {"text": "you will hear Native Americans\ngreeting each other with \"how.\"", "start": 4379.13, "duration": 3.54}, {"text": "And there, you know,\nso clearly these", "start": 4382.67, "duration": 2.76}, {"text": "are related to each other.", "start": 4385.43, "duration": 1.09}, {"text": "\"How\" actually is a\ngreeting in Lakota.", "start": 4386.52, "duration": 2.18}, {"text": "It's a greeting that Lakota\nmen use to greet other men.", "start": 4388.7, "duration": 3.73}, {"text": "It's not related to the\nMandarin expression \"nihao.\"", "start": 4392.43, "duration": 3.5}, {"text": "And the reason I can say\nthat with so much confidence", "start": 4395.93, "duration": 2.85}, {"text": "is that, well, no one has ever\nfound sound correspondences", "start": 4398.78, "duration": 3.6}, {"text": "or anything like that relating\nanything else in Lakota", "start": 4402.38, "duration": 2.7}, {"text": "to anything else in Chinese.", "start": 4405.08, "duration": 3.93}, {"text": "There are slightly\nless silly claims", "start": 4409.01, "duration": 3.48}, {"text": "that people have made\nusing what's sometimes", "start": 4412.49, "duration": 2.16}, {"text": "called megalocomparison.", "start": 4414.65, "duration": 1.3}, {"text": "So let's skip-- so\nglottochronology--", "start": 4415.95, "duration": 2.63}, {"text": "I'll leave this on the\nslide, but glottochronology", "start": 4418.58, "duration": 2.13}, {"text": "is an attempt to sort of\ncarbon date language splits.", "start": 4420.71, "duration": 2.88}, {"text": "So the idea is you take a\nlist of basic vocabulary.", "start": 4423.59, "duration": 4.53}, {"text": "You figure out how many\ncognates the two languages", "start": 4428.12, "duration": 2.37}, {"text": "share on the list, and you\nstart with the assumption", "start": 4430.49, "duration": 3.93}, {"text": "that cognate loss happens\nat a constant rate.", "start": 4434.42, "duration": 2.52}, {"text": "This is the figure that has been\noffered by glottochronologists.", "start": 4436.94, "duration": 3.06}, {"text": "And then you do some math.", "start": 4440.0, "duration": 2.85}, {"text": "And this is something that you\nsee people seriously saying.", "start": 4442.85, "duration": 3.51}, {"text": "So if you look in--", "start": 4446.36, "duration": 2.04}, {"text": "historical linguistics is\nusually not done by linguists.", "start": 4448.4, "duration": 2.37}, {"text": "It's often being\ndone by biologists.", "start": 4450.77, "duration": 2.19}, {"text": "They'll say, we know that\nthese languages are related", "start": 4452.96, "duration": 2.79}, {"text": "at a time depth of\nX. And what they", "start": 4455.75, "duration": 2.01}, {"text": "mean is we've done\nglottochronology,", "start": 4457.76, "duration": 1.725}, {"text": "which starts from the\nassumption that you can", "start": 4459.485, "duration": 1.875}, {"text": "do this kind of carbon dating\nof languages by looking", "start": 4461.36, "duration": 4.68}, {"text": "at cognate lists and figuring\nout the rate at which two", "start": 4466.04, "duration": 3.09}, {"text": "languages cease to have\ncognates with each other.", "start": 4469.13, "duration": 2.65}, {"text": "The problem is that\nthe base assumption--", "start": 4471.78, "duration": 2.42}, {"text": "that cognate loss happens at\na constant rate-- is false.", "start": 4474.2, "duration": 3.36}, {"text": "And no one has figured\nout a way around that.", "start": 4477.56, "duration": 4.365}, {"text": "There doesn't seem to be\nany way to correct for it.", "start": 4481.925, "duration": 2.125}, {"text": "So if you see people\nusing glottochronology,", "start": 4484.05, "duration": 2.78}, {"text": "you should treat\nthem with skepticism.", "start": 4486.83, "duration": 1.83}, {"text": "The other bad idea that's\nin here is megalocomparison.", "start": 4493.34, "duration": 2.79}, {"text": "This is attempts to reconstruct\nProto- World, which were very", "start": 4496.13, "duration": 3.51}, {"text": "en vogue at a certain time.", "start": 4499.64, "duration": 1.6}, {"text": "People thought if\nwe do lots and lots", "start": 4501.24, "duration": 1.79}, {"text": "of this cross-linguistic\ncomparison,", "start": 4503.03, "duration": 1.62}, {"text": "we'll be able to figure out\nthe ancestor language for all", "start": 4504.65, "duration": 2.46}, {"text": "of the languages in the world.", "start": 4507.11, "duration": 2.76}, {"text": "The work has never\ninvolved discovering", "start": 4509.87, "duration": 4.17}, {"text": "general sound changes that\nrelate languages to each other.", "start": 4514.04, "duration": 3.15}, {"text": "It always involves\ngoing back to saying,", "start": 4517.19, "duration": 1.747}, {"text": "\"Hey, look, that\nword in that language", "start": 4518.937, "duration": 1.583}, {"text": "looks kind of like that\nword in that language!", "start": 4520.52, "duration": 1.917}, {"text": "I bet they're related.\"", "start": 4522.437, "duration": 0.993}, {"text": "That's how that\nwork is always gone.", "start": 4523.43, "duration": 2.64}, {"text": "So those are two\nideas-- bad ideas", "start": 4526.07, "duration": 1.632}, {"text": "that you should be\nskeptical about.", "start": 4527.702, "duration": 1.458}, {"text": "This has been my public\nservice announcement for today.", "start": 4529.16, "duration": 2.88}, {"text": "Are there any questions about\neither of those bad ideas?", "start": 4532.04, "duration": 2.58}, {"text": "I put more detail about the\nbad ideas in the slides.", "start": 4534.62, "duration": 3.69}, {"text": "OK, cool.", "start": 4538.31, "duration": 0.93}, {"text": "Go forth, and I will\nsee you next week.", "start": 4539.24, "duration": 4.19}]
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+[{"text": "[SQUEAKING][RUSTLING][CLICKING]", "start": 0.0, "duration": 3.888}, {"text": "ROBERT TOWNSEND: OK.", "start": 11.147, "duration": 0.833}, {"text": "So let me update where we\nare in terms of the calendar.", "start": 11.98, "duration": 7.02}, {"text": "I guess a notable\nthing is that we", "start": 19.0, "duration": 3.36}, {"text": "have reached lecture 10\ntoday, Thursday, in terms", "start": 22.36, "duration": 4.77}, {"text": "of the reading list.", "start": 27.13, "duration": 2.46}, {"text": "We are-- having done\nall the risk-sharing.", "start": 29.59, "duration": 2.744}, {"text": "Yeah, we're at lecture 10.", "start": 32.334, "duration": 1.546}, {"text": "So there's a couple of\nthings that are starred here,", "start": 33.88, "duration": 3.54}, {"text": "and they obviously both come\nup in the lecture today.", "start": 37.42, "duration": 3.49}, {"text": "One is the early\nversion of this paper", "start": 40.91, "duration": 2.3}, {"text": "with Alvarez and\nPawasutipaisit sit", "start": 43.21, "duration": 3.81}, {"text": "cash, which has a star on it.", "start": 47.02, "duration": 2.55}, {"text": "It's a little bit rough because\nit's kind of, even then,", "start": 49.57, "duration": 3.33}, {"text": "in the process of revision.", "start": 52.9, "duration": 1.44}, {"text": "And I have added new material\nin the slides that haven't even", "start": 54.34, "duration": 3.51}, {"text": "made their way into\nthe working paper yet.", "start": 57.85, "duration": 2.13}, {"text": "And then there's\nSamphantharak and Townsend,", "start": 59.98, "duration": 2.64}, {"text": "which is describing\nthe tools we're", "start": 62.62, "duration": 2.31}, {"text": "going to be using a lot today--", "start": 64.93, "duration": 1.86}, {"text": "how to organize data, and think\nabout flows and stocks in terms", "start": 66.79, "duration": 4.95}, {"text": "of financial accounts and so on.", "start": 71.74, "duration": 3.43}, {"text": "So, again, the two\nstarred readings.", "start": 75.17, "duration": 2.72}, {"text": "Other things you might\nenjoy, time permitting,", "start": 77.89, "duration": 3.06}, {"text": "there's something\non Kenya, M-Pesa.", "start": 80.95, "duration": 2.58}, {"text": "And I have one slide\ndescribing-- actually", "start": 83.53, "duration": 2.28}, {"text": "two slides describing\nthat today;", "start": 85.81, "duration": 2.55}, {"text": "something on lifecycle planning.", "start": 88.36, "duration": 2.49}, {"text": "But none of those things\nhave stars on them.", "start": 90.85, "duration": 3.07}, {"text": "OK.", "start": 93.92, "duration": 0.5}, {"text": "So that's the reading list.", "start": 94.42, "duration": 2.17}, {"text": "The last thing, turning to\nthe study guide or the lecture", "start": 96.59, "duration": 3.77}, {"text": "from last time, which\nwas \"Risk and Return", "start": 100.36, "duration": 4.23}, {"text": "in Village Thailand.\"", "start": 104.59, "duration": 1.38}, {"text": "So explain intuitively in words\nwhy multiple technologies can", "start": 105.97, "duration": 5.34}, {"text": "be chosen to be\noperated simultaneously,", "start": 111.31, "duration": 2.88}, {"text": "and why the rate\nof return on some", "start": 114.19, "duration": 1.8}, {"text": "might be higher than\nthe rate of return", "start": 115.99, "duration": 2.34}, {"text": "for the others that\nare also operating.", "start": 118.33, "duration": 2.79}, {"text": "And for that matter, why some\nprojects are not chosen at all.", "start": 121.12, "duration": 4.26}, {"text": "If you can, try to use the\nlanguage of risk premium,", "start": 125.38, "duration": 3.03}, {"text": "but don't use it as jargon.", "start": 128.41, "duration": 2.31}, {"text": "Try to imagine you're telling\nsomeone in your household", "start": 130.72, "duration": 2.82}, {"text": "or a friend kind of what\nwe're studying in class.", "start": 133.54, "duration": 4.3}, {"text": "So I've been calling on people.", "start": 137.84, "duration": 2.15}, {"text": "Let me just ask for\nvolunteers today.", "start": 139.99, "duration": 2.16}, {"text": "Of course, I can call on people.", "start": 146.37, "duration": 2.52}, {"text": "Any volunteers?", "start": 148.89, "duration": 2.47}, {"text": "Carrie, you want to\ntake a crack at this?", "start": 151.36, "duration": 2.99}, {"text": "AUDIENCE: Is it because\nsome technologies", "start": 154.35, "duration": 2.91}, {"text": "have a lower rate of return\nbecause they're riskier?", "start": 157.26, "duration": 4.02}, {"text": "And the probability of\na high rate of return", "start": 161.28, "duration": 3.27}, {"text": "is lower for them?", "start": 164.55, "duration": 1.14}, {"text": "ROBERT TOWNSEND: That's true.", "start": 168.997, "duration": 1.208}, {"text": "At first blush,\nthe rate of return", "start": 173.32, "duration": 2.91}, {"text": "is simply all the possible\nreturns multiplied", "start": 176.23, "duration": 3.72}, {"text": "by the respective probability.", "start": 179.95, "duration": 2.83}, {"text": "So that's kind of inherent\nin the technology itself.", "start": 182.78, "duration": 2.78}, {"text": "But if that were the only\nthing going on, then why would", "start": 189.06, "duration": 2.9}, {"text": "they not choose the one with\nthe highest expected return?", "start": 191.96, "duration": 3.582}, {"text": "AUDIENCE: Can I\ntake a crack at it?", "start": 195.542, "duration": 1.458}, {"text": "ROBERT TOWNSEND: Yep.", "start": 197.0, "duration": 1.44}, {"text": "AUDIENCE: Well, I think\nthey've got-- yeah,", "start": 198.44, "duration": 2.13}, {"text": "I'm a bit behind\nin the readings.", "start": 200.57, "duration": 1.68}, {"text": "But what it looks\nlike here is that you", "start": 202.25, "duration": 2.52}, {"text": "have some technologies that\nhave a higher expected rate", "start": 204.77, "duration": 2.58}, {"text": "of return but more risk,\nand some technologies that", "start": 207.35, "duration": 2.52}, {"text": "have the low rate of\nreturn and lower risk.", "start": 209.87, "duration": 2.91}, {"text": "And basically--\nand some of them--", "start": 212.78, "duration": 3.88}, {"text": "so some of them are--", "start": 216.66, "duration": 1.7}, {"text": "some people-- it's like some\nhouseholds might be more like--", "start": 218.36, "duration": 2.5}, {"text": "it's like, you can have like--\nand if these aren't perfectly", "start": 220.86, "duration": 2.61}, {"text": "correlated, then you might\nbe able to get a better--", "start": 223.47, "duration": 3.48}, {"text": "sort of a less risky\nrate for the same-- less", "start": 226.95, "duration": 3.48}, {"text": "risk for the same rate of\nreturn by diversification.", "start": 230.43, "duration": 3.3}, {"text": "And the reason that\nyou would have lower--", "start": 233.73, "duration": 4.29}, {"text": "you would have-- you would\nhave lower rate of return", "start": 238.02, "duration": 3.99}, {"text": "technologies in the same--", "start": 242.01, "duration": 1.41}, {"text": "used at the same time as higher\nrate of return technologies,", "start": 243.42, "duration": 2.64}, {"text": "as the lower rate of\nreturn points, have a--", "start": 246.06, "duration": 4.55}, {"text": "the lower rate of return\npoints have a lower risk,", "start": 250.61, "duration": 2.908}, {"text": "and the higher rate\nof return points,", "start": 253.518, "duration": 1.542}, {"text": "you have to basically\npay a risk--", "start": 255.06, "duration": 2.01}, {"text": "there's risk\npremium there, which", "start": 257.07, "duration": 1.579}, {"text": "is why it's less desirable\nor something like that.", "start": 258.649, "duration": 2.918}, {"text": "ROBERT TOWNSEND: Yep.", "start": 261.567, "duration": 0.933}, {"text": "OK.", "start": 262.5, "duration": 0.5}, {"text": "That's pretty good.", "start": 263.0, "duration": 0.792}, {"text": "Thank you.", "start": 263.792, "duration": 0.618}, {"text": "Yeah.", "start": 267.97, "duration": 0.9}, {"text": "What you're\ndescribing is correct.", "start": 268.87, "duration": 1.53}, {"text": "There's like a mean\nvariability trade-off", "start": 270.4, "duration": 3.33}, {"text": "here, a downward-sloping\nfrontier,", "start": 273.73, "duration": 4.53}, {"text": "if you want to think\nabout it that way.", "start": 278.26, "duration": 1.95}, {"text": "As you move across\ndifferent projects", "start": 280.21, "duration": 2.22}, {"text": "they may have higher\nand higher means,", "start": 282.43, "duration": 3.15}, {"text": "but they come with higher\nand higher variance.", "start": 285.58, "duration": 3.55}, {"text": "So there's a trade-off.", "start": 289.13, "duration": 1.175}, {"text": "And since households\nare risk-averse,", "start": 293.33, "duration": 1.81}, {"text": "they don't like the variance.", "start": 295.14, "duration": 2.76}, {"text": "So they pay attention to that.", "start": 297.9, "duration": 1.325}, {"text": "And you said this also.", "start": 302.55, "duration": 1.79}, {"text": "You could have two technologies\nwith the same mean return--", "start": 304.34, "duration": 3.75}, {"text": "one with a higher variance\nthan the other one,", "start": 308.09, "duration": 2.11}, {"text": "and they would never do\nthe higher variability one", "start": 310.2, "duration": 3.2}, {"text": "because then there's\nno trade-off.", "start": 313.4, "duration": 2.87}, {"text": "Since they get the same\nmean but higher risk,", "start": 316.27, "duration": 2.31}, {"text": "they wouldn't choose that.", "start": 318.58, "duration": 2.43}, {"text": "There is a\ndiversification aspect", "start": 321.01, "duration": 2.91}, {"text": "that we featured quite a\nbit in terms of land plots", "start": 323.92, "duration": 4.56}, {"text": "and how they want to\ndiversify, or in village India", "start": 328.48, "duration": 2.82}, {"text": "over crops and income\nsources and so on.", "start": 331.3, "duration": 3.57}, {"text": "And that's kind of\ncaptured here in a new way,", "start": 334.87, "duration": 3.54}, {"text": "but it is in here.", "start": 338.41, "duration": 1.71}, {"text": "Namely, a guess of\nwhat technologies", "start": 340.12, "duration": 7.08}, {"text": "to operate overall, you can\ncompute the variability.", "start": 347.2, "duration": 5.34}, {"text": "And then you look on the\nmargin about whether to add", "start": 352.54, "duration": 2.61}, {"text": "or subtract one more.", "start": 355.15, "duration": 3.24}, {"text": "And you look at its variability\nrelative to this village", "start": 358.39, "duration": 4.86}, {"text": "average.", "start": 363.25, "duration": 2.28}, {"text": "So if it's going to\nadd to diversification,", "start": 365.53, "duration": 6.2}, {"text": "it's going to have a return\nstream which is low when--", "start": 371.73, "duration": 4.32}, {"text": "well, say high when the\nrest of the village is low.", "start": 376.05, "duration": 3.52}, {"text": "So that's kind of the\nway the diversification", "start": 379.57, "duration": 2.12}, {"text": "aspect is coming out in this\nmean variance framework.", "start": 381.69, "duration": 6.68}, {"text": "But great.", "start": 388.37, "duration": 0.67}, {"text": "That's very helpful.", "start": 389.04, "duration": 1.58}, {"text": "All right.", "start": 390.62, "duration": 0.5}, {"text": "So here's another one.", "start": 391.12, "duration": 3.45}, {"text": "Explain how it can be\nthat while the magnitude", "start": 394.57, "duration": 2.22}, {"text": "of idiosyncratic risk is\nhigher than the magnitude", "start": 396.79, "duration": 3.51}, {"text": "of aggregate risk, nevertheless\nthe idiosyncratic risk premium", "start": 400.3, "duration": 5.46}, {"text": "is smaller than the\naggregate risk premium.", "start": 405.76, "duration": 4.46}, {"text": "So, again, I'll take volunteers.", "start": 410.22, "duration": 3.41}, {"text": "AUDIENCE: Yeah.", "start": 413.63, "duration": 2.07}, {"text": "So is it-- so I think\nit's because when", "start": 415.7, "duration": 4.74}, {"text": "it comes with\nidiosyncratic risk,", "start": 420.44, "duration": 1.89}, {"text": "it's possible for the village\nto distribute the returns", "start": 422.33, "duration": 4.93}, {"text": "amongst each other.", "start": 427.26, "duration": 0.92}, {"text": "It's like ex-post.", "start": 428.18, "duration": 1.77}, {"text": "Whereas, for aggregate\nrisk, it's like", "start": 429.95, "duration": 2.79}, {"text": "is risk affecting\nthe whole village.", "start": 432.74, "duration": 1.5}, {"text": "And so there's not-- and so\nredistribution can't really", "start": 434.24, "duration": 3.54}, {"text": "benefit anyone when it\ncomes to things that", "start": 437.78, "duration": 3.45}, {"text": "affect the village as a whole.", "start": 441.23, "duration": 2.0}, {"text": "ROBERT TOWNSEND: Yep.", "start": 443.23, "duration": 0.9}, {"text": "Perfect.", "start": 444.13, "duration": 1.49}, {"text": "Yeah, the last part,\nwhich I didn't read out,", "start": 445.62, "duration": 2.85}, {"text": "explain in words what gifts\nand loans have to do with it,", "start": 448.47, "duration": 2.56}, {"text": "but you kind of did already.", "start": 451.03, "duration": 1.79}, {"text": "That's the way they pool\naway most, if not all,", "start": 452.82, "duration": 5.07}, {"text": "of the idiosyncratic risk.", "start": 457.89, "duration": 1.92}, {"text": "Whereas, in the\naggregate, it's common.", "start": 463.17, "duration": 1.68}, {"text": "It's hitting everyone.", "start": 464.85, "duration": 0.96}, {"text": "So essentially, you\ncan't pool it away.", "start": 465.81, "duration": 3.46}, {"text": "And this next part\nis related to that.", "start": 469.27, "duration": 2.63}, {"text": "Is there full insurance in these\nThai village economies or not?", "start": 471.9, "duration": 3.33}, {"text": "And to give it away a bit, not.", "start": 475.23, "duration": 2.67}, {"text": "And, in particular,\nwhat is it in the data", "start": 477.9, "duration": 2.82}, {"text": "that is inconsistent\nwith full risk-sharing?", "start": 480.72, "duration": 3.72}, {"text": "Volunteers?", "start": 484.44, "duration": 3.13}, {"text": "AUDIENCE: We find\nthat in the data", "start": 487.57, "duration": 2.31}, {"text": "household consumption is still--", "start": 489.88, "duration": 1.95}, {"text": "is positively correlated with\nthe idiosyncratic shocks.", "start": 491.83, "duration": 6.3}, {"text": "So that shows that it's\nnot full risk-sharing.", "start": 498.13, "duration": 4.05}, {"text": "But there's still\nsome risk-sharing", "start": 502.18, "duration": 1.5}, {"text": "because the coefficient\nis really, really small", "start": 503.68, "duration": 2.49}, {"text": "compared to other coefficients.", "start": 506.17, "duration": 2.132}, {"text": "ROBERT TOWNSEND: Right.", "start": 508.302, "duration": 0.958}, {"text": "Compared to the coefficients\non gifts and lending,", "start": 509.26, "duration": 3.899}, {"text": "which absorbs the\nbulk of the risk.", "start": 513.159, "duration": 3.581}, {"text": "So that's a perfect answer.", "start": 516.74, "duration": 1.28}, {"text": "I am so happy with this class.", "start": 518.02, "duration": 1.98}, {"text": "I enjoy teaching\nyou tremendously.", "start": 520.0, "duration": 2.669}, {"text": "It's very gratifying.", "start": 522.669, "duration": 3.391}, {"text": "OK.", "start": 526.06, "duration": 0.5}, {"text": "Thank you.", "start": 526.56, "duration": 0.54}, {"text": "There's one more-- see\nif we can get it in.", "start": 527.1, "duration": 3.15}, {"text": "Describe one example from\nThai villages of propagation", "start": 530.25, "duration": 4.32}, {"text": "through networks that\nwould be inconsistent", "start": 534.57, "duration": 2.52}, {"text": "with full risk-sharing\nand investment efficiency.", "start": 537.09, "duration": 2.79}, {"text": "And I'm abbreviating.", "start": 543.08, "duration": 2.63}, {"text": "So this happened at the end of\nthe lecture, just as a hint.", "start": 545.71, "duration": 3.24}, {"text": "Can someone described what we\ndid at the end of the lecture?", "start": 548.95, "duration": 3.657}, {"text": "Well, it's kind of given away\nhere in this bullet point,", "start": 552.607, "duration": 2.333}, {"text": "but I'll read it out anyway.", "start": 554.94, "duration": 1.95}, {"text": "How can an individual\nspecific illness shock", "start": 556.89, "duration": 2.7}, {"text": "turn into an aggregate\nvillage-level downturn?", "start": 559.59, "duration": 4.17}, {"text": "Volunteers?", "start": 563.76, "duration": 0.86}, {"text": "AUDIENCE: I think at\nthe end of the class,", "start": 571.83, "duration": 2.98}, {"text": "we were talking about how\nsome of the networks--", "start": 574.81, "duration": 2.597}, {"text": "how different kinds of networks\nare different from each other.", "start": 577.407, "duration": 2.583}, {"text": "I'm not sure which specific\nnetworks were being compared,", "start": 579.99, "duration": 2.43}, {"text": "but yeah.", "start": 582.42, "duration": 2.967}, {"text": "ROBERT TOWNSEND: That's true.", "start": 585.387, "duration": 1.208}, {"text": "So what happens,\ndo you recall, when", "start": 589.29, "duration": 1.58}, {"text": "a household gets hit with\nan illness shock that", "start": 590.87, "duration": 2.28}, {"text": "increases its expenditure?", "start": 593.15, "duration": 1.71}, {"text": "AUDIENCE: Right.", "start": 598.66, "duration": 2.41}, {"text": "ROBERT TOWNSEND:\nDid nothing happen?", "start": 601.07, "duration": 2.11}, {"text": "Something?", "start": 603.18, "duration": 1.5}, {"text": "You remember, or\nanyone else remember?", "start": 604.68, "duration": 4.21}, {"text": "AUDIENCE: I remember\nthat the households who", "start": 608.89, "duration": 3.96}, {"text": "are directly connected to\nthe household who got illness", "start": 612.85, "duration": 5.1}, {"text": "shocks would [INAUDIBLE] down\ntheir working opportunity", "start": 617.95, "duration": 4.77}, {"text": "much more than households\nwho are unconnected", "start": 622.72, "duration": 4.14}, {"text": "to those illness households.", "start": 626.86, "duration": 3.33}, {"text": "So through the network,\nhouseholds who are connected,", "start": 630.19, "duration": 7.05}, {"text": "who are related to each\nother much more maybe shock--", "start": 637.24, "duration": 6.12}, {"text": "there was an actual\nshock between them.", "start": 643.36, "duration": 2.74}, {"text": "So sudden illness shocks\nto these households", "start": 646.1, "duration": 4.94}, {"text": "may transfer to the\naggregate village", "start": 651.04, "duration": 4.31}, {"text": "through the [INAUDIBLE].", "start": 655.35, "duration": 2.92}, {"text": "ROBERT TOWNSEND: OK.", "start": 658.27, "duration": 1.42}, {"text": "That's a pretty good.", "start": 659.69, "duration": 1.41}, {"text": "And it's a bit\ntricky, this question.", "start": 661.1, "duration": 2.73}, {"text": "Because there are different\nnetworks in the village.", "start": 663.83, "duration": 3.99}, {"text": "There's kind of the\nrisk-sharing insurance network.", "start": 667.82, "duration": 2.41}, {"text": "There's the labor network.", "start": 670.23, "duration": 1.38}, {"text": "There's the supply chain\nproduction network.", "start": 671.61, "duration": 3.35}, {"text": "And they don't coincide.", "start": 674.96, "duration": 3.54}, {"text": "So if you got hit\nwith an illness shock,", "start": 678.5, "duration": 3.27}, {"text": "but nevertheless, you're in this\nrisk-sharing insurance network,", "start": 681.77, "duration": 3.96}, {"text": "then part of the-- or\nalmost all of the shock", "start": 685.73, "duration": 3.06}, {"text": "gets covered, in come the gifts,\njust like we were describing", "start": 688.79, "duration": 3.99}, {"text": "with the production shock.", "start": 692.78, "duration": 3.44}, {"text": "However, when that illness\nshock is not covered by gifts,", "start": 696.22, "duration": 4.77}, {"text": "then the household has to\nrespond on its own in some way.", "start": 700.99, "duration": 3.09}, {"text": "And it does this by cutting\nthe number of laborers", "start": 704.08, "duration": 5.41}, {"text": "that it hires,\nand by shrinking--", "start": 709.49, "duration": 3.99}, {"text": "saving costs by shrinking\nits production operations.", "start": 713.48, "duration": 4.24}, {"text": "And that is what spills\nover to other households", "start": 717.72, "duration": 3.53}, {"text": "along the production network.", "start": 721.25, "duration": 2.87}, {"text": "So networks could\nbe good or bad.", "start": 724.12, "duration": 2.84}, {"text": "Networks are good\nfor sharing risk,", "start": 726.96, "duration": 2.94}, {"text": "but they also can be bad because\nthey propagate contagion.", "start": 729.9, "duration": 6.44}, {"text": "So that was--", "start": 736.34, "duration": 2.5}, {"text": "AUDIENCE: So if there was a\nfull risk-sharing, then the--", "start": 738.84, "duration": 5.42}, {"text": "then there were no effect on\nthe employment for the household", "start": 744.26, "duration": 7.07}, {"text": "who did not get any shock?", "start": 751.33, "duration": 2.34}, {"text": "Network-- I mean, network--", "start": 753.67, "duration": 2.43}, {"text": "that was a factor.", "start": 756.1, "duration": 1.47}, {"text": "Those houses who did\nnot get any shock", "start": 757.57, "duration": 2.13}, {"text": "because they are more related\nto the households with illness.", "start": 759.7, "duration": 5.94}, {"text": "But if there was\nfull risk-sharing,", "start": 765.64, "duration": 3.54}, {"text": "those households will\nnot have any effect?", "start": 769.18, "duration": 3.3}, {"text": "ROBERT TOWNSEND: That's right.", "start": 772.48, "duration": 2.4}, {"text": "So the emphasis here is on\na very specific household", "start": 774.88, "duration": 4.83}, {"text": "idiosyncratic shock.", "start": 779.71, "duration": 3.74}, {"text": "And this-- I drew an\nanalogy with COVID-19,", "start": 783.45, "duration": 3.99}, {"text": "but it's a bit unfair.", "start": 787.44, "duration": 1.02}, {"text": "Because COVID, as we know,\nhas a contagion effect", "start": 788.46, "duration": 3.63}, {"text": "literally in the health sense.", "start": 792.09, "duration": 2.89}, {"text": "And if one person gets it,\npeople around that person", "start": 794.98, "duration": 3.19}, {"text": "get it.", "start": 798.17, "duration": 0.5}, {"text": "So here, though, it's a\ndifferent kind of illness.", "start": 798.67, "duration": 6.26}, {"text": "But it-- and it could be\njust an elderly person", "start": 804.93, "duration": 2.82}, {"text": "in the household.", "start": 807.75, "duration": 0.9}, {"text": "But still, there\nare big expenses--", "start": 808.65, "duration": 2.64}, {"text": "double the normal expenses.", "start": 811.29, "duration": 1.87}, {"text": "So they don't have\nthe budget to manage,", "start": 813.16, "duration": 2.75}, {"text": "and they have to start either\ngetting a gift from someone", "start": 815.91, "duration": 3.24}, {"text": "or cutting.", "start": 819.15, "duration": 2.01}, {"text": "So when they start\ncutting expenses,", "start": 821.16, "duration": 2.13}, {"text": "that's when it spills over to\nother people that they hire", "start": 823.29, "duration": 3.66}, {"text": "or people.", "start": 826.95, "duration": 0.75}, {"text": "So this is very\nreminiscent, as I", "start": 827.7, "duration": 2.1}, {"text": "said in class, of what's\ngoing on in the supply chain", "start": 829.8, "duration": 3.72}, {"text": "networks in the US, for example,\nand many other countries.", "start": 833.52, "duration": 5.07}, {"text": "Although, that's more of a\ndifferent kind of health shock.", "start": 838.59, "duration": 3.685}, {"text": "OK.", "start": 845.56, "duration": 0.5}, {"text": "Any questions about-- any other\nquestions about the lecture?", "start": 846.06, "duration": 5.11}, {"text": "OK.", "start": 851.17, "duration": 0.5}, {"text": "So then we come to the\nlecture for today--", "start": 851.67, "duration": 3.93}, {"text": "ledgers and management.", "start": 855.6, "duration": 1.92}, {"text": "In fact, there's a lot\nin the lecture today.", "start": 857.52, "duration": 2.94}, {"text": "I would say I'm\ngoing to give you", "start": 860.46, "duration": 1.56}, {"text": "a tool to think about,\nnamely, financial accounts--", "start": 862.02, "duration": 3.97}, {"text": "income and balance sheet\naccounts, in particular.", "start": 865.99, "duration": 3.74}, {"text": "And then we'll go to\nthe Thai monthly data", "start": 869.73, "duration": 3.63}, {"text": "that we were just talking\nabout, and use the tool", "start": 873.36, "duration": 4.02}, {"text": "to think about planning--\nabout wealth planning.", "start": 877.38, "duration": 3.57}, {"text": "Then we'll take a step back\nand add another account.", "start": 880.95, "duration": 3.72}, {"text": "I'll motivate that account\nby thinking about Bitcoin,", "start": 884.67, "duration": 4.02}, {"text": "as I promised in lecture one,\nand link the ledgers of Bitcoin", "start": 888.69, "duration": 5.64}, {"text": "to the statement of cash flow.", "start": 894.33, "duration": 2.04}, {"text": "And hence, back to\nthe Thai villages.", "start": 896.37, "duration": 2.73}, {"text": "In particular, I'll talk about\ndistributed ledgers, which", "start": 899.1, "duration": 2.73}, {"text": "is a big part of Bitcoin--", "start": 901.83, "duration": 2.64}, {"text": "Bitcoin, blockchain,\nand distributed ledgers.", "start": 904.47, "duration": 2.97}, {"text": "And then having\nintroduced that concept,", "start": 907.44, "duration": 2.7}, {"text": "I'll focus on the use\nalmost exclusively", "start": 910.14, "duration": 4.11}, {"text": "of paper currency\nin Thailand, the use", "start": 914.25, "duration": 3.78}, {"text": "of almost exclusively\nelectronic transfers in Sweden,", "start": 918.03, "duration": 3.87}, {"text": "and something in\nbetween in Kenya,", "start": 921.9, "duration": 2.95}, {"text": "which has two different kinds\nof monies, essentially--", "start": 924.85, "duration": 3.44}, {"text": "privately issued e-money\nfrom a cell phone", "start": 928.29, "duration": 2.58}, {"text": "provider, and a public Fiat\nmoney, Kenyan shillings.", "start": 930.87, "duration": 4.26}, {"text": "And then I'll end-- and so\nthese three things for Thailand,", "start": 935.13, "duration": 3.54}, {"text": "Sweden, and Kenya\nare about cash--", "start": 938.67, "duration": 2.1}, {"text": "various concepts of cash\nand cash management.", "start": 940.77, "duration": 2.64}, {"text": "And then we'll come\nback to the ledgers", "start": 943.41, "duration": 3.0}, {"text": "again and talk about trusted\nthird parties, some problems", "start": 946.41, "duration": 3.3}, {"text": "and management\nthat may or may not", "start": 949.71, "duration": 2.04}, {"text": "show up at the individual\nlevel, but definitely", "start": 951.75, "duration": 2.13}, {"text": "show up at the wholesale\nlevel at the level", "start": 953.88, "duration": 2.85}, {"text": "of financial infrastructure.", "start": 956.73, "duration": 1.92}, {"text": "OK.", "start": 958.65, "duration": 1.02}, {"text": "So here's a statement of income.", "start": 959.67, "duration": 4.5}, {"text": "And forgive me if this is\na review for some of you.", "start": 964.17, "duration": 2.94}, {"text": "These things aren't hard,\nbut they're a bit tedious.", "start": 967.11, "duration": 3.46}, {"text": "So we talk about sources of\nincome and uses of income.", "start": 970.57, "duration": 3.68}, {"text": "And the sources of income,\nas in the Thai data,", "start": 974.25, "duration": 2.88}, {"text": "come from cultivation,\nlivestock, fish and shrimp.", "start": 977.13, "duration": 3.3}, {"text": "This is a wage-earning\nhousehold primarily,", "start": 980.43, "duration": 3.72}, {"text": "a little bit of livestock.", "start": 984.15, "duration": 1.29}, {"text": "So the line entry here\nis almost entirely", "start": 985.44, "duration": 2.97}, {"text": "from wage, labor, income.", "start": 988.41, "duration": 2.49}, {"text": "Those are the sources.", "start": 990.9, "duration": 1.14}, {"text": "And then the uses, so\nto speak, or you could", "start": 992.04, "duration": 2.7}, {"text": "say revenues versus costs--", "start": 994.74, "duration": 2.01}, {"text": "you have expenses from each\nof the activities-- livestock.", "start": 996.75, "duration": 5.31}, {"text": "If they're in debt, they\nhave interest expenses.", "start": 1002.06, "duration": 2.43}, {"text": "There's that depreciation that\nwe talked about last time.", "start": 1004.49, "duration": 3.09}, {"text": "And then this is\ncharges against revenue.", "start": 1007.58, "duration": 2.56}, {"text": "So in addition to having\nexpenses for production,", "start": 1010.14, "duration": 2.84}, {"text": "they might pay taxes--", "start": 1012.98, "duration": 1.41}, {"text": "these guys don't.", "start": 1014.39, "duration": 0.87}, {"text": "But they can either\nconsume the rest or save.", "start": 1015.26, "duration": 4.89}, {"text": "Advantage of the\nfinancial accounts", "start": 1020.15, "duration": 1.68}, {"text": "is that everything balances.", "start": 1021.83, "duration": 1.48}, {"text": "So in this case,\nrevenue is totally", "start": 1023.31, "duration": 1.789}, {"text": "balanced by charges\nagainst revenue.", "start": 1025.099, "duration": 2.191}, {"text": "And if you're-- as we\ndid-- taking the Thai data", "start": 1027.29, "duration": 2.52}, {"text": "and thinking of all the\nline items then creating", "start": 1029.81, "duration": 2.73}, {"text": "the accounts, and if these\nleft- and right-hand sides", "start": 1032.54, "duration": 2.49}, {"text": "don't balance, we know\nwe something wrong.", "start": 1035.03, "duration": 2.039}, {"text": "And we have to go back and\niterate and figure out--", "start": 1037.069, "duration": 3.061}, {"text": "excluded a variable, or put\nit in the inappropriate spot.", "start": 1040.13, "duration": 3.209}, {"text": "So it's a great\ndiscipline device.", "start": 1043.339, "duration": 2.791}, {"text": "The balance sheet is stocks\nof stuff at a point in time,", "start": 1046.13, "duration": 4.53}, {"text": "namely, liabilities and assets.", "start": 1050.66, "duration": 3.96}, {"text": "So the obvious\nliability would be", "start": 1054.62, "duration": 1.86}, {"text": "debt, which this household has.", "start": 1056.48, "duration": 3.12}, {"text": "This is really\nsomebody's numbers.", "start": 1059.6, "duration": 1.86}, {"text": "This is a real person,\nI want to remind you.", "start": 1061.46, "duration": 3.06}, {"text": "More on that momentarily.", "start": 1064.52, "duration": 2.02}, {"text": "And the debt's\nabout 37,000 baht.", "start": 1066.54, "duration": 2.9}, {"text": "And the assets that\nthe household has", "start": 1069.44, "duration": 3.33}, {"text": "could be real or financial.", "start": 1072.77, "duration": 2.145}, {"text": "The financial assets are a big\nchunk of it in paper currency", "start": 1074.915, "duration": 4.995}, {"text": "and some deposits at the bank.", "start": 1079.91, "duration": 1.95}, {"text": "And real assets, in this\ncase, household fixed assets.", "start": 1081.86, "duration": 4.69}, {"text": "So we went through\nsome examples last time", "start": 1086.55, "duration": 2.09}, {"text": "when we talked about rates\nof return, because we", "start": 1088.64, "duration": 2.55}, {"text": "had in the numerator\nprofits, which", "start": 1091.19, "duration": 2.91}, {"text": "is on the previous account\nrevenue minus expenses.", "start": 1094.1, "duration": 3.69}, {"text": "And here, profits over capital.", "start": 1097.79, "duration": 2.16}, {"text": "And here we have the real\nand also financial capital.", "start": 1099.95, "duration": 5.64}, {"text": "Now, again, these\nthings balance.", "start": 1105.59, "duration": 3.09}, {"text": "But here, there's a big\nitem that I deliberately", "start": 1108.68, "duration": 3.72}, {"text": "didn't mention at first to\nget your attention, which", "start": 1112.4, "duration": 3.12}, {"text": "is if you take assets\nminus liabilities,", "start": 1115.52, "duration": 3.42}, {"text": "hopefully net worth is positive.", "start": 1118.94, "duration": 3.33}, {"text": "If liabilities were\ngreater than assets,", "start": 1122.27, "duration": 2.31}, {"text": "this guy's bankrupt, at least\nin the accounting sense.", "start": 1124.58, "duration": 3.43}, {"text": "So for almost all\nthese households,", "start": 1128.01, "duration": 2.09}, {"text": "assets are greater\nthan liabilities.", "start": 1130.1, "duration": 2.19}, {"text": "And the difference is something\nwe call equity or net worth.", "start": 1132.29, "duration": 3.75}, {"text": "And that enters oddly\non the right-hand side", "start": 1136.04, "duration": 2.73}, {"text": "with liabilities, precisely\nso that the two sides", "start": 1138.77, "duration": 3.12}, {"text": "of the financial account, or\nthe balance sheet account,", "start": 1141.89, "duration": 3.06}, {"text": "are equal to each other.", "start": 1144.95, "duration": 1.92}, {"text": "OK.", "start": 1146.87, "duration": 0.9}, {"text": "So now with those concepts, the\nstatement and balance sheet,", "start": 1147.77, "duration": 3.92}, {"text": "would take it to an application.", "start": 1151.69, "duration": 2.2}, {"text": "So this is a wealth\nplanner, which", "start": 1153.89, "duration": 2.36}, {"text": "we implemented to that household\nand all of the other ones.", "start": 1156.25, "duration": 4.83}, {"text": "What is the household\nwe imagine to be doing?", "start": 1161.08, "duration": 3.63}, {"text": "Namely, maximize discounted\nexpected utility.", "start": 1164.71, "duration": 3.45}, {"text": "So you've kind of seen\nversions of this before.", "start": 1168.16, "duration": 2.43}, {"text": "You saw it first with\nrespect to storage of seed", "start": 1170.59, "duration": 3.66}, {"text": "and so on in the\nmedieval village economy.", "start": 1174.25, "duration": 3.37}, {"text": "We've got a finite\nhorizon here that happens,", "start": 1177.62, "duration": 2.99}, {"text": "but more on that momentarily.", "start": 1180.61, "duration": 2.05}, {"text": "So it's discounted utility.", "start": 1182.66, "duration": 2.06}, {"text": "This is constant relative risk\naversion, with a risk averse", "start": 1184.72, "duration": 3.54}, {"text": "coefficient of kappa.", "start": 1188.26, "duration": 2.19}, {"text": "Delta is the discount rate.", "start": 1190.45, "duration": 2.13}, {"text": "And the end of life,\nwhich is T, they", "start": 1192.58, "duration": 3.48}, {"text": "may bequest assets\nto their kids.", "start": 1196.06, "duration": 3.19}, {"text": "It looks like a\nsimilar function,", "start": 1199.25, "duration": 1.76}, {"text": "but there's an extra\nterm here, which", "start": 1201.01, "duration": 1.59}, {"text": "is beta, almost for bequest.", "start": 1202.6, "duration": 2.46}, {"text": "And again, the notation changes\nfrom one lecture to the next.", "start": 1205.06, "duration": 4.02}, {"text": "But anyway, so that's\nanother parameter.", "start": 1209.08, "duration": 1.98}, {"text": "We have delta, kappa, and beta.", "start": 1211.06, "duration": 1.86}, {"text": "We're going to have to figure\nout what they are because they", "start": 1212.92, "duration": 2.5}, {"text": "will impact the solution.", "start": 1215.42, "duration": 1.52}, {"text": "Subject to the big\nconstraint-- now,", "start": 1216.94, "duration": 2.22}, {"text": "again, you've seen a version\nof this in the medieval village", "start": 1219.16, "duration": 3.36}, {"text": "economy because we had\nresources available today, which", "start": 1222.52, "duration": 3.72}, {"text": "they could eat or store in\ntwo different ways, which", "start": 1226.24, "duration": 4.26}, {"text": "would determine resources\navailable next period.", "start": 1230.5, "duration": 2.97}, {"text": "Here, they have\nwealth today, and they", "start": 1233.47, "duration": 2.7}, {"text": "have resources\navailable today, which", "start": 1236.17, "duration": 2.58}, {"text": "is the beginning of period\nstocks, their wealth,", "start": 1238.75, "duration": 3.48}, {"text": "plus income--", "start": 1242.23, "duration": 1.17}, {"text": "more on that momentarily.", "start": 1243.4, "duration": 1.72}, {"text": "And they can either eat\nit-- and the difference", "start": 1245.12, "duration": 2.13}, {"text": "between what they have and\nwhat they eat, they invest.", "start": 1247.25, "duration": 2.69}, {"text": "So some fraction, Z,\ngoes into risky assets,", "start": 1249.94, "duration": 4.14}, {"text": "and the residual 1 minus Z\nfraction goes into safe assets.", "start": 1254.08, "duration": 4.23}, {"text": "So this is a lifecycle\nportfolio allocation problem.", "start": 1258.31, "duration": 5.07}, {"text": "A little bit more detail\nabout these numbers--", "start": 1263.38, "duration": 2.46}, {"text": "so the income term is the\nsecond and third term.", "start": 1265.84, "duration": 3.45}, {"text": "If gamma is equal to 1, then the\nmu, which is the mean income,", "start": 1269.29, "duration": 4.17}, {"text": "cancels out.", "start": 1273.46, "duration": 1.0}, {"text": "And this household is\nentirely on its own", "start": 1274.46, "duration": 2.72}, {"text": "with income fluctuations\naround the mean.", "start": 1277.18, "duration": 3.15}, {"text": "When gamma is equal to 0,\nthis whole term is gone,", "start": 1280.33, "duration": 3.94}, {"text": "and the household\nhas its mean income.", "start": 1284.27, "duration": 2.4}, {"text": "So gamma here, between 0 and 1,\nis capturing the risk-sharing", "start": 1286.67, "duration": 4.7}, {"text": "that we know is prevalent\nin the Thai villages.", "start": 1291.37, "duration": 2.97}, {"text": "So that's the way all that\nrisk-sharing stuff entered", "start": 1294.34, "duration": 2.4}, {"text": "into the individual program.", "start": 1296.74, "duration": 1.44}, {"text": "It looks like self\ninsurance, but it isn't.", "start": 1298.18, "duration": 3.24}, {"text": "Because the income stream can\nbe attenuated due to the gifts.", "start": 1301.42, "duration": 4.38}, {"text": "But it can also vary\nover households.", "start": 1305.8, "duration": 2.25}, {"text": "We have to elicit\nfrom the households", "start": 1308.05, "duration": 2.31}, {"text": "how big or small gamma is.", "start": 1310.36, "duration": 1.86}, {"text": "This is a premium if the--", "start": 1312.22, "duration": 2.91}, {"text": "sorry-- an indemnity if\nthe household head dies,", "start": 1315.13, "duration": 4.02}, {"text": "all these village villagers\nget together and contribute", "start": 1319.15, "duration": 3.33}, {"text": "something to help the bereaved\nhousehold with expenses", "start": 1322.48, "duration": 3.3}, {"text": "and so on. c is consumption.", "start": 1325.78, "duration": 1.95}, {"text": "Big C is committed consumption.", "start": 1327.73, "duration": 2.26}, {"text": "So these are things the\nhousehold tells us they're", "start": 1329.99, "duration": 2.69}, {"text": "going to do no matter what.", "start": 1332.68, "duration": 1.57}, {"text": "And so we enter as a\nparticular expense.", "start": 1334.25, "duration": 4.01}, {"text": "All right.", "start": 1338.26, "duration": 0.54}, {"text": "So here is a bit of what\nwe show the household.", "start": 1338.8, "duration": 3.84}, {"text": "We explain to them--", "start": 1342.64, "duration": 1.47}, {"text": "we go and interview them.", "start": 1344.11, "duration": 2.01}, {"text": "And that we have been getting\ndata from them all along,", "start": 1346.12, "duration": 3.12}, {"text": "but this is extra.", "start": 1349.24, "duration": 1.59}, {"text": "So we tell them we want\nto know how much they're", "start": 1350.83, "duration": 2.91}, {"text": "planning to give to\ntheir kids, if anything.", "start": 1353.74, "duration": 2.79}, {"text": "Try to elicit their\ncurrent income profile", "start": 1356.53, "duration": 2.82}, {"text": "and future movements and income.", "start": 1359.35, "duration": 2.07}, {"text": "Get their goals, and get\ntheir current wealth.", "start": 1361.42, "duration": 4.355}, {"text": "And then we're\ngoing to tell them", "start": 1365.775, "duration": 1.375}, {"text": "how much they should be\nsaving, and how to save it", "start": 1367.15, "duration": 3.03}, {"text": "in risky versus safe things.", "start": 1370.18, "duration": 2.25}, {"text": "And particular, whether they\nmight want to be borrowing.", "start": 1372.43, "duration": 3.358}, {"text": "I don't know.", "start": 1375.788, "duration": 0.542}, {"text": "Some people don't like these\nlittle cartoon characters.", "start": 1376.33, "duration": 2.55}, {"text": "It's an attempt to\ncommunicate clearly.", "start": 1378.88, "duration": 3.3}, {"text": "So we don't say,\ntell us everything.", "start": 1382.18, "duration": 1.92}, {"text": "We say, let us demonstrate\nto you how this works.", "start": 1384.1, "duration": 2.94}, {"text": "We'll show you the results\nof another villager.", "start": 1387.04, "duration": 3.78}, {"text": "We asked that household\nwhether or not", "start": 1390.82, "duration": 2.43}, {"text": "they want to leave\nmoney to their kids.", "start": 1393.25, "duration": 1.83}, {"text": "And this household said, no.", "start": 1395.08, "duration": 2.46}, {"text": "My kids are going to be\nmuch richer than I am.", "start": 1397.54, "duration": 2.31}, {"text": "They're going to\nwork in Bangkok.", "start": 1399.85, "duration": 1.8}, {"text": "I don't think I need to\nleave anything to my children", "start": 1401.65, "duration": 3.45}, {"text": "after my death.", "start": 1405.1, "duration": 1.66}, {"text": "So this household\nsaid zero baht.", "start": 1406.76, "duration": 3.02}, {"text": "I made the mistake\nonce of having", "start": 1409.78, "duration": 1.56}, {"text": "this interview with the\nmother and the daughter", "start": 1411.34, "duration": 2.76}, {"text": "present in the room\nat the same time.", "start": 1414.1, "duration": 2.67}, {"text": "Obviously, that was awkward.", "start": 1416.77, "duration": 2.302}, {"text": "[LAUGHS] OK.", "start": 1419.072, "duration": 2.318}, {"text": "Collect inputs-- so we need to\ncalibrate this income process.", "start": 1421.39, "duration": 4.11}, {"text": "And we give, for example, Chen.", "start": 1425.5, "duration": 3.473}, {"text": "Now you're going\nto see some Thai.", "start": 1428.973, "duration": 1.417}, {"text": "Sorry.", "start": 1430.39, "duration": 0.54}, {"text": "Anyway, wage earners earn a\nregular income of 10,000 baht.", "start": 1430.93, "duration": 5.67}, {"text": "Expects to work to age\n65, and then income", "start": 1436.6, "duration": 4.59}, {"text": "drops to something very\nsmall, which is a pension.", "start": 1441.19, "duration": 3.33}, {"text": "So that's this picture.", "start": 1444.52, "duration": 1.41}, {"text": "10,000 baht, age\n65, the household's", "start": 1445.93, "duration": 2.46}, {"text": "currently young, actually.", "start": 1448.39, "duration": 1.99}, {"text": "Drops to zero.", "start": 1450.38, "duration": 0.78}, {"text": "Or this guy--\ndifferent example--", "start": 1451.16, "duration": 2.58}, {"text": "has a little shop\nas a business--", "start": 1453.74, "duration": 2.22}, {"text": "very volatile income.", "start": 1455.96, "duration": 2.82}, {"text": "Expects to keep its business\nrunning until age 60--", "start": 1458.78, "duration": 3.3}, {"text": "currently age 25.", "start": 1462.08, "duration": 2.64}, {"text": "And then receive some small\nincome, again, from the kids.", "start": 1464.72, "duration": 3.96}, {"text": "Oh, yeah.", "start": 1468.68, "duration": 0.57}, {"text": "Kids give money to\nthe parents, you guys.", "start": 1469.25, "duration": 2.68}, {"text": "You hear that?", "start": 1471.93, "duration": 1.4}, {"text": "[LAUGHS]", "start": 1473.33, "duration": 3.78}, {"text": "OK.", "start": 1477.11, "duration": 1.49}, {"text": "Depends on where you're from\nwhether you can relate to this.", "start": 1478.6, "duration": 3.17}, {"text": "Another example-- this household\nhas regular increasing income", "start": 1481.77, "duration": 4.71}, {"text": "for 30 years.", "start": 1486.48, "duration": 1.57}, {"text": "But, again, income\nstarts to drop.", "start": 1488.05, "duration": 2.09}, {"text": "However, they're going to\ngo into a second occupation,", "start": 1490.14, "duration": 2.91}, {"text": "and income only slowly.", "start": 1493.05, "duration": 1.71}, {"text": "So I stay-- we used to stay in\nthe village with the headman.", "start": 1494.76, "duration": 3.57}, {"text": "But eventually,\nThailand has motels.", "start": 1498.33, "duration": 2.76}, {"text": "And you'll often see an elderly\ncouple running the motel.", "start": 1501.09, "duration": 4.17}, {"text": "That's now their new\nbusiness, relative to what", "start": 1505.26, "duration": 2.64}, {"text": "they used to do, et cetera.", "start": 1507.9, "duration": 1.98}, {"text": "So these are just\nthree examples.", "start": 1509.88, "duration": 2.47}, {"text": "So what about goals?", "start": 1512.35, "duration": 2.38}, {"text": "So do you expect to send\nyour kids to college?", "start": 1514.73, "duration": 3.16}, {"text": "Is that a planned expense?", "start": 1517.89, "duration": 1.98}, {"text": "Or in the future open a\nbusiness or buy a new TV?", "start": 1519.87, "duration": 4.53}, {"text": "But what we want\nare expenses they're", "start": 1524.4, "duration": 2.64}, {"text": "going to be no matter what.", "start": 1527.04, "duration": 1.36}, {"text": "So yes or no, depending.", "start": 1528.4, "duration": 3.02}, {"text": "In this particular\nexample household,", "start": 1531.42, "duration": 2.52}, {"text": "we give them car purchase.", "start": 1533.94, "duration": 1.89}, {"text": "Was that obligatory?", "start": 1535.83, "duration": 1.17}, {"text": "No.", "start": 1537.0, "duration": 0.6}, {"text": "Send the kids to college?", "start": 1537.6, "duration": 1.44}, {"text": "Yes.", "start": 1539.04, "duration": 1.05}, {"text": "How many years away?", "start": 1540.09, "duration": 1.26}, {"text": "15 years-- kids are young.", "start": 1541.35, "duration": 2.37}, {"text": "And it's going to cost\n$10,000 for three years--", "start": 1543.72, "duration": 3.84}, {"text": "30,000 baht.", "start": 1547.56, "duration": 1.74}, {"text": "That's about-- it's a lot\nless than US expenses.", "start": 1549.3, "duration": 3.69}, {"text": "It's not an MIT tuition.", "start": 1552.99, "duration": 2.19}, {"text": "All right.", "start": 1555.18, "duration": 0.6}, {"text": "So now we have wealth, so w.", "start": 1555.78, "duration": 3.24}, {"text": "This is tricky.", "start": 1559.02, "duration": 0.99}, {"text": "Money available to save\nor spend or invest.", "start": 1560.01, "duration": 3.84}, {"text": "So if you have a car\nthat's worth 10,000 baht.", "start": 1563.85, "duration": 3.06}, {"text": "You think-- it's used, but\nyou could sell it easily.", "start": 1566.91, "duration": 3.22}, {"text": "Then we would count that as\na household asset or business", "start": 1570.13, "duration": 2.93}, {"text": "asset-- could be sold.", "start": 1573.06, "duration": 1.65}, {"text": "If they own land\nworth 100,000 baht,", "start": 1574.71, "duration": 3.3}, {"text": "they may never plan to\nsell it, and may not even", "start": 1578.01, "duration": 2.91}, {"text": "be productive land.", "start": 1580.92, "duration": 1.56}, {"text": "So we don't count it\nunless they said it was.", "start": 1582.48, "duration": 3.09}, {"text": "If it's productive, we want\nto avoid double counting.", "start": 1585.57, "duration": 4.84}, {"text": "So here's the thing.", "start": 1590.41, "duration": 1.25}, {"text": "You would count\nthe asset, or you", "start": 1591.66, "duration": 1.56}, {"text": "would count the return stream.", "start": 1593.22, "duration": 1.71}, {"text": "You cannot count both.", "start": 1594.93, "duration": 1.845}, {"text": "The value of land should be the\ndiscounted capitalized value", "start": 1596.775, "duration": 5.835}, {"text": "of net profits from farming.", "start": 1602.61, "duration": 2.49}, {"text": "That's how much\nthe land is worth.", "start": 1605.1, "duration": 2.28}, {"text": "You don't want to count\nboth the land as an asset,", "start": 1607.38, "duration": 2.58}, {"text": "and also ask the households\nabout the income stream.", "start": 1609.96, "duration": 3.21}, {"text": "So generally, we\ndon't count assets", "start": 1613.17, "duration": 2.43}, {"text": "that we are using in calculating\nthe income stream unless they", "start": 1615.6, "duration": 3.45}, {"text": "say, I'm going to stop\nfarming at a certain date.", "start": 1619.05, "duration": 3.15}, {"text": "And how much would the\nland be worth then?", "start": 1622.2, "duration": 1.98}, {"text": "If we count income up to that\npoint, then we count the land.", "start": 1624.18, "duration": 3.6}, {"text": "So let's run the planner.", "start": 1627.78, "duration": 2.13}, {"text": "I'll give you examples.", "start": 1629.91, "duration": 1.41}, {"text": "We created an Excel\nspreadsheet with the answers", "start": 1631.32, "duration": 2.94}, {"text": "to all the\nhousehold's questions,", "start": 1634.26, "duration": 2.1}, {"text": "and then enter it into\nthe computer and run it.", "start": 1636.36, "duration": 3.7}, {"text": "I'm not showing you all of them.", "start": 1640.06, "duration": 1.36}, {"text": "The second household--\nwe told this household", "start": 1641.42, "duration": 2.42}, {"text": "to cut its expenses on\nconsumption quite a bit.", "start": 1643.84, "duration": 3.52}, {"text": "They weren't saving enough,\nand to put almost all of it", "start": 1647.36, "duration": 2.93}, {"text": "in safe assets.", "start": 1650.29, "duration": 1.8}, {"text": "More interesting is\nthe life cycle picture.", "start": 1652.09, "duration": 3.28}, {"text": "So here's what the\nplanner recommends", "start": 1655.37, "duration": 2.3}, {"text": "that the household should do.", "start": 1657.67, "duration": 2.31}, {"text": "Namely, let's start down here.", "start": 1659.98, "duration": 3.12}, {"text": "We've got income in red.", "start": 1663.1, "duration": 1.95}, {"text": "That's the elicited\nprofile over time", "start": 1665.05, "duration": 3.54}, {"text": "that I just told you about.", "start": 1668.59, "duration": 1.8}, {"text": "The consumption is endogenous\nvariable, obviously.", "start": 1670.39, "duration": 3.96}, {"text": "It's in black.", "start": 1674.35, "duration": 1.14}, {"text": "So here, we told the household\nto cut its consumption", "start": 1675.49, "duration": 3.06}, {"text": "expenditure a lot and much\nlower than its current income", "start": 1678.55, "duration": 3.9}, {"text": "in order to build up the assets.", "start": 1682.45, "duration": 2.32}, {"text": "So here's the total\nlevel of assets.", "start": 1684.77, "duration": 2.12}, {"text": "And then when income drops\nto little or nothing,", "start": 1686.89, "duration": 4.68}, {"text": "they eat off the assets.", "start": 1691.57, "duration": 1.84}, {"text": "So this is just\nsaving for retirement.", "start": 1693.41, "duration": 2.39}, {"text": "Most of it's in safe assets,\nnot so much in risky,", "start": 1695.8, "duration": 3.3}, {"text": "and there's no borrowing.", "start": 1699.1, "duration": 1.56}, {"text": "Another household basically\nhad committed consumption", "start": 1700.66, "duration": 4.05}, {"text": "that is going to get\nit in big trouble,", "start": 1704.71, "duration": 2.22}, {"text": "even though they said they were\ngoing to do it no matter what.", "start": 1706.93, "duration": 3.84}, {"text": "When we ran the\nplanner at the time", "start": 1710.77, "duration": 2.64}, {"text": "that they have\nthis high expense--", "start": 1713.41, "duration": 1.89}, {"text": "I think it was for starting a\nbusiness-- they really didn't", "start": 1715.3, "duration": 2.58}, {"text": "have the resources to cover it.", "start": 1717.88, "duration": 1.77}, {"text": "Now, they try to\nincrease their savings", "start": 1719.65, "duration": 4.62}, {"text": "with income over consumption.", "start": 1724.27, "duration": 3.66}, {"text": "But in this median simulation\nscenario, it's just not enough.", "start": 1727.93, "duration": 6.34}, {"text": "So when that big expense\ncomes, on average, they", "start": 1734.27, "duration": 3.32}, {"text": "use up all of their assets.", "start": 1737.59, "duration": 2.73}, {"text": "Consumption isn't\ndropping to zero.", "start": 1740.32, "duration": 2.59}, {"text": "You remember, it's constant\nrelative risk aversion.", "start": 1742.91, "duration": 2.16}, {"text": "So marginal utility\nof consumption at zero", "start": 1745.07, "duration": 3.17}, {"text": "is infinite.", "start": 1748.24, "duration": 0.9}, {"text": "Although, you can't see\nthis, but we gave them", "start": 1749.14, "duration": 2.91}, {"text": "some subsistence bundle.", "start": 1752.05, "duration": 1.95}, {"text": "So they don't\nreally go bankrupt.", "start": 1754.0, "duration": 1.65}, {"text": "They survive.", "start": 1755.65, "duration": 1.02}, {"text": "Well, they don't die\nwhen they go bankrupt.", "start": 1756.67, "duration": 2.85}, {"text": "They continue to survive because\nof that subsistence bundle.", "start": 1759.52, "duration": 4.56}, {"text": "What else is going on here?", "start": 1764.08, "duration": 1.77}, {"text": "They kind of know in advance--", "start": 1765.85, "duration": 1.86}, {"text": "the planner knows-- state\nby state, year by year", "start": 1767.71, "duration": 3.84}, {"text": "that they're in trouble.", "start": 1771.55, "duration": 2.23}, {"text": "So actually, they\nstart borrowing.", "start": 1773.78, "duration": 2.54}, {"text": "Of course, given our\nsubsistence consumption rule,", "start": 1776.32, "duration": 2.88}, {"text": "if the median scenario\noccurs, they're", "start": 1779.2, "duration": 2.85}, {"text": "not going to pay back the loan.", "start": 1782.05, "duration": 1.5}, {"text": "They get to default on the\nloan, and they know that.", "start": 1783.55, "duration": 2.64}, {"text": "Call this gambling\nfor redemption.", "start": 1786.19, "duration": 2.22}, {"text": "They're starting to\ndo risky things too,", "start": 1788.41, "duration": 2.94}, {"text": "and borrowing, leveraging\nup, with the idea", "start": 1791.35, "duration": 3.51}, {"text": "that there's a good chance\nthey're not going to make it.", "start": 1794.86, "duration": 3.0}, {"text": "Here, the planner\nis not the bank.", "start": 1797.86, "duration": 2.82}, {"text": "Whether the bank would make\nthis loan is another issue.", "start": 1800.68, "duration": 3.33}, {"text": "Anyway, they\nsurvive this episode", "start": 1804.01, "duration": 2.31}, {"text": "and continue to live another day\nwith their fluctuating income.", "start": 1806.32, "duration": 3.76}, {"text": "So the rest of this looks\nlike the other diagram", "start": 1810.08, "duration": 2.27}, {"text": "to some extent.", "start": 1812.35, "duration": 1.32}, {"text": "OK.", "start": 1813.67, "duration": 0.51}, {"text": "So we show the households\nthese pictures,", "start": 1814.18, "duration": 2.46}, {"text": "and try to explain to\nthem what's going on.", "start": 1816.64, "duration": 3.15}, {"text": "And there are all kinds\nof households in the data.", "start": 1819.79, "duration": 2.44}, {"text": "And some of them, in fact,\nare very conservative,", "start": 1822.23, "duration": 2.81}, {"text": "and they have fluctuations\nin income and consumption.", "start": 1825.04, "duration": 2.67}, {"text": "Consumption is never more than\nthe lowest possible income", "start": 1827.71, "duration": 3.93}, {"text": "draw, and mostly, a lot\nlower than their income draw.", "start": 1831.64, "duration": 3.36}, {"text": "So they're saving like\ncrazy, and their net worth", "start": 1835.0, "duration": 3.45}, {"text": "is growing at 20% per year.", "start": 1838.45, "duration": 2.46}, {"text": "Sounds good to me, by the way.", "start": 1840.91, "duration": 1.44}, {"text": "But they're probably\nover-saving.", "start": 1842.35, "duration": 2.49}, {"text": "But we're very conservative\nabout what we tell them.", "start": 1844.84, "duration": 3.24}, {"text": "We don't tell them\nthat that's bad.", "start": 1848.08, "duration": 2.4}, {"text": "That's fine if they\nwant to do that.", "start": 1850.48, "duration": 1.59}, {"text": "It's the ones who\nare eating too much", "start": 1852.07, "duration": 1.86}, {"text": "and not saving that\nwe're more worried about.", "start": 1853.93, "duration": 3.15}, {"text": "OK.", "start": 1857.08, "duration": 0.9}, {"text": "So this looks like\nThai villages,", "start": 1857.98, "duration": 2.01}, {"text": "but the life cycle\nmodel is universal.", "start": 1859.99, "duration": 2.7}, {"text": "And just to shift gears, this\nis Larry Kotlikoff's website.", "start": 1862.69, "duration": 6.51}, {"text": "He's both a professor\nand an entrepreneur.", "start": 1869.2, "duration": 3.04}, {"text": "So he is selling this\nproduct, this ESB planner.", "start": 1872.24, "duration": 5.3}, {"text": "But he has a lot of great\neconomic research on life cycle", "start": 1877.54, "duration": 3.51}, {"text": "planning.", "start": 1881.05, "duration": 1.02}, {"text": "And no one wants to\nsplurge today and starve", "start": 1882.07, "duration": 3.9}, {"text": "tomorrow, nor the opposite.", "start": 1885.97, "duration": 2.37}, {"text": "Lifecycle consumption-smoothing\nbalances our goals.", "start": 1888.34, "duration": 4.51}, {"text": "Now, you would think,\ncould everyone do that?", "start": 1892.85, "duration": 2.08}, {"text": "The answer is no.", "start": 1894.93, "duration": 1.72}, {"text": "There's only two companies I\nknow of in the US that do this.", "start": 1896.65, "duration": 3.78}, {"text": "And it's not Vanguard.", "start": 1900.43, "duration": 1.35}, {"text": "It's not Fidelity.", "start": 1901.78, "duration": 1.5}, {"text": "They're adopting kind\nof a rule of thumb.", "start": 1903.28, "duration": 2.37}, {"text": "They ask you what's\nyour current expenses?", "start": 1905.65, "duration": 3.21}, {"text": "And then say 70% of that\nis target for retirement.", "start": 1908.86, "duration": 5.17}, {"text": "And then how much do you have\nto save to make that goal?", "start": 1914.03, "duration": 3.78}, {"text": "And so consumption could be low\nbecause you're saving a lot.", "start": 1917.81, "duration": 3.8}, {"text": "And that can end up in a\nvery imbalanced profile", "start": 1921.61, "duration": 2.94}, {"text": "in which you're starving today\nin order to splurge tomorrow.", "start": 1924.55, "duration": 3.99}, {"text": "Whereas, we're using this\nstrictly concave utility,", "start": 1928.54, "duration": 4.48}, {"text": "and so is Larry, to say we\nwant to smooth over time.", "start": 1933.02, "duration": 3.11}, {"text": "Just like we want to\nsmooth over bad shocks,", "start": 1936.13, "duration": 2.67}, {"text": "we want to smooth over time,\nas in the medieval village seed", "start": 1938.8, "duration": 4.81}, {"text": "and so on.", "start": 1943.61, "duration": 1.61}, {"text": "OK.", "start": 1945.22, "duration": 1.89}, {"text": "So let me make a transition\nthen to the other account, which", "start": 1947.11, "duration": 4.83}, {"text": "is cash flow.", "start": 1951.94, "duration": 0.72}, {"text": "And I'm going to do this\nby explaining a little bit", "start": 1952.66, "duration": 2.34}, {"text": "about Bitcoin, and many of\nyou probably know about this", "start": 1955.0, "duration": 3.33}, {"text": "already.", "start": 1958.33, "duration": 0.58}, {"text": "So every transection in Bitcoin\nis an encoded message sent out", "start": 1958.91, "duration": 5.6}, {"text": "with a-- generated with a\nprivate/public key scheme,", "start": 1964.51, "duration": 3.51}, {"text": "which has the advantage\nthat it's known", "start": 1968.02, "duration": 3.73}, {"text": "which node sent the message.", "start": 1971.75, "duration": 2.09}, {"text": "And there's full\ncommitment to the message.", "start": 1973.84, "duration": 2.1}, {"text": "You can't go back and\ndeny that you sent it.", "start": 1975.94, "duration": 2.22}, {"text": "And it prevents fraud.", "start": 1978.16, "duration": 1.93}, {"text": "Nobody can transact on\nyour ID because nobody else", "start": 1980.09, "duration": 2.9}, {"text": "has the private key,\nunless you get careless.", "start": 1982.99, "duration": 3.45}, {"text": "So a transection in\nBitcoin is the moving", "start": 1986.44, "duration": 3.99}, {"text": "of the coin from one\nperson to another.", "start": 1990.43, "duration": 3.55}, {"text": "The message sent\nmight be, I want", "start": 1993.98, "duration": 2.27}, {"text": "to give the coin to\nperson X. Arguably,", "start": 1996.25, "duration": 3.33}, {"text": "because person X is a merchant\nand you're buying something", "start": 1999.58, "duration": 3.42}, {"text": "or whatever.", "start": 2003.0, "duration": 1.44}, {"text": "The various transactions are\naccumulated into a block,", "start": 2004.44, "duration": 4.2}, {"text": "and the block is subject to a\nvalidation routine, which is", "start": 2008.64, "duration": 3.81}, {"text": "mining and it's quite costly.", "start": 2012.45, "duration": 3.15}, {"text": "I'll come back to that later.", "start": 2015.6, "duration": 1.96}, {"text": "The point here is\nthat Bitcoin is", "start": 2017.56, "duration": 1.76}, {"text": "combining two different things.", "start": 2019.32, "duration": 2.02}, {"text": "One is the statement\nof cash flow", "start": 2021.34, "duration": 1.76}, {"text": "as the coin moves from out or\nin to the person in question.", "start": 2023.1, "duration": 5.22}, {"text": "And the other is\nthe balance sheet,", "start": 2028.32, "duration": 1.69}, {"text": "which is at a moment in time\nhow many coins do you own?", "start": 2030.01, "duration": 5.24}, {"text": "So the accounting of the\ncash flow works for Bitcoin.", "start": 2035.25, "duration": 3.69}, {"text": "It also works for paper\ncurrency in Thailand.", "start": 2038.94, "duration": 3.42}, {"text": "So let me show you a\nstatement of cash flow", "start": 2042.36, "duration": 2.385}, {"text": "as an accounting statement.", "start": 2044.745, "duration": 1.125}, {"text": "Remember, before, I showed\nyou income and balance sheet.", "start": 2045.87, "duration": 2.64}, {"text": "I haven't shown you the cash\nflow statement until now.", "start": 2048.51, "duration": 3.54}, {"text": "It's pretty small print.", "start": 2052.05, "duration": 1.47}, {"text": "Let me just give you\nthe big picture here.", "start": 2053.52, "duration": 2.31}, {"text": "We have cash flow\nfrom production,", "start": 2055.83, "duration": 2.11}, {"text": "which you can\nimagine, if you sold", "start": 2057.94, "duration": 2.42}, {"text": "something in got paper\ncurrency as a consequence,", "start": 2060.36, "duration": 3.24}, {"text": "you'd have a plus.", "start": 2063.6, "duration": 1.44}, {"text": "If you're buying fertilizer\nto grow the rice,", "start": 2065.04, "duration": 2.34}, {"text": "you have a minus sign.", "start": 2067.38, "duration": 2.259}, {"text": "So you have inflows and outflows\nassociated with production.", "start": 2069.639, "duration": 3.411}, {"text": "You can spend money\non consumption.", "start": 2073.05, "duration": 2.04}, {"text": "That's typically an outflow.", "start": 2075.09, "duration": 1.319}, {"text": "You can spend money\non investment, also", "start": 2076.409, "duration": 2.461}, {"text": "typically an outflow.", "start": 2078.87, "duration": 1.93}, {"text": "So we have cash flow from\nconsumption and investment,", "start": 2080.8, "duration": 2.66}, {"text": "and then we have cash\nflow from financing,", "start": 2083.46, "duration": 3.009}, {"text": "which is, you can put cash\nin the bank as a deposit,", "start": 2086.469, "duration": 3.111}, {"text": "or you could borrow cash.", "start": 2089.58, "duration": 1.47}, {"text": "Hopefully, you get\nit as an inflow,", "start": 2091.05, "duration": 1.919}, {"text": "through gifts and so on.", "start": 2092.969, "duration": 1.451}, {"text": "So cash flow from production,\nconsumption, and financing", "start": 2094.42, "duration": 5.36}, {"text": "are the three categories.", "start": 2099.78, "duration": 1.72}, {"text": "And this stuff up\nhere is complicated.", "start": 2101.5, "duration": 1.73}, {"text": "When I said I'd shown you\nthe income statement, but not", "start": 2103.23, "duration": 3.39}, {"text": "the cash flow statement, you\nmay have been thinking, well,", "start": 2106.62, "duration": 3.18}, {"text": "aren't they the same?", "start": 2109.8, "duration": 1.75}, {"text": "And the answer is, well, they\ncould be, but not necessarily.", "start": 2111.55, "duration": 3.32}, {"text": "So if you're a business, and\nyou sell something and the guy", "start": 2114.87, "duration": 3.54}, {"text": "doesn't pay you, then\nhe's going to pay later,", "start": 2118.41, "duration": 3.12}, {"text": "that's an account receivable,\nbut there's no cash.", "start": 2121.53, "duration": 3.57}, {"text": "So the sale would\ncount as revenue", "start": 2125.1, "duration": 2.37}, {"text": "in the income statement\nusing the accrued", "start": 2127.47, "duration": 2.22}, {"text": "notion of accounting,\nbut it would not", "start": 2129.69, "duration": 1.83}, {"text": "count as a cash inflow.", "start": 2131.52, "duration": 1.57}, {"text": "So oddly enough,\nthis top stuff here", "start": 2133.09, "duration": 2.39}, {"text": "is just starting with\nthe income statement", "start": 2135.48, "duration": 2.01}, {"text": "and making adjustments\nto it according", "start": 2137.49, "duration": 2.16}, {"text": "to whether the\nmovement of cash you", "start": 2139.65, "duration": 2.49}, {"text": "have to adjust one\nway or the other.", "start": 2142.14, "duration": 2.41}, {"text": "So, I mean, if you have\nan account receivable,", "start": 2144.55, "duration": 2.48}, {"text": "and you didn't get\nthe cash, then you", "start": 2147.03, "duration": 1.83}, {"text": "have to subtract off\nfrom accrued income", "start": 2148.86, "duration": 2.4}, {"text": "to get the cash\nflow because you're", "start": 2151.26, "duration": 2.37}, {"text": "counting something that\nis not yet associated", "start": 2153.63, "duration": 2.07}, {"text": "with the cash inflow.", "start": 2155.7, "duration": 1.81}, {"text": "All right.", "start": 2157.51, "duration": 0.5}, {"text": "Mainly, I'm just trying to\ngive you the big picture here.", "start": 2158.01, "duration": 2.58}, {"text": "This is the statement\nof cash flow.", "start": 2160.59, "duration": 2.14}, {"text": "And it is true, and this is\nautomatically true in Bitcoin,", "start": 2162.73, "duration": 4.25}, {"text": "that you can check whether the\nchange in cash holdings that", "start": 2166.98, "duration": 4.08}, {"text": "come at the bottom line of\nthe statement of cash flow", "start": 2171.06, "duration": 3.0}, {"text": "are exactly equal or not\nto the change in cash", "start": 2174.06, "duration": 3.66}, {"text": "that we have on\nthe balance sheet.", "start": 2177.72, "duration": 1.93}, {"text": "So you have cash in\na moment in time,", "start": 2179.65, "duration": 1.85}, {"text": "and then you have these\ninflows and outflows.", "start": 2181.5, "duration": 2.25}, {"text": "You have cash in\na future period.", "start": 2183.75, "duration": 2.46}, {"text": "In each of those periods\nnow and in the future,", "start": 2186.21, "duration": 2.4}, {"text": "you have two balance sheets.", "start": 2188.61, "duration": 1.24}, {"text": "Take the difference in\nthe balance sheet, that's", "start": 2189.85, "duration": 2.0}, {"text": "the change in the cash\nflow on the balance sheet,", "start": 2191.85, "duration": 2.5}, {"text": "and it should be\nexactly equal to what's", "start": 2194.35, "duration": 1.7}, {"text": "showing up here in the cash\nflow from the statement of cash", "start": 2196.05, "duration": 3.12}, {"text": "flow.", "start": 2199.17, "duration": 1.06}, {"text": "So we run a check\non the Thai data.", "start": 2200.23, "duration": 2.15}, {"text": "And, again, if we're making a\nmistake these are not equal,", "start": 2202.38, "duration": 3.24}, {"text": "and that's a big guide to us.", "start": 2205.62, "duration": 1.95}, {"text": "I should save this\nfor later, but I", "start": 2207.57, "duration": 1.62}, {"text": "will tell you that no\ntop US survey does this.", "start": 2209.19, "duration": 4.38}, {"text": "Not the Survey of Consumer\nFinances, not the PSID.", "start": 2213.57, "duration": 5.16}, {"text": "They did not gather\nvariables and check", "start": 2218.73, "duration": 2.4}, {"text": "what they gathered against\nthese comprehensive statements", "start": 2221.13, "duration": 3.84}, {"text": "of integrated accounts.", "start": 2224.97, "duration": 2.19}, {"text": "And Bitcoin is automatic.", "start": 2227.16, "duration": 1.65}, {"text": "Because you either have it in\nyour account and you spend it,", "start": 2228.81, "duration": 3.03}, {"text": "or you don't spend it and\nit's still in the account.", "start": 2231.84, "duration": 3.37}, {"text": "So that's kind of the\nunspoken advantage of Bitcoin.", "start": 2235.21, "duration": 3.17}, {"text": "There is something that people\ntalk about a lot on Bitcoin", "start": 2238.38, "duration": 5.22}, {"text": "and that is consensus.", "start": 2243.6, "duration": 4.13}, {"text": "So I keep giving this\nexample in Bitcoin", "start": 2247.73, "duration": 1.97}, {"text": "that Bob wants to\ntransfer a coin to Alice.", "start": 2249.7, "duration": 4.62}, {"text": "We have both Alice's\naccounts and Bob's account.", "start": 2254.32, "duration": 3.51}, {"text": "And what Bob gives up\nis what Alice gets.", "start": 2257.83, "duration": 4.05}, {"text": "So the accounts have to be\nconsistent with each other", "start": 2261.88, "duration": 3.96}, {"text": "across the households.", "start": 2265.84, "duration": 1.77}, {"text": "And that is true in Bitcoin.", "start": 2267.61, "duration": 2.01}, {"text": "But it is not--\nwell, and again, this", "start": 2269.62, "duration": 2.46}, {"text": "is a bit technical for\nnow, but the whole thing", "start": 2272.08, "duration": 2.4}, {"text": "about the mining and the\nvalidation of the transactions", "start": 2274.48, "duration": 3.27}, {"text": "in Bitcoin is to precisely\nbe assured that Bob is not", "start": 2277.75, "duration": 5.55}, {"text": "double-spending the coin.", "start": 2283.3, "duration": 1.44}, {"text": "You can't spend it twice.", "start": 2284.74, "duration": 2.243}, {"text": "And they kind of\nfigured out a way", "start": 2286.983, "duration": 1.417}, {"text": "to do that-- a very\ningenious way to do that.", "start": 2288.4, "duration": 2.83}, {"text": "But anyway, the concept of\nreconciliation and validation", "start": 2291.23, "duration": 4.22}, {"text": "could be taken to accounting\nin the Thai villages,", "start": 2295.45, "duration": 3.84}, {"text": "in the sense that we\nreally did try to measure", "start": 2299.29, "duration": 2.97}, {"text": "all the transactions.", "start": 2302.26, "duration": 1.33}, {"text": "And when a household says that\nit bought something with cash,", "start": 2303.59, "duration": 3.14}, {"text": "if the person they bought\nit from is in the village,", "start": 2306.73, "duration": 2.43}, {"text": "then that person\nshould get the cash,", "start": 2309.16, "duration": 2.1}, {"text": "while the person in\nquestion is giving it up.", "start": 2311.26, "duration": 2.22}, {"text": "So it should appear twice, both\nin the accounts of the person", "start": 2313.48, "duration": 3.87}, {"text": "buying and the accounts\nof the person selling.", "start": 2317.35, "duration": 2.37}, {"text": "So with one of your\nformer classmates,", "start": 2319.72, "duration": 3.06}, {"text": "who was a student in this class\nabout two years ago, Chad,", "start": 2322.78, "duration": 3.99}, {"text": "we set out--", "start": 2326.77, "duration": 1.29}, {"text": "he wanted to help\non these projects.", "start": 2328.06, "duration": 2.7}, {"text": "He was an RA.", "start": 2330.76, "duration": 1.56}, {"text": "And I'm not pushing that\nhard, but if any of you", "start": 2332.32, "duration": 2.973}, {"text": "are interested, let me know.", "start": 2335.293, "duration": 1.167}, {"text": "There's a lot of\ninteresting stuff to do.", "start": 2336.46, "duration": 2.37}, {"text": "So Chad was very interested,\nso here's what he did.", "start": 2338.83, "duration": 2.83}, {"text": "He looked literally to\nsee whether what shows up", "start": 2341.66, "duration": 3.08}, {"text": "in one person's account\nis also showing up", "start": 2344.74, "duration": 2.46}, {"text": "in the other one or not.", "start": 2347.2, "duration": 2.04}, {"text": "And these are some\nof the details", "start": 2349.24, "duration": 2.07}, {"text": "of going through and doing\nthat as an algorithm.", "start": 2351.31, "duration": 2.88}, {"text": "He created these accounts.", "start": 2354.19, "duration": 1.29}, {"text": "He checks to see\nif it's reported.", "start": 2355.48, "duration": 2.22}, {"text": "If not, et cetera, et cetera.", "start": 2357.7, "duration": 2.28}, {"text": "Now, right in the\nmiddle of this slide", "start": 2359.98, "duration": 2.22}, {"text": "it jumps from\nThailand and the thing", "start": 2362.2, "duration": 2.7}, {"text": "that Chad was doing to a very\ndifferent application, which is", "start": 2364.9, "duration": 3.96}, {"text": "the stock market in Australia.", "start": 2368.86, "duration": 2.29}, {"text": "So the stock market\nin Australia is", "start": 2371.15, "duration": 2.9}, {"text": "about to run on distributed\nledgers the way Bitcoin does.", "start": 2374.05, "duration": 4.11}, {"text": "Not using Bitcoin,\nbut using the ledgers.", "start": 2378.16, "duration": 3.27}, {"text": "And so the idea is when\nsomeone owns the stock,", "start": 2381.43, "duration": 2.82}, {"text": "and there's a\nbuyer and a seller,", "start": 2384.25, "duration": 1.77}, {"text": "the traditional legacy system\nis that they enter into a deal.", "start": 2386.02, "duration": 4.71}, {"text": "And then only after a\nday, or maybe three,", "start": 2390.73, "duration": 4.17}, {"text": "the process of reconciliation\nkicks in and then they settle.", "start": 2394.9, "duration": 5.52}, {"text": "So the trade of the stocks is\nseparate from the settlement", "start": 2400.42, "duration": 3.12}, {"text": "of the stocks.", "start": 2403.54, "duration": 0.96}, {"text": "And believe it or not, there's\noften huge discrepancies.", "start": 2404.5, "duration": 4.91}, {"text": "For one thing,\nprices have moved.", "start": 2409.41, "duration": 2.16}, {"text": "So a household could\nclaim, I didn't buy it.", "start": 2411.57, "duration": 3.15}, {"text": "And in the New York\nfinancial markets,", "start": 2414.72, "duration": 2.49}, {"text": "there was an attempt to provide\nthis in the repo market.", "start": 2417.21, "duration": 3.09}, {"text": "Because every day in\nthe US repo market", "start": 2420.3, "duration": 2.73}, {"text": "with treasuries and so\non, they spend two hours", "start": 2423.03, "duration": 2.43}, {"text": "at the end of each day\nafter the end of trading", "start": 2425.46, "duration": 3.36}, {"text": "trying to reconcile accounts.", "start": 2428.82, "duration": 1.65}, {"text": "State Street Bank here in Boston\nis a big third-party broker", "start": 2430.47, "duration": 5.22}, {"text": "for people that hold\naccounts, and it does", "start": 2435.69, "duration": 2.73}, {"text": "this kind of reconciliation.", "start": 2438.42, "duration": 1.53}, {"text": "It's quite costly and\nquite time-consuming.", "start": 2439.95, "duration": 3.72}, {"text": "But if you're entering these\ntrades onto the ledgers,", "start": 2443.67, "duration": 4.17}, {"text": "there's instantaneous\nreconciliation.", "start": 2447.84, "duration": 2.82}, {"text": "And so they could settle\nright away if they wanted to.", "start": 2450.66, "duration": 2.74}, {"text": "The decision to not pay for\nit is a credit decision.", "start": 2453.4, "duration": 3.23}, {"text": "They're not forced to\nsettle immediately.", "start": 2456.63, "duration": 2.67}, {"text": "But in principle,\ntrade and settlement", "start": 2459.3, "duration": 2.4}, {"text": "can happen at exactly\nthe same time all", "start": 2461.7, "duration": 3.15}, {"text": "through the distributed ledgers.", "start": 2464.85, "duration": 2.55}, {"text": "And the one in Australia\nis able to process", "start": 2467.4, "duration": 3.3}, {"text": "115 million daily trades.", "start": 2470.7, "duration": 3.03}, {"text": "It's 6,300 trades per second\ncontinuously over five hours.", "start": 2473.73, "duration": 4.92}, {"text": "That well exceeds the\nvolume in Bitcoin.", "start": 2478.65, "duration": 3.72}, {"text": "Bitcoin is not capable of doing\nthis because of the mining.", "start": 2482.37, "duration": 3.33}, {"text": "But these other\nledger technologies", "start": 2485.7, "duration": 2.25}, {"text": "are a lot faster\nand a lot cheaper.", "start": 2487.95, "duration": 2.8}, {"text": "So let's come back\nto the village", "start": 2490.75, "duration": 2.84}, {"text": "and think about how an\nindividual household is", "start": 2493.59, "duration": 2.37}, {"text": "managing its currency.", "start": 2495.96, "duration": 2.19}, {"text": "Let me back up for a second.", "start": 2498.15, "duration": 1.89}, {"text": "That seemed like an\nabrupt transition.", "start": 2500.04, "duration": 2.67}, {"text": "I featured in lecture one that\nwe will say a lot about Bitcoin", "start": 2502.71, "duration": 3.99}, {"text": "and cryptocurrencies,\nand it's spread out", "start": 2506.7, "duration": 3.78}, {"text": "throughout the lectures.", "start": 2510.48, "duration": 1.11}, {"text": "So Bitcoin, blockchain,\nand distributed ledgers--", "start": 2511.59, "duration": 3.06}, {"text": "it's the first time\nit really came up.", "start": 2514.65, "duration": 2.37}, {"text": "And I started with a ledger.", "start": 2517.02, "duration": 1.62}, {"text": "So when we're talking\nabout financial accounts,", "start": 2518.64, "duration": 2.28}, {"text": "that's why I started\nto bring in Bitcoin.", "start": 2520.92, "duration": 2.07}, {"text": "And we will revisit\nBitcoin in other lectures", "start": 2522.99, "duration": 3.69}, {"text": "when we talk about monetary\neconomics and so on.", "start": 2526.68, "duration": 3.21}, {"text": "OK.", "start": 2529.89, "duration": 0.51}, {"text": "So now, back to paper\ncurrency management.", "start": 2530.4, "duration": 4.11}, {"text": "I say paper currency just\nto constantly remind myself", "start": 2534.51, "duration": 3.15}, {"text": "that cash is kind of ambiguous.", "start": 2537.66, "duration": 1.83}, {"text": "When you talk about cash in the\nUS you mean, currency, yeah.", "start": 2539.49, "duration": 3.06}, {"text": "But also, demand deposits\nand other variables,", "start": 2542.55, "duration": 2.97}, {"text": "like maybe even debit cards.", "start": 2545.52, "duration": 1.98}, {"text": "But in Thailand,\nit's paper currency.", "start": 2547.5, "duration": 2.31}, {"text": "They love it.", "start": 2549.81, "duration": 0.75}, {"text": "That's what they use.", "start": 2550.56, "duration": 1.47}, {"text": "We're on that momentarily.", "start": 2552.03, "duration": 1.87}, {"text": "So I'm going to, in notation,\ndescribe a Miller/Orr model--", "start": 2553.9, "duration": 4.4}, {"text": "the management of\ncash for firms,", "start": 2558.3, "duration": 3.06}, {"text": "for business firms,\nwhich do not have", "start": 2561.36, "duration": 2.13}, {"text": "regular nor predictable flows.", "start": 2563.49, "duration": 2.01}, {"text": "And the result solving the\nmodel is rather intuitive.", "start": 2565.5, "duration": 4.59}, {"text": "There's going to be bounds.", "start": 2570.09, "duration": 1.86}, {"text": "So cash holdings\ncan drift around.", "start": 2571.95, "duration": 2.85}, {"text": "But when they go\nabove an upper bound,", "start": 2574.8, "duration": 2.43}, {"text": "it's time to make an adjustment\nand deposit the paper", "start": 2577.23, "duration": 3.78}, {"text": "in the bank, or lend it out.", "start": 2581.01, "duration": 1.59}, {"text": "And likewise, when it\ngoes below a lower bound,", "start": 2582.6, "duration": 2.915}, {"text": "they're going to\nhave to withdraw", "start": 2585.515, "duration": 1.375}, {"text": "money or call in a loan.", "start": 2586.89, "duration": 2.01}, {"text": "So sometimes that lower\nbound is zero, obviously.", "start": 2588.9, "duration": 3.3}, {"text": "You can't run out of\nstock of something.", "start": 2592.2, "duration": 2.16}, {"text": "It can't go negative.", "start": 2594.36, "duration": 1.35}, {"text": "So that's going to be what\nthe solution looks like.", "start": 2595.71, "duration": 3.43}, {"text": "So let me introduce a little\nbit of notation, e being", "start": 2599.14, "duration": 4.16}, {"text": "expenditure outflows of paper\ncurrency, which looks like c.", "start": 2603.3, "duration": 5.55}, {"text": "But it's basically\nmore than consumption.", "start": 2608.85, "duration": 2.67}, {"text": "It's all expenses out, and\nthen y being stuff coming in.", "start": 2611.52, "duration": 5.34}, {"text": "OK.", "start": 2616.86, "duration": 0.87}, {"text": "So expenditure is outflows\nminus inflows, which", "start": 2617.73, "duration": 3.69}, {"text": "could be positive or negative.", "start": 2621.42, "duration": 1.51}, {"text": "So we postulate a\nstochastic process", "start": 2622.93, "duration": 3.35}, {"text": "for the cash flows,\nexpenditure flows, and estimate", "start": 2626.28, "duration": 4.71}, {"text": "in the Thai data.", "start": 2630.99, "duration": 1.38}, {"text": "We postulate that\nmostly things are", "start": 2632.37, "duration": 2.67}, {"text": "pretty smooth and predictable.", "start": 2635.04, "duration": 1.95}, {"text": "Delta refers to the length\nof the time interval.", "start": 2636.99, "duration": 2.55}, {"text": "And it's easier conceptually to\nthink of delta as equal to 1.", "start": 2639.54, "duration": 4.83}, {"text": "So with roughly\nprobability 1/2, they're", "start": 2644.37, "duration": 3.54}, {"text": "going to have an\nexpenditure of c,", "start": 2647.91, "duration": 2.97}, {"text": "but it could be a higher\norder of magnitude, sigma.", "start": 2650.88, "duration": 3.78}, {"text": "Or with residual\nprobability roughly 1/2,", "start": 2654.66, "duration": 4.29}, {"text": "it's c minus sigma.", "start": 2658.95, "duration": 1.75}, {"text": "So these are the ups and\ndowns of expenditures--", "start": 2660.7, "duration": 3.59}, {"text": "probabilistic basis.", "start": 2664.29, "duration": 1.68}, {"text": "How big or small depends\non how big sigma is.", "start": 2665.97, "duration": 2.88}, {"text": "And I keep saying\nroughly probability 1/2,", "start": 2668.85, "duration": 2.64}, {"text": "because there are these\nzapper things that are very", "start": 2671.49, "duration": 4.44}, {"text": "large inflows and outflows.", "start": 2675.93, "duration": 2.7}, {"text": "So expenditure is an outflow.", "start": 2678.63, "duration": 2.44}, {"text": "So positive zapper, Zp, is a\nvery large expenditure that", "start": 2681.07, "duration": 6.89}, {"text": "happens with probability kappa.", "start": 2687.96, "duration": 2.85}, {"text": "Again, say delta equal 1.", "start": 2690.81, "duration": 2.22}, {"text": "So this could be like\n2% or 3% of the time,", "start": 2693.03, "duration": 3.36}, {"text": "there is an outflow\nwhich is more", "start": 2696.39, "duration": 1.92}, {"text": "than two standard\ndeviations away", "start": 2698.31, "duration": 2.28}, {"text": "from the mean positive outflow.", "start": 2700.59, "duration": 2.97}, {"text": "Or it could be an inflow.", "start": 2703.56, "duration": 1.78}, {"text": "So these are rare\nrevenues coming", "start": 2705.34, "duration": 2.54}, {"text": "in with different kappas\nand different Zs, which", "start": 2707.88, "duration": 4.33}, {"text": "will be estimated in the data.", "start": 2712.21, "duration": 1.74}, {"text": "And these shocks-- you\ntake the probability", "start": 2713.95, "duration": 3.72}, {"text": "of the positive\noutflow, the probability", "start": 2717.67, "duration": 2.61}, {"text": "of the negative outflow add\nthem together, delta, say,", "start": 2720.28, "duration": 4.59}, {"text": "is still equal to 1.", "start": 2724.87, "duration": 1.59}, {"text": "So with probability\n1, something happens.", "start": 2726.46, "duration": 3.69}, {"text": "With probability 1 minus\nthe sum of those kappas,", "start": 2730.15, "duration": 3.84}, {"text": "you're in this middle branch.", "start": 2733.99, "duration": 1.89}, {"text": "And that's the 1/2\nadjusted up or down.", "start": 2735.88, "duration": 4.08}, {"text": "As always, I'm assuming\nyou will interrupt me", "start": 2739.96, "duration": 2.31}, {"text": "if things are not clear.", "start": 2742.27, "duration": 1.66}, {"text": "OK.", "start": 2743.93, "duration": 0.74}, {"text": "So let's think about\nhow much cash they", "start": 2744.67, "duration": 2.55}, {"text": "have in house that's paper.", "start": 2747.22, "duration": 4.57}, {"text": "So they have a certain amount\nof cash in a moment in time.", "start": 2751.79, "duration": 4.26}, {"text": "They have an expenditure\noutflow, which", "start": 2756.05, "duration": 2.61}, {"text": "could be positive or negative.", "start": 2758.66, "duration": 2.4}, {"text": "And they're at t,\nand we're going", "start": 2761.06, "duration": 3.54}, {"text": "to try to do the accounting\nfor how much money they would", "start": 2764.6, "duration": 2.94}, {"text": "have at t plus delta,\nwhere again, delta", "start": 2767.54, "duration": 2.4}, {"text": "could be equal to 1.", "start": 2769.94, "duration": 1.98}, {"text": "Money at t less outflows,\nand then they could adjust.", "start": 2771.92, "duration": 4.82}, {"text": "They could either withdraw\nmoney or deposit it.", "start": 2776.74, "duration": 3.36}, {"text": "So these two things the\nw and d is endogenous.", "start": 2780.1, "duration": 3.69}, {"text": "And the model is going to\nhave to solve for w and d,", "start": 2783.79, "duration": 3.36}, {"text": "when to do it, as I was\nsaying, and how much to do.", "start": 2787.15, "duration": 3.21}, {"text": "And that will result in\nthis endogenously determined", "start": 2790.36, "duration": 4.08}, {"text": "statement of cash flow.", "start": 2794.44, "duration": 1.77}, {"text": "You can think about this\nlike life cycle planning,", "start": 2796.21, "duration": 2.34}, {"text": "except now it's\nnot over 50 years.", "start": 2798.55, "duration": 3.18}, {"text": "It may be a matter of a\ncouple of weeks or 30 days.", "start": 2801.73, "duration": 4.26}, {"text": "In the data, it's 30\ndays because that's", "start": 2805.99, "duration": 2.25}, {"text": "when we get the data.", "start": 2808.24, "duration": 1.96}, {"text": "They're trying to\nminimize costs.", "start": 2810.2, "duration": 1.53}, {"text": "Now, there's two costs.", "start": 2811.73, "duration": 1.71}, {"text": "One is kind of obvious,\nreally, for economists,", "start": 2813.44, "duration": 3.7}, {"text": "which is if you're holding cash\nand it doesn't earn interest,", "start": 2817.14, "duration": 3.53}, {"text": "you've lost the interest\nyou could have earned if you", "start": 2820.67, "duration": 2.31}, {"text": "had deposited it in the bank.", "start": 2822.98, "duration": 1.83}, {"text": "So that's a real cost\nto the household.", "start": 2824.81, "duration": 2.04}, {"text": "That's the opportunity\ncost to the household.", "start": 2826.85, "duration": 2.59}, {"text": "We're going to let the\ninterest rate in the bank", "start": 2829.44, "duration": 2.0}, {"text": "be capital R. If you\nhold too much cash,", "start": 2831.44, "duration": 2.88}, {"text": "you're giving up a lot\nof foregone interest.", "start": 2834.32, "duration": 2.82}, {"text": "That's a cost.", "start": 2837.14, "duration": 1.85}, {"text": "There's also a physical\nadjustment cost", "start": 2838.99, "duration": 2.57}, {"text": "to get to the bank, which you\ncan think of as the hassle,", "start": 2841.56, "duration": 3.48}, {"text": "or in these villages you've\ngot to get in your truck", "start": 2845.04, "duration": 2.31}, {"text": "and drive to the village,\nto the town, et cetera.", "start": 2847.35, "duration": 3.18}, {"text": "So that should have\nhad the notation here,", "start": 2850.53, "duration": 2.4}, {"text": "but it's a little b.", "start": 2852.93, "duration": 1.44}, {"text": "You'll see a little\nb momentarily.", "start": 2854.37, "duration": 2.77}, {"text": "So the next slide-- don't panic.", "start": 2857.14, "duration": 2.03}, {"text": "I'm going to walk you\nthrough the value function.", "start": 2859.17, "duration": 4.2}, {"text": "It looks pretty\nintense at first.", "start": 2863.37, "duration": 2.43}, {"text": "They're sitting here with a\ncertain amount of money, m,", "start": 2865.8, "duration": 4.62}, {"text": "and then deciding\nwhether they want", "start": 2870.42, "duration": 2.16}, {"text": "to stay put and carry m into\nthe second period or adjust.", "start": 2872.58, "duration": 6.06}, {"text": "Now, if m is already\nnegative, they're in trouble.", "start": 2878.64, "duration": 4.77}, {"text": "Can't go negative, so\nthey have to adjust.", "start": 2883.41, "duration": 2.91}, {"text": "And you get this cost,\nb, which is gone.", "start": 2886.32, "duration": 3.09}, {"text": "This cost function\nis not utility.", "start": 2889.41, "duration": 2.04}, {"text": "It's not net profits.", "start": 2891.45, "duration": 1.62}, {"text": "It's a cost, and they're\ntrying to minimize the cost.", "start": 2893.07, "duration": 4.36}, {"text": "So this is enters positively\nbecause it's a cost.", "start": 2897.43, "duration": 3.47}, {"text": "They've gone to all the\ncosts, to getting to the bank,", "start": 2900.9, "duration": 2.28}, {"text": "they get to make an\nadjustment, which", "start": 2903.18, "duration": 1.71}, {"text": "means they can choose a\nnew m prime going out.", "start": 2904.89, "duration": 2.89}, {"text": "And so they'll try to minimize\nthe value from that point", "start": 2907.78, "duration": 5.18}, {"text": "on by that choice of m prime--", "start": 2912.96, "duration": 3.06}, {"text": "minimize the cost\nfrom that point on.", "start": 2916.02, "duration": 2.94}, {"text": "Here, m is positive,\nbut they still", "start": 2918.96, "duration": 2.31}, {"text": "get to choose whether\nto adjust or not.", "start": 2921.27, "duration": 2.5}, {"text": "And if they don't\nadjust, they keep it.", "start": 2923.77, "duration": 3.02}, {"text": "They suffer the\nopportunity cost,", "start": 2926.79, "duration": 1.92}, {"text": "the lost interest in the bank.", "start": 2928.71, "duration": 1.65}, {"text": "And then they'll have their\nvalue function tomorrow,", "start": 2930.36, "duration": 2.62}, {"text": "which is discounted by little r.", "start": 2932.98, "duration": 2.75}, {"text": "That's like a discount rate.", "start": 2935.73, "duration": 2.19}, {"text": "And things next\nperiod are stochastic.", "start": 2937.92, "duration": 3.24}, {"text": "So you take expectations\nover the future e values", "start": 2941.16, "duration": 3.96}, {"text": "following that\nstochastic process.", "start": 2945.12, "duration": 1.87}, {"text": "So this is v of m minus\ne is all expectation,", "start": 2946.99, "duration": 3.71}, {"text": "is all written down here in\nterms of these branches, which", "start": 2950.7, "duration": 3.18}, {"text": "is positive zappers, negative\nzappers, ups and downs, roughly", "start": 2953.88, "duration": 5.52}, {"text": "probability 1/2, et cetera.", "start": 2959.4, "duration": 1.86}, {"text": "So this is the expected\ncost in the future", "start": 2961.26, "duration": 3.9}, {"text": "if you don't make a\nmonetary adjustment today.", "start": 2965.16, "duration": 4.12}, {"text": "So this is the\nsecond or third time", "start": 2969.28, "duration": 2.66}, {"text": "you've seen these\nvalue functions.", "start": 2971.94, "duration": 1.5}, {"text": "I introduced them at the\nend of the medieval village", "start": 2973.44, "duration": 2.58}, {"text": "dynamic programming problem.", "start": 2976.02, "duration": 1.71}, {"text": "We then used that last class\nto talk about implications", "start": 2977.73, "duration": 4.2}, {"text": "of risk sharing for production,\nwith the planner's value", "start": 2981.93, "duration": 3.085}, {"text": "function.", "start": 2985.015, "duration": 0.5}, {"text": "This is the third time.", "start": 2985.515, "duration": 1.405}, {"text": "This is the value function for a\nhousehold minimizing its costs.", "start": 2986.92, "duration": 5.06}, {"text": "More fun-- let me show\nyou some pictures.", "start": 2991.98, "duration": 1.99}, {"text": "So these are real live people.", "start": 2993.97, "duration": 3.08}, {"text": "This is the cash flow\nof this house-- the cash", "start": 2997.05, "duration": 2.58}, {"text": "holdings of this household.", "start": 2999.63, "duration": 2.13}, {"text": "Up and up and up\nand up she goes.", "start": 3001.76, "duration": 3.0}, {"text": "This one also had a\ntrend, and then boom,", "start": 3004.76, "duration": 2.7}, {"text": "down, and then to zero,\nand then back up again.", "start": 3007.46, "duration": 4.59}, {"text": "You can't see it very well.", "start": 3012.05, "duration": 1.71}, {"text": "I'm sorry.", "start": 3013.76, "duration": 0.57}, {"text": "The pictures are too small.", "start": 3014.33, "duration": 1.89}, {"text": "But what's plotted over here are\nnet cash inflows or outflows,", "start": 3016.22, "duration": 5.82}, {"text": "along with, say, a deposit\nwhen you have a net inflow,", "start": 3022.04, "duration": 4.56}, {"text": "or a withdrawal when\nyou have a net outflow.", "start": 3026.6, "duration": 3.73}, {"text": "So there's three lines\nhere, and sometimes", "start": 3030.33, "duration": 2.93}, {"text": "things correspond the\nway I was just implying.", "start": 3033.26, "duration": 2.61}, {"text": "You're short, so you\nwithdraw, et cetera.", "start": 3035.87, "duration": 3.57}, {"text": "But when-- you\ncan't see much here,", "start": 3039.44, "duration": 1.77}, {"text": "but when you integrate\nit out and look", "start": 3041.21, "duration": 2.34}, {"text": "at the consequence\nfor the levels", "start": 3043.55, "duration": 2.13}, {"text": "using this flow equation,\nthen you can see what", "start": 3045.68, "duration": 4.44}, {"text": "their stocks are.", "start": 3050.12, "duration": 1.822}, {"text": "It looks like a lot of money.", "start": 3051.942, "duration": 1.208}, {"text": "It is going to be unbelievable--", "start": 3053.15, "duration": 3.0}, {"text": "unbelievable in\nthe sense of three", "start": 3056.15, "duration": 1.86}, {"text": "years research running to try\nto understand this pattern.", "start": 3058.01, "duration": 3.64}, {"text": "So how much money does\na typical household", "start": 3061.65, "duration": 2.3}, {"text": "have-- currency, paper,\nsquirreled away in the house?", "start": 3063.95, "duration": 3.42}, {"text": "In the rural villages\nthat we were looking at,", "start": 3067.37, "duration": 3.81}, {"text": "roughly 32 months\nworth of consumption.", "start": 3071.18, "duration": 3.87}, {"text": "What's in your wallet?", "start": 3075.05, "duration": 1.62}, {"text": "You're going to say credit card.", "start": 3076.67, "duration": 2.13}, {"text": "These guys-- it's\nnot in a wallet.", "start": 3078.8, "duration": 1.74}, {"text": "It's in the house or\nhidden in the backyard.", "start": 3080.54, "duration": 3.27}, {"text": "Almost three years worth\nof expenditures in cash--", "start": 3083.81, "duration": 3.99}, {"text": "cash equivalent consumption.", "start": 3087.8, "duration": 1.56}, {"text": "We measure the consumption\nfor each household,", "start": 3089.36, "duration": 3.09}, {"text": "and we see how much\ncash they have,", "start": 3092.45, "duration": 1.71}, {"text": "which we measured in the data.", "start": 3094.16, "duration": 1.8}, {"text": "32 months-- it's unbelievable.", "start": 3095.96, "duration": 2.67}, {"text": "And we also get\ndeposits and withdrawals", "start": 3098.63, "duration": 2.88}, {"text": "measured in the data.", "start": 3101.51, "duration": 1.26}, {"text": "That's a lot of\ndetail to absorb.", "start": 3102.77, "duration": 1.68}, {"text": "Let me show you what's\ngoing on in the model.", "start": 3104.45, "duration": 3.78}, {"text": "We estimate the cash flow.", "start": 3108.23, "duration": 2.43}, {"text": "We recover all the\nparameters that we need,", "start": 3110.66, "duration": 3.87}, {"text": "take a stand on the\ninterest rate in the bank,", "start": 3114.53, "duration": 3.39}, {"text": "and then look at how small\nor big the cost would be.", "start": 3117.92, "duration": 3.98}, {"text": "b is varying down here.", "start": 3121.9, "duration": 3.16}, {"text": "And the consequences for\ncurrency, especially but also", "start": 3125.06, "duration": 4.92}, {"text": "withdrawals and deposits.", "start": 3129.98, "duration": 2.38}, {"text": "So taking the reality to be\nthe calibrated expenditure", "start": 3132.36, "duration": 3.74}, {"text": "flows we see in the data, along\nwith the few other reasonable", "start": 3136.1, "duration": 3.74}, {"text": "assumptions, I assure\nyou we can look", "start": 3139.84, "duration": 2.82}, {"text": "at how much cash they\nshould be holding relative", "start": 3142.66, "duration": 2.49}, {"text": "to consumption.", "start": 3145.15, "duration": 0.99}, {"text": "That's this blue line.", "start": 3146.14, "duration": 1.77}, {"text": "And we can barely\nget it up to three.", "start": 3147.91, "duration": 4.78}, {"text": "The number in the data is 32.", "start": 3152.69, "duration": 2.46}, {"text": "I mean, you could imagine\nincreasing those costs", "start": 3155.15, "duration": 3.69}, {"text": "and decreasing the interest.", "start": 3158.84, "duration": 1.85}, {"text": "And this is like asymptoting\nout to something flat.", "start": 3160.69, "duration": 5.11}, {"text": "So you end up with\nsomething ridiculous.", "start": 3165.8, "duration": 2.79}, {"text": "The model isn't working.", "start": 3168.59, "duration": 1.56}, {"text": "You don't go to the bank\nand forego two years", "start": 3170.15, "duration": 3.125}, {"text": "worth of consumption\nwhile you're", "start": 3173.275, "duration": 1.375}, {"text": "doing your banking transection.", "start": 3174.65, "duration": 2.46}, {"text": "It's just not a\nreasonable value.", "start": 3177.11, "duration": 2.43}, {"text": "The sign makes sense.", "start": 3179.54, "duration": 2.97}, {"text": "The higher the cost,\nb, of going to the bank", "start": 3182.51, "duration": 3.63}, {"text": "to either withdraw or deposit,\nthe less you're going to do it.", "start": 3186.14, "duration": 3.61}, {"text": "So when you do it, the\ntransactions are bigger.", "start": 3189.75, "duration": 3.08}, {"text": "And meanwhile, you're\nholding more cash.", "start": 3192.83, "duration": 2.685}, {"text": "If b goes to infinity,\nthen it's all in cash.", "start": 3195.515, "duration": 4.185}, {"text": "Forget the bank.", "start": 3199.7, "duration": 1.308}, {"text": "And when you go\nrarely, then you have", "start": 3201.008, "duration": 1.542}, {"text": "to make up a big difference.", "start": 3202.55, "duration": 1.96}, {"text": "And this is the\nfrequency, which again,", "start": 3204.51, "duration": 1.94}, {"text": "as b goes up, the frequency\nof going to the bank", "start": 3206.45, "duration": 3.09}, {"text": "is going down.", "start": 3209.54, "duration": 1.47}, {"text": "Question-- so because we\ndid that life cycle planner,", "start": 3211.01, "duration": 5.7}, {"text": "we wanted to evaluate as a\nrandomized controlled trial", "start": 3216.71, "duration": 4.05}, {"text": "how well or poorly it was\nworking, and in the process,", "start": 3220.76, "duration": 3.97}, {"text": "we gathered monthly data\nfor the urban household.", "start": 3224.73, "duration": 3.44}, {"text": "So we're not in\nvillages anymore.", "start": 3228.17, "duration": 2.16}, {"text": "We're in towns or even\ncity neighborhoods.", "start": 3230.33, "duration": 3.45}, {"text": "In each of the four\nprovinces, we basically", "start": 3233.78, "duration": 3.33}, {"text": "replicated all the\nexisting surveys.", "start": 3237.11, "duration": 2.8}, {"text": "So the same questions\nare being asked.", "start": 3239.91, "duration": 2.52}, {"text": "And this is kind of\nburied here, but if you", "start": 3242.43, "duration": 2.0}, {"text": "look at the normalized cash\nin terms of consumption", "start": 3244.43, "duration": 3.99}, {"text": "for the urban sample,\nand look over here,", "start": 3248.42, "duration": 4.38}, {"text": "we got a number of 3.87--", "start": 3252.8, "duration": 3.48}, {"text": "much closer to 3.", "start": 3256.28, "duration": 1.14}, {"text": "Nothing like the 37.", "start": 3257.42, "duration": 1.65}, {"text": "Well, actually, I should\nbe over here at the median.", "start": 3259.07, "duration": 2.82}, {"text": "So it's 1.94.", "start": 3261.89, "duration": 1.74}, {"text": "But when we do some\nadjustments in the data,", "start": 3263.63, "duration": 2.13}, {"text": "I'm happy to tell\nyou about them.", "start": 3265.76, "duration": 3.44}, {"text": "That's within\nreach of the model.", "start": 3269.2, "duration": 2.46}, {"text": "We calibrate the model again\nusing the cash statistics--", "start": 3271.66, "duration": 5.7}, {"text": "the zapping, big\nshock, small shock,", "start": 3277.36, "duration": 2.88}, {"text": "how often they happen,\net cetera et cetera,", "start": 3280.24, "duration": 2.4}, {"text": "and get a model prediction.", "start": 3282.64, "duration": 1.71}, {"text": "And the implied\nvalue, m, depending", "start": 3284.35, "duration": 3.96}, {"text": "on whether you use the\nmean or the median,", "start": 3288.31, "duration": 2.43}, {"text": "is something like 2,\nwhich is close to what", "start": 3290.74, "duration": 4.59}, {"text": "we're getting in the data.", "start": 3295.33, "duration": 1.66}, {"text": "So now we're in\nkind of business,", "start": 3296.99, "duration": 1.88}, {"text": "in the sense that a reasonable\neconomic model is actually", "start": 3298.87, "duration": 3.3}, {"text": "predicting pretty well how\nmuch cash they're holding.", "start": 3302.17, "duration": 3.06}, {"text": "Whereas, in the rural\ndata it was a disaster.", "start": 3305.23, "duration": 2.61}, {"text": "We didn't get close.", "start": 3307.84, "duration": 1.11}, {"text": "So now we switch into how\ncan we understand the error", "start": 3308.95, "duration": 6.09}, {"text": "that the households are making\nwith their cash management?", "start": 3315.04, "duration": 3.54}, {"text": "And the guess is--", "start": 3318.58, "duration": 1.35}, {"text": "several guesses.", "start": 3319.93, "duration": 1.26}, {"text": "Some turned out to be\ncorrect and some not.", "start": 3321.19, "duration": 2.94}, {"text": "So why would cash\nholdings be so much lower", "start": 3324.13, "duration": 2.82}, {"text": "in the urban area relative\nto the rural area?", "start": 3326.95, "duration": 2.85}, {"text": "Is it because households\nin the urban survey deposit", "start": 3329.8, "duration": 2.88}, {"text": "more often in larger amounts?", "start": 3332.68, "duration": 2.31}, {"text": "Or is it because they withdraw\nin the urban areas less", "start": 3334.99, "duration": 3.42}, {"text": "and withdraw smaller amounts?", "start": 3338.41, "duration": 2.38}, {"text": "So for deposits, it turns out\nhouseholds in the rural area", "start": 3340.79, "duration": 4.1}, {"text": "deposit more and not less, and\nthey deposit larger amounts.", "start": 3344.89, "duration": 4.13}, {"text": "So this is exactly\nthe opposite of what", "start": 3349.02, "duration": 2.14}, {"text": "we would have predicted because\nthe cash is going into the bank", "start": 3351.16, "duration": 3.12}, {"text": "or into the local money market.", "start": 3354.28, "duration": 2.08}, {"text": "However, for\nwithdrawals, it works", "start": 3356.36, "duration": 2.12}, {"text": "the way we would\nhave conjectured,", "start": 3358.48, "duration": 2.13}, {"text": "that when urban households\nput money in the bank", "start": 3360.61, "duration": 2.25}, {"text": "they don't withdraw\nit very often,", "start": 3362.86, "duration": 1.86}, {"text": "and they withdraw a lot less.", "start": 3364.72, "duration": 2.04}, {"text": "It almost looks like\nthey're putting their proxy", "start": 3366.76, "duration": 3.18}, {"text": "for their salary into the bank.", "start": 3369.94, "duration": 1.77}, {"text": "And any other money which they\nhave, from business and so on,", "start": 3371.71, "duration": 3.45}, {"text": "goes into the bank\nand stays there.", "start": 3375.16, "duration": 2.04}, {"text": "They just withdraw what\nthey need for consumption,", "start": 3377.2, "duration": 2.76}, {"text": "taking a, quote unquote,\nsalary equivalent out", "start": 3379.96, "duration": 3.03}, {"text": "and leaving the rest in.", "start": 3382.99, "duration": 1.45}, {"text": "So this is why their\nmoney value's a lot lower.", "start": 3384.44, "duration": 3.98}, {"text": "There's still something to fix,\nwhich just like in life cycle", "start": 3388.42, "duration": 3.87}, {"text": "planner, we could create from\nthe research cash flow app", "start": 3392.29, "duration": 4.5}, {"text": "and put it on the phone and tell\nhouseholds how to manage it.", "start": 3396.79, "duration": 3.64}, {"text": "And, in fact, the\nquestion is, why are they", "start": 3400.43, "duration": 2.6}, {"text": "having cash at all?", "start": 3403.03, "duration": 1.38}, {"text": "Why don't they just put\nit on their cell phone?", "start": 3404.41, "duration": 2.28}, {"text": "And that brings us to--", "start": 3406.69, "duration": 2.44}, {"text": "oh.", "start": 3409.13, "duration": 0.5}, {"text": "And the costs of\nmismanagement of currency", "start": 3409.63, "duration": 3.93}, {"text": "are very high--\nsomething like 9 and 1/2%", "start": 3413.56, "duration": 2.97}, {"text": "of monthly consumption.", "start": 3416.53, "duration": 1.98}, {"text": "That's huge in economics.", "start": 3418.51, "duration": 2.25}, {"text": "Say, exaggerate a bit--", "start": 3420.76, "duration": 1.53}, {"text": "10, or call it 5 if you want.", "start": 3422.29, "duration": 2.34}, {"text": "5% of monthly consumption\ncould be saved or used", "start": 3424.63, "duration": 3.54}, {"text": "for consumption if they just\nmanaged their currency better.", "start": 3428.17, "duration": 3.43}, {"text": "So one way to put this--", "start": 3431.6, "duration": 1.7}, {"text": "enormous cost of\nmismanagement of petty cash.", "start": 3433.3, "duration": 4.5}, {"text": "Businesses get cash\nadvisory services.", "start": 3437.8, "duration": 2.85}, {"text": "They pay for it.", "start": 3440.65, "duration": 1.69}, {"text": "Why should these poor\nhouseholds not have access", "start": 3442.34, "duration": 2.33}, {"text": "to better management tools?", "start": 3444.67, "duration": 2.28}, {"text": "OK.", "start": 3446.95, "duration": 0.54}, {"text": "Sorry.", "start": 3447.49, "duration": 0.9}, {"text": "That's my view.", "start": 3448.39, "duration": 1.29}, {"text": "OK.", "start": 3449.68, "duration": 1.23}, {"text": "Go to Sweden.", "start": 3450.91, "duration": 1.54}, {"text": "How much paper currency\nare they using?", "start": 3452.45, "duration": 2.3}, {"text": "Close to nothing.", "start": 3454.75, "duration": 1.14}, {"text": "They're gone-- it's gone.", "start": 3455.89, "duration": 1.47}, {"text": "This is the amount of currency\nrelative to GDP ever-declining.", "start": 3457.36, "duration": 5.73}, {"text": "This is the absolute\nlevel of cash,", "start": 3463.09, "duration": 3.36}, {"text": "going down in an absolute\nnot only relative basis.", "start": 3466.45, "duration": 3.73}, {"text": "So I got this and this\nslide from the governor", "start": 3470.18, "duration": 2.9}, {"text": "of the Riksbank in Sweden.", "start": 3473.08, "duration": 3.15}, {"text": "So I don't know whether you\nwill appreciate the humor here.", "start": 3476.23, "duration": 2.59}, {"text": "But this is a\npicture of a stone.", "start": 3478.82, "duration": 2.12}, {"text": "So economists and others\nhave written books", "start": 3480.94, "duration": 2.88}, {"text": "about the first coins,\nthe first use of cash,", "start": 3483.82, "duration": 3.9}, {"text": "and there were claims on\nstones that were buried", "start": 3487.72, "duration": 2.37}, {"text": "at the bottom of the lake.", "start": 3490.09, "duration": 1.35}, {"text": "So now in Sweden, they're\ntransferring the stone around", "start": 3491.44, "duration": 3.18}, {"text": "on their cell phone.", "start": 3494.62, "duration": 0.93}, {"text": "Well, not really.", "start": 3495.55, "duration": 1.35}, {"text": "It's Swish, basically.", "start": 3496.9, "duration": 2.04}, {"text": "They have a bank account,\nand for no money at all", "start": 3498.94, "duration": 3.69}, {"text": "households can transfer cash\nto each other, buy things,", "start": 3502.63, "duration": 4.18}, {"text": "and so on.", "start": 3506.81, "duration": 0.99}, {"text": "And it's replaced\nthe paper currency.", "start": 3507.8, "duration": 1.94}, {"text": "It's actually a bit of a\nconcern for them, which", "start": 3509.74, "duration": 2.55}, {"text": "is why they're thinking\nif there's no paper", "start": 3512.29, "duration": 2.61}, {"text": "currency other than\nreserves, there's", "start": 3514.9, "duration": 2.4}, {"text": "no role for the central bank.", "start": 3517.3, "duration": 2.79}, {"text": "So they feel they should\nbe providing a payment", "start": 3520.09, "duration": 3.93}, {"text": "service as a backup.", "start": 3524.02, "duration": 1.26}, {"text": "So they're going to create,\nalmost surely, a central bank", "start": 3525.28, "duration": 3.33}, {"text": "digital currency.", "start": 3528.61, "duration": 1.3}, {"text": "So households will\nhave digital accounts", "start": 3529.91, "duration": 2.33}, {"text": "in the central bank, which is\nwhat South Africa is doing.", "start": 3532.24, "duration": 3.57}, {"text": "China has a different\nversion of it and so on.", "start": 3535.81, "duration": 3.0}, {"text": "This happened in the Bahamas.", "start": 3538.81, "duration": 2.25}, {"text": "They created something\ncalled the Sand Dollar.", "start": 3541.06, "duration": 2.52}, {"text": "The virus is\naccelerating this problem", "start": 3543.58, "duration": 2.19}, {"text": "because people need\ngovernment aid,", "start": 3545.77, "duration": 2.28}, {"text": "and they can't get the aid--", "start": 3548.05, "duration": 1.68}, {"text": "truck the paper\ncurrency over there.", "start": 3549.73, "duration": 2.01}, {"text": "When this disastrous Hurricane\nDorian destroyed an island", "start": 3551.74, "duration": 3.54}, {"text": "in the Bahamas, they couldn't\nget emergency assistance.", "start": 3555.28, "duration": 3.31}, {"text": "So these are things that are\nhappening all over the world", "start": 3558.59, "duration": 2.48}, {"text": "right now.", "start": 3561.07, "duration": 1.05}, {"text": "This last slide is Kenya.", "start": 3562.12, "duration": 2.49}, {"text": "And I mentioned they have\ntwo kinds of currency.", "start": 3564.61, "duration": 2.88}, {"text": "One is Kenyan shillings--\nused to be a British colony.", "start": 3567.49, "duration": 3.26}, {"text": "And the other is\ne-credits at Safaricom,", "start": 3570.75, "duration": 3.6}, {"text": "which is a cell phone provider.", "start": 3574.35, "duration": 1.98}, {"text": "So what you do is you\ntake your shillings,", "start": 3576.33, "duration": 2.55}, {"text": "you go to this Safaricom agent.", "start": 3578.88, "duration": 2.76}, {"text": "You give him your\nFiat money, and you", "start": 3581.64, "duration": 3.39}, {"text": "get credited cell\naccounts called M-Pesa.", "start": 3585.03, "duration": 3.66}, {"text": "And then you can use\nthat to give to your mom", "start": 3588.69, "duration": 2.49}, {"text": "back in the village, who\ngoes to the agent there", "start": 3591.18, "duration": 3.36}, {"text": "and transfers it back\nout into shillings,", "start": 3594.54, "duration": 2.4}, {"text": "or you can buy stuff.", "start": 3596.94, "duration": 2.02}, {"text": "So here you see the use\nof the paper currency,", "start": 3598.96, "duration": 3.57}, {"text": "but also this e-currency,\nwhich is created by Safaricom.", "start": 3602.53, "duration": 4.31}, {"text": "And it has reached\nalmost everybody.", "start": 3606.84, "duration": 2.46}, {"text": "Some economies try to do this.", "start": 3609.3, "duration": 1.53}, {"text": "We kind of tried in Thailand.", "start": 3610.83, "duration": 1.5}, {"text": "I have not yet succeeded.", "start": 3612.33, "duration": 2.01}, {"text": "In Kenya, even the\nlowest income quartile--", "start": 3614.34, "duration": 3.42}, {"text": "we need to update this graph.", "start": 3617.76, "duration": 2.13}, {"text": "Tavneet Suri did this.", "start": 3619.89, "duration": 2.01}, {"text": "Roughly, 85% of the\nlow-income population,", "start": 3621.9, "duration": 4.35}, {"text": "and a similar, higher number\nfor those with no bank accounts,", "start": 3626.25, "duration": 3.48}, {"text": "are using Safaricom.", "start": 3629.73, "duration": 2.13}, {"text": "With no bank accounts--\nin other words,", "start": 3631.86, "duration": 1.75}, {"text": "you don't need the traditional\nlegacy infrastructure.", "start": 3633.61, "duration": 3.41}, {"text": "And this is, again, the allure,\nthe so-called disintermediation", "start": 3637.02, "duration": 4.62}, {"text": "that the fintechs are\nbringing to the world.", "start": 3641.64, "duration": 2.7}, {"text": "Of course, the commercial\nbankers don't like it much.", "start": 3644.34, "duration": 2.97}, {"text": "We talked about risk-sharing.", "start": 3647.31, "duration": 1.59}, {"text": "And Tavneet and her\nco-author, Billy Jack,", "start": 3648.9, "duration": 4.8}, {"text": "looked at how much consumption\nis being smooth in Kenya,", "start": 3653.7, "duration": 5.01}, {"text": "comparing households\nwho have not yet", "start": 3658.71, "duration": 2.13}, {"text": "gotten early on the M-Pesa\nexpansion versus those", "start": 3660.84, "duration": 3.6}, {"text": "that did.", "start": 3664.44, "duration": 0.99}, {"text": "And there's a lot more\nsmoother consumption,", "start": 3665.43, "duration": 4.21}, {"text": "which you see these\ncommon themes.", "start": 3669.64, "duration": 1.43}, {"text": "We did risk-sharing.", "start": 3671.07, "duration": 1.26}, {"text": "We did gift giving\nin Thai villages.", "start": 3672.33, "duration": 2.58}, {"text": "Now people are giving gifts\nand transfers through M-Pesa.", "start": 3674.91, "duration": 5.46}, {"text": "And so it has an impact.", "start": 3680.37, "duration": 2.356}, {"text": "Well, what's the big deal?", "start": 3682.726, "duration": 1.374}, {"text": "It's a big deal for Kenya.", "start": 3684.1, "duration": 2.81}, {"text": "Sweden already has\nthis infrastructure.", "start": 3686.91, "duration": 1.92}, {"text": "It's not a big deal.", "start": 3688.83, "duration": 1.97}, {"text": "But it makes a big deal\nfor low-income countries.", "start": 3690.8, "duration": 2.79}, {"text": "There are some\nqualifications, though.", "start": 3693.59, "duration": 2.85}, {"text": "First of all, it's not\non a distributed ledger.", "start": 3696.44, "duration": 2.65}, {"text": "So you have to trust Safaricom\nto keep the accounts properly,", "start": 3699.09, "duration": 4.22}, {"text": "and they have the cash.", "start": 3703.31, "duration": 1.72}, {"text": "So they're supposed to put\nit in a commercial bank.", "start": 3705.03, "duration": 2.66}, {"text": "You trust them to do that.", "start": 3707.69, "duration": 2.32}, {"text": "So you have to rely on a\nthird-party vendor in Kenya.", "start": 3710.01, "duration": 3.56}, {"text": "Not only that, the\nmoney's in the bank,", "start": 3713.57, "duration": 1.98}, {"text": "and Kenya is subject to runs.", "start": 3715.55, "duration": 1.5}, {"text": "So how safe is that?", "start": 3717.05, "duration": 1.948}, {"text": "You may think you're going\nto get the money back,", "start": 3718.998, "duration": 2.042}, {"text": "but will you really?", "start": 3721.04, "duration": 1.74}, {"text": "And in other economies, they\ndon't have that kind of trust,", "start": 3722.78, "duration": 3.09}, {"text": "so it doesn't take off.", "start": 3725.87, "duration": 2.5}, {"text": "The other thing is those\nagents, these guys,", "start": 3728.37, "duration": 4.7}, {"text": "they run out of stuff.", "start": 3733.07, "duration": 1.88}, {"text": "So you go and take\nyour shillings", "start": 3734.95, "duration": 1.92}, {"text": "and say I want M-Pesa.", "start": 3736.87, "duration": 1.71}, {"text": "And they can't create it.", "start": 3738.58, "duration": 2.58}, {"text": "There's no net creation.", "start": 3741.16, "duration": 1.62}, {"text": "It has to be a\none-to-one transfer.", "start": 3742.78, "duration": 1.56}, {"text": "They have to have it in\ntheir accounts already.", "start": 3744.34, "duration": 2.17}, {"text": "And if don't have\nit in the account,", "start": 3746.51, "duration": 1.67}, {"text": "they've got to say, well,\nwait, or come back tomorrow.", "start": 3748.18, "duration": 2.43}, {"text": "Likewise, and perhaps\nmore obviously", "start": 3750.61, "duration": 2.22}, {"text": "for the currency withdrawal,\nsay here's my cell account.", "start": 3752.83, "duration": 4.05}, {"text": "I want to cash it out.", "start": 3756.88, "duration": 1.11}, {"text": "Oh, I don't have that\ncash in my drawer.", "start": 3757.99, "duration": 2.175}, {"text": "What Tavneet discovered is\nthese agents are kind of linked", "start": 3760.165, "duration": 3.735}, {"text": "to each other in an\ninformal money market,", "start": 3763.9, "duration": 2.52}, {"text": "giving gifts to each\nother, actually,", "start": 3766.42, "duration": 1.86}, {"text": "and borrowing and\nlending in order", "start": 3768.28, "duration": 1.59}, {"text": "to smooth the fluctuation,\nfrom smoothing at the household", "start": 3769.87, "duration": 2.85}, {"text": "level, to smoothing at\nthe wholesale level,", "start": 3772.72, "duration": 2.25}, {"text": "and similar models would apply.", "start": 3774.97, "duration": 3.57}, {"text": "So this brings us to\nthe theme of building", "start": 3778.54, "duration": 2.22}, {"text": "financial infrastructure.", "start": 3780.76, "duration": 2.17}, {"text": "How can we not just\nget currency on ledgers", "start": 3782.93, "duration": 2.72}, {"text": "and transfer it\naround in a cheap way?", "start": 3785.65, "duration": 2.43}, {"text": "How can we build in the trust?", "start": 3788.08, "duration": 1.62}, {"text": "And how can we deal\nwith this shortage", "start": 3789.7, "duration": 2.76}, {"text": "problem among over-the-counter\nvendors and agents and so on?", "start": 3792.46, "duration": 3.51}, {"text": "And next lecture,\nstarting next time,", "start": 3795.97, "duration": 2.04}, {"text": "we're going to do mechanism\ndesign and private information,", "start": 3798.01, "duration": 3.04}, {"text": "and I'll tell you\nhow to design--", "start": 3801.05, "duration": 1.49}, {"text": "at some point-- how\nto design this system.", "start": 3802.54, "duration": 2.99}, {"text": "All right.", "start": 3805.53, "duration": 0.69}, {"text": "Went over by an\nextra minute today.", "start": 3806.22, "duration": 2.61}, {"text": "Questions?", "start": 3808.83, "duration": 2.16}, {"text": "All right.", "start": 3810.99, "duration": 1.72}, {"text": "So otherwise, I'll see you\nnext Thursday or in my office", "start": 3812.71, "duration": 3.45}, {"text": "momentarily.", "start": 3816.16, "duration": 2.15}]
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+[{"text": "ADAM MARTIN: All right, so\ntoday, I'm trying something", "start": 16.71, "duration": 4.86}, {"text": "different this semester.", "start": 21.57, "duration": 1.86}, {"text": "I wanted to tell you\nguys about one way", "start": 23.43, "duration": 3.87}, {"text": "that you can discover\nthings in biology.", "start": 27.3, "duration": 3.6}, {"text": "And this is going to fall in the\ngenetics cluster of lectures.", "start": 30.9, "duration": 6.48}, {"text": "I want to show you how you\ncan go from being interested", "start": 37.38, "duration": 4.2}, {"text": "in some property of an\norganism, or even its behavior--", "start": 41.58, "duration": 6.0}, {"text": "how would you go from\nthere to identifying", "start": 47.58, "duration": 2.52}, {"text": "genes and mechanisms that\nare responsible for that type", "start": 50.1, "duration": 4.05}, {"text": "of behavior or appearance?", "start": 54.15, "duration": 2.8}, {"text": "OK, so today, we're going to\ngo from some type of phenotype,", "start": 56.95, "duration": 5.33}, {"text": "or process that you're\ninterested in, such as maybe", "start": 62.28, "duration": 4.23}, {"text": "the appearance of an organism.", "start": 66.51, "duration": 2.73}, {"text": "But we're even going\nto go more abstract", "start": 69.24, "duration": 2.26}, {"text": "than that because\nat the end, I'm", "start": 71.5, "duration": 1.61}, {"text": "going to tell you if you're\ninterested in behavior,", "start": 73.11, "duration": 3.63}, {"text": "you can try to figure out\nthe genes and mechanisms that", "start": 76.74, "duration": 2.97}, {"text": "are involved in determining\nthe behavior of an organism.", "start": 79.71, "duration": 5.16}, {"text": "So the question is, how\ndo you go from something", "start": 84.87, "duration": 3.54}, {"text": "you're interested in learning\nabout an organism to actually", "start": 88.41, "duration": 3.18}, {"text": "identifying genes and mechanisms\nthat are important for that?", "start": 91.59, "duration": 5.67}, {"text": "And on my title slide\nhere, I have three fruit", "start": 101.48, "duration": 3.96}, {"text": "fly mutant phenotypes\nthat you can see,", "start": 105.44, "duration": 3.93}, {"text": "and each of these\nmutants defined", "start": 109.37, "duration": 3.96}, {"text": "genes that were subsequently\nfound to be present--", "start": 113.33, "duration": 5.46}, {"text": "or homologous genes\nwere present in humans", "start": 118.79, "duration": 3.48}, {"text": "and were shown to play important\nroles in human biology.", "start": 122.27, "duration": 5.58}, {"text": "So later on in the\nlecture, hall kind", "start": 127.85, "duration": 2.28}, {"text": "explain what each of\nthese phenotypes is.", "start": 130.13, "duration": 3.48}, {"text": "But first, I want\nto just highlight", "start": 133.61, "duration": 2.43}, {"text": "the importance of\nmodel organisms", "start": 136.04, "duration": 2.55}, {"text": "and their use in biology.", "start": 138.59, "duration": 2.79}, {"text": "You've been seeing them already.", "start": 141.38, "duration": 2.61}, {"text": "I've talked a bit\nabout flies, we", "start": 143.99, "duration": 1.59}, {"text": "talked about\nMendel's pea plants.", "start": 145.58, "duration": 2.97}, {"text": "I just now have a compendium\nof model organisms", "start": 148.55, "duration": 2.91}, {"text": "that I'm going to throw\nup to tell you about.", "start": 151.46, "duration": 2.64}, {"text": "So we've talked about bacteria\nand the importance of bacteria", "start": 154.1, "duration": 4.41}, {"text": "in elucidating the flow\nof information from DNA", "start": 158.51, "duration": 3.42}, {"text": "to RNA to protein.", "start": 161.93, "duration": 2.7}, {"text": "Bacteria we're also extremely\nimportant for elucidating", "start": 164.63, "duration": 4.44}, {"text": "the initial mechanisms\nof gene regulation.", "start": 169.07, "duration": 5.16}, {"text": "I mentioned yeast a little\nbit in the last lecture when", "start": 174.23, "duration": 3.24}, {"text": "I mentioned tetrad analysis,\nbut we'll talk about yeast a lot", "start": 177.47, "duration": 4.5}, {"text": "more later, when\nwe start talking", "start": 181.97, "duration": 1.74}, {"text": "about the regulation of cell\ndivision and the cell cycle,", "start": 183.71, "duration": 4.26}, {"text": "because yeast played a\npivotal role in identifying", "start": 187.97, "duration": 4.38}, {"text": "the gene that's critical for\nthis decision of a cell whether", "start": 192.35, "duration": 3.84}, {"text": "or not to divide.", "start": 196.19, "duration": 3.21}, {"text": "Also, one terrific\nmodel organism in plants", "start": 199.4, "duration": 3.63}, {"text": "is a Arabidopsis Thaliana.", "start": 203.03, "duration": 2.49}, {"text": "And Arabidopsis has also\nplayed an important role", "start": 205.52, "duration": 2.61}, {"text": "in elucidating mechanisms\nof development, but also,", "start": 208.13, "duration": 3.48}, {"text": "in making advances in\nscientific research that", "start": 211.61, "duration": 4.56}, {"text": "relate to agriculture, such as\ndisease resistance and pathogen", "start": 216.17, "duration": 5.88}, {"text": "interactions.", "start": 222.05, "duration": 1.11}, {"text": "So the two heroes\nof today's lecture", "start": 225.8, "duration": 3.03}, {"text": "will be the roundworm,\nCaenorhabditis elegans,", "start": 228.83, "duration": 4.77}, {"text": "and the fruit fly,\nDrosophila melanogaster.", "start": 233.6, "duration": 3.33}, {"text": "But before getting into\nstudy is in those organisms,", "start": 236.93, "duration": 3.87}, {"text": "I wanted to highlight a couple\nimportant vertebrate-model", "start": 240.8, "duration": 3.3}, {"text": "organisms--", "start": 244.1, "duration": 1.05}, {"text": "the zebrafish and the mouse.", "start": 245.15, "duration": 3.27}, {"text": "And so you can see the\nmouse is our lab mascot,", "start": 248.42, "duration": 3.72}, {"text": "but it's also an\nimportant genetic model.", "start": 252.14, "duration": 2.52}, {"text": "In particular, there\nare many models", "start": 254.66, "duration": 2.16}, {"text": "in mice that mimic cancer.", "start": 256.82, "duration": 3.37}, {"text": "And so these have been\nuseful for elucidating", "start": 260.19, "duration": 2.24}, {"text": "mechanisms of cancer.", "start": 262.43, "duration": 3.25}, {"text": "So it's really\nunethical for us to do", "start": 265.68, "duration": 3.5}, {"text": "a lot of different types\nof experiments on humans,", "start": 269.18, "duration": 3.09}, {"text": "but I will mention that\nthere are human cell", "start": 272.27, "duration": 3.06}, {"text": "lines, such as the\nHeLa cell line,", "start": 275.33, "duration": 2.73}, {"text": "and these also play an important\nrole in biology research.", "start": 278.06, "duration": 3.96}, {"text": "But these cell lines are\ntaken out of context.", "start": 282.02, "duration": 2.94}, {"text": "They're not functioning in the\ncontext of an entire organism.", "start": 284.96, "duration": 4.99}, {"text": "So human cell lines\nare important,", "start": 289.95, "duration": 3.11}, {"text": "but you have to\nunderstand that they're", "start": 293.06, "duration": 3.69}, {"text": "sort of an in-vitro\nsystem, that they're out", "start": 296.75, "duration": 2.52}, {"text": "of the context of a\nfunctioning organism.", "start": 299.27, "duration": 4.29}, {"text": "OK, so why is it that we\nresearch these model organisms?", "start": 303.56, "duration": 4.6}, {"text": "So there are some\npractical reasons.", "start": 308.16, "duration": 3.24}, {"text": "Most of them are fairly\nsmall, and they're", "start": 311.4, "duration": 1.85}, {"text": "easy to house large\nnumbers of them in a lab.", "start": 313.25, "duration": 3.51}, {"text": "They're often cheap to house\nin the lab and work with.", "start": 316.76, "duration": 5.55}, {"text": "Also, they develop fast.", "start": 322.31, "duration": 3.36}, {"text": "And especially when\nwe consider genetics,", "start": 325.67, "duration": 2.88}, {"text": "the rate-limiting step\nin genetics research", "start": 328.55, "duration": 2.79}, {"text": "is the time it takes\nfrom the conception", "start": 331.34, "duration": 3.27}, {"text": "of an organism to the time\nthat that organism can", "start": 334.61, "duration": 2.76}, {"text": "reproduce sexually.", "start": 337.37, "duration": 2.43}, {"text": "So these model organisms--", "start": 339.8, "duration": 2.07}, {"text": "most of them reproduce\nvery quickly,", "start": 341.87, "duration": 2.8}, {"text": "and so that accelerates\nthe pace of research.", "start": 344.67, "duration": 4.49}, {"text": "But maybe most\nimportantly is the fact", "start": 349.16, "duration": 3.06}, {"text": "that we are related to each\nof these model organisms", "start": 352.22, "duration": 3.72}, {"text": "through evolution because we all\narose from a common ancestor.", "start": 355.94, "duration": 5.61}, {"text": "And just to highlight this\nexample, using the fruit fly,", "start": 361.55, "duration": 3.63}, {"text": "the fruit fly has 17,000 genes\nwhen compared to our 20,000", "start": 365.18, "duration": 5.89}, {"text": "genes, so we have roughly the\nsame order of magnitude number", "start": 371.07, "duration": 5.45}, {"text": "of genes as the fruit fly.", "start": 376.52, "duration": 2.35}, {"text": "And so let's think\nabout important genes.", "start": 378.87, "duration": 4.01}, {"text": "Let's think about\njust genes that are", "start": 382.88, "duration": 2.1}, {"text": "associated with human diseases.", "start": 384.98, "duration": 2.34}, {"text": "If we just consider\nhuman-disease causing genes,", "start": 387.32, "duration": 3.54}, {"text": "75% of the human-disease\ncausing genes", "start": 390.86, "duration": 4.2}, {"text": "have a homologous\ngene in the fruit fly.", "start": 395.06, "duration": 3.48}, {"text": "So we're similar to these model\norganisms, such as the fruit", "start": 398.54, "duration": 3.48}, {"text": "fly, in particular, genes that\nare important for understanding", "start": 402.02, "duration": 4.68}, {"text": "human disease.", "start": 406.7, "duration": 0.615}, {"text": "So I came across this quote\nwhen preparing for the lecture,", "start": 410.46, "duration": 3.59}, {"text": "and I liked it.", "start": 414.05, "duration": 0.81}, {"text": "It's from John Rinn, who\nis a contemporary of ours.", "start": 414.86, "duration": 3.69}, {"text": "And John Rinn said,\n\"Genetic approaches", "start": 418.55, "duration": 2.61}, {"text": "are as fundamental to biology\nas math is to physics.\"", "start": 421.16, "duration": 4.11}, {"text": "And I think this is an apt quote\nbecause both genetics and math", "start": 425.27, "duration": 4.68}, {"text": "themselves are\nscientific disciplines,", "start": 429.95, "duration": 2.97}, {"text": "but they can be leveraged to\nlearn things about biology", "start": 432.92, "duration": 4.86}, {"text": "and physics respectively.", "start": 437.78, "duration": 3.93}, {"text": "So genetics really plays a\nfundamental role in biology", "start": 441.71, "duration": 4.11}, {"text": "and the discovery of new\nbiological mechanisms.", "start": 445.82, "duration": 4.7}, {"text": "OK, so now, I want to just\nbriefly take you through,", "start": 450.52, "duration": 4.66}, {"text": "how is it that we discover\nthings using genetics?", "start": 455.18, "duration": 3.96}, {"text": "And I'm going to take you\nthrough a type of approach", "start": 459.14, "duration": 2.64}, {"text": "that's called a \"forward\ngenetic screen.\"", "start": 461.78, "duration": 2.1}, {"text": "And I'll get to the\norchestra in just a minute,", "start": 468.91, "duration": 2.89}, {"text": "but I briefly just\nwant to define what", "start": 471.8, "duration": 2.19}, {"text": "a forward genetic screen is.", "start": 473.99, "duration": 2.64}, {"text": "So a forward genetic\nscreen is type of approach", "start": 476.63, "duration": 3.87}, {"text": "you would do if you\ndon't know the genes that", "start": 480.5, "duration": 2.73}, {"text": "are involved in a\nspecific process,", "start": 483.23, "duration": 1.95}, {"text": "but you want to identify them.", "start": 485.18, "duration": 3.16}, {"text": "So in a forward\ngenetic screen, you", "start": 488.34, "duration": 2.18}, {"text": "don't know the genes\nand mechanisms involved.", "start": 490.52, "duration": 3.36}, {"text": "So you don't know\nwhat these genes are.", "start": 497.415, "duration": 1.625}, {"text": "You might not even have a\ngenome sequence of the organism.", "start": 499.04, "duration": 3.07}, {"text": "You don't need a genome\nsequence in order", "start": 502.11, "duration": 1.79}, {"text": "to do a forward genetic\nscreen because you don't know", "start": 503.9, "duration": 3.9}, {"text": "the genes, but you're interested\nin a particular aspect", "start": 507.8, "duration": 4.17}, {"text": "of development, or of\norganismal function,", "start": 511.97, "duration": 4.949}, {"text": "and you want to\nidentify the genes that", "start": 516.919, "duration": 1.831}, {"text": "are important for that.", "start": 518.75, "duration": 1.77}, {"text": "So when starting a forward\ngenetic screen, you have to,", "start": 520.52, "duration": 3.539}, {"text": "then, infer what a possible\nphenotype would look", "start": 524.059, "duration": 3.541}, {"text": "like if you broke genes that\nwere involved in that process.", "start": 527.6, "duration": 4.59}, {"text": "So the mantra of\ngeneticists is that we", "start": 532.19, "duration": 3.39}, {"text": "are going to break genes\nand then look at the result", "start": 535.58, "duration": 4.44}, {"text": "and see if it gives the\nphenotype we're interested in.", "start": 540.02, "duration": 3.72}, {"text": "So in a forward genetic screen,\nyou're looking for a phenotype", "start": 543.74, "duration": 11.34}, {"text": "that you would expect if you\naffected a certain process,", "start": 555.08, "duration": 7.47}, {"text": "if you disrupt a process.", "start": 562.55, "duration": 7.17}, {"text": "So think about this\norchestra up here.", "start": 569.72, "duration": 4.11}, {"text": "Let's say you are\ninterested in what", "start": 573.83, "duration": 2.04}, {"text": "regulates each of these\nsections in the orchestra.", "start": 575.87, "duration": 5.07}, {"text": "What is the master regulator\nof this orchestra, if you will?", "start": 580.94, "duration": 5.76}, {"text": "And so conceptually, what a\ngenetic screen would involve", "start": 586.7, "duration": 4.59}, {"text": "is taking hundreds,\nmaybe thousands,", "start": 591.29, "duration": 2.37}, {"text": "of orchestras like this\none, and just shooting", "start": 593.66, "duration": 3.39}, {"text": "an individual in this\norchestra, and removing them", "start": 597.05, "duration": 2.61}, {"text": "from the orchestra.", "start": 599.66, "duration": 2.16}, {"text": "And so let's say you remove--", "start": 601.82, "duration": 5.68}, {"text": "let's say you remove\nthis guy right here,", "start": 607.5, "duration": 2.21}, {"text": "then maybe nothing really\nhappens because they are, like,", "start": 609.71, "duration": 3.44}, {"text": "30 or 40 other\nviolinists, and that's", "start": 613.15, "duration": 2.98}, {"text": "not the major control circuit.", "start": 616.13, "duration": 3.12}, {"text": "So then you would infer\nthat this gene is not", "start": 619.25, "duration": 3.48}, {"text": "important for the\nregulation of the orchestra.", "start": 622.73, "duration": 2.7}, {"text": "But let's say you\ntook out Bernstein,", "start": 625.43, "duration": 2.91}, {"text": "and then you listen\nto the orchestra", "start": 628.34, "duration": 3.18}, {"text": "and find that the sections\nare uncoordinated,", "start": 631.52, "duration": 4.75}, {"text": "the bassists start doing\ncrazy things on their own.", "start": 636.27, "duration": 3.57}, {"text": "So then the logic of\nDrosophila genetics,", "start": 639.84, "duration": 4.07}, {"text": "you would then name\nthat gene uncoordinated", "start": 643.91, "duration": 2.64}, {"text": "and infer that that gene\nhas some important role", "start": 646.55, "duration": 3.21}, {"text": "in coordinating the different\nsections of the orchestra.", "start": 649.76, "duration": 6.27}, {"text": "So the goal in genetics is\nto identify a mutation that", "start": 656.03, "duration": 4.98}, {"text": "alters a gene function\nthat gives you a phenotype", "start": 661.01, "duration": 3.15}, {"text": "that you're interested in.", "start": 664.16, "duration": 1.96}, {"text": "And rather than taking\na gun and shooting", "start": 666.12, "duration": 2.12}, {"text": "members of the\norchestra, in genetics,", "start": 668.24, "duration": 3.33}, {"text": "you try to identify mutations.", "start": 671.57, "duration": 1.77}, {"text": "So you try to induce mutations.", "start": 673.34, "duration": 4.02}, {"text": "So we're looking for mutations.", "start": 677.36, "duration": 1.71}, {"text": "And these mutations could\nbe spontaneous mutations,", "start": 682.22, "duration": 4.5}, {"text": "meaning you didn't do\nanything to induce it,", "start": 686.72, "duration": 4.14}, {"text": "but they just appear as a\nvariant in the population.", "start": 690.86, "duration": 4.99}, {"text": "And so we've talked\nabout Thomas Hunt", "start": 695.85, "duration": 1.67}, {"text": "Morgan and the white\nmutant, and the white gene.", "start": 697.52, "duration": 3.74}, {"text": "So the white mutant was\na spontaneous mutation.", "start": 701.26, "duration": 3.57}, {"text": "Morgan's lab didn't\ndo anything special.", "start": 704.83, "duration": 2.07}, {"text": "They just looked at lots of\nflies, and over the decades,", "start": 706.9, "duration": 2.7}, {"text": "they identified this\none special male", "start": 709.6, "duration": 2.16}, {"text": "fly that they could work on.", "start": 711.76, "duration": 3.33}, {"text": "But nowadays, researchers have a\nway to accelerate this process.", "start": 715.09, "duration": 6.31}, {"text": "And so we can induce mutations.", "start": 721.4, "duration": 2.21}, {"text": "In the way we can\ninduce mutations is", "start": 730.12, "duration": 2.18}, {"text": "by using some type of mutagen.", "start": 732.3, "duration": 3.06}, {"text": "So for example, you could have\nsome sort of chemical mutagen", "start": 735.36, "duration": 3.99}, {"text": "that increases the error\nrate in DNA replication,", "start": 739.35, "duration": 5.07}, {"text": "or you could use radiation\nto induce DNA damage,", "start": 744.42, "duration": 4.5}, {"text": "and that essentially\naccelerates the frequency", "start": 748.92, "duration": 2.79}, {"text": "of mutations that occur in\nthe genome of an organism.", "start": 751.71, "duration": 3.57}, {"text": "And so the process of\nmutagenizing an organism", "start": 758.58, "duration": 4.38}, {"text": "isn't specific to genes.", "start": 762.96, "duration": 1.68}, {"text": "You're just inducing\nrandom mutations", "start": 764.64, "duration": 2.16}, {"text": "across the genome\nof the individual.", "start": 766.8, "duration": 5.34}, {"text": "Let's say this piece I'm drawing\nhere is part of a chromosome,", "start": 772.14, "duration": 3.85}, {"text": "and these boxes are genes.", "start": 775.99, "duration": 4.85}, {"text": "You're inducing\nrandom mutations,", "start": 780.84, "duration": 2.79}, {"text": "and maybe one mutation\nhits this gene.", "start": 783.63, "duration": 3.39}, {"text": "So that's a mutation\nthat might affect", "start": 787.02, "duration": 2.64}, {"text": "the function of an organism.", "start": 789.66, "duration": 2.4}, {"text": "You might have other mutations\nthat are outside genes", "start": 792.06, "duration": 4.29}, {"text": "and may have no\neffect, or you could", "start": 796.35, "duration": 3.78}, {"text": "have a different kind\nof mutation which", "start": 800.13, "duration": 2.25}, {"text": "isn't in the coding\nregion of the gene,", "start": 802.38, "duration": 2.01}, {"text": "but maybe affects the regulation\nof this blue gene over here.", "start": 804.39, "duration": 6.21}, {"text": "So this is a random process.", "start": 810.6, "duration": 1.74}, {"text": "If you're feeding an organism\nsome chemical mutagen,", "start": 812.34, "duration": 4.35}, {"text": "you're inducing random\nmutations in different places,", "start": 816.69, "duration": 3.57}, {"text": "and you don't know which are\nthe ones that you want until you", "start": 820.26, "duration": 4.8}, {"text": "look at their phenotypes\nand try to find", "start": 825.06, "duration": 2.005}, {"text": "the needle in the haystack.", "start": 827.065, "duration": 1.125}, {"text": "So let me show\nyou some examples.", "start": 831.6, "duration": 2.48}, {"text": "So let's say we were\ninterested in our body pattern.", "start": 834.08, "duration": 4.36}, {"text": "We all have a body.", "start": 838.44, "duration": 1.56}, {"text": "Our head is in\nour head position,", "start": 840.0, "duration": 1.71}, {"text": "our ass is in our\nass position, we", "start": 841.71, "duration": 2.1}, {"text": "have arms that are\nin a right position,", "start": 843.81, "duration": 1.95}, {"text": "our legs are in\nthe right position.", "start": 845.76, "duration": 2.13}, {"text": "Let's say we're\ninterested in figuring out", "start": 847.89, "duration": 2.34}, {"text": "what genes were responsible\nfor that body pattern.", "start": 850.23, "duration": 3.15}, {"text": "What kind of a mutant\nmight you look for?", "start": 853.38, "duration": 2.16}, {"text": "Anyone?", "start": 859.761, "duration": 0.579}, {"text": "Rachel.", "start": 860.34, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 860.84, "duration": 1.898}, {"text": "ADAM MARTIN: What's that?", "start": 862.738, "duration": 1.042}, {"text": "A mutant with his body\nparts in the wrong place.", "start": 863.78, "duration": 3.27}, {"text": "Maybe you have like a leg where\nyour arm should be coming out,", "start": 867.05, "duration": 4.23}, {"text": "or maybe you have two heads,\nor something like that.", "start": 871.28, "duration": 2.52}, {"text": "So you look for\nsome sort of defect", "start": 873.8, "duration": 2.94}, {"text": "in the pattern formation.", "start": 876.74, "duration": 2.74}, {"text": "And so this would be, obviously,\nunethical to do in humans,", "start": 879.48, "duration": 4.67}, {"text": "but in model organisms,\nwe can actually", "start": 884.15, "duration": 2.97}, {"text": "find these types of mutations.", "start": 887.12, "duration": 2.25}, {"text": "I'm just going to\nhighlight a couple mutants.", "start": 889.37, "duration": 2.28}, {"text": "This one's an obvious one.", "start": 891.65, "duration": 1.26}, {"text": "So this fly has two wings.", "start": 892.91, "duration": 2.85}, {"text": "You can see them folded\nover each other right here.", "start": 895.76, "duration": 3.21}, {"text": "But there's a specific\nclass of mutant", "start": 898.97, "duration": 2.16}, {"text": "that was called \"wingless\"--", "start": 901.13, "duration": 1.68}, {"text": "where the flies have\nfewer than two wings.", "start": 902.81, "duration": 2.79}, {"text": "This particular fly\nhas only one wing.", "start": 905.6, "duration": 3.72}, {"text": "And this wingless\nmutant defined a gene", "start": 909.32, "duration": 3.24}, {"text": "that became known as\nwingless, and it's", "start": 912.56, "duration": 4.2}, {"text": "a gene that has a\nhomologous gene in humans.", "start": 916.76, "duration": 3.79}, {"text": "And this particular gene defines\nan entire signaling pathway,", "start": 920.55, "duration": 4.67}, {"text": "which--", "start": 925.22, "duration": 1.44}, {"text": "whoops, sorry-- which is\nimportant in stem-cell biology", "start": 926.66, "duration": 3.99}, {"text": "and is also over\nactivated in cancer.", "start": 930.65, "duration": 3.36}, {"text": "But obviously, we\ndon't have wings,", "start": 934.01, "duration": 1.83}, {"text": "so this gene didn't get\ndiscovered in humans.", "start": 935.84, "duration": 2.97}, {"text": "It was discovered\nin flies, and then", "start": 938.81, "duration": 2.13}, {"text": "only later on, it\nwas inferred-- or it", "start": 940.94, "duration": 2.52}, {"text": "was discovered that there\nis a related gene in humans.", "start": 943.46, "duration": 3.55}, {"text": "OK, so that's one example.", "start": 947.01, "duration": 3.14}, {"text": "One of the other phenotypes I\nshowed you is called \"notch.\"", "start": 950.15, "duration": 3.81}, {"text": "Normally, a fly wing has\na nice, smooth margin.", "start": 953.96, "duration": 3.42}, {"text": "But notch mutants have wings\nthat have this chunk taken out", "start": 957.38, "duration": 4.5}, {"text": "of them at the end.", "start": 961.88, "duration": 2.46}, {"text": "So again, the gene became known\nas \"notch\" because of this fly", "start": 964.34, "duration": 3.42}, {"text": "phenotype.", "start": 967.76, "duration": 0.65}, {"text": "But again, there's\na human notch,", "start": 968.41, "duration": 2.02}, {"text": "and human notch, again, is\ninvolved in human diseases,", "start": 970.43, "duration": 3.15}, {"text": "such as cancer.", "start": 973.58, "duration": 1.65}, {"text": "OK, so that's two examples.", "start": 975.23, "duration": 2.55}, {"text": "But now, I want to talk to\nyou about how one might find", "start": 977.78, "duration": 3.03}, {"text": "the needle in the haystack.", "start": 980.81, "duration": 1.35}, {"text": "How can you have\na concerted effort", "start": 982.16, "duration": 3.18}, {"text": "to identify genes that have that\nfunction in a given process?", "start": 985.34, "duration": 6.048}, {"text": "I'm going to tell\nyou about work done", "start": 991.388, "duration": 1.542}, {"text": "by Eric Wieschaus and\nChristiane Nusslein-Volhard", "start": 992.93, "duration": 3.6}, {"text": "because they did one of the\nmore famous genetic screens that", "start": 996.53, "duration": 3.0}, {"text": "had been done, and they won the\nNobel Prize for their results", "start": 999.53, "duration": 3.87}, {"text": "in 1995.", "start": 1003.4, "duration": 2.46}, {"text": "So I mean I take you through\nthis classic genetic screen.", "start": 1005.86, "duration": 2.85}, {"text": "In this screen, they're\ngoing to induce mutations.", "start": 1011.6, "duration": 3.35}, {"text": "So I'm going to take\na parental generation.", "start": 1014.95, "duration": 1.83}, {"text": "And this screen was\ndone using fruit flies.", "start": 1016.78, "duration": 3.87}, {"text": "And they took male fruit\nflies and treated the males", "start": 1020.65, "duration": 3.929}, {"text": "with a mutagen to\ninduce mutations", "start": 1024.579, "duration": 3.361}, {"text": "in the gametes these male\nflies that would then be passed", "start": 1027.94, "duration": 4.53}, {"text": "to subsequent generations.", "start": 1032.47, "duration": 3.57}, {"text": "And they mated the\nmutagenized males to females,", "start": 1036.04, "duration": 6.39}, {"text": "and then they went\non to look at--", "start": 1042.43, "duration": 2.22}, {"text": "to isolate individual\nF1 progeny.", "start": 1044.65, "duration": 4.06}, {"text": "So we're going to\nlook at individual F1", "start": 1048.71, "duration": 4.58}, {"text": "progeny in this generation.", "start": 1053.29, "duration": 2.11}, {"text": "So in the F1 progeny\nhave the potential", "start": 1057.95, "duration": 4.04}, {"text": "to get one mutagenized\nchromosome from their father", "start": 1061.99, "duration": 3.87}, {"text": "and will get a normal\nchromosome from the mother.", "start": 1065.86, "duration": 4.77}, {"text": "So I'll just drawn\nthis like this,", "start": 1070.63, "duration": 2.39}, {"text": "where independent mutations are\ngoing to be different colors.", "start": 1073.02, "duration": 4.27}, {"text": "So that has maybe a mutation\non one of its chromosomes.", "start": 1077.29, "duration": 5.58}, {"text": "Another fly, because\nthis is random,", "start": 1082.87, "duration": 2.25}, {"text": "might have a different\nmutation on the same", "start": 1085.12, "duration": 3.72}, {"text": "or a different chromosome.", "start": 1088.84, "duration": 1.23}, {"text": "I'll draw a couple more.", "start": 1092.79, "duration": 1.03}, {"text": "And maybe one of these\nflies doesn't have", "start": 1093.82, "duration": 3.42}, {"text": "a mutation that's been induced.", "start": 1097.24, "duration": 2.4}, {"text": "And then I'll draw just\none independent mutation", "start": 1099.64, "duration": 2.91}, {"text": "right there.", "start": 1102.55, "duration": 1.77}, {"text": "So again, this is random.", "start": 1104.32, "duration": 1.33}, {"text": "So to see random mutations, you\nhave to take individual flies.", "start": 1105.65, "duration": 4.28}, {"text": "Now, are you're going to\nsee a phenotype in this F1", "start": 1109.93, "duration": 2.49}, {"text": "generation?", "start": 1112.42, "duration": 0.69}, {"text": "So Miles-- is it\nthe Malik or Miles?", "start": 1116.41, "duration": 3.73}, {"text": "Sorry.", "start": 1120.14, "duration": 0.5}, {"text": "AUDIENCE: Miles.", "start": 1120.64, "duration": 0.51}, {"text": "ADAM MARTIN: Miles.", "start": 1121.15, "duration": 0.33}, {"text": "Good.", "start": 1121.48, "duration": 0.5}, {"text": "OK.", "start": 1121.98, "duration": 0.585}, {"text": "AUDIENCE: Most likely\nnot because any mutation", "start": 1122.565, "duration": 5.045}, {"text": "[INAUDIBLE] spontaneous\nwould be overshadowed", "start": 1127.61, "duration": 4.532}, {"text": "by the direct gene, the female.", "start": 1132.142, "duration": 4.403}, {"text": "ADAM MARTIN: Exactly.", "start": 1136.545, "duration": 0.875}, {"text": "So what Miles just\nsaid is that--", "start": 1137.42, "duration": 3.42}, {"text": "basically, he said\nthat these mutations", "start": 1140.84, "duration": 2.07}, {"text": "if their loss-of-function\nmutations are going to be", "start": 1142.91, "duration": 2.55}, {"text": "recessive--", "start": 1145.46, "duration": 1.26}, {"text": "because they're going\nto be overshadowed", "start": 1146.72, "duration": 2.22}, {"text": "by a normal functioning gene\non the other chromosome.", "start": 1148.94, "duration": 4.59}, {"text": "So if you're looking for a\nloss-of-function mutation,", "start": 1153.53, "duration": 3.45}, {"text": "that's likely going\nto be recessive,", "start": 1156.98, "duration": 2.4}, {"text": "and you would not see\nit in the F1 generation.", "start": 1159.38, "duration": 3.6}, {"text": "So in order to\nlook for organisms", "start": 1162.98, "duration": 4.44}, {"text": "that have incorrect\nbody patterning,", "start": 1167.42, "duration": 3.18}, {"text": "you need to get\na situation where", "start": 1170.6, "duration": 2.91}, {"text": "each of the mutated chromosomes\nis homozygous recessive.", "start": 1173.51, "duration": 5.25}, {"text": "And to do that, you\nhave to do more crosses.", "start": 1178.76, "duration": 1.845}, {"text": "So what the researchers\ndid was to take", "start": 1184.45, "duration": 2.25}, {"text": "independent individual\norganisms, and cross them all,", "start": 1186.7, "duration": 6.48}, {"text": "again, to non-mutated flies.", "start": 1193.18, "duration": 3.99}, {"text": "And remember, flies\ndon't self-cross.", "start": 1197.17, "duration": 3.66}, {"text": "So they need a male\nand a female that", "start": 1200.83, "duration": 2.25}, {"text": "has the same mutated\nchromosome mating to each other", "start": 1203.08, "duration": 3.51}, {"text": "in order to see a\nrecessive phenotype.", "start": 1206.59, "duration": 3.6}, {"text": "So because you only\nhave an individual fly", "start": 1210.19, "duration": 2.61}, {"text": "for each of these, you need\nto get more than one fly", "start": 1212.8, "duration": 3.21}, {"text": "with the same mutation.", "start": 1216.01, "duration": 2.49}, {"text": "So they mate to a normal fly.", "start": 1218.5, "duration": 6.48}, {"text": "But now, you can get an F2--", "start": 1224.98, "duration": 3.39}, {"text": "multiple F2 males\nand females that", "start": 1228.37, "duration": 7.11}, {"text": "will have the same\nmutated chromosome.", "start": 1235.48, "duration": 4.5}, {"text": "So here, let's draw these.", "start": 1239.98, "duration": 1.56}, {"text": "They're still heterozygous.", "start": 1248.46, "duration": 2.35}, {"text": "At this point.", "start": 1250.81, "duration": 1.39}, {"text": "But at this point, you just\ngenerated multiple organisms,", "start": 1252.2, "duration": 3.22}, {"text": "male and female, that have\nthe same chromosome that", "start": 1255.42, "duration": 4.57}, {"text": "arose from, essentially, the\nsame chromosome and the father,", "start": 1259.99, "duration": 4.982}, {"text": "or the male gamete and\nthe parental generation.", "start": 1264.972, "duration": 5.178}, {"text": "Oh, I did green.", "start": 1270.15, "duration": 1.13}, {"text": "OK.", "start": 1271.28, "duration": 0.5}, {"text": "OK, so now we have males\nand females, both of which", "start": 1278.17, "duration": 5.43}, {"text": "are heterozygous.", "start": 1283.6, "duration": 2.1}, {"text": "And I'm skipping some of\nthe details of this cross.", "start": 1285.7, "duration": 4.79}, {"text": "You'll want to take\nmy word for the fact", "start": 1290.49, "duration": 1.75}, {"text": "that they can keep track of\nwhich chromosome is which.", "start": 1292.24, "duration": 3.68}, {"text": "And I'm not going to tell you\nhow they did that because it's", "start": 1295.92, "duration": 4.27}, {"text": "fly genetics, and it's\nnot terribly important", "start": 1300.19, "duration": 2.742}, {"text": "that you know it.", "start": 1302.932, "duration": 0.708}, {"text": "So now, you have\nmales and females.", "start": 1307.51, "duration": 3.09}, {"text": "And now you can look an F3.", "start": 1310.6, "duration": 2.34}, {"text": "And from each of these lines--", "start": 1312.94, "duration": 3.04}, {"text": "each of these lines, you're\ngoing to cross siblings", "start": 1315.98, "duration": 2.15}, {"text": "to each other.", "start": 1318.13, "duration": 0.6}, {"text": "So you're doing a sibling-cross.", "start": 1322.39, "duration": 1.59}, {"text": "What fraction of the progeny for\neach of these sibling crosses", "start": 1326.62, "duration": 3.63}, {"text": "should be homozygous for\nthe mutant chromosome?", "start": 1330.25, "duration": 2.623}, {"text": "Yes, Steven.", "start": 1336.12, "duration": 0.65}, {"text": "AUDIENCE: One-fourth.", "start": 1336.77, "duration": 1.035}, {"text": "ADAM MARTIN: One-fourth,\nexactly right.", "start": 1337.805, "duration": 1.625}, {"text": "So Steven's exactly right.", "start": 1339.43, "duration": 2.46}, {"text": "A quarter of the progeny\nshould get two copies", "start": 1341.89, "duration": 4.65}, {"text": "of the mutated chromosome.", "start": 1346.54, "duration": 2.07}, {"text": "So 25% should be\nhomozygous recessive.", "start": 1348.61, "duration": 5.46}, {"text": "And so you can screen\nthis F3 progeny", "start": 1358.24, "duration": 3.93}, {"text": "for each of these\nindependent lines,", "start": 1362.17, "duration": 2.16}, {"text": "and look for flies at some\nstage of development that", "start": 1364.33, "duration": 4.02}, {"text": "are defective in patterning.", "start": 1368.35, "duration": 2.872}, {"text": "And so I'll show you how--", "start": 1371.222, "duration": 2.618}, {"text": "where'd my clicker go?", "start": 1373.84, "duration": 1.13}, {"text": "All right, so they're looking\nfor incorrect body pattern.", "start": 1378.18, "duration": 3.687}, {"text": "Yes, your question--\nwhat's your name again?", "start": 1381.867, "duration": 1.833}, {"text": "AUDIENCE: Georgia.", "start": 1383.7, "duration": 0.72}, {"text": "ADAM MARTIN: Georgia, yeah.", "start": 1384.42, "duration": 0.71}, {"text": "AUDIENCE: Would there\nbe some [INAUDIBLE]", "start": 1385.13, "duration": 1.708}, {"text": "in the F2 [INAUDIBLE] normal?", "start": 1386.838, "duration": 4.652}, {"text": "[INAUDIBLE]", "start": 1391.49, "duration": 3.71}, {"text": "ADAM MARTIN: Yes.", "start": 1395.2, "duration": 0.84}, {"text": "So they're able to select for\nthe mutated chromosome, yeah.", "start": 1396.04, "duration": 3.44}, {"text": "And I'm skipping over how\nthey did that because it's", "start": 1399.48, "duration": 2.26}, {"text": "kind of esoteric.", "start": 1401.74, "duration": 1.452}, {"text": "But you're right.", "start": 1403.192, "duration": 0.708}, {"text": "Some would be normal.", "start": 1403.9, "duration": 1.5}, {"text": "But I'm just telling you\nthey're able to figure out", "start": 1405.4, "duration": 2.88}, {"text": "the ones that have\nthe mutant chromosome,", "start": 1408.28, "duration": 2.37}, {"text": "and they made sure to keep\nthose in the next generation.", "start": 1410.65, "duration": 3.39}, {"text": "Good question, Georgia.", "start": 1414.04, "duration": 1.71}, {"text": "All right, so they can\nscreen F3 for a phenotype.", "start": 1415.75, "duration": 5.13}, {"text": "It turns out all\nof the mutations", "start": 1420.88, "duration": 1.78}, {"text": "they're interested\nin are lethal,", "start": 1422.66, "duration": 1.74}, {"text": "so they have to look at the\nlarval stages for ones that", "start": 1424.4, "duration": 3.05}, {"text": "have a defect in patterning.", "start": 1427.45, "duration": 1.92}, {"text": "So this is what a Drosophila\nlarvae looks like.", "start": 1429.37, "duration": 2.77}, {"text": "And you can see it has a\nsegmental pattern here.", "start": 1432.14, "duration": 3.38}, {"text": "This is the head of the\nlarvae, the tail of the larvae.", "start": 1435.52, "duration": 3.09}, {"text": "But you see there are\nthese segments that", "start": 1438.61, "duration": 2.16}, {"text": "alternate between smooth\ncuticle and hairy cuticle.", "start": 1440.77, "duration": 4.38}, {"text": "They have things\ncalled \"denticles,\"", "start": 1445.15, "duration": 2.2}, {"text": "which are these hairlike\nprojections, which", "start": 1447.35, "duration": 2.3}, {"text": "are essentially, what the\nmaggot uses for traction so it", "start": 1449.65, "duration": 3.84}, {"text": "can crawl around.", "start": 1453.49, "duration": 2.61}, {"text": "So they're basically just\nlooking at maggots here", "start": 1456.1, "duration": 2.07}, {"text": "and looking at the pattern\nof segments in the maggots.", "start": 1458.17, "duration": 5.01}, {"text": "But what they found is a mutant.", "start": 1463.18, "duration": 2.08}, {"text": "And here's a mutant\nhere which just", "start": 1465.26, "duration": 1.88}, {"text": "has these hairlike projections\nall across the cuticle", "start": 1467.14, "duration": 3.12}, {"text": "without these intervening\nregions of naked cuticle.", "start": 1470.26, "duration": 5.31}, {"text": "And because there's a lot\nof hairlike projections", "start": 1475.57, "duration": 3.0}, {"text": "here, it reminded the\nresearchers of a hedgehog,", "start": 1478.57, "duration": 3.33}, {"text": "and so this mutant became\nknown as \"hedgehog.\"", "start": 1481.9, "duration": 3.15}, {"text": "And the hedgehog gene\nwas the founding member", "start": 1485.05, "duration": 4.17}, {"text": "of an entire signaling\npathway, known as the \"hedgehog", "start": 1489.22, "duration": 2.88}, {"text": "pathway,\" that plays important\nroles in human development", "start": 1492.1, "duration": 4.5}, {"text": "and also, human cancer.", "start": 1496.6, "duration": 2.59}, {"text": "So the human gene\nfor a hedgehog,", "start": 1499.19, "duration": 3.32}, {"text": "or one of the most\nimportant ones in humans,", "start": 1502.51, "duration": 1.98}, {"text": "is known as sonic hedgehog.", "start": 1504.49, "duration": 2.01}, {"text": "So you see that geneticists have\nkind of an odd sense of humor.", "start": 1506.5, "duration": 6.18}, {"text": "But the sonic-hedgehog gene\nis important in cancer.", "start": 1512.68, "duration": 4.26}, {"text": "And actually, there\nare now a number", "start": 1516.94, "duration": 2.22}, {"text": "of drugs that are\nbeing developed", "start": 1519.16, "duration": 1.77}, {"text": "to target the hedgehog pathway.", "start": 1520.93, "duration": 2.67}, {"text": "And one was approved\nback in 2012 for use", "start": 1523.6, "duration": 3.9}, {"text": "in treating\nbasal-cell carcinoma.", "start": 1527.5, "duration": 2.4}, {"text": "And there's currently\nanother drug", "start": 1529.9, "duration": 1.95}, {"text": "that's in phase-II clinical\ntrials for treating", "start": 1531.85, "duration": 3.09}, {"text": "some forms of leukemia.", "start": 1534.94, "duration": 2.52}, {"text": "So this is a story that\ngoes from identifying", "start": 1537.46, "duration": 3.24}, {"text": "this weird fly mutant all\nthe way to clinical trials,", "start": 1540.7, "duration": 3.9}, {"text": "developing drugs,\nwhose purpose is", "start": 1544.6, "duration": 4.41}, {"text": "to inhibit this signaling\npathway, which hedgehog", "start": 1549.01, "duration": 3.33}, {"text": "is the signal--", "start": 1552.34, "duration": 1.73}, {"text": "the extracellular ligand for.", "start": 1554.07, "duration": 2.08}, {"text": "OK, so now, I'm going to\nswitch gears and tell you", "start": 1559.3, "duration": 2.94}, {"text": "about another story.", "start": 1562.24, "duration": 2.1}, {"text": "It's a bit like this one, except\nthis one has an MIT connection.", "start": 1564.34, "duration": 5.67}, {"text": "So I'm going to tell you about\nwork done at MIT in the worm", "start": 1570.01, "duration": 7.91}, {"text": "Caenorhabditis elegans.", "start": 1577.92, "duration": 1.7}, {"text": "And this work was\ndone in the lab", "start": 1582.91, "duration": 1.56}, {"text": "of Robert Horvitz, who is\na member of our biology", "start": 1584.47, "duration": 8.79}, {"text": "department.", "start": 1593.26, "duration": 1.35}, {"text": "And Robert Horvitz,\nfor his work,", "start": 1594.61, "duration": 3.36}, {"text": "won the Nobel Prize,\nalong with John Sulston", "start": 1597.97, "duration": 2.59}, {"text": "and Sydney Brenner\nfor their work", "start": 1600.56, "duration": 3.68}, {"text": "on how cells decide what\nfates they give rise to.", "start": 1604.24, "duration": 4.35}, {"text": "And one thing that the\nHorvitz Lab has done", "start": 1608.59, "duration": 5.1}, {"text": "is to elucidate the mechanisms\nthat determine whether or not", "start": 1613.69, "duration": 4.47}, {"text": "a cell lives or dies\nduring development.", "start": 1618.16, "duration": 3.52}, {"text": "So if we think about the\ndevelopment of an organism,", "start": 1624.43, "duration": 3.51}, {"text": "we all start from a single cell.", "start": 1627.94, "duration": 2.37}, {"text": "And the cell divides\ninto different cells,", "start": 1630.31, "duration": 4.68}, {"text": "but different cells\nin our body give rise", "start": 1634.99, "duration": 2.22}, {"text": "to different cell fates.", "start": 1637.21, "duration": 2.94}, {"text": "So if we consider just a\ngeneric cell division here,", "start": 1640.15, "duration": 3.18}, {"text": "you have a parent\ncell, A. It might", "start": 1643.33, "duration": 2.73}, {"text": "divide into cell B and cell C.", "start": 1646.06, "duration": 3.72}, {"text": "And maybe cell B might\nhave a particular fate.", "start": 1649.78, "duration": 3.64}, {"text": "It might go on to develop\ninto a neuron, or a muscle", "start": 1653.42, "duration": 2.87}, {"text": "cell, whatever.", "start": 1656.29, "duration": 1.41}, {"text": "It doesn't matter.", "start": 1657.7, "duration": 1.59}, {"text": "But one fate that Horvitz,\nSulston, and Brenner saw", "start": 1659.29, "duration": 7.02}, {"text": "is that sometimes, cells--", "start": 1666.31, "duration": 1.8}, {"text": "their fate was to just die.", "start": 1668.11, "duration": 2.7}, {"text": "And this was very stereotypical.", "start": 1670.81, "duration": 1.89}, {"text": "You get a death.", "start": 1672.7, "duration": 0.9}, {"text": "And this was defined as\n\"programmed cell death\"", "start": 1676.71, "duration": 3.49}, {"text": "because it followed a very\nstereotypic pattern, where", "start": 1680.2, "duration": 5.82}, {"text": "the same cell, each time,\nwould undergo cell death,", "start": 1686.02, "duration": 4.8}, {"text": "so it seems like there's\na program for it.", "start": 1690.82, "duration": 3.62}, {"text": "This also is called \"apoptosis.\"", "start": 1694.44, "duration": 4.7}, {"text": "So what really enabled this work\nis the biology of C. elegans.", "start": 1699.14, "duration": 7.92}, {"text": "And, here, I'm showing you\nC. elegans development.", "start": 1707.06, "duration": 3.75}, {"text": "This is the C. elegans zygote.", "start": 1710.81, "duration": 2.38}, {"text": "This cell divides into two\ncells that are different.", "start": 1713.19, "duration": 2.73}, {"text": "One is called AB,\none is called P1.", "start": 1715.92, "duration": 3.47}, {"text": "And we know exactly what the\nfates for the descendants", "start": 1719.39, "duration": 3.27}, {"text": "of both these cells are based\non the work of Sulston, Brenner,", "start": 1722.66, "duration": 4.32}, {"text": "and Horvitz.", "start": 1726.98, "duration": 1.59}, {"text": "Now, you get a\nfour-cell stage where", "start": 1728.57, "duration": 2.37}, {"text": "AB divides into two cells,\nand P1 divides into two cells.", "start": 1730.94, "duration": 4.66}, {"text": "And again, we know the\nfates of all these cells.", "start": 1735.6, "duration": 3.77}, {"text": "And what C. elegans\nresearchers have", "start": 1739.37, "duration": 2.64}, {"text": "done, because C. elegans is a\nrelatively simple organism--", "start": 1742.01, "duration": 5.29}, {"text": "there are only 947 cells\nin every individual worm,", "start": 1747.3, "duration": 5.09}, {"text": "so there are 947 somatic cells.", "start": 1752.39, "duration": 3.015}, {"text": "And this is stereotypic.", "start": 1758.48, "duration": 1.74}, {"text": "Every worm has these 947 cells.", "start": 1760.22, "duration": 4.11}, {"text": "How many cells do you have?", "start": 1764.33, "duration": 1.34}, {"text": "More than or less than 1,000?", "start": 1769.69, "duration": 3.27}, {"text": "You have more than\n1,000 cells, right?", "start": 1772.96, "duration": 2.25}, {"text": "That makes you much\nmore complicated.", "start": 1775.21, "duration": 3.03}, {"text": "So really, the practical\naspect of C. elegans", "start": 1778.24, "duration": 3.18}, {"text": "is it has a much\nsimpler composition,", "start": 1781.42, "duration": 4.2}, {"text": "and they can track what\nhappens to every single one", "start": 1785.62, "duration": 3.3}, {"text": "of these cells.", "start": 1788.92, "duration": 1.5}, {"text": "They know when\nevery cell divides", "start": 1790.42, "duration": 2.07}, {"text": "and what the daughter cells of\nthat division will turn into.", "start": 1792.49, "duration": 3.51}, {"text": "In other words, they know the\nentire lineage of this animal.", "start": 1796.0, "duration": 4.53}, {"text": "So this is a picture\nof the lineage.", "start": 1800.53, "duration": 1.71}, {"text": "That's showing you what\nhappens to every single cell", "start": 1802.24, "duration": 3.12}, {"text": "in the development\nof an adult worm.", "start": 1805.36, "duration": 3.87}, {"text": "And so what particularly\ninterested Robert Horvitz", "start": 1809.23, "duration": 5.73}, {"text": "is 131 cells, during the\ndevelopment of this animal,", "start": 1814.96, "duration": 5.34}, {"text": "underwent programmed cell death.", "start": 1820.3, "duration": 3.65}, {"text": "And this is not\nrandom cell death.", "start": 1823.95, "duration": 3.4}, {"text": "It's the same cells every time.", "start": 1827.35, "duration": 2.28}, {"text": "They know what happens to every\nsingle cell in the development", "start": 1829.63, "duration": 2.94}, {"text": "of this organism, so they\nknow when there's a division,", "start": 1832.57, "duration": 3.03}, {"text": "and one specific cell dies\nevery time in the organism.", "start": 1835.6, "duration": 5.1}, {"text": "So it's really a\nunique scenario,", "start": 1840.7, "duration": 1.89}, {"text": "where you can really see what\nbecomes of every cell that", "start": 1842.59, "duration": 5.43}, {"text": "is present in the organism.", "start": 1848.02, "duration": 3.3}, {"text": "OK, so now, let's talk a little\nbit about the death process.", "start": 1851.32, "duration": 5.01}, {"text": "So I'll make the\ncell-death process simple.", "start": 1856.33, "duration": 3.66}, {"text": "You start with a live cell.", "start": 1859.99, "duration": 4.0}, {"text": "So you have a live cell.", "start": 1863.99, "duration": 3.35}, {"text": "That live cell dies such that\nyou then have a dead cell.", "start": 1867.34, "duration": 4.47}, {"text": "And then after the cell dies--", "start": 1877.18, "duration": 3.33}, {"text": "after the cell dies, the\nremnants of that dead cell", "start": 1880.51, "duration": 3.39}, {"text": "are engulfed by\nneighboring cells, such", "start": 1883.9, "duration": 2.04}, {"text": "that you no longer\nsee that cell.", "start": 1885.94, "duration": 3.54}, {"text": "So the last step in this\nprocess is engulfment.", "start": 1889.48, "duration": 3.165}, {"text": "Now, a key aspect of\none of Horvitz's screens", "start": 1897.4, "duration": 4.89}, {"text": "is that other researchers had\nidentified a mutation that", "start": 1902.29, "duration": 5.34}, {"text": "affected cell death that\nspecifically blocked", "start": 1907.63, "duration": 2.85}, {"text": "this engulfment process.", "start": 1910.48, "duration": 1.215}, {"text": "And this gene is called ced-1.", "start": 1914.83, "duration": 3.24}, {"text": "There's the first cell-death\nmutant that was identified.", "start": 1918.07, "duration": 3.57}, {"text": "\"Ced\" stands for\n\"Cell Death abnormal\"", "start": 1921.64, "duration": 11.35}, {"text": "so C-E-D is short for \"ced.\"", "start": 1932.99, "duration": 3.78}, {"text": "So researchers in\nthe C. elegans field", "start": 1936.77, "duration": 2.99}, {"text": "started isolating these\ncell-death-abnormal mutants,", "start": 1939.76, "duration": 3.72}, {"text": "where something happened in\nthe cell-death process that", "start": 1943.48, "duration": 3.39}, {"text": "was abnormal.", "start": 1946.87, "duration": 2.49}, {"text": "And I'll tell you how this was\nleveraged by the Horvitz lab", "start": 1949.36, "duration": 3.75}, {"text": "to identify, basically,\na pathway of genes", "start": 1953.11, "duration": 3.3}, {"text": "that were involved\nin cell death.", "start": 1956.41, "duration": 3.52}, {"text": "So this is now a worm.", "start": 1959.93, "duration": 2.39}, {"text": "And what you see\nin this worm are", "start": 1962.32, "duration": 1.38}, {"text": "these bubble-like\nstructures that", "start": 1963.7, "duration": 1.77}, {"text": "are cells that are dead\nbut haven't been engulfed.", "start": 1965.47, "duration": 3.93}, {"text": "So these dead cells, because\nthey're not engulfed,", "start": 1969.4, "duration": 4.02}, {"text": "are visible in the adult worm.", "start": 1973.42, "duration": 2.28}, {"text": "And so you can basically\njust look at adult worms,", "start": 1975.7, "duration": 3.36}, {"text": "and see whether or not these\nbubble-like structures are", "start": 1979.06, "duration": 3.12}, {"text": "present in a ced- mutant.", "start": 1982.18, "duration": 2.97}, {"text": "In a wild-type worm,\nyou don't see this,", "start": 1985.15, "duration": 2.19}, {"text": "and so it's harder to see.", "start": 1987.34, "duration": 1.92}, {"text": "But this provided a\nvisual assay to look", "start": 1989.26, "duration": 3.99}, {"text": "for mutations that block\nthe cell-death process", "start": 1993.25, "duration": 4.26}, {"text": "because if you block the\nprocess upstream of ced-1", "start": 1997.51, "duration": 4.56}, {"text": "in an engulfment, you\nno longer will see", "start": 2002.07, "duration": 2.07}, {"text": "these bubble-like structures.", "start": 2004.14, "duration": 3.6}, {"text": "And so that is what\nthe Horvitz Lab did.", "start": 2007.74, "duration": 4.02}, {"text": "They started with\nced-1 mutant worms.", "start": 2011.76, "duration": 4.62}, {"text": "So they're starting\nwith the ced-1 mutants.", "start": 2016.38, "duration": 2.97}, {"text": "And they then mutagenized\nthese ced-1 mutants.", "start": 2019.35, "duration": 6.19}, {"text": "Sorry-- mutagenized.", "start": 2025.54, "duration": 1.23}, {"text": "And so they're essentially,\nlooking for second mutants", "start": 2030.93, "duration": 3.57}, {"text": "in this animal that will\naffect the death process.", "start": 2034.5, "duration": 3.51}, {"text": "OK, I'll take you through\nthe logic of this.", "start": 2042.15, "duration": 4.09}, {"text": "So for the remainder\nof the generations", "start": 2046.24, "duration": 2.3}, {"text": "I'm going to tell you about,\nthey're all ced-1 mutant.", "start": 2048.54, "duration": 2.64}, {"text": "Ced-1 is homozygous,\nin this case.", "start": 2055.139, "duration": 4.29}, {"text": "And the worms are\nhermaphrodites,", "start": 2059.429, "duration": 3.721}, {"text": "meaning they are both male\nand female sex organs.", "start": 2063.15, "duration": 2.88}, {"text": "And therefore, they\ncan self-fertilize.", "start": 2066.03, "duration": 2.419}, {"text": "So this is a self-cross.", "start": 2068.449, "duration": 1.381}, {"text": "And so ced-1 remains\nhomozygous mutant", "start": 2072.92, "duration": 3.509}, {"text": "throughout all these crosses.", "start": 2076.429, "duration": 3.451}, {"text": "Now similar to the fly screen,\nthey can look for individual--", "start": 2079.88, "duration": 5.22}, {"text": "or you get individual\nworms here.", "start": 2085.1, "duration": 4.106}, {"text": "Let's get some colors so we can\ncompare different chromosomes.", "start": 2089.206, "duration": 5.521}, {"text": "All right, so this chromosome\nmight have one mutant,", "start": 2094.727, "duration": 3.553}, {"text": "this chromosome could\nhave another mutant,", "start": 2098.28, "duration": 2.75}, {"text": "and this chromosome could\nhave another mutant,", "start": 2101.03, "duration": 2.39}, {"text": "and maybe this one\ndoesn't have a mutant.", "start": 2103.42, "duration": 3.79}, {"text": "OK, but again, these are\nheterozygous animals,", "start": 2107.21, "duration": 4.35}, {"text": "so if you're looking for\na loss-of-function mutant,", "start": 2111.56, "duration": 3.36}, {"text": "you would not see the\nphenotype at this stage.", "start": 2114.92, "duration": 4.68}, {"text": "So what was done in this screen\nis, because these are worms", "start": 2119.6, "duration": 3.99}, {"text": "and they're hermaphrodites,\nthey basically", "start": 2123.59, "duration": 3.03}, {"text": "allowed each of these\nworms to self-cross.", "start": 2126.62, "duration": 5.19}, {"text": "So now, were talking\njust about a self-cross.", "start": 2131.81, "duration": 2.28}, {"text": "And because a single worm has\njust one of these chromosomes,", "start": 2138.29, "duration": 6.06}, {"text": "when it undergoes a self-cross,\na quarter of the progeny", "start": 2144.35, "duration": 4.23}, {"text": "will be homozygous\nrecessive for the mutation.", "start": 2148.58, "duration": 3.09}, {"text": "OK, so here, we have\nthe F1 generation.", "start": 2154.85, "duration": 3.31}, {"text": "And now, they can just\nlook at the F2 generation,", "start": 2158.16, "duration": 3.31}, {"text": "and they're looking for some\nfraction of the worms resulting", "start": 2161.47, "duration": 4.96}, {"text": "from each individual\nthat has a phenotype that", "start": 2166.43, "duration": 4.14}, {"text": "looks like a cell-death\nmutant phenotype.", "start": 2170.57, "duration": 3.51}, {"text": "And so they're\nessentially, going", "start": 2180.655, "duration": 1.375}, {"text": "to screen through\nthe F2 generation,", "start": 2182.03, "duration": 3.24}, {"text": "and look for worms\nthat fail to have", "start": 2185.27, "duration": 3.09}, {"text": "these bubble-like structures\nin the adult world.", "start": 2188.36, "duration": 4.77}, {"text": "So they're looking for a loss\nof these refractile structures.", "start": 2193.13, "duration": 4.65}, {"text": "And they got one.", "start": 2197.78, "duration": 2.86}, {"text": "This is now a double mutant\nbetween ced-1 and ced-3,", "start": 2200.64, "duration": 4.01}, {"text": "and you see how\nyou no longer have", "start": 2204.65, "duration": 2.04}, {"text": "these big bubble-like\nstructures in the worm.", "start": 2206.69, "duration": 2.49}, {"text": "So they identified a\nmutant, and thus, a gene,", "start": 2212.81, "duration": 3.63}, {"text": "that's called \"ced-3,\" which\nbasically causes a failure", "start": 2216.44, "duration": 6.24}, {"text": "of the cells to\nundergo cell death.", "start": 2222.68, "duration": 2.61}, {"text": "Now given what I've given\nwhat I've shown you,", "start": 2225.29, "duration": 3.84}, {"text": "is this necessarily a mutant\nthat's involved in cell death?", "start": 2229.13, "duration": 3.93}, {"text": "Can you think of an\nalternative explanation", "start": 2233.06, "duration": 2.07}, {"text": "for why you would lose these\nsort of bubble-like structures?", "start": 2235.13, "duration": 8.93}, {"text": "What else could be happening?", "start": 2244.06, "duration": 1.83}, {"text": "When you do a screen\nlike this, and when", "start": 2245.89, "duration": 1.92}, {"text": "you do science in\ngeneral, you have", "start": 2247.81, "duration": 2.713}, {"text": "to think through all\nthe different types", "start": 2250.523, "duration": 1.667}, {"text": "of possibilities.", "start": 2252.19, "duration": 1.08}, {"text": "Yes, Georgia.", "start": 2253.27, "duration": 1.033}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2254.303, "duration": 3.319}, {"text": "ADAM MARTIN: Excellent.", "start": 2257.622, "duration": 0.958}, {"text": "Georgia said you could\nhave re-mutated ced-1.", "start": 2258.58, "duration": 3.96}, {"text": "So one possibility is that you\nisolated a ced-1 revertant,", "start": 2262.54, "duration": 5.22}, {"text": "which means you changed its\nDNA sequence so that now,", "start": 2267.76, "duration": 4.83}, {"text": "the ced-1 gene is functional.", "start": 2272.59, "duration": 2.88}, {"text": "So one scenario\nhere is you could", "start": 2275.47, "duration": 2.7}, {"text": "have some type of revertant,\nor you could have a suppressor", "start": 2278.17, "duration": 5.25}, {"text": "mutation.", "start": 2283.42, "duration": 0.66}, {"text": "Maybe you have a\nmutation that bypasses", "start": 2284.08, "duration": 4.89}, {"text": "the function of ced-1\nsuch that now, the cells", "start": 2288.97, "duration": 3.9}, {"text": "can engulf the dead cell.", "start": 2292.87, "duration": 1.97}, {"text": "So you could also\nhave a suppressor.", "start": 2294.84, "duration": 2.212}, {"text": "Or the alternative scenario,\nthe one that we want,", "start": 2300.5, "duration": 3.44}, {"text": "is that we've affected\nthe cell-death process", "start": 2303.94, "duration": 2.4}, {"text": "and identified something that is\na bona-fide cell-death mutant.", "start": 2306.34, "duration": 6.39}, {"text": "How would you differentiate\nbetween these two?", "start": 2312.73, "duration": 2.13}, {"text": "Any ideas?", "start": 2319.185, "duration": 0.5}, {"text": "Should this have an extra cell?", "start": 2323.11, "duration": 1.54}, {"text": "No.", "start": 2329.21, "duration": 0.75}, {"text": "Stevens says no.", "start": 2329.96, "duration": 1.41}, {"text": "I agree.", "start": 2331.37, "duration": 1.08}, {"text": "There should be\nno extra cell here", "start": 2332.45, "duration": 4.83}, {"text": "because if you restore\nthe phagocytic process,", "start": 2337.28, "duration": 2.74}, {"text": "then the cell should die,\nit should be engulfed,", "start": 2340.02, "duration": 2.0}, {"text": "and there shouldn't\nbe an extra cell.", "start": 2342.02, "duration": 2.62}, {"text": "But if this is a bona-fide\ncell-death mutant,", "start": 2344.64, "duration": 3.86}, {"text": "then you should\nhave extra cells.", "start": 2348.5, "duration": 3.51}, {"text": "And it turns out the\nced-3 mutant blocks", "start": 2352.01, "duration": 3.24}, {"text": "all 131 of these cell deaths so\nthat you have 131 extra cells.", "start": 2355.25, "duration": 5.64}, {"text": "Because they know the entire\ncell lineage of this worm", "start": 2360.89, "duration": 4.2}, {"text": "and can see whether or not\ncells are present or not,", "start": 2365.09, "duration": 3.15}, {"text": "they can tell if there\nare extra cells or not.", "start": 2368.24, "duration": 2.41}, {"text": "And therefore, that\nallowed them to infer", "start": 2370.65, "duration": 2.48}, {"text": "that they had an\nactual mutant that", "start": 2373.13, "duration": 2.43}, {"text": "was affecting the mechanism\nthat promotes the cell to die.", "start": 2375.56, "duration": 5.67}, {"text": "And this shows that\nthe cell death--", "start": 2381.23, "duration": 3.95}, {"text": "it shows the cell death\nis an active process.", "start": 2385.18, "duration": 3.46}, {"text": "It's not just some random\nevent that's happening.", "start": 2388.64, "duration": 3.07}, {"text": "It's an active process that\nis controlled by genes.", "start": 2391.71, "duration": 5.3}, {"text": "So there's an active mechanism\ninvolved in the cell death.", "start": 2397.01, "duration": 2.85}, {"text": "Any questions about how these\nscreens go in the crosses", "start": 2403.15, "duration": 4.03}, {"text": "before I move on?", "start": 2407.18, "duration": 0.9}, {"text": "OK, so I have one more\nstory to tell you about,", "start": 2411.16, "duration": 4.05}, {"text": "and this relates to behavior.", "start": 2415.21, "duration": 2.795}, {"text": "So now, I want to tell\nyou about behavior.", "start": 2418.005, "duration": 1.75}, {"text": "We all behave, some of\nus better than others.", "start": 2422.63, "duration": 5.25}, {"text": "So how is it we can\ngo from something", "start": 2427.88, "duration": 2.61}, {"text": "as abstract as behavior to\nspecific genes and mechanisms", "start": 2430.49, "duration": 4.74}, {"text": "that control this?", "start": 2435.23, "duration": 2.77}, {"text": "And I'm going to tell you about\nwork that was awarded the Nobel", "start": 2438.0, "duration": 3.41}, {"text": "Prize last year.", "start": 2441.41, "duration": 2.07}, {"text": "Two of these researchers--", "start": 2443.48, "duration": 2.22}, {"text": "their careers are at Brandeis.", "start": 2445.7, "duration": 2.7}, {"text": "And so what they discovered\nis the mechanism that controls", "start": 2448.4, "duration": 4.89}, {"text": "circadian rhythm in organisms--", "start": 2453.29, "duration": 3.09}, {"text": "so circadian rhythm.", "start": 2456.38, "duration": 2.97}, {"text": "So circadian rhythm\nis a behavior.", "start": 2459.35, "duration": 3.51}, {"text": "We are awake during\ncertain parts of the day", "start": 2462.86, "duration": 4.59}, {"text": "and are asleep at night.", "start": 2467.45, "duration": 2.235}, {"text": "If you're hidden from\nthe light-dark cycle,", "start": 2473.81, "duration": 2.1}, {"text": "you continue this cycle\nfor some amount of time.", "start": 2475.91, "duration": 3.96}, {"text": "So there's something\nintrinsic in our system", "start": 2479.87, "duration": 2.67}, {"text": "such that we want to exist on\nthis 24-hour wake-sleep cycle.", "start": 2482.54, "duration": 6.63}, {"text": "That's why it's\na pain in the ass", "start": 2489.17, "duration": 1.65}, {"text": "to travel to the other\nside of the world.", "start": 2490.82, "duration": 3.45}, {"text": "So we want to identify what\ncontrols this behavior.", "start": 2499.38, "duration": 3.86}, {"text": "What, then, might be a\nphenotype you might look for?", "start": 2503.24, "duration": 2.28}, {"text": "What would happen if you\nbreak circadian rhythm?", "start": 2511.42, "duration": 2.43}, {"text": "Yeah, Rachel.", "start": 2516.68, "duration": 0.57}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2517.25, "duration": 2.15}, {"text": "ADAM MARTIN: It wouldn't have\na nice, clear wake-sleep cycle.", "start": 2519.4, "duration": 3.67}, {"text": "Exactly.", "start": 2523.07, "duration": 1.91}, {"text": "So this screen--\nwhat they did is", "start": 2524.98, "duration": 2.88}, {"text": "to look for flies\nwhere they didn't have", "start": 2527.86, "duration": 3.96}, {"text": "this robust wake-sleep cycle.", "start": 2531.82, "duration": 3.51}, {"text": "So you basically look for\nflies that are awake at night,", "start": 2535.33, "duration": 4.53}, {"text": "and identify the mutations\nthat cause this to happen.", "start": 2539.86, "duration": 7.24}, {"text": "OK, I'll show you an example\nof what the data looks like.", "start": 2547.1, "duration": 3.29}, {"text": "So what each of these\nlines is each tick mark", "start": 2550.39, "duration": 4.11}, {"text": "is a measurement\nof fly activity.", "start": 2554.5, "duration": 3.54}, {"text": "So what you see are flies\nasleep, they're awake,", "start": 2558.04, "duration": 3.45}, {"text": "they're asleep, they're awake.", "start": 2561.49, "duration": 2.62}, {"text": "And researchers\nidentified mutants that", "start": 2564.11, "duration": 3.08}, {"text": "didn't show this 24-hour cycle.", "start": 2567.19, "duration": 2.68}, {"text": "So some are just\ntotally arrhythmic.", "start": 2569.87, "duration": 2.48}, {"text": "Other mutants alter the\nperiod of this cycle", "start": 2572.35, "duration": 2.69}, {"text": "so that it's either\nlonger or shorter.", "start": 2575.04, "duration": 3.4}, {"text": "So this is a really\nelegant way to look", "start": 2578.44, "duration": 2.25}, {"text": "for genes that are important\nfor circadian rhythm.", "start": 2580.69, "duration": 3.645}, {"text": "And I'll take you through\nthe genetic screen.", "start": 2584.335, "duration": 1.89}, {"text": "This was done by\nKonopka and Benzer.", "start": 2590.89, "duration": 4.575}, {"text": "And they did a nice screen.", "start": 2598.32, "duration": 2.56}, {"text": "It involves a genetic\ntrick which I'll show you.", "start": 2600.88, "duration": 5.56}, {"text": "There's a type of chromosome\ncalled \"attached-X\" in flies,", "start": 2606.44, "duration": 4.22}, {"text": "where two X chromosomes\nare fused to each other--", "start": 2610.66, "duration": 2.46}, {"text": "so two X chromosomes fused.", "start": 2616.61, "duration": 1.76}, {"text": "And if a fly has two X\nchromosomes, it's female.", "start": 2624.82, "duration": 3.42}, {"text": "If it just has one X\nchromosome, it's male.", "start": 2628.24, "duration": 2.79}, {"text": "So that's determines fly gender.", "start": 2631.03, "duration": 6.005}, {"text": "So then these researchers took\nmales and mutagenized them.", "start": 2639.76, "duration": 4.25}, {"text": "And they crossed these\nmales to attached X females.", "start": 2649.36, "duration": 4.06}, {"text": "And when you cross males\nto attached X females,", "start": 2653.42, "duration": 4.25}, {"text": "you do something clever,\nwhich is half of the progeny", "start": 2657.67, "duration": 3.42}, {"text": "dies because you\nneed an X chromosome", "start": 2661.09, "duration": 2.19}, {"text": "and you can't have\nthree X chromosomes.", "start": 2663.28, "duration": 2.85}, {"text": "But your females\nare all attached XY.", "start": 2666.13, "duration": 4.56}, {"text": "So the females actually\nget their X chromosomes", "start": 2670.69, "duration": 2.37}, {"text": "from their mom, which is the\nopposite of the way it normally", "start": 2673.06, "duration": 2.76}, {"text": "works.", "start": 2675.82, "duration": 1.23}, {"text": "And males get their\nX chromosome from dad", "start": 2677.05, "duration": 3.6}, {"text": "because the attached X\nstrain has a Y chromosome.", "start": 2680.65, "duration": 4.41}, {"text": "So this is a little\nbit of a genetic trick.", "start": 2685.06, "duration": 2.46}, {"text": "And the fly-- the reason it\nwas done, in this case, is they", "start": 2687.52, "duration": 3.24}, {"text": "wanted to mutate\nthe X chromosome", "start": 2690.76, "duration": 2.37}, {"text": "and then have the fathers\npass on their X chromosome", "start": 2693.13, "duration": 3.54}, {"text": "to their sons because there's\nonly one copy of the X", "start": 2696.67, "duration": 3.27}, {"text": "chromosome.", "start": 2699.94, "duration": 0.61}, {"text": "So if you get a\nmutation on X, you", "start": 2700.55, "duration": 2.81}, {"text": "don't have to homozygous\nit because there's", "start": 2703.36, "duration": 2.76}, {"text": "only one copy of it.", "start": 2706.12, "duration": 2.19}, {"text": "So it's a little bit of\na genetic trick that,", "start": 2708.31, "duration": 1.98}, {"text": "in this case, served\nthe researchers", "start": 2710.29, "duration": 1.92}, {"text": "a generation on their screen.", "start": 2712.21, "duration": 3.14}, {"text": "OK, so you take this, and\nthen you identify males now", "start": 2715.35, "duration": 5.89}, {"text": "that have a mutated\nX chromosome,", "start": 2721.24, "duration": 2.88}, {"text": "and they have only\none X chromosomes", "start": 2724.12, "duration": 1.74}, {"text": "so you should be able to\nobserve the behavior even here.", "start": 2725.86, "duration": 4.26}, {"text": "But to establish a line of\nflies that have this mutation,", "start": 2732.64, "duration": 4.23}, {"text": "they then took these\nF1 mutated males,", "start": 2736.87, "duration": 4.41}, {"text": "and crossed them, again,\nto attached X flies.", "start": 2741.28, "duration": 3.99}, {"text": "And again, in doing this,\nall the males from this cross", "start": 2747.8, "duration": 3.08}, {"text": "are mutant.", "start": 2750.88, "duration": 2.38}, {"text": "So now, you have multiple\nmales, all of which are mutant.", "start": 2753.26, "duration": 3.9}, {"text": "So you can start with\na single male F1.", "start": 2757.16, "duration": 5.57}, {"text": "And by crossing it\nto this strain here,", "start": 2762.73, "duration": 4.32}, {"text": "you get a lot of males now that\nhave the mutant chromosome,", "start": 2767.05, "duration": 3.51}, {"text": "and you can look\nat their behavior", "start": 2770.56, "duration": 2.04}, {"text": "to determine whether you've\naffected circadian rhythm.", "start": 2772.6, "duration": 4.8}, {"text": "Does everyone understand how\nthe attached X works here?", "start": 2777.4, "duration": 3.75}, {"text": "It's kind of a little\nbit of a trick,", "start": 2781.15, "duration": 1.83}, {"text": "but flies have these\ntools that you can use", "start": 2782.98, "duration": 3.02}, {"text": "to save your time in the lab.", "start": 2786.0, "duration": 4.99}, {"text": "OK, so these mutants that\nthe Benzer Lab identified had", "start": 2790.99, "duration": 6.78}, {"text": "altered period of\nthe sleep-wake cycle,", "start": 2797.77, "duration": 2.76}, {"text": "and therefore, the gene\nwas named \"period.\"", "start": 2800.53, "duration": 3.57}, {"text": "So this screen identified\na gene called \"period.\"", "start": 2804.1, "duration": 6.24}, {"text": "This is a gene.", "start": 2812.95, "duration": 1.36}, {"text": "And there's a hammer log of\nthe period gene in humans.", "start": 2814.31, "duration": 2.345}, {"text": "And the gene in\nhumans is associated", "start": 2819.31, "duration": 2.46}, {"text": "with familial advanced\nsleep-phase syndrome.", "start": 2821.77, "duration": 3.15}, {"text": "So defects in the genes\nthat were identified", "start": 2824.92, "duration": 2.49}, {"text": "in Drosophila actually are\nrelevant to human sleep", "start": 2827.41, "duration": 5.31}, {"text": "disorders.", "start": 2832.72, "duration": 0.69}, {"text": "All right, I'm all set.", "start": 2837.4, "duration": 2.84}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.984}, {"text": "[RUSTLING]", "start": 1.984, "duration": 2.48}, {"text": "[CLICKING]", "start": 4.464, "duration": 3.968}, {"text": "MICHAEL SIPSER: OK, everybody.", "start": 25.23, "duration": 1.575}, {"text": "Let's begin.", "start": 26.805, "duration": 0.5}, {"text": "Welcome back.", "start": 30.0, "duration": 1.85}, {"text": "Good to see you\nall here on Zoom.", "start": 31.85, "duration": 4.26}, {"text": "So we're going to\npick up with what", "start": 36.11, "duration": 2.31}, {"text": "we had been\ndiscussing last week,", "start": 38.42, "duration": 4.99}, {"text": "which was an introduction\nto NP-completeness.", "start": 43.41, "duration": 7.14}, {"text": "So we're following on our\ndescription of time complexity.", "start": 50.55, "duration": 5.46}, {"text": "We started talking\nabout the time", "start": 56.01, "duration": 2.66}, {"text": "complexity classes, the class\nP, the nondeterministic classes,", "start": 58.67, "duration": 5.49}, {"text": "the class NP, P versus\nNP problem, and then", "start": 64.16, "duration": 2.97}, {"text": "leading to this discussion\nof NP-completeness.", "start": 67.13, "duration": 3.063}, {"text": "And today we're going\nto prove the big theorem", "start": 70.193, "duration": 1.917}, {"text": "in the field, which really\nkind of got things going back", "start": 72.11, "duration": 3.78}, {"text": "in the early 1970s\nby Cook and Levin", "start": 75.89, "duration": 3.54}, {"text": "that there was actually\nan NP-complete problem,", "start": 79.43, "duration": 3.42}, {"text": "that SAT in particular is\nan NP-complete problem.", "start": 82.85, "duration": 2.7}, {"text": "And then we'll also talk about\n3SAT, which is a useful tool.", "start": 85.55, "duration": 3.51}, {"text": "Just to remember, we had this\nnotion of NP-completeness.", "start": 92.0, "duration": 5.76}, {"text": "A language is NP-complete\nif it's in NP.", "start": 97.76, "duration": 3.15}, {"text": "And everything else in NP\nis polynomial time reducible", "start": 100.91, "duration": 2.76}, {"text": "to it.", "start": 103.67, "duration": 1.75}, {"text": "And if an NP-complete\nproblem turns out", "start": 105.42, "duration": 3.21}, {"text": "to have a polynomial\ntime solution,", "start": 108.63, "duration": 2.1}, {"text": "then every NP-problem has\na polynomial time solution.", "start": 110.73, "duration": 3.69}, {"text": "And that's part of the\nimportance of NP-completeness,", "start": 114.42, "duration": 3.0}, {"text": "because since we consider it\nunlikely that P equals NP,", "start": 117.42, "duration": 7.2}, {"text": "and that there probably are\nsome problems that are an NP,", "start": 124.62, "duration": 4.919}, {"text": "but are not solvable\nin polynomial time.", "start": 129.539, "duration": 3.121}, {"text": "That would imply that\nan NP-complete problem", "start": 132.66, "duration": 3.45}, {"text": "would have that property.", "start": 136.11, "duration": 1.57}, {"text": "And so proving a problem\nbeing NP-complete", "start": 137.68, "duration": 3.77}, {"text": "is evidence, very\nstrong evidence,", "start": 141.45, "duration": 2.16}, {"text": "that it doesn't have a\npolynomial time solution.", "start": 143.61, "duration": 3.4}, {"text": "And so therefore it's\ncalled intractable.", "start": 147.01, "duration": 2.13}, {"text": "It's a very difficult problem.", "start": 149.14, "duration": 1.25}, {"text": "So the way we are going\nto typically show problems", "start": 153.59, "duration": 5.69}, {"text": "NP-complete is by reducing\na known-- a previously", "start": 159.28, "duration": 3.63}, {"text": "known NP-complete\nproblem to that problem.", "start": 162.91, "duration": 3.48}, {"text": "Often it's 3SAT, as we've seen\nin several examples already,", "start": 166.39, "duration": 4.11}, {"text": "or it could be\nsome other example.", "start": 170.5, "duration": 2.53}, {"text": "So let's just survey briefly\nthe things that we've already--", "start": 173.03, "duration": 4.73}, {"text": "languages that we've already\nseen, which are NP-complete.", "start": 177.76, "duration": 4.18}, {"text": "So we have the\nlanguages SAT, which", "start": 181.94, "duration": 2.54}, {"text": "has a direct reduction\nfrom every NP problem.", "start": 184.48, "duration": 2.74}, {"text": "And so we're going to show\nthat today, that every NP", "start": 187.22, "duration": 10.41}, {"text": "language is polynomial time\nreducible to SAT, which", "start": 197.63, "duration": 2.64}, {"text": "is, in turn, reducible to 3SAT.", "start": 200.27, "duration": 3.52}, {"text": "And we showed\npreviously that 3SAT", "start": 203.79, "duration": 4.94}, {"text": "is reducible to\nCLIQUE and HAMPATH.", "start": 208.73, "duration": 1.8}, {"text": "And in recitation,\nif you went to that,", "start": 213.46, "duration": 3.87}, {"text": "they showed that the SUBSET-SUM\nproblem and the undirected", "start": 217.33, "duration": 3.36}, {"text": "HAMPATH problems are also\nreducible from previously", "start": 220.69, "duration": 4.98}, {"text": "shown--", "start": 225.67, "duration": 0.81}, {"text": "well, either from\n3SAT, or in the case", "start": 226.48, "duration": 4.2}, {"text": "of the undirected\nHAMPATH problem,", "start": 230.68, "duration": 1.56}, {"text": "it's reducible from\nthe HAMPATH problem.", "start": 232.24, "duration": 3.39}, {"text": "And the conclusion, once we have\nthese two blue reducibilities", "start": 235.63, "duration": 7.56}, {"text": "shown, then we know that all of\nthese problems are NP-complete.", "start": 243.19, "duration": 4.26}, {"text": "So the class NP\nbasically breaks down", "start": 250.15, "duration": 2.66}, {"text": "into the NP-complete\nproblems, P problems, problems", "start": 252.81, "duration": 3.93}, {"text": "that are in P, and then\nthere might be problems", "start": 256.74, "duration": 2.76}, {"text": "in between as well.", "start": 259.5, "duration": 1.105}, {"text": "So there are some\nproblems that are not", "start": 260.605, "duration": 1.625}, {"text": "known to be in either category.", "start": 262.23, "duration": 1.65}, {"text": "And in fact, there's\nan old theorem", "start": 263.88, "duration": 2.19}, {"text": "which shows that if P\nis different from NP,", "start": 266.07, "duration": 2.49}, {"text": "then there are\nactually problems that", "start": 268.56, "duration": 2.19}, {"text": "are in the intermediate state.", "start": 270.75, "duration": 2.05}, {"text": "And of course, it's\npossible that P equals NP,", "start": 272.8, "duration": 5.73}, {"text": "and then everything\ncollapses down", "start": 278.53, "duration": 2.13}, {"text": "to be the same with the\ntiny exception of the sigma", "start": 280.66, "duration": 3.57}, {"text": "star and empty set languages,\nwhich can never be complete.", "start": 284.23, "duration": 3.15}, {"text": "OK.", "start": 290.62, "duration": 1.23}, {"text": "So that's our quick review.", "start": 291.85, "duration": 2.37}, {"text": "Here is a check-in\nthat I'm going", "start": 294.22, "duration": 1.74}, {"text": "to use to get us ready\nfor the big proof", "start": 295.96, "duration": 3.965}, {"text": "that we're going to be\nspending most of the lecture", "start": 299.925, "duration": 2.125}, {"text": "on about showing\nSAT is NP-complete,", "start": 302.05, "duration": 3.96}, {"text": "but just to define a\nlittle notation, which", "start": 306.01, "duration": 1.92}, {"text": "you might have-- maybe\nyou've seen already.", "start": 307.93, "duration": 3.06}, {"text": "But I'm going to do it in\nthe form of a check-in.", "start": 310.99, "duration": 3.46}, {"text": "So I'm sure you've\nall seen the big sum", "start": 314.45, "duration": 4.1}, {"text": "notation using a big\nsigma to represent a sum", "start": 318.55, "duration": 4.89}, {"text": "over some set of possibilities.", "start": 323.44, "duration": 5.97}, {"text": "Just as there is the big\nsigma notation, we have--", "start": 329.41, "duration": 2.76}, {"text": "you can have other\noperations that", "start": 332.17, "duration": 2.94}, {"text": "apply to a set of elements.", "start": 335.11, "duration": 3.97}, {"text": "So in this case, we're going\nto be seeing the big end AND", "start": 339.08, "duration": 3.47}, {"text": "and the big OR operation--", "start": 342.55, "duration": 2.37}, {"text": "it's going to--\nnotation, which is", "start": 344.92, "duration": 2.46}, {"text": "going to allow us to talk about\ntaking the AND of many things", "start": 347.38, "duration": 5.16}, {"text": "or the OR of many\nthings, because we're", "start": 352.54, "duration": 2.88}, {"text": "going to be building\nthese Boolean formulas.", "start": 355.42, "duration": 2.07}, {"text": "And so ANDs and ORs are going\nto be the operations that we're", "start": 357.49, "duration": 3.42}, {"text": "going to be focusing on.", "start": 360.91, "duration": 1.6}, {"text": "And so just as an\nexample just to make sure", "start": 362.51, "duration": 3.44}, {"text": "we're all understanding\nthis notation,", "start": 365.95, "duration": 2.56}, {"text": "if you have two strings x\nand y written out in terms", "start": 368.51, "duration": 7.04}, {"text": "of their individual symbols.", "start": 375.55, "duration": 1.173}, {"text": "So they're both of length n.", "start": 376.723, "duration": 1.167}, {"text": "So x is x1 to xn.", "start": 377.89, "duration": 1.74}, {"text": "Y is y1 to yn.", "start": 379.63, "duration": 2.52}, {"text": "And now I write the\nfollowing expression.", "start": 382.15, "duration": 3.97}, {"text": "The big AND for i ranging\nbetween 1 and n of xi", "start": 386.12, "duration": 6.14}, {"text": "equal to yi.", "start": 392.26, "duration": 1.41}, {"text": "If that big AND is true, what\ndoes it tell us about x and y?", "start": 393.67, "duration": 4.14}, {"text": "And I'm just going to offer\nyou two possibilities,", "start": 397.81, "duration": 2.49}, {"text": "that either x and y agree\non some symbol or are equal,", "start": 400.3, "duration": 4.68}, {"text": "namely that they\nagree on every symbol.", "start": 404.98, "duration": 2.61}, {"text": "And so let's just pull\nthat up as a quick poll", "start": 407.59, "duration": 4.71}, {"text": "to get us going here.", "start": 412.3, "duration": 1.095}, {"text": "I just want to make sure\nyou understand the notation", "start": 416.393, "duration": 2.167}, {"text": "because we're going\nto be using that a lot", "start": 418.56, "duration": 2.07}, {"text": "in describing the polynomial\ntime reduction from languages", "start": 420.63, "duration": 8.01}, {"text": "in NP to the SAT language.", "start": 428.64, "duration": 3.28}, {"text": "OK.", "start": 431.92, "duration": 0.5}, {"text": "I think most of you\nhave got the idea.", "start": 432.42, "duration": 3.51}, {"text": "So let's finish this up quick.", "start": 435.93, "duration": 1.38}, {"text": "So another 15\nseconds, please, just", "start": 442.14, "duration": 2.73}, {"text": "to give you a chance\nto participate.", "start": 444.87, "duration": 1.56}, {"text": "OK.", "start": 451.68, "duration": 0.99}, {"text": "We're going to close this poll.", "start": 452.67, "duration": 3.6}, {"text": "Last chance, last call.", "start": 456.27, "duration": 2.16}, {"text": "All right.", "start": 458.43, "duration": 1.23}, {"text": "So yes, the big AND--", "start": 459.66, "duration": 3.81}, {"text": "as most of you can see, the\nbig AND says that x1 equals y1,", "start": 463.47, "duration": 6.69}, {"text": "and x2 equals y2, and x3\nequals y3 so they're all--", "start": 470.16, "duration": 6.89}, {"text": "every symbol in x is equal to\nthe corresponding symbol in y.", "start": 477.05, "duration": 3.81}, {"text": "If we had a big OR\ninstead of a big AND,", "start": 480.86, "duration": 3.36}, {"text": "then A would be\nthe correct answer,", "start": 484.22, "duration": 1.648}, {"text": "because then just there\nwould be some place where", "start": 485.868, "duration": 2.042}, {"text": "they agree instead of every\nplace where they agree.", "start": 487.91, "duration": 3.21}, {"text": "So let's then start to\nlaunch into this big theorem.", "start": 494.09, "duration": 6.705}, {"text": "The proof itself is\na mass of details", "start": 503.47, "duration": 4.41}, {"text": "with one underlying idea.", "start": 507.88, "duration": 2.14}, {"text": "And in fact, it's an\nidea we've seen before.", "start": 510.02, "duration": 3.139}, {"text": "But let's-- before we\nget ahead of ourselves,", "start": 513.159, "duration": 2.341}, {"text": "let's just understand\nwhat we're trying to do.", "start": 515.5, "duration": 3.309}, {"text": "So we want to show that this\nlanguage SAT is NP-complete.", "start": 518.809, "duration": 5.091}, {"text": "We remember what SAT is.", "start": 523.9, "duration": 1.38}, {"text": "It's Boolean formulas\nthat are satisfiable.", "start": 525.28, "duration": 2.58}, {"text": "So we already showed that the\nSAT prob-- so being NP-complete", "start": 530.5, "duration": 3.59}, {"text": "means it has these two features.", "start": 534.09, "duration": 2.34}, {"text": "It's in NP, and everything\nin NP is reducible to it.", "start": 536.43, "duration": 3.97}, {"text": "So first of all, SAT is in\nNP, as we've already seen.", "start": 540.4, "duration": 3.44}, {"text": "The witness that shows\nthe formula is satisfiable", "start": 543.84, "duration": 3.39}, {"text": "is simply the\nsatisfying assignment", "start": 547.23, "duration": 2.22}, {"text": "that evaluates to true.", "start": 549.45, "duration": 2.77}, {"text": "So now we're going to pick\nsome language in NP, A,", "start": 552.22, "duration": 4.43}, {"text": "and show that A is polynomial\ntime reducible to SAT.", "start": 556.65, "duration": 3.84}, {"text": "So this is going to apply\nto any language A in NP.", "start": 563.35, "duration": 2.64}, {"text": "So let A be some language in NP.", "start": 565.99, "duration": 2.49}, {"text": "It's decided by some\nnondeterministic Turing machine", "start": 568.48, "duration": 2.55}, {"text": "M in time n to the k.", "start": 571.03, "duration": 2.87}, {"text": "That's what it\nmeans to be an NP.", "start": 573.9, "duration": 2.91}, {"text": "I'm going to be ignoring\nthe constant factors when", "start": 576.81, "duration": 2.49}, {"text": "we could carry that\nthroughout the proof.", "start": 579.3, "duration": 2.1}, {"text": "It just would make\nthe description", "start": 581.4, "duration": 2.82}, {"text": "a little more\ncumbersome and wouldn't", "start": 584.22, "duration": 2.25}, {"text": "change any of the ideas.", "start": 586.47, "duration": 1.17}, {"text": "So let's just say it's M\nruns in time n to the k,", "start": 587.64, "duration": 4.02}, {"text": "and recognizes or decides\nthis language in A.", "start": 591.66, "duration": 6.0}, {"text": "So it's a\nnondeterministic machine.", "start": 597.66, "duration": 5.28}, {"text": "So we've got to give\na polynomial time", "start": 602.94, "duration": 2.04}, {"text": "reduction from A to SAT.", "start": 604.98, "duration": 1.95}, {"text": "That's what I have to\ndemonstrate to you.", "start": 606.93, "duration": 4.0}, {"text": "So what does that\nreduction look like?", "start": 610.93, "duration": 2.03}, {"text": "It's going to map strings,\nwhich may or may not", "start": 612.96, "duration": 3.3}, {"text": "be in A, to formulas, which\nmay or may not be satisfied.", "start": 616.26, "duration": 5.47}, {"text": "That's what the\nreduction has got to do.", "start": 621.73, "duration": 2.73}, {"text": "So saying that out\nmore formally is it's", "start": 624.46, "duration": 7.26}, {"text": "going to take some\nstring w and map it", "start": 631.72, "duration": 2.31}, {"text": "to a formula we'll\ncall phi sub M, w,", "start": 634.03, "duration": 2.88}, {"text": "where M is the machine that\ndecides A and w is the input.", "start": 636.91, "duration": 8.86}, {"text": "So f is going to map w\nto this formula, where", "start": 645.77, "duration": 4.14}, {"text": "the string is in the language\nexactly when the formula is", "start": 649.91, "duration": 3.39}, {"text": "satisfied.", "start": 653.3, "duration": 1.63}, {"text": "And the formula is going\nto depend upon M and w.", "start": 654.93, "duration": 2.55}, {"text": "That's why it just has--\nit's written in this way.", "start": 657.48, "duration": 2.83}, {"text": "So we've seen that\nkind of thing before.", "start": 660.31, "duration": 2.15}, {"text": "So basically, my job--", "start": 662.46, "duration": 3.3}, {"text": "we have this language\nA that's in NP.", "start": 665.76, "duration": 3.57}, {"text": "And now we have some string\nw, which might be in A,", "start": 669.33, "duration": 4.32}, {"text": "or maybe not is in A. And I have\nto quickly in polynomial time", "start": 673.65, "duration": 5.86}, {"text": "now produce a formula which is\ngoing to be satisfiable exactly", "start": 679.51, "duration": 4.96}, {"text": "when the string w is in A.", "start": 684.47, "duration": 6.17}, {"text": "So how is that\nformula going to work?", "start": 690.64, "duration": 2.63}, {"text": "How can I produce\nsuch a formula?", "start": 693.27, "duration": 2.08}, {"text": "Which I mean, of course, I don't\nknow whether w is in A or not,", "start": 695.35, "duration": 3.84}, {"text": "because I'm just the\npolynomial time reduction.", "start": 699.19, "duration": 3.21}, {"text": "And A is an NP language.", "start": 702.4, "duration": 3.06}, {"text": "So polynomial time\nprobably is not", "start": 705.46, "duration": 2.34}, {"text": "enough to solve\nwhether w is in A.", "start": 707.8, "duration": 2.94}, {"text": "So I've got to do that mapping\nwithout knowing the answer.", "start": 710.74, "duration": 7.06}, {"text": "And the idea is that--", "start": 717.8, "duration": 2.07}, {"text": "and this is where we've seen\nthings like this before--", "start": 719.87, "duration": 3.42}, {"text": "the formula we're\ngoing to construct", "start": 723.29, "duration": 2.49}, {"text": "simulates the machine on w.", "start": 725.78, "duration": 2.835}, {"text": "So in some way it's going\nto do that simulation.", "start": 731.87, "duration": 2.67}, {"text": "The trick is figuring out\nhow to-- what that means.", "start": 734.54, "duration": 3.99}, {"text": "But the interpretation\nof that formula", "start": 738.53, "duration": 4.38}, {"text": "is that in a sense describes,\nsays, in my informal language,", "start": 742.91, "duration": 5.1}, {"text": "that M accepts w.", "start": 748.01, "duration": 3.73}, {"text": "Very much like-- there's a lot\nof parallel here between this", "start": 751.74, "duration": 7.08}, {"text": "construction and, for\nexample, the construction,", "start": 758.82, "duration": 3.15}, {"text": "the PCP construction,\nwhere we made an instant--", "start": 761.97, "duration": 4.62}, {"text": "given a machine and\nan input, we made", "start": 766.59, "duration": 5.01}, {"text": "a set of those dominoes,\nwhere finding a match", "start": 771.6, "duration": 2.85}, {"text": "forced you to\nsimulate the machine.", "start": 774.45, "duration": 2.48}, {"text": "Here finding a\nsatisfying assignment", "start": 776.93, "duration": 3.003}, {"text": "is going to force you\nto simulate the machine.", "start": 779.933, "duration": 1.917}, {"text": "So the satisfying\nassignment is going", "start": 785.33, "duration": 2.01}, {"text": "to be a computation\nhistory for M on w.", "start": 787.34, "duration": 4.44}, {"text": "And I'm just going to\nwrite that computation", "start": 791.78, "duration": 1.95}, {"text": "history in a particular way.", "start": 793.73, "duration": 2.083}, {"text": "So it's going to have a somewhat\ndifferent encoding, which", "start": 795.813, "duration": 2.417}, {"text": "is going to help us to visualize\nwhat's going on better.", "start": 798.23, "duration": 3.15}, {"text": "So that's the approach.", "start": 804.08, "duration": 4.13}, {"text": "That's the basic idea\nof what we're trying", "start": 808.21, "duration": 1.75}, {"text": "to-- what we're going to do.", "start": 809.96, "duration": 1.167}, {"text": "So I'm happy to take\na minute if you have", "start": 811.127, "duration": 2.793}, {"text": "any questions about this part.", "start": 813.92, "duration": 1.86}, {"text": "But otherwise, I'll\njust move on to start", "start": 815.78, "duration": 4.11}, {"text": "doing the actual construction\nof what the formula looks like.", "start": 819.89, "duration": 3.27}, {"text": "How is it going to do that?", "start": 823.16, "duration": 1.18}, {"text": "How is that formula\ngoing to work?", "start": 824.34, "duration": 2.85}, {"text": "OK.", "start": 827.19, "duration": 0.5}, {"text": "So no questions.", "start": 827.69, "duration": 1.26}, {"text": "Hopefully, we are all together.", "start": 828.95, "duration": 5.58}, {"text": "So first of all, let me\ndescribe what my computation", "start": 834.53, "duration": 6.29}, {"text": "history is going to look like.", "start": 840.82, "duration": 1.8}, {"text": "And the situation\nis a little bit", "start": 842.62, "duration": 1.8}, {"text": "different than what we\nhad before because when", "start": 844.42, "duration": 4.332}, {"text": "we were talking about the\nPost correspondence problem", "start": 848.752, "duration": 2.208}, {"text": "we had a deterministic machine.", "start": 850.96, "duration": 2.22}, {"text": "And now our machine\nis nondeterministic.", "start": 853.18, "duration": 4.06}, {"text": "So we're going to\ncall the object--", "start": 857.24, "duration": 4.56}, {"text": "instead of an accepting\ncomputation or a computation", "start": 861.8, "duration": 3.12}, {"text": "history, we're just\ngoing to-- we're", "start": 864.92, "duration": 1.5}, {"text": "going to call it a tableau, or\nsometimes an accepting tableau", "start": 866.42, "duration": 2.97}, {"text": "if you want to emphasize\nthe accepting nature of it.", "start": 869.39, "duration": 3.33}, {"text": "But generally, we're just\ngoing to call it a tableau.", "start": 872.72, "duration": 3.18}, {"text": "So a tableau is really an\naccepting computation history", "start": 875.9, "duration": 5.07}, {"text": "for the machine on\nan accepting branch", "start": 880.97, "duration": 7.55}, {"text": "of its nondeterministic\ncomputation.", "start": 888.52, "duration": 3.86}, {"text": "So if M accepts w, it's got\nto have some accepting branch,", "start": 892.38, "duration": 7.22}, {"text": "and the tableau is going to be\nthe sequence of configurations", "start": 899.6, "duration": 5.19}, {"text": "that the machine goes through\non that accepting branch.", "start": 904.79, "duration": 3.27}, {"text": "If there are several\naccepting branches,", "start": 908.06, "duration": 1.86}, {"text": "there may be several tableaus.", "start": 909.92, "duration": 1.86}, {"text": "There will be several tableaus.", "start": 911.78, "duration": 1.71}, {"text": "So there's going\nto be one tableau", "start": 913.49, "duration": 2.28}, {"text": "for each accepting branch of\nthe machine's computation on w.", "start": 915.77, "duration": 6.13}, {"text": "If the machine does not accept\nw, there won't be any tableaus.", "start": 921.9, "duration": 4.65}, {"text": "And so the whole\npoint is that we're", "start": 926.55, "duration": 2.94}, {"text": "going to make our formula\nrepresent the statement", "start": 929.49, "duration": 6.29}, {"text": "that there is a tableau.", "start": 935.78, "duration": 3.59}, {"text": "And satisfying that\nformula is going", "start": 939.37, "duration": 1.98}, {"text": "to correspond to filling out the\nsymbols in the tableau to make", "start": 941.35, "duration": 5.4}, {"text": "it a tableau.", "start": 946.75, "duration": 2.16}, {"text": "So here is a tableau.", "start": 948.91, "duration": 2.64}, {"text": "So a tableau is just, again, an\naccepting computation history", "start": 951.55, "duration": 4.41}, {"text": "on some branch, some accepting\nbranch of the machine's", "start": 955.96, "duration": 3.48}, {"text": "computation.", "start": 959.44, "duration": 2.85}, {"text": "The rows are the--", "start": 962.29, "duration": 1.35}, {"text": "instead of writing the\ncomputation history", "start": 963.64, "duration": 3.45}, {"text": "out linearly, we're going to\nrepresent it in a table form", "start": 967.09, "duration": 4.08}, {"text": "where each configuration is\ngoing to be on a separate row.", "start": 971.17, "duration": 5.62}, {"text": "Now, the dimensions\nof that table", "start": 976.79, "duration": 2.43}, {"text": "are going to be n to\nthe k by n to the k,", "start": 979.22, "duration": 3.86}, {"text": "because the machine runs\nfor n to the k steps.", "start": 983.08, "duration": 7.42}, {"text": "So there's going to-- if\nthere's an accepting branch,", "start": 990.5, "duration": 3.2}, {"text": "it's going to accept within\nthat number of steps.", "start": 993.7, "duration": 2.91}, {"text": "And we'll have enough\nrows here to write down", "start": 996.61, "duration": 2.76}, {"text": "all of the configurations that\nthe machine goes through one", "start": 999.37, "duration": 3.03}, {"text": "after the next, row by\nrow, each one having", "start": 1002.4, "duration": 3.06}, {"text": "a configuration in it.", "start": 1005.46, "duration": 3.56}, {"text": "And then at the bottom,\nthere'll be an accept.", "start": 1009.02, "duration": 3.67}, {"text": "Minor detail, if the\nmachine accepts earlier,", "start": 1012.69, "duration": 3.3}, {"text": "we'll just say the\nmachine stays in the--", "start": 1015.99, "duration": 2.01}, {"text": "once it enters an\naccept, the machine", "start": 1018.0, "duration": 3.3}, {"text": "does not change\nfrom that point on.", "start": 1021.3, "duration": 2.17}, {"text": "So the rule of the machine\nis nothing changes.", "start": 1023.47, "duration": 2.629}, {"text": "And it just remains in the same\nconfiguration from that point", "start": 1026.099, "duration": 2.73}, {"text": "on.", "start": 1028.829, "duration": 0.5}, {"text": "So important to understand what\nwe're-- if you're not following", "start": 1033.47, "duration": 5.67}, {"text": "what I mean by a tableau,\nyou're doomed for this lecture.", "start": 1039.14, "duration": 4.66}, {"text": "So it makes sense for\nyou to ask a question", "start": 1043.8, "duration": 5.63}, {"text": "to understand what\nwe mean by tableau.", "start": 1049.43, "duration": 4.38}, {"text": "So just a few more\nelements here.", "start": 1053.81, "duration": 2.41}, {"text": "So this is going to be the\nstart configuration for M on w.", "start": 1056.22, "duration": 2.733}, {"text": "This would be an\naccepting configuration", "start": 1058.953, "duration": 1.667}, {"text": "here down at the very last row.", "start": 1060.62, "duration": 3.75}, {"text": "And you might imagine--", "start": 1064.37, "duration": 2.13}, {"text": "I think I've filled out\nsome hypothetical first step", "start": 1066.5, "duration": 6.77}, {"text": "of the machine after the start\nwhere maybe the machine was--", "start": 1073.27, "duration": 5.43}, {"text": "when it's in-- remember how\nwe encoded our configurations.", "start": 1078.7, "duration": 4.36}, {"text": "So this is the machine\nis in state q0,", "start": 1083.06, "duration": 2.93}, {"text": "looking at the w, the first\nsymbol of the input, w1.", "start": 1085.99, "duration": 3.9}, {"text": "And maybe when it's in q0\nlooking at that first symbol,", "start": 1089.89, "duration": 4.62}, {"text": "it moves to state q7,\nand goes right, and then", "start": 1094.51, "duration": 4.83}, {"text": "changes that w1 to an A. And\nso now here is the head shown", "start": 1099.34, "duration": 5.62}, {"text": "moved one position to the\nright in the new state q7.", "start": 1104.96, "duration": 3.72}, {"text": "I mean, of course,\nthat depends on what", "start": 1108.68, "duration": 1.89}, {"text": "the machine is designed to do,\nwhat the transition function", "start": 1110.57, "duration": 3.16}, {"text": "is.", "start": 1113.73, "duration": 0.5}, {"text": "But this possibly\nis what happens.", "start": 1114.23, "duration": 5.2}, {"text": "So does the--", "start": 1119.43, "duration": 1.25}, {"text": "OK, so good.", "start": 1120.68, "duration": 0.96}, {"text": "Does the tableau trace\nall steps of all branches?", "start": 1121.64, "duration": 3.18}, {"text": "No.", "start": 1124.82, "duration": 1.17}, {"text": "The tableau corresponds\nto one accepting branch.", "start": 1125.99, "duration": 5.67}, {"text": "Each different\naccepting branch is", "start": 1131.66, "duration": 1.95}, {"text": "going to have its own tableau.", "start": 1133.61, "duration": 1.35}, {"text": "So there might be several\ndifferent ways of filling out", "start": 1134.96, "duration": 2.46}, {"text": "that second row even.", "start": 1137.42, "duration": 1.02}, {"text": "Of course, the first row is\ngoing to be-- in any tableau,", "start": 1138.44, "duration": 3.03}, {"text": "it's got to be the same.", "start": 1141.47, "duration": 2.55}, {"text": "Once I know w--", "start": 1144.02, "duration": 2.76}, {"text": "here I've written down--", "start": 1146.78, "duration": 1.32}, {"text": "maybe I should\nunpack this for you.", "start": 1148.1, "duration": 2.07}, {"text": "It's in the start state here,\nthen here are the first--", "start": 1150.17, "duration": 3.24}, {"text": "here are n symbols of\nw, w's of length n.", "start": 1153.41, "duration": 3.27}, {"text": "So there's w1, w2, up to wn.", "start": 1156.68, "duration": 2.55}, {"text": "And then I'm padding out\nthe rest with blanks.", "start": 1159.23, "duration": 3.95}, {"text": "So I should have said that, too.", "start": 1163.18, "duration": 1.59}, {"text": "But OK.", "start": 1164.77, "duration": 1.53}, {"text": "So I want to make my table\nn to the k by n to the k", "start": 1166.3, "duration": 3.09}, {"text": "because that's going to\nbe enough to represent", "start": 1169.39, "duration": 3.48}, {"text": "the entire--", "start": 1172.87, "duration": 2.73}, {"text": "all of these configurations of\nM running for most n to the k", "start": 1175.6, "duration": 6.15}, {"text": "steps, because the machine,\neven if it sends its head", "start": 1181.75, "duration": 5.91}, {"text": "moving to the right as\nfast as it possibly can,", "start": 1187.66, "duration": 3.82}, {"text": "it's never going to have--", "start": 1191.48, "duration": 2.06}, {"text": "it's never going to\ngo outside this box", "start": 1193.54, "duration": 5.56}, {"text": "if it only runs for\nn to the k steps.", "start": 1199.1, "duration": 2.02}, {"text": "So this is going\nto be big enough", "start": 1201.12, "duration": 1.4}, {"text": "to represent the entire\ncomputation of M.", "start": 1202.52, "duration": 2.865}, {"text": "So it means running\nfor n to the k time.", "start": 1205.385, "duration": 3.075}, {"text": "And the input w is of length n.", "start": 1208.46, "duration": 4.55}, {"text": "All right.", "start": 1213.01, "duration": 1.5}, {"text": "What is k?", "start": 1214.51, "duration": 0.66}, {"text": "So k is the running\ntime of the machine.", "start": 1215.17, "duration": 2.19}, {"text": "So we assumed from the previous\nslide that M runs in time n", "start": 1217.36, "duration": 4.36}, {"text": "to the k.", "start": 1221.72, "duration": 0.5}, {"text": "OK.", "start": 1225.365, "duration": 0.5}, {"text": "So a good question here.", "start": 1231.7, "duration": 1.23}, {"text": "How can the tableau\nbe a square table", "start": 1232.93, "duration": 2.22}, {"text": "if we have a low number\nof computation histories,", "start": 1235.15, "duration": 2.4}, {"text": "but a lot of tape?", "start": 1237.55, "duration": 3.04}, {"text": "Well, the low number computation\nhistory, that's a problem.", "start": 1240.59, "duration": 3.66}, {"text": "You're not saying that well.", "start": 1244.25, "duration": 1.44}, {"text": "You know, each\ncomputation history", "start": 1245.69, "duration": 3.81}, {"text": "is in a different table.", "start": 1249.5, "duration": 2.2}, {"text": "So this, I'm representing a\nsingle computation history", "start": 1251.7, "duration": 2.45}, {"text": "here.", "start": 1254.15, "duration": 0.55}, {"text": "There may be-- there are going\nto be many configurations.", "start": 1254.7, "duration": 4.55}, {"text": "So I can't have a small\nnumber of configurations", "start": 1259.25, "duration": 2.39}, {"text": "using a lot of tape,\nbecause I can only", "start": 1261.64, "duration": 3.69}, {"text": "use one more cell, one\nadditional tape cell each time", "start": 1265.33, "duration": 3.69}, {"text": "I--", "start": 1269.02, "duration": 1.275}, {"text": "each additional\nstep of the machine.", "start": 1270.295, "duration": 1.5}, {"text": "Yeah.", "start": 1274.36, "duration": 0.54}, {"text": "So there's really no\ndifference between this.", "start": 1274.9, "duration": 2.07}, {"text": "If you want to think of this\nas a computation history,", "start": 1276.97, "duration": 2.25}, {"text": "that's fine.", "start": 1279.22, "duration": 0.9}, {"text": "This is really just the\nstandard terminology", "start": 1280.12, "duration": 2.04}, {"text": "that's used when you're proving\nthis particular theorem.", "start": 1282.16, "duration": 4.797}, {"text": "Typically people talk\nabout it as a tableau,", "start": 1286.957, "duration": 1.833}, {"text": "but it's really just\na computation history.", "start": 1288.79, "duration": 1.792}, {"text": "The q state--", "start": 1295.45, "duration": 0.69}, {"text": "I mean, the question about\nwhat are these states' q,", "start": 1296.14, "duration": 3.69}, {"text": "this is the way we\nrepresent configurations.", "start": 1299.83, "duration": 2.85}, {"text": "So this means the\nmachine is in a state.", "start": 1302.68, "duration": 4.123}, {"text": "They're not all going\ndown the diagonal.", "start": 1306.803, "duration": 1.667}, {"text": "The states are going to zigzag\nhere through this picture", "start": 1308.47, "duration": 4.05}, {"text": "here, depending upon how the\nhead of the machine moves.", "start": 1312.52, "duration": 3.77}, {"text": "So you have to go\nback and review", "start": 1316.29, "duration": 1.41}, {"text": "how we represent the\nconfigurations of the machine.", "start": 1317.7, "duration": 2.67}, {"text": "Remember the configuration\nis a snapshot of the machine", "start": 1320.37, "duration": 3.24}, {"text": "at a given point.", "start": 1323.61, "duration": 0.81}, {"text": "How do we know that M\nruns in polynomial time?", "start": 1327.703, "duration": 1.917}, {"text": "We're assuming M\nruns in polynomial.", "start": 1329.62, "duration": 2.1}, {"text": "We started off with a\nlanguage that's in NP.", "start": 1331.72, "duration": 4.32}, {"text": "So it's a nondeterministic\npolynomial time machine,", "start": 1336.04, "duration": 3.75}, {"text": "and we're picking one\nbranch that accepts", "start": 1339.79, "duration": 3.78}, {"text": "and writing down all the\nsequence of configurations", "start": 1343.57, "duration": 2.138}, {"text": "the machine goes through.", "start": 1345.708, "duration": 1.042}, {"text": "Let's move on.", "start": 1346.75, "duration": 1.02}, {"text": "And maybe ask more questions\nas they come to you,", "start": 1347.77, "duration": 3.96}, {"text": "and I'll pick out some\nto answer if that's", "start": 1351.73, "duration": 2.965}, {"text": "going to be helpful to others.", "start": 1354.695, "duration": 1.25}, {"text": "So we're going to now\nconstruct this formula", "start": 1361.49, "duration": 9.61}, {"text": "to say that M accepts w.", "start": 1371.1, "duration": 1.65}, {"text": "Again, that was what we--", "start": 1372.75, "duration": 1.544}, {"text": "that's our goal.", "start": 1374.294, "duration": 1.696}, {"text": "And it says that a\ntableau for M on w exists.", "start": 1375.99, "duration": 2.865}, {"text": "And basically what\nthat means is we", "start": 1382.73, "duration": 2.01}, {"text": "want to say that it starts\nright, it ends right,", "start": 1384.74, "duration": 3.3}, {"text": "and everything in\nbetween is right,", "start": 1388.04, "duration": 3.09}, {"text": "and then we're going to need\nsome other stuff to talk", "start": 1391.13, "duration": 2.28}, {"text": "about how we're going to be\nencoding those symbols using", "start": 1393.41, "duration": 3.21}, {"text": "Boolean variables.", "start": 1396.62, "duration": 1.63}, {"text": "So those are going\nto be the four parts.", "start": 1398.25, "duration": 2.04}, {"text": "Here's the start.", "start": 1400.29, "duration": 0.75}, {"text": "It starts right.", "start": 1401.04, "duration": 1.01}, {"text": "Here it ends right.", "start": 1402.05, "duration": 1.29}, {"text": "Here it moves right.", "start": 1403.34, "duration": 1.32}, {"text": "And here it talks about\nthe encoding of the symbols", "start": 1404.66, "duration": 2.73}, {"text": "into Boolean variables.", "start": 1407.39, "duration": 3.43}, {"text": "So those are the four\nparts of this formula", "start": 1410.82, "duration": 3.08}, {"text": "that I'm going to describe.", "start": 1413.9, "duration": 1.125}, {"text": "I hope you got your\nquestion answered", "start": 1418.71, "duration": 2.25}, {"text": "as to why the total number\nof columns is n to the k,", "start": 1420.96, "duration": 2.88}, {"text": "because it's just big\nenough to fit the entire--", "start": 1423.84, "duration": 3.27}, {"text": "all configurations\nthat the machine", "start": 1427.11, "duration": 2.19}, {"text": "is running for at\nmost n to the k", "start": 1429.3, "duration": 1.83}, {"text": "steps, which is\nwhat we're assuming.", "start": 1431.13, "duration": 2.29}, {"text": "OK.", "start": 1436.97, "duration": 0.5}, {"text": "So now just getting\nback to that,", "start": 1437.47, "duration": 2.94}, {"text": "I'm going to describe these\ndifferent components now", "start": 1440.41, "duration": 2.988}, {"text": "on separate slides.", "start": 1443.398, "duration": 0.792}, {"text": "Let me start out with this\ncomponent phi cell, which", "start": 1448.03, "duration": 3.36}, {"text": "is sort of the most\nfundamental one", "start": 1451.39, "duration": 1.687}, {"text": "because it talks\nabout how we're going", "start": 1453.077, "duration": 1.583}, {"text": "to be encoding those symbols\nof the tableau into the Boolean", "start": 1454.66, "duration": 6.0}, {"text": "variables.", "start": 1460.66, "duration": 0.72}, {"text": "So again, here's kind of the\npicture to have in mind of this", "start": 1465.07, "duration": 3.06}, {"text": "tableau, this n to the\nk by n to the k table,", "start": 1468.13, "duration": 3.95}, {"text": "representing some accepting\nbranch of the machine's", "start": 1472.08, "duration": 6.6}, {"text": "computation if there is one.", "start": 1478.68, "duration": 4.15}, {"text": "And so now let me draw\none of the cells here.", "start": 1482.83, "duration": 6.12}, {"text": "I'm going to magnify it.", "start": 1488.95, "duration": 2.41}, {"text": "So this is the i, j cell here.", "start": 1491.36, "duration": 4.44}, {"text": "And I'm going to--", "start": 1495.8, "duration": 2.24}, {"text": "there are going\nto be a collection", "start": 1498.04, "duration": 4.48}, {"text": "of Boolean variables associated\nwith each one of the cells.", "start": 1502.52, "duration": 4.805}, {"text": "So each one of\nthe cells is going", "start": 1507.325, "duration": 1.375}, {"text": "to have a bunch of\nvariables all to itself.", "start": 1508.7, "duration": 4.38}, {"text": "And those are going to be\nbasically indicator variables.", "start": 1513.08, "duration": 2.93}, {"text": "They're going to\nindicate which symbol", "start": 1516.01, "duration": 2.94}, {"text": "that cell gets to have in it.", "start": 1518.95, "duration": 5.16}, {"text": "So again, picture here--", "start": 1524.11, "duration": 3.81}, {"text": "in this tableau,\nwe don't know how", "start": 1527.92, "duration": 2.072}, {"text": "it's going to get filled out.", "start": 1529.992, "duration": 1.208}, {"text": "But however it gets filled\nout, each one of these cells", "start": 1531.2, "duration": 3.65}, {"text": "gets some symbol.", "start": 1534.85, "duration": 1.275}, {"text": "And that symbol could\neither be a tape alphabet", "start": 1538.622, "duration": 1.958}, {"text": "symbol, or a symbol\nrepresenting a state.", "start": 1540.58, "duration": 3.95}, {"text": "That's the way we do\nour configurations.", "start": 1544.53, "duration": 2.2}, {"text": "So it could be a\ntape alphabet symbol", "start": 1546.73, "duration": 1.67}, {"text": "here showing the magnification.", "start": 1548.4, "duration": 4.68}, {"text": "Maybe it's the tape\nalphabet symbol, which", "start": 1553.08, "duration": 1.75}, {"text": "represents the blank symbol.", "start": 1554.83, "duration": 2.64}, {"text": "Or maybe it's\nrepresents some state.", "start": 1557.47, "duration": 2.97}, {"text": "Now, how am I going to\nencode that with variables?", "start": 1563.5, "duration": 3.7}, {"text": "So this-- let me--", "start": 1567.2, "duration": 3.19}, {"text": "this is the collection\nof variables", "start": 1570.39, "duration": 1.89}, {"text": "that's going to apply to the\nentire formula phi sub M, w.", "start": 1572.28, "duration": 4.381}, {"text": "Each cell is-- so\neach cell i, j is", "start": 1580.27, "duration": 3.78}, {"text": "going to have a\nset of variables,", "start": 1584.05, "duration": 3.57}, {"text": "one for each\npossible symbol sigma", "start": 1587.62, "duration": 5.88}, {"text": "that's in the configuration\nalphabet, namely a tape", "start": 1593.5, "duration": 5.58}, {"text": "symbol or a state symbol.", "start": 1599.08, "duration": 2.37}, {"text": "So I'm going to have--", "start": 1607.45, "duration": 2.63}, {"text": "well, maybe this will become\nclear as I'm writing it.", "start": 1610.08, "duration": 2.86}, {"text": "So if I turn the variable x\ni, j, sigma equal to true,", "start": 1612.94, "duration": 9.0}, {"text": "that's just a way of saying\nthat cell i, j contains a sigma.", "start": 1621.94, "duration": 4.61}, {"text": "So if I have x i, j, a, that\nmeans the symbol contains an a.", "start": 1626.55, "duration": 5.91}, {"text": "So I'm going to illustrate\nthat now for you.", "start": 1632.46, "duration": 2.65}, {"text": "So imagine you have\nlights representing all", "start": 1635.11, "duration": 4.28}, {"text": "the different x i, j's\nfor the different sigmas.", "start": 1639.39, "duration": 6.375}, {"text": "Didn't say that well.", "start": 1645.765, "duration": 0.875}, {"text": "So we're in cell i, j.", "start": 1646.64, "duration": 3.48}, {"text": "So these are all\nx i, j variables.", "start": 1650.12, "duration": 2.4}, {"text": "They're all x i,\nj sigma variables", "start": 1652.52, "duration": 1.95}, {"text": "for the different sigmas\nthat can go in this cell.", "start": 1654.47, "duration": 6.43}, {"text": "So all different\npossible sigmas.", "start": 1660.9, "duration": 1.88}, {"text": "So this is gamma union Q.", "start": 1662.78, "duration": 5.08}, {"text": "So now if I have an A\nhere in that cell, so then", "start": 1667.86, "duration": 10.41}, {"text": "the variable x i, j, a is true.", "start": 1678.27, "duration": 5.25}, {"text": "And just helping\nyou visualize that,", "start": 1683.52, "duration": 2.76}, {"text": "that's going to correspond\nto turning the light on.", "start": 1686.28, "duration": 2.437}, {"text": "There's going to be\na light associated", "start": 1688.717, "duration": 1.583}, {"text": "with each one of\nthese variables.", "start": 1690.3, "duration": 1.375}, {"text": "And it's going to be turned\non when that variable is true.", "start": 1691.675, "duration": 3.985}, {"text": "Similarly, if I have\nthe blank symbol", "start": 1695.66, "duration": 3.68}, {"text": "is the thing that\ngoes in that cell,", "start": 1699.34, "duration": 3.09}, {"text": "then that variable\ngets turned on.", "start": 1702.43, "duration": 1.763}, {"text": "I hope you can see it.", "start": 1704.193, "duration": 0.917}, {"text": "Maybe it's a little bit\nsmall on your screen.", "start": 1705.11, "duration": 3.71}, {"text": "The x i, j blank,\na variable is true.", "start": 1708.82, "duration": 4.08}, {"text": "And similarly, if it's q7 here,\nthe x i, j q7 variable is true.", "start": 1712.9, "duration": 6.65}, {"text": "So that's the way we're\ngoing to be encoding", "start": 1719.55, "duration": 2.91}, {"text": "the contents of these\ncells using these indicator", "start": 1722.46, "duration": 4.26}, {"text": "variables.", "start": 1726.72, "duration": 1.89}, {"text": "And now we have to start making\nsome Boolean logic to make sure", "start": 1728.61, "duration": 5.88}, {"text": "that those variables reasonably\nrepresent the cell con--", "start": 1734.49, "duration": 6.65}, {"text": "the contents of these cells.", "start": 1741.14, "duration": 1.545}, {"text": "So for example, what\nwould be the first thing", "start": 1742.685, "duration": 1.875}, {"text": "that comes to your mind?", "start": 1744.56, "duration": 2.82}, {"text": "Well, we better not\nhave two lights going on", "start": 1747.38, "duration": 4.213}, {"text": "in any one of the\ncells, because then we", "start": 1751.593, "duration": 1.667}, {"text": "have two symbols in that cell.", "start": 1753.26, "duration": 1.26}, {"text": "And that's not allowed.", "start": 1754.52, "duration": 1.303}, {"text": "Each cell is going-- we want\neach cell to have exactly one", "start": 1755.823, "duration": 2.417}, {"text": "symbol.", "start": 1758.24, "duration": 0.66}, {"text": "And that corresponds\nto each cell having", "start": 1758.9, "duration": 2.97}, {"text": "exactly one of its\nlights turned on,", "start": 1761.87, "duration": 1.86}, {"text": "or equivalently,\neach cell should", "start": 1763.73, "duration": 2.07}, {"text": "have exactly one of\nthe variables be true.", "start": 1765.8, "duration": 4.0}, {"text": "That's the very first\npart of the formula", "start": 1769.8, "duration": 1.94}, {"text": "is just going to say that.", "start": 1771.74, "duration": 1.23}, {"text": "So let me show you\nwhat that looks like.", "start": 1772.97, "duration": 2.61}, {"text": "So here we're talking\nabout this phi cell.", "start": 1778.84, "duration": 2.31}, {"text": "It says that there's exactly\none light on per cell,", "start": 1781.15, "duration": 3.57}, {"text": "or in other words,\nexactly one of the x i,", "start": 1784.72, "duration": 2.647}, {"text": "j sigmas is true for each i, j.", "start": 1787.367, "duration": 2.375}, {"text": "So this is how I'm going\nto actually express", "start": 1796.15, "duration": 2.25}, {"text": "that using my Boolean formula.", "start": 1798.4, "duration": 2.73}, {"text": "I'm sort of color coding\nthe different parts", "start": 1804.657, "duration": 1.833}, {"text": "of the formula, which I'm\nwriting out to you here", "start": 1806.49, "duration": 2.042}, {"text": "in English.", "start": 1808.532, "duration": 1.018}, {"text": "So first, I want to say this.", "start": 1809.55, "duration": 1.53}, {"text": "So in every cell, there's at\nleast one light that's on,", "start": 1811.08, "duration": 3.69}, {"text": "and there's at most\none light that's on.", "start": 1814.77, "duration": 1.83}, {"text": "So here's the green part.", "start": 1819.32, "duration": 1.64}, {"text": "This is going to say at\nleast one light is on.", "start": 1820.96, "duration": 2.07}, {"text": "So I'm going to say that\nby taking all of the var--", "start": 1823.03, "duration": 4.26}, {"text": "all of the symbols that\ncan appear in that cell,", "start": 1827.29, "duration": 4.62}, {"text": "and taking an OR over all of\nthose different associated", "start": 1831.91, "duration": 5.13}, {"text": "variables.", "start": 1837.04, "duration": 1.33}, {"text": "So it's either got\nthe first symbol on,", "start": 1838.37, "duration": 1.91}, {"text": "or the second symbol is\nthere, or dot dot dot,", "start": 1840.28, "duration": 3.9}, {"text": "or the last symbol is there.", "start": 1844.18, "duration": 1.23}, {"text": "One of those has\ngot to be there.", "start": 1845.41, "duration": 2.26}, {"text": "I'm going to write this\nusing my big OR notation.", "start": 1847.67, "duration": 5.12}, {"text": "So for sigma appearing in\nthis set of possibilities,", "start": 1852.79, "duration": 5.78}, {"text": "one of those variables\nhas got to be on at least.", "start": 1858.57, "duration": 4.01}, {"text": "That's what this\nbig OR tells you.", "start": 1862.58, "duration": 2.83}, {"text": "Now we want to make sure that\nthere's at most one that's on.", "start": 1865.41, "duration": 4.65}, {"text": "So that there are not--", "start": 1870.06, "duration": 1.32}, {"text": "there's at least one on, but\nthere are not two that are on.", "start": 1871.38, "duration": 4.5}, {"text": "So I'm going to have an\nadditional part of the formula", "start": 1875.88, "duration": 3.78}, {"text": "here, which says--", "start": 1879.66, "duration": 1.71}, {"text": "and I hope you can read this.", "start": 1881.37, "duration": 2.036}, {"text": "It's a little small.", "start": 1883.406, "duration": 3.454}, {"text": "If I have two different\nsymbols, sigma and tau,", "start": 1886.86, "duration": 6.88}, {"text": "that are configuration--", "start": 1893.74, "duration": 2.91}, {"text": "possible configuration symbols,\nwhere sigma and tau are not", "start": 1896.65, "duration": 3.18}, {"text": "equal.", "start": 1899.83, "duration": 0.58}, {"text": "So that's I'm\nreading it out to you", "start": 1900.41, "duration": 1.46}, {"text": "if it's too small\nfor your screen.", "start": 1901.87, "duration": 3.12}, {"text": "Then I'm going to say\nit's not possible.", "start": 1904.99, "duration": 2.59}, {"text": "So I have the negation of x\ni, j sigma, and x i, j tau.", "start": 1907.58, "duration": 4.91}, {"text": "So saying it another\nway, it's not the case", "start": 1912.49, "duration": 4.23}, {"text": "that that cell contains both\nsigma and tau for any two", "start": 1916.72, "duration": 4.98}, {"text": "symbols sigma and tau as\nlong as they're different.", "start": 1921.7, "duration": 5.09}, {"text": "And we want to take these two\nformulas and add them together.", "start": 1926.79, "duration": 3.49}, {"text": "And this tells me\nin the cell i, j,", "start": 1930.28, "duration": 4.87}, {"text": "there's exactly one of\nthe variables is true.", "start": 1935.15, "duration": 3.3}, {"text": "Exactly one of the lights is on.", "start": 1938.45, "duration": 1.68}, {"text": "And that's going\nto represent which", "start": 1940.13, "duration": 2.07}, {"text": "symbol goes into that cell.", "start": 1942.2, "duration": 2.39}, {"text": "And then I want to take the\nAND over all possible cells", "start": 1944.59, "duration": 4.05}, {"text": "to make sure that I'm going\nto now apply that everywhere.", "start": 1948.64, "duration": 4.94}, {"text": "And so now I do an AND for i\nand j ranging between 1 and n", "start": 1953.58, "duration": 4.34}, {"text": "to the k to apply this logic\nthroughout the picture.", "start": 1957.92, "duration": 4.485}, {"text": "Yeah.", "start": 1965.55, "duration": 0.5}, {"text": "Sigma unions--\nasking sigma union Q", "start": 1966.05, "duration": 3.03}, {"text": "contains the input, output, yes.", "start": 1969.08, "duration": 2.61}, {"text": "This is not a sigma.", "start": 1971.69, "duration": 0.84}, {"text": "This is a gamma.", "start": 1972.53, "duration": 2.01}, {"text": "Gamma is the tape alphabet.", "start": 1974.54, "duration": 1.53}, {"text": "This is any symbol, including\nan input symbol, from sigma", "start": 1976.07, "duration": 4.92}, {"text": "is going to be in gamma.", "start": 1980.99, "duration": 2.29}, {"text": "So this is any symbol\ncan appear on the tape.", "start": 1983.28, "duration": 2.71}, {"text": "And this expression here, that\nis the expression phi sub cell.", "start": 1990.35, "duration": 7.08}, {"text": "So here's a little\ncheck-in for you.", "start": 1997.43, "duration": 2.19}, {"text": "But maybe before we\njump into the check-in,", "start": 1999.62, "duration": 2.22}, {"text": "let's just make sure--", "start": 2001.84, "duration": 1.59}, {"text": "it may be better to\ntake some questions,", "start": 2003.43, "duration": 2.64}, {"text": "and then we can ask\nthe check-in for you.", "start": 2006.07, "duration": 5.748}, {"text": "Do you understand?", "start": 2011.818, "duration": 1.302}, {"text": "I mean, if you're\nnot getting this,", "start": 2013.12, "duration": 4.27}, {"text": "you should try to figure\nout how to get it,", "start": 2017.39, "duration": 4.82}, {"text": "because this is really\njust the foundation.", "start": 2022.21, "duration": 3.78}, {"text": "It only gets more--", "start": 2025.99, "duration": 1.763}, {"text": "it is not a very\ncomplicated proof", "start": 2027.753, "duration": 1.417}, {"text": "once you sort of get the\nidea of what's going on,", "start": 2029.17, "duration": 2.042}, {"text": "but if you're not\ngetting this part,", "start": 2031.212, "duration": 1.798}, {"text": "you won't be able\nto get the rest.", "start": 2033.01, "duration": 1.71}, {"text": "OK.", "start": 2041.31, "duration": 0.5}, {"text": "I have no idea what the--\nwhat that means, but I'll", "start": 2041.81, "duration": 2.85}, {"text": "read it out to you guys.", "start": 2044.66, "duration": 1.41}, {"text": "This looks like a one-hot tensor\nencoding, same from common--", "start": 2046.07, "duration": 3.87}, {"text": "same form commonly used in ML.", "start": 2049.94, "duration": 2.699}, {"text": "OK.", "start": 2052.639, "duration": 2.341}, {"text": "It's just an indicate--", "start": 2054.98, "duration": 0.967}, {"text": "I would just call them\nindicator variables.", "start": 2055.947, "duration": 1.792}, {"text": "Why is it sigma union\nQ for the big AND here?", "start": 2063.42, "duration": 3.989}, {"text": "Sigma union Q?", "start": 2070.179, "duration": 1.921}, {"text": "You mean gamma union Q?", "start": 2072.1, "duration": 2.349}, {"text": "[GASPING]", "start": 2074.449, "duration": 0.5}, {"text": "This is wrong.", "start": 2074.949, "duration": 1.98}, {"text": "OK.", "start": 2076.929, "duration": 1.091}, {"text": "Now I understand why\neverybody is upset.", "start": 2078.02, "duration": 2.21}, {"text": "This should be a\ngamma, not a sigma.", "start": 2080.23, "duration": 3.77}, {"text": "There's a boo-boo.", "start": 2084.0, "duration": 1.699}, {"text": "Sorry about that.", "start": 2085.699, "duration": 1.252}, {"text": "I don't know if I can\nfix that without breaking", "start": 2086.951, "duration": 1.958}, {"text": "the whole slide, so I'm\nnot going to even try.", "start": 2088.909, "duration": 2.551}, {"text": "This symbol here should\nbe gamma, not sigma.", "start": 2091.46, "duration": 3.42}, {"text": "It's a typo.", "start": 2094.88, "duration": 1.668}, {"text": "Thanks for catching that.", "start": 2096.548, "duration": 1.042}, {"text": "Yes.", "start": 2104.8, "duration": 0.75}, {"text": "So the question is--", "start": 2105.55, "duration": 3.12}, {"text": "OK.", "start": 2108.67, "duration": 0.57}, {"text": "So phi sub cell is just\ntrying to make sure", "start": 2109.24, "duration": 8.0}, {"text": "that the encoding represents\nsetting a bunch of symbols", "start": 2117.24, "duration": 4.74}, {"text": "into the tableau.", "start": 2121.98, "duration": 1.32}, {"text": "Not-- so each cell is\ngoing to have one symbol", "start": 2123.3, "duration": 2.94}, {"text": "exactly, not two, not zero.", "start": 2126.24, "duration": 3.57}, {"text": "So that's what phi sub--", "start": 2129.81, "duration": 1.17}, {"text": "if you've satisfied, if\nyou've set the variables", "start": 2130.98, "duration": 3.15}, {"text": "to satisfy phi sub\ncell, then there's", "start": 2134.13, "duration": 2.97}, {"text": "going to be one\nsymbol on in each--", "start": 2137.1, "duration": 2.97}, {"text": "one symbol in each\nof those cells.", "start": 2140.07, "duration": 3.3}, {"text": "Now, another question,\nthis is not a CNF.", "start": 2143.37, "duration": 2.61}, {"text": "No, this is not a CNF.", "start": 2145.98, "duration": 1.74}, {"text": "That's the second half\nof-- that's going to be--", "start": 2147.72, "duration": 2.82}, {"text": "I hope we don't run out of time.", "start": 2150.54, "duration": 1.47}, {"text": "But I have a way of converting\ngeneral SAT formulas to CNFs", "start": 2152.01, "duration": 6.66}, {"text": "and preserving satisfiability.", "start": 2158.67, "duration": 1.6}, {"text": "So we're going to do\nthat reduction afterward.", "start": 2160.27, "duration": 2.308}, {"text": "Here's a little check\nto see if you understand", "start": 2168.21, "duration": 3.3}, {"text": "at some level what's going on.", "start": 2171.51, "duration": 2.07}, {"text": "How many variables does\nthis formula actually have?", "start": 2177.68, "duration": 4.34}, {"text": "Is order n?", "start": 2185.0, "duration": 1.01}, {"text": "Order n square?", "start": 2186.01, "duration": 1.36}, {"text": "n to the k?", "start": 2187.37, "duration": 1.55}, {"text": "Remember, k is the running\ntime of the machine.", "start": 2188.92, "duration": 3.66}, {"text": "Or n to the 2k?", "start": 2192.58, "duration": 2.3}, {"text": "What do you think?", "start": 2194.88, "duration": 2.02}, {"text": "So I mean, for how\nmany variables.", "start": 2196.9, "duration": 3.72}, {"text": "I mean that in all of\nphi sub M. How many", "start": 2200.62, "duration": 5.58}, {"text": "variables do we have all\ntogether in this formula", "start": 2206.2, "duration": 4.018}, {"text": "if that's what the question is.", "start": 2210.218, "duration": 1.292}, {"text": "And here are the variables.", "start": 2216.68, "duration": 1.96}, {"text": "So describing them\nhere-- x i, j, sigma.", "start": 2218.64, "duration": 3.89}, {"text": "OK.", "start": 2222.53, "duration": 0.84}, {"text": "I'm going to close this.", "start": 2223.37, "duration": 2.25}, {"text": "So pick something.", "start": 2225.62, "duration": 2.65}, {"text": "All right.", "start": 2228.27, "duration": 0.69}, {"text": "Ending polling, 1, 2, 3.", "start": 2228.96, "duration": 4.23}, {"text": "OK.", "start": 2233.19, "duration": 1.54}, {"text": "Yeah.", "start": 2234.73, "duration": 0.5}, {"text": "OK.", "start": 2241.43, "duration": 0.5}, {"text": "That's a good question.", "start": 2241.93, "duration": 1.87}, {"text": "So first of all,\nthe correct answer", "start": 2243.8, "duration": 1.91}, {"text": "is, in fact, D. It's\norder n to the 2k.", "start": 2245.71, "duration": 3.57}, {"text": "Now, I'm getting\nsome questions about,", "start": 2249.28, "duration": 4.66}, {"text": "what about the size\nof gamma and Q?", "start": 2253.94, "duration": 3.42}, {"text": "Well, those are\ngoing to be fixed.", "start": 2257.36, "duration": 3.3}, {"text": "They depend only on the machine,\nbut they don't depend on n.", "start": 2260.66, "duration": 5.16}, {"text": "So thinking about it\nfunctionally in terms of n,", "start": 2265.82, "duration": 3.72}, {"text": "that's going to be a\nconstant multiplier.", "start": 2269.54, "duration": 4.78}, {"text": "And so it's going to be\nabsorbed within the big O.", "start": 2274.32, "duration": 5.24}, {"text": "So that's why we have--", "start": 2279.56, "duration": 4.314}, {"text": "these are constant\nrelative to n.", "start": 2283.874, "duration": 2.084}, {"text": "These are fixed.", "start": 2285.958, "duration": 0.667}, {"text": "There are not n to the\nk possible symbols.", "start": 2291.38, "duration": 2.453}, {"text": "There's a fixed\nnumber of symbols.", "start": 2293.833, "duration": 1.417}, {"text": "It depends only on the machine.", "start": 2295.25, "duration": 1.425}, {"text": "So we're looking at\na particular machine,", "start": 2300.35, "duration": 2.06}, {"text": "and what happens when\nyou look at large inputs.", "start": 2302.41, "duration": 1.995}, {"text": "So why is D and not C?", "start": 2311.25, "duration": 2.888}, {"text": "Well, don't forget--\nhow big is this table?", "start": 2314.138, "duration": 1.792}, {"text": "This is n to the\nk by n to the k.", "start": 2318.67, "duration": 2.64}, {"text": "So there are n to the 2k cells,\nn to the k quantity squared,", "start": 2321.31, "duration": 3.99}, {"text": "or n to the 2k cells here.", "start": 2325.3, "duration": 4.81}, {"text": "And so there's a\ncollection of variables", "start": 2330.11, "duration": 1.7}, {"text": "for each cell, some fixed number\nof variables for each cell.", "start": 2331.81, "duration": 2.98}, {"text": "So that's why its\norder n to the 2k.", "start": 2334.79, "duration": 1.685}, {"text": "Good.", "start": 2340.36, "duration": 0.87}, {"text": "So let's move on.", "start": 2341.23, "duration": 2.7}, {"text": "I think we're\nactually-- hold on.", "start": 2343.93, "duration": 3.27}, {"text": "So we have one more\nslide, and I think", "start": 2347.2, "duration": 3.0}, {"text": "then we have a break after.", "start": 2350.2, "duration": 2.46}, {"text": "So now let's next talk about\nconstructing two more pieces", "start": 2352.66, "duration": 7.98}, {"text": "of the phi sub M, w formula.", "start": 2360.64, "duration": 3.85}, {"text": "So we already got\nphi sub cell done.", "start": 2364.49, "duration": 4.07}, {"text": "Let's look at phi sub\nstart and phi sub accept.", "start": 2368.56, "duration": 4.75}, {"text": "And phi start is\ngoing to tell us", "start": 2373.31, "duration": 3.63}, {"text": "that the start configuration\nhas exactly these symbols.", "start": 2376.94, "duration": 5.6}, {"text": "And phi accept tells us that the\nbottom configuration contains", "start": 2382.54, "duration": 8.85}, {"text": "an accepting state somewhere.", "start": 2391.39, "duration": 2.93}, {"text": "So how are we going\nto write that down?", "start": 2394.32, "duration": 2.03}, {"text": "Well, first of all, I'm going\nto write these down just cell", "start": 2396.35, "duration": 3.54}, {"text": "by cell.", "start": 2399.89, "duration": 1.36}, {"text": "So first of all, phi start\nis going to say the cell 1,", "start": 2401.25, "duration": 3.46}, {"text": "1 contains a q0.", "start": 2404.71, "duration": 3.16}, {"text": "I mean, I know what the\nstart configuration should", "start": 2407.87, "duration": 4.17}, {"text": "be, because thinking of me, or\nthink of us as the reduction,", "start": 2412.04, "duration": 7.21}, {"text": "the reduction is\ngiven M. It's given w.", "start": 2419.25, "duration": 2.61}, {"text": "So it knows what\nthe start state is.", "start": 2421.86, "duration": 1.62}, {"text": "It knows what the\nsymbols of w are.", "start": 2423.48, "duration": 4.86}, {"text": "So it knows what that\nstart configuration is.", "start": 2428.34, "duration": 3.48}, {"text": "It's just q0 followed\nby the n symbols", "start": 2431.82, "duration": 3.81}, {"text": "of w followed by blanks.", "start": 2435.63, "duration": 2.19}, {"text": "So it wants the very first\ncell in the left-hand corner", "start": 2437.82, "duration": 6.54}, {"text": "here to be a q0, the start state\nof the machine, which it knows.", "start": 2444.36, "duration": 4.38}, {"text": "So it's going to say x sub 1,\n1, q0, that has to be turned on.", "start": 2448.74, "duration": 6.46}, {"text": "So it's going to be AND of\na bunch of variables here.", "start": 2455.2, "duration": 3.83}, {"text": "And in order to satisfy phi sub\nstart, all of those variables", "start": 2459.03, "duration": 4.14}, {"text": "have to be set to true.", "start": 2463.17, "duration": 2.64}, {"text": "So that means we have to\nhave a q0 in that cell.", "start": 2465.81, "duration": 4.05}, {"text": "So now we're going to\ndo the next cell here.", "start": 2469.86, "duration": 3.29}, {"text": "The 1, 2, the next cell of\nthe start configuration.", "start": 2473.15, "duration": 4.68}, {"text": "So phi start is\ngoing to have x 1, 2.", "start": 2477.83, "duration": 4.08}, {"text": "So that's the next place.", "start": 2481.91, "duration": 1.755}, {"text": "It contains w1.", "start": 2483.665, "duration": 2.265}, {"text": "And so on.", "start": 2485.93, "duration": 1.26}, {"text": "x 1, 3 contains w2,\nall the way up to wn,", "start": 2487.19, "duration": 5.6}, {"text": "and then there's going to be\na bunch of additional parts", "start": 2492.79, "duration": 7.22}, {"text": "which say that we have\nblanks in the rest,", "start": 2500.01, "duration": 3.45}, {"text": "just spelling out exactly all\nof the symbols in that top row.", "start": 2503.46, "duration": 5.29}, {"text": "Because that's what\nthe phi start formula,", "start": 2508.75, "duration": 8.42}, {"text": "or sub formula of\nthe overall formula", "start": 2517.17, "duration": 2.67}, {"text": "we're making looks like.", "start": 2519.84, "duration": 4.02}, {"text": "Now let's take a\nlook at phi accept.", "start": 2523.86, "duration": 2.85}, {"text": "Phi accept, because\nI'm just looking", "start": 2526.71, "duration": 2.88}, {"text": "for q accept to appear\nsomewhere in that bottom row,", "start": 2529.59, "duration": 6.76}, {"text": "I'm going to do that\nin terms of an OR.", "start": 2536.35, "duration": 2.81}, {"text": "So here is-- the variables\nnow, notice, have n to the k", "start": 2539.16, "duration": 4.77}, {"text": "because it's the last\nrow in the table.", "start": 2543.93, "duration": 3.22}, {"text": "So row n to the k here.", "start": 2547.15, "duration": 3.31}, {"text": "And then I'm going to vary\nj from 1 to n to the k.", "start": 2550.46, "duration": 3.25}, {"text": "So j, the column\nnumber, is going", "start": 2553.71, "duration": 2.03}, {"text": "to range from 1 to n to the k.", "start": 2555.74, "duration": 1.77}, {"text": "And I'm looking\nfor that to accept.", "start": 2557.51, "duration": 1.74}, {"text": "So x n to the k j, where\nj's vary, and q accept.", "start": 2559.25, "duration": 5.19}, {"text": "One of those has to be true.", "start": 2564.44, "duration": 2.8}, {"text": "One of those has\nto be turned on.", "start": 2567.24, "duration": 1.63}, {"text": "And so that's why it's a big OR.", "start": 2568.87, "duration": 3.69}, {"text": "And that's my phi accept piece.", "start": 2572.56, "duration": 7.473}, {"text": "And now we'll take\na little break.", "start": 2580.033, "duration": 1.417}, {"text": "And feel free to ask\nme some more questions.", "start": 2581.45, "duration": 3.24}, {"text": "Let me just start our clock.", "start": 2584.69, "duration": 1.445}, {"text": "Go grab yourself some coffee,\nor ask me some questions.", "start": 2595.37, "duration": 4.76}, {"text": "I'm happy to answer them.", "start": 2600.13, "duration": 2.63}, {"text": "Why don't we check that q\naccept only appears once?", "start": 2602.76, "duration": 5.16}, {"text": "Is it possible for q\naccept to appear twice?", "start": 2607.92, "duration": 2.915}, {"text": "That's a great question.", "start": 2610.835, "duration": 1.0}, {"text": "So that would definitely\nbe a broken configuration", "start": 2614.59, "duration": 3.35}, {"text": "if that happened,\nbecause a configuration", "start": 2617.94, "duration": 1.8}, {"text": "can have-- must have exactly\none state symbol appearing.", "start": 2619.74, "duration": 5.22}, {"text": "The way we're going to enforce\nthat is with the phi move", "start": 2624.96, "duration": 5.58}, {"text": "part of the formula,\nwhich we haven't seen yet.", "start": 2630.54, "duration": 2.05}, {"text": "So phi move is\ngoing to guarantee", "start": 2632.59, "duration": 2.33}, {"text": "that the machine is\nacting correctly,", "start": 2634.92, "duration": 2.58}, {"text": "so that all of the\nrows of the tableau", "start": 2637.5, "duration": 3.99}, {"text": "are all legal configurations,\nand they all legally follow", "start": 2641.49, "duration": 2.97}, {"text": "from the previous.", "start": 2644.46, "duration": 2.04}, {"text": "So really, in a sense,\nthe hard-- heavy lifting", "start": 2646.5, "duration": 2.52}, {"text": "is coming in phi move, but\nit's really not that bad.", "start": 2649.02, "duration": 2.94}, {"text": "Somebody says, out of\ncuriosity, how close", "start": 2658.67, "duration": 1.75}, {"text": "is this intuition proof\nto the actual proof?", "start": 2660.42, "duration": 2.97}, {"text": "This is the actual proof.", "start": 2663.39, "duration": 1.53}, {"text": "There's no-- I'm\nnot hiding anything.", "start": 2664.92, "duration": 3.21}, {"text": "I mean, we're being\na little loose here,", "start": 2668.13, "duration": 3.12}, {"text": "but you can turn this--", "start": 2671.25, "duration": 2.445}, {"text": "we're not cutting\nany corners here.", "start": 2673.695, "duration": 1.695}, {"text": "This is exactly\nhow the proof goes.", "start": 2675.39, "duration": 3.18}, {"text": "And so not-- you're\ngetting the real deal here.", "start": 2678.57, "duration": 5.46}, {"text": "Somebody wanted to see the\nprevious slide, so here we are.", "start": 2684.03, "duration": 2.79}, {"text": "Whoops.", "start": 2686.82, "duration": 2.52}, {"text": "Is there something\nyou want to ask?", "start": 2689.34, "duration": 1.545}, {"text": "So phi cell says there's\nexactly one symbol per cell.", "start": 2694.99, "duration": 7.25}, {"text": "And the variables are set in\na way in terms of thinking", "start": 2702.24, "duration": 2.58}, {"text": "of them as indicator variables.", "start": 2704.82, "duration": 1.68}, {"text": "There's exactly one variable\nset to true in each cell.", "start": 2706.5, "duration": 4.66}, {"text": "So there's exactly\none symbol per cell.", "start": 2711.16, "duration": 2.3}, {"text": "That's what phi cell tells you.", "start": 2713.46, "duration": 3.0}, {"text": "If you don't have that,\nthen you have a mess.", "start": 2716.46, "duration": 2.22}, {"text": "So you've got to\nstart with that.", "start": 2718.68, "duration": 2.14}, {"text": "And then with the--\nother things are", "start": 2720.82, "duration": 1.5}, {"text": "going to be\nadditional conditions,", "start": 2722.32, "duration": 1.56}, {"text": "which when satisfied are\ngoing to enforce the rest", "start": 2723.88, "duration": 3.15}, {"text": "of the properties that we want.", "start": 2727.03, "duration": 2.34}, {"text": "Why would the proof fail if\nwe replace n to the k with 2", "start": 2729.37, "duration": 3.39}, {"text": "to the n to the k?", "start": 2732.76, "duration": 1.02}, {"text": "So OK.", "start": 2736.92, "duration": 2.18}, {"text": "I presume where does-- we'll\njust use the polynomial running", "start": 2739.1, "duration": 4.2}, {"text": "time of the machine of M,\nthe nondeterministic machine.", "start": 2743.3, "duration": 5.13}, {"text": "I mean, if you had\nan enormous tab--", "start": 2748.43, "duration": 1.92}, {"text": "we have to show ultimately\nthat this reduction is", "start": 2750.35, "duration": 3.3}, {"text": "a polynomial time reduction.", "start": 2753.65, "duration": 2.31}, {"text": "And that's going to depend\non how big the tableau is,", "start": 2755.96, "duration": 2.25}, {"text": "because that's going to tell\nus how big the formula we're", "start": 2758.21, "duration": 2.375}, {"text": "producing is, phi sub M, w.", "start": 2760.585, "duration": 1.945}, {"text": "If phi sub M, w is\nexponentially big,", "start": 2762.53, "duration": 1.95}, {"text": "we don't have a prayer of being\nable to output that formula", "start": 2764.48, "duration": 3.27}, {"text": "in polynomial time.", "start": 2767.75, "duration": 0.99}, {"text": "If there were less\nthan n to the k steps,", "start": 2771.83, "duration": 2.82}, {"text": "do we repeat the\nlast configuration?", "start": 2774.65, "duration": 1.89}, {"text": "Yeah, that's what I said.", "start": 2776.54, "duration": 1.71}, {"text": "If the machine ends early,\nthe last configuration", "start": 2778.25, "duration": 2.91}, {"text": "just stays there.", "start": 2781.16, "duration": 1.75}, {"text": "So we're going to modify the\ndefinition of the machine", "start": 2782.91, "duration": 2.81}, {"text": "slightly so it just stays.", "start": 2785.72, "duration": 3.88}, {"text": "Yeah.", "start": 2789.6, "duration": 0.5}, {"text": "OK.", "start": 2795.09, "duration": 0.5}, {"text": "Yeah.", "start": 2806.88, "duration": 0.5}, {"text": "Let me not take\nthe other-- there's", "start": 2807.38, "duration": 1.513}, {"text": "a bunch of other\nquestions, some of them", "start": 2808.893, "duration": 1.667}, {"text": "a little on the technical side.", "start": 2810.56, "duration": 3.6}, {"text": "Let me-- maybe I'll\ntry to address them", "start": 2814.16, "duration": 3.04}, {"text": "as they come along if it\nturns out to work to do that.", "start": 2817.2, "duration": 4.14}, {"text": "So the break is over.", "start": 2821.34, "duration": 4.8}, {"text": "Why don't we-- is it possible\nthat the encoding configuration", "start": 2826.14, "duration": 4.32}, {"text": "will not fit in n to the k?", "start": 2830.46, "duration": 2.37}, {"text": "So the question is,\nis there a possibility", "start": 2835.95, "duration": 1.75}, {"text": "that the encoding\nof the configuration", "start": 2837.7, "duration": 1.59}, {"text": "won't fit in n to the k?", "start": 2839.29, "duration": 1.38}, {"text": "If the machine runs\nfor n to the k steps,", "start": 2840.67, "duration": 3.29}, {"text": "the configuration has to\nfit within n to the k,", "start": 2843.96, "duration": 2.76}, {"text": "because it can't use anything\nmore within n to the k steps.", "start": 2846.72, "duration": 4.39}, {"text": "So think about it.", "start": 2851.11, "duration": 0.76}, {"text": "But no.", "start": 2851.87, "duration": 1.11}, {"text": "The answer is the\nconfigurations--", "start": 2852.98, "duration": 3.71}, {"text": "if the machine runs\nin time n to the k,", "start": 2856.69, "duration": 2.67}, {"text": "that whole tableau is\nbig enough to write down", "start": 2859.36, "duration": 4.14}, {"text": "the entire computation history.", "start": 2863.5, "duration": 2.94}, {"text": "All right, so let's continue.", "start": 2866.44, "duration": 2.17}, {"text": "Phi sub move, this\nis, in a sense,", "start": 2868.61, "duration": 5.25}, {"text": "the part which is going\nto tell us that we", "start": 2873.86, "duration": 4.07}, {"text": "started right, we ended right.", "start": 2877.93, "duration": 4.15}, {"text": "Phi cell says every cell\ncontains one symbol.", "start": 2882.08, "duration": 3.91}, {"text": "And now we have to say that\nthe whole interior is correct.", "start": 2885.99, "duration": 4.76}, {"text": "How are we going to do that?", "start": 2890.75, "duration": 1.53}, {"text": "So these are the parts\nwe've already done.", "start": 2892.28, "duration": 3.295}, {"text": "And the way I'm\ngoing to describe", "start": 2895.575, "duration": 1.375}, {"text": "that is in terms of these\nkind of little windows", "start": 2896.95, "duration": 4.36}, {"text": "I'm calling neighborhoods.", "start": 2901.31, "duration": 1.56}, {"text": "So imagine here we have a 2 by\n3 rectangle, which I'm going", "start": 2902.87, "duration": 5.76}, {"text": "to call a 2 by 3 neighborhood.", "start": 2908.63, "duration": 2.93}, {"text": "And what I'm going to argue,\nbut I'm not going to prove here.", "start": 2911.56, "duration": 3.803}, {"text": "I'm just going to\nreally state it,", "start": 2915.363, "duration": 1.417}, {"text": "but it's really just a sort\nof more or less obvious fact.", "start": 2916.78, "duration": 4.5}, {"text": "But the proof-- the book has\nthe formal proof, that if any--", "start": 2921.28, "duration": 5.79}, {"text": "every one of these\nhere is legitimate,", "start": 2927.07, "duration": 3.03}, {"text": "is legal according to\nthe rules of the machine,", "start": 2930.1, "duration": 2.58}, {"text": "if every single--\nimagine you have these--", "start": 2932.68, "duration": 4.12}, {"text": "oops.", "start": 2936.8, "duration": 0.5}, {"text": "Let me put myself back on\nhere so you can see me.", "start": 2937.3, "duration": 2.37}, {"text": "If you have here\nevery 2 by 3 window,", "start": 2942.19, "duration": 9.85}, {"text": "you can take this\nas a window, and you", "start": 2952.04, "duration": 2.88}, {"text": "slide that over the entire\npicture of the tableau.", "start": 2954.92, "duration": 4.61}, {"text": "And everything here\nlooks OK as far", "start": 2959.53, "duration": 3.0}, {"text": "as the running of the machine.", "start": 2962.53, "duration": 1.32}, {"text": "So I'll say what that\nmeans in a second.", "start": 2963.85, "duration": 2.85}, {"text": "But if everything looks\nlocally fine everywhere,", "start": 2966.7, "duration": 3.99}, {"text": "then the whole tableau\nhas to be a valid tableau", "start": 2970.69, "duration": 3.96}, {"text": "in terms of the rules of M.", "start": 2974.65, "duration": 5.14}, {"text": "Maybe it's easier\nif I describe what", "start": 2979.79, "duration": 2.55}, {"text": "I mean by these being legal.", "start": 2982.34, "duration": 1.785}, {"text": "So these neighborhoods,\nthese 2 by 3 neighborhoods", "start": 2987.0, "duration": 5.52}, {"text": "are legal if they're consistent\nwith M's transition function.", "start": 2992.52, "duration": 3.94}, {"text": "So I'm going to\ndescribe rather than--", "start": 2996.46, "duration": 1.94}, {"text": "I mean, to do this\nformally, I would", "start": 2998.4, "duration": 1.95}, {"text": "have to go through a\nprocess that we went--", "start": 3000.35, "duration": 3.12}, {"text": "like what we did when we\nwent through the construction", "start": 3003.47, "duration": 4.35}, {"text": "for the Post\ncorrespondence problem,", "start": 3007.82, "duration": 1.65}, {"text": "and say if the machine moves\nleft, this thing happens.", "start": 3009.47, "duration": 2.31}, {"text": "If it moves right, that's--", "start": 3011.78, "duration": 1.22}, {"text": "I think that it's\nnot really necessary.", "start": 3013.0, "duration": 2.69}, {"text": "You can kind of get\nthe idea very clearly", "start": 3015.69, "duration": 2.63}, {"text": "by doing it at a little\nbit of a higher level.", "start": 3018.32, "duration": 1.92}, {"text": "So let's look at what I mean\nby a legal neighborhood.", "start": 3023.18, "duration": 3.33}, {"text": "So a legal neighborhood is\na setting of the values,", "start": 3026.51, "duration": 3.35}, {"text": "the six values of this\n2 by 3 neighborhood,", "start": 3029.86, "duration": 5.13}, {"text": "in a way which doesn't\nviolate M's rules.", "start": 3034.99, "duration": 4.78}, {"text": "So for example, if M, when\nit's in state q7 reading of b,", "start": 3039.77, "duration": 7.75}, {"text": "goes into state\nq3 and moves left,", "start": 3047.52, "duration": 4.87}, {"text": "then this would be a legal\nneighborhood, because it", "start": 3052.39, "duration": 4.29}, {"text": "shows the head moving\nleft, the b becoming a c.", "start": 3056.68, "duration": 5.45}, {"text": "So reading a b,\nI should also say", "start": 3062.13, "duration": 1.77}, {"text": "that it converts that b to a c.", "start": 3063.9, "duration": 3.31}, {"text": "And we just head\nleft into state q3.", "start": 3067.21, "duration": 1.82}, {"text": "So this would be a\nlegal neighborhood", "start": 3069.03, "duration": 2.07}, {"text": "if that's the way--", "start": 3071.1, "duration": 1.44}, {"text": "so being legal depends upon\nthe transition function", "start": 3072.54, "duration": 5.58}, {"text": "of the machine.", "start": 3078.12, "duration": 1.6}, {"text": "So given the\ntransition function,", "start": 3079.72, "duration": 2.1}, {"text": "that's going to tell you which\nare the legal neighborhoods.", "start": 3081.82, "duration": 2.64}, {"text": "So another legal neighborhood--\nthis would always", "start": 3084.46, "duration": 2.28}, {"text": "be a legal neighborhood--\nis that if nothing changes.", "start": 3086.74, "duration": 3.03}, {"text": "So that means the head of the\nmachine was somewhere else.", "start": 3089.77, "duration": 3.49}, {"text": "And so whatever was on\nthe tape in this step", "start": 3093.26, "duration": 5.63}, {"text": "is going to be the same stuff\nin those places one step later.", "start": 3098.89, "duration": 4.35}, {"text": "Here's another possible\nlegal neighborhood.", "start": 3107.15, "duration": 5.06}, {"text": "If the head suddenly\nappears on one of the cells", "start": 3112.21, "duration": 7.84}, {"text": "either in the left\nor the right, that", "start": 3120.05, "duration": 3.99}, {"text": "would correspond to the machine\nmoving its head from somewhere", "start": 3124.04, "duration": 4.68}, {"text": "off the neighborhood into the\nneighborhood in that step.", "start": 3128.72, "duration": 5.74}, {"text": "So this could be a\nlegal neighborhood,", "start": 3134.46, "duration": 2.27}, {"text": "provided the machine\nactually does", "start": 3136.73, "duration": 1.74}, {"text": "move its head left\ninto a state q5", "start": 3138.47, "duration": 2.55}, {"text": "at some point under\nsome conditions.", "start": 3141.02, "duration": 5.07}, {"text": "And here is another kind of\na weird legal neighborhood.", "start": 3146.09, "duration": 2.61}, {"text": "If you have a, b, c, and\nthen the a changes to a d,", "start": 3148.7, "duration": 4.11}, {"text": "that could also be\na legal neighborhood", "start": 3152.81, "duration": 2.1}, {"text": "if the machine transition\nfunction allows", "start": 3154.91, "duration": 4.36}, {"text": "an a to get converted\nto a d when there", "start": 3159.27, "duration": 2.67}, {"text": "is some machine-- when there\nis some state reading that a,", "start": 3161.94, "duration": 2.73}, {"text": "and that state also\nmoves its head left.", "start": 3164.67, "duration": 2.28}, {"text": "So it doesn't move\ninto this picture.", "start": 3166.95, "duration": 2.835}, {"text": "So those are examples\nof legal neighborhoods.", "start": 3169.785, "duration": 1.875}, {"text": "Let me show you some\nillegal neighborhoods.", "start": 3171.66, "duration": 2.828}, {"text": "Just I'm doing this-- this is\nkind of a proof by example now.", "start": 3174.488, "duration": 2.542}, {"text": "This is perhaps the\nmost intuitive part.", "start": 3177.03, "duration": 2.46}, {"text": "But I claim that this is easy\nto turn this into something", "start": 3179.49, "duration": 3.72}, {"text": "airtight and formal.", "start": 3183.21, "duration": 3.05}, {"text": "So this would be\nclearly illegal.", "start": 3186.26, "duration": 2.07}, {"text": "If you have a piece of the\ntape in the previous step where", "start": 3188.33, "duration": 7.35}, {"text": "it's a, b, c, and then\nsuddenly the b changes to a d.", "start": 3195.68, "duration": 3.66}, {"text": "The symbol on the tape\nchanges out of nowhere", "start": 3199.34, "duration": 3.69}, {"text": "without having a head\nnearby to a different--", "start": 3203.03, "duration": 4.2}, {"text": "to something else.", "start": 3207.23, "duration": 1.14}, {"text": "That could never happen.", "start": 3208.37, "duration": 1.36}, {"text": "So that would be illegal.", "start": 3209.73, "duration": 1.172}, {"text": "Another thing that\nwould be illegal", "start": 3210.902, "duration": 1.458}, {"text": "is if a state\nappears from nowhere.", "start": 3212.36, "duration": 2.84}, {"text": "That could never happen.", "start": 3215.2, "duration": 2.16}, {"text": "Or if it just disappears.", "start": 3217.36, "duration": 1.29}, {"text": "That could never happen.", "start": 3218.65, "duration": 1.99}, {"text": "And here's another--\nhere's an interesting one.", "start": 3220.64, "duration": 2.64}, {"text": "If a state becomes two states.", "start": 3223.28, "duration": 1.725}, {"text": "Don't forget the machine\nis nondeterministic.", "start": 3229.06, "duration": 2.07}, {"text": "So the machine in\nprinciple could", "start": 3231.13, "duration": 1.98}, {"text": "move its head left on one\nbranch and move its head right", "start": 3233.11, "duration": 3.6}, {"text": "on a different branch,\nbut those would have", "start": 3236.71, "duration": 2.04}, {"text": "to be in different tableaus.", "start": 3238.75, "duration": 1.32}, {"text": "They can't be in\nthe same tableau,", "start": 3240.07, "duration": 2.28}, {"text": "because that doesn't\ncorrespond to any", "start": 3242.35, "duration": 1.89}, {"text": "of the threads of the\ncomputation, those", "start": 3244.24, "duration": 1.83}, {"text": "with multiple threads.", "start": 3246.07, "duration": 2.34}, {"text": "And I say this because if you\nthink about my claim, which", "start": 3248.41, "duration": 6.31}, {"text": "is going to put down over\nhere, that if every 2", "start": 3254.72, "duration": 3.48}, {"text": "by 3 neighborhood is legal, then\nthe tableau overall corresponds", "start": 3258.2, "duration": 3.78}, {"text": "to a computation history.", "start": 3261.98, "duration": 2.89}, {"text": "This illustrates why it's\nnot enough to have a 2", "start": 3264.87, "duration": 4.02}, {"text": "by 2 neighborhood, where\nyou really need the 2 by 3.", "start": 3268.89, "duration": 4.41}, {"text": "Because if this was a\n2 by 2 neighborhood,", "start": 3273.3, "duration": 2.91}, {"text": "if you just look at these four--", "start": 3276.21, "duration": 2.76}, {"text": "this leftmost 2 by 2, that could\nbe a legal neighborhood if it", "start": 3278.97, "duration": 7.89}, {"text": "was a 2 by 2, if the rules of\nthe machine allowed for that.", "start": 3286.86, "duration": 4.38}, {"text": "And the right four box--", "start": 3291.24, "duration": 2.76}, {"text": "right four cells could also\nbe a legal neighborhood.", "start": 3294.0, "duration": 2.97}, {"text": "So you could have\nsomething that looks", "start": 3296.97, "duration": 2.52}, {"text": "OK from the perspective\nof 2 by 2 neighborhoods,", "start": 3299.49, "duration": 3.18}, {"text": "but globally, in terms\nof the overall tableau,", "start": 3302.67, "duration": 3.12}, {"text": "it's completely nonsensical\nbecause it has multiple hits.", "start": 3305.79, "duration": 2.505}, {"text": "But if you have a 2\nby 3 neighborhood,", "start": 3311.37, "duration": 2.01}, {"text": "it's big enough to prevent\nthis situation from occurring.", "start": 3313.38, "duration": 4.24}, {"text": "And then you can\ncheck the details.", "start": 3317.62, "duration": 4.55}, {"text": "And I think it's very\nplausible that it guarantees", "start": 3322.17, "duration": 3.45}, {"text": "that the overall\ntableau is legitimate", "start": 3325.62, "duration": 4.35}, {"text": "if all of the 2 by 3\nneighborhoods are legal.", "start": 3329.97, "duration": 4.68}, {"text": "And so that's what we're\ngoing to turn into a Boolean", "start": 3334.65, "duration": 5.22}, {"text": "expression.", "start": 3339.87, "duration": 1.44}, {"text": "We're going to say for\neach cell that the set--", "start": 3341.31, "duration": 5.07}, {"text": "for each neighborhood-- so\nhere's a neighborhood at the i,", "start": 3346.38, "duration": 3.45}, {"text": "j location.", "start": 3349.83, "duration": 1.35}, {"text": "I'm calling this\nposition here sort", "start": 3351.18, "duration": 2.61}, {"text": "of the home location\nfor that neighborhood.", "start": 3353.79, "duration": 3.195}, {"text": "For each neighborhood,\nit has to be set to one", "start": 3360.066, "duration": 4.924}, {"text": "of the legal possibilities.", "start": 3364.99, "duration": 2.49}, {"text": "And there's, again, only\na fixed number of those", "start": 3367.48, "duration": 2.7}, {"text": "because there's a fixed\nnumber of possible symbols", "start": 3370.18, "duration": 2.97}, {"text": "that can appear in those cells.", "start": 3373.15, "duration": 2.98}, {"text": "So this is that fixed number\nto the sixth power at most.", "start": 3376.13, "duration": 3.44}, {"text": "And I'm going to say that\nthe cell in the upper left,", "start": 3379.57, "duration": 4.96}, {"text": "which would be\nthis one, is in r.", "start": 3384.53, "duration": 3.35}, {"text": "And this one here is an s.", "start": 3387.88, "duration": 1.44}, {"text": "And this one is a t.", "start": 3389.32, "duration": 1.63}, {"text": "And this one is a v, if\nyou just trace down what", "start": 3390.95, "duration": 2.66}, {"text": "the indices are telling you.", "start": 3393.61, "duration": 2.43}, {"text": "It says that that piece of the\ntape, that piece of the tableau", "start": 3396.04, "duration": 4.08}, {"text": "here is set according to one\nof the possible legal settings.", "start": 3400.12, "duration": 6.43}, {"text": "And we're just going to OR over\nall of those possible fixed", "start": 3406.55, "duration": 3.84}, {"text": "number of legal settings.", "start": 3410.39, "duration": 2.19}, {"text": "And then I take an AND over\nall possible tape cells,", "start": 3412.58, "duration": 5.31}, {"text": "over all possible neighborhoods.", "start": 3417.89, "duration": 2.007}, {"text": "And so that's going\nto be my phi move.", "start": 3422.58, "duration": 1.77}, {"text": "And that's it.", "start": 3426.87, "duration": 1.08}, {"text": "OK.", "start": 3430.42, "duration": 0.5}, {"text": "Let's see.", "start": 3430.92, "duration": 0.84}, {"text": "Can I explain again the\nthird example of illegal?", "start": 3431.76, "duration": 3.48}, {"text": "So this one over here, I\npresume, I'm being asked about.", "start": 3435.24, "duration": 3.78}, {"text": "Well, if the machine is\nin a state q7 reading a c,", "start": 3439.02, "duration": 6.68}, {"text": "the head has to move\neither left or right.", "start": 3445.7, "duration": 1.8}, {"text": "So at the next\nconfiguration, there's", "start": 3447.5, "duration": 6.07}, {"text": "got to be a state symbol\nappearing either in this cell", "start": 3453.57, "duration": 3.75}, {"text": "or in this cell.", "start": 3457.32, "duration": 2.65}, {"text": "And here the tape--", "start": 3459.97, "duration": 1.05}, {"text": "the head has basically\njust vanished with nowhere", "start": 3461.02, "duration": 5.1}, {"text": "to-- it's gone.", "start": 3466.12, "duration": 2.43}, {"text": "That could not happen\naccording to the rules", "start": 3468.55, "duration": 4.312}, {"text": "of the machine the way we\ntalk about Turing machines.", "start": 3472.862, "duration": 2.208}, {"text": "So that's not possible.", "start": 3475.07, "duration": 1.26}, {"text": "So this would be an\nillegal neighborhood.", "start": 3476.33, "duration": 6.2}, {"text": "You want to prevent\nany of the bad stuff", "start": 3482.53, "duration": 2.61}, {"text": "from happening anywhere in here.", "start": 3485.14, "duration": 1.62}, {"text": "So only good stuff can\nbe happening locally.", "start": 3486.76, "duration": 2.31}, {"text": "And that guarantees the\noverall picture is OK.", "start": 3489.07, "duration": 2.37}, {"text": "Do we have to check\nthat the head doesn't", "start": 3496.72, "duration": 2.663}, {"text": "leave the tableau from the\nleft most to right right?", "start": 3499.383, "duration": 2.167}, {"text": "Yeah, there are some little\ndetails here like that.", "start": 3501.55, "duration": 2.125}, {"text": "So the question is, do I\nhave to make sure that the--", "start": 3503.675, "duration": 3.38}, {"text": "yeah, you probably need to mark.", "start": 3507.055, "duration": 2.415}, {"text": "I think the book probably\ndoes this correctly.", "start": 3509.47, "duration": 2.4}, {"text": "You may have to mark\nthe left and right ends", "start": 3511.87, "duration": 2.61}, {"text": "to make sure that--", "start": 3514.48, "duration": 1.41}, {"text": "I mean, the right\nend is not a problem,", "start": 3515.89, "duration": 1.96}, {"text": "because the machine can\nnever go off the right end.", "start": 3517.85, "duration": 7.84}, {"text": "And if you design the\nmachine so that it never", "start": 3525.69, "duration": 2.49}, {"text": "moves its head off the left\nend either, which you can do,", "start": 3528.18, "duration": 3.018}, {"text": "then you wouldn't have to\nworry about that possibility.", "start": 3531.198, "duration": 2.292}, {"text": "But otherwise, you would have to\nput some sort of delimiter here", "start": 3533.49, "duration": 3.45}, {"text": "to enforce the head not\nmoving off the left end.", "start": 3536.94, "duration": 4.17}, {"text": "So there are some\ndetails like that, too.", "start": 3541.11, "duration": 1.92}, {"text": "There will be two\nheads in the same row.", "start": 3545.923, "duration": 1.667}, {"text": "No, this can-- I don't know\nwhat you-- somebody says,", "start": 3547.59, "duration": 2.43}, {"text": "there will be two\nheads in the same row.", "start": 3550.02, "duration": 2.76}, {"text": "Please elaborate, because\nthis is designed not to allow", "start": 3552.78, "duration": 3.93}, {"text": "two heads in the same row.", "start": 3556.71, "duration": 1.29}, {"text": "Could I go over the\nOR for legal again?", "start": 3561.25, "duration": 2.26}, {"text": "OK.", "start": 3563.51, "duration": 0.5}, {"text": "The OR, the big OR here, what\nI have in mind is I take--", "start": 3564.01, "duration": 6.55}, {"text": "there's going to be-- first\nof all, I look at the machine", "start": 3570.56, "duration": 2.46}, {"text": "and I look at the\ntransition function.", "start": 3573.02, "duration": 2.56}, {"text": "And based on that, I write down\nthe list of all the legal 2", "start": 3575.58, "duration": 6.32}, {"text": "by 3 neighborhoods.", "start": 3581.9, "duration": 1.08}, {"text": "So all the settings which\ncorrespond to legal 2", "start": 3582.98, "duration": 3.06}, {"text": "by 3 neighborhoods.", "start": 3586.04, "duration": 1.05}, {"text": "There's going to be some\nfixed number of those.", "start": 3587.09, "duration": 2.37}, {"text": "100.", "start": 3589.46, "duration": 2.94}, {"text": "There's 100 possible legal\nneighborhoods of which", "start": 3592.4, "duration": 2.91}, {"text": "I've written down here four.", "start": 3595.31, "duration": 2.51}, {"text": "But maybe there's\nsome number, say 100.", "start": 3597.82, "duration": 2.49}, {"text": "So now there's going to\nbe an OR over those 100", "start": 3600.31, "duration": 3.42}, {"text": "different possibilities.", "start": 3603.73, "duration": 1.63}, {"text": "It's either going to be\nthis legal neighborhood,", "start": 3605.36, "duration": 2.0}, {"text": "or some other\nlegal neighborhood,", "start": 3607.36, "duration": 1.26}, {"text": "or some other\nlegal neighborhood.", "start": 3608.62, "duration": 1.47}, {"text": "And for each one of those\nlegal neighborhoods,", "start": 3610.09, "duration": 2.49}, {"text": "I'm going to say, well, the\nvariables are set according", "start": 3612.58, "duration": 4.36}, {"text": "to that legal neighborhood, or\nthe variables are set according", "start": 3616.94, "duration": 4.59}, {"text": "to the next legal neighborhood,\nor the variables are", "start": 3621.53, "duration": 2.445}, {"text": "set according to the\nnext legal neighborhood,", "start": 3623.975, "duration": 1.875}, {"text": "and do that 100 times.", "start": 3625.85, "duration": 2.45}, {"text": "One of those has got to end up--", "start": 3628.3, "duration": 2.23}, {"text": "I mean it's an OR, so\none of them has to work.", "start": 3630.53, "duration": 2.64}, {"text": "Otherwise, the formula fails.", "start": 3633.17, "duration": 1.31}, {"text": "And it will be\nfalse, because you're", "start": 3634.48, "duration": 2.04}, {"text": "going to AND that over\nall of the neighborhoods", "start": 3636.52, "duration": 3.45}, {"text": "in the picture.", "start": 3639.97, "duration": 0.63}, {"text": "Is it possible to have\na head on the far left", "start": 3646.63, "duration": 2.28}, {"text": "of the configuration and\none on the far right?", "start": 3648.91, "duration": 2.325}, {"text": "You mean a head over here\nand a head over there?", "start": 3655.24, "duration": 2.87}, {"text": "I mean, how'd the\nhead get there?", "start": 3658.11, "duration": 2.37}, {"text": "It can't happen.", "start": 3660.48, "duration": 3.25}, {"text": "You know, the head has to\ncome from a head above it.", "start": 3663.73, "duration": 5.24}, {"text": "If you're going to be\nworrying about the details", "start": 3668.97, "duration": 2.7}, {"text": "of the boundaries here,\nall that's fixable.", "start": 3671.67, "duration": 5.31}, {"text": "So let's not lose\nsight of the main idea.", "start": 3676.98, "duration": 4.613}, {"text": "I mean, if you\nunderstand the main idea,", "start": 3681.593, "duration": 1.667}, {"text": "you can fix the little details.", "start": 3683.26, "duration": 1.83}, {"text": "So I want to make sure you\nunderstand the main idea", "start": 3685.09, "duration": 2.375}, {"text": "of what's happening.", "start": 3687.465, "duration": 2.235}, {"text": "So let's finish up this proof.", "start": 3689.7, "duration": 1.695}, {"text": "So in summary, we gave a\nreduction from 8 to SAT.", "start": 3694.01, "duration": 4.94}, {"text": "This is what we needed.", "start": 3698.95, "duration": 2.94}, {"text": "It was in those four pieces.", "start": 3701.89, "duration": 2.07}, {"text": "And you really\njust need to argue", "start": 3703.96, "duration": 1.56}, {"text": "that that formula we're\nbuilding is not too big.", "start": 3705.52, "duration": 4.22}, {"text": "And it's going to be basically\nthe size of the tableau", "start": 3709.74, "duration": 2.28}, {"text": "if you look at what\nwe constructed.", "start": 3712.02, "duration": 2.94}, {"text": "The number of variables\nis roughly the size", "start": 3714.96, "duration": 1.8}, {"text": "of the tableau.", "start": 3716.76, "duration": 1.05}, {"text": "And the amount of logic that\nwe're putting into the formula", "start": 3717.81, "duration": 2.73}, {"text": "is also going to\nbe a fixed amount", "start": 3720.54, "duration": 1.77}, {"text": "of logic independent\nof n for each", "start": 3722.31, "duration": 3.42}, {"text": "of the variables\nin that tableau.", "start": 3725.73, "duration": 2.7}, {"text": "And somebody asked me about the\nsize-- how big the indices are.", "start": 3728.43, "duration": 3.42}, {"text": "The indices for the x i\nvalue, the i and j values,", "start": 3734.47, "duration": 7.59}, {"text": "technically, they're going\nto be numbers between 1", "start": 3742.06, "duration": 2.85}, {"text": "and n to the k.", "start": 3744.91, "duration": 1.08}, {"text": "So you're going to have\nto write those down.", "start": 3745.99, "duration": 1.87}, {"text": "And so that's going to be a\nslight additional logarithmic", "start": 3747.86, "duration": 2.375}, {"text": "cost to write those things down.", "start": 3750.235, "duration": 2.045}, {"text": "It's not really that\ninteresting a point.", "start": 3752.28, "duration": 1.72}, {"text": "And so the overall\nf is going to be", "start": 3756.76, "duration": 2.73}, {"text": "computable in polynomial time\nbecause the output is not", "start": 3759.49, "duration": 2.49}, {"text": "very big.", "start": 3761.98, "duration": 0.82}, {"text": "And it's also not complicated\nto write the output down.", "start": 3762.8, "duration": 3.79}, {"text": "So that's the end of the proof.", "start": 3766.59, "duration": 4.08}, {"text": "I can take a couple\nof questions.", "start": 3770.67, "duration": 3.91}, {"text": "Why can't we just check\nthat the whole-- this", "start": 3774.58, "duration": 1.875}, {"text": "is a good question.", "start": 3776.455, "duration": 0.535}, {"text": "Why can't we just check\nthat the whole row is legal?", "start": 3776.99, "duration": 2.167}, {"text": "You can check that a row\nactually is a configuration.", "start": 3785.2, "duration": 3.33}, {"text": "But to check that the row\nfollows from the previous row,", "start": 3788.53, "duration": 6.86}, {"text": "ultimately, the operation\nof a Turing machine", "start": 3795.39, "duration": 3.21}, {"text": "is a local thing.", "start": 3798.6, "duration": 2.22}, {"text": "I mean, the way it moves from\none configuration to the next", "start": 3800.82, "duration": 5.91}, {"text": "depends locally on\nhow where the head is.", "start": 3806.73, "duration": 4.5}, {"text": "And so really, that's\njust another way of--", "start": 3811.23, "duration": 2.97}, {"text": "the way I'm saying it\nis just really checking", "start": 3814.2, "duration": 2.25}, {"text": "the whole configuration,\nbut just doing it locally.", "start": 3816.45, "duration": 3.032}, {"text": "I don't know if that's\nsatisfying to you.", "start": 3819.482, "duration": 1.708}, {"text": "Why don't I move\non because I just", "start": 3824.7, "duration": 1.578}, {"text": "want to make sure\nwe have enough time", "start": 3826.278, "duration": 1.542}, {"text": "to get to the very last\npart, which is a little bit--", "start": 3827.82, "duration": 2.58}, {"text": "I'm afraid, a little technical.", "start": 3830.4, "duration": 2.31}, {"text": "So we're going to kind of\nshift gears now and talk", "start": 3832.71, "duration": 3.6}, {"text": "about reducing SAT to 3SAT.", "start": 3836.31, "duration": 4.56}, {"text": "And let's see how it goes.", "start": 3840.87, "duration": 6.14}, {"text": "I don't always have\nthe most success", "start": 3847.01, "duration": 1.55}, {"text": "with presenting\nthis little piece,", "start": 3848.56, "duration": 2.82}, {"text": "because it's slightly\na technical argument.", "start": 3851.38, "duration": 1.81}, {"text": "But if you don't\nget it, don't worry.", "start": 3853.19, "duration": 3.08}, {"text": "Just you have to\naccept that it's true.", "start": 3856.27, "duration": 2.502}, {"text": "But I'd like to\nshow it to you just", "start": 3858.772, "duration": 1.458}, {"text": "to make the whole presentation\ncomplete in that sense.", "start": 3860.23, "duration": 7.19}, {"text": "So I'm going to give a reduction\nthat maps general formulas", "start": 3867.42, "duration": 5.82}, {"text": "to 3CNF formulas.", "start": 3873.24, "duration": 2.64}, {"text": "So that's how we\nmap SAT to 3SAT.", "start": 3875.88, "duration": 4.22}, {"text": "If you remember 3SAT\nis satisfiability", "start": 3880.1, "duration": 2.61}, {"text": "but for three CNFs.", "start": 3882.71, "duration": 2.43}, {"text": "So a conjunctive normal form\nin the form of those clauses,", "start": 3885.14, "duration": 3.72}, {"text": "which are ANDed together.", "start": 3888.86, "duration": 1.56}, {"text": "And each clause is an OR of a\nbunch of literals, which are", "start": 3890.42, "duration": 4.11}, {"text": "variables or negated variables.", "start": 3894.53, "duration": 3.55}, {"text": "So I want to convert phi to phi\nprime, which is 3CNF formula,", "start": 3898.08, "duration": 6.14}, {"text": "but preserve the satisfiability.", "start": 3904.22, "duration": 2.85}, {"text": "And phi prime is not going to\nbe logically equivalent to phi,", "start": 3907.07, "duration": 3.39}, {"text": "because I could do that, too.", "start": 3910.46, "duration": 2.22}, {"text": "I can convert any formula to\na logically equivalent CNF", "start": 3912.68, "duration": 4.8}, {"text": "formula.", "start": 3917.48, "duration": 0.72}, {"text": "Maybe not even a\n3CNF, but yeah, you", "start": 3918.2, "duration": 2.475}, {"text": "won't be able to get a\n3CNF, but you can get a CNF.", "start": 3920.675, "duration": 3.195}, {"text": "But it might be\nexponentially larger.", "start": 3923.87, "duration": 2.535}, {"text": "And that's not good enough.", "start": 3926.405, "duration": 1.125}, {"text": "I have to do the reduction\nin polynomial time.", "start": 3927.53, "duration": 2.74}, {"text": "So I can't generate\na much larger formula", "start": 3930.27, "duration": 2.45}, {"text": "that's exponentially larger.", "start": 3932.72, "duration": 1.47}, {"text": "And so I'm going to do that by\nadding additional variables.", "start": 3934.19, "duration": 6.46}, {"text": "So it won't be\nlogically equivalent", "start": 3940.65, "duration": 1.49}, {"text": "because the new formula\nis going to have", "start": 3942.14, "duration": 1.98}, {"text": "additional variables in it.", "start": 3944.12, "duration": 2.39}, {"text": "I'm going to kind\nof do it by example.", "start": 3946.51, "duration": 2.74}, {"text": "And we'll see how that goes.", "start": 3949.25, "duration": 2.59}, {"text": "So here's phi, which\nis not in 3CNF.", "start": 3951.84, "duration": 4.93}, {"text": "It's not even in\nCNF, because it's", "start": 3956.77, "duration": 2.96}, {"text": "got ORs of ANDs\nappearing, which is not", "start": 3959.73, "duration": 4.11}, {"text": "allowed to happen in a CNF.", "start": 3963.84, "duration": 3.76}, {"text": "So how are we going\nto convert that", "start": 3967.6, "duration": 3.36}, {"text": "into a 3CNF formula\npreserving the satisfiability?", "start": 3970.96, "duration": 4.02}, {"text": "And just working it\nthrough with this example,", "start": 3974.98, "duration": 2.82}, {"text": "I hope to at least give\nyou some idea of how you", "start": 3977.8, "duration": 2.34}, {"text": "do the conversion in general.", "start": 3980.14, "duration": 1.9}, {"text": "So first of all, I'm going\nto represent this formula", "start": 3982.04, "duration": 2.3}, {"text": "as a tree using its\nnatural tree structure.", "start": 3984.34, "duration": 4.76}, {"text": "So you understand.", "start": 3989.1, "duration": 1.04}, {"text": "So a AND B becomes a\nAND b written as a tree.", "start": 3990.14, "duration": 4.77}, {"text": "And then I OR that with c.", "start": 3994.91, "duration": 2.92}, {"text": "So I get the tree structure\nhere in sort of the natural way.", "start": 3997.83, "duration": 3.48}, {"text": "And I'm going to label all of\nthese intermediate nodes, which", "start": 4001.31, "duration": 3.81}, {"text": "are associated now\nwith operations.", "start": 4005.12, "duration": 4.28}, {"text": "And I'm assuming also that the\nformula is fully parenthesized", "start": 4009.4, "duration": 6.36}, {"text": "so that each operation\nI'm only thinking about", "start": 4015.76, "duration": 2.52}, {"text": "is applying just the two--\nit's a binary operation.", "start": 4018.28, "duration": 4.32}, {"text": "And let's ignore negations for\nthe minute, because negations,", "start": 4022.6, "duration": 3.15}, {"text": "you can always push those\nthrough down to the leaves.", "start": 4025.75, "duration": 2.47}, {"text": "But it's just going to\nmake it too complicated.", "start": 4028.22, "duration": 3.445}, {"text": "So negations turn out\nnot to be a problem.", "start": 4031.665, "duration": 1.75}, {"text": "So there's only\ngoing to be negations", "start": 4036.14, "duration": 1.55}, {"text": "at the level of the\ninputs, not at the negation", "start": 4037.69, "duration": 4.92}, {"text": "operations in the middle.", "start": 4042.61, "duration": 2.76}, {"text": "So we have this\ntree structure here.", "start": 4045.37, "duration": 2.05}, {"text": "And now I'm going to use\nthese two logical facts.", "start": 4047.42, "duration": 4.16}, {"text": "And I don't know if--", "start": 4051.58, "duration": 2.46}, {"text": "you've probably all seen\nANDs and ORs, I hope.", "start": 4054.04, "duration": 2.7}, {"text": "Otherwise, it's going\nto be really tough.", "start": 4056.74, "duration": 2.25}, {"text": "But there's also other\nlogical operators,", "start": 4058.99, "duration": 1.98}, {"text": "such as the\nimplication operator,", "start": 4060.97, "duration": 2.88}, {"text": "where you have A implies B\nsort of as a logical operation.", "start": 4063.85, "duration": 8.65}, {"text": "And so this requires that if\nA is true, then B is true.", "start": 4072.5, "duration": 6.09}, {"text": "However, if A is false,\nB can be anything.", "start": 4082.92, "duration": 4.46}, {"text": "And similarly if B is\ntrue, A can be anything.", "start": 4087.38, "duration": 2.28}, {"text": "The only thing that's\nprohibited is that if A is true", "start": 4092.57, "duration": 3.14}, {"text": "and B is false.", "start": 4095.71, "duration": 1.47}, {"text": "That's the only thing\nthat would be invalid.", "start": 4097.18, "duration": 3.389}, {"text": "And so if you think\nabout it, that's", "start": 4100.569, "duration": 1.951}, {"text": "going to be equivalent to\nsaying that either A is false", "start": 4102.52, "duration": 3.66}, {"text": "or B is true.", "start": 4106.18, "duration": 1.59}, {"text": "One of those has to be.", "start": 4107.77, "duration": 2.339}, {"text": "And that's going to be\nlogically equivalent to saying", "start": 4110.109, "duration": 2.641}, {"text": "that A implies B.", "start": 4112.75, "duration": 3.899}, {"text": "Another logical equivalence\nmay be more familiar to you.", "start": 4116.649, "duration": 2.761}, {"text": "It's just simply\nDe Morgan's law,", "start": 4119.41, "duration": 2.79}, {"text": "which says that if you have\nthe not of A AND B, that's", "start": 4122.2, "duration": 5.01}, {"text": "equivalent to saying the\nnot of A or the not of B.", "start": 4127.21, "duration": 7.54}, {"text": "I'm going to make\nuse of both of these.", "start": 4134.75, "duration": 3.21}, {"text": "Now, here, I want to--", "start": 4137.96, "duration": 3.7}, {"text": "I ran out of room on this slide.", "start": 4141.66, "duration": 1.42}, {"text": "So I'm going to take myself\nout of the picture here", "start": 4143.08, "duration": 2.125}, {"text": "for a minute.", "start": 4145.205, "duration": 0.745}, {"text": "I had no place else to put this.", "start": 4148.93, "duration": 1.88}, {"text": "So here we have--", "start": 4150.81, "duration": 1.919}, {"text": "if you're going to\nthink of the AND", "start": 4152.729, "duration": 2.25}, {"text": "in terms of its truth\ntable, so here's a and b", "start": 4154.979, "duration": 4.38}, {"text": "in terms of a and b.", "start": 4159.359, "duration": 2.641}, {"text": "So 1 and 1 is 1, but all\nother settings of a and b", "start": 4162.0, "duration": 5.79}, {"text": "yield 0 for the AND.", "start": 4167.79, "duration": 2.63}, {"text": "And I'm going to\nrepresent those--", "start": 4170.42, "duration": 1.814}, {"text": "if you imagine a and b\nis going to be called c.", "start": 4175.3, "duration": 3.03}, {"text": "I'm going to represent\nthis information", "start": 4178.33, "duration": 2.91}, {"text": "with four small formulas, which\ntaken together, you AND them", "start": 4181.24, "duration": 7.38}, {"text": "together, are going to force\nc to have the correct behavior", "start": 4188.62, "duration": 3.87}, {"text": "associated with a AND b.", "start": 4192.49, "duration": 1.706}, {"text": "So if a AND b are\nboth 1, then c is 1.", "start": 4200.61, "duration": 3.36}, {"text": "If a is 0 and b is 1,\nthen it forces c to be 0.", "start": 4203.97, "duration": 10.29}, {"text": "And similarly, every other\nsetting besides a AND", "start": 4214.26, "duration": 4.44}, {"text": "b being true, for C to\nbe false, which is what", "start": 4218.7, "duration": 5.82}, {"text": "you want when you have AND.", "start": 4224.52, "duration": 1.89}, {"text": "So I'm going to write\nthis expression here down", "start": 4226.41, "duration": 2.76}, {"text": "with z1 being in the place of\nc by just taking those four", "start": 4229.17, "duration": 6.29}, {"text": "expressions and\nANDing them together.", "start": 4235.46, "duration": 2.86}, {"text": "So this is exactly those same\nfour expressions written out", "start": 4238.32, "duration": 2.87}, {"text": "linearly.", "start": 4241.19, "duration": 1.61}, {"text": "Now I want to do the\nsame thing for z2,", "start": 4242.8, "duration": 3.0}, {"text": "but now that's written\nin terms of an OR.", "start": 4245.8, "duration": 2.348}, {"text": "So there's a slightly\ndifferent truth table", "start": 4248.148, "duration": 1.792}, {"text": "here up in this corner.", "start": 4249.94, "duration": 1.575}, {"text": "So now if either one is\n1, we get a 1 result.", "start": 4255.03, "duration": 4.39}, {"text": "And so now if a AND b are\ntrue, you get c is true.", "start": 4259.42, "duration": 6.96}, {"text": "However, if a is\ntrue and b is false,", "start": 4266.38, "duration": 2.36}, {"text": "that still implies c is true.", "start": 4268.74, "duration": 3.47}, {"text": "So I'm going to write down\nthose rules for specifying", "start": 4272.21, "duration": 8.13}, {"text": "how z2 must be set.", "start": 4280.34, "duration": 4.98}, {"text": "And each one of\nthese things is going", "start": 4285.32, "duration": 1.83}, {"text": "to get converted into clauses,\nthree clauses with three", "start": 4287.15, "duration": 4.14}, {"text": "literals, using these\nrules over here.", "start": 4291.29, "duration": 5.5}, {"text": "So I'm going to do\nthat for each zi.", "start": 4296.79, "duration": 2.78}, {"text": "And lastly, to make sure the\nwhole thing is satisfied,", "start": 4299.57, "duration": 2.86}, {"text": "which means there's\nan output of one here,", "start": 4302.43, "duration": 1.91}, {"text": "I'm going to have one\nclause associated, which", "start": 4304.34, "duration": 3.51}, {"text": "says that z4, the output, is 1.", "start": 4307.85, "duration": 4.85}, {"text": "Now, I can convert all of those\nwhen I have a AND b implies c.", "start": 4312.7, "duration": 5.25}, {"text": "That's logically equivalent\nto not a OR not b OR c.", "start": 4317.95, "duration": 5.197}, {"text": "And the way you can\nsee that is really", "start": 4323.147, "duration": 1.583}, {"text": "by repeated application\nof these rules here.", "start": 4324.73, "duration": 4.05}, {"text": "We're running a\nlittle low on time.", "start": 4328.78, "duration": 2.29}, {"text": "So maybe you'll just have\nto check this offline.", "start": 4331.07, "duration": 3.23}, {"text": "But quickly, a AND b implies\nc using the first equivalence", "start": 4334.3, "duration": 7.09}, {"text": "is the not of this\npart, OR C. And then", "start": 4341.39, "duration": 4.8}, {"text": "I can use De Morgan to\nconvert that not of an AND", "start": 4346.19, "duration": 4.23}, {"text": "to an OR of the nots.", "start": 4350.42, "duration": 2.94}, {"text": "And then I can remove\nthe parentheses", "start": 4353.36, "duration": 3.45}, {"text": "because OR is associative.", "start": 4356.81, "duration": 3.03}, {"text": "And so I get a clause,\nwhich is what I need.", "start": 4359.84, "duration": 3.93}, {"text": "So each one of these guys is\nreally equivalent to a clause.", "start": 4363.77, "duration": 3.36}, {"text": "And so I just get\na bunch of clauses.", "start": 4367.13, "duration": 1.908}, {"text": "And actually,\ntechnically, this needs", "start": 4369.038, "duration": 1.542}, {"text": "to be three, a copy\nof three things here.", "start": 4370.58, "duration": 4.83}, {"text": "It should be z4 OR z4\nOR z4, which is a lot.", "start": 4375.41, "duration": 7.5}, {"text": "So check-in--\n[INAUDIBLE] I realize", "start": 4382.91, "duration": 2.61}, {"text": "my check-in is broken, because\nI only realized that last point", "start": 4385.52, "duration": 3.39}, {"text": "just now as I was talking.", "start": 4388.91, "duration": 1.53}, {"text": "So the actual value\nthat you get in terms", "start": 4390.44, "duration": 5.7}, {"text": "of-- oh, no, the number\nof clauses is correct.", "start": 4396.14, "duration": 3.06}, {"text": "No, I take it back.", "start": 4399.2, "duration": 1.44}, {"text": "This is fine.", "start": 4400.64, "duration": 1.18}, {"text": "So if you understood\nwhat I was saying,", "start": 4401.82, "duration": 1.88}, {"text": "hopefully, you can see\nhow big the formula", "start": 4403.7, "duration": 4.26}, {"text": "phi prime is in terms of the\nnumber of operations in phi.", "start": 4407.96, "duration": 5.88}, {"text": "So let's see how\nmany people get that.", "start": 4413.84, "duration": 2.1}, {"text": "I acknowledge this may be a\nlittle on the technical side.", "start": 4415.94, "duration": 5.88}, {"text": "OK.", "start": 4421.82, "duration": 0.57}, {"text": "I'm going to close\nit, close it down.", "start": 4422.39, "duration": 3.65}, {"text": "Please enter your value.", "start": 4426.04, "duration": 1.0}, {"text": "OK.", "start": 4430.44, "duration": 2.23}, {"text": "Yeah, the correct\nanswer is 4k plus 1,", "start": 4432.67, "duration": 4.2}, {"text": "because each one\nof these operations", "start": 4436.87, "duration": 6.07}, {"text": "is going to end up being\na row in this picture.", "start": 4442.94, "duration": 2.025}, {"text": "Each operation is going to have\na variable associated to it.", "start": 4447.52, "duration": 2.52}, {"text": "It's going to become\na row in this picture.", "start": 4450.04, "duration": 2.05}, {"text": "And so then each row is going\nto have four clauses, which", "start": 4452.09, "duration": 7.97}, {"text": "define what you need--\nset what you need in order", "start": 4460.06, "duration": 6.03}, {"text": "to force that variable to have\nthe right value corresponding", "start": 4466.09, "duration": 4.8}, {"text": "to that operation.", "start": 4470.89, "duration": 0.96}, {"text": "And so then you need-- and\nyou need one extra clause here", "start": 4474.8, "duration": 3.42}, {"text": "for saying that this whole\nthing evaluates to true.", "start": 4478.22, "duration": 4.8}, {"text": "So that's all I\nwanted to do today.", "start": 4485.63, "duration": 5.1}, {"text": "We proved those\ntwo main theorems.", "start": 4490.73, "duration": 2.13}, {"text": "And now we know that there\nare NP-complete problems.", "start": 4492.86, "duration": 2.89}, {"text": "And all of the other problems\nthat we can get from--", "start": 4495.75, "duration": 3.92}, {"text": "by reductions from\nthese problems", "start": 4499.67, "duration": 2.88}, {"text": "are also going to be NP-complete\nas long as they're in NP.", "start": 4502.55, "duration": 4.62}, {"text": "So that's it.", "start": 4507.17, "duration": 1.86}, {"text": "Feel free to put some\nquestions into the chat,", "start": 4509.03, "duration": 4.65}, {"text": "or move on to whatever else\nyou're going to be doing next.", "start": 4513.68, "duration": 3.9}, {"text": "So a good question here\nis, why is phi prime", "start": 4517.58, "duration": 2.37}, {"text": "not logically equivalent\nwith this construction?", "start": 4519.95, "duration": 2.355}, {"text": "It can't be\nlogically equivalent.", "start": 4522.305, "duration": 2.475}, {"text": "Logically equivalent\nmeans that it gives you", "start": 4524.78, "duration": 2.4}, {"text": "exactly the same function.", "start": 4527.18, "duration": 1.77}, {"text": "If you set the variables\nin the same way,", "start": 4528.95, "duration": 2.07}, {"text": "you get the same\nresult coming out.", "start": 4531.02, "duration": 3.23}, {"text": "Well, phi prime has more\nvariables than phi does.", "start": 4534.25, "duration": 3.45}, {"text": "So it wouldn't even\nmake sense to talk", "start": 4537.7, "duration": 1.98}, {"text": "about logical equivalence\nbecause they're", "start": 4539.68, "duration": 1.74}, {"text": "two functions on different\nnumbers of variables.", "start": 4541.42, "duration": 2.65}, {"text": "So in that sense, it\ndoesn't really make sense.", "start": 4544.07, "duration": 3.08}, {"text": "What you could say is\nthat for every setting", "start": 4547.15, "duration": 3.24}, {"text": "of the overlapping\nvariables, so the variables", "start": 4550.39, "duration": 3.66}, {"text": "that appear in both\nphi and phi prime--", "start": 4554.05, "duration": 2.02}, {"text": "so those are the original\nvariables of phi--", "start": 4556.07, "duration": 2.6}, {"text": "there's going to exist some\nsetting of new variables, which", "start": 4558.67, "duration": 4.23}, {"text": "is going to make the--", "start": 4562.9, "duration": 2.06}, {"text": "there's going to\nbe-- there will exist", "start": 4571.997, "duration": 1.583}, {"text": "some setting of the\nnew variables which", "start": 4573.58, "duration": 1.68}, {"text": "will make the two\nformulas agree,", "start": 4575.26, "duration": 2.4}, {"text": "but that's not the definition\nof logical equivalence.", "start": 4577.66, "duration": 3.254}, {"text": "So why-- going back to the\nproof, the satisfiability proof", "start": 4583.97, "duration": 4.92}, {"text": "and the legal\nneighborhoods, could I", "start": 4588.89, "duration": 1.95}, {"text": "go over why the number of legal\nneighborhoods is polynomial.", "start": 4590.84, "duration": 4.17}, {"text": "The number of\nlegal neighborhoods", "start": 4595.01, "duration": 1.38}, {"text": "is not only polynomial.", "start": 4596.39, "duration": 1.71}, {"text": "It's constant.", "start": 4598.1, "duration": 2.71}, {"text": "It depends only on the machine.", "start": 4600.81, "duration": 1.8}, {"text": "It does not depend on M.\nBecause each cell can have", "start": 4602.61, "duration": 7.23}, {"text": "at most some fixed number of--", "start": 4609.84, "duration": 2.64}, {"text": "can have the number\nof tape symbols", "start": 4612.48, "duration": 2.73}, {"text": "plus the number\nof state symbols.", "start": 4615.21, "duration": 1.68}, {"text": "That depends on\nthe machine only.", "start": 4616.89, "duration": 3.09}, {"text": "So now we have six tape cells\nfor the six cells in a 2", "start": 4619.98, "duration": 6.36}, {"text": "by 3 neighborhood.", "start": 4626.34, "duration": 1.02}, {"text": "So you're going to have that\nnumber to the sixth power.", "start": 4627.36, "duration": 2.61}, {"text": "But still, it's a constant\nto the sixth power.", "start": 4629.97, "duration": 1.93}, {"text": "It's still a constant.", "start": 4631.9, "duration": 0.917}, {"text": "It doesn't depend on M.\nSo it's not a question", "start": 4632.817, "duration": 2.523}, {"text": "of even being polynomial.", "start": 4635.34, "duration": 3.0}, {"text": "It's a constant value.", "start": 4638.34, "duration": 1.06}, {"text": "It's a constant\nmultiplier if you", "start": 4639.4, "duration": 2.18}, {"text": "want to think about it in terms\nof the size of the formula", "start": 4641.58, "duration": 4.71}, {"text": "that's going to result.", "start": 4646.29, "duration": 1.68}, {"text": "Don't forget we're trying\nto make a formula which is--", "start": 4647.97, "duration": 8.34}, {"text": "the reduction has\nto be polynomial.", "start": 4656.31, "duration": 4.03}, {"text": "It's a polynomial\ntime reduction.", "start": 4660.34, "duration": 1.46}, {"text": "So that means that\nas n increases,", "start": 4661.8, "duration": 3.61}, {"text": "the time to calculate\nthe reduction increases", "start": 4665.41, "duration": 2.36}, {"text": "as a polynomial.", "start": 4667.77, "duration": 2.52}, {"text": "But we're fixing M.\nSo M does not change.", "start": 4670.29, "duration": 7.8}, {"text": "So therefore anything\nthat depends on M only", "start": 4678.09, "duration": 2.48}, {"text": "is just going to be a constant\nimpact on the formula.", "start": 4680.57, "duration": 3.19}, {"text": "It's not going to be--", "start": 4683.76, "duration": 1.07}, {"text": "it doesn't depend on M.", "start": 4684.83, "duration": 3.37}, {"text": "OK, everybody.", "start": 4688.2, "duration": 2.78}, {"text": "Bye bye.", "start": 4690.98, "duration": 1.23}, {"text": "See you.", "start": 4692.21, "duration": 1.73}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.924}, {"text": "[RUSTLING]", "start": 1.924, "duration": 1.924}, {"text": "[CLICKING]", "start": 3.848, "duration": 2.405}, {"text": "SCOTT HUGHES: So\nwe're just picking up", "start": 9.817, "duration": 1.583}, {"text": "where we stopped last time.", "start": 11.4, "duration": 1.125}, {"text": "So we are beginning\nto discuss how", "start": 12.525, "duration": 3.315}, {"text": "we are going to sort of\ndo a geometrical approach", "start": 15.84, "duration": 3.87}, {"text": "to physics, using a more\ngeneral set of coordinates now.", "start": 19.71, "duration": 4.5}, {"text": "So we began talking about how\nthings change when I discuss", "start": 24.21, "duration": 3.06}, {"text": "special relativity,\nso for the moment", "start": 27.27, "duration": 1.59}, {"text": "keeping ourselves just\nat special relativity.", "start": 28.86, "duration": 2.22}, {"text": "We, by the way, are going to\nbegin lifting our assumptions", "start": 31.08, "duration": 2.49}, {"text": "that it is simply special\nrelativity fairly soon.", "start": 33.57, "duration": 3.342}, {"text": "But to set that\nup, I need to start", "start": 36.912, "duration": 1.458}, {"text": "thinking about how to work\nin more general coordinate", "start": 38.37, "duration": 2.52}, {"text": "systems.", "start": 40.89, "duration": 1.02}, {"text": "So we're going to do it in the\nsimplest possible curvilinear", "start": 41.91, "duration": 2.71}, {"text": "coordinates.", "start": 44.62, "duration": 0.5}, {"text": "So it's basically just going\nfrom Cartesian coordinates", "start": 45.12, "duration": 2.73}, {"text": "in the spatial sector to\nplane polar coordinates.", "start": 47.85, "duration": 3.36}, {"text": "One of the things which I\nhave emphasized a few times,", "start": 51.21, "duration": 2.25}, {"text": "and I'm going to\ncontinue to hammer on,", "start": 53.46, "duration": 1.74}, {"text": "is that these are a little bit\ndifferent from the curvilinear", "start": 55.2, "duration": 4.44}, {"text": "coordinates that you are\nused to in your past life.", "start": 59.64, "duration": 3.36}, {"text": "In particular, if I write\nout the displacement,", "start": 63.0, "duration": 3.02}, {"text": "the little vector of\nthe displacement element", "start": 66.02, "duration": 2.59}, {"text": "in the usual way,\nI am using what's", "start": 68.61, "duration": 2.34}, {"text": "called a \"coordinate basis,\"\nwhich means that the vector", "start": 70.95, "duration": 3.3}, {"text": "dx is related to the\ndisplacement, the differential", "start": 74.25, "duration": 3.24}, {"text": "of the coordinates, by\njust that thing contracted", "start": 77.49, "duration": 2.28}, {"text": "with all the basis vectors.", "start": 79.77, "duration": 1.98}, {"text": "And so what that means is I have\na little displacement in time,", "start": 81.75, "duration": 2.73}, {"text": "which looks normal.", "start": 84.48, "duration": 1.14}, {"text": "Displacement in radius,\nwhich looks normal.", "start": 85.62, "duration": 2.55}, {"text": "Displacement in the z\ndirection, which looks normal,", "start": 88.17, "duration": 2.25}, {"text": "and a displacement in an\nangle, which does not.", "start": 90.42, "duration": 2.828}, {"text": "In order for this whole thing\nto be dimensionally consistent,", "start": 93.248, "duration": 2.542}, {"text": "that's telling me e phi has to\nhave the dimensions of length.", "start": 95.79, "duration": 3.74}, {"text": "And that is a\nfeature, not a bug.", "start": 99.53, "duration": 1.75}, {"text": "Last time, we\nintroduced the matrix", "start": 103.89, "duration": 1.86}, {"text": "that allows me to convert\nbetween one coordinate system", "start": 105.75, "duration": 2.4}, {"text": "and another, so just\nbasically the matrix--", "start": 108.15, "duration": 2.302}, {"text": "it's sort of a Jacobi matrix.", "start": 110.452, "duration": 1.208}, {"text": "It's a matrix of\npartials between the two", "start": 111.66, "duration": 2.43}, {"text": "coordinate systems.", "start": 114.09, "duration": 1.83}, {"text": "And this idea that things are--", "start": 115.92, "duration": 1.37}, {"text": "they look a little weird.", "start": 117.29, "duration": 1.06}, {"text": "So the way I did that was I\ndidn't actually write it out,", "start": 118.35, "duration": 2.375}, {"text": "but I did the usual mapping\nbetween x, y and r and phi,", "start": 120.725, "duration": 3.925}, {"text": "worked out all of\nmy derivatives.", "start": 124.65, "duration": 2.388}, {"text": "And sure enough,\nyou've got something", "start": 127.038, "duration": 1.542}, {"text": "that looks very standard,\nwith the possible exception", "start": 128.58, "duration": 1.89}, {"text": "of these r's that are\nappearing in here.", "start": 130.47, "duration": 1.6}, {"text": "So notice the elements\nof this matrix.", "start": 132.07, "duration": 1.64}, {"text": "These do not have\nconsistent units--", "start": 133.71, "duration": 1.98}, {"text": "again, feature, not bug.", "start": 135.69, "duration": 2.34}, {"text": "This guy is basically\njust the inverse of that.", "start": 138.03, "duration": 2.462}, {"text": "This is the matrix that\naffects the coordinates", "start": 140.492, "duration": 1.958}, {"text": "in the opposite direction.", "start": 142.45, "duration": 1.083}, {"text": "And notice in this case,\nyou have some elements where", "start": 143.533, "duration": 2.757}, {"text": "their units are 1 over length.", "start": 146.29, "duration": 3.53}, {"text": "So let's just continue\nto sort of catalog", "start": 149.82, "duration": 3.65}, {"text": "what some of the things we are\ngoing to be working with look", "start": 153.47, "duration": 2.5}, {"text": "like in this new\ncoordinate representation.", "start": 155.97, "duration": 3.31}, {"text": "And this will lead\nus to introduce", "start": 159.28, "duration": 1.88}, {"text": "one of the mathematical\nobjects that we", "start": 161.16, "duration": 1.74}, {"text": "are going to use extensively\nas we move forward", "start": 162.9, "duration": 3.95}, {"text": "in studying this subject.", "start": 166.85, "duration": 1.55}, {"text": "So what I want to do\nnext is look at what", "start": 168.4, "duration": 1.91}, {"text": "my basis vectors look like.", "start": 170.31, "duration": 1.34}, {"text": "So what I want to do\nis characterize what", "start": 175.09, "duration": 2.09}, {"text": "my e r and my e phi look like.", "start": 177.18, "duration": 4.13}, {"text": "And these are going to look very\nfamiliar from your intuition,", "start": 181.31, "duration": 3.07}, {"text": "from having studied\nthings like E&M", "start": 184.38, "duration": 2.13}, {"text": "in non-Cartesian coordinates.", "start": 186.51, "duration": 2.04}, {"text": "So your e r is just related to\nthe original Cartesian basis", "start": 188.55, "duration": 5.04}, {"text": "vectors, like so.", "start": 193.59, "duration": 1.005}, {"text": "And if you like, you\ncan easily read that out", "start": 198.69, "duration": 2.03}, {"text": "by performing the\nfollowing matrix", "start": 200.72, "duration": 3.48}, {"text": "multiplication on the original\nCartesian basis vectors.", "start": 204.2, "duration": 4.56}, {"text": "Your e phi perhaps\nlooks a little wacky.", "start": 208.76, "duration": 5.35}, {"text": "So you can see the length\ncoming into play there.", "start": 228.17, "duration": 3.21}, {"text": "A good way to think about\nthis is if your intuition", "start": 231.38, "duration": 4.14}, {"text": "about basis factors--", "start": 235.52, "duration": 3.19}, {"text": "I have to be careful with\nthis language myself--", "start": 238.71, "duration": 2.0}, {"text": "your intuition\nabout basis vectors", "start": 240.71, "duration": 1.417}, {"text": "is typically that\nthey are unit vectors.", "start": 242.127, "duration": 1.883}, {"text": "These are not unit vectors.", "start": 244.01, "duration": 1.53}, {"text": "They do form a nice basis,\nbut they are not unit vectors.", "start": 245.54, "duration": 3.15}, {"text": "In particular, the basic idea\nwe're going to go with here", "start": 248.69, "duration": 2.43}, {"text": "is that e phi, it's always\ngoing to sort of point", "start": 251.12, "duration": 2.94}, {"text": "in the tangential direction.", "start": 254.06, "duration": 1.65}, {"text": "But no matter where\nI put it in radius,", "start": 255.71, "duration": 3.004}, {"text": "I want that vector\nto always sort", "start": 258.714, "duration": 1.375}, {"text": "of subtend the same\namount of angle.", "start": 260.089, "duration": 2.971}, {"text": "In order to do that, its\nlength needs to grow with r.", "start": 263.06, "duration": 3.192}, {"text": "So that's where\nthat's a little bit", "start": 266.252, "duration": 1.458}, {"text": "different from your intuition.", "start": 267.71, "duration": 1.89}, {"text": "And there's a very\ngood reason for this,", "start": 269.6, "duration": 1.68}, {"text": "which we will get to, hopefully,\nwell before the end of today's", "start": 271.28, "duration": 2.625}, {"text": "class.", "start": 273.905, "duration": 1.825}, {"text": "So last time, when\nwe first began", "start": 275.73, "duration": 4.91}, {"text": "to talk about tensors a\ncouple of lectures ago,", "start": 280.64, "duration": 2.49}, {"text": "the first tensor I gave you--", "start": 283.13, "duration": 1.65}, {"text": "so confining ourselves just\nto Cartesian coordinates--", "start": 289.43, "duration": 3.04}, {"text": "was the metric,\nwhich was originally", "start": 292.47, "duration": 4.44}, {"text": "introduced as this\nmathematical object that", "start": 296.91, "duration": 3.63}, {"text": "came out of looking at dot\nproducts between basis vectors.", "start": 300.54, "duration": 2.418}, {"text": "It's essentially a\ntensor that allows", "start": 302.958, "duration": 1.542}, {"text": "me to feed in two\ndisplacements and get", "start": 304.5, "duration": 2.73}, {"text": "the invariant interval between\nthose displacements that", "start": 307.23, "duration": 4.11}, {"text": "comes out of that.", "start": 311.34, "duration": 0.75}, {"text": "I am going to continue to call\nthe dot product of two basis", "start": 316.08, "duration": 8.28}, {"text": "vectors the \"metric.\"", "start": 324.36, "duration": 2.99}, {"text": "But I'm going to use a slightly\ndifferent symbol for this.", "start": 327.35, "duration": 3.55}, {"text": "I'm going to call\nthis g alpha beta.", "start": 330.9, "duration": 1.5}, {"text": "In the coordinate representation\nthat we are using right now,", "start": 335.34, "duration": 3.25}, {"text": "so in plane polar\ncoordinates, this becomes--", "start": 338.59, "duration": 7.09}, {"text": "you can work it out from what\nI've written down right here.", "start": 345.68, "duration": 3.97}, {"text": "This is just the diagonal\nof minus 1, 1 r squared 1.", "start": 349.65, "duration": 6.33}, {"text": "So this equals dot here.", "start": 358.65, "duration": 1.32}, {"text": "This is-- I'll put PPC for plane\npolar coordinates under that.", "start": 359.97, "duration": 3.62}, {"text": "And then using that, you\nknow that you can always", "start": 369.16, "duration": 3.03}, {"text": "work out the invariant\ndisplacement between two", "start": 372.19, "duration": 4.65}, {"text": "events.", "start": 376.84, "duration": 1.51}, {"text": "It's always going to be\nthe metric contracted", "start": 378.35, "duration": 6.31}, {"text": "with the differential\ndisplacement element.", "start": 384.66, "duration": 6.15}, {"text": "And this is going to\nbe minus dt squared", "start": 390.81, "duration": 3.75}, {"text": "plus dr squared plus r squared\nd phi squared plus dz squared.", "start": 394.56, "duration": 6.66}, {"text": "That, I hope, makes\na lot of sense.", "start": 401.22, "duration": 1.565}, {"text": "This is exactly\nwhat you'd expect", "start": 402.785, "duration": 1.375}, {"text": "if I have two events\nthat are separated", "start": 404.16, "duration": 2.52}, {"text": "in plane polar coordinates\nby dt, dr, d phi, dz.", "start": 406.68, "duration": 4.62}, {"text": "This is what the distance\nbetween them should be.", "start": 411.3, "duration": 3.36}, {"text": "So the fact that\nmy basis vectors", "start": 414.66, "duration": 2.07}, {"text": "have this slightly annoying\nform associated with them,", "start": 416.73, "duration": 4.31}, {"text": "it all sort of comes\nout in the wash here.", "start": 421.04, "duration": 1.75}, {"text": "Remember at the end of the day,\nif we think about quantities", "start": 422.79, "duration": 3.27}, {"text": "that are representation\nindependent--", "start": 426.06, "duration": 1.728}, {"text": "and that's going to\nbe the key thing.", "start": 427.788, "duration": 1.542}, {"text": "When you assemble scalars\nout of these things,", "start": 429.33, "duration": 4.23}, {"text": "the individual\ntensor components,", "start": 433.56, "duration": 3.43}, {"text": "they can be a little\nbit confusing sometimes.", "start": 436.99, "duration": 2.18}, {"text": "They are not things\nthat we measure.", "start": 439.17, "duration": 1.56}, {"text": "They are not things that\nreally characterize what we", "start": 440.73, "duration": 2.52}, {"text": "are going to be working with.", "start": 443.25, "duration": 1.44}, {"text": "And we really want to\nget into the physics,", "start": 444.69, "duration": 1.792}, {"text": "unless we're very\ncareful about it.", "start": 446.482, "duration": 2.318}, {"text": "This is something\nyou can measure.", "start": 448.8, "duration": 1.535}, {"text": "And so sure enough,\nit comes out,", "start": 450.335, "duration": 1.375}, {"text": "and it's got a\ngood meaning to it.", "start": 451.71, "duration": 1.56}, {"text": "Let me just wrap\nup one last thing", "start": 453.27, "duration": 1.71}, {"text": "before I talk about sort of\nwhere we're going with this.", "start": 454.98, "duration": 3.25}, {"text": "So just for completeness, let me\nwrite down the basis one forms.", "start": 458.23, "duration": 5.52}, {"text": "Just as the basis vectors had a\nbit of a funny form associated", "start": 463.75, "duration": 6.54}, {"text": "with them, you're going to find\nthe basis one forms likewise", "start": 470.29, "duration": 3.42}, {"text": "have a bit of a funny\nform associated with them.", "start": 473.71, "duration": 2.0}, {"text": "And the way I'm\ngoing to get these--", "start": 475.71, "duration": 2.81}, {"text": "and so these are going to be\nthe Cartesian basis one forms--", "start": 478.52, "duration": 4.04}, {"text": "basically, I'm not carefully\nproving all these relations", "start": 482.56, "duration": 3.235}, {"text": "at this point, because you\nall know how to do that.", "start": 485.795, "duration": 2.125}, {"text": "I'm just using line\nup the indices rule.", "start": 487.92, "duration": 2.71}, {"text": "And when you do\nthat, you get this.", "start": 490.63, "duration": 14.12}, {"text": "And likewise, your basis one\nform for the axial direction,", "start": 504.75, "duration": 5.44}, {"text": "I'll just write down the result.\nIt's going to look like this.", "start": 510.19, "duration": 9.79}, {"text": "So the key place where all\nof this-- so right now, these", "start": 526.25, "duration": 5.495}, {"text": "are all just sort\nof definitions.", "start": 531.745, "duration": 1.375}, {"text": "Nothing I've done here\nshould be anything", "start": 533.12, "duration": 3.27}, {"text": "that even approaches a\nsurprise, I hope, just", "start": 536.39, "duration": 2.07}, {"text": "given the you guys have done--", "start": 538.46, "duration": 2.645}, {"text": "the key thing\nthat's probably new", "start": 541.105, "duration": 1.375}, {"text": "is all this garbage associated\nwith coordinate bases,", "start": 542.48, "duration": 2.49}, {"text": "this extra factors of r and\n1 over r that are popping up.", "start": 544.97, "duration": 2.85}, {"text": "But provided you're willing to\nsort of swallow your discomfort", "start": 547.82, "duration": 3.27}, {"text": "and go through\nthe motions, these", "start": 551.09, "duration": 1.77}, {"text": "are not difficult calculations.", "start": 552.86, "duration": 2.7}, {"text": "The key place where all\nof this really matters", "start": 555.56, "duration": 2.28}, {"text": "is going to be when we\ncalculate derivatives of things.", "start": 557.84, "duration": 4.02}, {"text": "It'll turn out there is\nan important rule when", "start": 576.523, "duration": 1.917}, {"text": "we talk about integrals as\nwell a little bit later,", "start": 578.44, "duration": 1.76}, {"text": "but let's just say that.", "start": 580.2, "duration": 1.0}, {"text": "So for now, we'll\nfocus on derivatives.", "start": 581.2, "duration": 1.785}, {"text": "So all the derivatives that\nwe've been looking at so far,", "start": 582.985, "duration": 2.375}, {"text": "we have, indeed, done a couple\nof calculations where we've", "start": 585.36, "duration": 2.49}, {"text": "computed the derivatives\nof various vector valued", "start": 587.85, "duration": 3.55}, {"text": "and tensor valued quantities.", "start": 591.4, "duration": 1.85}, {"text": "And it was helped by the\nfact that all the bases, when", "start": 593.25, "duration": 3.51}, {"text": "I work in Cartesian\ncoordinates, are constant.", "start": 596.76, "duration": 2.76}, {"text": "Well, that's not the case now.", "start": 599.52, "duration": 2.61}, {"text": "So now, we need to\naccount for the fact", "start": 602.13, "duration": 10.02}, {"text": "that the bases all vary\nwith our coordinates.", "start": 612.15, "duration": 5.98}, {"text": "So let me just\nquickly make a catalog", "start": 624.02, "duration": 2.37}, {"text": "of all the non-trivial--\nthere's basically four.", "start": 626.39, "duration": 3.15}, {"text": "In this one, where I'm just\ndoing plane polar coordinates,", "start": 629.54, "duration": 2.64}, {"text": "there are four\nnon-trivial derivatives", "start": 632.18, "duration": 1.86}, {"text": "we need to worry about.", "start": 634.04, "duration": 2.1}, {"text": "One of them actually\nturns out to be 0.", "start": 636.14, "duration": 2.7}, {"text": "So the radial derivative of\nthe radial unit vector is 0.", "start": 638.84, "duration": 3.33}, {"text": "But the phi derivative of\nthe phi unit vector is not.", "start": 644.93, "duration": 5.38}, {"text": "you go and take the phi\nderivative of this guy,", "start": 650.31, "duration": 3.99}, {"text": "and you basically get--", "start": 654.3, "duration": 2.04}, {"text": "take the phi derivative\nof this, you're", "start": 656.34, "duration": 1.74}, {"text": "going to get this back,\nmodulo factor of radius.", "start": 658.08, "duration": 3.57}, {"text": "So I can write d e r\nd phi as e phi over r.", "start": 661.65, "duration": 6.27}, {"text": "If I take the derivative\nof e phi with respect to r,", "start": 673.99, "duration": 3.3}, {"text": "I get e phi back, divided by r.", "start": 677.29, "duration": 2.73}, {"text": "So the simplest way to\nwrite this is like so.", "start": 680.02, "duration": 5.4}, {"text": "And finally, if I take the\nphi derivative of the phi unit", "start": 691.015, "duration": 3.165}, {"text": "vector, I get e r back, with\nan extra factor of r thrown in.", "start": 694.18, "duration": 4.526}, {"text": "And a minus sign.", "start": 704.42, "duration": 0.9}, {"text": "So we're going to see a way of\ndoing this that's a little bit", "start": 712.32, "duration": 2.58}, {"text": "more systematic\nlater, but I want", "start": 714.9, "duration": 1.5}, {"text": "to just keep the simple example,\nwhere you can just basically", "start": 716.4, "duration": 2.67}, {"text": "by hand calculate all the\nnon-trivial derivatives easily.", "start": 719.07, "duration": 4.08}, {"text": "Of course, there's also a t\nunit vector and a z unit vector.", "start": 723.15, "duration": 2.625}, {"text": "But they're constants,\nso I'm not going", "start": 725.775, "duration": 1.625}, {"text": "to bother writing them out.", "start": 727.4, "duration": 1.125}, {"text": "All the derivatives associated\nwith them are equal to 0.", "start": 728.525, "duration": 2.845}, {"text": "So let's imagine now that I\nhave assembled some vector.", "start": 731.37, "duration": 6.23}, {"text": "So I have some vector field\nthat lives in this spacetime.", "start": 737.6, "duration": 3.65}, {"text": "And I'm using this basis.", "start": 741.25, "duration": 1.33}, {"text": "And so I would write this\nvector with components v alpha.", "start": 742.58, "duration": 4.25}, {"text": "And let's let the--", "start": 746.83, "duration": 0.798}, {"text": "so this is going to be a\ncurvilinear coordinate system,", "start": 747.628, "duration": 2.292}, {"text": "so this will be plane polar\ncoordinates being used here,", "start": 749.92, "duration": 3.57}, {"text": "plane polar coordinate\nbasis vectors.", "start": 753.49, "duration": 3.57}, {"text": "And what I would like to\ndo is assemble the tensor", "start": 760.03, "duration": 3.815}, {"text": "that you can think\nof essentially", "start": 763.845, "duration": 1.375}, {"text": "as the gradient of this vector.", "start": 765.22, "duration": 2.57}, {"text": "So let's begin by doing this\nin a sort of abstract notation.", "start": 767.79, "duration": 3.34}, {"text": "So the gradient of this guy--\nthis is sort of ugly notation,", "start": 771.13, "duration": 3.9}, {"text": "but live with it.", "start": 775.03, "duration": 2.83}, {"text": "Following what we have\nbeen doing all along, what", "start": 777.86, "duration": 3.56}, {"text": "you would want to\ndo is just take", "start": 781.42, "duration": 2.73}, {"text": "the root of this whole thing.", "start": 784.15, "duration": 1.95}, {"text": "It's going to have a\ndownstairs component on it.", "start": 786.1, "duration": 2.46}, {"text": "So attach to it\nthe basis one form.", "start": 788.56, "duration": 3.93}, {"text": "If you prefer, you can write\nit using the d notation", "start": 792.49, "duration": 2.67}, {"text": "like I have there,\nbut I just want", "start": 795.16, "duration": 1.688}, {"text": "to stick with the form\nI wrote in my notes.", "start": 796.848, "duration": 1.792}, {"text": "Looking at this the way I've\nsort of got this right now,", "start": 803.81, "duration": 3.48}, {"text": "I can think of, if I\ndon't include the basis", "start": 807.29, "duration": 5.31}, {"text": "one forms here, this should be\nthe components of a one form.", "start": 812.6, "duration": 8.69}, {"text": "So this should be\na kind of object.", "start": 821.29, "duration": 2.46}, {"text": "So let's just expand\nout that derivative.", "start": 830.49, "duration": 2.394}, {"text": "Let's write it like this.", "start": 835.61, "duration": 1.34}, {"text": "So you just-- we haven't\nchanged calculus.", "start": 839.54, "duration": 3.995}, {"text": "So when I do this, I'm\ngoing to basically use", "start": 843.535, "duration": 1.875}, {"text": "the old-fashioned Leibniz\nrule for expanding", "start": 845.41, "duration": 2.76}, {"text": "the derivative\nproduct of two things.", "start": 848.17, "duration": 1.67}, {"text": "Here's the key thing which\nI want to emphasize--", "start": 866.29, "duration": 2.73}, {"text": "in order for this\nwhole thing to be--", "start": 869.02, "duration": 1.77}, {"text": "for this to be a tensorial\nobject, something that I couple", "start": 870.79, "duration": 3.99}, {"text": "to this basis one form, the\nsum of these two objects", "start": 874.78, "duration": 6.53}, {"text": "must obey the rules for\ntransforming tensors.", "start": 881.31, "duration": 3.09}, {"text": "But the two objects\nindividually will not.", "start": 884.4, "duration": 2.28}, {"text": "So this is an\nimportant point which", "start": 901.822, "duration": 1.458}, {"text": "I'm going to emphasize in\nslightly different words", "start": 903.28, "duration": 2.37}, {"text": "in just a few moments again.", "start": 905.65, "duration": 1.355}, {"text": "This is one of the key\nthings I want you to get out", "start": 907.005, "duration": 2.125}, {"text": "of this lecture, is that\nwhen I'm taking derivatives", "start": 909.13, "duration": 2.167}, {"text": "of things like this,\nyou've got to be", "start": 911.297, "duration": 1.981}, {"text": "a little bit careful about what\nyou consider to be components", "start": 913.278, "duration": 2.542}, {"text": "of tensors and what is not.", "start": 915.82, "duration": 1.29}, {"text": "Now as written like that,\nthis is kind of annoying.", "start": 919.87, "duration": 3.18}, {"text": "So my first object has a nice\nbasis vector attached to it.", "start": 925.64, "duration": 4.46}, {"text": "My second object involves a\nderivative of the basis vector.", "start": 930.1, "duration": 3.72}, {"text": "However, something\nwe saw over here", "start": 933.82, "duration": 1.89}, {"text": "is that derivatives\nof basis vectors", "start": 935.71, "duration": 1.89}, {"text": "are themselves proportional\nto basis vectors.", "start": 937.6, "duration": 2.31}, {"text": "So what I'm going to do is\nintroduce a bit of notation.", "start": 944.858, "duration": 2.292}, {"text": "So let me switch\nnotation slightly here.", "start": 959.44, "duration": 2.07}, {"text": "So the beta derivative of\ne alpha can be written as--", "start": 961.51, "duration": 10.71}, {"text": "in general, it can be written\nas a linear combination", "start": 972.22, "duration": 3.75}, {"text": "of basis vectors.", "start": 975.97, "duration": 0.93}, {"text": "So what we're going\nto do is define d--", "start": 993.1, "duration": 4.25}, {"text": "I want to make sure my Greek\nletters are legible to everyone", "start": 997.35, "duration": 2.5}, {"text": "in the room here.", "start": 999.85, "duration": 0.63}, {"text": "So let me write this\nnice and clearly.", "start": 1000.48, "duration": 1.583}, {"text": "d beta of e alpha, I'm going to\nwrite that as capital gamma mu", "start": 1005.61, "duration": 10.25}, {"text": "beta alpha e mu.", "start": 1015.86, "duration": 5.34}, {"text": "This gamma that I've just\nintroduced here in this context", "start": 1021.2, "duration": 4.47}, {"text": "is known as the\nChristoffel symbol.", "start": 1025.67, "duration": 2.64}, {"text": "Fact I'm calling this a symbol,\nit's got three indices on it.", "start": 1035.138, "duration": 2.542}, {"text": "You might look at it and go,\nooh, smells like a tensor.", "start": 1037.68, "duration": 2.449}, {"text": "Be a little bit careful.", "start": 1040.129, "duration": 1.0}, {"text": "In much the same way that these\ntwo terms are not individually", "start": 1044.099, "duration": 4.321}, {"text": "components of a tensor,\nbut their sum is,", "start": 1048.42, "duration": 3.18}, {"text": "this guy individually\nis actually", "start": 1051.6, "duration": 1.86}, {"text": "not a component of\na tensor, but when", "start": 1053.46, "duration": 2.16}, {"text": "combined with other things, it\nallows us to assemble tensors.", "start": 1055.62, "duration": 3.72}, {"text": "So for our plane\npolar coordinates,", "start": 1068.22, "duration": 22.31}, {"text": "there are exactly three\nnon-zero Christoffel symbols.", "start": 1090.53, "duration": 4.54}, {"text": "So gamma phi r phi is equal\nto 1 over r, which is also", "start": 1095.07, "duration": 7.9}, {"text": "equal to gamma phi phi r.", "start": 1102.97, "duration": 5.16}, {"text": "Gamma r phi phi is minus r.", "start": 1111.29, "duration": 4.53}, {"text": "And you can basically just\nread that out of that table", "start": 1115.82, "duration": 2.25}, {"text": "that I wrote down over there.", "start": 1118.07, "duration": 2.01}, {"text": "All the others\nwill be equal to 0.", "start": 1120.08, "duration": 1.56}, {"text": "Now from this\nexample, this is what", "start": 1130.31, "duration": 2.916}, {"text": "it makes it smell like\nevery time you introduce", "start": 1133.226, "duration": 2.274}, {"text": "a new coordinate representation.", "start": 1135.5, "duration": 3.57}, {"text": "You're going to need to sit\ndown for an hour and a half,", "start": 1139.07, "duration": 3.002}, {"text": "or something like\nthat, and just work out", "start": 1142.072, "duration": 1.708}, {"text": "all the bloody derivatives, and\nthen go, oh, crap, and read out", "start": 1143.78, "duration": 2.625}, {"text": "all the different\ncomponents of this thing,", "start": 1146.405, "duration": 1.792}, {"text": "and assemble them together.", "start": 1148.197, "duration": 1.36}, {"text": "There actually is\nan algorithm that we", "start": 1149.557, "duration": 1.583}, {"text": "will get to at the\nend of this class that", "start": 1151.14, "duration": 1.708}, {"text": "allows you to easily extract\nthe Christoffel symbols provided", "start": 1152.848, "duration": 4.462}, {"text": "you know the metric.", "start": 1157.31, "duration": 1.11}, {"text": "But right now, I just want\nto illustrate this thing", "start": 1158.42, "duration": 2.64}, {"text": "conceptually.", "start": 1161.06, "duration": 0.6}, {"text": "The key thing which you\nshould know about it", "start": 1161.66, "duration": 1.95}, {"text": "is that it is essentially the--", "start": 1163.61, "duration": 3.67}, {"text": "I almost said the word \"matrix,\"\nbut it's got three indices.", "start": 1167.28, "duration": 2.84}, {"text": "It's a table of\nfunctions that allows", "start": 1170.12, "duration": 4.35}, {"text": "me to relate derivatives\nof basis vectors", "start": 1174.47, "duration": 3.57}, {"text": "to the basis vectors.", "start": 1178.04, "duration": 0.93}, {"text": "So before I go on to talk\nabout some of that stuff,", "start": 1184.58, "duration": 3.11}, {"text": "let's take a look at the\nderivative a little bit more", "start": 1187.69, "duration": 3.75}, {"text": "carefully.", "start": 1191.44, "duration": 0.883}, {"text": "So the derivative\nof the vector--", "start": 1220.255, "duration": 1.375}, {"text": "so let's basically take what\nI've written out up there.", "start": 1221.63, "duration": 2.6}, {"text": "I'm going to write this as\nthe beta derivative of vector", "start": 1224.23, "duration": 3.84}, {"text": "v. And I can write that as\nthe beta derivative of e of v", "start": 1228.07, "duration": 7.44}, {"text": "alpha--", "start": 1235.51, "duration": 1.44}, {"text": "so the first term\nwhere the derivative", "start": 1236.95, "duration": 2.34}, {"text": "hits the vector components.", "start": 1239.29, "duration": 1.611}, {"text": "And then I've got\na second term where", "start": 1243.55, "duration": 1.94}, {"text": "the derivative hits the basis.", "start": 1245.49, "duration": 4.81}, {"text": "I'm going to write this like so.", "start": 1250.3, "duration": 1.46}, {"text": "This is sort of annoying.", "start": 1258.84, "duration": 1.2}, {"text": "One term is\nproportional to e alpha,", "start": 1260.04, "duration": 2.16}, {"text": "one is proportional to e mu.", "start": 1262.2, "duration": 1.77}, {"text": "But notice, especially in the\nsecond term, both alpha and mu", "start": 1263.97, "duration": 4.59}, {"text": "are dummy indices, so\nI'm free to relabel them.", "start": 1268.56, "duration": 3.18}, {"text": "So what I'm going to\ndo is relabel alpha", "start": 1271.74, "duration": 2.13}, {"text": "and mu by exchanging them.", "start": 1273.87, "duration": 6.47}, {"text": "As long as I do\nthat consistently,", "start": 1283.57, "duration": 8.09}, {"text": "that is totally kosher.", "start": 1291.66, "duration": 1.83}, {"text": "And when I do that, I can\nfactor out an overall factor", "start": 1293.49, "duration": 12.65}, {"text": "of the basis object.", "start": 1306.14, "duration": 0.9}, {"text": "This combination\nthat pops up here--", "start": 1309.98, "duration": 4.36}, {"text": "so we give this a name.", "start": 1317.29, "duration": 2.19}, {"text": "And this is a combination\nwhich, by the time", "start": 1319.48, "duration": 2.18}, {"text": "you have finished this semester,\nif you don't have at least", "start": 1321.66, "duration": 3.48}, {"text": "one nightmare in which\nthis name appears,", "start": 1325.14, "duration": 2.04}, {"text": "I will not have done\nmy job properly.", "start": 1327.18, "duration": 1.78}, {"text": "This shows up a\nlot at this point.", "start": 1328.96, "duration": 3.62}, {"text": "This is called the\n\"covariant derivative.\"", "start": 1332.58, "duration": 4.553}, {"text": "And it shows up enough\nthat we introduce", "start": 1344.24, "duration": 2.85}, {"text": "a whole new notation\nfor the derivative", "start": 1347.09, "duration": 3.69}, {"text": "to take it into account.", "start": 1350.78, "duration": 1.77}, {"text": "I'm going to call\nthis combination", "start": 1352.55, "duration": 1.74}, {"text": "of the partial\nderivative of v and v", "start": 1354.29, "duration": 2.94}, {"text": "coupled to the\nChristoffel symbol--", "start": 1357.23, "duration": 3.71}, {"text": "I'm going to write this using\nthe, if you're talking LaTeX,", "start": 1363.56, "duration": 7.27}, {"text": "this would be the\nnabla operator.", "start": 1370.83, "duration": 3.63}, {"text": "So I made a point\nearlier when we", "start": 1374.46, "duration": 3.07}, {"text": "were talking about\nderivatives a couple of weeks", "start": 1377.53, "duration": 2.0}, {"text": "ago that we were reserving\nthe gradient symbol", "start": 1379.53, "duration": 6.21}, {"text": "for a special purpose later.", "start": 1385.74, "duration": 1.83}, {"text": "Here it is.", "start": 1387.57, "duration": 1.41}, {"text": "So whenever I make\na derivative that", "start": 1388.98, "duration": 2.34}, {"text": "involves the gradient\nsymbol like this,", "start": 1391.32, "duration": 2.67}, {"text": "it is this covariant derivative.", "start": 1393.99, "duration": 2.01}, {"text": "And the covariant derivative\nacting on vector components,", "start": 1396.0, "duration": 4.89}, {"text": "it generates tensor components.", "start": 1400.89, "duration": 2.82}, {"text": "Partial derivative does not.", "start": 1403.71, "duration": 2.467}, {"text": "And what I'm going to do,\njust in the interest of time--", "start": 1406.177, "duration": 2.333}, {"text": "it's one of those calculations\nthat's straightforward", "start": 1408.51, "duration": 2.208}, {"text": "but fairly tedious--", "start": 1410.718, "duration": 0.882}, {"text": "I have a set of\nnotes that I meant", "start": 1411.6, "duration": 2.55}, {"text": "to make live before I headed\nover here, but I forgot.", "start": 1414.15, "duration": 2.4}, {"text": "I have a set of notes that I'm\ngoing to show on the website", "start": 1416.55, "duration": 2.61}, {"text": "by this evening which explicitly\nworks out what happens when you", "start": 1419.16, "duration": 4.65}, {"text": "apply the coordinate\ntransformation using that--", "start": 1423.81, "duration": 2.55}, {"text": "it's been erased--", "start": 1426.36, "duration": 1.05}, {"text": "when you use that L\nmatrix to construct", "start": 1427.41, "duration": 2.11}, {"text": "the coordinate transformation\nbetween two representations.", "start": 1429.52, "duration": 2.75}, {"text": "If you try to do it to\npartial derivatives of vector", "start": 1432.27, "duration": 3.72}, {"text": "components, basically\nwhat you find", "start": 1435.99, "duration": 1.89}, {"text": "is that there's an extra\nterm that spoils your ability", "start": 1437.88, "duration": 3.03}, {"text": "to call that-- it spoils the\ntensor transformation law,", "start": 1440.91, "duration": 3.6}, {"text": "spoils your ability to call\nthat a tensor component.", "start": 1444.51, "duration": 2.85}, {"text": "So the partial on its\nown doesn't let you.", "start": 1447.36, "duration": 2.43}, {"text": "You get some extra terms that\ncome along and mess it all up.", "start": 1449.79, "duration": 4.05}, {"text": "On next p set,\nyou guys are going", "start": 1453.84, "duration": 1.86}, {"text": "to show that if you then try to\napply the tensor transformation", "start": 1455.7, "duration": 5.1}, {"text": "law to the Christoffel\nsymbols, you", "start": 1460.8, "duration": 2.7}, {"text": "get something that\nlooks tensorial,", "start": 1463.5, "duration": 1.89}, {"text": "but with an extra term\nthat spoils your ability", "start": 1465.39, "duration": 2.49}, {"text": "to call it tensorial.", "start": 1467.88, "duration": 1.33}, {"text": "There's a little bit\nof extra junk there.", "start": 1469.21, "duration": 2.45}, {"text": "But the two terms\nexactly conspire", "start": 1471.66, "duration": 2.01}, {"text": "to cancel each other out so\nthat the sum is tensorial.", "start": 1473.67, "duration": 4.32}, {"text": "So part one of\nthis will be notes", "start": 1477.99, "duration": 1.62}, {"text": "that I post to the website\nno later than this evening.", "start": 1479.61, "duration": 2.88}, {"text": "Part two, you guys\nwill do on the p set.", "start": 1482.49, "duration": 1.775}, {"text": "So just saying in\nmath what I just", "start": 1502.88, "duration": 3.39}, {"text": "said in words, if I\ndo this, like I said,", "start": 1506.27, "duration": 4.02}, {"text": "you basically will\neventually reach the point", "start": 1510.29, "duration": 3.24}, {"text": "where what I am\nwriting out right now", "start": 1513.53, "duration": 4.38}, {"text": "will become so automatic\nit will haunt your dreams.", "start": 1517.91, "duration": 6.29}, {"text": "Wait a minute, I\nscrewed that up.", "start": 1524.2, "duration": 1.38}, {"text": "It's so automatic I can't\neven write it properly.", "start": 1525.58, "duration": 2.042}, {"text": "Anyhow, something like that\nwill-- modulo my typo--", "start": 1535.05, "duration": 3.432}, {"text": "that should become automatic.", "start": 1538.482, "duration": 1.208}, {"text": "And the key thing\nwhich I want to note", "start": 1539.69, "duration": 1.583}, {"text": "is that if I take these\nguys, and I attach", "start": 1541.273, "duration": 10.567}, {"text": "the appropriate basis\nobjects to them,", "start": 1551.84, "duration": 6.75}, {"text": "this is an honest-to-god tensor.", "start": 1558.59, "duration": 1.8}, {"text": "And so this derivative is\nitself an honest-to-god tensor.", "start": 1560.39, "duration": 3.43}, {"text": "A typical application\nof this, so one", "start": 1563.82, "duration": 2.03}, {"text": "that will come up a\nfair bit, is how do you", "start": 1565.85, "duration": 3.33}, {"text": "compute a spacetime divergence\nin each coordinate system?", "start": 1569.18, "duration": 3.42}, {"text": "So suppose I take the divergence\nof some vector field v.", "start": 1579.94, "duration": 18.208}, {"text": "So you're going to\nhave four terms that", "start": 1598.148, "duration": 2.202}, {"text": "are just the usual, like\nwhen you guys learned", "start": 1600.35, "duration": 2.58}, {"text": "how to do divergence in freshman\nE&M in Cartesian coordinates.", "start": 1602.93, "duration": 3.91}, {"text": "You get one term that's just\ndv x dx, dv y dy, et cetera.", "start": 1606.84, "duration": 5.0}, {"text": "So you got one term that\nlooks just like that,", "start": 1611.84, "duration": 2.16}, {"text": "and you're going to have\nsomething that brings", "start": 1614.0, "duration": 1.917}, {"text": "in all of Christoffel symbols.", "start": 1615.917, "duration": 1.323}, {"text": "Notice the symmetry that\nwe have on this one.", "start": 1617.24, "duration": 3.85}, {"text": "Actually, there is Einstein\nsummation convention", "start": 1621.09, "duration": 2.0}, {"text": "being imposed here.", "start": 1623.09, "duration": 1.53}, {"text": "But when we look\nat this, there's", "start": 1624.62, "duration": 1.62}, {"text": "actually only one\nChristoffel symbol", "start": 1626.24, "duration": 2.97}, {"text": "that has repeated indices\nin that first position.", "start": 1629.21, "duration": 3.31}, {"text": "So when I put all\nthis together, you", "start": 1632.52, "duration": 19.307}, {"text": "wind up with something\nthat looks like this.", "start": 1651.827, "duration": 1.833}, {"text": "So go back and check your\ncopy of Jackson, or Purcell,", "start": 1658.76, "duration": 3.563}, {"text": "or Griffith, whatever your\nfavorite E&M textbook is.", "start": 1662.323, "duration": 2.167}, {"text": "And you'll see when you work\nin cylindrical coordinates,", "start": 1664.49, "duration": 2.44}, {"text": "you indeed find that there's a\ncorrection to the radial term", "start": 1666.93, "duration": 2.5}, {"text": "that involves 1 over r.", "start": 1669.43, "duration": 1.23}, {"text": "That's popped out exactly\nlike you think it should.", "start": 1670.66, "duration": 2.37}, {"text": "You have a bit of a wacky\nlooking thing with your phi", "start": 1673.03, "duration": 3.06}, {"text": "component, of course.", "start": 1676.09, "duration": 3.18}, {"text": "And let me just spend a\nsecond or two making sure.", "start": 1679.27, "duration": 3.73}, {"text": "It's often, especially while\nwe're developing intuition", "start": 1683.0, "duration": 2.3}, {"text": "about working in a\ncoordinate basis,", "start": 1685.3, "duration": 4.08}, {"text": "it's not a bad idea to\ndo a little sanity check.", "start": 1689.38, "duration": 3.3}, {"text": "So here's a sanity check\nthat I would do with this.", "start": 1697.66, "duration": 4.08}, {"text": "If I take the divergence,\nI take a derivative", "start": 1701.74, "duration": 2.22}, {"text": "of a vector field, the\nfinal object that comes out", "start": 1703.96, "duration": 2.7}, {"text": "of that should have the\ndimensions of that vector", "start": 1706.66, "duration": 2.76}, {"text": "divided by length.", "start": 1709.42, "duration": 2.22}, {"text": "Remembering c equals 1,\nthat will clearly have", "start": 1711.64, "duration": 2.29}, {"text": "that vector divided by length.", "start": 1713.93, "duration": 1.25}, {"text": "That will clearly\nhave that vector", "start": 1715.18, "duration": 1.417}, {"text": "divided by length, vector\ndivided by length, explicitly", "start": 1716.597, "duration": 2.603}, {"text": "vector divided by length.", "start": 1719.2, "duration": 1.168}, {"text": "That's weird.", "start": 1720.368, "duration": 0.542}, {"text": "But remember, the basis objects\nthemselves are a little weird.", "start": 1724.67, "duration": 14.26}, {"text": "One of the things we\nsaw was that e phi", "start": 1744.87, "duration": 2.73}, {"text": "has the dimensions of length.", "start": 1747.6, "duration": 1.31}, {"text": "In order for the vector\nto itself be consistent,", "start": 1755.98, "duration": 3.03}, {"text": "v phi must have the dimensions\nof v divided by length.", "start": 1759.01, "duration": 7.9}, {"text": "So in fact, when I just\ntake its phi derivative,", "start": 1766.91, "duration": 2.0}, {"text": "I get something\nthat looks exactly", "start": 1768.91, "duration": 1.417}, {"text": "like it should if it\nis to be a divergence.", "start": 1770.327, "duration": 2.166}, {"text": "Let's move on and\nthink about how", "start": 1785.25, "duration": 2.04}, {"text": "I take a covariant\nderivative of other kinds", "start": 1787.29, "duration": 3.33}, {"text": "of tensorial objects.", "start": 1790.62, "duration": 2.58}, {"text": "This is all you need to know\nif you are worried about taking", "start": 1793.2, "duration": 3.24}, {"text": "derivatives of vectors.", "start": 1796.44, "duration": 1.812}, {"text": "But we're going to work with\na lot of different kinds", "start": 1798.252, "duration": 2.208}, {"text": "of tensor objects.", "start": 1800.46, "duration": 0.87}, {"text": "One of the most\nimportant lectures", "start": 1807.753, "duration": 1.417}, {"text": "we're going to do\nin about a month", "start": 1809.17, "duration": 2.19}, {"text": "actually involves looking at a\nbunch of covariant derivatives", "start": 1811.36, "duration": 3.24}, {"text": "of some four-indexed\nobjects, so it gets messy.", "start": 1814.6, "duration": 4.708}, {"text": "Let's walk our way there.", "start": 1819.308, "duration": 1.042}, {"text": "So suppose I want to take\nthe derivative of a scalar.", "start": 1823.6, "duration": 4.02}, {"text": "Scalar have no basis\nobject attached to them.", "start": 1827.62, "duration": 2.37}, {"text": "There's no basis object.", "start": 1838.38, "duration": 1.11}, {"text": "When I take the\nderivative, I don't", "start": 1839.49, "duration": 1.05}, {"text": "have to worry about\nanything wiggling around.", "start": 1840.54, "duration": 1.875}, {"text": "No Christoffel symbols come in.", "start": 1842.415, "duration": 3.625}, {"text": "If I want to take the covariant\nderivative of some field phi,", "start": 1846.04, "duration": 4.4}, {"text": "it is nothing more than\nthe partial derivative", "start": 1850.44, "duration": 2.79}, {"text": "of that field phi--", "start": 1853.23, "duration": 1.14}, {"text": "boom.", "start": 1854.37, "duration": 1.47}, {"text": "Happy days.", "start": 1855.84, "duration": 0.57}, {"text": "How about a one form?", "start": 1859.125, "duration": 0.875}, {"text": "The long way to do this would\nbe to essentially say, well,", "start": 1866.54, "duration": 6.49}, {"text": "the way I started\nthis was by looking", "start": 1873.03, "duration": 1.83}, {"text": "at how my basis vectors varied\nas I took their derivatives.", "start": 1874.86, "duration": 3.71}, {"text": "Let's do the same thing\nfor the basis one forms,", "start": 1878.57, "duration": 5.08}, {"text": "assemble my table, do a lot\nof math, blah, blah, blah.", "start": 1883.65, "duration": 4.635}, {"text": "Knock yourselves out if\nthat's what you want to do.", "start": 1888.285, "duration": 2.125}, {"text": "There's a shortcut.", "start": 1890.41, "duration": 2.87}, {"text": "Let's use the fact that\nwhen I contract a one form", "start": 1893.28, "duration": 6.45}, {"text": "on a vector, I get a scalar.", "start": 1899.73, "duration": 1.42}, {"text": "So let's say I am looking at the\nbeta covariant derivative of p", "start": 1915.2, "duration": 9.06}, {"text": "alpha on a alpha.", "start": 1924.26, "duration": 2.73}, {"text": "That's a scalar.", "start": 1926.99, "duration": 0.9}, {"text": "So this is just the\npartial derivative.", "start": 1927.89, "duration": 10.265}, {"text": "And a partial derivative of\nthe product of something I", "start": 1947.38, "duration": 2.78}, {"text": "can expand out really easily.", "start": 1950.16, "duration": 1.34}, {"text": "So using the fact that this\njust becomes the partial,", "start": 1964.55, "duration": 2.35}, {"text": "I can write this\nas a alpha d beta p", "start": 1966.9, "duration": 8.0}, {"text": "alpha plus p downstairs alpha.", "start": 1974.9, "duration": 3.45}, {"text": "So now what?", "start": 1983.58, "duration": 3.28}, {"text": "Well, let's rewrite this using\nthe covariant derivative.", "start": 1986.86, "duration": 6.4}, {"text": "Pardon me a second while I\nget caught up in my notes.", "start": 1998.862, "duration": 2.208}, {"text": "Here we are.", "start": 2001.07, "duration": 3.16}, {"text": "I can write this as the\ncovariant derivative", "start": 2004.23, "duration": 6.98}, {"text": "minus the correction that comes\nfrom that Christoffel symbol.", "start": 2011.21, "duration": 3.0}, {"text": "Pardon me just a second.", "start": 2025.595, "duration": 1.385}, {"text": "There's a couple lines here I\nwant to write out very neatly.", "start": 2026.98, "duration": 2.5}, {"text": "So when I put this in--", "start": 2035.74, "duration": 1.38}, {"text": "oops typo.", "start": 2062.48, "duration": 0.69}, {"text": "That last typo is important,\nbecause I'm now going", "start": 2069.6, "duration": 2.28}, {"text": "to do the relabeling trick.", "start": 2071.88, "duration": 2.611}, {"text": "So what I'm going to\ndo is take advantage", "start": 2074.491, "duration": 1.708}, {"text": "of the fact that in this\nlast term, alpha and mu", "start": 2076.199, "duration": 4.081}, {"text": "are both dummy indices.", "start": 2080.28, "duration": 1.77}, {"text": "So on this last term that\nI have written down here,", "start": 2082.05, "duration": 4.98}, {"text": "I'm going to swap\nout alpha and mu.", "start": 2087.03, "duration": 1.53}, {"text": "When I do that, notice that the\nfirst term and the last term", "start": 2123.77, "duration": 5.8}, {"text": "will both be proportional\nto the component a alpha.", "start": 2129.57, "duration": 2.49}, {"text": "Now, let's require that\nthe covariant derivative", "start": 2152.48, "duration": 4.65}, {"text": "when it acts on two things\nthat are multiplied together,", "start": 2157.13, "duration": 3.09}, {"text": "it's a derivative, so it should\ndo what derivatives ordinarily", "start": 2160.22, "duration": 4.21}, {"text": "do.", "start": 2164.43, "duration": 0.5}, {"text": "So what we're going\nto do is require", "start": 2164.93, "duration": 4.75}, {"text": "that when I take this\ncovariant derivative,", "start": 2169.68, "duration": 5.55}, {"text": "I should be able to\nwrite the result like so.", "start": 2175.23, "duration": 14.81}, {"text": "It's a healthy thing that\nany derivative should do.", "start": 2190.04, "duration": 5.71}, {"text": "So comparing, I look\nat that, and go,", "start": 2195.75, "duration": 1.93}, {"text": "oh, I've got the covariant\nderivative of my one form", "start": 2197.68, "duration": 3.15}, {"text": "there.", "start": 2200.83, "duration": 0.5}, {"text": "Just compare forms.", "start": 2201.33, "duration": 0.81}, {"text": "Very, very similar, but\nnotice the minus sign.", "start": 2226.84, "duration": 5.01}, {"text": "There's a minus sign that's\nbeen introduced there,", "start": 2231.85, "duration": 2.68}, {"text": "and that minus sign guarantees,\nif you actually expand out", "start": 2234.53, "duration": 4.94}, {"text": "that combination of\ncovariant derivatives", "start": 2239.47, "duration": 2.82}, {"text": "I have on the previous line,\nthere's a nice cancellation", "start": 2242.29, "duration": 2.37}, {"text": "so that the scalar that\nI get when I contract p", "start": 2244.66, "duration": 3.39}, {"text": "on a, in fact, doesn't have\nanything special going on when", "start": 2248.05, "duration": 3.69}, {"text": "I do the covariant derivative.", "start": 2251.74, "duration": 2.293}, {"text": "So I'm going to\ngeneralize this further,", "start": 2261.483, "duration": 1.667}, {"text": "but let me just make\na quick comment here.", "start": 2263.15, "duration": 1.98}, {"text": "I began this little\ncalculation by saying,", "start": 2265.13, "duration": 3.69}, {"text": "given how we started\nour calculation", "start": 2268.82, "duration": 4.44}, {"text": "of the covariant\nderivative of a vector,", "start": 2273.26, "duration": 1.98}, {"text": "we could have begun\nby just taking", "start": 2275.24, "duration": 1.68}, {"text": "lots of derivatives of the\nbasis one forms, and assembling", "start": 2276.92, "duration": 2.7}, {"text": "all these various tables,\nand things like that.", "start": 2279.62, "duration": 2.22}, {"text": "If you had done this,\nit's simple to find,", "start": 2281.84, "duration": 9.12}, {"text": "based on an analysis\nlike this, that if you", "start": 2290.96, "duration": 11.09}, {"text": "take a partial\nderivative of a one form,", "start": 2302.05, "duration": 12.59}, {"text": "that you get sort of a linear\ncombination of one forms back.", "start": 2314.64, "duration": 3.1}, {"text": "Looks just like\nwhat you got when", "start": 2317.74, "duration": 1.427}, {"text": "you took a partial derivative\nof the basis vector,", "start": 2319.167, "duration": 2.083}, {"text": "but with a minus sign.", "start": 2321.25, "duration": 1.31}, {"text": "And what that minus sign does\nis it enforces, if you go back", "start": 2322.56, "duration": 6.11}, {"text": "to a lecture from ages ago, when\nI first introduced basis one", "start": 2328.67, "duration": 3.06}, {"text": "forms, it enforces the idea that\nwhen I combine basis one forms", "start": 2331.73, "duration": 12.75}, {"text": "with basis vectors, I get an\nidentity object out of this,", "start": 2344.48, "duration": 3.63}, {"text": "which is itself a constant.", "start": 2348.11, "duration": 1.8}, {"text": "If you are the\nkind of person who", "start": 2349.91, "duration": 2.28}, {"text": "likes that sort of\nmathematical rigor,", "start": 2352.19, "duration": 2.13}, {"text": "some textbooks will\nstart with this,", "start": 2354.32, "duration": 1.77}, {"text": "and then derive other\nthings from that--", "start": 2356.09, "duration": 2.7}, {"text": "sort of six of one, half\na dozen of the other.", "start": 2358.79, "duration": 2.52}, {"text": "So we could go on at this point.", "start": 2361.31, "duration": 3.15}, {"text": "And I could say,\nhow do I do this", "start": 2364.46, "duration": 2.85}, {"text": "with a tensor that has two\nindices in the upstairs", "start": 2367.31, "duration": 2.76}, {"text": "position?", "start": 2370.07, "duration": 0.82}, {"text": "How do I do this\nwith a tensor that", "start": 2370.89, "duration": 1.46}, {"text": "has two indices in the\ndownstairs position?", "start": 2372.35, "duration": 2.023}, {"text": "How do I do it for\na tensor that's", "start": 2374.373, "duration": 1.417}, {"text": "got 17 indices in\nthe upstairs position", "start": 2375.79, "duration": 2.17}, {"text": "and 38 in the\ndownstairs position?", "start": 2377.96, "duration": 2.53}, {"text": "The answer is easily\ndeduced from doing", "start": 2380.49, "duration": 2.99}, {"text": "these kinds of\nrules, so I'm just", "start": 2383.48, "duration": 1.49}, {"text": "going to write down a\ncouple of examples and state", "start": 2384.97, "duration": 1.93}, {"text": "what it turns out to be.", "start": 2386.9, "duration": 1.0}, {"text": "So basically, imagine I want to\ntake the covariant derivative--", "start": 2396.66, "duration": 4.73}, {"text": "let's do the stress\nenergy tensor--", "start": 2401.39, "duration": 2.08}, {"text": "covariant derivative of T mu nu.", "start": 2403.47, "duration": 3.277}, {"text": "So remember, the way that the\nChristoffel got into there", "start": 2406.747, "duration": 2.333}, {"text": "is that when I looked at\nthe derivative of a vector,", "start": 2409.08, "duration": 2.34}, {"text": "I was looking at derivatives\nof basis objects.", "start": 2411.42, "duration": 3.58}, {"text": "Well, now I'm going\nto look at derivatives", "start": 2415.0, "duration": 1.75}, {"text": "of two different basis objects.", "start": 2416.75, "duration": 2.12}, {"text": "So I'm going to wind up with\ntwo Christoffel symbols.", "start": 2418.87, "duration": 3.27}, {"text": "You can kind of think of it\nas coming along and correcting", "start": 2429.1, "duration": 13.443}, {"text": "each of these indices.", "start": 2442.543, "duration": 0.917}, {"text": "I can do this with the indices\nin the downstairs position.", "start": 2446.44, "duration": 4.08}, {"text": "Guess what?", "start": 2457.29, "duration": 0.96}, {"text": "Comes along and corrects\nall them with minus signs.", "start": 2458.25, "duration": 9.26}, {"text": "Just for completeness,\nlet me just", "start": 2489.86, "duration": 2.07}, {"text": "write down the general rule.", "start": 2491.93, "duration": 3.32}, {"text": "If I am looking at the\ncovariant derivative of a tensor", "start": 2495.25, "duration": 5.08}, {"text": "with a gajillion\nupstairs indices", "start": 2500.33, "duration": 8.0}, {"text": "and a gajillion\ndownstairs indices,", "start": 2508.33, "duration": 3.66}, {"text": "you get one term that's just a\npartial derivative of that guy,", "start": 2511.99, "duration": 7.7}, {"text": "and you get a\nChristoffel coupling", "start": 2519.69, "duration": 11.11}, {"text": "for every one of these.", "start": 2530.8, "duration": 2.47}, {"text": "Plus sign for all the\nupstairs, minus sign", "start": 2533.27, "duration": 18.75}, {"text": "for all the downstairs.", "start": 2552.02, "duration": 3.8}, {"text": "That was a little tedious.", "start": 2563.38, "duration": 1.12}, {"text": "You basically just, when I\ngive you a tensor like that,", "start": 2564.5, "duration": 1.95}, {"text": "you just kind of\nhave to go through.", "start": 2566.45, "duration": 1.5}, {"text": "And it becomes sort\nof almost monkey work.", "start": 2567.95, "duration": 1.773}, {"text": "You just have to rotely\ngo through and correct", "start": 2569.723, "duration": 1.917}, {"text": "every one of the indices using\nan algorithm that kind of looks", "start": 2571.64, "duration": 2.86}, {"text": "like this.", "start": 2574.5, "duration": 0.5}, {"text": "Oh, jeez, there's absolutely a\nminus sign on the second one.", "start": 2579.8, "duration": 2.5}, {"text": "Thank you.", "start": 2582.3, "duration": 2.785}, {"text": "I appreciate that.", "start": 2585.085, "duration": 0.955}, {"text": "So the way that we have\ndone things so far,", "start": 2594.16, "duration": 5.527}, {"text": "and I kind of emphasized, it\nsort of smells like the way", "start": 2599.687, "duration": 2.333}, {"text": "to do this is you pick your\nnew coordinate representation,", "start": 2602.02, "duration": 4.17}, {"text": "you throw together all of\nyour various basis objects,", "start": 2606.19, "duration": 7.23}, {"text": "and then you just\nstart going whee,", "start": 2613.42, "duration": 2.047}, {"text": "let's start taking\nderivatives and see", "start": 2615.467, "duration": 1.583}, {"text": "how all these things vary\nwith respect to each other,", "start": 2617.05, "duration": 2.33}, {"text": "assemble my table of\nthe gammas, and then do", "start": 2619.38, "duration": 3.4}, {"text": "my covariant derivative.", "start": 2622.78, "duration": 2.77}, {"text": "If that were, in fact,\nthe way we did it,", "start": 2625.55, "duration": 2.67}, {"text": "I would not have chosen\nmy research career", "start": 2628.22, "duration": 2.04}, {"text": "to focus on this field.", "start": 2630.26, "duration": 1.22}, {"text": "That would suck.", "start": 2631.48, "duration": 1.51}, {"text": "Certainly prior to Odin\nproviding us with Mathematica,", "start": 2632.99, "duration": 5.04}, {"text": "it would have been\nabsolutely undoable.", "start": 2638.03, "duration": 3.72}, {"text": "Even with it, though, it\nwould be incredibly tedious.", "start": 2641.75, "duration": 3.54}, {"text": "So there is a better\nway to do this,", "start": 2645.29, "duration": 23.6}, {"text": "and it comes via the metric.", "start": 2668.89, "duration": 4.28}, {"text": "Before I derive what the\nalgorithm actually is,", "start": 2673.17, "duration": 6.63}, {"text": "I want to introduce an extremely\nimportant property of tensor", "start": 2679.8, "duration": 3.45}, {"text": "relationships that we are\ngoing to come back to and use", "start": 2683.25, "duration": 3.18}, {"text": "quite a bit in this course.", "start": 2686.43, "duration": 1.32}, {"text": "So this is something that we\nhave actually kind of alluded", "start": 2697.923, "duration": 2.417}, {"text": "to repeatedly, but I want to\nmake it a little more formal", "start": 2700.34, "duration": 2.94}, {"text": "and just clearly state it.", "start": 2703.28, "duration": 1.462}, {"text": "So this relationship\nthat I'm going to use", "start": 2712.18, "duration": 2.19}, {"text": "is some kind of a tensor\nequation, a tensorial equation", "start": 2714.37, "duration": 12.98}, {"text": "that holds in one\nrepresentation must", "start": 2727.35, "duration": 10.27}, {"text": "hold in all representations.", "start": 2737.62, "duration": 4.562}, {"text": "Come back to the\nintuition when I first", "start": 2746.25, "duration": 2.1}, {"text": "began describing physics in\nterms of geometric objects", "start": 2748.35, "duration": 2.43}, {"text": "in spacetime.", "start": 2750.78, "duration": 0.68}, {"text": "One of the key points I\ntried to really emphasize", "start": 2751.46, "duration": 3.1}, {"text": "the difference of is that\nI can have different--", "start": 2754.56, "duration": 2.85}, {"text": "let's say my arm is a\nparticular vector in spacetime.", "start": 2757.41, "duration": 3.047}, {"text": "Someone running through\nthe room at three-quarters", "start": 2760.457, "duration": 2.083}, {"text": "the speed of light will use\ndifferent representations", "start": 2762.54, "duration": 2.49}, {"text": "to describe my arm.", "start": 2765.03, "duration": 0.983}, {"text": "They will see\nlength contractions.", "start": 2766.013, "duration": 1.417}, {"text": "They will see things sort of\nspanning different things.", "start": 2767.43, "duration": 2.292}, {"text": "But the geometric\nobject, the thing", "start": 2769.722, "duration": 1.728}, {"text": "which goes between two events\nin spacetime, that does not", "start": 2771.45, "duration": 4.95}, {"text": "change, even though the\nrepresentation of those events", "start": 2776.4, "duration": 2.52}, {"text": "might.", "start": 2778.92, "duration": 1.218}, {"text": "This remains true not just\nfor Lorentz transformations,", "start": 2780.138, "duration": 2.292}, {"text": "but for all classes\nof transformations", "start": 2782.43, "duration": 2.64}, {"text": "that we might care to\nuse in our analysis.", "start": 2785.07, "duration": 3.78}, {"text": "Changing the representation\ncannot change the equation.", "start": 2788.85, "duration": 3.71}, {"text": "Written that way, it\nsounds like, well, duh,", "start": 2799.48, "duration": 3.87}, {"text": "but as we'll see, it's got\nimportant consequences.", "start": 2803.35, "duration": 4.391}, {"text": "So as a warm-up exercise of\nhow we might want to use this,", "start": 2821.98, "duration": 4.46}, {"text": "let's think about the\ndouble gradient of a scalar.", "start": 2826.44, "duration": 3.27}, {"text": "So let's define-- let's just say\nthat this is the object that I", "start": 2860.54, "duration": 7.17}, {"text": "want to compute.", "start": 2867.71, "duration": 2.61}, {"text": "Let's first do this in a\nCartesian representation.", "start": 2870.32, "duration": 3.724}, {"text": "In a Cartesian\nrepresentation, I just", "start": 2877.92, "duration": 1.79}, {"text": "take two partial derivatives.", "start": 2879.71, "duration": 3.165}, {"text": "I've got a couple basis\none forms for this.", "start": 2885.49, "duration": 2.3}, {"text": "So I've got something like this.", "start": 2897.52, "duration": 2.582}, {"text": "The thing which I\nwant to emphasize", "start": 2900.102, "duration": 1.458}, {"text": "is that as written, in\nCartesian coordinates, d", "start": 2901.56, "duration": 3.66}, {"text": "alpha d beta of phi--", "start": 2905.22, "duration": 2.13}, {"text": "those are the components of a\ntensor in this representation.", "start": 2907.35, "duration": 5.214}, {"text": "And the key thing is\nthat they are obviously", "start": 2920.15, "duration": 2.73}, {"text": "symmetric on exchange of\nthe indices alpha and beta.", "start": 2922.88, "duration": 5.81}, {"text": "If I'm just taking\npartial derivatives,", "start": 2933.795, "duration": 1.625}, {"text": "doesn't matter what\norder I take them in.", "start": 2935.42, "duration": 1.98}, {"text": "That's got to be symmetric.", "start": 2937.4, "duration": 1.394}, {"text": "Let's now look at\nthe double gradient", "start": 2942.97, "duration": 2.81}, {"text": "of a scalar in a more\ngeneral representation.", "start": 2945.78, "duration": 2.594}, {"text": "So in a general\nrepresentation, I'm", "start": 2971.63, "duration": 5.8}, {"text": "going to require\nthese two derivatives", "start": 2977.43, "duration": 2.79}, {"text": "to be covariant derivatives.", "start": 2980.22, "duration": 2.65}, {"text": "Now, we know one of them can\nbe very trivially replaced with", "start": 2982.87, "duration": 4.82}, {"text": "a partial, but the\nother one cannot.", "start": 2987.69, "duration": 2.4}, {"text": "Hold that thought\nfor just a second.", "start": 2990.09, "duration": 1.5}, {"text": "If this thing is symmetric in\nthe Cartesian representation,", "start": 2995.61, "duration": 5.61}, {"text": "I claim it must also be true\nin a general representation.", "start": 3001.22, "duration": 3.602}, {"text": "In other words, exchanging the\norder of covariant derivatives", "start": 3017.37, "duration": 10.52}, {"text": "when they act on a scalar should\ngive me the same thing back.", "start": 3027.89, "duration": 3.963}, {"text": "Let's see what this implies.", "start": 3031.853, "duration": 1.167}, {"text": "So if I require the following\nto be true, that's saying--", "start": 3062.54, "duration": 9.185}, {"text": "oops.", "start": 3078.63, "duration": 0.5}, {"text": "So let's expand this\nout one more level.", "start": 3089.23, "duration": 1.8}, {"text": "So now, I'm correcting that\ndownstairs index and over here.", "start": 3097.68, "duration": 11.02}, {"text": "So the terms involving\nnothing but partials,", "start": 3124.64, "duration": 4.1}, {"text": "they obviously cancel.", "start": 3128.74, "duration": 2.2}, {"text": "I have a common\nfactor of d mu of phi.", "start": 3130.94, "duration": 2.307}, {"text": "So let's move one of these\nover to the other side.", "start": 3133.247, "duration": 2.083}, {"text": "What we've learned is\nthat this requirement,", "start": 3138.24, "duration": 2.12}, {"text": "that this combination of\nderivatives be symmetric,", "start": 3140.36, "duration": 12.737}, {"text": "tells me something about the\nsymmetry of the Christoffel", "start": 3153.097, "duration": 2.333}, {"text": "symbols itself.", "start": 3155.43, "duration": 0.71}, {"text": "If you go back to\nthat little table", "start": 3163.64, "duration": 3.24}, {"text": "that I wrote down for\nplane polar coordinates,", "start": 3166.88, "duration": 2.37}, {"text": "that was one where\nI just calculated", "start": 3169.25, "duration": 1.5}, {"text": "only three non-trivial\ncomponents,", "start": 3170.75, "duration": 2.97}, {"text": "but there was a\nsymmetry in there.", "start": 3173.72, "duration": 1.482}, {"text": "And if you go and\nyou check it, you", "start": 3175.202, "duration": 1.458}, {"text": "will see it's consistent with\nwhat I just found right here.", "start": 3176.66, "duration": 4.013}, {"text": "Pardon me for just a second.", "start": 3180.673, "duration": 1.167}, {"text": "I want to organize\na few of my notes.", "start": 3181.84, "duration": 4.76}, {"text": "These have gotten\nall out of order.", "start": 3186.6, "duration": 1.72}, {"text": "Here it is.", "start": 3195.96, "duration": 0.5}, {"text": "So let me just use\nthis as an opportunity", "start": 3229.897, "duration": 1.708}, {"text": "to introduce a bit of notation.", "start": 3231.605, "duration": 1.292}, {"text": "Whenever I give you a tensor\nthat's got two indices,", "start": 3236.21, "duration": 4.56}, {"text": "if I write parentheses\naround those indices,", "start": 3240.77, "duration": 10.1}, {"text": "this is going to\nmean that I do what", "start": 3250.87, "duration": 3.24}, {"text": "is called \"symmetrization.\"", "start": 3254.11, "duration": 1.821}, {"text": "We're going to use\nthis from time to time.", "start": 3259.02, "duration": 2.07}, {"text": "If I write square braces,\nthis is what we call", "start": 3261.09, "duration": 8.22}, {"text": "\"anti-symmetrization.\"", "start": 3269.31, "duration": 1.747}, {"text": "And so what we just learned\nis that gamma mu alpha beta", "start": 3273.8, "duration": 7.42}, {"text": "is equal to gamma mu alpha\nbeta with symmetrization", "start": 3281.22, "duration": 4.23}, {"text": "on those last two indices.", "start": 3285.45, "duration": 3.18}, {"text": "We have likewise learned\nthat if I contract", "start": 3288.63, "duration": 4.8}, {"text": "this against some object, if\nthese were anti-symmetric,", "start": 3293.43, "duration": 10.35}, {"text": "I must get a 0 out of it.", "start": 3303.78, "duration": 3.247}, {"text": "So that's a brief aside, but\nthese are important things,", "start": 3307.027, "duration": 2.333}, {"text": "and I want to make sure you\nhave a chance to see them.", "start": 3309.36, "duration": 2.25}, {"text": "So trying to make a decision\nhere about where we're going to", "start": 3314.64, "duration": 5.07}, {"text": "want to carry things forward.", "start": 3319.71, "duration": 2.7}, {"text": "We're approaching the\nend of one set of notes.", "start": 3322.41, "duration": 2.73}, {"text": "There's still one more\nthing I want to do.", "start": 3325.14, "duration": 2.67}, {"text": "So I set this whole\nthing up by saying", "start": 3327.81, "duration": 1.95}, {"text": "that I wanted to give you\nguys an algorithm for how", "start": 3329.76, "duration": 3.0}, {"text": "to generate the\nChristoffel symbols.", "start": 3332.76, "duration": 1.88}, {"text": "The way I'm going to\ndo this is by examining", "start": 3351.23, "duration": 10.97}, {"text": "the gradient of the metric.", "start": 3362.2, "duration": 9.1}, {"text": "So suppose I want to\ncompute the following tensor", "start": 3371.3, "duration": 4.84}, {"text": "quantity-- let's say\nis g the metric tensor,", "start": 3376.14, "duration": 2.25}, {"text": "written here in the\nfairly abstract notation.", "start": 3378.39, "duration": 2.5}, {"text": "And this is my full-on tensor\ngradient of this thing.", "start": 3380.89, "duration": 5.64}, {"text": "So if you want to write\nthis out in its full glory,", "start": 3392.5, "duration": 3.88}, {"text": "I might write this as\nsomething like this.", "start": 3396.38, "duration": 1.77}, {"text": "But if you stop and think\nabout this for just a second,", "start": 3404.03, "duration": 3.29}, {"text": "let's go back to this principle.", "start": 3407.32, "duration": 6.05}, {"text": "An equation that is tensorial\nin one representation", "start": 3413.37, "duration": 2.46}, {"text": "must be tensorial in all.", "start": 3415.83, "duration": 2.16}, {"text": "Suppose I choose the Cartesian\nrepresentation of this thing.", "start": 3417.99, "duration": 5.61}, {"text": "Well, then here's what\nit looks like there.", "start": 3431.33, "duration": 15.54}, {"text": "But this is a constant.", "start": 3446.87, "duration": 3.1}, {"text": "So if I do this in Cartesian\ncoordinates, it has to be 0.", "start": 3449.97, "duration": 6.06}, {"text": "The only way that I can\nmake this sort of comport", "start": 3456.03, "duration": 3.81}, {"text": "with this principle\nthat an equation that", "start": 3459.84, "duration": 3.33}, {"text": "is tensorial in\none representation", "start": 3463.17, "duration": 2.31}, {"text": "holds in all representations--", "start": 3465.48, "duration": 2.89}, {"text": "this leads me to say,\nI need to require", "start": 3468.37, "duration": 8.78}, {"text": "that the covariant derivative\nof the metric be equal to 0.", "start": 3477.15, "duration": 5.82}, {"text": "We're going to use this.", "start": 3486.41, "duration": 1.05}, {"text": "And I think this will be the\nlast detailed calculation", "start": 3487.46, "duration": 2.25}, {"text": "I do in today's lecture.", "start": 3489.71, "duration": 1.54}, {"text": "We're going to use\nthis to find a way", "start": 3491.25, "duration": 1.58}, {"text": "to get the Christoffel symbol\nfrom partial derivatives", "start": 3492.83, "duration": 3.197}, {"text": "of the metric.", "start": 3496.027, "duration": 0.583}, {"text": "There's a lot of\nterms here and there's", "start": 3525.86, "duration": 2.19}, {"text": "a lot of little indices.", "start": 3528.05, "duration": 1.21}, {"text": "So I'm going to do my best\nto make my handwriting neat.", "start": 3529.26, "duration": 2.292}, {"text": "I'm going to write\ndown a relationship", "start": 3534.137, "duration": 1.583}, {"text": "that I call \"Roman numeral I.\"", "start": 3535.72, "duration": 1.38}, {"text": "The covariant derivative in the\ngamma direction, G alpha beta--", "start": 3539.74, "duration": 4.01}, {"text": "you know what, let me put\nthis down a little bit lower,", "start": 3555.298, "duration": 2.292}, {"text": "so I can get these two\nterms on the same line.", "start": 3557.59, "duration": 1.917}, {"text": "So I get this thing that\ninvolves two Christoffel", "start": 3569.14, "duration": 4.88}, {"text": "symbols correcting\nthose two indices.", "start": 3574.02, "duration": 4.77}, {"text": "This is going to equal 0.", "start": 3583.418, "duration": 1.042}, {"text": "I don't really seem to\nhave gotten very far.", "start": 3589.49, "duration": 3.19}, {"text": "This is true, but I now\nhave two bloody Christoffel", "start": 3592.68, "duration": 4.44}, {"text": "symbols that I've somehow\nmanaged to work into this.", "start": 3597.12, "duration": 2.64}, {"text": "What I'm trying to\ndo is find a way", "start": 3599.76, "duration": 1.65}, {"text": "to get one, and equate it to\nthings involving derivatives", "start": 3601.41, "duration": 3.06}, {"text": "of the metric.", "start": 3604.47, "duration": 1.05}, {"text": "So this is sort of a\nruh-roh kind of moment.", "start": 3605.52, "duration": 4.15}, {"text": "But there's nothing\nspecial about this order", "start": 3609.67, "duration": 2.1}, {"text": "of the indices.", "start": 3611.77, "duration": 2.26}, {"text": "So with the audacity\nthat only comes", "start": 3614.03, "duration": 4.76}, {"text": "from knowing the answer in\nadvance, what I'm going to do", "start": 3618.79, "duration": 3.0}, {"text": "is permute the indices.", "start": 3621.79, "duration": 1.71}, {"text": "Then go, oh, let's permute\nthe indices once more.", "start": 3654.62, "duration": 3.18}, {"text": "So I'll give you guys a\nmoment to catch up with me.", "start": 3685.665, "duration": 2.125}, {"text": "Don't forget, these notes\nwill be scanned and added", "start": 3687.79, "duration": 1.73}, {"text": "to the web page.", "start": 3689.52, "duration": 0.667}, {"text": "So if you don't want to\nfollow along writing down", "start": 3690.187, "duration": 3.053}, {"text": "every little detail,\nI understand,", "start": 3693.24, "duration": 2.52}, {"text": "although personally, I\nfind that these things gel", "start": 3695.76, "duration": 2.808}, {"text": "a little bit better\nwhen you actually", "start": 3698.568, "duration": 1.542}, {"text": "write them out yourself.", "start": 3700.11, "duration": 1.0}, {"text": "So those are three ways that I\ncan assert that the metric has", "start": 3705.78, "duration": 6.48}, {"text": "no covariant derivative.", "start": 3712.26, "duration": 1.865}, {"text": "They all are\nbasically expressing", "start": 3714.125, "duration": 1.375}, {"text": "that same physical fact.", "start": 3715.5, "duration": 1.29}, {"text": "I'm just permuting the indices.", "start": 3716.79, "duration": 2.94}, {"text": "Now there's no better\nway to describe this", "start": 3719.73, "duration": 3.35}, {"text": "than you sort of just stare\nat this for a few moments,", "start": 3723.08, "duration": 3.16}, {"text": "and then go, gee, I wonder\nwhat would happen if--", "start": 3726.24, "duration": 4.454}, {"text": "so stare at this\nfor a little while.", "start": 3730.694, "duration": 2.066}, {"text": "And then construct-- you\nknow I have three things that", "start": 3732.76, "duration": 3.09}, {"text": "are equal to 0.", "start": 3735.85, "duration": 1.47}, {"text": "So I can add them together,\nI can subtract one", "start": 3737.32, "duration": 2.7}, {"text": "from the other.", "start": 3740.02, "duration": 0.81}, {"text": "I can add two and\nsubtract one, whatever.", "start": 3740.83, "duration": 3.93}, {"text": "They should all give me 0.", "start": 3744.76, "duration": 2.04}, {"text": "And the particular\ncombination I want to look at", "start": 3746.8, "duration": 6.36}, {"text": "is what I get when I\ntake relationship one", "start": 3753.16, "duration": 3.37}, {"text": "and I subtract from\nit two and three.", "start": 3756.53, "duration": 4.31}, {"text": "So I'm going to\nget one term that", "start": 3764.76, "duration": 3.71}, {"text": "are just these three\ncombinations of derivatives,", "start": 3768.47, "duration": 5.74}, {"text": "gamma.", "start": 3774.21, "duration": 0.5}, {"text": "And I get something\nthat looks like--", "start": 3783.02, "duration": 2.02}, {"text": "let me write this out and\nthen pause and make a comment.", "start": 3802.57, "duration": 2.92}, {"text": "So I sort of made some lame\njokes a few moments ago", "start": 3832.47, "duration": 2.22}, {"text": "that essentially, the only\nreason I was able to get", "start": 3834.69, "duration": 1.56}, {"text": "this was by knowing the answer\nin the back of the book,", "start": 3836.25, "duration": 1.68}, {"text": "essentially.", "start": 3837.93, "duration": 0.96}, {"text": "And to be perfectly blunt,\nfor me personally, that's", "start": 3838.89, "duration": 2.67}, {"text": "probably true.", "start": 3841.56, "duration": 0.66}, {"text": "When I first wrote\nthis down, I probably", "start": 3842.22, "duration": 1.937}, {"text": "did need to follow an algorithm.", "start": 3844.157, "duration": 1.333}, {"text": "But if I was doing this ab\ninitio, if I was sitting down", "start": 3845.49, "duration": 2.333}, {"text": "to first do this, what's\nreally going on here", "start": 3847.823, "duration": 2.017}, {"text": "is the reason I wrote out all\nthese different combinations", "start": 3849.84, "duration": 2.76}, {"text": "of things is that I was trying\nto gather terms together", "start": 3852.6, "duration": 4.02}, {"text": "in such a way that I could take\nadvantage of that symmetry.", "start": 3856.62, "duration": 3.39}, {"text": "A few moments ago, we showed\nthat the Christoffel symbols", "start": 3860.01, "duration": 4.32}, {"text": "are symmetric on the\nlower two indices.", "start": 3864.33, "duration": 3.88}, {"text": "And so by putting out all\nthese different combinations", "start": 3868.21, "duration": 2.42}, {"text": "of things, I was then able\nto combine them in such a way", "start": 3870.63, "duration": 3.03}, {"text": "that certain\nterms-- look at this", "start": 3873.66, "duration": 1.85}, {"text": "and go, ah, symmetry on\nalpha and gamma means", "start": 3875.51, "duration": 3.1}, {"text": "this whole term dies.", "start": 3878.61, "duration": 2.88}, {"text": "Symmetry on beta and gamma\nmeans this whole term dies.", "start": 3881.49, "duration": 4.13}, {"text": "Symmetry on alpha and beta\nmeans these two guys combine,", "start": 3885.62, "duration": 3.4}, {"text": "and I get a factor of 2.", "start": 3889.02, "duration": 1.08}, {"text": "So let's clean up our algebra.", "start": 3905.15, "duration": 1.25}, {"text": "Move a bunch of our terms\nto the other side equation,", "start": 3916.2, "duration": 2.86}, {"text": "since it's a blah,\nblah, blah equals 0.", "start": 3919.06, "duration": 3.195}, {"text": "And what we get when we\ndo this is g mu downstairs", "start": 3922.255, "duration": 4.755}, {"text": "gamma is equal to 1/2.", "start": 3927.01, "duration": 5.13}, {"text": "What we're going to do now\nis we will define everything", "start": 3950.45, "duration": 2.32}, {"text": "on the right-hand side--", "start": 3952.77, "duration": 1.0}, {"text": "I've kind of emphasized earlier\nthat the Christoffels are not", "start": 3953.77, "duration": 4.61}, {"text": "themselves tensors, but we're\ngoing to imagine that we can", "start": 3958.38, "duration": 2.822}, {"text": "nonetheless-- we're\nnot going to imagine,", "start": 3961.202, "duration": 1.708}, {"text": "we're just going to define--", "start": 3962.91, "duration": 1.1}, {"text": "we're going to say that we're\nallowed to raise and lower", "start": 3964.01, "duration": 2.23}, {"text": "their indices using the metric,\nin the same way you guys been", "start": 3966.24, "duration": 2.542}, {"text": "doing with vectors and one forms\nand other kinds of tensors.", "start": 3968.782, "duration": 2.858}, {"text": "So let's call everything\non the right-hand side", "start": 3971.64, "duration": 2.94}, {"text": "here gamma with all the indices\nin the downstairs position,", "start": 3974.58, "duration": 7.31}, {"text": "gamma sub gamma alpha beta.", "start": 3981.89, "duration": 2.35}, {"text": "And then this is\nsimply what I get", "start": 3984.24, "duration": 5.26}, {"text": "when I click all of these\nthings together like so.", "start": 3989.5, "duration": 7.87}, {"text": "If you go and you\nlook up the formulas", "start": 4001.87, "duration": 2.52}, {"text": "for this in various\ntextbooks that", "start": 4004.39, "duration": 1.65}, {"text": "give these different\nkinds of formulas,", "start": 4006.04, "duration": 3.03}, {"text": "you will typically see it\nwritten as 1/2 g upstairs", "start": 4009.07, "duration": 4.45}, {"text": "indices, and then all this\nstuff in parentheses after that.", "start": 4013.52, "duration": 4.07}, {"text": "When you look things up,\nthis is the typical formula", "start": 4017.59, "duration": 2.19}, {"text": "that is given in these books.", "start": 4019.78, "duration": 1.353}, {"text": "This is where it comes from.", "start": 4021.133, "duration": 1.167}, {"text": "So I need to check one thing\nbecause it appears my notes are", "start": 4028.75, "duration": 7.1}, {"text": "a little bit out of order here.", "start": 4035.85, "duration": 2.68}, {"text": "But nonetheless,\nthis is a good point,", "start": 4038.53, "duration": 3.68}, {"text": "since we've just finished\na pretty long calculation,", "start": 4042.21, "duration": 7.28}, {"text": "this is a good\npoint to introduce", "start": 4049.49, "duration": 1.41}, {"text": "an important physical point.", "start": 4050.9, "duration": 1.275}, {"text": "We're going to\ncome back to this.", "start": 4052.175, "duration": 1.375}, {"text": "We're going to start\nthis on Thursday.", "start": 4053.55, "duration": 2.285}, {"text": "But I want to begin making\nsome physical points that", "start": 4058.94, "duration": 2.52}, {"text": "are going to take us\nfrom special relativity", "start": 4061.46, "duration": 2.34}, {"text": "to general relativity.", "start": 4063.8, "duration": 1.4}, {"text": "So despite the fact\nthat I've introduced", "start": 4068.433, "duration": 1.667}, {"text": "this new mathematical\nframework, everything", "start": 4070.1, "duration": 4.71}, {"text": "that I have done so\nfar is in the context", "start": 4074.81, "duration": 9.24}, {"text": "of special relativity.", "start": 4084.05, "duration": 2.76}, {"text": "I'm going to make a\nmore precise definition", "start": 4086.81, "duration": 2.07}, {"text": "of special relativity right now.", "start": 4088.88, "duration": 1.61}, {"text": "So special relativity--\nwe are going", "start": 4097.39, "duration": 1.5}, {"text": "to think of this moving forward\nas the theory which allows us", "start": 4098.89, "duration": 14.1}, {"text": "to cover the entire\nspacetime manifold", "start": 4112.99, "duration": 17.28}, {"text": "using inertial reference frames.", "start": 4130.27, "duration": 2.25}, {"text": "So we use inertial reference\nframes or essentially,", "start": 4140.865, "duration": 2.125}, {"text": "Lorenz reference frames, and\nsaying that Lorentz coordinates", "start": 4142.99, "duration": 2.67}, {"text": "are good everywhere.", "start": 4145.66, "duration": 1.56}, {"text": "We know we can go between\ndifferent Lorentz reference", "start": 4147.22, "duration": 2.67}, {"text": "frames using Lorentz\ntransformations.", "start": 4149.89, "duration": 3.66}, {"text": "But the key thing is that\nif special relativity were", "start": 4153.55, "duration": 2.25}, {"text": "correct, the entire universe\nwould be accurately described", "start": 4155.8, "duration": 3.3}, {"text": "by any inertial reference\nframe you care to write down.", "start": 4159.1, "duration": 4.62}, {"text": "And I will probably only be able\nto do about half of this right", "start": 4163.72, "duration": 4.44}, {"text": "now.", "start": 4168.16, "duration": 1.17}, {"text": "We'll pick it up next time,\nif I cannot finish this.", "start": 4169.33, "duration": 2.779}, {"text": "The key thing which\nI want to emphasize", "start": 4172.109, "duration": 1.691}, {"text": "is, gravity breaks this.", "start": 4173.8, "duration": 4.2}, {"text": "As soon as you put gravity\ninto your theory of relativity,", "start": 4185.899, "duration": 5.761}, {"text": "you cannot have--", "start": 4191.66, "duration": 1.56}, {"text": "so we will call this a\nglobal inertial frame,", "start": 4193.22, "duration": 5.6}, {"text": "an inertial frame that\nis good everywhere,", "start": 4198.82, "duration": 5.13}, {"text": "so \"global\" in the\nmathematical sense,", "start": 4203.95, "duration": 2.13}, {"text": "not \"global\" in the geographic\nsense-- not just earth,", "start": 4206.08, "duration": 2.25}, {"text": "the whole universe, essentially.", "start": 4208.33, "duration": 2.87}, {"text": "As soon as we put in\ngravity, we no longer", "start": 4211.2, "duration": 2.38}, {"text": "have global reference frames\nand global inertial reference", "start": 4213.58, "duration": 3.0}, {"text": "frames.", "start": 4216.58, "duration": 1.65}, {"text": "That word \"inertial\"\nis important.", "start": 4218.23, "duration": 1.747}, {"text": "But we are going to be allowed\nto have local inertial frames.", "start": 4229.73, "duration": 4.92}, {"text": "I have not precisely\ndefined the difference", "start": 4234.65, "duration": 1.92}, {"text": "what \"local\" means in this case,\nand I won't for a few lectures.", "start": 4236.57, "duration": 3.465}, {"text": "But to give you a preview\nas to what that means,", "start": 4248.44, "duration": 4.558}, {"text": "it's essentially\ngoing to say that we", "start": 4252.998, "duration": 1.542}, {"text": "can define an\ninertial coordinate", "start": 4254.54, "duration": 1.56}, {"text": "system that is good over a\nparticular region of spacetime.", "start": 4256.1, "duration": 5.1}, {"text": "And we're going to have\nto discuss and come up", "start": 4261.2, "duration": 1.92}, {"text": "with ways of understanding what\nthe boundaries of that region", "start": 4263.12, "duration": 2.618}, {"text": "are, and how to\nmake this precise.", "start": 4265.738, "duration": 1.417}, {"text": "So the statement\nthat gravity breaks", "start": 4271.16, "duration": 1.86}, {"text": "the existence of global\nLorentz frames, like I said,", "start": 4273.02, "duration": 3.97}, {"text": "it's a two-part thing.", "start": 4276.99, "duration": 1.01}, {"text": "I'm going to use a very\nhandwavy argument which", "start": 4284.07, "duration": 6.66}, {"text": "can be made quite\nrigorous later,", "start": 4290.73, "duration": 1.89}, {"text": "but I want to keep it to this\nhandwaving level, because first", "start": 4292.62, "duration": 2.76}, {"text": "of all, it actually\nwas first done", "start": 4295.38, "duration": 1.65}, {"text": "by a very high-level\nmathematical physicist named", "start": 4297.03, "duration": 4.175}, {"text": "Alfred Schild, who worked in\nthe early theory of relativity.", "start": 4301.205, "duration": 2.5}, {"text": "It's sort of like he\nwas so mathematical,", "start": 4303.705, "duration": 1.708}, {"text": "if it was good enough for him,\nthat's good enough for me.", "start": 4305.413, "duration": 3.137}, {"text": "And I think even though it's\na little handwavy, and kind", "start": 4308.55, "duration": 2.64}, {"text": "of goofy in at\nleast one place, it", "start": 4311.19, "duration": 2.7}, {"text": "gives a good physical sense\nas to why it is gravity", "start": 4313.89, "duration": 3.33}, {"text": "begins to mess things up.", "start": 4317.22, "duration": 1.77}, {"text": "So part one is the\nfact that there exists", "start": 4318.99, "duration": 5.998}, {"text": "a gravitational redshift.", "start": 4324.988, "duration": 1.042}, {"text": "So here's where I'm going\nto be particularly silly,", "start": 4340.02, "duration": 5.74}, {"text": "but I will back up my silliness\nby the fact that everything", "start": 4345.76, "duration": 2.993}, {"text": "silly that I say\nhere has actually", "start": 4348.753, "duration": 1.417}, {"text": "been experimentally\nverified, or at least", "start": 4350.17, "duration": 2.93}, {"text": "the key physical output of this.", "start": 4353.1, "duration": 1.7}, {"text": "So imagine you are\non top of a tower", "start": 4354.8, "duration": 4.04}, {"text": "and you drop a rock of rest mass\nm off the top of this tower.", "start": 4358.84, "duration": 10.27}, {"text": "So here you are.", "start": 4379.484, "duration": 0.916}, {"text": "Here's your rock.", "start": 4384.112, "duration": 0.708}, {"text": "The rock falls.", "start": 4388.06, "duration": 0.66}, {"text": "There's a wonderful device down\nhere which I label with a p.", "start": 4395.77, "duration": 7.04}, {"text": "It's called a photonulater.", "start": 4402.81, "duration": 1.491}, {"text": "And what the\nphotonulater does, it", "start": 4407.07, "duration": 7.75}, {"text": "converts the rock\ninto a single photon,", "start": 4414.82, "duration": 9.55}, {"text": "and it does so\nconserving energy.", "start": 4424.37, "duration": 2.31}, {"text": "So when this rock\nfalls, the instant", "start": 4433.79, "duration": 2.92}, {"text": "before it goes into\nyour photonulater,", "start": 4436.71, "duration": 9.17}, {"text": "just use Newtonian physics\nplus the notion of rest energy.", "start": 4445.88, "duration": 4.71}, {"text": "So it's got an energy of m--\nmC squared, if you prefer,", "start": 4450.59, "duration": 4.92}, {"text": "its rest energy--", "start": 4455.51, "duration": 1.59}, {"text": "plus what it acquired\nafter falling--", "start": 4457.1, "duration": 2.848}, {"text": "pardon me, I forgot to\ngive you a distance here--", "start": 4459.948, "duration": 2.042}, {"text": "after falling a distance h.", "start": 4461.99, "duration": 1.46}, {"text": "So that means that the\nphoton that I shoot up", "start": 4470.33, "duration": 2.102}, {"text": "from this thing--", "start": 4472.432, "duration": 0.708}, {"text": "let me put a few\nthings on this board.", "start": 4476.09, "duration": 3.21}, {"text": "So the instant that\nI create this photon,", "start": 4489.86, "duration": 10.49}, {"text": "this thing goes\nout, and it's going", "start": 4500.35, "duration": 2.38}, {"text": "to have a frequency omega\nbottom, which is simply", "start": 4502.73, "duration": 3.152}, {"text": "related to that energy.", "start": 4505.882, "duration": 0.958}, {"text": "This photon immediately is\nshot back up to the top,", "start": 4515.32, "duration": 2.56}, {"text": "where clever you,\nyou happen to have", "start": 4517.88, "duration": 2.88}, {"text": "in your hands a rerockulater.", "start": 4520.76, "duration": 2.747}, {"text": "The rerockulater, as the\nname obviously implies,", "start": 4526.31, "duration": 3.12}, {"text": "converts the photon\nback into a rock.", "start": 4529.43, "duration": 1.65}, {"text": "Now, suppose it does so--\nboth the photonulater", "start": 4552.5, "duration": 2.43}, {"text": "and the rerockulater are\nfine MIT engineering.", "start": 4554.93, "duration": 2.73}, {"text": "There are no losses\nanywhere in this thing.", "start": 4557.66, "duration": 3.27}, {"text": "So there's no friction.", "start": 4560.93, "duration": 1.23}, {"text": "There's no extra heat generated.", "start": 4562.16, "duration": 1.35}, {"text": "It does it conserving\nenergy, 100%.", "start": 4563.51, "duration": 4.32}, {"text": "What is the energy at the top?", "start": 4567.83, "duration": 1.79}, {"text": "Well, you might naively\nsay, ah, it's just", "start": 4578.45, "duration": 3.267}, {"text": "going to go up to the top.", "start": 4581.717, "duration": 1.083}, {"text": "It's going to have\nthat same energy.", "start": 4582.8, "duration": 1.5}, {"text": "It might just have it in the\nform of a photon and omega b.", "start": 4584.3, "duration": 3.48}, {"text": "There will be some\nfrequency at the top.", "start": 4590.74, "duration": 4.11}, {"text": "And your initial\nguess might be it's", "start": 4594.85, "duration": 2.253}, {"text": "going to be the same as the\nfrequency at the bottom.", "start": 4597.103, "duration": 2.167}, {"text": "But if you do that, you're\ngoing to suddenly discover", "start": 4599.27, "duration": 2.208}, {"text": "that your rock has more energy\nthan it started out with,", "start": 4601.478, "duration": 2.372}, {"text": "and you can redirect it\nback down, send it back up.", "start": 4603.85, "duration": 2.04}, {"text": "Next thing you know, you've\ngot yourself a perpetual motion", "start": 4605.89, "duration": 1.59}, {"text": "machine.", "start": 4607.48, "duration": 1.29}, {"text": "So all you need to do\nis get your photonulater", "start": 4608.77, "duration": 1.98}, {"text": "and your rerockulater\ngoing, and you've", "start": 4610.75, "duration": 1.625}, {"text": "got yourself a perpetual\nmotion machine here.", "start": 4612.375, "duration": 2.255}, {"text": "I will grant that's\nprobably not the weakest", "start": 4614.63, "duration": 1.833}, {"text": "part of this argument.", "start": 4616.463, "duration": 2.087}, {"text": "Suppose you had this.", "start": 4618.55, "duration": 0.95}, {"text": "I mean, you look at this.", "start": 4619.5, "duration": 1.042}, {"text": "If technology allowed you\nto make these goofy devices,", "start": 4620.542, "duration": 4.668}, {"text": "you would instantly look\nat this and say, look,", "start": 4625.21, "duration": 2.79}, {"text": "if I am not to have--", "start": 4628.0, "duration": 1.542}, {"text": "let's just say I\nlive in a universe", "start": 4629.542, "duration": 1.458}, {"text": "where I'm fine\nwith photonulaters.", "start": 4631.0, "duration": 1.417}, {"text": "I'm fine with\nrerockulaters, but damn it,", "start": 4632.417, "duration": 2.363}, {"text": "energy has to be conserved.", "start": 4634.78, "duration": 1.32}, {"text": "I am not fine with\nperpetual motion machines.", "start": 4636.1, "duration": 3.0}, {"text": "If that's the case, we always\nfight perpetual motion.", "start": 4639.1, "duration": 7.1}, {"text": "We must have that\nthe energy at the top", "start": 4651.99, "duration": 3.495}, {"text": "is equal to the energy\nthis guy started with.", "start": 4655.485, "duration": 1.875}, {"text": "When it sort of gets back into--", "start": 4657.36, "duration": 1.62}, {"text": "imagine that your\nrerockulater is shaped", "start": 4658.98, "duration": 2.16}, {"text": "like a baseball catcher's mitt.", "start": 4661.14, "duration": 1.32}, {"text": "You want that thing to just\nland gently in your mitt,", "start": 4662.46, "duration": 2.64}, {"text": "and just be a perfectly\ngentle, little landing there.", "start": 4665.1, "duration": 3.07}, {"text": "And when you put all this\ntogether, going through this,", "start": 4668.17, "duration": 19.12}, {"text": "taking advantage of the fact\nthat if you work in units where", "start": 4687.29, "duration": 2.933}, {"text": "you've put your\nc's back in, there", "start": 4690.223, "duration": 1.417}, {"text": "will be a factor of g h over c\nsquared appearing in here, what", "start": 4691.64, "duration": 10.22}, {"text": "you find is that the\nfrequency at the top", "start": 4701.86, "duration": 3.48}, {"text": "is less than the\nfrequency at the bottom.", "start": 4705.34, "duration": 4.66}, {"text": "In other words, the light has\ngotten a little bit redder.", "start": 4710.0, "duration": 3.34}, {"text": "now I fully confess, I did\nthis via the silliest argument", "start": 4713.34, "duration": 3.29}, {"text": "possible.", "start": 4716.63, "duration": 1.02}, {"text": "But I want to\nemphasize that this", "start": 4717.65, "duration": 2.07}, {"text": "is one of the most precisely\nverified predictions of gravity", "start": 4719.72, "duration": 5.34}, {"text": "and relativity theory.", "start": 4725.06, "duration": 2.19}, {"text": "This was first done, actually,\nup the street at Harvard,", "start": 4727.25, "duration": 3.78}, {"text": "by what's called the\nPound-Rebka experiment.", "start": 4731.03, "duration": 3.71}, {"text": "And the basic principles of\nwhat is going on with this right", "start": 4734.74, "duration": 2.5}, {"text": "now--", "start": 4737.24, "duration": 0.718}, {"text": "I just took this out to\nmake sure my alarm is not", "start": 4737.958, "duration": 2.042}, {"text": "about to go off, but\nI want to emphasize", "start": 4740.0, "duration": 1.667}, {"text": "it's actually built\ninto the workings", "start": 4741.667, "duration": 1.541}, {"text": "of the global\npositioning system.", "start": 4743.208, "duration": 1.422}, {"text": "Because this fact that\nlight signals may travel out", "start": 4744.63, "duration": 2.54}, {"text": "of a gravitational\npotential, they", "start": 4747.17, "duration": 2.79}, {"text": "get redshifted, needs to be\ntaken into account in order", "start": 4749.96, "duration": 2.43}, {"text": "to do the precise\nmetrology that GPS allows.", "start": 4752.39, "duration": 2.82}, {"text": "Now, this is part one,\nthis idea that light", "start": 4755.21, "duration": 6.42}, {"text": "gets redder as it climbs out\nof a gravitational field.", "start": 4761.63, "duration": 3.09}, {"text": "Part two, which I\nwill do on Thursday,", "start": 4764.72, "duration": 2.51}, {"text": "is to show that if there\nis a global inertial frame,", "start": 4767.23, "duration": 4.27}, {"text": "there is no way for light to\nget redder as it climbs out", "start": 4771.5, "duration": 3.33}, {"text": "of a gravitational potential.", "start": 4774.83, "duration": 3.25}, {"text": "You cannot have both gravity\nand a global inertial reference", "start": 4778.08, "duration": 4.2}, {"text": "frame.", "start": 4782.28, "duration": 0.618}, {"text": "That's where I will\npick it up on Thursday.", "start": 4782.898, "duration": 1.792}, {"text": "So we'll do that.", "start": 4784.69, "duration": 1.01}, {"text": "And we will then begin\ntalking about how", "start": 4785.7, "duration": 3.3}, {"text": "we can try to put the principles\nof relativity and gravity", "start": 4789.0, "duration": 3.51}, {"text": "together.", "start": 4792.51, "duration": 1.185}, {"text": "And in some sense, this is when\nour study of general relativity", "start": 4793.695, "duration": 2.625}, {"text": "will begin in earnest.", "start": 4796.32, "duration": 1.74}, {"text": "All right, so let us stop there.", "start": 4798.06, "duration": 3.05}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.48}, {"text": "[RUSTLING]", "start": 2.48, "duration": 1.488}, {"text": "[CLICKING]", "start": 3.968, "duration": 2.48}, {"text": "NORVIN W. RICHARDS: I was\nthinking about today's topic", "start": 11.408, "duration": 3.232}, {"text": "earlier.", "start": 14.64, "duration": 0.78}, {"text": "And I thought of a metaphor.", "start": 15.42, "duration": 4.29}, {"text": "I haven't tried this\nmetaphor before.", "start": 19.71, "duration": 1.57}, {"text": "This is the first time I\nhave tried this metaphor", "start": 21.28, "duration": 2.042}, {"text": "on people in class.", "start": 23.322, "duration": 1.736}, {"text": "It's always dangerous\nthinking of metaphors", "start": 25.058, "duration": 1.792}, {"text": "for all kinds of reasons.", "start": 26.85, "duration": 1.042}, {"text": "One of them is that\nit's entirely possible", "start": 27.892, "duration": 1.898}, {"text": "that I'm about to beat this\nmetaphor into the ground.", "start": 29.79, "duration": 2.259}, {"text": "I'm going to talk\nabout it for a while.", "start": 32.049, "duration": 2.841}, {"text": "But-- so I apologize in\nadvance if that happens.", "start": 34.89, "duration": 3.012}, {"text": "It's also possible that I\nwill tell you the metaphor,", "start": 37.902, "duration": 2.208}, {"text": "and you will wonder, what\nthe heck is he talking about?", "start": 40.11, "duration": 2.7}, {"text": "It will be too metaphorical.", "start": 42.81, "duration": 1.273}, {"text": "But, hopefully, as\nthe class goes along,", "start": 44.083, "duration": 1.667}, {"text": "it'll become clear\nwhat I'm talking about.", "start": 45.75, "duration": 2.28}, {"text": "Or maybe it'll be\nclear immediately.", "start": 48.03, "duration": 1.5}, {"text": "Who knows?", "start": 49.53, "duration": 0.44}, {"text": "OK.", "start": 49.97, "duration": 0.25}, {"text": "Here's the metaphor.", "start": 50.22, "duration": 0.833}, {"text": "You have to try to\nimagine for this metaphor", "start": 53.28, "duration": 3.42}, {"text": "that the United States\nis the kind of country--", "start": 56.7, "duration": 3.42}, {"text": "bless you-- in which board\ngames are extremely popular.", "start": 60.12, "duration": 4.979}, {"text": "Everyone plays board\ngames all the time.", "start": 65.099, "duration": 2.461}, {"text": "It's like the standard\nway for people", "start": 67.56, "duration": 2.31}, {"text": "to interact with each other.", "start": 69.87, "duration": 2.16}, {"text": "So if you are on a\nlong plane flight,", "start": 72.03, "duration": 3.03}, {"text": "you'll probably\nplay a board game", "start": 75.06, "duration": 1.53}, {"text": "with the person\nsitting next to you.", "start": 76.59, "duration": 2.964}, {"text": "You go-- you move\ninto your new dorm,", "start": 79.554, "duration": 2.076}, {"text": "and you start\nplaying board games", "start": 81.63, "duration": 1.38}, {"text": "with your new roommate and\nthe other people on your hall.", "start": 83.01, "duration": 2.375}, {"text": "That's just the\nnormal way for people", "start": 85.385, "duration": 1.735}, {"text": "to interact with each other--\nall board games all the time.", "start": 87.12, "duration": 3.25}, {"text": "And try to imagine that there\nare various board games that", "start": 90.37, "duration": 3.98}, {"text": "are popular.", "start": 94.35, "duration": 0.84}, {"text": "But in the US, for some\nreason, the two big ones", "start": 95.19, "duration": 3.06}, {"text": "are chess and checkers.", "start": 98.25, "duration": 1.912}, {"text": "So those are the two board\ngames that are the most popular.", "start": 100.162, "duration": 2.458}, {"text": "There are other\ngames people play.", "start": 102.62, "duration": 1.417}, {"text": "But those are the two big ones.", "start": 104.037, "duration": 1.813}, {"text": "And the following kind of\nweird thing has happened.", "start": 105.85, "duration": 3.42}, {"text": "There are families in which\neverybody plays chess,", "start": 109.27, "duration": 4.94}, {"text": "let's say.", "start": 114.21, "duration": 0.78}, {"text": "Families specialize.", "start": 114.99, "duration": 1.47}, {"text": "So if you're born\nin a chess family,", "start": 116.46, "duration": 2.85}, {"text": "then mom and dad play chess.", "start": 119.31, "duration": 1.732}, {"text": "And your older brothers\nand sisters play chess.", "start": 121.042, "duration": 1.958}, {"text": "And your uncles, and your\naunts, and your ankles--", "start": 123.0, "duration": 2.31}, {"text": "your ankles do not play chess.", "start": 125.31, "duration": 1.32}, {"text": "Your uncles, and your aunts,\nand your grandparents, they", "start": 126.63, "duration": 3.0}, {"text": "all play chess.", "start": 129.63, "duration": 0.9}, {"text": "And maybe nobody ever actually\nsits you down and explains", "start": 130.53, "duration": 3.63}, {"text": "the rules of chess to you.", "start": 134.16, "duration": 1.56}, {"text": "But you see everybody\nplaying chess,", "start": 135.72, "duration": 1.71}, {"text": "and you eventually get to\nwhere you're pretty good at it.", "start": 137.43, "duration": 1.95}, {"text": "In fact, by the time you're\nold enough to go to school,", "start": 139.38, "duration": 2.292}, {"text": "you're very good\nat playing chess", "start": 141.672, "duration": 1.458}, {"text": "if you grow up in\na chess family.", "start": 143.13, "duration": 1.672}, {"text": "And then there are the\ncheckers families, which", "start": 144.802, "duration": 1.958}, {"text": "are the same except checkers.", "start": 146.76, "duration": 1.38}, {"text": "So everybody plays checkers.", "start": 148.14, "duration": 1.75}, {"text": "If you grew up in\na checkers family,", "start": 149.89, "duration": 1.76}, {"text": "mom and dad play checkers.", "start": 151.65, "duration": 1.29}, {"text": "Older brothers and\nsisters play checkers.", "start": 152.94, "duration": 1.44}, {"text": "You watch them play checkers.", "start": 154.38, "duration": 1.208}, {"text": "You become a checkers\nexpert by the time you're", "start": 155.588, "duration": 3.472}, {"text": "old enough to go to school.", "start": 159.06, "duration": 1.56}, {"text": "So there are chess kids and\nthere are checkers kids.", "start": 160.62, "duration": 2.75}, {"text": "And then when you go to\nschool, the following kind", "start": 163.37, "duration": 3.06}, {"text": "of weird thing happens.", "start": 166.43, "duration": 1.65}, {"text": "The teachers act as though\nthere is no such game as chess.", "start": 168.08, "duration": 5.16}, {"text": "So when they see kids\nplaying checkers,", "start": 173.24, "duration": 2.97}, {"text": "they're like, oh, yeah.", "start": 176.21, "duration": 0.992}, {"text": "And they watch the\nkids playing checkers.", "start": 177.202, "duration": 1.708}, {"text": "Maybe they make tactical\nsuggestions or whatever.", "start": 178.91, "duration": 2.19}, {"text": "Maybe the teachers play\ncheckers with each other.", "start": 181.1, "duration": 2.55}, {"text": "Maybe they play checkers\nwith the kids sometimes.", "start": 183.65, "duration": 3.12}, {"text": "But when they see\nkids playing chess,", "start": 186.77, "duration": 2.16}, {"text": "they say things like,\nwhat are you doing?", "start": 188.93, "duration": 3.4}, {"text": "That's not the right\nway to play checkers.", "start": 192.33, "duration": 3.15}, {"text": "You just took that one piece and\nyou moved it a zillion diagonal", "start": 195.48, "duration": 4.01}, {"text": "spaces.", "start": 199.49, "duration": 0.51}, {"text": "You can't do that.", "start": 200.0, "duration": 1.11}, {"text": "You're just violating all\nthe rules of checkers.", "start": 201.11, "duration": 3.84}, {"text": "That's not how checkers works.", "start": 204.95, "duration": 1.8}, {"text": "And what is the deal with\nthese weird checkers pieces--", "start": 206.75, "duration": 2.5}, {"text": "this one that looks like\na horse, and this one that", "start": 209.25, "duration": 2.125}, {"text": "looks like a castle?", "start": 211.375, "duration": 0.865}, {"text": "Put all that stuff away.", "start": 212.24, "duration": 1.17}, {"text": "Get yourself a real\ncheckers board.", "start": 213.41, "duration": 2.37}, {"text": "And play checkers\nlike a normal person.", "start": 215.78, "duration": 4.44}, {"text": "There are tests that\nkids get in school where", "start": 220.22, "duration": 4.95}, {"text": "they are asked questions like\n\"Is it OK to take a piece", "start": 225.17, "duration": 4.08}, {"text": "and move it two steps forward\nand one step to the right?\"", "start": 229.25, "duration": 3.72}, {"text": "And the kids are\nsupposed to say,", "start": 232.97, "duration": 1.59}, {"text": "no, it's not OK to\ndo that, because this", "start": 234.56, "duration": 4.26}, {"text": "is a checkers test, and in\ncheckers you can't do that.", "start": 238.82, "duration": 3.79}, {"text": "So if you're from\na checkers family,", "start": 242.61, "duration": 1.59}, {"text": "this is an easy test for you\nbecause, in fact, you can't", "start": 244.2, "duration": 2.69}, {"text": "make that move in checkers.", "start": 246.89, "duration": 2.13}, {"text": "If you're from a chess\nfamily, then it's", "start": 249.02, "duration": 2.01}, {"text": "a little harder\nbecause, of course,", "start": 251.03, "duration": 1.03}, {"text": "that's how you move your knight.", "start": 252.06, "duration": 1.34}, {"text": "That's one way you\ncan move your knight.", "start": 253.4, "duration": 1.68}, {"text": "And so maybe you made that\nmove just this morning", "start": 255.08, "duration": 2.73}, {"text": "playing with your\nmom or your dad.", "start": 257.81, "duration": 2.55}, {"text": "And so kids from chess\nfamilies have a tendency", "start": 260.36, "duration": 3.27}, {"text": "to do badly on this\nthese tests, which", "start": 263.63, "duration": 2.1}, {"text": "means that when it comes\ntime to put the kids", "start": 265.73, "duration": 2.07}, {"text": "in the checkers classes--", "start": 267.8, "duration": 1.86}, {"text": "there are checkers\nclasses in schools.", "start": 269.66, "duration": 2.49}, {"text": "There are no chess classes,\nonly checkers classes.", "start": 272.15, "duration": 3.42}, {"text": "The kids from\ncheckers families tend", "start": 275.57, "duration": 2.22}, {"text": "to be the ones who get\ninto Advanced Checkers,", "start": 277.79, "duration": 2.25}, {"text": "and later they go on to AP\nCheckers where they get--", "start": 280.04, "duration": 2.377}, {"text": "AUDIENCE: [LAUGHTER]", "start": 282.417, "duration": 0.833}, {"text": "NORVIN W. RICHARDS:\n--where they get", "start": 283.25, "duration": 1.5}, {"text": "college credit for their\ncollege checkers classes.", "start": 284.75, "duration": 3.09}, {"text": "The kids from chess families--", "start": 287.84, "duration": 2.31}, {"text": "it varies.", "start": 290.15, "duration": 1.06}, {"text": "Some of them learn quickly how\nto play checkers and suppress", "start": 291.21, "duration": 3.35}, {"text": "their knowledge of chess.", "start": 294.56, "duration": 1.105}, {"text": "But some of them have a hard\ntime, and it's hard for them", "start": 295.665, "duration": 2.375}, {"text": "to switch that quickly.", "start": 298.04, "duration": 2.43}, {"text": "Every so often, you\nwill get a teacher who's", "start": 300.47, "duration": 3.12}, {"text": "maybe a little more\nenlightened and admits", "start": 303.59, "duration": 2.13}, {"text": "that there is such\na game as chess,", "start": 305.72, "duration": 2.07}, {"text": "and who will say to\nthe kids, it's OK.", "start": 307.79, "duration": 3.032}, {"text": "The kids who are from chess\nfamilies-- they'll say to them,", "start": 310.822, "duration": 2.458}, {"text": "it's OK for you to play chess\nin the privacy of your own home", "start": 313.28, "duration": 3.57}, {"text": "with your family.", "start": 316.85, "duration": 1.26}, {"text": "But it's important for you\nnot to play it in public", "start": 318.11, "duration": 2.4}, {"text": "because people will\nget the wrong idea.", "start": 320.51, "duration": 2.175}, {"text": "It's really important for\nyou to be good at checkers.", "start": 322.685, "duration": 2.505}, {"text": "Checkers is the\nreally important game.", "start": 325.19, "duration": 1.71}, {"text": "That's what the\nteachers will say.", "start": 326.9, "duration": 2.18}, {"text": "And the teachers have\na point because this", "start": 329.08, "duration": 1.75}, {"text": "is a version of America in\nwhich checkers is what people", "start": 330.83, "duration": 4.44}, {"text": "expect you to be good at.", "start": 335.27, "duration": 1.26}, {"text": "If you go for a job interview\nor in political campaigns--", "start": 336.53, "duration": 3.36}, {"text": "presidential campaigns always\ninvolve a huge checkers", "start": 339.89, "duration": 2.4}, {"text": "tournament between\nthe candidates,", "start": 342.29, "duration": 2.94}, {"text": "political correspondents\nwatching the game", "start": 345.23, "duration": 3.423}, {"text": "and commenting on the moves.", "start": 348.653, "duration": 1.167}, {"text": "And if somebody tries to make a\nchess move in a checkers game,", "start": 349.82, "duration": 2.97}, {"text": "well, then, no one\nwill vote for them.", "start": 352.79, "duration": 2.82}, {"text": "That's the metaphor.", "start": 355.61, "duration": 2.4}, {"text": "There.", "start": 358.01, "duration": 0.57}, {"text": "Now, if it's not yet clear\nwhat I'm talking about,", "start": 358.58, "duration": 2.91}, {"text": "hopefully it will\nbe in a second.", "start": 361.49, "duration": 1.385}, {"text": "Are there any questions about\nthe metaphor other than, what?", "start": 362.875, "duration": 2.5}, {"text": "[CHUCKLES] OK.", "start": 365.375, "duration": 1.933}, {"text": "AUDIENCE: [? Is it a ?] fact\nthat [? humans ?] see that", "start": 367.308, "duration": 2.292}, {"text": "checkers is [? used ?]\n[INAUDIBLE] will be superior", "start": 369.6, "duration": 4.93}, {"text": "[INAUDIBLE]?", "start": 374.53, "duration": 0.5}, {"text": "NORVIN W. RICHARDS: Yeah.", "start": 375.03, "duration": 0.33}, {"text": "So you have to imagine that\ncheckers is the superior game", "start": 375.36, "duration": 2.91}, {"text": "in this version of the story.", "start": 378.27, "duration": 1.348}, {"text": "I could have told the\nstory the other way around.", "start": 379.618, "duration": 2.042}, {"text": "But I told it this way.", "start": 381.66, "duration": 1.2}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 382.86, "duration": 0.88}, {"text": "NORVIN W. RICHARDS: Yeah.", "start": 383.74, "duration": 0.29}, {"text": "Yeah.", "start": 384.03, "duration": 0.57}, {"text": "Other questions?", "start": 384.6, "duration": 1.12}, {"text": "OK.", "start": 385.72, "duration": 1.85}, {"text": "So seemingly unrelated topic--", "start": 387.57, "duration": 4.56}, {"text": "remember negative\npolarity items?", "start": 392.13, "duration": 2.16}, {"text": "Negative polarity items\nwere these expressions", "start": 394.29, "duration": 3.03}, {"text": "that you used together\nwith negation to say things", "start": 397.32, "duration": 5.22}, {"text": "like, \"I didn't see anything.\"", "start": 402.54, "duration": 2.433}, {"text": "And what we said about\nthem-- so \"anything\" is", "start": 404.973, "duration": 1.917}, {"text": "a negative polarity item.", "start": 406.89, "duration": 1.23}, {"text": "And to call it a\nnegative polarity item", "start": 408.12, "duration": 1.65}, {"text": "is to say it's an expression\nwith some restrictions on where", "start": 409.77, "duration": 4.41}, {"text": "it can be used.", "start": 414.18, "duration": 1.15}, {"text": "We talked a little bit\nabout the different kinds", "start": 415.33, "duration": 2.0}, {"text": "of quantifiers that\nmake it possible to use", "start": 417.33, "duration": 2.07}, {"text": "a negative polarity item.", "start": 419.4, "duration": 1.68}, {"text": "One of them is--", "start": 421.08, "duration": 1.052}, {"text": "well, negation makes it possible\nto use a negative polarity", "start": 422.132, "duration": 2.458}, {"text": "item.", "start": 424.59, "duration": 0.5}, {"text": "That's how they get their name.", "start": 425.09, "duration": 1.72}, {"text": "But in a sentence\nlike, \"I saw anything,\"", "start": 426.81, "duration": 3.51}, {"text": "there's something\nwrong with that.", "start": 430.32, "duration": 1.72}, {"text": "Yeah?", "start": 432.04, "duration": 0.5}, {"text": "AUDIENCE: What about,\n\"I will eat anything?\"", "start": 432.54, "duration": 1.635}, {"text": "NORVIN W. RICHARDS: Ah!", "start": 434.175, "duration": 0.958}, {"text": "So negative polarity items\noften have another use.", "start": 435.133, "duration": 3.907}, {"text": "Let me find a piece of chalk.", "start": 439.04, "duration": 1.81}, {"text": "For some reason,\nthis always happens.", "start": 440.85, "duration": 2.01}, {"text": "There are many\nerasers but no chalk.", "start": 442.86, "duration": 3.24}, {"text": "There's actually\nliterally no chalk.", "start": 446.1, "duration": 1.5}, {"text": "Where are the-- what the heck?", "start": 447.6, "duration": 3.24}, {"text": "\"I will eat anything.\"", "start": 450.84, "duration": 1.32}, {"text": "This is sometimes called \"free\nchoice 'any.'\" And it's very", "start": 457.27, "duration": 6.28}, {"text": "interesting.", "start": 463.55, "duration": 1.505}, {"text": "Notice that it's\nalso restricted.", "start": 465.055, "duration": 1.375}, {"text": "So \"I saw anything\"\nis actually no good.", "start": 466.43, "duration": 2.552}, {"text": "You can't use either free choice\n\"any\" or negative polarity", "start": 468.982, "duration": 2.458}, {"text": "\"any.\"", "start": 471.44, "duration": 0.24}, {"text": "But you're right there's\nanother possible use", "start": 471.68, "duration": 1.98}, {"text": "of these kinds of things.", "start": 473.66, "duration": 1.56}, {"text": "Having admitted\nthat you're right,", "start": 475.22, "duration": 1.65}, {"text": "let me just suppress that point.", "start": 476.87, "duration": 1.44}, {"text": "Yeah.", "start": 478.31, "duration": 0.5}, {"text": "You're absolutely right.", "start": 478.81, "duration": 1.15}, {"text": "There are complications.", "start": 479.96, "duration": 1.56}, {"text": "Yeah.", "start": 481.52, "duration": 0.51}, {"text": "Yeah?", "start": 482.03, "duration": 0.5}, {"text": "So, plenty of languages have\nnegative polarity items.", "start": 484.85, "duration": 4.53}, {"text": "And maybe unsurprisingly\nif you are using--", "start": 489.38, "duration": 6.697}, {"text": "if you're going to answer a\nquestion like, \"What did you", "start": 496.077, "duration": 2.333}, {"text": "see?\"", "start": 498.41, "duration": 1.59}, {"text": "in the language that\nI'm now speaking,", "start": 500.0, "duration": 2.52}, {"text": "\"anything\" is not\na possible answer.", "start": 502.52, "duration": 4.2}, {"text": "We can be unsurprised by\nthat in a couple of ways.", "start": 506.72, "duration": 2.74}, {"text": "One would be to say, well,\nyeah, this gets us back", "start": 509.46, "duration": 2.388}, {"text": "to the kinds of things we\nwere talking about when", "start": 511.848, "duration": 2.042}, {"text": "we were talking about ellipses.", "start": 513.89, "duration": 1.71}, {"text": "So if we want to think of\nthis as an utterance that just", "start": 515.6, "duration": 3.809}, {"text": "consists of a noun\nphrase-- \"anything\"--", "start": 519.409, "duration": 2.281}, {"text": "then it's unsurprising\nthat it's bad.", "start": 521.69, "duration": 3.75}, {"text": "It's bad, well,\nbecause \"anything\"", "start": 525.44, "duration": 1.8}, {"text": "doesn't have any negation\nanywhere to make it happy.", "start": 527.24, "duration": 2.8}, {"text": "Yeah.", "start": 530.04, "duration": 0.5}, {"text": "That's what NPIs need--", "start": 530.54, "duration": 1.23}, {"text": "Negative Polarity Items.", "start": 531.77, "duration": 3.21}, {"text": "Getting back to your\npoint-- if the question", "start": 534.98, "duration": 2.07}, {"text": "was, \"What will you eat?\"", "start": 537.05, "duration": 1.59}, {"text": "a possible answer is \"anything.\"", "start": 538.64, "duration": 2.79}, {"text": "You can also do the free\nchoice version of \"any.\"", "start": 541.43, "duration": 2.13}, {"text": "If we want to think about\nthis as ellipsis-- that", "start": 546.378, "duration": 2.042}, {"text": "is, if we want to think of it\nas, I ask you \"What did you", "start": 548.42, "duration": 2.85}, {"text": "see?\" and you are in some sense\nsaying, \"I saw anything,\" well,", "start": 551.27, "duration": 4.14}, {"text": "that's bad because \"I\nsaw anything\" is bad.", "start": 555.41, "duration": 2.07}, {"text": "There's no negation\nin the sentence.", "start": 557.48, "duration": 2.28}, {"text": "And I guess what we're\nlearning-- maybe you remember--", "start": 559.76, "duration": 2.25}, {"text": "when we were talking\nabout ellipsis,", "start": 562.01, "duration": 1.5}, {"text": "we talked about the fact\nthat when you do ellipsis--", "start": 563.51, "duration": 4.02}, {"text": "when you say things like,\n\"John likes his father,", "start": 567.53, "duration": 7.92}, {"text": "and Bill does too,\" there's\nsome kind of requirement", "start": 575.45, "duration": 5.73}, {"text": "that the missing phrase--", "start": 581.18, "duration": 1.86}, {"text": "the missing verb\nphrase, in this case--", "start": 583.04, "duration": 1.8}, {"text": "be the same as\nanother verb phrase", "start": 584.84, "duration": 1.882}, {"text": "and we talked about the\nfact that you sometimes", "start": 586.722, "duration": 1.958}, {"text": "have to do some work to figure\nout what counts as the same.", "start": 588.68, "duration": 3.08}, {"text": "So we decided that this\nwas an ambiguous sentence.", "start": 591.76, "duration": 2.86}, {"text": "\"John likes his father, and\nBill does too\" can mean at least", "start": 594.62, "duration": 3.69}, {"text": "two things, possibly\nsome others as well.", "start": 598.31, "duration": 3.84}, {"text": "It's unclear whose\nfather we're talking", "start": 602.15, "duration": 1.79}, {"text": "about in this second clause.", "start": 603.94, "duration": 1.92}, {"text": "All right.", "start": 605.86, "duration": 0.73}, {"text": "So this could mean that John and\nBill both like John's father,", "start": 606.59, "duration": 3.92}, {"text": "or that John likes John's father\nand Bill likes Bill's father.", "start": 610.51, "duration": 3.51}, {"text": "I guess it could\nalso mean that they", "start": 614.02, "duration": 1.5}, {"text": "both like Seymour's father--", "start": 615.52, "duration": 1.65}, {"text": "some other person.", "start": 617.17, "duration": 1.92}, {"text": "It could mean that.", "start": 619.09, "duration": 1.21}, {"text": "Yeah.", "start": 620.3, "duration": 0.5}, {"text": "So when we do ellipsis, we\nhave something that's missing,", "start": 620.8, "duration": 4.95}, {"text": "that is understood as being the\nsame as something that's there.", "start": 625.75, "duration": 3.523}, {"text": "And I guess what we're learning\nhere is that if I ask you,", "start": 629.273, "duration": 2.417}, {"text": "\"What did you see?\", if we want\nto think of that as involving", "start": 631.69, "duration": 2.76}, {"text": "ellipsis, we want to think of\nourselves as being required", "start": 634.45, "duration": 3.36}, {"text": "to fill in \"I saw anything.\"", "start": 637.81, "duration": 4.74}, {"text": "We don't, for example, have\nthe option of putting in", "start": 642.55, "duration": 3.63}, {"text": "\"didn't see.\"", "start": 646.18, "duration": 1.707}, {"text": "And that's got something\nto do with the fact", "start": 647.887, "duration": 1.833}, {"text": "that the question doesn't\nhave negation in it.", "start": 649.72, "duration": 2.01}, {"text": "It's a positive question.", "start": 651.73, "duration": 1.42}, {"text": "So a couple of ways of not\nbeing surprised by this fact.", "start": 653.15, "duration": 2.57}, {"text": "Is everybody\nsufficiently unsurprised?", "start": 655.72, "duration": 3.49}, {"text": "How do you answer a\nquestion like this?", "start": 659.21, "duration": 1.68}, {"text": "\"What did you see?\"", "start": 660.89, "duration": 1.575}, {"text": "Well, one way you can do\nit is by saying \"Nothing.\"", "start": 662.465, "duration": 4.855}, {"text": "So we have another\nkind of expression", "start": 667.32, "duration": 2.07}, {"text": "that you use that's\nnegative all by itself.", "start": 669.39, "duration": 2.82}, {"text": "It's not an NPI.", "start": 672.21, "duration": 1.56}, {"text": "It doesn't need to\ncombine with negation.", "start": 673.77, "duration": 3.432}, {"text": "OK so far?", "start": 677.202, "duration": 1.025}, {"text": "I'm just describing\nfacts about the language", "start": 678.227, "duration": 1.833}, {"text": "that I'm speaking--", "start": 680.06, "duration": 2.603}, {"text": "not just the language\nthat I'm speaking.", "start": 682.663, "duration": 1.667}, {"text": "There are plenty of languages\nlike this out there.", "start": 684.33, "duration": 2.49}, {"text": "Here are some Greek\ndata that are the same.", "start": 686.82, "duration": 1.89}, {"text": "So in Greek there's an\nexpression, [GREEK],,", "start": 688.71, "duration": 4.348}, {"text": "which is like \"anything.\"", "start": 693.058, "duration": 1.042}, {"text": "Anybody here speak Greek?", "start": 694.1, "duration": 2.12}, {"text": "Cool.", "start": 696.22, "duration": 0.5}, {"text": "Then I won't mispronounce\nGreek at you.", "start": 696.72, "duration": 1.625}, {"text": "I'm afraid I don't speak Greek.", "start": 698.345, "duration": 1.855}, {"text": "[GREEK]-- that means \"anything.\"", "start": 700.2, "duration": 1.92}, {"text": "And it combines\nwith the Greek word", "start": 702.12, "duration": 2.37}, {"text": "for \"not,\" which is \"then.\"", "start": 704.49, "duration": 2.28}, {"text": "And so you can say\nin Greek, literally,", "start": 706.77, "duration": 2.49}, {"text": "\"He or she didn't see\nanything,\" with \"not\"--", "start": 709.26, "duration": 3.45}, {"text": "[GREEK]---- but [GREEK] can't\nbe in a positive sentence.", "start": 712.71, "duration": 3.24}, {"text": "You can't say, \"He\nor she saw anything.\"", "start": 715.95, "duration": 1.98}, {"text": "And before anybody asks, I don't\nknow how to say things like,", "start": 717.93, "duration": 2.67}, {"text": "\"I will eat anything\" in Greek.", "start": 720.6, "duration": 1.38}, {"text": "I don't know whether\nthey can do that here.", "start": 721.98, "duration": 2.26}, {"text": "Yeah.", "start": 724.24, "duration": 0.5}, {"text": "So this is just to show you\nwhen we were talking about NPIs,", "start": 724.74, "duration": 3.91}, {"text": "we were talking about English.", "start": 728.65, "duration": 1.25}, {"text": "But it's not just\nan English thing.", "start": 729.9, "duration": 1.32}, {"text": "It's cross-linguistically\nvery common to have NPIs", "start": 731.22, "duration": 2.13}, {"text": "and for them to\nbehave this way--", "start": 733.35, "duration": 2.25}, {"text": "NPIs-- Negative Polarity Items.", "start": 735.6, "duration": 1.74}, {"text": "But there is another kind\nof language out there.", "start": 739.91, "duration": 3.31}, {"text": "Here's a Ukrainian sentence.", "start": 743.22, "duration": 3.5}, {"text": "In Ukrainian, if I ask\nyou, \"Who did you tell?\"", "start": 746.72, "duration": 3.33}, {"text": "A possible response\nis this word,", "start": 750.05, "duration": 1.753}, {"text": "which I won't try to\npronounce because I", "start": 751.803, "duration": 1.667}, {"text": "don't speak Ukrainian.", "start": 753.47, "duration": 1.32}, {"text": "We might as well\ntranslate it as \"nobody\"", "start": 754.79, "duration": 2.25}, {"text": "because it's a\npossible response that", "start": 757.04, "duration": 2.46}, {"text": "means \"I didn't tell anybody.\"", "start": 759.5, "duration": 3.968}, {"text": "Anybody want to pronounce\nthis word for us?", "start": 763.468, "duration": 1.792}, {"text": "Do you--", "start": 765.26, "duration": 0.39}, {"text": "AUDIENCE: [UKRAINIAN]", "start": 765.65, "duration": 0.78}, {"text": "NORVIN W. RICHARDS: [UKRAINIAN]?", "start": 766.43, "duration": 0.57}, {"text": "OK.", "start": 767.0, "duration": 0.24}, {"text": "Cool.", "start": 767.24, "duration": 0.5}, {"text": "But Ukrainian is\ndifferent from English", "start": 770.32, "duration": 2.13}, {"text": "in that the same\nword, [UKRAINIAN],,", "start": 772.45, "duration": 2.89}, {"text": "can combine with their negation.", "start": 775.34, "duration": 2.76}, {"text": "So it's not an NPI.", "start": 778.1, "duration": 3.36}, {"text": "It can combine with\ntheir negation.", "start": 781.46, "duration": 1.89}, {"text": "And the result is\na single negation.", "start": 783.35, "duration": 2.423}, {"text": "So if you want to say, \"I didn't\ntell anybody,\" in Ukrainian,", "start": 785.773, "duration": 2.542}, {"text": "you say [UKRAINIAN]---- that\nsame word that you would use", "start": 788.315, "duration": 2.625}, {"text": "to answer the question,\n\"Who did you tell?\"", "start": 790.94, "duration": 2.82}, {"text": "We could think of that\nword as meaning \"nobody.\"", "start": 793.76, "duration": 2.83}, {"text": "But if you want\nto say, \"I didn't", "start": 796.59, "duration": 2.67}, {"text": "tell anybody,\" in Ukrainian,\nyou use that word.", "start": 799.26, "duration": 1.98}, {"text": "And you also use\nthe word for \"not.\"", "start": 801.24, "duration": 2.34}, {"text": "So you say, literally,\n\"I didn't tell nobody.\"", "start": 803.58, "duration": 4.14}, {"text": "But they don't have--", "start": 807.72, "duration": 1.56}, {"text": "so the word-- that\ndoesn't mean--", "start": 809.28, "duration": 2.23}, {"text": "so that means \"I\ndidn't tell anybody.\"", "start": 811.51, "duration": 1.73}, {"text": "That's what that means.", "start": 813.24, "duration": 0.958}, {"text": "Ukrainian is not the\nonly language like this.", "start": 817.8, "duration": 3.75}, {"text": "Italian is like that.", "start": 821.55, "duration": 1.21}, {"text": "So in Italian, if I ask\nyou, \"What did you say see?\"", "start": 822.76, "duration": 2.9}, {"text": "you can say in\nItalian, \"niente.\"", "start": 825.66, "duration": 2.19}, {"text": "So we can translate\n\"niente\" as \"nothing.\"", "start": 827.85, "duration": 2.83}, {"text": "But if you want to say,\n\"I didn't see anything,\"", "start": 830.68, "duration": 2.0}, {"text": "in Italian, you say,\n\"Non ho visto niente,\"--", "start": 832.68, "duration": 2.37}, {"text": "literally, \"I have\nnot seen nothing.\"", "start": 835.05, "duration": 3.54}, {"text": "\"I have not seen 'niente.'\"\nSo this is a different system.", "start": 838.59, "duration": 4.99}, {"text": "In English, we have these--", "start": 843.58, "duration": 1.68}, {"text": "the language I'm speaking,\nin Greek as well--", "start": 845.26, "duration": 2.85}, {"text": "we have these expressions--\nthese negative polarity", "start": 848.11, "duration": 2.46}, {"text": "expressions-- which\naren't possible", "start": 850.57, "duration": 1.86}, {"text": "answers to positive questions\nlike, \"What did you see?\"", "start": 852.43, "duration": 3.065}, {"text": "If I ask you,\n\"What did you see,\"", "start": 855.495, "duration": 1.375}, {"text": "you cannot say \"anything.\"", "start": 856.87, "duration": 1.14}, {"text": "You have to say, \"nothing.\"", "start": 858.01, "duration": 1.59}, {"text": "If we use that as a test for\nwhether we're looking at an NPI", "start": 859.6, "duration": 3.39}, {"text": "or not-- as a test for figuring\nout whether we're looking", "start": 862.99, "duration": 2.49}, {"text": "at \"anything\" or\n\"nothing,\" then Ukrainian", "start": 865.48, "duration": 2.82}, {"text": "and Italian and\nmany other languages", "start": 868.3, "duration": 2.16}, {"text": "have a different system.", "start": 870.46, "duration": 1.05}, {"text": "One in which instead\nof having NPIs,", "start": 871.51, "duration": 2.73}, {"text": "you have these expressions\nwhich express negation", "start": 874.24, "duration": 2.77}, {"text": "all by themselves--", "start": 877.01, "duration": 1.1}, {"text": "[UKRAINIAN] and [ITALIAN],,\nwhich mean things like \"nobody\"", "start": 878.11, "duration": 2.73}, {"text": "or \"nothing\"-- that can be\nanswers to questions like,", "start": 880.84, "duration": 2.31}, {"text": "\"Who did you tell?\"\nor \"What did you see?\"", "start": 883.15, "duration": 2.34}, {"text": "But in question-- statements\nthat are longer than that--", "start": 885.49, "duration": 4.41}, {"text": "they don't have ellipses--", "start": 889.9, "duration": 1.95}, {"text": "if you want to say things\nlike \"I didn't see anything\"", "start": 891.85, "duration": 2.43}, {"text": "or \"I didn't tell anybody,\"\nyou use these same expressions.", "start": 894.28, "duration": 2.55}, {"text": "There isn't a specialized\nclass of NPIs,", "start": 896.83, "duration": 2.37}, {"text": "at least not for this\nkind of sentence.", "start": 899.2, "duration": 2.85}, {"text": "Is that clear?", "start": 902.05, "duration": 2.35}, {"text": "Does that make sense?", "start": 904.4, "duration": 2.38}, {"text": "The second kind of\nlanguage is sometimes", "start": 906.78, "duration": 1.79}, {"text": "called a negative\nconcord language.", "start": 908.57, "duration": 2.32}, {"text": "And let me give you some\nbackground for that.", "start": 910.89, "duration": 3.39}, {"text": "Concord is a phenomenon\nwhich I think we haven't", "start": 914.28, "duration": 2.01}, {"text": "talked about in this class.", "start": 916.29, "duration": 1.738}, {"text": "There are plenty of\nlanguages out there in which,", "start": 918.028, "duration": 2.042}, {"text": "when you have a noun phrase\nthat has multiple things in it--", "start": 920.07, "duration": 4.05}, {"text": "say it has-- there\nare adjectives", "start": 924.12, "duration": 1.74}, {"text": "or there are demonstratives.", "start": 925.86, "duration": 1.822}, {"text": "There will be morphology\non the noun of the kind", "start": 930.366, "duration": 3.804}, {"text": "that we have talked\nabout a little bit--", "start": 934.17, "duration": 1.92}, {"text": "morphology that indicates\nthings like, this is masculine,", "start": 936.09, "duration": 3.36}, {"text": "or this is feminine.", "start": 939.45, "duration": 1.21}, {"text": "It tells you what noun\nclass the noun is in.", "start": 940.66, "duration": 2.42}, {"text": "Or it'll tell you whether the\nnoun is singular or plural.", "start": 943.08, "duration": 3.24}, {"text": "Or sometimes there'll\nbe morphology", "start": 946.32, "duration": 1.5}, {"text": "telling you the\ncase of the noun,", "start": 947.82, "duration": 1.86}, {"text": "whether it's a subject or\nan object or something else.", "start": 949.68, "duration": 4.54}, {"text": "So Italian is a\nlanguage, for example,", "start": 954.22, "duration": 1.697}, {"text": "in which there's concord--", "start": 955.917, "duration": 1.083}, {"text": "the word for \"butterfly\"\nin Italian is \"farfalla.\"", "start": 957.0, "duration": 2.64}, {"text": "And the \"ah\" at the\nend marks the butterfly", "start": 959.64, "duration": 3.21}, {"text": "as being singular\nand also feminine.", "start": 962.85, "duration": 2.5}, {"text": "It's in the feminine noun class.", "start": 965.35, "duration": 1.85}, {"text": "It's of the feminine gender.", "start": 967.2, "duration": 2.163}, {"text": "And to say that it's of\nthe feminine gender is", "start": 969.363, "duration": 1.917}, {"text": "to say that if you want\nto modify this butterfly", "start": 971.28, "duration": 2.0}, {"text": "with adjectives--", "start": 973.28, "duration": 1.63}, {"text": "a beautiful butterfly\nis a \"farfalla bella\"", "start": 974.91, "duration": 2.7}, {"text": "So you use the feminine\nmarker on the adjective", "start": 977.61, "duration": 3.81}, {"text": "as well as on the noun.", "start": 981.42, "duration": 1.165}, {"text": "And if you want to say, \"this\nbeautiful butterfly,\" well,", "start": 982.585, "duration": 2.375}, {"text": "you use that \"ah\" again.", "start": 984.96, "duration": 1.292}, {"text": "So \"this beautiful butterfly\"--\nyou can see there are three", "start": 986.252, "duration": 2.458}, {"text": "\"ahs,\" all of them saying\nover and over again,", "start": 988.71, "duration": 2.76}, {"text": "this butterfly is\nfeminine and singular.", "start": 991.47, "duration": 3.0}, {"text": "You don't just realize that\nfact on the butterfly itself.", "start": 994.47, "duration": 2.58}, {"text": "You realize it all\nover the noun phrase.", "start": 997.05, "duration": 4.23}, {"text": "And if any of you have studied--", "start": 1001.28, "duration": 1.47}, {"text": "this is cross-linguistically\na very popular phenomenon.", "start": 1002.75, "duration": 3.45}, {"text": "It's all over the\nIndo-European languages.", "start": 1006.2, "duration": 2.058}, {"text": "English doesn't have\nit because we're", "start": 1008.258, "duration": 1.542}, {"text": "not big on morphology in\ngeneral but especially not", "start": 1009.8, "duration": 3.78}, {"text": "on our nouns.", "start": 1013.58, "duration": 0.555}, {"text": "But it's widespread.", "start": 1017.15, "duration": 1.48}, {"text": "If you study Italian, or\nSpanish, or French, or German,", "start": 1018.63, "duration": 3.14}, {"text": "you'll have to learn\nabout things like this.", "start": 1021.77, "duration": 3.36}, {"text": "And it's found outside\nIndo-European as well.", "start": 1025.13, "duration": 2.26}, {"text": "So there's a Lardil\nexample here--", "start": 1027.39, "duration": 1.67}, {"text": "[LARDIL], \"this big rock.\"", "start": 1029.06, "duration": 2.009}, {"text": "This is an accusative big rock.", "start": 1031.069, "duration": 1.351}, {"text": "It's the kind of phrase\nyou'd use to say,", "start": 1032.42, "duration": 2.1}, {"text": "\"I picked up this big rock.\"", "start": 1034.52, "duration": 2.49}, {"text": "It's an object.", "start": 1037.01, "duration": 0.9}, {"text": "You're going to mark the\nrock with accusative,", "start": 1037.91, "duration": 2.22}, {"text": "but also the word for \"this\"\nand the word for \"big.\"", "start": 1040.13, "duration": 2.61}, {"text": "So this is called concord.", "start": 1042.74, "duration": 2.55}, {"text": "And there's an Icelandic\nexample there which", "start": 1045.29, "duration": 1.95}, {"text": "I took from a paper--\n\"four little snails,\" which", "start": 1047.24, "duration": 2.55}, {"text": "are nominative.", "start": 1049.79, "duration": 1.44}, {"text": "\"Four\" and \"little\"\nand \"snails\" all", "start": 1051.23, "duration": 1.985}, {"text": "have suffixes on\nthem telling you", "start": 1053.215, "duration": 1.375}, {"text": "that the snails are nominative\nand masculine and plural.", "start": 1054.59, "duration": 4.17}, {"text": "So Italian has concord\nfor number and gender--", "start": 1058.76, "duration": 5.62}, {"text": "so feminine and singular.", "start": 1064.38, "duration": 1.79}, {"text": "Lardil has concord\njust for case.", "start": 1066.17, "duration": 2.28}, {"text": "Icelandic has concord\nfor all three--", "start": 1068.45, "duration": 2.88}, {"text": "case, number, and gender.", "start": 1071.33, "duration": 1.9}, {"text": "So concord-- it's a phenomenon.", "start": 1073.23, "duration": 2.507}, {"text": "It's a phenomenon with\nthe following shape--", "start": 1075.737, "duration": 1.833}, {"text": "sometimes a fact-- in\nthis case, say the fact", "start": 1077.57, "duration": 4.5}, {"text": "that a noun is feminine,\nor that it's singular,", "start": 1082.07, "duration": 2.7}, {"text": "or that its accusative is\nmarked not just on the noun", "start": 1084.77, "duration": 2.815}, {"text": "but on a bunch of\nthings near the noun,", "start": 1087.585, "duration": 1.625}, {"text": "and so the noun, but also\nadjectives and demonstratives", "start": 1089.21, "duration": 2.67}, {"text": "and other kinds of things.", "start": 1091.88, "duration": 1.47}, {"text": "It's called concord.", "start": 1093.35, "duration": 2.55}, {"text": "And to say that these languages\nare negative concord languages", "start": 1095.9, "duration": 3.6}, {"text": "is to say, yeah, in a\nlanguage like Italian,", "start": 1099.5, "duration": 3.147}, {"text": "if you want to say, \"I\ndidn't see anything,\"", "start": 1102.647, "duration": 1.833}, {"text": "you're going to mark negation\nnot just in what's called", "start": 1104.48, "duration": 3.24}, {"text": "sentential negation-- the\nItalian word for \"not\"", "start": 1107.72, "duration": 2.52}, {"text": "which is \"non\"--", "start": 1110.24, "duration": 1.44}, {"text": "yes, you'll use that word.", "start": 1111.68, "duration": 1.23}, {"text": "But you'll also mark\nit on the object.", "start": 1112.91, "duration": 2.32}, {"text": "So you will say, in effect,\n\"I not saw nothing.\"", "start": 1115.23, "duration": 5.0}, {"text": "That's how you do this\nin Italian, or Ukrainian,", "start": 1120.23, "duration": 2.28}, {"text": "or Russian, or a zillion\nother languages--", "start": 1122.51, "duration": 3.27}, {"text": "lots of languages that do this--\nnegative concord languages.", "start": 1125.78, "duration": 2.55}, {"text": "Now, we have talked\nabout English", "start": 1131.83, "duration": 3.6}, {"text": "as though English has\nnegative polarity items.", "start": 1135.43, "duration": 2.53}, {"text": "And that is true of the version\nof English that I am speaking.", "start": 1137.96, "duration": 4.02}, {"text": "But there are other\nversions of English", "start": 1141.98, "duration": 2.98}, {"text": "in which there is,\ninstead, negative concord.", "start": 1144.96, "duration": 3.66}, {"text": "So there are versions of\nEnglish in which the right way", "start": 1148.62, "duration": 2.67}, {"text": "to say, \"I didn't\nsee anything,\" is,", "start": 1151.29, "duration": 2.07}, {"text": "\"I didn't see nothing,\" in which\nthat's the way you say this.", "start": 1153.36, "duration": 5.58}, {"text": "Has anybody encountered\nthis version of English?", "start": 1158.94, "duration": 2.82}, {"text": "Did anybody grow up speaking\nthis version of English?", "start": 1161.76, "duration": 3.16}, {"text": "Yes?", "start": 1164.92, "duration": 0.5}, {"text": "Yeah?", "start": 1165.42, "duration": 0.42}, {"text": "Sort of.", "start": 1165.84, "duration": 0.54}, {"text": "So I grew up in Alabama.", "start": 1166.38, "duration": 1.14}, {"text": "I was surrounded by people who\nspoke this version of English.", "start": 1167.52, "duration": 4.11}, {"text": "I grew up in Alabama\nin a university town.", "start": 1171.63, "duration": 2.19}, {"text": "My parents are\nfrom further north,", "start": 1173.82, "duration": 1.59}, {"text": "so I have always had\nthe accent that I have.", "start": 1175.41, "duration": 3.25}, {"text": "It made-- it was the beginning\nof a long life of being", "start": 1178.66, "duration": 3.8}, {"text": "peculiar, surrounded by people\nwho talk differently than me.", "start": 1182.46, "duration": 5.55}, {"text": "And one of the\nthings that I did was", "start": 1188.01, "duration": 2.7}, {"text": "that I spoke negative polarity\nitem English, not negative", "start": 1190.71, "duration": 5.58}, {"text": "concord English.", "start": 1196.29, "duration": 2.19}, {"text": "But we were given tests\nwhen I was a kid--", "start": 1198.48, "duration": 3.03}, {"text": "I noticed recently my\nson, who's in fifth grade,", "start": 1201.51, "duration": 2.61}, {"text": "he's also given\ntests and homework", "start": 1204.12, "duration": 2.04}, {"text": "assignments in which he is asked\nto fix problems with sentences.", "start": 1206.16, "duration": 6.31}, {"text": "So sometimes the sentences--\nthe capitalization is wrong,", "start": 1212.47, "duration": 3.56}, {"text": "or there's a word that's\nmisspelled, or the punctuation", "start": 1216.03, "duration": 3.43}, {"text": "is wrong.", "start": 1219.46, "duration": 0.5}, {"text": "But sometimes the sentences\nhave negative concord in them.", "start": 1219.96, "duration": 2.7}, {"text": "And his job is to say, no,\nthat's not the right way", "start": 1222.66, "duration": 2.322}, {"text": "to speak English.", "start": 1224.982, "duration": 0.708}, {"text": "You should speak--\nyou should have NPIs.", "start": 1225.69, "duration": 2.4}, {"text": "You shouldn't have\nnegative concord.", "start": 1228.09, "duration": 2.16}, {"text": "I remember taking\ntests like that too.", "start": 1230.25, "duration": 2.16}, {"text": "Those of you who grew up\nin English-speaking places,", "start": 1232.41, "duration": 2.49}, {"text": "do you remember being\ngiven tests like this?", "start": 1234.9, "duration": 2.603}, {"text": "So these are tests\nin which people", "start": 1237.503, "duration": 1.417}, {"text": "are checking which dialect\nof English do you speak?", "start": 1238.92, "duration": 2.91}, {"text": "Are you from a checkers\nfamily or a chess family?", "start": 1241.83, "duration": 2.91}, {"text": "And if you're from\na checkers family,", "start": 1244.74, "duration": 2.16}, {"text": "these tests are easy for you.", "start": 1246.9, "duration": 1.71}, {"text": "Because, well, checkers\nis what you play at home.", "start": 1248.61, "duration": 2.38}, {"text": "Yeah, it's easy.", "start": 1250.99, "duration": 1.59}, {"text": "But if you're from\na chess family,", "start": 1252.58, "duration": 1.76}, {"text": "then you have to\nremember, oh, yeah,", "start": 1254.34, "duration": 1.5}, {"text": "I'm surrounded by\npeople who don't believe", "start": 1255.84, "duration": 1.75}, {"text": "in the existence of chess.", "start": 1257.59, "duration": 2.03}, {"text": "They only believe in checkers.", "start": 1259.62, "duration": 1.41}, {"text": "And so it's your job\nto try to pretend", "start": 1261.03, "duration": 3.42}, {"text": "to be a speaker of this\nother dialect of English.", "start": 1264.45, "duration": 2.25}, {"text": "To put it another way, if you're\ngrowing up in the States--", "start": 1266.7, "duration": 2.89}, {"text": "and I think this is not\njust true of the States.", "start": 1269.59, "duration": 2.0}, {"text": "This is pretty common\nin a lot of places.", "start": 1271.59, "duration": 2.43}, {"text": "There are a variety of ways to\nspeak the majority language.", "start": 1274.02, "duration": 2.82}, {"text": "And there's a certain set\nof them that are approved--", "start": 1276.84, "duration": 4.71}, {"text": "that schools approve of.", "start": 1281.55, "duration": 1.74}, {"text": "And there are\nothers that schools", "start": 1283.29, "duration": 2.37}, {"text": "feel it's their job to try\nto steer you away from,", "start": 1285.66, "duration": 2.46}, {"text": "even if it's, in fact,\nyour native language.", "start": 1288.12, "duration": 2.4}, {"text": "This is a tricky position\nfor schools to be in.", "start": 1290.52, "duration": 4.14}, {"text": "Does this ring true with\nyour experiences in school?", "start": 1294.66, "duration": 3.65}, {"text": "Do you remember doing this?", "start": 1298.31, "duration": 2.06}, {"text": "There's this weird disconnect\nbetween different kinds", "start": 1300.37, "duration": 3.06}, {"text": "of things that happen.", "start": 1303.43, "duration": 0.93}, {"text": "Negative concord is\nthe kind of thing", "start": 1304.36, "duration": 1.89}, {"text": "that I was explicitly\ntaught not to do.", "start": 1306.25, "duration": 3.52}, {"text": "And when I was\ngrowing up in Alabama,", "start": 1309.77, "duration": 1.73}, {"text": "I could see why they\nwere teaching us", "start": 1311.5, "duration": 1.71}, {"text": "not to do this because,\nwell, I was surrounded", "start": 1313.21, "duration": 3.63}, {"text": "by people who were doing it.", "start": 1316.84, "duration": 1.24}, {"text": "And so you could see why the\nteachers felt as though they", "start": 1318.08, "duration": 3.74}, {"text": "had to stamp it out.", "start": 1321.82, "duration": 1.14}, {"text": "Like I said, it wasn't my\ndialect of English, so it was--", "start": 1322.96, "duration": 3.0}, {"text": "these tests were easier for me.", "start": 1325.96, "duration": 2.58}, {"text": "There are other kinds\nof things that are not--", "start": 1328.54, "duration": 6.03}, {"text": "not been targeted by education.", "start": 1334.57, "duration": 3.66}, {"text": "And so they have a\ndifferent status.", "start": 1338.23, "duration": 2.4}, {"text": "This is another one.", "start": 1340.63, "duration": 1.507}, {"text": "The percentage sign at the\nbeginning of this sentence is", "start": 1342.137, "duration": 2.333}, {"text": "a mark linguists sometimes use\nto indicate that some speakers", "start": 1344.47, "duration": 3.33}, {"text": "accept this and others don't.", "start": 1347.8, "duration": 1.248}, {"text": "It's what the\npercentage sign is for.", "start": 1349.048, "duration": 1.542}, {"text": "So you guys have\nseen stars on things", "start": 1350.59, "duration": 1.65}, {"text": "that say they're ungrammatical--\nother kinds of marks--", "start": 1352.24, "duration": 2.678}, {"text": "percentage sign says a certain\npercentage of English speakers", "start": 1354.918, "duration": 2.542}, {"text": "can say this.", "start": 1357.46, "duration": 1.41}, {"text": "So I grew up with this.", "start": 1358.87, "duration": 1.29}, {"text": "It's called positive anymore.", "start": 1360.16, "duration": 2.118}, {"text": "This is a version\nof English in which", "start": 1362.278, "duration": 1.542}, {"text": "you can say things like\n\"I used to walk to work,", "start": 1363.82, "duration": 2.04}, {"text": "but anymore, I take the T.\"", "start": 1365.86, "duration": 3.68}, {"text": "Is there anybody\nhere who can do this?", "start": 1369.54, "duration": 3.1}, {"text": "Yes?", "start": 1372.64, "duration": 0.66}, {"text": "Cool.", "start": 1373.3, "duration": 0.915}, {"text": "AUDIENCE: My brother\ntalks like that a lot.", "start": 1374.215, "duration": 2.355}, {"text": "And I think it has\nto do with the fact", "start": 1376.57, "duration": 1.74}, {"text": "that in Spanish, the word\n\"ya,\" and \"yano,\" is \"anymore,\"", "start": 1378.31, "duration": 6.04}, {"text": "or \"already,\" or \"now.\"", "start": 1384.35, "duration": 1.922}, {"text": "And it can kind of\nmean \"anything.\"", "start": 1386.272, "duration": 1.458}, {"text": "NORVIN W. RICHARDS:\nOh, that's interesting.", "start": 1387.73, "duration": 0.75}, {"text": "AUDIENCE: Yeah.", "start": 1388.48, "duration": 0.75}, {"text": "NORVIN W. RICHARDS: OK.", "start": 1389.23, "duration": 0.958}, {"text": "Cool.", "start": 1390.188, "duration": 0.919}, {"text": "Is there anybody\nelse who can do this?", "start": 1391.107, "duration": 1.583}, {"text": "Is there anybody who\nis looking at this", "start": 1392.69, "duration": 1.2}, {"text": "and wondering if I suffered\nsome kind of injury on the way", "start": 1393.89, "duration": 2.7}, {"text": "to class today, and this\ncan't possibly-- yeah.", "start": 1396.59, "duration": 2.47}, {"text": "OK.", "start": 1399.06, "duration": 0.5}, {"text": "So I often-- when I get to\nthis slide in this lecture,", "start": 1399.56, "duration": 2.88}, {"text": "I get these kinds of looks.", "start": 1402.44, "duration": 1.17}, {"text": "They're like, what?", "start": 1403.61, "duration": 1.68}, {"text": "So I don't come from a\nSpanish-speaking background.", "start": 1405.29, "duration": 2.425}, {"text": "I come from a West\nVirginia background.", "start": 1407.715, "duration": 1.625}, {"text": "So my mother is\nfrom West Virginia.", "start": 1409.34, "duration": 1.74}, {"text": "And positive\nanymore is a feature", "start": 1411.08, "duration": 2.19}, {"text": "of the area around West\nVirginia and Pennsylvania.", "start": 1413.27, "duration": 2.61}, {"text": "There's this place\nwhere, if you go there,", "start": 1415.88, "duration": 2.68}, {"text": "you will hear people\nsaying things like this.", "start": 1418.56, "duration": 2.39}, {"text": "It means something\nlike, \"these days.\"", "start": 1420.95, "duration": 3.46}, {"text": "\"Anymore\"-- so \"Anymore I take\nthe T,\" means, \"as of now,", "start": 1424.41, "duration": 4.7}, {"text": "I take the T.\"", "start": 1429.11, "duration": 0.75}, {"text": "For me, at least--", "start": 1429.86, "duration": 1.41}, {"text": "I was doing some\ngoogling about it.", "start": 1431.27, "duration": 1.98}, {"text": "It's most common\nin places like this", "start": 1433.25, "duration": 2.22}, {"text": "where you're contrasting the\nmodern day with the past.", "start": 1435.47, "duration": 3.72}, {"text": "Yeah.", "start": 1439.19, "duration": 1.38}, {"text": "So here's another place\nwhere my English is odd.", "start": 1440.57, "duration": 3.84}, {"text": "And I'm very much\nin the minority.", "start": 1444.41, "duration": 1.6}, {"text": "So there's me, and there's Faith\nsort of, and Faith's brother.", "start": 1446.01, "duration": 3.42}, {"text": "Yeah.", "start": 1449.43, "duration": 0.5}, {"text": "And the rest of you\nhave me outvoted.", "start": 1449.93, "duration": 1.635}, {"text": "But this particular feature\nof a certain regional version", "start": 1454.07, "duration": 5.13}, {"text": "of English is somehow not on\nthe radar of the people who", "start": 1459.2, "duration": 3.93}, {"text": "write textbooks.", "start": 1463.13, "duration": 0.93}, {"text": "So I don't remember any teacher\never telling me not to do this.", "start": 1464.06, "duration": 3.09}, {"text": "I think people didn't notice\nthat I was doing this.", "start": 1467.15, "duration": 2.85}, {"text": "I got away with it.", "start": 1470.0, "duration": 1.05}, {"text": "But, yes, this is a feature\nof some versions of English.", "start": 1474.23, "duration": 3.6}, {"text": "Or, similarly, we've\ntalked about other things", "start": 1477.83, "duration": 3.65}, {"text": "in this class.", "start": 1481.48, "duration": 1.23}, {"text": "So people vary to the--", "start": 1482.71, "duration": 2.525}, {"text": "about the extent there are\nphonological differences", "start": 1485.235, "duration": 2.125}, {"text": "between different\nversions of English.", "start": 1487.36, "duration": 1.8}, {"text": "People vary with respect\nto whether the name \"Mary,\"", "start": 1489.16, "duration": 3.06}, {"text": "and the adjective \"merry,\"\nand the verb \"marry\"", "start": 1492.22, "duration": 3.06}, {"text": "sound the same.", "start": 1495.28, "duration": 0.96}, {"text": "To me, they do all\nsound the same.", "start": 1496.24, "duration": 2.01}, {"text": "But there are people for\nwhom the verb, in particular,", "start": 1498.25, "duration": 2.91}, {"text": "is \"maeh-ry\"--", "start": 1501.16, "duration": 0.96}, {"text": "a different vowel.", "start": 1502.12, "duration": 1.54}, {"text": "And I believe there are\neven people for whom all", "start": 1503.66, "duration": 2.0}, {"text": "three of them have\ndifferent pronunciations.", "start": 1505.66, "duration": 1.84}, {"text": "This is a feature of the area\naround New York and New Jersey,", "start": 1507.5, "duration": 4.31}, {"text": "whether you speak\nlike this or not.", "start": 1511.81, "duration": 1.77}, {"text": "I grew up in Alabama where \"pen\"\nand \"pin\" sound pretty similar.", "start": 1518.35, "duration": 4.69}, {"text": "They're both like \"pin.\"", "start": 1523.04, "duration": 3.17}, {"text": "I grew up in Alabama where the\ndefault word for a soft drink", "start": 1526.21, "duration": 4.44}, {"text": "is a Coke.", "start": 1530.65, "duration": 1.32}, {"text": "So a fizzy drink with\nlots of sugar in it--", "start": 1531.97, "duration": 2.67}, {"text": "I think-- now, let's see--", "start": 1534.64, "duration": 2.16}, {"text": "I live in a soda\nplace now, right?", "start": 1536.8, "duration": 2.25}, {"text": "Don't-- aren't we-- this is\nthe soda part of the world?", "start": 1539.05, "duration": 3.15}, {"text": "And there's a pop\npart of the world.", "start": 1542.2, "duration": 3.6}, {"text": "Who here grew up saying soda\nfor those kinds of drinks?", "start": 1545.8, "duration": 2.91}, {"text": "Did anybody grow up saying pop?", "start": 1548.71, "duration": 2.576}, {"text": "AUDIENCE: My mom did--", "start": 1551.286, "duration": 1.054}, {"text": "NORVIN W. RICHARDS:\nYour mom did.", "start": 1552.34, "duration": 1.02}, {"text": "AUDIENCE: --when she was a girl.", "start": 1553.36, "duration": 0.45}, {"text": "NORVIN W. RICHARDS:\nAnd did she--", "start": 1553.81, "duration": 0.735}, {"text": "she survived to\nadulthood, didn't she?", "start": 1554.545, "duration": 1.305}, {"text": "She's OK.", "start": 1555.85, "duration": 0.63}, {"text": "AUDIENCE: Yeah.", "start": 1556.48, "duration": 0.165}, {"text": "NORVIN W. RICHARDS: Yes.", "start": 1556.645, "duration": 0.165}, {"text": "OK.", "start": 1556.81, "duration": 0.27}, {"text": "Cool.", "start": 1557.08, "duration": 0.36}, {"text": "AUDIENCE: [LAUGHTER]", "start": 1557.44, "duration": 0.93}, {"text": "NORVIN W. RICHARDS: And did\nanybody grow up saying Coke", "start": 1558.37, "duration": 2.667}, {"text": "for these kinds of things?", "start": 1561.037, "duration": 1.083}, {"text": "AUDIENCE: Yeah.", "start": 1562.12, "duration": 0.21}, {"text": "NORVIN W. RICHARDS:\nOh, well, yeah, Peter", "start": 1562.33, "duration": 1.56}, {"text": "did because Peter is like me.", "start": 1563.89, "duration": 1.17}, {"text": "He's from the South.", "start": 1565.06, "duration": 0.54}, {"text": "Where are you from?", "start": 1565.6, "duration": 0.69}, {"text": "AUDIENCE: Mississippi.", "start": 1566.29, "duration": 0.93}, {"text": "NORVIN W. RICHARDS: Yeah.", "start": 1567.22, "duration": 0.34}, {"text": "OK.", "start": 1567.56, "duration": 0.59}, {"text": "So Southerners-- represent.", "start": 1568.15, "duration": 3.66}, {"text": "So in my version of English--\nthe version of English", "start": 1571.81, "duration": 2.34}, {"text": "I grew up with, \"Coke\"\nwas the default name", "start": 1574.15, "duration": 2.82}, {"text": "for all of these things.", "start": 1576.97, "duration": 1.0}, {"text": "It's kind of like \"Xerox\" for\na copying machine or whatever.", "start": 1577.97, "duration": 2.73}, {"text": "So people would ask questions\nlike, \"Would you like a Coke?\"", "start": 1580.7, "duration": 2.865}, {"text": "And if the answer was, \"yes,\"\nthe next question was, \"OK.", "start": 1583.565, "duration": 2.375}, {"text": "So would you like\nSprite or Mountain Dew?", "start": 1585.94, "duration": 2.34}, {"text": "Because that's what we've got.\"", "start": 1588.28, "duration": 2.64}, {"text": "So \"Coke\" is just\nthe default word", "start": 1590.92, "duration": 2.4}, {"text": "for these kinds of beverages.", "start": 1593.32, "duration": 1.44}, {"text": "Or-- and this is a place--\nanother place where languages", "start": 1597.7, "duration": 4.47}, {"text": "or dialects of English vary\na lot with each other--", "start": 1602.17, "duration": 2.79}, {"text": "English used to have a\ndistinction between singular", "start": 1604.96, "duration": 3.87}, {"text": "\"you,\" which was\npronounced \"thou,\"", "start": 1608.83, "duration": 2.88}, {"text": "and plural \"you,\" which\nwas pronounced \"you.\"", "start": 1611.71, "duration": 3.3}, {"text": "And the plural \"you\" was\nalso used for formal.", "start": 1615.01, "duration": 3.51}, {"text": "And then it kind of took over.", "start": 1618.52, "duration": 1.69}, {"text": "So it got used both for\nsingular and plural.", "start": 1620.21, "duration": 2.57}, {"text": "And modern standard English--\nthe version of English that", "start": 1622.78, "duration": 2.82}, {"text": "I'm currently speaking--", "start": 1625.6, "duration": 1.41}, {"text": "doesn't distinguish \"you\"\nsingular and \"you\" plural.", "start": 1627.01, "duration": 3.15}, {"text": "But it's handy being\nable to distinguish \"you\"", "start": 1630.16, "duration": 2.01}, {"text": "singular and \"you\" plural.", "start": 1632.17, "duration": 1.74}, {"text": "And so various\ndialects of English", "start": 1633.91, "duration": 1.59}, {"text": "have come up with\nsolutions for this.", "start": 1635.5, "duration": 1.542}, {"text": "I come from the \"y'all\"\npart of the country.", "start": 1637.042, "duration": 3.318}, {"text": "I used \"y'all\" until\nI came up here,", "start": 1640.36, "duration": 3.24}, {"text": "and then I was mocked\ninto coming up with other", "start": 1643.6, "duration": 2.43}, {"text": "expressions.", "start": 1646.03, "duration": 0.78}, {"text": "I seem to have fallen\ninto \"you guys\"", "start": 1646.81, "duration": 2.28}, {"text": "as the plural of\nyou, which I wish", "start": 1649.09, "duration": 2.52}, {"text": "I didn't have because\n\"you guys\" I think", "start": 1651.61, "duration": 2.07}, {"text": "of as being markedly masculine.", "start": 1653.68, "duration": 2.77}, {"text": "So I need to--", "start": 1656.45, "duration": 1.61}, {"text": "I don't know-- embark on\na series of self-hypnosis", "start": 1658.06, "duration": 2.94}, {"text": "sessions or something like that\nand get myself back to using", "start": 1661.0, "duration": 2.67}, {"text": "\"y'all.\"", "start": 1663.67, "duration": 1.47}, {"text": "And then, there is,\nagain, an area--", "start": 1665.14, "duration": 2.667}, {"text": "I think around Pittsburgh--\nwhere people say", "start": 1667.807, "duration": 1.833}, {"text": "\"y'unz\" as the-- or \"you'ns\"\nas the plural of you.", "start": 1669.64, "duration": 2.33}, {"text": "Did anybody here grow up with\nan interesting plural for you?", "start": 1671.97, "duration": 2.5}, {"text": "Yeah?", "start": 1674.47, "duration": 0.36}, {"text": "AUDIENCE: Yeah.", "start": 1674.83, "duration": 0.6}, {"text": "So, basically, when\nI lived in Minnesota,", "start": 1675.43, "duration": 1.708}, {"text": "I grew up in a very small\ntown with a very, very", "start": 1677.138, "duration": 2.192}, {"text": "high Dutch population where\na lot of people said \"yous\".", "start": 1679.33, "duration": 2.853}, {"text": "NORVIN W. RICHARDS: \"Yous\"--", "start": 1682.183, "duration": 1.167}, {"text": "oh, yeah.", "start": 1683.35, "duration": 0.42}, {"text": "I left \"yous\" out of here.", "start": 1683.77, "duration": 1.05}, {"text": "Yeah, you're absolutely right.", "start": 1684.82, "duration": 1.25}, {"text": "So \"yous\" is absolutely\nanother option.", "start": 1686.07, "duration": 2.35}, {"text": "Anybody else have\nanother option?", "start": 1688.42, "duration": 2.96}, {"text": "\"Y'all\"-- I think \"y'all\" is\nstill markedly Southern, right?", "start": 1691.38, "duration": 2.5}, {"text": "If I were to say, \"y'all,\"\npeople would think of me", "start": 1693.88, "duration": 2.46}, {"text": "as being from\nAlabama, which I am.", "start": 1696.34, "duration": 3.04}, {"text": "Raquel?", "start": 1699.38, "duration": 0.825}, {"text": "AUDIENCE: I've heard\nmy mom and my uncle,", "start": 1700.205, "duration": 3.135}, {"text": "who are both from\nPittsburgh, saying \"yenses\"", "start": 1703.34, "duration": 3.45}, {"text": "but like as a joke.", "start": 1706.79, "duration": 1.06}, {"text": "NORVIN W. RICHARDS: \"Yenses?\"", "start": 1707.85, "duration": 0.74}, {"text": "AUDIENCE: I don't know\nif it's because they", "start": 1708.59, "duration": 1.792}, {"text": "have heard people say \"yenses.\"", "start": 1710.382, "duration": 1.718}, {"text": "NORVIN W. RICHARDS: Wow.", "start": 1712.1, "duration": 0.42}, {"text": "AUDIENCE: It might have just\nbeen like a possessive thing,", "start": 1712.52, "duration": 1.5}, {"text": "like \"Yenses family\nis here\" or something.", "start": 1714.02, "duration": 1.65}, {"text": "NORVIN W. RICHARDS: Oh, oh, OK.", "start": 1715.67, "duration": 0.78}, {"text": "Yes.", "start": 1716.45, "duration": 0.32}, {"text": "That I could kind\nof get a handle on.", "start": 1716.77, "duration": 1.33}, {"text": "I thought of the\nplural as being \"yens,\"", "start": 1718.1, "duration": 1.667}, {"text": "but maybe there's also \"yenses.\"", "start": 1719.767, "duration": 1.658}, {"text": "This is a thing that\nhappens, actually,", "start": 1721.425, "duration": 1.625}, {"text": "that something that\nwas already plural", "start": 1723.05, "duration": 1.62}, {"text": "gets marked plural again.", "start": 1724.67, "duration": 2.31}, {"text": "This is the story of \"children,\"\nwhich plural of \"child\"", "start": 1726.98, "duration": 5.28}, {"text": "used to be \"childer.\"", "start": 1732.26, "duration": 2.34}, {"text": "And then \"-er\" became a very\nuncommon-- in fact, \"childer\"", "start": 1734.6, "duration": 3.48}, {"text": "was the only noun that\nhad \"-er\" for it's plural.", "start": 1738.08, "duration": 2.28}, {"text": "And so people just added\nanother plural at the end", "start": 1740.36, "duration": 3.14}, {"text": "that you get in \"oxen.\"", "start": 1743.5, "duration": 2.32}, {"text": "And so now it's like \"childses.\"", "start": 1745.82, "duration": 3.105}, {"text": "That's children.", "start": 1748.925, "duration": 0.945}, {"text": "That's our modern\nword for \"child.\"", "start": 1749.87, "duration": 1.5}, {"text": "So the German plural\nfor child, \"Kinder,\"", "start": 1751.37, "duration": 2.14}, {"text": "still has that \"-er\"-- that\n\"er\" suffix, [? single. ?]", "start": 1753.51, "duration": 5.15}, {"text": "So big surprise-- there are\ndifferent dialects of English.", "start": 1758.66, "duration": 3.87}, {"text": "There are different dialects\nof lots of different languages.", "start": 1762.53, "duration": 2.535}, {"text": "I'm bringing this up for\na variety of reasons.", "start": 1765.065, "duration": 3.985}, {"text": "One is that there's a model that\nyou get exposed to-- at least", "start": 1769.05, "duration": 2.99}, {"text": "in school, at least I was; let's\nsee whether all of you were--", "start": 1772.04, "duration": 5.88}, {"text": "in which, well, there are\ndifferent dialects of English,", "start": 1777.92, "duration": 3.69}, {"text": "but there's a correct\nversion of English.", "start": 1781.61, "duration": 2.13}, {"text": "And then there are\nfailures to speak", "start": 1783.74, "duration": 1.89}, {"text": "the correct version of English.", "start": 1785.63, "duration": 1.38}, {"text": "Like, that's the picture you're\ngiven in English classes.", "start": 1787.01, "duration": 3.85}, {"text": "So you're given assignments\nlike the one I was just", "start": 1790.86, "duration": 2.33}, {"text": "talking about for\nmy son, where it's", "start": 1793.19, "duration": 1.5}, {"text": "like, fix the problems\nin these sentences.", "start": 1794.69, "duration": 2.592}, {"text": "And some of the\nproblems are things", "start": 1797.282, "duration": 1.458}, {"text": "like, oh, this person\napparently speaks", "start": 1798.74, "duration": 1.47}, {"text": "a different dialect of English.", "start": 1800.21, "duration": 1.292}, {"text": "We can't have that.", "start": 1801.502, "duration": 1.016}, {"text": "That's wrong.", "start": 1802.518, "duration": 0.542}, {"text": "We've got to fix that.", "start": 1803.06, "duration": 2.01}, {"text": "Is that the picture of\nEnglish that you guys grew up", "start": 1805.07, "duration": 3.57}, {"text": "with as well?", "start": 1808.64, "duration": 2.38}, {"text": "And so just to be clear, I mean,\nif we were going to figure out", "start": 1811.02, "duration": 3.95}, {"text": "what counts as English,\nthese descriptions", "start": 1814.97, "duration": 8.34}, {"text": "are things that\npeople talk about.", "start": 1823.31, "duration": 1.95}, {"text": "Maybe-- and so from\nyour reactions,", "start": 1825.26, "duration": 2.85}, {"text": "I think maybe nobody\nhad exposed most of you", "start": 1828.11, "duration": 2.07}, {"text": "to positive \"anymore.\"", "start": 1830.18, "duration": 1.17}, {"text": "So don't say you didn't\nlearn anything in this class.", "start": 1831.35, "duration": 2.758}, {"text": "Positive \"anymore\"-- it exists.", "start": 1834.108, "duration": 1.292}, {"text": "It's a thing.", "start": 1835.4, "duration": 2.64}, {"text": "But these kinds of\nthings are things", "start": 1838.04, "duration": 1.5}, {"text": "that people talk\nabout-- about there", "start": 1839.54, "duration": 1.5}, {"text": "being variations in English.", "start": 1841.04, "duration": 1.74}, {"text": "And people's reactions\nto these variations vary.", "start": 1842.78, "duration": 2.92}, {"text": "So I think, probably, I\nnever got an assignment", "start": 1845.7, "duration": 4.49}, {"text": "in English class growing up in\nAlabama in which somebody said,", "start": 1850.19, "duration": 4.86}, {"text": "fix the problem with this\nsentence, and the problem was,", "start": 1855.05, "duration": 3.06}, {"text": "\"Would you like a Coke?\"", "start": 1858.11, "duration": 1.14}, {"text": "\"Yes, I'd like a Sprite.\"", "start": 1859.25, "duration": 3.45}, {"text": "Nobody said, oh, this is wrong.", "start": 1862.7, "duration": 1.72}, {"text": "You should change 'Coke'\nto 'soda' or 'pop.'\"", "start": 1864.42, "duration": 3.35}, {"text": "When I was growing\nup in Alabama,", "start": 1867.77, "duration": 2.13}, {"text": "when we wanted to mock\npeople from the North--", "start": 1869.9, "duration": 2.28}, {"text": "and it was a thing\nwe did sometimes--", "start": 1872.18, "duration": 2.4}, {"text": "we would use words\nlike \"pop\" and \"soda.\"", "start": 1874.58, "duration": 2.58}, {"text": "We thought that was funny\nthat y'all talked this way.", "start": 1877.16, "duration": 4.218}, {"text": "[COUGH] Excuse me.", "start": 1881.378, "duration": 1.17}, {"text": "So there are some of these\nkinds of things that are not", "start": 1882.548, "duration": 2.292}, {"text": "the subject of\ndeliberate repression", "start": 1884.84, "duration": 3.96}, {"text": "by the educational system.", "start": 1888.8, "duration": 1.81}, {"text": "But there are others that\nare, like negative concord.", "start": 1890.61, "duration": 2.39}, {"text": "So there are dialects of\nEnglish that have negative", "start": 1893.0, "duration": 2.125}, {"text": "concord-- a dialect of\nEnglish in which you say,", "start": 1895.125, "duration": 2.735}, {"text": "\"I didn't see nothing.\"", "start": 1897.86, "duration": 1.98}, {"text": "\"I haven't done nothing.\"", "start": 1899.84, "duration": 1.65}, {"text": "And those dialects are\nthe subject of deliberate", "start": 1901.49, "duration": 6.03}, {"text": "repression by teachers.", "start": 1907.52, "duration": 1.29}, {"text": "So teachers attempt to\nstop you from doing that.", "start": 1908.81, "duration": 4.06}, {"text": "And if you've ever\nheard speakers of--", "start": 1912.87, "duration": 4.4}, {"text": "I have some websites coming\nup on the next slide.", "start": 1917.27, "duration": 2.97}, {"text": "I'll put these links\nup on the website.", "start": 1920.24, "duration": 4.32}, {"text": "There are people\nwho self-describe", "start": 1924.56, "duration": 3.12}, {"text": "as speakers of English who\nI, at least, have a very", "start": 1927.68, "duration": 3.06}, {"text": "difficult time understanding.", "start": 1930.74, "duration": 1.29}, {"text": "So one of the\nwebsites I'll show you", "start": 1932.03, "duration": 1.62}, {"text": "is to the Scots Dialect Atlas.", "start": 1933.65, "duration": 2.97}, {"text": "There's this wonderful\ngroup of linguists", "start": 1936.62, "duration": 2.7}, {"text": "who are going around\nvarious parts of Scotland", "start": 1939.32, "duration": 2.85}, {"text": "chronicling different\naspects of regional speech", "start": 1942.17, "duration": 3.12}, {"text": "in various places.", "start": 1945.29, "duration": 1.26}, {"text": "And these people are not\nspeaking a Celtic language.", "start": 1946.55, "duration": 3.42}, {"text": "They're not speaking Gaelic.", "start": 1949.97, "duration": 1.62}, {"text": "They would describe themselves\nas speaking English.", "start": 1951.59, "duration": 2.4}, {"text": "But, boy, you can't\ntell [LAUGHS] listening", "start": 1953.99, "duration": 3.09}, {"text": "to some of these recordings.", "start": 1957.08, "duration": 3.15}, {"text": "It's very opaque.", "start": 1960.23, "duration": 1.02}, {"text": "When we-- I had a--", "start": 1961.25, "duration": 3.75}, {"text": "when I was in grad\nschool, there was", "start": 1965.0, "duration": 1.68}, {"text": "a guy in the class above my--", "start": 1966.68, "duration": 3.06}, {"text": "a really excellent linguist\nnamed Andrew Carnie,", "start": 1969.74, "duration": 2.5}, {"text": "who's now teaching at\nUniversity of Arizona.", "start": 1972.24, "duration": 2.87}, {"text": "And he grew up in Canada, but\nhis parents were Scottish.", "start": 1975.11, "duration": 2.91}, {"text": "And they came down\nwhen he graduated.", "start": 1978.02, "duration": 2.19}, {"text": "And I was sitting\naround with them", "start": 1980.21, "duration": 1.92}, {"text": "attempting to make small talk.", "start": 1982.13, "duration": 1.32}, {"text": "And I could just barely\nunderstand his mother.", "start": 1983.45, "duration": 2.85}, {"text": "But his father could have\nbeen speaking Hebrew.", "start": 1986.3, "duration": 2.033}, {"text": "I mean, I just--", "start": 1988.333, "duration": 0.667}, {"text": "I had no idea.", "start": 1989.0, "duration": 1.08}, {"text": "And I can remember doing a\nlot of nodding and smiling.", "start": 1990.08, "duration": 3.31}, {"text": "It was just opaque.", "start": 1993.39, "duration": 1.43}, {"text": "I couldn't understand\nthis at all.", "start": 1994.82, "duration": 1.53}, {"text": "But this is a guy\nwho would have said", "start": 1996.35, "duration": 1.542}, {"text": "that he was speaking English.", "start": 1997.892, "duration": 1.668}, {"text": "So-- yeah, and so here\nare some websites--", "start": 1999.56, "duration": 4.53}, {"text": "one to a group at Yale that's\ndoing a study of dialect", "start": 2004.09, "duration": 6.48}, {"text": "variation within English.", "start": 2010.57, "duration": 1.11}, {"text": "And this other is the\nScots Syntax Atlas.", "start": 2011.68, "duration": 3.03}, {"text": "I'll put links to both\nof these up in the chat.", "start": 2014.71, "duration": 3.64}, {"text": "So, I've been\ntalking about English", "start": 2018.35, "duration": 2.51}, {"text": "because here we are in America.", "start": 2020.86, "duration": 1.59}, {"text": "And I had this metaphor\nand everything.", "start": 2022.45, "duration": 3.15}, {"text": "But this is a pretty\ncommon phenomenon.", "start": 2025.6, "duration": 2.405}, {"text": "There are lots of\nlanguages where", "start": 2028.005, "duration": 1.375}, {"text": "there is regional variation\nin the way that language is", "start": 2029.38, "duration": 2.31}, {"text": "spoken.", "start": 2031.69, "duration": 1.14}, {"text": "And what we do in\nAmerica about this--", "start": 2032.83, "duration": 3.96}, {"text": "where you fixate on\nparticular properties", "start": 2036.79, "duration": 3.3}, {"text": "of particular dialects and\nattempt to wipe them out,", "start": 2040.09, "duration": 2.92}, {"text": "things like negative concord--", "start": 2043.01, "duration": 2.27}, {"text": "attempt, I should say,\ncompletely unsuccessfully.", "start": 2045.28, "duration": 2.64}, {"text": "So negative concord\nhas been around", "start": 2047.92, "duration": 1.77}, {"text": "in English for centuries.", "start": 2049.69, "duration": 1.59}, {"text": "It's still around.", "start": 2051.28, "duration": 1.12}, {"text": "It's not clear that\nEnglish teachers have ever", "start": 2052.4, "duration": 2.39}, {"text": "had any effect on it.", "start": 2054.79, "duration": 1.29}, {"text": "But they have succeeded in--", "start": 2056.08, "duration": 2.01}, {"text": "probably not just them, and\nsociety kind of generally", "start": 2058.09, "duration": 2.22}, {"text": "have succeeded in making\nnegative concord stigmatized.", "start": 2060.31, "duration": 2.25}, {"text": "So we're all taught that\nnegative concord is illogical.", "start": 2062.56, "duration": 3.599}, {"text": "Two negations make a positive.", "start": 2066.159, "duration": 1.951}, {"text": "Is that something you were\nall taught at some point?", "start": 2068.11, "duration": 3.4}, {"text": "So the next time someone\ntells you that negative--", "start": 2071.51, "duration": 3.74}, {"text": "if you ever In casual\nconversation have somebody tell", "start": 2075.25, "duration": 2.37}, {"text": "you that negative concord is\nillogical and that people who", "start": 2077.62, "duration": 2.417}, {"text": "say, \"I didn't see nothing,\"\nthey just can't think", "start": 2080.037, "duration": 2.682}, {"text": "straight-- they're not logical--", "start": 2082.719, "duration": 1.651}, {"text": "you should point them to\nUkrainian and Italian.", "start": 2084.37, "duration": 2.22}, {"text": "There are plenty of\nlanguages out there", "start": 2086.59, "duration": 1.73}, {"text": "where this is what you do.", "start": 2088.32, "duration": 2.02}, {"text": "It's just that there's a dialect\nof English that's like them.", "start": 2090.34, "duration": 4.64}, {"text": "So-- but this is a\nquestion that comes up", "start": 2094.98, "duration": 2.94}, {"text": "when people are doing things\nlike trying to count languages,", "start": 2097.92, "duration": 4.11}, {"text": "for example.", "start": 2102.03, "duration": 0.76}, {"text": "so if you're trying\nto figure out", "start": 2102.79, "duration": 1.375}, {"text": "how many languages are\nspoken in the world,", "start": 2104.165, "duration": 2.365}, {"text": "or if you're trying to make\npolicy decisions about how", "start": 2106.53, "duration": 2.61}, {"text": "many languages are\nspoken in the country,", "start": 2109.14, "duration": 1.98}, {"text": "or how many languages a\ngovernment document ought", "start": 2111.12, "duration": 3.45}, {"text": "to be translated\ninto, for example,", "start": 2114.57, "duration": 1.92}, {"text": "you have to make decisions about\nhow many languages there are--", "start": 2116.49, "duration": 4.11}, {"text": "where to draw lines.", "start": 2120.6, "duration": 2.28}, {"text": "What counts as English?", "start": 2122.88, "duration": 1.47}, {"text": "What counts as\nJapanese or German?", "start": 2124.35, "duration": 1.56}, {"text": "How do you know if two people\nspeak the same language?", "start": 2125.91, "duration": 2.25}, {"text": "What do you think?", "start": 2130.35, "duration": 0.75}, {"text": "What's the answer\nto that question?", "start": 2131.1, "duration": 1.77}, {"text": "What should we do?", "start": 2132.87, "duration": 0.93}, {"text": "Are people clear on\nwhat the question is?", "start": 2137.83, "duration": 1.777}, {"text": "So what's-- how do you decide\nif two people are speaking", "start": 2139.607, "duration": 2.333}, {"text": "the same language or not?", "start": 2141.94, "duration": 1.73}, {"text": "Yeah?", "start": 2143.67, "duration": 0.94}, {"text": "AUDIENCE: My first guess\nis if two speakers--", "start": 2144.61, "duration": 3.67}, {"text": "if it's mutually intelligible,\nif one can understand", "start": 2148.28, "duration": 2.73}, {"text": "the other when they\ntalk and vice versa,", "start": 2151.01, "duration": 3.023}, {"text": "then they speak\nthe same language.", "start": 2154.033, "duration": 1.417}, {"text": "NORVIN W. RICHARDS:\nThat's a popular answer.", "start": 2155.45, "duration": 1.833}, {"text": "Are there-- yeah?", "start": 2157.283, "duration": 1.287}, {"text": "AUDIENCE: As a counter argument,\nI had a friend in middle school", "start": 2158.57, "duration": 3.93}, {"text": "who I spoke German too, and\nhe spoke Italian back to me.", "start": 2162.5, "duration": 3.18}, {"text": "And I knew a little\nbit of Spanish,", "start": 2165.68, "duration": 1.5}, {"text": "and he knew a little bit\nof Polish or something,", "start": 2167.18, "duration": 3.11}, {"text": "so we could kind of\nunderstand each other.", "start": 2170.29, "duration": 1.75}, {"text": "NORVIN W. RICHARDS: Mm-hmm.", "start": 2172.04, "duration": 0.455}, {"text": "AUDIENCE: [? Even ?]\n[? though ?] [? it ?]", "start": 2172.495, "duration": 0.794}, {"text": "[? wasn't ?] in\nthe same language.", "start": 2173.289, "duration": 0.571}, {"text": "NORVIN W. RICHARDS: Yes.", "start": 2173.86, "duration": 1.0}, {"text": "[LAUGHTER]", "start": 2174.86, "duration": 0.62}, {"text": "That is an awesome story.", "start": 2175.48, "duration": 1.545}, {"text": "[LAUGHS] Yes?", "start": 2177.025, "duration": 1.005}, {"text": "AUDIENCE: Yeah.", "start": 2178.03, "duration": 0.81}, {"text": "If I run into someone\nwho speaks Portuguese,", "start": 2178.84, "duration": 2.1}, {"text": "I can get a sense of\nwhat they're saying.", "start": 2180.94, "duration": 2.2}, {"text": "I don't speak Portuguese,\nbut I do speak Spanish.", "start": 2183.14, "duration": 2.4}, {"text": "NORVIN W. RICHARDS: Mm-hmm.", "start": 2185.54, "duration": 0.5}, {"text": "Yeah.", "start": 2186.04, "duration": 0.76}, {"text": "So this is-- I was going to use\nSpanish and Portuguese in just", "start": 2186.8, "duration": 2.79}, {"text": "a second.", "start": 2189.59, "duration": 0.55}, {"text": "What I had heard about\nSpanish and Portuguese was--", "start": 2190.14, "duration": 3.14}, {"text": "and I heard this from\nPortuguese speakers,", "start": 2193.28, "duration": 1.83}, {"text": "so I don't know\nwhether it's true.", "start": 2195.11, "duration": 1.59}, {"text": "Portuguese speakers believe\nthat Portuguese speakers", "start": 2196.7, "duration": 2.46}, {"text": "are better at\nunderstanding Spanish", "start": 2199.16, "duration": 1.92}, {"text": "than Spanish speakers are\nat understanding Portuguese.", "start": 2201.08, "duration": 2.85}, {"text": "I don't know if\nthis is true or not.", "start": 2203.93, "duration": 1.62}, {"text": "Raquel?", "start": 2205.55, "duration": 0.5}, {"text": "AUDIENCE: My native speaker\nis a speaker of Portuguese.", "start": 2206.05, "duration": 3.79}, {"text": "And she said that,\nlike, exactly.", "start": 2209.84, "duration": 1.408}, {"text": "NORVIN W. RICHARDS: Yeah, yeah.", "start": 2211.248, "duration": 1.292}, {"text": "That's the kind of thing\nPortuguese speakers say.", "start": 2212.54, "duration": 2.042}, {"text": "There are all kinds of\nreasons that it could be true.", "start": 2214.582, "duration": 2.728}, {"text": "Portuguese has undergone\nvarious sound changes", "start": 2217.31, "duration": 2.79}, {"text": "that have eliminated sounds\nthat are present in Spanish.", "start": 2220.1, "duration": 5.61}, {"text": "So I can-- I don't\nknow very much", "start": 2225.71, "duration": 1.787}, {"text": "about either of these languages.", "start": 2227.497, "duration": 1.333}, {"text": "But for example, the Spanish\nword for \"hot\" is \"caliente.\"", "start": 2228.83, "duration": 6.33}, {"text": "And the Portuguese\nword for that--", "start": 2235.16, "duration": 1.98}, {"text": "I'll spell it in IPA.", "start": 2237.14, "duration": 1.47}, {"text": "It's something\nlike [PORTUGUESE]..", "start": 2238.61, "duration": 3.64}, {"text": "So that's Brazilian\nPortuguese for \"hot.\"", "start": 2242.25, "duration": 4.19}, {"text": "And what's happened\nis, first of all,", "start": 2246.44, "duration": 2.04}, {"text": "the A has palatalized the\nT, so it's become a \"chuh,\"", "start": 2248.48, "duration": 3.57}, {"text": "and you've also lost the final\nE. So T has become \"chuh.\"", "start": 2252.05, "duration": 4.59}, {"text": "And the final E is gone.", "start": 2256.64, "duration": 2.76}, {"text": "And the intervocalic L is gone.", "start": 2259.4, "duration": 1.853}, {"text": "That's another\nthing that happened", "start": 2261.253, "duration": 1.417}, {"text": "in the course of the\nevolution of Portuguese.", "start": 2262.67, "duration": 2.73}, {"text": "So-- and then some other fancy\nthings happened to the vowels.", "start": 2265.4, "duration": 3.4}, {"text": "So we ended up from\n\"caliente\" to [PORTUGUESE]..", "start": 2268.8, "duration": 2.42}, {"text": "Actually, Portuguese isn't\ndescended from Spanish.", "start": 2271.22, "duration": 2.4}, {"text": "These are both from Latin--", "start": 2273.62, "duration": 1.75}, {"text": "\"calentem.\"", "start": 2275.37, "duration": 0.5}, {"text": "And then like that, it\nbecame both of these forms.", "start": 2278.947, "duration": 2.083}, {"text": "Spanish was much\nmore conservative.", "start": 2281.03, "duration": 1.65}, {"text": "And Portuguese has\ndone a lot of things", "start": 2282.68, "duration": 1.78}, {"text": "including getting\nrid of sounds that", "start": 2284.46, "duration": 1.73}, {"text": "are still present in Spanish.", "start": 2286.19, "duration": 2.67}, {"text": "And it's probably easier to\nignore sounds that are there--", "start": 2288.86, "duration": 5.945}, {"text": "which is what\nPortuguese speakers", "start": 2294.805, "duration": 1.375}, {"text": "have to do if they want\nto understand Spanish--", "start": 2296.18, "duration": 3.51}, {"text": "than it is to figure out what\nsounds would have been there", "start": 2299.69, "duration": 3.81}, {"text": "if they were not gone, which\nis what Spanish speakers", "start": 2303.5, "duration": 2.49}, {"text": "have to do when they're trying\nto understand Portuguese.", "start": 2305.99, "duration": 2.01}, {"text": "That's one theory anyway\nabout what's going on.", "start": 2308.0, "duration": 1.958}, {"text": "Another is just that there\nare more situations in which", "start": 2309.958, "duration": 4.342}, {"text": "Portuguese speakers need\nto understand Spanish", "start": 2314.3, "duration": 2.37}, {"text": "than there are situations in\nwhich Spanish speakers need", "start": 2316.67, "duration": 2.49}, {"text": "to understand Portuguese.", "start": 2319.16, "duration": 1.14}, {"text": "Yeah.", "start": 2320.3, "duration": 0.577}, {"text": "So that's the kind\nof thing that may--", "start": 2320.877, "duration": 1.583}, {"text": "I don't want to pick on\nKateryna's proposal, which", "start": 2322.46, "duration": 2.4}, {"text": "is a popular proposal.", "start": 2324.86, "duration": 1.35}, {"text": "It's about mutual\nintelligibility.", "start": 2326.21, "duration": 1.858}, {"text": "But there are places where\nthe intelligibility is", "start": 2328.068, "duration": 2.042}, {"text": "kind of one way, or\nwhere, in fact, people", "start": 2330.11, "duration": 4.2}, {"text": "who don't understand--\ndon't have", "start": 2334.31, "duration": 1.74}, {"text": "a common language can\nspeak to each other", "start": 2336.05, "duration": 2.22}, {"text": "through the magic of\ninterpretive dance.", "start": 2338.27, "duration": 2.28}, {"text": "Yeah.", "start": 2340.55, "duration": 1.08}, {"text": "Yeah.", "start": 2341.63, "duration": 1.08}, {"text": "That's a thing that happens.", "start": 2342.71, "duration": 2.28}, {"text": "There are other bunch\nof examples here.", "start": 2344.99, "duration": 3.16}, {"text": "There's a popular linguist's\nresponse to that question--", "start": 2348.15, "duration": 5.12}, {"text": "how do you know when you're\nlooking at two languages", "start": 2353.27, "duration": 2.19}, {"text": "as opposed to--", "start": 2355.46, "duration": 1.05}, {"text": "it's often phrased as,\nwhat two things count", "start": 2356.51, "duration": 2.67}, {"text": "as two languages as\nopposed to two dialects", "start": 2359.18, "duration": 2.16}, {"text": "of a single language?", "start": 2361.34, "duration": 1.98}, {"text": "And there's a popular linguistic\nresponse to that which says,", "start": 2363.32, "duration": 3.36}, {"text": "you should really try to\nstop asking that question.", "start": 2366.68, "duration": 2.46}, {"text": "So here are two\nclassic statements", "start": 2372.3, "duration": 2.87}, {"text": "from linguists about that.", "start": 2375.17, "duration": 1.6}, {"text": "One of them is by the great\nYiddish scholar, Max Weinreich,", "start": 2376.77, "duration": 5.75}, {"text": "who said--", "start": 2382.52, "duration": 1.17}, {"text": "he said it in Yiddish.", "start": 2383.69, "duration": 1.44}, {"text": "\"A shprakh iz a dyalekt\nmit an armey un flot,\"", "start": 2385.13, "duration": 2.75}, {"text": "\"A language is a dialect\nwith an army and a navy.\"", "start": 2387.88, "duration": 3.49}, {"text": "So what he meant was we\ndon't draw distinctions", "start": 2391.37, "duration": 4.02}, {"text": "like is this a language\nor a dialect on the basis", "start": 2395.39, "duration": 3.12}, {"text": "of anything linguistic.", "start": 2398.51, "duration": 1.08}, {"text": "It's not about how different\nthey are linguistically.", "start": 2399.59, "duration": 2.208}, {"text": "It's about political power,\nwhether they are spoken", "start": 2401.798, "duration": 4.542}, {"text": "in different countries or not.", "start": 2406.34, "duration": 3.28}, {"text": "So lots of kinds of cases,\nincluding the Portuguese,", "start": 2409.62, "duration": 3.12}, {"text": "Spanish example that\nwe talked about before.", "start": 2412.74, "duration": 3.23}, {"text": "Danish, Norwegian, and Swedish--", "start": 2415.97, "duration": 2.25}, {"text": "anybody speak any\nof those languages?", "start": 2418.22, "duration": 2.697}, {"text": "So I'm not making this up.", "start": 2420.917, "duration": 1.083}, {"text": "I promise.", "start": 2422.0, "duration": 1.77}, {"text": "I was once on--", "start": 2423.77, "duration": 3.21}, {"text": "I was in Norway flying\nto a conference.", "start": 2426.98, "duration": 1.77}, {"text": "I was flying from Southern\nNorway up to Northern Norway", "start": 2428.75, "duration": 2.76}, {"text": "up to Tromso.", "start": 2431.51, "duration": 1.02}, {"text": "I was sitting next to\na Norwegian linguist.", "start": 2432.53, "duration": 2.79}, {"text": "And we were flying\nNorwegian Air.", "start": 2435.32, "duration": 3.24}, {"text": "And various people were making\nannouncements over the--", "start": 2438.56, "duration": 3.18}, {"text": "so the captain came on and made\nan announcement in Norwegian.", "start": 2441.74, "duration": 2.79}, {"text": "A plane full of Norwegians--\nall of them are understanding.", "start": 2444.53, "duration": 3.6}, {"text": "The copilot came on and made\nan announcement in Norwegian.", "start": 2448.13, "duration": 3.658}, {"text": "And then somebody else came on.", "start": 2451.788, "duration": 1.292}, {"text": "And I forget-- the purser or\nsomething came on and made", "start": 2453.08, "duration": 1.8}, {"text": "an announcement.", "start": 2454.88, "duration": 0.63}, {"text": "And the Norwegian linguist\nwho was sitting next to me", "start": 2455.51, "duration": 2.208}, {"text": "said, \"He's speaking Danish.\"", "start": 2457.718, "duration": 2.202}, {"text": "Because there's no reason\nnot to, apparently.", "start": 2459.92, "duration": 3.07}, {"text": "If you're speaking Danish\nto a bunch of Norwegians", "start": 2462.99, "duration": 2.21}, {"text": "on Norwegian Air, ah,\nthey'll figure it out.", "start": 2465.2, "duration": 2.385}, {"text": "AUDIENCE: [LAUGHTER]", "start": 2467.585, "duration": 1.431}, {"text": "NORVIN W. RICHARDS: So we\ncall them Norwegian and Danish", "start": 2469.016, "duration": 2.694}, {"text": "because they're spoken\nin Norway and Denmark.", "start": 2471.71, "duration": 3.13}, {"text": "And they are different\nfrom each other.", "start": 2474.84, "duration": 1.85}, {"text": "Actually, Danish\nis more different", "start": 2476.69, "duration": 1.71}, {"text": "from Norwegian and Swedish\nthan Norwegian and Swedish", "start": 2478.4, "duration": 2.88}, {"text": "are from each other.", "start": 2481.28, "duration": 0.85}, {"text": "Norwegian and Swedish are\nquite similar in lots of ways.", "start": 2482.13, "duration": 2.81}, {"text": "Danish is a little\nbit different.", "start": 2484.94, "duration": 1.78}, {"text": "But, as I say, close enough\nthat on Norwegian Air,", "start": 2486.72, "duration": 3.883}, {"text": "you can announce\nthings in Danish.", "start": 2490.603, "duration": 1.417}, {"text": "It probably helps that if\nyou're announcing something", "start": 2492.02, "duration": 2.4}, {"text": "on a plane, probably\nthe passengers", "start": 2494.42, "duration": 1.68}, {"text": "know what you're saying,\nusually, unless there's", "start": 2496.1, "duration": 3.21}, {"text": "something unusual happening.", "start": 2499.31, "duration": 2.36}, {"text": "There are examples of\nthe other kind, too.", "start": 2501.67, "duration": 1.75}, {"text": "I've got Mandarin and\nCantonese up here.", "start": 2503.42, "duration": 2.73}, {"text": "I encounter this a lot.", "start": 2506.15, "duration": 1.2}, {"text": "I work on Tagalog\nsometimes, which", "start": 2507.35, "duration": 1.92}, {"text": "is a language spoken\nin the Philippines.", "start": 2509.27, "duration": 2.35}, {"text": "The Philippines is a country\nwith many, many languages--", "start": 2511.62, "duration": 3.65}, {"text": "lots and lots of\nrelated languages.", "start": 2515.27, "duration": 2.85}, {"text": "But they are very different\nfrom each other in lots of ways.", "start": 2518.12, "duration": 3.46}, {"text": "So I speak Tagalog, which is the\nlanguage spoken around Manila.", "start": 2521.58, "duration": 3.02}, {"text": "If I'm listening to somebody\nspeaking Cebuano, or Ilocano,", "start": 2524.6, "duration": 3.93}, {"text": "or Hiligaynon, or any of a\nzillion other languages that", "start": 2528.53, "duration": 2.52}, {"text": "are spoken in the Philippines,\nI cannot understand them.", "start": 2531.05, "duration": 2.333}, {"text": "I mean, they're at\nleast as different", "start": 2533.383, "duration": 1.597}, {"text": "as Spanish and Italian.", "start": 2534.98, "duration": 2.94}, {"text": "You can tell they're\nrelated but quite", "start": 2537.92, "duration": 2.91}, {"text": "different from each other.", "start": 2540.83, "duration": 1.26}, {"text": "But Filipinos are used\nto calling them dialects.", "start": 2542.09, "duration": 4.92}, {"text": "And I've had arguments\nwith Filipinos", "start": 2547.01, "duration": 1.65}, {"text": "in which I will ask one\nwho's from some area", "start": 2548.66, "duration": 3.33}, {"text": "of the Philippines\nfar away from Manila--", "start": 2551.99, "duration": 1.855}, {"text": "I'll say, \"What\nlanguage do you speak?\"", "start": 2553.845, "duration": 1.625}, {"text": "And they'll say, \"Oh, I\nspeak a dialect of Filipino.\"", "start": 2555.47, "duration": 3.42}, {"text": "And I'll be like,\n\"Which dialect?\"", "start": 2558.89, "duration": 1.44}, {"text": "And he'll say,\n\"Cebuano,\" which is OK--", "start": 2560.33, "duration": 2.94}, {"text": "related to Tagalog but not\nmutually intelligible with it.", "start": 2563.27, "duration": 4.665}, {"text": "There's something similar going\non with Mandarin and Cantonese.", "start": 2567.935, "duration": 2.625}, {"text": "We tend to call those\ndialects of Chinese", "start": 2570.56, "duration": 2.22}, {"text": "because they're both\nspoken in China.", "start": 2572.78, "duration": 2.64}, {"text": "But-- and they do use-- it's a\nbeauty of the Chinese writing", "start": 2575.42, "duration": 4.23}, {"text": "system that if you write them\ndown, they look very similar.", "start": 2579.65, "duration": 2.89}, {"text": "But if you are\nspeaking Cantonese", "start": 2582.54, "duration": 2.24}, {"text": "to someone who only\nunderstands Mandarin,", "start": 2584.78, "duration": 2.28}, {"text": "then you will have a hard\ntime getting anything across", "start": 2587.06, "duration": 2.34}, {"text": "is my understanding.", "start": 2589.4, "duration": 0.99}, {"text": "They're different enough that--", "start": 2590.39, "duration": 2.495}, {"text": "they have different\ntone systems.", "start": 2592.885, "duration": 1.375}, {"text": "They have different phonologies.", "start": 2594.26, "duration": 3.62}, {"text": "The Mandarin word for \"I,\" the\nfirst-person singular pronoun,", "start": 2597.88, "duration": 2.89}, {"text": "is [MANDARIN].", "start": 2600.77, "duration": 0.69}, {"text": "In Mandarin, it's\nsomething like [CANTONESE]..", "start": 2601.46, "duration": 2.09}, {"text": "They're just different.", "start": 2603.55, "duration": 1.1}, {"text": "They're different languages.", "start": 2604.65, "duration": 1.68}, {"text": "Sorry.", "start": 2606.33, "duration": 0.5}, {"text": "Yeah?", "start": 2606.83, "duration": 0.723}, {"text": "AUDIENCE: Wait.", "start": 2607.553, "duration": 0.707}, {"text": "Which one is [INAUDIBLE]?", "start": 2608.26, "duration": 1.26}, {"text": "NORVIN W. RICHARDS: In Mandarin,\nI think it's [MANDARIN]..", "start": 2609.52, "duration": 1.83}, {"text": "AUDIENCE: Yes.", "start": 2611.35, "duration": 0.36}, {"text": "NORVIN W. RICHARDS: Yeah.", "start": 2611.71, "duration": 0.36}, {"text": "And in Cantonese, I\nbelieve it's [CANTONESE]----", "start": 2612.07, "duration": 2.441}, {"text": "just different,\ndifferent [INAUDIBLE]..", "start": 2614.511, "duration": 1.625}, {"text": "AUDIENCE: [INAUDIBLE]\n[? vowels ?] [INAUDIBLE]", "start": 2616.136, "duration": 1.864}, {"text": "NORVIN W. RICHARDS: Oh, it's--", "start": 2618.0, "duration": 0.69}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2618.69, "duration": 0.9}, {"text": "NORVIN W. RICHARDS: Do you--", "start": 2619.59, "duration": 0.9}, {"text": "AUDIENCE: Yeah.", "start": 2620.49, "duration": 0.21}, {"text": "NORVIN W. RICHARDS: What is it?", "start": 2620.7, "duration": 0.42}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2621.12, "duration": 0.806}, {"text": "NORVIN W. RICHARDS: [INAUDIBLE].", "start": 2621.926, "duration": 1.333}, {"text": "AUDIENCE: Like, the\nvowel is pretty similar.", "start": 2623.259, "duration": 2.001}, {"text": "NORVIN W. RICHARDS: Oh, OK.", "start": 2625.26, "duration": 0.57}, {"text": "AUDIENCE: But that\nfirst consonant--", "start": 2625.83, "duration": 1.545}, {"text": "NORVIN W. RICHARDS: The\nconsonant is different.", "start": 2627.375, "duration": 1.335}, {"text": "OK.", "start": 2628.71, "duration": 0.27}, {"text": "Cool.", "start": 2628.98, "duration": 0.69}, {"text": "Thanks.", "start": 2629.67, "duration": 0.63}, {"text": "Yeah?", "start": 2630.3, "duration": 0.96}, {"text": "AUDIENCE: I think it's\ninteresting that you brought up", "start": 2631.26, "duration": 1.53}, {"text": "Spanish and Italian.", "start": 2632.79, "duration": 1.07}, {"text": "NORVIN W. RICHARDS: Yeah?", "start": 2633.86, "duration": 1.042}, {"text": "AUDIENCE: Because one time\nI gave a story in Italian", "start": 2634.902, "duration": 2.588}, {"text": "to my mom, and she understood\nit 100% without even trying.", "start": 2637.49, "duration": 4.775}, {"text": "I was like, how\ndo you know that?", "start": 2642.265, "duration": 1.375}, {"text": "It's just like Spanish.", "start": 2643.64, "duration": 1.23}, {"text": "NORVIN W. RICHARDS: Oh, yeah.", "start": 2644.87, "duration": 1.208}, {"text": "Cool.", "start": 2646.078, "duration": 0.772}, {"text": "So your mom is clearly\nlinguistically gifted.", "start": 2646.85, "duration": 2.43}, {"text": "AUDIENCE: [LAUGHS]", "start": 2649.28, "duration": 0.97}, {"text": "NORVIN W. RICHARDS: I think\nif someone had-- you gave it", "start": 2650.25, "duration": 1.7}, {"text": "to her written down?", "start": 2651.95, "duration": 0.988}, {"text": "AUDIENCE: No.", "start": 2652.938, "duration": 0.542}, {"text": "I just read it out loud.", "start": 2653.48, "duration": 0.72}, {"text": "NORVIN W. RICHARDS: Oh,\nyou read it out loud.", "start": 2654.2, "duration": 0.75}, {"text": "Wow.", "start": 2654.95, "duration": 0.33}, {"text": "So, wait, do you speak Italian?", "start": 2655.28, "duration": 1.17}, {"text": "AUDIENCE: No.", "start": 2656.45, "duration": 0.57}, {"text": "But I was just pronouncing--", "start": 2657.02, "duration": 0.99}, {"text": "NORVIN W. RICHARDS: You were\npronouncing it out loud.", "start": 2658.01, "duration": 1.44}, {"text": "Cool.", "start": 2659.45, "duration": 0.5}, {"text": "No, that's awesome.", "start": 2659.95, "duration": 2.6}, {"text": "Neat.", "start": 2662.55, "duration": 0.5}, {"text": "I have had the\nopposite experience.", "start": 2663.05, "duration": 2.122}, {"text": "I don't speak Spanish at all.", "start": 2665.172, "duration": 1.208}, {"text": "I speak a little bit of Italian.", "start": 2666.38, "duration": 1.45}, {"text": "And so I have attempted to speak\nin Italian to Spanish speakers,", "start": 2667.83, "duration": 2.985}, {"text": "to which the response is\nalways, \"I don't speak English.\"", "start": 2670.815, "duration": 2.375}, {"text": "AUDIENCE: [LAUGHTER]", "start": 2673.19, "duration": 1.172}, {"text": "NORVIN W. RICHARDS: OK.", "start": 2674.362, "duration": 0.958}, {"text": "Sorry.", "start": 2675.32, "duration": 0.39}, {"text": "My Italian is not all that good.", "start": 2675.71, "duration": 1.333}, {"text": "Maybe that was the problem.", "start": 2677.043, "duration": 1.247}, {"text": "Yeah?", "start": 2678.29, "duration": 1.84}, {"text": "AUDIENCE: So, aside from\nMandarin and Cantonese", "start": 2680.13, "duration": 2.38}, {"text": "[? being-- ?] most\ndialects in China,", "start": 2682.51, "duration": 4.98}, {"text": "[INAUDIBLE] [? they ?]\n[? still use ?] the same", "start": 2687.49, "duration": 2.976}, {"text": "writing systems.", "start": 2690.466, "duration": 0.994}, {"text": "NORVIN W. RICHARDS: Yes.", "start": 2691.46, "duration": 1.0}, {"text": "AUDIENCE: [INAUDIBLE] some\nsort of [INAUDIBLE] system.", "start": 2692.46, "duration": 5.967}, {"text": "So [? could ?] I say that having\nalmost the same [INAUDIBLE]----", "start": 2698.427, "duration": 4.914}, {"text": "does that count as\n[INAUDIBLE] or [INAUDIBLE]", "start": 2703.341, "duration": 3.914}, {"text": "NORVIN W. RICHARDS:\nWell, so I wonder--", "start": 2707.255, "duration": 1.625}, {"text": "I mean, so Engl-- if I\nunderstood what you said", "start": 2708.88, "duration": 2.52}, {"text": "correctly, there are a\ncouple of different--", "start": 2711.4, "duration": 2.447}, {"text": "I don't know if this is\nwhat you're talking about.", "start": 2713.847, "duration": 2.083}, {"text": "There are a couple of variations\non the Chinese writing system.", "start": 2715.93, "duration": 2.625}, {"text": "I've heard them called the\ntraditional and the simplified", "start": 2718.555, "duration": 2.535}, {"text": "characters.", "start": 2721.09, "duration": 0.75}, {"text": "Is that what you're\ntalking about,", "start": 2721.84, "duration": 1.417}, {"text": "where you have slightly\ndifferent ways of writing", "start": 2723.257, "duration": 3.083}, {"text": "particular characters?", "start": 2726.34, "duration": 1.523}, {"text": "Is that what you\nmean when you say", "start": 2727.863, "duration": 1.417}, {"text": "Mandarin and Cantonese\nare using different--", "start": 2729.28, "duration": 2.762}, {"text": "AUDIENCE: No.", "start": 2732.042, "duration": 0.738}, {"text": "It's just when they already\nknow [INAUDIBLE] They're", "start": 2732.78, "duration": 5.9}, {"text": "most definitely\nChinese [? culture. ?]", "start": 2738.68, "duration": 1.665}, {"text": "NORVIN W. RICHARDS: Yeah.", "start": 2740.345, "duration": 1.042}, {"text": "AUDIENCE: But I can\nread them, actually.", "start": 2741.387, "duration": 2.181}, {"text": "NORVIN W. RICHARDS:\nOh, that's interesting.", "start": 2743.568, "duration": 1.792}, {"text": "OK.", "start": 2745.36, "duration": 0.39}, {"text": "Yeah.", "start": 2745.75, "duration": 0.57}, {"text": "So I don't know\nwhy that would be.", "start": 2746.32, "duration": 2.07}, {"text": "So look-- the\ndifferent-- whatever", "start": 2748.39, "duration": 2.222}, {"text": "we're going to call them within\nChina because it's not just", "start": 2750.612, "duration": 2.458}, {"text": "Mandarin and Cantonese.", "start": 2753.07, "duration": 0.9}, {"text": "You're absolutely right.", "start": 2753.97, "duration": 1.0}, {"text": "There are many of them.", "start": 2754.97, "duration": 1.67}, {"text": "They're all related\nto each other.", "start": 2756.64, "duration": 1.5}, {"text": "They're members of a language\nfamily of the Sino- Tibetan", "start": 2758.14, "duration": 3.87}, {"text": "language family, it's\nsometimes called.", "start": 2762.01, "duration": 2.68}, {"text": "And my understanding\nis that most of them", "start": 2764.69, "duration": 2.48}, {"text": "have a lot in common\nsyntactically,", "start": 2767.17, "duration": 3.3}, {"text": "like the basic word\norder is the same.", "start": 2770.47, "duration": 2.28}, {"text": "And they have\n[INAUDIBLE],, and they have", "start": 2772.75, "duration": 3.06}, {"text": "a lot of properties in common.", "start": 2775.81, "duration": 2.01}, {"text": "There's a lot of careful work\non the syntax of, for example,", "start": 2777.82, "duration": 2.88}, {"text": "Mandarin and Cantonese showing\nthat they're not exactly", "start": 2780.7, "duration": 2.36}, {"text": "the same.", "start": 2783.06, "duration": 0.5}, {"text": "There are lots of interesting\ndistinctions between them.", "start": 2783.56, "duration": 2.333}, {"text": "So, for example,\nMandarin will allow you--", "start": 2785.893, "duration": 3.267}, {"text": "Mandarin has what are\ncalled numeral classifiers.", "start": 2789.16, "duration": 2.23}, {"text": "So if you want to\ncount things, there's", "start": 2791.39, "duration": 2.72}, {"text": "a morpheme that goes between\nthe number and the thing", "start": 2794.11, "duration": 2.64}, {"text": "that you are counting\nwhich tells you", "start": 2796.75, "duration": 1.595}, {"text": "something about the nature\nof what you're counting.", "start": 2798.345, "duration": 2.125}, {"text": "So if you want to\nsay three books,", "start": 2800.47, "duration": 2.31}, {"text": "there's a morpheme\nthat goes between three", "start": 2802.78, "duration": 2.16}, {"text": "and books that\nclarifies that it is", "start": 2804.94, "duration": 2.482}, {"text": "a book you are talking about.", "start": 2807.422, "duration": 1.208}, {"text": "And you'll use that\nfor anything book-like.", "start": 2808.63, "duration": 1.98}, {"text": "If you're talking\nabout three pens,", "start": 2810.61, "duration": 1.23}, {"text": "there's another\nclassifier which is", "start": 2811.84, "duration": 1.458}, {"text": "used for things that are long\nand thin, things like that.", "start": 2813.298, "duration": 3.702}, {"text": "Mandarin and Cantonese\nboth have those.", "start": 2817.0, "duration": 2.16}, {"text": "Cantonese is unlike\nMandarin in that", "start": 2819.16, "duration": 1.77}, {"text": "it can use numeral classifiers\neven when there is no number.", "start": 2820.93, "duration": 3.12}, {"text": "So it can just\nstart a noun phrase", "start": 2824.05, "duration": 2.31}, {"text": "with a numeral classifier.", "start": 2826.36, "duration": 1.33}, {"text": "So there are those\nsmallish differences", "start": 2827.69, "duration": 3.17}, {"text": "between these approaches.", "start": 2830.86, "duration": 1.51}, {"text": "Sorry.", "start": 2832.37, "duration": 0.5}, {"text": "You're raising your hand.", "start": 2832.87, "duration": 0.72}, {"text": "[INAUDIBLE]", "start": 2833.59, "duration": 0.15}, {"text": "AUDIENCE: No.", "start": 2833.74, "duration": 0.542}, {"text": "I just-- I was going\nto say something.", "start": 2834.282, "duration": 2.518}, {"text": "Sorry.", "start": 2836.8, "duration": 0.51}, {"text": "NORVIN W. RICHARDS: Yeah.", "start": 2837.31, "duration": 0.3}, {"text": "AUDIENCE: Never mind.", "start": 2837.61, "duration": 0.875}, {"text": "NORVIN W. RICHARDS: Oh, OK.", "start": 2838.485, "duration": 1.565}, {"text": "There are those\nkinds of differences", "start": 2840.05, "duration": 1.5}, {"text": "between Mandarin and\nCantonese, but they", "start": 2841.55, "duration": 2.99}, {"text": "have many properties in common.", "start": 2844.54, "duration": 1.5}, {"text": "And I think this is probably\ntrue of a lot of the, again,", "start": 2846.04, "duration": 2.375}, {"text": "dialects or languages-- whatever\nwe're going to call them--", "start": 2848.415, "duration": 2.458}, {"text": "within China that, you know--", "start": 2850.873, "duration": 1.654}, {"text": "[INAUDIBLE] or\n[INAUDIBLE] or whatever.", "start": 2852.527, "duration": 2.023}, {"text": "There are all of these\ndifferent versions.", "start": 2854.55, "duration": 1.75}, {"text": "They have lots of\nthings in common.", "start": 2856.3, "duration": 4.0}, {"text": "It's a property of the\nChinese writing system", "start": 2860.3, "duration": 3.44}, {"text": "that if you write\na character down,", "start": 2863.74, "duration": 2.64}, {"text": "it doesn't matter what\nlanguage you're speaking.", "start": 2866.38, "duration": 3.36}, {"text": "So for that matter, if I\nwere to write English using", "start": 2869.74, "duration": 2.88}, {"text": "Chinese characters, someone\nwho didn't speak English", "start": 2872.62, "duration": 3.18}, {"text": "but could read\nChinese characters", "start": 2875.8, "duration": 1.62}, {"text": "would probably be able to figure\nout what I had written down.", "start": 2877.42, "duration": 3.18}, {"text": "So if I use this symbol--", "start": 2880.6, "duration": 4.778}, {"text": "this is the Chinese\ncharacter for a person.", "start": 2885.378, "duration": 1.792}, {"text": "I apologize.", "start": 2887.17, "duration": 0.81}, {"text": "My handwriting is bad\nin every language.", "start": 2887.98, "duration": 2.23}, {"text": "But it's something like this.", "start": 2890.21, "duration": 2.12}, {"text": "That's got a pronunciation\nin Mandarin that's", "start": 2892.33, "duration": 2.67}, {"text": "something like [MANDARIN].", "start": 2895.0, "duration": 2.73}, {"text": "If I decided to write English\nusing Chinese characters,", "start": 2897.73, "duration": 2.82}, {"text": "I would use this character\nfor the word \"person.\"", "start": 2900.55, "duration": 2.64}, {"text": "And it would be your job\nto read it as \"person.\"", "start": 2903.19, "duration": 3.66}, {"text": "And you'd-- if you--", "start": 2906.85, "duration": 1.77}, {"text": "again, if you knew\nChinese characters", "start": 2908.62, "duration": 1.59}, {"text": "but couldn't-- didn't\nspeak any English,", "start": 2910.21, "duration": 2.13}, {"text": "you'd be able to read that.", "start": 2912.34, "duration": 1.2}, {"text": "Not because you knew\nEnglish, but because you", "start": 2913.54, "duration": 1.875}, {"text": "knew these characters.", "start": 2915.415, "duration": 1.815}, {"text": "And when Mandarin and\nCantonese speakers--", "start": 2917.23, "duration": 3.78}, {"text": "if you have a monolingual\nMandarin speaker", "start": 2921.01, "duration": 1.83}, {"text": "and a monolingual\nCantonese speaker,", "start": 2922.84, "duration": 1.638}, {"text": "and they're both\nwriting things down,", "start": 2924.478, "duration": 1.542}, {"text": "if they do use the\nsame characters,", "start": 2926.02, "duration": 1.65}, {"text": "they'll be able to read--", "start": 2927.67, "duration": 1.962}, {"text": "each will be able to read\nwhat the other has written.", "start": 2929.632, "duration": 2.208}, {"text": "But it's not-- that\ndoesn't have anything", "start": 2931.84, "duration": 2.298}, {"text": "to do with whether they speak\nthe same language or not.", "start": 2934.138, "duration": 2.292}, {"text": "It's a property of the\nChinese writing system.", "start": 2936.43, "duration": 2.07}, {"text": "You're writing down not\nsounds but words in a sense.", "start": 2938.5, "duration": 5.02}, {"text": "Does that make sense?", "start": 2943.52, "duration": 2.35}, {"text": "It's a very long,\ninvolved response.", "start": 2945.87, "duration": 3.45}, {"text": "Yeah?", "start": 2949.32, "duration": 1.27}, {"text": "OK.", "start": 2950.59, "duration": 2.59}, {"text": "Yeah.", "start": 2953.18, "duration": 0.5}, {"text": "So various examples--\nSerbo-Croatian", "start": 2953.68, "duration": 2.31}, {"text": "is another example.", "start": 2955.99, "duration": 0.9}, {"text": "Down here you have\nto be careful--", "start": 2956.89, "duration": 1.86}, {"text": "there used to be a language\nthat was called Serbo-Croatian", "start": 2958.75, "duration": 3.57}, {"text": "before the breakup of\nthe former Yugoslavia.", "start": 2962.32, "duration": 3.96}, {"text": "There are now people who are\nvery fierce about the fact", "start": 2966.28, "duration": 3.833}, {"text": "that they are\ndistinct languages--", "start": 2970.113, "duration": 1.417}, {"text": "Serbian and Croatian.", "start": 2971.53, "duration": 2.04}, {"text": "They are, again, written with\ndifferent writing systems--", "start": 2973.57, "duration": 3.45}, {"text": "actually, different alphabets.", "start": 2977.02, "duration": 1.41}, {"text": "And there are differences\nin their grammars.", "start": 2978.43, "duration": 3.69}, {"text": "But the fact that\npeople are fierce", "start": 2982.12, "duration": 1.68}, {"text": "about them being\ndifferent languages", "start": 2983.8, "duration": 1.5}, {"text": "has to do with where national\nborderlines have been drawn", "start": 2985.3, "duration": 2.67}, {"text": "and other things about history.", "start": 2987.97, "duration": 1.305}, {"text": "So a popular linguist's\nresponse to this question,", "start": 2992.71, "duration": 3.912}, {"text": "how do you know\nwhen you're looking", "start": 2996.622, "duration": 1.458}, {"text": "at two languages or two\ndialects of a single language,", "start": 2998.08, "duration": 3.75}, {"text": "is to say--", "start": 3001.83, "duration": 2.13}, {"text": "I think I did this\nin class-- \"mu!\"", "start": 3003.96, "duration": 1.83}, {"text": "Yeah.", "start": 3005.79, "duration": 1.23}, {"text": "Don't ask that question!", "start": 3007.02, "duration": 1.86}, {"text": "That question contains some\nkind of false presupposition.", "start": 3008.88, "duration": 4.68}, {"text": "Chomsky in '96, in a book\ncalled Knowledge of Language,", "start": 3013.56, "duration": 3.948}, {"text": "laid out a way of\nthinking about this", "start": 3017.508, "duration": 1.542}, {"text": "that I have always thought\nmade a lot of sense.", "start": 3019.05, "duration": 1.958}, {"text": "He said, look, there\nare-- and his claim", "start": 3021.008, "duration": 3.982}, {"text": "was there aren't actually\nsuch things as languages", "start": 3024.99, "duration": 2.64}, {"text": "or dialects.", "start": 3027.63, "duration": 1.38}, {"text": "What there are are people.", "start": 3029.01, "duration": 2.22}, {"text": "So there are people.", "start": 3031.23, "duration": 1.2}, {"text": "We can agree that\nthere are people.", "start": 3032.43, "duration": 1.74}, {"text": "And people have\nmental grammars--", "start": 3034.17, "duration": 4.2}, {"text": "all the stuff we've been talking\nabout all semester, all the--", "start": 3038.37, "duration": 3.21}, {"text": "if we knew everything about\nwhat was going on in your brain", "start": 3041.58, "duration": 3.29}, {"text": "as it interacted with language--\nif we knew everything about", "start": 3044.87, "duration": 2.5}, {"text": "your lexicon and the\nphonological and syntactic", "start": 3047.37, "duration": 3.78}, {"text": "and semantic status of every\nrepresentation that you were", "start": 3051.15, "duration": 2.64}, {"text": "messing with, and we had\na perfect description", "start": 3053.79, "duration": 2.1}, {"text": "of everything that was\ngoing on in your head--", "start": 3055.89, "duration": 2.05}, {"text": "imagine that we had that--", "start": 3057.94, "duration": 1.91}, {"text": "we can call that\nyour I-language,", "start": 3059.85, "duration": 1.74}, {"text": "call it your\nindividual language.", "start": 3061.59, "duration": 1.92}, {"text": "So that's your mental state.", "start": 3063.51, "duration": 3.55}, {"text": "And now, Chomsky\nsaid, it is a fact", "start": 3067.06, "duration": 3.72}, {"text": "about the way that people tend\nto interact with each other,", "start": 3070.78, "duration": 4.68}, {"text": "and the way that people\ngrow up and learn to speak,", "start": 3075.46, "duration": 5.55}, {"text": "and the way that people interact\nwith each other as adults", "start": 3081.01, "duration": 3.45}, {"text": "that we tend to\nend up growing up", "start": 3084.46, "duration": 2.79}, {"text": "in domains where there are\nlots of people with pretty", "start": 3087.25, "duration": 3.24}, {"text": "similar I-languages.", "start": 3090.49, "duration": 2.58}, {"text": "And that's what\ngives us the illusion", "start": 3093.07, "duration": 1.92}, {"text": "of this other kind of thing.", "start": 3094.99, "duration": 1.2}, {"text": "He called it an E-language,\nan external language--", "start": 3096.19, "duration": 2.61}, {"text": "things like English, or\nMandarin, or Japanese,", "start": 3098.8, "duration": 4.98}, {"text": "or French, or whatever--", "start": 3103.78, "duration": 1.23}, {"text": "these objects that are\nabstractions over many people's", "start": 3107.89, "duration": 6.33}, {"text": "I-languages.", "start": 3114.22, "duration": 1.32}, {"text": "And it's OK to talk this way\nas a loose way of talking.", "start": 3115.54, "duration": 3.99}, {"text": "This is the way we're used\nto talking about languages.", "start": 3119.53, "duration": 2.25}, {"text": "But we should bear\nin mind, he was", "start": 3121.78, "duration": 1.417}, {"text": "saying, that in\nthe final analysis,", "start": 3123.197, "duration": 2.093}, {"text": "these things don't exist.", "start": 3125.29, "duration": 1.62}, {"text": "They're just\ngeneralizations over lots", "start": 3126.91, "duration": 3.0}, {"text": "of different I-languages.", "start": 3129.91, "duration": 1.57}, {"text": "So if we knew everything\nabout the I-languages", "start": 3131.48, "duration": 2.09}, {"text": "of-- let's stick to every\nnative speaker of English", "start": 3133.57, "duration": 2.34}, {"text": "in this room.", "start": 3135.91, "duration": 1.54}, {"text": "If we looked at\neach of us in turn,", "start": 3137.45, "duration": 2.12}, {"text": "we'd discover that we have lots\nand lots of things in common.", "start": 3139.57, "duration": 3.347}, {"text": "But that there are small\ndifferences between them.", "start": 3142.917, "duration": 2.083}, {"text": "I'm apparently the only one\nwith positive \"anymore,\"", "start": 3145.0, "duration": 2.58}, {"text": "maybe Faith too.", "start": 3147.58, "duration": 3.081}, {"text": "I and a couple of other people\nhave \"y'all\" as a second person", "start": 3150.661, "duration": 4.209}, {"text": "plural pronoun.", "start": 3154.87, "duration": 0.96}, {"text": "So there are these\nlittle differences", "start": 3155.83, "duration": 1.83}, {"text": "between pairs of us.", "start": 3157.66, "duration": 1.445}, {"text": "And some of us\nare \"soda\" people.", "start": 3159.105, "duration": 1.375}, {"text": "Some of us are \"pop\" people.", "start": 3160.48, "duration": 1.167}, {"text": "Some of us are \"Coke\" people--", "start": 3161.647, "duration": 2.073}, {"text": "little differences\nbetween pairs of us.", "start": 3163.72, "duration": 2.25}, {"text": "And that's all we\nreally need to say.", "start": 3165.97, "duration": 3.723}, {"text": "So what we have are a\nbunch of people who have", "start": 3169.693, "duration": 1.917}, {"text": "pretty similar I-languages.", "start": 3171.61, "duration": 1.56}, {"text": "And if we work too hard to\ntry to figure out, well,", "start": 3173.17, "duration": 5.08}, {"text": "which of those languages\nis really English", "start": 3178.25, "duration": 2.99}, {"text": "and which of them are\ndeviations from English,", "start": 3181.24, "duration": 2.55}, {"text": "then we're, Chomsky was\nsaying, asking ourselves", "start": 3183.79, "duration": 2.61}, {"text": "the wrong question.", "start": 3186.4, "duration": 1.92}, {"text": "Trying to decide whether two\npeople speak the same language", "start": 3188.32, "duration": 3.0}, {"text": "or not, it's like trying\nto decide on a fall day", "start": 3191.32, "duration": 3.81}, {"text": "whether two leaves\nare the same color.", "start": 3195.13, "duration": 2.91}, {"text": "So you could look at two\nleaves, and say, yeah, those", "start": 3198.04, "duration": 3.69}, {"text": "are both red.", "start": 3201.73, "duration": 1.157}, {"text": "But if you looked\nhard enough at them,", "start": 3202.887, "duration": 1.583}, {"text": "you'd convince yourself\nthey're not exactly the same.", "start": 3204.47, "duration": 2.278}, {"text": "One of them is a little deeper.", "start": 3206.748, "duration": 1.292}, {"text": "One of them's a little browner.", "start": 3208.04, "duration": 1.88}, {"text": "So what's the right answer?", "start": 3209.92, "duration": 2.175}, {"text": "Well, there isn't\na right answer.", "start": 3212.095, "duration": 1.375}, {"text": "It's just a question\nof how fine-grained do", "start": 3213.47, "duration": 2.6}, {"text": "you want your analysis to be?", "start": 3216.07, "duration": 1.44}, {"text": "That was Chomsky's way\nof talking about this.", "start": 3217.51, "duration": 4.86}, {"text": "I bring this up because it short\ncircuits a lot of ways people", "start": 3222.37, "duration": 6.52}, {"text": "have had of talking\nabout dialects.", "start": 3228.89, "duration": 1.87}, {"text": "So I started off with\nthis metaphor about chess", "start": 3230.76, "duration": 4.1}, {"text": "and checkers and the teachers\nwho pretended that there", "start": 3234.86, "duration": 3.06}, {"text": "was no such game as chess.", "start": 3237.92, "duration": 2.19}, {"text": "And I've already\ntalked a little bit", "start": 3240.11, "duration": 1.5}, {"text": "about ways in which this\nmetaphor has correspondences", "start": 3241.61, "duration": 5.01}, {"text": "in real life.", "start": 3246.62, "duration": 0.82}, {"text": "So there are dialects--\nnegative concord dialects--", "start": 3247.44, "duration": 2.69}, {"text": "that are the subject\nof deliberate", "start": 3250.13, "duration": 2.7}, {"text": "suppression by the\neducation system.", "start": 3252.83, "duration": 1.69}, {"text": "And this has consequences\nfor people who grow up", "start": 3254.52, "duration": 2.03}, {"text": "speaking these dialects.", "start": 3256.55, "duration": 2.37}, {"text": "There are dialects that have\nbeen particularly attacked", "start": 3258.92, "duration": 3.28}, {"text": "which go by various names--", "start": 3262.2, "duration": 2.27}, {"text": "sometimes called African\nAmerican English.", "start": 3264.47, "duration": 2.31}, {"text": "It's also been called African\nAmerican Vernacular English.", "start": 3266.78, "duration": 3.42}, {"text": "Decades ago, it was\nonce called Ebonics.", "start": 3270.2, "duration": 2.31}, {"text": "Does anyone still use this term?", "start": 3272.51, "duration": 1.77}, {"text": "Has anyone heard the\nterm Ebonics used", "start": 3274.28, "duration": 1.8}, {"text": "for African American English?", "start": 3276.08, "duration": 1.92}, {"text": "It was an attempt to\nmake African American", "start": 3278.0, "duration": 4.23}, {"text": "English sound different\nfrom African American", "start": 3282.23, "duration": 2.677}, {"text": "English-- make it\nsound like something", "start": 3284.907, "duration": 1.583}, {"text": "you might want to study.", "start": 3286.49, "duration": 2.79}, {"text": "When people first--\nso people have", "start": 3289.28, "duration": 2.4}, {"text": "been talking about this version\nof English for a long time.", "start": 3291.68, "duration": 2.79}, {"text": "And a lot of the discussion\nhas been like the teachers", "start": 3294.47, "duration": 4.95}, {"text": "that I was asking you to\nthink about in the metaphor--", "start": 3299.42, "duration": 2.25}, {"text": "the ones who said,\nwhat are you doing?", "start": 3301.67, "duration": 2.19}, {"text": "That's not how\nyou play checkers.", "start": 3303.86, "duration": 2.04}, {"text": "You're just moving the\npieces around randomly.", "start": 3305.9, "duration": 2.85}, {"text": "Stop it and learn to play\na game with some rules.", "start": 3308.75, "duration": 2.672}, {"text": "So the people who talk about\nAfrican American English often", "start": 3311.422, "duration": 2.458}, {"text": "make a point of saying that it's\na version of English-- this is", "start": 3313.88, "duration": 2.97}, {"text": "William Raspberry, who's\nAfrican-American, I believe,", "start": 3316.85, "duration": 3.43}, {"text": "saying it's a version of\nEnglish that has no rules.", "start": 3320.28, "duration": 3.87}, {"text": "There's a lot of really\ninteresting reasons", "start": 3324.15, "duration": 2.0}, {"text": "and not-so-recent research on\nAfrican American English, some", "start": 3326.15, "duration": 5.16}, {"text": "of it by African-American\nlinguists.", "start": 3331.31, "duration": 3.36}, {"text": "There's a really\nexcellent series", "start": 3334.67, "duration": 2.73}, {"text": "of works by a linguist,\nLisa Green, who", "start": 3337.4, "duration": 3.12}, {"text": "I recommend that you look\nup if you get interested", "start": 3340.52, "duration": 2.22}, {"text": "in these topics.", "start": 3342.74, "duration": 2.187}, {"text": "It has a number of properties,\nwhich because we're running out", "start": 3344.927, "duration": 2.583}, {"text": "of time, we probably won't\nget a chance to talk about all", "start": 3347.51, "duration": 2.07}, {"text": "of them.", "start": 3349.58, "duration": 0.5}, {"text": "But I'll run through\na couple of them.", "start": 3350.08, "duration": 2.6}, {"text": "First of all, to talk about\nit as a monolithic entity", "start": 3352.68, "duration": 2.36}, {"text": "is an oversimplification.", "start": 3355.04, "duration": 1.255}, {"text": "There are a lot of varieties\nof African American English,", "start": 3356.295, "duration": 2.375}, {"text": "just as there are of\nnon-African American English.", "start": 3358.67, "duration": 2.73}, {"text": "But it's characterized by\nnegative concord, which", "start": 3361.4, "duration": 2.79}, {"text": "is one of the reasons that\nnegative concord is picked out", "start": 3364.19, "duration": 2.82}, {"text": "for abuse.", "start": 3367.01, "duration": 1.32}, {"text": "It has a richer tense\nand aspect system", "start": 3368.33, "duration": 2.82}, {"text": "than the version of\nEnglish that I'm speaking.", "start": 3371.15, "duration": 2.71}, {"text": "So a version of the\nEnglish that I'm speaking", "start": 3373.86, "duration": 2.51}, {"text": "would use the same kind of\nverb to express these things.", "start": 3376.37, "duration": 4.48}, {"text": "So I would say\nfor both of these,", "start": 3380.85, "duration": 1.58}, {"text": "\"They are usually tired\nwhen they come home,\"", "start": 3382.43, "duration": 2.04}, {"text": "and \"They are tired right now.\"", "start": 3384.47, "duration": 2.31}, {"text": "African American English\ndistinguishes these.", "start": 3386.78, "duration": 1.92}, {"text": "So you use \"be\" for the\nhabitual one, the first one,", "start": 3388.7, "duration": 2.73}, {"text": "and nothing--", "start": 3391.43, "duration": 1.83}, {"text": "so \"They tired right\nnow,\" for the second one.", "start": 3393.26, "duration": 2.89}, {"text": "Again, is anybody familiar\nwith this dialect of English?", "start": 3396.15, "duration": 3.14}, {"text": "Is this something any of\nyou have grown up around?", "start": 3399.29, "duration": 2.61}, {"text": "Have you heard this?", "start": 3401.9, "duration": 1.092}, {"text": "Have you heard\npeople saying things", "start": 3402.992, "duration": 1.458}, {"text": "like, \"They tired right now?\"", "start": 3404.45, "duration": 1.74}, {"text": "Yeah.", "start": 3406.19, "duration": 0.54}, {"text": "So I certainly have growing up.", "start": 3406.73, "duration": 2.19}, {"text": "And, at the time,\nI believed and was", "start": 3408.92, "duration": 2.61}, {"text": "taught to believe that this was\nbecause these speakers were,", "start": 3411.53, "duration": 2.558}, {"text": "you know, they were lazy.", "start": 3414.088, "duration": 1.042}, {"text": "They were leaving out words\nthat they should have said.", "start": 3415.13, "duration": 2.13}, {"text": "What they were\nactually doing was", "start": 3417.26, "duration": 1.375}, {"text": "expressing an\naspectual distinction", "start": 3418.635, "duration": 1.948}, {"text": "that my version of\nEnglish doesn't express.", "start": 3420.583, "duration": 1.792}, {"text": "This is a distinction that's\nalso expressed in Spanish.", "start": 3426.65, "duration": 2.43}, {"text": "It's a distinction\nbetween what's", "start": 3429.08, "duration": 2.01}, {"text": "sometimes called stage level\nand individual level properties.", "start": 3431.09, "duration": 5.01}, {"text": "So individual level\nproperties are", "start": 3436.1, "duration": 1.59}, {"text": "properties that hold of someone\nover a long period of time,", "start": 3437.69, "duration": 3.97}, {"text": "so use \"ser\" in Spanish for--", "start": 3441.66, "duration": 3.95}, {"text": "to express individual\nlevel properties", "start": 3445.61, "duration": 2.07}, {"text": "like \"I'm North American.\"", "start": 3447.68, "duration": 2.03}, {"text": "\"Estar\" is used for temporary\nproperties like being tired.", "start": 3449.71, "duration": 3.4}, {"text": "That's a distinction that\nmy version of English", "start": 3453.11, "duration": 2.01}, {"text": "doesn't make, but African\nAmerican English does.", "start": 3455.12, "duration": 4.59}, {"text": "It's also got, famously,\na rule-governed version", "start": 3459.71, "duration": 5.61}, {"text": "of copula drop.", "start": 3465.32, "duration": 0.96}, {"text": "So I do want to talk about\nthis in a little bit of detail.", "start": 3466.28, "duration": 4.81}, {"text": "So in the context in which\nyou can leave out the copula--", "start": 3471.09, "duration": 3.49}, {"text": "when the aspectual\ndistinctions allow", "start": 3477.83, "duration": 2.52}, {"text": "you to use the null copula\nin African American English,", "start": 3480.35, "duration": 2.52}, {"text": "there are rules about\nwhere you can do it.", "start": 3482.87, "duration": 2.62}, {"text": "So, for example, you can do it\nin a sentence like \"He rich.\"", "start": 3485.49, "duration": 2.895}, {"text": "But you can't do it at\nthe end of a sentence.", "start": 3488.385, "duration": 1.875}, {"text": "So you can't ask--\nyou can't say things", "start": 3490.26, "duration": 1.76}, {"text": "like, \"I don't\nknow how rich he,\"", "start": 3492.02, "duration": 1.98}, {"text": "in this version of English.", "start": 3494.0, "duration": 3.18}, {"text": "You also can't do\nit in infinitives.", "start": 3497.18, "duration": 2.51}, {"text": "And you can't do it\nin the past tense.", "start": 3499.69, "duration": 2.29}, {"text": "So the past tense\nis \"He was rich.\"", "start": 3501.98, "duration": 1.74}, {"text": "It's not, \"He rich.\"", "start": 3503.72, "duration": 1.86}, {"text": "And you don't do it\nwhen there's negation.", "start": 3505.58, "duration": 3.6}, {"text": "So there is this\nphenomenon of copula drop", "start": 3509.18, "duration": 3.36}, {"text": "if you're describing\na temporary property.", "start": 3512.54, "duration": 2.98}, {"text": "But it's copula drop that's\nsubject to these rules which", "start": 3515.52, "duration": 3.26}, {"text": "I've just gone\nthrough real fast.", "start": 3518.78, "duration": 1.75}, {"text": "It's not just say\nwhatever you want.", "start": 3520.53, "duration": 2.1}, {"text": "There are these\nrestrictions which linguists", "start": 3522.63, "duration": 2.42}, {"text": "have studied and figured out.", "start": 3525.05, "duration": 2.19}, {"text": "These particular\ndistinctions are of interest", "start": 3527.24, "duration": 2.25}, {"text": "because they have\na correspondent", "start": 3529.49, "duration": 4.86}, {"text": "in the version of English that I\nam speaking, which is sometimes", "start": 3534.35, "duration": 3.36}, {"text": "called standard English.", "start": 3537.71, "duration": 1.95}, {"text": "So standard English\nhas a phenomenon", "start": 3539.66, "duration": 3.0}, {"text": "where we can contract\nvarious kinds of things", "start": 3542.66, "duration": 2.425}, {"text": "including the copula.", "start": 3545.085, "duration": 0.875}, {"text": "So you can say, \"He is rich.\"", "start": 3545.96, "duration": 1.32}, {"text": "But you can also\nsay, \"He's rich.\"", "start": 3547.28, "duration": 2.79}, {"text": "And this is also\nsubject to restrictions.", "start": 3550.07, "duration": 2.203}, {"text": "So you can't, for example, do\nit at the end of a sentence.", "start": 3552.273, "duration": 2.417}, {"text": "You can't say-- you can say,\n\"I don't know how rich he is.\"", "start": 3554.69, "duration": 2.458}, {"text": "You can't say, \"I don't\nknow how rich he's.\"", "start": 3557.148, "duration": 2.872}, {"text": "And I'm about to go\nthrough all of the context", "start": 3560.02, "duration": 4.225}, {"text": "that we did on the\nlast slide, but what", "start": 3564.245, "duration": 1.625}, {"text": "we're going to see is that what\nAfrican American English is", "start": 3565.87, "duration": 2.67}, {"text": "doing is dropping copulas under\njust the circumstances where", "start": 3568.54, "duration": 4.698}, {"text": "my version of English-- the\nversion of English that I'm", "start": 3573.238, "duration": 2.292}, {"text": "speaking-- can contract copulas.", "start": 3575.53, "duration": 2.16}, {"text": "And that's it.", "start": 3577.69, "duration": 1.29}, {"text": "So they're not being\nlazy or stupid.", "start": 3578.98, "duration": 5.04}, {"text": "They're not failing to say a\nword that they ought to say.", "start": 3584.02, "duration": 2.79}, {"text": "They just have a\nversion of a contraction", "start": 3586.81, "duration": 1.71}, {"text": "that's a little more emphatic\nthan the version that I use.", "start": 3588.52, "duration": 3.57}, {"text": "They don't just get\nrid of the vowel.", "start": 3592.09, "duration": 1.74}, {"text": "They get rid of the whole thing.", "start": 3593.83, "duration": 1.53}, {"text": "But the restrictions on\nwhere you can do this", "start": 3595.36, "duration": 2.91}, {"text": "are the same restrictions.", "start": 3598.27, "duration": 1.56}, {"text": "So just like in my\nversion of English,", "start": 3599.83, "duration": 2.37}, {"text": "you can't say \"He'sn't\nrich,\" doing contraction both", "start": 3602.2, "duration": 6.06}, {"text": "of the copula and of\nnegation, similarly,", "start": 3608.26, "duration": 2.22}, {"text": "you can't do copula drop there\nin African American English.", "start": 3610.48, "duration": 3.69}, {"text": "Did anybody get a chance to\nlook at the optional reading", "start": 3614.17, "duration": 3.84}, {"text": "for today?", "start": 3618.01, "duration": 1.192}, {"text": "I put up an optional reading.", "start": 3619.202, "duration": 1.208}, {"text": "And as I put up the\noptional reading,", "start": 3620.41, "duration": 1.542}, {"text": "I thought, here I am putting\nup an optional reading", "start": 3621.952, "duration": 2.178}, {"text": "for a one-day topic on the\nday when a paper is due.", "start": 3624.13, "duration": 3.09}, {"text": "What are the odds\nthat anyone will", "start": 3627.22, "duration": 1.95}, {"text": "have a chance to even consider\nthinking about actually", "start": 3629.17, "duration": 3.433}, {"text": "even reading the\nannouncement that there", "start": 3632.603, "duration": 1.667}, {"text": "is an optional reading?", "start": 3634.27, "duration": 1.02}, {"text": "These people-- it's the\nend of the semester.", "start": 3635.29, "duration": 2.34}, {"text": "The optional reading is\nstill on the website.", "start": 3637.63, "duration": 2.43}, {"text": "It's worth having a look at\nsometime when you have time.", "start": 3640.06, "duration": 2.61}, {"text": "I can just describe\nfor you what it is.", "start": 3642.67, "duration": 1.81}, {"text": "It's an African-American\nauthor who", "start": 3644.48, "duration": 3.17}, {"text": "is addressing arguments\nabout how African", "start": 3647.65, "duration": 3.51}, {"text": "American English ought\nto be treated in schools.", "start": 3651.16, "duration": 3.18}, {"text": "And he has a very\nsophisticated set of arguments.", "start": 3654.34, "duration": 3.51}, {"text": "He's replying to\nvarious people who", "start": 3657.85, "duration": 2.127}, {"text": "have argued the\nconservative position, which", "start": 3659.977, "duration": 1.833}, {"text": "is that it's fine for people\nto speak African American", "start": 3661.81, "duration": 4.2}, {"text": "English in the privacy\nof their own homes,", "start": 3666.01, "duration": 1.77}, {"text": "but it is important\nthat we teach", "start": 3667.78, "duration": 2.31}, {"text": "them standard English\nin schools in order", "start": 3670.09, "duration": 3.0}, {"text": "for them to get ahead in life.", "start": 3673.09, "duration": 1.92}, {"text": "He's taking issue\nwith these arguments.", "start": 3675.01, "duration": 2.28}, {"text": "But the cool thing\nabout the essay", "start": 3677.29, "duration": 1.47}, {"text": "is not just that he takes\nissue with these arguments,", "start": 3678.76, "duration": 2.208}, {"text": "but that it's written in\nAfrican American English.", "start": 3680.968, "duration": 2.622}, {"text": "So the essay is written\nin the version of English", "start": 3683.59, "duration": 2.73}, {"text": "that he is describing.", "start": 3686.32, "duration": 1.62}, {"text": "And it's a cool and\ndifficult experience", "start": 3687.94, "duration": 3.57}, {"text": "attempting to read it.", "start": 3691.51, "duration": 1.5}, {"text": "So if it's not your\nnative dialect of English,", "start": 3693.01, "duration": 2.91}, {"text": "it's not trivial figuring\nout how to read the article.", "start": 3695.92, "duration": 3.33}, {"text": "So it's an interesting\nexperience.", "start": 3699.25, "duration": 1.5}, {"text": "I recommend it to everybody.", "start": 3700.75, "duration": 3.15}, {"text": "Questions about any of this?", "start": 3703.9, "duration": 1.89}, {"text": "Other things people\nwant to talk about?", "start": 3705.79, "duration": 2.97}, {"text": "So the goal-- and we are now\nin the part of the semester", "start": 3708.76, "duration": 2.37}, {"text": "where I attempt as\na public service", "start": 3711.13, "duration": 1.86}, {"text": "to combat various things\npeople believe about language", "start": 3712.99, "duration": 3.69}, {"text": "or maybe have heard\nabout language.", "start": 3716.68, "duration": 2.17}, {"text": "So the goal of today was\nto get you to at least hear", "start": 3718.85, "duration": 3.89}, {"text": "the idea that when people\nspeak English or whatever", "start": 3722.74, "duration": 2.277}, {"text": "your native language is in a way\nthat's different from the way", "start": 3725.017, "duration": 2.583}, {"text": "that you speak it, it's\nnot because they're stupid.", "start": 3727.6, "duration": 3.81}, {"text": "It's because languages do that.", "start": 3731.41, "duration": 2.88}, {"text": "There are varieties\nof languages.", "start": 3734.29, "duration": 3.163}, {"text": "Maybe it's because\nthere aren't actually", "start": 3737.453, "duration": 1.667}, {"text": "such things as languages.", "start": 3739.12, "duration": 1.11}, {"text": "There are just people.", "start": 3740.23, "duration": 1.09}, {"text": "And people are different\nfrom each other.", "start": 3741.32, "duration": 2.68}, {"text": "Yeah?", "start": 3744.0, "duration": 1.34}, {"text": "All right.", "start": 3745.34, "duration": 0.5}, {"text": "Go forth and frolic.", "start": 3745.84, "duration": 1.08}, {"text": "Thank you for listening\nto me talk about this.", "start": 3746.92, "duration": 2.34}, {"text": "And I will see you\nagain on Thursday.", "start": 3749.26, "duration": 4.22}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.922}, {"text": "[RUSTLING]", "start": 2.922, "duration": 1.461}, {"text": "[CLICKING]", "start": 4.383, "duration": 0.974}, {"text": "BERTHOLD HORN: \"Quick,\" meaning\npattern recognition quickly.", "start": 12.18, "duration": 6.15}, {"text": "And that's in distinction\nfrom another pattern", "start": 18.33, "duration": 3.18}, {"text": "we'll look at later,\nwhich is slower but gets", "start": 21.51, "duration": 5.91}, {"text": "a more accurate answer.", "start": 27.42, "duration": 2.76}, {"text": "So a number of terms\nwere defined there.", "start": 30.18, "duration": 3.65}, {"text": "One of them was that of a model.", "start": 33.83, "duration": 2.62}, {"text": "So there's a training step\nthat produces a model.", "start": 36.45, "duration": 6.81}, {"text": "And the model\nconsists of probes.", "start": 43.26, "duration": 4.17}, {"text": "And the probes are places where\nwe will be collecting evidence", "start": 47.43, "duration": 6.27}, {"text": "for a match to produce\na scoring function.", "start": 53.7, "duration": 4.98}, {"text": "And we think of that\nscore as a surface", "start": 58.68, "duration": 3.51}, {"text": "in a multidimensional\nspace which has as its axes", "start": 62.19, "duration": 7.17}, {"text": "the various degrees of freedom.", "start": 69.36, "duration": 2.37}, {"text": "And we're looking for a peak\nin that score surface that's", "start": 71.73, "duration": 5.46}, {"text": "above a threshold as\na way of indicating", "start": 77.19, "duration": 5.19}, {"text": "that there's an instance of\nthat pattern in the image.", "start": 82.38, "duration": 4.92}, {"text": "And there may be more than\none, and there may be none.", "start": 87.3, "duration": 5.39}, {"text": "And at the highest\nlevel, we look at quote,", "start": 92.69, "duration": 3.81}, {"text": "\"all poses,\" meaning we're\ngoing to quantize them,", "start": 96.5, "duration": 3.63}, {"text": "but we have to consider the\nfull range of rotations,", "start": 100.13, "duration": 4.56}, {"text": "translations, scaling, whatever.", "start": 104.69, "duration": 3.19}, {"text": "And so the complexity\ngoes exponentially", "start": 107.88, "duration": 4.72}, {"text": "with the number of\ndegrees of freedom.", "start": 112.6, "duration": 3.3}, {"text": "So even if we quantize\nfairly coarsely,", "start": 115.9, "duration": 3.18}, {"text": "say somewhere between\n10 and 100 steps,", "start": 119.08, "duration": 3.24}, {"text": "that means we're multiplying the\namount of work by 10 and 100,", "start": 122.32, "duration": 4.92}, {"text": "something like that.", "start": 127.24, "duration": 1.26}, {"text": "So normalized\ncorrelation was expensive", "start": 128.5, "duration": 5.04}, {"text": "and couldn't handle\nmore than two degrees", "start": 133.54, "duration": 2.85}, {"text": "of freedom, translation.", "start": 136.39, "duration": 1.62}, {"text": "Well, this method is looking at\nvery few points in the image.", "start": 138.01, "duration": 4.21}, {"text": "And so it can afford to deal\nwith a large number of degrees", "start": 142.22, "duration": 4.79}, {"text": "of freedom.", "start": 147.01, "duration": 1.66}, {"text": "OK.", "start": 148.67, "duration": 0.81}, {"text": "That's a great question.", "start": 149.48, "duration": 2.14}, {"text": "So at one level,\nwe're building up.", "start": 151.62, "duration": 2.25}, {"text": "So we're starting off looking\nat very low-level issues,", "start": 153.87, "duration": 3.17}, {"text": "and then we're building\non top of them.", "start": 157.04, "duration": 2.55}, {"text": "Then as to why did we\npick these patterns, well,", "start": 159.59, "duration": 4.05}, {"text": "one reason is that\nit's a package", "start": 163.64, "duration": 3.33}, {"text": "of things that are related.", "start": 166.97, "duration": 1.78}, {"text": "So we don't have to re-learn\nterminology and whatever.", "start": 168.75, "duration": 3.0}, {"text": "So for example, the front\nend for this one, as you saw,", "start": 171.75, "duration": 3.08}, {"text": "is the pattern we\ntalked about before.", "start": 174.83, "duration": 2.28}, {"text": "And the next one we're\ngoing to talk about", "start": 177.11, "duration": 2.94}, {"text": "is closely related to this.", "start": 180.05, "duration": 1.49}, {"text": "It uses this one to get a\nfirst guess at the answer.", "start": 181.54, "duration": 4.63}, {"text": "And then the one after\nthat is a fast way", "start": 186.17, "duration": 3.18}, {"text": "of computing a step that we\nneed to do the subsampling.", "start": 189.35, "duration": 4.76}, {"text": "So is it a random sampling?", "start": 194.11, "duration": 3.52}, {"text": "Well, kind of, because machine\nvision has exponentially grown.", "start": 197.63, "duration": 6.81}, {"text": "And there was a time\nwhere there wasn't enough", "start": 204.44, "duration": 3.57}, {"text": "material to fill a whole term.", "start": 208.01, "duration": 2.17}, {"text": "So I taught this course, which\nI called \"Making Machines See", "start": 210.18, "duration": 4.76}, {"text": "and Feel,\" because half of\nit was vision, and half of it", "start": 214.94, "duration": 3.15}, {"text": "was robotics manipulation.", "start": 218.09, "duration": 3.48}, {"text": "And we can't do that anymore.", "start": 221.57, "duration": 2.89}, {"text": "Now we've got multiple\ncourses on machine vision.", "start": 224.46, "duration": 2.16}, {"text": "So this is a particular approach\nto machine vision, which", "start": 226.62, "duration": 3.83}, {"text": "some people refer to as\nthe physics-based approach", "start": 230.45, "duration": 3.78}, {"text": "to machine vision.", "start": 234.23, "duration": 2.4}, {"text": "By the way, they made me\nchange-- the head of department", "start": 236.63, "duration": 2.73}, {"text": "contacted me and\nsaid I couldn't have", "start": 239.36, "duration": 1.95}, {"text": "a frivolous title like \"Making\nMachines See and Feel.\"", "start": 241.31, "duration": 3.63}, {"text": "And that's why now it's\ncalled \"Machine Vision.\"", "start": 244.94, "duration": 4.32}, {"text": "So the patterns we're\nlooking at hang together,", "start": 249.26, "duration": 3.73}, {"text": "which makes it easier\nto discuss them.", "start": 252.99, "duration": 1.79}, {"text": "Their patterns of the most\nsuccessful machine vision", "start": 254.78, "duration": 4.049}, {"text": "company.", "start": 258.829, "duration": 0.63}, {"text": "So there's some weight there.", "start": 259.459, "duration": 1.44}, {"text": "Is it what they're doing today?", "start": 260.899, "duration": 2.311}, {"text": "Well, a lot of the\nmachines they sell do this.", "start": 263.21, "duration": 3.0}, {"text": "Others do other things,\nwhich we have yet", "start": 266.21, "duration": 2.79}, {"text": "to find out, because we don't\nknow their trade secrets.", "start": 269.0, "duration": 4.53}, {"text": "And the things we're talking\nabout in the pattern discussion", "start": 273.53, "duration": 5.13}, {"text": "is mostly 2D.", "start": 278.66, "duration": 2.94}, {"text": "So it's restricted\nto situations where", "start": 281.6, "duration": 2.61}, {"text": "we're dealing with\ntwo-dimensional surfaces,", "start": 284.21, "duration": 2.1}, {"text": "like integrated circuits,\nprinted circuit boards,", "start": 286.31, "duration": 3.45}, {"text": "conveyor belts, the ground\noutside an autonomous car,", "start": 289.76, "duration": 5.19}, {"text": "things of that nature.", "start": 294.95, "duration": 1.39}, {"text": "So after this, we'll go\non to higher level still.", "start": 296.34, "duration": 7.71}, {"text": "So it's part of a progression.", "start": 304.05, "duration": 2.34}, {"text": "And yes, we're not covering\neverything possible.", "start": 306.39, "duration": 4.78}, {"text": "And so we're taking\nstabs at things", "start": 311.17, "duration": 2.06}, {"text": "that give you a feeling for\nwhat's there rather than try", "start": 313.23, "duration": 5.28}, {"text": "to cover everything.", "start": 318.51, "duration": 3.02}, {"text": "So in this-- back to this.", "start": 321.53, "duration": 4.63}, {"text": "So there's a training step\nwhere we show it an image,", "start": 326.16, "duration": 3.27}, {"text": "and it automatically\ncomputes this model.", "start": 329.43, "duration": 4.54}, {"text": "And that was very\nimportant for them,", "start": 333.97, "duration": 2.24}, {"text": "because we can send someone\nto MIT and get a degree", "start": 336.21, "duration": 5.52}, {"text": "and handcraft some\ncode to do something.", "start": 341.73, "duration": 3.36}, {"text": "But that's only\nworthwhile if you have", "start": 345.09, "duration": 3.72}, {"text": "a huge application for that.", "start": 348.81, "duration": 3.6}, {"text": "I forget what the example\nwas-- pencils or something,", "start": 352.41, "duration": 3.21}, {"text": "earphones--", "start": 355.62, "duration": 1.53}, {"text": "toothbrush, sorry.", "start": 357.15, "duration": 1.74}, {"text": "There was someone who was asked\nabout supporting startups,", "start": 358.89, "duration": 5.1}, {"text": "and his test was the toothbrush.", "start": 363.99, "duration": 2.46}, {"text": "So if he can sell a billion of\nthem, then maybe he'll fund it.", "start": 366.45, "duration": 4.23}, {"text": "But if for every visual task\nyou have to expend that effort", "start": 370.68, "duration": 6.03}, {"text": "to program it, that's not good.", "start": 376.71, "duration": 2.17}, {"text": "So the training\nmethod is very good,", "start": 378.88, "duration": 3.23}, {"text": "because someone with not\na great deal of experience", "start": 382.11, "duration": 5.49}, {"text": "can show the system the object,\nhopefully a good sample of it,", "start": 387.6, "duration": 5.79}, {"text": "and get a training image.", "start": 393.39, "duration": 2.55}, {"text": "There are some\nrefinements you can do.", "start": 395.94, "duration": 2.61}, {"text": "As we discussed, for example,\nyou can have negative weights.", "start": 398.55, "duration": 2.79}, {"text": "But those are things\nthat a person has to--", "start": 401.34, "duration": 4.56}, {"text": "can't think of an automated\nway of doing that yet.", "start": 405.9, "duration": 2.68}, {"text": "And so that's actually\nsomething that's never done,", "start": 408.58, "duration": 3.05}, {"text": "because it's much\neasier to just go", "start": 411.63, "duration": 4.14}, {"text": "with that if it's satisfactory.", "start": 415.77, "duration": 3.48}, {"text": "So what do we do\nwith this model?", "start": 419.25, "duration": 2.07}, {"text": "Well, then we map the model\nonto the real-time image.", "start": 421.32, "duration": 5.225}, {"text": "And in the process,\nwe use the pose,", "start": 433.93, "duration": 3.72}, {"text": "which is translation, rotation,\nand all these other things.", "start": 437.65, "duration": 5.054}, {"text": "So our model now is mapped\non top of the image.", "start": 442.704, "duration": 10.766}, {"text": "And then at each of\nthe probe positions,", "start": 453.47, "duration": 3.3}, {"text": "we look at the\nbrightness gradient.", "start": 456.77, "duration": 3.24}, {"text": "So actually, we pre-process--", "start": 460.01, "duration": 4.77}, {"text": "we don't really go\nback to the image.", "start": 464.78, "duration": 2.16}, {"text": "We go to the\nbrightness gradient.", "start": 466.94, "duration": 2.22}, {"text": "And we perform a test to collect\nevidence, to collect evidence,", "start": 469.16, "duration": 7.77}, {"text": "that this object\nis actually there.", "start": 476.93, "duration": 2.49}, {"text": "And the evidence is cumulative.", "start": 479.42, "duration": 3.0}, {"text": "So we just add it up.", "start": 482.42, "duration": 1.86}, {"text": "And so that's the idea of doing\na lot of local operations,", "start": 484.28, "duration": 3.81}, {"text": "where the final result\nis just the sum of those,", "start": 488.09, "duration": 4.16}, {"text": "a little bit like the\nbinary imaging processing--", "start": 492.25, "duration": 2.95}, {"text": "binary image processing\nmethods that I mentioned.", "start": 495.2, "duration": 3.0}, {"text": "OK.", "start": 498.2, "duration": 0.54}, {"text": "And then we do this\nfor quote, \"all poses,\"", "start": 498.74, "duration": 3.45}, {"text": "meaning that we need to\nquantize the pose space.", "start": 502.19, "duration": 2.97}, {"text": "And that's where the\nlimitation of this method", "start": 505.16, "duration": 3.0}, {"text": "comes from, which\nis that we will", "start": 508.16, "duration": 3.84}, {"text": "be limited in accuracy by the\nquantization of pose space", "start": 512.0, "duration": 3.63}, {"text": "that we have.", "start": 515.63, "duration": 2.029}, {"text": "So what are all of these\ncomponents of pose?", "start": 517.659, "duration": 5.15}, {"text": "Well, obviously translation.", "start": 522.809, "duration": 1.951}, {"text": "And when we were\nlooking at the pattern,", "start": 531.023, "duration": 1.667}, {"text": "there was a whole page.", "start": 532.69, "duration": 1.29}, {"text": "But they were\nredundant in that we", "start": 533.98, "duration": 2.91}, {"text": "had a scaling one that worked\nin a logarithmic scale,", "start": 536.89, "duration": 4.02}, {"text": "and one that worked in the\nlinear scale, and so on.", "start": 540.91, "duration": 2.68}, {"text": "But let's just list the\nones that aren't redundant.", "start": 543.59, "duration": 2.75}, {"text": "So there's going to be\ntranslation, rotation.", "start": 546.34, "duration": 4.27}, {"text": "And again, depending on the\napplication, not all of these", "start": 550.61, "duration": 2.78}, {"text": "may be necessary.", "start": 553.39, "duration": 1.81}, {"text": "Then there's scaling.", "start": 555.2, "duration": 3.14}, {"text": "Now, scaling may\nnot be necessary,", "start": 558.34, "duration": 1.98}, {"text": "because maybe your objects\nare all the same size,", "start": 560.32, "duration": 2.67}, {"text": "and maybe you're not dealing\nwith the change in size", "start": 562.99, "duration": 3.75}, {"text": "due to change in\ndistance, because you're", "start": 566.74, "duration": 2.49}, {"text": "using a telecentric\nlens so there", "start": 569.23, "duration": 2.1}, {"text": "won't be a change in size.", "start": 571.33, "duration": 1.89}, {"text": "But we allow for that.", "start": 573.22, "duration": 3.7}, {"text": "Then there's skew, where, if you\nlike, instead of rotating both", "start": 576.92, "duration": 5.99}, {"text": "x- and y-axes by the\nsame angle, we rotate one", "start": 582.91, "duration": 3.81}, {"text": "by a different angle.", "start": 586.72, "duration": 1.53}, {"text": "And again, that may\nor may not apply", "start": 588.25, "duration": 2.31}, {"text": "in a particular situation.", "start": 590.56, "duration": 1.78}, {"text": "And then we have aspect ratio.", "start": 592.34, "duration": 2.36}, {"text": "So in a way, this\nallows a certain degree", "start": 597.23, "duration": 2.3}, {"text": "of generalization.", "start": 599.53, "duration": 1.36}, {"text": "So you have a pattern.", "start": 600.89, "duration": 1.28}, {"text": "But if you want to, you can\nalso deal with the same pattern", "start": 602.17, "duration": 4.11}, {"text": "in a different size, the same\npattern that has been squashed", "start": 606.28, "duration": 4.41}, {"text": "in one direction\nand maybe extended", "start": 610.69, "duration": 1.95}, {"text": "in the other direction.", "start": 612.64, "duration": 2.32}, {"text": "So translation, two degrees of\nfreedom, rotation one in 2D,", "start": 614.96, "duration": 7.82}, {"text": "scaling one, skew one,\naspect ratio one, so a total", "start": 622.78, "duration": 4.38}, {"text": "of six independent parameters.", "start": 627.16, "duration": 3.39}, {"text": "And so we're dealing with\na potential six-dimensional", "start": 630.55, "duration": 3.6}, {"text": "space.", "start": 634.15, "duration": 0.72}, {"text": "And if you quantize\nthat even to 10,", "start": 634.87, "duration": 3.33}, {"text": "then you are up at a million.", "start": 638.2, "duration": 2.46}, {"text": "And if you quantize it to\nsomething more reasonable", "start": 640.66, "duration": 2.37}, {"text": "like 100, then you're\nup to 10 to the 12--", "start": 643.03, "duration": 4.65}, {"text": "really?", "start": 647.68, "duration": 0.57}, {"text": "Yeah, 10 to the 12,\nwhich is impractical.", "start": 648.25, "duration": 2.64}, {"text": "So in most applications,\nwe don't use all of these.", "start": 650.89, "duration": 4.42}, {"text": "By the way, if we put\nthem all together,", "start": 655.31, "duration": 4.11}, {"text": "we get a general\nlinear transformation.", "start": 659.42, "duration": 3.29}, {"text": "I'm doing this partly\nbecause when we get to 3D,", "start": 665.8, "duration": 6.24}, {"text": "it'll be handy to be\nfamiliar with these terms.", "start": 672.04, "duration": 3.015}, {"text": "So that's a general\nlinear transformation.", "start": 684.54, "duration": 2.93}, {"text": "We've got six\nparameters and affine.", "start": 687.47, "duration": 6.09}, {"text": "It's an affine transformation.", "start": 693.56, "duration": 2.31}, {"text": "And we could say, you know,\nforget this categorization.", "start": 695.87, "duration": 5.79}, {"text": "We're just going to think about\nthe transformation in term", "start": 701.66, "duration": 2.64}, {"text": "of those six coefficients,\nwhich is fine,", "start": 704.3, "duration": 3.72}, {"text": "except that for us people,\nit's easier to think about", "start": 708.02, "duration": 4.83}, {"text": "rotational, translation,\nand scaling,", "start": 712.85, "duration": 2.58}, {"text": "because the individual-- what\ndoes it mean if I change a1,1,", "start": 715.43, "duration": 3.54}, {"text": "and I keep the other\ncoefficients constant?", "start": 718.97, "duration": 3.81}, {"text": "And we'll talk some more\nabout that transformation.", "start": 722.78, "duration": 5.12}, {"text": "OK.", "start": 727.9, "duration": 0.5}, {"text": "So I want to talk next\nabout the scoring functions.", "start": 728.4, "duration": 5.56}, {"text": "So it's clear what we're doing.", "start": 733.96, "duration": 2.3}, {"text": "We create this model.", "start": 736.26, "duration": 1.8}, {"text": "We map the model\nonto a runtime image.", "start": 738.06, "duration": 4.59}, {"text": "We collect evidence.", "start": 742.65, "duration": 1.32}, {"text": "We get a score.", "start": 743.97, "duration": 1.44}, {"text": "We find the peak in\nthe score surface", "start": 745.41, "duration": 2.79}, {"text": "in that multidimensional space.", "start": 748.2, "duration": 2.02}, {"text": "And if it's above a\nthreshold, then there's", "start": 750.22, "duration": 2.3}, {"text": "a potential candidate--", "start": 752.52, "duration": 2.31}, {"text": "there could be more than\none, or there could be none.", "start": 754.83, "duration": 2.7}, {"text": "And so that's the\noverall process", "start": 760.07, "duration": 5.3}, {"text": "at the top level, where we\nexplore the whole space.", "start": 765.37, "duration": 4.11}, {"text": "And we talked about\nthe way we perform", "start": 769.48, "duration": 4.9}, {"text": "the scoring, which\nis mostly based", "start": 774.38, "duration": 1.65}, {"text": "on the direction\nof the gradient.", "start": 776.03, "duration": 2.35}, {"text": "So.", "start": 778.38, "duration": 0.5}, {"text": "But it can take into\naccount the magnitude", "start": 783.61, "duration": 3.39}, {"text": "of the gradient, as well.", "start": 787.0, "duration": 1.9}, {"text": "And we had this issue\nthat it's possible", "start": 788.9, "duration": 4.58}, {"text": "that we get a match\neven when the we're not", "start": 793.48, "duration": 5.46}, {"text": "on the right part of the\nobject, just because there's", "start": 798.94, "duration": 4.44}, {"text": "a certain range of angles\nwhich are going to be accepted.", "start": 803.38, "duration": 3.34}, {"text": "And so there's going\nto be some probability", "start": 806.72, "duration": 2.51}, {"text": "that a random gradient\nin the background texture", "start": 809.23, "duration": 5.19}, {"text": "is going to match, and we--", "start": 814.42, "duration": 2.46}, {"text": "So this was the function\nused for grading", "start": 834.11, "duration": 3.75}, {"text": "the quality of match in terms of\nthe direction of the gradient.", "start": 837.86, "duration": 3.94}, {"text": "And this was, of\ncourse, just a sample.", "start": 841.8, "duration": 1.94}, {"text": "But it's the one that's\nhighlighted in the pattern.", "start": 843.74, "duration": 3.45}, {"text": "And for this one,\nthis is 3 over 32.", "start": 847.19, "duration": 6.47}, {"text": "So there's roughly a\n10% chance that even", "start": 853.66, "duration": 3.87}, {"text": "if we plunk the probe down\nin some totally wrong place", "start": 857.53, "duration": 4.35}, {"text": "that we'll get a match.", "start": 861.88, "duration": 2.41}, {"text": "And so in the pattern, this\nis referred to as noise.", "start": 864.29, "duration": 4.61}, {"text": "A little-- I guess\nit's background noise.", "start": 868.9, "duration": 2.77}, {"text": "I don't know, it's\na little confusing.", "start": 871.67, "duration": 1.79}, {"text": "It'd be better if they\ndidn't use that term.", "start": 873.46, "duration": 3.27}, {"text": "If we have the version that\nignores polarity, then,", "start": 876.73, "duration": 5.86}, {"text": "of course, it'll be twice that.", "start": 882.59, "duration": 3.99}, {"text": "So that's one disadvantage of\nthat version of the matching", "start": 886.58, "duration": 4.97}, {"text": "function.", "start": 891.55, "duration": 1.3}, {"text": "It allows you to\nreverse the contrast.", "start": 892.85, "duration": 2.63}, {"text": "But at the same time, the\nnoise contribution goes up.", "start": 895.48, "duration": 4.72}, {"text": "OK.", "start": 900.2, "duration": 0.5}, {"text": "So then they define a\nnumber of scoring function.", "start": 900.7, "duration": 4.2}, {"text": "And they're kind of trade-offs\nbetween accuracy, speed,", "start": 904.9, "duration": 5.52}, {"text": "whether it's normalized, whether\nthe actual value of the result", "start": 910.42, "duration": 5.1}, {"text": "is meaningful, or whether it's\njust something that's bigger", "start": 915.52, "duration": 4.5}, {"text": "if you have a better match.", "start": 920.02, "duration": 2.08}, {"text": "And so let's look at that.", "start": 922.1, "duration": 1.76}, {"text": "So we've got--", "start": 923.86, "duration": 0.63}, {"text": "Now, if you remember,\nthe probe was", "start": 950.44, "duration": 4.47}, {"text": "something that had a position,\na direction, and a weight,", "start": 954.91, "duration": 4.02}, {"text": "and possibly some other stuff.", "start": 958.93, "duration": 2.14}, {"text": "But those were the top things.", "start": 961.07, "duration": 1.5}, {"text": "So here is the\nweight of the probe.", "start": 962.57, "duration": 5.0}, {"text": "So we stepped\nthrough the probes.", "start": 967.57, "duration": 1.53}, {"text": "I stepped through the probes,\nand that's the weight.", "start": 969.1, "duration": 3.96}, {"text": "And what does that do?", "start": 973.06, "duration": 1.39}, {"text": "Well, it discards things\nthat have negative weight.", "start": 974.45, "duration": 3.24}, {"text": "So just in case you've used that\ncapability, for this scoring", "start": 977.69, "duration": 4.88}, {"text": "function, you throw those out.", "start": 982.57, "duration": 2.31}, {"text": "This is R dir, the\ndirection scoring function.", "start": 988.33, "duration": 6.36}, {"text": "And it's looking at the\ndifference between the angle,", "start": 994.69, "duration": 4.77}, {"text": "the direction of the probe--\nso that's the direction", "start": 999.46, "duration": 5.79}, {"text": "of the probe--", "start": 1005.25, "duration": 1.68}, {"text": "and the gradient at the position\nthat the probe is placed in,", "start": 1006.93, "duration": 8.34}, {"text": "position--", "start": 1015.27, "duration": 0.84}, {"text": "And big D is just a\nfunction that gives you", "start": 1022.28, "duration": 2.61}, {"text": "the arctangent of ey over ex.", "start": 1024.89, "duration": 4.11}, {"text": "It's the direction of the\ngradient in the runtime image.", "start": 1029.0, "duration": 3.069}, {"text": "So let's look at that.", "start": 1032.069, "duration": 1.951}, {"text": "So what happened to the\nother components of the pose?", "start": 1034.02, "duration": 4.88}, {"text": "Well, at this point we're\ndealing with compiled probes.", "start": 1038.9, "duration": 3.105}, {"text": "So here we're just\nvarying the translation.", "start": 1046.63, "duration": 5.31}, {"text": "We're only varying\nthe translation a.", "start": 1051.94, "duration": 3.75}, {"text": "We've already mapped\nthe probes according", "start": 1055.69, "duration": 3.96}, {"text": "to the other\ncomponents of the pose.", "start": 1059.65, "duration": 4.14}, {"text": "Yeah?", "start": 1063.79, "duration": 1.11}, {"text": "Oh, that's a vertical bar,\nmeaning absolute value.", "start": 1064.9, "duration": 4.65}, {"text": "Sorry.", "start": 1069.55, "duration": 2.31}, {"text": "And in some sense, that's just\nto take account of the fact", "start": 1071.86, "duration": 3.57}, {"text": "that this wraps around.", "start": 1075.43, "duration": 1.86}, {"text": "And we could have done\nthat some other way,", "start": 1077.29, "duration": 1.89}, {"text": "like mod 360 or something.", "start": 1079.18, "duration": 4.96}, {"text": "OK.", "start": 1084.14, "duration": 1.29}, {"text": "And this version is normalized\nin that we divide through", "start": 1085.43, "duration": 8.72}, {"text": "by the sum of weights, such\nthat if we get a perfect match", "start": 1094.15, "duration": 5.13}, {"text": "the result will be 1.", "start": 1099.28, "duration": 1.71}, {"text": "And so the absolute\nvalue of this score,", "start": 1100.99, "duration": 2.67}, {"text": "of this particular\nscore, has a meaning.", "start": 1103.66, "duration": 3.42}, {"text": "It's not just that\nit gets bigger", "start": 1107.08, "duration": 1.5}, {"text": "if you have a better score.", "start": 1108.58, "duration": 2.88}, {"text": "And this is used in the\ncoarse step of the algorithm.", "start": 1115.38, "duration": 4.89}, {"text": "What else can we say about it?", "start": 1123.28, "duration": 1.89}, {"text": "Then there's a second version.", "start": 1129.91, "duration": 4.49}, {"text": "What's the other version?", "start": 1134.4, "duration": 1.2}, {"text": "It's 1b.", "start": 1135.6, "duration": 3.75}, {"text": "Sorry, this is S1a.", "start": 1139.35, "duration": 2.22}, {"text": "This is S1b.", "start": 1141.57, "duration": 2.31}, {"text": "And this one doesn't\nmultiply by the weight.", "start": 1143.88, "duration": 3.75}, {"text": "And this is a slightly\nweird notation,", "start": 1151.78, "duration": 2.01}, {"text": "but it's kind of clear\nonce you think about it.", "start": 1153.79, "duration": 6.76}, {"text": "So this is just a\npredicate that computes", "start": 1163.68, "duration": 2.6}, {"text": "whether the weight\nis greater than 0,", "start": 1166.28, "duration": 3.12}, {"text": "whether it's positive weight.", "start": 1169.4, "duration": 1.92}, {"text": "And it's 1 if that's the case\nand 0 if it's not the case.", "start": 1171.32, "duration": 5.38}, {"text": "So that's just a\nfunny way of saying", "start": 1176.7, "duration": 1.82}, {"text": "we're only going\nto process probes", "start": 1178.52, "duration": 3.9}, {"text": "that have a positive weight.", "start": 1182.42, "duration": 1.65}, {"text": "And the advantage of that is we\ndon't need that multiplication.", "start": 1184.07, "duration": 3.84}, {"text": "And so it's cheaper\nthan the other one.", "start": 1187.91, "duration": 3.54}, {"text": "And so this is faster.", "start": 1194.61, "duration": 4.12}, {"text": "We haven't done anything with\nthat quote, \"noise term.\"", "start": 1201.99, "duration": 6.21}, {"text": "So when we get to the\npreferred embodiment--", "start": 1208.2, "duration": 5.92}, {"text": "So it's very similar to 1b,\nexcept that now we're saying,", "start": 1252.77, "duration": 6.24}, {"text": "well, if we apply this in a\nrandom place in the image,", "start": 1259.01, "duration": 3.26}, {"text": "we'll get a non-zero\nresult because", "start": 1262.27, "duration": 3.15}, {"text": "of this random matching.", "start": 1265.42, "duration": 2.1}, {"text": "And so by subtracting\nout that component N,", "start": 1267.52, "duration": 3.93}, {"text": "which is an estimate of the\nnumber that will be matched", "start": 1271.45, "duration": 3.54}, {"text": "randomly, we can improve\nthe result. Yeah?", "start": 1274.99, "duration": 4.83}, {"text": "AUDIENCE: What's the D function?", "start": 1279.82, "duration": 2.8}, {"text": "BERTHOLD HORN:\nThis function, OK.", "start": 1282.62, "duration": 1.47}, {"text": "So D is the function\nthat tells you", "start": 1284.09, "duration": 3.57}, {"text": "what the gradient direction\nis in the runtime image.", "start": 1287.66, "duration": 14.475}, {"text": "Gradient-- sorry, gradient\ndirection at a plus p i.", "start": 1306.78, "duration": 9.8}, {"text": "So I didn't underline\nthese, but they are vectors.", "start": 1316.58, "duration": 3.84}, {"text": "a is a translation, and\np i is a vector that's", "start": 1320.42, "duration": 3.66}, {"text": "the position of that probe, so.", "start": 1324.08, "duration": 3.74}, {"text": "And so then when I\nsubtract the little di,", "start": 1327.82, "duration": 3.99}, {"text": "get the error in the direction.", "start": 1331.81, "duration": 2.05}, {"text": "And then I use that to\naccess this function", "start": 1333.86, "duration": 3.2}, {"text": "to decide how much to penalize\nthe result based on that error.", "start": 1337.06, "duration": 7.74}, {"text": "OK.", "start": 1347.97, "duration": 0.5}, {"text": "So this one now has the\nfeature that if you're", "start": 1348.47, "duration": 5.67}, {"text": "throwing the probe--", "start": 1354.14, "duration": 1.53}, {"text": "throwing the model\ndown at a random place,", "start": 1355.67, "duration": 2.1}, {"text": "on a random texture,\nthe answer will", "start": 1357.77, "duration": 2.31}, {"text": "tend to be 0, because\nwe've taken out", "start": 1360.08, "duration": 3.48}, {"text": "the random coincidental matches.", "start": 1363.56, "duration": 4.2}, {"text": "And so unlike this\none, where, yes,", "start": 1367.76, "duration": 4.74}, {"text": "if you have a perfect match\nyou get a 1, but if it's just", "start": 1372.5, "duration": 3.51}, {"text": "garbage background, you don't\nget a 0 you get whatever N is.", "start": 1376.01, "duration": 4.9}, {"text": "So this is slightly\nbetter in that respect.", "start": 1380.91, "duration": 3.68}, {"text": "It's slightly more\ncomputation not much.", "start": 1384.59, "duration": 3.04}, {"text": "So that's the quote,\n\"preferred\" method.", "start": 1387.63, "duration": 2.61}, {"text": "And if your implementation\ndoesn't use that,", "start": 1390.24, "duration": 3.125}, {"text": "that doesn't help you\nbecause they don't", "start": 1393.365, "duration": 2.775}, {"text": "say that you have to use that.", "start": 1396.14, "duration": 1.59}, {"text": "They give you\nother alternatives.", "start": 1397.73, "duration": 1.71}, {"text": "And they just say that,\nwell, this is the one", "start": 1399.44, "duration": 2.16}, {"text": "that we think is the best.", "start": 1401.6, "duration": 1.27}, {"text": "So OK.", "start": 1402.87, "duration": 3.14}, {"text": "So then we get as S2.", "start": 1406.01, "duration": 4.71}, {"text": "Now, this one is not normalized.", "start": 1413.9, "duration": 2.49}, {"text": "So it will not--", "start": 1416.39, "duration": 6.05}, {"text": "its absolute value will\nnot be significant.", "start": 1422.44, "duration": 2.65}, {"text": "It's just going to be larger\nif you have a better match.", "start": 1425.09, "duration": 2.855}, {"text": "And so what's this?", "start": 1433.65, "duration": 2.33}, {"text": "So this is similar to this\nfunction, M of a plus p", "start": 1435.98, "duration": 5.715}, {"text": "i is the gradient magnitude,\nwhich we haven't used so far.", "start": 1441.695, "duration": 11.725}, {"text": "So this one actually takes into\naccount the gradient magnitude,", "start": 1453.42, "duration": 3.33}, {"text": "and it uses the\nmagnitude directly.", "start": 1456.75, "duration": 2.49}, {"text": "And it means there's\nanother multiplication.", "start": 1464.32, "duration": 4.08}, {"text": "And this version\nis used in the--", "start": 1468.4, "duration": 2.97}, {"text": "first of all, it's\nnot normalized", "start": 1471.37, "duration": 3.6}, {"text": "and is used in the\nfine scan step.", "start": 1474.97, "duration": 3.311}, {"text": "And then finally--\nso a lot of this", "start": 1482.9, "duration": 5.54}, {"text": "is used in getting to a\npotential candidate solution.", "start": 1488.44, "duration": 6.9}, {"text": "And then there's a\nfine scanning step--", "start": 1495.34, "duration": 3.78}, {"text": "there's a scoring step that\ngives us an actual value.", "start": 1499.12, "duration": 4.32}, {"text": "And this one is more\nwork to compute.", "start": 1510.98, "duration": 2.565}, {"text": "So this one, again,\nis normalized.", "start": 1519.97, "duration": 1.82}, {"text": "And it uses the magnitude\nof the gradient,", "start": 1524.58, "duration": 4.13}, {"text": "but it uses it\naccording to the scoring", "start": 1528.71, "duration": 2.94}, {"text": "function that we defined,\nwhich was that it saturates.", "start": 1531.65, "duration": 8.55}, {"text": "So that's the direction\nscoring function,", "start": 1540.2, "duration": 2.94}, {"text": "and this is the magnitude\nscoring function.", "start": 1543.14, "duration": 2.745}, {"text": "So in S2 a, we would just\nkeep on going up, multiplying", "start": 1550.44, "duration": 5.75}, {"text": "by the magnitude.", "start": 1556.19, "duration": 1.29}, {"text": "In that one, we limit\nthe contribution.", "start": 1557.48, "duration": 3.94}, {"text": "So you don't have one\nsingle very good edge", "start": 1561.42, "duration": 4.22}, {"text": "dominating everything else.", "start": 1565.64, "duration": 3.37}, {"text": "OK.", "start": 1569.01, "duration": 0.5}, {"text": "And there are lots\nof details on how", "start": 1569.51, "duration": 3.09}, {"text": "to make this run fast and so\non, which we won't go into.", "start": 1572.6, "duration": 5.52}, {"text": "I do want to talk about a\ncouple of interesting points.", "start": 1578.12, "duration": 3.76}, {"text": "Another thing we're not going to\ntalk about is the granularity.", "start": 1581.88, "duration": 2.9}, {"text": "So we mentioned this, that\nwe might work at a scale", "start": 1584.78, "duration": 6.36}, {"text": "where these computations are\ncheaper as long as we can get", "start": 1591.14, "duration": 4.54}, {"text": "a satisfactory\nresult. And mind you,", "start": 1595.68, "duration": 3.365}, {"text": "what's a satisfactory\nresult here", "start": 1599.045, "duration": 1.815}, {"text": "is very different from\nsome machine vision, where", "start": 1600.86, "duration": 4.515}, {"text": "if you can improve the\nrecognition accuracy from 71%", "start": 1605.375, "duration": 5.715}, {"text": "to 73%, you've got a paper.", "start": 1611.09, "duration": 2.67}, {"text": "This is more like this has\nto work 99.9% of the time.", "start": 1613.76, "duration": 5.67}, {"text": "And so granularity is\ndetermined basically", "start": 1619.43, "duration": 3.02}, {"text": "by decreasing the\nresolution until it doesn't", "start": 1622.45, "duration": 3.6}, {"text": "work well enough anymore.", "start": 1626.05, "duration": 2.82}, {"text": "So if for your task you\nknow what \"well enough\" is,", "start": 1628.87, "duration": 3.6}, {"text": "you can perform that task.", "start": 1632.47, "duration": 2.1}, {"text": "And basically, for\neach granularity", "start": 1634.57, "duration": 5.19}, {"text": "you have to go through\nthe whole process.", "start": 1639.76, "duration": 1.89}, {"text": "You have to build the\nmodel, because the probes", "start": 1641.65, "duration": 4.29}, {"text": "will be different depending\non the resolution.", "start": 1645.94, "duration": 3.24}, {"text": "And then you run through, and\nyou see how well it works.", "start": 1649.18, "duration": 5.86}, {"text": "Yeah?", "start": 1655.04, "duration": 0.5}, {"text": "AUDIENCE: When wouldn't\nyou want to normalize?", "start": 1655.54, "duration": 3.065}, {"text": "BERTHOLD HORN: Mostly\nwhen you're in a hurry.", "start": 1658.605, "duration": 1.875}, {"text": "So it's just a\ncomputational issue.", "start": 1660.48, "duration": 3.776}, {"text": "If you're at a part\nof the computation", "start": 1664.256, "duration": 3.114}, {"text": "where you have to do it\nfor every possible pose,", "start": 1667.37, "duration": 2.46}, {"text": "you might want to\nsave that step.", "start": 1669.83, "duration": 2.13}, {"text": "If you at the end, where\nyou near the correct answer", "start": 1671.96, "duration": 2.79}, {"text": "and you only have to do it a few\ntimes, then you can normalize.", "start": 1674.75, "duration": 8.98}, {"text": "OK.", "start": 1683.73, "duration": 0.99}, {"text": "So the granularity-- and they\nhave a very sophisticated", "start": 1684.72, "duration": 3.51}, {"text": "method for doing this.", "start": 1688.23, "duration": 1.17}, {"text": "And I think we've seen enough\nof that part of the pattern,", "start": 1689.4, "duration": 4.68}, {"text": "so I'm not going\nto go through it.", "start": 1694.08, "duration": 2.38}, {"text": "But it is, obviously,\nin practical terms", "start": 1696.46, "duration": 3.35}, {"text": "an important component,\nbecause you want this", "start": 1699.81, "duration": 2.76}, {"text": "to run as fast as possible.", "start": 1702.57, "duration": 2.25}, {"text": "If you're at Amazon, and you\nwatch the boxes come down", "start": 1704.82, "duration": 3.03}, {"text": "the conveyor belt, and it's\nreading all kinds of stuff", "start": 1707.85, "duration": 2.46}, {"text": "off the box and determining\nits position and orientation,", "start": 1710.31, "duration": 2.97}, {"text": "you realize that you\ndon't have a lot of time", "start": 1713.28, "duration": 2.55}, {"text": "to do the computation.", "start": 1715.83, "duration": 2.28}, {"text": "These things run at a\nhundred frames a second.", "start": 1718.11, "duration": 8.63}, {"text": "And all of this\ncomputation can be", "start": 1726.74, "duration": 1.8}, {"text": "done in that time in a\nrelatively cheap processor.", "start": 1728.54, "duration": 7.58}, {"text": "OK.", "start": 1740.67, "duration": 0.69}, {"text": "But I do want to\ntalk about a couple", "start": 1741.36, "duration": 2.01}, {"text": "of minor issues that\nmay not be obvious.", "start": 1743.37, "duration": 2.73}, {"text": "One of them is getting\nthe directions right.", "start": 1746.1, "duration": 5.06}, {"text": "So we're really focused\non gradient directions.", "start": 1751.16, "duration": 2.5}, {"text": "So we need to make\nsure that when", "start": 1753.66, "duration": 3.14}, {"text": "we perform these\ntransformations that we", "start": 1756.8, "duration": 3.0}, {"text": "transform the gradient\ndirection correctly.", "start": 1759.8, "duration": 2.82}, {"text": "And so here's the issue.", "start": 1762.62, "duration": 2.11}, {"text": "So here's my edge.", "start": 1764.73, "duration": 2.45}, {"text": "This line is the iso fold.", "start": 1767.18, "duration": 1.92}, {"text": "And here's my gradient,\nwhich, of course, is", "start": 1769.1, "duration": 5.12}, {"text": "perpendicular to the iso fold.", "start": 1774.22, "duration": 2.31}, {"text": "And now suppose that I\nhave an operation that", "start": 1776.53, "duration": 7.23}, {"text": "changes the aspect ratio.", "start": 1783.76, "duration": 2.79}, {"text": "So I suppose I squash it.", "start": 1786.55, "duration": 1.4}, {"text": "So I'm changing\nthe aspect ratio.", "start": 1790.99, "duration": 1.83}, {"text": "Then of course,\nthis line is going", "start": 1792.82, "duration": 1.95}, {"text": "to have a lower slope, because\nthe top is moving down,", "start": 1794.77, "duration": 6.621}, {"text": "the bottom is moving up.", "start": 1801.391, "duration": 2.269}, {"text": "So OK.", "start": 1803.66, "duration": 1.85}, {"text": "And hmm, the gradient also is\ngoing to have a lower slope.", "start": 1805.51, "duration": 6.0}, {"text": "Right, so it's no longer\nperpendicular to the iso fold.", "start": 1811.51, "duration": 4.79}, {"text": "So that is kind of obvious.", "start": 1816.3, "duration": 3.72}, {"text": "And now if you're\ntransforming x and y,", "start": 1820.02, "duration": 2.46}, {"text": "it may be that the derivatives\nwith respect to x and y", "start": 1822.48, "duration": 3.33}, {"text": "transform in a different way.", "start": 1825.81, "duration": 2.29}, {"text": "And so what do we do about this?", "start": 1828.1, "duration": 2.58}, {"text": "Of course, this doesn't\naffect translation.", "start": 1830.68, "duration": 2.88}, {"text": "This doesn't happen\nfor translation,", "start": 1833.56, "duration": 1.82}, {"text": "doesn't happen for rotation.", "start": 1835.38, "duration": 3.37}, {"text": "You rotate, and the\nright angle is preserved.", "start": 1838.75, "duration": 3.61}, {"text": "Doesn't happen for scaling.", "start": 1842.36, "duration": 1.43}, {"text": "But it does happen\nfor the other two.", "start": 1843.79, "duration": 2.14}, {"text": "So how do we deal with this?", "start": 1845.93, "duration": 2.58}, {"text": "Well, we have the\ngradient direction.", "start": 1848.51, "duration": 4.2}, {"text": "That's our input.", "start": 1852.71, "duration": 1.46}, {"text": "That's what the box we have in\nfront of all of this computes.", "start": 1854.17, "duration": 5.47}, {"text": "OK.", "start": 1859.64, "duration": 0.5}, {"text": "So that's where we start.", "start": 1860.14, "duration": 1.32}, {"text": "And now all we need to do\nis compute the iso fold.", "start": 1861.46, "duration": 3.96}, {"text": "So from the gradient\ndirection, we get the iso fold.", "start": 1865.42, "duration": 5.31}, {"text": "Then we transform that.", "start": 1870.73, "duration": 3.08}, {"text": "And then we construct\nsomething at right angles", "start": 1873.81, "duration": 2.4}, {"text": "to the iso fold.", "start": 1876.21, "duration": 2.58}, {"text": "So here's our new\ngradient direction.", "start": 1878.79, "duration": 2.91}, {"text": "So the solutions\nare kind of obvious,", "start": 1881.7, "duration": 2.76}, {"text": "but it's something that\none might easily forget.", "start": 1884.46, "duration": 4.56}, {"text": "How expensive is it?", "start": 1889.02, "duration": 1.62}, {"text": "Well, not terribly, because\n90-degree rotations are simple.", "start": 1890.64, "duration": 4.26}, {"text": "So cosine of 90 is 0, sine\nof 90 is 1, minus sign.", "start": 1894.9, "duration": 5.58}, {"text": "So they just-- we don't even\nneed to do multiplication.", "start": 1900.48, "duration": 3.99}, {"text": "We just interchange x and y and\nflip the sign of one of them.", "start": 1904.47, "duration": 3.51}, {"text": "And then after the\ntransformation,", "start": 1907.98, "duration": 1.71}, {"text": "we have to do the\ninverse, which is", "start": 1909.69, "duration": 2.31}, {"text": "the transpose of that matrix.", "start": 1912.0, "duration": 2.67}, {"text": "So again, we just\ninterchange x and y", "start": 1914.67, "duration": 3.22}, {"text": "and flip the sign of one\nof them and we're done.", "start": 1917.89, "duration": 2.0}, {"text": "But it's something\nthat's easy to forget.", "start": 1919.89, "duration": 2.34}, {"text": "And until you run into\nthe last two operations,", "start": 1922.23, "duration": 3.6}, {"text": "it doesn't matter.", "start": 1925.83, "duration": 2.6}, {"text": "OK.", "start": 1928.43, "duration": 0.5}, {"text": "Another thing which was\nalmost like an add-on", "start": 1928.93, "duration": 4.35}, {"text": "that they thought of, because\nit's not discussed much", "start": 1933.28, "duration": 3.99}, {"text": "in the specification but\nit shows up in the claims--", "start": 1937.27, "duration": 3.9}, {"text": "and there's some\ndiscussion at the end", "start": 1941.17, "duration": 1.92}, {"text": "of this, which is inspection.", "start": 1943.09, "duration": 1.86}, {"text": "So first of all, the main\nfocus here is figuring out", "start": 1950.27, "duration": 3.09}, {"text": "where something is--", "start": 1953.36, "duration": 1.53}, {"text": "position, pose.", "start": 1954.89, "duration": 2.25}, {"text": "A second aspect is recognition.", "start": 1957.14, "duration": 3.75}, {"text": "And how does that work?", "start": 1960.89, "duration": 1.42}, {"text": "Well, you just\nlook at the score.", "start": 1962.31, "duration": 2.6}, {"text": "If it's close to\n1, you've got it", "start": 1964.91, "duration": 2.91}, {"text": "and again, this may occur\nin more than one place", "start": 1967.82, "duration": 2.37}, {"text": "in the image.", "start": 1970.19, "duration": 1.32}, {"text": "If you-- typically,\n\"recognition\"", "start": 1971.51, "duration": 2.638}, {"text": "means that you're\ndistinguishing different things", "start": 1974.148, "duration": 2.042}, {"text": "like cats and dogs.", "start": 1976.19, "duration": 1.65}, {"text": "And so how does that work?", "start": 1977.84, "duration": 2.38}, {"text": "Well, you have a\nlibrary of models.", "start": 1980.22, "duration": 2.66}, {"text": "Suppose that you have\ndifferent types of screw heads,", "start": 1982.88, "duration": 2.73}, {"text": "then there's a model\nfor each of them.", "start": 1985.61, "duration": 3.72}, {"text": "You run this process, and you\nsee where there is a match.", "start": 1989.33, "duration": 4.38}, {"text": "And if necessary, you can\ncompare the match score", "start": 1993.71, "duration": 3.87}, {"text": "to figure out what\ntype exactly it is.", "start": 1997.58, "duration": 3.48}, {"text": "So that's recognition\nand position.", "start": 2001.06, "duration": 3.84}, {"text": "And they also talk\nabout inspections.", "start": 2004.9, "duration": 1.98}, {"text": "So inspection is based here\non a fractional match--", "start": 2006.88, "duration": 4.465}, {"text": "runtime image.", "start": 2025.63, "duration": 4.55}, {"text": "OK.", "start": 2030.18, "duration": 0.5}, {"text": "So the model consists of probes.", "start": 2030.68, "duration": 3.42}, {"text": "We put the probes\ndown on the image.", "start": 2034.1, "duration": 1.98}, {"text": "And for each place, we\ncan determine whether it's", "start": 2036.08, "duration": 3.69}, {"text": "a reasonable match or not.", "start": 2039.77, "duration": 1.63}, {"text": "And in the process, we can\ncalculate a percentage.", "start": 2041.4, "duration": 4.07}, {"text": "And if the object is\npartly obscured, well,", "start": 2045.47, "duration": 3.269}, {"text": "then that fraction\nwill be lower.", "start": 2048.739, "duration": 2.46}, {"text": "If, say, you're looking at\na gear and some of its teeth", "start": 2051.199, "duration": 3.361}, {"text": "are missing, then\nyou'll get a match,", "start": 2054.56, "duration": 2.86}, {"text": "but the score won't be 1.", "start": 2057.42, "duration": 2.06}, {"text": "And so that's one direction.", "start": 2059.48, "duration": 2.73}, {"text": "The other one is--", "start": 2062.21, "duration": 0.915}, {"text": "so we can look at\nthe runtime image,", "start": 2076.09, "duration": 4.319}, {"text": "and see where it has edges, and\nthen discover how many of those", "start": 2080.409, "duration": 6.496}, {"text": "are actually matching\nsomething in the model.", "start": 2086.905, "duration": 5.33}, {"text": "Now of course, if\nthere's clutter", "start": 2092.235, "duration": 1.375}, {"text": "and there's some\nbackground, then there", "start": 2093.61, "duration": 2.4}, {"text": "would be a lot of edges that\nwill not match the model.", "start": 2096.01, "duration": 2.55}, {"text": "But that's also\nuseful information.", "start": 2098.56, "duration": 1.99}, {"text": "So that's a way of measuring\nclutter, basically that.", "start": 2100.55, "duration": 3.59}, {"text": "Yes.", "start": 2104.14, "duration": 0.6}, {"text": "And there are some more\nthings to say about that,", "start": 2104.74, "duration": 2.2}, {"text": "but that's the basic idea.", "start": 2106.94, "duration": 3.55}, {"text": "OK.", "start": 2110.49, "duration": 2.19}, {"text": "A couple of more things\nI want to do here,", "start": 2112.68, "duration": 3.24}, {"text": "partly in preparation for\nthe 3D work we'll be doing.", "start": 2115.92, "duration": 3.93}, {"text": "And that's to elaborate\na little bit more", "start": 2119.85, "duration": 3.15}, {"text": "on these transformations\nand to vaccinate you", "start": 2123.0, "duration": 6.7}, {"text": "against some bad\nideas, hopefully.", "start": 2129.7, "duration": 3.75}, {"text": "So let's go 3D but in a\nkind of simplified world.", "start": 2137.41, "duration": 8.64}, {"text": "So we know already\na lot about that.", "start": 2146.05, "duration": 2.6}, {"text": "We know about\nperspective projection.", "start": 2148.65, "duration": 3.22}, {"text": "So let's think about the\nprojection of a plane.", "start": 2151.87, "duration": 2.555}, {"text": "And this comes up a lot.", "start": 2161.1, "duration": 2.88}, {"text": "I mean, we could be talking\nabout tabletop, conveyor belt,", "start": 2163.98, "duration": 7.5}, {"text": "integrated circuit,\nprinted circuit board.", "start": 2171.48, "duration": 3.12}, {"text": "And it's all in 3D.", "start": 2174.6, "duration": 1.89}, {"text": "Now, we can carefully line\nup the optics and so on", "start": 2176.49, "duration": 3.81}, {"text": "so that we get an orthographic\nprojection, in effect.", "start": 2180.3, "duration": 5.64}, {"text": "Or we can deal with\nthe real full 3D world.", "start": 2185.94, "duration": 6.61}, {"text": "Could also be the road\nin front of a car.", "start": 2192.55, "duration": 4.71}, {"text": "Lots of examples\nof flat surfaces.", "start": 2197.26, "duration": 2.97}, {"text": "OK, so two things.", "start": 2200.23, "duration": 3.22}, {"text": "One thing we remember is good\nold perspective projection.", "start": 2203.45, "duration": 9.28}, {"text": "And the other\nthing is that there", "start": 2212.73, "duration": 3.33}, {"text": "is a camera coordinate\nsystem where this applies.", "start": 2216.06, "duration": 3.15}, {"text": "And then there's other\ncoordinate systems.", "start": 2219.21, "duration": 3.12}, {"text": "Let's call them world\ncoordinate system.", "start": 2222.33, "duration": 1.98}, {"text": "And what's the relationship?", "start": 2224.31, "duration": 6.16}, {"text": "Well, there's going\nto be a translation.", "start": 2230.47, "duration": 1.92}, {"text": "The camera has its\ncoordinate system", "start": 2232.39, "duration": 2.31}, {"text": "has its origin at the\ncenter of projection.", "start": 2234.7, "duration": 3.6}, {"text": "And the world has wherever.", "start": 2238.3, "duration": 2.22}, {"text": "If it's a robot arm, it might\nbe the base of the robot arm.", "start": 2240.52, "duration": 3.33}, {"text": "If it's a box, it might\nbe a corner of a box.", "start": 2243.85, "duration": 3.3}, {"text": "And then there's a rotation,\nso in world coordinates", "start": 2247.15, "duration": 11.72}, {"text": "and in camera coordinates.", "start": 2258.87, "duration": 2.07}, {"text": "And we talked about how that\nsimple formula for perspective", "start": 2260.94, "duration": 3.48}, {"text": "projection only applies\nif we're dealing", "start": 2264.42, "duration": 2.25}, {"text": "with a camera-centric\ncoordinate system.", "start": 2266.67, "duration": 4.44}, {"text": "OK.", "start": 2271.11, "duration": 0.5}, {"text": "And this matrix here is\nan orthonormal matrix", "start": 2275.35, "duration": 11.42}, {"text": "that encodes the rotation.", "start": 2286.77, "duration": 1.545}, {"text": "And we'll talk quite a\nbit about that later.", "start": 2296.15, "duration": 4.23}, {"text": "OK.", "start": 2300.38, "duration": 0.54}, {"text": "Now, what I want is the\ntransformation from world", "start": 2300.92, "duration": 5.25}, {"text": "coordinates, object coordinates,\nto image coordinates.", "start": 2306.17, "duration": 4.71}, {"text": "And so I combine these two.", "start": 2310.88, "duration": 2.11}, {"text": "So what I'm going to get--", "start": 2312.99, "duration": 1.7}, {"text": "So this is just multiplying\nout that matrix.", "start": 2339.76, "duration": 2.705}, {"text": "And this is, again,\nthe same thing.", "start": 2362.57, "duration": 1.8}, {"text": "So as we know,\nperspective projection", "start": 2367.38, "duration": 3.93}, {"text": "has this nasty property\nthat it involves", "start": 2371.31, "duration": 2.43}, {"text": "a division that's nonlinear,\nand it's kind of a bit messy.", "start": 2373.74, "duration": 6.19}, {"text": "So that's a general case.", "start": 2379.93, "duration": 1.46}, {"text": "And we'll find ways\nof dealing with that.", "start": 2381.39, "duration": 3.61}, {"text": "But I want to look at\nthe particular case", "start": 2385.0, "duration": 1.88}, {"text": "where the thing we're\nlooking at is planar.", "start": 2386.88, "duration": 3.96}, {"text": "And that means that we can\nerect our coordinate system", "start": 2390.84, "duration": 3.39}, {"text": "in that object.", "start": 2394.23, "duration": 0.735}, {"text": "Here's our planar surface.", "start": 2397.81, "duration": 1.83}, {"text": "Rather than pick some arbitrary\ncoordinate system, let's", "start": 2403.155, "duration": 3.435}, {"text": "pick one where z is 0 so we only\nhave two of these coordinates", "start": 2406.59, "duration": 6.79}, {"text": "to deal with.", "start": 2413.38, "duration": 0.6}, {"text": "So what we're sort\nof doing is we're", "start": 2425.4, "duration": 2.51}, {"text": "kind of halfway\nbetween 2D and 3D,", "start": 2427.91, "duration": 2.61}, {"text": "because we started off looking\nat a 2D surface embedded in 3D.", "start": 2430.52, "duration": 6.63}, {"text": "And where we're going is some\nmapping from the 2D surface", "start": 2437.15, "duration": 3.99}, {"text": "out there into the 2D\nsurface and the image.", "start": 2441.14, "duration": 2.86}, {"text": "Yes?", "start": 2444.0, "duration": 0.5}, {"text": "AUDIENCE: Where does the e w\ncome from, the top-- numerator?", "start": 2444.5, "duration": 3.944}, {"text": "BERTHOLD HORN:\nE-- sorry, which--", "start": 2448.444, "duration": 2.186}, {"text": "e w?", "start": 2450.63, "duration": 1.02}, {"text": "AUDIENCE: Oh, yeah,\nnext to the yw is a e w.", "start": 2451.65, "duration": 3.768}, {"text": "Or is that a z?", "start": 2455.418, "duration": 1.425}, {"text": "BERTHOLD HORN: Oh, sorry.", "start": 2456.843, "duration": 1.042}, {"text": "Oh, here?", "start": 2462.35, "duration": 0.66}, {"text": "AUDIENCE: Up top.", "start": 2463.01, "duration": 1.26}, {"text": "BERTHOLD HORN: Oh, sorry.", "start": 2464.27, "duration": 1.62}, {"text": "That's my bad writing, yeah.", "start": 2465.89, "duration": 3.385}, {"text": "zw.", "start": 2469.275, "duration": 2.625}, {"text": "OK, and that's the\none that's actually 0.", "start": 2471.9, "duration": 2.55}, {"text": "So that, when I do that\nmatrix multiplication then,", "start": 2474.45, "duration": 3.51}, {"text": "that means that I can ignore\nthe third column, because it's", "start": 2477.96, "duration": 4.05}, {"text": "going to get multiplied by zw.", "start": 2482.01, "duration": 3.48}, {"text": "And so I can make\nthat anything I want.", "start": 2485.49, "duration": 4.8}, {"text": "So this column here doesn't\nmatter, because it's", "start": 2490.29, "duration": 3.24}, {"text": "going to get multiplied by zw.", "start": 2493.53, "duration": 2.11}, {"text": "And then I can kind\nof conveniently", "start": 2498.93, "duration": 3.12}, {"text": "fold in the translation.", "start": 2502.05, "duration": 1.78}, {"text": "So one of the\nannoying things about", "start": 2503.83, "duration": 1.67}, {"text": "Euclidean transformations,\nreal-world movement,", "start": 2505.5, "duration": 3.66}, {"text": "is there's rotation and\nthere's translation.", "start": 2509.16, "duration": 2.43}, {"text": "And it's hard to treat\nthem as one thing.", "start": 2511.59, "duration": 2.52}, {"text": "It'd be nice to have\nnotation, some magic thing.", "start": 2514.11, "duration": 7.54}, {"text": "Let's call it a glob.", "start": 2521.65, "duration": 1.19}, {"text": "So the glob, you multiply\nit by your vector,", "start": 2522.84, "duration": 5.07}, {"text": "and out comes another vector.", "start": 2527.91, "duration": 2.4}, {"text": "And that single thing encodes\nboth translation and rotation.", "start": 2530.31, "duration": 3.67}, {"text": "So the way we've written it\nthere, we've split those two.", "start": 2533.98, "duration": 3.5}, {"text": "Well, it'd be really\nnice to have them", "start": 2537.48, "duration": 2.4}, {"text": "as a single operation--\nmultiplication of something,", "start": 2539.88, "duration": 3.66}, {"text": "for example.", "start": 2543.54, "duration": 1.05}, {"text": "Well, we can do that here\nbecause if we drop out", "start": 2544.59, "duration": 3.03}, {"text": "that third column, we can\nbring in the x0, y0, and z0,", "start": 2547.62, "duration": 5.85}, {"text": "and we end up with--", "start": 2553.47, "duration": 3.63}, {"text": "let's see.", "start": 2557.1, "duration": 0.69}, {"text": "So we've got--", "start": 2557.79, "duration": 2.58}, {"text": "I called it r1,1.", "start": 2560.37, "duration": 17.65}, {"text": "And--", "start": 2578.02, "duration": 0.5}, {"text": "So you see what we've done here.", "start": 2584.49, "duration": 2.4}, {"text": "We've taken\nadvantage of the fact", "start": 2586.89, "duration": 1.59}, {"text": "that we don't need that\nthird column for zw,", "start": 2588.48, "duration": 3.09}, {"text": "because zw will be 0.", "start": 2591.57, "duration": 1.74}, {"text": "And then we can\nfold that addition", "start": 2593.31, "duration": 3.78}, {"text": "in by just multiplying\nthat last column by 1.", "start": 2597.09, "duration": 4.8}, {"text": "So in this particular\ncase, where", "start": 2601.89, "duration": 3.99}, {"text": "we're dealing with a\nplanar surface out in 3D,", "start": 2605.88, "duration": 3.84}, {"text": "we can fold rotation\nand translation", "start": 2609.72, "duration": 3.3}, {"text": "into a single matrix.", "start": 2613.02, "duration": 4.02}, {"text": "And let-- call\nthis matrix T. Let", "start": 2617.04, "duration": 4.82}, {"text": "me call that matrix up there R.", "start": 2621.86, "duration": 4.29}, {"text": "So R has some special properties\nthat we'll talk about later.", "start": 2626.15, "duration": 5.37}, {"text": "One of them is that\nit's orthonormal.", "start": 2631.52, "duration": 2.73}, {"text": "And that means if you take its\ntranspose and multiply it by R,", "start": 2634.25, "duration": 4.68}, {"text": "you get the identity matrix.", "start": 2638.93, "duration": 1.75}, {"text": "And the other one is that\nits determinant is plus 1.", "start": 2640.68, "duration": 3.35}, {"text": "T doesn't have those properties.", "start": 2648.77, "duration": 2.97}, {"text": "So that's very important,\nbecause how many degrees", "start": 2651.74, "duration": 5.96}, {"text": "of freedom do we have?", "start": 2657.7, "duration": 1.39}, {"text": "Well, in 2D it was a little\neasier to figure out.", "start": 2659.09, "duration": 2.36}, {"text": "We had two for translation,\none for rotation.", "start": 2661.45, "duration": 3.07}, {"text": "So those already give you\nthree degrees of freedom.", "start": 2664.52, "duration": 2.81}, {"text": "And it's pretty\nobvious how you could", "start": 2667.33, "duration": 2.25}, {"text": "represent them-- some x offset,\nsome y offset, and some angle.", "start": 2669.58, "duration": 5.31}, {"text": "In 3D, it's a little bit harder.", "start": 2674.89, "duration": 2.59}, {"text": "We have three degrees of freedom\nfor translation-- a change", "start": 2677.48, "duration": 3.293}, {"text": "x, a change in y, a change in z.", "start": 2680.773, "duration": 2.817}, {"text": "And then there's rotation\nand the various ways", "start": 2683.59, "duration": 2.7}, {"text": "of thinking about that,\nwhich we'll get to later.", "start": 2686.29, "duration": 2.56}, {"text": "But basically, there\nare three rotations.", "start": 2688.85, "duration": 3.08}, {"text": "There's one that\npreserves the xy-axis,", "start": 2691.93, "duration": 3.31}, {"text": "there's one that\npreserves the yz-axis,", "start": 2695.24, "duration": 2.27}, {"text": "and there's one that\npreserves the zx-axis.", "start": 2697.51, "duration": 3.39}, {"text": "And as a mental\nshortcut, you can", "start": 2700.9, "duration": 2.52}, {"text": "say there's rotation\nabout the x-axis,", "start": 2703.42, "duration": 2.34}, {"text": "rotation about the y-axis,\nrotation about the z-axis.", "start": 2705.76, "duration": 2.97}, {"text": "That's actually a very bad\nway of thinking about it.", "start": 2708.73, "duration": 2.19}, {"text": "But it gives you the right\nnumber, which is 3, so.", "start": 2710.92, "duration": 3.28}, {"text": "OK.", "start": 2714.2, "duration": 0.5}, {"text": "So that means that if we have\ntranslation and rotation,", "start": 2714.7, "duration": 2.79}, {"text": "there should be six things--", "start": 2717.49, "duration": 1.5}, {"text": "six degrees of freedom.", "start": 2718.99, "duration": 1.62}, {"text": "And then you look at that\nmatrix up there and stuff,", "start": 2720.61, "duration": 2.52}, {"text": "and there's already\nnine just in the matrix,", "start": 2723.13, "duration": 3.34}, {"text": "and then there's another\nthree for the translation.", "start": 2726.47, "duration": 2.43}, {"text": "So there's 12.", "start": 2728.9, "duration": 1.42}, {"text": "So there's a redundancy.", "start": 2730.32, "duration": 2.17}, {"text": "There's something wrong.", "start": 2732.49, "duration": 1.14}, {"text": "We've got many more\nvariables than there", "start": 2733.63, "duration": 3.39}, {"text": "are degrees of freedom.", "start": 2737.02, "duration": 2.89}, {"text": "And so that's because there\nare these constraints.", "start": 2739.91, "duration": 4.47}, {"text": "So that R matrix isn't\njust any old 3-by-3 matrix.", "start": 2744.38, "duration": 3.53}, {"text": "It has to satisfy all\nof those constraints.", "start": 2747.91, "duration": 2.58}, {"text": "And it's the usual thing.", "start": 2750.49, "duration": 1.65}, {"text": "You have a number of variables,\na bunch of constraints.", "start": 2752.14, "duration": 3.99}, {"text": "You subtract them, and you\nget the degrees of freedom.", "start": 2756.13, "duration": 2.74}, {"text": "So in this case, when we\nsubtract out the constraints,", "start": 2758.87, "duration": 4.61}, {"text": "it turns out we get 9 minus\n6 equals 3 for rotation.", "start": 2763.48, "duration": 5.49}, {"text": "The 9 is because it's a 3-by-3\nmatrix, there are nine numbers.", "start": 2768.97, "duration": 4.41}, {"text": "What's the 6?", "start": 2773.38, "duration": 1.05}, {"text": "Well, the orthonormality\nconstraint", "start": 2774.43, "duration": 2.67}, {"text": "provides six constraints.", "start": 2777.1, "duration": 1.8}, {"text": "Why?", "start": 2778.9, "duration": 0.82}, {"text": "Well, each row has to be unit\nsize vector, so that's 3.", "start": 2779.72, "duration": 7.1}, {"text": "The rows have to mutually\nbe perpendicular.", "start": 2786.82, "duration": 3.36}, {"text": "Well, there are three ways of\npairing them up, so then 6.", "start": 2790.18, "duration": 4.7}, {"text": "So 9 minus 6 is 3.", "start": 2794.88, "duration": 1.9}, {"text": "OK.", "start": 2796.78, "duration": 0.5}, {"text": "So then we get to this.", "start": 2797.28, "duration": 3.36}, {"text": "And you know, this\nis an interesting way", "start": 2800.64, "duration": 4.59}, {"text": "of dealing with perspective\nprojection in the case", "start": 2805.23, "duration": 3.09}, {"text": "of a planar surface.", "start": 2808.32, "duration": 1.74}, {"text": "We just have to be a\nlittle bit careful.", "start": 2810.06, "duration": 2.29}, {"text": "So suppose, for example,\nthat we determine", "start": 2812.35, "duration": 2.51}, {"text": "this matrix T experimentally\nby matching up", "start": 2814.86, "duration": 3.735}, {"text": "an image of a calibration\nobject like, I don't know, cube,", "start": 2818.595, "duration": 3.585}, {"text": "or checkerboard, or whatever.", "start": 2822.18, "duration": 2.4}, {"text": "Somehow we find this 3-by-3\nmatrix, and then we're done.", "start": 2824.58, "duration": 4.53}, {"text": "Well, no.", "start": 2829.11, "duration": 1.05}, {"text": "Because this is a matrix with\nnine independent elements,", "start": 2830.16, "duration": 3.93}, {"text": "which is way more than the\ntransformation deserves.", "start": 2834.09, "duration": 4.77}, {"text": "And so actually, we need to\nenforce some constraints.", "start": 2838.86, "duration": 7.19}, {"text": "For example, it's derived\nfrom a rotation matrix.", "start": 2850.595, "duration": 3.375}, {"text": "So that first column\nshould be a unit vector.", "start": 2853.97, "duration": 2.86}, {"text": "The second column\nshould be a unit vector.", "start": 2856.83, "duration": 1.97}, {"text": "The third column we lost.", "start": 2862.73, "duration": 1.25}, {"text": "We don't know what that\nis, although, of course,", "start": 2863.98, "duration": 2.34}, {"text": "we can reconstruct it.", "start": 2866.32, "duration": 1.44}, {"text": "Because it's perpendicular\nto the first two columns,", "start": 2867.76, "duration": 2.41}, {"text": "so it's their cross product.", "start": 2870.17, "duration": 3.525}, {"text": "That's, by the way, a\nuseful programming trick.", "start": 2876.89, "duration": 3.84}, {"text": "You don't really need to keep\na 3-by-3 matrix for rotation.", "start": 2880.73, "duration": 3.6}, {"text": "You just keep two of its\nrows or two of its columns,", "start": 2884.33, "duration": 2.61}, {"text": "because you can always\ncompute the other one.", "start": 2886.94, "duration": 2.02}, {"text": "And in fact, in a\nsense, it might be more", "start": 2888.96, "duration": 1.79}, {"text": "consistent to work that way.", "start": 2890.75, "duration": 2.01}, {"text": "OK, two constraints.", "start": 2892.76, "duration": 1.047}, {"text": "Well, there's another one.", "start": 2893.807, "duration": 1.083}, {"text": "These have to be orthogonal.", "start": 2894.89, "duration": 2.07}, {"text": "So r1,1, r1,2 plus r21, r22,\nplus r31, r32, has to be 0.", "start": 2896.96, "duration": 11.21}, {"text": "OK.", "start": 2908.17, "duration": 0.5}, {"text": "So this matrix T should\nreally satisfy those three", "start": 2908.67, "duration": 6.54}, {"text": "constraints.", "start": 2915.21, "duration": 1.11}, {"text": "And let's add things up.", "start": 2916.32, "duration": 1.74}, {"text": "So it has 3 by 3.", "start": 2918.06, "duration": 1.86}, {"text": "It has 9 elements.", "start": 2919.92, "duration": 1.32}, {"text": "Three constraints, that leaves\nus six, six degrees of freedom.", "start": 2921.24, "duration": 4.26}, {"text": "That's correct.", "start": 2925.5, "duration": 1.18}, {"text": "So that's all true\nand wonderful.", "start": 2926.68, "duration": 3.44}, {"text": "It's just that typically, we\ndon't enforce that constraint.", "start": 2930.12, "duration": 7.95}, {"text": "Why?", "start": 2938.07, "duration": 0.66}, {"text": "Well, because the rest of it\nyou can do linear least squares", "start": 2938.73, "duration": 3.06}, {"text": "to fit to your calibration data.", "start": 2941.79, "duration": 1.98}, {"text": "But how do you enforce these\nsecond-order equations?", "start": 2943.77, "duration": 5.28}, {"text": "And so you will\nsee a large number", "start": 2949.05, "duration": 1.92}, {"text": "of publications that\nexpound this approach, which", "start": 2950.97, "duration": 4.65}, {"text": "would be valid if only\nthey had enforced this.", "start": 2955.62, "duration": 4.26}, {"text": "So that's like a kind of\nattempt at generalization", "start": 2959.88, "duration": 4.59}, {"text": "from what's covered\nin this pattern,", "start": 2964.47, "duration": 2.73}, {"text": "namely 2D transformations, to\nwhere we'll be going later,", "start": 2967.2, "duration": 4.89}, {"text": "which will be 3D\ntransformations,", "start": 2972.09, "duration": 2.07}, {"text": "and a kind of warning\nabout this stuff", "start": 2974.16, "duration": 5.04}, {"text": "that we have to be careful.", "start": 2979.2, "duration": 3.25}, {"text": "So by the way, if\nI'm going to use", "start": 2982.45, "duration": 4.74}, {"text": "this to predict where I'm in the\nimage, I'm just going to use--", "start": 2987.19, "duration": 4.17}, {"text": "of course, the equations, I'm\njust repeating the equations", "start": 2991.36, "duration": 2.94}, {"text": "from up there.", "start": 2994.3, "duration": 0.69}, {"text": "And so that means that if I\ntake the camera coordinates", "start": 2997.9, "duration": 4.25}, {"text": "and multiply them by some\narbitrary non-zero factor,", "start": 3002.15, "duration": 2.76}, {"text": "nothing changes.", "start": 3004.91, "duration": 1.08}, {"text": "And of course, that's the\nscale factor ambiguity", "start": 3005.99, "duration": 2.25}, {"text": "we already talked about.", "start": 3008.24, "duration": 1.5}, {"text": "What does that mean?", "start": 3009.74, "duration": 1.06}, {"text": "Well, one thing it means is\nthat you can take this matrix", "start": 3010.8, "duration": 2.54}, {"text": "and multiply it by some\narbitrary constant,", "start": 3013.34, "duration": 2.43}, {"text": "non-zero constant,\nand nothing changes.", "start": 3015.77, "duration": 2.67}, {"text": "So that's another clue that\nthis is a funny kind of matrix.", "start": 3018.44, "duration": 5.16}, {"text": "And yes, you could try to\nadjust its size by trying", "start": 3023.6, "duration": 4.29}, {"text": "to impose these constraints.", "start": 3027.89, "duration": 3.0}, {"text": "But-- OK, oh, this is called--", "start": 3030.89, "duration": 3.64}, {"text": "I should say this is\ncalled homography.", "start": 3034.53, "duration": 2.64}, {"text": "And we'll talk later about its\nuse in photogrammetry or misuse", "start": 3041.45, "duration": 4.53}, {"text": "in photogrammetry.", "start": 3045.98, "duration": 1.18}, {"text": "OK.", "start": 3047.16, "duration": 0.5}, {"text": "The other thing I\nwanted to talk about", "start": 3047.66, "duration": 1.583}, {"text": "was, you may remember\nright when we", "start": 3049.243, "duration": 2.629}, {"text": "started talking\nabout this pattern,", "start": 3051.872, "duration": 1.458}, {"text": "I said, well, there's prior art.", "start": 3053.33, "duration": 1.74}, {"text": "And we listed blob analysis\nor binary image processing,", "start": 3055.07, "duration": 5.04}, {"text": "and we listed binary\ntemplates, and we listed--", "start": 3060.11, "duration": 5.94}, {"text": "what else?", "start": 3066.05, "duration": 0.96}, {"text": "Anyone remember\nwhat else we listed?", "start": 3067.01, "duration": 1.575}, {"text": "And there was a fourth one,\nwhich we didn't discuss.", "start": 3072.65, "duration": 2.73}, {"text": "The other three we did discuss.", "start": 3075.38, "duration": 1.68}, {"text": "And the fourth one\nis Hough transform", "start": 3077.06, "duration": 3.12}, {"text": "and its generalization.", "start": 3080.18, "duration": 1.35}, {"text": "So let's just briefly\ntalk about that.", "start": 3081.53, "duration": 3.31}, {"text": "So that's because we picked\nour world coordinate system", "start": 3084.84, "duration": 4.94}, {"text": "so that in the plane--", "start": 3089.78, "duration": 1.95}, {"text": "it's only working\nfor this plane.", "start": 3091.73, "duration": 1.83}, {"text": "And in that plane, zw is 0.", "start": 3093.56, "duration": 2.55}, {"text": "What it means is\nthat, suppose I want", "start": 3096.11, "duration": 1.71}, {"text": "to deal with an\nimage of this table,", "start": 3097.82, "duration": 2.26}, {"text": "and then I want to refer to\nwhere my phone is on the table.", "start": 3100.08, "duration": 4.19}, {"text": "I'm going to pick a\ncoordinate system that's,", "start": 3104.27, "duration": 2.37}, {"text": "say, lined up with the edges.", "start": 3106.64, "duration": 1.75}, {"text": "But the important thing is\nthat z is perpendicular to that", "start": 3108.39, "duration": 3.38}, {"text": "surface, so that whatever I'm--", "start": 3111.77, "duration": 3.6}, {"text": "where is this paperclip?", "start": 3115.37, "duration": 1.38}, {"text": "I only need to give x and y,\nbecause if it's in that plane,", "start": 3116.75, "duration": 3.45}, {"text": "z is 0.", "start": 3120.2, "duration": 1.77}, {"text": "And so this will\nnot apply if I have", "start": 3121.97, "duration": 2.49}, {"text": "a true three-dimensional object.", "start": 3124.46, "duration": 2.01}, {"text": "It's only the case where I'm\nconfining attention to a plane.", "start": 3126.47, "duration": 4.45}, {"text": "And so it comes up in industrial\nmachine vision, because--", "start": 3130.92, "duration": 5.3}, {"text": "in many ways.", "start": 3136.22, "duration": 0.76}, {"text": "One is, obviously you want to\ntry and get your optical axis", "start": 3136.98, "duration": 4.25}, {"text": "as perpendicular as possible\nto the surface you're", "start": 3141.23, "duration": 2.88}, {"text": "interested in, whether it's a\nconveyor belt, or the surface", "start": 3144.11, "duration": 3.21}, {"text": "of the road, or whatever.", "start": 3147.32, "duration": 1.68}, {"text": "But inevitably there\nwill be some small error,", "start": 3149.0, "duration": 3.42}, {"text": "and inevitably someone's\ngoing to bump into it", "start": 3152.42, "duration": 3.45}, {"text": "and change it slightly.", "start": 3155.87, "duration": 1.47}, {"text": "And this takes\ncare of it, because", "start": 3157.34, "duration": 2.49}, {"text": "this slight\ngeneralization allows", "start": 3159.83, "duration": 1.74}, {"text": "you to deal with other\ncamera orientation", "start": 3161.57, "duration": 3.225}, {"text": "so that you don't have to\nhave a perfect orthographic", "start": 3164.795, "duration": 2.925}, {"text": "projection.", "start": 3167.72, "duration": 1.02}, {"text": "You can have a\nslightly skew one.", "start": 3168.74, "duration": 2.49}, {"text": "Thinking of other\napplications, in some countries", "start": 3177.812, "duration": 4.008}, {"text": "there's like a surveillance\ncamera at every intersection,", "start": 3181.82, "duration": 4.92}, {"text": "and it's looking\ndown at the road.", "start": 3186.74, "duration": 1.74}, {"text": "Well, if you're mapping\npoints on the road,", "start": 3188.48, "duration": 3.18}, {"text": "you don't need the\nfull 3D transformation.", "start": 3191.66, "duration": 2.1}, {"text": "You just need this.", "start": 3193.76, "duration": 0.99}, {"text": "But you just have to remember\nthat now your world coordinate", "start": 3194.75, "duration": 3.6}, {"text": "system has the\nconstraint that it", "start": 3198.35, "duration": 2.19}, {"text": "has to be lined up with\nthe surface of the road", "start": 3200.54, "duration": 2.82}, {"text": "so that zw is 0--", "start": 3203.36, "duration": 3.27}, {"text": "assuming the road\nis really flat, but.", "start": 3206.63, "duration": 3.84}, {"text": "OK.", "start": 3210.47, "duration": 1.59}, {"text": "Hough transform.", "start": 3212.06, "duration": 0.94}, {"text": "So when I was a student,\nwhich is centuries ago,", "start": 3216.86, "duration": 7.27}, {"text": "NASA had a large part of one of\nthe Tech Square buildings, one", "start": 3224.13, "duration": 4.722}, {"text": "of the original Tech Square--\nthey've since been renovated,", "start": 3228.852, "duration": 2.458}, {"text": "so.", "start": 3231.31, "duration": 1.02}, {"text": "I guess it was 535.", "start": 3232.33, "duration": 1.5}, {"text": "And there was a floor or\nmaybe two floors dedicated", "start": 3233.83, "duration": 4.44}, {"text": "to the following thing.", "start": 3238.27, "duration": 2.25}, {"text": "At that time, people\nwere very interested", "start": 3240.52, "duration": 3.27}, {"text": "in various kinds of processes\nof elementary particles.", "start": 3243.79, "duration": 3.33}, {"text": "And you studied them\nby shooting them", "start": 3247.12, "duration": 3.12}, {"text": "into a cloud chamber, Wilson's\ndesign of a cloud chamber.", "start": 3250.24, "duration": 3.6}, {"text": "You shoot them in, you\nquickly decrease the pressure,", "start": 3253.84, "duration": 5.31}, {"text": "and it's saturated\nwith some vapor--", "start": 3259.15, "duration": 2.64}, {"text": "alcohol or something.", "start": 3261.79, "duration": 1.32}, {"text": "And the ionized\npoints in that space", "start": 3263.11, "duration": 4.56}, {"text": "then form nucleation\npoints for the liquid.", "start": 3267.67, "duration": 5.28}, {"text": "And then you take\na picture of it.", "start": 3272.95, "duration": 1.65}, {"text": "And you find that there's\nparticles zooming through", "start": 3274.6, "duration": 5.16}, {"text": "in a certain direction.", "start": 3279.76, "duration": 1.23}, {"text": "And then you can see how that\ndepends on the magnetic field", "start": 3280.99, "duration": 7.83}, {"text": "that's applied.", "start": 3288.82, "duration": 0.72}, {"text": "If it's charged particle,\nit'll be curling around.", "start": 3289.54, "duration": 3.43}, {"text": "And so people spent many,\nmany, many man-years", "start": 3292.97, "duration": 6.97}, {"text": "and women-years\nporing over a table", "start": 3299.94, "duration": 2.79}, {"text": "like this, where these\nimages were projected down,", "start": 3302.73, "duration": 3.09}, {"text": "and then they were fitting\nlines to them or arcs.", "start": 3305.82, "duration": 3.1}, {"text": "And so there was a huge interest\nin automating this process,", "start": 3308.92, "duration": 3.35}, {"text": "because it was clear that it\nwas only going to get worse.", "start": 3312.27, "duration": 2.79}, {"text": "Because the higher\nenergy you get to,", "start": 3315.06, "duration": 1.89}, {"text": "the more pictures\nyou have to look", "start": 3316.95, "duration": 1.56}, {"text": "at before you find\nthe interesting stuff,", "start": 3318.51, "duration": 2.07}, {"text": "and the more complicated\nthe pictures get.", "start": 3320.58, "duration": 1.98}, {"text": "So it was-- doing it\nmanually was hopeless.", "start": 3322.56, "duration": 2.64}, {"text": "So edge detection, line\ndetection was important.", "start": 3325.2, "duration": 5.98}, {"text": "And then what do you\ndo with the lines?", "start": 3331.18, "duration": 1.97}, {"text": "Well, Hough came up\nwith this thing, and--", "start": 3333.15, "duration": 3.15}, {"text": "this one idea.", "start": 3336.3, "duration": 1.05}, {"text": "And this is probably--", "start": 3337.35, "duration": 3.99}, {"text": "as far as I know, this is the\nfirst machine vision pattern.", "start": 3341.34, "duration": 3.255}, {"text": "I think this was submitted\nin 1960 and issued in 1962.", "start": 3347.84, "duration": 5.1}, {"text": "And it's pretty short.", "start": 3352.94, "duration": 3.42}, {"text": "I don't remember whether\nI loaded it up on Stellar.", "start": 3356.36, "duration": 2.31}, {"text": "It's not particularly\ninteresting,", "start": 3358.67, "duration": 1.53}, {"text": "but we'll go through it.", "start": 3360.2, "duration": 3.22}, {"text": "And at that time, there\nwas quite a bit of negative", "start": 3363.42, "duration": 5.16}, {"text": "feeling in the machine\nvision community,", "start": 3368.58, "duration": 2.29}, {"text": "which was, I don't know, a\ndozen people at that time.", "start": 3370.87, "duration": 3.14}, {"text": "You know, why\npattern this thing?", "start": 3374.01, "duration": 1.83}, {"text": "Anyway, he patterned it.", "start": 3375.84, "duration": 1.05}, {"text": "So what is it?", "start": 3376.89, "duration": 1.74}, {"text": "And again, the context\nis we're trying", "start": 3378.63, "duration": 2.46}, {"text": "to see lines in photographs of\nWilson bubble chamber pictures.", "start": 3381.09, "duration": 6.15}, {"text": "And so he's looking\nfor possible lines.", "start": 3387.24, "duration": 3.78}, {"text": "And you say, well, just use\nthe edge detection methods", "start": 3391.02, "duration": 2.94}, {"text": "we've talked about already.", "start": 3393.96, "duration": 1.62}, {"text": "Well, the trouble is that these\nlines were little dotted lines.", "start": 3395.58, "duration": 6.63}, {"text": "They were little bubbles.", "start": 3402.21, "duration": 1.32}, {"text": "And the bubbles were\nnot spaced equally,", "start": 3403.53, "duration": 2.28}, {"text": "and they were not\nall the same size.", "start": 3405.81, "duration": 1.9}, {"text": "So it wasn't clean.", "start": 3407.71, "duration": 3.05}, {"text": "And also, because\nthey weren't edges,", "start": 3410.76, "duration": 1.59}, {"text": "they weren't transitions\nfrom dark to bright.", "start": 3412.35, "duration": 2.1}, {"text": "They were transitions from\nsomething to something and then", "start": 3414.45, "duration": 2.55}, {"text": "back again.", "start": 3417.0, "duration": 1.2}, {"text": "But that would have been\nnot too hard to deal with.", "start": 3418.2, "duration": 2.7}, {"text": "So he came up with this idea\nthat we map from image space.", "start": 3420.9, "duration": 5.56}, {"text": "so here's our image space.", "start": 3426.46, "duration": 2.39}, {"text": "And now in this image space,\nwe can have all kinds of lines.", "start": 3428.85, "duration": 6.09}, {"text": "And we map to a parameter\nspace four lines.", "start": 3434.94, "duration": 3.78}, {"text": "So you know how many numbers\ndo we need to describe a line?", "start": 3438.72, "duration": 5.13}, {"text": "Well, we already did that.", "start": 3443.85, "duration": 1.69}, {"text": "So one way, which I'm not too\nexcited about, but there it is,", "start": 3445.54, "duration": 5.96}, {"text": "is y equals mx c.", "start": 3451.5, "duration": 1.65}, {"text": "So it apparently takes two\nnumbers to describe a line.", "start": 3453.15, "duration": 3.45}, {"text": "And then we-- did I use m here?", "start": 3456.6, "duration": 2.28}, {"text": "Let's see here.", "start": 3458.88, "duration": 2.09}, {"text": "OK.", "start": 3460.97, "duration": 0.66}, {"text": "And so if I have a\nline in this space,", "start": 3461.63, "duration": 6.21}, {"text": "that maps into a\npoint in this space.", "start": 3467.84, "duration": 4.27}, {"text": "And so if I have some local\nevidence for a piece of one", "start": 3472.11, "duration": 3.86}, {"text": "of these bubble tracks, maybe\nI can map that into this space", "start": 3475.97, "duration": 5.4}, {"text": "and accumulate evidence for\ndifferent possible lines.", "start": 3481.37, "duration": 6.78}, {"text": "And so like, that\nfragment might go there.", "start": 3488.15, "duration": 4.2}, {"text": "And then this fragment, that's--", "start": 3492.35, "duration": 2.61}, {"text": "I can fit a line to that.", "start": 3494.96, "duration": 1.59}, {"text": "And then hopefully, that'll\ncome to near the same place,", "start": 3496.55, "duration": 4.53}, {"text": "and so on.", "start": 3501.08, "duration": 0.66}, {"text": "So the whole idea is that, then,\nto have an accumulated array", "start": 3501.74, "duration": 5.64}, {"text": "and count the evidence for\neach of the possible parameter", "start": 3507.38, "duration": 9.06}, {"text": "combinations, and\nthen look for peaks.", "start": 3516.44, "duration": 2.4}, {"text": "And those will correspond\nto lines in the image.", "start": 3518.84, "duration": 5.1}, {"text": "And this can be generalized\nto other shapes,", "start": 3523.94, "duration": 1.95}, {"text": "but let's stick with lines.", "start": 3525.89, "duration": 1.33}, {"text": "So here's another thing.", "start": 3527.22, "duration": 1.22}, {"text": "So suppose that I have\na line in this space.", "start": 3528.44, "duration": 5.42}, {"text": "What does that correspond to\nin the original image space?", "start": 3533.86, "duration": 3.59}, {"text": "Well, it turns out because this\nequation is kind of symmetric--", "start": 3540.48, "duration": 3.95}, {"text": "if you write it the right way.", "start": 3544.43, "duration": 1.36}, {"text": "Let's rewrite it.", "start": 3545.79, "duration": 0.71}, {"text": "I can write the equation of\nthe line this way or that way.", "start": 3549.73, "duration": 10.22}, {"text": "And then it's clear that really,\nthose two spaces are symmetric.", "start": 3559.95, "duration": 4.98}, {"text": "They're complementary,\nmapping from one to the other.", "start": 3564.93, "duration": 3.22}, {"text": "And so what does that mean?", "start": 3568.15, "duration": 1.26}, {"text": "Well, that means that a line\nin this space on the right", "start": 3569.41, "duration": 4.55}, {"text": "corresponds to a point\nin the space on the left.", "start": 3573.96, "duration": 4.92}, {"text": "So that corresponds\nto, let's say, that.", "start": 3578.88, "duration": 7.28}, {"text": "And so what use is that?", "start": 3586.16, "duration": 1.91}, {"text": "Well, that's pretty\nexciting, because I may not", "start": 3588.07, "duration": 4.74}, {"text": "have a good estimate\nof the line at all.", "start": 3592.81, "duration": 3.27}, {"text": "Maybe all I've got is a bubble.", "start": 3596.08, "duration": 2.34}, {"text": "I don't really know what it is\nin the larger scheme of things.", "start": 3598.42, "duration": 4.65}, {"text": "Well, suppose this is my bubble.", "start": 3603.07, "duration": 2.13}, {"text": "What does it tell me?", "start": 3605.2, "duration": 1.605}, {"text": "It does tell-- it doesn't\ntell me what the line is.", "start": 3606.805, "duration": 2.625}, {"text": "But it's one of those\nthings, where it", "start": 3609.43, "duration": 2.1}, {"text": "constrains the number of lines.", "start": 3611.53, "duration": 1.63}, {"text": "So all of the lines that\nthis could give evidence", "start": 3613.16, "duration": 2.87}, {"text": "will go through that point.", "start": 3616.03, "duration": 1.51}, {"text": "And those are all of\nthe lines along here.", "start": 3617.54, "duration": 3.78}, {"text": "OK, so that's an\nimportant insight,", "start": 3621.32, "duration": 3.66}, {"text": "that if I have a\nnice clean edge.", "start": 3624.98, "duration": 4.88}, {"text": "I can fit a line and I'm done.", "start": 3629.86, "duration": 1.94}, {"text": "Well, if I have a\nbubble chamber picture,", "start": 3631.8, "duration": 1.92}, {"text": "I just have these bubbles.", "start": 3633.72, "duration": 2.5}, {"text": "But each bubble gives me\nevidence about a possible line.", "start": 3636.22, "duration": 5.51}, {"text": "I don't know exactly what it is.", "start": 3641.73, "duration": 1.71}, {"text": "I've reduced the problem\nfrom a 2D unknown to 1D.", "start": 3643.44, "duration": 4.5}, {"text": "Should sound familiar.", "start": 3647.94, "duration": 1.83}, {"text": "And so what do I do?", "start": 3649.77, "duration": 1.15}, {"text": "Well, I just take\nevery bubble, and I", "start": 3650.92, "duration": 3.47}, {"text": "find it's transform\nin this space,", "start": 3654.39, "duration": 3.48}, {"text": "and I use that to\naccumulate some total.", "start": 3657.87, "duration": 4.89}, {"text": "So there's a bubble.", "start": 3662.76, "duration": 0.99}, {"text": "Now I'm going to\nget another bubble.", "start": 3663.75, "duration": 2.52}, {"text": "And maybe that will\ngive me that line.", "start": 3666.27, "duration": 2.67}, {"text": "And then I'll get, I don't\nknow, another bubble,", "start": 3668.94, "duration": 4.05}, {"text": "and that'll give me\nthis line, and so on.", "start": 3672.99, "duration": 2.53}, {"text": "And you can see how\neach of these bubbles", "start": 3675.52, "duration": 3.29}, {"text": "contribute some evidence.", "start": 3678.81, "duration": 1.44}, {"text": "And then if I keep track of\nthat by having accumulators", "start": 3680.25, "duration": 4.74}, {"text": "over here, I can look for\nthe peaks in this accumulator", "start": 3684.99, "duration": 3.57}, {"text": "array.", "start": 3688.56, "duration": 0.54}, {"text": "And they will correspond\nto bubbles that line up", "start": 3689.1, "duration": 3.36}, {"text": "along some line.", "start": 3692.46, "duration": 1.14}, {"text": "So that's the basic\nidea of transform.", "start": 3693.6, "duration": 5.79}, {"text": "And the key idea is that\nthere's this mapping,", "start": 3699.39, "duration": 7.8}, {"text": "and that it's symmetric.", "start": 3707.19, "duration": 1.89}, {"text": "Let me just actually\ndo an example.", "start": 3709.08, "duration": 3.19}, {"text": "Oh, let's see.", "start": 3712.27, "duration": 0.6}, {"text": "How does this work?", "start": 3712.87, "duration": 0.792}, {"text": "So here's my image.", "start": 3717.476, "duration": 2.824}, {"text": "And I have a line here.", "start": 3720.3, "duration": 1.875}, {"text": "This was supposed to be 0,\n1, and this is minus 1, 0.", "start": 3726.59, "duration": 8.18}, {"text": "And this point would\nbe minus 1/2, 1/2.", "start": 3734.77, "duration": 4.876}, {"text": "And let's put one more in.", "start": 3739.646, "duration": 2.724}, {"text": "Four is 1 comma 2.", "start": 3742.37, "duration": 4.77}, {"text": "OK.", "start": 3747.14, "duration": 0.54}, {"text": "So let's suppose we have\nbubbles at those points.", "start": 3747.68, "duration": 5.06}, {"text": "Then we go to the\ntransform space.", "start": 3752.74, "duration": 1.785}, {"text": "And let's take number 1.", "start": 3757.43, "duration": 2.22}, {"text": "So number 1 says\nx is 0 and y is 1.", "start": 3759.65, "duration": 5.45}, {"text": "So that's this one,\npoint number 1.", "start": 3765.1, "duration": 5.61}, {"text": "And if I write that\ninto the equation,", "start": 3770.71, "duration": 3.12}, {"text": "y equals mx plus c,\nthat means that c is 1,", "start": 3773.83, "duration": 6.77}, {"text": "So then I can plot that in here,\nand I-- do I have it reversed?", "start": 3780.6, "duration": 6.7}, {"text": "m going up, yeah.", "start": 3787.3, "duration": 0.99}, {"text": "OK, c equals 1 in this\nspace is that line--", "start": 3791.12, "duration": 4.38}, {"text": "oops.", "start": 3795.5, "duration": 1.8}, {"text": "That's the line c equals 1.", "start": 3797.3, "duration": 1.26}, {"text": "So this point gives me evidence\nthat the line I'm looking for", "start": 3798.56, "duration": 6.15}, {"text": "is one of those lines.", "start": 3804.71, "duration": 3.87}, {"text": "Well, each point\nhere corresponds", "start": 3808.58, "duration": 2.58}, {"text": "to a line in that space.", "start": 3811.16, "duration": 2.15}, {"text": "OK.", "start": 3813.31, "duration": 0.5}, {"text": "Now suppose I pick another one.", "start": 3813.81, "duration": 1.99}, {"text": "So let me take point 2, x\nequals minus 1, y equals 0.", "start": 3815.8, "duration": 5.81}, {"text": "That's this one, point 2.", "start": 3821.61, "duration": 3.64}, {"text": "And if I plug that into y equals\nmx plus c, I get m equals c.", "start": 3825.25, "duration": 8.218}, {"text": "And so that-- so this\nis line number 1.", "start": 3833.468, "duration": 3.642}, {"text": "So that line looks like this.", "start": 3837.11, "duration": 3.09}, {"text": "This is line number 1.", "start": 3840.2, "duration": 3.62}, {"text": "And so I'll go into\nthe accumulator ray,", "start": 3843.82, "duration": 2.61}, {"text": "and all of these cells\nwill be incremented.", "start": 3846.43, "duration": 4.65}, {"text": "Let's just do one more.", "start": 3851.08, "duration": 1.96}, {"text": "Let's do this one, point 3.", "start": 3853.04, "duration": 3.4}, {"text": "So for 3, we have\nx is 1, and y is 2.", "start": 3856.44, "duration": 4.38}, {"text": "And for that, the equation\nis m equals 2 minus c.", "start": 3860.82, "duration": 5.88}, {"text": "So that line, 2 minus c.", "start": 3866.7, "duration": 4.48}, {"text": "So that'll start at 2 and then\ngo negative, go like that.", "start": 3871.18, "duration": 3.81}, {"text": "So that's line 3.", "start": 3874.99, "duration": 1.71}, {"text": "And you can see\nwhat's happening,", "start": 3876.7, "duration": 1.93}, {"text": "which is that there's\none accumulator that", "start": 3878.63, "duration": 4.46}, {"text": "will be repeatedly updated.", "start": 3883.09, "duration": 2.4}, {"text": "Now, in the presence of noise\nthey won't be all perfect.", "start": 3885.49, "duration": 3.84}, {"text": "And instead of just always\nhitting that accumulator,", "start": 3889.33, "duration": 3.09}, {"text": "we'll be hitting neighboring\ncells a little bit.", "start": 3892.42, "duration": 3.67}, {"text": "But the idea is\nthat the cell that", "start": 3896.09, "duration": 3.77}, {"text": "has the right parameter in it\nwill be incremental the most.", "start": 3899.86, "duration": 4.96}, {"text": "And you can do more\nsophisticated things.", "start": 3904.82, "duration": 2.89}, {"text": "But the key idea is\nthat we have a space", "start": 3907.71, "duration": 4.4}, {"text": "for the possible parameters\nof the transformation.", "start": 3912.11, "duration": 4.98}, {"text": "We have each point\nin here corresponds", "start": 3917.09, "duration": 3.06}, {"text": "to a particular line.", "start": 3920.15, "duration": 1.68}, {"text": "And then, by the way, each line\nin here corresponds to a point.", "start": 3921.83, "duration": 4.9}, {"text": "And so we can gather\nup the evidence.", "start": 3926.73, "duration": 4.82}, {"text": "And even if the line\nis really ratty,", "start": 3931.55, "duration": 3.12}, {"text": "just these bubbles distributed\nin unequal intervals,", "start": 3934.67, "duration": 5.52}, {"text": "we can get a large count there.", "start": 3940.19, "duration": 5.16}, {"text": "So here it's used\nin line detection,", "start": 3945.35, "duration": 2.88}, {"text": "but it could be equally\nused in edge detection.", "start": 3948.23, "duration": 2.65}, {"text": "And it was in some cases.", "start": 3950.88, "duration": 3.77}, {"text": "It's not used much\nin edge detection--", "start": 3954.65, "duration": 2.28}, {"text": "in line detection\nnow, because we have--", "start": 3956.93, "duration": 3.51}, {"text": "if the image is reasonable,\nwe have much better methods.", "start": 3960.44, "duration": 3.33}, {"text": "Their problem was that\nat high magnification", "start": 3963.77, "duration": 2.85}, {"text": "they just had these\nisolated bubbles that", "start": 3966.62, "duration": 2.34}, {"text": "weren't quite on the\nline and were different--", "start": 3968.96, "duration": 2.75}, {"text": "and so this is a good way of\ntrying to deal with that noise,", "start": 3971.71, "duration": 3.73}, {"text": "if you like.", "start": 3975.44, "duration": 0.52}, {"text": "So.", "start": 3975.96, "duration": 0.5}, {"text": "Absolutely.", "start": 3986.41, "duration": 2.37}, {"text": "You've just invented the\nextended Gauss Hough transform.", "start": 3988.78, "duration": 3.06}, {"text": "So yes.", "start": 3991.84, "duration": 2.55}, {"text": "So that's definitely\na way to go.", "start": 3994.39, "duration": 2.67}, {"text": "And they're going to be\nobviously trade-offs.", "start": 3997.06, "duration": 2.07}, {"text": "Like, if you have something\nthat has a lot of parameters,", "start": 3999.13, "duration": 2.61}, {"text": "that space gets large.", "start": 4001.74, "duration": 1.53}, {"text": "And then you have to deal\nwith the cost of storing", "start": 4003.27, "duration": 3.15}, {"text": "the quantized version of it.", "start": 4006.42, "duration": 1.89}, {"text": "And there are\nlittle tricky things", "start": 4008.31, "duration": 1.56}, {"text": "like, if you divide\nup the space,", "start": 4009.87, "duration": 2.16}, {"text": "you quantize it\ninto little boxes.", "start": 4012.03, "duration": 2.76}, {"text": "If you make a tiny change in the\ndata, you may go from one cell", "start": 4014.79, "duration": 3.78}, {"text": "to the neighboring cell.", "start": 4018.57, "duration": 1.2}, {"text": "And what do you do about that?", "start": 4019.77, "duration": 1.81}, {"text": "So there are tricks\nfor dealing with that.", "start": 4021.58, "duration": 2.69}, {"text": "But let me do another simple\nexample, which is circles.", "start": 4024.27, "duration": 6.4}, {"text": "And let's suppose we know\nthe radius of the circle.", "start": 4030.67, "duration": 10.65}, {"text": "So we're looking\nfor, again, is just", "start": 4041.32, "duration": 1.65}, {"text": "x and y, just two parameters,\ncenter of the circle.", "start": 4042.97, "duration": 5.08}, {"text": "So one way to introduce\nthis story is that in LTE--", "start": 4048.05, "duration": 8.69}, {"text": "Long-Term Evolution--\nin cell phones,", "start": 4056.74, "duration": 5.99}, {"text": "the signal from your cell phone\narrives at a tower at a time", "start": 4062.73, "duration": 6.06}, {"text": "after you sent it, of course,\nby an amount which depends", "start": 4068.79, "duration": 3.63}, {"text": "on how far away you are.", "start": 4072.42, "duration": 1.87}, {"text": "And LTE, unlike CDMA, uses\ntime division multiplexing.", "start": 4074.29, "duration": 6.77}, {"text": "So you get a slot\nto send your data,", "start": 4081.06, "duration": 2.7}, {"text": "and somebody else gets a\nslot to send their data,", "start": 4083.76, "duration": 2.91}, {"text": "and somebody else gets a\nslot to send their data.", "start": 4086.67, "duration": 2.64}, {"text": "And if they don't\nfit in that slot,", "start": 4089.31, "duration": 3.018}, {"text": "they're going to\ninterfere with each other.", "start": 4092.328, "duration": 1.792}, {"text": "So it's very important that your\nphone use a timing advance--", "start": 4094.12, "duration": 6.18}, {"text": "in other words, that\nit knows my signal", "start": 4100.3, "duration": 2.12}, {"text": "is going to take 5 microseconds\nto get to the tower,", "start": 4102.42, "duration": 3.149}, {"text": "so I have to send\nit 5 microseconds", "start": 4105.569, "duration": 2.611}, {"text": "before the appointed\nbeginning of the time slot.", "start": 4108.18, "duration": 4.66}, {"text": "S actually, it's\neven worse than that,", "start": 4112.84, "duration": 1.79}, {"text": "because it doesn't\nknow the time.", "start": 4114.63, "duration": 2.46}, {"text": "I mean, it's got its\nown internal clock,", "start": 4117.09, "duration": 1.74}, {"text": "but it's not accurate\nto nanosecond accuracy.", "start": 4118.83, "duration": 3.87}, {"text": "There's a different clock\nin the cell tower which is.", "start": 4122.7, "duration": 3.0}, {"text": "But so how does this work?", "start": 4125.7, "duration": 3.19}, {"text": "Well, the cell tower\nsends out a signal,", "start": 4128.89, "duration": 2.87}, {"text": "and that arrives at the phone.", "start": 4131.76, "duration": 3.0}, {"text": "And then the phone\nsends something back.", "start": 4134.76, "duration": 2.37}, {"text": "So it is possible to\nget the round trip time,", "start": 4137.13, "duration": 3.42}, {"text": "even if the two clocks\nare not synchronized.", "start": 4140.55, "duration": 2.86}, {"text": "So details we'll leave\nout, but basically, you", "start": 4143.41, "duration": 5.81}, {"text": "can get the timing\nadvance, which", "start": 4149.22, "duration": 2.52}, {"text": "is what the cell phone\nneeds to use so it correctly", "start": 4151.74, "duration": 3.329}, {"text": "inserts its message into\nthe string of messages.", "start": 4155.069, "duration": 3.301}, {"text": "And that, then, obviously\ntells you how far away you are.", "start": 4158.37, "duration": 3.9}, {"text": "So in Android, you can\nwrite an app which--", "start": 4162.27, "duration": 7.45}, {"text": "well, apparently with\nchalk on my fingertip,", "start": 4169.72, "duration": 2.58}, {"text": "the fingertip\nsensor doesn't work.", "start": 4172.3, "duration": 1.62}, {"text": "Anyway, we can get\nthe timing advance,", "start": 4173.92, "duration": 3.3}, {"text": "and then you can do\nvarious games with it.", "start": 4177.22, "duration": 2.46}, {"text": "One of them is if you know\nwhere cell towers are,", "start": 4179.68, "duration": 4.74}, {"text": "and you have the timing advance\nfrom more than one of them,", "start": 4184.42, "duration": 3.059}, {"text": "you can determine where you are.", "start": 4187.479, "duration": 3.09}, {"text": "Or you can turn\nit around and say,", "start": 4190.569, "duration": 4.236}, {"text": "I don't know where\nthe cell towers are,", "start": 4194.805, "duration": 1.625}, {"text": "but I'd like to know where they\nare, and you wander around.", "start": 4196.43, "duration": 3.15}, {"text": "And you measure the\ndistance from various places", "start": 4199.58, "duration": 3.15}, {"text": "that you know from,\nsay, GPS where you are.", "start": 4202.73, "duration": 5.23}, {"text": "So there are problems of that\ntype which involve circles.", "start": 4207.96, "duration": 3.78}, {"text": "So let's see how we might\nuse an extension of the Hough", "start": 4211.74, "duration": 5.3}, {"text": "transform to do that.", "start": 4217.04, "duration": 3.09}, {"text": "And keep in mind that\nwe know the radios.", "start": 4223.26, "duration": 3.96}, {"text": "So the timing advance\ngives us the radius.", "start": 4227.22, "duration": 2.97}, {"text": "So that makes it\na little simpler.", "start": 4230.19, "duration": 2.01}, {"text": "We'll talk about the more\ngeneral case in a second.", "start": 4232.2, "duration": 3.06}, {"text": "OK, so I'm here\nand my cell phone", "start": 4235.26, "duration": 11.4}, {"text": "told me that the timing\nadvance was a microsecond.", "start": 4246.66, "duration": 5.26}, {"text": "So the tower is,\nwhat, 300 meters away.", "start": 4251.92, "duration": 5.81}, {"text": "And actually, the\nquantization isn't very good.", "start": 4257.73, "duration": 5.01}, {"text": "It's like 150-meter increments.", "start": 4262.74, "duration": 3.72}, {"text": "But anyway.", "start": 4266.46, "duration": 1.02}, {"text": "So that means that I don't\nknow where the tower is,", "start": 4267.48, "duration": 2.74}, {"text": "but I know it's on the circle.", "start": 4270.22, "duration": 2.43}, {"text": "And that's just the same thing\nwe've been doing all along,", "start": 4272.65, "duration": 3.29}, {"text": "that we get a measurement.", "start": 4275.94, "duration": 1.98}, {"text": "It doesn't give us the answer,\nbut it constrains the answer.", "start": 4277.92, "duration": 3.28}, {"text": "And then we take\nanother measurement.", "start": 4281.2, "duration": 1.92}, {"text": "So now you can imagine\nthat we could move around.", "start": 4283.12, "duration": 4.73}, {"text": "And say now we're here, and\nwe get a different radius.", "start": 4287.85, "duration": 4.305}, {"text": "Well, it's not a--", "start": 4296.4, "duration": 1.92}, {"text": "move it there.", "start": 4298.32, "duration": 1.33}, {"text": "So that's radius 1.", "start": 4299.65, "duration": 2.66}, {"text": "And you'll say,\noh, well, obviously", "start": 4302.31, "duration": 1.83}, {"text": "the answer is here and there.", "start": 4304.14, "duration": 1.95}, {"text": "Well, yeah, OK.", "start": 4306.09, "duration": 1.86}, {"text": "That's assuming that these\nmeasurements very accurately,", "start": 4307.95, "duration": 3.61}, {"text": "which you don't.", "start": 4311.56, "duration": 1.22}, {"text": "And it leaves you with\na two-way ambiguity.", "start": 4312.78, "duration": 2.43}, {"text": "So a better way is to\njust keep on going.", "start": 4315.21, "duration": 2.62}, {"text": "So we've got x2, y2, draw a\ncircle based on that radius.", "start": 4317.83, "duration": 6.48}, {"text": "And in this case, they don't\nintersect so something's", "start": 4324.31, "duration": 3.8}, {"text": "gone wrong, which can happen.", "start": 4328.11, "duration": 2.55}, {"text": "And in practice, you would\nhave a situation like this.", "start": 4330.66, "duration": 4.3}, {"text": "So that's a Hough\ntransform-like method.", "start": 4334.96, "duration": 3.02}, {"text": "All we need to do is\nhave an accumulator array", "start": 4337.98, "duration": 2.67}, {"text": "that covers the possible\ngeographic position.", "start": 4340.65, "duration": 4.23}, {"text": "And then we use this\nmethod to update it.", "start": 4344.88, "duration": 2.98}, {"text": "So we reset it all to 0.", "start": 4347.86, "duration": 1.65}, {"text": "The first measurement we\nget, we go around the circle,", "start": 4349.51, "duration": 2.99}, {"text": "and we increment all\nof the accumulators", "start": 4352.5, "duration": 1.98}, {"text": "we hit on that circle.", "start": 4354.48, "duration": 1.47}, {"text": "Next measurement, we\ngo around that circle.", "start": 4355.95, "duration": 3.09}, {"text": "And hopefully, the true\nlocation of the cell tower", "start": 4359.04, "duration": 4.32}, {"text": "will then be the\none where there's", "start": 4363.36, "duration": 1.92}, {"text": "a very large accumulated total.", "start": 4365.28, "duration": 3.12}, {"text": "So that's a simple\ngeneralization.", "start": 4368.4, "duration": 4.6}, {"text": "And a more interesting\ngeneralization,", "start": 4373.0, "duration": 2.51}, {"text": "you know someone mentioned\nhigher-order polynomials,", "start": 4375.51, "duration": 2.91}, {"text": "and that's certainly\na possibility.", "start": 4378.42, "duration": 3.81}, {"text": "In that direction, what if\nwe don't know the radius?", "start": 4382.23, "duration": 5.325}, {"text": "Suppose we have a\ncircle searching--", "start": 4392.1, "duration": 4.877}, {"text": "this is now a different problem.", "start": 4396.977, "duration": 1.333}, {"text": "We're searching for--", "start": 4398.31, "duration": 1.02}, {"text": "So there's a circle with the\ncenter x0, y0, and radius x0.", "start": 4402.39, "duration": 7.49}, {"text": "And we get these measurements.", "start": 4409.88, "duration": 3.6}, {"text": "Now, the parameter\nspace is larger.", "start": 4413.48, "duration": 2.34}, {"text": "So over here, conveniently\nthe parameter space", "start": 4415.82, "duration": 2.67}, {"text": "was two dimensional,\njust as the theta space.", "start": 4418.49, "duration": 4.87}, {"text": "Well, here we're going to have\na three-dimensional parameter", "start": 4423.36, "duration": 7.64}, {"text": "space.", "start": 4431.0, "duration": 0.66}, {"text": "And we can set up an\naccumulator right here.", "start": 4431.66, "duration": 2.7}, {"text": "And each point in\nthis space corresponds", "start": 4434.36, "duration": 3.06}, {"text": "to a circle at a particular\nposition in the plane", "start": 4437.42, "duration": 5.13}, {"text": "and a particular radius.", "start": 4442.55, "duration": 1.93}, {"text": "And so we can just collect\nup the evidence for it.", "start": 4444.48, "duration": 4.23}, {"text": "And every time we find a\npoint that is on the circle,", "start": 4448.71, "duration": 5.66}, {"text": "we update all of the\naccumulators in a cone,", "start": 4454.37, "duration": 9.55}, {"text": "because, OK, it could be zero\nradius, meaning it's right", "start": 4463.92, "duration": 3.72}, {"text": "where I am, or it could\nbe slightly larger radius", "start": 4467.64, "duration": 2.97}, {"text": "and it's on a\nsmall circle, or it", "start": 4470.61, "duration": 1.89}, {"text": "could be a big radius\nand on a big circle.", "start": 4472.5, "duration": 2.52}, {"text": "I don't know.", "start": 4475.02, "duration": 1.14}, {"text": "But now-- and again, I don't\nget the answer from that single", "start": 4476.16, "duration": 3.69}, {"text": "measurement--", "start": 4479.85, "duration": 0.84}, {"text": "I do this again and again,\nand I get a bunch of cones.", "start": 4480.69, "duration": 3.87}, {"text": "And they all intersect\nin some complicated way,", "start": 4484.56, "duration": 3.0}, {"text": "and, you know, I\ndon't really care.", "start": 4487.56, "duration": 1.93}, {"text": "All I care about is\nthat the answer is going", "start": 4489.49, "duration": 3.71}, {"text": "to have a lot of contributions.", "start": 4493.2, "duration": 1.86}, {"text": "A lot of these cones--", "start": 4495.06, "duration": 1.71}, {"text": "well, ideally all\nof the cones will go", "start": 4496.77, "duration": 2.43}, {"text": "through the answer with noise--", "start": 4499.2, "duration": 2.79}, {"text": "most of them will,\nnot all of them.", "start": 4501.99, "duration": 3.04}, {"text": "And so that's kind of the\nidea of the generalized Hough", "start": 4505.03, "duration": 3.86}, {"text": "transform, that we can\npick some other shape.", "start": 4508.89, "duration": 5.1}, {"text": "And just the key idea is that\nwe have the original space,", "start": 4513.99, "duration": 4.14}, {"text": "and we have the parameter space.", "start": 4518.13, "duration": 1.68}, {"text": "And we collect evidence,\njust as in the pattern,", "start": 4519.81, "duration": 3.48}, {"text": "and we accumulate the evidence.", "start": 4523.29, "duration": 2.34}, {"text": "And we have a score surface.", "start": 4525.63, "duration": 4.92}, {"text": "And we find the peak\nof the score surface.", "start": 4530.55, "duration": 2.13}, {"text": "And if it's above\nsome threshold,", "start": 4532.68, "duration": 2.35}, {"text": "then we accept\nthat as the answer.", "start": 4535.03, "duration": 3.17}, {"text": "Think about the\nr equals 0 plane.", "start": 4545.45, "duration": 5.58}, {"text": "Well, if r equals\n0, then I'm there.", "start": 4551.03, "duration": 2.62}, {"text": "It's a circle of zero radius.", "start": 4553.65, "duration": 1.73}, {"text": "So I can just\ncontribute to this cell.", "start": 4555.38, "duration": 3.3}, {"text": "But now suppose that r\nhas some non-zero value.", "start": 4558.68, "duration": 4.38}, {"text": "Well, that means that I'm\nnot at the correct answer,", "start": 4563.06, "duration": 3.63}, {"text": "but I'm higher up in here.", "start": 4566.69, "duration": 4.53}, {"text": "And the possible\nlocations for the--", "start": 4571.22, "duration": 4.5}, {"text": "so I'm here.", "start": 4575.72, "duration": 1.02}, {"text": "And the possible locations\nare on the circle.", "start": 4576.74, "duration": 3.75}, {"text": "And then when I\nchange the radius,", "start": 4580.49, "duration": 3.48}, {"text": "I'm going to get larger\nand larger circles.", "start": 4583.97, "duration": 3.81}, {"text": "And these are the\nsections of that.", "start": 4587.78, "duration": 2.28}, {"text": "So the parameter space\ncan get complicated.", "start": 4594.91, "duration": 4.51}, {"text": "These are simple examples.", "start": 4599.42, "duration": 2.9}, {"text": "And if it's a\nhigh-dimensional problem,", "start": 4602.32, "duration": 3.27}, {"text": "the parameter space can\nbe expensive to maintain", "start": 4605.59, "duration": 3.36}, {"text": "and, in the presence of\nnoise, may not work that well.", "start": 4608.95, "duration": 5.97}, {"text": "So Hough transform\nis typically not", "start": 4614.92, "duration": 3.39}, {"text": "used in its normal,\noriginally defined mode", "start": 4618.31, "duration": 5.195}, {"text": "to find bubble chamber\ntracks or lines or edges.", "start": 4623.505, "duration": 5.165}, {"text": "But the idea of\nthe Hough transform", "start": 4628.67, "duration": 1.79}, {"text": "is used often as\nlike a subroutine", "start": 4630.46, "duration": 3.39}, {"text": "of something more advanced.", "start": 4633.85, "duration": 2.52}, {"text": "And the key idea, again, is\njust that we have this parameter", "start": 4636.37, "duration": 4.02}, {"text": "space.", "start": 4640.39, "duration": 0.63}, {"text": "And we quantize it, and we\naccumulate evidence in it.", "start": 4641.02, "duration": 4.05}, {"text": "And it doesn't need to be about\nedges or something like that.", "start": 4645.07, "duration": 4.91}, {"text": "OK.", "start": 4649.98, "duration": 1.38}, {"text": "Now, we didn't say much\nabout it in this pattern,", "start": 4651.36, "duration": 5.29}, {"text": "but it's important\npart of the pattern.", "start": 4656.65, "duration": 2.22}, {"text": "And right in figure\n1, it started off", "start": 4658.87, "duration": 2.76}, {"text": "by saying, basically, low-pass\nfilter sample, subsample.", "start": 4661.63, "duration": 4.62}, {"text": "So let's talk a little bit about\nsampling, subsampling, low-pass", "start": 4666.25, "duration": 7.2}, {"text": "filtering.", "start": 4673.45, "duration": 1.35}, {"text": "And that was part of the\nworking at multiple scales.", "start": 4674.8, "duration": 4.61}, {"text": "Now, there are\ndifferent motivations", "start": 4679.41, "duration": 1.98}, {"text": "for working at multiple scales.", "start": 4681.39, "duration": 1.98}, {"text": "One is that you can\nreduce the computation", "start": 4683.37, "duration": 5.55}, {"text": "by working at lower resolution.", "start": 4688.92, "duration": 2.47}, {"text": "So if you can get the result\nyou want at lower resolution,", "start": 4691.39, "duration": 3.14}, {"text": "it makes a lot of\nsense to do so.", "start": 4694.53, "duration": 3.45}, {"text": "Another reason is that\nsometimes, features", "start": 4697.98, "duration": 4.89}, {"text": "like edges or texture are\napparent at one particular", "start": 4702.87, "duration": 3.78}, {"text": "resolution level,\nbut they're not", "start": 4706.65, "duration": 2.01}, {"text": "so obvious at other\nresolution levels.", "start": 4708.66, "duration": 2.55}, {"text": "So we think of an edge as\na kind of ideal step edge.", "start": 4711.21, "duration": 4.29}, {"text": "But we saw, for\nexample, in defocusing,", "start": 4715.5, "duration": 2.79}, {"text": "it won't be an ideal step edge.", "start": 4718.29, "duration": 1.77}, {"text": "And there will be a scale at\nwhich it's the most apparent.", "start": 4720.06, "duration": 4.35}, {"text": "And at other scales, it might be\nsuch a slow, smooth transition", "start": 4724.41, "duration": 3.87}, {"text": "that it's hard to detect.", "start": 4728.28, "duration": 2.76}, {"text": "So let's talk about multiple\nscales and subsampling.", "start": 4731.04, "duration": 4.24}, {"text": "So we already hinted at\nthis, that it's often not", "start": 4735.28, "duration": 12.7}, {"text": "that costly.", "start": 4747.98, "duration": 2.77}, {"text": "So let's suppose we reduce\nthe number of columns", "start": 4750.75, "duration": 12.25}, {"text": "and the number of rows by a\nmultiplication by a factor r,", "start": 4763.0, "duration": 3.42}, {"text": "where r could be 1/2.", "start": 4766.42, "duration": 2.52}, {"text": "But let's keep a general.", "start": 4768.94, "duration": 2.82}, {"text": "So then the amount of work\nis going to go as work,", "start": 4771.76, "duration": 8.03}, {"text": "and also the amount of\nspace if you keep things", "start": 4779.79, "duration": 2.97}, {"text": "around, nm plus r\nsquared nm plus,", "start": 4782.76, "duration": 6.57}, {"text": "r to the fourth nm, et cetera.", "start": 4789.33, "duration": 2.31}, {"text": "So the overall work\nis larger than what", "start": 4800.6, "duration": 4.31}, {"text": "we have for just the\nhigher-resolution image", "start": 4804.91, "duration": 2.64}, {"text": "but not very.", "start": 4807.55, "duration": 1.47}, {"text": "So let's look at r equals 1/2.", "start": 4809.02, "duration": 2.91}, {"text": "I think we already\nlooked at that case.", "start": 4811.93, "duration": 1.98}, {"text": "Then we get 4 over 3 nm.", "start": 4813.91, "duration": 3.21}, {"text": "so in that case, it's\njust like 30% more work.", "start": 4817.12, "duration": 2.67}, {"text": "It's not huge.", "start": 4819.79, "duration": 0.91}, {"text": "How about r equals 1\nover square root of 2?", "start": 4823.21, "duration": 3.84}, {"text": "Then we get 1\nminus 1/2 is a 1/2.", "start": 4827.05, "duration": 2.34}, {"text": "And we flip that, we get 2nm.", "start": 4829.39, "duration": 3.57}, {"text": "So that's more work.", "start": 4832.96, "duration": 3.15}, {"text": "But this turns out\nto be important.", "start": 4836.11, "duration": 2.11}, {"text": "So we're-- the Hough\nis the obvious thing.", "start": 4838.22, "duration": 4.31}, {"text": "We're just going to take,\nfor example, 2-by-2 blocks", "start": 4842.53, "duration": 3.84}, {"text": "and take the average,\nand that's the new value.", "start": 4846.37, "duration": 3.953}, {"text": "And we find that that's\nactually not a very good way", "start": 4850.323, "duration": 2.167}, {"text": "of doing it.", "start": 4852.49, "duration": 0.52}, {"text": "But conceptually, we can\nthink of that as a very simple", "start": 4853.01, "duration": 4.97}, {"text": "subsampling method.", "start": 4857.98, "duration": 2.94}, {"text": "And so why would we\ngo to something else?", "start": 4860.92, "duration": 2.11}, {"text": "Well, it turns out\nthat's very aggressive.", "start": 4863.03, "duration": 1.82}, {"text": "And you can find serious\naliasing problems", "start": 4864.85, "duration": 5.61}, {"text": "when you squish\nthings down that much.", "start": 4870.46, "duration": 3.09}, {"text": "So it might be better\nnot to be as aggressive.", "start": 4873.55, "duration": 2.7}, {"text": "And so 1 over square root\nof 2 is halfway there.", "start": 4876.25, "duration": 4.2}, {"text": "And that one is used.", "start": 4883.5, "duration": 1.54}, {"text": "So how do you do that?", "start": 4885.04, "duration": 1.86}, {"text": "Well, here's one way.", "start": 4886.9, "duration": 1.25}, {"text": "You know, what we're going\nto do is basically reduce", "start": 4892.34, "duration": 6.9}, {"text": "the number of cells by 2.", "start": 4899.24, "duration": 3.96}, {"text": "So over here, we reduce\nthe number of cells", "start": 4903.2, "duration": 2.67}, {"text": "by a factor of 4 going from\nthe 2-by-2 blocks to the 1.", "start": 4905.87, "duration": 4.41}, {"text": "So can you think of a way\nof subsampling this grid so", "start": 4910.28, "duration": 4.38}, {"text": "that you reduce the number\nof cells by 2 rather than 4?", "start": 4914.66, "duration": 3.525}, {"text": "Anyone play chess or draughts?", "start": 4925.4, "duration": 5.18}, {"text": "And so a checkerboard\nwill do it.", "start": 4930.58, "duration": 2.19}, {"text": "So we can do a red,\nblack or red, white--", "start": 4932.77, "duration": 4.11}, {"text": "red, black.", "start": 4936.88, "duration": 1.07}, {"text": "So if we just retain one of the\ncolors, one of the two colors,", "start": 4943.821, "duration": 7.059}, {"text": "by definition, then, we've\nhalved the number of cells.", "start": 4950.88, "duration": 4.62}, {"text": "And it's probably not the first\nthing that came to your mind,", "start": 4955.5, "duration": 3.3}, {"text": "because it doesn't look like\nit's a nice rectangular grid.", "start": 4958.8, "duration": 5.87}, {"text": "But it is, because all we\nneed to do is think of it", "start": 4964.67, "duration": 3.08}, {"text": "as a grid running\nin that direction.", "start": 4967.75, "duration": 2.73}, {"text": "So because these cells follow\na regular pattern here,", "start": 4973.37, "duration": 4.44}, {"text": "and then the next row is here,\nand same in this direction.", "start": 4977.81, "duration": 7.15}, {"text": "So if we're willing to deal\nwith a 45-degree rotation,", "start": 4984.96, "duration": 5.97}, {"text": "this gives us a square\nroot of 2 reduction.", "start": 4990.93, "duration": 3.8}, {"text": "And the other thing it does\nis it increases the spacing", "start": 4994.73, "duration": 6.06}, {"text": "by square root of 2.", "start": 5000.79, "duration": 2.25}, {"text": "So in this case, the spacing\nincreased by a factor of 2.", "start": 5003.04, "duration": 4.35}, {"text": "So now the spacing\nbetween neighboring cells", "start": 5007.39, "duration": 3.93}, {"text": "is multiplied by the\nsquare root of 2.", "start": 5011.32, "duration": 5.22}, {"text": "And so that's a\nlittle odd 45 degrees.", "start": 5016.54, "duration": 2.67}, {"text": "But think of it.", "start": 5019.21, "duration": 0.81}, {"text": "You do it the next time, you're\nback in sync with the original.", "start": 5020.02, "duration": 3.76}, {"text": "So on a related point,\nthere's a method", "start": 5023.78, "duration": 3.62}, {"text": "called SIFT, which\nis used for finding", "start": 5027.4, "duration": 4.17}, {"text": "corresponding points\nin different images", "start": 5031.57, "duration": 2.91}, {"text": "of the same scene.", "start": 5034.48, "duration": 1.14}, {"text": "And it's used widely to patch\ntogether multiple images", "start": 5035.62, "duration": 6.36}, {"text": "to produce 3D information about,\nfor example, popular sites", "start": 5041.98, "duration": 7.62}, {"text": "that tourists go to where you\nhave thousands of pictures.", "start": 5049.6, "duration": 3.36}, {"text": "And you are trying to\ntake two pictures taken", "start": 5052.96, "duration": 4.02}, {"text": "from two different positions,\nwith different cameras,", "start": 5056.98, "duration": 2.64}, {"text": "under different\nlighting conditions,", "start": 5059.62, "duration": 1.5}, {"text": "and you're trying\nto match them up.", "start": 5061.12, "duration": 1.458}, {"text": "There's this method\ndue to Lowe called", "start": 5062.578, "duration": 3.912}, {"text": "SIFT, which gets\ndescriptors of points", "start": 5066.49, "duration": 4.68}, {"text": "in the image that are attempting\nto be as unique as possible.", "start": 5071.17, "duration": 4.71}, {"text": "And he uses much smaller--", "start": 5075.88, "duration": 3.42}, {"text": "much less aggressive.", "start": 5079.3, "duration": 1.51}, {"text": "So he uses multiple\nsteps per octave.", "start": 5080.81, "duration": 2.9}, {"text": "So we've gone down a whole\noctave in one step, you know,", "start": 5083.71, "duration": 4.935}, {"text": "a factor of 2.", "start": 5088.645, "duration": 1.335}, {"text": "Here we go down\na half an octave.", "start": 5089.98, "duration": 3.0}, {"text": "It takes two steps to\ngo down a whole octave.", "start": 5092.98, "duration": 2.28}, {"text": "And I forget what he\nrecommends in his pattern.", "start": 5095.26, "duration": 2.4}, {"text": "It's, I don't know,\nsix or something.", "start": 5097.66, "duration": 1.95}, {"text": "So it's more like a\nmusical scale, where", "start": 5099.61, "duration": 2.28}, {"text": "an octave is divided into--", "start": 5101.89, "duration": 2.28}, {"text": "eight nodes?", "start": 5104.17, "duration": 2.68}, {"text": "Anyone know?", "start": 5106.85, "duration": 1.23}, {"text": "OK.", "start": 5108.08, "duration": 1.05}, {"text": "And so they're not equally\nspaced, but that's the idea.", "start": 5109.13, "duration": 3.48}, {"text": "So yes, it might\nseem a little odd", "start": 5112.61, "duration": 2.22}, {"text": "that we're not going so\naggressive with a factor of 2.", "start": 5114.83, "duration": 2.73}, {"text": "But actually, there are good\nreasons not to always do that.", "start": 5117.56, "duration": 4.24}, {"text": "And, you know, SIFT\nis a classic example", "start": 5121.8, "duration": 2.81}, {"text": "of a situation where we do\nnot subsample as aggressively.", "start": 5124.61, "duration": 4.53}, {"text": "But we're out of time, so sorry.", "start": 5129.14, "duration": 3.99}, {"text": "OK.", "start": 5133.13, "duration": 1.29}, {"text": "I've got proposals\nfor those of you", "start": 5134.42, "duration": 3.18}, {"text": "in 6.866, of almost everyone.", "start": 5137.6, "duration": 2.94}, {"text": "If you're one of those\npeople who hasn't yet", "start": 5140.54, "duration": 3.63}, {"text": "sent in a proposal,\nplease send it in.", "start": 5144.17, "duration": 5.79}, {"text": "And yesterday, I\nopened a cookie,", "start": 5149.96, "duration": 4.8}, {"text": "and it said, slaying\nthe dragon of delay", "start": 5154.76, "duration": 3.6}, {"text": "is no sport for the long winded.", "start": 5158.36, "duration": 2.44}, {"text": "So please take that\nto heart if you're", "start": 5160.8, "duration": 2.45}, {"text": "one of the people who has not\nsent this proposal in yet.", "start": 5163.25, "duration": 3.77}]
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+[{"text": "ROBERT TOWNSEND: Welcome,\neverybody, today,", "start": 11.44, "duration": 2.31}, {"text": "for the next segment\nof the class.", "start": 13.75, "duration": 3.06}, {"text": "Actually, this is\nliterally a continuation.", "start": 16.81, "duration": 4.03}, {"text": "It's not a sharp break between\nthe last lecture and today.", "start": 20.84, "duration": 2.9}, {"text": "Fortunately, the\nlecture today has", "start": 23.74, "duration": 2.49}, {"text": "some repeat of the equations,\nor at least a version", "start": 26.23, "duration": 3.45}, {"text": "of those equations.", "start": 29.68, "duration": 1.65}, {"text": "Plus, I know you're all\ntotally fresh from the exam,", "start": 31.33, "duration": 3.9}, {"text": "so you know what the\nlast lecture was anyway.", "start": 35.23, "duration": 3.75}, {"text": "Just teasing you a little bit.", "start": 38.98, "duration": 1.5}, {"text": "Sorry.", "start": 40.48, "duration": 1.035}, {"text": "I'll just say a few\nwords about the calendar.", "start": 41.515, "duration": 3.525}, {"text": "So we are right here,\ntoday, Thursday, 10/1.", "start": 45.04, "duration": 6.09}, {"text": "Oh, my goodness.", "start": 51.13, "duration": 0.75}, {"text": "It is October.", "start": 51.88, "duration": 1.74}, {"text": "And we're going to do\nrisk-sharing applications today", "start": 53.62, "duration": 4.11}, {"text": "and then also 9.", "start": 57.73, "duration": 2.13}, {"text": "Although this says\nrisk-sharing applications,", "start": 59.86, "duration": 2.58}, {"text": "I want to feature that we'll\ncombine it with a production", "start": 62.44, "duration": 3.58}, {"text": "even in a more direct\nway than we will today.", "start": 66.02, "duration": 2.75}, {"text": "So two lectures today, Thursday\nand Tuesday, on risk-sharing.", "start": 68.77, "duration": 5.16}, {"text": "So that's the calendar.", "start": 73.93, "duration": 2.67}, {"text": "The second thing would\nbe the reading list.", "start": 76.6, "duration": 3.36}, {"text": "And we are here at lecture 8.", "start": 79.96, "duration": 2.1}, {"text": "So the two readings today\nare risk and insurance", "start": 82.06, "duration": 3.0}, {"text": "in Village India, my\npaper in Econometrica.", "start": 85.06, "duration": 3.06}, {"text": "And we will cover that in\na fair amount of detail", "start": 88.12, "duration": 2.64}, {"text": "today, although not\nevery word, obviously.", "start": 90.76, "duration": 3.0}, {"text": "And also, chapter 2 in\nMedieval Village Economy.", "start": 93.76, "duration": 4.12}, {"text": "So that's the reading list.", "start": 97.88, "duration": 2.83}, {"text": "So today is lecture\n8, and that is here.", "start": 100.71, "duration": 6.37}, {"text": "So risk-sharing\napplications-- we're", "start": 107.08, "duration": 2.54}, {"text": "going to do two\ndifferent economies using", "start": 109.62, "duration": 2.28}, {"text": "the same theory, although\nthe questions to be", "start": 111.9, "duration": 2.37}, {"text": "asked, though related, are\na little bit different.", "start": 114.27, "duration": 2.46}, {"text": "One is Village India using\nconsumption and income", "start": 116.73, "duration": 4.2}, {"text": "data, which I refer to\nas an ex-post version", "start": 120.93, "duration": 3.99}, {"text": "of the implications of\nthe risk-sharing model,", "start": 124.92, "duration": 2.58}, {"text": "and also, as anticipated,\nthe medieval village economy,", "start": 127.5, "duration": 4.26}, {"text": "where we're going to talk\nabout dividing up the land.", "start": 131.76, "duration": 3.09}, {"text": "And you've seen\nmaps of this before,", "start": 134.85, "duration": 2.83}, {"text": "but we didn't have\nall of the tools we", "start": 137.68, "duration": 2.03}, {"text": "needed to really do a good job.", "start": 139.71, "duration": 2.04}, {"text": "But we do now.", "start": 141.75, "duration": 1.6}, {"text": "OK.", "start": 143.35, "duration": 0.5}, {"text": "So for India, here's the\nmotivation from my paper.", "start": 143.85, "duration": 4.43}, {"text": "A large part of the population\nin developing countries", "start": 148.28, "duration": 3.94}, {"text": "live in high-risk environments.", "start": 152.22, "duration": 2.58}, {"text": "That said, there are numerous\nways to cope with it.", "start": 154.8, "duration": 4.09}, {"text": "One is to diversify the\nactivities you're undertaking--", "start": 158.89, "duration": 4.52}, {"text": "trying to have a\nportfolio, as it were--", "start": 163.41, "duration": 3.45}, {"text": "or ex-post, after\nincomes get realized,", "start": 166.86, "duration": 4.2}, {"text": "to engage in financial\ntransactions,", "start": 171.06, "duration": 2.23}, {"text": "including gifts and transfers\namong family and family", "start": 173.29, "duration": 3.35}, {"text": "networks.", "start": 176.64, "duration": 1.2}, {"text": "How well do any one of these\nex-post or ex-ante mechanisms", "start": 177.84, "duration": 3.72}, {"text": "work?", "start": 181.56, "duration": 1.17}, {"text": "Well, the main, quote,\n\"insight\" of the paper", "start": 182.73, "duration": 3.15}, {"text": "was that we really\ndon't necessarily", "start": 185.88, "duration": 2.28}, {"text": "have to enumerate the mechanism.", "start": 188.16, "duration": 2.04}, {"text": "We just look at the outcome.", "start": 190.2, "duration": 2.36}, {"text": "I'll qualify that a\nlittle bit, and we", "start": 192.56, "duration": 1.74}, {"text": "can keep coming back to this.", "start": 194.3, "duration": 1.95}, {"text": "If they diversified perfectly\nand everyone had a balanced", "start": 196.25, "duration": 4.26}, {"text": "portfolio, then they would\nall have the same outcome,", "start": 200.51, "duration": 3.94}, {"text": "and there would be no\nfurther risk to share.", "start": 204.45, "duration": 2.94}, {"text": "So in some sense,\nwhat we're going", "start": 207.39, "duration": 1.61}, {"text": "to go through today would not\nhave much content in the sense", "start": 209.0, "duration": 4.32}, {"text": "that today, we're\nreferring to risk sharing,", "start": 213.32, "duration": 3.9}, {"text": "but it's not done, per se, by\nsharing risk after the fact.", "start": 217.22, "duration": 4.42}, {"text": "It's done by ex-ante\ndiversification.", "start": 221.64, "duration": 2.9}, {"text": "Anyway, those two\nstrands to repeat", "start": 224.54, "duration": 1.86}, {"text": "are going to be in\ntoday's lecture.", "start": 226.4, "duration": 2.17}, {"text": "We're going to do the\nex-post part first,", "start": 228.57, "duration": 2.94}, {"text": "which assumes partial but\nnot complete diversification,", "start": 231.51, "duration": 3.56}, {"text": "and then look at\nhow they could do", "start": 235.07, "duration": 1.89}, {"text": "it ex-ante with partial but\npotentially not complete", "start": 236.96, "duration": 4.14}, {"text": "diversification.", "start": 241.1, "duration": 2.23}, {"text": "All right.", "start": 243.33, "duration": 0.68}, {"text": "So characteristics of village\neconomies as in India--", "start": 244.01, "duration": 5.57}, {"text": "very risky place, in large part\nbecause agriculture does not", "start": 249.58, "duration": 5.57}, {"text": "provide a stable\nsource of income.", "start": 255.15, "duration": 3.24}, {"text": "There's a lot of\nrisk, idiosyncratic", "start": 258.39, "duration": 2.759}, {"text": "and aggregate risk.", "start": 261.149, "duration": 1.381}, {"text": "Households diversify\nin many ways.", "start": 262.53, "duration": 2.8}, {"text": "One-- not planting\nall of the same crops.", "start": 265.33, "duration": 4.1}, {"text": "And we are going to use\nthis benchmark which", "start": 269.43, "duration": 2.76}, {"text": "assumes there's no information\nproblem, no moral hazard", "start": 272.19, "duration": 3.42}, {"text": "problem, no contract\nenforcement problem.", "start": 275.61, "duration": 4.02}, {"text": "All of those words at\nthis point in the class", "start": 279.63, "duration": 2.87}, {"text": "don't make a whole lot\nof sense because we", "start": 282.5, "duration": 1.75}, {"text": "haven't studied anything but\nthese frictionless economies.", "start": 284.25, "duration": 5.47}, {"text": "But that was the premise.", "start": 289.72, "duration": 1.43}, {"text": "And again, to anticipate\nsubsequent lectures,", "start": 291.15, "duration": 2.79}, {"text": "today we'll see how\nwell this theory does", "start": 293.94, "duration": 2.19}, {"text": "without any of these frictions.", "start": 296.13, "duration": 2.97}, {"text": "And then subsequent\nliterature has", "start": 299.1, "duration": 2.4}, {"text": "started to assume things\nlike contract enforcement", "start": 301.5, "duration": 3.36}, {"text": "and information\nasymmetries, but we are not", "start": 304.86, "duration": 2.1}, {"text": "going to do that today.", "start": 306.96, "duration": 2.51}, {"text": "So how do they diversify?", "start": 309.47, "duration": 2.0}, {"text": "Well, in a village\nAurepalle, which", "start": 311.47, "duration": 2.94}, {"text": "was under the auspices of\nthe Institute for Crops", "start": 314.41, "duration": 4.04}, {"text": "in the Semi-Arid\nTropics, ICRISAT, farmers", "start": 318.45, "duration": 4.36}, {"text": "are a poly-growth sorghum.", "start": 322.81, "duration": 1.71}, {"text": "They grow castor.", "start": 324.52, "duration": 1.26}, {"text": "Sorghum is a grain like wheat.", "start": 325.78, "duration": 2.34}, {"text": "Castor you may have heard\nof as in castor oil.", "start": 328.12, "duration": 4.11}, {"text": "It's both used in\ndiet, but also, it", "start": 332.23, "duration": 2.61}, {"text": "turns out to be a\nlubricant for jet engines.", "start": 334.84, "duration": 3.57}, {"text": "Anyway, the coefficients of\nvariation are 0.5 and about 1.", "start": 338.41, "duration": 5.61}, {"text": "Now, you may not remember\nthat in medieval villages,", "start": 344.02, "duration": 3.21}, {"text": "we talked about a\nvery risky environment", "start": 347.23, "duration": 2.31}, {"text": "with the coefficient\nof variation of yields", "start": 349.54, "duration": 2.43}, {"text": "of about 0.35 or something\nlike that, which delivered", "start": 351.97, "duration": 4.59}, {"text": "a disaster every 12 years.", "start": 356.56, "duration": 2.08}, {"text": "So it's more risky than\nthat taking any one crop", "start": 358.64, "duration": 3.35}, {"text": "one at a time.", "start": 361.99, "duration": 0.96}, {"text": "But they can\ndiversify over crops.", "start": 362.95, "duration": 2.79}, {"text": "So looking at the\ncrop correlation,", "start": 365.74, "duration": 3.12}, {"text": "those numbers range\nfrom 0.09 to 0.81.", "start": 368.86, "duration": 4.425}, {"text": "At .09, it's almost the\ncase that the yields", "start": 373.285, "duration": 3.915}, {"text": "on one type of crop are\nindependent of the yields", "start": 377.2, "duration": 3.09}, {"text": "on the other one.", "start": 380.29, "duration": 1.59}, {"text": "Again, you can go back and look\nat the lecture under Consumer", "start": 381.88, "duration": 3.51}, {"text": "Preferences where we\nwere introducing risk", "start": 385.39, "duration": 2.55}, {"text": "and derived these\nkinds of statistics.", "start": 387.94, "duration": 2.88}, {"text": "Soil isn't uniform\neither, so even taking", "start": 390.82, "duration": 3.18}, {"text": "as given that they're\ngoing to do castor,", "start": 394.0, "duration": 2.19}, {"text": "they can plant it in one\ntype of soil or another.", "start": 396.19, "duration": 3.1}, {"text": "Each type is risky with a\ncoefficient of variation", "start": 399.29, "duration": 3.32}, {"text": "from 0.7 to, again,\na little over 1.", "start": 402.61, "duration": 3.03}, {"text": "But you can diversify\nover soil as well", "start": 405.64, "duration": 3.63}, {"text": "with a correlation of only 0.37,\nso pretty good diversification", "start": 409.27, "duration": 4.53}, {"text": "possibilities.", "start": 413.8, "duration": 1.77}, {"text": "That said, households don't hold\ncompletely balanced portfolios", "start": 415.57, "duration": 4.68}, {"text": "across soils and crops.", "start": 420.25, "duration": 1.65}, {"text": "One household will plant more\nof one crop than the other,", "start": 421.9, "duration": 3.15}, {"text": "or for castor, have more of\none type of soil than the other", "start": 425.05, "duration": 4.62}, {"text": "despite all the\ndiversification possibilities.", "start": 429.67, "duration": 2.94}, {"text": "And going outwards from crops\nto other income-generating", "start": 432.61, "duration": 5.7}, {"text": "activities, they can\nengage in wage labor.", "start": 438.31, "duration": 4.38}, {"text": "They can do trade in\nhandicrafts or animal husbandry.", "start": 442.69, "duration": 5.19}, {"text": "So for example, trade in\nhandicrafts in Aurepalle", "start": 447.88, "duration": 3.63}, {"text": "consists of climbing\npalm trees to get", "start": 451.51, "duration": 4.41}, {"text": "the fruit from which they will\nmake palm liquor, for example.", "start": 455.92, "duration": 4.08}, {"text": "And it's a pretty\nspecialized activity.", "start": 460.0, "duration": 2.43}, {"text": "It looks like telephone\nrepairmen climbing poles", "start": 462.43, "duration": 3.87}, {"text": "with pretty heavy\nand fancy equipment.", "start": 466.3, "duration": 3.78}, {"text": "Animal husbandry consists of\ngrazing animals and so on.", "start": 470.08, "duration": 4.21}, {"text": "Anyway, if you look at\nhow much land they hold,", "start": 474.29, "duration": 2.96}, {"text": "it varies from no land at all to\nbeing a small holder or medium", "start": 477.25, "duration": 4.89}, {"text": "or large holder.", "start": 482.14, "duration": 1.57}, {"text": "And so for example,\nnot surprisingly,", "start": 483.71, "duration": 3.69}, {"text": "the more land they\nhave, the more", "start": 487.4, "duration": 2.12}, {"text": "is their income from crops,\ngoing from about 2% to 56%", "start": 489.52, "duration": 5.04}, {"text": "of the total income.", "start": 494.56, "duration": 1.38}, {"text": "Likewise, when they hold very\nlittle land, most of the income", "start": 495.94, "duration": 3.69}, {"text": "is from labor, wage\nlabor, and that", "start": 499.63, "duration": 2.67}, {"text": "drops to 4% for the rich\nguys, large landholders", "start": 502.3, "duration": 4.53}, {"text": "in the village, and so on.", "start": 506.83, "duration": 2.67}, {"text": "Those patterns are pretty\nmuch repeated in the other two", "start": 509.5, "duration": 3.27}, {"text": "villages, and\nKanzara especially.", "start": 512.77, "duration": 2.88}, {"text": "Shirapur is much\nflatter in the sense", "start": 515.65, "duration": 2.909}, {"text": "that we don't see very\nsharp gradients in terms", "start": 518.559, "duration": 3.421}, {"text": "of percentage of income\nfrom various sources", "start": 521.98, "duration": 3.81}, {"text": "as we move from small.", "start": 525.79, "duration": 1.5}, {"text": "So villages are\nkind of a metaphor.", "start": 527.29, "duration": 3.15}, {"text": "Villages are not all alike.", "start": 530.44, "duration": 2.198}, {"text": "But the techniques\nwe're going to use today", "start": 532.638, "duration": 1.792}, {"text": "do take into account\nthe differences.", "start": 534.43, "duration": 2.49}, {"text": "Now let's look at\ndiversification", "start": 536.92, "duration": 1.77}, {"text": "over income sources the way we\ndid for crops and soil types.", "start": 538.69, "duration": 4.57}, {"text": "This is a little bit difficult\nto read, and I'll tell you why.", "start": 543.26, "duration": 4.55}, {"text": "Going down the diagonal here\nis the coefficient of variation", "start": 547.81, "duration": 4.95}, {"text": "of each income source.", "start": 552.76, "duration": 1.45}, {"text": "So for example,\ncrop production is", "start": 554.21, "duration": 3.47}, {"text": "quite risky with a coefficient\nof 0.42, which I almost", "start": 557.68, "duration": 4.05}, {"text": "said a minute ago.", "start": 561.73, "duration": 2.49}, {"text": "Of livestock income, the\nCV is 0.21, et cetera.", "start": 564.22, "duration": 5.31}, {"text": "Now, these other off\ndiagonal elements", "start": 569.53, "duration": 2.52}, {"text": "here represent the covariation.", "start": 572.05, "duration": 3.15}, {"text": "So what would have\nbeen better would", "start": 575.2, "duration": 3.45}, {"text": "have been to list profits,\nlivestock, income,", "start": 578.65, "duration": 3.45}, {"text": "earned wages, and\ntrade and handicrafts", "start": 582.1, "duration": 2.46}, {"text": "going down the rows,\nand then picking", "start": 584.56, "duration": 2.76}, {"text": "a row, move across the column\nto find the covariance.", "start": 587.32, "duration": 4.54}, {"text": "So for example, this guy\nhere is the covariance", "start": 591.86, "duration": 3.23}, {"text": "between profits from crop\nproduction and livestock", "start": 595.09, "duration": 3.61}, {"text": "income.", "start": 598.7, "duration": 0.5}, {"text": "And it's actually negative.", "start": 599.2, "duration": 1.93}, {"text": "So huge diversification\npossibilities for a household", "start": 601.13, "duration": 4.22}, {"text": "if they were doing both\ncrops and livestock.", "start": 605.35, "duration": 3.45}, {"text": "These lower\noff-diagonal elements", "start": 608.8, "duration": 3.24}, {"text": "are not filled in because\nthe matrix is symmetric.", "start": 612.04, "duration": 3.33}, {"text": "The covariation of\nactivity i with activity j", "start": 615.37, "duration": 3.93}, {"text": "is the same as the\nvariation of i with i.", "start": 619.3, "duration": 3.54}, {"text": "So it would be redundant\nto fill them all in,", "start": 622.84, "duration": 2.61}, {"text": "and they were deleted to\nmake it easier to read.", "start": 625.45, "duration": 3.92}, {"text": "So taking into account different\nsoils, different crops,", "start": 629.37, "duration": 3.62}, {"text": "different income sources,\npiling them all together,", "start": 632.99, "duration": 2.73}, {"text": "and plotting income over\nthe 10 years for which we", "start": 635.72, "duration": 4.15}, {"text": "have the data, we look\nwhat happens over time", "start": 639.87, "duration": 4.86}, {"text": "from 1976 to 1985, essentially.", "start": 644.73, "duration": 5.47}, {"text": "And what's getting\nplotted is not just", "start": 650.2, "duration": 2.79}, {"text": "the time series\nof one household.", "start": 652.99, "duration": 3.14}, {"text": "All of them are\ngetting plotted here.", "start": 656.13, "duration": 1.73}, {"text": "In fact, the way\nthe data were coded,", "start": 657.86, "duration": 4.17}, {"text": "low numbers correspond\nto little or no land,", "start": 662.03, "duration": 2.97}, {"text": "and high numbers\ncorrespond to lots of land.", "start": 665.0, "duration": 3.63}, {"text": "So as we move backwards\nalong the household number,", "start": 668.63, "duration": 4.02}, {"text": "the households are\ngetting more and more land", "start": 672.65, "duration": 2.67}, {"text": "and are actually--", "start": 675.32, "duration": 2.16}, {"text": "net worth is going up.", "start": 677.48, "duration": 2.98}, {"text": "So that 1% of the\npopulation that", "start": 680.46, "duration": 2.1}, {"text": "owns 50% of the wealth,\nthat's this guy back here.", "start": 682.56, "duration": 3.96}, {"text": "Now, I refer to this graph\nas the Rocky Mountains", "start": 686.52, "duration": 5.4}, {"text": "because you can\nsee all the peaks--", "start": 691.92, "duration": 2.22}, {"text": "well, not quite.", "start": 694.14, "duration": 0.84}, {"text": "I was going to say you can\nsee all the peaks and valleys.", "start": 694.98, "duration": 3.5}, {"text": "That's wrong.", "start": 698.48, "duration": 1.32}, {"text": "When you have a peak, you\ncan't see the valley behind it.", "start": 699.8, "duration": 4.63}, {"text": "If all these incomes\ncommuned with each other,", "start": 704.43, "duration": 3.99}, {"text": "then everyone's peak would\nhappen at the same time,", "start": 708.42, "duration": 2.74}, {"text": "and it would look like waves.", "start": 711.16, "duration": 2.06}, {"text": "Instead, we see this rather\njagged, sharp picture.", "start": 713.22, "duration": 3.51}, {"text": "And again, when you're able\nto see the valley behind,", "start": 716.73, "duration": 3.39}, {"text": "it's because there's not\na peak in front of it.", "start": 720.12, "duration": 2.4}, {"text": "Now, the other thing is\nmoving along this gradient--", "start": 722.52, "duration": 2.79}, {"text": "I should have pointed this out\nearlier-- there is a 0 here.", "start": 725.31, "duration": 3.42}, {"text": "This 0 corresponds to the\noverall average of income", "start": 728.73, "duration": 4.35}, {"text": "both over households\nand over time.", "start": 733.08, "duration": 2.89}, {"text": "So these guys are\nbelow-average income.", "start": 735.97, "duration": 3.26}, {"text": "These guys behind it are\nhigher-average income.", "start": 739.23, "duration": 2.79}, {"text": "And again, you can see\nthat that's quite a salient", "start": 742.02, "duration": 3.0}, {"text": "gradient.", "start": 745.02, "duration": 1.96}, {"text": "Here is the corresponding\npicture for grain.", "start": 746.98, "duration": 3.9}, {"text": "And I could have plotted\nall consumption items,", "start": 750.88, "duration": 2.97}, {"text": "but it would have\nlooked similar.", "start": 753.85, "duration": 1.56}, {"text": "The paper actually does that.", "start": 755.41, "duration": 2.28}, {"text": "When I say corresponding, I\nmean the scale hasn't changed.", "start": 757.69, "duration": 4.68}, {"text": "The scale that was used to\nplot income, 4,000 at the peak,", "start": 762.37, "duration": 4.83}, {"text": "is the same as the scale that's\nbeing used to plot consumption.", "start": 767.2, "duration": 4.47}, {"text": "So you can see everybody's\nconsumption is compressed,", "start": 771.67, "duration": 3.53}, {"text": "so they're smoothing.", "start": 775.2, "duration": 2.11}, {"text": "They're smoothing over time.", "start": 777.31, "duration": 2.25}, {"text": "And to a degree\nthere, a large degree,", "start": 779.56, "duration": 2.82}, {"text": "they're actually smoothing\nover households as well.", "start": 782.38, "duration": 3.75}, {"text": "Those very wealthy\nguys are consuming", "start": 786.13, "duration": 2.64}, {"text": "more than the poor guys\nbut not nearly as much", "start": 788.77, "duration": 2.7}, {"text": "as income is higher for them\nrelative to income of low guys.", "start": 791.47, "duration": 5.8}, {"text": "The main point of\nthe picture, however,", "start": 797.27, "duration": 2.35}, {"text": "is that here, you can\nalmost see the waves.", "start": 799.62, "duration": 3.77}, {"text": "Grain consumption is\nkind of co-moving.", "start": 803.39, "duration": 3.39}, {"text": "That would be easier to\nsee if we blew it up,", "start": 806.78, "duration": 2.64}, {"text": "but we will look at\nthis statistically", "start": 809.42, "duration": 1.89}, {"text": "as well in a few\nsubsequent slides.", "start": 811.31, "duration": 3.51}, {"text": "And I refer to this as Kansas.", "start": 814.82, "duration": 2.28}, {"text": "I don't if any of you\nhave ever been in Kansas.", "start": 817.1, "duration": 3.48}, {"text": "I ask this every time\nI teach this diagram.", "start": 820.58, "duration": 3.93}, {"text": "At one point, some\nstudent in the class", "start": 824.51, "duration": 2.49}, {"text": "said, I'm from Kansas.", "start": 827.0, "duration": 1.29}, {"text": "And I said, oh, I'm sorry.", "start": 828.29, "duration": 1.14}, {"text": "I hope I haven't insulted you.", "start": 829.43, "duration": 1.627}, {"text": "And he said, no, no.", "start": 831.057, "duration": 0.833}, {"text": "It is really boring there.", "start": 831.89, "duration": 2.79}, {"text": "So I like Kansas.", "start": 834.68, "duration": 1.11}, {"text": "I'm not saying that.", "start": 835.79, "duration": 0.99}, {"text": "But anyway, amber\nwaves of grain,", "start": 836.78, "duration": 3.21}, {"text": "so consumption versus income.", "start": 839.99, "duration": 3.34}, {"text": "So let's think about\na theory to try", "start": 843.33, "duration": 2.66}, {"text": "to explain the difference\nbetween those two diagrams.", "start": 845.99, "duration": 3.82}, {"text": "And this is the bit that's\na little bit of a review,", "start": 849.81, "duration": 2.76}, {"text": "but I think a useful one.", "start": 852.57, "duration": 1.45}, {"text": "So we're going to talk\nabout individual k", "start": 854.02, "duration": 3.23}, {"text": "alive at date t\nthat has experienced", "start": 857.25, "duration": 3.06}, {"text": "a history of shocks ht.", "start": 860.31, "duration": 3.52}, {"text": "This history is the shock at\ndate 1, the shock at date 2,", "start": 863.83, "duration": 3.32}, {"text": "and the shock at date 3.", "start": 867.15, "duration": 2.19}, {"text": "So again, this is the\nstate space representation", "start": 869.34, "duration": 4.83}, {"text": "of the tree that\nyou saw in Debreu,", "start": 874.17, "duration": 3.45}, {"text": "and I featured at\nleast twice already.", "start": 877.62, "duration": 2.67}, {"text": "What is the objective function?", "start": 880.29, "duration": 1.72}, {"text": "We're going to solve\nthat programming problem", "start": 882.01, "duration": 2.45}, {"text": "to go back and forth between\nsolutions to that problem", "start": 884.46, "duration": 3.18}, {"text": "in Pareto optimal allocations.", "start": 887.64, "duration": 2.13}, {"text": "So we're going to maximize\na lambda-weighted sum", "start": 889.77, "duration": 3.39}, {"text": "of discounted\nexpected utilities,", "start": 893.16, "duration": 2.55}, {"text": "weighted lambda k for weight\nk over all the individuals", "start": 895.71, "duration": 4.08}, {"text": "and their capital M of them.", "start": 899.79, "duration": 2.1}, {"text": "The contemporary utility\nfunctions have as arguments", "start": 901.89, "duration": 4.56}, {"text": "the consumption of individual k\nat date thq, which we just did,", "start": 906.45, "duration": 3.87}, {"text": "and then this age-gender index.", "start": 910.32, "duration": 3.63}, {"text": "So not everyone is the same age.", "start": 913.95, "duration": 2.49}, {"text": "Not everyone is the same gender.", "start": 916.44, "duration": 2.52}, {"text": "18-year-old males\neat twice as much", "start": 918.96, "duration": 2.85}, {"text": "as anybody else, essentially.", "start": 921.81, "duration": 1.8}, {"text": "So we want to adjust\nthe utility for", "start": 923.61, "duration": 2.52}, {"text": "these metabolic requirements.", "start": 926.13, "duration": 2.31}, {"text": "And they may not be treating\nthe women very equitably either.", "start": 928.44, "duration": 5.07}, {"text": "But we are going to take these\nas metabolic weights that were", "start": 933.51, "duration": 3.39}, {"text": "measured in a dietary survey.", "start": 936.9, "duration": 3.16}, {"text": "So the other objects\nhere are the probability", "start": 940.06, "duration": 4.61}, {"text": "of that history\nactually happening.", "start": 944.67, "duration": 2.52}, {"text": "Note that for any day t, we\nsum over all possible histories", "start": 947.19, "duration": 5.13}, {"text": "that could have generated\nthat node at date t.", "start": 952.32, "duration": 4.66}, {"text": "And then in addition,\nthere are multiple dates,", "start": 956.98, "duration": 2.47}, {"text": "so we sum over those dates\nand discount them by beta.", "start": 959.45, "duration": 4.01}, {"text": "And again, the lambdas\nare the Pareto weights", "start": 963.46, "duration": 2.85}, {"text": "that vary between 0 and\n1, and they sum to 1,", "start": 966.31, "duration": 2.91}, {"text": "and we take the weighted sum.", "start": 969.22, "duration": 1.95}, {"text": "There are many, many\nresource constraints.", "start": 971.17, "duration": 2.55}, {"text": "There is a particular\nconstraint for every date t", "start": 973.72, "duration": 3.12}, {"text": "and all possible\nhistories that could", "start": 976.84, "duration": 1.86}, {"text": "have led to t that simply\nsays that the way you hand out", "start": 978.7, "duration": 3.69}, {"text": "consumption must not\nsum to something greater", "start": 982.39, "duration": 3.63}, {"text": "than the total that's available.", "start": 986.02, "duration": 2.43}, {"text": "So usually, we\ntalk about income.", "start": 988.45, "duration": 1.92}, {"text": "Now we just went to\ntotal expenditure.", "start": 990.37, "duration": 2.88}, {"text": "But obviously, whatever\nincome is, if it were spent,", "start": 993.25, "duration": 4.23}, {"text": "it would lead to\nexpenditure, and then you", "start": 997.48, "duration": 2.04}, {"text": "could reallocate it.", "start": 999.52, "duration": 1.17}, {"text": "And some people might be\nconsuming more than others.", "start": 1000.69, "duration": 3.39}, {"text": "But here we take the total\naggregate consumption as fixed.", "start": 1004.08, "duration": 3.9}, {"text": "We're not going to\nput labor in here.", "start": 1007.98, "duration": 1.89}, {"text": "There's just consumption.", "start": 1009.87, "duration": 1.98}, {"text": "And we get first-order\nconditions.", "start": 1011.85, "duration": 2.62}, {"text": "So if you pick a particular\nconsumption for a household", "start": 1014.47, "duration": 3.68}, {"text": "k at day t as a function\nof a particular history ht,", "start": 1018.15, "duration": 4.5}, {"text": "it would appear in the\nw contemporary utility", "start": 1022.65, "duration": 3.36}, {"text": "function with the prime for the\nderivative weighted by lambda k", "start": 1026.01, "duration": 5.28}, {"text": "And that beta to the\nt probability of ht", "start": 1031.29, "duration": 2.97}, {"text": "would also be over there,\nbut we've multiplied through.", "start": 1034.26, "duration": 2.89}, {"text": "So that now becomes a\nterm in the denominator.", "start": 1037.15, "duration": 3.449}, {"text": "And the numerator\nterm here is mu.", "start": 1040.599, "duration": 2.51}, {"text": "So let me go back.", "start": 1043.109, "duration": 1.421}, {"text": "So the mu is the\nLagrange multiplier", "start": 1044.53, "duration": 3.62}, {"text": "on this resource constraint.", "start": 1048.15, "duration": 2.41}, {"text": "And it really should have a mu\nindexed by t and the history", "start": 1050.56, "duration": 4.76}, {"text": "h of t because there is\na constraint like this", "start": 1055.32, "duration": 2.91}, {"text": "for every single possible\nhistory end date.", "start": 1058.23, "duration": 3.31}, {"text": "So there are many,\nmany constraints.", "start": 1061.54, "duration": 2.03}, {"text": "That's why I caught\nmyself when I", "start": 1063.57, "duration": 1.53}, {"text": "said subject to one constraint.", "start": 1065.1, "duration": 1.47}, {"text": "That's wrong.", "start": 1066.57, "duration": 1.02}, {"text": "There's only one\ngood, but there's", "start": 1067.59, "duration": 1.89}, {"text": "many dates and many states.", "start": 1069.48, "duration": 2.58}, {"text": "The mu that's appearing here--", "start": 1072.06, "duration": 1.74}, {"text": "I didn't write an\nadditional little t which", "start": 1073.8, "duration": 3.57}, {"text": "ought to be there probably.", "start": 1077.37, "duration": 1.35}, {"text": "But anyway, mu tilde is\nthe normalized version", "start": 1078.72, "duration": 3.93}, {"text": "after dividing through\nby the discount", "start": 1082.65, "duration": 1.92}, {"text": "rate and the probability.", "start": 1084.57, "duration": 1.93}, {"text": "And if you started with\nparticular utility functions", "start": 1086.5, "duration": 3.35}, {"text": "like one of our favorites,\nconstant exponential utility,", "start": 1089.85, "duration": 4.14}, {"text": "where sigma is the\ndegree of risk aversion,", "start": 1093.99, "duration": 2.98}, {"text": "it is of this form.", "start": 1096.97, "duration": 1.58}, {"text": "Now, there is a step\nthat's happening here", "start": 1098.55, "duration": 2.29}, {"text": "which is imposing the way\nthat these age and gender", "start": 1100.84, "duration": 3.89}, {"text": "weights are entering into\nthe utility function.", "start": 1104.73, "duration": 2.85}, {"text": "Namely, it's consumption\nper unit index.", "start": 1107.58, "duration": 4.23}, {"text": "So pick a 30-year-old male\nand then look at the other age", "start": 1111.81, "duration": 4.14}, {"text": "groups and the other genders.", "start": 1115.95, "duration": 1.56}, {"text": "And the question\nis whether they're", "start": 1117.51, "duration": 1.5}, {"text": "consuming more or consuming\nless than that baseline case.", "start": 1119.01, "duration": 4.47}, {"text": "So we, for short, can talk about\nthis consumption per unit age.", "start": 1123.48, "duration": 3.93}, {"text": "That's really the object that's\nentering into individual K's", "start": 1127.41, "duration": 3.99}, {"text": "utility function.", "start": 1131.4, "duration": 1.47}, {"text": "And c tilde then replaces\nthat normalized consumption c", "start": 1132.87, "duration": 4.02}, {"text": "over a.", "start": 1136.89, "duration": 1.11}, {"text": "And when you do the math, you'll\nget the consumption formula,", "start": 1138.0, "duration": 3.99}, {"text": "the risk-sharing\nformula, as it were.", "start": 1141.99, "duration": 2.35}, {"text": "So this is the\nper-unit consumption", "start": 1144.34, "duration": 3.26}, {"text": "of household\nindividual K at date t.", "start": 1147.6, "duration": 3.0}, {"text": "It has an intercept\nterm, a term that", "start": 1150.6, "duration": 3.06}, {"text": "depends on the\ndemographics, and a term", "start": 1153.66, "duration": 2.28}, {"text": "that depends on this Pareto,\nthis shadow price mu.", "start": 1155.94, "duration": 4.17}, {"text": "You've kind of seen this\nbefore, but let me remind you", "start": 1160.11, "duration": 2.73}, {"text": "this intercept term,\nquite logically, has", "start": 1162.84, "duration": 2.61}, {"text": "to do with the Pareto weight.", "start": 1165.45, "duration": 1.33}, {"text": "The higher is the Pareto\nweight of individual K,", "start": 1166.78, "duration": 2.63}, {"text": "the higher is the log\nof the Pareto weight,", "start": 1169.41, "duration": 2.13}, {"text": "it's normalized by this\ndegree of risk aversion.", "start": 1171.54, "duration": 3.75}, {"text": "If we move over\nhere to the mu term,", "start": 1175.29, "duration": 4.08}, {"text": "mu is the shadow\nprice of consumption.", "start": 1179.37, "duration": 3.09}, {"text": "It's how much the\nobjective function", "start": 1182.46, "duration": 1.92}, {"text": "would increase if you\nincrease consumption", "start": 1184.38, "duration": 2.46}, {"text": "by an infinitesimally small\namount in the aggregate.", "start": 1186.84, "duration": 3.49}, {"text": "So as mu goes up,\nconsumption is going down.", "start": 1190.33, "duration": 4.53}, {"text": "Why is that?", "start": 1194.86, "duration": 0.89}, {"text": "Mu is the shadow price.", "start": 1195.75, "duration": 1.68}, {"text": "So the lower is\naggregate consumption.", "start": 1197.43, "duration": 2.46}, {"text": "The higher will be\nthe shadow price.", "start": 1199.89, "duration": 1.99}, {"text": "So as mu goes up, there's\nless consumption to go around,", "start": 1201.88, "duration": 2.78}, {"text": "so individual consumption\nis also dropping.", "start": 1204.66, "duration": 3.03}, {"text": "And we will replace this\nby aggregate consumption", "start": 1207.69, "duration": 2.49}, {"text": "and get a positive\nsign momentarily.", "start": 1210.18, "duration": 3.21}, {"text": "The other interesting\nthing about this equation", "start": 1213.39, "duration": 2.16}, {"text": "is, again, this 1 over sigma\nwhich I feature in this term,", "start": 1215.55, "duration": 3.39}, {"text": "although it's on all\nthe other ones as well.", "start": 1218.94, "duration": 2.25}, {"text": "And that is if individual\nrisk aversion goes up,", "start": 1221.19, "duration": 3.81}, {"text": "this coefficient is going down.", "start": 1225.0, "duration": 2.4}, {"text": "So as risk aversion goes\nup, this individual K", "start": 1227.4, "duration": 4.08}, {"text": "should not experience\ntoo much variation", "start": 1231.48, "duration": 2.52}, {"text": "in his or her consumption\nwhen the aggregate is moving", "start": 1234.0, "duration": 3.54}, {"text": "because other people would\nbe in a better position", "start": 1237.54, "duration": 3.09}, {"text": "to absorb the aggregate\nshock if they were", "start": 1240.63, "duration": 2.97}, {"text": "less-risk averse\nthan individual K.", "start": 1243.6, "duration": 2.73}, {"text": "And again, you'll\nsee that momentarily.", "start": 1246.33, "duration": 3.48}, {"text": "Questions?", "start": 1249.81, "duration": 1.85}, {"text": "STUDENT: My question\nis why there", "start": 1251.66, "duration": 2.6}, {"text": "was a negative sign before\nthe A, log A, the age and sex", "start": 1254.26, "duration": 7.17}, {"text": "index.", "start": 1261.43, "duration": 1.38}, {"text": "It looks like in the utility\nfunction when A goes up,", "start": 1262.81, "duration": 5.0}, {"text": "the utility will go up.", "start": 1267.81, "duration": 1.71}, {"text": "ROBERT TOWNSEND:\nWhen A is going up,", "start": 1273.96, "duration": 1.5}, {"text": "though, consumption per\nunit age is going down.", "start": 1275.46, "duration": 6.35}, {"text": "STUDENT: But in the\nutility function--", "start": 1281.81, "duration": 2.31}, {"text": "ROBERT TOWNSEND: And they're\nbecoming more urgent,", "start": 1284.12, "duration": 2.41}, {"text": "so to speak, other things equal.", "start": 1286.53, "duration": 3.15}, {"text": "So I'm sorry.", "start": 1289.68, "duration": 5.3}, {"text": "I think I said it\nright the first time.", "start": 1294.98, "duration": 3.71}, {"text": "Holding aggregate consumption\nfixed, for example,", "start": 1298.69, "duration": 4.05}, {"text": "as their index is going up,\nthe consumption per unit index", "start": 1302.74, "duration": 4.59}, {"text": "is going down.", "start": 1307.33, "duration": 1.08}, {"text": "And that's the negative sign.", "start": 1308.41, "duration": 1.402}, {"text": "It's really just that simple.", "start": 1309.812, "duration": 1.208}, {"text": "All right.", "start": 1317.4, "duration": 1.69}, {"text": "But thank you for\nasking the question.", "start": 1319.09, "duration": 3.57}, {"text": "All right.", "start": 1322.66, "duration": 0.5}, {"text": "Now, that was just\none individual.", "start": 1323.16, "duration": 2.7}, {"text": "We can put all the individuals\ntogether and allow explicitly", "start": 1325.86, "duration": 4.41}, {"text": "for different risk aversion.", "start": 1330.27, "duration": 1.95}, {"text": "And this formula\nappears in the paper,", "start": 1332.22, "duration": 1.86}, {"text": "and I'm not going\nto try to derive it.", "start": 1334.08, "duration": 1.98}, {"text": "It's somewhat tedious algebra.", "start": 1336.06, "duration": 3.46}, {"text": "But the interpretation is easy.", "start": 1339.52, "duration": 1.82}, {"text": "Namely, there's an\nintercept, something", "start": 1341.34, "duration": 2.61}, {"text": "to do with demographics,\nand something", "start": 1343.95, "duration": 2.49}, {"text": "to do with aggregate\nconsumption.", "start": 1346.44, "duration": 3.15}, {"text": "In a little bit more\ndetail, this is no longer", "start": 1349.59, "duration": 3.27}, {"text": "individual I consumption.", "start": 1352.86, "duration": 1.86}, {"text": "It's all the individuals\nin a household J.", "start": 1354.72, "duration": 3.45}, {"text": "And unfortunately, that's\nall we see in the data.", "start": 1358.17, "duration": 2.07}, {"text": "We don't see individual eating\napart from that dietary survey.", "start": 1360.24, "duration": 3.84}, {"text": "We just see aggregate\nhousehold consumption.", "start": 1364.08, "duration": 3.09}, {"text": "But that functional\nform allowed us", "start": 1367.17, "duration": 1.8}, {"text": "to sum up over all\nthe consumptions,", "start": 1368.97, "duration": 2.4}, {"text": "and that's what we see.", "start": 1371.37, "duration": 1.41}, {"text": "And we also have the age\nand sex of all the members.", "start": 1372.78, "duration": 4.21}, {"text": "So we also have the denominator.", "start": 1376.99, "duration": 2.79}, {"text": "So this is household-level\nconsumption per unit age.", "start": 1379.78, "duration": 4.04}, {"text": "And that should be higher.", "start": 1383.82, "duration": 1.57}, {"text": "The higher is household\nJ's lambda weight", "start": 1385.39, "duration": 2.93}, {"text": "relative to the lambda\nweights of the other people", "start": 1388.32, "duration": 2.64}, {"text": "in the village.", "start": 1390.96, "duration": 2.25}, {"text": "It's a bit more complicated\nbecause these lambda weights", "start": 1393.21, "duration": 2.76}, {"text": "are weighted by the\ndegree of risk aversion.", "start": 1395.97, "duration": 2.95}, {"text": "So it's a risk-aversion-weighted\nversion of the Lambda", "start": 1398.92, "duration": 3.71}, {"text": "that we care about,\ncomparing it to lambda", "start": 1402.63, "duration": 2.73}, {"text": "K. This is the demographic.", "start": 1405.36, "duration": 3.6}, {"text": "I may come back to that.", "start": 1408.96, "duration": 1.3}, {"text": "This is the formula now in\nterms of aggregate consumption.", "start": 1410.26, "duration": 3.06}, {"text": "This is the consumption of\nindividual K and household J--", "start": 1413.32, "duration": 4.52}, {"text": "I, actually-- but then\nsumming over all households I.", "start": 1417.84, "duration": 3.51}, {"text": "So this is aggregate\nconsumption per unit age", "start": 1421.35, "duration": 3.06}, {"text": "in the whole village.", "start": 1424.41, "duration": 1.05}, {"text": "And again, you can see quite\nexplicitly that J's consumption", "start": 1425.46, "duration": 3.87}, {"text": "will move with that when\nsigma J is going down,", "start": 1429.33, "duration": 3.06}, {"text": "or the other way around--\nwhen household J is very risk", "start": 1432.39, "duration": 2.88}, {"text": "averse, this coefficient\nis going to 0,", "start": 1435.27, "duration": 2.61}, {"text": "and individual\nconsumption would not", "start": 1437.88, "duration": 1.92}, {"text": "very much with the aggregate.", "start": 1439.8, "duration": 1.83}, {"text": "That's the aggregate\nallocation of risk bearing.", "start": 1441.63, "duration": 3.9}, {"text": "Because the theory has those\nage and gender weights in it,", "start": 1445.53, "duration": 3.57}, {"text": "you can treat those as shocks.", "start": 1449.1, "duration": 1.65}, {"text": "Even though they're quite\nnot moving in a surprise way,", "start": 1450.75, "duration": 2.91}, {"text": "they are moving over time.", "start": 1453.66, "duration": 1.382}, {"text": "They're moving intertemporally,\nand maybe the whole village", "start": 1455.042, "duration": 2.458}, {"text": "is getting older.", "start": 1457.5, "duration": 1.23}, {"text": "Maybe one household is moving\nacross metabolic categories", "start": 1458.73, "duration": 4.5}, {"text": "faster than the\nother households are.", "start": 1463.23, "duration": 2.23}, {"text": "And so the formula allows\nfor that adjustment,", "start": 1465.46, "duration": 3.65}, {"text": "comparing household\nj to the other ones.", "start": 1469.11, "duration": 3.31}, {"text": "So let's look at an empirical\nimplication, a linear equation.", "start": 1472.42, "duration": 4.91}, {"text": "The aggregate consumption,\nage weighted, of household", "start": 1477.33, "duration": 4.11}, {"text": "J has an intercept.", "start": 1481.44, "duration": 2.97}, {"text": "It depends on\naggregate consumption.", "start": 1484.41, "duration": 2.43}, {"text": "It depends on the\nindex of household J", "start": 1486.84, "duration": 4.05}, {"text": "and maybe on other things.", "start": 1490.89, "duration": 2.5}, {"text": "This is just a version of this.", "start": 1493.39, "duration": 3.02}, {"text": "Household J's\nconsumption depends", "start": 1496.41, "duration": 2.16}, {"text": "on an intercept, its age,\nand aggregate consumption.", "start": 1498.57, "duration": 3.87}, {"text": "It's just much easier\nto write this way.", "start": 1502.44, "duration": 2.52}, {"text": "And the theory has implications.", "start": 1504.96, "duration": 2.34}, {"text": "Namely, if everyone had\nthe same risk aversion,", "start": 1507.3, "duration": 3.21}, {"text": "then this beta J on aggregate\nconsumption would be 1.", "start": 1510.51, "duration": 4.47}, {"text": "You can convince\nyourself this would", "start": 1514.98, "duration": 1.62}, {"text": "be 1 because the sigmas\nare all alike, for example.", "start": 1516.6, "duration": 4.95}, {"text": "Likewise, this demographic thing\nwould have a coefficient of 1", "start": 1521.55, "duration": 4.17}, {"text": "over sigma, the common sigma.", "start": 1525.72, "duration": 2.01}, {"text": "And this other stuff--", "start": 1527.73, "duration": 1.59}, {"text": "I saved the best for last.", "start": 1529.32, "duration": 2.29}, {"text": "This is any other variable,\nincluding household income.", "start": 1531.61, "duration": 3.53}, {"text": "And the theory is saying that\nthis coefficient should be 0.", "start": 1535.14, "duration": 4.65}, {"text": "Now, that's very\ncounterintuitive.", "start": 1539.79, "duration": 2.73}, {"text": "How could I possibly be claiming\nthat household consumption", "start": 1542.52, "duration": 3.75}, {"text": "doesn't depend on\nhousehold income?", "start": 1546.27, "duration": 3.31}, {"text": "What about marginal propensity\nto consume and all of that?", "start": 1549.58, "duration": 3.37}, {"text": "Well, the answer is they're\npooling their incomes together", "start": 1552.95, "duration": 3.95}, {"text": "as if in a mutual fund\nand then redistributing it", "start": 1556.9, "duration": 3.42}, {"text": "as a function of\nthe Pareto weights.", "start": 1560.32, "duration": 2.28}, {"text": "So household J's income\nis kind of in there,", "start": 1562.6, "duration": 3.67}, {"text": "but it's in the pooled\nversion, and it shows up", "start": 1566.27, "duration": 2.36}, {"text": "in aggregate consumption.", "start": 1568.63, "duration": 1.26}, {"text": "And if you control for that,\nthen there's nothing leftover.", "start": 1569.89, "duration": 3.97}, {"text": "There's no idiosyncratic\nrisk for household J to bear.", "start": 1573.86, "duration": 4.58}, {"text": "Another way to say\nthat is we're going", "start": 1578.44, "duration": 1.92}, {"text": "to get perfect\nconsumption insurance", "start": 1580.36, "duration": 2.31}, {"text": "because, like a\nlarge mutual fund,", "start": 1582.67, "duration": 2.49}, {"text": "all the individual\nshocks go to 0.", "start": 1585.16, "duration": 3.53}, {"text": "A version of this in China\nthat I'm becoming aware of--", "start": 1588.69, "duration": 4.29}, {"text": "Alibaba runs a mutual\nfund over health shocks.", "start": 1592.98, "duration": 3.33}, {"text": "There's 100 million\nhouseholds joining,", "start": 1596.31, "duration": 2.34}, {"text": "and they pay ex-post premia.", "start": 1598.65, "duration": 2.28}, {"text": "Typical medical expense\nmust be as high as $20,000.", "start": 1600.93, "duration": 4.89}, {"text": "How much do they pay in?\n$9 in yuan equivalent.", "start": 1605.82, "duration": 4.93}, {"text": "So when you spread that damage\nof an individual household,", "start": 1610.75, "duration": 3.54}, {"text": "which is high, over\nall the hundreds", "start": 1614.29, "duration": 3.18}, {"text": "of thousands of households,\nit almost goes to 0.", "start": 1617.47, "duration": 3.51}, {"text": "And this is the extreme\nversion of perfect pooling.", "start": 1620.98, "duration": 3.15}, {"text": "That's contemporary China, not\na village in India in 1985.", "start": 1624.13, "duration": 5.31}, {"text": "So we can test the theory by\nlooking at each household one", "start": 1629.44, "duration": 3.0}, {"text": "at a time over the 10 years,\nand we can test the theory", "start": 1632.44, "duration": 2.94}, {"text": "by pooling households\ntogether into one", "start": 1635.38, "duration": 2.49}, {"text": "big cross-sectional\ntime-dependent regression.", "start": 1637.87, "duration": 3.78}, {"text": "This is a little hard to\nsee, but what's going on here", "start": 1641.65, "duration": 3.75}, {"text": "statistically is testing\nthese coefficients xe, which", "start": 1645.4, "duration": 4.59}, {"text": "should be 0, to see whether\nthey actually are in practice.", "start": 1649.99, "duration": 3.72}, {"text": "Under the null\nhypothesis that it's 0,", "start": 1653.71, "duration": 3.3}, {"text": "can you reject in a\nstatistically significant way", "start": 1657.01, "duration": 3.18}, {"text": "that it's greater\nthan 0 or less than 0?", "start": 1660.19, "duration": 2.82}, {"text": "And for most households,\nthe bulk of the households,", "start": 1663.01, "duration": 4.38}, {"text": "you can't reject much\none way or the other.", "start": 1667.39, "duration": 2.94}, {"text": "There's just a\nhandful of households", "start": 1670.33, "duration": 2.01}, {"text": "on either side of the null.", "start": 1672.34, "duration": 2.25}, {"text": "This test has power.", "start": 1674.59, "duration": 1.95}, {"text": "This thing is, oh, well,\nmaybe it's just noisy data,", "start": 1676.54, "duration": 2.76}, {"text": "and we can't infer\nmuch of anything.", "start": 1679.3, "duration": 2.19}, {"text": "Maybe they're literally\nhand-to-mouth,", "start": 1681.49, "duration": 1.92}, {"text": "and they're eating entirely\ntheir income, in which case", "start": 1683.41, "duration": 2.65}, {"text": "the coefficient would be 1.", "start": 1686.06, "duration": 2.15}, {"text": "And we can't reject\nthat for half of them.", "start": 1688.21, "duration": 4.78}, {"text": "But for the other half,\nwe can statistically", "start": 1692.99, "duration": 2.78}, {"text": "reject that it's 1.", "start": 1695.77, "duration": 2.55}, {"text": "So there is a lot of\nsmoothing going on.", "start": 1698.32, "duration": 2.67}, {"text": "And this is for the other\ntwo villages down here.", "start": 1700.99, "duration": 3.96}, {"text": "Now let's talk about\npooling it together.", "start": 1704.95, "duration": 4.02}, {"text": "Actually, let's just jump\nhere, and then I'll go back.", "start": 1708.97, "duration": 3.07}, {"text": "So here's the villages--", "start": 1712.04, "duration": 1.25}, {"text": "Aurepalle, Shirapur, Kandara.", "start": 1713.29, "duration": 2.76}, {"text": "And we're going to somehow\ntake each household over time", "start": 1716.05, "duration": 3.78}, {"text": "and take households\nin the cross-section", "start": 1719.83, "duration": 3.09}, {"text": "and come up with a\ncoefficient on how much", "start": 1722.92, "duration": 2.4}, {"text": "consumption is moving on\naverage with household income.", "start": 1725.32, "duration": 5.52}, {"text": "And the answer is roughly--", "start": 1730.84, "duration": 1.91}, {"text": "should be in rupees--", "start": 1732.75, "duration": 1.29}, {"text": "$0.07 for the dollar.", "start": 1734.04, "duration": 2.77}, {"text": "So for every dollar\nchange in income,", "start": 1736.81, "duration": 3.05}, {"text": "consumption is\nmoving by only $0.07.", "start": 1739.86, "duration": 4.2}, {"text": "It's positive.", "start": 1744.06, "duration": 0.99}, {"text": "It's statistically significant.", "start": 1745.05, "duration": 2.01}, {"text": "We now reject the model.", "start": 1747.06, "duration": 2.32}, {"text": "But as an approximation,\nwe're doing", "start": 1749.38, "duration": 2.27}, {"text": "quite well because these\ncoefficients are small.", "start": 1751.65, "duration": 3.27}, {"text": "So most, although\nnot all, of the", "start": 1754.92, "duration": 3.24}, {"text": "household-specific idiosyncratic\nrisk is being pooled.", "start": 1758.16, "duration": 3.99}, {"text": "And you can peruse\nthis table and see--", "start": 1762.15, "duration": 3.51}, {"text": "this is profits as opposed\nto all income, labor income,", "start": 1765.66, "duration": 5.16}, {"text": "profits from trade\nand handicraft.", "start": 1770.82, "duration": 2.41}, {"text": "You can look for\nthe high numbers.", "start": 1773.23, "duration": 2.19}, {"text": "So there are certain\nactivities in certain villages", "start": 1775.42, "duration": 2.57}, {"text": "that look relatively\nunder-insured.", "start": 1777.99, "duration": 2.49}, {"text": "This is who's the\nmost vulnerable.", "start": 1780.48, "duration": 2.96}, {"text": "If we had the ability\nto come in externally", "start": 1783.44, "duration": 2.43}, {"text": "and introduce a better\ninsurance product,", "start": 1785.87, "duration": 2.4}, {"text": "we would want to offer it\nto households that need it.", "start": 1788.27, "duration": 3.06}, {"text": "Or if no one needed it, we\nwould expect take-up to be zero.", "start": 1791.33, "duration": 3.39}, {"text": "So labor incomes had a pretty\nhigh coefficient in Shirapur", "start": 1794.72, "duration": 5.37}, {"text": "and so on.", "start": 1800.09, "duration": 0.73}, {"text": "But a lot of these are 0--", "start": 1800.82, "duration": 2.58}, {"text": "that is to say, not\nstatistically different from 0.", "start": 1803.4, "duration": 3.03}, {"text": "So in that sense, it's\na good approximation.", "start": 1806.43, "duration": 3.48}, {"text": "Remember, according to Lucas,\nmodels are abstractions.", "start": 1809.91, "duration": 4.56}, {"text": "They're meant to be stylized\nversions of reality.", "start": 1814.47, "duration": 3.57}, {"text": "Because we have a model,\nwe have an exact prediction", "start": 1818.04, "duration": 2.82}, {"text": "of what we should expect to see.", "start": 1820.86, "duration": 1.95}, {"text": "And through the\nlens of the model,", "start": 1822.81, "duration": 1.62}, {"text": "we can decide how reality is\ndoing relative to the model.", "start": 1824.43, "duration": 3.99}, {"text": "So I'm not overly\nalarmed that we're going", "start": 1828.42, "duration": 2.1}, {"text": "to get statistical rejections.", "start": 1830.52, "duration": 2.4}, {"text": "The question is, is it\na useful starting point", "start": 1832.92, "duration": 2.85}, {"text": "as an approximation?", "start": 1835.77, "duration": 1.84}, {"text": "And the answer seems to be yes.", "start": 1837.61, "duration": 2.72}, {"text": "I will share with you that\nwhen I wrote this paper,", "start": 1840.33, "duration": 3.3}, {"text": "it kind of created\na firestorm of alarm", "start": 1843.63, "duration": 2.91}, {"text": "among policymakers\nwho were astounded", "start": 1846.54, "duration": 3.36}, {"text": "that poor households in villages\nin the caste system, and so on,", "start": 1849.9, "duration": 4.5}, {"text": "could ever possibly be achieving\nanything close to an optimum.", "start": 1854.4, "duration": 4.71}, {"text": "It just went against the grain\nof their prior presumptions.", "start": 1859.11, "duration": 4.23}, {"text": "But it doesn't fit perfectly.", "start": 1863.34, "duration": 2.2}, {"text": "So this slide which I\ndeliberately skipped over just", "start": 1865.54, "duration": 2.9}, {"text": "now is to say, look,\nmaybe I'm getting", "start": 1868.44, "duration": 3.24}, {"text": "into statistical stuff a bit,\nand we can follow up later.", "start": 1871.68, "duration": 4.11}, {"text": "One reason why this\ncoefficient might be low", "start": 1875.79, "duration": 2.97}, {"text": "is because this variable\nx is very poorly measured.", "start": 1878.76, "duration": 4.2}, {"text": "Say it just got a lot\nof measurement error", "start": 1882.96, "duration": 2.0}, {"text": "that is not real.", "start": 1884.96, "duration": 1.24}, {"text": "Then it's moving around a\nlot for spurious reasons,", "start": 1886.2, "duration": 3.74}, {"text": "and you would not expect that\nto influence consumption.", "start": 1889.94, "duration": 2.59}, {"text": "So that biases this coefficient\nto something close to 0.", "start": 1892.53, "duration": 3.56}, {"text": "Fortunately, we can correct\nfor it with the panel.", "start": 1896.09, "duration": 3.96}, {"text": "And it's putting explicitly\nthis measurement error", "start": 1900.05, "duration": 3.21}, {"text": "into, in this case,\nidiosyncratic income", "start": 1903.26, "duration": 4.17}, {"text": "and then substituting\nthat into those equations.", "start": 1907.43, "duration": 3.9}, {"text": "We now see a correlation\nbetween the measurement error", "start": 1911.33, "duration": 3.54}, {"text": "and the measured\nversion of income,", "start": 1914.87, "duration": 2.86}, {"text": "which means you can't\nrun an OLS regression.", "start": 1917.73, "duration": 2.93}, {"text": "But on the other hand,\nanother way to do this", "start": 1920.66, "duration": 2.34}, {"text": "is just to take\nfirst differences.", "start": 1923.0, "duration": 2.1}, {"text": "Differences over\ntime over households", "start": 1925.1, "duration": 2.43}, {"text": "gives you another version.", "start": 1927.53, "duration": 1.41}, {"text": "And it turns out this\nwithin coefficient", "start": 1928.94, "duration": 3.58}, {"text": "and this across-time coefficient\nallow you to essentially get", "start": 1932.52, "duration": 5.36}, {"text": "rid of the measurement error.", "start": 1937.88, "duration": 1.27}, {"text": "So that's this IV\nGriliches-Hausman thing,", "start": 1939.15, "duration": 4.43}, {"text": "which I'm not going to go over.", "start": 1943.58, "duration": 2.76}, {"text": "I still don't know what the\nbest strategy is for me.", "start": 1946.34, "duration": 3.87}, {"text": "If I skip stuff, then it looks\nlike it came out of nowhere,", "start": 1950.21, "duration": 3.66}, {"text": "and you don't really\nunderstand it.", "start": 1953.87, "duration": 1.59}, {"text": "Hence, I try in all\nthese slides to show you", "start": 1955.46, "duration": 3.33}, {"text": "the steps that are being taken.", "start": 1958.79, "duration": 1.69}, {"text": "I'm deliberately not\nconcealing something from you.", "start": 1960.48, "duration": 2.51}, {"text": "But on the other hand,\nthis particular sequence", "start": 1962.99, "duration": 2.88}, {"text": "involves statistical material\nyou may not have seen", "start": 1965.87, "duration": 3.36}, {"text": "something similar to before.", "start": 1969.23, "duration": 1.81}, {"text": "So if it's still quite opaque,\ndon't worry too much about it.", "start": 1971.04, "duration": 3.36}, {"text": "I'm just trying to be clearer.", "start": 1974.4, "duration": 2.18}, {"text": "OK.", "start": 1976.58, "duration": 0.63}, {"text": "So that's summary, risk and\ninsurance and village India.", "start": 1977.21, "duration": 3.75}, {"text": "These villages are\ndoing reasonably well,", "start": 1980.96, "duration": 2.05}, {"text": "although not perfectly.", "start": 1983.01, "duration": 1.25}, {"text": "They're sharing a\nlot of the risk.", "start": 1984.26, "duration": 2.08}, {"text": "The reason that\nconsumption looks so flat", "start": 1986.34, "duration": 2.15}, {"text": "relative to income is because\nthey're actively, somehow", "start": 1988.49, "duration": 4.11}, {"text": "or another, engaged in\nborrowing and lending", "start": 1992.6, "duration": 2.82}, {"text": "or transfers to bridge the gap\nbetween consumption and income.", "start": 1995.42, "duration": 4.48}, {"text": "Now, another way they could\nhandle the situation--", "start": 1999.9, "duration": 3.09}, {"text": "so for this, we're going to\njump to medieval villages--", "start": 2002.99, "duration": 3.38}, {"text": "is to potentially\ndivide up the land.", "start": 2006.37, "duration": 3.69}, {"text": "So this is the\ndiversification part,", "start": 2010.06, "duration": 2.49}, {"text": "whether land holdings\nof a typical village", "start": 2012.55, "duration": 2.49}, {"text": "would be consistent with the\noptimal allocation of risk", "start": 2015.04, "duration": 3.21}, {"text": "predicted in that model\njust now on the premise", "start": 2018.25, "duration": 3.69}, {"text": "that what you get\nis what you eat.", "start": 2021.94, "duration": 2.04}, {"text": "You have these strips.", "start": 2023.98, "duration": 1.35}, {"text": "The strips are subject to risk.", "start": 2025.33, "duration": 1.71}, {"text": "You add it all up across\nall your land holdings,", "start": 2027.04, "duration": 2.26}, {"text": "then you eat it.", "start": 2029.3, "duration": 0.8}, {"text": "So this is the other extreme--", "start": 2030.1, "duration": 1.74}, {"text": "no expo smoothing,\nno credit markets.", "start": 2031.84, "duration": 3.75}, {"text": "Even going back to lecture 1\nor something where I presented", "start": 2035.59, "duration": 3.99}, {"text": "all the different\neconomies-- we talked", "start": 2039.58, "duration": 1.68}, {"text": "about the medieval\nvillage economy.", "start": 2041.26, "duration": 1.89}, {"text": "We're about to do it now in\nterms of dividing up the land.", "start": 2043.15, "duration": 3.72}, {"text": "We also talked about\nThai village economy", "start": 2046.87, "duration": 2.25}, {"text": "with that temple where\nhouseholds did not diversify.", "start": 2049.12, "duration": 3.72}, {"text": "Some had low land.", "start": 2052.84, "duration": 1.02}, {"text": "Some had high land.", "start": 2053.86, "duration": 1.5}, {"text": "They made donations\nto the temple.", "start": 2055.36, "duration": 1.89}, {"text": "And people that had a\nbad year, God gives back.", "start": 2057.25, "duration": 3.659}, {"text": "So the second thing is\nwhat's going on in the first,", "start": 2060.909, "duration": 6.0}, {"text": "some mechanism for\nrisk sharing ex-post.", "start": 2066.909, "duration": 2.971}, {"text": "This is the mechanism\nin the second, which", "start": 2069.88, "duration": 2.549}, {"text": "is ex-ante division of land.", "start": 2072.429, "duration": 2.881}, {"text": "I said that in reverse\norder, but anyway.", "start": 2075.31, "duration": 2.099}, {"text": "So you've seen this\npicture twice before.", "start": 2077.409, "duration": 2.971}, {"text": "This is Elford Stratfordshire.", "start": 2080.38, "duration": 2.64}, {"text": "Mr. Darlaston's land\nis shaded in black,", "start": 2083.02, "duration": 3.3}, {"text": "and he's got something like 50\nstrips throughout the village.", "start": 2086.32, "duration": 6.649}, {"text": "So why were they doing that--", "start": 2092.969, "duration": 2.281}, {"text": "not just Mr. Darlaston, but\nall of them to some degree?", "start": 2095.25, "duration": 3.73}, {"text": "So if you think about\nthis map, for example,", "start": 2098.98, "duration": 4.89}, {"text": "are these types of\nland differ in some way", "start": 2103.87, "duration": 4.33}, {"text": "from these types of land\nin terms of soil or slope", "start": 2108.2, "duration": 4.14}, {"text": "or elevation?", "start": 2112.34, "duration": 1.41}, {"text": "Or alternatively,\nland is all alike.", "start": 2113.75, "duration": 2.97}, {"text": "And then the question is, when\nthe storm comes and destroys", "start": 2116.72, "duration": 4.02}, {"text": "crops, it could destroy\nthese crops and not these.", "start": 2120.74, "duration": 4.02}, {"text": "So there's really\ntwo different models,", "start": 2124.76, "duration": 2.01}, {"text": "and we're only going\nto have time to do one,", "start": 2126.77, "duration": 2.16}, {"text": "although the other\none is covered", "start": 2128.93, "duration": 1.38}, {"text": "in that missing medieval\nvillage chapter.", "start": 2130.31, "duration": 2.77}, {"text": "We're going to do uniform\nshocks on non-uniform land,", "start": 2133.08, "duration": 3.41}, {"text": "and the non-uniform shocks\nwe'll save for another time.", "start": 2136.49, "duration": 5.23}, {"text": "So there are two types of land.", "start": 2141.72, "duration": 2.1}, {"text": "Start off keeping this simple.", "start": 2143.82, "duration": 1.75}, {"text": "Say high-low or clay-sandy.", "start": 2145.57, "duration": 3.83}, {"text": "There's only two households,\nanother abstraction.", "start": 2149.4, "duration": 4.05}, {"text": "And there's only one date.", "start": 2153.45, "duration": 1.68}, {"text": "And land type k has\na yield vector which", "start": 2155.13, "duration": 4.68}, {"text": "varies with the shock epsilon.", "start": 2159.81, "duration": 2.37}, {"text": "And epsilon can take\non capital S values.", "start": 2162.18, "duration": 3.1}, {"text": "So this epsilon is a measure\nof rainfall, temperature,", "start": 2165.28, "duration": 3.54}, {"text": "humidity, or other\nevents which have", "start": 2168.82, "duration": 3.44}, {"text": "beneficial or adverse\nconsequences for the yield", "start": 2172.26, "duration": 3.15}, {"text": "as captured by the way which\nthe yield of type k land", "start": 2175.41, "duration": 4.29}, {"text": "varies with those shocks.", "start": 2179.7, "duration": 1.98}, {"text": "You've, again, seen\nthis before a bit.", "start": 2181.68, "duration": 2.64}, {"text": "When we did the dynamics,\nwe planted land with seed", "start": 2184.32, "duration": 4.32}, {"text": "and talked about how the yield\ncould vary with low, medium,", "start": 2188.64, "duration": 4.51}, {"text": "and high shock.", "start": 2193.15, "duration": 0.76}, {"text": "So this is very\nsimilar notation.", "start": 2193.91, "duration": 3.59}, {"text": "Now, let's be serious\neven though we're", "start": 2197.5, "duration": 2.84}, {"text": "trying to keep this simple.", "start": 2200.34, "duration": 1.47}, {"text": "What numbers do we\nuse for this vector?", "start": 2201.81, "duration": 4.37}, {"text": "One thing we want to\ncapture is how much", "start": 2206.18, "duration": 3.81}, {"text": "that yield is varying as\nmeasured by the coefficient", "start": 2209.99, "duration": 3.72}, {"text": "of variation.", "start": 2213.71, "duration": 1.2}, {"text": "And in medieval villages,\nit was about 0.35,", "start": 2214.91, "duration": 3.835}, {"text": "which we've covered\nbefore, and I'm not", "start": 2218.745, "duration": 1.625}, {"text": "going to go back and dig\nup those slides for you.", "start": 2220.37, "duration": 3.04}, {"text": "But that was the\nnumber we used before.", "start": 2223.41, "duration": 1.73}, {"text": "The other one is--", "start": 2225.14, "duration": 1.98}, {"text": "there's two types of land\nhere, k equal 1 or 2.", "start": 2227.12, "duration": 4.14}, {"text": "And we want to choose\nvectors of returns for both.", "start": 2231.26, "duration": 4.05}, {"text": "So we want to capture\nthe covariance", "start": 2235.31, "duration": 2.13}, {"text": "in the two types of land,\nhow different are they", "start": 2237.44, "duration": 2.46}, {"text": "from one another.", "start": 2239.9, "duration": 1.66}, {"text": "And again, going back in the\nearlier lecture, the estates", "start": 2241.56, "duration": 3.26}, {"text": "of the Bishop of Winchester, we\nhad a cross-space correlation", "start": 2244.82, "duration": 5.22}, {"text": "of 0.6.", "start": 2250.04, "duration": 1.24}, {"text": "So we're going to take\nthose numbers, .6 and .347,", "start": 2251.28, "duration": 3.56}, {"text": "as givens.", "start": 2254.84, "duration": 1.8}, {"text": "But here's a simple\nrepresentation.", "start": 2256.64, "duration": 3.93}, {"text": "Let's take, again,\nonly two types", "start": 2260.57, "duration": 1.77}, {"text": "of land, 1 or 2, only three\nevents, epsilon equal 1, 2, 3.", "start": 2262.34, "duration": 6.12}, {"text": "Type 1 land has the highest\nreturn in event 1, then medium,", "start": 2268.46, "duration": 5.34}, {"text": "then low.", "start": 2273.8, "duration": 1.08}, {"text": "Type 2 land has\nthe highest return", "start": 2274.88, "duration": 4.26}, {"text": "at event 2 surrounded by\nthe lower numbers, 3 and 2.", "start": 2279.14, "duration": 4.8}, {"text": "So if you aggregated up the\ntotal yield over all types,", "start": 2283.94, "duration": 5.46}, {"text": "it would just be the\nsum of those columns.", "start": 2289.4, "duration": 2.1}, {"text": "And it would go 12, 10, 7.", "start": 2291.5, "duration": 3.19}, {"text": "Now suppose we divided\nup the types of land", "start": 2294.69, "duration": 3.99}, {"text": "in a very extreme way.", "start": 2298.68, "duration": 1.8}, {"text": "We let household 1\nhave all of type 1 land", "start": 2300.48, "duration": 3.66}, {"text": "and household two\nall of type 2 land.", "start": 2304.14, "duration": 3.03}, {"text": "And the question for you\nis whether that would be", "start": 2307.17, "duration": 2.67}, {"text": "an optimal allocation of land.", "start": 2309.84, "duration": 2.34}, {"text": "If we did it that way\nand they were forced", "start": 2312.18, "duration": 2.85}, {"text": "to eat the grain\noff their strips,", "start": 2315.03, "duration": 2.19}, {"text": "would the consumption\nthat we see", "start": 2317.22, "duration": 2.13}, {"text": "correspond to the\nimplications of the model?", "start": 2319.35, "duration": 3.61}, {"text": "And the answer is going to be no\nbecause the aggregate is going", "start": 2322.96, "duration": 4.13}, {"text": "down as epsilon is going up.", "start": 2327.09, "duration": 3.19}, {"text": "And that's true of\nhousehold 1's consumption,", "start": 2330.28, "duration": 2.06}, {"text": "but it is not true of\nhousehold 2's consumption.", "start": 2332.34, "duration": 2.79}, {"text": "This proposal fails the\nmonotonicity requirement", "start": 2335.13, "duration": 3.93}, {"text": "of the theory that as\naggregate consumption", "start": 2339.06, "duration": 3.24}, {"text": "goes down everybody's\nconsumption ought", "start": 2342.3, "duration": 2.13}, {"text": "to go down, although some\npeople's consumption go", "start": 2344.43, "duration": 2.52}, {"text": "down more than others.", "start": 2346.95, "duration": 1.99}, {"text": "So we reject this proposal\nfor the allocation of land", "start": 2348.94, "duration": 3.86}, {"text": "if the goal is to achieve an\noptimal allocation of risk", "start": 2352.8, "duration": 3.21}, {"text": "bearing by land division alone.", "start": 2356.01, "duration": 3.24}, {"text": "Well, there are\nother ways to do it.", "start": 2359.25, "duration": 3.4}, {"text": "Let's take the land type\nand give household J", "start": 2362.65, "duration": 4.43}, {"text": "a proportional number\nof shares in the output", "start": 2367.08, "duration": 3.42}, {"text": "of each type of land.", "start": 2370.5, "duration": 2.37}, {"text": "So that means\nhousehold J would get", "start": 2372.87, "duration": 2.88}, {"text": "fraction alpha J of the\noutput over each type of land.", "start": 2375.75, "duration": 4.23}, {"text": "So we're kind of\nre-dividing things here.", "start": 2379.98, "duration": 3.07}, {"text": "We're going to have\nhousehold 1 getting", "start": 2383.05, "duration": 2.75}, {"text": "some proportion of this column\nbut also some proportion,", "start": 2385.8, "duration": 4.26}, {"text": "not necessarily-- yes,\nin this case, the same", "start": 2390.06, "duration": 3.57}, {"text": "of the other type of land.", "start": 2393.63, "duration": 2.56}, {"text": "So this alpha J\ndoesn't have a K on it.", "start": 2396.19, "duration": 3.41}, {"text": "The shares depend\nonly on the household,", "start": 2399.6, "duration": 2.25}, {"text": "not on the type of land.", "start": 2401.85, "duration": 1.89}, {"text": "The shares can depend\non the household.", "start": 2403.74, "duration": 4.61}, {"text": "All right.", "start": 2408.35, "duration": 0.5}, {"text": "So it's linear in the aggregate.", "start": 2408.85, "duration": 3.56}, {"text": "If we were over at school,\nyou'd come up to my office,", "start": 2412.41, "duration": 2.57}, {"text": "and you'll see my\nbookshelf filled", "start": 2414.98, "duration": 1.47}, {"text": "with stacks of books devoted\nto medieval English villages.", "start": 2416.45, "duration": 4.68}, {"text": "I had a happy time\ndoing a lot of research.", "start": 2421.13, "duration": 3.27}, {"text": "And you'd discover\nthese amazing things.", "start": 2424.4, "duration": 3.12}, {"text": "Holdings were\nscattered over fields", "start": 2427.52, "duration": 1.86}, {"text": "so that each household\npartook in equal proportion", "start": 2429.38, "duration": 3.63}, {"text": "of fertilizer and poor soils.", "start": 2433.01, "duration": 3.12}, {"text": "Dividing up the\nland in accordance", "start": 2436.13, "duration": 1.65}, {"text": "with drainage and\nexposure, resources", "start": 2437.78, "duration": 2.19}, {"text": "were divided into shares.", "start": 2439.97, "duration": 1.95}, {"text": "One man might have more\nshares than another,", "start": 2441.92, "duration": 2.25}, {"text": "but the shares\nthemselves were equal.", "start": 2444.17, "duration": 3.98}, {"text": "Now, there are\npotential problems.", "start": 2448.15, "duration": 2.94}, {"text": "For the theory to\nfit exactly, we", "start": 2451.09, "duration": 1.78}, {"text": "got to worry a little\nbit about the intercepts", "start": 2452.87, "duration": 2.63}, {"text": "because those divisions did\nnot allow the intercepts to be", "start": 2455.5, "duration": 4.08}, {"text": "other than 0.", "start": 2459.58, "duration": 1.23}, {"text": "If you go back to where we\nfirst introduced risk sharing", "start": 2460.81, "duration": 4.26}, {"text": "and looked at particular\nutility functions,", "start": 2465.07, "duration": 3.24}, {"text": "I showed you, as example\nof the risk-sharing rules,", "start": 2468.31, "duration": 3.42}, {"text": "two equations--\nconstant relative risk", "start": 2471.73, "duration": 2.67}, {"text": "aversion, constant\nabsolute risk aversion.", "start": 2474.4, "duration": 3.06}, {"text": "And the intercept was 0\nunder these various types", "start": 2477.46, "duration": 4.74}, {"text": "of conditions.", "start": 2482.2, "duration": 0.76}, {"text": "So it's not like\nthey can't be 0,", "start": 2482.96, "duration": 2.69}, {"text": "but it does require\ncertain parameters", "start": 2485.65, "duration": 2.79}, {"text": "to hold in order for\nthat to be the case.", "start": 2488.44, "duration": 2.8}, {"text": "So a little bit of\na qualification.", "start": 2491.24, "duration": 3.04}, {"text": "But all is not lost.", "start": 2494.28, "duration": 2.59}, {"text": "We can even do more.", "start": 2496.87, "duration": 2.34}, {"text": "And namely, we don't have to\nhave a given household having", "start": 2499.21, "duration": 4.05}, {"text": "the same number of shares\nin every type of land.", "start": 2503.26, "duration": 4.48}, {"text": "And that's going to allow\nvarious kinds of intercepts", "start": 2507.74, "duration": 3.36}, {"text": "and so on.", "start": 2511.1, "duration": 2.23}, {"text": "So here's the idea finally.", "start": 2513.33, "duration": 3.14}, {"text": "Suppose there are at\nleast as many land types", "start": 2516.47, "duration": 3.78}, {"text": "with independent return vectors\nas there are states of nature.", "start": 2520.25, "duration": 4.68}, {"text": "So what I showed you\njust now violated that.", "start": 2524.93, "duration": 2.45}, {"text": "There were three states of\nnature and two types of land.", "start": 2527.38, "duration": 4.05}, {"text": "But if we had three\nstates of nature,", "start": 2531.43, "duration": 3.05}, {"text": "we'd have to have\nthree types of land", "start": 2534.48, "duration": 2.67}, {"text": "with independent return streams.", "start": 2537.15, "duration": 1.77}, {"text": "And likewise, s types\nof land, we need", "start": 2538.92, "duration": 3.515}, {"text": "s dimensional return vectors.", "start": 2542.435, "duration": 3.725}, {"text": "So one column cannot be\nderived as a linear combination", "start": 2546.16, "duration": 3.84}, {"text": "of the other columns.", "start": 2550.0, "duration": 1.83}, {"text": "Now let's solve the\nrisk-sharing problem", "start": 2551.83, "duration": 2.7}, {"text": "and take this consumption to\nbe the target, this consumption", "start": 2554.53, "duration": 3.3}, {"text": "of household J in state epsilon.", "start": 2557.83, "duration": 2.4}, {"text": "And we're going to do that,\nobviously, over all states", "start": 2560.23, "duration": 3.09}, {"text": "epsilon and all households\nj, their little n of them.", "start": 2563.32, "duration": 4.77}, {"text": "We get an equation of this form.", "start": 2568.09, "duration": 2.67}, {"text": "So don't get lost\nin the notation.", "start": 2570.76, "duration": 1.65}, {"text": "I'll help.", "start": 2572.41, "duration": 1.32}, {"text": "This is consumption of household\nJ in state 1, consumption", "start": 2573.73, "duration": 4.11}, {"text": "of household J in state 2,\nlikewise in state capital S.", "start": 2577.84, "duration": 5.99}, {"text": "That's a target.", "start": 2583.83, "duration": 1.32}, {"text": "And just imagine it\nsolved the Pareto problem.", "start": 2585.15, "duration": 3.16}, {"text": "How can we achieve it?", "start": 2588.31, "duration": 1.79}, {"text": "We have as controls the\nfraction of type k land held", "start": 2590.1, "duration": 4.65}, {"text": "by household J. And now\nthose fractions, alpha j,", "start": 2594.75, "duration": 4.11}, {"text": "vary with k.", "start": 2598.86, "duration": 1.62}, {"text": "So we're allowing\nland-type-specific allocation", "start": 2600.48, "duration": 4.11}, {"text": "of shares.", "start": 2604.59, "duration": 1.5}, {"text": "Anyway, if you do the\nlinear algebra here,", "start": 2606.09, "duration": 2.31}, {"text": "here's the yield of\ntype 1 land in state", "start": 2608.4, "duration": 3.54}, {"text": "1, the yield of type 2\nland in state 1, et cetera.", "start": 2611.94, "duration": 4.5}, {"text": "These alphas would\nthen multiply--", "start": 2616.44, "duration": 2.64}, {"text": "e1, alpha 1, e2,\nalpha 2, et cetera.", "start": 2619.08, "duration": 4.42}, {"text": "So adding it up like\nthe dot product,", "start": 2623.5, "duration": 2.49}, {"text": "we would get consumption.", "start": 2625.99, "duration": 2.33}, {"text": "Consumption is coming from\na share-weighted version", "start": 2628.32, "duration": 3.15}, {"text": "of the yield.", "start": 2631.47, "duration": 3.09}, {"text": "Hopefully, the algebra is clear.", "start": 2634.56, "duration": 2.67}, {"text": "Writing it in matrix\nnotation, we just", "start": 2637.23, "duration": 2.1}, {"text": "want to get this\nquote endowment matrix", "start": 2639.33, "duration": 2.82}, {"text": "e times the share vector for\nhousehold J varying over type k", "start": 2642.15, "duration": 5.53}, {"text": "land.", "start": 2647.68, "duration": 0.5}, {"text": "It's a vector equal to the\nstate-dependent consumptions.", "start": 2648.18, "duration": 4.35}, {"text": "So e times alpha equals cj.", "start": 2652.53, "duration": 3.69}, {"text": "So then the question is,\nto achieve this target,", "start": 2656.22, "duration": 2.79}, {"text": "can we find alphas that do it?", "start": 2659.01, "duration": 1.68}, {"text": "And that's like\nsolving this equation.", "start": 2660.69, "duration": 1.93}, {"text": "So essentially, take an\ninverse of something.", "start": 2662.62, "duration": 3.97}, {"text": "If there are as many return\nvectors over types of land", "start": 2666.59, "duration": 4.44}, {"text": "that are independent of each\nother as there are states,", "start": 2671.03, "duration": 3.27}, {"text": "then this matrix has an inverse.", "start": 2674.3, "duration": 3.42}, {"text": "It's non-singular, so you\ncan solve this equation.", "start": 2677.72, "duration": 4.27}, {"text": "So now we'll have\nsolutions for the alphas.", "start": 2681.99, "duration": 3.14}, {"text": "And it turns out if you do\nthat not just for household j", "start": 2685.13, "duration": 3.09}, {"text": "but over all of them,\nyou'll get an implication", "start": 2688.22, "duration": 3.39}, {"text": "that the sum of the\nalphas will add up to 1.", "start": 2691.61, "duration": 4.94}, {"text": "So they do look like shares.", "start": 2696.55, "duration": 2.13}, {"text": "Type k land held in fraction\nalpha j by the j-th household", "start": 2698.68, "duration": 6.24}, {"text": "when summed over-- there\nshould be a sum here--", "start": 2704.92, "duration": 3.24}, {"text": "there was one there--", "start": 2708.16, "duration": 1.56}, {"text": "when summed over\nj would equal 1.", "start": 2709.72, "duration": 2.22}, {"text": "So all the land is divided.", "start": 2711.94, "duration": 2.55}, {"text": "All the land of each\ntype k is totally divided", "start": 2714.49, "duration": 2.64}, {"text": "among all the households.", "start": 2717.13, "duration": 2.55}, {"text": "You could run into a\nlittle bit of problem", "start": 2719.68, "duration": 2.1}, {"text": "if the alphas went\nnegative because then", "start": 2721.78, "duration": 2.7}, {"text": "that's like trying to go short.", "start": 2724.48, "duration": 2.02}, {"text": "We're not going to\nallow that to happen.", "start": 2726.5, "duration": 2.97}, {"text": "So there's a little bit\nof a fly in the ointment.", "start": 2729.47, "duration": 2.51}, {"text": "But roughly speaking,\nthere's a way", "start": 2731.98, "duration": 1.65}, {"text": "to achieve an optimal allocation\nof risk sharing just by shares.", "start": 2733.63, "duration": 5.44}, {"text": "So they don't need to\ntransfer risk around ex post.", "start": 2739.07, "duration": 4.25}, {"text": "They can do it all ex ante.", "start": 2743.32, "duration": 2.67}, {"text": "Now, in order to\nachieve that, we", "start": 2745.99, "duration": 2.19}, {"text": "had to ignore the\nnegative alphas.", "start": 2748.18, "duration": 2.1}, {"text": "But more to the point,\nwe had to assume", "start": 2750.28, "duration": 2.34}, {"text": "there are as many\ntypes of land as there", "start": 2752.62, "duration": 2.16}, {"text": "are states of the world.", "start": 2754.78, "duration": 1.8}, {"text": "Maybe that's not true.", "start": 2756.58, "duration": 1.228}, {"text": "I don't know.", "start": 2757.808, "duration": 0.542}, {"text": "It could go both ways.", "start": 2758.35, "duration": 1.56}, {"text": "How many different\ntypes of land are there,", "start": 2759.91, "duration": 2.28}, {"text": "and how many different states\ncan a given land type take on?", "start": 2762.19, "duration": 3.57}, {"text": "If there's incredible\nheterogeneity over land,", "start": 2765.76, "duration": 2.73}, {"text": "it's entirely possible\nthat the number of types", "start": 2768.49, "duration": 2.19}, {"text": "was equal if not greater\nthan the number of states.", "start": 2770.68, "duration": 3.69}, {"text": "But I could also imagine\nthe other way around.", "start": 2774.37, "duration": 2.67}, {"text": "Like the Thai village, you've\ngot low land and high land.", "start": 2777.04, "duration": 2.7}, {"text": "You put them in two\ncategories, and then you", "start": 2779.74, "duration": 2.07}, {"text": "have multiple states.", "start": 2781.81, "duration": 1.05}, {"text": "You'd have an\nincomplete version.", "start": 2782.86, "duration": 3.12}, {"text": "Let's see how bad it is, though.", "start": 2785.98, "duration": 1.68}, {"text": "Maybe as an approximation,\nthey were doing pretty well", "start": 2787.66, "duration": 3.87}, {"text": "by dividing up the\nland even if they", "start": 2791.53, "duration": 1.83}, {"text": "couldn't achieve the optimal\nallocation perfectly.", "start": 2793.36, "duration": 4.57}, {"text": "So let's put in two\ndifferent utility functions.", "start": 2797.93, "duration": 3.75}, {"text": "For household 1, we have\nconstant relative risk", "start": 2801.68, "duration": 3.27}, {"text": "aversion, and for household\n2, it's a quadratic function.", "start": 2804.95, "duration": 4.29}, {"text": "This quadratic thing is\na pain and always scary", "start": 2809.24, "duration": 3.93}, {"text": "when you see it.", "start": 2813.17, "duration": 0.79}, {"text": "It's like there's a bliss point.", "start": 2813.96, "duration": 1.7}, {"text": "We've talked about this.", "start": 2815.66, "duration": 1.08}, {"text": "Consumption is less\nthan the bliss point", "start": 2816.74, "duration": 2.46}, {"text": "assumed so that the marginal\nutility of consumption", "start": 2819.2, "duration": 3.3}, {"text": "is always positive.", "start": 2822.5, "duration": 1.898}, {"text": "Otherwise, you see a\nlot of negative signs,", "start": 2824.398, "duration": 1.792}, {"text": "and it's kind of disturbing.", "start": 2826.19, "duration": 1.74}, {"text": "Can this consumption be\nhigher than the bliss point?", "start": 2827.93, "duration": 2.94}, {"text": "No, because you'll get marginal\nutility being negative,", "start": 2830.87, "duration": 3.99}, {"text": "moving negatively\nwith consumption.", "start": 2834.86, "duration": 1.9}, {"text": "So anyway, just so you feel\na bit more comfortable,", "start": 2836.76, "duration": 3.35}, {"text": "let's put in alpha equal\nto 0.5, k equal 0.002,", "start": 2840.11, "duration": 3.99}, {"text": "and be equal to 80.", "start": 2844.1, "duration": 2.94}, {"text": "So we have completely\nparameterized this family", "start": 2847.04, "duration": 2.97}, {"text": "of utility functions.", "start": 2850.01, "duration": 1.26}, {"text": "And again, we have\ndifferent preferences here", "start": 2851.27, "duration": 2.64}, {"text": "but nice concave utility,\nstrictly, for both.", "start": 2853.91, "duration": 3.34}, {"text": "We've got two types of land,\nand we're back to, say,", "start": 2857.25, "duration": 3.62}, {"text": "having three or more\nstates of the world.", "start": 2860.87, "duration": 3.01}, {"text": "So ex ante division into\nshares cannot work perfectly.", "start": 2863.88, "duration": 4.7}, {"text": "To see how far we get, we\nconstrain the programming", "start": 2868.58, "duration": 3.18}, {"text": "problem to nevertheless\nsearch over these shares,", "start": 2871.76, "duration": 5.97}, {"text": "alpha jk of household\nJ share of type k land.", "start": 2877.73, "duration": 4.5}, {"text": "And we maximize a\nlambda-weighted sum", "start": 2882.23, "duration": 3.06}, {"text": "of ex ante expected utilities.", "start": 2885.29, "duration": 2.58}, {"text": "Oh, well there's only one date\nhere, so ignore the dynamics.", "start": 2887.87, "duration": 5.52}, {"text": "But there are multiple states.", "start": 2893.39, "duration": 2.25}, {"text": "And we're going to max this\nthing subject to shares", "start": 2895.64, "duration": 2.16}, {"text": "can't go negative, and\nthey have to add up to 1.", "start": 2897.8, "duration": 2.94}, {"text": "So it's a constrained\nprogramming problem.", "start": 2900.74, "duration": 3.03}, {"text": "We could call the solution\nto this constrained optimal.", "start": 2903.77, "duration": 3.27}, {"text": "It's constrained by the\npremise that the mechanism only", "start": 2907.04, "duration": 3.24}, {"text": "allows ex-ante\ndivision into shares", "start": 2910.28, "duration": 2.7}, {"text": "and not ex-post consumption\ntransfers, not gifts, not", "start": 2912.98, "duration": 5.59}, {"text": "borrowing and lending, nothing.", "start": 2918.57, "duration": 2.4}, {"text": "Now, you know from\nour work on Pareto", "start": 2920.97, "duration": 2.82}, {"text": "optimal allocations there's\ngoing to be a Pareto frontier.", "start": 2923.79, "duration": 3.93}, {"text": "So it's not like\nthere's one solution.", "start": 2927.72, "duration": 2.67}, {"text": "It's going to vary\nwith the lambdas.", "start": 2930.39, "duration": 3.12}, {"text": "So we'll do something\nspecial as an example, which", "start": 2933.51, "duration": 3.42}, {"text": "is to maximize the\nutility of household 1", "start": 2936.93, "duration": 3.12}, {"text": "subject to the\nutility of household", "start": 2940.05, "duration": 2.31}, {"text": "2 at an arbitrary constant.", "start": 2942.36, "duration": 3.37}, {"text": "So let me show you a picture,\nand then I'll go back.", "start": 2945.73, "duration": 4.43}, {"text": "We're in utility space,\nso we have the utilities", "start": 2950.16, "duration": 2.55}, {"text": "of household 1 and household 2.", "start": 2952.71, "duration": 2.34}, {"text": "And we have-- if we didn't\nhave a constrained problem,", "start": 2955.05, "duration": 3.42}, {"text": "we'd have this outer\nfrontier of the set", "start": 2958.47, "duration": 2.73}, {"text": "of all possible utilities\non the boundary.", "start": 2961.2, "duration": 3.1}, {"text": "And we'll call that the utility\nat the full risk sharing.", "start": 2964.3, "duration": 3.86}, {"text": "There are many solutions.", "start": 2968.16, "duration": 1.92}, {"text": "We got these through\nhyperplanes previously.", "start": 2970.08, "duration": 3.63}, {"text": "There is an equivalent\nway to do it,", "start": 2973.71, "duration": 3.1}, {"text": "which is to fix the utility\nof one household, namely 2,", "start": 2976.81, "duration": 4.1}, {"text": "and maximize the utility\nof the other one.", "start": 2980.91, "duration": 3.01}, {"text": "So we would end up right here.", "start": 2983.92, "duration": 2.15}, {"text": "But in the constrained\nproblem, we're", "start": 2986.07, "duration": 2.19}, {"text": "limited to dividing\nup land by shares.", "start": 2988.26, "duration": 3.03}, {"text": "That constrained Pareto\nfrontier is interior, still", "start": 2991.29, "duration": 4.56}, {"text": "a bit concave.", "start": 2995.85, "duration": 1.92}, {"text": "And we would move,\ntherefore, from where", "start": 2997.77, "duration": 2.37}, {"text": "that horizontal utility\nlevel for household 2", "start": 3000.14, "duration": 2.46}, {"text": "hits the outer frontier\nversus the inner frontier.", "start": 3002.6, "duration": 3.1}, {"text": "So let's focus on\nthe inner frontier,", "start": 3005.7, "duration": 1.73}, {"text": "the constrained\nproblem, and then see", "start": 3007.43, "duration": 2.1}, {"text": "how close they're going to\nget to the outer frontier.", "start": 3009.53, "duration": 3.59}, {"text": "I solved that thing numerically.", "start": 3013.12, "duration": 1.89}, {"text": "I was trying to give you all\nthe parameters for utility", "start": 3015.01, "duration": 2.73}, {"text": "functions.", "start": 3017.74, "duration": 1.17}, {"text": "Some of it's missing\nhere-- covariance,", "start": 3018.91, "duration": 3.06}, {"text": "coefficient of variation.", "start": 3021.97, "duration": 1.98}, {"text": "And you get a solution that\nhousehold 1 has about 3/4,", "start": 3023.95, "duration": 5.52}, {"text": "72%, of land type I 2 and\nabout a quarter of land type 2.", "start": 3029.47, "duration": 6.06}, {"text": "And household 2 would\nbe on the other side", "start": 3035.53, "duration": 2.16}, {"text": "of this at roughly 1/4, 3/4.", "start": 3037.69, "duration": 3.73}, {"text": "So one thing to\nnote is that that", "start": 3041.42, "duration": 3.41}, {"text": "generates a non-linear sharing\nrule but non-optimal rule.", "start": 3044.83, "duration": 6.21}, {"text": "I think I missed--", "start": 3051.04, "duration": 1.93}, {"text": "when I presented this\nconstraint problem,", "start": 3052.97, "duration": 2.01}, {"text": "I neglected the little\nparagraph at the bottom.", "start": 3054.98, "duration": 3.87}, {"text": "No, it's not there.", "start": 3058.85, "duration": 2.3}, {"text": "Well, let me remind you.", "start": 3061.15, "duration": 2.76}, {"text": "Again, back to the preference\nlecture where we did risk,", "start": 3063.91, "duration": 3.39}, {"text": "and I showed you two\nparticular utility functions,", "start": 3067.3, "duration": 3.96}, {"text": "constant exponential and\nconstant relative risk aversion", "start": 3071.26, "duration": 4.23}, {"text": "with linear schedules.", "start": 3075.49, "duration": 1.44}, {"text": "But then I showed you another\nfigure which was non-linear--", "start": 3076.93, "duration": 4.23}, {"text": "monotone increasing for both\nhouseholds, but nonlinear.", "start": 3081.16, "duration": 3.54}, {"text": "That came from this\nspecification of utilities.", "start": 3084.7, "duration": 4.32}, {"text": "So that's what I was looking\nfor, seen in previous lecture", "start": 3089.02, "duration": 3.0}, {"text": "7.", "start": 3092.02, "duration": 1.11}, {"text": "So we know the optimal\nsharing rules are nonlinear.", "start": 3093.13, "duration": 4.86}, {"text": "Dividing up into shares\nsuggests we're going", "start": 3097.99, "duration": 3.6}, {"text": "to end up with linear rules.", "start": 3101.59, "duration": 2.71}, {"text": "So we're not going to\nend up with the optimum.", "start": 3104.3, "duration": 2.75}, {"text": "But we can still\ntry to figure out", "start": 3107.05, "duration": 2.1}, {"text": "how close the inner frontier\nis to the outer frontier.", "start": 3109.15, "duration": 5.17}, {"text": "So let's look at the transfers.", "start": 3114.32, "duration": 3.24}, {"text": "Let me state this clearly.", "start": 3117.56, "duration": 1.77}, {"text": "We're going to try to do it\nex-ante by division of shares,", "start": 3119.33, "duration": 4.53}, {"text": "get the constrained\noptimum, and then look", "start": 3123.86, "duration": 3.66}, {"text": "at transfers across the\ntwo households, who's", "start": 3127.52, "duration": 4.05}, {"text": "paying who depending\non the state, and then", "start": 3131.57, "duration": 2.73}, {"text": "finally, how those transfers\nwould need potentially", "start": 3134.3, "duration": 2.97}, {"text": "to be augmented.", "start": 3137.27, "duration": 3.49}, {"text": "So here's the\naggregate endowment.", "start": 3140.76, "duration": 1.59}, {"text": "This is the sum of the yields\nover the two types of land.", "start": 3142.35, "duration": 3.95}, {"text": "That's also\naggregate consumption", "start": 3146.3, "duration": 1.92}, {"text": "because this is\na static problem.", "start": 3148.22, "duration": 2.43}, {"text": "Here is consumption of\nthe individual agents,", "start": 3150.65, "duration": 3.18}, {"text": "both of them.", "start": 3153.83, "duration": 1.47}, {"text": "This is the consumption\nof person 1, constrained,", "start": 3155.3, "duration": 4.53}, {"text": "linear dotted line.", "start": 3159.83, "duration": 2.52}, {"text": "Here's the consumption\nof person 2.", "start": 3162.35, "duration": 2.61}, {"text": "Constrained is this dot\ndashed line for person 2.", "start": 3164.96, "duration": 4.29}, {"text": "Constrained is the\ndot-dot-dot line for person 1.", "start": 3169.25, "duration": 3.84}, {"text": "They're both linear schedules.", "start": 3173.09, "duration": 2.07}, {"text": "Now, remember, they're not\ndoing this with transfers--", "start": 3175.16, "duration": 2.64}, {"text": "I kind of misspoke\na minute ago--", "start": 3177.8, "duration": 1.56}, {"text": "because they're doing it with\nex-ante division into shares.", "start": 3179.36, "duration": 3.03}, {"text": "But nevertheless, it's not\nthe full-blown optimum.", "start": 3182.39, "duration": 2.82}, {"text": "It's not the outer frontier\nin which you can not only", "start": 3185.21, "duration": 3.33}, {"text": "have division but\nalso ex-post transfers", "start": 3188.54, "duration": 3.21}, {"text": "to get to the full optimum.", "start": 3191.75, "duration": 1.38}, {"text": "And those schedules are\nlisted here as unconstrained.", "start": 3193.13, "duration": 3.18}, {"text": "And they are non-linear, as\nI was trying to say earlier.", "start": 3196.31, "duration": 3.85}, {"text": "So if we look at these\nstates, say five states,", "start": 3200.16, "duration": 5.36}, {"text": "and look at consumption under\nex-ante division of land", "start": 3205.52, "duration": 3.36}, {"text": "versus consumption under the\nfull optimum, for household 1,", "start": 3208.88, "duration": 4.8}, {"text": "you can see household\n1 is monotonic.", "start": 3213.68, "duration": 3.3}, {"text": "Household consumption\nis logically", "start": 3216.98, "duration": 2.04}, {"text": "increasing with the\naggregate, but it's", "start": 3219.02, "duration": 2.4}, {"text": "a bit different,\nalthough monotonic,", "start": 3221.42, "duration": 2.01}, {"text": "from what it would be\nunder the full optimum.", "start": 3223.43, "duration": 1.95}, {"text": "And here you can see\nat the lowest state,", "start": 3225.38, "duration": 3.18}, {"text": "household 1 would be consuming\nmore under the full optimum", "start": 3228.56, "duration": 3.63}, {"text": "but then less under the\nfull optimum relative", "start": 3232.19, "duration": 3.93}, {"text": "to the division, less, and\nthen back to being more.", "start": 3236.12, "duration": 4.38}, {"text": "So here it is over here.", "start": 3240.5, "duration": 2.14}, {"text": "Why am I struggling so hard?", "start": 3242.64, "duration": 2.04}, {"text": "So this is the amount\nof the transfer", "start": 3244.68, "duration": 2.93}, {"text": "from household 2\nto household 1 that", "start": 3247.61, "duration": 3.87}, {"text": "is necessary to add\non to the solution", "start": 3251.48, "duration": 4.38}, {"text": "from the ex-ante division\nof land shares only.", "start": 3255.86, "duration": 4.04}, {"text": "If you wanted to look\nat it in a picture,", "start": 3259.9, "duration": 2.74}, {"text": "the picture is\nliterally the difference", "start": 3262.64, "duration": 4.76}, {"text": "between these two lines.", "start": 3267.4, "duration": 2.38}, {"text": "So here, the amount\nthat household 1", "start": 3269.78, "duration": 2.78}, {"text": "ought to be getting under the\nfull optimum would be higher,", "start": 3272.56, "duration": 5.28}, {"text": "and therefore, ought to\nget a positive transfer.", "start": 3277.84, "duration": 3.15}, {"text": "Here, it would be lower,\nhence the negative transfer.", "start": 3280.99, "duration": 3.58}, {"text": "And finally, at the\nend, positive again.", "start": 3284.57, "duration": 3.05}, {"text": "So that's consistent\nwith these numbers", "start": 3287.62, "duration": 2.55}, {"text": "where these states,\ngoing from 1 to 5,", "start": 3290.17, "duration": 3.09}, {"text": "is like moving across\nthe different values", "start": 3293.26, "duration": 2.4}, {"text": "of the aggregate endowment.", "start": 3295.66, "duration": 1.89}, {"text": "So in summary, I guess\nthere is a couple", "start": 3297.55, "duration": 3.78}, {"text": "of takeaways from the\nsecond half of this lecture.", "start": 3301.33, "duration": 3.12}, {"text": "One, we looked at special\nmechanisms-- in this case,", "start": 3304.45, "duration": 3.51}, {"text": "ex-ante division of land\nand whether or not we", "start": 3307.96, "duration": 3.45}, {"text": "could get to an\noptimal allocation", "start": 3311.41, "duration": 1.89}, {"text": "of risk bearing that way.", "start": 3313.3, "duration": 2.13}, {"text": "And we saw some special\ncases where could.", "start": 3315.43, "duration": 3.53}, {"text": "We had to make the shares\ndifferent across the different", "start": 3318.96, "duration": 3.25}, {"text": "households and maybe different\nacross the different land", "start": 3322.21, "duration": 3.18}, {"text": "types, especially so if we\naccommodated more and more", "start": 3325.39, "duration": 3.6}, {"text": "diversity and preferences.", "start": 3328.99, "duration": 1.93}, {"text": "The second takeaway\nfrom the second part", "start": 3330.92, "duration": 2.75}, {"text": "is we might not\nachieve a full optimum,", "start": 3333.67, "duration": 3.66}, {"text": "so we would have expected some\nkind of borrowing and lending", "start": 3337.33, "duration": 2.61}, {"text": "and gift-giving in that\nmedieval village economy", "start": 3339.94, "duration": 2.37}, {"text": "even if we can't find it\nin the historical records.", "start": 3342.31, "duration": 4.08}, {"text": "Or we could just say, evidently,\nfor institutional reasons", "start": 3346.39, "duration": 3.6}, {"text": "we don't understand, they\njust weren't doing it.", "start": 3349.99, "duration": 2.79}, {"text": "But we don't lose our tools.", "start": 3352.78, "duration": 1.78}, {"text": "Not all is lost.", "start": 3354.56, "duration": 1.1}, {"text": "We are still able to solve for\na constrained optimal allocation", "start": 3355.66, "duration": 4.38}, {"text": "solving the so-called Pareto\nproblem or programming", "start": 3360.04, "duration": 3.18}, {"text": "problem, maximizing\nlambda-weighted sums of utility", "start": 3363.22, "duration": 3.67}, {"text": "subject to constraints with the\nappropriate control variables,", "start": 3366.89, "duration": 3.8}, {"text": "in this case shares.", "start": 3370.69, "duration": 2.17}, {"text": "And then the big\npicture of this lecture", "start": 3372.86, "duration": 1.67}, {"text": "is we're looking\nat the application", "start": 3374.53, "duration": 2.73}, {"text": "of the theory of the optimal\nallocation of risk bearing.", "start": 3377.26, "duration": 3.51}, {"text": "We did that in\nvillages in India,", "start": 3380.77, "duration": 2.13}, {"text": "looking at consumption\nand income data.", "start": 3382.9, "duration": 2.2}, {"text": "So from a science point\nof view, we have a model.", "start": 3385.1, "duration": 2.84}, {"text": "We have data.", "start": 3387.94, "duration": 0.9}, {"text": "The data can vary\nacross the applications.", "start": 3388.84, "duration": 2.55}, {"text": "You can still ask,\neven if we don't", "start": 3391.39, "duration": 1.71}, {"text": "have the data on\neverything, whether we can", "start": 3393.1, "duration": 2.34}, {"text": "see how well the theory fits.", "start": 3395.44, "duration": 1.83}, {"text": "And we could do that in--", "start": 3397.27, "duration": 2.34}, {"text": "in the medieval\nvillages, we don't even", "start": 3399.61, "duration": 1.89}, {"text": "have data on consumption\nof individual households,", "start": 3401.5, "duration": 2.76}, {"text": "and all we see are\npictures of land.", "start": 3404.26, "duration": 1.8}, {"text": "But we do have the covariance\nand variance statistics.", "start": 3406.06, "duration": 3.45}, {"text": "So we're kind of\nable to calibrate", "start": 3409.51, "duration": 1.74}, {"text": "the model a bit the way we were\ncalibrating the dynamic storage", "start": 3411.25, "duration": 3.48}, {"text": "model, but in this\ncase, not to try", "start": 3414.73, "duration": 2.16}, {"text": "to explain why they didn't\nstore very often, but rather,", "start": 3416.89, "duration": 3.24}, {"text": "to explain this very salient\npattern of dividing land", "start": 3420.13, "duration": 3.6}, {"text": "into different strips.", "start": 3423.73, "duration": 1.59}, {"text": "OK.", "start": 3425.32, "duration": 0.51}, {"text": "So that's all I have for today.", "start": 3425.83, "duration": 3.03}, {"text": "All right.", "start": 3428.86, "duration": 1.55}, {"text": "See you soon.", "start": 3430.41, "duration": 1.06}, {"text": "Thank you so much.", "start": 3431.47, "duration": 1.96}]
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+[{"text": "The following\ncontent is provided", "start": 0.57, "duration": 1.8}, {"text": "by MIT OpenCourseWare under\na Creative Commons license.", "start": 2.37, "duration": 3.96}, {"text": "Additional information\nabout our license,", "start": 6.33, "duration": 2.1}, {"text": "and MIT OpenCourseWare\nin general,", "start": 8.43, "duration": 2.37}, {"text": "is available at ocw.mit.edu.", "start": 10.8, "duration": 1.94}, {"text": "TAFT BROOME: Let's see--", "start": 15.42, "duration": 1.59}, {"text": "I've got two issues that\ncame to my attention", "start": 17.01, "duration": 4.11}, {"text": "since the last class\nthat I want to go over.", "start": 21.12, "duration": 2.94}, {"text": "I want to give your\npapers back, but I don't", "start": 24.06, "duration": 2.422}, {"text": "want to give them back today.", "start": 26.482, "duration": 1.208}, {"text": "Also, do can Thursday wait\nor do you want comments on it", "start": 31.73, "duration": 3.54}, {"text": "tonight?", "start": 35.27, "duration": 1.41}, {"text": "AUDIENCE: I can work\nwith Thursday, yeah.", "start": 36.68, "duration": 2.82}, {"text": "TAFT BROOME: Thursday--", "start": 39.5, "duration": 2.23}, {"text": "I have some thoughts\non your papers,", "start": 41.73, "duration": 1.645}, {"text": "and I just could not come to\none conclusion [INAUDIBLE]..", "start": 43.375, "duration": 3.416}, {"text": "That's what happens\nwith this business.", "start": 50.228, "duration": 3.092}, {"text": "Then, I want to--", "start": 53.32, "duration": 3.09}, {"text": "did you get my news article\nand what I discussed there?", "start": 56.41, "duration": 4.933}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 61.343, "duration": 0.917}, {"text": "TAFT BROOME: Then we have a\ncouple of cases outstanding.", "start": 62.26, "duration": 5.5}, {"text": "How many, two?", "start": 67.76, "duration": 2.905}, {"text": "Ford Pinto--", "start": 70.665, "duration": 2.251}, {"text": "AUDIENCE: And Challenger.", "start": 72.916, "duration": 1.214}, {"text": "TAFT BROOME: And Challenger--", "start": 74.13, "duration": 1.66}, {"text": "no, no, Challenger?", "start": 75.79, "duration": 1.653}, {"text": "I thought we were going to--", "start": 77.443, "duration": 1.167}, {"text": "AUDIENCE: Well,\nyou said we would", "start": 78.61, "duration": 0.18}, {"text": "finish talking about that,\nand then talk about Pinto.", "start": 78.79, "duration": 3.3}, {"text": "So it's like one and a half.", "start": 82.09, "duration": 1.47}, {"text": "TAFT BROOME: All right, and\nthen we'll assign some more,", "start": 83.56, "duration": 4.91}, {"text": "and then we'll be ready to go.", "start": 88.47, "duration": 6.72}, {"text": "Let's deal with the\ntwo issues first.", "start": 95.19, "duration": 2.15}, {"text": "Dr. [INAUDIBLE] brought up one.", "start": 97.34, "duration": 1.32}, {"text": "And I'll tell you my\nthoughts on the matter,", "start": 104.34, "duration": 3.54}, {"text": "but I'd like for it to\nbe a class discussion.", "start": 107.88, "duration": 3.36}, {"text": "Now, the way I understand\nthe problem is,", "start": 111.24, "duration": 5.222}, {"text": "let's see if we can't--", "start": 116.462, "duration": 0.958}, {"text": "well, I was going to act it out.", "start": 120.33, "duration": 3.05}, {"text": "I'll try.", "start": 123.38, "duration": 0.61}, {"text": "So I'll act two parts.", "start": 123.99, "duration": 2.87}, {"text": "I'll try that.", "start": 126.86, "duration": 0.63}, {"text": "I don't know if\nit's going to work.", "start": 127.49, "duration": 1.48}, {"text": "But the situation\nis a job interview", "start": 128.97, "duration": 7.71}, {"text": "And I am just\ngraduated from MIT,", "start": 136.68, "duration": 9.37}, {"text": "and you're going\nto interview me.", "start": 146.05, "duration": 1.41}, {"text": "You're this big boss on the job.", "start": 147.46, "duration": 1.35}, {"text": "And you are my friend, my\npersonal friend from years.", "start": 151.45, "duration": 6.76}, {"text": "So the job is one in which\nI'm going to be an engineer,", "start": 158.21, "duration": 4.063}, {"text": "but I'm going to\nhave to interface", "start": 162.273, "duration": 1.417}, {"text": "the general public a lot.", "start": 163.69, "duration": 1.23}, {"text": "You know me as a person\nwho is not exactly", "start": 167.896, "duration": 4.624}, {"text": "the nicest person in the world--", "start": 172.52, "duration": 2.25}, {"text": "a little bit moody,\nand can generally", "start": 174.77, "duration": 5.79}, {"text": "irritate people occasionally.", "start": 180.56, "duration": 3.3}, {"text": "But I want this job.", "start": 183.86, "duration": 1.68}, {"text": "So the situation is this--", "start": 185.54, "duration": 1.71}, {"text": "I go in, and I'm all happy.", "start": 187.25, "duration": 4.08}, {"text": "And you tell me, well,\nsit down, Mr. So-and-so.", "start": 191.33, "duration": 3.3}, {"text": "And this is company X,\nand this is what we do.", "start": 194.63, "duration": 3.72}, {"text": "How can you help us out?", "start": 198.35, "duration": 1.02}, {"text": "And I'm going to say, I'm going\nto meet with these people.", "start": 199.37, "duration": 3.3}, {"text": "I'm going to make\nthem love company X.", "start": 202.67, "duration": 2.49}, {"text": "And we are going to make\na lot of money together.", "start": 205.16, "duration": 2.235}, {"text": "End of situation.", "start": 210.58, "duration": 3.36}, {"text": "Have I lied?", "start": 213.94, "duration": 1.57}, {"text": "Have I misrepresented myself\nto this potential employer just", "start": 215.51, "duration": 4.32}, {"text": "to get a job?", "start": 219.83, "duration": 2.54}, {"text": "Should I have\nportrayed myself more", "start": 222.37, "duration": 1.98}, {"text": "like quote unquote \"myself\"?", "start": 224.35, "duration": 1.95}, {"text": "Is this an ethical situation,\nor just some other kind", "start": 233.752, "duration": 2.208}, {"text": "of situation?", "start": 235.96, "duration": 0.96}, {"text": "Is it legal?", "start": 236.92, "duration": 0.56}, {"text": "Is it business?", "start": 237.48, "duration": 0.625}, {"text": "Now, I have the unfair\nadvantage of having", "start": 243.12, "duration": 3.27}, {"text": "thought about this thing for\nabout six days, five days.", "start": 246.39, "duration": 3.465}, {"text": "So if you want me to give you\nmy reaction first, I will do it.", "start": 252.91, "duration": 3.2}, {"text": "But I'd prefer if\nyou gave me yours.", "start": 256.11, "duration": 2.335}, {"text": "Let me give you a\nfew minutes to think.", "start": 258.445, "duration": 1.625}, {"text": "Talk if you want.", "start": 260.07, "duration": 0.708}, {"text": "AUDIENCE: So did you\npose this question?", "start": 268.72, "duration": 2.332}, {"text": "[SIDE CONVERSATION]", "start": 271.052, "duration": 3.472}, {"text": "AUDIENCE: Well, that-- your\nbackground helps a little bit", "start": 317.225, "duration": 2.375}, {"text": "because as you were\nexplaining the situation,", "start": 319.6, "duration": 4.153}, {"text": "I was thinking about,\nwell, he's talking", "start": 323.753, "duration": 1.667}, {"text": "about the representation\nof personality traits.", "start": 325.42, "duration": 4.86}, {"text": "Because you said you're moody,\nyou tend to irritate people.", "start": 330.28, "duration": 3.51}, {"text": "But what you're talking\nabout is skills--", "start": 333.79, "duration": 2.79}, {"text": "what you talk about first,\nanyway, is skill sets.", "start": 336.58, "duration": 2.37}, {"text": "And misrepresenting skill\nsets in a job interview", "start": 338.95, "duration": 3.66}, {"text": "is different than\nportraying yourself", "start": 342.61, "duration": 3.09}, {"text": "to have a certain personality.", "start": 345.7, "duration": 2.13}, {"text": "Both things are important\nfor job [INAUDIBLE],, I guess,", "start": 347.83, "duration": 3.126}, {"text": "personality and skill set, but--", "start": 350.956, "duration": 2.704}, {"text": "TAFT BROOME: Well, would\nyou say that interacting", "start": 356.048, "duration": 2.042}, {"text": "with the general public requires\na certain skill set, also?", "start": 358.09, "duration": 4.11}, {"text": "AUDIENCE: Mm-hmm.", "start": 362.2, "duration": 2.74}, {"text": "I feel like if you're hiring\nsomeone whose job will involve", "start": 364.94, "duration": 5.19}, {"text": "a lot of public relations,\nthe burden perhaps", "start": 370.13, "duration": 3.15}, {"text": "falls on you to\nreally find out what", "start": 373.28, "duration": 3.24}, {"text": "that person is like\ninteracting with the public.", "start": 376.52, "duration": 4.98}, {"text": "I don't know.", "start": 381.5, "duration": 1.1}, {"text": "TAFT BROOME: Can you do\nit in a job interview?", "start": 382.6, "duration": 1.917}, {"text": "Is there enough time?", "start": 384.517, "duration": 1.533}, {"text": "Do you have a test case?", "start": 386.05, "duration": 1.74}, {"text": "Do you have a random person\nin the room that you could--", "start": 387.79, "duration": 3.45}, {"text": "AUDIENCE: Maybe, yeah.", "start": 391.24, "duration": 1.395}, {"text": "Or do a panel of\ninterviewers or something.", "start": 392.635, "duration": 2.895}, {"text": "TAFT BROOME: Well, I'm trying to\nmake it as simple as possible,", "start": 395.53, "duration": 2.79}, {"text": "just one, just two persons.", "start": 398.32, "duration": 1.19}, {"text": "AUDIENCE: Well, [INAUDIBLE]", "start": 399.51, "duration": 3.051}, {"text": "Great, they just\nhaven't seen you--", "start": 407.38, "duration": 1.767}, {"text": "TAFT BROOME: Be that\nway all the time.", "start": 409.147, "duration": 1.583}, {"text": "AUDIENCE: --that way at the job.", "start": 410.73, "duration": 2.135}, {"text": "But maybe I make\nthe distinction.", "start": 412.865, "duration": 1.375}, {"text": "I think it's possible to be a\ncertain way on the job and not", "start": 414.24, "duration": 3.69}, {"text": "really that way, because I\njust know a lot of people who", "start": 417.93, "duration": 2.44}, {"text": "have a different work persona.", "start": 420.37, "duration": 1.732}, {"text": "And when they get home,\nthat's really not them,", "start": 422.102, "duration": 1.958}, {"text": "but they make it\nwork for the job.", "start": 424.06, "duration": 4.34}, {"text": "TAFT BROOME: Now, can we put\nany of this in the language", "start": 428.4, "duration": 5.43}, {"text": "of ethics, any of these views?", "start": 433.83, "duration": 1.98}, {"text": "Can we defend it, if we\nhad to, among scholars?", "start": 435.81, "duration": 8.13}, {"text": "Does the literature help\nin any way with this?", "start": 443.94, "duration": 4.14}, {"text": "AUDIENCE: So one moral\nrule, you're suggesting,", "start": 448.08, "duration": 4.19}, {"text": "is that one should always\nreveal their personality", "start": 452.27, "duration": 6.56}, {"text": "flaws in setting up\na new relationship.", "start": 458.83, "duration": 5.52}, {"text": "TAFT BROOME: I'm\nnot suggesting that.", "start": 464.35, "duration": 1.83}, {"text": "Take that part away.", "start": 466.18, "duration": 0.93}, {"text": "I'm not suggesting that.", "start": 467.11, "duration": 2.51}, {"text": "That is really the\nquestion, isn't it?", "start": 469.62, "duration": 1.807}, {"text": "AUDIENCE: Yeah, I mean, that's--", "start": 471.427, "duration": 1.333}, {"text": "AUDIENCE: Or maybe\nit isn't imperative", "start": 472.76, "duration": 1.583}, {"text": "that you present yourself as you\ntruly are at a job interview.", "start": 474.343, "duration": 3.237}, {"text": "I don't know.", "start": 477.58, "duration": 2.1}, {"text": "AUDIENCE: The interviewer\ndidn't say, are you moody?", "start": 479.68, "duration": 3.41}, {"text": "They just said,\nhow can you help?", "start": 483.09, "duration": 2.8}, {"text": "How can you help our company?", "start": 485.89, "duration": 1.87}, {"text": "So we're thinking about ethics--", "start": 487.76, "duration": 4.58}, {"text": "the applicant\ndidn't directly lie.", "start": 492.34, "duration": 2.385}, {"text": "Unless we know more about\nwhat went on in the interview,", "start": 498.777, "duration": 2.333}, {"text": "we can't say that he lied.", "start": 501.11, "duration": 2.86}, {"text": "He just talked about\nthe skills that he", "start": 503.97, "duration": 3.6}, {"text": "thought would be helpful to\nthe question that was asked.", "start": 507.57, "duration": 3.75}, {"text": "TAFT BROOME: Well, the\nperson that I was portraying,", "start": 511.32, "duration": 3.54}, {"text": "and the way I understood\nfrom your email,", "start": 514.86, "duration": 3.48}, {"text": "was a person that was\nworried that he or she might", "start": 518.34, "duration": 6.45}, {"text": "be using another person as\na means to his own ends.", "start": 524.79, "duration": 5.55}, {"text": "And Kant says-- another\nformulation of the Kantian rule", "start": 530.34, "duration": 3.03}, {"text": "is that you don't\nuse another person", "start": 533.37, "duration": 3.0}, {"text": "to advance your own ends.", "start": 536.37, "duration": 3.51}, {"text": "And the question is can it--", "start": 539.88, "duration": 2.38}, {"text": "so the question for\nme is whether or not", "start": 542.26, "duration": 3.89}, {"text": "all I'm interested in\nis using this person.", "start": 546.15, "duration": 5.38}, {"text": "The second question is--", "start": 551.53, "duration": 2.01}, {"text": "there's another question.", "start": 553.54, "duration": 2.01}, {"text": "And that's a question\nthat has a legal term,", "start": 555.55, "duration": 4.41}, {"text": "but which is also a moral term.", "start": 559.96, "duration": 1.86}, {"text": "I want to use this word from\nthe moral point of view.", "start": 561.82, "duration": 3.57}, {"text": "The word is contract.", "start": 565.39, "duration": 2.67}, {"text": "So we're here.", "start": 568.06, "duration": 1.395}, {"text": "You may wish to\nestablish a contract.", "start": 569.455, "duration": 3.765}, {"text": "And the contract is not going\nto be to act out my real,", "start": 573.22, "duration": 5.61}, {"text": "or whatever I think\nmy personality is", "start": 578.83, "duration": 2.37}, {"text": "with this public.", "start": 581.2, "duration": 0.81}, {"text": "The contract is to act\npersonable with these people.", "start": 582.01, "duration": 4.14}, {"text": "And the question is, from a\npsychological point of view,", "start": 586.15, "duration": 2.46}, {"text": "can I play this game for the\nduration of my employment?", "start": 588.61, "duration": 7.08}, {"text": "Or will the real me set in?", "start": 595.69, "duration": 3.66}, {"text": "And I think you said something\nthat I see the point to,", "start": 599.35, "duration": 5.56}, {"text": "and that is that we do\nhave multiple personas.", "start": 604.91, "duration": 6.87}, {"text": "One of them is our personality.", "start": 611.78, "duration": 2.39}, {"text": "But we can put on a\npersona from 9:00 to 5:00,", "start": 614.17, "duration": 3.57}, {"text": "Monday through\nFriday, for 20 years.", "start": 617.74, "duration": 4.37}, {"text": "And the contract is you don't\ncare what my personality is.", "start": 622.11, "duration": 3.06}, {"text": "You want to if I can\ndo this particular job,", "start": 625.17, "duration": 2.91}, {"text": "and if I can really\nbe the nice person.", "start": 628.08, "duration": 3.69}, {"text": "Let's put one more\nlittle piece in the game.", "start": 631.77, "duration": 2.7}, {"text": "There's a book--", "start": 639.24, "duration": 0.75}, {"text": "I forget the author's name,\nbut if you find the book", "start": 645.26, "duration": 6.34}, {"text": "and you have any questions,\nthe author is a faculty member", "start": 651.6, "duration": 2.84}, {"text": "right up the street at Harvard.", "start": 654.44, "duration": 1.59}, {"text": "And the book is called\nPygmalion in the Classroom.", "start": 656.03, "duration": 20.763}, {"text": "Now, this word Pygmalion, have\nyou heard of that word before?", "start": 681.23, "duration": 6.705}, {"text": "It's a name.", "start": 687.935, "duration": 0.5}, {"text": "What have you heard?", "start": 691.408, "duration": 2.46}, {"text": "AUDIENCE: A play.", "start": 693.868, "duration": 1.482}, {"text": "It's a play.", "start": 695.35, "duration": 1.98}, {"text": "TAFT BROOME: Oh,\nGeorge Bernard Shaw", "start": 697.33, "duration": 2.22}, {"text": "wrote a play called Pygmalion.", "start": 699.55, "duration": 2.27}, {"text": "You may know it better\nas a musical that", "start": 704.62, "duration": 5.79}, {"text": "was made for movies.", "start": 710.41, "duration": 2.56}, {"text": "It's called My Fair Lady.", "start": 712.97, "duration": 1.677}, {"text": "Actually, Pygmalion\ngoes back to,", "start": 718.06, "duration": 5.0}, {"text": "I think, second or\nthird century BC.", "start": 723.06, "duration": 2.21}, {"text": "It's a myth.", "start": 725.27, "duration": 2.85}, {"text": "But let's deal\nwith My Fair Lady.", "start": 728.12, "duration": 2.28}, {"text": "Do you remember the\ntheme in My Fair Lady?", "start": 730.4, "duration": 3.114}, {"text": "AUDIENCE: Yeah, I think\nthere's a [INAUDIBLE]", "start": 733.514, "duration": 1.992}, {"text": "and he takes a lady some\nflowers [INAUDIBLE]..", "start": 735.506, "duration": 3.486}, {"text": "I think he's in\nbed with someone.", "start": 744.98, "duration": 1.74}, {"text": "TAFT BROOME: That's\nwhat the key is, yeah.", "start": 746.72, "duration": 1.38}, {"text": "AUDIENCE: And they can't\ntell that she was just a lady", "start": 748.1, "duration": 2.25}, {"text": "selling flowers\na few months ago.", "start": 750.35, "duration": 1.86}, {"text": "They thought she came\nfrom even royalty", "start": 752.21, "duration": 3.33}, {"text": "just because she\nchanged her manners", "start": 755.54, "duration": 1.506}, {"text": "and she spoke [INAUDIBLE].", "start": 757.046, "duration": 2.264}, {"text": "TAFT BROOME: Yes, the\nissue was whether or not", "start": 759.31, "duration": 5.28}, {"text": "gentility and\nnobility was inborn", "start": 764.59, "duration": 5.04}, {"text": "or whether it could be taught.", "start": 769.63, "duration": 2.58}, {"text": "And these young\nguys had this bet.", "start": 772.21, "duration": 3.34}, {"text": "And this one guy\nsaid, well, I'll", "start": 775.55, "duration": 1.67}, {"text": "take that flower lady selling\nthe flowers here on the street,", "start": 777.22, "duration": 4.14}, {"text": "and a year from now\nshe'll be a lady.", "start": 781.36, "duration": 2.37}, {"text": "And they made this money bet.", "start": 783.73, "duration": 3.18}, {"text": "And so at the end of the year,\nhe has this coming-out party", "start": 786.91, "duration": 4.5}, {"text": "for her after training her.", "start": 791.41, "duration": 2.1}, {"text": "And all three of the guys fall\nin love with her, all three", "start": 793.51, "duration": 5.285}, {"text": "of these these\naristocrats or whatever.", "start": 798.795, "duration": 3.445}, {"text": "Pygmalion in the\nClassroom actually", "start": 802.24, "duration": 4.86}, {"text": "is an empirical science study\nthat asks whether or not", "start": 807.1, "duration": 9.06}, {"text": "a person, a teacher, can\nhave a preconceived notion", "start": 816.16, "duration": 4.92}, {"text": "about a student consciously\nand unconsciously,", "start": 821.08, "duration": 5.15}, {"text": "but mainly unconsciously,\nand whether or not", "start": 826.23, "duration": 2.64}, {"text": "that predisposition\nwill have an effect", "start": 828.87, "duration": 4.11}, {"text": "on the student's performance.", "start": 832.98, "duration": 1.29}, {"text": "So he deals with\ngender and race issues.", "start": 837.35, "duration": 4.74}, {"text": "And he says if the teacher has\na predisposition that women", "start": 842.09, "duration": 3.69}, {"text": "cannot learn math, and\nthis is a math class,", "start": 845.78, "duration": 3.69}, {"text": "then no matter how he--", "start": 849.47, "duration": 3.42}, {"text": "I'm going to say\nhe in this case--", "start": 852.89, "duration": 1.99}, {"text": "no matter how he\ntries to be fair,", "start": 854.88, "duration": 2.84}, {"text": "chances are the women will\nnot perform as well as they", "start": 857.72, "duration": 4.83}, {"text": "would ordinarily.", "start": 862.55, "duration": 2.4}, {"text": "Now let's see if they can\nget a real case like that.", "start": 864.95, "duration": 3.99}, {"text": "When I was in\ngraduate school, that", "start": 868.94, "duration": 4.59}, {"text": "was actually my first\neducational experience that", "start": 873.53, "duration": 4.35}, {"text": "was not dominated by Blacks.", "start": 877.88, "duration": 1.485}, {"text": "So I go into the\nclassroom, and the teacher", "start": 882.7, "duration": 3.06}, {"text": "would ask particularly\ndeep questions that have", "start": 885.76, "duration": 4.92}, {"text": "a particularly deep answer.", "start": 890.68, "duration": 3.57}, {"text": "And I'd raise my hand and give\nthat particularly deep answer.", "start": 894.25, "duration": 4.08}, {"text": "Decent person, 20\nminutes later, he", "start": 898.33, "duration": 3.93}, {"text": "would attribute that\nanswer to another student.", "start": 902.26, "duration": 2.91}, {"text": "I raised my hand,\nand said, hold it.", "start": 905.17, "duration": 1.5}, {"text": "Kowalski didn't say that, I\nwas the one who said that.", "start": 909.22, "duration": 3.81}, {"text": "And I'd take my chances\nwith irritating the person", "start": 913.03, "duration": 2.22}, {"text": "and getting a bad grade\nfor personality conflict.", "start": 915.25, "duration": 3.12}, {"text": "The good news is, this\nis a decent person.", "start": 918.37, "duration": 2.46}, {"text": "And person said, oh, how could\nI have made that mistake?", "start": 920.83, "duration": 3.39}, {"text": "This person's research says\nthat the brain operates off", "start": 924.22, "duration": 4.47}, {"text": "of preconceived notions--", "start": 928.69, "duration": 2.52}, {"text": "that you are set up.", "start": 931.21, "duration": 1.29}, {"text": "Your brain is set\nup to see or hear", "start": 932.5, "duration": 2.52}, {"text": "a certain thing a certain way.", "start": 935.02, "duration": 1.968}, {"text": "You really have to\ngo out of your way", "start": 936.988, "duration": 1.542}, {"text": "to retrain your brain\nin certain cases.", "start": 938.53, "duration": 2.43}, {"text": "Now we see why we're\ntalking about why", "start": 943.877, "duration": 1.583}, {"text": "he calls it Pygmalion.", "start": 945.46, "duration": 1.29}, {"text": "There's another\nterm that came out,", "start": 946.75, "duration": 1.74}, {"text": "I think he did not invent,\nwas called Pygmalion effect.", "start": 948.49, "duration": 3.97}, {"text": "So it's more broadly\nthan in the classroom.", "start": 952.46, "duration": 4.81}, {"text": "So the question is, if\nI am a moody person--", "start": 957.27, "duration": 6.39}, {"text": "going back to our situation--", "start": 963.66, "duration": 2.16}, {"text": "a moody, mean-spirited\nperson, can I", "start": 965.82, "duration": 6.99}, {"text": "deliver my term of the contract?", "start": 972.81, "duration": 5.5}, {"text": "Let's go a little bit further,\njust in case you're interested.", "start": 978.31, "duration": 2.583}, {"text": "A big literature on this\nsame subject, and I'll", "start": 983.6, "duration": 4.38}, {"text": "give you one name\nthat I remember.", "start": 987.98, "duration": 1.59}, {"text": "I call this one, call this two.", "start": 994.31, "duration": 1.83}, {"text": "This is an author's\nname, Nel Noddings.", "start": 996.14, "duration": 5.16}, {"text": "Nel Noddings has\nwritten some books,", "start": 1001.3, "duration": 2.43}, {"text": "but she mainly has collaborated\nwith professors of nursing.", "start": 1003.73, "duration": 8.41}, {"text": "The professors of\nnursing want to make", "start": 1015.73, "duration": 1.8}, {"text": "a distinction between\ncaring and care-giving,", "start": 1017.53, "duration": 6.72}, {"text": "and the nurses want to say\nthat a doctor can give care", "start": 1024.25, "duration": 6.03}, {"text": "without caring,\nstrictly business,", "start": 1030.28, "duration": 3.72}, {"text": "but that a nurse can't give\nnursing care without actually", "start": 1034.0, "duration": 3.745}, {"text": "caring.", "start": 1037.745, "duration": 0.5}, {"text": "Because of these effects--", "start": 1041.93, "duration": 2.873}, {"text": "that the patient\nwill look at you,", "start": 1044.803, "duration": 1.417}, {"text": "and say, you really don't care\nabout me, and then suffer,", "start": 1046.22, "duration": 5.13}, {"text": "maybe die.", "start": 1051.35, "duration": 1.65}, {"text": "But we don't ask that\nquestion with the doctor.", "start": 1053.0, "duration": 1.99}, {"text": "The doctor comes\nin there, we want", "start": 1054.99, "duration": 1.417}, {"text": "the doctor to do the surgery\nor whatever and do it right.", "start": 1056.407, "duration": 2.593}, {"text": "We don't care if the\nperson cares about us.", "start": 1059.0, "duration": 2.34}, {"text": "So they make that statement.", "start": 1061.34, "duration": 1.78}, {"text": "So the question then is, can--", "start": 1063.12, "duration": 3.38}, {"text": "another question is, can we\nactually do these things?", "start": 1066.5, "duration": 4.26}, {"text": "Well, I want to say that my\nthought about the whole matter", "start": 1070.76, "duration": 3.24}, {"text": "is that you have to assume that\nyou can do it when you come", "start": 1074.0, "duration": 4.71}, {"text": "into an interview, and portray\nyourself in this particular way", "start": 1078.71, "duration": 3.36}, {"text": "to get this job, and to keep it.", "start": 1082.07, "duration": 2.76}, {"text": "You have to assume\nthat you can do it,", "start": 1084.83, "duration": 3.14}, {"text": "that you can put on\nthat business persona,", "start": 1087.97, "duration": 3.28}, {"text": "and that you are\nsincere about it.", "start": 1091.25, "duration": 2.16}, {"text": "And if you are, then I think\nthat you can portray yourself", "start": 1093.41, "duration": 3.85}, {"text": "in that persona that has nothing\nto do with the way you see it", "start": 1097.26, "duration": 4.22}, {"text": "yourself or the way\nothers, your best friend,", "start": 1101.48, "duration": 2.19}, {"text": "sees you, and just do that job.", "start": 1103.67, "duration": 2.61}, {"text": "I think that those\nare the issues.", "start": 1109.2, "duration": 3.51}, {"text": "And they work themselves\naround ethically", "start": 1112.71, "duration": 3.12}, {"text": "in the mind of the person\nwho is taking the interview,", "start": 1115.83, "duration": 5.37}, {"text": "whether or not they are\nreally using somebody else--", "start": 1121.2, "duration": 3.06}, {"text": "you don't know--\nand whether or not", "start": 1124.26, "duration": 2.452}, {"text": "they can keep up the persona.", "start": 1126.712, "duration": 1.208}, {"text": "And the two issues then are--\nthe last one is the contract,", "start": 1130.94, "duration": 5.52}, {"text": "and the first one is\nrespect for persons.", "start": 1136.46, "duration": 3.115}, {"text": "So therefore, if I had to make\nthis argument in a situation", "start": 1142.31, "duration": 6.135}, {"text": "where it counted--", "start": 1148.445, "duration": 0.75}, {"text": "let's say, for example,\nI'm being interviewed", "start": 1151.94, "duration": 4.17}, {"text": "by a judge in the Enron case.", "start": 1156.11, "duration": 5.73}, {"text": "That's a good one.", "start": 1161.84, "duration": 2.25}, {"text": "And the judge wants to know\nmy opinions about this matter.", "start": 1164.09, "duration": 3.84}, {"text": "Well, the judge is not going\nto be very impressed if I'm", "start": 1167.93, "duration": 2.52}, {"text": "giving my personal opinions.", "start": 1170.45, "duration": 2.28}, {"text": "The judge is going\nto be impressed", "start": 1172.73, "duration": 1.47}, {"text": "if I start grounding my\nopinions in good ethical theory.", "start": 1174.2, "duration": 6.033}, {"text": "And I've just done it twice.", "start": 1180.233, "duration": 1.167}, {"text": "We have just done it twice.", "start": 1181.4, "duration": 3.29}, {"text": "So that's the way I\nthought about that one.", "start": 1184.69, "duration": 2.99}, {"text": "My wife gave me approval.", "start": 1187.68, "duration": 4.09}, {"text": "Another one is Joel\nwrote me this note,", "start": 1191.77, "duration": 4.77}, {"text": "and it picked up\nfrom the last class.", "start": 1196.54, "duration": 3.18}, {"text": "Oh, are we done with this one?", "start": 1199.72, "duration": 1.44}, {"text": "I really apologize if I\nswitch subjects too fast.", "start": 1205.04, "duration": 5.732}, {"text": "Somebody else has\nsomething to say.", "start": 1210.772, "duration": 1.458}, {"text": "And that had to do\nwith the discussion", "start": 1215.77, "duration": 4.44}, {"text": "we had last time, where I made\na statement that engineering was", "start": 1220.21, "duration": 7.26}, {"text": "a regal [INAUDIBLE] discipline.", "start": 1227.47, "duration": 2.976}, {"text": "And Joel wanted to make\na remark that it's really", "start": 1233.08, "duration": 4.32}, {"text": "aristocratic in its nature.", "start": 1237.4, "duration": 6.42}, {"text": "And he and I've\ndiscussed this before.", "start": 1243.82, "duration": 1.89}, {"text": "And where we agree is that\nengineering has never been", "start": 1245.71, "duration": 9.42}, {"text": "done, and cannot be done,\noutside of the context", "start": 1255.13, "duration": 5.67}, {"text": "of authority and power.", "start": 1260.8, "duration": 1.482}, {"text": "You don't go out\nand build a bridge", "start": 1262.282, "duration": 1.458}, {"text": "because you think it's cute.", "start": 1263.74, "duration": 1.863}, {"text": "I think I'll build a bridge.", "start": 1265.603, "duration": 1.167}, {"text": "Engineering has always been\ndone under the auspices,", "start": 1270.79, "duration": 6.0}, {"text": "or under the control,\nto some extent, of kings", "start": 1276.79, "duration": 6.32}, {"text": "and high priests, local\npopulations getting", "start": 1283.11, "duration": 2.85}, {"text": "involved as a brand\nnew issue for us, as we", "start": 1285.96, "duration": 4.53}, {"text": "went through last time.", "start": 1290.49, "duration": 1.41}, {"text": "And I remember the\nname out of Denmark--", "start": 1291.9, "duration": 3.78}, {"text": "they call it technology shops,\nwhere a local citizen group can", "start": 1295.68, "duration": 6.26}, {"text": "go to a place and get\ntechnological advice about how", "start": 1301.94, "duration": 5.79}, {"text": "to participate effectively\nin public decision making.", "start": 1307.73, "duration": 3.86}, {"text": "So the city wants to\nbuild a nuclear waste", "start": 1314.37, "duration": 2.39}, {"text": "dump in your\nbackyard, not in mine,", "start": 1316.76, "duration": 5.07}, {"text": "and the city has--\nthe city engineer", "start": 1321.83, "duration": 1.74}, {"text": "comes up with all of these\nexplanations as to why", "start": 1323.57, "duration": 3.27}, {"text": "we want to put it behind\nyours and not behind mine.", "start": 1326.84, "duration": 3.09}, {"text": "Then you can go to\nthese technology shops", "start": 1329.93, "duration": 2.28}, {"text": "and get an engineer to\nhelp you build your case.", "start": 1332.21, "duration": 3.21}, {"text": "But that's brand new.", "start": 1339.11, "duration": 1.41}, {"text": "We want to think about that.", "start": 1340.52, "duration": 1.18}, {"text": "And so here's the way I thought\nabout responding to that.", "start": 1341.7, "duration": 2.99}, {"text": "I need to give him some email,\nbut it really didn't come to me", "start": 1344.69, "duration": 3.87}, {"text": "until last night about 10:00.", "start": 1348.56, "duration": 3.23}, {"text": "I stayed up until 1:00\nuntil I thought it through.", "start": 1351.79, "duration": 2.93}, {"text": "And thinking it through really\nmeant finding a concise way", "start": 1354.72, "duration": 4.65}, {"text": "to put it to the class.", "start": 1359.37, "duration": 1.11}, {"text": "Because it's in my\nbook and I've already", "start": 1360.48, "duration": 1.667}, {"text": "written 200 pages on this.", "start": 1362.147, "duration": 3.595}, {"text": "So I'm going to see how\nit works, if I can just", "start": 1365.742, "duration": 1.958}, {"text": "do it with a few bullets.", "start": 1367.7, "duration": 3.01}, {"text": "Ready?", "start": 1370.71, "duration": 0.63}, {"text": "Let's try.", "start": 1371.34, "duration": 1.09}, {"text": "Yes.", "start": 1372.43, "duration": 0.5}, {"text": "AUDIENCE: Can I ask a\nclarifying question first?", "start": 1372.93, "duration": 2.13}, {"text": "TAFT BROOME: Yes.", "start": 1375.06, "duration": 1.5}, {"text": "AUDIENCE: So the dispute or\nthe conflict, you're saying", "start": 1376.56, "duration": 4.35}, {"text": "is regal, and Joel is\nsaying it's aristocratic.", "start": 1380.91, "duration": 2.838}, {"text": "TAFT BROOME: Right.", "start": 1383.748, "duration": 0.792}, {"text": "AUDIENCE: And can you\nput that in other terms?", "start": 1384.54, "duration": 3.82}, {"text": "TAFT BROOME: Let me put\nit in my terms first,", "start": 1388.36, "duration": 2.36}, {"text": "and lay out a logic.", "start": 1390.72, "duration": 0.99}, {"text": "And then we'll put it in Joel's\nterms if he doesn't come--", "start": 1391.71, "duration": 2.778}, {"text": "AUDIENCE: I just\nwanted to understand", "start": 1394.488, "duration": 1.542}, {"text": "where the concept was.", "start": 1396.03, "duration": 1.68}, {"text": "TAFT BROOME: Let's see\nit after I lay one out", "start": 1397.71, "duration": 2.19}, {"text": "because this is kind\nof thinking that you", "start": 1399.9, "duration": 4.32}, {"text": "won't see in any textbooks yet.", "start": 1404.22, "duration": 2.762}, {"text": "But I think that's\nwhat a class like this", "start": 1406.982, "duration": 1.708}, {"text": "is about, particularly when you\nhave faculty members sitting in", "start": 1408.69, "duration": 2.625}, {"text": "on the class.", "start": 1411.315, "duration": 1.245}, {"text": "You get more out of\nit this way, I think.", "start": 1412.56, "duration": 4.55}, {"text": "My starting point for\nanswering this question", "start": 1417.11, "duration": 5.38}, {"text": "was one of the biggest problems\nI had in writing this book.", "start": 1422.49, "duration": 5.13}, {"text": "Actually, it was in\nhow to set up the book,", "start": 1427.62, "duration": 2.52}, {"text": "how to organize it, how\nto organize 14 chapters.", "start": 1430.14, "duration": 5.16}, {"text": "And what I had to do was do\nwhat Jacob Bronowski said to do.", "start": 1435.3, "duration": 6.47}, {"text": "I don't know if you all know\nhim, but you don't have to.", "start": 1441.77, "duration": 2.56}, {"text": "He worked in the\nManhattan Project.", "start": 1444.33, "duration": 2.07}, {"text": "He had a good TV\nprogram and a book", "start": 1446.4, "duration": 2.88}, {"text": "called The Ascent of\nMan, which if you recall,", "start": 1449.28, "duration": 7.37}, {"text": "is a mirror image of--", "start": 1456.65, "duration": 2.36}, {"text": "I'll tell you the book's name--", "start": 1464.61, "duration": 1.66}, {"text": "The Descent of Man.", "start": 1466.27, "duration": 2.096}, {"text": "Remember who wrote it?", "start": 1468.366, "duration": 0.964}, {"text": "Charles Darwin.", "start": 1472.205, "duration": 0.625}, {"text": "And what he said was\nthat all the people", "start": 1475.4, "duration": 5.82}, {"text": "he knew that made really\nimportant contributions", "start": 1481.22, "duration": 3.36}, {"text": "to science started\noff by asking what he", "start": 1484.58, "duration": 2.4}, {"text": "called an impertinent question.", "start": 1486.98, "duration": 1.515}, {"text": "So I'm going to ask an\nimpertinent question.", "start": 1491.15, "duration": 3.38}, {"text": "And the impertinent\nquestion is, is engineering,", "start": 1494.53, "duration": 6.18}, {"text": "the learned discipline,\nindependent of engineers", "start": 1500.71, "duration": 5.1}, {"text": "and what engineers think and do?", "start": 1505.81, "duration": 2.978}, {"text": "And you know that\ncan't be true, right?", "start": 1508.788, "duration": 2.902}, {"text": "I called it impertinent.", "start": 1511.69, "duration": 1.0}, {"text": "Let's start with it.", "start": 1512.69, "duration": 0.833}, {"text": "Is there something\nabout engineering", "start": 1513.523, "duration": 2.467}, {"text": "that is distinct from what\nengineers think and do?", "start": 1515.99, "duration": 9.58}, {"text": "Now, let me bring up\none point, maybe two.", "start": 1525.57, "duration": 3.45}, {"text": "Scientists in the Manhattan\nProject were not doing science.", "start": 1533.24, "duration": 5.16}, {"text": "They were doing engineering.", "start": 1538.4, "duration": 1.654}, {"text": "So therefore,\nthere's a difference.", "start": 1543.69, "duration": 1.75}, {"text": "So the scientists,\none could say--", "start": 1545.44, "duration": 4.25}, {"text": "what scientists were\nthinking about and doing", "start": 1549.69, "duration": 2.453}, {"text": "was not science.", "start": 1552.143, "duration": 0.667}, {"text": "Do engineers ever do science?", "start": 1557.47, "duration": 3.75}, {"text": "But I think the invention\nof thermodynamics was done", "start": 1561.22, "duration": 8.76}, {"text": "by engineers, but\nthey really weren't--", "start": 1569.98, "duration": 4.89}, {"text": "they started out doing\nherky jerky engineering", "start": 1574.87, "duration": 3.99}, {"text": "on thermodynamics.", "start": 1578.86, "duration": 0.96}, {"text": "But at the end, they\nwere doing science.", "start": 1579.82, "duration": 4.86}, {"text": "So what I want to say to Joel\nand to you all is that you", "start": 1584.68, "duration": 5.22}, {"text": "cannot deduce what engineering\nis by observing and talking", "start": 1589.9, "duration": 4.35}, {"text": "to engineers.", "start": 1594.25, "duration": 2.65}, {"text": "There's something else.", "start": 1596.9, "duration": 2.105}, {"text": "Now, why is there\nsomething else?", "start": 1599.005, "duration": 1.375}, {"text": "Why is there this gap?", "start": 1600.38, "duration": 1.08}, {"text": "Can I make sense out\nof what I just said?", "start": 1601.46, "duration": 2.89}, {"text": "Yes, because what\nengineers think about", "start": 1604.35, "duration": 4.05}, {"text": "is divided between\ntheir conscious minds", "start": 1608.4, "duration": 1.8}, {"text": "and their unconscious minds.", "start": 1610.2, "duration": 1.2}, {"text": "And so to find out what\nengineering really is,", "start": 1614.62, "duration": 3.03}, {"text": "you have to somehow get it out\nof both what they say and do.", "start": 1617.65, "duration": 4.83}, {"text": "And some things that they\ndon't say and don't do,", "start": 1622.48, "duration": 5.19}, {"text": "you have to look down and get\nthe unconscious dimension.", "start": 1627.67, "duration": 3.302}, {"text": "Now, that sounds like\nan impossible thing", "start": 1630.972, "duration": 1.708}, {"text": "for anybody other than\na clinical psychologist.", "start": 1632.68, "duration": 5.13}, {"text": "No, there are other\nways to do it.", "start": 1637.81, "duration": 1.81}, {"text": "And here's one way\nto do it, and I'm", "start": 1639.62, "duration": 2.54}, {"text": "going to have some special\nlectures from some faculty come", "start": 1642.16, "duration": 3.84}, {"text": "in and talk about this.", "start": 1646.0, "duration": 1.29}, {"text": "Already got this arranged, just\nhave to settle on the date.", "start": 1647.29, "duration": 2.88}, {"text": "And that is that you can get\nthe unconscious dimension out", "start": 1650.17, "duration": 3.66}, {"text": "of what somebody thinks\nby having them write it", "start": 1653.83, "duration": 3.06}, {"text": "down in a story.", "start": 1656.89, "duration": 3.34}, {"text": "Because the story won't make\nsense unless their unconscious", "start": 1660.23, "duration": 3.21}, {"text": "plays a role.", "start": 1663.44, "duration": 0.63}, {"text": "And so what you can do is take\na learned work of engineering--", "start": 1667.38, "duration": 7.31}, {"text": "a book, a research paper, a\nlaboratory demonstration--", "start": 1674.69, "duration": 8.58}, {"text": "what you can do is look at that\nbook or that research paper,", "start": 1683.27, "duration": 3.39}, {"text": "and organize it in story terms.", "start": 1686.66, "duration": 4.23}, {"text": "And that's one of the things\nwe had talked about already.", "start": 1690.89, "duration": 4.39}, {"text": "And so what I want to do is\nto talk about engineering", "start": 1695.28, "duration": 5.15}, {"text": "in story terms.", "start": 1700.43, "duration": 2.4}, {"text": "And what makes one discipline\ndifferent from another", "start": 1702.83, "duration": 4.53}, {"text": "is chiefly--", "start": 1707.36, "duration": 1.23}, {"text": "this is my argument in my book--", "start": 1708.59, "duration": 2.13}, {"text": "is chiefly the story term that\nwe call the point of view.", "start": 1710.72, "duration": 5.52}, {"text": "Because I can take one document\nand put it here, and look at it", "start": 1716.24, "duration": 3.3}, {"text": "from an engineering\npoint of view,", "start": 1719.54, "duration": 2.98}, {"text": "and get a whole\ndifferent interpretation,", "start": 1722.52, "duration": 3.62}, {"text": "or another point\nfrom looking at it", "start": 1726.14, "duration": 3.42}, {"text": "from a scientific and ethical,\nor a musician's point.", "start": 1729.56, "duration": 5.88}, {"text": "Now this is the last\npiece of the argument--", "start": 1738.35, "duration": 4.3}, {"text": "remember, I'm distilling\nout of 200 pages--", "start": 1742.65, "duration": 4.66}, {"text": "the last piece of\nthe argument is", "start": 1747.31, "duration": 1.65}, {"text": "that I claim, I\nstand on this point,", "start": 1748.96, "duration": 9.09}, {"text": "that the learned\ndisciplines don't", "start": 1758.05, "duration": 3.3}, {"text": "have but three points of view.", "start": 1761.35, "duration": 1.89}, {"text": "They are the points of\nview of social order.", "start": 1766.64, "duration": 2.73}, {"text": "That if you want to read\nethics from the standpoint", "start": 1772.54, "duration": 5.58}, {"text": "of Greek philosophy, if you\nwant to read science the way", "start": 1778.12, "duration": 4.47}, {"text": "Aristotle would read it and the\nway most Westerners read it,", "start": 1782.59, "duration": 6.46}, {"text": "then the point of view is a\nperson like Socrates who's", "start": 1789.05, "duration": 5.1}, {"text": "looking at doing two things--", "start": 1794.15, "duration": 4.26}, {"text": "number one, he is accommodating\nthe individual to Nature.", "start": 1798.41, "duration": 6.69}, {"text": "What you're saying there is\nthat Nature is what it is.", "start": 1805.1, "duration": 3.33}, {"text": "And I want to find out how I fit\nwith it, that is, find truth.", "start": 1808.43, "duration": 5.82}, {"text": "And the second thing is\nto accommodate society", "start": 1814.25, "duration": 3.24}, {"text": "to the individual.", "start": 1817.49, "duration": 2.04}, {"text": "Society is no better,\ncan be no better,", "start": 1819.53, "duration": 3.3}, {"text": "than its worst treatment\nof the individual.", "start": 1822.83, "duration": 4.86}, {"text": "The individual is\nthe unit of analysis.", "start": 1827.69, "duration": 4.44}, {"text": "The Greek concept of\nethics is that there's", "start": 1832.13, "duration": 4.14}, {"text": "only one moral agent,\nonly one being that", "start": 1836.27, "duration": 4.44}, {"text": "can make an ethical choice,\nand that's an individual, not", "start": 1840.71, "duration": 4.86}, {"text": "a corporation.", "start": 1845.57, "duration": 2.34}, {"text": "The notion of a corporation\nhaving personhood in law", "start": 1847.91, "duration": 5.25}, {"text": "comes out of the Latin\ntradition, not out", "start": 1853.16, "duration": 2.91}, {"text": "of the Greek.", "start": 1856.07, "duration": 0.6}, {"text": "So it comes out of looking\nat society from a regal point", "start": 1859.24, "duration": 5.94}, {"text": "of view, which is a point\nof view where you do not", "start": 1865.18, "duration": 4.23}, {"text": "accommodate society\nto the individual,", "start": 1869.41, "duration": 3.54}, {"text": "you accommodate the individual\nand Nature to society.", "start": 1872.95, "duration": 4.955}, {"text": "And when I say\naccommodate Nature", "start": 1877.905, "duration": 1.375}, {"text": "to society, what\nI'm talking about", "start": 1879.28, "duration": 2.31}, {"text": "is if you want to\ncross that river,", "start": 1881.59, "duration": 8.72}, {"text": "and Nature does not\nhave a bridge for you,", "start": 1890.31, "duration": 3.0}, {"text": "then you accommodate Nature\nto the will of society.", "start": 1893.31, "duration": 2.76}, {"text": "You build a bridge.", "start": 1896.07, "duration": 0.87}, {"text": "And the third point of view\nwhen you look at something,", "start": 1901.81, "duration": 4.35}, {"text": "a learned document--\nyou'll catch up--", "start": 1906.16, "duration": 3.15}, {"text": "is to look at it in a way where\nyou accommodate the individual", "start": 1909.31, "duration": 7.35}, {"text": "and society to Nature,\nto a higher cause.", "start": 1916.66, "duration": 6.3}, {"text": "So when I say that\nengineering is regal,", "start": 1926.99, "duration": 3.78}, {"text": "what I'm really saying\nis that if you pick up", "start": 1930.77, "duration": 3.0}, {"text": "a learned document\nand you want to look", "start": 1933.77, "duration": 2.46}, {"text": "at it from an engineering point\nof view, one of the things--", "start": 1936.23, "duration": 3.63}, {"text": "I haven't gone through all\nof the other story terms.", "start": 1939.86, "duration": 5.01}, {"text": "I'm looking at only one\nright now, the main one.", "start": 1944.87, "duration": 3.6}, {"text": "If you look at it from\na regal point of view,", "start": 1948.47, "duration": 3.72}, {"text": "then I claim that you\nwill look at it the way", "start": 1952.19, "duration": 3.242}, {"text": "that engineers look at it on\nboth conscious and unconscious", "start": 1955.432, "duration": 2.458}, {"text": "levels.", "start": 1957.89, "duration": 0.5}, {"text": "Now, how does that work\nout with aristocratic?", "start": 1961.93, "duration": 1.99}, {"text": "Well, if you look at societies\nover time from the beginning,", "start": 1963.92, "duration": 5.93}, {"text": "I think we're talking when\nhuman beings settled, began", "start": 1969.85, "duration": 8.73}, {"text": "living a settled life\nin the Fertile Crescent,", "start": 1978.58, "duration": 4.65}, {"text": "even from that point of\nview, that what you'll see", "start": 1983.23, "duration": 5.07}, {"text": "is all three of these\nprinciples at work,", "start": 1988.3, "duration": 4.15}, {"text": "and that when they started\nbuilding irrigation systems,", "start": 1992.45, "duration": 5.595}, {"text": "you'll see that they've\nbuilt them from point", "start": 1998.045, "duration": 3.395}, {"text": "of view of authority.", "start": 2001.44, "duration": 1.42}, {"text": "And if for no other reason than\nyou cannot build a bridge four", "start": 2006.29, "duration": 8.34}, {"text": "different correct ways.", "start": 2014.63, "duration": 2.22}, {"text": "If all of us have\ncorrect ways of building", "start": 2020.01, "duration": 2.94}, {"text": "a bridge across that river,\nand those correct ways", "start": 2022.95, "duration": 3.78}, {"text": "are different, we'll\nnever get it built.", "start": 2026.73, "duration": 3.203}, {"text": "AUDIENCE: There\nhas to be someone.", "start": 2029.933, "duration": 1.417}, {"text": "TAFT BROOME: There has to be\nan authority, that's right,", "start": 2031.35, "duration": 2.34}, {"text": "a higher authority than\nany of the four of us,", "start": 2033.69, "duration": 4.17}, {"text": "that says we'll build it his\nway and not yours, mine, or his.", "start": 2037.86, "duration": 5.52}, {"text": "You don't operate like\nthat, with a [INAUDIBLE]..", "start": 2043.38, "duration": 4.73}, {"text": "Let's clean up any\nloose ends that we", "start": 2053.489, "duration": 2.67}, {"text": "have with the Challenger.", "start": 2056.159, "duration": 2.431}, {"text": "Ta-da-- Washington Post,\nWednesday, August 27, 2003.", "start": 2058.59, "duration": 5.609}, {"text": "The headline is \"Report\nblames flawed NASA culture", "start": 2064.199, "duration": 3.121}, {"text": "for tragedy.\"", "start": 2067.32, "duration": 2.73}, {"text": "So I'll pass this around.", "start": 2070.05, "duration": 1.189}, {"text": "AUDIENCE: That's from\nthe [INAUDIBLE],, right?", "start": 2071.239, "duration": 3.471}, {"text": "TAFT BROOME: Yeah.", "start": 2074.71, "duration": 2.44}, {"text": "So you can write\ndown that reference.", "start": 2077.15, "duration": 3.622}, {"text": "Well, I tell you what-- you\ncan hold onto that if you want.", "start": 2080.772, "duration": 2.458}, {"text": "Just bring it back.", "start": 2083.23, "duration": 1.98}, {"text": "[INAUDIBLE]", "start": 2085.21, "duration": 0.656}, {"text": "AUDIENCE: That's OK.", "start": 2085.866, "duration": 0.833}, {"text": "We can find it online and then--", "start": 2086.699, "duration": 3.641}, {"text": "TAFT BROOME: Yeah, download it.", "start": 2090.34, "duration": 2.42}, {"text": "So any loose ends with\nthe Challenger discussion?", "start": 2092.76, "duration": 2.858}, {"text": "AUDIENCE: I think\npart of thing we do--", "start": 2101.845, "duration": 2.735}, {"text": "maybe there's no answer,\nbut we talked about--", "start": 2104.58, "duration": 2.09}, {"text": "TAFT BROOME: There\nwill be an answer.", "start": 2106.67, "duration": 2.602}, {"text": "AUDIENCE: Are there\ndifferences, and is", "start": 2109.272, "duration": 1.878}, {"text": "the problem with\nbehaviors of management", "start": 2111.15, "duration": 3.04}, {"text": "as opposed to the engineers?", "start": 2114.19, "duration": 2.0}, {"text": "TAFT BROOME: Yes.", "start": 2116.19, "duration": 1.847}, {"text": "AUDIENCE: I was doing a little\nmore reading in the book,", "start": 2118.037, "duration": 2.333}, {"text": "and it discussed\n[INAUDIBLE] interesting.", "start": 2120.37, "duration": 2.788}, {"text": "TAFT BROOME: Well, did\nyou come up with anything?", "start": 2123.158, "duration": 2.042}, {"text": "AUDIENCE: We went-- what\nthe reading talks about", "start": 2130.78, "duration": 2.61}, {"text": "is dividing decisions between\nmanagers and engineers,", "start": 2133.39, "duration": 5.535}, {"text": "such that managers are\nresponsible for thinking", "start": 2138.925, "duration": 4.275}, {"text": "about the well-being of the\ncompany, the organization.", "start": 2143.2, "duration": 2.72}, {"text": "So that involves\ncosts and profits.", "start": 2145.92, "duration": 2.75}, {"text": "And engineers are responsible\nfor the technical expertise", "start": 2148.67, "duration": 5.1}, {"text": "and the well-being of the\nclients and the public.", "start": 2153.77, "duration": 3.12}, {"text": "And it's debatable whether it's\nclients, or public, or both.", "start": 2156.89, "duration": 4.87}, {"text": "And so there's always\npushback between those two", "start": 2161.76, "duration": 6.02}, {"text": "kinds of decision making,\nwhich is a good thing.", "start": 2167.78, "duration": 2.14}, {"text": "So the managers are expecting\nthe engineers will always", "start": 2169.92, "duration": 3.71}, {"text": "err on the side of safety.", "start": 2173.63, "duration": 1.57}, {"text": "So when they propose\ncuts in safety,", "start": 2175.2, "duration": 3.05}, {"text": "the engineers will\npush back on them,", "start": 2178.25, "duration": 2.34}, {"text": "and the engineers are supposing\nthat the managers will always", "start": 2180.59, "duration": 3.87}, {"text": "want to cut costs.", "start": 2184.46, "duration": 0.96}, {"text": "So they'll make sure that\nthey think about safety.", "start": 2185.42, "duration": 5.17}, {"text": "Is that what you were thinking?", "start": 2190.59, "duration": 1.712}, {"text": "AUDIENCE: That's what I read.", "start": 2192.302, "duration": 1.208}, {"text": "That's what I understand.", "start": 2193.51, "duration": 1.042}, {"text": "I'm not sure that I\nnecessarily disagree.", "start": 2194.552, "duration": 2.108}, {"text": "But from someone\nwho doesn't have", "start": 2196.66, "duration": 2.01}, {"text": "a very extensive\nbackground in ethics,", "start": 2198.67, "duration": 2.49}, {"text": "is that OK to have two\ndifferent groups operating", "start": 2201.16, "duration": 4.03}, {"text": "on such different ethical\nprinciples like that?", "start": 2205.19, "duration": 2.04}, {"text": "TAFT BROOME: Well, yeah, I\nmean, that's unavoidable.", "start": 2207.23, "duration": 3.78}, {"text": "AUDIENCE: Even if it's within\nan organization [INAUDIBLE]??", "start": 2211.01, "duration": 2.64}, {"text": "TAFT BROOME: Right.", "start": 2213.65, "duration": 1.08}, {"text": "Now here's where you get\nwhat I was talking about,", "start": 2214.73, "duration": 2.61}, {"text": "this question about\nthe unconscious.", "start": 2217.34, "duration": 2.4}, {"text": "Because you're going to get\nsome conflict in what people", "start": 2219.74, "duration": 3.985}, {"text": "will say.", "start": 2223.725, "duration": 0.5}, {"text": "I think it's right for me to\nsay that 100% of the engineering", "start": 2229.84, "duration": 4.02}, {"text": "managers that I have\nknown and read about", "start": 2233.86, "duration": 5.74}, {"text": "do not make a distinction.", "start": 2239.6, "duration": 2.11}, {"text": "All call themselves engineers.", "start": 2241.71, "duration": 1.71}, {"text": "I will say something\naround 50% of the engineers", "start": 2246.86, "duration": 4.95}, {"text": "will say that they\nare engineers,", "start": 2251.81, "duration": 2.61}, {"text": "and 50% say that they\nare not engineers.", "start": 2254.42, "duration": 5.58}, {"text": "This debate came to a head\nabout 10 or 12 years ago with", "start": 2260.0, "duration": 10.47}, {"text": "accreditation,\nwith A-B-E-T, ABET.", "start": 2270.47, "duration": 5.34}, {"text": "Because there was this\nargument that engineers", "start": 2275.81, "duration": 9.02}, {"text": "become engineering managers, and\nthe argument was based on data.", "start": 2284.83, "duration": 5.34}, {"text": "Two out of three persons\nwho are engineers", "start": 2290.17, "duration": 3.96}, {"text": "will become or wind up\nin a job description that", "start": 2294.13, "duration": 3.573}, {"text": "says engineering management.", "start": 2297.703, "duration": 1.167}, {"text": "That's what you do\nwhen you call going up.", "start": 2298.87, "duration": 2.86}, {"text": "There is this other line, which\nthey call line engineer, which", "start": 2301.73, "duration": 3.44}, {"text": "remains a hard-core engineer\nfor all of his or her career.", "start": 2305.17, "duration": 6.96}, {"text": "But that, they say,\nis about one-third,", "start": 2312.13, "duration": 4.32}, {"text": "and even that's debatable\nbecause most of them", "start": 2316.45, "duration": 3.21}, {"text": "have somebody, engineer\nworking under them.", "start": 2319.66, "duration": 2.19}, {"text": "There's an analogy in\nuniversities between faculty", "start": 2324.5, "duration": 5.01}, {"text": "and administration.", "start": 2329.51, "duration": 2.52}, {"text": "And there's this book--", "start": 2332.03, "duration": 2.68}, {"text": "I can't remember the\nname of it right now.", "start": 2334.71, "duration": 2.27}, {"text": "I will figure it out.", "start": 2336.98, "duration": 1.38}, {"text": "I think it's the book called--", "start": 2338.36, "duration": 1.305}, {"text": "well, I'll get it out before\nthe end of this discussion--", "start": 2346.85, "duration": 6.15}, {"text": "where the author\npoint says, what", "start": 2353.0, "duration": 4.21}, {"text": "is everybody talking about?", "start": 2357.21, "duration": 2.4}, {"text": "The administration president\nversus the faculty--", "start": 2359.61, "duration": 3.33}, {"text": "what are you talking about?", "start": 2362.94, "duration": 1.23}, {"text": "I don't know what people\nare talking about.", "start": 2364.17, "duration": 1.86}, {"text": "They are all professors.", "start": 2366.03, "duration": 1.83}, {"text": "They've all got PhDs.", "start": 2367.86, "duration": 1.86}, {"text": "They all taught at one time.", "start": 2369.72, "duration": 1.32}, {"text": "They all did\nresearch at one time.", "start": 2371.04, "duration": 2.64}, {"text": "You're splitting a hair.", "start": 2373.68, "duration": 3.48}, {"text": "So there is this issue that goes\non, not just in engineering,", "start": 2377.16, "duration": 3.51}, {"text": "but other places.", "start": 2380.67, "duration": 1.81}, {"text": "And it comes out in\nthe end, I think,", "start": 2382.48, "duration": 3.17}, {"text": "that in organizations there\nis a line that's drawn.", "start": 2385.65, "duration": 6.36}, {"text": "And the line is\ndrawn between persons", "start": 2392.01, "duration": 3.81}, {"text": "who are in engineering\nor management", "start": 2395.82, "duration": 1.74}, {"text": "and persons who are in\nthe line profession.", "start": 2397.56, "duration": 5.37}, {"text": "And it varies from\ninstitution to institution.", "start": 2402.93, "duration": 4.91}, {"text": "In the universities,\nmy university-- well,", "start": 2407.84, "duration": 3.63}, {"text": "my other university,\nHoward University--", "start": 2411.47, "duration": 3.78}, {"text": "is pretty much typical.", "start": 2415.25, "duration": 2.01}, {"text": "The department chairs will\nbe categorized pretty much", "start": 2417.26, "duration": 5.52}, {"text": "as faculty because\nin most institutions,", "start": 2422.78, "duration": 3.82}, {"text": "the department chair can be\nfired by either administration", "start": 2426.6, "duration": 2.46}, {"text": "or faculty.", "start": 2429.06, "duration": 0.5}, {"text": "But deans are on the side\nof the administration.", "start": 2432.99, "duration": 5.05}, {"text": "And so I think the\nethical issue comes", "start": 2438.04, "duration": 2.12}, {"text": "in with this question,\nagain, of contract.", "start": 2440.16, "duration": 5.59}, {"text": "What am I contracted to do?", "start": 2445.75, "duration": 2.28}, {"text": "AUDIENCE: Who am I\nprimarily responsible for?", "start": 2448.03, "duration": 2.37}, {"text": "Who or what?", "start": 2450.4, "duration": 1.41}, {"text": "The student or the\nhealth department.", "start": 2451.81, "duration": 2.779}, {"text": "AUDIENCE: You know what\nbothered me though?", "start": 2454.589, "duration": 1.792}, {"text": "This has bothered\nme-- the problem.", "start": 2456.381, "duration": 1.549}, {"text": "If you said that engineering\nis this regal discipline,", "start": 2457.93, "duration": 4.5}, {"text": "and [INAUDIBLE] come\nfrom some authority,", "start": 2462.43, "duration": 2.34}, {"text": "it seems like the\nauthority's ethics.", "start": 2464.77, "duration": 2.173}, {"text": "They're the ones who\nreally, at the end,", "start": 2466.943, "duration": 1.667}, {"text": "say this is going to go,\nthis isn't going to go.", "start": 2468.61, "duration": 1.71}, {"text": "You do this.", "start": 2470.32, "duration": 0.72}, {"text": "But it bothers me\nthat their ethics", "start": 2471.04, "duration": 1.51}, {"text": "aren't grounded in\nsomething somewhat tied", "start": 2472.55, "duration": 2.775}, {"text": "to what the engineers\nare doing, namely", "start": 2475.325, "duration": 1.625}, {"text": "safety and things like that.", "start": 2476.95, "duration": 1.95}, {"text": "It seems like they need to\nhave some component of that", "start": 2478.9, "duration": 2.25}, {"text": "[INAUDIBLE].", "start": 2481.15, "duration": 1.302}, {"text": "AUDIENCE: Wait, why are\nyou saying their ethics", "start": 2482.452, "duration": 1.958}, {"text": "aren't grounded in--", "start": 2484.41, "duration": 1.718}, {"text": "AUDIENCE: Because we just say\npeople in management positions,", "start": 2486.128, "duration": 2.542}, {"text": "and I'm assuming.", "start": 2488.67, "duration": 1.14}, {"text": "I put authority\nin that category.", "start": 2489.81, "duration": 2.28}, {"text": "I'm pretty much concerned--\nthey are the bottom line.", "start": 2492.09, "duration": 2.34}, {"text": "They don't care.", "start": 2494.43, "duration": 1.083}, {"text": "They just want\nthis project to go.", "start": 2495.513, "duration": 1.417}, {"text": "They want this\nthing to make money.", "start": 2496.93, "duration": 1.67}, {"text": "But I just think [INAUDIBLE]\nyou need to be as safe as--", "start": 2498.6, "duration": 5.11}, {"text": "I guess you can't [INAUDIBLE].", "start": 2503.71, "duration": 1.468}, {"text": "TAFT BROOME: Well, no, you can.", "start": 2505.178, "duration": 1.292}, {"text": "I think the times have changed--\nlet me put it this way.", "start": 2506.47, "duration": 6.03}, {"text": "I think that there\nwas a time when--", "start": 2512.5, "duration": 2.355}, {"text": "let me back up just a minute.", "start": 2518.08, "duration": 1.98}, {"text": "I don't want my\nbook and my theories", "start": 2520.06, "duration": 3.12}, {"text": "about engineering to be\nthe dominant position", "start": 2523.18, "duration": 2.13}, {"text": "in this class.", "start": 2525.31, "duration": 0.69}, {"text": "I don't want that to\nhappen because I've got", "start": 2529.1, "duration": 2.45}, {"text": "to assign some other readings.", "start": 2531.55, "duration": 1.44}, {"text": "Point about it when it comes to\nit, philosophy of engineering,", "start": 2532.99, "duration": 2.73}, {"text": "is there are only\na couple of places", "start": 2535.72, "duration": 1.5}, {"text": "you have to do that at all.", "start": 2537.22, "duration": 2.35}, {"text": "So that's where you're\ngetting a unique experience", "start": 2539.57, "duration": 4.85}, {"text": "because nobody else is really\ntalking about this yet.", "start": 2544.42, "duration": 5.83}, {"text": "But I do have one\nreference down there,", "start": 2550.25, "duration": 1.77}, {"text": "Billy Vaughn Koen's book called\nDiscussion of the Method.", "start": 2552.02, "duration": 5.73}, {"text": "There's probably-- and\nanother one, one other one.", "start": 2557.75, "duration": 3.625}, {"text": "It's called What\nEngineers Know and How", "start": 2561.375, "duration": 1.625}, {"text": "They Know It, written\nby a man named", "start": 2563.0, "duration": 2.46}, {"text": "Walter Vincenti from Stanford.", "start": 2565.46, "duration": 1.86}, {"text": "He retired several years ago.", "start": 2567.32, "duration": 2.43}, {"text": "Those are about the only two\nthat are out that I really", "start": 2569.75, "duration": 2.52}, {"text": "think go into depth in\nthe philosophical thought", "start": 2572.27, "duration": 2.94}, {"text": "about what engineering is\nas a learned discipline.", "start": 2575.21, "duration": 2.4}, {"text": "AUDIENCE: Do you consider\nFlorman's work, The Existential", "start": 2577.61, "duration": 3.612}, {"text": "Pleasures of Engineering,\nas in the category", "start": 2581.222, "duration": 3.043}, {"text": "with those other two?", "start": 2584.265, "duration": 0.875}, {"text": "TAFT BROOME: A lot of people do.", "start": 2585.14, "duration": 1.333}, {"text": "I don't.", "start": 2586.473, "duration": 1.787}, {"text": "Because when you look\nat Florman's work", "start": 2588.26, "duration": 4.02}, {"text": "and you look to see what\nhe thinks engineering", "start": 2592.28, "duration": 4.32}, {"text": "is as a learned discipline, he's\ngot a short paragraph in there", "start": 2596.6, "duration": 3.81}, {"text": "about two sentences long.", "start": 2600.41, "duration": 2.55}, {"text": "He's going to talk about the\nnature of the profession.", "start": 2602.96, "duration": 2.4}, {"text": "AUDIENCE: So the other\ntwo books are engineering", "start": 2608.61, "duration": 2.31}, {"text": "as a learned discipline.", "start": 2610.92, "duration": 1.05}, {"text": "This one is observations\nof the professionals.", "start": 2611.97, "duration": 1.932}, {"text": "TAFT BROOME: Did you ever\nread Existential Pleasures?", "start": 2613.902, "duration": 2.208}, {"text": "AUDIENCE: Yeah.", "start": 2616.11, "duration": 0.15}, {"text": "That's the only one I've\nread of all the books", "start": 2616.26, "duration": 2.13}, {"text": "that you've mentioned,\nso that's why I asked.", "start": 2618.39, "duration": 2.51}, {"text": "TAFT BROOME: What\ndo you think of it?", "start": 2620.9, "duration": 2.68}, {"text": "AUDIENCE: For me,\nit mostly served", "start": 2623.58, "duration": 2.58}, {"text": "to be an inspirational\nbook about the engineering", "start": 2626.16, "duration": 2.43}, {"text": "profession, and also informative\non the history of engineering.", "start": 2628.59, "duration": 4.82}, {"text": "It's enjoyable reading and puts\nforth a vision, a lofty vision,", "start": 2636.01, "duration": 6.01}, {"text": "of engineering, I think.", "start": 2642.02, "duration": 2.778}, {"text": "TAFT BROOME: I think his\nundergraduate degree was", "start": 2644.798, "duration": 2.042}, {"text": "engineering, but his graduate\ndegree was literature.", "start": 2646.84, "duration": 3.75}, {"text": "And he writes, uses his\ntalents in literature well.", "start": 2650.59, "duration": 4.86}, {"text": "So he talks about\nGreece, ancient Greece,", "start": 2655.45, "duration": 3.21}, {"text": "and all these things.", "start": 2658.66, "duration": 1.9}, {"text": "And I would say that any\nengineer of the engineers who", "start": 2660.56, "duration": 6.83}, {"text": "are in the generation older than\nme, and hardly any are still", "start": 2667.39, "duration": 3.87}, {"text": "around working, but in\nSam Florman's generation,", "start": 2671.26, "duration": 8.4}, {"text": "I would say offhand\n85% to 95% of engineers", "start": 2679.66, "duration": 4.08}, {"text": "think that he has got it right.", "start": 2683.74, "duration": 3.29}, {"text": "My generation is a\nlittle bit different.", "start": 2687.03, "duration": 2.33}, {"text": "We were freedom fighters and all\nof that other stuff, anti-war.", "start": 2689.36, "duration": 4.88}, {"text": "So we're a different generation.", "start": 2694.24, "duration": 1.5}, {"text": "But I was on a panel\nwith Sam Florman once.", "start": 2695.74, "duration": 4.86}, {"text": "And actually, here's what\nit was-- it was a panel,", "start": 2700.6, "duration": 7.9}, {"text": "but he gave the keynote address.", "start": 2708.5, "duration": 2.92}, {"text": "So he gave the keynote address.", "start": 2711.42, "duration": 1.31}, {"text": "I really wasn't on\nthe panel with him,", "start": 2712.73, "duration": 2.19}, {"text": "but we were there together.", "start": 2714.92, "duration": 1.77}, {"text": "And he got up--", "start": 2716.69, "duration": 1.783}, {"text": "this was right after\nhe wrote his book--", "start": 2718.473, "duration": 1.667}, {"text": "and he said that his\nmotivation for writing the book", "start": 2720.14, "duration": 3.84}, {"text": "was his sons.", "start": 2723.98, "duration": 2.1}, {"text": "Said one day his sons told\nhim-- and I don't remember", "start": 2726.08, "duration": 3.96}, {"text": "his exact words, but\nthey were very harsh,", "start": 2730.04, "duration": 2.178}, {"text": "that he and the rest\nof the engineers", "start": 2732.218, "duration": 1.542}, {"text": "out here were just\nmurdering people.", "start": 2733.76, "duration": 2.52}, {"text": "So he sat down and wrote\nthat book for them.", "start": 2736.28, "duration": 3.91}, {"text": "And so it was an answer\nof a father to his sons.", "start": 2740.19, "duration": 4.028}, {"text": "AUDIENCE: That was\ninteresting for me", "start": 2744.218, "duration": 1.542}, {"text": "to learn that in\nthe 1960s and 1970s,", "start": 2745.76, "duration": 4.63}, {"text": "society was anti-technological.", "start": 2750.39, "duration": 2.51}, {"text": "They were out to get\nengineers that they accused", "start": 2752.9, "duration": 3.66}, {"text": "of polluting the waterways.", "start": 2756.56, "duration": 2.1}, {"text": "I mean, just because we\ndon't hear that message,", "start": 2758.66, "duration": 3.3}, {"text": "or I hadn't heard\nit before, anyway.", "start": 2761.96, "duration": 1.95}, {"text": "TAFT BROOME: Well, if you're\ninterested in the history", "start": 2763.91, "duration": 1.65}, {"text": "of engineering, I'll tell you\nwhat I think is definitely", "start": 2765.56, "duration": 2.333}, {"text": "a most interesting book.", "start": 2767.893, "duration": 1.567}, {"text": "Now, let's not rule out Henry\nPetroski and David Billington.", "start": 2769.46, "duration": 5.04}, {"text": "But I tell you where I\nthink we should start--", "start": 2774.5, "duration": 2.16}, {"text": "it's a book called The\nRevolt of the Engineers.", "start": 2776.66, "duration": 2.985}, {"text": "And I'll think of\nthis man's name.", "start": 2784.76, "duration": 3.06}, {"text": "I haven't talked\nto him in 15 years.", "start": 2787.82, "duration": 4.11}, {"text": "It's called Revolt\nof the Engineers,", "start": 2791.93, "duration": 1.54}, {"text": "and when you get the book, let\nme suggest the first thing you", "start": 2793.47, "duration": 3.63}, {"text": "do is look in the index\nfor the word technocracy,", "start": 2797.1, "duration": 5.391}, {"text": "the Technocracy Movement.", "start": 2802.491, "duration": 1.269}, {"text": "And you read that, and\nyou will be compelled", "start": 2806.47, "duration": 2.38}, {"text": "to read rest of that book.", "start": 2808.85, "duration": 2.09}, {"text": "Layton, L-A-Y-T-O-N,\nEdwin Layton.", "start": 2810.94, "duration": 3.57}, {"text": "And so if you remember\nbasically what people said was,", "start": 2818.08, "duration": 4.417}, {"text": "well, we live in a\ntechnological world", "start": 2822.497, "duration": 1.583}, {"text": "now, so the world ought\nto be run by engineers.", "start": 2824.08, "duration": 3.968}, {"text": "AUDIENCE: So what you\nargue in the editorial,", "start": 2830.86, "duration": 4.05}, {"text": "perhaps, is that engineers\nneed to inform the public,", "start": 2834.91, "duration": 3.94}, {"text": "so the shared running.", "start": 2838.85, "duration": 1.67}, {"text": "TAFT BROOME: Shared\nrunning, yeah.", "start": 2840.52, "duration": 1.83}, {"text": "I argue straight out\nin my office preface", "start": 2842.35, "duration": 4.34}, {"text": "that everybody should\nlearn engineering.", "start": 2846.69, "duration": 5.522}, {"text": "But on the other hand--\nthat's on the one", "start": 2852.212, "duration": 1.708}, {"text": "hand-- on the other\nhand, engineers", "start": 2853.92, "duration": 1.458}, {"text": "have not proven to be better\ncitizens than anybody else.", "start": 2855.378, "duration": 4.005}, {"text": "So there's something\nthat falls in the middle,", "start": 2859.383, "duration": 1.917}, {"text": "and I call it generalist\nexpertise as opposed", "start": 2861.3, "duration": 2.79}, {"text": "to specialist.", "start": 2864.09, "duration": 1.53}, {"text": "So a specialist expert\ndoes not necessarily", "start": 2865.62, "duration": 6.27}, {"text": "possess what I call\ngeneralist expertise.", "start": 2871.89, "duration": 2.004}, {"text": "So that's where\nI'm going with it.", "start": 2876.76, "duration": 2.19}, {"text": "But you'll find other people\nwho have other points of view.", "start": 2878.95, "duration": 3.78}, {"text": "But a lot of this\ndiscussion is quite new.", "start": 2882.73, "duration": 3.12}, {"text": "OK, can I shift gears and\nstart talking about Ford Pinto?", "start": 2890.06, "duration": 2.675}, {"text": "AUDIENCE: Yeah.", "start": 2892.735, "duration": 0.625}, {"text": "TAFT BROOME: All\nright, then I said", "start": 2893.36, "duration": 1.14}, {"text": "something I really didn't mean.", "start": 2894.5, "duration": 1.53}, {"text": "I want to shift gears.", "start": 2896.03, "duration": 1.06}, {"text": "But you're going to\ntalk about Ford Pinto.", "start": 2897.09, "duration": 2.24}, {"text": "OK, start.", "start": 2899.33, "duration": 0.81}, {"text": "Just start talking.", "start": 2900.14, "duration": 2.24}, {"text": "Ford Pinto.", "start": 2902.38, "duration": 1.052}, {"text": "Let's talk about facts.", "start": 2906.11, "duration": 2.98}, {"text": "Did you get the chance\nto read this case?", "start": 2909.09, "duration": 3.53}, {"text": "Then I think we can go through\nand get a lot of the facts", "start": 2912.62, "duration": 2.6}, {"text": "without spending a\nwhole lot of time.", "start": 2915.22, "duration": 3.4}, {"text": "Anybody want to go first?", "start": 2918.62, "duration": 1.13}, {"text": "Start with the year.", "start": 2923.5, "duration": 1.83}, {"text": "AUDIENCE: What year-- so\nwe're in the late 1960s,", "start": 2925.33, "duration": 3.36}, {"text": "and Ford deciding that they\nwant to design a car that", "start": 2928.69, "duration": 5.01}, {"text": "will sell for less\nthan $2,000 and weigh", "start": 2933.7, "duration": 2.37}, {"text": "less than 2,000 pounds.", "start": 2936.07, "duration": 1.8}, {"text": "And they to compete,\nrush the production", "start": 2937.87, "duration": 4.35}, {"text": "to happen a little\nmore than two years", "start": 2942.22, "duration": 2.22}, {"text": "compared to the usual\nthree and a half years.", "start": 2944.44, "duration": 4.24}, {"text": "And the book says so this\nmeans that a lot of the design", "start": 2948.68, "duration": 3.63}, {"text": "and styling happened before\nthe mechanical engineering,", "start": 2952.31, "duration": 5.02}, {"text": "so some engineering\ndecisions were", "start": 2957.33, "duration": 2.19}, {"text": "based on design\nrather than design", "start": 2959.52, "duration": 2.065}, {"text": "coming after engineering.", "start": 2961.585, "duration": 2.005}, {"text": "So they decided that the\nbest place for the gas tank", "start": 2963.59, "duration": 4.11}, {"text": "was between the rear\naxle and the bumper,", "start": 2967.7, "duration": 3.99}, {"text": "between the gas\ntank and the bumper.", "start": 2971.69, "duration": 1.56}, {"text": "No, they decided the best\nplace for the gas tank", "start": 2976.35, "duration": 2.97}, {"text": "is between the axle\nand the bumper.", "start": 2979.32, "duration": 2.13}, {"text": "And there were\nbolt heads on the--", "start": 2981.45, "duration": 3.45}, {"text": "TAFT BROOME: Did they\nuse the term sheet metal?", "start": 2988.692, "duration": 2.308}, {"text": "AUDIENCE: No, just says there\nwere exposed bolt heads that", "start": 2991.0, "duration": 3.3}, {"text": "could puncture the gas tank if\nthe tank were driven forward", "start": 2994.3, "duration": 4.2}, {"text": "towards the axle upon impact.", "start": 2998.5, "duration": 2.58}, {"text": "What's the sheet metal?", "start": 3001.08, "duration": 1.6}, {"text": "TAFT BROOME: There\nwas a code that", "start": 3002.68, "duration": 6.69}, {"text": "said a certain\namount of sheet metal", "start": 3009.37, "duration": 1.74}, {"text": "should exist between the\ngas tank and passengers.", "start": 3011.11, "duration": 3.72}, {"text": "AUDIENCE: It doesn't\ntalk about that.", "start": 3018.28, "duration": 1.65}, {"text": "TAFT BROOME: By taking\nthat sheet metal out,", "start": 3019.93, "duration": 1.833}, {"text": "it can reduce some of\nthe weight of the car.", "start": 3021.763, "duration": 2.586}, {"text": "AUDIENCE: So anyway,\nwe have this gas tank", "start": 3028.75, "duration": 2.97}, {"text": "in a precarious position.", "start": 3031.72, "duration": 1.2}, {"text": "And they did crash tests\nto see how often the bolt", "start": 3032.92, "duration": 3.81}, {"text": "heads were driven into the gas\ntank, causing the explosions.", "start": 3036.73, "duration": 4.04}, {"text": "And the results were that at\n21 miles per hour is enough,", "start": 3040.77, "duration": 8.63}, {"text": "was high enough speed for\nthe gas tank to be puncture.", "start": 3049.4, "duration": 4.5}, {"text": "Then they made adjustments,\njust of putting the tank", "start": 3053.9, "duration": 4.45}, {"text": "above the rear axle\nrather than behind it,", "start": 3058.35, "duration": 3.21}, {"text": "or adding rubber bumpers\non the gas tank itself.", "start": 3061.56, "duration": 4.44}, {"text": "Those minor\nadjustments, that would", "start": 3066.0, "duration": 1.68}, {"text": "have cost like $11 per\ncar, prevented the tank", "start": 3067.68, "duration": 3.45}, {"text": "from being punctured\nin a crash test.", "start": 3071.13, "duration": 1.802}, {"text": "But the manager's\ndecision was that the cost", "start": 3078.42, "duration": 5.35}, {"text": "of those adjustments,\nthe $11 a vehicle,", "start": 3083.77, "duration": 3.26}, {"text": "didn't outweigh the benefits.", "start": 3087.03, "duration": 4.26}, {"text": "Those costs were too great.", "start": 3091.29, "duration": 1.26}, {"text": "So the cost of the deaths\nand destroyed vehicles", "start": 3092.55, "duration": 7.59}, {"text": "were less than the\ncost of $11 per car.", "start": 3100.14, "duration": 6.228}, {"text": "Does that make sense?", "start": 3106.368, "duration": 1.984}, {"text": "AUDIENCE: You put\na monetary value", "start": 3108.352, "duration": 1.488}, {"text": "on a person's life [INAUDIBLE]", "start": 3109.84, "duration": 3.472}, {"text": "AUDIENCE: [INAUDIBLE]\n$11 so [INAUDIBLE]", "start": 3117.776, "duration": 4.241}, {"text": "TAFT BROOME: Say\nthat part again, now.", "start": 3122.017, "duration": 1.583}, {"text": "AUDIENCE: Based on a monetary\nvalue of the lives that", "start": 3123.6, "duration": 3.42}, {"text": "would be lost.", "start": 3127.02, "duration": 1.479}, {"text": "They issued a report\nafter the crash tests to--", "start": 3131.93, "duration": 4.06}, {"text": "I can't believe it.", "start": 3135.99, "duration": 1.25}, {"text": "It's in writing.", "start": 3137.24, "duration": 2.1}, {"text": "A memo attached to the report\nhad those cost and benefits.", "start": 3139.34, "duration": 3.88}, {"text": "TAFT BROOME: That's\nthe technical term,", "start": 3143.22, "duration": 3.28}, {"text": "cost-benefit analysis.", "start": 3146.5, "duration": 1.53}, {"text": "I don't think the word\nrequired is the right word,", "start": 3151.027, "duration": 2.083}, {"text": "but in that method, it is\nuseful to put a monetary value", "start": 3153.11, "duration": 8.39}, {"text": "on a human life.", "start": 3161.5, "duration": 1.95}, {"text": "I mean, that's what engineers\nused to do all of the time.", "start": 3163.45, "duration": 3.97}, {"text": "I don't if they do it now, but\nwe used to do it all the time,", "start": 3167.42, "duration": 4.49}, {"text": "and include that in\nas the cost as opposed", "start": 3171.91, "duration": 6.8}, {"text": "to how much you think\nyou could get in profit.", "start": 3178.71, "duration": 3.82}, {"text": "So keep talking.", "start": 3182.53, "duration": 2.402}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 3184.932, "duration": 1.878}, {"text": "TAFT BROOME: You're right.", "start": 3186.81, "duration": 1.32}, {"text": "AUDIENCE: I know.", "start": 3188.13, "duration": 0.893}, {"text": "Seems a little cheap.", "start": 3189.023, "duration": 2.017}, {"text": "TAFT BROOME: OK, are we done?", "start": 3191.04, "duration": 1.26}, {"text": "Let me give you some background.", "start": 3192.3, "duration": 1.845}, {"text": "AUDIENCE: Some more\nbackground would be great.", "start": 3194.145, "duration": 1.917}, {"text": "TAFT BROOME: Something\nthat you probably--", "start": 3200.81, "duration": 3.27}, {"text": "something you have\ncertainly never experienced.", "start": 3204.08, "duration": 2.89}, {"text": "I doubt if you've\never heard of--", "start": 3206.97, "duration": 1.95}, {"text": "it's called a gas line.", "start": 3208.92, "duration": 0.99}, {"text": "That is driving up\nto a gas station,", "start": 3213.13, "duration": 2.22}, {"text": "and standing in line to get gas.", "start": 3215.35, "duration": 3.25}, {"text": "And you've got a quota, like\nbeing in war in England.", "start": 3218.6, "duration": 4.85}, {"text": "Where I lived in\nVirginia at the time,", "start": 3223.45, "duration": 3.09}, {"text": "if you wanted to get\ngasoline at a gas station,", "start": 3226.54, "duration": 2.7}, {"text": "and you had to be at work\nat 9:00 in the morning,", "start": 3229.24, "duration": 3.03}, {"text": "you had to be in a\ngas line at 7:00.", "start": 3232.27, "duration": 3.62}, {"text": "And you were taking your\nchances that by the time", "start": 3235.89, "duration": 2.19}, {"text": "you got up there, they'd\nhave some gas left.", "start": 3238.08, "duration": 1.95}, {"text": "What had happened was OPEC had\nincreased the cost per barrel,", "start": 3242.95, "duration": 7.44}, {"text": "and et cetera, et cetera.", "start": 3250.39, "duration": 1.75}, {"text": "So it was really a\npsychological crisis in the US,", "start": 3252.14, "duration": 4.79}, {"text": "given the way we\nthink about cars--", "start": 3256.93, "duration": 2.97}, {"text": "that you have to stand in\nline for two or three hours", "start": 3259.9, "duration": 3.3}, {"text": "to get a fill up.", "start": 3263.2, "duration": 1.588}, {"text": "And you couldn't get a fill up.", "start": 3264.788, "duration": 1.292}, {"text": "You could only get so\nmany dollars worth.", "start": 3266.08, "duration": 2.64}, {"text": "And then you might stand in line\nthat morning, and get there,", "start": 3268.72, "duration": 3.37}, {"text": "and they're out.", "start": 3272.09, "duration": 2.45}, {"text": "So that was going on.", "start": 3274.54, "duration": 2.79}, {"text": "The most significant way\nto increase gas mileage", "start": 3277.33, "duration": 9.0}, {"text": "was to reduce weight,\nthe weight of a car.", "start": 3286.33, "duration": 3.925}, {"text": "Now we don't think\nabout it in those terms.", "start": 3292.99, "duration": 1.8}, {"text": "We think about it in other terms\nof how to get more gas mileage.", "start": 3294.79, "duration": 6.35}, {"text": "But then, it hit us\nfor the first time.", "start": 3301.14, "duration": 3.48}, {"text": "We liked heavy cars.", "start": 3304.62, "duration": 2.94}, {"text": "It was a mistake.", "start": 3307.56, "duration": 0.75}, {"text": "I remember one time my dad\nhad just bought this car.", "start": 3312.45, "duration": 4.606}, {"text": "It was a Chrysler.", "start": 3317.056, "duration": 1.804}, {"text": "And it came out--", "start": 3318.86, "duration": 1.38}, {"text": "this was called the\nPush Button Age.", "start": 3320.24, "duration": 2.19}, {"text": "And the first car came out,\nat least an American car,", "start": 3322.43, "duration": 4.41}, {"text": "came out with push\nbutton transmission.", "start": 3326.84, "duration": 3.6}, {"text": "You ever heard of that?", "start": 3330.44, "duration": 2.37}, {"text": "Where you want to\ngo in reverse, you", "start": 3332.81, "duration": 2.28}, {"text": "push R. When you\nwant to go forward,", "start": 3335.09, "duration": 2.4}, {"text": "you push D. It was\na push button thing.", "start": 3337.49, "duration": 5.64}, {"text": "And this is back in\nthe late, late '50s.", "start": 3343.13, "duration": 3.87}, {"text": "And I had this date.", "start": 3347.0, "duration": 4.105}, {"text": "I was in high school.", "start": 3351.105, "duration": 0.875}, {"text": "I just gotten my\nlicense, and I was", "start": 3351.98, "duration": 2.31}, {"text": "going to take this little girl\nto this dance in my daddy's", "start": 3354.29, "duration": 2.85}, {"text": "new car with the\npush-button drive.", "start": 3357.14, "duration": 3.81}, {"text": "And I took her to this dance.", "start": 3360.95, "duration": 1.53}, {"text": "And when we came\nout of the dance,", "start": 3362.48, "duration": 2.46}, {"text": "people were crowded\naround the car.", "start": 3364.94, "duration": 2.61}, {"text": "How can you have\npush-button drive?", "start": 3367.55, "duration": 3.48}, {"text": "And so this was the first and\nthe last time I showed off,", "start": 3371.03, "duration": 3.82}, {"text": "or what we used to call\nshowing out in a car.", "start": 3374.85, "duration": 3.5}, {"text": "We got in the car, and\nI wanted to demonstrate", "start": 3378.35, "duration": 5.4}, {"text": "that now that I have\npush-button drive,", "start": 3383.75, "duration": 3.66}, {"text": "I didn't have to pay attention\nto putting the car in gear", "start": 3387.41, "duration": 4.92}, {"text": "like everybody else had to.", "start": 3392.33, "duration": 1.5}, {"text": "Most cars had four gears--", "start": 3393.83, "duration": 2.13}, {"text": "a lot of them, not most of them.", "start": 3395.96, "duration": 1.81}, {"text": "And so I was looking at my date\nand putting the car in gear,", "start": 3397.77, "duration": 7.4}, {"text": "but I made a mistake and put\nit in reverse and hit the gas.", "start": 3405.17, "duration": 5.56}, {"text": "And instead of going forward, I\nwent back and hit a brick wall.", "start": 3410.73, "duration": 7.13}, {"text": "Now, the point that I'm\nmaking is the damage", "start": 3417.86, "duration": 2.19}, {"text": "was done to the wall.", "start": 3420.05, "duration": 0.96}, {"text": "It wasn't done to the car.", "start": 3421.01, "duration": 1.56}, {"text": "That car had a fender that--", "start": 3422.57, "duration": 4.98}, {"text": "we used to call it\n1/4-inch armor plate.", "start": 3427.55, "duration": 3.0}, {"text": "But it wasn't 1/4 of an inch.", "start": 3430.55, "duration": 1.32}, {"text": "But I mean, the\nfender of that car--", "start": 3431.87, "duration": 3.495}, {"text": "was something like they\ndon't make at all today.", "start": 3435.365, "duration": 4.725}, {"text": "A whole new concept\nabout fenders today.", "start": 3440.09, "duration": 2.55}, {"text": "They want it to dent.", "start": 3442.64, "duration": 1.62}, {"text": "Back then, you wanted to\nbreak up anything that it hit.", "start": 3444.26, "duration": 3.4}, {"text": "So there was this heavy\naesthetic back in those days.", "start": 3447.66, "duration": 5.25}, {"text": "And so it was very competitive\nto get a car out and get it out", "start": 3452.91, "duration": 5.84}, {"text": "with high gas mileage.", "start": 3458.75, "duration": 1.62}, {"text": "So that was a compulsion.", "start": 3460.37, "duration": 2.4}, {"text": "There's a formal\nterm that people", "start": 3462.77, "duration": 2.88}, {"text": "use when they talk\nabout engineering,", "start": 3465.65, "duration": 2.19}, {"text": "and they call it the\nengineering imperatives.", "start": 3467.84, "duration": 4.25}, {"text": "Cost is 1.", "start": 3472.09, "duration": 3.06}, {"text": "So now, when a gas\ncrisis came out,", "start": 3475.15, "duration": 5.88}, {"text": "there's another thing\nto be said about that--", "start": 3481.03, "duration": 3.87}, {"text": "food prices went up\ndramatically because the food", "start": 3484.9, "duration": 4.26}, {"text": "that was brought into\nthe grocery stores", "start": 3489.16, "duration": 2.67}, {"text": "was brought by trucks.", "start": 3491.83, "duration": 2.22}, {"text": "And if the trucks had to pay\nmore money for the diesel fuel,", "start": 3494.05, "duration": 4.36}, {"text": "then they raised\nthe price of food.", "start": 3498.41, "duration": 2.03}, {"text": "So a can of beans went up.", "start": 3500.44, "duration": 2.73}, {"text": "So everything started\ngoing up, everything.", "start": 3503.17, "duration": 3.03}, {"text": "So there's this big\ncompulsion to get cars", "start": 3506.2, "duration": 2.52}, {"text": "with a lot of high gas mileage.", "start": 3508.72, "duration": 3.2}, {"text": "Back in those days,\nI drove a diesel.", "start": 3511.92, "duration": 3.026}, {"text": "So I'd go out to the truck\nstops and get my fuel.", "start": 3514.946, "duration": 2.756}, {"text": "I didn't stand in line.", "start": 3517.702, "duration": 0.958}, {"text": "So there was this other issue.", "start": 3522.24, "duration": 4.76}, {"text": "And the newspapers made\na big issue out of it.", "start": 3527.0, "duration": 6.03}, {"text": "I don't know how it\nwound up in the courts,", "start": 3533.03, "duration": 3.09}, {"text": "but it became a big issue for\npeople in engineering ethics.", "start": 3536.12, "duration": 4.95}, {"text": "And that was that the newspapers\nput the spin on the story,", "start": 3541.07, "duration": 9.36}, {"text": "that the engineers had not only\ncalculated how much profit they", "start": 3550.43, "duration": 6.69}, {"text": "would get, but\nthey had calculated", "start": 3557.12, "duration": 6.05}, {"text": "how many lawsuits they would\nget and how many lawsuits they", "start": 3563.17, "duration": 4.05}, {"text": "would lose.", "start": 3567.22, "duration": 0.51}, {"text": "And that irritated the American\npublic to the n-th degree.", "start": 3572.48, "duration": 6.06}, {"text": "And the newspapers had\nit out where this one", "start": 3578.54, "duration": 2.82}, {"text": "lady got hit, got rear-ended.", "start": 3581.36, "duration": 2.97}, {"text": "She was sitting still at a\nred light and the car that", "start": 3584.33, "duration": 3.21}, {"text": "hit her was only going 20 miles\nan hour or something like that.", "start": 3587.54, "duration": 3.19}, {"text": "And the car exploded. .", "start": 3590.73, "duration": 1.55}, {"text": "And they had pictures\nof her with all", "start": 3592.28, "duration": 2.01}, {"text": "of her skin burned off.", "start": 3594.29, "duration": 1.59}, {"text": "Oh, it was just a big to-do.", "start": 3595.88, "duration": 4.92}, {"text": "And so that part, the ethical\npart that was being discussed", "start": 3600.8, "duration": 7.67}, {"text": "had a lot to do with putting a\nmonetary value on human life,", "start": 3608.47, "duration": 4.72}, {"text": "and whether or not it is\nright to just calculate", "start": 3613.19, "duration": 2.43}, {"text": "how many lawsuits will they\nbe able-- will you lose.", "start": 3615.62, "duration": 3.9}, {"text": "Because technicalities--\nyou've got the better lawyers", "start": 3619.52, "duration": 2.25}, {"text": "than the individual person\nwho is driving the car.", "start": 3621.77, "duration": 3.57}, {"text": "The companies have\nthese big lawyers.", "start": 3625.34, "duration": 2.52}, {"text": "And they just said that\nthey'll just pay the cost.", "start": 3627.86, "duration": 2.895}, {"text": "So what were some of the\nissues that the authors here", "start": 3636.25, "duration": 5.64}, {"text": "point out as legitimate\npoints of view on this thing?", "start": 3641.89, "duration": 8.66}, {"text": "You remember?", "start": 3650.55, "duration": 1.08}, {"text": "AUDIENCE: Well, it's a\nlegitimate cost-benefit", "start": 3651.63, "duration": 4.9}, {"text": "analysis from a\nutilitarian point of view.", "start": 3656.53, "duration": 2.82}, {"text": "I mean, the method of analysis,\nat least, is legitimate.", "start": 3659.35, "duration": 6.09}, {"text": "[INAUDIBLE] utilitarian\nethics gone wrong.", "start": 3665.44, "duration": 4.94}, {"text": "I mean, maybe that\nis a perfectly valid", "start": 3670.38, "duration": 2.69}, {"text": "cost-benefit analysis, but\nI think their point of view", "start": 3673.07, "duration": 2.28}, {"text": "is skewed somewhat,\nthat it doesn't really", "start": 3675.35, "duration": 3.57}, {"text": "get at the essence of what\na cost-benefit analysis", "start": 3678.92, "duration": 2.46}, {"text": "and what a utilitarian approach\nwould kind of force you to do.", "start": 3681.38, "duration": 6.23}, {"text": "AUDIENCE: Yeah, I mean,\nit's interesting--", "start": 3687.61, "duration": 2.652}, {"text": "yeah, I feel like this is\na utilitarian approach that", "start": 3690.262, "duration": 2.208}, {"text": "came to the wrong conclusion.", "start": 3692.47, "duration": 1.8}, {"text": "AUDIENCE: That's what\nI want to conclude.", "start": 3694.27, "duration": 2.258}, {"text": "I want to say that what\nFord did was wrong.", "start": 3696.528, "duration": 1.792}, {"text": "AUDIENCE: Did they\nget the numbers wrong?", "start": 3698.32, "duration": 1.892}, {"text": "AUDIENCE: Did they\nget the numbers wrong?", "start": 3700.212, "duration": 1.708}, {"text": "Is that what you're saying?", "start": 3701.92, "duration": 1.05}, {"text": "Yeah, so that's\nwhat I want to say", "start": 3702.97, "duration": 1.44}, {"text": "is, well they just didn't put a\nhigh enough cost on human life.", "start": 3704.41, "duration": 3.9}, {"text": "If they had put a higher\ncost, then the conclusion", "start": 3708.31, "duration": 3.78}, {"text": "would have been to put the\nsafety features into the car", "start": 3712.09, "duration": 3.48}, {"text": "because they wouldn't\nhave been saving.", "start": 3715.57, "duration": 2.43}, {"text": "AUDIENCE: But I think\ntheir audience is off, too.", "start": 3718.0, "duration": 2.405}, {"text": "I mean, from their\npoint of view,", "start": 3720.405, "duration": 1.375}, {"text": "if you just consider\ntheir corporation, yes, it", "start": 3721.78, "duration": 2.22}, {"text": "makes sense to not do it.", "start": 3724.0, "duration": 1.32}, {"text": "But they're not considering.", "start": 3725.32, "duration": 1.35}, {"text": "AUDIENCE: I think they are,\nwhen they assign their value", "start": 3729.117, "duration": 2.333}, {"text": "to this person's life.", "start": 3731.45, "duration": 1.15}, {"text": "But I think they're looking\nat it a little too narrowly.", "start": 3732.6, "duration": 2.51}, {"text": "Something went wrong, I\nthink, in that analysis.", "start": 3735.11, "duration": 2.86}, {"text": "AUDIENCE: But there must have\nbeen society [INAUDIBLE]..", "start": 3737.97, "duration": 2.925}, {"text": "TAFT BROOME: But is a company\nsupposed to serve society?", "start": 3743.74, "duration": 3.21}, {"text": "AUDIENCE: Well, you were talking\nabout management, strictly", "start": 3746.95, "duration": 2.782}, {"text": "the company and shareholders.", "start": 3749.732, "duration": 1.266}, {"text": "And then the\nengineers are supposed", "start": 3750.998, "duration": 1.892}, {"text": "to do some of that, so some\nof the safety of the public.", "start": 3752.89, "duration": 5.61}, {"text": "Doesn't sound like they\nput any weight at all", "start": 3758.5, "duration": 4.482}, {"text": "in the safety [INAUDIBLE].", "start": 3762.982, "duration": 1.768}, {"text": "Because even the\ncost on the life", "start": 3764.75, "duration": 2.31}, {"text": "was from a management point of\nview in terms of [INAUDIBLE]..", "start": 3767.06, "duration": 5.552}, {"text": "TAFT BROOME: Well, how\nwould you have done", "start": 3775.9, "duration": 4.19}, {"text": "if you were an engineer there?", "start": 3780.09, "duration": 3.81}, {"text": "Make me the bad guy.", "start": 3783.9, "duration": 1.05}, {"text": "I'm the one who\ntold you to do it.", "start": 3784.95, "duration": 1.417}, {"text": "I'm your boss.", "start": 3786.367, "duration": 0.683}, {"text": "AUDIENCE: What was the cost\n[INAUDIBLE] management?", "start": 3789.924, "duration": 2.876}, {"text": "What mandate did\nmanagement [INAUDIBLE]??", "start": 3792.8, "duration": 2.398}, {"text": "TAFT BROOME: Sink that cost.", "start": 3797.54, "duration": 2.7}, {"text": "You guys are coming up\nwith too much weight.", "start": 3800.24, "duration": 3.42}, {"text": "I want the weight of this\nvehicle down another 12 pounds.", "start": 3803.66, "duration": 6.22}, {"text": "Go back and do it.", "start": 3809.88, "duration": 2.52}, {"text": "AUDIENCE: Wait, what\nabout the regulation?", "start": 3812.4, "duration": 2.19}, {"text": "TAFT BROOME: OK, now we want\nto talk about regulations.", "start": 3817.79, "duration": 3.7}, {"text": "I want to put a BUT in there.", "start": 3821.49, "duration": 1.77}, {"text": "I don't want the Ethics class\nto turn into a legal class,", "start": 3823.26, "duration": 4.41}, {"text": "but what I want to do is to say,\nwell, what are the regulations?", "start": 3827.67, "duration": 4.5}, {"text": "And I want to ask, do we\nhave an ethical obligation", "start": 3832.17, "duration": 8.09}, {"text": "to abide by the regulations?", "start": 3840.26, "duration": 1.59}, {"text": "That is, to use, for example--", "start": 3841.85, "duration": 8.94}, {"text": "here's my example, now.", "start": 3850.79, "duration": 0.97}, {"text": "It goes back to what\nyou've all said.", "start": 3851.76, "duration": 3.65}, {"text": "The regulations allow\ncost-benefit analysis,", "start": 3855.41, "duration": 4.23}, {"text": "or allowed.", "start": 3859.64, "duration": 2.25}, {"text": "So it was legal to do that.", "start": 3861.89, "duration": 2.04}, {"text": "AUDIENCE: I think\na regulation maybe", "start": 3863.93, "duration": 1.5}, {"text": "to protect [INAUDIBLE] same\nway tenure protects [INAUDIBLE]", "start": 3865.43, "duration": 7.03}, {"text": "management tells them cut\nthe costs all the way down", "start": 3872.46, "duration": 3.28}, {"text": "[INAUDIBLE] much, putting\nsome numbers on lives.", "start": 3875.74, "duration": 7.74}, {"text": "Because it doesn't [INAUDIBLE].", "start": 3883.48, "duration": 2.364}, {"text": "TAFT BROOME: Well,\nthat's exactly what", "start": 3888.807, "duration": 1.583}, {"text": "all the engineers did,\nand all the engineers", "start": 3890.39, "duration": 2.13}, {"text": "had a right to do--", "start": 3892.52, "duration": 1.05}, {"text": "point to the regulations,\nsay, we live within the law.", "start": 3893.57, "duration": 3.09}, {"text": "What are you talking about?", "start": 3896.66, "duration": 3.08}, {"text": "AUDIENCE: [INAUDIBLE] I'm\nsure more regulations came out", "start": 3899.74, "duration": 5.66}, {"text": "of this case, right?", "start": 3905.4, "duration": 1.64}, {"text": "TAFT BROOME: Yes, a\nwhole flood of them.", "start": 3907.04, "duration": 1.958}, {"text": "AUDIENCE: [INAUDIBLE]\nsomething was [INAUDIBLE]..", "start": 3912.902, "duration": 4.282}, {"text": "TAFT BROOME: I think that\none of the things that", "start": 3920.53, "duration": 5.15}, {"text": "made this case what\nit was, was really", "start": 3925.68, "duration": 6.45}, {"text": "the question that\nhurt engineers a lot", "start": 3932.13, "duration": 3.36}, {"text": "that came from citizen groups.", "start": 3935.49, "duration": 2.01}, {"text": "How could you all do that?", "start": 3937.5, "duration": 3.19}, {"text": "How could you do-- how\ncould you just sit down,", "start": 3940.69, "duration": 3.36}, {"text": "and just say, well, we we're\ngoing to kill so many people,", "start": 3944.05, "duration": 2.97}, {"text": "but we can make a profit\noff of it because they won't", "start": 3947.02, "duration": 3.09}, {"text": "win a lot of these law cases?", "start": 3950.11, "duration": 1.86}, {"text": "How can you just-- how could\nyou do something like that?", "start": 3951.97, "duration": 2.97}, {"text": "And engineers\npersonally-- I mean,", "start": 3954.94, "duration": 3.21}, {"text": "I was going to conferences\nroughly once every", "start": 3958.15, "duration": 4.12}, {"text": "four to six weeks\nback in those days.", "start": 3962.27, "duration": 2.88}, {"text": "And I think that I didn't go\nto a single conference where", "start": 3965.15, "duration": 5.63}, {"text": "somebody didn't\nlose it emotionally,", "start": 3970.78, "duration": 2.91}, {"text": "either in the audience\nor on the panel.", "start": 3973.69, "duration": 2.145}, {"text": "AUDIENCE: Because they\ngot attacked for it.", "start": 3975.835, "duration": 2.325}, {"text": "TAFT BROOME: Either\nbecause they felt attacked", "start": 3978.16, "duration": 1.917}, {"text": "or because they\nwere on the attack.", "start": 3980.077, "duration": 4.533}, {"text": "And some of the people\nwho were on the attack", "start": 3984.61, "duration": 4.98}, {"text": "could point to a relative\nof somebody who died.", "start": 3989.59, "duration": 2.04}, {"text": "And the people who were\ndefending themselves", "start": 3994.41, "duration": 4.8}, {"text": "were ordinary, decent people.", "start": 3999.21, "duration": 3.96}, {"text": "Engineers go to work at\n9:00, get off at 5:00,", "start": 4003.17, "duration": 4.08}, {"text": "do the best they can do.", "start": 4007.25, "duration": 3.37}, {"text": "And they had engineers--", "start": 4010.62, "duration": 1.77}, {"text": "there was a whole\ngeneration of engineers who", "start": 4012.39, "duration": 1.92}, {"text": "had never been attacked before.", "start": 4014.31, "duration": 2.72}, {"text": "The last ones were in the\nearly, early '40s and late '30s.", "start": 4017.03, "duration": 4.41}, {"text": "So we're talking about\nlate '60s or early '70s.", "start": 4021.44, "duration": 5.13}, {"text": "Engineers always thought of\nthemselves as decent people.", "start": 4026.57, "duration": 4.95}, {"text": "There was an article--", "start": 4031.52, "duration": 0.96}, {"text": "I'm still trying to find it.", "start": 4032.48, "duration": 1.74}, {"text": "Maybe you all can\nfind it for me.", "start": 4034.22, "duration": 3.12}, {"text": "It came out in a magazine.", "start": 4037.34, "duration": 2.79}, {"text": "It was one of two magazines--\nit was either Look or Life.", "start": 4040.13, "duration": 5.96}, {"text": "Those were magazines\nthat were big magazines", "start": 4046.09, "duration": 3.96}, {"text": "back in the '50s and '60s, maybe\neven the '40s and '30s, '20s.", "start": 4050.05, "duration": 6.58}, {"text": "Everybody read\neither Look or Life.", "start": 4056.63, "duration": 4.59}, {"text": "And I remember in there,\nthere was an article,", "start": 4061.22, "duration": 4.71}, {"text": "and it had this picture\nintroducing the article.", "start": 4065.93, "duration": 4.41}, {"text": "And the picture was the ideal\nof American life in the 1950s--", "start": 4070.34, "duration": 7.83}, {"text": "a husband and wife and two\nkids living in the suburbs.", "start": 4078.17, "duration": 4.69}, {"text": "The wife stays home, the\nhusband goes to work.", "start": 4082.86, "duration": 2.81}, {"text": "And the kids look up\nto dad like he's--", "start": 4085.67, "duration": 2.34}, {"text": "that was the-- it\nhad that picture.", "start": 4088.01, "duration": 3.06}, {"text": "And the wife was\nstanding in the doorway", "start": 4091.07, "duration": 4.2}, {"text": "handing him,\nhanding the husband,", "start": 4095.27, "duration": 1.86}, {"text": "his lunch pail, as I recall it.", "start": 4097.13, "duration": 2.07}, {"text": "And the kids were\nwaving goodbye.", "start": 4099.2, "duration": 2.369}, {"text": "And the title of it were\nwords to the effect,", "start": 4101.569, "duration": 7.171}, {"text": "he's an engineer, and\nhis family doesn't know", "start": 4108.74, "duration": 2.789}, {"text": "what he's going to do today.", "start": 4111.529, "duration": 2.79}, {"text": "And it was based on\nsome national surveys", "start": 4114.319, "duration": 2.16}, {"text": "that the families\nof engineers had", "start": 4116.479, "duration": 2.041}, {"text": "not a clue as to what\ntheir husband or father was", "start": 4118.52, "duration": 3.24}, {"text": "going to do.", "start": 4121.76, "duration": 0.519}, {"text": "They were all men in those days.", "start": 4122.279, "duration": 1.671}, {"text": "When I say all men,\nI don't mean 100%.", "start": 4123.95, "duration": 2.294}, {"text": "98%.", "start": 4129.17, "duration": 1.2}, {"text": "They did not know what their\nfather was going to do all day.", "start": 4130.37, "duration": 3.967}, {"text": "They didn't know\nwhat engineering was.", "start": 4134.337, "duration": 1.583}, {"text": "I'm still trying to\nfind that article.", "start": 4140.132, "duration": 3.158}, {"text": "There was another\narticle that I'm still", "start": 4143.29, "duration": 1.77}, {"text": "trying to find that came out\nin one of those magazines,", "start": 4145.06, "duration": 3.66}, {"text": "where they had these pictures\nof graduation at Berkeley.", "start": 4148.72, "duration": 7.8}, {"text": "And the students, the\nengineering students,", "start": 4160.189, "duration": 5.641}, {"text": "had these placards, and\nthe liberal arts students", "start": 4165.83, "duration": 2.37}, {"text": "had other placards.", "start": 4168.2, "duration": 1.89}, {"text": "And they were not\nanti-war placards.", "start": 4170.09, "duration": 2.79}, {"text": "The liberal arts students\nhad placards that said,", "start": 4175.56, "duration": 3.83}, {"text": "we got an education.", "start": 4179.39, "duration": 2.79}, {"text": "And the engineering\nplacards said, we got jobs.", "start": 4182.18, "duration": 3.21}, {"text": "[LAUGHS] And they were directed\none towards each other.", "start": 4185.39, "duration": 4.049}, {"text": "So there was this--", "start": 4192.37, "duration": 1.909}, {"text": "I'm trying to describe\nthe mood of the times that", "start": 4194.279, "duration": 3.301}, {"text": "govern your ethical decisions.", "start": 4197.58, "duration": 1.53}, {"text": "Because I argue that\nethical decisions,", "start": 4199.11, "duration": 2.4}, {"text": "no matter what Plato said--", "start": 4201.51, "duration": 2.34}, {"text": "actually, no matter\nwhat Aristotle said--", "start": 4203.85, "duration": 2.67}, {"text": "have a lot to do\nwith your passions.", "start": 4206.52, "duration": 2.46}, {"text": "You're trying to put your\npassions and your reason", "start": 4208.98, "duration": 2.22}, {"text": "in some kind of harmony\nin a lot of them.", "start": 4211.2, "duration": 3.18}, {"text": "But Aristotle said,\nno, it's all reason.", "start": 4214.38, "duration": 2.94}, {"text": "And Plato said, no,\nit's all character.", "start": 4217.32, "duration": 2.733}, {"text": "Well, are you willing to take\na stand on the Ford Pinto case?", "start": 4224.6, "duration": 5.67}, {"text": "Can you point to somebody\nwho did something wrong?", "start": 4230.27, "duration": 3.7}, {"text": "Can you point to somebody\nelse who did something right?", "start": 4233.97, "duration": 4.19}, {"text": "Can you tell me what you would\ndo if you were in a situation?", "start": 4238.16, "duration": 5.31}, {"text": "Would you have blown the\nwhistle on your company", "start": 4243.47, "duration": 3.0}, {"text": "when the word came down?", "start": 4246.47, "duration": 2.877}, {"text": "Notice that nobody in\nFord blew the whistle.", "start": 4249.347, "duration": 1.833}, {"text": "AUDIENCE: Yeah, I\nmean, I feel like if--", "start": 4254.28, "duration": 5.13}, {"text": "I wonder how much\nthe engineers that", "start": 4265.3, "duration": 2.11}, {"text": "were working on the car design\nknew about the crash test", "start": 4267.41, "duration": 4.47}, {"text": "results.", "start": 4271.88, "duration": 1.367}, {"text": "TAFT BROOME: I don't know.", "start": 4273.247, "duration": 1.083}, {"text": "AUDIENCE: [INAUDIBLE]\nthey listened to the boss.", "start": 4279.51, "duration": 4.06}, {"text": "Whatever your boss says,\n[INAUDIBLE] they just", "start": 4283.57, "duration": 2.48}, {"text": "did whatever they could do.", "start": 4286.05, "duration": 2.08}, {"text": "And there was no\n[INAUDIBLE] back in the day.", "start": 4288.13, "duration": 2.84}, {"text": "If you're talking about\nthe type of [INAUDIBLE],,", "start": 4290.97, "duration": 3.586}, {"text": "they don't question.", "start": 4294.556, "duration": 1.204}, {"text": "They don't-- now people are more\nlikely to think about standing", "start": 4295.76, "duration": 5.665}, {"text": "up for what they think is right.", "start": 4301.425, "duration": 1.98}, {"text": "I think back then, [INAUDIBLE].", "start": 4303.405, "duration": 2.97}, {"text": "TAFT BROOME: That's a\nfair characterization.", "start": 4310.47, "duration": 2.073}, {"text": "Whistleblowing was\nnot new in those days.", "start": 4315.32, "duration": 4.37}, {"text": "Ed Layton would show\nthe whistleblowing--", "start": 4319.69, "duration": 5.08}, {"text": "I think he traces it back\nto the late 19th century,", "start": 4324.77, "duration": 3.51}, {"text": "but you would find it.", "start": 4328.28, "duration": 1.62}, {"text": "But it was so rare and so--", "start": 4329.9, "duration": 2.175}, {"text": "it was equivalent to\nheresy in religion.", "start": 4335.42, "duration": 4.47}, {"text": "I mean, if you did it,\nyou'd get blackballed.", "start": 4339.89, "duration": 3.48}, {"text": "And people thought of\nyou as a terrible person.", "start": 4343.37, "duration": 4.236}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 4347.606, "duration": 1.404}, {"text": "So if the whole city of\nautomobiles [INAUDIBLE]..", "start": 4351.55, "duration": 4.515}, {"text": "TAFT BROOME: Right, you\ncouldn't live there anymore", "start": 4356.065, "duration": 2.125}, {"text": "if you blew the whistle.", "start": 4358.19, "duration": 0.75}, {"text": "You couldn't go home\nwith your neighbors,", "start": 4358.94, "duration": 1.708}, {"text": "even if they were not engineers.", "start": 4360.648, "duration": 1.502}, {"text": "They'd say, oh, how could\nyou do a thing like that?", "start": 4362.15, "duration": 2.31}, {"text": "The times were\ndifferent, but times", "start": 4364.46, "duration": 2.883}, {"text": "were changing in those days.", "start": 4367.343, "duration": 1.167}, {"text": "Well, let me say that we're\nnot done with the Ford Pinto.", "start": 4371.12, "duration": 5.13}, {"text": "I want, in the next class,\nto come back and tell me", "start": 4376.25, "duration": 6.54}, {"text": "if you're willing to take\na stand on this case.", "start": 4382.79, "duration": 5.61}, {"text": "Let me assign another case.", "start": 4388.4, "duration": 1.125}, {"text": "On the list in the\nsyllabus, we're at a point", "start": 4392.06, "duration": 2.58}, {"text": "now where we can start\npicking and choosing.", "start": 4394.64, "duration": 6.51}, {"text": "Do you have any preferences?", "start": 4401.15, "duration": 3.28}, {"text": "We don't have to go in the order\nthat I presented, but the Pinto", "start": 4404.43, "duration": 5.07}, {"text": "is a little more--", "start": 4409.5, "duration": 2.07}, {"text": "you can see why I picked\nthis one after A7-D. A7-D was", "start": 4411.57, "duration": 4.2}, {"text": "pretty straightforward.", "start": 4415.77, "duration": 1.8}, {"text": "Pinto is a little hard.", "start": 4417.57, "duration": 2.1}, {"text": "AUDIENCE: And I want to be able\nto say that a company shouldn't", "start": 4423.825, "duration": 2.625}, {"text": "sell a car that they know is\ngoing to kill someone, but--", "start": 4426.45, "duration": 4.38}, {"text": "TAFT BROOME: All cars.", "start": 4430.83, "duration": 2.634}, {"text": "AUDIENCE: So where's\nthe threshold?", "start": 4433.464, "duration": 1.976}, {"text": "How many deaths are\nallowable [INAUDIBLE]??", "start": 4435.44, "duration": 4.64}, {"text": "TAFT BROOME: And\nI'll tell you where", "start": 4440.08, "duration": 2.7}, {"text": "I'm willing to stand on this.", "start": 4442.78, "duration": 5.08}, {"text": "And I think that there\nare contrary stands", "start": 4447.86, "duration": 4.76}, {"text": "you can take, too.", "start": 4452.62, "duration": 0.84}, {"text": "I tell you what--\nlet's play a game.", "start": 4453.46, "duration": 3.06}, {"text": "Let's start playing a game,\nand that is whenever I ask you", "start": 4456.52, "duration": 4.02}, {"text": "or whenever you decide\nto take a stand,", "start": 4460.54, "duration": 3.62}, {"text": "it could be a stand that you\nwill defend because you believe", "start": 4464.16, "duration": 4.05}, {"text": "in it, or you can tell us you're\ngoing to be devil's advocate.", "start": 4468.21, "duration": 4.63}, {"text": "Take a stand that\nyou don't believe in.", "start": 4472.84, "duration": 1.65}, {"text": "See how far you can defend it.", "start": 4474.49, "duration": 2.227}, {"text": "Well, let me see the list\nand let's do Chernobyl.", "start": 4481.49, "duration": 22.17}, {"text": "And now, I'll tell you\nwhat, let's do two together.", "start": 4503.66, "duration": 4.45}, {"text": "Let's do Chernobyl\nand Three Mile Island.", "start": 4508.11, "duration": 4.57}, {"text": "Now, the reason for\ndoing them together", "start": 4512.68, "duration": 2.4}, {"text": "is that we can make a\ncultural comparison.", "start": 4515.08, "duration": 3.74}]
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+[{"text": "ADAM MARTIN: So I\nguess I will start by,", "start": 17.22, "duration": 1.72}, {"text": "first of all,\ncongratulating you all.", "start": 18.94, "duration": 2.6}, {"text": "Since the last\ntime I've seen you,", "start": 21.54, "duration": 2.1}, {"text": "you've all regenerated\nyour intestine.", "start": 23.64, "duration": 4.42}, {"text": "So it's like you're\na brand new person.", "start": 28.06, "duration": 3.11}, {"text": "So there's that.", "start": 36.6, "duration": 2.01}, {"text": "I want to start the lecture\nby talking about something", "start": 38.61, "duration": 3.3}, {"text": "I've been putting off\ntelling you about,", "start": 41.91, "duration": 3.13}, {"text": "which is the Nobel Prize\nin physiology or medicine", "start": 45.04, "duration": 3.05}, {"text": "that was awarded this year.", "start": 48.09, "duration": 2.37}, {"text": "And it was awarded to James\nAllison and Tasuku Honjo", "start": 50.46, "duration": 5.37}, {"text": "for their discovery of a way\nto harness the immune system", "start": 55.83, "duration": 5.31}, {"text": "to fight cancer.", "start": 61.14, "duration": 2.58}, {"text": "And we're going to talk\nabout the immune system", "start": 63.72, "duration": 3.18}, {"text": "later in the course,\nand it turns out,", "start": 66.9, "duration": 5.22}, {"text": "I will lecture on it.", "start": 72.12, "duration": 1.11}, {"text": "And I've actually\nhad immunology,", "start": 73.23, "duration": 2.25}, {"text": "and in fact, I had immunology\nwith James Allison.", "start": 75.48, "duration": 3.66}, {"text": "So I will do my best to\nchannel James Allison when", "start": 79.14, "duration": 3.12}, {"text": "I talk about the immune system.", "start": 82.26, "duration": 2.13}, {"text": "But what they won\nthe prize for is,", "start": 84.39, "duration": 2.46}, {"text": "they figured out a way\nto essentially release", "start": 86.85, "duration": 2.67}, {"text": "the brake on the\nimmune system in order", "start": 89.52, "duration": 2.76}, {"text": "to allow the immune system\nto better fight cancer.", "start": 92.28, "duration": 4.59}, {"text": "And this is a technique that's\nbeen used in the clinic,", "start": 96.87, "duration": 3.24}, {"text": "and there are currently a\nnumber of clinical trials", "start": 100.11, "duration": 3.69}, {"text": "that are also looking\nto see whether this", "start": 103.8, "duration": 3.06}, {"text": "can be used in a variety\nof different cancer types.", "start": 106.86, "duration": 4.24}, {"text": "OK.", "start": 111.1, "duration": 0.62}, {"text": "So I just wanted to\npoint that out now", "start": 111.72, "duration": 1.65}, {"text": "because we're\ntalking about cancer,", "start": 113.37, "duration": 1.8}, {"text": "and I'll go more\ninto the mechanism", "start": 115.17, "duration": 1.77}, {"text": "as how this works\nwhen we start talking", "start": 116.94, "duration": 2.28}, {"text": "about the immune system.", "start": 119.22, "duration": 3.61}, {"text": "So as I mentioned\nin the last lecture,", "start": 122.83, "duration": 3.41}, {"text": "cancer is basically\na progressive loss", "start": 126.24, "duration": 3.0}, {"text": "of tissue organization.", "start": 129.24, "duration": 2.49}, {"text": "And luckily for us,\nour body has a number", "start": 131.73, "duration": 6.63}, {"text": "of different barriers to cells\nbecoming cancerous and forming", "start": 138.36, "duration": 4.32}, {"text": "a tumor.", "start": 142.68, "duration": 0.99}, {"text": "And so I wanted\nto start out just", "start": 143.67, "duration": 1.62}, {"text": "by having you guys tell me what\nyou feel the barriers would", "start": 145.29, "duration": 4.2}, {"text": "be to this process.", "start": 149.49, "duration": 2.46}, {"text": "So who has an idea of a barrier?", "start": 151.95, "duration": 3.06}, {"text": "What are the barriers\nin place by your body", "start": 155.01, "duration": 4.14}, {"text": "to prevent cancer cells from\narising and forming a tumor,", "start": 159.15, "duration": 3.93}, {"text": "and for this process to\nform a malignant tumor?", "start": 163.08, "duration": 4.02}, {"text": "What's that?", "start": 173.23, "duration": 1.22}, {"text": "Oh, Rachel, sorry.", "start": 174.45, "duration": 1.36}, {"text": "STUDENT: Apoptosis.", "start": 175.81, "duration": 1.38}, {"text": "ADAM MARTIN: Apoptosis\nis a good one, right.", "start": 177.19, "duration": 4.44}, {"text": "So there's a careful\nprocess in your body", "start": 181.63, "duration": 5.31}, {"text": "to limit how long certain\ncells are resident in the body.", "start": 186.94, "duration": 5.34}, {"text": "And all of this depends\non communication", "start": 192.28, "duration": 3.06}, {"text": "between different cell\ntypes in your body--", "start": 195.34, "duration": 5.28}, {"text": "so barriers to tumor agenesis.", "start": 200.62, "duration": 3.27}, {"text": "And one type of signal\nis a survival signal.", "start": 207.97, "duration": 3.12}, {"text": "And if a cell is not\ngetting a survival signal,", "start": 211.09, "duration": 2.76}, {"text": "then the cell will\nundergo apoptosis,", "start": 213.85, "duration": 3.06}, {"text": "which is what Rachel\nwas referring to.", "start": 216.91, "duration": 3.18}, {"text": "So one barrier is that\nthere is a highly regulated", "start": 220.09, "duration": 4.86}, {"text": "system of determining\nwhether or not cells divide", "start": 224.95, "duration": 3.39}, {"text": "and also whether\nor not cells live.", "start": 228.34, "duration": 2.47}, {"text": "OK.", "start": 230.81, "duration": 0.5}, {"text": "So there are growth\nsurvival signals,", "start": 231.31, "duration": 8.1}, {"text": "which means that the decision\nfor a cell to go off its rocker", "start": 239.41, "duration": 4.38}, {"text": "and just start\ndividing uncontrollably", "start": 243.79, "duration": 2.73}, {"text": "is not likely for a normal cell.", "start": 246.52, "duration": 3.6}, {"text": "Something has to happen to that\ncell in order to perturb it.", "start": 250.12, "duration": 4.38}, {"text": "So what are some other\nbarriers to forming a tumor", "start": 254.5, "duration": 4.92}, {"text": "and for that tumor\nto become invasive?", "start": 259.42, "duration": 3.51}, {"text": "Yes, Jeremy?", "start": 262.93, "duration": 0.74}, {"text": "STUDENT: You just mentioned\nit, but the immune system.", "start": 263.67, "duration": 3.34}, {"text": "ADAM MARTIN: Yeah.", "start": 267.01, "duration": 0.75}, {"text": "So this cancer cell can't\nactivate the immune system.", "start": 267.76, "duration": 5.53}, {"text": "So you could have some\ntype of immunosuppression", "start": 273.29, "duration": 4.867}, {"text": "of the cancer.", "start": 278.157, "duration": 0.583}, {"text": "And I won't talk\nabout that today,", "start": 281.78, "duration": 2.3}, {"text": "but maybe we'll come back\nand talk about it when we", "start": 284.08, "duration": 2.55}, {"text": "talk about the immune system.", "start": 286.63, "duration": 2.71}, {"text": "OK.", "start": 289.34, "duration": 0.5}, {"text": "Looking at this diagram,\nwhen the tumor proceeds", "start": 289.84, "duration": 5.37}, {"text": "to invasive cancer,\nwhat do you think", "start": 295.21, "duration": 2.1}, {"text": "are some barriers to\nthat process happening?", "start": 297.31, "duration": 2.674}, {"text": "What are cells normally\ndoing in an organ?", "start": 306.15, "duration": 4.44}, {"text": "The cells that line\nyour intestine,", "start": 310.59, "duration": 2.94}, {"text": "are they invading into\nthe surrounding tissue?", "start": 313.53, "duration": 2.83}, {"text": "No.", "start": 316.36, "duration": 0.5}, {"text": "Jeremy is shaking\nhis head no, right?", "start": 316.86, "duration": 2.28}, {"text": "So normally, cells don't do\nthat, or certain types of cells", "start": 319.14, "duration": 4.92}, {"text": "do, but normally,\nif you have cells", "start": 324.06, "duration": 2.49}, {"text": "that are the lining\nof an epithelium,", "start": 326.55, "duration": 1.89}, {"text": "they're not going off\nto a blood vessel.", "start": 328.44, "duration": 4.02}, {"text": "OK.", "start": 332.46, "duration": 1.02}, {"text": "So I'm just going to review\nthe structure of the tissue,", "start": 333.48, "duration": 6.57}, {"text": "and then we'll talk about\nsome of the barriers that", "start": 340.05, "duration": 2.94}, {"text": "prevent this from happening.", "start": 342.99, "duration": 2.89}, {"text": "So I'm drawing a\ntubular organ here.", "start": 345.88, "duration": 4.25}, {"text": "This could be the\ntube of the intestine.", "start": 350.13, "duration": 3.84}, {"text": "There'd be a lumen inside here.", "start": 353.97, "duration": 2.31}, {"text": "It could be some ductal\nstructure in an organ,", "start": 356.28, "duration": 2.49}, {"text": "like a mammary gland.", "start": 358.77, "duration": 1.8}, {"text": "It could be that this\nis the airway of a lung,", "start": 360.57, "duration": 2.79}, {"text": "and there's an epithelial\nlining around that airway.", "start": 363.36, "duration": 3.9}, {"text": "So these cells here are\nforming an epithelial lining.", "start": 367.26, "duration": 6.09}, {"text": "And one important aspect\nof epithelial biology", "start": 373.35, "duration": 3.99}, {"text": "is, immature epithelia,\nthey have a floor", "start": 377.34, "duration": 4.86}, {"text": "that the cells stand on.", "start": 382.2, "duration": 4.35}, {"text": "So this structure that I\njust drew around these cells", "start": 386.55, "duration": 4.92}, {"text": "in green is known as\nthe basement membrane.", "start": 391.47, "duration": 2.55}, {"text": "It's the basement because it's\nthe floor that this other thing", "start": 398.27, "duration": 3.67}, {"text": "is built on.", "start": 401.94, "duration": 1.95}, {"text": "And this basement\nmembrane is made out", "start": 403.89, "duration": 2.13}, {"text": "of what is known as the\nextracellular matrix, which", "start": 406.02, "duration": 3.9}, {"text": "I'll just call matrix right now,\nand the extracellular matrix", "start": 409.92, "duration": 3.09}, {"text": "are basically\nextracellular proteins", "start": 413.01, "duration": 2.7}, {"text": "that form a mesh work that\nforms a rigid structure on which", "start": 415.71, "duration": 5.34}, {"text": "epithelial cells can sit on.", "start": 421.05, "duration": 1.8}, {"text": "OK, now if we think about\nwhat surrounds this organ,", "start": 426.02, "duration": 5.36}, {"text": "there's also matrix proteins\nin the intervening areas.", "start": 431.38, "duration": 8.015}, {"text": "And this is known as\nconnective tissue.", "start": 442.78, "duration": 1.675}, {"text": "And so if we think\nabout the cells that", "start": 447.92, "duration": 2.88}, {"text": "are the epithelial cells\nhere, they are in one state,", "start": 450.8, "duration": 4.08}, {"text": "and this state is known as\nepithelial, as I just said.", "start": 454.88, "duration": 3.78}, {"text": "So these are epithelial cells.", "start": 458.66, "duration": 2.88}, {"text": "Epithelial cells\nhave a few properties", "start": 461.54, "duration": 3.9}, {"text": "that are really distinguishing.", "start": 465.44, "duration": 2.37}, {"text": "The first is that they have\nhigh intercellular adhesion.", "start": 467.81, "duration": 3.39}, {"text": "And the next is\nthat, if you consider", "start": 478.91, "duration": 2.46}, {"text": "their relative mobility,\nthey can obviously", "start": 481.37, "duration": 3.15}, {"text": "move within the epithelium\nbecause we talked", "start": 484.52, "duration": 2.73}, {"text": "about the intestine\nand how cells", "start": 487.25, "duration": 1.68}, {"text": "are moving from the base of\nthe crypts up to the villus.", "start": 488.93, "duration": 3.51}, {"text": "But in general, these cells\naren't moving in and out", "start": 492.44, "duration": 2.61}, {"text": "of the organ.", "start": 495.05, "duration": 2.01}, {"text": "So I would say that they have\na low migratory potential.", "start": 497.06, "duration": 4.2}, {"text": "And so these are the\nepithelial cells that are here.", "start": 509.42, "duration": 3.33}, {"text": "Now there are also cells that\nare in this interstitial space,", "start": 512.75, "duration": 5.6}, {"text": "and I'll draw-- they often\nhave this highly elongated", "start": 518.35, "duration": 2.68}, {"text": "morphology.", "start": 521.03, "duration": 1.74}, {"text": "And these cells are in a\nfundamentally different state.", "start": 522.77, "duration": 4.8}, {"text": "And this state is known\nas mesenchymal or stromal.", "start": 527.57, "duration": 7.65}, {"text": "So this area outside the organ\nis also known as the stroma.", "start": 538.01, "duration": 4.95}, {"text": "So they're known as stromal\ncells in this location.", "start": 542.96, "duration": 4.53}, {"text": "And these cells have\nvery different properties", "start": 547.49, "duration": 3.54}, {"text": "than the epithelial cells in\nthat they have low adhesion--", "start": 551.03, "duration": 6.96}, {"text": "I should say low\ncell-to-cell adhesion.", "start": 557.99, "duration": 2.625}, {"text": "And in contrast to\nthese epithelial cells,", "start": 565.22, "duration": 3.36}, {"text": "these stromal cells, as you\nsee in this example up here--", "start": 568.58, "duration": 3.75}, {"text": "that's a human neutrophil--", "start": 572.33, "duration": 1.96}, {"text": "these stromal cells\nare highly migratory.", "start": 574.29, "duration": 3.11}, {"text": "So that neutrophil is\nchasing a bacterium,", "start": 581.36, "duration": 5.16}, {"text": "and they'll eventually get\nit, but the movie will loop,", "start": 586.52, "duration": 2.64}, {"text": "and so you'll see it constantly\nchasing that bacterium.", "start": 589.16, "duration": 4.14}, {"text": "So some examples\nof stromal cells", "start": 593.3, "duration": 3.54}, {"text": "would be immune cells,\nlike this human neutrophil.", "start": 596.84, "duration": 3.1}, {"text": "And you probably know\nthat immune cells", "start": 603.84, "duration": 1.85}, {"text": "have to traverse\ndifferent organ systems.", "start": 605.69, "duration": 3.9}, {"text": "They have to be rapidly\nrecruited to sites of infection", "start": 609.59, "duration": 3.12}, {"text": "or sites of injury.", "start": 612.71, "duration": 1.68}, {"text": "And so this type of\ncell is fundamentally", "start": 614.39, "duration": 3.93}, {"text": "different from the types of\ncells that line your organs,", "start": 618.32, "duration": 3.39}, {"text": "where you basically need\nthose cells to stay put.", "start": 621.71, "duration": 2.49}, {"text": "When considering cancer, you\nhave these different types", "start": 627.05, "duration": 3.27}, {"text": "of cells in your body.", "start": 630.32, "duration": 1.53}, {"text": "90% of cancer comes from a\ncell of epithelial origin.", "start": 631.85, "duration": 4.665}, {"text": "So 90% of cancers are\nepithelial in origin.", "start": 639.2, "duration": 7.5}, {"text": "Some other examples\nof stromal cells", "start": 653.57, "duration": 2.61}, {"text": "are cells like fibroblasts.", "start": 656.18, "duration": 4.2}, {"text": "And fibroblasts are cells\nthat secrete and remodel", "start": 660.38, "duration": 3.87}, {"text": "the matrix that's in\nconnective tissue.", "start": 664.25, "duration": 2.91}, {"text": "And they're also important for\nwound healing and secreting", "start": 667.16, "duration": 2.94}, {"text": "matrix during the\nwound-healing process.", "start": 670.1, "duration": 3.17}, {"text": "So that's just to give\nyou a few examples.", "start": 673.27, "duration": 1.75}, {"text": "OK.", "start": 680.63, "duration": 0.5}, {"text": "So now let's come back to this\nexample and talk about what", "start": 681.13, "duration": 5.91}, {"text": "happens to get a cell to\ngo all the way from being", "start": 687.04, "duration": 6.24}, {"text": "a normal epithelial cell to\nhaving this type of behavior,", "start": 693.28, "duration": 5.4}, {"text": "where initially you\nhave growth and a loss", "start": 698.68, "duration": 2.49}, {"text": "of the control over growth\nand survival signaling,", "start": 701.17, "duration": 3.48}, {"text": "and eventually, the\ncancer can become", "start": 704.65, "duration": 2.76}, {"text": "what's known as malignant?", "start": 707.41, "duration": 1.35}, {"text": "So it's a progression, and\ninitially, you might just", "start": 712.69, "duration": 3.0}, {"text": "get increased in-cell division\nand abnormal cell shape, which", "start": 715.69, "duration": 4.35}, {"text": "is known as dysplasia,\nand at that point,", "start": 720.04, "duration": 3.15}, {"text": "it's known as something like\nan adenoma or something that's", "start": 723.19, "duration": 3.96}, {"text": "benign.", "start": 727.15, "duration": 2.76}, {"text": "But it's this last\npoint here, up here,", "start": 729.91, "duration": 4.35}, {"text": "where the cells breach\nthis basement membrane.", "start": 734.26, "duration": 4.47}, {"text": "When that happens, then the\ncancer is known as carcinoma,", "start": 738.73, "duration": 3.57}, {"text": "and it's malignant.", "start": 742.3, "duration": 1.23}, {"text": "So malignant cancer is cancer\nthat has breached the basement", "start": 748.0, "duration": 12.63}, {"text": "membrane.", "start": 760.63, "duration": 0.5}, {"text": "So I want to take you through\nthe progression of tumor", "start": 778.99, "duration": 4.79}, {"text": "genesis.", "start": 783.78, "duration": 1.63}, {"text": "And first, I'm going to\nstart with the breakdown", "start": 785.41, "duration": 4.05}, {"text": "of this growth\nsurvival signaling.", "start": 789.46, "duration": 2.07}, {"text": "And I just wanted to\nremind you about what", "start": 794.28, "duration": 3.16}, {"text": "we talked about with the\nintestine as our model organ.", "start": 797.44, "duration": 4.78}, {"text": "And in the intestine,\nremember that this is all", "start": 802.22, "duration": 2.99}, {"text": "regulated by signals between\nstem cells and niche cells.", "start": 805.21, "duration": 8.29}, {"text": "So the niche cells are\nsending the stem cells", "start": 813.5, "duration": 3.08}, {"text": "signals like Wnts that\ncontrol their self renewal,", "start": 816.58, "duration": 3.9}, {"text": "and then it's the loss\nof this signaling that", "start": 820.48, "duration": 4.38}, {"text": "allows these cells to eventually\nundergo apoptosis and get", "start": 824.86, "duration": 3.69}, {"text": "shed into the lumen\nof the intestine.", "start": 828.55, "duration": 3.06}, {"text": "So one of the first\nsteps in cancer", "start": 831.61, "duration": 6.57}, {"text": "is this breakdown in\ngrowth survival signaling.", "start": 838.18, "duration": 13.461}, {"text": "So this first breakdown is going\nto enable the cells to overcome", "start": 854.59, "duration": 5.58}, {"text": "this first barrier.", "start": 860.17, "duration": 0.81}, {"text": "And so as I just\npointed out, remember,", "start": 865.05, "duration": 4.2}, {"text": "it helps to think of\nwhat has to happen", "start": 869.25, "duration": 2.1}, {"text": "in a normal tissue or organ.", "start": 871.35, "duration": 2.61}, {"text": "Normally, the decision whether\nor not a cell divides or dies--", "start": 873.96, "duration": 6.21}, {"text": "so cell division\nand also death--", "start": 880.17, "duration": 6.69}, {"text": "is highly regulated.", "start": 886.86, "duration": 3.33}, {"text": "And it's regulated by\ncommunication with other cells.", "start": 890.19, "duration": 2.64}, {"text": "So in cancer, this\nregulation goes awry.", "start": 899.38, "duration": 2.645}, {"text": "And how would this\nregulation go awry?", "start": 905.38, "duration": 1.91}, {"text": "Yeah, Jeremy?", "start": 910.938, "duration": 2.124}, {"text": "STUDENT: Loss of function\nin a tumor suppressor", "start": 913.062, "duration": 3.278}, {"text": "or an over-activation\nof the oncogene.", "start": 916.34, "duration": 3.679}, {"text": "ADAM MARTIN: Mm-hmm.", "start": 920.019, "duration": 0.941}, {"text": "So Jeremy suggested that\nthere could be mutations,", "start": 920.96, "duration": 3.34}, {"text": "like oncogenic mutations\nor tumor suppressor", "start": 924.3, "duration": 2.73}, {"text": "loss, that lead to abnormal\ncell division and death.", "start": 927.03, "duration": 4.93}, {"text": "And that is exactly right.", "start": 931.96, "duration": 2.75}, {"text": "So you could have\noncogenic mutations,", "start": 934.71, "duration": 6.18}, {"text": "and these oncogenic mutations,\nthey often hyperactivate", "start": 940.89, "duration": 4.83}, {"text": "or constitutively activate these\ngrowth-signaling pathways that", "start": 945.72, "duration": 4.35}, {"text": "are normally downstream of\ngrowth factors and receptor", "start": 950.07, "duration": 3.12}, {"text": "tyrosine kinases.", "start": 953.19, "duration": 2.4}, {"text": "And if you\nhyperactivate those, you", "start": 955.59, "duration": 3.57}, {"text": "reduce the dependency of\nthe cells on these signals.", "start": 959.16, "duration": 4.26}, {"text": "So these oncogenic\nmutations can reduce", "start": 963.42, "duration": 5.13}, {"text": "the dependency of cells on\ngrowth factors and growth", "start": 968.55, "duration": 6.52}, {"text": "signals.", "start": 975.07, "duration": 0.5}, {"text": "OK.", "start": 981.18, "duration": 2.19}, {"text": "But one important point is\nthat this is not enough.", "start": 983.37, "duration": 6.33}, {"text": "And you can think about this\nin the case of the intestine", "start": 989.7, "duration": 3.87}, {"text": "because if you had an oncogenic\nmutation in one of these cells", "start": 993.57, "duration": 4.23}, {"text": "here, it might not\nbe as dependent", "start": 997.8, "duration": 2.85}, {"text": "on signals for growth.", "start": 1000.65, "duration": 2.64}, {"text": "But it doesn't matter\nbecause even though you", "start": 1003.29, "duration": 2.16}, {"text": "had that mutation,\nit's going to die,", "start": 1005.45, "duration": 1.95}, {"text": "and it's going to shed\nout of the tissue.", "start": 1007.4, "duration": 3.39}, {"text": "And actually what\nhappens in many cases", "start": 1010.79, "duration": 3.69}, {"text": "where you activate a\nsignaling pathway that", "start": 1014.48, "duration": 3.57}, {"text": "allows the cell to,\nin an abnormal way,", "start": 1018.05, "duration": 3.24}, {"text": "go through the cell\ncycle, you actually", "start": 1021.29, "duration": 2.31}, {"text": "induce a failsafe mechanism at\nthe cell which causes the cell", "start": 1023.6, "duration": 3.989}, {"text": "to undergo apoptosis.", "start": 1027.589, "duration": 3.48}, {"text": "So often, you get\nthis step happening,", "start": 1031.069, "duration": 2.971}, {"text": "and the cells just\nundergo apoptosis", "start": 1034.04, "duration": 2.37}, {"text": "because you've evolved\nto protect your organs", "start": 1036.41, "duration": 3.6}, {"text": "from this type of mutation.", "start": 1040.01, "duration": 2.609}, {"text": "So it's the oncogenic\nmutation, in collaboration", "start": 1042.619, "duration": 3.901}, {"text": "with loss of tumor suppression,\nand one of the main tumor", "start": 1046.52, "duration": 9.78}, {"text": "suppressive mechanisms\nour body has is apoptosis,", "start": 1056.3, "duration": 4.71}, {"text": "where if a cell is doing\nsomething abnormal,", "start": 1061.01, "duration": 2.22}, {"text": "the cells simply dies.", "start": 1063.23, "duration": 1.185}, {"text": "So loss of the tumor\nsuppressor could", "start": 1068.1, "duration": 3.05}, {"text": "be loss of a gene that promotes\napoptosis, and in that case,", "start": 1071.15, "duration": 4.05}, {"text": "if the cell loses\nthat mechanism,", "start": 1075.2, "duration": 2.64}, {"text": "the cell will avoid apoptosis.", "start": 1077.84, "duration": 2.43}, {"text": "OK.", "start": 1088.05, "duration": 0.5}, {"text": "So this is oncogenic\nmutations and the loss", "start": 1088.55, "duration": 5.64}, {"text": "of tumor suppressors\nwhich subverts", "start": 1094.19, "duration": 4.11}, {"text": "the normal communication\nbetween cells which is required", "start": 1098.3, "duration": 3.87}, {"text": "for normal tissue homeostasis.", "start": 1102.17, "duration": 2.31}, {"text": "OK.", "start": 1104.48, "duration": 2.19}, {"text": "Now another example of this\ngrowth and survival signaling", "start": 1106.67, "duration": 4.11}, {"text": "is not one which\ninvolves, necessarily,", "start": 1110.78, "duration": 4.98}, {"text": "a genetic change, but one that\ninvolves changes in expression.", "start": 1115.76, "duration": 4.47}, {"text": "And it also involves\ninteraction between the tumor", "start": 1120.23, "duration": 3.39}, {"text": "and the surrounding\ncells of the body.", "start": 1123.62, "duration": 3.51}, {"text": "So I'm going to tell you\na little bit about tumor", "start": 1127.13, "duration": 2.61}, {"text": "microenvironment.", "start": 1129.74, "duration": 1.2}, {"text": "And this is something\nthat's important to consider", "start": 1137.49, "duration": 3.14}, {"text": "in cancer because a tumor in\na body, it's not in isolation.", "start": 1140.63, "duration": 5.7}, {"text": "It's surrounded by other cells\nin your body and other things", "start": 1146.33, "duration": 4.86}, {"text": "in your body, like\nmatrix, and so here is", "start": 1151.19, "duration": 5.01}, {"text": "a picture showing you\na tumor, and the tumor", "start": 1156.2, "duration": 3.45}, {"text": "is stained with this membrane\nprotein which is shown here", "start": 1159.65, "duration": 3.48}, {"text": "in the rust color.", "start": 1163.13, "duration": 1.23}, {"text": "So that's the tumor.", "start": 1164.36, "duration": 1.89}, {"text": "And what's also stained in this\npiece of tissue is the DNA.", "start": 1166.25, "duration": 6.27}, {"text": "It's stained in blue.", "start": 1172.52, "duration": 1.96}, {"text": "And so you see the nuclei\nof the tumor cells in there.", "start": 1174.48, "duration": 4.04}, {"text": "But you see all these blue\nnuclei surrounding the tumor.", "start": 1178.52, "duration": 4.29}, {"text": "And these are stromal cells\nthat are around the tumor.", "start": 1182.81, "duration": 5.46}, {"text": "And they've actually been\nrecruited to the tumor", "start": 1188.27, "duration": 2.94}, {"text": "by the cancer cells.", "start": 1191.21, "duration": 3.52}, {"text": "So what I mean by\ntumor microenvironment", "start": 1194.73, "duration": 3.37}, {"text": "is just the region\naround the tumor.", "start": 1198.1, "duration": 3.22}, {"text": "And so if you have cancer,\nand you have a tumor,", "start": 1201.32, "duration": 3.33}, {"text": "the tumor cells can\nactually secrete signals", "start": 1204.65, "duration": 3.57}, {"text": "which recruit stromal cells.", "start": 1208.22, "duration": 3.87}, {"text": "So there can be an\ninteraction where", "start": 1212.09, "duration": 5.91}, {"text": "the tumor sends recruitment\nsignals that causes", "start": 1218.0, "duration": 4.59}, {"text": "stromal cells to come by.", "start": 1222.59, "duration": 1.68}, {"text": "And what the stromal cells can\ndo, what they do for the tumor", "start": 1227.57, "duration": 4.98}, {"text": "and why this is\nbeneficial for the tumor,", "start": 1232.55, "duration": 2.58}, {"text": "is that stromal cells can\nsecrete growth signals", "start": 1235.13, "duration": 4.38}, {"text": "or survival signals that\npromote the growth of the tumor.", "start": 1239.51, "duration": 5.37}, {"text": "So there can be a reciprocal\ninteraction here where", "start": 1244.88, "duration": 6.69}, {"text": "you get an abnormal\nconversation between cancer", "start": 1251.57, "duration": 6.24}, {"text": "cells and the surrounding\nstromal cells.", "start": 1257.81, "duration": 2.88}, {"text": "But again, this is\nvery similar, if you", "start": 1260.69, "duration": 1.89}, {"text": "think about it, to the\nway a normal organ works.", "start": 1262.58, "duration": 3.75}, {"text": "You often have these\nsignals going between cells.", "start": 1266.33, "duration": 3.96}, {"text": "And that is involved in\nnormal tissue homeostasis.", "start": 1270.29, "duration": 5.22}, {"text": "What's happening here,\nthough, is abnormal", "start": 1275.51, "duration": 2.19}, {"text": "and that the cancer\ncells are constitutively", "start": 1277.7, "duration": 2.55}, {"text": "recruiting these\nstromal cells just", "start": 1280.25, "duration": 1.86}, {"text": "to get this growth signal\nthat they're addicted to.", "start": 1282.11, "duration": 4.83}, {"text": "And because you have\njust the presence", "start": 1286.94, "duration": 3.63}, {"text": "of such a loop suggests\nthat these cancer cells,", "start": 1290.57, "duration": 4.11}, {"text": "even if they have\noncogenic mutations", "start": 1294.68, "duration": 2.625}, {"text": "and have lost tumor\nsuppressors, they", "start": 1297.305, "duration": 2.985}, {"text": "are not totally independent\nof growth signals.", "start": 1300.29, "duration": 3.48}, {"text": "They still, to some extent,\nrely on growth signals.", "start": 1303.77, "duration": 5.25}, {"text": "So these oncogenic mutations,\nthey reduce the dependency", "start": 1309.02, "duration": 4.71}, {"text": "on growth signals,\nbut this dependency,", "start": 1313.73, "duration": 4.8}, {"text": "the dependency on growth\nsignals, is not eliminated.", "start": 1318.53, "duration": 10.32}, {"text": "And one experiment that showed\nthis was an experiment that", "start": 1338.12, "duration": 5.76}, {"text": "was done back in the 1950s where\npatients with a type of skin", "start": 1343.88, "duration": 5.16}, {"text": "cancer, basal cell\ncarcinoma, were taken,", "start": 1349.04, "duration": 4.56}, {"text": "and they had their\ntumors excised", "start": 1353.6, "duration": 2.31}, {"text": "from one part of their body.", "start": 1355.91, "duration": 2.04}, {"text": "And then the tumor was\ngrafted back onto them,", "start": 1357.95, "duration": 3.78}, {"text": "to another part of their body,\ndistant from the original site", "start": 1361.73, "duration": 3.63}, {"text": "of the tumor.", "start": 1365.36, "duration": 1.65}, {"text": "And this grafting\nexperiment was done either", "start": 1367.01, "duration": 3.81}, {"text": "with the stromal\ncells that surrounded", "start": 1370.82, "duration": 2.67}, {"text": "the tumor or the stromal\ncells surrounding the tumor", "start": 1373.49, "duration": 3.15}, {"text": "were removed, and\njust the tumor cells", "start": 1376.64, "duration": 2.19}, {"text": "were grafted back onto the body.", "start": 1378.83, "duration": 3.0}, {"text": "OK.", "start": 1381.83, "duration": 0.87}, {"text": "Now this experiment\nprobably would not", "start": 1382.7, "duration": 1.8}, {"text": "be allowed today, but back in\nthe '50s, I guess it was legal.", "start": 1384.5, "duration": 4.62}, {"text": "And so the\nexperimental result is", "start": 1389.12, "duration": 3.12}, {"text": "that if you graft the tumor\ncells with the surrounding", "start": 1392.24, "duration": 3.06}, {"text": "stroma, the tumor was able\nto establish a second tumor,", "start": 1395.3, "duration": 5.43}, {"text": "or the tumor cells survived\nthis grafting procedure,", "start": 1400.73, "duration": 4.35}, {"text": "whereas tumor cells that\nwere taken without the stroma", "start": 1405.08, "duration": 4.83}, {"text": "underwent cell death when they\nwere put in a new location.", "start": 1409.91, "duration": 4.23}, {"text": "So there's something about this\nspecialized microenvironment", "start": 1414.14, "duration": 4.41}, {"text": "that the tumor creates for\nitself that is enabling", "start": 1418.55, "duration": 3.54}, {"text": "the tumor to grow and survive.", "start": 1422.09, "duration": 3.36}, {"text": "And the model is that it's\nbecause these stromal cells are", "start": 1425.45, "duration": 3.99}, {"text": "secreting growth factors that\nthese cancer cells are still", "start": 1429.44, "duration": 3.54}, {"text": "dependent on.", "start": 1432.98, "duration": 0.96}, {"text": "So this dependency on\ngrowth signals is important,", "start": 1438.71, "duration": 3.99}, {"text": "clinically, because\nsome types of cancer,", "start": 1442.7, "duration": 5.4}, {"text": "there is an elevation of\ngrowth factor receptors", "start": 1448.1, "duration": 3.06}, {"text": "that are associated\nwith the cancer.", "start": 1451.16, "duration": 2.49}, {"text": "And the famous example of that\nis, in 30% of breast cancers,", "start": 1453.65, "duration": 6.48}, {"text": "there is a growth factor\nreceptor, the HER2 receptor,", "start": 1460.13, "duration": 3.85}, {"text": "which is over expressed\nin the cancer cells.", "start": 1463.98, "duration": 5.0}, {"text": "So I just drew a receptor\nhere, and I'm now talking", "start": 1468.98, "duration": 4.77}, {"text": "about the HER2 receptor.", "start": 1473.75, "duration": 1.95}, {"text": "HER2 stands for human epidermal\ngrowth factor, EGF, receptor 2.", "start": 1475.7, "duration": 8.19}, {"text": "So this is a receptor\ntyrosine kinase,", "start": 1487.55, "duration": 4.5}, {"text": "which is a transmembrane\nprotein receptor.", "start": 1492.05, "duration": 2.85}, {"text": "It's expressed on the\nsurface of the cell.", "start": 1494.9, "duration": 3.03}, {"text": "And so about 30% of\nhuman breast cancers", "start": 1497.93, "duration": 6.87}, {"text": "are HER2 positive, which means\nthat the cancer cells are over", "start": 1504.8, "duration": 12.06}, {"text": "expressing this receptor\ntyrosine kinase.", "start": 1516.86, "duration": 4.08}, {"text": "The fact that you have these\ncancer cells over expressing", "start": 1520.94, "duration": 4.41}, {"text": "a growth factor\nreceptor suggests", "start": 1525.35, "duration": 2.88}, {"text": "that the cancer\nrequires some type", "start": 1528.23, "duration": 4.32}, {"text": "of growth stimulus in order\nfor the cancer to be growing.", "start": 1532.55, "duration": 7.11}, {"text": "And the fact that\nthis was discovered,", "start": 1539.66, "duration": 4.23}, {"text": "that 30% of breast\ncancers over express HER2,", "start": 1543.89, "duration": 4.38}, {"text": "has been used by\nresearchers to develop", "start": 1548.27, "duration": 3.24}, {"text": "a treatment for this type of\ncancer, this HER2 positive.", "start": 1551.51, "duration": 4.59}, {"text": "The treatment is\nknown as Herceptin.", "start": 1556.1, "duration": 5.07}, {"text": "Possibly some of you\nhave heard of this.", "start": 1561.17, "duration": 2.94}, {"text": "It was developed at Genentech.", "start": 1564.11, "duration": 3.04}, {"text": "And what Herceptin\nis, it's an antibody", "start": 1567.15, "duration": 5.03}, {"text": "that was raised against\na human HER2 protein.", "start": 1572.18, "duration": 4.8}, {"text": "OK.", "start": 1576.98, "duration": 0.81}, {"text": "So Herceptin is an antibody.", "start": 1577.79, "duration": 2.64}, {"text": "It recognizes HER2 on the\nsurface of these cancer cells,", "start": 1583.11, "duration": 5.97}, {"text": "and you can treat patients\nwith this antibody,", "start": 1589.08, "duration": 4.07}, {"text": "and an antibody binds to\nthe HER2 positive cells.", "start": 1593.15, "duration": 3.93}, {"text": "And it either blocks\nthe function of HER2", "start": 1597.08, "duration": 3.12}, {"text": "or recruits immune cells\nto kill those cells off.", "start": 1600.2, "duration": 3.87}, {"text": "The exact mechanism, I\ndon't believe, is known.", "start": 1604.07, "duration": 3.94}, {"text": "But what is known is\nthat Herceptin has really", "start": 1608.01, "duration": 2.3}, {"text": "changed how we're able to treat\nHER2 positive breast cancers.", "start": 1610.31, "duration": 5.98}, {"text": "And it's been a\nhuge success story", "start": 1616.29, "duration": 3.2}, {"text": "in the fight against cancer.", "start": 1619.49, "duration": 1.425}, {"text": "All right.", "start": 1629.26, "duration": 0.52}, {"text": "So we've talked about this first\nbarrier, the barrier to tumor", "start": 1629.78, "duration": 8.26}, {"text": "cells becoming at\nleast semi-independent", "start": 1638.04, "duration": 3.27}, {"text": "of these growth factors.", "start": 1641.31, "duration": 3.75}, {"text": "And so now I want to\ntalk about other barriers", "start": 1645.06, "duration": 2.82}, {"text": "to tumor genesis.", "start": 1647.88, "duration": 2.08}, {"text": "And if you consider an\nepithelial cell here,", "start": 1649.96, "duration": 3.23}, {"text": "even if these cells\nare able to grow,", "start": 1653.19, "duration": 2.43}, {"text": "they won't be able\nto leave the organ", "start": 1655.62, "duration": 2.88}, {"text": "until something else happens.", "start": 1658.5, "duration": 2.43}, {"text": "And one thing that would need\nto happen for these cells", "start": 1660.93, "duration": 2.64}, {"text": "to become malignant and to\nleave the organ that they were", "start": 1663.57, "duration": 4.08}, {"text": "initially part of is for\nthere to be a breakdown", "start": 1667.65, "duration": 4.92}, {"text": "in the adhesion between cells.", "start": 1672.57, "duration": 2.97}, {"text": "So for the next\nfew minutes, I want", "start": 1675.54, "duration": 3.72}, {"text": "to talk about the breakdown\nin cell-to-cell adhesion.", "start": 1679.26, "duration": 4.59}, {"text": "So how would a\ncancer cell basically", "start": 1692.28, "duration": 4.8}, {"text": "unstick itself\nfrom the cells that", "start": 1697.08, "duration": 2.43}, {"text": "surround it in order to leave\nan organ and go somewhere else?", "start": 1699.51, "duration": 5.64}, {"text": "And for that, to explain\nthat, I have to remind you", "start": 1707.67, "duration": 2.85}, {"text": "about some of the normal biology\nof these epithelial cells,", "start": 1710.52, "duration": 4.69}, {"text": "which we talked\nabout earlier, which", "start": 1715.21, "duration": 1.97}, {"text": "is that they express these\ntransmembrane proteins", "start": 1717.18, "duration": 4.02}, {"text": "that are adhesion proteins.", "start": 1721.2, "duration": 2.37}, {"text": "So normally, epithelial\ncells have adhesion proteins.", "start": 1723.57, "duration": 3.66}, {"text": "And the famous\none for epithelia,", "start": 1730.5, "duration": 2.19}, {"text": "or one of the famous\nones, is called", "start": 1732.69, "duration": 3.06}, {"text": "epithelial or E-cadherin.", "start": 1735.75, "duration": 2.74}, {"text": "And E-cadherin is a\ntransmembrane protein.", "start": 1743.38, "duration": 3.62}, {"text": "It has an extracellular\ndomain, but rather", "start": 1747.0, "duration": 3.42}, {"text": "than that extracellular\ndomain binding", "start": 1750.42, "duration": 2.79}, {"text": "to some secreted ligand,\nthis extracellular domain", "start": 1753.21, "duration": 4.01}, {"text": "recognizes E-cadherin\nmolecules on other cells,", "start": 1757.22, "duration": 3.97}, {"text": "and they stick to each other.", "start": 1761.19, "duration": 1.56}, {"text": "And it essentially functions\nlike cellular Velcro.", "start": 1762.75, "duration": 3.48}, {"text": "So the cells link together, and\nthey stick to each other such", "start": 1766.23, "duration": 4.11}, {"text": "that they form a\ncoherent tissue.", "start": 1770.34, "duration": 1.545}, {"text": "So the way that cancer\ncells subvert this mechanism", "start": 1775.96, "duration": 7.19}, {"text": "of adhesion is, they\nhave to do something", "start": 1783.15, "duration": 3.33}, {"text": "that inhibits E-cadherin.", "start": 1786.48, "duration": 3.33}, {"text": "And so cancer cells,\nwhat they can do", "start": 1789.81, "duration": 4.92}, {"text": "is to decrease the\ncell-to-cell adhesion,", "start": 1794.73, "duration": 4.65}, {"text": "and I'll tell you\nhow in just a minute.", "start": 1799.38, "duration": 1.89}, {"text": "And in addition to decreasing\nthis cell-to-cell adhesion,", "start": 1804.75, "duration": 3.54}, {"text": "they can also promote the genes\nthat are involved in motility.", "start": 1808.29, "duration": 6.93}, {"text": "So we have to\nunderstand, then, how", "start": 1823.85, "duration": 3.66}, {"text": "it is a cancer cell would\ndo both of these things.", "start": 1827.51, "duration": 4.11}, {"text": "And I'll start with\ncell-to-cell adhesion.", "start": 1831.62, "duration": 3.6}, {"text": "And in contrast to what we've\ntalked about with the growth", "start": 1835.22, "duration": 4.11}, {"text": "and survival signaling, where\nyou have mutations that happen", "start": 1839.33, "duration": 3.78}, {"text": "in cancer cells,\nand you basically", "start": 1843.11, "duration": 1.98}, {"text": "have an irreversible change\nto the genome of the cell,", "start": 1845.09, "duration": 4.36}, {"text": "this change in the adhesive\nproperties of the cell,", "start": 1849.45, "duration": 6.83}, {"text": "and essentially\ntheir cell state--", "start": 1856.28, "duration": 1.98}, {"text": "because what you see\nhere, if a cancer cell is", "start": 1858.26, "duration": 3.45}, {"text": "having less adhesion and\ngetting more migratory,", "start": 1861.71, "duration": 4.08}, {"text": "it's switching from an\nepithelial type of state", "start": 1865.79, "duration": 4.14}, {"text": "to a mesenchymal type of state.", "start": 1869.93, "duration": 3.15}, {"text": "And what this is called is\nan epithelial-to-mesenchymal", "start": 1873.08, "duration": 10.17}, {"text": "transition, and that\nis EMT, for short.", "start": 1883.25, "duration": 12.83}, {"text": "And this EMT is not\na genetic change.", "start": 1900.03, "duration": 3.18}, {"text": "It's not caused by\na genetic change,", "start": 1903.21, "duration": 2.73}, {"text": "but it appears that EMT\nresults from changes", "start": 1905.94, "duration": 4.29}, {"text": "in gene regulation.", "start": 1910.23, "duration": 1.57}, {"text": "So you can think of it as\nmore of an epigenetic change,", "start": 1911.8, "duration": 7.79}, {"text": "an epigenetic change\nin gene expression.", "start": 1919.59, "duration": 7.87}, {"text": "So there's a change\nin gene expression", "start": 1927.46, "duration": 3.89}, {"text": "such that this can\nreverse later on.", "start": 1931.35, "duration": 2.19}, {"text": "And there are master\nregulators of this process,", "start": 1941.73, "duration": 3.91}, {"text": "which alter gene expression.", "start": 1945.64, "duration": 1.92}, {"text": "And so the type of gene\nthat alters gene expression,", "start": 1947.56, "duration": 5.25}, {"text": "these are often called\ntranscription factors.", "start": 1952.81, "duration": 2.555}, {"text": "And there are several\ntranscription factors", "start": 1963.03, "duration": 3.12}, {"text": "that are master regulators\nof this EMT process.", "start": 1966.15, "duration": 3.015}, {"text": "And their names\nare Twist, Snail--", "start": 1971.67, "duration": 5.475}, {"text": "another one's called Slug.", "start": 1980.64, "duration": 2.89}, {"text": "There's an Escargot.", "start": 1983.53, "duration": 1.1}, {"text": "You can see this got\na little out of hand.", "start": 1984.63, "duration": 2.7}, {"text": "And you can tell by the\nnames that they probably", "start": 1987.33, "duration": 3.81}, {"text": "were not discovered in humans.", "start": 1991.14, "duration": 2.19}, {"text": "And in fact, these\ngenes were discovered", "start": 1993.33, "duration": 3.06}, {"text": "in the same genetic screen\nthat I outlined before,", "start": 1996.39, "duration": 3.21}, {"text": "where Hedgehog was discovered.", "start": 1999.6, "duration": 1.87}, {"text": "OK.", "start": 2001.47, "duration": 0.5}, {"text": "So it was a genetic\nscreen in the flies,", "start": 2001.97, "duration": 3.78}, {"text": "and these are genes that affect\nthe embryonic development", "start": 2005.75, "duration": 4.35}, {"text": "of the fly.", "start": 2010.1, "duration": 2.16}, {"text": "And I'll show you this\nview of the fly embryo.", "start": 2012.26, "duration": 5.35}, {"text": "So this is an embryo\nhere, and you see,", "start": 2017.61, "duration": 2.15}, {"text": "it's an epithelial sheet\nsurrounding the yolk.", "start": 2019.76, "duration": 3.93}, {"text": "And what happens is, in\nearly stages of development,", "start": 2023.69, "duration": 3.54}, {"text": "a population of cells\nexpress the Twist gene.", "start": 2027.23, "duration": 3.87}, {"text": "So that's Twist\nin the dark here.", "start": 2031.1, "duration": 3.03}, {"text": "And this Twist gene causes\nthese cells to basically invade", "start": 2034.13, "duration": 4.59}, {"text": "into the middle of the embryo.", "start": 2038.72, "duration": 2.76}, {"text": "So here are the Twist\ncells now, going", "start": 2041.48, "duration": 1.95}, {"text": "into the inside of the embryo.", "start": 2043.43, "duration": 2.97}, {"text": "And then these\ncells undergo EMT,", "start": 2046.4, "duration": 2.13}, {"text": "and they start to migrate\naround inside the embryo.", "start": 2048.53, "duration": 3.959}, {"text": "What this is doing\nfor the fly is", "start": 2052.489, "duration": 2.281}, {"text": "that these are the\ncells that are going on", "start": 2054.77, "duration": 2.369}, {"text": "to form the muscle.", "start": 2057.139, "duration": 2.75}, {"text": "And if you look\nat your neighbor,", "start": 2059.889, "duration": 1.506}, {"text": "you might notice that\ntheir muscles are", "start": 2061.395, "duration": 1.625}, {"text": "on the inside of their body.", "start": 2063.02, "duration": 2.19}, {"text": "So this process is basically\nputting these cells,", "start": 2065.21, "duration": 6.27}, {"text": "by getting them to move,\nit's putting the cells", "start": 2071.48, "duration": 2.4}, {"text": "in the right place\nfor what they are", "start": 2073.88, "duration": 2.009}, {"text": "going to differentiate into\nduring embryonic development.", "start": 2075.889, "duration": 3.571}, {"text": "But this process, if\nactivated during cancer,", "start": 2082.37, "duration": 4.289}, {"text": "can allow these cells to be more\nmobile and to leave one organ", "start": 2086.659, "duration": 4.651}, {"text": "and go into another organ.", "start": 2091.31, "duration": 2.7}, {"text": "So cancer isn't inventing\nanything new here.", "start": 2094.01, "duration": 4.02}, {"text": "It's corrupting a normal\nprogram that cells have and need", "start": 2098.03, "duration": 3.9}, {"text": "during development, and\nit's inactivating it", "start": 2101.93, "duration": 2.82}, {"text": "at an inappropriate time.", "start": 2104.75, "duration": 3.12}, {"text": "So these are all\ntranscription factors.", "start": 2107.87, "duration": 2.88}, {"text": "And what they do\nis, they repress", "start": 2110.75, "duration": 3.66}, {"text": "the expression or\nfunction of cadherin", "start": 2114.41, "duration": 4.47}, {"text": "such that the cells are\nno longer as sticky.", "start": 2118.88, "duration": 4.41}, {"text": "So basically, when these\ntranscription factors", "start": 2123.29, "duration": 2.7}, {"text": "get turned on, it\nmakes the cells", "start": 2125.99, "duration": 2.13}, {"text": "less sticky to each other.", "start": 2128.12, "duration": 2.35}, {"text": "And it also promotes\ntheir migration.", "start": 2130.47, "duration": 2.42}, {"text": "So it turns on genes that\nare important for migration.", "start": 2132.89, "duration": 2.82}, {"text": "This process of EMT, as I\nmentioned, is reversible,", "start": 2139.4, "duration": 4.8}, {"text": "and it also involves\ninteractions between tumor", "start": 2144.2, "duration": 3.21}, {"text": "and stromal cells.", "start": 2147.41, "duration": 2.41}, {"text": "I'll show you an example of--", "start": 2149.82, "duration": 2.78}, {"text": "so in the fly embryo, one thing\nthat's nice about the flies", "start": 2152.6, "duration": 4.41}, {"text": "is, you can actually\nwatch this happen live.", "start": 2157.01, "duration": 3.78}, {"text": "And so I'm going to show\nyou a movie now, showing you", "start": 2160.79, "duration": 3.36}, {"text": "the invasion process.", "start": 2164.15, "duration": 2.202}, {"text": "We're going to have\nan embryo here.", "start": 2166.352, "duration": 1.458}, {"text": "And what I'm going\nto show you is,", "start": 2173.46, "duration": 1.73}, {"text": "we're looking at the cells that\nare expressing Twist and Snail,", "start": 2175.19, "duration": 3.79}, {"text": "and they're on one\nside of the embryo.", "start": 2178.98, "duration": 2.84}, {"text": "And I'm going to show you a\nsection of the embryo that", "start": 2181.82, "duration": 3.54}, {"text": "is analogous to this.", "start": 2185.36, "duration": 3.12}, {"text": "So when the cells\nmove inside, they're", "start": 2188.48, "duration": 2.88}, {"text": "going to disappear\nin this movie.", "start": 2191.36, "duration": 2.01}, {"text": "So when you see the\ncrease in the embryo,", "start": 2193.37, "duration": 3.33}, {"text": "that's when the\ncells are invading", "start": 2196.7, "duration": 1.47}, {"text": "into the middle of the embryo.", "start": 2198.17, "duration": 2.37}, {"text": "And so the cell outlines\nare in magenta here.", "start": 2200.54, "duration": 3.57}, {"text": "And what's labeled in green\nis a type of motor protein", "start": 2204.11, "duration": 4.86}, {"text": "that's involved in the mobility\nof cells and, in this case,", "start": 2208.97, "duration": 3.72}, {"text": "is involved in\nthese cells moving", "start": 2212.69, "duration": 1.74}, {"text": "into the interior of the embryo.", "start": 2214.43, "duration": 3.37}, {"text": "So here, you see the\nmotor protein appearing,", "start": 2217.8, "duration": 2.24}, {"text": "and that's when these cells are\ngoing to dive into the embryo.", "start": 2220.04, "duration": 2.957}, {"text": "So it's almost like a waterfall.", "start": 2222.997, "duration": 1.333}, {"text": "These cells are moving into\nthe inside of the embryo", "start": 2224.33, "duration": 4.23}, {"text": "through this process of\ninvagination and, subsequently,", "start": 2228.56, "duration": 4.29}, {"text": "EMT.", "start": 2232.85, "duration": 1.65}, {"text": "There it goes again.", "start": 2234.5, "duration": 1.317}, {"text": "You can see the cells\nare now on the inside.", "start": 2235.817, "duration": 1.833}, {"text": "So this process of\nEMT also involves", "start": 2240.26, "duration": 2.91}, {"text": "interactions between the\ncancer cells and the stroma.", "start": 2243.17, "duration": 4.74}, {"text": "And that's illustrated here\nbecause what you can see,", "start": 2247.91, "duration": 3.413}, {"text": "what's being labeled\nhere, you can", "start": 2251.323, "duration": 1.417}, {"text": "see the nuclei of the\ncells, but these cells", "start": 2252.74, "duration": 4.35}, {"text": "at the edge of the tumor are\nup-regulating this gene, which", "start": 2257.09, "duration": 4.05}, {"text": "is an alpha-beta integrin, which\nI'll mention in just a minute.", "start": 2261.14, "duration": 3.96}, {"text": "And this is getting\nup-regulated right where", "start": 2265.1, "duration": 2.01}, {"text": "the tumor contacts the stroma.", "start": 2267.11, "duration": 2.25}, {"text": "And this gene,\nalpha-beta integrin,", "start": 2269.36, "duration": 2.07}, {"text": "is a gene that's associated\nwith motility and EMT.", "start": 2271.43, "duration": 4.77}, {"text": "So on that slide here, one\ngene involved in motility", "start": 2276.2, "duration": 4.52}, {"text": "is a class of genes\ncalled integrins.", "start": 2280.72, "duration": 2.1}, {"text": "And so this also results from\nthe signaling between the tumor", "start": 2286.25, "duration": 5.82}, {"text": "and the surrounding cells.", "start": 2292.07, "duration": 2.32}, {"text": "And again, this is not\nsomething that cancer created.", "start": 2294.39, "duration": 3.44}, {"text": "This is what happens\nduring wound healing.", "start": 2297.83, "duration": 2.92}, {"text": "So during wound healing,\nif you injure yourself,", "start": 2300.75, "duration": 3.75}, {"text": "the wound recruits immune\ncells, and the immune cells", "start": 2304.5, "duration": 3.05}, {"text": "signal to the surrounding\nskin or epithelial cells", "start": 2307.55, "duration": 3.75}, {"text": "to undergo EMT in order to\nclose and fill in the wound.", "start": 2311.3, "duration": 4.71}, {"text": "So this is a\nnatural process that", "start": 2316.01, "duration": 3.15}, {"text": "happens in your body\nthat is simply getting", "start": 2319.16, "duration": 2.49}, {"text": "corrupted by cancer cells.", "start": 2321.65, "duration": 2.04}, {"text": "All right.", "start": 2327.62, "duration": 0.5}, {"text": "So now let's talk about\nthis last step of motility.", "start": 2328.12, "duration": 3.87}, {"text": "So this is now how the cells\nwould break out and move away.", "start": 2334.55, "duration": 7.14}, {"text": "Let's come back to\nthis movie here.", "start": 2349.28, "duration": 2.29}, {"text": "There are a few things I want\nyou to notice about this movie.", "start": 2351.57, "duration": 3.38}, {"text": "The first is, holy shit,\nthat cell is moving.", "start": 2354.95, "duration": 4.74}, {"text": "And so the first aspect of this\nis, because the cell is moving,", "start": 2359.69, "duration": 7.2}, {"text": "it suggests that there's some\nsort of force being generated.", "start": 2366.89, "duration": 4.2}, {"text": "So the cell is generating force.", "start": 2371.09, "duration": 8.84}, {"text": "And I'm not talking about like\nsome type of mystical Jedi", "start": 2379.93, "duration": 3.17}, {"text": "force.", "start": 2383.1, "duration": 0.78}, {"text": "I'm talking about the mass\ntimes acceleration force,", "start": 2383.88, "duration": 4.14}, {"text": "so like a physical force, OK?", "start": 2388.02, "duration": 2.43}, {"text": "The second thing I want to\npoint out about this movie", "start": 2390.45, "duration": 3.39}, {"text": "is that you see that bacterium,\nand it's moving around,", "start": 2393.84, "duration": 3.66}, {"text": "this cell is able to\nfollow that bacterium.", "start": 2397.5, "duration": 3.09}, {"text": "So the cell, in the\nforce generation process,", "start": 2400.59, "duration": 3.06}, {"text": "is very responsive\nto the signals", "start": 2403.65, "duration": 2.85}, {"text": "that that cell is getting.", "start": 2406.5, "duration": 2.25}, {"text": "So the cell is generating\nforce, and this force", "start": 2408.75, "duration": 3.81}, {"text": "is responsive to signals.", "start": 2412.56, "duration": 1.695}, {"text": "So for the remaining\npart of the lecture,", "start": 2422.79, "duration": 2.07}, {"text": "I basically just\nwant to tell you", "start": 2424.86, "duration": 1.65}, {"text": "about how it is that the cell\ngenerates the force required", "start": 2426.51, "duration": 4.08}, {"text": "to move itself around.", "start": 2430.59, "duration": 3.66}, {"text": "And it involves a\nparticular type of protein.", "start": 2434.25, "duration": 4.33}, {"text": "It's a component of\nthe cytoskeleton,", "start": 2438.58, "duration": 1.94}, {"text": "and we've talked\nabout microtubules", "start": 2440.52, "duration": 2.13}, {"text": "and the microtubule\ncytoskeleton and its role", "start": 2442.65, "duration": 2.37}, {"text": "in segregating the chromosome.", "start": 2445.02, "duration": 2.04}, {"text": "But there are other cytoskeletal\nsystems that the cell has,", "start": 2447.06, "duration": 4.41}, {"text": "and one is called the\nactin cytoskeleton, which", "start": 2451.47, "duration": 3.81}, {"text": "is shown on the side above.", "start": 2455.28, "duration": 3.66}, {"text": "And actin, the\nactin cytoskeleton,", "start": 2458.94, "duration": 3.66}, {"text": "is a system that is a\nbiopolymer in the cell.", "start": 2462.6, "duration": 3.43}, {"text": "So this is a biopolymer,\nlike microtubules.", "start": 2466.03, "duration": 5.84}, {"text": "And actin is a gene.", "start": 2471.87, "duration": 2.26}, {"text": "And the actin gene encodes for\na protein, the actin protein,", "start": 2474.13, "duration": 4.32}, {"text": "and when the actin protein\nis made in the cell,", "start": 2478.45, "duration": 3.16}, {"text": "it starts out as being just\na single globular protein.", "start": 2481.61, "duration": 5.17}, {"text": "And when the actin\nis in this state,", "start": 2486.78, "duration": 3.18}, {"text": "it is called\nglobular or G-actin.", "start": 2489.96, "duration": 5.04}, {"text": "But these subunits,\nthese proteins,", "start": 2498.51, "duration": 3.36}, {"text": "can come together\nand form a polymer.", "start": 2501.87, "duration": 3.54}, {"text": "So they can go from being\nindividual, isolated proteins", "start": 2505.41, "duration": 4.23}, {"text": "to forming a polymer that\nforms a long skinny filament.", "start": 2509.64, "duration": 3.825}, {"text": "And this form of the protein\nthat's forming a biopolymer", "start": 2519.99, "duration": 5.13}, {"text": "is known as\nfilamentous or F-actin.", "start": 2525.12, "duration": 3.09}, {"text": "And these are long,\nskinny filaments.", "start": 2538.13, "duration": 2.61}, {"text": "They can be hundreds\nof nanometers,", "start": 2540.74, "duration": 2.88}, {"text": "even microns, in length, so\nhundreds of nanometers long.", "start": 2543.62, "duration": 4.98}, {"text": "And the filament width\nis about 10 nanometers.", "start": 2548.6, "duration": 3.45}, {"text": "So I'm just trying to give\nyou a sense of dimensions,", "start": 2552.05, "duration": 2.49}, {"text": "that this is a long, skinny\nfilament that the cell can", "start": 2554.54, "duration": 5.58}, {"text": "assemble.", "start": 2560.12, "duration": 0.81}, {"text": "And it assembles into these\ndense meshworks, which you", "start": 2560.93, "duration": 3.33}, {"text": "can see in the slide up here.", "start": 2564.26, "duration": 2.97}, {"text": "So this is the leading\nedge of the cell.", "start": 2567.23, "duration": 2.11}, {"text": "So the cell would be\nmigrating this way.", "start": 2569.34, "duration": 2.3}, {"text": "And what you see in this cell is\nthis densely branched network,", "start": 2571.64, "duration": 5.88}, {"text": "and these are all\nactin filaments.", "start": 2577.52, "duration": 2.7}, {"text": "So you get this huge dense\nforest of actin filaments", "start": 2580.22, "duration": 5.13}, {"text": "that's right at the edge of the\ncell that is moving forward.", "start": 2585.35, "duration": 3.285}, {"text": "One thing I want to point out\nis, like all things in biology,", "start": 2591.65, "duration": 3.72}, {"text": "this is not a one-way street.", "start": 2595.37, "duration": 2.62}, {"text": "And so these biopolymers\nare very dynamic,", "start": 2597.99, "duration": 3.75}, {"text": "meaning they can undergo\nassembly and disassembly,", "start": 2601.74, "duration": 2.9}, {"text": "and they can do so on\nthe timescale of seconds.", "start": 2604.64, "duration": 4.32}, {"text": "One last thing I want to point\nout about the actin filament", "start": 2608.96, "duration": 3.45}, {"text": "is, there's a polarity\nto the filament such", "start": 2612.41, "duration": 3.87}, {"text": "that there's an end,\nknown as the plus end,", "start": 2616.28, "duration": 2.91}, {"text": "where growth is\nfavored, and there's", "start": 2619.19, "duration": 2.13}, {"text": "an end, known as the\nminus end, where there's", "start": 2621.32, "duration": 2.52}, {"text": "often de-polymerization.", "start": 2623.84, "duration": 1.92}, {"text": "So you can get a directional\ngrowth of the filament.", "start": 2625.76, "duration": 3.96}, {"text": "So this is where growth happens.", "start": 2629.72, "duration": 1.41}, {"text": "And so in this network\nthat you're looking at,", "start": 2635.37, "duration": 2.81}, {"text": "the way the actin is oriented--", "start": 2638.18, "duration": 2.01}, {"text": "so I'm going to draw\njust a cell here--", "start": 2640.19, "duration": 3.33}, {"text": "you have this dense meshwork\nof actin, and in this meshwork,", "start": 2643.52, "duration": 8.31}, {"text": "there's a polarity to the\nway the actin filaments are", "start": 2651.83, "duration": 2.76}, {"text": "oriented.", "start": 2654.59, "duration": 1.15}, {"text": "So the cell is\nmigrating this way,", "start": 2655.74, "duration": 2.6}, {"text": "and the plus ends of\nthe actin filaments", "start": 2658.34, "duration": 2.76}, {"text": "are facing out right\nat the surface.", "start": 2661.1, "duration": 2.64}, {"text": "And the minus ends\nare back here.", "start": 2663.74, "duration": 3.57}, {"text": "And so what you have, when\nthe cell is migrating,", "start": 2667.31, "duration": 3.15}, {"text": "is you have this\nbiopolymer network that's", "start": 2670.46, "duration": 3.93}, {"text": "growing on this end, but\nshrinking on the other end.", "start": 2674.39, "duration": 3.63}, {"text": "And that allows the cell to\ngenerate a constant protrusive", "start": 2678.02, "duration": 4.53}, {"text": "force.", "start": 2682.55, "duration": 1.74}, {"text": "So it's the growth\nof actin filaments,", "start": 2684.29, "duration": 3.21}, {"text": "the growth of F-actin, which\ngenerates a protrusive force.", "start": 2687.5, "duration": 8.12}, {"text": "Now if we consider the whole\nprocess of cell migration, what", "start": 2704.34, "duration": 3.93}, {"text": "you can see is that\ninitially, you're", "start": 2708.27, "duration": 2.37}, {"text": "going to push the\ncell membrane forward.", "start": 2710.64, "duration": 3.45}, {"text": "So you get a protrusion.", "start": 2714.09, "duration": 1.95}, {"text": "It pushes it forward.", "start": 2716.04, "duration": 1.65}, {"text": "That's often called a\nlamellipodium, or a pseudopod,", "start": 2717.69, "duration": 5.04}, {"text": "and so this part of\nthe cell moves forward.", "start": 2722.73, "duration": 3.49}, {"text": "But in order for the cell to\nhave a net motion forward,", "start": 2726.22, "duration": 3.95}, {"text": "it then has to stabilize\nthat protrusion.", "start": 2730.17, "duration": 2.82}, {"text": "And it stabilizes the protrusion\nby adhering to the substrate.", "start": 2732.99, "duration": 4.508}, {"text": "So right now, we're\njust considering a cell", "start": 2737.498, "duration": 1.792}, {"text": "moving on a flat substrate.", "start": 2739.29, "duration": 4.05}, {"text": "And so the way it\nattaches to the substrate", "start": 2743.34, "duration": 2.91}, {"text": "is through cell matrix adhesion.", "start": 2746.25, "duration": 1.905}, {"text": "And this cell matrix\nadhesion is mediated", "start": 2751.17, "duration": 2.76}, {"text": "by another type of adhesion\nreceptor known as an integrin.", "start": 2753.93, "duration": 3.81}, {"text": "So the cell pushes\nforward, anchors itself", "start": 2763.86, "duration": 3.21}, {"text": "on the substrate, pulls its\nbody along, and then just", "start": 2767.07, "duration": 3.45}, {"text": "repeats that cycle\nover and over again.", "start": 2770.52, "duration": 3.46}, {"text": "So the best way I can illustrate\nthis is, if you think about it,", "start": 2773.98, "duration": 7.58}, {"text": "you get your protrusion.", "start": 2781.56, "duration": 1.38}, {"text": "You get your elbow out.", "start": 2782.94, "duration": 1.71}, {"text": "You put down.", "start": 2784.65, "duration": 0.93}, {"text": "You anchor.", "start": 2785.58, "duration": 1.9}, {"text": "And it's just a\nrepeated cycle, and it's", "start": 2787.48, "duration": 2.39}, {"text": "able to migrate\nacross the substrate.", "start": 2789.87, "duration": 3.49}, {"text": "So it's kind of like a\nfrontal toe mechanism.", "start": 2793.36, "duration": 3.65}, {"text": "You have cycles of protrusion.", "start": 2797.01, "duration": 2.34}, {"text": "You generate\ntraction, and then you", "start": 2799.35, "duration": 2.43}, {"text": "pull, in order to translocate.", "start": 2801.78, "duration": 2.48}, {"text": "And so that's how cells\nare migrating intuitively.", "start": 2804.26, "duration": 4.96}, {"text": "This is just showing you\nthat cells can pull on stuff.", "start": 2809.22, "duration": 4.83}, {"text": "So not all cells\nmigrate in this way.", "start": 2814.05, "duration": 2.73}, {"text": "I just wanted to say that.", "start": 2816.78, "duration": 2.16}, {"text": "So 3D cells have\nother mechanisms", "start": 2818.94, "duration": 3.33}, {"text": "to migrate that de-emphasize\nthis traction mechanism", "start": 2822.27, "duration": 4.83}, {"text": "that cells have.", "start": 2827.1, "duration": 2.19}, {"text": "So you can get rid\nof all the integrins", "start": 2829.29, "duration": 2.49}, {"text": "that a cell has, and they're\nstill able to migrate.", "start": 2831.78, "duration": 3.9}, {"text": "And that's because 2D\nemphasizes the role of adhesion,", "start": 2835.68, "duration": 5.38}, {"text": "but if you can find the\ncell, then the cells", "start": 2841.06, "duration": 2.82}, {"text": "are able to migrate.", "start": 2843.88, "duration": 1.75}, {"text": "So what's shown here are\ncells that are not confined.", "start": 2845.63, "duration": 4.25}, {"text": "This is a confined\ncell in a micropipette.", "start": 2849.88, "duration": 3.27}, {"text": "And you can see, it's\nthe same type of cell,", "start": 2853.15, "duration": 2.37}, {"text": "but the cell can\nmigrate in confinement,", "start": 2855.52, "duration": 2.68}, {"text": "but it can't migrate\noutside of confinement.", "start": 2858.2, "duration": 4.43}, {"text": "So in this sense,\nthe cell is migrating", "start": 2862.63, "duration": 2.07}, {"text": "through a different mode.", "start": 2864.7, "duration": 1.71}, {"text": "And you can think\nof it as the cell", "start": 2866.41, "duration": 2.7}, {"text": "is doing some type of\nchimney-ing maneuver.", "start": 2869.11, "duration": 2.85}, {"text": "So it's able to get in a\nconfined environment, push out", "start": 2871.96, "duration": 3.03}, {"text": "against its surroundings,\nand that's how the cell then", "start": 2874.99, "duration": 2.91}, {"text": "is able to generate traction\nin the absence of an integrin", "start": 2877.9, "duration": 3.87}, {"text": "molecule.", "start": 2881.77, "duration": 2.31}, {"text": "All right.", "start": 2884.08, "duration": 0.51}, {"text": "Great.", "start": 2884.59, "duration": 1.05}, {"text": "So we are set for now.", "start": 2885.64, "duration": 4.43}]
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+[{"text": "The following content is provided under a\nCreative Commons license.", "start": 1.11, "duration": 3.72}, {"text": "Your support will help MIT OpenCourseWare\ncontinue to offer high quality educational", "start": 4.83, "duration": 4.47}, {"text": "resources for free.", "start": 9.3, "duration": 1.77}, {"text": "To make a donation or to view additional materials\nfrom hundreds of MIT courses, visit MIT OpenCourseWare", "start": 11.07, "duration": 8.33}, {"text": "at ocw.mit.edu.", "start": 19.4, "duration": 2.03}, {"text": "TADGE DRYJA: So today will be some sort of\nfuture technologies, future developments that", "start": 21.43, "duration": 6.11}, {"text": "might not be around yet, but are interesting\nthings to look for.", "start": 27.54, "duration": 3.55}, {"text": "And if you're interested in researching these\nkinds of things, you want to make a EmenG", "start": 31.09, "duration": 3.51}, {"text": "out of this or want to make a-- who knows?", "start": 34.6, "duration": 3.02}, {"text": "PhD probably is a little overkill for a lot\nof these things.", "start": 37.62, "duration": 4.55}, {"text": "But if you're interested in this kind of research,\nhere's some things we'll talk about today--", "start": 42.17, "duration": 5.36}, {"text": "block slash block filters or committed bloom\nfilters, sharding, accumulators, and UTXO", "start": 47.53, "duration": 6.36}, {"text": "commitments.", "start": 53.89, "duration": 1.0}, {"text": "OK, so, first one I'll talk about is block\nfilters.", "start": 54.89, "duration": 7.62}, {"text": "So I don't think I ever really talked about\nwhat a Bloom filter is.", "start": 62.51, "duration": 4.12}, {"text": "I'm still not really going to explain how\nthey work, but the basic idea, the sort of", "start": 66.63, "duration": 4.9}, {"text": "high level-- here's the prototype.", "start": 71.53, "duration": 2.64}, {"text": "Here's the function prototype.", "start": 74.17, "duration": 1.08}, {"text": "Here's the interface that Bloom filters have.", "start": 75.25, "duration": 2.64}, {"text": "So you make a filter from a bunch of objects.", "start": 77.89, "duration": 4.1}, {"text": "And in this case, objects are just bytes,\nright?", "start": 81.99, "duration": 2.418}, {"text": "Or some string of bytes.", "start": 84.408, "duration": 3.012}, {"text": "And Bloom filters usually use hash functions\nunder the hood.", "start": 87.42, "duration": 2.54}, {"text": "A lot of times, they don't use cryptographic\nhash functions.", "start": 89.96, "duration": 2.448}, {"text": "They can use sort of faster functions, where\nthere may be collisions.", "start": 92.408, "duration": 3.902}, {"text": "But in this case, it's not like a security\nproblem.", "start": 96.31, "duration": 3.39}, {"text": "So you've got a bunch of objects.", "start": 99.7, "duration": 1.739}, {"text": "They might be addresses, which are 20 byte\npubkey hashes, or your UTXOs, which you can", "start": 101.439, "duration": 5.621}, {"text": "represent as a 36 byte TIXD and out point,\nor TIXD and index.", "start": 107.06, "duration": 6.629}, {"text": "So they're small, right?", "start": 113.689, "duration": 1.561}, {"text": "So either 20 bytes, 36 bytes, sometimes 32\nbytes.", "start": 115.25, "duration": 3.979}, {"text": "You put these list of data objects and make\na filter, and you get a filter out.", "start": 119.229, "duration": 5.191}, {"text": "And the filters are usually a kilobyte sometimes.", "start": 124.42, "duration": 5.42}, {"text": "But the idea is it's sort of a mix of hash\nfunctions.", "start": 129.84, "duration": 3.17}, {"text": "And then you say, OK, I want to match filters.", "start": 133.01, "duration": 1.55}, {"text": "Usually, a different person does this and\nsays, OK, I've got a filter that someone generated.", "start": 134.56, "duration": 4.42}, {"text": "And I compare it against this object and see\nif there's a hit, all right?", "start": 138.98, "duration": 4.349}, {"text": "So I see, OK, that matched.", "start": 143.329, "duration": 1.981}, {"text": "This object matched the filter, or this object\ndid not match the filter.", "start": 145.31, "duration": 4.35}, {"text": "And this returns a true or false.", "start": 149.66, "duration": 3.6}, {"text": "And so what's interesting about these is you\ncan have false positives.", "start": 153.26, "duration": 2.47}, {"text": "So it may be that this object was not in here.", "start": 155.73, "duration": 4.259}, {"text": "It was not used when creating the filter,\nbut it still returns true.", "start": 159.989, "duration": 5.58}, {"text": "So it's sort of matching against multiple\ndifferent hash functions, seeing, hey, do", "start": 165.569, "duration": 3.901}, {"text": "any of these bits match?", "start": 169.47, "duration": 1.01}, {"text": "And it says, oh, yeah, this object may have\nbeen in this filter.", "start": 170.48, "duration": 4.63}, {"text": "However, there's no false negatives.", "start": 175.11, "duration": 2.3}, {"text": "So if you did put, say, address A into this\nfilter and then matched this filter against", "start": 177.41, "duration": 7.219}, {"text": "address A, it would always return true.", "start": 184.629, "duration": 2.94}, {"text": "There's no way you can put something into\nthe filter, and then it doesn't show up when", "start": 187.569, "duration": 6.571}, {"text": "you try to match against it.", "start": 194.14, "duration": 2.37}, {"text": "So this is useful for lots of things.", "start": 196.51, "duration": 2.839}, {"text": "Bloom filters are definitely not restricted\nto cryptocurrency, Bitcoin, or anything like", "start": 199.349, "duration": 5.25}, {"text": "that.", "start": 204.599, "duration": 1.0}, {"text": "They're used all the time in various databases,\nall the time in things like that.", "start": 205.599, "duration": 4.541}, {"text": "The current way they're used in Bitcoin is\nfor SPV filtering.", "start": 210.14, "duration": 6.12}, {"text": "So we defined SPV, like, months ago.", "start": 216.26, "duration": 2.36}, {"text": "The basic idea is I'm a client.", "start": 218.62, "duration": 2.63}, {"text": "I don't want to download and verify the whole\nblockchain.", "start": 221.25, "duration": 2.65}, {"text": "I want someone else to do that.", "start": 223.9, "duration": 2.69}, {"text": "I assume the miners are doing the right thing.", "start": 226.59, "duration": 1.83}, {"text": "I assume the rest of the network is doing\nthe right thing.", "start": 228.42, "duration": 2.99}, {"text": "And I just want to know about my data.", "start": 231.41, "duration": 2.54}, {"text": "So I'm not going to download the whole block.", "start": 233.95, "duration": 1.68}, {"text": "I'm not going to verify all the signatures\nor keep a UTXO set on my own.", "start": 235.63, "duration": 4.35}, {"text": "I'm just concerned with my UTXOs in my wallet.", "start": 239.98, "duration": 4.33}, {"text": "So what I do-- and this exists today.", "start": 244.31, "duration": 2.81}, {"text": "You can do this.", "start": 247.12, "duration": 1.99}, {"text": "You make a Bloom filter of all your UTXOs\nand addresses.", "start": 249.11, "duration": 3.31}, {"text": "So you say, OK, here's all my addresses that\nI'm hoping to receive money on.", "start": 252.42, "duration": 4.659}, {"text": "I've got 20 of them, 30 of them, 100 of them--\nhowever many-- although Bloom filters don't", "start": 257.079, "duration": 5.131}, {"text": "really work once you have too many.", "start": 262.21, "duration": 1.629}, {"text": "But so the idea is if you have five addresses,\nlet's say, you start a wallet.", "start": 263.839, "duration": 4.371}, {"text": "You don't have any money.", "start": 268.21, "duration": 1.329}, {"text": "You're pretty sure you don't know of any money\nyet existing.", "start": 269.539, "duration": 3.84}, {"text": "But you say, OK, I made five addresses.", "start": 273.379, "duration": 2.82}, {"text": "I told these addresses to people.", "start": 276.199, "duration": 1.291}, {"text": "They might have sent me money.", "start": 277.49, "duration": 1.079}, {"text": "That'd be nice.", "start": 278.569, "duration": 1.1}, {"text": "So you make a Bloom filter of all these addresses,\nright?", "start": 279.669, "duration": 2.83}, {"text": "So let's say you've got, OK, address A-- dot\ndot dot-- A through E. And you make a filter.", "start": 282.499, "duration": 8.559}, {"text": "OK, so you say I've got my filter F. I then\nsend that filter F to a remote server.", "start": 291.058, "duration": 7.671}, {"text": "So there's the cloud.", "start": 298.729, "duration": 1.15}, {"text": "There's some Bitcoin full node out here.", "start": 299.879, "duration": 4.421}, {"text": "It receives filter F. OK, so this got filter\nF. And it knows that this filter F is specific", "start": 304.3, "duration": 6.359}, {"text": "to me, right?", "start": 310.659, "duration": 1.1}, {"text": "So it sees that, hey, I'm a client.", "start": 311.759, "duration": 5.83}, {"text": "I'm an SPV client.", "start": 317.589, "duration": 1.31}, {"text": "I connect to a full node, and I say, hey,\nI sent a message that's called load filter.", "start": 318.899, "duration": 4.17}, {"text": "And I say, hey, load filter, here's my filter\nF. Only send stuff to me that matches this", "start": 323.069, "duration": 5.57}, {"text": "filter.", "start": 328.639, "duration": 1.49}, {"text": "99% of all the whole thing-- everything going\non in Bitcoin, I don't care about.", "start": 330.129, "duration": 4.929}, {"text": "Here's a filter, and only send me messages\nthat match this filter.", "start": 335.058, "duration": 4.242}, {"text": "And so when it sends a transact-- well, they\nsend INV messages, right?", "start": 339.3, "duration": 6.5}, {"text": "When it sends an INV message with inventory,\nsaying, hey, I found this thing that you might", "start": 345.8, "duration": 3.94}, {"text": "be interested in, normally, a full node to\nanother full node-- so let's say there's communication", "start": 349.74, "duration": 5.47}, {"text": "between two full nodes, Full2.", "start": 355.21, "duration": 5.569}, {"text": "These guys will talk to each other about every\ntransaction they see, right?", "start": 360.779, "duration": 3.431}, {"text": "So if they see a transaction, it's valid.", "start": 364.21, "duration": 2.879}, {"text": "There's nothing wrong with it.", "start": 367.089, "duration": 1.45}, {"text": "They'll just send it to each other to propagate\ntransaction throughout the network, so they", "start": 368.539, "duration": 3.53}, {"text": "can get mined later.", "start": 372.069, "duration": 1.27}, {"text": "However, if a filter has been loaded, it says,\noh, OK, I will only send you INV messages", "start": 373.339, "duration": 5.88}, {"text": "that match this filter.", "start": 379.219, "duration": 1.53}, {"text": "So if there's a transaction that doesn't have\nany of these five addresses as an output,", "start": 380.749, "duration": 4.551}, {"text": "they're just not going to send it to you.", "start": 385.3, "duration": 3.5}, {"text": "Similarly, when a block comes out-- this is\nthe big one.", "start": 388.8, "duration": 4.489}, {"text": "Normally, blocks get propagated the same.", "start": 393.289, "duration": 2.331}, {"text": "They just send you the block.", "start": 395.62, "duration": 2.329}, {"text": "Here, we do something called a Merkle block.", "start": 397.949, "duration": 3.7}, {"text": "I don't send you a regular block.", "start": 401.649, "duration": 2.24}, {"text": "I filter everything within the block and send\nyou only the things that match to that filter.", "start": 403.889, "duration": 7.24}, {"text": "So generally, it gets very small.", "start": 411.129, "duration": 3.681}, {"text": "So the Merkle block might just have one transaction\nin it.", "start": 414.81, "duration": 2.969}, {"text": "And it has the sort of Merkle proof up to\nthe root.", "start": 417.779, "duration": 3.64}, {"text": "So the server sends only the matching transactions\nin the block, which can drop from a megabyte", "start": 421.419, "duration": 4.87}, {"text": "to less than a kilobyte.", "start": 426.289, "duration": 1.9}, {"text": "And then the client says, oh, cool.", "start": 428.189, "duration": 2.32}, {"text": "There's a transaction where I received money.", "start": 430.509, "duration": 2.27}, {"text": "Great.", "start": 432.779, "duration": 1.0}, {"text": "Also, let me update my filter to include this\nnew transaction that I received.", "start": 433.779, "duration": 6.31}, {"text": "So if that gets spent later, I want to know\nabout it, even if it doesn't send to one of", "start": 440.089, "duration": 3.811}, {"text": "these five addresses, right?", "start": 443.9, "duration": 1.25}, {"text": "So if you're only matching on addresses, you\ncan only sort of get money.", "start": 445.15, "duration": 4.21}, {"text": "But if you're matching on these UTXOs, you\ncan lose the money as well.", "start": 449.36, "duration": 5.179}, {"text": "And you don't want to lose money, but you\nsort of want to know when everyone else thinks", "start": 454.539, "duration": 3.94}, {"text": "you lost money.", "start": 458.479, "duration": 2.84}, {"text": "So this works today.", "start": 461.319, "duration": 1.34}, {"text": "This was implemented 2012-ish.", "start": 462.659, "duration": 1.88}, {"text": "The history behind it was the first Android\nBitcoin wallet.", "start": 464.539, "duration": 6.63}, {"text": "Andreas Schildbach wrote it, and it didn't\ndo this, right?", "start": 471.169, "duration": 3.761}, {"text": "It just downloaded the whole block and then\nthrew away most of the data and only kept--", "start": 474.93, "duration": 5.87}, {"text": "it wasn't a full node, and then it didn't\nkeep a UTXO set.", "start": 480.8, "duration": 3.429}, {"text": "But it did download everything.", "start": 484.229, "duration": 3.56}, {"text": "And then they were saying, OK, this is really\nslow.", "start": 487.789, "duration": 1.95}, {"text": "We want a decentralized way to do this kind\nof thing, where instead of just connecting", "start": 489.739, "duration": 5.1}, {"text": "to a server-- so the other model I explained,\nagain, weeks ago was, you just have some server.", "start": 494.839, "duration": 7.05}, {"text": "And you tell it the address and say, hey,\nhere's my address.", "start": 501.889, "duration": 2.23}, {"text": "How much money do I have?", "start": 504.119, "duration": 1.35}, {"text": "And it sends you transactions, and you maintain\nyour wallet that way.", "start": 505.469, "duration": 4.29}, {"text": "This is nicer because it's decentralized,\nright?", "start": 509.759, "duration": 2.441}, {"text": "Every full node can do this.", "start": 512.2, "duration": 1.709}, {"text": "And by default, if you download Bitcoin 0.16\nor whatever recent versions-- not even recent--", "start": 513.909, "duration": 5.3}, {"text": "since like 0.7?", "start": 519.209, "duration": 1.06}, {"text": "I don't know.", "start": 520.269, "duration": 1.88}, {"text": "Most of the versions will have this capability,\nwhere if a client says, hey, here's a Bloom", "start": 522.149, "duration": 7.25}, {"text": "filter.", "start": 529.399, "duration": 1.0}, {"text": "Load it.", "start": 530.399, "duration": 1.0}, {"text": "Your full node will load that filter.", "start": 531.399, "duration": 1.421}, {"text": "And then every block that comes in or every\nblock that's requested, they will match against", "start": 532.82, "duration": 4.689}, {"text": "the filter.", "start": 537.509, "duration": 1.0}, {"text": "The filter match function call's not too heavy.", "start": 538.509, "duration": 2.39}, {"text": "It involves a bunch of hash functions.", "start": 540.899, "duration": 1.38}, {"text": "It's not too slow, but it's slower than doing\nnothing, right?", "start": 542.279, "duration": 3.411}, {"text": "It's slower than just sending it directly.", "start": 545.69, "duration": 1.86}, {"text": "OK, so this is nice, right?", "start": 547.55, "duration": 2.32}, {"text": "You can sync the entire chain in way less\ndata and having SPV security.", "start": 549.87, "duration": 7.62}, {"text": "Problems-- it's really bad for privacy.", "start": 557.49, "duration": 3.17}, {"text": "You're sending a Bloom filter, right?", "start": 560.66, "duration": 1.56}, {"text": "So it's this thing that's created from your\nlist of addresses.", "start": 562.22, "duration": 4.59}, {"text": "But in practice, it's got about the same security\nas just telling them all your addresses, right?", "start": 566.81, "duration": 6.5}, {"text": "So it's sort of like, oh, I'm sending a hash\nof my address, instead of my address.", "start": 573.31, "duration": 3.34}, {"text": "Well, yeah, but I know all the addresses in\nexistence on the Bitcoin network.", "start": 576.65, "duration": 4.45}, {"text": "I can just try to match it, try to hash and\nstuff like that.", "start": 581.1, "duration": 4.54}, {"text": "When you do Bloom filters, there's this sort\nof false positive rate that's sort of a knob", "start": 585.64, "duration": 3.8}, {"text": "you can twist.", "start": 589.44, "duration": 1.0}, {"text": "And you can say, oh, I'm going to make a Bloom\nfilter where 10% of the time, when you perform", "start": 590.44, "duration": 5.56}, {"text": "this match filter for any given object, I'm\ngoing to create a filter where 10% of the", "start": 596.0, "duration": 6.68}, {"text": "time, it'll just return true.", "start": 602.68, "duration": 1.24}, {"text": "So I can dial in a false positive rate.", "start": 603.92, "duration": 1.69}, {"text": "So I can say, OK, I'll make it 1%.", "start": 605.61, "duration": 3.2}, {"text": "And then when I get these matching transactions\nfrom the full node, yeah, I'll get an extra", "start": 608.81, "duration": 8.219}, {"text": "few transactions that don't match my filter.", "start": 617.029, "duration": 2.42}, {"text": "Or they match my filter, but they don't actually\nmatch anything I'm looking at.", "start": 619.449, "duration": 4.711}, {"text": "And that will improve my privacy, right?", "start": 624.16, "duration": 1.93}, {"text": "Because then the full node doesn't see what's--\nhe doesn't know what's truly mine.", "start": 626.09, "duration": 6.01}, {"text": "In fact, you don't even know what the false\npositive rate is.", "start": 632.1, "duration": 3.229}, {"text": "When you receive a filter, you don't know\nwhat the false positive rate is.", "start": 635.329, "duration": 4.331}, {"text": "You just see, OK, these things match, and\nyou send them.", "start": 639.66, "duration": 3.419}, {"text": "Another strategy is OK, I'm a SPV client.", "start": 643.079, "duration": 5.38}, {"text": "I connect to a bunch of full nodes, and I\ncan give different filters to each one.", "start": 648.459, "duration": 7.081}, {"text": "I think the initial software did this.", "start": 655.54, "duration": 2.58}, {"text": "And because you can sort of put some randomness\ninto your different filters to hope-- why", "start": 658.12, "duration": 4.969}, {"text": "did they do this?", "start": 663.089, "duration": 1.701}, {"text": "It actually makes it worse.", "start": 664.79, "duration": 1.87}, {"text": "It actually makes it worse because if these\nfull nodes collude-- collaborate-- whatever.", "start": 666.66, "duration": 5.679}, {"text": "If these full nodes share the information\nof the filters, it makes it easier to determine,", "start": 672.339, "duration": 5.0}, {"text": "to sort of filter out the false positives.", "start": 677.339, "duration": 1.73}, {"text": "Because they'll have different false positives\nbecause they had a different filter.", "start": 679.069, "duration": 3.631}, {"text": "And so if they collaborate, if they work together,\nthey can say, oh, well, I got some false positive", "start": 682.7, "duration": 5.87}, {"text": "transactions.", "start": 688.57, "duration": 1.0}, {"text": "I did, too.", "start": 689.57, "duration": 1.0}, {"text": "We can filter out the ones that one of us\nhad as a false positive and not the other,", "start": 690.57, "duration": 4.42}, {"text": "right?", "start": 694.99, "duration": 1.0}, {"text": "So we can detect the false positives we're\nsending to the client.", "start": 695.99, "duration": 2.55}, {"text": "So privacy is really bad.", "start": 698.54, "duration": 2.489}, {"text": "There's a paper written I think 2013 or 2014,\nwhere they basically broke the whole privacy", "start": 701.029, "duration": 5.161}, {"text": "argument for this Bloom filter based SPV.", "start": 706.19, "duration": 3.589}, {"text": "And they said in practice, you can get like\n90 something percent of the addresses and", "start": 709.779, "duration": 3.98}, {"text": "UTXOs that people are sending for the software.", "start": 713.759, "duration": 3.68}, {"text": "And their recommendations were like, yeah,\nI don't see how you make this work privately.", "start": 717.439, "duration": 5.101}, {"text": "There's just no privacy here.", "start": 722.54, "duration": 2.95}, {"text": "It's slow for the servers, so when you're\nrunning-- I don't know if you can see.", "start": 725.49, "duration": 4.98}, {"text": "When you're running a full node-- OK, I should\nclose that.", "start": 730.47, "duration": 4.83}, {"text": "Don't even know what that is.", "start": 735.3, "duration": 2.279}, {"text": "When you're running a full node, you can see\nhere's all the nodes that are connected to", "start": 737.579, "duration": 11.69}, {"text": "my full node and running downstairs.", "start": 749.269, "duration": 3.521}, {"text": "Most of them are other full nodes.", "start": 752.79, "duration": 2.45}, {"text": "Oh, OK, these are not.", "start": 755.24, "duration": 1.209}, {"text": "I don't know what those are.", "start": 756.449, "duration": 1.281}, {"text": "Those are not true.", "start": 757.73, "duration": 1.58}, {"text": "All these 0.9, 0.99s, they're not actually\nnodes at all.", "start": 759.31, "duration": 2.829}, {"text": "They don't seem to ask for anything.", "start": 762.139, "duration": 2.531}, {"text": "And then some people put their version message.", "start": 764.67, "duration": 2.079}, {"text": "They put an address.", "start": 766.749, "duration": 1.241}, {"text": "Hopefully, someone will send them lots of\nmoney.", "start": 767.99, "duration": 1.81}, {"text": "It's not going to happen.", "start": 769.8, "duration": 2.849}, {"text": "That's weird.", "start": 772.649, "duration": 1.151}, {"text": "There's like no SPV-- well, OK, bitcoinj.", "start": 773.8, "duration": 3.82}, {"text": "So that's a Java implementation, which does\nfilter load.", "start": 777.62, "duration": 5.44}, {"text": "And so we can look-- hm.", "start": 783.06, "duration": 2.759}, {"text": "A fee filter, but no filter load.", "start": 785.819, "duration": 9.01}, {"text": "Well, that's weird.", "start": 794.829, "duration": 2.24}, {"text": "Someone's sending me lots of different fee\nfilter messages.", "start": 797.069, "duration": 2.76}, {"text": "There's lots of weird stuff going on in the\nBitcoin network.", "start": 799.829, "duration": 1.87}, {"text": "But I weirdly don't have any SPV filter load\nthings going on right now, which is unusual.", "start": 801.699, "duration": 6.83}, {"text": "I don't know.", "start": 808.529, "duration": 3.031}, {"text": "It changes a lot, too, based on-- so also,\nyou can sort of track your hourly data usage.", "start": 811.56, "duration": 8.76}, {"text": "And this server basically is only for-- all\nthis traffic is the clients connected.", "start": 820.32, "duration": 5.509}, {"text": "You know, Bitcoin.", "start": 825.829, "duration": 2.19}, {"text": "And so I'm doing, like, a gigabyte every hour,\nwhich is a lot for a home connection, but", "start": 828.019, "duration": 6.37}, {"text": "not too bad for here.", "start": 834.389, "duration": 1.291}, {"text": "But in December, everyone was interested in\nBitcoin.", "start": 835.68, "duration": 2.8}, {"text": "And so you had lots of people downloading\nit, running it.", "start": 838.48, "duration": 2.849}, {"text": "And it would be something like 10 times this,\nwhere just tons of people were installing", "start": 841.329, "duration": 4.43}, {"text": "it, downloading it, getting a whole blockchain,\nand then probably after losing interest, deleting", "start": 845.759, "duration": 5.06}, {"text": "it, but whatever.", "start": 850.819, "duration": 1.63}, {"text": "And a lot of SPV clients doing filter loads\ncan slow down your server.", "start": 852.449, "duration": 5.101}, {"text": "It can take CPU time.", "start": 857.55, "duration": 3.199}, {"text": "Right now, yeah, OK, so 6%, 2%.", "start": 860.749, "duration": 3.75}, {"text": "It's pretty low CPU usage generally for Bitcoin,\neven with that many-- however many that was--", "start": 864.499, "duration": 6.601}, {"text": "30 or 40 different other nodes connecting\nand downloading stuff.", "start": 871.1, "duration": 3.82}, {"text": "Basically, this is like receiving transactions,\nverifying the signatures, and sending them", "start": 874.92, "duration": 4.66}, {"text": "out.", "start": 879.58, "duration": 1.0}, {"text": "And granted-- but this is per core, right?", "start": 880.58, "duration": 1.949}, {"text": "So if I have 2%, that's 2% of a single core.", "start": 882.529, "duration": 3.261}, {"text": "It's really not much.", "start": 885.79, "duration": 1.299}, {"text": "And then I guess Cryptokernel's only using\n1%, so even less.", "start": 887.089, "duration": 5.521}, {"text": "So yeah, it's not much, but when you have\na lot of SPV clients, it can start using a", "start": 892.61, "duration": 7.669}, {"text": "lot of CPU.", "start": 900.279, "duration": 1.73}, {"text": "OK, so how do we improve this?", "start": 902.009, "duration": 3.56}, {"text": "This is a new-ish idea.", "start": 905.569, "duration": 1.291}, {"text": "It's actually about two years old.", "start": 906.86, "duration": 1.909}, {"text": "And it was kind of interesting.", "start": 908.769, "duration": 1.721}, {"text": "It was just a random anonymous internet person\nposted on the mailing list.", "start": 910.49, "duration": 6.219}, {"text": "I think his email address was some inappropriate\nswear word or something.", "start": 916.709, "duration": 4.591}, {"text": "Anyway.", "start": 921.3, "duration": 1.27}, {"text": "But whoever this person was just said, hey,\nwhy don't we do it the other way?", "start": 922.57, "duration": 5.84}, {"text": "Why don't we do it backwards?", "start": 928.41, "duration": 1.76}, {"text": "And instead of having the client create a\nBloom filter and send it to the full node,", "start": 930.17, "duration": 5.849}, {"text": "have the full nodes make Bloom filters from\nall the transactions within a block.", "start": 936.019, "duration": 6.12}, {"text": "And then the client will just ask for that\nfilter.", "start": 942.139, "duration": 3.26}, {"text": "The client can then perform the filter match\nfunction on their own UTXO set.", "start": 945.399, "duration": 6.141}, {"text": "And then if they do find a match, they request\nthe entire block.", "start": 951.54, "duration": 3.669}, {"text": "Right?", "start": 955.209, "duration": 1.11}, {"text": "So this is a different model.", "start": 956.319, "duration": 2.051}, {"text": "I don't know.", "start": 958.37, "duration": 1.2}, {"text": "Does it get the idea where, OK, so you're\na client.", "start": 959.57, "duration": 5.16}, {"text": "All you do is request filters.", "start": 964.73, "duration": 1.549}, {"text": "So you say, filter please.", "start": 966.279, "duration": 2.34}, {"text": "So you have some kind of filter request.", "start": 968.619, "duration": 4.47}, {"text": "And then the full node just says, OK, for\nevery block in the blockchain, I'm going to", "start": 973.089, "duration": 5.081}, {"text": "create a filter, right?", "start": 978.17, "duration": 3.07}, {"text": "I take all the objects in the block, which\nare basically all the addresses used in every", "start": 981.24, "duration": 5.51}, {"text": "transaction, all the UTXOs spent in every\ntransaction.", "start": 986.75, "duration": 3.24}, {"text": "I concatenate that, so there's going to be\n5,000, 10,000-- a lot of these objects.", "start": 989.99, "duration": 5.2}, {"text": "Put it into a really big Bloom filter, generally\nbigger than the ones used in this method.", "start": 995.19, "duration": 4.63}, {"text": "Because usually, a wallet won't have thousands\nof addresses or thousands of UTXOs.", "start": 999.82, "duration": 5.999}, {"text": "It's possible, but in this model, usually,\nyou've got 20, 30, maybe 100.", "start": 1005.819, "duration": 5.091}, {"text": "But in this case, you're going to have thousands.", "start": 1010.91, "duration": 2.409}, {"text": "Make a larger filter, create the filter, and\nstore it for each block.", "start": 1013.319, "duration": 5.14}, {"text": "So maybe it's 20 kilobytes or something.", "start": 1018.459, "duration": 2.291}, {"text": "And maybe in this case, they're only like\n1 kilobyte.", "start": 1020.75, "duration": 2.619}, {"text": "So you have a filter.", "start": 1023.369, "duration": 1.131}, {"text": "And then the node will request these filters\nfor every block.", "start": 1024.5, "duration": 3.439}, {"text": "So it's OK, this block, get the filter.", "start": 1027.939, "duration": 1.0}, {"text": "Get the filter.", "start": 1028.939, "duration": 1.42}, {"text": "And then perform the matching on their own,\nright?", "start": 1030.359, "duration": 3.361}, {"text": "So they've got the filter.", "start": 1033.72, "duration": 1.8}, {"text": "They see, hey, does this filter match any\nof my addresses?", "start": 1035.52, "duration": 3.099}, {"text": "So is there anything in this block that may\nhave paid me or anything in this block where", "start": 1038.619, "duration": 5.07}, {"text": "my transactions may have been spent?", "start": 1043.689, "duration": 3.251}, {"text": "And if they get a true, they just request\nthe whole block.", "start": 1046.94, "duration": 2.62}, {"text": "They just download the whole 1 megabyte block\nor whatever it is.", "start": 1049.56, "duration": 3.749}, {"text": "And there may be false positives, right?", "start": 1053.309, "duration": 1.761}, {"text": "So they might be downloading the block for\nno reason.", "start": 1055.07, "duration": 3.19}, {"text": "They download the whole block, see there's\nnothing of their address.", "start": 1058.26, "duration": 2.63}, {"text": "Yeah.", "start": 1060.89, "duration": 1.0}, {"text": "AUDIENCE: How does that work if we increase\nthe block size to a ridiculous amount?", "start": 1061.89, "duration": 6.602}, {"text": "[INAUDIBLE]", "start": 1068.492, "duration": 1.0}, {"text": "TADGE DRYJA: Wait, ridiculous amount block\nsize?", "start": 1069.492, "duration": 1.0}, {"text": "Yeah, I guess.", "start": 1070.492, "duration": 1.0}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1071.492, "duration": 1.0}, {"text": "TADGE DRYJA: Well, I mean, they're not going\nto actually-- I don't think any of these have", "start": 1072.492, "duration": 6.148}, {"text": "actually 32 megabyte blocks and that no one's\nusing them.", "start": 1078.64, "duration": 4.0}, {"text": "Even Bitcoin now, right, where the actual\nblock usage has gone down substantially.", "start": 1082.64, "duration": 5.669}, {"text": "You've got like-- I don't know-- 500k or something\naverage now?", "start": 1088.309, "duration": 4.34}, {"text": "It's low.", "start": 1092.649, "duration": 1.0}, {"text": "Occasionally, you have lots of little transactions\nsaturating the mempool and then full blocks", "start": 1093.649, "duration": 5.281}, {"text": "for a few hours.", "start": 1098.93, "duration": 1.7}, {"text": "But it's gone down, and it's not even at full\nusage.", "start": 1100.63, "duration": 2.13}, {"text": "So and Bitcoin cash, yeah, you've got 8 megabyte\nmax size, but--", "start": 1102.76, "duration": 4.46}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1107.22, "duration": 1.05}, {"text": "TADGE DRYJA: Right, right.", "start": 1108.27, "duration": 2.11}, {"text": "And they're going to do 32 megs full sized.", "start": 1110.38, "duration": 2.12}, {"text": "But still, the actual blocks are like 10k,\n20k, whatever.", "start": 1112.5, "duration": 5.11}, {"text": "I mean, yeah, but if you did have actually\n32 megabyte blocks, a false positive would", "start": 1117.61, "duration": 7.87}, {"text": "be a big problem for a light node.", "start": 1125.48, "duration": 2.47}, {"text": "Because now you have to download this 32 megabyte\nblock, look through the whole thing.", "start": 1127.95, "duration": 4.0}, {"text": "Actually, there was nothing of interest.", "start": 1131.95, "duration": 2.2}, {"text": "It was a false positive.", "start": 1134.15, "duration": 1.98}, {"text": "OK, try again.", "start": 1136.13, "duration": 3.25}, {"text": "But yeah, you can download 32 megs.", "start": 1139.38, "duration": 2.06}, {"text": "It's not the end of the world.", "start": 1141.44, "duration": 1.619}, {"text": "And if you're only downloading one out of\nevery 100 maybe, if you have a 1% false positive", "start": 1143.059, "duration": 5.251}, {"text": "rate, it's not too bad.", "start": 1148.31, "duration": 1.76}, {"text": "That's like 32 megs a day or so.", "start": 1150.07, "duration": 3.7}, {"text": "But anyway this model is-- and not only that,\nyou can request all the filters, match them,", "start": 1153.77, "duration": 6.289}, {"text": "and then download from someone else, the full\nblock, right?", "start": 1160.059, "duration": 3.781}, {"text": "You can request a block, download it from\nsomeone else.", "start": 1163.84, "duration": 3.42}, {"text": "So this full node, they know you requested\nall the filters.", "start": 1167.26, "duration": 3.05}, {"text": "They don't see anything else other than that.", "start": 1170.31, "duration": 3.089}, {"text": "And then another full node just sees you requesting\nblocks and thinks nothing of it.", "start": 1173.399, "duration": 4.751}, {"text": "Because that's totally normal.", "start": 1178.15, "duration": 1.45}, {"text": "This is a lot nicer model for privacy because\nthe full nodes don't learn anything other.", "start": 1179.6, "duration": 4.89}, {"text": "At most, they learn you downloaded this block\nand not this other block.", "start": 1184.49, "duration": 4.11}, {"text": "So maybe you have transactions in this block,\nbut not this one.", "start": 1188.6, "duration": 3.64}, {"text": "But that's a much bigger sort of needle in\na haystack problem, where OK, here are the", "start": 1192.24, "duration": 5.34}, {"text": "blocks they used.", "start": 1197.58, "duration": 1.05}, {"text": "What are the commonalities between these sets\nof blocks they were downloading?", "start": 1198.63, "duration": 4.63}, {"text": "Possible to maybe weed things out, right?", "start": 1203.26, "duration": 1.919}, {"text": "If the blocks are small, and there's only\na few transactions, and they download the", "start": 1205.179, "duration": 4.211}, {"text": "entire blockchain from a single node, and\nthat node can track, OK, which blocks are", "start": 1209.39, "duration": 4.409}, {"text": "being downloaded?", "start": 1213.799, "duration": 1.0}, {"text": "What are the common transactions or addresses\nin these?", "start": 1214.799, "duration": 2.711}, {"text": "It's possible.", "start": 1217.51, "duration": 1.0}, {"text": "But it's a lot better for privacy than the\ncurrent model and a lot better for CPU, right?", "start": 1218.51, "duration": 6.389}, {"text": "So privacy-- great.", "start": 1224.899, "duration": 1.791}, {"text": "Great improvement.", "start": 1226.69, "duration": 1.8}, {"text": "The server has much lower CPU, because it\ncan pre-compute all the filters for every", "start": 1228.49, "duration": 6.47}, {"text": "block, right?", "start": 1234.96, "duration": 1.1}, {"text": "So as soon as it downloads a block-- or a\nfew seconds later-- there's no rush.", "start": 1236.06, "duration": 3.71}, {"text": "Compute a Bloom filter for it, store it on\ndisk-- because it doesn't change-- and then", "start": 1239.77, "duration": 4.24}, {"text": "when anyone requests it, you've already got\nit on disk.", "start": 1244.01, "duration": 3.58}, {"text": "So you just read it off the disk, send it\nover the network, you're done.", "start": 1247.59, "duration": 2.99}, {"text": "The current model where you don't write these\nto disk because they're sort of client specific,", "start": 1250.58, "duration": 4.66}, {"text": "so client connects in, sends you a Bloom filter,\nyou have to keep that in RAM, and then match", "start": 1255.24, "duration": 4.95}, {"text": "all the things against this specific filter\nfor this specific user.", "start": 1260.19, "duration": 2.94}, {"text": "Whereas in this model, you make a filter for\nthe block, save it, you're good.", "start": 1263.13, "duration": 6.38}, {"text": "Yes.", "start": 1269.51, "duration": 1.0}, {"text": "AUDIENCE: Is the filter for the block [INAUDIBLE]\ngiven you're just sending the addresses and", "start": 1270.51, "duration": 9.55}, {"text": "not [INAUDIBLE]?", "start": 1280.06, "duration": 1.0}, {"text": "Or is it just less data?", "start": 1281.06, "duration": 1.6}, {"text": "It's just not the full block, right?", "start": 1282.66, "duration": 2.68}, {"text": "It's just the--", "start": 1285.34, "duration": 1.0}, {"text": "TADGE DRYJA: Yeah.", "start": 1286.34, "duration": 1.0}, {"text": "So if it were the addresses and the UTXOs,\nthen it would be really big.", "start": 1287.34, "duration": 2.189}, {"text": "It would be-- oh, maybe like 40% of the whole\nblock size.", "start": 1289.529, "duration": 5.201}, {"text": "So the idea of the Bloom filter is you squish\nit down.", "start": 1294.73, "duration": 4.069}, {"text": "So the Boom filter itself might only be like\n20k.", "start": 1298.799, "duration": 4.951}, {"text": "And so yeah, the basic way a Bloom filter\nwill work is you take sort of a bunch of hashes", "start": 1303.75, "duration": 8.059}, {"text": "and populate a bit field with them.", "start": 1311.809, "duration": 3.561}, {"text": "So the thing is, if you keep adding objects\nto the filter, the filter will eventually", "start": 1315.37, "duration": 4.84}, {"text": "just be like FFFF.", "start": 1320.21, "duration": 2.3}, {"text": "And everything will match it.", "start": 1322.51, "duration": 1.33}, {"text": "So you need to sort of decide how big the\nfilter should be when you start creating and", "start": 1323.84, "duration": 6.339}, {"text": "adding objects to it.", "start": 1330.179, "duration": 1.261}, {"text": "So with this, you can get it down to about\n20k, and then it'll have a pretty low false", "start": 1331.44, "duration": 6.29}, {"text": "positive rate, but not tell you exactly what\nthe addresses and UTXOs were.", "start": 1337.73, "duration": 6.72}, {"text": "So it's a nice trade-off to have.", "start": 1344.45, "duration": 3.07}, {"text": "Yeah, so I mean, the perfect sort of easiest\nBloom filter would be, here's a list of all", "start": 1347.52, "duration": 5.97}, {"text": "the addresses and all the UTXOs-- basically\na block minus the signatures, which is sort", "start": 1353.49, "duration": 5.569}, {"text": "of what you can get with segwit, where you\nsay, hey.", "start": 1359.059, "duration": 2.511}, {"text": "In segwit, you can say, hey, give me the block\nwithout all the segwit data.", "start": 1361.57, "duration": 4.969}, {"text": "Because I'm just looking for things.", "start": 1366.539, "duration": 1.831}, {"text": "I don't want to actually validate the signatures.", "start": 1368.37, "duration": 3.57}, {"text": "So if you did that with regular-- yeah, it\ndrops it by about 50%.", "start": 1371.94, "duration": 5.07}, {"text": "But the Bloom filter drops it substantially\nmore.", "start": 1377.01, "duration": 5.07}, {"text": "So if you did this, it'd be better-- lower\nCPU for the server.", "start": 1382.08, "duration": 5.219}, {"text": "It's also harder to lie and omit things.", "start": 1387.299, "duration": 2.311}, {"text": "So in the current SPV model, if someone is\nrunning a client-- it says, hey, here's my", "start": 1389.61, "duration": 5.86}, {"text": "Bloom filter.", "start": 1395.47, "duration": 1.22}, {"text": "And the full node responds.", "start": 1396.69, "duration": 1.57}, {"text": "The full node can easily just omit things.", "start": 1398.26, "duration": 4.45}, {"text": "So there was a transaction that did hit the\nBloom filter and did match.", "start": 1402.71, "duration": 3.819}, {"text": "And address A was present in a transaction,\nand the full node just doesn't send it.", "start": 1406.529, "duration": 7.211}, {"text": "There's really nothing the client can do to\ndetect that kind of thing, which in general,", "start": 1413.74, "duration": 6.2}, {"text": "it's not the end of the world.", "start": 1419.94, "duration": 2.489}, {"text": "In normal Bitcoin usage, if you don't hear\nabout a transaction, maybe you'll hear about", "start": 1422.429, "duration": 5.011}, {"text": "it eventually.", "start": 1427.44, "duration": 2.14}, {"text": "The worst they can do is sort of lie about\nyou-- they say you didn't get paid, but you", "start": 1429.58, "duration": 3.439}, {"text": "actually did.", "start": 1433.019, "duration": 1.04}, {"text": "Not the worst thing in the world, although\nin Lightning Network, that can change a little", "start": 1434.059, "duration": 4.571}, {"text": "bit in that you want to know about the transactions\nthat potentially close the channel and immediately", "start": 1438.63, "duration": 5.21}, {"text": "respond to them.", "start": 1443.84, "duration": 1.04}, {"text": "So that's more of a security problem with\nLightning.", "start": 1444.88, "duration": 4.04}, {"text": "So with this, it could be harder to omit things,\nespecially if you commit the Bloom filter", "start": 1448.92, "duration": 6.93}, {"text": "into the Coinbase transaction.", "start": 1455.85, "duration": 2.12}, {"text": "So if this committed filter becomes like a\nconsensus rule, and you say, OK, everyone", "start": 1457.97, "duration": 5.171}, {"text": "makes a 20 kilobyte Bloom filter.", "start": 1463.141, "duration": 2.378}, {"text": "Everyone takes the hash of that and puts it\ninto an op return in the Coinbase transaction", "start": 1465.519, "duration": 5.101}, {"text": "the way they do a segwit.", "start": 1470.62, "duration": 2.38}, {"text": "Then it's a consensus rule.", "start": 1473.0, "duration": 1.0}, {"text": "Then it becomes essentially impossible for\nthe full nodes to lie or omit anything.", "start": 1474.0, "duration": 6.289}, {"text": "Because you can say, hey, I've got the headers.", "start": 1480.289, "duration": 3.861}, {"text": "Give me the Coinbase transaction and a Merkle\nproof for it.", "start": 1484.15, "duration": 3.61}, {"text": "And now I've got the Coinbase transaction.", "start": 1487.76, "duration": 1.33}, {"text": "And now, hey, give me that filter that matches\nthis committed hash in the Coinbase transaction.", "start": 1489.09, "duration": 7.75}, {"text": "So they would have to do valid proof of work\nto lie or omit.", "start": 1496.84, "duration": 4.589}, {"text": "Whereas now, they can just easily omit anything\nthey want.", "start": 1501.429, "duration": 3.411}, {"text": "Oh, lying also.", "start": 1504.84, "duration": 3.15}, {"text": "So it becomes harder to lie because it's in\na block, right?", "start": 1507.99, "duration": 3.559}, {"text": "So this is operating on the block level.", "start": 1511.549, "duration": 1.87}, {"text": "The current SPV does not operate on the block\nlevel.", "start": 1513.419, "duration": 2.731}, {"text": "So you can get unconfirmed transactions over\nthe wire that match your filter.", "start": 1516.15, "duration": 5.21}, {"text": "I think this is a really bad idea.", "start": 1521.36, "duration": 2.53}, {"text": "I'm not 100% sure why they put it in.", "start": 1523.89, "duration": 2.789}, {"text": "But there's still people who like it.", "start": 1526.679, "duration": 2.63}, {"text": "But the whole idea of SPV is that you're verifying\nthe proof of work, right?", "start": 1529.309, "duration": 5.141}, {"text": "You're verifying that the miners validated\nthis.", "start": 1534.45, "duration": 3.03}, {"text": "And you think, well, the incentives are such\nthat miners don't want to mine invalid things.", "start": 1537.48, "duration": 3.569}, {"text": "They won't get paid.", "start": 1541.049, "duration": 1.181}, {"text": "So if it's in a block, I'll accept it as OK.", "start": 1542.23, "duration": 4.909}, {"text": "For mempool transactions, if it's just an\ninv message for a transaction that's not in", "start": 1547.139, "duration": 4.741}, {"text": "a block yet, there's no SPV security at all.", "start": 1551.88, "duration": 2.83}, {"text": "And it's trivial to send an invalid transaction\nto an SPV client, this currently.", "start": 1554.71, "duration": 6.52}, {"text": "So if you say, hey, here's-- and it's not\nonly is it trivial, but you can also try to", "start": 1561.23, "duration": 4.189}, {"text": "figure out what their addresses are, and lie\nto them, and say that, hey, you just got thousands", "start": 1565.419, "duration": 4.601}, {"text": "of coins.", "start": 1570.02, "duration": 2.029}, {"text": "So that's the current problem with SPV usage.", "start": 1572.049, "duration": 4.87}, {"text": "You're basically telling the full load your\naddresses, and you're accepting transactions", "start": 1576.919, "duration": 3.88}, {"text": "without proof of work.", "start": 1580.799, "duration": 1.351}, {"text": "So the full load can say, hey, here's a transaction\nthat sends you 5,000 coins to an address that", "start": 1582.15, "duration": 5.87}, {"text": "I think you have.", "start": 1588.02, "duration": 1.0}, {"text": "Because I tried to figure out your address\nfrom your filter.", "start": 1589.02, "duration": 3.1}, {"text": "And it's got an input that doesn't actually\nexist, right?", "start": 1592.12, "duration": 2.769}, {"text": "So I'm just saying I'm spending 5,000 coins\nfrom here.", "start": 1594.889, "duration": 2.951}, {"text": "And the from part isn't actually a thing.", "start": 1597.84, "duration": 3.05}, {"text": "But since you're an SPV node, you don't know\nthat.", "start": 1600.89, "duration": 2.57}, {"text": "So there's like a-- let's see.", "start": 1603.46, "duration": 2.05}, {"text": "Lie to SPV is like a branch on Bitcoin [INAUDIBLE].", "start": 1605.51, "duration": 8.9}, {"text": "OK, yeah.", "start": 1614.41, "duration": 5.1}, {"text": "So there's a branch that Peter Todd made called\nLie to SPV.", "start": 1619.51, "duration": 5.25}, {"text": "I don't know.", "start": 1624.76, "duration": 5.83}, {"text": "Quick and dirty hack to lie to SPV wallets.", "start": 1630.59, "duration": 2.62}, {"text": "They can't verify amounts, so yeah.", "start": 1633.21, "duration": 5.07}, {"text": "So you can just sort of detect-- well, if\nyou want to look at it.", "start": 1638.28, "duration": 3.21}, {"text": "You can detect their addresses.", "start": 1641.49, "duration": 2.97}, {"text": "And then I think that one just sort of opportunistically,\nif it finds a match, just multiplies the amount", "start": 1644.46, "duration": 5.32}, {"text": "that they're receiving by, like, 100.", "start": 1649.78, "duration": 2.83}, {"text": "And there's no way that they can validate\nthat since it's in mempool.", "start": 1652.61, "duration": 3.37}, {"text": "So this also makes it on the block level,\nwhich is what SPV really should be.", "start": 1655.98, "duration": 4.37}, {"text": "So that's nice.", "start": 1660.35, "duration": 2.35}, {"text": "Downsides-- mainly that it's going to be higher\nnetwork traffic for the client, right?", "start": 1662.7, "duration": 4.059}, {"text": "So even at low false positive rates, the entire\nrest of the block is essentially a false positive,", "start": 1666.759, "duration": 6.481}, {"text": "right?", "start": 1673.24, "duration": 1.0}, {"text": "So they're like, hey, there's one transaction\nin this block I want to get.", "start": 1674.24, "duration": 2.159}, {"text": "I have to download the whole block to get\nit.", "start": 1676.399, "duration": 2.65}, {"text": "So yeah, more network traffic for the client,\nwhich is a downside, but it helps with privacy.", "start": 1679.049, "duration": 4.701}, {"text": "So there is current development.", "start": 1683.75, "duration": 2.44}, {"text": "Lighting Labs-- basically [INAUDIBLE] working\non-- it's called neutrino.", "start": 1686.19, "duration": 3.93}, {"text": "It's a variant of this.", "start": 1690.12, "duration": 2.23}, {"text": "So, and then hopefully, something like this\nwill eventually get into Bitcoin Core itself", "start": 1692.35, "duration": 6.539}, {"text": "and replace the current server side Bloom\nfilter code.", "start": 1698.889, "duration": 5.001}, {"text": "Hopefully, but something to work on.", "start": 1703.89, "duration": 3.85}, {"text": "Any questions about the Bloom filter stuff?", "start": 1707.74, "duration": 3.64}, {"text": "Cool, OK.", "start": 1711.38, "duration": 2.86}, {"text": "OK, other issue, sharding.", "start": 1714.24, "duration": 3.809}, {"text": "So this is mainly being worked on in the context\nof Ethereum.", "start": 1718.049, "duration": 3.431}, {"text": "And it's sort of their sort of holy grail\nof scalability.", "start": 1721.48, "duration": 4.48}, {"text": "It's common in the database world, where you've\ngot d data objects, n servers.", "start": 1725.96, "duration": 5.65}, {"text": "So in the case of Bitcoin or these blockchains,\nyou just store d times n, right?", "start": 1731.61, "duration": 4.53}, {"text": "Every node stores all data.", "start": 1736.14, "duration": 2.22}, {"text": "Instead, store something closer to d itself\nand shard the data over all the servers, so", "start": 1738.36, "duration": 4.83}, {"text": "that each server holds like d divided by n,\nright?", "start": 1743.19, "duration": 3.27}, {"text": "So if you have 10 servers and a gigabyte,\nhave them each store 100 megs.", "start": 1746.46, "duration": 4.67}, {"text": "And then you still got all the data.", "start": 1751.13, "duration": 1.74}, {"text": "Of course, if they actually store exactly\nd over n-- and you need to coordinate it so", "start": 1752.87, "duration": 5.21}, {"text": "they all store their own little shard-- and\nthen if any single node goes down, well, you're", "start": 1758.08, "duration": 6.36}, {"text": "stuck.", "start": 1764.44, "duration": 1.0}, {"text": "So this is sort of the limit.", "start": 1765.44, "duration": 2.359}, {"text": "And there's no redundancy there.", "start": 1767.799, "duration": 5.5}, {"text": "But you can have different redundancy ratings.", "start": 1773.299, "duration": 1.941}, {"text": "So you could say, OK, well, any-- you could\nhave [INAUDIBLE] you're coding.", "start": 1775.24, "duration": 3.5}, {"text": "So if any five nodes or any 20% of the nodes\ndisappear, we're still OK.", "start": 1778.74, "duration": 4.319}, {"text": "So in the database world, this is a well studied\nproblem.", "start": 1783.059, "duration": 5.35}, {"text": "But in the context of Bitcoin, Ethereum, and\nblockchains, it's more difficult.", "start": 1788.409, "duration": 5.291}, {"text": "It's difficult here because you're in this\nadversarial environment, where people are", "start": 1793.7, "duration": 4.08}, {"text": "trying to break your system at all times.", "start": 1797.78, "duration": 3.81}, {"text": "People want to create transactions that are\ninvalid.", "start": 1801.59, "duration": 4.88}, {"text": "Because that can be worth a lot of money.", "start": 1806.47, "duration": 2.179}, {"text": "I can say, hey, you don't know about this\nshard, but I'm telling you that on this shard,", "start": 1808.649, "duration": 7.231}, {"text": "I have a lot of money.", "start": 1815.88, "duration": 1.14}, {"text": "And I'm sending it to you, so give me your\nhouse or whatever.", "start": 1817.02, "duration": 4.149}, {"text": "So the idea is to split a single UTXO set\ninto multiple smaller sets, and that part", "start": 1821.169, "duration": 7.51}, {"text": "is OK.", "start": 1828.679, "duration": 1.0}, {"text": "But you need communication between the shards,\nright?", "start": 1829.679, "duration": 2.21}, {"text": "So you could say, OK, well, making sort of\na bunch of different UTXO sets, each node", "start": 1831.889, "duration": 6.211}, {"text": "can choose their own UTXO set that they're\nkeeping track of.", "start": 1838.1, "duration": 3.05}, {"text": "And then you have some kind of merge mining\nbetween the UTXO sets, but you need swaps", "start": 1841.15, "duration": 4.609}, {"text": "between the shards.", "start": 1845.759, "duration": 1.061}, {"text": "It's kind of an interesting thing to think\nof.", "start": 1846.82, "duration": 4.83}, {"text": "We already have multiple UTXO sets, right?", "start": 1851.65, "duration": 3.04}, {"text": "So as of this morning, coinmarketcap.com tracks\n1,614 different currencies, 10,000 markets.", "start": 1854.69, "duration": 7.67}, {"text": "There's supposedly $434 billion going around.", "start": 1862.36, "duration": 3.6}, {"text": "Is this sharding, right?", "start": 1865.96, "duration": 4.24}, {"text": "And it's sort of a joke, but in a real sense,\nit has taken scalability pressure off of Bitcoin", "start": 1870.2, "duration": 7.59}, {"text": "and off of any individual currency because\nthere's so many of them.", "start": 1877.79, "duration": 5.219}, {"text": "So if you didn't have Dogecoin, maybe there\nwill be more Bitcoin transactions.", "start": 1883.009, "duration": 3.331}, {"text": "AUDIENCE: And how does this play into Bitcoins\nthat are just running on Ether?", "start": 1886.34, "duration": 4.54}, {"text": "TADGE DRYJA: Right, so in the case of ERC-20\nor ERC-721, it actually is worse.", "start": 1890.88, "duration": 6.69}, {"text": "Because now you've got sort of multiple UTXO\nsets all being managed by a single UTXO set.", "start": 1897.57, "duration": 9.38}, {"text": "So if you want to keep track of how many--\nI don't know.", "start": 1906.95, "duration": 4.26}, {"text": "What's an ECR-20 token?", "start": 1911.21, "duration": 1.949}, {"text": "If you want to keep track of how many Pied\nPiper coins there are, you need to download", "start": 1913.159, "duration": 5.22}, {"text": "the entire Ethereum blockchain.", "start": 1918.379, "duration": 2.5}, {"text": "So that's sort of the opposite of sharding\nin that now any single UTXO set you want to", "start": 1920.879, "duration": 4.611}, {"text": "keep track of, you need to keep track of all\nof them.", "start": 1925.49, "duration": 2.55}, {"text": "However, in this case, if I want to keep track\nof my Bitcoin UTXO set, I don't need to download", "start": 1928.04, "duration": 4.609}, {"text": "Dogecoin.", "start": 1932.649, "duration": 1.0}, {"text": "So that's great.", "start": 1933.649, "duration": 1.0}, {"text": "And if people want to swap between Dogecoin\nand Bitcoin, they can do so-- well, Dogecoin", "start": 1934.649, "duration": 4.851}, {"text": "doesn't have segwit support, right?", "start": 1939.5, "duration": 1.509}, {"text": "So it's a little harder.", "start": 1941.009, "duration": 1.861}, {"text": "But Vertcoin, Litecoin-- a lot of different\ncoins have fairly easy swaps.", "start": 1942.87, "duration": 5.75}, {"text": "But it's more than just swaps.", "start": 1948.62, "duration": 1.75}, {"text": "We need actual fungibility between the shards.", "start": 1950.37, "duration": 5.189}, {"text": "Because if I can say, oh, I'm going to use\nLitecoin, and I can just swap to Bitcoin whenever", "start": 1955.559, "duration": 6.49}, {"text": "I need to pay someone who accepts Bitcoin,\nright, maybe.", "start": 1962.049, "duration": 2.691}, {"text": "But maybe Litecoin drops in value 20% with\nrespect to Bitcoin.", "start": 1964.74, "duration": 5.51}, {"text": "And then I tried to pay.", "start": 1970.25, "duration": 2.75}, {"text": "And this is sort of getting ahead of the real\nuse cases of these things.", "start": 1973.0, "duration": 4.289}, {"text": "Because well, Bitcoin also drops 20% randomly\nagainst whatever asset you're trying to buy.", "start": 1977.289, "duration": 7.591}, {"text": "And so but Bitcoin does tend to be a bit more\nstable than most of the smaller market cap", "start": 1984.88, "duration": 4.84}, {"text": "coins.", "start": 1989.72, "duration": 1.0}, {"text": "I mean, you can sort of think that generally,\nif you have a bigger market capitalization,", "start": 1990.72, "duration": 5.069}, {"text": "you're going to tend to be less volatile.", "start": 1995.789, "duration": 4.01}, {"text": "And we've seen that in Bitcoin, where it still\nseems ridiculously volatile, right?", "start": 1999.799, "duration": 5.0}, {"text": "It's gone down 50% since January.", "start": 2004.799, "duration": 2.47}, {"text": "And most currencies in the developed world\ndon't do that.", "start": 2007.269, "duration": 5.15}, {"text": "But if you actually compare it to in 2011,\nit dropped, like, 95% in a month or two.", "start": 2012.419, "duration": 4.781}, {"text": "Yeah.", "start": 2017.2, "duration": 1.0}, {"text": "AUDIENCE: It's more likely to be liquid supply\n[INAUDIBLE]", "start": 2018.2, "duration": 4.839}, {"text": "TADGE DRYJA: Yeah, so sometimes, there is\na currency that has these really inflated", "start": 2023.039, "duration": 7.24}, {"text": "market caps.", "start": 2030.279, "duration": 2.1}, {"text": "So you'll see one where someone makes a coin\nand says, OK, I'm making a million coins.", "start": 2032.379, "duration": 5.611}, {"text": "And I'll sell you one for $100.", "start": 2037.99, "duration": 2.84}, {"text": "And really, I still have all of the coins,\nand one other person has one of them.", "start": 2040.83, "duration": 4.75}, {"text": "But we can sort of do the math and get a market\ncap of $100 million that way.", "start": 2045.58, "duration": 3.74}, {"text": "So a lot of the coins do that to sort of inflate.", "start": 2049.32, "duration": 3.04}, {"text": "Because a coin market cap is literally a ranking.", "start": 2052.36, "duration": 4.31}, {"text": "And it even says rank.", "start": 2056.67, "duration": 3.7}, {"text": "So if you click EOS, it'll say rank.", "start": 2060.37, "duration": 4.119}, {"text": "Where does it say there?", "start": 2064.489, "duration": 1.5}, {"text": "Yeah, rank five.", "start": 2065.989, "duration": 1.0}, {"text": "So it's the fifth best, presumably.", "start": 2066.989, "duration": 3.42}, {"text": "And yeah, to what extent-- how many actual\npeople hold these things?", "start": 2070.409, "duration": 4.971}, {"text": "They just sort of made them up.", "start": 2075.38, "duration": 6.009}, {"text": "But there's all sorts of problems with this.", "start": 2081.389, "duration": 2.103}, {"text": "But the idea is, if you really want sharding,\nyou want the swaps between the shards to not", "start": 2083.492, "duration": 4.348}, {"text": "really have counter parties and to maintain\nthe same value.", "start": 2087.84, "duration": 4.589}, {"text": "You want fungibility between the shards, so\nthat you can quickly and easily say, OK, well,", "start": 2092.429, "duration": 4.301}, {"text": "I've got something on shard A. I'm going to\npay someone who's using shard B. And I don't", "start": 2096.73, "duration": 4.89}, {"text": "want any friction.", "start": 2101.62, "duration": 1.0}, {"text": "I don't want any exchange between there.", "start": 2102.62, "duration": 4.21}, {"text": "So this is hard.", "start": 2106.83, "duration": 1.98}, {"text": "There's a lot of cool research going on here.", "start": 2108.81, "duration": 3.23}, {"text": "And if it works, it's a real scalability improvement.", "start": 2112.04, "duration": 2.75}, {"text": "This is sort of the holy grail.", "start": 2114.79, "duration": 2.32}, {"text": "I don't really see much in-- in Bitcoin, they're\nsort of like side chains.", "start": 2117.11, "duration": 4.22}, {"text": "But those weren't really talked about as a\nscalability improvement.", "start": 2121.33, "duration": 3.56}, {"text": "And it's mostly the Ethereum crowd that are\nlike, this is our real sort of holy grail", "start": 2124.89, "duration": 4.06}, {"text": "for scalability.", "start": 2128.95, "duration": 1.79}, {"text": "So it's interesting to look at.", "start": 2130.74, "duration": 1.02}, {"text": "I haven't kept up.", "start": 2131.76, "duration": 1.0}, {"text": "I've read a little bit about their most recent\nsharding ideas.", "start": 2132.76, "duration": 3.74}, {"text": "So it's cool if it works.", "start": 2136.5, "duration": 2.04}, {"text": "But there's a lot of sort of different assumptions\nthat go in.", "start": 2138.54, "duration": 3.06}, {"text": "Yeah.", "start": 2141.6, "duration": 1.0}, {"text": "AUDIENCE: What are some of the current plans\nto do sharding?", "start": 2142.6, "duration": 4.76}, {"text": "TADGE DRYJA: They sort of like-- a lot of\nthem hinge on fraud proofs.", "start": 2147.36, "duration": 2.32}, {"text": "So the idea is, you've got, say, five different\nchains going along.", "start": 2149.68, "duration": 4.42}, {"text": "And you don't validate the other four.", "start": 2154.1, "duration": 2.45}, {"text": "You say I'm going to only validate this one.", "start": 2156.55, "duration": 2.01}, {"text": "There's four others going on.", "start": 2158.56, "duration": 1.82}, {"text": "And if, in my chain, something bad happens,\nlike a transaction with an invalid signature", "start": 2160.38, "duration": 4.65}, {"text": "gets confirmed, or transaction has more coins\ncoming out than going in-- something like", "start": 2165.03, "duration": 6.34}, {"text": "that-- you provide a small fraud proof.", "start": 2171.37, "duration": 3.07}, {"text": "You provide a proof that says, OK, you don't\nneed to know everything that's going on in", "start": 2174.44, "duration": 3.98}, {"text": "this chain.", "start": 2178.42, "duration": 1.0}, {"text": "But I'll provide enough data to convince you\nthat this specific transaction is broken.", "start": 2179.42, "duration": 6.21}, {"text": "And then I try to broadcast to the other people\nin those other four subchains.", "start": 2185.63, "duration": 4.37}, {"text": "And then they know, OK, something's going\non wrong here.", "start": 2190.0, "duration": 3.01}, {"text": "Let's freeze-- let's not accept any cross\nshard swaps from that one.", "start": 2193.01, "duration": 4.67}, {"text": "And then the other-- this chain will have\nto reorg.", "start": 2197.68, "duration": 4.49}, {"text": "So the idea is as long as you have-- and it\nsort of makes sense.", "start": 2202.17, "duration": 2.84}, {"text": "As long as you have some number of people\nchecking it that can then broadcast it between", "start": 2205.01, "duration": 4.65}, {"text": "the different shards, you can assume that\nthey're doing OK.", "start": 2209.66, "duration": 2.35}, {"text": "Yeah.", "start": 2212.01, "duration": 1.0}, {"text": "AUDIENCE: Problems temporarily arise from\n[INAUDIBLE].", "start": 2213.01, "duration": 1.0}, {"text": "So you'll have a situation where [INAUDIBLE].", "start": 2214.01, "duration": 7.42}, {"text": "And then you wait two days, and then the transaction\n[INAUDIBLE] which relies on data from two", "start": 2221.43, "duration": 18.051}, {"text": "years ago for that shard.", "start": 2239.481, "duration": 1.0}, {"text": "All of those shards have disappeared.", "start": 2240.481, "duration": 1.0}, {"text": "So you have a choice.", "start": 2241.481, "duration": 1.0}, {"text": "Do you do it to your real or just accept that\nthat money is gone?", "start": 2242.481, "duration": 1.0}, {"text": "TADGE DRYJA: Yeah.", "start": 2243.481, "duration": 1.0}, {"text": "Or just accept that, oh, well, it's two years\nago.", "start": 2244.481, "duration": 1.0}, {"text": "So I'll assume it's OK.", "start": 2245.481, "duration": 1.0}, {"text": "AUDIENCE: Yeah.", "start": 2246.481, "duration": 1.0}, {"text": "TADGE DRYJA: Yeah.", "start": 2247.481, "duration": 1.0}, {"text": "Which is probably more dangerous.", "start": 2248.481, "duration": 1.0}, {"text": "Yeah, so sort of availability and liveness\nare other issues here, where if in Bitcoin", "start": 2249.481, "duration": 1.0}, {"text": "or Ethereum-- well, it's more of an issue\nin Ethereum.", "start": 2250.481, "duration": 2.929}, {"text": "In Bitcoin, there's a lot of copies of the\nfull set.", "start": 2253.41, "duration": 2.99}, {"text": "So if you're not sure about something, you\ncan pretty easily get the entire blockchain,", "start": 2256.4, "duration": 4.87}, {"text": "even though it's like 180 gigs, and go through\nit.", "start": 2261.27, "duration": 2.83}, {"text": "There's so many copies of it out there.", "start": 2264.1, "duration": 1.91}, {"text": "In Ethereum, a little bit less so.", "start": 2266.01, "duration": 2.26}, {"text": "Well, there's more full nodes.", "start": 2268.27, "duration": 1.68}, {"text": "But full is sort of redefined.", "start": 2269.95, "duration": 1.87}, {"text": "And so it may be harder to get the full thing.", "start": 2271.82, "duration": 2.05}, {"text": "And in the case of sharding, if you divide\nit too finally, it may be that you lose data,", "start": 2273.87, "duration": 5.91}, {"text": "and no one has it.", "start": 2279.78, "duration": 1.99}, {"text": "And then you're in real trouble.", "start": 2281.77, "duration": 1.92}, {"text": "OK, so that's sharding.", "start": 2283.69, "duration": 3.33}, {"text": "OK, accumulators-- this is something I'm actually\nlooking at.", "start": 2287.02, "duration": 3.61}, {"text": "I'm not going to go into the details of what\nI'm working on, but accumulators in general.", "start": 2290.63, "duration": 6.89}, {"text": "This is a cool-- so accumulators, as I will\ndescribe, are nothing new.", "start": 2297.52, "duration": 5.43}, {"text": "But if you read the papers-- so one of the\nfirst papers was called One Way Accumulators", "start": 2302.95, "duration": 4.2}, {"text": "in, like, '93.", "start": 2307.15, "duration": 1.25}, {"text": "And if you read the paper, a lot of the words\njump out.", "start": 2308.4, "duration": 3.16}, {"text": "It's like, hey, this might be useful for Bitcoin.", "start": 2311.56, "duration": 1.97}, {"text": "It's like, set membership, and timestamping,\nand signature aggregate.", "start": 2313.53, "duration": 4.97}, {"text": "It's got a lot of stuff in there that's like,\nhey, this could be useful.", "start": 2318.5, "duration": 2.89}, {"text": "So an accumulator is basically a cryptographic\nset.", "start": 2321.39, "duration": 5.51}, {"text": "And there's some set operations that you can\ndo and then provide proofs.", "start": 2326.9, "duration": 4.97}, {"text": "So, the simplest-- well, not even the simplest.", "start": 2331.87, "duration": 3.06}, {"text": "The simplest would just be add and prove.", "start": 2334.93, "duration": 2.39}, {"text": "But sometimes you can add.", "start": 2337.32, "duration": 1.6}, {"text": "Sometimes you can remove.", "start": 2338.92, "duration": 1.02}, {"text": "Sometimes you can prove something's in there.", "start": 2339.94, "duration": 1.48}, {"text": "Sometimes you can prove something's not in\nthere.", "start": 2341.42, "duration": 3.09}, {"text": "And if you can do all four, that's even better.", "start": 2344.51, "duration": 1.98}, {"text": "So the idea is, you take an accumulator.", "start": 2346.49, "duration": 2.97}, {"text": "And you add an object to it.", "start": 2349.46, "duration": 1.69}, {"text": "And in general, objects are going to be strings\nof bytes or just numbers, right?", "start": 2351.15, "duration": 4.35}, {"text": "And then it spits out a new accumulator.", "start": 2355.5, "duration": 1.49}, {"text": "Essentially, it modifies the accumulator in\nplace.", "start": 2356.99, "duration": 3.7}, {"text": "So if you delete-- you say OK, I've got an\naccumulator.", "start": 2360.69, "duration": 2.52}, {"text": "And I want to delete this object.", "start": 2363.21, "duration": 1.78}, {"text": "Well, it'll modify in place and return a different\naccumulator.", "start": 2364.99, "duration": 4.18}, {"text": "And then maybe I want to prove that this object\nis in this accumulator.", "start": 2369.17, "duration": 4.15}, {"text": "And it will return a Boolean.", "start": 2373.32, "duration": 1.47}, {"text": "Like, yep, that worked, or no, it didn't.", "start": 2374.79, "duration": 2.16}, {"text": "So the simplest example, which I think is\nkind of fun, composite numbers.", "start": 2376.95, "duration": 6.39}, {"text": "So accumulate prime numbers.", "start": 2383.34, "duration": 3.77}, {"text": "So to add, multiply.", "start": 2387.11, "duration": 1.68}, {"text": "To delete, divide.", "start": 2388.79, "duration": 1.66}, {"text": "So really, if you're going to do this, you\nstart with 1.", "start": 2390.45, "duration": 5.06}, {"text": "1 is not a prime, I guess, but whatever.", "start": 2395.51, "duration": 4.79}, {"text": "So let's say you've got-- so yeah.", "start": 2400.3, "duration": 2.14}, {"text": "1 is not a prime, so that works.", "start": 2402.44, "duration": 1.31}, {"text": "So you cannot prove any prime exists within\nthat accumulator.", "start": 2403.75, "duration": 3.9}, {"text": "Anyway, but let's say you start with 1, and\nthen you added 3 to the accumulator.", "start": 2407.65, "duration": 3.47}, {"text": "So you multiplied by 3, and you get 3.", "start": 2411.12, "duration": 1.78}, {"text": "Now I want to add the number 5 to the accumulator.", "start": 2412.9, "duration": 2.31}, {"text": "So I multiply by 5.", "start": 2415.21, "duration": 1.41}, {"text": "I get 15.", "start": 2416.62, "duration": 1.32}, {"text": "And now I want to add 7 to this accumulator.", "start": 2417.94, "duration": 3.8}, {"text": "So I've got my accumulator, which is 15.", "start": 2421.74, "duration": 2.12}, {"text": "I add the number 7 into it, and I get 105,\nright?", "start": 2423.86, "duration": 3.39}, {"text": "I just multiply by 7.", "start": 2427.25, "duration": 1.66}, {"text": "I get 105.", "start": 2428.91, "duration": 2.16}, {"text": "Wait, is it called fundamental theorem of\narithmetic?", "start": 2431.07, "duration": 2.87}, {"text": "I think that's what it's called, where everything's\na product of primes.", "start": 2433.94, "duration": 2.76}, {"text": "It's got some cool name.", "start": 2436.7, "duration": 3.31}, {"text": "So everything's a product of primes.", "start": 2440.01, "duration": 3.3}, {"text": "And everything has a unique factorization.", "start": 2443.31, "duration": 1.75}, {"text": "So 105 is 3 times 5 times 7, right?", "start": 2445.06, "duration": 3.92}, {"text": "There's no other ways around it.", "start": 2448.98, "duration": 5.38}, {"text": "And if you want to delete, you can say, OK,\nwell, I'm going to delete the number 5 from", "start": 2454.36, "duration": 4.92}, {"text": "this accumulator.", "start": 2459.28, "duration": 1.0}, {"text": "Just divide.", "start": 2460.28, "duration": 1.0}, {"text": "Now I get 21.", "start": 2461.28, "duration": 1.0}, {"text": "And then I want to prove 7 is in there.", "start": 2462.28, "duration": 2.54}, {"text": "So I can say, hey, 7 is in this accumulator.", "start": 2464.82, "duration": 2.43}, {"text": "It was added, but not deleted.", "start": 2467.25, "duration": 2.34}, {"text": "And I can do that, right?", "start": 2469.59, "duration": 1.05}, {"text": "I tried to divide 21 by 7, and it worked.", "start": 2470.64, "duration": 2.66}, {"text": "I want to divide, and I want to make sure\nthere's no remainder.", "start": 2473.3, "duration": 2.51}, {"text": "I want to see that it divides evenly.", "start": 2475.81, "duration": 1.57}, {"text": "So I get a true.", "start": 2477.38, "duration": 2.03}, {"text": "Yep, if I divide 21 by 7, I get 3.", "start": 2479.41, "duration": 3.14}, {"text": "3 is a natural number.", "start": 2482.55, "duration": 2.0}, {"text": "It works.", "start": 2484.55, "duration": 1.0}, {"text": "So this is kind of cool.", "start": 2485.55, "duration": 4.05}, {"text": "It is not really [INAUDIBLE].", "start": 2489.6, "duration": 2.88}, {"text": "Oh, but this works even if you do modulo.", "start": 2492.48, "duration": 2.81}, {"text": "So you could do modulo some big prime and\nhave just formality based accumulators.", "start": 2495.29, "duration": 5.68}, {"text": "So anyway, you get the idea, right?", "start": 2500.97, "duration": 3.29}, {"text": "I think in this case, you can also prove things\nare not in there.", "start": 2504.26, "duration": 4.4}, {"text": "But this is limited to prime numbers.", "start": 2508.66, "duration": 1.3}, {"text": "Anyway, but the idea is, keep adding things\nto it, removing things from it, and proving", "start": 2509.96, "duration": 3.19}, {"text": "that things are in it.", "start": 2513.15, "duration": 2.54}, {"text": "So there's RSA accumulators, which are some\nof the most well-known.", "start": 2515.69, "duration": 4.1}, {"text": "And that's you've got some RSA number, which\nis basically a product of two large primes.", "start": 2519.79, "duration": 5.47}, {"text": "And the accumulator itself is of constant\nsize.", "start": 2525.26, "duration": 3.95}, {"text": "And the proofs are also of constant size.", "start": 2529.21, "duration": 2.23}, {"text": "So we call this a proof.", "start": 2531.44, "duration": 1.85}, {"text": "You're just giving the number itself in this\ncase.", "start": 2533.29, "duration": 4.48}, {"text": "So it's efficient, but the RSA accumulators\nuse trusted setup.", "start": 2537.77, "duration": 6.4}, {"text": "So the idea is you need to find some composite\nnumber n, which is p times q, where p and", "start": 2544.17, "duration": 5.44}, {"text": "q are prime, where nobody knows p and q.", "start": 2549.61, "duration": 3.64}, {"text": "Or nobody knows or you trust that the person\nwho does know p and q not to screw around", "start": 2553.25, "duration": 3.97}, {"text": "with the accumulator.", "start": 2557.22, "duration": 1.77}, {"text": "Because the person who-- if knowledge of p--\nI think it's actually knowledge of p or q--", "start": 2558.99, "duration": 5.0}, {"text": "will let you create proofs that, hey, this\nobject is in the accumulator when really,", "start": 2563.99, "duration": 6.06}, {"text": "it isn't.", "start": 2570.05, "duration": 2.269}, {"text": "So that's not so much fun for Bitcoin.", "start": 2572.319, "duration": 3.181}, {"text": "If you need trusted setup, people don't really\nlike that.", "start": 2575.5, "duration": 4.58}, {"text": "There's all these other accumulator assay\nideas.", "start": 2580.08, "duration": 1.79}, {"text": "Some are one way where you can't delete.", "start": 2581.87, "duration": 1.91}, {"text": "You can add things to the accumulator, but\nthere's no way to remove it.", "start": 2583.78, "duration": 4.6}, {"text": "Sometimes you can batch things, where, OK,\nif I want-- so you can see in the composite", "start": 2588.38, "duration": 4.33}, {"text": "number accumulator, you could batch things.", "start": 2592.71, "duration": 2.12}, {"text": "Where if I add 105 to the accumulator, I'm\nperforming one operation that essentially", "start": 2594.83, "duration": 5.66}, {"text": "adds three objects, right?", "start": 2600.49, "duration": 2.32}, {"text": "3, 5, and 7.", "start": 2602.81, "duration": 2.37}, {"text": "Some can be batched like that, some cannot.", "start": 2605.18, "duration": 2.24}, {"text": "Some have trusted setup, some don't.", "start": 2607.42, "duration": 2.11}, {"text": "So there's different tradeoffs for all these\ndifferent use cases.", "start": 2609.53, "duration": 4.04}, {"text": "And in the case of Bitcoin, the idea of an\naccumulator would be put the UTXO set in it,", "start": 2613.57, "duration": 5.17}, {"text": "or put the STXO.", "start": 2618.74, "duration": 1.85}, {"text": "Like, spent the transaction outputs into it.", "start": 2620.59, "duration": 3.69}, {"text": "And then prove, in the case of UTXOs, prove\nthat it's in the accumulator.", "start": 2624.28, "duration": 5.37}, {"text": "Or in the case of STXOs, prove that it's no\nlonger in the accumulator.", "start": 2629.65, "duration": 3.66}, {"text": "Right?", "start": 2633.31, "duration": 1.34}, {"text": "Provided proof of non-inclusion, that, hey,\nit's not in this STXO set.", "start": 2634.65, "duration": 4.1}, {"text": "So, well, with the STXO inclusion-- so let's\nsay you did it that way.", "start": 2638.75, "duration": 4.48}, {"text": "You'd have headers, and then you've got this\nSTXO accumulator.", "start": 2643.23, "duration": 7.51}, {"text": "And what you can do there is say I've got\na transaction.", "start": 2650.74, "duration": 7.21}, {"text": "It's got some inputs.", "start": 2657.95, "duration": 1.52}, {"text": "I prove that this input exists in the headers,\nright?", "start": 2659.47, "duration": 4.09}, {"text": "I provide you an SPV proof.", "start": 2663.56, "duration": 2.09}, {"text": "So I say, OK, at some point, this was created,\nright?", "start": 2665.65, "duration": 3.63}, {"text": "This input.", "start": 2669.28, "duration": 1.29}, {"text": "Maybe a year ago, I showed you, OK, there\nis this header.", "start": 2670.57, "duration": 3.05}, {"text": "Here's a Merkle proof that this was in a block.", "start": 2673.62, "duration": 2.21}, {"text": "So this exists.", "start": 2675.83, "duration": 2.03}, {"text": "Then I also prove somehow that it doesn't\nexist in here, right?", "start": 2677.86, "duration": 3.63}, {"text": "It exists, but it was never spent.", "start": 2681.49, "duration": 2.44}, {"text": "So now you can accept that, oh, OK, he gave\nme an SPV proof.", "start": 2683.93, "duration": 4.14}, {"text": "He gave me a non-inclusion to the STXO set\nproof.", "start": 2688.07, "duration": 2.98}, {"text": "So I know this transaction, this input still\nexists and can be spent.", "start": 2691.05, "duration": 7.14}, {"text": "So what this would do, if you get it working,\nyou don't need to store the UTXOs anymore.", "start": 2698.19, "duration": 5.41}, {"text": "You just store the accumulator, and then everyone\nprovides proofs that, hey, I've got these", "start": 2703.6, "duration": 4.48}, {"text": "coins.", "start": 2708.08, "duration": 1.39}, {"text": "But so right now, if you store the UTXO set,\nit's a couple of gigabytes-- 3 or 4 gigs.", "start": 2709.47, "duration": 4.71}, {"text": "And when someone sends a transaction, you\njust look in your UTXO set, right?", "start": 2714.18, "duration": 7.82}, {"text": "So you see this input.", "start": 2722.0, "duration": 1.19}, {"text": "You say, hey, does that exist in my UTXO set?", "start": 2723.19, "duration": 2.66}, {"text": "OK, it does.", "start": 2725.85, "duration": 1.23}, {"text": "Cool.", "start": 2727.08, "duration": 1.0}, {"text": "We'll now verify the signature, verify everything\nelse about the transaction.", "start": 2728.08, "duration": 3.15}, {"text": "If it doesn't exist in my UTXO set, I'm like,\nhey, you're trying to spend something that", "start": 2731.23, "duration": 3.16}, {"text": "isn't there.", "start": 2734.39, "duration": 2.83}, {"text": "So what would be cool is if you got rid of\nthe UTXO set and only used an accumulator.", "start": 2737.22, "duration": 5.14}, {"text": "Because the accumulators are constant size.", "start": 2742.36, "duration": 2.84}, {"text": "So even if the UTXO set is 20 gigabytes, well,\nI've got this 10 kilobyte accumulator thing", "start": 2745.2, "duration": 6.65}, {"text": "on my hard drive.", "start": 2751.85, "duration": 1.38}, {"text": "And I just modify that in place.", "start": 2753.23, "duration": 2.12}, {"text": "And now I don't need to store a bazillion\ngigabytes.", "start": 2755.35, "duration": 3.74}, {"text": "And I basically can have the same security\nas a full node.", "start": 2759.09, "duration": 5.03}, {"text": "I'm still a full node, but I just don't store\nthe UTXO set.", "start": 2764.12, "duration": 3.08}, {"text": "I just require either SPV proofs or STXOs--\ndifferent proofs from the people trying to", "start": 2767.2, "duration": 6.75}, {"text": "spend the transactions.", "start": 2773.95, "duration": 1.84}, {"text": "So this is really cool.", "start": 2775.79, "duration": 1.43}, {"text": "Constant size, the proofs are small.", "start": 2777.22, "duration": 2.21}, {"text": "Sometimes the proofs are really small.", "start": 2779.43, "duration": 2.03}, {"text": "And then the wallets track the proofs.", "start": 2781.46, "duration": 1.94}, {"text": "So some questions.", "start": 2783.4, "duration": 1.96}, {"text": "Proofs can be like constant size, or sometimes\nthey're log n.", "start": 2785.36, "duration": 4.69}, {"text": "If the proofs are o of n, then it's not useful,\nright?", "start": 2790.05, "duration": 5.42}, {"text": "Because you might as well store the UTXO set\nat that point.", "start": 2795.47, "duration": 2.12}, {"text": "Also, what is n?", "start": 2797.59, "duration": 1.35}, {"text": "Is it the number of transactions, blocks?", "start": 2798.94, "duration": 2.93}, {"text": "Can you aggregate these operations?", "start": 2801.87, "duration": 1.66}, {"text": "So there's a bunch of questions there.", "start": 2803.53, "duration": 3.4}, {"text": "Another really big problem-- so I was talking\nto Peter Wool, who's sort of one of the premier", "start": 2806.93, "duration": 5.24}, {"text": "researchers on Bitcoin.", "start": 2812.17, "duration": 1.74}, {"text": "He had been talking to people at Stanford\nabout a lattice based accumulator that did", "start": 2813.91, "duration": 4.48}, {"text": "not need trusted setup.", "start": 2818.39, "duration": 1.57}, {"text": "And he was very excited about it because it\nwas like, hey, there's no trusted setup.", "start": 2819.96, "duration": 3.61}, {"text": "You have constant size proofs.", "start": 2823.57, "duration": 1.91}, {"text": "The accumulator itself is pretty small.", "start": 2825.48, "duration": 1.88}, {"text": "CPU wise, it seems doable.", "start": 2827.36, "duration": 2.54}, {"text": "The thing that sort of killed it was you couldn't\nbatch operations that accumulated.", "start": 2829.9, "duration": 7.4}, {"text": "And the other thing is we need some kind of\nbridge node.", "start": 2837.3, "duration": 3.17}, {"text": "So the idea is, normal transactions, right?", "start": 2840.47, "duration": 3.57}, {"text": "They just say, here's my input.", "start": 2844.04, "duration": 2.22}, {"text": "I've got a couple inputs.", "start": 2846.26, "duration": 1.44}, {"text": "I've got a couple outputs.", "start": 2847.7, "duration": 2.67}, {"text": "I don't provide any proofs or anything.", "start": 2850.37, "duration": 1.81}, {"text": "I just point to what I'm spending.", "start": 2852.18, "duration": 2.49}, {"text": "And you look in your UTXO set and see if it's\nthere.", "start": 2854.67, "duration": 3.5}, {"text": "With this new idea with accumulators, you're\ngoing to have to stick proofs on.", "start": 2858.17, "duration": 3.87}, {"text": "So really, it's an extra data structure, probably\nper input.", "start": 2862.04, "duration": 5.11}, {"text": "So you say, hey, I'm a node.", "start": 2867.15, "duration": 3.79}, {"text": "I run an accumulator.", "start": 2870.94, "duration": 1.19}, {"text": "I don't keep the whole set.", "start": 2872.13, "duration": 1.51}, {"text": "So for all your inputs, please provide proofs.", "start": 2873.64, "duration": 5.01}, {"text": "And wallets can maintain these proofs and\nattach them to their transactions.", "start": 2878.65, "duration": 6.96}, {"text": "And then the nodes will verify them.", "start": 2885.61, "duration": 1.67}, {"text": "However, right now, most wallets don't have\nthese proofs-- have no idea that this is a", "start": 2887.28, "duration": 4.41}, {"text": "thing, right?", "start": 2891.69, "duration": 1.0}, {"text": "So if you're the first node to do this and\nsay, hey, I'm getting rid of my UTXO set.", "start": 2892.69, "duration": 4.64}, {"text": "I'm only going to verify proofs that these\nUTXOs exist.", "start": 2897.33, "duration": 5.24}, {"text": "Most of the wallets won't provide those proofs.", "start": 2902.57, "duration": 2.34}, {"text": "And so as a new node, say, hey, I got rid\nof my UTXO set, but no one's giving you proofs.", "start": 2904.91, "duration": 3.85}, {"text": "OK, I'm just stuck, right?", "start": 2908.76, "duration": 1.11}, {"text": "I see a block come out.", "start": 2909.87, "duration": 1.38}, {"text": "I can't validate it.", "start": 2911.25, "duration": 1.0}, {"text": "So you're going to need some kind of transition,\nright?", "start": 2912.25, "duration": 3.46}, {"text": "If you started from scratch and say, OK, the\nresponsibility of every wallet is not just", "start": 2915.71, "duration": 4.82}, {"text": "keep your private keys and keep track of what\nyour UTXO is, it's also to keep track of a", "start": 2920.53, "duration": 5.36}, {"text": "proof.", "start": 2925.89, "duration": 1.0}, {"text": "So that when you want to spend it, you give\nit to someone else.", "start": 2926.89, "duration": 2.67}, {"text": "If you started that way, great.", "start": 2929.56, "duration": 2.82}, {"text": "But if you want to transition, what you're\nkind of going to need is a bridge node.", "start": 2932.38, "duration": 3.97}, {"text": "And the idea of a bridge node is you've got--\nso here's an accumulator node, where it requires", "start": 2936.35, "duration": 9.11}, {"text": "proofs.", "start": 2945.46, "duration": 1.2}, {"text": "Here's a old node that just has regular UTXOs.", "start": 2946.66, "duration": 4.1}, {"text": "So when the old node sends a transaction,\nthis gives TX proof, right?", "start": 2950.76, "duration": 6.7}, {"text": "So this basically has proofs for everything,\nlike all proofs.", "start": 2957.46, "duration": 5.61}, {"text": "So the bridge node can provide proofs.", "start": 2963.07, "duration": 5.81}, {"text": "You'll need one bridge node, right?", "start": 2968.88, "duration": 1.74}, {"text": "So if these accumulator nodes talk to each\nother, they can send the proofs along to each", "start": 2970.62, "duration": 5.94}, {"text": "other and stuff like that.", "start": 2976.56, "duration": 1.42}, {"text": "The old nodes cannot send proofs because they're\nnot aware of it in their software.", "start": 2977.98, "duration": 4.35}, {"text": "But if you have the new nodes, you can say,\nOK, well, when I receive a transaction, I", "start": 2982.33, "duration": 3.56}, {"text": "verify the proofs.", "start": 2985.89, "duration": 1.08}, {"text": "I also keep the proofs and give them to other\npeers who want to verify them.", "start": 2986.97, "duration": 5.26}, {"text": "But you need some kind of bridge between these\ntwo networks.", "start": 2992.23, "duration": 2.86}, {"text": "Yeah.", "start": 2995.09, "duration": 1.0}, {"text": "AUDIENCE: You would just keep that running\nuntil everyone switches?", "start": 2996.09, "duration": 3.98}, {"text": "TADGE DRYJA: Probably forever.", "start": 3000.07, "duration": 3.23}, {"text": "So yeah.", "start": 3003.3, "duration": 1.0}, {"text": "So the issue with the bridge node is like,\nwell, if you're an old wallet, you don't to", "start": 3004.3, "duration": 3.97}, {"text": "keep track of these proofs.", "start": 3008.27, "duration": 2.22}, {"text": "So, how much of a problem is this?", "start": 3010.49, "duration": 3.61}, {"text": "And the lattice based accumulator, that was\nsort of what killed it, was that you couldn't", "start": 3014.1, "duration": 7.41}, {"text": "batch operations.", "start": 3021.51, "duration": 1.19}, {"text": "Sorry, and the proofs changed.", "start": 3022.7, "duration": 4.9}, {"text": "That's not the case with the sort of silly\nprime number accumulator that I showed.", "start": 3027.6, "duration": 7.23}, {"text": "But in the lattice space one, the proofs changed\nevery time an accumulator operation happened.", "start": 3034.83, "duration": 4.89}, {"text": "So every time an ad happened, your proof had\nto change.", "start": 3039.72, "duration": 3.65}, {"text": "So you didn't just need to add something and\nmodify the accumulator in place.", "start": 3043.37, "duration": 3.94}, {"text": "You had to modify your proofs in place as\nwell.", "start": 3047.31, "duration": 3.42}, {"text": "And so if you're a wallet, and you've got\nthree UTXOs, that meant that every block,", "start": 3050.73, "duration": 6.1}, {"text": "you'd have to do a couple thousand operations,\nright?", "start": 3056.83, "duration": 2.92}, {"text": "Because every block, you're going to have\na few thousand adds and a few thousand deletes", "start": 3059.75, "duration": 4.94}, {"text": "to this accumulator.", "start": 3064.69, "duration": 1.47}, {"text": "Every time one of those happened, you'd have\nto modify your proof for each of your three", "start": 3066.16, "duration": 3.58}, {"text": "UTXOs.", "start": 3069.74, "duration": 1.24}, {"text": "So, a little ugly but doable, because you've\ngot three UTXOs.", "start": 3070.98, "duration": 4.03}, {"text": "You basically 3x the number of operations,\nset operations in the block.", "start": 3075.01, "duration": 4.92}, {"text": "The bridge node, on the other hand, has to\nkeep track of something like 70 million UTXOs.", "start": 3079.93, "duration": 7.03}, {"text": "Right?", "start": 3086.96, "duration": 1.0}, {"text": "That's about how many there are right now.", "start": 3087.96, "duration": 1.42}, {"text": "And so since there's no way to batch it, that\nmeans you're going to have maybe 10k times", "start": 3089.38, "duration": 6.64}, {"text": "70 million every block.", "start": 3096.02, "duration": 2.09}, {"text": "It's just not going to happen.", "start": 3098.11, "duration": 5.62}, {"text": "And then it's like, well, maybe you can sort\nof try to shard the bridge nodes.", "start": 3103.73, "duration": 2.88}, {"text": "And this bridge node only keeps track of this\nportion of the set.", "start": 3106.61, "duration": 3.69}, {"text": "But it just looked really daunting.", "start": 3110.3, "duration": 2.56}, {"text": "And that was why he was sort of like, yeah,\nI don't think this lattice-- I think it's", "start": 3112.86, "duration": 3.72}, {"text": "really key that either there's some kind of\nbatching operation, where we can consolidate", "start": 3116.58, "duration": 5.83}, {"text": "all the operations within a single block to\none set operation for the accumulator, or", "start": 3122.41, "duration": 5.43}, {"text": "try to make it so that the proofs don't have\nto be updated or something like that.", "start": 3127.84, "duration": 6.0}, {"text": "So this is still an unsolved problem, although\nI'm working on a fun way that I think might", "start": 3133.84, "duration": 5.67}, {"text": "work to do this.", "start": 3139.51, "duration": 2.44}, {"text": "And I don't want to-- because this is videotaped.", "start": 3141.95, "duration": 1.61}, {"text": "It's going on the internet and stuff.", "start": 3143.56, "duration": 1.41}, {"text": "I don't want to talk about it.", "start": 3144.97, "duration": 1.29}, {"text": "But if you have questions, we can talk about\nit at office hours or something.", "start": 3146.26, "duration": 6.01}, {"text": "So if it works, it'll be cool, although in\nsome cases, it might-- so in the case of that", "start": 3152.27, "duration": 5.02}, {"text": "bridge node, it was the bridge node that really\nkilled it.", "start": 3157.29, "duration": 3.57}, {"text": "Because it was just like, oh, you're going\nto have to do billions of operations per block.", "start": 3160.86, "duration": 4.38}, {"text": "But in other cases, it's like, well, you can\nhave accumulators that seem good, but aren't", "start": 3165.24, "duration": 5.02}, {"text": "actually faster.", "start": 3170.26, "duration": 1.8}, {"text": "Because verifying the proofs takes a long\ntime or something like that.", "start": 3172.06, "duration": 2.4}, {"text": "So it's sort of like with the range proofs\nor something like nimble-wear where the o", "start": 3174.46, "duration": 7.18}, {"text": "of n is great.", "start": 3181.64, "duration": 1.45}, {"text": "But you've got these constant factors that,\nin practice, end up meaning you're not actually", "start": 3183.09, "duration": 4.68}, {"text": "faster, right?", "start": 3187.77, "duration": 1.0}, {"text": "Because the Bitcoin UTXO set, well, it's 4\ngigs.", "start": 3188.77, "duration": 3.02}, {"text": "Not even, right?", "start": 3191.79, "duration": 1.0}, {"text": "It's 3 and 1/2 gigs now.", "start": 3192.79, "duration": 2.76}, {"text": "So in practice, there's probably a lot of\ncool cryptographic technologies.", "start": 3195.55, "duration": 4.5}, {"text": "And you can write a whole paper and have all\nthese cool things.", "start": 3200.05, "duration": 2.23}, {"text": "And then if you actually implement it, it's\nlike, well, it actually goes twice as slow", "start": 3202.28, "duration": 4.19}, {"text": "as just using the regular.", "start": 3206.47, "duration": 1.44}, {"text": "Also, this is super optimized.", "start": 3207.91, "duration": 2.65}, {"text": "One of the biggest sort of code engineering\nthings that has happened in Bitcoin Core is", "start": 3210.56, "duration": 5.6}, {"text": "OK, how can we make database updates to this?", "start": 3216.16, "duration": 2.38}, {"text": "How can we make different caching, different\nflushes to disk, and editing level DB itself.", "start": 3218.54, "duration": 6.13}, {"text": "So making this UTXO set database operation\nfaster is a big thing in Bitcoin.", "start": 3224.67, "duration": 5.22}, {"text": "So it's pretty optimized.", "start": 3229.89, "duration": 2.08}, {"text": "And even if you've got something that seems\nlike in computer science terms, hey, this", "start": 3231.97, "duration": 4.33}, {"text": "is log n instead of n, like, yeah, but what\nabout the constant factors?", "start": 3236.3, "duration": 6.9}, {"text": "So that's another issue for these.", "start": 3243.2, "duration": 3.0}, {"text": "OK.", "start": 3246.2, "duration": 1.13}, {"text": "Other things-- I was going to talk-- well,\nyeah.", "start": 3247.33, "duration": 3.76}, {"text": "I'll do last one, and then we can maybe end\na little early and talk about projects if", "start": 3251.09, "duration": 5.83}, {"text": "you want.", "start": 3256.92, "duration": 1.0}, {"text": "UTXO commitments, which is somewhat in the\nsame region as accumulators-- a little bit", "start": 3257.92, "duration": 5.24}, {"text": "different idea.", "start": 3263.16, "duration": 1.51}, {"text": "And this exists in some coins.", "start": 3264.67, "duration": 2.37}, {"text": "Like in Ethereum, Joe Bonneau was saying that\nyou basically have a tree of all the different", "start": 3267.04, "duration": 6.44}, {"text": "contracts that exist, all the different addresses\nin Ethereum.", "start": 3273.48, "duration": 4.1}, {"text": "And the root of that tree appears in every\nblock header.", "start": 3277.58, "duration": 2.73}, {"text": "So you can make these proofs that coins exist\nbased on a block header.", "start": 3280.31, "duration": 4.511}, {"text": "So it exists in Ethereum.", "start": 3284.821, "duration": 1.489}, {"text": "It doesn't exist in Bitcoin, but people have\nbeen talking about it for years.", "start": 3286.31, "duration": 4.18}, {"text": "The simplest would say take a hash of the\nUTXO set and put it in every Coinbase transaction.", "start": 3290.49, "duration": 6.15}, {"text": "And make that a consensus rule, so that when\nyou mine a block, you have to take the hash", "start": 3296.64, "duration": 5.62}, {"text": "of the UTXO set that you're aware of.", "start": 3302.26, "duration": 2.17}, {"text": "Put it in the block so that everyone can see\nit.", "start": 3304.43, "duration": 2.38}, {"text": "And if everyone disagrees, they're going to\ninvalidate that block.", "start": 3306.81, "duration": 4.03}, {"text": "This is really simple.", "start": 3310.84, "duration": 1.14}, {"text": "You probably want to do a little bit fancier\nthan this.", "start": 3311.98, "duration": 4.5}, {"text": "A bit more useful-- instead of just taking\na linear hash of the entire UTXO set, make", "start": 3316.48, "duration": 5.851}, {"text": "it a Merkle tree, right?", "start": 3322.331, "duration": 2.839}, {"text": "And that way, yeah, sure, it's very little\nextra hashing.", "start": 3325.17, "duration": 3.59}, {"text": "Well, no, wait, twice as much hashing, right?", "start": 3328.76, "duration": 3.07}, {"text": "But anyway.", "start": 3331.83, "duration": 1.0}, {"text": "2x the hashing, but now you've got the ability\nto make small proofs.", "start": 3332.83, "duration": 5.6}, {"text": "And then you can prove an output exists at\na given block height pretty easily at SPV", "start": 3338.43, "duration": 6.57}, {"text": "level security.", "start": 3345.0, "duration": 1.01}, {"text": "So currently, you can prove that a transaction\nexists at a block height.", "start": 3346.01, "duration": 4.94}, {"text": "And you can also prove that a transaction\nwas consumed at a certain block height, right?", "start": 3350.95, "duration": 4.75}, {"text": "So if you have all these different blocks,\n2, 3, 4, 5, you can say, hey, here's a Merkle", "start": 3355.7, "duration": 8.74}, {"text": "proof that transaction 1 was included in block\n2.", "start": 3364.44, "duration": 5.21}, {"text": "And then you can prove here, OK, here's transaction\n2 that consumes one of the outputs from transaction", "start": 3369.65, "duration": 7.11}, {"text": "1.", "start": 3376.76, "duration": 2.06}, {"text": "But you can't prove just given-- but also,\nyou can omit this proof, right?", "start": 3378.82, "duration": 6.92}, {"text": "So if you want to prove that-- so at block\n6, how do I prove that the outputs from transaction", "start": 3385.74, "duration": 7.29}, {"text": "1 still exist at block 6?", "start": 3393.03, "duration": 3.33}, {"text": "You're stuck, right?", "start": 3396.36, "duration": 1.0}, {"text": "You basically have to go through blocks 3\nthrough 6 and look at the whole thing.", "start": 3397.36, "duration": 6.77}, {"text": "So with current SPV proofs, we can prove inclusion,\nright?", "start": 3404.13, "duration": 3.72}, {"text": "You sort of think of this as an accumulator,\nwhere you've got-- a Merkle tree is kind of", "start": 3407.85, "duration": 3.59}, {"text": "an accumulator.", "start": 3411.44, "duration": 1.81}, {"text": "I can prove inclusion, and then I can prove\ntransaction 1 is in block 2.", "start": 3413.25, "duration": 3.23}, {"text": "I can prove that transaction 2 consumes transaction\n1 in block 5.", "start": 3416.48, "duration": 6.2}, {"text": "But you have to rely on me to give you that\nproof honestly, right?", "start": 3422.68, "duration": 4.13}, {"text": "If I'm trying to cheat you and say, oh yeah,\nI've totally still got money, I can't prove", "start": 3426.81, "duration": 6.12}, {"text": "that it hasn't been deleted.", "start": 3432.93, "duration": 1.73}, {"text": "Whereas with a UTXO set commitment, if every\nblock, there was a total commitment to every", "start": 3434.66, "duration": 6.93}, {"text": "UTXO, I could just say, hey, at block 6, my\noutput from transaction 1, it's still in there.", "start": 3441.59, "duration": 5.58}, {"text": "Well, it wouldn't be in this case.", "start": 3447.17, "duration": 1.14}, {"text": "But I could prove it at block 4, right?", "start": 3448.31, "duration": 1.78}, {"text": "And say, hey, look, transaction 1, it's still\nin there at block 4.", "start": 3450.09, "duration": 3.56}, {"text": "No longer there at block 6.", "start": 3453.65, "duration": 2.34}, {"text": "Depending on how you construct the UTXO commitment,\nyou may be able to provide non inclusion proofs,", "start": 3455.99, "duration": 7.47}, {"text": "which is also really cool.", "start": 3463.46, "duration": 1.95}, {"text": "So for example, if you had it be a Merkle\ntree, if it was just in order insertion--", "start": 3465.41, "duration": 7.85}, {"text": "so this is TX1, this is TX2, this is TX3,\nand you make a Merkle tree that way, then", "start": 3473.26, "duration": 8.32}, {"text": "you cannot prove that something's not in it,\nright?", "start": 3481.58, "duration": 4.32}, {"text": "So when TX3 gets deleted and now TX4 goes\nhere, and TX5 comes here, you can't prove", "start": 3485.9, "duration": 8.12}, {"text": "the TX3's not there anymore in any real way.", "start": 3494.02, "duration": 2.62}, {"text": "However, if you sort them so that every time\nso now you sort them canonically, so like", "start": 3496.64, "duration": 6.54}, {"text": "by hash, just like greater than, less than,\nand then the order gets all weird, right?", "start": 3503.18, "duration": 5.56}, {"text": "So now TX5 is here and TX6 is here because\nTX5's hash is closer to 1 and stuff like that.", "start": 3508.74, "duration": 8.31}, {"text": "Then you can prove non-inclusion.", "start": 3517.05, "duration": 1.69}, {"text": "So then you can say, hey, TX3 is not here\nbecause TX3 would be between 5 and 4, right?", "start": 3518.74, "duration": 7.57}, {"text": "Just based on what the hash looks like.", "start": 3526.31, "duration": 2.08}, {"text": "And I can show you 5.", "start": 3528.39, "duration": 1.0}, {"text": "I'm going to prove for it.", "start": 3529.39, "duration": 1.15}, {"text": "I can show you 4 and approve for it.", "start": 3530.54, "duration": 1.75}, {"text": "I can show that these two things are adjacent,\nright, in the tree.", "start": 3532.29, "duration": 4.03}, {"text": "And there's no 3 there, and it would be there.", "start": 3536.32, "duration": 2.43}, {"text": "If it existed, it would be right here.", "start": 3538.75, "duration": 2.531}, {"text": "And I can show that it's not there.", "start": 3541.281, "duration": 1.519}, {"text": "So then I have non-inclusion proofs in the\nUTXO set, which could be used for some kind", "start": 3542.8, "duration": 4.05}, {"text": "of fraud proof.", "start": 3546.85, "duration": 1.05}, {"text": "So if someone makes a transaction spending\nsomething, you can say, no, look, here is", "start": 3547.9, "duration": 5.91}, {"text": "the last block.", "start": 3553.81, "duration": 1.0}, {"text": "Here's the UTXO set hash.", "start": 3554.81, "duration": 1.65}, {"text": "And here's a proof that this input doesn't\nexist.", "start": 3556.46, "duration": 3.7}, {"text": "So this must be an invalid transaction.", "start": 3560.16, "duration": 2.01}, {"text": "That would be really cool, too.", "start": 3562.17, "duration": 1.23}, {"text": "Because then you could propagate that on the\nnetwork and sort of prove fraud.", "start": 3563.4, "duration": 6.25}, {"text": "So this is an idea that's been around for\na long time.", "start": 3569.65, "duration": 2.92}, {"text": "I think maybe the reason it hasn't yet been\nimplemented is, no one can really agree on", "start": 3572.57, "duration": 7.37}, {"text": "exactly how to do it.", "start": 3579.94, "duration": 1.51}, {"text": "A lot of people are like, yeah, we should\ndo that.", "start": 3581.45, "duration": 1.97}, {"text": "That would be cool.", "start": 3583.42, "duration": 1.28}, {"text": "Yeah, you can prove [INAUDIBLE].", "start": 3584.7, "duration": 4.1}, {"text": "So, one thing you could do would be to skip\nyears of initial block download.", "start": 3588.8, "duration": 4.01}, {"text": "So I don't really care what happened from\n2009 to 2015.", "start": 3592.81, "duration": 3.74}, {"text": "I assume it was fine, right?", "start": 3596.55, "duration": 2.84}, {"text": "I'm going to start my synchronization in 2016\nand just synchronize the last two years.", "start": 3599.39, "duration": 5.13}, {"text": "So I'll go get this UTXO commitment from end\nof 2015.", "start": 3604.52, "duration": 5.12}, {"text": "I will then not just get the commitment, but\ndownload a UTXO snapshot from that time.", "start": 3609.64, "duration": 5.62}, {"text": "And then I'll check that it matches the committed\nUTXO set hash.", "start": 3615.26, "duration": 4.81}, {"text": "And then I'll just start from there and then\nbecome a full node, where I didn't check the", "start": 3620.07, "duration": 6.05}, {"text": "first six years or something.", "start": 3626.12, "duration": 3.05}, {"text": "And its interesting mix of SPV security and\nregular full node security, and I think personally", "start": 3629.17, "duration": 6.51}, {"text": "that's probably OK, right?", "start": 3635.68, "duration": 2.89}, {"text": "If you only verify the last six months of\nsignatures, well, if everyone's been wrong", "start": 3638.57, "duration": 4.87}, {"text": "for six months, we have bigger problems, right?", "start": 3643.44, "duration": 2.54}, {"text": "If there's some erroneous transaction in 2015\nand the entire network has been just extending", "start": 3645.98, "duration": 7.81}, {"text": "for three years without reorging, like, wait,\nwhat?", "start": 3653.79, "duration": 4.93}, {"text": "So on the one hand, you don't want to do this\nfor today's blocks, right?", "start": 3658.72, "duration": 5.16}, {"text": "Because then the miners have full control.", "start": 3663.88, "duration": 2.67}, {"text": "And the miners can just make up transactions.", "start": 3666.55, "duration": 1.96}, {"text": "And if you really just say, oh, well, the\nminers are doing the right thing, then they", "start": 3668.51, "duration": 4.241}, {"text": "get a lot more power.", "start": 3672.751, "duration": 1.579}, {"text": "But if you say, well, other people are validating\nit in real time.", "start": 3674.33, "duration": 3.98}, {"text": "And I assume that that's the case, and I'll\nvalidate six months' worth of transactions.", "start": 3678.31, "duration": 4.54}, {"text": "So I'll pick up any errors in the last six\nmonths and be able to report them.", "start": 3682.85, "duration": 3.56}, {"text": "But I will assume that after a certain amount\nof time, I'm pretty sure it's been OK.", "start": 3686.41, "duration": 4.17}, {"text": "Everyone else has been looking for this.", "start": 3690.58, "duration": 1.97}, {"text": "So that's a slightly different model than\nfull nodes.", "start": 3692.55, "duration": 3.46}, {"text": "But in practice, not really.", "start": 3696.01, "duration": 1.77}, {"text": "Because if you look at the code for Bitcoin\ntoday, there's assume valid, which doesn't", "start": 3697.78, "duration": 6.5}, {"text": "check signatures.", "start": 3704.28, "duration": 1.0}, {"text": "It sort of has a block hash and says, OK,\nanything before this, don't check signatures.", "start": 3705.28, "duration": 4.51}, {"text": "The developers themselves have said, yeah,\nevery signature before here is OK, so you", "start": 3709.79, "duration": 4.42}, {"text": "have to check the signatures, which is a little\nnicer.", "start": 3714.21, "duration": 4.17}, {"text": "Before they had check points, where it would\njust not validate anything before a certain", "start": 3718.38, "duration": 4.151}, {"text": "block hash.", "start": 3722.531, "duration": 1.0}, {"text": "So you sort of already have things like that\nto speed up the initial synchronization process.", "start": 3723.531, "duration": 5.009}, {"text": "But a UTXO commitment would make it a lot\nmore sort of decentralized.", "start": 3728.54, "duration": 4.02}, {"text": "Because right now, it's just the programmers\nare like, well, this is last year.", "start": 3732.56, "duration": 5.03}, {"text": "Everyone's validated.", "start": 3737.59, "duration": 1.0}, {"text": "Let's just hard code this into the code, into\nthe client.", "start": 3738.59, "duration": 5.02}, {"text": "Anyway.", "start": 3743.61, "duration": 1.97}, {"text": "So this is an idea.", "start": 3745.58, "duration": 2.22}, {"text": "The issues-- timing is probably one of the\nbiggest issues.", "start": 3747.8, "duration": 3.7}, {"text": "If it's consensus critical, then the miners\nneed to put this into their blocks.", "start": 3751.5, "duration": 6.18}, {"text": "And miners also need to verify it when they\nget a block.", "start": 3757.68, "duration": 3.84}, {"text": "And adding even a second to creating and verifying\na block can centralize mining a bit.", "start": 3761.52, "duration": 6.54}, {"text": "Because the idea isl I want to be able to\nimmediately start mining as soon as I see", "start": 3768.06, "duration": 4.15}, {"text": "a block.", "start": 3772.21, "duration": 2.44}, {"text": "Because a larger miner doesn't need to verify\nthe block that just came out, right?", "start": 3774.65, "duration": 5.45}, {"text": "Because they created it.", "start": 3780.1, "duration": 1.0}, {"text": "If they created a block themselves, they know\nit's fine.", "start": 3781.1, "duration": 3.16}, {"text": "They build on top of it immediately with zero\npropagation delays, zero verification delay.", "start": 3784.26, "duration": 5.14}, {"text": "Smaller miners or miners receiving that block\nhave to make sure it's correct before mining", "start": 3789.4, "duration": 4.4}, {"text": "on top of it.", "start": 3793.8, "duration": 2.01}, {"text": "So adding even a one second creation verification\ndelay is something that a lot of the programmers", "start": 3795.81, "duration": 5.33}, {"text": "are like, mm, if you can get it down to half\na second, maybe we're OK.", "start": 3801.14, "duration": 3.92}, {"text": "We want this functionality, but not at the\ncost of increasing that.", "start": 3805.06, "duration": 4.86}, {"text": "That's the worst time to add something.", "start": 3809.92, "duration": 1.6}, {"text": "If you can defer it, if you can say, oh, well,\nyou need to verify this, but you can do it", "start": 3811.52, "duration": 5.91}, {"text": "after the fact or something, then it's fine.", "start": 3817.43, "duration": 2.14}, {"text": "So this I ran up against this because I had\nthis fun idea, where you could half aggregate", "start": 3819.57, "duration": 3.88}, {"text": "Schnorr signatures within a block and do it\nnon-interactively.", "start": 3823.45, "duration": 3.21}, {"text": "And it was really cool, and I'm pretty sure\nit works.", "start": 3826.66, "duration": 4.08}, {"text": "But it added, like, three seconds to block\nverification, so that killed that idea.", "start": 3830.74, "duration": 7.3}, {"text": "So one of the issues, yeah, timing.", "start": 3838.04, "duration": 2.99}, {"text": "Another issue is it does encourage more SPV\nlevel verification, where you can sort of", "start": 3841.03, "duration": 5.71}, {"text": "see that a lot of people will now use this\nmethod to not run a full node.", "start": 3846.74, "duration": 4.85}, {"text": "Because they're like, well, I can just get\nthese compact proofs for all the UTXOs, whether", "start": 3851.59, "duration": 5.04}, {"text": "inclusion or non-inclusion.", "start": 3856.63, "duration": 2.0}, {"text": "So why run a full node?", "start": 3858.63, "duration": 1.0}, {"text": "I don't need to verify it because other people\nare.", "start": 3859.63, "duration": 4.12}, {"text": "You don't really want to encourage that because\nthere's so much of that already.", "start": 3863.75, "duration": 2.99}, {"text": "Also, the biggest is probably there's got\nto be a better way to do this.", "start": 3866.74, "duration": 3.88}, {"text": "So there's all these different ideas on how\nto do it.", "start": 3870.62, "duration": 1.98}, {"text": "And they never seem to settle or converge\non a single way.", "start": 3872.6, "duration": 2.96}, {"text": "So the three main ideas are sort of hash based\nUTXO sets, elliptic curve based commitments,", "start": 3875.56, "duration": 8.19}, {"text": "and RSA based commitments.", "start": 3883.75, "duration": 2.67}, {"text": "And there's a lot of overlap with accumulators,\nin that you're sort of-- the UTXO commitment", "start": 3886.42, "duration": 5.22}, {"text": "could be the sort of route or the hash of\nthe accumulator itself.", "start": 3891.64, "duration": 4.07}, {"text": "That you want to prove that something's in\nthere or prove that something's not in there.", "start": 3895.71, "duration": 4.77}, {"text": "And the EC one is the current one that Sip\nwas looking at was looking at, but it never", "start": 3900.48, "duration": 3.51}, {"text": "made sense to me.", "start": 3903.99, "duration": 1.0}, {"text": "Because it's trivially-- you can provide invalid\nproofs really easily.", "start": 3904.99, "duration": 4.97}, {"text": "So it's all trusted.", "start": 3909.96, "duration": 1.569}, {"text": "But his idea was, well, let's say you have\na node that you synced up, and you want to", "start": 3911.529, "duration": 5.641}, {"text": "sort of port that to somewhere else.", "start": 3917.17, "duration": 4.32}, {"text": "You can do that very compactly with an elliptic\ncurve based UTXO commitment, which is cool,", "start": 3921.49, "duration": 5.51}, {"text": "but you can't trust the inclusion or non-inclusion\nproofs.", "start": 3927.0, "duration": 3.779}, {"text": "And there's RSA ones that also-- yeah, so\nthere's some overlap there.", "start": 3930.779, "duration": 5.561}, {"text": "Anyway it's a pretty cool idea.", "start": 3936.34, "duration": 2.36}, {"text": "It does exist in Ethereum, which is just hash\nbased that Joe Bonneau sort of explained the", "start": 3938.7, "duration": 5.02}, {"text": "tree thing they used.", "start": 3943.72, "duration": 2.55}, {"text": "But that doesn't provide for non-inclusion\nproofs, which would be fun.", "start": 3946.27, "duration": 3.2}, {"text": "So yeah, so this is another research area.", "start": 3949.47, "duration": 3.01}, {"text": "Any questions about UTXO commitments?", "start": 3952.48, "duration": 5.23}, {"text": "There's a bunch of-- Bram Cohen's Bitfield\nthing.", "start": 3957.71, "duration": 4.67}, {"text": "Have you seen that?", "start": 3962.38, "duration": 1.34}, {"text": "Yeah.", "start": 3963.72, "duration": 1.0}, {"text": "So that was a really interesting case of--\nin computer science terms, it's o of n.", "start": 3964.72, "duration": 5.09}, {"text": "But he got it so that it's actually one bit\nper spent transaction output.", "start": 3969.81, "duration": 5.86}, {"text": "So the idea would be maintain a TXO set, right?", "start": 3975.67, "duration": 7.14}, {"text": "So for every transaction output ever created\nin order, you have just bits, right?", "start": 3982.81, "duration": 5.85}, {"text": "So if eight transaction outputs are created,\nthat's a byte.", "start": 3988.66, "duration": 3.61}, {"text": "And you leave it all as zeros when they're\nunspent.", "start": 3992.27, "duration": 2.56}, {"text": "And when they have been spent, you just set\nit to 1.", "start": 3994.83, "duration": 3.1}, {"text": "And the thing is, yeah, there's 70 million,\nbut if it's that-- well, there's more.", "start": 3997.93, "duration": 6.05}, {"text": "There's hundreds of millions.", "start": 4003.98, "duration": 1.37}, {"text": "But if it's bits instead of bytes, that's\npretty small, right?", "start": 4005.35, "duration": 3.11}, {"text": "It's maybe 100 megabytes if you have 800 million\noutputs ever.", "start": 4008.46, "duration": 5.64}, {"text": "And then you can quickly see on your hard\ndrive, OK, this output has been spent.", "start": 4014.1, "duration": 4.21}, {"text": "And you can provide proofs and stuff.", "start": 4018.31, "duration": 1.75}, {"text": "So the Bitfield thing was a kind of an interesting\none.", "start": 4020.06, "duration": 2.42}, {"text": "OK, it's o of n, but 1 bit per object.", "start": 4022.48, "duration": 6.02}, {"text": "And you can sort of quickly sort between them.", "start": 4028.5, "duration": 2.41}, {"text": "So these are some of the things that-- I think\nthat's it for today, right?", "start": 4030.91, "duration": 4.27}, {"text": "I was going to talk about covenants, but that's\nanother story.", "start": 4035.18, "duration": 7.0}, {"text": "So these are some of the current research\nissues in Bitcoin, blockchain, cryptocurrency.", "start": 4042.18, "duration": 8.0}, {"text": "And there's lots of other topics.", "start": 4050.18, "duration": 1.08}, {"text": "But these are some of the big ones that I'm\naware of and I know people working on.", "start": 4051.26, "duration": 3.46}, {"text": "But yeah, there's lots of ways to improve\nprivacy, scalability, functionality.", "start": 4054.72, "duration": 6.3}, {"text": "It's certainly not like-- and sometimes people\nsay, oh, well, Bitcoin was made in 2009.", "start": 4061.02, "duration": 4.67}, {"text": "And it's like blockchain version 1.0, and\nwe need to make blockchain 4.0 or whatever.", "start": 4065.69, "duration": 7.68}, {"text": "And to some extent, yeah, Bitcoin is annoying\nto change, right?", "start": 4073.37, "duration": 3.14}, {"text": "It's difficult to change, and you've got the\nidea of a bridge node, and can't we just start", "start": 4076.51, "duration": 5.03}, {"text": "over?", "start": 4081.54, "duration": 1.0}, {"text": "It'd be so much easier.", "start": 4082.54, "duration": 1.0}, {"text": "In some cases, yes, it would be nicer to start\nover.", "start": 4083.54, "duration": 3.41}, {"text": "But that's sort of the challenge.", "start": 4086.95, "duration": 1.06}, {"text": "It's like, wait, can we make this system better,\nbut maintain backwards compatibility?", "start": 4088.01, "duration": 8.03}, {"text": "And so, in a lot of cases, like the accumulators\nor the client side Bloom filter checking,", "start": 4096.04, "duration": 7.759}, {"text": "it's not a fork at all, right?", "start": 4103.799, "duration": 3.471}, {"text": "The miners don't have to change anything.", "start": 4107.27, "duration": 1.629}, {"text": "If you don't know about this new change, you\ndon't have to change anything.", "start": 4108.899, "duration": 4.889}, {"text": "And so there are totally optional ways to\nimprove some of these things.", "start": 4113.788, "duration": 4.361}, {"text": "And that's a fun challenge, right?", "start": 4118.149, "duration": 1.811}, {"text": "You're given this system.", "start": 4119.96, "duration": 1.0}, {"text": "It's sort of like trying to improve an airplane\nwhile it's in flight, where you're like, OK,", "start": 4120.96, "duration": 5.299}, {"text": "I'm going to make it faster, make it better\nwhile it's flying.", "start": 4126.259, "duration": 3.51}, {"text": "We can't even land.", "start": 4129.769, "duration": 2.41}, {"text": "So yeah, that definitely makes it harder.", "start": 4132.179, "duration": 3.389}, {"text": "But other things are-- but what's also interesting\nis that there's not that many things in it", "start": 4135.568, "duration": 6.13}, {"text": "that really require starting over from scratch.", "start": 4141.698, "duration": 4.281}, {"text": "So I know at the New York City Bitcoin Core\nDeveloper Meetup in March, Bram Cohen, who", "start": 4145.979, "duration": 6.901}, {"text": "made BitTorrent-- he's making his own coin,\nI guess, now.", "start": 4152.88, "duration": 3.78}, {"text": "And it's kind of interesting because usually,\nthe Bitcoin people don't like alt coins or", "start": 4156.66, "duration": 4.86}, {"text": "are sort of wary of them, and don't invite\nalt coin people to their events and stuff.", "start": 4161.52, "duration": 5.11}, {"text": "But Bram Cohen invented BitTorrent, so everyone\nsort of owes him in some spiritual way a couple", "start": 4166.63, "duration": 5.169}, {"text": "thousand bucks for all the music and movies\nthey've downloaded, right?", "start": 4171.799, "duration": 5.321}, {"text": "So it's like, oh, Bram, he helped us out.", "start": 4177.12, "duration": 3.09}, {"text": "So he comes to these things.", "start": 4180.21, "duration": 1.608}, {"text": "And he was asking at the thing in March, OK--\nasking a lot of people-- if you were going", "start": 4181.818, "duration": 4.941}, {"text": "to start Bitcoin over from scratch, what would\nyou change?", "start": 4186.759, "duration": 4.27}, {"text": "All the people who were programming this for\nyears and dealing with all the annoying problems", "start": 4191.029, "duration": 4.67}, {"text": "in it gave, if you started from scratch, what\ncode do you change?", "start": 4195.699, "duration": 4.92}, {"text": "Or what sort of basic infrastructure things\ndo you change in the system?", "start": 4200.619, "duration": 4.201}, {"text": "And there weren't that many, right?", "start": 4204.82, "duration": 1.58}, {"text": "A lot of people were like, oh, there's the\nlittle things.", "start": 4206.4, "duration": 2.469}, {"text": "Like, oh, get rid of the little silly op zero\nin multi sig.", "start": 4208.869, "duration": 3.431}, {"text": "Get rid of this, or change a couple of these\nthings.", "start": 4212.3, "duration": 2.59}, {"text": "But not a lot of really fundamental changes\npeople would want to have made.", "start": 4214.89, "duration": 6.29}, {"text": "Some people were saying, hey, maybe instead\nof pointing based on TXID, be able to point", "start": 4221.18, "duration": 4.789}, {"text": "height and index, so you can have a lot smaller\nthere.", "start": 4225.969, "duration": 4.891}, {"text": "Some different opcode things, but what was\ninteresting is that-- and also, it's a super", "start": 4230.86, "duration": 5.94}, {"text": "biased sample.", "start": 4236.8, "duration": 1.0}, {"text": "And it's like, if you're asking all the people\nwho work on Bitcoin, well, yeah, they sort", "start": 4237.8, "duration": 4.299}, {"text": "of like how Bitcoin works, or at least, they've\ngrown accustomed to it.", "start": 4242.099, "duration": 3.89}, {"text": "So you might want to ask other people if you\nwant to sort of think out of the box.", "start": 4245.989, "duration": 3.25}, {"text": "But there weren't a ton of major changes that\npeople wanted to have made.", "start": 4249.239, "duration": 3.701}, {"text": "So it does seem that it's a fairly well thought\nout base of a system.", "start": 4252.94, "duration": 7.82}, {"text": "And then I'd say the Ethereum design is the\nother design that's very different, right?", "start": 4260.76, "duration": 4.04}, {"text": "The account based versus UTXO base.", "start": 4264.8, "duration": 2.819}, {"text": "And a lot of the people who work on Bitcoin\nthink that account based is worse.", "start": 4267.619, "duration": 4.181}, {"text": "A lot of people maybe in Ethereum case think\nUTXO base is worse.", "start": 4271.8, "duration": 3.719}, {"text": "They do have tradeoffs.", "start": 4275.52, "duration": 2.18}]
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+[{"text": "all right let's get started", "start": 12.88, "duration": 4.319}, {"text": "welcome back to double06 today we are", "start": 15.36, "duration": 3.2}, {"text": "doing some of the coolest data", "start": 17.199, "duration": 2.961}, {"text": "structures we will see in this class", "start": 18.56, "duration": 2.96}, {"text": "maybe some of the coolest data", "start": 20.16, "duration": 4.24}, {"text": "structures ever binary trees", "start": 21.52, "duration": 5.519}, {"text": "uh you've certainly seen trees in many", "start": 24.4, "duration": 3.28}, {"text": "forms", "start": 27.039, "duration": 3.441}, {"text": "uh in the past including in this class", "start": 27.68, "duration": 4.559}, {"text": "we've talked to use trees as a lower", "start": 30.48, "duration": 2.48}, {"text": "bound tool", "start": 32.239, "duration": 4.081}, {"text": "for uh in the decision tree model", "start": 32.96, "duration": 5.439}, {"text": "but this lecture and the next lecture", "start": 36.32, "duration": 3.759}, {"text": "we're going to build", "start": 38.399, "duration": 4.32}, {"text": "one data structure that is almost", "start": 40.079, "duration": 3.921}, {"text": "superior to all data", "start": 42.719, "duration": 3.921}, {"text": "structures we have seen and can do", "start": 44.0, "duration": 4.0}, {"text": "almost anything", "start": 46.64, "duration": 4.8}, {"text": "really fast first recall all the data", "start": 48.0, "duration": 5.12}, {"text": "structures we've seen so far arrays", "start": 51.44, "duration": 2.56}, {"text": "linked lists", "start": 53.12, "duration": 4.24}, {"text": "dynamic arrays sorted arrays hash tables", "start": 54.0, "duration": 6.079}, {"text": "and the two sets of operations we're", "start": 57.36, "duration": 3.92}, {"text": "interested in supporting", "start": 60.079, "duration": 3.28}, {"text": "the two interfaces one was sequences", "start": 61.28, "duration": 3.519}, {"text": "where we're maintaining items in a", "start": 63.359, "duration": 3.041}, {"text": "specified order we want to be able to", "start": 64.799, "duration": 2.161}, {"text": "insert", "start": 66.4, "duration": 2.32}, {"text": "an item right after another item or", "start": 66.96, "duration": 3.44}, {"text": "delete an item in the middle of the list", "start": 68.72, "duration": 3.28}, {"text": "and always be able to access the ith", "start": 70.4, "duration": 3.36}, {"text": "item we haven't seen", "start": 72.0, "duration": 3.28}, {"text": "any good data structures for that", "start": 73.76, "duration": 3.84}, {"text": "problem we we're really good at", "start": 75.28, "duration": 3.519}, {"text": "inserting and deleting", "start": 77.6, "duration": 2.559}, {"text": "at the beginning or the end of the", "start": 78.799, "duration": 3.841}, {"text": "sequence but we haven't seen anything", "start": 80.159, "duration": 4.32}, {"text": "that's efficient at ins", "start": 82.64, "duration": 3.68}, {"text": "inserting in the middle of the list or", "start": 84.479, "duration": 3.041}, {"text": "deleting in the middle of the list", "start": 86.32, "duration": 1.92}, {"text": "linked list", "start": 87.52, "duration": 2.8}, {"text": "you can't even get to the middle in less", "start": 88.24, "duration": 3.28}, {"text": "than linear time", "start": 90.32, "duration": 3.04}, {"text": "uh array you can get to the middle but", "start": 91.52, "duration": 3.44}, {"text": "if you make any changes you have to do", "start": 93.36, "duration": 3.68}, {"text": "this shift which is very expensive", "start": 94.96, "duration": 5.28}, {"text": "so today or sorry next lecture for the", "start": 97.04, "duration": 5.119}, {"text": "first time we will see", "start": 100.24, "duration": 6.08}, {"text": "all of those operations efficient", "start": 102.159, "duration": 4.161}, {"text": "i'll mention our goal where efficient", "start": 106.64, "duration": 5.04}, {"text": "means", "start": 110.399, "duration": 5.281}, {"text": "logarithmic so we're not quite as good", "start": 111.68, "duration": 6.079}, {"text": "as linked lists and dynamic arrays at", "start": 115.68, "duration": 3.119}, {"text": "inserting and", "start": 117.759, "duration": 3.121}, {"text": "deleting at the ends those there that we", "start": 118.799, "duration": 4.161}, {"text": "achieve constant or constant amortized", "start": 120.88, "duration": 2.8}, {"text": "time", "start": 122.96, "duration": 2.88}, {"text": "but up to this log factor we're going to", "start": 123.68, "duration": 3.92}, {"text": "get the best of all worlds where we can", "start": 125.84, "duration": 2.16}, {"text": "solve", "start": 127.6, "duration": 3.279}, {"text": "all the things all the operations that", "start": 128.0, "duration": 3.52}, {"text": "don't", "start": 130.879, "duration": 2.0}, {"text": "build or iterate through the entire", "start": 131.52, "duration": 2.96}, {"text": "structure that of course takes linear", "start": 132.879, "duration": 2.481}, {"text": "time", "start": 134.48, "duration": 2.0}, {"text": "but we can do all the others in", "start": 135.36, "duration": 3.599}, {"text": "logarithmic time for sets", "start": 136.48, "duration": 4.32}, {"text": "sets were maintained maintaining a bunch", "start": 138.959, "duration": 3.041}, {"text": "of items which have", "start": 140.8, "duration": 4.32}, {"text": "intrinsic keys and we want to", "start": 142.0, "duration": 6.319}, {"text": "search by key so hash tables are great", "start": 145.12, "duration": 5.6}, {"text": "if you're only doing exact searches if", "start": 148.319, "duration": 3.841}, {"text": "you want to find a key", "start": 150.72, "duration": 3.04}, {"text": "and get yes or no is it in there and if", "start": 152.16, "duration": 4.0}, {"text": "it's in there give me the item", "start": 153.76, "duration": 5.36}, {"text": "that's what python dictionaries do and", "start": 156.16, "duration": 3.28}, {"text": "they're", "start": 159.12, "duration": 2.32}, {"text": "great at inserting and deleting but", "start": 159.44, "duration": 3.519}, {"text": "they're really bad", "start": 161.44, "duration": 4.879}, {"text": "at find previous and find next this is a", "start": 162.959, "duration": 5.521}, {"text": "the unsuccessful case if i search for a", "start": 166.319, "duration": 4.481}, {"text": "key and it's not in my structure", "start": 168.48, "duration": 4.16}, {"text": "i would like to know more than just the", "start": 170.8, "duration": 4.24}, {"text": "answer no i'd like to know what the", "start": 172.64, "duration": 4.4}, {"text": "previous and next items that are", "start": 175.04, "duration": 3.44}, {"text": "actually in the structure", "start": 177.04, "duration": 3.68}, {"text": "so what are my nearest matches when i", "start": 178.48, "duration": 4.64}, {"text": "search by key that's a natural query", "start": 180.72, "duration": 4.48}, {"text": "and the only data structure we have", "start": 183.12, "duration": 4.24}, {"text": "that's good at it is a sorted array", "start": 185.2, "duration": 4.48}, {"text": "because binary search gives this to us", "start": 187.36, "duration": 4.239}, {"text": "if we search for a key by binary search", "start": 189.68, "duration": 3.36}, {"text": "and we don't find it", "start": 191.599, "duration": 3.441}, {"text": "the position that we end up at is right", "start": 193.04, "duration": 4.64}, {"text": "between the previous and next one", "start": 195.04, "duration": 4.32}, {"text": "but of course sorted arrays are terrible", "start": 197.68, "duration": 3.04}, {"text": "for dynamic", "start": 199.36, "duration": 4.4}, {"text": "operations we don't know how to maintain", "start": 200.72, "duration": 4.799}, {"text": "we can't maintain a sorted array without", "start": 203.76, "duration": 3.039}, {"text": "any gaps", "start": 205.519, "duration": 2.401}, {"text": "when we're doing insertions and", "start": 206.799, "duration": 3.201}, {"text": "deletions in some sense today", "start": 207.92, "duration": 4.239}, {"text": "and next class binary trees let us", "start": 210.0, "duration": 3.28}, {"text": "represent", "start": 212.159, "duration": 3.36}, {"text": "a sorted order or in general an order of", "start": 213.28, "duration": 3.28}, {"text": "items", "start": 215.519, "duration": 4.161}, {"text": "dynamically and still allow us to do", "start": 216.56, "duration": 5.759}, {"text": "very fast things like get out of i and", "start": 219.68, "duration": 4.24}, {"text": "find previous of the key", "start": 222.319, "duration": 3.521}, {"text": "so that's our goal we're not going to", "start": 223.92, "duration": 3.76}, {"text": "quite get to this goal today", "start": 225.84, "duration": 6.16}, {"text": "we're going to get an incomparable thing", "start": 227.68, "duration": 6.479}, {"text": "called the height of the tree and then", "start": 232.0, "duration": 3.92}, {"text": "on thursday we'll be able to finish and", "start": 234.159, "duration": 3.521}, {"text": "achieve this goal today is just", "start": 235.92, "duration": 5.92}, {"text": "in service to that goal", "start": 237.68, "duration": 4.16}, {"text": "so what is a binary tree", "start": 242.239, "duration": 7.2}, {"text": "let me draw an example", "start": 245.68, "duration": 6.72}, {"text": "and then define it more precisely", "start": 249.439, "duration": 4.8}, {"text": "mathematicians will call this a rooted", "start": 252.4, "duration": 2.8}, {"text": "binary tree", "start": 254.239, "duration": 2.96}, {"text": "because in case you've seen that in o42", "start": 255.2, "duration": 4.24}, {"text": "say", "start": 257.199, "duration": 2.241}, {"text": "here is a picture", "start": 259.84, "duration": 10.0}, {"text": "so this is an example of a binary tree", "start": 276.32, "duration": 4.08}, {"text": "it has a bunch of nodes which we're", "start": 279.04, "duration": 2.64}, {"text": "drawing in circles it has", "start": 280.4, "duration": 3.28}, {"text": "items in the nodes which were i'm", "start": 281.68, "duration": 3.76}, {"text": "writing as letters here", "start": 283.68, "duration": 4.64}, {"text": "so this is item a item b item c and it", "start": 285.44, "duration": 3.6}, {"text": "has these", "start": 288.32, "duration": 2.4}, {"text": "links between them this is like linked", "start": 289.04, "duration": 3.439}, {"text": "lists", "start": 290.72, "duration": 5.28}, {"text": "but in general a node", "start": 292.479, "duration": 8.561}, {"text": "x is going to have a parent pointer", "start": 296.0, "duration": 5.04}, {"text": "a left child", "start": 301.52, "duration": 6.239}, {"text": "left pointer and a right child", "start": 304.56, "duration": 6.96}, {"text": "right pointer and it also has", "start": 307.759, "duration": 6.72}, {"text": "an item inside of it so i'm going to", "start": 311.52, "duration": 4.48}, {"text": "talk about node.left", "start": 314.479, "duration": 4.881}, {"text": "is a pointer to the left", "start": 316.0, "duration": 5.52}, {"text": "the node down here node.right", "start": 319.36, "duration": 4.08}, {"text": "node.parent node.item", "start": 321.52, "duration": 5.2}, {"text": "gives me so if i", "start": 323.44, "duration": 6.4}, {"text": "look at the node a its item is", "start": 326.72, "duration": 8.64}, {"text": "a so let me draw for you", "start": 329.84, "duration": 5.52}, {"text": "some examples", "start": 337.12, "duration": 19.76}, {"text": "okay the parent of a is nothing so we", "start": 353.759, "duration": 3.681}, {"text": "call a", "start": 356.88, "duration": 1.84}, {"text": "the root node there's going to be a", "start": 357.44, "duration": 3.92}, {"text": "unique node that has no parent", "start": 358.72, "duration": 5.68}, {"text": "it's uh sad to have no parents but there", "start": 361.36, "duration": 4.0}, {"text": "you go", "start": 364.4, "duration": 3.2}, {"text": "then we have node b which whose parent", "start": 365.36, "duration": 3.279}, {"text": "is a", "start": 367.6, "duration": 3.52}, {"text": "node c is parent its apparent is a node", "start": 368.639, "duration": 4.161}, {"text": "d its parent is b", "start": 371.12, "duration": 4.48}, {"text": "node e its parent is b and node f its", "start": 372.8, "duration": 5.36}, {"text": "parent is d", "start": 375.6, "duration": 4.24}, {"text": "alphabetical order here happens to be", "start": 378.16, "duration": 4.479}, {"text": "ordered by parent", "start": 379.84, "duration": 2.799}, {"text": "then we have left pointers i'll just do", "start": 383.039, "duration": 3.681}, {"text": "a few of them so left pointer of", "start": 384.72, "duration": 5.919}, {"text": "a is b right pointer of a", "start": 386.72, "duration": 6.56}, {"text": "sorry b the node uh these should all be", "start": 390.639, "duration": 4.961}, {"text": "notes", "start": 393.28, "duration": 2.32}, {"text": "i'm circling for nodes and just writing", "start": 396.88, "duration": 3.2}, {"text": "the letter for the item", "start": 398.639, "duration": 2.641}, {"text": "make it clear that those are different", "start": 400.08, "duration": 3.76}, {"text": "things uh the right pointer for a", "start": 401.28, "duration": 5.919}, {"text": "is c left pointer for b is d", "start": 403.84, "duration": 7.199}, {"text": "right pointer for b is e and so on", "start": 407.199, "duration": 5.361}, {"text": "okay so in other words each of these", "start": 411.039, "duration": 4.0}, {"text": "lines is a bi-directional pointer", "start": 412.56, "duration": 4.16}, {"text": "uh in this direction it's the parent", "start": 415.039, "duration": 3.6}, {"text": "direction in this direction it's left in", "start": 416.72, "duration": 3.36}, {"text": "this case", "start": 418.639, "duration": 2.96}, {"text": "because it's bidirectional we don't draw", "start": 420.08, "duration": 4.239}, {"text": "the arrows we just draw", "start": 421.599, "duration": 6.16}, {"text": "undirected lines okay", "start": 424.319, "duration": 4.961}, {"text": "this is in general what a binary tree", "start": 427.759, "duration": 3.521}, {"text": "looks like", "start": 429.28, "duration": 4.8}, {"text": "a key invariant is that if you take a", "start": 431.28, "duration": 3.759}, {"text": "node", "start": 434.08, "duration": 4.0}, {"text": "and say go to its left pointer left", "start": 435.039, "duration": 7.361}, {"text": "child and then go to that node's parent", "start": 438.08, "duration": 7.36}, {"text": "this should be the same as node right so", "start": 442.4, "duration": 4.4}, {"text": "that's just saying these", "start": 445.44, "duration": 3.68}, {"text": "are in parent is always the inverse of a", "start": 446.8, "duration": 3.679}, {"text": "left or right operation", "start": 449.12, "duration": 4.72}, {"text": "this is also true for write", "start": 450.479, "duration": 3.361}, {"text": "okay and that's a binary tree now the", "start": 454.479, "duration": 4.081}, {"text": "intuition of what's going on here", "start": 456.639, "duration": 4.241}, {"text": "is you could you could say it's we're", "start": 458.56, "duration": 3.12}, {"text": "inspired by", "start": 460.88, "duration": 3.759}, {"text": "a linked list linked list had a very", "start": 461.68, "duration": 5.76}, {"text": "similar structure", "start": 464.639, "duration": 5.761}, {"text": "maybe an item or there's a node it had", "start": 467.44, "duration": 4.479}, {"text": "an item in it", "start": 470.4, "duration": 3.919}, {"text": "and it had a next pointer and it had a", "start": 471.919, "duration": 4.641}, {"text": "previous pointer", "start": 474.319, "duration": 3.921}, {"text": "so in some sense what we're if it's", "start": 476.56, "duration": 3.12}, {"text": "doubly linked we had a previous pointer", "start": 478.24, "duration": 3.04}, {"text": "it was singly linked we only had a next", "start": 479.68, "duration": 2.72}, {"text": "pointer", "start": 481.28, "duration": 4.24}, {"text": "and if you think about the limits of", "start": 482.4, "duration": 4.72}, {"text": "linked lists especially singly linked", "start": 485.52, "duration": 2.239}, {"text": "lists", "start": 487.12, "duration": 2.96}, {"text": "if you just have one pointer per node", "start": 487.759, "duration": 4.401}, {"text": "you can only build a list", "start": 490.08, "duration": 6.0}, {"text": "and so the result is uh", "start": 492.16, "duration": 3.92}, {"text": "you know this this node is going to have", "start": 497.12, "duration": 6.479}, {"text": "depth linear depth means how many", "start": 500.319, "duration": 5.521}, {"text": "pointers do i have to follow to get here", "start": 503.599, "duration": 4.241}, {"text": "from the root of the structure which for", "start": 505.84, "duration": 3.359}, {"text": "linked lists was the head", "start": 507.84, "duration": 3.199}, {"text": "it was doubly linked okay i can have a", "start": 509.199, "duration": 3.441}, {"text": "head and a tail and i can put", "start": 511.039, "duration": 2.8}, {"text": "bi-directions", "start": 512.64, "duration": 2.959}, {"text": "on here but then still the middle item", "start": 513.839, "duration": 3.76}, {"text": "has depth linear so there's no way to", "start": 515.599, "duration": 2.88}, {"text": "get there", "start": 517.599, "duration": 2.721}, {"text": "in less than linear time with binary", "start": 518.479, "duration": 3.601}, {"text": "trees because we use", "start": 520.32, "duration": 4.079}, {"text": "two types of next pointers left and", "start": 522.08, "duration": 3.36}, {"text": "right", "start": 524.399, "duration": 3.041}, {"text": "we can build a tree and we know trees in", "start": 525.44, "duration": 3.6}, {"text": "general have logarithmic", "start": 527.44, "duration": 4.64}, {"text": "can have logarithmic height", "start": 529.04, "duration": 6.239}, {"text": "and so it's possible in a tree to get to", "start": 532.08, "duration": 5.68}, {"text": "any node starting from the root in only", "start": 535.279, "duration": 4.481}, {"text": "log n traversals so that's the intuition", "start": 537.76, "duration": 3.28}, {"text": "of what's going on", "start": 539.76, "duration": 3.92}, {"text": "now today", "start": 541.04, "duration": 2.64}, {"text": "we're going to talk about the height of", "start": 544.8, "duration": 3.28}, {"text": "a tree", "start": 546.8, "duration": 4.32}, {"text": "so let me define", "start": 548.08, "duration": 3.04}, {"text": "i'm going to need a couple definitions", "start": 552.56, "duration": 3.68}, {"text": "here", "start": 554.08, "duration": 2.16}, {"text": "subtree and height", "start": 558.56, "duration": 8.48}, {"text": "of a node uh", "start": 563.839, "duration": 6.641}, {"text": "so a tree decomposes into sub trees", "start": 567.04, "duration": 6.4}, {"text": "so for example the subtree rooted at b", "start": 570.48, "duration": 4.56}, {"text": "or the subtree of b", "start": 573.44, "duration": 6.56}, {"text": "is this portion of the tree", "start": 575.04, "duration": 4.96}, {"text": "so it's that node and all of the", "start": 580.32, "duration": 4.32}, {"text": "descendants of this node so because we", "start": 582.64, "duration": 3.44}, {"text": "have parents and children", "start": 584.64, "duration": 4.319}, {"text": "we can generalize in the familial tree", "start": 586.08, "duration": 3.52}, {"text": "sense", "start": 588.959, "duration": 3.041}, {"text": "we can talk about ancestors of a node so", "start": 589.6, "duration": 3.6}, {"text": "the ancestors of f", "start": 592.0, "duration": 3.519}, {"text": "are its parent its grandparents its", "start": 593.2, "duration": 4.079}, {"text": "great grandparents and so on", "start": 595.519, "duration": 4.32}, {"text": "together all of these are called", "start": 597.279, "duration": 3.921}, {"text": "ancestors", "start": 599.839, "duration": 2.961}, {"text": "it's a it doesn't quite correspond to", "start": 601.2, "duration": 3.759}, {"text": "familiar trees because familial trees", "start": 602.8, "duration": 3.039}, {"text": "you have", "start": 604.959, "duration": 2.721}, {"text": "two parents here you only have a unique", "start": 605.839, "duration": 4.161}, {"text": "parent", "start": 607.68, "duration": 5.52}, {"text": "or the poor root has no parent", "start": 610.0, "duration": 5.839}, {"text": "we also talk about it's like mixed", "start": 613.2, "duration": 3.28}, {"text": "metaphors", "start": 615.839, "duration": 3.68}, {"text": "leaves of the tree", "start": 616.48, "duration": 5.599}, {"text": "these are", "start": 619.519, "duration": 2.56}, {"text": "people with no children parents will", "start": 623.519, "duration": 4.161}, {"text": "complain about this", "start": 626.72, "duration": 5.2}, {"text": "but many like many of us in this room we", "start": 627.68, "duration": 5.68}, {"text": "have no children yet so we were called", "start": 631.92, "duration": 2.56}, {"text": "leaves", "start": 633.36, "duration": 2.64}, {"text": "you can tell your parents hey i'm just a", "start": 634.48, "duration": 4.96}, {"text": "leaf you know blowing in the wind", "start": 636.0, "duration": 6.32}, {"text": "so uh you know like this it's so many", "start": 639.44, "duration": 4.0}, {"text": "mixed metaphors but we", "start": 642.32, "duration": 4.32}, {"text": "always draw trees downwards like the", "start": 643.44, "duration": 5.28}, {"text": "root structure of a tree", "start": 646.64, "duration": 4.96}, {"text": "yet we call the ends of the roots leaves", "start": 648.72, "duration": 3.92}, {"text": "which is upside down", "start": 651.6, "duration": 4.32}, {"text": "anyway that's trees for you lots of", "start": 652.64, "duration": 4.8}, {"text": "entertaining analogies okay but", "start": 655.92, "duration": 3.52}, {"text": "ancestors are useful descendants are", "start": 657.44, "duration": 2.56}, {"text": "also useful", "start": 659.44, "duration": 2.639}, {"text": "so the descendants of b are all of its", "start": 660.0, "duration": 3.839}, {"text": "children and all of its grandchildren", "start": 662.079, "duration": 2.721}, {"text": "and all the way down", "start": 663.839, "duration": 3.921}, {"text": "but just within the subtree so subtree", "start": 664.8, "duration": 3.68}, {"text": "of x", "start": 667.76, "duration": 8.079}, {"text": "consists of x and its descendants", "start": 668.48, "duration": 7.359}, {"text": "and we think of x being the root", "start": 676.88, "duration": 5.36}, {"text": "of that subtree so we're kind of", "start": 680.56, "duration": 3.68}, {"text": "forgetting about everything outside of", "start": 682.24, "duration": 2.88}, {"text": "the sub tree", "start": 684.24, "duration": 4.159}, {"text": "when we talk about sub tree of x let's", "start": 685.12, "duration": 4.32}, {"text": "talk about the", "start": 688.399, "duration": 3.841}, {"text": "depth of a node", "start": 689.44, "duration": 2.8}, {"text": "depth of the node is", "start": 693.279, "duration": 3.12}, {"text": "i guess the number of its ancestors", "start": 696.88, "duration": 10.24}, {"text": "right um but way i usually think of it", "start": 703.44, "duration": 3.92}, {"text": "is", "start": 707.12, "duration": 5.2}, {"text": "the number of number of edges", "start": 707.36, "duration": 4.96}, {"text": "and in the path from", "start": 712.88, "duration": 8.88}, {"text": "x up to the root", "start": 717.279, "duration": 4.481}, {"text": "so every node has a unique path that", "start": 722.48, "duration": 3.68}, {"text": "goes upwards", "start": 724.88, "duration": 4.0}, {"text": "until it can't go up anymore so the", "start": 726.16, "duration": 3.52}, {"text": "depth of e", "start": 728.88, "duration": 3.92}, {"text": "is two because there are two edges uh", "start": 729.68, "duration": 6.719}, {"text": "one two in the path from the root a to e", "start": 732.8, "duration": 6.159}, {"text": "so maybe i'll write some depths uh depth", "start": 736.399, "duration": 3.921}, {"text": "of e is two", "start": 738.959, "duration": 3.601}, {"text": "depth of these guys is one depth of the", "start": 740.32, "duration": 4.079}, {"text": "root is zero", "start": 742.56, "duration": 5.839}, {"text": "two three so those are", "start": 744.399, "duration": 8.641}, {"text": "depth i'm going to", "start": 748.399, "duration": 10.481}, {"text": "clean this up a little bit", "start": 753.04, "duration": 8.239}, {"text": "so we can focus on the image all right", "start": 758.88, "duration": 4.16}, {"text": "height so depth is measuring", "start": 761.279, "duration": 3.521}, {"text": "downwards because we you know if you", "start": 763.04, "duration": 3.599}, {"text": "imagine depth within water", "start": 764.8, "duration": 4.56}, {"text": "this is uh the surface of the water and", "start": 766.639, "duration": 4.561}, {"text": "then we measure how deep you are from", "start": 769.36, "duration": 2.8}, {"text": "the surface", "start": 771.2, "duration": 2.96}, {"text": "height is in the reverse direction we're", "start": 772.16, "duration": 3.84}, {"text": "going to measure from the leaf level", "start": 774.16, "duration": 3.919}, {"text": "up because leaves are the bottom of the", "start": 776.0, "duration": 3.6}, {"text": "tree so height", "start": 778.079, "duration": 5.361}, {"text": "of a node is going to be", "start": 779.6, "duration": 7.6}, {"text": "the number of edges", "start": 783.44, "duration": 8.079}, {"text": "in the longest downward path", "start": 787.2, "duration": 4.319}, {"text": "okay which is the same thing as the", "start": 799.519, "duration": 6.481}, {"text": "maximum depth of a node", "start": 802.8, "duration": 6.4}, {"text": "in x's subtree", "start": 806.0, "duration": 3.2}, {"text": "let's do height in red", "start": 812.8, "duration": 6.32}, {"text": "so uh how long is the longest path from", "start": 817.04, "duration": 4.0}, {"text": "f to a leaf well f is a leaf so all", "start": 819.12, "duration": 3.04}, {"text": "leaves have", "start": 821.04, "duration": 4.88}, {"text": "depth zero sorry height zero", "start": 822.16, "duration": 7.119}, {"text": "get it backwards um", "start": 825.92, "duration": 6.479}, {"text": "d here it's so there are two", "start": 829.279, "duration": 5.12}, {"text": "ways to go down this doesn't go to a", "start": 832.399, "duration": 4.081}, {"text": "leaf uh this one goes to a leaf", "start": 834.399, "duration": 5.201}, {"text": "and its height is zero so this height is", "start": 836.48, "duration": 6.32}, {"text": "one there's one edge to a leaf here b", "start": 839.6, "duration": 5.599}, {"text": "has two leaves it can get to we take the", "start": 842.8, "duration": 5.52}, {"text": "longest one so that's length two", "start": 845.199, "duration": 11.041}, {"text": "a similarly has height three", "start": 848.32, "duration": 11.36}, {"text": "okay so height we measure upward depth", "start": 856.24, "duration": 4.24}, {"text": "we measure", "start": 859.68, "duration": 3.68}, {"text": "downward well one thing we care about uh", "start": 860.48, "duration": 3.84}, {"text": "is just the height", "start": 863.36, "duration": 4.0}, {"text": "of the overall tree uh which", "start": 864.32, "duration": 7.519}, {"text": "is the height of the root", "start": 867.36, "duration": 4.479}, {"text": "and i'm going to call that h because", "start": 872.72, "duration": 4.16}, {"text": "we're going to use it a lot", "start": 873.92, "duration": 2.96}, {"text": "and what we're going to achieve today is", "start": 879.44, "duration": 3.759}, {"text": "all of these running times instead of", "start": 881.519, "duration": 2.721}, {"text": "being log n", "start": 883.199, "duration": 4.561}, {"text": "they're going to be order h", "start": 884.24, "duration": 3.52}, {"text": "so today our goal is to get all the", "start": 888.72, "duration": 4.32}, {"text": "operations we care about", "start": 891.6, "duration": 4.72}, {"text": "in order h type", "start": 893.04, "duration": 3.28}, {"text": "and then next lecture we're going to", "start": 897.04, "duration": 4.56}, {"text": "guarantee that h is always log n", "start": 899.519, "duration": 4.481}, {"text": "and then we'll get log n time so we need", "start": 901.6, "duration": 4.0}, {"text": "to do a bunch of work to achieve log n", "start": 904.0, "duration": 3.12}, {"text": "today we'll do the work that's all the", "start": 905.6, "duration": 2.88}, {"text": "tree manipulation", "start": 907.12, "duration": 3.36}, {"text": "and as long as your tree is nice and", "start": 908.48, "duration": 4.4}, {"text": "shallow it doesn't have high height", "start": 910.48, "duration": 3.84}, {"text": "if it has logarithmic height everything", "start": 912.88, "duration": 3.6}, {"text": "will be log n of course there are trees", "start": 914.32, "duration": 3.759}, {"text": "that are really bad", "start": 916.48, "duration": 4.719}, {"text": "right we can have a tree", "start": 918.079, "duration": 3.12}, {"text": "a tree like this which is basically a", "start": 924.8, "duration": 4.399}, {"text": "linked list", "start": 927.76, "duration": 3.36}, {"text": "where we only use right pointers and all", "start": 929.199, "duration": 3.44}, {"text": "the left pointers are none", "start": 931.12, "duration": 3.68}, {"text": "so there are height there are trees that", "start": 932.639, "duration": 3.12}, {"text": "are very high", "start": 934.8, "duration": 3.839}, {"text": "have high height um we want to avoid", "start": 935.759, "duration": 4.32}, {"text": "these but we won't worry about that till", "start": 938.639, "duration": 4.32}, {"text": "next lecture question", "start": 940.079, "duration": 2.88}, {"text": "what is the height of node c height of", "start": 945.44, "duration": 3.36}, {"text": "node c is zero", "start": 947.199, "duration": 3.2}, {"text": "because the length of the longest path", "start": 948.8, "duration": 3.2}, {"text": "the number of edges in the longest", "start": 950.399, "duration": 4.321}, {"text": "downward path is zero yeah we're", "start": 952.0, "duration": 6.079}, {"text": "counting edges not vertices", "start": 954.72, "duration": 3.359}, {"text": "uh yeah so the height of the tree is of", "start": 958.399, "duration": 5.201}, {"text": "course just the depth", "start": 962.399, "duration": 3.041}, {"text": "the maximum depth i think that's right", "start": 963.6, "duration": 3.84}, {"text": "so the height here is", "start": 965.44, "duration": 4.16}, {"text": "three and the maximum depth is this", "start": 967.44, "duration": 3.759}, {"text": "terribly drawn three", "start": 969.6, "duration": 3.28}, {"text": "so these happen to correspond in the", "start": 971.199, "duration": 3.121}, {"text": "maximum case", "start": 972.88, "duration": 4.399}, {"text": "but we use height to always mean maximum", "start": 974.32, "duration": 4.4}, {"text": "and so that's why", "start": 977.279, "duration": 3.36}, {"text": "we talk about the height of the tree", "start": 978.72, "duration": 3.359}, {"text": "depth of the tree is not defined", "start": 980.639, "duration": 5.281}, {"text": "just depths of notes okay", "start": 982.079, "duration": 6.961}, {"text": "um how do we use these trees to", "start": 985.92, "duration": 3.76}, {"text": "represent", "start": 989.04, "duration": 4.239}, {"text": "either a sequence or a set uh", "start": 989.68, "duration": 6.959}, {"text": "i claim that there is a natural order", "start": 993.279, "duration": 7.36}, {"text": "in trees called the traversal order", "start": 996.639, "duration": 4.0}, {"text": "of nodes or items", "start": 1007.839, "duration": 6.56}, {"text": "and the tree so i'm going to define a", "start": 1011.6, "duration": 4.32}, {"text": "particular order", "start": 1014.399, "duration": 5.281}, {"text": "uh say in this example", "start": 1015.92, "duration": 8.32}, {"text": "let's do the example first the", "start": 1019.68, "duration": 7.519}, {"text": "traversal order", "start": 1024.24, "duration": 2.959}, {"text": "is going to be f", "start": 1029.839, "duration": 6.96}, {"text": "d b", "start": 1032.959, "duration": 3.84}, {"text": "e a", "start": 1036.839, "duration": 6.521}, {"text": "c i feel like i'm in music class this is", "start": 1040.319, "duration": 5.12}, {"text": "my guitar or something but it's not i", "start": 1043.36, "duration": 3.52}, {"text": "hope um", "start": 1045.439, "duration": 5.201}, {"text": "if it is a coincidence so", "start": 1046.88, "duration": 6.08}, {"text": "what is this order what i'd like to do", "start": 1050.64, "duration": 3.84}, {"text": "is um", "start": 1052.96, "duration": 4.48}, {"text": "recursively define an order where the", "start": 1054.48, "duration": 4.24}, {"text": "root of the tree is somewhere in the", "start": 1057.44, "duration": 2.08}, {"text": "middle", "start": 1058.72, "duration": 3.68}, {"text": "and everything in the left subtree is", "start": 1059.52, "duration": 3.44}, {"text": "left", "start": 1062.4, "duration": 2.48}, {"text": "earlier in the order than the root and", "start": 1062.96, "duration": 4.16}, {"text": "everything in the right subtree is later", "start": 1064.88, "duration": 5.28}, {"text": "so you can see here c comes after a and", "start": 1067.12, "duration": 4.64}, {"text": "then all the other nodes come before", "start": 1070.16, "duration": 5.759}, {"text": "a and recursively if i look at a node b", "start": 1071.76, "duration": 7.2}, {"text": "this node b which appears over here e is", "start": 1075.919, "duration": 4.321}, {"text": "to the right of it", "start": 1078.96, "duration": 4.16}, {"text": "but it's this is all to the left of a so", "start": 1080.24, "duration": 3.2}, {"text": "e", "start": 1083.12, "duration": 3.84}, {"text": "is between b and a would be on the left", "start": 1083.44, "duration": 5.52}, {"text": "and then f and d are to the left of that", "start": 1086.96, "duration": 3.76}, {"text": "and again f comes before d", "start": 1088.96, "duration": 5.68}, {"text": "because f is in the left subtree of d", "start": 1090.72, "duration": 6.959}, {"text": "okay so we say", "start": 1094.64, "duration": 3.039}, {"text": "for every node", "start": 1098.0, "duration": 3.84}, {"text": "the nodes", "start": 1104.4, "duration": 9.12}, {"text": "in x dot left are before x", "start": 1107.6, "duration": 5.92}, {"text": "and the nodes in x dot right are come", "start": 1114.48, "duration": 8.64}, {"text": "after x", "start": 1117.919, "duration": 6.801}, {"text": "and this uniquely defines an order", "start": 1123.12, "duration": 3.2}, {"text": "called a traversal order", "start": 1124.72, "duration": 3.28}, {"text": "it's also called the in-order traversal", "start": 1126.32, "duration": 4.16}, {"text": "order it's called in order because it's", "start": 1128.0, "duration": 4.32}, {"text": "in the traversal order so it's very", "start": 1130.48, "duration": 3.6}, {"text": "circular but", "start": 1132.32, "duration": 3.44}, {"text": "you may have seen inorder traversal this", "start": 1134.08, "duration": 3.12}, {"text": "is the same thing", "start": 1135.76, "duration": 2.88}, {"text": "there's a very simple algorithm for", "start": 1137.2, "duration": 3.52}, {"text": "computing this", "start": 1138.64, "duration": 5.44}, {"text": "if i want to iterate", "start": 1140.72, "duration": 6.64}, {"text": "uh let's call this yeah if i want to", "start": 1144.08, "duration": 4.24}, {"text": "iterate", "start": 1147.36, "duration": 4.24}, {"text": "all the nodes within a subtree x rooted", "start": 1148.32, "duration": 4.8}, {"text": "by x", "start": 1151.6, "duration": 4.959}, {"text": "i just iterate on all of the", "start": 1153.12, "duration": 6.799}, {"text": "nodes in the left subtree then i output", "start": 1156.559, "duration": 6.081}, {"text": "x itself", "start": 1159.919, "duration": 2.721}, {"text": "then i iterate on all the nodes in the", "start": 1162.799, "duration": 5.041}, {"text": "right subtree", "start": 1165.2, "duration": 2.64}, {"text": "okay you may have seen that algorithm", "start": 1170.72, "duration": 3.6}, {"text": "before this is just another way to", "start": 1172.559, "duration": 3.12}, {"text": "codify the same thing", "start": 1174.32, "duration": 3.2}, {"text": "the result is all the nodes within a", "start": 1175.679, "duration": 3.921}, {"text": "subtree appear continuously with no", "start": 1177.52, "duration": 3.279}, {"text": "interruptions", "start": 1179.6, "duration": 3.76}, {"text": "and then the parent parent's going to", "start": 1180.799, "duration": 4.0}, {"text": "come before after depending on whether", "start": 1183.36, "duration": 4.72}, {"text": "it's the left or right child", "start": 1184.799, "duration": 3.281}, {"text": "okay so and now it's just a matter of", "start": 1188.4, "duration": 4.32}, {"text": "connecting the dots because we're", "start": 1191.36, "duration": 3.28}, {"text": "representing an order", "start": 1192.72, "duration": 4.0}, {"text": "and for sequence that is going to be the", "start": 1194.64, "duration": 3.68}, {"text": "sequence order if we want to store n", "start": 1196.72, "duration": 3.44}, {"text": "items x0 through x1", "start": 1198.32, "duration": 4.479}, {"text": "we're going to build some kind of tree", "start": 1200.16, "duration": 3.999}, {"text": "we're going to put x0 here", "start": 1202.799, "duration": 4.721}, {"text": "x1 here x2 here x3 here x4 here x5", "start": 1204.159, "duration": 5.361}, {"text": "here you can see i'm very used to", "start": 1207.52, "duration": 3.44}, {"text": "dealing with traversal orders it takes a", "start": 1209.52, "duration": 2.24}, {"text": "little while", "start": 1210.96, "duration": 2.0}, {"text": "uh you could also see it here we're", "start": 1211.76, "duration": 3.76}, {"text": "going to put x1 on this node x2", "start": 1212.96, "duration": 5.36}, {"text": "sorry x0 here x1 here x2 here and so on", "start": 1215.52, "duration": 6.24}, {"text": "that's the same order that i gave", "start": 1218.32, "duration": 5.28}, {"text": "okay that's for sequences for sets that", "start": 1221.76, "duration": 3.36}, {"text": "order is just going to be the sorted", "start": 1223.6, "duration": 2.16}, {"text": "order", "start": 1225.12, "duration": 2.08}, {"text": "and we're going to be effectively", "start": 1225.76, "duration": 3.6}, {"text": "representing the sorted order of keys", "start": 1227.2, "duration": 6.08}, {"text": "say increasing but before we get to that", "start": 1229.36, "duration": 7.12}, {"text": "let's talk about different operations we", "start": 1233.28, "duration": 5.6}, {"text": "can do", "start": 1236.48, "duration": 2.4}, {"text": "just playing around with traversal order", "start": 1239.52, "duration": 4.08}, {"text": "and then we're going to use these to", "start": 1243.84, "duration": 3.76}, {"text": "build the sequence and set operations", "start": 1245.12, "duration": 4.4}, {"text": "that we care about", "start": 1247.6, "duration": 5.12}, {"text": "so first operation i'll call", "start": 1249.52, "duration": 5.92}, {"text": "subtree first seems appropriate that", "start": 1252.72, "duration": 5.439}, {"text": "it's called first", "start": 1255.44, "duration": 2.719}, {"text": "it's the first one so given a node", "start": 1258.48, "duration": 7.6}, {"text": "which i'll call node uh this defines", "start": 1262.64, "duration": 6.24}, {"text": "a subtree", "start": 1266.08, "duration": 2.8}, {"text": "which usually we draw subtrees as", "start": 1270.08, "duration": 6.16}, {"text": "triangles hanging off of the node", "start": 1272.48, "duration": 6.88}, {"text": "so here i would write x", "start": 1276.24, "duration": 4.96}, {"text": "and then there's some subtree of all the", "start": 1279.36, "duration": 3.76}, {"text": "descendants of x", "start": 1281.2, "duration": 4.24}, {"text": "so with subtree first i would like to", "start": 1283.12, "duration": 3.28}, {"text": "say among", "start": 1285.44, "duration": 6.4}, {"text": "all the nodes in this subtree", "start": 1286.4, "duration": 5.44}, {"text": "which comes first in traversal order", "start": 1294.24, "duration": 4.559}, {"text": "so just restricting to", "start": 1303.12, "duration": 3.52}, {"text": "that subtree so tree of that", "start": 1306.96, "duration": 4.32}, {"text": "so where is it in this tree", "start": 1315.039, "duration": 4.801}, {"text": "uh note is actually part of many sub", "start": 1323.84, "duration": 3.36}, {"text": "trees good question uh", "start": 1325.52, "duration": 4.48}, {"text": "f f is in its own in the sub tree of f", "start": 1327.2, "duration": 3.2}, {"text": "uh", "start": 1330.0, "duration": 2.48}, {"text": "f is also in the subtree of d f is in", "start": 1330.4, "duration": 3.68}, {"text": "the sub tree of b like i drew", "start": 1332.48, "duration": 3.36}, {"text": "f is in the subtree of a it's in the", "start": 1334.08, "duration": 5.76}, {"text": "subtree of exactly its ancestors", "start": 1335.84, "duration": 4.0}, {"text": "but in this operation when we define", "start": 1340.559, "duration": 3.441}, {"text": "node", "start": 1343.12, "duration": 3.2}, {"text": "our node only defines one sub-tree it is", "start": 1344.0, "duration": 4.08}, {"text": "the root of only one sub-tree", "start": 1346.32, "duration": 3.04}, {"text": "and that's the sub-tree we're talking", "start": 1348.08, "duration": 4.16}, {"text": "about and then i want to know among all", "start": 1349.36, "duration": 5.199}, {"text": "those nodes which includes node itself", "start": 1352.24, "duration": 4.96}, {"text": "and other things uh which one comes", "start": 1354.559, "duration": 3.12}, {"text": "first", "start": 1357.2, "duration": 2.08}, {"text": "in this traversal order this is like", "start": 1357.679, "duration": 4.721}, {"text": "practice with traversal orders", "start": 1359.28, "duration": 6.48}, {"text": "so where should i look for this node", "start": 1362.4, "duration": 3.36}, {"text": "yeah the leftmost leaf", "start": 1369.2, "duration": 5.76}, {"text": "in the picture it's here but pictures", "start": 1372.799, "duration": 4.321}, {"text": "can be deceiving", "start": 1374.96, "duration": 5.28}, {"text": "we just want to go left", "start": 1377.12, "duration": 5.36}, {"text": "as much as possible when i say go left i", "start": 1380.24, "duration": 6.24}, {"text": "mean this iteration node equals", "start": 1382.48, "duration": 4.0}, {"text": "node.left you just look at our", "start": 1386.84, "duration": 3.56}, {"text": "definition", "start": 1388.799, "duration": 4.481}, {"text": "all the nodes on the left come before x", "start": 1390.4, "duration": 4.48}, {"text": "and all the nodes in the right so", "start": 1393.28, "duration": 3.04}, {"text": "it's got to be in the left subtree if", "start": 1394.88, "duration": 3.679}, {"text": "there is one uh", "start": 1396.32, "duration": 5.28}, {"text": "of course we can't do this forever so", "start": 1398.559, "duration": 8.081}, {"text": "say until we would fall off the tree", "start": 1401.6, "duration": 5.04}, {"text": "which means uh node is none", "start": 1408.159, "duration": 5.681}, {"text": "okay but we stopped uh before that would", "start": 1414.72, "duration": 4.959}, {"text": "happen", "start": 1418.559, "duration": 3.041}, {"text": "so this is like uh the directions like", "start": 1419.679, "duration": 3.681}, {"text": "oh you keep driving until you see the", "start": 1421.6, "duration": 2.319}, {"text": "store", "start": 1423.36, "duration": 2.319}, {"text": "and it's the block right before that", "start": 1423.919, "duration": 3.76}, {"text": "it's like well that's not very helpful", "start": 1425.679, "duration": 3.841}, {"text": "so uh you keep iterating node equals no", "start": 1427.679, "duration": 3.281}, {"text": "dot left until node becomes", "start": 1429.52, "duration": 4.32}, {"text": "none and then you undo one step okay you", "start": 1430.96, "duration": 4.24}, {"text": "all know how to program that it's not", "start": 1433.84, "duration": 2.079}, {"text": "hard", "start": 1435.2, "duration": 3.76}, {"text": "um so that last non-none", "start": 1435.919, "duration": 4.961}, {"text": "node which might actually be the root it", "start": 1438.96, "duration": 3.44}, {"text": "might be node", "start": 1440.88, "duration": 4.0}, {"text": "maybe it has no left children but in", "start": 1442.4, "duration": 4.56}, {"text": "that case i claim node is the very first", "start": 1444.88, "duration": 4.0}, {"text": "in its in its subtree traversal order", "start": 1446.96, "duration": 2.719}, {"text": "because", "start": 1448.88, "duration": 3.039}, {"text": "if there are no nodes in the left that", "start": 1449.679, "duration": 5.441}, {"text": "come before x then x is actually first", "start": 1451.919, "duration": 6.481}, {"text": "okay and that so that's it uh return", "start": 1455.12, "duration": 5.6}, {"text": "node", "start": 1458.4, "duration": 2.32}, {"text": "so i'm modifying node in place here and", "start": 1462.4, "duration": 4.08}, {"text": "the very last one before i hit none", "start": 1464.64, "duration": 2.8}, {"text": "that's the minimum", "start": 1466.48, "duration": 3.199}, {"text": "that's the first item in the traversal", "start": 1467.44, "duration": 4.239}, {"text": "order similarly you can define subtree", "start": 1469.679, "duration": 3.12}, {"text": "last", "start": 1471.679, "duration": 3.681}, {"text": "okay let's do a more interesting one", "start": 1472.799, "duration": 5.201}, {"text": "successor", "start": 1475.36, "duration": 2.64}, {"text": "node so in this case i want to know what", "start": 1481.36, "duration": 4.08}, {"text": "is", "start": 1485.039, "duration": 3.12}, {"text": "the next", "start": 1485.44, "duration": 2.719}, {"text": "after node in the", "start": 1490.0, "duration": 6.96}, {"text": "overall tree's traversal order okay here", "start": 1493.6, "duration": 5.24}, {"text": "i was restricting to", "start": 1496.96, "duration": 4.959}, {"text": "uh a single sub tree now i'm thinking", "start": 1498.84, "duration": 4.68}, {"text": "about the entire tree in the entire", "start": 1501.919, "duration": 2.561}, {"text": "traversal order", "start": 1503.52, "duration": 2.88}, {"text": "and given a node i want to know which", "start": 1504.48, "duration": 3.6}, {"text": "one comes next", "start": 1506.4, "duration": 4.96}, {"text": "call this the successor i feel like i", "start": 1508.08, "duration": 3.68}, {"text": "should", "start": 1511.36, "duration": 3.52}, {"text": "make some kind of royal family joke now", "start": 1511.76, "duration": 3.6}, {"text": "but", "start": 1514.88, "duration": 3.76}, {"text": "i don't know how um so", "start": 1515.36, "duration": 5.28}, {"text": "every node has a unique successor let's", "start": 1518.64, "duration": 4.0}, {"text": "do let's do some examples", "start": 1520.64, "duration": 5.44}, {"text": "so we can start with f the successor of", "start": 1522.64, "duration": 5.36}, {"text": "f if we just index into this", "start": 1526.08, "duration": 5.04}, {"text": "list the successor is d okay", "start": 1528.0, "duration": 6.0}, {"text": "successor of d is b successor b is ease", "start": 1531.12, "duration": 4.64}, {"text": "okay it's very easy to read successors", "start": 1534.0, "duration": 2.159}, {"text": "off", "start": 1535.76, "duration": 1.84}, {"text": "when i have the traversal order written", "start": 1536.159, "duration": 3.281}, {"text": "down but let's think about how to do it", "start": 1537.6, "duration": 3.84}, {"text": "in the tree", "start": 1539.44, "duration": 5.44}, {"text": "okay uh", "start": 1541.44, "duration": 3.44}, {"text": "let's see there are going to be two", "start": 1545.039, "duration": 3.441}, {"text": "cases", "start": 1546.559, "duration": 5.6}, {"text": "if i look at the successor of a it has a", "start": 1548.48, "duration": 5.36}, {"text": "right child", "start": 1552.159, "duration": 4.0}, {"text": "and in this case the right child of a is", "start": 1553.84, "duration": 4.079}, {"text": "the successor but that's not always the", "start": 1556.159, "duration": 2.481}, {"text": "case", "start": 1557.919, "duration": 3.841}, {"text": "i don't have a good example but if i had", "start": 1558.64, "duration": 5.44}, {"text": "another node here let's call it", "start": 1561.76, "duration": 6.32}, {"text": "g uh the successor of a", "start": 1564.08, "duration": 7.28}, {"text": "is actually g right because", "start": 1568.08, "duration": 6.079}, {"text": "all of these items come after a in the", "start": 1571.36, "duration": 3.52}, {"text": "order", "start": 1574.159, "duration": 3.041}, {"text": "but which one comes first the leftmost", "start": 1574.88, "duration": 3.679}, {"text": "leaf", "start": 1577.2, "duration": 3.52}, {"text": "okay that's the problem we just solved", "start": 1578.559, "duration": 4.081}, {"text": "so if a has a right child", "start": 1580.72, "duration": 4.0}, {"text": "what we want is the leftmost leaf the", "start": 1582.64, "duration": 3.039}, {"text": "first", "start": 1584.72, "duration": 5.199}, {"text": "thing in that subtree", "start": 1585.679, "duration": 4.24}, {"text": "the right subtree right child sub tree", "start": 1590.0, "duration": 3.919}, {"text": "so this is case one", "start": 1592.48, "duration": 5.28}, {"text": "if uh node.right", "start": 1593.919, "duration": 6.88}, {"text": "so if we have a right child then", "start": 1597.76, "duration": 6.799}, {"text": "what we want is", "start": 1600.799, "duration": 3.76}, {"text": "subtree first", "start": 1604.64, "duration": 2.88}, {"text": "of the right child", "start": 1608.72, "duration": 5.12}, {"text": "great we can reduce to this other", "start": 1614.799, "duration": 3.921}, {"text": "operation", "start": 1616.799, "duration": 4.88}, {"text": "but what if the node doesn't have a", "start": 1618.72, "duration": 4.0}, {"text": "right child", "start": 1621.679, "duration": 3.841}, {"text": "so for example it could be a leaf say", "start": 1622.72, "duration": 3.28}, {"text": "we're taking", "start": 1625.52, "duration": 2.88}, {"text": "the successor of i mean it doesn't have", "start": 1626.0, "duration": 3.919}, {"text": "to be a leaf could be f which has no", "start": 1628.4, "duration": 3.2}, {"text": "children it could be d which has one", "start": 1629.919, "duration": 4.161}, {"text": "child but no right child", "start": 1631.6, "duration": 5.52}, {"text": "so what's the successor of f well it's d", "start": 1634.08, "duration": 5.76}, {"text": "which in this case is the parent but", "start": 1637.12, "duration": 4.4}, {"text": "it's not always for example if we do", "start": 1639.84, "duration": 2.559}, {"text": "successor of e", "start": 1641.52, "duration": 2.96}, {"text": "its parent is actually earlier in the", "start": 1642.399, "duration": 4.081}, {"text": "order because e was a right child", "start": 1644.48, "duration": 4.72}, {"text": "here f was a left child and so its", "start": 1646.48, "duration": 3.919}, {"text": "parent", "start": 1649.2, "duration": 3.92}, {"text": "was after", "start": 1650.399, "duration": 2.721}, {"text": "successor of d happens to be b because", "start": 1653.76, "duration": 5.68}, {"text": "uh it's per it was the left child of its", "start": 1656.88, "duration": 3.279}, {"text": "parent", "start": 1659.44, "duration": 2.32}, {"text": "okay so that seems like the easy case if", "start": 1660.159, "duration": 3.041}, {"text": "we're the left child of our parent", "start": 1661.76, "duration": 5.279}, {"text": "then our successor is our parent okay", "start": 1663.2, "duration": 5.839}, {"text": "basing on this small example but we can", "start": 1667.039, "duration": 3.201}, {"text": "argue it generally in a moment", "start": 1669.039, "duration": 3.76}, {"text": "what's the successor of e uh well it's", "start": 1670.24, "duration": 4.88}, {"text": "not b because that comes earlier in fact", "start": 1672.799, "duration": 4.24}, {"text": "all the things in this in b sub tree", "start": 1675.12, "duration": 4.4}, {"text": "come earlier or equal to", "start": 1677.039, "duration": 6.721}, {"text": "e um so we have to keep going up", "start": 1679.52, "duration": 6.08}, {"text": "and then it turns out the successor of e", "start": 1683.76, "duration": 4.0}, {"text": "is a because this subtree", "start": 1685.6, "duration": 5.12}, {"text": "was the left child of a because b was a", "start": 1687.76, "duration": 4.639}, {"text": "left child with a", "start": 1690.72, "duration": 4.319}, {"text": "so the general strategy is walk up the", "start": 1692.399, "duration": 5.121}, {"text": "tree", "start": 1695.039, "duration": 5.76}, {"text": "until we are we we go", "start": 1697.52, "duration": 5.519}, {"text": "up a traversal whose reverse direction", "start": 1700.799, "duration": 3.76}, {"text": "would be left", "start": 1703.039, "duration": 4.88}, {"text": "okay so um walk", "start": 1704.559, "duration": 6.24}, {"text": "up the tree when i say walk up i mean", "start": 1707.919, "duration": 4.48}, {"text": "node equals node.parent", "start": 1710.799, "duration": 4.161}, {"text": "iteration", "start": 1712.399, "duration": 2.561}, {"text": "until", "start": 1720.32, "duration": 2.479}, {"text": "we go up a left", "start": 1723.36, "duration": 5.84}, {"text": "branch", "start": 1726.799, "duration": 2.401}, {"text": "so this would mean that node before we", "start": 1730.48, "duration": 4.16}, {"text": "do the change", "start": 1733.679, "duration": 6.561}, {"text": "node equals node.parent node.parent.left", "start": 1734.64, "duration": 5.6}, {"text": "okay so we can check that and then after", "start": 1742.96, "duration": 4.319}, {"text": "we do that traversal that parent", "start": 1744.96, "duration": 8.56}, {"text": "is exactly the node we're looking for", "start": 1747.279, "duration": 8.241}, {"text": "okay why is this true in general let me", "start": 1753.52, "duration": 4.159}, {"text": "draw a more generic picture", "start": 1755.52, "duration": 5.759}, {"text": "so we're starting at some node", "start": 1757.679, "duration": 3.6}, {"text": "and let's say its parent is to the right", "start": 1761.76, "duration": 5.68}, {"text": "so it comes later in the order", "start": 1765.36, "duration": 5.12}, {"text": "for a while sorry get this backwards", "start": 1767.44, "duration": 5.92}, {"text": "we're doing successor", "start": 1770.48, "duration": 2.88}, {"text": "so it goes to left for a while", "start": 1774.48, "duration": 5.439}, {"text": "so these are all these nodes will come", "start": 1778.32, "duration": 2.959}, {"text": "earlier in the order because by the", "start": 1779.919, "duration": 2.561}, {"text": "definition everything in the right", "start": 1781.279, "duration": 2.64}, {"text": "subtree comes after", "start": 1782.48, "duration": 2.96}, {"text": "and at some point we have a parent", "start": 1783.919, "duration": 3.281}, {"text": "that's to the right meaning this node", "start": 1785.44, "duration": 2.88}, {"text": "was the left", "start": 1787.2, "duration": 3.76}, {"text": "child of this parent and that node by", "start": 1788.32, "duration": 3.839}, {"text": "definition will come", "start": 1790.96, "duration": 4.319}, {"text": "after all of the nodes in here", "start": 1792.159, "duration": 5.041}, {"text": "and could there be anything in between", "start": 1795.279, "duration": 3.52}, {"text": "node and this", "start": 1797.2, "duration": 6.0}, {"text": "uh this parent grandparent ancestor", "start": 1798.799, "duration": 5.841}, {"text": "only if there was something in this", "start": 1803.2, "duration": 3.76}, {"text": "subtree and we're in the case here", "start": 1804.64, "duration": 4.159}, {"text": "where there is no right subtree of our", "start": 1806.96, "duration": 3.28}, {"text": "original node", "start": 1808.799, "duration": 3.281}, {"text": "so this this is where all the nodes in", "start": 1810.24, "duration": 3.52}, {"text": "between node and here would be", "start": 1812.08, "duration": 3.52}, {"text": "but there aren't any and therefore this", "start": 1813.76, "duration": 3.919}, {"text": "is the successor", "start": 1815.6, "duration": 4.64}, {"text": "so that's sort of the general argument", "start": 1817.679, "duration": 3.681}, {"text": "why this", "start": 1820.24, "duration": 16.799}, {"text": "works i see a question yeah", "start": 1821.36, "duration": 17.199}, {"text": "placed into the traverse order so the", "start": 1837.039, "duration": 3.281}, {"text": "traversal order is never explicitly", "start": 1838.559, "duration": 3.12}, {"text": "computed", "start": 1840.32, "duration": 3.76}, {"text": "what we're taught it's always implicit", "start": 1841.679, "duration": 4.161}, {"text": "we can't afford to maintain", "start": 1844.08, "duration": 5.12}, {"text": "this as say an array this is just", "start": 1845.84, "duration": 7.92}, {"text": "in our heads maybe i will draw it with a", "start": 1849.2, "duration": 8.319}, {"text": "cloud around it we're just thinking this", "start": 1853.76, "duration": 6.48}, {"text": "okay it's not in the computer explicitly", "start": 1857.519, "duration": 5.601}, {"text": "in the computer all we store is this", "start": 1860.24, "duration": 4.88}, {"text": "and the reason is this is expensive we", "start": 1863.12, "duration": 3.76}, {"text": "don't we can't maintain an array of", "start": 1865.12, "duration": 3.2}, {"text": "things and be able to insert in the", "start": 1866.88, "duration": 1.919}, {"text": "middle", "start": 1868.32, "duration": 2.64}, {"text": "whereas this is cheap i can afford to", "start": 1868.799, "duration": 3.76}, {"text": "maintain this structure", "start": 1870.96, "duration": 3.199}, {"text": "and do all these things and so the", "start": 1872.559, "duration": 2.72}, {"text": "reason we're talking about these", "start": 1874.159, "duration": 2.481}, {"text": "operations is they're letting us", "start": 1875.279, "duration": 3.681}, {"text": "manipulate the order or in this case", "start": 1876.64, "duration": 3.2}, {"text": "letting us", "start": 1878.96, "duration": 2.959}, {"text": "iterate through the order so this was an", "start": 1879.84, "duration": 3.28}, {"text": "algorithm for iterating through the", "start": 1881.919, "duration": 2.24}, {"text": "entire order", "start": 1883.12, "duration": 4.08}, {"text": "but that takes linear time this was", "start": 1884.159, "duration": 5.041}, {"text": "getting started in the order find me the", "start": 1887.2, "duration": 3.359}, {"text": "first", "start": 1889.2, "duration": 3.04}, {"text": "first thing the order and this was given", "start": 1890.559, "duration": 4.401}, {"text": "one node find me the next one", "start": 1892.24, "duration": 15.6}, {"text": "how long do these operations take", "start": 1894.96, "duration": 12.88}, {"text": "right at most the height of the entire", "start": 1916.48, "duration": 3.679}, {"text": "tree in fact it's going to be", "start": 1918.399, "duration": 4.081}, {"text": "the depth of that first node but in the", "start": 1920.159, "duration": 3.76}, {"text": "worst case that's the height of the", "start": 1922.48, "duration": 2.4}, {"text": "entire tree", "start": 1923.919, "duration": 2.64}, {"text": "in general all of these operations are", "start": 1924.88, "duration": 3.84}, {"text": "going to be order h", "start": 1926.559, "duration": 4.641}, {"text": "we need to think about it in each case", "start": 1928.72, "duration": 4.959}, {"text": "except for this one which is order n", "start": 1931.2, "duration": 5.04}, {"text": "so iterating through the whole thing um", "start": 1933.679, "duration": 4.161}, {"text": "this in this case we're just calling", "start": 1936.24, "duration": 2.72}, {"text": "subtree first so", "start": 1937.84, "duration": 3.04}, {"text": "that takes order h time here we're", "start": 1938.96, "duration": 3.52}, {"text": "walking up the tree instead of down but", "start": 1940.88, "duration": 2.399}, {"text": "that's going to cost", "start": 1942.48, "duration": 3.199}, {"text": "exactly the height of the node we happen", "start": 1943.279, "duration": 5.041}, {"text": "to stop early but worst case order h", "start": 1945.679, "duration": 4.961}, {"text": "for all this all the operations we", "start": 1948.32, "duration": 3.599}, {"text": "consider today we just want to get an", "start": 1950.64, "duration": 2.24}, {"text": "order h bound", "start": 1951.919, "duration": 3.921}, {"text": "and later we will bound h so the point", "start": 1952.88, "duration": 3.76}, {"text": "is these are", "start": 1955.84, "duration": 4.079}, {"text": "fast if h is small like log n these are", "start": 1956.64, "duration": 5.12}, {"text": "almost instantaneous", "start": 1959.919, "duration": 4.401}, {"text": "whereas if i had to update the explicit", "start": 1961.76, "duration": 3.6}, {"text": "traversal order", "start": 1964.32, "duration": 2.8}, {"text": "say as an array i would have to spend", "start": 1965.36, "duration": 4.319}, {"text": "linear time every time i make a change", "start": 1967.12, "duration": 5.36}, {"text": "and yes it would be fast to do successor", "start": 1969.679, "duration": 4.801}, {"text": "if i had this stored explicitly", "start": 1972.48, "duration": 3.84}, {"text": "but maintaining it would be impossible", "start": 1974.48, "duration": 3.12}, {"text": "maintaining it efficiently would be", "start": 1976.32, "duration": 1.839}, {"text": "impossible", "start": 1977.6, "duration": 3.919}, {"text": "question questions", "start": 1978.159, "duration": 3.36}, {"text": "yes okay", "start": 1984.96, "duration": 6.88}, {"text": "cool um so these were queries", "start": 1993.84, "duration": 7.36}, {"text": "where i want to follow", "start": 1997.679, "duration": 5.761}, {"text": "see what's what's next in the traversal", "start": 2001.2, "duration": 4.079}, {"text": "sequence now let's talk about actually", "start": 2003.44, "duration": 3.52}, {"text": "changing the traversal sequence so these", "start": 2005.279, "duration": 3.52}, {"text": "are insert and delete operations", "start": 2006.96, "duration": 4.559}, {"text": "these will correspond roughly to insert", "start": 2008.799, "duration": 4.401}, {"text": "at or delete at", "start": 2011.519, "duration": 3.921}, {"text": "but they're not quite we're not quite in", "start": 2013.2, "duration": 3.44}, {"text": "sequence world yet", "start": 2015.44, "duration": 2.88}, {"text": "instead we're going to focus on", "start": 2016.64, "duration": 3.759}, {"text": "inserting or deleting in the middle", "start": 2018.32, "duration": 4.959}, {"text": "of a subtree", "start": 2020.399, "duration": 2.88}, {"text": "so i'm going to have two nodes", "start": 2027.44, "duration": 6.4}, {"text": "so the", "start": 2036.24, "duration": 2.799}, {"text": "in the traversal order", "start": 2040.64, "duration": 6.08}, {"text": "so node already exists in the tree new", "start": 2043.679, "duration": 4.96}, {"text": "is a new node that does not yet exist in", "start": 2046.72, "duration": 3.439}, {"text": "the tree hence i call it new", "start": 2048.639, "duration": 5.28}, {"text": "and what i'd like to do is insert new", "start": 2050.159, "duration": 6.801}, {"text": "right after node and there's a symmetric", "start": 2053.919, "duration": 4.72}, {"text": "operation which is insert before", "start": 2056.96, "duration": 2.959}, {"text": "it will be implemented almost", "start": 2058.639, "duration": 6.0}, {"text": "identically so we'll just focus on after", "start": 2059.919, "duration": 6.48}, {"text": "so i want to insert this new node in the", "start": 2064.639, "duration": 3.2}, {"text": "traversal order which again is in our", "start": 2066.399, "duration": 2.401}, {"text": "heads this is all", "start": 2067.839, "duration": 4.481}, {"text": "in in our thought bubble", "start": 2068.8, "duration": 3.52}, {"text": "that's what we want to achieve and we", "start": 2073.28, "duration": 4.24}, {"text": "have to do it by manipulating", "start": 2075.359, "duration": 4.401}, {"text": "this tree and however we change the tree", "start": 2077.52, "duration": 5.359}, {"text": "it defines a new traversal order", "start": 2079.76, "duration": 10.079}, {"text": "so maybe let's do an example first", "start": 2082.879, "duration": 6.96}, {"text": "actually i probably want this universal", "start": 2101.68, "duration": 4.56}, {"text": "order", "start": 2104.64, "duration": 4.88}, {"text": "keep track of that so uh", "start": 2106.24, "duration": 7.119}, {"text": "let's say the first thing we want to do", "start": 2109.52, "duration": 9.04}, {"text": "uh is insert", "start": 2113.359, "duration": 5.201}, {"text": "g before e", "start": 2119.28, "duration": 5.6}, {"text": "i want to illustrate both of the", "start": 2122.88, "duration": 4.56}, {"text": "operations", "start": 2124.88, "duration": 5.84}, {"text": "insert h", "start": 2127.44, "duration": 6.639}, {"text": "after e", "start": 2130.72, "duration": 5.52}, {"text": "a", "start": 2134.079, "duration": 2.161}, {"text": "okay um", "start": 2137.92, "duration": 3.199}, {"text": "so insert g before e so conceptually", "start": 2141.28, "duration": 5.2}, {"text": "what we want to do is insert g", "start": 2144.56, "duration": 5.76}, {"text": "here and the way so we're given the node", "start": 2146.48, "duration": 4.639}, {"text": "e", "start": 2150.32, "duration": 3.12}, {"text": "and we're given a sort of empty node i", "start": 2151.119, "duration": 3.841}, {"text": "mean a node that just contains g it", "start": 2153.44, "duration": 3.2}, {"text": "doesn't have any pointers yet", "start": 2154.96, "duration": 4.56}, {"text": "and we would like to put it before e", "start": 2156.64, "duration": 5.36}, {"text": "where should i put it", "start": 2159.52, "duration": 6.16}, {"text": "left child all right so that's", "start": 2162.0, "duration": 5.44}, {"text": "this is an easy case if i'm trying to", "start": 2165.68, "duration": 4.08}, {"text": "insert before and there's no left child", "start": 2167.44, "duration": 4.0}, {"text": "stick it there if i'm trying to insert", "start": 2169.76, "duration": 3.44}, {"text": "after and there's no right child", "start": 2171.44, "duration": 4.32}, {"text": "stick it there easy so let me write down", "start": 2173.2, "duration": 5.12}, {"text": "case one", "start": 2175.76, "duration": 2.56}, {"text": "so here we're inserting after so if", "start": 2180.56, "duration": 4.279}, {"text": "there's no", "start": 2183.2, "duration": 5.6}, {"text": "uh right child", "start": 2184.839, "duration": 3.961}, {"text": "put new", "start": 2191.359, "duration": 6.641}, {"text": "there okay i'm using informal language", "start": 2194.48, "duration": 4.48}, {"text": "here putting", "start": 2198.0, "duration": 4.72}, {"text": "this new node there", "start": 2198.96, "duration": 5.52}, {"text": "b instead of writing for example", "start": 2202.72, "duration": 4.879}, {"text": "node.write equals new", "start": 2204.48, "duration": 4.879}, {"text": "because that's only one operation you", "start": 2207.599, "duration": 3.52}, {"text": "need to do one thing you would do is set", "start": 2209.359, "duration": 3.841}, {"text": "node.write equals to new but you also", "start": 2211.119, "duration": 3.601}, {"text": "have to set new's parent to be", "start": 2213.2, "duration": 2.8}, {"text": "node.write", "start": 2214.72, "duration": 3.52}, {"text": "so instead of worrying about those two", "start": 2216.0, "duration": 3.599}, {"text": "pointer changes because we always do", "start": 2218.24, "duration": 2.8}, {"text": "bi-directional pointer changes i'm just", "start": 2219.599, "duration": 2.561}, {"text": "going to use", "start": 2221.04, "duration": 2.64}, {"text": "pseudocode and then in recitation you'll", "start": 2222.16, "duration": 3.199}, {"text": "see actual python code that does all", "start": 2223.68, "duration": 3.76}, {"text": "this", "start": 2225.359, "duration": 6.881}, {"text": "uh so then there's the other case", "start": 2227.44, "duration": 4.8}, {"text": "so that should be the second example", "start": 2232.4, "duration": 3.6}, {"text": "insert h", "start": 2234.64, "duration": 5.76}, {"text": "after a right", "start": 2236.0, "duration": 6.8}, {"text": "insert h after a so we already have a", "start": 2240.4, "duration": 3.36}, {"text": "node after a", "start": 2242.8, "duration": 5.84}, {"text": "in the right child in this right subtree", "start": 2243.76, "duration": 4.88}, {"text": "so where do i want to put", "start": 2249.119, "duration": 6.561}, {"text": "h relative to a", "start": 2252.24, "duration": 6.64}, {"text": "well it should be to the right of a but", "start": 2255.68, "duration": 4.72}, {"text": "it should be", "start": 2258.88, "duration": 4.4}, {"text": "before c it should be to the left of c", "start": 2260.4, "duration": 4.719}, {"text": "so that would mean we want to put it", "start": 2263.28, "duration": 4.72}, {"text": "here okay in this case it was pretty", "start": 2265.119, "duration": 5.121}, {"text": "easy because this tree was small", "start": 2268.0, "duration": 4.0}, {"text": "where do i want to put it in general", "start": 2270.24, "duration": 4.64}, {"text": "well wherever", "start": 2272.0, "duration": 2.88}, {"text": "subtree first tells me to put it right", "start": 2275.359, "duration": 4.48}, {"text": "subtree first is going to give me", "start": 2277.92, "duration": 3.76}, {"text": "the successor these are all kind of", "start": 2279.839, "duration": 5.201}, {"text": "parallel um", "start": 2281.68, "duration": 5.439}, {"text": "we're in the case now where our node has", "start": 2285.04, "duration": 3.76}, {"text": "a right child", "start": 2287.119, "duration": 3.601}, {"text": "and then successor tells us where the", "start": 2288.8, "duration": 4.24}, {"text": "successor is it is the first", "start": 2290.72, "duration": 5.44}, {"text": "node which is the leftmost descendant in", "start": 2293.04, "duration": 3.52}, {"text": "the", "start": 2296.16, "duration": 3.52}, {"text": "right subtree of the node okay a lot of", "start": 2296.56, "duration": 6.0}, {"text": "pointers to follow in that sentence but", "start": 2299.68, "duration": 3.28}, {"text": "it's", "start": 2302.56, "duration": 3.519}, {"text": "clear in the picture so this", "start": 2302.96, "duration": 5.44}, {"text": "in this case we had node and there was", "start": 2306.079, "duration": 4.721}, {"text": "no right child so we just added", "start": 2308.4, "duration": 5.76}, {"text": "new to be its right child okay in the", "start": 2310.8, "duration": 5.12}, {"text": "other case", "start": 2314.16, "duration": 6.88}, {"text": "we had a right child so here is node", "start": 2315.92, "duration": 7.679}, {"text": "there's uh there's this node here", "start": 2321.04, "duration": 3.76}, {"text": "node.right", "start": 2323.599, "duration": 4.801}, {"text": "which now we're supposing exists", "start": 2324.8, "duration": 3.6}, {"text": "and it defines a whole subtree there's", "start": 2329.04, "duration": 3.92}, {"text": "this one", "start": 2331.04, "duration": 5.68}, {"text": "which is the first node in the traversal", "start": 2332.96, "duration": 5.36}, {"text": "order of the subtree also known as the", "start": 2336.72, "duration": 3.28}, {"text": "successor of node", "start": 2338.32, "duration": 5.279}, {"text": "so i'll call this successor", "start": 2340.0, "duration": 3.599}, {"text": "of node in the current traversal order", "start": 2344.24, "duration": 3.839}, {"text": "but of course we'd like to make", "start": 2346.64, "duration": 4.32}, {"text": "new the new successor of the node so", "start": 2348.079, "duration": 5.361}, {"text": "where does it go", "start": 2350.96, "duration": 4.879}, {"text": "here", "start": 2353.44, "duration": 2.399}, {"text": "we want to add it as a left child", "start": 2356.88, "duration": 6.479}, {"text": "to the old successor", "start": 2360.079, "duration": 3.28}, {"text": "okay so put uh", "start": 2363.599, "duration": 7.921}, {"text": "node as", "start": 2368.56, "duration": 2.96}, {"text": "so take the successor and if you look at", "start": 2380.32, "duration": 3.36}, {"text": "the code for successor we're in this", "start": 2382.16, "duration": 3.36}, {"text": "case so we know it will just call", "start": 2383.68, "duration": 5.28}, {"text": "subtree first of node.right and remember", "start": 2385.52, "duration": 4.48}, {"text": "subtree first", "start": 2388.96, "duration": 3.76}, {"text": "went left as much as it possibly could", "start": 2390.0, "duration": 4.4}, {"text": "so what that means is this successor", "start": 2392.72, "duration": 3.28}, {"text": "node is guaranteed to not", "start": 2394.4, "duration": 4.32}, {"text": "have a left child right because it was", "start": 2396.0, "duration": 4.32}, {"text": "defined by going right once and then", "start": 2398.72, "duration": 3.68}, {"text": "going left as much as you could", "start": 2400.32, "duration": 3.92}, {"text": "so there's no more left which means we", "start": 2402.4, "duration": 3.36}, {"text": "can make one more left", "start": 2404.24, "duration": 4.96}, {"text": "just add new there and we're done", "start": 2405.76, "duration": 5.28}, {"text": "now if you look at the traversal order", "start": 2409.2, "duration": 3.52}, {"text": "it will be node then new", "start": 2411.04, "duration": 3.36}, {"text": "then the old successor and then the rest", "start": 2412.72, "duration": 3.44}, {"text": "of that subtree", "start": 2414.4, "duration": 4.959}, {"text": "okay it's kind of cool in all cases", "start": 2416.16, "duration": 6.48}, {"text": "uh i mean this was constant time", "start": 2419.359, "duration": 4.881}, {"text": "here we spent constant time after we", "start": 2422.64, "duration": 4.24}, {"text": "called successor successor costs order h", "start": 2424.24, "duration": 3.2}, {"text": "time", "start": 2426.88, "duration": 3.6}, {"text": "so this is order h", "start": 2427.44, "duration": 3.04}, {"text": "new new okay", "start": 2434.24, "duration": 7.119}, {"text": "put new there", "start": 2438.56, "duration": 2.799}, {"text": "clear okay that was insertion", "start": 2444.64, "duration": 9.199}, {"text": "let's do deletion", "start": 2447.68, "duration": 6.159}, {"text": "get the spec right and the example", "start": 2454.4, "duration": 13.439}, {"text": "all of these are going to have two cases", "start": 2470.319, "duration": 5.04}, {"text": "uh so let me", "start": 2472.64, "duration": 6.56}, {"text": "oh i didn't update so now h is after a", "start": 2475.359, "duration": 5.121}, {"text": "so it should be like this", "start": 2479.2, "duration": 2.8}, {"text": "you can check the new traverse order of", "start": 2480.48, "duration": 4.8}, {"text": "this tree is exactly that", "start": 2482.0, "duration": 3.28}, {"text": "next i'm going to do a couple of", "start": 2486.16, "duration": 3.04}, {"text": "deletions", "start": 2487.44, "duration": 4.639}, {"text": "let's delete", "start": 2489.2, "duration": 2.879}, {"text": "f first and then we're going to", "start": 2493.119, "duration": 8.401}, {"text": "well this is", "start": 2498.72, "duration": 2.8}, {"text": "confusing", "start": 2502.0, "duration": 2.64}, {"text": "and then we're going to delete a so", "start": 2507.599, "duration": 5.441}, {"text": "where's f we're supposing we're given a", "start": 2511.359, "duration": 3.681}, {"text": "pointer to f this node", "start": 2513.04, "duration": 4.0}, {"text": "well it's a leaf so if i want to delete", "start": 2515.04, "duration": 4.48}, {"text": "it i just erase it", "start": 2517.04, "duration": 5.76}, {"text": "easy leaves are easy to delete there's", "start": 2519.52, "duration": 5.68}, {"text": "no work to do so what that means is i'm", "start": 2522.8, "duration": 3.76}, {"text": "removing the pointer from d", "start": 2525.2, "duration": 5.6}, {"text": "to f okay we just erase that guy", "start": 2526.56, "duration": 5.92}, {"text": "uh okay now here's a trickier one", "start": 2530.8, "duration": 3.279}, {"text": "suppose i want to delete the root of the", "start": 2532.48, "duration": 2.56}, {"text": "tree this is kind of", "start": 2534.079, "duration": 3.52}, {"text": "the hardest case but in general it would", "start": 2535.04, "duration": 5.2}, {"text": "be somewhere in between leaf and root", "start": 2537.599, "duration": 5.121}, {"text": "so if i want to delete a if i just", "start": 2540.24, "duration": 4.079}, {"text": "erased it then suddenly there are these", "start": 2542.72, "duration": 2.879}, {"text": "pointers to nowhere", "start": 2544.319, "duration": 3.121}, {"text": "and i disconnect the tree into two parts", "start": 2545.599, "duration": 3.041}, {"text": "i don't want to do that i need to keep", "start": 2547.44, "duration": 2.96}, {"text": "my tree connected", "start": 2548.64, "duration": 5.439}, {"text": "so i'm going to play this trick", "start": 2550.4, "duration": 6.48}, {"text": "which is i forget if i use successor or", "start": 2554.079, "duration": 4.561}, {"text": "predecessor", "start": 2556.88, "duration": 4.56}, {"text": "predecessor", "start": 2558.64, "duration": 2.8}, {"text": "so i'm going to uh look at a we already", "start": 2563.52, "duration": 5.599}, {"text": "have defined successor and", "start": 2567.52, "duration": 4.0}, {"text": "there by predecessor so i'm going to", "start": 2569.119, "duration": 4.641}, {"text": "look at the predecessor of a", "start": 2571.52, "duration": 5.839}, {"text": "which is e you can check that here the", "start": 2573.76, "duration": 4.24}, {"text": "one before", "start": 2577.359, "duration": 3.841}, {"text": "a is e this is in the left subtree", "start": 2578.0, "duration": 5.44}, {"text": "uh find me the rightmost item keep going", "start": 2581.2, "duration": 4.48}, {"text": "right until i can't that's e", "start": 2583.44, "duration": 3.76}, {"text": "so now these guys are adjacent in the", "start": 2585.68, "duration": 3.36}, {"text": "order and i'm about to remove a from the", "start": 2587.2, "duration": 2.56}, {"text": "order", "start": 2589.04, "duration": 3.6}, {"text": "so i can momentarily cheat and swap", "start": 2589.76, "duration": 4.079}, {"text": "their labels", "start": 2592.64, "duration": 3.84}, {"text": "i'm going to erase a and e here and put", "start": 2593.839, "duration": 4.0}, {"text": "e", "start": 2596.48, "duration": 4.96}, {"text": "after a why because it moves a", "start": 2597.839, "duration": 5.681}, {"text": "down in the tree and if i get to the", "start": 2601.44, "duration": 3.2}, {"text": "leaf i'm done", "start": 2603.52, "duration": 2.4}, {"text": "so i'm not quite done because this is", "start": 2604.64, "duration": 3.12}, {"text": "not a leaf so again i look at a's", "start": 2605.92, "duration": 2.88}, {"text": "predecessor it's now", "start": 2607.76, "duration": 4.079}, {"text": "g predecessor", "start": 2608.8, "duration": 6.16}, {"text": "we hope is always in the uh", "start": 2611.839, "duration": 6.161}, {"text": "farther down in the tree and then i swap", "start": 2614.96, "duration": 6.879}, {"text": "a with g", "start": 2618.0, "duration": 3.839}, {"text": "okay i have preserved the traversal", "start": 2622.24, "duration": 3.52}, {"text": "order except where a", "start": 2624.56, "duration": 3.84}, {"text": "falls just by moving a earlier in the", "start": 2625.76, "duration": 3.52}, {"text": "order here", "start": 2628.4, "duration": 5.84}, {"text": "and now a is a leaf and i can erase it", "start": 2629.28, "duration": 6.88}, {"text": "okay so that's what we're going to", "start": 2634.24, "duration": 3.92}, {"text": "follow now in actuality it's a little", "start": 2636.16, "duration": 3.199}, {"text": "tricky sometimes we need to use", "start": 2638.16, "duration": 3.28}, {"text": "predecessors sometimes we need to use", "start": 2639.359, "duration": 6.24}, {"text": "successor okay so the cases are", "start": 2641.44, "duration": 7.44}, {"text": "if the node is a leaf just", "start": 2645.599, "duration": 8.24}, {"text": "detach it from the parent easy", "start": 2648.88, "duration": 4.959}, {"text": "that's sort of our base case in the", "start": 2653.92, "duration": 4.96}, {"text": "recursion otherwise", "start": 2655.28, "duration": 3.6}, {"text": "there are two cases if", "start": 2658.96, "duration": 5.68}, {"text": "so if we're not a leaf that means we", "start": 2662.0, "duration": 3.2}, {"text": "have", "start": 2664.64, "duration": 3.199}, {"text": "a left child or a right child or both", "start": 2665.2, "duration": 4.24}, {"text": "both is going to be the easy case", "start": 2667.839, "duration": 4.0}, {"text": "but in general i have either there's a", "start": 2669.44, "duration": 3.919}, {"text": "left child", "start": 2671.839, "duration": 4.561}, {"text": "or there's a right child in either case", "start": 2673.359, "duration": 4.72}, {"text": "i'm going to be happy so i don't need a", "start": 2676.4, "duration": 4.4}, {"text": "both case", "start": 2678.079, "duration": 6.0}, {"text": "uh okay so what do i do in if i have a", "start": 2680.8, "duration": 4.319}, {"text": "left child", "start": 2684.079, "duration": 3.841}, {"text": "that guarantees to me that if the node's", "start": 2685.119, "duration": 3.521}, {"text": "predecessor", "start": 2687.92, "duration": 2.72}, {"text": "is inside that left sub-tree which means", "start": 2688.64, "duration": 4.0}, {"text": "it's lower in the tree", "start": 2690.64, "duration": 3.439}, {"text": "if i didn't have a left child the", "start": 2692.64, "duration": 3.199}, {"text": "predecessor would actually be higher in", "start": 2694.079, "duration": 3.681}, {"text": "the tree and i don't want to go higher", "start": 2695.839, "duration": 4.0}, {"text": "okay so if i have a left child i know", "start": 2697.76, "duration": 3.68}, {"text": "the predecessor is lower", "start": 2699.839, "duration": 5.041}, {"text": "and so i'm going to swap", "start": 2701.44, "duration": 7.36}, {"text": "my item the contents of my node", "start": 2704.88, "duration": 14.08}, {"text": "with my predecessor's item", "start": 2708.8, "duration": 13.92}, {"text": "and then i'm going to recursively delete", "start": 2718.96, "duration": 13.76}, {"text": "the predecessor okay that's the case", "start": 2722.72, "duration": 11.52}, {"text": "that we looked at in this code", "start": 2732.72, "duration": 3.2}, {"text": "in this example because we always had a", "start": 2734.24, "duration": 3.599}, {"text": "left child if we have a right child but", "start": 2735.92, "duration": 3.679}, {"text": "no left child we just do the reverse we", "start": 2737.839, "duration": 3.441}, {"text": "swap with our successors", "start": 2739.599, "duration": 4.161}, {"text": "item and then delete the successor in", "start": 2741.28, "duration": 4.079}, {"text": "either case we're going down", "start": 2743.76, "duration": 3.359}, {"text": "and so if we start at some node like the", "start": 2745.359, "duration": 4.881}, {"text": "route every time we do this operation", "start": 2747.119, "duration": 5.681}, {"text": "we're walking down and then we're", "start": 2750.24, "duration": 3.44}, {"text": "walking down", "start": 2752.8, "duration": 2.559}, {"text": "and in general we'll keep walking down", "start": 2753.68, "duration": 3.679}, {"text": "resuming where we left off which means", "start": 2755.359, "duration": 3.841}, {"text": "total amount of time we spend is", "start": 2757.359, "duration": 3.201}, {"text": "proportional to", "start": 2759.2, "duration": 5.68}, {"text": "the height of the tree in the worst case", "start": 2760.56, "duration": 4.32}, {"text": "question", "start": 2772.839, "duration": 4.441}, {"text": "right so e didn't used to have a right", "start": 2775.52, "duration": 3.36}, {"text": "child so we're changing identities of", "start": 2777.28, "duration": 2.799}, {"text": "nodes when we do this", "start": 2778.88, "duration": 3.76}, {"text": "because we uh this that we didn't", "start": 2780.079, "duration": 3.52}, {"text": "actually move this", "start": 2782.64, "duration": 2.64}, {"text": "circle the circle stayed in place and", "start": 2783.599, "duration": 3.121}, {"text": "what we changed was the item that was", "start": 2785.28, "duration": 3.2}, {"text": "stored in that circle", "start": 2786.72, "duration": 5.28}, {"text": "so whether you call this node e or a", "start": 2788.48, "duration": 5.52}, {"text": "it doesn't really matter it is just the", "start": 2792.0, "duration": 3.28}, {"text": "root note", "start": 2794.0, "duration": 3.04}, {"text": "okay so we're gonna play a lot of these", "start": 2795.28, "duration": 3.52}, {"text": "tricks of moving the items around so far", "start": 2797.04, "duration": 2.799}, {"text": "we hadn't been doing that we've just", "start": 2798.8, "duration": 2.0}, {"text": "been creating", "start": 2799.839, "duration": 4.161}, {"text": "nodes and placing them somewhere but now", "start": 2800.8, "duration": 3.76}, {"text": "we're", "start": 2804.0, "duration": 1.92}, {"text": "in this delete operation is the first", "start": 2804.56, "duration": 3.44}, {"text": "time where we're changing what's stored", "start": 2805.92, "duration": 3.199}, {"text": "in the nodes", "start": 2808.0, "duration": 2.72}, {"text": "but we still can define the traversal", "start": 2809.119, "duration": 2.96}, {"text": "order right the traverse order of this", "start": 2810.72, "duration": 4.639}, {"text": "tree is dbgehc", "start": 2812.079, "duration": 4.881}, {"text": "which should be what we get here if i", "start": 2815.359, "duration": 4.0}, {"text": "delete f and", "start": 2816.96, "duration": 4.56}, {"text": "a", "start": 2819.359, "duration": 2.161}, {"text": "and sorry can f", "start": 2822.8, "duration": 10.559}, {"text": "trees will not preserve connections", "start": 2831.76, "duration": 3.76}, {"text": "that's just the name of the game we are", "start": 2833.359, "duration": 3.681}, {"text": "we have to allow this otherwise we can't", "start": 2835.52, "duration": 3.04}, {"text": "do anything that's the short", "start": 2837.04, "duration": 5.12}, {"text": "version okay okay in the last few", "start": 2838.56, "duration": 5.68}, {"text": "minutes let me talk about how we take", "start": 2842.16, "duration": 5.12}, {"text": "these trees and implement a set", "start": 2844.24, "duration": 5.839}, {"text": "or sequence okay i've already alluded to", "start": 2847.28, "duration": 5.039}, {"text": "this", "start": 2850.079, "duration": 2.24}, {"text": "so for a sequence", "start": 2854.8, "duration": 5.039}, {"text": "we just make the traversal order", "start": 2860.16, "duration": 4.08}, {"text": "equal to the the order that we're trying", "start": 2864.559, "duration": 4.56}, {"text": "to represent", "start": 2868.24, "duration": 5.2}, {"text": "the sequence order", "start": 2869.119, "duration": 6.24}, {"text": "and if we're trying to source set items", "start": 2873.44, "duration": 3.679}, {"text": "with keys we're going to make the", "start": 2875.359, "duration": 4.641}, {"text": "traversal order", "start": 2877.119, "duration": 2.881}, {"text": "equal to ordered by increasing key", "start": 2880.8, "duration": 7.519}, {"text": "increasing item", "start": 2884.839, "duration": 5.72}, {"text": "key", "start": 2888.319, "duration": 2.24}, {"text": "some sense that's it but then we need to", "start": 2893.04, "duration": 4.079}, {"text": "think about how do we implement", "start": 2895.28, "duration": 4.88}, {"text": "all of these operations so maybe most", "start": 2897.119, "duration": 6.321}, {"text": "enlightening is for starters is", "start": 2900.16, "duration": 7.36}, {"text": "finding a key in a tree", "start": 2903.44, "duration": 6.159}, {"text": "so this is going to correspond to binary", "start": 2907.52, "duration": 4.0}, {"text": "search", "start": 2909.599, "duration": 5.281}, {"text": "if i'm searching for a key let's say i'm", "start": 2911.52, "duration": 4.48}, {"text": "searching for", "start": 2914.88, "duration": 4.239}, {"text": "g's key and i know this", "start": 2916.0, "duration": 5.2}, {"text": "may be hard in this example maybe i'll", "start": 2919.119, "duration": 4.561}, {"text": "replace these all with numbers", "start": 2921.2, "duration": 7.359}, {"text": "so i can think about key values", "start": 2923.68, "duration": 8.0}, {"text": "okay so let's say 1 7", "start": 2928.559, "duration": 6.401}, {"text": "12 17", "start": 2931.68, "duration": 6.639}, {"text": "19 and 23.", "start": 2934.96, "duration": 6.159}, {"text": "this is now in key order if you think of", "start": 2938.319, "duration": 3.921}, {"text": "the traversal order", "start": 2941.119, "duration": 3.761}, {"text": "the property is that all the keys in the", "start": 2942.24, "duration": 4.16}, {"text": "left subtree of the root", "start": 2944.88, "duration": 3.199}, {"text": "are less than the root and the root is", "start": 2946.4, "duration": 3.04}, {"text": "less than all the keys in the right", "start": 2948.079, "duration": 3.441}, {"text": "subtree and recursively all the way down", "start": 2949.44, "duration": 5.52}, {"text": "this is something called the", "start": 2951.52, "duration": 7.12}, {"text": "binary search tree property bst property", "start": 2954.96, "duration": 6.8}, {"text": "these here we're calling them binary", "start": 2958.64, "duration": 4.16}, {"text": "tree", "start": 2961.76, "duration": 3.839}, {"text": "sets or set binary trees but they're", "start": 2962.8, "duration": 4.48}, {"text": "also known in the literature as binary", "start": 2965.599, "duration": 3.041}, {"text": "search trees term you may have heard", "start": 2967.28, "duration": 2.0}, {"text": "before", "start": 2968.64, "duration": 2.16}, {"text": "so this is a special case of what we're", "start": 2969.28, "duration": 3.2}, {"text": "doing where we're storing the keys in", "start": 2970.8, "duration": 2.559}, {"text": "order", "start": 2972.48, "duration": 2.48}, {"text": "and then if i want to search for a key", "start": 2973.359, "duration": 4.401}, {"text": "like uh 13", "start": 2974.96, "duration": 5.04}, {"text": "i compare that key with the root i see", "start": 2977.76, "duration": 3.2}, {"text": "oh it's not", "start": 2980.0, "duration": 3.52}, {"text": "equal and it's to the left because it's", "start": 2980.96, "duration": 3.04}, {"text": "less than", "start": 2983.52, "duration": 4.24}, {"text": "17. so 13 is left of here 13 is right of", "start": 2984.0, "duration": 4.48}, {"text": "7", "start": 2987.76, "duration": 3.839}, {"text": "13 is right of 12 and so i know that", "start": 2988.48, "duration": 5.839}, {"text": "this is where 13 would belong", "start": 2991.599, "duration": 4.161}, {"text": "but there's no right child there and so", "start": 2994.319, "duration": 4.24}, {"text": "i know in find i just returned nothing", "start": 2995.76, "duration": 5.599}, {"text": "if i was doing find previous i would", "start": 2998.559, "duration": 4.881}, {"text": "return this note", "start": 3001.359, "duration": 4.401}, {"text": "because i have tried to go to the right", "start": 3003.44, "duration": 4.72}, {"text": "the last time before i fell off the tree", "start": 3005.76, "duration": 3.839}, {"text": "i was trying to go to the right and", "start": 3008.16, "duration": 3.84}, {"text": "therefore that last note i had was the", "start": 3009.599, "duration": 4.161}, {"text": "previous item if i was trying to define", "start": 3012.0, "duration": 3.68}, {"text": "next what would i do i would just take", "start": 3013.76, "duration": 4.4}, {"text": "this node and compute its successor", "start": 3015.68, "duration": 4.32}, {"text": "which we already know how to do and that", "start": 3018.16, "duration": 3.52}, {"text": "happens to be the root", "start": 3020.0, "duration": 4.0}, {"text": "okay so now i can do these inexact", "start": 3021.68, "duration": 3.84}, {"text": "searches when i do find previous and", "start": 3024.0, "duration": 2.72}, {"text": "find next", "start": 3025.52, "duration": 2.96}, {"text": "when i fall off the tree i find either", "start": 3026.72, "duration": 3.119}, {"text": "the previous or the next", "start": 3028.48, "duration": 3.04}, {"text": "and then with predecessor or successor i", "start": 3029.839, "duration": 3.121}, {"text": "can find the other one", "start": 3031.52, "duration": 4.559}, {"text": "okay so that's how we can do find and", "start": 3032.96, "duration": 5.04}, {"text": "find previous", "start": 3036.079, "duration": 6.721}, {"text": "and find next to do", "start": 3038.0, "duration": 8.16}, {"text": "uh sequences we need a little bit more", "start": 3042.8, "duration": 4.319}, {"text": "work", "start": 3046.16, "duration": 9.679}, {"text": "we'll do that next time", "start": 3047.119, "duration": 8.72}, {"text": "you", "start": 3057.76, "duration": 2.079}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 1.09, "duration": 2.37}, {"text": "Commons license.", "start": 3.46, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.85, "duration": 2.21}, {"text": "continue to offer high-quality\neducational resources for free.", "start": 7.06, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 11.15, "duration": 2.54}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.69, "duration": 3.96}, {"text": "at ocw.mit.edu.", "start": 17.65, "duration": 1.02}, {"text": "GARY GENSLER: We're going\nto turn back to ICOs", "start": 22.364, "duration": 2.716}, {"text": "and spend a little bit\nmore time on initial coin", "start": 25.08, "duration": 2.4}, {"text": "offerings in the markets and\nthe regulation of initial coin", "start": 27.48, "duration": 5.34}, {"text": "offerings today.", "start": 32.82, "duration": 3.1}, {"text": "But before I did\nthat, I was going", "start": 35.92, "duration": 1.66}, {"text": "to talk about one short\nannouncement that happened.", "start": 37.58, "duration": 4.465}, {"text": "In the US, we've talked\nabout how fiat currencies are", "start": 42.045, "duration": 3.255}, {"text": "accepted for taxes.", "start": 45.3, "duration": 2.208}, {"text": "AUDIENCE: Ohio!", "start": 47.508, "duration": 0.828}, {"text": "GARY GENSLER: Ohio.", "start": 48.336, "duration": 2.577}, {"text": "James, what do you want\nto tell me about Ohio?", "start": 50.913, "duration": 1.917}, {"text": "AUDIENCE: They're taking\nBitcoin for taxes, right?", "start": 52.83, "duration": 2.147}, {"text": "AUDIENCE: Yes.", "start": 54.977, "duration": 0.583}, {"text": "AUDIENCE: Yep.", "start": 55.56, "duration": 0.583}, {"text": "GARY GENSLER: Yeah.", "start": 56.143, "duration": 1.247}, {"text": "What's that?", "start": 57.39, "duration": 1.345}, {"text": "So do you want to\nsay a little bit more", "start": 58.735, "duration": 1.625}, {"text": "about it, Hugo, or Ross?", "start": 60.36, "duration": 1.393}, {"text": "AUDIENCE: Go ahead.", "start": 61.753, "duration": 0.792}, {"text": "AUDIENCE: Sure.", "start": 62.545, "duration": 1.215}, {"text": "Yeah, so they're accepting\nBitcoin for taxes", "start": 63.76, "duration": 3.41}, {"text": "through BitPay, which\nmeans that it's instantly", "start": 67.17, "duration": 3.15}, {"text": "transferred into fiat.", "start": 70.32, "duration": 1.68}, {"text": "But still, that's\na pretty big thing.", "start": 72.0, "duration": 2.13}, {"text": "You know?", "start": 74.13, "duration": 0.5}, {"text": "GARY GENSLER: Yeah, so the state\nof Ohio, I guess it was the--", "start": 74.63, "duration": 3.572}, {"text": "AUDIENCE: Treasurer.", "start": 78.202, "duration": 0.833}, {"text": "GARY GENSLER: --treasurer.", "start": 79.035, "duration": 1.725}, {"text": "Tom, you're shaking your head.", "start": 80.76, "duration": 1.29}, {"text": "AUDIENCE: Oh, as an Ohioan,\njust Ohio today breaks my heart,", "start": 82.05, "duration": 4.177}, {"text": "not related to this-- unrelated.", "start": 86.227, "duration": 1.333}, {"text": "GARY GENSLER: So Ohio\nbreaks your heart", "start": 87.56, "duration": 2.092}, {"text": "because they're accepting\nBitcoin for taxes?", "start": 89.652, "duration": 1.833}, {"text": "AUDIENCE: Unrelated.", "start": 91.485, "duration": 0.833}, {"text": "GARY GENSLER: Unrelated.", "start": 92.318, "duration": 2.412}, {"text": "Do you want to share\nfor the class, or?", "start": 94.73, "duration": 1.94}, {"text": "AUDIENCE: I'll let [INAUDIBLE]\nand his next four years", "start": 96.67, "duration": 2.375}, {"text": "of policy speak for itself.", "start": 99.045, "duration": 1.305}, {"text": "AUDIENCE: Oh, yes.", "start": 100.35, "duration": 0.832}, {"text": "GARY GENSLER: Oh, I see.", "start": 101.182, "duration": 1.138}, {"text": "So the state of\nOhio has announced,", "start": 102.32, "duration": 3.64}, {"text": "the state treasurer-- is this\nan elected office, the state", "start": 105.96, "duration": 3.24}, {"text": "treasurer?", "start": 109.2, "duration": 1.18}, {"text": "So he saw that it would be good\nfor Ohio, for the economics", "start": 110.38, "duration": 4.43}, {"text": "and for the job creation\nin Ohio, and maybe", "start": 114.81, "duration": 2.04}, {"text": "for his politics,\nto move forward", "start": 116.85, "duration": 4.32}, {"text": "and say the state of Ohio\nwould accept Bitcoin for taxes.", "start": 121.17, "duration": 5.28}, {"text": "It's the only US jurisdiction\nthat I know that has done that.", "start": 126.45, "duration": 3.1}, {"text": "Now, you can think\nof them as a vendor,", "start": 129.55, "duration": 2.18}, {"text": "like they're saying\nthey will take it.", "start": 131.73, "duration": 1.98}, {"text": "And they've arranged it, as\nHugo said, through BitPay.", "start": 133.71, "duration": 4.47}, {"text": "BitPay is an application\nwhere, whether you're Starbucks", "start": 138.18, "duration": 4.83}, {"text": "or the state of Ohio, you can\ntake a cryptocurrency like", "start": 143.01, "duration": 5.67}, {"text": "Bitcoin, and they will\ntake that Bitcoin,", "start": 148.68, "duration": 5.58}, {"text": "sell it quickly on an\nexchange, take some price risk-", "start": 154.26, "duration": 3.03}, {"text": "BitPay takes a little\nbit of price risk--", "start": 157.29, "duration": 2.51}, {"text": "and for a 1% fee, give\nyou fiat currency.", "start": 159.8, "duration": 5.12}, {"text": "Now, it's 1% and\nwhatever exchange rate,", "start": 164.92, "duration": 2.51}, {"text": "because I don't know how\nmuch VIG, or margin, is", "start": 167.43, "duration": 2.97}, {"text": "in the exchange\nrate transaction.", "start": 170.4, "duration": 3.33}, {"text": "But their stated fee is 1%.", "start": 173.73, "duration": 1.83}, {"text": "Hugo?", "start": 175.56, "duration": 0.563}, {"text": "AUDIENCE: I think the big\nquestion is whether or not", "start": 176.123, "duration": 2.167}, {"text": "that's a taxable event, too.", "start": 178.29, "duration": 1.89}, {"text": "GARY GENSLER: Is a\ntaxable event for who?", "start": 180.18, "duration": 2.35}, {"text": "AUDIENCE: For the person who's\npaying their taxes in Bitcoin,", "start": 182.53, "duration": 3.27}, {"text": "if any transaction from Bitcoin\nto fiat is a taxable event.", "start": 185.8, "duration": 2.92}, {"text": "GARY GENSLER: All right.", "start": 188.72, "duration": 1.0}, {"text": "So Hugo's raised the\nquestion, is the sale", "start": 189.72, "duration": 2.73}, {"text": "of the Bitcoin to fiat--", "start": 192.45, "duration": 1.77}, {"text": "because the fiat is,\nin essence, being", "start": 194.22, "duration": 2.64}, {"text": "used to pay the\nstate of Ohio taxes--", "start": 196.86, "duration": 2.73}, {"text": "is the sale of that\nBitcoin a taxable event?", "start": 199.59, "duration": 4.01}, {"text": "And I think somebody\nin the class will know.", "start": 203.6, "duration": 2.892}, {"text": "It's knowable.", "start": 206.492, "duration": 0.583}, {"text": "AUDIENCE: If you sold Bitcoin\nto acquire fiat, it would be.", "start": 207.075, "duration": 3.235}, {"text": "But if you use fiat\nto acquire Bitcoin,", "start": 210.31, "duration": 4.04}, {"text": "which I think the\nbig application here", "start": 214.35, "duration": 1.86}, {"text": "is the marijuana\nindustry in Ohio,", "start": 216.21, "duration": 2.81}, {"text": "if they're not able to back the\nbank-- if they are acquiring", "start": 219.02, "duration": 2.95}, {"text": "Bitcoins and then paying\nthem to the government,", "start": 221.97, "duration": 3.748}, {"text": "I think they don't\nhave to pay taxes.", "start": 225.718, "duration": 1.542}, {"text": "GARY GENSLER: What if you\nbought Bitcoin at $3,700,", "start": 227.26, "duration": 3.05}, {"text": "and the day that you\nsent in your taxes", "start": 230.31, "duration": 1.89}, {"text": "it's valued at $3,800 bitcoin?", "start": 232.2, "duration": 3.362}, {"text": "AUDIENCE: Congratulations.", "start": 235.562, "duration": 1.138}, {"text": "AUDIENCE: Yeah.", "start": 236.7, "duration": 0.625}, {"text": "AUDIENCE: You would pay\ntaxes on the profit.", "start": 237.325, "duration": 2.005}, {"text": "GARY GENSLER: That's correct.", "start": 239.33, "duration": 2.65}, {"text": "So at least here in the US--", "start": 241.98, "duration": 2.7}, {"text": "the IRS has spoken to this--\nif you acquire Bitcoin", "start": 244.68, "duration": 3.96}, {"text": "and then you use the\nBitcoin in commerce,", "start": 248.64, "duration": 2.45}, {"text": "if you're using it to fulfill\nan obligation, in this case", "start": 251.09, "duration": 4.78}, {"text": "a debt to the Ohio government,\nand if it moved from $3,700", "start": 255.87, "duration": 4.35}, {"text": "to $3,800, you would, yes.", "start": 260.22, "duration": 1.812}, {"text": "You would have a\nshort-term capital", "start": 262.032, "duration": 1.458}, {"text": "gains on the $100 difference.", "start": 263.49, "duration": 4.5}, {"text": "Whether everybody will\ncomply and report properly", "start": 267.99, "duration": 3.78}, {"text": "is another thing.", "start": 271.77, "duration": 0.81}, {"text": "But that is certainly my\nreading of US law at this time.", "start": 272.58, "duration": 5.61}, {"text": "Ross?", "start": 278.19, "duration": 1.34}, {"text": "AUDIENCE: This rate--", "start": 279.53, "duration": 1.0}, {"text": "I saw this, and I looked\nup a couple of things--", "start": 280.53, "duration": 3.81}, {"text": "it strikes me it\nwould be taxable", "start": 284.34, "duration": 1.5}, {"text": "given what you've said\nabout the US thing.", "start": 285.84, "duration": 3.15}, {"text": "And it really is just\nchanging it for fiat.", "start": 288.99, "duration": 2.25}, {"text": "It's just the structure, really.", "start": 291.24, "duration": 2.95}, {"text": "But what might make it\nseem more interesting", "start": 294.19, "duration": 5.09}, {"text": "or gain a little\ntraction is if, Ohio,", "start": 299.28, "duration": 2.91}, {"text": "if they have a state income\ntax, agreed not to tax the gain.", "start": 302.19, "duration": 5.1}, {"text": "Ohio could agree not to do it.", "start": 307.29, "duration": 2.01}, {"text": "You split the pay\non the federal side.", "start": 309.3, "duration": 2.07}, {"text": "But then they could make it\nmore like a real transaction", "start": 311.37, "duration": 2.668}, {"text": "if you're paying Bitcoin.", "start": 314.038, "duration": 1.042}, {"text": "GARY GENSLER: And\nhow many of you", "start": 317.515, "duration": 1.375}, {"text": "are from Ohio here\nother than Tom?", "start": 318.89, "duration": 3.074}, {"text": "Tom, as an Ohioan,\nwould you want", "start": 321.964, "duration": 2.526}, {"text": "them to not charge the taxes?", "start": 324.49, "duration": 3.44}, {"text": "You're one voter, I know.", "start": 327.93, "duration": 1.481}, {"text": "AUDIENCE: So\nthere's [INAUDIBLE]..", "start": 329.411, "duration": 1.417}, {"text": "GARY GENSLER: Oh, [LAUGHS] OK.", "start": 330.828, "duration": 1.855}, {"text": "AUDIENCE: So they charge\nthe state income tax.", "start": 332.683, "duration": 1.917}, {"text": "But I don't know if they charge\na state capital gains tax.", "start": 334.6, "duration": 2.48}, {"text": "AUDIENCE: But\nthat's the question.", "start": 337.08, "duration": 1.417}, {"text": "I'm just saying that's how they\ncould make it more real than--", "start": 338.497, "duration": 2.618}, {"text": "like Hugo was saying.", "start": 341.115, "duration": 0.875}, {"text": "It's not real right now.", "start": 341.99, "duration": 1.112}, {"text": "We're just converting it to\ndollars and taking the dollars.", "start": 343.102, "duration": 2.458}, {"text": "GARY GENSLER: They did,\nin this announcement--", "start": 345.56, "duration": 1.94}, {"text": "if you read the fine print as\nI was want to do because I was", "start": 347.5, "duration": 3.33}, {"text": "fascinated by this--", "start": 350.83, "duration": 2.4}, {"text": "for the first three\nmonths of the program,", "start": 353.23, "duration": 2.31}, {"text": "Ohio negotiated with BitPay\nthat BitPay would charge a 0%", "start": 355.54, "duration": 4.98}, {"text": "fee for the first three months.", "start": 360.52, "duration": 1.86}, {"text": "But this was BitPay foregoing--", "start": 362.38, "duration": 2.82}, {"text": "it appears that that was their\nbonus to the state of Ohio--", "start": 365.2, "duration": 6.835}, {"text": "0% fee for three\nmonths, again, not", "start": 372.035, "duration": 3.065}, {"text": "knowing exactly what\nexchange rate you're getting", "start": 375.1, "duration": 3.46}, {"text": "and so forth.", "start": 378.56, "duration": 3.03}, {"text": "And you think that it would\nbe the cannabis industry?", "start": 381.59, "duration": 2.975}, {"text": "AUDIENCE: Yeah, so Ohio passed\na state constitutional amendment", "start": 384.565, "duration": 4.305}, {"text": "two years ago.", "start": 388.87, "duration": 0.718}, {"text": "GARY GENSLER: We're talking\nabout Ohio that's now", "start": 389.588, "duration": 2.042}, {"text": "accepting Bitcoin for taxes.", "start": 391.63, "duration": 2.74}, {"text": "And Tom is our\nresident Ohio expert.", "start": 394.37, "duration": 2.785}, {"text": "AUDIENCE: I guess so.", "start": 397.155, "duration": 0.875}, {"text": "So yeah, Ohio will\nlegalize-- the state voters", "start": 398.03, "duration": 5.54}, {"text": "passed an amendment to allow\nmarijuana legalization.", "start": 403.57, "duration": 4.486}, {"text": "It's subject to,\nI think, some time", "start": 408.056, "duration": 1.784}, {"text": "delay or regulatory approval.", "start": 409.84, "duration": 1.76}, {"text": "But the expectation is\nit will be approved.", "start": 411.6, "duration": 2.55}, {"text": "And the marijuana\nindustry is still", "start": 414.15, "duration": 2.5}, {"text": "restricted from accessing\nthe federal banking system.", "start": 416.65, "duration": 3.63}, {"text": "So an alternate way\nfor them to avoid", "start": 420.28, "duration": 4.14}, {"text": "carrying large sums of cash--", "start": 424.42, "duration": 2.83}, {"text": "GARY GENSLER: Is carry the\nvalue in cryptocurrency.", "start": 427.25, "duration": 3.59}, {"text": "And do you think that's what\nmotivated the Ohio State", "start": 430.84, "duration": 2.43}, {"text": "Treasurer?", "start": 433.27, "duration": 1.72}, {"text": "I see.", "start": 434.99, "duration": 0.615}, {"text": "Shawn?", "start": 435.605, "duration": 0.175}, {"text": "AUDIENCE: I was just curious.", "start": 435.78, "duration": 1.32}, {"text": "So if that's the\ncase, and if I may--", "start": 437.1, "duration": 2.64}, {"text": "well, look, I don't\nknow of capital gains,", "start": 439.74, "duration": 1.76}, {"text": "but if we can cut losses on\nBitcoin, does that part of loss", "start": 441.5, "duration": 3.92}, {"text": "get carried forward\nthat allows you", "start": 445.42, "duration": 1.56}, {"text": "to upset some of your income?", "start": 446.98, "duration": 2.36}, {"text": "GARY GENSLER: Yeah,\nit's a capital loss,", "start": 449.34, "duration": 3.31}, {"text": "just as if you\nbought Apple stock", "start": 452.65, "duration": 2.07}, {"text": "and had a loss on Apple stock.", "start": 454.72, "duration": 2.25}, {"text": "AUDIENCE: So this cannot be\ncarried forward to offset", "start": 456.97, "duration": 3.62}, {"text": "the future--", "start": 460.59, "duration": 0.59}, {"text": "AUDIENCE: Yeah.", "start": 461.18, "duration": 1.275}, {"text": "GARY GENSLER: Under US law--", "start": 462.455, "duration": 1.445}, {"text": "I can't speak to other\njurisdictions' tax--", "start": 463.9, "duration": 2.25}, {"text": "but you can apply\nlosses against gains.", "start": 466.15, "duration": 5.1}, {"text": "And to the extent you have\ngreater losses than gains,", "start": 471.25, "duration": 3.0}, {"text": "you can actually take\nsome of those losses", "start": 474.25, "duration": 2.515}, {"text": "against your income--", "start": 476.765, "duration": 0.875}, {"text": "I don't remember the limit any\nlonger; it's 3,000 US dollars--", "start": 477.64, "duration": 5.54}, {"text": "and then, otherwise,\ncarry it forward.", "start": 483.18, "duration": 3.53}, {"text": "So for most citizens, they\nwould just take that loss.", "start": 486.71, "duration": 5.54}, {"text": "If you had greater than that,\nyou would carry it forward.", "start": 492.25, "duration": 4.39}, {"text": "Any other thoughts on Ohio?", "start": 496.64, "duration": 1.57}, {"text": "I mean--", "start": 498.21, "duration": 1.003}, {"text": "AUDIENCE: Yeah, I'm\njust wondering, sort", "start": 499.213, "duration": 1.667}, {"text": "of philosophically,\nOhio isn't actually", "start": 500.88, "duration": 1.95}, {"text": "carrying the price for this.", "start": 502.83, "duration": 1.58}, {"text": "But given they're converting\nit to fiat instantaneously,", "start": 504.41, "duration": 4.08}, {"text": "philosophically are\nthey really accepting", "start": 508.49, "duration": 2.38}, {"text": "Bitcoin as payment for taxes?", "start": 510.87, "duration": 2.309}, {"text": "Or is it just a\nmarketing gimmick?", "start": 513.179, "duration": 2.521}, {"text": "GARY GENSLER: I don't know.", "start": 515.7, "duration": 1.14}, {"text": "I mean, any other views on that?", "start": 516.84, "duration": 2.699}, {"text": "So the question\nis, is Ohio really", "start": 519.539, "duration": 1.741}, {"text": "taking cryptocurrencies,\nBitcoin,", "start": 521.28, "duration": 3.27}, {"text": "or is it just marketing?", "start": 524.55, "duration": 3.366}, {"text": "AUDIENCE: I think it's marketing\nbecause if you have BitPay,", "start": 527.916, "duration": 2.571}, {"text": "the whole point of\nBitPay is turning it back", "start": 530.487, "duration": 1.833}, {"text": "into fiat, which is why I think\nthey should pay taxes on it.", "start": 532.32, "duration": 4.98}, {"text": "If the state of Ohio had\na wallet with Bitcoin", "start": 537.3, "duration": 2.55}, {"text": "and they would accept those\nbitcoins into their wallet", "start": 539.85, "duration": 3.27}, {"text": "and hold those proceedings\nin their wallet,", "start": 543.12, "duration": 3.33}, {"text": "then they would be formally\naccepting Bitcoin for taxes.", "start": 546.45, "duration": 4.86}, {"text": "And you will not need to pay\ntaxes on that transaction.", "start": 551.31, "duration": 5.7}, {"text": "GARY GENSLER: But I\nwould raise the question,", "start": 557.01, "duration": 2.82}, {"text": "with all respect,\nwhat's the relevance?", "start": 559.83, "duration": 1.81}, {"text": "Why does it matter\nto a taxpayer in Ohio", "start": 561.64, "duration": 4.76}, {"text": "if this facilitates\nmy paying my taxes,", "start": 566.4, "duration": 3.33}, {"text": "whether it's in the cannabis\ntrade or some other trade?", "start": 569.73, "duration": 4.11}, {"text": "They're facilitating another\nmeans of paying my taxes,", "start": 573.84, "duration": 3.51}, {"text": "fulfilling my\nobligation to society.", "start": 577.35, "duration": 2.31}, {"text": "AUDIENCE: Yeah.", "start": 579.66, "duration": 1.12}, {"text": "So my response to\nthat would be in how", "start": 580.78, "duration": 1.85}, {"text": "we define what a currency is.", "start": 582.63, "duration": 1.74}, {"text": "And one of those criteria is,\nare they accepted to pay taxes?", "start": 584.37, "duration": 4.53}, {"text": "I think it's relevant\nto that distinction.", "start": 588.9, "duration": 2.907}, {"text": "GARY GENSLER: All right.", "start": 591.807, "duration": 1.343}, {"text": "Tom, do you want to defend\nyour fellow Ohioans?", "start": 593.15, "duration": 2.41}, {"text": "AUDIENCE: No.", "start": 595.56, "duration": 2.35}, {"text": "I mean, I think it's relevant.", "start": 597.91, "duration": 1.25}, {"text": "I mean, the Ohio State\nTreasurer doesn't", "start": 599.16, "duration": 3.0}, {"text": "take pork bellies or cotton or\neven corn as paying for taxes.", "start": 602.16, "duration": 5.978}, {"text": "I don't know if they take gold.", "start": 608.138, "duration": 1.292}, {"text": "GARY GENSLER: No.", "start": 609.43, "duration": 1.18}, {"text": "To the best of my knowledge, no.", "start": 610.61, "duration": 1.54}, {"text": "AUDIENCE: Yeah, so even for\nthe short-term transfer,", "start": 612.15, "duration": 3.24}, {"text": "I think it's relevant.", "start": 615.39, "duration": 2.62}, {"text": "GARY GENSLER: So it's\na bit of a hybrid,", "start": 618.01, "duration": 1.67}, {"text": "I guess, is what Tom's saying.", "start": 619.68, "duration": 3.27}, {"text": "Ross?", "start": 622.95, "duration": 1.975}, {"text": "AUDIENCE: There's a real\nquestion about whether they", "start": 624.925, "duration": 2.355}, {"text": "could take it\ndirectly for taxes,", "start": 627.28, "duration": 3.21}, {"text": "because under the Constitution,\nthe states cannot make anything", "start": 630.49, "duration": 3.54}, {"text": "legal tender.", "start": 634.03, "duration": 0.72}, {"text": "Only the federal government\ncan make that determination.", "start": 634.75, "duration": 3.84}, {"text": "Only the federal government\ncan establish legal tender, not", "start": 638.59, "duration": 3.46}, {"text": "the states, other than gold.", "start": 642.05, "duration": 3.57}, {"text": "So it would actually\nbe a question", "start": 645.62, "duration": 1.55}, {"text": "about whether Ohio could--", "start": 647.17, "duration": 2.105}, {"text": "who would object is\nanother question.", "start": 649.275, "duration": 2.155}, {"text": "But it's an issue.", "start": 651.43, "duration": 2.22}, {"text": "What they're doing is\nmarketing, I think.", "start": 653.65, "duration": 2.09}, {"text": "But they could, for example--", "start": 655.74, "duration": 1.45}, {"text": "GARY GENSLER: Though\nI'm not studied", "start": 657.19, "duration": 3.33}, {"text": "in the law of legal tender,\nI could see a case that says,", "start": 660.52, "duration": 6.36}, {"text": "this is not making\nit legal tender.", "start": 666.88, "duration": 1.95}, {"text": "This is just saying\nyou can pay your taxes", "start": 668.83, "duration": 2.88}, {"text": "in another form of property.", "start": 671.71, "duration": 2.556}, {"text": "AUDIENCE: That's the question.", "start": 674.266, "duration": 1.359}, {"text": "GARY GENSLER: You know?", "start": 675.625, "duration": 0.958}, {"text": "Does that make it legal tender?", "start": 676.583, "duration": 1.297}, {"text": "No.", "start": 677.88, "duration": 0.5}, {"text": "It just makes it that we,\nthe government of Ohio,", "start": 678.38, "duration": 2.78}, {"text": "will accept it for taxes.", "start": 681.16, "duration": 2.22}, {"text": "But it doesn't mean that we\nare saying that Starbucks has", "start": 683.38, "duration": 2.97}, {"text": "to take it for a cup of coffee.", "start": 686.35, "duration": 2.05}, {"text": "AUDIENCE: I also\nsee it as a gateway", "start": 688.4, "duration": 1.61}, {"text": "as taking it in a few years,\nhaving their own wallet.", "start": 690.01, "duration": 3.48}, {"text": "So testing it out, see how\nmany people actually use it.", "start": 693.49, "duration": 3.21}, {"text": "And if they want\nto eventually avoid", "start": 696.7, "duration": 1.5}, {"text": "the fees of the\nprocessing service,", "start": 698.2, "duration": 2.67}, {"text": "they could eventually\nrule that out of it.", "start": 700.87, "duration": 2.18}, {"text": "If they set it is\na precedent now,", "start": 703.05, "duration": 2.44}, {"text": "and whether or not they're\nconverting it immediately,", "start": 705.49, "duration": 3.28}, {"text": "doesn't really have an\neffect as to whether it", "start": 708.77, "duration": 2.48}, {"text": "sets a precedent\nfor future years", "start": 711.25, "duration": 2.74}, {"text": "to actually use it as legal--", "start": 713.99, "duration": 1.35}, {"text": "GARY GENSLER: Right.", "start": 715.34, "duration": 0.833}, {"text": "AUDIENCE: --tender,\nas their own wallet,", "start": 716.173, "duration": 2.207}, {"text": "as [INAUDIBLE] was saying.", "start": 718.38, "duration": 2.523}, {"text": "GARY GENSLER: And they might\njust be testing it out.", "start": 720.903, "duration": 2.167}, {"text": "James?", "start": 723.07, "duration": 0.5}, {"text": "AUDIENCE: I guess, reverting to\nRoss's point, in legal tender,", "start": 723.57, "duration": 3.042}, {"text": "the money is different.", "start": 726.612, "duration": 0.958}, {"text": "Right?", "start": 727.57, "duration": 0.69}, {"text": "So the criteria here,\nwhere you're talking money,", "start": 728.26, "duration": 2.46}, {"text": "you could pay taxes,\nwhich, in this case,", "start": 730.72, "duration": 2.25}, {"text": "I think this is verging\non to the hybrid situation", "start": 732.97, "duration": 2.8}, {"text": "where it's not a cow.", "start": 735.77, "duration": 1.95}, {"text": "It's not some corn.", "start": 737.72, "duration": 1.2}, {"text": "But it certainly can pay\nthe taxes via [INAUDIBLE]..", "start": 738.92, "duration": 3.63}, {"text": "So they kind of make it\nmore and more like money.", "start": 742.55, "duration": 2.81}, {"text": "Where about this legal\ntender, that's money,", "start": 745.36, "duration": 3.27}, {"text": "[? well, ?] [? 2.0. ?]", "start": 748.63, "duration": 1.04}, {"text": "AUDIENCE: I think it's--", "start": 749.67, "duration": 1.0}, {"text": "[INTERPOSING VOICES]", "start": 750.67, "duration": 0.5}, {"text": "AUDIENCE: --a question\nof whether you", "start": 751.17, "duration": 1.69}, {"text": "can get to a hybrid using bits.", "start": 752.86, "duration": 2.105}, {"text": "I agree with that.", "start": 754.965, "duration": 1.033}, {"text": "GARY GENSLER: Yeah.", "start": 755.998, "duration": 0.792}, {"text": "And they're testing it out.", "start": 756.79, "duration": 1.35}, {"text": "And maybe this state\ntreasurer feels", "start": 758.14, "duration": 1.86}, {"text": "that it's good for\nhis politics, it", "start": 760.0, "duration": 1.56}, {"text": "will appeal to some\nportion of the electorate,", "start": 761.56, "duration": 4.05}, {"text": "whether it's\nmillennials, whether it's", "start": 765.61, "duration": 2.1}, {"text": "Bitcoin maximalist, whether\nit's the cannabis trade.", "start": 767.71, "duration": 4.68}, {"text": "Or maybe he just\nlooks more tech savvy,", "start": 772.39, "duration": 2.968}, {"text": "that they can put\nout an announcement", "start": 775.358, "duration": 1.542}, {"text": "saying we are the only\nstate in the land.", "start": 776.9, "duration": 2.585}, {"text": "The website says that they're\npromoting it to lower fees.", "start": 782.35, "duration": 6.06}, {"text": "Now, I don't know\nhow many people", "start": 788.41, "duration": 1.5}, {"text": "would pay their taxes in Ohio\nusing the credit card rails.", "start": 789.91, "duration": 4.17}, {"text": "But literally on\nthe website, they", "start": 794.08, "duration": 1.53}, {"text": "talk about, well, this has lower\nfees than the 2 and 1/2% or 3%", "start": 795.61, "duration": 4.77}, {"text": "you get charged on\nyour credit cards.", "start": 800.38, "duration": 2.26}, {"text": "But I think that that would\nonly be a very small portion", "start": 802.64, "duration": 3.14}, {"text": "of taxpayers.", "start": 805.78, "duration": 1.86}, {"text": "And they're accepting\nit for sales tax.", "start": 807.64, "duration": 2.19}, {"text": "They're accepting it\nfor all forms of tax.", "start": 809.83, "duration": 2.82}, {"text": "It's not just income tax.", "start": 812.65, "duration": 2.02}, {"text": "So it's all the small\ntransactional taxes as well as", "start": 814.67, "duration": 6.8}, {"text": "income tax and real estate tax.", "start": 821.47, "duration": 1.74}, {"text": "So it's just an\ninteresting thing.", "start": 823.21, "duration": 5.05}, {"text": "Jake?", "start": 828.26, "duration": 0.5}, {"text": "AUDIENCE: What's the\nactual benefit for it,", "start": 828.76, "duration": 1.792}, {"text": "because can't they just go\nsell the Bitcoin on the market", "start": 830.552, "duration": 2.468}, {"text": "and pay the taxes in cash?", "start": 833.02, "duration": 1.935}, {"text": "GARY GENSLER: So benefit for?", "start": 834.955, "duration": 1.54}, {"text": "AUDIENCE: For the taxpayer.", "start": 836.495, "duration": 1.125}, {"text": "GARY GENSLER: For the taxpayer?", "start": 837.62, "duration": 1.57}, {"text": "This is a good question.", "start": 839.19, "duration": 1.0}, {"text": "What's the benefit\nfor the taxpayer?", "start": 840.19, "duration": 1.55}, {"text": "It's the same\nquestion of, what's", "start": 844.42, "duration": 1.44}, {"text": "the benefit for any consumer if\nI want to use Bitcoin, maybe,", "start": 845.86, "duration": 4.5}, {"text": "to buy a Starbucks?", "start": 850.36, "duration": 2.07}, {"text": "So any vendor could say,\nwe'll accept Bitcoin here.", "start": 852.43, "duration": 6.45}, {"text": "The benefit for the\nconsumer or taxpayer", "start": 858.88, "duration": 4.26}, {"text": "is if they find it\nmore convenient,", "start": 863.14, "duration": 1.68}, {"text": "if it's lower fees, if this\nis where they're storing", "start": 864.82, "duration": 3.57}, {"text": "their value rather than fiat.", "start": 868.39, "duration": 1.68}, {"text": "Not many people are.", "start": 870.07, "duration": 3.36}, {"text": "But that would be--", "start": 873.43, "duration": 1.53}, {"text": "and maybe as Tom\npointed out, that there", "start": 874.96, "duration": 3.75}, {"text": "is a specific\nidiosyncratic thing in Ohio", "start": 878.71, "duration": 3.75}, {"text": "that they've just moved forward.", "start": 882.46, "duration": 1.59}, {"text": "And they legalized the\nmarijuana trade in Ohio?", "start": 884.05, "duration": 4.005}, {"text": "AUDIENCE: I don't think\nit's fully legalized.", "start": 888.055, "duration": 1.875}, {"text": "It's been authorized\nto be legalized.", "start": 889.93, "duration": 1.815}, {"text": "But I don't think that they--", "start": 891.745, "duration": 1.828}, {"text": "GARY GENSLER: So\nthey're in the process.", "start": 893.573, "duration": 1.667}, {"text": "And Tom has a theory\nthat maybe there's", "start": 895.24, "duration": 2.46}, {"text": "some that can't access the\nbanking system, the fiat.", "start": 897.7, "duration": 4.65}, {"text": "In essence, they're\noff fiat rails.", "start": 902.35, "duration": 3.37}, {"text": "So here's, at least,\nTom's theory of the case.", "start": 905.72, "duration": 4.1}, {"text": "So those might be some of the--", "start": 912.65, "duration": 2.98}, {"text": "anyway.", "start": 915.63, "duration": 0.73}, {"text": "So what else happened\nin the last week,", "start": 916.36, "duration": 2.15}, {"text": "by the way, since\nwe came together?", "start": 918.51, "duration": 2.36}, {"text": "Anything else in\nthe crypto space?", "start": 920.87, "duration": 3.015}, {"text": "AUDIENCE: 30% drop in Bitcoin.", "start": 923.885, "duration": 2.445}, {"text": "GARY GENSLER: 30% drop.", "start": 926.33, "duration": 2.82}, {"text": "I haven't checked\nrecently, but yeah.", "start": 929.15, "duration": 3.48}, {"text": "Do you have any theories\non that before we", "start": 932.63, "duration": 2.07}, {"text": "go to crypto exchanges\nand ICOs and everything?", "start": 934.7, "duration": 4.898}, {"text": "AUDIENCE: Not that come up.", "start": 939.598, "duration": 1.476}, {"text": "GARY GENSLER: No.", "start": 941.074, "duration": 0.708}, {"text": "No theories.", "start": 941.782, "duration": 2.008}, {"text": "Oh, well, Brotish we\nhaven't heard from Brotish.", "start": 943.79, "duration": 2.01}, {"text": "You have a theory\nas to the 30% drop", "start": 945.8, "duration": 3.45}, {"text": "since we were last together?", "start": 949.25, "duration": 1.2}, {"text": "AUDIENCE: I have\na different point", "start": 950.45, "duration": 0.7}, {"text": "about what happened recently.", "start": 951.15, "duration": 1.4}, {"text": "We saw the news\narticle [INAUDIBLE]", "start": 952.55, "duration": 2.34}, {"text": "postponing the launch\nof the Bitcoin future", "start": 954.89, "duration": 2.745}, {"text": "to February, which was\nsupposed to happen in November.", "start": 957.635, "duration": 2.25}, {"text": "GARY GENSLER: Do you think\nthat was because they were here", "start": 959.885, "duration": 2.417}, {"text": "to talk with us?", "start": 962.302, "duration": 1.368}, {"text": "I mean, your\nquestions were good.", "start": 963.67, "duration": 1.375}, {"text": "Do you have any views on--", "start": 967.98, "duration": 2.0}, {"text": "Sean, we'll come\nback to the back.", "start": 969.98, "duration": 2.744}, {"text": "AUDIENCE: Because\nof the hard fork,", "start": 972.724, "duration": 1.696}, {"text": "there was a hard fork that\nhappened last Saturday,", "start": 974.42, "duration": 3.47}, {"text": "a week ago, on Bitcoin Cash.", "start": 977.89, "duration": 1.745}, {"text": "And then people, kind of, caused\nthe skepticism in the market", "start": 979.635, "duration": 3.515}, {"text": "to say which is going to be\nthe majority of the consensus", "start": 983.15, "duration": 3.75}, {"text": "for the currency.", "start": 986.9, "duration": 3.09}, {"text": "GARY GENSLER: So there was\na hard fork in Bitcoin Cash,", "start": 989.99, "duration": 3.6}, {"text": "that Bitcoin Cash split\ninto, yet, Bitcoin Cash.", "start": 993.59, "duration": 4.2}, {"text": "And is it now settled\nas Bitcoin SV?", "start": 997.79, "duration": 3.367}, {"text": "S-- what's that?", "start": 1001.157, "duration": 1.778}, {"text": "AUDIENCE: Satoshi's Vision.", "start": 1002.935, "duration": 1.125}, {"text": "GARY GENSLER: Satoshi's\nVision, so SV.", "start": 1004.06, "duration": 2.31}, {"text": "I couldn't make this stuff up.", "start": 1011.33, "duration": 4.04}, {"text": "But that hard fork\nwas, timing wise,", "start": 1015.37, "duration": 5.01}, {"text": "right at the center of\na break in the markets.", "start": 1020.38, "duration": 5.217}, {"text": "And so there's some\nthat have written, well,", "start": 1025.597, "duration": 1.833}, {"text": "is that the reason?", "start": 1027.43, "duration": 2.85}, {"text": "I've been around\nmarkets long enough", "start": 1030.28, "duration": 2.16}, {"text": "to think that might\nbe a news event.", "start": 1032.44, "duration": 3.49}, {"text": "But I don't think that\nwas the reason there", "start": 1035.93, "duration": 2.0}, {"text": "was such a softness in demand,\nthat a news event like that", "start": 1037.93, "duration": 4.26}, {"text": "comes along, and then the market\nbreaks and finds no support,", "start": 1042.19, "duration": 5.895}, {"text": "and it drops from,\nwhat was it around,", "start": 1048.085, "duration": 4.145}, {"text": "$6,300 all the way through\nto $3,700 or $3,800?", "start": 1052.23, "duration": 4.72}, {"text": "I don't know where\nit's trading right now.", "start": 1056.95, "duration": 1.75}, {"text": "But it's somewhere\nin that range.", "start": 1058.7, "duration": 1.375}, {"text": "AUDIENCE: $3,714.", "start": 1060.075, "duration": 1.495}, {"text": "GARY GENSLER: I'm sorry.", "start": 1061.57, "duration": 1.0}, {"text": "AUDIENCE: $3,714.", "start": 1062.57, "duration": 0.99}, {"text": "GARY GENSLER: The\nOhioan has spoken--", "start": 1063.56, "duration": 2.8}, {"text": "$3,714.", "start": 1066.36, "duration": 3.64}, {"text": "So that type of not\nfinding a price support,", "start": 1070.0, "duration": 4.71}, {"text": "there's other reasons,\nI would think,", "start": 1074.71, "duration": 4.44}, {"text": "which really goes back to the\nheart and soul of valuation.", "start": 1079.15, "duration": 3.13}, {"text": "Yes.", "start": 1082.28, "duration": 0.5}, {"text": "AUDIENCE: What about, we were\ntalking about tax stability", "start": 1082.78, "duration": 2.375}, {"text": "earlier.", "start": 1085.155, "duration": 0.535}, {"text": "It is approaching December,\nso tax-loss selling for people", "start": 1085.69, "duration": 3.898}, {"text": "in taxable [? jurisdictions. ?]", "start": 1089.588, "duration": 1.292}, {"text": "GARY GENSLER: So maybe\ntax-loss selling.", "start": 1090.88, "duration": 2.15}, {"text": "[INAUDIBLE]", "start": 1093.03, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]\n[? for a ?]", "start": 1093.53, "duration": 1.375}, {"text": "company and news about\nVisa and MasterCard", "start": 1094.905, "duration": 2.035}, {"text": "[INAUDIBLE] anything\nrelated to cryptocurrencies", "start": 1096.94, "duration": 3.45}, {"text": "and initial coin offering,\nso any transaction related", "start": 1100.39, "duration": 4.21}, {"text": "to them.", "start": 1104.6, "duration": 0.717}, {"text": "So there was something\nin the news about it.", "start": 1105.317, "duration": 1.833}, {"text": "GARY GENSLER:\nThere is also news,", "start": 1107.15, "duration": 1.55}, {"text": "which we're going to review\ntoday, that the Securities", "start": 1108.7, "duration": 2.49}, {"text": "and Exchange Commission\ntook two additional actions", "start": 1111.19, "duration": 4.73}, {"text": "in the initial coin\noffering space.", "start": 1115.92, "duration": 2.56}, {"text": "But these actions were\na little different", "start": 1118.48, "duration": 3.12}, {"text": "than the past actions.", "start": 1121.6, "duration": 1.16}, {"text": "So they've already taken about\na dozen enforcement actions,", "start": 1122.76, "duration": 4.24}, {"text": "or settlements, or orders,\nin the initial coin offering", "start": 1127.0, "duration": 2.41}, {"text": "space.", "start": 1129.41, "duration": 0.5}, {"text": "But these two, Paragon and--", "start": 1129.91, "duration": 2.16}, {"text": "AUDIENCE: Airfox.", "start": 1132.07, "duration": 0.76}, {"text": "GARY GENSLER: --Airfox were\ndifferent in that, one, they", "start": 1132.83, "duration": 7.76}, {"text": "weren't surrounded by\nobvious scam or fraud.", "start": 1140.59, "duration": 6.81}, {"text": "I'm not going to speak\nto their motivations.", "start": 1147.4, "duration": 2.71}, {"text": "But they were more traditional,\n$12, $15, $18 million", "start": 1150.11, "duration": 3.8}, {"text": "raised in each of\nthem, situations.", "start": 1153.91, "duration": 4.23}, {"text": "Two, they're about a year old.", "start": 1158.14, "duration": 2.19}, {"text": "And here they are finally\ncoming to a settlement", "start": 1160.33, "duration": 3.24}, {"text": "where the entrepreneurs, the\nventure capitalists behind it,", "start": 1163.57, "duration": 4.08}, {"text": "said, all right, we get it.", "start": 1167.65, "duration": 2.56}, {"text": "We're going to come\ninto compliance.", "start": 1170.21, "duration": 2.96}, {"text": "We're going to do an\noffering statement.", "start": 1173.17, "duration": 2.31}, {"text": "We're going to put out the\nfull and fair information", "start": 1175.48, "duration": 3.33}, {"text": "about this.", "start": 1178.81, "duration": 1.09}, {"text": "But also, we're going to be\nwilling to give back money", "start": 1179.9, "duration": 5.66}, {"text": "to people who were--", "start": 1185.56, "duration": 2.5}, {"text": "so they're not\nfighting in a court.", "start": 1188.06, "duration": 2.24}, {"text": "Some have gone into\ncourt against the SEC.", "start": 1190.3, "duration": 3.06}, {"text": "But here, also, the other\nthing was the first time", "start": 1193.36, "duration": 2.46}, {"text": "they paid penalties,\nI think they", "start": 1195.82, "duration": 1.56}, {"text": "were modest, relatively modest--\nquarter million dollars,", "start": 1197.38, "duration": 3.51}, {"text": "if I saw.", "start": 1200.89, "duration": 2.44}, {"text": "But that also happened\nin the midst of this.", "start": 1203.33, "duration": 2.96}, {"text": "The SEC for the first time\nactually assessed penalties,", "start": 1206.29, "duration": 3.78}, {"text": "had settlements.", "start": 1210.07, "duration": 1.43}, {"text": "They were also not\nthe, sort of, clear,", "start": 1211.5, "duration": 3.48}, {"text": "obvious scam and fraud cases.", "start": 1214.98, "duration": 2.22}, {"text": "They were simply, hey,\nyou didn't register,", "start": 1217.2, "duration": 2.37}, {"text": "and you were\nsupposed to register.", "start": 1219.57, "duration": 1.83}, {"text": "You're, in essence, an\nillegal securities offering.", "start": 1221.4, "duration": 4.29}, {"text": "But now, come into compliance,\npay a penalty, move forward,", "start": 1225.69, "duration": 4.35}, {"text": "as well.", "start": 1230.04, "duration": 1.57}, {"text": "So a lot going on.", "start": 1231.61, "duration": 2.79}, {"text": "So today, we already did\nOhio, which was more fun", "start": 1234.4, "duration": 4.61}, {"text": "than the rest of this stuff.", "start": 1239.01, "duration": 1.26}, {"text": "We're going to talk a little\nbit about the Howey Test", "start": 1240.27, "duration": 2.55}, {"text": "again, which we talked\nabout about a month ago.", "start": 1242.82, "duration": 2.28}, {"text": "But I wanted to bring it\nback into the discussion", "start": 1245.1, "duration": 2.79}, {"text": "about initial coin offerings.", "start": 1247.89, "duration": 2.97}, {"text": "We're going to talk a little\nbit about some realities.", "start": 1250.86, "duration": 2.25}, {"text": "Ernst & Young put\nout a recent report", "start": 1253.11, "duration": 1.98}, {"text": "that wasn't in your readings.", "start": 1255.09, "duration": 1.29}, {"text": "It just came out last week.", "start": 1256.38, "duration": 1.26}, {"text": "But I want to review some of the\nfindings that Ernst & Young did", "start": 1257.64, "duration": 3.04}, {"text": "on, what they call,\nthe class of 2017.", "start": 1260.68, "duration": 4.1}, {"text": "They look at the top\n140 ICOs from 2017,", "start": 1264.78, "duration": 4.14}, {"text": "and where are they as of the\nend of September of this year,", "start": 1268.92, "duration": 4.26}, {"text": "not even speaking about the\nlast six or eight weeks.", "start": 1273.18, "duration": 3.9}, {"text": "Some SEC enforcement\nactions I want", "start": 1277.08, "duration": 2.52}, {"text": "to walk through just to give\nyou a flavor for, at least,", "start": 1279.6, "duration": 3.06}, {"text": "this country's approach\nto initial coin offerings,", "start": 1282.66, "duration": 3.9}, {"text": "how you can actually\ncomply with securities law.", "start": 1286.56, "duration": 3.33}, {"text": "I promise you that I'm not\ngoing to go deep diving.", "start": 1289.89, "duration": 3.99}, {"text": "But I want to give you a\nlittle bit of a flavor for,", "start": 1293.88, "duration": 4.11}, {"text": "if you were to be involved\nin an initial coin offering,", "start": 1297.99, "duration": 2.79}, {"text": "how to do it in a compliant way.", "start": 1300.78, "duration": 2.29}, {"text": "And some personal thoughts\non the path forward", "start": 1303.07, "duration": 3.85}, {"text": "in ICO [INAUDIBLE].", "start": 1306.92, "duration": 1.39}, {"text": "So that's what\nwe're going to do.", "start": 1308.31, "duration": 2.46}, {"text": "The study questions,\nwe'll get to.", "start": 1310.77, "duration": 3.8}, {"text": "But I just want to ask the\nclass the middle question,", "start": 1314.57, "duration": 5.59}, {"text": "which is the easiest,\nor maybe the hardest.", "start": 1320.16, "duration": 3.57}, {"text": "Why is this market so rife with\nscams and fraud, whether it's", "start": 1323.73, "duration": 4.71}, {"text": "Christian Catalini's\nwork that said", "start": 1328.44, "duration": 1.65}, {"text": "25% of the market or\nthe smaller survey", "start": 1330.09, "duration": 4.47}, {"text": "status group that was part of\ntoday's readings, up to 80%?", "start": 1334.56, "duration": 4.83}, {"text": "Why do you think this\nmarket has so many scams?", "start": 1339.39, "duration": 2.14}, {"text": "Aline what do you--", "start": 1341.53, "duration": 1.46}, {"text": "AUDIENCE: It's so easy to con.", "start": 1342.99, "duration": 2.302}, {"text": "GARY GENSLER: What's easy?", "start": 1345.292, "duration": 1.178}, {"text": "The question's easy, or\nscamming the market's easy?", "start": 1346.47, "duration": 2.387}, {"text": "AUDIENCE: It's so\neasy to scam people.", "start": 1348.857, "duration": 1.583}, {"text": "Like, why wouldn't you do it?", "start": 1350.44, "duration": 1.25}, {"text": "It's so damn easy.", "start": 1351.69, "duration": 2.99}, {"text": "GARY GENSLER: I'm sorry.", "start": 1354.68, "duration": 1.0}, {"text": "The first part I got.", "start": 1355.68, "duration": 1.53}, {"text": "Remember we're on video.", "start": 1357.21, "duration": 3.01}, {"text": "All right.", "start": 1360.22, "duration": 0.5}, {"text": "AUDIENCE: It's a\nrhetorical question.", "start": 1360.72, "duration": 1.72}, {"text": "GARY GENSLER: It's a\nrhetorical question.", "start": 1362.44, "duration": 1.708}, {"text": "It's so easy.", "start": 1364.148, "duration": 1.552}, {"text": "And thus, it's easy\nfor bad actors.", "start": 1365.7, "duration": 2.74}, {"text": "Jihee.", "start": 1368.44, "duration": 0.655}, {"text": "AUDIENCE: I thought there\nwere two main reasons.", "start": 1369.095, "duration": 2.045}, {"text": "One is because it's\nsuch a new thing,", "start": 1371.14, "duration": 1.94}, {"text": "there is lack of the\nregulatory environment", "start": 1373.08, "duration": 3.33}, {"text": "that happens with the IPO and\nother ways of raising funds.", "start": 1376.41, "duration": 5.05}, {"text": "And I think the second one\nis it's, as Alin pointed out,", "start": 1381.46, "duration": 3.8}, {"text": "I think it's very easy to\njust go say, I'm going to do", "start": 1385.26, "duration": 3.51}, {"text": "ICO when there is only an idea.", "start": 1388.77, "duration": 3.72}, {"text": "So I think that's why a lot\nof investors or consumers", "start": 1392.49, "duration": 4.05}, {"text": "just fall into these\nscams and fraud.", "start": 1396.54, "duration": 2.606}, {"text": "AUDIENCE: And I mean,\nthe fact that you're just", "start": 1399.146, "duration": 3.424}, {"text": "publishing a white paper, that\nno one actually is interacting", "start": 1402.57, "duration": 3.99}, {"text": "with you unless it's on a\nblog or something like that,", "start": 1406.56, "duration": 2.598}, {"text": "they're publishing\na white paper that", "start": 1409.158, "duration": 1.542}, {"text": "could have this grandiose\nidea, and then all of a sudden", "start": 1410.7, "duration": 3.09}, {"text": "they just run.", "start": 1413.79, "duration": 0.87}, {"text": "And there's really nothing\nstopping them from doing that.", "start": 1414.66, "duration": 3.39}, {"text": "So it's just difficult.", "start": 1418.05, "duration": 2.165}, {"text": "GARY GENSLER: So\nI've heard it's easy.", "start": 1420.215, "duration": 2.485}, {"text": "It's not yet in a\nregulatory space.", "start": 1422.7, "duration": 3.52}, {"text": "It's at a distance.", "start": 1426.22, "duration": 2.43}, {"text": "It's just the publishing\nof a white paper.", "start": 1428.65, "duration": 2.383}, {"text": "AUDIENCE: And there's simply\ndemand because of immediate--", "start": 1431.033, "duration": 2.417}, {"text": "GARY GENSLER: So demand.", "start": 1433.45, "duration": 0.76}, {"text": "AUDIENCE: Yeah, there's\njust a lot of demand.", "start": 1434.21, "duration": 1.22}, {"text": "With the media around Bitcoin\ngoing up towards $20,000", "start": 1435.43, "duration": 2.81}, {"text": "last year, there's demand to\nget into the bottom of one", "start": 1438.24, "duration": 3.72}, {"text": "of these ICOs to hope to get\nthe same kind of returns.", "start": 1441.96, "duration": 2.25}, {"text": "GARY GENSLER: So there is\ntremendous demand and, related", "start": 1444.21, "duration": 2.85}, {"text": "to demand, fear of missing\nout, so whether it's greed--", "start": 1447.06, "duration": 7.35}, {"text": "the animal spirits, the\nhuman spirits of market's", "start": 1454.41, "duration": 2.76}, {"text": "around fear and greed.", "start": 1457.17, "duration": 1.185}, {"text": "So the greed of participating\nor the fear of missing out", "start": 1458.355, "duration": 3.915}, {"text": "was certainly part of\nlate 2017 and into 2018.", "start": 1462.27, "duration": 6.27}, {"text": "Kelly?", "start": 1468.54, "duration": 0.5}, {"text": "AUDIENCE: We could\ntalk a little bit more", "start": 1469.04, "duration": 0.58}, {"text": "about what Jihee\nsaid about the lack", "start": 1469.62, "duration": 1.5}, {"text": "of a regulatory environment.", "start": 1471.12, "duration": 2.07}, {"text": "That sort of leads to--\nbecause a lot of these ICOs", "start": 1473.19, "duration": 3.87}, {"text": "are not in compliance\nwith securities acts", "start": 1477.06, "duration": 3.75}, {"text": "and regulations that allows\nthem to sort of skirmish", "start": 1480.81, "duration": 3.41}, {"text": "around investor protection.", "start": 1484.22, "duration": 1.46}, {"text": "So investors, they're\nnot necessarily", "start": 1485.68, "duration": 3.11}, {"text": "privy to material information\nabout the financing", "start": 1488.79, "duration": 3.66}, {"text": "and what they might\nreasonably expect as a return.", "start": 1492.45, "duration": 2.79}, {"text": "So it kind of--", "start": 1495.24, "duration": 0.68}, {"text": "GARY GENSLER: Right.", "start": 1495.92, "duration": 0.61}, {"text": "AUDIENCE: They're just taking\nadvantage of it a little bit.", "start": 1496.53, "duration": 2.612}, {"text": "GARY GENSLER: I agree,\nbut I think the court--", "start": 1499.142, "duration": 2.308}, {"text": "Kelly is touching\non one other thing.", "start": 1501.45, "duration": 1.81}, {"text": "Guillermo.", "start": 1503.26, "duration": 0.5}, {"text": "AUDIENCE: I had one\nquestion on this.", "start": 1503.76, "duration": 2.245}, {"text": "The scams are\ndefined as a company", "start": 1506.005, "duration": 1.955}, {"text": "that you can no\nlonger reach or see", "start": 1507.96, "duration": 2.01}, {"text": "if they came out with a product.", "start": 1509.97, "duration": 1.47}, {"text": "But I was wondering,\ngiven that this", "start": 1511.44, "duration": 1.98}, {"text": "is a very early-stage\nventure, how much, really,", "start": 1513.42, "duration": 2.19}, {"text": "do people maliciously\nrun away with the money,", "start": 1515.61, "duration": 3.96}, {"text": "or just tried\nsomething and failed?", "start": 1519.57, "duration": 3.68}, {"text": "Do they just raise money,\nand because they did it", "start": 1523.25, "duration": 3.667}, {"text": "with a PowerPoint, they\nrealized this is not", "start": 1526.917, "duration": 1.833}, {"text": "going to be a good\nbusiness case,", "start": 1528.75, "duration": 1.59}, {"text": "and they just abandon\nit, not as a scam", "start": 1530.34, "duration": 2.55}, {"text": "but as a new\nventure that failed?", "start": 1532.89, "duration": 2.6}, {"text": "GARY GENSLER: I think Guillermo\nraises the right question.", "start": 1535.49, "duration": 3.78}, {"text": "It's why one study says it's\n5% to 25% scams or frauds,", "start": 1539.27, "duration": 4.33}, {"text": "and another study says 80%.", "start": 1543.6, "duration": 3.04}, {"text": "It's what's in the definition.", "start": 1546.64, "duration": 2.21}, {"text": "A good-faith actor could\nsay this is easy money.", "start": 1548.85, "duration": 4.94}, {"text": "A good-faith actor could\nsay this is cheap money.", "start": 1553.79, "duration": 2.8}, {"text": "I can raise money\nfast just on the backs", "start": 1556.59, "duration": 2.55}, {"text": "of a white paper in the middle\nof a bull market, maybe even", "start": 1559.14, "duration": 6.39}, {"text": "a bubble, and then find\nout three months later", "start": 1565.53, "duration": 4.26}, {"text": "that their idea\ndoesn't work out.", "start": 1569.79, "duration": 2.9}, {"text": "And I accept that\nthere are probably", "start": 1572.69, "duration": 3.28}, {"text": "a lot of good-faith actors\nthat raised tens of millions", "start": 1575.97, "duration": 3.48}, {"text": "of dollars.", "start": 1579.45, "duration": 2.56}, {"text": "And I wouldn't necessarily\npersonally call that a scam.", "start": 1582.01, "duration": 3.89}, {"text": "But nonetheless, somebody\nelse might call that a scam.", "start": 1585.9, "duration": 3.09}, {"text": "So Telegram raised $1.7 billion\nin February of this year.", "start": 1588.99, "duration": 6.57}, {"text": "I don't know-- how\nmany people have ever", "start": 1595.56, "duration": 2.58}, {"text": "read the white paper, I mean,\nnot that it was ever assigned?", "start": 1598.14, "duration": 4.255}, {"text": "All right, all right.", "start": 1602.395, "duration": 0.875}, {"text": "So all right, I've\nread the white paper.", "start": 1603.27, "duration": 2.22}, {"text": "I couldn't figure\nout in February", "start": 1605.49, "duration": 2.16}, {"text": "when they raised the\nmoney what they were going", "start": 1607.65, "duration": 2.04}, {"text": "to use that $1.7 billion for.", "start": 1609.69, "duration": 3.19}, {"text": "Now, it's a\nremarkable technology.", "start": 1612.88, "duration": 2.54}, {"text": "And they have, I think,\nsomewhere around 200 million", "start": 1615.42, "duration": 2.37}, {"text": "users in their\nnon-blockchain use.", "start": 1617.79, "duration": 4.92}, {"text": "And so they were able\nto raise a lot of money", "start": 1622.71, "duration": 3.37}, {"text": "with a lot of fancy words.", "start": 1626.08, "duration": 2.91}, {"text": "But they still\nhaven't gone live.", "start": 1628.99, "duration": 3.22}, {"text": "They haven't taken the $1.7\nbillion and created a network.", "start": 1632.21, "duration": 5.59}, {"text": "Filecoin seemed\nto be a good-faith", "start": 1637.8, "duration": 6.0}, {"text": "concept about using\na token to motivate", "start": 1643.8, "duration": 4.26}, {"text": "the exchange of file storage.", "start": 1648.06, "duration": 4.26}, {"text": "Assume for a moment\nit's good-faith actors.", "start": 1652.32, "duration": 3.0}, {"text": "They raised the money\nin October of 2017.", "start": 1655.32, "duration": 2.73}, {"text": "It's 13 months later.", "start": 1658.05, "duration": 1.36}, {"text": "They still do not\nhave a live network.", "start": 1659.41, "duration": 3.32}, {"text": "And the latest\nannouncement says it", "start": 1662.73, "duration": 2.7}, {"text": "will come either in the first\nor second quarter of 2019.", "start": 1665.43, "duration": 5.04}, {"text": "Some people might\ncall that a scam.", "start": 1670.47, "duration": 2.14}, {"text": "I wouldn't.", "start": 1672.61, "duration": 0.89}, {"text": "But so I think you're right.", "start": 1673.5, "duration": 1.9}, {"text": "There's a range of activity.", "start": 1675.4, "duration": 4.2}, {"text": "But there's one\nother thing about why", "start": 1679.6, "duration": 1.7}, {"text": "I think this has been an easy\nplace for scams and frauds.", "start": 1681.3, "duration": 4.5}, {"text": "And it's the technical\nnature of it, as well.", "start": 1685.8, "duration": 4.78}, {"text": "Like, I hope at the end\nof this class, whatever", "start": 1690.58, "duration": 1.995}, {"text": "you think of the lectures,\nwhatever you think", "start": 1692.575, "duration": 1.875}, {"text": "of the assignments,\nyou come away", "start": 1694.45, "duration": 1.375}, {"text": "with some critical reasoning\nskills, that the 80 or so", "start": 1695.825, "duration": 3.695}, {"text": "of you who have been on\nthis journey together", "start": 1699.52, "duration": 3.42}, {"text": "will leave and say,\nall right, I get it.", "start": 1702.94, "duration": 2.59}, {"text": "But for most, for the\nhundreds of thousands", "start": 1705.53, "duration": 3.59}, {"text": "or even millions of\npeople that have invested,", "start": 1709.12, "duration": 3.91}, {"text": "there's a lot of technical--", "start": 1713.03, "duration": 2.27}, {"text": "whether it's hash functions\nor digital signatures.", "start": 1715.3, "duration": 4.26}, {"text": "And so I think it's\neasier to scam the public", "start": 1719.56, "duration": 5.04}, {"text": "when it's shrouded in jargon.", "start": 1724.6, "duration": 4.7}, {"text": "And so maybe it's a\nlesson for all of us", "start": 1729.3, "duration": 2.56}, {"text": "to always be careful\nabout our own investments", "start": 1731.86, "duration": 3.27}, {"text": "when something is\nshrouded in jargon.", "start": 1735.13, "duration": 2.49}, {"text": "And it doesn't have to\nbe cryptographic jargon.", "start": 1737.62, "duration": 3.0}, {"text": "It could be other types\nof jargon, as well.", "start": 1740.62, "duration": 2.28}, {"text": "I think that's also\none of the reasons", "start": 1742.9, "duration": 2.94}, {"text": "why it's been easier\nto scam and fleece", "start": 1745.84, "duration": 4.14}, {"text": "the public in the midst\nof a bubble, in the midst", "start": 1749.98, "duration": 3.42}, {"text": "of a nonregulated\nspace, in the midst of,", "start": 1753.4, "duration": 2.64}, {"text": "just throw a white paper up.", "start": 1756.04, "duration": 3.38}, {"text": "Jake?", "start": 1759.42, "duration": 0.5}, {"text": "AUDIENCE: It's also the\nnature of it just being,", "start": 1759.92, "duration": 1.715}, {"text": "we're investing in\nsuch an early stage.", "start": 1761.635, "duration": 1.685}, {"text": "So plenty of tech that\nends up IPOing and has", "start": 1763.32, "duration": 3.94}, {"text": "public investors when it's early\non, it's only VCs investing.", "start": 1767.26, "duration": 4.59}, {"text": "And they understand the tech.", "start": 1771.85, "duration": 1.36}, {"text": "But you don't have regular\nconsumer retail investors", "start": 1773.21, "duration": 2.293}, {"text": "actually putting money into\nthose really early-stage", "start": 1775.503, "duration": 2.167}, {"text": "companies, where\nwith ICOs, we're", "start": 1777.67, "duration": 2.1}, {"text": "investing at the white paper.", "start": 1779.77, "duration": 1.28}, {"text": "So regardless of\nwhether it's blockchain", "start": 1781.05, "duration": 2.44}, {"text": "or a robotics\ncompany or whatever,", "start": 1783.49, "duration": 2.01}, {"text": "it is very confusing\nthat early on.", "start": 1785.5, "duration": 2.556}, {"text": "GARY GENSLER: Right.", "start": 1788.056, "duration": 0.894}, {"text": "So it's also very\nearly-stage investing,", "start": 1788.95, "duration": 2.59}, {"text": "which is a good point.", "start": 1791.54, "duration": 2.43}, {"text": "So I'm going to skip\nover the reading.", "start": 1793.97, "duration": 1.76}, {"text": "So investor protection.", "start": 1795.73, "duration": 1.77}, {"text": "I found in a conference in\nParis, an OECD conference--", "start": 1797.5, "duration": 5.97}, {"text": "we got into a debate.", "start": 1803.47, "duration": 1.05}, {"text": "And there were regulators--", "start": 1804.52, "duration": 1.71}, {"text": "I was not a regulator\nat the time;", "start": 1806.23, "duration": 1.53}, {"text": "this was earlier this year--", "start": 1807.76, "duration": 1.74}, {"text": "regulators from 30\nor 40 countries.", "start": 1809.5, "duration": 1.95}, {"text": "And we got in a\ndebate of, what's", "start": 1811.45, "duration": 1.86}, {"text": "the difference between investor\nprotection and consumer", "start": 1813.31, "duration": 2.61}, {"text": "protection?", "start": 1815.92, "duration": 1.32}, {"text": "And so these are\njust some thoughts.", "start": 1817.24, "duration": 1.92}, {"text": "But investor protection, which\nhas been the hallmark of the US", "start": 1819.16, "duration": 4.23}, {"text": "markets that's in the 1930s,\nand in other jurisdictions,", "start": 1823.39, "duration": 3.66}, {"text": "other decades it's\nbeen adopted, I", "start": 1827.05, "duration": 2.49}, {"text": "think is part of why the US\ncapital markets were really", "start": 1829.54, "duration": 5.07}, {"text": "at the forefront of this\nincredible economy for 70", "start": 1834.61, "duration": 3.63}, {"text": "or 80 years here in the US.", "start": 1838.24, "duration": 1.53}, {"text": "And it's helped other\neconomies subsequently.", "start": 1839.77, "duration": 2.95}, {"text": "But it's four big things.", "start": 1842.72, "duration": 1.25}, {"text": "Investors do take risk.", "start": 1843.97, "duration": 3.48}, {"text": "But they get full and fair\ndisclosure from an issuer.", "start": 1847.45, "duration": 3.48}, {"text": "And there's a concept that\nthere's asymmetric knowledge,", "start": 1850.93, "duration": 4.87}, {"text": "that an issuer has a\nbunch of information", "start": 1855.8, "duration": 2.78}, {"text": "and an investor does not.", "start": 1858.58, "duration": 2.31}, {"text": "Through the laws\nof the land, can we", "start": 1860.89, "duration": 2.61}, {"text": "balance that a little bit?", "start": 1863.5, "duration": 2.25}, {"text": "Investors still have every\nopportunity to take risk.", "start": 1865.75, "duration": 3.27}, {"text": "But can we address the\nasymmetry of information?", "start": 1869.02, "duration": 3.66}, {"text": "And that's really a core\npart of investor protection,", "start": 1872.68, "duration": 5.86}, {"text": "a little bit different\nthan consumer protection.", "start": 1878.54, "duration": 2.0}, {"text": "You still want to be protected\nthat a crib that you buy", "start": 1880.54, "duration": 3.42}, {"text": "is not going to hurt your\nchild or that the clothing you", "start": 1883.96, "duration": 2.85}, {"text": "put on an infant isn't\ninstantly flammable.", "start": 1886.81, "duration": 3.03}, {"text": "Those are important\nconsumer protections.", "start": 1889.84, "duration": 2.16}, {"text": "And often, we protect\nthem in the laws, as well.", "start": 1892.0, "duration": 3.42}, {"text": "But information asymmetry\nand the difference", "start": 1895.42, "duration": 3.21}, {"text": "between information between an\nissuer, somebody raising money,", "start": 1898.63, "duration": 3.0}, {"text": "and an investor is\nsomething we try", "start": 1901.63, "duration": 1.92}, {"text": "to embed in securities\nlaws around the globe.", "start": 1903.55, "duration": 4.34}, {"text": "Two is the concept\nof sales practices.", "start": 1907.89, "duration": 3.79}, {"text": "Various fraud and sales\npractices are prohibited.", "start": 1911.68, "duration": 3.06}, {"text": "Sometimes you hear this\naround securities laws", "start": 1914.74, "duration": 1.98}, {"text": "about the marketing\ninformation, what information", "start": 1916.72, "duration": 2.79}, {"text": "you need to provide.", "start": 1919.51, "duration": 2.61}, {"text": "So the first and\nsecond are principles", "start": 1922.12, "duration": 2.97}, {"text": "that go into why there's\ninformation statements.", "start": 1925.09, "duration": 3.3}, {"text": "Or securities offerings come\nwith all that boilerplate,", "start": 1928.39, "duration": 3.6}, {"text": "and sometimes you might\nsay it's too much.", "start": 1931.99, "duration": 3.93}, {"text": "But all of that is to address\ninformation asymmetries", "start": 1935.92, "duration": 3.9}, {"text": "and try to lessen\nor make it harder", "start": 1939.82, "duration": 2.22}, {"text": "to have fraud and\ndeceptive practices.", "start": 1942.04, "duration": 3.18}, {"text": "Then we have something called\nsecondary markets, where", "start": 1947.97, "duration": 2.84}, {"text": "buyers and sellers meet, like\non the New York Stock Exchange", "start": 1950.81, "duration": 3.3}, {"text": "or on a crypto exchange,\nand the concept being,", "start": 1954.11, "duration": 5.04}, {"text": "can we promote market integrity?", "start": 1959.15, "duration": 2.7}, {"text": "Can we promote those markets\neither through transparency--", "start": 1961.85, "duration": 5.14}, {"text": "transparency is really being\nable to see what buy orders", "start": 1966.99, "duration": 3.65}, {"text": "and sell orders--", "start": 1970.64, "duration": 0.885}, {"text": "what's the price that\npeople are willing to pay?", "start": 1974.45, "duration": 4.47}, {"text": "What's the amount they're\nwilling to buy or sell?", "start": 1978.92, "duration": 3.64}, {"text": "So pre-trade\ntransparency says, I'm", "start": 1982.56, "duration": 2.24}, {"text": "going to share in\nthe marketplace,", "start": 1984.8, "duration": 1.63}, {"text": "that there's not somebody\nover here, some high frequency", "start": 1986.43, "duration": 2.99}, {"text": "traders, that get\ntransparency, but retail public", "start": 1989.42, "duration": 2.73}, {"text": "does not get transparency.", "start": 1992.15, "duration": 3.03}, {"text": "It brings it into one market.", "start": 1995.18, "duration": 2.49}, {"text": "And some rules\nagainst manipulation.", "start": 1997.67, "duration": 2.76}, {"text": "Now one person's manipulation's\nanother person's market", "start": 2000.43, "duration": 3.78}, {"text": "practice.", "start": 2004.21, "duration": 1.17}, {"text": "I respect that, too, just\nlike the word \"scam.\"", "start": 2005.38, "duration": 3.57}, {"text": "But there's traditional\nthings about manipulation", "start": 2008.95, "duration": 2.85}, {"text": "that have come to\nbe, no, we should", "start": 2011.8, "duration": 3.66}, {"text": "forbid certain practices.", "start": 2015.46, "duration": 2.97}, {"text": "Front-running is one,\nwhere a customer gives you", "start": 2018.43, "duration": 2.97}, {"text": "a sell order, and you say,\nwell, the customers sell order,", "start": 2021.4, "duration": 2.88}, {"text": "good, I'll sell in\nfront of them because I", "start": 2024.28, "duration": 2.04}, {"text": "know that when they\nsell, it's going", "start": 2026.32, "duration": 2.6}, {"text": "to be market pressure, either\nup pressure with a buy order", "start": 2028.92, "duration": 5.215}, {"text": "or down pressure\nwith a sell order.", "start": 2034.135, "duration": 3.505}, {"text": "So one is address asymmetries\nthrough information.", "start": 2037.64, "duration": 5.3}, {"text": "Prohibit or limit fraud and\ndeceptive sales practices", "start": 2042.94, "duration": 3.66}, {"text": "and marketing--", "start": 2046.6, "duration": 1.41}, {"text": "lying, sort of.", "start": 2048.01, "duration": 1.919}, {"text": "Promote the integrity\nof the secondary markets", "start": 2049.929, "duration": 2.911}, {"text": "through, first,\nprice transparency", "start": 2052.84, "duration": 3.22}, {"text": "and, secondly, antimanipulation.", "start": 2056.06, "duration": 2.63}, {"text": "And then, lastly, recognizing\nthat all financial markets", "start": 2058.69, "duration": 2.85}, {"text": "have conflicts.", "start": 2061.54, "duration": 1.679}, {"text": "And we are not going\nto repeal conflicts.", "start": 2063.219, "duration": 2.52}, {"text": "Anytime any one of\nyou goes to a broker,", "start": 2065.739, "duration": 2.641}, {"text": "that broker does\nwant you to transact", "start": 2068.38, "duration": 2.31}, {"text": "so that they earn more money.", "start": 2070.69, "duration": 3.52}, {"text": "But by the way, when you\nsit down at a restaurant", "start": 2074.21, "duration": 2.12}, {"text": "and they ask you if you want\na drink before you order,", "start": 2076.33, "duration": 2.77}, {"text": "there is a bit of\na conflict, too.", "start": 2079.1, "duration": 2.869}, {"text": "They want you to buy the\ndrink because your tip", "start": 2081.969, "duration": 2.52}, {"text": "amount is a percent of your\nfinal bill, well, in most", "start": 2084.489, "duration": 6.301}, {"text": "countries.", "start": 2090.79, "duration": 0.619}, {"text": "I can't speak for\nevery country here.", "start": 2091.409, "duration": 3.161}, {"text": "But in finance,\nthose conflicts are", "start": 2094.57, "duration": 2.25}, {"text": "so evident that there are\nsets of rules, usually, that", "start": 2096.82, "duration": 5.37}, {"text": "promote some transparency\nthat you know", "start": 2102.19, "duration": 2.137}, {"text": "what the advisor is getting.", "start": 2104.327, "duration": 2.513}, {"text": "But some practices\nare prohibited.", "start": 2106.84, "duration": 2.62}, {"text": "So these are some of the\ncore things that, at least,", "start": 2109.46, "duration": 3.95}, {"text": "I think are embedded as\nconcepts in our securities laws,", "start": 2113.41, "duration": 4.44}, {"text": "and not just here in the\nUS but around the globe.", "start": 2117.85, "duration": 3.12}, {"text": "Any questions on that before--", "start": 2120.97, "duration": 2.1}, {"text": "Brotish?", "start": 2123.07, "duration": 0.93}, {"text": "AUDIENCE: So on the\nfirst point, if we", "start": 2124.0, "duration": 2.49}, {"text": "are saying that we have some\nsort of a minimum disclosure", "start": 2126.49, "duration": 2.67}, {"text": "requirement for ICOs, do you\nthink in this kind of a field,", "start": 2129.16, "duration": 4.225}, {"text": "do we have the regulators\nwho have the expertise", "start": 2133.385, "duration": 2.495}, {"text": "to judge whether those\nrequirements are met or not?", "start": 2135.88, "duration": 3.458}, {"text": "Like, they can say that--", "start": 2139.338, "duration": 1.042}, {"text": "GARY GENSLER: Are you\nasking whether the investors", "start": 2140.38, "duration": 1.98}, {"text": "will have the expertise,\nor the regulators?", "start": 2142.36, "duration": 1.89}, {"text": "AUDIENCE: Regulators.", "start": 2144.25, "duration": 1.671}, {"text": "GARY GENSLER: It's\na good question.", "start": 2145.921, "duration": 1.579}, {"text": "I think that the concept is\nthat issuers should share", "start": 2147.5, "duration": 6.41}, {"text": "a certain level of\nmaterial information", "start": 2153.91, "duration": 3.33}, {"text": "with potential investors, and\nthen investors assess the risk,", "start": 2157.24, "duration": 4.23}, {"text": "not that the regulator assesses\nthe risk but the investors.", "start": 2161.47, "duration": 4.15}, {"text": "So the question is,\nwhat is material?", "start": 2165.62, "duration": 2.6}, {"text": "And what needs to be shared\nin what readable fashion?", "start": 2168.22, "duration": 3.6}, {"text": "And maybe it's the\ncase in this ecosystem", "start": 2171.82, "duration": 4.56}, {"text": "that the information should\nbe a little different.", "start": 2176.38, "duration": 3.15}, {"text": "Historically, you'd have to\nshare three years of financials", "start": 2179.53, "duration": 2.97}, {"text": "or two years of financials.", "start": 2182.5, "duration": 1.77}, {"text": "But what do financials mean if\nit's a new concept, a new idea?", "start": 2184.27, "duration": 4.9}, {"text": "So I think you\nraise a good point", "start": 2189.17, "duration": 2.36}, {"text": "that it might need to\nshift a little bit.", "start": 2191.53, "duration": 2.88}, {"text": "But the core concept is that\nthe material information", "start": 2194.41, "duration": 4.2}, {"text": "to make an investment\ndecision should be shared,", "start": 2198.61, "duration": 3.27}, {"text": "and then investors\nhave an opportunity", "start": 2201.88, "duration": 1.71}, {"text": "to assess that risk.", "start": 2203.59, "duration": 1.752}, {"text": "And you're right.", "start": 2205.342, "duration": 0.708}, {"text": "The regulators are less\nexperienced in this space", "start": 2206.05, "duration": 4.45}, {"text": "to say what is a material bit\nof information beyond here's", "start": 2210.5, "duration": 5.08}, {"text": "the team, and\nhere's the concept.", "start": 2215.58, "duration": 1.995}, {"text": "The Howey Test.", "start": 2222.57, "duration": 1.94}, {"text": "So there is an\nindividual in Florida.", "start": 2224.51, "duration": 4.23}, {"text": "He ran for governor\ntwice in Florida", "start": 2228.74, "duration": 2.01}, {"text": "and lost twice, just\na little background--", "start": 2230.75, "duration": 2.64}, {"text": "William Howey.", "start": 2233.39, "duration": 2.28}, {"text": "He was also very\nsuccessful in real estate,", "start": 2235.67, "duration": 1.89}, {"text": "and he had a hotel.", "start": 2237.56, "duration": 1.05}, {"text": "And he had something\ncalled Howey on the Hills.", "start": 2238.61, "duration": 2.91}, {"text": "And he started buying\na bunch of land.", "start": 2241.52, "duration": 1.95}, {"text": "And then he thought, well,\nI'll sell some of the land", "start": 2243.47, "duration": 2.4}, {"text": "and grow orange groves.", "start": 2245.87, "duration": 5.19}, {"text": "And when he sold the land,\nhe gave the opportunity", "start": 2251.06, "duration": 3.24}, {"text": "to investors in\nthe land to enter", "start": 2254.3, "duration": 2.55}, {"text": "into a separate\ncontract with a company", "start": 2256.85, "duration": 3.36}, {"text": "he had, but it was not required.", "start": 2260.21, "duration": 1.74}, {"text": "You could buy the land, you\nknow, an acre, three acres.", "start": 2261.95, "duration": 4.35}, {"text": "But he said, if\nyou want, you can", "start": 2266.3, "duration": 2.16}, {"text": "enter into a contract\nwith my affiliate--", "start": 2268.46, "duration": 3.58}, {"text": "Howey on the Hills, I think,\nwas the affiliate, as well--", "start": 2272.04, "duration": 3.35}, {"text": "and we'll grow your\noranges for you", "start": 2275.39, "duration": 2.52}, {"text": "and give you the revenues\nfrom growing the oranges.", "start": 2277.91, "duration": 5.2}, {"text": "So there was a new law\nin the US in the 1930s.", "start": 2283.11, "duration": 5.54}, {"text": "He was doing this\nin the late 1930s.", "start": 2288.65, "duration": 2.43}, {"text": "And the new law was called the\nSecurities Laws of '33 and '34.", "start": 2291.08, "duration": 4.56}, {"text": "The question was, was what\nWilliam Howey was doing--", "start": 2295.64, "duration": 3.09}, {"text": "and then he passed\naway-- was his estate", "start": 2298.73, "duration": 2.505}, {"text": "and what they were doing\na security under the US", "start": 2301.235, "duration": 4.305}, {"text": "Securities Law?", "start": 2305.54, "duration": 1.68}, {"text": "Well, in the US,\nthe word \"security\"", "start": 2307.22, "duration": 2.34}, {"text": "was defined by our Congress to\ninclude equity, bonds, options,", "start": 2309.56, "duration": 6.85}, {"text": "and there was a comma, and\nsaid, \"investment contracts.\"", "start": 2316.41, "duration": 3.74}, {"text": "So the real question\nwas, what was", "start": 2320.15, "duration": 1.92}, {"text": "the definition of this, two\nwords, \"investment contracts?\"", "start": 2322.07, "duration": 3.72}, {"text": "In 1946, it went to\nour US Supreme Court.", "start": 2325.79, "duration": 3.57}, {"text": "And this was the four-part test.", "start": 2329.36, "duration": 2.22}, {"text": "And this four-part test is going\nback to the US Supreme Court", "start": 2331.58, "duration": 3.93}, {"text": "three or four times since then.", "start": 2335.51, "duration": 2.04}, {"text": "And it's been\naffirmed every time,", "start": 2337.55, "duration": 2.24}, {"text": "in the Edwards case and\nother cases and so forth", "start": 2339.79, "duration": 3.22}, {"text": "over 70 years.", "start": 2343.01, "duration": 1.86}, {"text": "This same four-part test went\nto the Taiwanese high court", "start": 2344.87, "duration": 4.35}, {"text": "in 2011, and they adopted it.", "start": 2349.22, "duration": 2.91}, {"text": "I don't know enough\nabout Taiwan law.", "start": 2352.13, "duration": 2.91}, {"text": "But it was adopted\nin Taiwan in 2011.", "start": 2355.04, "duration": 2.61}, {"text": "And it's a similar\ntest as in Canada.", "start": 2357.65, "duration": 2.61}, {"text": "So there's three jurisdictions\nthat basically have this.", "start": 2360.26, "duration": 3.17}, {"text": "Is it an investment\nof money or assets?", "start": 2363.43, "duration": 2.41}, {"text": "Is the investment in\na common enterprise?", "start": 2365.84, "duration": 2.55}, {"text": "Do you have a reasonable\nexpectation of profits?", "start": 2368.39, "duration": 2.67}, {"text": "And is it based on\nthe efforts of others?", "start": 2371.06, "duration": 3.91}, {"text": "So they determined that William\nHowey, and then his estate", "start": 2374.97, "duration": 5.52}, {"text": "afterwards, was basically\na common enterprise growing", "start": 2380.49, "duration": 3.09}, {"text": "all these oranges, and so it\nwas the expectation of profits.", "start": 2383.58, "duration": 3.66}, {"text": "That's the Howey Test.", "start": 2389.85, "duration": 2.99}, {"text": "I've talked to you before\nabout the Duck Test.", "start": 2392.84, "duration": 2.55}, {"text": "But when I see an investment\nthat walks like a duck,", "start": 2395.39, "duration": 6.24}, {"text": "swims like a duck, and\nquacks like a duck,", "start": 2401.63, "duration": 2.1}, {"text": "I call that investment\na security, in a way.", "start": 2403.73, "duration": 3.69}, {"text": "But that's really it, you\nknow, using your common sense.", "start": 2407.42, "duration": 4.73}, {"text": "Ethereum, when it was\nfirst promoted in 2014,", "start": 2412.15, "duration": 5.76}, {"text": "I believe passed this test.", "start": 2417.91, "duration": 4.52}, {"text": "And the word \"passed\" means\nthat you are a security, just", "start": 2422.43, "duration": 4.08}, {"text": "a little vocabulary thing.", "start": 2426.51, "duration": 1.95}, {"text": "You want to fail the\nHowey Test, by the way.", "start": 2428.46, "duration": 3.2}, {"text": "Like, if you are a\nventure capitalist", "start": 2431.66, "duration": 2.71}, {"text": "and don't want to be regulated,\nyou want to fail this test.", "start": 2434.37, "duration": 3.27}, {"text": "But to pass the Howey\ntest, Ethereum, in 2014,", "start": 2437.64, "duration": 5.76}, {"text": "exchanged Bitcoin for an ETH.", "start": 2443.4, "duration": 4.65}, {"text": "It was an investment\nin a common enterprise", "start": 2448.05, "duration": 1.86}, {"text": "at that point in time, a 20-\nor 21-year-old Vitalik Buterin", "start": 2449.91, "duration": 4.08}, {"text": "running Ethereum Foundation\nout of Switzerland.", "start": 2453.99, "duration": 4.87}, {"text": "It was one group.", "start": 2458.86, "duration": 3.41}, {"text": "An expectation of profits--", "start": 2462.27, "duration": 2.01}, {"text": "they had no functioning network.", "start": 2464.28, "duration": 1.62}, {"text": "It was just an idea and a white\npaper-- a really good idea--", "start": 2465.9, "duration": 3.33}, {"text": "and good-faith actors.", "start": 2469.23, "duration": 3.39}, {"text": "And it was reliant on whether\nVitalik and his team of coders", "start": 2472.62, "duration": 5.58}, {"text": "were going to stand\nthis project up.", "start": 2478.2, "duration": 3.3}, {"text": "To me, I don't even think\nthere's much doubt what", "start": 2481.5, "duration": 2.22}, {"text": "this was in 2014 when they\nraised the $18 million.", "start": 2483.72, "duration": 4.17}, {"text": "Now, it was the largest\nICO done at the time.", "start": 2487.89, "duration": 3.75}, {"text": "There hadn't been anything\nof its size, at $18 million.", "start": 2491.64, "duration": 3.886}, {"text": "And our US Securities agency\nand others around the globe", "start": 2495.526, "duration": 4.544}, {"text": "really weren't\nlooking and watching", "start": 2500.07, "duration": 2.19}, {"text": "until the DAO happened in 2016\nand raised $160 or so million.", "start": 2502.26, "duration": 7.08}, {"text": "And then that sort of\ncaught the attention.", "start": 2509.34, "duration": 2.51}, {"text": "So regulators start to wake up\nand think about it after that.", "start": 2511.85, "duration": 6.04}, {"text": "So initial coin offerings,\nwe've already talked about this.", "start": 2520.54, "duration": 2.66}, {"text": "But the proceeds are\nused to build networks.", "start": 2523.2, "duration": 2.76}, {"text": "And purchasers anticipate\nprofits through appreciation.", "start": 2525.96, "duration": 2.73}, {"text": "So that's like the\ncore of the Howey Test.", "start": 2528.69, "duration": 3.66}, {"text": "Now, some jurisdictions\ndon't have the Howey Test.", "start": 2532.35, "duration": 2.34}, {"text": "And some jurisdictions\ndon't have those two words", "start": 2534.69, "duration": 2.1}, {"text": "in the definition of security--\n\"investment contract.\"", "start": 2536.79, "duration": 4.65}, {"text": "So I actually think, in\na lot of jurisdictions,", "start": 2541.44, "duration": 3.06}, {"text": "an initial coin offering may not\nbe a security because it's not", "start": 2544.5, "duration": 3.06}, {"text": "defined in their statutes.", "start": 2547.56, "duration": 2.52}, {"text": "It's not some legislative\nbody like ours in the 1930s", "start": 2550.08, "duration": 3.27}, {"text": "included it in a definition.", "start": 2553.35, "duration": 3.03}, {"text": "But I believe if this\nmarket were to grow,", "start": 2556.38, "duration": 2.403}, {"text": "and it might not grow,\nbut if it were to grow,", "start": 2558.783, "duration": 1.917}, {"text": "other countries might want\nto address that and change", "start": 2560.7, "duration": 2.37}, {"text": "their statutory language\nbecause investors still", "start": 2563.07, "duration": 3.15}, {"text": "have an asymmetry and could\nbenefit with more disclosure.", "start": 2566.22, "duration": 5.31}, {"text": "As we've talked\nabout, the tokens", "start": 2571.53, "duration": 1.65}, {"text": "are usually prior\nto being functional.", "start": 2573.18, "duration": 2.52}, {"text": "What was the statistic?", "start": 2575.7, "duration": 1.26}, {"text": "Does anybody remember?", "start": 2576.96, "duration": 1.92}, {"text": "In the third quarter\nof 2018, what", "start": 2578.88, "duration": 3.3}, {"text": "was the percent\nthat was functional?", "start": 2582.18, "duration": 3.19}, {"text": "Anybody?", "start": 2585.37, "duration": 1.42}, {"text": "What's that, Alpha?", "start": 2586.79, "duration": 1.67}, {"text": "5%?", "start": 2588.46, "duration": 0.775}, {"text": "You're a little high.", "start": 2589.235, "duration": 0.875}, {"text": "AUDIENCE: 2%-- 2% or 3%?", "start": 2590.11, "duration": 2.065}, {"text": "GARY GENSLER: Yeah.", "start": 2592.175, "duration": 0.935}, {"text": "1.4%-- 1.37% was\nfully-ready product.", "start": 2593.11, "duration": 6.44}, {"text": "Or 1.7 was code,\nso we'll round up.", "start": 2599.55, "duration": 3.72}, {"text": "But 76% were on ideas.", "start": 2603.27, "duration": 2.67}, {"text": "And this is in the third quarter\nof 2018 by CryptoCompare.", "start": 2605.94, "duration": 6.1}, {"text": "And here are some\nlarge tokens offerings", "start": 2612.04, "duration": 3.21}, {"text": "that have yet to go live.", "start": 2615.25, "duration": 3.16}, {"text": "And I just picked\nfive really big ones.", "start": 2618.41, "duration": 4.19}, {"text": "That doesn't mean that all\nbig ones haven't gone live.", "start": 2622.6, "duration": 2.97}, {"text": "But you were asking me about\nFilecoin in our last class.", "start": 2625.57, "duration": 5.88}, {"text": "I think Filecoin--", "start": 2631.45, "duration": 1.415}, {"text": "I went back, and I looked\nat the white paper;", "start": 2635.695, "duration": 1.875}, {"text": "I've looked at a lot of\nthings about Filecoin", "start": 2637.57, "duration": 1.875}, {"text": "since last Tuesday--", "start": 2639.445, "duration": 1.685}, {"text": "Filecoin is basically\ncoin that says", "start": 2641.13, "duration": 2.2}, {"text": "you can use this coin when we\ngo live, which hopefully will be", "start": 2643.33, "duration": 5.01}, {"text": "by the second quarter of '19,\nto buy file storage from others", "start": 2648.34, "duration": 4.77}, {"text": "that are on the network.", "start": 2653.11, "duration": 3.24}, {"text": "Their business model--\nFilecoin sold 10% of the token.", "start": 2656.35, "duration": 4.75}, {"text": "So if it was truly worth\n$257 million at the time,", "start": 2661.1, "duration": 4.82}, {"text": "they, in essence, had a total\nvalue of $2 and 1/2 billion.", "start": 2665.92, "duration": 4.94}, {"text": "Some of the tokens were\nkept by the company.", "start": 2670.86, "duration": 4.2}, {"text": "Some of the tokens\nwere kept by founders.", "start": 2675.06, "duration": 2.23}, {"text": "But it, in essence, capitalized\nthe total stock 10 times that.", "start": 2677.29, "duration": 6.05}, {"text": "So in that model,\nthe usage of the coin", "start": 2683.34, "duration": 4.98}, {"text": "was amongst the\ncommunity, to answer--", "start": 2688.32, "duration": 4.11}, {"text": "I think that was a question\nyou asked me to go back.", "start": 2692.43, "duration": 2.55}, {"text": "But that's not the\ncase for every ICO.", "start": 2694.98, "duration": 3.6}, {"text": "There's two stark variations.", "start": 2698.58, "duration": 1.89}, {"text": "One is one where you use the\ntoken to buy a good or service", "start": 2700.47, "duration": 3.84}, {"text": "from a service provider.", "start": 2704.31, "duration": 2.35}, {"text": "Let's, in the case\nof Filecoin, say", "start": 2706.66, "duration": 2.21}, {"text": "it's directly from Filecoin.", "start": 2708.87, "duration": 2.46}, {"text": "Or you use the token to\nbuy a good or service", "start": 2711.33, "duration": 2.82}, {"text": "from other people\nin the community.", "start": 2714.15, "duration": 2.25}, {"text": "The Filecoin white\npaper suggests--", "start": 2716.4, "duration": 2.07}, {"text": "it's a year since\nthey wrote it--", "start": 2718.47, "duration": 2.54}, {"text": "that it's a token to be used\namongst the community, which", "start": 2721.01, "duration": 5.93}, {"text": "I think was your--", "start": 2726.94, "duration": 1.5}, {"text": "it's a little confusing\nbecause they haven't gone live.", "start": 2728.44, "duration": 3.99}, {"text": "We don't really know.", "start": 2732.43, "duration": 1.59}, {"text": "Hugo?", "start": 2734.02, "duration": 0.5}, {"text": "AUDIENCE: So I have a\nquestion about Ripple--", "start": 2734.52, "duration": 1.875}, {"text": "GARY GENSLER: Yes.", "start": 2736.395, "duration": 0.865}, {"text": "AUDIENCE: --and if\nyou have an opinion", "start": 2737.26, "duration": 1.65}, {"text": "on whether XRP is a security\nthat was sold by Ripple,", "start": 2738.91, "duration": 4.7}, {"text": "or currently continuing\nto be sold by Ripple,", "start": 2743.61, "duration": 2.47}, {"text": "as they own, like, 55\nbillion of the clients,", "start": 2746.08, "duration": 4.02}, {"text": "because, also,\ntheir product, what", "start": 2750.1, "duration": 3.81}, {"text": "they want XRP to be used on,\nxRapid, isn't really live.", "start": 2753.91, "duration": 3.83}, {"text": "xCurrent is the thing that\nthey're using most right now.", "start": 2757.74, "duration": 2.808}, {"text": "And that's just an alternative\nfor SWIFT that doesn't even", "start": 2760.548, "duration": 2.417}, {"text": "use their coin.", "start": 2762.965, "duration": 1.505}, {"text": "GARY GENSLER: So Hugo has\nasked about the token XRP", "start": 2764.47, "duration": 4.29}, {"text": "and whether I think it's\na non-compliant security.", "start": 2768.76, "duration": 2.37}, {"text": "I've spoken publicly.", "start": 2771.13, "duration": 1.08}, {"text": "Yes, I do think it's a\nnon-compliant security.", "start": 2772.21, "duration": 3.99}, {"text": "But this will not be resolved\njust by the Securities", "start": 2776.2, "duration": 2.36}, {"text": "and Exchange Commission.", "start": 2778.56, "duration": 1.0}, {"text": "It will be resolved\nby some courts,", "start": 2779.56, "duration": 1.98}, {"text": "whether it's appellate\ncourts or the Supreme Court.", "start": 2781.54, "duration": 2.76}, {"text": "So what I believe is just that.", "start": 2784.3, "duration": 3.3}, {"text": "It's a belief.", "start": 2787.6, "duration": 1.23}, {"text": "But why would I say that?", "start": 2788.83, "duration": 2.85}, {"text": "I think back to the Howey Test.", "start": 2791.68, "duration": 1.92}, {"text": "I think they are exchanging XRP.", "start": 2793.6, "duration": 2.71}, {"text": "Ripple, the company,\nis exchanging", "start": 2796.31, "duration": 1.88}, {"text": "XRP for something of value.", "start": 2798.19, "duration": 3.03}, {"text": "And they're using it right now.", "start": 2801.22, "duration": 1.71}, {"text": "They sell it every month.", "start": 2802.93, "duration": 1.37}, {"text": "It's in a lock-up.", "start": 2804.3, "duration": 1.16}, {"text": "It's in an escrow.", "start": 2805.46, "duration": 1.07}, {"text": "And they sell XRP every month.", "start": 2806.53, "duration": 3.36}, {"text": "Ripple, the company, initially\ndid the genesis block back", "start": 2809.89, "duration": 4.65}, {"text": "in 2013 but kept\n80% of the tokens.", "start": 2814.54, "duration": 4.18}, {"text": "Now they have about\n60% of the token.", "start": 2818.72, "duration": 3.74}, {"text": "But they sell it on a continuous\n100 million to 200 million", "start": 2822.46, "duration": 4.59}, {"text": "or so a month of value.", "start": 2827.05, "duration": 3.93}, {"text": "Two, I think it is reliant\non a common enterprise.", "start": 2830.98, "duration": 3.12}, {"text": "I think Ripple, the company--", "start": 2834.1, "duration": 3.73}, {"text": "XRP investors are very much\nreliant on Ripple, the company,", "start": 2837.83, "duration": 5.88}, {"text": "and that if Ripple, the company,\nwent away, as you noted,", "start": 2843.71, "duration": 3.88}, {"text": "there's not much use of XRP.", "start": 2847.59, "duration": 1.85}, {"text": "In fact, for the first\nthree or four years,", "start": 2849.44, "duration": 3.57}, {"text": "or five years even,\nthere was no use.", "start": 2853.01, "duration": 1.98}, {"text": "And then they prototyped\nsomething called xRapid.", "start": 2854.99, "duration": 6.42}, {"text": "xCurrent, the main product\nof Ripple, the company,", "start": 2861.41, "duration": 3.18}, {"text": "is a messaging-- and\napparently a clever one", "start": 2864.59, "duration": 4.2}, {"text": "that's competing with SWIFT.", "start": 2868.79, "duration": 2.43}, {"text": "But xRapid, the prototype,\ndoesn't have a large community", "start": 2871.22, "duration": 8.19}, {"text": "right now.", "start": 2879.41, "duration": 0.54}, {"text": "So it's highly centralized\naround Ripple, the company.", "start": 2879.95, "duration": 5.1}, {"text": "The development,\nthe node network--", "start": 2885.05, "duration": 2.55}, {"text": "the ownership is 55%\nor 60% owned by them.", "start": 2887.6, "duration": 5.05}, {"text": "They're promoting it as such.", "start": 2892.65, "duration": 2.63}, {"text": "But it will be settled in some\ncourt at some point in time.", "start": 2895.28, "duration": 4.03}, {"text": "And there might be\nregulatory forbearance.", "start": 2899.31, "duration": 2.0}, {"text": "And maybe they'll be\ndetermined not to be.", "start": 2901.31, "duration": 2.52}, {"text": "But I've expressed my thoughts.", "start": 2903.83, "duration": 3.51}, {"text": "I don't own any of this stuff.", "start": 2907.34, "duration": 1.41}, {"text": "I don't have any\nparticular conflict.", "start": 2908.75, "duration": 1.96}, {"text": "I'm just speaking as I believe.", "start": 2910.71, "duration": 3.71}, {"text": "Catalina?", "start": 2914.42, "duration": 1.02}, {"text": "AUDIENCE: Regarding\nhow do you determine", "start": 2915.44, "duration": 2.68}, {"text": "where the ICO took place--", "start": 2918.12, "duration": 1.87}, {"text": "GARY GENSLER: Where, what?", "start": 2919.99, "duration": 1.175}, {"text": "AUDIENCE: Where\nthe ICO took place,", "start": 2921.165, "duration": 2.885}, {"text": "what is the jurisdiction?", "start": 2924.05, "duration": 1.47}, {"text": "Like, which will\nbe the regulator", "start": 2925.52, "duration": 2.8}, {"text": "if they are under the laws\nof the US or everywhere else,", "start": 2928.32, "duration": 4.67}, {"text": "because the blockchain--", "start": 2932.99, "duration": 1.177}, {"text": "[INTERPOSING VOICES]", "start": 2934.167, "duration": 0.833}, {"text": "GARY GENSLER: No, it's\na very good question.", "start": 2935.0, "duration": 1.99}, {"text": "So jurisdiction.", "start": 2936.99, "duration": 2.135}, {"text": "When does any country\nhave jurisdiction?", "start": 2939.125, "duration": 2.805}, {"text": "Or maybe I should\nask it differently.", "start": 2941.93, "duration": 1.8}, {"text": "When do you think countries\ntry to exert their jurisdiction", "start": 2943.73, "duration": 4.68}, {"text": "in the context of\ncapital markets?", "start": 2948.41, "duration": 2.25}, {"text": "We're not talking about the\ncontext of consumable goods.", "start": 2950.66, "duration": 5.67}, {"text": "But in terms of the\ncapital markets,", "start": 2956.33, "duration": 2.28}, {"text": "where do jurisdictions usually\nexert their jurisdiction?", "start": 2958.61, "duration": 2.85}, {"text": "AUDIENCE: I think that this\nshould be a [INAUDIBLE]", "start": 2961.46, "duration": 3.07}, {"text": "which investor\nwill take the ICO.", "start": 2964.53, "duration": 5.22}, {"text": "GARY GENSLER: OK.", "start": 2969.75, "duration": 0.87}, {"text": "AUDIENCE: So even if they're\nnot majority of investor,", "start": 2970.62, "duration": 2.25}, {"text": "it will be a US person.", "start": 2972.87, "duration": 1.53}, {"text": "So it should be a US\nregulator who handles this.", "start": 2974.4, "duration": 3.42}, {"text": "GARY GENSLER: So\none approach theory", "start": 2977.82, "duration": 2.21}, {"text": "is it's where the investors are.", "start": 2980.03, "duration": 2.18}, {"text": "And you even used the word\na \"majority\" of investors,", "start": 2982.21, "duration": 2.47}, {"text": "or just where the investors are?", "start": 2984.68, "duration": 1.47}, {"text": "AUDIENCE: Yeah, that's correct.", "start": 2986.15, "duration": 1.76}, {"text": "GARY GENSLER: All right.", "start": 2987.91, "duration": 1.0}, {"text": "So where the investors are.", "start": 2988.91, "duration": 1.387}, {"text": "And then the question is, how\nmany investors-- minority,", "start": 2990.297, "duration": 2.333}, {"text": "majority, de minimis, so forth.", "start": 2992.63, "duration": 2.97}, {"text": "Another point of view,\nany, just, counter--", "start": 2995.6, "duration": 4.375}, {"text": "AUDIENCE: Where the\ncompany was incorporated.", "start": 2999.975, "duration": 1.875}, {"text": "GARY GENSLER: All right.", "start": 3001.85, "duration": 1.0}, {"text": "So where the company's\nlegal jurisdiction is.", "start": 3002.85, "duration": 2.35}, {"text": "Maybe the company's\nincorporated somewhere.", "start": 3005.2, "duration": 2.43}, {"text": "So in essence,\nwhere the issuer is.", "start": 3007.63, "duration": 3.15}, {"text": "And there's a third one.", "start": 3010.78, "duration": 1.56}, {"text": "AUDIENCE: Tax considerations.", "start": 3012.34, "duration": 1.217}, {"text": "GARY GENSLER: What's that?", "start": 3013.557, "duration": 1.083}, {"text": "AUDIENCE: Tax considerations.", "start": 3014.64, "duration": 1.208}, {"text": "GARY GENSLER: Tax\nconsiderations, you know,", "start": 3015.848, "duration": 2.532}, {"text": "can you collect taxes?", "start": 3018.38, "duration": 1.34}, {"text": "AUDIENCE: Where the team\nis physically located.", "start": 3019.72, "duration": 2.01}, {"text": "GARY GENSLER: Where the, what?", "start": 3021.73, "duration": 0.96}, {"text": "AUDIENCE: Where the\nteam is physically--", "start": 3022.69, "duration": 0.96}, {"text": "GARY GENSLER: The team,\nthe physical team.", "start": 3023.65, "duration": 1.7}, {"text": "So you might legally incorporate\nin the Cayman Islands,", "start": 3025.35, "duration": 2.292}, {"text": "but your executive team might\nbe in New York or in Beijing.", "start": 3027.642, "duration": 3.163}, {"text": "And the one other, which I\nthink all of these go in--", "start": 3034.27, "duration": 3.03}, {"text": "AUDIENCE: The exchange.", "start": 3037.3, "duration": 1.25}, {"text": "GARY GENSLER: The exchange.", "start": 3038.55, "duration": 1.24}, {"text": "All right.", "start": 3039.79, "duration": 0.5}, {"text": "The secondary markets.", "start": 3040.29, "duration": 2.09}, {"text": "So all of these things\nsomehow influence", "start": 3042.38, "duration": 3.83}, {"text": "the concept of jurisdiction.", "start": 3046.21, "duration": 3.39}, {"text": "And there's various laws.", "start": 3049.6, "duration": 1.29}, {"text": "And each country has\ntheir own different--", "start": 3050.89, "duration": 2.37}, {"text": "I'm not going to do a\nwhole review of this.", "start": 3053.26, "duration": 3.57}, {"text": "But usually countries want\nto exert their jurisdiction", "start": 3056.83, "duration": 4.435}, {"text": "if their citizens\nsomehow are affected", "start": 3061.265, "duration": 2.765}, {"text": "or if their tax base\nis somehow affected.", "start": 3064.03, "duration": 3.78}, {"text": "So in the US securities laws,\nif it's affecting US citizens", "start": 3067.81, "duration": 6.06}, {"text": "or if the exchange\nor secondary markets", "start": 3073.87, "duration": 2.37}, {"text": "are in our physical\njurisdiction, in the 50 states", "start": 3076.24, "duration": 3.45}, {"text": "and so forth, or the issuer, so\nit's all three of these, often", "start": 3079.69, "duration": 7.71}, {"text": "there's some exertion\nof jurisdiction.", "start": 3087.4, "duration": 3.66}, {"text": "And it's upheld in the courts.", "start": 3091.06, "duration": 2.61}, {"text": "And then you get\nto some issuers who", "start": 3093.67, "duration": 1.98}, {"text": "have to deal with\nmultiple jurisdictions.", "start": 3095.65, "duration": 2.4}, {"text": "And almost every\nlarge corporation", "start": 3098.05, "duration": 2.73}, {"text": "that has investors in\nmultiple jurisdictions", "start": 3100.78, "duration": 2.82}, {"text": "has to deal with the investor\nlaws in multiple jurisdictions.", "start": 3103.6, "duration": 4.66}, {"text": "So initial coin\nofferings, if they", "start": 3108.26, "duration": 3.65}, {"text": "want to tap into US 328 million\npeople to buy some of these,", "start": 3111.91, "duration": 4.665}, {"text": "it's more than a de minimis.", "start": 3116.575, "duration": 1.845}, {"text": "It's not a majority.", "start": 3118.42, "duration": 1.59}, {"text": "US law doesn't need a majority.", "start": 3120.01, "duration": 2.497}, {"text": "It just has to be\nmore than a handful.", "start": 3122.507, "duration": 1.583}, {"text": "US Securities and\nExchange Commission", "start": 3128.05, "duration": 2.16}, {"text": "might exert its jurisdiction.", "start": 3130.21, "duration": 1.365}, {"text": "It doesn't always.", "start": 3131.575, "duration": 0.96}, {"text": "So please.", "start": 3135.27, "duration": 1.645}, {"text": "AUDIENCE: So some of these\nICOs, Filecoin, I think,", "start": 3136.915, "duration": 3.525}, {"text": "included, only sold to\naccredited investors.", "start": 3140.44, "duration": 3.21}, {"text": "In my mind, that\ndoesn't really change", "start": 3143.65, "duration": 1.71}, {"text": "the definition of security or\nhighly taxed or jurisdiction.", "start": 3145.36, "duration": 3.725}, {"text": "So what is the benefit\nof only selling", "start": 3149.085, "duration": 2.725}, {"text": "to accredited investors?", "start": 3151.81, "duration": 1.01}, {"text": "GARY GENSLER: Can I\nhold that, because I'm", "start": 3152.82, "duration": 1.75}, {"text": "going to slide on that?", "start": 3154.57, "duration": 0.958}, {"text": "But it's a very good question.", "start": 3155.528, "duration": 3.272}, {"text": "So the Ernst & Young study--", "start": 3158.8, "duration": 2.58}, {"text": "and I promise we'll get to it.", "start": 3161.38, "duration": 1.38}, {"text": "So one year later, they looked\nat the top 141 ICOs of 2017.", "start": 3162.76, "duration": 6.702}, {"text": "I haven't looked\nat the whole list.", "start": 3169.462, "duration": 1.458}, {"text": "But I think they pretty\nmuch got the top end.", "start": 3170.92, "duration": 4.18}, {"text": "86% are trading below listed\nprice as of September 30.", "start": 3175.1, "duration": 5.48}, {"text": "This does not take into\nconsideration the last week.", "start": 3180.58, "duration": 3.03}, {"text": "But the number would go up--", "start": 3183.61, "duration": 1.52}, {"text": "86% nine months later.", "start": 3185.13, "duration": 2.8}, {"text": "30% have lost substantially\nall their value, and not", "start": 3187.93, "duration": 5.52}, {"text": "necessarily scams and frauds.", "start": 3193.45, "duration": 1.87}, {"text": "But it's interesting to compare\nthat to Christian Catalini's", "start": 3195.32, "duration": 2.72}, {"text": "25% scam or fraud number.", "start": 3198.04, "duration": 2.34}, {"text": "But these are the\ntop 141 in size.", "start": 3200.38, "duration": 3.27}, {"text": "These aren't the\nsmall riff-raff size.", "start": 3203.65, "duration": 4.98}, {"text": "Collectively, the\nportfolio is down 66%.", "start": 3208.63, "duration": 3.6}, {"text": "I didn't go back to\ncompare what that", "start": 3212.23, "duration": 2.22}, {"text": "would be versus Bitcoin\nbecause some of these", "start": 3214.45, "duration": 3.6}, {"text": "were issued in\nOctober, some December.", "start": 3218.05, "duration": 3.42}, {"text": "But collectively, if you\ninvested in the port--", "start": 3221.47, "duration": 2.88}, {"text": "it's not January\n1 to September 30.", "start": 3224.35, "duration": 2.33}, {"text": "It's from investment day.", "start": 3226.68, "duration": 3.16}, {"text": "And only 13% have\nworking products and 16%", "start": 3229.84, "duration": 3.93}, {"text": "have prototypes.", "start": 3233.77, "duration": 3.47}, {"text": "Another interesting\nthing is the 13%", "start": 3237.24, "duration": 2.34}, {"text": "that have working products,\nwhich is about 25 of these.", "start": 3239.58, "duration": 4.59}, {"text": "Is that right?", "start": 3244.17, "duration": 1.2}, {"text": "Roughly, yeah, about\n25 or so, 20 to 25.", "start": 3245.37, "duration": 3.615}, {"text": "Seven of them have decided\nsubsequent to launch", "start": 3251.51, "duration": 3.51}, {"text": "to accept fiat currency to\nget the good or service.", "start": 3255.02, "duration": 5.9}, {"text": "So literally, if you dig into\nthe Ernst & Young report,", "start": 3260.92, "duration": 3.95}, {"text": "they've chosen to\ntake something else.", "start": 3264.87, "duration": 3.76}, {"text": "And Hugo, back to your question\nabout XRP, as I understand it", "start": 3268.63, "duration": 5.0}, {"text": "and as I studied it, I might\nbe mistaken, but xRapid,", "start": 3273.63, "duration": 7.26}, {"text": "you can actually use\nsomething other than XRP", "start": 3280.89, "duration": 2.88}, {"text": "as the bridge currency.", "start": 3283.77, "duration": 0.96}, {"text": "It has to be another crypto.", "start": 3288.55, "duration": 1.74}, {"text": "But 7 of 25 live projects\nthat Ernst & Young followed", "start": 3290.29, "duration": 6.33}, {"text": "have decided subsequently\nmaybe to take a fiat currency", "start": 3296.62, "duration": 3.09}, {"text": "for the good or\nservice, as well.", "start": 3299.71, "duration": 3.89}, {"text": "So that kind of\ngives you the sense", "start": 3303.6, "duration": 1.86}, {"text": "this was a note about the\nCatalini report and that status", "start": 3305.46, "duration": 4.26}, {"text": "report, as well.", "start": 3309.72, "duration": 3.78}, {"text": "What's going on on Ethereum?", "start": 3313.5, "duration": 2.43}, {"text": "This is the most recent report.", "start": 3315.93, "duration": 2.22}, {"text": "I summarized\nsomething from a site.", "start": 3318.15, "duration": 3.21}, {"text": "These are exchanges.", "start": 3321.36, "duration": 3.99}, {"text": "There's 179 DApps.", "start": 3325.35, "duration": 2.49}, {"text": "This is just\nlooking at Ethereum.", "start": 3327.84, "duration": 5.28}, {"text": "But there's only 25,000\nuses a day for 179 sites.", "start": 3333.12, "duration": 8.76}, {"text": "17,000 in gambling.", "start": 3341.88, "duration": 1.77}, {"text": "But it's exchanges, gambling,\ngames, finance fourth.", "start": 3343.65, "duration": 4.45}, {"text": "And then you can go down.", "start": 3348.1, "duration": 2.16}, {"text": "The other category, which\nonly has 275 daily uses,", "start": 3350.26, "duration": 5.73}, {"text": "covers governance, identity,\nsecurity, energy, insurance,", "start": 3355.99, "duration": 3.09}, {"text": "and health.", "start": 3359.08, "duration": 1.43}, {"text": "Of six of those use cases--", "start": 3360.51, "duration": 3.0}, {"text": "218 DApps, which means they're\nall being used zero or once", "start": 3363.51, "duration": 4.9}, {"text": "a day.", "start": 3368.41, "duration": 0.5}, {"text": "I believe I pulled this\nfor the month of October.", "start": 3371.97, "duration": 3.57}, {"text": "I think all these stats are--", "start": 3375.54, "duration": 1.56}, {"text": "yeah, this was for\nthe month of October.", "start": 3379.83, "duration": 3.44}, {"text": "So it might be September, but\nit's all current information.", "start": 3383.27, "duration": 5.593}, {"text": "So what has the SEC\ndone in this space?", "start": 3393.03, "duration": 3.15}, {"text": "Well, they brought the DAO\nreport in July of 2017.", "start": 3396.18, "duration": 3.61}, {"text": "If you remember, this was\nthe big $150, $160 million", "start": 3399.79, "duration": 5.86}, {"text": "big ICO in 2016.", "start": 3405.65, "duration": 2.55}, {"text": "A third of it was hacked.", "start": 3408.2, "duration": 2.25}, {"text": "It led to the break in\nthe Ethereum network", "start": 3410.45, "duration": 3.0}, {"text": "between Ethereum Classic,\nthe hard fork, and Ethereum.", "start": 3413.45, "duration": 2.595}, {"text": "DAO actually shut down.", "start": 3418.7, "duration": 3.26}, {"text": "It didn't take off.", "start": 3421.96, "duration": 3.68}, {"text": "And a year later,\nthe SEC did not", "start": 3425.64, "duration": 2.3}, {"text": "bring an enforcement action.", "start": 3427.94, "duration": 1.65}, {"text": "They chose not to\npenalize anybody.", "start": 3429.59, "duration": 3.37}, {"text": "But they laid out in pretty\ngood detail as to why", "start": 3432.96, "duration": 3.89}, {"text": "these things were securities.", "start": 3436.85, "duration": 2.85}, {"text": "I don't think they\nhad planned for what", "start": 3439.7, "duration": 1.728}, {"text": "was going to happen next.", "start": 3441.428, "duration": 1.042}, {"text": "But the ICO, boom, took off, I\ndon't think because of the DAO", "start": 3442.47, "duration": 4.22}, {"text": "report.", "start": 3446.69, "duration": 1.02}, {"text": "But it's an\ninteresting coincidence", "start": 3447.71, "duration": 1.83}, {"text": "whether this kind of\ngave a bunch of lawyers", "start": 3449.54, "duration": 2.278}, {"text": "and entrepreneurs\na sense, all right,", "start": 3451.818, "duration": 1.542}, {"text": "if I avoid doing what\nthey did specifically--", "start": 3453.36, "duration": 3.62}, {"text": "and the DAO, they actually\npaid part of the revenues", "start": 3456.98, "duration": 5.19}, {"text": "to the token holders, and they\ngave a sense of voting rights.", "start": 3462.17, "duration": 5.14}, {"text": "So it was so security-looking\nbecause there", "start": 3467.31, "duration": 2.81}, {"text": "were a form of\nparticipation in governance", "start": 3470.12, "duration": 3.21}, {"text": "and a form of\nparticipation in profits", "start": 3473.33, "duration": 2.7}, {"text": "that everything took off.", "start": 3476.03, "duration": 1.73}, {"text": "Then then the SEC\ndid two other things.", "start": 3477.76, "duration": 2.27}, {"text": "One was-- the REcoin complaint\nwas a real fraudulent player,", "start": 3480.03, "duration": 7.55}, {"text": "and the Munchee order\nin December last year.", "start": 3487.58, "duration": 3.78}, {"text": "I read that in\nJanuary or February.", "start": 3491.36, "duration": 2.1}, {"text": "And I thought, well,\nthat's pretty clear.", "start": 3493.46, "duration": 1.98}, {"text": "And Jay Clayton,\nwho runs the SEC,", "start": 3495.44, "duration": 2.19}, {"text": "has said in congressional\ntestimony in February", "start": 3497.63, "duration": 2.25}, {"text": "that he hadn't met an ICO that\nhe didn't think was a security.", "start": 3499.88, "duration": 3.78}, {"text": "His words were a\nlittle different.", "start": 3503.66, "duration": 1.74}, {"text": "But I thought between\nthe Munchee order", "start": 3505.4, "duration": 3.92}, {"text": "and Chairman Clayton's\nstatement in February,", "start": 3509.32, "duration": 2.44}, {"text": "he had really said it.", "start": 3511.76, "duration": 3.63}, {"text": "But it wasn't quite enough.", "start": 3515.39, "duration": 3.59}, {"text": "And the Munchee order, again,\nthey didn't assess penalties.", "start": 3518.98, "duration": 2.47}, {"text": "But it was an offering--", "start": 3521.45, "duration": 1.53}, {"text": "I can't remember the\nsize-- $20 to $30 million.", "start": 3522.98, "duration": 3.06}, {"text": "They knocked on Munchee's--", "start": 3526.04, "duration": 2.97}, {"text": "Munchee, by the way, does\nanybody know what the coin did?", "start": 3529.01, "duration": 2.8}, {"text": "It was for restaurant reviews--", "start": 3531.81, "duration": 2.54}, {"text": "munchie, food.", "start": 3534.35, "duration": 1.56}, {"text": "Yeah.", "start": 3535.91, "duration": 0.75}, {"text": "But they knocked on the\nMunchee folks' door right", "start": 3536.66, "duration": 3.45}, {"text": "as they were doing the offering.", "start": 3540.11, "duration": 1.36}, {"text": "And they basically\nshut down the offering.", "start": 3541.47, "duration": 1.76}, {"text": "But then they did\na whole bunch of--", "start": 3547.41, "duration": 2.51}, {"text": "there's five or six of\nthese, almost all of which", "start": 3549.92, "duration": 2.4}, {"text": "are really scammy,\nfraudy-type things.", "start": 3552.32, "duration": 3.31}, {"text": "I mean, I can't\nspeak to each one.", "start": 3555.63, "duration": 1.43}, {"text": "But they'd have some celebrity\nthat was paid a lot of money", "start": 3557.06, "duration": 2.7}, {"text": "to go out to hawk the coins.", "start": 3559.76, "duration": 2.13}, {"text": "And there wasn't much\nbehind it, and so forth.", "start": 3561.89, "duration": 5.19}, {"text": "Asset freezes, filing\ncomplaints in courts,", "start": 3567.08, "duration": 3.41}, {"text": "emergency court orders,\none settlement--", "start": 3570.49, "duration": 3.97}, {"text": "it takes a long time\nto build a case.", "start": 3574.46, "duration": 2.07}, {"text": "Having been the chairman of\na smaller regulatory agency,", "start": 3576.53, "duration": 3.72}, {"text": "I can tell you it just takes\na long time to build cases.", "start": 3580.25, "duration": 3.54}, {"text": "It's not, like, three months.", "start": 3583.79, "duration": 2.82}, {"text": "Sometimes it's a year.", "start": 3586.61, "duration": 1.17}, {"text": "Sometimes it's even three years.", "start": 3587.78, "duration": 1.65}, {"text": "But the last two, Airfox\nand Paragon orders,", "start": 3592.26, "duration": 4.11}, {"text": "were two offerings that were\ndone 12 to 15 months ago,", "start": 3596.37, "duration": 4.71}, {"text": "so a long time to\nbring it together.", "start": 3601.08, "duration": 2.1}, {"text": "But they were settlements.", "start": 3603.18, "duration": 1.74}, {"text": "And Paragon and Airfox,\nwhich each raised,", "start": 3604.92, "duration": 2.55}, {"text": "I don't know, $12 or $18 million\neach or $15 or $18 million", "start": 3607.47, "duration": 3.45}, {"text": "each, appeared on the surface\nto be more good-faith actors.", "start": 3610.92, "duration": 4.02}, {"text": "I can't speak-- I\ndon't know for sure,", "start": 3614.94, "duration": 2.91}, {"text": "but the first time the\nSEC has gotten penalties,", "start": 3617.85, "duration": 3.322}, {"text": "the first time they've\ngotten somebody", "start": 3621.172, "duration": 1.583}, {"text": "to say yes, if somebody wants\ntheir money back a year later,", "start": 3622.755, "duration": 3.675}, {"text": "we'll do that.", "start": 3626.43, "duration": 1.41}, {"text": "And yes, we'll come\ninto compliance,", "start": 3627.84, "duration": 1.8}, {"text": "and we'll do offering documents.", "start": 3629.64, "duration": 3.807}, {"text": "So now I'm going to\ntalk a little bit about,", "start": 3633.447, "duration": 1.833}, {"text": "what can you do?", "start": 3635.28, "duration": 2.07}, {"text": "And I think Zhenyu asked this\nquestion, what can you do?", "start": 3637.35, "duration": 4.222}, {"text": "And I'm going to do it\nin two different charts.", "start": 3641.572, "duration": 1.958}, {"text": "But the first one is called\nrestricted offerings.", "start": 3643.53, "duration": 3.54}, {"text": "And this is not a\nsecurities law class.", "start": 3647.07, "duration": 1.99}, {"text": "This is just to give you a sense\nof what are the potentials.", "start": 3649.06, "duration": 3.61}, {"text": "A restricted offering,\nwhich came out 30-plus years", "start": 3652.67, "duration": 5.77}, {"text": "ago at first, was\nthe concept of,", "start": 3658.44, "duration": 3.44}, {"text": "I'm not doing a public\noffering, I'm only", "start": 3661.88, "duration": 2.95}, {"text": "selling these securities\nin a private placement.", "start": 3664.83, "duration": 3.438}, {"text": "In my day, when I\nwas on Wall Street,", "start": 3668.268, "duration": 1.542}, {"text": "we called these\nprivate placements.", "start": 3669.81, "duration": 2.4}, {"text": "But a restricted offering-- and\nthere's three different ones.", "start": 3672.21, "duration": 3.81}, {"text": "The most likely\none is the 506(c)", "start": 3676.02, "duration": 5.16}, {"text": "which came out of a recent law\npassed in 2012 called the JOBS", "start": 3681.18, "duration": 5.52}, {"text": "Act in Congress.", "start": 3686.7, "duration": 1.905}, {"text": "Don't you love how we\nname our laws in the US?", "start": 3688.605, "duration": 2.745}, {"text": "The JOBS Act.", "start": 3691.35, "duration": 1.11}, {"text": "Accredited investors only.", "start": 3695.79, "duration": 1.63}, {"text": "And an accredited investor--\nand every jurisdiction", "start": 3697.42, "duration": 2.51}, {"text": "is different--\nthe concept is you", "start": 3699.93, "duration": 3.06}, {"text": "have a little bit of net\nworth, or a lot of net worth,", "start": 3702.99, "duration": 3.42}, {"text": "depending upon your\nview about money,", "start": 3706.41, "duration": 2.46}, {"text": "but you have enough net\nworth that you supposedly", "start": 3708.87, "duration": 3.6}, {"text": "are sophisticated or\naccredited or you can have less", "start": 3712.47, "duration": 3.96}, {"text": "protection under\nthis securities law,", "start": 3716.43, "duration": 2.7}, {"text": "unless you need\nless information.", "start": 3719.13, "duration": 4.32}, {"text": "So 506(c) says,\n\"accredited investors.\"", "start": 3723.45, "duration": 6.33}, {"text": "If that's all it is, it's\na restricted security,", "start": 3729.78, "duration": 3.0}, {"text": "\"restricted\" meaning you cannot\nsell it publicly for either six", "start": 3732.78, "duration": 3.96}, {"text": "months or 12 months depending\nupon how you structure these", "start": 3736.74, "duration": 2.98}, {"text": "things.", "start": 3739.72, "duration": 0.5}, {"text": "And the big thing about all\nof the restricted offerings", "start": 3742.94, "duration": 3.48}, {"text": "is you don't have to do one\nof those detailed information", "start": 3746.42, "duration": 3.03}, {"text": "statements.", "start": 3749.45, "duration": 2.13}, {"text": "So the SEC says, all right,\nif you keep it restricted,", "start": 3751.58, "duration": 2.62}, {"text": "it's only accredited investors.", "start": 3754.2, "duration": 1.88}, {"text": "Or the 506(b)--\naccredited investors,", "start": 3756.08, "duration": 2.73}, {"text": "but 35 people can be\nsophisticated rather than", "start": 3758.81, "duration": 3.45}, {"text": "accredited.", "start": 3762.26, "duration": 0.87}, {"text": "Please don't challenge\nme on the definitions", "start": 3763.13, "duration": 2.07}, {"text": "of what's sophisticated\nand not accredited.", "start": 3765.2, "duration": 2.28}, {"text": "It's basically, you\ncan show sophistication", "start": 3767.48, "duration": 2.94}, {"text": "even if you don't have money.", "start": 3770.42, "duration": 1.29}, {"text": "Accredited is about how\nmuch money you have.", "start": 3771.71, "duration": 3.27}, {"text": "Sophisticated is knowledge but\nnot money, roughly speaking.", "start": 3774.98, "duration": 6.82}, {"text": "And then there's a small\nthing for small offerings.", "start": 3781.8, "duration": 2.61}, {"text": "Regulation D is\nwhat most of them--", "start": 3784.41, "duration": 1.74}, {"text": "Telegram did a Regulation D.\n[INAUDIBLE],, to let you know,", "start": 3786.15, "duration": 4.92}, {"text": "I think Filecoin did\na Reg D offering.", "start": 3791.07, "duration": 3.3}, {"text": "Generally speaking, it's, quote,\n\"accredited investors,\" meaning", "start": 3794.37, "duration": 5.13}, {"text": "they have enough money.", "start": 3799.5, "duration": 1.08}, {"text": "They have over,\nI can't remember,", "start": 3800.58, "duration": 1.5}, {"text": "a million bucks or\nwhatever that number is.", "start": 3802.08, "duration": 4.42}, {"text": "Regulation A is\noffering statement.", "start": 3806.5, "duration": 3.8}, {"text": "So you have to give a statement.", "start": 3810.3, "duration": 1.59}, {"text": "You have to give something\nwith the financials.", "start": 3811.89, "duration": 3.64}, {"text": "Not many ICOs want to\ndo a Reg A offering.", "start": 3815.53, "duration": 3.96}, {"text": "But if you were doing a startup,\nif you're thinking about,", "start": 3819.49, "duration": 2.46}, {"text": "like, you're in one of\nthe wonderful venture", "start": 3821.95, "duration": 3.03}, {"text": "classes, fintech ventures\nor other venture classes,", "start": 3824.98, "duration": 3.24}, {"text": "you might consider doing a Reg\nA offering rather than a Reg D.", "start": 3828.22, "duration": 4.62}, {"text": "The benefit of Reg\nA, Regulation A,", "start": 3832.84, "duration": 3.12}, {"text": "is you can go to any investors.", "start": 3835.96, "duration": 2.2}, {"text": "You don't have to only limit\nto accredited investors.", "start": 3838.16, "duration": 2.87}, {"text": "So Regulation D, only\naccredited investors, generally,", "start": 3841.03, "duration": 4.06}, {"text": "with a little footnote about\nsophisticated investors.", "start": 3845.09, "duration": 2.89}, {"text": "Regulation A, you've got to\ngive them more information.", "start": 3847.98, "duration": 4.78}, {"text": "You have to address some of\nthat information asymmetry.", "start": 3852.76, "duration": 3.03}, {"text": "There's two tiers-- $20\nmillion and $50 million.", "start": 3855.79, "duration": 4.26}, {"text": "The $50 million offering,\nyou have ongoing reporting", "start": 3860.05, "duration": 3.39}, {"text": "obligations.", "start": 3863.44, "duration": 0.81}, {"text": "The $20 million, you\njust have to get yourself", "start": 3864.25, "duration": 2.85}, {"text": "around doing something\nat the beginning.", "start": 3867.1, "duration": 3.02}, {"text": "But how do you do financials\nfor an ICO when there's--", "start": 3870.12, "duration": 3.48}, {"text": "oh, I guess you just say you\nhave no revenues, no income,", "start": 3873.6, "duration": 3.16}, {"text": "et cetera.", "start": 3876.76, "duration": 1.79}, {"text": "There's something very\nnew called Regulation CF,", "start": 3878.55, "duration": 3.5}, {"text": "or crowdfunding.", "start": 3882.05, "duration": 1.87}, {"text": "Unless you're raising less\nthan a million dollars,", "start": 3883.92, "duration": 3.66}, {"text": "you wouldn't put\nit on your list.", "start": 3887.58, "duration": 2.37}, {"text": "So almost no initial\ncoin offerings", "start": 3889.95, "duration": 2.07}, {"text": "are looking at Reg CF.", "start": 3892.02, "duration": 1.86}, {"text": "They're basically\nlooking mostly at what", "start": 3893.88, "duration": 2.76}, {"text": "we used to call private\nplacements or restricted", "start": 3896.64, "duration": 4.41}, {"text": "offerings, Regulation D.\nThat's where most of them are.", "start": 3901.05, "duration": 3.06}, {"text": "And you have to use\ngood-faith efforts", "start": 3906.83, "duration": 2.1}, {"text": "to make sure that every\none of your investors", "start": 3908.93, "duration": 3.24}, {"text": "is, in fact, an\naccredited investor.", "start": 3912.17, "duration": 3.95}, {"text": "And that's where it is.", "start": 3916.12, "duration": 0.96}, {"text": "Questions.", "start": 3917.08, "duration": 0.57}, {"text": "AUDIENCE: Do all of\nthese regulations, D, A,", "start": 3917.65, "duration": 2.616}, {"text": "and CF, entail KYC and AML?", "start": 3920.266, "duration": 4.104}, {"text": "GARY GENSLER: Yeah,\nso the question", "start": 3924.37, "duration": 1.47}, {"text": "is, do you have to know\nyour customer and any money", "start": 3925.84, "duration": 5.17}, {"text": "laundering?", "start": 3931.01, "duration": 0.5}, {"text": "And the answer is yes because\nover the last couple of decades", "start": 3931.51, "duration": 3.81}, {"text": "what's happened is finance\nministries around the globe,", "start": 3935.32, "duration": 3.87}, {"text": "and this is not\njust here in the US,", "start": 3939.19, "duration": 1.95}, {"text": "have kind of layered\non top of securities", "start": 3941.14, "duration": 2.37}, {"text": "laws, hey, we need\nyour help here", "start": 3943.51, "duration": 2.1}, {"text": "because there's this public\npolicy goal of making sure", "start": 3945.61, "duration": 3.24}, {"text": "that you can't money launder.", "start": 3948.85, "duration": 2.88}, {"text": "So yes, but in varying degrees.", "start": 3951.73, "duration": 4.63}, {"text": "So in the Regulation\nD requirements,", "start": 3956.36, "duration": 2.475}, {"text": "you have to make the\ngood-faith efforts", "start": 3958.835, "duration": 1.625}, {"text": "when you do the initial sale.", "start": 3960.46, "duration": 3.09}, {"text": "And purportedly,\nit's restricted.", "start": 3963.55, "duration": 1.72}, {"text": "And it's not supposed to be\nresold for either six or 12", "start": 3965.27, "duration": 2.94}, {"text": "months.", "start": 3968.21, "duration": 1.47}, {"text": "But on the resale,\nthe issuer doesn't", "start": 3969.68, "duration": 2.28}, {"text": "have the same obligations,\nwhere some of the others, you", "start": 3971.96, "duration": 5.32}, {"text": "would have more continuing\nobligations on the resale.", "start": 3977.28, "duration": 3.66}, {"text": "So I think that some\nhave tried to get around", "start": 3980.94, "duration": 2.4}, {"text": "this in doing a Reg D\noffering and then said,", "start": 3983.34, "duration": 2.49}, {"text": "can I get some crypto\nexchange to list this ICO?", "start": 3985.83, "duration": 4.35}, {"text": "And I'm going to\nturn a blind eye--", "start": 3990.18, "duration": 2.88}, {"text": "I think it's bad legal\nadvice they're taking--", "start": 3993.06, "duration": 2.61}, {"text": "but turn a blind eye as to\nwhere it gets sold on that.", "start": 3995.67, "duration": 3.54}, {"text": "I wouldn't recommend it.", "start": 3999.21, "duration": 1.13}, {"text": "But I think some are doing\nthat on the resale and not,", "start": 4000.34, "duration": 4.69}, {"text": "maybe, doing KYC or\nAML on the resale.", "start": 4005.03, "duration": 4.14}, {"text": "At least that's\nwhat some tell me.", "start": 4009.17, "duration": 3.43}, {"text": "Please.", "start": 4012.6, "duration": 0.58}, {"text": "AUDIENCE: I've heard\nsome crypto folks argue", "start": 4013.18, "duration": 2.3}, {"text": "that the definition of\nthe accredited investor", "start": 4015.48, "duration": 2.44}, {"text": "is not particularly\nrelevant in this ICO space.", "start": 4017.92, "duration": 2.81}, {"text": "And actually, having\ninvestable assets", "start": 4020.73, "duration": 2.49}, {"text": "doesn't make you well-placed\nto understand whether an ICO is", "start": 4023.22, "duration": 2.735}, {"text": "a good product.", "start": 4025.955, "duration": 0.625}, {"text": "And actually, having\ntechnical skills", "start": 4026.58, "duration": 1.68}, {"text": "and being able to\nread a white paper", "start": 4028.26, "duration": 1.71}, {"text": "is a more relevant qualification\nto allow you to invest", "start": 4029.97, "duration": 3.42}, {"text": "and that by having these\nregulations, in a way", "start": 4033.39, "duration": 2.43}, {"text": "you're restricting access.", "start": 4035.82, "duration": 1.35}, {"text": "And that promotes inequality,\nthat only rich people", "start": 4037.17, "duration": 2.348}, {"text": "are getting these\ninvestment opportunities.", "start": 4039.518, "duration": 1.792}, {"text": "So I've heard crypto\npeople make this argument.", "start": 4041.31, "duration": 1.958}, {"text": "So I guess, what would\nyour response to that be?", "start": 4043.268, "duration": 2.362}, {"text": "GARY GENSLER: And I will hear\nyour classmate's response.", "start": 4045.63, "duration": 3.45}, {"text": "AUDIENCE: Yeah, I would\nsay that rich people don't", "start": 4049.08, "duration": 2.61}, {"text": "know how to handle money,\nnecessarily, anyway.", "start": 4051.69, "duration": 2.49}, {"text": "So there isn't a\ndirect correlation", "start": 4054.18, "duration": 2.19}, {"text": "between having wealth and\nknowing how to use it.", "start": 4056.37, "duration": 2.26}, {"text": "The law exists the way it does\nbecause of diversification", "start": 4058.63, "duration": 3.22}, {"text": "and because of asset allocation\ntheory and the idea that people", "start": 4061.85, "duration": 2.89}, {"text": "don't understand that.", "start": 4064.74, "duration": 1.44}, {"text": "And I think that even if\nyou have technical expertise", "start": 4066.18, "duration": 2.42}, {"text": "in crypto, you may not\nunderstand asset allocation", "start": 4068.6, "duration": 3.16}, {"text": "theory and be able to\nbalance what you need when.", "start": 4071.76, "duration": 3.18}, {"text": "And basically, the\nlaw is set up such", "start": 4074.94, "duration": 2.31}, {"text": "that you can lose all of that.", "start": 4077.25, "duration": 1.66}, {"text": "And even if you're very\nsavvy, you can be very savvy", "start": 4078.91, "duration": 3.17}, {"text": "and still be wrong, and\nyou've lost more than you own.", "start": 4082.08, "duration": 3.08}, {"text": "And that wouldn't be OK.", "start": 4085.16, "duration": 1.55}, {"text": "So I think from the government's\nperspective, it is what it is.", "start": 4086.71, "duration": 3.73}, {"text": "AUDIENCE: I would\njust respond to say", "start": 4090.44, "duration": 1.63}, {"text": "that I don't know if it's\nthe government's role", "start": 4092.07, "duration": 1.958}, {"text": "to police that.", "start": 4094.028, "duration": 1.152}, {"text": "GARY GENSLER: Sorry,\ncan you speak up?", "start": 4095.18, "duration": 1.79}, {"text": "AUDIENCE: I think both\nof the points are right.", "start": 4096.97, "duration": 3.74}, {"text": "It's my opinion that it's\nnot the government's role", "start": 4100.71, "duration": 2.609}, {"text": "to decide that you don't get\nto invest in something that you", "start": 4103.319, "duration": 3.031}, {"text": "believe in or worked on\nbecause you may not understand", "start": 4106.35, "duration": 4.71}, {"text": "portfolio theory,\njust because you", "start": 4111.06, "duration": 2.219}, {"text": "don't have a two-year\ntrack record of making", "start": 4113.279, "duration": 3.08}, {"text": "$200,000 a year.", "start": 4116.359, "duration": 1.58}, {"text": "GARY GENSLER: No, it's\na very good question.", "start": 4117.939, "duration": 3.621}, {"text": "And there's this public\npolicy debate as to,", "start": 4121.56, "duration": 3.089}, {"text": "if you have a belief that\ninvestor protection helps", "start": 4124.649, "duration": 4.891}, {"text": "promote markets and investor\nprotection is about addressing", "start": 4129.54, "duration": 5.46}, {"text": "some information asymmetries\nand protecting against fraud", "start": 4135.0, "duration": 4.27}, {"text": "and bad actors, do you tier it?", "start": 4139.27, "duration": 5.02}, {"text": "Now, in the US, we've decided\non some multiple-decade--", "start": 4144.29, "duration": 5.88}, {"text": "Republicans and Democrats\nalike, somehow we've", "start": 4150.17, "duration": 2.43}, {"text": "come to a tiered system,\nmeaning that there's", "start": 4152.6, "duration": 3.719}, {"text": "more investor protection,\nmore rules and regulations,", "start": 4156.319, "duration": 4.231}, {"text": "for what's usually called the\nretail public than some tiering", "start": 4160.55, "duration": 7.33}, {"text": "of usually higher net\nworth individuals,", "start": 4167.88, "duration": 2.769}, {"text": "this term \"accredited investor.\"", "start": 4170.649, "duration": 2.601}, {"text": "And that tiering, you could\ncome to a point of view", "start": 4173.25, "duration": 2.37}, {"text": "that we shouldn't have any\ntiering, that everybody should", "start": 4175.62, "duration": 3.449}, {"text": "have the same protections, and\nit should be, maybe, somewhere", "start": 4179.069, "duration": 3.33}, {"text": "in the middle of the two.", "start": 4182.399, "duration": 1.741}, {"text": "Or you might be\nmore pro-protection", "start": 4184.14, "duration": 2.219}, {"text": "or less pro-protection.", "start": 4186.359, "duration": 2.821}, {"text": "But we have come to\na place in the US", "start": 4189.18, "duration": 2.16}, {"text": "over multiple decades\nof this tiering, where", "start": 4191.34, "duration": 3.03}, {"text": "the, quote, \"accredited\ninvestors\" get a little less.", "start": 4194.37, "duration": 3.435}, {"text": "They're allowed to risk their\ncapital with less information.", "start": 4200.49, "duration": 5.47}, {"text": "That's, in essence, what\nhappens in the system.", "start": 4205.96, "duration": 3.72}, {"text": "And Congress even pressed\nharder because the Regulation", "start": 4209.68, "duration": 3.9}, {"text": "D, restricted\nofferings, the 506(c)", "start": 4213.58, "duration": 4.17}, {"text": "was added in this thing\ncalled the JOBS Act in 2012.", "start": 4217.75, "duration": 7.68}, {"text": "Some of the politics behind\nit was a venture capital space", "start": 4225.43, "duration": 3.33}, {"text": "and a lot of entrepreneurial\nspace were saying,", "start": 4228.76, "duration": 3.54}, {"text": "we'd like a less-regulated,\nrestricted offering exemption.", "start": 4232.3, "duration": 7.42}, {"text": "Remember, these are all called\nexempt security offerings.", "start": 4239.72, "duration": 2.55}, {"text": "They're exempt from\nthe traditional roles.", "start": 4242.27, "duration": 4.11}, {"text": "And there was a coalition\nthat came together in Congress", "start": 4246.38, "duration": 4.26}, {"text": "with the support\nof President Obama,", "start": 4250.64, "duration": 2.82}, {"text": "actually not with the support\nof the head of his Securities", "start": 4253.46, "duration": 2.87}, {"text": "and Exchange Commission.", "start": 4256.33, "duration": 1.0}, {"text": "Mary Shapiro at the time was\nnot in favor of some of this.", "start": 4257.33, "duration": 3.31}, {"text": "So it was an interesting\nevent in 2012.", "start": 4260.64, "duration": 5.12}, {"text": "But I think 506(c),\nif I remember,", "start": 4265.76, "duration": 2.34}, {"text": "was either expanded or\nwas added, to say, well,", "start": 4268.1, "duration": 3.322}, {"text": "if it's accredited\ninvestors, there", "start": 4271.422, "duration": 1.458}, {"text": "will be no limitation\non general solicitation.", "start": 4272.88, "duration": 3.23}, {"text": "If you see, 506(b),\ntraditionally, there", "start": 4276.11, "duration": 2.46}, {"text": "was a limitation on\ngeneral solicitation.", "start": 4278.57, "duration": 2.85}, {"text": "And the thought was, in\n2012, now with the internet,", "start": 4281.42, "duration": 2.58}, {"text": "we should be able to--", "start": 4284.0, "duration": 1.53}, {"text": "and crowdsourcing had started.", "start": 4285.53, "duration": 3.93}, {"text": "And Kickstarter and\nGoFundMe had started.", "start": 4289.46, "duration": 3.27}, {"text": "So maybe we can have, quote,\n\"general solicitation\" if it's", "start": 4292.73, "duration": 4.56}, {"text": "only accredited investors.", "start": 4297.29, "duration": 1.53}, {"text": "So it was a bit of a legislative\nand policy compromise.", "start": 4298.82, "duration": 4.685}, {"text": "But you could take\nthe other side", "start": 4303.505, "duration": 1.375}, {"text": "and say everybody should have\nthe same, one way or the other.", "start": 4304.88, "duration": 5.5}, {"text": "But whether you're\nthinking about blockchain", "start": 4310.38, "duration": 2.987}, {"text": "or you're thinking about all the\nother wonderful things you're", "start": 4313.367, "duration": 2.583}, {"text": "thinking about as startups,\nthese are your three main ways.", "start": 4315.95, "duration": 4.17}, {"text": "And really, probably,\nRegulation D and Regulation A", "start": 4320.12, "duration": 3.21}, {"text": "more than the small million.", "start": 4323.33, "duration": 2.457}, {"text": "I have high hopes for\nall of you that you'll", "start": 4325.787, "duration": 1.833}, {"text": "be raising more than a million\ndollars in your startups.", "start": 4327.62, "duration": 3.285}, {"text": "This is a much more detailed--", "start": 4333.47, "duration": 1.38}, {"text": "I'm not going to go through it.", "start": 4334.85, "duration": 0.97}, {"text": "But it's going to be in Canvas.", "start": 4335.82, "duration": 1.292}, {"text": "I decided to throw it in the\nslide deck so you have it.", "start": 4337.112, "duration": 2.388}, {"text": "But this really is a\nmuch more detailed review", "start": 4339.5, "duration": 3.63}, {"text": "of the CrowdCheck put together.", "start": 4343.13, "duration": 2.67}, {"text": "And I thought it was a\ngood review of all these.", "start": 4345.8, "duration": 2.25}, {"text": "So what do I think\nthe path forward is?", "start": 4348.05, "duration": 2.34}, {"text": "And then we'll wrap.", "start": 4350.39, "duration": 3.18}, {"text": "So I think we're\ngoing to continue", "start": 4353.57, "duration": 1.68}, {"text": "to see high failure rates.", "start": 4355.25, "duration": 1.74}, {"text": "Something like 3,000 ICOs have\nraised some bits of money.", "start": 4360.75, "duration": 4.35}, {"text": "I mean, some of them\nonly raised $200,000.", "start": 4365.1, "duration": 2.43}, {"text": "But you can only\nfind about 700 or 800", "start": 4367.53, "duration": 3.84}, {"text": "of them listed on\nvarious websites,", "start": 4371.37, "duration": 2.1}, {"text": "if you want to see\nwhere they're traded.", "start": 4373.47, "duration": 2.73}, {"text": "But there's probably more than\n700 that are still around.", "start": 4376.2, "duration": 5.07}, {"text": "But I think you're\ngoing to continue", "start": 4381.27, "duration": 1.59}, {"text": "to see high failure rates like\nthe Ernst & Young study showed.", "start": 4382.86, "duration": 6.12}, {"text": "I think it's going to lead to\na further decline in funding", "start": 4388.98, "duration": 3.33}, {"text": "totals.", "start": 4392.31, "duration": 0.9}, {"text": "We've already seen\nthat we were running", "start": 4393.21, "duration": 3.6}, {"text": "$1 and 1/2 to $3 billion\na month earlier this year.", "start": 4396.81, "duration": 4.3}, {"text": "And now we're less than a\nbillion dollars a month.", "start": 4401.11, "duration": 2.81}, {"text": "But I think high failure\nrates will probably", "start": 4403.92, "duration": 2.73}, {"text": "lead to lower funding totals.", "start": 4406.65, "duration": 4.95}, {"text": "It's just Gensler's view.", "start": 4411.6, "duration": 1.77}, {"text": "Predicting markets is always\na treacherous thing to do.", "start": 4413.37, "duration": 3.87}, {"text": "I think that there'll be an\nincreased number of enforcement", "start": 4420.242, "duration": 2.458}, {"text": "cases and private litigation.", "start": 4422.7, "duration": 1.68}, {"text": "We've seen only 11 or\n12 actually at the SEC.", "start": 4424.38, "duration": 2.82}, {"text": "These cases are hard\nto put together.", "start": 4427.2, "duration": 2.39}, {"text": "They take a long time.", "start": 4429.59, "duration": 1.39}, {"text": "A lot of evidence\nand a lot of paper", "start": 4430.98, "duration": 1.71}, {"text": "trails to put\ntogether and so forth.", "start": 4432.69, "duration": 2.93}, {"text": "And even a civil law enforcement\nagency like the SEC--", "start": 4435.62, "duration": 3.893}, {"text": "I don't know their\nheadcount right now--", "start": 4439.513, "duration": 1.667}, {"text": "the whole agency might\nbe about 4,000 people.", "start": 4441.18, "duration": 2.28}, {"text": "Their enforcement arm\nmight be 1,000 people.", "start": 4443.46, "duration": 2.85}, {"text": "They can't dedicate--\nyou know, what are they", "start": 4446.31, "duration": 2.52}, {"text": "dedicating to this?", "start": 4448.83, "duration": 1.06}, {"text": "I don't know the number.", "start": 4449.89, "duration": 1.0}, {"text": "It's not a public figure.", "start": 4450.89, "duration": 1.55}, {"text": "But could it be 50\nor 100 people at most", "start": 4452.44, "duration": 3.38}, {"text": "to this whole world, which\nprobably has hundreds of frauds", "start": 4455.82, "duration": 4.14}, {"text": "and scams and a couple thousand\nof unregistered, basically", "start": 4459.96, "duration": 6.46}, {"text": "illegal, offerings?", "start": 4466.42, "duration": 3.81}, {"text": "But I do think the enforcement\nactions will pick up,", "start": 4470.23, "duration": 4.29}, {"text": "and also private\nlitigation, which is also", "start": 4474.52, "duration": 3.24}, {"text": "what you have in the XRP case.", "start": 4477.76, "duration": 1.8}, {"text": "But you have it in\nother cases, as well.", "start": 4479.56, "duration": 3.21}, {"text": "I think regulators and courts\nwill bring greater clarity", "start": 4482.77, "duration": 2.61}, {"text": "to the security definition.", "start": 4485.38, "duration": 1.29}, {"text": "At some point in time, things\nlike XRP will decide it.", "start": 4486.67, "duration": 2.7}, {"text": "It might be decided\nit's not a security.", "start": 4489.37, "duration": 1.97}, {"text": "You know?", "start": 4491.34, "duration": 2.08}, {"text": "But I think that's\ngoing to roll out", "start": 4493.42, "duration": 1.8}, {"text": "over the next 18 to 36 months.", "start": 4495.22, "duration": 2.22}, {"text": "It's not like the next\nthree weeks or six weeks.", "start": 4497.44, "duration": 3.3}, {"text": "But I think that even the\nSecurities and Exchange", "start": 4500.74, "duration": 3.69}, {"text": "Commission will speak more\ndefinitively than Bill Hinman's", "start": 4504.43, "duration": 5.16}, {"text": "speech he gave in, was it June?", "start": 4509.59, "duration": 3.45}, {"text": "Yeah, June.", "start": 4513.04, "duration": 1.08}, {"text": "That was one of the\nreadings, right--", "start": 4514.12, "duration": 1.62}, {"text": "Director Hinman's.", "start": 4515.74, "duration": 1.81}, {"text": "I like that he used my name\nin his speech, the title.", "start": 4517.55, "duration": 3.41}, {"text": "He was talking about\nGary, Indiana, though.", "start": 4520.96, "duration": 3.66}, {"text": "But I do think, just like\nwhat happened with Airfox", "start": 4524.62, "duration": 4.18}, {"text": "and Paragon, more ICOs will\nbe brought into compliance", "start": 4528.8, "duration": 3.59}, {"text": "either by registering in\nthe US under Reg D, or maybe", "start": 4532.39, "duration": 3.84}, {"text": "Regulation A. Or they'll just\ncome into compliance even", "start": 4536.23, "duration": 3.18}, {"text": "if they didn't earlier\ncome into compliance.", "start": 4539.41, "duration": 3.75}, {"text": "I think that the\nearly tokens will", "start": 4543.16, "duration": 4.53}, {"text": "be tested as some platforms\nbecome functional.", "start": 4547.69, "duration": 3.57}, {"text": "Most will fail.", "start": 4551.26, "duration": 2.41}, {"text": "Most we'll never hear from.", "start": 4553.67, "duration": 2.25}, {"text": "But what happens when\nFilecoin actually-- they", "start": 4555.92, "duration": 2.16}, {"text": "raised a quarter of\na billion dollars.", "start": 4558.08, "duration": 1.635}, {"text": "Let's at least for now presume\nthey will become functional", "start": 4562.751, "duration": 3.309}, {"text": "sometime in 2019, or Telegraph.", "start": 4566.06, "duration": 3.35}, {"text": "That will be\ninteresting to see what", "start": 4569.41, "duration": 1.6}, {"text": "the test of these\nlarge-cap ICOs are.", "start": 4571.01, "duration": 4.13}, {"text": "We'll learn from that.", "start": 4575.14, "duration": 1.36}, {"text": "I also think markets will\nbetter differentiate viability.", "start": 4576.5, "duration": 4.6}, {"text": "They'll go through,\nwhen do you need", "start": 4581.1, "duration": 1.65}, {"text": "an append-only log, consensus\namong multiple parties,", "start": 4582.75, "duration": 5.63}, {"text": "and a native token on\na distributed ledger?", "start": 4588.38, "duration": 5.43}, {"text": "That wasn't happening,\nprobably, enough", "start": 4593.81, "duration": 2.43}, {"text": "in late 2017 and early 2018.", "start": 4596.24, "duration": 3.23}, {"text": "I don't think they had to take\nthis class, even though we'll", "start": 4599.47, "duration": 2.5}, {"text": "put it out live, and people\nwill be able to see it.", "start": 4601.97, "duration": 3.1}, {"text": "But I think markets will start\nto differentiate viability", "start": 4605.07, "duration": 3.02}, {"text": "by CO use cases a little better\nthan they have the last 12", "start": 4608.09, "duration": 3.12}, {"text": "months.", "start": 4611.21, "duration": 2.41}, {"text": "So any questions?", "start": 4613.62, "duration": 2.51}, {"text": "Eric?", "start": 4616.13, "duration": 0.5}, {"text": "AUDIENCE: Yeah.", "start": 4616.63, "duration": 1.31}, {"text": "There's a bunch of startups\nwe've been checking out.", "start": 4617.94, "duration": 3.05}, {"text": "They're going through\na new approach.", "start": 4620.99, "duration": 2.4}, {"text": "There is actually a lot\nof venture capital firms", "start": 4623.39, "duration": 2.82}, {"text": "that are doing a\nfinancing stage pre-ICO", "start": 4626.21, "duration": 4.53}, {"text": "to help these startups\nbuild the actual network.", "start": 4630.74, "duration": 3.32}, {"text": "And in that case, when\nthey go to post-ICO,", "start": 4634.06, "duration": 4.36}, {"text": "you could argue that that helps,\nbuilding the network before", "start": 4638.42, "duration": 4.32}, {"text": "the ICOs can actually make\nthem fail the Howey Test,", "start": 4642.74, "duration": 4.32}, {"text": "because there's no--", "start": 4647.06, "duration": 1.95}, {"text": "in a sense, you have a network,\na decentralized arrangement,", "start": 4649.01, "duration": 4.02}, {"text": "that you don't have\nthe single enterprise--", "start": 4653.03, "duration": 2.8}, {"text": "GARY GENSLER: So I think, Eric,\nyou're raising two questions.", "start": 4655.83, "duration": 3.14}, {"text": "Are there ways to\nstage your financing", "start": 4658.97, "duration": 3.57}, {"text": "to help build a network, just\nas a pure money and finance?", "start": 4662.54, "duration": 6.06}, {"text": "And secondly, what is the\nregulatory implication,", "start": 4668.6, "duration": 2.88}, {"text": "because I think it's two-part.", "start": 4671.48, "duration": 3.15}, {"text": "I think, like in\nany form of venture,", "start": 4674.63, "duration": 2.94}, {"text": "you might stage your\nfinancing and, in this case,", "start": 4677.57, "duration": 3.22}, {"text": "sort of address the\nnetwork possibility", "start": 4680.79, "duration": 3.98}, {"text": "before you do the regulatory.", "start": 4684.77, "duration": 2.55}, {"text": "And it may be enough.", "start": 4687.32, "duration": 1.63}, {"text": "I mean, the US Securities\nand Exchange Commission", "start": 4688.95, "duration": 2.39}, {"text": "and Hinman's speech sort of\nsaid you could be sufficiently", "start": 4691.34, "duration": 4.26}, {"text": "decentralized as Ethereum.", "start": 4695.6, "duration": 3.456}, {"text": "They, in essence, had some\nregulatory forbearance.", "start": 4699.056, "duration": 3.744}, {"text": "And there's a key sentence\nin that speech as to,", "start": 4702.8, "duration": 3.45}, {"text": "I think the words were,\nregardless of what Ethereum", "start": 4706.25, "duration": 2.86}, {"text": "might have been in 2014--", "start": 4709.11, "duration": 2.35}, {"text": "like, Hinman kind of pushed\nthat to the side and said,", "start": 4711.46, "duration": 2.8}, {"text": "I'm not going to address\nthat question implicitly.", "start": 4714.26, "duration": 4.41}, {"text": "But it's sufficiently\ndecentralized.", "start": 4718.67, "duration": 2.22}, {"text": "That's the debate\nthat's going on now", "start": 4720.89, "duration": 1.89}, {"text": "between a bunch of\nventure firms and the SEC.", "start": 4722.78, "duration": 3.48}, {"text": "When are you sufficiently\ndecentralized?", "start": 4726.26, "duration": 1.95}, {"text": "And so that form that you\njust mentioned might get us", "start": 4728.21, "duration": 7.51}, {"text": "there-- might.", "start": 4735.72, "duration": 1.18}, {"text": "I don't know.", "start": 4736.9, "duration": 1.408}, {"text": "Did you have one last question?", "start": 4738.308, "duration": 1.292}, {"text": "And then we're going to--", "start": 4739.6, "duration": 0.683}, {"text": "AUDIENCE: Maybe, just on the\nsecond point about likelihood", "start": 4740.283, "duration": 2.417}, {"text": "of [INAUDIBLE],, [? which I ?]\nobviously agree,", "start": 4742.7, "duration": 2.967}, {"text": "is there any research on--", "start": 4745.667, "duration": 1.083}, {"text": "GARY GENSLER: This\nis just a prediction.", "start": 4746.75, "duration": 1.667}, {"text": "AUDIENCE: Yeah.", "start": 4748.417, "duration": 1.328}, {"text": "I'll bet on it.", "start": 4749.745, "duration": 1.875}, {"text": "How much of the ICO\nfunding was crypto to fiat", "start": 4751.62, "duration": 3.33}, {"text": "to crypto, people selling\nappreciated bitcoins--", "start": 4754.95, "duration": 5.435}, {"text": "GARY GENSLER: Terrific question.", "start": 4760.385, "duration": 1.435}, {"text": "Almost all ICOs are\npriced crypto to crypto.", "start": 4761.82, "duration": 7.71}, {"text": "So if you look at\nwhether the initial ones,", "start": 4769.53, "duration": 2.37}, {"text": "all the way back when the\nEthereum was priced vis-\u00e1-vis", "start": 4771.9, "duration": 2.61}, {"text": "Bitcoin or, the most recent,\niOS that raised $4.2 billion,", "start": 4774.51, "duration": 6.11}, {"text": "their actual pricing mechanism--", "start": 4780.62, "duration": 2.56}, {"text": "I'm not familiar with any\nthat priced versus fiat.", "start": 4783.18, "duration": 5.64}, {"text": "Their pricing mechanism in\ntheir auction or offering,", "start": 4788.82, "duration": 5.12}, {"text": "it's almost always\ncrypto to crypto.", "start": 4793.94, "duration": 3.01}, {"text": "But somebody might be\nfunding it fiat to crypto.", "start": 4796.95, "duration": 2.988}, {"text": "But I think, to\nanswer your question,", "start": 4799.938, "duration": 1.542}, {"text": "you should assume 99% the actual\nexchange is crypto to crypto.", "start": 4801.48, "duration": 5.44}, {"text": "AUDIENCE: So I mean,\njust the decline", "start": 4806.92, "duration": 1.97}, {"text": "in the price of Ethereum to\nBitcoin, Bitcoin to cash almost", "start": 4808.89, "duration": 4.57}, {"text": "has to--", "start": 4813.46, "duration": 0.5}, {"text": "GARY GENSLER: It has\nto put pressure on it.", "start": 4813.96, "duration": 2.31}, {"text": "But I also think it is likely\nthat the decline in the ICO", "start": 4816.27, "duration": 3.75}, {"text": "market has put price pressure\ndownward on Ethereum, for sure.", "start": 4820.02, "duration": 4.34}, {"text": "And so Ethereum was the\nsecond-most valued crypto.", "start": 4824.36, "duration": 5.11}, {"text": "And now it's third.", "start": 4829.47, "duration": 2.43}, {"text": "And it's had more price\ndecline than Bitcoin or XRP.", "start": 4831.9, "duration": 5.13}, {"text": "And I think part of\nthat's narrative.", "start": 4837.03, "duration": 1.92}, {"text": "Part of that story is\nthe decline in ICO space", "start": 4838.95, "duration": 3.99}, {"text": "is likely to put a\nlittle decline on that.", "start": 4842.94, "duration": 3.32}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.992}, {"text": "[RUSTLING]", "start": 1.992, "duration": 1.494}, {"text": "[CLICKING]", "start": 3.486, "duration": 2.988}, {"text": "MICHAEL SIPSER: Welcome back.", "start": 24.93, "duration": 1.84}, {"text": "I hope you had a\ngood Thanksgiving", "start": 26.77, "duration": 1.91}, {"text": "and all refreshed\nand ready to think", "start": 28.68, "duration": 7.62}, {"text": "about some theory\nof computation.", "start": 36.3, "duration": 2.25}, {"text": "We're in the homestretch now.", "start": 38.55, "duration": 2.76}, {"text": "We have this lecture\nand two more to go.", "start": 41.31, "duration": 2.82}, {"text": "And so today, I have for you,\na completion of the theorem", "start": 44.13, "duration": 9.75}, {"text": "we started before the\nbreak, where we introduced", "start": 53.88, "duration": 8.49}, {"text": "probabilistic computation and\nwe talked about the class BPP,", "start": 62.37, "duration": 7.2}, {"text": "as I hope you remember, and\nwe looked, in particular,", "start": 69.57, "duration": 3.63}, {"text": "at these problems involving\nbranching programs, where", "start": 73.2, "duration": 7.44}, {"text": "we started the proof that the\nproblem of equivalence of two", "start": 80.64, "duration": 6.99}, {"text": "read-once branching programs\ncan be solved in this class BPP.", "start": 87.63, "duration": 4.53}, {"text": "So what I'm going to do is\nspend the first 15 minutes", "start": 92.16, "duration": 3.96}, {"text": "or so just reviewing where we\nwere, because we started this,", "start": 96.12, "duration": 5.32}, {"text": "it feels like a\nlong time ago now.", "start": 101.44, "duration": 1.92}, {"text": "And I just want to make\nsure that you're all", "start": 103.36, "duration": 4.43}, {"text": "on the same page and we're all\nremembering what we were doing.", "start": 107.79, "duration": 4.5}, {"text": "And then, I will\nfinish off the proof.", "start": 112.29, "duration": 2.91}, {"text": "And along with doing\nthat, we're going", "start": 115.2, "duration": 2.91}, {"text": "to introduce an\nimportant method.", "start": 118.11, "duration": 3.24}, {"text": "Well, we started that.", "start": 121.35, "duration": 0.99}, {"text": "We looked at the method of\narithmetization last time.", "start": 122.34, "duration": 3.28}, {"text": "So we'll review that.", "start": 125.62, "duration": 2.27}, {"text": "We're going to use\nthat again in the work", "start": 127.89, "duration": 6.09}, {"text": "that we're going to start on\nThursday on interactive proof", "start": 133.98, "duration": 2.61}, {"text": "systems.", "start": 136.59, "duration": 0.75}, {"text": "So this is a kind\nof, in some ways,", "start": 137.34, "duration": 2.5}, {"text": "both an interesting theorem in\nits own right, and a warm up", "start": 139.84, "duration": 3.86}, {"text": "for what we're going to\nbe doing in the last topic", "start": 143.7, "duration": 6.84}, {"text": "of the semester.", "start": 150.54, "duration": 3.48}, {"text": "OK.", "start": 154.02, "duration": 2.58}, {"text": "So let's just remember\nwhat we were doing.", "start": 156.6, "duration": 6.31}, {"text": "So we introduced\nprobabilistic Turing machines.", "start": 162.91, "duration": 4.95}, {"text": "So those are these\nmachines that have--", "start": 167.86, "duration": 3.38}, {"text": "a kind of\nnon-deterministic machine,", "start": 171.24, "duration": 1.86}, {"text": "but there's a different\nrule for acceptance.", "start": 173.1, "duration": 3.03}, {"text": "And these are also\nnon-deterministic machines", "start": 176.13, "duration": 3.63}, {"text": "which can either\nmake one choice, just", "start": 179.76, "duration": 3.24}, {"text": "to have a deterministic\nmove at a step,", "start": 183.0, "duration": 2.46}, {"text": "or they can make two choices.", "start": 185.46, "duration": 2.25}, {"text": "And when the machine\nmakes two choices,", "start": 187.71, "duration": 1.9}, {"text": "we actually think of there\nbeing a probability there,", "start": 189.61, "duration": 2.81}, {"text": "where the machine\nis tossing a coin", "start": 192.42, "duration": 1.77}, {"text": "to decide which branch to go on.", "start": 194.19, "duration": 3.79}, {"text": "So with that, there is a\ntree of possible branches.", "start": 197.98, "duration": 4.67}, {"text": "And the probability of\nsome particular branch", "start": 202.65, "duration": 2.52}, {"text": "is going to be 1 over\n2 to the number of coin", "start": 205.17, "duration": 3.09}, {"text": "tosses on that branch.", "start": 208.26, "duration": 2.82}, {"text": "And so we then use that\nto define the probability", "start": 211.08, "duration": 4.65}, {"text": "that the machine\naccepts, which is", "start": 215.73, "duration": 2.67}, {"text": "the sum over all of\nthe probabilities", "start": 218.4, "duration": 1.68}, {"text": "of the accepting branches.", "start": 220.08, "duration": 1.83}, {"text": "And the probability\nthat it rejects", "start": 221.91, "duration": 1.98}, {"text": "is 1 minus the probability\nthat it accepts.", "start": 223.89, "duration": 2.07}, {"text": "So thinking about it--", "start": 229.17, "duration": 3.54}, {"text": "this captures the\nidea that if you just", "start": 232.71, "duration": 4.8}, {"text": "run the machine on a random set\nof inputs from the coin tosses,", "start": 237.51, "duration": 9.61}, {"text": "what the probability that\nyou're going to end up", "start": 247.12, "duration": 2.07}, {"text": "with the machine accepting.", "start": 249.19, "duration": 1.83}, {"text": "That's the probability\nof acceptance,", "start": 251.02, "duration": 3.0}, {"text": "defined in that way.", "start": 254.02, "duration": 2.938}, {"text": "Now, if we're thinking\nabout the machine deciding", "start": 256.958, "duration": 2.042}, {"text": "some particular\nlanguage, it's supposed", "start": 259.0, "duration": 2.94}, {"text": "to accept the strings\nin the language", "start": 261.94, "duration": 1.65}, {"text": "and reject the strings which\nare not in the language.", "start": 263.59, "duration": 2.46}, {"text": "But because of the probabilistic\nnature of the machine,", "start": 266.05, "duration": 2.4}, {"text": "it might get the wrong\nanswer on some branches.", "start": 268.45, "duration": 2.82}, {"text": "And so we say that\na machine decides", "start": 271.27, "duration": 2.59}, {"text": "a language with a certain\nerror probability,", "start": 273.86, "duration": 2.42}, {"text": "means that the probability\nof getting the wrong answer", "start": 276.28, "duration": 2.88}, {"text": "is going to be, at most,\nthat error probability", "start": 279.16, "duration": 2.7}, {"text": "epsilon over all of the\npossible inputs to the machine.", "start": 281.86, "duration": 3.87}, {"text": "So if we say that the machine\nis error probability 1/3", "start": 285.73, "duration": 2.93}, {"text": "that means that it gets the\nright answer for every string", "start": 288.66, "duration": 4.47}, {"text": "with probability at least 2/3.", "start": 293.13, "duration": 1.77}, {"text": "OK, so that led us to the\ndefinition of this complexity", "start": 299.04, "duration": 4.56}, {"text": "class BPP, which I don't\neven remember if I told you", "start": 303.6, "duration": 3.15}, {"text": "what it stands for.", "start": 306.75, "duration": 0.94}, {"text": "It's bounded probabilistic\npolynomial time.", "start": 307.69, "duration": 3.59}, {"text": "That's what BPP stands for.", "start": 311.28, "duration": 1.62}, {"text": "The \"bounded\" means is\nbounded away from 1/2", "start": 316.05, "duration": 2.69}, {"text": "because we don't want\nto allow the machine", "start": 318.74, "duration": 1.75}, {"text": "to have probability 1/2,\nbecause then bad things happen.", "start": 320.49, "duration": 5.748}, {"text": "The machine can just\ntoss a coin when", "start": 326.238, "duration": 1.542}, {"text": "it decides to make\nan answer, and not", "start": 327.78, "duration": 3.9}, {"text": "really give us any information.", "start": 331.68, "duration": 4.26}, {"text": "Then, we also went over\nthe amplification lemma.", "start": 335.94, "duration": 5.43}, {"text": "We did not give\nthe proof, but we", "start": 341.37, "duration": 1.41}, {"text": "went over the statement\nof the theorem.", "start": 342.78, "duration": 1.625}, {"text": "The proof is really\njust a calculation", "start": 344.405, "duration": 2.275}, {"text": "that you can drive down that\nerror probability to something", "start": 346.68, "duration": 3.66}, {"text": "extremely tiny just by\nbasically repeating the machine", "start": 350.34, "duration": 5.31}, {"text": "and taking the majority\nvote of what it", "start": 355.65, "duration": 2.61}, {"text": "does on several different runs.", "start": 358.26, "duration": 2.37}, {"text": "If you run the machine\n100 times and you", "start": 360.63, "duration": 2.58}, {"text": "see if it's mostly accepting,\nthen you want to accept.", "start": 363.21, "duration": 2.94}, {"text": "And the chances that the\nmachine was really biased", "start": 366.15, "duration": 4.02}, {"text": "toward rejecting,\neven though you're", "start": 370.17, "duration": 1.68}, {"text": "in your sample see mostly\nacceptance, is extremely small.", "start": 371.85, "duration": 3.27}, {"text": "And you can calculate that, but\nyou can make that very tiny.", "start": 375.12, "duration": 2.7}, {"text": "So small that, for all\npractical purposes,", "start": 377.82, "duration": 2.62}, {"text": "it's really giving\nyou the right answer.", "start": 380.44, "duration": 2.43}, {"text": "But it's not deterministic.", "start": 382.87, "duration": 1.4}, {"text": "So it's not quite\n100% guaranteed.", "start": 384.27, "duration": 3.144}, {"text": "And the way I like\nto think about BPP", "start": 390.08, "duration": 5.85}, {"text": "in terms of the computation\ntree of the machine,", "start": 395.93, "duration": 3.42}, {"text": "so that when it's accepting,\nmost of the branches", "start": 399.35, "duration": 3.66}, {"text": "are accepting, weighted by\ntheir probability, of course.", "start": 403.01, "duration": 5.14}, {"text": "So the there are many accepting\nbranches when you're accepting,", "start": 408.15, "duration": 4.01}, {"text": "and many rejecting branches\nwhen you're rejecting.", "start": 412.16, "duration": 3.42}, {"text": "So just another way of\nsaying the same thing.", "start": 415.58, "duration": 3.89}, {"text": "Now, we're going to jump\nright in with a check-in.", "start": 419.47, "duration": 4.65}, {"text": "And this is a little bit\nmore, not exactly the material", "start": 424.12, "duration": 3.66}, {"text": "of the course, but a little bit\nmore on the philosophical side.", "start": 427.78, "duration": 3.36}, {"text": "But let's just see\nhow you do with it.", "start": 431.14, "duration": 4.28}, {"text": "When you're actually running\na probabilistic machine,", "start": 435.42, "duration": 4.64}, {"text": "you imagine the\nmachine, as we're", "start": 440.06, "duration": 2.16}, {"text": "kind of informally describing\nit, is tossing coins.", "start": 442.22, "duration": 5.11}, {"text": "Every time it has a\nnon-deterministic--", "start": 447.33, "duration": 2.67}, {"text": "every time it has a choice.", "start": 450.0, "duration": 2.79}, {"text": "So it choice tosses a coin\nto decide which way to go.", "start": 452.79, "duration": 2.58}, {"text": "Of course, a real computer\ndoes not have a coin to toss,", "start": 455.37, "duration": 4.89}, {"text": "presumably.", "start": 460.26, "duration": 0.66}, {"text": "Well, maybe you might\nactually build some hardware", "start": 460.92, "duration": 2.94}, {"text": "into the machine\nthat lets it access", "start": 463.86, "duration": 2.25}, {"text": "randomness in some sense.", "start": 466.11, "duration": 1.47}, {"text": "Maybe it uses some\nquantum mechanical effect", "start": 467.58, "duration": 3.93}, {"text": "to get some random value\nor maybe it uses the timer.", "start": 471.51, "duration": 4.65}, {"text": "I'm not exactly sure.", "start": 476.16, "duration": 1.44}, {"text": "You can imagine having a bunch\nof ways of implementing that.", "start": 477.6, "duration": 4.77}, {"text": "A typical way that people\nimplement randomness", "start": 482.37, "duration": 4.14}, {"text": "in an algorithm is to use\na pseudo random number", "start": 486.51, "duration": 3.66}, {"text": "generator, which is a\nprocedure that might give you", "start": 490.17, "duration": 4.08}, {"text": "some kind of a value that looks\nrandom, but may not actually", "start": 494.25, "duration": 4.89}, {"text": "be random.", "start": 499.14, "duration": 1.71}, {"text": "It's, for example, giving\nyou the digits of pi.", "start": 500.85, "duration": 4.89}, {"text": "If you want binary, expressing\npi as a binary number,", "start": 505.74, "duration": 8.73}, {"text": "then you might calculate the\ndifferent successive digits", "start": 514.47, "duration": 3.27}, {"text": "of pi and use that as for\nyour random number generator.", "start": 517.74, "duration": 4.497}, {"text": "Of course, that's a\ndeterministic procedure,", "start": 522.237, "duration": 1.833}, {"text": "so it's not really random.", "start": 524.07, "duration": 3.15}, {"text": "But often, people do use\nthose kinds of things", "start": 527.22, "duration": 3.18}, {"text": "when they're simulating\nrandom machines.", "start": 530.4, "duration": 2.13}, {"text": "So what do you think\nabout doing that?", "start": 532.53, "duration": 2.46}, {"text": "Could we use a pseudo\nrandom generator", "start": 534.99, "duration": 4.41}, {"text": "as the source of randomness\nfor our randomized algorithm?", "start": 539.4, "duration": 3.296}, {"text": "Yes, or no, or\nwhat do you think?", "start": 546.19, "duration": 3.87}, {"text": "So let's launch a poll on\nthat, so I can see what", "start": 550.06, "duration": 2.91}, {"text": "your opinion about using\npseudo random number", "start": 552.97, "duration": 3.27}, {"text": "generators instead of true\nrandomness for our algorithms.", "start": 556.24, "duration": 4.29}, {"text": "I'll give you a few seconds,\na minute to weigh in on that.", "start": 563.32, "duration": 5.1}, {"text": "OK.", "start": 571.4, "duration": 0.988}, {"text": "We're going to close this down.", "start": 572.388, "duration": 1.292}, {"text": "Everybody's participated\nwho wants to?", "start": 573.68, "duration": 4.2}, {"text": "1, 2, 3.", "start": 577.88, "duration": 0.615}, {"text": "OK.", "start": 581.53, "duration": 2.17}, {"text": "Yeah, I think probably the best\nanswer is A. Let's take a look.", "start": 583.7, "duration": 5.91}, {"text": "There were a couple of answers\nhere that, really, that", "start": 589.61, "duration": 2.76}, {"text": "don't make--", "start": 592.37, "duration": 0.99}, {"text": "that aren't as good.", "start": 593.36, "duration": 1.14}, {"text": "I would say, B,\nwell, usually people", "start": 594.5, "duration": 3.33}, {"text": "think of pseudo\nrandom generators", "start": 597.83, "duration": 1.8}, {"text": "as pretty fast procedures.", "start": 599.63, "duration": 2.16}, {"text": "They're not that\ninteresting, otherwise.", "start": 601.79, "duration": 2.04}, {"text": "So I wouldn't say that\nB is a good choice", "start": 603.83, "duration": 2.76}, {"text": "because they're usually\npretty quick to implement.", "start": 606.59, "duration": 6.48}, {"text": "C is a worse choice, even,\nbecause Turing machines", "start": 613.07, "duration": 5.34}, {"text": "can do anything that any\nother algorithm can do.", "start": 618.41, "duration": 2.22}, {"text": "So, certainly, if\nthere is such a thing", "start": 620.63, "duration": 2.537}, {"text": "as a pseudo random number\ngenerator, and there is,", "start": 623.167, "duration": 2.083}, {"text": "then you could implement\nit on the Turing machine.", "start": 625.25, "duration": 4.68}, {"text": "D is kind of an\ninteresting answer", "start": 629.93, "duration": 2.04}, {"text": "because you're saying, well,\nthat would imply that P equals", "start": 631.97, "duration": 3.27}, {"text": "BPP if you could actually\nsimulate randomness", "start": 635.24, "duration": 4.02}, {"text": "with a deterministic procedure.", "start": 639.26, "duration": 3.09}, {"text": "But in fact, the reason\nI would not choose D", "start": 642.35, "duration": 3.96}, {"text": "is because it's\nperfectly conceivable", "start": 646.31, "duration": 2.52}, {"text": "that P does equal BPP.", "start": 648.83, "duration": 2.91}, {"text": "We don't know that P\nis different from BPP,", "start": 651.74, "duration": 2.13}, {"text": "so it's conceivable\nthat they're equal.", "start": 653.87, "duration": 2.32}, {"text": "And in fact, I think if\nyou polled most complexity", "start": 656.19, "duration": 4.58}, {"text": "theorists, most\npeople in my field", "start": 660.77, "duration": 5.43}, {"text": "would believe that P does equal\nBPP just for this very reason,", "start": 666.2, "duration": 5.73}, {"text": "that if you had sufficiently\ngood pseudo random number", "start": 671.93, "duration": 3.39}, {"text": "generators, you could\nactually eliminate", "start": 675.32, "duration": 2.88}, {"text": "the probabalism in these\nprobabilistic computations.", "start": 678.2, "duration": 3.03}, {"text": "You could just run them on the\npseudo random number generator.", "start": 681.23, "duration": 2.67}, {"text": "And in fact, there is\nsome theory around that", "start": 683.9, "duration": 3.51}, {"text": "that has been developed.", "start": 687.41, "duration": 2.13}, {"text": "But at the present\ntime, we do not", "start": 689.54, "duration": 2.43}, {"text": "know how to prove that there\nwere pseudo random number", "start": 691.97, "duration": 3.09}, {"text": "generators.", "start": 695.06, "duration": 0.57}, {"text": "And it has some,\nactually, there's", "start": 695.63, "duration": 1.693}, {"text": "actually, in some\nline of this research,", "start": 697.323, "duration": 1.667}, {"text": "has some connection with\nthe P versus NP problem,", "start": 698.99, "duration": 2.32}, {"text": "but we don't know how\nto prove that there", "start": 701.31, "duration": 1.88}, {"text": "are sufficiently good pseudo\nrandom number generators that", "start": 703.19, "duration": 3.3}, {"text": "would allow you to run them\non a probabilistic algorithm", "start": 706.49, "duration": 4.47}, {"text": "and have a guaranteed behavior\nwhich is as good as running", "start": 710.96, "duration": 3.06}, {"text": "truly random numbers into\nthe probabilistic algorithm.", "start": 714.02, "duration": 6.04}, {"text": "And so the answer\nthat I would pick", "start": 720.06, "duration": 2.45}, {"text": "would be A, that you\ncould use it, sure.", "start": 722.51, "duration": 2.257}, {"text": "You might get the right answer,\nbut it's not guaranteed.", "start": 724.767, "duration": 2.333}, {"text": "We just don't know\nhow to do the analysis", "start": 727.1, "duration": 2.07}, {"text": "for the pseudo random\nnumber generators.", "start": 729.17, "duration": 1.95}, {"text": "And if you had ones\nthat were good enough,", "start": 731.12, "duration": 3.34}, {"text": "they would show P\nis equal to BPP.", "start": 734.46, "duration": 2.84}, {"text": "But that might be, in\nfact, the correct--", "start": 737.3, "duration": 3.06}, {"text": "that might actually be true.", "start": 740.36, "duration": 2.82}, {"text": "OK, so let's continue on.", "start": 743.18, "duration": 3.53}, {"text": "And remember, now,\nbranching programs.", "start": 746.71, "duration": 4.74}, {"text": "We had these kind of\nnetworks of nodes and edges.", "start": 751.45, "duration": 5.88}, {"text": "And there was a procedure,\nwe'll see a couple of examples", "start": 757.33, "duration": 2.682}, {"text": "again, some of the\nones that we had", "start": 760.012, "duration": 1.458}, {"text": "from before where\nyou have branching", "start": 761.47, "duration": 3.84}, {"text": "programs that look like this.", "start": 765.31, "duration": 2.46}, {"text": "And you have a bunch\nof query nodes.", "start": 767.77, "duration": 2.58}, {"text": "You look at the settings\nof the variables", "start": 770.35, "duration": 2.55}, {"text": "to decide whether to go\ndown to 0 edge or a 1 edge.", "start": 772.9, "duration": 3.175}, {"text": "And eventually, you're going\nto end up at an output node,", "start": 776.075, "duration": 2.375}, {"text": "and that's going\nto be the output", "start": 778.45, "duration": 2.28}, {"text": "of the branching program.", "start": 780.73, "duration": 1.2}, {"text": "And in such a way,\nthese branching programs", "start": 781.93, "duration": 1.95}, {"text": "defined Boolean functions,\nfrom the settings of the input", "start": 783.88, "duration": 3.12}, {"text": "variables to a 0 or 1 output.", "start": 787.0, "duration": 3.78}, {"text": "Now, you might have\ntwo branching programs", "start": 790.78, "duration": 2.43}, {"text": "and wonder whether they're\ncomputing the same Boolean", "start": 793.21, "duration": 2.34}, {"text": "function or not.", "start": 795.55, "duration": 1.09}, {"text": "And testing that is a\ncoNP complete problem,", "start": 796.64, "duration": 3.68}, {"text": "as you're asked to\nshow on your homework.", "start": 800.32, "duration": 1.98}, {"text": "Now, if the branching program,\nhowever, has a restriction,", "start": 806.01, "duration": 4.2}, {"text": "namely, that it's\nnot allowed to ask", "start": 810.21, "duration": 4.05}, {"text": "to query the same variable\nmore than once on a path,", "start": 814.26, "duration": 4.26}, {"text": "then with that restriction, we\ncall it a read-once branching", "start": 818.52, "duration": 6.66}, {"text": "program.", "start": 825.18, "duration": 1.91}, {"text": "And then, the situation\nfor testing equivalence", "start": 827.09, "duration": 3.48}, {"text": "seems to be different.", "start": 830.57, "duration": 1.75}, {"text": "In fact, we can\ngive a BPP algorithm", "start": 832.32, "duration": 2.63}, {"text": "for testing the equivalence of\nread-once branching programs,", "start": 834.95, "duration": 3.51}, {"text": "even though such a\nthing is unlikely to be", "start": 838.46, "duration": 2.01}, {"text": "the case for general branching\nprograms because of the coNP", "start": 840.47, "duration": 3.3}, {"text": "completeness.", "start": 843.77, "duration": 2.32}, {"text": "OK, so I hope you're\ncomfortable and with me", "start": 846.09, "duration": 2.43}, {"text": "on all of that reasoning.", "start": 848.52, "duration": 1.2}, {"text": "OK.", "start": 855.92, "duration": 0.5}, {"text": "All right.", "start": 867.65, "duration": 0.5}, {"text": "So the idea for proving this\nis, what we're going to do", "start": 868.15, "duration": 3.42}, {"text": "is we want to take the\ntwo branching programs", "start": 871.57, "duration": 2.01}, {"text": "and run them on a\nrandomly-selected input.", "start": 873.58, "duration": 2.82}, {"text": "But as we observed\nlast time, if you just", "start": 876.4, "duration": 2.76}, {"text": "run them on a\nrandomly-selected Boolean input", "start": 879.16, "duration": 3.09}, {"text": "where we assign the\nvariable 0s and 1s,", "start": 882.25, "duration": 2.46}, {"text": "then that doesn't give\nyou the right answer", "start": 884.71, "duration": 2.91}, {"text": "with high probability, because\nthe two branching programs", "start": 887.62, "duration": 3.57}, {"text": "might be different, computing\ndifferent Boolean functions,", "start": 891.19, "duration": 3.51}, {"text": "but they differ only on\na single input setting.", "start": 894.7, "duration": 3.09}, {"text": "And then, just picking\nthem at random,", "start": 897.79, "duration": 3.22}, {"text": "you're not going to have a very\nhigh probability of finding", "start": 901.01, "duration": 2.9}, {"text": "that one place of difference.", "start": 903.91, "duration": 2.83}, {"text": "So instead, what we're going to\ndo is define a way to run these", "start": 906.74, "duration": 3.74}, {"text": "branching programs on\nnon-Boolean inputs,", "start": 910.48, "duration": 3.03}, {"text": "where the variables are set\nto values other than 0 and 1--", "start": 913.51, "duration": 4.089}, {"text": "2, 3, 7, 22--", "start": 917.599, "duration": 2.871}, {"text": "and make sense of that.", "start": 920.47, "duration": 1.63}, {"text": "And then argue that, by running\nthe two branching programs", "start": 922.1, "duration": 4.76}, {"text": "on a randomly-selected\nnon-Boolean input,", "start": 926.86, "duration": 4.12}, {"text": "that that's very\nhigh probability", "start": 930.98, "duration": 2.52}, {"text": "of giving you the right answer.", "start": 933.5, "duration": 3.25}, {"text": "So somehow, by expanding\nthe domain of possibilities,", "start": 936.75, "duration": 3.47}, {"text": "you're going to\nbetter your chance", "start": 940.22, "duration": 3.3}, {"text": "of getting the right\nanswer very significantly.", "start": 943.52, "duration": 3.98}, {"text": "OK.", "start": 947.5, "duration": 0.5}, {"text": "So even though these\ntwo branching programs", "start": 948.0, "duration": 2.16}, {"text": "might agree on almost all\nof the Boolean inputs,", "start": 950.16, "duration": 5.88}, {"text": "we're going to show that by\ndoing this arithmetization--", "start": 956.04, "duration": 4.952}, {"text": "so this is the method--", "start": 960.992, "duration": 0.958}, {"text": "if they're really\nnot equivalent,", "start": 965.33, "duration": 2.67}, {"text": "they're going to differ\nalmost all of the time", "start": 968.0, "duration": 3.18}, {"text": "on the expanded domain.", "start": 971.18, "duration": 2.188}, {"text": "OK, and then we have the proof.", "start": 973.368, "duration": 1.292}, {"text": "That's where today's\nwork is going to be.", "start": 978.87, "duration": 4.33}, {"text": "OK.", "start": 983.2, "duration": 0.96}, {"text": "So why don't we\njust stop and make", "start": 984.16, "duration": 5.1}, {"text": "sure we're all together on this?", "start": 989.26, "duration": 3.87}, {"text": "I can take any questions.", "start": 993.13, "duration": 3.34}, {"text": "I'll also review how the\narithmetization goes.", "start": 996.47, "duration": 3.21}, {"text": "But I'll do that next.", "start": 999.68, "duration": 2.78}, {"text": "So, are we all OK on this?", "start": 1002.46, "duration": 5.85}, {"text": "Good.", "start": 1008.31, "duration": 0.51}, {"text": "So let's move on.", "start": 1008.82, "duration": 3.04}, {"text": "So in order to move\ntoward understanding", "start": 1011.86, "duration": 3.23}, {"text": "what it means to run\nthe branching programs", "start": 1015.09, "duration": 2.88}, {"text": "on these non-Boolean\nvalues, we're", "start": 1017.97, "duration": 3.03}, {"text": "going to have to get a\nsomewhat different perspective", "start": 1021.0, "duration": 4.859}, {"text": "on the computation of\na branching program.", "start": 1025.859, "duration": 3.451}, {"text": "So the standard perspective\nis that you take your setting,", "start": 1029.31, "duration": 7.5}, {"text": "your assignment to\nthe input, which", "start": 1036.81, "duration": 2.37}, {"text": "is 0,1,1 for x1, x2, and x3, and\nuse that to follow an execution", "start": 1039.18, "duration": 7.32}, {"text": "path through the machine.", "start": 1046.5, "duration": 2.85}, {"text": "So we know x1 is 0,\nx2 is 1, x3 is 1,", "start": 1049.35, "duration": 3.12}, {"text": "the output is 1, as I've\nindicated in yellow.", "start": 1052.47, "duration": 3.3}, {"text": "This other perspective\nsays, well, we're", "start": 1058.8, "duration": 2.82}, {"text": "going to operate by labeling the\nnodes and edges of the machine.", "start": 1061.62, "duration": 4.93}, {"text": "And that's going to have a\nvery direct correspondence", "start": 1066.55, "duration": 5.5}, {"text": "with the execution\npath perspective.", "start": 1072.05, "duration": 2.8}, {"text": "So we're going to label all of\nthe nodes and edges on the path", "start": 1074.85, "duration": 3.08}, {"text": "with a 1, as\nindicated in yellow,", "start": 1077.93, "duration": 3.36}, {"text": "and all of the nodes\nand edges that are not", "start": 1081.29, "duration": 2.52}, {"text": "on the path, all the\nother nodes and edges", "start": 1083.81, "duration": 1.86}, {"text": "are going to be labeled 0.", "start": 1085.67, "duration": 1.083}, {"text": "So by following the 1s,\nit's like the breadcrumbs", "start": 1090.95, "duration": 3.66}, {"text": "in Hansel and Gretel.", "start": 1094.61, "duration": 1.71}, {"text": "This is the path\nyou need to follow", "start": 1096.32, "duration": 2.1}, {"text": "to get through the machine.", "start": 1098.42, "duration": 3.99}, {"text": "The 0s are the places\nwhere you don't go.", "start": 1102.41, "duration": 1.86}, {"text": "OK, so the output\nlabel, here, the output", "start": 1107.4, "duration": 3.45}, {"text": "is going to be the label of\nthe one output node, whatever", "start": 1110.85, "duration": 3.925}, {"text": "you're labeling that.", "start": 1114.775, "duration": 0.875}, {"text": "Because if it's a 1, that\nmeans the path went to the 1,", "start": 1115.65, "duration": 3.367}, {"text": "and if it's a 0, that means\nthe path didn't go to the 1,", "start": 1119.017, "duration": 2.333}, {"text": "it went to the 0.", "start": 1121.35, "duration": 2.53}, {"text": "So just by looking\nat this value,", "start": 1123.88, "duration": 1.81}, {"text": "you can see what the\noutput of the machine is.", "start": 1125.69, "duration": 4.33}, {"text": "All right.", "start": 1130.02, "duration": 0.57}, {"text": "So let's describe\na different way", "start": 1130.59, "duration": 5.52}, {"text": "of defining this\nlabeling without just", "start": 1136.11, "duration": 3.42}, {"text": "looking at the path.", "start": 1139.53, "duration": 2.35}, {"text": "Well, it's going to capture\nexactly the same thing.", "start": 1141.88, "duration": 2.18}, {"text": "So we're going to say, if\nyou've already labeled a node,", "start": 1147.46, "duration": 8.85}, {"text": "I'll tell you how to\nlabel the two edges that", "start": 1156.31, "duration": 2.1}, {"text": "emanate from that node.", "start": 1158.41, "duration": 1.23}, {"text": "I'm going to label the one\nedge a and the query variable.", "start": 1163.83, "duration": 5.61}, {"text": "Why is that?", "start": 1169.44, "duration": 1.26}, {"text": "Well, a is going to\nbe either a 0 or 1.", "start": 1170.7, "duration": 4.983}, {"text": "And it's going to\ntell us whether or not", "start": 1175.683, "duration": 1.667}, {"text": "the path entered that node.", "start": 1177.35, "duration": 3.37}, {"text": "So if it's a 1, it\nentered that node, if 0,", "start": 1180.72, "duration": 2.33}, {"text": "it didn't enter that node.", "start": 1183.05, "duration": 1.29}, {"text": "The only way it's going\nto go down this branch", "start": 1184.34, "duration": 2.67}, {"text": "here is if it did\nenter the xi node.", "start": 1187.01, "duration": 5.185}, {"text": "If it didn't enter\nthe xi node, there's", "start": 1192.195, "duration": 1.625}, {"text": "no way it can go\ndown this branch.", "start": 1193.82, "duration": 2.14}, {"text": "So we're going to\nand that value.", "start": 1195.96, "duration": 3.55}, {"text": "So the only way you\ncan go down this branch", "start": 1199.51, "duration": 3.38}, {"text": "is if it went\nthrough that node--", "start": 1202.89, "duration": 2.29}, {"text": "so that's the a,\nthe value of a--", "start": 1205.18, "duration": 2.3}, {"text": "and the xi is a 1.", "start": 1207.48, "duration": 2.82}, {"text": "That's why we say a and xi.", "start": 1210.3, "duration": 2.078}, {"text": "So you really have to understand\nthis little expression here.", "start": 1212.378, "duration": 2.542}, {"text": "If you don't understand\nthat, you're toast.", "start": 1214.92, "duration": 3.76}, {"text": "OK, so you better understand\nthis so we can move forward.", "start": 1218.68, "duration": 2.46}, {"text": "I'm happy to take a question.", "start": 1221.14, "duration": 1.32}, {"text": "These are the simplest\nquestions are sometimes", "start": 1222.46, "duration": 1.917}, {"text": "the most valuable.", "start": 1224.377, "duration": 1.395}, {"text": "If you don't understand why\nI'm labeling it this way,", "start": 1225.772, "duration": 2.208}, {"text": "shoot me a chat.", "start": 1227.98, "duration": 1.44}, {"text": "OK.", "start": 1232.02, "duration": 0.5}, {"text": "Now, the other branch,\nI'm going to say,", "start": 1232.52, "duration": 3.16}, {"text": "well, I'm only going to go down\nthis edge if, well, a is true,", "start": 1235.68, "duration": 5.05}, {"text": "so I did go through that node.", "start": 1240.73, "duration": 1.69}, {"text": "And xi is false.", "start": 1242.42, "duration": 2.56}, {"text": "So this is going to be a\nand the complement of xi.", "start": 1244.98, "duration": 4.45}, {"text": "All right.", "start": 1249.43, "duration": 0.5}, {"text": "So that's how I'm\ngoing to label these.", "start": 1249.93, "duration": 1.625}, {"text": "This is another way,\ngiving these expressions", "start": 1251.555, "duration": 3.935}, {"text": "for labeling these edges based\non the label of that node.", "start": 1255.49, "duration": 3.57}, {"text": "And similarly, in order\nto complete the picture,", "start": 1259.06, "duration": 2.82}, {"text": "I've got to tell you how\nto label the nodes based", "start": 1261.88, "duration": 2.25}, {"text": "on the edges that\nare coming into it.", "start": 1264.13, "duration": 2.02}, {"text": "So if I know that I have\na1, a2, and a3, which", "start": 1266.15, "duration": 2.6}, {"text": "tell me the status in terms of\nthe path of whether the path", "start": 1268.75, "duration": 6.3}, {"text": "went through any of\nthese edges, well,", "start": 1275.05, "duration": 2.76}, {"text": "I know that it's going\nto go to that node", "start": 1277.81, "duration": 1.77}, {"text": "if the or of these values--", "start": 1279.58, "duration": 4.917}, {"text": "if the path went through here,\nor it went through there,", "start": 1284.497, "duration": 2.333}, {"text": "or went through there, then\nit's going to go to that node.", "start": 1286.83, "duration": 3.25}, {"text": "That's why the or is\nthe right thing to say.", "start": 1290.08, "duration": 2.3}, {"text": "So this gives me another\nway of constructing", "start": 1292.38, "duration": 2.88}, {"text": "the labeling over here without\neven talking about paths.", "start": 1295.26, "duration": 5.54}, {"text": "As I describe it,\nI argue that it's", "start": 1300.8, "duration": 1.92}, {"text": "going to give the same\nresult. All right.", "start": 1302.72, "duration": 3.6}, {"text": "So there's a question.", "start": 1310.223, "duration": 0.917}, {"text": "Can we quickly say again why\nwe can't do that on Boolean?", "start": 1311.14, "duration": 2.735}, {"text": "I'm not sure I\nunderstand the question.", "start": 1313.875, "duration": 1.625}, {"text": "So send it to me again.", "start": 1315.5, "duration": 1.61}, {"text": "Right now, everything\nis Boolean.", "start": 1317.11, "duration": 1.59}, {"text": "We haven't done,\narithmetically, anything yet.", "start": 1318.7, "duration": 4.363}, {"text": "And the reason why we can't\njust live in the Boolean world", "start": 1323.063, "duration": 2.417}, {"text": "is that, just by taking Boolean\nvalues of Boolean assignments", "start": 1325.48, "duration": 4.77}, {"text": "here, we don't have a\nhigh enough probability", "start": 1330.25, "duration": 2.97}, {"text": "of catching a difference\nbetween the two machines.", "start": 1333.22, "duration": 2.73}, {"text": "All right.", "start": 1340.64, "duration": 0.5}, {"text": "So let's continue.", "start": 1341.14, "duration": 0.75}, {"text": "All right.", "start": 1344.81, "duration": 0.66}, {"text": "So now, I'm going\nto talk about how", "start": 1345.47, "duration": 2.55}, {"text": "we're going to extend this\nto the non-Boolean case,", "start": 1348.02, "duration": 5.13}, {"text": "using the\narithmetization method.", "start": 1353.15, "duration": 2.38}, {"text": "So first of all, arithmetization\nis a simulation of and and", "start": 1355.53, "duration": 3.2}, {"text": "or with plus and times,\nsuch that if I think", "start": 1358.73, "duration": 3.84}, {"text": "about true as a 1\nand false as a 0,", "start": 1362.57, "duration": 7.71}, {"text": "this is going to give me\na faithful simulation.", "start": 1370.28, "duration": 2.31}, {"text": "It's going to do\nthe right thing.", "start": 1372.59, "duration": 2.16}, {"text": "It's going to compute exactly\nthe same values that we expect.", "start": 1374.75, "duration": 3.18}, {"text": "So like a and b, well,\ntimes works just like and.", "start": 1377.93, "duration": 6.27}, {"text": "It does for 1 and 0\nas true and false,", "start": 1388.97, "duration": 4.05}, {"text": "times exactly works like and.", "start": 1393.02, "duration": 3.39}, {"text": "And negation is 1 minus.", "start": 1396.41, "duration": 4.82}, {"text": "Or is going to be the\nsum minus the product.", "start": 1401.23, "duration": 5.13}, {"text": "And then, these just give\nyou the right values, a or b.", "start": 1406.36, "duration": 4.8}, {"text": "If you just calculate it\nout by plugging in 1s or 0s,", "start": 1411.16, "duration": 3.33}, {"text": "you get the right answer just\nby using this arithmetic.", "start": 1414.49, "duration": 2.61}, {"text": "So now, what we're going to do,\ninstead of using the Boolean", "start": 1419.82, "duration": 3.81}, {"text": "labeling, we'll just use\nthe arithmetical labeling.", "start": 1423.63, "duration": 2.25}, {"text": "But it's going to compute\nexactly the same thing", "start": 1425.88, "duration": 2.76}, {"text": "because the arithmetic\nsimulates the Boolean.", "start": 1428.64, "duration": 5.07}, {"text": "So we always go\nthrough the start node.", "start": 1433.71, "duration": 3.19}, {"text": "So there's no question about\nlabeling the very start", "start": 1436.9, "duration": 3.5}, {"text": "node with a 1.", "start": 1440.4, "duration": 1.14}, {"text": "But now, I'm going to\ngive expressions just", "start": 1441.54, "duration": 2.37}, {"text": "like the Boolean\nexpressions, but now they're", "start": 1443.91, "duration": 1.95}, {"text": "going to use plus and times\ninstead of ands and ors.", "start": 1445.86, "duration": 3.63}, {"text": "So let's just see.", "start": 1449.49, "duration": 1.2}, {"text": "Remember what we\ndid from before.", "start": 1450.69, "duration": 1.65}, {"text": "We had a and xi for this edge.", "start": 1452.34, "duration": 3.69}, {"text": "I'm going to replace that.", "start": 1456.03, "duration": 1.14}, {"text": "What is and?", "start": 1457.17, "duration": 0.96}, {"text": "We just look up\nhere in our table,", "start": 1458.13, "duration": 1.83}, {"text": "in our translation table.", "start": 1459.96, "duration": 2.37}, {"text": "And becomes times.", "start": 1462.33, "duration": 1.84}, {"text": "So we're going to replace\nthat with a times xi.", "start": 1464.17, "duration": 2.385}, {"text": "And it's going to\nwork exactly the same.", "start": 1469.24, "duration": 2.23}, {"text": "But the difference is that\nthis makes sense even when we", "start": 1471.47, "duration": 4.97}, {"text": "have non-Boolean values.", "start": 1476.44, "duration": 2.94}, {"text": "Times and plus are defined\nfor non-Boolean values,", "start": 1479.38, "duration": 6.1}, {"text": "whereas ands and or are not.", "start": 1485.48, "duration": 2.83}, {"text": "So what goes down on this edge?", "start": 1488.31, "duration": 2.67}, {"text": "Well, this was a and\nthe complement of xi,", "start": 1490.98, "duration": 3.09}, {"text": "as you remember.", "start": 1494.07, "duration": 2.46}, {"text": "So that's going to become\na times 1 minus xi.", "start": 1496.53, "duration": 4.16}, {"text": "And then similarly,\nwe had or over here.", "start": 1500.69, "duration": 3.972}, {"text": "And here's a little\nbit of a trick,", "start": 1504.662, "duration": 1.458}, {"text": "but that's going to be\nimportant for the analysis", "start": 1506.12, "duration": 3.42}, {"text": "that we're going to do.", "start": 1509.54, "duration": 1.05}, {"text": "Instead of using the recipe for\nor in terms of plus and times,", "start": 1510.59, "duration": 6.72}, {"text": "we're going to have\nsomething a little simpler.", "start": 1517.31, "duration": 2.56}, {"text": "It's just going to be the sum.", "start": 1519.87, "duration": 1.58}, {"text": "And the reason why that works--", "start": 1521.45, "duration": 2.28}, {"text": "good to understand-- is that\nbecause of the acyclic nature", "start": 1523.73, "duration": 5.1}, {"text": "of the branching programs,\nat most, one of these edges", "start": 1528.83, "duration": 3.51}, {"text": "can have a path through it.", "start": 1532.34, "duration": 1.96}, {"text": "So this is a kind\nof very special", "start": 1534.3, "duration": 1.67}, {"text": "or, sometimes called\nthe disjoint or.", "start": 1535.97, "duration": 4.55}, {"text": "You're not allowed to have more\nthan one of the values be 1,", "start": 1540.52, "duration": 4.29}, {"text": "because that never happens when\nyou have an acyclical graph.", "start": 1544.81, "duration": 3.0}, {"text": "You can never have the path\ncoming down this way, and then,", "start": 1547.81, "duration": 2.55}, {"text": "again, coming down that way.", "start": 1550.36, "duration": 1.35}, {"text": "Then it would be\nentering that node twice.", "start": 1551.71, "duration": 1.92}, {"text": "Have to be a cycle.", "start": 1553.63, "duration": 2.0}, {"text": "So it's going to be\ngood enough for us,", "start": 1555.63, "duration": 1.98}, {"text": "and necessary for us to\nrepresent this or as a sum.", "start": 1557.61, "duration": 6.81}, {"text": "OK.", "start": 1564.42, "duration": 1.96}, {"text": "So I think that's all I\nwanted to say on this slide.", "start": 1566.38, "duration": 4.14}, {"text": "So somebody is asking,\nis it possible for some", "start": 1570.52, "duration": 2.12}, {"text": "of these values to be negative?", "start": 1572.64, "duration": 1.47}, {"text": "Yes.", "start": 1574.11, "duration": 1.868}, {"text": "As it stands right now, some of\nthese values can be negative.", "start": 1575.978, "duration": 2.542}, {"text": "I haven't put any\nrestriction on what", "start": 1578.52, "duration": 1.542}, {"text": "the values are going to be.", "start": 1580.062, "duration": 2.728}, {"text": "So the input could\nbe a negative number.", "start": 1582.79, "duration": 1.86}, {"text": "And then, you're going to just\nget negative stuff happening.", "start": 1584.65, "duration": 3.08}, {"text": "In fact, there's\nsubtractions going on here.", "start": 1587.73, "duration": 3.13}, {"text": "So even with positive numbers--", "start": 1590.86, "duration": 1.34}, {"text": "I think we did an\nexample last time.", "start": 1592.2, "duration": 1.5}, {"text": "I think I'm going to do that\nexample again of exclusive", "start": 1593.7, "duration": 3.06}, {"text": "or, where you get negative\nnumbers coming up.", "start": 1596.76, "duration": 3.937}, {"text": "That doesn't matter.", "start": 1600.697, "duration": 0.833}, {"text": "But actually, what we're\ngoing to end up doing", "start": 1601.53, "duration": 2.31}, {"text": "is doing these calculations\nmodulo some prime number q.", "start": 1603.84, "duration": 8.09}, {"text": "OK.", "start": 1611.93, "duration": 0.9}, {"text": "I'm going to pick\nsome prime like 17,", "start": 1612.83, "duration": 2.79}, {"text": "and do all the\ncalculations mod 17.", "start": 1615.62, "duration": 2.91}, {"text": "And the reason for\ndoing it that way", "start": 1618.53, "duration": 1.74}, {"text": "is really because we're going\nto be picking random assignments", "start": 1620.27, "duration": 3.06}, {"text": "to the variables as our input.", "start": 1623.33, "duration": 3.78}, {"text": "And it makes the most\nsense to do that when", "start": 1627.11, "duration": 3.81}, {"text": "you have a finite set of\npossibilities to pick them up.", "start": 1630.92, "duration": 5.05}, {"text": "So we're not going to pick\nlike a random integer.", "start": 1635.97, "duration": 2.42}, {"text": "There's infinitely\nmany possibilities.", "start": 1638.39, "duration": 1.74}, {"text": "And yeah, you could set\nup a distribution there,", "start": 1640.13, "duration": 2.07}, {"text": "but that's very complicated.", "start": 1642.2, "duration": 1.47}, {"text": "That actually might work.", "start": 1643.67, "duration": 1.17}, {"text": "I'm not sure.", "start": 1644.84, "duration": 0.66}, {"text": "I haven't actually gone\nthrough that analysis.", "start": 1645.5, "duration": 2.07}, {"text": "But the typical\nway people do this", "start": 1647.57, "duration": 1.59}, {"text": "is by looking at what's\ncalled a finite field.", "start": 1649.16, "duration": 2.4}, {"text": "So I'll talk about\nthat in a second.", "start": 1651.56, "duration": 3.58}, {"text": "Why is there at most one\n1 among a1, a2, and a3?", "start": 1655.14, "duration": 2.88}, {"text": "The 1s-- I'll say once\nagain-- but the 1s correspond", "start": 1662.01, "duration": 3.6}, {"text": "to the path.", "start": 1665.61, "duration": 1.24}, {"text": "So this is a 1 if the\npath went this way.", "start": 1666.85, "duration": 3.23}, {"text": "Just think about it.", "start": 1670.08, "duration": 1.17}, {"text": "The path cannot go through\na1 and can, at the same time,", "start": 1671.25, "duration": 4.92}, {"text": "go through a2, because that\nmeans the path went through", "start": 1676.17, "duration": 3.24}, {"text": "this node.", "start": 1679.41, "duration": 1.02}, {"text": "Then, how is it going\nto get over to a2?", "start": 1680.43, "duration": 2.64}, {"text": "It's going to go\nthrough that node twice.", "start": 1683.07, "duration": 2.47}, {"text": "In an acyclic graph, you cannot\nhave a path going through", "start": 1685.54, "duration": 3.42}, {"text": "it's the same node\nmore than once.", "start": 1688.96, "duration": 2.83}, {"text": "So you're going to have\nto think about that.", "start": 1691.79, "duration": 4.62}, {"text": "OK, let's move on.", "start": 1696.41, "duration": 3.008}, {"text": "So now we're going to\ntalk about the same--", "start": 1699.418, "duration": 1.792}, {"text": "we're going to look at that\nnon-Boolean labeling applied", "start": 1704.52, "duration": 3.98}, {"text": "to an example.", "start": 1708.5, "duration": 1.0}, {"text": "So here is a very\nsimple branching program", "start": 1709.5, "duration": 3.23}, {"text": "that actually\ncomputes the exclusive", "start": 1712.73, "duration": 1.59}, {"text": "or function in\nthe Boolean world.", "start": 1714.32, "duration": 1.56}, {"text": "So this is the\nlabeling that I just", "start": 1718.84, "duration": 2.6}, {"text": "developed for you, the\narithmetical labeling.", "start": 1721.44, "duration": 6.06}, {"text": "And we always label\nthe start node with 1,", "start": 1727.5, "duration": 1.8}, {"text": "because the path always\ngoes through there.", "start": 1729.3, "duration": 2.61}, {"text": "And now, let's look at this\nbefore we jump ahead, let's", "start": 1731.91, "duration": 3.21}, {"text": "look at this edge here.", "start": 1735.12, "duration": 2.85}, {"text": "Remember what it is.", "start": 1737.97, "duration": 0.9}, {"text": "We have to apply this rule here.", "start": 1738.87, "duration": 1.62}, {"text": "This is the one edge\ncoming out of a node that", "start": 1740.49, "duration": 2.13}, {"text": "already is labeled.", "start": 1742.62, "duration": 2.01}, {"text": "So it's that label on\nthat node times the xi.", "start": 1744.63, "duration": 4.173}, {"text": "Because if you're thinking\nabout it, that, that's the and,", "start": 1748.803, "duration": 2.417}, {"text": "captures the and.", "start": 1751.22, "duration": 1.47}, {"text": "So it's just a times xi.", "start": 1752.69, "duration": 2.64}, {"text": "So it's x1, in this case.", "start": 1755.33, "duration": 2.59}, {"text": "So x1 is a 2 in our input.", "start": 1757.92, "duration": 4.8}, {"text": "So it's going to be\n1, which is the a,", "start": 1762.72, "duration": 2.39}, {"text": "times the x1, which is 2.", "start": 1765.11, "duration": 1.65}, {"text": "So this edge gets labeled 2.", "start": 1766.76, "duration": 4.87}, {"text": "Now this-- well, OK, let's\nlook at this edge now.", "start": 1771.63, "duration": 2.1}, {"text": "I think that's next.", "start": 1773.73, "duration": 1.98}, {"text": "This is the 1 minus xi,\nit's the 1 minus x1.", "start": 1775.71, "duration": 3.06}, {"text": "So it's 1 minus 2.", "start": 1778.77, "duration": 0.96}, {"text": "So you're going to\nend up with a minus 1.", "start": 1779.73, "duration": 1.708}, {"text": "1 minus times minus 2.", "start": 1781.438, "duration": 1.682}, {"text": "1 times 1 minus 2, which is\nminus 1, so it's a minus 1.", "start": 1783.12, "duration": 6.52}, {"text": "Now we're going to label these\ntwo nodes using the other rule.", "start": 1789.64, "duration": 3.9}, {"text": "So this gets a 2 because that's\na sum of the incoming edges.", "start": 1793.54, "duration": 2.91}, {"text": "This gets a minus\n1, because that's", "start": 1796.45, "duration": 1.5}, {"text": "the sum of its incoming edges.", "start": 1797.95, "duration": 2.35}, {"text": "And now we're going to look at--", "start": 1800.3, "duration": 1.595}, {"text": "which order did I do this in?", "start": 1806.92, "duration": 1.38}, {"text": "OK, I'm going to\ndo this edge now.", "start": 1808.3, "duration": 5.62}, {"text": "0 edge, which is going to be\n2 times 1 minus its variable.", "start": 1813.92, "duration": 6.63}, {"text": "So it's 1 minus x2.", "start": 1820.55, "duration": 1.97}, {"text": "X2 is a 3.", "start": 1822.52, "duration": 2.35}, {"text": "So it's 1 minus 3 to minus 2.", "start": 1824.87, "duration": 3.39}, {"text": "So 2 times minus 2 is minus 4.", "start": 1828.26, "duration": 3.207}, {"text": "OK, I don't want to\nrush through this.", "start": 1831.467, "duration": 1.583}, {"text": "No point in just blabbering on.", "start": 1833.05, "duration": 2.04}, {"text": "I'm just trying to work this\nexample so you get the idea.", "start": 1835.09, "duration": 4.93}, {"text": "OK, so could you fill this\nnext one out yourself?", "start": 1840.02, "duration": 3.25}, {"text": "So this is the one outgoing\nedge from this x2 node.", "start": 1843.27, "duration": 5.06}, {"text": "So x2 is labeled with 2 here.", "start": 1848.33, "duration": 6.52}, {"text": "So there's a is 2.", "start": 1854.85, "duration": 1.82}, {"text": "This is the one edge going out,\nso it's one on this side here.", "start": 1856.67, "duration": 3.22}, {"text": "So it's 2 times the x2. x2\nis a 3, so it's 2 times 3.", "start": 1859.89, "duration": 6.89}, {"text": "So this should be 6.", "start": 1866.78, "duration": 1.53}, {"text": "Oops.", "start": 1868.31, "duration": 1.98}, {"text": "Right here-- 6.", "start": 1870.29, "duration": 2.94}, {"text": "I'm going to do the same thing.", "start": 1873.23, "duration": 1.65}, {"text": "So x2 is labeled minus 1.", "start": 1874.88, "duration": 2.21}, {"text": "So minus 1 times 1 minus.", "start": 1882.13, "duration": 1.44}, {"text": "So you get a 2 here,\nyou get a minus 3 here,", "start": 1883.57, "duration": 3.84}, {"text": "just following, again,\nthe same process.", "start": 1887.41, "duration": 3.51}, {"text": "And now, what is the\nlabel on this 0 node here?", "start": 1890.92, "duration": 4.13}, {"text": "So again, you take the sum\nof its incoming labels.", "start": 1895.05, "duration": 3.61}, {"text": "So there was a 2 and a 6.", "start": 1898.66, "duration": 3.75}, {"text": "So that's an 8.", "start": 1902.41, "duration": 1.87}, {"text": "And this is a a minus 3\nand a minus 4 coming in.", "start": 1904.28, "duration": 6.14}, {"text": "So it's a minus 7.", "start": 1910.42, "duration": 1.25}, {"text": "What's the output?", "start": 1911.67, "duration": 1.65}, {"text": "The output is minus 7, because\nthat's the label on the 1 node.", "start": 1913.32, "duration": 4.37}, {"text": "OK, output is minus 7.", "start": 1917.69, "duration": 2.16}, {"text": "OK.", "start": 1919.85, "duration": 1.38}, {"text": "So this is going to\nbe our way of defining", "start": 1921.23, "duration": 5.76}, {"text": "the output of a\nbranching program when", "start": 1926.99, "duration": 4.71}, {"text": "it has a non-Boolean\nsetting on its inputs.", "start": 1931.7, "duration": 4.1}, {"text": "If you had the Boolean\nsetting on its inputs", "start": 1935.8, "duration": 2.91}, {"text": "and you followed this procedure,\nwhat would you get out?", "start": 1938.71, "duration": 2.895}, {"text": "You would get the\nsame answer that you", "start": 1945.64, "duration": 1.77}, {"text": "would get by following\nthe path because", "start": 1947.41, "duration": 3.34}, {"text": "the arithmetical simulation\nis a faithful simulation", "start": 1950.75, "duration": 5.24}, {"text": "of the ands and ors.", "start": 1955.99, "duration": 1.02}, {"text": "And the ands and\nors capture exactly", "start": 1957.01, "duration": 1.62}, {"text": "when-- what the path does.", "start": 1958.63, "duration": 1.26}, {"text": "So this is a strict\nextension of the operation", "start": 1962.41, "duration": 4.5}, {"text": "of the branching program\ninto a new realm,", "start": 1966.91, "duration": 2.73}, {"text": "these non-Boolean values.", "start": 1969.64, "duration": 1.77}, {"text": "On the old realm, it behaves\njust as it did originally.", "start": 1971.41, "duration": 3.82}, {"text": "And that's critical\nto understand that.", "start": 1975.23, "duration": 2.42}, {"text": "Yeah, somebody's asking what\nthe final value of the 0s,", "start": 1983.788, "duration": 2.292}, {"text": "they'd also be the same.", "start": 1986.08, "duration": 1.0}, {"text": "Sure.", "start": 1987.08, "duration": 1.07}, {"text": "In the Boolean case, if we\nfollow this in the Boolean", "start": 1988.15, "duration": 4.71}, {"text": "cases, all of the labels would\nbe exactly what they were.", "start": 1992.86, "duration": 4.47}, {"text": "They would just be the 0s and\n1s that we had from before.", "start": 1997.33, "duration": 4.665}, {"text": "So does this exactly mimic x\nor if you take this all mod 2?", "start": 2008.82, "duration": 5.785}, {"text": "I don't know.", "start": 2018.9, "duration": 0.64}, {"text": "I'd have to think about that.", "start": 2019.54, "duration": 1.28}, {"text": "I don't think that\nthat's essential.", "start": 2020.82, "duration": 2.55}, {"text": "In this case, it\nmight behave correctly", "start": 2023.37, "duration": 2.16}, {"text": "if you take the\nanswer mod 2 for XOR.", "start": 2025.53, "duration": 2.85}, {"text": "But the XOR is going\nto be very special.", "start": 2028.38, "duration": 1.77}, {"text": "And I'm not sure.", "start": 2030.15, "duration": 0.78}, {"text": "That might happen to be true.", "start": 2030.93, "duration": 2.083}, {"text": "I'd have to think\nabout it for a second,", "start": 2033.013, "duration": 1.667}, {"text": "but I'm not sure\nthat's relevant.", "start": 2034.68, "duration": 4.085}, {"text": "OK, so this is a good question.", "start": 2043.978, "duration": 1.292}, {"text": "If I picked a different\nbranching program that also", "start": 2045.27, "duration": 3.6}, {"text": "implements XOR-- or--", "start": 2048.87, "duration": 3.5}, {"text": "so it would be an equivalent\nbranching program--", "start": 2052.37, "duration": 2.46}, {"text": "would it behave the same way\non the non-Boolean values?", "start": 2054.83, "duration": 4.395}, {"text": "And the answer to\nthat is yes and no.", "start": 2061.84, "duration": 4.413}, {"text": "You understand the question?", "start": 2066.253, "duration": 1.167}, {"text": "It's a very good question.", "start": 2067.42, "duration": 1.09}, {"text": "And actually, we're going to\nprove this in the analysis.", "start": 2068.51, "duration": 6.238}, {"text": "It's going to be easy to\nprove because I gave you", "start": 2074.748, "duration": 2.042}, {"text": "both possibilities, yes and no.", "start": 2076.79, "duration": 1.83}, {"text": "But let me tell you\nwhat I mean by that.", "start": 2078.62, "duration": 3.098}, {"text": "So you understand the question.", "start": 2081.718, "duration": 1.292}, {"text": "Suppose I had a different\nbranching program.", "start": 2083.01, "duration": 1.7}, {"text": "I'm not sure you can come up\nwith a different branching", "start": 2084.71, "duration": 2.292}, {"text": "program, but let's\nsay you could.", "start": 2087.002, "duration": 2.045}, {"text": "You have a different\nbranching program, yeah, sure", "start": 2089.047, "duration": 2.083}, {"text": "you can come--", "start": 2091.13, "duration": 0.54}, {"text": "you can do the variables in a\ndifferent order, for example.", "start": 2091.67, "duration": 2.469}, {"text": "So suppose you come up with\na different branching program", "start": 2094.139, "duration": 3.111}, {"text": "that gives you XOR.", "start": 2097.25, "duration": 2.97}, {"text": "And now you plugged in 2 and 3.", "start": 2100.22, "duration": 3.15}, {"text": "Would I always get\nthe same value out?", "start": 2103.37, "duration": 4.16}, {"text": "Yes, if that other branching\nprogram was read-once.", "start": 2107.53, "duration": 5.62}, {"text": "No, not necessarily\nif it's not read-once.", "start": 2113.15, "duration": 4.5}, {"text": "And that's why\nread-once is critical.", "start": 2120.16, "duration": 1.725}, {"text": "As we will prove, for two\nread-once branching programs,", "start": 2124.5, "duration": 4.67}, {"text": "if they behave the same\nway on the Boolean values,", "start": 2129.17, "duration": 4.53}, {"text": "they behave the same way even\non the non-Boolean values.", "start": 2133.7, "duration": 3.525}, {"text": "That's not necessarily true if\nthe branching programs are not", "start": 2140.16, "duration": 3.36}, {"text": "read-once.", "start": 2143.52, "duration": 0.72}, {"text": "OK, we will see that.", "start": 2149.69, "duration": 1.95}, {"text": "We will prove that and use that.", "start": 2151.64, "duration": 4.72}, {"text": "That's going to be important.", "start": 2156.36, "duration": 2.53}, {"text": "OK, so here is the\nalgorithm sketch,", "start": 2158.89, "duration": 1.8}, {"text": "which is kind of a little\nbit even sort of suggested", "start": 2160.69, "duration": 2.4}, {"text": "by that very good question.", "start": 2163.09, "duration": 3.165}, {"text": "So what we're going\nto do is we want", "start": 2170.32, "duration": 1.5}, {"text": "to take the two branching\nprograms that we're trying", "start": 2171.82, "duration": 4.98}, {"text": "to test if they're equivalent.", "start": 2176.8, "duration": 2.1}, {"text": "We're going to pick a random\nnon-Boolean input assignment--", "start": 2178.9, "duration": 3.48}, {"text": "so set the values here\nchosen from the field,", "start": 2182.38, "duration": 3.15}, {"text": "but we'll get there.", "start": 2185.53, "duration": 1.71}, {"text": "A random value for x1, random\nvalue for x2, and so on.", "start": 2187.24, "duration": 5.4}, {"text": "These could be numbers like\n17, and 25, and 23, and so on.", "start": 2192.64, "duration": 4.35}, {"text": "And then, using this process,\nrun the branching programs", "start": 2196.99, "duration": 4.77}, {"text": "to evaluate them on that\nnon-Boolean assignment.", "start": 2201.76, "duration": 3.66}, {"text": "If they disagree,\nthen we're going", "start": 2205.42, "duration": 2.64}, {"text": "to know that the two branching\nprograms were not equivalent,", "start": 2208.06, "duration": 3.09}, {"text": "even on the non-Boolean case.", "start": 2211.15, "duration": 3.95}, {"text": "Even on the Boolean case.", "start": 2215.1, "duration": 1.14}, {"text": "Did I say that wrong?", "start": 2216.24, "duration": 0.88}, {"text": "So if they disagree, even\non the non-Boolean case,", "start": 2217.12, "duration": 2.69}, {"text": "they have to be an equivalent\neven in the Boolean case.", "start": 2219.81, "duration": 3.39}, {"text": "Not obvious.", "start": 2223.2, "duration": 2.71}, {"text": "But if they agree, then\nit's not a guarantee", "start": 2225.91, "duration": 4.955}, {"text": "that they're\nequivalent, but it's", "start": 2230.865, "duration": 1.375}, {"text": "going to be very strong evidence\nthat they're equivalent.", "start": 2232.24, "duration": 4.537}, {"text": "OK, so that's where the\nprobabilistic nature", "start": 2236.777, "duration": 1.833}, {"text": "is going to come in.", "start": 2238.61, "duration": 3.04}, {"text": "So we're going to prove that.", "start": 2241.65, "duration": 1.93}, {"text": "So first, we have to\ndevelop an algebraic fact.", "start": 2243.58, "duration": 4.25}, {"text": "And that involves polynomials.", "start": 2247.83, "duration": 2.672}, {"text": "This is a simple thing\nthat I think many of you", "start": 2250.502, "duration": 1.958}, {"text": "have run into already,\nperhaps even in high school.", "start": 2252.46, "duration": 5.25}, {"text": "I'm not going to prove\nthe algebraic facts,", "start": 2257.71, "duration": 1.86}, {"text": "but I'm going to state them.", "start": 2259.57, "duration": 0.93}, {"text": "And actually, the\nproofs are not hard.", "start": 2260.5, "duration": 1.29}, {"text": "They're in the textbook.", "start": 2261.79, "duration": 1.0}, {"text": "So suppose we have a\npolynomial of degree d here.", "start": 2265.315, "duration": 4.455}, {"text": "It happens to have p.", "start": 2269.77, "duration": 1.185}, {"text": "So there's a bunch of constants.", "start": 2270.955, "duration": 3.315}, {"text": "These a's are constants.", "start": 2274.27, "duration": 1.62}, {"text": "x is the variable\nof the polynomial.", "start": 2275.89, "duration": 2.52}, {"text": "And I presume you've seen\npolynomials written out", "start": 2278.41, "duration": 2.97}, {"text": "like this.", "start": 2281.38, "duration": 1.54}, {"text": "And so if you assign x to some\nvalue, some constant value z,", "start": 2282.92, "duration": 7.93}, {"text": "and the polynomial\nevaluates to 0,", "start": 2290.85, "duration": 3.78}, {"text": "we often call that a\nroot of the polynomial.", "start": 2294.63, "duration": 2.58}, {"text": "So these are the places where\nthe polynomial evaluates to 0", "start": 2300.92, "duration": 3.082}, {"text": "that I've of shown over here.", "start": 2304.002, "duration": 1.208}, {"text": "Those are the roots.", "start": 2305.21, "duration": 0.84}, {"text": "It's not hard to show that a\nlow-degree polynomial cannot", "start": 2309.92, "duration": 3.93}, {"text": "have lots of roots.", "start": 2313.85, "duration": 2.61}, {"text": "Basically, if the polynomial\nhas degree at most d,", "start": 2316.46, "duration": 3.12}, {"text": "it can have at most d roots,\nas long as the polynomial", "start": 2319.58, "duration": 2.79}, {"text": "itself is not the\neverywhere 0 polynomial,", "start": 2322.37, "duration": 3.36}, {"text": "because obviously, then\neverything is a root.", "start": 2325.73, "duration": 2.31}, {"text": "Oops, typo.", "start": 2331.05, "duration": 1.47}, {"text": "Thank you.", "start": 2332.52, "duration": 0.78}, {"text": "Should be d minus 2 over there.", "start": 2333.3, "duration": 1.68}, {"text": "Pretend that's a 2.", "start": 2339.14, "duration": 1.08}, {"text": "All right, so if we have\na low-degree polynomial--", "start": 2343.14, "duration": 6.175}, {"text": "let's not get\nahead of ourselves.", "start": 2349.315, "duration": 1.375}, {"text": "If we have a\nlow-degree polynomial,", "start": 2350.69, "duration": 3.1}, {"text": "a polynomial of degree at most\nd, it has at most d roots.", "start": 2353.79, "duration": 3.72}, {"text": "And that's a simple proof.", "start": 2357.51, "duration": 1.98}, {"text": "The basic idea is\nevery time you have", "start": 2359.49, "duration": 2.32}, {"text": "a-- if you have a root\nof the polynomial,", "start": 2361.81, "duration": 2.84}, {"text": "so if setting x equal to 5 gives\nyou a root of the polynomial,", "start": 2364.65, "duration": 10.68}, {"text": "it's a 0 of the polynomial,\nthen x-- you can easily to see", "start": 2375.33, "duration": 3.51}, {"text": "that x minus 5 is a\nfactor of the polynomial.", "start": 2378.84, "duration": 2.43}, {"text": "You can divide by x minus 5,\nand you get a new polynomial", "start": 2385.54, "duration": 3.2}, {"text": "of degree one less.", "start": 2388.74, "duration": 1.39}, {"text": "And you can just, which\nis going by induction,", "start": 2390.13, "duration": 3.86}, {"text": "has one fewer root.", "start": 2393.99, "duration": 3.09}, {"text": "So you can just divide out\nby the roots, basically.", "start": 2397.08, "duration": 2.37}, {"text": "It's very straightforward.", "start": 2399.45, "duration": 1.968}, {"text": "And other very important thing--", "start": 2410.09, "duration": 4.14}, {"text": "if I have two polynomials\nthat are both low-degree,", "start": 2414.23, "duration": 4.68}, {"text": "they cannot agree\non very many places.", "start": 2418.91, "duration": 2.88}, {"text": "That follows from what\nI just proved above.", "start": 2424.88, "duration": 4.26}, {"text": "Because what I'll do is I\ntake those two polynomials,", "start": 2429.14, "duration": 3.12}, {"text": "and they look at the\ndifference, which is also", "start": 2432.26, "duration": 2.28}, {"text": "a low-degree polynomial.", "start": 2434.54, "duration": 1.86}, {"text": "Every time there's an\nagreement between those two", "start": 2436.4, "duration": 2.55}, {"text": "original polynomials,\nthere's a zero", "start": 2438.95, "duration": 2.49}, {"text": "of the difference polynomial.", "start": 2441.44, "duration": 2.25}, {"text": "And because that difference\npolynomial cannot have too many", "start": 2443.69, "duration": 2.55}, {"text": "zeroes, the two original\npolynomials cannot have too", "start": 2446.24, "duration": 2.82}, {"text": "many agreements.", "start": 2449.06, "duration": 0.93}, {"text": "So the corollary is that if\nx and y are both polynomials", "start": 2453.27, "duration": 3.24}, {"text": "of degree at most d, and\nthey're not the same polynomial,", "start": 2456.51, "duration": 3.9}, {"text": "because then the difference\nwould be the 0 polynomial,", "start": 2460.41, "duration": 3.37}, {"text": "then the number of places where\nthey're equal is at most d.", "start": 2463.78, "duration": 4.05}, {"text": "So the proof is\njust letting p be", "start": 2467.83, "duration": 1.68}, {"text": "the difference of p1 and p2--", "start": 2469.51, "duration": 3.41}, {"text": "very standard kind of a trick.", "start": 2472.92, "duration": 2.7}, {"text": "Now the above is going\nto hold for any field.", "start": 2475.62, "duration": 3.57}, {"text": "A field is just a set\nwith plus and times", "start": 2479.19, "duration": 3.0}, {"text": "with the familiar properties\nof distributive law and so on", "start": 2482.19, "duration": 5.19}, {"text": "and identities and\nall the stuff that you", "start": 2487.38, "duration": 2.61}, {"text": "would expect plus and times\nto have in the normal world.", "start": 2489.99, "duration": 4.36}, {"text": "And so we're going to talk\nabout the finite field that", "start": 2494.35, "duration": 4.16}, {"text": "has only q elements--", "start": 2498.51, "duration": 3.3}, {"text": "that has exactly q elements,\nwhere q is a prime number.", "start": 2501.81, "duration": 3.032}, {"text": "So it turns out that-- and I'm\nnot going to prove all this,", "start": 2504.842, "duration": 2.458}, {"text": "but it's pretty simple stuff--", "start": 2507.3, "duration": 2.31}, {"text": "that if you just take the\nnumbers from 1 to q minus 1--", "start": 2509.61, "duration": 5.1}, {"text": "from 0 to q minus 1, and\nuse plus n times mod q,", "start": 2514.71, "duration": 6.69}, {"text": "that has all the right\nproperties to be a field.", "start": 2521.4, "duration": 4.54}, {"text": "So just think of it--", "start": 2525.94, "duration": 1.41}, {"text": "just modular arithmetic,\nmod some prime q.", "start": 2527.35, "duration": 4.98}, {"text": "And then we can in a natural\nway pick a random assignment", "start": 2532.33, "duration": 7.78}, {"text": "to a variable from the field\nbecause it's just choosing", "start": 2540.11, "duration": 4.05}, {"text": "from among q possibilities.", "start": 2544.16, "duration": 1.927}, {"text": "Yeah, so getting\na question here.", "start": 2557.505, "duration": 1.375}, {"text": "The coefficients of the\npolynomial and the assignment", "start": 2558.88, "duration": 4.23}, {"text": "to the variables-- they're all\ngoing to come from this field.", "start": 2563.11, "duration": 3.3}, {"text": "So everything's going to\nbe operating in this field.", "start": 2566.41, "duration": 6.38}, {"text": "Don't let that throw you off.", "start": 2572.79, "duration": 3.57}, {"text": "Just your ordinary intuition\nabout the way arithmetic works", "start": 2576.36, "duration": 3.218}, {"text": "is going to be just fine.", "start": 2579.578, "duration": 1.042}, {"text": "But this is important here from\nthe perspective of thinking", "start": 2591.53, "duration": 2.79}, {"text": "about this probabilistically.", "start": 2594.32, "duration": 1.32}, {"text": "So I'm going to rethink about\nthis polynomial lemma, which", "start": 2595.64, "duration": 2.67}, {"text": "says there are not\ntoo many roots.", "start": 2598.31, "duration": 3.42}, {"text": "In terms of the\nprobability of picking", "start": 2601.73, "duration": 2.13}, {"text": "an element of the field,\nwhat are the chances", "start": 2603.86, "duration": 2.28}, {"text": "that it happens to be a root?", "start": 2606.14, "duration": 2.94}, {"text": "So if you have a\nlow-degree polynomial,", "start": 2609.08, "duration": 3.38}, {"text": "and you pick a random\nvalue in the field,", "start": 2612.46, "duration": 3.49}, {"text": "what's the probability\nthat you've got a root?", "start": 2615.95, "duration": 3.65}, {"text": "Well, it's just the\nnumber of roots divided", "start": 2619.6, "duration": 1.86}, {"text": "by the size of the field.", "start": 2621.46, "duration": 2.438}, {"text": "So if you have this\nreally big field,", "start": 2623.898, "duration": 1.542}, {"text": "and you have this\nlow-degree polynomial,", "start": 2625.44, "duration": 1.71}, {"text": "it's going to be pretty\nunlikely that you're", "start": 2627.15, "duration": 3.33}, {"text": "going to end up picking one of\nthe zeroes, one of the roots,", "start": 2630.48, "duration": 5.04}, {"text": "just at random.", "start": 2635.52, "duration": 1.63}, {"text": "That's all that this is saying.", "start": 2637.15, "duration": 3.53}, {"text": "So there's at most d roots\nout of the q possibilities.", "start": 2640.68, "duration": 3.33}, {"text": "And the last thing I'm\ngoing to introduce here", "start": 2644.01, "duration": 2.4}, {"text": "is the multivariable\nversion of this", "start": 2646.41, "duration": 4.93}, {"text": "which is called, perhaps\nsomewhat unfairly,", "start": 2651.34, "duration": 3.08}, {"text": "but it's called the\nSchwartz-Zippel lemma,", "start": 2654.42, "duration": 3.99}, {"text": "though in various forms, it had\nbeen known prior to their work.", "start": 2658.41, "duration": 7.47}, {"text": "In some cases, the literature\nactually goes back a long ways.", "start": 2665.88, "duration": 5.23}, {"text": "But anyway, this is called\nthe Schwartz-Zippel lemma.", "start": 2671.11, "duration": 2.91}, {"text": "Doesn't really matter,\nexcept to the people whose", "start": 2674.02, "duration": 7.55}, {"text": "credit is being denied.", "start": 2681.57, "duration": 1.62}, {"text": "But that's not one of us.", "start": 2683.19, "duration": 2.98}, {"text": "So anyway, the Schwartz-Zippel\nlemma says that if you have now", "start": 2686.17, "duration": 3.47}, {"text": "a polynomial in\nseveral variables,", "start": 2689.64, "duration": 2.44}, {"text": "which is not the 0 polynomial,\nwhere each variable has low", "start": 2692.08, "duration": 3.62}, {"text": "degree--", "start": 2695.7, "duration": 0.88}, {"text": "so if I say if it has\ndegree at most d in each xi.", "start": 2696.58, "duration": 4.34}, {"text": "So each variable is going to\nhave at most an exponent of d", "start": 2700.92, "duration": 3.09}, {"text": "appearing in that polynomial.", "start": 2704.01, "duration": 3.37}, {"text": "And now if we pick random values\nto assign to all of those n", "start": 2707.38, "duration": 5.27}, {"text": "variables from the\nfield, the probability", "start": 2712.65, "duration": 4.53}, {"text": "that we ended up with a root,\nthat we ended up with a 0,", "start": 2717.18, "duration": 5.17}, {"text": "is something you can bound.", "start": 2722.35, "duration": 2.39}, {"text": "So it's m times d, so\nthe number of variables", "start": 2724.74, "duration": 3.23}, {"text": "times this maximum\ndegree, divided", "start": 2727.97, "duration": 2.73}, {"text": "by the size of the field.", "start": 2730.7, "duration": 2.29}, {"text": "And this is going to\ncome up later for us.", "start": 2732.99, "duration": 3.5}, {"text": "And this is another fairly\nsimple proof, a little bit more", "start": 2736.49, "duration": 5.6}, {"text": "sophisticated than the\none that we had above.", "start": 2742.09, "duration": 1.89}, {"text": "And in fact, it uses that one as\na lemma to prove this theorem.", "start": 2743.98, "duration": 8.37}, {"text": "So we're going to--", "start": 2752.35, "duration": 1.742}, {"text": "not going to prove any of that,\nbut I refer you to the book", "start": 2754.092, "duration": 2.458}, {"text": "if you're curious.", "start": 2756.55, "duration": 0.75}, {"text": "Yeah, so a couple of\ngood questions here.", "start": 2768.31, "duration": 2.98}, {"text": "What happens if these values\nare bigger than q, for example?", "start": 2771.29, "duration": 4.352}, {"text": "Then it's not\ntelling you anything.", "start": 2775.642, "duration": 1.458}, {"text": "If d is bigger than\nq, m is bigger than q,", "start": 2777.1, "duration": 2.13}, {"text": "or the product is bigger than\nq, then you learn nothing", "start": 2779.23, "duration": 5.07}, {"text": "from this lemma--", "start": 2784.3, "duration": 0.93}, {"text": "from this theorem.", "start": 2785.23, "duration": 1.5}, {"text": "So typically in applications,\nyou're going to pick a large--", "start": 2786.73, "duration": 4.848}, {"text": "you're going to have\nthe flexibility.", "start": 2791.578, "duration": 1.542}, {"text": "You get to choose q to be\nsomething that you want.", "start": 2793.12, "duration": 3.13}, {"text": "So we're going to pick\nthe field to be big", "start": 2796.25, "duration": 1.94}, {"text": "enough so that the m and d are\ngoing to be relatively small.", "start": 2798.19, "duration": 7.67}, {"text": "In fact, d is going to end\nup being 1, as we will see.", "start": 2805.86, "duration": 4.03}, {"text": "And m is the number\nof variables.", "start": 2809.89, "duration": 1.42}, {"text": "So we're going to\npick q, which is", "start": 2811.31, "duration": 1.43}, {"text": "going to be substantially larger\nthan the number of variables.", "start": 2812.74, "duration": 4.95}, {"text": "And how is the degree defined\nin multivariable polynomials?", "start": 2817.69, "duration": 3.615}, {"text": "If the polynomial has xy squared\nplus 3x to the 5th y squared z,", "start": 2821.305, "duration": 8.805}, {"text": "you just pull out each\nvariable separately.", "start": 2830.11, "duration": 2.73}, {"text": "And you look at the maximum\ndegree of that variable.", "start": 2832.84, "duration": 2.89}, {"text": "So the x in that case had\nhad a degree 5 appearance.", "start": 2835.73, "duration": 4.49}, {"text": "The y had a degree 2 appearance.", "start": 2840.22, "duration": 2.58}, {"text": "So you take the maximum\nover all of the variables", "start": 2842.8, "duration": 2.4}, {"text": "of the degree of that variable.", "start": 2845.2, "duration": 1.353}, {"text": "And that's going to be\nthe bound on the degree", "start": 2846.553, "duration": 1.917}, {"text": "of the polynomial.", "start": 2848.47, "duration": 1.86}, {"text": "So in fact, in our case,\nd is going to be 1.", "start": 2850.33, "duration": 3.545}, {"text": "So all of the\nvariables-- there's", "start": 2853.875, "duration": 1.375}, {"text": "not going to be any\nexponents on anything.", "start": 2855.25, "duration": 2.428}, {"text": "Everything is going\nto be exponent 1.", "start": 2857.678, "duration": 1.542}, {"text": "Is q related to the number\nwe choose for the mod?", "start": 2865.025, "duration": 2.385}, {"text": "Yeah, q is the number\nwe're choosing for the mod.", "start": 2867.41, "duration": 2.91}, {"text": "We're doing everything mod q.", "start": 2870.32, "duration": 1.35}, {"text": "So all the arithmetic is\ngoing to operate in mod q,", "start": 2875.56, "duration": 4.23}, {"text": "and that's the size of the\nfield that we're going to pick.", "start": 2879.79, "duration": 4.56}, {"text": "So I think we're\nhere at the break.", "start": 2887.07, "duration": 2.66}, {"text": "Happy to take some\nmore questions,", "start": 2889.73, "duration": 2.49}, {"text": "but why don't we\njust start that off.", "start": 2892.22, "duration": 1.59}, {"text": "And I will see you\nin five minutes.", "start": 2898.39, "duration": 4.15}, {"text": "But in the meantime, happy\nto shoot me questions.", "start": 2902.54, "duration": 3.68}, {"text": "So what happens if we use\nBoolean assignments in the XOR", "start": 2906.22, "duration": 2.335}, {"text": "example?", "start": 2908.555, "duration": 0.5}, {"text": "Would that work to be\nable to check agreement?", "start": 2913.47, "duration": 5.26}, {"text": "It would.", "start": 2924.25, "duration": 0.72}, {"text": "So it's hard to make an argument\nbased on just a single example.", "start": 2924.97, "duration": 7.29}, {"text": "I think the better\nthing would be", "start": 2932.26, "duration": 3.96}, {"text": "to look at two\nbranching programs that", "start": 2936.22, "duration": 9.5}, {"text": "just differ in a single place.", "start": 2945.72, "duration": 1.66}, {"text": "So I can even suggest two.", "start": 2947.38, "duration": 2.72}, {"text": "You can make a branching program\nthat always outputs true.", "start": 2950.1, "duration": 6.4}, {"text": "It doesn't even\nread its variables.", "start": 2956.5, "duration": 1.86}, {"text": "Or if it reads them, they\nalways go to the same place.", "start": 2958.36, "duration": 2.25}, {"text": "And it ends up always\nat the q output.", "start": 2960.61, "duration": 2.74}, {"text": "So you imagine a\nbranching program", "start": 2963.35, "duration": 1.568}, {"text": "that always outputs\n1, no matter what", "start": 2964.918, "duration": 1.542}, {"text": "the assignments to\nthe variables are.", "start": 2966.46, "duration": 1.542}, {"text": "And you can easily\nmake such a thing.", "start": 2968.002, "duration": 2.658}, {"text": "And then you make\nanother branching program", "start": 2970.66, "duration": 1.83}, {"text": "that computes the or function.", "start": 2972.49, "duration": 3.3}, {"text": "So it reads every variable.", "start": 2975.79, "duration": 1.46}, {"text": "And it's going to be 1 if\nany one of those variables", "start": 2977.25, "duration": 5.5}, {"text": "is set to 1.", "start": 2982.75, "duration": 0.78}, {"text": "So the only time\nthe or function is", "start": 2986.27, "duration": 3.66}, {"text": "0 is if everything is set to 0.", "start": 2989.93, "duration": 2.505}, {"text": "But now if you're\ntrying to randomly check", "start": 2995.17, "duration": 5.07}, {"text": "whether the always one function\nis equal to the or function--", "start": 3000.24, "duration": 5.093}, {"text": "of course, without knowing\nin advance what they are,", "start": 3005.333, "duration": 2.167}, {"text": "because that's cheating.", "start": 3007.5, "duration": 1.02}, {"text": "You're just given\nthese two functions,", "start": 3008.52, "duration": 2.04}, {"text": "and you want to know-- these\ntwo branching programs.", "start": 3010.56, "duration": 2.49}, {"text": "And you want to know,\nare they computing", "start": 3013.05, "duration": 1.68}, {"text": "the same thing or not?", "start": 3014.73, "duration": 2.67}, {"text": "And by this procedure\nof randomly sampling,", "start": 3017.4, "duration": 3.357}, {"text": "you're always going to get\nthese branching programs both", "start": 3020.757, "duration": 2.333}, {"text": "to say 1, unless you just happen\nto pick the random assignment", "start": 3023.09, "duration": 4.95}, {"text": "of everything set to 0.", "start": 3028.04, "duration": 2.69}, {"text": "And that's very unlikely that\nyou're going to pick that.", "start": 3030.73, "duration": 2.4}, {"text": "If you imagine you have--\nyour branching program", "start": 3033.13, "duration": 2.64}, {"text": "has 100 variables in it.", "start": 3035.77, "duration": 1.71}, {"text": "It's only 2 to the\nminus 100 chance", "start": 3037.48, "duration": 2.7}, {"text": "that you're going to set\nthem all to 0 randomly.", "start": 3040.18, "duration": 3.46}, {"text": "And so you're extremely\nunlikely to find", "start": 3043.64, "duration": 4.07}, {"text": "that one place of difference\nif there's only a single place.", "start": 3047.71, "duration": 3.39}, {"text": "If there's lots of\nplaces of difference,", "start": 3051.1, "duration": 1.83}, {"text": "then it's not so bad.", "start": 3052.93, "duration": 2.92}, {"text": "But if the number, the fraction\nof differences, is low,", "start": 3055.85, "duration": 2.788}, {"text": "you're going to have\nto do a lot of samples", "start": 3058.638, "duration": 1.792}, {"text": "in order to find that--", "start": 3060.43, "duration": 2.04}, {"text": "possibly exponentially\nmany samples.", "start": 3062.47, "duration": 1.95}, {"text": "And then you won't run\nin polynomial time.", "start": 3064.42, "duration": 2.13}, {"text": "So let me just see if\nthere's other questions here.", "start": 3066.55, "duration": 2.125}, {"text": "Why can we accept--", "start": 3071.1, "duration": 2.4}, {"text": "going back to the\nBoolean labeling", "start": 3073.5, "duration": 1.65}, {"text": "side, why can we accept that\nb1 equals b2 if b1 and b2", "start": 3075.15, "duration": 3.81}, {"text": "agree on--", "start": 3078.96, "duration": 1.82}, {"text": "only on just one\ninput assignment?", "start": 3080.78, "duration": 1.74}, {"text": "No, we didn't say that.", "start": 3082.52, "duration": 2.37}, {"text": "All right, I'll go back there.", "start": 3084.89, "duration": 1.53}, {"text": "Boolean assignment-- is this--", "start": 3086.42, "duration": 3.85}, {"text": "I'm not sure which one you mean.", "start": 3090.27, "duration": 1.56}, {"text": "Is this the one you mean?", "start": 3091.83, "duration": 2.12}, {"text": "I don't know--", "start": 3093.95, "duration": 0.99}, {"text": "Boolean labeling,\nso it must be it.", "start": 3094.94, "duration": 2.16}, {"text": "Why do we non-Boolean labeling?", "start": 3097.1, "duration": 3.87}, {"text": "No, I see what you're saying.", "start": 3113.19, "duration": 1.81}, {"text": "You're saying about this here.", "start": 3115.0, "duration": 1.25}, {"text": "We're just going to pick\none random assignment.", "start": 3116.25, "duration": 3.93}, {"text": "And if they agree on\nthat one random case,", "start": 3120.18, "duration": 3.87}, {"text": "then we will say accept,\nbecause you might think,", "start": 3124.05, "duration": 3.773}, {"text": "well, we should take a\nwhole bunch of samples.", "start": 3127.823, "duration": 1.917}, {"text": "That's a good question.", "start": 3129.74, "duration": 1.76}, {"text": "But in fact, we're going to\narrange the probability such", "start": 3131.5, "duration": 2.91}, {"text": "that if the two things\nare not equivalent, then", "start": 3134.41, "duration": 4.02}, {"text": "it's going to be--", "start": 3138.43, "duration": 2.91}, {"text": "the values will be\ndifferent almost everywhere,", "start": 3141.34, "duration": 2.04}, {"text": "or a large number of places.", "start": 3143.38, "duration": 1.99}, {"text": "So just picking one\nand having them agree", "start": 3145.37, "duration": 2.228}, {"text": "is going to be strong enough\nevidence that you're still", "start": 3147.598, "duration": 2.292}, {"text": "going to accept.", "start": 3149.89, "duration": 0.75}, {"text": "And you'll have still\na low probability", "start": 3150.64, "duration": 1.8}, {"text": "of getting an error.", "start": 3152.44, "duration": 1.7}, {"text": "You'd have to see the analysis.", "start": 3154.14, "duration": 3.453}, {"text": "Are we assuming the roots of\nthe polynomials are integers?", "start": 3157.593, "duration": 2.417}, {"text": "No, we're operating\nover a field here.", "start": 3160.01, "duration": 3.968}, {"text": "Even talking about integers\ndoesn't totally make sense.", "start": 3163.978, "duration": 2.292}, {"text": "But it doesn't really matter.", "start": 3166.27, "duration": 2.075}, {"text": "We're not assuming that.", "start": 3168.345, "duration": 1.0}, {"text": "Oh, I should have\ntaken this away.", "start": 3173.83, "duration": 3.21}, {"text": "The bound still works.", "start": 3177.04, "duration": 1.2}, {"text": "The bound still works even\nif we have non-integers.", "start": 3181.09, "duration": 6.86}, {"text": "I'm not sure if I'm\nbeing helpful here.", "start": 3187.95, "duration": 1.65}, {"text": "Why don't we just move on?", "start": 3189.6, "duration": 1.895}, {"text": "But we're not\nassuming that these", "start": 3191.495, "duration": 1.375}, {"text": "are integers because the\nbound doesn't matter.", "start": 3192.87, "duration": 2.19}, {"text": "If it says there is at most\nfive roots, including the reals,", "start": 3195.06, "duration": 5.13}, {"text": "there's still going to be five\nroots, including the integers.", "start": 3200.19, "duration": 2.55}, {"text": "All right, so let's continue.", "start": 3202.74, "duration": 1.395}, {"text": "Good, all right.", "start": 3207.07, "duration": 1.71}, {"text": "So now everybody's back, I hope?", "start": 3208.78, "duration": 3.57}, {"text": "Let's talk about\nmoving forward here.", "start": 3212.35, "duration": 3.345}, {"text": "Where we're going\nwith this is we", "start": 3218.47, "duration": 1.62}, {"text": "want to analyze the\nalgorithm, which", "start": 3220.09, "duration": 4.2}, {"text": "picks a random non-Boolean\ninput and evaluates the two", "start": 3224.29, "duration": 4.89}, {"text": "branching programs.", "start": 3229.18, "duration": 3.11}, {"text": "And in order to do that, we're\ngoing to look a little bit more", "start": 3232.29, "duration": 3.36}, {"text": "carefully at what happens\nwhen we arithmetize", "start": 3235.65, "duration": 6.75}, {"text": "the branching\nprogram, and we run it", "start": 3242.4, "duration": 3.27}, {"text": "on these non-Boolean values.", "start": 3245.67, "duration": 1.78}, {"text": "And so what I'm going to do is\ntake this branching program.", "start": 3247.45, "duration": 8.1}, {"text": "Let's say this is the\nsame XOR, exclusive", "start": 3255.55, "duration": 3.57}, {"text": "or, branching program.", "start": 3259.12, "duration": 1.08}, {"text": "But instead of labeling it as\nwe did before by setting x1", "start": 3260.2, "duration": 5.65}, {"text": "to 2 and x2 to 3, I'm going\nto leave x1 and x2 variables", "start": 3265.85, "duration": 5.26}, {"text": "and just do a\nsymbolic execution.", "start": 3271.11, "duration": 2.67}, {"text": "So I'm going to label\nthese things, just", "start": 3273.78, "duration": 2.64}, {"text": "leaving x1 and x2 as variables.", "start": 3276.42, "duration": 4.39}, {"text": "So let's just see what\nwe get if we do that.", "start": 3280.81, "duration": 2.35}, {"text": "So remember, we\nassigned this to be 1.", "start": 3283.16, "duration": 3.32}, {"text": "Now this edge here is--", "start": 3286.48, "duration": 3.825}, {"text": "here's the rule.", "start": 3292.995, "duration": 1.035}, {"text": "It's a, which is 1, times x1.", "start": 3294.03, "duration": 5.07}, {"text": "So this should be--", "start": 3299.1, "duration": 1.26}, {"text": "without knowing what\nthe value of x1 is,", "start": 3300.36, "duration": 1.8}, {"text": "leaving it as a\nvariable, we're just", "start": 3302.16, "duration": 1.5}, {"text": "going to put down x1 over here.", "start": 3303.66, "duration": 2.05}, {"text": "Over here, what goes over there?", "start": 3305.71, "duration": 2.34}, {"text": "Well, it's 1 times 1 minus x1--", "start": 3308.05, "duration": 3.0}, {"text": "just 1 minus x1.", "start": 3311.05, "duration": 2.01}, {"text": "Now we're going to add\nthings up, as we did before.", "start": 3313.06, "duration": 4.112}, {"text": "And now what happens,\nfor example--", "start": 3317.172, "duration": 1.458}, {"text": "I think I have this\nedge coming next.", "start": 3318.63, "duration": 1.542}, {"text": "Let's look at this edge,\nthe one edge coming out.", "start": 3320.172, "duration": 4.068}, {"text": "The label now is\nx1 on this node.", "start": 3324.24, "duration": 2.835}, {"text": "This is the one edge\ncoming out, so you", "start": 3330.21, "duration": 1.68}, {"text": "multiply by the value of x2.", "start": 3331.89, "duration": 4.095}, {"text": "We're leaving it as a\nvariable, so we're just", "start": 3335.985, "duration": 1.875}, {"text": "going to multiply it by x2.", "start": 3337.86, "duration": 1.83}, {"text": "And so we're just going\nto get x1 times x2--", "start": 3339.69, "duration": 4.51}, {"text": "x1x2 on this edge.", "start": 3344.2, "duration": 2.08}, {"text": "And now what happens\non this edge?", "start": 3346.28, "duration": 2.7}, {"text": "So this x1 times--", "start": 3348.98, "duration": 1.76}, {"text": "think with me--\ntimes 1 minus x2.", "start": 3350.74, "duration": 5.65}, {"text": "And similarly over here, we\nhave 1 minus x1 on this node.", "start": 3359.05, "duration": 3.64}, {"text": "So I think on the one edge\ncoming out, it's 1 minus x1,", "start": 3362.69, "duration": 3.8}, {"text": "now times x2, because\nthat's this rule again.", "start": 3366.49, "duration": 3.24}, {"text": "1 minus x, 1 times x2.", "start": 3372.32, "duration": 1.92}, {"text": "And this is going to be 1\nminus x1 times 1 minus x2.", "start": 3374.24, "duration": 4.35}, {"text": "Now we're going to add\nthis up for the 0 node.", "start": 3378.59, "duration": 4.47}, {"text": "So we have this value, 1 minus\nx1, 1 minus x2, plus x1 x2.", "start": 3383.06, "duration": 4.98}, {"text": "And on this note\nhere, we're going", "start": 3391.14, "duration": 2.37}, {"text": "to add these two values up.", "start": 3393.51, "duration": 5.47}, {"text": "So 1 minus x1 times x2\nplus x1 times 1 minus x2.", "start": 3398.98, "duration": 5.48}, {"text": "And that's the output, now\nexpressed symbolically.", "start": 3404.46, "duration": 4.863}, {"text": "Now you could plug\nthings in, and you're", "start": 3409.323, "duration": 1.667}, {"text": "going to get the same value\nout as you did before.", "start": 3410.99, "duration": 3.96}, {"text": "But let's leave it as\na polynomial for now", "start": 3414.95, "duration": 3.6}, {"text": "because that's going to\nhelp us and analyze this.", "start": 3418.55, "duration": 6.61}, {"text": "So now, notice the\nform of this polynomial", "start": 3425.16, "duration": 2.715}, {"text": "is something special.", "start": 3427.875, "duration": 0.875}, {"text": "What happens is\nit's going to look", "start": 3433.29, "duration": 1.92}, {"text": "like a bunch of products of\nxi's and 1 minus xi's added up.", "start": 3435.21, "duration": 9.52}, {"text": "So it's a sum of\nproducts of that form.", "start": 3444.73, "duration": 3.16}, {"text": "So each row here is a product\nof xi's and 1 minus xi's.", "start": 3447.89, "duration": 7.7}, {"text": "And then those rows\nare all added together.", "start": 3455.59, "duration": 3.27}, {"text": "I claim that's going to be\nthe form of this polynomial.", "start": 3458.86, "duration": 3.45}, {"text": "You see this already\nhas that form.", "start": 3462.31, "duration": 3.58}, {"text": "And the reason for that is\nevery time you go to a node,", "start": 3465.89, "duration": 5.55}, {"text": "you're just adding things up.", "start": 3471.44, "duration": 1.56}, {"text": "So that's just going to be\nlike adding up more rows.", "start": 3473.0, "duration": 3.78}, {"text": "And every time you go\ndown to through an edge,", "start": 3476.78, "duration": 2.94}, {"text": "you're multiplying what\nyou have so far either", "start": 3479.72, "duration": 3.0}, {"text": "by an xi or a 1 minus xi.", "start": 3482.72, "duration": 4.33}, {"text": "So you're just accumulating\nproducts of xi's and 1 minus", "start": 3487.05, "duration": 3.12}, {"text": "xi's, and you're\njust adding them up.", "start": 3490.17, "duration": 2.53}, {"text": "So this is what that polynomial\nis going to look like.", "start": 3492.7, "duration": 3.02}, {"text": "Now let's look a little bit more\ncarefully at the form of this.", "start": 3499.24, "duration": 6.16}, {"text": "So for one thing, could we\nhave higher powers here,", "start": 3505.4, "duration": 10.13}, {"text": "like x2 cubed?", "start": 3515.53, "duration": 2.46}, {"text": "Could that happen?", "start": 3517.99, "duration": 0.75}, {"text": "And when I say it's products\nof the xi's and 1 minus xi's,", "start": 3524.76, "duration": 3.18}, {"text": "maybe there's going to be some\nxi's that appear several times", "start": 3527.94, "duration": 2.97}, {"text": "in the product.", "start": 3530.91, "duration": 2.03}, {"text": "Well, that cannot happen.", "start": 3532.94, "duration": 2.235}, {"text": "Why?", "start": 3535.175, "duration": 0.5}, {"text": "It's a read once\nbranching program.", "start": 3538.21, "duration": 2.35}, {"text": "So every time you multiply\nby an xi or a 1 minus xi,", "start": 3540.56, "duration": 4.94}, {"text": "you're never going\nto do that again,", "start": 3545.5, "duration": 1.5}, {"text": "because doing that would\nimply you're querying", "start": 3547.0, "duration": 5.31}, {"text": "that variable more than once.", "start": 3552.31, "duration": 3.78}, {"text": "So this can't happen.", "start": 3556.09, "duration": 1.325}, {"text": "So I cross that out.", "start": 3562.14, "duration": 1.1}, {"text": "This just appeared.", "start": 3563.24, "duration": 0.87}, {"text": "It's off to the side, here.", "start": 3564.11, "duration": 1.125}, {"text": "But yeah, I'm crossing that out.", "start": 3565.235, "duration": 1.615}, {"text": "That does not happen.", "start": 3566.85, "duration": 1.51}, {"text": "Another thing that is\npart of-- that's worthy--", "start": 3568.36, "duration": 5.33}, {"text": "that's going to be helpful to\nnotice about this polynomial--", "start": 3573.69, "duration": 4.61}, {"text": "and by the way, maybe\nI'm being confusing here.", "start": 3578.3, "duration": 3.24}, {"text": "This I'm supposed to be\nrepresenting as a generic form", "start": 3581.54, "duration": 4.17}, {"text": "of the polynomial.", "start": 3585.71, "duration": 0.88}, {"text": "This is not some\nparticularly-- yeah,", "start": 3586.59, "duration": 1.22}, {"text": "I should have said\nthis at the beginning.", "start": 3587.81, "duration": 1.708}, {"text": "This is not some\nparticular polynomial", "start": 3589.518, "duration": 1.772}, {"text": "that came from anything.", "start": 3591.29, "duration": 1.39}, {"text": "I'm just trying to describe\nwhat the general form", "start": 3592.68, "duration": 2.06}, {"text": "of the polynomial looks like,\njust as an illustration.", "start": 3594.74, "duration": 5.68}, {"text": "So this polynomial's\n1 minus x1 times", "start": 3600.42, "duration": 2.37}, {"text": "x2 times 1 minus x3\ntimes x4 and so on,", "start": 3602.79, "duration": 4.2}, {"text": "and adding up a bunch\nof rows like this.", "start": 3606.99, "duration": 2.19}, {"text": "I'm just saying this is\nwhat the polynomial will", "start": 3609.18, "duration": 2.19}, {"text": "look like for maybe\nsome branching program.", "start": 3611.37, "duration": 3.27}, {"text": "So every branching\nprogram is either", "start": 3614.64, "duration": 1.5}, {"text": "going to have some polynomial\nthat looks sort of like this.", "start": 3616.14, "duration": 4.83}, {"text": "And what I'm also going to say--", "start": 3620.97, "duration": 2.64}, {"text": "for convenience,\nnow, I want to say", "start": 3623.61, "duration": 2.22}, {"text": "that each row is going to have\nevery single variable appear", "start": 3625.83, "duration": 4.08}, {"text": "either as an xi or\nas a 1 minus xi.", "start": 3629.91, "duration": 5.14}, {"text": "So in order to get\nthat, I need to make", "start": 3635.05, "duration": 2.13}, {"text": "a further minor assumption\nabout the branching program--", "start": 3637.18, "duration": 3.24}, {"text": "that it's a read exactly once.", "start": 3640.42, "duration": 3.07}, {"text": "Currently when I\nsay \"read once,\"", "start": 3643.49, "duration": 1.8}, {"text": "it can avoid reading some\nvariables on some branches,", "start": 3645.29, "duration": 4.32}, {"text": "because it's like a\nread at most once.", "start": 3649.61, "duration": 1.77}, {"text": "But now I want to say that every\nvariable gets read exactly one", "start": 3651.38, "duration": 3.09}, {"text": "time on every branch.", "start": 3654.47, "duration": 2.25}, {"text": "And what that's going to\nmean is that every row", "start": 3656.72, "duration": 2.64}, {"text": "is going to contain every\nvariable, either as an xi", "start": 3659.36, "duration": 4.5}, {"text": "or as a 1 minus xi.", "start": 3663.86, "duration": 2.51}, {"text": "We can eliminate that\nextra assumption easily.", "start": 3666.37, "duration": 2.38}, {"text": "And I'm going to leave\nthat as an exercise to you.", "start": 3668.75, "duration": 2.083}, {"text": "It's not very hard to do.", "start": 3670.833, "duration": 1.637}, {"text": "So I think if you\nfollow me, you can see--", "start": 3672.47, "duration": 2.422}, {"text": "and you play with it\nfor a minute or two,", "start": 3674.892, "duration": 1.708}, {"text": "you'll see that it\ndoesn't really matter.", "start": 3676.6, "duration": 1.708}, {"text": "But I think just for the\nfirst time through this,", "start": 3681.088, "duration": 3.652}, {"text": "let's assume that every\nrow has every variable--", "start": 3684.74, "duration": 3.92}, {"text": "so important to understand.", "start": 3691.29, "duration": 1.68}, {"text": "So this is the output polynomial\nof this branching program.", "start": 3697.51, "duration": 3.7}, {"text": "So let's look furthermore\nat this polynomial", "start": 3701.21, "duration": 3.59}, {"text": "and understand the rows.", "start": 3704.8, "duration": 3.81}, {"text": "Let's take one row\nout of this polynomial", "start": 3708.61, "duration": 4.14}, {"text": "to understand what\nit represents.", "start": 3712.75, "duration": 10.28}, {"text": "So one row here--", "start": 3723.03, "duration": 1.82}, {"text": "it's a product of a\nbunch of things, product", "start": 3724.85, "duration": 2.67}, {"text": "of a bunch of variables,\neither variables", "start": 3727.52, "duration": 2.49}, {"text": "or 1 minus the variables.", "start": 3730.01, "duration": 1.29}, {"text": "Let's think about this in the\nBoolean setting, first of all.", "start": 3736.11, "duration": 4.08}, {"text": "So in the Boolean setting, each\nof these variables are going", "start": 3740.19, "duration": 3.35}, {"text": "to be 0's and 1's.", "start": 3743.54, "duration": 1.59}, {"text": "And the 1 minus the variables\nare also going to be", "start": 3745.13, "duration": 2.22}, {"text": "0's and 1's.", "start": 3747.35, "duration": 0.96}, {"text": "So it's going to be a\nproduct of 0's and 1's.", "start": 3748.31, "duration": 3.6}, {"text": "If there's a 0 that\nappears in that product,", "start": 3751.91, "duration": 3.33}, {"text": "that product is going to be a\n0, because 0 times anything is", "start": 3755.24, "duration": 3.98}, {"text": "a 0.", "start": 3759.22, "duration": 1.71}, {"text": "So the only way that product\ncannot be 0 is if all of those", "start": 3760.93, "duration": 10.95}, {"text": "values are 1's in\nthe Boolean case.", "start": 3771.88, "duration": 3.46}, {"text": "So that means that x1--", "start": 3775.34, "duration": 5.98}, {"text": "well, let's look\nat the second row.", "start": 3781.32, "duration": 2.46}, {"text": "So x1 had to be a 1. x2 had\nto be a 1. x3 had to be a 1.", "start": 3783.78, "duration": 4.11}, {"text": "x4 had to be a 0 in\norder to continue", "start": 3787.89, "duration": 4.32}, {"text": "the product of 1's, and so on.", "start": 3792.21, "duration": 4.55}, {"text": "So in fact, there's only a\nsingle Boolean assignment", "start": 3796.76, "duration": 4.58}, {"text": "to these variables\nwhich make that row 1.", "start": 3801.34, "duration": 4.23}, {"text": "Every other assignment to those\nvariables makes that row 0.", "start": 3805.57, "duration": 4.05}, {"text": "Saying that another\nway, each of these rows", "start": 3815.04, "duration": 4.32}, {"text": "corresponds to one of\nthe rows of the truth", "start": 3819.36, "duration": 6.51}, {"text": "table for the Boolean function,\nwhere the truth table is true,", "start": 3825.87, "duration": 7.22}, {"text": "gives a true value,\ngives a 1 value", "start": 3833.09, "duration": 2.49}, {"text": "for the function on that row.", "start": 3835.58, "duration": 2.34}, {"text": "So I hope you're all familiar\nwith the notion of a truth", "start": 3837.92, "duration": 2.85}, {"text": "table of a Boolean function.", "start": 3840.77, "duration": 1.83}, {"text": "You just write down\nthe Boolean function,", "start": 3842.6, "duration": 2.94}, {"text": "every possible assignment\nto the Boolean function,", "start": 3845.54, "duration": 2.28}, {"text": "and you write down 1 or\n0 or true or false for", "start": 3847.82, "duration": 3.492}, {"text": "what the value of\nthat function is.", "start": 3851.312, "duration": 1.458}, {"text": "It's just a tabular\nrepresentation", "start": 3852.77, "duration": 1.8}, {"text": "of the Boolean function.", "start": 3854.57, "duration": 1.32}, {"text": "It's called a truth table.", "start": 3855.89, "duration": 2.96}, {"text": "This thing here gives\nyou all of the 1's--", "start": 3858.85, "duration": 2.52}, {"text": "all of the rows that are 1\nin that Boolean function.", "start": 3861.37, "duration": 4.06}, {"text": "That's what this\npolynomial gives you.", "start": 3865.43, "duration": 2.63}, {"text": "So I think we're at a\npause point for this slide.", "start": 3872.62, "duration": 5.45}, {"text": "It's deathly silent on the chat.", "start": 3882.44, "duration": 3.75}, {"text": "So I have a feeling that\nthat went down rough for you.", "start": 3886.19, "duration": 7.46}, {"text": "It's important to understand the\nform of this polynomial here.", "start": 3896.2, "duration": 5.335}, {"text": "It corresponds to the truth\ntable of the Boolean function.", "start": 3904.33, "duration": 3.07}, {"text": "So each one of these rows\nis only going to be--", "start": 3907.4, "duration": 2.93}, {"text": "again, thinking Boolean\nnow, each one of these rows", "start": 3910.33, "duration": 3.09}, {"text": "is only going to be 1\non an assignment which", "start": 3913.42, "duration": 4.38}, {"text": "makes the function 1--", "start": 3917.8, "duration": 3.508}, {"text": "one of the assignments\nthat makes the function 1.", "start": 3921.308, "duration": 2.042}, {"text": "And somebody says, and similarly\nfor the expression for the 0", "start": 3927.28, "duration": 2.79}, {"text": "node.", "start": 3930.07, "duration": 0.54}, {"text": "Yeah, the 0 node, which\nI'm not focusing on, but,", "start": 3930.61, "duration": 2.94}, {"text": "yeah, the 0 node would be all\nof the false rows of the truth", "start": 3933.55, "duration": 3.84}, {"text": "table.", "start": 3937.39, "duration": 2.63}, {"text": "But the 1 node, the\npolynomial for the 1 node,", "start": 3940.02, "duration": 2.91}, {"text": "are all of the true rows--", "start": 3942.93, "duration": 1.95}, {"text": "correspond to all\nof the true rows", "start": 3944.88, "duration": 1.62}, {"text": "in the function of the\nbranching-- the function", "start": 3946.5, "duration": 10.242}, {"text": "that branching program computes.", "start": 3956.742, "duration": 1.333}, {"text": "Let me just tell you\nwhere we're going.", "start": 3960.885, "duration": 1.625}, {"text": "Is it possible to have two\nrows that are the same?", "start": 3973.59, "duration": 3.91}, {"text": "If you think about how the\nrows are being produced, no.", "start": 3977.5, "duration": 3.2}, {"text": "You can't have two\nrows that are going", "start": 3980.7, "duration": 1.65}, {"text": "to be the same,\nbecause for one thing,", "start": 3982.35, "duration": 6.182}, {"text": "you have to think about what\nthis looks like in the Boolean", "start": 3988.532, "duration": 2.458}, {"text": "case.", "start": 3990.99, "duration": 1.35}, {"text": "If you have two\nrows are the same,", "start": 3992.34, "duration": 1.44}, {"text": "that means this thing is going\nto-- would have an output which", "start": 3993.78, "duration": 2.583}, {"text": "is non-Boolean because\nyou're going to end up", "start": 3996.363, "duration": 4.227}, {"text": "with a 2 coming out that way\nby adding those rows together.", "start": 4000.59, "duration": 4.403}, {"text": "That can never happen.", "start": 4004.993, "duration": 0.917}, {"text": "And if you just look at\nthe way it's constructed,", "start": 4005.91, "duration": 1.43}, {"text": "you're never going to--\nbecause every time you have", "start": 4007.34, "duration": 2.125}, {"text": "a branching, one way is an xi.", "start": 4009.465, "duration": 3.995}, {"text": "The other one is 1 minus xi.", "start": 4013.46, "duration": 1.57}, {"text": "So every time you're\nbranching there,", "start": 4015.03, "duration": 1.73}, {"text": "every time there's a\nnode, they're different.", "start": 4016.76, "duration": 3.308}, {"text": "So you're never going\nto have two rows that", "start": 4020.068, "duration": 1.792}, {"text": "are going to be the same.", "start": 4021.86, "duration": 1.042}, {"text": "But let me tell you the\nimportance of connecting up", "start": 4022.902, "duration": 5.768}, {"text": "this polynomial with\nthe truth table,", "start": 4028.67, "duration": 4.48}, {"text": "because that tells us that if\nthe two functions of the two", "start": 4033.15, "duration": 4.5}, {"text": "branching programs that\nwe started off with", "start": 4037.65, "duration": 2.52}, {"text": "agree in their Boolean values,\nthen the two polynomials are", "start": 4040.17, "duration": 4.71}, {"text": "going to be the same.", "start": 4044.88, "duration": 0.875}, {"text": "Because if the two branching\nprograms have the same Boolean", "start": 4054.8, "duration": 5.91}, {"text": "function, so they're equivalent,\nthen the truth tables", "start": 4060.71, "duration": 5.01}, {"text": "will be the same.", "start": 4065.72, "duration": 0.9}, {"text": "And therefore, these\npolynomials will be the same.", "start": 4066.62, "duration": 3.06}, {"text": "And therefore, they\nwill behave the same way", "start": 4069.68, "duration": 2.85}, {"text": "on all non-Boolean\nvalues, because they're", "start": 4072.53, "duration": 4.23}, {"text": "the same polynomial.", "start": 4076.76, "duration": 0.99}, {"text": "So I'm getting ahead\nof myself, but that's", "start": 4080.54, "duration": 2.49}, {"text": "what we're going to argue.", "start": 4083.03, "duration": 1.23}, {"text": "That's why it's\nimportant to understand", "start": 4084.26, "duration": 1.625}, {"text": "the connection with\nthe truth table,", "start": 4085.885, "duration": 3.545}, {"text": "because it builds on the--", "start": 4089.43, "duration": 2.25}, {"text": "understanding something\nabout how this thing behaves", "start": 4095.593, "duration": 2.167}, {"text": "in the Boolean case\nis going to give us", "start": 4097.76, "duration": 1.83}, {"text": "information about how it\nbehaves in the non-Boolean case.", "start": 4099.59, "duration": 2.46}, {"text": "But let's continue here, then.", "start": 4105.41, "duration": 1.25}, {"text": "Yeah, this is essentially\nthe last slide,", "start": 4118.59, "duration": 3.779}, {"text": "but we're going to spend\nsome time on this one.", "start": 4122.369, "duration": 2.141}, {"text": "So here's the algorithm.", "start": 4124.51, "duration": 3.679}, {"text": "We are going to take our\ntwo branching programs.", "start": 4128.189, "duration": 3.121}, {"text": "The variables are x1 to xm.", "start": 4131.31, "duration": 2.615}, {"text": "First of all,\nwe're going to find", "start": 4133.925, "duration": 1.375}, {"text": "a prime which is\nat least 3 times m,", "start": 4135.3, "duration": 4.29}, {"text": "the number of variables.", "start": 4139.59, "duration": 2.29}, {"text": "m is not a very big number.", "start": 4141.88, "duration": 2.34}, {"text": "It's just the\nnumber of variables.", "start": 4144.22, "duration": 1.9}, {"text": "So finding a prime that's bigger\nthan that is straightforward.", "start": 4146.12, "duration": 3.412}, {"text": "We're not talking\nabout huge primes here.", "start": 4149.532, "duration": 1.708}, {"text": "We're talking about very\nmodest-sized primes.", "start": 4151.24, "duration": 1.875}, {"text": "Even trial and error is\ngoing to be good enough.", "start": 4157.175, "duration": 2.0}, {"text": "Now that's going to be\nthe size of the field.", "start": 4162.77, "duration": 3.709}, {"text": "It's going to be\na field of size q.", "start": 4166.479, "duration": 3.63}, {"text": "And now we're going to pick\na non-Boolean assignment", "start": 4170.109, "duration": 3.21}, {"text": "to the variables.", "start": 4173.319, "duration": 1.021}, {"text": "We're going to pick a\nnon-Boolean assignment", "start": 4184.177, "duration": 1.833}, {"text": "to the variables and evaluate\nthe two branching programs", "start": 4186.01, "duration": 8.89}, {"text": "on that non-Boolean assignment\nusing the arithmetization.", "start": 4194.9, "duration": 4.38}, {"text": "If they agree,\nthen we'll accept.", "start": 4199.28, "duration": 2.43}, {"text": "If they don't agree, then\nwe're going to reject.", "start": 4201.71, "duration": 3.86}, {"text": "Now we have to argue\nthat this works.", "start": 4205.57, "duration": 2.59}, {"text": "So we're going to first of\nall arithmetize these two", "start": 4208.16, "duration": 2.477}, {"text": "branching programs,\nand we're going", "start": 4210.637, "duration": 1.458}, {"text": "to get these two polynomials.", "start": 4212.095, "duration": 2.395}, {"text": "They each have the form that--\nas I described, so a bunch", "start": 4214.49, "duration": 5.5}, {"text": "of rows that correspond to\nthe truth tables of those two", "start": 4219.99, "duration": 2.52}, {"text": "respective branching programs.", "start": 4222.51, "duration": 1.995}, {"text": "First claim-- that if the\nbranching programs were", "start": 4227.31, "duration": 2.61}, {"text": "equivalent, so they compute\nthe same Boolean function,", "start": 4229.92, "duration": 4.35}, {"text": "then the two polynomials\nagree everywhere.", "start": 4234.27, "duration": 3.732}, {"text": "So then the two\nbranching programs", "start": 4240.84, "duration": 1.8}, {"text": "are going to get the same\nvalue on every non-Boolean case", "start": 4242.64, "duration": 5.357}, {"text": "as well as on the Boolean cases.", "start": 4247.997, "duration": 1.333}, {"text": "So they agree in the Boolean.", "start": 4249.33, "duration": 1.38}, {"text": "That means they always agree,\neven on the non-Boolean.", "start": 4250.71, "duration": 2.67}, {"text": "And I kind of\nargued that already.", "start": 4253.38, "duration": 2.97}, {"text": "The other point is that if the\ntwo branching programs are not", "start": 4256.35, "duration": 3.87}, {"text": "equivalent, so they differ\nat some Boolean value,", "start": 4260.22, "duration": 4.74}, {"text": "now picking a random value\nfor the polynomial evaluation,", "start": 4264.96, "duration": 4.53}, {"text": "you're going to have only a\n1/3 chance that they're going", "start": 4269.49, "duration": 3.36}, {"text": "to agree, so a small chance.", "start": 4272.85, "duration": 2.59}, {"text": "All right, so now let's\nprove these two facts.", "start": 4280.34, "duration": 4.9}, {"text": "The first one I\nalready kind of argued.", "start": 4285.24, "duration": 1.64}, {"text": "If the two branching\nprograms agree", "start": 4286.88, "duration": 2.55}, {"text": "on all the Boolean values,\nthen their functions", "start": 4289.43, "duration": 4.85}, {"text": "have the same truth table.", "start": 4294.28, "duration": 2.66}, {"text": "So then the polynomials\nare identical", "start": 4296.94, "duration": 2.09}, {"text": "because the polynomials\ncorrespond to the truth table.", "start": 4299.03, "duration": 3.0}, {"text": "And so therefore, they\nalways agree, even", "start": 4304.69, "duration": 2.802}, {"text": "on the non-Boolean values.", "start": 4307.492, "duration": 1.083}, {"text": "So that means that\nthe probability", "start": 4314.15, "duration": 2.82}, {"text": "that if you evaluate the two\npolynomials on a random place,", "start": 4316.97, "duration": 5.07}, {"text": "whether they'll be equal, that's\na certainty, because in fact,", "start": 4322.04, "duration": 3.78}, {"text": "in this case, p1 and p2\nare the same polynomial.", "start": 4325.82, "duration": 3.0}, {"text": "Now for two, if the branching\nprograms differ somewhere,", "start": 4332.77, "duration": 6.72}, {"text": "even in one place, well you\nknow the polynomials could not", "start": 4339.49, "duration": 3.51}, {"text": "be the same.", "start": 4343.0, "duration": 1.51}, {"text": "They have to be\ndifferent polynomials", "start": 4344.51, "duration": 2.27}, {"text": "because the polynomials include\nthe behavior in the Boolean", "start": 4346.78, "duration": 3.66}, {"text": "case as well as all\nthe rest of the field.", "start": 4350.44, "duration": 3.97}, {"text": "So the polynomials\nhave to be the same.", "start": 4354.41, "duration": 1.89}, {"text": "And now we're going to apply\nthe Schwartz-Zippel lemma.", "start": 4356.3, "duration": 2.82}, {"text": "We have two different\npolynomials.", "start": 4359.12, "duration": 6.02}, {"text": "They can only agree in a\nrelatively small number", "start": 4365.14, "duration": 2.76}, {"text": "of places.", "start": 4367.9, "duration": 1.72}, {"text": "So that says that, from the\nSchwartz-Zippel theorem,", "start": 4369.62, "duration": 4.13}, {"text": "then the probability\nthat p1 and p2 agree", "start": 4373.75, "duration": 3.69}, {"text": "at this random location\nis at most this value", "start": 4377.44, "duration": 3.09}, {"text": "that we had from\nbefore, the degree", "start": 4380.53, "duration": 2.67}, {"text": "times the number of\nvariables divided", "start": 4383.2, "duration": 1.65}, {"text": "by the size of the field.", "start": 4384.85, "duration": 2.56}, {"text": "The degree is 1.", "start": 4387.41, "duration": 0.93}, {"text": "And the field is\nat least 3 times", "start": 4391.5, "duration": 3.99}, {"text": "the number of variables in size.", "start": 4395.49, "duration": 1.89}, {"text": "So that means you get\nthis inequality here.", "start": 4397.38, "duration": 4.39}, {"text": "And so therefore, the\nprobability is a 1/3--", "start": 4401.77, "duration": 3.93}, {"text": "at most 1/3.", "start": 4405.7, "duration": 2.34}, {"text": "And that's good enough.", "start": 4408.04, "duration": 2.2}, {"text": "This is the probability that\nyou get the wrong answer is", "start": 4410.24, "duration": 2.36}, {"text": "going to be at most 1/3.", "start": 4412.6, "duration": 1.615}, {"text": "So you're going to\nget the right answer", "start": 4414.215, "duration": 1.625}, {"text": "with at least 2/3 probability.", "start": 4415.84, "duration": 1.44}, {"text": "So even just doing a\nsingle sample point", "start": 4417.28, "duration": 2.79}, {"text": "is going to be enough to\ngive it a PPP algorithm.", "start": 4420.07, "duration": 3.346}, {"text": "What I have are a couple of\ncheck-ins here now for you.", "start": 4426.42, "duration": 3.96}, {"text": "Whoops, somehow this-- going\nto take me out of here.", "start": 4434.47, "duration": 4.08}, {"text": "All right, so this\nis a little hard,", "start": 4442.79, "duration": 3.535}, {"text": "but let's see how you do on it.", "start": 4446.325, "duration": 2.325}, {"text": "Suppose the branching\nprogram is--", "start": 4448.65, "duration": 3.57}, {"text": "well, maybe I a little bit\ndiscussed this already,", "start": 4452.22, "duration": 2.34}, {"text": "but that's OK.", "start": 4454.56, "duration": 0.71}, {"text": "The branching programs\nwere not read once.", "start": 4455.27, "duration": 1.75}, {"text": "The polynomials might have\nexponents bigger than 1.", "start": 4457.02, "duration": 3.03}, {"text": "So where would the proof fail?", "start": 4460.05, "duration": 3.99}, {"text": "Would they fail at the point\nwhere b1 and equivalent to b2", "start": 4464.04, "duration": 4.41}, {"text": "implies that they agree\non all Boolean inputs?", "start": 4468.45, "duration": 2.08}, {"text": "So that's the first step here.", "start": 4470.53, "duration": 3.47}, {"text": "Or was it that agreeing\non all Boolean inputs", "start": 4474.0, "duration": 4.11}, {"text": "implies that the\npolynomials are the same?", "start": 4478.11, "duration": 2.81}, {"text": "Or would it be that having the\ntwo polynomials being equal", "start": 4480.92, "duration": 3.51}, {"text": "implies that they always agree?", "start": 4484.43, "duration": 2.21}, {"text": "So those are the three steps\nin the proof of part one.", "start": 4486.64, "duration": 6.21}, {"text": "So let's see.", "start": 4492.85, "duration": 1.37}, {"text": "What do you think there?", "start": 4494.22, "duration": 1.0}, {"text": "I'm getting a\ncouple of questions", "start": 4497.255, "duration": 1.375}, {"text": "about picking the prime number.", "start": 4498.63, "duration": 1.292}, {"text": "The prime number here is--", "start": 4504.77, "duration": 3.27}, {"text": "this is a very\nsmall prime number.", "start": 4508.04, "duration": 3.33}, {"text": "You could even represent\nthat prime number in unary", "start": 4511.37, "duration": 3.697}, {"text": "within the amount of time we\nhave, because don't forget,", "start": 4515.067, "duration": 2.333}, {"text": "this is a prime number\nwhose magnitude is at most", "start": 4517.4, "duration": 3.9}, {"text": "the number of variables.", "start": 4521.3, "duration": 1.0}, {"text": "So you can write that\nprime number in unary.", "start": 4522.3, "duration": 2.09}, {"text": "And finding the prime\nand testing primality,", "start": 4524.39, "duration": 7.48}, {"text": "testing whether the\nnumber is prime,", "start": 4531.87, "duration": 1.74}, {"text": "is something that\nyou can do even", "start": 4533.61, "duration": 1.74}, {"text": "with a brute-force algorithm,\nand it would be good enough.", "start": 4535.35, "duration": 5.52}, {"text": "You don't have to do anything\nfancy about testing primality", "start": 4540.87, "duration": 3.24}, {"text": "in this case.", "start": 4544.11, "duration": 0.555}, {"text": "So why does it have to be prime?", "start": 4547.53, "duration": 2.07}, {"text": "You need it to prime in\norder for it to be a field.", "start": 4549.6, "duration": 5.58}, {"text": "So this is just\nthe algebra part.", "start": 4555.18, "duration": 3.76}, {"text": "If you did not have\na prime number,", "start": 4558.94, "duration": 1.86}, {"text": "then some of the field\nproperties don't work.", "start": 4560.8, "duration": 2.85}, {"text": "And you may no\nlonger get the fact", "start": 4563.65, "duration": 3.57}, {"text": "that the polynomial has\na small number of roots.", "start": 4567.22, "duration": 4.76}, {"text": "So that's all I\ncan say about that.", "start": 4571.98, "duration": 5.96}, {"text": "Is the polynomial\nlike a hash function", "start": 4577.94, "duration": 1.68}, {"text": "for the branching program?", "start": 4579.62, "duration": 1.44}, {"text": "Are they equal if\nthey are the same,", "start": 4581.06, "duration": 1.59}, {"text": "but sometimes the\nvalue is also equal", "start": 4582.65, "duration": 1.71}, {"text": "if the programs are different?", "start": 4584.36, "duration": 1.53}, {"text": "That's an interesting idea.", "start": 4585.89, "duration": 3.03}, {"text": "Is the polynomial acting\nlike a hash function?", "start": 4588.92, "duration": 2.13}, {"text": "I think there is something\nto what you're saying,", "start": 4591.05, "duration": 2.43}, {"text": "but I think it's actually\nin the other direction.", "start": 4593.48, "duration": 2.25}, {"text": "It's related to a hash function,\nbut it's actually acting more", "start": 4600.85, "duration": 2.67}, {"text": "like an error-correcting code.", "start": 4603.52, "duration": 3.19}, {"text": "Let's save that for later.", "start": 4606.71, "duration": 1.13}, {"text": "It's a very good point.", "start": 4607.84, "duration": 0.82}, {"text": "It's a very good question.", "start": 4608.66, "duration": 1.083}, {"text": "Maybe we can talk about\nit after if you remind me.", "start": 4609.743, "duration": 4.037}, {"text": "OK, let's end this poll here.", "start": 4613.78, "duration": 2.37}, {"text": "Should C be-- if\nhaving these two agree", "start": 4618.77, "duration": 5.63}, {"text": "implies-- well, I mean,\nthe question is, should we", "start": 4624.4, "duration": 5.49}, {"text": "change p1 and p2 always agree\nto b1 and b2 always agree?", "start": 4629.89, "duration": 4.76}, {"text": "Well, b1 and b2 are\nbehaving exactly the way p1", "start": 4634.65, "duration": 2.64}, {"text": "and p2 behave, so I'm not\nsure it really matters.", "start": 4637.29, "duration": 2.145}, {"text": "Too much time on this\nchat, on this poll here.", "start": 4644.25, "duration": 2.25}, {"text": "Let's end this poll--", "start": 4646.5, "duration": 2.09}, {"text": "oh, sharing results.", "start": 4648.59, "duration": 1.315}, {"text": "Yeah, so the\ncorrect answer is B,", "start": 4654.13, "duration": 3.39}, {"text": "that agreeing on\nall Boolean inputs", "start": 4657.52, "duration": 1.77}, {"text": "implies that they are equal.", "start": 4659.29, "duration": 3.57}, {"text": "The other two\nfollow immediately.", "start": 4662.86, "duration": 2.07}, {"text": "They're still true.", "start": 4664.93, "duration": 1.21}, {"text": "But if it's not read\nonce, even though they", "start": 4666.14, "duration": 2.84}, {"text": "agree on all the Boolean\ninputs, they won't necessarily", "start": 4668.98, "duration": 2.64}, {"text": "agree as polynomials.", "start": 4671.62, "duration": 2.91}, {"text": "For one thing, if you just take\nthe two polynomials x1 squared", "start": 4674.53, "duration": 4.65}, {"text": "and x1, they agree on\nall the Boolean inputs,", "start": 4679.18, "duration": 4.51}, {"text": "but they're not the same.", "start": 4683.69, "duration": 3.06}, {"text": "They agree in the Boolean\nworld, because 0 squared is 0,", "start": 4686.75, "duration": 2.97}, {"text": "and 1 squared is 1.", "start": 4689.72, "duration": 1.23}, {"text": "But they're not the\nsame polynomial.", "start": 4690.95, "duration": 4.0}, {"text": "Let's move on.", "start": 4694.95, "duration": 0.72}, {"text": "Actually, I have\nanother check-in", "start": 4695.67, "duration": 3.12}, {"text": "on the same slide here.", "start": 4698.79, "duration": 3.062}, {"text": "And this is actually\nanswering a question", "start": 4701.852, "duration": 1.708}, {"text": "that I got in the chat.", "start": 4703.56, "duration": 1.47}, {"text": "If p1 and p2 were--", "start": 4705.03, "duration": 1.02}, {"text": "how big are these polynomials?", "start": 4709.16, "duration": 1.83}, {"text": "These look like\nthey could be big.", "start": 4710.99, "duration": 2.34}, {"text": "If they're exponentially\nlarge, would that", "start": 4713.33, "duration": 2.37}, {"text": "be a problem for\nthe time complexity?", "start": 4715.7, "duration": 1.68}, {"text": "So pick A or B here.", "start": 4720.21, "duration": 3.95}, {"text": "We're running out of time here.", "start": 4724.16, "duration": 1.65}, {"text": "So why don't I not say too much\nand just let you go with it.", "start": 4725.81, "duration": 6.6}, {"text": "I'm going to close this down.", "start": 4735.15, "duration": 2.95}, {"text": "All in?", "start": 4738.1, "duration": 0.85}, {"text": "Well, oh, my god, by one point.", "start": 4741.9, "duration": 4.69}, {"text": "This is like Georgia here--", "start": 4751.06, "duration": 3.02}, {"text": "do a recount.", "start": 4754.08, "duration": 2.34}, {"text": "In fact, B is correct by a hair.", "start": 4756.42, "duration": 7.74}, {"text": "They are not polynomial in size.", "start": 4764.16, "duration": 1.56}, {"text": "The truth tables\ncan be very large.", "start": 4765.72, "duration": 3.3}, {"text": "As we did with the\nbranching program", "start": 4769.02, "duration": 4.17}, {"text": "for the exclusive or\ncase, you don't actually", "start": 4773.19, "duration": 5.07}, {"text": "write down the polynomials\nto evaluate them.", "start": 4778.26, "duration": 2.07}, {"text": "You can evaluate them\nas you're going along.", "start": 4780.33, "duration": 2.37}, {"text": "The polynomials are huge.", "start": 4782.7, "duration": 1.87}, {"text": "But you don't have to\nwrite down the polynomials", "start": 4784.57, "duration": 2.0}, {"text": "to evaluate them.", "start": 4786.57, "duration": 0.84}, {"text": "That's only part of the proof.", "start": 4787.41, "duration": 1.26}, {"text": "The algorithm doesn't have\nto deal with the polynomials", "start": 4792.03, "duration": 2.73}, {"text": "itself, so maybe good\nto think about this.", "start": 4794.76, "duration": 6.89}, {"text": "And somebody says, did\nI invent this proof?", "start": 4801.65, "duration": 1.86}, {"text": "No, I did not invent this proof.", "start": 4803.51, "duration": 1.62}, {"text": "It's a wonderful proof,\nbut it's not mine.", "start": 4805.13, "duration": 2.28}, {"text": "I would love to have been--", "start": 4807.41, "duration": 1.46}, {"text": "get to take the credit for it.", "start": 4808.87, "duration": 2.44}, {"text": "So why don't we wrap this up?", "start": 4811.31, "duration": 4.77}, {"text": "Is there some way to\nsimplify the polynomials", "start": 4818.99, "duration": 2.49}, {"text": "as we're going along\nso that we don't end up", "start": 4821.48, "duration": 2.88}, {"text": "with them being too big and\nso that we can then just", "start": 4824.36, "duration": 4.44}, {"text": "look at the polynomials?", "start": 4828.8, "duration": 1.02}, {"text": "Not that I know of.", "start": 4829.82, "duration": 1.08}, {"text": "I think the polynomials\nare really going to be big.", "start": 4835.32, "duration": 3.44}, {"text": "And so there's not going to be\nany way to view it just as--", "start": 4838.76, "duration": 4.86}, {"text": "if you could, it\nwould be fantastic,", "start": 4843.62, "duration": 1.5}, {"text": "because that would give you\na deterministic algorithm.", "start": 4845.12, "duration": 3.258}, {"text": "I think the only\nway that people know", "start": 4848.378, "duration": 1.542}, {"text": "how to do this in\nterms of random inputs", "start": 4849.92, "duration": 3.36}, {"text": "to a polynomial, which\nis too big to write down.", "start": 4853.28, "duration": 2.16}, {"text": "If you could write it down and\njust analyze the polynomials,", "start": 4855.44, "duration": 2.97}, {"text": "you'd have a huge,\nhuge result there.", "start": 4858.41, "duration": 2.34}, {"text": "Oh, I'm glad people\nlike this proof.", "start": 4866.475, "duration": 2.295}, {"text": "That's good.", "start": 4868.77, "duration": 0.69}, {"text": "How many actual quantities\nare there in the formula?", "start": 4874.52, "duration": 2.41}, {"text": "I'm not sure what that means.", "start": 4876.93, "duration": 1.22}, {"text": "What formula?", "start": 4878.15, "duration": 2.4}, {"text": "I mean, the polynomial is huge.", "start": 4880.55, "duration": 3.05}, {"text": "The number of\ndifferent polynomials--", "start": 4883.6, "duration": 1.97}, {"text": "well, I guess I don't\nunderstand the question.", "start": 4885.57, "duration": 2.89}, {"text": "What motivates the idea\nof arithmetization?", "start": 4888.46, "duration": 4.345}, {"text": "What would make\nsomebody think of this?", "start": 4892.805, "duration": 2.31}, {"text": "I'm not sure, actually.", "start": 4895.115, "duration": 1.635}, {"text": "But we're going to use it\neven in a more remarkable way", "start": 4901.36, "duration": 3.57}, {"text": "in the last two lectures of\nthe course, so stay tuned.", "start": 4904.93, "duration": 5.41}, {"text": "I mean, this is sort of clever,\nbut seems very specialized.", "start": 4910.34, "duration": 3.2}, {"text": "But the next part, where we\ngo to the next application,", "start": 4913.54, "duration": 4.38}, {"text": "we're going to use this\nto analyze satisfiability,", "start": 4917.92, "duration": 2.22}, {"text": "which is a much more\ngeneral kind of a situation.", "start": 4920.14, "duration": 2.71}, {"text": "And that, I think, is\nespecially remarkable.", "start": 4922.85, "duration": 2.75}, {"text": "For the polynomials p1 and p2,\nit's only a polynomial number--", "start": 4933.16, "duration": 7.16}, {"text": "I don't think so, because--", "start": 4940.32, "duration": 1.44}, {"text": "well, it depends on\nthe size of the field.", "start": 4941.76, "duration": 2.1}, {"text": "The size of-- no, it's\ngoing to be something", "start": 4943.86, "duration": 2.1}, {"text": "like m to the mth power, right?", "start": 4945.96, "duration": 3.75}, {"text": "So those are the number\nof possible inputs.", "start": 4949.71, "duration": 3.36}, {"text": "Each field element has 3m\npossibilities, roughly.", "start": 4953.07, "duration": 6.36}, {"text": "And there are m field\nelements, so it's", "start": 4959.43, "duration": 2.4}, {"text": "m to the 3m different\npossible inputs", "start": 4961.83, "duration": 5.35}, {"text": "that you're picking at random.", "start": 4967.18, "duration": 1.99}, {"text": "So anyway, I'm going to\nshut this down and move over", "start": 4969.17, "duration": 2.57}, {"text": "to the office hours Zoom.", "start": 4971.74, "duration": 4.77}, {"text": "Feel free to join me there.", "start": 4976.51, "duration": 1.44}, {"text": "Otherwise, I will see\nyou all on Thursday.", "start": 4977.95, "duration": 3.38}, {"text": "Take care.", "start": 4981.33, "duration": 1.6}]
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+[{"text": "NARRATOR: The following content\nis provided under a Creative", "start": 0.96, "duration": 2.5}, {"text": "Commons license.", "start": 3.46, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.85, "duration": 2.21}, {"text": "continue to offer high-quality\neducational resources for free.", "start": 7.06, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 11.15, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.72, "duration": 3.93}, {"text": "at ocw.mit.edu.", "start": 17.65, "duration": 0.9}, {"text": "MIKE SHORT: OK, guys.", "start": 24.045, "duration": 0.875}, {"text": "Welcome to the first filmed\nand hands-on installation", "start": 24.92, "duration": 3.75}, {"text": "of 22.01, Introduction\nto Ionizing Radiation.", "start": 28.67, "duration": 2.73}, {"text": "I'm Mike Short.", "start": 31.4, "duration": 1.05}, {"text": "I'm the department's\nundergrad coordinator.", "start": 32.45, "duration": 1.98}, {"text": "I'm also your 22.01 instructor.", "start": 34.43, "duration": 2.07}, {"text": "But I also want to introduce\nyou to Amelia Trainer", "start": 36.5, "duration": 2.13}, {"text": "in the back, who one of the\nthree TAs for the course.", "start": 38.63, "duration": 2.73}, {"text": "She took it last year.", "start": 41.36, "duration": 1.13}, {"text": "Everything is still very\nfresh in your head, I bet.", "start": 42.49, "duration": 2.155}, {"text": "AUDIENCE: More or less.", "start": 44.645, "duration": 1.125}, {"text": "MIKE SHORT: Cool.", "start": 45.77, "duration": 0.708}, {"text": "So she'll be-- she and\nKa-Yen Yau and Caitlin Fisher", "start": 46.478, "duration": 2.772}, {"text": "will be with us all\nthroughout the term.", "start": 49.25, "duration": 2.11}, {"text": "So if there's something that you\ndon't like my explanation for,", "start": 51.36, "duration": 2.63}, {"text": "you've got three people\nwho just took the course,", "start": 53.99, "duration": 2.4}, {"text": "and struggled through\nmy own explanations,", "start": 56.39, "duration": 1.92}, {"text": "and can say it in\na different way.", "start": 58.31, "duration": 2.16}, {"text": "So let's start off by taking\nyour knowledge of physics", "start": 60.47, "duration": 3.39}, {"text": "from the roughly 1800s education\nof the GIRs, the a General", "start": 63.86, "duration": 3.9}, {"text": "Institute Requirements,\nup till 1932", "start": 67.76, "duration": 3.317}, {"text": "when the neutron was discovered.", "start": 71.077, "duration": 1.333}, {"text": "And I would argue that\nthis particle is what", "start": 72.41, "duration": 1.833}, {"text": "makes us nuclear engineers.", "start": 74.243, "duration": 1.917}, {"text": "It's the basis behind reactors.", "start": 76.16, "duration": 1.93}, {"text": "It's what differentiates us\nfrom the high energy physics", "start": 78.09, "duration": 2.568}, {"text": "folks and everything,\nbecause we've studied these", "start": 80.658, "duration": 2.042}, {"text": "and use them quite a lot.", "start": 82.7, "duration": 1.78}, {"text": "And so we want to\nretrace Chadwick's steps", "start": 84.48, "duration": 2.78}, {"text": "in discovering the neutron.", "start": 87.26, "duration": 1.59}, {"text": "And this is the only\ntime you're ever", "start": 88.85, "duration": 2.04}, {"text": "going to see me have a\nbunch of words on a slide.", "start": 90.89, "duration": 2.19}, {"text": "It's not a presentation\ntechnique I like,", "start": 93.08, "duration": 2.37}, {"text": "but this paper is awesome in\nthe clarity and expressiveness", "start": 95.45, "duration": 4.32}, {"text": "of him saying I\nran this experiment", "start": 99.77, "duration": 1.74}, {"text": "and found something unknown.", "start": 101.51, "duration": 2.01}, {"text": "I'll use basic conservation\nof energy and things", "start": 103.52, "duration": 2.67}, {"text": "you learned in 8.01\nand 8.02 to prove", "start": 106.19, "duration": 2.94}, {"text": "that it has to be a neutron,\nthat a neutron must exist.", "start": 109.13, "duration": 2.49}, {"text": "It's elegant and\nbrilliant, and I want", "start": 111.62, "duration": 2.13}, {"text": "to walk you guys through it.", "start": 113.75, "duration": 1.52}, {"text": "Did any of you get a chance to\nread the Chadwick article yet?", "start": 115.27, "duration": 4.61}, {"text": "OK.", "start": 119.88, "duration": 0.5}, {"text": "I'll show you where that is,\nbecause hopefully by now you're", "start": 120.38, "duration": 2.88}, {"text": "all aware that we have\na learning module site.", "start": 123.26, "duration": 2.13}, {"text": "It's where I'm going\nto post everything.", "start": 125.39, "duration": 2.127}, {"text": "It's where you're going\nto submit everything", "start": 127.517, "duration": 1.833}, {"text": "for the class.", "start": 129.35, "duration": 0.757}, {"text": "But I'll save to the\nend of this class", "start": 130.107, "duration": 1.583}, {"text": "to go through the\nactual syllabus", "start": 131.69, "duration": 1.375}, {"text": "because I want to\nget into the physics.", "start": 133.065, "duration": 1.835}, {"text": "So let's bring your knowledge\nfrom classical mechanics", "start": 134.9, "duration": 2.43}, {"text": "and E&M up till about 1895 when\nWilhelm Roentgen used X-rays", "start": 137.33, "duration": 5.55}, {"text": "and used them to, well, image\nsomething for the first time", "start": 142.88, "duration": 3.63}, {"text": "ever.", "start": 146.51, "duration": 0.66}, {"text": "Showing the contrast\nbetween bone and tissue,", "start": 147.17, "duration": 2.12}, {"text": "he was able to illuminate\nthe bones in a hand.", "start": 149.29, "duration": 3.25}, {"text": "And then about a year later, the\nX-rays got a whole lot better.", "start": 152.54, "duration": 3.52}, {"text": "So by then, it was known that\nthere were high-energy photons", "start": 156.06, "duration": 3.86}, {"text": "that had differential contrast\nbetween different types", "start": 159.92, "duration": 3.24}, {"text": "of material.", "start": 163.16, "duration": 2.57}, {"text": "A year later, after\nthe nicer X-ray,", "start": 165.73, "duration": 2.47}, {"text": "J.J. Thompson\nconclusively proved", "start": 168.2, "duration": 2.31}, {"text": "that there is an electron\nby taking these cathode", "start": 170.51, "duration": 3.17}, {"text": "rays, as they were\ncalled at one point,", "start": 173.68, "duration": 2.15}, {"text": "and sending them through\ntwo charged plates.", "start": 175.83, "duration": 2.36}, {"text": "And he was able to show\na slight deflection.", "start": 178.19, "duration": 2.36}, {"text": "So these cathode rays, as they\npass through an electric field,", "start": 180.55, "duration": 3.3}, {"text": "change direction a little bit.", "start": 183.85, "duration": 1.715}, {"text": "And from the change\nin direction,", "start": 185.565, "duration": 1.375}, {"text": "you may not know the\nmass or the charge,", "start": 186.94, "duration": 1.89}, {"text": "but you can get the\nmass to charge ratio.", "start": 188.83, "duration": 2.39}, {"text": "Because if you guys remember\nfrom 8.02, from electricity", "start": 191.22, "duration": 2.98}, {"text": "and magnetism, as\na charged particle", "start": 194.2, "duration": 2.22}, {"text": "passes through an electric\nfield, it's deflected.", "start": 196.42, "duration": 2.94}, {"text": "And the amount of that\ndeflection, or the curvature,", "start": 199.36, "duration": 2.4}, {"text": "is based on the mass\nto charge ratio.", "start": 201.76, "duration": 2.11}, {"text": "So Chadwick knew that\nelectrons existed.", "start": 203.87, "duration": 3.21}, {"text": "This was a known thing, as well\nas alpha, beta, and gamma rays.", "start": 207.08, "duration": 4.715}, {"text": "So the electrons that\ncame out of the nucleus", "start": 211.795, "duration": 1.875}, {"text": "were later renamed beta rays.", "start": 213.67, "duration": 1.8}, {"text": "And at around the same time,\nErnest Rutherford and Paul", "start": 215.47, "duration": 3.09}, {"text": "Villard, working in\nCanada and France,", "start": 218.56, "duration": 2.82}, {"text": "discovered that there are some\nheavy charge particles that", "start": 221.38, "duration": 2.91}, {"text": "have very little penetrating\npower, while Paul", "start": 224.29, "duration": 2.67}, {"text": "Villard discovered that there\nare some other radiations--", "start": 226.96, "duration": 3.9}, {"text": "I think he called it produced\nby disintegration of nuclei--", "start": 230.86, "duration": 3.63}, {"text": "that have very high\npenetrating power.", "start": 234.49, "duration": 2.0}, {"text": "And they named them\nalpha, beta, gamma", "start": 236.49, "duration": 1.63}, {"text": "in order of their penetrating\npower or their range.", "start": 238.12, "duration": 3.803}, {"text": "And so it was later figured\nout that these were also", "start": 241.923, "duration": 2.167}, {"text": "high-energy photons.", "start": 244.09, "duration": 1.36}, {"text": "So this is something to note is\nthat gamma rays, x-rays, light,", "start": 245.45, "duration": 3.89}, {"text": "whatever, it's all photons.", "start": 249.34, "duration": 2.43}, {"text": "However, once this pops\nback up, gamma rays", "start": 251.77, "duration": 4.309}, {"text": "emanate from the nucleus.", "start": 256.079, "duration": 1.541}, {"text": "So when we refer\nto a gamma ray, we", "start": 257.62, "duration": 1.52}, {"text": "mean a photon that came out\nof a nuclear interaction", "start": 259.14, "duration": 3.57}, {"text": "or a nuclear disintegration,\nnot an electron transition.", "start": 262.71, "duration": 4.468}, {"text": "So this is one-- this is what\nmakes a gamma ray a gamma", "start": 267.178, "duration": 2.292}, {"text": "ray, is where it comes from.", "start": 269.47, "duration": 1.47}, {"text": "Otherwise it's a photon.", "start": 270.94, "duration": 2.07}, {"text": "It behaves just\nlike any photons.", "start": 273.01, "duration": 2.5}, {"text": "So what did Chadwick\nsee in 1932?", "start": 275.51, "duration": 2.96}, {"text": "This is the first\none-page article", "start": 278.47, "duration": 2.46}, {"text": "that he sent out to Nature to\nsay, I found something weird.", "start": 280.93, "duration": 3.85}, {"text": "So he found out that when\nyou take alpha particles", "start": 284.78, "duration": 3.32}, {"text": "from polonium-- so let's say\nwe had a source of polonium", "start": 288.1, "duration": 6.54}, {"text": "sending off alpha particles,\nwhich I haven't told you", "start": 294.64, "duration": 2.46}, {"text": "what they are yet.", "start": 297.1, "duration": 0.83}, {"text": "It emits a radiation of\ngreat penetrating power", "start": 297.93, "duration": 4.33}, {"text": "when it hits a\nfoil of beryllium.", "start": 302.26, "duration": 2.82}, {"text": "And it was not known\nwhat these things were.", "start": 305.08, "duration": 2.16}, {"text": "So in goes the\nalphas to beryllium.", "start": 307.24, "duration": 2.64}, {"text": "Something happens,\nand something comes", "start": 309.88, "duration": 3.39}, {"text": "streaming out that couldn't be\nexplained by current theories.", "start": 313.27, "duration": 3.81}, {"text": "It was also noticed\nthat when hydrogen", "start": 317.08, "duration": 2.4}, {"text": "was placed in front of it,\nwhen a piece of hydrogen", "start": 319.48, "duration": 2.76}, {"text": "in the form of wax, which\ncontains a lot of hydrogen,", "start": 322.24, "duration": 3.18}, {"text": "was put in front of it,\nthe amount of ionization", "start": 325.42, "duration": 2.94}, {"text": "increased, as measured by\nwhat's called an ionization", "start": 328.36, "duration": 4.44}, {"text": "chamber and an\noscillograph, nothing", "start": 332.8, "duration": 2.46}, {"text": "more than an\nalmost-sealed chamber,", "start": 335.26, "duration": 4.89}, {"text": "a piston with some charge on\nit that would then deflect.", "start": 340.15, "duration": 5.03}, {"text": "As it were to pick up\npositive or negative charges,", "start": 345.18, "duration": 2.79}, {"text": "it would move\ninwards or outwards", "start": 347.97, "duration": 2.16}, {"text": "and send an electrical signal to\nsomething like an oscilloscope.", "start": 350.13, "duration": 4.05}, {"text": "So this was a way that\nyou could figure out", "start": 354.18, "duration": 2.07}, {"text": "how many ions were\ncreated by this highly", "start": 356.25, "duration": 2.73}, {"text": "penetrating radiation\ninteracting in the ionization", "start": 358.98, "duration": 3.15}, {"text": "chamber.", "start": 362.13, "duration": 1.26}, {"text": "And they estimated that\nwith the old theories,", "start": 363.39, "duration": 3.39}, {"text": "if this highly penetrating thing\nwere a photon or a gamma ray,", "start": 366.78, "duration": 4.29}, {"text": "it would have to have\nan energy of 50 times 10", "start": 371.07, "duration": 3.0}, {"text": "to the 6 electron\nvolts, or 50 MeV.", "start": 374.07, "duration": 5.1}, {"text": "He said, OK.", "start": 379.17, "duration": 0.6}, {"text": "Well, if that's to be basically\nthe experimental observation,", "start": 379.77, "duration": 3.75}, {"text": "say, a 50 MeV photon must be\nresponsible for the ionizations", "start": 383.52, "duration": 4.23}, {"text": "that we saw.", "start": 387.75, "duration": 1.892}, {"text": "And so again, this is\nwhat the experiment", "start": 389.642, "duration": 1.708}, {"text": "looks like where you've got\na polonium source naturally", "start": 391.35, "duration": 3.09}, {"text": "emitting alpha rays.", "start": 394.44, "duration": 1.34}, {"text": "They hit a foil, a beryllium.", "start": 395.78, "duration": 1.81}, {"text": "They produce what he did not\nknow at the time was neutrons.", "start": 397.59, "duration": 3.45}, {"text": "We actually do know that\nberyllium produces neutrons", "start": 401.04, "duration": 2.31}, {"text": "pretty well.", "start": 403.35, "duration": 1.23}, {"text": "Beryllium is an interesting\nneutron multiplier.", "start": 404.58, "duration": 2.97}, {"text": "It undergoes what's called\nan n 2n reaction where", "start": 407.55, "duration": 6.15}, {"text": "one neutron comes in, two\nneutrons can come out,", "start": 413.7, "duration": 3.2}, {"text": "and it transmutes\ninto something else.", "start": 416.9, "duration": 1.94}, {"text": "And we'll go over what\nthis notation means, what", "start": 418.84, "duration": 2.0}, {"text": "these nuclear reactions mean.", "start": 420.84, "duration": 1.29}, {"text": "If you don't understand\nit, don't worry.", "start": 422.13, "duration": 2.22}, {"text": "The whole point of today\nis to open up questions", "start": 424.35, "duration": 2.73}, {"text": "that we'll spend the rest of the\nsemester closing and answering.", "start": 427.08, "duration": 3.06}, {"text": "So again, if you're\nlost, don't worry.", "start": 430.14, "duration": 1.583}, {"text": "It's the first day of class,\nand it's your first day", "start": 431.723, "duration": 2.167}, {"text": "of Modern Physics.", "start": 433.89, "duration": 0.82}, {"text": "So not to worry.", "start": 434.71, "duration": 2.37}, {"text": "And this is an actual\npicture of what", "start": 437.08, "duration": 1.85}, {"text": "it looked like in the\npaper, a simple polonium", "start": 438.93, "duration": 2.43}, {"text": "source on a disk that was made\nby the natural decomposition", "start": 441.36, "duration": 3.84}, {"text": "of radium into polonium, a piece\nof beryllium, a vacuum chamber.", "start": 445.2, "duration": 4.62}, {"text": "Because it was already known\nthat the alpha particles", "start": 449.82, "duration": 2.61}, {"text": "coming from polonium have\nan extremely short range.", "start": 452.43, "duration": 2.76}, {"text": "We're going to figure out\nwhy as part of this class.", "start": 455.19, "duration": 3.36}, {"text": "But without that vacuum\nthere, the alpha particles", "start": 458.55, "duration": 2.663}, {"text": "wouldn't make it\nto the beryllium.", "start": 461.213, "duration": 1.417}, {"text": "So that much was known.", "start": 462.63, "duration": 1.2}, {"text": "What wasn't known was why are\nwe getting so many ionizations.", "start": 463.83, "duration": 4.65}, {"text": "They attributed it to\nwhat they called a process", "start": 468.48, "duration": 2.31}, {"text": "similar to the Compton effect.", "start": 470.79, "duration": 2.32}, {"text": "To tell you what\nthat is, in 1923,", "start": 473.11, "duration": 3.8}, {"text": "Arthur Compton figured\nout, among other things,", "start": 476.91, "duration": 2.88}, {"text": "Compton scattering, where a\nphoton can strike an electron.", "start": 479.79, "duration": 4.23}, {"text": "The photon changes energy.", "start": 484.02, "duration": 1.95}, {"text": "The electron picks\nup some energy.", "start": 485.97, "duration": 2.1}, {"text": "They exit at very\nwell-known angles,", "start": 488.07, "duration": 2.1}, {"text": "and they transfer very\nwell-known amounts of energy.", "start": 490.17, "duration": 3.34}, {"text": "So this is how they knew how\nmuch energy the photon, if it", "start": 493.51, "duration": 4.22}, {"text": "were to exist, should have.", "start": 497.73, "duration": 2.67}, {"text": "And they said the process\nwas analogous to Compton", "start": 500.4, "duration": 2.34}, {"text": "scattering because\nthey said in this case,", "start": 502.74, "duration": 2.97}, {"text": "a proton would be ejected.", "start": 505.71, "duration": 2.23}, {"text": "It would take a lot of energy to\neject a proton using a photon.", "start": 507.94, "duration": 4.2}, {"text": "And Chadwick saw\nthis and said, well,", "start": 512.14, "duration": 3.169}, {"text": "if we ascribe this phenomenon\nto a Compton recoil,", "start": 515.309, "duration": 4.171}, {"text": "we should see about 10,000 ions.", "start": 519.48, "duration": 2.429}, {"text": "We actually saw about 30,000.", "start": 521.909, "duration": 2.911}, {"text": "So there was more\nionization going", "start": 524.82, "duration": 1.71}, {"text": "on than can be explained\nby what's going on.", "start": 526.53, "duration": 2.49}, {"text": "In addition, those\nprotons should", "start": 529.02, "duration": 2.49}, {"text": "have a range in air of\nabout 1.3 millimeters,", "start": 531.51, "duration": 2.82}, {"text": "and they saw much more.", "start": 534.33, "duration": 1.99}, {"text": "So this is something simple--", "start": 536.32, "duration": 1.4}, {"text": "theory and experiment\ndon't match.", "start": 537.72, "duration": 2.58}, {"text": "There's got to be a different\ntheoretical explanation", "start": 540.3, "duration": 2.73}, {"text": "if the experiment was correct.", "start": 543.03, "duration": 2.55}, {"text": "And so finally, what I love--\nthe last sentence in this--", "start": 545.58, "duration": 3.07}, {"text": "the quantum\nhypothesis-- a quantum", "start": 548.65, "duration": 2.27}, {"text": "was the way they\nreferred to a photon.", "start": 550.92, "duration": 2.22}, {"text": "It was called a\nquantum back then,", "start": 553.14, "duration": 1.56}, {"text": "a little packet of energy.", "start": 554.7, "duration": 1.44}, {"text": "Can only be upheld if we\nforget about conservation", "start": 556.14, "duration": 3.57}, {"text": "of energy and momentum.", "start": 559.71, "duration": 1.77}, {"text": "Now, I'll ask you guys\nfrom 8.01 to 8.02.", "start": 561.48, "duration": 2.35}, {"text": "So Sean, when can you throw\nout energy and momentum", "start": 563.83, "duration": 3.32}, {"text": "conservation?", "start": 567.15, "duration": 2.025}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 569.175, "duration": 1.773}, {"text": "MIKE SHORT: That's\npretty much right.", "start": 570.948, "duration": 1.542}, {"text": "You can't.", "start": 572.49, "duration": 1.14}, {"text": "A situation probably\nwasn't given to you", "start": 573.63, "duration": 1.82}, {"text": "where you can just\nthrow away conservation", "start": 575.45, "duration": 1.75}, {"text": "of momentum and energy.", "start": 577.2, "duration": 1.5}, {"text": "In fact, nature gives\nus three quantities", "start": 578.7, "duration": 2.393}, {"text": "that we can measure\nand conserve--", "start": 581.093, "duration": 1.417}, {"text": "mass, momentum, and energy.", "start": 582.51, "duration": 2.42}, {"text": "And throughout this course,\nif something is not conserved,", "start": 584.93, "duration": 3.25}, {"text": "you've probably got the\nmath or the physics wrong.", "start": 588.18, "duration": 2.22}, {"text": "So this is something to\nremember throughout the course", "start": 590.4, "duration": 2.25}, {"text": "and our derivations and\nin your problem sets,", "start": 592.65, "duration": 2.37}, {"text": "is conserve mass, conserve\nmomentum, conserve energy, just", "start": 595.02, "duration": 4.29}, {"text": "like what was taught\nin 8.01 and 8.02.", "start": 599.31, "duration": 1.62}, {"text": "So I'll call your\nanswer correct.", "start": 600.93, "duration": 1.6}, {"text": "You don't remember a situation\nbecause, well, it didn't exist.", "start": 602.53, "duration": 3.26}, {"text": "And that's what Chadwick noted.", "start": 605.79, "duration": 1.92}, {"text": "He said theory and\nexperiment don't", "start": 607.71, "duration": 1.71}, {"text": "work unless we throw\nout conservation", "start": 609.42, "duration": 2.28}, {"text": "of energy and momentum.", "start": 611.7, "duration": 1.65}, {"text": "Whether this was a kind of\npassive-aggressive thing", "start": 613.35, "duration": 2.58}, {"text": "to say-- well,\nthis clearly can't", "start": 615.93, "duration": 1.86}, {"text": "exist-- or he was suggesting\nmaybe it doesn't work,", "start": 617.79, "duration": 3.298}, {"text": "I don't know.", "start": 621.088, "duration": 0.542}, {"text": "I wasn't there.", "start": 621.63, "duration": 1.47}, {"text": "But later on,\nabout a year later,", "start": 623.1, "duration": 1.59}, {"text": "he published a follow-on\npaper confirming the existence", "start": 624.69, "duration": 3.45}, {"text": "of a neutron by reconciling\nthese differences", "start": 628.14, "duration": 2.31}, {"text": "in theory and experiment.", "start": 630.45, "duration": 1.83}, {"text": "So he restated\nwhat he saw before.", "start": 632.28, "duration": 2.74}, {"text": "This was the first\nparagraph of it.", "start": 635.02, "duration": 2.3}, {"text": "And again, it said that\nradiation excited in beryllium.", "start": 637.32, "duration": 3.6}, {"text": "Whatever happened after the\nalpha particle came out.", "start": 640.92, "duration": 2.34}, {"text": "It had a highly penetrating\nradiation, distinctly greater", "start": 643.26, "duration": 3.81}, {"text": "than that of any\ngamma radiation found", "start": 647.07, "duration": 1.657}, {"text": "from radioactive elements.", "start": 648.727, "duration": 1.083}, {"text": "Something is different.", "start": 649.81, "duration": 2.69}, {"text": "And I want us to take\na sec to digest this.", "start": 652.5, "duration": 2.08}, {"text": "This is the part I actually\nwant you guys to read,", "start": 654.58, "duration": 2.19}, {"text": "so take a minute and read\nthrough some of this stuff.", "start": 656.77, "duration": 2.91}, {"text": "And then we'll begin\nexplaining his argument.", "start": 659.68, "duration": 2.4}, {"text": "Let me know when you\nguys are done reading.", "start": 686.628, "duration": 1.792}, {"text": "OK.", "start": 697.66, "duration": 0.5}, {"text": "I see some folks\nstarting to look down.", "start": 698.16, "duration": 2.5}, {"text": "So let's take this\napart and figure out", "start": 700.66, "duration": 2.6}, {"text": "what was Chadwick saying.", "start": 703.26, "duration": 1.68}, {"text": "He was saying that if a\nquantum was responsible", "start": 704.94, "duration": 3.42}, {"text": "for this energy,\na photon, then we", "start": 708.36, "duration": 2.25}, {"text": "can write a nuclear reaction.", "start": 710.61, "duration": 2.52}, {"text": "I'll write it in the\nnotation that we use now,", "start": 713.13, "duration": 1.99}, {"text": "which would be beryllium-9,\nthe only naturally occurring", "start": 715.12, "duration": 5.54}, {"text": "isotope of beryllium,\nplus an alpha particle", "start": 720.66, "duration": 3.63}, {"text": "would lead to carbon-13\nplus a gamma ray.", "start": 724.29, "duration": 5.55}, {"text": "And that gamma ray\nwould take away", "start": 729.84, "duration": 2.22}, {"text": "the energy from this reaction.", "start": 732.06, "duration": 2.04}, {"text": "So now we can start to figure\nout, is energy conserved?", "start": 734.1, "duration": 3.3}, {"text": "Could this gamma\nray actually exist?", "start": 737.4, "duration": 1.96}, {"text": "And if it does, does it\naccount for the ionizations", "start": 739.36, "duration": 2.69}, {"text": "that Chadwick saw?", "start": 742.05, "duration": 1.59}, {"text": "So for each of\nthese isotopes, we", "start": 743.64, "duration": 2.64}, {"text": "know a few different quantities.", "start": 746.28, "duration": 1.89}, {"text": "We know what's called its rest\nmass energy, which is this.", "start": 748.17, "duration": 8.4}, {"text": "It's rest mass times\nspeed of light squared.", "start": 756.57, "duration": 2.35}, {"text": "This should look\nfamiliar to everyone.", "start": 758.92, "duration": 2.04}, {"text": "I've seen it on t-shirts\nall over campus.", "start": 760.96, "duration": 2.67}, {"text": "And it may take\ntwo or three weeks", "start": 763.63, "duration": 1.77}, {"text": "to really wrap your head around\nwhat Einstein's equation really", "start": 765.4, "duration": 4.44}, {"text": "means.", "start": 769.84, "duration": 0.93}, {"text": "It is that mass and\nenergy are equivalent.", "start": 770.77, "duration": 2.28}, {"text": "You can express mass in terms\nof energy, and vise versa.", "start": 773.05, "duration": 3.76}, {"text": "And you will be doing so\nto conserve energy and mass", "start": 776.81, "duration": 3.95}, {"text": "in nuclear reactions, one of\nwhich is written right here.", "start": 780.76, "duration": 3.18}, {"text": "So if each of these things\nhas a given rest mass energy,", "start": 783.94, "duration": 3.27}, {"text": "let's say a rest mass\nenergy of beryllium", "start": 787.21, "duration": 2.91}, {"text": "and a rest mass energy\nof an alpha particle,", "start": 790.12, "duration": 3.24}, {"text": "and this alpha particle maybe\nhad some kinetic energy--", "start": 793.36, "duration": 3.21}, {"text": "it was moving pretty\nfast, so we'll", "start": 796.57, "duration": 1.53}, {"text": "give that the symbol\nt for kinetic energy,", "start": 798.1, "duration": 3.402}, {"text": "because that's what you're\ngoing to see in your notes", "start": 801.502, "duration": 2.208}, {"text": "and in the reading\nand everywhere.", "start": 803.71, "duration": 1.89}, {"text": "And then this\ncarbon-13 nucleus has", "start": 805.6, "duration": 1.92}, {"text": "got to have a rest mass\nand a kinetic energy,", "start": 807.52, "duration": 5.33}, {"text": "and then this gamma\nray, it's going", "start": 812.85, "duration": 2.71}, {"text": "to have some e gamma energy.", "start": 815.56, "duration": 2.31}, {"text": "Now, the question is,\nis the mass and energy", "start": 817.87, "duration": 2.9}, {"text": "conserved in this equation?", "start": 820.77, "duration": 1.788}, {"text": "What we're actually\nstarting to write", "start": 822.558, "duration": 1.542}, {"text": "is what's called the q\nequation, or the universal mass", "start": 824.1, "duration": 3.9}, {"text": "and energy balance for any\nkind of nuclear reaction.", "start": 828.0, "duration": 3.54}, {"text": "So let's say we have a\nlarge initial nucleus", "start": 831.54, "duration": 3.9}, {"text": "i and some small\nparticle i moving", "start": 835.44, "duration": 4.08}, {"text": "at it with some great speed.", "start": 839.52, "duration": 2.94}, {"text": "And after some\nreaction occurs, you", "start": 842.46, "duration": 3.12}, {"text": "have a small, final\nparticle leaving", "start": 845.58, "duration": 3.14}, {"text": "and a different, large\nfinal particle leaving.", "start": 848.72, "duration": 3.52}, {"text": "They don't necessarily\nhave to be the same.", "start": 852.24, "duration": 2.92}, {"text": "Let's give these particles\ndesignations 1, 2, 3, and 4.", "start": 855.16, "duration": 7.25}, {"text": "In the end, we should be\nable to write the difference", "start": 862.41, "duration": 2.37}, {"text": "in either total\nenergy or total mass", "start": 864.78, "duration": 2.28}, {"text": "of the system as this value q.", "start": 867.06, "duration": 3.78}, {"text": "q is, let's say,\nthe amount of energy", "start": 870.84, "duration": 3.36}, {"text": "that turns into\nmass, or vise versa.", "start": 874.2, "duration": 2.042}, {"text": "So let's say energy transfer.", "start": 876.242, "duration": 1.208}, {"text": "And so if we start writing some\nmass conservation equation,", "start": 882.84, "duration": 2.58}, {"text": "we can say that the\nmass of nucleus 1", "start": 885.42, "duration": 3.42}, {"text": "plus the mass of\nnucleus 2 should", "start": 888.84, "duration": 2.7}, {"text": "equal the mass of nucleus 3\nplus the mass of nucleus 4", "start": 891.54, "duration": 4.71}, {"text": "plus however much energy\nfrom nuclei 1 and 2 turned", "start": 896.25, "duration": 5.43}, {"text": "into energy into 3 and 4.", "start": 901.68, "duration": 3.173}, {"text": "We could also write\nthe same thing", "start": 904.853, "duration": 1.417}, {"text": "for their kinetic energies.", "start": 906.27, "duration": 1.86}, {"text": "In this case, the\nfinals are on the end.", "start": 908.13, "duration": 4.338}, {"text": "So I'm sorry.", "start": 912.468, "duration": 0.542}, {"text": "I should use t for\nkinetic energy.", "start": 913.01, "duration": 1.9}, {"text": "So what this is saying is\nthat if some mass has turned", "start": 926.2, "duration": 3.15}, {"text": "into energy at the\nend, that energy", "start": 929.35, "duration": 2.1}, {"text": "had to come from somewhere.", "start": 931.45, "duration": 1.92}, {"text": "It had to come from the initial\nkinetic energy or conversion", "start": 933.37, "duration": 2.85}, {"text": "of mass to energy\nfrom this reaction.", "start": 936.22, "duration": 2.773}, {"text": "And so notice that\nnow, you can actually", "start": 938.993, "duration": 1.667}, {"text": "express the masses of the\nnuclei in terms of their energy,", "start": 940.66, "duration": 3.72}, {"text": "of their initial and\nfinal kinetic energies.", "start": 944.38, "duration": 2.495}, {"text": "And this right\nhere is what we're", "start": 946.875, "duration": 1.375}, {"text": "going to be spending the first\ntwo or three weeks deriving,", "start": 948.25, "duration": 3.39}, {"text": "using, and exploring in order\nto balance nuclear reactions", "start": 951.64, "duration": 3.39}, {"text": "and explain why they\nare the way they are.", "start": 955.03, "duration": 3.37}, {"text": "So let's make sure-- we'll keep\nthis nuclear reaction up here,", "start": 958.4, "duration": 3.8}, {"text": "because Chadwick proposed\na different one to explain", "start": 962.2, "duration": 2.76}, {"text": "what he saw.", "start": 964.96, "duration": 2.23}, {"text": "And some of the\nevidence for this", "start": 967.19, "duration": 2.13}, {"text": "was that he put\nsome aluminum foil", "start": 969.32, "duration": 3.39}, {"text": "in between the beryllium where\nthings were being liberated", "start": 972.71, "duration": 7.81}, {"text": "and the ionization\nchamber and oscilloscope,", "start": 980.52, "duration": 3.19}, {"text": "or oscillograph, as\nhe liked to call it.", "start": 983.71, "duration": 2.36}, {"text": "And that way, by putting\nmore and more pieces of foil", "start": 986.07, "duration": 3.02}, {"text": "in there, you can\ndeduce what's called", "start": 989.09, "duration": 1.59}, {"text": "the range, or the distance\nthat the radiation will travel", "start": 990.68, "duration": 6.55}, {"text": "before it stops by losing\nenergy through a whole host", "start": 997.23, "duration": 3.143}, {"text": "of different processes that\nwe'll be working through", "start": 1000.373, "duration": 2.167}, {"text": "together.", "start": 1002.54, "duration": 1.08}, {"text": "If this were to be\nascribed to a proton,", "start": 1003.62, "duration": 3.58}, {"text": "then it should have had\na certain range in air", "start": 1007.2, "duration": 3.44}, {"text": "by this curve b right here.", "start": 1010.64, "duration": 2.1}, {"text": "Instead, he found this curve a\nwhere things moved about three", "start": 1012.74, "duration": 2.94}, {"text": "times farther than\ncould have been", "start": 1015.68, "duration": 1.44}, {"text": "explained if that\nwere a proton to be", "start": 1017.12, "duration": 3.21}, {"text": "liberated by all this stuff.", "start": 1020.33, "duration": 1.77}, {"text": "So he's saying, OK, something\nhas got more penetrating power.", "start": 1022.1, "duration": 3.57}, {"text": "We know now that part\nof the reason for this", "start": 1025.67, "duration": 2.159}, {"text": "is if there's a neutron,\nand there's no charge on it,", "start": 1027.829, "duration": 4.748}, {"text": "then it's not going to interact\nwith the electrons in matter.", "start": 1032.577, "duration": 2.542}, {"text": "It won't even see them.", "start": 1035.119, "duration": 1.561}, {"text": "Whereas protons or\nany other charged", "start": 1036.68, "duration": 1.679}, {"text": "particles will see the\nelectrons in matter", "start": 1038.359, "duration": 2.551}, {"text": "and will interact with the\nelectrons and the nuclei.", "start": 1040.91, "duration": 3.04}, {"text": "So a little flash\nforward to say,", "start": 1043.95, "duration": 2.0}, {"text": "we can explain this pretty\nsimply with what we generally", "start": 1045.95, "duration": 2.77}, {"text": "know.", "start": 1048.72, "duration": 0.5}, {"text": "But this was the\nfirst time somebody", "start": 1049.22, "duration": 1.86}, {"text": "had to come up with\n[INAUDIBLE] explanation,", "start": 1051.08, "duration": 2.133}, {"text": "and it was quite hard.", "start": 1053.213, "duration": 0.917}, {"text": "And so moving on,\nhe can say, well, I", "start": 1057.3, "duration": 1.92}, {"text": "know what protons should\nbe injected from paraffin.", "start": 1059.22, "duration": 3.6}, {"text": "I know a formula to describe\nwhat quantum or photon", "start": 1062.82, "duration": 4.59}, {"text": "energy had to create them.", "start": 1067.41, "duration": 2.58}, {"text": "And then instead, he says-- this\nis where his major hypothesis", "start": 1069.99, "duration": 2.97}, {"text": "is--", "start": 1072.96, "duration": 0.69}, {"text": "either we relinquish\nconservation", "start": 1073.65, "duration": 1.98}, {"text": "of energy or neutron or\nadopt another hypothesis.", "start": 1075.63, "duration": 5.28}, {"text": "And this was already put\nforth by Rutherford back", "start": 1080.91, "duration": 4.26}, {"text": "in the '20s that there\nmay be a neutron,", "start": 1085.17, "duration": 1.77}, {"text": "but there wasn't any proof.", "start": 1086.94, "duration": 1.68}, {"text": "And this is what\nprovided the proof.", "start": 1088.62, "duration": 2.64}, {"text": "He gave an alternate\nnuclear reaction", "start": 1091.26, "duration": 3.27}, {"text": "if there were to be\na neutron which had", "start": 1094.53, "duration": 2.01}, {"text": "roughly the mass of a proton.", "start": 1096.54, "duration": 2.29}, {"text": "Then let's write a\nsecond one down here.", "start": 1098.83, "duration": 1.79}, {"text": "I'm going to erase\nthese extra notation,", "start": 1100.62, "duration": 2.7}, {"text": "and we'll write the competing\nnuclear action below.", "start": 1103.32, "duration": 3.42}, {"text": "And he said that-- let's say\nwe start with beryllium-9", "start": 1106.74, "duration": 8.22}, {"text": "plus an alpha\nparticle could instead", "start": 1114.96, "duration": 3.09}, {"text": "become carbon-12 and a neutron.", "start": 1118.05, "duration": 4.79}, {"text": "So I'd like to ask you guys\nright now to work this out.", "start": 1127.53, "duration": 2.55}, {"text": "Are both of these reactions\nbalanced in terms of mass?", "start": 1130.08, "duration": 3.48}, {"text": "Are there the same number\nof protons, neutrons,", "start": 1133.56, "duration": 3.25}, {"text": "and electrons at either side?", "start": 1136.81, "duration": 2.12}, {"text": "And just to let you\nknow, an alpha particle", "start": 1138.93, "duration": 2.46}, {"text": "is better known as\na helium nucleus.", "start": 1141.39, "duration": 3.69}, {"text": "So that means that\nthere's two protons.", "start": 1145.08, "duration": 3.09}, {"text": "There's four protons\nplus neutrons,", "start": 1148.17, "duration": 3.24}, {"text": "and beryllium-9 has four protons\nand nine protons plus neutrons.", "start": 1151.41, "duration": 11.32}, {"text": "And carbon-12 has six protons.", "start": 1162.73, "duration": 3.92}, {"text": "A neutron has zero protons.", "start": 1166.65, "duration": 2.365}, {"text": "So in each of these-- and I'll\nfill in the other ones here.", "start": 1171.89, "duration": 2.89}, {"text": "So that's a 4, 4, 2, and 6.", "start": 1174.78, "duration": 4.91}, {"text": "Do we have the same number\nof protons and neutrons", "start": 1179.69, "duration": 2.13}, {"text": "on both sides of both equations?", "start": 1181.82, "duration": 1.86}, {"text": "I see a number of heads and\none person saying yes, we do.", "start": 1187.03, "duration": 3.9}, {"text": "So both of these reactions\nare balanced in terms of mass.", "start": 1190.93, "duration": 3.27}, {"text": "The next thing to do is balance\nthem in terms of energy.", "start": 1194.2, "duration": 3.21}, {"text": "Now, they can both be\nbalanced in terms of energy", "start": 1197.41, "duration": 2.67}, {"text": "because you could attribute the\nchange in the amount of mass", "start": 1200.08, "duration": 4.62}, {"text": "from here to there\nand attribute that", "start": 1204.7, "duration": 2.58}, {"text": "to the energy of the photon.", "start": 1207.28, "duration": 2.37}, {"text": "That's when you'd have to have a\nphoton of energy around 50 MeV.", "start": 1209.65, "duration": 6.39}, {"text": "But if a proton--", "start": 1216.04, "duration": 1.2}, {"text": "I'm sorry-- a photon\nof energy around 50 MeV", "start": 1217.24, "duration": 2.46}, {"text": "can't explain what we saw.", "start": 1219.7, "duration": 1.73}, {"text": "Instead, if there is something\nlike a neutron which also", "start": 1221.43, "duration": 3.01}, {"text": "has its own rest mass and\nits own kinetic energy,", "start": 1224.44, "duration": 6.86}, {"text": "and that neutron were\nhighly penetrating,", "start": 1231.3, "duration": 2.25}, {"text": "it could explain\nwhat Chadwick saw.", "start": 1233.55, "duration": 3.48}, {"text": "And so the masses and\nthings of these nuclei", "start": 1237.03, "duration": 3.0}, {"text": "were fairly well known\nback then to, well,", "start": 1240.03, "duration": 3.0}, {"text": "six significant digits\nbased on some very careful", "start": 1243.03, "duration": 2.97}, {"text": "experimentation.", "start": 1246.0, "duration": 1.29}, {"text": "And all he did is\nsay, all right.", "start": 1247.29, "duration": 1.44}, {"text": "Let's take all of the\nenergies in this reaction.", "start": 1248.73, "duration": 2.88}, {"text": "Remember how I\ntold you over here,", "start": 1251.61, "duration": 2.43}, {"text": "you can write any\nnuclear reaction", "start": 1254.04, "duration": 1.65}, {"text": "in terms of its\nkinetic energies,", "start": 1255.69, "duration": 2.04}, {"text": "and the difference will\ngive you the q value,", "start": 1257.73, "duration": 2.26}, {"text": "which you can attribute to the\nconversion of mass to energy?", "start": 1259.99, "duration": 3.62}, {"text": "That's what Chadwick\ndid right here.", "start": 1263.61, "duration": 2.13}, {"text": "He took the full\nreaction, saying here's", "start": 1265.74, "duration": 2.82}, {"text": "the mass of beryllium, the\nmass of the alpha particle,", "start": 1268.56, "duration": 3.96}, {"text": "the kinetic energy of\nthe alpha particle.", "start": 1272.52, "duration": 2.515}, {"text": "Note that he assumed that the\nkinetic energy of beryllium", "start": 1275.035, "duration": 2.375}, {"text": "was zero.", "start": 1277.41, "duration": 0.54}, {"text": "It was just sitting\nat room temperature.", "start": 1277.95, "duration": 2.34}, {"text": "Does anyone know the approximate\nkinetic energy of atoms", "start": 1280.29, "duration": 2.58}, {"text": "at room temperature?", "start": 1282.87, "duration": 3.01}, {"text": "Order of magnitude, even?", "start": 1285.88, "duration": 2.56}, {"text": "It's around 1/100 to 1/1,000\nof an EV, or an electron volt.", "start": 1288.44, "duration": 4.89}, {"text": "So when we're talking\nabout beryllium,", "start": 1293.33, "duration": 2.4}, {"text": "whose kinetic energy, we'll\nsay, is around 0.01 EV,", "start": 1295.73, "duration": 4.74}, {"text": "and the alpha particle whose\nkinetic energy was around 4", "start": 1300.47, "duration": 3.93}, {"text": "times 10 to the 6th EV, you\ncan see why it's neglected.", "start": 1304.4, "duration": 5.52}, {"text": "And you can do that too.", "start": 1309.92, "duration": 1.2}, {"text": "You do not have to account\nfor the initial kinetic energy", "start": 1311.12, "duration": 5.97}, {"text": "of a nucleus at rest.", "start": 1317.09, "duration": 1.98}, {"text": "This is the first\napproximation that we", "start": 1319.07, "duration": 1.86}, {"text": "tend to make to the q equation\nto just have fewer variables.", "start": 1320.93, "duration": 3.592}, {"text": "And don't worry if you\ndon't remember this now,", "start": 1324.522, "duration": 1.958}, {"text": "because we have a whole\nlecture on the q equation.", "start": 1326.48, "duration": 3.45}, {"text": "And so finally, he\nsaid, all right.", "start": 1329.93, "duration": 1.79}, {"text": "We'll subtract all the masses.", "start": 1331.72, "duration": 1.63}, {"text": "We're left with the kinetic\nenergies and a little bit", "start": 1333.35, "duration": 2.91}, {"text": "of excess rest mass.", "start": 1336.26, "duration": 2.94}, {"text": "That's got to be--", "start": 1339.2, "duration": 2.63}, {"text": "this has got to exist.", "start": 1341.83, "duration": 1.14}, {"text": "And so this inequality has to be\nsatisfied, which indeed it was.", "start": 1342.97, "duration": 4.92}, {"text": "Using this inequality,\nhe said that the velocity", "start": 1347.89, "duration": 2.64}, {"text": "of the neutron has to be\nless than its kinetic energy", "start": 1350.53, "duration": 3.39}, {"text": "if it had all of that\nenergy, 3.9 times 10", "start": 1353.92, "duration": 2.94}, {"text": "to the 9 centimeter per second.", "start": 1356.86, "duration": 1.77}, {"text": "Indeed it was lower--", "start": 1358.63, "duration": 1.56}, {"text": "not by that much, but it still\nsatisfied this criterion.", "start": 1360.19, "duration": 3.27}, {"text": "So things are checking out.", "start": 1363.46, "duration": 1.83}, {"text": "That's pretty cool.", "start": 1365.29, "duration": 1.92}, {"text": "He looked at another\nnuclear reaction", "start": 1367.21, "duration": 2.19}, {"text": "that was known at the time.", "start": 1369.4, "duration": 1.47}, {"text": "If you were to bombard\nboron-11 with helium,", "start": 1370.87, "duration": 3.24}, {"text": "you end up with\nnitrogen-14 and either--", "start": 1374.11, "duration": 3.84}, {"text": "either end up with\nnitrogen-15 and a photon", "start": 1377.95, "duration": 2.67}, {"text": "or nitrogen-14 and a\nneutron, explaining", "start": 1380.62, "duration": 3.09}, {"text": "another reaction that\nwasn't as well known before.", "start": 1383.71, "duration": 3.67}, {"text": "So I'd like to write\nthis nuclear reaction,", "start": 1387.38, "duration": 3.357}, {"text": "because I want you all to get\nvery familiar with writing", "start": 1390.737, "duration": 2.333}, {"text": "nuclear reactions.", "start": 1393.07, "duration": 1.81}, {"text": "Let's say boron-11 plus\nan alpha particle--", "start": 1394.88, "duration": 5.03}, {"text": "we'll say it has a mass of 4--", "start": 1399.91, "duration": 2.7}, {"text": "becomes nitrogen\n14 and a neutron.", "start": 1402.61, "duration": 3.93}, {"text": "We also have a\nshorthand of writing", "start": 1409.81, "duration": 1.65}, {"text": "this nuclear reaction\nwhich I'll use", "start": 1411.46, "duration": 1.59}, {"text": "on the board for speed's sake.", "start": 1413.05, "duration": 2.13}, {"text": "Usually if you put\nthe initial nucleus", "start": 1415.18, "duration": 4.56}, {"text": "and the initial incoming\nradiation, comma,", "start": 1419.74, "duration": 3.24}, {"text": "the exiting radiation,\nand the final nucleus,", "start": 1422.98, "duration": 5.83}, {"text": "these two right\nhere are equivalent.", "start": 1428.81, "duration": 2.33}, {"text": "This is just a shorthand\nfor nuclear reactions.", "start": 1431.14, "duration": 2.64}, {"text": "This is what you'll\ntend to see because it's", "start": 1433.78, "duration": 2.22}, {"text": "a lot easier to write this\nshorthand and parse it visually", "start": 1436.0, "duration": 3.24}, {"text": "than it is to parse a\nwhole nuclear reaction.", "start": 1439.24, "duration": 3.44}, {"text": "So I just want you to know if\nyou don't know what these are,", "start": 1442.68, "duration": 2.5}, {"text": "just remember to\nstick the arrow here,", "start": 1445.18, "duration": 2.49}, {"text": "stick plus signs in\nfor the parentheses,", "start": 1447.67, "duration": 1.86}, {"text": "and you've got the same thing.", "start": 1449.53, "duration": 1.77}, {"text": "And using these, you should be\nable to very quickly determine", "start": 1451.3, "duration": 2.82}, {"text": "is this reaction balanced.", "start": 1454.12, "duration": 1.23}, {"text": "What's actually going on?", "start": 1455.35, "duration": 1.59}, {"text": "And there will be tabulated\nvalues of q values or energy", "start": 1456.94, "duration": 3.3}, {"text": "amounts for these\nsorts of reactions", "start": 1460.24, "duration": 1.988}, {"text": "in all sorts of tables\nI'll be showing you.", "start": 1462.228, "duration": 1.792}, {"text": "And so finally, he\nfigured out what", "start": 1467.5, "duration": 2.67}, {"text": "the energy or the mass defect\nof the neutrons should be.", "start": 1470.17, "duration": 3.66}, {"text": "Does anyone know what\na mass defect is?", "start": 1473.83, "duration": 1.8}, {"text": "This is another core concept.", "start": 1478.21, "duration": 2.25}, {"text": "Let's say you were to want\nto make an atom of helium.", "start": 1480.46, "duration": 3.75}, {"text": "So you would have to take\ntwo protons whose masses are", "start": 1484.21, "duration": 5.01}, {"text": "very well known,\nand two neutrons,", "start": 1489.22, "duration": 4.7}, {"text": "and bring them together.", "start": 1493.92, "duration": 1.0}, {"text": "So if you were to\nhave-- let's say", "start": 1499.76, "duration": 1.58}, {"text": "the initial mass\nwould be 2 times", "start": 1501.34, "duration": 3.56}, {"text": "the mass of a neutron plus 2\ntimes the mass of a proton.", "start": 1504.9, "duration": 6.03}, {"text": "And the final mass is just\nthe mass of a helium nucleus.", "start": 1510.93, "duration": 5.36}, {"text": "You'll actually find that\nthe initial mass does not", "start": 1516.29, "duration": 2.34}, {"text": "equal the final mass.", "start": 1518.63, "duration": 3.45}, {"text": "In bringing nuclei\nor nucleons together,", "start": 1522.08, "duration": 3.475}, {"text": "they actually release what's\ncalled their binding energy.", "start": 1525.555, "duration": 2.375}, {"text": "It's what keeps the\nnucleus bound together.", "start": 1527.93, "duration": 2.4}, {"text": "There's a little bit of\nmass turned into energy.", "start": 1530.33, "duration": 2.55}, {"text": "And so you know how we like\nsay the whole is usually", "start": 1532.88, "duration": 3.15}, {"text": "more than the sum of its parts?", "start": 1536.03, "duration": 1.325}, {"text": "In nuclear\nengineering, the whole", "start": 1537.355, "duration": 1.375}, {"text": "is a little less than\nthe sum of its parts.", "start": 1538.73, "duration": 2.01}, {"text": "It definitely is not equal.", "start": 1540.74, "duration": 2.19}, {"text": "And Chadwick was proposing\nthat a neutron should actually", "start": 1542.93, "duration": 3.81}, {"text": "be made up of a\nproton and an electron", "start": 1546.74, "duration": 6.96}, {"text": "in very close proximity.", "start": 1553.7, "duration": 1.835}, {"text": "And since the masses of\nthe proton and the electron", "start": 1555.535, "duration": 2.125}, {"text": "were known, he said, well,\nif we bring the proton", "start": 1557.66, "duration": 2.67}, {"text": "and electron very\nclose together to have", "start": 1560.33, "duration": 2.76}, {"text": "an overall neutral\nneutron particle,", "start": 1563.09, "duration": 3.81}, {"text": "it should have roughly that\nmass defect or that difference", "start": 1566.9, "duration": 4.32}, {"text": "between the energy of\nits constituent nucleons", "start": 1571.22, "duration": 3.63}, {"text": "and the energy of the\nassembled nucleus.", "start": 1574.85, "duration": 2.7}, {"text": "And you'll hear the\nwords \"mass defect\"", "start": 1582.38, "duration": 2.14}, {"text": "and \"binding energy\" used.", "start": 1584.52, "duration": 1.53}, {"text": "Mass defect is in terms\nof mass in either--", "start": 1586.05, "duration": 3.69}, {"text": "you can give it in kilograms\nor in atomic mass units,", "start": 1589.74, "duration": 4.0}, {"text": "or AMU, or in, let's\nsay, MeV c squared.", "start": 1593.74, "duration": 7.212}, {"text": "And you'll also hear of the\nbinding energy just given", "start": 1600.952, "duration": 2.208}, {"text": "in things like MeV.", "start": 1603.16, "duration": 3.05}, {"text": "I want to show you where you\ncan find these things now.", "start": 1606.21, "duration": 2.7}, {"text": "I'll give you the single\nmost useful website", "start": 1608.91, "duration": 4.23}, {"text": "that you'll be referring to.", "start": 1613.14, "duration": 2.12}, {"text": "And I've posted it up on\nthe Learning Module site,", "start": 1615.26, "duration": 2.47}, {"text": "so now is a good time for me to\nshow you that the site exists.", "start": 1617.73, "duration": 4.11}, {"text": "And let me just clone\nmy screen real quick.", "start": 1621.84, "duration": 1.85}, {"text": "It's a wireless HDMI thing, so\nit takes a sec to pop back up.", "start": 1627.14, "duration": 4.228}, {"text": "Great.", "start": 1634.36, "duration": 1.05}, {"text": "Has anyone not been\nto the site yet?", "start": 1635.41, "duration": 3.21}, {"text": "It's OK.", "start": 1638.62, "duration": 0.5}, {"text": "You don't have to\nbe embarrassed.", "start": 1639.12, "duration": 0.99}, {"text": "OK.", "start": 1640.11, "duration": 0.5}, {"text": "About half of you.", "start": 1640.61, "duration": 1.18}, {"text": "I recommend tonight that you\nstart looking through the site.", "start": 1641.79, "duration": 3.33}, {"text": "One, make sure that\nyou can log in,", "start": 1645.12, "duration": 2.07}, {"text": "because you'll need to log in\nto see some of the copyrighted", "start": 1647.19, "duration": 2.97}, {"text": "materials that I've posted,\nand two, because this is where", "start": 1650.16, "duration": 2.58}, {"text": "you'll be posting\nall your homeworks,", "start": 1652.74, "duration": 2.07}, {"text": "getting the assignments,\nchecking due dates.", "start": 1654.81, "duration": 2.31}, {"text": "Especially if I\npostpone a problem set,", "start": 1657.12, "duration": 2.82}, {"text": "I'll put out an announcement\nand post it here.", "start": 1659.94, "duration": 2.22}, {"text": "So this is the place\nto look for everything.", "start": 1662.16, "duration": 2.91}, {"text": "And in addition, I've posted\na lot of useful materials", "start": 1665.07, "duration": 2.55}, {"text": "for you guys.", "start": 1667.62, "duration": 2.62}, {"text": "They're all at the\nbottom, and the top one", "start": 1670.24, "duration": 1.75}, {"text": "is the [INAUDIBLE]\ntable of nuclides.", "start": 1671.99, "duration": 3.9}, {"text": "Anyone seen this\nkind of thing before?", "start": 1675.89, "duration": 2.16}, {"text": "We have posters of it down on\nall the first-floor classrooms", "start": 1678.05, "duration": 2.64}, {"text": "in Building 24.", "start": 1680.69, "duration": 1.47}, {"text": "This is our go-to chart.", "start": 1682.16, "duration": 1.44}, {"text": "When you want to find out\nall of the nuclear half-life,", "start": 1683.6, "duration": 2.88}, {"text": "radioactive decay\nand decay of energy,", "start": 1686.48, "duration": 2.67}, {"text": "probability of certain\ndirection, whatever,", "start": 1689.15, "duration": 2.55}, {"text": "this is where you go.", "start": 1691.7, "duration": 1.87}, {"text": "So let's take a look\nat, well, helium-4", "start": 1693.57, "duration": 2.873}, {"text": "since we've been\ntalking about it,", "start": 1696.443, "duration": 1.417}, {"text": "better known as\nan alpha particle.", "start": 1697.86, "duration": 1.83}, {"text": "And you'll notice a few\ndifferent quantities visible.", "start": 1699.69, "duration": 3.39}, {"text": "The atomic mass, 4.0026032 AMU.", "start": 1703.08, "duration": 6.69}, {"text": "And this is another tip I want\nto give you guys right now.", "start": 1709.77, "duration": 2.52}, {"text": "Don't round these numbers.", "start": 1712.29, "duration": 2.46}, {"text": "That's one of the\nmajor trip up points.", "start": 1714.75, "duration": 1.98}, {"text": "If you say that's\napproximately 4 or 4.003,", "start": 1716.73, "duration": 3.66}, {"text": "you probably won't get\nthe p-set questions right,", "start": 1720.39, "duration": 2.76}, {"text": "because 1/1,000 of an AMU can\nstill represent almost an MeV", "start": 1723.15, "duration": 4.35}, {"text": "of lost energy.", "start": 1727.5, "duration": 1.47}, {"text": "So let's say you have\na nuclear reaction that", "start": 1728.97, "duration": 2.28}, {"text": "liberates a 1 mega electron\nvolt or one MeV gamma ray,", "start": 1731.25, "duration": 4.5}, {"text": "and you get the\nfourth digit wrong", "start": 1735.75, "duration": 2.16}, {"text": "in one of your\nmass calculations.", "start": 1737.91, "duration": 1.5}, {"text": "It's like that gamma\nray didn't exist,", "start": 1739.41, "duration": 1.92}, {"text": "and you won't get\nthe answer right.", "start": 1741.33, "duration": 1.74}, {"text": "So again, word to the\nwise-- do not round.", "start": 1743.07, "duration": 3.36}, {"text": "You'll also see what's known as\nthe excess mass or the binding", "start": 1746.43, "duration": 3.3}, {"text": "energy.", "start": 1749.73, "duration": 0.51}, {"text": "So this binding\nenergy right here,", "start": 1750.24, "duration": 2.58}, {"text": "if you were to take two\nprotons and two neutrons", "start": 1752.82, "duration": 3.48}, {"text": "and bring them together and\nlook at the difference in masses", "start": 1756.3, "duration": 3.84}, {"text": "from, let's say, the same\nold formula as before,", "start": 1760.14, "duration": 3.0}, {"text": "you would get a difference of\n28,295 keV, or about 28.295673", "start": 1763.14, "duration": 10.74}, {"text": "MeV.", "start": 1773.88, "duration": 0.93}, {"text": "Again, don't round.", "start": 1774.81, "duration": 1.775}, {"text": "Let's figure this\nout right here.", "start": 1776.585, "duration": 1.375}, {"text": "So we have 28.295673 MeV.", "start": 1777.96, "duration": 8.58}, {"text": "And there is a conversion factor\nthat you should either memorize", "start": 1786.54, "duration": 3.03}, {"text": "or write down.", "start": 1789.57, "duration": 0.87}, {"text": "Either way, it's good.", "start": 1790.44, "duration": 1.53}, {"text": "It's about 931.49 MeV\nper atomic mass unit.", "start": 1791.97, "duration": 7.5}, {"text": "This is your mass\nenergy equivalence", "start": 1799.47, "duration": 2.67}, {"text": "that you'll be using over\nand over and over again.", "start": 1802.14, "duration": 2.22}, {"text": "And again, don't round.", "start": 1804.36, "duration": 1.71}, {"text": "Those last two\ndigits are important.", "start": 1806.07, "duration": 4.48}, {"text": "So by taking this energy and\ndividing by this conversion", "start": 1810.55, "duration": 2.91}, {"text": "factor, you can figure out\nhow many atomic mass units are", "start": 1813.46, "duration": 3.72}, {"text": "lost in terms of\nactual mass when", "start": 1817.18, "duration": 2.49}, {"text": "you assemble an alpha particle\nfrom its constituent pieces.", "start": 1819.67, "duration": 4.23}, {"text": "And the rest of the stuff\nwe will get into later.", "start": 1823.9, "duration": 2.302}, {"text": "It's not really relevant\nto today's discussion,", "start": 1826.202, "duration": 1.958}, {"text": "but it's definitely\nrelevant to today's course.", "start": 1828.16, "duration": 4.5}, {"text": "Cool.", "start": 1832.66, "duration": 1.96}, {"text": "OK.", "start": 1834.62, "duration": 1.57}, {"text": "And then on to--", "start": 1836.19, "duration": 1.603}, {"text": "one of the last things\nthat he mentioned", "start": 1837.793, "duration": 1.667}, {"text": "is some predictions to say, OK,\nlet's say this neutron exists.", "start": 1839.46, "duration": 4.21}, {"text": "It doesn't have charge.", "start": 1843.67, "duration": 1.67}, {"text": "Most matter interacts\nwith other matter", "start": 1845.34, "duration": 2.73}, {"text": "by virtue of Coulombic\nor charge interactions.", "start": 1848.07, "duration": 2.85}, {"text": "If the neutron has no\ncharge, it shouldn't really", "start": 1850.92, "duration": 2.19}, {"text": "see matter except for nuclei.", "start": 1853.11, "duration": 2.68}, {"text": "This is exactly what he\nsaid, is an electrical field", "start": 1855.79, "duration": 3.23}, {"text": "of a neutron will be\nextremely small except", "start": 1859.02, "duration": 2.74}, {"text": "at small distances, because\nhe proposed that a neutron is", "start": 1861.76, "duration": 3.53}, {"text": "a proton plus an electron.", "start": 1865.29, "duration": 1.83}, {"text": "So once you get to around\nthe radius of the neutron,", "start": 1867.12, "duration": 2.58}, {"text": "you might start to see some\ncharge, but not before.", "start": 1869.7, "duration": 3.48}, {"text": "And so most other\nmatter, unless you", "start": 1873.18, "duration": 1.62}, {"text": "have a head-on collision with a\nnucleus, neutrons won't see it.", "start": 1874.8, "duration": 5.37}, {"text": "And that helps explain\nwhy the neutrons", "start": 1880.17, "duration": 2.01}, {"text": "had such high penetrating\npower or high range--", "start": 1882.18, "duration": 2.79}, {"text": "because they just went streaming\nthrough most materials,", "start": 1884.97, "duration": 3.0}, {"text": "invisible to the electrons.", "start": 1887.97, "duration": 1.95}, {"text": "So very forward thinking, and\nturned out to be very correct.", "start": 1889.92, "duration": 3.85}, {"text": "And then finally, as a kind\nof mic drop conclusion,", "start": 1893.77, "duration": 3.56}, {"text": "came up with the final\nconcluding statements.", "start": 1897.33, "duration": 5.13}, {"text": "OK, we know there's a neutron.", "start": 1902.46, "duration": 2.04}, {"text": "We know its mass.", "start": 1904.5, "duration": 1.59}, {"text": "The actual mass of the\nneutron is about 1.0087 AMU so", "start": 1906.09, "duration": 6.84}, {"text": "within 0.1% of Chadwick's\ncalculations and predictions", "start": 1912.93, "duration": 4.83}, {"text": "based on 1930s equipment,\nwhich is strikingly awesome.", "start": 1917.76, "duration": 4.65}, {"text": "And there you have it.", "start": 1922.41, "duration": 1.72}, {"text": "That's the discovery\nof the neutron using", "start": 1924.13, "duration": 2.188}, {"text": "most of the concepts that we're\ngoing to be teaching you here", "start": 1926.318, "duration": 2.542}, {"text": "in 22.01.", "start": 1928.86, "duration": 1.5}, {"text": "So right now, I'd say\nyour scientific knowledge,", "start": 1930.36, "duration": 2.19}, {"text": "if we don't count what\nyou read on the news,", "start": 1932.55, "duration": 1.86}, {"text": "is roughly around\n1850 when all the E&M", "start": 1934.41, "duration": 2.52}, {"text": "stuff was being figured out.", "start": 1936.93, "duration": 1.49}, {"text": "We are going to bring you\nscreaming into the 1930s.", "start": 1938.42, "duration": 2.86}, {"text": "And by about month 1,\nwe'll hit the present day", "start": 1941.28, "duration": 3.39}, {"text": "when we can start to talk\nabout the super heavy elements", "start": 1944.67, "duration": 2.43}, {"text": "like the ones that were\ndiscovered last year.", "start": 1947.1, "duration": 2.55}, {"text": "I think there was\neven some this year.", "start": 1949.65, "duration": 1.753}, {"text": "But we'll look at the Physics\nToday article from last year", "start": 1951.403, "duration": 2.417}, {"text": "to get to the\npoint of explaining", "start": 1953.82, "duration": 2.1}, {"text": "why super heavy elements\nmight be stable.", "start": 1955.92, "duration": 2.28}, {"text": "Why are we even\nlooking for them?", "start": 1958.2, "duration": 1.74}, {"text": "Where do cosmic rays come from?", "start": 1959.94, "duration": 1.705}, {"text": "How do we know that they're\ncosmic rays and not something", "start": 1961.645, "duration": 2.375}, {"text": "else?", "start": 1964.02, "duration": 0.63}, {"text": "How can you tell a reactor\nturns on anywhere in the world", "start": 1964.65, "duration": 2.52}, {"text": "by measuring different\nbits of radiation, which", "start": 1967.17, "duration": 2.64}, {"text": "is an active defense\nproject that folks", "start": 1969.81, "duration": 2.28}, {"text": "are pursuing right now?", "start": 1972.09, "duration": 1.44}, {"text": "Lots of really fun questions.", "start": 1973.53, "duration": 2.43}, {"text": "And speaking of\nquestions, do you guys", "start": 1975.96, "duration": 2.19}, {"text": "have any questions about\nwhat we've explained here,", "start": 1978.15, "duration": 2.7}, {"text": "how we've retraced Chadwick's\ndiscovery of the neutron", "start": 1980.85, "duration": 2.82}, {"text": "from basic nuclear\nscience principles?", "start": 1983.67, "duration": 1.98}, {"text": "So who here has seen these\nnuclear reactions before?", "start": 1988.83, "duration": 3.99}, {"text": "Cool.", "start": 1992.82, "duration": 0.5}, {"text": "This is something\nthat I hope folks", "start": 1993.32, "duration": 1.458}, {"text": "would cover in high school.", "start": 1994.778, "duration": 1.212}, {"text": "But with a general\ntrend of watering down", "start": 1995.99, "duration": 1.795}, {"text": "science education, I didn't\nwant to make any assumptions.", "start": 1997.785, "duration": 2.375}, {"text": "I'm glad to hear\nthis was covered.", "start": 2000.16, "duration": 2.58}, {"text": "Was this coveted at MIT?", "start": 2002.74, "duration": 2.77}, {"text": "Are you guys relying on\nhigh school knowledge?", "start": 2005.51, "duration": 2.45}, {"text": "OK, good.", "start": 2007.96, "duration": 1.59}, {"text": "Not good.", "start": 2009.55, "duration": 2.367}, {"text": "Good I know where you are.", "start": 2011.917, "duration": 1.083}, {"text": "Not good that MIT doesn't\nteach anything nuclear", "start": 2013.0, "duration": 2.01}, {"text": "until year two.", "start": 2015.01, "duration": 1.17}, {"text": "That's OK.", "start": 2016.18, "duration": 1.14}, {"text": "You guys, along with\nthe Physics Department,", "start": 2017.32, "duration": 1.99}, {"text": "will get at least a 20th-century\nknowledge of physics and 21st", "start": 2019.31, "duration": 3.98}, {"text": "by the end of month 1.", "start": 2023.29, "duration": 2.49}, {"text": "So I want to come back\nto the Stellar site,", "start": 2025.78, "duration": 4.47}, {"text": "and specifically the syllabus.", "start": 2030.25, "duration": 1.47}, {"text": "I've taken a lot of care to\nwrite a very detailed syllabus", "start": 2031.72, "duration": 3.33}, {"text": "of what we're going to do,\nwhat I expect of you guys, what", "start": 2035.05, "duration": 4.44}, {"text": "you can expect of\nme, and what we'll", "start": 2039.49, "duration": 2.04}, {"text": "be doing every single day.", "start": 2041.53, "duration": 1.42}, {"text": "So if you want to\nknow what we're", "start": 2042.95, "duration": 1.64}, {"text": "going to be doing, if you have\na class that you miss, and you", "start": 2044.59, "duration": 2.19}, {"text": "want to know what notes\nyou're going to miss,", "start": 2046.78, "duration": 1.875}, {"text": "it's all written up here.", "start": 2048.655, "duration": 1.875}, {"text": "I want to get right\ninto assignments,", "start": 2050.53, "duration": 2.91}, {"text": "because everyone wants to know\nwhat am I responsible for.", "start": 2053.44, "duration": 2.549}, {"text": "Well, not too much--", "start": 2055.989, "duration": 1.71}, {"text": "nine problems sets,\nthree quizzes.", "start": 2057.699, "duration": 2.881}, {"text": "The final exam is just a quiz.", "start": 2060.58, "duration": 2.28}, {"text": "It's only worth 24% of\nyour grade instead of 20", "start": 2062.86, "duration": 3.658}, {"text": "to get the math to work\nout, because I eliminated", "start": 2066.518, "duration": 2.042}, {"text": "one problem set to avoid running\nafoul of MIT regulations,", "start": 2068.56, "duration": 3.99}, {"text": "but not assigning things\nat the last week of class.", "start": 2072.55, "duration": 2.64}, {"text": "But there are three quizzes,\nso the final exam is just", "start": 2075.19, "duration": 2.61}, {"text": "another quiz.", "start": 2077.8, "duration": 1.109}, {"text": "It's not a super\nhigh-stress, crazy thing,", "start": 2078.909, "duration": 2.221}, {"text": "because I don't see a\npoint in doing that.", "start": 2081.13, "duration": 2.759}, {"text": "You can make your\nassignments however you want.", "start": 2083.889, "duration": 2.551}, {"text": "I don't care as long\nas I can read them.", "start": 2086.44, "duration": 3.0}, {"text": "But I do ask that in the\nend, you submit a PDF", "start": 2089.44, "duration": 2.549}, {"text": "file on the Stellar site.", "start": 2091.989, "duration": 1.581}, {"text": "And the reason for\nthis is my first course", "start": 2093.57, "duration": 1.75}, {"text": "that I ever taught at\nMIT as a professor were", "start": 2095.32, "duration": 2.58}, {"text": "the graduate modules, 22.13,\nIntro to Nuclear Systems,", "start": 2097.9, "duration": 3.87}, {"text": "and 22.14, Intro to\nNuclear Materials.", "start": 2101.77, "duration": 3.27}, {"text": "I accepted paper submissions.", "start": 2105.04, "duration": 2.16}, {"text": "And by week 3, I had\nto microwave them.", "start": 2107.2, "duration": 2.82}, {"text": "Because three or four times,\nI definitely saw blood.", "start": 2110.02, "duration": 3.3}, {"text": "And there were also\nsome weird stains", "start": 2113.32, "duration": 2.31}, {"text": "that I didn't want to explain.", "start": 2115.63, "duration": 1.32}, {"text": "So I added the habit of\nunstapling, microwaving,", "start": 2116.95, "duration": 3.57}, {"text": "and re-stapling the\np-sets before grading.", "start": 2120.52, "duration": 2.61}, {"text": "So in the digital\nworld, it's sterile.", "start": 2123.13, "duration": 2.73}, {"text": "I'm not a germophobe.", "start": 2125.86, "duration": 1.11}, {"text": "I just don't like\nblood in my house,", "start": 2126.97, "duration": 2.23}, {"text": "especially if it's not mine.", "start": 2129.2, "duration": 1.55}, {"text": "So I ask that you guys submit\nPDFs on the Stellar site.", "start": 2130.75, "duration": 4.11}, {"text": "They're due at 5:00 PM to\nmake sure that you're done", "start": 2134.86, "duration": 3.0}, {"text": "and you can go home and relax\nor work on something else.", "start": 2137.86, "duration": 3.248}, {"text": "I used to some have\nthings due at midnight,", "start": 2141.108, "duration": 1.792}, {"text": "and I had every\nsubmission was 11:59 PM.", "start": 2142.9, "duration": 3.12}, {"text": "I'm not going to\ndo that anymore.", "start": 2146.02, "duration": 1.47}, {"text": "Do make sure to submit\n15 minutes early.", "start": 2147.49, "duration": 1.96}, {"text": "So if your computer or the\nStellar site has trouble,", "start": 2149.45, "duration": 2.69}, {"text": "send me an email or a\ntext or whatever saying,", "start": 2152.14, "duration": 2.498}, {"text": "I'm trying to submit,\nand it's not working.", "start": 2154.638, "duration": 1.792}, {"text": "Here is a backup, or I'm leaving\nsomething under your door.", "start": 2156.43, "duration": 3.42}, {"text": "And if you want my\ncell phone number,", "start": 2159.85, "duration": 1.59}, {"text": "that's also my office number.", "start": 2161.44, "duration": 1.21}, {"text": "It's also my only number.", "start": 2162.65, "duration": 1.34}, {"text": "It's in the MIT directory.", "start": 2163.99, "duration": 1.802}, {"text": "So if there is some emergency\nyou need to make me aware of,", "start": 2165.792, "duration": 2.458}, {"text": "please do communicate.", "start": 2168.25, "duration": 1.11}, {"text": "I'd rather you tell me than be\nworried about not telling me", "start": 2169.36, "duration": 2.91}, {"text": "and then find out later.", "start": 2172.27, "duration": 1.473}, {"text": "So are we all clear on that?", "start": 2173.743, "duration": 1.167}, {"text": "As far as what the\nassignments are,", "start": 2177.98, "duration": 2.37}, {"text": "each assignment is going to be\nabout 50% basic calculations,", "start": 2180.35, "duration": 3.03}, {"text": "working out things like these\nto make sure you've mastered", "start": 2183.38, "duration": 2.94}, {"text": "the material, that\nyou understand", "start": 2186.32, "duration": 1.71}, {"text": "writing nuclear reactions,\nyou can balance a q equation,", "start": 2188.03, "duration": 3.3}, {"text": "you can tell me about\nwhat your cancer", "start": 2191.33, "duration": 1.68}, {"text": "risk would be from a\ncertain dose of material.", "start": 2193.01, "duration": 1.967}, {"text": "So this is like when you\ngo out in the real world,", "start": 2194.977, "duration": 2.083}, {"text": "the sort of\ncalculations everyone", "start": 2197.06, "duration": 1.41}, {"text": "would expect you as a nuclear\nengineer to be able to do.", "start": 2198.47, "duration": 3.85}, {"text": "And then 50% of each\nproblem set is either", "start": 2202.32, "duration": 2.03}, {"text": "going to be analytical questions\nof considerable difficulty.", "start": 2204.35, "duration": 3.9}, {"text": "This is MIT.", "start": 2208.25, "duration": 1.29}, {"text": "We're not just here\nto give you the basics", "start": 2209.54, "duration": 2.46}, {"text": "so that you can\nregurgitate a textbook", "start": 2212.0, "duration": 1.62}, {"text": "onto the first person who asks.", "start": 2213.62, "duration": 1.9}, {"text": "We're here to make sure\nthat you can go farther.", "start": 2215.52, "duration": 2.0}, {"text": "Because you guys are\nthe future of this very", "start": 2217.52, "duration": 2.16}, {"text": "small and diminishing field\nat the moment if you look", "start": 2219.68, "duration": 3.27}, {"text": "at the nuclear power in the US.", "start": 2222.95, "duration": 2.01}, {"text": "I would say growing\nin terms of the world,", "start": 2224.96, "duration": 2.23}, {"text": "but not in terms of the US.", "start": 2227.19, "duration": 1.125}, {"text": "And you guys are going to be\nin charge of leading this field", "start": 2228.315, "duration": 2.5}, {"text": "and determining where\nit's going to go.", "start": 2230.815, "duration": 1.653}, {"text": "So you've got to be up\nat the cutting edge,", "start": 2232.468, "duration": 1.792}, {"text": "and we're going to take you\nto the edge of your abilities.", "start": 2234.26, "duration": 3.24}, {"text": "My favorite kind of\nproblem is to give", "start": 2237.5, "duration": 1.98}, {"text": "one sentence for the question,\nfive or 10 pages for the answer", "start": 2239.48, "duration": 4.08}, {"text": "if you don't get the trick.", "start": 2243.56, "duration": 1.65}, {"text": "Now, that's OK.", "start": 2245.21, "duration": 1.13}, {"text": "It's perfectly fine\nnot to figure out", "start": 2246.34, "duration": 3.743}, {"text": "the answer in the end.", "start": 2250.083, "duration": 0.917}, {"text": "In fact, I'll usually\ngive you the answer", "start": 2251.0, "duration": 2.64}, {"text": "for the analytical\nquestions because I", "start": 2253.64, "duration": 1.95}, {"text": "want to see your approach.", "start": 2255.59, "duration": 1.74}, {"text": "I'm not interested in\nyou nailing the answer.", "start": 2257.33, "duration": 2.31}, {"text": "I'm interested in\nseeing how you think.", "start": 2259.64, "duration": 2.19}, {"text": "And copious partial credit will\nbe given for the way you think.", "start": 2261.83, "duration": 3.36}, {"text": "So if you have a missing\nstep, and you say,", "start": 2265.19, "duration": 2.372}, {"text": "I don't know the step, I'm\ngoing to assume variable a", "start": 2267.562, "duration": 2.208}, {"text": "and keep going,\nyou will get credit", "start": 2269.77, "duration": 1.84}, {"text": "for the subsequent steps.", "start": 2271.61, "duration": 1.94}, {"text": "I want to see how you\nthink from start to finish", "start": 2273.55, "duration": 2.68}, {"text": "and how you cover for holes\nthat you can't get through.", "start": 2276.23, "duration": 3.38}, {"text": "So everyone clear on that?", "start": 2279.61, "duration": 1.44}, {"text": "Partial credit, yes.", "start": 2281.05, "duration": 2.04}, {"text": "Use it to your fullest ability.", "start": 2283.09, "duration": 3.17}, {"text": "The other half of\nthe problem sets", "start": 2286.26, "duration": 1.59}, {"text": "will have take-home\nlaboratory assignments.", "start": 2287.85, "duration": 2.93}, {"text": "It's not just enough\nfor me to tell you", "start": 2290.78, "duration": 1.81}, {"text": "about nuclear engineering.", "start": 2292.59, "duration": 1.53}, {"text": "You have to see it\nfor yourself, and you", "start": 2294.12, "duration": 2.1}, {"text": "have to feel it for yourself.", "start": 2296.22, "duration": 1.69}, {"text": "And once in a while, you'll\nget a mild electric shock", "start": 2297.91, "duration": 2.42}, {"text": "by yourself if things\ngo wrong, but that's OK.", "start": 2300.33, "duration": 2.7}, {"text": "It happens to the best of us.", "start": 2303.03, "duration": 2.13}, {"text": "I got zapped by our--", "start": 2305.16, "duration": 0.953}, {"text": "you guys have all made\nGeiger counters, right?", "start": 2306.113, "duration": 1.917}, {"text": "Has anyone not made\na Geiger counter yet?", "start": 2308.03, "duration": 2.67}, {"text": "Oh, OK.", "start": 2310.7, "duration": 0.78}, {"text": "It sounds like we need\nto run another workshop.", "start": 2311.48, "duration": 2.41}, {"text": "Well, our Geiger counters\nrely on a neat little boost", "start": 2313.89, "duration": 3.86}, {"text": "converter power supply\nthat takes 9 volts", "start": 2317.75, "duration": 2.55}, {"text": "and steps it up to 400 volts\nvia some switching things.", "start": 2320.3, "duration": 4.08}, {"text": "That means you have 400\nvolts on a big metal tube.", "start": 2324.38, "duration": 2.278}, {"text": "And if you're working\non your circuit", "start": 2326.658, "duration": 1.542}, {"text": "and you happen to brush against\nit, you get zero current,", "start": 2328.2, "duration": 3.05}, {"text": "so it doesn't hurt you in the\nmedical sense, but it hurts.", "start": 2331.25, "duration": 4.77}, {"text": "I also have a dance I\ncall the 60 Hertz shuffle.", "start": 2336.02, "duration": 2.91}, {"text": "It's the high speed\nshaking that you", "start": 2338.93, "duration": 2.37}, {"text": "do when you're\nconnected to 60 Hertz", "start": 2341.3, "duration": 2.098}, {"text": "somewhere from the wall outlet.", "start": 2343.398, "duration": 1.292}, {"text": "None of you guys will\nbe exposed to this,", "start": 2344.69, "duration": 1.708}, {"text": "but I've done it\nenough times that I", "start": 2346.398, "duration": 1.802}, {"text": "have a name for the dance.", "start": 2348.2, "duration": 2.1}, {"text": "If you get 400 volts,\nyou'll just kind of scream.", "start": 2350.3, "duration": 2.34}, {"text": "And I don't care how\nmanly men you guys are.", "start": 2352.64, "duration": 3.09}, {"text": "Everyone makes the same\npitch scream with 400 volts.", "start": 2355.73, "duration": 3.75}, {"text": "We're all equal in the\neyes of electricity.", "start": 2359.48, "duration": 4.53}, {"text": "For these laboratory\nquestions, I'm", "start": 2364.01, "duration": 1.77}, {"text": "going to ask you to both\ncomplete an assignment where", "start": 2365.78, "duration": 2.4}, {"text": "you'll, for example, measure\nthe half-life of uranium,", "start": 2368.18, "duration": 3.54}, {"text": "measure the radioactivity\nof one banana, confirm", "start": 2371.72, "duration": 3.21}, {"text": "or refute the\nlinear no threshold", "start": 2374.93, "duration": 2.13}, {"text": "hypothesis of the dose.", "start": 2377.06, "duration": 1.8}, {"text": "And the experiment itself\nwon't take that long,", "start": 2378.86, "duration": 2.31}, {"text": "but I want you to write it up in\nproper documented format using", "start": 2381.17, "duration": 4.83}, {"text": "these sections.", "start": 2386.0, "duration": 0.76}, {"text": "So I'm going to be\nteaching you guys how", "start": 2386.76, "duration": 1.667}, {"text": "to write scientific articles.", "start": 2388.427, "duration": 2.513}, {"text": "So actually, this is kind of\na good time to ask you guys.", "start": 2390.94, "duration": 2.95}, {"text": "How would you define\nthe word \"science?\"", "start": 2393.89, "duration": 3.02}, {"text": "Luke, what do you think?", "start": 2396.91, "duration": 1.0}, {"text": "AUDIENCE: It's a process\nof getting knowledge", "start": 2400.53, "duration": 2.88}, {"text": "by fitting theories\nto empirical evidence.", "start": 2403.41, "duration": 5.158}, {"text": "MIKE SHORT: Gaining\nknowledge by fitting theories", "start": 2408.568, "duration": 2.042}, {"text": "to empirical evidence.", "start": 2410.61, "duration": 0.94}, {"text": "OK.", "start": 2411.55, "duration": 0.5}, {"text": "So I hear knowledge\ngaining by some sort", "start": 2412.05, "duration": 2.61}, {"text": "of well-justified and\naccepted means, right?", "start": 2414.66, "duration": 3.43}, {"text": "Monica, what do you think?", "start": 2418.09, "duration": 3.02}, {"text": "AUDIENCE: Science is the\nstudy of the natural world", "start": 2421.11, "duration": 3.85}, {"text": "through patterns and\nmathematics, I suppose.", "start": 2424.96, "duration": 5.49}, {"text": "MIKE SHORT: Cool, yeah.", "start": 2430.45, "duration": 0.99}, {"text": "Let's say the studying,\nmodeling, and abstraction", "start": 2431.44, "duration": 2.042}, {"text": "of the natural world into\nways we can understand.", "start": 2433.482, "duration": 3.748}, {"text": "Jared, what would you say?", "start": 2437.23, "duration": 2.952}, {"text": "AUDIENCE: Which one?", "start": 2440.182, "duration": 0.833}, {"text": "MIKE SHORT: Oh,\nthere's two Jareds.", "start": 2441.015, "duration": 2.455}, {"text": "I want to hear both,\nand then I'll--", "start": 2443.47, "duration": 2.73}, {"text": "yeah.", "start": 2446.2, "duration": 1.77}, {"text": "AUDIENCE: Science is--", "start": 2447.97, "duration": 1.755}, {"text": "I'd probably go with\nit's the same thing", "start": 2453.306, "duration": 2.424}, {"text": "Luke said, gaining knowledge\nthrough experimentation", "start": 2455.73, "duration": 4.75}, {"text": "and trial.", "start": 2460.48, "duration": 1.44}, {"text": "MIKE SHORT: Cool.", "start": 2461.92, "duration": 0.88}, {"text": "And other Jared?", "start": 2462.8, "duration": 1.25}, {"text": "AUDIENCE: I think what Luke\nsaid about fitting theories", "start": 2464.05, "duration": 4.18}, {"text": "to empirical evidence and\ntesting them that way.", "start": 2468.23, "duration": 2.52}, {"text": "MIKE SHORT: OK, cool.", "start": 2470.75, "duration": 0.928}, {"text": "I like these.", "start": 2471.678, "duration": 0.542}, {"text": "And these are the\ngenerally accepted theories", "start": 2472.22, "duration": 2.37}, {"text": "and descriptions I've\nheard of science.", "start": 2474.59, "duration": 2.21}, {"text": "And I want to pose a\nquestion to you guys.", "start": 2476.8, "duration": 2.14}, {"text": "If a tree falls in the woods\nand nobody is around to hear it,", "start": 2478.94, "duration": 2.76}, {"text": "can it win the Nobel Prize?", "start": 2481.7, "duration": 1.18}, {"text": "It's kind of an expression.", "start": 2487.88, "duration": 1.24}, {"text": "So if somebody\ndiscovered the neutron,", "start": 2489.12, "duration": 3.89}, {"text": "and they wrote up\ntheir findings,", "start": 2493.01, "duration": 1.47}, {"text": "and proved that it exists,\nand they put it in their desk,", "start": 2494.48, "duration": 2.79}, {"text": "and the house burned\ndown, and the person died,", "start": 2497.27, "duration": 2.43}, {"text": "was the neutron discovered?", "start": 2499.7, "duration": 4.01}, {"text": "What does discovered mean?", "start": 2503.71, "duration": 1.37}, {"text": "So to me, science is\nequal parts everything you", "start": 2510.03, "duration": 3.54}, {"text": "guys said and communication.", "start": 2513.57, "duration": 3.05}, {"text": "If you discover something\nand you don't tell anyone,", "start": 2516.62, "duration": 3.42}, {"text": "the information\ntechnically doesn't exist.", "start": 2520.04, "duration": 3.83}, {"text": "It dies with you.", "start": 2523.87, "duration": 1.14}, {"text": "And you don't want\nthat to happen.", "start": 2525.01, "duration": 1.493}, {"text": "So I want to make sure that\nyou guys both understand", "start": 2526.503, "duration": 2.167}, {"text": "the science and understand the\nimportance of communicating it", "start": 2528.67, "duration": 4.38}, {"text": "effectively to people.", "start": 2533.05, "duration": 0.93}, {"text": "Because that's the\nother thing you're", "start": 2533.98, "duration": 1.542}, {"text": "going to be doing as\nleaders in this field", "start": 2535.522, "duration": 2.148}, {"text": "is explaining things.", "start": 2537.67, "duration": 1.69}, {"text": "You better believe when\nFukushima happened--", "start": 2539.36, "duration": 2.75}, {"text": "I was a postdoc at the time.", "start": 2542.11, "duration": 1.35}, {"text": "I was not a person, I guess,\nin the academic sense.", "start": 2543.46, "duration": 4.17}, {"text": "People here treated\nme very well,", "start": 2547.63, "duration": 1.56}, {"text": "but I was also very aware that\nI was not one of the greats.", "start": 2549.19, "duration": 2.91}, {"text": "Still I am not old enough yet.", "start": 2552.1, "duration": 2.37}, {"text": "I was getting calls all\nday, all night from news", "start": 2554.47, "duration": 2.79}, {"text": "agencies saying, you're at MIT.", "start": 2557.26, "duration": 1.8}, {"text": "I saw your name\non the directory.", "start": 2559.06, "duration": 1.62}, {"text": "Do a radio interview and tell\nus all if we're going to die.", "start": 2560.68, "duration": 3.65}, {"text": "And you can only imagine what\nthe professors on this hall", "start": 2564.33, "duration": 2.41}, {"text": "were dealing with.", "start": 2566.74, "duration": 0.63}, {"text": "So folks were traveling\naround, answering things", "start": 2567.37, "duration": 2.0}, {"text": "left and right.", "start": 2569.37, "duration": 0.91}, {"text": "I ended up doing some weird\npodcast on a Brazilian news", "start": 2570.28, "duration": 2.49}, {"text": "channel that I don't\nthink ever got aired", "start": 2572.77, "duration": 1.83}, {"text": "and stopped doing it after that.", "start": 2574.6, "duration": 1.72}, {"text": "You as undergrads even\nmight be called if somebody", "start": 2576.32, "duration": 2.63}, {"text": "wants to know something.", "start": 2578.95, "duration": 1.68}, {"text": "And so it's best that you\nnot only know the material,", "start": 2580.63, "duration": 2.43}, {"text": "but you can convey\nit effectively,", "start": 2583.06, "duration": 2.37}, {"text": "briefly, and in a way that\nyour audience can understand.", "start": 2585.43, "duration": 3.78}, {"text": "The audience for these\narticles is any undergraduate", "start": 2589.21, "duration": 3.24}, {"text": "in any engineering\nprogram anywhere.", "start": 2592.45, "duration": 2.1}, {"text": "That's your lowest\ncommon denominator--", "start": 2594.55, "duration": 2.322}, {"text": "not to say that\nthat's a bad thing,", "start": 2596.872, "duration": 1.458}, {"text": "but it is the audience that you\nwant to aim your writing at.", "start": 2598.33, "duration": 3.48}, {"text": "So what I want you\nto be able to do", "start": 2601.81, "duration": 1.83}, {"text": "is say what you did, why you\ndid it, and what it means.", "start": 2603.64, "duration": 4.53}, {"text": "In communication terms, this\nmeans a less-than-100-word", "start": 2608.17, "duration": 3.87}, {"text": "abstract, a very brief synopsis\nof what you did and why", "start": 2612.04, "duration": 4.26}, {"text": "it's important.", "start": 2616.3, "duration": 1.08}, {"text": "That's the teaser.", "start": 2617.38, "duration": 0.81}, {"text": "This is the trailer to make\nsomebody read what you actually", "start": 2618.19, "duration": 2.49}, {"text": "did and see why they care.", "start": 2620.68, "duration": 1.59}, {"text": "This is the main\nmethod and currency", "start": 2622.27, "duration": 1.77}, {"text": "through which\nscientists communicate", "start": 2624.04, "duration": 1.5}, {"text": "is articles of this type.", "start": 2625.54, "duration": 2.32}, {"text": "An introduction and\nbackground which", "start": 2627.86, "duration": 2.3}, {"text": "says why are we\nstudying this problem.", "start": 2630.16, "duration": 2.29}, {"text": "And the answer is not\nbecause I told you to,", "start": 2632.45, "duration": 1.97}, {"text": "and your grade depends on it.", "start": 2634.42, "duration": 1.81}, {"text": "I want you to think about why\nthis problem is important,", "start": 2636.23, "duration": 2.81}, {"text": "and put it into\ncontext, and give", "start": 2639.04, "duration": 2.64}, {"text": "any of the scientific\nbackground to understand", "start": 2641.68, "duration": 2.22}, {"text": "what's going to come next,\nlike the experimental section.", "start": 2643.9, "duration": 3.63}, {"text": "Describe what you did in nitty\ngritty scientific detail.", "start": 2647.53, "duration": 2.73}, {"text": "This is usually the easy part.", "start": 2650.26, "duration": 1.71}, {"text": "I put this gamma ray in this\nbucket, and it made this color,", "start": 2651.97, "duration": 4.59}, {"text": "and I made this noise, whatever.", "start": 2656.56, "duration": 4.62}, {"text": "A results section\nwhere you show all", "start": 2661.18, "duration": 1.62}, {"text": "of your data and a\ndiscussion section--", "start": 2662.8, "duration": 2.68}, {"text": "notice that these are different.", "start": 2665.48, "duration": 1.56}, {"text": "You want to separate\nyour actual results", "start": 2667.04, "duration": 2.27}, {"text": "from your interpretation\nof your results,", "start": 2669.31, "duration": 2.19}, {"text": "because someone else may have\na very different interpretation", "start": 2671.5, "duration": 4.17}, {"text": "of results--", "start": 2675.67, "duration": 1.11}, {"text": "for example, Chadwick.", "start": 2676.78, "duration": 3.01}, {"text": "Somebody found that\nberyllium bombarded", "start": 2679.79, "duration": 4.14}, {"text": "by alpha particles\nemitted radiation", "start": 2683.93, "duration": 1.89}, {"text": "of great penetrating power.", "start": 2685.82, "duration": 1.23}, {"text": "That's the result. The\ninterpretation or discussion", "start": 2687.05, "duration": 3.63}, {"text": "said it's probably a\nCompton-like effect", "start": 2690.68, "duration": 3.03}, {"text": "from a photon.", "start": 2693.71, "duration": 1.05}, {"text": "By separating your results\nand your discussion,", "start": 2694.76, "duration": 2.73}, {"text": "you allow people to mentally\nsay, OK, I get your results.", "start": 2697.49, "duration": 2.79}, {"text": "I believe that you\nfound these numbers.", "start": 2700.28, "duration": 2.01}, {"text": "I have a different explanation.", "start": 2702.29, "duration": 1.628}, {"text": "And you all may have\ndifferent explanations", "start": 2703.918, "duration": 1.792}, {"text": "for what you see\nin your own labs,", "start": 2705.71, "duration": 1.83}, {"text": "because you're also probably\ngoing to get different results.", "start": 2707.54, "duration": 2.95}, {"text": "And then finally, a conclusion\nwhere you quickly re-summarize", "start": 2710.49, "duration": 2.84}, {"text": "your major contributions.", "start": 2713.33, "duration": 1.62}, {"text": "Your abstract is the teaser.", "start": 2714.95, "duration": 1.86}, {"text": "Your conclusion is like your\nre-abstract with the context", "start": 2716.81, "duration": 3.12}, {"text": "that people now believe--", "start": 2719.93, "duration": 1.26}, {"text": "or don't-- what you did.", "start": 2721.19, "duration": 3.168}, {"text": "And think about how\nyou guys read articles.", "start": 2724.358, "duration": 1.792}, {"text": "So who here has read\nscientific articles before?", "start": 2726.15, "duration": 3.99}, {"text": "More than half of you.", "start": 2730.14, "duration": 1.74}, {"text": "Let's see.", "start": 2731.88, "duration": 1.05}, {"text": "Alex, what do you read first?", "start": 2732.93, "duration": 3.015}, {"text": "AUDIENCE: If it's a journal,\nprobably the abstract.", "start": 2735.945, "duration": 2.805}, {"text": "But given that I'm mostly\ninterested in the topic,", "start": 2738.75, "duration": 3.19}, {"text": "I tend to go to the\nconclusion section.", "start": 2741.94, "duration": 1.738}, {"text": "MIKE SHORT: That's right.", "start": 2743.678, "duration": 1.042}, {"text": "OK.", "start": 2744.72, "duration": 0.48}, {"text": "I'm glad you said that.", "start": 2745.2, "duration": 0.81}, {"text": "That was my next question.", "start": 2746.01, "duration": 1.17}, {"text": "You read the abstract.", "start": 2747.18, "duration": 1.41}, {"text": "The next thing you\nread is the conclusion.", "start": 2748.59, "duration": 2.07}, {"text": "The next thing you\nusually read is", "start": 2750.66, "duration": 1.5}, {"text": "you skim through the\nresults and the figures", "start": 2752.16, "duration": 1.95}, {"text": "and see if it's\nworth looking at.", "start": 2754.11, "duration": 1.59}, {"text": "Then if you're like, OK,\nthis is worth my time,", "start": 2755.7, "duration": 2.79}, {"text": "then you slog through\nand read everything", "start": 2758.49, "duration": 2.43}, {"text": "to make sure you\nunderstand it all.", "start": 2760.92, "duration": 1.95}, {"text": "So when you're writing\nthese articles,", "start": 2762.87, "duration": 1.77}, {"text": "think about who's reading\nthem and how they read them.", "start": 2764.64, "duration": 3.163}, {"text": "Because if you guys don't tend\nto read an article from top", "start": 2767.803, "duration": 2.417}, {"text": "to bottom, neither\nwill your audience.", "start": 2770.22, "duration": 2.07}, {"text": "And that's true.", "start": 2772.29, "duration": 0.96}, {"text": "Most scientists skim things\nbecause we have a lot to read.", "start": 2773.25, "duration": 2.76}, {"text": "So that's OK.", "start": 2776.01, "duration": 1.45}, {"text": "And I am very interested\nin you guys completely", "start": 2777.46, "duration": 3.29}, {"text": "documenting your experiment.", "start": 2780.75, "duration": 1.38}, {"text": "Pictures are also\nawesome to use.", "start": 2782.13, "duration": 2.91}, {"text": "Accuracy of results\nand analysis--", "start": 2785.04, "duration": 1.62}, {"text": "so did you round when\nyou weren't supposed to?", "start": 2786.66, "duration": 2.7}, {"text": "Did you have a clear numerical\ntypo that you can't explain?", "start": 2789.36, "duration": 3.02}, {"text": "And the readability\nof the report--", "start": 2792.38, "duration": 1.69}, {"text": "I want you to spend time\nmaking this readable.", "start": 2794.07, "duration": 3.33}, {"text": "I expect that this\npart of the assignment", "start": 2797.4, "duration": 1.86}, {"text": "will take roughly five hours,\nwhereas the basic questions", "start": 2799.26, "duration": 3.57}, {"text": "will take roughly three\nto four hours depending", "start": 2802.83, "duration": 2.19}, {"text": "on how well you're doing.", "start": 2805.02, "duration": 1.29}, {"text": "And that leaves three\nhours of class time", "start": 2806.31, "duration": 2.16}, {"text": "and a couple hours for\nwhatever else happens in life,", "start": 2808.47, "duration": 2.91}, {"text": "let's call it.", "start": 2811.38, "duration": 2.35}, {"text": "Since you've never\nwritten these before--", "start": 2813.73, "duration": 2.087}, {"text": "wait a minute.", "start": 2815.817, "duration": 0.583}, {"text": "I shouldn't say that.", "start": 2816.4, "duration": 0.875}, {"text": "Who's written these\nkinds of things before?", "start": 2817.275, "duration": 2.095}, {"text": "Anyone here wrote a\nscientific article?", "start": 2819.37, "duration": 2.16}, {"text": "Two.", "start": 2821.53, "duration": 0.5}, {"text": "OK, three.", "start": 2822.03, "duration": 1.35}, {"text": "Cool.", "start": 2823.38, "duration": 0.813}, {"text": "So most of you\nhaven't, and that's", "start": 2824.193, "duration": 1.417}, {"text": "where I assumed you'd all be.", "start": 2825.61, "duration": 1.86}, {"text": "We have a whole lab dedicated to\nscientific communication called", "start": 2827.47, "duration": 3.0}, {"text": "the Comm Lab run by\nsomeone, who happens", "start": 2830.47, "duration": 2.43}, {"text": "to be my wife, four doors down.", "start": 2832.9, "duration": 1.92}, {"text": "We live and work\nnext to each other.", "start": 2834.82, "duration": 2.76}, {"text": "It's pretty cool.", "start": 2837.58, "duration": 1.26}, {"text": "And you get an automatic\nthree-day extension", "start": 2838.84, "duration": 2.13}, {"text": "on the lab assignment if\nyou go to the Comm Lab.", "start": 2840.97, "duration": 2.79}, {"text": "There are three\nreasons for this.", "start": 2843.76, "duration": 1.66}, {"text": "One, I want you to\nget better grades,", "start": 2845.42, "duration": 2.33}, {"text": "so I want you to learn\nhow to communicate.", "start": 2847.75, "duration": 1.98}, {"text": "Two, I don't want to spend\ntime trying to figure out", "start": 2849.73, "duration": 2.61}, {"text": "what you were trying to say.", "start": 2852.34, "duration": 1.53}, {"text": "So better articles means\nless grading time for me.", "start": 2853.87, "duration": 3.18}, {"text": "And three-- OK, let's\njust say it's two reasons.", "start": 2857.05, "duration": 3.36}, {"text": "That's enough.", "start": 2860.41, "duration": 1.77}, {"text": "And for everything\nexcept for the quizzes,", "start": 2862.18, "duration": 2.82}, {"text": "it's perfectly OK\nto work together", "start": 2865.0, "duration": 2.07}, {"text": "as long as you\nattribute who did what,", "start": 2867.07, "duration": 2.79}, {"text": "you write your own articles,\ndon't Xerox anything,", "start": 2869.86, "duration": 3.03}, {"text": "and say who took the data.", "start": 2872.89, "duration": 1.47}, {"text": "So if the whole class wants\nto get together and take one", "start": 2874.36, "duration": 2.46}, {"text": "set of data and\nwork for that, fine.", "start": 2876.82, "duration": 2.33}, {"text": "If you all want to do\nthe labs yourselves,", "start": 2879.15, "duration": 1.75}, {"text": "which I highly recommend, fine.", "start": 2880.9, "duration": 2.19}, {"text": "But I'm not going\nto tell you how", "start": 2883.09, "duration": 2.01}, {"text": "to do the lab assignment\nin this, as long as you", "start": 2885.1, "duration": 2.94}, {"text": "say what you did.", "start": 2888.04, "duration": 1.56}, {"text": "And I want all of you,\nif you haven't yet,", "start": 2889.6, "duration": 2.73}, {"text": "to head to integrity.mit.edu\nto see our official policies", "start": 2892.33, "duration": 4.41}, {"text": "on what is considered\nplagiarism, what is considered", "start": 2896.74, "duration": 2.76}, {"text": "working together, what's\nconsidered academic honesty.", "start": 2899.5, "duration": 3.42}, {"text": "I will assume, because\nit's on the syllabus", "start": 2902.92, "duration": 2.13}, {"text": "and I'm telling you now,\nthat you've all read this,", "start": 2905.05, "duration": 2.7}, {"text": "and that there will\nbe no cheating.", "start": 2907.75, "duration": 1.46}, {"text": "It's just not something that's\npart of my job description,", "start": 2909.21, "duration": 2.83}, {"text": "and I don't want\nto deal with it,", "start": 2912.04, "duration": 1.485}, {"text": "which means I\nwon't deal with it,", "start": 2913.525, "duration": 1.375}, {"text": "which means the\nconsequences will be severe.", "start": 2914.9, "duration": 3.27}, {"text": "So I don't think I'll\nhave to worry about that.", "start": 2918.17, "duration": 3.53}, {"text": "And then for the late\npolicy, it's just 10%", "start": 2921.7, "duration": 2.23}, {"text": "of the value of assignment\nfor each calendar day, not", "start": 2923.93, "duration": 2.85}, {"text": "each business day.", "start": 2926.78, "duration": 1.42}, {"text": "So if you're running really\nlate and you haven't started", "start": 2928.2, "duration": 2.42}, {"text": "an assignment the day it's due,\nbetter to take the 10% penalty", "start": 2930.62, "duration": 4.08}, {"text": "and do really well than\nhand in nothing on time.", "start": 2934.7, "duration": 3.73}, {"text": "So keep in mind how\ncan you maximize", "start": 2938.43, "duration": 1.73}, {"text": "the points in this course.", "start": 2940.16, "duration": 1.77}, {"text": "I'd rather you hand\nin something good late", "start": 2941.93, "duration": 2.4}, {"text": "than terrible on time.", "start": 2944.33, "duration": 1.75}, {"text": "So if you really need that extra\nday if MIT gets crazy, take it.", "start": 2946.08, "duration": 4.1}, {"text": "10% of a problem set is\n0.4 points on your grade.", "start": 2950.18, "duration": 2.85}, {"text": "It's not that big a deal.", "start": 2953.03, "duration": 3.31}, {"text": "Then as far as the syllabus, I\nwant to show you very quickly.", "start": 2956.34, "duration": 3.09}, {"text": "We've got when things are due.", "start": 2959.43, "duration": 2.04}, {"text": "I'm going to change these dates\nto basically just shift them", "start": 2961.47, "duration": 2.67}, {"text": "all forward by\none day to account", "start": 2964.14, "duration": 1.65}, {"text": "for the new Tuesday,\nThursday classes.", "start": 2965.79, "duration": 2.79}, {"text": "So I've got when the\nproblem sets are due.", "start": 2968.58, "duration": 2.28}, {"text": "And Friday is\nrecitation activities.", "start": 2970.86, "duration": 2.67}, {"text": "If there aren't\ntoo many questions", "start": 2973.53, "duration": 1.77}, {"text": "on a particular\nFriday, I have a lot", "start": 2975.3, "duration": 2.1}, {"text": "of fun stuff in store for you.", "start": 2977.4, "duration": 1.62}, {"text": "For example,\ntomorrow we're going", "start": 2979.02, "duration": 1.67}, {"text": "to be talking about radiation\nutilizing technology, including", "start": 2980.69, "duration": 3.37}, {"text": "plasma sputter coders, one of\nwhich we have set up in my lab,", "start": 2984.06, "duration": 2.94}, {"text": "and I'd like to show you.", "start": 2987.0, "duration": 1.23}, {"text": "Because it's a way\nthat you can coat", "start": 2988.23, "duration": 1.5}, {"text": "materials and other\nmaterials, and you", "start": 2989.73, "duration": 1.8}, {"text": "have to generate this beautiful,\nglowing purple plasma in order", "start": 2991.53, "duration": 3.27}, {"text": "to do so.", "start": 2994.8, "duration": 1.0}, {"text": "So you ionize nitrogen. You\ninduce sputtering, which", "start": 2995.8, "duration": 3.02}, {"text": "is a radiation damage process\nwhich we'll be going over,", "start": 2998.82, "duration": 2.58}, {"text": "to coat things in other things.", "start": 3001.4, "duration": 2.232}, {"text": "There will be once\nin a while where", "start": 3003.632, "duration": 1.458}, {"text": "I have to shift a class into\nrecitation because I'll be", "start": 3005.09, "duration": 2.94}, {"text": "at Westinghouse or in Russia.", "start": 3008.03, "duration": 2.18}, {"text": "And I think that's only\ntwice during the whole year.", "start": 3010.21, "duration": 2.32}, {"text": "So you won't miss any classes.", "start": 3012.53, "duration": 1.26}, {"text": "We'll just use the\nrecitation time.", "start": 3013.79, "duration": 1.98}, {"text": "And then other,\ntimes we'll be doing", "start": 3015.77, "duration": 2.01}, {"text": "measuring the radioactivity\nof banana hashes.", "start": 3017.78, "duration": 2.7}, {"text": "Or once we talk about\nelectron interactions,", "start": 3020.48, "duration": 2.79}, {"text": "we're going to go use a\nscanning electron microscope.", "start": 3023.27, "duration": 3.45}, {"text": "The carrot at the end of\nthe stick to make sure", "start": 3026.72, "duration": 2.4}, {"text": "that you guys do well--", "start": 3029.12, "duration": 2.16}, {"text": "the top two people performing\non the quizzes get to pilot", "start": 3031.28, "duration": 4.05}, {"text": "and choose the samples for\nthe SEM and elemental analysis", "start": 3035.33, "duration": 3.69}, {"text": "and the focused ion\nbeam demonstration.", "start": 3039.02, "duration": 2.34}, {"text": "So you guys get to pilot\nsomething that's, let's", "start": 3041.36, "duration": 3.51}, {"text": "say, as complicated as a\nspace shuttle but deals", "start": 3044.87, "duration": 2.61}, {"text": "with things much, much smaller.", "start": 3047.48, "duration": 1.86}, {"text": "So I'll put you in\nthe driver's seat", "start": 3049.34, "duration": 1.5}, {"text": "in the machines of\nour lab, and you", "start": 3050.84, "duration": 1.23}, {"text": "get to bring whatever you\nwant to analyze and find", "start": 3052.07, "duration": 2.083}, {"text": "the elemental analysis of\nand use the world's smallest", "start": 3054.153, "duration": 3.172}, {"text": "machining instrument\nthat can cut", "start": 3057.325, "duration": 1.375}, {"text": "5-nanometer slices of things\nusing processes that we're", "start": 3058.7, "duration": 3.24}, {"text": "going to discuss in this class.", "start": 3061.94, "duration": 1.568}, {"text": "So the better you do, the\nmore you get to use it.", "start": 3063.508, "duration": 2.042}, {"text": "And at the end, we'll\nhave a nice debate.", "start": 3068.39, "duration": 2.25}, {"text": "I call it arguing\nwith Greenpeace", "start": 3070.64, "duration": 2.33}, {"text": "when we'll talk\nabout-- now that you'll", "start": 3072.97, "duration": 1.75}, {"text": "have known all of the nuclear\nscience and engineering", "start": 3074.72, "duration": 3.21}, {"text": "and can speak\nscientifically about topics,", "start": 3077.93, "duration": 2.16}, {"text": "we're going to go after a lot\nof societal misconceptions.", "start": 3080.09, "duration": 3.33}, {"text": "Do cell phones cause cancer?", "start": 3083.42, "duration": 2.04}, {"text": "Does living near a nuclear\npower plant cause cancer?", "start": 3085.46, "duration": 3.45}, {"text": "Does arguing with\nGreenpeace cause cancer,", "start": 3088.91, "duration": 3.1}, {"text": "whatever it's going to be?", "start": 3092.01, "duration": 1.1}, {"text": "So I want to make sure\nthat you're well-equipped", "start": 3093.11, "duration": 2.01}, {"text": "and confident enough to\ngo out there and hold", "start": 3095.12, "duration": 2.46}, {"text": "your own in a vigorous debate\nwith an angry, emotional", "start": 3097.58, "duration": 3.0}, {"text": "environmentalist.", "start": 3100.58, "duration": 1.38}, {"text": "You guys will be calm, peaceful,\nand informed environmentalists.", "start": 3101.96, "duration": 4.71}, {"text": "After all, that's why a\nlot of us are here, is we", "start": 3106.67, "duration": 2.79}, {"text": "want nuclear energy\nto happen because we", "start": 3109.46, "duration": 2.01}, {"text": "care about the environment.", "start": 3111.47, "duration": 1.14}, {"text": "There's other people\nthat don't want", "start": 3112.61, "duration": 1.5}, {"text": "nuclear energy to\nhappen because they", "start": 3114.11, "duration": 1.542}, {"text": "care about the environment.", "start": 3115.652, "duration": 1.428}, {"text": "To each their own, I\nguess, motivations.", "start": 3117.08, "duration": 2.607}, {"text": "But I want to make sure\nyou're well equipped", "start": 3119.687, "duration": 1.833}, {"text": "to also tackle things like\nis food irradiation bad.", "start": 3121.52, "duration": 3.57}, {"text": "That there's all sorts of\nwebsites with dancing babies", "start": 3125.09, "duration": 3.42}, {"text": "and weird Geocities-like\ngraphics saying", "start": 3128.51, "duration": 2.22}, {"text": "food irradiation is evil.", "start": 3130.73, "duration": 1.56}, {"text": "You won't find a lot\nof scientific articles", "start": 3132.29, "duration": 2.16}, {"text": "if that's the case.", "start": 3134.45, "duration": 1.44}, {"text": "And to see if you'll\nput your, let's", "start": 3135.89, "duration": 2.028}, {"text": "say, cancer risk\nwhere your mouth is,", "start": 3137.918, "duration": 1.542}, {"text": "the last day of class, we'll\nhave an irradiated fruit", "start": 3139.46, "duration": 2.31}, {"text": "party where I'll be buying\nonly the kinds of fruit that", "start": 3141.77, "duration": 3.15}, {"text": "can be imported into the US\nbecause food irradiation is", "start": 3144.92, "duration": 3.3}, {"text": "done.", "start": 3148.22, "duration": 0.81}, {"text": "Otherwise, the USDA would\nnot let it into the country.", "start": 3149.03, "duration": 2.78}, {"text": "And this is mostly things like\nmangosteens from Thailand,", "start": 3151.81, "duration": 3.1}, {"text": "pineapple from Costa Rica.", "start": 3154.91, "duration": 1.73}, {"text": "And interestingly\nenough, Hawaii is", "start": 3156.64, "duration": 2.41}, {"text": "considered a different\ncountry agriculturally.", "start": 3159.05, "duration": 3.09}, {"text": "It is so far away that they have\ndifferent agricultural pests.", "start": 3162.14, "duration": 3.09}, {"text": "And without\nirradiation, we couldn't", "start": 3165.23, "duration": 1.5}, {"text": "import some of the\nproduce from Hawaii,", "start": 3166.73, "duration": 1.95}, {"text": "because it could decimate some\nof the crops in the Continental", "start": 3168.68, "duration": 3.13}, {"text": "US.", "start": 3171.81, "duration": 0.83}, {"text": "Pretty crazy, huh?", "start": 3172.64, "duration": 1.88}, {"text": "Yeah.", "start": 3174.52, "duration": 0.63}, {"text": "It's the-- what, it's the 49th\nstate, but agriculturally,", "start": 3175.15, "duration": 3.18}, {"text": "a different country.", "start": 3178.33, "duration": 1.63}, {"text": "So it's about 5 till, so\nI'm going to stop here.", "start": 3179.96, "duration": 3.6}, {"text": "And we will start with\nradiation-utilizing technology", "start": 3183.56, "duration": 3.06}, {"text": "on Friday, tomorrow,\ndownstairs in Room 24-121.", "start": 3186.62, "duration": 4.56}, {"text": "And then we'll move over\nto my lab at 2 o'clock", "start": 3191.18, "duration": 3.24}, {"text": "to see the plasma sputter coder.", "start": 3194.42, "duration": 2.66}]
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+[{"text": "[SQUEAKING]\n[RUSTLING] [CLICKING]", "start": 0.0, "duration": 6.253}, {"text": "PROFESSOR: OK, good morning.", "start": 10.12, "duration": 1.33}, {"text": "So today, we're going to begin\nour discussion of nitrogen", "start": 11.45, "duration": 6.29}, {"text": "metabolism, which\nis really going", "start": 17.74, "duration": 2.16}, {"text": "to continue over the final\nthree lectures in the class.", "start": 19.9, "duration": 4.59}, {"text": "Now, nitrogen, of course,\nis critical for life.", "start": 24.49, "duration": 3.87}, {"text": "You need nitrogen to make RNA\nand DNA, as well as protein.", "start": 28.36, "duration": 5.49}, {"text": "And so what we will see\nis that as we discuss", "start": 33.85, "duration": 4.77}, {"text": "the metabolism of amino acids,\nand nucleic acids, not so", "start": 38.62, "duration": 10.89}, {"text": "much how they contribute\nto protein and RNA and DNA", "start": 49.51, "duration": 4.35}, {"text": "but rather how they\ninterface with other pathways", "start": 53.86, "duration": 3.54}, {"text": "and metabolism to lead to\nhow these molecules are", "start": 57.4, "duration": 3.33}, {"text": "synthesized, how\nthey're broken down--", "start": 60.73, "duration": 2.16}, {"text": "and what you will see as we\ngo through these discussions", "start": 62.89, "duration": 4.2}, {"text": "is that understanding the\nmetabolism of these molecules", "start": 67.09, "duration": 3.36}, {"text": "really is all about how\norganisms handle nitrogen.", "start": 70.45, "duration": 4.68}, {"text": "Now, of course, we've spent\nmuch of the class talking", "start": 75.13, "duration": 3.66}, {"text": "about how fat and sugar can\nbe oxidized as a way for cells", "start": 78.79, "duration": 4.86}, {"text": "to get energy.", "start": 83.65, "duration": 1.59}, {"text": "And of course, that's\nvery important.", "start": 85.24, "duration": 1.92}, {"text": "A major role of fat and\nsugar is energy transduction.", "start": 87.16, "duration": 3.81}, {"text": "But of course, cells are\nmostly made out of protein.", "start": 90.97, "duration": 3.58}, {"text": "And so roughly 50% of a\ncell by mass is protein.", "start": 94.55, "duration": 4.88}, {"text": "And protein, therefore, is\na key part of our diets,", "start": 99.43, "duration": 3.36}, {"text": "and really, any animal's diet\nthat eats other organisms.", "start": 102.79, "duration": 3.7}, {"text": "So anything that's\nnonphotosynthetic", "start": 106.49, "duration": 2.18}, {"text": "has to be taking\nin a lot of protein", "start": 108.67, "duration": 1.59}, {"text": "because it's eating\nother organisms in one", "start": 110.26, "duration": 2.94}, {"text": "way or another.", "start": 113.2, "duration": 1.78}, {"text": "Now, you will, of course,\nknow that nucleotides", "start": 114.98, "duration": 5.9}, {"text": "are central for and the\nheritability of life, and so", "start": 120.88, "duration": 4.44}, {"text": "life couldn't exist, at\nleast in a heritable form,", "start": 125.32, "duration": 2.879}, {"text": "without those.", "start": 128.199, "duration": 1.84}, {"text": "And often, we equate\nthings like amino acids,", "start": 130.039, "duration": 3.951}, {"text": "and nucleic-acid metabolism,\nnitrogen metabolism as all", "start": 133.99, "duration": 3.87}, {"text": "about energy and weight-lifting,\nso weightlifters--", "start": 137.86, "duration": 5.04}, {"text": "all the supplements that are\nsold to help people get huge--", "start": 142.9, "duration": 3.78}, {"text": "all of those things\nusually involve", "start": 146.68, "duration": 2.37}, {"text": "heavy loads of nitrogen-- so\ncreatine-- we talked about", "start": 149.05, "duration": 3.21}, {"text": "that earlier in the course.", "start": 152.26, "duration": 1.5}, {"text": "Leucine is a very common\nweightlifting supplement.", "start": 153.76, "duration": 3.36}, {"text": "These are all\nnitrogen-containing compounds,", "start": 157.12, "duration": 2.312}, {"text": "and it makes sense because if\nwe're going to build new mass", "start": 159.432, "duration": 2.458}, {"text": "for cells, we certainly need\nnitrogen to build the protein--", "start": 161.89, "duration": 3.48}, {"text": "that's what half the cells are--", "start": 165.37, "duration": 1.74}, {"text": "as well as the\nnucleic acids that", "start": 167.11, "duration": 2.04}, {"text": "enable cells to go on\nand build new cells.", "start": 169.15, "duration": 3.49}, {"text": "And in fact, roughly 50%, as\nI said, of the mass of a cell", "start": 172.64, "duration": 4.88}, {"text": "is protein, and another\n10% is nucleic acid.", "start": 177.52, "duration": 3.36}, {"text": "So really, a large chunk\nof what our cells are", "start": 180.88, "duration": 3.48}, {"text": "comes from these\nnitrogen-containing compounds.", "start": 184.36, "duration": 3.39}, {"text": "However may be something you\ndon't think about as much", "start": 187.75, "duration": 2.37}, {"text": "is that we also, because we\nhave to eat other organisms,", "start": 190.12, "duration": 3.57}, {"text": "consume a lot of\nprotein in our diet.", "start": 193.69, "duration": 2.25}, {"text": "And therefore, protein\nand particularly,", "start": 195.94, "duration": 3.78}, {"text": "different amino\nacids, also end up", "start": 199.72, "duration": 2.43}, {"text": "being a very important nutrient.", "start": 202.15, "duration": 2.58}, {"text": "And in fact, our\nmuscles and our liver", "start": 204.73, "duration": 3.07}, {"text": "are storage organs, if\nyou will, for amino acids.", "start": 207.8, "duration": 5.03}, {"text": "And so our muscles are always\ngetting bigger and smaller,", "start": 212.83, "duration": 3.3}, {"text": "breaking down,\nrebuilding each other", "start": 216.13, "duration": 3.09}, {"text": "as we go through life as\nthey really participate", "start": 219.22, "duration": 4.41}, {"text": "in our body's metabolism.", "start": 223.63, "duration": 4.92}, {"text": "In fact, you have tons of energy\nbuilt up into your muscles.", "start": 228.55, "duration": 6.07}, {"text": "And if you starve\nyourself, stop eating,", "start": 234.62, "duration": 3.05}, {"text": "you can live off of muscle\ntissue for quite a lot of time.", "start": 237.67, "duration": 3.57}, {"text": "And that is really using\nthe amino-acid breakdown", "start": 241.24, "duration": 2.67}, {"text": "from our muscle tissue,\nreally, there as a way", "start": 243.91, "duration": 2.76}, {"text": "to keep glucose\nin our blood high", "start": 246.67, "duration": 4.83}, {"text": "and keep our brain\nthinking right.", "start": 251.5, "duration": 3.08}, {"text": "That's why we talked last\ntime about the keto diet.", "start": 254.58, "duration": 3.61}, {"text": "When we talked\nabout the keto diet,", "start": 258.19, "duration": 1.537}, {"text": "remember, if you're going to\ndo this properly and really", "start": 259.727, "duration": 2.333}, {"text": "be ketogenic, you can't\neat glucose, of course,", "start": 262.06, "duration": 3.36}, {"text": "but you also can't\neat-- or carbohydrates.", "start": 265.42, "duration": 3.03}, {"text": "But you also can't eat\nprotein, and the reason", "start": 268.45, "duration": 2.73}, {"text": "is because the liver will\nturn your amino acids back", "start": 271.18, "duration": 3.21}, {"text": "into glucose.", "start": 274.39, "duration": 2.79}, {"text": "And that's true whether\nthose amino acids come", "start": 277.18, "duration": 2.22}, {"text": "from the diet or\nthose amino acids", "start": 279.4, "duration": 1.71}, {"text": "can come from the\nbreakdown of muscle.", "start": 281.11, "duration": 2.69}, {"text": "All right.", "start": 283.8, "duration": 1.32}, {"text": "So if we use amino acids\nas a source of energy", "start": 285.12, "duration": 5.94}, {"text": "as a way to support\ngluconeogenesis", "start": 291.06, "duration": 2.22}, {"text": "to keep our carbohydrates\navailable for our brain,", "start": 293.28, "duration": 3.3}, {"text": "we need a way to metabolize\nthose amino acids.", "start": 296.58, "duration": 3.31}, {"text": "And if we metabolize\nthose amino acids,", "start": 299.89, "duration": 1.91}, {"text": "we also then need a way to deal\nwith all the excess nitrogen.", "start": 301.8, "duration": 4.56}, {"text": "And so, indeed, we already\nintroduced how this works.", "start": 306.36, "duration": 4.98}, {"text": "And if you remember\nback when we talked", "start": 311.34, "duration": 1.92}, {"text": "about the malate-aspartate\nshuttle, which you'll", "start": 313.26, "duration": 10.58}, {"text": "recall was a way for us\nto transfer electrons", "start": 323.84, "duration": 3.78}, {"text": "from the cytosol\ninto the mitochondria", "start": 327.62, "duration": 2.91}, {"text": "and involved this convoluted\nswaps between aspartate,", "start": 330.53, "duration": 5.31}, {"text": "and oxalacetate, and glutamate,\nand alpha-ketoglutarate,", "start": 335.84, "duration": 3.51}, {"text": "and at the time, we\nintroduced how amino acids are", "start": 339.35, "duration": 2.73}, {"text": "related to alpha-keto acids.", "start": 342.08, "duration": 2.73}, {"text": "And so I draw out how\noxalacetate, an amino acid,", "start": 344.81, "duration": 9.17}, {"text": "is related to the\nalpha-keto acid--", "start": 353.98, "duration": 2.61}, {"text": "sorry-- how the amino\nacid aspartame is related", "start": 363.93, "duration": 3.51}, {"text": "to the alpha-keto\nacid oxalacetate,", "start": 367.44, "duration": 3.87}, {"text": "as well as how the\namino acid glutamate", "start": 371.31, "duration": 4.11}, {"text": "is related to the amino\nacid alpha-ketoglutarate.", "start": 375.42, "duration": 4.89}, {"text": "Just to be very explicit remind\nyou what I meant for this,", "start": 380.31, "duration": 3.72}, {"text": "and so here is the\namino acid alanine.", "start": 384.03, "duration": 5.71}, {"text": "This is the amino acid alanine.", "start": 396.94, "duration": 2.43}, {"text": "It is related to the\nalpha-keto acid pyruvate.", "start": 399.37, "duration": 4.47}, {"text": "And again the same relationship,\nif you look back in your notes", "start": 412.1, "duration": 2.76}, {"text": "when we discussed the\nmalate-aspartate shuttle--", "start": 414.86, "duration": 2.16}, {"text": "glutamate to\nalpha-ketoglutarate,", "start": 417.02, "duration": 1.41}, {"text": "aspartate to oxalacetate.", "start": 418.43, "duration": 1.89}, {"text": "Really, the keto group,\nthe alpha-keto group,", "start": 420.32, "duration": 4.08}, {"text": "is being replaced\nwith the amino group.", "start": 424.4, "duration": 2.94}, {"text": "And what should be clear to you\nnow is that if you can convert", "start": 427.34, "duration": 6.39}, {"text": "an amino acid into\nan alpha-keto acid--", "start": 433.73, "duration": 2.79}, {"text": "that is dispose of the\nnitrogen, get the ketone back--", "start": 436.52, "duration": 3.33}, {"text": "it should be very\nclear how you can then", "start": 439.85, "duration": 2.58}, {"text": "oxidize pyruvate, oxidize\noxalacetate, oxidize", "start": 442.43, "duration": 3.93}, {"text": "alpha-ketoglutarate-- as a\nway to get energy directly,", "start": 446.36, "duration": 5.76}, {"text": "burn it in the TCA cycle,\nget ATP, NADH that way,", "start": 452.12, "duration": 4.11}, {"text": "or turn it into glucose\nby gluconeogenesis.", "start": 456.23, "duration": 4.84}, {"text": "However, if we're\ngoing to do this,", "start": 461.07, "duration": 2.39}, {"text": "obviously, these nitrogenous\nhave to go somewhere.", "start": 463.46, "duration": 4.41}, {"text": "And if you're going\nto build amino acids,", "start": 467.87, "duration": 2.07}, {"text": "those nitrogenous have\nto come from somewhere.", "start": 469.94, "duration": 2.92}, {"text": "And that's really why\nthe pathways that we're", "start": 472.86, "duration": 2.51}, {"text": "going to discuss really, are\nabout nitrogen metabolism", "start": 475.37, "duration": 4.17}, {"text": "and how cells deal with\neither the excess nitrogen", "start": 479.54, "duration": 3.78}, {"text": "from breaking down amino\nacids and nucleic acids", "start": 483.32, "duration": 4.02}, {"text": "or how cells obtain\nthat nitrogen as a way", "start": 487.34, "duration": 5.36}, {"text": "to build these molecules.", "start": 492.7, "duration": 4.6}, {"text": "Now, by way of introduction,\nwe have to discuss also,", "start": 497.3, "duration": 4.58}, {"text": "where is it then that nitrogen,\nfor biological systems,", "start": 501.88, "duration": 4.02}, {"text": "really comes from\nin the first place?", "start": 505.9, "duration": 3.13}, {"text": "Now this is almost never\nan issue for animals,", "start": 509.03, "duration": 3.23}, {"text": "and that's because we and other\nanimals eat other organisms.", "start": 512.26, "duration": 4.659}, {"text": "And so we eat other\norganisms-- usually,", "start": 516.919, "duration": 1.911}, {"text": "we have a problem of dealing\nwith too much nitrogen.", "start": 518.83, "duration": 3.57}, {"text": "However, for photosynthetic\norganisms, how to get nitrogen", "start": 522.4, "duration": 3.81}, {"text": "ends up being a real problem.", "start": 526.21, "duration": 2.41}, {"text": "And so any of you who\nhave done any gardening", "start": 528.62, "duration": 2.51}, {"text": "know that you need to add\nfertilizer to your plants.", "start": 531.13, "duration": 3.06}, {"text": "What is fertilizer?", "start": 534.19, "duration": 1.14}, {"text": "Well, it's primarily\na source of nitrogen,", "start": 535.33, "duration": 2.91}, {"text": "as well as phosphorus.", "start": 538.24, "duration": 3.6}, {"text": "And really, it's the nitrogen\nin the fertilizer that's", "start": 541.84, "duration": 3.24}, {"text": "helping solve the\nproblem of where", "start": 545.08, "duration": 2.58}, {"text": "the photosynthetic\norganisms are going", "start": 547.66, "duration": 1.74}, {"text": "to get the nitrogen\nthat they need to grow.", "start": 549.4, "duration": 2.97}, {"text": "Now, of course, there's a lot\nof nitrogen, nitrogen gas,", "start": 552.37, "duration": 5.31}, {"text": "in our atmosphere, all right?", "start": 557.68, "duration": 2.22}, {"text": "But nitrogen gas is\nincredibly inert.", "start": 559.9, "duration": 3.42}, {"text": "You use nitrogen\ngas is an inert gas", "start": 563.32, "duration": 2.55}, {"text": "to basically stop things that\nare too reactive from reacting", "start": 565.87, "duration": 5.43}, {"text": "with the air in the lab, OK?", "start": 571.3, "duration": 2.25}, {"text": "Nitrogen gas as a\nvery stable molecule", "start": 573.55, "duration": 2.58}, {"text": "is not at all useful to biology.", "start": 576.13, "duration": 3.51}, {"text": "However, if we take this\nnitrogen gas and we reduce it--", "start": 579.64, "duration": 5.82}, {"text": "that is we add a\nbunch of electrons--", "start": 585.46, "duration": 3.36}, {"text": "what we end up with\nnow is we end up", "start": 588.82, "duration": 2.58}, {"text": "with all of these\nreduced nitrogen groups,", "start": 591.4, "duration": 8.9}, {"text": "these amino groups that are\nincredibly useful for biology.", "start": 600.3, "duration": 6.27}, {"text": "These come up over\nand over again.", "start": 606.57, "duration": 1.47}, {"text": "These are the side chains\nof our amino acids.", "start": 608.04, "duration": 2.97}, {"text": "They're found on\nall the cofactors.", "start": 611.01, "duration": 2.13}, {"text": "They're forming\nthe hydrogen bonds", "start": 613.14, "duration": 2.16}, {"text": "between our different\nnucleosides, OK?", "start": 615.3, "duration": 3.0}, {"text": "And so enzymes work.", "start": 618.3, "duration": 3.03}, {"text": "Genetics happen.", "start": 621.33, "duration": 1.14}, {"text": "Hydrogen bonds\nform because of all", "start": 622.47, "duration": 2.97}, {"text": "of these nitrogen-containing\ncompounds.", "start": 625.44, "duration": 3.84}, {"text": "But you need a way to get\nfrom this nitrogen gas", "start": 629.28, "duration": 3.54}, {"text": "down to this reduced\nnitrogen. And that is really,", "start": 632.82, "duration": 4.41}, {"text": "so-called nitrogen\nfixation, which is basically", "start": 637.23, "duration": 12.05}, {"text": "taking nitrogen\ngas and reducing it", "start": 649.28, "duration": 5.89}, {"text": "to be a compound like\nammonia, which involves adding", "start": 655.17, "duration": 4.29}, {"text": "electrons, that ends up\nbeing one of the things,", "start": 659.46, "duration": 5.1}, {"text": "the magic of biology, that\nreally makes life possible.", "start": 664.56, "duration": 4.92}, {"text": "Now, you don't often think about\nnitrogen fixation very much,", "start": 669.48, "duration": 4.53}, {"text": "so obviously, we all\nknow that photosynthesis", "start": 674.01, "duration": 3.48}, {"text": "is really central to\nwhat makes life happen.", "start": 677.49, "duration": 3.0}, {"text": "And we spent a lot of time\ntalking about photosynthesis.", "start": 680.49, "duration": 4.5}, {"text": "Apart from\nphotosynthesis, which,", "start": 684.99, "duration": 1.59}, {"text": "of course, takes the\nenergy from the Sun", "start": 686.58, "duration": 1.83}, {"text": "and gives us a way\nto get reduced carbon", "start": 688.41, "duration": 2.62}, {"text": "that all life depends on--", "start": 691.03, "duration": 2.99}, {"text": "nitrogen fixation is a\nway to take nitrogen gas", "start": 694.02, "duration": 2.88}, {"text": "from the atmosphere and turn\nit into ammonia, a useful form", "start": 696.9, "duration": 3.84}, {"text": "of nitrogen for life to use.", "start": 700.74, "duration": 2.4}, {"text": "And what you may not realize\nis nitrogen fixation really", "start": 703.14, "duration": 4.77}, {"text": "only occurs in a select group\nof prokaryotic organisms.", "start": 707.91, "duration": 4.32}, {"text": "So these are really the\nunsung heroes of life,", "start": 719.54, "duration": 5.15}, {"text": "or at least the unsung\nheroes of metabolism.", "start": 724.69, "duration": 3.42}, {"text": "It's probably the most\ncentral topic to life", "start": 728.11, "duration": 2.498}, {"text": "that we're not going\nto spend a lot of time", "start": 730.608, "duration": 1.792}, {"text": "talking about in 705 simply\nbecause we don't have time.", "start": 732.4, "duration": 4.54}, {"text": "But it's basically redox\nchemistry to take nitrogen gas,", "start": 736.94, "duration": 4.46}, {"text": "add electrons to it, and end\nup with reduced nitrogen.", "start": 741.4, "duration": 5.43}, {"text": "This is very energy intensive--\nrequires on the order of 16 ATP", "start": 746.83, "duration": 3.87}, {"text": "molecules.", "start": 750.7, "duration": 0.99}, {"text": "It's covered well\nin various textbooks", "start": 751.69, "duration": 3.09}, {"text": "if you're interested in\nreading about this further.", "start": 754.78, "duration": 2.86}, {"text": "But I really want\nyou to appreciate", "start": 757.64, "duration": 1.67}, {"text": "that this is something\nthat really has to happen,", "start": 759.31, "duration": 4.02}, {"text": "and it's really\nrelatively few organisms", "start": 763.33, "duration": 2.73}, {"text": "that allow this to happen for\nall other life on the planet", "start": 766.06, "duration": 3.81}, {"text": "to be dependent on.", "start": 769.87, "duration": 2.1}, {"text": "This is really why\nfertilizer ends up", "start": 771.97, "duration": 3.12}, {"text": "being the thing that\nyou add to your garden.", "start": 775.09, "duration": 2.52}, {"text": "So in the wild, nature would\nset up symbiotic relationships", "start": 777.61, "duration": 3.36}, {"text": "with other organisms, with\nthese nitrogen-fixing organisms,", "start": 780.97, "duration": 3.51}, {"text": "in order to get the\nnitrogen they can get.", "start": 784.48, "duration": 2.13}, {"text": "However, we can help\nthat process along", "start": 786.61, "duration": 2.82}, {"text": "by giving fertilizer.", "start": 789.43, "duration": 3.33}, {"text": "If there's a lot of fertilizer\nrunoff, you get algae blooms.", "start": 792.76, "duration": 3.63}, {"text": "That's really because\nall this nitrogen now", "start": 796.39, "duration": 2.79}, {"text": "gets dumped into the water.", "start": 799.18, "duration": 1.2}, {"text": "That ends up being\nrate-limiting, often,", "start": 800.38, "duration": 1.83}, {"text": "for photosynthetic organisms,\nlike algae, to grow.", "start": 802.21, "duration": 2.88}, {"text": "And so this ends up being\na really important topic", "start": 805.09, "duration": 3.225}, {"text": "if you're interested in\nenvironmental science", "start": 808.315, "duration": 1.875}, {"text": "or if you're interested\nin agriculture.", "start": 810.19, "duration": 2.19}, {"text": "And it's at least\nsomething I want", "start": 812.38, "duration": 1.5}, {"text": "to make you aware of from\nthis introductory course.", "start": 813.88, "duration": 5.88}, {"text": "All right.", "start": 819.76, "duration": 0.51}, {"text": "Now, for most organisms, we\nget, from either our diet", "start": 822.95, "duration": 6.41}, {"text": "or from the environment,\nfixed nitrogen.", "start": 829.36, "duration": 3.15}, {"text": "And the two forms\nof fixed nitrogen", "start": 832.51, "duration": 3.69}, {"text": "that we need to discuss\nis ammonia, as well as", "start": 836.2, "duration": 5.31}, {"text": "the conjugate base of\nammonia, which is ammonium.", "start": 841.51, "duration": 4.71}, {"text": "Now, fertilizer is, of\ncourse, very rich in ammonia.", "start": 850.39, "duration": 5.43}, {"text": "And animals that eat other\norganisms get lots of nitrogen", "start": 855.82, "duration": 4.41}, {"text": "from breakdown of proteins.", "start": 860.23, "duration": 1.86}, {"text": "And that is a source of\nammonia or ammonium ions.", "start": 862.09, "duration": 4.35}, {"text": "And so photosynthetic\norganisms have", "start": 866.44, "duration": 1.71}, {"text": "the problem of getting these.", "start": 868.15, "duration": 1.32}, {"text": "Animals off and have the problem\nof, how do we get rid of this?", "start": 869.47, "duration": 4.15}, {"text": "Now, if you've ever\ncleaned with ammonia,", "start": 873.62, "duration": 3.53}, {"text": "you know that it's pretty nasty.", "start": 877.15, "duration": 1.65}, {"text": "It smells bad.", "start": 878.8, "duration": 0.96}, {"text": "It's a cleaning agent.", "start": 879.76, "duration": 1.32}, {"text": "It's very toxic to\nlots of organisms", "start": 881.08, "duration": 4.56}, {"text": "at high enough levels.", "start": 885.64, "duration": 1.65}, {"text": "And so animals really need\nstrategies-- or, all life,", "start": 887.29, "duration": 4.41}, {"text": "really, cells need\nstrategies about how they're", "start": 891.7, "duration": 3.15}, {"text": "going to handle and deal with\nthese nitrogen-containing", "start": 894.85, "duration": 7.68}, {"text": "compounds, either to incorporate\nit or to get rid of it.", "start": 902.53, "duration": 4.08}, {"text": "Now, I'm going to spend a lot\nof time today talking about how", "start": 906.61, "duration": 2.67}, {"text": "animals who take in a lot of--", "start": 909.28, "duration": 3.03}, {"text": "eat other organisms,\ntake in a lot of nitrogen", "start": 912.31, "duration": 2.82}, {"text": "have to deal with\nthe nitrogen excess.", "start": 915.13, "duration": 2.28}, {"text": "And it turns out that you can\ndeal with the ammonia that's", "start": 917.41, "duration": 5.19}, {"text": "generated from the breakdown\nof your amino acids", "start": 922.6, "duration": 3.72}, {"text": "in lots of different ways.", "start": 926.32, "duration": 2.68}, {"text": "And basically, there\nis no one solution", "start": 929.0, "duration": 2.75}, {"text": "that life uses that's\nuniversal for how you deal", "start": 931.75, "duration": 3.33}, {"text": "with the excess\nnitrogen. Really,", "start": 935.08, "duration": 2.1}, {"text": "different strategies\nhave been involved", "start": 937.18, "duration": 2.25}, {"text": "incorporating the\nmetabolism of amino acids", "start": 939.43, "duration": 3.24}, {"text": "and nucleic acids\nthat fit the lifestyle", "start": 942.67, "duration": 3.21}, {"text": "of different creatures.", "start": 945.88, "duration": 2.31}, {"text": "And so fish and\nother aquatic life", "start": 948.19, "duration": 9.77}, {"text": "really deals with nitrogen\nbecause they can just", "start": 957.96, "duration": 3.84}, {"text": "excrete ammonia directly.", "start": 961.8, "duration": 4.04}, {"text": "They live in the ocean--", "start": 968.66, "duration": 2.34}, {"text": "lots of excess space\ninto the ocean.", "start": 971.0, "duration": 3.3}, {"text": "Just take the ammonia.", "start": 974.3, "duration": 1.65}, {"text": "Send it off into the ocean.", "start": 975.95, "duration": 1.47}, {"text": "The large volume of\nwater in the ocean", "start": 977.42, "duration": 2.94}, {"text": "means dealing with ammonia\nis not such a big problem--", "start": 980.36, "duration": 5.1}, {"text": "literally pissing into\nthe ocean to get rid", "start": 985.46, "duration": 3.93}, {"text": "of their excess ammonia,\ntheir nitrogen waste.", "start": 989.39, "duration": 5.31}, {"text": "Now, terrestrial animals--", "start": 994.7, "duration": 1.845}, {"text": "I'll just say\nterrestrial creatures--", "start": 1001.706, "duration": 3.164}, {"text": "have a different\nproblem to deal with.", "start": 1004.87, "duration": 2.73}, {"text": "And that is they can't tolerate\nthe high concentrations", "start": 1007.6, "duration": 3.87}, {"text": "of ammonia that would be\nnecessary to just release it", "start": 1011.47, "duration": 2.61}, {"text": "into the environment, so\nthey need another solution.", "start": 1014.08, "duration": 3.27}, {"text": "And of course, our solution is\nto excrete our excess nitrogen", "start": 1017.35, "duration": 5.34}, {"text": "as urea.", "start": 1022.69, "duration": 0.75}, {"text": "So that's urea.", "start": 1035.95, "duration": 1.29}, {"text": "This is why we make urine.", "start": 1037.24, "duration": 2.25}, {"text": "And really, our solution to\neliminate excess nitrogen", "start": 1039.49, "duration": 5.339}, {"text": "is to concentrate that nitrogen,\nrather than excreting it", "start": 1044.829, "duration": 2.911}, {"text": "as ammonia--", "start": 1047.74, "duration": 1.83}, {"text": "but to make urea, put\nit into our urine,", "start": 1049.57, "duration": 2.76}, {"text": "and eliminate it\nthrough urination.", "start": 1052.33, "duration": 5.76}, {"text": "Now, not all animals make urea.", "start": 1058.09, "duration": 4.26}, {"text": "Things like reptiles\nand birds, which--", "start": 1062.35, "duration": 3.69}, {"text": "turns out making urea requires\naccess to lots of water.", "start": 1066.04, "duration": 5.52}, {"text": "Reptiles don't always have\naccess to lots of water.", "start": 1071.56, "duration": 2.82}, {"text": "They live in dry climates.", "start": 1074.38, "duration": 1.8}, {"text": "Birds don't want\nto have to carry", "start": 1076.18, "duration": 1.53}, {"text": "around all the extra water\nweight of dealing with urea.", "start": 1077.71, "duration": 3.63}, {"text": "So instead of urea, it\nturns out that they excrete", "start": 1081.34, "duration": 3.87}, {"text": "their nitrogen as uric acid.", "start": 1085.21, "duration": 3.25}, {"text": "So what's uric acid?", "start": 1088.46, "duration": 1.085}, {"text": "So this here is uric acid.", "start": 1104.33, "duration": 1.485}, {"text": "So uric acid is\nbasically a purine.", "start": 1115.95, "duration": 3.65}, {"text": "So it should look very similar\nto the adenine and guanine", "start": 1119.6, "duration": 3.63}, {"text": "rings that you saw\nearlier in the class.", "start": 1123.23, "duration": 2.5}, {"text": "And so they basically\ngenerate uric acid,", "start": 1125.73, "duration": 4.92}, {"text": "which allows them to excrete\nmore nitrogen with less water.", "start": 1130.65, "duration": 5.58}, {"text": "And so bird poop-- birds\ndon't urinate-- the bird poop", "start": 1136.23, "duration": 4.08}, {"text": "that you get, that\nslurry of material,", "start": 1140.31, "duration": 2.73}, {"text": "is basically a mixture of\nsolid waste and uric acid.", "start": 1143.04, "duration": 3.54}, {"text": "And that's how birds eliminate\ntheir waste all in one", "start": 1146.58, "duration": 6.21}, {"text": "go as a way to save\nsome water as they deal", "start": 1152.79, "duration": 5.19}, {"text": "with their excess nitrogen.", "start": 1157.98, "duration": 2.55}, {"text": "All right, the fact that\ndifferent terrestrial", "start": 1160.53, "duration": 3.09}, {"text": "creatures-- some, like us, make\nurea-- some make uric acid--", "start": 1163.62, "duration": 3.87}, {"text": "really deals with,\nshows that urea--", "start": 1167.49, "duration": 2.76}, {"text": "you will see today is from\namino-acid metabolism--", "start": 1170.25, "duration": 2.34}, {"text": "uric acid is, of\ncourse, from purine,", "start": 1172.59, "duration": 2.623}, {"text": "from purine metabolism-- we'll\ntalk about that in the last", "start": 1175.213, "duration": 2.417}, {"text": "lecture of the course--", "start": 1177.63, "duration": 1.53}, {"text": "they really illustrate\nhow the metabolism", "start": 1179.16, "duration": 3.42}, {"text": "of amino acids and\nnucleic acids is really", "start": 1182.58, "duration": 2.46}, {"text": "about the metabolism of nitrogen\nand how these pathways are", "start": 1185.04, "duration": 5.88}, {"text": "really set up in a way that\nallows exchange of ammonia", "start": 1190.92, "duration": 5.97}, {"text": "with amino acids, as well\nas with nucleic acids,", "start": 1196.89, "duration": 14.42}, {"text": "as the nitrogen can\nreally flow between all", "start": 1211.31, "duration": 3.3}, {"text": "of these different\nbiological molecules.", "start": 1214.61, "duration": 3.54}, {"text": "And along the way,\nwell, this allows", "start": 1218.15, "duration": 1.71}, {"text": "a way to excrete nitrogen.\nIt also, obviously, involves", "start": 1219.86, "duration": 3.09}, {"text": "ways to incorporate it and\nis really the pathway cells", "start": 1222.95, "duration": 4.05}, {"text": "use to both make and break\ndown these compounds.", "start": 1227.0, "duration": 5.93}, {"text": "All right.", "start": 1232.93, "duration": 1.23}, {"text": "Now, as humans,\nwe, of course, eat", "start": 1234.16, "duration": 3.81}, {"text": "a diet that's high in protein--", "start": 1237.97, "duration": 2.61}, {"text": "higher in protein.", "start": 1240.58, "duration": 1.29}, {"text": "Now the current fad is to\neat high-protein diets.", "start": 1241.87, "duration": 3.39}, {"text": "That's the latest\ntrend that's healthy.", "start": 1245.26, "duration": 2.79}, {"text": "And this involves lots\nof nitrogen excess,", "start": 1248.05, "duration": 4.83}, {"text": "and so we have to,\nas humans, urinate", "start": 1252.88, "duration": 2.82}, {"text": "several times a\nday because we need", "start": 1255.7, "duration": 1.62}, {"text": "to excrete lots of nitrogen.", "start": 1257.32, "duration": 2.65}, {"text": "Now, that's really our\namount of urea out.", "start": 1259.97, "duration": 7.64}, {"text": "So that urea out,\nreally, in a healthy", "start": 1267.61, "duration": 3.0}, {"text": "person is balanced with the\nnitrogen in from the diet?", "start": 1270.61, "duration": 11.31}, {"text": "Makes sense?", "start": 1281.92, "duration": 1.59}, {"text": "If we are not growing and we\neat a certain amount of protein,", "start": 1283.51, "duration": 5.72}, {"text": "if we eat more\nprotein, that means", "start": 1289.23, "duration": 6.08}, {"text": "we need to excrete\nmore nitrogen.", "start": 1295.31, "duration": 6.26}, {"text": "If we eat less protein, then we\nneed to excrete less nitrogen.", "start": 1301.57, "duration": 12.11}, {"text": "And so the nitrogen in and\nout should be balanced.", "start": 1313.68, "duration": 4.85}, {"text": "Now the reality is that\nnot all of our nitrogen", "start": 1318.53, "duration": 3.72}, {"text": "is excreted as urea.", "start": 1322.25, "duration": 2.76}, {"text": "Some of it ends up in the\nstool as other compounds.", "start": 1325.01, "duration": 4.32}, {"text": "And so for a healthy\nperson, nitrogen in", "start": 1329.33, "duration": 4.53}, {"text": "is greater than nitrogen\nout in the urine, the urea.", "start": 1333.86, "duration": 9.19}, {"text": "Nitrogen is really\ngreater than nitrogen out.", "start": 1343.05, "duration": 2.94}, {"text": "And this is what is referred to\nmedically as positive nitrogen", "start": 1345.99, "duration": 5.275}, {"text": "balance.", "start": 1351.265, "duration": 0.5}, {"text": "So if I collect all of\nyour urine for 24 hours", "start": 1356.41, "duration": 2.93}, {"text": "and keep track of all the food\nthat you eat, and I measure", "start": 1359.34, "duration": 3.3}, {"text": "all the nitrogen in the unit\nand all the nitrogen in the food", "start": 1362.64, "duration": 3.15}, {"text": "you eat, there's\ngoing to be more taken", "start": 1365.79, "duration": 2.04}, {"text": "in than I measure\nin the urine, that's", "start": 1367.83, "duration": 2.49}, {"text": "positive nitrogen balance.", "start": 1370.32, "duration": 1.47}, {"text": "And that is what is standard,\nhealthy for most humans.", "start": 1371.79, "duration": 7.08}, {"text": "Now, if there's positive\nnitrogen balance,", "start": 1378.87, "duration": 3.75}, {"text": "it means you can also have\nnegative nitrogen balance,", "start": 1382.62, "duration": 9.43}, {"text": "which really means that\nthe amount of nitrogen", "start": 1392.05, "duration": 4.71}, {"text": "in is less than the\namount of nitrogen out.", "start": 1396.76, "duration": 4.5}, {"text": "That is you are losing\nmore nitrogen in the urine", "start": 1401.26, "duration": 3.87}, {"text": "than you're taking in.", "start": 1405.13, "duration": 2.13}, {"text": "Medically, this is\na very bad thing.", "start": 1407.26, "duration": 3.78}, {"text": "When does this occur?", "start": 1411.04, "duration": 1.18}, {"text": "Well, it occurs during\nperiods of starvation.", "start": 1412.22, "duration": 3.95}, {"text": "Make sense?", "start": 1416.17, "duration": 1.08}, {"text": "If you're not eating\nany food, you still", "start": 1417.25, "duration": 2.16}, {"text": "need to get energy\nfrom somewhere.", "start": 1419.41, "duration": 2.7}, {"text": "You'll catabolize your glycogen,\nyou'll catabolize your fat,", "start": 1422.11, "duration": 3.09}, {"text": "but you'll also catabolize the\namino acids in your muscle.", "start": 1425.2, "duration": 3.81}, {"text": "Those amino acids will generate\nexcess nitrogen, more nitrogen", "start": 1429.01, "duration": 3.78}, {"text": "out than you've\ntaken in the diet.", "start": 1432.79, "duration": 4.44}, {"text": "This also occurs\nduring some illnesses--", "start": 1437.23, "duration": 5.19}, {"text": "famously, cancer, AIDS, sepsis,\nall of these really horrible", "start": 1442.42, "duration": 8.19}, {"text": "conditions that some people--", "start": 1450.61, "duration": 3.36}, {"text": "can be very life threatening.", "start": 1453.97, "duration": 1.86}, {"text": "Many of these lead to a\nphenomenon known as cachexia.", "start": 1455.83, "duration": 5.97}, {"text": "So what's cachexia?", "start": 1461.8, "duration": 1.95}, {"text": "You waste away, lose all\nof your lean body mass.", "start": 1463.75, "duration": 3.96}, {"text": "This is also basically a state\nof negative nitrogen balance.", "start": 1467.71, "duration": 5.37}, {"text": "And why this is\nreally, a current topic", "start": 1473.08, "duration": 6.15}, {"text": "that lots of people are\ntrying to figure out.", "start": 1479.23, "duration": 2.61}, {"text": "But it's really a case\nwhere you are breaking down", "start": 1481.84, "duration": 2.85}, {"text": "more of your muscle protein,\nmore amino acids, and losing", "start": 1484.69, "duration": 4.68}, {"text": "that nitrogen than\nyou're taking in.", "start": 1489.37, "duration": 3.21}, {"text": "And treatment of the\nunderlying condition", "start": 1492.58, "duration": 3.37}, {"text": "is really required for\nthis to get better.", "start": 1495.95, "duration": 3.38}, {"text": "All right.", "start": 1499.33, "duration": 0.99}, {"text": "Now, it turns out I\ncan experimentally", "start": 1500.32, "duration": 3.15}, {"text": "cause negative nitrogen\nbalance in an animal", "start": 1503.47, "duration": 4.26}, {"text": "if I remove certain amino\nacids from your diet.", "start": 1507.73, "duration": 6.09}, {"text": "Why is that?", "start": 1513.82, "duration": 1.09}, {"text": "Well, it's because\nprokaryotes, plants, yeast,", "start": 1514.91, "duration": 13.55}, {"text": "lots of organisms, many\norganisms, can make all 20", "start": 1528.46, "duration": 7.05}, {"text": "of the amino acids that are\nrequired to build protein.", "start": 1535.51, "duration": 6.69}, {"text": "But it turns out that\nanimals, including humans,", "start": 1542.2, "duration": 7.91}, {"text": "cannot make all 20 amino acids.", "start": 1550.11, "duration": 9.285}, {"text": "It's a quirk of our physiology.", "start": 1564.29, "duration": 3.72}, {"text": "But it turns out some of the\n20 amino acids that are needed", "start": 1568.01, "duration": 3.6}, {"text": "to build protein are essential.", "start": 1571.61, "duration": 2.19}, {"text": "That is they have to come\nfrom external sources.", "start": 1573.8, "duration": 3.888}, {"text": "So remember, there's\nlots of vitamins", "start": 1577.688, "duration": 1.542}, {"text": "out there that we can't make.", "start": 1579.23, "duration": 1.56}, {"text": "We have to get\nthose from our diet.", "start": 1580.79, "duration": 1.5}, {"text": "There's essential lipids.", "start": 1582.29, "duration": 1.38}, {"text": "We talked about that\nlast time again--", "start": 1583.67, "duration": 3.06}, {"text": "have to get those from our diet.", "start": 1586.73, "duration": 1.77}, {"text": "And some of the amino acids\nthat we need to live also", "start": 1588.5, "duration": 3.75}, {"text": "have to come from\nan external source.", "start": 1592.25, "duration": 2.16}, {"text": "And in the 1950s, experiments\nactually done on humans,", "start": 1594.41, "duration": 4.08}, {"text": "on medical students,\nactually found", "start": 1598.49, "duration": 2.28}, {"text": "that if you take these essential\namino acids out of the diet,", "start": 1600.77, "duration": 3.99}, {"text": "what happens is that you can\nshift those medical students", "start": 1604.76, "duration": 4.08}, {"text": "into a state of negative\nnitrogen balance.", "start": 1608.84, "duration": 2.61}, {"text": "And that's because they're\nunable to synthesize protein.", "start": 1611.45, "duration": 3.6}, {"text": "You're always synthesizing\nand breaking down protein.", "start": 1615.05, "duration": 3.63}, {"text": "If you don't have the essential\namino acids to resynthesize", "start": 1618.68, "duration": 3.0}, {"text": "your protein, you now\nbreak down more protein", "start": 1621.68, "duration": 2.52}, {"text": "than you synthesize,\nand you end up", "start": 1624.2, "duration": 1.77}, {"text": "with negative nitrogen balance.", "start": 1625.97, "duration": 4.23}, {"text": "So what are these\nessential amino acids?", "start": 1630.2, "duration": 4.17}, {"text": "Well, I post them\nhere on this picture.", "start": 1634.37, "duration": 3.8}, {"text": "And so here's the\nessential amino acid.", "start": 1638.17, "duration": 3.72}, {"text": "They have to be\nobtained from nutrition.", "start": 1641.89, "duration": 2.01}, {"text": "Here's the non-essential\namino acid.", "start": 1643.9, "duration": 2.55}, {"text": "These can be obtained\nfrom the outside,", "start": 1646.45, "duration": 3.15}, {"text": "but we also have the pathways\nin order to make them.", "start": 1649.6, "duration": 4.68}, {"text": "If you count these\nup, you will see", "start": 1659.392, "duration": 1.458}, {"text": "that there are nine\nessential amino acids and 11", "start": 1660.85, "duration": 3.66}, {"text": "non-essential amino acids.", "start": 1664.51, "duration": 2.53}, {"text": "It turns out that two of the\nnon-essential amino acids", "start": 1667.04, "duration": 4.07}, {"text": "require essential\namino acids to make,", "start": 1671.11, "duration": 2.338}, {"text": "so they're sort of\nconditionally essential.", "start": 1673.448, "duration": 1.792}, {"text": "From a trivia\nstandpoint, I guess,", "start": 1678.84, "duration": 3.36}, {"text": "the answer is that there's\nnine essential amino acids,", "start": 1682.2, "duration": 6.24}, {"text": "and they are--", "start": 1688.44, "duration": 0.955}, {"text": "I'll use the one-letter\nabbreviation.", "start": 1689.395, "duration": 2.445}, {"text": "So there's lysine, histidine,\nisoleucine, leucine, valine,", "start": 1691.84, "duration": 9.41}, {"text": "threonine, tryptophan,\nphenylalanine, and methionine.", "start": 1701.25, "duration": 8.13}, {"text": "Now, there's two other ones.", "start": 1709.38, "duration": 2.04}, {"text": "If you have enough\nphenylalanine,", "start": 1711.42, "duration": 2.43}, {"text": "we can synthesize tyrosine.", "start": 1713.85, "duration": 2.19}, {"text": "And if you have\nenough methionine,", "start": 1716.04, "duration": 1.95}, {"text": "we can synthesize cystine.", "start": 1717.99, "duration": 2.46}, {"text": "But it turns out that\ntyrosine and cystine", "start": 1720.45, "duration": 3.6}, {"text": "because they require\nphenylalanine and methionine,", "start": 1724.05, "duration": 2.58}, {"text": "for all intents and\npurposes, are also essential.", "start": 1726.63, "duration": 2.35}, {"text": "So really, 11 of the 20 amino\nacids come from our diet,", "start": 1728.98, "duration": 15.7}, {"text": "either directly or\nindirectly in the case", "start": 1744.68, "duration": 3.6}, {"text": "of tyrosine and cystine.", "start": 1748.28, "duration": 2.7}, {"text": "Now, of course, our diets\ninvolve lots of proteins.", "start": 1750.98, "duration": 3.09}, {"text": "We eat other animals,\nand so rarely is it", "start": 1754.07, "duration": 2.34}, {"text": "an issue that we need these,\nwhich is probably how evolution", "start": 1756.41, "duration": 2.61}, {"text": "was able to lose the\nability to make them,", "start": 1759.02, "duration": 2.4}, {"text": "because we take in lots of\namino acids all the time anyway.", "start": 1761.42, "duration": 5.49}, {"text": "And these are amino acids that\nare primarily important only", "start": 1766.91, "duration": 4.56}, {"text": "for making proteins.", "start": 1771.47, "duration": 4.38}, {"text": "But this also really\nillustrates that proteins", "start": 1775.85, "duration": 3.99}, {"text": "are a large reservoir of\nthe nitrogen we take in,", "start": 1779.84, "duration": 3.6}, {"text": "and we just take it in premade\nalready as these amino acids,", "start": 1783.44, "duration": 7.32}, {"text": "even though we can synthesize\nthe remaining nine.", "start": 1790.76, "duration": 4.99}, {"text": "All right, now of the\nremaining nine amino acids--", "start": 1795.75, "duration": 3.958}, {"text": "these are the ones that\nwe can synthesize-- these", "start": 1799.708, "duration": 2.042}, {"text": "are really largely ones about\nhow we move nitrogen around", "start": 1801.75, "duration": 5.19}, {"text": "through biological systems.", "start": 1806.94, "duration": 1.393}, {"text": "We'll see that as we\ngo through the rest", "start": 1808.333, "duration": 1.667}, {"text": "of the lectures on\nthe pathways involving", "start": 1810.0, "duration": 3.99}, {"text": "amino-acid metabolism.", "start": 1813.99, "duration": 1.89}, {"text": "And where I want\nto start with this", "start": 1815.88, "duration": 3.18}, {"text": "is how we're going to deal\nwith ammonia, which is really,", "start": 1819.06, "duration": 5.22}, {"text": "exchanged in and out of\nthe biological molecules,", "start": 1824.28, "duration": 12.88}, {"text": "mostly the two of the\nremaining amino acids.", "start": 1837.16, "duration": 7.17}, {"text": "And those two are\nglutamate and glutamine.", "start": 1844.33, "duration": 4.29}, {"text": "So I'll just remind you\nbecause this is important--", "start": 1848.62, "duration": 3.89}, {"text": "E is the one-letter\nabbreviation for glutamate.", "start": 1852.51, "duration": 3.04}, {"text": "Q is the one letter\nabbreviation for glutamine.", "start": 1855.55, "duration": 4.08}, {"text": "And glutamate and\nglutamine are really", "start": 1859.63, "duration": 2.7}, {"text": "central to exchanging ammonia\nin and out of molecules.", "start": 1862.33, "duration": 5.46}, {"text": "Just to remind you\nwhat these look like--", "start": 1872.73, "duration": 3.3}, {"text": "so this is the alpha-keto acid,\nalpha-ketoglutarate, ketone,", "start": 1887.03, "duration": 6.3}, {"text": "alpha to the carboxylic\nacid, alpha-keto acid,", "start": 1893.33, "duration": 3.39}, {"text": "alpha-ketoglutarate.", "start": 1896.72, "duration": 2.4}, {"text": "So remember, it differs from\nthe amino acid glutamate.", "start": 1899.12, "duration": 16.08}, {"text": "So exchange that alpha-keto\ngroup for the amino group.", "start": 1915.2, "duration": 3.66}, {"text": "Now I have glutamate.", "start": 1918.86, "duration": 1.47}, {"text": "And glutamine is, rather\nthan carboxylic acid", "start": 1920.33, "duration": 9.78}, {"text": "on the side chain, you add\nthis second nitrogen group.", "start": 1930.11, "duration": 12.39}, {"text": "And so what you will see as\nwe go through the lectures,", "start": 1942.5, "duration": 3.5}, {"text": "that glutamate is really--", "start": 1946.0, "duration": 2.01}, {"text": "the major glutamate,\nalpha-ketoglutarate", "start": 1948.01, "duration": 2.31}, {"text": "is really the major\nnitrogen donor and acceptor", "start": 1950.32, "duration": 3.3}, {"text": "to get nitrogen in and\nout of other amino acids.", "start": 1953.62, "duration": 3.66}, {"text": "In the last lecture,\nyou'll see that glutamine", "start": 1957.28, "duration": 2.58}, {"text": "is an important nitrogen donor.", "start": 1959.86, "duration": 2.59}, {"text": "This nitrogen on the\nside chain ends up", "start": 1962.45, "duration": 5.36}, {"text": "being important for getting\nnitrogen into nucleic acids.", "start": 1967.81, "duration": 7.74}, {"text": "Now, a really key enzyme\nto getting these nitrogen", "start": 1975.55, "duration": 5.49}, {"text": "in and out is the one that\ncatalyzes this step right here.", "start": 1981.04, "duration": 4.76}, {"text": "This is catalyzed by an enzyme\ncalled glutamate dehydrogenase.", "start": 1985.8, "duration": 8.946}, {"text": "And glutamate\ndehydrogenase really", "start": 1998.9, "duration": 3.27}, {"text": "carries out the\nfollowing reaction.", "start": 2002.17, "duration": 2.145}, {"text": "There's alpha-ketoglutarate.", "start": 2015.142, "duration": 2.213}, {"text": "So this can pick up\nan ammonia molecule.", "start": 2025.81, "duration": 4.57}, {"text": "OK.", "start": 2079.28, "duration": 1.33}, {"text": "So with this intermediate.", "start": 2080.61, "duration": 3.859}, {"text": "And now we have two electrons\nhere as a hydride ion,", "start": 2084.469, "duration": 20.271}, {"text": "which, of course, we're\ndonating two electrons.", "start": 2104.74, "duration": 3.3}, {"text": "That's why it's a dehydrogenase.", "start": 2108.04, "duration": 1.45}, {"text": "It Involves\nnicotinamide cofactor.", "start": 2109.49, "duration": 4.4}, {"text": "So these can come from\neither NADPH or NADH,", "start": 2113.89, "duration": 6.96}, {"text": "generating NAD+ or NADP+.", "start": 2120.85, "duration": 6.07}, {"text": "And so reduce this molecule--", "start": 2126.92, "duration": 3.57}, {"text": "oxidized NADH, or\nNADPH, NAD+, or NADP--", "start": 2130.49, "duration": 6.6}, {"text": "and you get the\namino acid glutamate.", "start": 2137.09, "duration": 16.71}, {"text": "And so here's a\nreaction catalyzed", "start": 2153.8, "duration": 2.97}, {"text": "by glutamate dehydrogenase\nthat can convert", "start": 2156.77, "duration": 3.9}, {"text": "the alpha-keto acid,\nalpha-ketoglutarate,", "start": 2160.67, "duration": 2.58}, {"text": "into the amino acid glutamate.", "start": 2163.25, "duration": 4.38}, {"text": "This reaction, which\neffectively is ammonia plus", "start": 2167.63, "duration": 8.64}, {"text": "alpha-ketoglutarate plus NADH\nor NADPH can reversibility", "start": 2176.27, "duration": 11.7}, {"text": "generate glutamate plus\nNAD+ or NADP+ plus water.", "start": 2187.97, "duration": 10.78}, {"text": "So this reaction, again,\nglutamate dehydrogenase--", "start": 2201.93, "duration": 11.84}, {"text": "very reversible reaction--\ncan use either NADH, or NADP,", "start": 2219.22, "duration": 6.78}, {"text": "or NAD+, or NADP+.", "start": 2226.0, "duration": 3.18}, {"text": "Either factor works,\nand it's a key reaction", "start": 2229.18, "duration": 3.33}, {"text": "to convert the alpha-keto\nacid, alpha-ketoglutarate,", "start": 2232.51, "duration": 3.81}, {"text": "with the amino acid glutamate\nand get ammonia in and out", "start": 2236.32, "duration": 5.22}, {"text": "of the amino-acid pool.", "start": 2241.54, "duration": 3.96}, {"text": "All right, so I\nmentioned glutamine", "start": 2245.5, "duration": 6.14}, {"text": "is the other major\nnitrogen carrier.", "start": 2251.64, "duration": 4.53}, {"text": "And so how is this made?", "start": 2256.17, "duration": 2.55}, {"text": "Well, you can make it.", "start": 2258.72, "duration": 1.66}, {"text": "So if you start with glutamate,\nand you phosphorylate", "start": 2260.38, "duration": 6.1}, {"text": "that glutamate with ATP--", "start": 2266.48, "duration": 3.15}, {"text": "so that's now a phospho acid\non the side chain of glutamate.", "start": 2287.19, "duration": 6.06}, {"text": "Lose the inorganic\nphosphate, and now we", "start": 2305.64, "duration": 2.46}, {"text": "end up with glutamine--", "start": 2308.1, "duration": 1.89}, {"text": "glutamine.", "start": 2312.72, "duration": 2.41}, {"text": "All right, this is\ncarried out by an enzyme", "start": 2315.13, "duration": 3.27}, {"text": "called glutamine synthase.", "start": 2318.4, "duration": 9.05}, {"text": "And it's basically another\nway to pick up ammonia.", "start": 2327.45, "duration": 4.98}, {"text": "This process can be reversed.", "start": 2332.43, "duration": 2.74}, {"text": "So we can take glutamine.", "start": 2335.17, "duration": 2.78}, {"text": "So I'm going to draw\nout the whole molecule.", "start": 2337.95, "duration": 1.965}, {"text": "I'll just draw here\nthe side chain.", "start": 2339.915, "duration": 3.475}, {"text": "So this here would be the\nside chain of glutamine.", "start": 2346.2, "duration": 2.19}, {"text": "Can just use water to remove\nthe ammonia and regenerate", "start": 2354.18, "duration": 9.1}, {"text": "glutamate carried out by an\nenzyme called glutaminase--", "start": 2363.28, "duration": 5.2}, {"text": "so glutamate to glutamine,\nglutamine to glutamate--", "start": 2372.99, "duration": 4.29}, {"text": "glutamine synthase--", "start": 2377.28, "duration": 1.33}, {"text": "glutaminase.", "start": 2378.61, "duration": 1.99}, {"text": "Notice, just like any\nother reaction or pathway", "start": 2380.6, "duration": 3.69}, {"text": "we talked about, one\ndirection is favorable.", "start": 2384.29, "duration": 3.12}, {"text": "The other direction is not.", "start": 2387.41, "duration": 1.71}, {"text": "So this direction requires\nenergy input for it to work.", "start": 2389.12, "duration": 3.72}, {"text": "ATP is used in\nglutamine synthase.", "start": 2392.84, "duration": 3.12}, {"text": "Glutaminase doesn't require\nATP because it's favorable--", "start": 2395.96, "duration": 3.75}, {"text": "makes sense with all the\nother stuff we talked about.", "start": 2399.71, "duration": 3.46}, {"text": "And so as animals, the way\nour tissues deal with nitrogen", "start": 2403.17, "duration": 4.88}, {"text": "is that if we catabolize an\namino acid in our tissue,", "start": 2408.05, "duration": 4.65}, {"text": "we end up generating ammonia.", "start": 2412.7, "duration": 1.98}, {"text": "That ammonia ends up\neither in glutamate", "start": 2414.68, "duration": 5.25}, {"text": "via the glutamate\nhydrogenation reaction,", "start": 2419.93, "duration": 2.76}, {"text": "or it involves in glutamine.", "start": 2422.69, "duration": 3.51}, {"text": "And then we carry that nitrogen\nas glutamate or glutamine", "start": 2426.2, "duration": 6.72}, {"text": "in our blood.", "start": 2432.92, "duration": 1.02}, {"text": "It gets transported to\nour liver and kidneys,", "start": 2433.94, "duration": 3.33}, {"text": "and our liver and kidney\nhandle that excess nitrogen by,", "start": 2437.27, "duration": 4.05}, {"text": "in our case, turning\nit into urea.", "start": 2441.32, "duration": 2.1}, {"text": "Other organisms might turn\nit into something else", "start": 2443.42, "duration": 3.39}, {"text": "in specialized tissues,\nwhere it can then", "start": 2446.81, "duration": 2.19}, {"text": "be excreted, all right?", "start": 2449.0, "duration": 3.28}, {"text": "And again, it also\nends up being that", "start": 2452.28, "duration": 2.9}, {"text": "glutamate-- if we're going\nto make amino acids-- ends up", "start": 2455.18, "duration": 2.4}, {"text": "being a good source of nitrogen.\nAnd glutamine, if we're going", "start": 2457.58, "duration": 2.91}, {"text": "to make nucleic\nacids, end up being", "start": 2460.49, "duration": 2.52}, {"text": "a good source of nitrogen. And\nso for catabolizing amino acids", "start": 2463.01, "duration": 4.56}, {"text": "for energy, we can\nrelease ammonia", "start": 2467.57, "duration": 3.33}, {"text": "via the glutamate\ndehydrogenase reaction moving", "start": 2470.9, "duration": 2.61}, {"text": "in this direction, or we\ncan incorporate ammonia", "start": 2473.51, "duration": 3.87}, {"text": "by running in the\nopposite direction.", "start": 2477.38, "duration": 4.83}, {"text": "And so what you will see\nthen is that the synthesis", "start": 2482.21, "duration": 2.88}, {"text": "and breakdown, now\nfocusing on amino acids,", "start": 2485.09, "duration": 2.7}, {"text": "is really going to\ninvolve exchanging", "start": 2487.79, "duration": 3.84}, {"text": "the nitrogen between alpha-keto\nacids and amino acids", "start": 2491.63, "duration": 4.59}, {"text": "and glutamine and\nglutamate as we", "start": 2496.22, "duration": 3.24}, {"text": "described for the\nmalate-aspartate shuttle, OK?", "start": 2499.46, "duration": 4.23}, {"text": "So let's just show\nan example of that.", "start": 2503.69, "duration": 1.87}, {"text": "So this is what was involved in\nthe malate-aspartate shuttle.", "start": 2505.56, "duration": 5.25}, {"text": "OK, so here's oxalacetate.", "start": 2510.81, "duration": 5.63}, {"text": "So alpha ketone to the\nacid-- so alpha-keto acid.", "start": 2516.44, "duration": 5.46}, {"text": "This here is the\namino acid aspartate.", "start": 2524.72, "duration": 11.36}, {"text": "Remember, in the\nmalate-aspartate shuttle,", "start": 2536.08, "duration": 6.14}, {"text": "we basically exchanged the\namino group and aspartate to be", "start": 2542.22, "duration": 5.76}, {"text": "glutamate and the alpha-keto\nacid, oxalacetate,", "start": 2547.98, "duration": 4.71}, {"text": "for alpha-keto glutarate--", "start": 2552.69, "duration": 2.85}, {"text": "so alpha-keto acid, amino\nacid, alpha-keto acid,", "start": 2555.54, "duration": 3.91}, {"text": "amino acid balanced\non both sides.", "start": 2559.45, "duration": 2.81}, {"text": "And nature can basically use\nthis system to now get nitrogen", "start": 2562.26, "duration": 5.52}, {"text": "in and out of systems, OK?", "start": 2567.78, "duration": 2.34}, {"text": "So take an amino acid alanine.", "start": 2570.12, "duration": 3.51}, {"text": "It's related to the\nalpha-keto acid pyruvate.", "start": 2573.63, "duration": 4.21}, {"text": "You can exchange\nthat amino group", "start": 2577.84, "duration": 5.33}, {"text": "onto alpha-keto glutarate, OK?", "start": 2583.17, "duration": 2.73}, {"text": "That will generate glutamate.", "start": 2585.9, "duration": 3.424}, {"text": "You can use that glutamate.", "start": 2589.324, "duration": 7.366}, {"text": "Transfer the amino\ngroup on to oxalacetate.", "start": 2596.69, "duration": 4.32}, {"text": "That can generate aspartate.", "start": 2601.01, "duration": 2.79}, {"text": "And so really, here, you have\na system where you can use", "start": 2603.8, "duration": 4.44}, {"text": "transfer of these amino acids\nbetween alpha-keto glutarate", "start": 2608.24, "duration": 4.74}, {"text": "and glutamate and\nreally, any alpha--", "start": 2612.98, "duration": 4.41}, {"text": "or sorry-- any amino acid\nand any alpha-keto acid, OK?", "start": 2617.39, "duration": 12.51}, {"text": "And so if we're going to\ncatabolize an amino acid, say,", "start": 2629.9, "duration": 5.97}, {"text": "alanine, give the nitrogen\nto alpha-ketoglutarate,", "start": 2635.87, "duration": 3.51}, {"text": "now it ends up on\nglutamate-- that glutamate", "start": 2639.38, "duration": 2.4}, {"text": "can go off in the blood.", "start": 2641.78, "duration": 1.21}, {"text": "It can be used elsewhere\nto synthesize aspartate", "start": 2642.99, "duration": 4.05}, {"text": "from oxaloacetate or\nsome other amino acid", "start": 2647.04, "duration": 5.06}, {"text": "from some other alpha-keto acid.", "start": 2652.1, "duration": 3.27}, {"text": "Or you can just\nstay on glutamate,", "start": 2655.37, "duration": 3.15}, {"text": "go here to the\nglutamate-dehydrogenase", "start": 2658.52, "duration": 1.8}, {"text": "reaction and generate ammonia.", "start": 2660.32, "duration": 3.85}, {"text": "And so for catabolism\nof amino acids,", "start": 2664.17, "duration": 2.69}, {"text": "the first step involves\ntransferring the nitrogen", "start": 2666.86, "duration": 3.57}, {"text": "to alpha-ketoglutarate, and that\ngenerates glutamate, as well as", "start": 2670.43, "duration": 5.4}, {"text": "the alpha-keto acid, which\ncan then be metabolized.", "start": 2675.83, "duration": 3.99}, {"text": "If we're going to\nmake an amino acid,", "start": 2679.82, "duration": 2.4}, {"text": "we can start with\nthe alpha-keto acid", "start": 2682.22, "duration": 2.55}, {"text": "and transfer the\nnitrogen from glutamate.", "start": 2684.77, "duration": 3.21}, {"text": "And that's a way, then,\nto make the amino acid.", "start": 2687.98, "duration": 3.7}, {"text": "And so glutamate dehydrogenase\nlets you get ammonia in and out", "start": 2691.68, "duration": 3.23}, {"text": "of the system, and then\nthis basically transferring", "start": 2694.91, "duration": 4.71}, {"text": "of nitrogen between\nalpha-keto acids", "start": 2699.62, "duration": 5.25}, {"text": "and amino acids\ninvolving glutamate and", "start": 2704.87, "duration": 3.87}, {"text": "alpha-ketoglutarate now\nallows you to move nitrogen", "start": 2708.74, "duration": 7.37}, {"text": "around the system.", "start": 2716.11, "duration": 1.75}, {"text": "And so that's basically,\nin a nutshell,", "start": 2717.86, "duration": 3.17}, {"text": "how you synthesize and\nbreak down many amino acids,", "start": 2721.03, "duration": 4.11}, {"text": "although, of course,\nthere are some exceptions.", "start": 2725.14, "duration": 2.88}, {"text": "And so glutamine\nwe just described.", "start": 2728.02, "duration": 4.38}, {"text": "It's the glutamine synthase\nand the glutaminase reaction.", "start": 2732.4, "duration": 5.91}, {"text": "Obviously, that's how you\nsynthesize and break down", "start": 2738.31, "duration": 2.91}, {"text": "glutamine relative to glutamate.", "start": 2741.22, "duration": 1.92}, {"text": "Asparagine is like glutamine.", "start": 2746.71, "duration": 6.67}, {"text": "Remember, asparagine--\nalso, it's", "start": 2753.38, "duration": 2.36}, {"text": "aspartate with an amino\ngroup on the side chain,", "start": 2755.74, "duration": 5.01}, {"text": "just like glutamine.", "start": 2760.75, "duration": 1.14}, {"text": "And so its metabolism\nis similar to glutamine.", "start": 2761.89, "duration": 6.78}, {"text": "Arginine-- arginine is\na special amino acid", "start": 2768.67, "duration": 4.41}, {"text": "with three nitrogen molecules.", "start": 2773.08, "duration": 2.04}, {"text": "We'll discuss that at\nlength in a little bit.", "start": 2775.12, "duration": 3.6}, {"text": "Prolene-- if you look up\nthe structure of prolene,", "start": 2778.72, "duration": 3.39}, {"text": "what you'll find is that it's\nglutamate that's been cyclized,", "start": 2782.11, "duration": 4.56}, {"text": "then reduced.", "start": 2786.67, "duration": 1.17}, {"text": "And so prolene is also\na little bit different.", "start": 2787.84, "duration": 2.85}, {"text": "You make glutamate,\ncyclize it, and reduce it.", "start": 2790.69, "duration": 2.46}, {"text": "That's how you get prolene.", "start": 2793.15, "duration": 1.65}, {"text": "And then glycine, it turns\nout, is generated from serine.", "start": 2794.8, "duration": 3.9}, {"text": "And we'll discuss that at\nlength in the next lecture.", "start": 2798.7, "duration": 3.61}, {"text": "But for the other--", "start": 2802.31, "duration": 1.49}, {"text": "most of the other amino\nacids, reactions really", "start": 2803.8, "duration": 3.18}, {"text": "involve interconversion\nbetween the alpha-keto acid", "start": 2806.98, "duration": 4.11}, {"text": "and the amino acid and\nglutamine-glutamate", "start": 2811.09, "duration": 3.15}, {"text": "via series of reactions\nreferred to as transamination.", "start": 2814.24, "duration": 3.85}, {"text": "OK and so\ntransamination is really", "start": 2822.19, "duration": 4.47}, {"text": "these reactions that allow\nthis swapping of nitrogen", "start": 2826.66, "duration": 4.11}, {"text": "between amino acids\nand alpha-keto acids", "start": 2830.77, "duration": 2.61}, {"text": "and alpha-ketoglutarate\nand glutamate.", "start": 2833.38, "duration": 3.33}, {"text": "Some of these are very famous.", "start": 2836.71, "duration": 3.588}, {"text": "Many of you want to\ngo to medical school.", "start": 2840.298, "duration": 2.442}, {"text": "You're going to do\nliver-function tests, where you", "start": 2842.74, "duration": 3.03}, {"text": "measure levels of ALT and AST.", "start": 2845.77, "duration": 3.6}, {"text": "These are the liver-function\nenzymes, or the transaminases,", "start": 2849.37, "duration": 5.61}, {"text": "all right?", "start": 2854.98, "duration": 0.87}, {"text": "They're basically\nthe transaminases", "start": 2855.85, "duration": 2.79}, {"text": "that catalyze the exchange\nin the case of ALT", "start": 2858.64, "duration": 3.6}, {"text": "between alanine pyruvate and\nglutamate alpha-ketoglutarate.", "start": 2862.24, "duration": 10.83}, {"text": "AST is the transaminase that\ncatalyzes the exchange between", "start": 2873.07, "duration": 6.87}, {"text": "aspartate oxalacetate and\nglutamine alpha-ketoglutarate--", "start": 2879.94, "duration": 7.04}, {"text": "very active, highly\nreversible enzymes,", "start": 2886.98, "duration": 3.15}, {"text": "very abundant in the liver.", "start": 2890.13, "duration": 2.07}, {"text": "The liver is important\nto get nitrogen", "start": 2892.2, "duration": 2.25}, {"text": "in and out of across\ndifferent amino acids--", "start": 2894.45, "duration": 2.46}, {"text": "high levels in the liver cells--\nso when the liver is damaged,", "start": 2896.91, "duration": 2.82}, {"text": "they leak out, and they\nmeasure in the blood,", "start": 2899.73, "duration": 2.11}, {"text": "and that's a sign\nof liver damage.", "start": 2901.84, "duration": 3.05}, {"text": "And so again, just to\ndrive this point home,", "start": 2904.89, "duration": 5.25}, {"text": "so you have alpha-ketoglutarate.", "start": 2910.14, "duration": 2.85}, {"text": "Alpha-ketoglutarate can\nbe converted to glutamate.", "start": 2912.99, "duration": 5.34}, {"text": "This is the\nglutamate-dehydrogenase", "start": 2918.33, "duration": 2.01}, {"text": "reaction, so it involves a\nredox step with NADH or NADPH.", "start": 2920.34, "duration": 6.012}, {"text": "That allows you to\ninterconvert the ammonia,", "start": 2931.1, "duration": 10.09}, {"text": "basically, take nitrogen in and\nout of the system as ammonia.", "start": 2941.19, "duration": 4.02}, {"text": "And then once it's\nin the system,", "start": 2945.21, "duration": 3.26}, {"text": "now you can do\ntransamination to move", "start": 2948.47, "duration": 3.78}, {"text": "the nitrogen between\nglutamate alpha-ketoglutarate", "start": 2952.25, "duration": 3.54}, {"text": "with any other alpha-keto acid\nand amino acid, all right?", "start": 2955.79, "duration": 10.64}, {"text": "And so if you're going\nto catalyze amino acids,", "start": 2966.43, "duration": 3.75}, {"text": "you go in that direction.", "start": 2970.18, "duration": 1.38}, {"text": "And you're a fish--", "start": 2977.54, "duration": 1.83}, {"text": "you go this direction,\nrelease it as ammonia.", "start": 2979.37, "duration": 5.18}, {"text": "Or you can come\nin this direction,", "start": 2984.55, "duration": 2.25}, {"text": "and that is anabolism.", "start": 2986.8, "duration": 2.0}, {"text": "That allows you to build\namino acids, all right?", "start": 2988.8, "duration": 6.98}, {"text": "OK.", "start": 2995.78, "duration": 0.5}, {"text": "So these transamination\nreactions then", "start": 2996.28, "duration": 2.7}, {"text": "become very important, and we\nneed to discuss how they work.", "start": 2998.98, "duration": 4.27}, {"text": "So Transamination itself\nrequires a cofactor.", "start": 3003.25, "duration": 3.86}, {"text": "This cofactor is called\npyridoxal phosphate, OK?", "start": 3007.11, "duration": 8.22}, {"text": "It's derived from a vitamin,\nlike many cofactors.", "start": 3015.33, "duration": 4.59}, {"text": "In this case, it's\nvitamin B6, also referred", "start": 3019.92, "duration": 5.31}, {"text": "to as pyridoxine, vitamin B6.", "start": 3025.23, "duration": 6.52}, {"text": "Vitamin B6 looks like this.", "start": 3031.75, "duration": 2.385}, {"text": "OK, so that's pyridoxine.", "start": 3051.29, "duration": 1.65}, {"text": "That's vitamin B6.", "start": 3052.94, "duration": 1.86}, {"text": "Turns out we eat vitamin B6.", "start": 3054.8, "duration": 3.0}, {"text": "And the active form in\nthe cell is this molecule,", "start": 3057.8, "duration": 23.98}, {"text": "where this alcohol has been\noxidized to the aldehyde.", "start": 3081.78, "duration": 8.38}, {"text": "And this Coke factor is referred\nto as pyridoxal phosphate", "start": 3090.16, "duration": 12.46}, {"text": "and abbreviated PLP,\nfor Pyridoxal Phosphate.", "start": 3102.62, "duration": 7.78}, {"text": "All right.", "start": 3110.4, "duration": 0.6}, {"text": "All right, now let's go over\nnow pyridoxal phosphate allows", "start": 3192.12, "duration": 9.32}, {"text": "these transamination\nreactions to occur.", "start": 3201.44, "duration": 5.2}, {"text": "So let's start off here with\njust some generic amino acid,", "start": 3206.64, "duration": 10.85}, {"text": "OK?", "start": 3217.49, "duration": 0.96}, {"text": "And so the transaminase has--", "start": 3218.45, "duration": 7.04}, {"text": "so here's pyridoxal phosphate.", "start": 3236.37, "duration": 3.03}, {"text": "I'm not going to draw the whole\nmolecule-- just a skeleton", "start": 3239.4, "duration": 3.42}, {"text": "of the pyridoxal phosphate.", "start": 3242.82, "duration": 3.36}, {"text": "So it reacts with\nthe amino acid.", "start": 3246.18, "duration": 2.1}, {"text": "OK?", "start": 3270.5, "duration": 1.11}, {"text": "So that's that middle\npart here of the molecule.", "start": 3271.61, "duration": 3.66}, {"text": "OK?", "start": 3312.38, "duration": 0.78}, {"text": "Generate the shift base.", "start": 3313.16, "duration": 1.245}, {"text": "Just draw the top part here.", "start": 3393.43, "duration": 2.49}, {"text": "OK, so here now we generate\nthe alpha-keto acid.", "start": 3456.78, "duration": 3.6}, {"text": "And this alternative version\nof pyridoxal phosphate called", "start": 3499.19, "duration": 8.61}, {"text": "pyridoxamine, which is\nalso abbreviated PMP--", "start": 3507.8, "duration": 10.585}, {"text": "and so basically, I've\nexchanged the amino acid,", "start": 3522.72, "duration": 9.03}, {"text": "transferring the nitrogen\nonto PLP to make PMP", "start": 3531.75, "duration": 6.21}, {"text": "and generating the\nalpha-keto acid.", "start": 3537.96, "duration": 4.08}, {"text": "That PMP can now react with\nsome other alpha-keto acid.", "start": 3548.79, "duration": 11.02}, {"text": "So here's our PMP.", "start": 3571.21, "duration": 5.19}, {"text": "And basically, if I just reverse\nall of those exact same steps", "start": 3576.4, "duration": 4.56}, {"text": "that I just did--", "start": 3580.96, "duration": 0.93}, {"text": "so I'll do, for the\nsake of brevity here,", "start": 3617.79, "duration": 4.05}, {"text": "I'll do two steps in one.", "start": 3621.84, "duration": 1.8}, {"text": "OK, so I broke this up here\ninto two different steps before,", "start": 3631.95, "duration": 3.54}, {"text": "but to save me some drawing,\nI'm just going to do one here.", "start": 3635.49, "duration": 4.71}, {"text": "And all I did is just\nrun the same mechanism", "start": 3756.467, "duration": 4.553}, {"text": "in the opposite direction.", "start": 3761.02, "duration": 1.5}, {"text": "And now I've taken\nmy alpha-keto acid,", "start": 3765.91, "duration": 3.27}, {"text": "got the nitrogen from PMP,\nregenerated now a new amino", "start": 3769.18, "duration": 5.52}, {"text": "acid, as well as--", "start": 3774.7, "duration": 2.13}, {"text": "I'm not going to\ndraw it all out,", "start": 3781.04, "duration": 1.53}, {"text": "but regenerated\npyridoxal phosphate.", "start": 3782.57, "duration": 4.84}, {"text": "And so pyridoxal\nphosphate ends up", "start": 3787.41, "duration": 3.89}, {"text": "being this really\nuseful cofactor that", "start": 3791.3, "duration": 3.78}, {"text": "enables this transamination\nreaction that", "start": 3795.08, "duration": 3.36}, {"text": "is this interconversion\nbetween an amino acid", "start": 3798.44, "duration": 4.47}, {"text": "and alpha-keto acid and another\namino acid or alpha-keto acid.", "start": 3802.91, "duration": 7.42}, {"text": "And so pyridoxal phosphate is\na co-factor that also useful", "start": 3810.33, "duration": 5.21}, {"text": "for other amino-acid-containing\nreactions--", "start": 3815.54, "duration": 3.87}, {"text": "basically enables\nthis sort of chemistry", "start": 3819.41, "duration": 3.48}, {"text": "that enables nitrogen to--", "start": 3822.89, "duration": 4.72}, {"text": "this sort of chemistry\nto facilitate reactions", "start": 3827.61, "duration": 3.59}, {"text": "with amino acids.", "start": 3831.2, "duration": 1.44}, {"text": "We will see in the\nnext lecture that we", "start": 3832.64, "duration": 3.0}, {"text": "will use pyridoxal phosphate\nin a slightly different way", "start": 3835.64, "duration": 2.76}, {"text": "to convert serine to glycine\nplus a one-carbon unit", "start": 3838.4, "duration": 3.72}, {"text": "that we can use\nfor something else.", "start": 3842.12, "duration": 2.34}, {"text": "I don't have time\nto go into them", "start": 3844.46, "duration": 3.33}, {"text": "in this introductory course,\nbut pyridoxal phosphate", "start": 3847.79, "duration": 4.11}, {"text": "is also involved in other\namino-acid reactions.", "start": 3851.9, "duration": 3.01}, {"text": "So last time, we\ndiscussed ethanolamine.", "start": 3854.91, "duration": 3.0}, {"text": "And remember,\nethanolamine is an alcohol", "start": 3857.91, "duration": 2.09}, {"text": "that's found in phospholipids,\nphosphatidylethanolamine.", "start": 3860.0, "duration": 3.45}, {"text": "Serine is used to\ngenerate ethanolamine.", "start": 3863.45, "duration": 3.27}, {"text": "And pyridoxal\nphosphate basically,", "start": 3866.72, "duration": 2.28}, {"text": "enables decarboxylation\nof serine", "start": 3869.0, "duration": 2.43}, {"text": "to generate ethanolamine.", "start": 3871.43, "duration": 2.52}, {"text": "Serine can also be turned\ninto pyruvate and ammonia.", "start": 3873.95, "duration": 2.8}, {"text": "It's an alternative way\nto generate ammonia.", "start": 3876.75, "duration": 3.08}, {"text": "That also involves\npyridoxal phosphate.", "start": 3879.83, "duration": 2.375}, {"text": "And if you're\ninterested, you can", "start": 3882.205, "duration": 1.375}, {"text": "look up these reactions\nand their mechanisms", "start": 3883.58, "duration": 3.0}, {"text": "and see how pyridoxal\nphosphate is repurposed", "start": 3886.58, "duration": 3.06}, {"text": "for those reactions, all right?", "start": 3889.64, "duration": 3.72}, {"text": "But for today's purposes, this\nis what pyridoxal phosphate is.", "start": 3893.36, "duration": 3.54}, {"text": "This is how it allows\ntransamination.", "start": 3896.9, "duration": 2.52}, {"text": "And so now it\nshould be very clear", "start": 3899.42, "duration": 2.1}, {"text": "how it is that fish\ncan eat a bunch", "start": 3901.52, "duration": 2.7}, {"text": "of protein-containing\nfood and excrete nitrogen", "start": 3904.22, "duration": 3.51}, {"text": "into the ocean, all right?", "start": 3907.73, "duration": 2.54}, {"text": "And that is they can take\nwhatever, some amino acid.", "start": 3910.27, "duration": 6.39}, {"text": "They can do a\npyridoxal-phosphate-containing", "start": 3916.66, "duration": 4.47}, {"text": "transamination reaction and\ngenerate the alpha-keto acid", "start": 3921.13, "duration": 5.79}, {"text": "with the nitrogen going\non to alpha-ketoglutarate", "start": 3926.92, "duration": 5.19}, {"text": "to generate glutamate.", "start": 3932.11, "duration": 3.12}, {"text": "This alpha-keto acid\ncan now be oxidized.", "start": 3935.23, "duration": 5.89}, {"text": "That's favorable.", "start": 3941.12, "duration": 2.11}, {"text": "That can be used to generate\nATP and allow the fish to get", "start": 3943.23, "duration": 4.5}, {"text": "the energy it needs to swim.", "start": 3947.73, "duration": 3.69}, {"text": "That glutamate can now\nbasically carry out", "start": 3951.42, "duration": 4.87}, {"text": "the glutamate-dehydrogenase\nreaction, generating ammonia,", "start": 3956.29, "duration": 5.07}, {"text": "regenerating alpha-ketoglutarate\nto accept the next nitrogen", "start": 3961.36, "duration": 4.41}, {"text": "to allow oxidation of the carbon\nbackbone in the amino acid.", "start": 3965.77, "duration": 4.65}, {"text": "And the ammonia can\nfloat off into the ocean", "start": 3970.42, "duration": 4.89}, {"text": "where it doesn't\nhurt anybody and be", "start": 3975.31, "duration": 2.61}, {"text": "fertilizer for some algae.", "start": 3977.92, "duration": 3.3}, {"text": "All right?", "start": 3981.22, "duration": 0.57}, {"text": "And so there is a way to take\ncatabolism of amino acids,", "start": 3981.79, "duration": 4.59}, {"text": "get energy, and excrete\nthe nitrogen as ammonia,", "start": 3986.38, "duration": 4.71}, {"text": "basically involving\ntransamination,", "start": 3991.09, "duration": 11.3}, {"text": "which requires pyridoxal\nphosphate and glutamate", "start": 4002.39, "duration": 7.71}, {"text": "dehydrogenase.", "start": 4010.1, "duration": 1.17}, {"text": "All right.", "start": 4016.29, "duration": 2.27}, {"text": "Now, it turns out\ntadpoles do the same thing", "start": 4018.56, "duration": 4.62}, {"text": "because they live in water.", "start": 4023.18, "duration": 1.68}, {"text": "But when a tadpole becomes a\nfrog or if you're a mammal,", "start": 4024.86, "duration": 4.55}, {"text": "you don't do this anymore\nbecause now you don't have", "start": 4029.41, "duration": 4.14}, {"text": "infinite water to excrete into.", "start": 4033.55, "duration": 2.43}, {"text": "And so instead, as I\nsaid earlier, we're", "start": 4035.98, "duration": 3.42}, {"text": "going to generate urea\nas a way to excrete", "start": 4039.4, "duration": 4.95}, {"text": "nitrogen. And of course,\nI mentioned earlier--", "start": 4044.35, "duration": 2.5}, {"text": "I'm not going to draw it\nagain, but birds and reptiles--", "start": 4046.85, "duration": 2.72}, {"text": "because you'll see making\nurea requires a lot of water--", "start": 4049.57, "duration": 4.32}, {"text": "you can save even\nthat water by making", "start": 4053.89, "duration": 3.09}, {"text": "uric acid appearing instead.", "start": 4056.98, "duration": 2.28}, {"text": "Now, how you make\npurines will be", "start": 4059.26, "duration": 1.41}, {"text": "discussed in the last lecture.", "start": 4060.67, "duration": 1.51}, {"text": "You'll see how you\nmake uric acid there.", "start": 4062.18, "duration": 1.94}, {"text": "But for now, I want to discuss\nhow we generate urea as a way--", "start": 4064.12, "duration": 8.08}, {"text": "an alternative way to deal\nwith amino-acid metabolism", "start": 4072.2, "duration": 4.79}, {"text": "and excrete nitrogen.", "start": 4076.99, "duration": 3.63}, {"text": "Turns out that as we discuss\nhow you synthesize urea also", "start": 4080.62, "duration": 7.08}, {"text": "discusses how we're going\nto make and break down", "start": 4087.7, "duration": 2.79}, {"text": "arginine, one of those\nexception amino acids.", "start": 4090.49, "duration": 4.5}, {"text": "And you'll see why arginine\nand urea are really", "start": 4094.99, "duration": 5.28}, {"text": "tied to metabolism\nin the way they are.", "start": 4100.27, "duration": 4.629}, {"text": "And so let me just remind\nyou what arginine looks like.", "start": 4104.899, "duration": 6.121}, {"text": "OK?", "start": 4145.08, "duration": 1.17}, {"text": "So this here is the amino\nacid arginine, all right?", "start": 4146.25, "duration": 6.33}, {"text": "I'm going to redraw\npart of this side chain", "start": 4152.58, "duration": 3.81}, {"text": "here in a different color.", "start": 4156.39, "duration": 1.2}, {"text": "OK?", "start": 4168.51, "duration": 0.649}, {"text": "And I did it that way\nbecause I want to show you", "start": 4169.159, "duration": 2.501}, {"text": "how this is related to urea?", "start": 4171.66, "duration": 5.19}, {"text": "So if I take water--", "start": 4176.85, "duration": 0.945}, {"text": "taking off of that end\nof the arginine molecule", "start": 4228.18, "duration": 3.93}, {"text": "generates urea, all right?", "start": 4232.11, "duration": 4.85}, {"text": "And so what we're\nleft with after we", "start": 4236.96, "duration": 6.77}, {"text": "do that is this\nother amino acid,", "start": 4243.73, "duration": 17.58}, {"text": "which is not found in protein\nbut is found in metabolism.", "start": 4261.31, "duration": 4.94}, {"text": "And it is an amino\nacid called ornithine.", "start": 4266.25, "duration": 6.46}, {"text": "And so basically, if you break\ndown arginine into ornithine,", "start": 4272.71, "duration": 7.32}, {"text": "you generate urea.", "start": 4280.03, "duration": 2.31}, {"text": "And so it should be\nclear that if I can now", "start": 4282.34, "duration": 2.76}, {"text": "create a cycle where\nI take ornithine,", "start": 4285.1, "duration": 2.88}, {"text": "pick up a couple of nitrogen\nand regenerate arginine,", "start": 4287.98, "duration": 3.57}, {"text": "now I have a way to basically,\nproduce urea because then I", "start": 4291.55, "duration": 6.25}, {"text": "can cycle arginine to ornithine,\nmake urea, pick up two more", "start": 4297.8, "duration": 4.32}, {"text": "nitrogen, regenerate\narginine, and that's", "start": 4302.12, "duration": 3.3}, {"text": "a way to generate urea.", "start": 4305.42, "duration": 3.66}, {"text": "Now, this series of\nreactions occurs via cycle", "start": 4309.08, "duration": 7.26}, {"text": "called the urea cycle.", "start": 4316.34, "duration": 3.54}, {"text": "And the urea cycle\nwas also described", "start": 4319.88, "duration": 2.55}, {"text": "by our old friend, Hans Krebs.", "start": 4322.43, "duration": 2.47}, {"text": "So remember, Hans Krebs\ndescribed the TCA cycle.", "start": 4324.9, "duration": 3.74}, {"text": "Turns out the urea cycle\nwas described by Hans Krebs", "start": 4328.64, "duration": 3.48}, {"text": "before the TCA cycle and\nis really the first cycle", "start": 4332.12, "duration": 4.83}, {"text": "described.", "start": 4336.95, "duration": 1.24}, {"text": "And so part of the\ninspiration for the TCA cycle", "start": 4338.19, "duration": 3.2}, {"text": "came because Hans Krebs\nalready had cycles on the brain", "start": 4341.39, "duration": 2.82}, {"text": "from describing\ntheir urea cycle.", "start": 4344.21, "duration": 2.91}, {"text": "Now, it is a common\nmisconception", "start": 4347.12, "duration": 1.74}, {"text": "that all cells do\nthe urea cycle.", "start": 4348.86, "duration": 1.83}, {"text": "That is absolutely not true.", "start": 4350.69, "duration": 1.92}, {"text": "Lots of cells\ncarry out reactions", "start": 4352.61, "duration": 1.98}, {"text": "that involve the urea\ncycle because it's also", "start": 4354.59, "duration": 2.31}, {"text": "involved in arginine\nmetabolism, all right?", "start": 4356.9, "duration": 2.49}, {"text": "But the urea cycle, as\nwe're going to describe it,", "start": 4359.39, "duration": 4.35}, {"text": "is really, at least in us,\nselective for our livers", "start": 4363.74, "duration": 4.08}, {"text": "and our kidneys because this is\nreally the series of reactions", "start": 4367.82, "duration": 3.99}, {"text": "that we run to\nnet-generate urea, which", "start": 4371.81, "duration": 3.36}, {"text": "ends up in our urine.", "start": 4375.17, "duration": 2.62}, {"text": "OK?", "start": 4377.79, "duration": 0.98}, {"text": "And so remember, it would\nbe nitrogen transported", "start": 4378.77, "duration": 2.91}, {"text": "to the kidneys or the liver via\nglutamate or glutamine and then", "start": 4381.68, "duration": 4.44}, {"text": "and end up ultimately,\nentering this urea cycle", "start": 4386.12, "duration": 4.83}, {"text": "to generate urea.", "start": 4390.95, "duration": 2.22}, {"text": "Now, this involves\nreactions that", "start": 4393.17, "duration": 2.46}, {"text": "will occur in multiple\ncompartments in the cell.", "start": 4395.63, "duration": 3.4}, {"text": "And so most of it\nhappens on the cytosol,", "start": 4399.03, "duration": 2.3}, {"text": "but there's one reaction that\noccurs in the mitochondria.", "start": 4401.33, "duration": 3.3}, {"text": "And so a general overview\nis as follows, OK?", "start": 4404.63, "duration": 3.99}, {"text": "So I just showed you how you\ncan start from the amino acid", "start": 4408.62, "duration": 4.98}, {"text": "arginine and generate the\nnon-proteinogenic amino acid", "start": 4413.6, "duration": 6.54}, {"text": "ornithine, all right?", "start": 4420.14, "duration": 1.59}, {"text": "And this will involve\nproduction of urea, all right?", "start": 4426.53, "duration": 6.7}, {"text": "That reaction occurs\nin the cytosol.", "start": 4433.23, "duration": 3.3}, {"text": "But the next reaction, which\nis ornithine picking up a CO2,", "start": 4436.53, "duration": 8.4}, {"text": "as well as or anything picking\nup an ammonia to generate", "start": 4444.93, "duration": 5.37}, {"text": "another non-proteinogenic\namino acid called citrulline--", "start": 4450.3, "duration": 6.21}, {"text": "this reaction occurs\nin the mitochondria.", "start": 4456.51, "duration": 3.21}, {"text": "And then that citrulline will\npick up another nitrogen--", "start": 4464.02, "duration": 7.71}, {"text": "show you how it does\nthis in a minute--", "start": 4471.73, "duration": 2.22}, {"text": "to make a molecule\ncalled argininosuccinate.", "start": 4473.95, "duration": 4.41}, {"text": "And then that\nargininosuccinate will", "start": 4481.6, "duration": 2.19}, {"text": "be turned back into arginine.", "start": 4483.79, "duration": 3.81}, {"text": "And so a four-step cycle--", "start": 4487.6, "duration": 2.76}, {"text": "this reaction--\nornithine to citrulline", "start": 4490.36, "duration": 2.28}, {"text": "happening in the mitochondria\nand then regenerating", "start": 4492.64, "duration": 3.48}, {"text": "the arginine from citrulline\nin two steps happening", "start": 4496.12, "duration": 3.96}, {"text": "in the cytosol and then the\narginine-backed ornithine", "start": 4500.08, "duration": 2.88}, {"text": "in the cytosol to generate urea.", "start": 4502.96, "duration": 3.87}, {"text": "All right.", "start": 4506.83, "duration": 1.56}, {"text": "Now let's go through the\ndetails of how this works.", "start": 4508.39, "duration": 4.71}, {"text": "And we're going to start\nhere and the mitochondria", "start": 4513.1, "duration": 3.54}, {"text": "at this ornithine to\ncitrulline reaction.", "start": 4516.64, "duration": 4.6}, {"text": "So it turns out the\nfirst part of this", "start": 4521.24, "duration": 2.57}, {"text": "is generating a\nmolecule referred", "start": 4523.81, "duration": 3.48}, {"text": "to as carbamoyl phosphate.", "start": 4527.29, "duration": 2.88}, {"text": "I'll write that out in a second.", "start": 4530.17, "duration": 2.35}, {"text": "And so this comes\nfrom CO2, which,", "start": 4532.52, "duration": 4.67}, {"text": "of course, is in equilibrium\nand cells with bicarbonate, OK?", "start": 4537.19, "duration": 6.0}, {"text": "So there's bicarbonate.", "start": 4547.95, "duration": 1.77}, {"text": "Just like we saw when we did\ncarboxylation reactions, if I", "start": 4553.29, "duration": 5.31}, {"text": "phosphrylate the\nbicarbonate with ATP,", "start": 4558.6, "duration": 8.46}, {"text": "this molecule here then\nwould react with biotin,", "start": 4567.06, "duration": 3.66}, {"text": "and that was a way I did\ncarboxylation reactions.", "start": 4570.72, "duration": 3.65}, {"text": "Well, it turns out\nthat rather than react", "start": 4574.37, "duration": 6.39}, {"text": "with the nitrogen on biotin,\nI can also react with ammonia.", "start": 4580.76, "duration": 4.575}, {"text": "That generates this\ncarbamic-acid intermediate,", "start": 4588.11, "duration": 8.12}, {"text": "which can then be\nphosphorylated with ATP, again,", "start": 4596.23, "duration": 7.58}, {"text": "to generate this molecule, which\nis called carbamoyl phosphate.", "start": 4603.81, "duration": 16.11}, {"text": "OK, so carbamoyl phosphate.", "start": 4619.92, "duration": 3.13}, {"text": "It turns out this whole step--", "start": 4623.05, "duration": 2.57}, {"text": "two ATPs taking CO2 and\nammonia and generating", "start": 4625.62, "duration": 3.6}, {"text": "carbamoyl phosphate is carried\nout by a single enzyme.", "start": 4629.22, "duration": 4.92}, {"text": "This carbamoyl\nphosphate will then", "start": 4634.14, "duration": 3.48}, {"text": "react with an\nornithine molecule.", "start": 4637.62, "duration": 2.7}, {"text": "So here's ornithine.", "start": 4660.84, "duration": 2.07}, {"text": "OK.", "start": 4673.74, "duration": 0.5}, {"text": "And that will generate\nthis molecule,", "start": 4682.67, "duration": 34.35}, {"text": "which is the amino acid\ncitrulline, ornithine and", "start": 4717.02, "duration": 9.55}, {"text": "citrulline being the two\nmajor amino acids not found", "start": 4726.57, "duration": 4.11}, {"text": "in protein.", "start": 4730.68, "duration": 2.33}, {"text": "All right, now this citrulline,\nthen, in the cytosol", "start": 4733.01, "duration": 6.15}, {"text": "can undergo a reaction with ATP.", "start": 4739.16, "duration": 4.44}, {"text": "And it's easier to\nsee if I rearrange", "start": 4743.6, "duration": 2.7}, {"text": "this part here of the\nside chain of citrulline.", "start": 4746.3, "duration": 4.44}, {"text": "So I'm just here going\nto draw the side chain.", "start": 4750.74, "duration": 2.88}, {"text": "So it turns out this\nwill react with ATP.", "start": 4765.14, "duration": 8.05}, {"text": "So I'm just going to draw ATP\nhere in this stylized way.", "start": 4773.19, "duration": 8.32}, {"text": "That's going to release\npyrophosphate, which can be,", "start": 4787.97, "duration": 11.3}, {"text": "of course, pulled\nforward by cleaving", "start": 4799.27, "duration": 3.24}, {"text": "the pyrophosphate into two\ninorganic-phosphate molecules.", "start": 4802.51, "duration": 7.71}, {"text": "And so now you have\ncitrulline with an AMP on it.", "start": 4851.14, "duration": 10.36}, {"text": "And that can react\nwith an aspartate,", "start": 4861.5, "duration": 7.46}, {"text": "the amino acid aspartate--", "start": 4868.96, "duration": 1.89}, {"text": "so this is the amino\nacid aspartate--", "start": 4879.04, "duration": 2.4}, {"text": "losing the AMP to generate\nthis intermediate--", "start": 4886.52, "duration": 11.947}, {"text": "this intermediate, which is\ncalled argininosuccinate.", "start": 4945.69, "duration": 3.96}, {"text": "So argininosuccinate--\nwhy is it called that?", "start": 4954.97, "duration": 3.45}, {"text": "Because this is a\nsuccinate molecule here.", "start": 4958.42, "duration": 3.93}, {"text": "And this part here is\nan arginine molecule.", "start": 4962.35, "duration": 4.53}, {"text": "And now what can happen next?", "start": 4966.88, "duration": 3.15}, {"text": "Oh, by the way, this\nreaction here from basically,", "start": 4970.03, "duration": 4.89}, {"text": "adding citrulline to\nargininosuccinate-- it's", "start": 4974.92, "duration": 3.93}, {"text": "carried out by one of my\nfavorite enzyme names.", "start": 4978.85, "duration": 3.22}, {"text": "It's called Argininosuccinate\nSynthase, abbreviated ASS.", "start": 4982.07, "duration": 4.73}, {"text": "So the enzyme is\nthe ASS enzyme--", "start": 4986.8, "duration": 5.36}, {"text": "A-S-S-- Argininosuccinate\nSynthase--", "start": 4992.16, "duration": 3.06}, {"text": "to turn citrulline\ninto argininosuccinate.", "start": 4995.22, "duration": 3.13}, {"text": "Once you have\nargininosuccinate, you", "start": 4998.35, "duration": 3.05}, {"text": "can now carry out that reaction,\nwhich will generate two things.", "start": 5001.4, "duration": 14.79}, {"text": "From the purple half\nhere, you will now", "start": 5016.19, "duration": 3.45}, {"text": "end up with this molecule, which\nis fumarate from the TCA cycle,", "start": 5019.64, "duration": 19.59}, {"text": "as well as I've regenerated one\nof the most tedious amino acids", "start": 5039.23, "duration": 8.49}, {"text": "to draw, which is arginine.", "start": 5047.72, "duration": 2.85}, {"text": "So here, we have our\namino acid arginine.", "start": 5077.11, "duration": 5.44}, {"text": "OK?", "start": 5082.55, "duration": 1.02}, {"text": "And so that fumarate\nnow needs to be,", "start": 5083.57, "duration": 4.45}, {"text": "of course, turned\nback into aspartate.", "start": 5088.02, "duration": 3.95}, {"text": "You know how to do that.", "start": 5091.97, "duration": 1.23}, {"text": "I can take fumarate,\nturn it into malate.", "start": 5093.2, "duration": 3.46}, {"text": "That's adding water.", "start": 5096.66, "duration": 1.23}, {"text": "That's the TCA cycle Then\nmalate to oxalacetate--", "start": 5097.89, "duration": 3.87}, {"text": "that's NAD to NADH.", "start": 5101.76, "duration": 2.43}, {"text": "And then aspartate can be\ntransaminated into aspartate.", "start": 5104.19, "duration": 4.47}, {"text": "And you can basically see how\nI can run that you urea cycle", "start": 5108.66, "duration": 4.74}, {"text": "as a way to excrete\nnitrogen one,", "start": 5113.4, "duration": 5.97}, {"text": "from carbamoyl phosphate,\none from aspartate", "start": 5119.37, "duration": 3.87}, {"text": "to generate urea.", "start": 5123.24, "duration": 3.24}, {"text": "And so this complete\ncycle is actually", "start": 5126.48, "duration": 5.82}, {"text": "a few cycles put together,\nsometimes referred to as Krebs", "start": 5132.3, "duration": 4.35}, {"text": "bicycle, or Krebs tricycle.", "start": 5136.65, "duration": 3.27}, {"text": "And I'll just draw it out here.", "start": 5139.92, "duration": 3.01}, {"text": "So if you start with\nargininosuccinate here", "start": 5142.93, "duration": 7.7}, {"text": "in the middle, that\nargininosuccinate", "start": 5150.63, "duration": 5.11}, {"text": "will generate fumarate\nand arginine, OK?", "start": 5155.74, "duration": 11.16}, {"text": "Arginine into ornithine will\nallow generation of urea.", "start": 5166.9, "duration": 15.38}, {"text": "Ornithine can be\nturned into citrulline,", "start": 5182.28, "duration": 8.63}, {"text": "picking up a carbamoyl\nphosphate, which, of course, is", "start": 5190.91, "duration": 11.88}, {"text": "from CO2 plus ammonia.", "start": 5202.79, "duration": 4.34}, {"text": "That citrulline and\naspartate come together", "start": 5207.13, "duration": 15.44}, {"text": "to give you argininosuccinate.", "start": 5222.57, "duration": 2.14}, {"text": "And then that fumarate\ncan run via the TCA cycle", "start": 5224.71, "duration": 7.67}, {"text": "to generate malate.", "start": 5232.38, "duration": 4.86}, {"text": "So that's water.", "start": 5237.24, "duration": 2.97}, {"text": "Malate can be used to\ngenerate oxalacetate.", "start": 5240.21, "duration": 6.84}, {"text": "So that is, of course--", "start": 5247.05, "duration": 1.505}, {"text": "OK.", "start": 5253.78, "duration": 0.89}, {"text": "That oxalacetate can be\nused to generate aspartate.", "start": 5254.67, "duration": 5.56}, {"text": "That's a transamination\nreaction.", "start": 5260.23, "duration": 3.63}, {"text": "So that transamination\nreaction [INAUDIBLE]", "start": 5263.86, "duration": 3.06}, {"text": "glutamate to alpha-ketoglutarate\nand then glutamate", "start": 5266.92, "duration": 4.62}, {"text": "to alpha-ketoglutarate.", "start": 5271.54, "duration": 1.77}, {"text": "Glutamate-dehydrogenase reaction\ncan bring the nitrogen in.", "start": 5303.24, "duration": 4.95}, {"text": "And so this here\ncomplete cycle--", "start": 5308.19, "duration": 3.84}, {"text": "what you'll see is actually\nbalanced with respect", "start": 5312.03, "duration": 2.67}, {"text": "to both electrons because of\nthe glutamate-dehydrogenase", "start": 5314.7, "duration": 3.78}, {"text": "reaction and the\nmalate-oxalacetate direction,", "start": 5318.48, "duration": 2.88}, {"text": "as well as all the\nnitrogen, really", "start": 5321.36, "duration": 2.37}, {"text": "allows you to take\nnitrogen as ammonia, put it", "start": 5323.73, "duration": 4.23}, {"text": "in the system as aspartate, use\nthat to combine with citrulline", "start": 5327.96, "duration": 4.33}, {"text": "to make argininosuccinate.", "start": 5332.29, "duration": 1.23}, {"text": "Go to arginine, make urea\nwith the other nitrogens", "start": 5333.52, "duration": 3.72}, {"text": "coming from carbamoyl phosphate\nto generate the citrulline.", "start": 5337.24, "duration": 5.76}, {"text": "And so the ammonia\nthat's brought", "start": 5343.0, "duration": 2.91}, {"text": "to the liver and the kidneys\nvia glutamate or glutamine", "start": 5345.91, "duration": 4.92}, {"text": "can then be incorporated\ninto aspartame and carbamoyl", "start": 5350.83, "duration": 3.51}, {"text": "phosphate and ultimately,\nexcreted as ammonia.", "start": 5354.34, "duration": 4.5}, {"text": "You can see that there's lots\nof ATP that's required here.", "start": 5358.84, "duration": 3.61}, {"text": "You need two ATP here to\ngenerate carbamoyl phosphate.", "start": 5362.45, "duration": 5.18}, {"text": "And you need\nanother two ATP here", "start": 5367.63, "duration": 5.52}, {"text": "at the argininosuccinate\nsynthase step", "start": 5373.15, "duration": 3.96}, {"text": "to generate argininosuccinate.", "start": 5377.11, "duration": 3.03}, {"text": "And you also need CO2,\nbut the net effect", "start": 5380.14, "duration": 3.09}, {"text": "is that you generate urea.", "start": 5383.23, "duration": 3.83}, {"text": "OK, I know that the urea\ncycle is complicated.", "start": 5387.06, "duration": 3.58}, {"text": "I will start out\nnext time running", "start": 5390.64, "duration": 2.24}, {"text": "through another\nreview of it just", "start": 5392.88, "duration": 2.22}, {"text": "to make sure you have it clear.", "start": 5395.1, "duration": 1.63}, {"text": "Thank you.", "start": 5396.73, "duration": 1.72}]
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+[{"text": "So today, we're going\non from zero dimensions", "start": 16.082, "duration": 4.939}, {"text": "to one dimensions, and we're\ntalking about line defects", "start": 21.021, "duration": 3.937}, {"text": "in order to understand\nwhat they mean.", "start": 24.958, "duration": 4.538}, {"text": "We're going to\ncontextualize it in terms", "start": 29.496, "duration": 2.736}, {"text": "of stress/strain curve.", "start": 32.232, "duration": 1.701}, {"text": "So we'll talk about that.", "start": 33.933, "duration": 3.537}, {"text": "And all of this is\ncalled the dislocation.", "start": 37.47, "duration": 2.603}, {"text": "So that's our goal for today.", "start": 40.073, "duration": 1.668}, {"text": "Now, on Monday, after\nlecture actually,", "start": 41.741, "duration": 3.37}, {"text": "a student came up to me and\nasked a really good question.", "start": 45.111, "duration": 3.904}, {"text": "And it was related to\nthe Hume-Rothery rule.", "start": 49.015, "duration": 3.971}, {"text": "Remember, on Monday, we\ntalked about point defects,", "start": 52.986, "duration": 3.17}, {"text": "zero dimensional.", "start": 56.156, "duration": 2.102}, {"text": "So you have a\nlocalized disturbance", "start": 58.258, "duration": 3.503}, {"text": "in the lattice-- of vacancy.", "start": 61.761, "duration": 1.335}, {"text": "You take it out.", "start": 63.096, "duration": 2.869}, {"text": "You can have that occur in\na material that's ionic.", "start": 65.965, "duration": 5.339}, {"text": "Not a metal, but maybe\nan ionic material.", "start": 71.304, "duration": 1.835}, {"text": "And then you got to think about\ncharge neutrality, Schottky", "start": 73.139, "duration": 2.469}, {"text": "and Frenkel.", "start": 75.608, "duration": 1.769}, {"text": "And then we talked about\nsubstitutional defects, which", "start": 77.377, "duration": 3.17}, {"text": "would be where you take\nan atom out of the lattice", "start": 80.547, "duration": 2.402}, {"text": "and you put another one in.", "start": 82.949, "duration": 1.334}, {"text": "And Hume-Rothery, I\nmentioned, had come up", "start": 84.283, "duration": 3.004}, {"text": "with some empirical observations\nand so I listed these.", "start": 87.287, "duration": 6.106}, {"text": "So he studied a class\nof metals and came up", "start": 93.393, "duration": 2.636}, {"text": "with these general guidelines.", "start": 96.029, "duration": 1.568}, {"text": "And as with so many things\nthat we've learned so far,", "start": 97.597, "duration": 2.903}, {"text": "these are general rules\nthat get broken sometimes.", "start": 100.5, "duration": 4.67}, {"text": "So the question the student\nasked was a very good one.", "start": 105.17, "duration": 2.237}, {"text": "Said, well, if the\nvalence of something", "start": 107.407, "duration": 3.136}, {"text": "you're trying to substitute\ninto something else", "start": 110.543, "duration": 2.269}, {"text": "has to be the same or higher,\nhow does p-doping work?", "start": 112.812, "duration": 5.005}, {"text": "How does a p-type\nsemiconductor work?", "start": 117.817, "duration": 2.77}, {"text": "That's a really good\nquestion, right?", "start": 120.587, "duration": 1.535}, {"text": "Because the valence is\nlower, by definition,", "start": 122.122, "duration": 3.036}, {"text": "that's how you make it p-type.", "start": 125.158, "duration": 1.735}, {"text": "A-ha.", "start": 126.893, "duration": 1.001}, {"text": "So my response was, well,\nbecause Hume-Rothery", "start": 127.894, "duration": 2.835}, {"text": "was designed around metal,\nI'm not sure how much of these", "start": 130.729, "duration": 3.838}, {"text": "apply to semiconductors.", "start": 134.567, "duration": 1.435}, {"text": "Although for semiconductors,\nyou do want to make sure", "start": 136.002, "duration": 2.236}, {"text": "the sizes are similar,\nat the very least.", "start": 138.238, "duration": 2.836}, {"text": "But that got me thinking.", "start": 141.074, "duration": 1.201}, {"text": "And so I went and I read\nsome papers last night.", "start": 142.275, "duration": 4.304}, {"text": "Here's one on the\nvalence effects", "start": 146.579, "duration": 2.436}, {"text": "and relative stabilities--\nvalency effects.", "start": 149.015, "duration": 2.669}, {"text": "So this is from\nthe '80s and I just", "start": 151.684, "duration": 2.036}, {"text": "wanted to cite something here.", "start": 153.72, "duration": 1.868}, {"text": "So here they say almost\na half century ago--", "start": 155.588, "duration": 3.604}, {"text": "so that's Hume-Rothery, so\nit's the '80s or the '30s--", "start": 159.192, "duration": 4.271}, {"text": "pioneered the study of\nthe effect of valency", "start": 163.463, "duration": 2.235}, {"text": "on metal alloy phase equilibria.", "start": 165.698, "duration": 1.635}, {"text": "They found that a lower\nvalence metal, like silver,", "start": 167.333, "duration": 2.937}, {"text": "had only a very small solubility\nin a higher valence element,", "start": 170.27, "duration": 3.703}, {"text": "like antimony, but that the\nsolubility of the reverse", "start": 173.973, "duration": 2.503}, {"text": "was large.", "start": 176.476, "duration": 0.6}, {"text": "So that's where\nthat rule came from.", "start": 177.076, "duration": 1.802}, {"text": "And here's the next part of\nthis paper I want to share.", "start": 178.878, "duration": 3.103}, {"text": "\"Although the relative\nvalency works well", "start": 181.981, "duration": 2.336}, {"text": "for that select\ngroup of alloys, it", "start": 184.317, "duration": 1.802}, {"text": "does not apply to the\nperiodic table as a whole.\"", "start": 186.119, "duration": 2.335}, {"text": "So this other guy looked\nat 607 different systems", "start": 188.454, "duration": 4.438}, {"text": "and found that 22% of the\ntime, the vacancy rule", "start": 192.892, "duration": 2.803}, {"text": "works, and 27% of the\ntime, it violated the rule.", "start": 195.695, "duration": 3.837}, {"text": "And honestly, I'm not\nsure we can call it a rule", "start": 199.532, "duration": 2.403}, {"text": "anymore if more times\nthan not, it's violated.", "start": 201.935, "duration": 3.269}, {"text": "This is a new thing for me.", "start": 205.204, "duration": 1.469}, {"text": "So that is just to say\nthat this rule probably", "start": 206.673, "duration": 8.174}, {"text": "is really conditional on\nthe specific elements you're", "start": 214.847, "duration": 4.438}, {"text": "talking about.", "start": 219.285, "duration": 0.834}, {"text": "I think the much more important\nones are these three here.", "start": 220.119, "duration": 4.271}, {"text": "The valency rule certainly\ndepends on the system.", "start": 224.39, "duration": 2.937}, {"text": "And all of the Hume-Rothery\nobservations were empirical--", "start": 227.327, "duration": 3.837}, {"text": "it's important to keep in mind.", "start": 231.164, "duration": 1.468}, {"text": "General guidelines meant\nto be broken more than half", "start": 232.632, "duration": 4.036}, {"text": "the time, apparently.", "start": 236.668, "duration": 0.902}, {"text": "[CHUCKLES]", "start": 237.57, "duration": 0.668}, {"text": "So where were we?", "start": 239.939, "duration": 1.669}, {"text": "But thank you for that question.", "start": 241.608, "duration": 1.334}, {"text": "It was a great question.", "start": 242.942, "duration": 1.001}, {"text": "It gave me some great reading\nlast night-- materials.", "start": 243.943, "duration": 2.836}, {"text": "Zero dimensional, Monday.", "start": 249.716, "duration": 1.902}, {"text": "One dimensional, today.", "start": 251.618, "duration": 1.601}, {"text": "There we are.", "start": 253.219, "duration": 1.368}, {"text": "So that's the focus.", "start": 254.587, "duration": 1.201}, {"text": "Now, the story\ntoday starts at MIT.", "start": 255.788, "duration": 4.004}, {"text": "It starts at MIT in the 1940s.", "start": 259.792, "duration": 3.07}, {"text": "Because there were\nthese two students--", "start": 262.862, "duration": 1.969}, {"text": "there they are, Harold\nHindman and George Burr.", "start": 264.831, "duration": 5.405}, {"text": "MIT students back then were\na little bit older, I guess.", "start": 270.236, "duration": 4.304}, {"text": "So those guys, they\nwere in an MIT lab", "start": 274.54, "duration": 2.97}, {"text": "and they were trying to\nstudy how parachutes break.", "start": 277.51, "duration": 4.538}, {"text": "How does a parachute break?", "start": 282.048, "duration": 1.668}, {"text": "Because why is that\nan important question?", "start": 283.716, "duration": 2.57}, {"text": "Because you don't\nwant it to break.", "start": 286.286, "duration": 2.569}, {"text": "Right?", "start": 288.855, "duration": 0.634}, {"text": "And it's one of\nthese things where", "start": 289.489, "duration": 1.501}, {"text": "you want it to never break.", "start": 290.99, "duration": 2.403}, {"text": "Like, you really\nwant almost 100--", "start": 293.393, "duration": 3.169}, {"text": "so they were studying\nwhy it breaks.", "start": 296.562, "duration": 1.902}, {"text": "So they were taking a\nparachute and pulling it apart,", "start": 298.464, "duration": 2.436}, {"text": "and there it broke.", "start": 300.9, "duration": 1.335}, {"text": "Take another kind of\nmaterial, pull that apart.", "start": 302.235, "duration": 2.769}, {"text": "It broke.", "start": 305.004, "duration": 0.901}, {"text": "This one didn't,\nbut it's too heavy.", "start": 305.905, "duration": 2.87}, {"text": "They were studying\nthe relationship", "start": 308.775, "duration": 2.335}, {"text": "of the mechanical breaking to\nthe material of the parachute.", "start": 311.11, "duration": 5.673}, {"text": "I love that logo there.", "start": 316.783, "duration": 1.601}, {"text": "That's the two of\nthem in the lab", "start": 318.384, "duration": 1.535}, {"text": "at MIT pulling on a parachute.", "start": 319.919, "duration": 2.77}, {"text": "They just have a tug of\nwar with a parachute.", "start": 322.689, "duration": 2.669}, {"text": "But the problem\nwas that there was", "start": 325.358, "duration": 2.903}, {"text": "no instrument at the\ntime that could give them", "start": 328.261, "duration": 4.037}, {"text": "the sensitivity to the force\nthat they were pulling.", "start": 332.298, "duration": 4.271}, {"text": "There was no instrument that\ncould capture what they needed", "start": 336.569, "duration": 4.037}, {"text": "to make a better parachute.", "start": 340.606, "duration": 1.836}, {"text": "So being MIT students,\nthey built their own.", "start": 342.442, "duration": 3.837}, {"text": "They built their\nown and they added", "start": 346.279, "duration": 1.468}, {"text": "a whole bunch of electronics\ninto this instrument.", "start": 347.747, "duration": 3.103}, {"text": "And that is where\nthe name comes from.", "start": 350.85, "duration": 1.602}, {"text": "It's an instrument that\nhad a lot of electronics", "start": 352.452, "duration": 2.002}, {"text": "for the time.", "start": 354.454, "duration": 0.567}, {"text": "Instron is the name\nof their company.", "start": 355.021, "duration": 2.402}, {"text": "Instron is now synonymous\nwith stress/strain curves.", "start": 357.423, "duration": 4.939}, {"text": "So you go into any\nuniversity, any company,", "start": 362.362, "duration": 2.335}, {"text": "you look at how-- if they\nneed to measure something,", "start": 364.697, "duration": 2.603}, {"text": "like whether an egg breaks\nor not at what force,", "start": 367.3, "duration": 5.472}, {"text": "it's an Instron machine.", "start": 372.772, "duration": 2.502}, {"text": "It's an Instron machine.", "start": 375.274, "duration": 1.001}, {"text": "There it is-- same logo.", "start": 376.275, "duration": 3.27}, {"text": "And because those\nmachines give you", "start": 379.545, "duration": 2.503}, {"text": "the most accurate and\nwell-calibrated description", "start": 382.048, "duration": 6.606}, {"text": "of the force that you're\napplying on this material", "start": 388.654, "duration": 3.938}, {"text": "and you can apply it\nvery, very slowly--", "start": 392.592, "duration": 1.735}, {"text": "so these are very common\nmachines to look at the force", "start": 394.327, "duration": 7.04}, {"text": "you apply, to take\nit how much distance.", "start": 401.367, "duration": 4.038}, {"text": "So we're going to\ntalk about that today.", "start": 405.405, "duration": 2.102}, {"text": "Now, we're not going to talk\nabout it in terms of eggs.", "start": 407.507, "duration": 4.537}, {"text": "We're going talk about\nit in terms of a wire.", "start": 412.044, "duration": 2.203}, {"text": "So there's a wire.", "start": 414.247, "duration": 0.8}, {"text": "It's a little hard to see there.", "start": 415.047, "duration": 1.335}, {"text": "There it is.", "start": 416.382, "duration": 0.501}, {"text": "There's another\nInstron machine--", "start": 416.883, "duration": 1.535}, {"text": "this is a red one.", "start": 418.418, "duration": 1.935}, {"text": "And here they are and\nthey're looking at this wire.", "start": 420.353, "duration": 2.302}, {"text": "And this wire is some\nmaterial-- maybe it's copper,", "start": 422.655, "duration": 2.302}, {"text": "maybe it's aluminum.", "start": 424.957, "duration": 1.702}, {"text": "And they're saying, what\nhappens to this thing", "start": 426.659, "duration": 3.37}, {"text": "as I just pull it\nin small increments?", "start": 430.029, "duration": 4.605}, {"text": "What is the force that\nI have to put on this", "start": 434.634, "duration": 2.202}, {"text": "to pull it a certain amount?", "start": 436.836, "duration": 1.168}, {"text": "Now, that is an important\ngraph, and it's so important", "start": 438.004, "duration": 5.439}, {"text": "that I really want you guys\nto understand this graph.", "start": 443.443, "duration": 6.106}, {"text": "Because it is the way\nthat mechanical properties", "start": 449.549, "duration": 3.37}, {"text": "of materials are\nfirst often analyzed", "start": 452.919, "duration": 4.304}, {"text": "and it's a plot of\nthe stress, which", "start": 457.223, "duration": 4.004}, {"text": "is equal to the force per\narea versus the strain, which", "start": 461.227, "duration": 7.274}, {"text": "is equal to the change\nin the length divided", "start": 468.501, "duration": 4.137}, {"text": "by the original length.", "start": 472.638, "duration": 1.235}, {"text": "Now, what I mean by that?", "start": 473.873, "duration": 1.068}, {"text": "Well, let's take a wire.", "start": 474.941, "duration": 1.001}, {"text": "Here's the wire.", "start": 475.942, "duration": 1.301}, {"text": "There's that wire in there.", "start": 477.243, "duration": 1.702}, {"text": "OK.", "start": 478.945, "duration": 0.8}, {"text": "So here's a wire.", "start": 479.745, "duration": 1.769}, {"text": "And I'm going to apply\na force this way.", "start": 481.514, "duration": 3.37}, {"text": "That's what the\nInstron is doing.", "start": 484.884, "duration": 2.269}, {"text": "So there's some force\nbeing applied to it", "start": 487.153, "duration": 2.369}, {"text": "and there's some\narea of the wire", "start": 489.522, "duration": 2.669}, {"text": "and there was some\noriginal length.", "start": 492.191, "duration": 3.737}, {"text": "OK.", "start": 495.928, "duration": 1.802}, {"text": "This is called a\nstress/strain curve.", "start": 497.73, "duration": 2.302}, {"text": "It's the force\ndivided by the area", "start": 500.032, "duration": 4.438}, {"text": "that you apply to get the thing\nto stretch a certain amount.", "start": 504.47, "duration": 5.305}, {"text": "Now, those MIT students\nwere also very smart.", "start": 509.775, "duration": 5.706}, {"text": "They knew that many\nmaterials, as you first", "start": 515.481, "duration": 4.505}, {"text": "start stretching them, the\nbonds between the atoms", "start": 519.986, "duration": 2.836}, {"text": "are kind of elastic.", "start": 522.822, "duration": 3.503}, {"text": "What does that mean?", "start": 526.325, "duration": 0.901}, {"text": "Well, it means that if I stretch\nit a little bit, it goes back.", "start": 527.226, "duration": 3.103}, {"text": "Might stretch it a little\nbit more-- it goes back.", "start": 530.329, "duration": 2.069}, {"text": "They're like springs.", "start": 532.398, "duration": 2.202}, {"text": "So when you think\nabout the deformation", "start": 534.6, "duration": 3.804}, {"text": "of that wire and\nmany other materials,", "start": 538.404, "duration": 3.971}, {"text": "you've got this elastic regime.", "start": 542.375, "duration": 5.238}, {"text": "And that means that it's\nreversible, as I just said.", "start": 547.613, "duration": 3.304}, {"text": "Reversible.", "start": 550.917, "duration": 0.834}, {"text": "And the displacement-- so\nit's reversible displacement.", "start": 555.955, "duration": 4.137}, {"text": "If I stretch it, it goes back.", "start": 560.092, "duration": 2.736}, {"text": "Reversible displacement\nonly occurring", "start": 562.828, "duration": 5.74}, {"text": "under some applied force.", "start": 568.568, "duration": 2.669}, {"text": "Applied force.", "start": 571.237, "duration": 4.771}, {"text": "This is an elastic stretch.", "start": 578.544, "duration": 3.103}, {"text": "If I've stretched this\nmaterial elastically", "start": 581.647, "duration": 1.802}, {"text": "and I let it go and it goes\nback, it's like a spring.", "start": 583.449, "duration": 2.269}, {"text": "Hooke's law is going to apply.", "start": 585.718, "duration": 2.336}, {"text": "So Hooke's law applies.", "start": 588.054, "duration": 1.368}, {"text": "So F equals kx or minus kx.", "start": 589.422, "duration": 5.772}, {"text": "You can press it or--", "start": 595.194, "duration": 1.402}, {"text": "OK.", "start": 596.596, "duration": 0.5}, {"text": "Hooke's law.", "start": 597.096, "duration": 1.568}, {"text": "So that means that if\nI start pulling on this", "start": 598.664, "duration": 4.371}, {"text": "and I start here--", "start": 603.035, "duration": 2.403}, {"text": "so there's no stress\nand there's no strain,", "start": 605.438, "duration": 4.471}, {"text": "and if I start pulling\non this, then I'm", "start": 609.909, "duration": 3.603}, {"text": "going to get a straight\nline, like that.", "start": 613.512, "duration": 5.84}, {"text": "So that's going to be\nthe elastic regime.", "start": 619.352, "duration": 8.108}, {"text": "But these MIT students--", "start": 627.46, "duration": 1.735}, {"text": "the thing is, they\nknew something else.", "start": 629.195, "duration": 2.702}, {"text": "They knew that for\na lot of materials,", "start": 631.897, "duration": 4.071}, {"text": "it didn't keep going like this.", "start": 635.968, "duration": 2.569}, {"text": "It didn't keep going linearly in\nthis nice, elastic spring way.", "start": 638.537, "duration": 5.539}, {"text": "They knew that either the\nthing broke completely", "start": 644.076, "duration": 5.406}, {"text": "or it deformed--", "start": 649.482, "duration": 1.968}, {"text": "or it started deforming.", "start": 651.45, "duration": 1.135}, {"text": "And that is called\nthe plastic regime.", "start": 652.585, "duration": 4.137}, {"text": "We're coming to plastics later.", "start": 656.722, "duration": 2.469}, {"text": "And this is a\npermanent shape change.", "start": 659.191, "duration": 4.338}, {"text": "Permanent shape change.", "start": 663.529, "duration": 2.503}, {"text": "And you can imagine,\nif I'm going", "start": 671.971, "duration": 2.369}, {"text": "to permanently change\nthe shape of a material,", "start": 674.34, "duration": 2.769}, {"text": "it's got to be ductile.", "start": 677.109, "duration": 1.869}, {"text": "So if it's something\nthat's going to break--", "start": 678.978, "duration": 4.071}, {"text": "remember, we talked about\nionic versus metallic.", "start": 683.049, "duration": 2.402}, {"text": "The sea of electrons allows\nthose metals to be ductile.", "start": 689.088, "duration": 6.173}, {"text": "And that has to do\nwith the bonding", "start": 695.261, "duration": 1.735}, {"text": "with the electronic structure.", "start": 696.996, "duration": 1.768}, {"text": "If you want a material to\nbe able to change shape", "start": 698.764, "duration": 2.236}, {"text": "permanently and\nnot crack, you need", "start": 701.0, "duration": 2.135}, {"text": "that ability to be ductile.", "start": 703.135, "duration": 2.369}, {"text": "So there's a plastic regime.", "start": 705.504, "duration": 2.803}, {"text": "And that makes this\nchange dramatically.", "start": 708.307, "duration": 5.873}, {"text": "So what happens now is,\nif I keep stretching it", "start": 714.18, "duration": 3.537}, {"text": "beyond this elastic regime,\nthe stress/strain curve", "start": 717.717, "duration": 3.236}, {"text": "is no longer linear.", "start": 720.953, "duration": 1.301}, {"text": "And in fact, it might\nlook something like this", "start": 722.254, "duration": 4.271}, {"text": "until, at some point-- so this\nwould be the plastic part where", "start": 726.525, "duration": 4.205}, {"text": "it's literally deforming,\nit's changing its shape.", "start": 730.73, "duration": 4.27}, {"text": "And then finally,\nI've stretched it", "start": 735.0, "duration": 2.103}, {"text": "to the point where it fractures.", "start": 737.103, "duration": 1.801}, {"text": "So that's called\nthe fracture point--", "start": 738.904, "duration": 1.669}, {"text": "you just can't pull it anymore.", "start": 740.573, "duration": 1.902}, {"text": "You just can't pull it anymore.", "start": 745.077, "duration": 2.069}, {"text": "And they're studying\nparachutes, but they", "start": 747.146, "duration": 2.069}, {"text": "knew that there were a lot\nof surprises out there,", "start": 749.215, "duration": 2.869}, {"text": "there's a lot of\ncomplexity in this.", "start": 752.084, "duration": 2.136}, {"text": "And they needed to understand\nthis regime and this regime", "start": 754.22, "duration": 3.503}, {"text": "in order to really engineer the\nparachute to make it better.", "start": 757.723, "duration": 3.971}, {"text": "They had to get that data\nand there were no instruments", "start": 761.694, "duration": 2.903}, {"text": "that could move it and\nmeasure it and calibrate it", "start": 764.597, "duration": 3.403}, {"text": "carefully enough.", "start": 768.0, "duration": 2.603}, {"text": "By the way, this plastic\ndeformation that happens--", "start": 770.603, "duration": 8.041}, {"text": "this permanent shape change,\nbut without breaking, that", "start": 778.644, "duration": 5.239}, {"text": "happens very early on.", "start": 783.883, "duration": 3.336}, {"text": "So there were people\nworking, for example,", "start": 787.219, "duration": 1.735}, {"text": "with aluminum, saying,\nwell, given the bond", "start": 788.954, "duration": 4.371}, {"text": "strength of aluminum, I predict\na certain mechanical strength", "start": 793.325, "duration": 5.105}, {"text": "that aluminum could go to.", "start": 798.43, "duration": 1.769}, {"text": "And then they find that it\nstarts deforming 100 times", "start": 800.199, "duration": 3.87}, {"text": "lower than that.", "start": 804.069, "duration": 1.802}, {"text": "100 times lower.", "start": 805.871, "duration": 2.102}, {"text": "Why?", "start": 807.973, "duration": 0.868}, {"text": "Because it enters into\nthis plastic regime.", "start": 808.841, "duration": 3.503}, {"text": "It doesn't stay elastic.", "start": 812.344, "duration": 1.836}, {"text": "So what I want to talk\nabout today is how--", "start": 814.18, "duration": 4.137}, {"text": "I hope I've convinced you\nhow important this is,", "start": 818.317, "duration": 2.002}, {"text": "and I'll have a why this\nmatters on that as well.", "start": 820.319, "duration": 4.171}, {"text": "But what I want to\ntalk about today", "start": 824.49, "duration": 1.802}, {"text": "is how these one dimensional\ndefects fit in with this.", "start": 826.292, "duration": 5.405}, {"text": "How these one dimensional\ndefects fit in.", "start": 831.697, "duration": 1.702}, {"text": "And in fact, they\nexplain it all.", "start": 833.399, "duration": 3.303}, {"text": "They explain it all.", "start": 836.702, "duration": 1.235}, {"text": "This is what the\nwire looks like.", "start": 837.937, "duration": 2.535}, {"text": "When you stretch a wire and\nyou look at it carefully,", "start": 840.472, "duration": 4.171}, {"text": "it's not just a\nlittle bit longer.", "start": 844.643, "duration": 4.038}, {"text": "It has these very set\nfeatures that occur.", "start": 848.681, "duration": 5.939}, {"text": "It's not just deforming\nin any random way.", "start": 854.62, "duration": 3.77}, {"text": "It's deforming in a\nvery specific way.", "start": 858.39, "duration": 3.604}, {"text": "It's deforming in a\nvery specific way.", "start": 861.994, "duration": 3.003}, {"text": "And so what I want to\ntalk about is that way.", "start": 864.997, "duration": 4.238}, {"text": "The plastic deformation\nmechanism is called slip.", "start": 873.105, "duration": 5.072}, {"text": "The mechanism is\ncalled slip that", "start": 878.177, "duration": 6.64}, {"text": "leads to plastic deformation.", "start": 884.817, "duration": 2.769}, {"text": "And it leads to that picture\nand it leads to the data", "start": 887.586, "duration": 7.741}, {"text": "that they got from\nthe Instron machine.", "start": 895.327, "duration": 3.837}, {"text": "So where does it come from?", "start": 899.164, "duration": 2.603}, {"text": "This is a 2D picture\nof a lattice.", "start": 901.767, "duration": 3.804}, {"text": "This is a 2D picture\nof a lattice.", "start": 905.571, "duration": 4.004}, {"text": "So you can imagine what\nI've done-- oh, I'm", "start": 909.575, "duration": 2.703}, {"text": "going to hand this out.", "start": 912.278, "duration": 1.034}, {"text": "I love this.", "start": 913.312, "duration": 0.534}, {"text": "I can just sit\nand look at this--", "start": 913.846, "duration": 1.535}, {"text": "this is so cool.", "start": 918.217, "duration": 1.001}, {"text": "So this is a cubic--", "start": 919.218, "duration": 2.102}, {"text": "you can think about it as\na simple cubic lattice.", "start": 921.32, "duration": 2.035}, {"text": "Here's a plane, here's another\nplane, there's another one.", "start": 923.355, "duration": 5.573}, {"text": "Look at that yellow one there.", "start": 928.928, "duration": 1.801}, {"text": "So many planes.", "start": 930.729, "duration": 0.901}, {"text": "I got lost there just\nthinking about it.", "start": 934.3, "duration": 3.937}, {"text": "I'm going to the other side.", "start": 938.237, "duration": 2.502}, {"text": "You could get lost, too.", "start": 940.739, "duration": 4.038}, {"text": "That's one of the planes.", "start": 944.777, "duration": 1.935}, {"text": "That's one of the planes.", "start": 946.712, "duration": 1.034}, {"text": "Imagine it.", "start": 947.746, "duration": 0.834}, {"text": "Now, you notice here, I've got\nhanging out-- because why not?", "start": 948.58, "duration": 4.004}, {"text": "Oh, why not?", "start": 952.584, "duration": 2.503}, {"text": "Because there's no\nother possibility.", "start": 955.087, "duration": 2.87}, {"text": "Because vacancies always\nexist, as we learned Monday.", "start": 957.957, "duration": 4.537}, {"text": "They cannot not exist.", "start": 962.494, "duration": 2.102}, {"text": "So there is one right there.", "start": 964.596, "duration": 1.502}, {"text": "Cool.", "start": 966.098, "duration": 0.767}, {"text": "There's an interstitial\npoint defect,", "start": 966.865, "duration": 2.703}, {"text": "there's a substitutional\npoint defect.", "start": 969.568, "duration": 2.169}, {"text": "That's all from Monday.", "start": 971.737, "duration": 1.301}, {"text": "They're just hanging out.", "start": 973.038, "duration": 1.168}, {"text": "But here's what we're\ntalking about now.", "start": 974.206, "duration": 1.802}, {"text": "Look at this.", "start": 976.008, "duration": 0.834}, {"text": "I want to take this\nlittle symbol--", "start": 976.842, "duration": 2.636}, {"text": "this T, and I want to\nlook at the lines that", "start": 979.478, "duration": 3.203}, {"text": "come down from it.", "start": 982.681, "duration": 0.934}, {"text": "So there they are.", "start": 983.615, "duration": 1.268}, {"text": "So these are now planes.", "start": 984.883, "duration": 3.037}, {"text": "These are planes.", "start": 987.92, "duration": 1.301}, {"text": "These are\ncrystallographic planes.", "start": 989.221, "duration": 1.435}, {"text": "And now, look at\nthe other side of it", "start": 990.656, "duration": 2.569}, {"text": "and notice those same\nplanes are following--", "start": 993.225, "duration": 4.438}, {"text": "see to the left there?", "start": 997.663, "duration": 1.468}, {"text": "You see how that's\nnow a plane, a plane?", "start": 999.131, "duration": 2.169}, {"text": "So this is actually lined\nup from the outside in.", "start": 1001.3, "duration": 3.537}, {"text": "It's lined up, it's lined up.", "start": 1004.837, "duration": 1.201}, {"text": "Ah!", "start": 1006.038, "duration": 0.701}, {"text": "Right here, I put\nan extra one in.", "start": 1006.739, "duration": 2.669}, {"text": "You see that?", "start": 1009.408, "duration": 1.969}, {"text": "That's an extra plane that\ndoesn't go all the way through.", "start": 1011.377, "duration": 2.669}, {"text": "If it went all the way through,\nit wouldn't be an extra plane.", "start": 1014.046, "duration": 3.637}, {"text": "So it's sandwiched in here.", "start": 1017.683, "duration": 3.103}, {"text": "And then here, it\ncontinues over there.", "start": 1020.786, "duration": 1.735}, {"text": "That one kind of goes like that,\nand that one goes like that,", "start": 1022.521, "duration": 2.769}, {"text": "and then they go back\nto the normal planes.", "start": 1025.29, "duration": 2.903}, {"text": "I have inserted a half-- if\nyou want to think about it--", "start": 1028.193, "duration": 4.104}, {"text": "of a plane into--", "start": 1032.297, "duration": 2.737}, {"text": "right there.", "start": 1035.034, "duration": 1.133}, {"text": "Look at that.", "start": 1036.167, "duration": 1.134}, {"text": "That is called a dislocation.", "start": 1037.301, "duration": 3.305}, {"text": "That is a one\ndimensional defect.", "start": 1040.606, "duration": 1.701}, {"text": "It's a dislocation\nthat is caused", "start": 1042.307, "duration": 2.67}, {"text": "by putting an extra plane\nthat stopped somewhere,", "start": 1044.977, "duration": 4.471}, {"text": "and where it stops, you draw\na little T in the crystal.", "start": 1049.448, "duration": 5.606}, {"text": "Oh, let's go with the mean.", "start": 1055.054, "duration": 1.334}, {"text": "Come on.", "start": 1056.388, "duration": 0.601}, {"text": "There we go.", "start": 1056.989, "duration": 0.667}, {"text": "We'll go back to this.", "start": 1057.656, "duration": 1.101}, {"text": "So that is called a dislocation.", "start": 1058.757, "duration": 3.137}, {"text": "That is called a dislocation.", "start": 1061.894, "duration": 2.235}, {"text": "That is the 1D defect.", "start": 1064.129, "duration": 3.37}, {"text": "It's called a dislocation.", "start": 1067.499, "duration": 6.04}, {"text": "It's a line defect formed\nby what is essentially", "start": 1073.539, "duration": 11.378}, {"text": "a misregistry of atoms that\ngives you an extra plane.", "start": 1084.917, "duration": 4.671}, {"text": "Now, you can already see that\nif I put a line defect in there,", "start": 1099.531, "duration": 3.637}, {"text": "it's messing with the\nbonds at this place here.", "start": 1103.168, "duration": 3.37}, {"text": "Here, the bonds just go\nalong, they go along.", "start": 1106.538, "duration": 1.969}, {"text": "And then all of a sudden, I've\ngot a misregistry now because", "start": 1108.507, "duration": 3.27}, {"text": "of that dislocation--", "start": 1111.777, "duration": 2.836}, {"text": "because of that dislocation.", "start": 1114.613, "duration": 1.935}, {"text": "One way to look at\nit is with the model.", "start": 1119.418, "duration": 2.135}, {"text": "Another way is just\nget ears of corn.", "start": 1121.553, "duration": 3.571}, {"text": "I did this last night.", "start": 1125.124, "duration": 1.301}, {"text": "I actually-- I got ears of corn.", "start": 1126.425, "duration": 3.904}, {"text": "That's really true.", "start": 1130.329, "duration": 1.434}, {"text": "And I looked inside.", "start": 1131.763, "duration": 1.469}, {"text": "This isn't from there.", "start": 1133.232, "duration": 1.501}, {"text": "This is from the internet.", "start": 1134.733, "duration": 2.136}, {"text": "But there it is.", "start": 1136.869, "duration": 2.002}, {"text": "The corn needed to grow\nanother row and so--", "start": 1138.871, "duration": 4.004}, {"text": "it's not going to\ngrow a half kernel.", "start": 1142.875, "duration": 1.568}, {"text": "Well, actually, it could.", "start": 1144.443, "duration": 1.034}, {"text": "It does sometimes.", "start": 1145.477, "duration": 0.801}, {"text": "But here, it grew another\nfull row of kernels.", "start": 1146.278, "duration": 2.336}, {"text": "And there it is.", "start": 1148.614, "duration": 0.7}, {"text": "There's a dislocation.", "start": 1149.314, "duration": 2.269}, {"text": "It's very similar to\nwhat we're looking at.", "start": 1151.583, "duration": 3.237}, {"text": "Now, there are two\ntypes of dislocations.", "start": 1154.82, "duration": 4.071}, {"text": "This one, where you insert\nan extra plane in this way", "start": 1158.891, "duration": 3.036}, {"text": "is called an edge dislocation.", "start": 1161.927, "duration": 3.57}, {"text": "There's another\ntype of dislocation", "start": 1165.497, "duration": 1.468}, {"text": "that we won't talk about in\nthis class called the screw", "start": 1166.965, "duration": 2.269}, {"text": "dislocation.", "start": 1169.234, "duration": 0.901}, {"text": "You can look it up.", "start": 1170.135, "duration": 0.801}, {"text": "It's a different\ntype of line defect.", "start": 1170.936, "duration": 3.503}, {"text": "But the one that\nwe're concerned with", "start": 1174.439, "duration": 1.802}, {"text": "is called an edge\ndislocation and it's", "start": 1176.241, "duration": 2.102}, {"text": "described exactly in this way.", "start": 1178.343, "duration": 1.569}, {"text": "And the way you note\nit in an atomic scale", "start": 1179.912, "duration": 4.07}, {"text": "drawing like this--", "start": 1183.982, "duration": 0.968}, {"text": "by putting that upside\ndown T where the edge is.", "start": 1184.95, "duration": 5.806}, {"text": "An edge dislocation.", "start": 1190.756, "duration": 2.269}, {"text": "Edge dislocations in corn.", "start": 1193.025, "duration": 1.635}, {"text": "Now, you can actually\nsee these things.", "start": 1194.66, "duration": 2.302}, {"text": "And on these models,\nthe dislocations", "start": 1196.962, "duration": 2.536}, {"text": "look very nice and uniform and\nyou can hold it and look at it.", "start": 1199.498, "duration": 4.337}, {"text": "But in reality, here's an\nactual video of dislocations.", "start": 1203.835, "duration": 6.44}, {"text": "These are groups\nof dislocations.", "start": 1210.275, "duration": 2.136}, {"text": "Notice, these are\n1D line defects.", "start": 1212.411, "duration": 2.569}, {"text": "They're places where you've\ngot this extra plane.", "start": 1214.98, "duration": 4.471}, {"text": "Notice, that they're\nall over the place.", "start": 1219.451, "duration": 2.703}, {"text": "They're not just straight,\nthey bend around in the crystal", "start": 1222.154, "duration": 4.905}, {"text": "and they move.", "start": 1227.059, "duration": 1.067}, {"text": "And the movement is critical.", "start": 1228.126, "duration": 2.403}, {"text": "The movement is critical.", "start": 1230.529, "duration": 1.668}, {"text": "That's what's going to get us\nback to this, the movement.", "start": 1232.197, "duration": 4.571}, {"text": "This is the defect, and then the\nmovement is what gets us this.", "start": 1236.768, "duration": 5.005}, {"text": "So let's take a look.", "start": 1241.773, "duration": 0.868}, {"text": "So here's an here's an example.", "start": 1242.641, "duration": 2.102}, {"text": "This is a piece of material\nthat under the microscope", "start": 1244.743, "duration": 2.436}, {"text": "is being pulled.", "start": 1247.179, "duration": 1.234}, {"text": "Watch what happens.", "start": 1248.413, "duration": 2.136}, {"text": "Well, those things are moving.", "start": 1250.549, "duration": 1.768}, {"text": "They're forming, they're\nending, they're reforming,", "start": 1252.317, "duration": 2.87}, {"text": "they're interacting\nwith each other.", "start": 1255.187, "duration": 1.835}, {"text": "That one didn't, but whatever.", "start": 1257.022, "duration": 2.002}, {"text": "And they're spreading\nout, they're growing.", "start": 1259.024, "duration": 2.603}, {"text": "Those dislocations\nand their movement", "start": 1261.627, "duration": 5.772}, {"text": "is why this doesn't crack.", "start": 1267.399, "duration": 2.169}, {"text": "It's why this can\nmove, this can bend.", "start": 1269.568, "duration": 3.837}, {"text": "It's why this point\nis 100 times lower", "start": 1273.405, "duration": 4.338}, {"text": "than you might have thought.", "start": 1277.743, "duration": 1.167}, {"text": "And that can be understood\nby thinking about the bonds.", "start": 1281.513, "duration": 4.805}, {"text": "That can be understood by\nthinking about the bonds.", "start": 1286.318, "duration": 3.603}, {"text": "Here's a sequence of pictures.", "start": 1289.921, "duration": 1.302}, {"text": "So this is the dislocation.", "start": 1294.359, "duration": 3.938}, {"text": "You see it there.", "start": 1298.297, "duration": 2.335}, {"text": "Now, what I'm doing\nis, I'm pushing--", "start": 1300.632, "duration": 3.537}, {"text": "or let's not push yet.", "start": 1304.169, "duration": 2.402}, {"text": "We'll do that on the next slide.", "start": 1306.571, "duration": 1.769}, {"text": "For now, I'm just\nwatching it move.", "start": 1308.34, "duration": 2.069}, {"text": "Here you see it moving.", "start": 1310.409, "duration": 2.435}, {"text": "There it is.", "start": 1312.844, "duration": 0.501}, {"text": "How does it move?", "start": 1313.345, "duration": 1.401}, {"text": "Well, here's a model.", "start": 1314.746, "duration": 1.835}, {"text": "There is a dislocation and you\ncan see that if I take this", "start": 1316.581, "duration": 4.038}, {"text": "bonding area around here and\nI connect this atom to there", "start": 1320.619, "duration": 4.705}, {"text": "and then you start pushing--\nthere's a strain field around", "start": 1325.324, "duration": 2.435}, {"text": "there--", "start": 1327.759, "duration": 0.534}, {"text": "and then you push it\nover, you might be", "start": 1328.293, "duration": 1.769}, {"text": "able to move it over to there.", "start": 1330.062, "duration": 3.637}, {"text": "And maybe you could\nkeep on doing that", "start": 1333.699, "duration": 2.335}, {"text": "and keep on moving it\nover and over until it", "start": 1336.034, "duration": 2.236}, {"text": "gets all the way to that end--", "start": 1338.27, "duration": 2.002}, {"text": "all the way to the\nend of the material.", "start": 1340.272, "duration": 1.635}, {"text": "Here is a super\npolished, high detail", "start": 1345.444, "duration": 5.105}, {"text": "animation of that process.", "start": 1350.549, "duration": 2.969}, {"text": "Here it is.", "start": 1353.518, "duration": 0.768}, {"text": "I'm starting over here\nand watch the dislocation.", "start": 1354.286, "duration": 3.637}, {"text": "There it is.", "start": 1357.923, "duration": 0.5}, {"text": "There it is!", "start": 1358.423, "duration": 2.202}, {"text": "And it's moving and it's moving,\nand those bonds are breaking.", "start": 1360.625, "duration": 3.804}, {"text": "Let's watch that again.", "start": 1364.429, "duration": 2.002}, {"text": "Here it is.", "start": 1366.431, "duration": 0.601}, {"text": "There, it formed.", "start": 1367.032, "duration": 1.201}, {"text": "But why did it form?", "start": 1368.233, "duration": 2.202}, {"text": "Because, you see, what happened\nis, I took this material", "start": 1370.435, "duration": 5.472}, {"text": "and I applied a force to it.", "start": 1375.907, "duration": 2.87}, {"text": "I went back to the wire and I\ndid this or maybe I did this.", "start": 1378.777, "duration": 5.639}, {"text": "And the material\nsaid, OK, hold on, how", "start": 1384.416, "duration": 2.302}, {"text": "can I respond to this thing?", "start": 1386.718, "duration": 2.002}, {"text": "Well, either I can\nrespond elastically", "start": 1388.72, "duration": 2.236}, {"text": "and all my bonds\ncould stretch, but I'm", "start": 1390.956, "duration": 2.002}, {"text": "getting to this\nuncomfortable place here.", "start": 1392.958, "duration": 4.504}, {"text": "Or a dislocation could\ncome in and allow", "start": 1397.462, "duration": 3.771}, {"text": "me to translate a whole\nset of bonds over by one.", "start": 1401.233, "duration": 4.604}, {"text": "So I'm applying a\nforce to this material.", "start": 1405.837, "duration": 3.637}, {"text": "You can think about it as a\nforce maybe on the bottom g--", "start": 1409.474, "duration": 5.139}, {"text": "here, let's watch what happens.", "start": 1414.613, "duration": 2.803}, {"text": "Look at this.", "start": 1417.416, "duration": 0.533}, {"text": "I've got a little\nextra room here.", "start": 1417.949, "duration": 2.403}, {"text": "Now watch what happens.", "start": 1420.352, "duration": 1.001}, {"text": "There it is, there it is.", "start": 1421.353, "duration": 3.703}, {"text": "And I have moved\nthe whole top row", "start": 1425.056, "duration": 3.07}, {"text": "of atoms over-- the whole\ntop three rows over by one.", "start": 1428.126, "duration": 3.47}, {"text": "So I have transformed\nthis so that the force--", "start": 1431.596, "duration": 2.97}, {"text": "if you think about it,\nthe force on the bottom", "start": 1434.566, "duration": 1.902}, {"text": "could be applied that way and\nthe force on the top that way.", "start": 1436.468, "duration": 2.869}, {"text": "The atoms get to a\ncertain point where it's", "start": 1439.337, "duration": 1.802}, {"text": "like, no, my elasticnesss--", "start": 1441.139, "duration": 2.536}, {"text": "I'm not sure I\nwant to go anymore.", "start": 1443.675, "duration": 2.035}, {"text": "But a dislocation comes\nin and saves the day", "start": 1445.71, "duration": 3.771}, {"text": "and it allows that to happen.", "start": 1449.481, "duration": 1.501}, {"text": "Because here's the alternative.", "start": 1450.982, "duration": 2.903}, {"text": "if I want that same translation\nto happen, that same slip,", "start": 1453.885, "duration": 3.571}, {"text": "I would have had to break\nall the bonds at once.", "start": 1457.456, "duration": 2.902}, {"text": "If I didn't have a dislocation,\nthis is what would-- ah,", "start": 1460.358, "duration": 2.67}, {"text": "there's the dislocation.", "start": 1463.028, "duration": 1.701}, {"text": "One bond at a time,\none bond at a time.", "start": 1464.729, "duration": 3.07}, {"text": "Or the much, much\nharder ask, especially", "start": 1467.799, "duration": 4.772}, {"text": "since there's 10 to the\n20 something of these,", "start": 1472.571, "duration": 2.903}, {"text": "is to break them all at once.", "start": 1475.474, "duration": 1.234}, {"text": "There it is.", "start": 1476.708, "duration": 0.868}, {"text": "Bam.", "start": 1477.576, "duration": 1.534}, {"text": "That's why that doesn't happen.", "start": 1479.11, "duration": 3.304}, {"text": "It just takes too much energy.", "start": 1482.414, "duration": 2.502}, {"text": "But if I can just call up a\ndislocation to the rescue,", "start": 1484.916, "duration": 3.637}, {"text": "I can translate an\nentire set of atoms", "start": 1488.553, "duration": 3.537}, {"text": "with much, much,\nmuch less energy.", "start": 1492.09, "duration": 2.536}, {"text": "Did you see that?", "start": 1494.626, "duration": 0.901}, {"text": "So the dislocation\nmoving is what", "start": 1495.527, "duration": 3.403}, {"text": "allows plastic\ndeformation, it's what", "start": 1498.93, "duration": 3.203}, {"text": "allows these atoms to\nslide over one another.", "start": 1502.133, "duration": 4.572}, {"text": "It is what enables\nthis region to be there", "start": 1506.705, "duration": 4.471}, {"text": "and it's what defines it.", "start": 1511.176, "duration": 2.869}, {"text": "A very important point here--", "start": 1514.045, "duration": 2.57}, {"text": "aw, you got a goody bag.", "start": 1516.615, "duration": 2.702}, {"text": "That's OK.", "start": 1519.317, "duration": 1.602}, {"text": "Was he in the class?", "start": 1520.919, "duration": 1.001}, {"text": "It doesn't matter.", "start": 1521.92, "duration": 0.834}, {"text": "We share.", "start": 1522.754, "duration": 0.768}, {"text": "[LAUGHTER]", "start": 1523.522, "duration": 0.5}, {"text": "If you guys have friends--", "start": 1524.022, "duration": 2.469}, {"text": "just came in and took one.", "start": 1526.491, "duration": 1.235}, {"text": "If you guys have friends\nthat need goody bags,", "start": 1527.726, "duration": 1.902}, {"text": "we are here to help.", "start": 1529.628, "duration": 1.401}, {"text": "I will never turn\ndown a goody bag.", "start": 1531.029, "duration": 2.236}, {"text": "There is a plane here that's\nmoving on another plane.", "start": 1536.568, "duration": 4.371}, {"text": "There is a plane that's\nmoving on another plane", "start": 1540.939, "duration": 2.302}, {"text": "and it's doing it only because\nof this location, that one", "start": 1543.241, "duration": 3.57}, {"text": "dimensional defect.", "start": 1546.811, "duration": 2.803}, {"text": "Now, that is slipping, so\nit's called a slip plane.", "start": 1549.614, "duration": 3.704}, {"text": "It's called a slip plane.", "start": 1558.189, "duration": 1.836}, {"text": "And it's the plane along\nwhich the dislocation moves.", "start": 1560.025, "duration": 8.942}, {"text": "[PHONE RINGING]", "start": 1573.538, "duration": 1.735}, {"text": "OK.", "start": 1575.273, "duration": 0.501}, {"text": "We got a phone going on there.", "start": 1575.774, "duration": 2.836}, {"text": "Now, I want to make a\nreally important point here.", "start": 1578.61, "duration": 2.703}, {"text": "Because what the\ndislocation is allowing,", "start": 1581.313, "duration": 2.736}, {"text": "what this defect is allowing\nyou to do is resolve forces.", "start": 1584.049, "duration": 6.973}, {"text": "That's what you're doing.", "start": 1591.022, "duration": 1.335}, {"text": "I'm putting this force on--", "start": 1592.357, "duration": 2.736}, {"text": "it's again, the Instron.", "start": 1595.093, "duration": 1.602}, {"text": "I'm pulling the wire and the\nmaterial is like, hold on,", "start": 1596.695, "duration": 3.637}, {"text": "I got to respond to this.", "start": 1600.332, "duration": 2.202}, {"text": "How can I do--", "start": 1602.534, "duration": 1.501}, {"text": "yeah?", "start": 1604.035, "duration": 0.734}, {"text": "[INAUDIBLE]", "start": 1604.769, "duration": 3.304}, {"text": "Yes.", "start": 1608.073, "duration": 0.567}, {"text": "And I will come back to that.", "start": 1608.64, "duration": 1.268}, {"text": "It's this plane.", "start": 1609.908, "duration": 2.369}, {"text": "Where's the model?", "start": 1612.277, "duration": 0.801}, {"text": "Who's got the model?", "start": 1613.078, "duration": 1.334}, {"text": "Is that the dislocation model?", "start": 1614.412, "duration": 1.969}, {"text": "It's the plane where\nthe dislocation", "start": 1616.381, "duration": 2.936}, {"text": "comes in and can move.", "start": 1619.317, "duration": 3.704}, {"text": "Why?", "start": 1623.021, "duration": 0.834}, {"text": "Because that's the\nplane that is--", "start": 1623.855, "duration": 3.704}, {"text": "by motion of the\ndislocation, that's", "start": 1627.559, "duration": 2.769}, {"text": "the plane that's slipping\nalong another one", "start": 1630.328, "duration": 2.803}, {"text": "by exactly this animation.", "start": 1633.131, "duration": 2.87}, {"text": "I'll talk about this\nslip plane in a minute", "start": 1636.001, "duration": 1.768}, {"text": "also and more about it.", "start": 1637.769, "duration": 1.068}, {"text": "So what this motion,\nwhat this slip plane,", "start": 1642.407, "duration": 3.67}, {"text": "what these movements of\nthe planes allow is is it", "start": 1646.077, "duration": 3.637}, {"text": "allows you to resolve\nan applied force.", "start": 1649.714, "duration": 2.903}, {"text": "So I come at this material\nwith a force and I resolve it.", "start": 1652.617, "duration": 7.608}, {"text": "It's resolved at\nthe atomic level--", "start": 1660.225, "duration": 11.111}, {"text": "and I'll finish this-- at the\natomic level along that slip", "start": 1671.336, "duration": 4.071}, {"text": "plane.", "start": 1675.407, "duration": 2.736}, {"text": "That's what it does.", "start": 1678.143, "duration": 2.035}, {"text": "The Instron pulls or I pull on\nthe parachute, like the logo,", "start": 1680.178, "duration": 8.041}, {"text": "and then either the\nmaterial is going to break", "start": 1688.219, "duration": 4.872}, {"text": "or maybe it's just in\nthat elastic region", "start": 1693.091, "duration": 3.136}, {"text": "and then it will go all the way\nback or it's going to deform.", "start": 1696.227, "duration": 3.204}, {"text": "And if it deforms,\nwhat's it doing?", "start": 1699.431, "duration": 1.534}, {"text": "It's feeling the force and\nit's trying to resolve it.", "start": 1700.965, "duration": 3.804}, {"text": "And it resolves it by\nthose dislocations moving.", "start": 1704.769, "duration": 2.77}, {"text": "The planes move on\ntop of each other.", "start": 1707.539, "duration": 3.937}, {"text": "Well, so let's go\nback to this plane.", "start": 1711.476, "duration": 2.769}, {"text": "What plane is it?", "start": 1714.245, "duration": 1.936}, {"text": "If I look at the planes, which\nare somewhere out there--", "start": 1716.181, "duration": 5.972}, {"text": "you can imagine that if\nI've got all those planes", "start": 1722.153, "duration": 4.672}, {"text": "and they're looking at the\nInstron and the force being", "start": 1726.825, "duration": 2.736}, {"text": "applied to me, which one is\ngoing to do the slipping?", "start": 1729.561, "duration": 4.638}, {"text": "Well, you can imagine this\nwith a very simple analogy.", "start": 1734.199, "duration": 3.904}, {"text": "If I push on something--\nif I push on a rope,", "start": 1738.103, "duration": 3.536}, {"text": "what does it do?", "start": 1741.639, "duration": 1.235}, {"text": "Well, it kind of\ncurls up, it doesn't", "start": 1742.874, "duration": 1.535}, {"text": "do too much-- it doesn't move.", "start": 1744.409, "duration": 3.27}, {"text": "But if I really want to\ntry to resolve force,", "start": 1747.679, "duration": 3.27}, {"text": "I got to move those atoms.", "start": 1750.949, "duration": 1.301}, {"text": "But if I push on a\nstick and not a rope,", "start": 1754.986, "duration": 2.703}, {"text": "then the stick just all moves.", "start": 1757.689, "duration": 3.336}, {"text": "So the plane that is going\nto move across another plane", "start": 1761.025, "duration": 5.005}, {"text": "is going to be the most dense--", "start": 1766.03, "duration": 2.203}, {"text": "the closest packed.", "start": 1768.233, "duration": 2.102}, {"text": "It's going to be\nthe closest packed.", "start": 1770.335, "duration": 1.835}, {"text": "So the slip plane--", "start": 1775.24, "duration": 3.003}, {"text": "let's write it here.", "start": 1778.243, "duration": 1.468}, {"text": "Slip plane-- and I'll give\nyou an example in a minute.", "start": 1787.819, "duration": 5.072}, {"text": "Slip plane, closest packed\nor highest planar density.", "start": 1792.891, "duration": 10.744}, {"text": "Because then I'm\npushing on the stick.", "start": 1809.808, "duration": 2.102}, {"text": "In the material, I've got stick\nand ropes defined by the plane.", "start": 1811.91, "duration": 4.337}, {"text": "You can see it over there.", "start": 1816.247, "duration": 1.068}, {"text": "Some of those planes, they're\nbeautiful-- the yellow one,", "start": 1817.315, "duration": 3.203}, {"text": "but it doesn't have that\nmany atoms per area.", "start": 1820.518, "duration": 3.904}, {"text": "So if I try to\nmove that one, it's", "start": 1824.422, "duration": 2.87}, {"text": "not as strong of a plane to\nmove and to resolve my forces", "start": 1827.292, "duration": 4.638}, {"text": "at the atomic scale with.", "start": 1831.93, "duration": 1.034}, {"text": "So I'm always going to go\nfor that strongest plane.", "start": 1832.964, "duration": 5.105}, {"text": "So that's a slip plane.", "start": 1838.069, "duration": 1.668}, {"text": "Now, a great analogy\nfor this is the rug.", "start": 1839.737, "duration": 6.707}, {"text": "So if you're helping people\nmove or you're setting up", "start": 1846.444, "duration": 3.504}, {"text": "your own rug, and you\nget it and you put down", "start": 1849.948, "duration": 1.968}, {"text": "the rug base like that,\nand then you put it down,", "start": 1851.916, "duration": 3.237}, {"text": "and you're, ah!", "start": 1855.153, "duration": 0.6}, {"text": "I missed it by a foot.", "start": 1855.753, "duration": 2.403}, {"text": "I got it wrong.", "start": 1858.156, "duration": 1.334}, {"text": "This rug weighs--\nrugs are really heavy.", "start": 1859.49, "duration": 4.405}, {"text": "You pick it up, you're\nlike, oh, I'll just move it.", "start": 1863.895, "duration": 2.936}, {"text": "You call a friend and you both\npick it up, and you're like,", "start": 1866.831, "duration": 2.603}, {"text": "this is 1,000 pounds.", "start": 1869.434, "duration": 1.902}, {"text": "Who knew?", "start": 1871.336, "duration": 2.035}, {"text": "It's really a pain.", "start": 1873.371, "duration": 1.735}, {"text": "And so then you think\nabout dislocations", "start": 1875.106, "duration": 4.271}, {"text": "and you think about\nhow a material would", "start": 1879.377, "duration": 4.071}, {"text": "handle this situation.", "start": 1883.448, "duration": 1.568}, {"text": "And you say, well, if I just\nmake a little dislocation,", "start": 1885.016, "duration": 3.303}, {"text": "like a little\ncrinkle there, and I", "start": 1888.319, "duration": 1.869}, {"text": "move that, think about\nhow much effort it", "start": 1890.188, "duration": 3.503}, {"text": "takes to move that instead.", "start": 1893.691, "duration": 2.136}, {"text": "Not much.", "start": 1895.827, "duration": 0.634}, {"text": "You make a little crinkle,\nand then you move it,", "start": 1896.461, "duration": 2.202}, {"text": "and then you move it.", "start": 1898.663, "duration": 0.867}, {"text": "It doesn't take much\nforce to do that.", "start": 1899.53, "duration": 2.169}, {"text": "It takes a lot less than\npicking up the whole rug.", "start": 1901.699, "duration": 4.838}, {"text": "That's the motion\nof a dislocation.", "start": 1906.537, "duration": 2.436}, {"text": "We just talked about\nthe plane that it is,", "start": 1908.973, "duration": 2.97}, {"text": "but which direction?", "start": 1911.943, "duration": 1.435}, {"text": "Which way should you move it?", "start": 1913.378, "duration": 4.037}, {"text": "And so this is the second part.", "start": 1917.415, "duration": 1.368}, {"text": "So you have the slip\nplane, the closest packed", "start": 1918.783, "duration": 3.237}, {"text": "or highest planar\ndensity, and then", "start": 1922.02, "duration": 2.035}, {"text": "you also have the\nslip direction.", "start": 1924.055, "duration": 2.936}, {"text": "The slip direction\nis the other part.", "start": 1926.991, "duration": 3.504}, {"text": "Which way does it go?", "start": 1930.495, "duration": 1.468}, {"text": "I've got the closest\npacked plane.", "start": 1931.963, "duration": 2.402}, {"text": "Which way should it go?", "start": 1934.365, "duration": 1.101}, {"text": "Well, for this, you can\nsee from the experiments,", "start": 1935.466, "duration": 4.638}, {"text": "and when you look at the wire--\nagain, if I take a copper wire", "start": 1940.104, "duration": 3.604}, {"text": "and I pull it and I\nlook at it with my eyes,", "start": 1943.708, "duration": 3.136}, {"text": "it just looks like the\nuniform wire's been stretched.", "start": 1946.844, "duration": 2.203}, {"text": "But now I magnify it.", "start": 1949.047, "duration": 1.468}, {"text": "This is what you see.", "start": 1950.515, "duration": 0.901}, {"text": "So you can see that there\nare very definite directions.", "start": 1954.118, "duration": 4.905}, {"text": "This is actually all\nthe same direction.", "start": 1959.023, "duration": 2.703}, {"text": "So that's a slip plane\nand there's a direction", "start": 1961.726, "duration": 3.437}, {"text": "that it slides.", "start": 1965.163, "duration": 0.6}, {"text": "I think this can be understood--", "start": 1968.766, "duration": 3.304}, {"text": "I love this picture,\nbecause I love ping pong.", "start": 1972.07, "duration": 3.67}, {"text": "These are ping pong\nballs and you guys", "start": 1975.74, "duration": 1.568}, {"text": "can do these\nexperiments yourself.", "start": 1977.308, "duration": 3.57}, {"text": "You put a bunch of ping\npong balls in a row,", "start": 1980.878, "duration": 1.869}, {"text": "and then measure\nthe force that it", "start": 1982.747, "duration": 1.802}, {"text": "takes to slide it depending on\nwhether they're closely packed", "start": 1984.549, "duration": 3.503}, {"text": "or not.", "start": 1988.052, "duration": 1.702}, {"text": "This is a little\ncounterintuitive sometimes", "start": 1989.754, "duration": 2.135}, {"text": "when you first see it,\nbut it makes sense.", "start": 1991.889, "duration": 2.603}, {"text": "The more densely\npacked the plane", "start": 1994.492, "duration": 2.636}, {"text": "is, the easier it is\nfor one set of atoms", "start": 1997.128, "duration": 4.137}, {"text": "to slide across the other.", "start": 2001.265, "duration": 2.303}, {"text": "The easier it is.", "start": 2003.568, "duration": 1.201}, {"text": "So you can feel it.", "start": 2004.769, "duration": 1.835}, {"text": "If I have to let this one--", "start": 2006.604, "duration": 1.902}, {"text": "and they showed it\njust by angle at which", "start": 2008.506, "duration": 1.835}, {"text": "it would slide or roll.", "start": 2010.341, "duration": 0.968}, {"text": "I like the idea of two\npeople going in there--", "start": 2011.309, "duration": 3.27}, {"text": "and here, you'd have to apply\nmore force to make that one", "start": 2014.579, "duration": 3.537}, {"text": "slide than this one.", "start": 2018.116, "duration": 2.636}, {"text": "You can see it, again, with\nthis super precise animation.", "start": 2020.752, "duration": 4.371}, {"text": "There it is.", "start": 2025.123, "duration": 1.401}, {"text": "One of them and\nthere's the other one.", "start": 2026.524, "duration": 1.602}, {"text": "Look at how much more work you\ngot to do to get that thing", "start": 2028.126, "duration": 2.736}, {"text": "to go over and over.", "start": 2030.862, "duration": 2.702}, {"text": "No.", "start": 2033.564, "duration": 0.534}, {"text": "If you've got a high\ndensity of atoms,", "start": 2034.098, "duration": 2.703}, {"text": "it's actually easier to slide.", "start": 2036.801, "duration": 2.869}, {"text": "It's easier to slide because\nyou've got more bonds.", "start": 2039.67, "duration": 4.739}, {"text": "And so I'm not having\nto fully break a bond", "start": 2044.409, "duration": 2.569}, {"text": "before I get to the next one.", "start": 2046.978, "duration": 1.301}, {"text": "So the slip direction then is\ngoing to be the highest density", "start": 2051.549, "duration": 10.677}, {"text": "direction, so it's\nalso the close-packed--", "start": 2062.226, "duration": 3.671}, {"text": "I've got an example there--\nclose-packed direction.", "start": 2065.897, "duration": 2.502}, {"text": "So notice, this would be like\na direction-- a vector and this", "start": 2072.27, "duration": 5.705}, {"text": "is a plane.", "start": 2077.975, "duration": 1.335}, {"text": "Well, that's jogging\nsome memories", "start": 2079.31, "duration": 2.636}, {"text": "of understanding crystals\nby their Miller planes", "start": 2081.946, "duration": 3.07}, {"text": "and directions.", "start": 2085.016, "duration": 0.901}, {"text": "We say, well, what would\nthis be for, say, FCC?", "start": 2088.619, "duration": 2.77}, {"text": "There's an FCC crystal and\nthere's an FCC lattice.", "start": 2091.389, "duration": 3.603}, {"text": "So if I had, say,\nFCC as an example--", "start": 2094.992, "duration": 4.472}, {"text": "well, OK, so let's see\nif I can really quickly--", "start": 2099.464, "duration": 3.536}, {"text": "oh, boy, here we go.", "start": 2103.0, "duration": 2.87}, {"text": "There it is.", "start": 2105.87, "duration": 2.336}, {"text": "And here are the face atoms.", "start": 2108.206, "duration": 3.069}, {"text": "There we go.", "start": 2111.275, "duration": 2.102}, {"text": "OK.", "start": 2113.377, "duration": 1.302}, {"text": "That's the outer part of\nFCC-- three of the faces.", "start": 2114.679, "duration": 2.869}, {"text": "And now, OK, but if\nI take a 100 plane--", "start": 2117.548, "duration": 5.673}, {"text": "so let's take the 100 plane.", "start": 2123.221, "duration": 2.903}, {"text": "Then I've got that.", "start": 2126.124, "duration": 2.235}, {"text": "And you'll remember, I've got\nthese atoms on the corner.", "start": 2128.359, "duration": 2.369}, {"text": "Why did I draw that\nso much bigger?", "start": 2130.728, "duration": 2.403}, {"text": "Let's not do that.", "start": 2133.131, "duration": 1.501}, {"text": "That would be like\nthe 100 plane.", "start": 2134.632, "duration": 1.668}, {"text": "And this one might be the usual\nlattice constant A. You could", "start": 2139.137, "duration": 5.638}, {"text": "also look at the 110 plane.", "start": 2144.775, "duration": 3.904}, {"text": "Here it is.", "start": 2148.679, "duration": 0.968}, {"text": "The 110 plane.", "start": 2149.647, "duration": 2.569}, {"text": "That would look\nlike this and this.", "start": 2152.216, "duration": 4.438}, {"text": "That would be the 110 This is\njust bringing back memories--", "start": 2156.654, "duration": 3.47}, {"text": "I know good ones.", "start": 2160.124, "duration": 1.068}, {"text": "Here is the 111 plane.", "start": 2163.995, "duration": 1.935}, {"text": "So here, we've got this\none, this one, and this one.", "start": 2171.569, "duration": 3.57}, {"text": "In an FCC metal or\ncrystal, which plane", "start": 2178.476, "duration": 4.838}, {"text": "is going to slip and\nalong which direction?", "start": 2183.314, "duration": 3.337}, {"text": "You can get that now.", "start": 2186.651, "duration": 2.135}, {"text": "Because you can calculate\nthe planar densities.", "start": 2188.786, "duration": 3.904}, {"text": "In which case is the\npacking of atoms-- in which", "start": 2192.69, "duration": 5.606}, {"text": "of these planes\nis it the highest?", "start": 2198.296, "duration": 3.336}, {"text": "Well, you've got to know\nthe number of atoms.", "start": 2201.632, "duration": 2.336}, {"text": "So how many atoms are in this?", "start": 2203.968, "duration": 2.135}, {"text": "2.", "start": 2206.103, "duration": 2.036}, {"text": "How many atoms are in this?", "start": 2208.139, "duration": 1.535}, {"text": "Oh, why?", "start": 2209.674, "duration": 0.7}, {"text": "1/4, 1/4-- I'm just counting\nin the unit cell of the plane.", "start": 2210.374, "duration": 6.507}, {"text": "So 1/4, 1/4, 1/4, 1/4--", "start": 2216.881, "duration": 1.535}, {"text": "1.", "start": 2218.416, "duration": 1.635}, {"text": "It only counts in the plane\nif the plane goes right", "start": 2220.051, "duration": 4.137}, {"text": "through the atom.", "start": 2224.188, "duration": 0.701}, {"text": "So here in the 110 I've\ngot 1/4, 1/4, 1/4, 1/4.", "start": 2227.725, "duration": 4.671}, {"text": "OK.", "start": 2232.396, "duration": 0.501}, {"text": "That's 1, plus 1/2, 1/2.", "start": 2232.897, "duration": 2.402}, {"text": "Two.", "start": 2235.299, "duration": 2.836}, {"text": "I've got two atoms\nin that plane--", "start": 2238.135, "duration": 2.136}, {"text": "effectively, two\natoms in that plane.", "start": 2240.271, "duration": 2.936}, {"text": "But what about here?", "start": 2243.207, "duration": 0.834}, {"text": "Oh, boy.", "start": 2244.041, "duration": 1.235}, {"text": "OK.", "start": 2245.276, "duration": 0.5}, {"text": "1/6, 1/6, 1/6.", "start": 2245.776, "duration": 3.938}, {"text": "You see it from the\ngeometry it's a triangle.", "start": 2249.714, "duration": 2.736}, {"text": "So that's 1/2 from those\ncorners, plus 1/2, 1/2, 1/2.", "start": 2252.45, "duration": 3.87}, {"text": "2.", "start": 2256.32, "duration": 1.835}, {"text": "I've got the same\nnumber of atoms", "start": 2258.155, "duration": 4.105}, {"text": "in those planes of the unit\ncell-- of those planes drawn", "start": 2262.26, "duration": 4.304}, {"text": "within these unit cell boxes.", "start": 2266.564, "duration": 3.17}, {"text": "But they're different\nplanar densities.", "start": 2269.734, "duration": 1.902}, {"text": "They're different\nplanar densities.", "start": 2271.636, "duration": 2.235}, {"text": "Because the area here is equal\nto a squared in this case,", "start": 2273.871, "duration": 9.276}, {"text": "it's equal to root 2 a\nsquared in this case.", "start": 2283.147, "duration": 3.637}, {"text": "So it's larger.", "start": 2286.784, "duration": 1.201}, {"text": "Same atoms, larger area.", "start": 2287.985, "duration": 2.236}, {"text": "That's not going to have a\nhigher packing than that.", "start": 2290.221, "duration": 3.804}, {"text": "And now I get to have really\na lot of fun with triangles", "start": 2294.025, "duration": 2.702}, {"text": "and thinking about the height\nhere and stuff like that.", "start": 2296.727, "duration": 2.937}, {"text": "And the area of this\none is equal to root", "start": 2299.664, "duration": 3.637}, {"text": "3 over 2 a squared less than 1.", "start": 2303.301, "duration": 9.576}, {"text": "That's going to have the\nhighest planar density.", "start": 2312.877, "duration": 4.438}, {"text": "You know it.", "start": 2317.315, "duration": 1.968}, {"text": "That's going to have the\nhighest planar density.", "start": 2319.283, "duration": 2.069}, {"text": "So that's a connection now.", "start": 2321.352, "duration": 1.835}, {"text": "So you can connect\nnow what we've", "start": 2323.187, "duration": 2.503}, {"text": "learned about\nMiller planes, about", "start": 2325.69, "duration": 1.968}, {"text": "crystallography to this simple\ncalculations of density,", "start": 2327.658, "duration": 6.807}, {"text": "to this incredibly important\nbehavior of materials--", "start": 2334.465, "duration": 4.338}, {"text": "plastic deformation.", "start": 2338.803, "duration": 1.668}, {"text": "Because now you know how that's\ngoing to plastically deform.", "start": 2340.471, "duration": 5.105}, {"text": "It's going to deform along\nits closest packed plane.", "start": 2345.576, "duration": 5.539}, {"text": "And you can also look\nat the directions.", "start": 2351.115, "duration": 2.069}, {"text": "And it's shown here\nthat the slip direction", "start": 2353.184, "duration": 2.235}, {"text": "will be along one of those--", "start": 2355.419, "duration": 2.102}, {"text": "that's the highest density\ndirection, the 110.", "start": 2357.521, "duration": 4.772}, {"text": "So it's going to slip along\none of those directions.", "start": 2362.293, "duration": 4.304}, {"text": "Good.", "start": 2366.597, "duration": 0.868}, {"text": "Slip plane plus this\ntogether combined--", "start": 2367.465, "duration": 6.473}, {"text": "these are called slip systems.", "start": 2373.938, "duration": 1.368}, {"text": "The slip plane\nand the direction.", "start": 2385.549, "duration": 3.771}, {"text": "That's called the slip system.", "start": 2389.32, "duration": 2.035}, {"text": "OK.", "start": 2391.355, "duration": 0.667}, {"text": "Now, there's another\nthing that happens", "start": 2392.022, "duration": 4.405}, {"text": "with this location that's\nso cool and so important", "start": 2396.427, "duration": 3.57}, {"text": "to materials and to the things\nwe want to do with materials.", "start": 2399.997, "duration": 6.073}, {"text": "It has to do with the\nfact that, like I said,", "start": 2406.07, "duration": 2.002}, {"text": "the dislocations come\nin and they can be", "start": 2408.072, "duration": 5.539}, {"text": "a total mess and entanglement.", "start": 2413.611, "duration": 3.804}, {"text": "By the way, how did it\ncome in the first place?", "start": 2417.415, "duration": 1.935}, {"text": "If I started with\na perfect crystal,", "start": 2419.35, "duration": 2.169}, {"text": "where did it come from?", "start": 2421.519, "duration": 2.602}, {"text": "How could there\nbe a dislocation?", "start": 2424.121, "duration": 3.704}, {"text": "It can come in from the edge.", "start": 2427.825, "duration": 3.103}, {"text": "You've got an edge there.", "start": 2430.928, "duration": 1.502}, {"text": "There can be a mismatch\nand I call it up--", "start": 2432.43, "duration": 3.37}, {"text": "I need a dislocation\nor I'm going to break.", "start": 2436.2, "duration": 3.07}, {"text": "Boom.", "start": 2439.27, "duration": 0.6}, {"text": "Comes in from the edge,\ncomes in from the edge.", "start": 2439.87, "duration": 2.736}, {"text": "They come to the rescue.", "start": 2442.606, "duration": 2.937}, {"text": "This is a simulation\nof exactly that done", "start": 2445.543, "duration": 3.637}, {"text": "by the chair of the Department\nof Civil Engineering, Marcus", "start": 2449.18, "duration": 5.305}, {"text": "Beuhler--", "start": 2454.485, "duration": 2.336}, {"text": "a simulation he\ndid some years ago.", "start": 2456.821, "duration": 1.901}, {"text": "But he's modeling\nthe dislocations--", "start": 2458.722, "duration": 2.002}, {"text": "that's what you're\ngoing to see here--", "start": 2460.724, "duration": 1.602}, {"text": "as a piece of metal is cracked.", "start": 2462.326, "duration": 2.669}, {"text": "Watch this.", "start": 2464.995, "duration": 0.768}, {"text": "Watch them come in.", "start": 2465.763, "duration": 1.134}, {"text": "It's saying, I\nneed you, help me.", "start": 2466.897, "duration": 2.369}, {"text": "And there they go.", "start": 2469.266, "duration": 1.702}, {"text": "Now, look at what\nhappen-- there's", "start": 2470.968, "duration": 1.401}, {"text": "so many of them forming and\nforming, and now tangling", "start": 2472.369, "duration": 3.304}, {"text": "and tangling and tangling.", "start": 2475.673, "duration": 1.735}, {"text": "Then he's going to zoom in.", "start": 2477.408, "duration": 1.134}, {"text": "It's very cool.", "start": 2478.542, "duration": 0.668}, {"text": "Those are dislocations like\nwe saw in the experiments,", "start": 2479.21, "duration": 3.536}, {"text": "but this is a computer\nsimulation of them.", "start": 2482.746, "duration": 1.769}, {"text": "They're still kind of tangling.", "start": 2484.515, "duration": 1.268}, {"text": "Here they go.", "start": 2485.783, "duration": 0.967}, {"text": "They come in, they get called\nin to relieve the atomic force", "start": 2486.75, "duration": 5.873}, {"text": "and let the material slip.", "start": 2492.623, "duration": 2.502}, {"text": "But there's something\nthat happens now.", "start": 2495.125, "duration": 2.47}, {"text": "There's something that happens.", "start": 2497.595, "duration": 2.269}, {"text": "Because now we go\nback to the rug--", "start": 2499.864, "duration": 3.336}, {"text": "we go back to the rug.", "start": 2503.2, "duration": 1.302}, {"text": "And look at what's happened.", "start": 2504.502, "duration": 1.368}, {"text": "I'm going along and I\ndid the calculations", "start": 2505.87, "duration": 1.768}, {"text": "and I had no one to\nlift it, it's too heavy.", "start": 2507.638, "duration": 1.835}, {"text": "But I'm going to create a little\ndislocation and move it along.", "start": 2509.473, "duration": 2.903}, {"text": "And I come across someone\nelse's dislocation here.", "start": 2512.376, "duration": 3.403}, {"text": "Look at this.", "start": 2515.779, "duration": 0.668}, {"text": "I'm trying to roll mine and\nthere's another one there.", "start": 2516.447, "duration": 2.969}, {"text": "What's going to happen?", "start": 2519.416, "duration": 1.268}, {"text": "I can't go anymore.", "start": 2523.521, "duration": 1.901}, {"text": "I'm blocked.", "start": 2525.422, "duration": 2.57}, {"text": "I'm blocked.", "start": 2527.992, "duration": 1.201}, {"text": "So when dislocations\ntangle up, you", "start": 2529.193, "duration": 4.271}, {"text": "can imagine now it prevents\ndislocations from moving.", "start": 2533.464, "duration": 5.305}, {"text": "But dislocations moving is what\ngives me the plastic regime.", "start": 2538.769, "duration": 5.873}, {"text": "So as I introduce\ndislocations, I", "start": 2544.642, "duration": 3.77}, {"text": "make it so that it's harder\nfor dislocations to move.", "start": 2548.412, "duration": 4.404}, {"text": "There's actually\na name for that.", "start": 2552.816, "duration": 1.635}, {"text": "There's a name for that\nbecause it really changes", "start": 2554.451, "duration": 3.137}, {"text": "the mechanical properties.", "start": 2557.588, "duration": 1.435}, {"text": "It's called cold hardening\nor work hardening or strain", "start": 2559.023, "duration": 2.736}, {"text": "hardening-- sorry, cold work.", "start": 2561.759, "duration": 1.501}, {"text": "Cold working.", "start": 2563.26, "duration": 0.968}, {"text": "So work hardening or\nsometimes strain hardening.", "start": 2564.228, "duration": 12.346}, {"text": "Why is it called hardening?", "start": 2576.574, "duration": 3.103}, {"text": "Because you're literally\nmaking this material harder.", "start": 2579.677, "duration": 5.472}, {"text": "What's happened is, I've\ntaken away ductility,", "start": 2585.149, "duration": 4.438}, {"text": "so I've made it more brittle.", "start": 2589.587, "duration": 2.002}, {"text": "I've taken away the\nplastic deformation.", "start": 2591.589, "duration": 4.204}, {"text": "It can't do as much\nplastic deformation,", "start": 2595.793, "duration": 2.002}, {"text": "because that only happens\nby motion of dislocations", "start": 2597.795, "duration": 2.536}, {"text": "and I'm locking them in.", "start": 2600.331, "duration": 1.968}, {"text": "But I'm letting it maybe go\na little further in how much", "start": 2602.299, "duration": 4.338}, {"text": "it can elastically deform.", "start": 2606.637, "duration": 2.002}, {"text": "Maybe now, once it\ngets to here, it says,", "start": 2608.639, "duration": 3.27}, {"text": "you know what, I've got all\nthese dislocations in there,", "start": 2611.909, "duration": 4.971}, {"text": "It's not letting me\nplastically deform,", "start": 2616.88, "duration": 2.203}, {"text": "so I'll keep\nelastically deforming.", "start": 2619.083, "duration": 4.037}, {"text": "But that gets you up to\nmuch higher stresses.", "start": 2623.12, "duration": 3.07}, {"text": "It gets you up to\nmuch higher stresses", "start": 2626.19, "duration": 1.802}, {"text": "with elastic deformation.", "start": 2627.992, "duration": 2.502}, {"text": "And so this is a plot--", "start": 2630.494, "duration": 1.235}, {"text": "look at that.", "start": 2631.729, "duration": 0.567}, {"text": "That's called the-- oh, I\nshould have put that down there.", "start": 2632.296, "duration": 2.569}, {"text": "Let me label that because\nit's a pretty important point.", "start": 2634.865, "duration": 2.302}, {"text": "I labeled the fracture point.", "start": 2637.167, "duration": 1.335}, {"text": "This is the yield point.", "start": 2638.502, "duration": 1.768}, {"text": "There it is, the yield strength.", "start": 2640.27, "duration": 3.537}, {"text": "That's called the yield\nbecause it's where it", "start": 2643.807, "duration": 3.671}, {"text": "yields to plastic deformation.", "start": 2647.478, "duration": 4.304}, {"text": "So here you go.", "start": 2651.782, "duration": 0.701}, {"text": "You've got some steel,\nyou've got some brass,", "start": 2652.483, "duration": 3.436}, {"text": "and you've got some copper.", "start": 2655.919, "duration": 2.336}, {"text": "This is plotting-- look at that.", "start": 2658.255, "duration": 1.502}, {"text": "This is the percent cold work.", "start": 2659.757, "duration": 2.002}, {"text": "Cold work is work hardening.", "start": 2661.759, "duration": 2.168}, {"text": "Work hardening is adding\ndislocations on purpose--", "start": 2663.927, "duration": 4.004}, {"text": "on purpose.", "start": 2667.931, "duration": 1.268}, {"text": "So that what?", "start": 2669.199, "duration": 1.202}, {"text": "So that I increase\nthe yield strength", "start": 2670.401, "duration": 2.569}, {"text": "so that this material\ncan elastically", "start": 2672.97, "duration": 3.103}, {"text": "deform now up to higher and\nhigher and higher strengths.", "start": 2676.073, "duration": 6.006}, {"text": "But the ductility goes down.", "start": 2682.079, "duration": 1.868}, {"text": "When you bend a\npaperclip, don't you", "start": 2683.947, "duration": 2.136}, {"text": "go and tell anybody it's\nbecause of heat that it breaks.", "start": 2686.083, "duration": 3.203}, {"text": "That's not why a\npaperclip breaks.", "start": 2689.286, "duration": 2.035}, {"text": "It gets hot-- or warm.", "start": 2691.321, "duration": 1.802}, {"text": "You bend it back\nand forth, it breaks", "start": 2693.123, "duration": 2.036}, {"text": "because you are putting\ndislocations into it", "start": 2695.159, "duration": 3.169}, {"text": "and you're making\nit more brittle.", "start": 2698.328, "duration": 1.802}, {"text": "In fact, if you\nheated it up, you", "start": 2700.13, "duration": 1.769}, {"text": "would anneal those out and\nmake it more ductile again.", "start": 2701.899, "duration": 4.738}, {"text": "That's how you get rid of\nthe dislocations-- you've", "start": 2706.637, "duration": 2.135}, {"text": "got to heat it back up.", "start": 2708.772, "duration": 1.969}, {"text": "It makes it brittle,\nthe ductility goes down.", "start": 2710.741, "duration": 4.404}, {"text": "Why does this matter?", "start": 2715.145, "duration": 0.868}, {"text": "Well, this is one reason.", "start": 2716.013, "duration": 1.535}, {"text": "If you don't plan your\ncold work carefully,", "start": 2717.548, "duration": 4.538}, {"text": "you might make the\nmaterial too brittle.", "start": 2722.086, "duration": 2.268}, {"text": "You wanted it to be\nso hard because this", "start": 2724.354, "duration": 1.902}, {"text": "was such an important ship and\nit was going to be a big deal", "start": 2726.256, "duration": 3.804}, {"text": "and the launch was\nreally exciting.", "start": 2730.06, "duration": 1.468}, {"text": "And then it cracks in\nhalf, the entire ship.", "start": 2731.528, "duration": 3.671}, {"text": "Why?", "start": 2735.199, "duration": 0.6}, {"text": "Because you didn't look\nup what dislocations mean.", "start": 2735.799, "duration": 3.771}, {"text": "You didn't take\n3.091, that's why.", "start": 2739.57, "duration": 5.505}, {"text": "That's a pretty big crack.", "start": 2745.075, "duration": 1.101}, {"text": "The main why this matters--", "start": 2749.213, "duration": 1.401}, {"text": "oh, I couldn't help it.", "start": 2750.614, "duration": 1.802}, {"text": "I am a big fan of wind.", "start": 2752.416, "duration": 3.804}, {"text": "Wind energy is\ngrowing and growing", "start": 2756.22, "duration": 2.202}, {"text": "and it's such a great\nnational resource.", "start": 2758.422, "duration": 4.304}, {"text": "Here's the global capacity.", "start": 2762.726, "duration": 2.569}, {"text": "This is install capacity\nfor wind turbines.", "start": 2765.295, "duration": 5.306}, {"text": "But see, this is a\nmechanical materials problem", "start": 2770.601, "duration": 4.871}, {"text": "that you are now equipped\nto think about more deeply.", "start": 2775.472, "duration": 7.207}, {"text": "Because, you see, you can do\na lot of different experiments", "start": 2782.679, "duration": 4.638}, {"text": "on those turbines.", "start": 2787.317, "duration": 0.768}, {"text": "So the blades here are critical.", "start": 2788.085, "duration": 2.969}, {"text": "You can imagine that you\nwant them to be light,", "start": 2791.054, "duration": 3.07}, {"text": "but if they're too light,\nthey may not be strong enough.", "start": 2794.124, "duration": 2.736}, {"text": "And then how do they\nneed to be strong?", "start": 2796.86, "duration": 1.635}, {"text": "Because you've got huge\namounts of wind coming at them.", "start": 2798.495, "duration": 4.872}, {"text": "And it turns out, you need\nto hit just the right balance", "start": 2803.367, "duration": 3.57}, {"text": "of elastic deformation before it\ngoes into some plastic regime.", "start": 2806.937, "duration": 5.939}, {"text": "You need to hit just the\nright balance of ductility.", "start": 2812.876, "duration": 2.536}, {"text": "So here's, for example--", "start": 2815.412, "duration": 1.568}, {"text": "these are some simulations.", "start": 2816.98, "duration": 1.168}, {"text": "Here are some experiments on a\nnew material for a wind turbine", "start": 2818.148, "duration": 3.437}, {"text": "blade.", "start": 2821.585, "duration": 0.934}, {"text": "And then you put it out there\nand look at what happens-- ice.", "start": 2822.519, "duration": 4.338}, {"text": "By the way, this ice comes off\nat hundreds of miles an hour", "start": 2826.857, "duration": 3.603}, {"text": "in chunks.", "start": 2830.46, "duration": 1.035}, {"text": "These farmers are\nnot happy about that.", "start": 2831.495, "duration": 3.003}, {"text": "Seriously.", "start": 2834.498, "duration": 1.435}, {"text": "And those are bugs.", "start": 2835.933, "duration": 0.834}, {"text": "Actually, bugs in wind turbine\nblades is a serious problem.", "start": 2839.369, "duration": 3.27}, {"text": "How do you clean bugs off of it?", "start": 2842.639, "duration": 2.369}, {"text": "Because it dramatically\nchanges the aerodynamics", "start": 2845.008, "duration": 2.536}, {"text": "and the efficiency.", "start": 2847.544, "duration": 1.035}, {"text": "It also can damage\nthe blade itself.", "start": 2848.579, "duration": 3.27}, {"text": "So there's all sorts\nof work going on.", "start": 2851.849, "duration": 1.801}, {"text": "How do you make bug-proof\nwind turbine blades?", "start": 2853.65, "duration": 3.237}, {"text": "OK.", "start": 2856.887, "duration": 0.5}, {"text": "Well, now just spray\nit with something.", "start": 2857.387, "duration": 1.602}, {"text": "Ah, but then does it have\nthe right plastic deform--", "start": 2858.989, "duration": 2.87}, {"text": "does it have the\nright yield point", "start": 2861.859, "duration": 1.634}, {"text": "or is it just going to crack?", "start": 2863.493, "duration": 1.202}, {"text": "And by the way, it's got to\nhave 5 times 10 to the 9 cycles", "start": 2867.431, "duration": 4.037}, {"text": "before it can fail.", "start": 2871.468, "duration": 1.335}, {"text": "That's the metric.", "start": 2872.803, "duration": 1.468}, {"text": "So that's a pretty\nbig ask of a material.", "start": 2874.271, "duration": 2.202}, {"text": "It all comes down to\nunderstanding this curve.", "start": 2876.473, "duration": 3.036}, {"text": "And in the broader sense\nof materials, this to me", "start": 2879.509, "duration": 4.271}, {"text": "is a very exciting ask.", "start": 2883.78, "duration": 2.903}, {"text": "Why?", "start": 2886.683, "duration": 1.435}, {"text": "Because if you look at a plot\nof the density of materials--", "start": 2888.118, "duration": 5.439}, {"text": "heavy, light.", "start": 2893.557, "duration": 1.435}, {"text": "Good.", "start": 2894.992, "duration": 0.834}, {"text": "Kilograms per meter cubed.", "start": 2895.826, "duration": 1.301}, {"text": "And the Young's modulus--", "start": 2897.127, "duration": 1.935}, {"text": "now, this is a measure of\nthe strength of the material.", "start": 2899.062, "duration": 4.705}, {"text": "It's a measure of\nhow much strain", "start": 2903.767, "duration": 3.27}, {"text": "you could put on the material\nbefore it breaks or goes", "start": 2907.037, "duration": 3.103}, {"text": "through deformation.", "start": 2910.14, "duration": 0.834}, {"text": "But look at this.", "start": 2910.974, "duration": 1.335}, {"text": "Different materials are here--", "start": 2912.309, "duration": 2.436}, {"text": "rubbers, foams.", "start": 2914.745, "duration": 1.868}, {"text": "OK, foams have relatively\nlow Young's modulus,", "start": 2916.613, "duration": 3.904}, {"text": "but they're really light.", "start": 2920.517, "duration": 1.068}, {"text": "That could be good.", "start": 2921.585, "duration": 1.468}, {"text": "Up here you've got metals\nand alloys, ceramics,", "start": 2923.053, "duration": 3.971}, {"text": "you've got polymers in here.", "start": 2927.024, "duration": 1.902}, {"text": "But notice, I've got so\nmany different applications", "start": 2928.926, "duration": 3.903}, {"text": "and needs in the\napplications and I've", "start": 2932.829, "duration": 2.603}, {"text": "got this plot where I've got\nnothing here and nothing here,", "start": 2935.432, "duration": 4.171}, {"text": "even though, if I could\nfill this out and dial up", "start": 2939.603, "duration": 4.571}, {"text": "any stress/strain curve for\nany density or Young's modulus,", "start": 2944.174, "duration": 5.773}, {"text": "you can make a big\ndifference in a lot", "start": 2949.947, "duration": 1.568}, {"text": "of different applications.", "start": 2951.515, "duration": 1.067}, {"text": "So I think this is\na great challenge.", "start": 2952.582, "duration": 2.636}, {"text": "Have a good night.", "start": 2955.218, "duration": 0.768}, {"text": "See you guys on Friday.", "start": 2955.986, "duration": 2.269}]
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+[{"text": "ADAM MARTIN: All right,\nlet's get started.", "start": 16.54, "duration": 2.01}, {"text": "So I'm starting with\nthis video here.", "start": 18.55, "duration": 3.12}, {"text": "What's happening here\nis there's this mouse,", "start": 21.67, "duration": 3.04}, {"text": "and you see there's like\nthis fiber optic cable going", "start": 24.71, "duration": 2.99}, {"text": "into its brain.", "start": 27.7, "duration": 1.88}, {"text": "And the mouse is\nasleep right now.", "start": 29.58, "duration": 2.59}, {"text": "And now the researchers\nare shining light", "start": 32.17, "duration": 3.9}, {"text": "into its brain, a specific\nregion of the brain,", "start": 36.07, "duration": 2.97}, {"text": "to activate specific\nneurons in order", "start": 39.04, "duration": 2.67}, {"text": "to test whether they\nfunction in arousal.", "start": 41.71, "duration": 2.91}, {"text": "And here, you see the\nmouse is going to wake up.", "start": 44.62, "duration": 3.617}, {"text": "There it goes.", "start": 48.237, "duration": 0.583}, {"text": "It's awake now.", "start": 48.82, "duration": 0.69}, {"text": "So for today's\nlecture, we're going", "start": 52.57, "duration": 2.29}, {"text": "to work towards understanding\nhow this experiment works.", "start": 54.86, "duration": 5.15}, {"text": "And we're going to talk\nabout how neurons function", "start": 60.01, "duration": 3.03}, {"text": "and how researchers are able to\ncontrol that function in order", "start": 63.04, "duration": 4.47}, {"text": "to modify behavior--", "start": 67.51, "duration": 2.16}, {"text": "in this case, the\narousal of this mouse.", "start": 69.67, "duration": 2.73}, {"text": "OK, so this is going to involve\na particular type of cell", "start": 75.67, "duration": 3.9}, {"text": "in our body, which\nis the neuron.", "start": 79.57, "duration": 2.13}, {"text": "And neurons are highly\nspecialized cells", "start": 81.7, "duration": 3.36}, {"text": "that have a function to\ntransmit information from one", "start": 85.06, "duration": 3.45}, {"text": "part of the body to another.", "start": 88.51, "duration": 3.45}, {"text": "And so neurons are\nhighly polarized cells,", "start": 91.96, "duration": 4.47}, {"text": "which you can see here.", "start": 96.43, "duration": 1.68}, {"text": "On the left of this neuron, you\nsee this arbor of protrusions,", "start": 98.11, "duration": 4.98}, {"text": "which are called dendrites.", "start": 103.09, "duration": 2.88}, {"text": "And then on this side\nof the cell body,", "start": 105.97, "duration": 2.01}, {"text": "you see a single\nextension, which", "start": 107.98, "duration": 2.55}, {"text": "is an axon, and then the\nterminus of the axon over here.", "start": 110.53, "duration": 4.62}, {"text": "And this nerve cell\ntransmits information", "start": 115.15, "duration": 3.51}, {"text": "in a single direction.", "start": 118.66, "duration": 1.83}, {"text": "It will transmit information\nfrom this side to this side.", "start": 120.49, "duration": 5.85}, {"text": "And these neurons are able to\ncommunicate with each other.", "start": 126.34, "duration": 3.84}, {"text": "And they communicate at the\nends of the neuron, which", "start": 130.18, "duration": 3.03}, {"text": "are known as synapses,\nwhich I'll come back to", "start": 133.21, "duration": 2.31}, {"text": "and talk about later\non in the lecture.", "start": 135.52, "duration": 3.06}, {"text": "So neurons could be making\nsynapses on this side", "start": 138.58, "duration": 3.42}, {"text": "and also making synapses on\nthis side with other neurons.", "start": 142.0, "duration": 2.805}, {"text": "So to start to unpack the\nfunction of this neuron--", "start": 148.84, "duration": 4.24}, {"text": "and I should highlight that\nthis flow of information", "start": 153.08, "duration": 3.05}, {"text": "can occur over very\nlong distances, right?", "start": 156.13, "duration": 2.86}, {"text": "Your sciatic nerve extends\nfrom the base of your spine", "start": 158.99, "duration": 3.68}, {"text": "all the way down\ninto your foot, OK?", "start": 162.67, "duration": 2.31}, {"text": "So that axon is one\nmeter in length.", "start": 164.98, "duration": 4.15}, {"text": "So that's an extremely\nlong distance", "start": 169.13, "duration": 2.21}, {"text": "to transmit information\nalong a single cell.", "start": 171.34, "duration": 3.21}, {"text": "And so we're going to go from\nthinking about how signals are", "start": 177.1, "duration": 3.45}, {"text": "transmitted in single\ncells, and this will", "start": 180.55, "duration": 2.52}, {"text": "evolve electrical signaling.", "start": 183.07, "duration": 2.43}, {"text": "Then we'll talk about synapses\nand how synapses function", "start": 185.5, "duration": 3.81}, {"text": "to communicate between neurons.", "start": 189.31, "duration": 2.41}, {"text": "And this is going\nto involve also", "start": 191.72, "duration": 3.32}, {"text": "sort of understanding how\ncertain antidepressants,", "start": 195.04, "duration": 3.15}, {"text": "like Prozac, work.", "start": 198.19, "duration": 1.62}, {"text": "And then we'll end\nby talking about how", "start": 199.81, "duration": 2.07}, {"text": "researchers did this experiment\nto wake up the mouse.", "start": 201.88, "duration": 4.55}, {"text": "And it all starts with\nsomething that I told you", "start": 206.43, "duration": 2.23}, {"text": "about at the beginning\nof the semester, which", "start": 208.66, "duration": 3.27}, {"text": "is that the plasma\nmembrane separates", "start": 211.93, "duration": 3.78}, {"text": "distinct compartments\nthe outside of the cell", "start": 215.71, "duration": 2.67}, {"text": "from the cytoplasm.", "start": 218.38, "duration": 1.53}, {"text": "And there are distinct\nion concentrations", "start": 219.91, "duration": 2.79}, {"text": "on either side of this boundary.", "start": 222.7, "duration": 4.29}, {"text": "So we're starting now talking\nabout a single neuron cell.", "start": 226.99, "duration": 4.125}, {"text": "And we're going to talk\nabout a type of signal", "start": 235.69, "duration": 4.1}, {"text": "known as an action potential.", "start": 239.79, "duration": 3.222}, {"text": "Oh, that's right.", "start": 243.012, "duration": 0.708}, {"text": "So we're going to talk\nabout an action potential.", "start": 248.46, "duration": 2.91}, {"text": "And what an action\npotential is, is it's", "start": 251.37, "duration": 2.13}, {"text": "an electrical\nsignal that travels", "start": 253.5, "duration": 1.89}, {"text": "the length of the neuron.", "start": 255.39, "duration": 2.29}, {"text": "So this action potential,\nI'll abbreviate this AP.", "start": 257.68, "duration": 5.03}, {"text": "So when I refer to\nAP, I'm not referring", "start": 262.71, "duration": 2.55}, {"text": "to advanced placement,\nbut action potential, OK?", "start": 265.26, "duration": 4.59}, {"text": "So this is an\nelectrical signal that", "start": 269.85, "duration": 7.17}, {"text": "travels the length of\nthe axon and the neuron.", "start": 277.02, "duration": 3.9}, {"text": "And so in order to have an\nelectrical signal propagate,", "start": 291.29, "duration": 3.34}, {"text": "we need some sort of\nelectrical property", "start": 294.63, "duration": 2.37}, {"text": "that the cell has\nthat enables this.", "start": 297.0, "duration": 4.18}, {"text": "And so I showed you or I told\nyou earlier in the semester", "start": 301.18, "duration": 3.89}, {"text": "how sodium ions are concentrated\non the outside of the cell", "start": 305.07, "duration": 4.26}, {"text": "and potassium ions are\nconcentrated on the inside.", "start": 309.33, "duration": 4.21}, {"text": "You see here's the\nsodium gradient here,", "start": 313.54, "duration": 2.36}, {"text": "potassium gradient here.", "start": 315.9, "duration": 1.79}, {"text": "And now I'm going to tell you\nhow it is that this happens,", "start": 317.69, "duration": 2.47}, {"text": "because this is\nthermodynamically not favored,", "start": 320.16, "duration": 2.15}, {"text": "right?", "start": 322.31, "duration": 0.5}, {"text": "These ions would\nprefer, by diffusion,", "start": 322.81, "duration": 3.38}, {"text": "to be equal concentrations\non both sides of this plasma", "start": 326.19, "duration": 3.9}, {"text": "membrane, which means that\nthe cell to shift this", "start": 330.09, "duration": 5.58}, {"text": "from equilibrium\nhas to expend energy", "start": 335.67, "duration": 2.67}, {"text": "to set up this situation.", "start": 338.34, "duration": 3.64}, {"text": "And so in the plasma membrane\nof the cell, there is a protein.", "start": 341.98, "duration": 4.62}, {"text": "It's an integral\nmembrane protein", "start": 346.6, "duration": 1.76}, {"text": "and sits inside the\nplasma membrane.", "start": 348.36, "duration": 2.98}, {"text": "So this here is the\nplasma membrane.", "start": 351.34, "duration": 3.74}, {"text": "And this integral\nmembrane protein", "start": 355.08, "duration": 2.13}, {"text": "is called a sodium\npotassium ATPase.", "start": 357.21, "duration": 4.8}, {"text": "So it's going to have a subunit\nthat hydrolyzes ATP to ADP.", "start": 362.01, "duration": 8.76}, {"text": "And the protein uses the\nenergy of ATP hydrolysis", "start": 370.77, "duration": 5.1}, {"text": "to pump sodium ions up their\nconcentration gradient.", "start": 375.87, "duration": 4.78}, {"text": "So the sodium ions are\ngoing out of the cell.", "start": 380.65, "duration": 3.79}, {"text": "And this is going\nagainst the flow", "start": 384.44, "duration": 2.35}, {"text": "that sodium would\nnormally like to take,", "start": 386.79, "duration": 2.11}, {"text": "which would be going downstream.", "start": 388.9, "duration": 2.9}, {"text": "And it pumps potassium ions\ninto the cytoplasm such", "start": 391.8, "duration": 5.58}, {"text": "that there's a higher\nconcentration of potassium", "start": 397.38, "duration": 2.97}, {"text": "ions in the cytoplasm, OK?", "start": 400.35, "duration": 2.79}, {"text": "So these neurons expend a huge--", "start": 403.14, "duration": 3.99}, {"text": "a quarter of their ATP is used\nby pumping ions like this, such", "start": 407.13, "duration": 5.16}, {"text": "that there is gradients of ions\nacross the plasma membrane.", "start": 412.29, "duration": 4.305}, {"text": "Now, if one sodium\nion was pumped out", "start": 419.31, "duration": 3.72}, {"text": "for every potassium\nion pumped in,", "start": 423.03, "duration": 2.97}, {"text": "there'd be no charge\ndifference between the exterior", "start": 426.0, "duration": 3.3}, {"text": "and the cytoplasm.", "start": 429.3, "duration": 2.79}, {"text": "But what happens in\nthe plasma membrane", "start": 432.09, "duration": 4.17}, {"text": "is that in addition to the\nsodium potassium ATPase,", "start": 436.26, "duration": 3.75}, {"text": "there are other channels\nthat are present.", "start": 440.01, "duration": 3.33}, {"text": "There are sodium channels.", "start": 443.34, "duration": 1.96}, {"text": "These are mostly closed,\nbut there are some potassium", "start": 445.3, "duration": 4.1}, {"text": "channels that are leaky.", "start": 449.4, "duration": 1.83}, {"text": "And they're basically leaking\npotassium from the cytoplasm", "start": 451.23, "duration": 3.63}, {"text": "out into the exoplasm, OK?", "start": 454.86, "duration": 3.27}, {"text": "And if you have positive\ncharges going out the cell,", "start": 458.13, "duration": 4.2}, {"text": "then the inside of\nthe membrane is going", "start": 462.33, "duration": 1.94}, {"text": "to have a net negative charge.", "start": 464.27, "duration": 3.143}, {"text": "And the outside of\nthe membrane is going", "start": 467.413, "duration": 1.667}, {"text": "to have a net positive charge.", "start": 469.08, "duration": 3.99}, {"text": "And this charge\nacross the membrane,", "start": 473.07, "duration": 2.67}, {"text": "where you have\npositive on the outside", "start": 475.74, "duration": 2.95}, {"text": "and minus on the inside--", "start": 478.69, "duration": 1.63}, {"text": "I should label this exterior,\nand this is cytoplasm.", "start": 480.32, "duration": 6.07}, {"text": "This voltage difference is\nknown as a membrane potential.", "start": 491.58, "duration": 5.07}, {"text": "So this is a membrane potential.", "start": 496.65, "duration": 1.6}, {"text": "And it's an electrical\npotential across the membrane.", "start": 504.95, "duration": 3.57}, {"text": "If you're an\nelectrical engineer,", "start": 508.52, "duration": 1.5}, {"text": "you can think of the plasma\nmembrane as a capacitor, OK?", "start": 510.02, "duration": 3.72}, {"text": "So this plasma membrane is\nholding this charge difference", "start": 513.74, "duration": 3.809}, {"text": "across it.", "start": 517.549, "duration": 2.01}, {"text": "And so there's a voltage\nacross the membrane.", "start": 519.559, "duration": 2.61}, {"text": "And in a resting state, the\ncell's resting potential", "start": 522.169, "duration": 8.851}, {"text": "is negative 70 millivolts.", "start": 531.02, "duration": 2.16}, {"text": "So if the cell is not getting\nstimulated by something", "start": 537.41, "duration": 3.54}, {"text": "like a neurotransmitter,\nthe resting potential", "start": 540.95, "duration": 2.49}, {"text": "is negative 70 millivolts,\nwhere the inside is negative", "start": 543.44, "duration": 3.87}, {"text": "and the outside is positive, OK?", "start": 547.31, "duration": 3.06}, {"text": "So now I just want to\ndefine some terms that", "start": 550.37, "duration": 2.208}, {"text": "are going to be\nuseful for us when we", "start": 552.578, "duration": 1.542}, {"text": "talk about action potentials.", "start": 554.12, "duration": 3.04}, {"text": "So when there's this\nnegative inside potential,", "start": 557.16, "duration": 7.295}, {"text": "a negative inside potential\nis referred to as polarized.", "start": 564.455, "duration": 4.305}, {"text": "So it's polarized\nbecause there's", "start": 568.76, "duration": 5.64}, {"text": "a polarity across this membrane,\nwhere one side is positive", "start": 574.4, "duration": 3.72}, {"text": "and the other side\nis negative, OK?", "start": 578.12, "duration": 3.54}, {"text": "So polarized refers\nto if there's", "start": 581.66, "duration": 2.28}, {"text": "a negative inside potential.", "start": 583.94, "duration": 1.89}, {"text": "So the resting state of the\nside is there's a polarized--", "start": 585.83, "duration": 3.32}, {"text": "it's polarized.", "start": 589.15, "duration": 2.95}, {"text": "However, the cell can\nlose this polarity", "start": 592.1, "duration": 3.54}, {"text": "and not have a\ncharge differential,", "start": 595.64, "duration": 1.86}, {"text": "or it can flip and be\npositive on the inside.", "start": 597.5, "duration": 3.45}, {"text": "And when that happens, if\nthere's either zero or positive", "start": 600.95, "duration": 4.8}, {"text": "inside potential, this is\nreferred to as depolarized.", "start": 605.75, "duration": 4.32}, {"text": "Anyone have an idea as\nto how the cell would", "start": 617.33, "duration": 3.09}, {"text": "flip the potential?", "start": 620.42, "duration": 2.16}, {"text": "What would have to happen\nin the plasma membrane", "start": 622.58, "duration": 2.7}, {"text": "to flip this potential\nand depolarize the cell?", "start": 625.28, "duration": 3.03}, {"text": "Yes, Stephen?", "start": 628.31, "duration": 0.59}, {"text": "AUDIENCE: You could\nopen the ion channels.", "start": 628.9, "duration": 1.81}, {"text": "ADAM MARTIN: So Stephen\nsuggested opening ion channels.", "start": 630.71, "duration": 2.89}, {"text": "Which ion channels\nwould you open?", "start": 633.6, "duration": 2.831}, {"text": "AUDIENCE: The sodium channels.", "start": 636.431, "duration": 1.689}, {"text": "ADAM MARTIN: Yeah.", "start": 638.12, "duration": 0.75}, {"text": "So Stephen suggested\nif you open these,", "start": 638.87, "duration": 3.39}, {"text": "it's going to\ndepolarize the cell.", "start": 642.26, "duration": 1.71}, {"text": "Because remember, sodium is\nhigh on the outside, out here.", "start": 643.97, "duration": 4.48}, {"text": "And so if you open\nthese channels,", "start": 648.45, "duration": 1.73}, {"text": "positive ions are\ngoing to flow in.", "start": 650.18, "duration": 2.55}, {"text": "And that's going to make this\nless negative and this less", "start": 652.73, "duration": 3.39}, {"text": "positive, OK?", "start": 656.12, "duration": 2.68}, {"text": "So this is the situation here,\nwhere these sodium channels", "start": 658.8, "duration": 4.07}, {"text": "open, and the sodium\nchannels-- or the sodium", "start": 662.87, "duration": 3.18}, {"text": "ions rushing in is going\nto create a depolarization,", "start": 666.05, "duration": 3.6}, {"text": "where you now flip\nthe potential.", "start": 669.65, "duration": 2.13}, {"text": "And there's a greater\npositive charge", "start": 671.78, "duration": 2.34}, {"text": "on the inside of\nthe plasma membrane.", "start": 674.12, "duration": 4.5}, {"text": "Everyone see how?", "start": 678.62, "duration": 1.65}, {"text": "Because the sodium ions are\ngoing to just go downstream.", "start": 680.27, "duration": 3.09}, {"text": "They're higher\nconcentration out here.", "start": 683.36, "duration": 2.04}, {"text": "So just by opening\nthese channels,", "start": 685.4, "duration": 2.34}, {"text": "the cell doesn't have to\ndo any work to do this.", "start": 687.74, "duration": 2.67}, {"text": "Sodium is just going to\nflow down its gradient", "start": 690.41, "duration": 2.19}, {"text": "into the cytoplasm.", "start": 692.6, "duration": 1.32}, {"text": "So what an action\npotential is, is it's", "start": 701.11, "duration": 2.64}, {"text": "a transient depolarization\nof the nerve cell.", "start": 703.75, "duration": 5.34}, {"text": "So the Action Potential, or AP,\nis a transient depolarization", "start": 709.09, "duration": 13.09}, {"text": "of the neuron, which\nmeans it doesn't just", "start": 722.18, "duration": 4.98}, {"text": "depolarize and stay depolarized,\nbut it depolarizes and then", "start": 727.16, "duration": 4.86}, {"text": "restores itself back to\nthe resting polarity.", "start": 732.02, "duration": 3.99}, {"text": "And so what you see when\nyou measure the voltage", "start": 736.01, "duration": 3.3}, {"text": "across the plasma\nmembrane in a neuron,", "start": 739.31, "duration": 2.7}, {"text": "you see that it can\nspike and depolarize,", "start": 742.01, "duration": 2.88}, {"text": "but then it's rapidly restored\nto its resting state, OK?", "start": 744.89, "duration": 3.99}, {"text": "So it's a transient process.", "start": 748.88, "duration": 1.32}, {"text": "When we think about the neuron\nat higher resolution, what", "start": 753.08, "duration": 3.39}, {"text": "you're going to see is\nnot only is it transient,", "start": 756.47, "duration": 2.67}, {"text": "but it's also a traveling\nwave that propagates along", "start": 759.14, "duration": 3.36}, {"text": "the entire length of the cell.", "start": 762.5, "duration": 3.37}, {"text": "So this is also\na traveling wave.", "start": 765.87, "duration": 2.0}, {"text": "And one thing that you can\nnotice about these neurons,", "start": 776.83, "duration": 4.41}, {"text": "or the action potentials\nhere, is that they all", "start": 781.24, "duration": 4.27}, {"text": "depolarize to the same extent.", "start": 785.51, "duration": 2.49}, {"text": "So they all depolarize to\nthis positive 50 millivolts.", "start": 788.0, "duration": 4.38}, {"text": "And so this illustrates\na key property", "start": 792.38, "duration": 2.33}, {"text": "of neurons, in that the\nlevel of activity of a neuron", "start": 794.71, "duration": 5.16}, {"text": "is not determined by the size\nof this action potential.", "start": 799.87, "duration": 5.61}, {"text": "This action potential is\nan all-or-nothing event.", "start": 805.48, "duration": 2.97}, {"text": "It either happens or it doesn't.", "start": 808.45, "duration": 1.69}, {"text": "And when it happens, it\ndepolarizes to the same level.", "start": 810.14, "duration": 2.93}, {"text": "So the action potential\nis all or nothing.", "start": 815.89, "duration": 2.58}, {"text": "You can think of it\nas a binary signal.", "start": 822.68, "duration": 2.81}, {"text": "And therefore, the\nway that neurons", "start": 825.49, "duration": 2.04}, {"text": "encode sort of the\nmagnitude of activation", "start": 827.53, "duration": 3.42}, {"text": "is not through the\nlevel of depolarization", "start": 830.95, "duration": 3.09}, {"text": "of a single action\npotential, but it", "start": 834.04, "duration": 2.88}, {"text": "is able to distinguish between\ndifferent frequencies of action", "start": 836.92, "duration": 3.36}, {"text": "potentials that are\npropagating along the neuron.", "start": 840.28, "duration": 2.94}, {"text": "So signal strength,\nin this case,", "start": 845.77, "duration": 6.87}, {"text": "is related to the frequency\nof action potentials firing.", "start": 852.64, "duration": 3.6}, {"text": "So now we're going\nto unpack how it", "start": 866.66, "duration": 1.68}, {"text": "is a nerve cell fires\nan action potential", "start": 868.34, "duration": 3.48}, {"text": "and how it propagates along\nthe entire cell length, right?", "start": 871.82, "duration": 3.12}, {"text": "In the case of\nthe sciatic nerve,", "start": 874.94, "duration": 1.8}, {"text": "this has to happen across\nan entire meter, OK?", "start": 876.74, "duration": 2.49}, {"text": "That's a very long\ndistance to propagate", "start": 879.23, "duration": 2.61}, {"text": "this change in electrical\nsignal, at least for a cell.", "start": 881.84, "duration": 4.57}, {"text": "And so we're going to\ntalk about the mechanism.", "start": 886.41, "duration": 2.6}, {"text": "And I'm going to start at the\nbeginning, when this action", "start": 889.01, "duration": 3.06}, {"text": "potential initiates.", "start": 892.07, "duration": 3.27}, {"text": "So we'll start at the initiation\nof the action potential.", "start": 895.34, "duration": 4.17}, {"text": "So how is it that\nthis nerve cell", "start": 903.39, "duration": 3.75}, {"text": "is told to start depolarizing\nat the dendrites?", "start": 907.14, "duration": 4.16}, {"text": "Because there's going to\nbe another neuron here,", "start": 911.3, "duration": 2.95}, {"text": "which is going to communicate\nto this neuron over here", "start": 914.25, "duration": 3.57}, {"text": "to tell it to\nstart depolarizing.", "start": 917.82, "duration": 3.34}, {"text": "It does this at the location\nknown as the synapse, which", "start": 921.16, "duration": 3.56}, {"text": "is basically sort of the\nconnection between the two", "start": 924.72, "duration": 3.36}, {"text": "neurons.", "start": 928.08, "duration": 2.79}, {"text": "And the way this\nprocess is initiated", "start": 930.87, "duration": 2.1}, {"text": "is similar to the\ntype of signaling", "start": 932.97, "duration": 2.01}, {"text": "that you saw in the past\nfew lectures, where you have", "start": 934.98, "duration": 2.88}, {"text": "a ligand and a receptor, OK?", "start": 937.86, "duration": 3.57}, {"text": "In this case, the\nligand is going", "start": 941.43, "duration": 8.88}, {"text": "to be what's known as a\nneurotransmitter, which", "start": 950.31, "duration": 5.65}, {"text": "is a small molecule.", "start": 955.96, "duration": 1.44}, {"text": "And I'll show you some later on.", "start": 957.4, "duration": 3.81}, {"text": "And the receptor is going\nto be a receptor that", "start": 961.21, "duration": 4.38}, {"text": "binds to this ligand.", "start": 965.59, "duration": 2.07}, {"text": "But in this case, rather\nthan being something", "start": 967.66, "duration": 2.16}, {"text": "like a G protein coupled\nreceptor or a receptor tyrosine", "start": 969.82, "duration": 3.69}, {"text": "kinase, the receptor is going\nto be an ion channel, OK?", "start": 973.51, "duration": 4.65}, {"text": "So the receptor is going\nto be an ion channel.", "start": 978.16, "duration": 2.4}, {"text": "And so you see one\nexample in the slide", "start": 985.15, "duration": 2.1}, {"text": "up here, where\nhere's a receptor.", "start": 987.25, "duration": 3.57}, {"text": "And these receptors are what\nare known as ligand-gated ion", "start": 990.82, "duration": 4.59}, {"text": "channels.", "start": 995.41, "duration": 0.54}, {"text": "In this case, it's\na sodium channel.", "start": 995.95, "duration": 2.2}, {"text": "So it's going to be--", "start": 998.15, "duration": 1.88}, {"text": "whether or not it's open depends\non the presence of the ligand.", "start": 1000.03, "duration": 3.97}, {"text": "So if we take a\nneurotransmitter like serotonin,", "start": 1004.0, "duration": 4.18}, {"text": "if it's not bound\nto the receptor,", "start": 1008.18, "duration": 2.05}, {"text": "the receptor is closed.", "start": 1010.23, "duration": 1.86}, {"text": "But if serotonin\nbinds to the receptor,", "start": 1012.09, "duration": 2.97}, {"text": "it opens up the channel,\nwhich can selectively", "start": 1015.06, "duration": 3.3}, {"text": "let in a type of ion--", "start": 1018.36, "duration": 1.71}, {"text": "in this case, sodium.", "start": 1020.07, "duration": 1.95}, {"text": "In this case, this is\nan activating channel,", "start": 1022.02, "duration": 3.21}, {"text": "because letting\nin sodium is going", "start": 1025.23, "duration": 1.92}, {"text": "to depolarize the cell, OK?", "start": 1027.15, "duration": 4.59}, {"text": "So this ligand receptor\nbinding uses a ligand-gated--", "start": 1031.74, "duration": 4.73}, {"text": "there's a ligand-gated\nsodium channel.", "start": 1039.06, "duration": 2.385}, {"text": "And it's this ligand-gated\nsodium channel which", "start": 1045.03, "duration": 4.65}, {"text": "starts the depolarization.", "start": 1049.68, "duration": 1.71}, {"text": "So that's how you sort of knock\nover the first domino, right?", "start": 1059.94, "duration": 5.46}, {"text": "But then there has\nto be some mechanism", "start": 1065.4, "duration": 2.4}, {"text": "to propagate this along the\nlength of a very long cell.", "start": 1067.8, "duration": 4.77}, {"text": "And so I'll tell you this\ninvolves a different type", "start": 1072.57, "duration": 5.82}, {"text": "of sort of signaling\nmechanism from what you're", "start": 1078.39, "duration": 3.3}, {"text": "used to thinking about, because\nthis involves a different type", "start": 1081.69, "duration": 3.27}, {"text": "of an ion channel.", "start": 1084.96, "duration": 1.77}, {"text": "And it's called a voltage gated.", "start": 1086.73, "duration": 2.13}, {"text": "And I'll abbreviate\nvoltage gated just VG.", "start": 1092.44, "duration": 4.36}, {"text": "And in this case, it\nwill be a sodium channel.", "start": 1096.8, "duration": 2.2}, {"text": "So what's a voltage-gated\nsodium channel?", "start": 1103.89, "duration": 3.4}, {"text": "This is a voltage-gated\nsodium channel here.", "start": 1107.29, "duration": 2.66}, {"text": "And you can see, in the\nresting state of the cell,", "start": 1109.95, "duration": 2.98}, {"text": "this channel is closed.", "start": 1112.93, "duration": 2.09}, {"text": "And it's closed because\nof this red rod structure", "start": 1115.02, "duration": 3.45}, {"text": "that's positively charged.", "start": 1118.47, "duration": 1.98}, {"text": "That's a positively\ncharged alpha helix", "start": 1120.45, "duration": 2.79}, {"text": "that is a part of\nthis protein and is", "start": 1123.24, "duration": 2.19}, {"text": "embedded in the membrane.", "start": 1125.43, "duration": 3.09}, {"text": "But this alpha helix\nis positioned down", "start": 1128.52, "duration": 4.08}, {"text": "towards the cytoplasm, because\nit's positively charged.", "start": 1132.6, "duration": 3.42}, {"text": "And the cytosolic face\nof the plasma membrane", "start": 1136.02, "duration": 2.52}, {"text": "is negatively charged, OK?", "start": 1138.54, "duration": 2.58}, {"text": "And the confirmation\nof this protein", "start": 1141.12, "duration": 2.58}, {"text": "then depends on the charge\nacross this membrane.", "start": 1143.7, "duration": 4.11}, {"text": "Because when there\nis depolarization,", "start": 1147.81, "duration": 2.91}, {"text": "that shifts the position of this\nalpha helix, such that now it", "start": 1150.72, "duration": 4.35}, {"text": "shifts up towards the exterior\nface of the plasma membrane.", "start": 1155.07, "duration": 4.09}, {"text": "And that opens the channel,\nwhich lets sodium ions rush in,", "start": 1159.16, "duration": 3.88}, {"text": "OK?", "start": 1163.04, "duration": 1.71}, {"text": "Again, sodium ions here, they're\nalways rushing downstream.", "start": 1164.75, "duration": 4.12}, {"text": "They're concentration gradient.", "start": 1168.87, "duration": 3.42}, {"text": "So in this case, whether or not\nthis channel is open or closed", "start": 1172.29, "duration": 3.9}, {"text": "depends not on the\npresence of a ligand,", "start": 1176.19, "duration": 2.64}, {"text": "but on the membrane potential\nacross the plasma membrane.", "start": 1178.83, "duration": 4.5}, {"text": "So these voltage-gated\nsodium channels,", "start": 1183.33, "duration": 2.88}, {"text": "they're opened by\ndepolarization.", "start": 1186.21, "duration": 3.78}, {"text": "And then the question\nbecomes, if you", "start": 1201.31, "duration": 1.68}, {"text": "open these channels at the\nvery end of the neuron,", "start": 1202.99, "duration": 3.78}, {"text": "how do you get it such that\nthis electrical signal moves", "start": 1206.77, "duration": 3.78}, {"text": "unidirectionally\nalong the neuron?", "start": 1210.55, "duration": 3.39}, {"text": "So what leads to\nunidirectionality?", "start": 1213.94, "duration": 3.57}, {"text": "Who's been to a\nsporting event lately?", "start": 1225.3, "duration": 3.86}, {"text": "OK, good.", "start": 1229.16, "duration": 1.59}, {"text": "You guys know the wave?", "start": 1230.75, "duration": 2.94}, {"text": "So we're going to do the wave.", "start": 1233.69, "duration": 2.062}, {"text": "Once you to stand up,\nyou're going to be tired,", "start": 1235.752, "duration": 1.958}, {"text": "and you're going to have\nto sit down for a while.", "start": 1237.71, "duration": 2.73}, {"text": "I'm going to be a ligand--", "start": 1240.44, "duration": 2.22}, {"text": "I'm a ligand-gated\nsodium channel,", "start": 1242.66, "duration": 2.68}, {"text": "so I'm going to\nstart things off, OK?", "start": 1245.34, "duration": 3.75}, {"text": "You ready?", "start": 1249.09, "duration": 2.42}, {"text": "All right, here we go.", "start": 1251.51, "duration": 0.97}, {"text": "OK, that's basically\nan action potential.", "start": 1257.55, "duration": 4.17}, {"text": "So the way that this\nwas unidirectional", "start": 1261.72, "duration": 4.95}, {"text": "is once you stood up and did\nthe wave, you then sat down,", "start": 1266.67, "duration": 5.25}, {"text": "and you stopped doing anything.", "start": 1271.92, "duration": 3.6}, {"text": "And so these voltage-gated\nsodium channels", "start": 1275.52, "duration": 3.54}, {"text": "have a similar property.", "start": 1279.06, "duration": 1.02}, {"text": "If we look at the\nnext step in this,", "start": 1282.69, "duration": 2.79}, {"text": "the sodium channel is\nopened by depolarization.", "start": 1285.48, "duration": 3.68}, {"text": "And you see there's this ball\nof chain segment of the protein.", "start": 1289.16, "duration": 4.3}, {"text": "You see that yellow ball?", "start": 1293.46, "duration": 1.83}, {"text": "Once the sodium channel opens,\nafter about a millisecond,", "start": 1295.29, "duration": 3.87}, {"text": "that ball sticks in the\nchannel pore and blocks it, OK?", "start": 1299.16, "duration": 4.92}, {"text": "So these sodium channels\nopen to let in sodium ions,", "start": 1304.08, "duration": 4.14}, {"text": "but then they're\nimmediately inactivated", "start": 1308.22, "duration": 2.37}, {"text": "after about a millisecond, OK?", "start": 1310.59, "duration": 4.2}, {"text": "And so that enables\nunidirectionality.", "start": 1314.79, "duration": 5.04}, {"text": "So this is what I'll call\nvoltage-gated sodium channel", "start": 1319.83, "duration": 6.26}, {"text": "inactivation.", "start": 1326.09, "duration": 0.91}, {"text": "And how this\npromotes a traveling", "start": 1334.26, "duration": 2.34}, {"text": "wave of depolarization is\nthat if we consider an action", "start": 1336.6, "duration": 5.01}, {"text": "potential moving along this\naxon from left to right", "start": 1341.61, "duration": 4.06}, {"text": "and if the sodium\nchannels in the green zone", "start": 1345.67, "duration": 2.72}, {"text": "are currently open,\nit came from the left,", "start": 1348.39, "duration": 3.49}, {"text": "which means that all\nthe sodium channels", "start": 1351.88, "duration": 2.06}, {"text": "to the left of this green zone\nare going to be inactivated.", "start": 1353.94, "duration": 5.4}, {"text": "So because they're\ninactivated here,", "start": 1359.34, "duration": 2.25}, {"text": "there won't be\nfurther depolarization", "start": 1361.59, "duration": 2.34}, {"text": "going to the left,\nbut depolarization", "start": 1363.93, "duration": 2.64}, {"text": "will have to move to the right.", "start": 1366.57, "duration": 2.07}, {"text": "And you basically get\nthis traveling wave.", "start": 1368.64, "duration": 2.7}, {"text": "And it goes one\ndirection, because if it", "start": 1371.34, "duration": 2.61}, {"text": "came from somewhere, which it\nalways does, then where it just", "start": 1373.95, "duration": 3.96}, {"text": "was coming from,\nall those sodium", "start": 1377.91, "duration": 2.61}, {"text": "channels, the voltage-gated\nsodium channels", "start": 1380.52, "duration": 2.19}, {"text": "are going to be closed.", "start": 1382.71, "duration": 2.01}, {"text": "So this allows it to move\nin a single direction", "start": 1384.72, "duration": 3.27}, {"text": "along the neuron.", "start": 1387.99, "duration": 1.23}, {"text": "Also, once the action potential\ngets to the end of the neuron,", "start": 1389.22, "duration": 3.45}, {"text": "it doesn't reflect back the\nother way in the neuron.", "start": 1392.67, "duration": 2.89}, {"text": "This can only go one direction.", "start": 1395.56, "duration": 3.17}, {"text": "So this provides\nunidirectionality.", "start": 1398.73, "duration": 3.09}, {"text": "So it's this inactive\nor refractory period", "start": 1401.82, "duration": 6.75}, {"text": "of the voltage-gated\nsodium channel", "start": 1408.57, "duration": 2.49}, {"text": "which prevents the\naction potential", "start": 1411.06, "duration": 3.12}, {"text": "from moving backwards.", "start": 1414.18, "duration": 1.2}, {"text": "Now, if you look at these\naction potentials in the cell,", "start": 1419.2, "duration": 4.27}, {"text": "you see that they happen,\nbut you don't just", "start": 1423.47, "duration": 4.07}, {"text": "depolarize and stay depolarized.", "start": 1427.54, "duration": 2.61}, {"text": "The cell body depolarizes and\nthen repolarizes very rapidly.", "start": 1430.15, "duration": 4.68}, {"text": "So there's an oscillation.", "start": 1434.83, "duration": 2.31}, {"text": "So there has to be some way to\nterminate the action potential.", "start": 1437.14, "duration": 6.04}, {"text": "So there's a termination or\nrepolarization of the cell.", "start": 1443.18, "duration": 5.99}, {"text": "So there has to be a\nway for this nerve cell", "start": 1454.67, "duration": 2.42}, {"text": "to rapidly restore\nmembrane potential.", "start": 1457.09, "duration": 4.86}, {"text": "And I want you to think for\njust a couple of seconds", "start": 1461.95, "duration": 2.58}, {"text": "about what type of\nchannel might you open", "start": 1464.53, "duration": 3.0}, {"text": "to re-establish this polarity.", "start": 1467.53, "duration": 1.86}, {"text": "What ion do you need to flow\nfrom where to where in order", "start": 1473.67, "duration": 3.72}, {"text": "to get a net negative\ncharge on the inside?", "start": 1477.39, "duration": 2.85}, {"text": "Udo?", "start": 1484.26, "duration": 0.867}, {"text": "AUDIENCE: You need to\nmove the sodium ions", "start": 1485.127, "duration": 1.828}, {"text": "from the inside to the outside.", "start": 1486.955, "duration": 2.285}, {"text": "ADAM MARTIN: OK, you could\npump the sodium ions out,", "start": 1489.24, "duration": 3.03}, {"text": "and that's totally accurate.", "start": 1492.27, "duration": 2.19}, {"text": "So that's going to\nrequire moving sodium ions", "start": 1494.46, "duration": 2.97}, {"text": "up a concentration gradient,\nwhich is going to take energy", "start": 1497.43, "duration": 3.84}, {"text": "and is going to be slow.", "start": 1501.27, "duration": 1.68}, {"text": "So is there another option we\ncould take advantage of here", "start": 1502.95, "duration": 2.94}, {"text": "to repolarize?", "start": 1505.89, "duration": 1.38}, {"text": "Rachel?", "start": 1507.27, "duration": 1.38}, {"text": "AUDIENCE: Move the\npotassium ions.", "start": 1508.65, "duration": 2.19}, {"text": "ADAM MARTIN: So\nRachel has suggested", "start": 1510.84, "duration": 1.5}, {"text": "to moving the potassium\nions to the outside, which", "start": 1512.34, "duration": 4.86}, {"text": "is how this is done.", "start": 1517.2, "duration": 1.99}, {"text": "So remember, potassium is\nhigh in the cytoplasmic,", "start": 1519.19, "duration": 3.74}, {"text": "low on the exoplasm.", "start": 1522.93, "duration": 2.25}, {"text": "And therefore, if you have\na voltage-gated potassium", "start": 1525.18, "duration": 2.43}, {"text": "channel, that's going to cause\na rush of positive ions out", "start": 1527.61, "duration": 3.6}, {"text": "of the cell.", "start": 1531.21, "duration": 1.33}, {"text": "And that will be able to restore\nthe net negative potential", "start": 1532.54, "duration": 3.8}, {"text": "on the inside of the cell.", "start": 1536.34, "duration": 3.33}, {"text": "So this termination\nor repolarization", "start": 1539.67, "duration": 3.99}, {"text": "is the result of the opening\nof voltage gated, in this case,", "start": 1543.66, "duration": 5.73}, {"text": "not sodium channels,\nbut potassium channels.", "start": 1549.39, "duration": 4.72}, {"text": "When do you think these\nhave to open relative", "start": 1554.11, "duration": 2.0}, {"text": "to the sodium channel?", "start": 1556.11, "duration": 1.11}, {"text": "Should they open right\nwith the sodium channel?", "start": 1562.43, "duration": 2.91}, {"text": "Carmen's shaking her head no.", "start": 1565.34, "duration": 1.83}, {"text": "Do you want to\nexplain your logic?", "start": 1567.17, "duration": 3.442}, {"text": "AUDIENCE: Well, I mean, they\nboth carry the same charge,", "start": 1570.612, "duration": 2.39}, {"text": "so they wind up getting out\nat the same time [INAUDIBLE]..", "start": 1573.002, "duration": 3.828}, {"text": "ADAM MARTIN: Exactly.", "start": 1576.83, "duration": 1.95}, {"text": "So what Carmen said is if\nthey open simultaneously,", "start": 1578.78, "duration": 3.3}, {"text": "you have sodium flowing in.", "start": 1582.08, "duration": 2.07}, {"text": "You have potassium flowing out.", "start": 1584.15, "duration": 1.65}, {"text": "And that's not going to\nnecessarily change the charge.", "start": 1585.8, "duration": 3.96}, {"text": "So when would these have to open\nrelative to sodium channels?", "start": 1589.76, "duration": 3.75}, {"text": "Yeah, Carmen?", "start": 1597.34, "duration": 0.66}, {"text": "AUDIENCE: When it reaches\nthat potential [INAUDIBLE]..", "start": 1598.0, "duration": 3.1}, {"text": "ADAM MARTIN: So after\nit's depolarized, yeah.", "start": 1601.1, "duration": 3.05}, {"text": "So this has to be delayed\nrelative to the sodium", "start": 1604.15, "duration": 2.67}, {"text": "channels, OK?", "start": 1606.82, "duration": 1.65}, {"text": "So this has to be\ndelayed relative", "start": 1608.47, "duration": 4.62}, {"text": "to the voltage-gated\nsodium channels.", "start": 1613.09, "duration": 3.45}, {"text": "Because if you're thinking\nabout this traveling", "start": 1622.03, "duration": 2.04}, {"text": "wave of depolarization,\nthe depolarization", "start": 1624.07, "duration": 4.11}, {"text": "is going to be high where\nthe sodium channels are only", "start": 1628.18, "duration": 2.67}, {"text": "entering.", "start": 1630.85, "duration": 1.02}, {"text": "And then following\nthat, you would", "start": 1631.87, "duration": 1.83}, {"text": "have potassium ions\ngetting pumped out", "start": 1633.7, "duration": 2.31}, {"text": "and basically\nrepolarizing the cell.", "start": 1636.01, "duration": 3.27}, {"text": "Everyone see how you sort\nof get depolarization", "start": 1639.28, "duration": 3.84}, {"text": "with sodium rushing in,\nand then after that, you", "start": 1643.12, "duration": 2.64}, {"text": "repolarize with the potassium\ngetting pumped out, right?", "start": 1645.76, "duration": 4.53}, {"text": "So here, you have a spike,\nand you complete the cycle.", "start": 1650.29, "duration": 3.36}, {"text": "It can even get hyperpolarized,\nwhere it gets even more", "start": 1653.65, "duration": 2.76}, {"text": "negative than it normally does.", "start": 1656.41, "duration": 2.32}, {"text": "And then it eventually gets\nback to this resting potential", "start": 1658.73, "duration": 3.44}, {"text": "of around negative 60 or\nnegative 70 millivolts.", "start": 1662.17, "duration": 2.91}, {"text": "OK, so this has to happen fast.", "start": 1672.35, "duration": 2.62}, {"text": "And I want to tell you about one\nprocess or property of neurons", "start": 1674.97, "duration": 4.53}, {"text": "and another helpful\ncell that enables", "start": 1679.5, "duration": 2.61}, {"text": "this to go extremely fast.", "start": 1682.11, "duration": 3.57}, {"text": "And that is that there are\nthese glial cells in your body", "start": 1685.68, "duration": 4.26}, {"text": "and your brain that\nwrap around the axons", "start": 1689.94, "duration": 3.06}, {"text": "of the neurons and basically\nfunction like electrical tape", "start": 1693.0, "duration": 3.72}, {"text": "for neurons, OK?", "start": 1696.72, "duration": 2.1}, {"text": "So they are these--", "start": 1698.82, "duration": 2.72}, {"text": "there's electrical\ninsulation around the axons", "start": 1701.54, "duration": 10.78}, {"text": "of these neurons.", "start": 1712.32, "duration": 2.44}, {"text": "And this is provided by\nanother specialized cell", "start": 1714.76, "duration": 2.6}, {"text": "type called a glial cell.", "start": 1717.36, "duration": 2.47}, {"text": "So this is by a glial cell.", "start": 1719.83, "duration": 1.43}, {"text": "And here are two\nexamples of glial cells.", "start": 1727.63, "duration": 3.33}, {"text": "There are\noligodendrocytes-- and you", "start": 1730.96, "duration": 1.98}, {"text": "can see how the cell\nis extending processes", "start": 1732.94, "duration": 3.42}, {"text": "that wrap around the axons\nof these two neurons.", "start": 1736.36, "duration": 4.17}, {"text": "Here's a Schwann\ncell over here, which", "start": 1740.53, "duration": 2.46}, {"text": "again, wraps around the axon.", "start": 1742.99, "duration": 2.31}, {"text": "And these cells basically form\nwhat's called a myelin sheath.", "start": 1745.3, "duration": 7.12}, {"text": "So they form a myelin\nsheath around the axons.", "start": 1752.42, "duration": 4.39}, {"text": "And that insulates the\nplasma membrane of the axon", "start": 1756.81, "duration": 4.78}, {"text": "such that--", "start": 1761.59, "duration": 0.78}, {"text": "so here is an axon.", "start": 1765.17, "duration": 2.63}, {"text": "You have glial cells\nthat are wrapped around,", "start": 1767.8, "duration": 3.49}, {"text": "and it sort of forms\nlike beads on a string.", "start": 1771.29, "duration": 2.88}, {"text": "And so there are these gaps\nbetween the myelin sheath", "start": 1774.17, "duration": 4.16}, {"text": "that are known as\nthe nodes of Ranvier.", "start": 1778.33, "duration": 4.62}, {"text": "So there are these\nnodes of Ranvier, which", "start": 1782.95, "duration": 8.52}, {"text": "are gaps in the myelin sheath.", "start": 1791.47, "duration": 3.27}, {"text": "And these nodes perform\nan important function", "start": 1799.54, "duration": 2.46}, {"text": "for the neuron, because\nwhere the axon is wrapped,", "start": 1802.0, "duration": 3.72}, {"text": "the membrane is\nelectrically insulated.", "start": 1805.72, "duration": 3.48}, {"text": "And so the sodium ions--", "start": 1809.2, "duration": 2.73}, {"text": "or the sodium channels\nand potassium channels,", "start": 1811.93, "duration": 2.31}, {"text": "the voltage gated ones,\nlocalize to these nodes.", "start": 1814.24, "duration": 3.93}, {"text": "And when the action potential\nis traveling along the axon,", "start": 1818.17, "duration": 4.02}, {"text": "because these regions\nwhere the myelin sheath is", "start": 1822.19, "duration": 3.93}, {"text": "are electrically insulated,\nthe axon potential", "start": 1826.12, "duration": 3.48}, {"text": "doesn't just move continuously,\nbut jumps from node", "start": 1829.6, "duration": 3.27}, {"text": "to node, such that you are\njust opening the sodium", "start": 1832.87, "duration": 3.18}, {"text": "channels at these nodes.", "start": 1836.05, "duration": 1.65}, {"text": "And that allows the\naction potential", "start": 1837.7, "duration": 2.01}, {"text": "to travel about 100-fold\nfaster along the axon.", "start": 1839.71, "duration": 4.11}, {"text": "And that's what\nallows your neurons", "start": 1843.82, "duration": 1.65}, {"text": "to transmit these\nelectrical signals", "start": 1845.47, "duration": 1.95}, {"text": "from the base of your spine\nto your foot so rapidly.", "start": 1847.42, "duration": 2.4}, {"text": "So you get an increase in speed\nbecause the action potential", "start": 1853.32, "duration": 6.25}, {"text": "is jumping from node to node.", "start": 1859.57, "duration": 1.68}, {"text": "And one important\nreason to bring this up", "start": 1864.7, "duration": 2.91}, {"text": "is because there is an\nimportant human disease that", "start": 1867.61, "duration": 4.32}, {"text": "affects the electrical\ninsulation in the myelin sheath", "start": 1871.93, "duration": 3.33}, {"text": "here, and that's\nmultiple sclerosis.", "start": 1875.26, "duration": 2.88}, {"text": "So we're going to unpack\nmultiple sclerosis in a couple", "start": 1884.12, "duration": 2.66}, {"text": "lectures.", "start": 1886.78, "duration": 0.91}, {"text": "This is an autoimmune disorder.", "start": 1887.69, "duration": 2.183}, {"text": "And so we're going to talk about\nimmunity later in the semester,", "start": 1889.873, "duration": 2.667}, {"text": "and we'll talk about\nhow that happens.", "start": 1892.54, "duration": 2.68}, {"text": "But for now, I just\nwant to point out", "start": 1895.22, "duration": 1.67}, {"text": "that multiple sclerosis happens\nwhen the immune system attacks", "start": 1896.89, "duration": 3.72}, {"text": "this myelin sheath.", "start": 1900.61, "duration": 1.26}, {"text": "So in multiple sclerosis,\nthe myelin sheath is damaged.", "start": 1905.36, "duration": 3.17}, {"text": "And if you damage this\nelectrical insulation,", "start": 1911.8, "duration": 3.33}, {"text": "you greatly slow down\nthese action potentials,", "start": 1915.13, "duration": 3.6}, {"text": "and that has a\nsignificant impact", "start": 1918.73, "duration": 2.25}, {"text": "on nerve impulses in the brain\nand throughout the entire body.", "start": 1920.98, "duration": 5.04}, {"text": "And that's why\nmultiple sclerosis", "start": 1926.02, "duration": 1.74}, {"text": "is such a devastating disease.", "start": 1927.76, "duration": 1.35}, {"text": "All right, I'm going\nto start moving now", "start": 1933.34, "duration": 2.01}, {"text": "to consider more\nthan one neuron.", "start": 1935.35, "duration": 2.49}, {"text": "So until now, we've\njust talked about how", "start": 1937.84, "duration": 1.89}, {"text": "an electrical signal is sent\nalong the length of one cell.", "start": 1939.73, "duration": 4.01}, {"text": "And now we're going to start\nthinking about multiple neurons", "start": 1943.74, "duration": 2.5}, {"text": "and how they connect and how\nneurons integrate information", "start": 1946.24, "duration": 3.54}, {"text": "from multiple other neurons\nto decide whether or not", "start": 1949.78, "duration": 2.97}, {"text": "to send an action potential.", "start": 1952.75, "duration": 3.73}, {"text": "And so if we consider this\nconnection right here,", "start": 1956.48, "duration": 2.96}, {"text": "there's a synapse right here.", "start": 1959.44, "duration": 1.98}, {"text": "Here's a cell that's\nsending information", "start": 1961.42, "duration": 3.3}, {"text": "and a cell that is\nreceiving that information.", "start": 1964.72, "duration": 5.97}, {"text": "When we're considering\na synapse--", "start": 1970.69, "duration": 2.43}, {"text": "so if we consider\na synapse, there's", "start": 1973.12, "duration": 4.23}, {"text": "a cell that is sending\nthe signal, which", "start": 1977.35, "duration": 3.06}, {"text": "is called the presynapse.", "start": 1980.41, "duration": 1.61}, {"text": "This is the sender cell.", "start": 1985.6, "duration": 1.35}, {"text": "And there's a postsynaptic cell.", "start": 1990.44, "duration": 1.64}, {"text": "But you can have\nmore than one neuron", "start": 1999.01, "duration": 2.31}, {"text": "sending a signal to a neuron\nat a given time, right?", "start": 2001.32, "duration": 4.92}, {"text": "So here, you have\none neuron that's", "start": 2006.24, "duration": 2.18}, {"text": "sending a signal\nat this synapse,", "start": 2008.42, "duration": 2.8}, {"text": "but you might have another\nneuron sending a signal", "start": 2011.22, "duration": 2.94}, {"text": "to a synapse on this\npart of the cell.", "start": 2014.16, "duration": 2.46}, {"text": "And you could have another\nsignal coming in here.", "start": 2016.62, "duration": 3.3}, {"text": "And so this neuron\nwill then have", "start": 2019.92, "duration": 2.04}, {"text": "to decide whether or\nnot to fire an action", "start": 2021.96, "duration": 2.43}, {"text": "potential down its axon.", "start": 2024.39, "duration": 4.35}, {"text": "And the way that the\nneuron decides this", "start": 2028.74, "duration": 3.36}, {"text": "is to integrate the signals.", "start": 2032.1, "duration": 2.85}, {"text": "So there's a signal\nintegration process.", "start": 2034.95, "duration": 1.96}, {"text": "And what's important for signal\nintegration in a neuron is", "start": 2041.21, "duration": 3.8}, {"text": "whether or not the cell body--", "start": 2045.01, "duration": 2.67}, {"text": "whether the voltage increases\nabove a certain threshold", "start": 2047.68, "duration": 3.33}, {"text": "potential.", "start": 2051.01, "duration": 1.26}, {"text": "So if the cell body\ndoesn't increase--", "start": 2052.27, "duration": 2.61}, {"text": "if the voltage doesn't\nincrease above this potential,", "start": 2054.88, "duration": 3.279}, {"text": "there will be no\naction potential fired.", "start": 2058.159, "duration": 2.73}, {"text": "But if the voltage increases\nabove the threshold potential,", "start": 2060.889, "duration": 4.85}, {"text": "then it fires the\naction potential", "start": 2065.739, "duration": 2.101}, {"text": "and signals to a\ndownstream neuron", "start": 2067.84, "duration": 2.28}, {"text": "or muscle or another cell.", "start": 2070.12, "duration": 4.47}, {"text": "So here, it is the threshold\npotential in the cell body", "start": 2074.59, "duration": 14.43}, {"text": "that determines whether or\nnot an action potential is", "start": 2089.02, "duration": 2.73}, {"text": "sent down the axon.", "start": 2091.75, "duration": 0.9}, {"text": "And there are different\ntypes of signals", "start": 2095.59, "duration": 2.67}, {"text": "that nerve cells can send.", "start": 2098.26, "duration": 3.688}, {"text": "So there are different\ntypes of signals.", "start": 2101.948, "duration": 1.667}, {"text": "Signals can be excitatory,\nmeaning it will", "start": 2108.22, "duration": 3.42}, {"text": "tend to depolarize the neuron.", "start": 2111.64, "duration": 3.3}, {"text": "So there are excitatory signals,\nwhich result in depolarization.", "start": 2114.94, "duration": 10.17}, {"text": "For example, with\nserotonin, that", "start": 2127.72, "duration": 4.05}, {"text": "opens the sodium channel, and\nthat results in depolarization,", "start": 2131.77, "duration": 3.54}, {"text": "so that's an excitatory signal.", "start": 2135.31, "duration": 2.58}, {"text": "But there are other\ntypes of signals", "start": 2137.89, "duration": 2.7}, {"text": "that bind to different types of\nreceptors that are inhibitory.", "start": 2140.59, "duration": 3.87}, {"text": "What might be a type\nof receptor that", "start": 2147.61, "duration": 1.68}, {"text": "would inhibit this process of\nsending an action potential?", "start": 2149.29, "duration": 3.93}, {"text": "What might an\ninhibitory receptor", "start": 2158.62, "duration": 2.31}, {"text": "be to lower the chance that this\naction potential will be fired?", "start": 2160.93, "duration": 5.94}, {"text": "What if I told you\nit's an ion channel?", "start": 2169.75, "duration": 3.21}, {"text": "What ion would you\nexpect it might pass?", "start": 2172.96, "duration": 4.374}, {"text": "Udo?", "start": 2177.334, "duration": 1.496}, {"text": "AUDIENCE: Potassium.", "start": 2178.83, "duration": 1.252}, {"text": "ADAM MARTIN: Potassium.", "start": 2180.082, "duration": 0.958}, {"text": "Udo is exactly right, right?", "start": 2181.04, "duration": 2.42}, {"text": "If it passes\npotassium, then it's", "start": 2183.46, "duration": 2.19}, {"text": "going to make the\ninside more negative.", "start": 2185.65, "duration": 3.43}, {"text": "And that's what's known\nas hyperpolarization.", "start": 2189.08, "duration": 3.17}, {"text": "So receptors that result\nin hyperpolarization", "start": 2192.25, "duration": 3.81}, {"text": "would have an inhibitory\neffect on this process.", "start": 2196.06, "duration": 2.415}, {"text": "And remember, if\nyou're hyperpolarizing,", "start": 2205.3, "duration": 3.03}, {"text": "then you could cause this\nto actually go down and get", "start": 2208.33, "duration": 3.3}, {"text": "even farther away from this\nthreshold potential, right?", "start": 2211.63, "duration": 2.98}, {"text": "And if you have an\nactivating signal", "start": 2214.61, "duration": 1.94}, {"text": "and an inhibitory signal,\nthey might cancel out,", "start": 2216.55, "duration": 2.31}, {"text": "because one will depolarize and\nthe other will hyperpolarize.", "start": 2218.86, "duration": 4.05}, {"text": "So it's in this way a neuron\nis able to integrate signals", "start": 2222.91, "duration": 5.19}, {"text": "coming from different neurons.", "start": 2228.1, "duration": 1.62}, {"text": "And that influences\nwhether or not", "start": 2229.72, "duration": 2.1}, {"text": "it will send the signal\nto a downstream cell.", "start": 2231.82, "duration": 5.73}, {"text": "OK, so now we're\nfocusing on what", "start": 2237.55, "duration": 2.46}, {"text": "is the communication between\none neuron and another.", "start": 2240.01, "duration": 3.78}, {"text": "And this revolves\naround this thing", "start": 2243.79, "duration": 3.795}, {"text": "that's called the synapse,\nwhich is basically", "start": 2247.585, "duration": 1.875}, {"text": "the gap between the axon\nterminal of one neuron", "start": 2249.46, "duration": 4.14}, {"text": "and the dendrites of\na postsynaptic neuron.", "start": 2253.6, "duration": 2.755}, {"text": "And so the way that\nmultiple neurons communicate", "start": 2260.23, "duration": 3.36}, {"text": "with each other are\nthrough a type of signal", "start": 2263.59, "duration": 2.64}, {"text": "known as a neurotransmitter.", "start": 2266.23, "duration": 4.86}, {"text": "And this is what\ninitiates the signal.", "start": 2271.09, "duration": 3.13}, {"text": "So there's a signal initiation\nprocess at the synapse.", "start": 2274.22, "duration": 4.55}, {"text": "Initiation.", "start": 2278.77, "duration": 2.66}, {"text": "And this involves the\npresynaptic neuron", "start": 2281.43, "duration": 3.43}, {"text": "secreting a neurotransmitter.", "start": 2284.86, "duration": 3.31}, {"text": "So the signal, in this case,\nsignals between neurons", "start": 2288.17, "duration": 3.11}, {"text": "are called neurotransmitters.", "start": 2291.28, "duration": 3.7}, {"text": "And as you see on\nthe slide, these", "start": 2294.98, "duration": 3.11}, {"text": "are examples of\nneurotransmitters.", "start": 2298.09, "duration": 1.99}, {"text": "They're often derived\nfrom amino acids,", "start": 2300.08, "duration": 2.06}, {"text": "and so they're small molecules.", "start": 2302.14, "duration": 1.8}, {"text": "They're not the\nproteins that you often", "start": 2303.94, "duration": 2.34}, {"text": "see with receptor\ntyrosine kinase ligands.", "start": 2306.28, "duration": 3.18}, {"text": "This is a different\nclass of signal.", "start": 2309.46, "duration": 3.03}, {"text": "So one example is serotonin.", "start": 2312.49, "duration": 1.83}, {"text": "And if you look up at those,\nwe'll find serotonin here.", "start": 2318.08, "duration": 5.12}, {"text": "There it is.", "start": 2323.2, "duration": 0.51}, {"text": "Here, you can see it's a\nderivative of tryptophan.", "start": 2323.71, "duration": 3.48}, {"text": "So it's a small\nmolecule, and it's", "start": 2327.19, "duration": 2.34}, {"text": "able to bind to a receptor\non the postsynaptic cell", "start": 2329.53, "duration": 4.54}, {"text": "and induce depolarization.", "start": 2334.07, "duration": 1.58}, {"text": "And so neurons are-- the\nway that they communicate", "start": 2338.83, "duration": 3.94}, {"text": "is-- neurons are a case of\nwhere luck favors the prepared.", "start": 2342.77, "duration": 3.71}, {"text": "Neurons are totally prepared\nto send signals to each other.", "start": 2346.48, "duration": 4.86}, {"text": "They have everything ready\nto go when they get word", "start": 2351.34, "duration": 3.12}, {"text": "from upstream, and they're\nready to send signals", "start": 2354.46, "duration": 3.69}, {"text": "to the next cell.", "start": 2358.15, "duration": 2.1}, {"text": "And that's because if\nwe look at the synapse", "start": 2360.25, "duration": 3.39}, {"text": "prior to an action potential,\neverything is ready to go.", "start": 2363.64, "duration": 4.68}, {"text": "The cell has\nneurotransmitter, and it's", "start": 2368.32, "duration": 2.88}, {"text": "packaged in these vesicles,\nand it's tethered to the plasma", "start": 2371.2, "duration": 4.14}, {"text": "membrane, ready to be released.", "start": 2375.34, "duration": 3.63}, {"text": "So prior to the\naction potential,", "start": 2378.97, "duration": 2.03}, {"text": "there are vesicles filled\nwith neurotransmitter that are", "start": 2381.0, "duration": 3.4}, {"text": "docked at the plasma membrane.", "start": 2384.4, "duration": 1.71}, {"text": "I abbreviate plasma\nmembrane PM, just so I", "start": 2390.49, "duration": 2.85}, {"text": "don't have to write it out, OK?", "start": 2393.34, "duration": 2.1}, {"text": "So these contain\nneurotransmitter, right?", "start": 2395.44, "duration": 3.15}, {"text": "But you see in this\ndocked vesicle,", "start": 2398.59, "duration": 2.1}, {"text": "the neurotransmitter\nis in red, and it", "start": 2400.69, "duration": 2.49}, {"text": "can't get out if\nthat vesicle does not", "start": 2403.18, "duration": 2.16}, {"text": "fuse with the plasma membrane.", "start": 2405.34, "duration": 1.47}, {"text": "So these contain\nneurotransmitter.", "start": 2410.83, "duration": 2.369}, {"text": "But at this point, the\nvesicles haven't fused.", "start": 2422.49, "duration": 3.63}, {"text": "But the vesicle's not fused.", "start": 2426.12, "duration": 2.55}, {"text": "When should they fuse?", "start": 2438.258, "duration": 0.917}, {"text": "In this system of neuron\nsignaling to each other,", "start": 2441.89, "duration": 2.3}, {"text": "when should the vesicle fuse\nwith the plasma membrane?", "start": 2444.19, "duration": 6.54}, {"text": "What should trigger\nthe fusion process?", "start": 2450.73, "duration": 3.48}, {"text": "Yes, Miles?", "start": 2454.21, "duration": 1.256}, {"text": "AUDIENCE: So after\n[INAUDIBLE] axon", "start": 2455.466, "duration": 7.692}, {"text": "when it's time for\nthe [INAUDIBLE]", "start": 2463.158, "duration": 5.368}, {"text": "that's when the vesicles fuse.", "start": 2468.526, "duration": 2.439}, {"text": "ADAM MARTIN: Yeah, so\nMiles is exactly right.", "start": 2470.965, "duration": 1.875}, {"text": "If we consider my\ndiagram here, there's", "start": 2472.84, "duration": 4.23}, {"text": "an action potential\ntraveling along this axon.", "start": 2477.07, "duration": 3.39}, {"text": "When it gets to\nthe axon terminus,", "start": 2480.46, "duration": 2.49}, {"text": "that should be the\nsignal for these vesicles", "start": 2482.95, "duration": 3.06}, {"text": "to fuse to the plasma\nmembrane and to release", "start": 2486.01, "duration": 2.52}, {"text": "neurotransmitter.", "start": 2488.53, "duration": 2.46}, {"text": "So it's the arrival of the\naction potential, right?", "start": 2490.99, "duration": 2.97}, {"text": "So remember, in\nthis case, serotonin", "start": 2493.96, "duration": 2.79}, {"text": "is going to be in blue.", "start": 2496.75, "duration": 1.9}, {"text": "If serotonin is inside\nmy vesicle here,", "start": 2498.65, "duration": 3.16}, {"text": "it's going to need to exocytose.", "start": 2501.81, "duration": 2.08}, {"text": "And now the serotonin is\ngoing to be outside the cell,", "start": 2503.89, "duration": 4.62}, {"text": "ready to bind to the receptor.", "start": 2508.51, "duration": 1.71}, {"text": "All right, so as\nMiles pointed out,", "start": 2513.79, "duration": 2.95}, {"text": "you have an action potential.", "start": 2516.74, "duration": 1.73}, {"text": "The fusion should be triggered\nby the action potential.", "start": 2518.47, "duration": 2.94}, {"text": "In order to fuse,\nthere needs to be", "start": 2521.41, "duration": 1.74}, {"text": "some signal inside the cytoplasm\nto tell the vesicles to fuse.", "start": 2523.15, "duration": 4.74}, {"text": "That signal is increased\ncalcium ion concentration.", "start": 2527.89, "duration": 4.82}, {"text": "And then when\ncalcium concentration", "start": 2532.71, "duration": 2.23}, {"text": "increases in the\ncytoplasm, that triggers", "start": 2534.94, "duration": 2.76}, {"text": "the fusion of these vesicles.", "start": 2537.7, "duration": 1.23}, {"text": "And when you get fusion,\nthat's exocytosis,", "start": 2542.17, "duration": 3.03}, {"text": "and the serotonin is now\non the outside of the cell,", "start": 2545.2, "duration": 3.18}, {"text": "where it can travel across\nthe synaptic cleft and bind", "start": 2548.38, "duration": 3.54}, {"text": "to a receptor on the\npostsynaptic neuron.", "start": 2551.92, "duration": 3.42}, {"text": "So this fusion is when\nneurotransmitter is released.", "start": 2555.34, "duration": 3.195}, {"text": "Neurotransmitter\nis released here.", "start": 2563.59, "duration": 2.16}, {"text": "And the way that this increasing\ncalcium has to happen,", "start": 2572.24, "duration": 3.99}, {"text": "when the action potential\narrives at the axon terminus.", "start": 2576.23, "duration": 4.54}, {"text": "So when it arrives\nin the axon terminus,", "start": 2580.77, "duration": 2.3}, {"text": "there's depolarization\nof that part of the cell.", "start": 2583.07, "duration": 4.32}, {"text": "And so there's a\nspecial type of protein", "start": 2587.39, "duration": 2.43}, {"text": "called a voltage-gated\ncalcium channel.", "start": 2589.82, "duration": 4.86}, {"text": "All these channels are very\nselective for different ions.", "start": 2594.68, "duration": 3.19}, {"text": "So a voltage-gated\nsodium channel", "start": 2597.87, "duration": 2.6}, {"text": "isn't letting in all of\nthe ions outside the cell.", "start": 2600.47, "duration": 4.14}, {"text": "It's selective to sodium.", "start": 2604.61, "duration": 1.8}, {"text": "And this case, this\nvoltage-gated calcium channel", "start": 2606.41, "duration": 2.82}, {"text": "is just going to let in calcium.", "start": 2609.23, "duration": 2.31}, {"text": "And then there's a mechanism\nthat links calcium entry", "start": 2611.54, "duration": 2.97}, {"text": "to vesicle fusion.", "start": 2614.51, "duration": 2.19}, {"text": "And that's going\nto be shown here.", "start": 2616.7, "duration": 1.93}, {"text": "What you see on this\ndocked synaptic vesicle", "start": 2618.63, "duration": 2.75}, {"text": "is this calcium-binding\nprotein called synaptotagmin", "start": 2621.38, "duration": 3.93}, {"text": "that's present on the vesicle.", "start": 2625.31, "duration": 2.07}, {"text": "And so when calcium\ngoes into the cytoplasm,", "start": 2627.38, "duration": 3.33}, {"text": "that protein binds to calcium,\nand it activates the fusion", "start": 2630.71, "duration": 4.35}, {"text": "machinery such that the plasma\nmembrane of the vesicle fuses--", "start": 2635.06, "duration": 4.29}, {"text": "or the membrane of the vesicle\nfuses with the plasma membrane", "start": 2639.35, "duration": 3.3}, {"text": "of the cell, thus releasing\nthe neurotransmitter", "start": 2642.65, "duration": 3.03}, {"text": "into the synaptic cleft.", "start": 2645.68, "duration": 1.29}, {"text": "So this is what\nstarts the signal.", "start": 2652.26, "duration": 2.7}, {"text": "Now, you probably know that\nthese neurons are not active", "start": 2654.96, "duration": 4.47}, {"text": "or on all the time.", "start": 2659.43, "duration": 1.4}, {"text": "So something has to\nterminate the signal, usually", "start": 2660.83, "duration": 3.19}, {"text": "quite rapidly.", "start": 2664.02, "duration": 1.26}, {"text": "So now I want to\ntalk about that.", "start": 2665.28, "duration": 1.5}, {"text": "So like all signaling\npathways, signaling", "start": 2669.66, "duration": 3.21}, {"text": "is useless if you\ncan just turn it on.", "start": 2672.87, "duration": 2.13}, {"text": "You have to be able to\ntoggle it on and off in order", "start": 2675.0, "duration": 3.18}, {"text": "for biological systems to\nfunction properly, right?", "start": 2678.18, "duration": 3.06}, {"text": "And that's the\ncase with neurons.", "start": 2681.24, "duration": 1.65}, {"text": "If you just turn\non a neuron and you", "start": 2682.89, "duration": 2.1}, {"text": "don't have a way to\nturn it back off again,", "start": 2684.99, "duration": 1.8}, {"text": "then that's pretty useless.", "start": 2686.79, "duration": 1.125}, {"text": "And so we have to have a\nway to turn off the signal.", "start": 2690.48, "duration": 3.66}, {"text": "And if we consider\nthe synapse, this", "start": 2694.14, "duration": 2.19}, {"text": "is the presynaptic neuron here.", "start": 2696.33, "duration": 2.76}, {"text": "I'm going to draw a\npostsynaptic neuron here.", "start": 2699.09, "duration": 2.91}, {"text": "And neurotransmitter is released\nby the presynaptic neuron", "start": 2705.54, "duration": 4.85}, {"text": "to the postsynaptic neuron here.", "start": 2710.39, "duration": 3.42}, {"text": "Neurotransmitter is released\ninto the synaptic cleft.", "start": 2713.81, "duration": 5.86}, {"text": "So the sort of\nextracellular region", "start": 2719.67, "duration": 4.02}, {"text": "between these two neurons is\ncalled the synaptic cleft.", "start": 2723.69, "duration": 3.585}, {"text": "So now the cell just\ndumped a whole boatload", "start": 2733.72, "duration": 3.05}, {"text": "of neurotransmitter into\nthe synaptic cleft, right?", "start": 2736.77, "duration": 2.88}, {"text": "How is it going\nto turn this off?", "start": 2739.65, "duration": 2.0}, {"text": "What does it have to do?", "start": 2741.65, "duration": 1.0}, {"text": "Yeah, Stephen?", "start": 2748.61, "duration": 0.928}, {"text": "AUDIENCE: It could absorb the--", "start": 2749.538, "duration": 1.712}, {"text": "take back in the [INAUDIBLE].", "start": 2751.25, "duration": 3.958}, {"text": "ADAM MARTIN: Stephen's\nexactly right.", "start": 2755.208, "duration": 1.542}, {"text": "What Stephen\nsuggested is, is there", "start": 2756.75, "duration": 1.71}, {"text": "a way for the presynaptic\nneuron to reabsorb", "start": 2758.46, "duration": 3.9}, {"text": "this neurotransmitter\nand, thus, recycle it?", "start": 2762.36, "duration": 2.31}, {"text": "So it could either\nreabsorb it or degrade", "start": 2770.43, "duration": 2.13}, {"text": "the neurotransmitter.", "start": 2772.56, "duration": 2.31}, {"text": "Different process for\ndifferent neurotransmitters.", "start": 2774.87, "duration": 2.64}, {"text": "For serotonin,\nthere are channels", "start": 2777.51, "duration": 3.3}, {"text": "that are present in\nthe plasma membrane,", "start": 2780.81, "duration": 3.18}, {"text": "and these mediate\nreuptake of the serotonin.", "start": 2783.99, "duration": 5.46}, {"text": "So you have channels\nthat are basically--", "start": 2789.45, "duration": 2.07}, {"text": "after the neurotransmitter\nis released,", "start": 2791.52, "duration": 2.34}, {"text": "it sucks the neurotransmitter\nback into the presynaptic cell", "start": 2793.86, "duration": 3.81}, {"text": "such that it can then reuse\nthe neurotransmitter later on.", "start": 2797.67, "duration": 3.84}, {"text": "And so this process of reuptake\nhighlights a very important", "start": 2804.66, "duration": 8.91}, {"text": "process that's been\nutilized by drug companies", "start": 2813.57, "duration": 3.12}, {"text": "to create antidepressants.", "start": 2816.69, "duration": 3.51}, {"text": "So antidepressants\nlike Prozac and Zoloft", "start": 2820.2, "duration": 4.05}, {"text": "affect this reuptake process.", "start": 2824.25, "duration": 2.37}, {"text": "And what that does is it\nkeeps the neurotransmitter", "start": 2826.62, "duration": 3.3}, {"text": "in the synaptic cleft\nfor longer, such", "start": 2829.92, "duration": 2.78}, {"text": "that it enhances the signaling.", "start": 2832.7, "duration": 2.29}, {"text": "And so the idea\nbehind these drugs", "start": 2834.99, "duration": 2.43}, {"text": "is that if you are\nsuffering depression", "start": 2837.42, "duration": 2.52}, {"text": "from a lack of\nserotonin, then you", "start": 2839.94, "duration": 2.85}, {"text": "can rescue that by\npreventing the rapid reuptake", "start": 2842.79, "duration": 5.04}, {"text": "of the neurotransmitter\ninto the cell", "start": 2847.83, "duration": 2.49}, {"text": "after the synapse is stimulated\nand the neurotransmitter", "start": 2850.32, "duration": 3.85}, {"text": "is released.", "start": 2854.17, "duration": 0.5}, {"text": "And so Prozac, Zoloft,\nthese are a class", "start": 2859.01, "duration": 7.23}, {"text": "of drugs that are known as\nselective serotonin reuptake", "start": 2866.24, "duration": 7.26}, {"text": "inhibitors.", "start": 2873.5, "duration": 0.72}, {"text": "It's kind of a mouthful.", "start": 2880.6, "duration": 1.0}, {"text": "This is abbreviated SSRIs.", "start": 2884.36, "duration": 1.5}, {"text": "But the way they function is\nto leave the neurotransmitter", "start": 2888.87, "duration": 3.35}, {"text": "in the synaptic\ncleft for longer so", "start": 2892.22, "duration": 1.92}, {"text": "that you enhance\nsignaling, even if you", "start": 2894.14, "duration": 2.28}, {"text": "have low levels of the\nneurotransmitter to begin with.", "start": 2896.42, "duration": 3.33}, {"text": "I also want to point out that\nif we look at this diagram here,", "start": 2909.0, "duration": 3.71}, {"text": "the synaptic vesicle\nfuses, and then this", "start": 2912.71, "duration": 3.36}, {"text": "releases the neurotransmitter.", "start": 2916.07, "duration": 1.8}, {"text": "But all the machinery\non this vesicle", "start": 2917.87, "duration": 2.22}, {"text": "is recycled by endocytosis such\nthat it can be reused again,", "start": 2920.09, "duration": 4.38}, {"text": "OK?", "start": 2924.47, "duration": 0.75}, {"text": "So cells are really\ngood at recycling stuff.", "start": 2925.22, "duration": 2.67}, {"text": "If this is sort of the membrane,\nyou endocytose and then", "start": 2927.89, "duration": 3.96}, {"text": "you can use it\nagain later on, OK?", "start": 2931.85, "duration": 4.91}, {"text": "And so there's recycling not\nonly of the neurotransmitter,", "start": 2936.76, "duration": 3.7}, {"text": "but also all of the machinery\non the synaptic vesicles", "start": 2940.46, "duration": 3.63}, {"text": "that are responsible\nfor the fusion event.", "start": 2944.09, "duration": 4.23}, {"text": "All right, now I want to\nend by just telling you", "start": 2948.32, "duration": 2.34}, {"text": "how this experiment\nworks, where we're", "start": 2950.66, "duration": 3.57}, {"text": "able to activate specific\nneurons in a brain", "start": 2954.23, "duration": 3.63}, {"text": "and that leads to the\nanimal sort of waking up.", "start": 2957.86, "duration": 5.82}, {"text": "So in a normal neuron--", "start": 2963.68, "duration": 1.8}, {"text": "so this is the last\npart, optogenetics.", "start": 2965.48, "duration": 3.27}, {"text": "And I'm going to go\nthrough this very fast.", "start": 2968.75, "duration": 3.36}, {"text": "But normally, you need\na neurotransmitter", "start": 2972.11, "duration": 2.4}, {"text": "to induce depolarization.", "start": 2974.51, "duration": 2.34}, {"text": "But what optogenetics\nis, is an approach", "start": 2976.85, "duration": 2.76}, {"text": "to control the activity\nof a cell with light, OK?", "start": 2979.61, "duration": 4.53}, {"text": "So in this case,\nwe're going to have", "start": 2984.14, "duration": 2.16}, {"text": "light inducing depolarization.", "start": 2986.3, "duration": 2.58}, {"text": "And the way this is done is\nthere's a protein discovered", "start": 2992.84, "duration": 2.67}, {"text": "from photosynthetic algae\nthat's responsive to light,", "start": 2995.51, "duration": 5.29}, {"text": "and it is a sodium channel.", "start": 3000.8, "duration": 2.78}, {"text": "And this protein is called\nchannelrhodopsin, specifically", "start": 3003.58, "duration": 8.82}, {"text": "ChR2.", "start": 3012.4, "duration": 2.19}, {"text": "And this is a light-sensitive\nprotein where light", "start": 3014.59, "duration": 3.96}, {"text": "induces sodium channel opening.", "start": 3018.55, "duration": 2.25}, {"text": "So that's going to\ndepolarize the cell.", "start": 3024.67, "duration": 1.845}, {"text": "And what you can do is if\nyou have a gene that you know", "start": 3029.8, "duration": 3.69}, {"text": "is specifically expressed\nin a certain type of neuron,", "start": 3033.49, "duration": 3.57}, {"text": "you can take the promoter and\nenhancer region of that gene", "start": 3037.06, "duration": 3.81}, {"text": "and hook it up to this single\ncomponent, channelrhodopsin,", "start": 3040.87, "duration": 4.05}, {"text": "that open reading frame, using\nrecombinant DNA technology.", "start": 3044.92, "duration": 5.05}, {"text": "And if that's expressed\nspecifically in the neurons", "start": 3049.97, "duration": 2.48}, {"text": "that you're trying\nto test, you can then", "start": 3052.45, "duration": 1.89}, {"text": "shine a light into the brain\nof the organism and activate,", "start": 3054.34, "duration": 3.75}, {"text": "specifically, this\ntype of neuron.", "start": 3058.09, "duration": 2.46}, {"text": "And that allows you to test\nthe function of the neuron", "start": 3060.55, "duration": 3.51}, {"text": "in the behavior of an organism.", "start": 3064.06, "duration": 2.26}, {"text": "So, in this case,\nthis mouse, the light", "start": 3066.32, "duration": 2.39}, {"text": "is shined into its\nbrain, and they're", "start": 3068.71, "duration": 1.95}, {"text": "testing a specific\ntype of neuron", "start": 3070.66, "duration": 2.88}, {"text": "that is involved in arousal\nof the mouse, and it wakes up.", "start": 3073.54, "duration": 4.68}, {"text": "Oh, it's not playing.", "start": 3078.22, "duration": 2.11}, {"text": "So here, this is the\nbrain activity on the top,", "start": 3080.33, "duration": 5.69}, {"text": "and the muscle\nactivity on the bottom.", "start": 3086.02, "duration": 2.95}, {"text": "So you're going to see light.", "start": 3088.97, "duration": 1.37}, {"text": "There's the light.", "start": 3090.34, "duration": 0.75}, {"text": "You see it?", "start": 3091.09, "duration": 0.5}, {"text": "Light going into the brain.", "start": 3091.59, "duration": 3.29}, {"text": "They induce light at that\nfrequency for a while.", "start": 3094.88, "duration": 4.05}, {"text": "And then they're\ngoing to wait and see", "start": 3098.93, "duration": 2.96}, {"text": "when the mouse wakes up.", "start": 3101.89, "duration": 1.26}, {"text": "And it's going to\nwake up right now.", "start": 3103.15, "duration": 2.957}, {"text": "There it goes.", "start": 3106.107, "duration": 0.583}, {"text": "It woke up.", "start": 3106.69, "duration": 0.51}, {"text": "You see now its muscle\nactivity is going, OK?", "start": 3107.2, "duration": 3.03}, {"text": "So you can test the function\nof specific nerve cells", "start": 3110.23, "duration": 2.85}, {"text": "using this approach,\nand it's because you", "start": 3113.08, "duration": 2.4}, {"text": "have a light-sensitive\nsodium channel.", "start": 3115.48, "duration": 2.35}, {"text": "So I'm done for today.", "start": 3117.83, "duration": 1.05}, {"text": "Have a great weekend.", "start": 3118.88, "duration": 1.11}, {"text": "I will see you on Monday.", "start": 3119.99, "duration": 2.17}]
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+[{"text": "PROFESSOR: OK.", "start": 16.42, "duration": 0.6}, {"text": "Let's get going here.", "start": 17.02, "duration": 2.56}, {"text": "So this week I'll be talking\nabout bacteria and viruses.", "start": 19.58, "duration": 3.83}, {"text": "And these are really\nsignificant topics,", "start": 23.41, "duration": 2.97}, {"text": "because I think it's\nsomething that we often", "start": 26.38, "duration": 2.88}, {"text": "don't think about the\nmagnitude of the problems", "start": 29.26, "duration": 2.969}, {"text": "and what kind of crises\nwe're approaching", "start": 32.229, "duration": 3.361}, {"text": "with respect to the\ntherapeutic treatment", "start": 35.59, "duration": 2.16}, {"text": "of infectious disease.", "start": 37.75, "duration": 1.502}, {"text": "So what I want to try\nand get home to you", "start": 39.252, "duration": 1.708}, {"text": "this week is the variety\nof different microorganisms", "start": 40.96, "duration": 4.44}, {"text": "that threaten our\nhealth, and just", "start": 45.4, "duration": 3.09}, {"text": "talk to you about\nthe sorts of issues", "start": 48.49, "duration": 1.95}, {"text": "that are really prominent in\nthe news concerning resistance", "start": 50.44, "duration": 4.08}, {"text": "to therapeutic agents.", "start": 54.52, "duration": 1.65}, {"text": "But in order to do that, we've\ngot to meet some bacteria,", "start": 56.17, "duration": 2.83}, {"text": "meet some viruses,\nand understand", "start": 59.0, "duration": 2.81}, {"text": "that some of their\nlifestyles, their mechanisms,", "start": 61.81, "duration": 3.179}, {"text": "so that we can understand\nwhat kinds of agents", "start": 64.989, "duration": 3.901}, {"text": "are used and developed to try\nto mitigate these diseases,", "start": 68.89, "duration": 3.9}, {"text": "because it's only through\na molecular mechanistic", "start": 72.79, "duration": 2.4}, {"text": "understanding of the life\ncycles of viruses and bacteria", "start": 75.19, "duration": 4.11}, {"text": "that we can understand how many\nof these therapeutic agents", "start": 79.3, "duration": 4.11}, {"text": "work and what may be happening\nin resistance development.", "start": 83.41, "duration": 3.04}, {"text": "Now I find this particular\nslide a little daunting,", "start": 86.45, "duration": 5.96}, {"text": "but I want to point out to you\nthat it concerns the world's", "start": 92.41, "duration": 3.36}, {"text": "deadliest animals.", "start": 95.77, "duration": 1.68}, {"text": "So we worry a lot about\ntigers, and sharks,", "start": 97.45, "duration": 3.21}, {"text": "and things like that,\nnasty poisonous snakes,", "start": 100.66, "duration": 4.59}, {"text": "bites from dogs with\nrabies, and so on.", "start": 105.25, "duration": 3.3}, {"text": "I'm going to leave this black\nbar here, sort of unmentioned.", "start": 108.55, "duration": 3.48}, {"text": "I don't know what year this is,\nbut if we talk about daunting,", "start": 112.03, "duration": 2.73}, {"text": "that's pretty serious.", "start": 114.76, "duration": 1.38}, {"text": "And then the biggest killer on\nthis screen is the mosquito.", "start": 116.14, "duration": 4.08}, {"text": "But it isn't actually\nthe mosquito,", "start": 120.22, "duration": 2.34}, {"text": "it's the protozoal\nmicroorganisms", "start": 122.56, "duration": 2.94}, {"text": "that the mosquito carries\nfrom one person to another", "start": 125.5, "duration": 3.539}, {"text": "that really make that such\na serious consideration.", "start": 129.039, "duration": 5.911}, {"text": "But what's not here are all\nthe bacteria and viruses that", "start": 134.95, "duration": 4.23}, {"text": "actually are far more serious.", "start": 139.18, "duration": 2.6}, {"text": "And the numbers\non the next stage", "start": 141.78, "duration": 1.45}, {"text": "will show you just quite how\nshocking these numbers are.", "start": 143.23, "duration": 4.87}, {"text": "If you're interested\nin infectious disease", "start": 148.1, "duration": 3.26}, {"text": "as a field, because I think\nanyone going towards MD,", "start": 151.36, "duration": 5.25}, {"text": "MD/PhD infectious\ndiseases, it really", "start": 156.61, "duration": 3.015}, {"text": "is a critical area that we\nhave to get to grips with.", "start": 159.625, "duration": 3.315}, {"text": "There are not enough\nvaccines in the world.", "start": 162.94, "duration": 2.74}, {"text": "There is not enough\ntreatment with a very microbe", "start": 165.68, "duration": 4.22}, {"text": "specific anti-infective agents.", "start": 169.9, "duration": 3.74}, {"text": "So I encourage you\nto look at the CDC.", "start": 173.64, "duration": 3.563}, {"text": "There's a few other\nplaces where there's", "start": 177.203, "duration": 1.667}, {"text": "loads of information collated,\nsuch as the NIAID, which", "start": 178.87, "duration": 4.86}, {"text": "is the NIH Center for\nInfectious Disease,", "start": 183.73, "duration": 3.27}, {"text": "and the World\nHealth Organization.", "start": 187.0, "duration": 1.71}, {"text": "So there's lots of places\nwhere you can find stuff out.", "start": 188.71, "duration": 3.64}, {"text": "So what we're going to be\ntalking about in the next three", "start": 192.35, "duration": 2.42}, {"text": "classes are our smallest\nenemies, things like bacteria,", "start": 194.77, "duration": 5.94}, {"text": "fungal infections from things\nlike yeast or Aspergillus,", "start": 200.71, "duration": 4.26}, {"text": "which would cause candida\nand aspergillosis.", "start": 204.97, "duration": 3.81}, {"text": "Protozoal disease\nwe won't mention,", "start": 208.78, "duration": 2.59}, {"text": "but those are the\ntypes of diseases", "start": 211.37, "duration": 1.64}, {"text": "that are carried by things\nlike ticks, mosquitoes,", "start": 213.01, "duration": 4.53}, {"text": "tsetse flies.", "start": 217.54, "duration": 1.98}, {"text": "We think of those as\nthe infectious agent,", "start": 219.52, "duration": 2.47}, {"text": "but it's really what those\norganisms carry and cause", "start": 221.99, "duration": 4.64}, {"text": "the spread of disease\nthat's important there.", "start": 226.63, "duration": 2.43}, {"text": "And we won't either talk\nabout prion diseases, which", "start": 229.06, "duration": 3.36}, {"text": "are the diseases\nthat don't involve", "start": 232.42, "duration": 2.67}, {"text": "an infectious\nmicroorganism, but are", "start": 235.09, "duration": 2.13}, {"text": "believed to be spread\nfrom protein to protein", "start": 237.22, "duration": 3.48}, {"text": "through the nucleation of new\nprions from existing prions.", "start": 240.7, "duration": 4.38}, {"text": "What we'll focus on\nin the first class", "start": 245.08, "duration": 2.82}, {"text": "is bacteria and in the\nother two on viruses,", "start": 247.9, "duration": 4.89}, {"text": "with an eye to\nlooking at antibiotics", "start": 252.79, "duration": 2.76}, {"text": "and antiviral agents, how they\nwork, where they go wrong.", "start": 255.55, "duration": 4.18}, {"text": "And this is where the\nnumbers get fairly shocking.", "start": 259.73, "duration": 2.39}, {"text": "So for example,\nbacterial infections", "start": 262.12, "duration": 3.09}, {"text": "of the lower respiratory tract,\nthat's deep in the lungs,", "start": 265.21, "duration": 4.11}, {"text": "cause 4 million deaths a year.", "start": 269.32, "duration": 2.01}, {"text": "Think back to the numbers you\njust saw on that first slide.", "start": 271.33, "duration": 4.2}, {"text": "These are things like\nstrep pneumoniae,", "start": 275.53, "duration": 3.81}, {"text": "Klebsiella pneumoniae.", "start": 279.34, "duration": 1.8}, {"text": "They're called pneumonias\nbecause they're", "start": 281.14, "duration": 1.83}, {"text": "infectious diseases of the\nlung, but the organisms", "start": 282.97, "duration": 3.18}, {"text": "that cause them are of the\nStreptomyces, and Klebsiella,", "start": 286.15, "duration": 4.5}, {"text": "and Staphylococcus\naureus specifically.", "start": 290.65, "duration": 3.3}, {"text": "But there are others that\ncause lung infections and lower", "start": 293.95, "duration": 3.87}, {"text": "respiratory disease.", "start": 297.82, "duration": 2.02}, {"text": "These are particularly\ntroublesome in areas", "start": 299.84, "duration": 3.74}, {"text": "where the atmosphere is bad.", "start": 303.58, "duration": 2.94}, {"text": "In big cities where there's a\nlot of insult from emissions", "start": 306.52, "duration": 5.73}, {"text": "and such that make\nthe lungs weaker,", "start": 312.25, "duration": 2.22}, {"text": "then these sorts of\norganisms can really", "start": 314.47, "duration": 2.5}, {"text": "take a hold more readily,\nso they are more serious.", "start": 316.97, "duration": 4.45}, {"text": "There are many,\nmany microorganisms", "start": 321.42, "duration": 2.09}, {"text": "that cause pneumonias.", "start": 323.51, "duration": 2.14}, {"text": "And sometimes it's\na real problem", "start": 325.65, "duration": 1.85}, {"text": "to track down the precise\nmicroorganism, which", "start": 327.5, "duration": 3.87}, {"text": "makes the issue of treatment\nreally difficult, really", "start": 331.37, "duration": 4.17}, {"text": "challenging.", "start": 335.54, "duration": 1.05}, {"text": "So I'm going to talk in a minute\nabout absolute identification", "start": 336.59, "duration": 3.57}, {"text": "of infectious agents, so we can\ndo better jobs of specifically", "start": 340.16, "duration": 3.93}, {"text": "targeting the causative agents.", "start": 344.09, "duration": 3.32}, {"text": "Diarrheal disease--\n2 million deaths.", "start": 347.41, "duration": 3.25}, {"text": "These are organisms like\nCampylobacter jejuni", "start": 350.66, "duration": 2.85}, {"text": "and Salmonella enterica.", "start": 353.51, "duration": 2.16}, {"text": "We tend to have these\ncrises, because romaine my", "start": 355.67, "duration": 7.11}, {"text": "is contaminated with infection.", "start": 362.78, "duration": 3.28}, {"text": "There are very few deaths\nin the developed world.", "start": 366.06, "duration": 3.27}, {"text": "We get down to\nthat very quickly,", "start": 369.33, "duration": 2.51}, {"text": "say stop eating Romaine\nlettuce until we figure out", "start": 371.84, "duration": 2.94}, {"text": "what's going on here--", "start": 374.78, "duration": 1.53}, {"text": "very, very few.", "start": 376.31, "duration": 1.42}, {"text": "But once again, in\nthe developing world,", "start": 377.73, "duration": 2.24}, {"text": "these can run rampant.", "start": 379.97, "duration": 1.8}, {"text": "And they can grab small\nchildren and older people who", "start": 381.77, "duration": 3.48}, {"text": "are already compromised,\nalready a little bit not quite", "start": 385.25, "duration": 3.96}, {"text": "with strong immune systems,\nand people generally", "start": 389.21, "duration": 4.05}, {"text": "die of dehydration, because\nthese diseases really", "start": 393.26, "duration": 3.36}, {"text": "hit the GI tract.", "start": 396.62, "duration": 1.32}, {"text": "It causes leaking us in the\nGI tract and really, really", "start": 397.94, "duration": 3.3}, {"text": "serious diarrheal disease.", "start": 401.24, "duration": 1.63}, {"text": "So those are the bad boys there.", "start": 402.87, "duration": 1.75}, {"text": "But once again, there\nare many others.", "start": 404.62, "duration": 3.04}, {"text": "Tuberculosis is yet\nanother really serious", "start": 407.66, "duration": 4.32}, {"text": "infectious disease caused by\nMycobacterium tuberculosis,", "start": 411.98, "duration": 4.62}, {"text": "that's the main one of the\nmycobacteria that is a threat.", "start": 416.6, "duration": 6.26}, {"text": "It used to be called\nconsumption in the old days,", "start": 422.86, "duration": 3.65}, {"text": "because people almost looked\nconsumed by the disease.", "start": 426.51, "duration": 4.13}, {"text": "They would just get\nthinner and thinner.", "start": 430.64, "duration": 2.91}, {"text": "Literally it was\na wasting disease.", "start": 433.55, "duration": 2.64}, {"text": "People would be sent up into\nthe mountains of Switzerland", "start": 436.19, "duration": 2.97}, {"text": "to try to recover\nfrom consumption,", "start": 439.16, "duration": 2.7}, {"text": "to where the air is\nclearer and cleaner,", "start": 441.86, "duration": 3.0}, {"text": "and maybe hope that\nthey can recuperate.", "start": 444.86, "duration": 2.55}, {"text": "But TB-- look at these numbers.", "start": 447.41, "duration": 3.0}, {"text": "In 2015 there were almost\n10 million new cases.", "start": 450.41, "duration": 4.23}, {"text": "There are about 1.2\nmillion deaths from TB.", "start": 454.64, "duration": 4.31}, {"text": "A serious situation with\nTB is that it's often", "start": 458.95, "duration": 3.85}, {"text": "found co-infecting with the\nHIV virus, where you just", "start": 462.8, "duration": 4.08}, {"text": "can't fight the TB.", "start": 466.88, "duration": 1.32}, {"text": "So eventually, if you're\ninfected with the HIV virus,", "start": 468.2, "duration": 4.23}, {"text": "it's the TB that gets you\ndue to the weakening caused", "start": 472.43, "duration": 4.2}, {"text": "by the infection with TB.", "start": 476.63, "duration": 1.95}, {"text": "So these numbers are\nshocking in light", "start": 478.58, "duration": 2.13}, {"text": "of the numbers I showed you\non the previous slide, right.", "start": 480.71, "duration": 2.94}, {"text": "Look at these numbers if you go\nto snakes and things like that.", "start": 483.65, "duration": 4.56}, {"text": "They're meaningless\nnumbers compared", "start": 488.21, "duration": 2.22}, {"text": "to infectious diseases.", "start": 490.43, "duration": 3.45}, {"text": "So now, and I'm going to talk to\nyou about the origins of this,", "start": 493.88, "duration": 8.28}, {"text": "many, many infectious\nagents that we thought we", "start": 502.16, "duration": 4.2}, {"text": "had conquered--", "start": 506.36, "duration": 1.32}, {"text": "we thought we could\ntake care of it.", "start": 507.68, "duration": 1.5}, {"text": "You just take this course of\nantibiotics and you're off,", "start": 509.18, "duration": 3.824}, {"text": "you're set.", "start": 513.004, "duration": 1.096}, {"text": "But now, because of the\nrapid mutation rates", "start": 514.1, "duration": 3.78}, {"text": "in bacteria and viruses,\ncertain pathogens", "start": 517.88, "duration": 3.69}, {"text": "have completely\nworked out mechanisms", "start": 521.57, "duration": 2.85}, {"text": "to escape therapeutic agent.", "start": 524.42, "duration": 2.1}, {"text": "And I'm going to talk to\nyou about those mechanisms", "start": 526.52, "duration": 2.16}, {"text": "towards the end of this class.", "start": 528.68, "duration": 2.01}, {"text": "So basically you can\ndose a person one day", "start": 530.69, "duration": 3.09}, {"text": "with a normal dose of\nan antibiotic agent,", "start": 533.78, "duration": 2.97}, {"text": "and then 10 months later\nthat normal dose or 10 times", "start": 536.75, "duration": 3.87}, {"text": "or 100 times that\ndose stops working.", "start": 540.62, "duration": 3.12}, {"text": "Why is that?", "start": 543.74, "duration": 1.2}, {"text": "It's due to resistance\nacquisition due to rapid cell", "start": 544.94, "duration": 3.93}, {"text": "division and mistakes made on\nreplication and transcription,", "start": 548.87, "duration": 5.49}, {"text": "that then may one\nin a million times", "start": 554.36, "duration": 2.79}, {"text": "confer an advantage\non the microorganism.", "start": 557.15, "duration": 3.36}, {"text": "All of a sudden the\ndrugs don't work anymore.", "start": 560.51, "duration": 4.1}, {"text": "The WHO and various\ncommunity notice boards", "start": 564.61, "duration": 5.92}, {"text": "call this set of infectious\nagents the escape pathogens.", "start": 570.53, "duration": 4.79}, {"text": "It helps us remember\nwhich ones these are,", "start": 575.32, "duration": 2.47}, {"text": "because these are pathogens\nthat escape treatment,", "start": 577.79, "duration": 3.69}, {"text": "because they've\ndeveloped resistance", "start": 581.48, "duration": 2.4}, {"text": "to multiple drug cocktails.", "start": 583.88, "duration": 2.43}, {"text": "So commonly, when someone\nhas a particular disease", "start": 586.31, "duration": 3.24}, {"text": "they don't take one drug,\nthey take two or three", "start": 589.55, "duration": 2.91}, {"text": "to hit lots of pathways\nat once in the hope", "start": 592.46, "duration": 3.75}, {"text": "that resistance\nwon't develop fast.", "start": 596.21, "duration": 2.4}, {"text": "But the escape pathogens\nhave collectively", "start": 598.61, "duration": 3.21}, {"text": "acquired resistance to\nseveral antibiotics,", "start": 601.82, "duration": 3.09}, {"text": "meaning there's\nno good treatment.", "start": 604.91, "duration": 2.55}, {"text": "So the letters of escape stand\nfor Enterococcus faecium,", "start": 607.46, "duration": 4.98}, {"text": "Staph aureus, Klebsiella\npneumoniae, Acinetobacter", "start": 612.44, "duration": 4.59}, {"text": "baumannii, Pseudomonas\naeruginosa, and some", "start": 617.03, "duration": 3.18}, {"text": "of the Enterobacter species.", "start": 620.21, "duration": 2.88}, {"text": "Some of these infectious\nagents are what result from--", "start": 623.09, "duration": 7.12}, {"text": "I always say this wrong--", "start": 630.21, "duration": 2.34}, {"text": "nosocomial infections.", "start": 632.55, "duration": 2.01}, {"text": "Does anyone know what those are?", "start": 634.56, "duration": 3.12}, {"text": "These are infections that\npeople get in hospitals.", "start": 637.68, "duration": 3.77}, {"text": "So Tom Brady had\na knee operation.", "start": 641.45, "duration": 2.83}, {"text": "He got an infection in his knee\nthat came from the surgery,", "start": 644.28, "duration": 3.45}, {"text": "right.", "start": 647.73, "duration": 0.6}, {"text": "These are hospital\nacquired infections,", "start": 648.33, "duration": 2.64}, {"text": "because you can't sometimes\nclear an area enough,", "start": 650.97, "duration": 5.4}, {"text": "and there's infectious\nagents around.", "start": 656.37, "duration": 2.34}, {"text": "So Acinetobacter baumannii\nwas dubbed the Iraqi Bug", "start": 658.71, "duration": 4.53}, {"text": "for many, many years, because\nthe vets coming back from Iraq", "start": 663.24, "duration": 3.96}, {"text": "were going to\nmilitary hospitals,", "start": 667.2, "duration": 2.88}, {"text": "and these were\nabundant with cases", "start": 670.08, "duration": 3.15}, {"text": "of Acinetobacter baumannii.", "start": 673.23, "duration": 2.16}, {"text": "So that moved on to the\nescape pathogen list.", "start": 675.39, "duration": 3.51}, {"text": "So these are things\nto watch out for.", "start": 678.9, "duration": 2.19}, {"text": "It's the reason that\nnosocomial infections--", "start": 681.09, "duration": 2.79}, {"text": "I hope I'm saying\nit right, otherwise", "start": 683.88, "duration": 1.71}, {"text": "you're going to go off\nand Google it and realize", "start": 685.59, "duration": 2.67}, {"text": "I said it wrong.", "start": 688.26, "duration": 1.21}, {"text": "It's the reason why old school\nphysicians wore bow ties", "start": 689.47, "duration": 3.59}, {"text": "and not ties.", "start": 693.06, "duration": 2.58}, {"text": "Can you imagine why?", "start": 695.64, "duration": 2.85}, {"text": "So if you're wearing\na tie, which I seldom", "start": 698.49, "duration": 2.31}, {"text": "wear to be honest, and you're\nworking over a patient,", "start": 700.8, "duration": 3.99}, {"text": "the tie can be the thing\nthat carries the infection,", "start": 704.79, "duration": 3.06}, {"text": "because it gets closer\nto infected areas.", "start": 707.85, "duration": 2.67}, {"text": "This is old school stuff.", "start": 710.52, "duration": 1.62}, {"text": "And so originally the\nphysicians wore bow ties", "start": 712.14, "duration": 3.09}, {"text": "in order to distinguish\nthemselves as important people,", "start": 715.23, "duration": 3.07}, {"text": "but not to wear ties that\nmight carry infectious agents.", "start": 718.3, "duration": 4.16}, {"text": "That's sort of a scary thing.", "start": 722.46, "duration": 2.07}, {"text": "So with all this\nsaid, let me just", "start": 724.53, "duration": 3.93}, {"text": "lead you in to talk about\nbacteria antibiotics", "start": 728.46, "duration": 3.3}, {"text": "and resistance development.", "start": 731.76, "duration": 1.84}, {"text": "So we often name bacteria\nsomewhat by their shape.", "start": 733.6, "duration": 6.65}, {"text": "So the long rod\nshaped ones are cocci.", "start": 740.25, "duration": 4.86}, {"text": "The round ones are cocci.", "start": 745.11, "duration": 1.47}, {"text": "The rod ones, whatever they\nare, come on one of you.", "start": 746.58, "duration": 5.13}, {"text": "And then what did\nthe rod shape ones?", "start": 751.71, "duration": 2.97}, {"text": "Bacilli.", "start": 754.68, "duration": 1.31}, {"text": "I had a blank moment.", "start": 755.99, "duration": 0.88}, {"text": "So the rod shaped\nones are bacilli.", "start": 756.87, "duration": 2.64}, {"text": "And then there's\nsome others that", "start": 759.51, "duration": 1.65}, {"text": "have a different morphology\nlike Campylobacter jejuni", "start": 761.16, "duration": 3.39}, {"text": "that have kind of\na corkscrew shape.", "start": 764.55, "duration": 2.31}, {"text": "And that's thought to be\nimportant in their motility,", "start": 766.86, "duration": 3.15}, {"text": "digging through\nthe mucous layers", "start": 770.01, "duration": 1.98}, {"text": "in the epithelial layers.", "start": 771.99, "duration": 1.84}, {"text": "So here I show you several\nshapes of bacteria.", "start": 773.83, "duration": 3.103}, {"text": "And I'm just going\nto, once again,", "start": 776.933, "duration": 1.417}, {"text": "reinforce what diseases\nsome are associated", "start": 778.35, "duration": 3.6}, {"text": "with and some other diseases\nthat you might be surprised by.", "start": 781.95, "duration": 3.48}, {"text": "So yes, we know about\nsalmonella and the E.", "start": 785.43, "duration": 2.75}, {"text": "coli and food poisoning.", "start": 788.18, "duration": 1.57}, {"text": "But Helicobacter\npylori, which is", "start": 789.75, "duration": 2.85}, {"text": "one of these\nflagellated bacteria,", "start": 792.6, "duration": 3.09}, {"text": "can infect the stomach.", "start": 795.69, "duration": 3.21}, {"text": "It's often the cause of ulcers.", "start": 798.9, "duration": 2.1}, {"text": "So it's a causative\nagent of stomach ulcers,", "start": 801.0, "duration": 3.12}, {"text": "but that has in turn led\nto a considerable risk", "start": 804.12, "duration": 5.13}, {"text": "factor in stomach cancer.", "start": 809.25, "duration": 2.71}, {"text": "So what we thought\nwas just an infection", "start": 811.96, "duration": 2.42}, {"text": "causes a constellation of other\nproblems, including cancers.", "start": 814.38, "duration": 3.96}, {"text": "And more and more\nmicrobial agents", "start": 818.34, "duration": 3.54}, {"text": "are now associated with cancers,\nin particular the viruses.", "start": 821.88, "duration": 5.63}, {"text": "Neisseria, these come\nalong with the sexually", "start": 827.51, "duration": 3.55}, {"text": "transmitted diseases\nsuch as gonorrhea.", "start": 831.06, "duration": 3.22}, {"text": "Neisseria meningitidis is the\none that causes meningitis.", "start": 834.28, "duration": 2.855}, {"text": "It is a very, very often fatal\ninfection of the meninges.", "start": 837.135, "duration": 5.565}, {"text": "Staph aureus lots of\ninfections around the body,", "start": 842.7, "duration": 3.72}, {"text": "just gruesome things\nlike cellulitis,", "start": 846.42, "duration": 2.16}, {"text": "wound infections, toxic shock.", "start": 848.58, "duration": 2.73}, {"text": "Streptococcal\nbacteria, I've already", "start": 851.31, "duration": 1.89}, {"text": "mentioned-- the pneumonias,\nand then Campylobacter.", "start": 853.2, "duration": 3.33}, {"text": "And now another complicated\nfactor of infection--", "start": 856.53, "duration": 4.02}, {"text": "so I talked to you about stomach\nulcers and stomach cancer.", "start": 860.55, "duration": 5.94}, {"text": "Another thing that seems to be\ncoming along with infections", "start": 866.49, "duration": 3.72}, {"text": "is autoimmunity.", "start": 870.21, "duration": 1.68}, {"text": "So in the last section of the\nclass you heard about immunity", "start": 871.89, "duration": 3.66}, {"text": "and you also heard\nabout tolerance,", "start": 875.55, "duration": 3.33}, {"text": "that we don't react to\nthings that are ourselves,", "start": 878.88, "duration": 3.9}, {"text": "otherwise we'd be\nin deep trouble.", "start": 882.78, "duration": 2.16}, {"text": "Autoimmunity can\nsuddenly pop up from", "start": 884.94, "duration": 2.91}, {"text": "certain bacterial\ninfections, because bacteria", "start": 887.85, "duration": 2.82}, {"text": "tend to cloak themselves\nwith unusual sugar", "start": 890.67, "duration": 3.78}, {"text": "polymers and other\nkinds of structures", "start": 894.45, "duration": 2.4}, {"text": "that the body doesn't\nreally know what to do with.", "start": 896.85, "duration": 2.13}, {"text": "And in some cases\nthey kind of mimic", "start": 898.98, "duration": 2.52}, {"text": "things that are\nin the human body.", "start": 901.5, "duration": 2.28}, {"text": "So they they are mimetics\nof normal structures", "start": 903.78, "duration": 4.14}, {"text": "in the human body.", "start": 907.92, "duration": 1.41}, {"text": "And the body just doesn't\nnotice them at all.", "start": 909.33, "duration": 2.88}, {"text": "And then there are\nincidences where", "start": 912.21, "duration": 3.09}, {"text": "certain bacterial\ninfections later on", "start": 915.3, "duration": 3.12}, {"text": "cause autoimmune disease.", "start": 918.42, "duration": 2.41}, {"text": "So a bacteria may come along.", "start": 920.83, "duration": 1.82}, {"text": "It may have something that looks\nkind of like something human,", "start": 922.65, "duration": 3.03}, {"text": "but not quite.", "start": 925.68, "duration": 1.56}, {"text": "The human body responds,\ndevelops antibodies,", "start": 927.24, "duration": 2.91}, {"text": "and then they cross talk back\nto aspects of our physiology.", "start": 930.15, "duration": 5.07}, {"text": "So Campylobacter jejuni is\noften a contaminant in poultry.", "start": 935.22, "duration": 4.04}, {"text": "It's a severe GI infection.", "start": 939.26, "duration": 1.98}, {"text": "But later on people get\ndiseases such as Guillain-Barre,", "start": 941.24, "duration": 3.45}, {"text": "which is a neuropathy where\nthe ends of your limbs", "start": 944.69, "duration": 5.1}, {"text": "become numb and non-functional.", "start": 949.79, "duration": 2.52}, {"text": "So there was a famous\nfootball player,", "start": 952.31, "duration": 2.94}, {"text": "the one they called\n\"The Refrigerator,\" who", "start": 955.25, "duration": 1.86}, {"text": "had a serious case of\nGuillain-Barre resulting", "start": 957.11, "duration": 4.05}, {"text": "from very much an\ninfectious disease, which", "start": 961.16, "duration": 2.91}, {"text": "converted into autoimmunity.", "start": 964.07, "duration": 3.74}, {"text": "So let's now look at\nantibiotic targets.", "start": 967.81, "duration": 2.85}, {"text": "And to look at\nantibiotic targets,", "start": 970.66, "duration": 2.85}, {"text": "I think the first\nclear place to look", "start": 973.51, "duration": 2.79}, {"text": "is at the bacterial cell wall.", "start": 976.3, "duration": 2.31}, {"text": "Now when we first started\ntalking about prokaryotes,", "start": 988.61, "duration": 3.48}, {"text": "things that include bacteria,\nwe talked about the fact", "start": 992.09, "duration": 4.17}, {"text": "that these single\ncelled organisms", "start": 996.26, "duration": 2.43}, {"text": "have to have a robust cell\nwall to prevent osmotic shock.", "start": 998.69, "duration": 5.58}, {"text": "They have to have\nsome kind of thing", "start": 1004.27, "duration": 1.5}, {"text": "to keep them from\ntaking up too much water", "start": 1005.77, "duration": 3.96}, {"text": "and basically exploding\nbecause of osmosis.", "start": 1009.73, "duration": 3.69}, {"text": "Water floods in to balance\nthe salt concentrations.", "start": 1013.42, "duration": 4.11}, {"text": "So they have a\ncomplex cell wall,", "start": 1017.53, "duration": 3.73}, {"text": "which is made of a macro\nmolecule called peptidoglycan", "start": 1021.26, "duration": 8.24}, {"text": "And it's usually one word,\nbut I want to just underline", "start": 1029.5, "duration": 3.15}, {"text": "peptidoglycan because it's\na fascinating polymer that's", "start": 1032.65, "duration": 4.29}, {"text": "made up of peptides and\nlinear carbohydrate polymers.", "start": 1036.94, "duration": 4.635}, {"text": "So if you look at this\ntypical bacterium,", "start": 1042.29, "duration": 2.9}, {"text": "this is just a cartoon\nof the peptidoglycan.", "start": 1045.19, "duration": 4.72}, {"text": "So it's a cross-linked\npolymer, we", "start": 1049.91, "duration": 8.3}, {"text": "in one direction it has\nrepeating carbohydrate units.", "start": 1058.21, "duration": 5.04}, {"text": "I'm not drawing those complex\nhexose structures there.", "start": 1063.25, "duration": 3.66}, {"text": "I'm just drawing\nit in cartoon form.", "start": 1066.91, "duration": 2.34}, {"text": "And those are carbohydrates\nknown as NAG and NAN.", "start": 1069.25, "duration": 4.505}, {"text": "NAG is N-Acetyl Glucosamine.", "start": 1077.89, "duration": 5.25}, {"text": "It's a hexose sugar.", "start": 1083.14, "duration": 1.71}, {"text": "NAN is N-AcetylMuramic acid.", "start": 1084.85, "duration": 2.57}, {"text": "It's another modified sugar.", "start": 1087.42, "duration": 2.47}, {"text": "And on the one of\nthose sugars, there", "start": 1089.89, "duration": 2.12}, {"text": "is a reactive site that allows\nyou to basically cross-link", "start": 1092.01, "duration": 7.18}, {"text": "these polymers into a mesh work.", "start": 1099.19, "duration": 2.64}, {"text": "So it's a feat of engineering\nto build this amazing polymer.", "start": 1101.83, "duration": 4.32}, {"text": "It starts being built on the\ninside, on the cytoplasm.", "start": 1106.15, "duration": 3.72}, {"text": "And then the components get\nflipped onto the other side", "start": 1109.87, "duration": 3.09}, {"text": "of the cytoplasm of bacteria.", "start": 1112.96, "duration": 2.7}, {"text": "Then they get\npolymerized in place", "start": 1115.66, "duration": 2.46}, {"text": "to make this complex\nmesh work of a polymer", "start": 1118.12, "duration": 3.66}, {"text": "that creates the rigidity\nof the bacterial cell wall.", "start": 1121.78, "duration": 4.41}, {"text": "It's generically known\nas a peptidoglycan.", "start": 1126.19, "duration": 4.08}, {"text": "Different bacteria have\ndifferent peptidoglycans.", "start": 1130.27, "duration": 3.45}, {"text": "There are several\nmodifications that", "start": 1133.72, "duration": 2.52}, {"text": "might be specific to\nparticular bacterial sera", "start": 1136.24, "duration": 5.19}, {"text": "But this is the\ngeneric structure,", "start": 1141.43, "duration": 1.68}, {"text": "where you have a polymer\nthat's built of sugars.", "start": 1143.11, "duration": 2.49}, {"text": "You can recognize the\nsugar structure there", "start": 1145.6, "duration": 2.31}, {"text": "going in one direction and\nthe peptide component that", "start": 1147.91, "duration": 3.78}, {"text": "cross-links across in\norder to make this mesh.", "start": 1151.69, "duration": 3.66}, {"text": "And bacterial wall have\ndifferent amounts of this,", "start": 1155.35, "duration": 3.0}, {"text": "but it'll build up to a\nreally strong, rigid mesh", "start": 1158.35, "duration": 3.42}, {"text": "work that's permeable to things,\nsmall molecules and water.", "start": 1161.77, "duration": 3.6}, {"text": "There is holes, and so on.", "start": 1165.37, "duration": 1.59}, {"text": "But it creates a\nmechanical rigidity", "start": 1166.96, "duration": 2.64}, {"text": "so that osmotic shock doesn't\noccur on the bacteria.", "start": 1169.6, "duration": 3.51}, {"text": "Any questions about that?", "start": 1173.11, "duration": 1.05}, {"text": "Does that makes sense?", "start": 1174.16, "duration": 1.07}, {"text": "So that, in a sense,\nit's their exoskeleton,", "start": 1175.23, "duration": 2.83}, {"text": "if you want to think\nabout it like that.", "start": 1178.06, "duration": 2.61}, {"text": "So the properties are rigid.", "start": 1180.67, "duration": 2.94}, {"text": "Without it, the bacteria\nwould suffer osmotic shock.", "start": 1183.61, "duration": 3.0}, {"text": "And it's plenty permeable\nto allow 2-nanometer type", "start": 1186.61, "duration": 5.55}, {"text": "pores in order for nutrients and\nwater to go into the structure.", "start": 1192.16, "duration": 4.888}, {"text": "[VIDEO PLAYBACK]", "start": 1197.048, "duration": 0.667}, {"text": "- --have E. coli growing here.", "start": 1197.715, "duration": 1.25}, {"text": "And it's living.", "start": 1198.965, "duration": 0.747}, {"text": "You can see it start to grow.", "start": 1199.712, "duration": 1.208}, {"text": "Here we add penicillin.", "start": 1200.92, "duration": 1.19}, {"text": "We're going to see\nthese bacteria--", "start": 1202.11, "duration": 1.458}, {"text": "PROFESSOR: These are\nbacteria, rod-shaped bacteria.", "start": 1203.568, "duration": 2.872}, {"text": "- There wasn't any\nmicrophone on this, so--", "start": 1206.44, "duration": 2.055}, {"text": "PROFESSOR: And I'm going to\nask you to just keep watching", "start": 1208.495, "duration": 2.375}, {"text": "this kind of carefully.", "start": 1210.87, "duration": 1.03}, {"text": "- There goes another\none, boop, boop.", "start": 1211.9, "duration": 1.542}, {"text": "[LAUGHTER]", "start": 1213.442, "duration": 0.858}, {"text": "- Poking holes in the cell\nwall, boom, bacteria is dead.", "start": 1214.3, "duration": 3.09}, {"text": "PROFESSOR: Look at some of\nthe bacteria disappearing.", "start": 1217.39, "duration": 3.36}, {"text": "All right, I guess", "start": 1220.75, "duration": 1.41}, {"text": "[INTERPOSING VOICES]", "start": 1222.16, "duration": 3.81}, {"text": "OK, then we're going to--", "start": 1225.97, "duration": 1.4}, {"text": "[INTERPOSING VOICES]", "start": 1227.37, "duration": 1.75}, {"text": "So we're going to leave it.", "start": 1229.12, "duration": 2.117}, {"text": "[END PLAYBACK]", "start": 1231.237, "duration": 0.583}, {"text": "Let's go back one.", "start": 1231.82, "duration": 1.57}, {"text": "OK, now what was that?", "start": 1233.39, "duration": 2.24}, {"text": "OK, so I've told you bacteria\nwould suffer osmotic shock", "start": 1235.63, "duration": 4.8}, {"text": "without peptidoglycan.", "start": 1240.43, "duration": 2.55}, {"text": "Those are bacteria\nthat you see popping,", "start": 1242.98, "duration": 2.46}, {"text": "as the person who\nwas talking said,", "start": 1245.44, "duration": 4.05}, {"text": "because the peptidoglycan\ncannot be made.", "start": 1249.49, "duration": 4.39}, {"text": "There is an antibiotic\nthat's added.", "start": 1253.88, "duration": 2.03}, {"text": "It is penicillin that's\nadded to the bacteria.", "start": 1255.91, "duration": 4.08}, {"text": "And it stops-- as bacteria grow,\nthey have to make a bunch more", "start": 1259.99, "duration": 4.38}, {"text": "peptidoglycan, because\nif you're doubling,", "start": 1264.37, "duration": 2.54}, {"text": "you've got to make\ntwice as much peptido--", "start": 1266.91, "duration": 2.02}, {"text": "you've got to double the\namount of peptidoglycan.", "start": 1268.93, "duration": 2.49}, {"text": "If you have something\nthat inhibits", "start": 1271.42, "duration": 2.46}, {"text": "the peptidoglycan\nbeing made, you", "start": 1273.88, "duration": 3.21}, {"text": "have a bacterium that's trying\nto stretch out what it has,", "start": 1277.09, "duration": 3.57}, {"text": "it's not resistant\nto osmotic shock.", "start": 1280.66, "duration": 2.65}, {"text": "And what you saw was the\nbacteria basically undergoing", "start": 1283.31, "duration": 2.72}, {"text": "cell death via osmotic shock,\npretty graphic, pretty visual.", "start": 1286.03, "duration": 4.2}, {"text": "So penicillin was one\nof the first antibiotics", "start": 1290.23, "duration": 6.24}, {"text": "that was described\nfor the treatment", "start": 1296.47, "duration": 2.19}, {"text": "of bacterial infections.", "start": 1298.66, "duration": 2.19}, {"text": "And we'll go to the timeline\nof that in a moment.", "start": 1300.85, "duration": 3.13}, {"text": "So when we talk about bacteria,\nthe original definition", "start": 1303.98, "duration": 3.68}, {"text": "of bacteria is in three\ndifferent subtypes,", "start": 1307.66, "duration": 7.26}, {"text": "gram-negative, gram-positive,\nand mycobacterial.", "start": 1314.92, "duration": 11.11}, {"text": "This is actually the\nfirst way that people", "start": 1332.57, "duration": 3.93}, {"text": "would take a look at your\ncell-- at the bacterial cells", "start": 1336.5, "duration": 3.42}, {"text": "and diagnose roughly what\nkind of bacteria they were.", "start": 1339.92, "duration": 4.32}, {"text": "Did they fall-- which\nof these broad families", "start": 1344.24, "duration": 3.24}, {"text": "did they fall into?", "start": 1347.48, "duration": 1.05}, {"text": "Because it would\nhelp in defining how", "start": 1348.53, "duration": 2.37}, {"text": "you would treat the\ninfectious disease.", "start": 1350.9, "duration": 2.65}, {"text": "So I want to show you the\ndifference between the cell", "start": 1353.55, "duration": 8.9}, {"text": "wall of these various\ntypes of bacteria.", "start": 1362.45, "duration": 4.77}, {"text": "And the truth is, if you\nhave an infectious disease,", "start": 1367.22, "duration": 3.81}, {"text": "your wish is, if you had\nto pick one of the three,", "start": 1371.03, "duration": 4.74}, {"text": "that you have a\ngram-positive disease.", "start": 1375.77, "duration": 2.38}, {"text": "And I'll explain why\nthat is in a moment,", "start": 1378.15, "duration": 2.72}, {"text": "because it's all to do with how\ndrugs can get into the bacteria", "start": 1380.87, "duration": 4.26}, {"text": "to inhibit vital functions\nin order that they die", "start": 1385.13, "duration": 3.75}, {"text": "and they don't take\nover your system.", "start": 1388.88, "duration": 2.41}, {"text": "So let's look first at\ngram-positive bacteria.", "start": 1391.29, "duration": 3.57}, {"text": "They're shown here.", "start": 1394.86, "duration": 0.9}, {"text": "This is a section\nof a bacterium.", "start": 1395.76, "duration": 2.96}, {"text": "Gram-positive have\na single cell wall.", "start": 1398.72, "duration": 3.03}, {"text": "And they also have a thick\nlayer of peptidoglycan.", "start": 1408.43, "duration": 7.33}, {"text": "So they gain\nrigidity by basically", "start": 1418.49, "duration": 3.12}, {"text": "having an extracellular\nthick layer of peptidoglycan", "start": 1421.61, "duration": 4.14}, {"text": "coating them.", "start": 1425.75, "duration": 1.56}, {"text": "There is a schematic of it here.", "start": 1427.31, "duration": 1.77}, {"text": "So here would be\nthe inner cell wall.", "start": 1429.08, "duration": 2.34}, {"text": "And here would be\nthe peptidoglycan,", "start": 1431.42, "duration": 2.34}, {"text": "shown in orange and pale,\nbuff-colored circles.", "start": 1433.76, "duration": 5.28}, {"text": "So that would be where\ntheir peptidoglycan is.", "start": 1439.04, "duration": 2.97}, {"text": "And then there are some\nother glyco conjugates that", "start": 1442.01, "duration": 3.57}, {"text": "actually stick out beyond that.", "start": 1445.58, "duration": 1.48}, {"text": "But there is only one\ncytoplasmic membrane.", "start": 1447.06, "duration": 3.17}, {"text": "That's the standard\ndouble bilayer.", "start": 1450.23, "duration": 3.21}, {"text": "And the peptidoglycan is\nquite thick, relatively,", "start": 1453.44, "duration": 4.11}, {"text": "20 to 80 nanometers across.", "start": 1457.55, "duration": 4.0}, {"text": "So that's how wide it is.", "start": 1461.55, "duration": 1.31}, {"text": "And you can, if you've\ngot a-- if you've", "start": 1462.86, "duration": 2.34}, {"text": "stain a bacterium\nunder a microscope,", "start": 1465.2, "duration": 2.13}, {"text": "you would see that, the\nthickness of that wall,", "start": 1467.33, "duration": 3.15}, {"text": "but the absence\nof a double wall.", "start": 1470.48, "duration": 2.5}, {"text": "The gram-negative bacteria\nhave a double wall.", "start": 1472.98, "duration": 3.44}, {"text": "The inner membrane\nis pretty standard.", "start": 1483.92, "duration": 8.11}, {"text": "It's just typical phospholipids.", "start": 1492.03, "duration": 2.57}, {"text": "It looks like the inner\ncytoplasmic membrane", "start": 1494.6, "duration": 3.42}, {"text": "of the gram-positive bacteria.", "start": 1498.02, "duration": 3.21}, {"text": "And then it has an outer wall.", "start": 1501.23, "duration": 4.21}, {"text": "So the inner\nmembrane is typical.", "start": 1505.44, "duration": 3.56}, {"text": "And then the outer\nwall has one leaflet", "start": 1509.0, "duration": 5.61}, {"text": "that looks kind of normal.", "start": 1514.61, "duration": 1.71}, {"text": "And then it has a second leaflet\nthat's sort of decorated,", "start": 1516.32, "duration": 2.88}, {"text": "honestly, like a Christmas tree.", "start": 1519.2, "duration": 1.98}, {"text": "There is all kinds of\nthings sticking out", "start": 1521.18, "duration": 1.95}, {"text": "there that interact with hosts\nthat they infect, and so on.", "start": 1523.13, "duration": 4.02}, {"text": "And the space\nbetween the two walls", "start": 1527.15, "duration": 3.03}, {"text": "is called the periplasmic\nspace, because it's between.", "start": 1530.18, "duration": 14.1}, {"text": "It's not the cytoplasm.", "start": 1544.28, "duration": 1.84}, {"text": "It's what's called\nthe periplasm.", "start": 1546.12, "duration": 2.36}, {"text": "Now, what's interesting\nabout these,", "start": 1548.48, "duration": 1.845}, {"text": "the gram-negative bacteria,\nis they have quite a bit", "start": 1550.325, "duration": 3.945}, {"text": "less peptidoglycan, only\nabout 7 to 8 nanometers.", "start": 1554.27, "duration": 5.422}, {"text": "So that's pretty interesting.", "start": 1565.6, "duration": 1.65}, {"text": "But they sort of gain robustness\nfrom that second wall structure", "start": 1567.25, "duration": 4.47}, {"text": "that's coating on the outside.", "start": 1571.72, "duration": 2.32}, {"text": "Now, their challenge with\ngram-negative bacteria relative", "start": 1574.04, "duration": 4.22}, {"text": "to gram-positive bacteria is any\ndrugs you develop have to make", "start": 1578.26, "duration": 4.2}, {"text": "a pretty--", "start": 1582.46, "duration": 1.32}, {"text": "if they're targeted at\nintracellular sites,", "start": 1583.78, "duration": 3.48}, {"text": "they have to get through two\nwalls, not just one wall.", "start": 1587.26, "duration": 3.6}, {"text": "So they are harder to treat.", "start": 1590.86, "duration": 2.16}, {"text": "And they also have a\nlot of characteristics", "start": 1593.02, "duration": 2.28}, {"text": "that make them more prone\nto resistance development.", "start": 1595.3, "duration": 3.12}, {"text": "So I want to point out to you,\non this electron micrograph,", "start": 1598.42, "duration": 3.66}, {"text": "you can actually see the double\nwall, the dark band of space", "start": 1602.08, "duration": 4.32}, {"text": "and then another dark\nband, whereas here you", "start": 1606.4, "duration": 2.88}, {"text": "see a thin single\nwall, but you see", "start": 1609.28, "duration": 2.88}, {"text": "a lot of junk on the outside.", "start": 1612.16, "duration": 2.92}, {"text": "Is everyone seeing\nthe differences just", "start": 1615.08, "duration": 3.56}, {"text": "to look at them?", "start": 1618.64, "duration": 1.21}, {"text": "OK, so what's this\ngram thing about?", "start": 1619.85, "duration": 5.84}, {"text": "What does this stand for?", "start": 1625.69, "duration": 1.62}, {"text": "It simply stands for a chemical\ndye that stains peptidoglycan.", "start": 1630.19, "duration": 19.03}, {"text": "And it was invented or\ndiscovered by Professor Gram.", "start": 1649.22, "duration": 4.02}, {"text": "That was his name.", "start": 1653.24, "duration": 0.87}, {"text": "So when someone says you got\na gram-positive infection,", "start": 1654.11, "duration": 2.85}, {"text": "gram-negative\ninfection, it's how", "start": 1656.96, "duration": 2.46}, {"text": "those cells look when they've\nbeen treated with this stain.", "start": 1659.42, "duration": 3.45}, {"text": "Gram positives show up\nvery positive to the stain", "start": 1662.87, "duration": 5.37}, {"text": "because there is a\nlot of peptidoglycan", "start": 1668.24, "duration": 2.55}, {"text": "on the outside that absorbs the\ndye and shows a strong color.", "start": 1670.79, "duration": 5.16}, {"text": "The gram-negatives don't show\nvery well with a Gram stain,", "start": 1675.95, "duration": 5.55}, {"text": "because the peptidoglycan\nis tucked in the periplasm,", "start": 1681.5, "duration": 4.02}, {"text": "not on the outside of the cell.", "start": 1685.52, "duration": 2.35}, {"text": "So if someone does a quick\ncheck on a bacterial streak", "start": 1687.87, "duration": 3.71}, {"text": "or an infection\nthat you have, they", "start": 1691.58, "duration": 1.8}, {"text": "might treat it\nwith the Gram stain", "start": 1693.38, "duration": 1.8}, {"text": "and say gram-positive\nor gram-negative just", "start": 1695.18, "duration": 3.18}, {"text": "based on that simple\ncolor analysis.", "start": 1698.36, "duration": 5.13}, {"text": "And so in one case,\nthe peptidoglycan", "start": 1703.49, "duration": 3.87}, {"text": "is abundant and accessible.", "start": 1707.36, "duration": 2.01}, {"text": "In the other case, it's very,\nvery much thinner and less", "start": 1709.37, "duration": 4.29}, {"text": "accessible to the dyes.", "start": 1713.66, "duration": 1.74}, {"text": "Now, this probably looks\nlike stone-age stuff", "start": 1715.4, "duration": 2.37}, {"text": "to you, because how\nmuch can you learn", "start": 1717.77, "duration": 2.76}, {"text": "by these simple\ncolorimetric stains?", "start": 1720.53, "duration": 2.49}, {"text": "We're certainly moving in very,\nvery different directions.", "start": 1723.02, "duration": 3.45}, {"text": "But let me just finish off with\nthe third type of bacteria,", "start": 1726.47, "duration": 4.98}, {"text": "the mycobacteria, which include\nMycobacterium tuberculosis.", "start": 1731.45, "duration": 6.6}, {"text": "And they have a different\nkind of wall, again.", "start": 1738.05, "duration": 2.87}, {"text": "And they're pretty unusual.", "start": 1740.92, "duration": 1.42}, {"text": "And they are really,\nreally hard to treat,", "start": 1742.34, "duration": 2.61}, {"text": "because it's almost impossible\nto get therapeutic agents", "start": 1744.95, "duration": 3.66}, {"text": "into mycobacteria.", "start": 1748.61, "duration": 1.92}, {"text": "I used to work on a team\nwith Novartis in Singapore.", "start": 1750.53, "duration": 3.96}, {"text": "And they said, doing\nanything with mycobacteria", "start": 1754.49, "duration": 2.58}, {"text": "was like trying to do\nbiochemistry on a wax candle,", "start": 1757.07, "duration": 3.42}, {"text": "literally.", "start": 1760.49, "duration": 0.602}, {"text": "You just can't work\nwith it, because they", "start": 1761.092, "duration": 1.708}, {"text": "have a thick additional wall\nthat's kind of different again.", "start": 1762.8, "duration": 3.12}, {"text": "Did you have a question?", "start": 1765.92, "duration": 1.12}, {"text": "No.", "start": 1767.04, "duration": 0.5}, {"text": "Sorry, I thought I\nsaw your hand up.", "start": 1767.54, "duration": 2.82}, {"text": "So what they have\nis a typical cell", "start": 1770.36, "duration": 3.39}, {"text": "wall then some\npeptidoglycan, but then they", "start": 1773.75, "duration": 2.91}, {"text": "have this thick\nmycobacterial layer", "start": 1776.66, "duration": 5.1}, {"text": "which comprises what are\nknown as mycolic acids, which", "start": 1781.76, "duration": 3.96}, {"text": "basically add this thick layer\nof greasy hydrophobic material", "start": 1785.72, "duration": 4.92}, {"text": "on the outside of the\nmycobacteria that's", "start": 1790.64, "duration": 3.96}, {"text": "pretty impenetrable.", "start": 1794.6, "duration": 2.52}, {"text": "The cell wall is\nquite different.", "start": 1797.12, "duration": 1.92}, {"text": "It doesn't have an outer coat.", "start": 1799.04, "duration": 2.07}, {"text": "It's like gram-positives\nin that respect.", "start": 1801.11, "duration": 4.32}, {"text": "But it doesn't\nstain very strongly.", "start": 1805.43, "duration": 1.785}, {"text": "So it has a weak, what's\nknown as Gram stain.", "start": 1811.74, "duration": 8.27}, {"text": "So sometimes if\nyou've got something", "start": 1820.01, "duration": 1.5}, {"text": "that gives a sort a so-so\nresponse to the Gram stain,", "start": 1821.51, "duration": 3.27}, {"text": "you might say, oh, it\nlooks like a mycobacterium", "start": 1824.78, "duration": 2.91}, {"text": "because of what's happening.", "start": 1827.69, "duration": 1.62}, {"text": "Now, mycobacteria\nTB is a huge threat,", "start": 1829.31, "duration": 4.8}, {"text": "because its treatment, its\ncurrent treatment-- and it's", "start": 1834.11, "duration": 5.08}, {"text": "the same treatment that's\nbeen around for, like, 30", "start": 1839.19, "duration": 3.21}, {"text": "years or something-- is\na treatment with four", "start": 1842.4, "duration": 2.97}, {"text": "different antibacterial\nagents that", "start": 1845.37, "duration": 2.91}, {"text": "hit a bunch of different\nsites in the lifecycle", "start": 1848.28, "duration": 3.21}, {"text": "of the bacteria.", "start": 1851.49, "duration": 1.56}, {"text": "It includes these\ncompounds shown here", "start": 1853.05, "duration": 3.73}, {"text": "which are isoniazid, rifampicin,\nethambutol, and pyrazinamide.", "start": 1856.78, "duration": 7.1}, {"text": "And it's a six-month treatment\nwith those medications,", "start": 1863.88, "duration": 3.73}, {"text": "so handful, four different\nmedications for six months.", "start": 1867.61, "duration": 4.82}, {"text": "So what they were realizing\nin the developing world", "start": 1872.43, "duration": 3.09}, {"text": "is that there was\nterrible compliance.", "start": 1875.52, "duration": 2.4}, {"text": "The drugs are cheap, but\nthere was no compliance.", "start": 1877.92, "duration": 2.76}, {"text": "People just were not taking the\npills, because they're like,", "start": 1880.68, "duration": 2.91}, {"text": "I'm tired of taking these\npills every day for six months.", "start": 1883.59, "duration": 3.9}, {"text": "So what was developed was what's\nknown as the DOTs program.", "start": 1887.49, "duration": 4.08}, {"text": "Has anyone never heard of this?", "start": 1891.57, "duration": 1.73}, {"text": "Is anyone interested\nin infectious disease?", "start": 1893.3, "duration": 3.29}, {"text": "It was a situation where it\nwas a social system set up", "start": 1896.59, "duration": 4.22}, {"text": "in order to make\nsure people took", "start": 1900.81, "duration": 1.92}, {"text": "these drugs every day for six\nmonths in order to comply.", "start": 1902.73, "duration": 4.77}, {"text": "So social workers would go to\nthe villages in remote areas", "start": 1907.5, "duration": 3.9}, {"text": "and watch people\ntake the medications.", "start": 1911.4, "duration": 2.93}, {"text": "So it's directly\nobserved treatment", "start": 1914.33, "duration": 2.14}, {"text": "to make sure they followed\nthrough, because if they had", "start": 1916.47, "duration": 2.91}, {"text": "regular TB, not very resistant\nTB, you could overcome it,", "start": 1919.38, "duration": 5.25}, {"text": "provided that you took\nthese medications.", "start": 1924.63, "duration": 2.34}, {"text": "But still, it's a hugely\ndebilitating thing", "start": 1926.97, "duration": 2.64}, {"text": "to have to deal with\nthese treatments.", "start": 1929.61, "duration": 2.1}, {"text": "Now, there are\ntwo strains of TB.", "start": 1931.71, "duration": 2.24}, {"text": "One is called MDR-TB.", "start": 1933.95, "duration": 2.41}, {"text": "And the other ones called\nXMDR-TB You'll occasionally", "start": 1936.36, "duration": 4.23}, {"text": "hear of these on TV programs.", "start": 1940.59, "duration": 5.13}, {"text": "MDR is resistant to three\nof the four medications.", "start": 1945.72, "duration": 4.2}, {"text": "And XMDR, which stands for\nextremely MultiDrug Resistant,", "start": 1949.92, "duration": 4.68}, {"text": "is resistant to every single\none of those medications.", "start": 1954.6, "duration": 3.58}, {"text": "New medications, different\nmechanisms of action", "start": 1958.18, "duration": 2.48}, {"text": "are sorely needed.", "start": 1960.66, "duration": 2.412}, {"text": "All right, this is\njust what things", "start": 1963.072, "duration": 1.458}, {"text": "look like with the Gram stains.", "start": 1964.53, "duration": 2.43}, {"text": "So here you see gram-positive\nBacillus anthracis.", "start": 1966.96, "duration": 4.38}, {"text": "That's the deep purple rods.", "start": 1971.34, "duration": 2.847}, {"text": "You know that's a\ngram-positive because it's", "start": 1974.187, "duration": 1.833}, {"text": "a deep purple stain.", "start": 1976.02, "duration": 2.16}, {"text": "The other cells in this\npicture are white cells.", "start": 1978.18, "duration": 2.55}, {"text": "So you can really pick\nout the gram-positive.", "start": 1980.73, "duration": 3.6}, {"text": "This is the structure\nof the chemical dye", "start": 1984.33, "duration": 3.18}, {"text": "that stains peptidoglycan\nthrough absorbing", "start": 1987.51, "duration": 3.21}, {"text": "into the peptidoglycan.", "start": 1990.72, "duration": 2.58}, {"text": "It's a very sort of\nphysical interaction", "start": 1993.3, "duration": 2.19}, {"text": "of the dye with the polymer.", "start": 1995.49, "duration": 2.46}, {"text": "And over on this slide, it's\na mixture of gram-positive", "start": 1997.95, "duration": 3.21}, {"text": "and gram-negative.", "start": 2001.16, "duration": 1.38}, {"text": "And you can pick up\nthe gram-positive", "start": 2002.54, "duration": 5.5}, {"text": "and differentiate them from\nthe gram-negative, which", "start": 2008.04, "duration": 2.7}, {"text": "just stains sort of\nkind of weakly pink.", "start": 2010.74, "duration": 2.88}, {"text": "And then mycobacteria, which\nare formerly gram-positive,", "start": 2013.62, "duration": 4.08}, {"text": "don't stain very well\nbecause of that thick mycolic", "start": 2017.7, "duration": 3.51}, {"text": "acid hydrophobic wall.", "start": 2021.21, "duration": 2.19}, {"text": "So what would you do nowadays?", "start": 2023.4, "duration": 1.77}, {"text": "Would you pull out a stain\nand drop it on bacteria", "start": 2025.17, "duration": 3.63}, {"text": "and get some vague response?", "start": 2028.8, "duration": 3.88}, {"text": "What's open to you now\nin the 21st century?", "start": 2032.68, "duration": 5.2}, {"text": "You have a tiny\nsample of a bacterium.", "start": 2037.88, "duration": 2.75}, {"text": "Grow it up.", "start": 2040.63, "duration": 0.57}, {"text": "What would you do?", "start": 2041.2, "duration": 0.75}, {"text": "You could tell\nexactly what it is.", "start": 2041.95, "duration": 2.79}, {"text": "AUDIENCE: PCR.", "start": 2044.74, "duration": 0.94}, {"text": "PROFESSOR: Yeah, you'd\nPCR up the genomic DNA", "start": 2045.68, "duration": 3.17}, {"text": "and then go match it, because\nthe thing that we, in addition", "start": 2048.85, "duration": 3.15}, {"text": "to the human genome,\nthere are thousands", "start": 2052.0, "duration": 3.179}, {"text": "of pathogenic bacteria sequences\nthat are completely annotated,", "start": 2055.179, "duration": 5.04}, {"text": "known.", "start": 2060.219, "duration": 0.871}, {"text": "The [INAUDIBLE] has a massive\ncompilation of these sequences.", "start": 2061.09, "duration": 3.839}, {"text": "And you just go and you\nfind out what the bacterium", "start": 2064.929, "duration": 2.911}, {"text": "is based on the sequence.", "start": 2067.84, "duration": 1.87}, {"text": "So now rapid\nsequencing efforts--", "start": 2069.71, "duration": 3.63}, {"text": "maybe they're just a few number\nof key places in a genome", "start": 2073.34, "duration": 4.399}, {"text": "that you would go towards and\njust do a really fast array", "start": 2077.739, "duration": 3.96}, {"text": "and figure out what's there and\nwithin what bacterium it is,", "start": 2081.699, "duration": 4.411}, {"text": "which gives you a much better\nclue as to how to treat it", "start": 2086.11, "duration": 3.39}, {"text": "than the vague,\nambiguous stains.", "start": 2089.5, "duration": 2.159}, {"text": "So even though stains keep\ngoing, there is now other ways.", "start": 2091.659, "duration": 4.051}, {"text": "Unfortunately, not everyone\nhas the instrumentation", "start": 2095.71, "duration": 2.73}, {"text": "to do rapid sequencing.", "start": 2098.44, "duration": 2.04}, {"text": "So nowadays, there\nis a lot, lot,", "start": 2100.48, "duration": 2.06}, {"text": "lot of interest in faster\ndipstick sorts of tests", "start": 2102.54, "duration": 4.87}, {"text": "that can distinguish between\ndifferent bacterial strains", "start": 2107.41, "duration": 3.57}, {"text": "by, for example, interrogating\nthat coat of glyco-conjugates", "start": 2110.98, "duration": 5.52}, {"text": "that's on the outside\nof the bacteria,", "start": 2116.5, "duration": 2.28}, {"text": "dipstick paper tests\nthat can give you", "start": 2118.78, "duration": 2.79}, {"text": "an idea of what\norganism and what", "start": 2121.57, "duration": 1.89}, {"text": "serotype so you can move forward\nand do a much more rational", "start": 2123.46, "duration": 4.5}, {"text": "treatment of those organisms.", "start": 2127.96, "duration": 3.33}, {"text": "OK, let's see what's-- yes.", "start": 2131.29, "duration": 1.92}, {"text": "All right, so where did the\nantibiotics first come from?", "start": 2133.21, "duration": 5.07}, {"text": "Any questions so far?", "start": 2138.28, "duration": 3.06}, {"text": "OK, so where did the first\nantibiotics come from?", "start": 2141.34, "duration": 4.015}, {"text": "From a couple of\naccidental discoveries.", "start": 2145.355, "duration": 3.015}, {"text": "Who has heard of the\nFleming experiment?", "start": 2148.37, "duration": 4.32}, {"text": "Who knows about that\ndiscovery of penicillin?", "start": 2152.69, "duration": 3.92}, {"text": "Yeah, so there was an\noriginal observation", "start": 2156.61, "duration": 3.86}, {"text": "that predated that which\nsort of suggests that Pasteur", "start": 2160.47, "duration": 2.67}, {"text": "was a pretty smart guy,\nbecause he contributed", "start": 2163.14, "duration": 2.48}, {"text": "in a lot of different areas.", "start": 2165.62, "duration": 2.17}, {"text": "He discovered that some bacteria\ntend to release substances", "start": 2167.79, "duration": 5.04}, {"text": "that kill other bacteria.", "start": 2172.83, "duration": 2.31}, {"text": "That was in the 1870s.", "start": 2175.14, "duration": 4.11}, {"text": "Then later on, there\nwas another sort", "start": 2179.25, "duration": 2.34}, {"text": "of spread of antibiotic agents.", "start": 2181.59, "duration": 2.85}, {"text": "And it came with the\ndiscovery that we had things", "start": 2184.44, "duration": 3.48}, {"text": "like arsenic\nderivatives actually", "start": 2187.92, "duration": 2.58}, {"text": "showed some value in\ntreating the organism that", "start": 2190.5, "duration": 5.58}, {"text": "causes syphilis.", "start": 2196.08, "duration": 1.44}, {"text": "So talk about the\ntreatment being--", "start": 2197.52, "duration": 3.18}, {"text": "the cure being worse\nthan the infection.", "start": 2200.7, "duration": 2.5}, {"text": "People were being\ntreated, seriously,", "start": 2203.2, "duration": 1.91}, {"text": "with these arsenic derivatives\nin the hope of wiping out", "start": 2205.11, "duration": 3.87}, {"text": "the infectious agent\nthat caused syphilis.", "start": 2208.98, "duration": 2.19}, {"text": "But you know, sometimes\nit was a mixed bag.", "start": 2211.17, "duration": 2.82}, {"text": "But where things started to get\na lot more interesting was that", "start": 2213.99, "duration": 4.02}, {"text": "in 1928, there was this sort\nof famous historic story", "start": 2218.01, "duration": 4.71}, {"text": "of Fleming discovering\nthat some bacteria seemed", "start": 2222.72, "duration": 5.61}, {"text": "to be inhibited by a particular\nagent that came from a fungus.", "start": 2228.33, "duration": 7.26}, {"text": "And this was the\norigin of penicillin.", "start": 2235.59, "duration": 2.77}, {"text": "So he would have a Petri dish\nwhere he was growing bacteria.", "start": 2238.36, "duration": 3.23}, {"text": "And he noticed that in\nsome of his samples,", "start": 2241.59, "duration": 2.79}, {"text": "there was inhibition\nof bacterial growth", "start": 2244.38, "duration": 2.55}, {"text": "due to an exogenous\nagent that had somehow", "start": 2246.93, "duration": 3.06}, {"text": "contaminated the plates.", "start": 2249.99, "duration": 2.61}, {"text": "So in that story,\nthat was the substance", "start": 2252.6, "duration": 3.24}, {"text": "that was named as penicillin.", "start": 2255.84, "duration": 2.76}, {"text": "The mold from the--\nmold is the fungus--", "start": 2258.6, "duration": 3.06}, {"text": "actually inhibited the growth\nof staphylococcus bacteria.", "start": 2261.66, "duration": 3.54}, {"text": "And it was called penicillin.", "start": 2265.2, "duration": 1.95}, {"text": "And then a lot\nmore time went by.", "start": 2267.15, "duration": 3.15}, {"text": "But in the 1940s, the active\ningredient was discovered.", "start": 2270.3, "duration": 6.06}, {"text": "So 1940s is sort of slap\nbang about, I would say,", "start": 2276.36, "duration": 5.76}, {"text": "a couple of years into\nthe Second World War.", "start": 2282.12, "duration": 3.9}, {"text": "And they were able to mobilize\nthe production of this agent.", "start": 2286.02, "duration": 5.13}, {"text": "Towards the later\nend of the war,", "start": 2291.15, "duration": 1.56}, {"text": "people had penicillin\navailable to them.", "start": 2292.71, "duration": 2.76}, {"text": "And it's basically\npretty well believed", "start": 2295.47, "duration": 3.36}, {"text": "that, if it wasn't for\nthe antibiotic agents that", "start": 2298.83, "duration": 3.63}, {"text": "emerged--", "start": 2302.46, "duration": 1.23}, {"text": "you know, the war ended in 1945.", "start": 2303.69, "duration": 2.37}, {"text": "If it wasn't for those\nagents that emerged,", "start": 2306.06, "duration": 2.51}, {"text": "there would have been way way,\nway more deaths from the war.", "start": 2308.57, "duration": 3.55}, {"text": "As it was, there\nwere way too many.", "start": 2312.12, "duration": 2.88}, {"text": "So penicillin was\nthe first antibiotic", "start": 2315.0, "duration": 3.15}, {"text": "that was discovered with a\ndiscreet mechanism of action.", "start": 2318.15, "duration": 3.03}, {"text": "And it was discovered at a\nvery, very important time.", "start": 2321.18, "duration": 3.7}, {"text": "So that was all great news.", "start": 2324.88, "duration": 2.15}, {"text": "Penicillin was produced widely.", "start": 2327.03, "duration": 2.2}, {"text": "Some of you may be\nallergic to penicillin.", "start": 2329.23, "duration": 2.39}, {"text": "There are other\noptions nowadays.", "start": 2331.62, "duration": 2.13}, {"text": "But it's the cheapest\nand most viable", "start": 2333.75, "duration": 2.1}, {"text": "of the first-line antibiotics.", "start": 2335.85, "duration": 4.84}, {"text": "Here we go.", "start": 2340.69, "duration": 0.55}, {"text": "And this thing, this pointer\nhas a mind of its own.", "start": 2344.216, "duration": 2.764}, {"text": "It sort of changed its mind.", "start": 2346.98, "duration": 1.48}, {"text": "But the problem was\nthe bacterial species", "start": 2348.46, "duration": 3.7}, {"text": "started to survive treatment due\nto development of resistance.", "start": 2352.16, "duration": 4.84}, {"text": "And all of a sudden, something\nthat worked really well", "start": 2357.0, "duration": 2.25}, {"text": "wasn't working anymore.", "start": 2359.25, "duration": 1.47}, {"text": "So let's try and think\nabout peptidoglycan,", "start": 2360.72, "duration": 4.16}, {"text": "what penicillin looks\nlike and what it does,", "start": 2364.88, "duration": 3.24}, {"text": "and how penicillin\nresistance emerges.", "start": 2368.12, "duration": 2.97}, {"text": "Those are the three things\nI'm going to cover here.", "start": 2371.09, "duration": 2.58}, {"text": "OK, so what does penicillin do?", "start": 2373.67, "duration": 2.52}, {"text": "Penicillin stops the formation\nof this big macromolecular", "start": 2376.19, "duration": 8.49}, {"text": "peptidoglycan polymer by\nstopping the last cross-link,", "start": 2384.68, "duration": 4.11}, {"text": "stopping the\nchemistry that happens", "start": 2388.79, "duration": 2.22}, {"text": "to join the peptide chains to\nmake a cross-linked polymer.", "start": 2391.01, "duration": 3.96}, {"text": "And anyone who is in the\nmechanical engineering area", "start": 2394.97, "duration": 2.67}, {"text": "will know that polymers\nthat are just strands", "start": 2397.64, "duration": 3.27}, {"text": "are much weaker\nthan polymers that", "start": 2400.91, "duration": 2.07}, {"text": "are crossed-linked\nstructures which", "start": 2402.98, "duration": 1.92}, {"text": "have tensile strength\nin both directions.", "start": 2404.9, "duration": 2.89}, {"text": "So the uncross-linked\npeptidoglycan was weak.", "start": 2407.79, "duration": 3.37}, {"text": "And what penicillin\nspecifically did", "start": 2411.16, "duration": 2.98}, {"text": "was inhibit forming\nthat cross-link.", "start": 2414.14, "duration": 3.21}, {"text": "What does penicillin look like?", "start": 2417.35, "duration": 1.95}, {"text": "Here it is.", "start": 2419.3, "duration": 1.35}, {"text": "It's a cool structure.", "start": 2420.65, "duration": 1.5}, {"text": "It's what's known as a natural\nproduct, five ring, four ring,", "start": 2422.15, "duration": 4.68}, {"text": "an interesting structure.", "start": 2426.83, "duration": 1.77}, {"text": "And what it would do is it\nwould interact with the enzyme", "start": 2428.6, "duration": 3.45}, {"text": "the cross-linked\nthe peptidoglycan", "start": 2432.05, "duration": 2.42}, {"text": "and basically stop it\ndead in its tracks.", "start": 2434.47, "duration": 2.77}, {"text": "What did the bacteria do?", "start": 2437.24, "duration": 2.7}, {"text": "The key part of this structure\nis this four-membered ring", "start": 2439.94, "duration": 4.27}, {"text": "within amide bond in it.", "start": 2444.21, "duration": 3.0}, {"text": "The bacteria evolved an enzyme\nto chop it open basically", "start": 2447.21, "duration": 4.77}, {"text": "making it completely inactive.", "start": 2451.98, "duration": 1.92}, {"text": "So beta lactamase was evolved\nin the bacterial populations.", "start": 2453.9, "duration": 4.11}, {"text": "It was probably derived\nfrom some other enzyme that", "start": 2458.01, "duration": 3.03}, {"text": "did some useful\nfunction, but not", "start": 2461.04, "duration": 2.4}, {"text": "targeted to the penicillins.", "start": 2463.44, "duration": 2.46}, {"text": "But the bacteria\nstarted to survive", "start": 2465.9, "duration": 3.24}, {"text": "because they made a ton of an\nenzyme called beta lactamase.", "start": 2469.14, "duration": 3.09}, {"text": "And then it completely\nstopped working.", "start": 2472.23, "duration": 2.55}, {"text": "So the chemists came\nup with other options,", "start": 2474.78, "duration": 3.57}, {"text": "because they said, well, you\nknow, if that doesn't work,", "start": 2478.35, "duration": 3.09}, {"text": "we've got other\nantibiotics in our arsenal.", "start": 2481.44, "duration": 3.51}, {"text": "And there is a\ncompound that was used", "start": 2484.95, "duration": 1.89}, {"text": "for years as a last line\nof resort antibiotic known", "start": 2486.84, "duration": 4.56}, {"text": "as vancomycin.", "start": 2491.4, "duration": 1.62}, {"text": "It was very, very important,\nso very serious infections,", "start": 2493.02, "duration": 5.31}, {"text": "and really preserved\nfor that use.", "start": 2498.33, "duration": 2.73}, {"text": "And they thought that\nvancomycin might be a drug that", "start": 2501.06, "duration": 4.65}, {"text": "just couldn't be defeated.", "start": 2505.71, "duration": 1.74}, {"text": "This big molecule\nhere is vancomycin.", "start": 2507.45, "duration": 2.91}, {"text": "This little piece of peptide\nis actually the peptide", "start": 2510.36, "duration": 4.44}, {"text": "that's in that cross-link.", "start": 2514.8, "duration": 1.55}, {"text": "And vancomycin\nbasically, like a glove,", "start": 2516.35, "duration": 2.95}, {"text": "sat on that piece of peptide and\nstopped it being cross-linked.", "start": 2519.3, "duration": 4.56}, {"text": "And what did the bacteria do?", "start": 2523.86, "duration": 1.8}, {"text": "They evolved a set of\nenzymes to completely change", "start": 2525.66, "duration": 4.35}, {"text": "that little piece of\npeptide into something", "start": 2530.01, "duration": 2.39}, {"text": "that bound more poorly,\ngiving you resistance", "start": 2532.4, "duration": 3.73}, {"text": "to vancomycin as well.", "start": 2536.13, "duration": 1.9}, {"text": "So when there is\none drug involved,", "start": 2538.03, "duration": 3.68}, {"text": "it's pretty easy to get\nresistance quite quickly.", "start": 2541.71, "duration": 2.68}, {"text": "You just mutate one enzyme and\nyou get a resistant strain.", "start": 2544.39, "duration": 4.88}, {"text": "And the enzyme that can beat\nthe antibiotic will win.", "start": 2549.27, "duration": 3.93}, {"text": "If you've got a compound that\ntakes five different enzymes", "start": 2556.62, "duration": 4.32}, {"text": "or an antibiotic that has a very\ncomplex mechanism of action,", "start": 2560.94, "duration": 5.58}, {"text": "you might say, well, this is\nnever going to be defeated.", "start": 2566.52, "duration": 4.14}, {"text": "It took five additional\nenzymes to evolve", "start": 2570.66, "duration": 3.54}, {"text": "to make the peptidoglycan\na different structure.", "start": 2574.2, "duration": 3.3}, {"text": "And it's not that\nwithin every bacterium,", "start": 2577.5, "duration": 2.64}, {"text": "you mutate five\ndifferent enzymes", "start": 2580.14, "duration": 2.52}, {"text": "and get them all\nworking as a team.", "start": 2582.66, "duration": 2.04}, {"text": "What was happening\nin these infections", "start": 2584.7, "duration": 3.15}, {"text": "is that a plasmid with\nthe set of enzymes", "start": 2587.85, "duration": 2.91}, {"text": "was being passed around\namongst bacteria.", "start": 2590.76, "duration": 3.12}, {"text": "So a new bacterium could acquire\nresistance to this compound", "start": 2593.88, "duration": 4.29}, {"text": "without evolving a whole\nbunch of new enzymes,", "start": 2598.17, "duration": 2.91}, {"text": "but rather by lateral\ntransfer of plasmids", "start": 2601.08, "duration": 3.27}, {"text": "encoding the genes that it\ntook to make the vancomycin", "start": 2604.35, "duration": 4.35}, {"text": "inactive.", "start": 2608.7, "duration": 2.25}, {"text": "All right, so let me just\ntell you a few of the targets.", "start": 2610.95, "duration": 3.33}, {"text": "And then there is one\nmovie I want to show you", "start": 2614.28, "duration": 2.16}, {"text": "that's kind of cool.", "start": 2616.44, "duration": 1.27}, {"text": "So currently, when we inhibit\nbacteria with antibiotics,", "start": 2617.71, "duration": 5.24}, {"text": "there are a number of\nessential processes", "start": 2622.95, "duration": 2.07}, {"text": "that are targeted with\ncommon antibiotics.", "start": 2625.02, "duration": 3.22}, {"text": "So this would be a\ntypical bacterium.", "start": 2628.24, "duration": 2.24}, {"text": "One target of action is DNA\nsynthesis and DNA polymerase.", "start": 2630.48, "duration": 9.42}, {"text": "And the enzyme\nthat is targeted is", "start": 2639.9, "duration": 2.61}, {"text": "one we've talked\nabout, topoisomerase.", "start": 2642.51, "duration": 3.18}, {"text": "And that is inhibited\nby the fluoroquinolones", "start": 2645.69, "duration": 3.36}, {"text": "such as ciprofloxacin that\nactually targets specifically", "start": 2649.05, "duration": 4.65}, {"text": "the bacterial polymerase.", "start": 2653.7, "duration": 1.35}, {"text": "So that's one way,\ninhibit DNA replication,", "start": 2655.05, "duration": 3.78}, {"text": "bacteria can't divide.", "start": 2658.83, "duration": 1.86}, {"text": "Another set of\nantibiotics are those", "start": 2660.69, "duration": 4.44}, {"text": "that inhibit protein synthesis.", "start": 2665.13, "duration": 3.1}, {"text": "So in particular,\nyou know the tunnel", "start": 2668.23, "duration": 2.54}, {"text": "that comes out of the ribosome\nwhere the growing polypeptide", "start": 2670.77, "duration": 3.24}, {"text": "chain emerges after\nreading the messenger RNA", "start": 2674.01, "duration": 4.23}, {"text": "and translating the\nmessenger into protein?", "start": 2678.24, "duration": 2.58}, {"text": "There are antibiotics to\nbasically stick in that tunnel", "start": 2680.82, "duration": 2.96}, {"text": "and stop protein synthesis.", "start": 2683.78, "duration": 2.05}, {"text": "And those are things\nlike the aminoglycosides.", "start": 2685.83, "duration": 2.78}, {"text": "And they block exit\nfrom the ribosome.", "start": 2688.61, "duration": 2.35}, {"text": "But you could imagine\nthat mutating.", "start": 2690.96, "duration": 2.64}, {"text": "There are the ones that\ninhibit cell wall biosynthesis", "start": 2693.6, "duration": 2.73}, {"text": "that I've already talked\nto about, the penicillins,", "start": 2696.33, "duration": 3.21}, {"text": "the vancoymcin.", "start": 2699.54, "duration": 2.14}, {"text": "And then there are others\nthat inhibit folate synthesis.", "start": 2701.68, "duration": 5.14}, {"text": "And then there is a\nlot of synthetic drugs,", "start": 2706.82, "duration": 2.61}, {"text": "but also a lot of\nnatural product drugs.", "start": 2709.43, "duration": 2.41}, {"text": "So both nature and\nchemistry have teamed up", "start": 2711.84, "duration": 3.2}, {"text": "to inhibit all of\nthese essential steps.", "start": 2715.04, "duration": 3.66}, {"text": "OK, so how do you test\nfor antibiotic resistance?", "start": 2718.7, "duration": 3.91}, {"text": "You use plates where you're\ngrowing particular strains", "start": 2722.61, "duration": 4.05}, {"text": "of bacteria on a plate.", "start": 2726.66, "duration": 2.4}, {"text": "This would be a colony.", "start": 2729.06, "duration": 3.03}, {"text": "And it's growing outwards.", "start": 2732.09, "duration": 2.04}, {"text": "Where there is a colony but\nthere is no growth around it,", "start": 2734.13, "duration": 3.03}, {"text": "it means there is something\nin that plate that", "start": 2737.16, "duration": 2.61}, {"text": "is inhibiting bacterial growth.", "start": 2739.77, "duration": 2.53}, {"text": "So these are very\nclear types of ways", "start": 2742.3, "duration": 2.6}, {"text": "that people check\nto see if bacteria", "start": 2744.9, "duration": 2.55}, {"text": "have become resistant to drugs.", "start": 2747.45, "duration": 2.22}, {"text": "You would look for that\nzone of inhibition.", "start": 2749.67, "duration": 2.19}, {"text": "Does it disappear with some\nof the resistant strains,", "start": 2751.86, "duration": 3.15}, {"text": "for example?", "start": 2755.01, "duration": 1.86}, {"text": "And these get\npretty sophisticated", "start": 2756.87, "duration": 2.64}, {"text": "now where you can test a\nbunch of antibiotics in one", "start": 2759.51, "duration": 4.08}, {"text": "go, where each of\nthese colored dots", "start": 2763.59, "duration": 2.85}, {"text": "represents an area\nwhere there is treatment", "start": 2766.44, "duration": 2.46}, {"text": "with one antibiotic or another.", "start": 2768.9, "duration": 2.82}, {"text": "So what's the problem?", "start": 2771.72, "duration": 1.6}, {"text": "The problem is this\ngraph, that as soon", "start": 2773.32, "duration": 2.39}, {"text": "as an antibiotic is introduced,\njust a few years go by.", "start": 2775.71, "duration": 4.08}, {"text": "And there is resistance\nto that antibiotic.", "start": 2779.79, "duration": 2.7}, {"text": "So resistance basically\nis the gradual acquisition", "start": 2782.49, "duration": 4.74}, {"text": "of machinery to\nsomehow inactivate", "start": 2787.23, "duration": 2.97}, {"text": "the antibiotic treatment.", "start": 2790.2, "duration": 1.51}, {"text": "So if you take a\nlook, here on the top", "start": 2791.71, "duration": 2.69}, {"text": "is where the drug is introduced.", "start": 2794.4, "duration": 2.21}, {"text": "And on the bottom is when\nresistance was developed.", "start": 2796.61, "duration": 2.84}, {"text": "So let's go to something\nwe're familiar.", "start": 2799.45, "duration": 2.28}, {"text": "Here is penicillin, people\nintroduced about 1940", "start": 2801.73, "duration": 3.71}, {"text": "to the general population.", "start": 2805.44, "duration": 1.74}, {"text": "By about '47, there was\nresistance to penicillin.", "start": 2807.18, "duration": 4.41}, {"text": "And you can see, this is really\njust a really serious sort", "start": 2811.59, "duration": 4.29}, {"text": "of series of events.", "start": 2815.88, "duration": 1.44}, {"text": "So what I want to show you\nwas resistance in action.", "start": 2817.32, "duration": 4.18}, {"text": "And that'll be the last\nthing I talk about today,", "start": 2821.5, "duration": 3.86}, {"text": "because I just want to\ngive you a feel for what", "start": 2825.36, "duration": 4.26}, {"text": "does resistance look like.", "start": 2829.62, "duration": 1.545}, {"text": "So this was an\nexperiment that was", "start": 2834.1, "duration": 1.68}, {"text": "done at Harvard on just a\nvisualization of resistance", "start": 2835.78, "duration": 7.2}, {"text": "development.", "start": 2842.98, "duration": 1.71}, {"text": "I think what's so\nfascinating is you could then", "start": 2844.69, "duration": 3.09}, {"text": "go back to the plate and\npluck the first pioneers who", "start": 2847.78, "duration": 5.25}, {"text": "crossed that line and\nfind out what that was.", "start": 2853.03, "duration": 2.79}, {"text": "What was that mutation that\nlet the population expand,", "start": 2855.82, "duration": 3.96}, {"text": "and so on?", "start": 2859.78, "duration": 0.52}, {"text": "So you could really map out the\nentire evolution of very, very", "start": 2860.3, "duration": 4.16}, {"text": "strong resistance.", "start": 2864.46, "duration": 1.63}, {"text": "So in the next class,\nI'll talk to you", "start": 2866.09, "duration": 1.73}, {"text": "about resistance mechanisms.", "start": 2867.82, "duration": 1.69}, {"text": "And then we'll talk about\nviruses and resistance", "start": 2869.51, "duration": 3.95}, {"text": "to antivirals.", "start": 2873.46, "duration": 2.33}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 0.85, "duration": 2.37}, {"text": "Commons license.", "start": 3.22, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.61, "duration": 2.21}, {"text": "continue to offer high quality\neducational resources for free.", "start": 6.82, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 10.91, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.48, "duration": 3.96}, {"text": "at ocw.mit.edu.", "start": 17.44, "duration": 0.873}, {"text": "PROFESSOR: Sorry.", "start": 24.012, "duration": 0.708}, {"text": "I have a bit of a sore\nthroat, hoarse voice.", "start": 24.72, "duration": 3.29}, {"text": "I was talking a\nlot this weekend.", "start": 28.01, "duration": 2.08}, {"text": "OK.", "start": 30.09, "duration": 0.5}, {"text": "Also, today we're going to\ndo transaction malleability,", "start": 30.59, "duration": 2.55}, {"text": "segregated witness,\nand I'm endorsing", "start": 33.14, "duration": 2.25}, {"text": "an ICO for the first\ntime ever publicly,", "start": 35.39, "duration": 2.97}, {"text": "and it's Anne's intermittent\ncookie offering.", "start": 38.36, "duration": 1.92}, {"text": "So if you guys want cookies.", "start": 40.28, "duration": 1.167}, {"text": "It's an airdrop and\nyou just get them.", "start": 43.96, "duration": 2.85}, {"text": "so it's my first\nICO I'm endorsing.", "start": 54.74, "duration": 6.04}, {"text": "OK.", "start": 60.78, "duration": 0.5}, {"text": "So malleability.", "start": 61.28, "duration": 3.36}, {"text": "So malleability is\nthe ability to deform", "start": 64.64, "duration": 2.31}, {"text": "under pressure formateer.", "start": 66.95, "duration": 1.95}, {"text": "And so bitcoin is modeled\noff of gold, which", "start": 68.9, "duration": 2.19}, {"text": "is the most malleable metal.", "start": 71.09, "duration": 1.26}, {"text": "You can make gold\nleaf and stuff.", "start": 72.35, "duration": 1.95}, {"text": "So clearly we need to design\nbitcoin to be malleable.", "start": 74.3, "duration": 4.99}, {"text": "No, I'm joking.", "start": 79.29, "duration": 1.34}, {"text": "OK.", "start": 80.63, "duration": 0.5}, {"text": "Actually in the context\nof cryptography,", "start": 81.13, "duration": 5.74}, {"text": "it's not super hard\ndefinition, but it", "start": 86.87, "duration": 2.01}, {"text": "started with Cipher text, where\nif you can modify a Cipher", "start": 88.88, "duration": 2.85}, {"text": "text and that modification will\ncarry over into the plain text", "start": 91.73, "duration": 5.04}, {"text": "when it's encrypted.", "start": 96.77, "duration": 1.23}, {"text": "It also applies to sort of\nmessages and signatures.", "start": 98.0, "duration": 2.88}, {"text": "In our case, signatures\ncan be malleable,", "start": 100.88, "duration": 2.83}, {"text": "which means you can\nchange the signature", "start": 103.71, "duration": 2.51}, {"text": "and it's still a\nvalid signature.", "start": 106.22, "duration": 2.44}, {"text": "So given a signature\nS1 on message M1,", "start": 108.66, "duration": 5.0}, {"text": "you modify the signature\nto S2 or S prime", "start": 113.66, "duration": 4.47}, {"text": "and it still signs\nthe same message.", "start": 118.13, "duration": 1.83}, {"text": "It still validates as true.", "start": 119.96, "duration": 2.49}, {"text": "So when we were\ndefining signatures", "start": 122.45, "duration": 2.34}, {"text": "this wasn't really an\nattack we'd considered.", "start": 124.79, "duration": 3.719}, {"text": "There's still a signature and\nyou can't forge a signature,", "start": 128.509, "duration": 3.811}, {"text": "but you can dot\nan I or something", "start": 132.32, "duration": 2.64}, {"text": "and the signature is\nslightly different.", "start": 134.96, "duration": 2.23}, {"text": "You can't create one yourself,\nbut given a valid signature", "start": 137.19, "duration": 2.46}, {"text": "you can make a slightly\ndifferent valid signature.", "start": 139.65, "duration": 4.05}, {"text": "And that's how it works in\nthe bitcoin signing algorithm.", "start": 143.7, "duration": 4.25}, {"text": "But there's all sorts\nof different contexts", "start": 147.95, "duration": 2.25}, {"text": "where malleability\nexists in cryptography.", "start": 150.2, "duration": 3.96}, {"text": "And then part of\nit is things still", "start": 154.16, "duration": 1.74}, {"text": "have to work for\nwhatever definition.", "start": 155.9, "duration": 2.35}, {"text": "So if you malleates a signature\nand it no longer validates,", "start": 158.25, "duration": 4.077}, {"text": "well, that's sort\nof a trivial, like--", "start": 162.327, "duration": 1.583}, {"text": "yeah, sure, you can do\nthat to any bunch of bytes.", "start": 163.91, "duration": 2.64}, {"text": "You can just flip some of\nthem and the whole thing", "start": 166.55, "duration": 2.095}, {"text": "doesn't work anymore.", "start": 168.645, "duration": 0.875}, {"text": "That's easy.", "start": 169.52, "duration": 1.17}, {"text": "But properties where\nit still works.", "start": 170.69, "duration": 3.027}, {"text": "So this leads to some\nweird stuff in bitcoin", "start": 173.717, "duration": 1.833}, {"text": "where you can\nchange a transaction", "start": 175.55, "duration": 3.51}, {"text": "and it's still valid.", "start": 179.06, "duration": 2.49}, {"text": "And that's generally\nnot what you want.", "start": 181.55, "duration": 2.85}, {"text": "If you've got some\nkind of contract", "start": 184.4, "duration": 1.47}, {"text": "or some kind of payment\nand you write a check,", "start": 185.87, "duration": 3.672}, {"text": "you don't want someone to\nbe able to modify the check", "start": 189.542, "duration": 2.208}, {"text": "and still be able to cash it.", "start": 191.75, "duration": 1.95}, {"text": "And I don't really use checks\nmuch, but they draw the line.", "start": 193.7, "duration": 4.38}, {"text": "Like $100 and then\nthey draw a line", "start": 198.08, "duration": 2.79}, {"text": "so someone doesn't write and\n$0.99 or something after.", "start": 200.87, "duration": 3.09}, {"text": "Not that that's like the\ngreatest attack ever.", "start": 203.96, "duration": 2.91}, {"text": "Or $100 and then someone\nputs like $1,000.", "start": 206.87, "duration": 3.45}, {"text": "I don't know.", "start": 210.32, "duration": 1.41}, {"text": "But it's sort of like\nthat where someone", "start": 211.73, "duration": 1.83}, {"text": "can change the\nthing you sign, can", "start": 213.56, "duration": 1.56}, {"text": "change the thing you are\nagreeing to after the fact,", "start": 215.12, "duration": 3.0}, {"text": "and it's still valid and it\ndoes something you don't expect.", "start": 218.12, "duration": 3.88}, {"text": "OK.", "start": 222.0, "duration": 1.15}, {"text": "So a review of the\ntransaction format,", "start": 223.15, "duration": 4.52}, {"text": "which should be probably\nin people's minds", "start": 227.67, "duration": 2.49}, {"text": "if you were looking at the\nhomework, the problem set.", "start": 230.16, "duration": 3.5}, {"text": "And one thing to focus\non is that the outputs", "start": 233.66, "duration": 2.65}, {"text": "don't look like the inputs.", "start": 236.31, "duration": 2.55}, {"text": "These are fundamentally\ndifferent things.", "start": 238.86, "duration": 3.33}, {"text": "The outputs specify a\ntransaction ID and the inputs,", "start": 242.19, "duration": 6.45}, {"text": "and then the outputs specify\na script and an amount.", "start": 248.64, "duration": 4.15}, {"text": "There's another 4 byte field\nhere that doesn't matter.", "start": 252.79, "duration": 3.31}, {"text": "So basically you're spending\nfrom a transaction and a sort", "start": 256.1, "duration": 4.12}, {"text": "of row and you're spending too\njust this arbitrary pub key,", "start": 260.22, "duration": 4.29}, {"text": "but you're not\nspending from a pub key", "start": 264.51, "duration": 2.28}, {"text": "and you're not spending\nto a transaction.", "start": 266.79, "duration": 2.99}, {"text": "You don't identify your\ntransaction itself here.", "start": 269.78, "duration": 2.72}, {"text": "Almost every website that\nshows blockchains is it", "start": 278.41, "duration": 4.09}, {"text": "gets this wrong.", "start": 282.5, "duration": 1.47}, {"text": "So if you look at\nlike, I don't know,", "start": 283.97, "duration": 1.7}, {"text": "blockchain.info is\nprobably the most popular", "start": 285.67, "duration": 5.72}, {"text": "and you just look\nat a transaction.", "start": 291.39, "duration": 2.8}, {"text": "They don't have it anymore.", "start": 294.19, "duration": 1.22}, {"text": "OK.", "start": 295.41, "duration": 0.5}, {"text": "So you look at a block and\nthen you look at a transaction", "start": 295.91, "duration": 2.69}, {"text": "in the block.", "start": 298.6, "duration": 1.86}, {"text": "We're going.", "start": 300.46, "duration": 0.74}, {"text": "No.", "start": 301.2, "duration": 0.5}, {"text": "No.", "start": 301.7, "duration": 0.5}, {"text": "No, not yet.", "start": 302.2, "duration": 0.902}, {"text": "There we go OK.", "start": 303.102, "duration": 0.72}, {"text": "So you look at a transaction.", "start": 303.822, "duration": 1.208}, {"text": "Yeah, it shows.", "start": 305.03, "duration": 1.83}, {"text": "This address is sending\nto these two addresses.", "start": 306.86, "duration": 3.21}, {"text": "And blockchain.info is\nparticularly egregious", "start": 310.07, "duration": 2.74}, {"text": "and that there may actually\nbe more than one input and two", "start": 312.81, "duration": 2.84}, {"text": "outputs in this transaction.", "start": 315.65, "duration": 3.805}, {"text": "They hide change transactions.", "start": 319.455, "duration": 2.405}, {"text": "So it looks like, hey, this\naddress had some money in it", "start": 321.86, "duration": 4.78}, {"text": "and it sent it to\nthese two addresses.", "start": 326.64, "duration": 1.593}, {"text": "And if I click, oh, where\ndid this money come?", "start": 328.233, "duration": 1.917}, {"text": "It come from\n18eecz, and it shows", "start": 330.15, "duration": 3.84}, {"text": "here's the bitcoin\naddress, and, oh, it's", "start": 333.99, "duration": 2.31}, {"text": "got multiple transactions this\naddresses has been involved in.", "start": 336.3, "duration": 5.88}, {"text": "This is not how bitcoin works.", "start": 342.18, "duration": 2.4}, {"text": "They are running their\nown database and sort", "start": 344.58, "duration": 3.54}, {"text": "of making up this view of the\nnetwork, which is incorrect.", "start": 348.12, "duration": 5.61}, {"text": "Transactions don't\nsend from an address,", "start": 353.73, "duration": 3.06}, {"text": "they send from another\ntransactions previous output.", "start": 356.79, "duration": 4.17}, {"text": "And this is very confusing\nbecause in the case,", "start": 360.96, "duration": 2.28}, {"text": "let's say in this\ntransaction, there is a--", "start": 363.24, "duration": 2.66}, {"text": "what is it?", "start": 365.9, "duration": 0.91}, {"text": "767 something.", "start": 369.44, "duration": 2.115}, {"text": "So it says, yeah, it's\ncoming from 18ee whatever,", "start": 374.88, "duration": 4.897}, {"text": "and if I click on it I get\nthree different transactions.", "start": 379.777, "duration": 2.333}, {"text": "There is a specific\ntransaction that 18ee", "start": 382.11, "duration": 3.36}, {"text": "was involved in that is being\nspent from in this transaction.", "start": 385.47, "duration": 2.78}, {"text": "I can look it up because I\nhave an actual full node.", "start": 388.25, "duration": 2.99}, {"text": "So if I say get raw transaction\nand I put it in here", "start": 391.24, "duration": 6.49}, {"text": "and I can see, OK, it\nwas spending from c838.", "start": 397.73, "duration": 5.68}, {"text": "It was spending from this\ntransaction, not just", "start": 403.41, "duration": 3.46}, {"text": "an address.", "start": 406.87, "duration": 0.84}, {"text": "So I mean if you're coming at\nthis sort of new it's like, OK,", "start": 407.71, "duration": 4.5}, {"text": "fine, why do you keep\ntalking about this?", "start": 412.21, "duration": 3.24}, {"text": "But if you've been working on\nthese things, a lot of people,", "start": 415.45, "duration": 2.56}, {"text": "myself included, for\nlike six months a year", "start": 418.01, "duration": 3.363}, {"text": "I looked at these\nwebsites and I'm like,", "start": 421.373, "duration": 1.667}, {"text": "oh, this is how it works and\nthen six months in or something", "start": 423.04, "duration": 3.45}, {"text": "looking for code, and\nI'm like, wait, huh?", "start": 426.49, "duration": 2.61}, {"text": "This code is wrong, but no,\nthis is the bitcoin code", "start": 429.1, "duration": 2.97}, {"text": "that actually is running.", "start": 432.07, "duration": 1.71}, {"text": "And so it's a weird thing\nto sort of get used to.", "start": 433.78, "duration": 2.28}, {"text": "Like no, you're not\nspending from an address.", "start": 436.06, "duration": 1.875}, {"text": "You don't show the address at\nall when you spend from it,", "start": 437.935, "duration": 2.505}, {"text": "you spend from a\nspecific output.", "start": 440.44, "duration": 1.73}, {"text": "OK.", "start": 442.17, "duration": 0.58}, {"text": "So that leads to\nsome weird issues.", "start": 442.75, "duration": 1.71}, {"text": "Specifically, what gets signed?", "start": 447.81, "duration": 2.44}, {"text": "So to some extent you're\nsigning the whole transaction.", "start": 450.25, "duration": 2.91}, {"text": "You sign.", "start": 453.16, "duration": 1.66}, {"text": "You want to sign everything.", "start": 454.82, "duration": 1.25}, {"text": "When you're saying I'm\nsending money from here,", "start": 456.07, "duration": 2.13}, {"text": "I'm sending it to here,\nyou want to make sure", "start": 458.2, "duration": 2.61}, {"text": "that your signature covers\nthe entire transaction so", "start": 460.81, "duration": 3.06}, {"text": "that people can't add stuff\nafter or remove stuff.", "start": 463.87, "duration": 3.668}, {"text": "So you want to sign\nthe inputs and outputs.", "start": 467.538, "duration": 1.792}, {"text": "But the inputs\ncontain signatures", "start": 469.33, "duration": 2.13}, {"text": "and you can't sign\nthe signature.", "start": 471.46, "duration": 2.39}, {"text": "That doesn't make any sense.", "start": 473.85, "duration": 1.78}, {"text": "The signature is the thing\nyou're putting on at the end.", "start": 475.63, "duration": 2.373}, {"text": "So it's sort of weird.", "start": 478.003, "duration": 0.917}, {"text": "You've got this document\nand you have a little line", "start": 478.92, "duration": 1.87}, {"text": "at the bottom for the signature.", "start": 480.79, "duration": 1.41}, {"text": "But should the signatures be\nmaybe a separate page that", "start": 482.2, "duration": 3.36}, {"text": "refers to the previous page?", "start": 485.56, "duration": 1.86}, {"text": "It's actually kind of a\nweird confusing problem.", "start": 487.42, "duration": 3.03}, {"text": "So in practice, in bitcoin,\nwhat Satoshi did in 2009,", "start": 490.45, "duration": 5.94}, {"text": "you take the whole\ntransaction, but you", "start": 496.39, "duration": 1.8}, {"text": "remove the signature fields.", "start": 498.19, "duration": 1.55}, {"text": "You basically zero them out.", "start": 499.74, "duration": 1.27}, {"text": "Just put a zero\nthere and then you", "start": 501.01, "duration": 1.74}, {"text": "sign that sort of\nsignatureless transaction.", "start": 502.75, "duration": 4.86}, {"text": "And then you put that\nsignature in after the fact.", "start": 507.61, "duration": 5.39}, {"text": "And so that means if you change\nany bit of the stuff that gets", "start": 513.0, "duration": 4.07}, {"text": "signed other than the signature,\nthe signature will break.", "start": 517.07, "duration": 5.18}, {"text": "So does that make sense?", "start": 522.25, "duration": 1.0}, {"text": "You have these\nempty lines kind of,", "start": 525.76, "duration": 2.32}, {"text": "and the idea is you empty them\nout, you make them blank lines,", "start": 528.08, "duration": 3.36}, {"text": "and then you take that whole\nmessage, hash it, including", "start": 531.44, "duration": 3.09}, {"text": "the empty parts, and then\npaste in those signatures", "start": 534.53, "duration": 3.99}, {"text": "after you've signed.", "start": 538.52, "duration": 0.93}, {"text": "You don't empty out every\nline, the line that you're", "start": 544.49, "duration": 2.19}, {"text": "specifically putting\nthe signature in,", "start": 546.68, "duration": 1.8}, {"text": "you actually put a\ndifferent few bytes", "start": 548.48, "duration": 2.34}, {"text": "in there, which leads\nto other problems", "start": 550.82, "duration": 3.15}, {"text": "that I can maybe\nmention if I've done.", "start": 553.97, "duration": 2.73}, {"text": "So this seems OK.", "start": 556.7, "duration": 1.41}, {"text": "It's like well, look, I can't\nsign the signatures, sure,", "start": 558.11, "duration": 3.15}, {"text": "but if you change any bit\nof the stuff I'm signing,", "start": 561.26, "duration": 3.24}, {"text": "the signatures now break.", "start": 564.5, "duration": 1.57}, {"text": "So this seems perfectly safe.", "start": 566.07, "duration": 2.6}, {"text": "No one can change the\namounts I'm sending.", "start": 568.67, "duration": 1.98}, {"text": "No one can change where\nI'm sending it to.", "start": 570.65, "duration": 2.75}, {"text": "No one can change\nwhere I'm sending from.", "start": 573.4, "duration": 2.38}, {"text": "All these things get covered\nin my signature, so I'm good.", "start": 575.78, "duration": 3.55}, {"text": "Problem.", "start": 579.33, "duration": 1.23}, {"text": "The transaction ID, the way\nyou refer to transactions", "start": 580.56, "duration": 3.24}, {"text": "is the hash of the whole thing.", "start": 583.8, "duration": 2.22}, {"text": "The txid does not zero\nout the signature fields.", "start": 586.02, "duration": 4.05}, {"text": "So the identity of the\ntransaction itself, the way", "start": 590.07, "duration": 3.24}, {"text": "to point to and indicate\nwhere you're spending from,", "start": 593.31, "duration": 3.87}, {"text": "that includes the signatures.", "start": 597.18, "duration": 2.97}, {"text": "So that also seems\nlike, well, that's OK.", "start": 600.15, "duration": 2.7}, {"text": "When I point to\nsomething I'm indicating", "start": 602.85, "duration": 2.43}, {"text": "the whole transaction, the\nwhole signed transaction.", "start": 605.28, "duration": 4.34}, {"text": "But the problem is\nthat can change.", "start": 609.62, "duration": 3.15}, {"text": "The signature itself\nmay be malleable,", "start": 612.77, "duration": 2.82}, {"text": "and in bitcoin it is.", "start": 615.59, "duration": 2.11}, {"text": "There's third party\nmalleability problems.", "start": 617.7, "duration": 2.37}, {"text": "So the simplest one\nwas leading zeros", "start": 620.07, "duration": 2.41}, {"text": "where all these\nthings are numbers.", "start": 622.48, "duration": 2.35}, {"text": "You could say, OK,\nsomeone's got a signature.", "start": 624.83, "duration": 2.07}, {"text": "It's this big, long\nstring of bytes.", "start": 626.9, "duration": 3.28}, {"text": "I'm just going to put\nzeros in the front.", "start": 630.18, "duration": 2.0}, {"text": "I'm going to put a zero\nbyte in the front of it,", "start": 632.18, "duration": 2.57}, {"text": "and that doesn't\nchange the meaning.", "start": 634.75, "duration": 1.54}, {"text": "If someone says, I'm\nsending you $1,000", "start": 636.29, "duration": 4.02}, {"text": "and I put a 0 front\nof the one and 1,000.", "start": 640.31, "duration": 1.945}, {"text": "Well, it's still 1,000.", "start": 642.255, "duration": 1.445}, {"text": "However, for the purpose\nof a hash function,", "start": 643.7, "duration": 3.49}, {"text": "if you have a zero\nbyte in front,", "start": 647.19, "duration": 1.4}, {"text": "that changes the whole hash.", "start": 648.59, "duration": 2.79}, {"text": "And so they got rid\nof this pretty early.", "start": 651.38, "duration": 2.76}, {"text": "They sort of made\nit so that you had", "start": 654.14, "duration": 2.49}, {"text": "to have the exact right number.", "start": 656.63, "duration": 1.59}, {"text": "You can't have\nany leading zeros.", "start": 658.22, "duration": 1.44}, {"text": "But the first one was just,\noh, I put a 0 in the front.", "start": 659.66, "duration": 3.4}, {"text": "The harder one is\ncalled low s, where part", "start": 663.06, "duration": 3.2}, {"text": "of the ecdsa signature scheme.", "start": 666.26, "duration": 3.82}, {"text": "I showed before that\nit's this curve that's", "start": 670.08, "duration": 1.85}, {"text": "symmetric about the x-axis.", "start": 671.93, "duration": 3.14}, {"text": "Whether the thing\nyou're indicating", "start": 675.07, "duration": 1.62}, {"text": "is on top of the curve or\nit's sort of reflection", "start": 676.69, "duration": 3.15}, {"text": "on the bottom, it's\nvalid either way.", "start": 679.84, "duration": 2.82}, {"text": "So for any given\nsignature, there's", "start": 682.66, "duration": 1.56}, {"text": "another signature\nthat will be valid.", "start": 684.22, "duration": 1.86}, {"text": "You just sort of flip it,\nmake it negative or positive.", "start": 686.08, "duration": 3.65}, {"text": "So now there's a standard,\nOK, you need to have high s.", "start": 689.73, "duration": 2.71}, {"text": "Low s signatures\nshould be invalid.", "start": 692.44, "duration": 2.52}, {"text": "Both of these are really\ntricky because they're", "start": 694.96, "duration": 3.58}, {"text": "third party malleability.", "start": 698.54, "duration": 1.47}, {"text": "Anyone can just listen on the\nnetwork, see a transaction,", "start": 700.01, "duration": 3.12}, {"text": "change the signature.", "start": 703.13, "duration": 1.41}, {"text": "And in doing so they\nwill change the txid,", "start": 704.54, "duration": 2.28}, {"text": "which is how all the software\nrefers to transactions.", "start": 706.82, "duration": 2.43}, {"text": "So it looks like\na new transaction", "start": 709.25, "duration": 3.22}, {"text": "to most of the software.", "start": 712.47, "duration": 1.398}, {"text": "And the transactions\nare still valid.", "start": 713.868, "duration": 1.542}, {"text": "The signatures are still\nvalid and you're not", "start": 715.41, "duration": 1.94}, {"text": "sure which one will get in.", "start": 717.35, "duration": 2.16}, {"text": "There's also first party\nmalleability, or in some cases", "start": 719.51, "duration": 2.88}, {"text": "second party if you're\ndoing transactions", "start": 722.39, "duration": 1.74}, {"text": "with multiple people signing.", "start": 724.13, "duration": 2.76}, {"text": "So I'm not going to go back into\nthe elliptic curve signature", "start": 726.89, "duration": 3.65}, {"text": "algorithms, but\nthere is a nonce.", "start": 730.54, "duration": 1.72}, {"text": "There's randomness\nthat you inject", "start": 732.26, "duration": 1.59}, {"text": "into the signing process.", "start": 733.85, "duration": 3.15}, {"text": "It's not deterministic.", "start": 737.0, "duration": 1.08}, {"text": "It's not that given a\nmessage and my private key.", "start": 738.08, "duration": 3.24}, {"text": "I always compute\nthe same signature.", "start": 741.32, "duration": 1.68}, {"text": "No, that's not how it works.", "start": 743.0, "duration": 1.457}, {"text": "There are signature\nschemes like that,", "start": 744.457, "duration": 1.583}, {"text": "but in the case of the elliptic\ncurve stuff that bitcoin uses,", "start": 746.04, "duration": 3.47}, {"text": "you have to make up a random\nnumber to make each signature,", "start": 749.51, "duration": 3.8}, {"text": "and no one knows what\nthat random number is.", "start": 753.31, "duration": 2.05}, {"text": "So you could make up\ndifferent random numbers.", "start": 755.36, "duration": 2.88}, {"text": "You can make as many\nsignatures as you want.", "start": 758.24, "duration": 1.87}, {"text": "So given a message\nand your private key,", "start": 760.11, "duration": 4.49}, {"text": "you can make arbitrary\nnumber of signatures", "start": 764.6, "duration": 2.483}, {"text": "that are all\ndifferent signatures,", "start": 767.083, "duration": 1.417}, {"text": "but they're all\nvalid signatures.", "start": 768.5, "duration": 3.54}, {"text": "There is a sort of standard\nfor how to make them", "start": 772.04, "duration": 4.14}, {"text": "the right way not randomly.", "start": 776.18, "duration": 2.16}, {"text": "It's basically take the\nhash of your private key", "start": 778.34, "duration": 3.24}, {"text": "and the message being signed.", "start": 781.58, "duration": 2.7}, {"text": "Put them together,\nhash that, and use that", "start": 784.28, "duration": 2.76}, {"text": "as your random number because\nthen the idea is well,", "start": 787.04, "duration": 3.115}, {"text": "it's got secret\ninformation in it", "start": 790.155, "duration": 2.105}, {"text": "as well as the message\nspecific information in it.", "start": 792.26, "duration": 2.573}, {"text": "So no one's going to be\nable to guess what it is so,", "start": 794.833, "duration": 2.167}, {"text": "and it's still kind\nof message dependent", "start": 797.0, "duration": 1.94}, {"text": "so it'll change each time.", "start": 798.94, "duration": 2.47}, {"text": "So there is that, but\nthat's something you can do.", "start": 801.41, "duration": 3.46}, {"text": "It's a really good\nidea because if you", "start": 804.87, "duration": 2.81}, {"text": "use a non-random k,\nif someone can guess k", "start": 807.68, "duration": 2.97}, {"text": "or if your random number\ngenerator's broken,", "start": 810.65, "duration": 2.17}, {"text": "they can steal all your money.", "start": 812.82, "duration": 1.25}, {"text": "They can figure out\nyour private key.", "start": 814.07, "duration": 4.48}, {"text": "So you don't want to be\ndependent on generating", "start": 818.55, "duration": 2.23}, {"text": "randomness.", "start": 820.78, "duration": 0.75}, {"text": "A nice way to model it is, OK,\nhave some initial event where", "start": 821.53, "duration": 3.74}, {"text": "you're putting in random\nnumbers and you're storing them", "start": 825.27, "duration": 2.53}, {"text": "and then from then on you want\neverything to be deterministic,", "start": 827.8, "duration": 3.24}, {"text": "then you don't have to rely\non random number generators.", "start": 831.04, "duration": 2.85}, {"text": "So it's really a good\nidea to use this.", "start": 833.89, "duration": 1.92}, {"text": "And I use it in my software.", "start": 835.81, "duration": 1.545}, {"text": "Most things use this\nkind of standard.", "start": 837.355, "duration": 2.335}, {"text": "However, you can't verify that\nanyone's actually using it.", "start": 839.69, "duration": 2.72}, {"text": "It's purely internal.", "start": 842.41, "duration": 1.2}, {"text": "It's a internal way for you\nto make your own signatures,", "start": 843.61, "duration": 2.82}, {"text": "but no one can actually--", "start": 846.43, "duration": 2.46}, {"text": "can you prove?", "start": 848.89, "duration": 0.64}, {"text": "No.", "start": 849.53, "duration": 0.512}, {"text": "I'm not going to say you\ncan't prove you're using it,", "start": 850.042, "duration": 2.208}, {"text": "but not in any\nreasonable fashion.", "start": 852.25, "duration": 4.34}, {"text": "Yeah.", "start": 856.59, "duration": 0.5}, {"text": "So no one knows if\nyou're doing it.", "start": 857.09, "duration": 2.02}, {"text": "So this is an attack\nwhere you can say, OK,", "start": 859.11, "duration": 2.147}, {"text": "I'm going to make a whole\nbunch of different signatures.", "start": 861.257, "duration": 2.333}, {"text": "They're all going to\nbe valid, but that", "start": 863.59, "duration": 1.625}, {"text": "will mean I've got a whole\nbunch of different transactions", "start": 865.215, "duration": 3.325}, {"text": "that are doing the same thing.", "start": 868.54, "duration": 3.36}, {"text": "So maybe the question is,\nwhat does this really do?", "start": 871.9, "duration": 2.54}, {"text": "Does this really hurt?", "start": 874.44, "duration": 1.2}, {"text": "If someone dots an eye on your\ncheck, it's the same amount.", "start": 875.64, "duration": 3.82}, {"text": "It's going to the same place.", "start": 879.46, "duration": 2.69}, {"text": "Who cares.", "start": 882.15, "duration": 2.14}, {"text": "Outputs are the same.", "start": 884.29, "duration": 1.87}, {"text": "Inputs it's pointing\nto are the same.", "start": 886.16, "duration": 1.93}, {"text": "It's just this sort\nof annoying thing.", "start": 888.09, "duration": 2.03}, {"text": "OK, I tweaked it and\nI changed the txid.", "start": 890.12, "duration": 2.2}, {"text": "No big deal.", "start": 892.32, "duration": 1.3}, {"text": "Well, in some ways,\nyeah, it's no big deal,", "start": 893.62, "duration": 4.48}, {"text": "but a lot of wallets\ndidn't deal with this well.", "start": 898.1, "duration": 2.96}, {"text": "So let's say you're running a\nwallet, you make a transaction", "start": 901.06, "duration": 3.45}, {"text": "and you sign and you\nbroadcast transaction 2d5cac", "start": 904.51, "duration": 5.34}, {"text": "and it never gets confirmed, and\ninstead someone out there flips", "start": 909.85, "duration": 4.8}, {"text": "a bit, changes your\ntransaction to 9cba3e", "start": 914.65, "duration": 4.8}, {"text": "and that gets confirmed,\nand your wallet just", "start": 919.45, "duration": 2.1}, {"text": "says, yeah, this transaction\nyou sent never got confirmed.", "start": 921.55, "duration": 4.275}, {"text": "There's wallets that did that.", "start": 925.825, "duration": 1.425}, {"text": "Most of them have\nfixed it by now.", "start": 927.25, "duration": 1.82}, {"text": "But if you're thinking\nof transaction IDs", "start": 929.07, "duration": 2.05}, {"text": "as the identity txid, this is\nthe name of the transaction.", "start": 931.12, "duration": 5.24}, {"text": "I create it, I'm watching it\nto see when it gets confirmed,", "start": 936.36, "duration": 4.06}, {"text": "and I'm not looking for\nsome malleated version.", "start": 940.42, "duration": 2.43}, {"text": "I'm just watching this\nthing that I created, never", "start": 942.85, "duration": 2.34}, {"text": "gets in a block.", "start": 945.19, "duration": 1.53}, {"text": "Weird, and it's just\nstuck in the wallet.", "start": 946.72, "duration": 1.95}, {"text": "So there are definitely\nwallets, and I think", "start": 948.67, "duration": 2.43}, {"text": "everyone's fixed it by now.", "start": 951.1, "duration": 1.45}, {"text": "But a couple years\nago, definitely wallets", "start": 952.55, "duration": 1.76}, {"text": "that would have these problems.", "start": 954.31, "duration": 3.0}, {"text": "It's a wallet problem.", "start": 957.31, "duration": 1.35}, {"text": "Your money got to\nthe right place.", "start": 958.66, "duration": 2.55}, {"text": "You just need to sort of either\ndelete stuff in your wallet", "start": 961.21, "duration": 3.42}, {"text": "or upgrade the software or\ntell it to somehow forget", "start": 964.63, "duration": 2.58}, {"text": "about this transaction\nand actually", "start": 967.21, "duration": 1.47}, {"text": "look on the blockchain\nfor everything", "start": 968.68, "duration": 1.59}, {"text": "similar to your transaction.", "start": 970.27, "duration": 1.83}, {"text": "But it did do some damage.", "start": 972.1, "duration": 4.18}, {"text": "So, I don't know, 2014 the Mt.", "start": 976.28, "duration": 3.26}, {"text": "Gox thing where Mt.", "start": 979.54, "duration": 1.26}, {"text": "Gox got hacked supposedly\nand lost all the money,", "start": 980.8, "duration": 3.39}, {"text": "they blamed transaction\nmalleability,", "start": 984.19, "duration": 2.16}, {"text": "which was kind of interesting.", "start": 986.35, "duration": 1.99}, {"text": "There may have been an attack\non Mt Gox that used transaction", "start": 988.34, "duration": 4.73}, {"text": "malleability.", "start": 993.07, "duration": 2.31}, {"text": "The attack probably was\nthis, which was log into Mt.", "start": 995.38, "duration": 6.16}, {"text": "Gox, withdraw some coins,\nmodify the txid to this,", "start": 1001.54, "duration": 6.36}, {"text": "and then it gets confirmed,\nyou get your coins,", "start": 1007.9, "duration": 2.7}, {"text": "and then log into Mt.", "start": 1010.6, "duration": 1.477}, {"text": "Gox and say, hey,\nthis never happened.", "start": 1012.077, "duration": 1.583}, {"text": "My withdrawal\ndidn't work and then", "start": 1013.66, "duration": 1.62}, {"text": "their system would automatically\nissue a new withdrawal", "start": 1015.28, "duration": 2.292}, {"text": "transaction.", "start": 1017.572, "duration": 1.248}, {"text": "And so you could just start\ntaking all the money out", "start": 1018.82, "duration": 2.7}, {"text": "and your balance on\nthe system's like,", "start": 1021.52, "duration": 2.197}, {"text": "well, we keep trying\nto send you money", "start": 1023.717, "duration": 1.583}, {"text": "and it keeps never\ngetting confirmed.", "start": 1025.3, "duration": 1.9}, {"text": "And so we keep making new ones.", "start": 1027.2, "duration": 2.06}, {"text": "I don't know to what extent\nthat that actually happened.", "start": 1029.26, "duration": 2.609}, {"text": "It couldn't have been\nthe whole thing for Mt.", "start": 1034.555, "duration": 1.875}, {"text": "Gox definitely.", "start": 1036.43, "duration": 0.752}, {"text": "There's still a lot of\nuncertainty about that.", "start": 1037.182, "duration": 1.917}, {"text": "But it's indicative.", "start": 1039.099, "duration": 2.169}, {"text": "If you write your own\nsoftware and it's not", "start": 1041.268, "duration": 1.792}, {"text": "accounting for these things,\nyou may be losing money", "start": 1043.06, "duration": 3.21}, {"text": "once people say, hey, this\ndidn't work, make a new one,", "start": 1046.27, "duration": 2.76}, {"text": "and then you keep doing that\nand losing a ton of money.", "start": 1049.03, "duration": 2.76}, {"text": "But that's pretty\nsloppy practice.", "start": 1051.79, "duration": 4.29}, {"text": "Another issue.", "start": 1056.08, "duration": 1.05}, {"text": "If you're spending from\na unconfirmed change", "start": 1057.13, "duration": 5.31}, {"text": "output or an\nunconfirmed output--", "start": 1062.44, "duration": 1.65}, {"text": "so you make a transaction, you\nsend the two different outputs,", "start": 1064.09, "duration": 3.6}, {"text": "you've got a txid.", "start": 1067.69, "duration": 1.2}, {"text": "And you're sending five\ncoins to this person", "start": 1068.89, "duration": 2.55}, {"text": "and three coins\nback to yourself.", "start": 1071.44, "duration": 2.21}, {"text": "That three coins back\nto yourself output,", "start": 1073.65, "duration": 1.96}, {"text": "you might want to use\nit again pretty quickly.", "start": 1075.61, "duration": 2.46}, {"text": "Sometimes this happens.", "start": 1078.07, "duration": 2.49}, {"text": "And so you've got a\nchange output that's", "start": 1080.56, "duration": 4.83}, {"text": "from transaction 1, 7feec1.", "start": 1085.39, "duration": 2.22}, {"text": "So you're going to now spend\nthat change output, however", "start": 1087.61, "duration": 4.77}, {"text": "the txid of transaction\none changes.", "start": 1092.38, "duration": 2.49}, {"text": "So you're saying\nwhere you're spending", "start": 1094.87, "duration": 2.43}, {"text": "from is no longer valid.", "start": 1097.3, "duration": 2.547}, {"text": "And this is a big problem\nbecause now you've", "start": 1099.847, "duration": 1.833}, {"text": "signed a transaction that you\nthink is going to be valid,", "start": 1101.68, "duration": 2.7}, {"text": "but the money you thought\nyou were spending sort of", "start": 1104.38, "duration": 2.52}, {"text": "moves out from under you.", "start": 1106.9, "duration": 2.37}, {"text": "And so that transaction's\nno longer valid.", "start": 1109.27, "duration": 2.19}, {"text": "tx2 is now invalid.", "start": 1111.46, "duration": 1.32}, {"text": "It refers to something\nwhich can never", "start": 1112.78, "duration": 1.83}, {"text": "be confirmed because there's\na different transaction that's", "start": 1114.61, "duration": 3.78}, {"text": "almost the same, but they're\nmutually exclusive that", "start": 1118.39, "duration": 2.91}, {"text": "did get confirmed.", "start": 1121.3, "duration": 1.54}, {"text": "OK.", "start": 1122.84, "duration": 0.5}, {"text": "So this is bad.", "start": 1123.34, "duration": 2.35}, {"text": "It doesn't seem that bad.", "start": 1128.87, "duration": 1.56}, {"text": "And so for years in\nbitcoin this was a problem", "start": 1130.43, "duration": 2.67}, {"text": "that while it dealt\nwith, software and people", "start": 1133.1, "duration": 2.16}, {"text": "would be like, oh yeah, you\nhave to backup your keys,", "start": 1135.26, "duration": 3.63}, {"text": "delete your whole database,\nand rethink the blockchain", "start": 1138.89, "duration": 2.64}, {"text": "and then it'll find\nthe right transactions.", "start": 1141.53, "duration": 2.515}, {"text": "Kind of hacky work\narounds like that where", "start": 1144.045, "duration": 2.885}, {"text": "it didn't happen too much.", "start": 1146.93, "duration": 2.852}, {"text": "It wasn't a great attack.", "start": 1149.782, "duration": 1.858}, {"text": "You can annoy people.", "start": 1151.64, "duration": 0.93}, {"text": "You don't get any money.", "start": 1152.57, "duration": 1.92}, {"text": "So wasn't a huge deal,\nbut it was annoying.", "start": 1154.49, "duration": 3.565}, {"text": "But the idea is you\ncan always re-sign.", "start": 1158.055, "duration": 1.625}, {"text": "You've got your private keys.", "start": 1159.68, "duration": 1.208}, {"text": "If the money you are receiving\nsort of shifts around", "start": 1160.888, "duration": 4.142}, {"text": "and changes its location,\nwell it's still yours.", "start": 1165.03, "duration": 2.0}, {"text": "You just need to re-sign.", "start": 1167.03, "duration": 1.83}, {"text": "But what if you can't re-sign?", "start": 1168.86, "duration": 2.46}, {"text": "So the case of multisig where\nin most cases when you're", "start": 1171.32, "duration": 5.59}, {"text": "doing transactions if you just\nhave one key, it's just you,", "start": 1176.91, "duration": 3.57}, {"text": "that's fine.", "start": 1180.48, "duration": 1.08}, {"text": "In the case of\nmultisig usually you're", "start": 1181.56, "duration": 2.01}, {"text": "all friends to some\nextent and you're", "start": 1183.57, "duration": 2.64}, {"text": "all in the same organization or\nmultiple devices that you own.", "start": 1186.21, "duration": 4.95}, {"text": "But you can have sort\nof adversarial multisig", "start": 1191.16, "duration": 3.312}, {"text": "where you're\nassigning transactions", "start": 1194.472, "duration": 1.458}, {"text": "with people who are you're\nsort of cooperating with them,", "start": 1195.93, "duration": 2.46}, {"text": "but you may not\nreally trust them,", "start": 1198.39, "duration": 2.22}, {"text": "or they might be potentially\nattackers, things like that.", "start": 1200.61, "duration": 3.102}, {"text": "You can definitely sort of\nextend your multisig model", "start": 1203.712, "duration": 2.208}, {"text": "into that.", "start": 1205.92, "duration": 1.865}, {"text": "And there could be multisig\npre-signed transactions", "start": 1207.785, "duration": 2.125}, {"text": "where, OK, we've got\nthis two of three output", "start": 1209.91, "duration": 2.7}, {"text": "address, this\noutput that exists,", "start": 1212.61, "duration": 3.21}, {"text": "and one of the two or three\nhas pre-signed a transaction", "start": 1215.82, "duration": 2.7}, {"text": "and hands it over to me\nand then they disappear.", "start": 1218.52, "duration": 2.13}, {"text": "And they say, oh OK, well I'm\ngoing to now sign my side.", "start": 1220.65, "duration": 3.75}, {"text": "But if malleability occurs and\nthe transaction ID changes,", "start": 1224.4, "duration": 4.11}, {"text": "that signature is no longer\nvalid, signing something", "start": 1228.51, "duration": 4.92}, {"text": "that's not there anymore.", "start": 1233.43, "duration": 1.418}, {"text": "So this is very important in\npayment channels lightning", "start": 1234.848, "duration": 2.292}, {"text": "network stuff that I'll\nget to in a few days.", "start": 1237.14, "duration": 4.64}, {"text": "And so it wasn't so\nmuch that malleability", "start": 1241.78, "duration": 2.75}, {"text": "was like a showstopper bug\nand everyone was losing tons", "start": 1244.53, "duration": 3.12}, {"text": "of money, it was that\nit was preventing", "start": 1247.65, "duration": 2.49}, {"text": "kind of new, cool\nthings from happening", "start": 1250.14, "duration": 2.34}, {"text": "because there were a\nlot of problems with,", "start": 1252.48, "duration": 2.94}, {"text": "OK, let's make this\nconstruction where we put money", "start": 1255.42, "duration": 3.15}, {"text": "into a multisig account and\nthen I sign like a refund", "start": 1258.57, "duration": 2.85}, {"text": "transaction that's got a lock\ntime before I actually fund it", "start": 1261.42, "duration": 4.2}, {"text": "and things like that where\nyou couldn't reliably do it", "start": 1265.62, "duration": 2.47}, {"text": "because if either party\nmodified their signature,", "start": 1268.09, "duration": 2.63}, {"text": "they could break the whole thing\nand they could have a tax where", "start": 1270.72, "duration": 2.82}, {"text": "it's like, OK, we're\ndoing something together.", "start": 1273.54, "duration": 1.917}, {"text": "Oh look, it's got stuck.", "start": 1275.457, "duration": 1.323}, {"text": "Well both of our coins\ngot stuck in this place.", "start": 1276.78, "duration": 2.44}, {"text": "Hmm.", "start": 1279.22, "duration": 0.5}, {"text": "Now it's sort of a hostage\nsituation and you can say,", "start": 1279.72, "duration": 2.41}, {"text": "well, I think I should get 1\nand 1/2 and you should get 1.5.", "start": 1282.13, "duration": 3.53}, {"text": "It's like wait,\nwe both wanted 1.", "start": 1285.66, "duration": 1.95}, {"text": "So there is a tax\nthat could happen.", "start": 1287.61, "duration": 2.16}, {"text": "And so this malleability\nwas a problem", "start": 1289.77, "duration": 1.802}, {"text": "for people trying to\ndo new, cool things.", "start": 1291.572, "duration": 1.708}, {"text": "So how do you fix this?", "start": 1295.89, "duration": 1.35}, {"text": "Any ideas?", "start": 1297.24, "duration": 0.5}, {"text": "Non-malleable signatures?", "start": 1300.27, "duration": 1.5}, {"text": "So the one we did for\nthe first homework.", "start": 1301.77, "duration": 4.2}, {"text": "Does anyone have an idea about\nwhy the lamport signatures were", "start": 1305.97, "duration": 3.0}, {"text": "non-malleable, like\nfrom problems at one?", "start": 1308.97, "duration": 3.96}, {"text": "Yes, it was right.", "start": 1317.53, "duration": 2.8}, {"text": "But yeah, they weren't.", "start": 1320.33, "duration": 1.21}, {"text": "There's no randomness for one.", "start": 1324.35, "duration": 2.26}, {"text": "I'm pretty sure if you flip\nany of the bits it's not", "start": 1326.61, "duration": 2.347}, {"text": "going to work.", "start": 1328.957, "duration": 0.583}, {"text": "So lamport signatures are\nan example where, yeah, it's", "start": 1329.54, "duration": 2.67}, {"text": "non-malleable.", "start": 1332.21, "duration": 1.33}, {"text": "You can't produce multiple\ndifferent signatures", "start": 1333.54, "duration": 4.85}, {"text": "on the same message.", "start": 1338.39, "duration": 2.16}, {"text": "So that's good.", "start": 1340.55, "duration": 1.5}, {"text": "The thing is many\nuseful signature schemes", "start": 1342.05, "duration": 2.49}, {"text": "are malleable.", "start": 1344.54, "duration": 0.71}, {"text": "So to just say no, you have to\nuse a non-malleable signature", "start": 1345.25, "duration": 2.5}, {"text": "scheme, it's not a great\nanswer to the question.", "start": 1347.75, "duration": 2.25}, {"text": "I'm pretty sure there's\nsome weird malleability", "start": 1353.302, "duration": 1.958}, {"text": "stuff in RSA.", "start": 1355.26, "duration": 1.99}, {"text": "A lot of the systems\nhave randomness in there", "start": 1357.25, "duration": 3.59}, {"text": "and they're malleable.", "start": 1360.84, "duration": 2.19}, {"text": "So an idea that I\nhad like 2014 and I", "start": 1363.03, "duration": 3.24}, {"text": "was sort of going for was just\ndon't sign your inputs at all,", "start": 1366.27, "duration": 5.37}, {"text": "only sign your outputs.", "start": 1371.64, "duration": 1.327}, {"text": "So you don't actually specify\nwhere you're sending money", "start": 1372.967, "duration": 2.333}, {"text": "from in your signature.", "start": 1375.3, "duration": 1.53}, {"text": "You do have to still\nspecify in your transaction", "start": 1376.83, "duration": 2.7}, {"text": "because people need\nto know, but you", "start": 1379.53, "duration": 2.01}, {"text": "say I'm only going to\nsign off on the outputs.", "start": 1381.54, "duration": 2.74}, {"text": "The endorsement of\nmy inputs is implicit", "start": 1384.28, "duration": 3.71}, {"text": "because the keys match.", "start": 1387.99, "duration": 2.16}, {"text": "So I don't actually\nsign off on which", "start": 1390.15, "duration": 1.68}, {"text": "key I'm sending from to\nsomething that's redundant.", "start": 1391.83, "duration": 4.907}, {"text": "You know I'm sending\nfrom these inputs", "start": 1396.737, "duration": 1.583}, {"text": "because the keys match\nup and the signature's", "start": 1398.32, "duration": 1.875}, {"text": "valid for this key.", "start": 1400.195, "duration": 2.015}, {"text": "I really like this idea still.", "start": 1402.21, "duration": 1.76}, {"text": "I think it's really fun.", "start": 1403.97, "duration": 1.0}, {"text": "You can do a lot of\ncool stuff with it.", "start": 1404.97, "duration": 1.86}, {"text": "It's also dangerous.", "start": 1406.83, "duration": 1.95}, {"text": "It allows signatures\nto be replayed,", "start": 1408.78, "duration": 2.85}, {"text": "which is sort of one of\nthe big points of having", "start": 1411.63, "duration": 2.25}, {"text": "utxo's because if you\nsend two outputs--", "start": 1413.88, "duration": 3.84}, {"text": "I have address one.", "start": 1421.59, "duration": 3.27}, {"text": "I send two outputs.", "start": 1424.86, "duration": 1.76}, {"text": "So I've got output one,\noutput two, and this one", "start": 1426.62, "duration": 6.16}, {"text": "has five coins, this\none has three coins,", "start": 1432.78, "duration": 3.0}, {"text": "and they're both\nthe same address,", "start": 1435.78, "duration": 2.85}, {"text": "both the same public key, and\nthen I want to spend them.", "start": 1438.63, "duration": 2.7}, {"text": "And if I use this sort\nof signature scheme", "start": 1441.33, "duration": 1.86}, {"text": "where I don't actually sign\nwhich input I'm spending from,", "start": 1443.19, "duration": 3.24}, {"text": "it can be used on either.", "start": 1446.43, "duration": 1.36}, {"text": "So maybe I'm not\naware of this 5-1 yet,", "start": 1447.79, "duration": 3.332}, {"text": "or it just hasn't happened\nyet, or I haven't seen it,", "start": 1451.122, "duration": 2.208}, {"text": "and I say, yeah, I'm going\nto make a signature sending", "start": 1453.33, "duration": 2.46}, {"text": "three coins over\nhere and then someone", "start": 1455.79, "duration": 2.94}, {"text": "can malleate the transaction\nwithout touching the signature,", "start": 1458.73, "duration": 3.68}, {"text": "and pointing over\nhere, and the signature", "start": 1462.41, "duration": 2.64}, {"text": "wouldn't apply to either.", "start": 1465.05, "duration": 1.5}, {"text": "And then this is a really\ngood deal for the miners", "start": 1466.55, "duration": 2.88}, {"text": "because now I'm spending five\ncoins and only outputting three", "start": 1469.43, "duration": 3.0}, {"text": "and the miners get the\ntwo coins difference.", "start": 1472.43, "duration": 2.85}, {"text": "And so that's pretty dangerous.", "start": 1475.28, "duration": 1.71}, {"text": "And also, even if they're\nthe same I just say, hey,", "start": 1476.99, "duration": 3.76}, {"text": "I'm sending three coins\nto you and then as", "start": 1480.75, "duration": 3.03}, {"text": "soon as the receiver\nsees this output,", "start": 1483.78, "duration": 2.31}, {"text": "oh, it'll also work here.", "start": 1486.09, "duration": 1.38}, {"text": "I'm going to take\nanother three coins.", "start": 1487.47, "duration": 2.55}, {"text": "So this is mitigated by\nnot reusing addresses,", "start": 1490.02, "duration": 4.95}, {"text": "but people reuse addresses.", "start": 1494.97, "duration": 3.99}, {"text": "So it is dangerous.", "start": 1498.96, "duration": 1.95}, {"text": "I think in the context of\nmultisig you can reliably", "start": 1500.91, "duration": 2.762}, {"text": "say like, OK, we're\nnot reusing addresses", "start": 1503.672, "duration": 1.708}, {"text": "because these addresses are the\ncombination of multiple people", "start": 1505.38, "duration": 2.583}, {"text": "working together.", "start": 1507.963, "duration": 1.185}, {"text": "But it would allow\nreally cool things", "start": 1509.148, "duration": 1.542}, {"text": "where you could sort of work\nbackwards, compute a public key", "start": 1510.69, "duration": 3.323}, {"text": "that you could prove no one\nknew the private key to,", "start": 1514.013, "duration": 2.167}, {"text": "but you could\nstill sign with it.", "start": 1516.18, "duration": 1.375}, {"text": "Like really weird crazy stuff.", "start": 1517.555, "duration": 1.985}, {"text": "Anyway, people were\nstill talking about it", "start": 1519.54, "duration": 4.39}, {"text": "a week or two ago.", "start": 1523.93, "duration": 0.76}, {"text": "Like, oh, we could do\nthese cool things with it.", "start": 1524.69, "duration": 2.0}, {"text": "But it's dangerous and so\nit's like we're not sure", "start": 1526.69, "duration": 3.0}, {"text": "if it's worth it.", "start": 1529.69, "duration": 1.83}, {"text": "OK.", "start": 1531.52, "duration": 0.5}, {"text": "Any questions about this\ntransaction malleability", "start": 1532.02, "duration": 2.79}, {"text": "so far?", "start": 1534.81, "duration": 1.59}, {"text": "OK.", "start": 1536.4, "duration": 0.5}, {"text": "So any ideas of\nwhat you actually", "start": 1536.9, "duration": 2.12}, {"text": "do to fix malleability?", "start": 1539.02, "duration": 3.107}, {"text": "Nobody?", "start": 1545.71, "duration": 1.05}, {"text": "OK.", "start": 1546.76, "duration": 2.04}, {"text": "we'll find out in one minute.", "start": 1548.8, "duration": 2.79}, {"text": "Segregated Witness.", "start": 1551.59, "duration": 2.07}, {"text": "I don't think it's a good name.", "start": 1553.66, "duration": 3.07}, {"text": "Separate signatures would be a\nmuch easier to understand name.", "start": 1556.73, "duration": 6.12}, {"text": "So Peter Wuille who is\nreally good at bitcoin", "start": 1562.85, "duration": 2.058}, {"text": "and makes all these\ncool things, he's", "start": 1564.908, "duration": 1.542}, {"text": "not the best at naming things.", "start": 1566.45, "duration": 2.47}, {"text": "Makes lots of cool\nstuff, but just makes", "start": 1568.92, "duration": 2.04}, {"text": "whatever weird technical name.", "start": 1570.96, "duration": 1.25}, {"text": "So it's a pretty\nstraightforward idea.", "start": 1574.91, "duration": 1.83}, {"text": "The idea is when you're\nsigning a transaction you hash", "start": 1576.74, "duration": 5.72}, {"text": "a bunch of data design, but you\ndon't include the signatures", "start": 1582.46, "duration": 3.87}, {"text": "in the data you're\nhashing to sign them", "start": 1586.33, "duration": 1.71}, {"text": "because that wouldn't\nmake any sense.", "start": 1588.04, "duration": 1.17}, {"text": "You can't.", "start": 1589.21, "duration": 0.5}, {"text": "Do the same thing when you're\nreferring to transactions", "start": 1591.788, "duration": 2.292}, {"text": "themselves as txids.", "start": 1594.08, "duration": 2.02}, {"text": "So in the exact same way\nthat when you're signing,", "start": 1596.1, "duration": 2.752}, {"text": "you hash the data\nwithout the signatures.", "start": 1598.852, "duration": 1.708}, {"text": "When you're pointing\nto a transaction", "start": 1600.56, "duration": 1.86}, {"text": "to say I'm spending\nfrom there, also", "start": 1602.42, "duration": 2.07}, {"text": "don't include the\nsignature data.", "start": 1604.49, "duration": 2.19}, {"text": "Just take the hash of the\ndata without the signatures.", "start": 1606.68, "duration": 4.612}, {"text": "Yeah.", "start": 1615.53, "duration": 0.5}, {"text": "You just sort of\nhave this pointer.", "start": 1616.03, "duration": 1.95}, {"text": "You've got a pointer\nof previous input", "start": 1617.98, "duration": 2.88}, {"text": "and you've got the outputs, but\nthe signatures aren't in there.", "start": 1620.86, "duration": 2.89}, {"text": "So the idea is the signature can\nchange and the transaction ID", "start": 1623.75, "duration": 3.0}, {"text": "doesn't.", "start": 1626.75, "duration": 0.5}, {"text": "But what about\nbackwards compatibility?", "start": 1630.9, "duration": 1.96}, {"text": "So this is a great idea.", "start": 1632.86, "duration": 1.74}, {"text": "Why not go for it?", "start": 1634.6, "duration": 1.07}, {"text": "But how do you make it backwards\ncompatible so that old software", "start": 1635.67, "duration": 4.71}, {"text": "can still work with it?", "start": 1640.38, "duration": 2.85}, {"text": "This seems like a\nsoft fork is I'm", "start": 1643.23, "duration": 3.65}, {"text": "adding new rules to\nthe system I'm putting", "start": 1646.88, "duration": 3.03}, {"text": "further restrictions on.", "start": 1649.91, "duration": 3.16}, {"text": "This seems like just a change.", "start": 1653.07, "duration": 2.19}, {"text": "It seems like, look,\nI'm now defining", "start": 1655.26, "duration": 3.112}, {"text": "something in a different way.", "start": 1658.372, "duration": 1.208}, {"text": "I'm removing the\nsignatures from the txid.", "start": 1659.58, "duration": 2.4}, {"text": "How do we make this not\nappear to be a hard fork?", "start": 1661.98, "duration": 3.24}, {"text": "Hard fork's easy.", "start": 1665.22, "duration": 1.092}, {"text": "You just say, look, we're\nchanging the entire system.", "start": 1666.312, "duration": 2.208}, {"text": "From now on txids\ndon't have signatures.", "start": 1668.52, "duration": 3.83}, {"text": "So any ideas how you do this\nin a backwards compatible way", "start": 1672.35, "duration": 6.17}, {"text": "or just give up hard fork?", "start": 1678.52, "duration": 1.41}, {"text": "AUDIENCE: Adding restrictions\nthat screw with [INAUDIBLE]..", "start": 1683.834, "duration": 5.686}, {"text": "PROFESSOR: So you can't\nchange old transactions,", "start": 1689.52, "duration": 4.31}, {"text": "but having both at the\nsame time is tricky.", "start": 1693.83, "duration": 2.07}, {"text": "So the idea is it\nwould have been easier", "start": 1698.453, "duration": 1.667}, {"text": "to start off this way.", "start": 1700.12, "duration": 1.35}, {"text": "If Satoshi had just started this\nway, it would have went great.", "start": 1701.47, "duration": 2.823}, {"text": "He didn't think of it.", "start": 1704.293, "duration": 0.917}, {"text": "It wasn't a super\nobvious thing that--", "start": 1705.21, "duration": 2.397}, {"text": "so you can do it as a soft fork.", "start": 1707.607, "duration": 1.333}, {"text": "The way you do it is\nyou make new outputs", "start": 1708.94, "duration": 3.21}, {"text": "which don't require\nany signatures at all", "start": 1712.15, "duration": 2.43}, {"text": "and then you just don't\nhave any signatures.", "start": 1714.58, "duration": 3.06}, {"text": "This seems kind of silly.", "start": 1717.64, "duration": 1.05}, {"text": "Signatures are pretty important,\notherwise any arbitrary person", "start": 1718.69, "duration": 2.94}, {"text": "could just take all the money.", "start": 1721.63, "duration": 2.07}, {"text": "But you redefine things in a\nway that new people know about", "start": 1723.7, "duration": 2.79}, {"text": "and old people don't.", "start": 1726.49, "duration": 1.89}, {"text": "So this is actually what a\nsegwit output looks like.", "start": 1728.38, "duration": 2.76}, {"text": "The output script is just a\nzero and then a pubkey hash,", "start": 1731.14, "duration": 4.16}, {"text": "and then the sig script,\nthe field for a signature", "start": 1735.3, "duration": 3.0}, {"text": "is just nothing.", "start": 1738.3, "duration": 1.2}, {"text": "You just don't put\na signature there.", "start": 1739.5, "duration": 3.53}, {"text": "And then when you're\nrunning the stack", "start": 1743.03, "duration": 2.34}, {"text": "you end up with a pubkey hash\non the top of the stack, which", "start": 1745.37, "duration": 3.06}, {"text": "is some number and\nthe interpreter", "start": 1748.43, "duration": 3.84}, {"text": "looks at a number\nthat's non-zero as true.", "start": 1752.27, "duration": 3.21}, {"text": "Like in C or things like that.", "start": 1755.48, "duration": 1.573}, {"text": "And the bitcoins move.", "start": 1757.053, "duration": 0.917}, {"text": "It's great.", "start": 1757.97, "duration": 1.11}, {"text": "Someone was joking that you\ncould potentially make this", "start": 1759.08, "duration": 2.91}, {"text": "into a hard fork, because what\nif the pubkey hash was zero,", "start": 1761.99, "duration": 5.17}, {"text": "and you found a pubkey that\nhashed to zero and then you", "start": 1767.16, "duration": 3.708}, {"text": "signed signed with it and then\nsegwit would accept it but old", "start": 1770.868, "duration": 2.542}, {"text": "nodes wouldn't.", "start": 1773.41, "duration": 2.03}, {"text": "Actually, that doesn't\nwork, but it's sort of--", "start": 1775.44, "duration": 2.6}, {"text": "Anyway, if you're running\nthe regular bitcoin software,", "start": 1778.04, "duration": 4.38}, {"text": "you see this and no signature,\nand you're like yeah,", "start": 1782.42, "duration": 3.15}, {"text": "this doesn't need a signature.", "start": 1785.57, "duration": 1.44}, {"text": "It's just a hash.", "start": 1787.01, "duration": 1.71}, {"text": "I don't know what this is.", "start": 1788.72, "duration": 1.54}, {"text": "Fine, the coins move.", "start": 1790.26, "duration": 1.43}, {"text": "It evaluates to true.", "start": 1791.69, "duration": 2.91}, {"text": "But the new version\nof the software", "start": 1794.6, "duration": 3.0}, {"text": "sort of adds a restriction\nto this kind of output.", "start": 1797.6, "duration": 2.177}, {"text": "It says, look.", "start": 1799.777, "duration": 0.583}, {"text": "If you see this,\nthis is a template.", "start": 1800.36, "duration": 2.13}, {"text": "This doesn't actually mean\nput a zero on the stack", "start": 1802.49, "duration": 3.36}, {"text": "and put a pubkey\nhash on the stack.", "start": 1805.85, "duration": 1.83}, {"text": "It means something else.", "start": 1807.68, "duration": 2.01}, {"text": "Now, it means this is a pubkey\nhash and look for a signature.", "start": 1809.69, "duration": 4.23}, {"text": "But look for a signature\nin a different place.", "start": 1813.92, "duration": 2.663}, {"text": "Don't actually put\nit in the place", "start": 1816.583, "duration": 1.417}, {"text": "you're supposed\nto put signatures,", "start": 1818.0, "duration": 1.5}, {"text": "put it in a new place.", "start": 1819.5, "duration": 1.14}, {"text": "And don't tell the old\nsoftware about this place.", "start": 1820.64, "duration": 4.3}, {"text": "We add a new field to\nthe transaction inputs.", "start": 1824.94, "duration": 5.06}, {"text": "It's sort of in the inputs,\nbut they put it at the end.", "start": 1830.0, "duration": 3.61}, {"text": "It's kind of weird.", "start": 1833.61, "duration": 1.5}, {"text": "Logically, it's in the input.", "start": 1835.11, "duration": 2.13}, {"text": "It's the same, but physically\nit's not, which is silly.", "start": 1837.24, "duration": 4.88}, {"text": "I don't like that aspect of it.", "start": 1842.12, "duration": 2.142}, {"text": "But the idea is there's this\nnew field in the inputs called", "start": 1844.262, "duration": 2.458}, {"text": "the witness field,\nand in cryptography,", "start": 1846.72, "duration": 2.55}, {"text": "witness sort of means\nsignature in this case anyway.", "start": 1849.27, "duration": 4.05}, {"text": "It's a little bit more general.", "start": 1853.32, "duration": 2.98}, {"text": "But the old software\nnever sees it.", "start": 1856.3, "duration": 1.62}, {"text": "So the idea for here's the\nold transaction format.", "start": 1857.92, "duration": 2.49}, {"text": "You've got your tx id and\nindex, 36 bytes sort of pointer", "start": 1860.41, "duration": 4.38}, {"text": "to what you're\nspending, and then", "start": 1864.79, "duration": 1.68}, {"text": "a signature which is 100 bytes,\nand then this stays the same.", "start": 1866.47, "duration": 4.59}, {"text": "And the new tx format.", "start": 1871.06, "duration": 1.29}, {"text": "The idea is, yeah,\nthe signatures field", "start": 1872.35, "duration": 1.75}, {"text": "is still there.", "start": 1874.1, "duration": 0.83}, {"text": "You just leave it empty.", "start": 1874.93, "duration": 1.44}, {"text": "So you're not putting\nany signature.", "start": 1876.37, "duration": 1.51}, {"text": "It doesn't look like you\nneed to put a signature", "start": 1877.88, "duration": 2.0}, {"text": "to the old software.", "start": 1879.88, "duration": 1.8}, {"text": "And then you have\nthis third thing,", "start": 1881.68, "duration": 1.83}, {"text": "which is witness, which is the\nsame as signature basically.", "start": 1883.51, "duration": 4.62}, {"text": "Slightly different format.", "start": 1888.13, "duration": 1.35}, {"text": "And technically, they\nput them all together", "start": 1889.48, "duration": 2.28}, {"text": "and put it at the end,\nwhich is kind of annoying.", "start": 1891.76, "duration": 2.042}, {"text": "But anyway, logically\nthis is how they do it.", "start": 1893.802, "duration": 2.338}, {"text": "They make a new version\nof the transaction format.", "start": 1896.14, "duration": 3.21}, {"text": "So the old version looks\nlike empty signatures.", "start": 1899.35, "duration": 3.81}, {"text": "The new version\nlooks like here's", "start": 1903.16, "duration": 1.89}, {"text": "this useless empty\nsignature field,", "start": 1905.05, "duration": 1.652}, {"text": "and here's where the\nreal signatures are.", "start": 1906.702, "duration": 1.708}, {"text": "And you omit this\nto the old nodes.", "start": 1911.31, "duration": 2.51}, {"text": "So when people ask for\nwitness transactions,", "start": 1913.82, "duration": 4.89}, {"text": "when people know\nabout this new system,", "start": 1918.71, "duration": 2.797}, {"text": "yeah, you give it to them.", "start": 1921.507, "duration": 1.083}, {"text": "So they say hey, yeah, I'm\nhip to this new segwit thing.", "start": 1922.59, "duration": 3.86}, {"text": "Give me a segwit transaction.", "start": 1926.45, "duration": 1.62}, {"text": "And you're like, OK, here's\nthe witnesses at the end.", "start": 1928.07, "duration": 2.61}, {"text": "But when they don't\nseem to know about this", "start": 1930.68, "duration": 2.153}, {"text": "and they're running\nolder software", "start": 1932.833, "duration": 1.417}, {"text": "and they say, hey, just\ngive me the transaction,", "start": 1934.25, "duration": 2.0}, {"text": "you give it to them\nwithout the witness at all.", "start": 1936.25, "duration": 2.15}, {"text": "It still looks valid to--", "start": 1938.4, "duration": 1.94}, {"text": "either one looks valid.", "start": 1940.34, "duration": 1.83}, {"text": "However, the new people, they\nknow that if you see this,", "start": 1942.17, "duration": 6.21}, {"text": "it does not mean push a\nzero, push up pubkey has.", "start": 1948.38, "duration": 2.74}, {"text": "There is a new rule that\nno, this is a template.", "start": 1951.12, "duration": 2.0}, {"text": "This is segwit.", "start": 1953.12, "duration": 0.99}, {"text": "I need a signature, and I need\nit to be in the witness field.", "start": 1954.11, "duration": 4.78}, {"text": "So if a new node gets a\ntransaction without a witness", "start": 1958.89, "duration": 5.36}, {"text": "that they know needs a witness,\nthey will declare it invalid.", "start": 1964.25, "duration": 3.33}, {"text": "But the old nodes won't\nbe able to distinguish.", "start": 1967.58, "duration": 2.13}, {"text": "They'll say, well, it looks like\nno signature is needed here.", "start": 1969.71, "duration": 2.55}, {"text": "OK.", "start": 1972.26, "duration": 0.99}, {"text": "So you're sort of\ntricking the old software", "start": 1973.25, "duration": 3.197}, {"text": "into accepting things that\nthey shouldn't actually", "start": 1976.447, "duration": 2.083}, {"text": "accept in some cases.", "start": 1978.53, "duration": 1.53}, {"text": "There may not be a\nvalid signature that", "start": 1980.06, "duration": 2.19}, {"text": "goes into the\nsegwit transaction,", "start": 1982.25, "duration": 1.74}, {"text": "but old software will\nstill think it's OK.", "start": 1983.99, "duration": 3.5}, {"text": "So this is how you make\nit into a softfork.", "start": 1987.49, "duration": 2.95}, {"text": "It's kind of ugly.", "start": 1990.44, "duration": 0.75}, {"text": "But, yeah.", "start": 1991.19, "duration": 0.772}, {"text": "Do you have a question?", "start": 1991.962, "duration": 0.958}, {"text": "AUDIENCE: Yeah.", "start": 1992.92, "duration": 0.606}, {"text": "Is this still implicitly?", "start": 1993.526, "duration": 1.042}, {"text": "So when the signature\nis zero, [INAUDIBLE]..", "start": 1994.568, "duration": 3.134}, {"text": "PROFESSOR: No, because it's\nbased on the output script.", "start": 2000.65, "duration": 7.5}, {"text": "You could make you a\ndifferent output script that", "start": 2008.15, "duration": 3.72}, {"text": "would have a signature that\nno signature requirement,", "start": 2011.87, "duration": 2.7}, {"text": "and it would still work\neven with this new system.", "start": 2014.57, "duration": 3.06}, {"text": "So it's just based on--", "start": 2017.63, "duration": 1.61}, {"text": "we changed the definition\nof an output script.", "start": 2019.24, "duration": 3.51}, {"text": "So have this sort of template.", "start": 2022.75, "duration": 2.23}, {"text": "You can still do weird--", "start": 2024.98, "duration": 1.08}, {"text": "like you could put\nwithout a zero in front.", "start": 2026.06, "duration": 3.69}, {"text": "You could put just\na pubkey hash,", "start": 2029.75, "duration": 2.15}, {"text": "and that's not\ndefined in segwit.", "start": 2031.9, "duration": 1.48}, {"text": "That's not defined anywhere.", "start": 2033.38, "duration": 1.2}, {"text": "It would just be, OK,\nyeah, it evaluates", "start": 2034.58, "duration": 2.67}, {"text": "to true without a signature.", "start": 2037.25, "duration": 1.23}, {"text": "Anyone can spend it.", "start": 2038.48, "duration": 1.61}, {"text": "And you could do that--", "start": 2040.09, "duration": 3.37}, {"text": "that would have to be a\nnon-segwit transaction.", "start": 2043.46, "duration": 3.072}, {"text": "The only way to use\na segwit transaction", "start": 2046.532, "duration": 1.667}, {"text": "is to have the special\nformat for the output script.", "start": 2048.199, "duration": 4.301}, {"text": "Any other questions\nabout network stuff?", "start": 2052.5, "duration": 2.12}, {"text": "Yeah, and this\nsolves malleability", "start": 2054.62, "duration": 5.86}, {"text": "in a pretty good way.", "start": 2060.48, "duration": 1.53}, {"text": "For the old software,\nthe old nodes,", "start": 2062.01, "duration": 2.147}, {"text": "well, they can't\nchange the signature", "start": 2064.157, "duration": 1.542}, {"text": "because there isn't one.", "start": 2065.699, "duration": 1.0}, {"text": "There's nothing to malleate.", "start": 2066.699, "duration": 2.421}, {"text": "And from the new\nnode's perspective,", "start": 2069.12, "duration": 1.95}, {"text": "yes, the signature can\nchange, but that doesn't", "start": 2071.07, "duration": 2.879}, {"text": "affect the transaction ID.", "start": 2073.949, "duration": 1.5}, {"text": "Both old and new\nnodes still agree", "start": 2075.449, "duration": 2.641}, {"text": "on the exact same\ntransaction ID.", "start": 2078.09, "duration": 2.399}, {"text": "The transaction ID does not\ninclude the witness field.", "start": 2080.489, "duration": 5.831}, {"text": "So when you're\ncalculating a transaction,", "start": 2086.32, "duration": 2.2}, {"text": "you include all\nthis for backwards.", "start": 2088.52, "duration": 1.74}, {"text": "And if there's this\nactual signature there,", "start": 2090.26, "duration": 1.792}, {"text": "that gets into that the txid.", "start": 2092.052, "duration": 2.008}, {"text": "But if you're using\nempty signature", "start": 2094.06, "duration": 1.8}, {"text": "and only using witness, then\nit doesn't get into the txid", "start": 2095.86, "duration": 2.96}, {"text": "at all.", "start": 2098.82, "duration": 1.65}, {"text": "So both old and\nnew software agree,", "start": 2100.47, "duration": 2.64}, {"text": "and that's important, because\nif they didn't the merkle routes", "start": 2103.11, "duration": 3.42}, {"text": "would look wrong.", "start": 2106.53, "duration": 0.79}, {"text": "You take all the txids, put\nthem into a merkle route,", "start": 2107.32, "duration": 2.208}, {"text": "put that in the header.", "start": 2109.528, "duration": 1.272}, {"text": "And that's really important\nthat everyone agrees on that.", "start": 2110.8, "duration": 2.99}, {"text": "So they do work\ntogether, So that's cool.", "start": 2113.79, "duration": 2.22}, {"text": "So this is kind of interesting.", "start": 2119.62, "duration": 1.74}, {"text": "You've got two\ndifferent old version,", "start": 2121.36, "duration": 3.39}, {"text": "new version operating at the\nsame time on the network.", "start": 2124.75, "duration": 3.3}, {"text": "And they agree on\na lot of stuff,", "start": 2128.05, "duration": 2.13}, {"text": "but they also sort of\ndisagree on some things.", "start": 2130.18, "duration": 2.295}, {"text": "So they agree on outputs\nof the transactions,", "start": 2132.475, "duration": 3.495}, {"text": "and they agree on\nwhich inputs there are.", "start": 2135.97, "duration": 2.515}, {"text": "But they have a\nslightly different view", "start": 2138.485, "duration": 1.625}, {"text": "of what these inputs are.", "start": 2140.11, "duration": 1.042}, {"text": "Some of them think,\nno signatures here.", "start": 2141.152, "duration": 1.788}, {"text": "Some of them think, yeah,\nthere's a signature here.", "start": 2142.94, "duration": 2.125}, {"text": "That's weird.", "start": 2145.065, "duration": 1.105}, {"text": "They don't agree on\nhow things got spent.", "start": 2146.17, "duration": 1.98}, {"text": "What are some other things that\nthese two different classes", "start": 2148.15, "duration": 2.94}, {"text": "of nodes would not agree on?", "start": 2151.09, "duration": 1.634}, {"text": "Any ideas?", "start": 2155.47, "duration": 1.27}, {"text": "So you understand how they\nsee different transactions.", "start": 2156.74, "duration": 3.57}, {"text": "What are some other\naspects that may", "start": 2160.31, "duration": 2.35}, {"text": "be sort of interesting\nfor this consensus system", "start": 2162.66, "duration": 2.81}, {"text": "that we have different views on?", "start": 2165.47, "duration": 2.69}, {"text": "I forget what I put.", "start": 2168.16, "duration": 1.01}, {"text": "I put two things.", "start": 2169.17, "duration": 2.49}, {"text": "Any?", "start": 2171.66, "duration": 1.944}, {"text": "Hint.", "start": 2173.604, "duration": 1.956}, {"text": "Biggest argument\nsince 2010 in bitcoin.", "start": 2175.56, "duration": 4.8}, {"text": "What do these two different\nclasses of nodes not agree on?", "start": 2180.36, "duration": 2.96}, {"text": "Yeah.", "start": 2186.603, "duration": 1.407}, {"text": "AUDIENCE: Size?", "start": 2188.01, "duration": 1.41}, {"text": "PROFESSOR: Well, the\ntransaction size.", "start": 2189.42, "duration": 1.63}, {"text": "Yeah.", "start": 2191.05, "duration": 0.5}, {"text": "So they both see two\ndifferent transactions.", "start": 2191.55, "duration": 3.09}, {"text": "One of them sees it with\nthese signatures, one of them", "start": 2194.64, "duration": 2.25}, {"text": "sees it without.", "start": 2196.89, "duration": 1.14}, {"text": "They don't agree on how\nbig the transaction is.", "start": 2198.03, "duration": 2.13}, {"text": "They agree on the txid.", "start": 2200.16, "duration": 1.76}, {"text": "They agree on where the money is\ngoing, where it's coming from,", "start": 2201.92, "duration": 2.663}, {"text": "but they have completely\ndifferent views", "start": 2204.583, "duration": 1.667}, {"text": "of how big this transaction is\nin terms of number of bytes.", "start": 2206.25, "duration": 3.94}, {"text": "So this is really interesting,\nFor many, many years", "start": 2210.19, "duration": 5.59}, {"text": "since 2010, everyone's\nbeen arguing.", "start": 2215.78, "duration": 2.52}, {"text": "And one of the big\naspects of, oh, if we", "start": 2218.3, "duration": 1.77}, {"text": "want to increase the block\nsize, that's a hard fork.", "start": 2220.07, "duration": 2.91}, {"text": "Everyone up to now,\nwe're enforcing.", "start": 2222.98, "duration": 3.24}, {"text": "The block size must be\none million bytes or less.", "start": 2226.22, "duration": 3.473}, {"text": "There's no way\naround that, right?", "start": 2229.693, "duration": 1.417}, {"text": "You can't just increase it.", "start": 2231.11, "duration": 1.267}, {"text": "We've got this rule.", "start": 2232.377, "duration": 0.833}, {"text": "You're breaking that rule.", "start": 2233.21, "duration": 1.84}, {"text": "This is a sneaky way to break\nthe rule but still not tell", "start": 2235.05, "duration": 3.8}, {"text": "people you're breaking the rule.", "start": 2238.85, "duration": 2.32}, {"text": "Say, OK, I'm enforcing a rule\nthat there's one million bytes.", "start": 2241.17, "duration": 3.917}, {"text": "As far as I'm concerned, there\nare less than one million bytes", "start": 2245.087, "duration": 2.583}, {"text": "in this set of transactions.", "start": 2247.67, "duration": 2.43}, {"text": "The new nodes know, yeah,\nthere's more than one million.", "start": 2250.1, "duration": 2.43}, {"text": "There's like two\nmillion bytes in here.", "start": 2252.53, "duration": 1.74}, {"text": "We just didn't tell\nthe old software", "start": 2254.27, "duration": 3.42}, {"text": "about all these extra bytes.", "start": 2257.69, "duration": 1.93}, {"text": "So this is kind of an\ninteresting thing you can do.", "start": 2259.62, "duration": 3.68}, {"text": "So you can increase\nthe transaction size", "start": 2263.3, "duration": 2.73}, {"text": "without telling the old nodes.", "start": 2266.03, "duration": 1.86}, {"text": "So yeah, the old nodes don't\nsee the hundred something bytes", "start": 2267.89, "duration": 4.46}, {"text": "with the pubkey signature.", "start": 2272.35, "duration": 1.52}, {"text": "So they see transactions\nthat are much smaller.", "start": 2273.87, "duration": 3.07}, {"text": "Around half the size--", "start": 2276.94, "duration": 1.44}, {"text": "depends, but half the size ish.", "start": 2278.38, "duration": 3.39}, {"text": "So those bytes, they\nwon't count those bites", "start": 2281.77, "duration": 2.49}, {"text": "towards the one million\nbyte block size limit.", "start": 2284.26, "duration": 3.63}, {"text": "So this ends up being\na soft fork that allows", "start": 2287.89, "duration": 3.42}, {"text": "you to increase the block size.", "start": 2291.31, "duration": 1.65}, {"text": "In a kind of sneaky way, right?", "start": 2292.96, "duration": 1.35}, {"text": "The old nodes don't think\nthe block size is increased.", "start": 2294.31, "duration": 2.88}, {"text": "They think it's less than a\nmegabyte, and they also think,", "start": 2297.19, "duration": 4.157}, {"text": "this is weird.", "start": 2301.347, "duration": 0.583}, {"text": "I haven't seen any\nsignatures for a while.", "start": 2301.93, "duration": 2.28}, {"text": "| seems to be using these\ntransactions that don't require", "start": 2304.21, "duration": 3.21}, {"text": "signatures, and\nsomehow everyone's", "start": 2307.42, "duration": 1.71}, {"text": "getting along and not\nstealing each other's money", "start": 2309.13, "duration": 2.4}, {"text": "despite the lack of a\nneed for signatures.", "start": 2311.53, "duration": 3.3}, {"text": "But these are not\nintelligent people.", "start": 2314.83, "duration": 3.6}, {"text": "These are software programs,\nand it'll just run.", "start": 2318.43, "duration": 3.39}, {"text": "And it'll, OK, yup, yup, yup.", "start": 2321.82, "duration": 2.01}, {"text": "This evaluates to true.", "start": 2323.83, "duration": 2.725}, {"text": "So it's kind of cool.", "start": 2326.555, "duration": 0.875}, {"text": "Block size entry softfork.", "start": 2327.43, "duration": 2.32}, {"text": "However, you Institute\na new rule with segwit.", "start": 2329.75, "duration": 4.7}, {"text": "You don't want to just\nsay for the new rules,", "start": 2334.45, "duration": 4.02}, {"text": "we don't count signatures\ntowards the one megabyte limit,", "start": 2338.47, "duration": 2.4}, {"text": "right?", "start": 2340.87, "duration": 0.9}, {"text": "You could do that, but then\npeople might spam signatures.", "start": 2341.77, "duration": 3.54}, {"text": "Let me make a giant signature\nor some kind of like 50", "start": 2345.31, "duration": 2.7}, {"text": "out of a million pubkeys\nthing and spam the network,", "start": 2348.01, "duration": 4.86}, {"text": "and then it will still be under\na megabyte of non witness data.", "start": 2352.87, "duration": 4.317}, {"text": "So yes, so now I've got\ntwo classes of data.", "start": 2357.187, "duration": 1.833}, {"text": "You've got all the data\nthat everyone sees,", "start": 2359.02, "duration": 2.7}, {"text": "and all the witness data\nthat only the new nodes see.", "start": 2361.72, "duration": 3.33}, {"text": "So what they did is they said,\nOK, the witness data still", "start": 2365.05, "duration": 3.6}, {"text": "counts towards that limit.", "start": 2368.65, "duration": 1.81}, {"text": "But each witness byte counts\nas a 1/4 of a regular byte.", "start": 2370.46, "duration": 4.34}, {"text": "OK, kind of weird, but yeah.", "start": 2374.8, "duration": 2.49}, {"text": "So in practice in the software,\nwhat they do is they say, OK.", "start": 2377.29, "duration": 3.36}, {"text": "We multiply the non\nwitness bytes by four.", "start": 2380.65, "duration": 4.59}, {"text": "So every byte in the outputs\nand every byte in the txid input", "start": 2385.24, "duration": 3.78}, {"text": "things counts as\nlike four bytes.", "start": 2389.02, "duration": 2.07}, {"text": "And then, the witnesses just\ncount as one regular byte.", "start": 2391.09, "duration": 2.7}, {"text": "And then we now say,\nOK, the new block size", "start": 2393.79, "duration": 2.04}, {"text": "is four million bytes.", "start": 2395.83, "duration": 2.17}, {"text": "But four million weight units,\nbecause they're sort of, OK,", "start": 2398.0, "duration": 4.41}, {"text": "we've got different\nweights for things.", "start": 2402.41, "duration": 2.37}, {"text": "This actually makes sense,\nbecause the utxo set", "start": 2404.78, "duration": 5.14}, {"text": "is what you really\nwant to minimize,", "start": 2409.92, "duration": 2.06}, {"text": "that database we keep\nupdating every block.", "start": 2411.98, "duration": 2.58}, {"text": "And the signatures don't\ngo into the utxo set.", "start": 2414.56, "duration": 3.54}, {"text": "So the signatures\nyou don't actually", "start": 2418.1, "duration": 1.5}, {"text": "have to store on a fast,\nlow latency storage.", "start": 2419.6, "duration": 4.0}, {"text": "So in a very real\nsense, the signatures", "start": 2423.6, "duration": 2.6}, {"text": "are sort of OK to make bigger.", "start": 2426.2, "duration": 2.37}, {"text": "They don't really cost as\nmuch to the network to store.", "start": 2428.57, "duration": 3.12}, {"text": "So having this\ndiscount where you say,", "start": 2431.69, "duration": 2.08}, {"text": "OK, the signatures, you can\nhave a bunch of them that", "start": 2433.77, "duration": 2.982}, {"text": "doesn't really count as much.", "start": 2436.752, "duration": 1.208}, {"text": "But the outputs we\nreally need to minimize.", "start": 2437.96, "duration": 3.2}, {"text": "So this one fourth is\nsomewhat arbitrary,", "start": 2441.16, "duration": 3.28}, {"text": "but there are some calculations\nand a little handwaving.", "start": 2444.44, "duration": 2.51}, {"text": "But it's like yeah, this\nis about what it should", "start": 2446.95, "duration": 2.0}, {"text": "be to try to balance things.", "start": 2448.95, "duration": 3.57}, {"text": "So the end result. If\nyou have this discount,", "start": 2452.52, "duration": 2.93}, {"text": "you can put about 80% more\ntransactions in a block.", "start": 2455.45, "duration": 3.06}, {"text": "You get about 1.8 megs.", "start": 2458.51, "duration": 2.52}, {"text": "It depends, right?", "start": 2461.03, "duration": 0.75}, {"text": "It depends how big\nyour signatures are.", "start": 2461.78, "duration": 1.625}, {"text": "So the maximum would be\nyou have a block that", "start": 2465.75, "duration": 2.61}, {"text": "has one transaction with\njust a giant signature that's", "start": 2468.36, "duration": 5.13}, {"text": "like almost four megabytes.", "start": 2473.49, "duration": 1.84}, {"text": "And the old software\nwould see this block", "start": 2475.33, "duration": 2.06}, {"text": "as being really tiny,\nlike 100 something bytes.", "start": 2477.39, "duration": 2.203}, {"text": "And the new software\nwould see, oh yeah,", "start": 2479.593, "duration": 1.667}, {"text": "this block is almost\nfour megabytes.", "start": 2481.26, "duration": 2.73}, {"text": "But that's sort of\nthe extreme case.", "start": 2483.99, "duration": 1.74}, {"text": "I remember generating some\nlike 3.7 meg transaction blocks", "start": 2485.73, "duration": 4.2}, {"text": "and testing that awhile\nago just to test it out.", "start": 2489.93, "duration": 2.88}, {"text": "It works, but in practice\nyou're seeing about this.", "start": 2492.81, "duration": 2.9}, {"text": "In practice today, as segwit\nhas been seeing more adoption,", "start": 2495.71, "duration": 4.15}, {"text": "you see like 1.3\nmegabyte blocks.", "start": 2499.86, "duration": 2.55}, {"text": "Not everyone's using it.", "start": 2502.41, "duration": 1.747}, {"text": "The idea is it's\nbackwards compatible,", "start": 2504.157, "duration": 1.583}, {"text": "but you can still use\nyour old software.", "start": 2505.74, "duration": 1.667}, {"text": "But it seems like more and\nmore software is using this.", "start": 2507.407, "duration": 3.613}, {"text": "You get a discount on your\nfees because your transaction", "start": 2511.02, "duration": 3.48}, {"text": "seems to be smaller.", "start": 2514.5, "duration": 1.17}, {"text": "You can fit more\nof them in a block.", "start": 2515.67, "duration": 1.583}, {"text": "So that's kind of\ncool, and that's", "start": 2517.253, "duration": 1.417}, {"text": "sort of an incentive to use it.", "start": 2518.67, "duration": 1.292}, {"text": "OK, other thing you can do.", "start": 2522.41, "duration": 1.91}, {"text": "You can commit to signatures.", "start": 2524.32, "duration": 2.7}, {"text": "This is a little tricky.", "start": 2527.02, "duration": 2.55}, {"text": "If the signatures aren't\nin the transaction ID,", "start": 2529.57, "duration": 2.82}, {"text": "then they aren't in the\nmerkle route, right?", "start": 2532.39, "duration": 2.94}, {"text": "So there's nothing really\ncommitting the signatures", "start": 2535.33, "duration": 2.52}, {"text": "into the block chain.", "start": 2537.85, "duration": 1.56}, {"text": "And this would actually work.", "start": 2539.41, "duration": 2.077}, {"text": "You could say, no,\nI have a signature.", "start": 2541.487, "duration": 1.583}, {"text": "I'll give it to you,\nbut it could change.", "start": 2543.07, "duration": 3.36}, {"text": "It could be maleated, so\nit could be weird, though.", "start": 2546.43, "duration": 2.67}, {"text": "You could agree on a utxo\nset, but you could disagree", "start": 2549.1, "duration": 2.67}, {"text": "on how exactly you got there.", "start": 2551.77, "duration": 1.86}, {"text": "So one example\nwould be multisig,", "start": 2553.63, "duration": 3.6}, {"text": "where there's two of three\nmultisig, Alice, Bob and Carol.", "start": 2557.23, "duration": 2.79}, {"text": "Two of them need to sign.", "start": 2560.02, "duration": 1.59}, {"text": "And then on my computer, it\nsays that Alice and Bob signed,", "start": 2561.61, "duration": 2.78}, {"text": "and on your computer, it says\nthat Alison and Carol signed.", "start": 2564.39, "duration": 3.16}, {"text": "That's weird, right?", "start": 2567.55, "duration": 2.19}, {"text": "For accountability.", "start": 2569.74, "duration": 0.9}, {"text": "If we want to know who\nexactly endorsed these things,", "start": 2570.64, "duration": 3.21}, {"text": "we might disagree on it.", "start": 2573.85, "duration": 1.7}, {"text": "There would be no canonical\nhere's the blockchain,", "start": 2575.55, "duration": 2.74}, {"text": "here's who signed.", "start": 2578.29, "duration": 0.998}, {"text": "The transactions\nthemselves would all still", "start": 2579.288, "duration": 1.792}, {"text": "be the same but\nnot the signatures.", "start": 2581.08, "duration": 2.35}, {"text": "So that's kind of weird,\nbut it also seems like well,", "start": 2583.43, "duration": 3.05}, {"text": "maybe that's part of the price\nyou pay for fixing malleability", "start": 2586.48, "duration": 3.9}, {"text": "in this way.", "start": 2590.38, "duration": 0.72}, {"text": "If we're not putting the\nsignatures into the thing that", "start": 2591.1, "duration": 3.84}, {"text": "gets committed to in the\nblock chain, then yeah,", "start": 2594.94, "duration": 3.43}, {"text": "signatures can change.", "start": 2598.37, "duration": 1.8}, {"text": "So anyway around this?", "start": 2600.17, "duration": 3.79}, {"text": "It sort of seems like\nyeah, that's the trade off.", "start": 2603.96, "duration": 4.1}, {"text": "Sneaky way around it?", "start": 2608.06, "duration": 1.64}, {"text": "Sneaky fun?", "start": 2609.7, "duration": 0.606}, {"text": "No?", "start": 2610.306, "duration": 0.914}, {"text": "You know.", "start": 2611.22, "duration": 2.2}, {"text": "OK, so what you do actually,\nyou commit the signatures", "start": 2613.42, "duration": 7.758}, {"text": "but in a weird way.", "start": 2621.178, "duration": 0.792}, {"text": "OK, so here's the regular\nold merkle tree, right?", "start": 2621.97, "duration": 2.38}, {"text": "This is the merkle route\nthat you put in the header.", "start": 2624.35, "duration": 3.22}, {"text": "Here's all the transaction\nIDs, and so you", "start": 2627.57, "duration": 3.65}, {"text": "make these intermediate hashes.", "start": 2631.22, "duration": 1.892}, {"text": "This is the hash of these two\nthings concatenated together,", "start": 2633.112, "duration": 2.458}, {"text": "this is the hash of these two\nthings concatenated together.", "start": 2635.57, "duration": 4.44}, {"text": "Now, if the txids\ndon't have signatures,", "start": 2640.01, "duration": 2.64}, {"text": "there's no commitment to the\nsignatures in the top hash.", "start": 2642.65, "duration": 3.35}, {"text": "What you do is this.", "start": 2646.0, "duration": 1.445}, {"text": "You say, OK.", "start": 2647.445, "duration": 1.475}, {"text": "I'm going to make\nthese new witness", "start": 2648.92, "duration": 1.94}, {"text": "txids, hashes of transactions\nthat do include the signatures.", "start": 2650.86, "duration": 5.335}, {"text": "In practice, you could just make\na hash of just the signatures.", "start": 2656.195, "duration": 2.625}, {"text": "That would also work.", "start": 2658.82, "duration": 1.11}, {"text": "They just take the whole thing.", "start": 2659.93, "duration": 3.03}, {"text": "And now I've got\nthis other reflected", "start": 2662.96, "duration": 4.14}, {"text": "merkle tree kind of\nthing, where OK, I", "start": 2667.1, "duration": 2.07}, {"text": "take the hash of these two\nwitness transaction IDs,", "start": 2669.17, "duration": 3.9}, {"text": "put it here, and this\none just drops down.", "start": 2673.07, "duration": 2.7}, {"text": "It's another merkle\ntree, and then you", "start": 2675.77, "duration": 1.95}, {"text": "get a root for all those\nthings called the witness root.", "start": 2677.72, "duration": 3.78}, {"text": "And then what you do is\nyou put the witness root", "start": 2681.5, "duration": 2.4}, {"text": "in the coinbase transaction.", "start": 2683.9, "duration": 2.52}, {"text": "Put in an opp return.", "start": 2686.42, "duration": 1.29}, {"text": "And the idea is the\ncoinbase transaction", "start": 2687.71, "duration": 2.7}, {"text": "doesn't have any\nsignatures anyway, right?", "start": 2690.41, "duration": 1.98}, {"text": "So you can put it in there.", "start": 2692.39, "duration": 3.33}, {"text": "You don't need to\ninclude the transaction", "start": 2695.72, "duration": 2.88}, {"text": "zero in this witness tree.", "start": 2698.6, "duration": 2.815}, {"text": "Wait, they do though, right?", "start": 2701.415, "duration": 2.765}, {"text": "But maybe this is slightly\ninaccurate in that I think", "start": 2704.18, "duration": 5.04}, {"text": "they actually do\nmake a witness txid", "start": 2709.22, "duration": 3.21}, {"text": "for the coinbase transaction,\nbut they define it", "start": 2712.43, "duration": 2.04}, {"text": "as being zero or something.", "start": 2714.47, "duration": 3.794}, {"text": "I think-- I don't remember.", "start": 2718.264, "duration": 1.771}, {"text": "So it's weird, right?", "start": 2720.035, "duration": 0.875}, {"text": "But you could do that.", "start": 2720.91, "duration": 3.1}, {"text": "They define a zero, or they\nlet you pick anything you want.", "start": 2724.01, "duration": 2.49}, {"text": "I would have to\nlook at the code.", "start": 2726.5, "duration": 1.44}, {"text": "But anyway, the basic\nidea is for these anyway,", "start": 2727.94, "duration": 4.16}, {"text": "you take the hash of the whole\nthing including the signatures,", "start": 2732.1, "duration": 2.85}, {"text": "put it in the witness\nroot, put the witness root", "start": 2734.95, "duration": 2.31}, {"text": "in the coinbase transaction, and\nthe coinbase this transaction", "start": 2737.26, "duration": 2.97}, {"text": "gets in to the merkle root.", "start": 2740.23, "duration": 2.19}, {"text": "So you are committing\nto all the signatures", "start": 2742.42, "duration": 3.15}, {"text": "but on the block level,\nnot the transaction level.", "start": 2745.57, "duration": 3.81}, {"text": "So in the case where I\nthink Alice and Bob signed.", "start": 2749.38, "duration": 4.37}, {"text": "Oh, I think Alice\nand Carol signed.", "start": 2753.75, "duration": 2.26}, {"text": "You can have those two\ntransactions floating around", "start": 2756.01, "duration": 2.43}, {"text": "on the network, and\nthey have the same txid.", "start": 2758.44, "duration": 3.945}, {"text": "And so who knows which\none's getting into a block?", "start": 2762.385, "duration": 2.715}, {"text": "They look almost the same.", "start": 2765.1, "duration": 1.94}, {"text": "Some of the software won't\nbe able to pick between them.", "start": 2767.04, "duration": 2.45}, {"text": "However, once it gets\ninto a block, one of them", "start": 2769.49, "duration": 2.99}, {"text": "will be committed to.", "start": 2772.48, "duration": 1.22}, {"text": "It's like, oh, ended up\nbeing Alice and Carol.", "start": 2773.7, "duration": 4.01}, {"text": "Those two signatures actually\ngot into the blockchain.", "start": 2777.71, "duration": 4.63}, {"text": "However, you could\nprove, hey, no I", "start": 2782.34, "duration": 4.13}, {"text": "had this Alice Bob\nsignature, but then it", "start": 2786.47, "duration": 2.953}, {"text": "never got into the\nblockchain, and maybe", "start": 2789.423, "duration": 1.667}, {"text": "you made it after the fact.", "start": 2791.09, "duration": 0.94}, {"text": "It never gets committed to.", "start": 2792.03, "duration": 1.17}, {"text": "Yeah.", "start": 2793.2, "duration": 0.34}, {"text": "AUDIENCE: Also, a\nbunch of pool software", "start": 2793.54, "duration": 1.42}, {"text": "just doesn't always do this.", "start": 2794.96, "duration": 1.167}, {"text": "PROFESSOR: A bunch of pool\nsoftware doesn't do this?", "start": 2796.43, "duration": 2.167}, {"text": "What you mean?", "start": 2798.597, "duration": 0.643}, {"text": "AUDIENCE: It's\nthe responsibility", "start": 2799.24, "duration": 1.375}, {"text": "of the pool software to\nmake this construction,", "start": 2800.615, "duration": 3.123}, {"text": "but [INAUDIBLE]", "start": 2803.738, "duration": 2.935}, {"text": "PROFESSOR: Have it\nimplemented as in they just", "start": 2806.673, "duration": 1.917}, {"text": "don't support segwit?", "start": 2808.59, "duration": 0.875}, {"text": "AUDIENCE: No, so they\ndo the first part,", "start": 2809.465, "duration": 2.059}, {"text": "but [INAUDIBLE] segwit support.", "start": 2811.524, "duration": 5.986}, {"text": "PROFESSOR: OK, but wouldn't\nthat just not work?", "start": 2817.51, "duration": 2.64}, {"text": "How--", "start": 2820.15, "duration": 0.5}, {"text": "AUDIENCE: It works, because--", "start": 2820.65, "duration": 1.208}, {"text": "[INAUDIBLE]", "start": 2821.858, "duration": 1.03}, {"text": "PROFESSOR: But to the new\nsoftware, if you don't have--", "start": 2822.888, "duration": 2.292}, {"text": "so segwit is the\nsoftware, right?", "start": 2837.83, "duration": 1.5}, {"text": "You say, OK, we define\nthese new transaction types.", "start": 2839.33, "duration": 3.04}, {"text": "We define this template where\nif you have a zero and then", "start": 2842.37, "duration": 3.6}, {"text": "this pubkey hash.", "start": 2845.97, "duration": 1.93}, {"text": "It also says, I require\nthe coinbase transaction", "start": 2847.9, "duration": 6.96}, {"text": "to have this output that\nsays, op return aa9c", "start": 2854.86, "duration": 4.86}, {"text": "whatever this little\nfour random bytes,", "start": 2859.72, "duration": 3.18}, {"text": "and then I'd require it to\nhave the witness root in here.", "start": 2862.9, "duration": 2.937}, {"text": "AUDIENCE: I'm guessing\nthey just don't", "start": 2865.837, "duration": 1.583}, {"text": "include segwit transactions?", "start": 2867.42, "duration": 1.742}, {"text": "PROFESSOR: So I've\nseen that a lot.", "start": 2869.162, "duration": 1.458}, {"text": "Yeah, so a lot of--", "start": 2870.62, "duration": 0.92}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2871.54, "duration": 0.875}, {"text": "PROFESSOR: Yeah, a\nlot of the software", "start": 2872.415, "duration": 1.615}, {"text": "says, I'm not going to do this.", "start": 2874.03, "duration": 2.777}, {"text": "So the other thing that's nice--", "start": 2876.807, "duration": 1.333}, {"text": "segwit transactions to old\nsoftware look non-standard.", "start": 2878.14, "duration": 3.18}, {"text": "So I mentioned before that\nthere's standardness rules", "start": 2881.32, "duration": 2.67}, {"text": "where, this looks weird.", "start": 2883.99, "duration": 1.56}, {"text": "I'm not going to mine it.", "start": 2885.55, "duration": 1.38}, {"text": "I'm not going to relay it to my\npeers, but if I it in a block,", "start": 2886.93, "duration": 2.97}, {"text": "well, OK, fine.", "start": 2889.9, "duration": 1.95}, {"text": "So segwit transactions\nlook very non-standard.", "start": 2891.85, "duration": 2.892}, {"text": "It looks like\nthere's no signature.", "start": 2894.742, "duration": 1.458}, {"text": "That's weird.", "start": 2896.2, "duration": 0.76}, {"text": "There's this zero.", "start": 2896.96, "duration": 2.15}, {"text": "What's going on?", "start": 2899.11, "duration": 1.71}, {"text": "So yeah, you can you\ncan still run a miner", "start": 2900.82, "duration": 2.85}, {"text": "and just not even\nknow about segwit.", "start": 2903.67, "duration": 2.63}, {"text": "It's a little\ndangerous, because you", "start": 2906.3, "duration": 2.31}, {"text": "might see a block that\nis segwit invalid,", "start": 2908.61, "duration": 3.75}, {"text": "but you wouldn't\nknow it and so you", "start": 2912.36, "duration": 1.5}, {"text": "might try to mine on top of it.", "start": 2913.86, "duration": 1.292}, {"text": "So there are some\nrisks, but in general", "start": 2915.152, "duration": 1.668}, {"text": "if most people are\ndoing the right thing,", "start": 2916.82, "duration": 2.17}, {"text": "you could still mine without\nknowing about this stuff.", "start": 2918.99, "duration": 2.68}, {"text": "So any questions about\ncommitting to the signatures?", "start": 2921.67, "duration": 5.42}, {"text": "What else?", "start": 2927.09, "duration": 0.872}, {"text": "Oh yeah, so you've\ngot this upgrade path.", "start": 2927.962, "duration": 1.708}, {"text": "That's kind of cool.", "start": 2929.67, "duration": 2.8}, {"text": "So it defined zero\npubkey hash as hey,", "start": 2932.47, "duration": 4.31}, {"text": "this is now pay to\npubkey hash, right?", "start": 2936.78, "duration": 4.44}, {"text": "Interpret this weird\ntemplate as the regular hey,", "start": 2941.22, "duration": 3.81}, {"text": "verify this signature.", "start": 2945.03, "duration": 1.62}, {"text": "It also, when segwit\nsoftfork happened,", "start": 2946.65, "duration": 2.94}, {"text": "redefined a whole bunch of\nother templates like this.", "start": 2949.59, "duration": 4.05}, {"text": "So one and then some data,\nor two and then some data.", "start": 2953.64, "duration": 3.45}, {"text": "Just put a number, and\nthen put a bunch of data.", "start": 2957.09, "duration": 2.28}, {"text": "All of these are defined\nas future upgrades.", "start": 2959.37, "duration": 4.57}, {"text": "So if you see a three block of\ndata, you now say, yeah, OK.", "start": 2963.94, "duration": 5.46}, {"text": "I know that's segwit\nversion three.", "start": 2969.4, "duration": 1.68}, {"text": "My software will maybe pop\nup something saying hey,", "start": 2971.08, "duration": 2.44}, {"text": "people are using\nsegwit version three.", "start": 2973.52, "duration": 1.7}, {"text": "You're only aware of\nsegwit version zero.", "start": 2975.22, "duration": 3.03}, {"text": "But you'll consider\nit non-standard.", "start": 2978.25, "duration": 1.83}, {"text": "You won't relay it.", "start": 2980.08, "duration": 1.14}, {"text": "But if it's in a\nblock, yeah, sure.", "start": 2981.22, "duration": 1.8}, {"text": "And you don't require\nanything about the signature.", "start": 2983.02, "duration": 3.077}, {"text": "You'll just say, yeah,\nwhatever weird witness data", "start": 2986.097, "duration": 2.083}, {"text": "you provide for these\noutputs, I don't", "start": 2988.18, "duration": 2.28}, {"text": "know how to interpret them.", "start": 2990.46, "duration": 1.17}, {"text": "I'm just going to let\nit all go through.", "start": 2991.63, "duration": 2.64}, {"text": "What that means is--", "start": 2994.27, "duration": 1.77}, {"text": "there's no witness needed.", "start": 2996.04, "duration": 1.313}, {"text": "If a witness is\nprovided, you just", "start": 2997.353, "duration": 1.417}, {"text": "ignore it and you think\neverything's fine.", "start": 2998.77, "duration": 2.988}, {"text": "This allows easier upgrades.", "start": 3001.758, "duration": 1.167}, {"text": "You have 16 new\nversions to upgrade to.", "start": 3005.84, "duration": 1.83}, {"text": "Yeah, you don't require any\nspecific things about this,", "start": 3010.25, "duration": 2.973}, {"text": "so you can make new scripts, you\ncan make a completely different", "start": 3013.223, "duration": 2.667}, {"text": "script interpreter.", "start": 3015.89, "duration": 0.83}, {"text": "You could say, OK,\nwe're going to port EVM", "start": 3016.72, "duration": 1.75}, {"text": "to bitcoin and disable\nsome of the op codes", "start": 3018.47, "duration": 3.93}, {"text": "that don't apply, and\nhave that kind of thing.", "start": 3022.4, "duration": 2.01}, {"text": "Have new smart contracts.", "start": 3024.41, "duration": 1.26}, {"text": "So it's kind of a fun,\nlike yeah, we will--", "start": 3025.67, "duration": 2.94}, {"text": "and it's a nice,\neasy upgrade path.", "start": 3028.61, "duration": 1.892}, {"text": "You could have multiple\ndifferent things,", "start": 3030.502, "duration": 1.708}, {"text": "things like that.", "start": 3032.21, "duration": 1.8}, {"text": "The code will be easier.", "start": 3034.01, "duration": 2.49}, {"text": "Don't do it today.", "start": 3036.5, "duration": 1.14}, {"text": "You could construct\nan output that's", "start": 3037.64, "duration": 1.98}, {"text": "a two byte and then your\npubkey and send it out there.", "start": 3039.62, "duration": 4.44}, {"text": "It will be probably stealing by\nminers, because everyone else's", "start": 3044.06, "duration": 4.55}, {"text": "node will say, yeah, I don't\nknow how to interpret this yet.", "start": 3048.61, "duration": 2.5}, {"text": "There's no rules about this yet.", "start": 3051.11, "duration": 3.47}, {"text": "OK, let me show you some\nsegwit stuff I looked for.", "start": 3054.58, "duration": 7.41}, {"text": "OK, so there's\nactually nested segwit.", "start": 3066.8, "duration": 5.857}, {"text": "There's an an ugly--", "start": 3072.657, "duration": 0.833}, {"text": "I didn't like it, but--", "start": 3079.37, "duration": 1.38}, {"text": "this is like somewhat designed\nby committee E. There's also--", "start": 3080.75, "duration": 5.232}, {"text": "this is 2016, right?", "start": 3085.982, "duration": 2.848}, {"text": "AUDIENCE: People lose so much\nmoney on segwit two years ago.", "start": 3088.83, "duration": 2.5}, {"text": "PROFESSOR: So the other\nthing I would say with this,", "start": 3091.33, "duration": 2.775}, {"text": "I was like, OK.", "start": 3094.105, "duration": 0.625}, {"text": "You've got this witness txid.", "start": 3094.73, "duration": 1.82}, {"text": "And I remember people\nworking on segwit", "start": 3096.55, "duration": 2.49}, {"text": "and I said, hey, why don't\nyou make the transaction IDs", "start": 3099.04, "duration": 3.42}, {"text": "a merkle tree of the\ninputs and outputs instead", "start": 3102.46, "duration": 4.12}, {"text": "of just the hash of\neverything all together?", "start": 3106.58, "duration": 2.46}, {"text": "Then, if you had a\nreally big transaction,", "start": 3109.04, "duration": 2.15}, {"text": "you could prove that an input\nhad been spent without sending", "start": 3111.19, "duration": 2.5}, {"text": "the whole transaction over.", "start": 3113.69, "duration": 1.422}, {"text": "And I thought that\nwas a cool idea.", "start": 3115.112, "duration": 1.458}, {"text": "And then when I talked to\npeople, they're like yeah,", "start": 3116.57, "duration": 2.167}, {"text": "Peter Todd already said\nthat like three weeks ago.", "start": 3118.737, "duration": 2.543}, {"text": "And whatever, we're\nnot going to do it.", "start": 3121.28, "duration": 2.34}, {"text": "It's too late.", "start": 3123.62, "duration": 0.78}, {"text": "We already coded stuff.", "start": 3124.4, "duration": 1.32}, {"text": "Oh well.", "start": 3125.72, "duration": 2.7}, {"text": "And that's the fundamental\naspect of segwit.", "start": 3128.42, "duration": 2.64}, {"text": "You can't really upgrade that\nin the new script versions,", "start": 3131.06, "duration": 2.79}, {"text": "so whatever.", "start": 3133.85, "duration": 3.64}, {"text": "There's also still a hard rule\non transactions themselves", "start": 3137.49, "duration": 3.03}, {"text": "being less than a\nmegabyte, I think.", "start": 3140.52, "duration": 1.5}, {"text": "So it's not a huge deal,\nbut it would have been cool.", "start": 3142.02, "duration": 2.97}, {"text": "Another thing is\nthere's actually a way--", "start": 3144.99, "duration": 4.23}, {"text": "so there's no address\ndefined for this, right?", "start": 3149.22, "duration": 3.45}, {"text": "Address is mapped to output\nscripts in all the software.", "start": 3152.67, "duration": 3.42}, {"text": "And so when you\nsay, OK, I'm sending", "start": 3156.09, "duration": 1.5}, {"text": "into 1aeecc or\nwhatever, it knows", "start": 3157.59, "duration": 2.79}, {"text": "how to interpret that address,\nbuild the 20 byte pubkey hash", "start": 3160.38, "duration": 3.3}, {"text": "script, and send to it.", "start": 3163.68, "duration": 1.933}, {"text": "And vise versa, right?", "start": 3165.613, "duration": 0.917}, {"text": "So from the address, you\ncan get this output script,", "start": 3166.53, "duration": 2.167}, {"text": "and from the output script\nyou can get an address.", "start": 3168.697, "duration": 2.633}, {"text": "So when an old\nsoftware sees this,", "start": 3171.33, "duration": 1.992}, {"text": "it's just like,\nthere's no address.", "start": 3173.322, "duration": 1.458}, {"text": "I don't even know what that is.", "start": 3174.78, "duration": 1.5}, {"text": "I've never seen that.", "start": 3176.28, "duration": 2.19}, {"text": "And so people worried that\noh, it's going to be weird.", "start": 3178.47, "duration": 3.04}, {"text": "People are going to have to\nupgrade to even send to people", "start": 3181.51, "duration": 2.45}, {"text": "using segwit.", "start": 3183.96, "duration": 1.513}, {"text": "So it's backwards compatible,\nbut if you want to say, hey,", "start": 3185.473, "duration": 2.417}, {"text": "send me some money at the segwit\naddress and then they can't.", "start": 3187.89, "duration": 3.998}, {"text": "And so you say, OK, fine.", "start": 3191.888, "duration": 1.042}, {"text": "Send me the money with\na regular address,", "start": 3192.93, "duration": 1.708}, {"text": "and then we still have\nthis malleability problem.", "start": 3194.638, "duration": 2.399}, {"text": "And then I have a wallet\nthat supports both,", "start": 3197.037, "duration": 1.833}, {"text": "and I can move money\nto my own addresses,", "start": 3198.87, "duration": 1.71}, {"text": "and it's kind of ugly.", "start": 3200.58, "duration": 0.93}, {"text": "So they made this nested address\nthing, which I don't like,", "start": 3201.51, "duration": 4.05}, {"text": "because then it\nactually has both.", "start": 3205.56, "duration": 4.2}, {"text": "So you've got a\nsignature and a witness.", "start": 3209.76, "duration": 1.85}, {"text": "And the signature is\nnot a real signature.", "start": 3214.34, "duration": 1.75}, {"text": "It's just pointing\nto the witness.", "start": 3216.09, "duration": 1.417}, {"text": "It's really ugly.", "start": 3217.507, "duration": 0.851}, {"text": "There's a bunch of weird\nstuff in the segwit code", "start": 3218.358, "duration": 2.042}, {"text": "that I'm not super into.", "start": 3220.4, "duration": 1.348}, {"text": "I don't have to use\nit though, right?", "start": 3221.748, "duration": 1.542}, {"text": "That's the beauty of these\npermission-less innovation", "start": 3223.29, "duration": 2.7}, {"text": "kind of systems.", "start": 3225.99, "duration": 0.67}, {"text": "Like ew, I don't like that code.", "start": 3226.66, "duration": 1.55}, {"text": "OK, I'm not supporting it.", "start": 3228.21, "duration": 1.192}, {"text": "OK, so here's one that's nested.", "start": 3233.74, "duration": 7.625}, {"text": "So I was just randomly\nlooking through a block.", "start": 3245.98, "duration": 6.3}, {"text": "Here's one, and you\ncan see it's like, OK.", "start": 3252.28, "duration": 1.8}, {"text": "The outputs are probably\nalso nested segwit,", "start": 3254.08, "duration": 4.4}, {"text": "and the input has got both a\nscript sig and a tx witness,", "start": 3258.48, "duration": 5.59}, {"text": "right?", "start": 3264.07, "duration": 0.545}, {"text": "A tx input witness.", "start": 3264.615, "duration": 2.145}, {"text": "A pure one is this one f7.", "start": 3266.76, "duration": 4.89}, {"text": "OK, so you can see--", "start": 3277.11, "duration": 3.255}, {"text": "oh wait, am I not running--\nwhat version am I running?", "start": 3280.365, "duration": 2.475}, {"text": "I think I'm running\nto 15-1 still.", "start": 3282.84, "duration": 1.83}, {"text": "So I'm not seeing the address.", "start": 3284.67, "duration": 1.41}, {"text": "There's a new address format\ncalled beck 32, bech 32,", "start": 3286.08, "duration": 5.47}, {"text": "which will turn--", "start": 3291.55, "duration": 2.11}, {"text": "so it's zero and\nthen a script hash.", "start": 3293.66, "duration": 6.71}, {"text": "Zero and then a pubkey hash.", "start": 3300.37, "duration": 3.56}, {"text": "It says, witness,\nversion zero, key hash.", "start": 3303.93, "duration": 2.08}, {"text": "There's also an address\nassociated with these.", "start": 3306.01, "duration": 2.21}, {"text": "I think this version of\nbitcoin CLI does not show it,", "start": 3308.22, "duration": 4.63}, {"text": "but the new version does.", "start": 3312.85, "duration": 1.48}, {"text": "So I think if you guys have\nversion 0.16.0, it will show,", "start": 3314.33, "duration": 3.84}, {"text": "here's the address.", "start": 3318.17, "duration": 2.81}, {"text": "And then you can see\nin the single input", "start": 3320.98, "duration": 3.01}, {"text": "for this transaction,\nthere is a tx in witness.", "start": 3323.99, "duration": 3.44}, {"text": "And there's no scripts.", "start": 3327.43, "duration": 1.19}, {"text": "There's a script sig\nfield, and it's just empty.", "start": 3328.62, "duration": 2.87}, {"text": "There's no actual\nsignature traditionally.", "start": 3331.49, "duration": 2.97}, {"text": "There's instead this big thing.", "start": 3334.46, "duration": 1.8}, {"text": "Here's the signature, and here's\nthe pubkey being revealed.", "start": 3336.26, "duration": 3.09}, {"text": "And then it also says,\nOK, here's the txid", "start": 3339.35, "duration": 3.87}, {"text": "without the signature, and\nthen here's the hash or witness", "start": 3343.22, "duration": 2.94}, {"text": "transaction ID.", "start": 3346.16, "duration": 0.893}, {"text": "The hash of the whole thing\nincluding the signature,", "start": 3347.053, "duration": 2.167}, {"text": "and they're different, right?", "start": 3349.22, "duration": 1.89}, {"text": "Also you've got size so this\nis actually 235 bytes, right?", "start": 3351.11, "duration": 5.1}, {"text": "Because you're\nincluding the witnesses.", "start": 3356.21, "duration": 2.2}, {"text": "And then, v size,\nwhich is virtual size.", "start": 3358.41, "duration": 4.67}, {"text": "This is how big it looks\nto old software that", "start": 3363.08, "duration": 2.61}, {"text": "doesn't know about segwit.", "start": 3365.69, "duration": 2.76}, {"text": "So the new software,\nthis knows about both.", "start": 3368.45, "duration": 2.22}, {"text": "The actual size or witness\nsize is 235, v size is 153.", "start": 3370.67, "duration": 5.07}, {"text": "So yeah, it's not quite\n50%, because this one has", "start": 3375.74, "duration": 3.725}, {"text": "two outputs, and the outputs\ndon't get any smaller,", "start": 3379.465, "duration": 2.125}, {"text": "and the input just gets smaller.", "start": 3381.59, "duration": 2.4}, {"text": "And then, size, v\nsize, and then you", "start": 3383.99, "duration": 2.87}, {"text": "can see what block\nit's in when we", "start": 3386.86, "duration": 1.5}, {"text": "get the coinbase transaction.", "start": 3388.36, "duration": 1.784}, {"text": "OK, so the first\ntransaction in the list", "start": 3403.3, "duration": 2.93}, {"text": "is going to be the\ncoinbase transaction.", "start": 3406.23, "duration": 2.4}, {"text": "And I can get that one.", "start": 3408.63, "duration": 2.76}, {"text": "And yeah, the\ncoinbase transaction", "start": 3411.39, "duration": 4.59}, {"text": "has a different txid and hash.", "start": 3415.98, "duration": 1.9}, {"text": "Its size is 259, its v size 232.", "start": 3417.88, "duration": 3.14}, {"text": "Coinbase has whatever\nrandom data they want,", "start": 3421.02, "duration": 2.82}, {"text": "and there's the\nactual output, which", "start": 3423.84, "duration": 4.27}, {"text": "is sending to this address,\nand it's sending 12.79 coins.", "start": 3428.11, "duration": 4.17}, {"text": "And then, there's this\nzero value output.", "start": 3432.28, "duration": 1.8}, {"text": "So you can have an\noutput that's got", "start": 3434.08, "duration": 1.5}, {"text": "an amount of coins set to zero.", "start": 3435.58, "duration": 2.18}, {"text": "It's still OK, and it's\ngot this op return.", "start": 3437.76, "duration": 1.96}, {"text": "And the op return\nstarts with aa21a9ed,", "start": 3439.72, "duration": 3.12}, {"text": "and those four bytes mean\nhere's the segwit commitment.", "start": 3442.84, "duration": 5.07}, {"text": "Here's the witness commitment\nto the segwit transaction", "start": 3447.91, "duration": 3.51}, {"text": "hashes, the root of all those.", "start": 3451.42, "duration": 4.07}, {"text": "And you have to\nhave that in order", "start": 3455.49, "duration": 2.67}, {"text": "to have a valid segwit block.", "start": 3458.16, "duration": 2.22}, {"text": "And so then we can--", "start": 3460.38, "duration": 1.74}, {"text": "this is segwit in action.", "start": 3462.12, "duration": 1.59}, {"text": "I think most blocks\nnow will have that.", "start": 3463.71, "duration": 1.815}, {"text": "So there is size\nand v size, right?", "start": 3468.05, "duration": 1.72}, {"text": "And that makes sense.", "start": 3469.77, "duration": 1.5}, {"text": "But then you have strip--", "start": 3471.27, "duration": 3.0}, {"text": "no, v size is not size.", "start": 3474.27, "duration": 1.98}, {"text": "It's really confusing.", "start": 3476.25, "duration": 1.14}, {"text": "And size, weight,\nheight, like what?", "start": 3477.39, "duration": 5.21}, {"text": "So size is--", "start": 3482.6, "duration": 3.25}, {"text": "I don't actually know.", "start": 3485.85, "duration": 1.45}, {"text": "I think size is\ninterpreted the same.", "start": 3487.3, "duration": 1.91}, {"text": "This is the actual number\nof bytes for this block.", "start": 3489.21, "duration": 3.06}, {"text": "Weight is you multiply all\nnon witness bytes by four,", "start": 3492.27, "duration": 5.88}, {"text": "and you leave all witness\nbytes as weight one,", "start": 3498.15, "duration": 2.4}, {"text": "and that has to be\nless than four million.", "start": 3500.55, "duration": 1.75}, {"text": "And you can see here, it's\njust under four million.", "start": 3502.3, "duration": 2.81}, {"text": "And then stripped size is\nthe size that old nodes see.", "start": 3505.11, "duration": 5.72}, {"text": "Yeah.", "start": 3510.83, "duration": 0.5}, {"text": "Pretty sure.", "start": 3511.33, "duration": 0.55}, {"text": "Anyway, so it's\nkind of confusing.", "start": 3511.88, "duration": 3.337}, {"text": "One of the biggest\nproblems in bitcoin", "start": 3515.217, "duration": 1.583}, {"text": "is names, where it's like, wait.", "start": 3516.8, "duration": 1.79}, {"text": "Script pubkey, and\nscript sig script?", "start": 3518.59, "duration": 2.93}, {"text": "Like, what?", "start": 3521.52, "duration": 0.5}, {"text": "All these terms and names\nare really confusing,", "start": 3522.02, "duration": 2.13}, {"text": "and it's sort of getting worse.", "start": 3524.15, "duration": 2.59}, {"text": "So yeah.", "start": 3526.74, "duration": 1.45}, {"text": "Also, there's no v size here.", "start": 3528.19, "duration": 4.357}, {"text": "I think this is actually v size.", "start": 3532.547, "duration": 1.333}, {"text": "Anyway, so that's how segwit\nworks in the actual thing.", "start": 3533.88, "duration": 5.13}, {"text": "But it's nice, because now you\ncan reliably spend from things", "start": 3539.01, "duration": 2.88}, {"text": "before they're confirmed.", "start": 3541.89, "duration": 3.06}, {"text": "So segwit is cool.", "start": 3544.95, "duration": 2.31}, {"text": "Fixes malleability.", "start": 3547.26, "duration": 1.32}, {"text": "Increases the block size.", "start": 3548.58, "duration": 2.02}, {"text": "Oh, it does a whole bunch\nof other stuff, too.", "start": 3550.6, "duration": 2.18}, {"text": "OK, so one of the\naspects that it fixes.", "start": 3555.79, "duration": 3.2}, {"text": "When you're signing\na transaction,", "start": 3558.99, "duration": 3.23}, {"text": "let's say you have five inputs.", "start": 3562.22, "duration": 2.35}, {"text": "Each time you sign, you need\nto hash the whole transaction,", "start": 3567.36, "duration": 2.475}, {"text": "because it's slightly\ndifferent, right?", "start": 3569.835, "duration": 1.625}, {"text": "You zero out all the\nsignature fields,", "start": 3571.46, "duration": 1.837}, {"text": "but in the signature\nfield for the one", "start": 3573.297, "duration": 1.583}, {"text": "you're actually signing,\nyou don't zero it out.", "start": 3574.88, "duration": 1.958}, {"text": "You put the previous\nscript there.", "start": 3576.838, "duration": 3.642}, {"text": "So it's slightly different.", "start": 3580.48, "duration": 1.48}, {"text": "It's totally redundant.", "start": 3581.96, "duration": 1.685}, {"text": "There's no reason\nto put it there", "start": 3583.645, "duration": 1.375}, {"text": "because it's\nalready in the txid,", "start": 3585.02, "duration": 1.375}, {"text": "but you change things\naround a little bit.", "start": 3586.395, "duration": 2.765}, {"text": "So the idea is, I'm going\nto put a signature here,", "start": 3589.16, "duration": 3.233}, {"text": "I'm going to put\na signature here,", "start": 3592.393, "duration": 1.417}, {"text": "put a signature--\nall five of them.", "start": 3593.81, "duration": 1.83}, {"text": "Each time I put\na signature here,", "start": 3595.64, "duration": 1.8}, {"text": "I hash the transaction to get\na slightly different thing", "start": 3597.44, "duration": 3.48}, {"text": "to sign for each one.", "start": 3600.92, "duration": 2.61}, {"text": "It might not jump out at\nyou, but this is actually", "start": 3603.53, "duration": 3.27}, {"text": "o and squared, which is bad.", "start": 3606.8, "duration": 4.89}, {"text": "Because the idea is, as I\nextend the number of signatures", "start": 3611.69, "duration": 3.39}, {"text": "required in a transaction,\nthe number of inputs", "start": 3615.08, "duration": 1.98}, {"text": "in a transaction, the amount of\ndata that needs to be processed", "start": 3617.06, "duration": 4.29}, {"text": "goes up with the square\nof the number of inputs.", "start": 3621.35, "duration": 3.23}, {"text": "Because I had an input.", "start": 3624.58, "duration": 1.84}, {"text": "Now, the total size of the\ntransaction gets bigger,", "start": 3626.42, "duration": 3.05}, {"text": "so each time I sign, I need to\ntake a bigger amount of data", "start": 3629.47, "duration": 3.51}, {"text": "through my hash function.", "start": 3632.98, "duration": 1.2}, {"text": "Also, the number of\nsignatures gets bigger.", "start": 3634.18, "duration": 1.82}, {"text": "Or the number of inputs.", "start": 3636.0, "duration": 1.0}, {"text": "So this is in squared.", "start": 3637.0, "duration": 1.77}, {"text": "It seems fine, right?", "start": 3638.77, "duration": 0.96}, {"text": "You never notice,\nexcept when you do.", "start": 3639.73, "duration": 2.98}, {"text": "So there's pathological block.", "start": 3642.71, "duration": 2.12}, {"text": "There was one like 2015 early\nin the year where some miner was", "start": 3644.83, "duration": 3.032}, {"text": "like, I'm going to\nmake this block that's", "start": 3647.862, "duration": 1.708}, {"text": "one giant transaction\nwith thousands", "start": 3649.57, "duration": 2.58}, {"text": "and thousands of inputs.", "start": 3652.15, "duration": 1.8}, {"text": "And a lot of software choked\non it, and it took gigs of RAM", "start": 3653.95, "duration": 3.39}, {"text": "to process the transaction,\nand things like that.", "start": 3657.34, "duration": 3.01}, {"text": "So that was bad.", "start": 3660.35, "duration": 1.58}, {"text": "Just in general, if you have\na lot of little dust outputs,", "start": 3661.93, "duration": 2.79}, {"text": "if you're trying to\naggregate them into one big--", "start": 3664.72, "duration": 2.49}, {"text": "I'm going to have 100\ninputs and one output,", "start": 3667.21, "duration": 2.64}, {"text": "it takes forever to sign.", "start": 3669.85, "duration": 2.28}, {"text": "And it also takes\nforever to verify.", "start": 3672.13, "duration": 1.5}, {"text": "So it's pretty bad.", "start": 3673.63, "duration": 1.59}, {"text": "I remember sort\nof a silly story.", "start": 3675.22, "duration": 4.8}, {"text": "Tim Draper's coins.", "start": 3680.02, "duration": 1.2}, {"text": "He had all this dust.", "start": 3681.22, "duration": 1.17}, {"text": "And it was nerve wracking,\nbecause it was way more money", "start": 3682.39, "duration": 2.43}, {"text": "than I'm going to\nmake in my life.", "start": 3684.82, "duration": 1.417}, {"text": "And moving Tim Draper's\ncoins to somewhere else.", "start": 3686.237, "duration": 2.573}, {"text": "And the software by default\njust swept all the inputs", "start": 3688.81, "duration": 3.92}, {"text": "with that wallet controlled.", "start": 3692.73, "duration": 1.94}, {"text": "And they were looking at me\nlike, why doesn't this work?", "start": 3694.67, "duration": 2.54}, {"text": "Is it frozen?", "start": 3697.21, "duration": 0.6}, {"text": "I'm like, no, I'm not trying\nto steal the money, guys.", "start": 3697.81, "duration": 3.0}, {"text": "Because everyone was sending\nall these little outputs to Tim", "start": 3700.81, "duration": 3.24}, {"text": "Draper's 30,000 coins or\nwhatever, because he's--", "start": 3704.05, "duration": 3.012}, {"text": "and then when he\ntried to spend it,", "start": 3707.062, "duration": 1.458}, {"text": "it took five minutes to sign.", "start": 3708.52, "duration": 1.693}, {"text": "AUDIENCE: When\npeople use P2 pool,", "start": 3710.213, "duration": 1.967}, {"text": "the software really\nstruggles with this.", "start": 3712.18, "duration": 1.667}, {"text": "PROFESSOR: Yeah, so it's bad.", "start": 3713.847, "duration": 2.673}, {"text": "Any o event squared,\nthis is sort of a bug.", "start": 3716.52, "duration": 2.85}, {"text": "Segwit actually fixed this.", "start": 3719.37, "duration": 1.38}, {"text": "The way they do it\nis they say, OK,", "start": 3720.75, "duration": 3.81}, {"text": "we sort of pre compute these\nthree intermediate hashes.", "start": 3724.56, "duration": 6.27}, {"text": "Take the whole transaction.", "start": 3730.83, "duration": 3.41}, {"text": "This is sort of the\nglobal transaction data,", "start": 3734.24, "duration": 2.11}, {"text": "and pre compute\nthese three things.", "start": 3736.35, "duration": 1.95}, {"text": "And then for each of the\ninputs, add another thing.", "start": 3738.3, "duration": 3.56}, {"text": "Here's this input specific.", "start": 3741.86, "duration": 1.15}, {"text": "So this is global.", "start": 3743.01, "duration": 2.33}, {"text": "It's the hash of all the\ntx ends, the hash of all", "start": 3745.34, "duration": 2.83}, {"text": "the outputs, the hash of this.", "start": 3748.17, "duration": 2.28}, {"text": "And then here is that\nthe input specific.", "start": 3750.45, "duration": 2.24}, {"text": "Input specific.", "start": 3757.19, "duration": 1.08}, {"text": "And then hash all these\nthings into one thing", "start": 3758.27, "duration": 3.03}, {"text": "and then sign that.", "start": 3761.3, "duration": 1.23}, {"text": "So the idea is it's o of n in\nthat you compute these three", "start": 3762.53, "duration": 2.748}, {"text": "and then you sort\nof go down and keep", "start": 3765.278, "duration": 1.542}, {"text": "changing this for each one.", "start": 3766.82, "duration": 1.71}, {"text": "So that saves a lot of time.", "start": 3768.53, "duration": 2.1}, {"text": "It's a much nicer--", "start": 3770.63, "duration": 0.84}, {"text": "oh, you also put in the amount\nbeing spent in your signature", "start": 3771.47, "duration": 6.02}, {"text": "hash, which is also\nredundant, because that's", "start": 3777.49, "duration": 2.38}, {"text": "committed to in the txid\nthat you're sending.", "start": 3779.87, "duration": 2.25}, {"text": "But it's really nice\nfor hardware wallets,", "start": 3782.12, "duration": 2.088}, {"text": "because a lot of times hardware\nwallets are essentially", "start": 3784.208, "duration": 2.292}, {"text": "presented with here's a hash.", "start": 3786.5, "duration": 2.55}, {"text": "Sign it.", "start": 3789.05, "duration": 1.11}, {"text": "And it's a very small system.", "start": 3790.16, "duration": 2.315}, {"text": "It's a little chip somewhere,\nand it doesn't really", "start": 3792.475, "duration": 2.125}, {"text": "know too much about bitcoin.", "start": 3794.6, "duration": 1.27}, {"text": "It's just, here's a hash.", "start": 3795.87, "duration": 1.042}, {"text": "Sign it.", "start": 3796.912, "duration": 0.628}, {"text": "OK, and they don't know\nhow much they're spending,", "start": 3797.54, "duration": 2.853}, {"text": "so there could be attacks\non hardware wallets,", "start": 3800.393, "duration": 1.917}, {"text": "where they get a hardware wallet\nto sign something where it's", "start": 3802.31, "duration": 2.4}, {"text": "actually moving too much money.", "start": 3804.71, "duration": 1.41}, {"text": "So it's nice to be able\nto have the actual amount.", "start": 3806.12, "duration": 2.98}, {"text": "So there's a bunch\nof stuff like that.", "start": 3809.1, "duration": 1.73}, {"text": "It was a giant grab bag of all\nthese different little fixes,", "start": 3810.83, "duration": 3.03}, {"text": "things like that.", "start": 3813.86, "duration": 1.56}, {"text": "Fixes malleability.", "start": 3815.42, "duration": 1.5}, {"text": "It increases the block size.", "start": 3816.92, "duration": 1.6}, {"text": "Does all these\nother cool things.", "start": 3818.52, "duration": 1.91}, {"text": "People didn't like it.", "start": 3820.43, "duration": 2.47}, {"text": "I never really understood why.", "start": 3822.9, "duration": 4.008}, {"text": "AUDIENCE: For the reasons you've\nbeen telling everyone about?", "start": 3826.908, "duration": 2.542}, {"text": "PROFESSOR: All these reasons?", "start": 3829.45, "duration": 0.6}, {"text": "Wait, these seem like\ngood things, right?", "start": 3830.05, "duration": 1.78}, {"text": "AUDIENCE: Well,\nyeah, but [INAUDIBLE]", "start": 3832.33, "duration": 3.447}, {"text": "PROFESSOR: Oh.", "start": 3835.777, "duration": 0.583}, {"text": "No, that wasn't what--", "start": 3836.36, "duration": 1.5}, {"text": "it wasn't like\npeople were like, oh,", "start": 3837.86, "duration": 1.78}, {"text": "here's some little things\nI don't like about it.", "start": 3839.64, "duration": 2.0}, {"text": "Because that was what I said.", "start": 3841.64, "duration": 1.257}, {"text": "That was like what everyone\nworking on Bitcoin was like.", "start": 3842.897, "duration": 2.333}, {"text": "No one thinks it's perfect.", "start": 3845.23, "duration": 1.742}, {"text": "Everyone was like, oh,\nbut this thing is weird.", "start": 3846.972, "duration": 1.958}, {"text": "Why did you do that?", "start": 3848.93, "duration": 0.833}, {"text": "Or why didn't you put\nthis in kind of things.", "start": 3849.763, "duration": 2.797}, {"text": "But no, the people who didn't\nlike it really didn't like it.", "start": 3852.56, "duration": 3.65}, {"text": "There's still a bounty on\n[INAUDIBLE] head, right?", "start": 3856.21, "duration": 4.1}, {"text": "There's death threats.", "start": 3860.31, "duration": 1.09}, {"text": "Someone's like, I'll pay\nsomeone to kill this guy.", "start": 3861.4, "duration": 2.083}, {"text": "It's all, this is going\nto destroy Bitcoin,", "start": 3866.78, "duration": 1.95}, {"text": "that segwit isn't\nbitcoin anymore,", "start": 3868.73, "duration": 3.03}, {"text": "because there aren't\nany signatures.", "start": 3871.76, "duration": 1.602}, {"text": "It's like no, signatures\nare still committed to, just", "start": 3873.362, "duration": 2.208}, {"text": "in a different way.", "start": 3875.57, "duration": 0.87}, {"text": "You have to build\nthis other tree.", "start": 3876.44, "duration": 1.417}, {"text": "So lots of weird conspiracies.", "start": 3879.35, "duration": 1.468}, {"text": "I don't know.", "start": 3880.818, "duration": 0.542}, {"text": "It became this really\nsticking point,", "start": 3881.36, "duration": 3.54}, {"text": "and so that sort of\nled to Bitcoin Cash.", "start": 3884.9, "duration": 4.07}, {"text": "The whole idea is segwit is bad.", "start": 3888.97, "duration": 2.14}, {"text": "We're making Bitcoin Cash.", "start": 3891.11, "duration": 1.48}, {"text": "And Bitcoin Cash forked\noff before segwit", "start": 3892.59, "duration": 2.09}, {"text": "activated in the main network.", "start": 3894.68, "duration": 3.0}, {"text": "Interestingly, Bitcoin\nCash uses this.", "start": 3897.68, "duration": 3.005}, {"text": "So they took a bunch of\nthe code from segwit,", "start": 3900.685, "duration": 1.875}, {"text": "because this is a\nreally good improvement", "start": 3902.56, "duration": 2.45}, {"text": "to signing that\nBitcoin Cash used,", "start": 3905.01, "duration": 1.94}, {"text": "but they didn't like segwit.", "start": 3906.95, "duration": 2.73}, {"text": "Yeah, I'm still not like--", "start": 3909.68, "duration": 2.538}, {"text": "I don't know.", "start": 3912.218, "duration": 0.542}, {"text": "There's problems I have with\nit, too, but it's an upgrade,", "start": 3912.76, "duration": 2.58}, {"text": "and it's cool.", "start": 3915.34, "duration": 1.55}, {"text": "I think a lot of it was\npeople wanted a hard fork,", "start": 3916.89, "duration": 2.636}, {"text": "and this was a softfork.", "start": 3919.526, "duration": 1.339}, {"text": "And so there's\nbackwards compatibility,", "start": 3920.865, "duration": 1.625}, {"text": "and they wanted to\nshow that people", "start": 3922.49, "duration": 2.99}, {"text": "have more control over\nbitcoin than they maybe do.", "start": 3925.48, "duration": 3.12}, {"text": "It might never be possible\nto have a hard fork", "start": 3928.6, "duration": 2.58}, {"text": "to get everyone on\nboard to really switch.", "start": 3931.18, "duration": 2.01}, {"text": "So who knows.", "start": 3933.19, "duration": 1.35}, {"text": "So yeah, it was interesting.", "start": 3934.54, "duration": 1.89}, {"text": "It took forever, and\nthat was the last change", "start": 3936.43, "duration": 3.99}, {"text": "to the bitcoin code in\nterms of consensus code.", "start": 3940.42, "duration": 3.75}, {"text": "And it was initially\nannounced late 2015", "start": 3944.17, "duration": 5.07}, {"text": "in Hong Kong, and\nthen all of 2016", "start": 3949.24, "duration": 3.88}, {"text": "it never-- so it activated\nin August of last year.", "start": 3953.12, "duration": 2.93}, {"text": "And now you can use it.", "start": 3956.05, "duration": 1.018}, {"text": "AUDIENCE: People had big\ninterest in stopping it,", "start": 3957.068, "duration": 2.042}, {"text": "though.", "start": 3959.11, "duration": 0.89}, {"text": "At one point they were\nspending hundreds of thousands", "start": 3960.0, "duration": 2.95}, {"text": "of dollars a day to\nstop it from activating.", "start": 3962.95, "duration": 2.79}, {"text": "PROFESSOR: Yeah, so on your\nvert coin, you're like,", "start": 3965.74, "duration": 3.057}, {"text": "I'll just take the segwit code\nand activate it, and like cool.", "start": 3968.797, "duration": 2.583}, {"text": "And then people tried to stop\nit and spend a lot of money", "start": 3971.38, "duration": 2.19}, {"text": "to stop it.", "start": 3973.57, "duration": 0.5}, {"text": "OK, I want to say unclear\nwhy, because I don't know.", "start": 3977.05, "duration": 2.37}, {"text": "It's sort of weird.", "start": 3979.42, "duration": 1.18}, {"text": "There's a whole lot of opinions.", "start": 3980.6, "duration": 1.37}, {"text": "One theory is that\nthis breaks some mining", "start": 3981.97, "duration": 6.62}, {"text": "chips optimizations.", "start": 3988.59, "duration": 2.97}, {"text": "One of the optimizations--", "start": 3991.56, "duration": 2.25}, {"text": "it doesn't work with\na tree of height two.", "start": 3993.81, "duration": 2.15}, {"text": "But if you have a really tall\ntree, you can swap txids,", "start": 3995.96, "duration": 4.75}, {"text": "or you can swap intermediate\nnodes of the tree", "start": 4000.71, "duration": 2.67}, {"text": "and you'll get a\ndifferent merkle route.", "start": 4003.38, "duration": 2.76}, {"text": "So you can see--", "start": 4006.14, "duration": 2.58}, {"text": "so it doesn't work here, because\nthis has to stay in place.", "start": 4008.72, "duration": 2.55}, {"text": "But in many cases, the order of\nthe transactions is arbitrary.", "start": 4011.27, "duration": 4.17}, {"text": "So I could flip these two.", "start": 4015.44, "duration": 2.01}, {"text": "It's still valid.", "start": 4017.45, "duration": 2.79}, {"text": "So what I might do is say, OK.", "start": 4020.24, "duration": 2.19}, {"text": "I have this merkle\nroute I'm mining,", "start": 4022.43, "duration": 2.7}, {"text": "and then I want to flip\nthese two, calculate", "start": 4025.13, "duration": 3.57}, {"text": "a different merkle\nroute, and mine.", "start": 4028.7, "duration": 1.59}, {"text": "And there were some chips\nthat maybe did this and had", "start": 4030.29, "duration": 2.82}, {"text": "these kinds of optimizations.", "start": 4033.11, "duration": 1.5}, {"text": "There was also a patent on\nit and all this weird stuff", "start": 4034.61, "duration": 2.52}, {"text": "going on.", "start": 4037.13, "duration": 2.38}, {"text": "It doesn't break,\nbut it essentially", "start": 4039.51, "duration": 2.57}, {"text": "loses the optimization\nif you have this.", "start": 4042.08, "duration": 1.86}, {"text": "Because you're saying, OK, I'm\ngoing to have this big tree.", "start": 4043.94, "duration": 3.84}, {"text": "I'm going to swap\nsomething near the top,", "start": 4047.78, "duration": 2.79}, {"text": "and it only has to\nrecompute two hashes", "start": 4050.57, "duration": 2.04}, {"text": "to get a new merkle route.", "start": 4052.61, "duration": 2.16}, {"text": "However, if I now have this\nmirror image witness merkle", "start": 4054.77, "duration": 5.49}, {"text": "tree underneath, if I say,\nOK, I'm going to swap this,", "start": 4060.26, "duration": 3.51}, {"text": "I'm also swapping all these.", "start": 4063.77, "duration": 1.32}, {"text": "And I have to recompute this.", "start": 4065.09, "duration": 3.96}, {"text": "Maybe I can swap some of it, but\nI have to recompute what this.", "start": 4069.05, "duration": 2.73}, {"text": "This is going to\nchange just as well.", "start": 4071.78, "duration": 1.81}, {"text": "And then I have to\nput that in here,", "start": 4073.59, "duration": 1.07}, {"text": "and this is going\nto be at the bottom.", "start": 4074.66, "duration": 1.43}, {"text": "And then, I'm going to have\nto recompute everything", "start": 4076.09, "duration": 2.125}, {"text": "all the way up to\nthe merkle route.", "start": 4078.215, "duration": 1.615}, {"text": "So this was called AsicBoost,\nand then there was a post--", "start": 4079.83, "duration": 4.31}, {"text": "Greg Maxwell posted\nthis sort of like,", "start": 4084.14, "duration": 2.985}, {"text": "you guys, like accusatory mail\non the mailing list last spring", "start": 4087.125, "duration": 5.265}, {"text": "saying, look.", "start": 4092.39, "duration": 1.2}, {"text": "We were trying to figure out\na way to break AsicBoost,", "start": 4093.59, "duration": 3.9}, {"text": "because we think miners have\nthis patented algorithm that", "start": 4097.49, "duration": 3.3}, {"text": "optimizes and it gives\na 20%, 30% speed up.", "start": 4100.79, "duration": 3.029}, {"text": "And we're worried that the\npatents will make one miner,", "start": 4103.819, "duration": 2.521}, {"text": "have a monopoly, and everyone\nelse won't be competitive.", "start": 4106.34, "duration": 2.59}, {"text": "So we're trying\nto think, is there", "start": 4108.93, "duration": 1.417}, {"text": "a way we make software\nto prevent this", "start": 4110.347, "duration": 2.793}, {"text": "from this optimization?", "start": 4113.14, "duration": 2.009}, {"text": "And then once they\ntried to look at it,", "start": 4115.149, "duration": 2.071}, {"text": "they were like, oh, wait.", "start": 4117.22, "duration": 1.08}, {"text": "Segwit does that.", "start": 4118.3, "duration": 1.34}, {"text": "We want to make it costly\nto swap things in the tree,", "start": 4119.64, "duration": 3.67}, {"text": "and segwit does that.", "start": 4123.31, "duration": 1.14}, {"text": "Oh, so basically, we're good.", "start": 4124.45, "duration": 1.77}, {"text": "And then he was like, oh, wait.", "start": 4126.22, "duration": 1.41}, {"text": "Maybe that's why all\nthese people hate segwit.", "start": 4127.63, "duration": 2.58}, {"text": "Maybe this is these miners\nwho have billions of dollars", "start": 4130.21, "duration": 4.229}, {"text": "worth of equipment with\nthese optimizations in it,", "start": 4134.439, "duration": 2.731}, {"text": "which would be rendered unusable\nby this new software change,", "start": 4137.17, "duration": 4.439}, {"text": "maybe they're trying to\nprevent it from activating.", "start": 4141.609, "duration": 2.971}, {"text": "It's a theory, and the\nmining companies said,", "start": 4144.58, "duration": 2.43}, {"text": "oh, no that's a\nbunch of nonsense.", "start": 4147.01, "duration": 2.309}, {"text": "Although, the way they said\nit was sort of suspicious.", "start": 4149.319, "duration": 2.256}, {"text": "They were like, yeah, we\nput circuitry in our chips", "start": 4151.575, "duration": 2.125}, {"text": "to do this, but\nwe never used it.", "start": 4153.7, "duration": 1.8}, {"text": "That's strange.", "start": 4155.5, "duration": 1.71}, {"text": "So who knows.", "start": 4157.21, "duration": 2.31}, {"text": "But that's one theory.", "start": 4159.52, "duration": 2.04}, {"text": "I'm not sure how much I\nbelieve that's the real reason,", "start": 4161.56, "duration": 2.35}, {"text": "but yeah.", "start": 4163.91, "duration": 0.5}, {"text": "AUDIENCE: but if they want\nto calculate Merkle roots", "start": 4164.41, "duration": 2.167}, {"text": "in bitcoin, don't just--", "start": 4166.577, "duration": 1.663}, {"text": "order all of the transaction\nfees by transaction ID?", "start": 4168.24, "duration": 3.699}, {"text": "PROFESSOR: You can't,\nbecause the order matters.", "start": 4171.939, "duration": 3.42}, {"text": "Because when you\nvalidate, this transaction", "start": 4175.359, "duration": 3.42}, {"text": "might create an output that\nthis transaction spends.", "start": 4178.779, "duration": 2.705}, {"text": "And so if you swap them, so\nif you didn't have intra block", "start": 4181.484, "duration": 5.426}, {"text": "dependencies, then it\nwould all be arbitrary", "start": 4186.91, "duration": 2.159}, {"text": "and you could put in ordering.", "start": 4189.069, "duration": 1.381}, {"text": "But there are intra\nblock dependencies,", "start": 4190.45, "duration": 2.279}, {"text": "and so the order does matter.", "start": 4192.729, "duration": 1.801}, {"text": "In many cases, it doesn't.", "start": 4194.53, "duration": 1.175}, {"text": "In many cases, these are\ntwo separate transactions.", "start": 4195.705, "duration": 2.125}, {"text": "You can swap them.", "start": 4197.83, "duration": 1.23}, {"text": "But the software does\nuse the ordering.", "start": 4199.06, "duration": 3.29}, {"text": "And there's all sorts of other\nthings that would be better.", "start": 4202.35, "duration": 2.75}, {"text": "What I would want is\nprepend or append the height", "start": 4205.1, "duration": 6.05}, {"text": "at each stage of\nthe merkle tree.", "start": 4211.15, "duration": 2.28}, {"text": "That would have helped\nme out for some things.", "start": 4213.43, "duration": 2.915}, {"text": "Because then, it's\nlike you know,", "start": 4216.345, "duration": 1.375}, {"text": "since you're at\nthe bottom just put", "start": 4217.72, "duration": 1.458}, {"text": "a zero at the end of each hash.", "start": 4219.178, "duration": 1.735}, {"text": "And then when you get\nup here, put a one", "start": 4220.913, "duration": 1.667}, {"text": "at the end of each hash.", "start": 4222.58, "duration": 2.25}, {"text": "Doesn't really change anything.", "start": 4224.83, "duration": 1.92}, {"text": "But one problem is\nwhat if I request--", "start": 4226.75, "duration": 5.04}, {"text": "so what I want to\ndo in my software.", "start": 4231.79, "duration": 1.54}, {"text": "I want to request all the\ntransaction IDs in a block.", "start": 4233.33, "duration": 2.58}, {"text": "I don't actually care\nabout the transactions.", "start": 4235.91, "duration": 1.41}, {"text": "I just want to\nsee all the txids.", "start": 4237.32, "duration": 1.375}, {"text": "Like this.", "start": 4241.36, "duration": 0.87}, {"text": "If I get rid of the head 20,\nI get a giant list of txids.", "start": 4242.23, "duration": 4.6}, {"text": "The thing is, what this let me\ndo is to look for transactions.", "start": 4246.83, "duration": 3.592}, {"text": "If I have a txid I know\nI'm looking, I can say,", "start": 4250.422, "duration": 1.958}, {"text": "oh, I can look for it in here.", "start": 4252.38, "duration": 2.22}, {"text": "The problem is, what if\nthe person I'm asking", "start": 4254.6, "duration": 2.52}, {"text": "is giving me this\ninstead of this?", "start": 4257.12, "duration": 3.96}, {"text": "I won't know.", "start": 4261.08, "duration": 1.6}, {"text": "They all look like\nrandom numbers.", "start": 4262.68, "duration": 2.79}, {"text": "If I do the merkle tree algo,\nI'll get to the merkle route.", "start": 4265.47, "duration": 4.42}, {"text": "That's good.", "start": 4269.89, "duration": 0.65}, {"text": "But I don't really know\nthat I'm at the bottom.", "start": 4270.54, "duration": 3.42}, {"text": "It's OK if I'm\nrunning a full node", "start": 4273.96, "duration": 1.47}, {"text": "and I actually download all\nthe transactions and look,", "start": 4275.43, "duration": 2.44}, {"text": "and OK, it works.", "start": 4277.87, "duration": 1.34}, {"text": "But to have a way to say, hey,\ngive me a list of all the txids", "start": 4279.21, "duration": 3.822}, {"text": "and I can verify\nthat it's correct,", "start": 4283.032, "duration": 1.458}, {"text": "I can't do that right now.", "start": 4284.49, "duration": 1.472}, {"text": "There's ways around it.", "start": 4285.962, "duration": 0.958}, {"text": "But it would have\nbeen nice if then they", "start": 4286.92, "duration": 1.667}, {"text": "appended a zero or something.", "start": 4288.587, "duration": 1.585}, {"text": "Or even, all you\nhave to do is just", "start": 4290.172, "duration": 1.458}, {"text": "append something\nat the bottom row", "start": 4291.63, "duration": 2.34}, {"text": "or just append\nhigher or something.", "start": 4293.97, "duration": 2.01}, {"text": "Then, it would've\nbeen kind of cool.", "start": 4295.98, "duration": 0.87}, {"text": "It would've been easier for me.", "start": 4296.85, "duration": 1.292}, {"text": "But oh well.", "start": 4298.142, "duration": 1.163}, {"text": "And there's people who've\nwritten about this.", "start": 4299.305, "duration": 1.875}, {"text": "Yeah.", "start": 4301.18, "duration": 0.64}, {"text": "AUDIENCE: Did James say that's\npool operators are leaving off", "start": 4301.82, "duration": 2.83}, {"text": "the [? whipper? ?]\nAnd if so, does it", "start": 4304.65, "duration": 2.49}, {"text": "weaken the whole system?", "start": 4307.14, "duration": 1.032}, {"text": "PROFESSOR: I think\nwhat they really", "start": 4308.172, "duration": 1.458}, {"text": "do is they just\ndon't support segwit.", "start": 4309.63, "duration": 1.77}, {"text": "So I've seen, especially--", "start": 4311.4, "duration": 1.2}, {"text": "AUDIENCE: [INAUDIBLE] it's\nexpensive but then they--", "start": 4312.6, "duration": 2.53}, {"text": "PROFESSOR: Yeah, they say\nthey're going to support it,", "start": 4315.13, "duration": 2.25}, {"text": "and then they don't.", "start": 4317.38, "duration": 1.61}, {"text": "So they sort of flag their\ntransactions, yeah, segwit,", "start": 4318.99, "duration": 2.58}, {"text": "and then they haven't actually\nupgraded their software,", "start": 4321.57, "duration": 1.84}, {"text": "so they can't use it.", "start": 4323.41, "duration": 0.92}, {"text": "They can't mine it.", "start": 4324.33, "duration": 0.92}, {"text": "So you see this a lot\non TestNet as well.", "start": 4325.25, "duration": 1.96}, {"text": "If you're making TestNet\nsegwit transactions,", "start": 4327.21, "duration": 2.425}, {"text": "sometimes they just\ndon't get confirmed", "start": 4329.635, "duration": 1.625}, {"text": "for a few hours, because\nall the blocks that come out", "start": 4331.26, "duration": 3.278}, {"text": "don't support it, and\nso they won't use it.", "start": 4334.538, "duration": 1.792}, {"text": "AUDIENCE: The badly\nwritten pool software,", "start": 4336.33, "duration": 1.75}, {"text": "if they use segwit\nsupporting full load with it,", "start": 4338.08, "duration": 2.932}, {"text": "it will give them\nsegwit transactions,", "start": 4341.012, "duration": 3.628}, {"text": "and they'll try to include\nit but it won't do this, so--", "start": 4344.64, "duration": 2.545}, {"text": "PROFESSOR: So it's invalid.", "start": 4347.185, "duration": 1.125}, {"text": "Yes, so it's invalid.", "start": 4348.31, "duration": 1.35}, {"text": "AUDIENCE: I guess my\nquestion is does it", "start": 4349.66, "duration": 1.667}, {"text": "weaken the security in the\nsystem if for six months", "start": 4351.327, "duration": 3.973}, {"text": "they're not supporting this?", "start": 4355.3, "duration": 1.64}, {"text": "PROFESSOR: No, no.", "start": 4356.94, "duration": 0.93}, {"text": "It hurts the usability.", "start": 4357.87, "duration": 1.95}, {"text": "If I want to use a\nsegwit transact--", "start": 4359.82, "duration": 1.53}, {"text": "but as me running a\nsegwit compatible node,", "start": 4361.35, "duration": 3.36}, {"text": "I require signatures.", "start": 4364.71, "duration": 2.1}, {"text": "I require all this\nwhole construction.", "start": 4366.81, "duration": 2.25}, {"text": "If you make something\nthat looks like it", "start": 4369.06, "duration": 2.22}, {"text": "spends the segwit transaction\nwithout this, I just reject it.", "start": 4371.28, "duration": 3.54}, {"text": "So security wise, it's fine.", "start": 4374.82, "duration": 1.47}, {"text": "Yes.", "start": 4376.29, "duration": 0.5}, {"text": "AUDIENCE: I think it\nmight be important to note", "start": 4376.79, "duration": 1.24}, {"text": "that the way that these things\nare designed, and in particular", "start": 4378.03, "duration": 2.76}, {"text": "that softforks are designed, is\nthat anyone who doesn't update", "start": 4380.79, "duration": 4.02}, {"text": "the new functionality\ncan't hurt the security", "start": 4384.81, "duration": 3.93}, {"text": "of the new functionality.", "start": 4388.74, "duration": 1.23}, {"text": "That's sort of part\nof the design process.", "start": 4389.97, "duration": 3.54}, {"text": "PROFESSOR: Although, their\nsecurity might get hurt.", "start": 4393.51, "duration": 2.805}, {"text": "Not a ton, but yeah.", "start": 4396.315, "duration": 2.005}, {"text": "If you haven't\nupgraded, you might", "start": 4398.32, "duration": 2.18}, {"text": "see these segwit\ntransactions, and--", "start": 4400.5, "duration": 1.915}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4402.415, "duration": 0.875}, {"text": "PROFESSOR: Yeah,\nthey look weird,", "start": 4403.29, "duration": 1.697}, {"text": "but you're like, OK, fine.", "start": 4404.987, "duration": 1.083}, {"text": "But you can't actually\nverify the whole thing.", "start": 4406.07, "duration": 2.74}, {"text": "Given an invalid and a\nvalid segwit transaction,", "start": 4408.81, "duration": 3.483}, {"text": "the old software\ncan't distinguish", "start": 4412.293, "duration": 1.417}, {"text": "but the new software can.", "start": 4413.71, "duration": 1.793}, {"text": "AUDIENCE: That's even though the\npool operators, whether there's", "start": 4415.503, "duration": 2.667}, {"text": "six or eight key pool\noperators, might not", "start": 4418.17, "duration": 2.43}, {"text": "be supporting the witrootsub", "start": 4420.6, "duration": 1.73}, {"text": "PROFESSOR: If they\ndon't support it,", "start": 4422.33, "duration": 1.913}, {"text": "you have to wait until\nsomeone that does", "start": 4424.243, "duration": 1.667}, {"text": "support it mines the block.", "start": 4425.91, "duration": 2.88}, {"text": "So if they try to support\nit and support it wrong,", "start": 4428.79, "duration": 3.84}, {"text": "you ignore them.", "start": 4432.63, "duration": 1.73}, {"text": "You don't use their data.", "start": 4434.36, "duration": 1.48}, {"text": "You don't use their block.", "start": 4435.84, "duration": 1.19}, {"text": "AUDIENCE: you just want\nsegwit transactions stay", "start": 4437.03, "duration": 1.248}, {"text": "in the node pool a bit longer.", "start": 4438.278, "duration": 1.112}, {"text": "PROFESSOR: Yeah.", "start": 4439.39, "duration": 0.667}, {"text": "So I think in\nbitcoin now, it's OK.", "start": 4440.057, "duration": 2.953}, {"text": "TestNet is kind of weird,\nbut there's segwit.party,", "start": 4443.01, "duration": 3.97}, {"text": "and you can see what people\nare doing with segwit.", "start": 4446.98, "duration": 3.12}, {"text": "So yeah, it's about 30.", "start": 4452.71, "duration": 1.47}, {"text": "This is by transaction, it's\nsomewhere around 30 something", "start": 4454.18, "duration": 3.06}, {"text": "percent of the transactions\nare using segwit,", "start": 4457.24, "duration": 2.67}, {"text": "and then you can see witness\nsize percentage, block size.", "start": 4459.91, "duration": 3.5}, {"text": "OK, so sometimes you got--", "start": 4463.41, "duration": 1.39}, {"text": "oh wow, I had no idea.", "start": 4464.8, "duration": 1.92}, {"text": "Blocks are way under\na megabyte now.", "start": 4466.72, "duration": 2.54}, {"text": "Oh, OK, well free\ntransactions for everyone.", "start": 4469.26, "duration": 2.8}, {"text": "If you want to use\nbitcoin, now's the time.", "start": 4472.06, "duration": 1.98}, {"text": "You don't have to pay anything.", "start": 4474.04, "duration": 2.49}, {"text": "That looks very different\na month ago where", "start": 4476.53, "duration": 3.42}, {"text": "you had a solid red line.", "start": 4479.95, "duration": 1.83}, {"text": "You had to sort of--", "start": 4481.78, "duration": 1.44}, {"text": "nothing went below a\nmillion, and then you", "start": 4483.22, "duration": 2.49}, {"text": "had a little bit of segwit\nstuff going on here.", "start": 4485.71, "duration": 2.13}, {"text": "But now you've got most\nthings are below a million.", "start": 4487.84, "duration": 2.84}, {"text": "So interesting.", "start": 4490.68, "duration": 1.34}, {"text": "OK, so yeah.", "start": 4492.02, "duration": 0.71}, {"text": "So that's the basic\nidea of segwit.", "start": 4492.73, "duration": 3.51}, {"text": "And if people have\nany questions,", "start": 4496.24, "duration": 2.55}, {"text": "stick around and ask.", "start": 4498.79, "duration": 2.52}, {"text": "There's office hours tomorrow\nat 4:00 to 6:00 over there.", "start": 4501.31, "duration": 2.46}, {"text": "Look at the homework,\nand next time", "start": 4503.77, "duration": 1.68}, {"text": "I'll talk about lightning\nnetwork payment--", "start": 4505.45, "duration": 1.87}, {"text": "I'll try to get into\npayment channels", "start": 4507.32, "duration": 1.67}, {"text": "and see how far we get into\nlightning network stuff.", "start": 4508.99, "duration": 3.77}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.497}, {"text": "[RUSTLING]", "start": 1.497, "duration": 1.996}, {"text": "[CLICKING]", "start": 3.493, "duration": 3.493}, {"text": "MATTHEW VANDER\nHEIDEN: So today I", "start": 9.915, "duration": 1.375}, {"text": "want to continue our discussion\nof amino acid metabolism.", "start": 11.29, "duration": 5.13}, {"text": "And before we do\nthat, I just want", "start": 16.42, "duration": 1.92}, {"text": "to come back for a few\nminutes and revisit the urea", "start": 18.34, "duration": 3.74}, {"text": "cycle and the Krebs\nbicycle that we", "start": 22.08, "duration": 3.43}, {"text": "discussed at the very\nend of the last lecture.", "start": 25.51, "duration": 2.83}, {"text": "I only want to do\nthat because it--", "start": 28.34, "duration": 2.57}, {"text": "a lot going on with this cycle.", "start": 30.91, "duration": 2.35}, {"text": "It can appear on the\nsurface to be confusing,", "start": 33.26, "duration": 2.81}, {"text": "the molecules are hard to draw.", "start": 36.07, "duration": 2.98}, {"text": "And so I just wanted\nto draw it neatly here", "start": 39.05, "duration": 2.36}, {"text": "for you one last time\nand go through it again.", "start": 41.41, "duration": 5.25}, {"text": "And so remember, if we start\nfrom the amino acid arginine,", "start": 46.66, "duration": 5.13}, {"text": "arginine can be converted into\nthe non-proteinogenic amino", "start": 51.79, "duration": 3.81}, {"text": "acid ornithine, and in\nthe process, release urea.", "start": 55.6, "duration": 4.56}, {"text": "That ornithine can then be\nin the mitochondria converted", "start": 60.16, "duration": 4.049}, {"text": "to citrulline, another\nnon-proteinogenic amino acid.", "start": 64.209, "duration": 5.311}, {"text": "By picking up a\ncarbon and a nitrogen", "start": 69.52, "duration": 2.67}, {"text": "from this molecule,\ncarbamoyl phosphate, which", "start": 72.19, "duration": 3.84}, {"text": "is generated from\nCO2/bicarbonate, as well", "start": 76.03, "duration": 3.81}, {"text": "as ammonia and to\nphosphorylations with ATP", "start": 79.84, "duration": 5.04}, {"text": "to get carbamoyl\ncarbon phosphate,", "start": 84.88, "duration": 1.65}, {"text": "that's added to ornithine\nto get citrulline.", "start": 86.53, "duration": 2.82}, {"text": "That citrulline and then combine\nwith the amino acid aspertate", "start": 89.35, "duration": 4.53}, {"text": "to give this molecule,\nargininosuccinate.", "start": 93.88, "duration": 2.85}, {"text": "So arginine plus\na succinate on it.", "start": 96.73, "duration": 3.18}, {"text": "And then loss of fumarate\nleaves you with arginine.", "start": 99.91, "duration": 5.73}, {"text": "That fumarate a can, of course,\ngo through the TCA cycle", "start": 105.64, "duration": 2.97}, {"text": "to regenerate malate,\noxaloacetate, ultimately pick", "start": 108.61, "duration": 3.99}, {"text": "up nitrogen on oxaloacetate\nis that alpha-keto acid,", "start": 112.6, "duration": 4.77}, {"text": "is transaminated to\naspertate, of course", "start": 117.37, "duration": 2.82}, {"text": "getting that nitrogen\nfrom glutamate", "start": 120.19, "duration": 2.64}, {"text": "to alpha-ketoglutarate.", "start": 122.83, "duration": 2.13}, {"text": "And glutamate, of course,\ncan get its nitrogen", "start": 124.96, "duration": 2.61}, {"text": "either by transamination\nwith another amino acid", "start": 127.57, "duration": 5.73}, {"text": "to an alpha-keto\nacid, converting", "start": 133.3, "duration": 2.01}, {"text": "alpha-ketoglutarate\nto glutamate,", "start": 135.31, "duration": 1.71}, {"text": "or glutamate can be generated\nby this redox reaction", "start": 137.02, "duration": 4.05}, {"text": "where it picks up on ammonia\nvia the enzyme glutamate", "start": 141.07, "duration": 3.69}, {"text": "dehydrogenase.", "start": 144.76, "duration": 1.98}, {"text": "So, you'll notice in this cycle\nthat ultimately the arginine,", "start": 146.74, "duration": 5.01}, {"text": "the urea group-- what is\nreleased as urea from arginine,", "start": 151.75, "duration": 4.14}, {"text": "comes from the\ncarbamoyl phosphate.", "start": 155.89, "duration": 3.42}, {"text": "So that's one of\nthese nitrogens that", "start": 159.31, "duration": 2.49}, {"text": "was picked up in the synthesis\nof carbamoyl phosphate.", "start": 161.8, "duration": 2.97}, {"text": "And the other one\ncomes from aspertate,", "start": 164.77, "duration": 2.61}, {"text": "which, of course,\ncan come from ammonia", "start": 167.38, "duration": 1.83}, {"text": "via glutamate dehydrogenase\nand transamination,", "start": 169.21, "duration": 3.84}, {"text": "or from transamination\nfrom nitrogen picked up", "start": 173.05, "duration": 3.33}, {"text": "from any other amino acid to\nultimately end up on aspertate.", "start": 176.38, "duration": 5.52}, {"text": "You'll notice that\nthere's redox balance", "start": 181.9, "duration": 2.4}, {"text": "across this whole cycle.", "start": 184.3, "duration": 2.56}, {"text": "And so there's a\nNAD that's required", "start": 186.86, "duration": 2.57}, {"text": "to reconvert the malate\nto oxaloacetate to run", "start": 189.43, "duration": 2.58}, {"text": "this half of the reaction.", "start": 192.01, "duration": 1.56}, {"text": "But of course, if we\npick up an ammonia,", "start": 193.57, "duration": 2.31}, {"text": "we also have a redox\nreaction involved", "start": 195.88, "duration": 4.02}, {"text": "in the glutamate\ndehydrogenase reaction.", "start": 199.9, "duration": 3.03}, {"text": "You'll see that ATP is also--", "start": 202.93, "duration": 3.72}, {"text": "quite a bit of ATP is needed.", "start": 206.65, "duration": 1.72}, {"text": "You need 2 ATP to generate\neach carbamoyl phosphate,", "start": 208.37, "duration": 3.53}, {"text": "as well as 2 ATP equivalents\nto generate argininosuccinate,", "start": 211.9, "duration": 4.047}, {"text": "because remember, if you go back\nto your notes from last time,", "start": 215.947, "duration": 2.583}, {"text": "you'll see that ATP to\nAMP plus pyrophosphate", "start": 218.53, "duration": 3.24}, {"text": "was part of the citrulline\nand aspertate generating", "start": 221.77, "duration": 3.93}, {"text": "argininosuccinate reaction.", "start": 225.7, "duration": 2.13}, {"text": "And the last thing\nis that CO2 is", "start": 227.83, "duration": 2.28}, {"text": "required to run the urea cycle.", "start": 230.11, "duration": 1.53}, {"text": "That's where the carbon\nin urea comes from.", "start": 231.64, "duration": 2.29}, {"text": "And that CO2 is, of\ncourse, picked up", "start": 233.93, "duration": 2.24}, {"text": "in the generation of\ncarbamoyl phosphate.", "start": 236.17, "duration": 3.75}, {"text": "Now, I think sometimes we can\nfall into the misconception", "start": 239.92, "duration": 6.0}, {"text": "when we talk about these\nthat all cells generate urea.", "start": 245.92, "duration": 2.76}, {"text": "That's not true.", "start": 248.68, "duration": 1.36}, {"text": "So remember, different organisms\nuse different strategies", "start": 250.04, "duration": 3.11}, {"text": "to excrete nitrogen. So\nin us as humans, the liver", "start": 253.15, "duration": 3.629}, {"text": "and the kidney would run the\nrecycle as I have drawn it here", "start": 256.779, "duration": 3.541}, {"text": "as a way to ultimately\nproduce urea that", "start": 260.32, "duration": 3.15}, {"text": "gets excreted in the blood--", "start": 263.47, "duration": 1.92}, {"text": "I mean, sorry, in the\nurine, whereas most tissues", "start": 265.39, "duration": 3.51}, {"text": "in our body would\nsimply ship off", "start": 268.9, "duration": 3.03}, {"text": "excess nitrogen from the\ncatabolism of amino acids", "start": 271.93, "duration": 3.27}, {"text": "to the liver and the kidney\nby generating either glutamate", "start": 275.2, "duration": 3.3}, {"text": "or glutamine in the reactions\nthat we talked about last time,", "start": 278.5, "duration": 3.49}, {"text": "and then those organs would\ndeal with-- use the urea cycle", "start": 281.99, "duration": 3.65}, {"text": "to produce urea and get\nrid of excess nitrogen.", "start": 285.64, "duration": 3.66}, {"text": "But of course,\nthere's other animals", "start": 289.3, "duration": 1.65}, {"text": "that will use other strategies\nsecreted as ammonia directly", "start": 290.95, "duration": 4.02}, {"text": "or produce the purine uric\nacid, which, of course,", "start": 294.97, "duration": 3.03}, {"text": "we'll talk about next time,\nhow one can interconnect", "start": 298.0, "duration": 4.83}, {"text": "all this amino acid nitrogen\nmetabolism with nucleic acid", "start": 302.83, "duration": 4.35}, {"text": "nitrogen metabolism.", "start": 307.18, "duration": 2.7}, {"text": "I just want to stress that\nthis glutamate dehydrogenase", "start": 309.88, "duration": 4.17}, {"text": "reaction is a really\nkey reaction that", "start": 314.05, "duration": 4.29}, {"text": "is necessary to get nitrogen\nin and out of the system.", "start": 318.34, "duration": 5.17}, {"text": "And once you get nitrogen\nin and out of the system,", "start": 323.51, "duration": 3.62}, {"text": "you can then use these\ntransamination reactions", "start": 327.13, "duration": 3.24}, {"text": "to move nitrogens around\nbetween amino acids", "start": 330.37, "duration": 3.39}, {"text": "and alpha-keto acids using\npyridoxal phosphate as we", "start": 333.76, "duration": 3.39}, {"text": "discussed last time.", "start": 337.15, "duration": 3.68}, {"text": "This is shown up above also\nas the bicycle reaction.", "start": 340.83, "duration": 6.43}, {"text": "And again, just stresses\nthat you sort of", "start": 347.26, "duration": 2.36}, {"text": "are running the urea cycle on\nthe right, this other TCA--", "start": 349.62, "duration": 4.47}, {"text": "modified TCA cycle, if\nyou will, on the left,", "start": 354.09, "duration": 2.43}, {"text": "and ultimately illustrates how\nyou pick up those nitrogens", "start": 356.52, "duration": 4.2}, {"text": "and CO2 to generate urea.", "start": 360.72, "duration": 5.88}, {"text": "But, of course, if\nwe're going to talk", "start": 366.6, "duration": 2.22}, {"text": "about how you would make\namino acids, which is really", "start": 368.82, "duration": 3.03}, {"text": "the topic of today,\nhow you break down", "start": 371.85, "duration": 2.61}, {"text": "and synthesize the\ncarbon skeletons", "start": 374.46, "duration": 2.22}, {"text": "of different amino acids,\nwell, obviously here's", "start": 376.68, "duration": 3.15}, {"text": "arginine metabolism.", "start": 379.83, "duration": 1.17}, {"text": "You can imagine\nthat you could use", "start": 381.0, "duration": 1.56}, {"text": "the same reactions to produce\nor break down arginine,", "start": 382.56, "duration": 3.42}, {"text": "and that is what happens.", "start": 385.98, "duration": 3.12}, {"text": "But I also want to talk about\nthe remaining amino acids.", "start": 389.1, "duration": 3.54}, {"text": "In the remaining\namino acids, it's", "start": 392.64, "duration": 2.13}, {"text": "really about how do we\ndeal with the carbon", "start": 394.77, "duration": 2.58}, {"text": "skeleton, the alpha-keto acids.", "start": 397.35, "duration": 2.25}, {"text": "And of course,\nthese are linked via", "start": 399.6, "duration": 2.64}, {"text": "this pyridoxal phosphate-driven\ntransamination reaction.", "start": 402.24, "duration": 5.95}, {"text": "Now, I don't have\ntime to in this course", "start": 408.19, "duration": 4.08}, {"text": "to go through how each amino\nacid carbon skeleton is", "start": 412.27, "duration": 4.32}, {"text": "produced and broken down.", "start": 416.59, "duration": 2.52}, {"text": "We'll discuss some major themes.", "start": 419.11, "duration": 3.3}, {"text": "However, if I don't cover\nyour favorite amino acid,", "start": 422.41, "duration": 2.4}, {"text": "because of course,\nall people should", "start": 424.81, "duration": 2.13}, {"text": "have a favorite amino acid,\nyou can look up the pathways", "start": 426.94, "duration": 4.29}, {"text": "to make it or break\nit down, and I", "start": 431.23, "duration": 2.67}, {"text": "promise that if\nyou paid attention", "start": 433.9, "duration": 2.13}, {"text": "through the whole class, you\nhave the skills to understand", "start": 436.03, "duration": 3.39}, {"text": "that particular pathway even\nif we don't study it in class.", "start": 439.42, "duration": 4.66}, {"text": "So I want to remind\nyou that in general", "start": 444.08, "duration": 3.17}, {"text": "for amino acid catabolism--", "start": 447.25, "duration": 3.45}, {"text": "and this is in general.", "start": 457.46, "duration": 1.177}, {"text": "Of course, there are exceptions.", "start": 458.637, "duration": 1.333}, {"text": "Arginine would behave as I just\ndescribed for the urea cycle.", "start": 459.97, "duration": 4.38}, {"text": "But for most amino acids, you\nstart with transamination.", "start": 464.35, "duration": 7.79}, {"text": "So what does that give you?", "start": 477.7, "duration": 1.43}, {"text": "That gives the nitrogen\nto alpha-ketoglutarate", "start": 479.13, "duration": 4.77}, {"text": "to generate glutamate.", "start": 483.9, "duration": 2.61}, {"text": "And so that glutamate\ncan then be shipped off", "start": 486.51, "duration": 3.27}, {"text": "to generate ammonia\nif you're a fish,", "start": 489.78, "duration": 1.95}, {"text": "generate urea if you're\na human, et cetera.", "start": 491.73, "duration": 4.5}, {"text": "And what does that\nleave you with?", "start": 496.23, "duration": 2.19}, {"text": "That leaves you with a\nalpha-keto acid related", "start": 498.42, "duration": 7.56}, {"text": "to the amino acid that can\nthen be oxidized to CO2 using", "start": 505.98, "duration": 8.3}, {"text": "various pathways-- burn it and\nget energy, just like we've", "start": 514.28, "duration": 3.84}, {"text": "described for carbohydrates\nand fatty acids, or, of course,", "start": 518.12, "duration": 5.25}, {"text": "in some cases produce glucose\nor some other molecule that", "start": 523.37, "duration": 7.19}, {"text": "can then be used to support\ngluconeogenesis in the liver,", "start": 530.56, "duration": 3.15}, {"text": "keep glucose high in our blood.", "start": 533.71, "duration": 2.4}, {"text": "And so that's generally how\nmost amino acids are stabilized.", "start": 536.11, "duration": 6.3}, {"text": "It's very clear how this works.", "start": 542.41, "duration": 1.8}, {"text": "If we start with some of\nthe more obvious ones--", "start": 544.21, "duration": 2.7}, {"text": "so we talked last time about\nhow alanine, the amino acid,", "start": 546.91, "duration": 4.29}, {"text": "is related--", "start": 551.2, "duration": 1.33}, {"text": "so transamination, get\nthe alpha-keto acid.", "start": 552.53, "duration": 2.57}, {"text": "That alpha-keto acid\nis pyruvate, aspertate.", "start": 555.1, "duration": 4.77}, {"text": "Amino acid undergoes\ntransamination.", "start": 559.87, "duration": 3.035}, {"text": "The alpha-keto acid\nis oxaloacetate.", "start": 562.905, "duration": 2.755}, {"text": "Glutamate undergoes\ntransamination.", "start": 565.66, "duration": 5.4}, {"text": "alpha-keto acid is\nalpha-ketoglutarate.", "start": 571.06, "duration": 2.35}, {"text": "It's very clear how\nall of these can end up", "start": 573.41, "duration": 3.02}, {"text": "in the TCA cycle or\ngluconeogenesis for The cell", "start": 576.43, "duration": 9.2}, {"text": "to either oxidize for energy\nor to produce something", "start": 585.63, "duration": 5.91}, {"text": "like glucose that can\nbe used elsewhere.", "start": 591.54, "duration": 3.193}, {"text": "Now of course, there's\nother amino acids", "start": 594.733, "duration": 1.667}, {"text": "out there that we've\nalready talked about.", "start": 596.4, "duration": 1.75}, {"text": "So remember asparagine,\nvery similar to aspertate.", "start": 598.15, "duration": 3.08}, {"text": "Glutamine similar to glutamate.", "start": 601.23, "duration": 4.26}, {"text": "So those were the ammonia\ngroup on the side chain.", "start": 605.49, "duration": 3.49}, {"text": "We can simply remove those.", "start": 608.98, "duration": 2.3}, {"text": "Should be clear how to\nthen get those into the TCA", "start": 611.28, "duration": 4.59}, {"text": "cycle or gluconeogenesis.", "start": 615.87, "duration": 2.0}, {"text": "A little bit of\nmetabolic trivia.", "start": 617.87, "duration": 2.17}, {"text": "Humans, we actually\ndon't have an enzyme", "start": 620.04, "duration": 1.89}, {"text": "to break down asparagine.", "start": 621.93, "duration": 1.38}, {"text": "Other organisms do.", "start": 623.31, "duration": 2.86}, {"text": "And then the other one that\nwe alluded to last time", "start": 626.17, "duration": 2.18}, {"text": "was proline, which is cyclized\nand oxidized glutamate.", "start": 628.35, "duration": 8.74}, {"text": "And so I'll just\nillustrate here quickly how", "start": 637.09, "duration": 3.95}, {"text": "proline can be metabolized\njust so you can see this.", "start": 641.04, "duration": 5.46}, {"text": "So here's the\namino acid proline.", "start": 654.86, "duration": 4.91}, {"text": "And so proline,\nto show you, if we", "start": 659.77, "duration": 3.96}, {"text": "do oxidation of this\ncarbon-nitrogen bond,", "start": 663.73, "duration": 5.34}, {"text": "so that utilizes these\nan electron acceptor.", "start": 669.07, "duration": 5.13}, {"text": "That electron\nacceptor happens to be", "start": 674.2, "duration": 2.67}, {"text": "FAD being reduced to FADH2.", "start": 676.87, "duration": 3.87}, {"text": "That generates this molecule.", "start": 680.74, "duration": 10.18}, {"text": "We can then add water\nacross that double bond.", "start": 690.92, "duration": 3.93}, {"text": "Now we can open up\nthe ring like this.", "start": 713.42, "duration": 4.76}, {"text": "So just opened up the ring.", "start": 739.22, "duration": 2.1}, {"text": "Now I'm going to oxidize\nthis aldehyde to the acid.", "start": 741.32, "duration": 6.03}, {"text": "So if I do that, something\nelse has to be reduced.", "start": 747.35, "duration": 3.12}, {"text": "That something else can\nbe NAD+ or NADP+ depending", "start": 750.47, "duration": 7.86}, {"text": "on the enzyme.", "start": 758.33, "duration": 1.53}, {"text": "There's enzymes that use\neither NAD or NADP to make", "start": 759.86, "duration": 3.84}, {"text": "NADPH or NADH respectively.", "start": 763.7, "duration": 4.69}, {"text": "And then what I'm left with\nis this amino acid glutamate.", "start": 768.39, "duration": 23.5}, {"text": "And so that's how I turn\nproline into glutamate.", "start": 791.89, "duration": 3.12}, {"text": "Two additional oxidation\nsteps generating", "start": 795.01, "duration": 4.5}, {"text": "FADH2 and NAD or NADPH.", "start": 799.51, "duration": 3.09}, {"text": "And so that's how you\nwould derive energy", "start": 802.6, "duration": 3.81}, {"text": "from the catabolism of proline,\nby feeding it into glutamate,", "start": 806.41, "duration": 5.603}, {"text": "which can then, of\ncourse, be transaminated", "start": 812.013, "duration": 1.792}, {"text": "to alpha-ketoglutarate,\nand the rest of the carbon", "start": 813.805, "duration": 2.175}, {"text": "enter the TCA cycle.", "start": 815.98, "duration": 2.92}, {"text": "OK.", "start": 818.9, "duration": 0.66}, {"text": "So that covers 1, 2,\n3, 4, 5, 6 amino acids.", "start": 819.56, "duration": 6.06}, {"text": "7 if you count arginine\nthat we talked about", "start": 825.62, "duration": 3.16}, {"text": "with the urea cycle.", "start": 828.78, "duration": 1.61}, {"text": "That leaves 13\nadditional amino acids.", "start": 830.39, "duration": 4.63}, {"text": "Many of them are first\ntransaminated to the alpha-keto", "start": 835.02, "duration": 2.84}, {"text": "acid, and then ultimately use--", "start": 837.86, "duration": 3.54}, {"text": "the carbon skeleton\ncan be used to generate", "start": 841.4, "duration": 3.06}, {"text": "another intermediate\nthat's either involved", "start": 844.46, "duration": 3.24}, {"text": "in the TCA cycle or glycolysis.", "start": 847.7, "duration": 3.18}, {"text": "And shown here on the\nslide is basically", "start": 850.88, "duration": 2.16}, {"text": "just a figure from\na textbook that", "start": 853.04, "duration": 2.07}, {"text": "contains all of the various--", "start": 855.11, "duration": 3.84}, {"text": "all of the 20 amino\nacids from protein", "start": 858.95, "duration": 2.44}, {"text": "and what they generate either\nin the TCA cycle or up here.", "start": 861.39, "duration": 6.41}, {"text": "So you can see here [INAUDIBLE]\noxaloacetate, fumarate", "start": 867.8, "duration": 2.73}, {"text": "succinyl-CoA,\nalpha-ketoglutarate, acetyl-CoA", "start": 870.53, "duration": 2.4}, {"text": "pyruvate, acetyl acetate.", "start": 872.93, "duration": 2.37}, {"text": "Which, of course,\nas we saw last time,", "start": 875.3, "duration": 2.04}, {"text": "can be used to\ngenerate 2 acetyl-CoA", "start": 877.34, "duration": 3.27}, {"text": "or be used to generate the\nketone body beta-hydroxy", "start": 880.61, "duration": 4.23}, {"text": "butyrate.", "start": 884.84, "duration": 1.46}, {"text": "Now, obviously if you can\ngenerate any of these things,", "start": 886.3, "duration": 4.47}, {"text": "we already know the pathways\nabout how you can oxidize them,", "start": 890.77, "duration": 3.84}, {"text": "or, in some cases, how you\ncan turn them into glucose.", "start": 894.61, "duration": 3.99}, {"text": "But now I want to\nreturn to this idea", "start": 898.6, "duration": 2.43}, {"text": "that we've come to a\nbunch of different times", "start": 901.03, "duration": 4.26}, {"text": "that really comes down to this\nfact of what we talked about", "start": 905.29, "duration": 3.54}, {"text": "with the TCA cycle, how the TCA\ncycle can't net do anaplerosis", "start": 908.83, "duration": 5.73}, {"text": "from two carbon units.", "start": 914.56, "duration": 1.89}, {"text": "That is, you can't turn\nacetyl-CoA or acetoacetate,", "start": 916.45, "duration": 5.76}, {"text": "because that's just two\nacetylcholine molecules,", "start": 922.21, "duration": 2.61}, {"text": "into anything that\ncan generate glucose.", "start": 924.82, "duration": 3.18}, {"text": "that We don't have\nthe glyoxylate cycle.", "start": 928.0, "duration": 2.13}, {"text": "Organisms that have the\nglyoxylate cycle can do this,", "start": 930.13, "duration": 2.85}, {"text": "but we as humans cannot do that.", "start": 932.98, "duration": 2.55}, {"text": "Now, many of our\namino acids can be", "start": 935.53, "duration": 3.57}, {"text": "used to produce things like\nfumarate, succinyl-CoA,", "start": 939.1, "duration": 4.305}, {"text": "oxaloacetate.", "start": 943.405, "duration": 1.365}, {"text": "All of that stuff can easily\nbe turned into glucose.", "start": 944.77, "duration": 3.78}, {"text": "And so if we starve ourselves or\ngo on a low-carbohydrate diet,", "start": 948.55, "duration": 7.11}, {"text": "well, what happens is, our liver\nwill break down amino acids", "start": 955.66, "duration": 3.93}, {"text": "and use those amino\nacids to make glucose,", "start": 959.59, "duration": 3.33}, {"text": "but we can only make\nglucose from amino acids", "start": 962.92, "duration": 2.7}, {"text": "if those amino acids\nare broken down", "start": 965.62, "duration": 2.76}, {"text": "into something that's not\nacetyl-CoA or acetoacetate", "start": 968.38, "duration": 3.9}, {"text": "because we don't have\na glyoxylate cycle.", "start": 972.28, "duration": 3.36}, {"text": "Just remember I mentioned\na couple lectures", "start": 975.64, "duration": 2.82}, {"text": "ago when we talked about\nthe ketogenic diet,", "start": 978.46, "duration": 2.46}, {"text": "a true ketogenic diet isn't\njust low carbohydrates,", "start": 980.92, "duration": 4.11}, {"text": "it's also low protein\nbecause your liver will turn", "start": 985.03, "duration": 3.57}, {"text": "that protein back into glucose.", "start": 988.6, "duration": 2.76}, {"text": "And so if you really\nwant to be ketotic,", "start": 991.36, "duration": 2.16}, {"text": "you have to limit\nboth glucose and--", "start": 993.52, "duration": 4.56}, {"text": "both sugars and proteins,\nbecause fat, of course,", "start": 998.08, "duration": 4.11}, {"text": "will only be broken\ninto two carbon units,", "start": 1002.19, "duration": 1.787}, {"text": "and you can't turn\nthose into glucose,", "start": 1003.977, "duration": 1.583}, {"text": "so you instead turn\nthem into ketones.", "start": 1005.56, "duration": 3.71}, {"text": "Now, not all amino\nacid skeletons,", "start": 1009.27, "duration": 4.35}, {"text": "though, can be used\nto make something", "start": 1013.62, "duration": 1.98}, {"text": "that can generate glucose.", "start": 1015.6, "duration": 2.1}, {"text": "Some can only make stuff--", "start": 1017.7, "duration": 2.57}, {"text": "acetyl-CoA,\nacetoacetate-- that can", "start": 1020.27, "duration": 2.35}, {"text": "be used to generate ketones.", "start": 1022.62, "duration": 3.06}, {"text": "And so this defines another\nway to classify amino acids,", "start": 1025.68, "duration": 5.01}, {"text": "is so-called glucogenic amino\nacids or ketogenic amino acids.", "start": 1030.69, "duration": 12.754}, {"text": "And this is a direct consequence\nof what those amino acid carbon", "start": 1047.15, "duration": 3.26}, {"text": "skeletons are broken into.", "start": 1050.41, "duration": 2.13}, {"text": "And so a glucogenic\namino acid is really", "start": 1052.54, "duration": 4.29}, {"text": "any amino acid where\nthe product of breakdown", "start": 1056.83, "duration": 14.76}, {"text": "is greater than 2 carbons\nthat is not acetyl-CoA.", "start": 1071.59, "duration": 5.66}, {"text": "Whereas ketogenic amino\nacid is an amino acid", "start": 1080.59, "duration": 7.36}, {"text": "where the product of\nbreakdown is acetyl-CoA.", "start": 1087.95, "duration": 15.06}, {"text": "And I should mention,\nor acetoacetate,", "start": 1105.79, "duration": 7.5}, {"text": "because acetoacetate, as\nwe saw, is 2 acetyl-CoAs.", "start": 1113.29, "duration": 4.6}, {"text": "So acetyl-CoA, acetoacetate can\nbe turned into the ketone body", "start": 1123.64, "duration": 4.08}, {"text": "beta-hydroxybutyrate, an\nalternative fuel for the brain.", "start": 1127.72, "duration": 3.638}, {"text": "If you break down an\namino acid and all you", "start": 1131.358, "duration": 1.792}, {"text": "get is acetyl-CoA\nor acetoacetate,", "start": 1133.15, "duration": 2.37}, {"text": "you can't turn that carbon\nskeleton back into glucose;", "start": 1135.52, "duration": 6.75}, {"text": "therefore, it's a\nketogenic amino acid.", "start": 1142.27, "duration": 2.82}, {"text": "All other amino acids that\ngenerate oxaloacetate,", "start": 1145.09, "duration": 3.6}, {"text": "succinyl-CoA, whatever,\nsomething greater", "start": 1148.69, "duration": 3.3}, {"text": "than 2 carbons, not\nacetyl-CoA, it can then", "start": 1151.99, "duration": 4.5}, {"text": "be turned into glucose,\ntherefore, it's", "start": 1156.49, "duration": 1.92}, {"text": "a glucogenic amino acids.", "start": 1158.41, "duration": 4.18}, {"text": "Now if we come back\nover here to our slide", "start": 1162.59, "duration": 3.11}, {"text": "and you look at the\nvarious amino acids,", "start": 1165.7, "duration": 2.79}, {"text": "most of the amino acids are\nturned into something that", "start": 1168.49, "duration": 4.11}, {"text": "can be turned into glucose.", "start": 1172.6, "duration": 1.47}, {"text": "And so most amino acids\nare so-called glucogenic.", "start": 1174.07, "duration": 5.64}, {"text": "However, there's a few amino\nacids that are ketogenic,", "start": 1179.71, "duration": 6.15}, {"text": "and there's some\namino acids that are", "start": 1185.86, "duration": 2.22}, {"text": "both glucogenic and ketogenic.", "start": 1188.08, "duration": 2.46}, {"text": "And so if you look here\nthrough the slide, what you'll", "start": 1190.54, "duration": 2.79}, {"text": "find is that tyrosine and\nisoleucine-- so there's", "start": 1193.33, "duration": 3.03}, {"text": "isoleucine, here's tyrosine.", "start": 1196.36, "duration": 2.49}, {"text": "So they're turned into\nketones, but they can also be--", "start": 1198.85, "duration": 4.71}, {"text": "here's tyrosine,\nhere's isoleucine--", "start": 1203.56, "duration": 2.13}, {"text": "can also be turned\ninto something", "start": 1205.69, "duration": 1.685}, {"text": "that can be used\nto make glucose,", "start": 1207.375, "duration": 1.375}, {"text": "and so they're referred to as\nboth glucogenic and ketogenic.", "start": 1208.75, "duration": 5.31}, {"text": "Now, as I said before,\nwe don't have time", "start": 1214.06, "duration": 3.0}, {"text": "to go through how to break\ndown all of the amino acids,", "start": 1217.06, "duration": 4.41}, {"text": "but I will take you through\nhow you break down the three", "start": 1221.47, "duration": 3.72}, {"text": "branched chain amino acids.", "start": 1225.19, "duration": 2.98}, {"text": "And I will do that\nbecause, first of all,", "start": 1228.17, "duration": 1.742}, {"text": "it will illustrate\nthat you already", "start": 1229.912, "duration": 1.458}, {"text": "know a lot about metabolism.", "start": 1231.37, "duration": 2.01}, {"text": "You'll see that how\nthese are broken down", "start": 1233.38, "duration": 2.34}, {"text": "is just variations on pathways\nthat we've already discussed.", "start": 1235.72, "duration": 4.33}, {"text": "And so it really\ndrives home the fact", "start": 1240.05, "duration": 1.91}, {"text": "that the complexity\nof metabolism", "start": 1241.96, "duration": 2.16}, {"text": "is really just nature\nrepurposing relatively", "start": 1244.12, "duration": 4.35}, {"text": "few reactions over and\nover and over again", "start": 1248.47, "duration": 2.64}, {"text": "in a way that ultimately builds\ncomplexity and diversity,", "start": 1251.11, "duration": 3.63}, {"text": "but in the end,\nis actually quite", "start": 1254.74, "duration": 3.15}, {"text": "consistent across\nthe whole thing.", "start": 1257.89, "duration": 3.93}, {"text": "And you'll also see examples\nof how amino acid skeleton", "start": 1261.82, "duration": 4.02}, {"text": "breakdown can end up either\nas glucogenic or ketogenic,", "start": 1265.84, "duration": 4.92}, {"text": "and that's because of the\nvarious branched chain", "start": 1270.76, "duration": 3.84}, {"text": "amino acids.", "start": 1274.6, "duration": 0.98}, {"text": "So there's, of course, leucine,\nvaline, and isoleucine.", "start": 1275.58, "duration": 5.95}, {"text": "So those are the three\nbranched chain amino acids.", "start": 1281.53, "duration": 4.23}, {"text": "You'll see the\nleucine is ketogenic,", "start": 1285.76, "duration": 5.97}, {"text": "valine is glucogenic, and\nisoleucine, as I just said,", "start": 1291.73, "duration": 9.11}, {"text": "is both ketogenic\nand glucogenic.", "start": 1300.84, "duration": 4.84}, {"text": "So three very amino acids.", "start": 1310.5, "duration": 3.69}, {"text": "In genetic terms,\nvery conservative", "start": 1314.19, "duration": 2.07}, {"text": "substitutions within a protein.", "start": 1316.26, "duration": 1.59}, {"text": "Very related structures.", "start": 1320.61, "duration": 2.34}, {"text": "However, the way they're broken\ndown, in the case of leucine,", "start": 1322.95, "duration": 3.93}, {"text": "generates only things\nthat are ketogenic;", "start": 1326.88, "duration": 2.58}, {"text": "valine generates things\nthat are glucogenic;", "start": 1329.46, "duration": 2.13}, {"text": "and isoleucine generates both.", "start": 1331.59, "duration": 2.04}, {"text": "And so we'll go through each of\nthese and see how that happens.", "start": 1333.63, "duration": 6.54}, {"text": "So let's start with leucine.", "start": 1340.17, "duration": 1.35}, {"text": "So leucine is a--", "start": 1345.77, "duration": 2.416}, {"text": "I said above is a\nketogenic amino acid.", "start": 1348.186, "duration": 5.804}, {"text": "And so leucine, like\nmany amino acids,", "start": 1353.99, "duration": 4.83}, {"text": "starts break down\nby transamination.", "start": 1358.82, "duration": 2.94}, {"text": "So this transamination will,\nof course, take the nitrogen", "start": 1361.76, "duration": 4.71}, {"text": "from leucine, an alpha-keto\nacid, alpha-ketoglutarate,", "start": 1366.47, "duration": 4.5}, {"text": "generate glutamate, as well as\nthe alpha-keto acid of leucine,", "start": 1370.97, "duration": 5.64}, {"text": "which, just to remind\nyou leucine looks like,", "start": 1376.61, "duration": 2.58}, {"text": "looks like this.", "start": 1379.19, "duration": 0.975}, {"text": "So this is the side chain\nover here of leucine.", "start": 1391.68, "duration": 5.0}, {"text": "Here's the alpha-keto\nacid related to leucine.", "start": 1396.68, "duration": 2.73}, {"text": "If I take this\nalpha-keto group, turn it", "start": 1399.41, "duration": 2.13}, {"text": "into an amino group,\nthat's leucine.", "start": 1401.54, "duration": 2.1}, {"text": "So this is the alpha-keto\nacid related to leucine.", "start": 1403.64, "duration": 5.16}, {"text": "So the next step of\nleucine breakdown", "start": 1408.8, "duration": 3.9}, {"text": "involves oxidative\ndecarboxylation", "start": 1412.7, "duration": 4.23}, {"text": "of this alpha-keto acid.", "start": 1416.93, "duration": 3.13}, {"text": "So if you remember, we've\nseen this reaction before.", "start": 1420.06, "duration": 3.08}, {"text": "We did it in pyruvate to\ngenerate acetaldehyde,", "start": 1423.14, "duration": 4.08}, {"text": "an ethanol metabolism.", "start": 1427.22, "duration": 2.04}, {"text": "We did it in--", "start": 1429.26, "duration": 1.59}, {"text": "well, we did alpha\ndecarboxylation there,", "start": 1430.85, "duration": 2.1}, {"text": "and then we did oxidative\nalpha decarboxylation", "start": 1432.95, "duration": 2.76}, {"text": "when we turn pyruvate\ninto acetyl-CoA.", "start": 1435.71, "duration": 2.73}, {"text": "And we turned\nalpha-ketoglutarate", "start": 1438.44, "duration": 2.25}, {"text": "into succinyl-CoA.", "start": 1440.69, "duration": 1.71}, {"text": "Well, that exact\nreaction, which we", "start": 1442.4, "duration": 2.79}, {"text": "saw with pyruvate\ndecarboxylation,", "start": 1445.19, "duration": 1.95}, {"text": "as well as what we saw\nwith alpha-ketoglutarate", "start": 1447.14, "duration": 2.19}, {"text": "dehydrogenase generating\nacetyl-CoA and succinyl-CoA", "start": 1449.33, "duration": 4.14}, {"text": "is what happens here for the\nalpha-keto acids produced", "start": 1453.47, "duration": 5.07}, {"text": "from breakdown of leucine\nand other branched chain", "start": 1458.54, "duration": 3.93}, {"text": "amino acids.", "start": 1462.47, "duration": 1.41}, {"text": "And so if you look\nback in your notes,", "start": 1463.88, "duration": 2.91}, {"text": "we went through the\nmechanism of this in detail.", "start": 1466.79, "duration": 2.72}, {"text": "Remember, this involved\nedition of CoA, loss of CO2,", "start": 1469.51, "duration": 7.94}, {"text": "it's an oxidation reaction.", "start": 1477.45, "duration": 3.57}, {"text": "So remember, the electrons\nneeded to go somewhere,", "start": 1481.02, "duration": 3.68}, {"text": "and so they ended\nup going to NADH.", "start": 1484.7, "duration": 3.86}, {"text": "So that's oxidized.", "start": 1488.56, "duration": 0.95}, {"text": "NAD+ is reduced to NADH.", "start": 1489.51, "duration": 2.64}, {"text": "And remember, this involved that\nmini-electron transport chain", "start": 1492.15, "duration": 4.59}, {"text": "with FAD, lipoic acid, and TPP+.", "start": 1496.74, "duration": 8.13}, {"text": "And in the end, that\nreleases the CO2", "start": 1504.87, "duration": 4.11}, {"text": "and you end up with this\nbranched chain acyl-CoA.", "start": 1508.98, "duration": 12.88}, {"text": "So same reaction is PDH,\nalpha-ketoglutarate,", "start": 1524.55, "duration": 3.81}, {"text": "dehydrogenase.", "start": 1528.36, "duration": 1.53}, {"text": "Just like those two\nreactions, remember,", "start": 1529.89, "duration": 1.86}, {"text": "that had an E1, an\nE2, and an E3 subunit.", "start": 1531.75, "duration": 3.4}, {"text": "So this actually uses\nthe exact same E2 and E3", "start": 1535.15, "duration": 2.9}, {"text": "subunit as those reactions.", "start": 1538.05, "duration": 1.95}, {"text": "The E1 subunit is,\nof course, different", "start": 1540.0, "duration": 2.04}, {"text": "because it's unique to the\nbranched chain amino acids,", "start": 1542.04, "duration": 5.16}, {"text": "whereas in pyruvate\ndehydrogenase,", "start": 1547.2, "duration": 1.66}, {"text": "to be unique to pyruvate\nand alpha-ketoglutarate", "start": 1548.86, "duration": 2.0}, {"text": "dehydrogenase, you need\nthe alpha-ketoglutarate.", "start": 1550.86, "duration": 2.97}, {"text": "In this case, this enzyme is\ncalled BCKDH for Branched Chain", "start": 1553.83, "duration": 6.03}, {"text": "Keto Acid Dehydrogenase,\nand allows", "start": 1559.86, "duration": 5.04}, {"text": "the oxidative decarboxylation\nto generate this branched chain", "start": 1564.9, "duration": 4.98}, {"text": "acyl-CoA.", "start": 1569.88, "duration": 2.76}, {"text": "Now this branched chain acyl-CoA\nlooks a lot like a fatty acid,", "start": 1572.64, "duration": 5.25}, {"text": "and in fact, it's\nmetabolized very much like we", "start": 1577.89, "duration": 2.88}, {"text": "would do fatty acid oxidation.", "start": 1580.77, "duration": 2.49}, {"text": "So what's the first step in\nbeta oxidation of fatty acids?", "start": 1583.26, "duration": 4.29}, {"text": "Well, we would introduce\na double bond here.", "start": 1587.55, "duration": 3.36}, {"text": "And so that's exactly\nwhat happens next.", "start": 1590.91, "duration": 4.86}, {"text": "So this would be a\nmembrane-bound FAD", "start": 1595.77, "duration": 4.93}, {"text": "containing enzyme, part of\nthe electron transport chain.", "start": 1600.7, "duration": 3.15}, {"text": "Going to oxidize that\ncarbon-carbon bond.", "start": 1603.85, "duration": 4.033}, {"text": "There's that generate.", "start": 1607.883, "duration": 0.917}, {"text": "All right.", "start": 1619.86, "duration": 0.87}, {"text": "Now, if we are doing\nfatty acid oxidation,", "start": 1620.73, "duration": 2.452}, {"text": "we would, of course, add\nwater across the bond.", "start": 1623.182, "duration": 1.958}, {"text": "We'll do that in a minute.", "start": 1625.14, "duration": 2.07}, {"text": "Before that happens,\nthe next step, though,", "start": 1627.21, "duration": 2.98}, {"text": "is that to facilitate\nultimately break down of this,", "start": 1630.19, "duration": 3.56}, {"text": "we're going to end up\nadding our carboxyl group", "start": 1633.75, "duration": 2.61}, {"text": "to the end of the molecule.", "start": 1636.36, "duration": 1.72}, {"text": "So if we're going to add CO2\nto the end of the molecule,", "start": 1638.08, "duration": 3.18}, {"text": "how would we do that?", "start": 1641.26, "duration": 1.45}, {"text": "Well, we've seen that reaction\nmany times before as well.", "start": 1642.71, "duration": 3.83}, {"text": "So if we're going\nto add a CO2 group,", "start": 1646.54, "duration": 4.22}, {"text": "that's going to\ncome from biotin.", "start": 1650.76, "duration": 3.25}, {"text": "So the next enzyme would have\nbiotin in the active site that", "start": 1654.01, "duration": 5.88}, {"text": "can pick up a CO2.", "start": 1659.89, "duration": 2.32}, {"text": "How does it pick up the CO2?", "start": 1662.21, "duration": 2.87}, {"text": "Well, it picks up the CO2\nvia bicarbonate plus ATP,", "start": 1665.08, "duration": 8.74}, {"text": "and that's going to go to--", "start": 1673.82, "duration": 3.09}, {"text": "that's going to phosphorylate\nthe bicarbonate.", "start": 1676.91, "duration": 2.76}, {"text": "And then when we transfer that\nphosphorylated bicarbonate", "start": 1679.67, "duration": 4.17}, {"text": "onto biotin, we'll release the\nPI, then the CO2 from biotin", "start": 1683.84, "duration": 4.41}, {"text": "can be added to carboxylate.", "start": 1688.25, "duration": 4.02}, {"text": "That molecule, just\nlike we've saw before", "start": 1692.27, "duration": 2.31}, {"text": "with other\ncarboxylation reactions,", "start": 1694.58, "duration": 3.0}, {"text": "and that will generate\nthis intermediate.", "start": 1697.58, "duration": 8.24}, {"text": "This intermediate here.", "start": 1722.07, "duration": 1.83}, {"text": "OK.", "start": 1723.9, "duration": 0.51}, {"text": "So no new chemistry.", "start": 1724.41, "duration": 1.21}, {"text": "You've seen all this\nmany times before.", "start": 1725.62, "duration": 3.02}, {"text": "Now we're going\nto continue with--", "start": 1728.64, "duration": 1.65}, {"text": "what we would do is if we\nwere breaking this down--", "start": 1730.29, "duration": 3.63}, {"text": "oxidizing it as a fatty acid.", "start": 1733.92, "duration": 2.38}, {"text": "And so now we're going to add\nwater across that double bond.", "start": 1736.3, "duration": 4.85}, {"text": "OK.", "start": 1761.55, "duration": 0.5}, {"text": "Now we added water\nacross that double bond.", "start": 1762.05, "duration": 3.44}, {"text": "And then now we're just going\nto do this reaction, which", "start": 1765.49, "duration": 10.73}, {"text": "will generate from this side\nof the molecule an acetyl-CoA.", "start": 1776.22, "duration": 12.08}, {"text": "And if you look on the other\nside of the molecule, what we", "start": 1791.75, "duration": 4.23}, {"text": "are left with is acetoacetate.", "start": 1795.98, "duration": 13.51}, {"text": "Acetoacetate can be broken\ndown into two acetyl-CoAs.", "start": 1823.27, "duration": 10.86}, {"text": "If I break it in half, add\nCoA to each one of them", "start": 1834.13, "duration": 4.02}, {"text": "by reactions I showed you\nbefore as well, or, of course,", "start": 1838.15, "duration": 3.69}, {"text": "we can reduce this\nketone to the alcohol", "start": 1841.84, "duration": 4.68}, {"text": "and make the ketone body\nbeta-hydroxy butyrate.", "start": 1846.52, "duration": 6.09}, {"text": "You can look that up from\nthe end of the last lecture.", "start": 1852.61, "duration": 3.65}, {"text": "But in the end, this is\nhow one can break down", "start": 1856.26, "duration": 3.78}, {"text": "the leucine skeleton.", "start": 1860.04, "duration": 1.89}, {"text": "You get a acetyl-CoA\nor acetoacetate.", "start": 1861.93, "duration": 2.52}, {"text": "Can't generate glucose from any\nof those molecules as humans", "start": 1864.45, "duration": 3.24}, {"text": "because we don't have\na glyoxylate cycle.", "start": 1867.69, "duration": 1.83}, {"text": "Therefore, leucine is\na ketogenic amino acid.", "start": 1869.52, "duration": 4.47}, {"text": "All right.", "start": 1873.99, "duration": 1.6}, {"text": "Valine.", "start": 1875.59, "duration": 0.96}, {"text": "Let's look at valine.", "start": 1876.55, "duration": 0.96}, {"text": "So valine is glucogenic\ndespite the fact", "start": 1883.49, "duration": 5.55}, {"text": "that it's very\nsimilar to leucine", "start": 1889.04, "duration": 2.73}, {"text": "and broken down in a way\nthat's very similar to leucine.", "start": 1891.77, "duration": 3.54}, {"text": "So, how do we break it down?", "start": 1895.31, "duration": 1.72}, {"text": "So first step, transamination.", "start": 1897.03, "duration": 4.16}, {"text": "Nitrogen from valine\nto alpha-ketoglutarate", "start": 1901.19, "duration": 2.43}, {"text": "to generate glutamate, and\nas well as the branched", "start": 1903.62, "duration": 4.56}, {"text": "chain alpha-keto acid\nthat's related to valine.", "start": 1908.18, "duration": 4.665}, {"text": "So that's the alpha-keto\nacid related to valine.", "start": 1924.11, "duration": 2.79}, {"text": "One carbon shorter\nthan side chain, one", "start": 1926.9, "duration": 3.36}, {"text": "carbon shorter than leucine.", "start": 1930.26, "duration": 3.79}, {"text": "Just like we did\nwith leucine, we're", "start": 1934.05, "duration": 5.89}, {"text": "going to metabolize\nthe alpha-keto acid", "start": 1939.94, "duration": 3.84}, {"text": "with the branched chain\nketo acid dehydrogenase.", "start": 1943.78, "duration": 3.09}, {"text": "Same reaction.", "start": 1946.87, "duration": 1.86}, {"text": "Oxidative decarboxylation here.", "start": 1948.73, "duration": 2.91}, {"text": "That releases CO2, adds CoA.", "start": 1951.64, "duration": 5.64}, {"text": "Reaction involves\nalso NAD+ to NADH.", "start": 1957.28, "duration": 5.46}, {"text": "Requires lipoic acid, TPP+, FAD,\njust like we described before.", "start": 1962.74, "duration": 5.49}, {"text": "I'm not going to draw out\nall the pieces of it again,", "start": 1968.23, "duration": 3.76}, {"text": "but we're going to end up with\nthe branched chain acyl-CoA.", "start": 1971.99, "duration": 14.84}, {"text": "Metabolize this\nbranched chain acyl-CoA", "start": 1986.83, "duration": 2.67}, {"text": "as if it's a fatty acid.", "start": 1989.5, "duration": 1.99}, {"text": "And so first step, oxidize\nthis carbon-carbon bond.", "start": 1991.49, "duration": 5.21}, {"text": "That electrons go\nto FAD, make FADH2.", "start": 1996.7, "duration": 4.0}, {"text": "This product, add water\nacross that double bond.", "start": 2013.86, "duration": 7.475}, {"text": "Water across that double bond.", "start": 2040.25, "duration": 3.69}, {"text": "Next, if we oxidize\nthis alcohol twice--", "start": 2043.94, "duration": 6.36}, {"text": "so oxidize it once,\nwe'll get the aldehyde.", "start": 2050.3, "duration": 2.939}, {"text": "Oxidize it again, we can\nget the carboxylic acid.", "start": 2053.239, "duration": 3.42}, {"text": "And so oxidizing twice means\nNAD+ times 2 and NADH times 2.", "start": 2059.73, "duration": 12.259}, {"text": "And now that becomes the acid.", "start": 2071.989, "duration": 2.806}, {"text": "OK.", "start": 2092.389, "duration": 1.25}, {"text": "So same molecule, but now\nthis alcohol becomes an acid.", "start": 2093.639, "duration": 4.841}, {"text": "I drew it that way on purpose.", "start": 2098.48, "duration": 3.42}, {"text": "If you look back\nin your notes, this", "start": 2101.9, "duration": 1.67}, {"text": "is methyl\nmethylmalonyl-CoA, which", "start": 2103.57, "duration": 10.36}, {"text": "we saw before in our discussion\nof odd chain fatty acid", "start": 2113.93, "duration": 7.29}, {"text": "metabolism.", "start": 2121.22, "duration": 2.34}, {"text": "And you'll remember that there\nwas this B12-dependent reaction", "start": 2123.56, "duration": 7.39}, {"text": "where I can basically swap\nthe positions of this proton", "start": 2130.95, "duration": 6.27}, {"text": "and this thioester group here.", "start": 2137.22, "duration": 4.66}, {"text": "This is not aero-pushing.", "start": 2141.88, "duration": 1.37}, {"text": "This B12-dependent\nreaction that I described", "start": 2143.25, "duration": 5.64}, {"text": "before where I can\nrearrange methylmalonyl-CoA", "start": 2148.89, "duration": 6.57}, {"text": "to make this molecule,\nwhich is succinyl-CoA.", "start": 2155.46, "duration": 18.437}, {"text": "Succinyl-CoA oxidized in\nthe TCA cycle, generate ATP,", "start": 2176.7, "duration": 4.62}, {"text": "but also can use it as\na substrate anaplerosis", "start": 2181.32, "duration": 3.45}, {"text": "for the TCA cycle, so it can\nbe used to generate glucose.", "start": 2184.77, "duration": 3.04}, {"text": "And so that's why valine\nis a glucogenic amino acid.", "start": 2187.81, "duration": 5.21}, {"text": "All right.", "start": 2193.02, "duration": 1.53}, {"text": "Last branched chain\namino acid is isoleucine.", "start": 2194.55, "duration": 7.38}, {"text": "So isoleucine is both\nketogenic and glucogenic.", "start": 2201.93, "duration": 6.754}, {"text": "So let's see how that happens.", "start": 2213.98, "duration": 2.98}, {"text": "So if we start with\nisoleucine, first we", "start": 2216.96, "duration": 2.3}, {"text": "undergo transformation.", "start": 2219.26, "duration": 2.16}, {"text": "alpha-ketoglutarate\nto glutamate,", "start": 2221.42, "duration": 2.13}, {"text": "and you get the branched\nchain alpha-keto acid.", "start": 2223.55, "duration": 16.12}, {"text": "So that's isoleucine as an\nalpha-keto acid rather than", "start": 2239.67, "duration": 4.95}, {"text": "an amino acid.", "start": 2244.62, "duration": 1.86}, {"text": "Next step, do the\nalpha decarboxylation", "start": 2246.48, "duration": 5.05}, {"text": "with branched keto\nacid dehydrogenase.", "start": 2251.53, "duration": 5.08}, {"text": "That removes that CO2, oxidizes\nthat carbon to the acid,", "start": 2256.61, "duration": 6.15}, {"text": "and we end up with this\nbranched chain acyl-CoA.", "start": 2262.76, "duration": 14.92}, {"text": "Same first steps\nas we saw before.", "start": 2277.68, "duration": 2.46}, {"text": "Metabolize that as\nif it's a fatty acid.", "start": 2280.14, "duration": 3.285}, {"text": "So oxidize that\ncarbon-carbon bond.", "start": 2287.85, "duration": 2.55}, {"text": "Add water across\nthe double bond.", "start": 2301.41, "duration": 3.915}, {"text": "OK.", "start": 2324.41, "duration": 0.66}, {"text": "Get this intermediate.", "start": 2325.07, "duration": 2.43}, {"text": "Now oxidize this\nalcohol to the ketone.", "start": 2327.5, "duration": 7.19}, {"text": "Electrons go to an NAD+,\nwhich is reduced to NADH.", "start": 2334.69, "duration": 5.97}, {"text": "Now we can use CoA to take off\nthis end of the molecule here,", "start": 2358.47, "duration": 17.98}, {"text": "which is acetyl-CoA,\nhence ketogenic.", "start": 2376.45, "duration": 10.69}, {"text": "The remainder of the molecule\nis this three-carbon acyl-CoA.", "start": 2387.14, "duration": 17.19}, {"text": "We saw this from odd chain\nfatty acid metabolism.", "start": 2404.33, "duration": 2.71}, {"text": "This is propionyl-CoA.", "start": 2407.04, "duration": 2.33}, {"text": "Remember, to deal with\nthat, we can add CO2.", "start": 2412.43, "duration": 6.99}, {"text": "So that, of course,\nrequires biotin, and ATP.", "start": 2419.42, "duration": 7.225}, {"text": "So remember, we had\nCO2 to this molecule.", "start": 2426.645, "duration": 3.815}, {"text": "That gives us methyl--", "start": 2430.46, "duration": 1.64}, {"text": "not going to draw it all\nout for the sake of time,", "start": 2432.1, "duration": 2.5}, {"text": "but that gives us\nmethylmalonyl-CoA.", "start": 2434.6, "duration": 1.92}, {"text": "Methylmalonyl-CoA\nshown up there,", "start": 2439.94, "duration": 2.43}, {"text": "so it's adding CO2\nto this molecule.", "start": 2442.37, "duration": 3.54}, {"text": "And then we can do the\nvitamin B12 rearrangement", "start": 2445.91, "duration": 7.55}, {"text": "to get succinyl-CoA.", "start": 2453.46, "duration": 4.44}, {"text": "And so that can be\nturned into glucose.", "start": 2457.9, "duration": 2.67}, {"text": "And so it generates an\nacetyl-CoA and a succinyl-CoA,", "start": 2460.57, "duration": 3.15}, {"text": "isoleucine is both\nglucogenic and ketogenic.", "start": 2463.72, "duration": 5.11}, {"text": "And so a little tedious to go\nthrough how you break down all", "start": 2468.83, "duration": 6.56}, {"text": "three of those branched\nchain amino acids,", "start": 2475.39, "duration": 2.25}, {"text": "but it really illustrates\nthat it's just", "start": 2477.64, "duration": 2.19}, {"text": "variations on the same\nchemistry that we've", "start": 2479.83, "duration": 2.73}, {"text": "seen before with fatty\nacid metabolism, TCA cycle", "start": 2482.56, "duration": 4.05}, {"text": "reactions, that ultimately\ngenerate intermediates that", "start": 2486.61, "duration": 4.62}, {"text": "can be fed into the TCA cycle,\noxidized further to CO2,", "start": 2491.23, "duration": 4.65}, {"text": "generate ATP, generate NADH,\nelectron transport chain,", "start": 2495.88, "duration": 5.16}, {"text": "oxidative phosphorylation,\nsupply the cell with energy", "start": 2501.04, "duration": 3.84}, {"text": "to do various kinds of work.", "start": 2504.88, "duration": 1.86}, {"text": "Or can be turned into a\nketone if you're a human", "start": 2506.74, "duration": 3.99}, {"text": "and you start with acetyl--", "start": 2510.73, "duration": 1.27}, {"text": "and what you get is\nacetyl-CoA or acetoacetate.", "start": 2512.0, "duration": 2.72}, {"text": "Or even into\nglucose if you start", "start": 2514.72, "duration": 2.07}, {"text": "with something like\nsuccinyl-CoA that", "start": 2516.79, "duration": 3.33}, {"text": "can be turned back into\nglucose by the liver,", "start": 2520.12, "duration": 2.94}, {"text": "defining the difference\nbetween the glucogenic", "start": 2523.06, "duration": 2.07}, {"text": "and the ketogenic amino acids.", "start": 2525.13, "duration": 3.32}, {"text": "All right.", "start": 2528.45, "duration": 1.29}, {"text": "Now going through branched\nchain amino acid metabolism", "start": 2529.74, "duration": 5.55}, {"text": "also allows transition\ninto a discussion", "start": 2535.29, "duration": 4.65}, {"text": "of another topic which\nare the so-called inborn", "start": 2539.94, "duration": 12.68}, {"text": "errors of metabolism.", "start": 2552.62, "duration": 3.81}, {"text": "So what's an inborn\nerror of metabolism?", "start": 2559.9, "duration": 3.96}, {"text": "Well, sometimes\nindividuals are born", "start": 2563.86, "duration": 4.59}, {"text": "that have deficiencies\nin enzymes", "start": 2568.45, "duration": 3.3}, {"text": "that are necessary to carry out\nsome function of metabolism.", "start": 2571.75, "duration": 4.81}, {"text": "Some aspect of the biochemistry\nwe've been learning about.", "start": 2576.56, "duration": 4.94}, {"text": "Now you can imagine that some\nof these genetic deficiencies,", "start": 2581.5, "duration": 3.99}, {"text": "if it's somewhere smack in\nthe middle of central carbon", "start": 2585.49, "duration": 4.08}, {"text": "metabolism and you\ncan't generate energy,", "start": 2589.57, "duration": 2.01}, {"text": "it's not going to be\ncompatible with life.", "start": 2591.58, "duration": 2.37}, {"text": "But it turns out\nthat some of them", "start": 2593.95, "duration": 1.59}, {"text": "are quite compatible with\nlife, like deficiency", "start": 2595.54, "duration": 4.2}, {"text": "in branched chain keto\nacid dehydrogenase.", "start": 2599.74, "duration": 3.51}, {"text": "So BCKDH deficiency is something\nthat children are sometimes", "start": 2603.25, "duration": 11.7}, {"text": "born with, and this deficiency\nresults in a disorder", "start": 2614.95, "duration": 5.52}, {"text": "called maple syrup\nurine disease.", "start": 2620.47, "duration": 3.84}, {"text": "So it's called maple\nsyrup urine disease", "start": 2627.92, "duration": 2.18}, {"text": "because the unit smells\nlike maple syrup,", "start": 2630.1, "duration": 3.84}, {"text": "but effectively what this is\nis this is a disorder where", "start": 2633.94, "duration": 3.93}, {"text": "there's a deficiency in\nthe activity of branched", "start": 2637.87, "duration": 2.34}, {"text": "chain keto acid dehydrogenase.", "start": 2640.21, "duration": 2.28}, {"text": "That means the cells\ncan't break down", "start": 2642.49, "duration": 3.63}, {"text": "branched chain amino acids.", "start": 2646.12, "duration": 1.86}, {"text": "They end up generating some\notherwise side toxic product.", "start": 2647.98, "duration": 5.34}, {"text": "Some of it ends up in the\nurine, smells like maple syrup.", "start": 2653.32, "duration": 3.54}, {"text": "But it also can result\nin damage to the CNS", "start": 2656.86, "duration": 3.99}, {"text": "and problems with thinking,\nmental retardation, et cetera.", "start": 2660.85, "duration": 8.14}, {"text": "And so it can be quite\ndevastating to have", "start": 2668.99, "duration": 3.89}, {"text": "loss of this enzyme, which\nprevents you from breaking down", "start": 2672.88, "duration": 3.21}, {"text": "branched chain amino acids,\na so-called inborn error", "start": 2676.09, "duration": 3.96}, {"text": "of metabolism.", "start": 2680.05, "duration": 2.17}, {"text": "Now this is a\nrelatively rare disease.", "start": 2682.22, "duration": 2.99}, {"text": "All of these are.", "start": 2685.21, "duration": 1.38}, {"text": "But if you go to\nmedical school, these", "start": 2686.59, "duration": 3.0}, {"text": "are questions because\nthey lend themselves", "start": 2689.59, "duration": 2.37}, {"text": "to questions that often show\nup on various board-type exams.", "start": 2691.96, "duration": 5.73}, {"text": "And so it's good to\nknow that deficiencies", "start": 2697.69, "duration": 3.06}, {"text": "of some of these enzymes\ncan result in diseases.", "start": 2700.75, "duration": 5.08}, {"text": "So maple syrup urine disease\ncaused by an inability", "start": 2705.83, "duration": 3.41}, {"text": "to break down branched chain\namino acids because you're", "start": 2709.24, "duration": 2.52}, {"text": "deficient in the enzyme\nbranched chain amino acid--", "start": 2711.76, "duration": 3.09}, {"text": "or branched keto\nacid dehydrogenase,", "start": 2714.85, "duration": 2.88}, {"text": "which catalyzes the stuff\nI showed you up there", "start": 2717.73, "duration": 2.22}, {"text": "in the breakdown of all three\nbranched chain amino acids.", "start": 2719.95, "duration": 4.8}, {"text": "By no means is\nthis the only one.", "start": 2724.75, "duration": 1.86}, {"text": "Often these are associated\nwith amino acid breakdown.", "start": 2726.61, "duration": 4.95}, {"text": "And so two of the\nother more common--", "start": 2731.56, "duration": 2.62}, {"text": "all of these are very rare,\nbut relatively more common ones", "start": 2734.18, "duration": 3.89}, {"text": "is a disease called\nalkaptonuria.", "start": 2738.07, "duration": 2.25}, {"text": "So what's alkaptonuria?", "start": 2745.24, "duration": 1.71}, {"text": "Well, that's missing an enzyme--", "start": 2746.95, "duration": 1.68}, {"text": "so enzyme deficiency in\ntryptophan metabolism.", "start": 2752.43, "duration": 8.72}, {"text": "And another one is\nfennel phenylketonuria,", "start": 2765.82, "duration": 8.96}, {"text": "which is an enzyme deficiency\nin phenylalanine metabolism.", "start": 2774.78, "duration": 10.79}, {"text": "Branched chain amino acids are\nvery common, but tryptophan,", "start": 2788.71, "duration": 5.1}, {"text": "phenylalanine, two of the\nmore rare amino acids,", "start": 2793.81, "duration": 3.01}, {"text": "it turns out these are two\nof the amino acid breakdown", "start": 2796.82, "duration": 3.53}, {"text": "deficiencies that have\nless severe phenotypes,", "start": 2800.35, "duration": 4.68}, {"text": "and so they're somewhat--", "start": 2805.03, "duration": 4.05}, {"text": "more people walking around\nwith those conditions.", "start": 2809.08, "duration": 5.17}, {"text": "If any of you have had\nchildren or someday", "start": 2814.25, "duration": 2.64}, {"text": "when you have children,\nwhat will happen", "start": 2816.89, "duration": 2.61}, {"text": "is that you will notice\nthat when babies are born,", "start": 2819.5, "duration": 2.85}, {"text": "one of the first things\nthat's done with infants", "start": 2822.35, "duration": 2.46}, {"text": "is they have a\nblood test sent out.", "start": 2824.81, "duration": 2.19}, {"text": "They do a little heel\nstick, collect some blood,", "start": 2827.0, "duration": 2.64}, {"text": "and send it to the\nstate lab where", "start": 2829.64, "duration": 1.98}, {"text": "they test for various\ninborn errors of metabolism.", "start": 2831.62, "duration": 3.51}, {"text": "What they're looking for is\nthings like phenylketonuria,", "start": 2835.13, "duration": 3.99}, {"text": "maple syrup urine\ndisease, et cetera.", "start": 2839.12, "duration": 2.557}, {"text": "Why do they want to\nfind these things?", "start": 2841.677, "duration": 1.583}, {"text": "Well, it's because if you\nhave too much of the product,", "start": 2843.26, "duration": 4.56}, {"text": "too much phenylalanine, too much\ntryptophan, too much branched", "start": 2847.82, "duration": 2.94}, {"text": "chain amino acid, and you\ncan't break them down,", "start": 2850.76, "duration": 2.49}, {"text": "it's not the lack of the\nability to break them down", "start": 2853.25, "duration": 2.67}, {"text": "that's necessarily the problem.", "start": 2855.92, "duration": 2.11}, {"text": "The problem is is that the\ninability to break them down", "start": 2858.03, "duration": 2.51}, {"text": "leads to overwhelming\na system building up", "start": 2860.54, "duration": 2.37}, {"text": "of toxic intermediates\nthat damage the brain.", "start": 2862.91, "duration": 2.88}, {"text": "And so by doing these\nnewborn screening panels,", "start": 2865.79, "duration": 3.12}, {"text": "it's greatly enhanced the\nmanagement of these things,", "start": 2868.91, "duration": 2.55}, {"text": "because often you can\ncontrol the symptoms", "start": 2871.46, "duration": 2.85}, {"text": "by dietary intervention.", "start": 2874.31, "duration": 1.5}, {"text": "Simply limiting\nthe phenylalanine", "start": 2875.81, "duration": 2.49}, {"text": "or the branched chain amino\nacid or the tryptophan intake", "start": 2878.3, "duration": 3.6}, {"text": "in the diet is a treatment\nfor these diseases,", "start": 2881.9, "duration": 3.61}, {"text": "and so therefore, if you\nknow about them early,", "start": 2885.51, "duration": 3.47}, {"text": "limiting exposure\nto those things", "start": 2888.98, "duration": 2.22}, {"text": "limits the exposure to the\ntoxic breakdown products that", "start": 2891.2, "duration": 5.01}, {"text": "can't be metabolized because of\nthe deficiency, and therefore,", "start": 2896.21, "duration": 4.35}, {"text": "limits the effects on the brain.", "start": 2900.56, "duration": 4.17}, {"text": "If you drink diet soda and you\nlook at the side of your diet", "start": 2904.73, "duration": 4.71}, {"text": "soda can, what's written on the\nside of it is phenylketonurics,", "start": 2909.44, "duration": 4.83}, {"text": "contains phenylalanine.", "start": 2914.27, "duration": 2.04}, {"text": "Why is that written there?", "start": 2916.31, "duration": 1.35}, {"text": "Well, because if you happen\nto be a phenylketonuric,", "start": 2917.66, "duration": 3.18}, {"text": "you shouldn't drink diet soda.", "start": 2920.84, "duration": 3.57}, {"text": "Why?", "start": 2924.41, "duration": 0.54}, {"text": "Because the artificial\nsweetener in there contains", "start": 2924.95, "duration": 2.34}, {"text": "phenylalanine, and so\nthis would give you", "start": 2927.29, "duration": 2.34}, {"text": "a big dose of phenylalanine,\nand if you can't break down", "start": 2929.63, "duration": 2.67}, {"text": "phenylalanine, that's a problem.", "start": 2932.3, "duration": 1.69}, {"text": "So it's a warning to the\npeople in the population who", "start": 2933.99, "duration": 3.47}, {"text": "happen to have phenylketonuria\nnot to drink diet soda.", "start": 2937.46, "duration": 3.96}, {"text": "All right.", "start": 2945.15, "duration": 1.5}, {"text": "Now, I want to say\na few other things", "start": 2946.65, "duration": 2.7}, {"text": "about amino acid metabolism,\nonly because these things will", "start": 2949.35, "duration": 6.39}, {"text": "come up for you as you\ngo through other aspects", "start": 2955.74, "duration": 5.64}, {"text": "of biology.", "start": 2961.38, "duration": 1.035}, {"text": "And that is that amino acids are\nvery versatile starting points", "start": 2968.04, "duration": 6.68}, {"text": "to build all kinds of\nhormones and neurotransmitters", "start": 2974.72, "duration": 3.72}, {"text": "and bioactive molecules.", "start": 2978.44, "duration": 2.1}, {"text": "So I know some people--", "start": 2980.54, "duration": 2.07}, {"text": "some of the MIT students\nin the class are course 9.", "start": 2982.61, "duration": 3.34}, {"text": "That's the brain and\ncognitive science.", "start": 2985.95, "duration": 5.93}, {"text": "Classes you take,\nyou'll learn a lot", "start": 2991.88, "duration": 1.65}, {"text": "about different\nneurotransmitters.", "start": 2993.53, "duration": 1.5}, {"text": "Well, one of the canonical\nneurotransmitters", "start": 2995.03, "duration": 2.79}, {"text": "is an amino acid itself.", "start": 2997.82, "duration": 1.44}, {"text": "It's the amino acid glutamate.", "start": 2999.26, "duration": 2.76}, {"text": "So obviously that's important\nfor the brain to work.", "start": 3002.02, "duration": 2.762}, {"text": "But what are the other\nneurotransmitters?", "start": 3004.782, "duration": 1.708}, {"text": "Well, there's things\nlike dopamine,", "start": 3006.49, "duration": 4.37}, {"text": "epinephrine, norepinephrine.", "start": 3010.86, "duration": 6.265}, {"text": "These are all\nbioactive molecules,", "start": 3022.59, "duration": 3.21}, {"text": "have to come from somewhere.", "start": 3025.8, "duration": 1.71}, {"text": "Well, it turns out all\nof these ultimately come", "start": 3027.51, "duration": 3.06}, {"text": "from the metabolism of tyrosine,\nwhich, of course, can also", "start": 3030.57, "duration": 5.04}, {"text": "come from the metabolism\nof phenylalanine.", "start": 3035.61, "duration": 3.51}, {"text": "And so don't have\ntime to go into it,", "start": 3039.12, "duration": 2.13}, {"text": "but you can look up the\npathways to generate", "start": 3041.25, "duration": 2.37}, {"text": "these various\nneurotransmitters from tyrosine", "start": 3043.62, "duration": 3.94}, {"text": "if you're interested.", "start": 3047.56, "duration": 2.81}, {"text": "What's the other big\nneurotransmitter?", "start": 3050.37, "duration": 2.13}, {"text": "Well, it's acetylcholine.", "start": 3052.5, "duration": 1.89}, {"text": "What's acetylcholine?", "start": 3058.56, "duration": 1.29}, {"text": "Well, let's break it down.", "start": 3059.85, "duration": 1.39}, {"text": "Well, it's an acetyl group,\nso that comes from acetyl-CoA.", "start": 3061.24, "duration": 6.25}, {"text": "And choline-- and\nwhat's choline?", "start": 3067.49, "duration": 3.54}, {"text": "Well, choline comes from,\nultimately as I showed you--", "start": 3071.03, "duration": 5.28}, {"text": "alluded to before,\nethanolamine, and ethanolamine", "start": 3076.31, "duration": 5.46}, {"text": "comes from serine.", "start": 3081.77, "duration": 2.28}, {"text": "We'll come back to this later.", "start": 3084.05, "duration": 1.86}, {"text": "And so serine metabolism,\nas well acetyl-CoA,", "start": 3085.91, "duration": 3.285}, {"text": "is how you get acetylcholine.", "start": 3089.195, "duration": 2.625}, {"text": "It's also choline the\nphospholipids and ethanolamine", "start": 3091.82, "duration": 4.47}, {"text": "for the phospholipids.", "start": 3096.29, "duration": 2.96}, {"text": "If you're not into the\nbrain but into other aspects", "start": 3099.25, "duration": 3.15}, {"text": "pathophysiology--\nso thyroid hormone,", "start": 3102.4, "duration": 3.87}, {"text": "very common thing\nthat many people", "start": 3106.27, "duration": 2.01}, {"text": "need replacement of, very\nimportant to manage physiology", "start": 3108.28, "duration": 3.12}, {"text": "in our body.", "start": 3111.4, "duration": 0.96}, {"text": "Thyroid hormone also\ncomes from thyroxine.", "start": 3112.36, "duration": 7.0}, {"text": "Melanin, the pigment that makes\nour skin different shades,", "start": 3119.36, "duration": 9.87}, {"text": "melanin, the skin\npigment, it is basically", "start": 3129.23, "duration": 5.84}, {"text": "produced from dopamine--", "start": 3135.07, "duration": 2.88}, {"text": "or actually, a\ndopamine metabolite.", "start": 3137.95, "duration": 2.97}, {"text": "So dopamine precursor.", "start": 3140.92, "duration": 3.51}, {"text": "Which comes from\ntyrosine as well.", "start": 3144.43, "duration": 4.78}, {"text": "And so if you're\ninterested in any", "start": 3149.21, "duration": 2.27}, {"text": "of these particular\nmolecules, of course,", "start": 3151.48, "duration": 1.71}, {"text": "you can look up in the book and\nyou'll see how they're made,", "start": 3153.19, "duration": 3.0}, {"text": "and I promise, you have the\nability to understand it,", "start": 3156.19, "duration": 2.55}, {"text": "it's repurposing some reactions\nthat we've already seen.", "start": 3158.74, "duration": 4.08}, {"text": "There's some unique\nones in there", "start": 3162.82, "duration": 1.83}, {"text": "like melanin synthesis\nis actually parts", "start": 3164.65, "duration": 2.16}, {"text": "of it are non-enzymatic, even.", "start": 3166.81, "duration": 2.34}, {"text": "But this-- I like to mention\nthis because obviously we", "start": 3169.15, "duration": 4.63}, {"text": "don't have time to\nstudy and discuss", "start": 3173.78, "duration": 2.52}, {"text": "the entire complexity\nof the metabolic map,", "start": 3176.3, "duration": 3.09}, {"text": "but really, you understand\nthe basics, the central parts", "start": 3179.39, "duration": 4.38}, {"text": "of it, and it's the same\nreactions repurposed out", "start": 3183.77, "duration": 3.51}, {"text": "in different\ndirections that allows", "start": 3187.28, "duration": 2.13}, {"text": "this complexity and this\ndiversity of metabolism,", "start": 3189.41, "duration": 2.52}, {"text": "making all of these\ndifferent biomolecules that", "start": 3191.93, "duration": 3.21}, {"text": "are necessary for the cells\nto do things, and, of course,", "start": 3195.14, "duration": 2.88}, {"text": "you can go look these up\nif you're interested in any", "start": 3198.02, "duration": 3.48}, {"text": "of them specifically.", "start": 3201.5, "duration": 2.01}, {"text": "And regardless, you should\nhave some appreciation", "start": 3203.51, "duration": 2.49}, {"text": "of how these things\nall interconnect", "start": 3206.0, "duration": 2.52}, {"text": "with the other pathways\nthat we've talked about.", "start": 3208.52, "duration": 3.98}, {"text": "All right.", "start": 3212.5, "duration": 0.6}, {"text": "All right.", "start": 3218.48, "duration": 1.41}, {"text": "So now I want to turn\nto amino acid synthesis", "start": 3219.89, "duration": 4.8}, {"text": "and say a few words about\nhow amino acids are built.", "start": 3224.69, "duration": 5.37}, {"text": "So of course, we've covered\nsome of these already,", "start": 3230.06, "duration": 4.39}, {"text": "and as a very general\nstatement, many of them", "start": 3234.45, "duration": 3.05}, {"text": "are made by transamination.", "start": 3237.5, "duration": 1.8}, {"text": "So first you build\nthe alpha-keto acid,", "start": 3239.3, "duration": 3.03}, {"text": "and then you transaminate that\nalpha-keto acid from glutamate", "start": 3242.33, "duration": 5.16}, {"text": "to generate the amino acid.", "start": 3247.49, "duration": 3.79}, {"text": "Now of course, the pathways\nthat you use to make amino acids", "start": 3251.28, "duration": 4.94}, {"text": "are not the same as\nthe pathways that you", "start": 3256.22, "duration": 1.77}, {"text": "use to break down amino acids.", "start": 3257.99, "duration": 2.71}, {"text": "So again, if you paid attention\nfor the entire course,", "start": 3260.7, "duration": 3.15}, {"text": "it should be clear for both\nthermodynamic energetic reasons", "start": 3263.85, "duration": 4.43}, {"text": "that you can't have the same\npathways to build and break", "start": 3268.28, "duration": 3.03}, {"text": "stuff down because all pathways\ndelta G has to be less than 0.", "start": 3271.31, "duration": 5.19}, {"text": "So we saw this with\nglucose and fatty acids.", "start": 3276.5, "duration": 2.49}, {"text": "We can repurpose-- some\nsteps can be the same,", "start": 3278.99, "duration": 2.77}, {"text": "but the ones that allow\nthe energetic driving have", "start": 3281.76, "duration": 4.31}, {"text": "to be different because you\nhave to couple one direction", "start": 3286.07, "duration": 3.72}, {"text": "to energy consumption\nand the other one", "start": 3289.79, "duration": 2.7}, {"text": "could be spontaneous\nif it releases energy,", "start": 3292.49, "duration": 2.243}, {"text": "and you have to\nhave pathways that", "start": 3294.733, "duration": 1.417}, {"text": "can work in either direction.", "start": 3296.15, "duration": 3.16}, {"text": "But, in general, if you can\nbuild an alpha-keto acid", "start": 3299.31, "duration": 4.64}, {"text": "like oxaloacetic acid\nor alpha-ketoglutarate", "start": 3303.95, "duration": 4.23}, {"text": "or pyruvate, well,\nobviously we can", "start": 3308.18, "duration": 3.81}, {"text": "transaminate all of these\nthings to get the amino acid.", "start": 3311.99, "duration": 4.092}, {"text": "So alpha-ketoglutarate\nto glutamate", "start": 3316.082, "duration": 1.458}, {"text": "can also be from\nglutamate dehydrogenase.", "start": 3317.54, "duration": 2.13}, {"text": "That's how you can get new\nnitrogen into the system.", "start": 3319.67, "duration": 2.34}, {"text": "And that way we can\ngenerate aspartame", "start": 3322.01, "duration": 1.71}, {"text": "glutamate and alanine, and\naspertate into asparagine,", "start": 3323.72, "duration": 6.15}, {"text": "asparagine by adding\nthe ammonia to it.", "start": 3329.87, "duration": 3.6}, {"text": "That would be a very\nsimilar reaction", "start": 3333.47, "duration": 1.74}, {"text": "to glutamate into glutamine.", "start": 3335.21, "duration": 2.34}, {"text": "That's glutamate synthase,\nasparagine synthase.", "start": 3337.55, "duration": 3.0}, {"text": "Same mechanism describe\nglutamate synthase last time", "start": 3340.55, "duration": 2.97}, {"text": "to make glutamine.", "start": 3343.52, "duration": 1.41}, {"text": "And of course, proline,\nas I showed you earlier,", "start": 3344.93, "duration": 3.63}, {"text": "is cyclized, and in\nthis case, oxidized--", "start": 3348.56, "duration": 5.31}, {"text": "or sorry, cyclized\nthen reduced glutamate.", "start": 3353.87, "duration": 4.35}, {"text": "And then-- so that's\nsix of the amino acids.", "start": 3358.22, "duration": 4.7}, {"text": "We covered arginine\nearlier, that seven.", "start": 3362.92, "duration": 4.23}, {"text": "And so 13 other amino acids.", "start": 3367.15, "duration": 4.53}, {"text": "Here's another figure\nfrom a book just showing", "start": 3371.68, "duration": 2.67}, {"text": "the starting material to make\nall of the various amino acids.", "start": 3374.35, "duration": 6.24}, {"text": "Obviously we know how\nto make oxaloacetate,", "start": 3380.59, "duration": 2.53}, {"text": "phosphoenolpyruvate, erythrose\n4-phosphate, pyruvate,", "start": 3383.12, "duration": 3.41}, {"text": "ribose 5-phosphate,\n3-phosphoglycerate,", "start": 3386.53, "duration": 2.22}, {"text": "and alpha-ketoglutarate.", "start": 3388.75, "duration": 1.53}, {"text": "And so generation of\nthose by the pathways", "start": 3390.28, "duration": 2.91}, {"text": "we've already talked about\nthen allows those molecules", "start": 3393.19, "duration": 3.15}, {"text": "to be shunted into\npathways to generate", "start": 3396.34, "duration": 2.49}, {"text": "all of the various amino acids.", "start": 3398.83, "duration": 3.76}, {"text": "Now I want to\nreiterate, humans, we", "start": 3402.59, "duration": 2.99}, {"text": "can't make all 20 amino acids.", "start": 3405.58, "duration": 2.52}, {"text": "Animals can't do that.", "start": 3408.1, "duration": 0.99}, {"text": "Many organisms, of course, can.", "start": 3409.09, "duration": 2.07}, {"text": "We lost the ability to make\nnine of our amino acids,", "start": 3411.16, "duration": 3.87}, {"text": "and in fact, if you count the\ntwo conditional ones, really", "start": 3415.03, "duration": 3.69}, {"text": "11 of amino acids, even though\nwe can turn phenylalanine", "start": 3418.72, "duration": 3.39}, {"text": "into tyrosine, we still need\na source of phenylalanine", "start": 3422.11, "duration": 3.21}, {"text": "to do so.", "start": 3425.32, "duration": 1.21}, {"text": "And so each of these nine or 11,\ndepending on how you count it,", "start": 3426.53, "duration": 3.98}, {"text": "essential amino acids\nmust be eaten in the diet.", "start": 3430.51, "duration": 4.118}, {"text": "So there are obviously\npathways to do them,", "start": 3434.628, "duration": 1.792}, {"text": "we just don't have the\nenzymes in humans to do it.", "start": 3436.42, "duration": 4.47}, {"text": "And then the other\nones we do retain.", "start": 3440.89, "duration": 3.48}, {"text": "You can obviously\nlook up the pathway", "start": 3444.37, "duration": 2.25}, {"text": "that's used by whatever\norganism to make", "start": 3446.62, "duration": 2.34}, {"text": "your favorite amino acid.", "start": 3448.96, "duration": 2.73}, {"text": "Today what I want to discuss\nis how we will make--", "start": 3451.69, "duration": 4.965}, {"text": "today I want to discuss how we\nwill make serine and glycine,", "start": 3459.74, "duration": 6.36}, {"text": "because it turns out,\nserine and s metabolism", "start": 3466.1, "duration": 3.63}, {"text": "play a key role\nin other pathways,", "start": 3469.73, "duration": 3.76}, {"text": "including nucleotide\nsynthesis which we", "start": 3473.49, "duration": 2.21}, {"text": "will cover in the next lecture.", "start": 3475.7, "duration": 3.93}, {"text": "Serine glycine\nmetabolism also is a way", "start": 3479.63, "duration": 2.52}, {"text": "to make one carbon units that\nare more reduced than CO2.", "start": 3482.15, "duration": 4.77}, {"text": "And these will be critical for\none-carbon transfer reactions", "start": 3486.92, "duration": 4.26}, {"text": "that you'll encounter throughout\nother aspects of biology.", "start": 3491.18, "duration": 6.05}, {"text": "So, serine and glycine,\nvery important amino acids.", "start": 3497.23, "duration": 6.63}, {"text": "And so just to be\nclear about this,", "start": 3503.86, "duration": 2.15}, {"text": "so it turns out\nserine-glycine metabolism,", "start": 3506.01, "duration": 4.41}, {"text": "important for nucleotides\namong carbon units,", "start": 3510.42, "duration": 2.05}, {"text": "we'll see that a lot.", "start": 3512.47, "duration": 1.3}, {"text": "But serine and glycine also\nused to make phospholipid head", "start": 3513.77, "duration": 4.5}, {"text": "groups.", "start": 3518.27, "duration": 0.5}, {"text": "Nucleotides, one-carbon units\nwe're going to talk about.", "start": 3536.1, "duration": 2.43}, {"text": "I want you to\nappreciate, you also", "start": 3538.53, "duration": 1.71}, {"text": "need serine to make\nphospholipid head groups.", "start": 3540.24, "duration": 3.34}, {"text": "So what do I mean by that?", "start": 3543.58, "duration": 1.17}, {"text": "Well, of course, there's\nphosphatidylserine.", "start": 3544.75, "duration": 2.21}, {"text": "Obviously that's serine is the\nhead group, and so serine--", "start": 3550.71, "duration": 5.13}, {"text": "the amino acid is\nrequired for that.", "start": 3555.84, "duration": 2.13}, {"text": "But also used to\ngenerate ethanolamine.", "start": 3557.97, "duration": 4.25}, {"text": "So what is ethanolamine?", "start": 3565.8, "duration": 2.94}, {"text": "Well again, just to\nremind you of this,", "start": 3568.74, "duration": 11.68}, {"text": "so here is the\namino acid serine.", "start": 3580.42, "duration": 4.2}, {"text": "So, to generate\nethanolamine, it's", "start": 3584.62, "duration": 3.54}, {"text": "decarbonization of\nserine to do that.", "start": 3588.16, "duration": 5.1}, {"text": "So loss of this CO2.", "start": 3593.26, "duration": 3.55}, {"text": "This is a reaction I don't\nhave time to go into,", "start": 3596.81, "duration": 2.0}, {"text": "you can look it up.", "start": 3598.81, "duration": 0.792}, {"text": "It is another repurposing\nof pyridoxal phosphate.", "start": 3599.602, "duration": 3.708}, {"text": "And that generates\nthis molecule,", "start": 3603.31, "duration": 5.8}, {"text": "which is ethanolamine.", "start": 3609.11, "duration": 2.56}, {"text": "That ends up head group on\nphosphatidylethanolamine.", "start": 3611.67, "duration": 6.09}, {"text": "And if I want to\nturn it into choline,", "start": 3617.76, "duration": 3.27}, {"text": "either for acetylcholine\nas a neurotransmitter", "start": 3621.03, "duration": 3.51}, {"text": "or for phosphatidylcholine\nas a head group,", "start": 3624.54, "duration": 3.0}, {"text": "it's basically adding\n3 methyl groups", "start": 3627.54, "duration": 7.77}, {"text": "onto this nitrogen\nof ethanolamine.", "start": 3635.31, "duration": 4.5}, {"text": "And so those three\nmethyl groups,", "start": 3639.81, "duration": 6.87}, {"text": "that's a carbon that's\nmore reduced than CO2.", "start": 3646.68, "duration": 4.23}, {"text": "That's a so-called\none carbon unit.", "start": 3650.91, "duration": 1.98}, {"text": "It turns out, as you'll see,\nthose also come from serine.", "start": 3652.89, "duration": 5.43}, {"text": "Last thing is serine\nis necessary to make", "start": 3658.32, "duration": 2.82}, {"text": "head groups for a class of\nlipids called sphingolipids.", "start": 3661.14, "duration": 3.36}, {"text": "There's a-- sphingosine is\nanother amino alcohol that", "start": 3667.38, "duration": 6.3}, {"text": "is generated from serine\nand ends up being the head", "start": 3673.68, "duration": 3.21}, {"text": "group for sphingolipids.", "start": 3676.89, "duration": 2.04}, {"text": "Especially if you're\ninterested in the immune system", "start": 3678.93, "duration": 3.15}, {"text": "of the brain, these end up\nbeing important molecules.", "start": 3682.08, "duration": 2.8}, {"text": "And so you can\nlook up how they're", "start": 3684.88, "duration": 1.85}, {"text": "related to serine, but just\nappreciate that for now", "start": 3686.73, "duration": 3.09}, {"text": "that they--", "start": 3689.82, "duration": 0.81}, {"text": "another important\ndownstream thing that's", "start": 3690.63, "duration": 3.21}, {"text": "generated from\nserine metabolism.", "start": 3693.84, "duration": 2.94}, {"text": "Also illustrating\nhow amino acids", "start": 3696.78, "duration": 3.51}, {"text": "can be very\nimportant to generate", "start": 3700.29, "duration": 1.5}, {"text": "lots of other biomolecules.", "start": 3701.79, "duration": 2.77}, {"text": "OK.", "start": 3704.56, "duration": 0.93}, {"text": "So, how do we make serine?", "start": 3705.49, "duration": 3.9}, {"text": "Well, if we go over\nhere, you'll see", "start": 3709.39, "duration": 2.52}, {"text": "that serine is downstream\nof 3-phosphoglycerate", "start": 3711.91, "duration": 4.59}, {"text": "from glycolysis.", "start": 3716.5, "duration": 1.99}, {"text": "So what's 3-phosphoglycerate?", "start": 3718.49, "duration": 2.09}, {"text": "OK, here's 3-phosphoglycerate\nfrom glycolysis, or the product", "start": 3732.34, "duration": 5.49}, {"text": "of rubisco if you like.", "start": 3737.83, "duration": 2.88}, {"text": "So photosynthesis.", "start": 3740.71, "duration": 2.62}, {"text": "So there's 3-phosphoglycerate.", "start": 3743.33, "duration": 4.28}, {"text": "So if I oxidize this\nalcohol to ketone,", "start": 3747.61, "duration": 5.61}, {"text": "electrons have to go somewhere.", "start": 3753.22, "duration": 1.68}, {"text": "NAD+ reduced to NADH, I\nget this intermediate.", "start": 3754.9, "duration": 4.677}, {"text": "It's phosphohydroxypyruvate So\npyruvate with a phospho on it,", "start": 3766.41, "duration": 6.27}, {"text": "hydroxypyruvate.", "start": 3772.68, "duration": 2.43}, {"text": "This molecule can undergo\na transamination reaction.", "start": 3775.11, "duration": 6.22}, {"text": "So pick up nitrogen\nfrom glutamate,", "start": 3781.33, "duration": 3.08}, {"text": "make the alpha-keto acid.", "start": 3784.41, "duration": 1.77}, {"text": "Take this alpha-keto acid\nand generate phosphoserine.", "start": 3786.18, "duration": 20.11}, {"text": "The amino acid that's\nphosphorylated, phosphoserine.", "start": 3806.29, "duration": 3.75}, {"text": "And then all I need to\ndo is dephosphorylate it,", "start": 3810.04, "duration": 3.75}, {"text": "and I end up with the\namino acid serine.", "start": 3813.79, "duration": 3.61}, {"text": "Cool.", "start": 3817.4, "duration": 1.33}, {"text": "All right.", "start": 3818.73, "duration": 1.59}, {"text": "To make glycine from serine--", "start": 3820.32, "duration": 2.7}, {"text": "so remember, glycine is one\nbasically the amino acid", "start": 3823.02, "duration": 5.01}, {"text": "with no side chain on it.", "start": 3828.03, "duration": 1.66}, {"text": "So I need to remove this\ncarbon and the alcohol.", "start": 3829.69, "duration": 4.28}, {"text": "So I'll just redraw\nserine this way.", "start": 3833.97, "duration": 3.2}, {"text": "So that's redrawing serine.", "start": 3845.57, "duration": 2.85}, {"text": "Need to lose that\ngroup to get glycine.", "start": 3848.42, "duration": 4.41}, {"text": "This is helped along\nby pyridoxal phosphate.", "start": 3852.83, "duration": 6.97}, {"text": "So a reminder, this is\npyridoxal phosphate.", "start": 3859.8, "duration": 14.49}, {"text": "OK.", "start": 3956.26, "duration": 0.5}, {"text": "So this is exactly what we\ndrew, is the first steps", "start": 3956.76, "duration": 3.66}, {"text": "in transamination.", "start": 3960.42, "duration": 2.88}, {"text": "Except if instead of\nbasically going like this,", "start": 3963.3, "duration": 6.3}, {"text": "I do this to break this\ncarbon-carbon bond,", "start": 3969.6, "duration": 8.64}, {"text": "what do I get?", "start": 3978.24, "duration": 1.24}, {"text": "Well, I release a\none-carbon unit.", "start": 3979.48, "duration": 5.15}, {"text": "In this case, it's\nthe one-carbon unit", "start": 3984.63, "duration": 3.84}, {"text": "as formaldehyde.", "start": 3988.47, "duration": 1.95}, {"text": "The one-carbon\naldehyde, formaldehyde.", "start": 3993.8, "duration": 3.39}, {"text": "And generate this intermediate.", "start": 3997.19, "duration": 28.23}, {"text": "And it's just exactly what we\nshowed before for resolving", "start": 4074.41, "duration": 8.93}, {"text": "the transamination.", "start": 4083.34, "duration": 2.61}, {"text": "And I am left with glycine, as\nwell as I regenerated pyridoxal", "start": 4098.38, "duration": 15.51}, {"text": "phosphate for the next\ncatalytic cycle of the enzyme.", "start": 4113.89, "duration": 5.17}, {"text": "And so illustrates\nthe flexibility", "start": 4119.06, "duration": 2.78}, {"text": "of pyridoxal phosphate.", "start": 4121.84, "duration": 1.53}, {"text": "In this case, helping\nconvert serine into glycine", "start": 4123.37, "duration": 5.01}, {"text": "and a one-carbon unit\nshown here as formaldehyde.", "start": 4128.38, "duration": 5.76}, {"text": "Now the enzyme that\ncarries out this reaction", "start": 4134.14, "duration": 4.29}, {"text": "is an enzyme called\nSHMT, which stands", "start": 4138.43, "duration": 7.08}, {"text": "for serine\nhydroxymethyltransferase.", "start": 4145.51, "duration": 5.767}, {"text": "Serine hydroxymethyltransferase.", "start": 4163.06, "duration": 2.64}, {"text": "And it actually doesn't release\nthe formaldehyde directly.", "start": 4165.7, "duration": 5.67}, {"text": "Instead, it transfers\nthat formaldehyde", "start": 4171.37, "duration": 3.239}, {"text": "to an important one-carbon donor\nfor many one-carbon reactions", "start": 4174.609, "duration": 5.851}, {"text": "that is called folate\nspecies or folic acid.", "start": 4180.46, "duration": 4.3}, {"text": "So remember, if we transferred\nCO2 in a carboxylation", "start": 4184.76, "duration": 3.83}, {"text": "reaction, we use\na cofactor biotin.", "start": 4188.59, "duration": 2.49}, {"text": "Biotin's useful to transfer CO2.", "start": 4191.08, "duration": 2.64}, {"text": "But if we're going to do\nsomething like transfer", "start": 4193.72, "duration": 3.0}, {"text": "the methyl groups shown up there\nfor choline synthesis, that's", "start": 4196.72, "duration": 4.11}, {"text": "transferring carbon that's\nmore reduced than CO2,", "start": 4200.83, "duration": 2.82}, {"text": "and you don't use\nbiotin for that.", "start": 4203.65, "duration": 1.92}, {"text": "Instead, you use\na cofactor called", "start": 4205.57, "duration": 3.42}, {"text": "folate that's derived from\nthe vitamin folic acid.", "start": 4208.99, "duration": 5.94}, {"text": "So folic acid, very\nimportant vitamin.", "start": 4214.93, "duration": 6.06}, {"text": "It's the primary thing that's\nincluded in prenatal vitamins.", "start": 4220.99, "duration": 4.77}, {"text": "Why is that?", "start": 4225.76, "duration": 0.87}, {"text": "Because deficiency in folic\nacid was shown a while back", "start": 4226.63, "duration": 3.93}, {"text": "to cause neural tube defects--", "start": 4230.56, "duration": 2.68}, {"text": "so developmental defects where\nthe neural tube does not close.", "start": 4233.24, "duration": 3.5}, {"text": "This leads to things\nlike spina bifida.", "start": 4236.74, "duration": 2.91}, {"text": "One of the real successes of\npublic health intervention", "start": 4239.65, "duration": 3.54}, {"text": "was the recognition of this\nand fortifying various cereals", "start": 4243.19, "duration": 4.32}, {"text": "with folic acid.", "start": 4247.51, "duration": 1.65}, {"text": "And doing so has greatly\nreduced the incidence", "start": 4249.16, "duration": 3.9}, {"text": "of these birth defects\ninvolving folate deficiency.", "start": 4253.06, "duration": 4.92}, {"text": "Folate deficiency's also\na common cause of anemia.", "start": 4257.98, "duration": 2.97}, {"text": "And so folic acid is a\nvitamin that lots of people", "start": 4260.95, "duration": 2.4}, {"text": "take for that reason.", "start": 4263.35, "duration": 2.22}, {"text": "And in fact, folic acid, also\nvery important in the history", "start": 4265.57, "duration": 3.57}, {"text": "of cancer treatment.", "start": 4269.14, "duration": 1.262}, {"text": "And if you want to\nlearn more about that,", "start": 4270.402, "duration": 1.708}, {"text": "take 745, which is\noffered in the fall.", "start": 4272.11, "duration": 5.13}, {"text": "All right.", "start": 4277.24, "duration": 1.35}, {"text": "So, folic acid is\na complex molecule", "start": 4278.59, "duration": 4.38}, {"text": "that is converted in cells to\na molecule called THF, which", "start": 4282.97, "duration": 8.7}, {"text": "stands for tetrahydrofolate.", "start": 4291.67, "duration": 2.196}, {"text": "So I'll draw out folic acid\nfor you and tetrahydrofolate.", "start": 4298.93, "duration": 7.11}, {"text": "OK.", "start": 4357.21, "duration": 0.93}, {"text": "So, this here is folic acid.", "start": 4358.14, "duration": 5.07}, {"text": "The folic acid molecule\nis tetrahydrofolate.", "start": 4363.21, "duration": 3.15}, {"text": "It has a peptide bond here\nto a glutamate molecule,", "start": 4366.36, "duration": 4.74}, {"text": "and it's actually a\npolyglutamate tail that", "start": 4371.1, "duration": 3.09}, {"text": "is there to trap it in cells.", "start": 4374.19, "duration": 2.76}, {"text": "It's this central part\nof the molecule here", "start": 4376.95, "duration": 11.44}, {"text": "that actually carries\nthe one-carbon unit.", "start": 4388.39, "duration": 3.15}, {"text": "And so the way that the\nnitrogens are numbered,", "start": 4391.54, "duration": 3.69}, {"text": "this is nitrogen-5.", "start": 4395.23, "duration": 1.87}, {"text": "This is nitrogen-10.", "start": 4397.1, "duration": 1.82}, {"text": "That will be\nimportant in a minute.", "start": 4398.92, "duration": 1.92}, {"text": "But it's really this\nsort of central part here", "start": 4400.84, "duration": 5.5}, {"text": "of the molecule that I will\ndraw over and over again", "start": 4406.34, "duration": 3.48}, {"text": "as the one-carbon\nunit-carrying species.", "start": 4409.82, "duration": 5.87}, {"text": "To show how this\nworks, it's easier", "start": 4415.69, "duration": 2.1}, {"text": "if I start off by showing\nhow it can pick up a more", "start": 4417.79, "duration": 4.59}, {"text": "oxidized one-carbon unit.", "start": 4422.38, "duration": 2.32}, {"text": "So the one-carbon carboxylic\nacid is this, that's formate.", "start": 4424.7, "duration": 7.25}, {"text": "And so if I phosphorylate\nformic acid,", "start": 4431.95, "duration": 11.24}, {"text": "this formic acid can then\nbe picked up by the--", "start": 4443.19, "duration": 3.795}, {"text": "so here's that carrying\npart of the one-carbon--", "start": 4462.62, "duration": 5.37}, {"text": "the box part of\ntetrahydrofolate.", "start": 4467.99, "duration": 3.63}, {"text": "And so this can pick up\nformic acid like this.", "start": 4471.62, "duration": 12.5}, {"text": "OK.", "start": 4504.92, "duration": 0.5}, {"text": "So that gives us\nthis molecule, which", "start": 4505.42, "duration": 2.13}, {"text": "is called\nN10-formyltetrahydrofolate,", "start": 4507.55, "duration": 7.52}, {"text": "THF.", "start": 4515.07, "duration": 1.89}, {"text": "I can create a ring\nout of this molecule.", "start": 4516.96, "duration": 4.84}, {"text": "This.", "start": 4528.545, "duration": 0.5}, {"text": "OK.", "start": 4550.572, "duration": 0.508}, {"text": "And if I remove water from this\nring, we draw it like this.", "start": 4551.08, "duration": 12.425}, {"text": "OK.", "start": 4582.73, "duration": 0.5}, {"text": "This is called\nN5,N10-methenyl THF.", "start": 4583.23, "duration": 11.25}, {"text": "And if I reduce that\nmolecule, it's NADPH.", "start": 4594.48, "duration": 23.0}, {"text": "So hydride ion.", "start": 4617.48, "duration": 10.065}, {"text": "OK.", "start": 4642.18, "duration": 1.08}, {"text": "Then I end up with\nthis molecule,", "start": 4643.26, "duration": 15.62}, {"text": "which is N5,N10-methylene THF.", "start": 4658.88, "duration": 11.36}, {"text": "And if I further\nreduce this molecule,", "start": 4670.24, "duration": 21.75}, {"text": "then I end up with\nthis molecule,", "start": 4691.99, "duration": 14.59}, {"text": "which is N5-methyl THF.", "start": 4706.58, "duration": 9.69}, {"text": "Appears incredibly complex\nwhat's going on here,", "start": 4716.27, "duration": 5.58}, {"text": "but I went through this, because\nwhat I want you to realize", "start": 4721.85, "duration": 3.21}, {"text": "is that each of these\nspecies are simply", "start": 4725.06, "duration": 3.12}, {"text": "tetrahydrofolate carrying\na one-carbon unit", "start": 4728.18, "duration": 3.42}, {"text": "in a different oxidation state.", "start": 4731.6, "duration": 3.45}, {"text": "So this N10 formyl THF\nis carrying formic acid,", "start": 4735.05, "duration": 5.61}, {"text": "the one-carbon acid.", "start": 4740.66, "duration": 2.19}, {"text": "I can reduce it to\nN5,N10-methylene THF.", "start": 4742.85, "duration": 4.86}, {"text": "That's carrying the one-carbon\naldehyde, formaldehyde.", "start": 4747.71, "duration": 3.9}, {"text": "Or I could reduce it further.", "start": 4751.61, "duration": 1.65}, {"text": "This is carrying the one-carbon\nmethyl group as N5-methyl THF.", "start": 4753.26, "duration": 9.51}, {"text": "And it turns out that this\nallows a lot of flexibility", "start": 4762.77, "duration": 3.96}, {"text": "in carrying out\none-carbon reactions.", "start": 4766.73, "duration": 2.76}, {"text": "Here is a same thing\nwritten from a textbook.", "start": 4769.49, "duration": 4.2}, {"text": "The direction-- the order is\nshown a little bit differently,", "start": 4773.69, "duration": 3.84}, {"text": "the molecules are rotated.", "start": 4777.53, "duration": 1.74}, {"text": "And it includes a\ncouple other species", "start": 4779.27, "duration": 2.28}, {"text": "that are added in for\nhistodine metabolism.", "start": 4781.55, "duration": 2.262}, {"text": "But if you look at\nthis, you'll see", "start": 4783.812, "duration": 1.458}, {"text": "it's exactly what\nI just drawn where", "start": 4785.27, "duration": 3.12}, {"text": "you get these key species.", "start": 4788.39, "duration": 2.28}, {"text": "Where N5-methyl\nTHF is effectively", "start": 4790.67, "duration": 8.16}, {"text": "carrying a methyl group.", "start": 4798.83, "duration": 2.14}, {"text": "So a one-carbon methyl donor.", "start": 4800.97, "duration": 2.12}, {"text": "N5,N10-methylene THF is\ncarrying the formaldehyde.", "start": 4803.09, "duration": 14.4}, {"text": "And N10-formyl THF is\ncarrying the formate group", "start": 4817.49, "duration": 15.12}, {"text": "to donate as a one-carbon unit.", "start": 4832.61, "duration": 2.64}, {"text": "This will be the donor,\nultimately, for things", "start": 4835.25, "duration": 3.24}, {"text": "like choline synthesis.", "start": 4838.49, "duration": 2.1}, {"text": "Formaldehyde-- and\nN5,N10-methylene and formyl THF", "start": 4840.59, "duration": 3.6}, {"text": "will be important in nucleic\nacid synthesis and we'll see", "start": 4844.19, "duration": 3.18}, {"text": "that next time.", "start": 4847.37, "duration": 1.96}, {"text": "And so now if we go back\nto our SHMT reaction,", "start": 4849.33, "duration": 4.91}, {"text": "I can show you how these\nthings really work.", "start": 4854.24, "duration": 5.93}, {"text": "And so here's a THF molecule.", "start": 4860.17, "duration": 11.79}, {"text": "And so here is the intermediate\nin serine-glycine conversion", "start": 4871.96, "duration": 11.08}, {"text": "found to pyridoxal\nphosphate, et cetera.", "start": 4883.04, "duration": 13.85}, {"text": "And that will release\nglycine and eventually PLP.", "start": 4896.89, "duration": 8.74}, {"text": "So glycine and PLP can\nbe generated from that.", "start": 4905.63, "duration": 3.55}, {"text": "And what ends up here\non the folate is--", "start": 4909.18, "duration": 6.5}, {"text": "which is N5,N10-methylene THF.", "start": 4944.98, "duration": 10.69}, {"text": "And if I take this\nand I oxidize it,", "start": 4955.67, "duration": 4.47}, {"text": "I can take the\naldehyde to the acid.", "start": 4960.14, "duration": 3.93}, {"text": "So oxidation.", "start": 4964.07, "duration": 1.8}, {"text": "NAD+ is reduced to NADH.", "start": 4965.87, "duration": 2.76}, {"text": "Now I get an N10-formyl THF.", "start": 4968.63, "duration": 6.36}, {"text": "And if instead I reduce it,\nso electrons from NADPH go", "start": 4974.99, "duration": 8.01}, {"text": "to NADP+.", "start": 4983.0, "duration": 1.29}, {"text": "So NADPH gets oxidized,\nelectrons go there.", "start": 4984.29, "duration": 2.82}, {"text": "And then I get an N5-methyl THF.", "start": 4987.11, "duration": 7.14}, {"text": "This gives me a donor\nof methyl groups.", "start": 4994.25, "duration": 3.48}, {"text": "This gives me a donor\nof formyl groups.", "start": 4997.73, "duration": 4.52}, {"text": "All right.", "start": 5002.25, "duration": 1.17}, {"text": "Very last thing I want\nto talk about today", "start": 5003.42, "duration": 2.46}, {"text": "is we'll talk a lot about how\nwe use the more oxidized species", "start": 5005.88, "duration": 6.66}, {"text": "next time to\ngenerate nucleotides,", "start": 5012.54, "duration": 2.58}, {"text": "but I want to say a few\nwords about how these methyl", "start": 5015.12, "duration": 2.76}, {"text": "groups are used to be\ninvolved in methylation", "start": 5017.88, "duration": 3.93}, {"text": "reactions, things like\ncholine synthesis shown up", "start": 5021.81, "duration": 3.78}, {"text": "there, but also not\njust choline synthesis.", "start": 5025.59, "duration": 5.16}, {"text": "Also can be used for reactions\ninvolved in, say, epigenetics.", "start": 5030.75, "duration": 6.36}, {"text": "And so for those of\nyou who will never", "start": 5037.11, "duration": 2.28}, {"text": "think about biochemistry\nagain after taking", "start": 5039.39, "duration": 2.25}, {"text": "this class but we'll take--", "start": 5041.64, "duration": 2.67}, {"text": "think about genetics,\nyou'll certainly", "start": 5044.31, "duration": 2.25}, {"text": "know the gene\nexpression is controlled", "start": 5046.56, "duration": 2.07}, {"text": "by methylation of DNA and\nhistones and things like that.", "start": 5048.63, "duration": 4.44}, {"text": "Those methyl groups have\nto come from somewhere,", "start": 5053.07, "duration": 2.56}, {"text": "and they come ultimately from\nthese methylation reactions,", "start": 5055.63, "duration": 4.61}, {"text": "the serine there.", "start": 5060.24, "duration": 2.37}, {"text": "Now I don't have time\nto go through all", "start": 5062.61, "duration": 2.16}, {"text": "of one-carbon metabolism.", "start": 5064.77, "duration": 2.53}, {"text": "This is very complex.", "start": 5067.3, "duration": 1.82}, {"text": "But it turns out\nthe one-carbon donor", "start": 5069.12, "duration": 1.89}, {"text": "for most methylation\nreactions isn't N5-methyl THF,", "start": 5071.01, "duration": 3.822}, {"text": "even though that's where\nthe methyl group comes from.", "start": 5074.832, "duration": 2.208}, {"text": "It's actually this molecule.", "start": 5077.04, "duration": 2.04}, {"text": "So this here is the\namino acid methionine.", "start": 5102.49, "duration": 3.23}, {"text": "And if I put it here onto an\nadenine, what I end up with", "start": 5115.76, "duration": 4.5}, {"text": "is this molecule called\nS-adenosylmethionine or SAM.", "start": 5120.26, "duration": 15.35}, {"text": "This methyl group on\nSAM is very labile.", "start": 5135.61, "duration": 2.91}, {"text": "And so it is the\nuniversal methyl donor", "start": 5138.52, "duration": 5.52}, {"text": "to be used in\nmethylation reactions,", "start": 5144.04, "duration": 2.34}, {"text": "choline synthesis, epigenetic\nmethylation of DNA or histones,", "start": 5146.38, "duration": 4.26}, {"text": "whatever.", "start": 5150.64, "duration": 1.47}, {"text": "And if you transfer\nthat methyl group off,", "start": 5152.11, "duration": 2.4}, {"text": "you're left with this\nnon-proteinogenic amino acid", "start": 5154.51, "duration": 15.41}, {"text": "that's called homocysteine.", "start": 5169.92, "duration": 2.79}, {"text": "And that homocysteine\nis here onto an adenine", "start": 5172.71, "duration": 9.36}, {"text": "to make S-adenosylhomocysteine,\nwhich is abbreviated as SAH.", "start": 5182.07, "duration": 14.21}, {"text": "SAH picks up-- needs\nto regenerate SAM.", "start": 5196.28, "duration": 7.71}, {"text": "Methyl group has to\ncome from somewhere.", "start": 5203.99, "duration": 2.49}, {"text": "This comes from N5-methyl THF.", "start": 5206.48, "duration": 7.53}, {"text": "Of course, generates THF.", "start": 5214.01, "duration": 2.7}, {"text": "And then THF can pick up\nanother methyl group, ultimately", "start": 5216.71, "duration": 4.47}, {"text": "from serine-to-glycine\nconversion and reduction", "start": 5221.18, "duration": 3.0}, {"text": "with NADH to make N5-methyl THF.", "start": 5224.18, "duration": 4.5}, {"text": "I show here on the\nslide, here's just", "start": 5228.68, "duration": 3.03}, {"text": "a picture of\none-carbon metabolism", "start": 5231.71, "duration": 2.19}, {"text": "that I took from\na review article.", "start": 5233.9, "duration": 2.13}, {"text": "And so here's SAM metabolism.", "start": 5236.03, "duration": 3.3}, {"text": "Lots and lots of\ncomplicated reactions", "start": 5239.33, "duration": 2.4}, {"text": "that are linked to cystine\nmetabolism and polyamine", "start": 5241.73, "duration": 2.76}, {"text": "metabolism.", "start": 5244.49, "duration": 1.718}, {"text": "Obviously don't have\ntime to get into this,", "start": 5246.208, "duration": 1.792}, {"text": "but I want you to appreciate\nthat this happens, where", "start": 5248.0, "duration": 2.37}, {"text": "SAM and SAH come from,\nhow they're involved", "start": 5250.37, "duration": 2.61}, {"text": "in one-carbon metabolism,\nbecause this will come up", "start": 5252.98, "duration": 3.03}, {"text": "again in your future\nendeavors if you do something", "start": 5256.01, "duration": 2.94}, {"text": "with biology.", "start": 5258.95, "duration": 1.89}, {"text": "All right.", "start": 5260.84, "duration": 0.63}, {"text": "Final topic next time is\nnucleic acid metabolism,", "start": 5261.47, "duration": 4.9}, {"text": "and then we will\nhave covered all", "start": 5266.37, "duration": 2.54}, {"text": "of the basics of metabolism.", "start": 5268.91, "duration": 2.28}, {"text": "Thanks.", "start": 5271.19, "duration": 1.55}]
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+[{"text": "[CREAKING]", "start": 0.5, "duration": 2.979}, {"text": "BARBARA IMPERIALI: So what we\nare going to talk about today,", "start": 16.42, "duration": 2.68}, {"text": "and I'm going to do something\na little annoying, as usual,", "start": 19.1, "duration": 4.29}, {"text": "I want to take you\nsomewhere here.", "start": 23.39, "duration": 2.8}, {"text": "Yeah, sure, back to\ncarbon, that's fine.", "start": 26.19, "duration": 2.9}, {"text": "But what I want to\nshow you is the sizes", "start": 29.09, "duration": 2.21}, {"text": "of the molecular\nplayers in translation", "start": 31.3, "duration": 3.63}, {"text": "because we are going here now\nfrom the smallest carbon atom.", "start": 34.93, "duration": 4.29}, {"text": "And we spent the first four\nlectures on amino acids,", "start": 39.22, "duration": 3.18}, {"text": "nucleotides, sugars,\nphospholipids.", "start": 42.4, "duration": 2.7}, {"text": "But we're entering\nnew territory here,", "start": 45.1, "duration": 2.468}, {"text": "and I'm just going to\ndo this in such a way", "start": 47.568, "duration": 1.792}, {"text": "that it comes onto the screens.", "start": 49.36, "duration": 3.49}, {"text": "What you can see\nhere is, in order", "start": 52.85, "duration": 2.57}, {"text": "to make proteins like\nhemoglobin and antibodies--", "start": 55.42, "duration": 3.88}, {"text": "these are made up of amino\nacids, the really tiny things", "start": 59.3, "duration": 2.96}, {"text": "that are out of view right now--", "start": 62.26, "duration": 2.009}, {"text": "we need large entities that are\nmade up of either nucleic acids", "start": 64.269, "duration": 4.471}, {"text": "alone or nucleic\nacids plus proteins.", "start": 68.74, "duration": 3.4}, {"text": "And so the things that\nwill feature today", "start": 72.14, "duration": 2.0}, {"text": "are the transfer RNAs\nand the ribosome.", "start": 74.14, "duration": 3.34}, {"text": "And I want you to look at the\nsize of this molecular machine.", "start": 77.48, "duration": 3.5}, {"text": "This is we're getting\npretty large now.", "start": 80.98, "duration": 2.34}, {"text": "We're needing to\nuse large machines", "start": 83.32, "duration": 2.61}, {"text": "to make the smaller catalysts\nthat are essential in the cell.", "start": 85.93, "duration": 4.02}, {"text": "And, just so sort of maybe\nsize doesn't seem so important,", "start": 89.95, "duration": 4.05}, {"text": "but let's just go a\nlittle bit further here.", "start": 94.0, "duration": 3.0}, {"text": "And what to me is intriguing is\nthat the size of the ribosome", "start": 97.0, "duration": 8.09}, {"text": "is pretty similar to the\nsize of the rhinovirus,", "start": 105.09, "duration": 3.36}, {"text": "a little smaller than\nthe hepatitis virus,", "start": 108.45, "duration": 2.58}, {"text": "but quite a bit smaller than\nsome of these other viruses.", "start": 111.03, "duration": 3.06}, {"text": "So the ribosome organelle is\na large entity in the cell.", "start": 114.09, "duration": 3.87}, {"text": "And, when you do look at\nelectron micrographs of cells,", "start": 117.96, "duration": 5.97}, {"text": "you can see these dark dots,\nwhich represent ribosomes.", "start": 123.93, "duration": 3.45}, {"text": "They're big enough to see,\nwhereas the proteins themselves", "start": 127.38, "duration": 3.39}, {"text": "are not big enough to see.", "start": 130.77, "duration": 1.44}, {"text": "So that's what you're\ndestined for today.", "start": 132.21, "duration": 3.24}, {"text": "All right, OK, so I've\nstarted to place on this board", "start": 139.17, "duration": 7.55}, {"text": "some of the molecular players,\nthe messenger RNA, the transfer", "start": 146.72, "duration": 3.48}, {"text": "RNA, and the ribosomes,\nwhich are made up", "start": 150.2, "duration": 3.09}, {"text": "of ribosomal RNA plus protein.", "start": 153.29, "duration": 2.55}, {"text": "And I want to just remind\nyou about the structure", "start": 155.84, "duration": 3.84}, {"text": "of the mature messenger\nRNA just for a minute", "start": 159.68, "duration": 7.2}, {"text": "because, in the last\nclass, we talked", "start": 166.88, "duration": 1.8}, {"text": "about a lot of manipulations\nof that pre-messenger RNA,", "start": 168.68, "duration": 5.07}, {"text": "the fresh thing out\nof transcription.", "start": 173.75, "duration": 2.25}, {"text": "And now I just\nwant to remind you", "start": 176.0, "duration": 1.71}, {"text": "that the messenger is\nsingle-stranded RNA, obviously.", "start": 177.71, "duration": 5.52}, {"text": "It has a 5 prime cap, which\nhas got this funky 5 prime,", "start": 183.23, "duration": 5.46}, {"text": "5 prime bridge that's\nresistant to exonucleases.", "start": 188.69, "duration": 4.41}, {"text": "Somewhere in that\nsequence is a start codon.", "start": 193.1, "duration": 4.41}, {"text": "It's something that says this\nis the bit I want to translate.", "start": 197.51, "duration": 6.15}, {"text": "Often, there's a lot of stuff\nhere that you don't translate.", "start": 203.66, "duration": 5.7}, {"text": "It's part of what's known as\nthe ribosome binding site.", "start": 209.36, "duration": 7.08}, {"text": "And there are many\nfeatures in this part", "start": 216.44, "duration": 2.31}, {"text": "of the sequence that are very\nimportant for translation.", "start": 218.75, "duration": 3.66}, {"text": "They contribute to the\nefficiency of translation.", "start": 222.41, "duration": 3.18}, {"text": "Generically, we'd call it\nthe ribosome binding site,", "start": 225.59, "duration": 2.49}, {"text": "but there are funny things\ncalled Shine-Dalgarno sequences", "start": 228.08, "duration": 3.27}, {"text": "and stuff.", "start": 231.35, "duration": 0.69}, {"text": "Don't worry about any of that.", "start": 232.04, "duration": 1.87}, {"text": "I just want you to appreciate\nthat, the mature transcript,", "start": 233.91, "duration": 4.28}, {"text": "you don't translate\nthe whole thing.", "start": 238.19, "duration": 2.43}, {"text": "A lot of this stuff is\nstructural, functional", "start": 240.62, "duration": 2.61}, {"text": "for other reasons\nthat contribute", "start": 243.23, "duration": 1.98}, {"text": "to the success of translation.", "start": 245.21, "duration": 1.95}, {"text": "Once you see one of\nthese, the ribosome", "start": 247.16, "duration": 2.4}, {"text": "mows its way through and\nreads the nucleic acids", "start": 249.56, "duration": 4.5}, {"text": "in the message.", "start": 254.06, "duration": 1.05}, {"text": "So the message is being conveyed\nover to the new machinery.", "start": 255.11, "duration": 3.63}, {"text": "And then, when you hit\none of these three codons,", "start": 258.74, "duration": 2.9}, {"text": "and we'll discuss these\nproperly when we get to them,", "start": 261.64, "duration": 2.56}, {"text": "it's time to stop and\nfinish translating.", "start": 264.2, "duration": 3.03}, {"text": "The other end the message\nhas a poly-adenine tail.", "start": 267.23, "duration": 4.77}, {"text": "Remember that, once again,\nis structural to protect", "start": 272.0, "duration": 3.33}, {"text": "the ends of that transcript.", "start": 275.33, "duration": 1.95}, {"text": "Even if some of the hundreds\nof adenine nucleotides", "start": 277.28, "duration": 4.44}, {"text": "are nibbled off, you\ndon't get into the part", "start": 281.72, "duration": 3.09}, {"text": "of the gene that's\ncritical to be translated.", "start": 284.81, "duration": 3.24}, {"text": "At a certain stage,\nthough, you might get in.", "start": 288.05, "duration": 3.21}, {"text": "Exonucleases might\nchew up enough.", "start": 291.26, "duration": 2.7}, {"text": "And they may end up\nchewing up your transcript,", "start": 293.96, "duration": 2.97}, {"text": "but that probably suggests that\nthe messenger has been around", "start": 296.93, "duration": 3.21}, {"text": "too long, and it's time for it\nto retire to a better life, OK?", "start": 300.14, "duration": 4.44}, {"text": "So remember the poly-A tail.", "start": 304.58, "duration": 2.26}, {"text": "And this, once again, plays\nother functional roles", "start": 306.84, "duration": 2.96}, {"text": "with respect to being\nrecognized as a transcript", "start": 309.8, "duration": 2.97}, {"text": "and being helped to\nget out of the nucleus.", "start": 312.77, "duration": 2.14}, {"text": "So this was really what\nwe talked about last week.", "start": 314.91, "duration": 4.07}, {"text": "There's one more\nfeature in here.", "start": 318.98, "duration": 1.5}, {"text": "I'm just going to\nremind you that", "start": 320.48, "duration": 1.98}, {"text": "the final mature\ntranscript has also", "start": 322.46, "duration": 3.57}, {"text": "been through splicing\nwith removal of introns", "start": 326.03, "duration": 5.13}, {"text": "and the pasting together of\nexons, which is a wonderful way", "start": 331.16, "duration": 3.36}, {"text": "to diversify transcripts\nof translation", "start": 334.52, "duration": 3.45}, {"text": "and give you much more proteins\nthan one gene can encode, OK?", "start": 337.97, "duration": 4.62}, {"text": "And we talked about\nthat last time.", "start": 342.59, "duration": 1.5}, {"text": "Great.", "start": 344.09, "duration": 0.76}, {"text": "So the first thing we\nhave to think about here", "start": 344.85, "duration": 3.8}, {"text": "is how do we go from four\nbases to a language that", "start": 348.65, "duration": 6.18}, {"text": "includes 20 letters, right?", "start": 354.83, "duration": 2.02}, {"text": "Or it's better\nreally, more precise,", "start": 359.37, "duration": 2.01}, {"text": "for me to call them nucleotides.", "start": 361.38, "duration": 1.8}, {"text": "It's more precise\nbecause the base just", "start": 367.99, "duration": 4.83}, {"text": "represents the ring system\nthat's attached to the ribose.", "start": 372.82, "duration": 3.84}, {"text": "Nucleotide means the whole\nthing, including a phosphate.", "start": 376.66, "duration": 3.27}, {"text": "So we go from four bases\nto encoding 20 amino acids.", "start": 379.93, "duration": 5.445}, {"text": "Now there are a few organisms--", "start": 389.0, "duration": 2.09}, {"text": "and, in fact, we have one spare\none as well, selenocysteine.", "start": 391.09, "duration": 4.22}, {"text": "There are a couple\nof other amino acids", "start": 395.31, "duration": 2.47}, {"text": "that might be designated as\nthe so-called 21st, 22nd amino", "start": 397.78, "duration": 4.08}, {"text": "acid.", "start": 401.86, "duration": 0.81}, {"text": "They're not found\nglobally in all organisms.", "start": 402.67, "duration": 3.24}, {"text": "We have selenocysteine in\njust very, very few proteins.", "start": 405.91, "duration": 4.05}, {"text": "So it's something beyond\nthe list of 20 that you saw.", "start": 409.96, "duration": 3.57}, {"text": "There are other\norganisms, for example,", "start": 413.53, "duration": 2.67}, {"text": "in archaea, these\nguys who hang out", "start": 416.2, "duration": 1.89}, {"text": "in bubbling hot\npots in Yellowstone,", "start": 418.09, "duration": 3.03}, {"text": "for example, that have\nanother amino acid known", "start": 421.12, "duration": 4.08}, {"text": "as pyrrolysine.", "start": 425.2, "duration": 0.93}, {"text": "I'm going to mention that\na little bit later on,", "start": 426.13, "duration": 2.52}, {"text": "but the ones you really\nneed to think about", "start": 428.65, "duration": 2.25}, {"text": "are the ones we're encoding\nin the global genetic code.", "start": 430.9, "duration": 4.47}, {"text": "This is the ones that are\ncommon to everybody, all right?", "start": 435.37, "duration": 3.9}, {"text": "So, obviously, when you look\nat the language of bases,", "start": 439.27, "duration": 4.68}, {"text": "one base--", "start": 443.95, "duration": 1.74}, {"text": "if the language translated\ndirectly one base", "start": 445.69, "duration": 3.27}, {"text": "to one amino acid, we could\nonly encode for amino acids.", "start": 448.96, "duration": 7.93}, {"text": "So we know it's not one\nbase, one amino acid.", "start": 456.89, "duration": 2.43}, {"text": "And I know, at this stage, you\nknow that it's three bases,", "start": 459.32, "duration": 3.45}, {"text": "but let's just go through the\nmath or the original questions", "start": 462.77, "duration": 3.42}, {"text": "that were sort of circulating.", "start": 466.19, "duration": 2.64}, {"text": "Like how do we go from this\nlanguage to the other language?", "start": 468.83, "duration": 3.33}, {"text": "If two bases encoded\neach amino acid,", "start": 472.16, "duration": 9.96}, {"text": "we could only encode\neight amino acids.", "start": 482.12, "duration": 3.05}, {"text": "That's not enough still.", "start": 485.17, "duration": 3.53}, {"text": "16 amino-- wait a minute.", "start": 488.7, "duration": 3.71}, {"text": "16 amino acids,\nsorry, I can never--", "start": 492.41, "duration": 4.35}, {"text": "anyway, that's 4 to the 2.", "start": 496.76, "duration": 3.63}, {"text": "It's pretty good if I\ncan't get 4 to the 2", "start": 500.39, "duration": 1.92}, {"text": "up at the blackboard.", "start": 502.31, "duration": 1.2}, {"text": "This would be 4 to\nthe 1 power and then--", "start": 503.51, "duration": 3.27}, {"text": "so what that came\ndown to realizing", "start": 506.78, "duration": 2.1}, {"text": "there were not enough.", "start": 508.88, "duration": 1.68}, {"text": "That wouldn't be a\nsufficient language", "start": 510.56, "duration": 2.7}, {"text": "to encode the 20 amino acids.", "start": 513.26, "duration": 2.5}, {"text": "So it's finally deduced\nthat three bases", "start": 515.76, "duration": 5.47}, {"text": "encoded each amino acid.", "start": 521.23, "duration": 4.17}, {"text": "That would give us 64 possible\nwords in the language that", "start": 525.4, "duration": 6.97}, {"text": "needs to be translated.", "start": 532.37, "duration": 1.94}, {"text": "That's a lot more than we need.", "start": 534.31, "duration": 1.51}, {"text": "We only need 20 for the\nencoded amino acids,", "start": 535.82, "duration": 5.33}, {"text": "so 64 possibilities.", "start": 541.15, "duration": 3.48}, {"text": "But what else do we\nneed in the language?", "start": 544.63, "duration": 2.51}, {"text": "We need a few more\nthings anyway.", "start": 547.14, "duration": 1.435}, {"text": "Yeah, up there.", "start": 552.42, "duration": 2.185}, {"text": "AUDIENCE: Oh, I\ndon't [INAUDIBLE]", "start": 554.605, "duration": 1.375}, {"text": "BARBARA IMPERIALI:\nOh, you weren't.", "start": 555.98, "duration": 1.7}, {"text": "Up there.", "start": 557.68, "duration": 1.015}, {"text": "AUDIENCE: You need to know\nwhen to start and stop.", "start": 558.695, "duration": 2.083}, {"text": "BARBARA IMPERIALI: So, exactly,\nso here this isn't necessarily", "start": 560.778, "duration": 2.732}, {"text": "one of the ones that\nuniformly codes amino acid", "start": 563.51, "duration": 3.27}, {"text": "through the sequence.", "start": 566.78, "duration": 0.88}, {"text": "We need a precise\nway to say start.", "start": 567.66, "duration": 3.14}, {"text": "And, in fact, we need\na way to say stop.", "start": 570.8, "duration": 3.39}, {"text": "And there are multiple three\nletter words that say stop.", "start": 574.19, "duration": 3.76}, {"text": "So it turns out that\nthe genetic code, which", "start": 577.95, "duration": 3.17}, {"text": "forms the basis of\nthis entire concept,", "start": 581.12, "duration": 8.97}, {"text": "has some features to it where\nit does have some degeneracy.", "start": 590.09, "duration": 4.41}, {"text": "But we'll go through\nthe degeneracy,", "start": 594.5, "duration": 1.74}, {"text": "and we'll take a look\nat the genetic code", "start": 596.24, "duration": 1.8}, {"text": "because it will tell us\nexactly how the three letter--", "start": 598.04, "duration": 4.515}, {"text": "the words made of three\nbases encode everything", "start": 602.555, "duration": 3.015}, {"text": "we need for\ntranslation, all right?", "start": 605.57, "duration": 2.64}, {"text": "So let's just go back\nand take a look at this.", "start": 608.21, "duration": 2.91}, {"text": "So we've looked\nat the messenger.", "start": 611.12, "duration": 2.04}, {"text": "I've told you a little bit about\nthe tRNAs and the proteins.", "start": 613.16, "duration": 3.24}, {"text": "But then we just sort\nof give you a little bit", "start": 616.4, "duration": 2.25}, {"text": "of the back history.", "start": 618.65, "duration": 1.5}, {"text": "And, once the structure\nof double-stranded DNA", "start": 620.15, "duration": 2.55}, {"text": "was deduced,\nreally, everyone was", "start": 622.7, "duration": 2.1}, {"text": "moving on to trying to\nunderstand how that converted", "start": 624.8, "duration": 3.78}, {"text": "to the translation to proteins.", "start": 628.58, "duration": 2.25}, {"text": "And there were a lot of workers\ndeeply involved in this.", "start": 630.83, "duration": 2.97}, {"text": "Crick and Brenner realized\nit was three bases to code", "start": 633.8, "duration": 3.75}, {"text": "for one amino acid, but\nKhorana, Nirenberg, and Holley,", "start": 637.55, "duration": 4.62}, {"text": "Khorana who was part of our\nfaculty for many, many years,", "start": 642.17, "duration": 4.23}, {"text": "actually defined\nthat genetic code", "start": 646.4, "duration": 2.85}, {"text": "and got all of the details.", "start": 649.25, "duration": 2.85}, {"text": "Brenner and Crick started\nto have the ideas,", "start": 652.1, "duration": 2.85}, {"text": "but, really, the definition\nby doing a process known", "start": 654.95, "duration": 3.81}, {"text": "as cell-free translation where\nthey could very carefully add", "start": 658.76, "duration": 3.96}, {"text": "components to understand how\nthe code, the genetic code,", "start": 662.72, "duration": 5.97}, {"text": "was formulated where they\nput in specific messenger", "start": 668.69, "duration": 2.94}, {"text": "RNAs and amino\nacids and transfer", "start": 671.63, "duration": 2.7}, {"text": "RNAs and actually made\nproteins from that.", "start": 674.33, "duration": 3.24}, {"text": "So that's the work that\nKhorana and others did.", "start": 677.57, "duration": 3.31}, {"text": "And that was awarded them a\nNobel Prize for that work.", "start": 680.88, "duration": 2.69}, {"text": "And then, later on, things\nstarted to get-- you know,", "start": 686.45, "duration": 3.84}, {"text": "these are decades of work\nI want to point out to you.", "start": 690.29, "duration": 2.97}, {"text": "The ribosomes were discovered.", "start": 693.26, "duration": 1.65}, {"text": "That was a decade\nlater, the sort", "start": 694.91, "duration": 3.33}, {"text": "of details of the structure,\nbut not the structure itself.", "start": 698.24, "duration": 3.15}, {"text": "And it was really\nexciting in the 2000s", "start": 701.39, "duration": 3.06}, {"text": "when Ramakrishnan, Steitz, and\nYonath solved the structure", "start": 704.45, "duration": 3.63}, {"text": "of the prokaryotic ribosome.", "start": 708.08, "duration": 2.07}, {"text": "So each of these things has\ntaken a decade to happen,", "start": 710.15, "duration": 3.52}, {"text": "but they are fundamental,\nmajor, important things", "start": 713.67, "duration": 2.63}, {"text": "that we can act on and move\nforward to understand more.", "start": 716.3, "duration": 4.48}, {"text": "All right, so let's move\nto the transfer RNAs.", "start": 720.78, "duration": 5.44}, {"text": "And I've flashed up this\nslide a couple of times,", "start": 726.22, "duration": 2.82}, {"text": "but I actually now have\nthe movie of the structure", "start": 729.04, "duration": 3.9}, {"text": "of a transfer RNA.", "start": 732.94, "duration": 1.93}, {"text": "So the transfer RNA is\na linear segment of RNA,", "start": 734.87, "duration": 4.73}, {"text": "but it's folded up the\nway ribonucleic acids are", "start": 739.6, "duration": 5.43}, {"text": "with three, four stretches of\ndouble strand coming together", "start": 745.03, "duration": 4.23}, {"text": "and loops in between them.", "start": 749.26, "duration": 2.08}, {"text": "And the one end, this\nis the 3 prime end.", "start": 751.34, "duration": 2.06}, {"text": "I always try to\ndraw it on the left", "start": 753.4, "duration": 1.8}, {"text": "because, otherwise,\nthings get confusing.", "start": 755.2, "duration": 2.07}, {"text": "It's much easier to sort of\nsee where everything ends up", "start": 757.27, "duration": 2.82}, {"text": "if you put the long\narm on the 3 prime side", "start": 760.09, "duration": 3.38}, {"text": "to the left of your picture.", "start": 763.47, "duration": 1.833}, {"text": "And what I think\nis cool, when you", "start": 765.303, "duration": 1.417}, {"text": "look at the structure of RNA,\nwe think of messenger RNA", "start": 766.72, "duration": 3.54}, {"text": "as being a sort of\nrather floppy entity,", "start": 770.26, "duration": 2.62}, {"text": "but it actually\nreally likes to form", "start": 772.88, "duration": 2.42}, {"text": "short segments of double helix.", "start": 775.3, "duration": 2.13}, {"text": "It just doesn't do well\nwith the really long", "start": 777.43, "duration": 2.07}, {"text": "double-stranded structure\nthe same way that DNA does.", "start": 779.5, "duration": 3.48}, {"text": "But this folded up\nstructure is very important.", "start": 782.98, "duration": 2.97}, {"text": "And it was on the observation\nof these folded structures", "start": 785.95, "duration": 3.35}, {"text": "that the ribosome\nhypothesis was formulated.", "start": 789.3, "duration": 3.79}, {"text": "But the two things that you want\nto remember about the ribosome", "start": 793.09, "duration": 3.45}, {"text": "are that the 3\nprime hydroxyl group", "start": 796.54, "duration": 2.4}, {"text": "of the last ribose within\nthis ribosomal sequence", "start": 798.94, "duration": 4.68}, {"text": "is where the amino acid\nthat's going to be loaded", "start": 803.62, "duration": 3.3}, {"text": "into your protein is attached.", "start": 806.92, "duration": 2.31}, {"text": "So that's one point.", "start": 809.23, "duration": 1.51}, {"text": "And then there's another\nlandmark on this structure.", "start": 810.74, "duration": 3.05}, {"text": "And that's what's called--", "start": 813.79, "duration": 1.62}, {"text": "one of the loops\nhas a special name.", "start": 815.41, "duration": 2.35}, {"text": "It's called the anticodon loop.", "start": 817.76, "duration": 2.54}, {"text": "It comprises three\nnucleotides that", "start": 820.3, "duration": 3.6}, {"text": "are complementary to the\nnucleotides in your messenger", "start": 823.9, "duration": 5.07}, {"text": "sequence.", "start": 828.97, "duration": 1.08}, {"text": "So this really is a decoder\nbecause, at one end,", "start": 830.05, "duration": 2.85}, {"text": "it's carrying an\namino acid, but it's", "start": 832.9, "duration": 2.25}, {"text": "carrying the amino\nacid that corresponds", "start": 835.15, "duration": 3.45}, {"text": "to the code that's in the\nmessenger via that anticodon", "start": 838.6, "duration": 4.23}, {"text": "loop.", "start": 842.83, "duration": 0.63}, {"text": "So it's a large structure,\nbut don't mistake it", "start": 843.46, "duration": 2.88}, {"text": "for being something\nthat's just sort", "start": 846.34, "duration": 1.77}, {"text": "of amino acid and anticodon.", "start": 848.11, "duration": 2.19}, {"text": "A lot goes on with the\nrest of the structure.", "start": 850.3, "duration": 2.22}, {"text": "It's a very important structure\nin the mechanisms of protein", "start": 852.52, "duration": 4.08}, {"text": "translation and synthesis.", "start": 856.6, "duration": 2.76}, {"text": "OK, so here I've got to sum\nthat up with a couple more", "start": 859.36, "duration": 4.83}, {"text": "of the ways that you would\nsee the transfer RNAs.", "start": 864.19, "duration": 3.48}, {"text": "You might see it in\nthis globular form.", "start": 867.67, "duration": 2.22}, {"text": "And I pointed out\nthe anticodon loop.", "start": 869.89, "duration": 3.03}, {"text": "The place where the\namino acid gets linked", "start": 872.92, "duration": 2.67}, {"text": "is also called\nthe acceptor stem.", "start": 875.59, "duration": 2.52}, {"text": "And, up here, I show\nyou that linkage.", "start": 878.11, "duration": 2.91}, {"text": "And you should-- yes?", "start": 881.02, "duration": 1.36}, {"text": "AUDIENCE: I was\njust going to ask,", "start": 882.38, "duration": 1.417}, {"text": "I see how the anticodons\nare specialized.", "start": 883.797, "duration": 3.088}, {"text": "How does the 3 prime\nend of the tRNA", "start": 886.885, "duration": 3.558}, {"text": "know which protein is bound?", "start": 890.443, "duration": 1.167}, {"text": "BARBARA IMPERIALI: Yeah, and,\nin a moment, not quite yet,", "start": 891.61, "duration": 2.55}, {"text": "I will show you\nstructures of tRNAs", "start": 894.16, "duration": 2.55}, {"text": "bound to their\nsynthetases, which", "start": 896.71, "duration": 2.82}, {"text": "are the enzymes that load them.", "start": 899.53, "duration": 1.63}, {"text": "So there is specificity\nthroughout that whole thing.", "start": 901.16, "duration": 2.84}, {"text": "It's not just\nbystander stuffing.", "start": 904.0, "duration": 2.89}, {"text": "It's really involved.", "start": 906.89, "duration": 1.56}, {"text": "And it's a great\nquestion, and I hope", "start": 908.45, "duration": 2.27}, {"text": "you'll get an answer\nthat's reasonably satisfied", "start": 910.72, "duration": 2.43}, {"text": "from the structure perspective.", "start": 913.15, "duration": 2.14}, {"text": "And so, if you look up\nhere at the acceptor stem,", "start": 915.29, "duration": 3.83}, {"text": "the amino acid is\njoined by an ester bond", "start": 919.12, "duration": 2.79}, {"text": "to the 3 prime end\nof the transfer RNA,", "start": 921.91, "duration": 4.68}, {"text": "but, hopefully, you\ncan see in here.", "start": 926.59, "duration": 1.53}, {"text": "There's the carboxyl.", "start": 928.12, "duration": 1.92}, {"text": "There's the amine.", "start": 930.04, "duration": 1.23}, {"text": "And CHR designates\nthe amino acid", "start": 931.27, "duration": 3.63}, {"text": "where R would be the side\nchain of your amino acid.", "start": 934.9, "duration": 3.09}, {"text": "So that's what that looks like\nat that end of the transfer", "start": 937.99, "duration": 2.67}, {"text": "RNA.", "start": 940.66, "duration": 0.93}, {"text": "And, coming down to\nthe anticodon loop,", "start": 941.59, "duration": 2.97}, {"text": "you're going to read the\nmessenger 5 prime to 3 prime.", "start": 944.56, "duration": 4.86}, {"text": "And the anticodon\nloop, when you draw", "start": 949.42, "duration": 2.97}, {"text": "this in this\nconfiguration, actually", "start": 952.39, "duration": 2.28}, {"text": "shows you that\nthe anticodon loop", "start": 954.67, "duration": 3.21}, {"text": "is antiparallel\nto the codon loop", "start": 957.88, "duration": 2.85}, {"text": "to make that good\nhydrogen-bonding network.", "start": 960.73, "duration": 2.92}, {"text": "So that's why I like to\nbe consistent in the way I", "start": 963.65, "duration": 3.14}, {"text": "render this structure.", "start": 966.79, "duration": 1.44}, {"text": "So the anticodon loop of the RNA\ncomplements that triplet codon", "start": 968.23, "duration": 4.965}, {"text": "in the messenger RNA, all right?", "start": 973.195, "duration": 2.355}, {"text": "Yes?", "start": 975.55, "duration": 0.856}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 976.406, "duration": 1.488}, {"text": "What's between the G and T?", "start": 977.894, "duration": 1.499}, {"text": "BARBARA IMPERIALI: What's\nbetween the G and T?", "start": 979.393, "duration": 1.917}, {"text": "Hold on.", "start": 981.31, "duration": 0.5}, {"text": "I'm going to-- what's\nbetween the G and the--", "start": 981.81, "duration": 3.472}, {"text": "AUDIENCE: On the loop there.", "start": 985.282, "duration": 1.247}, {"text": "BARBARA IMPERIALI: Over here?", "start": 986.529, "duration": 1.208}, {"text": "AUDIENCE: No, above\nthat on the left.", "start": 987.737, "duration": 1.193}, {"text": "BARBARA IMPERIALI: On the left.", "start": 988.93, "duration": 1.292}, {"text": "Oh, this guy?", "start": 990.222, "duration": 2.518}, {"text": "So cool you ask that.", "start": 992.74, "duration": 1.44}, {"text": "So this guy is what's\nknown as a funny base.", "start": 994.18, "duration": 4.44}, {"text": "It's actually-- that's\nthe symbol for it", "start": 998.62, "duration": 4.262}, {"text": "that you've picked out.", "start": 1002.882, "duration": 0.958}, {"text": "And it's a base known\nas pseudouridine.", "start": 1003.84, "duration": 2.37}, {"text": "And it turns out that\nthese unusual bases show up", "start": 1010.92, "duration": 5.1}, {"text": "in RNA sequences.", "start": 1016.02, "duration": 2.19}, {"text": "Pseudouridine has an\ninteresting structure", "start": 1018.21, "duration": 2.82}, {"text": "where the bond to\nthe ribose ring", "start": 1021.03, "duration": 3.45}, {"text": "is not a carbon-nitrogen\nbond, but, rather,", "start": 1024.48, "duration": 2.46}, {"text": "a carbon-carbon bond.", "start": 1026.94, "duration": 1.02}, {"text": "And it's a bit more stable.", "start": 1027.96, "duration": 1.5}, {"text": "So, in RNA, there's some of\nthese other unusual bases.", "start": 1029.46, "duration": 4.23}, {"text": "And pseudouridine is the most\ncommon of the unusual ones.", "start": 1033.69, "duration": 3.81}, {"text": "It can still\nhydrogen bond, but it", "start": 1037.5, "duration": 2.13}, {"text": "tends to show up in these\nsort of different loops", "start": 1039.63, "duration": 3.239}, {"text": "and turn-type places, OK?", "start": 1042.869, "duration": 1.658}, {"text": "Thanks for noticing that.", "start": 1044.527, "duration": 1.042}, {"text": "Yeah?", "start": 1045.569, "duration": 0.658}, {"text": "AUDIENCE: So do you get\nthe G in parentheses", "start": 1046.227, "duration": 1.833}, {"text": "on the yellow part [INAUDIBLE]?", "start": 1048.06, "duration": 1.58}, {"text": "BARBARA IMPERIALI: The G,\nwhich is in parentheses,", "start": 1049.64, "duration": 2.32}, {"text": "designates that even\nthose sort of bulges", "start": 1051.96, "duration": 3.0}, {"text": "between the real loops\ncan vary in length.", "start": 1054.96, "duration": 2.85}, {"text": "So it could be more than one.", "start": 1057.81, "duration": 1.68}, {"text": "So that addresses-- comes\nback to that other question.", "start": 1059.49, "duration": 2.63}, {"text": "But that stuff in\nbetween has variables.", "start": 1062.12, "duration": 2.8}, {"text": "It has variable bulges and\nvariable shapes associated", "start": 1064.92, "duration": 6.0}, {"text": "with the synthetase enzymes\nthat I'll introduce in a minute", "start": 1070.92, "duration": 3.09}, {"text": "that it recognizes,\nall great questions.", "start": 1074.01, "duration": 2.67}, {"text": "OK, all right, cool.", "start": 1076.68, "duration": 4.48}, {"text": "OK, so [HUMMING]\nwe've got all of that.", "start": 1081.16, "duration": 5.13}, {"text": "So now let's move ourselves\nso we've looked at--", "start": 1086.29, "duration": 4.01}, {"text": "we know the messenger well.", "start": 1090.3, "duration": 1.95}, {"text": "We're starting to\nunderstand the tRNAs.", "start": 1092.25, "duration": 2.49}, {"text": "What we need to\nmove on to now is", "start": 1094.74, "duration": 2.22}, {"text": "sort of the most important\npart of the game, which", "start": 1096.96, "duration": 2.64}, {"text": "is really taking a look\nat the genetic code.", "start": 1099.6, "duration": 3.76}, {"text": "So this table is but one\nrendition of the genetic code.", "start": 1103.36, "duration": 7.118}, {"text": "Sometimes, you'll see it in\ndifferent shapes and sizes.", "start": 1110.478, "duration": 2.292}, {"text": "In a second, I'll show you\none of the other renditions.", "start": 1112.77, "duration": 2.79}, {"text": "But it is the absolute--", "start": 1115.56, "duration": 2.37}, {"text": "the sort of Rosetta\nStone for translating", "start": 1117.93, "duration": 13.01}, {"text": "messenger RNA to amino\nacid sequence using codons.", "start": 1130.94, "duration": 8.52}, {"text": "So this sort of-- whoa.", "start": 1139.46, "duration": 3.66}, {"text": "Getting a little--\nI love translation.", "start": 1143.12, "duration": 1.77}, {"text": "I'm sorry.", "start": 1144.89, "duration": 0.24}, {"text": "I'm getting a little bit\nexcited about translation.", "start": 1145.13, "duration": 2.125}, {"text": "OK, so there are a few\nfeatures of this genetic code.", "start": 1147.255, "duration": 4.445}, {"text": "Number one, you won't\nhave to remember it.", "start": 1151.7, "duration": 2.07}, {"text": "It would be foolish for\nus to think you could,", "start": 1153.77, "duration": 2.19}, {"text": "but there are characteristics\nabout the genetic code that", "start": 1155.96, "duration": 3.0}, {"text": "are very important.", "start": 1158.96, "duration": 0.88}, {"text": "But, first of all, let\nme sort of calibrate you.", "start": 1159.84, "duration": 2.27}, {"text": "This would be the first of the\nthree letters in the codon.", "start": 1162.11, "duration": 4.2}, {"text": "And, by the way,\nthe genetic code", "start": 1166.31, "duration": 2.22}, {"text": "gives you the\nidentities of what are", "start": 1168.53, "duration": 2.91}, {"text": "known as the codons,\nwhich is how we designate", "start": 1171.44, "duration": 6.51}, {"text": "the triplet of nucleotides.", "start": 1177.95, "duration": 2.34}, {"text": "So you'll hear a lot about\ncodons and anticodons", "start": 1184.72, "duration": 2.96}, {"text": "of course.", "start": 1187.68, "duration": 1.05}, {"text": "So the way you read this table\nis you read the first letter.", "start": 1188.73, "duration": 4.8}, {"text": "So all of these begin with\nU. All of these begin with C", "start": 1193.53, "duration": 3.63}, {"text": "and so on.", "start": 1197.16, "duration": 1.08}, {"text": "Then you read the second letter,\nand there's those designations.", "start": 1198.24, "duration": 4.47}, {"text": "So, if I'm going here, here,\nit's going to be starting UU.", "start": 1202.71, "duration": 4.71}, {"text": "And then, within\neach block, there", "start": 1207.42, "duration": 1.89}, {"text": "are the four alternatives\nfor the other four bases.", "start": 1209.31, "duration": 4.38}, {"text": "And then the third\none, basically,", "start": 1213.69, "duration": 2.43}, {"text": "just designates those.", "start": 1216.12, "duration": 1.74}, {"text": "So you can read, for each amino\nacid, what three-letter codon", "start": 1217.86, "duration": 4.59}, {"text": "would correspond to it.", "start": 1222.45, "duration": 1.72}, {"text": "Some people quite like--", "start": 1224.17, "duration": 1.68}, {"text": "oops.", "start": 1225.85, "duration": 1.26}, {"text": "I got rid of it too fast.", "start": 1227.11, "duration": 1.49}, {"text": "Some people quite like\nthis other rendition", "start": 1228.6, "duration": 2.82}, {"text": "where the first of the three\nletters is in the center.", "start": 1231.42, "duration": 3.74}, {"text": "So it's either G, U, A, or C.\nThen the second one comes out.", "start": 1235.16, "duration": 4.96}, {"text": "It's in the brown circle.", "start": 1240.12, "duration": 2.34}, {"text": "And then the third one is the\nthird letter in the codon.", "start": 1242.46, "duration": 5.19}, {"text": "And then that tells you what\namino acid that corresponds to.", "start": 1247.65, "duration": 3.99}, {"text": "And we'll generally tend to\njust stick with this one table", "start": 1251.64, "duration": 4.75}, {"text": "and stick with it.", "start": 1256.39, "duration": 1.2}, {"text": "So you might as well get used\nto that particular table.", "start": 1257.59, "duration": 3.53}, {"text": "Now there's a couple of\ncharacteristics in the table.", "start": 1261.12, "duration": 3.63}, {"text": "The first thing to notice\nis that, within that table,", "start": 1264.75, "duration": 3.78}, {"text": "there is a codon to start.", "start": 1268.53, "duration": 3.6}, {"text": "And it's AUG.", "start": 1272.13, "duration": 1.38}, {"text": "And the one thing that's sort\nof sent to drive you crazy", "start": 1273.51, "duration": 3.21}, {"text": "is that AUG codon equals start,\nbut it also equals methionine.", "start": 1276.72, "duration": 12.24}, {"text": "And, in bacteria, it equals a\nmodified version of methionine.", "start": 1288.96, "duration": 4.68}, {"text": "So, if the ribosome is\nreading the messenger RNA,", "start": 1293.64, "duration": 4.05}, {"text": "it will look for the first one\nof these and start reading.", "start": 1297.69, "duration": 4.41}, {"text": "But, once you find another\none of these further", "start": 1302.1, "duration": 2.37}, {"text": "into the sequence, it\nwill put in methionine.", "start": 1304.47, "duration": 2.79}, {"text": "Methionine is fairly rare.", "start": 1307.26, "duration": 1.38}, {"text": "There may only be one or\ntwo more in the protein.", "start": 1308.64, "duration": 2.6}, {"text": "And I hate the illogic of\nthat, but, nevertheless, it", "start": 1311.24, "duration": 3.55}, {"text": "is the case.", "start": 1314.79, "duration": 1.23}, {"text": "In some organisms, you start\nwith different amino acids,", "start": 1316.02, "duration": 3.1}, {"text": "but the most common start\nis the codon for methionine", "start": 1319.12, "duration": 3.68}, {"text": "is the start.", "start": 1322.8, "duration": 0.97}, {"text": "So what that means is that\nevery protein you translate", "start": 1323.77, "duration": 3.5}, {"text": "has a methionine at\none of the termini.", "start": 1327.27, "duration": 2.1}, {"text": "Which terminus would it be at?", "start": 1329.37, "duration": 1.81}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1331.18, "duration": 0.98}, {"text": "BARBARA IMPERIALI:\nYeah, OK, so that's", "start": 1332.16, "duration": 7.89}, {"text": "the details with methionine\nand the start codon.", "start": 1340.05, "duration": 3.6}, {"text": "Then there are\nseveral stop codons.", "start": 1343.65, "duration": 2.85}, {"text": "And I've shown you the\nthree of them there.", "start": 1346.5, "duration": 2.58}, {"text": "The stop codons tend\nto be used variously.", "start": 1349.08, "duration": 2.97}, {"text": "Some are more predominant in\nsome organisms than other.", "start": 1352.05, "duration": 3.57}, {"text": "And some of them\nrespond differently", "start": 1355.62, "duration": 2.34}, {"text": "when the process of\nstopping occurs, which", "start": 1357.96, "duration": 2.13}, {"text": "we'll talk about in a second.", "start": 1360.09, "duration": 1.89}, {"text": "But the next important thing to\nnotice about the genetic code", "start": 1361.98, "duration": 5.95}, {"text": "is that it's what's\ncalled degenerate.", "start": 1367.93, "duration": 2.03}, {"text": "Now, when you call\nsomething degenerate,", "start": 1376.323, "duration": 1.667}, {"text": "it seems like sort of a really\nnasty thing to call them.", "start": 1377.99, "duration": 2.333}, {"text": "And it doesn't mean,\noh, it's so bad.", "start": 1380.323, "duration": 2.137}, {"text": "It's just a degenerate.", "start": 1382.46, "duration": 1.05}, {"text": "It just means it is\nspecific, but it's not--", "start": 1383.51, "duration": 5.117}, {"text": "wait a minute.", "start": 1388.627, "duration": 0.583}, {"text": "I've got the right wording\nhere because I always", "start": 1389.21, "duration": 2.0}, {"text": "get this sort of--", "start": 1391.21, "duration": 1.18}, {"text": "degenerate, ah,\nit's not ambiguous.", "start": 1392.39, "duration": 6.0}, {"text": "It's degenerate.", "start": 1398.39, "duration": 1.423}, {"text": "That's the best thing.", "start": 1399.813, "duration": 0.917}, {"text": "But it's not ambiguous.", "start": 1400.73, "duration": 2.95}, {"text": "What this means\nis there are all,", "start": 1406.57, "duration": 2.19}, {"text": "for several amino acids, more\nthan one codon that specify it.", "start": 1408.76, "duration": 4.35}, {"text": "And let's take a look\nat some of the examples", "start": 1418.9, "duration": 2.8}, {"text": "of that degeneracy.", "start": 1421.7, "duration": 1.66}, {"text": "It's at its most\nextreme with residues", "start": 1423.36, "duration": 3.17}, {"text": "such as leucine where there\nare six codons that specify", "start": 1426.53, "duration": 3.96}, {"text": "leucine.", "start": 1430.49, "duration": 1.71}, {"text": "Alanine has four\ndifferent codons.", "start": 1432.2, "duration": 2.88}, {"text": "They all specify alanine.", "start": 1435.08, "duration": 2.55}, {"text": "Lysine has two codons.", "start": 1437.63, "duration": 2.13}, {"text": "And it's generally appreciated\nthat the residues that", "start": 1439.76, "duration": 3.09}, {"text": "have more codons tend to be the\nmore common in your messenger", "start": 1442.85, "duration": 4.5}, {"text": "RNAs, in your final protein\nsequence, because you'll find,", "start": 1447.35, "duration": 3.96}, {"text": "in your protein,\na lot of leucines.", "start": 1451.31, "duration": 2.62}, {"text": "So we need a few more codons\nto stack the deck in favor", "start": 1453.93, "duration": 3.62}, {"text": "of putting in more leucines.", "start": 1457.55, "duration": 2.17}, {"text": "But so it's ambiguous--", "start": 1459.72, "duration": 1.89}, {"text": "it's degenerate.", "start": 1461.61, "duration": 2.0}, {"text": "But, what I mean by\nit's not ambiguous,", "start": 1463.61, "duration": 2.4}, {"text": "you know what it's\ngoing to code for.", "start": 1466.01, "duration": 2.67}, {"text": "The other place where degenerate\ncodons can become important", "start": 1468.68, "duration": 5.01}, {"text": "is that there is\nspecies specificity.", "start": 1473.69, "duration": 2.22}, {"text": "So I'm going to write that in\nhere and explain what I mean.", "start": 1479.582, "duration": 2.458}, {"text": "And what that means is that\nsome organisms might prefer", "start": 1487.51, "duration": 4.17}, {"text": "two or three of the\ndegenerate codons,", "start": 1491.68, "duration": 2.64}, {"text": "and others may prefer\na couple of the others.", "start": 1494.32, "duration": 2.79}, {"text": "And what that means,\nonce in the laboratory,", "start": 1497.11, "duration": 2.37}, {"text": "is it's really\nannoying if we want", "start": 1499.48, "duration": 2.01}, {"text": "to express a protein in a really\nconvenient bacterial system", "start": 1501.49, "duration": 4.16}, {"text": "that we've taken from\na mammalian system.", "start": 1505.65, "duration": 2.38}, {"text": "Our codon mix may\nnot be the same.", "start": 1508.03, "duration": 3.18}, {"text": "And so there are\ncompanies now that", "start": 1511.21, "duration": 2.28}, {"text": "actually will fix the\ncodons in a gene for you", "start": 1513.49, "duration": 3.18}, {"text": "to make them compatible\nwith a different organism", "start": 1516.67, "duration": 2.88}, {"text": "for expression.", "start": 1519.55, "duration": 0.9}, {"text": "So it has huge\npractical implications", "start": 1520.45, "duration": 2.13}, {"text": "to be quite honest.", "start": 1522.58, "duration": 1.41}, {"text": "And it can be very\nannoying in the laboratory.", "start": 1523.99, "duration": 3.94}, {"text": "OK, and then so codon usage\nvaries amongst organisms.", "start": 1527.93, "duration": 6.77}, {"text": "All right, so now, one\nlast thing, so we've", "start": 1534.7, "duration": 3.15}, {"text": "talked about the genetic code.", "start": 1537.85, "duration": 3.68}, {"text": "It's the code that's going to\nbe embedded within the messenger", "start": 1541.53, "duration": 3.69}, {"text": "RNA.", "start": 1545.22, "duration": 2.22}, {"text": "The last thing I want to do\nis, basically, explain to you", "start": 1547.44, "duration": 3.03}, {"text": "one more time,\nwhen you're looking", "start": 1550.47, "duration": 1.86}, {"text": "to read what your amino\nacids that get put in", "start": 1552.33, "duration": 2.61}, {"text": "may be, you're going\nto look at the codon.", "start": 1554.94, "duration": 2.58}, {"text": "And it will tell you\nexactly the amino acid.", "start": 1557.52, "duration": 3.53}, {"text": "A long time ago, I\nused to be confused", "start": 1561.05, "duration": 2.29}, {"text": "because I thought I should\nbe looking at the anticodon.", "start": 1563.34, "duration": 2.31}, {"text": "And I was trying to\ntranslate everything,", "start": 1565.65, "duration": 1.772}, {"text": "and it was a real mess.", "start": 1567.422, "duration": 0.958}, {"text": "But it's the genetic\ncode in that box", "start": 1568.38, "duration": 2.31}, {"text": "that I just showed\nyou is written down", "start": 1570.69, "duration": 2.07}, {"text": "for maximum clarity\nand ease of use.", "start": 1572.76, "duration": 3.72}, {"text": "So, whenever you see a\nparticular three-letter code", "start": 1576.48, "duration": 3.84}, {"text": "on the messenger,\nyou will then be", "start": 1580.32, "duration": 2.37}, {"text": "able to know what amino\nacid it would code.", "start": 1582.69, "duration": 3.06}, {"text": "So this is kind of interesting.", "start": 1585.75, "duration": 1.57}, {"text": "It just reinforces to you that\nthe codon and the anticodon", "start": 1587.32, "duration": 4.48}, {"text": "are antiparallel.", "start": 1591.8, "duration": 2.12}, {"text": "And so what I want to do is,\nbasically, in this diagram,", "start": 1593.92, "duration": 3.57}, {"text": "you would be reading from the\n5 prime to the 3 prime end,", "start": 1597.49, "duration": 4.13}, {"text": "as the transfer RNAs attach\nto the messenger RNA.", "start": 1601.62, "duration": 4.2}, {"text": "And that would give you a\ncodon here that would be AUC.", "start": 1605.82, "duration": 5.49}, {"text": "If you'd written this\nthe wrong way round,", "start": 1611.31, "duration": 1.95}, {"text": "it would look like CUA.", "start": 1613.26, "duration": 1.41}, {"text": "So you really want to be\nreading 5 prime to 3 prime", "start": 1614.67, "duration": 2.91}, {"text": "in the codon.", "start": 1617.58, "duration": 1.12}, {"text": "And then you can go to your\nfavorite genetic code map", "start": 1618.7, "duration": 3.29}, {"text": "and say this thing is\nread 5 prime to 3 prime.", "start": 1621.99, "duration": 3.09}, {"text": "And the amino acid that gets\nput in is isoleucine, OK?", "start": 1625.08, "duration": 5.61}, {"text": "So you'll need to be able\nto do that quite readily.", "start": 1630.69, "duration": 4.56}, {"text": "All right, next\nportion, those monster--", "start": 1635.25, "duration": 4.53}, {"text": "loading the amino acid.", "start": 1639.78, "duration": 1.68}, {"text": "OK, so, as I said, this is a\nmany building block, many parts", "start": 1641.46, "duration": 3.46}, {"text": "thing.", "start": 1644.92, "duration": 0.5}, {"text": "So we've got the transfer RNAs.", "start": 1645.42, "duration": 1.56}, {"text": "We know where we load\nthem onto the amino acids.", "start": 1646.98, "duration": 4.56}, {"text": "We know where we load the amino\nacids onto the transfer RNA.", "start": 1651.54, "duration": 4.08}, {"text": "But we do not know\nhow that is done.", "start": 1655.62, "duration": 2.4}, {"text": "So I want to show you\nbriefly how that occurs.", "start": 1658.02, "duration": 2.82}, {"text": "So let me just start by\ndrawing transfer RNAs the way", "start": 1660.84, "duration": 4.89}, {"text": "I usually draw them in a\nvery sort of cartoon form.", "start": 1665.73, "duration": 8.48}, {"text": "And, to attach an amino acid to\nthe 3 prime end of the transfer", "start": 1674.21, "duration": 6.24}, {"text": "RNA, you have an\namino acid residue--", "start": 1680.45, "duration": 3.93}, {"text": "we're just going to go R here--", "start": 1684.38, "duration": 2.975}, {"text": "carboxylic acid, amine.", "start": 1687.355, "duration": 3.475}, {"text": "Actually, I'm going to draw them\nin their appropriate charged", "start": 1690.83, "duration": 3.3}, {"text": "states.", "start": 1694.13, "duration": 1.1}, {"text": "And what I need to be\nable to do is faithfully", "start": 1695.23, "duration": 2.74}, {"text": "fix this amino acid to the 3\nprime OH of the transfer RNA.", "start": 1697.97, "duration": 7.67}, {"text": "And what we do is\nwe need adenosine", "start": 1705.64, "duration": 2.61}, {"text": "triphosphate to\nactivate this chemistry.", "start": 1708.25, "duration": 5.82}, {"text": "And then the OH at the 3 prime\nend reacts with the amino acid.", "start": 1714.07, "duration": 5.698}, {"text": "So I'm just going to draw that.", "start": 1719.768, "duration": 1.292}, {"text": "I'm leaving out steps because,\notherwise, it's too many,", "start": 1721.06, "duration": 3.93}, {"text": "and you'll be cross with me.", "start": 1724.99, "duration": 1.41}, {"text": "So you attach through an\nester to the amino acid", "start": 1739.08, "duration": 3.84}, {"text": "from the 3 prime end\nof these transfer RNA.", "start": 1742.92, "duration": 3.69}, {"text": "That's what's done.", "start": 1746.61, "duration": 1.08}, {"text": "The ATP makes this\nchemistry feasible,", "start": 1747.69, "duration": 2.82}, {"text": "but there's one\nmore player here.", "start": 1750.51, "duration": 2.06}, {"text": "And that's the enzyme that\nbrings them all together,", "start": 1752.57, "duration": 2.99}, {"text": "which is known as an\naminoacyl-tRNA synthetase,", "start": 1755.56, "duration": 16.04}, {"text": "meaning it's an enzyme that\nmakes an aminoacyl-tRNA.", "start": 1771.6, "duration": 5.28}, {"text": "And it synthetases it.", "start": 1776.88, "duration": 1.39}, {"text": "So that's how its\nname gets subtracted.", "start": 1778.27, "duration": 3.42}, {"text": "So, with reference to an earlier\nquestion, what I'm showing", "start": 1781.69, "duration": 3.68}, {"text": "you here are\ndifferent synthetases", "start": 1785.37, "duration": 2.64}, {"text": "for different amino\nacids that show you", "start": 1788.01, "duration": 2.67}, {"text": "that there's a recognition\nnot just for the amino acid", "start": 1790.68, "duration": 3.45}, {"text": "that's being\nloaded, but, rather,", "start": 1794.13, "duration": 1.47}, {"text": "for the entire transfer RNA.", "start": 1795.6, "duration": 2.5}, {"text": "So some of these\nlook quite different.", "start": 1798.1, "duration": 2.18}, {"text": "The isoleucine one\ninteracts in one way.", "start": 1800.28, "duration": 4.17}, {"text": "The valine one is\na little different.", "start": 1804.45, "duration": 2.13}, {"text": "And the glutamine one\nis different again.", "start": 1806.58, "duration": 2.28}, {"text": "So they vary in the way they\ninteract with the transfer", "start": 1808.86, "duration": 4.77}, {"text": "RNAs.", "start": 1813.63, "duration": 0.55}, {"text": "So the transfer\nRNAs are specific", "start": 1814.18, "duration": 2.57}, {"text": "for the amino acid that\nis loaded onto them,", "start": 1816.75, "duration": 2.91}, {"text": "but also for the synthetase\nthat does the loading.", "start": 1819.66, "duration": 3.18}, {"text": "That's how you get\nthe specificity.", "start": 1822.84, "duration": 2.1}, {"text": "Does that address your\nquestion from earlier?", "start": 1824.94, "duration": 3.0}, {"text": "Hello?", "start": 1827.94, "duration": 0.54}, {"text": "OK.", "start": 1828.48, "duration": 1.36}, {"text": "That makes sense, right?", "start": 1829.84, "duration": 1.0}, {"text": "So they fall into a lot\nof different families,", "start": 1830.84, "duration": 2.92}, {"text": "but they're quite\nvaried when you", "start": 1833.76, "duration": 1.71}, {"text": "look at specific interactions\nbetween the synthetase", "start": 1835.47, "duration": 3.3}, {"text": "and the amino acid.", "start": 1838.77, "duration": 1.34}, {"text": "And, on those synthetases,\nthere will also", "start": 1840.11, "duration": 2.71}, {"text": "be specificity for\nthe amino acid side", "start": 1842.82, "duration": 3.6}, {"text": "chain of the amino\nacid that gets loaded.", "start": 1846.42, "duration": 3.96}, {"text": "Now let's look at the\nribosome components", "start": 1850.38, "duration": 2.28}, {"text": "because they're the\nlast big monsters.", "start": 1852.66, "duration": 2.73}, {"text": "Ribosomes have a\nsmall and a large--", "start": 1855.39, "duration": 5.19}, {"text": "that's the large\nand a small subunit.", "start": 1860.58, "duration": 2.76}, {"text": "They are made up, as\nI mentioned over here,", "start": 1863.34, "duration": 3.54}, {"text": "of RNA and protein, so\nsmall and large subunits.", "start": 1866.88, "duration": 10.82}, {"text": "And I've shown them there\nin two different colors.", "start": 1877.7, "duration": 3.52}, {"text": "The prokaryotic\nribosomes are pretty", "start": 1881.22, "duration": 2.79}, {"text": "different from the\neukaryotic ones.", "start": 1884.01, "duration": 2.16}, {"text": "There's a higher\nproportion of RNA", "start": 1886.17, "duration": 3.0}, {"text": "in the prokaryotic ones than\nthe eukaryotic ones, which", "start": 1889.17, "duration": 3.54}, {"text": "is kind of interesting.", "start": 1892.71, "duration": 2.02}, {"text": "And these complexes\nare so big, and they're", "start": 1894.73, "duration": 2.24}, {"text": "made up of so many\nprotein and RNA", "start": 1896.97, "duration": 3.0}, {"text": "strands, that we don't\nso much measure them", "start": 1899.97, "duration": 2.58}, {"text": "by the number of\nthose components,", "start": 1902.55, "duration": 2.31}, {"text": "but, rather, by what's\nknown as their sedimentation", "start": 1904.86, "duration": 2.61}, {"text": "coefficient, which gives\nus a sense of the weight", "start": 1907.47, "duration": 3.12}, {"text": "of the module or the complex.", "start": 1910.59, "duration": 2.53}, {"text": "So the small subunit--", "start": 1913.12, "duration": 1.335}, {"text": "oh, he's back [INAUDIBLE].", "start": 1918.26, "duration": 3.59}, {"text": "The small subunit would have a\n30S sedimentation coefficient.", "start": 1921.85, "duration": 5.53}, {"text": "The S stands for Svedberg units.", "start": 1927.38, "duration": 2.63}, {"text": "It's how fast its sediments\nin an ultra centrifuge.", "start": 1930.01, "duration": 3.48}, {"text": "And the large subunit would\nhave a 50S sedimentation", "start": 1933.49, "duration": 4.35}, {"text": "coefficient.", "start": 1937.84, "duration": 1.08}, {"text": "And those correspond to a\ncertain number of daltons.", "start": 1938.92, "duration": 2.88}, {"text": "If you see that S\nterm after a number,", "start": 1941.8, "duration": 3.868}, {"text": "that's what it's talking about.", "start": 1945.668, "duration": 1.292}, {"text": "It's talking about the\nsedimentation coefficient,", "start": 1946.96, "duration": 2.042}, {"text": "which gives us a sense of\nthe size of the complex.", "start": 1949.002, "duration": 2.773}, {"text": "And, when you start to bring\nall the pieces together now,", "start": 1955.14, "duration": 3.81}, {"text": "what we can see on this slide\nis the messenger, the transfer", "start": 1958.95, "duration": 3.87}, {"text": "RNAs, and the ribosomal\nall to scale in such a way", "start": 1962.82, "duration": 5.46}, {"text": "that it can really explain it.", "start": 1968.28, "duration": 1.83}, {"text": "So what I show you here is\nthe small and large subunit.", "start": 1970.11, "duration": 4.47}, {"text": "In orange-- well, that's\nkind of a burnt orange--", "start": 1974.58, "duration": 3.69}, {"text": "is a sneaky little\nbit of the messenger.", "start": 1978.27, "duration": 2.76}, {"text": "In yellow are the transfer RNAs.", "start": 1981.03, "duration": 2.61}, {"text": "And there's one\nmore unit on here", "start": 1983.64, "duration": 1.77}, {"text": "that I won't describe too much.", "start": 1985.41, "duration": 1.92}, {"text": "It's a protein factor that\nhelps all the processes occur.", "start": 1987.33, "duration": 3.9}, {"text": "Generally, it's thought to\nhelp the loaded tRNA come", "start": 1991.23, "duration": 4.38}, {"text": "to the ribosome, get it in\nplace, and then go away.", "start": 1995.61, "duration": 3.18}, {"text": "So it's some of\nthese extra helper", "start": 1998.79, "duration": 1.59}, {"text": "proteins that are involved.", "start": 2000.38, "duration": 1.95}, {"text": "OK, so let's build\na protein because I", "start": 2002.33, "duration": 1.74}, {"text": "know it's the moment we've\nall been waiting for,", "start": 2004.07, "duration": 2.13}, {"text": "and we're going to walk through\nhow those pieces come together.", "start": 2006.2, "duration": 3.57}, {"text": "It's a very clunky animation,\nbut I'm very proud of myself", "start": 2009.77, "duration": 3.09}, {"text": "because I did it myself.", "start": 2012.86, "duration": 1.48}, {"text": "So I'm just going to show\nyou how these things happen,", "start": 2014.34, "duration": 2.36}, {"text": "as you assemble a chunk\nof polypeptide chain", "start": 2016.7, "duration": 3.42}, {"text": "from a messenger.", "start": 2020.12, "duration": 1.19}, {"text": "And so here's the messenger.", "start": 2021.31, "duration": 2.14}, {"text": "It's being read 5\nprime to 3 prime.", "start": 2023.45, "duration": 2.52}, {"text": "What happens, first of all,\nis that the small subunit", "start": 2025.97, "duration": 3.75}, {"text": "kind of floats along,\nlooking for the place that", "start": 2029.72, "duration": 2.76}, {"text": "would be the ribosome binding\nsite that I mentioned here,", "start": 2032.48, "duration": 3.87}, {"text": "and then sliding its way\nto position the start", "start": 2036.35, "duration": 3.57}, {"text": "codon in the right place\nto start the synthesis.", "start": 2039.92, "duration": 3.6}, {"text": "Once that happens,\nthe methionine", "start": 2043.52, "duration": 3.3}, {"text": "that's on its tRNA, the\nstart one, gets into place.", "start": 2046.82, "duration": 4.89}, {"text": "And, at the same time,\nthe large subunit,", "start": 2051.71, "duration": 2.66}, {"text": "completing the ribosome\ncomplex, comes together.", "start": 2054.37, "duration": 3.099}, {"text": "So you now have large and\nsmall ribosomal complexes", "start": 2057.469, "duration": 4.651}, {"text": "stuck onto that messenger,\nready to carry on.", "start": 2062.12, "duration": 3.48}, {"text": "And, in each case,\nyou're translocating", "start": 2065.6, "duration": 2.25}, {"text": "through the messenger RNA.", "start": 2067.85, "duration": 2.619}, {"text": "And, in each step,\nyou're bringing in a tRNA", "start": 2070.469, "duration": 3.531}, {"text": "that's loaded with an amino\nacid where the anticodon", "start": 2074.0, "duration": 4.84}, {"text": "of the amino acid-- and I've\ngot those little letters shown", "start": 2078.84, "duration": 2.51}, {"text": "on the bottom here--", "start": 2081.35, "duration": 1.26}, {"text": "is complementary\nto the codon that's", "start": 2082.61, "duration": 2.85}, {"text": "within the messenger RNA.", "start": 2085.46, "duration": 1.96}, {"text": "So we can start\nbuilding this protein.", "start": 2087.42, "duration": 3.11}, {"text": "AUG is that start codon.", "start": 2090.53, "duration": 1.62}, {"text": "Methionine is the\nfirst amino acid.", "start": 2092.15, "duration": 2.04}, {"text": "And it's always\nat the N-terminus.", "start": 2094.19, "duration": 2.219}, {"text": "Then there's another\namino acid comes in.", "start": 2096.409, "duration": 2.671}, {"text": "The codon was UUU, and that\ncorresponds to phenylalanine.", "start": 2099.08, "duration": 4.47}, {"text": "And then the next\nthing that happens", "start": 2103.55, "duration": 1.86}, {"text": "is there's a movement such\nthat a new bond gets--", "start": 2105.41, "duration": 3.63}, {"text": "a new amide bond is formed\nbetween the methionine", "start": 2109.04, "duration": 3.84}, {"text": "and the phenylalanine.", "start": 2112.88, "duration": 1.14}, {"text": "And that new bond\nis an amide bond.", "start": 2116.96, "duration": 1.96}, {"text": "It's not any of the others.", "start": 2118.92, "duration": 1.32}, {"text": "So you're literally intercepting\nthis complex on the transfer", "start": 2120.24, "duration": 5.12}, {"text": "RNA with the amine\nof a new amino acid.", "start": 2125.36, "duration": 3.128}, {"text": "That's how that comes together.", "start": 2128.488, "duration": 1.292}, {"text": "I'm not going to worry you too\nmuch with the chemical details,", "start": 2129.78, "duration": 3.38}, {"text": "but a lot of them have\nbeen illuminated by having", "start": 2133.16, "duration": 3.15}, {"text": "the structure of the ribosome.", "start": 2136.31, "duration": 1.96}, {"text": "And it shows you, in fact,\nthat it's not proteins that", "start": 2138.27, "duration": 3.71}, {"text": "are catalyzing that reaction.", "start": 2141.98, "duration": 1.59}, {"text": "It's nucleic acids.", "start": 2143.57, "duration": 1.6}, {"text": "So now I'm just going to move\nyou on through the synthesis,", "start": 2145.17, "duration": 3.98}, {"text": "in each case, building\nthat polypeptide chain", "start": 2149.15, "duration": 4.41}, {"text": "and then moving, translocating.", "start": 2153.56, "duration": 3.21}, {"text": "This guy leaves.", "start": 2156.77, "duration": 0.87}, {"text": "The ribosome moves along.", "start": 2157.64, "duration": 1.44}, {"text": "This was a good Saturday\nafternoon's work.", "start": 2162.77, "duration": 3.21}, {"text": "We've got to use\nup all those tRNAs.", "start": 2165.98, "duration": 1.943}, {"text": "It doesn't get interesting\nuntil you get to the end.", "start": 2167.923, "duration": 2.167}, {"text": "So we're using them, but now\nwe come and hit a stop codon.", "start": 2170.09, "duration": 4.35}, {"text": "We have UAG.", "start": 2174.44, "duration": 1.47}, {"text": "So what happens here?", "start": 2175.91, "duration": 1.5}, {"text": "The whole process slows\ndown because you can either", "start": 2177.41, "duration": 4.05}, {"text": "load what's known as\na suppressor tRNA--", "start": 2181.46, "duration": 4.17}, {"text": "that's the one, the magenta\none, that went up there--", "start": 2185.63, "duration": 2.67}, {"text": "or a protein release factor\ncan come in and bind.", "start": 2188.3, "duration": 4.41}, {"text": "But, in either case, there's\nno new amino acid to come in,", "start": 2192.71, "duration": 3.54}, {"text": "and translation\nfinishes and releases", "start": 2196.25, "duration": 3.6}, {"text": "the protein in\nits complete form.", "start": 2199.85, "duration": 4.32}, {"text": "Now the reason I\nwant to differentiate", "start": 2204.17, "duration": 2.61}, {"text": "between the release\nfactor and an RNA that", "start": 2206.78, "duration": 4.38}, {"text": "has the complementary\nstop codon is", "start": 2211.16, "duration": 2.91}, {"text": "because the RNAs that are\nknown as the suppressor RNAs", "start": 2214.07, "duration": 4.17}, {"text": "have now been\ncompletely hijacked", "start": 2218.24, "duration": 2.43}, {"text": "to make an enhanced\ngenetic code where", "start": 2220.67, "duration": 2.88}, {"text": "we can load lots of\ndifferent amino acids using", "start": 2223.55, "duration": 3.42}, {"text": "the suppressor RNAs.", "start": 2226.97, "duration": 1.68}, {"text": "And, if anyone would like\nto chat to me about this,", "start": 2228.65, "duration": 2.4}, {"text": "I'd love to because I think\nit's a fascinating field,", "start": 2231.05, "duration": 2.94}, {"text": "but it's a bit\nbeyond the scope of.", "start": 2233.99, "duration": 2.12}, {"text": "OK, so this entire\nprocess took the following", "start": 2236.11, "duration": 4.18}, {"text": "where you've got small and large\nsubunits, all the elongation", "start": 2240.29, "duration": 3.72}, {"text": "factors and initiation\nand release.", "start": 2244.01, "duration": 2.94}, {"text": "And then, in each\ncase, the energy", "start": 2246.95, "duration": 1.68}, {"text": "is actually not provided by ATP.", "start": 2248.63, "duration": 2.22}, {"text": "It's provided by GTP.", "start": 2250.85, "duration": 2.04}, {"text": "But where ATP is important\nis in loading the amino acids", "start": 2252.89, "duration": 4.23}, {"text": "onto the transfer RNAs.", "start": 2257.12, "duration": 2.17}, {"text": "This occurs at about a rate\nof 20 amino acids per second,", "start": 2259.29, "duration": 4.49}, {"text": "meaning you're reading about\n60 bases per second, which", "start": 2263.78, "duration": 5.43}, {"text": "is pretty consistent with\nthe rate of transcription,", "start": 2269.21, "duration": 3.54}, {"text": "not the rate of replication.", "start": 2272.75, "duration": 1.5}, {"text": "That's far faster.", "start": 2274.25, "duration": 2.13}, {"text": "OK, sometimes, when you're\nmaking a lot of a protein,", "start": 2276.38, "duration": 4.02}, {"text": "you will see that ribosomes\nline up on the messenger RNA.", "start": 2280.4, "duration": 5.52}, {"text": "And you'll have\nmany proteins being", "start": 2285.92, "duration": 1.68}, {"text": "made at once and at\ndifferent stages in the game.", "start": 2287.6, "duration": 3.0}, {"text": "And this is a lovely electron\nmicrograph that actually", "start": 2290.6, "duration": 3.21}, {"text": "shows this process in action.", "start": 2293.81, "duration": 2.16}, {"text": "And, when you have a lot of\nribosomes on one messenger,", "start": 2295.97, "duration": 3.18}, {"text": "we call them polysomes.", "start": 2299.15, "duration": 1.41}, {"text": "They have that name.", "start": 2300.56, "duration": 1.2}, {"text": "OK, good, all right, so\nwhat I want to do now-- so", "start": 2301.76, "duration": 5.22}, {"text": "does everyone feel\ngood about how", "start": 2306.98, "duration": 1.41}, {"text": "you translate a messenger into\na protein and the various moving", "start": 2308.39, "duration": 4.14}, {"text": "parts?", "start": 2312.53, "duration": 0.96}, {"text": "You would always know the\namino acid structures,", "start": 2313.49, "duration": 2.58}, {"text": "have the genetic code.", "start": 2316.07, "duration": 1.56}, {"text": "Just be familiar with\nreading it and making", "start": 2317.63, "duration": 2.22}, {"text": "sure you could pick out\nwhich amino acid might", "start": 2319.85, "duration": 3.18}, {"text": "be incorporated in response\nto which particular codon.", "start": 2323.03, "duration": 4.56}, {"text": "So, when proteins are\nmade on the ribosome,", "start": 2327.59, "duration": 2.43}, {"text": "they have a bit of a choice.", "start": 2330.02, "duration": 1.48}, {"text": "They can get made\nand fold beautifully", "start": 2331.5, "duration": 2.42}, {"text": "into active proteins.", "start": 2333.92, "duration": 2.01}, {"text": "Those proteins\ncould be modified.", "start": 2335.93, "duration": 1.64}, {"text": "They could go to different\nplaces in the cell.", "start": 2337.57, "duration": 2.95}, {"text": "Occasionally, proteins misfold.", "start": 2340.52, "duration": 2.49}, {"text": "Maybe the rate of\nsynthesis is too fast,", "start": 2343.01, "duration": 2.37}, {"text": "or the environment isn't right.", "start": 2345.38, "duration": 1.86}, {"text": "So there will need to be\nmechanisms whereby proteins", "start": 2347.24, "duration": 3.51}, {"text": "get degraded if they're\nnot folded properly,", "start": 2350.75, "duration": 2.91}, {"text": "but that's the story\nfor another day.", "start": 2353.66, "duration": 1.95}, {"text": "It's not always perfect,\nbut what is known now", "start": 2355.61, "duration": 3.27}, {"text": "is that, as proteins are\nemerging from the ribosome,", "start": 2358.88, "duration": 3.06}, {"text": "they're starting to\nfold almost immediately", "start": 2361.94, "duration": 3.06}, {"text": "from that N-terminus\nto, ultimately,", "start": 2365.0, "duration": 2.79}, {"text": "attain their compact shape.", "start": 2367.79, "duration": 2.01}, {"text": "The last thing I\nwant to talk to you", "start": 2369.8, "duration": 1.5}, {"text": "about today is\nwhat happens-- what", "start": 2371.3, "duration": 2.79}, {"text": "are the types of errors\nwe get in translation.", "start": 2374.09, "duration": 3.55}, {"text": "Now translation, like\ntranscription and regulation,", "start": 2377.64, "duration": 3.53}, {"text": "has some editing\nmechanisms to fix errors,", "start": 2381.17, "duration": 3.3}, {"text": "but, occasionally, there\nare errors in the DNA that", "start": 2384.47, "duration": 3.12}, {"text": "put different amino acids.", "start": 2387.59, "duration": 2.16}, {"text": "And the editing at that stage,\nby the way, to fix errors", "start": 2389.75, "duration": 4.44}, {"text": "is editing when you've\nloaded the wrong amino acid", "start": 2394.19, "duration": 2.82}, {"text": "onto a tRNA.", "start": 2397.01, "duration": 1.68}, {"text": "But what happens when the\nDNA message, the DNA starting", "start": 2398.69, "duration": 4.5}, {"text": "point, is wrong, which means\nthe messenger is wrong,", "start": 2403.19, "duration": 3.36}, {"text": "which then means we get a\ndifferent translated proteins?", "start": 2406.55, "duration": 4.77}, {"text": "So I'm just going to give\nyou a couple of terms here.", "start": 2411.32, "duration": 3.48}, {"text": "When we have here-- and,\non all these slides,", "start": 2414.8, "duration": 2.94}, {"text": "I'm going to show you\nthe double-stranded DNA.", "start": 2417.74, "duration": 2.58}, {"text": "I'm going to show you the\nmessenger that gets made", "start": 2420.32, "duration": 2.58}, {"text": "and the protein\nthat comes forward.", "start": 2422.9, "duration": 1.56}, {"text": "And they're all lined up so you\ncan follow them really nicely,", "start": 2424.46, "duration": 3.63}, {"text": "always writing 5 prime\nto 3 prime, except when", "start": 2428.09, "duration": 3.18}, {"text": "we have double-stranded\nbecause we", "start": 2431.27, "duration": 1.68}, {"text": "have to put the bottom\nstrand in a different order.", "start": 2432.95, "duration": 3.88}, {"text": "First of all, this\nentire chunk would", "start": 2436.83, "duration": 2.39}, {"text": "be called the reading frame.", "start": 2439.22, "duration": 2.62}, {"text": "It's the portion\nof DNA that's going", "start": 2441.84, "duration": 2.51}, {"text": "to be read and transcribed\ninto the messenger RNA.", "start": 2444.35, "duration": 3.765}, {"text": "And, when you look\nat the two strands,", "start": 2450.93, "duration": 1.803}, {"text": "you're going to have\nto figure out which", "start": 2452.733, "duration": 1.667}, {"text": "one is the template strand.", "start": 2454.4, "duration": 2.16}, {"text": "And you would figure that out\nby knowing that you read 3 prime", "start": 2456.56, "duration": 4.02}, {"text": "to 5 prime, but that you\ntranscribe 5 prime to 3 prime,", "start": 2460.58, "duration": 5.14}, {"text": "right?", "start": 2465.72, "duration": 0.5}, {"text": "So you could recognize\nwhich of the two strands", "start": 2466.22, "duration": 2.93}, {"text": "you're going to make\nthe messenger out of.", "start": 2469.15, "duration": 2.32}, {"text": "Once you get the messenger,\nyou come straight", "start": 2471.47, "duration": 2.31}, {"text": "to the genetic code because\nyou can use the genetic code", "start": 2473.78, "duration": 2.97}, {"text": "to translate each of these.", "start": 2476.75, "duration": 1.59}, {"text": "Does that make sense?", "start": 2478.34, "duration": 1.47}, {"text": "So this would be\na situation where", "start": 2479.81, "duration": 1.44}, {"text": "you have a wild-type enzyme.", "start": 2481.25, "duration": 1.74}, {"text": "Everything is transcribed\nand translated properly.", "start": 2482.99, "duration": 4.53}, {"text": "Occasionally, though,\nthere are errors", "start": 2487.52, "duration": 2.1}, {"text": "that will introduce defects\ninto the ultimate protein.", "start": 2489.62, "duration": 3.91}, {"text": "The first type of error\nis a nonsense mutation,", "start": 2493.53, "duration": 3.95}, {"text": "which might be leaving\nout a base pair,", "start": 2497.48, "duration": 4.05}, {"text": "inserting one, substituting one.", "start": 2501.53, "duration": 2.34}, {"text": "And this would,\nultimately, cause an error", "start": 2503.87, "duration": 3.78}, {"text": "in the DNA that then causes\nan error in the messenger RNA.", "start": 2507.65, "duration": 5.11}, {"text": "So let's say we\ndelete by mistake,", "start": 2512.76, "duration": 3.86}, {"text": "or we're missing\nthe C-G base pair.", "start": 2516.62, "duration": 3.1}, {"text": "Then the messenger\nRNA is now different.", "start": 2519.72, "duration": 2.8}, {"text": "And a lot of the base\npairs-- the bases slide up", "start": 2522.52, "duration": 3.91}, {"text": "to fill the gap.", "start": 2526.43, "duration": 1.27}, {"text": "So we have what's known\nas a frame-shift mutation.", "start": 2527.7, "duration": 3.86}, {"text": "We've shifted things.", "start": 2531.56, "duration": 1.7}, {"text": "And what we've done by doing\nthat is introduce wrong codons.", "start": 2533.26, "duration": 4.63}, {"text": "So the first codon\nwas read properly.", "start": 2537.89, "duration": 3.78}, {"text": "The next one was read\nproperly, even though there", "start": 2541.67, "duration": 3.54}, {"text": "was a mistake, but then, all of\na sudden, we get in this mess", "start": 2545.21, "duration": 3.84}, {"text": "where one of the later\ncodons carries a mistake", "start": 2549.05, "duration": 3.36}, {"text": "and becomes a stop codon.", "start": 2552.41, "duration": 2.17}, {"text": "OK, does everybody see that?", "start": 2554.58, "duration": 1.64}, {"text": "So that would be called a\nframe-shift mutation that", "start": 2556.22, "duration": 3.51}, {"text": "introduces a nonsense\nmutation and puts a stop codon", "start": 2559.73, "duration": 4.53}, {"text": "into your messenger RNA, OK?", "start": 2564.26, "duration": 2.25}, {"text": "The next types of\nmistakes are ones", "start": 2569.69, "duration": 2.58}, {"text": "that are what are\ncalled silent mutations.", "start": 2572.27, "duration": 2.61}, {"text": "It doesn't matter, for\nexample, if you made an error", "start": 2574.88, "duration": 4.02}, {"text": "in the DNA, which ended up with\nan error in the messenger RNA,", "start": 2578.9, "duration": 4.89}, {"text": "if you still code the\nsame amino acid, right?", "start": 2583.79, "duration": 3.63}, {"text": "I go to the genetic code.", "start": 2587.42, "duration": 1.2}, {"text": "I'm like, oh my goodness,\nI've got a mutation.", "start": 2588.62, "duration": 2.07}, {"text": "Oh, it's fine.", "start": 2590.69, "duration": 1.11}, {"text": "CCC codes for proline, but\nCCA also codes for proline.", "start": 2591.8, "duration": 4.63}, {"text": "So that's called a\nsilent mutation, OK?", "start": 2596.43, "duration": 3.54}, {"text": "Then the last ones\nare the ones where", "start": 2599.97, "duration": 4.11}, {"text": "we start to encounter\nerrors in DNA that", "start": 2604.08, "duration": 3.27}, {"text": "result in errors in\nproteins that may cause", "start": 2607.35, "duration": 3.18}, {"text": "genetically inherited diseases.", "start": 2610.53, "duration": 2.05}, {"text": "So let's take a look at that.", "start": 2612.58, "duration": 1.46}, {"text": "Here it's a missense\nmutation where", "start": 2614.04, "duration": 4.05}, {"text": "we've got an error\nin the DNA, which", "start": 2618.09, "duration": 2.13}, {"text": "has resulted in an error\nin the messenger RNA.", "start": 2620.22, "duration": 3.91}, {"text": "So, instead of valine--", "start": 2624.13, "duration": 1.67}, {"text": "instead of leucine,\nwe've put in valine.", "start": 2625.8, "duration": 2.61}, {"text": "That's not so bad\nbecause it's quite what", "start": 2628.41, "duration": 2.97}, {"text": "we would call conservative.", "start": 2631.38, "duration": 2.04}, {"text": "They're sort of\nsimilar amino acids.", "start": 2633.42, "duration": 2.23}, {"text": "They have similar personalities.", "start": 2635.65, "duration": 1.97}, {"text": "So this is a missense\nmutation, but it", "start": 2637.62, "duration": 3.72}, {"text": "doesn't cause any dramatic\nchanges, probably, in the DNA.", "start": 2641.34, "duration": 4.47}, {"text": "And then the last\none I want to show", "start": 2645.81, "duration": 1.56}, {"text": "you is a missense mutation\nthat is non-conservative", "start": 2647.37, "duration": 4.47}, {"text": "and causes a serious defect.", "start": 2651.84, "duration": 2.23}, {"text": "And this takes you back to\nthe beginning of the class", "start": 2654.07, "duration": 3.08}, {"text": "where we've put a\nmistake in the sequence", "start": 2657.15, "duration": 2.79}, {"text": "where we've changed a\nglycine to an arginine.", "start": 2659.94, "duration": 3.105}, {"text": "And that's a big change.", "start": 2663.045, "duration": 1.575}, {"text": "And I just want to remind you\nof the situation in hemoglobin", "start": 2664.62, "duration": 3.59}, {"text": "when we had a missense mutation,\nand we incorporated a valine", "start": 2668.21, "duration": 4.93}, {"text": "instead of a glutamic acid,\njust through one change", "start": 2673.14, "duration": 3.42}, {"text": "in the DNA, which made one\nchange in the messenger, which", "start": 2676.56, "duration": 3.36}, {"text": "put a drastic change in the\nprotein that caused sickle cell", "start": 2679.92, "duration": 3.42}, {"text": "anemia.", "start": 2683.34, "duration": 1.23}, {"text": "So missense mutations\nare where you", "start": 2684.57, "duration": 1.5}, {"text": "put in the wrong amino acids.", "start": 2686.07, "duration": 1.98}, {"text": "And those are the ones where\nyou end up, in a lot of cases,", "start": 2688.05, "duration": 3.36}, {"text": "with inherited diseases.", "start": 2691.41, "duration": 2.11}, {"text": "Nonsense mutations\nare not so bad", "start": 2693.52, "duration": 2.03}, {"text": "because you probably just\ntruncate the protein.", "start": 2695.55, "duration": 2.49}, {"text": "You don't-- nonsense mutations\naren't so bad because you end", "start": 2698.04, "duration": 4.6}, {"text": "up with a truncated protein,\nwhich would be degraded.", "start": 2702.64, "duration": 3.51}, {"text": "The missense mutations\nare the more serious ones", "start": 2706.15, "duration": 3.167}, {"text": "because you end up with a\nfull length protein that", "start": 2709.317, "duration": 2.083}, {"text": "might have a mistake in it.", "start": 2711.4, "duration": 1.71}, {"text": "And then that would\naffect the function.", "start": 2713.11, "duration": 2.46}, {"text": "Am I being clear\nenough to everyone?", "start": 2715.57, "duration": 2.05}, {"text": "Yeah?", "start": 2717.62, "duration": 0.5}, {"text": "Good.", "start": 2718.12, "duration": 0.5}, {"text": "OK, I am going to tell you\nthat I'm handing over the baton", "start": 2718.62, "duration": 3.82}, {"text": "to my colleague,\nProfessor Martin.", "start": 2722.44, "duration": 2.91}, {"text": "He'll take over on Monday.", "start": 2725.35, "duration": 1.92}, {"text": "Mouse is pretty happy.", "start": 2727.27, "duration": 1.41}, {"text": "He's pretty excited\nabout genetics.", "start": 2728.68, "duration": 1.95}, {"text": "And these will be the\nlectures that will occur.", "start": 2730.63, "duration": 2.14}, {"text": "What?", "start": 2732.77, "duration": 0.5}, {"text": "You haven't seen him, have you?", "start": 2733.27, "duration": 1.56}, {"text": "He's keen on genetics, yeah.", "start": 2734.83, "duration": 2.132}, {"text": "AUDIENCE: Great.", "start": 2736.962, "duration": 0.886}, {"text": "BARBARA IMPERIALI:\nOK, and that's it.", "start": 2737.848, "duration": 1.542}, {"text": "Don't forget my office hours\non Monday if you need them.", "start": 2739.39, "duration": 3.96}, {"text": "I think this field\nis fascinating.", "start": 2743.35, "duration": 1.5}, {"text": "Once you get used to\nthe mechanics of it,", "start": 2744.85, "duration": 2.31}, {"text": "it's really cool to think\nof how you go from DNA", "start": 2747.16, "duration": 3.0}, {"text": "to RNA to folded proteins.", "start": 2750.16, "duration": 3.23}]
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+[{"text": "ADAM MARTIN: And so I just\nwant to say a couple sentences", "start": 17.06, "duration": 2.52}, {"text": "about DNA sequencing,\njust to finish that up.", "start": 19.58, "duration": 5.03}, {"text": "And so you'll remember this\nslide from last lecture.", "start": 24.61, "duration": 5.26}, {"text": "And remember, the way this\nSanger technique works", "start": 29.87, "duration": 5.76}, {"text": "is to set up four\ndifferent reactions where", "start": 35.63, "duration": 2.82}, {"text": "each reaction has\na different one", "start": 38.45, "duration": 2.67}, {"text": "of these dideoxynucleotides.", "start": 41.12, "duration": 3.85}, {"text": "OK, so there's four\nreactions, each", "start": 44.97, "duration": 6.15}, {"text": "with different dideoxy NTP.", "start": 51.12, "duration": 8.64}, {"text": "And I brought along a gel\nthat I ran a while ago,", "start": 59.76, "duration": 5.07}, {"text": "which is basically-- it's from\nsequencing gel, and you can--", "start": 64.83, "duration": 4.63}, {"text": "I'll pass this around so\nyou can take a look at it.", "start": 69.46, "duration": 3.09}, {"text": "So the four different\nlanes for each sample", "start": 72.55, "duration": 4.1}, {"text": "are the different\ndideoxynucleotide reactions.", "start": 76.65, "duration": 4.65}, {"text": "And what I want you to notice\nas that's passing around", "start": 81.3, "duration": 3.27}, {"text": "and you're looking at it is\nthat the different reactions", "start": 84.57, "duration": 3.21}, {"text": "with the different\ndideoxynucleotides", "start": 87.78, "duration": 3.96}, {"text": "give different patterns\nof DNA fragment lengths.", "start": 91.74, "duration": 4.76}, {"text": "So there are different\npatterns of fragment lengths.", "start": 96.5, "duration": 3.64}, {"text": "And the different patterns\nare based on the fact--", "start": 107.58, "duration": 5.37}, {"text": "this is based on the sequence,\nthe sequence of the template,", "start": 115.69, "duration": 3.31}, {"text": "OK?", "start": 119.0, "duration": 0.5}, {"text": "And so if we look at the\nexample up here, what you'll see", "start": 126.18, "duration": 5.01}, {"text": "is that in this banding\npattern for dideoxy TTP,", "start": 131.19, "duration": 4.71}, {"text": "you see that there's a really\nshort fragment at the bottom", "start": 135.9, "duration": 3.0}, {"text": "there, and so that fragment\nindicates that there must be", "start": 138.9, "duration": 3.93}, {"text": "an A in the template sequence.", "start": 142.83, "duration": 2.79}, {"text": "The next fragment up would be\nthis one in the dideoxy GTP", "start": 145.62, "duration": 4.62}, {"text": "lane, and that indicates that\none nucleotide beyond this A", "start": 150.24, "duration": 5.37}, {"text": "is a C position, and\nso on and so forth,", "start": 155.61, "duration": 3.51}, {"text": "such that you can sort\nof order the fragments", "start": 159.12, "duration": 3.15}, {"text": "and see which reaction\nhas a fragment", "start": 162.27, "duration": 3.36}, {"text": "and then read off\na DNA sequence.", "start": 165.63, "duration": 3.48}, {"text": "OK, so conceptually,\nthat's how you", "start": 169.11, "duration": 1.77}, {"text": "would read off the sequence\nof a given strand of DNA, OK?", "start": 170.88, "duration": 6.27}, {"text": "So you might be wondering,\nif now, we just read off", "start": 177.15, "duration": 3.57}, {"text": "sequence as a series of colors,\nwhy am I even introducing", "start": 180.72, "duration": 4.44}, {"text": "this technique?", "start": 185.16, "duration": 1.35}, {"text": "And the reason is\nbecause I think", "start": 186.51, "duration": 1.65}, {"text": "it's important for you as\npotentially future scientists", "start": 188.16, "duration": 6.57}, {"text": "to know that when you're\nfaced with a problem,", "start": 194.73, "duration": 4.14}, {"text": "how you might discover\nsomething new.", "start": 198.87, "duration": 2.61}, {"text": "And I see the\nSanger method of DNA", "start": 201.48, "duration": 3.06}, {"text": "sequencing as a really\nclever and elegant way", "start": 204.54, "duration": 4.71}, {"text": "in which Fred Sanger solved\nthe problem of DNA sequencing,", "start": 209.25, "duration": 4.26}, {"text": "and while we don't necessarily\ndo it that way today, it still", "start": 213.51, "duration": 4.2}, {"text": "illustrates a concept\nthat's important,", "start": 217.71, "duration": 2.79}, {"text": "the concept of\nchain termination,", "start": 220.5, "duration": 2.52}, {"text": "and I think there is something\nto be learned from this older", "start": 223.02, "duration": 3.24}, {"text": "technique, even if\nit's not exactly how we", "start": 226.26, "duration": 2.64}, {"text": "sequence DNA today.", "start": 228.9, "duration": 2.85}, {"text": "So for today's\nlecture, we're going", "start": 231.75, "duration": 2.27}, {"text": "to continue on our quest to\nbasically clone a gene that's", "start": 234.02, "duration": 6.28}, {"text": "responsible for a disease.", "start": 240.3, "duration": 1.635}, {"text": "And so we started this\nin the last lecture.", "start": 244.92, "duration": 5.04}, {"text": "And I guess one\nthing we would want", "start": 249.96, "duration": 2.97}, {"text": "to start with is\na disease, so I'm", "start": 252.93, "duration": 2.19}, {"text": "going to introduce to you now\na disease called aniridia.", "start": 255.12, "duration": 4.74}, {"text": "And in order to clone\nthe gene for a disease,", "start": 259.86, "duration": 3.86}, {"text": "it has to be a\nheritable disease,", "start": 263.72, "duration": 1.6}, {"text": "in this case, because we're\ngoing to use linkage analysis", "start": 265.32, "duration": 3.27}, {"text": "to identify it.", "start": 268.59, "duration": 1.83}, {"text": "So aniridia is a disease that's\nan eye disease in humans.", "start": 270.42, "duration": 4.83}, {"text": "It's a rare eye disease.", "start": 275.25, "duration": 2.55}, {"text": "So I want to show you a bit of\nan example of this eye disease.", "start": 277.8, "duration": 5.22}, {"text": "The way this disease\nmanifests itself", "start": 283.02, "duration": 2.16}, {"text": "is it's basically the\naffected individual", "start": 285.18, "duration": 3.75}, {"text": "has an eye that is\nlacking an iris.", "start": 288.93, "duration": 3.45}, {"text": "So I'm going to show you\nwhat this looks like.", "start": 292.38, "duration": 2.85}, {"text": "If you're squeamish or\ndon't like weird eyes", "start": 295.23, "duration": 3.72}, {"text": "and you don't want to\nlook, you can look away.", "start": 298.95, "duration": 3.37}, {"text": "But I will show you affected\nphenotype in 3, 2, 1, OK,", "start": 302.32, "duration": 6.83}, {"text": "everyone looking who\nwants to see weird eyes.", "start": 309.15, "duration": 2.76}, {"text": "OK, good.", "start": 311.91, "duration": 1.95}, {"text": "So that is a individual that\nhas aniridia, and also this one.", "start": 313.86, "duration": 4.11}, {"text": "So you see there's no\nclear iris in these eyes.", "start": 317.97, "duration": 3.78}, {"text": "And this disease is associated\nwith other abnormalities", "start": 321.75, "duration": 3.72}, {"text": "of the eye that\nseverely impair vision.", "start": 325.47, "duration": 4.08}, {"text": "And this is an\ninherited disease,", "start": 329.55, "duration": 4.39}, {"text": "and this is a\npedigree from a family", "start": 333.94, "duration": 4.64}, {"text": "or series of families where\nthe disease is propagating.", "start": 338.58, "duration": 4.02}, {"text": "And so anyone have a suggestion\nas to what mode of inheritance", "start": 342.6, "duration": 4.12}, {"text": "this is?", "start": 346.72, "duration": 0.5}, {"text": "Anyone want to rule a mode out?", "start": 354.31, "duration": 2.14}, {"text": "Rachel, you have an idea?", "start": 356.45, "duration": 1.56}, {"text": "AUDIENCE: I was going to\nsay X-linked dominant,", "start": 358.01, "duration": 2.406}, {"text": "but [INAUDIBLE]", "start": 360.416, "duration": 7.474}, {"text": "ADAM MARTIN: OK, so let's\ntake X-linked dominant.", "start": 367.89, "duration": 4.05}, {"text": "So if it was X-linked\ndominant, then this male", "start": 371.94, "duration": 5.01}, {"text": "would have an X chromosome\nwith the dominant allele", "start": 376.95, "duration": 3.0}, {"text": "of the disease and should\nonly pass it to his females.", "start": 379.95, "duration": 4.89}, {"text": "So I don't think that\nit would necessarily", "start": 384.84, "duration": 2.04}, {"text": "be X-linked dominant.", "start": 386.88, "duration": 1.47}, {"text": "Anyone else have an idea?", "start": 388.35, "duration": 2.617}, {"text": "Yeah, Georgia?", "start": 390.967, "duration": 0.583}, {"text": "AUDIENCE: Autosomal.", "start": 391.55, "duration": 1.14}, {"text": "ADAM MARTIN: Autosomal dominant.", "start": 392.69, "duration": 1.44}, {"text": "I like autosomal dominant.", "start": 394.13, "duration": 3.07}, {"text": "So in this case,\nyou see you have", "start": 397.2, "duration": 2.66}, {"text": "an individual with\nthe disease and they", "start": 399.86, "duration": 2.58}, {"text": "marry into a family with\nno history of the disease.", "start": 402.44, "duration": 3.822}, {"text": "One thing I'll point out,\nfor many of these diseases,", "start": 406.262, "duration": 2.208}, {"text": "they're extremely rare, so if\nyou see sort of a family tree", "start": 408.47, "duration": 4.5}, {"text": "where there's no\ninstance of the disease,", "start": 412.97, "duration": 2.85}, {"text": "if it's a rare\ndisease, it's likely", "start": 415.82, "duration": 2.1}, {"text": "that these individuals\nare not carriers.", "start": 417.92, "duration": 3.74}, {"text": "And so in this case, if you\nassume that this person doesn't", "start": 421.66, "duration": 3.61}, {"text": "have any form of the--", "start": 425.27, "duration": 2.48}, {"text": "isn't a carrier for\nthe disease, then this", "start": 427.75, "duration": 2.8}, {"text": "cross here resulting\nin about half", "start": 430.55, "duration": 2.43}, {"text": "of the individuals affected\nwith the disease, that", "start": 432.98, "duration": 2.73}, {"text": "would be a characteristic of\nan autosomal dominant disease.", "start": 435.71, "duration": 4.08}, {"text": "So everyone understand my logic?", "start": 439.79, "duration": 1.68}, {"text": "Yes, Carlos?", "start": 441.47, "duration": 0.72}, {"text": "AUDIENCE: What are--\nwhy is two and that", "start": 442.19, "duration": 2.707}, {"text": "looks like three on the slide,\nwhy are they crossed out?", "start": 444.897, "duration": 2.333}, {"text": "ADAM MARTIN: I think\nthey're deceased.", "start": 447.23, "duration": 2.07}, {"text": "Yes.", "start": 449.3, "duration": 0.5}, {"text": "OK, so let's say\nyou have a pedigree.", "start": 452.88, "duration": 3.24}, {"text": "You have pedigrees, you're able\nto try to link this marker to--", "start": 456.12, "duration": 6.81}, {"text": "or the disease phenotype with\nvarious molecular markers,", "start": 462.93, "duration": 3.55}, {"text": "which we discussed in\nlast week's lectures,", "start": 466.48, "duration": 3.08}, {"text": "then you're on the\nway to performing", "start": 469.56, "duration": 5.7}, {"text": "a process which is known\nas positional gene cloning.", "start": 475.26, "duration": 3.48}, {"text": "And what positional\ngene cloning is", "start": 481.38, "duration": 3.09}, {"text": "is it's basically cloning\na gene and a allele that's", "start": 484.47, "duration": 4.53}, {"text": "responsible for a disease based\non its position in the genome,", "start": 489.0, "duration": 4.71}, {"text": "it's position in a particular\nchromosomal region.", "start": 493.71, "duration": 4.29}, {"text": "So it's basically\ncloning a gene based", "start": 498.0, "duration": 7.74}, {"text": "on its chromosomal position\nor its chromosome position.", "start": 505.74, "duration": 6.18}, {"text": "And the first step of\npositional gene cloning", "start": 518.61, "duration": 3.42}, {"text": "would be to establish maybe\nwhat chromosome it's on.", "start": 522.03, "duration": 3.87}, {"text": "And a straightforward way to\ndo this, as we've basically", "start": 525.9, "duration": 5.07}, {"text": "been discussing almost from\nwhen I started lecturing,", "start": 530.97, "duration": 3.45}, {"text": "is to create some\nsort of linkage", "start": 534.42, "duration": 2.28}, {"text": "map or do linkage\nmapping to identify,", "start": 536.7, "duration": 5.52}, {"text": "in the case of humans, molecular\nmarkers that this disease", "start": 542.22, "duration": 3.94}, {"text": "allele is linked to.", "start": 546.16, "duration": 2.0}, {"text": "And remember, in\nlast week's lecture,", "start": 552.78, "duration": 3.15}, {"text": "we talked about a number\nof different polymorphisms", "start": 555.93, "duration": 3.6}, {"text": "that are present\nin the human genome", "start": 559.53, "duration": 2.88}, {"text": "that we can use to establish\nlinkage with a given phenotype.", "start": 562.41, "duration": 5.64}, {"text": "In this case, it's\na human disease.", "start": 568.05, "duration": 2.87}, {"text": "And we talked about this example\nfor a microsatellite marker.", "start": 570.92, "duration": 4.36}, {"text": "And in this case, we\ntalked through this example", "start": 575.28, "duration": 4.35}, {"text": "of how this dominant\nallele, P, is linked", "start": 579.63, "duration": 3.66}, {"text": "to this microsatellite\nallele m double prime,", "start": 583.29, "duration": 3.72}, {"text": "because if you look\nat the pedigree here,", "start": 587.01, "duration": 3.06}, {"text": "all of the affected\nindividuals here", "start": 590.07, "duration": 3.93}, {"text": "contain this m double\nprime sized fragment", "start": 594.0, "duration": 3.09}, {"text": "for this microsatellite.", "start": 597.09, "duration": 2.94}, {"text": "Another thing to\nnotice here is you", "start": 600.03, "duration": 2.19}, {"text": "can see that this couple has\nbeen faithful to each other,", "start": 602.22, "duration": 4.29}, {"text": "because basically,\neach of the children", "start": 606.51, "duration": 2.73}, {"text": "have an allele from the father\nand an allele from the mother.", "start": 609.24, "duration": 3.81}, {"text": "So you can see that type of--", "start": 613.05, "duration": 3.45}, {"text": "you can see that using this type\nof molecular marker as well.", "start": 616.5, "duration": 6.09}, {"text": "OK, so you establish linkage.", "start": 622.59, "duration": 2.29}, {"text": "So linkage mapping establishes\nthe chromosome position", "start": 624.88, "duration": 5.94}, {"text": "of a given allele and the gene.", "start": 630.82, "duration": 2.07}, {"text": "And this chromosome\nposition sort of", "start": 637.45, "duration": 1.86}, {"text": "gets maybe in the right\ncountry, but you still", "start": 639.31, "duration": 3.03}, {"text": "have a long way before you get\nto the specific street address.", "start": 642.34, "duration": 5.03}, {"text": "And so you have to then\nsort of narrow it in", "start": 647.37, "duration": 2.35}, {"text": "to identify a smaller region\nof the chromosome that could", "start": 649.72, "duration": 4.86}, {"text": "possibly contain this gene.", "start": 654.58, "duration": 3.15}, {"text": "And so what you would do is go\nfrom this linkage map, where", "start": 657.73, "duration": 4.41}, {"text": "you maybe identify the position\nof this gene within a couple", "start": 662.14, "duration": 4.38}, {"text": "map units, to this\nnext resolution of map", "start": 666.52, "duration": 4.32}, {"text": "called a physical map, OK?", "start": 670.84, "duration": 3.55}, {"text": "So we go from the\nlinkage position", "start": 674.39, "duration": 2.82}, {"text": "to the physical map\nof the chromosome.", "start": 677.21, "duration": 4.22}, {"text": "And the physical map,\nas the name implies,", "start": 684.93, "duration": 2.88}, {"text": "is when you have\nphysical pieces of DNA", "start": 687.81, "duration": 3.23}, {"text": "that are present in this\nregion of the chromosome.", "start": 691.04, "duration": 5.22}, {"text": "So the physical\nmap means you have", "start": 696.26, "duration": 2.25}, {"text": "cloned, so recombinant\npieces of DNA,", "start": 698.51, "duration": 4.02}, {"text": "cloned pieces of DNA which\nencompass a given chromosome", "start": 702.53, "duration": 6.69}, {"text": "region.", "start": 709.22, "duration": 1.3}, {"text": "So these are encompassing\na chromosome region.", "start": 710.52, "duration": 7.63}, {"text": "OK, so how would you\nget a piece of DNA", "start": 725.9, "duration": 5.01}, {"text": "that sort of is in this region?", "start": 730.91, "duration": 3.65}, {"text": "How would you start?", "start": 734.56, "duration": 1.23}, {"text": "How would you start\nfishing for that DNA?", "start": 735.79, "duration": 2.08}, {"text": "So you've gone through\nthe process of linkage,", "start": 741.49, "duration": 3.42}, {"text": "you've identified sort\nof a polymorphism that is", "start": 744.91, "duration": 4.29}, {"text": "linked to the disease allele.", "start": 749.2, "duration": 2.13}, {"text": "How would you go from there to\ngetting a physical piece of DNA", "start": 751.33, "duration": 4.32}, {"text": "that is present in that\nregion of the chromosome?", "start": 755.65, "duration": 6.04}, {"text": "So let's think back to--", "start": 761.69, "duration": 2.03}, {"text": "Jeremy, did you have an idea?", "start": 763.72, "duration": 4.04}, {"text": "AUDIENCE: Start by using PCR\nto just amplify that chunk.", "start": 767.76, "duration": 4.628}, {"text": "[INAUDIBLE]", "start": 772.388, "duration": 3.412}, {"text": "ADAM MARTIN: And what\nprimers, I guess,", "start": 775.8, "duration": 1.797}, {"text": "would you use for the PCR?", "start": 777.597, "duration": 1.083}, {"text": "AUDIENCE: Depending on which\nchunk you're trying to get,", "start": 781.902, "duration": 3.698}, {"text": "you'd use [INAUDIBLE]", "start": 785.6, "duration": 4.14}, {"text": "ADAM MARTIN: OK,\nso Jeremy is saying", "start": 789.74, "duration": 1.5}, {"text": "if you knew the\nsequence, and I guess", "start": 791.24, "duration": 2.91}, {"text": "if you're doing this\nmicrosatellite analysis,", "start": 794.15, "duration": 4.65}, {"text": "you had primers that recognize\na sequence at a given", "start": 798.8, "duration": 3.51}, {"text": "genomic position, so you\nactually know something", "start": 802.31, "duration": 2.79}, {"text": "about the sequence because\nof this polymorphism,", "start": 805.1, "duration": 3.96}, {"text": "so you can use that knowledge\nto then look for this sequence.", "start": 809.06, "duration": 5.67}, {"text": "And you could even look for\nthe microsatellite in a DNA", "start": 814.73, "duration": 3.31}, {"text": "library.", "start": 818.04, "duration": 0.5}, {"text": "OK, so you have\ncloned pieces of DNA,", "start": 821.36, "duration": 3.42}, {"text": "and you're going to start with--", "start": 824.78, "duration": 3.87}, {"text": "I'm going to swap this.", "start": 828.65, "duration": 1.23}, {"text": "Your starting\nposition could be one", "start": 834.2, "duration": 2.27}, {"text": "of these polymorphisms in\nthe sequence around it,", "start": 836.47, "duration": 3.73}, {"text": "which you already know.", "start": 840.2, "duration": 2.3}, {"text": "So let's say you had this\nmicrosatellite marker.", "start": 842.5, "duration": 2.64}, {"text": "You could then--\nwhat I'm drawing here", "start": 845.14, "duration": 2.67}, {"text": "is a piece of genomic DNA.", "start": 847.81, "duration": 2.8}, {"text": "So this is genomic DNA.", "start": 850.61, "duration": 1.195}, {"text": "I'm just drawing the insert.", "start": 858.04, "duration": 1.44}, {"text": "This would be recombinant DNA.", "start": 859.48, "duration": 1.95}, {"text": "It would be present in\nsome vector or plasmid.", "start": 861.43, "duration": 3.72}, {"text": "But if you can identify\nthe sequence that", "start": 865.15, "duration": 2.94}, {"text": "contains this\nmicrosatellite marker,", "start": 868.09, "duration": 4.68}, {"text": "then you would have the\nmicrosatellite, but also", "start": 872.77, "duration": 3.84}, {"text": "the surrounding DNA, OK?", "start": 876.61, "duration": 2.58}, {"text": "So that sort of anchors\nyou at a given position.", "start": 879.19, "duration": 3.81}, {"text": "Now, you don't know if your\ngene is in that piece of DNA,", "start": 883.0, "duration": 3.24}, {"text": "but you know that\nit's linked, and so it", "start": 886.24, "duration": 1.95}, {"text": "should be around that\npiece of DNA somewhere.", "start": 888.19, "duration": 4.08}, {"text": "And so it's unlikely\nyour gene is", "start": 892.27, "duration": 3.37}, {"text": "going to be on this small\npiece of DNA that's cloned.", "start": 895.64, "duration": 3.82}, {"text": "This is probably just a\nfew kb, and you could still", "start": 899.46, "duration": 2.89}, {"text": "be very far away\nfrom this, but that", "start": 902.35, "duration": 2.4}, {"text": "serves as a starting point\nfrom which you can go from", "start": 904.75, "duration": 3.48}, {"text": "to get more and\nmore pieces of DNA", "start": 908.23, "duration": 2.55}, {"text": "such that eventually, you\nhave a bunch of pieces of DNA", "start": 910.78, "duration": 2.55}, {"text": "that are going to span\nthe entire region.", "start": 913.33, "duration": 3.32}, {"text": "So the way you identify\nother pieces of DNA is you", "start": 916.65, "duration": 4.48}, {"text": "could start with a piece of DNA\nmaybe at the end of this insert", "start": 921.13, "duration": 5.04}, {"text": "and look for other\ninserts that are not", "start": 926.17, "duration": 2.34}, {"text": "identical to this piece that\nalso contain this piece here.", "start": 928.51, "duration": 5.29}, {"text": "So that might get\nyou a piece that's", "start": 933.8, "duration": 1.88}, {"text": "overlapping, but extends\nfarther than your initial piece.", "start": 935.68, "duration": 5.37}, {"text": "So now you've moved\nslightly farther away", "start": 941.05, "duration": 2.55}, {"text": "from your starting point, which\nis this starting polymorphism.", "start": 943.6, "duration": 6.05}, {"text": "Then you could choose maybe\nanother DNA sequence here", "start": 949.65, "duration": 3.3}, {"text": "and look for a piece\nof DNA that, again,", "start": 952.95, "duration": 3.33}, {"text": "is extending a bit farther out.", "start": 956.28, "duration": 2.46}, {"text": "And so you can see\nhow iteratively,", "start": 958.74, "duration": 2.61}, {"text": "you can get farther and farther\naway from this starting point", "start": 961.35, "duration": 3.36}, {"text": "that you know your\ngene is linked to.", "start": 964.71, "duration": 2.83}, {"text": "And this process of going\nsort piece by piece and clone", "start": 967.54, "duration": 3.74}, {"text": "by clone away from\na starting position", "start": 971.28, "duration": 3.42}, {"text": "is known as a chromosome walk.", "start": 974.7, "duration": 1.83}, {"text": "And you can do this\nbidirectionally.", "start": 982.93, "duration": 2.64}, {"text": "So you could also start\nwith a sequence of DNA", "start": 985.57, "duration": 2.79}, {"text": "here and look for a clone\nthat goes the other way.", "start": 988.36, "duration": 3.87}, {"text": "And you can see on\nmy slide up there,", "start": 995.23, "duration": 3.12}, {"text": "you can see that in\nthis case, they've", "start": 998.35, "duration": 2.61}, {"text": "taken a one map unit\nregion of the chromosome", "start": 1000.96, "duration": 3.33}, {"text": "and they're illustrating\nphysical pieces of DNA that", "start": 1004.29, "duration": 4.32}, {"text": "are overlapping that\nencompass this entire region.", "start": 1008.61, "duration": 4.14}, {"text": "So this could be much bigger\nthan the amount of DNA that", "start": 1012.75, "duration": 3.69}, {"text": "would fit in one of these\nclones in the bacteria,", "start": 1016.44, "duration": 2.94}, {"text": "but by sort of identify\noverlapping clones,", "start": 1019.38, "duration": 3.36}, {"text": "you get the entire region.", "start": 1022.74, "duration": 2.099}, {"text": "And what this is called here,\nbecause these pieces of DNA", "start": 1024.839, "duration": 5.041}, {"text": "are contiguous with each other,\nthis is known as a contig.", "start": 1029.88, "duration": 3.409}, {"text": "Yeah, Jeremy?", "start": 1041.4, "duration": 1.5}, {"text": "AUDIENCE: So would\nhow you get the--", "start": 1042.9, "duration": 1.89}, {"text": "once you find one\nof those pieces,", "start": 1044.79, "duration": 2.8}, {"text": "how do you get the primer\nfor the end of it to start?", "start": 1047.59, "duration": 2.274}, {"text": "Do you actually sequence\neach of these pieces of DNA?", "start": 1049.864, "duration": 2.306}, {"text": "ADAM MARTIN: You\ncould sequence it,", "start": 1052.17, "duration": 1.17}, {"text": "or you could use a\ntechnique that I'm", "start": 1053.34, "duration": 1.62}, {"text": "going to talk about at the\nend of my lecture, which", "start": 1054.96, "duration": 2.34}, {"text": "I'll come back to.", "start": 1057.3, "duration": 1.68}, {"text": "So nowadays, you'd probably just\nsequence it and then maybe look", "start": 1058.98, "duration": 3.21}, {"text": "for that in another clone.", "start": 1062.19, "duration": 3.33}, {"text": "But even before we could\nsequence DNA in entire genomes,", "start": 1065.52, "duration": 4.74}, {"text": "you could do that\ntype of experiment", "start": 1070.26, "duration": 2.58}, {"text": "by using a technique\ncalled hybridization,", "start": 1072.84, "duration": 2.2}, {"text": "which I'll come back to.", "start": 1075.04, "duration": 3.11}, {"text": "OK, so the question in this\nchromosome walk then becomes,", "start": 1078.15, "duration": 4.33}, {"text": "how do you know when to stop?", "start": 1082.48, "duration": 2.78}, {"text": "Because you could do this\nfor a very long time,", "start": 1085.26, "duration": 3.03}, {"text": "but it might not be useful.", "start": 1088.29, "duration": 1.66}, {"text": "So you have to\nknow when to stop,", "start": 1089.95, "duration": 2.45}, {"text": "and you need to know when\nyou arrive at the gene", "start": 1092.4, "duration": 3.36}, {"text": "that you're interested in,\nwhich would be the gene that", "start": 1095.76, "duration": 2.58}, {"text": "is responsible for the disease.", "start": 1098.34, "duration": 1.815}, {"text": "So another way to\nphrase this question is,", "start": 1102.87, "duration": 2.43}, {"text": "how do you know when you have\nan interesting gene on one", "start": 1105.3, "duration": 3.66}, {"text": "of these fragments?", "start": 1108.96, "duration": 1.02}, {"text": "So let's say this is an\ninteresting gene here.", "start": 1109.98, "duration": 4.68}, {"text": "How do you identify\ninteresting genes?", "start": 1114.66, "duration": 2.1}, {"text": "So now, let's talk about\nidentifying interesting genes.", "start": 1121.8, "duration": 2.895}, {"text": "Anyone have an idea\nfor how they would--", "start": 1132.99, "duration": 2.78}, {"text": "what criteria they would use\nto define a gene as being", "start": 1135.77, "duration": 4.27}, {"text": "interesting here?", "start": 1140.04, "duration": 0.87}, {"text": "I mean, one could say that\nall genes are interesting.", "start": 1148.81, "duration": 2.97}, {"text": "If it's a gene, it's\ninteresting, right?", "start": 1151.78, "duration": 1.67}, {"text": "How might we define whether or\nnot there's a gene even there?", "start": 1157.23, "duration": 3.54}, {"text": "It could be-- there\ncould be a gene--", "start": 1160.77, "duration": 2.91}, {"text": "how would you define a gene?", "start": 1163.68, "duration": 1.81}, {"text": "Can someone define\nfor me a gene?", "start": 1165.49, "duration": 1.64}, {"text": "Yeah, Miles?", "start": 1170.66, "duration": 1.97}, {"text": "Is it Miles?", "start": 1172.63, "duration": 1.31}, {"text": "No?", "start": 1173.94, "duration": 1.65}, {"text": "Malik, OK.", "start": 1175.59, "duration": 2.0}, {"text": "AUDIENCE: [INAUDIBLE] that would\ncreate a starting and stopping", "start": 1177.59, "duration": 6.062}, {"text": "point.", "start": 1183.652, "duration": 0.924}, {"text": "So like [INAUDIBLE]", "start": 1184.576, "duration": 3.041}, {"text": "ADAM MARTIN: So you'd look\nfor a piece of DNA that", "start": 1187.617, "duration": 2.083}, {"text": "has a start and a stop codon?", "start": 1189.7, "duration": 3.42}, {"text": "So you'd look for an open\nreading frame, basically.", "start": 1193.12, "duration": 2.85}, {"text": "Yeah.", "start": 1195.97, "duration": 0.87}, {"text": "You could look for an\nopen reading frame.", "start": 1196.84, "duration": 2.13}, {"text": "And so I totally agree\nwith Malik there.", "start": 1201.86, "duration": 3.8}, {"text": "And another criteria\nyou could use", "start": 1205.66, "duration": 2.64}, {"text": "is if it's encoding a\nprotein, at some point,", "start": 1208.3, "duration": 3.15}, {"text": "it also must have been\ntranscribed as an mRNA.", "start": 1211.45, "duration": 4.05}, {"text": "And there are some genes\nthat are transcribed as RNA", "start": 1215.5, "duration": 4.65}, {"text": "but don't make a protein,\nand they're often", "start": 1220.15, "duration": 1.83}, {"text": "involved in coding or in\nregulation of gene expression.", "start": 1221.98, "duration": 5.58}, {"text": "So I'm going to--", "start": 1227.56, "duration": 1.17}, {"text": "I'm going to say,\nis it transcribed?", "start": 1228.73, "duration": 3.73}, {"text": "So is there some\ntranscript that's made?", "start": 1232.46, "duration": 4.96}, {"text": "And specifically, is it\ntranscribed in the tissue", "start": 1237.42, "duration": 3.28}, {"text": "that we're interested in?", "start": 1240.7, "duration": 1.17}, {"text": "So if we're talking\naniridia, we might", "start": 1246.88, "duration": 2.91}, {"text": "be looking for genes that are\nbeing expressed or transcribed", "start": 1249.79, "duration": 3.96}, {"text": "specifically in eyes.", "start": 1253.75, "duration": 3.575}, {"text": "You're looking\nfor something that", "start": 1257.325, "duration": 1.375}, {"text": "might be expressed in the eye.", "start": 1258.7, "duration": 2.07}, {"text": "If it's not\nexpressed in the eye,", "start": 1260.77, "duration": 2.22}, {"text": "that gene's going to be\nmuch less interesting to you", "start": 1262.99, "duration": 2.4}, {"text": "because the phenotype of\naniridia is clearly in the eye.", "start": 1265.39, "duration": 3.51}, {"text": "OK, what might be some\nother criteria here?", "start": 1271.69, "duration": 3.99}, {"text": "Well, one criteria might be,\nis there a conserved gene that", "start": 1275.68, "duration": 4.44}, {"text": "has an interesting\nfunction that's", "start": 1280.12, "duration": 1.95}, {"text": "maybe similar to the\ndisease related phenotype?", "start": 1282.07, "duration": 3.68}, {"text": "So is there a conserved gene\nwith an interesting function?", "start": 1288.34, "duration": 11.195}, {"text": "And to take this\nexample of aniridia,", "start": 1308.45, "duration": 3.15}, {"text": "let's say you're doing\nthis chromosome walk,", "start": 1311.6, "duration": 2.97}, {"text": "and you identify\na gene, maybe you", "start": 1314.57, "duration": 2.01}, {"text": "sequence part of this clone,\nyou get a string of sequence,", "start": 1316.58, "duration": 4.05}, {"text": "and you realize that the\nsequence that you get", "start": 1320.63, "duration": 2.82}, {"text": "is related to a gene\nfrom a model organism,", "start": 1323.45, "duration": 4.83}, {"text": "and maybe that gene\nis called eyeless.", "start": 1328.28, "duration": 4.65}, {"text": "If you've identified a region\nof sequence in a human,", "start": 1332.93, "duration": 5.07}, {"text": "in the human genome that's\nmapping to an eye disease gene,", "start": 1338.0, "duration": 4.56}, {"text": "and you find out\nthat in that region,", "start": 1342.56, "duration": 1.98}, {"text": "there is a conserved\ngene called eyeless,", "start": 1344.54, "duration": 3.54}, {"text": "might be a very\ninteresting gene for you.", "start": 1348.08, "duration": 2.76}, {"text": "So eyeless is a gene.", "start": 1350.84, "duration": 1.83}, {"text": "So here's a normal fly.", "start": 1352.67, "duration": 1.83}, {"text": "You see it has that\nbright red eye.", "start": 1354.5, "duration": 3.17}, {"text": "The eyeless gene,\nwhen mutated, results", "start": 1357.67, "duration": 3.76}, {"text": "in a fly that now just\ndoesn't have a white eye,", "start": 1361.43, "duration": 3.03}, {"text": "but has no eye altogether.", "start": 1364.46, "duration": 3.66}, {"text": "So it turns out that the\naniridia gene is the homolog", "start": 1368.12, "duration": 3.69}, {"text": "of the eyeless gene in flies.", "start": 1371.81, "duration": 2.71}, {"text": "That's not how it was\nidentified initially,", "start": 1374.52, "duration": 2.72}, {"text": "but nowadays, there's a lot of\ninformation in model organisms.", "start": 1377.24, "duration": 4.57}, {"text": "And so if you're sort of\ntrying to identify a gene,", "start": 1381.81, "duration": 3.77}, {"text": "and you see that there's\na gene in the neighborhood", "start": 1385.58, "duration": 2.43}, {"text": "you're looking at\nwith a function that's", "start": 1388.01, "duration": 3.6}, {"text": "related to a gene\nlike eyeless, which", "start": 1391.61, "duration": 4.02}, {"text": "has a clear sort of analogy\nin terms of phenotypes,", "start": 1395.63, "duration": 3.33}, {"text": "then that's going to increase\nyour interest in that gene.", "start": 1398.96, "duration": 2.58}, {"text": "So I'm going to come\nback to this point", "start": 1404.87, "duration": 2.97}, {"text": "here, which is how\ndo we determine", "start": 1407.84, "duration": 3.87}, {"text": "whether a piece of DNA that's\non one of these inserts", "start": 1411.71, "duration": 3.93}, {"text": "that we're getting as we\nwalk across the chromosome,", "start": 1415.64, "duration": 2.7}, {"text": "how do we know whether\nit is transcribed or not?", "start": 1418.34, "duration": 4.65}, {"text": "And to get at this, I'm\ngoing to introduce you", "start": 1422.99, "duration": 1.95}, {"text": "to a concept which\nis important in", "start": 1424.94, "duration": 3.0}, {"text": "and of itself, which\nis the idea of cDNA.", "start": 1427.94, "duration": 6.29}, {"text": "So cDNA.", "start": 1434.23, "duration": 1.62}, {"text": "And specifically,\nI'm going to show you", "start": 1435.85, "duration": 1.8}, {"text": "how one would make a cDNA\nlibrary, which is basically", "start": 1437.65, "duration": 4.59}, {"text": "a library of different cDNAs.", "start": 1442.24, "duration": 2.94}, {"text": "And so what cDNA is, as\nshown up there on my slide,", "start": 1445.18, "duration": 4.46}, {"text": "a cDNA is complementary DNA.", "start": 1449.64, "duration": 4.525}, {"text": "It's complementary DNA,\nmeaning that is the complement", "start": 1462.92, "duration": 4.81}, {"text": "of an mRNA transcript.", "start": 1467.73, "duration": 3.48}, {"text": "This DNA is the complement\nof an RNA or mRNA transcript.", "start": 1471.21, "duration": 9.78}, {"text": "One thing to watch out for is\nit's not complimentary DNA.", "start": 1487.75, "duration": 6.42}, {"text": "So this is MIT.", "start": 1494.17, "duration": 2.01}, {"text": "This is a no compliment\nzone, so I don't want", "start": 1496.18, "duration": 3.6}, {"text": "to see any complimentary DNA.", "start": 1499.78, "duration": 1.965}, {"text": "All right, so let's think\nabout complementary DNA.", "start": 1506.01, "duration": 4.02}, {"text": "So remember, we've talked\nabout the central dogma", "start": 1510.03, "duration": 4.83}, {"text": "and how DNA encodes for RNA,\nwhich encodes for protein.", "start": 1514.86, "duration": 5.685}, {"text": "And so the information\nflows from DNA", "start": 1525.06, "duration": 2.54}, {"text": "through RNA to protein.", "start": 1527.6, "duration": 2.55}, {"text": "But there are some\nspecialized cases in biology", "start": 1530.15, "duration": 3.84}, {"text": "where this information\nflow is reversed.", "start": 1533.99, "duration": 3.96}, {"text": "So there can be a reverse\nof information flow", "start": 1537.95, "duration": 4.26}, {"text": "where information\nflows from RNA to DNA.", "start": 1542.21, "duration": 3.195}, {"text": "OK, so that's pretty cool.", "start": 1548.34, "duration": 1.88}, {"text": "Where does that happen?", "start": 1550.22, "duration": 1.87}, {"text": "Well, there are viruses,\nsuch as retroviruses,", "start": 1552.09, "duration": 4.61}, {"text": "one example of a retrovirus\nis HIV, and the virus life--", "start": 1556.7, "duration": 7.29}, {"text": "the virus genome is a\nsingle-stranded RNA molecule,", "start": 1563.99, "duration": 4.5}, {"text": "and the life cycle of the virus\nis that inserts into the host--", "start": 1568.49, "duration": 5.55}, {"text": "the host genome, which\nis double-stranded DNA.", "start": 1574.04, "duration": 3.06}, {"text": "For a retrovirus to do that,\nit needs to take its RNA genome", "start": 1577.1, "duration": 4.32}, {"text": "and make double-stranded DNA\nin order for it to insert.", "start": 1581.42, "duration": 4.17}, {"text": "So this is an example in\nbiology, which is basically", "start": 1585.59, "duration": 3.63}, {"text": "breaking the rules that we\ntalked to you about earlier", "start": 1589.22, "duration": 2.88}, {"text": "in the semester.", "start": 1592.1, "duration": 1.89}, {"text": "Also, there are\nretrotransposons which", "start": 1593.99, "duration": 3.87}, {"text": "do a similar process,\ngoing from an RNA molecule", "start": 1597.86, "duration": 4.77}, {"text": "to double-stranded DNA.", "start": 1602.63, "duration": 1.98}, {"text": "So this is a specialized\ncase, and it's interesting,", "start": 1604.61, "duration": 3.4}, {"text": "and we can take advantage of it\nto basically clone and identify", "start": 1608.01, "duration": 6.56}, {"text": "mRNA transcripts.", "start": 1614.57, "duration": 1.44}, {"text": "OK, so I'm going to tell you\nhow to make complementary DNA,", "start": 1619.87, "duration": 4.24}, {"text": "and I'll go through\na series of steps.", "start": 1624.11, "duration": 2.95}, {"text": "The first step is we want to\nmake complementary DNA of mRNA,", "start": 1627.06, "duration": 6.26}, {"text": "so we need a way\nto purify the mRNA.", "start": 1633.32, "duration": 2.085}, {"text": "So anyone have any idea\nhow to purify mRNA?", "start": 1638.04, "duration": 4.71}, {"text": "First, we could maybe\ndraw an RNA molecule here.", "start": 1642.75, "duration": 3.42}, {"text": "What are some salient\nfeatures of mature mRNA?", "start": 1646.17, "duration": 4.85}, {"text": "Yeah, Carlos?", "start": 1651.02, "duration": 0.545}, {"text": "AUDIENCE: It'll have\nthe five-prime cap", "start": 1651.565, "duration": 1.708}, {"text": "[INAUDIBLE] phosphate.", "start": 1653.273, "duration": 0.917}, {"text": "ADAM MARTIN: Yeah, it'll\nhave a five-prime cap.", "start": 1654.19, "duration": 2.04}, {"text": "Anything else?", "start": 1656.23, "duration": 1.06}, {"text": "Jeremy?", "start": 1657.29, "duration": 0.5}, {"text": "AUDIENCE: Poly-A tail.", "start": 1657.79, "duration": 0.79}, {"text": "ADAM MARTIN: It'll\nhave a five-prime cap", "start": 1658.58, "duration": 1.667}, {"text": "and a poly-A tail.", "start": 1660.247, "duration": 1.233}, {"text": "I'm going to take advantage\nmostly of the poly-A tail here.", "start": 1661.48, "duration": 3.12}, {"text": "So here, we have a poly-A tail.", "start": 1667.48, "duration": 3.1}, {"text": "OK, how might we use that\npoly-A tail to purify mRNA?", "start": 1670.58, "duration": 5.08}, {"text": "Natalie?", "start": 1675.66, "duration": 0.5}, {"text": "AUDIENCE: Well, you\ncan add a [INAUDIBLE]", "start": 1676.16, "duration": 2.503}, {"text": "because you know\nthey're [INAUDIBLE]", "start": 1678.663, "duration": 1.844}, {"text": "ADAM MARTIN: Mm-hmm.", "start": 1680.507, "duration": 0.833}, {"text": "What sequence would you use?", "start": 1681.34, "duration": 1.635}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1682.975, "duration": 0.875}, {"text": "ADAM MARTIN: Yes.", "start": 1683.85, "duration": 0.708}, {"text": "So Natalie has suggested\nusing poly T, which", "start": 1684.558, "duration": 4.992}, {"text": "she said would stick to\nthis poly A tail because", "start": 1689.55, "duration": 3.93}, {"text": "of base pair hybridization, OK?", "start": 1693.48, "duration": 3.57}, {"text": "So let's say we have a bead\nor some type of resin with dTs", "start": 1697.05, "duration": 5.64}, {"text": "hanging off of it.", "start": 1702.69, "duration": 2.76}, {"text": "So I'll draw a few\nof them, but you'd", "start": 1705.45, "duration": 1.74}, {"text": "have maybe a lot of\nthem sticking off, OK?", "start": 1707.19, "duration": 6.87}, {"text": "So you have a bead with\npieces of DNA, all of which", "start": 1714.06, "duration": 3.3}, {"text": "are poly dT hanging off of it.", "start": 1717.36, "duration": 2.58}, {"text": "And then these poly dTs, if\nyou add cytoplasm from cells,", "start": 1719.94, "duration": 6.18}, {"text": "the mRNA in that cytoplasm is\ngoing to stick to this poly dT", "start": 1726.12, "duration": 4.59}, {"text": "bead, and it will\nstick with a higher", "start": 1730.71, "duration": 4.83}, {"text": "affinity than other things that\nare non specifically sticking", "start": 1735.54, "duration": 3.12}, {"text": "to the beads, and you can\nwash these beads with buffer", "start": 1738.66, "duration": 4.11}, {"text": "and salt to get rid\nof everything that's", "start": 1742.77, "duration": 2.58}, {"text": "non-specifically\nsticking to the bead,", "start": 1745.35, "duration": 2.31}, {"text": "and then you're left\nwith just a bead that's", "start": 1747.66, "duration": 3.21}, {"text": "enriched with mRNA, which\nis what was specifically", "start": 1750.87, "duration": 2.88}, {"text": "sticking to this, OK?", "start": 1753.75, "duration": 2.01}, {"text": "So you could purify--", "start": 1755.76, "duration": 0.945}, {"text": "you're purifying the mRNA based\non its affinity for a poly dT,", "start": 1760.26, "duration": 16.49}, {"text": "OK?", "start": 1776.75, "duration": 0.5}, {"text": "So then you're going\nto have enrichment", "start": 1777.25, "duration": 4.92}, {"text": "of mRNA in your sample.", "start": 1782.17, "duration": 3.77}, {"text": "And so then once\nyou have your RNA,", "start": 1785.94, "duration": 5.33}, {"text": "you're going to want to\nsomehow go from RNA to DNA, OK?", "start": 1791.27, "duration": 3.88}, {"text": "So the next step will involve\nsomehow going from RNA to DNA.", "start": 1798.29, "duration": 6.42}, {"text": "So let's draw our\npiece of RNA here.", "start": 1804.71, "duration": 2.31}, {"text": "Here's our RNA.", "start": 1807.02, "duration": 1.13}, {"text": "It has a poly A\ntail so it's mRNA.", "start": 1808.15, "duration": 2.17}, {"text": "There is 5 prime.", "start": 1814.14, "duration": 0.955}, {"text": "OK, so now we need to\ntake advantage of a trick.", "start": 1818.29, "duration": 4.55}, {"text": "We can still take\nadvantage of dT", "start": 1822.84, "duration": 3.21}, {"text": "because we can use\nthis as a primer", "start": 1826.05, "duration": 3.03}, {"text": "because polymerase\nusually requires", "start": 1829.08, "duration": 3.23}, {"text": "some primer and a three prime\nhydroxyl in order to extend.", "start": 1832.31, "duration": 6.1}, {"text": "Now, can we use DNA polymerase\nto extend this primer?", "start": 1838.41, "duration": 5.04}, {"text": "Jeremy is shaking his head no.", "start": 1843.45, "duration": 1.43}, {"text": "Why?", "start": 1844.88, "duration": 0.5}, {"text": "AUDIENCE: Because\nDNA [INAUDIBLE]", "start": 1845.38, "duration": 5.66}, {"text": "ADAM MARTIN: Exactly.", "start": 1851.04, "duration": 1.42}, {"text": "So what Jeremy is\nsaying is DNA polymerase", "start": 1852.46, "duration": 2.94}, {"text": "is a DNA dependent\nDNA polymerase, OK?", "start": 1855.4, "duration": 3.72}, {"text": "DNA polymerase can only use\nthis if this is DNA here, OK?", "start": 1859.12, "duration": 4.56}, {"text": "So we need a different type\nof enzyme, essentially,", "start": 1863.68, "duration": 3.78}, {"text": "in order to make DNA\nfrom RNA, and luckily,", "start": 1867.46, "duration": 6.18}, {"text": "molecular biologists--", "start": 1873.64, "duration": 1.86}, {"text": "actually one of whom\nwas here at MIT--", "start": 1875.5, "duration": 2.46}, {"text": "discovered this type\nof enzyme, and it's", "start": 1877.96, "duration": 2.58}, {"text": "called reverse transcriptase.", "start": 1880.54, "duration": 1.78}, {"text": "Reverse transcriptase.", "start": 1885.67, "duration": 1.5}, {"text": "This is an enzyme that's\nencoded by retroviruses in order", "start": 1887.17, "duration": 5.25}, {"text": "to make double\nstranded DNA from RNA,", "start": 1892.42, "duration": 4.02}, {"text": "and that allows the retrovirus\nto insert into the host genome,", "start": 1896.44, "duration": 3.69}, {"text": "OK?", "start": 1900.13, "duration": 2.11}, {"text": "And what reverse transcriptase\nis is it's an RNA dependent DNA", "start": 1902.24, "duration": 4.91}, {"text": "polymerase, OK?", "start": 1907.15, "duration": 0.99}, {"text": "So it takes RNA\nas its substrate,", "start": 1908.14, "duration": 2.92}, {"text": "and then it synthesizes DNA\non the opposite strand, OK?", "start": 1911.06, "duration": 5.96}, {"text": "So this is an RNA\ndependent DNA polymerase.", "start": 1917.02, "duration": 8.202}, {"text": "OK, so if you add\nreverse transcriptase", "start": 1929.38, "duration": 3.57}, {"text": "to mRNAs that have these dT\nprimers, then what you get", "start": 1932.95, "duration": 5.85}, {"text": "is a new strand,\nwhich is DNA here.", "start": 1938.8, "duration": 3.51}, {"text": "This is the strand of DNA.", "start": 1942.31, "duration": 1.26}, {"text": "And then you have a strand\nof RNA opposite it, OK?", "start": 1947.33, "duration": 6.47}, {"text": "So at this step, you\nhave a DNA RNA hybrid.", "start": 1953.8, "duration": 5.49}, {"text": "So this is a DNA RNA hybrid.", "start": 1959.29, "duration": 3.57}, {"text": "Let's see.", "start": 1967.55, "duration": 2.04}, {"text": "Reveal some more of this.", "start": 1969.59, "duration": 1.55}, {"text": "This is the process\nwhich I'm basically", "start": 1971.14, "duration": 1.89}, {"text": "outlining on the board.", "start": 1973.03, "duration": 1.2}, {"text": "So then you want\ndouble stranded DNA,", "start": 1977.07, "duration": 2.79}, {"text": "so you don't want this strand\nof RNA that's down here,", "start": 1979.86, "duration": 3.21}, {"text": "so you have to get rid of it.", "start": 1983.07, "duration": 2.88}, {"text": "So you would degrade\nthe RNA, and this", "start": 1985.95, "duration": 7.32}, {"text": "is done using another\nenzymatic activity, which", "start": 1993.27, "duration": 3.27}, {"text": "is derived from reverse\ntranscriptase, which", "start": 1996.54, "duration": 3.03}, {"text": "is termed RNAs H activity.", "start": 1999.57, "duration": 2.94}, {"text": "So you can add an\nenzyme RNAs H, which", "start": 2002.51, "duration": 6.48}, {"text": "RNAs H takes this\nDNA RNA hybrids", "start": 2008.99, "duration": 3.54}, {"text": "and degrades the\nRNA part of it, OK?", "start": 2012.53, "duration": 3.27}, {"text": "So this is going to\ndegrade the RNA strand.", "start": 2015.8, "duration": 4.11}, {"text": "And if you degrade\nthe RNA strand,", "start": 2019.91, "duration": 2.26}, {"text": "then you're left with\na single strand of DNA.", "start": 2022.17, "duration": 2.27}, {"text": "So you have single\nstrand of DNA here,", "start": 2028.74, "duration": 5.08}, {"text": "and now what you need\nto do is to synthesize", "start": 2033.82, "duration": 2.72}, {"text": "the second strand of DNA.", "start": 2036.54, "duration": 3.15}, {"text": "So you need a second\nstrand synthesis.", "start": 2039.69, "duration": 2.25}, {"text": "And so you need, again,\na primer in order", "start": 2047.26, "duration": 2.7}, {"text": "to prime the synthesis here.", "start": 2049.96, "duration": 3.3}, {"text": "So there are a variety\nof ways to do this.", "start": 2053.26, "duration": 2.59}, {"text": "You can add some\ntype of hairpin,", "start": 2055.85, "duration": 2.51}, {"text": "which is five prime here\nand three prime here,", "start": 2058.36, "duration": 4.98}, {"text": "and then you can use\neither DNA, polymerase,", "start": 2063.34, "duration": 3.21}, {"text": "or reverse transcriptase, which\nalso can be a DNA dependent DNA", "start": 2066.55, "duration": 5.04}, {"text": "polymerase to transcribe\nthis strand here, OK?", "start": 2071.59, "duration": 3.799}, {"text": "So again, you add polymerase,\nand now you've gone", "start": 2078.19, "duration": 4.08}, {"text": "and you've generated\ndouble stranded DNA, OK?", "start": 2082.27, "duration": 4.71}, {"text": "So everyone see how we've\ngone from an mRNA transcript,", "start": 2086.98, "duration": 4.77}, {"text": "and we've done the reverse of\neverything we just told you", "start": 2091.75, "duration": 4.139}, {"text": "in the first half of the course\nbecause we've gone from RNA", "start": 2095.889, "duration": 4.891}, {"text": "and we've made DNA, OK?", "start": 2100.78, "duration": 2.16}, {"text": "But this will be really\nuseful because now we", "start": 2102.94, "duration": 2.16}, {"text": "have a stable piece of DNA that\nwe can clone into a plasmid", "start": 2105.1, "duration": 4.89}, {"text": "and we have a record of\nthis transcript being", "start": 2109.99, "duration": 2.7}, {"text": "present in our sample, and we\ncan propagate that on and on,", "start": 2112.69, "duration": 5.04}, {"text": "so we've cloned it, OK?", "start": 2117.73, "duration": 2.58}, {"text": "All right, what's going to be\nspecial about this piece of DNA", "start": 2120.31, "duration": 3.45}, {"text": "versus a piece of genomic DNA?", "start": 2123.76, "duration": 3.29}, {"text": "Natalie?", "start": 2127.05, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2127.55, "duration": 1.79}, {"text": "ADAM MARTIN: Yes, so\nNatalie suggesting", "start": 2129.34, "duration": 1.88}, {"text": "that it doesn't have introns,\nand that's totally right.", "start": 2131.22, "duration": 3.73}, {"text": "So this is not like\ngenomic DNA, and what", "start": 2134.95, "duration": 6.93}, {"text": "Natalie said is because\nmRNA is processed,", "start": 2141.88, "duration": 5.66}, {"text": "the introns are spliced out,\nsuch the mature mRNA only", "start": 2147.54, "duration": 4.27}, {"text": "has the axons, and so this\npiece of complementary cDNA", "start": 2151.81, "duration": 5.34}, {"text": "is going to have no introns.", "start": 2157.15, "duration": 3.07}, {"text": "How else is it different?", "start": 2162.85, "duration": 1.76}, {"text": "Yeah, Jeremy?", "start": 2170.26, "duration": 0.618}, {"text": "AUDIENCE: It's not\ngoing to have promoters.", "start": 2170.878, "duration": 1.792}, {"text": "ADAM MARTIN: It's not\ngoing to have a promoter.", "start": 2172.67, "duration": 1.42}, {"text": "Yes, Carmen?", "start": 2174.09, "duration": 0.68}, {"text": "AUDIENCE: It doesn't\nhave [INAUDIBLE]", "start": 2174.77, "duration": 5.05}, {"text": "ADAM MARTIN: You might\nsee a poly A and T", "start": 2179.82, "duration": 3.18}, {"text": "sequence in the cDNA.", "start": 2183.0, "duration": 1.86}, {"text": "Yes, that's true.", "start": 2184.86, "duration": 1.85}, {"text": "OK, so you might have\npoly A, poly T. I'm", "start": 2186.71, "duration": 2.89}, {"text": "going to focus on\nthe other part from--", "start": 2189.6, "duration": 2.23}, {"text": "there's going to be no promoter,\nenhancer, regulatory sequences.", "start": 2194.34, "duration": 6.84}, {"text": "Basically, it's got no sequence\nthat's not transcribed, right?", "start": 2201.18, "duration": 4.77}, {"text": "The DNA is only going to have\nthe part of the gene that", "start": 2205.95, "duration": 3.21}, {"text": "was physically transcribed by\nthe RNA polymerase originally.", "start": 2209.16, "duration": 5.02}, {"text": "OK, so no\nnon-transcribed regions.", "start": 2214.18, "duration": 4.935}, {"text": "No non-transcribed regions,\nand Carmen's absolutely right.", "start": 2222.29, "duration": 8.26}, {"text": "You will also have possibly\na poly A or poly T sequence.", "start": 2230.55, "duration": 3.56}, {"text": "OK, so when you get these\ncDNAs, you might have--", "start": 2241.51, "duration": 5.85}, {"text": "you have more than\none mRNA in a sample", "start": 2247.36, "duration": 2.55}, {"text": "like a cytoplasmic extract,\nso you're going to prime--", "start": 2249.91, "duration": 4.44}, {"text": "you're going to\nmake multiple cDNA", "start": 2254.35, "duration": 2.16}, {"text": "and different cDNAs will reflect\ndifferent transcripts that", "start": 2256.51, "duration": 3.99}, {"text": "are present in your sample, OK?", "start": 2260.5, "duration": 2.58}, {"text": "So you could have\none clone that's", "start": 2263.08, "duration": 2.55}, {"text": "one gene, another clone\nthat's a different gene,", "start": 2265.63, "duration": 3.72}, {"text": "and another clone\nthat's another gene,", "start": 2269.35, "duration": 2.1}, {"text": "and you could have thousands of\nclones of these different DNAs.", "start": 2271.45, "duration": 3.99}, {"text": "What's going to be special\nabout what types of genes", "start": 2275.44, "duration": 5.19}, {"text": "are you going to get for\nI guess different tissues.", "start": 2280.63, "duration": 3.18}, {"text": "Are they going to\nbe the same or not?", "start": 2283.81, "duration": 4.26}, {"text": "Yeah, Carlos?", "start": 2288.07, "duration": 0.66}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2288.73, "duration": 3.085}, {"text": "ADAM MARTIN: Exactly.", "start": 2291.815, "duration": 0.875}, {"text": "You're not going to see--\nif you've prepared a tissue", "start": 2292.69, "duration": 3.05}, {"text": "and there is no gene being--", "start": 2295.74, "duration": 2.7}, {"text": "if one gene was not expressed\nor transcribed in that tissue,", "start": 2298.44, "duration": 3.82}, {"text": "you will not get a cDNA\nfor that particular gene", "start": 2302.26, "duration": 3.09}, {"text": "in your library, OK?", "start": 2305.35, "duration": 2.28}, {"text": "So the representation of genes--", "start": 2307.63, "duration": 2.46}, {"text": "the representation of\ngenes in a cDNA library", "start": 2313.63, "duration": 8.58}, {"text": "is totally dependent on what\ngenes are being expressed, OK?", "start": 2322.21, "duration": 5.34}, {"text": "So this representation\nis going to be", "start": 2327.55, "duration": 1.92}, {"text": "proportional to the expression\nlevel, and the more genes--", "start": 2329.47, "duration": 6.66}, {"text": "the more a gene is\nexpressed in a given tissue,", "start": 2336.13, "duration": 2.91}, {"text": "the more copies of\ncDNA for that gene", "start": 2339.04, "duration": 3.39}, {"text": "you would see in\nthe library, OK?", "start": 2342.43, "duration": 1.77}, {"text": "So there's really\na proportionality", "start": 2344.2, "duration": 2.31}, {"text": "between the number of\nclones in a library", "start": 2346.51, "duration": 2.97}, {"text": "and the expression\nlevel of a gene,", "start": 2349.48, "duration": 2.64}, {"text": "where in the most extreme\ncase, if this gene is not", "start": 2352.12, "duration": 3.09}, {"text": "expressed at all,\nyou're not going", "start": 2355.21, "duration": 1.59}, {"text": "to see it represented at\nall in the cDNA library, OK?", "start": 2356.8, "duration": 5.09}, {"text": "And then a corollary\nto this statement", "start": 2361.89, "duration": 2.44}, {"text": "is that if you make cDNA\nlibraries from different cell", "start": 2364.33, "duration": 6.21}, {"text": "types or different tissue\ntypes, the cDNA libraries", "start": 2370.54, "duration": 4.14}, {"text": "are going to be different\nbetween those different types", "start": 2374.68, "duration": 2.34}, {"text": "of sources of mRNA, OK?", "start": 2377.02, "duration": 2.76}, {"text": "So in other words,\ndifferent tissues", "start": 2379.78, "duration": 7.08}, {"text": "give you different cDNA.", "start": 2386.86, "duration": 1.1}, {"text": "OK, so there is the process.", "start": 2399.55, "duration": 2.35}, {"text": "So I went through\nmost of the side.", "start": 2401.9, "duration": 1.68}, {"text": "Yes, miles?", "start": 2403.58, "duration": 0.96}, {"text": "AUDIENCE: Is this a way you can\ndetermine what gene sequences", "start": 2404.54, "duration": 3.875}, {"text": "are expressed in all cells?", "start": 2408.415, "duration": 2.305}, {"text": "Because in certain mRNA strands\nacross all tissue samples,", "start": 2410.72, "duration": 5.868}, {"text": "those are basic cell functions\nand expressed in a [INAUDIBLE]", "start": 2416.588, "duration": 6.282}, {"text": "organism?", "start": 2422.87, "duration": 1.413}, {"text": "ADAM MARTIN: So you're\nasking, if you grind up", "start": 2424.283, "duration": 1.917}, {"text": "like an entire\norganism and if you", "start": 2426.2, "duration": 2.43}, {"text": "get a cDNA from that\nlibrary, could you", "start": 2428.63, "duration": 2.52}, {"text": "tell if it's expressed in\nall different cell types?", "start": 2431.15, "duration": 5.22}, {"text": "Even if you have one cell\ntype that expresses a gene,", "start": 2436.37, "duration": 3.6}, {"text": "if you grind up the\nentire organism,", "start": 2439.97, "duration": 2.56}, {"text": "then you're going to have some\nmRNA that represents that gene.", "start": 2442.53, "duration": 3.32}, {"text": "So I don't think it would\nbe as an effective measure", "start": 2445.85, "duration": 2.97}, {"text": "to determine the ubiquity of\nexpression of a given gene,", "start": 2448.82, "duration": 3.78}, {"text": "but in just a minute,\nI'm going to give you", "start": 2452.6, "duration": 1.83}, {"text": "a tool that would allow you\nto answer the exact question", "start": 2454.43, "duration": 3.15}, {"text": "that you're asking, OK?", "start": 2457.58, "duration": 2.64}, {"text": "Any other questions\nabout the cDNA library?", "start": 2460.22, "duration": 4.37}, {"text": "OK.", "start": 2464.59, "duration": 2.33}, {"text": "So I just wanted to mention that\na comeback to this example I", "start": 2466.92, "duration": 3.93}, {"text": "gave on the identification\nof the human CDK gene.", "start": 2470.85, "duration": 4.15}, {"text": "So remember, we started\nwith yeast that were mutant.", "start": 2475.0, "duration": 5.15}, {"text": "They had\ntemperature-sensitive mutants,", "start": 2480.15, "duration": 2.28}, {"text": "and we transformed these\nmutants with a library,", "start": 2482.43, "duration": 2.61}, {"text": "but I didn't really tell\nyou what the library was.", "start": 2485.04, "duration": 2.1}, {"text": "It was in fact the cDNA\nlibrary from humans that", "start": 2487.14, "duration": 3.12}, {"text": "was transformed into yeast, OK?", "start": 2490.26, "duration": 2.48}, {"text": "And that's because yeast genes--", "start": 2492.74, "duration": 1.72}, {"text": "for the most part, they don't\nhave a lot of interests, and so", "start": 2494.46, "duration": 3.69}, {"text": "the yeast--", "start": 2498.15, "duration": 1.095}, {"text": "the machinery is not\nable to splice out", "start": 2499.245, "duration": 2.595}, {"text": "the human interactions\nand human genes, OK?", "start": 2501.84, "duration": 3.45}, {"text": "And so this was done\nwith a human cDNA", "start": 2505.29, "duration": 2.52}, {"text": "library, which then encoded--", "start": 2507.81, "duration": 2.49}, {"text": "one of which encoded the\ncumin CDK gene, and that", "start": 2510.3, "duration": 3.78}, {"text": "allowed Paul Nurse to\ndiscover the piece of DNA that", "start": 2514.08, "duration": 3.84}, {"text": "encoded for the human CDK, OK?", "start": 2517.92, "duration": 3.27}, {"text": "So I just wanted to\nkind of retroactively", "start": 2521.19, "duration": 2.25}, {"text": "go back and sort of tell you\nhow that experiment was done.", "start": 2523.44, "duration": 3.0}, {"text": "OK, so now I'm going to\nget to my final point", "start": 2529.87, "duration": 3.79}, {"text": "for this lecture, which is\nthis final technique, which", "start": 2533.66, "duration": 4.32}, {"text": "will allow us to determine\nwhether or not a transcript is", "start": 2537.98, "duration": 3.87}, {"text": "expressed in a single\ncell type or ubiquitously", "start": 2541.85, "duration": 3.03}, {"text": "through an organism, and this\ninvolves a technique, which", "start": 2544.88, "duration": 4.38}, {"text": "is known as hybridization.", "start": 2549.26, "duration": 1.52}, {"text": "And what hybridization\nis is if you're", "start": 2555.87, "duration": 3.05}, {"text": "starting with a\npiece of DNA, you", "start": 2558.92, "duration": 2.91}, {"text": "don't need to know\nits sequence in order", "start": 2561.83, "duration": 2.34}, {"text": "to determine whether\nthere are sequences that", "start": 2564.17, "duration": 2.52}, {"text": "are similar or identical to\nit, because hybridisation", "start": 2566.69, "duration": 4.53}, {"text": "is basically if you\nhave some sequence", "start": 2571.22, "duration": 5.94}, {"text": "and it's single stranded\nsuch that you have a DNA", "start": 2577.16, "duration": 3.15}, {"text": "backbone but you\nhave base pairs that", "start": 2580.31, "duration": 2.7}, {"text": "are able to pair with\ntheir complementary bases", "start": 2583.01, "duration": 3.78}, {"text": "and you can use a piece of\nsingle stranded DNA like this", "start": 2586.79, "duration": 4.05}, {"text": "and you can label it such that\nif the labeled piece sticks", "start": 2590.84, "duration": 5.04}, {"text": "to another piece that has\nidentical or similar sequence,", "start": 2595.88, "duration": 4.08}, {"text": "you'll be able to visualize\nit in some way, OK?", "start": 2599.96, "duration": 3.87}, {"text": "So this is called--", "start": 2603.83, "duration": 1.53}, {"text": "you're looking for things\nthat anneal or hybridize", "start": 2605.36, "duration": 7.41}, {"text": "to a particular\nspecific sequence.", "start": 2612.77, "duration": 4.59}, {"text": "So you don't need to know\nthe sequence a priori, OK?", "start": 2620.27, "duration": 3.15}, {"text": "You just need to have this\nphysical piece of DNA,", "start": 2623.42, "duration": 3.6}, {"text": "and you can use this single\nstranded piece of DNA", "start": 2627.02, "duration": 3.33}, {"text": "to then fish for\nsimilar sequences, OK?", "start": 2630.35, "duration": 5.16}, {"text": "So we could take a piece of DNA\nhere maybe that's in a gene,", "start": 2635.51, "duration": 4.2}, {"text": "and we could fish\nthrough a DNA library", "start": 2639.71, "duration": 2.49}, {"text": "to try to identify a cDNA clone\nthat has sequence identity", "start": 2642.2, "duration": 5.4}, {"text": "to that piece of DNA, OK?", "start": 2647.6, "duration": 2.88}, {"text": "And the way this is done\nis to take a cDNA library.", "start": 2650.48, "duration": 3.48}, {"text": "So each of these colonies\nhere would express or have", "start": 2653.96, "duration": 4.95}, {"text": "a different clone of DNA.", "start": 2658.91, "duration": 3.0}, {"text": "You can then take a\nnitrocellulose filter, put it", "start": 2661.91, "duration": 3.0}, {"text": "on this plate, which would\nstick the bacteria in place", "start": 2664.91, "duration": 3.54}, {"text": "to that filter, and you\ncould then lice the bacteria", "start": 2668.45, "duration": 4.02}, {"text": "and denature the DNA, and then\nthe DNA is stuck to the figure,", "start": 2672.47, "duration": 3.63}, {"text": "but now it's single stranded.", "start": 2676.1, "duration": 3.51}, {"text": "You can then add your\nprobe, which is labeled,", "start": 2679.61, "duration": 2.79}, {"text": "and look for the colonies\nthat this probe sticks to,", "start": 2682.4, "duration": 3.6}, {"text": "and that would then identify\na particular cDNA, which", "start": 2686.0, "duration": 3.18}, {"text": "would identify whether\nor not a piece of DNA", "start": 2689.18, "duration": 3.12}, {"text": "is expressed in a\ngiven tissue type, OK?", "start": 2692.3, "duration": 3.33}, {"text": "So everyone see how\nthat would work?", "start": 2695.63, "duration": 3.76}, {"text": "So in addition to doing this\non a nitrous cellulose filter,", "start": 2699.39, "duration": 3.29}, {"text": "you can also do\nthis in a tissue,", "start": 2702.68, "duration": 3.63}, {"text": "and that's known as\nin situ hybridization.", "start": 2706.31, "duration": 2.55}, {"text": "And in this case, in\nsitu hybridization,", "start": 2712.67, "duration": 3.15}, {"text": "you're searching for mRNA in\na section of fixed tissue.", "start": 2715.82, "duration": 3.33}, {"text": "OK, and I have an\nexample from this paper", "start": 2730.31, "duration": 3.24}, {"text": "here, which is the\npaper this are cloned.", "start": 2733.55, "duration": 3.45}, {"text": "In this paper was the\ncloning of the aniridia gene,", "start": 2737.0, "duration": 3.42}, {"text": "and they identified a gene of\ninterest, which is called Pax6", "start": 2740.42, "duration": 4.38}, {"text": "now, and they basically\nused a piece of DNA", "start": 2744.8, "duration": 3.6}, {"text": "that they thought\nwas interesting,", "start": 2748.4, "duration": 2.22}, {"text": "and they did in situ\nhybridization in an organism,", "start": 2750.62, "duration": 4.56}, {"text": "in this case, you see an eye.", "start": 2755.18, "duration": 1.44}, {"text": "This is an eye here,\nand the label Pax6", "start": 2756.62, "duration": 3.36}, {"text": "is labeled in\nyellow, and you can", "start": 2759.98, "duration": 1.83}, {"text": "see how this transcript\nis present throughout", "start": 2761.81, "duration": 2.58}, {"text": "the entire eye, right?", "start": 2764.39, "duration": 2.04}, {"text": "And the way you would see if\nit's tissue specific is you", "start": 2766.43, "duration": 2.41}, {"text": "look in other tissues and you\nwouldn't see this yellow label.", "start": 2768.84, "duration": 3.98}, {"text": "So that's how you\nwould determine", "start": 2772.82, "duration": 2.19}, {"text": "if it's expressed in a\nspecific tissue or ubiquitously", "start": 2775.01, "duration": 3.57}, {"text": "throughout an organism.", "start": 2778.58, "duration": 0.96}, {"text": "OK, so this Pax6 gene.", "start": 2782.4, "duration": 2.36}, {"text": "Oop.", "start": 2784.76, "duration": 0.563}, {"text": "So I was going to\nask, what do you think", "start": 2785.323, "duration": 1.667}, {"text": "would happen if you\nhyperactivate Pax6 in humans,", "start": 2786.99, "duration": 5.14}, {"text": "and this is one idea, but\nactually, I just made that up,", "start": 2792.13, "duration": 7.25}, {"text": "or Stan Lee made that up,\nbut actually, Stan Lee never", "start": 2799.38, "duration": 5.37}, {"text": "in fact mentioned whether or\nnot cyclops is a Pax6 mutant,", "start": 2804.75, "duration": 4.17}, {"text": "but we can do a different type\nof experiment, which might be", "start": 2808.92, "duration": 4.89}, {"text": "more ethical, which is we\nknow there's a fly gene that's", "start": 2813.81, "duration": 4.29}, {"text": "homologous to Pax6.", "start": 2818.1, "duration": 1.92}, {"text": "And what we can do in\nflies is we can topically", "start": 2820.02, "duration": 4.29}, {"text": "express this islets\ngene in non-eye tissues", "start": 2824.31, "duration": 3.6}, {"text": "and see what happens.", "start": 2827.91, "duration": 1.98}, {"text": "OK so, this is pretty wild.", "start": 2829.89, "duration": 1.62}, {"text": "This is my Halloween\nimage of the class.", "start": 2831.51, "duration": 4.48}, {"text": "So this is a fly\nwhere eyeless has been", "start": 2835.99, "duration": 2.42}, {"text": "expressed all over its body.", "start": 2838.41, "duration": 2.78}, {"text": "OK, so here you see\nthere's an eye--", "start": 2841.19, "duration": 1.75}, {"text": "It's normal eye-- here.", "start": 2842.94, "duration": 2.07}, {"text": "You can see there's\nnow another eye", "start": 2845.01, "duration": 1.65}, {"text": "growing in the\nfront of its head.", "start": 2846.66, "duration": 2.38}, {"text": "You can see here's an eye\ngrowing on this fly's back,", "start": 2849.04, "duration": 3.11}, {"text": "and you can see the legs.", "start": 2852.15, "duration": 2.37}, {"text": "There's eye tissue all over\nthe legs of this fly, OK?", "start": 2854.52, "duration": 3.81}, {"text": "So this Pax6 gene, which is\nconserved from flies to humans", "start": 2858.33, "duration": 4.8}, {"text": "is the master regulator\nof eye development, OK?", "start": 2863.13, "duration": 3.3}, {"text": "And at least in flies,\nif you topically", "start": 2866.43, "duration": 2.21}, {"text": "express this in other parts\nof the body, you get an eye.", "start": 2868.64, "duration": 4.52}, {"text": "I should say these are\nnot functionalized.", "start": 2873.16, "duration": 2.2}, {"text": "They don't hook up to\nthe brain the same way", "start": 2875.36, "duration": 2.29}, {"text": "the normal eye does.", "start": 2877.65, "duration": 1.86}, {"text": "So it's not like\nthis fly can see out", "start": 2879.51, "duration": 2.25}, {"text": "of the back of its head.", "start": 2881.76, "duration": 2.7}, {"text": "OK, that's it.", "start": 2884.46, "duration": 1.83}, {"text": "I'm done, and good luck\non your exam on Wednesday.", "start": 2886.29, "duration": 3.3}, {"text": "We will see you here.", "start": 2889.59, "duration": 2.18}]
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+[{"text": "MICHALE FEE: Today\nwe're going to continue", "start": 13.7, "duration": 1.75}, {"text": "building our equivalent\ncircuit model of a neuron.", "start": 15.45, "duration": 4.17}, {"text": "Again, this is the\nHodgkin-Huxley model,", "start": 19.62, "duration": 2.76}, {"text": "and the model was\nreally developed", "start": 22.38, "duration": 3.0}, {"text": "around explaining how neurons\ngenerate action potentials.", "start": 25.38, "duration": 5.37}, {"text": "There are two key\nion channels that are", "start": 30.75, "duration": 3.09}, {"text": "associated with making spikes.", "start": 33.84, "duration": 1.62}, {"text": "There's a sodium\nchannel that we model", "start": 35.46, "duration": 5.52}, {"text": "as a conductance in\nseries with a battery,", "start": 40.98, "duration": 3.28}, {"text": "and there's a\npotassium conductance", "start": 44.26, "duration": 3.2}, {"text": "that we model the same way.", "start": 47.46, "duration": 1.5}, {"text": "And again, those\ntwo conductances", "start": 48.96, "duration": 3.33}, {"text": "cooperate to produce\nan action potential.", "start": 52.29, "duration": 2.73}, {"text": "And we saw, essentially,\nhow those two conductances,", "start": 55.02, "duration": 4.56}, {"text": "together with their\nbatteries-- the sodium battery", "start": 59.58, "duration": 2.88}, {"text": "is up at plus 50\nor so millivolts.", "start": 62.46, "duration": 2.97}, {"text": "The potassium battery is down\nat minus 75 or so millivolts.", "start": 65.43, "duration": 3.75}, {"text": "And those two conductances then\nwork to essentially connect", "start": 69.18, "duration": 4.2}, {"text": "the inside of the neuron\nto the plus battery", "start": 73.38, "duration": 1.92}, {"text": "and then to the minus battery\nto give you an action potential.", "start": 75.3, "duration": 2.85}, {"text": "And you may remember that\nwe saw what that looks like.", "start": 78.15, "duration": 3.22}, {"text": "So here is plotting\nmembrane potential in blue.", "start": 81.37, "duration": 3.2}, {"text": "Here, we turn on this\nsodium conductance.", "start": 84.57, "duration": 2.79}, {"text": "The voltage of the cell\nraces up to about plus 55.", "start": 87.36, "duration": 4.17}, {"text": "Then we turn off the sodium.", "start": 91.53, "duration": 1.5}, {"text": "We turn on the potassium.", "start": 93.03, "duration": 1.56}, {"text": "The voltage goes down\nto minus 75 or so.", "start": 94.59, "duration": 3.3}, {"text": "And then we turn off\nboth conductances,", "start": 97.89, "duration": 1.95}, {"text": "and the cell recovers.", "start": 99.84, "duration": 1.42}, {"text": "So you can see that that\nbasically produces what", "start": 101.26, "duration": 3.05}, {"text": "looks like an action potential.", "start": 104.31, "duration": 1.92}, {"text": "That's the basis of action\npotential production.", "start": 106.23, "duration": 5.74}, {"text": "But in order to understand how\nthese things turn on and off", "start": 111.97, "duration": 4.5}, {"text": "in the time course\nthat they do, we", "start": 116.47, "duration": 2.7}, {"text": "need to understand\na little bit more", "start": 119.17, "duration": 1.65}, {"text": "about how these sodium and\npotassium conductances work.", "start": 120.82, "duration": 3.48}, {"text": "And that's what we're\ngoing to focus on today.", "start": 124.3, "duration": 4.66}, {"text": "So let's just start\nbuilding our model.", "start": 128.96, "duration": 4.8}, {"text": "So each one of those\nconductances with a battery", "start": 133.76, "duration": 3.8}, {"text": "is associated with a current.", "start": 137.56, "duration": 1.53}, {"text": "There's a current\nthat goes through each", "start": 139.09, "duration": 1.68}, {"text": "of those conductances.", "start": 140.77, "duration": 1.53}, {"text": "The total current\nthrough the membrane,", "start": 142.3, "duration": 2.96}, {"text": "the ionic current through the\nmembrane in the Hodgkin-Huxley", "start": 145.26, "duration": 2.5}, {"text": "model is a sum of three\ncomponents, actually--", "start": 147.76, "duration": 2.72}, {"text": "a sodium current, a\npotassium current--", "start": 150.48, "duration": 2.98}, {"text": "those two we just talked about--", "start": 153.46, "duration": 1.53}, {"text": "and a leak current that\nis just a fixed current.", "start": 154.99, "duration": 5.37}, {"text": "So the sodium and\npotassium currents", "start": 160.36, "duration": 2.25}, {"text": "are functions of\ntime and voltage.", "start": 162.61, "duration": 3.37}, {"text": "The leak current, the leak\nconductance, is just fixed.", "start": 165.98, "duration": 3.95}, {"text": "And it has a battery of\nabout minus 50 millivolts.", "start": 169.93, "duration": 3.24}, {"text": "And it just tends to keep the\ncell sort of hyperpolarized.", "start": 173.17, "duration": 3.63}, {"text": "And these two currents,\nthese two conductances,", "start": 176.8, "duration": 3.54}, {"text": "do the job of making\nan action potential.", "start": 180.34, "duration": 2.8}, {"text": "So the total membrane\ncurrent is just", "start": 183.14, "duration": 2.69}, {"text": "a sum of those three parts.", "start": 185.83, "duration": 1.92}, {"text": "And now we can just take\nthat membrane current", "start": 187.75, "duration": 4.05}, {"text": "and plug it into this equation\nfor the voltage as a function", "start": 191.8, "duration": 4.86}, {"text": "of current now and solve\nthat differential equation", "start": 196.66, "duration": 3.54}, {"text": "to get the voltage to calculate\nhow the voltage evolves", "start": 200.2, "duration": 5.4}, {"text": "in time in the presence of\nthese membrane currents.", "start": 205.6, "duration": 4.01}, {"text": "All right, so you recall\nfrom the last lecture", "start": 213.62, "duration": 4.57}, {"text": "that you watched on video\nthat these currents can be", "start": 218.19, "duration": 3.96}, {"text": "written down as a conductance.", "start": 222.15, "duration": 2.68}, {"text": "So let's just start here.", "start": 224.83, "duration": 1.8}, {"text": "This is the most\nsimilar one to the one", "start": 226.63, "duration": 1.97}, {"text": "that you saw in the\nprevious lecture.", "start": 228.6, "duration": 3.03}, {"text": "The current is\njust a conductance", "start": 231.63, "duration": 2.25}, {"text": "times a driving potential.", "start": 233.88, "duration": 1.8}, {"text": "And we described\nhow that equation", "start": 235.68, "duration": 2.67}, {"text": "can be summarized in\nelectrical circuit components", "start": 238.35, "duration": 3.69}, {"text": "as a resistor, which is\none over the conductance,", "start": 242.04, "duration": 3.83}, {"text": "times a driving potential,\nwhich is basically", "start": 245.87, "duration": 2.86}, {"text": "just the voltage drop\nacross the conductance.", "start": 248.73, "duration": 6.63}, {"text": "Now, each of these conductances,\neach of these currents,", "start": 255.36, "duration": 3.5}, {"text": "is going to be written down\nby a very similar equation.", "start": 258.86, "duration": 2.77}, {"text": "So the potassium current is\njust the potassium conductance", "start": 261.63, "duration": 3.48}, {"text": "times the driving\npotential for potassium,", "start": 265.11, "duration": 3.13}, {"text": "which is just the membrane\npotential minus the Ek.", "start": 268.24, "duration": 4.07}, {"text": "And the sodium current is\njust the sodium conductance", "start": 272.31, "duration": 3.27}, {"text": "times the driving\npotential for sodium,", "start": 275.58, "duration": 2.47}, {"text": "which is the membrane potential\nminus the sodium battery.", "start": 278.05, "duration": 4.56}, {"text": "Any questions?", "start": 282.61, "duration": 1.55}, {"text": "Yes?", "start": 284.16, "duration": 0.773}, {"text": "AUDIENCE: How did\nthe [INAUDIBLE]..", "start": 284.933, "duration": 3.317}, {"text": "MICHALE FEE: Yeah.", "start": 288.25, "duration": 2.66}, {"text": "So unless I've made a mistake,\nI've tried to put these--", "start": 290.91, "duration": 6.45}, {"text": "remember that the\npotassium battery is minus,", "start": 297.36, "duration": 5.52}, {"text": "is negative, right?", "start": 302.88, "duration": 1.8}, {"text": "And the sodium\nbattery is positive.", "start": 304.68, "duration": 2.1}, {"text": "So I've tried to\nshow that by putting", "start": 306.78, "duration": 1.98}, {"text": "the batteries in the\nopposite direction, right?", "start": 308.76, "duration": 2.2}, {"text": "So the battery\nsymbol has one side", "start": 310.96, "duration": 1.82}, {"text": "that's supposed to\nindicate positive voltage,", "start": 312.78, "duration": 3.328}, {"text": "and the other side is negative.", "start": 316.108, "duration": 1.292}, {"text": "So because they have\nthe opposite sign,", "start": 317.4, "duration": 1.74}, {"text": "I've put them in backwards,\nin the opposite direction.", "start": 319.14, "duration": 3.635}, {"text": "Does that make sense?", "start": 322.775, "duration": 0.875}, {"text": "Don't worry about that too much.", "start": 323.65, "duration": 2.21}, {"text": "If I ask you to draw\nthis, I don't really", "start": 325.86, "duration": 2.34}, {"text": "care that much which\nway these things go.", "start": 328.2, "duration": 2.22}, {"text": "I just want you to\nknow that this one is", "start": 330.42, "duration": 3.24}, {"text": "negative on the inside\nand that the sodium is", "start": 333.66, "duration": 3.63}, {"text": "positive on the inside.", "start": 337.29, "duration": 2.05}, {"text": "This is the inside of\nthe cell here, right?", "start": 339.34, "duration": 3.95}, {"text": "The sodium battery\ndrives the inside", "start": 343.29, "duration": 3.12}, {"text": "of the cell toward\npositive voltage,", "start": 346.41, "duration": 2.1}, {"text": "because you have positive\nions flowing into the cell.", "start": 348.51, "duration": 2.52}, {"text": "So you can see now that\nthe membrane potential here", "start": 356.47, "duration": 3.74}, {"text": "depends on the membrane currents\nthrough this differential", "start": 360.21, "duration": 3.54}, {"text": "equation.", "start": 363.75, "duration": 1.75}, {"text": "But the membrane currents--\nthe sodium, potassium, and leak", "start": 365.5, "duration": 3.54}, {"text": "currents-- all depend on\nthese conductances, right?", "start": 369.04, "duration": 3.54}, {"text": "And these conductances for\nthe sodium and potassium", "start": 372.58, "duration": 2.55}, {"text": "are voltage dependent\nand time dependent.", "start": 375.13, "duration": 4.12}, {"text": "So you can see that\nthe conductances", "start": 379.25, "duration": 1.58}, {"text": "depend on the voltage, right?", "start": 380.83, "duration": 3.12}, {"text": "So the membrane potential\ndepends on current.", "start": 383.95, "duration": 1.875}, {"text": "Current depends on conductances,\nbut the conductances", "start": 385.825, "duration": 2.895}, {"text": "depend on the\nmembrane potential.", "start": 388.72, "duration": 1.9}, {"text": "So it goes around and\naround and around, right?", "start": 390.62, "duration": 2.66}, {"text": "So those things all\ndepend on each other.", "start": 393.28, "duration": 2.7}, {"text": "And so what we are\nsetting out to do", "start": 395.98, "duration": 3.27}, {"text": "is to write down the way those\nthings depend on each other,", "start": 399.25, "duration": 3.96}, {"text": "the way you can think about\nthat system evolving in time.", "start": 403.21, "duration": 3.78}, {"text": "So let me just show\nyou what the plan is.", "start": 406.99, "duration": 2.37}, {"text": "So the plan is to write down\nan algorithm-- basically,", "start": 409.36, "duration": 2.91}, {"text": "a for loop--", "start": 412.27, "duration": 1.56}, {"text": "that describes how the neuron\ngenerates an action potential.", "start": 413.83, "duration": 4.412}, {"text": "Let me just walk you\nthrough the steps of that,", "start": 418.242, "duration": 1.958}, {"text": "and then I'll get\nto your question.", "start": 420.2, "duration": 2.85}, {"text": "So we're going to start with\nsome membrane potential V,", "start": 423.05, "duration": 4.47}, {"text": "and we're going\nto calculate that", "start": 427.52, "duration": 3.3}, {"text": "the voltage-dependent parameters\nof the sodium and potassium", "start": 430.82, "duration": 3.66}, {"text": "conductance using that\nmembrane potential.", "start": 434.48, "duration": 4.4}, {"text": "And once we have\nthose parameters,", "start": 438.88, "duration": 1.86}, {"text": "we can actually calculate the\nconductance for each of those,", "start": 440.74, "duration": 5.58}, {"text": "for the sodium and potassium.", "start": 446.32, "duration": 2.1}, {"text": "Once you know the conductance,\nyou can get the currents.", "start": 448.42, "duration": 4.39}, {"text": "Once you have the\ncurrents, you can", "start": 452.81, "duration": 1.47}, {"text": "compute the total\nmembrane current, just", "start": 454.28, "duration": 2.01}, {"text": "by adding them all together.", "start": 456.29, "duration": 2.66}, {"text": "Then, you can compute--", "start": 458.95, "duration": 1.345}, {"text": "once you have all\nthose currents,", "start": 460.295, "duration": 1.375}, {"text": "you just compute V infinity,\nwhich is just the current times", "start": 461.67, "duration": 4.95}, {"text": "the resistance, the\neffective resistance.", "start": 466.62, "duration": 2.79}, {"text": "Then we're going to\nintegrate our first order", "start": 469.41, "duration": 2.7}, {"text": "linear differential equation to\nget a new voltage as a function", "start": 472.11, "duration": 3.78}, {"text": "of time and V infinity.", "start": 475.89, "duration": 2.28}, {"text": "And we're just going to\ngo back and start again.", "start": 478.17, "duration": 2.77}, {"text": "The so that's the\nalgorithm that a neuron", "start": 480.94, "duration": 3.2}, {"text": "uses to generate a spike.", "start": 484.14, "duration": 2.88}, {"text": "And that's what we're\ngoing to work out.", "start": 490.37, "duration": 2.28}, {"text": "Now, we've talked\nabout these things", "start": 492.65, "duration": 2.04}, {"text": "over the last few\nlectures, how you", "start": 494.69, "duration": 3.21}, {"text": "can relate total\ncurrent to V infinity", "start": 497.9, "duration": 2.483}, {"text": "and then integrate a first\norder linear differential", "start": 500.383, "duration": 2.167}, {"text": "equation, which is just\nrelaxing exponentially", "start": 502.55, "duration": 2.94}, {"text": "toward V infinity.", "start": 505.49, "duration": 2.94}, {"text": "But now we're going to put\nthese things in, figure out", "start": 508.43, "duration": 2.82}, {"text": "the voltage and time\ndependence of the sodium", "start": 511.25, "duration": 3.39}, {"text": "and potassium conductances.", "start": 514.64, "duration": 1.409}, {"text": "Yes?", "start": 516.049, "duration": 1.312}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 517.361, "duration": 1.428}, {"text": "MICHALE FEE: Yes.", "start": 522.732, "duration": 0.708}, {"text": "It's primarily potassium.", "start": 523.44, "duration": 1.9}, {"text": "It has a negative potential.", "start": 525.34, "duration": 2.3}, {"text": "But it's just constant,\nso we're not really", "start": 527.64, "duration": 2.46}, {"text": "going to pay much\nattention to it.", "start": 530.1, "duration": 3.19}, {"text": "So if the sodium and\npotassium currents are off,", "start": 533.29, "duration": 3.96}, {"text": "then the leak current still\nkeeps the cell hyperpolarized.", "start": 537.25, "duration": 4.67}, {"text": "All right, any questions?", "start": 541.92, "duration": 1.27}, {"text": "That's the big picture.", "start": 543.19, "duration": 3.95}, {"text": "So here are our\nlearning objectives.", "start": 547.14, "duration": 2.64}, {"text": "I'd like you to be able to\ndraw that circuit diagram,", "start": 549.78, "duration": 4.68}, {"text": "not worrying about the long\nand short sides of the battery.", "start": 554.46, "duration": 3.24}, {"text": "We're going to talk\nabout how we measure", "start": 561.92, "duration": 2.16}, {"text": "the properties of ion channels.", "start": 564.08, "duration": 2.43}, {"text": "That's called a voltage clamp.", "start": 566.51, "duration": 1.29}, {"text": "So I want you to be able\nto describe what that is.", "start": 567.8, "duration": 2.52}, {"text": "I'd like you to be able to\nplot the voltage and time", "start": 570.32, "duration": 2.28}, {"text": "dependence of the potassium\ncurrent for today.", "start": 572.6, "duration": 3.75}, {"text": "The next lecture, we'll talk\nabout the sodium current,", "start": 576.35, "duration": 2.25}, {"text": "so we'll add that to our list\nof things that we need to know.", "start": 578.6, "duration": 2.782}, {"text": "But for today, I'd\nlike you to able", "start": 581.382, "duration": 1.458}, {"text": "to plot the voltage and time\ndependence of the potassium", "start": 582.84, "duration": 2.72}, {"text": "current and conductance.", "start": 585.56, "duration": 2.61}, {"text": "And be able to\nexplain, biophysically,", "start": 588.17, "duration": 3.18}, {"text": "where the time and voltage\ndependence of that potassium", "start": 591.35, "duration": 2.67}, {"text": "conductance comes from and\nbe able to write it down", "start": 594.02, "duration": 3.3}, {"text": "in terms of quantities\nthat are called", "start": 597.32, "duration": 3.81}, {"text": "the Hodgkin-Huxley\ngating variables.", "start": 601.13, "duration": 3.12}, {"text": "So that's the plan.", "start": 604.25, "duration": 3.28}, {"text": "All right, so let's come\nback to our circuit.", "start": 607.53, "duration": 2.27}, {"text": "Again, we have a\nsodium current that's", "start": 609.8, "duration": 3.6}, {"text": "sodium conductance times the\nsodium driving potential.", "start": 613.4, "duration": 3.51}, {"text": "The conductance is voltage\nand time dependent.", "start": 616.91, "duration": 2.7}, {"text": "The equilibrium\npotential for sodium,", "start": 619.61, "duration": 1.74}, {"text": "again, is plus 55 millivolts.", "start": 621.35, "duration": 2.61}, {"text": "The potassium current is\njust potassium conductance", "start": 623.96, "duration": 3.12}, {"text": "times the potassium\ndriving potential.", "start": 627.08, "duration": 3.04}, {"text": "The driving potential\nis reference", "start": 630.12, "duration": 1.67}, {"text": "to a battery in equilibrium\npotential at minus 75.", "start": 631.79, "duration": 3.51}, {"text": "And the leak has a battery\nat minus 50 millivolts.", "start": 635.3, "duration": 3.4}, {"text": "So those are the parts\nwe're going to use.", "start": 638.7, "duration": 3.95}, {"text": "We're going to describe now\nthe experiments that Hodgkin", "start": 642.65, "duration": 3.48}, {"text": "and Huxley did to extract\nthe parameters of the sodium", "start": 646.13, "duration": 4.05}, {"text": "and potassium conductances.", "start": 650.18, "duration": 1.68}, {"text": "Today, we're going to focus\non the potassium conductances.", "start": 651.86, "duration": 3.15}, {"text": "And then on next\nTuesday, I guess,", "start": 655.01, "duration": 3.51}, {"text": "we're going to do the sodium.", "start": 658.52, "duration": 3.27}, {"text": "All right, so the reason\nHodgkin and Huxley studied--", "start": 661.79, "duration": 3.81}, {"text": "so they studied these\nchannels, the potassium", "start": 665.6, "duration": 3.3}, {"text": "and sodium channels, in\nthe giant squid axon.", "start": 668.9, "duration": 2.95}, {"text": "Now, most of our\naxons are about a--", "start": 671.85, "duration": 2.72}, {"text": "most of the axons in our brain\nare about a micron across.", "start": 674.57, "duration": 4.47}, {"text": "This axon is about\na millimeter across.", "start": 679.04, "duration": 3.0}, {"text": "Action potentials propagate\nmuch faster in large axons,", "start": 682.04, "duration": 4.26}, {"text": "and this axon is involved\nin transmitting an action", "start": 686.3, "duration": 2.52}, {"text": "potential from the\nbrain to the tail that", "start": 688.82, "duration": 2.28}, {"text": "drives an escape reflex.", "start": 691.1, "duration": 1.98}, {"text": "The squid squirts water out\nof sort of a chamber that", "start": 693.08, "duration": 5.55}, {"text": "has water in it.", "start": 698.63, "duration": 1.08}, {"text": "If the squid senses\ndanger, it contracts", "start": 699.71, "duration": 2.37}, {"text": "muscles that squeeze water out\nof that, and it makes a jet.", "start": 702.08, "duration": 3.06}, {"text": "And it squirts the squid\nforward away from danger.", "start": 705.14, "duration": 3.91}, {"text": "So that action potential has\nto propagate very quickly", "start": 709.05, "duration": 2.81}, {"text": "from the brain to the\ntail, and it does that", "start": 711.86, "duration": 2.43}, {"text": "through this enormous axon.", "start": 714.29, "duration": 1.59}, {"text": "That axon is so big you can\nnow put multiple wires inside", "start": 715.88, "duration": 3.7}, {"text": "of it.", "start": 719.58, "duration": 0.5}, {"text": "You don't even need to pull\nthese glass electrodes.", "start": 720.08, "duration": 2.32}, {"text": "You can just take little\nwires and stick them in--", "start": 722.4, "duration": 2.33}, {"text": "chop out a little\npiece of the axon", "start": 724.73, "duration": 1.5}, {"text": "and stick wires inside\nof it and study it.", "start": 726.23, "duration": 2.97}, {"text": "Yes?", "start": 729.2, "duration": 0.65}, {"text": "AUDIENCE: So if the\nbody of this squid", "start": 729.85, "duration": 1.614}, {"text": "is like a giant [INAUDIBLE]\nit has arms coming out", "start": 731.464, "duration": 2.41}, {"text": "of its head?", "start": 733.874, "duration": 0.908}, {"text": "MICHALE FEE: Yes.", "start": 734.782, "duration": 0.708}, {"text": "You eat that part,\nand you eat that part.", "start": 739.09, "duration": 3.15}, {"text": "Not that.", "start": 742.24, "duration": 2.05}, {"text": "You throw away the\nmost interesting part.", "start": 744.29, "duration": 3.29}, {"text": "OK, any other questions?", "start": 747.58, "duration": 1.837}, {"text": "All right, so now\nwe're setting out", "start": 752.32, "duration": 3.21}, {"text": "to measure these sodium and\npotassium conductances, OK?", "start": 755.53, "duration": 4.05}, {"text": "So how do we do that?", "start": 759.58, "duration": 2.51}, {"text": "So what we really\nwant to do is to set--", "start": 762.09, "duration": 3.47}, {"text": "we want to measure\nconductance, which", "start": 765.56, "duration": 2.01}, {"text": "is the relation between\nvoltage and current.", "start": 767.57, "duration": 3.1}, {"text": "So we'd like to do\nis to be able to set", "start": 770.67, "duration": 1.91}, {"text": "the voltage at a certain level\nand measure the current that", "start": 772.58, "duration": 4.08}, {"text": "flows through these channels.", "start": 776.66, "duration": 3.49}, {"text": "So you really want to\nplot the IV curve, right?", "start": 780.15, "duration": 3.54}, {"text": "You want to set the voltage,\nmeasure the current,", "start": 783.69, "duration": 2.55}, {"text": "and do that at a bunch\nof different voltages.", "start": 786.24, "duration": 2.16}, {"text": "And you recall that the\nconductance is basically", "start": 788.4, "duration": 2.85}, {"text": "just the slope of that\ncurve, right, that line.", "start": 791.25, "duration": 7.33}, {"text": "So the job is set\nvoltage, measure current,", "start": 798.58, "duration": 3.0}, {"text": "extract conductance.", "start": 801.58, "duration": 2.16}, {"text": "Now, the problem with\nthat is that as soon", "start": 803.74, "duration": 2.85}, {"text": "as you set the\nvoltage of the axon", "start": 806.59, "duration": 3.63}, {"text": "somewhere up here in\nan interesting range,", "start": 810.22, "duration": 2.43}, {"text": "the thing begins to spike.", "start": 812.65, "duration": 3.37}, {"text": "And then the voltage is\nno longer constant, right?", "start": 816.02, "duration": 4.37}, {"text": "So it becomes really\nhard to make measurements", "start": 820.39, "duration": 2.97}, {"text": "like this if you depolarize\nthe cell a little bit", "start": 823.36, "duration": 3.377}, {"text": "to set try to set the\nvoltage and all of a sudden,", "start": 826.737, "duration": 2.083}, {"text": "it's [MIMICS BUZZING].", "start": 828.82, "duration": 0.917}, {"text": "It's generating spikes.", "start": 829.737, "duration": 2.443}, {"text": "So what do you do?", "start": 832.18, "duration": 1.33}, {"text": "So the trick is to develop a\ndevice called a voltage clamp.", "start": 833.51, "duration": 4.16}, {"text": "This thing basically\nholds the-- so,", "start": 837.67, "duration": 2.49}, {"text": "look, if the action potential\nwere really, really slow,", "start": 840.16, "duration": 4.03}, {"text": "then you could actually\nset the voltage.", "start": 844.19, "duration": 2.69}, {"text": "You could change the current\nbeing injected into the cell", "start": 846.88, "duration": 3.45}, {"text": "by hand.", "start": 850.33, "duration": 0.78}, {"text": "You say, OK, I'm trying to\nset the voltage at zero.", "start": 851.11, "duration": 2.625}, {"text": "Oh, it got a little\nbit too high,", "start": 853.735, "duration": 1.375}, {"text": "so I turn the current down.", "start": 855.11, "duration": 1.34}, {"text": "Now the voltage\nhas gone too low,", "start": 856.45, "duration": 1.83}, {"text": "so now I turn the current up.", "start": 858.28, "duration": 1.8}, {"text": "You could do it by hand\nif the action potential", "start": 860.08, "duration": 3.51}, {"text": "were super slow, if it took\na minute to generate, right?", "start": 863.59, "duration": 3.57}, {"text": "But the action potential\ntakes a millisecond.", "start": 867.16, "duration": 2.34}, {"text": "So that's just too\nfast for you to follow.", "start": 869.5, "duration": 2.22}, {"text": "So you just make a\nlittle electrical circuit", "start": 871.72, "duration": 2.43}, {"text": "that does that job for you.", "start": 874.15, "duration": 2.4}, {"text": "It uses feedback to set\nthe voltage where you want.", "start": 876.55, "duration": 3.21}, {"text": "So you put a--", "start": 879.76, "duration": 1.08}, {"text": "here's your cell.", "start": 880.84, "duration": 1.17}, {"text": "Here's your membrane\nresistance or conductance", "start": 882.01, "duration": 3.36}, {"text": "that you're trying to measure.", "start": 885.37, "duration": 2.23}, {"text": "You put a electrode in the cell.", "start": 887.6, "duration": 1.59}, {"text": "You put it into a\nlittle amplifier called", "start": 889.19, "duration": 1.86}, {"text": "an operational amplifier.", "start": 891.05, "duration": 3.42}, {"text": "And then on the other\nside of that amplifier,", "start": 894.47, "duration": 2.19}, {"text": "that differential\namplifier, you put", "start": 896.66, "duration": 3.39}, {"text": "the command voltage that\nyou're trying to set.", "start": 900.05, "duration": 3.46}, {"text": "So here's the way it works.", "start": 903.51, "duration": 2.52}, {"text": "Basically, this thing tries\nto set the membrane potential.", "start": 906.03, "duration": 3.56}, {"text": "It tries to make this\nvalue, this voltage,", "start": 909.59, "duration": 3.1}, {"text": "equal to that voltage.", "start": 912.69, "duration": 1.23}, {"text": "And it does that by feeding\ncurrent back into the cell.", "start": 913.92, "duration": 3.72}, {"text": "Does that make sense?", "start": 917.64, "duration": 2.13}, {"text": "OK, so you use an\noperational amplifier.", "start": 919.77, "duration": 2.65}, {"text": "An op amp has two inputs--", "start": 922.42, "duration": 1.85}, {"text": "a plus input, a minus input.", "start": 924.27, "duration": 1.96}, {"text": "The output is just a gain\ntimes the plus input minus--", "start": 926.23, "duration": 4.14}, {"text": "the positive input minus\nthe negative input.", "start": 930.37, "duration": 2.31}, {"text": "And the gain is really big.", "start": 932.68, "duration": 1.39}, {"text": "It's about a million.", "start": 934.07, "duration": 1.31}, {"text": "So if this input is a\nlittle bit above that input,", "start": 935.38, "duration": 2.31}, {"text": "this output is big and positive.", "start": 937.69, "duration": 2.92}, {"text": "If this input is\nless than that input,", "start": 940.61, "duration": 2.9}, {"text": "you can see this is negative.", "start": 943.51, "duration": 1.39}, {"text": "And so the output\nis big and negative.", "start": 944.9, "duration": 2.33}, {"text": "Any questions?", "start": 947.23, "duration": 2.74}, {"text": "So don't get confused here.", "start": 949.97, "duration": 1.28}, {"text": "That G is gain, not conductance,\njust for the next few slides.", "start": 951.25, "duration": 7.32}, {"text": "So how does this work?", "start": 958.57, "duration": 1.24}, {"text": "You can see that if the\nmembrane potential is", "start": 959.81, "duration": 2.64}, {"text": "less than the command\nvoltage, then the output", "start": 962.45, "duration": 3.99}, {"text": "voltage is positive and big.", "start": 966.44, "duration": 2.88}, {"text": "That drives current\ninto the cell, which", "start": 969.32, "duration": 2.22}, {"text": "increases the membrane\npotential and makes it", "start": 971.54, "duration": 2.55}, {"text": "approach the command voltage.", "start": 974.09, "duration": 2.89}, {"text": "If the membrane potential\nis larger than the command", "start": 976.98, "duration": 3.66}, {"text": "voltage, then this thing--", "start": 980.64, "duration": 2.34}, {"text": "this is bigger than this.", "start": 982.98, "duration": 1.27}, {"text": "So this is negative.", "start": 984.25, "duration": 1.67}, {"text": "And that pulls current\nout of the neuron", "start": 985.92, "duration": 2.67}, {"text": "and decreases the\nmembrane potential.", "start": 988.59, "duration": 2.13}, {"text": "And in both cases,\nthe membrane potential", "start": 990.72, "duration": 2.67}, {"text": "is being pulled toward\nthe command voltage.", "start": 993.39, "duration": 2.7}, {"text": "And you can show, if you\njust plug in these variables", "start": 996.09, "duration": 5.76}, {"text": "into a couple of\nequations, that as long", "start": 1001.85, "duration": 2.46}, {"text": "as the gain is big enough,\nthe membrane potential", "start": 1004.31, "duration": 3.24}, {"text": "is forced to be very close\nto the command voltage.", "start": 1007.55, "duration": 4.17}, {"text": "All right, so that's\nthe voltage clamp.", "start": 1011.72, "duration": 2.43}, {"text": "It drives whatever current\nis necessary to clamp", "start": 1014.15, "duration": 3.87}, {"text": "the voltage of the cell\nat the command voltage.", "start": 1018.02, "duration": 2.97}, {"text": "And then what we do is\nduring an experiment,", "start": 1020.99, "duration": 2.64}, {"text": "we step the command\nvoltage around.", "start": 1023.63, "duration": 3.12}, {"text": "The cell tries to spike.", "start": 1026.75, "duration": 1.68}, {"text": "Those currents turn on.", "start": 1028.43, "duration": 1.139}, {"text": "The cell tries to\nspike, but this thing", "start": 1029.569, "duration": 2.55}, {"text": "keeps the voltage locked\nat whatever it is that you", "start": 1032.119, "duration": 3.271}, {"text": "want the voltage to be.", "start": 1035.39, "duration": 2.459}, {"text": "And then you measure the\namount of current required.", "start": 1037.849, "duration": 2.914}, {"text": "You just measure the\namount of current flowing", "start": 1040.763, "duration": 1.917}, {"text": "through this\nresistor here that's", "start": 1042.68, "duration": 3.659}, {"text": "required to hold the\ncell at any voltage.", "start": 1046.339, "duration": 3.781}, {"text": "All right, any questions?", "start": 1050.12, "duration": 1.23}, {"text": "Voltage clamp-- very cool.", "start": 1051.35, "duration": 1.8}, {"text": "Yes?", "start": 1057.16, "duration": 0.5}, {"text": "AUDIENCE: Can you\nexplain gain again?", "start": 1057.66, "duration": 1.73}, {"text": "MICHALE FEE: Gain is\njust the multiplier", "start": 1059.39, "duration": 1.72}, {"text": "here in this equation.", "start": 1061.11, "duration": 1.78}, {"text": "So if there's a tiny difference\nbetween the two inputs,", "start": 1062.89, "duration": 4.22}, {"text": "the output is bigger.", "start": 1067.11, "duration": 1.86}, {"text": "That's what gain means, right?", "start": 1068.97, "duration": 1.52}, {"text": "If the gain is a million, if\nthere's a microvolt difference", "start": 1076.19, "duration": 3.03}, {"text": "between the two inputs, the\noutput will be about a volt.", "start": 1079.22, "duration": 5.0}, {"text": "And it would be a plus or minus,\ndepending on which of those two", "start": 1084.22, "duration": 2.81}, {"text": "was more positive.", "start": 1087.03, "duration": 1.84}, {"text": "OK, so now let's get to the\nactual voltage clamp experiment", "start": 1091.71, "duration": 2.94}, {"text": "that Hodgkin and Huxley did.", "start": 1094.65, "duration": 2.34}, {"text": "Here, we have two\nwires in our cell-- one", "start": 1096.99, "duration": 1.98}, {"text": "to measure voltage and the\nother one to inject current.", "start": 1098.97, "duration": 2.61}, {"text": "That's exactly what they did.", "start": 1101.58, "duration": 1.66}, {"text": "There's one wire here.", "start": 1103.24, "duration": 1.26}, {"text": "That's a little piece of axon.", "start": 1104.5, "duration": 1.25}, {"text": "You can literally cut the\nsquid open, find that axon.", "start": 1105.75, "duration": 3.3}, {"text": "It's a big, white-looking tube\nabout a millimeter across.", "start": 1109.05, "duration": 3.69}, {"text": "Cut two pieces of it, take two\nwires, stick one in each end.", "start": 1112.74, "duration": 4.74}, {"text": "I drew it like this, but\nif you did it that way,", "start": 1117.48, "duration": 2.37}, {"text": "they'd probably short together.", "start": 1119.85, "duration": 1.99}, {"text": "So then one of those\nmeasures the voltage.", "start": 1121.84, "duration": 2.3}, {"text": "You set a command,\nand the other wire", "start": 1124.14, "duration": 2.61}, {"text": "allows you to inject\ncurrent inside the axon.", "start": 1126.75, "duration": 2.43}, {"text": "And then you seal the ends\nwith a little bit of Vaseline.", "start": 1129.18, "duration": 4.05}, {"text": "Yes?", "start": 1133.23, "duration": 0.5}, {"text": "AUDIENCE: Sorry, what\nis the command VC?", "start": 1133.73, "duration": 1.82}, {"text": "MICHALE FEE: VC is\nthe command voltage", "start": 1135.55, "duration": 1.86}, {"text": "that you're trying to set\nthe inside of the cell to.", "start": 1137.41, "duration": 4.23}, {"text": "Remember, here,\nwe're setting the--", "start": 1141.64, "duration": 3.67}, {"text": "VC is what you're controlling\nas the experimenter.", "start": 1145.31, "duration": 4.73}, {"text": "You're setting the\nvoltage with that command.", "start": 1150.04, "duration": 2.715}, {"text": "So the voltage clamp\nthen holds the inside", "start": 1157.02, "duration": 2.34}, {"text": "of the cell at that\ncommand voltage,", "start": 1159.36, "duration": 3.44}, {"text": "and then you're measuring\nthe current with this device.", "start": 1162.8, "duration": 4.66}, {"text": "There's a readout that tells\nyou how much current it's", "start": 1167.46, "duration": 2.91}, {"text": "putting into the cell, or it\ngoes onto an oscilloscope,", "start": 1170.37, "duration": 2.73}, {"text": "because it's time dependent.", "start": 1173.1, "duration": 1.647}, {"text": "So let's do an experiment.", "start": 1178.61, "duration": 1.17}, {"text": "Here's an example\nof an experiment.", "start": 1179.78, "duration": 1.83}, {"text": "They hold the\ncommand at minus 65.", "start": 1181.61, "duration": 2.61}, {"text": "And suddenly, they drop the\ncommand voltage to minus 130.", "start": 1184.22, "duration": 4.08}, {"text": "What does the cell do?", "start": 1188.3, "duration": 2.16}, {"text": "What is the current?", "start": 1190.46, "duration": 0.85}, {"text": "Nothing.", "start": 1191.31, "duration": 0.5}, {"text": "There's a little transient here,\nwhich is the amount of current.", "start": 1195.6, "duration": 3.7}, {"text": "It took to charge that capacitor\nup to minus 130 millivolts,", "start": 1199.3, "duration": 4.34}, {"text": "and then nothing happens.", "start": 1203.64, "duration": 1.26}, {"text": "All right, let's do\nanother experiment.", "start": 1207.555, "duration": 1.625}, {"text": "Now we're going to start\nour cell at minus 65", "start": 1209.18, "duration": 3.48}, {"text": "and suddenly jump the\nvoltage up to zero.", "start": 1212.66, "duration": 4.41}, {"text": "So we're going to\ndepolarize our cell.", "start": 1217.07, "duration": 2.83}, {"text": "And now something happens.", "start": 1219.9, "duration": 2.725}, {"text": "We get a big pulse of\ncurrent that's negative.", "start": 1222.625, "duration": 4.825}, {"text": "What does negative mean?", "start": 1227.45, "duration": 1.89}, {"text": "Anybody remember\nwhat negative current", "start": 1229.34, "duration": 1.77}, {"text": "means by our definition?", "start": 1231.11, "duration": 4.15}, {"text": "Negative means that there\nare positive ions going", "start": 1235.26, "duration": 4.08}, {"text": "into this cell.", "start": 1239.34, "duration": 1.75}, {"text": "So it's charging the cell up.", "start": 1241.09, "duration": 3.68}, {"text": "This is membrane current now.", "start": 1244.77, "duration": 3.12}, {"text": "So you just have to\nremember that definition.", "start": 1247.89, "duration": 2.13}, {"text": "Negative membrane current\nmeans that positive charges", "start": 1250.02, "duration": 3.54}, {"text": "are going into the cell, and\nthat's depolarizing the cell.", "start": 1253.56, "duration": 5.43}, {"text": "And then that negative current\nlasts for a few milliseconds,", "start": 1258.99, "duration": 3.28}, {"text": "and then the current reverses\nsign and becomes positive", "start": 1262.27, "duration": 3.23}, {"text": "and stays on.", "start": 1265.5, "duration": 2.95}, {"text": "So what is that?", "start": 1268.45, "duration": 3.34}, {"text": "So the first thing that\nHodgkin and Huxley did was they", "start": 1271.79, "duration": 2.72}, {"text": "tried to figure out what causes\nthat pattern of currents.", "start": 1274.51, "duration": 6.33}, {"text": "So here's what they did.", "start": 1280.84, "duration": 2.47}, {"text": "They had this idea that part\nof this might be due to sodium.", "start": 1283.31, "duration": 6.142}, {"text": "And so what they did was\nthey did an experiment", "start": 1289.452, "duration": 1.958}, {"text": "where they replaced\nsodium outside the cell,", "start": 1291.41, "duration": 4.86}, {"text": "outside the axon, with an ion.", "start": 1296.27, "duration": 4.315}, {"text": "They kept the chloride, but\nthey replaced the sodium", "start": 1303.42, "duration": 2.28}, {"text": "with choline.", "start": 1305.7, "duration": 0.72}, {"text": "So they used choline chloride,\nso it's a salt solution,", "start": 1306.42, "duration": 4.02}, {"text": "but it has no sodium in it.", "start": 1310.44, "duration": 2.58}, {"text": "And then they redid\nthat experiment.", "start": 1313.02, "duration": 1.72}, {"text": "And here's what they found.", "start": 1314.74, "duration": 1.125}, {"text": "What they found was-- so\nhere it is-- with sodium,", "start": 1318.59, "duration": 3.48}, {"text": "and if they replace\nthe sodium, they", "start": 1322.07, "duration": 1.5}, {"text": "find that they get\nalmost the same thing,", "start": 1323.57, "duration": 2.68}, {"text": "except that initial\nnegative pulse goes away.", "start": 1326.25, "duration": 3.26}, {"text": "And so they hypothesized that\nthat part is due to sodium.", "start": 1333.55, "duration": 3.68}, {"text": "And so now you just\nsubtract this from this", "start": 1337.23, "duration": 5.16}, {"text": "to get the difference.", "start": 1342.39, "duration": 1.72}, {"text": "And that is the sodium current.", "start": 1344.11, "duration": 3.135}, {"text": "Does that make sense?", "start": 1347.245, "duration": 0.875}, {"text": "And then one other thing.", "start": 1350.648, "duration": 1.042}, {"text": "Through another\nset of experiments,", "start": 1351.69, "duration": 1.5}, {"text": "they were able to show\nthat this part that's", "start": 1353.19, "duration": 2.01}, {"text": "left after you block\nor remove sodium", "start": 1355.2, "duration": 3.18}, {"text": "is actually due to potassium.", "start": 1358.38, "duration": 2.52}, {"text": "So this is the\npotassium current.", "start": 1360.9, "duration": 2.64}, {"text": "That is a sodium current.", "start": 1363.54, "duration": 2.78}, {"text": "So by doing different\nkinds of experiments--", "start": 1366.32, "duration": 2.7}, {"text": "so one of the things that you're\nable to do that they didn't do", "start": 1369.02, "duration": 3.128}, {"text": "initially, but later, they\nwere able to do things", "start": 1372.148, "duration": 2.042}, {"text": "like take that\nlittle piece of axon,", "start": 1374.19, "duration": 2.28}, {"text": "take out a little miniature\npaint roller, squish the axon,", "start": 1376.47, "duration": 5.1}, {"text": "roll the roller over the axon,\nsquish its guts out, and then", "start": 1381.57, "duration": 3.51}, {"text": "fill it up again with solutions\nthat they control that have", "start": 1385.08, "duration": 3.33}, {"text": "different ions in them.", "start": 1388.41, "duration": 1.39}, {"text": "And so they're able to study--", "start": 1389.8, "duration": 2.21}, {"text": "just do multiple different\nkinds of experiments", "start": 1392.01, "duration": 3.57}, {"text": "to be sure that this\nslow thing that turns on,", "start": 1395.58, "duration": 3.33}, {"text": "this slow positive\ncurrent is potassium,", "start": 1398.91, "duration": 2.64}, {"text": "and this fast negative\ncurrent is sodium.", "start": 1401.55, "duration": 3.552}, {"text": "All right?", "start": 1405.102, "duration": 0.972}, {"text": "So now what you\ncan do is you can", "start": 1409.38, "duration": 1.44}, {"text": "do this experiment at\ndifferent voltages here, right?", "start": 1410.82, "duration": 5.43}, {"text": "We want to measure how\nthese currents depend", "start": 1416.25, "duration": 3.75}, {"text": "on voltage, right?", "start": 1420.0, "duration": 2.22}, {"text": "We can see here how\nthey depend on time.", "start": 1422.22, "duration": 2.59}, {"text": "We can also see how\nthey depend on voltage,", "start": 1424.81, "duration": 2.57}, {"text": "by doing this experiment\nat different voltages.", "start": 1427.38, "duration": 3.06}, {"text": "You start at some\nnegative potential.", "start": 1430.44, "duration": 2.13}, {"text": "You step the voltage up to minus\n40, or you step it up to zero,", "start": 1432.57, "duration": 3.36}, {"text": "or you step it up to 40.", "start": 1435.93, "duration": 1.65}, {"text": "And now you can measure\nthat potassium current", "start": 1437.58, "duration": 3.09}, {"text": "as a function of\ntime, or the sodium", "start": 1440.67, "duration": 2.52}, {"text": "current as a function of time.", "start": 1443.19, "duration": 3.11}, {"text": "All right?", "start": 1446.3, "duration": 1.732}, {"text": "At different voltages.", "start": 1448.032, "duration": 1.158}, {"text": "All right, so those look kind\nof weird, especially that one.", "start": 1454.67, "duration": 2.86}, {"text": "That looks kind of\nscary, like what", "start": 1457.53, "duration": 1.72}, {"text": "the heck is going on there?", "start": 1459.25, "duration": 2.66}, {"text": "But it turns out that\nboth of these things", "start": 1461.91, "duration": 2.97}, {"text": "are actually pretty simple.", "start": 1464.88, "duration": 2.43}, {"text": "Once we dig a little bit more\ninto how these currents are", "start": 1467.31, "duration": 3.75}, {"text": "produced, you're going to see\nthat there's a very simple way", "start": 1471.06, "duration": 3.63}, {"text": "to understand what's\nhappening there.", "start": 1474.69, "duration": 3.37}, {"text": "All right, any questions?", "start": 1478.06, "duration": 2.328}, {"text": "Bear with me.", "start": 1480.388, "duration": 0.542}, {"text": "So now what we want\nto do is we want", "start": 1483.9, "duration": 2.73}, {"text": "to measure the voltage\ndependence of these things", "start": 1486.63, "duration": 2.79}, {"text": "kind of separately from\nthe time dependence.", "start": 1489.42, "duration": 2.26}, {"text": "So what we're going\nto do is we're", "start": 1491.68, "duration": 1.88}, {"text": "going to measure the peak\npotassium current, kind", "start": 1493.56, "duration": 3.93}, {"text": "of this steady state\npotassium current", "start": 1497.49, "duration": 1.98}, {"text": "as a function of voltage.", "start": 1499.47, "duration": 2.43}, {"text": "So here's our IV\ncurve that I promised", "start": 1501.9, "duration": 2.94}, {"text": "that we were going to plot.", "start": 1504.84, "duration": 2.19}, {"text": "Peak current as a\nfunction of voltage.", "start": 1507.03, "duration": 3.56}, {"text": "You can see that it's\napproximately linear", "start": 1510.59, "duration": 3.24}, {"text": "above minus 50 or so millivolts.", "start": 1513.83, "duration": 5.71}, {"text": "The sodium current\nlooks kind of weird.", "start": 1519.54, "duration": 2.9}, {"text": "We're going to plot\nthe peak sodium current", "start": 1522.44, "duration": 3.29}, {"text": "as a function of voltage.", "start": 1525.73, "duration": 3.21}, {"text": "And we see that the peak sodium\ncurrent has this weird shape.", "start": 1528.94, "duration": 3.39}, {"text": "It's sort of linear up\nhere at positive voltages,", "start": 1532.33, "duration": 3.4}, {"text": "and then it crashes down to\nzero at negative voltages.", "start": 1535.73, "duration": 3.87}, {"text": "All right?", "start": 1543.58, "duration": 1.39}, {"text": "Still kind of weird and scary.", "start": 1544.97, "duration": 3.045}, {"text": "So let's see if\nwe can understand", "start": 1548.015, "duration": 1.375}, {"text": "where this comes from.", "start": 1549.39, "duration": 2.94}, {"text": "I just replotted them here.", "start": 1552.33, "duration": 1.35}, {"text": "So now, remember that we\nuse this voltage clamp", "start": 1553.68, "duration": 3.48}, {"text": "to measure current as\na [AUDIO OUT] voltage.", "start": 1557.16, "duration": 2.31}, {"text": "But what is it that we're\nreally trying to understand?", "start": 1559.47, "duration": 3.54}, {"text": "We're really trying to\nunderstand the conductances,", "start": 1563.01, "duration": 2.58}, {"text": "those resistors, right?", "start": 1565.59, "duration": 2.1}, {"text": "We're under trying to understand\nthe voltage and time dependence", "start": 1567.69, "duration": 3.0}, {"text": "of those conductances.", "start": 1570.69, "duration": 3.14}, {"text": "So we're trying to\nextract conductance", "start": 1573.83, "duration": 1.89}, {"text": "as a function of voltage.", "start": 1575.72, "duration": 1.86}, {"text": "And remember that [AUDIO OUT]\nis just conductance", "start": 1577.58, "duration": 2.34}, {"text": "times a driving\npotential for potassium.", "start": 1579.92, "duration": 3.66}, {"text": "Sodium current is just sodium\nconductance times the sodium", "start": 1583.58, "duration": 2.91}, {"text": "driving potential.", "start": 1586.49, "duration": 3.37}, {"text": "So we you could imagine\nextracting the conductance", "start": 1589.86, "duration": 4.67}, {"text": "as current divided by\nthe driving potential.", "start": 1594.53, "duration": 3.21}, {"text": "This is what we're\nreally trying to find.", "start": 1601.75, "duration": 1.83}, {"text": "Rather than doing this\ndivision, because this one", "start": 1607.38, "duration": 2.25}, {"text": "over-- this thing goes\nto zero at the places", "start": 1609.63, "duration": 3.15}, {"text": "where the voltage is equal\nto the equilibrium potential.", "start": 1612.78, "duration": 2.853}, {"text": "So we don't want to do that.", "start": 1615.633, "duration": 1.167}, {"text": "We're going to solve\nthis problem graphically.", "start": 1616.8, "duration": 2.85}, {"text": "So here's the driving\npotential, right, V minus Ek.", "start": 1619.65, "duration": 5.58}, {"text": "It goes to zero at Ek, right?", "start": 1625.23, "duration": 4.56}, {"text": "And we want to find\na conductance that", "start": 1632.46, "duration": 2.91}, {"text": "makes this look like this.", "start": 1635.37, "duration": 2.25}, {"text": "So if this is kind\nof a straight line,", "start": 1640.31, "duration": 2.6}, {"text": "if the current as a\nfunction of voltage", "start": 1642.91, "duration": 2.19}, {"text": "is kind of a straight line\nand this is a straight line,", "start": 1645.1, "duration": 3.79}, {"text": "what does that tell us about\nthe conductance in this region", "start": 1648.89, "duration": 3.32}, {"text": "up here?", "start": 1652.21, "duration": 2.54}, {"text": "It's constant.", "start": 1654.75, "duration": 1.35}, {"text": "Excellent.", "start": 1656.1, "duration": 1.44}, {"text": "Now, if the driving potential\nis very negative here", "start": 1657.54, "duration": 4.38}, {"text": "but the current is zero,\nthen what's the conductance?", "start": 1661.92, "duration": 3.54}, {"text": "Driving potential\nis big and negative.", "start": 1668.4, "duration": 2.58}, {"text": "Current is zero.", "start": 1670.98, "duration": 1.44}, {"text": "What does that tell us\nabout the conductance?", "start": 1672.42, "duration": 2.52}, {"text": "It's zero.", "start": 1674.94, "duration": 0.88}, {"text": "OK, so not so hard, right?", "start": 1675.82, "duration": 2.27}, {"text": "We have [AUDIO OUT] zero\nhere and constant here.", "start": 1678.09, "duration": 2.61}, {"text": "So can anyone just show me\nwhat that might look like?", "start": 1680.7, "duration": 2.64}, {"text": "Good.", "start": 1686.01, "duration": 0.51}, {"text": "It could be like a jump.", "start": 1686.52, "duration": 2.4}, {"text": "It could be kind of smooth.", "start": 1688.92, "duration": 2.04}, {"text": "And that's exactly\nwhat it looks like.", "start": 1690.96, "duration": 2.98}, {"text": "So the conductance is zero\nhere, which it has to be,", "start": 1693.94, "duration": 2.79}, {"text": "because the current is zero,\neven though the the potential", "start": 1696.73, "duration": 2.7}, {"text": "is negative.", "start": 1699.43, "duration": 1.26}, {"text": "And the conductance\nhere is constant,", "start": 1700.69, "duration": 2.13}, {"text": "because the driving\npotential is constant here.", "start": 1702.82, "duration": 2.73}, {"text": "The driving potential is linear,\nand the current is linear,", "start": 1705.55, "duration": 2.68}, {"text": "so this needs to be\nconstant, all right?", "start": 1708.23, "duration": 6.2}, {"text": "So the conductance\nis very simple.", "start": 1714.43, "duration": 2.79}, {"text": "It turns off at\nnegative voltages", "start": 1717.22, "duration": 1.79}, {"text": "and turns on and then stays\non at higher voltages.", "start": 1719.01, "duration": 5.03}, {"text": "Let's do that for sodium.", "start": 1724.04, "duration": 1.38}, {"text": "This thing looks\ncrazy, weird, right?", "start": 1725.42, "duration": 2.28}, {"text": "But let's go through\nthe same operation.", "start": 1727.7, "duration": 2.53}, {"text": "Here's our driving\npotential for sodium.", "start": 1730.23, "duration": 2.03}, {"text": "Remember, it's got a\nreversal at plus 55.", "start": 1732.26, "duration": 5.13}, {"text": "But it's a straight line, right?", "start": 1737.39, "duration": 1.89}, {"text": "That's a battery and a resistor.", "start": 1739.28, "duration": 2.1}, {"text": "So there's our\ndriving potential.", "start": 1741.38, "duration": 1.86}, {"text": "Now, this is linear.", "start": 1743.24, "duration": 2.47}, {"text": "This is linear.", "start": 1745.71, "duration": 0.84}, {"text": "So what does the conductance\nlook like up here?", "start": 1746.55, "duration": 4.19}, {"text": "Good.", "start": 1750.74, "duration": 1.04}, {"text": "This is zero, but this\nis big and negative, so", "start": 1751.78, "duration": 3.33}, {"text": "what does the conductance\nlook like down here?", "start": 1755.11, "duration": 3.06}, {"text": "Good .", "start": 1758.17, "duration": 0.9}, {"text": "Starting to look\npretty familiar, right?", "start": 1759.07, "duration": 2.55}, {"text": "Boom.", "start": 1761.62, "duration": 0.8}, {"text": "It's exactly the same.", "start": 1762.42, "duration": 1.18}, {"text": "Both of these conductances are\noff at negative potentials,", "start": 1768.34, "duration": 5.93}, {"text": "and they turn on at positive\nvoltages and remain constant.", "start": 1774.27, "duration": 3.885}, {"text": "Yes?", "start": 1785.32, "duration": 1.222}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 1786.542, "duration": 1.428}, {"text": "MICHALE FEE: Great.", "start": 1790.548, "duration": 0.792}, {"text": "Great question.", "start": 1791.34, "duration": 0.69}, {"text": "Because the sodium\nconductance turns on,", "start": 1792.03, "duration": 2.34}, {"text": "and then it shuts\noff right away.", "start": 1794.37, "duration": 1.71}, {"text": "And the shutting off is\na different mechanism.", "start": 1796.08, "duration": 2.16}, {"text": "So we're trying to figure out\nhow to ignore that and just", "start": 1798.24, "duration": 3.48}, {"text": "understand the voltage\ndepends of how it turns on.", "start": 1801.72, "duration": 4.3}, {"text": "Does that make sense?", "start": 1806.02, "duration": 1.89}, {"text": "And we'll get into\nthat next Tuesday.", "start": 1807.91, "duration": 3.28}, {"text": "But I'm showing both of\nthese at the same time", "start": 1811.19, "duration": 2.69}, {"text": "because they look\nsimilar at the level", "start": 1813.88, "duration": 3.12}, {"text": "of the voltage dependence.", "start": 1817.0, "duration": 2.35}, {"text": "In fact, the way they\nturn on is very similar.", "start": 1819.35, "duration": 4.706}, {"text": "It's just that the sodium has\nsome other weird thing that", "start": 1824.056, "duration": 3.034}, {"text": "shuts it off after\na few milliseconds,", "start": 1827.09, "duration": 1.59}, {"text": "and we'll talk about\nthat next time.", "start": 1828.68, "duration": 1.53}, {"text": "Yes?", "start": 1830.21, "duration": 0.773}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 1830.983, "duration": 3.544}, {"text": "MICHALE FEE: No, it's not.", "start": 1834.527, "duration": 1.083}, {"text": "But any non-linearity\nhere, we're", "start": 1835.61, "duration": 2.43}, {"text": "going to account for by\nchanges by voltage dependence", "start": 1838.04, "duration": 3.99}, {"text": "of the conductance.", "start": 1842.03, "duration": 1.38}, {"text": "So great point.", "start": 1843.41, "duration": 1.2}, {"text": "It's a subtlety that\nwe have kind of imposed", "start": 1844.61, "duration": 5.58}, {"text": "by this way of writing\ndown the voltage dependents", "start": 1850.19, "duration": 3.36}, {"text": "of the current.", "start": 1853.55, "duration": 1.17}, {"text": "Any other questions?", "start": 1857.84, "duration": 1.333}, {"text": "No?", "start": 1859.173, "duration": 2.167}, {"text": "OK, pushing on.", "start": 1861.34, "duration": 2.34}, {"text": "So this kind of gradual\nturning on, this sort of zero", "start": 1867.34, "duration": 6.51}, {"text": "conductance down here\nand a [INAUDIBLE] up", "start": 1873.85, "duration": 2.52}, {"text": "here, that's called a\nsigmoidal voltage dependence.", "start": 1876.37, "duration": 3.6}, {"text": "And it's the voltage\ndependence of activation.", "start": 1879.97, "duration": 2.79}, {"text": "It's how these channels turn on.", "start": 1882.76, "duration": 3.4}, {"text": "And as I said\nbefore, we're going", "start": 1886.16, "duration": 1.55}, {"text": "to deal with the other\nproperties of the sodium", "start": 1887.71, "duration": 4.35}, {"text": "channel that turn it off later.", "start": 1892.06, "duration": 1.9}, {"text": "So both have a sigmoidal voltage\ndependence of activation.", "start": 1893.96, "duration": 4.1}, {"text": "And if you plot this,\nyou can see that--", "start": 1904.32, "duration": 3.75}, {"text": "if you plot this on\na log scale here--", "start": 1908.07, "duration": 4.35}, {"text": "log scale on conductance,\nlinear here on potential.", "start": 1912.42, "duration": 3.81}, {"text": "You can see that\nboth of these curves,", "start": 1916.23, "duration": 2.91}, {"text": "both the potassium\nand the sodium,", "start": 1919.14, "duration": 1.77}, {"text": "have this very characteristic\nexponential turn-on followed", "start": 1920.91, "duration": 4.77}, {"text": "by his saturation and constant\nconductance at higher voltages.", "start": 1925.68, "duration": 5.485}, {"text": "All right, any questions?", "start": 1933.9, "duration": 1.82}, {"text": "That's voltage dependence.", "start": 1935.72, "duration": 2.55}, {"text": "Now we're going to turn\nto time dependence.", "start": 1938.27, "duration": 2.16}, {"text": "So you can see that\nthe time dependence--", "start": 1943.28, "duration": 3.22}, {"text": "so this driving potential,\nthat's just constant.", "start": 1946.5, "duration": 2.72}, {"text": "That just depends on the voltage\nand the reversal potential.", "start": 1949.22, "duration": 3.37}, {"text": "And so we can separate out--", "start": 1952.59, "duration": 3.68}, {"text": "this thing is just\nany time dependence", "start": 1956.27, "duration": 2.4}, {"text": "this has is dependent on the\ntime dependence of the voltage.", "start": 1958.67, "duration": 2.94}, {"text": "But in our voltage\nclamp experiments,", "start": 1961.61, "duration": 2.31}, {"text": "the voltage is constant.", "start": 1963.92, "duration": 1.5}, {"text": "So this thing is constant.", "start": 1965.42, "duration": 1.65}, {"text": "So any time\ndependence [AUDIO OUT]", "start": 1967.07, "duration": 1.56}, {"text": "current has to be due to time\ndependence of the conductance,", "start": 1968.63, "duration": 4.15}, {"text": "right?", "start": 1972.78, "duration": 1.573}, {"text": "And what that means\nis we can just", "start": 1974.353, "duration": 1.417}, {"text": "look at the shape of this\npotassium current-- remember,", "start": 1975.77, "duration": 4.32}, {"text": "this is the potassium\ncurrent here.", "start": 1980.09, "duration": 2.13}, {"text": "That time dependence is\njust due to time dependence", "start": 1982.22, "duration": 2.85}, {"text": "of the conductance.", "start": 1985.07, "duration": 1.77}, {"text": "Does that make sense?", "start": 1986.84, "duration": 1.28}, {"text": "So what's happening is\nthe potassium conductance", "start": 1988.12, "duration": 2.71}, {"text": "is starting at zero.", "start": 1990.83, "duration": 1.53}, {"text": "The moment you step\nthe voltage up,", "start": 1992.36, "duration": 2.25}, {"text": "that thing begins to\ngrow gradually and then", "start": 1994.61, "duration": 2.91}, {"text": "runs up to a constant\npotassium conductance in time.", "start": 1997.52, "duration": 4.65}, {"text": "It starts off, ramps\nup, and then becomes", "start": 2002.17, "duration": 2.94}, {"text": "constant, all right?", "start": 2005.11, "duration": 1.68}, {"text": "So that's the time dependence.", "start": 2006.79, "duration": 3.78}, {"text": "Sort of gracefully turns on.", "start": 2010.57, "duration": 4.22}, {"text": "That process of turning\non is called activation.", "start": 2014.79, "duration": 5.81}, {"text": "The sodium conductance--\nor current, the same thing.", "start": 2020.6, "duration": 2.9}, {"text": "The sodium current is just\nthe sodium conductance.", "start": 2023.5, "duration": 3.417}, {"text": "The sodium current is\na function [AUDIO OUT]", "start": 2026.917, "duration": 1.833}, {"text": "is the sodium conductance\nas a function of time,", "start": 2028.75, "duration": 2.66}, {"text": "times a constant.", "start": 2031.41, "duration": 0.85}, {"text": "In our voltage clamp\nexperiment, again, this voltage", "start": 2032.26, "duration": 2.28}, {"text": "is constant.", "start": 2034.54, "duration": 1.14}, {"text": "So the sodium\nconductance turns on.", "start": 2035.68, "duration": 4.77}, {"text": "That's activation.", "start": 2040.45, "duration": 1.08}, {"text": "But then it turns off, and\nthat's called inactivation.", "start": 2041.53, "duration": 4.65}, {"text": "So the sodium current\nhas [AUDIO OUT]", "start": 2046.18, "duration": 2.39}, {"text": "sodium conductance\nhas two things going", "start": 2048.57, "duration": 2.23}, {"text": "on-- one, activation, and\nthe second is inactivation.", "start": 2050.8, "duration": 5.31}, {"text": "And it turns out these are\ntwo separate biophysical", "start": 2056.11, "duration": 3.049}, {"text": "mechanisms.", "start": 2059.159, "duration": 1.551}, {"text": "And we're going to spend\nmore time on this next week.", "start": 2060.71, "duration": 6.59}, {"text": "So, notice something\ninteresting.", "start": 2067.3, "duration": 3.98}, {"text": "The sodium conductance turns on.", "start": 2071.28, "duration": 2.34}, {"text": "You depolarize the cell.", "start": 2073.62, "duration": 1.23}, {"text": "Sodium conductance turns on\nright away and then shuts off.", "start": 2074.85, "duration": 3.75}, {"text": "The potassium conductance has\na delay, and then it turns on.", "start": 2078.6, "duration": 5.13}, {"text": "Does that look familiar?", "start": 2083.73, "duration": 1.94}, {"text": "It looks an awful\nlot like this, right?", "start": 2085.67, "duration": 5.91}, {"text": "Here's the sodium conductance.", "start": 2091.58, "duration": 1.55}, {"text": "Turns on and then shuts off.", "start": 2093.13, "duration": 4.17}, {"text": "And then the\npotassium conductance", "start": 2097.3, "duration": 1.47}, {"text": "turns on with a delay.", "start": 2098.77, "duration": 3.16}, {"text": "And that gives us\nan action potential.", "start": 2101.93, "duration": 2.14}, {"text": "So you can see that when\nyou use voltage clamp", "start": 2104.07, "duration": 2.72}, {"text": "and dissected out the time\ndifference of the sodium", "start": 2106.79, "duration": 3.45}, {"text": "and potassium\nconductance, it looks just", "start": 2110.24, "duration": 2.37}, {"text": "like the thing we\nconcocted earlier, just", "start": 2112.61, "duration": 3.66}, {"text": "sort of our toy example for how\nto make an action potential.", "start": 2116.27, "duration": 4.49}, {"text": "Pretty cool, right?", "start": 2120.76, "duration": 2.01}, {"text": "OK, it's starting to come\ntogether piece by piece.", "start": 2122.77, "duration": 3.08}, {"text": "So we're now going to\ndig in a little bit", "start": 2131.44, "duration": 4.02}, {"text": "deeper into the biophysics\nof how you get these voltage", "start": 2135.46, "duration": 3.81}, {"text": "and time dependencies.", "start": 2139.27, "duration": 1.23}, {"text": "So we're going to\nderive the equation", "start": 2143.81, "duration": 4.89}, {"text": "for the voltage dependence.", "start": 2148.7, "duration": 1.29}, {"text": "Anybody want to\ntake a crazy guess", "start": 2149.99, "duration": 1.98}, {"text": "on how we're going to do that?", "start": 2151.97, "duration": 2.14}, {"text": "Just a wild guess, how you might\nderive the voltage dependence", "start": 2154.11, "duration": 3.86}, {"text": "of something?", "start": 2157.97, "duration": 2.8}, {"text": "No?", "start": 2160.77, "duration": 0.56}, {"text": "OK.", "start": 2161.33, "duration": 0.39}, {"text": "We're going to use the\nBoltzmann equation.", "start": 2161.72, "duration": 1.75}, {"text": "And we're going to derive\ndifferent equations that", "start": 2167.15, "duration": 2.13}, {"text": "describe the way those\nchannels turn on,", "start": 2169.28, "duration": 3.69}, {"text": "how those conductances turn on.", "start": 2172.97, "duration": 2.56}, {"text": "All right?", "start": 2175.53, "duration": 2.113}, {"text": "And once we do that,\nwe're going to have", "start": 2177.643, "duration": 1.667}, {"text": "a simple set of equations--", "start": 2179.31, "duration": 2.85}, {"text": "and not just equations.", "start": 2182.16, "duration": 1.17}, {"text": "We're going to have\na set of processes", "start": 2183.33, "duration": 3.18}, {"text": "that we can think of\nas happening a loop,", "start": 2186.51, "duration": 2.55}, {"text": "in a for loop.", "start": 2189.06, "duration": 1.2}, {"text": "That's our algorithm\nfor an action potential.", "start": 2190.26, "duration": 4.2}, {"text": "All right, so let's dive\ninto single channels", "start": 2194.46, "duration": 2.22}, {"text": "and see how they work.", "start": 2196.68, "duration": 3.05}, {"text": "So, of course, currents\nresult from ionic flow", "start": 2199.73, "duration": 3.74}, {"text": "through ion channels.", "start": 2203.47, "duration": 2.85}, {"text": "It's actually possible\nto record currents", "start": 2206.32, "duration": 3.09}, {"text": "from single ion channels.", "start": 2209.41, "duration": 2.52}, {"text": "We can actually make a\nversion of our voltage clamp", "start": 2211.93, "duration": 4.05}, {"text": "that we can attach to\na single ion channel.", "start": 2215.98, "duration": 4.56}, {"text": "And the way you do that is--", "start": 2220.54, "duration": 1.65}, {"text": "so when you take this piece\nof glass and you pull it,", "start": 2222.19, "duration": 2.79}, {"text": "instead of poking\nit through the cell,", "start": 2224.98, "duration": 2.37}, {"text": "instead of making\nit really sharp", "start": 2227.35, "duration": 2.07}, {"text": "and poking it through\nthe cell, what you do", "start": 2229.42, "duration": 1.98}, {"text": "is you make it a\nlittle bit blunter,", "start": 2231.4, "duration": 3.54}, {"text": "so it's got kind of a rough end.", "start": 2234.94, "duration": 1.41}, {"text": "And then you can\nfire a polish-- you", "start": 2236.35, "duration": 1.62}, {"text": "can hold the end of that\nelectrode into a flame.", "start": 2237.97, "duration": 4.97}, {"text": "Not quite.", "start": 2242.94, "duration": 0.5}, {"text": "It's usually a filament\nthat heats up hot.", "start": 2243.44, "duration": 2.435}, {"text": "You hold the end\nof the electrode", "start": 2245.875, "duration": 1.375}, {"text": "near this hot filament\nand it melts the tip", "start": 2247.25, "duration": 2.97}, {"text": "into a nice, round--", "start": 2250.22, "duration": 2.07}, {"text": "it's still a tube, but\nthe edges of the tube", "start": 2252.29, "duration": 2.34}, {"text": "are nice and smooth.", "start": 2254.63, "duration": 2.525}, {"text": "And now when you take that\ntube and you press it up", "start": 2257.155, "duration": 2.125}, {"text": "against the cell--", "start": 2259.28, "duration": 2.46}, {"text": "actually, you attach\na little plastic tube", "start": 2261.74, "duration": 3.03}, {"text": "to the end of the glass, and\nyou press that that electrode up", "start": 2264.77, "duration": 3.592}, {"text": "against the cell.", "start": 2268.362, "duration": 0.708}, {"text": "And you actually literally\nsuck on it with your mouth", "start": 2269.07, "duration": 3.14}, {"text": "onto that tube.", "start": 2272.21, "duration": 1.74}, {"text": "And it sucks the membrane\nup against that smooth end", "start": 2273.95, "duration": 3.83}, {"text": "of the electrode.", "start": 2277.78, "duration": 1.0}, {"text": "And it sticks.", "start": 2278.78, "duration": 1.74}, {"text": "The lipids of the membrane\nactually seal themselves", "start": 2280.52, "duration": 4.35}, {"text": "onto the end of the glass.", "start": 2284.87, "duration": 2.2}, {"text": "So now no currents can flow\nout through these edges", "start": 2287.07, "duration": 5.0}, {"text": "here, all right?", "start": 2292.07, "duration": 1.26}, {"text": "And then you hook it\nup to a very sensitive", "start": 2293.33, "duration": 1.8}, {"text": "current amplifier.", "start": 2295.13, "duration": 1.26}, {"text": "And now you can\ncontrol the voltage.", "start": 2296.39, "duration": 2.22}, {"text": "You can actually just\nrip that off of the cell,", "start": 2298.61, "duration": 2.133}, {"text": "so now there's no more cell.", "start": 2300.743, "duration": 1.167}, {"text": "You just have an ion\nchannel sitting there", "start": 2301.91, "duration": 2.04}, {"text": "on a piece [AUDIO OUT]\non the end of your glass.", "start": 2303.95, "duration": 2.35}, {"text": "Now you can do a\nvoltage clamp experiment", "start": 2306.3, "duration": 3.16}, {"text": "and study the current--", "start": 2309.46, "duration": 1.89}, {"text": "the voltage dependence\nof the current", "start": 2311.35, "duration": 2.52}, {"text": "through that ion channel.", "start": 2313.87, "duration": 3.198}, {"text": "So here's what this looks like.", "start": 2317.068, "duration": 1.292}, {"text": "Here's one experiment.", "start": 2318.36, "duration": 0.917}, {"text": "We're going to\nstart at minus 100.", "start": 2319.277, "duration": 1.533}, {"text": "This is a potassium channel.", "start": 2320.81, "duration": 2.9}, {"text": "You depolarize the potassium\nchannel up to 50 millivolts,", "start": 2323.71, "duration": 3.822}, {"text": "and you see that that current,\nthrough that single channel,", "start": 2327.532, "duration": 2.458}, {"text": "starts flickering on and off.", "start": 2329.99, "duration": 3.0}, {"text": "Here's another trial.", "start": 2332.99, "duration": 1.38}, {"text": "Turns on, turns off,\nturns on, turns off.", "start": 2334.37, "duration": 3.425}, {"text": "You can do that\na bunch of times.", "start": 2337.795, "duration": 1.375}, {"text": "You can see something\ninteresting.", "start": 2341.75, "duration": 1.8}, {"text": "The current is either off--", "start": 2343.55, "duration": 2.46}, {"text": "doesn't turn on gradually,\ndoesn't change smoothly.", "start": 2346.01, "duration": 4.29}, {"text": "It just flickers\nbetween on and off.", "start": 2350.3, "duration": 2.04}, {"text": "That's a very important\naspect of ion channels.", "start": 2352.34, "duration": 3.45}, {"text": "But if you average all\nthose trials together,", "start": 2355.79, "duration": 3.81}, {"text": "you see that you get an\naverage current that looks just", "start": 2359.6, "duration": 4.41}, {"text": "like the current\nthat Hodgkin-Huxley", "start": 2364.01, "duration": 4.93}, {"text": "measured in the whole axon.", "start": 2368.94, "duration": 4.6}, {"text": "How is that possible?", "start": 2373.54, "duration": 1.02}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 2383.075, "duration": 1.455}, {"text": "MICHALE FEE: Yeah.", "start": 2387.94, "duration": 1.21}, {"text": "Good.", "start": 2389.15, "duration": 0.5}, {"text": "So, basically,\nwhat we're doing is", "start": 2389.65, "duration": 1.95}, {"text": "we're measuring one\nion channel many times.", "start": 2391.6, "duration": 3.93}, {"text": "But on a cell, you're\nmeasuring a bunch", "start": 2395.53, "duration": 4.4}, {"text": "of ion channels, each of which\nis doing something like this.", "start": 2399.93, "duration": 3.54}, {"text": "But they're happening\nall at the same time,", "start": 2403.47, "duration": 2.43}, {"text": "and the current\nis being averaged.", "start": 2405.9, "duration": 2.24}, {"text": "So here, we're averaging\nthe current one at a time.", "start": 2408.14, "duration": 3.34}, {"text": "And on a whole cell, we're\njust averaging a bunch of them", "start": 2411.48, "duration": 3.03}, {"text": "at once.", "start": 2414.51, "duration": 1.26}, {"text": "It's called\nergodicity in physics.", "start": 2415.77, "duration": 2.01}, {"text": "It's called the\nensemble average.", "start": 2422.47, "duration": 3.78}, {"text": "OK, you can do the\nsame thing for sodium.", "start": 2426.25, "duration": 2.67}, {"text": "You take your patch,\na new patch electrode.", "start": 2428.92, "duration": 2.7}, {"text": "Fire polish it.", "start": 2431.62, "duration": 2.03}, {"text": "Push it up to a cell.", "start": 2433.65, "duration": 1.8}, {"text": "Apply some suction.", "start": 2435.45, "duration": 1.41}, {"text": "Glues on.", "start": 2436.86, "duration": 0.87}, {"text": "This time, we had\na sodium channel.", "start": 2437.73, "duration": 3.63}, {"text": "And now you can see\nthat the thing, again,", "start": 2441.36, "duration": 2.32}, {"text": "flickers on, flickers off,\nflickers on, flickers off.", "start": 2443.68, "duration": 3.15}, {"text": "But now, they all flicker\non right at the beginning,", "start": 2446.83, "duration": 3.0}, {"text": "and then they flicker\noff and stay off.", "start": 2449.83, "duration": 3.03}, {"text": "And if you average all\nthose different trials,", "start": 2452.86, "duration": 2.46}, {"text": "you see an ensemble\naverage sodium current", "start": 2455.32, "duration": 4.18}, {"text": "that looks just like when\nyou measure the sodium", "start": 2459.5, "duration": 4.18}, {"text": "current on a whole axon, OK?", "start": 2463.68, "duration": 1.84}, {"text": "But the key thing is that these\nchannels have two states--", "start": 2468.28, "duration": 3.59}, {"text": "on and off-- and they\nflicker back and forth", "start": 2471.87, "duration": 1.92}, {"text": "between those two states,\nconducting and non-conducting.", "start": 2473.79, "duration": 3.69}, {"text": "So we can now write down--", "start": 2477.48, "duration": 3.45}, {"text": "we could start\nworking with this idea", "start": 2480.93, "duration": 1.89}, {"text": "that our ion channels are\neither open or closed.", "start": 2482.82, "duration": 2.64}, {"text": "And we can think\nof a probability", "start": 2485.46, "duration": 2.16}, {"text": "that the channel is being\nopen, that the channel is open.", "start": 2487.62, "duration": 3.3}, {"text": "And we can have a total\nnumber of channels.", "start": 2490.92, "duration": 3.51}, {"text": "The number of open\nchannels is just", "start": 2494.43, "duration": 1.83}, {"text": "the number of channels you\nhave times the probability", "start": 2496.26, "duration": 2.52}, {"text": "that any one of them is open.", "start": 2498.78, "duration": 2.78}, {"text": "If g is the inductance\nof one open channel,", "start": 2501.56, "duration": 4.35}, {"text": "then we can write down the\ntotal potassium conductance", "start": 2505.91, "duration": 2.76}, {"text": "as the probability that any\ngiven ion channel is open", "start": 2508.67, "duration": 5.01}, {"text": "times the number of channels\ntimes the inductance of one", "start": 2513.68, "duration": 3.15}, {"text": "open channel.", "start": 2516.83, "duration": 1.535}, {"text": "Does that make sense?", "start": 2518.365, "duration": 0.875}, {"text": "And now the claim\nhere [AUDIO OUT]", "start": 2522.65, "duration": 2.55}, {"text": "all of the interesting\nvoltage and time dependence", "start": 2525.2, "duration": 3.72}, {"text": "of these channels happens here.", "start": 2528.92, "duration": 2.82}, {"text": "Obviously, the number of them\nisn't changing very rapidly.", "start": 2531.74, "duration": 3.3}, {"text": "The conductance per channel\nis constant, per open channel.", "start": 2535.04, "duration": 5.76}, {"text": "So the interesting stuff\nis in the probability", "start": 2540.8, "duration": 3.0}, {"text": "that the channel [AUDIO OUT].", "start": 2543.8, "duration": 1.79}, {"text": "And if we want to\nget the current,", "start": 2550.34, "duration": 2.85}, {"text": "we're just going to plug this\nconductance into here, OK?", "start": 2553.19, "duration": 3.84}, {"text": "All right, so let's start\nwith a potassium channel.", "start": 2557.03, "duration": 2.4}, {"text": "Let's dig in a little bit\ndeeper into what the potassium", "start": 2559.43, "duration": 2.4}, {"text": "channel looks like.", "start": 2561.83, "duration": 1.26}, {"text": "Potassium channel is formed\nby four identical subunits.", "start": 2563.09, "duration": 3.73}, {"text": "They're produced\nseparately by ribosomes.", "start": 2566.82, "duration": 6.41}, {"text": "They form a\nheteromer, a tetramer.", "start": 2573.23, "duration": 4.31}, {"text": "And that tetramer\nhas a hole that", "start": 2577.54, "duration": 1.82}, {"text": "runs down the middle of it,\nwhich is where the ions flow.", "start": 2579.36, "duration": 5.91}, {"text": "Each of these subunits\nhas a voltage sensor that", "start": 2585.27, "duration": 2.73}, {"text": "allows it to turn on and off.", "start": 2588.0, "duration": 1.96}, {"text": "In order for the channel to be\non, all four of those subunits", "start": 2589.96, "duration": 5.99}, {"text": "has to be open.", "start": 2595.95, "duration": 0.72}, {"text": "So each subunit has an open\nstate and a closed state.", "start": 2596.67, "duration": 3.17}, {"text": "And for the channel to\nbe open, all four of them", "start": 2599.84, "duration": 2.62}, {"text": "have to be in the open state.", "start": 2602.46, "duration": 1.41}, {"text": "So if n is the probability\nthat any one subunit is open--", "start": 2608.35, "duration": 6.08}, {"text": "I meant to make you guys\nanswer this question", "start": 2614.43, "duration": 2.985}, {"text": "before I showed the answer.", "start": 2617.415, "duration": 1.125}, {"text": "But is it clear how\nif any one subunit has", "start": 2618.54, "duration": 3.27}, {"text": "a probability of\nbeing open of n,", "start": 2621.81, "duration": 2.68}, {"text": "then the probability that\nthe whole channel is open", "start": 2624.49, "duration": 3.68}, {"text": "is n to the four?", "start": 2628.17, "duration": 1.14}, {"text": "This n is called\na gating variable.", "start": 2632.78, "duration": 2.76}, {"text": "I would like you to know that\nthe probability that a sodium", "start": 2635.54, "duration": 6.18}, {"text": "potassium channel is\nopen is n to the four.", "start": 2641.72, "duration": 3.24}, {"text": "That's an important thing\nfor you to remember.", "start": 2644.96, "duration": 4.72}, {"text": "That assumes that those four\nsubunits are independent.", "start": 2649.68, "duration": 4.29}, {"text": "And in potassium\nchannels, that's", "start": 2653.97, "duration": 1.83}, {"text": "a very good approximation.", "start": 2655.8, "duration": 3.91}, {"text": "So we can now write down the\nconductance of our potassium", "start": 2659.71, "duration": 4.07}, {"text": "channel--", "start": 2663.78, "duration": 1.05}, {"text": "something times n\nto the four, where", "start": 2664.83, "duration": 2.1}, {"text": "that something is that\ninductance of one ion channel.", "start": 2666.93, "duration": 6.16}, {"text": "So we can now write\ndown the current as n.", "start": 2680.03, "duration": 3.53}, {"text": "Open conductance times n to the\nfour times a driving potential.", "start": 2683.56, "duration": 4.17}, {"text": "And that n is called\nthe gating variable", "start": 2687.73, "duration": 2.94}, {"text": "for the potassium conductance.", "start": 2690.67, "duration": 3.14}, {"text": "All right, any questions?", "start": 2693.81, "duration": 1.5}, {"text": "No?", "start": 2699.15, "duration": 1.9}, {"text": "Yes?", "start": 2701.05, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 2701.55, "duration": 2.89}, {"text": "MICHALE FEE: n absolutely\ndoes depend on voltage.", "start": 2704.44, "duration": 2.13}, {"text": "Very good.", "start": 2706.57, "duration": 0.82}, {"text": "That's where we're going next.", "start": 2707.39, "duration": 1.25}, {"text": "But before we go on\nto that, I wanted", "start": 2716.15, "duration": 3.07}, {"text": "to add one other thing,\nwhich I think is really cool.", "start": 2719.22, "duration": 2.9}, {"text": "We're going to do the voltage\ndependence of a potassium", "start": 2722.12, "duration": 3.87}, {"text": "channel using the\nBoltzmann equation.", "start": 2725.99, "duration": 1.98}, {"text": "So here's the way you think\nabout a potassium channel", "start": 2730.94, "duration": 4.55}, {"text": "working.", "start": 2735.49, "duration": 2.105}, {"text": "Here's a potassium channel.", "start": 2737.595, "duration": 1.125}, {"text": "We're showing a cross-section.", "start": 2738.72, "duration": 2.22}, {"text": "Here it is.", "start": 2740.94, "duration": 0.52}, {"text": "Here's the membrane,\nthe lipid bilayer.", "start": 2741.46, "duration": 2.09}, {"text": "Here's our potassium channel,\nsitting in the membrane.", "start": 2743.55, "duration": 3.82}, {"text": "And we're taking a cross-section\nthrough that tetramer", "start": 2747.37, "duration": 2.55}, {"text": "that shows two subunits.", "start": 2749.92, "duration": 3.26}, {"text": "And I'm showing\nthe voltage sent--", "start": 2753.18, "duration": 2.1}, {"text": "I'm showing the mechanism\nthat that opens and closes", "start": 2755.28, "duration": 5.04}, {"text": "one of those subunits.", "start": 2760.32, "duration": 1.86}, {"text": "This subunit we'll also have a\nvoltage sensor and a gate that", "start": 2762.18, "duration": 4.35}, {"text": "looks the same.", "start": 2766.53, "duration": 1.47}, {"text": "So look, the voltage sensor--\nhow do you sense voltage?", "start": 2768.0, "duration": 3.98}, {"text": "You sense voltage\nwith charge, right?", "start": 2771.98, "duration": 2.73}, {"text": "Voltage differences, I should\nsay, you sense with a charge.", "start": 2774.71, "duration": 5.44}, {"text": "Because voltage gradients\nare electric fields,", "start": 2780.15, "duration": 3.39}, {"text": "and electric fields\npush on charges.", "start": 2783.54, "duration": 2.77}, {"text": "So if we want to detect\nthe voltage difference", "start": 2786.31, "duration": 3.74}, {"text": "across this membrane, we put\na charge in the membrane.", "start": 2790.05, "duration": 3.67}, {"text": "When the voltage\ndifference is zero,", "start": 2793.72, "duration": 2.19}, {"text": "there's little force\non those charges.", "start": 2795.91, "duration": 4.65}, {"text": "Now, if we suddenly\nhyperpolarize the [AUDIO OUT]", "start": 2800.56, "duration": 2.64}, {"text": "cell so it's very\nnegative, now there's", "start": 2803.2, "duration": 2.33}, {"text": "an electric field\ninside the membrane that", "start": 2805.53, "duration": 5.45}, {"text": "points toward the inside\nof the cell, which", "start": 2810.98, "duration": 2.25}, {"text": "pushes those charges toward\nthe inside of the cell.", "start": 2813.23, "duration": 4.06}, {"text": "And now you can just have a\nlittle mechanical linkage.", "start": 2817.29, "duration": 2.63}, {"text": "That's not really\nwhat it looks like,", "start": 2819.92, "duration": 2.19}, {"text": "but there's some way that the\namino acids and the protein", "start": 2822.11, "duration": 5.28}, {"text": "are configured so that when\nthose charges get pushed on,", "start": 2827.39, "duration": 3.12}, {"text": "it closes a gate.", "start": 2830.51, "duration": 2.52}, {"text": "And now the current\ncan no longer", "start": 2833.03, "duration": 1.77}, {"text": "flow through the ion channel.", "start": 2834.8, "duration": 4.65}, {"text": "OK, so now we're going\nto derive how this--", "start": 2846.3, "duration": 3.16}, {"text": "we're going to see how to\nderive this voltage dependence", "start": 2849.46, "duration": 3.48}, {"text": "from the Boltzmann equation.", "start": 2852.94, "duration": 2.16}, {"text": "All right, so, everybody,\nthis is just for fun.", "start": 2855.1, "duration": 4.62}, {"text": "I don't expect you to\nknow how to do this.", "start": 2859.72, "duration": 2.76}, {"text": "I just want you to see\nit, because I personally", "start": 2862.48, "duration": 4.14}, {"text": "get chills when I see this.", "start": 2866.62, "duration": 1.59}, {"text": "It's really cool.", "start": 2868.21, "duration": 1.45}, {"text": "But I'm not expecting you to\nbe able to reproduce it, OK?", "start": 2869.66, "duration": 3.29}, {"text": "So just watch.", "start": 2872.95, "duration": 3.44}, {"text": "So, again, the\nBoltzmann equation", "start": 2876.39, "duration": 1.78}, {"text": "says that the\nprobability of being", "start": 2878.17, "duration": 3.33}, {"text": "in two states, open or\nclosed, depends on the energy", "start": 2881.5, "duration": 2.94}, {"text": "difference between them.", "start": 2884.44, "duration": 3.56}, {"text": "So we have an open state\nand a closed state.", "start": 2888.0, "duration": 2.65}, {"text": "And when the voltage\ninside the cell", "start": 2890.65, "duration": 2.88}, {"text": "is zero-- when the voltage\ndifference between the inside", "start": 2893.53, "duration": 4.31}, {"text": "and the outside of the\ncell is zero, [AUDIO OUT]", "start": 2897.84, "duration": 2.86}, {"text": "know that the sodium\nchannel likes to be open.", "start": 2900.7, "duration": 3.6}, {"text": "So what that means is that the\nopen state has a lower energy", "start": 2904.3, "duration": 5.27}, {"text": "than the closed state, right?", "start": 2909.57, "duration": 2.4}, {"text": "Sodium channel likes to open\nwhen the cell is depolarized.", "start": 2911.97, "duration": 3.0}, {"text": "That means the voltage\ninside and outside", "start": 2914.97, "duration": 1.8}, {"text": "are close to each other, right?", "start": 2916.77, "duration": 3.9}, {"text": "Open state has a lower\nenergy than the closed state.", "start": 2920.67, "duration": 2.45}, {"text": "Let's call that energy\ndifference delta u.", "start": 2923.12, "duration": 3.82}, {"text": "And it's close to kt,\nbecause when it's open,", "start": 2926.94, "duration": 3.69}, {"text": "the channel kind of flickers\nback and forth between open", "start": 2930.63, "duration": 2.64}, {"text": "and closed.", "start": 2933.27, "duration": 1.11}, {"text": "Does that make sense?", "start": 2934.38, "duration": 2.78}, {"text": "Now let's put on--", "start": 2937.16, "duration": 1.02}, {"text": "let's hyperpolarize\nthe inside of our cell.", "start": 2941.74, "duration": 2.52}, {"text": "So now the voltage\ninside is low.", "start": 2944.26, "duration": 2.83}, {"text": "There's a voltage\ngradient, an electric field", "start": 2947.09, "duration": 2.67}, {"text": "that is trying to\npush those charges in.", "start": 2949.76, "duration": 4.22}, {"text": "Now, you can see that\nthose charges here", "start": 2953.98, "duration": 2.67}, {"text": "are sitting at a lower voltage.", "start": 2956.65, "duration": 2.64}, {"text": "So in the closed\nstate, those charges", "start": 2959.29, "duration": 3.21}, {"text": "are down here at\na lower potential.", "start": 2962.5, "duration": 2.16}, {"text": "What does that mean for the\nenergy of the closed state", "start": 2964.66, "duration": 4.86}, {"text": "when the cell is hyperpolarized?", "start": 2969.52, "duration": 3.12}, {"text": "Its lower.", "start": 2972.64, "duration": 1.41}, {"text": "The energy of the\nclosed state is low", "start": 2974.05, "duration": 2.19}, {"text": "because those charges are\ntoward the inside of the cell,", "start": 2976.24, "duration": 3.03}, {"text": "and the voltage is low.", "start": 2979.27, "duration": 2.37}, {"text": "Now, what happens if the\ncell is hyperpolarized,", "start": 2984.17, "duration": 3.42}, {"text": "but it happens to be\nin the open state?", "start": 2987.59, "duration": 1.8}, {"text": "You can see those charges\nare closer this way.", "start": 2989.39, "duration": 2.37}, {"text": "So you can see that the\nenergy of-- these charges", "start": 2991.76, "duration": 5.04}, {"text": "are still sitting in a voltage\nthat's lower than outside.", "start": 2996.8, "duration": 3.7}, {"text": "So that open state has\na slightly lower energy.", "start": 3000.5, "duration": 2.87}, {"text": "But you can see that\nthe closed state still", "start": 3003.37, "duration": 2.19}, {"text": "has a much lower energy\nthan the open state, OK?", "start": 3005.56, "duration": 3.06}, {"text": "And we can write down\nthat voltage difference", "start": 3008.62, "duration": 2.16}, {"text": "as a gating charge times\nthis voltage difference.", "start": 3010.78, "duration": 7.06}, {"text": "So now let's just take--", "start": 3020.48, "duration": 1.98}, {"text": "here is an open state.", "start": 3022.46, "duration": 2.76}, {"text": "It has an energy difference\nof a little amount, w.", "start": 3025.22, "duration": 3.63}, {"text": "Open state is lower than\nclosed by an amount w.", "start": 3028.85, "duration": 3.33}, {"text": "When the voltage\ninside the cell is low,", "start": 3032.18, "duration": 6.67}, {"text": "we've decreased the\nenergy of the closed state", "start": 3038.85, "duration": 3.45}, {"text": "by this amount-- gating charge\ntimes membrane potential.", "start": 3042.3, "duration": 4.32}, {"text": "And now we have an energy\ndifference in the open state", "start": 3046.62, "duration": 4.14}, {"text": "and the closed, the\nenergy difference", "start": 3050.76, "duration": 2.01}, {"text": "between the open\nstate and closed state", "start": 3052.77, "duration": 1.74}, {"text": "as a function of voltage.", "start": 3054.51, "duration": 2.62}, {"text": "We have a simple equation that\ndescribes the energy difference", "start": 3057.13, "duration": 3.36}, {"text": "between the open and\nclosed state as a function", "start": 3060.49, "duration": 2.37}, {"text": "of the membrane potential.", "start": 3062.86, "duration": 1.8}, {"text": "And now we can just plug that\ninto the Boltzmann equation", "start": 3064.66, "duration": 4.53}, {"text": "and derive the probability\nof being open and closed.", "start": 3069.19, "duration": 5.37}, {"text": "So we just plug that\ndelta u into here,", "start": 3074.56, "duration": 3.09}, {"text": "w minus gating\ncharge times voltage.", "start": 3077.65, "duration": 3.73}, {"text": "Now let's calculate the\nprobability of being open.", "start": 3081.38, "duration": 2.77}, {"text": "This gives us the ratio\nof open to closed.", "start": 3084.15, "duration": 3.84}, {"text": "How do we calculate the\nprobability of being open?", "start": 3087.99, "duration": 3.38}, {"text": "Well, n is the\nprobability of being open.", "start": 3091.37, "duration": 3.65}, {"text": "That's just probability\nof being open divided", "start": 3095.02, "duration": 2.54}, {"text": "by open plus closed.", "start": 3097.56, "duration": 2.23}, {"text": "What's the probability\nof being open", "start": 3099.79, "duration": 1.61}, {"text": "plus the probability\nof being closed?", "start": 3101.4, "duration": 1.71}, {"text": "Well, if it's in one or the\nother, then the sum of those", "start": 3103.11, "duration": 3.87}, {"text": "has to be one, OK?", "start": 3106.98, "duration": 2.67}, {"text": "And now divide both\ntop and bottom by p0.", "start": 3112.37, "duration": 3.28}, {"text": "The probability of being open\nit's just 1 over 1 plus p", "start": 3115.65, "duration": 4.47}, {"text": "closed over p open, which\nis just the inverse of this.", "start": 3120.12, "duration": 3.48}, {"text": "And that's equal to that.", "start": 3123.6, "duration": 1.07}, {"text": "All right, that may have gone\nby a little bit too fast.", "start": 3127.59, "duration": 3.84}, {"text": "And I wasn't very\nsmooth on that.", "start": 3131.43, "duration": 3.31}, {"text": "But you can see the idea, right?", "start": 3134.74, "duration": 2.03}, {"text": "It's estimating how\nthe energy difference", "start": 3140.97, "duration": 2.46}, {"text": "between the open\nand closed state", "start": 3143.43, "duration": 1.44}, {"text": "depends on the\nvoltage of the cell,", "start": 3144.87, "duration": 2.34}, {"text": "and it's just an\nenergy difference.", "start": 3147.21, "duration": 2.04}, {"text": "So it has to be a charge\ntimes a voltage, yeah?", "start": 3149.25, "duration": 4.52}, {"text": "And that's right [AUDIO OUT]\ncharge times a voltage.", "start": 3153.77, "duration": 3.98}, {"text": "And now we're just doing\na little bit of algebra", "start": 3157.75, "duration": 2.31}, {"text": "to extract the\nprobability of open", "start": 3160.06, "duration": 1.83}, {"text": "from open divided by closed.", "start": 3161.89, "duration": 4.1}, {"text": "And now if we just plug that\ninto there, we get this.", "start": 3165.99, "duration": 4.74}, {"text": "All right?", "start": 3170.73, "duration": 0.5}, {"text": "So now let's see how that\ncompares to the actual answer.", "start": 3171.23, "duration": 3.67}, {"text": "Probability of open is just 1\nover 1 plus this exponential.", "start": 3174.9, "duration": 6.3}, {"text": "Here's what that\ndata looked like.", "start": 3181.2, "duration": 1.68}, {"text": "Remember, that was the\ndata for the conductance", "start": 3182.88, "duration": 3.69}, {"text": "as a function of voltage.", "start": 3186.57, "duration": 1.065}, {"text": "Here's a fit to a functional\nform that looks like that.", "start": 3191.05, "duration": 5.11}, {"text": "And here is the\nprediction from Boltzmann.", "start": 3196.16, "duration": 3.614}, {"text": "You can see that it\nalmost exactly fits.", "start": 3202.45, "duration": 3.55}, {"text": "And you can actually\nextract, biophysically,", "start": 3206.0, "duration": 3.65}, {"text": "what the gating charge is\ninside this tiny, little protein", "start": 3209.65, "duration": 3.84}, {"text": "simply by fitting\nthis to the data.", "start": 3213.49, "duration": 3.57}, {"text": "Pretty cool, right?", "start": 3220.27, "duration": 0.99}, {"text": "Yes?", "start": 3221.26, "duration": 0.5}, {"text": "AUDIENCE: What is w?", "start": 3221.76, "duration": 2.735}, {"text": "MICHALE FEE: It's\nthe energy difference", "start": 3224.495, "duration": 1.625}, {"text": "between the open and closed\nstate when the voltage is zero.", "start": 3226.12, "duration": 4.7}, {"text": "So you kind of have\nto fit that, too.", "start": 3230.82, "duration": 3.81}, {"text": "If the voltage is zero,\nit's the energy difference", "start": 3234.63, "duration": 4.96}, {"text": "between the open and closed\nstate when the voltage is zero.", "start": 3239.59, "duration": 4.53}, {"text": "And then you subtract from\nthat the energy of the gating", "start": 3244.12, "duration": 4.38}, {"text": "charge as a function of\nvoltage inside the cell, OK?", "start": 3248.5, "duration": 3.74}, {"text": "Yes", "start": 3255.12, "duration": 1.92}, {"text": "AUDIENCE: So is that\nthe [INAUDIBLE]..", "start": 3257.04, "duration": 1.99}, {"text": "MICHALE FEE: Yes,\neach has the sensor,", "start": 3261.89, "duration": 2.7}, {"text": "and they all have to be open\nfor the ion channel to be open.", "start": 3264.59, "duration": 4.23}, {"text": "Yes?", "start": 3268.82, "duration": 0.833}, {"text": "AUDIENCE: Do you not need to\nput it to the power of four?", "start": 3269.653, "duration": 3.187}, {"text": "MICHALE FEE: No, because\nthis is the probability", "start": 3272.84, "duration": 2.0}, {"text": "that one subunit is open.", "start": 3274.84, "duration": 3.47}, {"text": "But that's a good point.", "start": 3278.31, "duration": 1.04}, {"text": "If you want to\ncompare that to the--", "start": 3279.35, "duration": 1.6}, {"text": "so you're right.", "start": 3280.95, "duration": 0.99}, {"text": "If you want to compare\nthat to the conductance", "start": 3281.94, "duration": 1.98}, {"text": "of the whole\nchannel, then it has", "start": 3283.92, "duration": 1.68}, {"text": "to be raised to\nthe power of four.", "start": 3285.6, "duration": 3.45}, {"text": "And that's been\naccounted for here.", "start": 3289.05, "duration": 2.22}, {"text": "Good question.", "start": 3291.27, "duration": 0.66}, {"text": "Any other questions?", "start": 3295.97, "duration": 2.89}, {"text": "Boltzmann men equation\nis pretty cool.", "start": 3298.86, "duration": 1.7}, {"text": "If you know the mass\nof a nitrogen molecule", "start": 3307.376, "duration": 5.424}, {"text": "and the acceleration\ndue to gravity,", "start": 3312.8, "duration": 2.1}, {"text": "what can you calculate with\nthe Boltzmann equation?", "start": 3314.9, "duration": 3.24}, {"text": "Any idea?", "start": 3318.14, "duration": 0.51}, {"text": "The mass of a nitrogen\nmolecule and the acceleration", "start": 3322.06, "duration": 4.74}, {"text": "due to gravity.", "start": 3326.8, "duration": 1.768}, {"text": "AUDIENCE: Pressure of nitrogen?", "start": 3328.568, "duration": 1.292}, {"text": "The partial pressure\nof nitrogen?", "start": 3329.86, "duration": 3.32}, {"text": "MICHALE FEE: Close.", "start": 3333.18, "duration": 1.88}, {"text": "You can calculate the\nheight of the atmosphere.", "start": 3335.06, "duration": 4.93}, {"text": "You can do all kinds\nof really cool stuff", "start": 3339.99, "duration": 2.183}, {"text": "with the Boltzmann equation.", "start": 3342.173, "duration": 1.167}, {"text": "OK, there was another\nquestion here.", "start": 3348.28, "duration": 3.325}, {"text": "No?", "start": 3351.605, "duration": 0.5}, {"text": "So you can extract,\nactually, these quantities--", "start": 3356.33, "duration": 2.43}, {"text": "the gating charge and this\nenergy difference in the zero", "start": 3358.76, "duration": 4.68}, {"text": "voltage state.", "start": 3363.44, "duration": 0.75}, {"text": "And the fit is very good.", "start": 3366.95, "duration": 3.65}, {"text": "OK, so that's\nvoltage dependence.", "start": 3370.6, "duration": 4.38}, {"text": "I highlighted\nthese slides that I", "start": 3374.98, "duration": 2.28}, {"text": "don't expect you to be\nable to reproduce in blue,", "start": 3377.26, "duration": 10.23}, {"text": "just to make it more\nclear for your review", "start": 3387.49, "duration": 3.69}, {"text": "what you have to focus on.", "start": 3391.18, "duration": 3.09}, {"text": "OK, let's look at\nthe time dependence.", "start": 3394.27, "duration": 1.77}, {"text": "The time dependence\nis pretty simple.", "start": 3396.04, "duration": 2.05}, {"text": "It's going to just involve a\nlinear first order differential", "start": 3398.09, "duration": 2.51}, {"text": "equation.", "start": 3400.6, "duration": 0.52}, {"text": "You guys are all super\nexperts on that now, right?", "start": 3401.12, "duration": 4.81}, {"text": "So we have an ion channel--", "start": 3405.93, "duration": 4.03}, {"text": "sorry, a subunit that's\neither open or closed, right?", "start": 3409.96, "duration": 3.58}, {"text": "We have an open\nstate, closed state.", "start": 3413.54, "duration": 2.31}, {"text": "What we're going to do is--", "start": 3415.85, "duration": 3.57}, {"text": "so the way to think about\nthis is the ion channel,", "start": 3419.42, "duration": 3.09}, {"text": "the subunit, if the\ncell is polarized,", "start": 3422.51, "duration": 2.58}, {"text": "is sitting in the\nclosed state, right?", "start": 3425.09, "duration": 2.91}, {"text": "When you depolarize the neuron,\nthat changes the energy levels.", "start": 3428.0, "duration": 6.33}, {"text": "[AUDIO OUT] Which way was it?", "start": 3434.33, "duration": 4.0}, {"text": "I forget.", "start": 3438.33, "duration": 1.28}, {"text": "The closed state\nhas a lower energy.", "start": 3439.61, "duration": 2.41}, {"text": "Now, when you\ndepolarize the cell,", "start": 3442.02, "duration": 3.02}, {"text": "the closed state suddenly\nhas a much higher energy,", "start": 3445.04, "duration": 2.4}, {"text": "and it's close to\nthe open state.", "start": 3447.44, "duration": 4.34}, {"text": "And so, at some\npoint, that subunit", "start": 3451.78, "duration": 3.9}, {"text": "will jump over to the\nopen state, right?", "start": 3455.68, "duration": 3.99}, {"text": "But that takes time.", "start": 3459.67, "duration": 1.26}, {"text": "You change the energy\nlevels, but it takes time", "start": 3460.93, "duration": 2.16}, {"text": "for the system to jump\ninto the open state.", "start": 3463.09, "duration": 4.74}, {"text": "Why is that?", "start": 3467.83, "duration": 0.69}, {"text": "Because that transition is\ncaused by thermal fluctuations.", "start": 3471.98, "duration": 5.35}, {"text": "And so you have to wait for\none of those fluctuations", "start": 3477.33, "duration": 2.21}, {"text": "to kick you over\ninto the open state.", "start": 3479.54, "duration": 2.49}, {"text": "So we're going to\nmodel those transitions", "start": 3484.95, "duration": 1.71}, {"text": "between open and closed states\nwith a simple rate equation", "start": 3486.66, "duration": 4.17}, {"text": "that's voltage dependent.", "start": 3490.83, "duration": 1.53}, {"text": "We have an open\nstate, and we imagine", "start": 3492.36, "duration": 1.74}, {"text": "that n is the probability\nof being in the open state.", "start": 3494.1, "duration": 4.13}, {"text": "And we can equivalently\nthink of it", "start": 3498.23, "duration": 2.11}, {"text": "as if we have a\npopulation of subunits.", "start": 3500.34, "duration": 3.78}, {"text": "And let's think of it\nmore as the fraction.", "start": 3504.12, "duration": 3.96}, {"text": "It's also equivalent to--", "start": 3508.08, "duration": 1.89}, {"text": "just whichever way you\nwant to think about it,", "start": 3509.97, "duration": 3.19}, {"text": "either works well.", "start": 3513.16, "duration": 1.24}, {"text": "But you can also think\nof it as the probability", "start": 3514.4, "duration": 2.56}, {"text": "of being in the open\nstate, or the number", "start": 3516.96, "duration": 2.33}, {"text": "of subunits that are in the\nopen state in a population.", "start": 3519.29, "duration": 5.69}, {"text": "You also have a closed state.", "start": 3524.98, "duration": 1.38}, {"text": "So if n is the\nprobability of being", "start": 3526.36, "duration": 1.56}, {"text": "in the open state,\n[AUDIO OUT] of a closed state", "start": 3527.92, "duration": 3.06}, {"text": "with probability\n1 minus n, right?", "start": 3530.98, "duration": 5.943}, {"text": "If you're in the\nclosed state, you", "start": 3536.923, "duration": 1.417}, {"text": "have some transition rate,\nprobability per unit time,", "start": 3538.34, "duration": 4.41}, {"text": "of going from the closed\nstate to the open state.", "start": 3542.75, "duration": 2.82}, {"text": "And if you're in\nthe open state, you", "start": 3545.57, "duration": 1.5}, {"text": "have some probability\nper unit time beta", "start": 3547.07, "duration": 3.31}, {"text": "of going into the closed state.", "start": 3550.38, "duration": 1.52}, {"text": "So those things have\nunits of per second,", "start": 3556.49, "duration": 2.85}, {"text": "probability per second.", "start": 3559.34, "duration": 1.5}, {"text": "Yes?", "start": 3560.84, "duration": 1.04}, {"text": "Rebecca, right?", "start": 3561.88, "duration": 0.89}, {"text": "AUDIENCE: Yeah.", "start": 3562.77, "duration": 0.697}, {"text": "What's the cause for\nthe fluctuations?", "start": 3563.467, "duration": 1.788}, {"text": "Just regular [INAUDIBLE]?", "start": 3565.255, "duration": 1.345}, {"text": "MICHALE FEE: Just warmth.", "start": 3566.6, "duration": 1.41}, {"text": "And these things are\nvoltage dependent, remember?", "start": 3576.03, "duration": 4.16}, {"text": "Those depend on the\nenergy difference", "start": 3580.19, "duration": 3.03}, {"text": "between that open\nand closed state.", "start": 3583.22, "duration": 2.17}, {"text": "All right, let's develop our\nfirst order linear equation.", "start": 3589.55, "duration": 4.15}, {"text": "It's going be very simple.", "start": 3593.7, "duration": 2.01}, {"text": "We have a closed\nstate, an open state.", "start": 3595.71, "duration": 2.66}, {"text": "The change in the\nnumber of open states", "start": 3598.37, "duration": 2.64}, {"text": "is just going to be the number\nof closed states, the number", "start": 3601.01, "duration": 3.39}, {"text": "of closed subunits that\nopen, minus the number", "start": 3604.4, "duration": 3.66}, {"text": "of open subunits that close.", "start": 3608.06, "duration": 2.55}, {"text": "That makes sense?", "start": 3610.61, "duration": 3.13}, {"text": "All right, that's simple enough.", "start": 3613.74, "duration": 2.56}, {"text": "The change in the number\nopen subunits per unit time", "start": 3616.3, "duration": 4.93}, {"text": "is going to be the\nnumber of closed subunits", "start": 3621.23, "duration": 3.57}, {"text": "that there are times\nthe probability", "start": 3624.8, "duration": 2.46}, {"text": "that a closed subunit\nopens per unit time--", "start": 3627.26, "duration": 4.28}, {"text": "that's alpha-- minus--", "start": 3631.54, "duration": 2.42}, {"text": "remember, the number\nof closed subunits", "start": 3633.96, "duration": 2.16}, {"text": "that open is the number\nof closed subunits", "start": 3636.12, "duration": 3.0}, {"text": "times the probability\nper unit time", "start": 3639.12, "duration": 2.34}, {"text": "that a closed subunit\nopens, all right?", "start": 3641.46, "duration": 2.85}, {"text": "And the number of open\nsubunits that close", "start": 3644.31, "duration": 1.935}, {"text": "is just the number of open\nsubunits times the probability", "start": 3646.245, "duration": 4.095}, {"text": "that any one of them\ncloses per unit time.", "start": 3650.34, "duration": 2.905}, {"text": "Does that make sense?", "start": 3653.245, "duration": 0.875}, {"text": "A lot of words, but the equation\nends up being very simple.", "start": 3656.7, "duration": 4.34}, {"text": "The change per unit\ntime of n is just", "start": 3661.04, "duration": 6.88}, {"text": "the number of close\nsubunits, one [AUDIO OUT],,", "start": 3667.92, "duration": 2.55}, {"text": "times the probability that\nthose open per unit time", "start": 3670.47, "duration": 3.48}, {"text": "alpha minus beta times n.", "start": 3673.95, "duration": 4.32}, {"text": "Alpha times 1 minus\nn minus beta times n.", "start": 3678.27, "duration": 3.15}, {"text": "Any questions about that?", "start": 3688.08, "duration": 1.44}, {"text": "Alpha, beta are\nvoltage dependent.", "start": 3689.52, "duration": 2.52}, {"text": "So I've rewritten that equation.", "start": 3694.88, "duration": 3.27}, {"text": "n is the probability\nthat a subunit is open.", "start": 3698.15, "duration": 3.33}, {"text": "Let's just rewrite this.", "start": 3705.72, "duration": 1.07}, {"text": "Let's expand this.", "start": 3706.79, "duration": 0.9}, {"text": "Alpha minus alpha times\nn minus beta times n.", "start": 3707.69, "duration": 3.47}, {"text": "Factor out the n.", "start": 3711.16, "duration": 1.54}, {"text": "So you have dn dt equals alpha\nminus alpha plus beta times n.", "start": 3712.7, "duration": 8.02}, {"text": "Divide both sides by 1\nover alpha plus beta.", "start": 3720.72, "duration": 5.34}, {"text": "What's the steady state\nof this-- the steady state", "start": 3726.06, "duration": 2.4}, {"text": "solution of this equation?", "start": 3728.46, "duration": 1.32}, {"text": "That is the steady\nstate solution, right?", "start": 3736.8, "duration": 2.43}, {"text": "If you set dn dt equal to\nzero, then n is equal to that.", "start": 3739.23, "duration": 4.77}, {"text": "[AUDIO OUT] just n infinity.", "start": 3744.0, "duration": 1.885}, {"text": "And what's that?", "start": 3748.56, "duration": 2.08}, {"text": "Alpha and beta have\nunits of per unit time.", "start": 3750.64, "duration": 3.43}, {"text": "So what is one-- what units do\n1 over alpha plus beta have?", "start": 3754.07, "duration": 3.2}, {"text": "Time.", "start": 3760.68, "duration": 0.66}, {"text": "So what might that be?", "start": 3761.34, "duration": 3.243}, {"text": "AUDIENCE: Tau.", "start": 3764.583, "duration": 1.357}, {"text": "MICHALE FEE: Tau.", "start": 3765.94, "duration": 0.79}, {"text": "It's a time constant.", "start": 3766.73, "duration": 0.93}, {"text": "So, after all of this,\nwhat we end up with", "start": 3770.37, "duration": 3.06}, {"text": "is an equation that looks\nexactly like what we had for--", "start": 3773.43, "duration": 7.8}, {"text": "we have a first order linear\ndifferential equation exactly", "start": 3781.23, "duration": 3.21}, {"text": "the same form as\nthe equation we used", "start": 3784.44, "duration": 2.55}, {"text": "to understand the way\nthe voltage changes", "start": 3786.99, "duration": 3.27}, {"text": "in a cell in response\nto current injection.", "start": 3790.26, "duration": 3.36}, {"text": "So if we change n infinity,\nwhat is this thing going to do?", "start": 3793.62, "duration": 4.6}, {"text": "What is n going to do?", "start": 3798.22, "duration": 2.19}, {"text": "It's going to relax [AUDIO OUT]\nn infinity with a time", "start": 3800.41, "duration": 6.54}, {"text": "constant tau.", "start": 3806.95, "duration": 3.36}, {"text": "In all of these\nthings, the tau is", "start": 3810.31, "duration": 2.19}, {"text": "tau sub n, because it's\nfor the n gating variable.", "start": 3812.5, "duration": 3.31}, {"text": "So that's why this\nhas an n here.", "start": 3815.81, "duration": 1.86}, {"text": "So n infinity and tau\nare voltage dependent,", "start": 3821.21, "duration": 5.17}, {"text": "because they come from\nalpha and beta, which", "start": 3826.38, "duration": 3.36}, {"text": "are voltage dependent.", "start": 3829.74, "duration": 1.478}, {"text": "But we actually just derived the\nsteady state voltage dependence", "start": 3834.03, "duration": 4.77}, {"text": "of the potassium\nconductance, right,", "start": 3838.8, "duration": 3.378}, {"text": "from the Boltzmann equation?", "start": 3842.178, "duration": 1.167}, {"text": "What is n infinity for\nvery negative voltages?", "start": 3849.16, "duration": 4.476}, {"text": "Do you remember it,\njust approximately?", "start": 3853.636, "duration": 3.754}, {"text": "Big, small, [AUDIO OUT]?", "start": 3857.39, "duration": 1.956}, {"text": "What is the steady state?", "start": 3862.84, "duration": 1.48}, {"text": "What's the probability that\na potassium channel is open,", "start": 3864.32, "duration": 3.74}, {"text": "that a subunit is open,\nat very negative voltages?", "start": 3868.06, "duration": 2.28}, {"text": "Do you remember?", "start": 3870.34, "duration": 1.44}, {"text": "Zero.", "start": 3871.78, "duration": 0.6}, {"text": "It's off.", "start": 3872.38, "duration": 1.03}, {"text": "For big voltage, n\ninfinity has to be--", "start": 3873.41, "duration": 3.84}, {"text": "if we think of it as a\nprobability, it's close to one.", "start": 3877.25, "duration": 4.96}, {"text": "So n infinity goes from\nzero at negative voltages,", "start": 3882.21, "duration": 4.34}, {"text": "sigmoidal activation up\nto one at high voltages.", "start": 3886.55, "duration": 5.73}, {"text": "OK, so now let's look at how n\nchanges as a function of time.", "start": 3892.28, "duration": 6.27}, {"text": "So here's our\n[AUDIO OUT] potential.", "start": 3898.55, "duration": 2.48}, {"text": "We're going do a voltage\nclamp experiment.", "start": 3901.03, "duration": 1.95}, {"text": "We're going to start at minus 80\nmillivolts and step up to zero.", "start": 3902.98, "duration": 4.81}, {"text": "So what is n\ninfinity going to do?", "start": 3907.79, "duration": 3.59}, {"text": "n infinity is just a\nfunction of voltage, right?", "start": 3911.38, "duration": 3.93}, {"text": "It's like those energy levels.", "start": 3915.31, "duration": 1.89}, {"text": "They change immediately.", "start": 3917.2, "duration": 2.31}, {"text": "So what is n\ninfinity going to do?", "start": 3919.51, "duration": 1.74}, {"text": "Good.", "start": 3924.73, "duration": 0.5}, {"text": "It's going to start at close\nto zero, jump up to one,", "start": 3925.23, "duration": 5.46}, {"text": "and then jump back to\nclose to zero immediately", "start": 3930.69, "duration": 4.32}, {"text": "following the voltage.", "start": 3935.01, "duration": 2.88}, {"text": "But what is n going to do?", "start": 3937.89, "duration": 1.51}, {"text": "Now let's plot n.", "start": 3939.4, "duration": 1.752}, {"text": "n is going to start at zero.", "start": 3941.152, "duration": 2.408}, {"text": "When you step the voltage\nup, n infinity will jump up,", "start": 3946.34, "duration": 2.86}, {"text": "and n will relax exponentially\nto a high n infinity", "start": 3949.2, "duration": 5.83}, {"text": "close to one, right?", "start": 3955.03, "duration": 4.32}, {"text": "And then when we\nturn back, n infinity", "start": 3959.35, "duration": 2.66}, {"text": "jumps back down to zero, and\nn relaxes exponentially back.", "start": 3962.01, "duration": 5.61}, {"text": "Yes?", "start": 3967.62, "duration": 0.834}, {"text": "AUDIENCE: On the n\n[INAUDIBLE],, that's not", "start": 3968.454, "duration": 1.896}, {"text": "relaxing [INAUDIBLE] to one.", "start": 3970.35, "duration": 1.896}, {"text": "It's to n infinity,\nright, at the top?", "start": 3972.246, "duration": 1.904}, {"text": "MICHALE FEE: Yes, but for\na voltage around zero,", "start": 3974.15, "duration": 3.36}, {"text": "n infinity is going\nto be close to one .", "start": 3977.51, "duration": 2.158}, {"text": "Any questions?", "start": 3982.36, "duration": 1.27}, {"text": "That is called activation.", "start": 3990.2, "duration": 4.4}, {"text": "That's the activation.", "start": 3994.6, "duration": 2.06}, {"text": "Now, this looks a\nlittle funny, right?", "start": 3996.66, "duration": 1.9}, {"text": "This thing is turning\non immediately.", "start": 3998.56, "duration": 2.49}, {"text": "It doesn't have that\nnice sigmoidal shape", "start": 4001.05, "duration": 2.13}, {"text": "that the potassium current had,\nor the potassium conductance.", "start": 4003.18, "duration": 4.44}, {"text": "Why is that?", "start": 4007.62, "duration": 1.033}, {"text": "What are we looking at here?", "start": 4008.653, "duration": 1.167}, {"text": "We're plotting n.", "start": 4009.82, "duration": 1.52}, {"text": "What is the potassium\nconductance or the current?", "start": 4011.34, "duration": 2.97}, {"text": "How does that relate to n?", "start": 4014.31, "duration": 3.3}, {"text": "n to the fourth.", "start": 4017.61, "duration": 1.48}, {"text": "So what do we do to plot\nthe potassium current", "start": 4019.09, "duration": 3.72}, {"text": "or the potassium conductance?", "start": 4022.81, "duration": 2.13}, {"text": "We just take this\n[AUDIO OUT],, right?", "start": 4024.94, "duration": 2.88}, {"text": "So what does that look like?", "start": 4027.82, "duration": 2.68}, {"text": "This process of turning off--", "start": 4030.5, "duration": 2.46}, {"text": "the gating variable getting\nbigger is called activation.", "start": 4032.96, "duration": 2.88}, {"text": "The gating variable getting\nsmaller, n getting smaller,", "start": 4035.84, "duration": 3.03}, {"text": "is called disactivation.", "start": 4038.87, "duration": 3.31}, {"text": "So now let's plot\nthis to the fourth.", "start": 4042.18, "duration": 3.27}, {"text": "So this conductance\nturns on gradually,", "start": 4045.45, "duration": 3.57}, {"text": "but the conductance\nis proportional to n", "start": 4049.02, "duration": 2.0}, {"text": "to the fourth.", "start": 4051.02, "duration": 0.76}, {"text": "So let's plot that.", "start": 4051.78, "duration": 1.69}, {"text": "So if we plot n\nto the fourth, you", "start": 4053.47, "duration": 1.43}, {"text": "can see that that function\nnow turns on smoothly in time.", "start": 4054.9, "duration": 5.13}, {"text": "This is time now, right?", "start": 4060.03, "duration": 1.97}, {"text": "So that gating variable\nn relaxes exponentially,", "start": 4065.25, "duration": 4.53}, {"text": "but the conductance goes as the\ngating variable to the fourth.", "start": 4069.78, "duration": 3.18}, {"text": "And so it has this nice,\ngraceful turn-on, right?", "start": 4072.96, "duration": 8.64}, {"text": "Because it's the\ngating [AUDIO OUT]", "start": 4081.6, "duration": 2.1}, {"text": "exponential to the fourth\nlooks exactly like this.", "start": 4083.7, "duration": 5.25}, {"text": "In fact, that's how Hodgkin\nand Huxley figured out", "start": 4088.95, "duration": 4.79}, {"text": "that it's n to the four, because\nthey knew that if they assume", "start": 4093.74, "duration": 5.909}, {"text": "that it's an exponentially\ndecaying gating", "start": 4099.649, "duration": 2.761}, {"text": "variable, that the only way\nthey could fit the turn on", "start": 4102.41, "duration": 3.52}, {"text": "of the conductance was by\nraising it to the fourth power.", "start": 4105.93, "duration": 3.41}, {"text": "If they raised it to the second\npower, it was still too sudden.", "start": 4109.34, "duration": 5.3}, {"text": "If they raised it\nto the third power,", "start": 4114.64, "duration": 2.19}, {"text": "it was still not quite right.", "start": 4116.83, "duration": 1.8}, {"text": "But if they raised it to\nthe fifth power, oops,", "start": 4118.63, "duration": 2.189}, {"text": "it's too delayed.", "start": 4120.819, "duration": 0.997}, {"text": "If they raised it\nto the fourth power,", "start": 4121.816, "duration": 1.583}, {"text": "it exactly fits the shape of\nthe conductance turning on.", "start": 4123.399, "duration": 7.761}, {"text": "And so they inferred--", "start": 4131.16, "duration": 1.96}, {"text": "they didn't know about subunits.", "start": 4133.12, "duration": 2.92}, {"text": "They just had a piece of\naxon, a piece of squid lying", "start": 4136.04, "duration": 3.87}, {"text": "on a table in front of them.", "start": 4139.91, "duration": 1.94}, {"text": "And they were able to\nfigure out that there", "start": 4141.85, "duration": 2.259}, {"text": "were four independent processes\nthat turn on the potassium", "start": 4144.109, "duration": 3.21}, {"text": "conductance.", "start": 4147.319, "duration": 0.721}, {"text": "Pretty cool, right?", "start": 4151.33, "duration": 1.92}, {"text": "That's what you get by\ndoing things quantitatively.", "start": 4153.25, "duration": 2.55}, {"text": "So they could\n[AUDIO OUT] the shape", "start": 4161.992, "duration": 1.458}, {"text": "of that potassium\nconductance turning", "start": 4163.45, "duration": 1.739}, {"text": "on by this exponential\ngating variable raised", "start": 4165.189, "duration": 2.701}, {"text": "to the fourth power.", "start": 4167.89, "duration": 0.9}, {"text": "And from that, they\nwere able to infer", "start": 4172.64, "duration": 1.78}, {"text": "that it's four independent first\norder processes that combine", "start": 4174.42, "duration": 6.28}, {"text": "to produce that activation.", "start": 4180.7, "duration": 3.56}, {"text": "OK, the offset also fits if you\nraise it to the fourth power.", "start": 4184.26, "duration": 5.11}, {"text": "They were able to measure\nthe size of the potassium", "start": 4189.37, "duration": 3.21}, {"text": "conductance to measure\nn infinity directly.", "start": 4192.58, "duration": 3.21}, {"text": "So we derived it using\nthe Boltzmann equation,", "start": 4195.79, "duration": 2.55}, {"text": "but they measured\nit directly just", "start": 4198.34, "duration": 1.56}, {"text": "by the size of the conductance.", "start": 4199.9, "duration": 3.87}, {"text": "And you can also\nmeasure the time course.", "start": 4203.77, "duration": 2.712}, {"text": "You don't need to\nworry about this.", "start": 4206.482, "duration": 1.458}, {"text": "I'm not expecting--\nyou should know this.", "start": 4207.94, "duration": 2.94}, {"text": "I'm just showing you\nthat just for fun.", "start": 4210.88, "duration": 1.683}, {"text": "You don't need to know that.", "start": 4212.563, "duration": 1.167}, {"text": "And you can extract\nthese tau's just", "start": 4220.16, "duration": 1.96}, {"text": "by measuring this exponential\ndecay at different voltages,", "start": 4222.12, "duration": 5.31}, {"text": "or measuring the inferred\nfirst order process.", "start": 4227.43, "duration": 5.76}, {"text": "You can infer the time constant\nof the first order process", "start": 4233.19, "duration": 3.04}, {"text": "on the onset and the offset\nto extract these tau's", "start": 4236.23, "duration": 4.87}, {"text": "as a function of voltage.", "start": 4241.1, "duration": 1.26}, {"text": "This is tau as a\nfunction of voltage.", "start": 4242.36, "duration": 1.785}, {"text": "From these two quantities,\nyou can actually", "start": 4249.9, "duration": 3.63}, {"text": "extract alpha and beta.", "start": 4253.53, "duration": 2.86}, {"text": "And so you can write down a\nsimple algebraic expression", "start": 4256.39, "duration": 4.85}, {"text": "for alpha and beta.", "start": 4261.24, "duration": 1.39}, {"text": "And that's the way they actually\nwrote those things down.", "start": 4262.63, "duration": 2.87}, {"text": "They wrote them down as\nalpha and beta, rather than n", "start": 4265.5, "duration": 2.43}, {"text": "infinity and tau.", "start": 4267.93, "duration": 3.34}, {"text": "Those are simple expressions\nfor alpha and beta", "start": 4271.27, "duration": 2.81}, {"text": "in units of per millisecond\nas a function of voltage", "start": 4274.08, "duration": 3.6}, {"text": "in units of millivolts.", "start": 4277.68, "duration": 3.33}, {"text": "I think-- yeah, it's millivolts.", "start": 4281.01, "duration": 2.83}, {"text": "There it is right there.", "start": 4283.84, "duration": 1.99}, {"text": "So you can actually just\ntake those parameters", "start": 4285.83, "duration": 4.26}, {"text": "and calculate n\ninfinity and tau n", "start": 4290.09, "duration": 4.77}, {"text": "and calculate the gating\nvariable from that using", "start": 4294.86, "duration": 4.44}, {"text": "that differential equation.", "start": 4299.3, "duration": 1.41}, {"text": "So we have these\nnice expressions", "start": 4300.71, "duration": 2.31}, {"text": "for what the steady state,\nn infinity, and tau n are.", "start": 4303.02, "duration": 5.16}, {"text": "Now, why did we-- yes?", "start": 4312.08, "duration": 2.145}, {"text": "AUDIENCE: [INAUDIBLE]?", "start": 4314.225, "duration": 2.675}, {"text": "MICHALE FEE: Yes,\nthey're per unit time.", "start": 4316.9, "duration": 2.27}, {"text": "Yeah, so they have units\nof per millisecond.", "start": 4319.17, "duration": 3.331}, {"text": "OK, so now let's come\nback to our picture.", "start": 4326.43, "duration": 3.14}, {"text": "We have n infinity and tau\nn as a function of voltage.", "start": 4329.57, "duration": 3.75}, {"text": "Now we just can plug those\ninto this differential equation", "start": 4333.32, "duration": 3.23}, {"text": "and solve for n.", "start": 4336.55, "duration": 0.9}, {"text": "Well, we already\nknow what that does.", "start": 4337.45, "duration": 2.37}, {"text": "n relaxes exponentially\ntoward n infinity", "start": 4339.82, "duration": 2.58}, {"text": "with a time constant tau.", "start": 4342.4, "duration": 2.96}, {"text": "But you can integrate\nthat numerically.", "start": 4345.36, "duration": 4.29}, {"text": "You get the potassium\nconductance as n to the four,", "start": 4349.65, "duration": 3.255}, {"text": "g times n to the four.", "start": 4352.905, "duration": 1.875}, {"text": "You get the potassium\ncurrent as g n to the four", "start": 4354.78, "duration": 3.36}, {"text": "times the driving\npotential, or V minus Ek.", "start": 4358.14, "duration": 5.17}, {"text": "And now let's come\nback to our algorithm", "start": 4363.31, "duration": 5.69}, {"text": "for making an action potential.", "start": 4369.0, "duration": 4.0}, {"text": "So we have the parts related\nto the potassium current.", "start": 4373.0, "duration": 2.87}, {"text": "We still have to add the\nparts related to sodium,", "start": 4375.87, "duration": 2.25}, {"text": "but it's going to\nlook very similar.", "start": 4378.12, "duration": 2.11}, {"text": "So here's the idea.", "start": 4380.23, "duration": 1.14}, {"text": "We start with the membrane\npotential at time step t.", "start": 4381.37, "duration": 3.05}, {"text": "We compute n infinity and tau n.", "start": 4384.42, "duration": 3.47}, {"text": "We integrate dn dt one time\nstep to get the next n.", "start": 4387.89, "duration": 4.8}, {"text": "Plug n into our equation to\nget the potassium current.", "start": 4395.53, "duration": 3.12}, {"text": "We then add that to\nall the other currents", "start": 4401.97, "duration": 2.7}, {"text": "to get the total\nmembrane current.", "start": 4404.67, "duration": 2.28}, {"text": "We compute V\ninfinity of the cell.", "start": 4406.95, "duration": 3.57}, {"text": "We integrate dv dt one time\nstep to get the next voltage.", "start": 4410.52, "duration": 5.31}, {"text": "And you plug that in and\ncalculate the next n infinity,", "start": 4415.83, "duration": 3.27}, {"text": "all right?", "start": 4419.1, "duration": 2.31}, {"text": "So we still have to\nadd the sodium parts,", "start": 4421.41, "duration": 2.28}, {"text": "but you can see we've\ngone through all", "start": 4423.69, "duration": 2.16}, {"text": "of these steps\nfor the potassium.", "start": 4425.85, "duration": 3.54}, {"text": "And so we're just\nthis shy of having", "start": 4429.39, "duration": 3.72}, {"text": "a full-blown algorithm\nfor [AUDIO OUT] an action", "start": 4433.11, "duration": 2.82}, {"text": "potential in a neuron.", "start": 4435.93, "duration": 2.19}, {"text": "And not only do you understand\nall the little steps,", "start": 4438.12, "duration": 2.43}, {"text": "but you understand the\nfundamental biophysics", "start": 4440.55, "duration": 2.64}, {"text": "that leads to that voltage\nand time dependence.", "start": 4443.19, "duration": 3.06}, {"text": "All right, so, again, what\nI'd like you to be able to do", "start": 4450.1, "duration": 3.25}, {"text": "is to draw that circuit,\nthe Hodgkin-Huxley model.", "start": 4453.35, "duration": 4.44}, {"text": "I'd like you to be able to\nexplain, at a basic level,", "start": 4457.79, "duration": 3.84}, {"text": "what a voltage clamp\nis and how it works.", "start": 4461.63, "duration": 3.435}, {"text": "I'd like you to be able to plot\nthe voltage and time dependence", "start": 4465.065, "duration": 2.625}, {"text": "of the potassium current--", "start": 4467.69, "duration": 1.38}, {"text": "remember, this\nsigmoidal activation", "start": 4469.07, "duration": 2.49}, {"text": "of the potassium current--\nand the conductance, voltage", "start": 4471.56, "duration": 3.27}, {"text": "and time dependence.", "start": 4474.83, "duration": 2.34}, {"text": "And be able to explain the\ntime and voltage dependence", "start": 4477.17, "duration": 2.28}, {"text": "of the potassium\nconductance in terms", "start": 4479.45, "duration": 1.86}, {"text": "of the Hodgkin-Huxley\ngating variables.", "start": 4481.31, "duration": 2.58}, {"text": "OK?", "start": 4483.89, "duration": 1.55}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 0.0, "duration": 2.49}, {"text": "Commons license.", "start": 2.49, "duration": 1.24}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 3.73, "duration": 2.39}, {"text": "continue to offer high quality\neducational resources for free.", "start": 6.12, "duration": 3.97}, {"text": "To make a donation or to\nview additional materials", "start": 10.09, "duration": 2.63}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 12.72, "duration": 3.93}, {"text": "at ocw.mit.edu.", "start": 16.65, "duration": 2.21}, {"text": "RAMESH RASKAR: So let's start\nwith a thermal IR camera.", "start": 21.41, "duration": 3.09}, {"text": "And as you can see, it has\nvery strange properties.", "start": 24.5, "duration": 5.25}, {"text": "Who are we looking at here?", "start": 29.75, "duration": 1.83}, {"text": "That's you?", "start": 31.58, "duration": 2.0}, {"text": "AUDIENCE: Oh, yeah.", "start": 33.58, "duration": 0.792}, {"text": "RAMESH RASKAR:\n[LAUGHS] And then,", "start": 34.372, "duration": 4.008}, {"text": "as it turns on his lighter, it\ncaused an automatic gain mode,", "start": 38.38, "duration": 5.55}, {"text": "I guess.", "start": 43.93, "duration": 1.078}, {"text": "And that's why the\nimage gets very dark.", "start": 45.008, "duration": 1.667}, {"text": "And who's in the\npicture, anyway?", "start": 50.96, "duration": 4.17}, {"text": "Oh, that's Seth.", "start": 55.13, "duration": 1.35}, {"text": "Excellent.", "start": 56.48, "duration": 1.24}, {"text": "Thought I could recognize\nyou in thermal IR", "start": 57.72, "duration": 3.2}, {"text": "And if you just put a\ncold finger on your cheek,", "start": 60.92, "duration": 2.7}, {"text": "you're going to see it.", "start": 63.62, "duration": 3.26}, {"text": "And take it off.", "start": 66.88, "duration": 0.77}, {"text": "Yeah, you can see the mark.", "start": 67.65, "duration": 2.89}, {"text": "Things that are completely\ntransparent in visible", "start": 70.54, "duration": 4.26}, {"text": "are actually completely opaque.", "start": 74.8, "duration": 2.07}, {"text": "And the focus is--", "start": 76.87, "duration": 1.77}, {"text": "yeah.", "start": 88.32, "duration": 1.178}, {"text": "That's completely opaque.", "start": 89.498, "duration": 1.042}, {"text": "Actually, if you just\nput your glasses down,", "start": 90.54, "duration": 1.833}, {"text": "this-- might as well.", "start": 92.373, "duration": 1.557}, {"text": "You won't see, but\nothers will see.", "start": 93.93, "duration": 1.63}, {"text": "AUDIENCE: Yeah, I will see.", "start": 95.56, "duration": 1.125}, {"text": "RAMESH RASKAR: [LAUGHS] So\nthey're completely opaque in--", "start": 96.685, "duration": 3.265}, {"text": "AUDIENCE: These are actually\nglass lenses, not plastic ones.", "start": 99.95, "duration": 2.5}, {"text": "There might be some difference.", "start": 102.45, "duration": 1.38}, {"text": "RAMESH RASKAR: OK.", "start": 103.83, "duration": 0.48}, {"text": "AUDIENCE: I don't know.", "start": 104.31, "duration": 0.958}, {"text": "But--", "start": 105.268, "duration": 1.082}, {"text": "RAMESH RASKAR: So\nit's really looking", "start": 106.35, "duration": 1.92}, {"text": "at about 8,000 nanometer\nto 12,000 nanometer,", "start": 108.27, "duration": 5.76}, {"text": "which fortunately is\nalso the wavelength", "start": 114.03, "duration": 1.68}, {"text": "in which the human bodies--", "start": 115.71, "duration": 2.88}, {"text": "the black body radiation\nof the human body peaks.", "start": 118.59, "duration": 3.45}, {"text": "So you can do some\namazing things with this.", "start": 124.89, "duration": 3.18}, {"text": "Chrysler and BMW are\nthinking about-- or maybe", "start": 128.07, "duration": 3.96}, {"text": "already put them in\nautomobiles so that you", "start": 132.03, "duration": 7.02}, {"text": "can see things very far away.", "start": 139.05, "duration": 1.45}, {"text": "So one benefit of\nthis, as you can see,", "start": 140.5, "duration": 2.15}, {"text": "is even if you turn\noff the room light,", "start": 142.65, "duration": 2.16}, {"text": "the intensity will not change.", "start": 144.81, "duration": 1.84}, {"text": "So if somebody must take the--", "start": 146.65, "duration": 1.31}, {"text": "it's completely independent\nof the room lighting,", "start": 151.56, "duration": 4.65}, {"text": "because it's not looking at the\nvisible spectrum that's being", "start": 156.21, "duration": 2.85}, {"text": "emitted by these tube lights.", "start": 159.06, "duration": 3.18}, {"text": "But it's a function of\njust thermal radiation.", "start": 162.24, "duration": 4.21}, {"text": "So at night when you're\ndriving, if there", "start": 166.45, "duration": 2.96}, {"text": "are any animals or even\nintruders in your backyard,", "start": 169.41, "duration": 5.28}, {"text": "you can detect them\nwith thermal IR", "start": 174.69, "duration": 2.345}, {"text": "AUDIENCE: There's a lot of\nreflection on the table.", "start": 177.035, "duration": 2.125}, {"text": "RAMESH RASKAR: Yes.", "start": 179.16, "duration": 0.63}, {"text": "Yes, because remember, this\nis a very large wavelength.", "start": 179.79, "duration": 2.37}, {"text": "So that wavelength-- the table's\nroughness disappears and it", "start": 182.16, "duration": 3.21}, {"text": "becomes highly reflective.", "start": 185.37, "duration": 1.751}, {"text": "Is this-- let's now try to\nfocus on things that count.", "start": 189.71, "duration": 3.358}, {"text": "All the people with\nglasses look very cool.", "start": 198.598, "duration": 1.792}, {"text": "[LAUGHTER]", "start": 200.39, "duration": 2.802}, {"text": "AUDIENCE: What is\nthe lens made out of?", "start": 204.13, "duration": 1.83}, {"text": "RAMESH RASKAR: So\nthat's a good question,", "start": 205.96, "duration": 1.708}, {"text": "because typically, glass\nwill not transmit thermal IR.", "start": 207.668, "duration": 3.692}, {"text": "AUDIENCE: Right,\n[INAUDIBLE],, yeah.", "start": 211.36, "duration": 1.5}, {"text": "RAMESH RASKAR: Yeah.", "start": 212.86, "duration": 0.54}, {"text": "That's a good demonstration.", "start": 213.4, "duration": 1.167}, {"text": "So a lot of these lenses\nare made up of germanium.", "start": 214.567, "duration": 3.633}, {"text": "And also certain types of\nplastic can be used for this.", "start": 218.2, "duration": 4.87}, {"text": "But the image quality\nis not that great.", "start": 223.07, "duration": 2.36}, {"text": "But germanium is very common.", "start": 225.43, "duration": 2.86}, {"text": "AUDIENCE: Does this have\ndifferent focal characteristics", "start": 228.29, "duration": 2.58}, {"text": "because it's such long\nlengths of long wavelengths?", "start": 230.87, "duration": 3.06}, {"text": "RAMESH RASKAR: It has 8 to 12--", "start": 233.93, "duration": 2.1}, {"text": "just in terms of the\nratios, it's 300 to 400.", "start": 236.03, "duration": 3.6}, {"text": "It's the same as 8\nmicrons to 12 microns.", "start": 239.63, "duration": 3.52}, {"text": "So it should be able to focus\nin the majority of that band.", "start": 243.15, "duration": 8.24}, {"text": "But because you need a larger\nlens, the depth of field", "start": 251.39, "duration": 5.699}, {"text": "is pretty narrow.", "start": 257.089, "duration": 1.116}, {"text": "AUDIENCE: Yeah.", "start": 258.205, "duration": 0.625}, {"text": "RAMESH RASKAR: So with this,\nyou can build a glass detector.", "start": 262.15, "duration": 2.5}, {"text": "And if I look outside\nthe window, for example,", "start": 264.65, "duration": 3.06}, {"text": "it's completely opaque.", "start": 267.71, "duration": 2.7}, {"text": "Can you wave, the last person?", "start": 270.41, "duration": 2.98}, {"text": "Yeah.", "start": 273.39, "duration": 0.66}, {"text": "So it's completely\nopaque, the glass.", "start": 274.05, "duration": 3.69}, {"text": "So you can build\na glass detector.", "start": 277.74, "duration": 1.59}, {"text": "You can take a photo with\na visible, regular camera.", "start": 279.33, "duration": 2.61}, {"text": "You can take a photo of this.", "start": 281.94, "duration": 1.29}, {"text": "And if it's opaque in one\nbut transparent and other,", "start": 283.23, "duration": 2.56}, {"text": "then that's glass.", "start": 285.79, "duration": 1.88}, {"text": "So you can do all kinds\nof interesting things.", "start": 287.67, "duration": 2.05}, {"text": "And again, if\nMattias is successful", "start": 289.72, "duration": 2.21}, {"text": "and other companies are\nsuccessful, not in five years", "start": 291.93, "duration": 3.93}, {"text": "but in six years, it might\nbe in your cell phone.", "start": 295.86, "duration": 4.56}, {"text": "[INAUDIBLE]", "start": 300.42, "duration": 2.38}, {"text": "All right.", "start": 302.8, "duration": 0.5}, {"text": "So let's continue here.", "start": 303.3, "duration": 2.61}, {"text": "Has anybody seen this\nsnake illusion before?", "start": 305.91, "duration": 4.725}, {"text": "Yeah.", "start": 310.635, "duration": 1.045}, {"text": "Does everybody see\nrotating snakes?", "start": 311.68, "duration": 4.25}, {"text": "AUDIENCE: No.", "start": 315.93, "duration": 0.84}, {"text": "RAMESH RASKAR: No?", "start": 316.77, "duration": 1.971}, {"text": "AUDIENCE: [INAUDIBLE]\na head-on [INAUDIBLE]..", "start": 318.741, "duration": 2.019}, {"text": "AUDIENCE: Yeah, it\ndoesn't work [INAUDIBLE]..", "start": 320.76, "duration": 1.7}, {"text": "RAMESH RASKAR: At an angle?", "start": 322.46, "duration": 0.69}, {"text": "AUDIENCE: Mm-hmm.", "start": 323.15, "duration": 0.84}, {"text": "AUDIENCE: Yeah.", "start": 323.99, "duration": 1.02}, {"text": "RAMESH RASKAR: All right.", "start": 325.01, "duration": 1.042}, {"text": "Maybe I can-- how many\nof you can see it?", "start": 326.052, "duration": 6.538}, {"text": "How many can see and how many\ncannot see a rotating pattern?", "start": 332.59, "duration": 7.71}, {"text": "So OK.", "start": 340.3, "duration": 1.35}, {"text": "I've heard this before.", "start": 341.65, "duration": 1.77}, {"text": "Because this is different\nthan those really annoying", "start": 343.42, "duration": 2.94}, {"text": "random dot stereograms, the\nMagic Eye that a lot of people", "start": 346.36, "duration": 4.29}, {"text": "have trouble seeing.", "start": 350.65, "duration": 1.23}, {"text": "But this is not\nbased on the same--", "start": 351.88, "duration": 1.81}, {"text": "it's based on a\ndifferent principle.", "start": 353.69, "duration": 1.5}, {"text": "It's just looking at the decay\nin your retina, how long it", "start": 355.19, "duration": 5.33}, {"text": "takes for your retina when it's\ndoing circuits to basically do", "start": 360.52, "duration": 4.98}, {"text": "center surround subtractions.", "start": 365.5, "duration": 1.77}, {"text": "So it's a very\ndifferent principle.", "start": 367.27, "duration": 1.65}, {"text": "So those of you who cannot\nperceive motion in this one--", "start": 368.92, "duration": 5.67}, {"text": "do you also have\nproblems with Magic Eye?", "start": 374.59, "duration": 2.278}, {"text": "AUDIENCE: Yeah, I\ncan't see anything.", "start": 376.868, "duration": 1.542}, {"text": "I can't see those Eye ones.", "start": 378.41, "duration": 1.213}, {"text": "RAMESH RASKAR: Yeah, I think\nMagic Eye is probably--", "start": 379.623, "duration": 2.167}, {"text": "how many people have\nproblems with Magic Eye?", "start": 381.79, "duration": 2.07}, {"text": "Yeah, I think that's a lot.", "start": 383.86, "duration": 1.62}, {"text": "But so it looks\nlike the two sets", "start": 385.48, "duration": 2.97}, {"text": "don't have any relationship\nwith those type of sets.", "start": 388.45, "duration": 3.82}, {"text": "So how can I take a\nphoto of a scene that", "start": 392.27, "duration": 2.66}, {"text": "has motion printed\non a piece of paper", "start": 394.93, "duration": 1.98}, {"text": "and create an\nillusion of motion?", "start": 396.91, "duration": 1.68}, {"text": "That's the first problem\nfor your project.", "start": 402.25, "duration": 2.64}, {"text": "AUDIENCE: You could\nprint that out.", "start": 404.89, "duration": 1.485}, {"text": "RAMESH RASKAR: Yeah, but that's\nonly for this particular scene.", "start": 406.375, "duration": 2.625}, {"text": "I want to take a photo of a car\nmoving, or somebody running.", "start": 409.0, "duration": 2.58}, {"text": "And I just want to\ntake a couple of,", "start": 411.58, "duration": 1.5}, {"text": "maybe five frames of that\nvideo and create one photo out", "start": 413.08, "duration": 3.09}, {"text": "of that so that it looks\nlike the person is constantly", "start": 416.17, "duration": 2.29}, {"text": "moving.", "start": 418.46, "duration": 0.5}, {"text": "I think we can put\non the lights again.", "start": 424.495, "duration": 1.625}, {"text": "Let me see this.", "start": 432.37, "duration": 1.08}, {"text": "So all right.", "start": 433.45, "duration": 1.41}, {"text": "Here was that question, and how\ncan I look around the corner.", "start": 434.86, "duration": 2.71}, {"text": "So this is actually a huge\nproject in our group of,", "start": 437.57, "duration": 4.052}, {"text": "how can you look\naround the corner?", "start": 441.622, "duration": 1.458}, {"text": "And the way we do\nit is, we actually", "start": 443.08, "duration": 3.03}, {"text": "use some really cheap devices--", "start": 446.11, "duration": 4.26}, {"text": "a so-called transit\nimaging camera,", "start": 450.37, "duration": 2.55}, {"text": "where we use an impulse\nresponse of a scene.", "start": 452.92, "duration": 3.36}, {"text": "We transmit a signal.", "start": 456.28, "duration": 2.5}, {"text": "Maybe I'll use that one.", "start": 458.78, "duration": 2.66}, {"text": "We transmit a very tiny pulse,\nwhich reflects off of the door,", "start": 461.44, "duration": 6.06}, {"text": "bounces around inside the scene,\nreflects back from the door.", "start": 467.5, "duration": 3.78}, {"text": "And it is captured back\nagain at the camera.", "start": 471.28, "duration": 3.07}, {"text": "And by analyzing these\nmultipass reflections,", "start": 474.35, "duration": 3.05}, {"text": "we can figure out what's\ninside the room by just", "start": 477.4, "duration": 3.12}, {"text": "looking at the door.", "start": 480.52, "duration": 2.19}, {"text": "So the devices are\nextremely cheap.", "start": 482.71, "duration": 1.98}, {"text": "We need a femtosecond laser.", "start": 484.69, "duration": 2.49}, {"text": "That costs about $200,000.", "start": 487.18, "duration": 3.54}, {"text": "And we need a photodetector.", "start": 490.72, "duration": 2.04}, {"text": "That costs about $3,000.", "start": 492.76, "duration": 1.98}, {"text": "But we find some\ncheaper versions.", "start": 494.74, "duration": 2.07}, {"text": "And then, we also need\na 10-gigahertz scope.", "start": 496.81, "duration": 2.97}, {"text": "That's about $50,000.", "start": 499.78, "duration": 1.47}, {"text": "So after about a\nquarter million dollars,", "start": 501.25, "duration": 4.446}, {"text": "you can look what's\naround the corner.", "start": 505.696, "duration": 3.574}, {"text": "So maybe not in 5 years, but\nmaybe in 10 years, or 20 years,", "start": 509.27, "duration": 5.48}, {"text": "you will have devices\nwhich will allow", "start": 514.75, "duration": 1.84}, {"text": "you to look around the corner.", "start": 516.59, "duration": 1.25}, {"text": "And right now, in our\nlab, you can do it.", "start": 517.84, "duration": 3.157}, {"text": "And this is going\nto completely change", "start": 520.997, "duration": 1.583}, {"text": "the way you think about\nphotography, because line", "start": 522.58, "duration": 2.37}, {"text": "of sight is almost a\nfundamental assumption.", "start": 524.95, "duration": 3.03}, {"text": "We think it's almost--", "start": 527.98, "duration": 1.77}, {"text": "a lot of us think that's\none of the laws of physics.", "start": 529.75, "duration": 2.28}, {"text": "We can only see things that\nare within the line of sight.", "start": 532.03, "duration": 3.75}, {"text": "But we are not violating\nany laws of physics.", "start": 535.78, "duration": 2.64}, {"text": "If we're violating the laws,\nyou're welcome to report us.", "start": 538.42, "duration": 3.55}, {"text": "but--", "start": 541.97, "duration": 0.5}, {"text": "[LAUGHTER]", "start": 542.47, "duration": 0.94}, {"text": "This is possible.", "start": 543.41, "duration": 1.22}, {"text": "So throughout this\nclass, what you'll see", "start": 544.63, "duration": 1.77}, {"text": "is that the laws that you take\nfor granted and the laws that", "start": 546.4, "duration": 4.56}, {"text": "are shackling the way you\nthink about visual capture", "start": 550.96, "duration": 3.48}, {"text": "and visual displays are\njust there because somebody", "start": 554.44, "duration": 5.94}, {"text": "taught you that.", "start": 560.38, "duration": 1.48}, {"text": "But you can challenge all those\nassumptions with modern tools,", "start": 561.86, "duration": 3.11}, {"text": "whether they're\nsensors, and optics,", "start": 564.97, "duration": 1.68}, {"text": "and modern\ncomputational methods.", "start": 566.65, "duration": 2.58}, {"text": "AUDIENCE: What's the point\nof the femtosecond laser", "start": 569.23, "duration": 2.13}, {"text": "if it has such a short\ncoherence length?", "start": 571.36, "duration": 3.88}, {"text": "You can't really\nbe using the laser.", "start": 575.24, "duration": 1.58}, {"text": "RAMESH RASKAR: So\nthe reason why you", "start": 576.82, "duration": 1.5}, {"text": "need an extremely short duration\nlaser is that if you just--", "start": 578.32, "duration": 5.22}, {"text": "imagine you build a camera.", "start": 583.54, "duration": 1.32}, {"text": "So those cameras, this\ntime of flight camera", "start": 584.86, "duration": 2.88}, {"text": "that Jay was showing--", "start": 587.74, "duration": 2.46}, {"text": "images of pulse at\nabout 50 megahertz.", "start": 590.2, "duration": 2.95}, {"text": "So it's 29 nanosecond\nrepetition.", "start": 593.15, "duration": 2.87}, {"text": "And light travels how\nmuch in one nanosecond?", "start": 596.02, "duration": 4.14}, {"text": "AUDIENCE: 1 millimeter\nper microsecond.", "start": 600.16, "duration": 1.83}, {"text": "RAMESH RASKAR: Yeah, but\nthat's too complicated here.", "start": 601.99, "duration": 2.208}, {"text": "How much in one nanosecond?", "start": 607.96, "duration": 1.568}, {"text": "AUDIENCE: About a micron.", "start": 609.528, "duration": 1.042}, {"text": "RAMESH RASKAR: No, much more.", "start": 610.57, "duration": 1.13}, {"text": "AUDIENCE: An inch.", "start": 611.7, "duration": 0.75}, {"text": "RAMESH RASKAR: More than that.", "start": 612.45, "duration": 1.936}, {"text": "AUDIENCE: 100 meters.", "start": 614.386, "duration": 1.884}, {"text": "AUDIENCE: A foot?", "start": 616.27, "duration": 0.87}, {"text": "RAMESH RASKAR: A foot.", "start": 617.14, "duration": 0.54}, {"text": "AUDIENCE: I guess--", "start": 617.68, "duration": 0.622}, {"text": "RAMESH RASKAR: That's right.", "start": 618.302, "duration": 0.218}, {"text": "That's right.", "start": 618.52, "duration": 0.553}, {"text": "AUDIENCE: Sorry, yeah.", "start": 619.073, "duration": 0.917}, {"text": "RAMESH RASKAR: So a bit\nsimple thing to remember.", "start": 619.99, "duration": 2.042}, {"text": "The light travels one\nfoot in one nanosecond.", "start": 622.032, "duration": 2.308}, {"text": "And what about sound\nat room temperature?", "start": 624.34, "duration": 5.46}, {"text": "How much does it take for\nsound to travel one foot?", "start": 629.8, "duration": 4.89}, {"text": "You know all the numbers.", "start": 637.791, "duration": 1.349}, {"text": "It's 330 meters per second for--", "start": 639.14, "duration": 2.18}, {"text": "[INTERPOSING VOICES]", "start": 641.32, "duration": 2.35}, {"text": "RAMESH RASKAR:\n--sound and say that's", "start": 643.67, "duration": 1.74}, {"text": "10 to the 8 meters\nper second for light.", "start": 645.41, "duration": 1.86}, {"text": "But that's too complicated\nto think about.", "start": 647.27, "duration": 1.89}, {"text": "We want some simple\nrules of thumb.", "start": 649.16, "duration": 1.72}, {"text": "So--", "start": 650.88, "duration": 0.71}, {"text": "AUDIENCE: 10 milliseconds.", "start": 651.59, "duration": 1.26}, {"text": "RAMESH RASKAR: 10\nmilliseconds for one foot?", "start": 652.85, "duration": 3.84}, {"text": "It's one millisecond, right?", "start": 656.69, "duration": 1.71}, {"text": "So very easy to remember.", "start": 658.4, "duration": 1.14}, {"text": "Light travels one foot\nin one nanosecond.", "start": 659.54, "duration": 4.09}, {"text": "Sound travels one foot\nin one millisecond.", "start": 663.63, "duration": 3.65}, {"text": "So light travels one nanosecond.", "start": 667.28, "duration": 3.06}, {"text": "Sound travels one millisecond.", "start": 670.34, "duration": 2.322}, {"text": "Unfortunately,\nthere's nothing that", "start": 672.662, "duration": 1.458}, {"text": "travels in one microsecond.", "start": 674.12, "duration": 2.34}, {"text": "If somebody can, with a\nnew physical propagation,", "start": 676.46, "duration": 4.11}, {"text": "physical propagation channel\nthat travels one foot in one", "start": 680.57, "duration": 5.43}, {"text": "microsecond rather\nthan milli and nano,", "start": 686.0, "duration": 3.24}, {"text": "then you'll see a completely\nnew range of applications.", "start": 689.24, "duration": 2.83}, {"text": "So you have electromagnetics,\nP-M spectrum.", "start": 692.07, "duration": 2.82}, {"text": "That's one nanosecond\nper one foot,", "start": 694.89, "duration": 2.24}, {"text": "and sound, one\nmillisecond for one foot.", "start": 697.13, "duration": 2.91}, {"text": "So sound is too\nslow, and light is", "start": 700.04, "duration": 1.83}, {"text": "too fast in almost\neverything we want to do.", "start": 701.87, "duration": 5.02}, {"text": "And so here, we want\nsomething that's", "start": 706.89, "duration": 2.54}, {"text": "even faster than traditional\nlight propagation.", "start": 709.43, "duration": 3.09}, {"text": "So in this room, if I\njust send a beam of light,", "start": 712.52, "duration": 5.67}, {"text": "very narrow pulse, by the time\nit goes to that wall and comes", "start": 718.19, "duration": 3.18}, {"text": "all the way back to me-- let's\nsay this is about 20 foot--", "start": 721.37, "duration": 3.15}, {"text": "it's going to take me about\n40 nanoseconds to come back.", "start": 724.52, "duration": 4.6}, {"text": "On the other hand,\nif I just want", "start": 729.12, "duration": 1.7}, {"text": "to see where somebody is within\na couple of feet of that wall,", "start": 730.82, "duration": 8.07}, {"text": "then I need to start measuring\nin picoseconds-- not 10", "start": 738.89, "duration": 3.09}, {"text": "to the minus 9 nanoseconds,\nbut 10 to the minus 12 seconds.", "start": 741.98, "duration": 2.79}, {"text": "And that's why you need\nto do this extremely", "start": 744.77, "duration": 2.04}, {"text": "fast to be able to do any--", "start": 746.81, "duration": 3.18}, {"text": "so a traditional\ntime of flight camera", "start": 749.99, "duration": 2.25}, {"text": "will just look at this door.", "start": 752.24, "duration": 1.53}, {"text": "And that's it.", "start": 753.77, "duration": 0.81}, {"text": "There's nothing more you can do.", "start": 754.58, "duration": 1.51}, {"text": "But if you want to look\nat the reflections,", "start": 756.09, "duration": 2.09}, {"text": "then you need to be able\nto resolve time at a much", "start": 758.18, "duration": 3.0}, {"text": "higher temporal resolution.", "start": 761.18, "duration": 3.63}, {"text": "So femtosecond lasers\nare not something--", "start": 764.81, "duration": 3.168}, {"text": "they're not exotic.", "start": 767.978, "duration": 0.792}, {"text": "They're used in OCT.", "start": 768.77, "duration": 1.59}, {"text": "They're used in\ntwo-photon microscopy.", "start": 770.36, "duration": 1.98}, {"text": "And they're used in a lot of\ntheir applications, but still", "start": 772.34, "duration": 2.52}, {"text": "not consumer applications.", "start": 774.86, "duration": 1.29}, {"text": "They're used in medical imaging.", "start": 776.15, "duration": 1.95}, {"text": "And once they become solid\nstate and easy to carry,", "start": 778.1, "duration": 3.75}, {"text": "we can do that.", "start": 781.85, "duration": 2.04}, {"text": "A lot of LiDAR also happens in\nnot femtosecond, but nanosecond", "start": 783.89, "duration": 4.11}, {"text": "ranges with very high power.", "start": 788.0, "duration": 4.19}, {"text": "So if you can look around\nthe corner like this,", "start": 792.19, "duration": 3.59}, {"text": "what about looking around\na beautiful artifact", "start": 795.78, "duration": 5.34}, {"text": "like this one?", "start": 801.12, "duration": 0.655}, {"text": "If I have a bottle--\nwhere's my bottle?", "start": 801.775, "duration": 1.625}, {"text": "If I, as a human, when I look at\nthis bottle, I look around it.", "start": 806.76, "duration": 6.12}, {"text": "And I create a\nmental representation", "start": 812.88, "duration": 1.83}, {"text": "of what this looks like.", "start": 814.71, "duration": 1.282}, {"text": "But if I capture a photo,\nit's going to be only", "start": 815.992, "duration": 1.958}, {"text": "from a [INAUDIBLE] view.", "start": 817.95, "duration": 1.15}, {"text": "It's trying to mimic my\nperspective and so on.", "start": 819.1, "duration": 3.12}, {"text": "But my mental representation is\nactually something like that,", "start": 822.22, "duration": 3.49}, {"text": "right?", "start": 825.71, "duration": 0.5}, {"text": "So how can we build a\ncamera that takes an object", "start": 826.21, "duration": 4.07}, {"text": "and creates a roll out imagery?", "start": 830.28, "duration": 2.792}, {"text": "Now, this particular\nobject is straightforward.", "start": 833.072, "duration": 1.958}, {"text": "I can just put it on\na flatbed scanner.", "start": 835.03, "duration": 1.625}, {"text": "And I can just roll it.", "start": 836.655, "duration": 1.725}, {"text": "But some other objects\nare not so easy.", "start": 838.38, "duration": 2.1}, {"text": "This object, for example, which\nis not completely cylindrical,", "start": 840.48, "duration": 6.006}, {"text": "doesn't have a constant radius\naround its axis of rotation.", "start": 846.486, "duration": 3.424}, {"text": "So if I just roll it\non a flatbed scanner,", "start": 849.91, "duration": 2.18}, {"text": "I will not get that.", "start": 852.09, "duration": 1.44}, {"text": "So maybe I need\na special camera,", "start": 853.53, "duration": 2.52}, {"text": "or I can use my\nexisting camera and use", "start": 856.05, "duration": 2.49}, {"text": "some interesting tricks,\ncomputational tricks", "start": 858.54, "duration": 3.15}, {"text": "to create rollout imagery.", "start": 861.69, "duration": 1.96}, {"text": "Another such problem.", "start": 863.65, "duration": 2.36}, {"text": "And I'm sure a\ncamera company would", "start": 866.01, "duration": 2.07}, {"text": "love to have this\nfeature, as you", "start": 868.08, "duration": 2.16}, {"text": "have all the boring features--", "start": 870.24, "duration": 1.84}, {"text": "AV, TV, panorama, movie.", "start": 872.08, "duration": 2.45}, {"text": "And then, you have rollout mode.", "start": 874.53, "duration": 3.09}, {"text": "So that would be fun.", "start": 877.62, "duration": 2.62}, {"text": "And maybe you can do it\nwith an ordinary camera.", "start": 880.24, "duration": 2.0}, {"text": "Or maybe you can do it\nwith a femtosecond laser,", "start": 882.24, "duration": 3.84}, {"text": "if you have a quarter\nmillion dollars.", "start": 886.08, "duration": 2.94}, {"text": "All right.", "start": 889.02, "duration": 0.5}, {"text": "So let's do a very\nfast forward preview", "start": 889.52, "duration": 2.7}, {"text": "of the rest of the class.", "start": 892.22, "duration": 1.56}, {"text": "And here, I'm mostly\ngoing to talk about what's", "start": 893.78, "duration": 3.06}, {"text": "the input, what's the output.", "start": 896.84, "duration": 2.28}, {"text": "I may not go into the detail\nof exactly how this works,", "start": 899.12, "duration": 2.67}, {"text": "because again, these are teasers\nof what's coming in the class.", "start": 901.79, "duration": 3.78}, {"text": "And what I would like you to\nthink about during this preview", "start": 905.57, "duration": 5.13}, {"text": "is how this applies\nto some problem", "start": 910.7, "duration": 1.98}, {"text": "you may be already\nworking on, or what", "start": 912.68, "duration": 1.95}, {"text": "are some parallels with\nthings you already know?", "start": 914.63, "duration": 2.67}, {"text": "And again, most of\nthese techniques", "start": 917.3, "duration": 2.13}, {"text": "will be about changing\nthe rules of the game.", "start": 919.43, "duration": 3.113}, {"text": "If you have a\nproject where you're", "start": 922.543, "duration": 1.417}, {"text": "tracking your fingers\nwith a cheap webcam", "start": 923.96, "duration": 3.143}, {"text": "and it's not\nworking, because when", "start": 927.103, "duration": 1.417}, {"text": "the light changes or a person\nwith a different skin color", "start": 928.52, "duration": 3.42}, {"text": "walks into the scene,\nthere are solutions here.", "start": 931.94, "duration": 3.21}, {"text": "If you're worried about\nhow to track crowds,", "start": 935.15, "duration": 2.52}, {"text": "there are solutions here.", "start": 937.67, "duration": 1.2}, {"text": "You want to see what's behind a\nglass that's murky and diffuse,", "start": 938.87, "duration": 5.25}, {"text": "the solution's here and so on.", "start": 944.12, "duration": 2.35}, {"text": "And then, of course,\nthere are really", "start": 946.47, "duration": 2.9}, {"text": "interesting devices\nthat you could use,", "start": 949.37, "duration": 2.7}, {"text": "and new forms of photography.", "start": 952.07, "duration": 3.56}, {"text": "So here's a really\nsimple example", "start": 955.63, "duration": 3.23}, {"text": "of how we can get started.", "start": 958.86, "duration": 1.81}, {"text": "So Paul [INAUDIBLE] in '92--", "start": 960.67, "duration": 3.77}, {"text": "simple idea.", "start": 964.44, "duration": 1.2}, {"text": "Take an object, turn on\nthe flashlight on the left.", "start": 965.64, "duration": 4.2}, {"text": "Turn on a flashlight\non the right.", "start": 969.84, "duration": 2.4}, {"text": "And then, you can form this\nimage by combining these two.", "start": 972.24, "duration": 3.24}, {"text": "How will you do it?", "start": 975.48, "duration": 2.25}, {"text": "This looks like a\nblue light, and this", "start": 977.73, "duration": 1.982}, {"text": "looks like a red light.", "start": 979.712, "duration": 0.958}, {"text": "Just from these two photos,\nyou want to create this.", "start": 980.67, "duration": 2.167}, {"text": "Yeah?", "start": 986.98, "duration": 0.545}, {"text": "AUDIENCE: Just mix the channels.", "start": 987.525, "duration": 1.165}, {"text": "RAMESH RASKAR: Exactly.", "start": 988.69, "duration": 0.958}, {"text": "Just take the blue channel from\nhere and red channel from here.", "start": 989.648, "duration": 2.812}, {"text": "That's it.", "start": 992.46, "duration": 0.81}, {"text": "And it creates this\nbeautiful lighting artifact.", "start": 993.27, "duration": 3.09}, {"text": "So that's going to be,\nactually, assignment number 1--", "start": 996.36, "duration": 2.91}, {"text": "just a warm-up assignment.", "start": 999.27, "duration": 3.94}, {"text": "All you to do is take an object,\nand take two or three photos", "start": 1003.21, "duration": 5.85}, {"text": "by moving your light source.", "start": 1009.06, "duration": 3.33}, {"text": "And then, mix and match\nthe color channels", "start": 1012.39, "duration": 1.89}, {"text": "to create very beautiful\ncolor artifacts.", "start": 1014.28, "duration": 2.82}, {"text": "And this will help you to\nget your whole pipeline", "start": 1017.1, "duration": 4.83}, {"text": "for a sensor going.", "start": 1021.93, "duration": 1.17}, {"text": "You will have your own camera.", "start": 1023.1, "duration": 1.83}, {"text": "You're welcome to use your\nregular camera, like even", "start": 1024.93, "duration": 2.54}, {"text": "a cell phone camera.", "start": 1027.47, "duration": 0.91}, {"text": "But ideally, you should\nstart using a camera that", "start": 1028.38, "duration": 2.459}, {"text": "has more manual controls.", "start": 1030.839, "duration": 2.371}, {"text": "And it will get you set up with\nyour MATLAB, or Java, or Flash,", "start": 1033.21, "duration": 3.81}, {"text": "whatever you want to use--", "start": 1037.02, "duration": 1.589}, {"text": "C++, Open CV.", "start": 1038.609, "duration": 2.671}, {"text": "There's a lot of\neasy ways to do this.", "start": 1041.28, "duration": 2.17}, {"text": "But I would like you to\nset up your environment", "start": 1043.45, "duration": 6.81}, {"text": "so that these type of\noperations are very easy to do.", "start": 1050.26, "duration": 2.6}, {"text": "And that will be your\nassignment number 1.", "start": 1052.86, "duration": 3.16}, {"text": "Should be very straightforward.", "start": 1056.02, "duration": 2.96}, {"text": "Of course, this is what\nyou would do at home.", "start": 1058.98, "duration": 2.232}, {"text": "But if you have a couple\nof million dollars,", "start": 1061.212, "duration": 1.833}, {"text": "then this is how you would\ndo it in the Hollywood.", "start": 1063.045, "duration": 3.165}, {"text": "So this is a project from Paul\n[INAUDIBLE] and his group--", "start": 1066.21, "duration": 3.45}, {"text": "really excellent set of\nwork, where they're building", "start": 1069.66, "duration": 2.31}, {"text": "different light stages.", "start": 1071.97, "duration": 2.16}, {"text": "And it's just turning\non one light at a time,", "start": 1074.13, "duration": 2.94}, {"text": "or moving it manually.", "start": 1077.07, "duration": 3.15}, {"text": "They have a dome with\nabout 150 lights.", "start": 1080.22, "duration": 4.05}, {"text": "And then, they use a\nhigh speed camera here,", "start": 1084.27, "duration": 3.96}, {"text": "and turn on one light at a time.", "start": 1088.23, "duration": 1.47}, {"text": "So they can photograph\nthis actress", "start": 1089.7, "duration": 2.97}, {"text": "under 150 lighting conditions\nin 150 frames very quickly.", "start": 1092.67, "duration": 5.34}, {"text": "And then, I can start from\nthe beginning, and so on.", "start": 1098.01, "duration": 2.73}, {"text": "That's one way to do it.", "start": 1100.74, "duration": 3.16}, {"text": "The other way to do that is,\nlet's say all you want to do--", "start": 1103.9, "duration": 3.65}, {"text": "insert this actress\nin a scene that may", "start": 1107.55, "duration": 5.16}, {"text": "have been shot somewhere else.", "start": 1112.71, "duration": 1.48}, {"text": "So she's in LA.", "start": 1114.19, "duration": 2.6}, {"text": "And you want to insert\nher on top of a photo that", "start": 1116.79, "duration": 5.7}, {"text": "was actually taken in Milan.", "start": 1122.49, "duration": 2.37}, {"text": "Now, if you just take the\nphoto and superimpose it,", "start": 1124.86, "duration": 2.22}, {"text": "it looks very fake, because\nthe lighting doesn't match up.", "start": 1127.08, "duration": 2.98}, {"text": "So the trick they\nuse is, some guy", "start": 1130.06, "duration": 4.37}, {"text": "puts a shiny sphere in Milan\nand takes an environment", "start": 1134.43, "duration": 4.14}, {"text": "map of that courtyard.", "start": 1138.57, "duration": 2.58}, {"text": "Then, you feed this\nimage onto this light.", "start": 1141.15, "duration": 3.21}, {"text": "So the left corner is reddish.", "start": 1144.36, "duration": 1.77}, {"text": "The light on the left\nside of this dome", "start": 1146.13, "duration": 4.71}, {"text": "is reddish if it's\nyellowish here, and so on.", "start": 1150.84, "duration": 4.15}, {"text": "So for all this 4 pi, you turn\non the lights correspondingly.", "start": 1154.99, "duration": 4.85}, {"text": "And now, she's bathed\nin light as if she", "start": 1159.84, "duration": 3.42}, {"text": "was in that courtyard in Milan.", "start": 1163.26, "duration": 2.37}, {"text": "And now, if you take\nher photo and cut out", "start": 1165.63, "duration": 3.18}, {"text": "and superimpose on\nthat background,", "start": 1168.81, "duration": 3.24}, {"text": "it will look more realistic.", "start": 1172.05, "duration": 2.25}, {"text": "And they have done videos where\nthey took these shiny spheres.", "start": 1174.3, "duration": 3.39}, {"text": "And Christmas is coming up.", "start": 1180.2, "duration": 1.24}, {"text": "So you can pick up\nyour shiny spheres.", "start": 1181.44, "duration": 3.3}, {"text": "And you just put\nthe shiny sphere,", "start": 1184.74, "duration": 2.01}, {"text": "and move in the\ncourtyard with it.", "start": 1186.75, "duration": 3.87}, {"text": "So you're constantly\ncapturing the environment map", "start": 1190.62, "duration": 3.0}, {"text": "as you move along.", "start": 1193.62, "duration": 1.11}, {"text": "And in the scene, she\njust stands in one place.", "start": 1194.73, "duration": 3.75}, {"text": "But the dome is lit\nup by the environment", "start": 1198.48, "duration": 3.12}, {"text": "map that was captured from\nthese shining spheres.", "start": 1201.6, "duration": 4.63}, {"text": "So in a video\nsequence, it appears", "start": 1206.23, "duration": 2.568}, {"text": "as though she's walking\nthrough this environment.", "start": 1208.798, "duration": 2.042}, {"text": "At least, she's lit\nup as if she's walking", "start": 1210.84, "duration": 2.25}, {"text": "through this environment.", "start": 1213.09, "duration": 2.02}, {"text": "So these are some of the tricks\nthat are being used currently", "start": 1215.11, "duration": 3.35}, {"text": "in major productions.", "start": 1218.46, "duration": 3.06}, {"text": "So Matrix-- all the movies\nthat came in the last 10 years", "start": 1221.52, "duration": 4.95}, {"text": "or so are using this\nparticular mechanism", "start": 1226.47, "duration": 3.33}, {"text": "to create maps that have correct\nlighting, match lighting.", "start": 1229.8, "duration": 7.91}, {"text": "And if you don't want\nto spend $2 million,", "start": 1241.5, "duration": 2.66}, {"text": "back to something really cheap--", "start": 1244.16, "duration": 4.05}, {"text": "to create those\nsilhouettes and so on,", "start": 1248.21, "duration": 2.01}, {"text": "you can use a Multiflash camera.", "start": 1250.22, "duration": 1.9}, {"text": "So here are some cameras\nthat you can buy.", "start": 1252.12, "duration": 4.46}, {"text": "This is, I believe,\na little more.", "start": 1256.58, "duration": 1.815}, {"text": "Yeah, this is a little more.", "start": 1258.395, "duration": 1.405}, {"text": "So I think it's about $30.", "start": 1259.8, "duration": 1.67}, {"text": "And what it does is,\nlet me see if it's--", "start": 1261.47, "duration": 3.495}, {"text": "did the lights go off?", "start": 1272.83, "duration": 0.93}, {"text": "So when you release\nthe shutter, it--", "start": 1276.81, "duration": 2.85}, {"text": "but too cheap to put the\nfilm inside of that manually.", "start": 1285.16, "duration": 4.35}, {"text": "I'll put that on.", "start": 1289.51, "duration": 1.444}, {"text": "I think we're out of\nbattery here, unfortunately.", "start": 1290.954, "duration": 3.676}, {"text": "But anyway, when you\nrelease the shutter,", "start": 1294.63, "duration": 3.12}, {"text": "it takes four photos by\nexposing one pinhole at a time.", "start": 1297.75, "duration": 5.94}, {"text": "And at the same time, because it\ncannot recharge the flash that", "start": 1303.69, "duration": 4.77}, {"text": "quickly, the simple solution was\nto actually put four different", "start": 1308.46, "duration": 2.85}, {"text": "flashes.", "start": 1311.31, "duration": 0.75}, {"text": "So this shutter goes off.", "start": 1312.06, "duration": 2.34}, {"text": "Then, this light goes off.", "start": 1314.4, "duration": 1.2}, {"text": "Then, this shutter goes off.", "start": 1315.6, "duration": 0.93}, {"text": "This light goes off, and so on.", "start": 1316.53, "duration": 1.292}, {"text": "So it takes four pictures.", "start": 1317.822, "duration": 1.678}, {"text": "Now, instead of\nputting the lights", "start": 1319.5, "duration": 1.47}, {"text": "all in one place,\nif you place them", "start": 1320.97, "duration": 1.98}, {"text": "around the camera, you can\ndo something interesting,", "start": 1322.95, "duration": 3.595}, {"text": "which would have been,\nthe flash is to the left.", "start": 1326.545, "duration": 2.0}, {"text": "You know that we get\nvery annoying slivers", "start": 1328.545, "duration": 3.675}, {"text": "of shadow in an ordinary photo.", "start": 1332.22, "duration": 3.81}, {"text": "Now, if you intentionally\npress the flash--", "start": 1336.03, "duration": 2.58}, {"text": "so you can see it here.", "start": 1338.61, "duration": 1.78}, {"text": "So there are all these\nslivers of shadow.", "start": 1340.39, "duration": 3.05}, {"text": "And that is continuous.", "start": 1343.44, "duration": 2.16}, {"text": "And you probably see it\nin your own photographs.", "start": 1345.6, "duration": 2.58}, {"text": "If you place the flash\nintentionally to the right,", "start": 1348.18, "duration": 2.67}, {"text": "then the slivers\nmove to the left.", "start": 1350.85, "duration": 2.97}, {"text": "If you put the flash\nat the top, the slivers", "start": 1353.82, "duration": 2.13}, {"text": "are shadows slivers at\nthe bottom, and so on.", "start": 1355.95, "duration": 3.4}, {"text": "So by taking these four\npictures and analyzing", "start": 1359.35, "duration": 2.99}, {"text": "those tiny slivers\nof shadows, you", "start": 1362.34, "duration": 2.1}, {"text": "can figure out where the\ndepth discontinuities are,", "start": 1364.44, "duration": 3.03}, {"text": "where the foreground\nis separated", "start": 1367.47, "duration": 1.432}, {"text": "from the background--\nnot just the whole person", "start": 1368.902, "duration": 1.958}, {"text": "and the wall behind them, but\nalso any internal changes.", "start": 1370.86, "duration": 2.93}, {"text": "See, for my hand\nhere, it will create", "start": 1373.79, "duration": 2.38}, {"text": "a boundary between my hand and\nmy body no matter how close", "start": 1376.17, "duration": 4.32}, {"text": "or how far I am from that.", "start": 1380.49, "duration": 4.33}, {"text": "So by doing that, you can\nestimate all the shape", "start": 1384.82, "duration": 4.94}, {"text": "contours.", "start": 1389.76, "duration": 0.87}, {"text": "And this is the edge\nmap you would get", "start": 1390.63, "duration": 1.95}, {"text": "if you had an ordinary camera.", "start": 1392.58, "duration": 2.25}, {"text": "And this edge map you get\nwith a Multiflash camera.", "start": 1394.83, "duration": 2.34}, {"text": "So now, if you have\nan application--", "start": 1397.17, "duration": 2.02}, {"text": "you want to track a\nhand or tract a gesture,", "start": 1399.19, "duration": 3.02}, {"text": "instead of taking a\nstandard 2D image,", "start": 1402.21, "duration": 2.1}, {"text": "if you take a Multiflash image,\nyou get very clean contours.", "start": 1404.31, "duration": 4.62}, {"text": "And from those contours, you\ncan build an XC application", "start": 1408.93, "duration": 3.03}, {"text": "that will perform very well,\neven in strange, ambient light.", "start": 1411.96, "duration": 5.13}, {"text": "And it's independent of the\ncolor of the foreground object.", "start": 1417.09, "duration": 5.61}, {"text": "It only relies on the shadow.", "start": 1422.7, "duration": 1.62}, {"text": "So again, if you want\nto track your hand,", "start": 1424.32, "duration": 2.67}, {"text": "you're not dependent on\nthe skin color anymore.", "start": 1426.99, "duration": 3.04}, {"text": "So you can play these tricks\nto overcome the limitations", "start": 1430.03, "duration": 3.32}, {"text": "of a traditional 2D camera.", "start": 1433.35, "duration": 1.14}, {"text": "Let me skip ahead\na little bit here.", "start": 1437.82, "duration": 1.5}, {"text": "Another assignment\nwe'll be looking at", "start": 1442.23, "duration": 1.89}, {"text": "is this vertical optical bench.", "start": 1444.12, "duration": 3.28}, {"text": "And it's a very nice toy\nthat Andrew Adams at Stanford", "start": 1447.4, "duration": 3.83}, {"text": "put together, which is a\nFlash-based application where", "start": 1451.23, "duration": 2.97}, {"text": "you can insert lenses, and\noccluders, and mirrors,", "start": 1454.2, "duration": 4.62}, {"text": "and ray emitters, and so on.", "start": 1458.82, "duration": 4.45}, {"text": "And it can basically do a\nvery quick setup, a very quick", "start": 1463.27, "duration": 4.43}, {"text": "optical design of a setup.", "start": 1467.7, "duration": 3.06}, {"text": "And what we'll do is,\nwe'll start with this.", "start": 1470.76, "duration": 2.01}, {"text": "One option is to start with\nthis his code, his source code,", "start": 1472.77, "duration": 4.08}, {"text": "and modify and insert a few\nmore optical elements-- maybe", "start": 1476.85, "duration": 3.78}, {"text": "a prism, maybe a\ngrating, and so on, OK?", "start": 1480.63, "duration": 4.29}, {"text": "This will be one option.", "start": 1484.92, "duration": 1.03}, {"text": "And as I said, you'll\nhave multiple options", "start": 1485.95, "duration": 2.06}, {"text": "for each assignment.", "start": 1488.01, "duration": 2.74}, {"text": "So thinking a little\nbit more about lenses,", "start": 1490.75, "duration": 3.89}, {"text": "one concept that we'll\ncome across quite a bit", "start": 1494.64, "duration": 2.31}, {"text": "in this class is light field.", "start": 1496.95, "duration": 3.01}, {"text": "And now, this particular\ncamera that we saw of the five", "start": 1499.96, "duration": 3.41}, {"text": "that Rod was showing us is\nactually a light field camera.", "start": 1503.37, "duration": 4.59}, {"text": "But that's made up of\nan array of cameras--", "start": 1507.96, "duration": 3.45}, {"text": "physical cameras.", "start": 1511.41, "duration": 1.35}, {"text": "And what we're\ngoing to do instead", "start": 1512.76, "duration": 1.95}, {"text": "is, we're going to\ntake an ordinary camera", "start": 1514.71, "duration": 2.94}, {"text": "and convert that into an\narray of virtual cameras.", "start": 1517.65, "duration": 4.3}, {"text": "So this is an array\nof physical cameras.", "start": 1521.95, "duration": 2.87}, {"text": "But it's expensive.", "start": 1524.82, "duration": 1.485}, {"text": "And so that will take\nan ordinary camera", "start": 1526.305, "duration": 1.995}, {"text": "and convert that into an\narray of virtual cameras.", "start": 1528.3, "duration": 4.78}, {"text": "So this is how it works.", "start": 1533.08, "duration": 2.6}, {"text": "In a traditional camera, you--", "start": 1535.68, "duration": 3.27}, {"text": "if the object is in\nsharp focus, the radius", "start": 1538.95, "duration": 3.6}, {"text": "along each of\nthese directions is", "start": 1542.55, "duration": 3.18}, {"text": "convergent on a single pixel.", "start": 1545.73, "duration": 2.14}, {"text": "So you get a very sharp\nimage of the point.", "start": 1547.87, "duration": 3.32}, {"text": "But any information\nabout the radius", "start": 1551.19, "duration": 3.03}, {"text": "along each of these\ndirections is completely lost.", "start": 1554.22, "duration": 4.09}, {"text": "So you get 2D image.", "start": 1558.31, "duration": 1.53}, {"text": "You have a 3D scene.", "start": 1559.84, "duration": 0.95}, {"text": "You get a 2D image.", "start": 1560.79, "duration": 1.44}, {"text": "So it's flattened.", "start": 1562.23, "duration": 0.75}, {"text": "The world is flat.", "start": 1562.98, "duration": 0.75}, {"text": "A trick you can do,\nwhich was actually", "start": 1567.51, "duration": 2.01}, {"text": "invented by Ted Ellison and\nhis student Wong that just left", "start": 1569.52, "duration": 5.73}, {"text": "is trying to\ncapture the radiance", "start": 1575.25, "duration": 5.1}, {"text": "along each of these directions.", "start": 1580.35, "duration": 1.62}, {"text": "So how can you do that?", "start": 1584.53, "duration": 1.46}, {"text": "You just displace the\nsensor a little bit back.", "start": 1585.99, "duration": 2.73}, {"text": "And in front of that, you\nput a microlens array.", "start": 1588.72, "duration": 3.06}, {"text": "This is the same microlens array\nyou use in lenticular displays,", "start": 1591.78, "duration": 3.87}, {"text": "those displays that\nchange with viewpoint.", "start": 1595.65, "duration": 2.85}, {"text": "So if you put that microlens\narray, then as you can see,", "start": 1598.5, "duration": 5.19}, {"text": "each of these rays is actually\nincident on a different pixel.", "start": 1603.69, "duration": 4.83}, {"text": "And then, you can\ncapture the variation", "start": 1608.52, "duration": 2.49}, {"text": "along each of the categories.", "start": 1611.01, "duration": 1.51}, {"text": "Now, why would you care about\ncapturing each of these rays?", "start": 1612.52, "duration": 5.27}, {"text": "It turns out that the\nappearance of the world coming", "start": 1617.79, "duration": 5.28}, {"text": "through a lens can be completely\ndescribed geometrically,", "start": 1623.07, "duration": 3.72}, {"text": "completely described by a\nfour-dimensional function,", "start": 1626.79, "duration": 3.21}, {"text": "which is this light field.", "start": 1630.0, "duration": 1.422}, {"text": "And that's a very\npowerful concept,", "start": 1631.422, "duration": 1.458}, {"text": "because if you do capture\nthis full representation,", "start": 1632.88, "duration": 3.33}, {"text": "then you can do--", "start": 1636.21, "duration": 1.98}, {"text": "that's all you\ncould ever capture.", "start": 1638.19, "duration": 2.578}, {"text": "Once you have this\n4D representation,", "start": 1640.768, "duration": 1.542}, {"text": "you can manipulate that\nin many interesting ways.", "start": 1642.31, "duration": 3.48}, {"text": "So Ted Ellison and\n[INAUDIBLE] at Stanford,", "start": 1645.79, "duration": 3.29}, {"text": "who also has a company now\ncalled Refocus Imaging,", "start": 1649.08, "duration": 3.78}, {"text": "are building these type of\ncameras with [INAUDIBLE]..", "start": 1652.86, "duration": 4.14}, {"text": "Now, how did the\nStanford team do it?", "start": 1657.0, "duration": 2.85}, {"text": "They started with a\nmedium format camera", "start": 1659.85, "duration": 2.34}, {"text": "with a digital back.", "start": 1662.19, "duration": 3.45}, {"text": "And on the digital back, they\nput this microlens array,", "start": 1665.64, "duration": 3.18}, {"text": "where the pitch of the\nmicrolens is 125 microns.", "start": 1668.82, "duration": 4.35}, {"text": "So pixels are\nabout nine microns.", "start": 1673.17, "duration": 2.61}, {"text": "So under each square tile, they\nhave about 14 by 14 pixels.", "start": 1675.78, "duration": 5.88}, {"text": "And so again, going back\nhere, under each microlens,", "start": 1681.66, "duration": 4.29}, {"text": "they have a 14 by\n14 array of pixels.", "start": 1685.95, "duration": 4.392}, {"text": "So what they're\ngoing to do now is,", "start": 1690.342, "duration": 1.458}, {"text": "they're going to take the\n16-megapixel detector, 4,000", "start": 1691.8, "duration": 2.7}, {"text": "or 4,000 pixels, and\nhave 292 by 292 pixel", "start": 1694.5, "duration": 5.49}, {"text": "array-- sorry, microlens array.", "start": 1699.99, "duration": 2.22}, {"text": "Under each microlens,\n14 by 14 pixels.", "start": 1702.21, "duration": 4.48}, {"text": "So at the end, they have\nthis 116-megapixel image,", "start": 1706.69, "duration": 5.69}, {"text": "which after reshaping,\ngives you this 292", "start": 1712.38, "duration": 5.1}, {"text": "by 292 pixel image, 1\nunder each microlens, OK?", "start": 1717.48, "duration": 4.68}, {"text": "So they had given up\na lot of resolution", "start": 1722.16, "duration": 2.52}, {"text": "from 16 megapixel right\ndown to 292 by 292, OK?", "start": 1724.68, "duration": 6.42}, {"text": "But with that, we can\ndo some amazing things.", "start": 1731.1, "duration": 4.11}, {"text": "We can do digital refocus\ncompletely in software.", "start": 1735.21, "duration": 4.485}, {"text": "OK?", "start": 1745.68, "duration": 0.5}, {"text": "So you have given up\na lot of resolution.", "start": 1746.18, "duration": 1.973}, {"text": "But now, you have\ncomplete control", "start": 1748.153, "duration": 1.417}, {"text": "over where you can focus.", "start": 1749.57, "duration": 1.54}, {"text": "And as you can imagine,\nthis is the same question", "start": 1751.11, "duration": 2.33}, {"text": "you asked earlier, from tests\nI can also estimate depth.", "start": 1753.44, "duration": 3.37}, {"text": "Because depending on when\nthings come in focus,", "start": 1756.81, "duration": 2.18}, {"text": "I can assign a\ndepth to each pixel.", "start": 1758.99, "duration": 1.98}, {"text": "So suddenly, from an\nordinary 2D sensor,", "start": 1760.97, "duration": 4.92}, {"text": "I have a camera which has\nhow many virtual cameras?", "start": 1765.89, "duration": 5.64}, {"text": "Here, we have five by five.", "start": 1771.53, "duration": 1.47}, {"text": "How many virtual cameras here?", "start": 1773.0, "duration": 2.445}, {"text": "AUDIENCE: 200--", "start": 1775.445, "duration": 0.625}, {"text": "AUDIENCE: 14 by--", "start": 1776.07, "duration": 1.25}, {"text": "RAMESH RASKAR: 14 by 14 cameras.", "start": 1777.32, "duration": 3.18}, {"text": "What is that, 228?", "start": 1780.5, "duration": 0.826}, {"text": "No, 496.", "start": 1781.326, "duration": 3.494}, {"text": "AUDIENCE: But then, each\ncamera is 292 by 292 and--", "start": 1784.82, "duration": 3.842}, {"text": "RAMESH RASKAR: Exactly.", "start": 1788.662, "duration": 0.958}, {"text": "It's very low resolution.", "start": 1789.62, "duration": 1.41}, {"text": "And so first\ncomplaint is, yes, it", "start": 1791.03, "duration": 5.19}, {"text": "gives you all this power,\nbut very low resolution.", "start": 1796.22, "duration": 2.1}, {"text": "And the argument\nnowadays against that", "start": 1798.32, "duration": 2.58}, {"text": "is, whether you have\n6-megapixel camera", "start": 1800.9, "duration": 3.57}, {"text": "or a 16-megapixel camera,\nit doesn't really matter.", "start": 1804.47, "duration": 2.79}, {"text": "We have reached-- we\nhave diminishing returns", "start": 1807.26, "duration": 4.89}, {"text": "after six megapixel.", "start": 1812.15, "duration": 1.59}, {"text": "So why not use those\npixels for capturing", "start": 1813.74, "duration": 2.91}, {"text": "some other information?", "start": 1816.65, "duration": 2.35}, {"text": "So that's what makes\nit extremely powerful.", "start": 1819.0, "duration": 3.02}, {"text": "And refocusing is only one.", "start": 1822.02, "duration": 2.49}, {"text": "Depth sensing is another.", "start": 1824.51, "duration": 1.44}, {"text": "Interaction, dealing with\naberrations in the scene--", "start": 1825.95, "duration": 4.11}, {"text": "a lot of interesting\nthings you can do.", "start": 1830.06, "duration": 1.68}, {"text": "And again, this is starting with\na static 16-megapixel camera.", "start": 1831.74, "duration": 4.29}, {"text": "So it's not video rate.", "start": 1836.03, "duration": 1.71}, {"text": "But this one is video\nrate, although it's", "start": 1837.74, "duration": 2.13}, {"text": "only 25 virtual cameras.", "start": 1839.87, "duration": 1.402}, {"text": "AUDIENCE: Does the\nmicrolens have any way", "start": 1841.272, "duration": 1.708}, {"text": "to read what's in\nand out in a way", "start": 1842.98, "duration": 1.75}, {"text": "so that you can\ncombine the images?", "start": 1844.73, "duration": 1.65}, {"text": "RAMESH RASKAR:\nYou could do that.", "start": 1846.38, "duration": 1.375}, {"text": "Unfortunately, the\nprecision that you require", "start": 1847.755, "duration": 2.345}, {"text": "is micrometer precision.", "start": 1850.1, "duration": 3.07}, {"text": "So it's a little\nbit challenging.", "start": 1853.17, "duration": 1.79}, {"text": "But you're right.", "start": 1854.96, "duration": 1.74}, {"text": "I'm sure when cameras were\ndesigned in the beginning,", "start": 1856.7, "duration": 2.28}, {"text": "they had physical apertures\nthat couldn't be changed.", "start": 1858.98, "duration": 2.73}, {"text": "And over time,\npeople figured out", "start": 1861.71, "duration": 1.41}, {"text": "how to create variable\napertures and so on.", "start": 1863.12, "duration": 2.32}, {"text": "So creating these\ndynamic elements", "start": 1865.44, "duration": 2.69}, {"text": "is going to be the key\nfor future cameras.", "start": 1868.13, "duration": 4.11}, {"text": "And people often ask\nme, what are the things", "start": 1872.24, "duration": 3.51}, {"text": "that you're going to\nsee in the camera next?", "start": 1875.75, "duration": 2.88}, {"text": "And we already have\nhigh dynamic range.", "start": 1878.63, "duration": 3.24}, {"text": "Next is color.", "start": 1881.87, "duration": 1.66}, {"text": "And we get a lot of journalists\nasking questions like this--", "start": 1883.53, "duration": 4.766}, {"text": "the future of photography.", "start": 1888.296, "duration": 2.644}, {"text": "A lot of popular magazines\nwith a lot of junk in it,", "start": 1890.94, "duration": 4.71}, {"text": "including people who\nare not credible,", "start": 1895.65, "duration": 3.35}, {"text": "the pictures in there.", "start": 1899.0, "duration": 1.32}, {"text": "So to me, the answer to that\nquestion is light fields.", "start": 1900.32, "duration": 4.14}, {"text": "That's going to be\nthe next big thing.", "start": 1904.46, "duration": 2.415}, {"text": "If you think about the\ntop five features that", "start": 1906.875, "duration": 1.875}, {"text": "will appear in a camera,\nit's exposure, color--", "start": 1908.75, "duration": 3.12}, {"text": "number 3 is light field.", "start": 1911.87, "duration": 2.16}, {"text": "So we'll see how long\nit's going to take", "start": 1914.03, "duration": 1.83}, {"text": "before we have a\nfull-fledged light field", "start": 1915.86, "duration": 2.34}, {"text": "camera as a consumer device.", "start": 1918.2, "duration": 3.16}, {"text": "And again, initially,\nthey're going to say, hey,", "start": 1921.36, "duration": 2.0}, {"text": "but it's only 292 by 292 pixels.", "start": 1923.36, "duration": 2.13}, {"text": "But my guess is that\nby then, we won't", "start": 1925.49, "duration": 3.36}, {"text": "care about the pixels\nin our business.", "start": 1928.85, "duration": 4.21}, {"text": "So my group was extremely\ninspired by this work in 2004,", "start": 1933.06, "duration": 4.7}, {"text": "2005.", "start": 1937.76, "duration": 1.02}, {"text": "But we thought, this\nis very challenging", "start": 1938.78, "duration": 1.86}, {"text": "to create because you\nneed a microlens array.", "start": 1940.64, "duration": 2.61}, {"text": "So we said, instead of\nusing a microlens array,", "start": 1943.25, "duration": 2.25}, {"text": "can I just print a\ntransparency at home", "start": 1945.5, "duration": 3.87}, {"text": "and create this\nlight field camera?", "start": 1949.37, "duration": 2.92}, {"text": "So that's what we did, which is\ncalled a mask-based light field", "start": 1952.29, "duration": 3.83}, {"text": "camera.", "start": 1956.12, "duration": 1.8}, {"text": "And this is how you do it.", "start": 1957.92, "duration": 1.39}, {"text": "You start with a\nmedium format camera--", "start": 1959.31, "duration": 4.34}, {"text": "in this case, a Mamiya.", "start": 1963.65, "duration": 3.1}, {"text": "On the digital back, you\njust remove the IR filter.", "start": 1966.75, "duration": 5.503}, {"text": "And it turns out,\nthere is already", "start": 1972.253, "duration": 1.417}, {"text": "some glass on top\nof the sensor, which", "start": 1973.67, "duration": 2.52}, {"text": "is about 1.2 millimeters thick.", "start": 1976.19, "duration": 1.38}, {"text": "So you just drop a\ntransparency on top of it,", "start": 1977.57, "duration": 3.57}, {"text": "snap back the IR filter.", "start": 1981.14, "duration": 2.01}, {"text": "And that's it.", "start": 1983.15, "duration": 1.08}, {"text": "For about $2, you can convert\na medium format camera", "start": 1984.23, "duration": 3.54}, {"text": "into a light field camera.", "start": 1987.77, "duration": 1.5}, {"text": "And the design looks\nsomething like this.", "start": 1991.84, "duration": 2.13}, {"text": "Traditional camera,\ntraditional sensor,", "start": 1993.97, "duration": 2.7}, {"text": "but about 1 millimeter in front\nof it, you have a printed mask.", "start": 1996.67, "duration": 5.3}, {"text": "Very cheap.", "start": 2001.97, "duration": 1.78}, {"text": "Using that, we were\nable to convert this 2D", "start": 2003.75, "duration": 4.64}, {"text": "camera into something that\ncaptures a 4D function.", "start": 2008.39, "duration": 4.68}, {"text": "And the concept is actually\nvery similar to radio frequency", "start": 2013.07, "duration": 4.11}, {"text": "heterodyne.", "start": 2017.18, "duration": 0.7}, {"text": "The reason why you can listen\nto multiple radio stations", "start": 2017.88, "duration": 3.47}, {"text": "on a single antenna is\nbecause all those stations", "start": 2021.35, "duration": 2.97}, {"text": "are transmitting using\neither amplitude or frequency", "start": 2024.32, "duration": 2.64}, {"text": "modulation.", "start": 2026.96, "duration": 1.02}, {"text": "And then, in\nsoftware in your car,", "start": 2027.98, "duration": 2.4}, {"text": "you can tune into any\none of those channels", "start": 2030.38, "duration": 2.97}, {"text": "and decode any one of\nthose radio stations.", "start": 2033.35, "duration": 6.27}, {"text": "And what we're doing\nhere is very similar.", "start": 2039.62, "duration": 1.9}, {"text": "We are doing that in\nthe optical domain.", "start": 2041.52, "duration": 2.09}, {"text": "And that's what we call\nit optical heterodyning", "start": 2043.61, "duration": 2.31}, {"text": "in space, not in time,\nwhere you have the object.", "start": 2045.92, "duration": 2.91}, {"text": "It's forming an\nimage on the sensor.", "start": 2048.83, "duration": 2.25}, {"text": "But we're going to take this\nphotographic signal, which", "start": 2051.08, "duration": 2.67}, {"text": "is four-dimensional,\nnot two-dimensional,", "start": 2053.75, "duration": 3.03}, {"text": "and use this carrier, and then\ncreate a modulated signal.", "start": 2056.78, "duration": 5.02}, {"text": "So again, for those of you with\na communication background,", "start": 2061.8, "duration": 2.899}, {"text": "this analogy will work.", "start": 2064.699, "duration": 1.23}, {"text": "And then, software--\nknowing this carrier,", "start": 2065.929, "duration": 2.821}, {"text": "we can demodulate\nthat and recover", "start": 2068.75, "duration": 2.159}, {"text": "this four-dimensional\nlight array.", "start": 2070.909, "duration": 2.321}, {"text": "So it's possible to do\nit with a very low cost.", "start": 2073.23, "duration": 4.08}, {"text": "Sorry, can you hit\nthe lights again?", "start": 2077.31, "duration": 2.53}, {"text": "AUDIENCE: This one here?", "start": 2079.84, "duration": 1.0}, {"text": "RAMESH RASKAR: Yeah.", "start": 2080.84, "duration": 1.2}, {"text": "Maybe the other one.", "start": 2082.04, "duration": 1.29}, {"text": "Thanks.", "start": 2083.33, "duration": 1.05}, {"text": "And this is a photo\nthat we captured", "start": 2084.38, "duration": 1.5}, {"text": "with our mask-based\nlight field camera.", "start": 2085.88, "duration": 2.04}, {"text": "If you zoom in, the in-focus\nparts are actually OK.", "start": 2087.92, "duration": 3.87}, {"text": "Autofocus part has a really\nstrange encoding because", "start": 2091.79, "duration": 3.27}, {"text": "of the high frequency mask.", "start": 2095.06, "duration": 1.45}, {"text": "But then, software-- and this\nis how the mask looks like,", "start": 2096.51, "duration": 4.04}, {"text": "the printed mask.", "start": 2100.55, "duration": 1.02}, {"text": "And in software, it turns\nout that by applying", "start": 2101.57, "duration": 4.77}, {"text": "appropriate signal\nprocessing framework,", "start": 2106.34, "duration": 2.4}, {"text": "we can decode that\nand recover it.", "start": 2108.74, "duration": 2.23}, {"text": "So this is a 2D\nfrequency transform", "start": 2110.97, "duration": 2.24}, {"text": "of a traditional photo,\nwhere most of the energy", "start": 2113.21, "duration": 2.1}, {"text": "is in the [INAUDIBLE].", "start": 2115.31, "duration": 1.95}, {"text": "And after applying this\nvery high frequency", "start": 2117.26, "duration": 2.31}, {"text": "mask in the optical\npart, it actually", "start": 2119.57, "duration": 2.4}, {"text": "encodes this information--\nin this particular case, a 9", "start": 2121.97, "duration": 3.84}, {"text": "by 9 windows of the\nFourier transform.", "start": 2125.81, "duration": 6.73}, {"text": "And this intentional\naliasing or heterodyning", "start": 2132.54, "duration": 3.38}, {"text": "allows you to capture\nthe additional two", "start": 2135.92, "duration": 1.95}, {"text": "degrees of freedom.", "start": 2137.87, "duration": 1.96}, {"text": "And so the process\nis very simple.", "start": 2139.83, "duration": 2.22}, {"text": "You take this photo, which\nis about four megapixel.", "start": 2142.05, "duration": 2.72}, {"text": "You take its 2D\nFourier transform.", "start": 2144.77, "duration": 1.98}, {"text": "You reshape that\nto a 4D function.", "start": 2146.75, "duration": 3.397}, {"text": "And then, you take\nthe inverse Fourier", "start": 2150.147, "duration": 1.583}, {"text": "transform to create these\n81 virtual cameras--", "start": 2151.73, "duration": 3.81}, {"text": "in this case, 9 by 9.", "start": 2155.54, "duration": 1.5}, {"text": "This was 5 by 5.", "start": 2157.04, "duration": 1.32}, {"text": "This is 9 by 9.", "start": 2158.36, "duration": 1.02}, {"text": "And the best way to\nshow that is to see", "start": 2159.38, "duration": 3.0}, {"text": "how that photo\nwill look like when", "start": 2162.38, "duration": 2.767}, {"text": "there is a small\nparallax between each", "start": 2165.147, "duration": 1.583}, {"text": "of the virtual cameras.", "start": 2166.73, "duration": 1.71}, {"text": "And again, from these 81\nimages, you can estimate depth.", "start": 2168.44, "duration": 3.6}, {"text": "You can create refocused\nimages and all that--", "start": 2172.04, "duration": 2.79}, {"text": "the same thing that\nRod was showing", "start": 2174.83, "duration": 2.49}, {"text": "for refocusing from\nhere to infinite-- yeah,", "start": 2177.32, "duration": 3.56}, {"text": "I guess infinitely\nback and forth.", "start": 2180.88, "duration": 3.68}, {"text": "So you can do that with\nan ordinary camera,", "start": 2184.56, "duration": 2.36}, {"text": "with a small change\non the [INAUDIBLE]..", "start": 2186.92, "duration": 3.388}, {"text": "And all the software is online.", "start": 2190.308, "duration": 1.292}, {"text": "And this will not be\npart of any assignment,", "start": 2191.6, "duration": 1.833}, {"text": "but you're welcome to take\nthat up as an assignment", "start": 2193.433, "duration": 2.247}, {"text": "or as a project.", "start": 2195.68, "duration": 2.103}, {"text": "Maybe we can get the\nlights back on and start.", "start": 2197.783, "duration": 1.917}, {"text": "What are some other\nthings you can do?", "start": 2203.31, "duration": 2.74}, {"text": "As I said, in terms of the\ndesired camera features,", "start": 2206.05, "duration": 3.38}, {"text": "it's dynamic range color,\nand then light field.", "start": 2209.43, "duration": 2.82}, {"text": "In terms of color,\nAnkit Mohan, who was", "start": 2212.25, "duration": 3.21}, {"text": "a scientist from the group--", "start": 2215.46, "duration": 1.185}, {"text": "as part of his\nthesis, he said, let's", "start": 2219.36, "duration": 2.52}, {"text": "think about color as not\nmultispectral imagery,", "start": 2221.88, "duration": 3.57}, {"text": "but more like an\naudio synthesizer.", "start": 2225.45, "duration": 2.59}, {"text": "If you have an audio\nsystem and you're", "start": 2228.04, "duration": 2.51}, {"text": "listening to rock, or jazz,\nor pop, or country music,", "start": 2230.55, "duration": 4.83}, {"text": "you tune your bass and\ntreble accordingly.", "start": 2235.38, "duration": 2.64}, {"text": "Or maybe you have a profile\nso that the frequency profile", "start": 2238.02, "duration": 5.15}, {"text": "of your synthesizer\nis appropriate for", "start": 2243.17, "duration": 3.16}, {"text": "that particular type of music.", "start": 2246.33, "duration": 3.24}, {"text": "The same thing should be\npossible for photography", "start": 2249.57, "duration": 2.97}, {"text": "as well.", "start": 2252.54, "duration": 1.05}, {"text": "If you are in the\nwoods, you would", "start": 2253.59, "duration": 3.39}, {"text": "like to look at most\nof the green channel", "start": 2256.98, "duration": 3.3}, {"text": "to see how the variation\nof different leaves and all", "start": 2260.28, "duration": 6.15}, {"text": "the nature is captured\nwith sufficient variation.", "start": 2266.43, "duration": 2.97}, {"text": "Maybe you don't care so much\nabout varieties and looks", "start": 2269.4, "duration": 2.64}, {"text": "there.", "start": 2272.04, "duration": 1.39}, {"text": "On the other hand, if\nyou are near an ocean,", "start": 2273.43, "duration": 2.45}, {"text": "maybe you mostly care about\nthe blue shades and so on.", "start": 2275.88, "duration": 3.49}, {"text": "So what I would like to do--", "start": 2279.37, "duration": 1.485}, {"text": "and photographers do\nthis all the time.", "start": 2280.855, "duration": 1.625}, {"text": "They carry a set of\nfilters with them.", "start": 2282.48, "duration": 2.16}, {"text": "And if they are looking\nat broad sunlight,", "start": 2284.64, "duration": 4.56}, {"text": "they put one type of filter.", "start": 2289.2, "duration": 1.47}, {"text": "If they are on a beach, they\nput another filter and so on.", "start": 2290.67, "duration": 3.12}, {"text": "What I would like to do\nis create a knob right", "start": 2293.79, "duration": 3.12}, {"text": "on the camera just like an\naudio synthesizer that says,", "start": 2296.91, "duration": 2.88}, {"text": "boost red, suppress green, and\ncreate any profile you want.", "start": 2299.79, "duration": 4.44}, {"text": "So creating this\nprogrammable wavelength", "start": 2304.23, "duration": 3.24}, {"text": "would be extremely powerful.", "start": 2307.47, "duration": 1.24}, {"text": "So Ankit's project\nbasically achieved", "start": 2308.71, "duration": 1.88}, {"text": "that, which it\ncalls Agile Spectrum", "start": 2310.59, "duration": 2.19}, {"text": "Imaging, or programmable\nwavelength imaging.", "start": 2312.78, "duration": 2.507}, {"text": "So it's a very powerful concept.", "start": 2315.287, "duration": 1.333}, {"text": "And hopefully, it will\nappear in cameras as well.", "start": 2316.62, "duration": 3.43}, {"text": "You can imagine, this is very\nuseful for medical imaging.", "start": 2320.05, "duration": 2.87}, {"text": "When you go to the dentist\nand they're putting--", "start": 2322.92, "duration": 4.1}, {"text": "what's it called?", "start": 2327.02, "duration": 0.85}, {"text": "Enamel?", "start": 2327.87, "duration": 0.5}, {"text": "AUDIENCE: What?", "start": 2328.37, "duration": 1.0}, {"text": "RAMESH RASKAR: To change\nthe color of your tooth?", "start": 2329.37, "duration": 3.02}, {"text": "AUDIENCE: The whitening?", "start": 2332.39, "duration": 1.0}, {"text": "RAMESH RASKAR:\nYeah, the whitening.", "start": 2333.39, "duration": 0.66}, {"text": "What is it called?", "start": 2334.05, "duration": 0.51}, {"text": "Enamel?", "start": 2334.56, "duration": 0.3}, {"text": "AUDIENCE: Bleach.", "start": 2334.86, "duration": 0.9}, {"text": "RAMESH RASKAR: Bleach.", "start": 2335.76, "duration": 0.42}, {"text": "AUDIENCE: Yeah, yeah.", "start": 2336.18, "duration": 0.6}, {"text": "RAMESH RASKAR: And\nthe problem with that", "start": 2336.78, "duration": 1.667}, {"text": "is in the dentist's office,\neverything looks fine.", "start": 2338.447, "duration": 4.483}, {"text": "But you go elsewhere,\nand somebody", "start": 2342.93, "duration": 1.92}, {"text": "takes a flash photo and\nthe guy with the fake teeth", "start": 2344.85, "duration": 3.99}, {"text": "or bleached teeth--", "start": 2348.84, "duration": 1.71}, {"text": "it looks extremely different.", "start": 2350.55, "duration": 2.58}, {"text": "And that's [INAUDIBLE]\nbecause the wavelength profile", "start": 2353.13, "duration": 2.64}, {"text": "of a flash is very different\nfrom the profile of tube", "start": 2355.77, "duration": 3.51}, {"text": "lights.", "start": 2359.28, "duration": 1.2}, {"text": "So what doctors would like\nto do is see the neighboring", "start": 2360.48, "duration": 4.44}, {"text": "teeth under all different\nlighting conditions", "start": 2364.92, "duration": 2.68}, {"text": "so that they're still\nmatched, for example.", "start": 2367.6, "duration": 2.36}, {"text": "And this is true of--", "start": 2369.96, "duration": 1.62}, {"text": "I did show you the\nvein viewer, where", "start": 2371.58, "duration": 1.77}, {"text": "you want to see the veins.", "start": 2373.35, "duration": 2.1}, {"text": "And depending on oxygenated\nor deoxygenated blood,", "start": 2375.45, "duration": 4.02}, {"text": "the hemoglobin\nyou can figure out", "start": 2379.47, "duration": 2.22}, {"text": "which veins should be\nused to poke the needles.", "start": 2381.69, "duration": 2.923}, {"text": "And again, that can be looked\ninto very narrow wavelength.", "start": 2384.613, "duration": 2.417}, {"text": "So they don't-- in that\ncase, they might know.", "start": 2387.03, "duration": 2.532}, {"text": "But in different\napplications, they", "start": 2389.562, "duration": 1.458}, {"text": "may not know probably\nwhich wavelength", "start": 2391.02, "duration": 1.92}, {"text": "you should be looking at.", "start": 2392.94, "duration": 1.12}, {"text": "And so they by creating this\nprogrammable spectrum camera,", "start": 2394.06, "duration": 2.96}, {"text": "you can do, again, very\ninteresting things.", "start": 2397.02, "duration": 3.63}, {"text": "So we'll be looking at that.", "start": 2400.65, "duration": 1.46}, {"text": "And glare is another\nchallenging problem, right?", "start": 2402.11, "duration": 2.55}, {"text": "If you have bright sunlight,\nit's going to be glare.", "start": 2404.66, "duration": 2.85}, {"text": "Sometimes, it's for\nartistic effect.", "start": 2407.51, "duration": 1.59}, {"text": "Sometimes, it's just annoying.", "start": 2409.1, "duration": 2.98}, {"text": "So can you take a photo that has\nthese concentric rings because", "start": 2412.08, "duration": 5.33}, {"text": "of glare and either\nboost the glare,", "start": 2417.41, "duration": 4.17}, {"text": "create some cheesy effects, like\nit's a rainbow transition here", "start": 2421.58, "duration": 4.56}, {"text": "from blue to red, or\nactually suppress the glare--", "start": 2426.14, "duration": 3.78}, {"text": "again, all from a single photo?", "start": 2429.92, "duration": 2.34}, {"text": "So it turns out,\nglare can also be", "start": 2432.26, "duration": 1.71}, {"text": "captured using a light\nfield camera if you have", "start": 2433.97, "duration": 2.97}, {"text": "a bright light such as this--", "start": 2436.94, "duration": 3.77}, {"text": "let's see.", "start": 2440.71, "duration": 0.52}, {"text": "This is a bright light.", "start": 2441.23, "duration": 0.958}, {"text": "And this is some other scene.", "start": 2442.188, "duration": 1.322}, {"text": "The bright light will\ncreate a sharp photo.", "start": 2443.51, "duration": 2.46}, {"text": "But because of interreflection,\nthe Fresnel reflection", "start": 2445.97, "duration": 3.15}, {"text": "in the lenses also\ncreate a glare effect", "start": 2449.12, "duration": 2.53}, {"text": "and contribute to the\nwrong part of the image.", "start": 2451.65, "duration": 3.39}, {"text": "But again, what we will\nlearn in this class is", "start": 2455.04, "duration": 2.42}, {"text": "that by doing this\n4D sampling, you", "start": 2457.46, "duration": 2.16}, {"text": "have complete control\nover the lens glare", "start": 2459.62, "duration": 3.09}, {"text": "and certain types of glare.", "start": 2462.71, "duration": 1.2}, {"text": "Again, light field concept\nfor a camera array--", "start": 2467.99, "duration": 3.54}, {"text": "Stanford and\nProfessor Mark Levoy", "start": 2471.53, "duration": 2.04}, {"text": "are the world leaders in\nthinking about light fields", "start": 2473.57, "duration": 3.48}, {"text": "and light field cameras.", "start": 2477.05, "duration": 1.47}, {"text": "So they built this amazing\ncamera array, the electronics", "start": 2478.52, "duration": 6.6}, {"text": "for its optics, and so on.", "start": 2485.12, "duration": 1.66}, {"text": "In this case, I believe\nabout 51 cameras.", "start": 2486.78, "duration": 3.2}, {"text": "And then, they can do\nvery interesting things.", "start": 2489.98, "duration": 1.93}, {"text": "So here is a scene.", "start": 2491.91, "duration": 1.76}, {"text": "We have about 51 cameras looking\nat the scene behind the bushes", "start": 2493.67, "duration": 10.23}, {"text": "and trees.", "start": 2503.9, "duration": 1.14}, {"text": "And this is how it looks.", "start": 2505.04, "duration": 3.93}, {"text": "Focus on that part.", "start": 2508.97, "duration": 1.41}, {"text": "And by doing refocusing, you can\nsee what's behind those trees.", "start": 2510.38, "duration": 5.2}, {"text": "So this is just--", "start": 2515.58, "duration": 1.73}, {"text": "you're just doing virtual\nrefocusing in the scene.", "start": 2517.31, "duration": 4.2}, {"text": "And by doing that, by using\nan extremely large aperture,", "start": 2521.51, "duration": 3.31}, {"text": "you can see what's\nbehind these bushes.", "start": 2524.82, "duration": 5.045}, {"text": "And it's pure refocusing.", "start": 2529.865, "duration": 1.275}, {"text": "You can do additional\ncomputational techniques", "start": 2531.14, "duration": 1.98}, {"text": "to recover what's\nbehind the trees.", "start": 2533.12, "duration": 2.01}, {"text": "So a lot of things in\ncomputational camera", "start": 2537.93, "duration": 1.75}, {"text": "and photography are\nreally about magic.", "start": 2539.68, "duration": 4.08}, {"text": "How can you look\naround a corner?", "start": 2543.76, "duration": 1.44}, {"text": "How you can look\nbehind the trees?", "start": 2545.2, "duration": 1.44}, {"text": "How can you look inside\nthe body, and so on?", "start": 2546.64, "duration": 3.257}, {"text": "So that's why I like this field.", "start": 2549.897, "duration": 1.333}, {"text": "It's like magic tricks.", "start": 2551.23, "duration": 1.2}, {"text": "And once in a while, you come\nup with your own magic trick.", "start": 2552.43, "duration": 4.47}, {"text": "And some other times, people\nshow you a magic trick.", "start": 2556.9, "duration": 3.33}, {"text": "And different people\nfigure out different ways", "start": 2560.23, "duration": 2.64}, {"text": "of achieving the same magic.", "start": 2562.87, "duration": 2.4}, {"text": "And that's why it's such\na vibrant new field.", "start": 2565.27, "duration": 5.1}, {"text": "The way synthetic aperture\nworks is the same way--", "start": 2570.37, "duration": 2.7}, {"text": "if I hold a needle next to\nmy eye, not poking my eye", "start": 2573.07, "duration": 3.66}, {"text": "but just right next to my eye,\nthen if I focus on the needle,", "start": 2576.73, "duration": 3.03}, {"text": "I'll see it.", "start": 2579.76, "duration": 1.29}, {"text": "But if I focus far\naway, then this needle", "start": 2581.05, "duration": 2.73}, {"text": "just becomes blurred.", "start": 2583.78, "duration": 1.05}, {"text": "And this does not\nocclude what's behind.", "start": 2584.83, "duration": 2.94}, {"text": "And the same concept is\nfor synthetic aperture.", "start": 2587.77, "duration": 3.03}, {"text": "It's used in radar.", "start": 2590.8, "duration": 0.99}, {"text": "It's used in astronomy.", "start": 2591.79, "duration": 2.49}, {"text": "And all you have is\nan array of receivers,", "start": 2594.28, "duration": 5.98}, {"text": "whether it's antennas,\nor whether it's", "start": 2600.26, "duration": 2.42}, {"text": "microphones, whatever it is.", "start": 2602.68, "duration": 2.07}, {"text": "In this case, cameras--", "start": 2604.75, "duration": 1.17}, {"text": "array of cameras.", "start": 2605.92, "duration": 2.31}, {"text": "And if you have a very,\nvery large aperture,", "start": 2608.23, "duration": 2.88}, {"text": "then a point that was\noccluding some point behind", "start": 2611.11, "duration": 3.67}, {"text": "ends up being extremely blurred.", "start": 2614.78, "duration": 2.06}, {"text": "So it does not impact\nwhat's behind that.", "start": 2616.84, "duration": 3.71}, {"text": "If you have a very\nnarrow aperture camera,", "start": 2620.55, "duration": 1.75}, {"text": "you cannot do that.", "start": 2622.3, "duration": 1.08}, {"text": "But you can do that if you have\na very wide aperture camera.", "start": 2623.38, "duration": 4.5}, {"text": "So we saw that.", "start": 2630.79, "duration": 1.5}, {"text": "OK.", "start": 2636.98, "duration": 0.5}, {"text": "So what about medical imaging,\nsuch as computer tomography?", "start": 2637.48, "duration": 6.21}, {"text": "And we're jumping from\nphotography to tomography.", "start": 2643.69, "duration": 5.61}, {"text": "But both are recording.", "start": 2649.3, "duration": 1.17}, {"text": "One is recording light.", "start": 2650.47, "duration": 1.23}, {"text": "The other one is\nrecording slices.", "start": 2651.7, "duration": 2.34}, {"text": "It turns out you can use\nvery similar principles.", "start": 2654.04, "duration": 2.91}, {"text": "So what's happening\nin tomography?", "start": 2656.95, "duration": 1.59}, {"text": "You have an X-ray\nsource that's emitting", "start": 2658.54, "duration": 3.42}, {"text": "in an omnidirectional fashion.", "start": 2661.96, "duration": 1.95}, {"text": "And you have detectors here.", "start": 2663.91, "duration": 3.42}, {"text": "Should I use this screen,\nbecause most people are--", "start": 2670.33, "duration": 3.317}, {"text": "which screen is better for\nthe majority of people?", "start": 2673.647, "duration": 2.083}, {"text": "That one?", "start": 2675.73, "duration": 0.51}, {"text": "Sorry.", "start": 2676.24, "duration": 0.24}, {"text": "AUDIENCE: Yeah, that one.", "start": 2676.48, "duration": 0.84}, {"text": "RAMESH RASKAR: All right.", "start": 2677.32, "duration": 0.39}, {"text": "I'll use this one.", "start": 2677.71, "duration": 1.21}, {"text": "Sorry, Rod [LAUGHS]", "start": 2678.92, "duration": 2.45}, {"text": "AUDIENCE: It's fine.", "start": 2681.37, "duration": 2.45}, {"text": "RAMESH RASKAR: This one\nwas convenient for me.", "start": 2683.82, "duration": 3.43}, {"text": "You have an X-ray source.", "start": 2687.25, "duration": 1.44}, {"text": "And you have an\narray of detectors.", "start": 2688.69, "duration": 1.98}, {"text": "And basically, when you put\nyour head inside this X-ray", "start": 2690.67, "duration": 4.29}, {"text": "under tomography,\nCAT scan machine,", "start": 2694.96, "duration": 2.07}, {"text": "the X-ray source spins.", "start": 2697.03, "duration": 1.68}, {"text": "And the detector moves in\nthe same direction, right?", "start": 2698.71, "duration": 3.39}, {"text": "And let me show you a video\nof how this actually works.", "start": 2705.82, "duration": 7.21}, {"text": "And let's start\nfrom the beginning.", "start": 2721.29, "duration": 2.86}, {"text": "All right.", "start": 2724.15, "duration": 0.5}, {"text": "It's been opened up.", "start": 2724.65, "duration": 1.143}, {"text": "So you know what's going on.", "start": 2725.793, "duration": 1.167}, {"text": "That's what's happening.", "start": 2733.07, "duration": 1.0}, {"text": "Imagine your head\nis inside that.", "start": 2734.07, "duration": 1.942}, {"text": "[LAUGHTER]", "start": 2736.012, "duration": 2.892}, {"text": "All right?", "start": 2742.77, "duration": 0.81}, {"text": "That's what the CAT\nscan machine is doing.", "start": 2743.58, "duration": 2.8}, {"text": "And while they put an eyepatch\nand you're just resting inside,", "start": 2746.38, "duration": 4.81}, {"text": "it's basically the a engine.", "start": 2751.19, "duration": 2.26}, {"text": "It's totally crazy, OK?", "start": 2753.45, "duration": 1.83}, {"text": "It's totally unnecessary.", "start": 2755.28, "duration": 1.44}, {"text": "We are the 21st century.", "start": 2756.72, "duration": 1.86}, {"text": "[LAUGHTER]", "start": 2758.58, "duration": 1.896}, {"text": "We are in the 21st century.", "start": 2760.476, "duration": 1.614}, {"text": "And we're building these\ndevices that are based", "start": 2762.09, "duration": 4.17}, {"text": "on 40-year-old principles.", "start": 2766.26, "duration": 1.71}, {"text": "It's unbelievable.", "start": 2767.97, "duration": 1.44}, {"text": "It's totally ridiculous.", "start": 2769.41, "duration": 1.56}, {"text": "What we need to do\nis completely rethink", "start": 2770.97, "duration": 3.42}, {"text": "how this imaging is done and\nuse new computational methods", "start": 2774.39, "duration": 4.2}, {"text": "to overcome these totally\nbizarre, multimillion dollar", "start": 2778.59, "duration": 4.02}, {"text": "devices.", "start": 2782.61, "duration": 1.59}, {"text": "So that will be\none of the things", "start": 2784.2, "duration": 1.92}, {"text": "we'll be learning\nin this class--", "start": 2786.12, "duration": 1.71}, {"text": "how we can take principles from\nsignal processing, photography,", "start": 2787.83, "duration": 3.93}, {"text": "scientific imaging, and mix and\nmatch them to build new things.", "start": 2791.76, "duration": 6.42}, {"text": "Both were tomography-- another\nvery interesting problem.", "start": 2798.18, "duration": 3.63}, {"text": "All you do is, you\ncreate your drill hole.", "start": 2801.81, "duration": 5.07}, {"text": "You put explosives here.", "start": 2806.88, "duration": 2.61}, {"text": "And you put sensors here-- or\nin this case, a [INAUDIBLE]..", "start": 2809.49, "duration": 3.06}, {"text": "And then, you fire off\nthese bombs, effectively.", "start": 2812.55, "duration": 2.7}, {"text": "And based on how long\nit takes for sound", "start": 2815.25, "duration": 2.97}, {"text": "to travel to these\ndetectors, it tells", "start": 2818.22, "duration": 2.67}, {"text": "you what the density\nof material--", "start": 2820.89, "duration": 2.17}, {"text": "whether it's rock or oil, or\nother types of formations.", "start": 2823.06, "duration": 4.49}, {"text": "And from that, the oil\ncompanies can figure out", "start": 2827.55, "duration": 3.33}, {"text": "whatever oil there\nis, and where it is.", "start": 2830.88, "duration": 2.04}, {"text": "So you can create a 3D\nmap of what's inside.", "start": 2832.92, "duration": 3.12}, {"text": "Again, multibillion\ndollar situations.", "start": 2836.04, "duration": 5.82}, {"text": "Microscopy, deconvolution-- also\nused in photography, also used", "start": 2841.86, "duration": 4.02}, {"text": "in a machine vision computer,\nwhich we'll talk about that.", "start": 2845.88, "duration": 4.11}, {"text": "Coded aperture imaging-- an\nidea that was used in astronomy,", "start": 2849.99, "duration": 3.66}, {"text": "because astronomy--\nyou're looking", "start": 2853.65, "duration": 1.8}, {"text": "at gamma rays and X-rays.", "start": 2855.45, "duration": 1.65}, {"text": "And you cannot build lenses\nfor them to form an image.", "start": 2857.1, "duration": 2.89}, {"text": "So you can either\ncreate an image", "start": 2859.99, "duration": 1.43}, {"text": "with a pinhole of the sky, or\nyou can use a coated aperture", "start": 2861.42, "duration": 3.21}, {"text": "so you can collect more light.", "start": 2864.63, "duration": 2.37}, {"text": "Now, that idea-- we'll\nlearn about that--", "start": 2867.0, "duration": 3.24}, {"text": "can also be used\nfor photography.", "start": 2870.24, "duration": 1.68}, {"text": "So what our group did was,\nwe used a coded aperture", "start": 2871.92, "duration": 2.92}, {"text": "in the lens.", "start": 2874.84, "duration": 0.5}, {"text": "Instead of having a clear,\ndisk-like aperture, we put a--", "start": 2875.34, "duration": 4.012}, {"text": "you can barely see it.", "start": 2879.352, "duration": 2.468}, {"text": "I'm sorry.", "start": 2881.82, "duration": 0.562}, {"text": "It's supposed to go this way.", "start": 2882.382, "duration": 1.208}, {"text": "[CHUCKLES] You have\na coded aperture,", "start": 2883.59, "duration": 3.61}, {"text": "which looks like a crossword\npuzzle-shaped mask.", "start": 2887.2, "duration": 4.748}, {"text": "And from that, you can\ntake a photo, again,", "start": 2891.948, "duration": 1.792}, {"text": "which could be out of focus,\nand then digitally refocus that.", "start": 2893.74, "duration": 5.37}, {"text": "So this is autofocus photo.", "start": 2899.11, "duration": 2.61}, {"text": "This is in-focus photo.", "start": 2901.72, "duration": 1.62}, {"text": "And you can capture\na glint in the eye,", "start": 2903.34, "duration": 2.52}, {"text": "or even a strand of the hair.", "start": 2905.86, "duration": 2.61}, {"text": "Again, very minor\nchange in the camera.", "start": 2908.47, "duration": 3.46}, {"text": "And originally, we\nwere talking about", "start": 2911.93, "duration": 3.35}, {"text": "successful biological vision.", "start": 2915.28, "duration": 2.4}, {"text": "If you think about the simplest\npossible biological vision,", "start": 2917.68, "duration": 5.82}, {"text": "which is a single pixel\ndetector in a world, right?", "start": 2923.5, "duration": 3.48}, {"text": "Just a single pixel.", "start": 2926.98, "duration": 2.58}, {"text": "It's in muddy, marshy\nwaters looking for food,", "start": 2929.56, "duration": 4.29}, {"text": "or maintaining its orientation.", "start": 2933.85, "duration": 3.16}, {"text": "It doesn't need a\nfull-fledged camera,", "start": 2937.01, "duration": 1.62}, {"text": "it just has a single\npixel detector.", "start": 2938.63, "duration": 2.27}, {"text": "It just knows if\nthere's light, there's", "start": 2940.9, "duration": 2.82}, {"text": "no light, if there's light,\nhow much there is this.", "start": 2943.72, "duration": 3.423}, {"text": "So you know when\nit's dark, when it's", "start": 2947.143, "duration": 1.542}, {"text": "day, when it's night,\nwhich way is more light,", "start": 2948.685, "duration": 2.655}, {"text": "which is less light.", "start": 2951.34, "duration": 1.89}, {"text": "But even that single\npixel detector", "start": 2953.23, "duration": 3.09}, {"text": "has some very interesting\noptics in front.", "start": 2956.32, "duration": 3.04}, {"text": "It has this very intriguing\nshielding pigment", "start": 2959.36, "duration": 3.29}, {"text": "in front of it.", "start": 2962.65, "duration": 2.67}, {"text": "Can anybody guess what's\nthe reason for that?", "start": 2965.32, "duration": 2.79}, {"text": "How does it benefit to have\nsome random pigment that's", "start": 2968.11, "duration": 3.24}, {"text": "blocking the light from\ndifferent directions?", "start": 2971.35, "duration": 2.49}, {"text": "AUDIENCE: For orientation?", "start": 2973.84, "duration": 1.14}, {"text": "RAMESH RASKAR: For orientation.", "start": 2974.98, "duration": 1.292}, {"text": "So if this worm wants\nto maintain an--", "start": 2976.272, "duration": 2.158}, {"text": "if there's a light source and\nif the sensor was hemispherical,", "start": 2978.43, "duration": 4.2}, {"text": "then if this worm\nmoves a little bit,", "start": 2982.63, "duration": 1.83}, {"text": "there will not be much change.", "start": 2984.46, "duration": 1.54}, {"text": "But if they have a very\nhigh frequency pigment,", "start": 2986.0, "duration": 2.39}, {"text": "if this worm moves\neven a little bit,", "start": 2988.39, "duration": 1.71}, {"text": "there'd be a big change\nin the lighting, right?", "start": 2990.1, "duration": 2.85}, {"text": "It's as if you have a\nvery high frequency mask", "start": 2992.95, "duration": 3.25}, {"text": "and you're looking at the sun.", "start": 2996.2, "duration": 1.25}, {"text": "As you move, the light\ngoes up and down.", "start": 2997.45, "duration": 2.73}, {"text": "So the worm knows\nthat as long as it's", "start": 3000.18, "duration": 1.65}, {"text": "maintaining the\nsame level of light,", "start": 3001.83, "duration": 1.71}, {"text": "it's maintaining\nits orientation.", "start": 3003.54, "duration": 2.16}, {"text": "That's all it needs to do.", "start": 3005.7, "duration": 1.41}, {"text": "AUDIENCE: Does it also increase\nthe effective dynamic range", "start": 3007.11, "duration": 2.67}, {"text": "of its sensor?", "start": 3009.78, "duration": 1.08}, {"text": "RAMESH RASKAR: It's possible.", "start": 3010.86, "duration": 0.19}, {"text": "AUDIENCE: As a neutral\ndensity filters", "start": 3011.05, "duration": 1.998}, {"text": "along certain directions, and--", "start": 3013.048, "duration": 1.292}, {"text": "RAMESH RASKAR: It's possible.", "start": 3014.34, "duration": 0.75}, {"text": "It's possible.", "start": 3015.09, "duration": 0.583}, {"text": "Maybe when it's looking at one\ndirection, it's too bright.", "start": 3015.673, "duration": 3.257}, {"text": "So it tries to block that.", "start": 3018.93, "duration": 1.44}, {"text": "We don't know.", "start": 3020.37, "duration": 0.72}, {"text": "And if you read\nthis book, there's", "start": 3021.09, "duration": 1.83}, {"text": "a beautiful book called Animal\nEyes by Land and Nilsson.", "start": 3022.92, "duration": 4.38}, {"text": "We have a whole\nclass on animal eyes.", "start": 3027.3, "duration": 2.79}, {"text": "I think it's the seventh\nclass, if I remember correctly.", "start": 3030.09, "duration": 3.24}, {"text": "And we'll discuss all\ndifferent types of animal eyes", "start": 3033.33, "duration": 3.03}, {"text": "and why they do it,\nwhether it's eagles or land", "start": 3036.36, "duration": 3.75}, {"text": "creatures, underwater\ncreatures, worms, and all that.", "start": 3040.11, "duration": 3.99}, {"text": "And frankly, most of these\nbiological visual systems", "start": 3044.1, "duration": 8.04}, {"text": "are based on hypothesis.", "start": 3052.14, "duration": 1.89}, {"text": "And they're verified in\na very, very scientific,", "start": 3054.03, "duration": 5.22}, {"text": "but at the same time,\nvery primitive equipment.", "start": 3059.25, "duration": 2.47}, {"text": "And one of the\ngreat projects would", "start": 3061.72, "duration": 1.67}, {"text": "be to take some of\nthese worms and put it", "start": 3063.39, "duration": 3.15}, {"text": "in a controlled lighting\nsetup to really verify", "start": 3066.54, "duration": 2.91}, {"text": "if this is how they work.", "start": 3069.45, "duration": 2.162}, {"text": "That'd be a lot of fun.", "start": 3071.612, "duration": 0.958}, {"text": "I'll provide the worms.", "start": 3075.272, "duration": 0.958}, {"text": "Don't worry.", "start": 3076.23, "duration": 0.845}, {"text": "[LAUGHTER]", "start": 3077.075, "duration": 2.275}, {"text": "So the squared aperture\nis somewhat similar.", "start": 3079.35, "duration": 4.56}, {"text": "Let me skip over this part,\nbecause we talked a little bit", "start": 3086.773, "duration": 2.417}, {"text": "about how these mask.", "start": 3089.19, "duration": 0.96}, {"text": "All right, wavefront coding.", "start": 3093.16, "duration": 2.61}, {"text": "This is a concept that was\ninvented by Cathey and Dowski", "start": 3095.77, "duration": 5.64}, {"text": "in 1995 for shaping light\nor shaping the wavefront", "start": 3101.41, "duration": 6.12}, {"text": "of incoming light.", "start": 3107.53, "duration": 2.92}, {"text": "So you have a traditional\nimaging setup.", "start": 3110.45, "duration": 2.27}, {"text": "You have an object.", "start": 3112.72, "duration": 0.84}, {"text": "You have a sensor.", "start": 3113.56, "duration": 1.21}, {"text": "You have some lenses.", "start": 3114.77, "duration": 1.4}, {"text": "What they proposed is placing\nan additional optical layer", "start": 3116.17, "duration": 4.53}, {"text": "in-between, which is\nnot a lens or a prism,", "start": 3120.7, "duration": 3.81}, {"text": "but has variable thickness or\nvariable refractive index, OK?", "start": 3124.51, "duration": 5.94}, {"text": "The simplest way\nto think about that", "start": 3130.45, "duration": 2.01}, {"text": "is, the light in the top part\nmight travel at one speed.", "start": 3132.46, "duration": 4.51}, {"text": "Remember, if you have a glass\nwith different thickness", "start": 3136.97, "duration": 5.57}, {"text": "or different refractive\nindex, the light", "start": 3142.54, "duration": 2.61}, {"text": "is going to slow down.", "start": 3145.15, "duration": 1.92}, {"text": "And when it comes down\non the other side in air,", "start": 3147.07, "duration": 2.72}, {"text": "it can go back to one foot per?", "start": 3149.79, "duration": 3.415}, {"text": "AUDIENCE: Nanosecond.", "start": 3153.205, "duration": 0.875}, {"text": "RAMESH RASKAR:\nNanosecond, very good.", "start": 3154.08, "duration": 1.59}, {"text": "But before that, it's going to\ntravel slightly less than one", "start": 3155.67, "duration": 2.5}, {"text": "foot per nanosecond, right?", "start": 3158.17, "duration": 1.29}, {"text": "If it's 1.5, it's\ngoing to travel 1", "start": 3159.46, "duration": 3.54}, {"text": "by 1.5, 1/2 foot per nanosecond.", "start": 3163.0, "duration": 2.73}, {"text": "So anyway, so by adding\nglass of different thickness", "start": 3165.73, "duration": 3.87}, {"text": "or different refractive\nindex, each of these rays", "start": 3169.6, "duration": 3.0}, {"text": "are going to be slightly out\nof phase with each other.", "start": 3172.6, "duration": 3.91}, {"text": "So when they combine\non the detector,", "start": 3176.51, "duration": 2.72}, {"text": "they will interfere\neither constructively", "start": 3179.23, "duration": 5.61}, {"text": "or destructively.", "start": 3184.84, "duration": 1.29}, {"text": "And from that, you'll\nform new images, right?", "start": 3186.13, "duration": 3.04}, {"text": "So this is how\nthey explained it.", "start": 3189.17, "duration": 2.382}, {"text": "And if you read the\npapers, unfortunately, they", "start": 3191.552, "duration": 1.958}, {"text": "are very difficult\nto understand.", "start": 3193.51, "duration": 2.28}, {"text": "And what you'll\nrealize is that instead", "start": 3195.79, "duration": 2.61}, {"text": "of going into the\nmath for your optics", "start": 3198.4, "duration": 2.91}, {"text": "and so on, in this class,\nwe will use very simple ray", "start": 3201.31, "duration": 3.63}, {"text": "diagrams and understand how this\nworks in a very visual manner.", "start": 3204.94, "duration": 4.42}, {"text": "OK.", "start": 3209.36, "duration": 1.35}, {"text": "So basically, what\nwavefront coding camera", "start": 3210.71, "duration": 3.33}, {"text": "does is, in a\ntraditional camera,", "start": 3214.04, "duration": 3.0}, {"text": "rays converge to a single point.", "start": 3217.04, "duration": 1.8}, {"text": "And you get a sharply\nfocused image.", "start": 3218.84, "duration": 1.78}, {"text": "So if the sensor goes in and out\nof focus, you get a large blur.", "start": 3220.62, "duration": 4.64}, {"text": "In case of wavefront\ncoded camera,", "start": 3225.26, "duration": 2.01}, {"text": "actually, you never\nget a sharp spot.", "start": 3227.27, "duration": 2.34}, {"text": "What you get is basically,\nthink of taking a lot of straws", "start": 3229.61, "duration": 3.75}, {"text": "and all of them converging\nto a single point,", "start": 3233.36, "duration": 2.52}, {"text": "taking them and\nthen twisting them", "start": 3235.88, "duration": 2.13}, {"text": "so that they go out\nagain as the straws.", "start": 3238.01, "duration": 3.3}, {"text": "But in-between, there's a\npart where all of them are--", "start": 3241.31, "duration": 6.24}, {"text": "the cross-section\nof them is roughly--", "start": 3247.55, "duration": 3.06}, {"text": "OK?", "start": 3250.61, "duration": 0.9}, {"text": "And by doing that, it turns out,\nfor a sufficiently large depth", "start": 3251.51, "duration": 7.14}, {"text": "range, the defocus\nis equivalent.", "start": 3258.65, "duration": 3.66}, {"text": "And we'll study this in\ndetail, and how this works,", "start": 3262.31, "duration": 2.31}, {"text": "and how you can use\nthe same techniques", "start": 3264.62, "duration": 1.89}, {"text": "for new types of photography\nand scientific imaging.", "start": 3266.51, "duration": 3.03}, {"text": "Now, this is also a very hot\ntopic in night vision goggles,", "start": 3269.54, "duration": 2.52}, {"text": "by the way, where they\nwant to wear night vision", "start": 3272.06, "duration": 3.6}, {"text": "goggles that when you look\nfar away, it's very clear.", "start": 3275.66, "duration": 4.873}, {"text": "And again, night vision goggles\nhave very large apertures.", "start": 3280.533, "duration": 2.417}, {"text": "And when you look\ncloser, if you want", "start": 3282.95, "duration": 2.076}, {"text": "to read a map, for example,\nit should still be in focus.", "start": 3285.026, "duration": 3.624}, {"text": "So how do you create\na passive device", "start": 3288.65, "duration": 3.15}, {"text": "that can focus on infinity and\nvery close up at the same time?", "start": 3291.8, "duration": 3.36}, {"text": "And they have been using\nwavefront coding as well.", "start": 3295.16, "duration": 4.23}, {"text": "Wow, I can barely see this.", "start": 3299.39, "duration": 2.02}, {"text": "All right.", "start": 3301.41, "duration": 1.64}, {"text": "This is a project called\n\"Decoding Depth via Defocus", "start": 3303.05, "duration": 4.17}, {"text": "Blur.\"", "start": 3307.22, "duration": 0.51}, {"text": "This is from Colorado\nfrom Rafael [INAUDIBLE]", "start": 3307.73, "duration": 2.64}, {"text": "and [INAUDIBLE].", "start": 3310.37, "duration": 3.03}, {"text": "And this is very\ncounterintuitive.", "start": 3313.4, "duration": 2.91}, {"text": "If you take a point\nlight-- and I wish", "start": 3316.31, "duration": 3.135}, {"text": "I could do this experiment.", "start": 3319.445, "duration": 1.125}, {"text": "I can do it here, but\nit'll take some time.", "start": 3320.57, "duration": 2.04}, {"text": "If you take a point\nlight and form an image", "start": 3322.61, "duration": 2.58}, {"text": "on this particular guy--", "start": 3325.19, "duration": 1.53}, {"text": "AUDIENCE: Do you want\na little flashlight?", "start": 3329.63, "duration": 1.75}, {"text": "RAMESH RASKAR: Yeah.", "start": 3331.38, "duration": 0.833}, {"text": "Thanks.", "start": 3337.86, "duration": 0.66}, {"text": "So as you can see here,\nthat's the image plane, right?", "start": 3338.52, "duration": 5.16}, {"text": "As I move it in and out, its\nshape is going to change--", "start": 3343.68, "duration": 4.44}, {"text": "the spotlight.", "start": 3348.12, "duration": 0.69}, {"text": "Now, imagine-- and that's what\nhappens in the bottom part", "start": 3348.81, "duration": 3.78}, {"text": "of the image.", "start": 3352.59, "duration": 0.75}, {"text": "As you are in sharp focus,\nyou get a small spot.", "start": 3357.39, "duration": 2.79}, {"text": "As you go out of focus,\nyou've got a bigger disk.", "start": 3360.18, "duration": 2.64}, {"text": "But the kind of optics\nthis group designed,", "start": 3362.82, "duration": 3.15}, {"text": "when you're in focus, you\nsee two spots that are left", "start": 3365.97, "duration": 2.91}, {"text": "and right of each other.", "start": 3368.88, "duration": 1.39}, {"text": "And when you go out of\nfocus, these two spots", "start": 3370.27, "duration": 2.21}, {"text": "rotate one way or the other way.", "start": 3372.48, "duration": 3.21}, {"text": "If you are closer than the other\nfocus, it rotates in one way,", "start": 3375.69, "duration": 3.3}, {"text": "if away from other focus,\nit rotates the other one.", "start": 3378.99, "duration": 2.62}, {"text": "So this rotational\npoint spread function", "start": 3381.61, "duration": 2.54}, {"text": "is a very powerful concept.", "start": 3384.15, "duration": 1.485}, {"text": "And right now, they're\nusing it in microscopy", "start": 3385.635, "duration": 1.875}, {"text": "for resolving fluorescent\nbeads at nanometer precision.", "start": 3387.51, "duration": 4.8}, {"text": "But it could also be\nused in photography.", "start": 3392.31, "duration": 1.98}, {"text": "Nobody knows how to do it.", "start": 3394.29, "duration": 1.5}, {"text": "This could be one of\nyour research projects.", "start": 3395.79, "duration": 3.39}, {"text": "And we can get some of these\nprototypes from our colleagues.", "start": 3399.18, "duration": 3.473}, {"text": "So it's a lot of\nfun to play with.", "start": 3402.653, "duration": 1.417}, {"text": "Another interesting thing\nwe will be looking at", "start": 3406.672, "duration": 1.958}, {"text": "is the relationship between\nFourier optics and ray optics.", "start": 3408.63, "duration": 6.06}, {"text": "Now, in high school,\nwe were taught,", "start": 3414.69, "duration": 2.28}, {"text": "there is particle\nand wave duality,", "start": 3416.97, "duration": 3.06}, {"text": "and a lot of confusion.", "start": 3420.03, "duration": 1.98}, {"text": "And in high school, we\nhave to answer questions", "start": 3422.01, "duration": 2.58}, {"text": "of what phenomena can be\nshown in particle way,", "start": 3424.59, "duration": 3.27}, {"text": "and what can be shown in using\nthe wave propagation model.", "start": 3427.86, "duration": 4.56}, {"text": "And one of the standard\nanswers was, oh,", "start": 3432.42, "duration": 2.19}, {"text": "if there's interference\nor diffraction,", "start": 3434.61, "duration": 2.07}, {"text": "then it can only be explained\nwith Fourier optics,", "start": 3436.68, "duration": 2.13}, {"text": "not with particle\nnature of light.", "start": 3438.81, "duration": 4.53}, {"text": "That's too simplistic.", "start": 3443.34, "duration": 2.49}, {"text": "It turns out that\nyou can really show", "start": 3445.83, "duration": 3.21}, {"text": "that there are the\nduals of each other", "start": 3449.04, "duration": 2.37}, {"text": "and explain diffraction,\nand interference,", "start": 3451.41, "duration": 2.97}, {"text": "and all these mechanisms\nusing purely ray propagation.", "start": 3454.38, "duration": 4.14}, {"text": "And so with Sadek--", "start": 3458.52, "duration": 2.053}, {"text": "his name is not here--", "start": 3460.573, "duration": 0.917}, {"text": "Sadek O and Josh\n[INAUDIBLE],, this is--", "start": 3461.49, "duration": 2.18}, {"text": "for mechanical engineering,\nwe have a project", "start": 3463.67, "duration": 2.59}, {"text": "where we have created a\nso-called augmented life", "start": 3466.26, "duration": 2.94}, {"text": "field, which can actually\nsupport all the wave optics", "start": 3469.2, "duration": 4.44}, {"text": "effects as well.", "start": 3473.64, "duration": 0.73}, {"text": "So traditional light field\nthat we just described earlier,", "start": 3474.37, "duration": 2.48}, {"text": "where you can capture with an\narray of cameras and so on,", "start": 3476.85, "duration": 4.02}, {"text": "can do this position\nangle representation", "start": 3480.87, "duration": 3.9}, {"text": "and the four-dimensional\nrepresentation.", "start": 3484.77, "duration": 3.81}, {"text": "And at that time, I made a claim\nthat if you can capture this 4D", "start": 3488.58, "duration": 4.05}, {"text": "incoming function,\nyou have captured", "start": 3492.63, "duration": 2.07}, {"text": "everything-- everything--\ngeometrically that", "start": 3494.7, "duration": 2.52}, {"text": "has come through the lens.", "start": 3497.22, "duration": 1.94}, {"text": "So it's a complete\nrepresentation of the light.", "start": 3499.16, "duration": 2.32}, {"text": "And some people would say, wow.", "start": 3501.48, "duration": 2.772}, {"text": "But then, you're not\ncapturing the phase.", "start": 3504.252, "duration": 1.708}, {"text": "And you're not capturing\nall these other things.", "start": 3505.96, "duration": 2.27}, {"text": "But it turns out that\nusing the same exact setup,", "start": 3508.23, "duration": 3.84}, {"text": "you are also able\nto capture phase.", "start": 3512.07, "duration": 2.61}, {"text": "The Fourier\nrepresentation actually", "start": 3514.68, "duration": 2.07}, {"text": "includes the amplitude and\nphase of the incoming wavefront.", "start": 3516.75, "duration": 4.8}, {"text": "And so simply by using different\nmathematical terminology,", "start": 3521.55, "duration": 4.83}, {"text": "we have augmented this\nlight Fourier presentation", "start": 3526.38, "duration": 3.99}, {"text": "to also represent, to also\nmodel wavefront effects.", "start": 3530.37, "duration": 3.97}, {"text": "So we'll study that\na little later.", "start": 3534.34, "duration": 2.338}, {"text": "What about\nphotographs like this?", "start": 3539.89, "duration": 2.44}, {"text": "If you look at this\nheater, it's creating", "start": 3542.33, "duration": 3.14}, {"text": "these beautiful\nstreams of hot air.", "start": 3545.47, "duration": 3.27}, {"text": "And also, this lamp\nfrom the lamp ship.", "start": 3551.59, "duration": 4.752}, {"text": "Again, we are trying to\nvisualize that cannot be seen", "start": 3556.342, "duration": 2.208}, {"text": "with the naked eye.", "start": 3558.55, "duration": 1.09}, {"text": "So this is known as the\nSchlieren photography, which", "start": 3559.64, "duration": 3.59}, {"text": "is, again, looking at very minor\nchanges in the optical path.", "start": 3563.23, "duration": 4.11}, {"text": "In this case, because of heat,\non a hot day on a highway,", "start": 3567.34, "duration": 6.36}, {"text": "you see the mirage.", "start": 3573.7, "duration": 1.92}, {"text": "But that happens at\nextremely high temperatures.", "start": 3575.62, "duration": 2.13}, {"text": "Now, even at not-so-high\ntemperatures,", "start": 3577.75, "duration": 3.03}, {"text": "you can actually\ncapture this mirage", "start": 3580.78, "duration": 2.37}, {"text": "and create a very\nbeautiful focus.", "start": 3583.15, "duration": 3.63}, {"text": "So this is student photography.", "start": 3586.78, "duration": 1.44}, {"text": "And we'll study that.", "start": 3588.22, "duration": 1.98}, {"text": "Polarization is beautiful.", "start": 3590.2, "duration": 3.03}, {"text": "You may have used polarization\nfor taking photos of the sky,", "start": 3593.23, "duration": 3.33}, {"text": "or on water.", "start": 3596.56, "duration": 1.62}, {"text": "But underwater photography\ncan be dramatically improved", "start": 3598.18, "duration": 3.15}, {"text": "with polarization.", "start": 3601.33, "duration": 2.81}, {"text": "So we'll study that.", "start": 3604.14, "duration": 1.17}, {"text": "We'll also study some\nnew type of sensors,", "start": 3608.12, "duration": 2.34}, {"text": "not just\ntwo-dimensional sensors,", "start": 3610.46, "duration": 1.56}, {"text": "but these other sensors--", "start": 3612.02, "duration": 3.146}, {"text": "a single-pixel camera,\ncompressed sensing.", "start": 3615.166, "duration": 3.664}, {"text": "How many of you have\nhardware compressed sensing?", "start": 3618.83, "duration": 3.13}, {"text": "Right?", "start": 3621.96, "duration": 0.5}, {"text": "There's a lot of hype about it.", "start": 3622.46, "duration": 1.39}, {"text": "And again, if you\nread the papers,", "start": 3623.85, "duration": 4.01}, {"text": "sometimes, it's very\ndifficult to follow", "start": 3627.86, "duration": 2.37}, {"text": "what exactly they're trying\nto say and how it's done.", "start": 3630.23, "duration": 2.73}, {"text": "But as you will\nsee in this class,", "start": 3632.96, "duration": 3.09}, {"text": "you'll get the whole idea\nof compressed sensing", "start": 3636.05, "duration": 2.52}, {"text": "in less than five minutes.", "start": 3638.57, "duration": 2.08}, {"text": "And we'll go through what\nworks, what doesn't work.", "start": 3640.65, "duration": 2.9}, {"text": "And actually, Rohit is working\non a project which hopefully", "start": 3643.55, "duration": 3.75}, {"text": "will show that compressed\nsensing is actually not", "start": 3647.3, "duration": 2.67}, {"text": "such a great idea for imaging.", "start": 3649.97, "duration": 1.92}, {"text": "But it is good for\nsomething else.", "start": 3651.89, "duration": 1.99}, {"text": "And we'll study what\nthat \"something else\"", "start": 3653.88, "duration": 1.91}, {"text": "is when he and Rashad's project\nis reaching some mature stage.", "start": 3655.79, "duration": 6.09}, {"text": "So very exciting ideas there.", "start": 3661.88, "duration": 2.95}, {"text": "So the original idea was to\ncreate a single-pixel camera.", "start": 3664.83, "duration": 3.14}, {"text": "In creating a\nmegapixel camera, you", "start": 3667.97, "duration": 2.4}, {"text": "have a single pixel that's going\nto take a coded combination", "start": 3670.37, "duration": 4.5}, {"text": "of incoming light.", "start": 3674.87, "duration": 1.17}, {"text": "This may be a scene.", "start": 3676.04, "duration": 1.14}, {"text": "It's being focused on the\nwhole reflective mirror array.", "start": 3677.18, "duration": 4.98}, {"text": "And you're usually going to\nflip this mirror on and off.", "start": 3682.16, "duration": 2.55}, {"text": "So the light you collect\nwill be a product", "start": 3684.71, "duration": 2.97}, {"text": "of the scene with this vector.", "start": 3687.68, "duration": 4.57}, {"text": "And if you change these\nflips, you get some other sum.", "start": 3692.25, "duration": 4.16}, {"text": "You're going to make a\nlinear sum of incoming light", "start": 3696.41, "duration": 2.7}, {"text": "and predict a million\nsuch measurements.", "start": 3699.11, "duration": 2.01}, {"text": "You can reconstruct\na megapixel photo.", "start": 3701.12, "duration": 3.75}, {"text": "But the claim of\nthis group from Rice", "start": 3704.87, "duration": 2.61}, {"text": "is that you don't\nhave to actually take", "start": 3707.48, "duration": 2.64}, {"text": "a million readings.", "start": 3710.12, "duration": 1.71}, {"text": "You might be able to get\naway with only 10,000", "start": 3711.83, "duration": 2.19}, {"text": "or 100,000 readings.", "start": 3714.02, "duration": 2.43}, {"text": "So you can capture\na megapixel photo", "start": 3716.45, "duration": 2.79}, {"text": "with possibly only 10,000\npixels of a camera.", "start": 3719.24, "duration": 4.71}, {"text": "And we'll look into that and\nwhat part of that statement", "start": 3723.95, "duration": 4.41}, {"text": "is true, and what\npart of the statement", "start": 3728.36, "duration": 1.71}, {"text": "requires more analysis.", "start": 3730.07, "duration": 1.562}, {"text": "And you'll also see\nthat this can be used", "start": 3731.632, "duration": 1.708}, {"text": "in a lot of other situations.", "start": 3733.34, "duration": 2.53}, {"text": "So for example, my group\nhas built a strobing camera", "start": 3735.87, "duration": 5.84}, {"text": "that can be used for\nlaryngoscopy, where", "start": 3741.71, "duration": 3.06}, {"text": "in a laryngoscope, you use\nvery high speed strobing", "start": 3744.77, "duration": 3.27}, {"text": "to slow down to visualize\nthe motion of vocal force.", "start": 3748.04, "duration": 5.97}, {"text": "But we just came up\nwith a new method", "start": 3754.01, "duration": 1.8}, {"text": "that is dramatically simple and\nuses dramatically less light.", "start": 3755.81, "duration": 4.68}, {"text": "So you don't burn your\nthroat when the doctor", "start": 3760.49, "duration": 2.16}, {"text": "is looking at your vocal force.", "start": 3762.65, "duration": 3.06}, {"text": "And that's based on\ncompressed sensing.", "start": 3765.71, "duration": 1.68}, {"text": "So let me stop here, because\nwe're almost at 4:30.", "start": 3770.05, "duration": 2.76}, {"text": "And we'll come back.", "start": 3772.81, "duration": 3.48}, {"text": "We'll come back and look at\nsome of these other projects.", "start": 3776.29, "duration": 4.5}, {"text": "So these are the kind of project\nassignments you will see--", "start": 3787.06, "duration": 3.44}, {"text": "relighting, the first one\nthat's already described.", "start": 3790.5, "duration": 2.61}, {"text": "Dual photography, where you\ncan read your opponent's card.", "start": 3793.11, "duration": 3.72}, {"text": "Virtual optical bench,\nlight field capture,", "start": 3796.83, "duration": 3.06}, {"text": "high-speed imaging, thermal\nimaging, multispectral imaging,", "start": 3799.89, "duration": 3.6}, {"text": "range imaging, and so on.", "start": 3803.49, "duration": 2.17}, {"text": "And then, a completely\nopen-ended final project, which", "start": 3805.66, "duration": 3.38}, {"text": "you can choose in any area.", "start": 3809.04, "duration": 2.422}, {"text": "This is the first assignment.", "start": 3811.462, "duration": 1.208}, {"text": "The instructions will go\nout on the Stellar web page.", "start": 3812.67, "duration": 3.19}, {"text": "Please make sure you\nhave the sign-up sheet.", "start": 3815.86, "duration": 5.39}, {"text": "Has it gone around?", "start": 3821.25, "duration": 2.532}, {"text": "OK, please make sure\nyour name and email", "start": 3823.782, "duration": 1.698}, {"text": "is on the sign-up sheet.", "start": 3825.48, "duration": 1.47}, {"text": "If you don't get an email\nfrom me by Monday morning,", "start": 3826.95, "duration": 2.203}, {"text": "please send me an email, which\nmeans that I could not read", "start": 3829.153, "duration": 2.417}, {"text": "your email address correctly.", "start": 3831.57, "duration": 3.64}, {"text": "So yeah, these will be\nsome of the assignments", "start": 3835.21, "duration": 2.15}, {"text": "you'll be doing.", "start": 3837.36, "duration": 2.04}, {"text": "And this one is due\non September 25.", "start": 3839.4, "duration": 3.54}, {"text": "And every class starting\nfrom next class,", "start": 3842.94, "duration": 3.09}, {"text": "we'll have a volunteer who takes\nnotes for the class and posts", "start": 3846.03, "duration": 4.14}, {"text": "it, because a lot\nof our discussion", "start": 3850.17, "duration": 2.19}, {"text": "is going to be on\nthe board and so on.", "start": 3852.36, "duration": 1.83}, {"text": "I'll send out\nspecific instructions.", "start": 3854.19, "duration": 1.5}, {"text": "So we need a volunteer\nfor next week.", "start": 3855.69, "duration": 2.467}, {"text": "You want to do that?", "start": 3858.157, "duration": 0.833}, {"text": "AUDIENCE: Yeah.", "start": 3858.99, "duration": 0.33}, {"text": "RAMESH RASKAR: What's your name?", "start": 3859.32, "duration": 0.54}, {"text": "AUDIENCE: Sam.", "start": 3859.86, "duration": 0.51}, {"text": "RAMESH RASKAR: Sam.", "start": 3860.37, "duration": 0.45}, {"text": "All right, Sam is going to\nvolunteer for next week.", "start": 3860.82, "duration": 2.125}, {"text": "And we'll decide who's going\nto do that another week.", "start": 3862.945, "duration": 3.363}, {"text": "[SIDE CONVERSATIONS]", "start": 3866.308, "duration": 2.37}, {"text": "AUDIENCE: [INAUDIBLE]?", "start": 3869.89, "duration": 1.64}, {"text": "RAMESH RASKAR: Sorry?", "start": 3871.53, "duration": 1.17}, {"text": "AUDIENCE: Do you\nhave a [INAUDIBLE]", "start": 3872.7, "duration": 2.13}, {"text": "from the [INAUDIBLE]?", "start": 3874.83, "duration": 1.622}, {"text": "RAMESH RASKAR: Probably not,\nbecause most of the people are", "start": 3876.452, "duration": 2.458}, {"text": "going to be-- many\npeople, not most--", "start": 3878.91, "duration": 1.77}, {"text": "but many people are\ngoing to be listening.", "start": 3880.68, "duration": 1.75}, {"text": "So as far as I know, it's\nnot going to cross the limit.", "start": 3882.43, "duration": 4.31}, {"text": "But if there is, there's a cap.", "start": 3886.74, "duration": 3.36}, {"text": "I don't think it's going\nto reach the campus.", "start": 3890.1, "duration": 2.662}, {"text": "There's a cap of authorities.", "start": 3892.762, "duration": 1.208}, {"text": "I don't [INAUDIBLE].", "start": 3893.97, "duration": 2.635}, {"text": "[SIDE CONVERSATIONS]", "start": 3896.605, "duration": 2.85}, {"text": "And we'll see some of\nthese demos next time.", "start": 3903.25, "duration": 2.87}]
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+[{"text": "BARBARA IMPERIALI: So\nwe're going to get started.", "start": 16.18, "duration": 2.25}, {"text": "This is a complicated\nlecture to choreograph,", "start": 18.43, "duration": 2.31}, {"text": "but I'm going to do my very,\nvery best because I think", "start": 20.74, "duration": 3.45}, {"text": "there's some pretty\namazing stuff", "start": 24.19, "duration": 2.69}, {"text": "that we have to explain that\nis carried out in nature.", "start": 26.88, "duration": 3.68}, {"text": "And one of those things is\nhow do we replicate the entire", "start": 30.56, "duration": 4.04}, {"text": "genome of organisms in one\nfell swoop almost perfectly--", "start": 34.6, "duration": 5.46}, {"text": "sometimes there\nare little errors--", "start": 40.06, "duration": 2.01}, {"text": "and fast.", "start": 42.07, "duration": 1.5}, {"text": "So we're going to refer to\nthese numbers in a moment.", "start": 43.57, "duration": 2.46}, {"text": "But first of all, I just\nwant to get you back", "start": 46.03, "duration": 2.01}, {"text": "in the picture of where we were\nat the end of the last section,", "start": 48.04, "duration": 3.93}, {"text": "the biochemistry section.", "start": 51.97, "duration": 1.71}, {"text": "And in the next\nfew classes we're", "start": 53.68, "duration": 1.95}, {"text": "going to address issues\nrelated to the central dogma", "start": 55.63, "duration": 4.66}, {"text": "and the use of nucleic acids\nfor information storage", "start": 60.29, "duration": 3.68}, {"text": "and information transfer.", "start": 63.97, "duration": 1.86}, {"text": "And before I do\nthat, I just want", "start": 65.83, "duration": 1.53}, {"text": "to highlight a couple of\nthings, just some terms", "start": 67.36, "duration": 3.27}, {"text": "that you should recall and recap\nfrom the biochemistry section", "start": 70.63, "duration": 4.56}, {"text": "about nucleic acids.", "start": 75.19, "duration": 2.02}, {"text": "So nucleic acids form\ncomplementary double strands", "start": 77.21, "duration": 4.31}, {"text": "through base pairing,\nand that base pairing", "start": 81.52, "duration": 2.82}, {"text": "involves hydrogen bonding\nbetween the nucleobases,", "start": 84.34, "duration": 4.02}, {"text": "one purine to one pyrimidine,\nand the AT base pair", "start": 88.36, "duration": 4.5}, {"text": "is worth two hydrogen bonds.", "start": 92.86, "duration": 2.35}, {"text": "The GC base pair is worth\nthree hydrogen bonds.", "start": 95.21, "duration": 3.38}, {"text": "And those are actually\npretty useful facts", "start": 98.59, "duration": 2.76}, {"text": "to remember because they\ntell us about the stability", "start": 101.35, "duration": 3.06}, {"text": "of double-stranded DNA, where\nit's easier to tease it apart,", "start": 104.41, "duration": 4.35}, {"text": "and other characteristics.", "start": 108.76, "duration": 1.6}, {"text": "So it's kind of a useful\nthing to keep in mind.", "start": 110.36, "duration": 2.91}, {"text": "So the base pairing\nbetween what--", "start": 113.27, "duration": 2.84}, {"text": "the purine pyrimidine pair,\nwhich sets the exact register,", "start": 116.11, "duration": 4.26}, {"text": "down the double-stranded DNA.", "start": 120.37, "duration": 1.7}, {"text": "The backbone is the\nexact distance apart", "start": 122.07, "duration": 3.34}, {"text": "because you always\ncombine a small pyrimidine", "start": 125.41, "duration": 3.81}, {"text": "with a much larger purine.", "start": 129.22, "duration": 2.35}, {"text": "So that's something you\nshould feel comfortable about.", "start": 131.57, "duration": 3.56}, {"text": "The components are organized in\nan anti-parallel orientation,", "start": 135.13, "duration": 4.86}, {"text": "so one end runs 5\nprime to 3 prime.", "start": 139.99, "duration": 3.76}, {"text": "The other end runs\n3 prime to 5 prime.", "start": 143.75, "duration": 2.56}, {"text": "And I showed you\nlast time an image", "start": 146.31, "duration": 2.71}, {"text": "that allows us to\nstate quite clearly", "start": 149.02, "duration": 3.72}, {"text": "that the anti-parallel\norientation is significantly", "start": 152.74, "duration": 3.72}, {"text": "more stable than the\nparallel orientation", "start": 156.46, "duration": 3.18}, {"text": "because you can't make all\nthose great hydrogen bonds well", "start": 159.64, "duration": 3.03}, {"text": "in the parallel\norganization apart", "start": 162.67, "duration": 2.19}, {"text": "from everything else\nthat becomes complicated.", "start": 164.86, "duration": 3.48}, {"text": "Another important\nthing that you're", "start": 168.34, "duration": 1.92}, {"text": "going to have to remember,\nespecially in this lecture,", "start": 170.26, "duration": 3.51}, {"text": "is that we add new\nnucleotides to the 3", "start": 173.77, "duration": 3.6}, {"text": "prime end of a nucleic acid.", "start": 177.37, "duration": 3.0}, {"text": "And so I'm just going to put\nthis little guy in the corner", "start": 180.37, "duration": 3.18}, {"text": "here.", "start": 183.55, "duration": 0.6}, {"text": "This is the ribose sugar.", "start": 184.15, "duration": 3.52}, {"text": "That would be where the\nnucleobase is attached.", "start": 187.67, "duration": 2.385}, {"text": "And it's a deoxy\nsugar, so there's", "start": 192.92, "duration": 2.82}, {"text": "no substituent at that carbon.", "start": 195.74, "duration": 3.31}, {"text": "This is the one position where\nthe base is. the 2 position,", "start": 199.05, "duration": 3.83}, {"text": "where it's deoxy,\nthe 3 position.", "start": 202.88, "duration": 4.38}, {"text": "And these are all prime numbers.", "start": 207.26, "duration": 1.56}, {"text": "Remember, the sugars\nhave prime numbers.", "start": 208.82, "duration": 2.61}, {"text": "The bases themselves have\nnumbers without primes", "start": 211.43, "duration": 2.64}, {"text": "to distinguish what\nwe're talking about.", "start": 214.07, "duration": 2.58}, {"text": "So 3, 4, 5, and\nthey're all prime.", "start": 216.65, "duration": 6.32}, {"text": "And when we grow the\nsingle strand of DNA,", "start": 222.97, "duration": 4.38}, {"text": "we always add new basis\nto the 3 prime end.", "start": 227.35, "duration": 4.62}, {"text": "That's an important\nnumbering system.", "start": 231.97, "duration": 1.7}, {"text": "I don't like that\npiece of chalk.", "start": 236.31, "duration": 2.58}, {"text": "So we always grow from\n5 prime to 3 prime.", "start": 238.89, "duration": 5.445}, {"text": "And that will be\nimportant to you", "start": 249.34, "duration": 1.69}, {"text": "as we go through the\ndiscussion today.", "start": 251.03, "duration": 2.49}, {"text": "And then finally, a feature\nof double-stranded DNA,", "start": 253.52, "duration": 4.59}, {"text": "quite unlike proteins,\nwhich sometimes you'll", "start": 258.11, "duration": 3.539}, {"text": "thermally or with pH\nmelt out and will often", "start": 261.649, "duration": 4.471}, {"text": "have a problem reforming their\nreliable structure because", "start": 266.12, "duration": 3.87}, {"text": "instead of the structure\nrefolding, they aggregate.", "start": 269.99, "duration": 4.02}, {"text": "Double-stranded DNA\ndoesn't aggregate", "start": 274.01, "duration": 2.19}, {"text": "because it's got all the\nnegative charges that", "start": 276.2, "duration": 2.55}, {"text": "would be quite repulsive.", "start": 278.75, "duration": 1.8}, {"text": "So it would be very\ndifficult for DNA strands", "start": 280.55, "duration": 3.0}, {"text": "to aggregate as\nsuch because there's", "start": 283.55, "duration": 1.59}, {"text": "too much of a concentration\nof negative charges.", "start": 285.14, "duration": 3.0}, {"text": "That would be repulsion\namongst the same type charges.", "start": 288.14, "duration": 3.57}, {"text": "So DNA can be peeled\napart with heat,", "start": 291.71, "duration": 3.49}, {"text": "and it will reanneal\nfaithfully to its partner", "start": 295.2, "duration": 2.78}, {"text": "a complementary strand.", "start": 297.98, "duration": 1.74}, {"text": "Once you get to six,\nseven, eight base pairs,", "start": 299.72, "duration": 3.12}, {"text": "that is a nice interaction\nbetween the strands,", "start": 302.84, "duration": 3.12}, {"text": "and it forms faithfully.", "start": 305.96, "duration": 1.68}, {"text": "If we have a mistake\nin the strands,", "start": 307.64, "duration": 2.46}, {"text": "the stability of the double\nstrand will be a bit less,", "start": 310.1, "duration": 3.32}, {"text": "and we can measure that\nthrough physical measurements", "start": 313.42, "duration": 2.68}, {"text": "that we carry out in the lab.", "start": 316.1, "duration": 1.62}, {"text": "So we can measure\nthe denaturation", "start": 317.72, "duration": 3.13}, {"text": "or the thermal melt temperature.", "start": 320.85, "duration": 2.36}, {"text": "So we call this\nprocess, after you", "start": 323.21, "duration": 6.48}, {"text": "separate double-stranded\nDNA, we call it reannealing,", "start": 329.69, "duration": 3.78}, {"text": "or it's also designated\nas hybridization", "start": 333.47, "duration": 2.82}, {"text": "to form a hybrid, which is\nthe composite of the two", "start": 336.29, "duration": 3.0}, {"text": "structures.", "start": 339.29, "duration": 1.11}, {"text": "Those terms are used\nfairly interchangeably.", "start": 340.4, "duration": 2.61}, {"text": "All right.", "start": 343.01, "duration": 0.5}, {"text": "So the goals in the\nnext four classes", "start": 343.51, "duration": 2.22}, {"text": "are to show you how the\nstructures of the nucleic acids", "start": 345.73, "duration": 3.97}, {"text": "really are purposed for\nthe sorts of processes", "start": 349.7, "duration": 3.24}, {"text": "that they undergo.", "start": 352.94, "duration": 1.32}, {"text": "So the replication of\nDNA, the conversion", "start": 354.26, "duration": 3.42}, {"text": "of a strand of DNA into\ncomplementary messenger", "start": 357.68, "duration": 3.93}, {"text": "RNA once the process\nof protein synthesis", "start": 361.61, "duration": 3.66}, {"text": "needs to be initiated,\nthat second step.", "start": 365.27, "duration": 3.28}, {"text": "The first step is\ncalled replication.", "start": 368.55, "duration": 2.96}, {"text": "The second step, when you\ntranscribe DNA into RNA,", "start": 371.51, "duration": 4.83}, {"text": "is called transcription.", "start": 376.34, "duration": 1.77}, {"text": "And then finally, when you\ntranslate messenger RNA", "start": 378.11, "duration": 4.2}, {"text": "into proteins.", "start": 382.31, "duration": 0.97}, {"text": "So going to a\ncompletely new language,", "start": 383.28, "duration": 2.27}, {"text": "we call it a translation.", "start": 385.55, "duration": 1.65}, {"text": "And that's the basis\nof these lectures.", "start": 387.2, "duration": 3.3}, {"text": "There is a little bit of\nstuff in these lectures", "start": 390.5, "duration": 2.37}, {"text": "about more complicated issues\nin the mammalian cell, where", "start": 392.87, "duration": 3.84}, {"text": "we have to process the\nmessenger RNA a bit", "start": 396.71, "duration": 3.15}, {"text": "before we can have\nit leave the nucleus.", "start": 399.86, "duration": 2.34}, {"text": "And I'll explain at\nthe time when it comes.", "start": 402.2, "duration": 3.48}, {"text": "So this is the lineup\nfor the four lectures.", "start": 405.68, "duration": 2.82}, {"text": "All right.", "start": 408.5, "duration": 2.18}, {"text": "Well, I already talked\nto you how when you add--", "start": 410.68, "duration": 2.81}, {"text": "I mentioned it over here--", "start": 413.49, "duration": 1.62}, {"text": "when you add cytidine\ntriphosphate, GTP, ATP, TTP,", "start": 415.11, "duration": 6.41}, {"text": "these are the\nactivated nucleobases,", "start": 421.52, "duration": 3.39}, {"text": "so they're the deoxy\nnucleoside triphosphates.", "start": 424.91, "duration": 5.61}, {"text": "They are nucleotides because\nthey include phosphate,", "start": 430.52, "duration": 3.66}, {"text": "but when we describe\nthem, we'll call", "start": 434.18, "duration": 2.79}, {"text": "them nucleoside\ntriphosphates if we're going", "start": 436.97, "duration": 2.99}, {"text": "to mention the phosphate part.", "start": 439.96, "duration": 2.68}, {"text": "I know that probably doesn't\nmake any sense at all.", "start": 442.64, "duration": 3.0}, {"text": "Is everyone OK with that?", "start": 445.64, "duration": 2.14}, {"text": "If you're just generically\ndescribing something", "start": 447.78, "duration": 3.39}, {"text": "with a phosphate in it,\nyou call it a nucleotide.", "start": 451.17, "duration": 2.88}, {"text": "If you want to be a\nlittle bit more specific,", "start": 454.05, "duration": 2.22}, {"text": "you say nucleoside, and then\nyou say how many phosphates.", "start": 456.27, "duration": 3.6}, {"text": "All right?", "start": 459.87, "duration": 0.66}, {"text": "And so for the building blocks,\nit's a nucleoside triphosphate.", "start": 460.53, "duration": 3.78}, {"text": "And believe me, I get\nthat wrong all the time,", "start": 464.31, "duration": 2.4}, {"text": "and my students correct me.", "start": 466.71, "duration": 1.8}, {"text": "So I don't have a\nproblem if you're not", "start": 468.51, "duration": 2.82}, {"text": "perfect with that nomenclature.", "start": 471.33, "duration": 2.86}, {"text": "So these are the building blocks\nfor DNA, for polymerization.", "start": 474.19, "duration": 3.92}, {"text": "And I just showed you how you\ngrow from the 5 prime end--", "start": 478.11, "duration": 5.34}, {"text": "that number's not shown there,\nbut it's shown over here--", "start": 483.45, "duration": 2.97}, {"text": "and you add to the 3 prime end.", "start": 486.42, "duration": 3.14}, {"text": "And the convention,\nremember, when", "start": 489.56, "duration": 1.6}, {"text": "we describe a strand of DNA,\nbecause we make it 5 prime", "start": 491.16, "duration": 3.81}, {"text": "to 3 prime, we write\nit 5 prime to 3 prime", "start": 494.97, "duration": 3.51}, {"text": "just so that we're\nall consistent", "start": 498.48, "duration": 1.5}, {"text": "and we know what\nwe're talking about.", "start": 499.98, "duration": 1.86}, {"text": "Now I want to talk about\ntwo experiments that", "start": 501.84, "duration": 4.23}, {"text": "enlist the use of isotopes\nbecause these were quite useful", "start": 506.07, "duration": 6.12}, {"text": "early on to describe some of the\ncharacteristics of replication,", "start": 512.19, "duration": 5.79}, {"text": "so some of the details of\nreplication, and also the fact", "start": 517.98, "duration": 3.39}, {"text": "that DNA was the\ngenetic material.", "start": 521.37, "duration": 3.06}, {"text": "So isotopes are\nelements that share", "start": 524.43, "duration": 3.24}, {"text": "the same number of\nprotons and electrons,", "start": 527.67, "duration": 3.28}, {"text": "but they differ in the\nnumber of neutrons.", "start": 530.95, "duration": 2.96}, {"text": "So the common isotopes\nof the elements", "start": 533.91, "duration": 3.39}, {"text": "that are in all the covalent\nstructures of the body", "start": 537.3, "duration": 4.08}, {"text": "are hydrogen,\ncarbon, and what I'm", "start": 541.38, "duration": 7.2}, {"text": "putting as the number next\nto it is the common isotope,", "start": 548.58, "duration": 3.69}, {"text": "so that number designates the\nsum of the number of neutrons", "start": 552.27, "duration": 5.34}, {"text": "and protons.", "start": 557.61, "duration": 0.87}, {"text": "So carbon-12, phosphorus-31.", "start": 558.48, "duration": 2.82}, {"text": "I should have put nitrogen here.", "start": 564.86, "duration": 1.95}, {"text": "Let's see.", "start": 566.81, "duration": 0.527}, {"text": "Wait a minute.", "start": 567.337, "duration": 0.583}, {"text": "I'm going to put these in order\nbecause it makes more sense.", "start": 567.92, "duration": 2.88}, {"text": "Phosphorus-31, nitrogen-14,\nPS, phosphorus-31, and sulfur.", "start": 570.8, "duration": 9.03}, {"text": "What's the sulfur isotope?", "start": 579.83, "duration": 1.53}, {"text": "32.", "start": 581.36, "duration": 2.31}, {"text": "So these are the\ncommon isotopes that", "start": 583.67, "duration": 3.99}, {"text": "comprise the majority of those\nelements within the body.", "start": 587.66, "duration": 4.11}, {"text": "But there are lots\nof experiments", "start": 591.77, "duration": 1.62}, {"text": "done that have different\nisotopes of these atoms", "start": 593.39, "duration": 3.95}, {"text": "that we can use as\ntraces or markers, kind", "start": 597.34, "duration": 10.84}, {"text": "of the same thing.", "start": 608.18, "duration": 0.79}, {"text": "But you'll see when I mention\nthe word tracer, to me,", "start": 608.97, "duration": 3.08}, {"text": "it brings up the radioactive\nisotopes because we", "start": 612.05, "duration": 3.48}, {"text": "use very little of them.", "start": 615.53, "duration": 1.84}, {"text": "So when we talk\nabout these elements,", "start": 617.37, "duration": 2.54}, {"text": "there are different isotopes\nthat we use commonly.", "start": 619.91, "duration": 3.51}, {"text": "There's the hydrogen that\nhas an extra neutron.", "start": 623.42, "duration": 3.15}, {"text": "That's also called deuterium.", "start": 626.57, "duration": 1.71}, {"text": "And then there's the\nhydrogen that is radioactive.", "start": 634.39, "duration": 4.29}, {"text": "It's metastable.", "start": 638.68, "duration": 1.23}, {"text": "It will decay and emit\na radioactive particle.", "start": 639.91, "duration": 4.08}, {"text": "So this one, we would\ncall it the heavy isotope,", "start": 643.99, "duration": 4.47}, {"text": "and this one we would call\nthe radioactive isotope.", "start": 648.46, "duration": 6.53}, {"text": "So we could trace certain\nhydrogens in biomolecules", "start": 654.99, "duration": 4.83}, {"text": "by either making those\nhydrogens the heavier ones,", "start": 659.82, "duration": 2.85}, {"text": "or making them the\nradioactive ones.", "start": 662.67, "duration": 2.34}, {"text": "Carbon also has useful isotopes.", "start": 665.01, "duration": 2.97}, {"text": "Carbon-13 is the heavy\nisotope and carbon-14", "start": 667.98, "duration": 7.34}, {"text": "is the radioactive isotope.", "start": 675.32, "duration": 1.93}, {"text": "So they're used quite commonly.", "start": 677.25, "duration": 2.13}, {"text": "And then things get a little\nbit different for nitrogen.", "start": 679.38, "duration": 3.09}, {"text": "We use a heavy isotope of\nnitrogen, which is N-15, just", "start": 682.47, "duration": 4.32}, {"text": "one extra neutron.", "start": 686.79, "duration": 1.6}, {"text": "But while there is a\nradioactive isotope of nitrogen,", "start": 688.39, "duration": 3.44}, {"text": "it's too short of a half-life\nto work within the lab.", "start": 691.83, "duration": 3.33}, {"text": "It's not useful to us, so\nwe never talk about it.", "start": 695.16, "duration": 2.73}, {"text": "But I will describe\nto you an experiment", "start": 697.89, "duration": 2.67}, {"text": "with the heavy N-15 when\nwe talk about the mechanism", "start": 700.56, "duration": 3.33}, {"text": "of replication.", "start": 703.89, "duration": 1.42}, {"text": "And then for\nphosphorus and sulfur,", "start": 705.31, "duration": 4.1}, {"text": "the most important\nones are P-32,", "start": 709.41, "duration": 4.14}, {"text": "which is a radioactive\nphosphorus,", "start": 713.55, "duration": 3.03}, {"text": "and S-35, which is a\nradioactive sulfur.", "start": 716.58, "duration": 5.97}, {"text": "There is another radioactive\nphosphorus that's P-33.", "start": 722.55, "duration": 3.66}, {"text": "Has a slightly longer half life.", "start": 726.21, "duration": 1.59}, {"text": "It's kind of handy\nto work with if you", "start": 727.8, "duration": 1.74}, {"text": "have certain experiments.", "start": 729.54, "duration": 1.95}, {"text": "The half-lives vary a lot, but\nthe half-life of tritium C-14", "start": 731.49, "duration": 4.56}, {"text": "are long.", "start": 736.05, "duration": 1.08}, {"text": "That's why we do carbon dating.", "start": 737.13, "duration": 2.01}, {"text": "The half-lives of P-32 are\nshort, less daytime frame,", "start": 739.14, "duration": 6.81}, {"text": "and sulfur 35 is a\nlittle bit longer.", "start": 745.95, "duration": 1.92}, {"text": "But those are nuances that\nyou don't need to worry about.", "start": 747.87, "duration": 2.94}, {"text": "Now how are these\nisotopes useful", "start": 750.81, "duration": 2.4}, {"text": "as traces and markers to tell\nus about biology and details", "start": 753.21, "duration": 5.07}, {"text": "of biology?", "start": 758.28, "duration": 1.15}, {"text": "So what I'm going to\njust show you here", "start": 759.43, "duration": 1.73}, {"text": "is a particular\nexperiment that's", "start": 761.16, "duration": 2.13}, {"text": "carried out with what\nare known as baculovirus.", "start": 763.29, "duration": 3.06}, {"text": "So viruses infect\neukaryotic cells.", "start": 766.35, "duration": 3.99}, {"text": "Baculoviruses infect bacteria.", "start": 770.34, "duration": 2.88}, {"text": "So there's a commonality there.", "start": 773.22, "duration": 2.04}, {"text": "And when baculoviruses infect\nbacteria, just as the parallel", "start": 775.26, "duration": 4.29}, {"text": "with eukaryotic cells,\nthey deposit material", "start": 779.55, "duration": 3.99}, {"text": "into the bacteria so\nthey can replicate,", "start": 783.54, "duration": 3.13}, {"text": "so they can hijack the bacteria\nto make new baculoviruses.", "start": 786.67, "duration": 5.45}, {"text": "So an early experiment\nwas done to ask", "start": 792.12, "duration": 3.18}, {"text": "what is the genetic material\nthat transfers the information", "start": 795.3, "duration": 4.47}, {"text": "from the baculovirus\nto the bacterial cell", "start": 799.77, "duration": 4.05}, {"text": "in order to make\nmore baculovirus.", "start": 803.82, "duration": 2.82}, {"text": "So they were able to\ndemonstrate, in this Hershey", "start": 806.64, "duration": 4.14}, {"text": "and Chase experiment,\nthat you could", "start": 810.78, "duration": 3.66}, {"text": "label protein and DNA\nwith particular isotopes", "start": 814.44, "duration": 6.39}, {"text": "and find out what part\nof the baculovirus", "start": 820.83, "duration": 3.39}, {"text": "was important for\ntransferring information", "start": 824.22, "duration": 3.0}, {"text": "for the production\nof new baculovirus.", "start": 827.22, "duration": 3.12}, {"text": "So they wanted to label\nthe capsid protein,", "start": 830.34, "duration": 3.46}, {"text": "so the proteinaceous\nmaterial that's", "start": 833.8, "duration": 2.33}, {"text": "on the outside of\nthis lunar lander.", "start": 836.13, "duration": 2.85}, {"text": "This is a baculovirus.", "start": 838.98, "duration": 1.2}, {"text": "It's sort of amazing\nhow it looks.", "start": 840.18, "duration": 2.1}, {"text": "So they wanted to\nlabel the protein.", "start": 842.28, "duration": 1.95}, {"text": "But they also wanted\nto label the contents", "start": 844.23, "duration": 3.0}, {"text": "of the baculovirus, the DNA,\nwith tracer radioisotopes.", "start": 847.23, "duration": 5.41}, {"text": "So what would be\nthe best isotopes", "start": 852.64, "duration": 1.82}, {"text": "to use if you wanted to\ndifferentiate between protein", "start": 854.46, "duration": 3.9}, {"text": "and nucleic acid?", "start": 858.36, "duration": 1.98}, {"text": "And what you want\nto think about is,", "start": 860.34, "duration": 1.69}, {"text": "what does protein have that\nnucleic acids don't have,", "start": 862.03, "duration": 2.81}, {"text": "and what do nucleic acids\nhave that proteins don't have?", "start": 864.84, "duration": 2.82}, {"text": "Which are the elements that are\nimportant for differentiating?", "start": 867.66, "duration": 4.21}, {"text": "Yeah.", "start": 871.87, "duration": 0.5}, {"text": "Over there.", "start": 872.37, "duration": 2.515}, {"text": "AUDIENCE: Phosphorus.", "start": 874.885, "duration": 0.875}, {"text": "BARBARA IMPERIALI:\nYes, phosphorus.", "start": 875.76, "duration": 1.458}, {"text": "Do you want to give a\nlittle bit more of a--", "start": 877.218, "duration": 3.014}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 880.232, "duration": 3.998}, {"text": "BARBARA IMPERIALI: OK.", "start": 884.23, "duration": 1.04}, {"text": "So the answer is\nwe'd use phosphorus", "start": 885.27, "duration": 2.94}, {"text": "to label nucleic acids because\nthat phosphodiester backbone is", "start": 888.21, "duration": 4.53}, {"text": "rich in phosphorus.", "start": 892.74, "duration": 1.44}, {"text": "There are a few\nphosphates in proteins,", "start": 894.18, "duration": 2.07}, {"text": "but they're very transient.", "start": 896.25, "duration": 1.2}, {"text": "They're part of signaling.", "start": 897.45, "duration": 1.32}, {"text": "But every nucleotide\nhas a phosphorus", "start": 898.77, "duration": 3.42}, {"text": "in every building block.", "start": 902.19, "duration": 1.45}, {"text": "And then in proteins,\nthey have sulfur in them", "start": 903.64, "duration": 3.44}, {"text": "where nucleic acids do not.", "start": 907.08, "duration": 2.19}, {"text": "And the sulfur is in two amino\nacids cystine and methionine.", "start": 909.27, "duration": 4.14}, {"text": "So you can use those two\ntracers for the building blocks.", "start": 913.41, "duration": 4.31}, {"text": "And the way the\nexperiment works is", "start": 917.72, "duration": 2.29}, {"text": "if you've labeled the protein\nwith sulfur, you infect a cell,", "start": 920.01, "duration": 5.07}, {"text": "the virus replicates.", "start": 925.08, "duration": 2.31}, {"text": "And what you're\ngoing to do is then", "start": 927.39, "duration": 2.85}, {"text": "centrifuge the bacterial cells\nto see what's in the cell,", "start": 930.24, "duration": 5.31}, {"text": "and then you can,\nalternatively, label the DNA--", "start": 935.55, "duration": 3.81}, {"text": "and in this case, I've\nshown it as green,", "start": 939.36, "duration": 1.74}, {"text": "but that would be\nthe other isotope--", "start": 941.1, "duration": 2.01}, {"text": "let it infect the cell\nand deposit its contents", "start": 943.11, "duration": 3.18}, {"text": "in the cell, centrifuge\nthe cells out.", "start": 946.29, "duration": 2.9}, {"text": "And you want to know where\nthe radioactivity is,", "start": 949.19, "duration": 3.07}, {"text": "and the radioactivity\nis strictly", "start": 952.26, "duration": 1.83}, {"text": "associated with phosphorus-32\nbecause the genetic material", "start": 954.09, "duration": 4.92}, {"text": "that coded for the\nproduction of new baculovirus", "start": 959.01, "duration": 3.36}, {"text": "is the thing that\nstays associated", "start": 962.37, "duration": 1.71}, {"text": "with the bacterial cell.", "start": 964.08, "duration": 1.69}, {"text": "In contrast, there's no\nradioactivity associated when", "start": 965.77, "duration": 5.74}, {"text": "you label the cells with S-35.", "start": 971.51, "duration": 3.45}, {"text": "All right?", "start": 974.96, "duration": 0.6}, {"text": "Nice experiment.", "start": 975.56, "duration": 1.47}, {"text": "Easy way to do it.", "start": 977.03, "duration": 1.83}, {"text": "Rather nice way to do it.", "start": 978.86, "duration": 1.803}, {"text": "The other experiment I\nwant to describe to you", "start": 980.663, "duration": 1.917}, {"text": "very briefly because it\nrelies on central irrigation", "start": 982.58, "duration": 2.88}, {"text": "technology that's very powerful.", "start": 985.46, "duration": 3.09}, {"text": "And it's a method that utilizes\nN-15 very, very nicely.", "start": 988.55, "duration": 9.43}, {"text": "So let me tell you\nabout that experiment.", "start": 997.98, "duration": 2.37}, {"text": "There are things\nin the laboratory", "start": 1000.35, "duration": 1.86}, {"text": "that we use every\nday, ultra centrifuges", "start": 1002.21, "duration": 2.76}, {"text": "and regular centrifuges, that\nspin at a very fast speed", "start": 1004.97, "duration": 3.51}, {"text": "where we can really\ndifferentiate things", "start": 1008.48, "duration": 2.16}, {"text": "by molecular mass, which relates\nto sedimentation coefficients.", "start": 1010.64, "duration": 5.07}, {"text": "How fast does the particle\nspin to the bottom of the tube", "start": 1015.71, "duration": 4.17}, {"text": "when it's under high\ncentrifugal force?", "start": 1019.88, "duration": 2.74}, {"text": "The heavier it is, the\nfaster it will spin.", "start": 1022.62, "duration": 3.199}, {"text": "So the question that came\nup very early on-- it", "start": 1025.819, "duration": 2.371}, {"text": "looks like a\nnonsense question now", "start": 1028.19, "duration": 1.59}, {"text": "because it looks so obvious that\nwe replicate DNA the way we do.", "start": 1029.78, "duration": 4.14}, {"text": "But originally, it\nwasn't absolutely certain", "start": 1033.92, "duration": 3.0}, {"text": "whether DNA was replicated\nthrough a semi-conservative", "start": 1036.92, "duration": 3.72}, {"text": "mechanism, where the\nstrands came apart", "start": 1040.64, "duration": 2.52}, {"text": "and you made two copies,\na copy of each strand,", "start": 1043.16, "duration": 2.909}, {"text": "to make two identical daughter\nnew double-stranded DNA.", "start": 1046.069, "duration": 5.191}, {"text": "Alternatively, could you\nhave a mechanism that", "start": 1051.26, "duration": 2.46}, {"text": "was quite conservative,\nyou kept your DNA,", "start": 1053.72, "duration": 2.16}, {"text": "and somehow you\nmade a copy of it.", "start": 1055.88, "duration": 2.29}, {"text": "A little harder for\nme to understand.", "start": 1058.17, "duration": 1.76}, {"text": "So your two new\nstrands, one would", "start": 1059.93, "duration": 2.94}, {"text": "look like the original one, but\none would be very different.", "start": 1062.87, "duration": 4.23}, {"text": "Or dispersive, where you're\njust copying bits of the DNA", "start": 1067.1, "duration": 2.97}, {"text": "and somehow reassembling\nthis gigantic jigsaw puzzle.", "start": 1070.07, "duration": 4.2}, {"text": "The centrifugation\nexperiment allowed", "start": 1074.27, "duration": 3.36}, {"text": "people to absolutely\nand clearly state", "start": 1077.63, "duration": 2.55}, {"text": "that the replication is via\na semi-conservative process.", "start": 1080.18, "duration": 4.31}, {"text": "So let's walk through it.", "start": 1084.49, "duration": 1.2}, {"text": "And what was done is that the\nnucleotides within the DNA", "start": 1085.69, "duration": 4.78}, {"text": "were all labeled\nwith heavy nitrogen.", "start": 1090.47, "duration": 2.82}, {"text": "So for every nucleic acid--", "start": 1093.29, "duration": 2.11}, {"text": "let's say, for\nexample, when there's", "start": 1095.4, "duration": 1.73}, {"text": "an adenine in the backbone,\nthere are five nitrogens,", "start": 1097.13, "duration": 4.41}, {"text": "so that would be\nfive atomic mass", "start": 1101.54, "duration": 1.98}, {"text": "units heavier than nitrogen-14\nin that nucleobase.", "start": 1103.52, "duration": 5.16}, {"text": "So N-15 nucleobase, five\nmass units heavier than N-14", "start": 1108.68, "duration": 4.11}, {"text": "nucleobase.", "start": 1112.79, "duration": 0.84}, {"text": "Make sense to everybody?", "start": 1113.63, "duration": 1.5}, {"text": "All right.", "start": 1115.13, "duration": 0.5}, {"text": "So it's heavier by some amount.", "start": 1115.63, "duration": 1.89}, {"text": "It's not a massive\namount, but it's", "start": 1117.52, "duration": 1.96}, {"text": "enough to differentiate in\na centrifugation experiment.", "start": 1119.48, "duration": 3.39}, {"text": "So the bacteria were first\ngrown up in heavy nitrogen,", "start": 1122.87, "duration": 3.81}, {"text": "so all of the DNA sediments\nat a certain rate and place.", "start": 1126.68, "duration": 6.48}, {"text": "And it's all got N-15\nin it, so it's as heavy", "start": 1133.16, "duration": 2.88}, {"text": "as it can sediment.", "start": 1136.04, "duration": 1.29}, {"text": "And then they let the\nbacteria replicate", "start": 1137.33, "duration": 2.82}, {"text": "in the presence of N-14, the\nlighter isotope of nitrogen.", "start": 1140.15, "duration": 5.2}, {"text": "And what one would\nanticipate to happen", "start": 1145.35, "duration": 2.12}, {"text": "is whenever you\nreplicate, you peel apart", "start": 1147.47, "duration": 2.13}, {"text": "the two heavy strands, and each\none pairs with a light strand.", "start": 1149.6, "duration": 5.07}, {"text": "So you now have two copies,\ntwo new identical copies of DNA", "start": 1154.67, "duration": 5.55}, {"text": "where half of one strand has\nN-15, one strand has N-14.", "start": 1160.22, "duration": 6.94}, {"text": "So it will sediment\nless quickly because it", "start": 1167.16, "duration": 3.26}, {"text": "is of a different\ndensity, a lighter", "start": 1170.42, "duration": 1.83}, {"text": "density than the all N-15.", "start": 1172.25, "duration": 2.28}, {"text": "So you would get an\nintermediate weight band", "start": 1174.53, "duration": 3.15}, {"text": "in the centrifuge tube\nwhen you're sedimenting.", "start": 1177.68, "duration": 2.88}, {"text": "If you peel those two\nstrands apart again,", "start": 1180.56, "duration": 3.57}, {"text": "you've got a heavy and a light.", "start": 1184.13, "duration": 1.89}, {"text": "If you're growing\nin N-14, the light", "start": 1186.02, "duration": 2.19}, {"text": "will combine with another light,\nand there are two of those.", "start": 1188.21, "duration": 5.88}, {"text": "And then the heavy will\ncombine with a light.", "start": 1194.09, "duration": 1.98}, {"text": "So you'll get new\nsedimentation where you still", "start": 1196.07, "duration": 3.15}, {"text": "have a band that's\nthe combination", "start": 1199.22, "duration": 2.28}, {"text": "of the light and heavy.", "start": 1201.5, "duration": 1.8}, {"text": "But then you start\nhaving some material", "start": 1203.3, "duration": 2.49}, {"text": "that is all of the light.", "start": 1205.79, "duration": 1.54}, {"text": "So this would be this cycle.", "start": 1207.33, "duration": 1.85}, {"text": "So two that are still light\nplus heavy, and then two that", "start": 1209.18, "duration": 4.62}, {"text": "are exclusively light.", "start": 1213.8, "duration": 2.13}, {"text": "You keep on\nreplicating, and you'll", "start": 1215.93, "duration": 1.8}, {"text": "keep on diluting the heavy.", "start": 1217.73, "duration": 1.86}, {"text": "Does that experiment make sense?", "start": 1219.59, "duration": 2.71}, {"text": "It's kind of a cool experiment.", "start": 1222.3, "duration": 1.34}, {"text": "You can hardly\nbelieve it's feasible,", "start": 1223.64, "duration": 1.86}, {"text": "but the centrifugation\nability to differentiate", "start": 1225.5, "duration": 3.6}, {"text": "with these isotopes\nis really valuable.", "start": 1229.1, "duration": 2.22}, {"text": "So I just want to put in a\nplug for the use of isotopes.", "start": 1231.32, "duration": 3.36}, {"text": "Obviously, they're used\nin nuclear physics.", "start": 1234.68, "duration": 2.25}, {"text": "We use a lot of the radioactive\nisotopes for different reasons.", "start": 1236.93, "duration": 4.38}, {"text": "But in biology, they are\nindispensable for some", "start": 1241.31, "duration": 3.03}, {"text": "of these experiments.", "start": 1244.34, "duration": 1.02}, {"text": "And even to this day,\nyou can do things", "start": 1245.36, "duration": 1.89}, {"text": "with isotopes you can't by\nother experiments, either", "start": 1247.25, "duration": 5.16}, {"text": "the radioactive or the heavy.", "start": 1252.41, "duration": 2.0}, {"text": "There's a great deal of work\ndone nowadays in proteomics", "start": 1254.41, "duration": 4.42}, {"text": "using mass spectrometry\nand heavy isotopes,", "start": 1258.83, "duration": 3.0}, {"text": "where you can really\ntrack where things go", "start": 1261.83, "duration": 2.85}, {"text": "and treat cancer cells\ndifferently from healthy cells,", "start": 1264.68, "duration": 4.35}, {"text": "but actually track\nwhat's happening", "start": 1269.03, "duration": 1.74}, {"text": "by putting heavy isotopes in one\nof the growing dishes of cells.", "start": 1270.77, "duration": 3.945}, {"text": "So I like both of those\nexperiments a lot.", "start": 1279.35, "duration": 3.54}, {"text": "I would put them in the\ncategory of oldies but goodies.", "start": 1282.89, "duration": 3.21}, {"text": "All right.", "start": 1286.1, "duration": 0.66}, {"text": "Now I've got some\ndetails over here", "start": 1286.76, "duration": 2.34}, {"text": "that we've got some explaining\nto do as we move forward.", "start": 1289.1, "duration": 3.815}, {"text": "And I just want\nto, first of all,", "start": 1292.915, "duration": 1.375}, {"text": "start with a couple\nof details that I want", "start": 1294.29, "duration": 2.25}, {"text": "to highlight on this board.", "start": 1296.54, "duration": 3.48}, {"text": "First of all, prokaryotes\nsuch as bacteria, E. Coli,", "start": 1303.63, "duration": 7.47}, {"text": "and eukaryotes such\nas human cells.", "start": 1311.1, "duration": 2.52}, {"text": "Have some differences\nin their DNA.", "start": 1313.62, "duration": 2.71}, {"text": "So the size of the\nbacterial genome", "start": 1316.33, "duration": 2.87}, {"text": "is about five\nmillion base pairs.", "start": 1319.2, "duration": 3.21}, {"text": "The size of the human genome is\nnot quite 1,000 times bigger,", "start": 1322.41, "duration": 3.9}, {"text": "but a good deal bigger.", "start": 1326.31, "duration": 4.26}, {"text": "The DNA in bacteria is\ncircular, whereas the DNA", "start": 1330.57, "duration": 5.07}, {"text": "in eukaryotic cells is linear.", "start": 1335.64, "duration": 2.58}, {"text": "And it's actually in the form--\nyou see all these little images", "start": 1338.22, "duration": 3.15}, {"text": "where you see the pairs of\nchromosomes sort of stuck", "start": 1341.37, "duration": 3.84}, {"text": "together at the\ncenter, and that's", "start": 1345.21, "duration": 2.19}, {"text": "linear DNA from one\nend to the other.", "start": 1347.4, "duration": 2.76}, {"text": "In bacteria, the\nDNA is circular,", "start": 1350.16, "duration": 3.34}, {"text": "so it doesn't have an end.", "start": 1353.5, "duration": 1.25}, {"text": "So they're different, all right?", "start": 1354.75, "duration": 2.1}, {"text": "So replicating circular\nDNA is a little bit", "start": 1356.85, "duration": 3.45}, {"text": "different from\nreplicating linear DNA.", "start": 1360.3, "duration": 4.32}, {"text": "Now in both cases, the\nDNA has to be packaged up", "start": 1364.62, "duration": 4.35}, {"text": "so it will fit in the cell.", "start": 1368.97, "duration": 1.99}, {"text": "Otherwise, it's just too\nmuch of a disordered thing.", "start": 1370.96, "duration": 2.97}, {"text": "In the case of bacteria, the\ncircular DNA is wrapped up", "start": 1373.93, "duration": 5.57}, {"text": "and super coiled\nwith what are known", "start": 1379.5, "duration": 1.5}, {"text": "as a polyamines, compounds\nthat are very positively", "start": 1381.0, "duration": 3.24}, {"text": "charged to neutralize all that\nnegative charge in the DNA.", "start": 1384.24, "duration": 4.95}, {"text": "And in man and other\neukaryotes, the chromosomes", "start": 1389.19, "duration": 4.05}, {"text": "are wrapped around very,\nvery positively charged", "start": 1393.24, "duration": 3.0}, {"text": "proteins known as histones.", "start": 1396.24, "duration": 2.43}, {"text": "They're similar principles,\nbut they're different entities.", "start": 1398.67, "duration": 3.87}, {"text": "So when we start talking\nabout replication", "start": 1402.54, "duration": 3.9}, {"text": "of a prokaryotic cell, here's\nthe typical circular DNA.", "start": 1406.44, "duration": 4.71}, {"text": "So you can see the\ndouble-stranded DNA.", "start": 1411.15, "duration": 2.19}, {"text": "And I've put a little symbol\nhere that I call the ORI.", "start": 1413.34, "duration": 5.23}, {"text": "So that's origin of initiation.", "start": 1422.8, "duration": 4.68}, {"text": "So that is the place where\nyou start copying your DNA.", "start": 1430.36, "duration": 3.935}, {"text": "And we're going\nto talk about how", "start": 1434.295, "duration": 1.375}, {"text": "to spot these places\nin genomes in a moment.", "start": 1435.67, "duration": 4.09}, {"text": "And so the bacterial genome\nis copied bidirectionally,", "start": 1439.76, "duration": 5.96}, {"text": "so you can go in both directions\ncopying in the appropriate", "start": 1445.72, "duration": 5.16}, {"text": "direction-- we'll talk\nabout that in a moment--", "start": 1450.88, "duration": 2.9}, {"text": "to make the entire circular DNA\nand a perfect copy of the DNA", "start": 1453.78, "duration": 5.29}, {"text": "with bidirectional copying.", "start": 1459.07, "duration": 2.4}, {"text": "And that's not bad\nfor small genomes", "start": 1461.47, "duration": 2.34}, {"text": "because you've only got\none origin of replication.", "start": 1463.81, "duration": 2.34}, {"text": "You've got to get all the\nway around the circular DNA.", "start": 1466.15, "duration": 3.9}, {"text": "It's quite a bit smaller\nthan the human one.", "start": 1470.05, "duration": 2.58}, {"text": "But what do you do\nwith gigantic genomes", "start": 1472.63, "duration": 4.68}, {"text": "such as the one that's\nabout 1,000 times bigger", "start": 1477.31, "duration": 3.21}, {"text": "than the bacterial one?", "start": 1480.52, "duration": 1.65}, {"text": "How do you manage\nto still catalyze", "start": 1482.17, "duration": 3.57}, {"text": "the replication of\nthe entire genome", "start": 1485.74, "duration": 2.28}, {"text": "quickly enough to\nmake the copy of DNA", "start": 1488.02, "duration": 3.27}, {"text": "in some reasonable\namount of time?", "start": 1491.29, "duration": 2.52}, {"text": "And that is taking\nalso into consideration", "start": 1493.81, "duration": 3.12}, {"text": "that the speed of\nbacterial replication", "start": 1496.93, "duration": 2.76}, {"text": "is 1,000 base pairs per second.", "start": 1499.69, "duration": 2.52}, {"text": "Pretty impressive-- 1,000 of\nthose bonds made every second--", "start": 1502.21, "duration": 3.63}, {"text": "whereas in eukaryotes,\nit sits somewhere down", "start": 1505.84, "duration": 2.31}, {"text": "from 50 base pairs per second,\ndepending on conditions.", "start": 1508.15, "duration": 4.5}, {"text": "These are not very\nexplicit numbers.", "start": 1512.65, "duration": 2.75}, {"text": "There's a little\nbit of variability.", "start": 1515.4, "duration": 3.19}, {"text": "So how would you do it?", "start": 1518.59, "duration": 1.25}, {"text": "If you had this\nmassive chunk of gene,", "start": 1519.84, "duration": 3.63}, {"text": "and you've got to copy it just\nreally pretty quickly in order", "start": 1523.47, "duration": 5.07}, {"text": "to replicate an entire cell\ncontents in eight hours,", "start": 1528.54, "duration": 3.99}, {"text": "what would you do?", "start": 1532.53, "duration": 1.29}, {"text": "How could you expedite things?", "start": 1533.82, "duration": 2.641}, {"text": "Yeah.", "start": 1536.461, "duration": 2.409}, {"text": "Yes.", "start": 1538.87, "duration": 1.41}, {"text": "So the answer here is start\nin a lot of different places", "start": 1540.28, "duration": 3.46}, {"text": "so there's a lot of\ncollaborative work going", "start": 1543.74, "duration": 2.15}, {"text": "on all along that large genome.", "start": 1545.89, "duration": 4.44}, {"text": "And so when the replication\nof the long linear chromosomes", "start": 1550.33, "duration": 5.15}, {"text": "that are in\neukaryotic cells, you", "start": 1555.48, "duration": 2.01}, {"text": "end up with just a lot of\norigins of replication.", "start": 1557.49, "duration": 3.93}, {"text": "So you're basically\nstarting all over the place", "start": 1561.42, "duration": 2.46}, {"text": "so you can get the job\ndone quickly enough for it", "start": 1563.88, "duration": 2.64}, {"text": "to make sense.", "start": 1566.52, "duration": 0.94}, {"text": "Does that make\nsense to everybody?", "start": 1567.46, "duration": 3.45}, {"text": "So start in a lot of places.", "start": 1570.91, "duration": 1.55}, {"text": "It's a pretty easy thing.", "start": 1572.46, "duration": 1.36}, {"text": "All right.", "start": 1573.82, "duration": 0.5}, {"text": "Now I mentioned very briefly\nthat before you can copy DNA,", "start": 1574.32, "duration": 7.35}, {"text": "you have to unpack it.", "start": 1581.67, "duration": 1.8}, {"text": "Now we think a lot\nabout packaging DNA,", "start": 1583.47, "duration": 4.47}, {"text": "less about unpacking it.", "start": 1587.94, "duration": 1.69}, {"text": "So I've got these pictures\nsort of in a reverse direction.", "start": 1589.63, "duration": 3.03}, {"text": "So it's only this form\nof DNA stretched out", "start": 1592.66, "duration": 4.58}, {"text": "that can be copied, whereas\nthe DNA in your cells", "start": 1597.24, "duration": 4.05}, {"text": "is bundled up very\ntightly into chromosomes.", "start": 1601.29, "duration": 3.24}, {"text": "How are they put together?", "start": 1604.53, "duration": 1.83}, {"text": "Those chromosomes are\nmade up of chromatin,", "start": 1606.36, "duration": 3.87}, {"text": "which is a bunch of balls which\nare histone proteins with DNA", "start": 1610.23, "duration": 4.17}, {"text": "wrapped around them.", "start": 1614.4, "duration": 3.18}, {"text": "That's compact chromatin.", "start": 1617.58, "duration": 2.37}, {"text": "Sorry, guys.", "start": 1619.95, "duration": 0.64}, {"text": "Let me go back,\nnot to go forwards.", "start": 1620.59, "duration": 3.26}, {"text": "So this is chromatin\nin a compact form.", "start": 1623.85, "duration": 3.18}, {"text": "This is chromatin now unraveled.", "start": 1627.03, "duration": 2.34}, {"text": "They look more like\nbeads on a string,", "start": 1629.37, "duration": 2.04}, {"text": "DNA wrapped around\neach histone protein", "start": 1631.41, "duration": 3.0}, {"text": "to form those\nnucleosomes structures.", "start": 1634.41, "duration": 3.03}, {"text": "And then each nucleosome\nlooks like this.", "start": 1637.44, "duration": 3.61}, {"text": "It's got protein in the middle\nand DNA wrapped around it.", "start": 1641.05, "duration": 3.63}, {"text": "So in order to go\nforward and replicate,", "start": 1644.68, "duration": 2.75}, {"text": "we have to unpackage DNA.", "start": 1647.43, "duration": 2.67}, {"text": "There are lots of signals\nto unpackage the DNA that we", "start": 1650.1, "duration": 3.18}, {"text": "will talk about later.", "start": 1653.28, "duration": 1.77}, {"text": "The nucleosomes look like this.", "start": 1655.05, "duration": 2.56}, {"text": "So you can trace the DNA and the\nproteins bundled in the middle.", "start": 1657.61, "duration": 4.975}, {"text": "And if we have\ntime at the end, I", "start": 1662.585, "duration": 1.375}, {"text": "will show you the video\nof the packaging of DNA", "start": 1663.96, "duration": 4.65}, {"text": "and the video of the\nreplication of DNA.", "start": 1668.61, "duration": 2.49}, {"text": "They're about a minute\nand a half each,", "start": 1671.1, "duration": 1.77}, {"text": "so it's not a whole bunch.", "start": 1672.87, "duration": 1.41}, {"text": "Later on, we will\ntalk about what", "start": 1674.28, "duration": 2.55}, {"text": "happens when there is a\ndetermination that a cell needs", "start": 1676.83, "duration": 3.45}, {"text": "to replicate its genome.", "start": 1680.28, "duration": 2.04}, {"text": "A bunch of things have\nto happen as signals", "start": 1682.32, "duration": 2.79}, {"text": "to do the unwrapping.", "start": 1685.11, "duration": 2.04}, {"text": "And one of those\nthings is actually", "start": 1687.15, "duration": 2.01}, {"text": "to alter the charged state\nof the histone proteins", "start": 1689.16, "duration": 3.99}, {"text": "so you neutralize\nthe positive charges", "start": 1693.15, "duration": 2.52}, {"text": "so the DNA can unravel for it.", "start": 1695.67, "duration": 1.95}, {"text": "Makes sense.", "start": 1697.62, "duration": 0.57}, {"text": "It's still just a plain old\nelectrostatic interaction.", "start": 1698.19, "duration": 3.18}, {"text": "So the synthesis\nof DNA is what's", "start": 1701.37, "duration": 3.81}, {"text": "known as template-driven\npolymerization.", "start": 1705.18, "duration": 10.35}, {"text": "OK.", "start": 1722.74, "duration": 0.5}, {"text": "So template-driven\npolymerization.", "start": 1723.24, "duration": 3.14}, {"text": "You'll get a sense of\nexactly what that means.", "start": 1726.38, "duration": 2.83}, {"text": "We know the two strands\nare complementary,", "start": 1729.21, "duration": 2.64}, {"text": "and we're going to use\none strand as the code", "start": 1731.85, "duration": 2.13}, {"text": "to make a new\ncomplementary strand.", "start": 1733.98, "duration": 2.58}, {"text": "So when we're making DNA,\nwe have one strand there.", "start": 1736.56, "duration": 3.36}, {"text": "That's what's known as\nthe template strand.", "start": 1739.92, "duration": 3.03}, {"text": "I want to make a complementary\ncopy of that strand.", "start": 1742.95, "duration": 3.69}, {"text": "So what the DNA\npolymerase is going to do", "start": 1746.64, "duration": 3.24}, {"text": "is systematically\nadd nucleotides", "start": 1749.88, "duration": 5.31}, {"text": "to the 3 prime OH of the ribose,\nand then you keep growing.", "start": 1755.19, "duration": 4.95}, {"text": "But the base that\ngets put in is the one", "start": 1760.14, "duration": 2.52}, {"text": "that's complementary to the\nbase on the template strand.", "start": 1762.66, "duration": 3.9}, {"text": "So if it's thiamine on\nthe template strand,", "start": 1766.56, "duration": 2.54}, {"text": "it's adenine put in on\nthe new strand, and so on.", "start": 1769.1, "duration": 5.2}, {"text": "And just to get\nthese numbers again,", "start": 1774.3, "duration": 2.01}, {"text": "the new strand is grown\nfrom 5 prime to 3 prime.", "start": 1776.31, "duration": 4.62}, {"text": "The old strand is read\n3 prime to 5 prime.", "start": 1780.93, "duration": 4.25}, {"text": "So you're reading a strand\nand you're reading it 3 to 5,", "start": 1785.18, "duration": 3.37}, {"text": "and you're making 5 to 3.", "start": 1788.55, "duration": 2.04}, {"text": "That's how you end up with\ncomplementary anti-parallel", "start": 1790.59, "duration": 3.21}, {"text": "strands.", "start": 1793.8, "duration": 1.8}, {"text": "OK with that, everyone?", "start": 1795.6, "duration": 2.48}, {"text": "All right.", "start": 1798.08, "duration": 0.61}, {"text": "And when you form\nthe bond, you go in", "start": 1798.69, "duration": 2.73}, {"text": "with nucleoside triphosphates,\nyou form a new phosphodiester", "start": 1801.42, "duration": 5.76}, {"text": "with just one of\nthose phosphoruses,", "start": 1807.18, "duration": 2.15}, {"text": "and you kick out\nphosphate phosphate,", "start": 1809.33, "duration": 2.53}, {"text": "which we would call\npyrophosphate or diphosphate.", "start": 1811.86, "duration": 4.84}, {"text": "OK.", "start": 1816.7, "duration": 0.5}, {"text": "So here you could\njust sort of see, just", "start": 1817.2, "duration": 1.96}, {"text": "check that you know\nwhat you're doing.", "start": 1819.16, "duration": 2.25}, {"text": "I'm going to just say this is\nreally a pretty simple thing.", "start": 1821.41, "duration": 2.73}, {"text": "We're going to put in a T,\nthen we're going to put in an a", "start": 1824.14, "duration": 2.82}, {"text": "then we're going to put in a C\nbecause our template is telling", "start": 1826.96, "duration": 3.42}, {"text": "us to put in the appropriate\npurine or pyrimidine that forms", "start": 1830.38, "duration": 4.53}, {"text": "a nice base pair with that.", "start": 1834.91, "duration": 1.86}, {"text": "So there's a question here.", "start": 1836.77, "duration": 3.21}, {"text": "But I've already given\nyou the answer to it.", "start": 1839.98, "duration": 2.35}, {"text": "So it should be\nvery straightforward", "start": 1842.33, "duration": 2.36}, {"text": "for you to look at\na template strand", "start": 1844.69, "duration": 3.54}, {"text": "and decide what would be on\nthe complementary strand,", "start": 1848.23, "duration": 3.48}, {"text": "and also decide on\nthe directionality", "start": 1851.71, "duration": 2.7}, {"text": "of the complementary strand.", "start": 1854.41, "duration": 3.56}, {"text": "Now origins of replication.", "start": 1857.97, "duration": 2.1}, {"text": "What do they look like?", "start": 1860.07, "duration": 3.69}, {"text": "It's the old where\ndo I start problem.", "start": 1863.76, "duration": 2.08}, {"text": "Where do I start?", "start": 1865.84, "duration": 0.783}, {"text": "What's the best place to start?", "start": 1866.623, "duration": 1.292}, {"text": "Someone?", "start": 1870.47, "duration": 2.14}, {"text": "Not you.", "start": 1872.61, "duration": 0.87}, {"text": "Not you.", "start": 1873.48, "duration": 1.57}, {"text": "Anyone else want to answer here?", "start": 1875.05, "duration": 2.06}, {"text": "I've got this whole genome.", "start": 1877.11, "duration": 1.183}, {"text": "I've got to get going.", "start": 1878.293, "duration": 0.917}, {"text": "I've got to start\nmaking a copy of it.", "start": 1879.21, "duration": 1.65}, {"text": "Where's the best place to break\ninto it to start making copies?", "start": 1880.86, "duration": 5.31}, {"text": "Yeah.", "start": 1886.17, "duration": 0.56}, {"text": "There.", "start": 1886.73, "duration": 2.4}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1889.13, "duration": 2.33}, {"text": "BARBARA IMPERIALI: Correct.", "start": 1891.46, "duration": 1.2}, {"text": "It's simple.", "start": 1892.66, "duration": 0.63}, {"text": "It's the difference\nbetween two and three.", "start": 1893.29, "duration": 2.07}, {"text": "If you go to the\narea where there's", "start": 1895.36, "duration": 1.59}, {"text": "lots of G's and C's, every\nGC has three hydrogen bonds.", "start": 1896.95, "duration": 4.26}, {"text": "If you go to a\ndifferent area where", "start": 1901.21, "duration": 1.59}, {"text": "there happen to be a lot\nof A's and T's in a row,", "start": 1902.8, "duration": 2.73}, {"text": "each pair is only worth\ntwo hydrogen bonds.", "start": 1905.53, "duration": 3.0}, {"text": "You're going to pick the\nstretch that has the most", "start": 1908.53, "duration": 2.73}, {"text": "A's and T's because it's the\nplace where the base pairing is", "start": 1911.26, "duration": 3.72}, {"text": "weaker.", "start": 1914.98, "duration": 1.26}, {"text": "It's actually very\nsimple concept.", "start": 1916.24, "duration": 2.56}, {"text": "So it would be\nthe AT-rich region", "start": 1918.8, "duration": 2.6}, {"text": "is the place where\norigins of replication", "start": 1921.4, "duration": 2.46}, {"text": "are more predominant.", "start": 1923.86, "duration": 1.06}, {"text": "OK.", "start": 1924.92, "duration": 0.5}, {"text": "So what we're going to do now--", "start": 1925.42, "duration": 1.59}, {"text": "and this is going to\nbe tricky, but I'm", "start": 1927.01, "duration": 2.1}, {"text": "going to make this work--", "start": 1929.11, "duration": 1.89}, {"text": "is we're going to\ntalk about replicating", "start": 1931.0, "duration": 2.67}, {"text": "an entire chunk of gene.", "start": 1933.67, "duration": 2.06}, {"text": "And what I've done here is\nI've put the pieces that we're", "start": 1935.73, "duration": 5.08}, {"text": "going to discuss over here.", "start": 1940.81, "duration": 3.54}, {"text": "That's my menu.", "start": 1944.35, "duration": 1.13}, {"text": "And we're going to work\nthrough what we need", "start": 1945.48, "duration": 2.62}, {"text": "to copy a large chunk of DNA.", "start": 1948.1, "duration": 2.22}, {"text": "All right?", "start": 1950.32, "duration": 0.96}, {"text": "Everybody with me?", "start": 1951.28, "duration": 1.17}, {"text": "So I redrew this this morning.", "start": 1952.45, "duration": 3.24}, {"text": "I promised myself\nI'm going to be", "start": 1955.69, "duration": 1.38}, {"text": "super tidy on this blackboard,\nwhich is a far stretch for me.", "start": 1957.07, "duration": 4.53}, {"text": "So replication, we know\nwhere replication starts,", "start": 1961.6, "duration": 3.295}, {"text": "AT-rich region.", "start": 1964.895, "duration": 2.135}, {"text": "We could pick those\nout in the genome.", "start": 1967.03, "duration": 2.04}, {"text": "We know that we've got to unwind\nthe DNA to make a copy of it,", "start": 1969.07, "duration": 4.65}, {"text": "so we must have had to\nunwrap the DNA beforehand.", "start": 1973.72, "duration": 3.43}, {"text": "These are all known things.", "start": 1977.15, "duration": 1.5}, {"text": "So let's now take a look\nat double-stranded DNA", "start": 1978.65, "duration": 2.87}, {"text": "and try and figure out how\nwe use all the components.", "start": 1981.52, "duration": 3.74}, {"text": "Actually, I'm going to bring\nthis board down because I", "start": 1985.26, "duration": 3.4}, {"text": "don't see it as well up there.", "start": 1988.66, "duration": 3.6}, {"text": "How do we make use of\nall these components", "start": 1992.26, "duration": 3.21}, {"text": "that are part of the\nmenu that we need", "start": 1995.47, "duration": 1.83}, {"text": "to make the new strand of DNA?", "start": 1997.3, "duration": 2.56}, {"text": "So we have double-stranded\nDNA and there are base pairs", "start": 1999.86, "duration": 15.385}, {"text": "across.", "start": 2015.245, "duration": 0.5}, {"text": "That's typical\ndouble-stranded DNA.", "start": 2019.18, "duration": 3.02}, {"text": "That's what we're\nstarting from, unwrapped.", "start": 2022.2, "duration": 2.91}, {"text": "I haven't made it helical\nbecause my helices will", "start": 2025.11, "duration": 2.46}, {"text": "get messy.", "start": 2027.57, "duration": 0.96}, {"text": "And so we need to start.", "start": 2028.53, "duration": 1.05}, {"text": "So the first thing\nthat will happen", "start": 2029.58, "duration": 2.49}, {"text": "is that the important\nenzymes like the helicase", "start": 2032.07, "duration": 3.48}, {"text": "will scan to find an\norigin of replication,", "start": 2035.55, "duration": 3.48}, {"text": "so somewhere for the process\nto start because that's where", "start": 2039.03, "duration": 7.857}, {"text": "they're going to break in.", "start": 2046.887, "duration": 1.083}, {"text": "So David, one of your TA's,\nworks in Steve Bell's lab.", "start": 2047.97, "duration": 4.8}, {"text": "And they study the\nmammalian origin", "start": 2052.77, "duration": 2.4}, {"text": "of replication complex,\nwhich is this much more", "start": 2055.17, "duration": 3.69}, {"text": "complicated situation\nthan what I'm", "start": 2058.86, "duration": 1.95}, {"text": "going to describe to you today.", "start": 2060.81, "duration": 2.13}, {"text": "But they do fabulous\nsingle molecule", "start": 2062.94, "duration": 2.1}, {"text": "work to show how those\npieces are assembled.", "start": 2065.04, "duration": 4.353}, {"text": "But I'll tell you the truth.", "start": 2069.393, "duration": 1.167}, {"text": "As dorky as I am,\nthe thing that I", "start": 2070.56, "duration": 1.71}, {"text": "find the most cool about the\norigin of replication complex", "start": 2072.27, "duration": 7.77}, {"text": "is that it spells ORC.", "start": 2080.04, "duration": 2.99}, {"text": "And if any of you\nare Lord of the Rings", "start": 2083.03, "duration": 2.23}, {"text": "fans, who can't be excited by a\ncomplex called the ORC complex?", "start": 2085.26, "duration": 4.979}, {"text": "So there's going\nto be the screening", "start": 2090.239, "duration": 4.23}, {"text": "of the genome for ORI.", "start": 2094.469, "duration": 1.77}, {"text": "And I want you to\nremember what is up here", "start": 2096.239, "duration": 5.131}, {"text": "is the rest of the chromosome.", "start": 2101.37, "duration": 2.14}, {"text": "It's not just a fuzzy end.", "start": 2103.51, "duration": 2.06}, {"text": "It's something that's\ngot a lot of stuff", "start": 2105.57, "duration": 1.77}, {"text": "there that's still base paired.", "start": 2107.34, "duration": 2.43}, {"text": "So the first thing\nthat happens is", "start": 2109.77, "duration": 1.56}, {"text": "that helicase needs\nto start unzippering", "start": 2111.33, "duration": 9.13}, {"text": "the double-stranded DNA, so\nyou get to a new intermediate.", "start": 2120.46, "duration": 4.93}, {"text": "We're going to draw like this.", "start": 2125.39, "duration": 1.37}, {"text": "And the helicase is going to\nintercept to basically start", "start": 2141.51, "duration": 6.93}, {"text": "separating those\ntwo strands of DNA", "start": 2148.44, "duration": 5.02}, {"text": "in order to do the replication.", "start": 2153.46, "duration": 2.33}, {"text": "But don't forget that these\nare still base paired,", "start": 2155.79, "duration": 3.0}, {"text": "and these now are\nsingle strands.", "start": 2158.79, "duration": 4.12}, {"text": "So I'm going to need\nsomething from that menu.", "start": 2162.91, "duration": 4.26}, {"text": "I'm going to need it quickly.", "start": 2167.17, "duration": 1.23}, {"text": "What do you think's the\nnext thing we're really", "start": 2168.4, "duration": 1.958}, {"text": "going to need in order to\nbe able to move forward", "start": 2170.358, "duration": 2.782}, {"text": "in our job?", "start": 2173.14, "duration": 1.78}, {"text": "What do we need from over here?", "start": 2174.92, "duration": 1.43}, {"text": "We're already using the\ndouble-stranded DNA.", "start": 2176.35, "duration": 2.59}, {"text": "It's not going to be too\ndifficult to figure out", "start": 2178.94, "duration": 2.0}, {"text": "the NTP's.", "start": 2180.94, "duration": 1.08}, {"text": "We're already using the\nunzip arrays, the helicase.", "start": 2182.02, "duration": 3.45}, {"text": "What are we going to need?", "start": 2185.47, "duration": 2.12}, {"text": "Yeah.", "start": 2187.59, "duration": 2.3}, {"text": "Primase.", "start": 2189.89, "duration": 1.05}, {"text": "Ah, primase shortly.", "start": 2190.94, "duration": 1.95}, {"text": "But we've really\ngot to do something", "start": 2192.89, "duration": 1.53}, {"text": "to stabilize our\nunzippered stuff.", "start": 2194.42, "duration": 3.81}, {"text": "Anyone else?", "start": 2198.23, "duration": 0.65}, {"text": "So those two single strands\nare right near each other,", "start": 2204.43, "duration": 4.26}, {"text": "and they're complementary.", "start": 2208.69, "duration": 1.92}, {"text": "What's going to stop them going\nstraight back together again", "start": 2210.61, "duration": 3.06}, {"text": "and not allowing replication?", "start": 2213.67, "duration": 1.95}, {"text": "So there are proteins\nthat basically", "start": 2215.62, "duration": 3.69}, {"text": "sit on the single-stranded\nparts of DNA", "start": 2219.31, "duration": 7.71}, {"text": "as are known a single strand\nbinding proteins that stabilize", "start": 2227.02, "duration": 5.25}, {"text": "this transiently made\ncomplex long enough for it", "start": 2232.27, "duration": 3.99}, {"text": "to be copied.", "start": 2236.26, "duration": 1.74}, {"text": "So so far, we've\nused the helicase.", "start": 2238.0, "duration": 2.79}, {"text": "We've used the single\nstrand binding proteins.", "start": 2240.79, "duration": 4.48}, {"text": "And I'm going to\ndraw them there,", "start": 2245.27, "duration": 1.98}, {"text": "still remembering that I have\nan entire chromosome up here.", "start": 2247.25, "duration": 4.98}, {"text": "Now the heavy lifting\nhas to start fairly soon,", "start": 2255.39, "duration": 3.06}, {"text": "so we need the\nenzyme that's going", "start": 2258.45, "duration": 1.74}, {"text": "to start making a copy of\none of those single strands.", "start": 2260.19, "duration": 4.26}, {"text": "That's going to be a\nDNA polymerase, which", "start": 2264.45, "duration": 3.0}, {"text": "is right here.", "start": 2267.45, "duration": 2.76}, {"text": "But DNA polymerase is\nkind of a finicky enzyme", "start": 2270.21, "duration": 3.09}, {"text": "because it doesn't\nlike to just start cold", "start": 2273.3, "duration": 2.7}, {"text": "on the genome, on\nthe single strand,", "start": 2276.0, "duration": 2.07}, {"text": "and start making a copy.", "start": 2278.07, "duration": 2.34}, {"text": "DNA polymerase needs\na primer of some kind.", "start": 2280.41, "duration": 4.47}, {"text": "So I'm going to just put\nthat as a note up here.", "start": 2284.88, "duration": 3.24}, {"text": "DNA polymerase needs\nwhat's called a primer.", "start": 2288.12, "duration": 9.33}, {"text": "And what is a primer?", "start": 2297.45, "duration": 1.05}, {"text": "A primer is a sequence--", "start": 2298.5, "duration": 1.89}, {"text": "I think I've got\nsomething up here--", "start": 2300.39, "duration": 2.1}, {"text": "a primer is a sequence that is\ncomplementary to a little bit", "start": 2302.49, "duration": 3.93}, {"text": "of DNA so that when DNA\npolymerase comes along,", "start": 2306.42, "duration": 3.21}, {"text": "it's actually grabbing\na double strand", "start": 2309.63, "duration": 1.695}, {"text": "and then filling up the\nrest of the single strand.", "start": 2311.325, "duration": 3.625}, {"text": "So this would be a typical\ndepiction of a primer.", "start": 2314.95, "duration": 3.36}, {"text": "Here's a strand we want to copy.", "start": 2318.31, "duration": 2.4}, {"text": "But the blue one is a primer\nstrand giving you something", "start": 2320.71, "duration": 3.47}, {"text": "double-stranded to hold onto.", "start": 2324.18, "duration": 2.07}, {"text": "And then in this\nsituation, DNA polymerase", "start": 2326.25, "duration": 3.42}, {"text": "would be happy to fill in\nthe rest of the sequence.", "start": 2329.67, "duration": 3.42}, {"text": "So for the purpose of\nthis discussion to start,", "start": 2333.09, "duration": 3.21}, {"text": "we're just going to\nprovide a primer that", "start": 2336.3, "duration": 5.09}, {"text": "is complementary to the\nDNA just to give us a go.", "start": 2341.39, "duration": 4.41}, {"text": "We have an alternative\nin the cell, where", "start": 2345.8, "duration": 2.46}, {"text": "it's to actually use a\nprimase and RNA building", "start": 2348.26, "duration": 3.57}, {"text": "blocks to build a primer.", "start": 2351.83, "duration": 1.47}, {"text": "But let's keep things\nsimple for a minute", "start": 2353.3, "duration": 2.04}, {"text": "and get on with a lot\nof the major work.", "start": 2355.34, "duration": 1.98}, {"text": "And then we'll come back\nto that in a second.", "start": 2357.32, "duration": 2.38}, {"text": "So this part is a primer.", "start": 2359.7, "duration": 2.09}, {"text": "And that primer-- if this\nis the 3 prime end, that's", "start": 2365.85, "duration": 2.58}, {"text": "5 prime 3 prime.", "start": 2368.43, "duration": 3.51}, {"text": "So the primer is complementary\nto the DNA in that direction.", "start": 2371.94, "duration": 4.02}, {"text": "It's anti-parallel.", "start": 2375.96, "duration": 1.92}, {"text": "And then DNA polymerase can go\nalong and fill in the strand.", "start": 2377.88, "duration": 6.582}, {"text": "And I'm going to draw\nit dashed, and it's", "start": 2384.462, "duration": 1.708}, {"text": "going to keep on growing.", "start": 2386.17, "duration": 3.77}, {"text": "And what I want you to\nnotice is DNA polymerase", "start": 2389.94, "duration": 3.3}, {"text": "grows from 5 prime to 3 prime.", "start": 2393.24, "duration": 6.72}, {"text": "That is a cardinal\nrule, the directionality", "start": 2399.96, "duration": 3.03}, {"text": "that we grow the new DNA in.", "start": 2402.99, "duration": 2.46}, {"text": "So basically, looking\nat this picture,", "start": 2405.45, "duration": 2.4}, {"text": "it's going in this direction\nbecause the 3 prime OH is free,", "start": 2407.85, "duration": 5.25}, {"text": "and you're building onto it.", "start": 2413.1, "duration": 1.8}, {"text": "So you use a primer\nfirst, and then you", "start": 2414.9, "duration": 2.82}, {"text": "use DNA polymerase plus deoxy\nnucleoside triphosphates.", "start": 2417.72, "duration": 16.95}, {"text": "So all those AT CG\nbuilding blocks.", "start": 2434.67, "duration": 3.69}, {"text": "So we've been using these.", "start": 2438.36, "duration": 2.61}, {"text": "We've used the single-stranded\nbinding proteins.", "start": 2440.97, "duration": 3.12}, {"text": "We've used a primer, but\nthere are an alternative.", "start": 2444.09, "duration": 4.05}, {"text": "I'll get to that\nin just a second.", "start": 2448.14, "duration": 1.89}, {"text": "But we now have a\ncomplex where I'm", "start": 2450.03, "duration": 2.91}, {"text": "going to briefly divert\nyou to tell you about,", "start": 2452.94, "duration": 2.64}, {"text": "in the cell, what else\nyou could use as a primer.", "start": 2455.58, "duration": 3.18}, {"text": "And then we're going\nto have to deal", "start": 2458.76, "duration": 1.5}, {"text": "with copying this other strand.", "start": 2460.26, "duration": 2.02}, {"text": "But this first\nstrand that is made", "start": 2462.28, "duration": 2.39}, {"text": "is called the leading strand.", "start": 2464.67, "duration": 2.46}, {"text": "It's the one that's easy.", "start": 2475.03, "duration": 1.17}, {"text": "I peel apart the DNA.", "start": 2476.2, "duration": 2.04}, {"text": "I have a primer there,\nand I can just build.", "start": 2478.24, "duration": 2.67}, {"text": "Goes really smoothly.", "start": 2480.91, "duration": 1.53}, {"text": "I'm building in the\nright direction.", "start": 2482.44, "duration": 1.72}, {"text": "If you look over on the\nother side of the fence,", "start": 2484.16, "duration": 2.0}, {"text": "you've got a problem\nbecause I can't build", "start": 2486.16, "duration": 2.88}, {"text": "on this side from here, right?", "start": 2489.04, "duration": 2.7}, {"text": "Why not?", "start": 2491.74, "duration": 1.424}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2493.164, "duration": 1.028}, {"text": "BARBARA IMPERIALI: Yes.", "start": 2494.192, "duration": 0.958}, {"text": "I'd be doing it the\nwrong direction.", "start": 2495.15, "duration": 1.9}, {"text": "I would be the\ntotal mess, frankly.", "start": 2497.05, "duration": 1.95}, {"text": "There would be a\ncrisis in the cell.", "start": 2499.0, "duration": 2.112}, {"text": "So we're going to have\nto deal with that.", "start": 2501.112, "duration": 1.708}, {"text": "So let me just get you out\nof the primer, just deal", "start": 2502.82, "duration": 2.66}, {"text": "with this primer issue.", "start": 2505.48, "duration": 1.53}, {"text": "In the cell, it's\nnot like we can micro", "start": 2507.01, "duration": 1.89}, {"text": "inject all these little primers\nto get our DNA synthesized.", "start": 2508.9, "duration": 3.48}, {"text": "So RNA polymerase, believe it\nor not, doesn't need a primer.", "start": 2512.38, "duration": 12.1}, {"text": "So you can build little\nbits of primer with RNA.", "start": 2524.48, "duration": 4.85}, {"text": "You don't build very much,\njust build short segments.", "start": 2529.33, "duration": 2.523}, {"text": "And then once you've got\nsort of enough there,", "start": 2531.853, "duration": 1.917}, {"text": "DNA polymerase can\nstart polymerizing.", "start": 2533.77, "duration": 2.79}, {"text": "So you use RNA polymerase and\nnucleoside triphosphates, not", "start": 2536.56, "duration": 6.63}, {"text": "the deoxy ones.", "start": 2543.19, "duration": 2.04}, {"text": "So later on, we've\ngot this piece here", "start": 2545.23, "duration": 2.61}, {"text": "that might be made\ndeoxy RNA, which is why,", "start": 2547.84, "duration": 3.66}, {"text": "coming over here to my menu--", "start": 2551.5, "duration": 2.38}, {"text": "do I have it?", "start": 2553.88, "duration": 0.64}, {"text": "Yes.", "start": 2554.52, "duration": 0.76}, {"text": "We need an RNA\nprimase, and we need", "start": 2555.28, "duration": 4.65}, {"text": "RNA's to chop them out so that\nDNA polymerase can come back", "start": 2559.93, "duration": 5.79}, {"text": "because now there is\ndouble-stranded material", "start": 2565.72, "duration": 2.97}, {"text": "and fill in the gap.", "start": 2568.69, "duration": 2.05}, {"text": "And then we need one more enzyme\nto stitch together the gaps.", "start": 2570.74, "duration": 4.13}, {"text": "And that's the ligase.", "start": 2574.87, "duration": 1.41}, {"text": "The logic of this\nstuff is great.", "start": 2576.28, "duration": 1.77}, {"text": "I think it's just really\namazing because all these moving", "start": 2578.05, "duration": 2.94}, {"text": "parts have evolved to make\nall these functions fall", "start": 2580.99, "duration": 3.21}, {"text": "into place.", "start": 2584.2, "duration": 1.12}, {"text": "Now we need to talk about\nthis pesky other strand.", "start": 2585.32, "duration": 3.32}, {"text": "So we have a problem\nhere because we've", "start": 2588.64, "duration": 3.09}, {"text": "got the wrong directionality.", "start": 2591.73, "duration": 2.07}, {"text": "So what happens in nature\nis as soon as there's", "start": 2593.8, "duration": 4.75}, {"text": "enough of a stretch, a\nprimer is put in place,", "start": 2598.55, "duration": 3.9}, {"text": "growing the DNA in\nthe right direction.", "start": 2602.45, "duration": 2.74}, {"text": "That's from where the\nhelicase is unzipping.", "start": 2605.19, "duration": 5.69}, {"text": "So we put in another primer.", "start": 2610.88, "duration": 2.28}, {"text": "And then DNA polymerase--", "start": 2613.16, "duration": 3.8}, {"text": "that's the white one--", "start": 2616.96, "duration": 1.94}, {"text": "can build its\ncomplementary strand,", "start": 2618.9, "duration": 3.78}, {"text": "building in the appropriate\ndirection to be consistent.", "start": 2622.68, "duration": 4.05}, {"text": "So you basically fill\nin a chunk and then", "start": 2626.73, "duration": 3.81}, {"text": "you have to wait awhile\ntill more is unzippered,", "start": 2630.54, "duration": 3.0}, {"text": "put in another primer,\nand then grow the DNA.", "start": 2633.54, "duration": 3.34}, {"text": "So in that other piece you're\nmaking little segments of DNA", "start": 2636.88, "duration": 4.67}, {"text": "intervened by RNA primers.", "start": 2641.55, "duration": 2.73}, {"text": "Later on, those small primers\nare going to be chewed up", "start": 2644.28, "duration": 2.91}, {"text": "by RNA's.", "start": 2647.19, "duration": 1.65}, {"text": "DNA polymerase is\ngoing to fill them in,", "start": 2648.84, "duration": 2.67}, {"text": "and ligase is\ngoing to join them.", "start": 2651.51, "duration": 2.23}, {"text": "Does that make sense?", "start": 2653.74, "duration": 1.26}, {"text": "It's a lot to grasp.", "start": 2655.0, "duration": 1.37}, {"text": "And this other side\nis called what's", "start": 2656.37, "duration": 3.03}, {"text": "known as the lagging strand.", "start": 2659.4, "duration": 4.34}, {"text": "And there are\npieces of short DNA", "start": 2666.63, "duration": 2.73}, {"text": "that are transiently made\nthat have their own name.", "start": 2669.36, "duration": 4.62}, {"text": "You can remember it or not.", "start": 2673.98, "duration": 1.83}, {"text": "I just feel I'm not\nbeing complete if I", "start": 2675.81, "duration": 1.95}, {"text": "don't mention their name.", "start": 2677.76, "duration": 2.33}, {"text": "They're called Okazaki\nfragments after the guy", "start": 2680.09, "duration": 7.06}, {"text": "who discovered them.", "start": 2687.15, "duration": 1.59}, {"text": "And they're longer in\nbacteria than in humans.", "start": 2688.74, "duration": 3.39}, {"text": "So Okazaki fragments are the\ntransient short stretches", "start": 2692.13, "duration": 4.22}, {"text": "of DNA that are made\nin the lagging strand,", "start": 2696.35, "duration": 3.43}, {"text": "and then they get\nzipped together.", "start": 2699.78, "duration": 1.72}, {"text": "So that's sort of the story\nfor replicating the DNA.", "start": 2701.5, "duration": 3.335}, {"text": "Let me make sure I've\ndescribed everything to you.", "start": 2704.835, "duration": 3.495}, {"text": "Leading strand, lagging strand.", "start": 2708.33, "duration": 1.67}, {"text": "Oh, can't believe I\nalmost forgot this.", "start": 2710.0, "duration": 3.5}, {"text": "All right.", "start": 2713.5, "duration": 0.5}, {"text": "Now we got a problem.", "start": 2714.0, "duration": 1.66}, {"text": "So we've come all this way.", "start": 2715.66, "duration": 2.93}, {"text": "We've used all the pieces.", "start": 2718.59, "duration": 1.2}, {"text": "We haven't used\none of the pieces.", "start": 2719.79, "duration": 3.81}, {"text": "So we're in a small\nbit of trouble", "start": 2723.6, "duration": 2.52}, {"text": "because what's going to happen\nwhen you're, for example,", "start": 2726.12, "duration": 6.17}, {"text": "trying to peel apart your DNA?", "start": 2732.29, "duration": 3.4}, {"text": "What trouble are you\ngoing to run into?", "start": 2735.69, "duration": 3.49}, {"text": "Who wants to come up here\nand get involved in my demo?", "start": 2739.18, "duration": 2.75}, {"text": "And you've got to be aware that\nyou're going to be on screen.", "start": 2741.93, "duration": 3.61}, {"text": "You and you up there.", "start": 2745.54, "duration": 1.08}, {"text": "You've got your hand up first.", "start": 2746.62, "duration": 1.38}, {"text": "OK.", "start": 2748.0, "duration": 2.27}, {"text": "I need someone who's\ngoing to hold onto this as", "start": 2750.27, "duration": 2.1}, {"text": "if their life depends on it.", "start": 2752.37, "duration": 1.38}, {"text": "You can't let the\nyellow ones slip out.", "start": 2753.75, "duration": 2.1}, {"text": "So you are the rest\nof the chromosome,", "start": 2755.85, "duration": 1.97}, {"text": "so make sure that you\nreally hold-- and you", "start": 2757.82, "duration": 2.14}, {"text": "don't let things come apart.", "start": 2759.96, "duration": 1.23}, {"text": "Now you are helicase, OK?", "start": 2761.19, "duration": 2.79}, {"text": "OK.", "start": 2763.98, "duration": 0.5}, {"text": "So come on.", "start": 2764.48, "duration": 0.64}, {"text": "Start helicasing and really\npull as hard as you can.", "start": 2765.12, "duration": 3.96}, {"text": "He's going to hold it.", "start": 2769.08, "duration": 2.15}, {"text": "No, I don't want you to\nunwind it because we're", "start": 2771.23, "duration": 2.01}, {"text": "in the middle of a chromosome.", "start": 2773.24, "duration": 1.25}, {"text": "So you've literally got\nto do what helicase does.", "start": 2774.49, "duration": 2.47}, {"text": "Yeah, keep on pulling.", "start": 2776.96, "duration": 0.99}, {"text": "Come on, you can do it.", "start": 2777.95, "duration": 2.55}, {"text": "Can you go much further?", "start": 2780.5, "duration": 1.17}, {"text": "I mean, your arms\naren't any longer.", "start": 2781.67, "duration": 1.59}, {"text": "But it's almost\nimpossible, right?", "start": 2783.26, "duration": 1.65}, {"text": "We get to a stage\nwhere we need help.", "start": 2784.91, "duration": 3.03}, {"text": "The help we have coming\nis from topoisomerase.", "start": 2787.94, "duration": 3.97}, {"text": "Topoisomerase does something--\nso walk just one step this way.", "start": 2791.91, "duration": 4.81}, {"text": "Yeah.", "start": 2796.72, "duration": 0.5}, {"text": "Topoisomerase some comes\nalong and it cuts the DNA.", "start": 2797.22, "duration": 5.54}, {"text": "It holds the pieces in\nits hands, if you will,", "start": 2802.76, "duration": 4.17}, {"text": "lets the super coiling\nrelax, and then it", "start": 2806.93, "duration": 2.52}, {"text": "joins them back again.", "start": 2809.45, "duration": 2.04}, {"text": "So topoisomerase-- thank\nyou very much, guys.", "start": 2811.49, "duration": 2.25}, {"text": "That's it.", "start": 2813.74, "duration": 0.66}, {"text": "Chromosome, helicase, thank you.", "start": 2814.4, "duration": 2.4}, {"text": "We really have some\ntightly wound DNA here.", "start": 2816.8, "duration": 2.16}, {"text": "So topoisomerase is the get out\nof jail free card because it", "start": 2818.96, "duration": 4.59}, {"text": "allows you to deal with all of\nthis tension you got in place", "start": 2823.55, "duration": 4.86}, {"text": "that you cannot unravel.", "start": 2828.41, "duration": 2.01}, {"text": "So you need someone who is\nliterally going to cut, hold,", "start": 2830.42, "duration": 3.09}, {"text": "let the thing relax, rejoin it.", "start": 2833.51, "duration": 2.57}, {"text": "And there are some\ntopoisomerases", "start": 2836.08, "duration": 2.53}, {"text": "called DNA gyrases.", "start": 2838.61, "duration": 1.95}, {"text": "But the really cool\nthing about topoisomerase", "start": 2840.56, "duration": 3.03}, {"text": "is that it's a\nwonderful drug target", "start": 2843.59, "duration": 3.4}, {"text": "in both mammalian\nand bacterial cells", "start": 2846.99, "duration": 2.87}, {"text": "because they're quite different\nin the two types of organisms.", "start": 2849.86, "duration": 4.69}, {"text": "So in bacteria the\nantibiotic ciprofloxacin", "start": 2854.55, "duration": 3.8}, {"text": "is a topoisomerase\ninhibitor that", "start": 2858.35, "duration": 2.58}, {"text": "actually stops your bacteria\ndividing because if topo", "start": 2860.93, "duration": 3.96}, {"text": "doesn't work, you can't go on.", "start": 2864.89, "duration": 2.04}, {"text": "And in human biology\nand cancer biology,", "start": 2866.93, "duration": 2.83}, {"text": "there are also topoisomerases--", "start": 2869.76, "duration": 1.94}, {"text": "there's one called\n[INAUDIBLE] --", "start": 2871.7, "duration": 1.71}, {"text": "that does the same thing in\nthe eukaryotic topoisomerase", "start": 2873.41, "duration": 4.62}, {"text": "to stop cancer cells dividing\nrapidly so that those cannot go", "start": 2878.03, "duration": 5.79}, {"text": "on and make larger tumors.", "start": 2883.82, "duration": 2.49}, {"text": "So I want to show you something.", "start": 2886.31, "duration": 1.41}, {"text": "And I am actually\ncertain that I have time.", "start": 2887.72, "duration": 3.84}, {"text": "Come on.", "start": 2891.56, "duration": 1.35}, {"text": "Now I'm going to show you.", "start": 2892.91, "duration": 1.12}, {"text": "[VIDEO PLAYBACK]", "start": 2894.03, "duration": 0.667}, {"text": "- In this animation, we'll\nsee the remarkable way", "start": 2894.697, "duration": 2.283}, {"text": "our DNA is tightly\npacked up so that six", "start": 2896.98, "duration": 3.16}, {"text": "feet of this long molecule fits\ninto the microscopic nucleus", "start": 2900.14, "duration": 3.72}, {"text": "of every cell.", "start": 2903.86, "duration": 0.93}, {"text": "The process starts when DNA is\nwrapped around special protein", "start": 2908.45, "duration": 3.45}, {"text": "molecules called histones.", "start": 2911.9, "duration": 2.54}, {"text": "The combined loop of DNA and\nprotein is called a nucleosome.", "start": 2914.44, "duration": 3.61}, {"text": "Next, the nucleosomes are\npackaged into a thread.", "start": 2922.5, "duration": 4.01}, {"text": "The end result is a\nfiber known as chromatin.", "start": 2926.51, "duration": 2.56}, {"text": "This fiber is then looped\nand coiled yet again,", "start": 2935.86, "duration": 21.52}, {"text": "leading finally to the\nfamiliar shapes known", "start": 2957.38, "duration": 2.16}, {"text": "as chromosomes, which can be\nseen in the nucleus of dividing", "start": 2959.54, "duration": 3.64}, {"text": "cells.", "start": 2963.18, "duration": 0.5}, {"text": "BARBARA IMPERIALI: Now I'm going\nto take you forward to DNA,", "start": 2967.748, "duration": 4.382}, {"text": "what we just talked about here.", "start": 2972.13, "duration": 1.86}, {"text": "- Using computer animation\nbased on molecular research,", "start": 2977.29, "duration": 3.39}, {"text": "we are now able to see\nhow DNA is actually", "start": 2980.68, "duration": 2.64}, {"text": "copied in living cells.", "start": 2983.32, "duration": 1.17}, {"text": "You are looking at\nan assembly line", "start": 2987.17, "duration": 1.71}, {"text": "of amazing miniature biochemical\nmachines that are pulling apart", "start": 2988.88, "duration": 3.72}, {"text": "the DNA double helix\nand cranking out", "start": 2992.6, "duration": 2.49}, {"text": "a copy of each strand.", "start": 2995.09, "duration": 1.24}, {"text": "The DNA to be copied\nenters the production line", "start": 2999.7, "duration": 2.67}, {"text": "from bottom left.", "start": 3002.37, "duration": 2.4}, {"text": "The whirling blue molecular\nmachine is called helicase.", "start": 3004.77, "duration": 4.44}, {"text": "It spins the DNA as\nfast as a jet engine", "start": 3009.21, "duration": 3.15}, {"text": "as it unwinds the double\nhelix into two strands.", "start": 3012.36, "duration": 4.86}, {"text": "One strand is\ncopied continuously", "start": 3017.22, "duration": 2.67}, {"text": "and can be seen spooling\noff to the right.", "start": 3019.89, "duration": 2.11}, {"text": "Things are not so simple\nfor the other strand", "start": 3024.87, "duration": 2.49}, {"text": "because it must be\ncopied backwards.", "start": 3027.36, "duration": 3.42}, {"text": "It is drawn out\nrepeatedly in loops", "start": 3030.78, "duration": 1.89}, {"text": "and copied one\nsection at a time.", "start": 3032.67, "duration": 3.66}, {"text": "The end result is two\nnew DNA molecules.", "start": 3036.33, "duration": 2.88}, {"text": "[END PLAYBACK]", "start": 3044.367, "duration": 0.583}, {"text": "BARBARA IMPERIALI: All right.", "start": 3044.95, "duration": 1.208}, {"text": "OK.", "start": 3046.158, "duration": 1.262}, {"text": "That's what you saw\ntoday, replication,", "start": 3047.42, "duration": 3.03}, {"text": "a lot of the mechanics, a\nlot of the moving parts.", "start": 3050.45, "duration": 3.54}, {"text": "There's this tricky\nstuff with primers.", "start": 3053.99, "duration": 2.49}, {"text": "You'll get used to that.", "start": 3056.48, "duration": 1.48}, {"text": "But this is really\nthe quintessential set", "start": 3057.96, "duration": 2.15}, {"text": "of pieces to replicate DNA.", "start": 3060.11, "duration": 2.73}, {"text": "It is an amazing process.", "start": 3062.84, "duration": 1.86}, {"text": "Look at the speed.", "start": 3064.7, "duration": 1.44}, {"text": "1,000 base pairs a second.", "start": 3066.14, "duration": 2.13}, {"text": "Can you even believe it?", "start": 3068.27, "duration": 2.37}, {"text": "An entire circular chromosome\ncopied in 20 minutes.", "start": 3070.64, "duration": 6.0}, {"text": "So these are really\nthings to think about", "start": 3076.64, "duration": 1.95}, {"text": "because they are so impressive\nthat it's a delight to actually", "start": 3078.59, "duration": 3.57}, {"text": "be able to teach them to you.", "start": 3082.16, "duration": 1.45}, {"text": "OK.", "start": 3083.61, "duration": 0.5}, {"text": "I'm done for today.", "start": 3084.11, "duration": 2.12}]
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+[{"text": "MARKUS KLUTE: Welcome back\nto 8.20, Special Relativity.", "start": 13.08, "duration": 2.4}, {"text": "In this section and\nalso the next one,", "start": 15.48, "duration": 2.85}, {"text": "we're going to make a\ncase against aether.", "start": 18.33, "duration": 2.07}, {"text": "Aether was presumed to be the\nmedium in which light traveled.", "start": 20.4, "duration": 4.92}, {"text": "We do this-- we make\nthis case by studying", "start": 25.32, "duration": 3.03}, {"text": "the Michelson-Morley experiment.", "start": 28.35, "duration": 2.47}, {"text": "Michelson and Morley\nwent out to detect", "start": 30.82, "duration": 2.72}, {"text": "the motion of the Earth\nrelative to aether.", "start": 33.54, "duration": 2.58}, {"text": "And by not finding\nthe result, we", "start": 36.12, "duration": 2.17}, {"text": "can conclude that, at\nleast in this form,", "start": 38.29, "duration": 2.15}, {"text": "aether doesn't exist.", "start": 40.44, "duration": 3.55}, {"text": "So what is the\nexperimental setup?", "start": 43.99, "duration": 2.04}, {"text": "Also, it's shown in\nthe pictures above.", "start": 46.03, "duration": 2.64}, {"text": "We have a light source\nhere, through which", "start": 48.67, "duration": 4.17}, {"text": "the light travel to\nsome mirror which", "start": 52.84, "duration": 2.17}, {"text": "reflects about half the light.", "start": 55.01, "duration": 1.65}, {"text": "About half the light\ngoes through reflected", "start": 56.66, "duration": 3.3}, {"text": "on the second mirror and\nthen comes to a screen.", "start": 59.96, "duration": 3.46}, {"text": "The other part of the\nlight is up and back down.", "start": 63.42, "duration": 3.66}, {"text": "So the light either travels\nagainst the aether wind", "start": 67.08, "duration": 3.89}, {"text": "or perpendicular\nto the aether wind.", "start": 70.97, "duration": 2.82}, {"text": "If aether is the medium\nin which light travels,", "start": 73.79, "duration": 3.6}, {"text": "then the velocity\nneeds to change.", "start": 77.39, "duration": 2.43}, {"text": "The velocity of light in\nthis medium will change.", "start": 79.82, "duration": 3.631}, {"text": "If there is no\naether wind, there", "start": 83.451, "duration": 1.375}, {"text": "is no change in the\nvelocity of the light.", "start": 84.826, "duration": 2.824}, {"text": "The result of the experiment\nis an interference pattern", "start": 87.65, "duration": 3.15}, {"text": "on the screen.", "start": 90.8, "duration": 2.13}, {"text": "The experiment is called\nan interferometer.", "start": 92.93, "duration": 4.32}, {"text": "So there are some systematic\nuncertainties here.", "start": 97.25, "duration": 5.62}, {"text": "There are some unknowns.", "start": 102.87, "duration": 1.93}, {"text": "For example, if you're\nbuilding your table,", "start": 104.8, "duration": 2.69}, {"text": "it's not really clear in which\ndirection aether actually--", "start": 107.49, "duration": 2.97}, {"text": "which direction is actually the\ndirection of the aether flow.", "start": 110.46, "duration": 3.15}, {"text": "But you can get by this\nby rotating the table", "start": 113.61, "duration": 3.66}, {"text": "and making various\nsets of experiments.", "start": 117.27, "duration": 2.68}, {"text": "And that's what\nMichelson and Morley did.", "start": 119.95, "duration": 3.15}, {"text": "I want you to show\nthat the effect they're", "start": 123.1, "duration": 6.73}, {"text": "about to observe--", "start": 129.83, "duration": 1.209}, {"text": "or they will not observe--", "start": 131.039, "duration": 1.851}, {"text": "is of the order of\nv over c squared.", "start": 132.89, "duration": 2.91}, {"text": "And what you want\nto do is compare", "start": 135.8, "duration": 6.63}, {"text": "the light as it travels on this\npath number 1 to one mirror", "start": 142.43, "duration": 4.98}, {"text": "and on the second path\nto the second mirror.", "start": 147.41, "duration": 2.52}, {"text": "So if you're\nfollowing the video,", "start": 152.91, "duration": 1.94}, {"text": "I ask you to just stop here\nand figure out how long does it", "start": 154.85, "duration": 3.57}, {"text": "take for the light to\ntravel on this path", "start": 158.42, "duration": 2.91}, {"text": "here-- on the lower path, path\nnumber 1, or path number 2.", "start": 161.33, "duration": 4.38}, {"text": "Well, obviously, I've\nworked this out already.", "start": 168.77, "duration": 2.13}, {"text": "So we want to\ncalculate the time it", "start": 170.9, "duration": 1.68}, {"text": "takes light to\ntravel path 1 that", "start": 172.58, "duration": 3.57}, {"text": "is going up and coming down--", "start": 176.15, "duration": 3.502}, {"text": "going left and going right.", "start": 179.652, "duration": 2.018}, {"text": "So in the first\ncase, the velocity", "start": 181.67, "duration": 2.31}, {"text": "is reduced by the\nvelocity of aether.", "start": 183.98, "duration": 2.49}, {"text": "So the time it takes\nis l1, the leg,", "start": 186.47, "duration": 3.9}, {"text": "divided by c minus v plus the\nreturn leg, l1 over c plus v.", "start": 190.37, "duration": 7.67}, {"text": "And you work this out, and\nyou simplify a little bit,", "start": 198.04, "duration": 2.77}, {"text": "you get this first equation.", "start": 200.81, "duration": 4.01}, {"text": "For the second part,\nthe one up and down,", "start": 204.82, "duration": 3.33}, {"text": "you want to draw\nthis triangle here", "start": 208.15, "duration": 2.82}, {"text": "to figure out that t\nis equal-- the time", "start": 210.97, "duration": 3.0}, {"text": "it takes is equal to the\nsquare root of l square", "start": 213.97, "duration": 2.91}, {"text": "over c square minus v square.", "start": 216.88, "duration": 1.95}, {"text": "And then you simplify again,\nyou get this [INAUDIBLE]", "start": 218.83, "duration": 4.05}, {"text": "square root [INAUDIBLE].", "start": 222.88, "duration": 1.645}, {"text": "What's important is\nthe time difference", "start": 224.525, "duration": 1.625}, {"text": "for the light traveling\nwith two legs.", "start": 226.15, "duration": 2.76}, {"text": "And we find that the time\ndifference t1 or t2 minus t1", "start": 228.91, "duration": 3.93}, {"text": "is given by this bit\ncomplicated looking equation.", "start": 232.84, "duration": 4.35}, {"text": "So now in the experiment, you\nwant to set up l1 equal to l2.", "start": 237.19, "duration": 3.29}, {"text": "To simplify, you might not be\nable to do it very precisely.", "start": 240.48, "duration": 4.14}, {"text": "What you can do, however,\nis rotate the table.", "start": 244.62, "duration": 2.94}, {"text": "If you rotate and then\ncompare the difference", "start": 247.56, "duration": 2.28}, {"text": "of the differences, you\nfind that here there's", "start": 249.84, "duration": 6.54}, {"text": "this v square over\nc square dependence.", "start": 256.38, "duration": 4.709}, {"text": "I used a little trick to\nsimplify the square root", "start": 261.089, "duration": 3.751}, {"text": "as I use this 1 plus or\nminus x to the nth power.", "start": 264.84, "duration": 5.14}, {"text": "It's about 1 plus minus\nn times x for x plus 1.", "start": 269.98, "duration": 4.86}, {"text": "And since the\nvelocity of aether is", "start": 274.84, "duration": 1.71}, {"text": "presumed to be small compared\nto the speed of light,", "start": 276.55, "duration": 3.09}, {"text": "that's a good approximation.", "start": 279.64, "duration": 4.69}, {"text": "The result of the experiment\nwas there was no effect.", "start": 284.33, "duration": 2.52}, {"text": "They tried-- they\nimproved the experiment.", "start": 286.85, "duration": 2.01}, {"text": "They tried to find\nsmaller effects.", "start": 288.86, "duration": 1.59}, {"text": "They didn't find any.", "start": 290.45, "duration": 1.65}, {"text": "The reason for this is\nthat there is no aether.", "start": 292.1, "duration": 3.57}, {"text": "But we can use this now to\nmake a case against the aether.", "start": 295.67, "duration": 4.63}, {"text": "But you could say\nthat maybe they", "start": 300.3, "duration": 1.89}, {"text": "didn't observe anything\nbecause the aether is", "start": 302.19, "duration": 2.19}, {"text": "dragged with the Earth.", "start": 304.38, "duration": 1.45}, {"text": "So instead of the Earth\ngoing through this aether,", "start": 305.83, "duration": 3.53}, {"text": "and therefore, we\nexperience aether winds,", "start": 309.36, "duration": 3.24}, {"text": "you could argue\nthat maybe aether is", "start": 312.6, "duration": 2.76}, {"text": "localized around the Earth,\nmoving with the Earth", "start": 315.36, "duration": 3.27}, {"text": "or maybe moving\nwith the universe.", "start": 318.63, "duration": 2.29}, {"text": "And so in the next video,\nwe'll look at a case", "start": 320.92, "duration": 2.06}, {"text": "against that scenario as well.", "start": 322.98, "duration": 2.42}]
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+[{"text": "[SQUEAKING]", "start": 0.5, "duration": 1.955}, {"text": "[RUSTLING]", "start": 2.455, "duration": 1.964}, {"text": "[CLICKING]", "start": 4.419, "duration": 0.982}, {"text": "GARY GENSLER: So\nthis FinTech course--", "start": 10.63, "duration": 1.65}, {"text": "this is for those who\nwant to explore FinTech,", "start": 12.28, "duration": 2.46}, {"text": "how the technologies are\ndisrupting financial services.", "start": 14.74, "duration": 2.97}, {"text": "That's the core of it.", "start": 17.71, "duration": 2.73}, {"text": "Technology is\ndisrupting finance.", "start": 20.44, "duration": 2.22}, {"text": "And we'll talk a lot about this,\nthat finance and technology", "start": 22.66, "duration": 2.98}, {"text": "have lived in simpatico,\nin some relationship", "start": 25.64, "duration": 3.26}, {"text": "together for thousands of years.", "start": 28.9, "duration": 1.9}, {"text": "In fact, money and ledgers were\ninitial financial technologies.", "start": 30.8, "duration": 6.29}, {"text": "And we'll talk about\nwhat makes something", "start": 37.09, "duration": 2.48}, {"text": "in this faculty's mind a\nfinancial technology that's", "start": 39.57, "duration": 4.63}, {"text": "really changing the\nworld and then just", "start": 44.2, "duration": 2.52}, {"text": "the technology that exists.", "start": 46.72, "duration": 1.53}, {"text": "The telephone, for\ninstance, at one point,", "start": 48.25, "duration": 2.13}, {"text": "in that time, in the\n1920s, was, in essence,", "start": 50.38, "duration": 3.96}, {"text": "a financial technology\nthat rapidly", "start": 54.34, "duration": 2.7}, {"text": "changed the world of finance.", "start": 57.04, "duration": 2.82}, {"text": "Or even in the 19th century,\nthe telegraph rapidly", "start": 59.86, "duration": 3.39}, {"text": "changed parts of finance, when\nyou could send your first money", "start": 63.25, "duration": 3.58}, {"text": "gram--", "start": 66.83, "duration": 0.823}, {"text": "or in those days, it was\ncalled something different,", "start": 67.653, "duration": 2.167}, {"text": "but it was a telegram\nattached with money", "start": 69.82, "duration": 2.7}, {"text": "in the 1870s and 1880s.", "start": 72.52, "duration": 2.97}, {"text": "But this course is going to\nbe about the cutting edge.", "start": 75.49, "duration": 2.323}, {"text": "We're going to be\ntalking about business", "start": 77.813, "duration": 1.667}, {"text": "models and the like\naround AI, deep learning,", "start": 79.48, "duration": 3.54}, {"text": "blockchain technology, OpenAPI.", "start": 83.02, "duration": 3.24}, {"text": "10 and 20 years\nfrom now, OpenAPI", "start": 86.26, "duration": 2.85}, {"text": "will not be taught, by my\nview, in a FinTech course.", "start": 89.11, "duration": 4.15}, {"text": "But it's the relevant\ntopics of the day.", "start": 93.26, "duration": 2.81}, {"text": "And we'll be looking at\nthe competitive landscape.", "start": 96.07, "duration": 2.88}, {"text": "Those of you that have decided\nto take this course on top", "start": 98.95, "duration": 6.43}, {"text": "of consumer finance course,\nthe half-semester course that", "start": 105.38, "duration": 3.12}, {"text": "was at the same\ntime, you will know", "start": 108.5, "duration": 2.67}, {"text": "that I usually teach in the\nconcept of business strategy.", "start": 111.17, "duration": 3.82}, {"text": "What is the strategy that these\nstartups which big tech, which", "start": 114.99, "duration": 4.49}, {"text": "incumbents are looking at this\npoint in time, in this day", "start": 119.48, "duration": 4.17}, {"text": "and age, in this sector?", "start": 123.65, "duration": 1.98}, {"text": "And this course is also, I\nshould say, being recorded.", "start": 125.63, "duration": 3.569}, {"text": "It's being recorded\nfor some students", "start": 129.199, "duration": 1.761}, {"text": "who can't join us\nsimultaneously or what's", "start": 130.96, "duration": 2.98}, {"text": "called synchronous learning.", "start": 133.94, "duration": 1.92}, {"text": "And these recordings\nwill be posted on Canvas", "start": 135.86, "duration": 3.51}, {"text": "within a day or two.", "start": 139.37, "duration": 1.74}, {"text": "Lena and Romain and I\njust have to remember", "start": 141.11, "duration": 2.28}, {"text": "how to do that and actually\npost each of the recordings.", "start": 143.39, "duration": 3.33}, {"text": "They also might be\nshared, just to alert you,", "start": 146.72, "duration": 3.42}, {"text": "in OpenCourseWare in\nthe fall or later.", "start": 150.14, "duration": 2.97}, {"text": "I've chose with MIT that if\nwe're recording them anyway,", "start": 153.11, "duration": 3.36}, {"text": "maybe if they come out\nbeing anywhere valuable,", "start": 156.47, "duration": 5.63}, {"text": "that we would up to\nthe broader community.", "start": 162.1, "duration": 2.37}, {"text": "So these might be shared more\nbroadly come the fall as well.", "start": 164.47, "duration": 5.87}, {"text": "It's also really to gain\ncritical reasoning skills", "start": 170.34, "duration": 2.87}, {"text": "around the ground\ntruths of FinTech,", "start": 173.21, "duration": 2.58}, {"text": "separating hype from reality.", "start": 175.79, "duration": 5.58}, {"text": "Every week, there's a posting\nof three or four readings.", "start": 181.37, "duration": 5.52}, {"text": "I understand that even\nif we were all on campus,", "start": 186.89, "duration": 2.64}, {"text": "you might not read\nevery word of that.", "start": 189.53, "duration": 2.04}, {"text": "But they really are\nsort of the foundation.", "start": 191.57, "duration": 3.69}, {"text": "And I hope that in each\nlecture, in each class,", "start": 195.26, "duration": 2.29}, {"text": "we can go beyond that.", "start": 197.55, "duration": 2.18}, {"text": "But this week, the Bank of\nInternational Settlement", "start": 199.73, "duration": 2.52}, {"text": "Working Paper and the\nFinancial Stability Board", "start": 202.25, "duration": 2.94}, {"text": "are two papers that a\nlot of people turn to.", "start": 205.19, "duration": 3.48}, {"text": "The Financial Stability\nBoard is a group", "start": 208.67, "duration": 2.55}, {"text": "of 20 countries, the\nG20 countries, that", "start": 211.22, "duration": 4.2}, {"text": "have banded together and their\ntreasury secretaries or finance", "start": 215.42, "duration": 4.92}, {"text": "ministers and central banks\nand securities regulators", "start": 220.34, "duration": 3.96}, {"text": "have formed this thing called\nthe Financial Stability Board.", "start": 224.3, "duration": 2.88}, {"text": "And they publish very good work.", "start": 227.18, "duration": 1.53}, {"text": "This paper came out in 2017.", "start": 228.71, "duration": 2.88}, {"text": "It feels a little\ndated right now.", "start": 231.59, "duration": 1.9}, {"text": "But it still felt\nquite relevant.", "start": 233.49, "duration": 2.33}, {"text": "And then, of course, the Bank\nof international Settlement", "start": 235.82, "duration": 2.4}, {"text": "is 60 or 70 central\nbanks out of Basel.", "start": 238.22, "duration": 4.02}, {"text": "And they write very good work.", "start": 242.24, "duration": 2.252}, {"text": "I thought it was also\ninteresting to take", "start": 244.492, "duration": 1.708}, {"text": "the current chair of the US bank\nregulator, the Federal Deposit", "start": 246.2, "duration": 4.53}, {"text": "Insurance Corporation, Chair\nMcWilliams, and her view", "start": 250.73, "duration": 5.789}, {"text": "as to the future of banking,\nwhat's going on right now.", "start": 256.519, "duration": 3.211}, {"text": "So that's why I grabbed\nthese three as an intro.", "start": 259.73, "duration": 3.42}, {"text": "If you've not yet\nread them, I think", "start": 263.15, "duration": 1.77}, {"text": "go back, try to at\nleast skim them,", "start": 264.92, "duration": 2.43}, {"text": "get your sense of what they are.", "start": 267.35, "duration": 4.17}, {"text": "And each class, I will\nalso list study questions.", "start": 271.52, "duration": 2.99}, {"text": "And the goal of my\nlisting study questions", "start": 274.51, "duration": 2.38}, {"text": "is not just for you to\nthink about these questions", "start": 276.89, "duration": 2.82}, {"text": "beforehand, but you\nwill also see where", "start": 279.71, "duration": 2.25}, {"text": "do I want to land the class?", "start": 281.96, "duration": 1.59}, {"text": "Where do I think these are the\ncentral learning objectives?", "start": 283.55, "duration": 5.11}, {"text": "And this is usually in\na classroom setting,", "start": 288.66, "duration": 2.9}, {"text": "where I'll say \"let's\npause here and I'll", "start": 291.56, "duration": 2.37}, {"text": "engage in some conversation.\"", "start": 293.93, "duration": 2.25}, {"text": "Now, I do cold call in\nthe regular classroom.", "start": 296.18, "duration": 3.0}, {"text": "I don't know if anybody wants to\nraise their hand now and answer", "start": 299.18, "duration": 3.54}, {"text": "any one of these\nquestions, but it", "start": 302.72, "duration": 2.19}, {"text": "would be great to get a little\nbit of life and community", "start": 304.91, "duration": 3.48}, {"text": "in this, if anybody\ncan address themselves.", "start": 308.39, "duration": 2.67}, {"text": "What are the major technological\ntrends materially influencing", "start": 311.06, "duration": 4.14}, {"text": "finance right now\nthat you think about,", "start": 315.2, "duration": 1.71}, {"text": "whether it's in the US or\nanywhere around the globe?", "start": 316.91, "duration": 4.8}, {"text": "And this course will be\ntaught from the perspective", "start": 321.71, "duration": 2.55}, {"text": "around the globe,\neven though I'm", "start": 324.26, "duration": 1.5}, {"text": "more knowledgeable in the US.", "start": 325.76, "duration": 1.38}, {"text": "We will be talking about Europe,\nLatin America, Asia throughout,", "start": 327.14, "duration": 4.84}, {"text": "a little bit about\nAfrica as well.", "start": 331.98, "duration": 3.98}, {"text": "Romain, I'm pausing\nfor you to do your--", "start": 335.96, "duration": 2.363}, {"text": "ROMAIN DE SAINT PERIER: We\nhave our first volunteer.", "start": 338.323, "duration": 2.167}, {"text": "Thank you very much, Luke.", "start": 340.49, "duration": 1.56}, {"text": "The floor is yours.", "start": 342.05, "duration": 0.92}, {"text": "AUDIENCE: I'll answer\nthe first question.", "start": 346.352, "duration": 1.708}, {"text": "The main technological\nchange that we see in US", "start": 348.06, "duration": 3.33}, {"text": "and outside of US is versus open\nbanking, use of a lot of APIs.", "start": 351.39, "duration": 3.93}, {"text": "They can be applicable\nto other websites.", "start": 355.32, "duration": 2.303}, {"text": "GARY GENSLER: All\nright, and we're", "start": 357.623, "duration": 1.417}, {"text": "going to spend a whole class\non OpenAPIs in two weeks.", "start": 359.04, "duration": 5.46}, {"text": "But this is an important\npart of marketing,", "start": 364.5, "duration": 2.04}, {"text": "opening up the banks'\nledgers and their data.", "start": 366.54, "duration": 3.39}, {"text": "And data, as people\nwould like to say,", "start": 369.93, "duration": 3.45}, {"text": "is sort of the new\noil in the business.", "start": 373.38, "duration": 4.11}, {"text": "It's very valuable for us.", "start": 377.49, "duration": 2.79}, {"text": "Anybody else, Romain?", "start": 380.28, "duration": 1.493}, {"text": "ROMAIN DE SAINT PERIER: Yes.", "start": 381.773, "duration": 1.167}, {"text": "AUDIENCE: The natural\nlanguage processing so that we", "start": 387.03, "duration": 2.17}, {"text": "can have the robotic advisors.", "start": 389.2, "duration": 3.607}, {"text": "GARY GENSLER: Right.", "start": 392.807, "duration": 0.833}, {"text": "So natural language\nprocessing is the concept", "start": 393.64, "duration": 2.67}, {"text": "that you can take something\nthat's in human language", "start": 396.31, "duration": 4.08}, {"text": "and put it into machine\nor computer language", "start": 400.39, "duration": 2.88}, {"text": "or go the vice versa.", "start": 403.27, "duration": 2.05}, {"text": "And it's not\nactually new in 2020.", "start": 405.32, "duration": 2.39}, {"text": "Some form of natural\nlanguage processing", "start": 407.71, "duration": 2.31}, {"text": "has been around for decades,\njust in terms of reading--", "start": 410.02, "duration": 3.84}, {"text": "reading computer code and\nputting it into an audio voice", "start": 413.86, "duration": 5.91}, {"text": "or going backwards.", "start": 419.77, "duration": 1.44}, {"text": "Or every postal service of a\nmajor country around the globe", "start": 421.21, "duration": 4.03}, {"text": "has had something to read\nour scribbled handwriting", "start": 425.24, "duration": 3.08}, {"text": "and trying to read\nthat handwriting", "start": 428.32, "duration": 2.74}, {"text": "and then put it into\nsomething where they know", "start": 431.06, "duration": 2.15}, {"text": "which post box to send it to.", "start": 433.21, "duration": 3.0}, {"text": "But natural language processing,\nwe'll spend a fair bit of time,", "start": 436.21, "duration": 3.0}, {"text": "and robotics.", "start": 439.21, "duration": 1.8}, {"text": "Romain?", "start": 441.01, "duration": 0.693}, {"text": "ROMAIN DE SAINT\nPERIER: And now we", "start": 441.703, "duration": 1.417}, {"text": "have Ivy, who raised her hand.", "start": 443.12, "duration": 3.63}, {"text": "AUDIENCE: Yeah, so I think\nwe've seen a lot of digitization", "start": 446.75, "duration": 3.57}, {"text": "in the e-commerce space\nas well, especially", "start": 450.32, "duration": 3.0}, {"text": "in places like China.", "start": 453.32, "duration": 1.56}, {"text": "And you see this kind of\ndivergence between China", "start": 454.88, "duration": 3.66}, {"text": "and, say, the US and the\nway we use mobile pay", "start": 458.54, "duration": 2.76}, {"text": "and the way that they've really\nadopted like Alipay and WePay", "start": 461.3, "duration": 3.9}, {"text": "as well.", "start": 465.2, "duration": 0.515}, {"text": "GARY GENSLER: And\nIvy, why do you", "start": 465.715, "duration": 1.375}, {"text": "think it happened so, as\nyou say, at this divergence,", "start": 467.09, "duration": 3.94}, {"text": "why it happened maybe a\nlittle faster in China?", "start": 471.03, "duration": 3.81}, {"text": "AUDIENCE: So I think it's pretty\ninteresting, because I think", "start": 474.84, "duration": 3.11}, {"text": "a place like China,\nas an example,", "start": 477.95, "duration": 1.71}, {"text": "is probably less\ndeveloped in terms", "start": 479.66, "duration": 3.48}, {"text": "of even just their financial\nstructure, whereas the place", "start": 483.14, "duration": 3.78}, {"text": "like the US, it's\nquite dominated.", "start": 486.92, "duration": 1.83}, {"text": "And it's really competitive.", "start": 488.75, "duration": 1.66}, {"text": "But it's also\nreally consolidated.", "start": 490.41, "duration": 1.64}, {"text": "So you see these\ncountries where--", "start": 492.05, "duration": 2.37}, {"text": "I mean, I think the\nway I think about it", "start": 494.42, "duration": 1.84}, {"text": "is the subway systems\nin China or Taiwan", "start": 496.26, "duration": 4.227}, {"text": "or a lot of these\ndeveloping countries", "start": 500.487, "duration": 1.583}, {"text": "are much better because\nthey were just--", "start": 502.07, "duration": 2.03}, {"text": "they came a little bit later.", "start": 504.1, "duration": 2.44}, {"text": "And I just look at that\nanalogy similarly to kind", "start": 506.54, "duration": 3.54}, {"text": "of where payments are,\nbecause you kind of go", "start": 510.08, "duration": 3.78}, {"text": "from 0 to 100 versus we\nare kind of something--", "start": 513.86, "duration": 2.503}, {"text": "GARY GENSLER: No, I think\nIvy's raised a good point.", "start": 516.363, "duration": 2.167}, {"text": "There's times when a\ncountry is growing rapidly.", "start": 518.53, "duration": 3.43}, {"text": "And China, for instance, had\nbeen growing at 8% to 10% GDP", "start": 521.96, "duration": 4.05}, {"text": "growth a year.", "start": 526.01, "duration": 1.76}, {"text": "And before corona, it had\ncome down to still a robust 6%", "start": 527.77, "duration": 3.88}, {"text": "a year.", "start": 531.65, "duration": 1.32}, {"text": "But within that\ncontext, many things", "start": 532.97, "duration": 2.99}, {"text": "leapfrogged incumbents in\nEurope and in North America.", "start": 535.96, "duration": 6.13}, {"text": "And in the payment space\nin particular, two big tech", "start": 542.09, "duration": 2.97}, {"text": "companies--", "start": 545.06, "duration": 2.4}, {"text": "Alibaba, that really is the\ndominant online retailing", "start": 547.46, "duration": 4.92}, {"text": "company, and Tencent, which\nwas the dominant online sort", "start": 552.38, "duration": 3.8}, {"text": "of social networking\nand messaging company--", "start": 556.18, "duration": 4.12}, {"text": "leapfrogged the banking system,\nthe traditional banking system,", "start": 560.3, "duration": 3.21}, {"text": "and now with WeChat\nPay and Alipay", "start": 563.51, "duration": 1.95}, {"text": "control well over 90% of\nretail payments, small dollar,", "start": 565.46, "duration": 4.32}, {"text": "and small and medium-sized\nenterprise payments.", "start": 569.78, "duration": 2.88}, {"text": "They don't dominate\nlarge wholesale payments,", "start": 572.66, "duration": 2.58}, {"text": "but put in the retail\nspace, absolutely.", "start": 575.24, "duration": 2.445}, {"text": "And I would agree with Ivy.", "start": 577.685, "duration": 1.125}, {"text": "They kind of leapfrogged us.", "start": 578.81, "duration": 1.2}, {"text": "But even Kenya leapfrogged us\nwith M-Pesa, a technology that", "start": 580.01, "duration": 5.52}, {"text": "was pushed forward by a\ntelephone company, Safaricom,", "start": 585.53, "duration": 3.87}, {"text": "when they noticed that folks\nwere trading mobile minutes", "start": 589.4, "duration": 3.63}, {"text": "as a form of money.", "start": 593.03, "duration": 1.928}, {"text": "ROMAIN DE SAINT\nPERIER: Gary, we have", "start": 594.958, "duration": 1.542}, {"text": "two more hands that are up.", "start": 596.5, "duration": 2.66}, {"text": "We can start with--", "start": 599.16, "duration": 0.88}, {"text": "GARY GENSLER: All\nright, why don't we", "start": 600.04, "duration": 0.42}, {"text": "do those and then move on?", "start": 600.46, "duration": 1.083}, {"text": "So who are the two people?", "start": 601.543, "duration": 1.967}, {"text": "And they can just go in turn.", "start": 603.51, "duration": 1.643}, {"text": "ROMAIN DE SAINT PERIER:\nSo we had Laira,", "start": 605.153, "duration": 1.667}, {"text": "but she just disappeared.", "start": 606.82, "duration": 1.27}, {"text": "So we'll go with Alida.", "start": 608.09, "duration": 1.64}, {"text": "GARY GENSLER: All\nright, one, thank you.", "start": 609.73, "duration": 2.82}, {"text": "AUDIENCE: Yeah, so I, to kind\nof add on to Ivy's point,", "start": 612.55, "duration": 2.9}, {"text": "is a lot of financial\ninstitutions in emerging", "start": 615.45, "duration": 2.65}, {"text": "markets did not typically\ncater towards the mass-market", "start": 618.1, "duration": 5.28}, {"text": "consumer population.", "start": 623.38, "duration": 2.02}, {"text": "And so it really allowed very\nquickly for these big tech", "start": 625.4, "duration": 3.17}, {"text": "companies to jump in a way that\nyou couldn't do so in the--", "start": 628.57, "duration": 3.81}, {"text": "in more developed markets,\nwhere the financial institutions", "start": 632.38, "duration": 3.63}, {"text": "already were catering to the\nlarge majority of the consumer", "start": 636.01, "duration": 3.12}, {"text": "population.", "start": 639.13, "duration": 1.97}, {"text": "GARY GENSLER:\nRight, so it's about", "start": 641.1, "duration": 1.83}, {"text": "actual financial inclusion\nand reaching out and so forth.", "start": 642.93, "duration": 4.96}, {"text": "So what I'm going to do today\nis try to cover, in the minutes", "start": 647.89, "duration": 4.16}, {"text": "we have, a little bit\nabout the financial world.", "start": 652.05, "duration": 2.79}, {"text": "What do we mean, FinTech\nshaping the future", "start": 654.84, "duration": 3.39}, {"text": "of the financial world?", "start": 658.23, "duration": 1.26}, {"text": "What do I what do I think of it,\nhaving spent my life-- first,", "start": 659.49, "duration": 3.39}, {"text": "I was 18 years at Goldman Sachs.", "start": 662.88, "duration": 3.3}, {"text": "Then I worked in\nthe public sector,", "start": 666.18, "duration": 2.4}, {"text": "but always sort of around\nfinance, with the US Treasury", "start": 668.58, "duration": 3.54}, {"text": "Department, with Paul Sarbanes\ndoing Sarbanes-Oxley, and then", "start": 672.12, "duration": 3.54}, {"text": "later running a market\nregulator, the Commodity", "start": 675.66, "duration": 3.81}, {"text": "Futures Trading Commission,\nin the Obama administration.", "start": 679.47, "duration": 4.82}, {"text": "What do we mean by\nthe financial world?", "start": 684.29, "duration": 3.04}, {"text": "A little touch on FinTech--", "start": 687.33, "duration": 1.53}, {"text": "that's the whole\nclass, of course,", "start": 688.86, "duration": 1.5}, {"text": "but just a little\ntouch on FinTech.", "start": 690.36, "duration": 2.4}, {"text": "Thirdly, again,\njust a little review", "start": 692.76, "duration": 2.58}, {"text": "of these three big trends--", "start": 695.34, "duration": 2.5}, {"text": "of AI, open banking,\nblockchain technology--", "start": 697.84, "duration": 3.45}, {"text": "what do these trends mean?", "start": 701.29, "duration": 3.23}, {"text": "And then the actors--", "start": 704.52, "duration": 1.53}, {"text": "and the actors, I think that\nsome people will use the word", "start": 706.05, "duration": 3.15}, {"text": "FinTech to mean these\ndisruptors, companies", "start": 709.2, "duration": 2.76}, {"text": "like Toast getting into the\npayment space for restaurants", "start": 711.96, "duration": 3.51}, {"text": "or Lending Club and peer-to-peer\nlending or Robinhood, an app", "start": 715.47, "duration": 4.62}, {"text": "you can download\nand trade stocks.", "start": 720.09, "duration": 2.91}, {"text": "A lot of people constrain the\nstudy and the topic of FinTech", "start": 723.0, "duration": 3.51}, {"text": "just to the disruptors.", "start": 726.51, "duration": 1.86}, {"text": "I think that that's too narrow.", "start": 728.37, "duration": 2.26}, {"text": "I think that we\nreally need to think", "start": 730.63, "duration": 2.09}, {"text": "of the actors and\nthe field, more", "start": 732.72, "duration": 1.89}, {"text": "broadly about the incumbents.", "start": 734.61, "duration": 2.58}, {"text": "This is sort of big\nfinance, we might say,", "start": 737.19, "duration": 3.08}, {"text": "the Barclays banks and the\nJPMorgans and so forth.", "start": 740.27, "duration": 5.92}, {"text": "And we need to\nthink of big tech,", "start": 746.19, "duration": 2.13}, {"text": "as we just talked with Ivy\nabout Alibaba and Tencent", "start": 748.32, "duration": 5.28}, {"text": "getting into this business.", "start": 753.6, "duration": 1.25}, {"text": "But we see Apple Credit Card\nand others and Facebook trying", "start": 754.85, "duration": 3.7}, {"text": "to stand up a world currency.", "start": 758.55, "duration": 2.4}, {"text": "And then it's the disruptors.", "start": 760.95, "duration": 1.92}, {"text": "So I think it's a much\nmore robust conversation", "start": 762.87, "duration": 4.14}, {"text": "and an important\nconversation, the strategy", "start": 767.01, "duration": 2.97}, {"text": "amongst these three pieces.", "start": 769.98, "duration": 1.228}, {"text": "And then, of course, we've\ngot to do a little bit", "start": 771.208, "duration": 2.042}, {"text": "on our teaching team, our\nschedule and assignments", "start": 773.25, "duration": 2.37}, {"text": "and so forth.", "start": 775.62, "duration": 2.38}, {"text": "So what do I think of is in the\nfinancial world and what it is?", "start": 778.0, "duration": 3.92}, {"text": "Well, finance basically\nstands, like this hourglass", "start": 781.92, "duration": 3.98}, {"text": "in the top-right-hand\ncorner, stands", "start": 785.9, "duration": 2.26}, {"text": "right at the neck of an\nhourglass, intermediating,", "start": 788.16, "duration": 3.42}, {"text": "standing between people that\nhave money and need money,", "start": 791.58, "duration": 4.5}, {"text": "people that have risk and want\nto get rid of it, lay it off,", "start": 796.08, "duration": 4.1}, {"text": "and somebody that\nwants to pick it up.", "start": 800.18, "duration": 2.41}, {"text": "And I have for decades,\nsince I was at Goldman Sachs,", "start": 802.59, "duration": 2.7}, {"text": "thought where we were, we were\nat the neck of the hourglass.", "start": 805.29, "duration": 3.57}, {"text": "And for good or for\nbad, that's also", "start": 808.86, "duration": 2.94}, {"text": "part of why finance\nin many countries", "start": 811.8, "duration": 3.0}, {"text": "is able to collect\neconomic rents.", "start": 814.8, "duration": 2.49}, {"text": "Economic rents is that\nclassic conceptual framework", "start": 817.29, "duration": 3.18}, {"text": "of collecting profits\nor revenues in excess", "start": 820.47, "duration": 3.39}, {"text": "of what classic\neconomics might tell you", "start": 823.86, "duration": 3.24}, {"text": "would be a competitive\nsupply and demand space.", "start": 827.1, "duration": 3.22}, {"text": "But if you stand at the\nneck of an hourglass,", "start": 830.32, "duration": 2.63}, {"text": "between trillions of money\nflowing from those who want it", "start": 832.95, "duration": 4.56}, {"text": "and those who have it,\nand effectively trillions", "start": 837.51, "duration": 3.27}, {"text": "of risk between those who have\nrisk and want to lay it off", "start": 840.78, "duration": 4.68}, {"text": "and others who are\nwilling to hedge it--", "start": 845.46, "duration": 1.83}, {"text": "if you're at that neck of\nthe hourglass, so to speak,", "start": 847.29, "duration": 2.94}, {"text": "if you just collect\na few grains of sand", "start": 850.23, "duration": 2.94}, {"text": "for the trillions that go\nby, it can collect a lot.", "start": 853.17, "duration": 3.3}, {"text": "In the United States,\nfor one, for instance,", "start": 856.47, "duration": 2.95}, {"text": "our financial sector\ntakes about 7 and 1/2%", "start": 859.42, "duration": 2.405}, {"text": "of our Gross Domestic Product.", "start": 861.825, "duration": 2.625}, {"text": "Nowhere is it written it has to.", "start": 864.45, "duration": 2.07}, {"text": "In fact, in the 1950s and\n'60s, it was more like 3", "start": 866.52, "duration": 2.76}, {"text": "and 1/2% to 4%.", "start": 869.28, "duration": 2.19}, {"text": "But persistently, it's\ngrown as a percentage", "start": 871.47, "duration": 2.49}, {"text": "of our economy, standing,\nintermediating money and risk.", "start": 873.96, "duration": 3.6}, {"text": "Let's just see if I\ncan get this to work.", "start": 881.67, "duration": 3.02}, {"text": "There, so the\nfunctions, the functions", "start": 884.69, "duration": 1.91}, {"text": "are intermediating credit.", "start": 886.6, "duration": 1.29}, {"text": "That's lending.", "start": 887.89, "duration": 1.24}, {"text": "Investments, we all know that.", "start": 889.13, "duration": 1.85}, {"text": "Risk transformation--\nthink of any time one of us", "start": 890.98, "duration": 2.91}, {"text": "buys insurance on an automobile\nor a car or on our life,", "start": 893.89, "duration": 4.62}, {"text": "but also risk transformation\nthat investment banks do, even", "start": 898.51, "duration": 3.9}, {"text": "between somebody that's issuing\nstock and somebody that's", "start": 902.41, "duration": 3.27}, {"text": "buying stock.", "start": 905.68, "duration": 0.87}, {"text": "That's a transference\nof risk in terms", "start": 906.55, "duration": 2.46}, {"text": "of whether that\nstartup will do well.", "start": 909.01, "duration": 2.52}, {"text": "Of course, there's\nthe capital markets.", "start": 911.53, "duration": 1.92}, {"text": "And at the center of\nthe capital markets", "start": 913.45, "duration": 2.01}, {"text": "is the price, the\nmoney and risk that's", "start": 915.46, "duration": 3.06}, {"text": "flowing through the system.", "start": 918.52, "duration": 1.6}, {"text": "And there's plenty of\nadvice to go around.", "start": 920.12, "duration": 2.45}, {"text": "Now, we usually think\nabout it in sectors.", "start": 922.57, "duration": 2.25}, {"text": "And every one of these\nsectors, whether it's", "start": 924.82, "duration": 2.01}, {"text": "commercial banking, asset\nmanagement, insurance,", "start": 926.83, "duration": 2.7}, {"text": "investment banking,\nadvisories, we", "start": 929.53, "duration": 2.82}, {"text": "will touch upon\nduring this semester.", "start": 932.35, "duration": 2.46}, {"text": "And please, interrupt.", "start": 934.81, "duration": 1.32}, {"text": "If your keen interest is\nabout insurance companies", "start": 936.13, "duration": 3.3}, {"text": "or your keen interest is\nabout investment banks,", "start": 939.43, "duration": 3.24}, {"text": "then pull the community into\nthat in these discussions.", "start": 942.67, "duration": 4.5}, {"text": "But we're going to try to\ntalk about multiple sectors,", "start": 947.17, "duration": 3.18}, {"text": "multiple functions,\nas contrasted", "start": 950.35, "duration": 2.16}, {"text": "to the half-semester consumer\nfinance course that was really", "start": 952.51, "duration": 3.27}, {"text": "just about one slice,\nhousehold lending, and largely", "start": 955.78, "duration": 5.31}, {"text": "the commercial banks and\ninvestment banks around that.", "start": 961.09, "duration": 3.93}, {"text": "This is a much broader topic.", "start": 965.02, "duration": 2.34}, {"text": "And I hope the learning\nobjective is ultimately", "start": 967.36, "duration": 2.4}, {"text": "to understand how technology\ncan transform finance", "start": 969.76, "duration": 4.56}, {"text": "at any particular given time.", "start": 974.32, "duration": 4.04}, {"text": "Romain, are there any hands up?", "start": 978.36, "duration": 1.78}, {"text": "I'm sort of every once in a\nwhile looking to you to see", "start": 980.14, "duration": 2.46}, {"text": "if I keep going or pause.", "start": 982.6, "duration": 1.722}, {"text": "ROMAIN DE SAINT PERIER: No\nhands at the moment, Gary.", "start": 984.322, "duration": 2.208}, {"text": "GARY GENSLER: All right.", "start": 986.53, "duration": 1.0}, {"text": "The financial world, in this,\nI think, four key things", "start": 987.53, "duration": 3.59}, {"text": "to think about.", "start": 991.12, "duration": 0.99}, {"text": "And this is sort of in\na framework of thinking", "start": 992.11, "duration": 2.22}, {"text": "about financial technology.", "start": 994.33, "duration": 1.35}, {"text": "Data-- of course, data is\nthat new oil, so to speak,", "start": 995.68, "duration": 5.04}, {"text": "for investing, for\nmarket-making, for marketing,", "start": 1000.72, "duration": 3.54}, {"text": "trying to get new customers.", "start": 1004.26, "duration": 1.5}, {"text": "I mean, how many times\ndo we get a pop-up ads.", "start": 1005.76, "duration": 2.79}, {"text": "I found in teaching\nabout student loans,", "start": 1008.55, "duration": 3.34}, {"text": "I was researching student loans.", "start": 1011.89, "duration": 1.65}, {"text": "And my god, the\nlast six weeks I've", "start": 1013.54, "duration": 2.24}, {"text": "got more advertisement\nfor student loans,", "start": 1015.78, "duration": 4.05}, {"text": "even now I'm a professor at MIT.", "start": 1019.83, "duration": 2.55}, {"text": "It's because I was researching\nthe topic of student loans,", "start": 1022.38, "duration": 3.209}, {"text": "and all of a sudden,\nnow I am getting", "start": 1025.589, "duration": 2.371}, {"text": "a lot of unsolicited ads and\nemails, even, on the topic.", "start": 1027.96, "duration": 7.2}, {"text": "The financial\nworld it always has", "start": 1035.16, "duration": 1.439}, {"text": "to think about the management\nof their balance sheet.", "start": 1036.599, "duration": 2.821}, {"text": "And if you're starting\na FinTech company,", "start": 1039.42, "duration": 2.669}, {"text": "are you using your balance\nsheet or somebody else's balance", "start": 1042.089, "duration": 2.821}, {"text": "sheet?", "start": 1044.91, "duration": 0.75}, {"text": "And just as there's\ncloud computing,", "start": 1045.66, "duration": 2.32}, {"text": "that today, cloud\ncomputing has dramatically", "start": 1047.98, "duration": 3.05}, {"text": "shifted the ability of\nstartups, a disruptor", "start": 1051.03, "duration": 3.24}, {"text": "can come into a business and\nbasically the rent versus bill", "start": 1054.27, "duration": 6.27}, {"text": "decision changes.", "start": 1060.54, "duration": 1.14}, {"text": "I can read somebody else's\ndata storage capacity.", "start": 1061.68, "duration": 3.54}, {"text": "I can basically rent the cloud\ninstead of building my own data", "start": 1065.22, "duration": 5.79}, {"text": "warehouse.", "start": 1071.01, "duration": 1.02}, {"text": "That was a big change\nabout 15 years ago.", "start": 1072.03, "duration": 2.16}, {"text": "And it's made startups\nmore viable in the 2020s.", "start": 1074.19, "duration": 4.05}, {"text": "Also, the ability to raise money\nin the capital markets, what's", "start": 1078.24, "duration": 4.08}, {"text": "called securitizations, which\nstarted decades ago, really", "start": 1082.32, "duration": 4.35}, {"text": "took off by the 1990s, also\nallows a startup like Lending", "start": 1086.67, "duration": 4.2}, {"text": "Club and others to say I'll\nraise my money elsewhere.", "start": 1090.87, "duration": 2.67}, {"text": "I don't have to have\na balance sheet.", "start": 1093.54, "duration": 2.7}, {"text": "And then there's the various\nrisks that you have to manage.", "start": 1096.24, "duration": 3.15}, {"text": "And most importantly, we're\ngoing to spend a lot of time", "start": 1099.39, "duration": 2.67}, {"text": "doing this class on\nthis fourth point-- user", "start": 1102.06, "duration": 2.07}, {"text": "experience, user interface.", "start": 1104.13, "duration": 2.07}, {"text": "Much of what's happened\nwith mobile phones,", "start": 1106.2, "duration": 3.66}, {"text": "with apps that you can download\nfor free have given all of us", "start": 1109.86, "duration": 5.25}, {"text": "a better user experience\nthan online banking.", "start": 1115.11, "duration": 3.96}, {"text": "Online banking has been\naround for over 20 years.", "start": 1119.07, "duration": 2.83}, {"text": "Most of the major\nbanks around the globe", "start": 1121.9, "duration": 1.97}, {"text": "had a viable platform for\nonline banking by the naughts,", "start": 1123.87, "duration": 4.05}, {"text": "whether it was 2005 for some\nor 2008 or others or so forth.", "start": 1127.92, "duration": 4.46}, {"text": "But by the naughts,\nmost had online banking.", "start": 1132.38, "duration": 3.64}, {"text": "And yet, their user\nexperience wasn't what", "start": 1136.02, "duration": 2.28}, {"text": "we all wanted, and certainly\nwasn't what-- maybe", "start": 1138.3, "duration": 3.0}, {"text": "if the newer users,\nas millennials,", "start": 1141.3, "duration": 3.0}, {"text": "were coming into\nthe marketplace,", "start": 1144.3, "duration": 2.19}, {"text": "to do it on your mobile\nphone, to do it conveniently.", "start": 1146.49, "duration": 3.4}, {"text": "So the user experience\nand the user interface", "start": 1149.89, "duration": 3.0}, {"text": "is the critical\ncompetitive place.", "start": 1152.89, "duration": 4.1}, {"text": "So what do we mean by FinTech?", "start": 1156.99, "duration": 1.53}, {"text": "I like going back to that\n2017 Financial Stability Board", "start": 1158.52, "duration": 3.69}, {"text": "report.", "start": 1162.21, "duration": 0.74}, {"text": "That doesn't mean that\nthey have it quite right.", "start": 1162.95, "duration": 3.07}, {"text": "But they basically\ntalk about that it's", "start": 1166.02, "duration": 1.86}, {"text": "technology-enabled innovation\nin the financial world that's", "start": 1167.88, "duration": 6.29}, {"text": "going to some new business\nand it's material.", "start": 1174.17, "duration": 5.48}, {"text": "So, as I mentioned earlier,\nthe telegraph in the 1830s", "start": 1179.65, "duration": 3.41}, {"text": "comes along.", "start": 1183.06, "duration": 0.69}, {"text": "And by the 1860s\nand 1870s, we're", "start": 1183.75, "duration": 2.43}, {"text": "starting to see digital money.", "start": 1186.18, "duration": 2.91}, {"text": "The first form of digital money\nis already about 140 years old.", "start": 1189.09, "duration": 7.04}, {"text": "I mean, we think we're living\nin this digital age, and we are.", "start": 1196.13, "duration": 4.17}, {"text": "And I would note this\nabout the corona crisis", "start": 1200.3, "duration": 3.0}, {"text": "that we're living in--", "start": 1203.3, "duration": 1.35}, {"text": "the corona crisis,\nin my opinion,", "start": 1204.65, "duration": 2.17}, {"text": "will accelerate\nthis digitization.", "start": 1206.82, "duration": 2.78}, {"text": "We've already, in\nthe last 30 years,", "start": 1209.6, "duration": 2.13}, {"text": "significantly\ndigitized our world.", "start": 1211.73, "duration": 4.23}, {"text": "And if we were all\ntogether in a classroom,", "start": 1215.96, "duration": 2.32}, {"text": "I would ask by a show\nof hands how many of you", "start": 1218.28, "duration": 2.19}, {"text": "have used paper money or\ncurrency in the last two", "start": 1220.47, "duration": 3.77}, {"text": "or three days.", "start": 1224.24, "duration": 1.53}, {"text": "And maybe a quarter\nof you might have", "start": 1225.77, "duration": 1.86}, {"text": "said you had used paper money\nin the last two or three days.", "start": 1227.63, "duration": 3.6}, {"text": "But let me ask you in the\nmiddle of the corona crisis--", "start": 1231.23, "duration": 2.68}, {"text": "and Romain, you can tell\nme if any hands go up--", "start": 1233.91, "duration": 3.33}, {"text": "we'll you use the\nblue hand, anybody", "start": 1237.24, "duration": 2.45}, {"text": "that's used paper, physical\nmoney in the last two days.", "start": 1239.69, "duration": 5.215}, {"text": "ROMAIN DE SAINT PERIER: Thank\nyou, Alida, for volunteering.", "start": 1246.492, "duration": 2.458}, {"text": "The floor is yours.", "start": 1248.95, "duration": 0.81}, {"text": "AUDIENCE: I have for grocery\nshopping and so forth.", "start": 1254.22, "duration": 2.918}, {"text": "GARY GENSLER: So you actually--", "start": 1257.138, "duration": 1.292}, {"text": "and they'll still take the\npaper money behind the counter", "start": 1258.43, "duration": 4.6}, {"text": "without wiping it down\nwith some cleaner?", "start": 1263.03, "duration": 3.89}, {"text": "AUDIENCE: Yes.", "start": 1266.92, "duration": 0.65}, {"text": "And I took out a lot of\ncash before everything", "start": 1267.57, "duration": 2.85}, {"text": "happened, so--", "start": 1270.42, "duration": 1.122}, {"text": "GARY GENSLER: Ah, ah.", "start": 1271.542, "duration": 1.768}, {"text": "Alida, may I ask, was that\njust sort of insurance,", "start": 1273.31, "duration": 2.78}, {"text": "managing risk, as we say, as\npart of finance, where you're--", "start": 1276.09, "duration": 2.747}, {"text": "AUDIENCE: Yes.", "start": 1278.837, "duration": 0.583}, {"text": "GARY GENSLER:\n--managing the risk", "start": 1279.42, "duration": 1.375}, {"text": "that the banking sector and the\nATMs and things might not work?", "start": 1280.795, "duration": 3.035}, {"text": "AUDIENCE: Yes.", "start": 1283.83, "duration": 1.65}, {"text": "GARY GENSLER: And do\nI see Devin's hand?", "start": 1285.48, "duration": 2.213}, {"text": "ROMAIN DE SAINT PERIER:\nThat is correct.", "start": 1287.693, "duration": 1.667}, {"text": "AUDIENCE: I can only\ndo laundry using cash.", "start": 1289.36, "duration": 3.662}, {"text": "So I use it for now, but--", "start": 1293.022, "duration": 3.468}, {"text": "GARY GENSLER: But see how\nfew of us, of 80 plus people,", "start": 1296.49, "duration": 3.07}, {"text": "two people.", "start": 1299.56, "duration": 0.69}, {"text": "Now, we're in the middle\nof a corona crisis.", "start": 1300.25, "duration": 2.49}, {"text": "I would predict that as we come\nout of this, whether this is--", "start": 1302.74, "duration": 4.44}, {"text": "whether this is a matter\nof a couple of few months", "start": 1307.18, "duration": 2.49}, {"text": "or whether this\nis, unfortunately,", "start": 1309.67, "duration": 1.74}, {"text": "as long as couple of years,\nwherever we come out,", "start": 1311.41, "duration": 4.26}, {"text": "that the corona\ncrisis will accelerate", "start": 1315.67, "duration": 2.64}, {"text": "an already existing trend.", "start": 1318.31, "duration": 2.16}, {"text": "And that already existing trend\ndistorts further and further", "start": 1320.47, "duration": 3.9}, {"text": "digitalization of commerce,\nthat that laundromat", "start": 1324.37, "duration": 3.54}, {"text": "that Devin goes to will take a\nQR code or a swipe of a phone", "start": 1327.91, "duration": 6.09}, {"text": "more readily.", "start": 1334.0, "duration": 1.41}, {"text": "And yes, I think it was Anita\nsaid that she took out cash", "start": 1335.41, "duration": 5.19}, {"text": "before the crisis.", "start": 1340.6, "duration": 1.12}, {"text": "And that's true.", "start": 1341.72, "duration": 1.13}, {"text": "There is still going to be\nsome people that probably", "start": 1342.85, "duration": 2.46}, {"text": "also went and bought gold.", "start": 1345.31, "duration": 2.22}, {"text": "And we should respect\nthat, that that's", "start": 1347.53, "duration": 2.43}, {"text": "sort of an insurance policy\nagainst the digital world", "start": 1349.96, "duration": 3.3}, {"text": "collapsing.", "start": 1353.26, "duration": 1.207}, {"text": "ROMAIN DE SAINT\nPERIER: Gary, it seems", "start": 1354.467, "duration": 1.583}, {"text": "like Devin has a follow-up.", "start": 1356.05, "duration": 1.47}, {"text": "GARY GENSLER: Yes, please.", "start": 1357.52, "duration": 2.454}, {"text": "No, and maybe Devin\njust left his hand up.", "start": 1359.974, "duration": 2.176}, {"text": "AUDIENCE: I apol--", "start": 1362.15, "duration": 0.75}, {"text": "GARY GENSLER: Maybe\nafter you speak,", "start": 1362.9, "duration": 1.64}, {"text": "you actually then\ntake your hand down.", "start": 1364.54, "duration": 1.975}, {"text": "AUDIENCE: All right.", "start": 1366.515, "duration": 0.285}, {"text": "GARY GENSLER: So what are the\ntechnologies of our times?", "start": 1366.8, "duration": 2.333}, {"text": "What's sort of rolling with it\nnow, no longer the telegraph", "start": 1369.133, "duration": 3.457}, {"text": "or so forth?", "start": 1372.59, "duration": 1.65}, {"text": "Well, I put up my favorites.", "start": 1374.24, "duration": 1.615}, {"text": "And then I kind of\nthink, well, maybe I", "start": 1375.855, "duration": 1.625}, {"text": "shouldn't have put\nthe cloud there.", "start": 1377.48, "duration": 1.458}, {"text": "Maybe the cloud really\nisn't a technology that's", "start": 1378.938, "duration": 2.742}, {"text": "pushing us forward right now.", "start": 1381.68, "duration": 2.22}, {"text": "And yet, what's interesting\nis finance uses the cloud less", "start": 1383.9, "duration": 3.96}, {"text": "than most industries.", "start": 1387.86, "duration": 1.59}, {"text": "And this is particularly\nthe case of incumbents.", "start": 1389.45, "duration": 3.795}, {"text": "Country by country-- it doesn't\nmatter whether we're in Brazil,", "start": 1393.245, "duration": 2.625}, {"text": "whether we're in Europe,\nwhether we're in the US--", "start": 1395.87, "duration": 3.8}, {"text": "big incumbents, like\nJPMorgan and Bank", "start": 1399.67, "duration": 2.7}, {"text": "of America and Barclays, tend\nto still have their own data", "start": 1402.37, "duration": 3.34}, {"text": "centers.", "start": 1405.71, "duration": 0.5}, {"text": "Now, that's shifting.", "start": 1406.21, "duration": 0.93}, {"text": "I think the 2020s will\nsee them shift over.", "start": 1407.14, "duration": 2.31}, {"text": "But they've tended to want to\nsort of control their destiny.", "start": 1409.45, "duration": 3.81}, {"text": "I think they will shift because\nit's lower cost and better", "start": 1413.26, "duration": 2.97}, {"text": "cybersecurity generally\nif you have it, frankly,", "start": 1416.23, "duration": 3.84}, {"text": "at Baidu in China or Microsoft\nor AWS and so forth here.", "start": 1420.07, "duration": 5.89}, {"text": "But startups dramatically\nuse the cloud.", "start": 1425.96, "duration": 2.72}, {"text": "This is this buy versus\nbuild sort of scenario.", "start": 1428.68, "duration": 3.3}, {"text": "Why build my own data center?", "start": 1431.98, "duration": 2.28}, {"text": "I can rent it.", "start": 1434.26, "duration": 1.02}, {"text": "I can use somebody else.", "start": 1435.28, "duration": 1.77}, {"text": "But all the others we're\ngoing to talk about--", "start": 1437.05, "duration": 2.19}, {"text": "and I should say that\nthere's a little--", "start": 1439.24, "duration": 3.24}, {"text": "a little sleight of hand by\nmy list, because many of these", "start": 1442.48, "duration": 3.84}, {"text": "are actually artificial\nintelligence and machine", "start": 1446.32, "duration": 3.12}, {"text": "learning, which is part of\nartificial intelligence.", "start": 1449.44, "duration": 2.16}, {"text": "Natural language\nprocessing, in essence,", "start": 1451.6, "duration": 2.43}, {"text": "is artificial intelligence.", "start": 1454.03, "duration": 2.01}, {"text": "Chatbots are sort of that\nas well, and robotic process", "start": 1456.04, "duration": 4.83}, {"text": "automation.", "start": 1460.87, "duration": 0.65}, {"text": "But I split them\nout because I think", "start": 1461.52, "duration": 2.35}, {"text": "it's relevant that we kind\nof have a chance to talk", "start": 1463.87, "duration": 2.43}, {"text": "about each of these as we go.", "start": 1466.3, "duration": 4.07}, {"text": "I'm pausing every once\nin a while, Romain,", "start": 1470.37, "duration": 2.58}, {"text": "but you can let me now.", "start": 1472.95, "duration": 1.05}, {"text": "I like to think of this\nin the context of history.", "start": 1476.6, "duration": 2.61}, {"text": "Maybe that's just because I've\nalways loved studying history.", "start": 1479.21, "duration": 3.08}, {"text": "But what's the\ncustomer interface", "start": 1482.29, "duration": 2.65}, {"text": "that we've seen all the way\nback from sort of prehistory,", "start": 1484.94, "duration": 4.59}, {"text": "that the customer interface was\nin tents or bricks and mortar", "start": 1489.53, "duration": 4.41}, {"text": "later, all the way\nup through where", "start": 1493.94, "duration": 3.42}, {"text": "we got credit cards invented\nin the 1940s and '50s?", "start": 1497.36, "duration": 3.6}, {"text": "That was a FinTech.", "start": 1500.96, "duration": 1.62}, {"text": "That was a new\nfinancial technology.", "start": 1502.58, "duration": 2.94}, {"text": "Visa, here in the\nUS, was a network", "start": 1505.52, "duration": 3.06}, {"text": "of banks started by a California\nbank called Bank of America.", "start": 1508.58, "duration": 3.87}, {"text": "And they wanted to have\na nationwide network.", "start": 1512.45, "duration": 2.82}, {"text": "And other banks joined it.", "start": 1515.27, "duration": 1.47}, {"text": "That became the Visa network.", "start": 1516.74, "duration": 2.39}, {"text": "But where are we now?", "start": 1519.13, "duration": 1.73}, {"text": "What are the\ntechnologies now that--", "start": 1520.86, "duration": 5.143}, {"text": "I want to make sure I'm\nclicking on the right.", "start": 1526.003, "duration": 1.917}, {"text": "So the base that you\nmight be thinking about--", "start": 1530.44, "duration": 2.37}, {"text": "mobile payments, the internet,\neven contactless cards--", "start": 1532.81, "duration": 4.68}, {"text": "I would say that was\nkind of a last phase.", "start": 1537.49, "duration": 2.88}, {"text": "That was the phase that\nreally shifted finance", "start": 1540.37, "duration": 3.27}, {"text": "in the naughts and early\nteens, and that we really", "start": 1543.64, "duration": 4.02}, {"text": "are in terms of\ncustomer interface", "start": 1547.66, "duration": 4.93}, {"text": "is now conversational\ninterfaces, chatbots", "start": 1552.59, "duration": 6.02}, {"text": "and conversational interfaces.", "start": 1558.61, "duration": 2.25}, {"text": "That's the cutting edge.", "start": 1560.86, "duration": 2.49}, {"text": "Yes, contactless\ncards are important.", "start": 1563.35, "duration": 2.64}, {"text": "Yes, of course, we\nneed mobile payments.", "start": 1565.99, "duration": 2.19}, {"text": "No doubt about it.", "start": 1568.18, "duration": 1.81}, {"text": "But if you're starting a\nnew business right now,", "start": 1569.99, "duration": 2.75}, {"text": "you're going to\nstart a disruptor", "start": 1572.74, "duration": 1.41}, {"text": "and say I'm going to do online\nbanking, that's yesterday.", "start": 1574.15, "duration": 3.96}, {"text": "You have to find a way\nto do that online banking", "start": 1578.11, "duration": 2.82}, {"text": "in a way that has such a\nbetter customer interface.", "start": 1580.93, "duration": 4.11}, {"text": "And you might be using\nsome form of OpenAPIs", "start": 1585.04, "duration": 3.39}, {"text": "or robotic process automation\nand chatbots to do it.", "start": 1588.43, "duration": 4.06}, {"text": "But these are all kind of\nbuild up on each other.", "start": 1592.49, "duration": 3.8}, {"text": "Then there's risk management.", "start": 1596.29, "duration": 1.9}, {"text": "So one is the customer side.", "start": 1598.19, "duration": 2.03}, {"text": "One is the funding and\nrisk management side.", "start": 1600.22, "duration": 2.22}, {"text": "And you can look\nthroughout history.", "start": 1602.44, "duration": 1.94}, {"text": "And I spent a lot of\nmy life in my career", "start": 1604.38, "duration": 2.86}, {"text": "around the capital markets.", "start": 1607.24, "duration": 1.8}, {"text": "I was at Goldman\nSachs for 18 years.", "start": 1609.04, "duration": 2.85}, {"text": "And I had to think\na lot with hundreds", "start": 1611.89, "duration": 2.58}, {"text": "of other people\nabout risk management", "start": 1614.47, "duration": 2.102}, {"text": "and what we were doing.", "start": 1616.572, "duration": 0.958}, {"text": "And in the 1980s and\nthe 1990s, a big thing", "start": 1617.53, "duration": 3.99}, {"text": "was asset-backed securitization\nand interest rate swaps", "start": 1621.52, "duration": 3.93}, {"text": "and even, yes, credit\ndefault swaps that helped", "start": 1625.45, "duration": 2.46}, {"text": "bring down several\neconomies in 2008.", "start": 1627.91, "duration": 3.87}, {"text": "But those innovations\nof the 1970s, the 1990s", "start": 1631.78, "duration": 4.41}, {"text": "were dramatically\nshifting, dramatically", "start": 1636.19, "duration": 3.36}, {"text": "shifting what was going on.", "start": 1639.55, "duration": 1.73}, {"text": "But I would say now, it's\nreally about machine learning.", "start": 1641.28, "duration": 3.86}, {"text": "Machine learning is an ability\nto extract correlations,", "start": 1645.14, "duration": 4.07}, {"text": "extract patterns from data in\na way that we couldn't before.", "start": 1649.21, "duration": 5.98}, {"text": "And many of you have\nstudied linear algebra.", "start": 1655.19, "duration": 4.76}, {"text": "We're blessed in this class\nto have remarkable science", "start": 1659.95, "duration": 4.02}, {"text": "technology and math folks.", "start": 1663.97, "duration": 3.33}, {"text": "Not all of you-- we accept all\nthe English majors and history", "start": 1667.3, "duration": 3.39}, {"text": "majors as well.", "start": 1670.69, "duration": 1.36}, {"text": "But I'm saying that you know\nthat from linear algebra", "start": 1672.05, "duration": 4.73}, {"text": "and basic statistics, you can\ndo a lot of regression analyses.", "start": 1676.78, "duration": 4.69}, {"text": "Machine learning is going\na little beyond that", "start": 1681.47, "duration": 2.42}, {"text": "and extracting\npatterns from that", "start": 1683.89, "duration": 2.13}, {"text": "which was more difficult to\nextract when you were just", "start": 1686.02, "duration": 2.79}, {"text": "doing regression analysis.", "start": 1688.81, "duration": 2.13}, {"text": "And so there's\npatterns that we might", "start": 1690.94, "duration": 3.56}, {"text": "see in the data that says you're\na good risk or a less good risk", "start": 1694.5, "duration": 5.31}, {"text": "that you wouldn't quite say in\na traditional credit scoring", "start": 1699.81, "duration": 3.93}, {"text": "systems.", "start": 1703.74, "duration": 0.69}, {"text": "I think that's where\nwe're going right now.", "start": 1704.43, "duration": 3.28}, {"text": "Romain, anything\nin the chat rooms?", "start": 1707.71, "duration": 2.15}, {"text": "Or I'm going to\npause for a second.", "start": 1709.86, "duration": 1.83}, {"text": "ROMAIN DE SAINT PERIER:\nNothing so far, Gary.", "start": 1715.545, "duration": 1.875}, {"text": "GARY GENSLER: All right.", "start": 1717.42, "duration": 1.18}, {"text": "So it's fertile ground.", "start": 1718.6, "duration": 3.41}, {"text": "And we talked a little\nbit about this before.", "start": 1722.01, "duration": 2.3}, {"text": "But the fertile\nground of finance", "start": 1724.31, "duration": 2.44}, {"text": "is we've basically digitized\nmoney securities and credit", "start": 1726.75, "duration": 4.17}, {"text": "over the last 30 years.", "start": 1730.92, "duration": 1.35}, {"text": "The corona crisis is just going\nto push that further faster,", "start": 1732.27, "duration": 4.68}, {"text": "in my opinion.", "start": 1736.95, "duration": 1.62}, {"text": "We have this vast\namount of data.", "start": 1738.57, "duration": 2.28}, {"text": "And we're starting to\nsee patterns in that data", "start": 1740.85, "duration": 2.46}, {"text": "that we didn't recognize before.", "start": 1743.31, "duration": 3.06}, {"text": "I mentioned this in the consumer\nfinance course that some of you", "start": 1746.37, "duration": 5.7}, {"text": "were with me on, but somebody\nhas actually studied something", "start": 1752.07, "duration": 4.41}, {"text": "like this to say\nthat if you charge", "start": 1756.48, "duration": 1.95}, {"text": "your phone overnight\nevery night, if you charge", "start": 1758.43, "duration": 4.05}, {"text": "your phone every\nnight, you apparently", "start": 1762.48, "duration": 2.25}, {"text": "are a better credit\nthan if you don't", "start": 1764.73, "duration": 1.68}, {"text": "charge your phone every night.", "start": 1766.41, "duration": 2.07}, {"text": "You might think, oh\nmy gosh, I'd better", "start": 1768.48, "duration": 1.92}, {"text": "be charging my phone\nbecause Apple is watching.", "start": 1770.4, "duration": 5.64}, {"text": "They're going to be watching\nwhether I charge my phone.", "start": 1776.04, "duration": 3.45}, {"text": "And in China, there's\na whole social credit", "start": 1779.49, "duration": 2.81}, {"text": "system that takes data from\nmany of your online apps.", "start": 1782.3, "duration": 4.84}, {"text": "It's not just taking\nyour payment information", "start": 1787.14, "duration": 2.24}, {"text": "from Alipay or WeChat Pay,\nbut that social credit system", "start": 1789.38, "duration": 3.84}, {"text": "is checking even\nyour participation", "start": 1793.22, "duration": 3.3}, {"text": "in dating websites.", "start": 1796.52, "duration": 2.07}, {"text": "I kid you not.", "start": 1798.59, "duration": 1.02}, {"text": "I kid you not.", "start": 1799.61, "duration": 1.32}, {"text": "So that social credit\nsystem in China", "start": 1800.93, "duration": 3.27}, {"text": "or the private sector's approach\nto collecting data in the West", "start": 1804.2, "duration": 4.8}, {"text": "have sort of the\nsame goal in mind--", "start": 1809.0, "duration": 4.11}, {"text": "to understand the customers\nmore and to basically", "start": 1813.11, "duration": 6.21}, {"text": "provide more marketing,\nbut also to assess risk.", "start": 1819.32, "duration": 3.97}, {"text": "And, by the way,\nthe corona crisis", "start": 1823.29, "duration": 1.52}, {"text": "might change even the\nWest's view of data sharing,", "start": 1824.81, "duration": 3.9}, {"text": "because when we have Google\nand the US partnering up to say", "start": 1828.71, "duration": 3.93}, {"text": "we can track everybody to\nsee how this disease, how", "start": 1832.64, "duration": 3.84}, {"text": "this disease is propagating\nthrough society, that we", "start": 1836.48, "duration": 3.84}, {"text": "need the modern technology of\nour position location trackers.", "start": 1840.32, "duration": 6.42}, {"text": "A position location tracker\nis called a cell phone.", "start": 1846.74, "duration": 3.36}, {"text": "A smartphone is\ntracking where we", "start": 1850.1, "duration": 2.01}, {"text": "are if you go running with\nit, if you go driving, hiking,", "start": 1852.11, "duration": 4.81}, {"text": "all of that data.", "start": 1856.92, "duration": 1.83}, {"text": "But now here, even in\nthe US and in Europe,", "start": 1858.75, "duration": 3.15}, {"text": "we're starting to\nsay do we partner,", "start": 1861.9, "duration": 1.74}, {"text": "as the official\nsector, with that data", "start": 1863.64, "duration": 3.75}, {"text": "to keep our societies maybe\na little safer, and then,", "start": 1867.39, "duration": 5.6}, {"text": "of course, the rapid\nexpansion of computation power", "start": 1872.99, "duration": 3.06}, {"text": "and so forth.", "start": 1876.05, "duration": 0.807}, {"text": "Now, I think it will\nchange something.", "start": 1876.857, "duration": 1.583}, {"text": "This disruptive potential, I\nthink, has a dramatic change.", "start": 1878.44, "duration": 3.34}, {"text": "We'll be talking about this\nslide the whole half semester.", "start": 1881.78, "duration": 3.72}, {"text": "But managing risks, updating\nthe customer user interfaces,", "start": 1885.5, "duration": 4.71}, {"text": "and financial\ninclusion are the three", "start": 1890.21, "duration": 1.77}, {"text": "that I want to focus a\nlot on, managing risk.", "start": 1891.98, "duration": 4.2}, {"text": "And AI is also about\ntargeting products as well.", "start": 1896.18, "duration": 4.02}, {"text": "I think the interesting\nchallenge is, near the bottom,", "start": 1900.2, "duration": 3.24}, {"text": "will some revenue models shift?", "start": 1903.44, "duration": 2.82}, {"text": "We saw a company called Credit\nKarma start here in the US.", "start": 1906.26, "duration": 4.86}, {"text": "Credit Karma started basically\nwith the idea to get a free--", "start": 1911.12, "duration": 5.13}, {"text": "free is the operative\nword-- a free credit score.", "start": 1916.25, "duration": 3.73}, {"text": "The founders of Credit Karma\ncouldn't get their credit score", "start": 1919.98, "duration": 3.44}, {"text": "from the traditional companies--", "start": 1923.42, "duration": 1.35}, {"text": "TransUnion, Experian,\nand the like.", "start": 1924.77, "duration": 3.5}, {"text": "And so they started an app\njust in the last 10 years.", "start": 1928.27, "duration": 5.08}, {"text": "And in January, they sold\nCredit Karma for $7 billion.", "start": 1933.35, "duration": 5.584}, {"text": "Now, Credit Karma\nis still a free app.", "start": 1938.934, "duration": 2.986}, {"text": "And you might say how can Credit\nKarma commercialize a free app?", "start": 1941.92, "duration": 5.01}, {"text": "In 2019, there was $1 billion\nin revenue for Credit Karma", "start": 1946.93, "duration": 3.39}, {"text": "because they basically had built\nfiles on 106 million Americans.", "start": 1950.32, "duration": 4.98}, {"text": "They built data files on 106\nmillion Americans providing", "start": 1955.3, "duration": 4.23}, {"text": "a free app.", "start": 1959.53, "duration": 0.69}, {"text": "And, by the way, they do not\nhave 106 million customers.", "start": 1960.22, "duration": 3.51}, {"text": "They even built\ncredit files on people", "start": 1963.73, "duration": 2.37}, {"text": "that weren't their customers.", "start": 1966.1, "duration": 1.82}, {"text": "And they were able to\ncommercialize and build", "start": 1967.92, "duration": 2.2}, {"text": "revenues around that data stream\nand, in essence, referencing.", "start": 1970.12, "duration": 4.83}, {"text": "They get referral fees when\nsomebody then does buy a loan", "start": 1974.95, "duration": 4.14}, {"text": "or takes out a loan through\nthe Credit Karma platform.", "start": 1979.09, "duration": 4.65}, {"text": "ROMAIN DE SAINT PERIER:\nGary, we have a question", "start": 1983.74, "duration": 2.0}, {"text": "from [INAUDIBLE].", "start": 1985.74, "duration": 1.26}, {"text": "GARY GENSLER: Please.", "start": 1987.0, "duration": 0.875}, {"text": "You might need to\nunmute yourself.", "start": 1991.0, "duration": 2.97}, {"text": "We--", "start": 1993.97, "duration": 0.92}, {"text": "ROMAIN DE SAINT PERIER:\nSo I am normally unmuting?", "start": 1994.89, "duration": 1.27}, {"text": "AUDIENCE: I'm just--", "start": 1996.16, "duration": 0.833}, {"text": "ROMAIN DE SAINT\nPERIER: Yeah, OK.", "start": 1996.993, "duration": 1.507}, {"text": "AUDIENCE: I'm just\nwondering, what", "start": 1998.5, "duration": 1.417}, {"text": "is the difference between\nbig tech and FinTech,", "start": 1999.917, "duration": 3.233}, {"text": "and why it is important\npreparing and learning", "start": 2003.15, "duration": 3.66}, {"text": "the FinTech now?", "start": 2006.81, "duration": 2.52}, {"text": "GARY GENSLER: So I\nunderstand the second part", "start": 2009.33, "duration": 1.943}, {"text": "of the question.", "start": 2011.273, "duration": 0.667}, {"text": "You said the difference\nbetween what and FinTech", "start": 2011.94, "duration": 2.31}, {"text": "at the beginning?", "start": 2014.25, "duration": 1.05}, {"text": "AUDIENCE: Big tech.", "start": 2015.3, "duration": 1.005}, {"text": "GARY GENSLER: OK, big tech.", "start": 2016.305, "duration": 1.125}, {"text": "So by that, I think of--", "start": 2017.43, "duration": 3.87}, {"text": "I use the word FinTech in\nthe broad way the Financial", "start": 2021.3, "duration": 3.96}, {"text": "Stability Board does.", "start": 2025.26, "duration": 1.44}, {"text": "I use it as is the intersection\nof finance and technology", "start": 2026.7, "duration": 3.96}, {"text": "where the technology is new--", "start": 2030.66, "duration": 2.12}, {"text": "so not the telephone,\nnot the internet,", "start": 2032.78, "duration": 3.4}, {"text": "but it's something new, like\nAI and machine learning,", "start": 2036.18, "duration": 3.78}, {"text": "that may materially change\nthe provision of finance.", "start": 2039.96, "duration": 4.9}, {"text": "So I use it to capture\nthe whole field.", "start": 2044.86, "duration": 4.31}, {"text": "Why it's important is I think\nit's important every decade.", "start": 2049.17, "duration": 2.819}, {"text": "I don't think it's\njust important now,", "start": 2051.989, "duration": 2.611}, {"text": "because I think technologies\nwill come along each half", "start": 2054.6, "duration": 3.389}, {"text": "decade, each decade\nthat will materially", "start": 2057.989, "duration": 2.371}, {"text": "change finance and provide the\nentrepreneurs in this class", "start": 2060.36, "duration": 4.74}, {"text": "an opportunity to break\ninto the wide margins.", "start": 2065.1, "duration": 5.4}, {"text": "In the US, 7 and 1/2% of our\neconomy or $1 and 1/2 trillion", "start": 2070.5, "duration": 4.56}, {"text": "is the revenues of finance.", "start": 2075.06, "duration": 4.079}, {"text": "So if you're an entrepreneur,\nyou want part of that $1", "start": 2079.139, "duration": 2.25}, {"text": "and 1/2 trillion.", "start": 2081.389, "duration": 0.961}, {"text": "You want an opportunity.", "start": 2082.35, "duration": 1.77}, {"text": "And usually, it's\ntechnology that's", "start": 2084.12, "duration": 1.89}, {"text": "changing business models.", "start": 2086.01, "duration": 1.41}, {"text": "When the internet came\nalong in the 1990s, that", "start": 2087.42, "duration": 3.45}, {"text": "provided an opportunity for\nPayPal to start and say maybe", "start": 2090.87, "duration": 3.48}, {"text": "we can provide a better\npayment solution.", "start": 2094.35, "duration": 2.82}, {"text": "And subsequent\npayment solutions,", "start": 2097.17, "duration": 2.25}, {"text": "like Venmo and\nTransferWise and Square,", "start": 2099.42, "duration": 3.9}, {"text": "have all been opportunities\nto chip away a little bit.", "start": 2103.32, "duration": 3.99}, {"text": "I would say only in\nthe opportunity--", "start": 2107.31, "duration": 3.48}, {"text": "the opportunities came\nbecause technology", "start": 2110.79, "duration": 2.31}, {"text": "was changing the field.", "start": 2113.1, "duration": 2.85}, {"text": "What's the difference\nbetween big tech and FinTech?", "start": 2115.95, "duration": 2.37}, {"text": "Big tech, to me, are\nbig platform companies--", "start": 2118.32, "duration": 3.69}, {"text": "in the US, the Facebooks and\nthe Amazons and the Apples,", "start": 2122.01, "duration": 5.01}, {"text": "in China, Baidu, Alibaba,\nTencent, in Africa,", "start": 2127.02, "duration": 4.71}, {"text": "even, Safaricom got in.", "start": 2131.73, "duration": 2.19}, {"text": "We could go country by country.", "start": 2133.92, "duration": 1.31}, {"text": "India, the big tech has\ngone into payments as well.", "start": 2135.23, "duration": 4.36}, {"text": "I think that big tech companies\nhave dramatic advantages.", "start": 2139.59, "duration": 5.04}, {"text": "And then I separate what I\nwould call FinTech startups", "start": 2144.63, "duration": 3.24}, {"text": "or FinTech disruptors.", "start": 2147.87, "duration": 2.16}, {"text": "I always put the second noun\nin there, disruptor or startup,", "start": 2150.03, "duration": 3.6}, {"text": "because to me, the word\nFinTech is the whole field.", "start": 2153.63, "duration": 4.0}, {"text": "I hope that helps.", "start": 2157.63, "duration": 0.903}, {"text": "ROMAIN DE SAINT PERIER: And\nwe have another question", "start": 2158.533, "duration": 2.167}, {"text": "from [INAUDIBLE].", "start": 2160.7, "duration": 0.985}, {"text": "GARY GENSLER: Please.", "start": 2161.685, "duration": 0.875}, {"text": "AUDIENCE: Yeah, hi, Professor.", "start": 2165.42, "duration": 1.45}, {"text": "One question that\nI have is actually", "start": 2166.87, "duration": 1.65}, {"text": "one concerned with privacy.", "start": 2168.52, "duration": 2.535}, {"text": "At some point, do\nyou think that we", "start": 2174.01, "duration": 2.64}, {"text": "would have up give up to some\nextent our privacy in order", "start": 2176.65, "duration": 3.66}, {"text": "to--", "start": 2180.31, "duration": 0.93}, {"text": "for me to get a\ncredit from a startup", "start": 2181.24, "duration": 3.36}, {"text": "or get a credit from somebody?", "start": 2184.6, "duration": 1.283}, {"text": "GARY GENSLER: Well,\nI think you've", "start": 2185.883, "duration": 1.417}, {"text": "raised a dramatic issue\nfor society at large.", "start": 2187.3, "duration": 3.84}, {"text": "And finance is\none example of it.", "start": 2191.14, "duration": 2.53}, {"text": "But yes, we have--", "start": 2193.67, "duration": 1.4}, {"text": "we have shared our personal\ndata much more broadly", "start": 2195.07, "duration": 3.96}, {"text": "in the last 10 years, and\ncertainly in the last 30 years,", "start": 2199.03, "duration": 3.09}, {"text": "than we did in\nsocieties before that.", "start": 2202.12, "duration": 2.69}, {"text": "And in terms of getting\ncredit card, yes, we've", "start": 2204.81, "duration": 4.6}, {"text": "been sharing data for 50\nyears through various credit--", "start": 2209.41, "duration": 6.81}, {"text": "consumer credit companies.", "start": 2216.22, "duration": 1.8}, {"text": "The Fair Isaac Company was\nfounded almost 60 years ago", "start": 2218.02, "duration": 7.35}, {"text": "by two people out of\nStanford, actually,", "start": 2225.37, "duration": 2.61}, {"text": "one named Fair and\none named Isaac.", "start": 2227.98, "duration": 2.7}, {"text": "And that led to something\ncalled FICO scores,", "start": 2230.68, "duration": 2.4}, {"text": "which are used in over 30\ncountries around the globe.", "start": 2233.08, "duration": 3.15}, {"text": "These FICO scores took\nsome personal data,", "start": 2236.23, "duration": 3.27}, {"text": "as to whether you were\npaying your bills on time.", "start": 2239.5, "duration": 3.36}, {"text": "But now, we can go beyond that\nand capture alternative data.", "start": 2242.86, "duration": 4.74}, {"text": "We can capture somebody's\ndigital footprint.", "start": 2247.6, "duration": 3.53}, {"text": "And in China, they are doing\nthat with social credit scoring", "start": 2251.13, "duration": 3.34}, {"text": "and Alibaba is with\nAlipay and WeChat Pay.", "start": 2254.47, "duration": 4.11}, {"text": "But Amazon is capturing\nour data as well.", "start": 2258.58, "duration": 2.46}, {"text": "Amazon captures any\nAmazon Prime customer.", "start": 2261.04, "duration": 3.29}, {"text": "And I'm sure amongst at of us,\nthere are many Amazon Prime", "start": 2264.33, "duration": 2.95}, {"text": "customers.", "start": 2267.28, "duration": 0.81}, {"text": "That data is being\ncaptured in some way.", "start": 2268.09, "duration": 3.4}, {"text": "Now, it leads to more\nfinancial inclusion.", "start": 2271.49, "duration": 3.17}, {"text": "But it also raises all sorts\nof issues around privacy", "start": 2274.66, "duration": 3.15}, {"text": "that we're grappling\nwith as societies.", "start": 2277.81, "duration": 2.49}, {"text": "In Europe, they passed\nsomething called", "start": 2280.3, "duration": 2.19}, {"text": "the GDPR, Global Directive\non Privacy Regulation.", "start": 2282.49, "duration": 6.27}, {"text": "Here in the US, only\nCalifornia's stepped into this", "start": 2288.76, "duration": 3.63}, {"text": "and passed something that\nwent into place last year,", "start": 2292.39, "duration": 3.06}, {"text": "the California Consumer\nProtection Act.", "start": 2295.45, "duration": 3.09}, {"text": "So these are things that\nsociety will grapple with.", "start": 2298.54, "duration": 2.7}, {"text": "Technology can enable privacy\nas well as take away privacy.", "start": 2301.24, "duration": 4.32}, {"text": "Technology actually can\nenable us to keep our privacy.", "start": 2305.56, "duration": 5.8}, {"text": "But the technology companies\nand the financial companies", "start": 2311.36, "duration": 2.82}, {"text": "want our data.", "start": 2314.18, "duration": 1.08}, {"text": "So they're not going\nto necessarily want", "start": 2315.26, "duration": 2.79}, {"text": "us to keep our privacy.", "start": 2318.05, "duration": 1.5}, {"text": "So it's an interesting--", "start": 2319.55, "duration": 2.43}, {"text": "technology can enable\nit, but technology", "start": 2321.98, "duration": 2.37}, {"text": "can take it away as well.", "start": 2324.35, "duration": 2.72}, {"text": "So just moving on a little\nbit, this three big areas--", "start": 2327.07, "duration": 4.045}, {"text": "we're not going to\nspend a lot of time,", "start": 2331.115, "duration": 1.625}, {"text": "but artificial intelligence,\nmachine learning.", "start": 2332.74, "duration": 2.28}, {"text": "I love to give a\nshout out to another", "start": 2335.02, "duration": 2.82}, {"text": "MITer, or Lex Fridman,\nwho has a wonderful set", "start": 2337.84, "duration": 3.6}, {"text": "of online courses, if you\nwanted to take Lex's courses.", "start": 2341.44, "duration": 3.51}, {"text": "This was online before online\nbecame such the vogue now", "start": 2344.95, "duration": 3.31}, {"text": "that we're all doing it.", "start": 2348.26, "duration": 1.43}, {"text": "But Lex has this\nwonderful course.", "start": 2349.69, "duration": 2.55}, {"text": "And I captured his one slide.", "start": 2352.24, "duration": 2.76}, {"text": "What is AI and machine learning?", "start": 2355.0, "duration": 2.94}, {"text": "It's extracting useful\npatterns from data.", "start": 2357.94, "duration": 3.27}, {"text": "You don't have to be\na computer scientist.", "start": 2361.21, "duration": 2.25}, {"text": "But it's basically that's\nthe key thing, and something", "start": 2363.46, "duration": 3.18}, {"text": "that might not be\nlinear, something", "start": 2366.64, "duration": 1.98}, {"text": "that might not fit into that old\nstatistics class and regression", "start": 2368.62, "duration": 3.81}, {"text": "analysis or linear algebra\nthat we think about.", "start": 2372.43, "duration": 3.42}, {"text": "It all relies on good\ndata, cleaning up", "start": 2375.85, "duration": 2.55}, {"text": "data, and good questions.", "start": 2378.4, "duration": 3.198}, {"text": "Where do we see it?", "start": 2381.598, "duration": 0.792}, {"text": "We see it in facial recognition,\nimage classification,", "start": 2382.39, "duration": 2.58}, {"text": "speech recognition, et cetera,\nthis list from Lex's list", "start": 2384.97, "duration": 3.24}, {"text": "that you can see online,\nmedical diagnoses--", "start": 2388.21, "duration": 4.47}, {"text": "in the midst of\nthe corona crisis,", "start": 2392.68, "duration": 1.68}, {"text": "a lot are turning to AI\nand machine learning to see", "start": 2394.36, "duration": 3.0}, {"text": "what patterns can we see\nbeyond the patterns you", "start": 2397.36, "duration": 3.06}, {"text": "can see by classic statistics?", "start": 2400.42, "duration": 2.73}, {"text": "It's going beyond that.", "start": 2403.15, "duration": 2.11}, {"text": "But in this field,\nin this field,", "start": 2405.26, "duration": 2.75}, {"text": "in finance, we're seeing it\nin every one of these areas.", "start": 2408.01, "duration": 3.48}, {"text": "And we have two classes, so\nI won't dive into it now.", "start": 2411.49, "duration": 4.05}, {"text": "But whether it's asset\nmanagement, where", "start": 2415.54, "duration": 1.87}, {"text": "BlackRock is literally taking--", "start": 2417.41, "duration": 3.35}, {"text": "and all the news items for the\ntop companies, every quarter", "start": 2420.76, "duration": 7.12}, {"text": "that a company\nreports its earnings,", "start": 2427.88, "duration": 2.39}, {"text": "BlackRock is listening digitally\nto their shareholder meetings", "start": 2430.27, "duration": 5.05}, {"text": "and their shareholder\nconference calls", "start": 2435.32, "duration": 2.46}, {"text": "and seeing which words in there,\nwhich words relate to stock", "start": 2437.78, "duration": 5.1}, {"text": "markets going up\nor stock markets", "start": 2442.88, "duration": 1.8}, {"text": "going down, using machine\nlearning and asset management.", "start": 2444.68, "duration": 3.27}, {"text": "We talked about call centers\nand chatbots and so forth.", "start": 2447.95, "duration": 5.43}, {"text": "I don't know how many of you\nare Bank of America customers.", "start": 2453.38, "duration": 3.84}, {"text": "But bank of America has millions\nof its customers using Erica.", "start": 2457.22, "duration": 4.68}, {"text": "Think the Siri of banking.", "start": 2461.9, "duration": 3.22}, {"text": "Think the Alexa of banking,\na virtual assistant", "start": 2465.12, "duration": 3.44}, {"text": "called Erica--", "start": 2468.56, "duration": 2.18}, {"text": "Bank of America, get it?", "start": 2470.74, "duration": 2.49}, {"text": "All right, that was their\nmarketing thing, I guess, now.", "start": 2473.23, "duration": 4.25}, {"text": "So AI and machine learning\nis dramatically shifting.", "start": 2477.48, "duration": 3.52}, {"text": "The question in FinTech\nfor the big incumbents,", "start": 2481.0, "duration": 2.94}, {"text": "how do I do it to\nraise my revenues,", "start": 2483.94, "duration": 4.2}, {"text": "lower the amount of\ncapital that I have to use,", "start": 2488.14, "duration": 3.57}, {"text": "raise my profits?", "start": 2491.71, "duration": 1.86}, {"text": "The question for big tech\nis how do I do this maybe", "start": 2493.57, "duration": 3.3}, {"text": "to get into the business,\nto leapfrog, as Ivy said,", "start": 2496.87, "duration": 3.69}, {"text": "that Alibaba and WeChat Pay\nleapfrogged the Chinese banks", "start": 2500.56, "duration": 3.96}, {"text": "and payments?", "start": 2504.52, "duration": 1.14}, {"text": "If I'm big tech, can I\nleapfrog big finance?", "start": 2505.66, "duration": 3.54}, {"text": "Because, frankly, if I'm Google,\nI'm better at it right now.", "start": 2509.2, "duration": 3.93}, {"text": "Google has a\ncomparative advantage.", "start": 2513.13, "duration": 2.61}, {"text": "Can I maybe use my comparative\nadvantage and AI and leapfrog?", "start": 2515.74, "duration": 3.87}, {"text": "If I'm a startup, maybe I\ncan give a better customer", "start": 2519.61, "duration": 3.48}, {"text": "interface.", "start": 2523.09, "duration": 0.85}, {"text": "I can do something with\nthis to better manage risk", "start": 2523.94, "duration": 3.68}, {"text": "with alternative data.", "start": 2527.62, "duration": 2.64}, {"text": "So that's how I think of it.", "start": 2530.26, "duration": 4.54}, {"text": "OpenAPI-- I should pause.", "start": 2534.8, "duration": 2.07}, {"text": "Romain, any questions\nor hands up?", "start": 2536.87, "duration": 2.003}, {"text": "ROMAIN DE SAINT PERIER:\nYes, we have one from Laira.", "start": 2538.873, "duration": 2.167}, {"text": "GARY GENSLER: Please.", "start": 2541.04, "duration": 0.875}, {"text": "AUDIENCE: Yeah, so I was\njust curious to know how,", "start": 2544.86, "duration": 2.51}, {"text": "internationally\nspeaking, regulation", "start": 2547.37, "duration": 4.14}, {"text": "hampers the capacity of FinTech\ncompanies to expand, just", "start": 2551.51, "duration": 5.13}, {"text": "on an international level.", "start": 2556.64, "duration": 1.27}, {"text": "So for the US, is it more\nregulated and, hence, more", "start": 2557.91, "duration": 5.43}, {"text": "harder for FinTech companies\nto expand than for in China?", "start": 2563.34, "duration": 4.442}, {"text": "GARY GENSLER: Great question.", "start": 2567.782, "duration": 1.208}, {"text": "And again, who asked?", "start": 2568.99, "duration": 1.24}, {"text": "I just didn't rem-- is Leia?", "start": 2570.23, "duration": 2.86}, {"text": "AUDIENCE: Laira.", "start": 2573.09, "duration": 1.04}, {"text": "GARY GENSLER: Laira, all right,\nLaira, good to see you again.", "start": 2574.13, "duration": 3.49}, {"text": "I'm sorry that I don't\nphysically see you.", "start": 2577.62, "duration": 3.33}, {"text": "But good to see you remotely.", "start": 2580.95, "duration": 3.47}, {"text": "Every country is taking a\nlittle bit different approach.", "start": 2584.42, "duration": 2.91}, {"text": "And the range of approaches\nhere could be from you're a--", "start": 2587.33, "duration": 5.46}, {"text": "let's call them a\nstartup or a disruptor.", "start": 2592.79, "duration": 2.46}, {"text": "You're starting something.", "start": 2595.25, "duration": 1.83}, {"text": "You'd better just\ncome into whatever", "start": 2597.08, "duration": 1.94}, {"text": "our traditional\nregulatory framework.", "start": 2599.02, "duration": 2.14}, {"text": "If you're taking deposits\nand offering loans,", "start": 2601.16, "duration": 3.57}, {"text": "you've got to be a bank.", "start": 2604.73, "duration": 1.44}, {"text": "If you're just\ndoing payments, you", "start": 2606.17, "duration": 1.83}, {"text": "might come under a European,\nUS African e-money law", "start": 2608.0, "duration": 5.52}, {"text": "and just have to do the\nthings around money laundering", "start": 2613.52, "duration": 3.75}, {"text": "and anti-money laundering.", "start": 2617.27, "duration": 1.74}, {"text": "If you're like Robinhood\nhere in the US,", "start": 2619.01, "duration": 4.09}, {"text": "you would need to register\nas a broker-dealer.", "start": 2623.1, "duration": 2.69}, {"text": "And there's been this big\ndebate around cryptocurrencies.", "start": 2625.79, "duration": 2.85}, {"text": "Are they securities or not?", "start": 2628.64, "duration": 1.68}, {"text": "And in some countries,\nlike the US,", "start": 2630.32, "duration": 1.79}, {"text": "they generally\nare, unless you're", "start": 2632.11, "duration": 4.75}, {"text": "like Bitcoin and Ethereum.", "start": 2636.86, "duration": 3.0}, {"text": "But the debate, Lyra, is\nreally country by country,", "start": 2639.86, "duration": 3.75}, {"text": "is are these startups\nand these technologies,", "start": 2643.61, "duration": 7.39}, {"text": "do they fit into the\ncurrent regulatory regimes?", "start": 2651.0, "duration": 3.24}, {"text": "By and large, if you take\ndeposits and you make loans,", "start": 2654.24, "duration": 2.97}, {"text": "you're a bank pretty much\nanywhere around the globe.", "start": 2657.21, "duration": 3.01}, {"text": "If you facilitate the\nmovement of money,", "start": 2660.22, "duration": 2.15}, {"text": "you're probably in some\ne-money laws around the globe.", "start": 2662.37, "duration": 4.02}, {"text": "Securities, if you're\nactually facilitating", "start": 2666.39, "duration": 3.39}, {"text": "the raising of money and\nthe selling of securities,", "start": 2669.78, "duration": 2.73}, {"text": "you usually have to register\nas a securities broker-dealer", "start": 2672.51, "duration": 2.97}, {"text": "somewhere around the globe.", "start": 2675.48, "duration": 1.98}, {"text": "But a lot of places\nalso have this concept", "start": 2677.46, "duration": 2.78}, {"text": "of some form of regulatory\nforbearance called sandboxes.", "start": 2680.24, "duration": 4.66}, {"text": "The idea is let's promote\nsome innovation, whether it's", "start": 2684.9, "duration": 3.72}, {"text": "in Hong Kong, whether it's in\nAsia, whether it's in the US,", "start": 2688.62, "duration": 2.97}, {"text": "promote some motivation by\nsaying if it stays small enough", "start": 2691.59, "duration": 4.74}, {"text": "and it's new enough,\nyou might not", "start": 2696.33, "duration": 2.16}, {"text": "have to comply with all\nof the regulatory regimes.", "start": 2698.49, "duration": 5.05}, {"text": "The other interesting challenge\nis sometimes things come along", "start": 2703.54, "duration": 2.79}, {"text": "that don't fit in a box.", "start": 2706.33, "duration": 1.38}, {"text": "They don't quite\nfit in to something.", "start": 2707.71, "duration": 2.49}, {"text": "So the internet came\nalong in the 1990s.", "start": 2710.2, "duration": 2.75}, {"text": "Internet in the 1990s\nwas facilitating", "start": 2712.95, "duration": 3.21}, {"text": "a rapid change in finance.", "start": 2716.16, "duration": 2.055}, {"text": "The internet comes\nalong and then", "start": 2718.215, "duration": 1.375}, {"text": "the question is\nliterally a question", "start": 2719.59, "duration": 2.13}, {"text": "that the securities\nregulators around the globe", "start": 2721.72, "duration": 2.43}, {"text": "had to deal with--", "start": 2724.15, "duration": 1.14}, {"text": "what if I put a\nbulletin board up", "start": 2725.29, "duration": 1.68}, {"text": "on the internet that offers\npeople to buy and sell", "start": 2726.97, "duration": 2.79}, {"text": "securities on the internet?", "start": 2729.76, "duration": 1.8}, {"text": "Now, it wasn't a\ntraditional exchange.", "start": 2731.56, "duration": 1.59}, {"text": "It didn't look like the Tokyo or\nShanghai or London or New York", "start": 2733.15, "duration": 4.11}, {"text": "exchanges of old, where\nthere were humans yelling", "start": 2737.26, "duration": 3.21}, {"text": "and screaming on the\nfloors of stock exchanges", "start": 2740.47, "duration": 2.28}, {"text": "around the globe.", "start": 2742.75, "duration": 1.17}, {"text": "It was just a\nbulletin board where", "start": 2743.92, "duration": 2.07}, {"text": "buyers and sellers could meet.", "start": 2745.99, "duration": 2.07}, {"text": "And usually they were insurance\ncompanies and various asset", "start": 2748.06, "duration": 3.24}, {"text": "managers.", "start": 2751.3, "duration": 1.5}, {"text": "That question was a ripe\nquestion in the 1990s.", "start": 2752.8, "duration": 3.09}, {"text": "And over time, we ended up\nwith two tiers of regulation", "start": 2755.89, "duration": 3.99}, {"text": "for exchanges.", "start": 2759.88, "duration": 0.93}, {"text": "We had fully-regulated\nexchanges,", "start": 2760.81, "duration": 2.45}, {"text": "and this was true in Europe\nand the US at the time.", "start": 2763.26, "duration": 2.8}, {"text": "China sort of got\nthere a little later.", "start": 2766.06, "duration": 3.7}, {"text": "But in Europe and the US,\nit was like all right,", "start": 2769.76, "duration": 2.1}, {"text": "there's going to be these\nfully-regulated traditional", "start": 2771.86, "duration": 2.208}, {"text": "exchanges.", "start": 2774.068, "duration": 0.942}, {"text": "And then there would\nbe another tier.", "start": 2775.01, "duration": 2.15}, {"text": "In the US, we called\nthem broker dealers,", "start": 2777.16, "duration": 2.01}, {"text": "alternative trading\nsystems, ATS's.", "start": 2779.17, "duration": 3.42}, {"text": "In Europe, there\nwere various rules", "start": 2782.59, "duration": 2.04}, {"text": "that became known as MiFID,\nwhich now I can't remember", "start": 2784.63, "duration": 4.59}, {"text": "what it all stands for.", "start": 2789.22, "duration": 1.32}, {"text": "But electronic trading platforms\nwere regulated a little", "start": 2790.54, "duration": 2.82}, {"text": "differently.", "start": 2793.36, "duration": 0.957}, {"text": "So I hope that gives\nyou a sense and puts it", "start": 2794.317, "duration": 1.833}, {"text": "in a historic concept.", "start": 2796.15, "duration": 1.86}, {"text": "I think over the\n2020s, AI and machine", "start": 2798.01, "duration": 2.91}, {"text": "learning will lead to\ntremendous challenges", "start": 2800.92, "duration": 3.72}, {"text": "around regulation, about if\nyou see a pattern in the data", "start": 2804.64, "duration": 6.3}, {"text": "but you can't explain\nwhy the pattern is there,", "start": 2810.94, "duration": 3.42}, {"text": "you fall into some\nchallenges of explainability.", "start": 2814.36, "duration": 3.0}, {"text": "And for the last 50 years,\nor in many countries,", "start": 2817.36, "duration": 3.42}, {"text": "if you deny somebody\ncredit, you're", "start": 2820.78, "duration": 1.74}, {"text": "supposed to be able to explain\nwhy you deny them credit.", "start": 2822.52, "duration": 3.72}, {"text": "We talked about privacy earlier.", "start": 2826.24, "duration": 2.04}, {"text": "It bumps up against\nprivacy issues.", "start": 2828.28, "duration": 2.78}, {"text": "And a third area it bumps\nup against is biases.", "start": 2831.06, "duration": 3.32}, {"text": "What if there is a\nbias in the data,", "start": 2834.38, "duration": 1.67}, {"text": "like when Apple Credit\nCard just rolled out", "start": 2836.05, "duration": 3.06}, {"text": "and it seemed like husbands were\ngetting more credit than wives", "start": 2839.11, "duration": 3.87}, {"text": "in the same household?", "start": 2842.98, "duration": 2.75}, {"text": "So biases, privacy,\nexplainability", "start": 2845.73, "duration": 3.26}, {"text": "are the three sort of cutting\nedge, when I call the big three", "start": 2848.99, "duration": 3.27}, {"text": "public policy issues around\nAI and finance, though there", "start": 2852.26, "duration": 4.53}, {"text": "are other issues as well.", "start": 2856.79, "duration": 1.63}, {"text": "Romain, did I see\nyou-- were you--", "start": 2858.42, "duration": 1.435}, {"text": "ROMAIN DE SAINT\nPERIER: Yes, sir.", "start": 2859.855, "duration": 1.375}, {"text": "We have Carlos, who\nhas his hand up.", "start": 2861.23, "duration": 2.105}, {"text": "GARY GENSLER: All\nright, and then", "start": 2863.335, "duration": 1.375}, {"text": "I'm going to keep\ngoing, because I", "start": 2864.71, "duration": 1.47}, {"text": "want to talk about where we're\ngoing in this class as well.", "start": 2866.18, "duration": 3.36}, {"text": "Carlos?", "start": 2869.54, "duration": 1.04}, {"text": "AUDIENCE: Hi, how are you?", "start": 2870.58, "duration": 1.69}, {"text": "Just a comment on regulations,\nsort of to build up on that.", "start": 2872.27, "duration": 3.06}, {"text": "So I think ironically,\nfor example,", "start": 2875.33, "duration": 2.16}, {"text": "in Latin America,\na lot of countries", "start": 2877.49, "duration": 2.46}, {"text": "have an issue where\nthe big banks have", "start": 2879.95, "duration": 1.8}, {"text": "a massive concentration\nof deposits.", "start": 2881.75, "duration": 2.157}, {"text": "But, for example, if you look\nat the Mexico FinTech law, which", "start": 2883.907, "duration": 2.583}, {"text": "was passed end of 2018, it\nactually raised the barriers", "start": 2886.49, "duration": 3.15}, {"text": "to entry for other FinTechs.", "start": 2889.64, "duration": 1.68}, {"text": "So sort of ironically--", "start": 2891.32, "duration": 1.488}, {"text": "GARY GENSLER: I'm sorry, Carlos,\nit raised what for FinTechs?", "start": 2892.808, "duration": 2.542}, {"text": "AUDIENCE: The barriers to entry.", "start": 2895.35, "duration": 1.2}, {"text": "GARY GENSLER:\nBarriers to entry, OK.", "start": 2896.55, "duration": 1.5}, {"text": "AUDIENCE: And so--", "start": 2898.05, "duration": 0.98}, {"text": "GARY GENSLER: I think our\nfaculty member, Luis Videgaray,", "start": 2899.03, "duration": 3.0}, {"text": "who helped work on that when he\nwas finance minister of Mexico,", "start": 2902.03, "duration": 3.33}, {"text": "we should ask him.", "start": 2905.36, "duration": 2.07}, {"text": "And I'll see if I can get his\nanswer for the next Wednesday", "start": 2907.43, "duration": 2.58}, {"text": "or next Monday's class.", "start": 2910.01, "duration": 1.17}, {"text": "But keep going.", "start": 2911.18, "duration": 1.39}, {"text": "AUDIENCE: OK, that\nwould be great.", "start": 2912.57, "duration": 1.76}, {"text": "But the question is\ndo you think there", "start": 2914.33, "duration": 1.75}, {"text": "is a risk that new regulations\nin the FinTech scope", "start": 2916.08, "duration": 2.66}, {"text": "are actually going to\nperpetuate some of the problems", "start": 2918.74, "duration": 2.34}, {"text": "that we saw before with the\nmore traditional banking sector?", "start": 2921.08, "duration": 3.63}, {"text": "GARY GENSLER: Great question.", "start": 2924.71, "duration": 1.69}, {"text": "Carlos, can I hold\nthat for a minute,", "start": 2926.4, "duration": 1.58}, {"text": "because I'm going to do\nthat when I do the actors?", "start": 2927.98, "duration": 2.16}, {"text": "But I think yes,\nincumbents in every field--", "start": 2930.14, "duration": 4.4}, {"text": "and these would be incumbents\nin the pharmaceutical field,", "start": 2934.54, "duration": 2.79}, {"text": "in the tech fields, in\nairlines, whatever-- incumbents", "start": 2937.33, "duration": 4.14}, {"text": "tend to be able to deal with\nregulation a little easier.", "start": 2941.47, "duration": 5.58}, {"text": "They're big.", "start": 2947.05, "duration": 1.65}, {"text": "They've got great resources.", "start": 2948.7, "duration": 1.5}, {"text": "They can build systems to\ncomply with those regulations.", "start": 2950.2, "duration": 4.68}, {"text": "Now, they don't necessarily\nembrace new regulation.", "start": 2954.88, "duration": 3.0}, {"text": "But once those regulations\nare put in place", "start": 2957.88, "duration": 2.43}, {"text": "by an official sector,\nthey tend to have", "start": 2960.31, "duration": 2.46}, {"text": "the resources to embrace them.", "start": 2962.77, "duration": 2.04}, {"text": "And startups sometimes\nhave more challenges.", "start": 2964.81, "duration": 2.7}, {"text": "And thus, you may be\nseeing that regulations", "start": 2967.51, "duration": 2.55}, {"text": "become a barrier to entry.", "start": 2970.06, "duration": 1.76}, {"text": "They're kind of grains in the\nsand of innovation at times.", "start": 2971.82, "duration": 4.33}, {"text": "So there's always a\npublic policy tradeoff--", "start": 2976.15, "duration": 2.16}, {"text": "protecting the\npublic, whether it's", "start": 2978.31, "duration": 2.49}, {"text": "protecting the public against\nconsumer fraud or investor", "start": 2980.8, "duration": 5.82}, {"text": "protection or protecting the\npublic against systemic risk,", "start": 2986.62, "duration": 3.77}, {"text": "that big banks will fail and\nhurt the rest of the economy,", "start": 2990.39, "duration": 3.58}, {"text": "also comes with some\ntradeoffs, that it could", "start": 2993.97, "duration": 3.45}, {"text": "raise the barriers to entry.", "start": 2997.42, "duration": 1.83}, {"text": "You're absolutely right there.", "start": 2999.25, "duration": 3.375}, {"text": "We're going to talk a lot\nabout OpenAPI and open banking.", "start": 3002.625, "duration": 2.985}, {"text": "We have a whole class on that.", "start": 3005.61, "duration": 2.43}, {"text": "So I'm going to keep moving\non just so that we finish", "start": 3008.04, "duration": 2.94}, {"text": "by our 10 o'clock deadline.", "start": 3010.98, "duration": 2.25}, {"text": "Blockchain technology--\nyou've heard about it.", "start": 3013.23, "duration": 2.88}, {"text": "We're going to have\na class on this,", "start": 3016.11, "duration": 1.53}, {"text": "about cryptocurrencies\nand blockchains.", "start": 3017.64, "duration": 2.4}, {"text": "Some of you actually were in\nour fall blockchain and money", "start": 3020.04, "duration": 4.12}, {"text": "class.", "start": 3024.16, "duration": 0.5}, {"text": "Some of you are in the\ncrypto finance class that", "start": 3024.66, "duration": 2.7}, {"text": "starts in about 30 minutes.", "start": 3027.36, "duration": 2.81}, {"text": "But we will talk about\nblockchain technology.", "start": 3030.17, "duration": 2.41}, {"text": "I want to say and\nlay it out right", "start": 3032.58, "duration": 2.07}, {"text": "from the beginning,\nthese two issues, AI", "start": 3034.65, "duration": 3.6}, {"text": "and machine learning, in these\neight areas are dramatically", "start": 3038.25, "duration": 4.17}, {"text": "more relevant.", "start": 3042.42, "duration": 1.62}, {"text": "And OpenAPI and open banking,\ndramatically more relevant", "start": 3044.04, "duration": 4.32}, {"text": "than blockchain technology\npotential use cases as of 2020.", "start": 3048.36, "duration": 4.98}, {"text": "The interesting question\nis will that shift?", "start": 3053.34, "duration": 3.48}, {"text": "Is there an overabundance of\ninvestment in AI and machine", "start": 3056.82, "duration": 4.53}, {"text": "learning and not enough\nin blockchain technology?", "start": 3061.35, "duration": 2.59}, {"text": "You get to decide\nfor yourselves.", "start": 3063.94, "duration": 2.24}, {"text": "But I'm saying as of 2020,\nsort of the real potential", "start": 3066.18, "duration": 5.43}, {"text": "that we're seeing and the\ndramatic changes around user", "start": 3071.61, "duration": 3.18}, {"text": "interface an OpenAPI and machine\nlearning and natural language", "start": 3074.79, "duration": 4.53}, {"text": "processing are more\ndramatic in this space.", "start": 3079.32, "duration": 3.37}, {"text": "And yet cryptocurrencies\nhave dramatically", "start": 3082.69, "duration": 1.94}, {"text": "changed what central\nbanks are doing.", "start": 3084.63, "duration": 2.2}, {"text": "And we saw Facebook trying to\nstand up a worldwide currency", "start": 3086.83, "duration": 3.14}, {"text": "last year.", "start": 3089.97, "duration": 1.18}, {"text": "So I don't think\nyou can adequately", "start": 3091.15, "duration": 1.91}, {"text": "discuss and have a course\non financial technology", "start": 3093.06, "duration": 2.85}, {"text": "without really having some\nslice of blockchain technology.", "start": 3095.91, "duration": 4.77}, {"text": "And it is shifting.", "start": 3100.68, "duration": 1.08}, {"text": "Everything that's on this list,\nit is a catalyst for change.", "start": 3101.76, "duration": 4.06}, {"text": "I would say my takeaway\non blockchain technology,", "start": 3105.82, "duration": 3.26}, {"text": "it is definitely pushing\nthe financial sector", "start": 3109.08, "duration": 3.54}, {"text": "in places that wouldn't\nbe pushed otherwise.", "start": 3112.62, "duration": 4.96}, {"text": "I guess that's\nreally saying OpenAPI", "start": 3117.58, "duration": 2.0}, {"text": "and artificial intelligence,\nmachine learning", "start": 3119.58, "duration": 2.2}, {"text": "are so much bigger in terms\nof what's happening in 2020.", "start": 3121.78, "duration": 5.573}, {"text": "Romain, unless\nthere's a question,", "start": 3127.353, "duration": 1.417}, {"text": "I'm going to do\nthe actors quickly.", "start": 3128.77, "duration": 1.802}, {"text": "Anything?", "start": 3130.572, "duration": 0.5}, {"text": "ROMAIN DE SAINT PERIER: We\nhave one specific question", "start": 3131.072, "duration": 2.208}, {"text": "from [INAUDIBLE] on whether\nmachine learning and AI can", "start": 3133.28, "duration": 3.65}, {"text": "cause a dark box, or creditors\ncould deny and approve credits", "start": 3136.93, "duration": 3.78}, {"text": "based on unreasonable grounds.", "start": 3140.71, "duration": 1.405}, {"text": "How do you see that?", "start": 3142.115, "duration": 0.833}, {"text": "GARY GENSLER: That\nabsolutely is a risk.", "start": 3142.948, "duration": 3.882}, {"text": "Our first big data\nrevolution in the US,", "start": 3146.83, "duration": 3.3}, {"text": "and then it was about a\ndecade later elsewhere,", "start": 3150.13, "duration": 2.18}, {"text": "was in the late\n'50s and early '60s,", "start": 3152.31, "duration": 3.1}, {"text": "credit cards came\nalong, invented really", "start": 3155.41, "duration": 3.4}, {"text": "in the late 1940s and then\npopularized by the mid 1960s,", "start": 3158.81, "duration": 5.52}, {"text": "came along.", "start": 3164.33, "duration": 0.66}, {"text": "And then the official\nsector passed laws.", "start": 3164.99, "duration": 2.1}, {"text": "And two of the first\nlaws we passed in the US", "start": 3167.09, "duration": 3.48}, {"text": "was something called the\nFair Credit Reporting", "start": 3170.57, "duration": 2.13}, {"text": "Act and the Equal\nCredit Opportunity Act.", "start": 3172.7, "duration": 2.37}, {"text": "And why I speak about\nthose two and this question", "start": 3175.07, "duration": 2.94}, {"text": "50 years later is\nthis was a question", "start": 3178.01, "duration": 2.55}, {"text": "with the first big data\nanalytics at that time.", "start": 3180.56, "duration": 3.37}, {"text": "And the idea was you couldn't--\nyou couldn't use data analytics", "start": 3183.93, "duration": 3.14}, {"text": "to deny somebody credit\nbecause of their race,", "start": 3187.07, "duration": 4.17}, {"text": "because of their color,\nbecause their ethnicity,", "start": 3191.24, "duration": 2.34}, {"text": "because of their gender and\nother protected attributes.", "start": 3193.58, "duration": 5.232}, {"text": "And that was called the\nEqual Credit Opportunity Act.", "start": 3198.812, "duration": 2.208}, {"text": "That same act is important\nnow as we move into machine", "start": 3201.02, "duration": 3.3}, {"text": "learning credit decisions.", "start": 3204.32, "duration": 2.91}, {"text": "Fair Credit Reporting\nAct also said in the US,", "start": 3207.23, "duration": 3.03}, {"text": "and Europe did some similar\nthings elsewhere later,", "start": 3210.26, "duration": 2.97}, {"text": "said if you deny credit, you\nhave to be able to explain why.", "start": 3213.23, "duration": 4.58}, {"text": "So to this question, just\nbecause you have a black box,", "start": 3217.81, "duration": 4.19}, {"text": "you still need to have those\nbasic tenets of explainability", "start": 3222.0, "duration": 4.89}, {"text": "and fairness or lack of bias.", "start": 3226.89, "duration": 3.0}, {"text": "And that's why I say the\nthree big challenges are", "start": 3229.89, "duration": 2.58}, {"text": "explainability, bias,\nand then privacy.", "start": 3232.47, "duration": 3.88}, {"text": "There's also challenges of\nrobustness and so forth,", "start": 3236.35, "duration": 3.255}, {"text": "but great question.", "start": 3239.605, "duration": 2.675}, {"text": "The actors-- I think\nof the actors--", "start": 3242.28, "duration": 2.31}, {"text": "we've talked about this a\nlittle bit in several buckets.", "start": 3244.59, "duration": 4.59}, {"text": "I think of big finance--", "start": 3249.18, "duration": 2.28}, {"text": "I apologize, I sort of\nborrowed this a little bit", "start": 3251.46, "duration": 2.43}, {"text": "from the central bank\ngovernor of Brazil.", "start": 3253.89, "duration": 2.06}, {"text": "I met with him last year.", "start": 3255.95, "duration": 1.72}, {"text": "And he and I were talking\nabout Brazilian banking.", "start": 3257.67, "duration": 2.55}, {"text": "And he said they're\nlike fortresses.", "start": 3260.22, "duration": 1.95}, {"text": "So this was actually his\nkind of articulation of Ita\u00fa", "start": 3262.17, "duration": 4.51}, {"text": "and the others in Brazil.", "start": 3266.68, "duration": 1.505}, {"text": "And I said how do you\nsee them as fortresses?", "start": 3268.185, "duration": 1.875}, {"text": "And he says they all\nhave their moats, towers,", "start": 3270.06, "duration": 3.72}, {"text": "and they have\nsovereign protection.", "start": 3273.78, "duration": 2.15}, {"text": "And to him-- and I liked\nit so much I repeat it--", "start": 3275.93, "duration": 3.49}, {"text": "their towers, their\nsort of basic tenets", "start": 3279.42, "duration": 2.97}, {"text": "of sort of financial\nstrength is around payments.", "start": 3282.39, "duration": 3.93}, {"text": "They usually control payments.", "start": 3286.32, "duration": 1.99}, {"text": "They have big balance\nsheets that they can use.", "start": 3288.31, "duration": 2.51}, {"text": "And balance sheets allow you\nto lower your risk, frankly,", "start": 3290.82, "duration": 5.04}, {"text": "and leverage.", "start": 3295.86, "duration": 1.05}, {"text": "They have a lot of data.", "start": 3296.91, "duration": 1.47}, {"text": "And yes, they have\nhundreds of legal entities.", "start": 3298.38, "duration": 2.05}, {"text": "Their corporate structure is\none of their both complexities", "start": 3300.43, "duration": 4.79}, {"text": "but benefits.", "start": 3305.22, "duration": 1.59}, {"text": "A company like a JPMorgan\nor a Goldman Sachs", "start": 3306.81, "duration": 2.97}, {"text": "or Barclays at a minimum has\nprobably 1,000 legal entities", "start": 3309.78, "duration": 4.26}, {"text": "and might have 3,000 or\n5,000 legal entities.", "start": 3314.04, "duration": 2.22}, {"text": "When I left Goldman Sachs,\nwhich was already 22 years ago,", "start": 3316.26, "duration": 3.12}, {"text": "I was the co-head of finance\nwith David Viniar, who", "start": 3319.38, "duration": 3.93}, {"text": "went on to be the CFO, we\nhad 700 legal entities.", "start": 3323.31, "duration": 5.07}, {"text": "But if I recall, in that quarter\nof a trillion balance sheet", "start": 3328.38, "duration": 3.33}, {"text": "that we had to sort of\nhelp manage and fund,", "start": 3331.71, "duration": 2.43}, {"text": "only about 70 or 80 of those\nwere regulated companies.", "start": 3334.14, "duration": 3.9}, {"text": "So we had a lot--", "start": 3338.04, "duration": 1.8}, {"text": "we did everything legal,\nI just want to say--", "start": 3339.84, "duration": 2.35}, {"text": "but we had a lot going\non amongst those 700", "start": 3342.19, "duration": 3.38}, {"text": "legal entities.", "start": 3345.57, "duration": 1.35}, {"text": "That's kind of big finance\nfrom a sort of central bank", "start": 3346.92, "duration": 4.05}, {"text": "governor of Brazil's point\nof view, like fortresses.", "start": 3350.97, "duration": 3.18}, {"text": "But then big tech--", "start": 3354.15, "duration": 2.27}, {"text": "the Bank of\nInternational Settlements", "start": 3356.42, "duration": 1.56}, {"text": "did a wonderful\nreport last year.", "start": 3357.98, "duration": 1.76}, {"text": "And they said it's like DNA--", "start": 3359.74, "duration": 1.94}, {"text": "data, networks, activities.", "start": 3361.68, "duration": 3.02}, {"text": "And if you're Alibaba\nor you're Facebook,", "start": 3364.7, "duration": 5.22}, {"text": "you want to layer another\nactivity on your network.", "start": 3369.92, "duration": 3.66}, {"text": "Facebook already has\n2 plus billion people", "start": 3373.58, "duration": 2.28}, {"text": "in their network.", "start": 3375.86, "duration": 1.27}, {"text": "They have a lot of data already.", "start": 3377.13, "duration": 2.3}, {"text": "They are supposedly a free app.", "start": 3379.43, "duration": 3.1}, {"text": "They are free if\nyou download it.", "start": 3382.53, "duration": 2.58}, {"text": "But it's data for services.", "start": 3385.11, "duration": 2.09}, {"text": "And if they can put another\nactivity on top of it,", "start": 3387.2, "duration": 2.38}, {"text": "that means they get more data.", "start": 3389.58, "duration": 2.61}, {"text": "So every time they add\nan activity, more data.", "start": 3392.19, "duration": 3.02}, {"text": "And data they can commercialize.", "start": 3395.21, "duration": 2.8}, {"text": "And so that DNA network is\nwhy you see big tech trying", "start": 3398.01, "duration": 4.86}, {"text": "to get in payments\naround the globe,", "start": 3402.87, "duration": 2.37}, {"text": "and then adding credit\nproducts on top of it.", "start": 3405.24, "duration": 3.55}, {"text": "Startups-- startups\nhave advantages.", "start": 3408.79, "duration": 2.57}, {"text": "Don't count them out.", "start": 3411.36, "duration": 1.89}, {"text": "Some people would just\ncall that the FinTech.", "start": 3413.25, "duration": 2.04}, {"text": "But they're flexible.", "start": 3415.29, "duration": 1.5}, {"text": "They're disruptive innovators.", "start": 3416.79, "duration": 1.74}, {"text": "They can sort of rent their\ndata storage on the cloud.", "start": 3418.53, "duration": 4.14}, {"text": "In some circumstances, they\ncan rent their balance sheets", "start": 3422.67, "duration": 2.58}, {"text": "by doing securitizations.", "start": 3425.25, "duration": 2.28}, {"text": "They also have some\nasymmetric risks.", "start": 3427.53, "duration": 2.71}, {"text": "And that asymmetric risk we'll\ntalk about all half semester.", "start": 3430.24, "duration": 3.69}, {"text": "The important asymmetries\nthey have is one,", "start": 3433.93, "duration": 4.46}, {"text": "they're not protecting\na business model.", "start": 3438.39, "duration": 2.71}, {"text": "So let's just talk about\npayments and credit", "start": 3441.1, "duration": 2.0}, {"text": "cards for a minute.", "start": 3443.1, "duration": 1.9}, {"text": "The big banks are protecting\na very profitable credit card", "start": 3445.0, "duration": 3.82}, {"text": "business.", "start": 3448.82, "duration": 0.5}, {"text": "And there's seven\nbig banks in the US.", "start": 3449.32, "duration": 2.72}, {"text": "There's seven big actors\nin the credit card space--", "start": 3452.04, "duration": 2.74}, {"text": "Bank of America and Chase\nand Citi, of course,", "start": 3454.78, "duration": 3.45}, {"text": "but also American Express and\nDiscover and the like, Cap One.", "start": 3458.23, "duration": 5.52}, {"text": "They're protecting\nthat business model.", "start": 3463.75, "duration": 2.23}, {"text": "But then somebody comes along.", "start": 3465.98, "duration": 1.97}, {"text": "Maybe it's a small company like\nToast in the payment system", "start": 3467.95, "duration": 3.54}, {"text": "space for restaurant payments.", "start": 3471.49, "duration": 3.03}, {"text": "And before corona crisis,\nToast was doing pretty well.", "start": 3474.52, "duration": 3.06}, {"text": "And they did a C or\nseries C or D round", "start": 3477.58, "duration": 2.76}, {"text": "at $4.9 billion valuation.", "start": 3480.34, "duration": 2.76}, {"text": "Well, Toast can come along\nand provide a payment product", "start": 3483.1, "duration": 2.88}, {"text": "for the restaurant business.", "start": 3485.98, "duration": 3.27}, {"text": "They're not protecting\nany business model.", "start": 3489.25, "duration": 2.61}, {"text": "Or even Lending Club\nthat came along 10", "start": 3491.86, "duration": 2.31}, {"text": "or 11 years ago can come\ninto the personal loan space", "start": 3494.17, "duration": 4.32}, {"text": "and say we're not\nprotecting wider profit", "start": 3498.49, "duration": 3.51}, {"text": "margins and interest rate\nmargins in the credit card", "start": 3502.0, "duration": 3.03}, {"text": "space.", "start": 3505.03, "duration": 1.29}, {"text": "You can come into the\npersonal lending space,", "start": 3506.32, "duration": 2.52}, {"text": "which is growing dramatically.", "start": 3508.84, "duration": 2.82}, {"text": "Personal lending in the US is\nabout $170 billion asset class.", "start": 3511.66, "duration": 4.8}, {"text": "Credit cards is $1 trillion.", "start": 3516.46, "duration": 2.43}, {"text": "So it's only one sixth the size,\nbut the personal loan space", "start": 3518.89, "duration": 2.87}, {"text": "is growing rapidly, in\npart because those actors", "start": 3521.76, "duration": 3.78}, {"text": "in the disruptive\nstartup space are not", "start": 3525.54, "duration": 1.92}, {"text": "protecting the trillion-dollar\nasset class, which", "start": 3527.46, "duration": 3.58}, {"text": "is called credit cards.", "start": 3531.04, "duration": 2.66}, {"text": "And then there's\nthe official sector.", "start": 3533.7, "duration": 2.05}, {"text": "So I think of these actors\nas, importantly, all of them.", "start": 3535.75, "duration": 3.77}, {"text": "And just some pictures,\njust for fun--", "start": 3539.52, "duration": 1.83}, {"text": "we don't need to\nstop, but big finance.", "start": 3541.35, "duration": 2.2}, {"text": "And, of course, I\nleft companies out.", "start": 3543.55, "duration": 2.6}, {"text": "But to give you a sense,\nit's an asset management,", "start": 3546.15, "duration": 2.43}, {"text": "like BlackRock and\nFidelity and Vanguard.", "start": 3548.58, "duration": 3.14}, {"text": "It's in banking.", "start": 3551.72, "duration": 1.45}, {"text": "It's in investment banking.", "start": 3553.17, "duration": 1.29}, {"text": "It's global.", "start": 3554.46, "duration": 1.2}, {"text": "If I left your country or\nyour favorite company out,", "start": 3555.66, "duration": 3.12}, {"text": "I apologize.", "start": 3558.78, "duration": 0.9}, {"text": "But I could have put 200,\n500 companies on this page.", "start": 3559.68, "duration": 3.78}, {"text": "But then there's also\nbig tech, which I only", "start": 3563.46, "duration": 3.36}, {"text": "picked six or seven at the top.", "start": 3566.82, "duration": 1.71}, {"text": "And then the\nstartups-- and we're", "start": 3568.53, "duration": 2.19}, {"text": "going to talk about startups\nin every one of our classes.", "start": 3570.72, "duration": 3.66}, {"text": "But I think you've got\nto sort of bear with me", "start": 3574.38, "duration": 2.67}, {"text": "and think about it\nmore broadly as well.", "start": 3577.05, "duration": 4.7}, {"text": "And then I'm just going\nto close before we", "start": 3581.75, "duration": 1.75}, {"text": "talk about our actual\ncourse and so forth, is", "start": 3583.5, "duration": 4.49}, {"text": "where's the investments?", "start": 3587.99, "duration": 1.15}, {"text": "Accenture puts out\nthis wonderful report,", "start": 3589.14, "duration": 2.67}, {"text": "I think on a quarterly\nbasis, as to the number", "start": 3591.81, "duration": 3.33}, {"text": "of deals in different\nsectors and then the funding.", "start": 3595.14, "duration": 4.06}, {"text": "And I don't ask you to study\nthis on your screen now.", "start": 3599.2, "duration": 2.72}, {"text": "But think about it.", "start": 3601.92, "duration": 0.84}, {"text": "Maybe pull up the\nAccenture report itself.", "start": 3602.76, "duration": 3.63}, {"text": "But the big bulk of it is\nin payments and credit.", "start": 3606.39, "duration": 3.96}, {"text": "If you look at the kind of\npurplish blue boxes, nearly 50%", "start": 3610.35, "duration": 4.41}, {"text": "of the funding is\nin those boxes.", "start": 3614.76, "duration": 2.52}, {"text": "Insurance, pretty\ngood size, too.", "start": 3617.28, "duration": 2.73}, {"text": "But it gives you the sectors\nthat actual funding is going on", "start": 3620.01, "duration": 4.26}, {"text": "in this marketplace.", "start": 3624.27, "duration": 1.65}, {"text": "Romain, questions?", "start": 3625.92, "duration": 2.742}, {"text": "AUDIENCE: No questions.", "start": 3628.662, "duration": 0.958}, {"text": "GARY GENSLER: My god,\nRomain, where did you", "start": 3629.62, "duration": 2.31}, {"text": "get this picture taken\nanyway that I grabbed off", "start": 3631.93, "duration": 2.7}, {"text": "the internet?", "start": 3634.63, "duration": 2.015}, {"text": "ROMAIN DE SAINT PERIER:\nThat was when I was working", "start": 3636.645, "duration": 2.125}, {"text": "in the Middle East for BCG.", "start": 3638.77, "duration": 2.25}, {"text": "GARY GENSLER: I see, I see.", "start": 3641.02, "duration": 1.95}, {"text": "All right, so you've met Romain.", "start": 3642.97, "duration": 2.7}, {"text": "You've met myself.", "start": 3645.67, "duration": 0.98}, {"text": "Lena is the course\nadministrator.", "start": 3646.65, "duration": 2.98}, {"text": "If you want to set up\noffice hours-- and, yes,", "start": 3649.63, "duration": 2.43}, {"text": "I am committed to office hours--", "start": 3652.06, "duration": 2.7}, {"text": "it's great to also copy Lena.", "start": 3654.76, "duration": 2.13}, {"text": "You can probably\ndo it with me, too.", "start": 3656.89, "duration": 1.85}, {"text": "But Lena is going to be\nbetter to sign it up as well.", "start": 3658.74, "duration": 6.58}, {"text": "The course-- so\nafter this intro,", "start": 3665.32, "duration": 2.28}, {"text": "we're going to take\nthe technologies.", "start": 3667.6, "duration": 1.82}, {"text": "We're going to take two classes\non artificial intelligence,", "start": 3669.42, "duration": 3.25}, {"text": "machine learning, natural\nlanguage processing", "start": 3672.67, "duration": 2.31}, {"text": "and the like, and then talk\nabout the customer interface", "start": 3674.98, "duration": 4.02}, {"text": "on April 8 and then\nblockchain and technology.", "start": 3679.0, "duration": 3.27}, {"text": "These three slices-- now,\nthere are other slices", "start": 3682.27, "duration": 2.46}, {"text": "we could address as well.", "start": 3684.73, "duration": 2.32}, {"text": "So then we're going to\ngo through the sectors.", "start": 3687.05, "duration": 2.24}, {"text": "We're going to talk\nabout these sectors.", "start": 3689.29, "duration": 1.8}, {"text": "And what I could see is payment\nand credit, trading, a little", "start": 3691.09, "duration": 4.74}, {"text": "less on the risk management.", "start": 3695.83, "duration": 1.74}, {"text": "So maybe on May 4, we'll squeeze\nthat down a little bit as well.", "start": 3697.57, "duration": 5.26}, {"text": "And then, of course,\nwe have the intro.", "start": 3702.83, "duration": 1.64}, {"text": "I've just, [INAUDIBLE] and\nI, revised the syllabus", "start": 3704.47, "duration": 3.06}, {"text": "this past week.", "start": 3707.53, "duration": 1.17}, {"text": "I want to take the\nnext-to-last class", "start": 3708.7, "duration": 2.73}, {"text": "and just talk\nabout corona crisis", "start": 3711.43, "duration": 2.11}, {"text": "and how it might be\nshifting the landscape.", "start": 3713.54, "duration": 2.96}, {"text": "I already said, I really\ndo think this shifting,", "start": 3716.5, "duration": 2.84}, {"text": "this deep trend towards\nonline from bricks and mortar,", "start": 3719.34, "duration": 5.77}, {"text": "that was already happening.", "start": 3725.11, "duration": 2.08}, {"text": "But we've even seen in\nthe last three weeks,", "start": 3727.19, "duration": 2.72}, {"text": "we've seen winners and losers.", "start": 3729.91, "duration": 1.99}, {"text": "I asked each of you\nto think about this.", "start": 3731.9, "duration": 2.21}, {"text": "Who are the winners and losers\nwithin the financial sector,", "start": 3734.11, "duration": 5.3}, {"text": "big tech, and the\nfinancial startups?", "start": 3739.41, "duration": 2.79}, {"text": "I talked a little\nbit about Toast.", "start": 3742.2, "duration": 1.47}, {"text": "Toast is a very\nsuccessful Boston company", "start": 3743.67, "duration": 3.45}, {"text": "that is providing\npayment services", "start": 3747.12, "duration": 2.22}, {"text": "and credit to restaurants.", "start": 3749.34, "duration": 1.823}, {"text": "For a moment, that would\nhave to-- you'd have to say", "start": 3751.163, "duration": 2.167}, {"text": "that's a company that's taking--", "start": 3753.33, "duration": 2.34}, {"text": "taking it on the chin,\nso to speak, not as badly", "start": 3755.67, "duration": 3.27}, {"text": "as all those individuals that\nhave health care worries,", "start": 3758.94, "duration": 2.58}, {"text": "that are ending up in the\nhospitals and the families", "start": 3761.52, "duration": 2.19}, {"text": "losing loved ones.", "start": 3763.71, "duration": 1.45}, {"text": "But I'm saying from an\neconomic perspective,", "start": 3765.16, "duration": 2.78}, {"text": "there are some\nwinners and losers.", "start": 3767.94, "duration": 1.53}, {"text": "Robinhood, an online app,\nmobile app for trading,", "start": 3769.47, "duration": 5.97}, {"text": "has crashed several times\nin the last three weeks.", "start": 3775.44, "duration": 3.42}, {"text": "And there's some\ndata out of Europe", "start": 3778.86, "duration": 1.65}, {"text": "already that online FinTech\napps as a sector have", "start": 3780.51, "duration": 6.3}, {"text": "seen usage up 70% and 100%,\nand some apps up 700%.", "start": 3786.81, "duration": 5.64}, {"text": "But not all will be winners.", "start": 3792.45, "duration": 1.68}, {"text": "Not all will be losers.", "start": 3794.13, "duration": 1.89}, {"text": "And so I thought we'll take\none class towards the end", "start": 3796.02, "duration": 3.78}, {"text": "and just discuss it and get\nyour feelings and thoughts", "start": 3799.8, "duration": 4.05}, {"text": "as well going forward\nhow this might play out.", "start": 3803.85, "duration": 5.23}, {"text": "So MIT chose this as pass-fail.", "start": 3809.08, "duration": 3.05}, {"text": "So welcome to not only\nremote learning MIT,", "start": 3812.13, "duration": 3.93}, {"text": "but technically pass\nemergency, no-credit emergency,", "start": 3816.06, "duration": 3.36}, {"text": "incomplete emergency.", "start": 3819.42, "duration": 1.68}, {"text": "Just so that you understand what\nthis is, it's almost pass-fail.", "start": 3821.1, "duration": 3.84}, {"text": "Pass emergency, PE, will\nbe on your transcript,", "start": 3824.94, "duration": 3.0}, {"text": "hopefully for all of you.", "start": 3827.94, "duration": 2.05}, {"text": "I can't commit to it,\nbecause it's up to you", "start": 3829.99, "duration": 2.54}, {"text": "whether you pass.", "start": 3832.53, "duration": 1.53}, {"text": "There are assignments.", "start": 3834.06, "duration": 2.1}, {"text": "And no credit emergency,\nyou can think of is an F,", "start": 3836.16, "duration": 4.5}, {"text": "but it's not going to\nbe on your transcript.", "start": 3840.66, "duration": 3.04}, {"text": "So this is an emergency\ncircumstance right now.", "start": 3843.7, "duration": 3.73}, {"text": "There's still\nassignments because we", "start": 3847.43, "duration": 2.01}, {"text": "want to give you\nthe most learning", "start": 3849.44, "duration": 2.94}, {"text": "experience you can have.", "start": 3852.38, "duration": 1.0}, {"text": "You might say wait a minute,\nwait a minute, I thought--", "start": 3853.38, "duration": 2.292}, {"text": "I thought assignments were\njust about so that a faculty", "start": 3855.672, "duration": 2.348}, {"text": "member can decide who gets A's\nand who gets B's and the like.", "start": 3858.02, "duration": 4.35}, {"text": "I look at assignments in\na different way than that.", "start": 3862.37, "duration": 2.46}, {"text": "I look at assignments\nreally as a way", "start": 3864.83, "duration": 2.25}, {"text": "to help you engage\nin this subject.", "start": 3867.08, "duration": 2.63}, {"text": "And so in this class--", "start": 3869.71, "duration": 1.33}, {"text": "and those of you\nwho know me, I do", "start": 3871.04, "duration": 1.83}, {"text": "this in a couple of classes-- is\none individual paper, one group", "start": 3872.87, "duration": 3.18}, {"text": "paper.", "start": 3876.05, "duration": 0.7}, {"text": "And it's all geared\nto writing a group", "start": 3876.75, "duration": 2.12}, {"text": "paper for either a big\nincumbent, Bank of America,", "start": 3878.87, "duration": 4.69}, {"text": "a big tech company, Jeff\nBezos and Amazon, or kind", "start": 3883.56, "duration": 5.61}, {"text": "of a startup company, a big VC\ncompany, Andreesen Horowitz,", "start": 3889.17, "duration": 4.7}, {"text": "that you form groups and\nyou decide on a sector.", "start": 3893.87, "duration": 2.68}, {"text": "You can decide on credit\nor payment or trading.", "start": 3896.55, "duration": 3.81}, {"text": "You choose, and it helps\nyou engage in the subject.", "start": 3900.36, "duration": 3.87}, {"text": "And then I ask you to split,\nif it's a three or four-person", "start": 3904.23, "duration": 2.94}, {"text": "team, or even if it's\na one-person team,", "start": 3907.17, "duration": 2.13}, {"text": "if you choose to do that,\nbecause we're all so separated,", "start": 3909.3, "duration": 4.8}, {"text": "then split up and write a\nthree or four page paper,", "start": 3914.1, "duration": 3.93}, {"text": "900 words or so, on one of the\ntopics that I lay out here--", "start": 3918.03, "duration": 6.05}, {"text": "the traditional competitors,\nthe startup competitors", "start": 3924.08, "duration": 4.54}, {"text": "and so forth, the technology\nthat you're interested in.", "start": 3928.62, "duration": 4.83}, {"text": "Why do I still do\nassignments when it's PE NE?", "start": 3933.45, "duration": 3.36}, {"text": "It's to help you\nengage in this subject.", "start": 3936.81, "duration": 2.16}, {"text": "And Romain and I are committed,\neven if we slap a PE on most", "start": 3938.97, "duration": 3.93}, {"text": "of these-- hopefully\nall of them--", "start": 3942.9, "duration": 2.19}, {"text": "we're trying to\ngive you feedback", "start": 3945.09, "duration": 1.8}, {"text": "so you engage in a subject.", "start": 3946.89, "duration": 1.5}, {"text": "And yes, I'm willing to do\nZoom group meetings, Zoom", "start": 3948.39, "duration": 5.07}, {"text": "individual meetings.", "start": 3953.46, "duration": 1.93}, {"text": "Look, this is not an\neasy time for any of us.", "start": 3955.39, "duration": 3.22}, {"text": "But I want to make sure that\nI deliver as much as I can", "start": 3958.61, "duration": 2.8}, {"text": "and that MIT\ncontinues to deliver", "start": 3961.41, "duration": 2.34}, {"text": "for you as we're going through\nthis sort of challenging time.", "start": 3963.75, "duration": 4.71}, {"text": "Class participation\nis still important.", "start": 3968.46, "duration": 3.34}, {"text": "If you can't sign up, if it's\nthe time zone doesn't work", "start": 3971.8, "duration": 3.53}, {"text": "or there's something going on\nin your family, it doesn't--", "start": 3975.33, "duration": 3.41}, {"text": "if you're interviewing\nfor a job, God bless,", "start": 3978.74, "duration": 3.46}, {"text": "then listen to the recording.", "start": 3982.2, "duration": 1.77}, {"text": "We'll put the recordings\nup on Canvas as well.", "start": 3983.97, "duration": 5.5}, {"text": "And so professionalism, I\njust want to say something.", "start": 3989.47, "duration": 2.93}, {"text": "ROMAIN DE SAINT PERIER: Gary?", "start": 3992.4, "duration": 0.15}, {"text": "GARY GENSLER: Yeah?", "start": 3992.55, "duration": 0.69}, {"text": "ROMAIN DE SAINT PERIER: Excuse\nme, just on the assignments,", "start": 3993.24, "duration": 2.458}, {"text": "I'm being asked\nwhether listeners also", "start": 3995.698, "duration": 1.772}, {"text": "have to comply with\nthese assignments.", "start": 3997.47, "duration": 1.74}, {"text": "GARY GENSLER: No.", "start": 3999.21, "duration": 1.723}, {"text": "ROMAIN DE SAINT\nPERIER: Thank you.", "start": 4000.933, "duration": 1.417}, {"text": "GARY GENSLER: I'm trying to\nget rid of the poll here.", "start": 4005.278, "duration": 2.942}, {"text": "OK.", "start": 4008.22, "duration": 0.5}, {"text": "I've never been\nasked that question.", "start": 4012.14, "duration": 3.09}, {"text": "A little word on\nprofessionalism,", "start": 4015.23, "duration": 1.77}, {"text": "just for my, God knows,\n30 plus years in business.", "start": 4017.0, "duration": 4.68}, {"text": "And this is just sort\nof my closing thing,", "start": 4021.68, "duration": 2.37}, {"text": "is my advice for\nall of us is success", "start": 4024.05, "duration": 4.11}, {"text": "goes for those prepared,\ncurious, and self-starters.", "start": 4028.16, "duration": 3.73}, {"text": "If you read the\nassignments for this,", "start": 4031.89, "duration": 2.06}, {"text": "you'll do better in this class.", "start": 4033.95, "duration": 2.02}, {"text": "But if you go into a meeting,\nif you go into a pitch,", "start": 4035.97, "duration": 2.75}, {"text": "you go into an interview, if\nyou read about the person,", "start": 4038.72, "duration": 4.47}, {"text": "you're going to learn\nmore about them.", "start": 4043.19, "duration": 1.932}, {"text": "And, by the way,\nif you're curious,", "start": 4045.122, "duration": 1.458}, {"text": "when you walk into\nsomebody's office,", "start": 4046.58, "duration": 1.69}, {"text": "whether it's a video office or a\nreal office, look at the walls.", "start": 4048.27, "duration": 5.92}, {"text": "What does it mean\nthat Gary Gensler has", "start": 4054.19, "duration": 2.25}, {"text": "this stuff behind him or not?", "start": 4056.44, "duration": 2.13}, {"text": "I'm not asking you to\nanalyze me right now.", "start": 4058.57, "duration": 2.79}, {"text": "But I'm telling you, if you\nwalk into somebody's office,", "start": 4061.36, "duration": 3.21}, {"text": "whether they're a US senator,\nthe president of the United", "start": 4064.57, "duration": 3.45}, {"text": "States, some job interview,\na colleague, and you look", "start": 4068.02, "duration": 4.2}, {"text": "at their walls and you ask\nthem about their families,", "start": 4072.22, "duration": 2.22}, {"text": "show some curiosity.", "start": 4074.44, "duration": 1.2}, {"text": "You'll do better off.", "start": 4075.64, "duration": 2.4}, {"text": "As I said, respect and courtesy\nbuilds reputation and networks", "start": 4078.04, "duration": 3.42}, {"text": "and so forth.", "start": 4081.46, "duration": 2.92}, {"text": "Engage.", "start": 4084.38, "duration": 0.87}, {"text": "It's going to be hard with\nthis many students online,", "start": 4085.25, "duration": 3.33}, {"text": "but engage in this class.", "start": 4088.58, "duration": 1.69}, {"text": "You'll learn more if\nyou engage with me", "start": 4090.27, "duration": 2.33}, {"text": "also offline, Gensler@MIT.edu,\nbut also engage", "start": 4092.6, "duration": 6.54}, {"text": "by setting up office time.", "start": 4099.14, "duration": 2.7}, {"text": "I also think understanding both\nstrategy and detail matter.", "start": 4101.84, "duration": 3.37}, {"text": "Some people are really\ngood tactical people,", "start": 4105.21, "duration": 2.569}, {"text": "really good detail folks.", "start": 4107.779, "duration": 2.721}, {"text": "They'll do fine\nin their careers.", "start": 4110.5, "duration": 1.5}, {"text": "But if you step back and\nunderstand the trends as well,", "start": 4112.0, "duration": 2.609}, {"text": "you'll do better.", "start": 4114.609, "duration": 1.241}, {"text": "Some people are really\nglobal strategists", "start": 4115.85, "duration": 1.91}, {"text": "and not really good\nat the details.", "start": 4117.76, "duration": 1.74}, {"text": "They'll probably do OK.", "start": 4119.5, "duration": 1.77}, {"text": "But I'll tell you,\nmy experience,", "start": 4121.27, "duration": 1.6}, {"text": "whether it's in finance,\nwhether it's watching people", "start": 4122.87, "duration": 3.56}, {"text": "at MIT and the faculty, or\nmy time in public service,", "start": 4126.43, "duration": 4.61}, {"text": "the people that can\nmerge both broad strategy", "start": 4131.04, "duration": 3.279}, {"text": "and can execute on the\ndetails, those folks", "start": 4134.319, "duration": 2.551}, {"text": "are unstoppable often.", "start": 4136.87, "duration": 1.668}, {"text": "Those are folks that\nyou really-- you", "start": 4138.538, "duration": 1.542}, {"text": "want them on your team, that\nthey can do a bit of both.", "start": 4140.08, "duration": 3.69}, {"text": "So we're going to talk a lot\nabout strategy and the trends.", "start": 4143.77, "duration": 3.089}, {"text": "But we're going to get into\nthe granular details as well.", "start": 4146.859, "duration": 3.372}, {"text": "And then lastly,\nit's always better", "start": 4150.231, "duration": 1.458}, {"text": "to stay true to your values.", "start": 4151.689, "duration": 1.831}, {"text": "Now, I do say this--", "start": 4153.52, "duration": 1.83}, {"text": "it's going to be a little--", "start": 4155.35, "duration": 1.28}, {"text": "we're in this pass-fail thing.", "start": 4156.63, "duration": 1.5}, {"text": "But if you want to know\none way that Romain and I,", "start": 4158.13, "duration": 3.19}, {"text": "it will drive us a\nlittle nutty, we're", "start": 4161.32, "duration": 2.249}, {"text": "going to try to put your\npapers through some plagiarism", "start": 4163.569, "duration": 3.091}, {"text": "software.", "start": 4166.66, "duration": 1.02}, {"text": "I use Grammarly.", "start": 4167.68, "duration": 1.74}, {"text": "I actually check, yes.", "start": 4169.42, "duration": 3.33}, {"text": "And if you have one like\neight or ten-word section", "start": 4172.75, "duration": 4.109}, {"text": "that you pulled\noff of Wikipedia,", "start": 4176.859, "duration": 1.801}, {"text": "and I've had students grab the\nfirst 15 words off of Wikipedia", "start": 4178.66, "duration": 3.75}, {"text": "and put it right in\ntheir paper, that's", "start": 4182.41, "duration": 2.67}, {"text": "kind of a sloppy thing to do.", "start": 4185.08, "duration": 1.8}, {"text": "And usually, if I was\ngrading, that paper", "start": 4186.88, "duration": 2.399}, {"text": "would get like a C or a D and\nit wouldn't get an A or a B.", "start": 4189.279, "duration": 3.0}, {"text": "And I'm not going to be a\nhard-nosed guy about 10 words.", "start": 4192.279, "duration": 4.111}, {"text": "But if you extensively\nplagiarize a couple hundred", "start": 4196.39, "duration": 3.48}, {"text": "words in a 900-word\npaper, you're", "start": 4199.87, "duration": 3.06}, {"text": "going to get an F on the paper.", "start": 4202.93, "duration": 2.37}, {"text": "Now, you can recover\non the group paper.", "start": 4205.3, "duration": 2.07}, {"text": "But don't plagiarize\non your group paper", "start": 4207.37, "duration": 2.047}, {"text": "because you're also going to\nbring down your colleagues.", "start": 4209.417, "duration": 2.333}, {"text": "I don't know in pass-fail\nland what I will do.", "start": 4211.75, "duration": 3.33}, {"text": "But if somebody really is\ntrying to test the limit,", "start": 4215.08, "duration": 3.69}, {"text": "you would test it by\nextensive plagiarism.", "start": 4218.77, "duration": 3.33}, {"text": "Enough on that.", "start": 4222.1, "duration": 0.72}, {"text": "I've had it in the\npast occasionally.", "start": 4222.82, "duration": 3.51}, {"text": "So I got to say it.", "start": 4226.33, "duration": 4.05}, {"text": "I would say speak up\nin class if you can.", "start": 4230.38, "duration": 2.37}, {"text": "Keep your videos on,\nas most of you have.", "start": 4232.75, "duration": 2.19}, {"text": "Keep your audios muted.", "start": 4234.94, "duration": 1.83}, {"text": "But please speak up.", "start": 4236.77, "duration": 1.59}, {"text": "I mean, don't be\nhesitant at all.", "start": 4238.36, "duration": 6.08}, {"text": "And then I do have office hours.", "start": 4244.44, "duration": 2.61}, {"text": "And the crazy thing was\nI set up office lunches.", "start": 4247.05, "duration": 3.75}, {"text": "So on those following Tuesdays\nand Thursdays, I had--", "start": 4250.8, "duration": 4.06}, {"text": "there's a spreadsheet.", "start": 4254.86, "duration": 1.73}, {"text": "Romain, maybe we should send\nit around to this group.", "start": 4256.59, "duration": 3.57}, {"text": "There's a Google Spreadsheet\nif you wanted to sign up.", "start": 4260.16, "duration": 3.36}, {"text": "And right before we left, before\nSIP week, a student said hey,", "start": 4263.52, "duration": 4.87}, {"text": "I'm signed up for the 31.", "start": 4268.39, "duration": 2.04}, {"text": "Will you still do the lunches?", "start": 4270.43, "duration": 1.59}, {"text": "I laughed.", "start": 4272.02, "duration": 0.75}, {"text": "I said listen, I'm\nwilling to do it.", "start": 4272.77, "duration": 3.1}, {"text": "I'm willing to do\nremote lunches.", "start": 4275.87, "duration": 1.88}, {"text": "It's crazy.", "start": 4277.75, "duration": 2.73}, {"text": "So if you want it-- if\nnobody signs up, I'm fine.", "start": 4280.48, "duration": 3.06}, {"text": "I'll go for a run.", "start": 4283.54, "duration": 1.77}, {"text": "I live in Baltimore and\nI'm still able to run here.", "start": 4285.31, "duration": 2.88}, {"text": "They might shut that down,\ntoo, at some point in time.", "start": 4288.19, "duration": 2.32}, {"text": "But for now, I'm\nable to do my runs.", "start": 4290.51, "duration": 2.7}, {"text": "So I think that's\nit on the slides.", "start": 4293.21, "duration": 3.2}, {"text": "And then I think I'm supposed\nto finish this class right now.", "start": 4296.41, "duration": 6.16}, {"text": "I went over.", "start": 4302.57, "duration": 0.718}, {"text": "I want to thank you all--", "start": 4303.288, "duration": 1.042}, {"text": "ROMAIN DE SAINT PERIER:\nMaybe just one--", "start": 4304.33, "duration": 1.13}, {"text": "GARY GENSLER: What's that?", "start": 4305.46, "duration": 1.01}, {"text": "ROMAIN DE SAINT PERIER:\nJust one clarification,", "start": 4306.47, "duration": 1.11}, {"text": "because I'm getting a lot\nof questions on the group", "start": 4307.58, "duration": 1.65}, {"text": "formation.", "start": 4309.23, "duration": 0.63}, {"text": "So groups will be from\nthree to four students,", "start": 4309.86, "duration": 3.08}, {"text": "and you are supposed\nto group yourselves,", "start": 4312.94, "duration": 2.71}, {"text": "right, through the\nCanvas function.", "start": 4315.65, "duration": 1.605}, {"text": "If that doesn't\nwork out for you,", "start": 4317.255, "duration": 1.375}, {"text": "we're going to send\nout a link where", "start": 4318.63, "duration": 1.58}, {"text": "you can find other\nteam members who also", "start": 4320.21, "duration": 2.49}, {"text": "are looking for team members.", "start": 4322.7, "duration": 1.69}, {"text": "So do not worry about\nthe group formation.", "start": 4324.39, "duration": 2.143}, {"text": "GARY GENSLER: And\nI thank you all.", "start": 4326.533, "duration": 1.417}, {"text": "I know this is unusual.", "start": 4327.95, "duration": 2.01}, {"text": "I see you on Wednesday\nmorning, 8:30 AM.", "start": 4329.96, "duration": 3.73}, {"text": "And please stay\nsafe and be well.", "start": 4333.69, "duration": 3.79}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.948}, {"text": "[RUSTLING]", "start": 1.948, "duration": 2.435}, {"text": "[CLICKING]", "start": 4.383, "duration": 5.857}, {"text": "NANCY KANWISHER: We are turning\nfrom our various other topics", "start": 10.24, "duration": 2.64}, {"text": "to talk about hearing today.", "start": 12.88, "duration": 1.71}, {"text": "And let's start by thinking\nabout all the cool stuff", "start": 14.59, "duration": 3.6}, {"text": "that you can do\njust by listening.", "start": 18.19, "duration": 3.75}, {"text": "So just by listening, you\ncan identify the scene", "start": 21.94, "duration": 3.57}, {"text": "that you're in and\nwhat's going on", "start": 25.51, "duration": 1.8}, {"text": "in it, like for example, this.", "start": 27.31, "duration": 2.715}, {"text": "[AUDIO PLAYBACK]", "start": 30.025, "duration": 5.862}, {"text": "[END PLAYBACK]", "start": 35.887, "duration": 0.583}, {"text": "OK, so you know what kind of\nroom you're in and roughly", "start": 36.47, "duration": 2.31}, {"text": "what's going on, just from\nthat little bit of sound.", "start": 38.78, "duration": 3.9}, {"text": "You can localize events\nand people and objects.", "start": 42.68, "duration": 3.18}, {"text": "So close your eyes, everyone.", "start": 45.86, "duration": 1.65}, {"text": "Keep them closed.", "start": 47.51, "duration": 1.3}, {"text": "And if you just\nlisten to me talking,", "start": 48.81, "duration": 3.32}, {"text": "it's really very\nvivid, isn't it,", "start": 52.13, "duration": 2.52}, {"text": "exactly how obvious\nit is where I am.", "start": 54.65, "duration": 3.39}, {"text": "And I will refrain\nfrom the temptation", "start": 58.04, "duration": 2.52}, {"text": "of coming up and speaking\nin somebody's ears", "start": 60.56, "duration": 2.602}, {"text": "because it's just too creepy.", "start": 63.162, "duration": 1.208}, {"text": "OK, you can open your eyes.", "start": 64.37, "duration": 1.17}, {"text": "It's very vivid.", "start": 65.54, "duration": 1.08}, {"text": "Just from listening, you know\nwhere the sound source is.", "start": 66.62, "duration": 3.72}, {"text": "You can recognize sound\nsources, so for example,", "start": 70.34, "duration": 3.36}, {"text": "sounds like this--", "start": 73.7, "duration": 1.17}, {"text": "[GLASS BREAKING]", "start": 74.87, "duration": 3.202}, {"text": "You know what happened there.", "start": 78.072, "duration": 1.208}, {"text": "It's a whole vivid event\njust unfolded there", "start": 79.28, "duration": 1.98}, {"text": "in a whole second and a\nhalf, or a random series", "start": 81.26, "duration": 3.6}, {"text": "of sounds like this.", "start": 84.86, "duration": 0.893}, {"text": "[AUDIO PLAYBACK]", "start": 85.753, "duration": 0.667}, {"text": "- It's supposed to\neither rain or snow.", "start": 86.42, "duration": 3.309}, {"text": "[RANDOM SOUNDS]", "start": 89.729, "duration": 5.047}, {"text": "- Hannah is good\nat compromising.", "start": 94.776, "duration": 2.755}, {"text": "[RANDOM SOUNDS]", "start": 97.531, "duration": 4.419}, {"text": "[LAUGHTER]", "start": 101.95, "duration": 2.387}, {"text": "[END PLAYBACK]", "start": 104.337, "duration": 0.583}, {"text": "NANCY KANWISHER: Anyway,\nevery one of those", "start": 104.92, "duration": 0.99}, {"text": "sounds you\nimmediately recognize.", "start": 105.91, "duration": 1.725}, {"text": "You know exactly what it is.", "start": 107.635, "duration": 3.045}, {"text": "And that's environmental\nsounds, things", "start": 110.68, "duration": 1.89}, {"text": "that happen outdoors,\nspeech, what is being said,", "start": 112.57, "duration": 2.97}, {"text": "voices, who is saying it.", "start": 115.54, "duration": 2.16}, {"text": "If you don't know the person,\nif they're male or female,", "start": 117.7, "duration": 2.62}, {"text": "young or old, much like faces--", "start": 120.32, "duration": 1.82}, {"text": "if you know them, you'll\nrecognize them pretty fast.", "start": 122.14, "duration": 3.84}, {"text": "You can selectively attend\nto one sound among others.", "start": 125.98, "duration": 3.469}, {"text": "Like if you had a little, hidden\nearphone that I didn't see,", "start": 129.449, "duration": 5.011}, {"text": "and you wanted to listen\nto your favorite podcast,", "start": 134.46, "duration": 2.083}, {"text": "you could listen to\nthat occasionally when", "start": 136.543, "duration": 1.75}, {"text": "I was getting boring.", "start": 138.293, "duration": 0.877}, {"text": "And then you could turn\nback and listen to me.", "start": 139.17, "duration": 2.52}, {"text": "And you could just\nselectively choose", "start": 141.69, "duration": 1.8}, {"text": "which of those different\naudio inputs to listen to.", "start": 143.49, "duration": 4.38}, {"text": "And we'll talk more in a moment\nabout this classic problem", "start": 147.87, "duration": 2.94}, {"text": "in hearing, which is known as\nthe \"cocktail party effect.\"", "start": 150.81, "duration": 2.76}, {"text": "I guess it was named in the '50s\nwhen cocktail parties were big.", "start": 153.57, "duration": 3.408}, {"text": "And it consists in\nthe fact that when", "start": 156.978, "duration": 1.542}, {"text": "there are multiple sound\nsources, such as many people", "start": 158.52, "duration": 2.49}, {"text": "talking in a room, you\ncan tune in one channel", "start": 161.01, "duration": 3.36}, {"text": "and then tune in\nanother channel.", "start": 164.37, "duration": 2.25}, {"text": "And you can just\nselectively attend", "start": 166.62, "duration": 1.95}, {"text": "to one of many\nsound sources, even", "start": 168.57, "duration": 2.43}, {"text": "though those sound sources are\nmassively overlapping on top", "start": 171.0, "duration": 3.27}, {"text": "of each other in the input.", "start": 174.27, "duration": 1.32}, {"text": "And it's a big\ncomputational challenge,", "start": 175.59, "duration": 2.07}, {"text": "as we'll talk about\nshortly, to do that.", "start": 177.66, "duration": 3.3}, {"text": "You can enjoy music.", "start": 180.96, "duration": 2.65}, {"text": "And you can determine\nwhat things are made of.", "start": 183.61, "duration": 2.288}, {"text": "So close your eyes and I'm going\nto drop things on the table.", "start": 185.898, "duration": 2.542}, {"text": "Don't look.", "start": 188.44, "duration": 0.5}, {"text": "I'm going to do various\nthings and you're", "start": 188.94, "duration": 1.708}, {"text": "going to identify them.", "start": 190.648, "duration": 1.062}, {"text": "So let's see-- don't\nopen your eyes.", "start": 194.29, "duration": 2.71}, {"text": "See if you can tell what's\nbeing dropped on the table,", "start": 197.0, "duration": 2.64}, {"text": "or at least what it's made of.", "start": 199.64, "duration": 1.25}, {"text": "Close your eyes.", "start": 200.89, "duration": 1.06}, {"text": "That's cheating.", "start": 201.95, "duration": 1.8}, {"text": "Wood, exactly.", "start": 203.75, "duration": 0.97}, {"text": "Very good.", "start": 204.72, "duration": 0.5}, {"text": "OK, what is this?", "start": 205.22, "duration": 0.9}, {"text": "Keep your eyes closed.", "start": 206.12, "duration": 1.14}, {"text": "What is this made of?", "start": 207.26, "duration": 2.92}, {"text": "- Plastic.", "start": 210.18, "duration": 0.5}, {"text": "NANCY KANWISHER: Yeah, good.", "start": 210.68, "duration": 0.63}, {"text": "Keep your eyes closed.", "start": 211.31, "duration": 0.93}, {"text": "What is this made of?", "start": 212.24, "duration": 2.49}, {"text": "STUDENT: [INAUDIBLE]", "start": 214.73, "duration": 2.113}, {"text": "NANCY KANWISHER: Yeah.", "start": 216.843, "duration": 0.917}, {"text": "OK, keep your eyes closed.", "start": 217.76, "duration": 1.32}, {"text": "What's this made of?", "start": 219.08, "duration": 2.964}, {"text": "STUDENT: [INAUDIBLE].", "start": 222.044, "duration": 0.946}, {"text": "NANCY KANWISHER: Awesome.", "start": 222.99, "duration": 0.42}, {"text": "OK, you can open your eyes.", "start": 223.41, "duration": 1.38}, {"text": "Perfect.", "start": 224.79, "duration": 0.63}, {"text": "You guys are awesome.", "start": 225.42, "duration": 1.63}, {"text": "I just dropped these objects\nthat I found from my kitchen", "start": 227.05, "duration": 2.48}, {"text": "this morning and you guys could\ntell what they're made of.", "start": 229.53, "duration": 3.21}, {"text": "That's amazing.", "start": 232.74, "duration": 3.12}, {"text": "OK, all of this that\nyou guys just did", "start": 235.86, "duration": 3.3}, {"text": "happens from the\nsimplest possible signal.", "start": 239.16, "duration": 2.965}, {"text": "We'll talk about what that\nsignal is exactly in a moment,", "start": 242.125, "duration": 2.375}, {"text": "but it's just sound compression\ncoming through the air.", "start": 244.5, "duration": 3.37}, {"text": "And it tells you all this rich\nstuff about your environment.", "start": 247.87, "duration": 3.27}, {"text": "So the question is,\nhow do we do that?", "start": 251.14, "duration": 2.4}, {"text": "And the first\nquestion is, how do we", "start": 253.54, "duration": 2.21}, {"text": "start to think about\nhow hearing works, how", "start": 255.75, "duration": 2.22}, {"text": "you're able to do all of that?", "start": 257.97, "duration": 1.53}, {"text": "And you guys know we start\nwith computational theory--", "start": 259.5, "duration": 3.9}, {"text": "considering what the inputs\nare, what the outputs are,", "start": 263.4, "duration": 3.45}, {"text": "the physics of sound,\nwhat would be involved", "start": 266.85, "duration": 3.33}, {"text": "if we tried to code up a machine\nto take those audio input", "start": 270.18, "duration": 2.91}, {"text": "and deliver the output\nthat you guys all", "start": 273.09, "duration": 1.98}, {"text": "just delivered with\nno trouble whatsoever.", "start": 275.07, "duration": 2.79}, {"text": "What cues are in the stimulus?", "start": 277.86, "duration": 1.74}, {"text": "What are the key\ncomputational challenges?", "start": 279.6, "duration": 2.16}, {"text": "And what makes those aspects\nof hearing challenging?", "start": 281.76, "duration": 3.462}, {"text": "And then after we\ndo all that stuff", "start": 285.222, "duration": 1.458}, {"text": "at the level of\ncomputational theory,", "start": 286.68, "duration": 1.8}, {"text": "we can, of course, study\nhearing in other ways,", "start": 288.48, "duration": 2.69}, {"text": "like studying it behaviorally.", "start": 291.17, "duration": 1.25}, {"text": "What can people do and not do?", "start": 292.42, "duration": 1.43}, {"text": "What's hard?", "start": 293.85, "duration": 0.51}, {"text": "What's less hard?", "start": 294.36, "duration": 1.68}, {"text": "And we can measure\nneural responses.", "start": 296.04, "duration": 1.84}, {"text": "So we'll talk about all of that.", "start": 297.88, "duration": 1.92}, {"text": "But let's start with a\nlittle more on what sound is.", "start": 299.8, "duration": 4.1}, {"text": "So sound is just a\nsingle univariate signal", "start": 303.9, "duration": 3.72}, {"text": "coming into the ears.", "start": 307.62, "duration": 1.217}, {"text": "We'll say more about\nthat in a second,", "start": 308.837, "duration": 1.583}, {"text": "but it's really, really simple.", "start": 310.42, "duration": 2.48}, {"text": "And from that, you get\nall this rich experience.", "start": 312.9, "duration": 4.05}, {"text": "And so the question\nis, what goes", "start": 316.95, "duration": 1.53}, {"text": "on in that magic\nbox in the middle", "start": 318.48, "duration": 2.22}, {"text": "to enable you to extract\nthis kind of information", "start": 320.7, "duration": 2.55}, {"text": "from this really simple signal?", "start": 323.25, "duration": 2.82}, {"text": "So let's start\nwith what is sound.", "start": 326.07, "duration": 2.4}, {"text": "Sound is just a set of\nlongitudinal compressions", "start": 328.47, "duration": 4.17}, {"text": "and decompressions of the\nair coming from the source", "start": 332.64, "duration": 3.96}, {"text": "into your ear.", "start": 336.6, "duration": 1.98}, {"text": "So these waves travel\nfrom the source", "start": 338.58, "duration": 2.76}, {"text": "to the ear in little\nwaves of compression", "start": 341.34, "duration": 3.25}, {"text": "where the air is\njust compressed,", "start": 344.59, "duration": 2.36}, {"text": "and rarefaction where\nthe air is spread out.", "start": 346.95, "duration": 2.94}, {"text": "And just to give you a sense\nof how physical sound is,", "start": 352.53, "duration": 2.52}, {"text": "there's a silly video here.", "start": 355.05, "duration": 1.38}, {"text": "It's a speaker in a sink\nwith a bunch of paint.", "start": 356.43, "duration": 2.37}, {"text": "And you can just see that\nthe movement of the speaker--", "start": 358.8, "duration": 2.52}, {"text": "normally, it makes those\ncompressions and rarefactions", "start": 361.32, "duration": 2.91}, {"text": "of air, but if you\nstick paint on it.", "start": 364.23, "duration": 1.63}, {"text": "It's going to shove the\npaint up in the air,", "start": 365.86, "duration": 2.33}, {"text": "too, just to show you\nhow physical it is.", "start": 368.19, "duration": 3.81}, {"text": "There's something called\nSchlieren photography,", "start": 372.0, "duration": 3.03}, {"text": "which is totally cool, and which\nis a way to visualize those", "start": 375.03, "duration": 2.82}, {"text": "compressions of the air\nto show you what's--", "start": 377.85, "duration": 2.753}, {"text": "[VIDEO PLAYBACK]", "start": 380.603, "duration": 0.667}, {"text": "[INTERPOSING VOICES]", "start": 381.27, "duration": 0.833}, {"text": "- --use it to study\naerodynamic flow.", "start": 382.103, "duration": 1.807}, {"text": "And sound-- well, that's just\nanother change in air density,", "start": 383.91, "duration": 3.48}, {"text": "a traveling compression wave.", "start": 387.39, "duration": 1.86}, {"text": "So Schlieren visualization,\nalong with a high-speed camera,", "start": 389.25, "duration": 3.27}, {"text": "can be used to see it as well.", "start": 392.52, "duration": 3.01}, {"text": "Here's a book\nlanding on a table,", "start": 395.53, "duration": 2.9}, {"text": "the end of a towel\nbeing snapped,", "start": 398.43, "duration": 3.21}, {"text": "a firecracker, an AK-47,\nand of course, a clap.", "start": 401.64, "duration": 7.62}, {"text": "[END PLAYBACK]", "start": 412.26, "duration": 0.9}, {"text": "NANCY KANWISHER: OK, so\njust compressions of air", "start": 413.16, "duration": 2.28}, {"text": "traveling from the source to\nyour ears-- that's all it is.", "start": 415.44, "duration": 4.56}, {"text": "So natural sounds happen at\nlots of different frequencies.", "start": 420.0, "duration": 3.03}, {"text": "And one of the ways\nwe describe sounds", "start": 423.03, "duration": 2.73}, {"text": "is by looking at\nthose frequencies.", "start": 425.76, "duration": 2.53}, {"text": "So there's an awesome website\nthat is here on your slides.", "start": 428.29, "duration": 4.53}, {"text": "You can play with it offline.", "start": 432.82, "duration": 1.34}, {"text": "But meanwhile, we're going to\nplay with it a little bit right", "start": 434.16, "duration": 2.88}, {"text": "now because it is so cool.", "start": 437.04, "duration": 5.243}, {"text": "So what we're going\nto do is we're", "start": 442.283, "duration": 1.417}, {"text": "going to look at spectrograms\nof different sounds.", "start": 443.7, "duration": 2.94}, {"text": "Let's start with a\nperson whistling.", "start": 446.64, "duration": 2.07}, {"text": "[WHISTLING]", "start": 448.71, "duration": 3.63}, {"text": "OK, so frequency\nis on this axis,", "start": 452.34, "duration": 2.67}, {"text": "higher frequencies up here,\nlower frequencies there.", "start": 455.01, "duration": 3.06}, {"text": "And it's going by in time.", "start": 458.07, "duration": 2.206}, {"text": "[WHISTLING]", "start": 460.276, "duration": 4.804}, {"text": "So whistling is unusual\nin that it's pretty much", "start": 465.08, "duration": 3.45}, {"text": "a single frequency at a time.", "start": 468.53, "duration": 2.1}, {"text": "Many natural sounds\nare not like that.", "start": 470.63, "duration": 2.0}, {"text": "So you see not single,\nbut a small, narrow band", "start": 472.63, "duration": 2.74}, {"text": "of frequencies at a time.", "start": 475.37, "duration": 1.17}, {"text": "OK, that's enough.", "start": 476.54, "duration": 2.16}, {"text": "[WHISTLING]", "start": 478.7, "duration": 1.56}, {"text": "Stop.", "start": 480.26, "duration": 1.05}, {"text": "All right.", "start": 481.31, "duration": 0.6}, {"text": "OK.", "start": 481.91, "duration": 0.849}, {"text": "[TROMBONE PLAYING]", "start": 482.759, "duration": 8.071}, {"text": "OK, so you see how\nwith the trombone,", "start": 490.83, "duration": 2.82}, {"text": "there were many different\nbands of frequencies.", "start": 493.65, "duration": 3.12}, {"text": "In contrast-- this is\nme talking, by the way.", "start": 496.77, "duration": 2.17}, {"text": "We'll talk about\nthat in a second.", "start": 498.94, "duration": 2.01}, {"text": "But with the whistling, you saw\njust a single band at a time.", "start": 500.95, "duration": 3.47}, {"text": "With the trombone, it has\nall of these harmonics,", "start": 504.42, "duration": 2.73}, {"text": "these parallel lines of\nmultiples of frequencies.", "start": 507.15, "duration": 5.7}, {"text": "Those are called\n\"pitched sounds.\"", "start": 512.85, "duration": 1.809}, {"text": "Sounds that have a pitch where\nyou could sing back the tune", "start": 514.659, "duration": 2.601}, {"text": "have those bands of\nfrequencies like that.", "start": 517.26, "duration": 3.345}, {"text": "And so that's what you\nsee with the trombone.", "start": 520.605, "duration": 1.875}, {"text": "You see a little bit of this\nwith natural speech here.", "start": 522.48, "duration": 2.79}, {"text": "You can see sets of\nbands, but mostly, you", "start": 525.27, "duration": 2.76}, {"text": "see vertical stripes.", "start": 528.03, "duration": 1.5}, {"text": "That's because I'm talking fast\nand mostly what's coming out", "start": 529.53, "duration": 3.06}, {"text": "is consonants.", "start": 532.59, "duration": 1.05}, {"text": "If I slowed down and\nstretched out the vowels,", "start": 533.64, "duration": 7.62}, {"text": "you would see more\nof those harmonics.", "start": 541.26, "duration": 7.277}, {"text": "Fun and games.", "start": 548.537, "duration": 0.583}, {"text": "OK, so that's what\nsound looks like.", "start": 551.64, "duration": 1.79}, {"text": "So everybody has to\nhave a sense of this", "start": 553.43, "duration": 1.667}, {"text": "is showing you the energy\nat each frequency over time", "start": 555.097, "duration": 2.693}, {"text": "in response to natural speech.", "start": 557.79, "duration": 1.8}, {"text": "We'll play with this a little\nbit more later in the lecture.", "start": 559.59, "duration": 3.54}, {"text": "So we did all that.", "start": 571.36, "duration": 1.47}, {"text": "We'll do some of that\nother stuff later.", "start": 572.83, "duration": 1.74}, {"text": "So now that we have some\nsense of what sound is", "start": 574.57, "duration": 2.67}, {"text": "and what that input\nis, how are we", "start": 577.24, "duration": 3.39}, {"text": "going to think about how to\nextract information from it?", "start": 580.63, "duration": 3.21}, {"text": "What we want to do is\nthink about how is it?", "start": 583.84, "duration": 2.13}, {"text": "Why is it challenging to\nget to that from this?", "start": 585.97, "duration": 2.94}, {"text": "There are several reasons\nthat's challenging.", "start": 593.14, "duration": 2.22}, {"text": "First is invariance\nproblems, much like we've", "start": 595.36, "duration": 2.76}, {"text": "discussed in the domain of\nvision and other domains", "start": 598.12, "duration": 2.79}, {"text": "already in this class.", "start": 600.91, "duration": 3.07}, {"text": "And so the way to think about\nthat here is that a given sound", "start": 603.98, "duration": 2.81}, {"text": "source sounds really different\nin different situations.", "start": 606.79, "duration": 4.14}, {"text": "So if we have different\npeople saying the same word,", "start": 610.93, "duration": 2.97}, {"text": "that will look very different\non those spectrograms.", "start": 613.9, "duration": 2.76}, {"text": "The stimulus is\nactually different,", "start": 616.66, "duration": 1.59}, {"text": "even though we want to just\nknow what word is being said.", "start": 618.25, "duration": 3.48}, {"text": "And conversely, if we\nhave the same person", "start": 621.73, "duration": 3.0}, {"text": "saying two different words,\nthat will look really different.", "start": 624.73, "duration": 2.89}, {"text": "And even if we want to\nknow just who's speaking,", "start": 627.62, "duration": 2.37}, {"text": "we have to deal with the\ninvariance of generalizing", "start": 629.99, "duration": 2.75}, {"text": "across those very different\nways, very different", "start": 632.74, "duration": 2.94}, {"text": "sounds that they produce when\nthey say different things.", "start": 635.68, "duration": 2.73}, {"text": "So those are kind of\nflips of each other.", "start": 638.41, "duration": 2.16}, {"text": "To recognize voices, we\nwant invariance of the voice", "start": 640.57, "duration": 3.27}, {"text": "with respect to the words.", "start": 643.84, "duration": 1.29}, {"text": "To recognize words, we want\ninvariance for the words", "start": 645.13, "duration": 2.7}, {"text": "independent of the voice.", "start": 647.83, "duration": 1.86}, {"text": "And those are all\ntied up together.", "start": 649.69, "duration": 1.695}, {"text": "So we need to appreciate the\nsameness of those stimuli", "start": 654.04, "duration": 2.49}, {"text": "across those changes.", "start": 656.53, "duration": 3.09}, {"text": "Here's another reason that\nhearing is challenging--", "start": 659.62, "duration": 2.157}, {"text": "I mentioned this briefly--", "start": 661.777, "duration": 1.083}, {"text": "in normal situations-- it's\npretty quiet in the room.", "start": 665.89, "duration": 2.497}, {"text": "There's some background\nnoise, but not", "start": 668.387, "duration": 1.583}, {"text": "a whole lot of other\nnoise, so it's mostly", "start": 669.97, "duration": 1.75}, {"text": "just me making\nthe noise in here.", "start": 671.72, "duration": 2.18}, {"text": "But in many situations, there\nare multiple sound sources.", "start": 673.9, "duration": 3.7}, {"text": "For example, listen to this.", "start": 677.6, "duration": 1.49}, {"text": "[AUDIO PLAYBACK]", "start": 679.09, "duration": 0.96}, {"text": "[INTERPOSING VOICES]", "start": 680.05, "duration": 1.23}, {"text": "- All right, Debbie\nWhittaker, Sterling James,", "start": 681.28, "duration": 2.04}, {"text": "wrapping things up.", "start": 683.32, "duration": 0.84}, {"text": "[END PLAYBACK]", "start": 684.16, "duration": 0.69}, {"text": "NANCY KANWISHER: OK, little\nsegment of radio, there's", "start": 684.85, "duration": 2.208}, {"text": "music, and a person\nspeaking both at once.", "start": 687.058, "duration": 1.902}, {"text": "And you had no\nproblem hearing what", "start": 688.96, "duration": 2.01}, {"text": "the person was\nsaying and knowing", "start": 690.97, "duration": 1.71}, {"text": "something about the gender\nand age of that person.", "start": 692.68, "duration": 3.15}, {"text": "You recognize the voice,\nthe content of the speech,", "start": 695.83, "duration": 2.25}, {"text": "even though the music\nis right on top of it.", "start": 698.08, "duration": 3.33}, {"text": "So the music might be like\nthis and the speech like that.", "start": 701.41, "duration": 3.63}, {"text": "And what you hear is\nthis, with those things", "start": 705.04, "duration": 2.73}, {"text": "right on top of each other.", "start": 707.77, "duration": 2.82}, {"text": "So you need to go backwards\nto hear these things,", "start": 710.59, "duration": 2.61}, {"text": "even though that's all you get.", "start": 713.2, "duration": 2.762}, {"text": "Everybody see how\nthat's a big challenge?", "start": 715.962, "duration": 1.708}, {"text": "If you had to write the code\nto take this and recover", "start": 717.67, "duration": 2.76}, {"text": "that, best of luck to you.", "start": 720.43, "duration": 2.43}, {"text": "Yeah, question?", "start": 722.86, "duration": 1.77}, {"text": "STUDENT: How does intensity or\nvolume come into this picture", "start": 724.63, "duration": 2.85}, {"text": "again?", "start": 727.48, "duration": 1.443}, {"text": "NANCY KANWISHER: It's\nnot really well depicted", "start": 728.923, "duration": 1.917}, {"text": "on these diagrams.", "start": 730.84, "duration": 1.05}, {"text": "This is just showing\nyou the entire source.", "start": 731.89, "duration": 2.58}, {"text": "So the intensity I showed before\nessentially takes this and does", "start": 734.47, "duration": 3.48}, {"text": "a Fourier analysis of it so that\nit gives you the energy at each", "start": 737.95, "duration": 2.91}, {"text": "of those frequencies.", "start": 740.86, "duration": 1.51}, {"text": "So you could just do a\nFourier analysis on this", "start": 742.37, "duration": 2.0}, {"text": "and you get a spectrogram.", "start": 744.37, "duration": 1.4}, {"text": "So the listener's\nusually interested", "start": 749.46, "duration": 2.07}, {"text": "in individual sources\neven though they're", "start": 751.53, "duration": 2.67}, {"text": "superimposed on other sources.", "start": 754.2, "duration": 2.02}, {"text": "And that's a real problem.", "start": 756.22, "duration": 1.5}, {"text": "So this is the input.", "start": 757.72, "duration": 1.25}, {"text": "They get added together, and the\nbrain has to pull them apart.", "start": 758.97, "duration": 4.92}, {"text": "So this is a classic,\nill-posed problem.", "start": 763.89, "duration": 2.88}, {"text": "That means just given\nthis, we have no way", "start": 766.77, "duration": 5.37}, {"text": "to go backwards to that\nif that's all we have,", "start": 772.14, "duration": 3.12}, {"text": "because there's multiple\npossible solutions.", "start": 775.26, "duration": 2.91}, {"text": "It's like saying,\n\"x plus y equals 9,", "start": 778.17, "duration": 2.91}, {"text": "now solve for x and y.\"", "start": 781.08, "duration": 1.95}, {"text": "And whenever we're\nin that situation", "start": 783.03, "duration": 2.52}, {"text": "of an ill-posed problem with\nmultiple possible solutions,", "start": 785.55, "duration": 3.51}, {"text": "only one of which is right in\nany situation in the world,", "start": 789.06, "duration": 3.75}, {"text": "the usual answer is\nthat we need to bring", "start": 792.81, "duration": 3.09}, {"text": "in some other assumptions or\nworld knowledge or something,", "start": 795.9, "duration": 2.82}, {"text": "to constrain that problem and\nnarrow that large, usually", "start": 798.72, "duration": 3.24}, {"text": "infinite, space of\npossible answers", "start": 801.96, "duration": 1.89}, {"text": "down to the one correct one.", "start": 803.85, "duration": 2.97}, {"text": "So this is a classic\nproblem that people", "start": 806.82, "duration": 1.95}, {"text": "have talked about in\naudition for many decades.", "start": 808.77, "duration": 2.58}, {"text": "Josh McDermott in this\ndepartment does a lot of work", "start": 811.35, "duration": 2.49}, {"text": "on it.", "start": 813.84, "duration": 1.38}, {"text": "And you can solve it\nin part by knowledge", "start": 815.22, "duration": 3.24}, {"text": "of natural sounds, which I\nwon't talk about in detail here.", "start": 818.46, "duration": 5.31}, {"text": "One more challenge for\nsolving problems in audition", "start": 823.77, "duration": 4.41}, {"text": "comes from the fact\nthat real world", "start": 828.18, "duration": 1.68}, {"text": "sounds, including the sound\nof my voice right now,", "start": 829.86, "duration": 3.45}, {"text": "have reverb.", "start": 833.31, "duration": 1.02}, {"text": "So \"reverb\" means--\nthis is an aerial view.", "start": 834.33, "duration": 2.16}, {"text": "That's a person, kind of hard\nto see in an aerial view.", "start": 836.49, "duration": 3.04}, {"text": "And that's a sound source.", "start": 839.53, "duration": 1.49}, {"text": "And some of the sound comes\nstraight from the sound source", "start": 841.02, "duration": 3.24}, {"text": "to the person's ears.", "start": 844.26, "duration": 1.77}, {"text": "But a lot of the sound goes\nand ricochets off the walls,", "start": 846.03, "duration": 3.87}, {"text": "god knows how many times,\nbefore it hits the ears.", "start": 849.9, "duration": 2.73}, {"text": "And all of those\ndifferent paths of sound", "start": 852.63, "duration": 2.73}, {"text": "are all kind of\nsuperimposed at the ears.", "start": 855.36, "duration": 2.37}, {"text": "And they arrive at\ndifferent times,", "start": 857.73, "duration": 1.86}, {"text": "making a hell of a mess\nof the input sound.", "start": 859.59, "duration": 2.7}, {"text": "So instead of that nice,\nclean, straightforward input,", "start": 862.29, "duration": 3.3}, {"text": "you have the input plus\na slightly delayed input,", "start": 865.59, "duration": 2.58}, {"text": "a more delayed input, another\ndelayed input, all superimposed", "start": 868.17, "duration": 2.97}, {"text": "on top of each other.", "start": 871.14, "duration": 1.08}, {"text": "That's reverb.", "start": 872.22, "duration": 1.59}, {"text": "Is that clear, what\nthe problem is?", "start": 873.81, "duration": 1.74}, {"text": "So now we have this\nreally messed-up signal", "start": 875.55, "duration": 2.85}, {"text": "that we're trying to go\nbackwards and understand", "start": 878.4, "duration": 2.46}, {"text": "what the input is.", "start": 880.86, "duration": 1.75}, {"text": "So I'll give you an example.", "start": 882.61, "duration": 1.47}, {"text": "This is a recording of\nwhat's known as \"dry speech.\"", "start": 884.08, "duration": 2.69}, {"text": "That means speech\nwith no reverb.", "start": 886.77, "duration": 1.68}, {"text": "Sorry, question?", "start": 888.45, "duration": 0.948}, {"text": "STUDENT: I'm just having a\nlittle trouble understanding", "start": 889.398, "duration": 2.292}, {"text": "why reverb poses a problem.", "start": 891.69, "duration": 2.52}, {"text": "The stimulus isn't changing,\nit's just delayed over time.", "start": 894.21, "duration": 3.66}, {"text": "NANCY KANWISHER: Yeah, OK.", "start": 897.87, "duration": 1.59}, {"text": "Let's do a vision example.", "start": 899.46, "duration": 1.958}, {"text": "This is a little crazy,\nbut let me just try this.", "start": 901.418, "duration": 2.042}, {"text": "Suppose we had a\nphotograph of my face", "start": 903.46, "duration": 2.382}, {"text": "and you have to recognize it.", "start": 905.842, "duration": 1.208}, {"text": "OK, fine.", "start": 907.05, "duration": 0.51}, {"text": "Various visual\nalgorithms can do that.", "start": 907.56, "duration": 2.02}, {"text": "But now suppose we took that\nphotograph and we moved it", "start": 909.58, "duration": 2.78}, {"text": "over 10%, and we superimposed\nit and added them together,", "start": 912.36, "duration": 3.847}, {"text": "and then we moved it over\nagain and added them together,", "start": 916.207, "duration": 2.333}, {"text": "and moved it over again\nand add them together.", "start": 918.54, "duration": 1.917}, {"text": "Pretty soon you\nhave a blurry mess.", "start": 920.457, "duration": 2.253}, {"text": "And those things are all\non top of each other,", "start": 922.71, "duration": 2.19}, {"text": "just as two people talking at\nonce are on top of each other.", "start": 924.9, "duration": 3.472}, {"text": "And so you have a real\nproblem going backwards.", "start": 928.372, "duration": 1.958}, {"text": "Does that make sense?", "start": 930.33, "duration": 1.14}, {"text": "OK.", "start": 931.47, "duration": 0.93}, {"text": "OK, so here's dry\nspeech with no reverb.", "start": 932.4, "duration": 2.483}, {"text": "[AUDIO PLAYBACK]", "start": 934.883, "duration": 0.667}, {"text": "- They ate the lemon pie.", "start": 935.55, "duration": 1.62}, {"text": "Father forgot the bread.", "start": 937.17, "duration": 1.62}, {"text": "[END PLAYBACK]", "start": 938.79, "duration": 0.6}, {"text": "NANCY KANWISHER: OK,\nhere's the same speech", "start": 939.39, "duration": 1.792}, {"text": "but with lots of reverb.", "start": 941.182, "duration": 1.038}, {"text": "- They ate the lemon pie.", "start": 942.22, "duration": 1.61}, {"text": "Father forgot the bread.", "start": 943.83, "duration": 1.354}, {"text": "[END PLAYBACK]", "start": 945.184, "duration": 0.966}, {"text": "NANCY KANWISHER: OK,\nnow you can still", "start": 946.15, "duration": 1.583}, {"text": "hear it because your\nauditory system knows", "start": 947.733, "duration": 2.107}, {"text": "how to solve this problem.", "start": 949.84, "duration": 2.28}, {"text": "But look what happens\nto the spectrogram.", "start": 952.12, "duration": 2.04}, {"text": "Here-- this is time this\nway, frequency this way,", "start": 954.16, "duration": 2.88}, {"text": "and the dark bits are where the\nenergy is, where the power is.", "start": 957.04, "duration": 2.7}, {"text": "In the dry speech, you see all\nthese nice, vertical things,", "start": 959.74, "duration": 3.57}, {"text": "and here you see a blurry mess.", "start": 963.31, "duration": 3.6}, {"text": "Nonetheless, you\ncan hear it fine.", "start": 966.91, "duration": 2.25}, {"text": "And further, what else could\nyou tell from the reverb?", "start": 969.16, "duration": 3.12}, {"text": "STUDENT: The size of the room.", "start": 976.89, "duration": 1.25}, {"text": "NANCY KANWISHER: Yeah, it's in\na cathedral or something, right?", "start": 978.14, "duration": 3.21}, {"text": "So it's not just that\nit causes a problem.", "start": 981.35, "duration": 4.02}, {"text": "Reverb also tells us\nsomething about the location", "start": 985.37, "duration": 2.55}, {"text": "we're in, if we know\nhow to extract it,", "start": 987.92, "duration": 2.26}, {"text": "which you guys' visual--", "start": 990.18, "duration": 2.61}, {"text": "auditory systems do.", "start": 992.79, "duration": 1.52}, {"text": "You can see I'm a\nvision scientist.", "start": 994.31, "duration": 2.76}, {"text": "So how to study this?", "start": 997.07, "duration": 2.19}, {"text": "There's a very beautiful\npaper that Josh McDermott", "start": 999.26, "duration": 2.13}, {"text": "published a few years ago.", "start": 1001.39, "duration": 1.27}, {"text": "And I'm going to try to give\nyou the gist of the paper", "start": 1002.66, "duration": 1.64}, {"text": "without all the\ntechnical details,", "start": 1004.3, "duration": 1.47}, {"text": "because I think\nit's just brilliant.", "start": 1005.77, "duration": 2.04}, {"text": "So they wanted to characterize\nwhat exactly is reverb.", "start": 1007.81, "duration": 4.71}, {"text": "And reverb is going to\nvary for different sounds.", "start": 1012.52, "duration": 2.28}, {"text": "You heard the reverb in\nthat cathedral-like space.", "start": 1014.8, "duration": 2.395}, {"text": "That's very different from\nthe reverb in this room, which", "start": 1017.195, "duration": 2.375}, {"text": "also happens.", "start": 1019.57, "duration": 0.66}, {"text": "It's harder to hear\nbecause it's less obvious.", "start": 1020.23, "duration": 2.07}, {"text": "But you can tell a\nlot about the space", "start": 1022.3, "duration": 1.71}, {"text": "you're in because the reverb\nproperties are different.", "start": 1024.01, "duration": 2.52}, {"text": "The distance to the\nwalls are different.", "start": 1026.53, "duration": 1.74}, {"text": "The reflective\nproperties are different.", "start": 1028.27, "duration": 2.92}, {"text": "And so there's\ninformation there.", "start": 1031.19, "duration": 1.659}, {"text": "So you can characterize the\nnature of the reverb in any one", "start": 1032.849, "duration": 3.881}, {"text": "location by making an\ninstantaneous, brief click", "start": 1036.73, "duration": 4.26}, {"text": "sound in that environment\nand recording what", "start": 1040.99, "duration": 3.03}, {"text": "happens after that.", "start": 1044.02, "duration": 1.059}, {"text": "And then you can collect all\nthe reverberant reflections", "start": 1045.079, "duration": 4.011}, {"text": "of that sound off the walls.", "start": 1049.09, "duration": 2.07}, {"text": "So what they did\nis they went around", "start": 1051.16, "duration": 1.5}, {"text": "to lots of natural locations and\nthey played a click like this.", "start": 1052.66, "duration": 3.06}, {"text": "[CLICK]", "start": 1055.72, "duration": 1.06}, {"text": "That's it, just a click.", "start": 1056.78, "duration": 1.37}, {"text": "And then they recorded.", "start": 1058.15, "duration": 1.98}, {"text": "So this is the initial\nclick, but this", "start": 1060.13, "duration": 2.25}, {"text": "is what you record in a single\nlocation, all this stuff.", "start": 1062.38, "duration": 4.03}, {"text": "And those are all the\nreverberant reflections", "start": 1066.41, "duration": 2.96}, {"text": "of that sound off the\nwalls-- make sense?", "start": 1069.37, "duration": 2.1}, {"text": "For one location.", "start": 1071.47, "duration": 3.31}, {"text": "So then they did that in a\nwhole bunch of locations.", "start": 1074.78, "duration": 4.07}, {"text": "And the idea is that\nhere is a description", "start": 1078.85, "duration": 3.33}, {"text": "of the basic problems, just\nthe same thing I said before,", "start": 1082.18, "duration": 3.46}, {"text": "but slightly more detailed.", "start": 1085.64, "duration": 2.54}, {"text": "So a sound source would\nbe something like this.", "start": 1088.18, "duration": 3.735}, {"text": "This looks like a\nperson speaking,", "start": 1091.915, "duration": 2.595}, {"text": "with those nice, harmonic,\nparallel bands, like you", "start": 1094.51, "duration": 3.0}, {"text": "saw when I was speaking.", "start": 1097.51, "duration": 1.348}, {"text": "Maybe it's a trombone.", "start": 1098.858, "duration": 0.917}, {"text": "So that's time.", "start": 1102.52, "duration": 0.75}, {"text": "That's the source.", "start": 1103.27, "duration": 1.06}, {"text": "That's what you want to know.", "start": 1104.33, "duration": 2.15}, {"text": "This is now the impulse\nresponse function", "start": 1106.48, "duration": 2.37}, {"text": "for the location where\nthat sound is being played,", "start": 1108.85, "duration": 2.91}, {"text": "determined by doing that\nclick and recording.", "start": 1111.76, "duration": 2.55}, {"text": "I showed you just\nyou do a Fourier", "start": 1114.31, "duration": 2.76}, {"text": "analysis of that black\ncurve in the previous slide", "start": 1117.07, "duration": 3.48}, {"text": "and you get something like this.", "start": 1120.55, "duration": 1.53}, {"text": "And that shows you all\nthe echoes that happen", "start": 1122.08, "duration": 2.37}, {"text": "in that sound in that location.", "start": 1124.45, "duration": 1.32}, {"text": "And there are\ndifferent time delays,", "start": 1125.77, "duration": 1.5}, {"text": "and different intensities,\nand frequency dependence.", "start": 1127.27, "duration": 4.17}, {"text": "What comes to your ear is\nbasically this times that.", "start": 1131.44, "duration": 4.215}, {"text": "So you're given\nthis and you have", "start": 1138.45, "duration": 2.37}, {"text": "to go backwards\nand solve for that.", "start": 1140.82, "duration": 2.61}, {"text": "Everybody see the problem?", "start": 1143.43, "duration": 2.82}, {"text": "So what McDermott and\nTraer showed is that--", "start": 1146.25, "duration": 6.778}, {"text": "just to state the problem\na little more clearly--", "start": 1153.028, "duration": 2.042}, {"text": "you're interested in the\nsource and/or the environment.", "start": 1155.07, "duration": 3.043}, {"text": "You might want to\nknow what kind of room", "start": 1158.113, "duration": 1.667}, {"text": "am I, if somebody is dragging\nyou around blindfolded.", "start": 1159.78, "duration": 2.4}, {"text": "You might want to know if\nyou're outside, or inside,", "start": 1162.18, "duration": 2.167}, {"text": "or in a cathedral,\nor a closet, or what.", "start": 1164.347, "duration": 3.533}, {"text": "And now this should seem\nvery analogous to the problem", "start": 1167.88, "duration": 3.03}, {"text": "of color vision.", "start": 1170.91, "duration": 1.53}, {"text": "Remember the problem\nof color vision?", "start": 1172.44, "duration": 2.43}, {"text": "We want to know the color\nof this object right here.", "start": 1174.87, "duration": 4.11}, {"text": "So this little,\npurple patch here,", "start": 1178.98, "duration": 1.62}, {"text": "we want to know that, but all\nwe have is the light coming", "start": 1180.6, "duration": 3.48}, {"text": "to our eyes from that patch.", "start": 1184.08, "duration": 3.112}, {"text": "And the light coming to\nour eyes from the patch", "start": 1187.192, "duration": 1.958}, {"text": "is a function not just of\nthe property of the object,", "start": 1189.15, "duration": 3.12}, {"text": "but whatever light happens\nto be coming onto it", "start": 1192.27, "duration": 2.58}, {"text": "and then reflecting to our eyes.", "start": 1194.85, "duration": 3.33}, {"text": "And so in color\nvision, we have one set", "start": 1198.18, "duration": 1.65}, {"text": "of tricks to try to\nsolve that problem", "start": 1199.83, "duration": 1.89}, {"text": "and recover the actual\nproperties of the object,", "start": 1201.72, "duration": 2.64}, {"text": "even though it's totally\nconfounded in the input", "start": 1204.36, "duration": 2.07}, {"text": "with the properties\nof the incident light.", "start": 1206.43, "duration": 2.31}, {"text": "This is extremely analogous.", "start": 1208.74, "duration": 2.16}, {"text": "We're trying to solve for\nwhat is the sound source.", "start": 1210.9, "duration": 3.21}, {"text": "And we have to deal\nwith this problem that", "start": 1214.11, "duration": 2.1}, {"text": "is completely confounded with\nthe reverberation of the room", "start": 1216.21, "duration": 3.13}, {"text": "it's in.", "start": 1219.34, "duration": 0.5}, {"text": "Does everybody see that analogy?", "start": 1219.84, "duration": 1.5}, {"text": "They're both classic ill-posed\nproblems in perception.", "start": 1221.34, "duration": 5.45}, {"text": "So here's another way of\nputting it-- we're given that", "start": 1226.79, "duration": 2.88}, {"text": "and we want to solve\nfor at least one", "start": 1229.67, "duration": 1.68}, {"text": "of these, ideally both of those.", "start": 1231.35, "duration": 2.76}, {"text": "And you can't do\nthat with just this.", "start": 1234.11, "duration": 2.32}, {"text": "So we need to make\nassumptions about the room.", "start": 1236.43, "duration": 1.97}, {"text": "And what Traer and\nMcDermott showed", "start": 1238.4, "duration": 2.28}, {"text": "is that first, they measured\nthose impulse response", "start": 1240.68, "duration": 2.61}, {"text": "functions in\nnatural environments", "start": 1243.29, "duration": 1.71}, {"text": "to characterize reverb in\ndifferent environments.", "start": 1245.0, "duration": 3.54}, {"text": "And they found that there's some\nsystematic properties of reverb", "start": 1248.54, "duration": 3.72}, {"text": "having to do with\nthe decay function", "start": 1252.26, "duration": 2.28}, {"text": "as a function of frequency.", "start": 1254.54, "duration": 1.5}, {"text": "And those systematic\nproperties are preserved", "start": 1256.04, "duration": 3.06}, {"text": "across different environments.", "start": 1259.1, "duration": 3.16}, {"text": "And then they showed that\nyour auditory system knows", "start": 1262.26, "duration": 5.18}, {"text": "about the way reverb\nworks, in the sense", "start": 1267.44, "duration": 2.85}, {"text": "that if you make up a different,\nnon-physical reverb property", "start": 1270.29, "duration": 4.75}, {"text": "and you play it to people,\nit sounds weird, number one.", "start": 1275.04, "duration": 3.41}, {"text": "And two, they can't\nrecover the sound source.", "start": 1278.45, "duration": 3.57}, {"text": "And what that means is, built\ninto your auditory system", "start": 1282.02, "duration": 3.39}, {"text": "is knowledge of the\nphysics of sound,", "start": 1285.41, "duration": 2.25}, {"text": "and in particular about the\nparticulars of the decay", "start": 1287.66, "duration": 3.39}, {"text": "function of reverb,\nsuch that you", "start": 1291.05, "duration": 2.37}, {"text": "can use that knowledge\nof how reverb", "start": 1293.42, "duration": 1.92}, {"text": "works in general to\nundo this problem,", "start": 1295.34, "duration": 2.76}, {"text": "and constrain this problem,\nand solve for the sound source.", "start": 1298.1, "duration": 3.033}, {"text": "I didn't give you\nall the details.", "start": 1301.133, "duration": 1.417}, {"text": "But I want you to get the gist.", "start": 1302.55, "duration": 1.34}, {"text": "Do you get the kind of idea?", "start": 1303.89, "duration": 3.22}, {"text": "OK.", "start": 1307.11, "duration": 0.5}, {"text": "But as I said, that's\nonly true for reverb", "start": 1310.64, "duration": 3.0}, {"text": "that has the reverb properties\nof real-world sound.", "start": 1313.64, "duration": 3.6}, {"text": "If you make up fake\nreverb, it doesn't work.", "start": 1317.24, "duration": 2.52}, {"text": "And people can't\nsolve this problem.", "start": 1319.76, "duration": 1.83}, {"text": "That tells you they're\nusing their knowledge.", "start": 1321.59, "duration": 2.1}, {"text": "Doesn't tell us whether that\nknowledge is built in innately,", "start": 1323.69, "duration": 2.82}, {"text": "or whether they\nlearned it, or what.", "start": 1326.51, "duration": 1.74}, {"text": "All right, good.", "start": 1333.11, "duration": 0.99}, {"text": "So in other words, we\nsolve the ill-posed problem", "start": 1334.1, "duration": 3.12}, {"text": "of recovering the sound\nsource despite reverb", "start": 1337.22, "duration": 2.85}, {"text": "by building a knowledge of\nthe physics of the world", "start": 1340.07, "duration": 3.0}, {"text": "into our auditory\nsystem and using", "start": 1343.07, "duration": 1.74}, {"text": "it to constrain the problem.", "start": 1344.81, "duration": 3.6}, {"text": "So we just said, why is this\ncomputationally challenging?", "start": 1348.41, "duration": 3.75}, {"text": "Invariance problems,\nappreciating the sameness", "start": 1352.16, "duration": 2.46}, {"text": "of a voice across\ndifferent words,", "start": 1354.62, "duration": 2.01}, {"text": "appreciating the sameness of a\nword across different voices.", "start": 1356.63, "duration": 5.43}, {"text": "Separating multiple\nsound sources that come", "start": 1362.06, "duration": 2.25}, {"text": "in simultaneously and are\njust massively superimposed", "start": 1364.31, "duration": 2.79}, {"text": "on the input-- the cocktail\nparty problem, also ill-posed--", "start": 1367.1, "duration": 4.74}, {"text": "and the reverb problem.", "start": 1371.84, "duration": 1.83}, {"text": "So everybody see how these are\nthree really big challenges", "start": 1373.67, "duration": 2.91}, {"text": "for audition?", "start": 1376.58, "duration": 0.63}, {"text": "Yeah.", "start": 1377.21, "duration": 0.5}, {"text": "STUDENT: So was brain imaging as\nwell a part of the [INAUDIBLE]??", "start": 1377.71, "duration": 4.18}, {"text": "NANCY KANWISHER: Nope.", "start": 1381.89, "duration": 1.58}, {"text": "One could do that\nand ask questions", "start": 1383.47, "duration": 1.595}, {"text": "about where that's\nsolved in the brain.", "start": 1385.065, "duration": 1.625}, {"text": "But the beauty of\nthat study is that", "start": 1386.69, "duration": 1.89}, {"text": "in a way, who cares\nwhere it's solved?", "start": 1388.58, "duration": 1.68}, {"text": "I mean, it's kind\nof interesting,", "start": 1390.26, "duration": 1.375}, {"text": "but it's such a beautiful story\nalready just from actually,", "start": 1391.635, "duration": 3.335}, {"text": "a big part of their study\nwas measuring reverb.", "start": 1394.97, "duration": 2.46}, {"text": "Nobody had done it before.", "start": 1397.43, "duration": 1.75}, {"text": "They sent people\nout with speakers,", "start": 1399.18, "duration": 1.94}, {"text": "and recording devices,\nand little random timers", "start": 1401.12, "duration": 3.63}, {"text": "on their iPhones.", "start": 1404.75, "duration": 1.17}, {"text": "And at random times--", "start": 1405.92, "duration": 1.14}, {"text": "how did this go--\noh, yeah, they had", "start": 1407.06, "duration": 1.5}, {"text": "people had to mark the location\nthey were in using their iPhone", "start": 1408.56, "duration": 3.36}, {"text": "GPS and then that's right--\nthey didn't send people out", "start": 1411.92, "duration": 2.49}, {"text": "with recording devices.", "start": 1414.41, "duration": 0.96}, {"text": "It's too hard.", "start": 1415.37, "duration": 0.7}, {"text": "And so then they sampled\nwhat kind of places", "start": 1416.07, "duration": 2.09}, {"text": "do people hang out in.", "start": 1418.16, "duration": 1.32}, {"text": "And then they went back\nwith their impulse sound", "start": 1419.48, "duration": 3.69}, {"text": "source and the recording\ndevice, and they", "start": 1423.17, "duration": 1.86}, {"text": "measured that impulse\nresponse function", "start": 1425.03, "duration": 1.92}, {"text": "in lots and lots of\ndifferent natural sounds", "start": 1426.95, "duration": 2.1}, {"text": "in order to characterize\nwhat is the nature of reverb", "start": 1429.05, "duration": 2.85}, {"text": "in the world.", "start": 1431.9, "duration": 0.61}, {"text": "Nobody had done that before.", "start": 1432.51, "duration": 1.34}, {"text": "So that's why I tell you\nthis, is that to me, it's", "start": 1433.85, "duration": 1.71}, {"text": "just one of the most\nbeautiful examples", "start": 1435.56, "duration": 1.625}, {"text": "of computational theory--", "start": 1437.185, "duration": 1.315}, {"text": "no measurement in the brain.", "start": 1438.5, "duration": 2.1}, {"text": "A big part of the study\nwas just characterizing", "start": 1440.6, "duration": 2.07}, {"text": "the physics of\nsound, and then some", "start": 1442.67, "duration": 2.67}, {"text": "psychophysics to say\nactually, do people", "start": 1445.34, "duration": 1.68}, {"text": "use that knowledge of how\nreverb works in the world?", "start": 1447.02, "duration": 2.64}, {"text": "And yes, they do.", "start": 1449.66, "duration": 0.87}, {"text": "So I've been talking\nabout hearing in general,", "start": 1455.58, "duration": 2.23}, {"text": "but let's talk about one of\nthe most interesting examples", "start": 1457.81, "duration": 3.17}, {"text": "of hearing, the one you're doing\nright now-- speech perception.", "start": 1460.98, "duration": 3.09}, {"text": "So what do speech\nsounds look like?", "start": 1466.59, "duration": 1.85}, {"text": "You saw a few of\nthem briefly before.", "start": 1468.44, "duration": 2.46}, {"text": "Here are a few spectra.", "start": 1470.9, "duration": 1.45}, {"text": "So just to remind you,\neach one of these things", "start": 1472.35, "duration": 2.39}, {"text": "has time going along the\nx-axis, frequency here.", "start": 1474.74, "duration": 3.93}, {"text": "And the color shows you\nthe intensity of energy", "start": 1478.67, "duration": 3.93}, {"text": "at that frequency band.", "start": 1482.6, "duration": 2.07}, {"text": "So this is a person saying,\n\"hot,\" and \"hat,\" and \"hit,\"", "start": 1484.67, "duration": 3.96}, {"text": "and \"head.\"", "start": 1488.63, "duration": 2.31}, {"text": "That's the same person saying\nthese four things, a person", "start": 1490.94, "duration": 3.6}, {"text": "with a high-pitched voice.", "start": 1494.54, "duration": 1.56}, {"text": "And here's a person with a\nslightly lower-pitched voice", "start": 1496.1, "duration": 2.82}, {"text": "saying the same things.", "start": 1498.92, "duration": 1.47}, {"text": "So what do we notice here?", "start": 1504.08, "duration": 2.19}, {"text": "Well, first of all, we see\nthat vowels have regularly", "start": 1506.27, "duration": 4.19}, {"text": "spaced harmonics.", "start": 1510.46, "duration": 1.3}, {"text": "That's the red stripes.", "start": 1511.76, "duration": 0.973}, {"text": "This is a vowel\nsound right there.", "start": 1512.733, "duration": 1.417}, {"text": "See those perfectly\nregularly spaced harmonics?", "start": 1514.15, "duration": 3.09}, {"text": "That makes a pitchy sound,\nso voices are pitchy.", "start": 1517.24, "duration": 3.54}, {"text": "You may not think that\nthere's a pitch to my voice", "start": 1520.78, "duration": 2.19}, {"text": "right now because I'm\ntalking, not singing,", "start": 1522.97, "duration": 1.89}, {"text": "but there is a pitch.", "start": 1524.86, "duration": 1.38}, {"text": "And you use that,\nactually, in the intonation", "start": 1526.24, "duration": 2.13}, {"text": "of speech, as you guys\nread about in the assigned", "start": 1528.37, "duration": 2.85}, {"text": "reading for yesterday.", "start": 1531.22, "duration": 2.46}, {"text": "So each of these things\nwith the stacked harmonics", "start": 1533.68, "duration": 2.85}, {"text": "is a vowel sound.", "start": 1536.53, "duration": 1.89}, {"text": "It's got a pitch and it\nlasts over a chunk of time.", "start": 1538.42, "duration": 4.02}, {"text": "And the consonants are\nthese kind of muckier things", "start": 1542.44, "duration": 3.21}, {"text": "that happen before and after.", "start": 1545.65, "duration": 1.59}, {"text": "And consonants don't have pitch.", "start": 1547.24, "duration": 2.07}, {"text": "They don't have harmonics.", "start": 1549.31, "duration": 1.23}, {"text": "They have kind of muck.", "start": 1550.54, "duration": 1.2}, {"text": "So there are certain\nband-- people", "start": 1555.61, "duration": 2.07}, {"text": "who study speech spend a lot\nof time staring at these things", "start": 1557.68, "duration": 2.52}, {"text": "and characterizing them.", "start": 1560.2, "duration": 1.47}, {"text": "And they like to talk about\nbands of frequency, of power.", "start": 1561.67, "duration": 5.49}, {"text": "And so this band\ndown here that's", "start": 1567.16, "duration": 2.79}, {"text": "present in all of\nthese speech sounds", "start": 1569.95, "duration": 3.87}, {"text": "here is called a \"formant.\"", "start": 1573.82, "duration": 1.92}, {"text": "It's just a chunk of\nthe frequency spectrum", "start": 1575.74, "duration": 2.787}, {"text": "that you hear with speech.", "start": 1578.527, "duration": 1.083}, {"text": "So that's a formant.", "start": 1583.03, "duration": 2.52}, {"text": "And some of those\nfrequency bands or formants", "start": 1585.55, "duration": 3.84}, {"text": "are particularly diagnostic\nfor different vowels.", "start": 1589.39, "duration": 4.29}, {"text": "So if you look in\nthis range here,", "start": 1593.68, "duration": 2.1}, {"text": "only in that mid-range\nhere, only for \"hat\"", "start": 1595.78, "duration": 3.36}, {"text": "and a little bit\nfor \"F\" sound do", "start": 1599.14, "duration": 2.07}, {"text": "you get an energy in\nthat frequency band,", "start": 1601.21, "duration": 3.06}, {"text": "not for \"hot\" or \"hit.\"", "start": 1604.27, "duration": 3.43}, {"text": "And that's true both for\nthe high-pitched voice", "start": 1607.7, "duration": 2.12}, {"text": "and the low-pitched voice.", "start": 1609.82, "duration": 1.23}, {"text": "This frequency band here is\nreally diagnostic to which", "start": 1611.05, "duration": 2.968}, {"text": "of those vowels you're hearing.", "start": 1614.018, "duration": 1.292}, {"text": "So we're going to play\nwith that spectrogram", "start": 1619.79, "duration": 3.9}, {"text": "again a little bit\nmore, although I now", "start": 1623.69, "duration": 5.11}, {"text": "have learned avoidance.", "start": 1628.8, "duration": 1.14}, {"text": "So this is me speaking\nagain, as you saw before.", "start": 1633.35, "duration": 6.76}, {"text": "So I'm going to say\nan A, an E, an I--", "start": 1640.11, "duration": 9.19}, {"text": "look how different\nthat one is, O, and U.", "start": 1649.3, "duration": 5.16}, {"text": "And there's lots\nof other vowels.", "start": 1654.46, "duration": 1.38}, {"text": "Do you see how that\nenergy moves around", "start": 1655.84, "duration": 1.733}, {"text": "for the different vowels?", "start": 1657.573, "duration": 1.042}, {"text": "Now as I said before, if I\ndo a long vowel like this,", "start": 1661.33, "duration": 6.62}, {"text": "it makes a big, long\nbunch of harmonics.", "start": 1667.95, "duration": 4.0}, {"text": "But a lot of the time, they're\njust these vertical lines.", "start": 1671.95, "duration": 3.51}, {"text": "The vertical lines are\nconsonants, t, p, k, r.", "start": 1675.46, "duration": 5.43}, {"text": "If I don't say a vowel, you\njust see a vertical line.", "start": 1680.89, "duration": 2.398}, {"text": "It's not quite a vertical line.", "start": 1683.288, "duration": 1.292}, {"text": "They are different from each\nother in ways you can tell.", "start": 1684.58, "duration": 3.87}, {"text": "So the consonants are\nthose bands of energy", "start": 1688.45, "duration": 3.99}, {"text": "that go vertically.", "start": 1692.44, "duration": 1.68}, {"text": "And the vowels are the big,\nlong harmonic structures", "start": 1694.12, "duration": 2.64}, {"text": "that stretch between them.", "start": 1696.76, "duration": 1.23}, {"text": "Now, I'm not sure you'll\nbe able to do this.", "start": 1700.58, "duration": 1.877}, {"text": "I'm going to need a volunteer\nin a second, and I'm", "start": 1702.457, "duration": 2.083}, {"text": "going to pick on\n[? Iadun, ?] because he's", "start": 1704.54, "duration": 1.74}, {"text": "most accessible right there.", "start": 1706.28, "duration": 1.167}, {"text": "So come on up here.", "start": 1707.447, "duration": 0.883}, {"text": "You know it won't be\nhorrible or embarrassing.", "start": 1708.33, "duration": 4.64}, {"text": "So you can stand\nhere for a second.", "start": 1712.97, "duration": 1.9}, {"text": "I'm going to say \"ba's\" and\n\"pa's\" and I'll tell you", "start": 1714.87, "duration": 3.77}, {"text": "in a moment what to say.", "start": 1718.64, "duration": 1.26}, {"text": "I'm not sure this\nis going to work.", "start": 1719.9, "duration": 1.458}, {"text": "I tried it before.", "start": 1721.358, "duration": 1.182}, {"text": "We're going to look at\ntwo different formants", "start": 1722.54, "duration": 2.01}, {"text": "when I say \"ba.\"", "start": 1724.55, "duration": 3.69}, {"text": "Actually, I'm going to do\nit rising-- ba, pa, ba, pa.", "start": 1728.24, "duration": 8.55}, {"text": "So there's two different\nformants, here and here,", "start": 1736.79, "duration": 2.13}, {"text": "with both of those.", "start": 1738.92, "duration": 0.9}, {"text": "I'm going to do it again.", "start": 1739.82, "duration": 1.14}, {"text": "And there's just a\ntiny, little difference", "start": 1740.96, "duration": 2.07}, {"text": "between a ba and a pa.", "start": 1743.03, "duration": 1.74}, {"text": "And it has to do with the\ninterval between the consonant,", "start": 1744.77, "duration": 3.6}, {"text": "which is the first\nvertical thing,", "start": 1748.37, "duration": 1.5}, {"text": "and the vowel, which is\nthe horizontal stuff.", "start": 1749.87, "duration": 1.89}, {"text": "So let's see if we\ncan see it again.", "start": 1751.76, "duration": 1.5}, {"text": "Here we go.", "start": 1753.26, "duration": 1.62}, {"text": "Ba, pa-- do you see how\nthe pa starts earlier there", "start": 1754.88, "duration": 5.86}, {"text": "and the ba is slightly delayed?", "start": 1760.74, "duration": 2.49}, {"text": "I'll show you diagrams\nthat show you more clearly.", "start": 1763.23, "duration": 2.14}, {"text": "OK, great.", "start": 1765.37, "duration": 0.65}, {"text": "Don't go away.", "start": 1766.02, "duration": 2.22}, {"text": "So we're going to do\nthe cocktail party", "start": 1768.24, "duration": 1.8}, {"text": "thing with the\nrecording devices here.", "start": 1770.04, "duration": 3.39}, {"text": "What is this?", "start": 1773.43, "duration": 0.915}, {"text": "This is just some boring\nadministrative thing", "start": 1774.345, "duration": 1.875}, {"text": "you can just read.", "start": 1776.22, "duration": 1.43}, {"text": "I actually brought it to crumple\nand make a crumpling sound,", "start": 1777.65, "duration": 2.5}, {"text": "but we'll do that afterwards.", "start": 1780.15, "duration": 2.43}, {"text": "Right now, you\nwill read from that", "start": 1782.58, "duration": 2.79}, {"text": "and I will recite\nsomething boring.", "start": 1785.37, "duration": 2.37}, {"text": "And we'll just do\nit simultaneously.", "start": 1787.74, "duration": 1.542}, {"text": "So just focus on\nwhat you're doing.", "start": 1789.282, "duration": 1.458}, {"text": "And everybody watch.", "start": 1790.74, "duration": 0.93}, {"text": "You can see my voice here.", "start": 1791.67, "duration": 1.93}, {"text": "And let's see what happens when\nwe're both talking at once.", "start": 1793.6, "duration": 3.23}, {"text": "OK, here we go.", "start": 1796.83, "duration": 1.78}, {"text": "Four score and seven years ago--", "start": 1798.61, "duration": 2.55}, {"text": "oh, geez, I forget how it\ngoes after that, so I'll just", "start": 1801.16, "duration": 2.82}, {"text": "have to make up some\nother random garbage.", "start": 1803.98, "duration": 1.86}, {"text": "[INTERPOSING VOICES]", "start": 1805.84, "duration": 0.33}, {"text": "STUDENT: --outstanding--", "start": 1806.17, "duration": 0.75}, {"text": "NANCY KANWISHER: OK.", "start": 1806.92, "duration": 0.48}, {"text": "STUDENT: --review the\nstudent's course--", "start": 1807.4, "duration": 1.44}, {"text": "[INTERPOSING VOICES]", "start": 1808.84, "duration": 0.3}, {"text": "NANCY KANWISHER: That's great.", "start": 1809.14, "duration": 1.32}, {"text": "That's great.", "start": 1810.46, "duration": 1.05}, {"text": "Don't go away.", "start": 1811.51, "duration": 1.277}, {"text": "I don't know if you could\ntell that it got muckier", "start": 1812.787, "duration": 2.083}, {"text": "when we were both talking.", "start": 1814.87, "duration": 1.74}, {"text": "Maybe it's mucky enough with\nme talking fast to begin with.", "start": 1816.61, "duration": 3.76}, {"text": "Let's try a few other things.", "start": 1820.37, "duration": 1.4}, {"text": "Let's have me say words\nand you say words.", "start": 1821.77, "duration": 2.01}, {"text": "And let's see how\ndifferent they look.", "start": 1823.78, "duration": 1.65}, {"text": "OK, so I'm going\nto say \"mousetrap.\"", "start": 1825.43, "duration": 6.52}, {"text": "STUDENT: Mousetrap.", "start": 1831.95, "duration": 0.855}, {"text": "NANCY KANWISHER: You can\nsee some similarity there,", "start": 1832.805, "duration": 2.125}, {"text": "can't you?", "start": 1834.93, "duration": 0.5}, {"text": "Let's do it again.", "start": 1835.43, "duration": 2.11}, {"text": "Mousetrap.", "start": 1837.54, "duration": 1.72}, {"text": "STUDENT: Mousetrap.", "start": 1839.26, "duration": 0.825}, {"text": "NANCY KANWISHER:\nOK, that's good.", "start": 1840.085, "duration": 1.375}, {"text": "It's funny, I see more\nlow-frequency band here.", "start": 1841.46, "duration": 1.77}, {"text": "I'm sure your voice\nis lower than mine.", "start": 1843.23, "duration": 1.68}, {"text": "Pitch, interestingly, isn't just\nabout how low the energy goes.", "start": 1844.91, "duration": 4.83}, {"text": "It's an interesting,\ncomplicated property", "start": 1849.74, "duration": 2.58}, {"text": "of the lowest common denominator\nof that whole frequency stack.", "start": 1852.32, "duration": 4.132}, {"text": "So I'm not going to do pitch.", "start": 1856.452, "duration": 1.208}, {"text": "It's complicated.", "start": 1857.66, "duration": 2.89}, {"text": "What else do we want to do?", "start": 1860.55, "duration": 1.26}, {"text": "Let's try some ba's and pa's.", "start": 1861.81, "duration": 4.357}, {"text": "But let's stick them\non the fronts of words.", "start": 1866.167, "duration": 1.833}, {"text": "Maybe that'll work better--", "start": 1868.0, "duration": 1.125}, {"text": "pat, bat.", "start": 1872.99, "duration": 3.97}, {"text": "STUDENT: Pat, bat.", "start": 1876.96, "duration": 1.318}, {"text": "NANCY KANWISHER: Oh, I could\nsee the commonality there.", "start": 1878.278, "duration": 2.292}, {"text": "Could you guys see that?", "start": 1880.57, "duration": 1.52}, {"text": "Let's do it again.", "start": 1882.09, "duration": 1.92}, {"text": "Pat, bat.", "start": 1884.01, "duration": 3.12}, {"text": "STUDENT: Pat, bat.", "start": 1887.13, "duration": 2.222}, {"text": "NANCY KANWISHER: Well,\nyours look more similar.", "start": 1889.352, "duration": 1.958}, {"text": "All right.", "start": 1891.31, "duration": 0.54}, {"text": "Anyway, thank you.", "start": 1891.85, "duration": 0.78}, {"text": "That's good.", "start": 1892.63, "duration": 0.5}, {"text": "That's all I need, just to\nshow you how hard this is,", "start": 1893.13, "duration": 2.86}, {"text": "and how there's variability\nacross speakers saying", "start": 1895.99, "duration": 2.37}, {"text": "the same thing, and very,\nvery subtle differences", "start": 1898.36, "duration": 3.78}, {"text": "between sounds that sound\ntotally different to us.", "start": 1902.14, "duration": 4.56}, {"text": "So back to lecture.", "start": 1906.7, "duration": 4.045}, {"text": "So you saw the harmonics, those\nred stripes, during the vowels.", "start": 1916.62, "duration": 5.37}, {"text": "You noticed that I\nshowed the consonants", "start": 1921.99, "duration": 5.34}, {"text": "and the ba's and pa's.", "start": 1927.33, "duration": 0.947}, {"text": "So here's a diagram.", "start": 1928.277, "duration": 0.833}, {"text": "I'm sorry, this\nis very abstracted", "start": 1929.11, "duration": 1.43}, {"text": "away from those\nspectrograms, which", "start": 1930.54, "duration": 1.458}, {"text": "are messy, as you can see.", "start": 1931.998, "duration": 1.932}, {"text": "The idea is that a consonant\nvowel sound, a single syllable", "start": 1933.93, "duration": 5.01}, {"text": "like ba or pa--", "start": 1938.94, "duration": 2.07}, {"text": "this is time this way-- has\nthis big, long formant which", "start": 1941.01, "duration": 2.88}, {"text": "is a band of energy that's\nthe vowel, the ah sound.", "start": 1943.89, "duration": 3.21}, {"text": "And it's these transitions\nthat happen just before", "start": 1947.1, "duration": 2.64}, {"text": "that that make the difference\nfor different consonants.", "start": 1949.74, "duration": 3.66}, {"text": "And in particular,\nthe difference", "start": 1953.4, "duration": 3.18}, {"text": "between a ba and a pa--", "start": 1956.58, "duration": 2.04}, {"text": "this is a ba, that's a pa--", "start": 1958.62, "duration": 2.28}, {"text": "the difference we were looking\nfor that didn't show up that", "start": 1960.9, "duration": 2.52}, {"text": "clearly, but you\ncan try it at home,", "start": 1963.42, "duration": 1.77}, {"text": "maybe you can get it clearer\nthan I just got it now--", "start": 1965.19, "duration": 2.85}, {"text": "has to do with that transition\nonto the first formant.", "start": 1968.04, "duration": 3.12}, {"text": "So with a ba, the transitions\nhappen in parallel.", "start": 1971.16, "duration": 4.65}, {"text": "And with a pa, this\ntransition happens", "start": 1975.81, "duration": 3.03}, {"text": "before that lower formant.", "start": 1978.84, "duration": 1.86}, {"text": "So that tiny, little--\nit's a 65 millisecond delay", "start": 1980.7, "duration": 4.05}, {"text": "in the case of pa that you\ndon't have in the case of ba,", "start": 1984.75, "duration": 3.69}, {"text": "is how you tell that difference.", "start": 1988.44, "duration": 1.99}, {"text": "It's very, very subtle.", "start": 1990.43, "duration": 1.31}, {"text": "So there's lots of\ndifferent kinds of phonemes.", "start": 1994.95, "duration": 2.91}, {"text": "We've been talking about\nvowels and consonants.", "start": 1997.86, "duration": 3.3}, {"text": "Each vowel or consonant\nsound is called a \"phoneme\"", "start": 2001.16, "duration": 4.41}, {"text": "if a distinction\nin that sound makes", "start": 2005.57, "duration": 3.5}, {"text": "the difference between\ntwo different words", "start": 2009.07, "duration": 1.75}, {"text": "in your language.", "start": 2010.82, "duration": 2.32}, {"text": "And that means that what counts\nas a phoneme in one language", "start": 2013.14, "duration": 3.02}, {"text": "may not be a phoneme\nin another language,", "start": 2016.16, "duration": 2.28}, {"text": "because it won't\nmake a distinction", "start": 2018.44, "duration": 1.47}, {"text": "between different words.", "start": 2019.91, "duration": 2.31}, {"text": "Many of the phonemes are shared\nacross languages, but not all.", "start": 2022.22, "duration": 3.54}, {"text": "We've talked about R and L that\naren't distinguished in Japan,", "start": 2025.76, "duration": 3.87}, {"text": "and two different\nD sounds that sound", "start": 2029.63, "duration": 1.71}, {"text": "the same to me that are\ndistinguished in Hindi,", "start": 2031.34, "duration": 3.09}, {"text": "and lots of others.", "start": 2034.43, "duration": 2.01}, {"text": "And so those are just variations\nacross natural languages", "start": 2036.44, "duration": 2.88}, {"text": "on which of those phonemes,\nwhich of those sounds,", "start": 2039.32, "duration": 2.7}, {"text": "are used to discriminate\ndifferent words,", "start": 2042.02, "duration": 1.8}, {"text": "and hence count as\nphonemes in that language.", "start": 2043.82, "duration": 3.43}, {"text": "So there's some particularly\nawesome phonemes", "start": 2047.25, "duration": 3.92}, {"text": "that use a particular\nkind of consonant", "start": 2051.17, "duration": 1.95}, {"text": "known as a click consonant.", "start": 2053.12, "duration": 1.98}, {"text": "And these are common in some\nSouthern African languages.", "start": 2055.1, "duration": 4.26}, {"text": "And a year ago, I was traveling\nin Mozambique, which was just", "start": 2059.36, "duration": 4.17}, {"text": "hit by a devastating flood.", "start": 2063.53, "duration": 1.5}, {"text": "It's really awful.", "start": 2065.03, "duration": 0.91}, {"text": "But anyway, I was there\nvisiting a game park", "start": 2065.94, "duration": 2.21}, {"text": "seeing all kinds of animals.", "start": 2068.15, "duration": 2.259}, {"text": "And I met this guy, Test.", "start": 2070.409, "duration": 4.671}, {"text": "And he's amazing.", "start": 2075.08, "duration": 0.777}, {"text": "I mean, his knowledge\nof the natural history", "start": 2075.857, "duration": 1.833}, {"text": "was mind blowing,\nbut he also speaks,", "start": 2077.69, "duration": 1.719}, {"text": "I think, six different\nlanguages fluently, one of which", "start": 2079.409, "duration": 2.961}, {"text": "is Xhosa, or as he would say,\n[SPEAKING Xhosa] or something", "start": 2082.37, "duration": 3.13}, {"text": "like that.", "start": 2085.5, "duration": 0.5}, {"text": "You'll hear him\nsay it in a moment.", "start": 2086.0, "duration": 1.69}, {"text": "And so he was illustrating\nclick languages.", "start": 2087.69, "duration": 2.0}, {"text": "And I'll play this\nfor you in a second.", "start": 2089.69, "duration": 1.815}, {"text": "And he says there's a\nsentence in Xhosa which", "start": 2091.505, "duration": 1.875}, {"text": "is a little bit crazy, but\nhas all the different clicks.", "start": 2093.38, "duration": 2.43}, {"text": "And it means, basically,\n\"the skunk was rolling", "start": 2095.81, "duration": 2.76}, {"text": "and accidentally got\ncut by the throat.\"", "start": 2098.57, "duration": 1.86}, {"text": "Doesn't mean a whole\nlot, but listen", "start": 2100.43, "duration": 1.77}, {"text": "to Test saying the\nsentence, first in English", "start": 2102.2, "duration": 2.73}, {"text": "and then in Xhosa.", "start": 2104.93, "duration": 1.31}, {"text": "[AUDIO PLAYBACK]", "start": 2106.24, "duration": 0.88}, {"text": "- The phrase in\nEnglish, it says skunk", "start": 2107.12, "duration": 2.82}, {"text": "was rolling and accidentally\ngot cut by the throat.", "start": 2109.94, "duration": 4.74}, {"text": "In Xhosa, or in east\nXhosa, [SPEAKING Xhosa].", "start": 2114.68, "duration": 4.987}, {"text": "[END PLAYBACK]", "start": 2123.514, "duration": 0.826}, {"text": "NANCY KANWISHER:\nIsn't that awesome?", "start": 2124.34, "duration": 0.78}, {"text": "I think we just have to\ncrank it up a little bit", "start": 2125.12, "duration": 2.0}, {"text": "and hear him again.", "start": 2127.12, "duration": 1.27}, {"text": "[AUDIO PLAYBACK]", "start": 2128.39, "duration": 5.58}, {"text": "- The phrase in English, it\nsays the skunk was rolling", "start": 2133.97, "duration": 3.45}, {"text": "and accidentally get\ncut by the throat.", "start": 2137.42, "duration": 4.08}, {"text": "In Xhosa or in east\nXhosa, [SPEAKING Xhosa].", "start": 2141.5, "duration": 4.796}, {"text": "[END PLAYBACK]", "start": 2151.54, "duration": 0.87}, {"text": "NANCY KANWISHER: OK,\nfor the most part,", "start": 2152.41, "duration": 1.625}, {"text": "we don't have click\nconsonants in English", "start": 2154.035, "duration": 2.585}, {"text": "that count as\nphonemes in the sense", "start": 2156.62, "duration": 1.47}, {"text": "of distinguishing\ndifferent words.", "start": 2158.09, "duration": 1.59}, {"text": "But we do have click consonants\nthat we use in other domains.", "start": 2159.68, "duration": 3.66}, {"text": "Anybody know what we use\nclick consonants for?", "start": 2163.34, "duration": 3.18}, {"text": "There's at least two.", "start": 2166.52, "duration": 2.71}, {"text": "Know any click consonants?", "start": 2169.23, "duration": 1.702}, {"text": "STUDENT: [INAUDIBLE]", "start": 2170.932, "duration": 1.328}, {"text": "NANCY KANWISHER: Yeah, what?", "start": 2172.26, "duration": 1.167}, {"text": "STUDENT: [INAUDIBLE] That's--", "start": 2173.427, "duration": 1.398}, {"text": "NANCY KANWISHER: Like what?", "start": 2174.825, "duration": 1.125}, {"text": "STUDENT: [INAUDIBLE]", "start": 2175.95, "duration": 2.25}, {"text": "NANCY KANWISHER: Yes, but\nthat's a regular consonant.", "start": 2178.2, "duration": 2.847}, {"text": "It's actually not a click.", "start": 2181.047, "duration": 1.083}, {"text": "It's just a regular consonant.", "start": 2182.13, "duration": 3.12}, {"text": "Well, one is when you go, tsk,\ntsk, tsk, the scolding sound.", "start": 2185.25, "duration": 5.58}, {"text": "It's not a phoneme.", "start": 2190.83, "duration": 0.96}, {"text": "It's not a word, but it has\na very particular meaning.", "start": 2191.79, "duration": 3.65}, {"text": "Another one is how you get a\nhorse to giddy up. (CLICKS)", "start": 2195.44, "duration": 6.282}, {"text": "So those are the click\nconsonants we have in English.", "start": 2201.722, "duration": 2.208}, {"text": "They're not phonemes,\nbut we have them,", "start": 2203.93, "duration": 2.19}, {"text": "and he's got a whole lot more.", "start": 2206.12, "duration": 2.22}, {"text": "That was just for fun.", "start": 2208.34, "duration": 2.43}, {"text": "So why is speech\nperception challenging?", "start": 2210.77, "duration": 3.66}, {"text": "Well, one is the essence of\nit is that a given speech", "start": 2214.43, "duration": 3.63}, {"text": "sound is highly variable.", "start": 2218.06, "duration": 2.25}, {"text": "One way it's\nvariable is that when", "start": 2220.31, "duration": 1.89}, {"text": "you speak at different\nrates, all the frequencies", "start": 2222.2, "duration": 2.94}, {"text": "go up and down and\nhaywire, making", "start": 2225.14, "duration": 1.89}, {"text": "them very different across\ndifferent talking rates.", "start": 2227.03, "duration": 3.69}, {"text": "Another is the context.", "start": 2230.72, "duration": 2.74}, {"text": "So a given phoneme, like a\nba, or a pa sound, or a vowel,", "start": 2233.46, "duration": 4.04}, {"text": "sounds totally different\ndepending on what phonemes", "start": 2237.5, "duration": 2.43}, {"text": "come before and after it.", "start": 2239.93, "duration": 1.47}, {"text": "They're not little punctate,\none at a time things.", "start": 2241.4, "duration": 3.09}, {"text": "They all overlap and affect\neach other in a big mess.", "start": 2244.49, "duration": 4.945}, {"text": "And the third is one\nwe've already mentioned,", "start": 2249.435, "duration": 1.875}, {"text": "which is the big\ndifferences across speakers", "start": 2251.31, "duration": 2.36}, {"text": "in the language.", "start": 2253.67, "duration": 1.47}, {"text": "So you have to\nrecognize a ba sound", "start": 2255.14, "duration": 4.05}, {"text": "even though it sounds\nquite different when", "start": 2259.19, "duration": 2.22}, {"text": "spoken by different speakers.", "start": 2261.41, "duration": 2.82}, {"text": "So all of these things make\nit very computationally", "start": 2264.23, "duration": 2.67}, {"text": "challenging to\nunderstand speech.", "start": 2266.9, "duration": 1.92}, {"text": "Here's an illustration of\nthat talker variability.", "start": 2268.82, "duration": 4.35}, {"text": "So what's shown here is not\na whole spectrogram, but just", "start": 2273.17, "duration": 3.75}, {"text": "the intensity of\nthe first formant", "start": 2276.92, "duration": 2.4}, {"text": "and the second formant,\nthose bands of energy", "start": 2279.32, "duration": 3.06}, {"text": "that I showed you\nin the spectrogram.", "start": 2282.38, "duration": 1.71}, {"text": "And so each dot here\nis a different person", "start": 2284.09, "duration": 5.46}, {"text": "pronouncing a vowel.", "start": 2289.55, "duration": 2.34}, {"text": "And each color-- this is\none vowel here in green,", "start": 2291.89, "duration": 3.15}, {"text": "in that green ellipse, with\nlots of different people", "start": 2295.04, "duration": 2.22}, {"text": "saying that vowel.", "start": 2297.26, "duration": 1.95}, {"text": "Here's another vowel\nup here in red,", "start": 2299.21, "duration": 1.83}, {"text": "with lots of different\npeople saying that vowel.", "start": 2301.04, "duration": 3.63}, {"text": "And what you see is\nthey're really overlapping.", "start": 2304.67, "duration": 4.98}, {"text": "So that means you can't just\ngo from the energy at those two", "start": 2309.65, "duration": 2.64}, {"text": "formants, a point in that space,\nand know what the vowel is.", "start": 2312.29, "duration": 3.21}, {"text": "What if you were right there?", "start": 2315.5, "duration": 1.5}, {"text": "Well, then it could be any\nof four different vowels.", "start": 2317.0, "duration": 4.05}, {"text": "So that's the problem of\ntalker variability illustrated", "start": 2321.05, "duration": 2.77}, {"text": "with vowels.", "start": 2323.82, "duration": 0.5}, {"text": "Does that make sense?", "start": 2324.32, "duration": 0.875}, {"text": "I think I just said all of\nthis, blah, blah, blah--", "start": 2328.26, "duration": 2.28}, {"text": "another classic ill-posed\nproblem in perception.", "start": 2330.54, "duration": 2.67}, {"text": "You're given a\npoint in this space.", "start": 2333.21, "duration": 1.66}, {"text": "How do you tell\nwhich vowel it is?", "start": 2334.87, "duration": 3.02}, {"text": "So one way we solve that is that\nwe learn each other's voices.", "start": 2337.89, "duration": 4.41}, {"text": "And we know how a\ngiven person pronounces", "start": 2342.3, "duration": 3.99}, {"text": "a given set of vowels or words.", "start": 2346.29, "duration": 2.43}, {"text": "And we use that to constrain\nwhat they're saying.", "start": 2348.72, "duration": 2.58}, {"text": "Have you ever\nnoticed, especially", "start": 2351.3, "duration": 1.44}, {"text": "if you meet somebody new--\nwell, actually, you just", "start": 2352.74, "duration": 2.125}, {"text": "experience this with Test.", "start": 2354.865, "duration": 1.385}, {"text": "When he first speaks,\nhis English is beautiful,", "start": 2356.25, "duration": 2.31}, {"text": "but he's from Zimbabwe and\nhe has kind of Zimbabwe,", "start": 2358.56, "duration": 2.61}, {"text": "British-type accent.", "start": 2361.17, "duration": 1.35}, {"text": "And at first it's hard to\nunderstand what he's saying.", "start": 2362.52, "duration": 2.25}, {"text": "Did you all experience\nthat briefly?", "start": 2364.77, "duration": 1.8}, {"text": "I mean, that's why I put\nthe text on the slide,", "start": 2366.57, "duration": 2.538}, {"text": "so you would get used to his\nEnglish and understand it.", "start": 2369.108, "duration": 2.292}, {"text": "If I hadn't, you probably\nwouldn't have understood", "start": 2371.4, "duration": 2.4}, {"text": "that sentence he spoke first.", "start": 2373.8, "duration": 1.26}, {"text": "That's because we don't\nknow his voice yet.", "start": 2375.06, "duration": 2.37}, {"text": "But did you notice, after\neven just a few words,", "start": 2377.43, "duration": 2.44}, {"text": "you start to like tune right\nin and you can understand him?", "start": 2379.87, "duration": 2.75}, {"text": "So learning about an\nindividual's voice", "start": 2382.62, "duration": 2.88}, {"text": "helps you pull apart the\nproperties of the voice,", "start": 2385.5, "duration": 2.73}, {"text": "and unconfound\nthem from the sound", "start": 2388.23, "duration": 2.04}, {"text": "so you can understand what\nthat person is saying.", "start": 2390.27, "duration": 2.28}, {"text": "So that's part of how we\nsolve this ill-posed problem.", "start": 2396.18, "duration": 3.32}, {"text": "And so evidence\nthat we do that is", "start": 2399.5, "duration": 3.0}, {"text": "that if you have people listen\nto voices they don't know", "start": 2402.5, "duration": 4.59}, {"text": "or voices that are\nchanging from word to word,", "start": 2407.09, "duration": 2.37}, {"text": "it's much harder to\nunderstand speech.", "start": 2409.46, "duration": 2.19}, {"text": "So you imagine you took the\nsentence I'm saying right now,", "start": 2411.65, "duration": 2.7}, {"text": "and you spliced in a different\nperson saying each word.", "start": 2414.35, "duration": 2.7}, {"text": "Actually, I should\nmake that demo.", "start": 2417.05, "duration": 2.49}, {"text": "One of you guys\nsend me an email--", "start": 2419.54, "duration": 1.47}, {"text": "make that demo of a\ndifferent person speaking", "start": 2421.01, "duration": 1.97}, {"text": "each word in a sentence.", "start": 2422.98, "duration": 1.0}, {"text": "It'd be really\nhard to understand.", "start": 2423.98, "duration": 1.83}, {"text": "Because you wouldn't\nhave been able to fix", "start": 2425.81, "duration": 1.76}, {"text": "this was a property\nof the voice,", "start": 2427.57, "duration": 1.375}, {"text": "now we can kind of separate\nthat from everything else.", "start": 2428.945, "duration": 2.085}, {"text": "Because the damn voice will\nbe changing on each word.", "start": 2431.03, "duration": 2.208}, {"text": "It'll be a mess.", "start": 2433.238, "duration": 1.692}, {"text": "So that's one problem.", "start": 2434.93, "duration": 2.77}, {"text": "So it turns out that the\nopposite is true, as well.", "start": 2437.7, "duration": 4.77}, {"text": "And that is, your ability to\nrecognize somebody's voice", "start": 2442.47, "duration": 4.85}, {"text": "is a function of what you\nknow about that language.", "start": 2447.32, "duration": 3.91}, {"text": "So you can recognize\nvoices better in a language", "start": 2451.23, "duration": 3.09}, {"text": "you know than a language\nyou don't because you're", "start": 2454.32, "duration": 3.42}, {"text": "doing the opposite.", "start": 2457.74, "duration": 0.96}, {"text": "You're using knowledge of\nthe language and its speech", "start": 2458.7, "duration": 2.61}, {"text": "properties that you\nalready know to constrain", "start": 2461.31, "duration": 4.14}, {"text": "the problem of figuring out\nwho is this person's voice.", "start": 2465.45, "duration": 2.805}, {"text": "So does everybody get this?", "start": 2468.255, "duration": 1.125}, {"text": "These two things are affecting\neach other-- the speaker", "start": 2469.38, "duration": 2.61}, {"text": "and what's being said.", "start": 2471.99, "duration": 1.5}, {"text": "And because they're\nso confounded,", "start": 2473.49, "duration": 1.8}, {"text": "massively confounded\nin the stimulus,", "start": 2475.29, "duration": 2.01}, {"text": "to solve that, the more\nyou know about the speaker,", "start": 2477.3, "duration": 3.36}, {"text": "the better you can\nunderstand what's being said.", "start": 2480.66, "duration": 2.16}, {"text": "And the more you know about the\nlanguage and its properties,", "start": 2482.82, "duration": 2.79}, {"text": "the more you can\nrecognize the voice.", "start": 2485.61, "duration": 2.22}, {"text": "Each one is a source of\ninformation about one", "start": 2487.83, "duration": 2.19}, {"text": "of those two\nconfounded variables.", "start": 2490.02, "duration": 4.08}, {"text": "And so people have shown\nthat psychophysically.", "start": 2494.1, "duration": 3.24}, {"text": "And I think I have\ntime to do this.", "start": 2497.34, "duration": 1.71}, {"text": "Here's a kind of cool\ncorollary of this,", "start": 2499.05, "duration": 2.79}, {"text": "and that is, it's commonly\nthought that dyslexia is most", "start": 2501.84, "duration": 4.89}, {"text": "fundamentally a problem of\nauditory speech perception, not", "start": 2506.73, "duration": 3.15}, {"text": "a visual problem.", "start": 2509.88, "duration": 0.85}, {"text": "There may also be a bit\nof a visual problem,", "start": 2510.73, "duration": 1.91}, {"text": "but it's thought\nthat at core, it's", "start": 2512.64, "duration": 2.1}, {"text": "a problem of auditory\nspeech perception.", "start": 2514.74, "duration": 4.02}, {"text": "So if that's true,\nthen you might", "start": 2518.76, "duration": 2.67}, {"text": "think that this ability to\nuse knowledge of the language", "start": 2521.43, "duration": 3.72}, {"text": "and its sounds to\nconstrain voice recognition", "start": 2525.15, "duration": 3.42}, {"text": "would be reduced in\npeople with dyslexia,", "start": 2528.57, "duration": 2.76}, {"text": "because they are less good\nat processing speech sounds.", "start": 2531.33, "duration": 4.33}, {"text": "And it turns out that's true.", "start": 2535.66, "duration": 1.81}, {"text": "So here's a beautiful study from\nGabrielli Lab a few years ago.", "start": 2537.47, "duration": 3.72}, {"text": "So first look at\nthe bars in blue.", "start": 2541.19, "duration": 2.37}, {"text": "So this is accuracy\nat voice recognition,", "start": 2543.56, "duration": 2.82}, {"text": "which person is speaking.", "start": 2546.38, "duration": 2.54}, {"text": "And this is native\nEnglish speakers", "start": 2548.92, "duration": 1.86}, {"text": "who don't speak Chinese.", "start": 2550.78, "duration": 1.32}, {"text": "They are much more\naccurate recognizing", "start": 2552.1, "duration": 2.13}, {"text": "who's speaking when they're\nspeaking English than when", "start": 2554.23, "duration": 2.25}, {"text": "they're speaking Chinese.", "start": 2556.48, "duration": 2.73}, {"text": "So that's kind of cool.", "start": 2559.21, "duration": 1.08}, {"text": "That shows you the\nway in which you", "start": 2560.29, "duration": 1.68}, {"text": "use knowledge of the language\nto constrain recognition", "start": 2561.97, "duration": 3.51}, {"text": "of the voice.", "start": 2565.48, "duration": 1.41}, {"text": "But now look what happens\nin the dyslexics--", "start": 2566.89, "duration": 2.31}, {"text": "no effect, exactly\nas they predicted.", "start": 2569.2, "duration": 3.15}, {"text": "Given that the dyslexics have a\nproblem with speech perception,", "start": 2572.35, "duration": 3.03}, {"text": "they're apparently\nnot able to use", "start": 2575.38, "duration": 1.77}, {"text": "that knowledge of the\nphonemes of the language", "start": 2577.15, "duration": 3.0}, {"text": "to constrain the problem\nof voice recognition.", "start": 2580.15, "duration": 2.13}, {"text": "They're just as bad\nat voice recognition--", "start": 2582.28, "duration": 2.94}, {"text": "I'm sorry, they're no\nbetter at voice recognition", "start": 2585.22, "duration": 2.67}, {"text": "in their native language\nthan in a foreign language.", "start": 2587.89, "duration": 3.24}, {"text": "They can't use that knowledge\nto constrain voice recognition.", "start": 2591.13, "duration": 2.94}, {"text": "Does that make sense?", "start": 2594.07, "duration": 2.15}, {"text": "Yeah, I love that study.", "start": 2596.22, "duration": 2.7}, {"text": "So we haven't done any\nbrain stuff so far.", "start": 2598.92, "duration": 4.32}, {"text": "We were just thinking about the\nproblem of hearing and speech", "start": 2603.24, "duration": 2.85}, {"text": "perception, and what\nwe know from behavior.", "start": 2606.09, "duration": 2.46}, {"text": "And we've learned a\nlot already, but we'll", "start": 2608.55, "duration": 1.8}, {"text": "learn more by looking at\nthe brain, and the meat,", "start": 2610.35, "duration": 2.25}, {"text": "and all of that.", "start": 2612.6, "duration": 0.79}, {"text": "So let's start with the ear.", "start": 2613.39, "duration": 2.84}, {"text": "Again, remember, compressions\nof air come into the ear.", "start": 2616.23, "duration": 4.92}, {"text": "They travel through\nthe ear canal.", "start": 2621.15, "duration": 1.89}, {"text": "They hit the tympanic membrane.", "start": 2623.04, "duration": 2.19}, {"text": "They go through a whole series\nof transducers, these three", "start": 2625.23, "duration": 3.93}, {"text": "little ear bones\nhere that connect", "start": 2629.16, "duration": 1.62}, {"text": "to this snail-shaped thing,\nwhich is called the \"cochlea.\"", "start": 2630.78, "duration": 5.39}, {"text": "Cochlea is really important.", "start": 2636.17, "duration": 1.36}, {"text": "You should remember that word.", "start": 2637.53, "duration": 1.25}, {"text": "It's the place where you\ntransduce incoming sound", "start": 2638.78, "duration": 4.35}, {"text": "into neural impulses,\nway in there.", "start": 2643.13, "duration": 5.76}, {"text": "And the cochlea is really cool.", "start": 2648.89, "duration": 2.055}, {"text": "It's this, as I said,\na snail-shaped thing.", "start": 2653.6, "duration": 2.76}, {"text": "And there are nerve endings\nall the way along this thing.", "start": 2656.36, "duration": 4.14}, {"text": "And because of the\nphysics of the cochlea,", "start": 2660.5, "duration": 2.74}, {"text": "there are different resonant\nfrequencies at different parts", "start": 2663.24, "duration": 3.68}, {"text": "of this snail.", "start": 2666.92, "duration": 1.78}, {"text": "So basically, here are some\nlow-frequency sound waves.", "start": 2668.7, "duration": 5.82}, {"text": "This is the cochlea stretched\nout with the base and the apex.", "start": 2674.52, "duration": 3.08}, {"text": "This is the base.", "start": 2677.6, "duration": 0.96}, {"text": "That's the apex.", "start": 2678.56, "duration": 1.32}, {"text": "And what you see is\nthe low frequencies", "start": 2679.88, "duration": 5.19}, {"text": "have transduced some energy\nat the base of the cochlea,", "start": 2685.07, "duration": 3.78}, {"text": "and also at the apex.", "start": 2688.85, "duration": 2.7}, {"text": "But midway range frequencies\nand high frequencies", "start": 2691.55, "duration": 3.48}, {"text": "do nothing at the apex.", "start": 2695.03, "duration": 1.44}, {"text": "This business, there's\nonly physical fluctuations", "start": 2696.47, "duration": 3.54}, {"text": "happening up here for\nlow frequency sounds.", "start": 2700.01, "duration": 4.14}, {"text": "So there's little\nnerve endings here", "start": 2704.15, "duration": 1.5}, {"text": "that detect those\nfluctuations up there", "start": 2705.65, "duration": 1.77}, {"text": "and send those signals\nup into the brain", "start": 2707.42, "duration": 2.64}, {"text": "through the auditory nerve.", "start": 2710.06, "duration": 1.42}, {"text": "And so in the middle,\nhere or something,", "start": 2711.48, "duration": 4.49}, {"text": "you have sensitivity to\nmid-range frequencies,", "start": 2715.97, "duration": 2.85}, {"text": "not high or low.", "start": 2718.82, "duration": 2.95}, {"text": "And at the base, it's sensitive\nmore to high frequencies", "start": 2721.77, "duration": 3.83}, {"text": "than mid or low.", "start": 2725.6, "duration": 1.92}, {"text": "So everybody get that?", "start": 2727.52, "duration": 1.05}, {"text": "So basically, the cochlea\nis doing a Fourier transform", "start": 2728.57, "duration": 3.21}, {"text": "on the acoustic signal.", "start": 2731.78, "duration": 2.31}, {"text": "It's taking these compressions\nof air, and it's just saying,", "start": 2734.09, "duration": 5.28}, {"text": "let's separate those out\ninto different frequencies,", "start": 2739.37, "duration": 2.46}, {"text": "just with this physical device.", "start": 2741.83, "duration": 2.37}, {"text": "It's like a physical Fourier\ntransform that's saying,", "start": 2744.2, "duration": 3.42}, {"text": "let's just physically\nseparate the energy", "start": 2747.62, "duration": 2.49}, {"text": "at each frequency range along\nthe length of the cochlea.", "start": 2750.11, "duration": 3.36}, {"text": "Does that make sense?", "start": 2753.47, "duration": 2.05}, {"text": "And then once you get different\nparts of the cochlea that", "start": 2755.52, "duration": 2.51}, {"text": "are sensitive to different\nfrequencies oscillating", "start": 2758.03, "duration": 2.55}, {"text": "to different degrees, then you\nstick some nerve cells there", "start": 2760.58, "duration": 3.12}, {"text": "to pick up those oscillations,\ngo up the auditory nerve,", "start": 2763.7, "duration": 3.42}, {"text": "and travel into the brain.", "start": 2767.12, "duration": 1.86}, {"text": "Everybody have a gist\nof how this works?", "start": 2768.98, "duration": 1.835}, {"text": "So that's cool.", "start": 2773.56, "duration": 1.02}, {"text": "But now, let's go\nup to the brain.", "start": 2774.58, "duration": 1.8}, {"text": "So now, this is\na view like this.", "start": 2776.38, "duration": 2.5}, {"text": "And so here are the cochleae--", "start": 2778.88, "duration": 1.83}, {"text": "I guess that's the plural--", "start": 2780.71, "duration": 1.67}, {"text": "on each side-- ears,\near canal, cochleae.", "start": 2782.38, "duration": 3.42}, {"text": "And the first thing to\nknow, which is important,", "start": 2785.8, "duration": 2.73}, {"text": "is that the path between the\ncochlea and the first step", "start": 2788.53, "duration": 3.72}, {"text": "up in the cortex is much\nmore complicated in hearing", "start": 2792.25, "duration": 3.39}, {"text": "than it is in vision.", "start": 2795.64, "duration": 2.4}, {"text": "Look at all these\nnuclei deep down", "start": 2798.04, "duration": 2.49}, {"text": "in the basement of the brain.", "start": 2800.53, "duration": 2.52}, {"text": "In contrast, in vision,\nhow many synapses", "start": 2803.05, "duration": 3.33}, {"text": "do you have to make\nbetween the retina", "start": 2806.38, "duration": 1.74}, {"text": "and primary visual cortex?", "start": 2808.12, "duration": 1.245}, {"text": "Sorry.", "start": 2813.16, "duration": 1.32}, {"text": "One synapse.", "start": 2814.48, "duration": 0.99}, {"text": "Right?", "start": 2815.47, "duration": 0.64}, {"text": "STUDENT: Well, I was thinking--", "start": 2816.11, "duration": 0.92}, {"text": "NANCY KANWISHER:\nYeah, two, that's", "start": 2817.03, "duration": 1.53}, {"text": "right, so retinal ganglion\ncells send their axons straight", "start": 2818.56, "duration": 2.73}, {"text": "into the LGN in the\nthalamus, make a synapse.", "start": 2821.29, "duration": 3.0}, {"text": "And then those LGN\nneurons go straight", "start": 2824.29, "duration": 2.19}, {"text": "up to primary visual cortex,\njust one stop on the way.", "start": 2826.48, "duration": 2.94}, {"text": "Look at all the stops\non the way here.", "start": 2829.42, "duration": 3.96}, {"text": "So audition is a\nreally different beast", "start": 2833.38, "duration": 2.04}, {"text": "from hearing in many ways.", "start": 2835.42, "duration": 2.04}, {"text": "Next time, we'll talk\nabout how audition--", "start": 2837.46, "duration": 2.58}, {"text": "not these parts of it, but\nafter you get up to the cortex--", "start": 2840.04, "duration": 2.91}, {"text": "audition, we in my lab\nand a few other labs", "start": 2842.95, "duration": 4.02}, {"text": "are really starting\nto suspect, is", "start": 2846.97, "duration": 1.59}, {"text": "profoundly different in humans\nfrom any non-human animal.", "start": 2848.56, "duration": 5.32}, {"text": "And I think that's for\nvery interesting reasons,", "start": 2853.88, "duration": 2.0}, {"text": "but this part is pretty\nsimilar in animals,", "start": 2855.88, "duration": 2.28}, {"text": "just getting information\nup to the cortex.", "start": 2858.16, "duration": 2.4}, {"text": "And audition is already very\ndifferent from vision just", "start": 2860.56, "duration": 3.18}, {"text": "in the number of relays\ngoing up to the brain.", "start": 2863.74, "duration": 2.86}, {"text": "So those structures down there\ndo all kinds of awesome things.", "start": 2866.6, "duration": 3.8}, {"text": "And last year, I\ntalked at great length", "start": 2870.4, "duration": 1.71}, {"text": "about how we detect the\nlocations of sounds.", "start": 2872.11, "duration": 2.46}, {"text": "It's absolutely beautiful\nwork, and elegant, and fun,", "start": 2874.57, "duration": 2.91}, {"text": "but I decided that was a\nlittle too much behavior.", "start": 2877.48, "duration": 2.58}, {"text": "We should get on to the brain.", "start": 2880.06, "duration": 1.62}, {"text": "But I recommend 9.35 if you want\nto learn more about audition--", "start": 2881.68, "duration": 3.75}, {"text": "awesome course.", "start": 2885.43, "duration": 0.84}, {"text": "Did you take it?", "start": 2886.27, "duration": 0.84}, {"text": "Really awesome course.", "start": 2887.11, "duration": 1.26}, {"text": "Yeah, exactly.", "start": 2888.37, "duration": 1.33}, {"text": "And so you'll learn more\nabout all that stuff.", "start": 2889.7, "duration": 2.75}, {"text": "So instead, we will\njust skip all that", "start": 2892.45, "duration": 2.37}, {"text": "and go straight up to cortex.", "start": 2894.82, "duration": 3.21}, {"text": "So the first place that\nauditory information", "start": 2898.03, "duration": 2.91}, {"text": "hits the cortex coming\nup from the cochleae", "start": 2900.94, "duration": 2.85}, {"text": "is primary auditory cortex,\njust like the first place", "start": 2903.79, "duration": 3.12}, {"text": "visual information hits the\ncortex coming up from the eyes", "start": 2906.91, "duration": 3.1}, {"text": "is primary visual cortex.", "start": 2910.01, "duration": 2.72}, {"text": "So you can see in here that in a\ncross-sectional view like that,", "start": 2912.73, "duration": 4.86}, {"text": "this is primary auditory cortex.", "start": 2917.59, "duration": 1.69}, {"text": "It's in that sulcus right there.", "start": 2919.28, "duration": 2.312}, {"text": "That's kind of a\ndrag, because when", "start": 2921.592, "duration": 1.458}, {"text": "we get occasional\nopportunities to test patients", "start": 2923.05, "duration": 3.06}, {"text": "who have grids of electrodes\non the surface of their brain,", "start": 2926.11, "duration": 3.9}, {"text": "the grids don't\nusually go in there", "start": 2930.01, "duration": 1.56}, {"text": "and we can't see\nprimary auditory cortex.", "start": 2931.57, "duration": 3.33}, {"text": "Although there are\nnew methods where", "start": 2934.9, "duration": 1.5}, {"text": "they stick depth\nelectrodes, which", "start": 2936.4, "duration": 1.71}, {"text": "is surprisingly, apparently,\nbetter on the patients.", "start": 2938.11, "duration": 2.46}, {"text": "And right now your TA,\nDana [? Bobinger, ?]", "start": 2940.57, "duration": 2.61}, {"text": "is over at Children's Hospital\nrecording from a 19-year-old", "start": 2943.18, "duration": 4.98}, {"text": "who has bad epilepsy and who has\ndepth electrodes in his brain.", "start": 2948.16, "duration": 5.09}, {"text": "And he's listening to\nall kinds of sounds.", "start": 2953.25, "duration": 1.75}, {"text": "And she's recorded his neural\nactivity with depth electrodes.", "start": 2955.0, "duration": 2.97}, {"text": "And so we are\nhopeful, one, that we", "start": 2957.97, "duration": 2.317}, {"text": "can find some\ninformation that will be", "start": 2960.287, "duration": 1.583}, {"text": "relevant to the neurosurgeons--", "start": 2961.87, "duration": 1.8}, {"text": "I don't know about that--", "start": 2963.67, "duration": 1.47}, {"text": "but two, that we'll\nget some information", "start": 2965.14, "duration": 2.428}, {"text": "from those deep structures\nthat you can't usually", "start": 2967.568, "duration": 2.042}, {"text": "see when you have just grids\nsitting on the surface.", "start": 2969.61, "duration": 2.167}, {"text": "So back to functional MRI--", "start": 2974.65, "duration": 2.74}, {"text": "so this is primary\nauditory cortex.", "start": 2977.39, "duration": 2.36}, {"text": "It's quite stylized.", "start": 2979.75, "duration": 1.187}, {"text": "Let me remind you where you are.", "start": 2980.937, "duration": 1.333}, {"text": "This is an inflated view\nof the right hemisphere--", "start": 2982.27, "duration": 2.91}, {"text": "back of the head, front of the\nhead, temporal lobe, all funny", "start": 2985.18, "duration": 3.24}, {"text": "looking because it's been\nmathematically unfolded", "start": 2988.42, "duration": 2.1}, {"text": "so you can see stuff in the\nsulcus where I just showed you.", "start": 2990.52, "duration": 2.94}, {"text": "Primary auditory cortex\nis in the sulcus.", "start": 2993.46, "duration": 2.04}, {"text": "But we've inflated\nit so you can see it.", "start": 2995.5, "duration": 2.35}, {"text": "And so this is primary auditory\ncortex, this whole thing here.", "start": 2997.85, "duration": 4.26}, {"text": "And it shows you a property\nwe've talked about before.", "start": 3002.11, "duration": 2.7}, {"text": "It's got a map, but the map\nin primary auditory cortex", "start": 3004.81, "duration": 4.53}, {"text": "is not a map of space\nlike it is in the retina", "start": 3009.34, "duration": 2.67}, {"text": "for visual information.", "start": 3012.01, "duration": 1.48}, {"text": "It's a map of frequency.", "start": 3013.49, "duration": 2.79}, {"text": "And that makes sense\nbecause the input transducer", "start": 3016.28, "duration": 2.49}, {"text": "is a cochlea, which\nalready physically creates", "start": 3018.77, "duration": 2.67}, {"text": "a map of frequency.", "start": 3021.44, "duration": 1.128}, {"text": "And so that gets\ntraveled through all", "start": 3022.568, "duration": 1.542}, {"text": "those intermediate stages\ndown in the basement,", "start": 3024.11, "duration": 1.958}, {"text": "and it comes up to\nthe brain, and makes", "start": 3026.068, "duration": 1.642}, {"text": "a map of frequency space.", "start": 3027.71, "duration": 2.59}, {"text": "So what this means,\nactually-- so here's", "start": 3030.3, "duration": 1.91}, {"text": "sensitivity to\ndifferent frequencies.", "start": 3032.21, "duration": 2.26}, {"text": "And so the classic structure\nof primary auditory cortex", "start": 3034.47, "duration": 3.29}, {"text": "in humans is high, low,\nhigh-- high frequencies,", "start": 3037.76, "duration": 3.57}, {"text": "low frequencies,\nhigh frequencies,", "start": 3041.33, "duration": 1.68}, {"text": "in that V-shaped pattern.", "start": 3043.01, "duration": 2.94}, {"text": "So this is the right hemisphere.", "start": 3045.95, "duration": 1.373}, {"text": "This is the left\nhemisphere that's", "start": 3047.323, "duration": 1.417}, {"text": "been mirror flipped so you\ncan compare them directly.", "start": 3048.74, "duration": 2.37}, {"text": "And you can see this highly\nstereotyped pattern of high,", "start": 3051.11, "duration": 3.6}, {"text": "low, high.", "start": 3054.71, "duration": 0.6}, {"text": "That's a tonotopic map.", "start": 3055.31, "duration": 1.41}, {"text": "Everybody clear on what\na tonotopic map is?", "start": 3056.72, "duration": 3.09}, {"text": "And we've just discretized\nit into two chunks,", "start": 3059.81, "duration": 2.7}, {"text": "but it's actually a gradient\nof high to low to high,", "start": 3062.51, "duration": 3.3}, {"text": "which you can kind of see\nby those intermediate colors", "start": 3065.81, "duration": 2.34}, {"text": "in there.", "start": 3068.15, "duration": 0.72}, {"text": "Yeah.", "start": 3068.87, "duration": 1.82}, {"text": "STUDENT: [INAUDIBLE] why\ndoes the [INAUDIBLE]??", "start": 3070.69, "duration": 7.352}, {"text": "NANCY KANWISHER: Yeah,\neverything in the brain", "start": 3082.24, "duration": 2.73}, {"text": "rearranges everything in\nthe input in multiple ways.", "start": 3084.97, "duration": 3.42}, {"text": "So we didn't talk about\nthis, but in visual cortex,", "start": 3088.39, "duration": 2.16}, {"text": "you have--", "start": 3090.55, "duration": 0.81}, {"text": "I don't know what the latest\ncount is, at least 10,", "start": 3091.36, "duration": 2.16}, {"text": "probably more than that,\nseparate retinotopic maps", "start": 3093.52, "duration": 3.12}, {"text": "in different patches of cortex--\nmap, map, map, map, loads", "start": 3096.64, "duration": 2.82}, {"text": "of them.", "start": 3099.46, "duration": 1.17}, {"text": "And so there's all kinds\nof transformations.", "start": 3100.63, "duration": 3.33}, {"text": "And so much less is known about\nthe functional responses and", "start": 3103.96, "duration": 4.74}, {"text": "functional organization\nof auditory cortex", "start": 3108.7, "duration": 2.22}, {"text": "than visual cortex, especially\nin humans where we really", "start": 3110.92, "duration": 4.08}, {"text": "don't know a lot, in fact.", "start": 3115.0, "duration": 2.01}, {"text": "So there's no real\nanswer to that, other", "start": 3117.01, "duration": 2.76}, {"text": "than it's not that\nshocking, in a way,", "start": 3119.77, "duration": 5.195}, {"text": "because you see that in\nvision and in other domains", "start": 3124.965, "duration": 2.125}, {"text": "anyway, with multiple maps\nthat differentially represent", "start": 3127.09, "duration": 3.03}, {"text": "different parts of space.", "start": 3130.12, "duration": 2.26}, {"text": "And so yeah, I didn't\nsay this, but many", "start": 3132.38, "duration": 1.7}, {"text": "of those dozen or so\nmaps in visual cortex", "start": 3134.08, "duration": 4.08}, {"text": "have differential representation\nof different parts of space.", "start": 3138.16, "duration": 3.828}, {"text": "Some focus on the\nupper visual field,", "start": 3141.988, "duration": 1.542}, {"text": "some on the lower visual field.", "start": 3143.53, "duration": 1.62}, {"text": "And the whole question of\nis that really one thing", "start": 3145.15, "duration": 4.32}, {"text": "or is it two--", "start": 3149.47, "duration": 1.56}, {"text": "this is all now\ngetting into the kind", "start": 3151.03, "duration": 2.07}, {"text": "of cutting-edge, ambiguous\nstate that we don't know.", "start": 3153.1, "duration": 5.03}, {"text": "All right, everybody clear\non tonotopy, primary auditory", "start": 3158.13, "duration": 2.41}, {"text": "cortex?", "start": 3160.54, "duration": 0.5}, {"text": "OK, good.", "start": 3161.04, "duration": 1.26}, {"text": "All right, the standard\nview from recording neurons", "start": 3162.3, "duration": 4.29}, {"text": "in primary auditory\ncortex in animals--", "start": 3166.59, "duration": 3.54}, {"text": "monkeys, ferrets are big\nin auditory neuroscience,", "start": 3170.13, "duration": 3.9}, {"text": "other animals--", "start": 3174.03, "duration": 2.25}, {"text": "is that the receptive\nfields of individual", "start": 3176.28, "duration": 2.49}, {"text": "neurons in primary\nauditory cortex", "start": 3178.77, "duration": 2.34}, {"text": "are linear filters in\nthe following sense--", "start": 3181.11, "duration": 3.57}, {"text": "so here's a\nspectrogram of a sound.", "start": 3184.68, "duration": 2.1}, {"text": "This is just a description\nof the stimulus.", "start": 3186.78, "duration": 1.92}, {"text": "As usual, time, frequency.", "start": 3188.7, "duration": 3.09}, {"text": "So it looks like it could be a\nspeech sound with some vowels", "start": 3191.79, "duration": 2.64}, {"text": "there.", "start": 3194.43, "duration": 0.24}, {"text": "Or it might be something else.", "start": 3194.67, "duration": 1.25}, {"text": "Who knows.", "start": 3195.92, "duration": 1.93}, {"text": "So that's a sound.", "start": 3197.85, "duration": 1.95}, {"text": "So now, imagine an\nelectrode sitting", "start": 3199.8, "duration": 5.22}, {"text": "next to a single neuron\nin primary auditory", "start": 3205.02, "duration": 3.75}, {"text": "cortex in, say, a ferret\nlistening to that sound,", "start": 3208.77, "duration": 3.33}, {"text": "and characterizing what\ndoes that neuron respond to.", "start": 3212.1, "duration": 3.21}, {"text": "Well, the typical\nfinding is that neurons", "start": 3215.31, "duration": 2.43}, {"text": "in primary auditory\ncortex are what's", "start": 3217.74, "duration": 3.15}, {"text": "known as spectral temporal\nreceptive fields, or STRFs", "start": 3220.89, "duration": 4.2}, {"text": "to their friends.", "start": 3225.09, "duration": 2.07}, {"text": "So what does that mean?", "start": 3227.16, "duration": 1.33}, {"text": "Here's an example of\nthe receptive field that", "start": 3228.49, "duration": 3.38}, {"text": "is the response dependence\nof a given auditory cell,", "start": 3231.87, "duration": 3.96}, {"text": "again, with time on this axis\nand frequency on that axis.", "start": 3235.83, "duration": 3.85}, {"text": "So what kind of sound\ndoes that cell like?", "start": 3239.68, "duration": 4.115}, {"text": "Can you see just\nby looking at this?", "start": 3249.239, "duration": 1.929}, {"text": "What kind of sound?", "start": 3251.168, "duration": 0.792}, {"text": "STUDENT: Increasing frequency.", "start": 3254.55, "duration": 1.29}, {"text": "NANCY KANWISHER:\nIncreasing frequency, yeah,", "start": 3255.84, "duration": 2.13}, {"text": "something like that right.", "start": 3257.97, "duration": 2.31}, {"text": "Here's one that also likes\nincreasing frequency,", "start": 3260.28, "duration": 2.67}, {"text": "but slower, shallower\nincreasing frequency.", "start": 3262.95, "duration": 3.6}, {"text": "Here's one that likes\ndecreasing frequency.", "start": 3266.55, "duration": 2.34}, {"text": "Now, you may be wondering\nwhat the stripes are.", "start": 3268.89, "duration": 2.19}, {"text": "We didn't talk about\nthis in visual cortex,", "start": 3271.08, "duration": 1.99}, {"text": "but this is a common\nproperty, that it", "start": 3273.07, "duration": 1.94}, {"text": "likes this particular\nset of frequencies", "start": 3275.01, "duration": 2.31}, {"text": "here, but is inhibited\nby adjacent frequencies.", "start": 3277.32, "duration": 4.59}, {"text": "So you also see something like\nthat with orientation tuning", "start": 3281.91, "duration": 3.75}, {"text": "in primary visual cortex.", "start": 3285.66, "duration": 3.78}, {"text": "And so here, these ones\nare changing faster,", "start": 3289.44, "duration": 4.26}, {"text": "both increasing and decreasing.", "start": 3293.7, "duration": 2.05}, {"text": "So the idea is primary\nauditory cortex in animals,", "start": 3295.75, "duration": 3.2}, {"text": "and presumably in humans,\nis full of a bunch", "start": 3298.95, "duration": 3.63}, {"text": "of cells that are basically\nspectrotemporal filters", "start": 3302.58, "duration": 3.0}, {"text": "like this.", "start": 3305.58, "duration": 1.02}, {"text": "They are picking out\nchanges in frequency", "start": 3306.6, "duration": 2.7}, {"text": "over time that happen\nto different degrees,", "start": 3309.3, "duration": 3.12}, {"text": "and at different rates, and\nin different frequency ranges.", "start": 3312.42, "duration": 5.382}, {"text": "Does that make\nsense, more or less?", "start": 3317.802, "duration": 1.458}, {"text": "Yes, [INAUDIBLE]", "start": 3319.26, "duration": 1.125}, {"text": "STUDENT: I have a question.", "start": 3320.385, "duration": 1.125}, {"text": "NANCY KANWISHER: Yeah.", "start": 3321.51, "duration": 0.917}, {"text": "STUDENT: [INAUDIBLE] how would\nyou tell that was [INAUDIBLE]??", "start": 3322.427, "duration": 7.528}, {"text": "NANCY KANWISHER: Yeah, how\ndo they figure that out?", "start": 3329.955, "duration": 2.125}, {"text": "I usually spend all this\ntime talking about the design", "start": 3332.08, "duration": 2.16}, {"text": "of the experiment.", "start": 3334.24, "duration": 0.75}, {"text": "I just skipped straight\nto the answer here.", "start": 3334.99, "duration": 2.98}, {"text": "Well, I don't know exactly\nwhat you do, but you probably--", "start": 3337.97, "duration": 2.75}, {"text": "I mean, this has\nbeen a whole thing", "start": 3340.72, "duration": 1.59}, {"text": "that went on for decades\nfor people to get at this.", "start": 3342.31, "duration": 2.32}, {"text": "So I'm guessing\nthat somehow, they", "start": 3344.63, "duration": 1.75}, {"text": "got into that general\nspace, and then they", "start": 3346.38, "duration": 1.75}, {"text": "generated stimuli that make\nall these different sounds.", "start": 3348.13, "duration": 2.923}, {"text": "And they just run\nthrough them, and they", "start": 3351.053, "duration": 1.667}, {"text": "find, for a given cell, you\nplay all these different sounds.", "start": 3352.72, "duration": 2.9}, {"text": "You go-- [MAKES SOUNDS],,\net cetera.", "start": 3355.62, "duration": 5.59}, {"text": "I'll spare you more imitations.", "start": 3361.21, "duration": 2.04}, {"text": "You play all these different\nsounds to the animal", "start": 3363.25, "duration": 2.58}, {"text": "and you record the\nresponse of that neuron.", "start": 3365.83, "duration": 1.86}, {"text": "And you would find,\nfor example, that it", "start": 3367.69, "duration": 1.71}, {"text": "responds much more when you\nplay that sound than any", "start": 3369.4, "duration": 1.98}, {"text": "of the others.", "start": 3371.38, "duration": 0.583}, {"text": "Does that make sense?", "start": 3375.305, "duration": 0.875}, {"text": "STUDENT: No, it makes sense.", "start": 3376.18, "duration": 1.717}, {"text": "NANCY KANWISHER: But how\ndo they ever hit on that?", "start": 3377.897, "duration": 2.083}, {"text": "STUDENT: No, what\nI was asking is", "start": 3379.98, "duration": 2.66}, {"text": "that are they using\nseparate [INAUDIBLE]??", "start": 3382.64, "duration": 3.82}, {"text": "NANCY KANWISHER: Oh,\nthe red and the blue?", "start": 3389.43, "duration": 2.31}, {"text": "How exactly they got-- rather\nthan just the simple thing with", "start": 3391.74, "duration": 3.12}, {"text": "just that--", "start": 3394.86, "duration": 1.5}, {"text": "how exactly they arrived on\nthat, I'm not totally sure.", "start": 3396.36, "duration": 3.51}, {"text": "I mean, there are mathematical\nreasons why it makes sense", "start": 3402.77, "duration": 2.61}, {"text": "to have that whole thing rather\nthan just a single stripe,", "start": 3405.38, "duration": 5.22}, {"text": "that I think are\nbeyond the scope", "start": 3410.6, "duration": 1.378}, {"text": "of this lecture for the moment.", "start": 3411.978, "duration": 1.292}, {"text": "But anyway, it wasn't just a\ntotally arbitrary thing to try.", "start": 3413.27, "duration": 4.5}, {"text": "Those are particularly\nuseful kind", "start": 3417.77, "duration": 2.22}, {"text": "of receptive fields for\nrepresenting the input.", "start": 3419.99, "duration": 5.5}, {"text": "So everybody sort of\nclear, approximately,", "start": 3425.49, "duration": 2.31}, {"text": "what this idea is?", "start": 3427.8, "duration": 0.75}, {"text": "So it's very\nlow-level basic, just", "start": 3428.55, "duration": 2.37}, {"text": "are the frequencies going\nup or down, and which range,", "start": 3430.92, "duration": 2.67}, {"text": "and how fast?", "start": 3433.59, "duration": 0.882}, {"text": "That's what primary\nauditory cortex", "start": 3434.472, "duration": 1.458}, {"text": "does organized in this\nmap, this tonotopic map.", "start": 3435.93, "duration": 4.125}, {"text": "So think of primary\nauditory cortex as just", "start": 3445.77, "duration": 2.73}, {"text": "this bank, this big\nset of linear filters", "start": 3448.5, "duration": 2.07}, {"text": "for particular frequency\nchanges over time.", "start": 3450.57, "duration": 3.6}, {"text": "So that's all based\non data from animals,", "start": 3454.17, "duration": 4.05}, {"text": "from recording\nindividual neurons.", "start": 3458.22, "duration": 2.07}, {"text": "But we want to know about\nhumans, not just because that's", "start": 3460.29, "duration": 2.97}, {"text": "what this course is about, but\nwe want to know about humans.", "start": 3463.26, "duration": 2.76}, {"text": "I mean, ferrets are\nnice, but really!", "start": 3466.02, "duration": 2.94}, {"text": "So is that true for humans.", "start": 3468.96, "duration": 2.86}, {"text": "Well, Josh McDermott\nand Sam Norman-Haignere", "start": 3471.82, "duration": 3.08}, {"text": "just published a\npaper a few months ago", "start": 3474.9, "duration": 2.4}, {"text": "in which they\naddressed this question", "start": 3477.3, "duration": 1.71}, {"text": "in a really interesting way.", "start": 3479.01, "duration": 1.912}, {"text": "So here's the logic-- this\nis a little bit technical.", "start": 3480.922, "duration": 2.208}, {"text": "I'm trying to give you the gist.", "start": 3483.13, "duration": 1.01}, {"text": "I hope it works.", "start": 3484.14, "duration": 0.87}, {"text": "Give it a try.", "start": 3485.01, "duration": 1.18}, {"text": "So they generated\nsynthetically, computationally,", "start": 3486.19, "duration": 3.5}, {"text": "what they call\n\"model-matched stimuli.\"", "start": 3489.69, "duration": 2.86}, {"text": "So the idea is this--", "start": 3492.55, "duration": 1.4}, {"text": "the idea is if you\npresent a natural sound--", "start": 3493.95, "duration": 2.52}, {"text": "like a dog barking, or a person\nspeaking, or a toilet flushing,", "start": 3496.47, "duration": 3.15}, {"text": "just some sound that\nyou would hear in life--", "start": 3499.62, "duration": 3.06}, {"text": "and then what they do is they\nmake a synthetic signal that", "start": 3502.68, "duration": 3.81}, {"text": "matches that sound with\nrespect to those STRFs", "start": 3506.49, "duration": 3.45}, {"text": "I just showed you.", "start": 3509.94, "duration": 1.32}, {"text": "That is, if you fed\nthe original sound", "start": 3511.26, "duration": 2.91}, {"text": "and you fed this synthetic\nsound into the STRFs,", "start": 3514.17, "duration": 3.0}, {"text": "you'd get the same\nthing in the STRFs.", "start": 3517.17, "duration": 3.09}, {"text": "So this is a way\nof saying, we're", "start": 3520.26, "duration": 2.07}, {"text": "assuming that those STRFs are\na good description of what", "start": 3522.33, "duration": 2.61}, {"text": "goes on in A1, so\nlet's test that", "start": 3524.94, "duration": 2.43}, {"text": "by taking a big, fancy,\nreal-world sound that", "start": 3527.37, "duration": 2.202}, {"text": "has meaning and\npeople know what it", "start": 3529.572, "duration": 1.458}, {"text": "is, and let's make\na control sound that", "start": 3531.03, "duration": 3.3}, {"text": "matches the in-STRF properties.", "start": 3534.33, "duration": 4.38}, {"text": "And let's see if we\nget the same response", "start": 3538.71, "duration": 1.95}, {"text": "in the brain in that region.", "start": 3540.66, "duration": 3.21}, {"text": "If that model is\na good description", "start": 3543.87, "duration": 1.74}, {"text": "of what that region\ndoes, then you", "start": 3545.61, "duration": 1.56}, {"text": "should get a very\nsimilar response", "start": 3547.17, "duration": 1.65}, {"text": "when you give the synthetic\nsound and the original sound", "start": 3548.82, "duration": 2.97}, {"text": "that you recorded in the world.", "start": 3551.79, "duration": 2.04}, {"text": "So they tested this\non a STRF-like model,", "start": 3553.83, "duration": 3.18}, {"text": "like this thing I\njust described before.", "start": 3557.01, "duration": 2.753}, {"text": "And so just to show you\nwhat these sounds are like--", "start": 3559.763, "duration": 2.167}, {"text": "so here's an original\nsound just recorded", "start": 3561.93, "duration": 2.102}, {"text": "in the world of somebody typing.", "start": 3564.032, "duration": 1.333}, {"text": "[AUDIO PLAYBACK]", "start": 3565.365, "duration": 0.667}, {"text": "[TYPING]", "start": 3566.032, "duration": 4.055}, {"text": "[END PLAYBACK]", "start": 3570.087, "duration": 0.583}, {"text": "OK, OK, OK, that's enough.", "start": 3570.67, "duration": 2.16}, {"text": "I know it's riveting,\nbut so then they run that", "start": 3572.83, "duration": 3.06}, {"text": "through their STRF model.", "start": 3575.89, "duration": 1.11}, {"text": "They get a STRF\ndescription and they", "start": 3577.0, "duration": 2.01}, {"text": "generate a matched stimulus\nfrom their STRF description.", "start": 3579.01, "duration": 3.89}, {"text": "And it sounds like this.", "start": 3582.9, "duration": 1.0}, {"text": "[AUDIO PLAYBACK]", "start": 3583.9, "duration": 0.667}, {"text": "[TYPING]", "start": 3584.567, "duration": 1.623}, {"text": "Pretty good.", "start": 3586.69, "duration": 1.068}, {"text": "It's kind of hard\nto tell them apart.", "start": 3587.758, "duration": 1.542}, {"text": "Sorry, enough.", "start": 3591.85, "duration": 1.47}, {"text": "[END PLAYBACK]", "start": 3593.32, "duration": 1.32}, {"text": "All right.", "start": 3594.64, "duration": 2.093}, {"text": "And you can see\ntheir spectrograms", "start": 3596.733, "duration": 1.417}, {"text": "are really similar.", "start": 3598.15, "duration": 1.92}, {"text": "So for a textury\nthing like typing,", "start": 3600.07, "duration": 2.07}, {"text": "it really captures the\nessence of what's being heard.", "start": 3602.14, "duration": 2.49}, {"text": "We're just telling you\nwhat these control stimuli", "start": 3604.63, "duration": 2.79}, {"text": "sound like.", "start": 3607.42, "duration": 0.953}, {"text": "Let's take another sound,\na person walking in heels.", "start": 3608.373, "duration": 2.167}, {"text": "And you can see all\nthose verticals.", "start": 3610.54, "duration": 1.77}, {"text": "Those are the clicks.", "start": 3612.31, "duration": 0.99}, {"text": "Clicks have energy across\nlots of different frequencies.", "start": 3613.3, "duration": 3.835}, {"text": "And that's what a\nvertical line means--", "start": 3617.135, "duration": 1.625}, {"text": "it means all those\ndifferent-- remember,", "start": 3618.76, "duration": 1.41}, {"text": "this is frequency on this axis.", "start": 3620.17, "duration": 1.292}, {"text": "So a vertical line\nmeans energy at lots", "start": 3621.462, "duration": 1.978}, {"text": "of different frequencies\nnot organized in harmonics,", "start": 3623.44, "duration": 4.14}, {"text": "so it's not pitchy.", "start": 3627.58, "duration": 1.47}, {"text": "Here we go.", "start": 3629.05, "duration": 0.54}, {"text": "[AUDIO PLAYBACK]", "start": 3629.59, "duration": 0.926}, {"text": "[HEELS CLICKING]", "start": 3630.516, "duration": 6.231}, {"text": "[END PLAYBACK]", "start": 3636.747, "duration": 0.583}, {"text": "OK, here's the STRF version,\nthe control stimulus.", "start": 3637.33, "duration": 3.03}, {"text": "[AUDIO PLAYBACK]", "start": 3640.36, "duration": 0.851}, {"text": "[CLICKING]", "start": 3641.211, "duration": 6.383}, {"text": "[END PLAYBACK]", "start": 3647.594, "duration": 0.996}, {"text": "So it captures some of\nit, but not all of it.", "start": 3648.59, "duration": 3.74}, {"text": "It captures the\nsound of each click,", "start": 3652.33, "duration": 1.8}, {"text": "but not the spacing between.", "start": 3654.13, "duration": 1.98}, {"text": "So it's getting the\nlocal properties, but not", "start": 3656.11, "duration": 2.04}, {"text": "all of the properties.", "start": 3658.15, "duration": 2.19}, {"text": "Yeah.", "start": 3660.34, "duration": 0.73}, {"text": "STUDENT: How did you say--", "start": 3661.07, "duration": 1.66}, {"text": "like just the [INAUDIBLE]?", "start": 3662.73, "duration": 1.18}, {"text": "NANCY KANWISHER:\nHow do they make it?", "start": 3663.91, "duration": 1.542}, {"text": "I didn't tell you\nbecause it's complicated.", "start": 3665.452, "duration": 1.908}, {"text": "They basically start with\npink noise, or white noise,", "start": 3667.36, "duration": 3.0}, {"text": "or some kind of noise.", "start": 3670.36, "duration": 1.08}, {"text": "They run it through\ntheir STRF thing.", "start": 3671.44, "duration": 1.925}, {"text": "They run the original sound\nthrough the STRF thing.", "start": 3673.365, "duration": 2.125}, {"text": "They compare them.", "start": 3675.49, "duration": 0.78}, {"text": "And they say, how are we\ngoing to adjust the noise", "start": 3676.27, "duration": 1.35}, {"text": "to make it more like that?", "start": 3677.62, "duration": 1.083}, {"text": "And they just iterate a lot, and\nthey end up with these stimuli.", "start": 3678.703, "duration": 5.297}, {"text": "And you can see\njust looking at it,", "start": 3684.0, "duration": 1.8}, {"text": "they ended up with\nsomething that's", "start": 3685.8, "duration": 1.458}, {"text": "pretty similar in terms\nof the spectrogram.", "start": 3687.258, "duration": 2.832}, {"text": "Let's listen to a\nperson speaking.", "start": 3690.09, "duration": 1.947}, {"text": "Here's the original sound.", "start": 3692.037, "duration": 1.083}, {"text": "[AUDIO PLAYBACK]", "start": 3693.12, "duration": 0.667}, {"text": "- Is that art offers a time\nwarp to the past, as well", "start": 3693.787, "duration": 3.053}, {"text": "as insight.", "start": 3696.84, "duration": 0.525}, {"text": "[END PLAYBACK]", "start": 3697.365, "duration": 0.375}, {"text": "NANCY KANWISHER: OK, now\nI'm going to turn it off.", "start": 3697.74, "duration": 1.8}, {"text": "Here's the synthetic version.", "start": 3699.54, "duration": 1.41}, {"text": "[AUDIO PLAYBACK]", "start": 3700.95, "duration": 0.667}, {"text": "[INAUDIBLE]", "start": 3701.617, "duration": 4.811}, {"text": "[END PLAYBACK]", "start": 3706.428, "duration": 0.942}, {"text": "OK, now we've lost something.", "start": 3707.37, "duration": 1.63}, {"text": "So does everybody see\nhow with keyboard typing,", "start": 3709.0, "duration": 2.78}, {"text": "it really sounds the same,\nthe synthetic version?", "start": 3711.78, "duration": 2.67}, {"text": "With walking in heels,\nkind of, sort of,", "start": 3714.45, "duration": 1.83}, {"text": "at least locally, but not\nglobally, and with speech,", "start": 3716.28, "duration": 3.18}, {"text": "we've just totally lost it.", "start": 3719.46, "duration": 2.23}, {"text": "The stuff that you can\ncapture with a STRF model", "start": 3721.69, "duration": 2.0}, {"text": "does not capture the\nfull richness of speech.", "start": 3723.69, "duration": 2.73}, {"text": "There's something more\nin a speech stimulus", "start": 3726.42, "duration": 2.55}, {"text": "than you can capture with\nthat just simple STRF model.", "start": 3728.97, "duration": 2.842}, {"text": "OK, let's listen to a violin.", "start": 3731.812, "duration": 1.208}, {"text": "[AUDIO PLAYBACK]", "start": 3733.02, "duration": 0.667}, {"text": "[MUSIC PLAYING]", "start": 3733.687, "duration": 5.22}, {"text": "[END PLAYBACK]", "start": 3738.907, "duration": 0.583}, {"text": "OK, what does the STRF\nmodel do with that?", "start": 3739.49, "duration": 1.92}, {"text": "[AUDIO PLAYBACK]", "start": 3741.41, "duration": 0.667}, {"text": "[MUDDY MUSIC PLAYING]", "start": 3742.077, "duration": 3.07}, {"text": "[END PLAYBACK]", "start": 3745.147, "duration": 0.583}, {"text": "I love that.", "start": 3745.73, "duration": 0.5}, {"text": "It sounds like a\nsea lion colony.", "start": 3746.23, "duration": 3.23}, {"text": "Anyway, so what you see\nis the STRF model totally", "start": 3749.46, "duration": 3.41}, {"text": "fails to capture\nspeech and music,", "start": 3752.87, "duration": 2.28}, {"text": "but it captures textury\nsounds like that.", "start": 3755.15, "duration": 3.06}, {"text": "And it loses some of the broader\ntemporal scale information.", "start": 3758.21, "duration": 6.42}, {"text": "So that's the stimuli.", "start": 3764.63, "duration": 3.84}, {"text": "Then you scan people\nlistening to these sounds.", "start": 3768.47, "duration": 3.42}, {"text": "Just pop them in the scanner\nand play those sounds.", "start": 3771.89, "duration": 3.82}, {"text": "And so then what they\ndo is they just ask.", "start": 3775.71, "duration": 3.2}, {"text": "So this is, again, the white\noutline is primary auditory", "start": 3778.91, "duration": 2.82}, {"text": "cortex where you have\nthat frequency map, mapped", "start": 3781.73, "duration": 2.46}, {"text": "in a separate experiment, and\njust plunk down on the brain", "start": 3784.19, "duration": 2.61}, {"text": "here.", "start": 3786.8, "duration": 0.5}, {"text": "We're zooming in on that part\nof the top of the temporal lobe.", "start": 3787.3, "duration": 2.59}, {"text": "And so what's shown\nhere is, for each voxel,", "start": 3789.89, "duration": 3.36}, {"text": "they're showing the correlation\nof the response of that voxel", "start": 3793.25, "duration": 3.6}, {"text": "to the original sound and\nthe synthetic, STRF-y sound.", "start": 3796.85, "duration": 4.62}, {"text": "And what you see is\nthose correlations", "start": 3801.47, "duration": 1.89}, {"text": "are really high in\nprimary auditory cortex.", "start": 3803.36, "duration": 3.15}, {"text": "In other words,\nprimary auditory cortex", "start": 3806.51, "duration": 2.58}, {"text": "responds pretty much the\nsame to the original sound", "start": 3809.09, "duration": 3.06}, {"text": "and the synthetic sound.", "start": 3812.15, "duration": 1.41}, {"text": "It doesn't detect\nthat difference.", "start": 3813.56, "duration": 2.07}, {"text": "But as soon as you get outside\nof primary auditory cortex,", "start": 3815.63, "duration": 3.18}, {"text": "you get something\ntotally different.", "start": 3818.81, "duration": 2.26}, {"text": "And so that was\nexactly the prediction,", "start": 3821.07, "duration": 2.12}, {"text": "is that model that's\nbeing tested here", "start": 3823.19, "duration": 2.28}, {"text": "is a model of how they\nthought primary auditory", "start": 3825.47, "duration": 2.22}, {"text": "cortex worked--", "start": 3827.69, "duration": 1.04}, {"text": "a bank of linear filters.", "start": 3828.73, "duration": 1.69}, {"text": "They test that model by\ngenerating a new set of stimuli", "start": 3830.42, "duration": 3.09}, {"text": "that are matched for\nthose linear filters,", "start": 3833.51, "duration": 2.67}, {"text": "and they get pretty\nmuch the same response", "start": 3836.18, "duration": 1.92}, {"text": "in primary auditory cortex.", "start": 3838.1, "duration": 1.63}, {"text": "So check-- that's a good model\nof primary auditory cortex.", "start": 3839.73, "duration": 3.12}, {"text": "But also, the blue\nshows you much lower", "start": 3842.85, "duration": 1.965}, {"text": "correlation out here.", "start": 3844.815, "duration": 0.875}, {"text": "It is not a good model of stuff\noutside of auditory cortex.", "start": 3845.69, "duration": 3.105}, {"text": "Josh.", "start": 3848.795, "duration": 1.135}, {"text": "STUDENT: So isn't this\nkind of self-fulfilling,", "start": 3849.93, "duration": 2.48}, {"text": "in the sense that I build\nmy synthetic stimuli based", "start": 3852.41, "duration": 4.62}, {"text": "on these kind of\nmodels, and then--", "start": 3857.03, "duration": 2.31}, {"text": "NANCY KANWISHER: It is,\nexcept the models were all", "start": 3859.34, "duration": 2.85}, {"text": "based on animal work and\nthis is human brains.", "start": 3862.19, "duration": 2.7}, {"text": "So this is a way--", "start": 3864.89, "duration": 1.238}, {"text": "but that's exactly right.", "start": 3866.128, "duration": 1.042}, {"text": "It's a way of saying all this\nwork from animals precisely", "start": 3867.17, "duration": 4.83}, {"text": "characterizing\nresponse properties", "start": 3872.0, "duration": 1.8}, {"text": "of individual neurons, which\nyou can do in animals and mostly", "start": 3873.8, "duration": 2.55}, {"text": "not in humans, do\nwe think that's", "start": 3876.35, "duration": 2.25}, {"text": "true of human primary\nauditory cortex?", "start": 3878.6, "duration": 1.86}, {"text": "And yes, it is.", "start": 3880.46, "duration": 0.675}, {"text": "Does everybody get at\nleast the gist of that?", "start": 3881.135, "duration": 1.875}, {"text": "I realize I skipped\nover lots of details", "start": 3883.01, "duration": 2.088}, {"text": "because I want you to\nget the general picture.", "start": 3885.098, "duration": 1.917}, {"text": "Yeah.", "start": 3889.61, "duration": 1.56}, {"text": "STUDENT: What are they\ntrying to achieve by doing", "start": 3891.17, "duration": 2.91}, {"text": "this type of [INAUDIBLE]?", "start": 3894.08, "duration": 1.36}, {"text": "I mean, the hypothesis\nis that the human", "start": 3895.44, "duration": 2.69}, {"text": "and the animal auditory\ncortex is the same?", "start": 3898.13, "duration": 4.543}, {"text": "NANCY KANWISHER: Primary\nauditory cortex, yes.", "start": 3902.673, "duration": 1.917}, {"text": "Yes.", "start": 3904.59, "duration": 0.95}, {"text": "They're basically testing--\nyou derive that model", "start": 3905.54, "duration": 2.31}, {"text": "from the animal work, then\nyou design a test of it,", "start": 3907.85, "duration": 4.03}, {"text": "which is making those\nsynthetic stimuli.", "start": 3911.88, "duration": 2.6}, {"text": "And I left this out\nbecause actually, I", "start": 3914.48, "duration": 1.8}, {"text": "don't think they've done\nthat, but presumably,", "start": 3916.28, "duration": 2.22}, {"text": "if you test those stimuli\nwith single units in ferrets,", "start": 3918.5, "duration": 2.612}, {"text": "you get the same thing.", "start": 3921.112, "duration": 0.958}, {"text": "You get very, very\nsimilar responses", "start": 3922.07, "duration": 1.74}, {"text": "in primary auditory cortex\nto the original sound", "start": 3923.81, "duration": 2.82}, {"text": "and the synthetic version of\nit based on the STRF model.", "start": 3926.63, "duration": 3.05}, {"text": "STUDENT: It's predicated on the\nassumption that both of them", "start": 3929.68, "duration": 2.5}, {"text": "are structurally the same.", "start": 3932.18, "duration": 1.083}, {"text": "NANCY KANWISHER:\nWell, it's testing.", "start": 3933.263, "duration": 1.5}, {"text": "It's asking that question.", "start": 3934.763, "duration": 1.317}, {"text": "It's asking that question.", "start": 3936.08, "duration": 2.32}, {"text": "Because I've occasionally in\nhere lamented about how crappy", "start": 3938.4, "duration": 3.71}, {"text": "our methods are in human\ncognitive neuroscience.", "start": 3942.11, "duration": 2.01}, {"text": "I mean, they're fun.", "start": 3944.12, "duration": 0.833}, {"text": "We can do something, but\nwe hit a wall pretty fast.", "start": 3944.953, "duration": 2.387}, {"text": "We want to see the\nactual neural code.", "start": 3947.34, "duration": 1.85}, {"text": "We don't have spatial\nand temporal resolution", "start": 3949.19, "duration": 2.34}, {"text": "at the same time.", "start": 3951.53, "duration": 1.29}, {"text": "We pretty much only\nget that in animals.", "start": 3952.82, "duration": 1.98}, {"text": "We can pretty much only do\nreally careful causal tests", "start": 3954.8, "duration": 3.58}, {"text": "in animals.", "start": 3958.38, "duration": 0.5}, {"text": "We can pretty much only see\nconnectivity in a precise way.", "start": 3958.88, "duration": 2.91}, {"text": "And all these things we\ncan do only in animals.", "start": 3961.79, "duration": 2.32}, {"text": "And so we need to know if\nthose animal models are", "start": 3964.11, "duration": 3.11}, {"text": "good models for humans.", "start": 3967.22, "duration": 1.012}, {"text": "And this is a way to test it.", "start": 3968.232, "duration": 1.208}, {"text": "And it passed with\nflying colors.", "start": 3969.44, "duration": 2.31}, {"text": "Make sense?", "start": 3971.75, "duration": 2.1}, {"text": "So primary auditory\ncortex seems in humans", "start": 3973.85, "duration": 3.18}, {"text": "that it's much like\nit is in ferrets,", "start": 3977.03, "duration": 1.83}, {"text": "a bank of linear filters\nwith STRF-y properties.", "start": 3978.86, "duration": 3.12}, {"text": "What about everything else?", "start": 3985.42, "duration": 2.1}, {"text": "After all, you guys\ncan hear the difference", "start": 3987.52, "duration": 2.7}, {"text": "between the original version\nand the synthetic version", "start": 3990.22, "duration": 3.03}, {"text": "of the woman talking\nand the violin.", "start": 3993.25, "duration": 2.16}, {"text": "And if I played you\nall the other stimuli", "start": 3995.41, "duration": 1.77}, {"text": "of real-world sounds, you\ncould hear the differences", "start": 3997.18, "duration": 2.167}, {"text": "in many of the\nother ones as well.", "start": 3999.347, "duration": 1.533}, {"text": "So what are you doing?", "start": 4000.88, "duration": 1.31}, {"text": "Well, there's lots\nof auditory cortex", "start": 4002.19, "duration": 1.95}, {"text": "beyond primary auditory\ncortex that could", "start": 4004.14, "duration": 2.76}, {"text": "represent that difference.", "start": 4006.9, "duration": 1.28}, {"text": "And what this is\nsuggesting is, whatever's", "start": 4008.18, "duration": 1.75}, {"text": "going on out here is doing\nsomething really different", "start": 4009.93, "duration": 2.4}, {"text": "with those sounds.", "start": 4012.33, "duration": 0.75}, {"text": "It is not fooled.", "start": 4013.08, "duration": 0.738}, {"text": "It does not think the synthetic\nthing is the same thing", "start": 4013.818, "duration": 2.292}, {"text": "as the original thing.", "start": 4016.11, "duration": 1.132}, {"text": "That's what the low\ncorrelation means.", "start": 4017.242, "duration": 1.583}, {"text": "So I'll tell you about just\none little patch of cortex", "start": 4022.21, "duration": 2.67}, {"text": "out there.", "start": 4024.88, "duration": 1.53}, {"text": "And that is-- again, this\nis just for reference.", "start": 4026.41, "duration": 3.81}, {"text": "We've zoomed in again on\nthis is the little code", "start": 4030.22, "duration": 3.36}, {"text": "for separate mapping of high,\nlow, high, primary auditory", "start": 4033.58, "duration": 2.7}, {"text": "cortex right there.", "start": 4036.28, "duration": 1.71}, {"text": "And what the yellow bands are is\nselective responses to speech.", "start": 4037.99, "duration": 4.717}, {"text": "So you compare a\nwhole bunch of speech", "start": 4042.707, "duration": 1.583}, {"text": "sounds to a whole bunch\nof non-speech sounds,", "start": 4044.29, "duration": 2.55}, {"text": "and you get a band\nof activation right", "start": 4046.84, "duration": 2.88}, {"text": "below primary auditory cortex.", "start": 4049.72, "duration": 2.19}, {"text": "Yes.", "start": 4051.91, "duration": 0.974}, {"text": "STUDENT: I thought the\nseparation was low, high,", "start": 4052.884, "duration": 2.0}, {"text": "medium [INAUDIBLE].", "start": 4054.884, "duration": 2.436}, {"text": "NANCY KANWISHER:\nHigh, low, high--", "start": 4057.32, "duration": 2.09}, {"text": "I probably said it backwards.", "start": 4059.41, "duration": 1.453}, {"text": "That would be like me.", "start": 4060.863, "duration": 0.917}, {"text": "But it's-- wait, wait.", "start": 4061.78, "duration": 2.73}, {"text": "What the hell is it?", "start": 4064.51, "duration": 2.37}, {"text": "I'm pretty sure it's\nhigh, low, high.", "start": 4066.88, "duration": 1.74}, {"text": "Let's go back and look.", "start": 4068.62, "duration": 2.318}, {"text": "I might have screwed it up on\nthe slide or said it backwards,", "start": 4070.938, "duration": 2.542}, {"text": "but I'm pretty sure\nit's high, low, high.", "start": 4073.48, "duration": 5.88}, {"text": "STUDENT: So the low\nfrequency is the [INAUDIBLE]..", "start": 4079.36, "duration": 3.135}, {"text": "NANCY KANWISHER: Yeah, just like\nthat's the code for frequency,", "start": 4082.495, "duration": 2.625}, {"text": "right there.", "start": 4085.12, "duration": 2.64}, {"text": "But ask me those\nquestions because I'm", "start": 4087.76, "duration": 1.64}, {"text": "very capable of getting things\nbackwards, as you've probably", "start": 4089.4, "duration": 2.5}, {"text": "already noticed.", "start": 4091.9, "duration": 0.667}, {"text": "So there is a band of\nspeech-selective cortex just", "start": 4096.069, "duration": 4.231}, {"text": "outside of primary\nauditory cortex,", "start": 4100.3, "duration": 2.16}, {"text": "in that region that we just\nsaw responds differently", "start": 4102.46, "duration": 4.019}, {"text": "to the original sound and the\nmodel-matched synthetic sound.", "start": 4106.479, "duration": 4.831}, {"text": "So that's pretty cool.", "start": 4111.31, "duration": 1.08}, {"text": "What do I mean by\n\"speech-selective cortex?\"", "start": 4112.39, "duration": 2.639}, {"text": "What I mean is--", "start": 4115.029, "duration": 2.851}, {"text": "this is some of our data.", "start": 4117.88, "duration": 1.375}, {"text": "I tried to find you\nsomeone else's data", "start": 4119.255, "duration": 1.625}, {"text": "and I went down a\n45-minute rabbit hole", "start": 4120.88, "duration": 3.203}, {"text": "trying to find a nice slide.", "start": 4124.083, "duration": 1.167}, {"text": "And I just couldn't\nfind a good picture.", "start": 4125.25, "duration": 1.54}, {"text": "I finally said, screw it,\nI'll show you my data,", "start": 4126.79, "duration": 1.58}, {"text": "even though I'm trying to--", "start": 4128.37, "duration": 1.125}, {"text": "we're not the only\nones who've shown this.", "start": 4129.495, "duration": 1.75}, {"text": "We just have the best data.", "start": 4131.245, "duration": 1.145}, {"text": "Other people had tested it with\nfour, five, six conditions.", "start": 4132.39, "duration": 3.12}, {"text": "We tested it with 165 sounds.", "start": 4135.51, "duration": 4.32}, {"text": "So this is the\nmagnitude of response", "start": 4139.83, "duration": 2.04}, {"text": "in that yellow region to 165\ndifferent sounds, color coded", "start": 4141.87, "duration": 4.92}, {"text": "by condition shown down here.", "start": 4146.79, "duration": 2.298}, {"text": "And so what you see\nif you look at it", "start": 4149.088, "duration": 1.542}, {"text": "is all the top sounds are\nlight green and dark green.", "start": 4150.63, "duration": 5.41}, {"text": "Speech-- notice, importantly,\nthat the response", "start": 4156.04, "duration": 5.93}, {"text": "is very similar to English\nspeech and foreign speech", "start": 4161.97, "duration": 3.87}, {"text": "which our subjects\ndo not understand.", "start": 4165.84, "duration": 3.83}, {"text": "So that tells us that this\nis not about language.", "start": 4169.67, "duration": 3.14}, {"text": "This is not about the meaning\nof a sentence, or syntax, or any", "start": 4172.81, "duration": 3.03}, {"text": "of that stuff.", "start": 4175.84, "duration": 1.33}, {"text": "This is about phonemes,\nthe difference", "start": 4177.17, "duration": 2.3}, {"text": "between a ba and a pa, which you\ncan do on a foreign language,", "start": 4179.47, "duration": 2.687}, {"text": "even if there's a few\nphonemes that are different.", "start": 4182.157, "duration": 2.083}, {"text": "You get most of them.", "start": 4184.24, "duration": 1.235}, {"text": "Does everybody\nget the difference", "start": 4185.475, "duration": 1.375}, {"text": "between speech and language?", "start": 4186.85, "duration": 3.91}, {"text": "Amazingly, the senior\nauthor of the paper", "start": 4190.76, "duration": 2.25}, {"text": "you read for last night does\nnot understand that difference.", "start": 4193.01, "duration": 3.39}, {"text": "He published a beautiful paper.", "start": 4196.4, "duration": 1.77}, {"text": "Every time he comes\nhere to speak,", "start": 4198.17, "duration": 1.83}, {"text": "he talks about language,\nlanguage, language, language.", "start": 4200.0, "duration": 2.76}, {"text": "And I say, Eddie, have you ever\npresented a stimulus that's", "start": 4202.76, "duration": 4.32}, {"text": "in a foreign language?", "start": 4207.08, "duration": 0.958}, {"text": "He's, like, oh, no, that'd\nbe really interesting.", "start": 4208.038, "duration": 2.042}, {"text": "It's like, Eddie, until you do\nthat, you don't know if you're", "start": 4210.08, "duration": 3.21}, {"text": "studying language or speech.", "start": 4213.29, "duration": 1.44}, {"text": "Oh, yeah, really interesting.", "start": 4214.73, "duration": 2.07}, {"text": "And then he comes\nback four years later", "start": 4216.8, "duration": 2.312}, {"text": "and he doesn't seem to know\nthe difference between language", "start": 4219.112, "duration": 2.458}, {"text": "and speech.", "start": 4221.57, "duration": 0.5}, {"text": "I'm, like, hello.", "start": 4222.07, "duration": 1.68}, {"text": "Anyway, he does beautiful\nexperiments, but it's just--", "start": 4223.75, "duration": 3.283}, {"text": "it's a blind spot, or\nit's a misuse of a word.", "start": 4227.033, "duration": 1.917}, {"text": "I don't know what it is,\nbut it drives me nuts.", "start": 4228.95, "duration": 1.958}, {"text": "Can you tell?", "start": 4230.908, "duration": 1.642}, {"text": "Anyway, you guys get that\ndifference even if Eddie", "start": 4232.55, "duration": 2.25}, {"text": "doesn't.", "start": 4234.8, "duration": 1.547}, {"text": "Let's look at some other things.", "start": 4236.347, "duration": 1.333}, {"text": "How about all this\nlight blue stuff?", "start": 4237.68, "duration": 1.29}, {"text": "There's a lot of light blue\nstuff that's almost as high.", "start": 4238.97, "duration": 2.46}, {"text": "Oh, that's music\nwith people singing.", "start": 4241.43, "duration": 2.7}, {"text": "That also has speech.", "start": 4244.13, "duration": 2.06}, {"text": "The speech is slightly\nless intelligible", "start": 4246.19, "duration": 1.74}, {"text": "because it's\nsinging, and there's", "start": 4247.93, "duration": 1.375}, {"text": "background instrumental music,\nso it's a little bit lower.", "start": 4249.305, "duration": 3.545}, {"text": "Oh, what's next?", "start": 4252.85, "duration": 0.93}, {"text": "We've got some\nlight purple stuff", "start": 4253.78, "duration": 2.13}, {"text": "and some dark purple stuff.", "start": 4255.91, "duration": 2.4}, {"text": "This is non-speech\nvocalizations.", "start": 4258.31, "duration": 2.25}, {"text": "That's stuff like laughing,\nand crying, and sighing--", "start": 4260.56, "duration": 4.23}, {"text": "pretty similar to\nspeech but not speech.", "start": 4264.79, "duration": 2.31}, {"text": "It's the next highest\nthing, but it's well down", "start": 4267.1, "duration": 2.55}, {"text": "from the speech sounds.", "start": 4269.65, "duration": 2.5}, {"text": "And then we have dogs\nbarking, and geese,", "start": 4272.15, "duration": 1.972}, {"text": "and stuff like that, that\nare yet further down.", "start": 4274.122, "duration": 1.958}, {"text": "And then we have all kinds\nof other stuff down there--", "start": 4276.08, "duration": 2.55}, {"text": "sirens, and toilets,\nand stuff like that.", "start": 4278.63, "duration": 3.3}, {"text": "Yeah.", "start": 4281.93, "duration": 0.69}, {"text": "STUDENT: Is instrumental\nmusic perceived as speech?", "start": 4282.62, "duration": 3.06}, {"text": "I mean, I can't\nmake out the colors.", "start": 4285.68, "duration": 1.942}, {"text": "NANCY KANWISHER: No.", "start": 4287.622, "duration": 0.833}, {"text": "The instrumental music\nis way down in here.", "start": 4288.455, "duration": 3.182}, {"text": "Yeah, it's a little hard to see.", "start": 4291.637, "duration": 1.333}, {"text": "That stuff up there is\nnon-speech vocalizations.", "start": 4292.97, "duration": 2.67}, {"text": "It's not a perfect slide.", "start": 4295.64, "duration": 2.61}, {"text": "So that's pretty strong evidence\nthat that band of cortex", "start": 4298.25, "duration": 4.83}, {"text": "is pretty selective for speech.", "start": 4303.08, "duration": 1.68}, {"text": "Everybody get that?", "start": 4304.76, "duration": 2.89}, {"text": "Yeah.", "start": 4307.65, "duration": 0.5}, {"text": "STUDENT: So you're\nsaying it's not", "start": 4308.15, "duration": 1.417}, {"text": "like it doesn't process\nlike the other one,", "start": 4309.567, "duration": 1.973}, {"text": "so the violin stuff would\nstill be that [INAUDIBLE]", "start": 4311.54, "duration": 3.18}, {"text": "NANCY KANWISHER: Yeah, right.", "start": 4314.72, "duration": 1.98}, {"text": "OK, good point.", "start": 4316.7, "duration": 1.05}, {"text": "Remember when I first showed\nyou the fusiform face area,", "start": 4317.75, "duration": 2.73}, {"text": "I showed you that time where\nit's faces are like this,", "start": 4320.48, "duration": 2.79}, {"text": "staring at dot is like\nthat, looking at objects", "start": 4323.27, "duration": 2.64}, {"text": "is like this.", "start": 4325.91, "duration": 1.412}, {"text": "So I said, OK, there's a little\nbit of a response to things", "start": 4327.322, "duration": 2.458}, {"text": "that aren't faces.", "start": 4329.78, "duration": 0.75}, {"text": "It's just much more to faces.", "start": 4330.53, "duration": 1.83}, {"text": "Now, you guys may\nnot have noticed this", "start": 4332.36, "duration": 1.68}, {"text": "because it went by kind of\nfast, but when I showed you", "start": 4334.04, "duration": 2.73}, {"text": "intracranial data\nfrom the fusiform face", "start": 4336.77, "duration": 2.97}, {"text": "area in that patient who\ngot stimulated there,", "start": 4339.74, "duration": 2.04}, {"text": "and saw the illusory faces,\nthe intracranial data", "start": 4341.78, "duration": 3.0}, {"text": "showed zero response to\nthings that are not faces.", "start": 4344.78, "duration": 3.88}, {"text": "So I think that that's\nbecause functional MRI is", "start": 4348.66, "duration": 3.92}, {"text": "the best we have in spatial\nresolution in the human brain,", "start": 4352.58, "duration": 2.85}, {"text": "except when we have\nintracranial data.", "start": 4355.43, "duration": 2.37}, {"text": "But it's still blurry.", "start": 4357.8, "duration": 0.96}, {"text": "It's blurry because there's\nblood flow and all of that.", "start": 4358.76, "duration": 4.62}, {"text": "So I would guess\nthe same thing here.", "start": 4363.38, "duration": 3.49}, {"text": "In fact, I guess it\nisn't in the paper you", "start": 4366.87, "duration": 2.06}, {"text": "read because he didn't\nhave any non-speech sounds,", "start": 4368.93, "duration": 2.46}, {"text": "but I will show you.", "start": 4371.39, "duration": 1.77}, {"text": "Dana's recording them right\nnow at Children's Hospital,", "start": 4373.16, "duration": 2.43}, {"text": "and we have some other ones\nthat I will show you next time,", "start": 4375.59, "duration": 2.73}, {"text": "of intracranial electrodes.", "start": 4378.32, "duration": 2.22}, {"text": "And they will be even\nmore selective than that.", "start": 4380.54, "duration": 2.49}, {"text": "But this is pretty good already.", "start": 4385.467, "duration": 1.333}, {"text": "Yeah, Nava.", "start": 4386.8, "duration": 1.14}, {"text": "STUDENT: What's the\nhuman non-vocal?", "start": 4387.94, "duration": 1.83}, {"text": "NANCY KANWISHER: I didn't hear.", "start": 4389.77, "duration": 0.42}, {"text": "What?", "start": 4390.19, "duration": 0.5}, {"text": "STUDENT: The human non-vocal?", "start": 4390.69, "duration": 2.08}, {"text": "NANCY KANWISHER: Oh, that's\nlike clapping, and footsteps,", "start": 4392.77, "duration": 5.38}, {"text": "and I forget what else, things\nwhere you hear it and you know", "start": 4398.15, "duration": 4.027}, {"text": "that's a person, but\nit doesn't sound at all", "start": 4402.177, "duration": 1.833}, {"text": "like speaking or speech.", "start": 4404.01, "duration": 2.25}, {"text": "So if it was about\nthe meaning, it", "start": 4406.26, "duration": 1.44}, {"text": "could have been all about\nthe meaning of people,", "start": 4407.7, "duration": 2.08}, {"text": "could be something telling\nyou there's a person there.", "start": 4409.78, "duration": 1.64}, {"text": "Deal with it.", "start": 4411.42, "duration": 0.66}, {"text": "But no, apparently not.", "start": 4412.08, "duration": 1.17}, {"text": "So we're not the first\nones to see this.", "start": 4416.72, "duration": 2.22}, {"text": "We've just tested it\nwith more conditions.", "start": 4418.94, "duration": 1.75}, {"text": "So our evidence for selectivity\nis stronger than everyone", "start": 4420.69, "duration": 2.99}, {"text": "else's.", "start": 4423.68, "duration": 1.92}, {"text": "Given what I've told you today,\ncan you think of a stronger way", "start": 4425.6, "duration": 4.08}, {"text": "to test this?", "start": 4429.68, "duration": 1.77}, {"text": "For example, suppose\nI was worried,", "start": 4431.45, "duration": 3.77}, {"text": "maybe the frequency\ncomposition of the speech", "start": 4435.22, "duration": 3.28}, {"text": "is different than\nthe non-speech.", "start": 4438.5, "duration": 2.7}, {"text": "After all, those\nare just recordings", "start": 4441.2, "duration": 1.68}, {"text": "of natural sounds in the world\nthat we went out and made,", "start": 4442.88, "duration": 2.94}, {"text": "or mostly got off the\nweb, someone else made.", "start": 4445.82, "duration": 5.21}, {"text": "And maybe they differ in\nreally low-level properties.", "start": 4451.03, "duration": 3.07}, {"text": "And so how do we know\nthat that's really", "start": 4454.1, "duration": 2.24}, {"text": "speech selectivity,\nnot just selectivity", "start": 4456.34, "duration": 3.33}, {"text": "for certain frequencies\nor frequency changes?", "start": 4459.67, "duration": 2.65}, {"text": "Yes.", "start": 4462.32, "duration": 0.5}, {"text": "STUDENT: You could run it\nwith the McDermott generate--", "start": 4462.82, "duration": 2.67}, {"text": "NANCY KANWISHER:\nBingo, absolutely.", "start": 4465.49, "duration": 2.25}, {"text": "Everybody get that?", "start": 4467.74, "duration": 0.87}, {"text": "So then we'd know, because\nthose are beautifully", "start": 4471.81, "duration": 2.82}, {"text": "designed to match all\nthose acoustic properties,", "start": 4474.63, "duration": 3.69}, {"text": "match the spectrogram for all\nthose lower level properties.", "start": 4478.32, "duration": 5.5}, {"text": "And McDermott and\nNorman-Haigenere", "start": 4483.82, "duration": 1.7}, {"text": "have done that.", "start": 4485.52, "duration": 0.93}, {"text": "And this region does\nnot respond strongly", "start": 4486.45, "duration": 2.94}, {"text": "to the model-matched\nversion, so it's not", "start": 4489.39, "duration": 1.92}, {"text": "just the acoustic properties.", "start": 4491.31, "duration": 1.38}, {"text": "Yeah.", "start": 4492.69, "duration": 1.17}, {"text": "STUDENT: Can we also do\nsomething like [INAUDIBLE] play", "start": 4493.86, "duration": 2.35}, {"text": "speech backwards?", "start": 4496.21, "duration": 1.4}, {"text": "NANCY KANWISHER: Yes,\npeople have done that, too.", "start": 4497.61, "duration": 3.06}, {"text": "It's a little bit complicated,\nbecause speech backward", "start": 4500.67, "duration": 2.82}, {"text": "sounds a lot like speech.", "start": 4503.49, "duration": 3.12}, {"text": "It's kind of in the\nintermediate zone.", "start": 4506.61, "duration": 2.19}, {"text": "So it balances many\nthings, but one, it", "start": 4508.8, "duration": 2.52}, {"text": "doesn't balance all the\nacoustic properties.", "start": 4511.32, "duration": 2.7}, {"text": "So speech has certain\nonset properties.", "start": 4514.02, "duration": 2.46}, {"text": "I forget how it goes, but\nif you play it backwards,", "start": 4516.48, "duration": 2.29}, {"text": "there's lots of--", "start": 4518.77, "duration": 0.708}, {"text": "[MAKING SOUNDS] You've heard\nbackward speech played, right?", "start": 4519.478, "duration": 3.572}, {"text": "And so the STRF model\nwould respond differently", "start": 4523.05, "duration": 3.99}, {"text": "to forward and backward speech,\nwhereas the STRF model responds", "start": 4527.04, "duration": 3.69}, {"text": "the same to the original\nand the synthetic speech.", "start": 4530.73, "duration": 3.27}, {"text": "Make sense?", "start": 4534.0, "duration": 2.37}, {"text": "So there's a very\nspeech-selective patch", "start": 4536.37, "duration": 3.33}, {"text": "of cortex.", "start": 4539.7, "duration": 2.01}, {"text": "And it's speech selective,\nnot language selective.", "start": 4541.71, "duration": 5.13}, {"text": "And of course, we want to know--", "start": 4546.84, "duration": 1.47}, {"text": "speech is lots of\ndifferent things.", "start": 4548.31, "duration": 2.83}, {"text": "It's what words you're saying.", "start": 4551.14, "duration": 2.45}, {"text": "It's who's saying it.", "start": 4553.59, "duration": 2.07}, {"text": "It's your intonation--\nare you making", "start": 4555.66, "duration": 2.1}, {"text": "a statement, or a\nquestion, or what", "start": 4557.76, "duration": 1.68}, {"text": "are you emphasizing\nin the sentence?", "start": 4559.44, "duration": 1.83}, {"text": "And it's lots of other things.", "start": 4561.27, "duration": 1.83}, {"text": "And the paper you read\nasked that question.", "start": 4563.1, "duration": 2.49}, {"text": "What's coded here about speech?", "start": 4565.59, "duration": 1.68}, {"text": "And so I made a\nwhole bunch of slides", "start": 4569.8, "duration": 2.01}, {"text": "to explain what the paper\nsaid because I thought people", "start": 4571.81, "duration": 3.195}, {"text": "would have trouble with it.", "start": 4575.005, "duration": 1.125}, {"text": "And everyone nailed\nit, so I'm not even", "start": 4576.13, "duration": 1.26}, {"text": "going to go through them.", "start": 4577.39, "duration": 1.042}, {"text": "Maybe I'll just\nshow one in closing.", "start": 4578.432, "duration": 2.018}, {"text": "So one thing a few\nof you got wrong--", "start": 4580.45, "duration": 2.28}, {"text": "and I totally get why,\nit didn't matter--", "start": 4582.73, "duration": 1.89}, {"text": "is that here is\nthis is one patient,", "start": 4584.62, "duration": 2.32}, {"text": "and this is the bank\nof electrodes placed", "start": 4586.94, "duration": 2.45}, {"text": "on the surface of the brain.", "start": 4589.39, "duration": 1.95}, {"text": "The red bits are\nthe bits where you", "start": 4591.34, "duration": 2.19}, {"text": "could account for the\nneural responses in terms", "start": 4593.53, "duration": 2.19}, {"text": "of any of those models--", "start": 4595.72, "duration": 1.41}, {"text": "intonation, speaker\nidentity, sentence,", "start": 4597.13, "duration": 3.21}, {"text": "or any of the interactions\nbetween those things.", "start": 4600.34, "duration": 2.608}, {"text": "And so that just says\nthat's where the action is,", "start": 4602.948, "duration": 2.042}, {"text": "is those electrodes there.", "start": 4604.99, "duration": 1.8}, {"text": "And that graph down here is\nfrom only three different--", "start": 4606.79, "duration": 4.95}, {"text": "each one is a single electrode,\njust so you get this.", "start": 4611.74, "duration": 2.46}, {"text": "So this critical graph here,\nthat shows electrode E1.", "start": 4614.2, "duration": 4.41}, {"text": "That's one of those\nelectrodes in one patient.", "start": 4618.61, "duration": 3.06}, {"text": "An electrode is typically\n2 millimeters on a side.", "start": 4621.67, "duration": 4.08}, {"text": "It's probably listening to a few\ntens of thousands of neurons.", "start": 4625.75, "duration": 4.78}, {"text": "So it's one or two\norders of magnitude", "start": 4630.53, "duration": 2.06}, {"text": "better than a voxel\nwith functional MRI,", "start": 4632.59, "duration": 1.793}, {"text": "but it's still\naveraging over lots", "start": 4634.383, "duration": 1.417}, {"text": "of neurons, not a single nerve.", "start": 4635.8, "duration": 1.95}, {"text": "STUDENT: The\nquestion [INAUDIBLE]", "start": 4637.75, "duration": 6.46}, {"text": "averaging over [INAUDIBLE] but\nit's averaged over [INAUDIBLE]..", "start": 4644.21, "duration": 5.91}, {"text": "NANCY KANWISHER: Yeah, that was\nthe response of one electrode", "start": 4650.12, "duration": 3.09}, {"text": "listening to male and female.", "start": 4653.21, "duration": 1.65}, {"text": "I forget which is which.", "start": 4654.86, "duration": 2.58}, {"text": "But other than that, you\nguys totally nailed it.", "start": 4657.44, "duration": 2.1}, {"text": "And notice how precise, and\nspecific, and fascinatingly", "start": 4659.54, "duration": 4.47}, {"text": "separated the responses\nof those electrodes", "start": 4664.01, "duration": 2.52}, {"text": "are, segregated for pitch\ncontour, or speaker identity,", "start": 4666.53, "duration": 5.58}, {"text": "or what sentence\nwas being spoken.", "start": 4672.11, "duration": 2.28}, {"text": "Those things seem to\nbe segregated spatially", "start": 4674.39, "duration": 2.01}, {"text": "in the brain at a fine grain.", "start": 4676.4, "duration": 1.61}, {"text": "Whether you'd see it\nwith functional MRI--", "start": 4678.01, "duration": 1.75}, {"text": "you might, might not.", "start": 4679.76, "duration": 1.08}, {"text": "Many of you pointed out we might\nhave not have the resolution.", "start": 4680.84, "duration": 2.712}, {"text": "Think about other\nmethods you might", "start": 4683.552, "duration": 1.458}, {"text": "use to look for that, even if\nwe didn't have the resolution", "start": 4685.01, "duration": 3.93}, {"text": "with a simple binary contrast.", "start": 4688.94, "duration": 2.43}, {"text": "And it's 12:26 and\nI'm going to stop.", "start": 4691.37, "duration": 1.805}, {"text": "I will see you\nguys on Wednesday,", "start": 4693.175, "duration": 1.375}, {"text": "and we will talk about music.", "start": 4694.55, "duration": 2.84}]
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+[{"text": "Today, we are going to continue\nthinking about reactions.", "start": 17.217, "duration": 5.005}, {"text": "Just to remind you, what\ndid we do on Friday?", "start": 24.791, "duration": 2.369}, {"text": "So we introduced-- here's\nwhat we did last time.", "start": 27.16, "duration": 3.704}, {"text": "We talked about constant--\nwe talked about reactions.", "start": 30.864, "duration": 2.969}, {"text": "And there, on Friday, we were\nreally interested in rates--", "start": 33.833, "duration": 4.972}, {"text": "how fast is it happening.", "start": 38.805, "duration": 1.401}, {"text": "So we talked about things that\naffect the reaction rate--", "start": 40.206, "duration": 3.771}, {"text": "concentration.", "start": 43.977, "duration": 1.201}, {"text": "Concentration versus time,\nand how you can measure that.", "start": 45.178, "duration": 4.771}, {"text": "And you can have rate loss based\non experimental measurements.", "start": 49.949, "duration": 6.373}, {"text": "And that can tell you\nthe reaction order.", "start": 56.322, "duration": 3.137}, {"text": "We talked about zero, first,\nsecond-order reactions,", "start": 59.459, "duration": 2.97}, {"text": "the rate constant,\nand then we also", "start": 62.429, "duration": 2.235}, {"text": "talked about the\ntemperature dependence.", "start": 64.664, "duration": 3.137}, {"text": "And at the very end, the role\nof a catalyst in lowering", "start": 67.801, "duration": 2.802}, {"text": "that activation barrier.", "start": 70.603, "duration": 2.903}, {"text": "Today, we're going to talk\nabout how things dissolve.", "start": 73.506, "duration": 3.771}, {"text": "So we're going to\ntalk about solubility,", "start": 77.277, "duration": 5.672}, {"text": "and this has to do with\nreactions because something", "start": 82.949, "duration": 3.504}, {"text": "dissolving is a reaction.", "start": 86.453, "duration": 2.669}, {"text": "But what's going\nto happen is we're", "start": 89.122, "duration": 2.402}, {"text": "going to talk about how that\nreaction finds its happy place.", "start": 91.524, "duration": 4.305}, {"text": "And we know a happy\nplace is a good thing,", "start": 95.829, "duration": 2.736}, {"text": "and it's called equilibrium.", "start": 98.565, "duration": 3.203}, {"text": "And so that's going to\ninvolve talking about things", "start": 101.768, "duration": 2.134}, {"text": "like equilibrium\nconstants, dissolution,", "start": 103.902, "duration": 4.573}, {"text": "we're going to look\nat some examples", "start": 108.475, "duration": 2.268}, {"text": "with ionic compounds-- so salts.", "start": 110.743, "duration": 1.769}, {"text": "We're going to be\ndissolving salts in water", "start": 112.512, "duration": 2.869}, {"text": "and looking at how to think\nabout how much of that", "start": 115.381, "duration": 3.871}, {"text": "dissolves in terms\nof the equilibrium", "start": 119.252, "duration": 2.703}, {"text": "constant for the reaction.", "start": 121.955, "duration": 1.935}, {"text": "So that's the goal today.", "start": 123.89, "duration": 2.436}, {"text": "I want to start, though, by\ntalking about why this matters,", "start": 126.326, "duration": 3.937}, {"text": "and that's directly\nrelated to your goodie bag.", "start": 130.263, "duration": 4.404}, {"text": "So this is something some\nof you may have seen.", "start": 134.667, "duration": 5.272}, {"text": "The data here in\nfrom the '50s is", "start": 139.939, "duration": 2.536}, {"text": "from the Mauna Loa measurements,\nthe top of a volcano.", "start": 142.475, "duration": 5.406}, {"text": "And this is CO2 concentration,\nparts per million", "start": 147.881, "duration": 3.837}, {"text": "in the atmosphere.", "start": 151.718, "duration": 1.268}, {"text": "But if you dig into the ice--", "start": 152.986, "duration": 3.27}, {"text": "we're going to be\ndoing a lot of that", "start": 156.256, "duration": 1.635}, {"text": "here in Boston over\nthe next three months.", "start": 157.891, "duration": 3.303}, {"text": "But if you dig deeper into\nthe ice, in the cores,", "start": 161.194, "duration": 4.337}, {"text": "you go back in time, and\nit's a beautiful thing.", "start": 165.531, "duration": 3.871}, {"text": "The ice as you go down\nis ancient atmosphere.", "start": 169.402, "duration": 4.571}, {"text": "That's cool-- because\nthere's little bubbles.", "start": 173.973, "duration": 2.102}, {"text": "Remember, we talked\nabout the half life", "start": 176.075, "duration": 3.604}, {"text": "of carbon-14 that's trapped from\na living thing breathing it in.", "start": 179.679, "duration": 6.473}, {"text": "Well, you can trap\ndirectly the little bubbles", "start": 186.152, "duration": 2.703}, {"text": "of atmosphere in the ice,\nand that's what happens.", "start": 188.855, "duration": 3.17}, {"text": "And that's why we know what\nCO2 levels-- we're going back", "start": 192.025, "duration": 3.303}, {"text": "almost a million years here.", "start": 195.328, "duration": 1.301}, {"text": "It's 800,000 years of data.", "start": 196.629, "duration": 2.603}, {"text": "And this is a graph that I\nthink many of you have seen.", "start": 199.232, "duration": 4.338}, {"text": "It's going up, a lot.", "start": 203.57, "duration": 3.503}, {"text": "And here it is.", "start": 207.073, "duration": 0.901}, {"text": "Now, this is just\nzooming in on the last 50", "start": 207.974, "duration": 3.537}, {"text": "or so-- this is just the\ndata, the Mauna Loa data.", "start": 211.511, "duration": 4.538}, {"text": "And The reason is\nbecause here we also", "start": 216.049, "duration": 2.035}, {"text": "have another kind of data.", "start": 218.084, "duration": 1.268}, {"text": "So there's a lot of\nattention paid on CO2,", "start": 219.352, "duration": 2.87}, {"text": "and there should be.", "start": 222.222, "duration": 2.002}, {"text": "There is a lot less\nattention paid to what", "start": 224.224, "duration": 4.104}, {"text": "that is doing to our oceans.", "start": 228.328, "duration": 3.403}, {"text": "And this is a reaction that\nwe will talk about more when", "start": 231.731, "duration": 2.603}, {"text": "we talk about acidification.", "start": 234.334, "duration": 1.401}, {"text": "So when we talk about\nacids and bases,", "start": 235.735, "duration": 1.602}, {"text": "which is coming up later--", "start": 237.337, "duration": 2.068}, {"text": "later being Wednesday\nand next week--", "start": 239.405, "duration": 2.837}, {"text": "we'll talk more about this.", "start": 242.242, "duration": 1.134}, {"text": "But I just want to\ntell you that when", "start": 243.376, "duration": 1.969}, {"text": "you have CO2 in the\natmosphere going up,", "start": 245.345, "duration": 3.203}, {"text": "then you also have CO2\nin the ocean going up.", "start": 248.548, "duration": 4.304}, {"text": "So the CO2 in the ocean--", "start": 252.852, "duration": 1.735}, {"text": "the CO2 in the atmosphere is\ngetting absorbed by the ocean.", "start": 254.587, "duration": 6.372}, {"text": "So what?", "start": 260.959, "duration": 1.369}, {"text": "No, it's a lot of what,\nbecause what happens", "start": 262.328, "duration": 4.171}, {"text": "is the CO2 in the ocean--", "start": 266.499, "duration": 2.336}, {"text": "the more CO2 in the ocean--", "start": 268.835, "duration": 2.302}, {"text": "is making the ocean more acidic.", "start": 271.137, "duration": 4.07}, {"text": "So if you just write\nthis number down--", "start": 275.207, "duration": 2.303}, {"text": "because it's so astonishing.", "start": 277.51, "duration": 1.969}, {"text": "Past 200 years, the ocean\nhas become 30% more acidic.", "start": 286.152, "duration": 11.912}, {"text": "Now that is the fastest-known\nchange in the ocean chemistry", "start": 303.903, "duration": 11.545}, {"text": "in 50 million years.", "start": 315.448, "duration": 3.971}, {"text": "That's a big and\nvery sudden change.", "start": 325.992, "duration": 4.838}, {"text": "So the ocean is absorbing about\n22 million tons per day of CO2.", "start": 330.83, "duration": 5.539}, {"text": "And that number is going up.", "start": 336.369, "duration": 1.601}, {"text": "Why does that matter?", "start": 337.97, "duration": 2.536}, {"text": "Maybe it will do\nto the oceans what", "start": 340.506, "duration": 1.468}, {"text": "it's doing to the atmosphere and\nmaking things a little warmer.", "start": 341.974, "duration": 2.67}, {"text": "No, it's doing more,\nbecause when it acidifies,", "start": 344.644, "duration": 4.571}, {"text": "then it has a direct\nimpact on things", "start": 349.215, "duration": 1.968}, {"text": "like this, which is a pteropod.", "start": 351.183, "duration": 5.006}, {"text": "You look at the food\nchain of the ocean-- there", "start": 356.189, "duration": 2.869}, {"text": "are three things at the bottom.", "start": 359.058, "duration": 1.735}, {"text": "That's one of them.", "start": 360.793, "duration": 2.636}, {"text": "I mean, there's plants.", "start": 363.429, "duration": 1.435}, {"text": "There's photosynthesis.", "start": 364.864, "duration": 1.935}, {"text": "And then there's the\nbottom of the food chain.", "start": 366.799, "duration": 2.703}, {"text": "Now you know what's\ngoing to happen", "start": 369.502, "duration": 1.869}, {"text": "when the bottom of the\nfood chain disappears.", "start": 371.371, "duration": 4.17}, {"text": "This is one of the\nmain kinds of animals", "start": 375.541, "duration": 3.137}, {"text": "that lives at the\nbottom of ocean", "start": 378.678, "duration": 1.368}, {"text": "because they've got these very\nsmall calcium carbonate shells.", "start": 380.046, "duration": 4.338}, {"text": "If you make the\nocean just a little", "start": 384.384, "duration": 3.57}, {"text": "more acidic, like we're doing,\nthose shells don't survive,", "start": 387.954, "duration": 5.439}, {"text": "and those animals don't survive.", "start": 393.393, "duration": 3.636}, {"text": "So that's what\nhappens to a pteropod.", "start": 397.029, "duration": 3.237}, {"text": "At the rate we're going--", "start": 400.266, "duration": 2.569}, {"text": "like decades of time from\nnow-- that's what happens.", "start": 402.835, "duration": 4.638}, {"text": "So what you have\nin your goodie bag", "start": 407.473, "duration": 3.17}, {"text": "is a way to see this a\nlittle bit more accelerated.", "start": 410.643, "duration": 4.371}, {"text": "So here's your goodie bag.", "start": 415.014, "duration": 1.335}, {"text": "So I wanted you to--", "start": 416.349, "duration": 1.868}, {"text": "I wanted you to see what's\nhappening in the ocean,", "start": 418.217, "duration": 3.137}, {"text": "and you have now the\ntools to do that.", "start": 421.354, "duration": 1.935}, {"text": "So in your goodie bag,\nyou've got citric powder.", "start": 423.289, "duration": 4.304}, {"text": "Imagine you take a lot of\nlimes, and you squeeze them,", "start": 427.593, "duration": 2.469}, {"text": "and then you dry it all out.", "start": 430.062, "duration": 1.235}, {"text": "And that's what you got--", "start": 431.297, "duration": 1.301}, {"text": "citric acid.", "start": 432.598, "duration": 1.802}, {"text": "Now you're going to mix that\nwith water to change the ph.", "start": 434.4, "duration": 3.704}, {"text": "And you're going to\ndissolve this powder.", "start": 438.104, "duration": 2.803}, {"text": "That's the topic of today's\nlecture-- dissolution", "start": 440.907, "duration": 2.802}, {"text": "and equilibrium.", "start": 443.709, "duration": 1.736}, {"text": "So you're going to\nmix that into water,", "start": 445.445, "duration": 1.634}, {"text": "and you've got a scale\nfrom a previous goodie bag.", "start": 447.079, "duration": 4.939}, {"text": "So my hope is that you've been\nusing that on a daily basis.", "start": 452.018, "duration": 2.803}, {"text": "You take it with you places,\nand you can use that again here.", "start": 454.821, "duration": 3.003}, {"text": "And you'll need that,\nbecause I want you to see", "start": 457.824, "duration": 2.736}, {"text": "how these shells dissolve.", "start": 460.56, "duration": 2.769}, {"text": "And if you lower\nthe acidity more--", "start": 463.329, "duration": 3.57}, {"text": "we don't want to wait 40--", "start": 466.899, "duration": 1.268}, {"text": "well, you can wait\n45 days, but I", "start": 468.167, "duration": 1.735}, {"text": "want you to be able to do\nthese experiments in minutes.", "start": 469.902, "duration": 3.07}, {"text": "So we're going to go a little\nlower in acidity, in ph,", "start": 472.972, "duration": 4.638}, {"text": "but you're going to\nget the same result.", "start": 477.61, "duration": 1.835}, {"text": "You're going to\ndissolve these shells.", "start": 479.445, "duration": 1.568}, {"text": "Some of you are going\non planes, and there's", "start": 485.852, "duration": 3.169}, {"text": "white powder and a scale\ninvolved in this goodie bag.", "start": 489.021, "duration": 5.105}, {"text": "Please don't put that\nin your carry-on.", "start": 494.126, "duration": 4.705}, {"text": "It's just not a good--", "start": 498.831, "duration": 1.001}, {"text": "it really isn't a good idea.", "start": 499.832, "duration": 1.869}, {"text": "We have data-- students sending\nme pictures with the airport", "start": 501.701, "duration": 5.305}, {"text": "screening person.", "start": 507.006, "duration": 2.703}, {"text": "So I love the\nexcitement of thinking", "start": 509.709, "duration": 3.837}, {"text": "about this over Thanksgiving,\nbut put it in your suitcase", "start": 513.546, "duration": 2.402}, {"text": "if you're going to take it home.", "start": 515.948, "duration": 1.302}, {"text": "That's my why this matters.", "start": 519.986, "duration": 3.47}, {"text": "So we're dissolving stuff today.", "start": 523.456, "duration": 1.902}, {"text": "That's the topic.", "start": 525.358, "duration": 0.967}, {"text": "How do things dissolve?", "start": 526.325, "duration": 2.002}, {"text": "There's a citric\npowder, that citric acid", "start": 528.327, "duration": 3.737}, {"text": "that's going to make\nwater more acidic.", "start": 532.064, "duration": 3.37}, {"text": "And again, we're going to move\ninto acids and bases next.", "start": 535.434, "duration": 2.736}, {"text": "Today we're just talking\nabout dissolution.", "start": 538.17, "duration": 2.169}, {"text": "And so here's citric acid.", "start": 540.339, "duration": 2.136}, {"text": "There it is.", "start": 542.475, "duration": 0.667}, {"text": "Now over Thanksgiving, I\nthought I'd throw this in,", "start": 543.142, "duration": 2.136}, {"text": "because you might have\nsugar at the table.", "start": 545.278, "duration": 2.335}, {"text": "You know to call it a c12h22o11.", "start": 547.613, "duration": 3.337}, {"text": "Don't ask for the sugar.", "start": 550.95, "duration": 1.335}, {"text": "If you want to add some\nsugar to something,", "start": 552.285, "duration": 1.768}, {"text": "ask for it by molecular name.", "start": 554.053, "duration": 2.736}, {"text": "But the question is\nwhy do these things", "start": 556.789, "duration": 1.635}, {"text": "dissolve in the first place.", "start": 558.424, "duration": 2.202}, {"text": "There is acetic acid,\ncitric acid, there's sugar.", "start": 560.626, "duration": 5.406}, {"text": "These are molecules\nthat look like that.", "start": 566.032, "duration": 1.868}, {"text": "Why do they dissolve\nin the first place?", "start": 567.9, "duration": 2.369}, {"text": "And the answer is\nbecause of the things", "start": 570.269, "duration": 4.771}, {"text": "that we learned about\nbonding and about things", "start": 575.04, "duration": 4.005}, {"text": "like whether a molecule\nis polar or not.", "start": 579.045, "duration": 4.738}, {"text": "Or in this case, whether\nyou've got the possibility", "start": 583.783, "duration": 3.436}, {"text": "to hydrogen bond or not.", "start": 587.219, "duration": 2.37}, {"text": "And so if you look\nat both of these,", "start": 592.391, "duration": 2.069}, {"text": "you can see that they both\nhave a whole bunch of oh groups", "start": 594.46, "duration": 4.872}, {"text": "that look a whole lot\nlike things we've seen", "start": 599.332, "duration": 3.403}, {"text": "that like to hydrogen bond.", "start": 602.735, "duration": 2.236}, {"text": "You see those ohs\non the end there,", "start": 604.971, "duration": 1.868}, {"text": "both for sugar, around the\noutside, and for citric acid.", "start": 606.839, "duration": 6.073}, {"text": "And so what happens is if I put\na sugar molecule into water,", "start": 612.912, "duration": 5.072}, {"text": "here's a picture of it.", "start": 617.984, "duration": 2.235}, {"text": "There's a picture of it.", "start": 620.219, "duration": 1.402}, {"text": "So there's sugar\nmolecules there.", "start": 621.621, "duration": 1.668}, {"text": "Now they start in a\ncrystal of sugar--", "start": 623.289, "duration": 3.537}, {"text": "you pour your sugar in,\na teaspoon of sugar.", "start": 626.826, "duration": 3.47}, {"text": "And it's in a solid,\nbut then it goes off,", "start": 630.296, "duration": 3.97}, {"text": "and it breaks away\ninto the water.", "start": 634.266, "duration": 2.57}, {"text": "And those little ones\nare the water molecules.", "start": 636.836, "duration": 2.836}, {"text": "Why?", "start": 639.672, "duration": 0.634}, {"text": "Because the water was\nbonding to itself.", "start": 640.306, "duration": 3.704}, {"text": "The water has dipoles--", "start": 644.01, "duration": 1.901}, {"text": "dipole-dipole.", "start": 645.911, "duration": 0.634}, {"text": "Remember that?", "start": 646.545, "duration": 0.568}, {"text": "The water has hydrogen bonds,\nbut the sugar does, too.", "start": 647.113, "duration": 7.207}, {"text": "The sugar does, too.", "start": 654.32, "duration": 1.368}, {"text": "And so the water sees\nthis crystal of sugar,", "start": 655.688, "duration": 3.003}, {"text": "and it says well, hang on.", "start": 658.691, "duration": 1.735}, {"text": "If you come out, we could bond\ntogether in much the same way", "start": 660.426, "duration": 4.471}, {"text": "that we're already\nbonding with each other.", "start": 664.897, "duration": 1.802}, {"text": "The water molecules are already\nbonding with hydrogen dipole.", "start": 666.699, "duration": 2.502}, {"text": "The sugar is like, well I've\ngot hydrogen. I've got dipole.", "start": 669.201, "duration": 3.137}, {"text": "And so it can break off, and it\ndoesn't cost that much energy.", "start": 672.338, "duration": 4.471}, {"text": "In fact, it gains\nenergy by doing this.", "start": 676.809, "duration": 3.971}, {"text": "They can gain.", "start": 680.78, "duration": 0.901}, {"text": "And so this can actually be\na lower energy state overall.", "start": 681.681, "duration": 5.772}, {"text": "Now that's because of\nsomething that many of you", "start": 687.453, "duration": 7.975}, {"text": "have probably heard, and now\nwe can put some bonding to it,", "start": 695.428, "duration": 5.505}, {"text": "but it's because\nlike dissolves like.", "start": 700.933, "duration": 4.905}, {"text": "Oh yeah.", "start": 705.838, "duration": 1.535}, {"text": "That's technical.", "start": 707.373, "duration": 0.967}, {"text": "That's technical because\nnow we know what like means.", "start": 711.143, "duration": 2.703}, {"text": "Like means a type of body.", "start": 713.846, "duration": 2.769}, {"text": "like means a type of--", "start": 716.615, "duration": 1.802}, {"text": "It's like water.", "start": 718.417, "duration": 1.302}, {"text": "It has hydrogen\nbonding potential.", "start": 719.719, "duration": 2.369}, {"text": "Therefore, it's able to\ndissolve in the water.", "start": 722.088, "duration": 4.07}, {"text": "So water has-- well,\nwhat does water have?", "start": 729.028, "duration": 4.204}, {"text": "It's got dipoles, so it\ncan do dipole-dipole stuff.", "start": 733.232, "duration": 4.104}, {"text": "It's got h-bonds.", "start": 737.336, "duration": 1.835}, {"text": "Oh, everything has London.", "start": 739.171, "duration": 3.504}, {"text": "Everything has London.", "start": 742.675, "duration": 3.437}, {"text": "So if you've got\nthose ingredients,", "start": 746.112, "duration": 1.468}, {"text": "if you've got that\nability, if you've got", "start": 747.58, "duration": 2.202}, {"text": "those likes, then you\nmight be able to dissolve.", "start": 749.782, "duration": 2.436}, {"text": "Well, this is called\na polar solvent", "start": 756.422, "duration": 8.775}, {"text": "because the molecules\nthat make it up are polar.", "start": 765.197, "duration": 2.97}, {"text": "They've got dipole.", "start": 770.736, "duration": 1.135}, {"text": "Actually, and so we're very\ninterested in understanding", "start": 771.871, "duration": 3.236}, {"text": "how things mix with\nother things and why", "start": 775.107, "duration": 2.136}, {"text": "they mix with other things.", "start": 777.243, "duration": 2.135}, {"text": "Let's take a look\nat another example.", "start": 779.378, "duration": 2.97}, {"text": "So here we have ethanol.", "start": 782.348, "duration": 1.201}, {"text": "I keep on bringing up ethanol.", "start": 783.549, "duration": 1.868}, {"text": "There might be some served,\nand if you're 21 or over,", "start": 785.417, "duration": 3.003}, {"text": "you can have some.", "start": 788.42, "duration": 1.502}, {"text": "Otherwise, it's illegal.", "start": 789.922, "duration": 3.103}, {"text": "Ethanol up there at the top.", "start": 793.025, "duration": 2.136}, {"text": "Thank goodness, you will say,\nat your Thanksgiving table,", "start": 795.161, "duration": 3.37}, {"text": "it is not methoxymethane.", "start": 798.531, "duration": 2.469}, {"text": "And because if it were, it would\nbe the same chemical formula,", "start": 801.0, "duration": 3.103}, {"text": "but the oh--", "start": 804.103, "duration": 1.234}, {"text": "the o would be in the\nmiddle of the two cs", "start": 805.337, "duration": 2.069}, {"text": "with the ch3s on the\nend, and you wouldn't", "start": 807.406, "duration": 2.169}, {"text": "be able to hydrogen bond it.", "start": 809.575, "duration": 1.168}, {"text": "It would all just be vapor.", "start": 810.743, "duration": 1.935}, {"text": "It'd be vapor.", "start": 812.678, "duration": 1.502}, {"text": "No, but it's ethanol because\nit has hydrogen bonding", "start": 814.18, "duration": 3.103}, {"text": "capabilities.", "start": 817.283, "duration": 0.667}, {"text": "But look at what happens\nif it's heptanol.", "start": 817.95, "duration": 2.002}, {"text": "So all I've done now is I've\ntaken the same end group,", "start": 819.952, "duration": 2.87}, {"text": "and I've given it more\nof a carbon chain.", "start": 822.822, "duration": 5.271}, {"text": "How is that going to\naffect how it dissolves?", "start": 828.093, "duration": 2.703}, {"text": "Given what we just\ntalked about that", "start": 830.796, "duration": 1.602}, {"text": "like dissolve-- they both\nhave hydrogen bond potential.", "start": 832.398, "duration": 4.805}, {"text": "They both have hy-- but\nlook, more and more of it,", "start": 837.203, "duration": 3.169}, {"text": "as you go from ethanol to\nheptanol, more and more", "start": 840.372, "duration": 3.003}, {"text": "and more of it is\nsomething else.", "start": 843.375, "duration": 2.303}, {"text": "It's only London.", "start": 845.678, "duration": 3.67}, {"text": "So what's going to happen\nnow if I put this into water?", "start": 849.348, "duration": 3.036}, {"text": "Well, we can see\nthis going series.", "start": 852.384, "duration": 2.503}, {"text": "Here's methanol, ethanol,\npropanol, butanol, pentanol,", "start": 854.887, "duration": 4.204}, {"text": "hexanol.", "start": 859.091, "duration": 0.801}, {"text": "Heptanol is down at\nthe bottom, and there's", "start": 859.892, "duration": 2.169}, {"text": "the water solubility.", "start": 862.061, "duration": 2.636}, {"text": "We've got to write that down--", "start": 864.697, "duration": 1.301}, {"text": "solubility.", "start": 865.998, "duration": 1.101}, {"text": "So solubility is kind\nof what it sounds like--", "start": 871.37, "duration": 4.371}, {"text": "the ability for a solute--", "start": 875.741, "duration": 4.638}, {"text": "that's the thing\nwe're dissolving--", "start": 880.379, "duration": 1.702}, {"text": "to dissolve in a solvent.", "start": 885.117, "duration": 7.241}, {"text": "That's the thing we're\ntrying to dissolve it into.", "start": 892.358, "duration": 3.87}, {"text": "That's the solubility.", "start": 896.228, "duration": 2.469}, {"text": "And we'll be talking about\nthe maximum solubility", "start": 898.697, "duration": 2.269}, {"text": "in just a few minutes,\nwhich is what we usually--", "start": 900.966, "duration": 2.569}, {"text": "what's the solubility?", "start": 903.535, "duration": 1.302}, {"text": "We often mean the maximum.", "start": 904.837, "duration": 2.803}, {"text": "Well, that's what's\nlisted here--", "start": 907.64, "duration": 1.534}, {"text": "the maximum.", "start": 909.174, "duration": 0.501}, {"text": "Methanol, ethanol miscible.", "start": 912.544, "duration": 1.936}, {"text": "So you can put as much as\nyou want, and it'll always", "start": 914.48, "duration": 3.303}, {"text": "keep mixing in with the water.", "start": 917.783, "duration": 2.302}, {"text": "But now look, once you get to\nbutanol, pentanol, hexanol,", "start": 920.085, "duration": 3.437}, {"text": "it starts going down.", "start": 923.522, "duration": 2.202}, {"text": "You can't mix as\nmuch as you want.", "start": 925.724, "duration": 3.304}, {"text": "In fact, it's less\nand less and less,", "start": 929.028, "duration": 1.801}, {"text": "and the reason we now know is\nbecause of what I just said.", "start": 930.829, "duration": 4.839}, {"text": "As you go down, the hydrogen\nbond and dipole-dipole", "start": 935.668, "duration": 4.204}, {"text": "becomes less important\nbecause you've", "start": 939.872, "duration": 1.935}, {"text": "got more and more of the\nmolecule that's only London.", "start": 941.807, "duration": 4.671}, {"text": "And so it's less like the\nwater environment, the bonding", "start": 946.478, "duration": 4.705}, {"text": "environment that the\nwater liked with itself.", "start": 951.183, "duration": 4.605}, {"text": "And so it has more\ntrouble dissolving", "start": 955.788, "duration": 3.27}, {"text": "and being\nenergetically favorable", "start": 959.058, "duration": 1.968}, {"text": "isolated by those\nwater monitors.", "start": 961.026, "duration": 1.568}, {"text": "By the way, does anybody know\nthe origin of the word proof,", "start": 962.594, "duration": 3.537}, {"text": "speaking of ethanol?", "start": 966.131, "duration": 2.469}, {"text": "If you buy a bottle of\nethanol at the supermarket--", "start": 968.6, "duration": 5.139}, {"text": "so there's gin or\nvodka or whatever,", "start": 973.739, "duration": 3.237}, {"text": "and it says it's something\npercent alcohol--", "start": 976.976, "duration": 2.669}, {"text": "20% alcohol, 40 proof.", "start": 979.645, "duration": 2.669}, {"text": "Does anybody know\nwhere that comes from?", "start": 982.314, "duration": 1.669}, {"text": "It's this.", "start": 983.983, "duration": 1.368}, {"text": "It's just-- but\nwhat they did, they", "start": 985.351, "duration": 2.235}, {"text": "didn't know if you were making\ngood alcohol back in the time.", "start": 987.586, "duration": 3.17}, {"text": "And they said,\nwell, I don't have", "start": 990.756, "duration": 2.302}, {"text": "all these detailed abilities\nto measure and quantify it,", "start": 993.058, "duration": 2.803}, {"text": "so I was going to\nlight it on fire.", "start": 995.861, "duration": 3.07}, {"text": "That is exactly what--", "start": 998.931, "duration": 2.102}, {"text": "is this a good bottle of gin?", "start": 1001.033, "duration": 1.802}, {"text": "I don't know.", "start": 1002.835, "duration": 0.8}, {"text": "Let's light it on fire.", "start": 1003.635, "duration": 1.235}, {"text": "That's what they did.", "start": 1007.406, "duration": 1.401}, {"text": "And it turns out that if ethanol\nand water are at 50/50 mixture", "start": 1008.807, "duration": 5.239}, {"text": "or more, it will light on fire.", "start": 1014.046, "duration": 3.303}, {"text": "Don't try that, please.", "start": 1017.349, "duration": 1.969}, {"text": "Don't do these experiments.", "start": 1019.318, "duration": 2.169}, {"text": "But so that meant is this\na good bottle of gin?", "start": 1021.487, "duration": 4.704}, {"text": "Well if it's 50/50, I'm going to\nsay it's a good bottle of gin.", "start": 1026.191, "duration": 3.671}, {"text": "So let's light it on fire.", "start": 1029.862, "duration": 1.234}, {"text": "Oh, it lit on fire.", "start": 1031.096, "duration": 1.368}, {"text": "That's 100% proof\nthat it's good.", "start": 1032.464, "duration": 4.004}, {"text": "That is true.", "start": 1036.468, "duration": 1.669}, {"text": "That is the origin\nof the word proof.", "start": 1038.137, "duration": 3.67}, {"text": "It is proof that it's mixed\nwell, and it's good stuff.", "start": 1041.807, "duration": 4.037}, {"text": "Dissolution-- dissolution--\nwell, what else", "start": 1049.882, "duration": 4.07}, {"text": "can we try to dissolve?", "start": 1053.952, "duration": 2.169}, {"text": "We're dissolving alcohol.", "start": 1056.121, "duration": 1.468}, {"text": "We're going down to heptanol.", "start": 1057.589, "duration": 1.202}, {"text": "We're lucky it's\nnot methoxymethane.", "start": 1058.791, "duration": 3.403}, {"text": "We talked about sugar.", "start": 1062.194, "duration": 1.969}, {"text": "So we've got to have a\nframework, by the way.", "start": 1064.163, "duration": 3.169}, {"text": "Solubility-- the ability\nfor a solute to dissolve.", "start": 1067.332, "duration": 3.07}, {"text": "And now, there's a\ncontext here, right?", "start": 1070.402, "duration": 2.903}, {"text": "Let's suppose I'm\ndissolving sugar.", "start": 1073.305, "duration": 2.469}, {"text": "So sugar-- how are we going\nto write this dissolving down?", "start": 1075.774, "duration": 5.939}, {"text": "Well, sugar is c12h22o11, and\nif we put it in water, we could", "start": 1081.713, "duration": 10.111}, {"text": "we could formally write\nthe whole thing out.", "start": 1091.824, "duration": 3.136}, {"text": "We can write it out.", "start": 1094.96, "duration": 0.901}, {"text": "We can say I'm going\nto add water to it,", "start": 1095.861, "duration": 7.608}, {"text": "and that's going to go to--", "start": 1103.469, "duration": 2.736}, {"text": "it's going to go to\nc12h22o11 plus more water.", "start": 1106.205, "duration": 6.172}, {"text": "But there's something very\nimportant that I'm leaving out,", "start": 1112.377, "duration": 4.171}, {"text": "and when you think\nabout dissolution,", "start": 1116.548, "duration": 1.502}, {"text": "you've got to keep track.", "start": 1118.05, "duration": 2.436}, {"text": "What was it?", "start": 1120.486, "duration": 0.9}, {"text": "Was it a solid?", "start": 1121.386, "duration": 1.335}, {"text": "Was it a liquid?", "start": 1122.721, "duration": 0.901}, {"text": "Or was it something\ndissolved in a liquid?", "start": 1123.622, "duration": 3.504}, {"text": "So this started as a solid,\nso we put an s there.", "start": 1127.126, "duration": 3.236}, {"text": "This started as a liquid.", "start": 1130.362, "duration": 1.702}, {"text": "This is the dissolved\nthing, so we put an aq.", "start": 1132.064, "duration": 3.737}, {"text": "And the aq means aqueous.", "start": 1135.801, "duration": 2.235}, {"text": "It is in an aqueous solution.", "start": 1138.036, "duration": 1.635}, {"text": "It is a dissolved molecule.", "start": 1139.671, "duration": 1.702}, {"text": "And so here, this is a liquid.", "start": 1144.476, "duration": 1.502}, {"text": "Now the other thing\nthat happens is-- well,", "start": 1145.978, "duration": 5.605}, {"text": "the h2o is kind of there.", "start": 1151.583, "duration": 3.671}, {"text": "It's all over the place.", "start": 1155.254, "duration": 1.368}, {"text": "It's that solvent,\nand so we often", "start": 1156.622, "duration": 3.67}, {"text": "leave it out because it's\neverywhere on both sides.", "start": 1160.292, "duration": 4.338}, {"text": "And so often, what\nyou'll see, and we'll", "start": 1164.63, "duration": 1.801}, {"text": "write more of these coming,\nis that you might write", "start": 1166.431, "duration": 3.37}, {"text": "a dissolution of sugar as this.", "start": 1169.801, "duration": 4.505}, {"text": "Solid, and it just goes to\nsomething that is dissolved.", "start": 1174.306, "duration": 5.072}, {"text": "And you know that what\nhappened there is sometimes", "start": 1184.917, "duration": 2.569}, {"text": "you'll also see it like this.", "start": 1187.486, "duration": 1.835}, {"text": "What did you do on the arrow?", "start": 1189.321, "duration": 1.301}, {"text": "I added water.", "start": 1190.622, "duration": 1.969}, {"text": "That's what the arrow did.", "start": 1192.591, "duration": 3.236}, {"text": "We're just getting comfortable\nwith writing these dissolution", "start": 1195.827, "duration": 3.771}, {"text": "reactions.", "start": 1199.598, "duration": 1.134}, {"text": "Now what else can I dissolve?", "start": 1200.732, "duration": 1.302}, {"text": "Well here's another\ngood example--", "start": 1202.034, "duration": 4.237}, {"text": "vitamin A. There's some\nvitamins you can have as much", "start": 1206.271, "duration": 3.737}, {"text": "as you want, pretty much.", "start": 1210.008, "duration": 1.535}, {"text": "Why?", "start": 1211.543, "duration": 0.634}, {"text": "Because they're water-soluble.", "start": 1212.177, "duration": 2.736}, {"text": "And other vitamins\nare fat-soluble.", "start": 1214.913, "duration": 1.769}, {"text": "That means they\ndon't like water as", "start": 1216.682, "duration": 4.671}, {"text": "much as they like the\nhydrophobic molecules", "start": 1221.353, "duration": 6.34}, {"text": "of fat cells.", "start": 1227.693, "duration": 1.067}, {"text": "And so they go\ninto fatty tissue,", "start": 1228.76, "duration": 3.07}, {"text": "where they don't come out.", "start": 1231.83, "duration": 2.669}, {"text": "That's why you not have\nunlimited amounts of vitamin", "start": 1234.499, "duration": 4.305}, {"text": "A. That's not good for you.", "start": 1238.804, "duration": 2.636}, {"text": "But vitamin C-- no problem.", "start": 1241.44, "duration": 2.636}, {"text": "No problem, because it's\ngoing to dissolve in water.", "start": 1244.076, "duration": 4.571}, {"text": "And so your body can take in\nand get rid of as much of it", "start": 1248.647, "duration": 2.603}, {"text": "as you want.", "start": 1251.25, "duration": 0.5}, {"text": "But if it's dissolved\nin fat cells,", "start": 1251.75, "duration": 2.135}, {"text": "that's a different thing.", "start": 1253.885, "duration": 1.068}, {"text": "So vitamin A,\nvitamin C-- and you", "start": 1254.953, "duration": 2.102}, {"text": "can see it right there\nfrom the chemistry.", "start": 1257.055, "duration": 2.069}, {"text": "This is it.", "start": 1259.124, "duration": 0.534}, {"text": "Look at all those oh\ngroups in vitamin c.", "start": 1259.658, "duration": 2.603}, {"text": "Look at that.", "start": 1262.261, "duration": 1.101}, {"text": "Oh, that's going to\nlove hydrogen bonding,", "start": 1263.362, "duration": 2.903}, {"text": "and on vitamin A, you've just\ngot the one all the way down", "start": 1266.265, "duration": 3.036}, {"text": "there at the bottom.", "start": 1269.301, "duration": 1.802}, {"text": "It's hydrophobic.", "start": 1271.103, "duration": 2.269}, {"text": "By the way, in this\nclass, we do not", "start": 1273.372, "duration": 2.702}, {"text": "say the words\nhydrophobic interaction", "start": 1276.074, "duration": 1.769}, {"text": "because that doesn't make sense.", "start": 1277.843, "duration": 1.568}, {"text": "There is no such thing as\na hydrophobic interaction.", "start": 1279.411, "duration": 4.004}, {"text": "No, hydrophobic\ninteraction is misused.", "start": 1283.415, "duration": 5.272}, {"text": "What it really means is that\nsomething that's hydrophobic", "start": 1288.687, "duration": 2.803}, {"text": "likes itself more--", "start": 1291.49, "duration": 2.435}, {"text": "being together with\nitself-- more than it", "start": 1293.925, "duration": 2.47}, {"text": "likes being in the water,\nor something hydrophilic.", "start": 1296.395, "duration": 3.703}, {"text": "That's what is meant, but\nthere's no actual interaction", "start": 1300.098, "duration": 3.404}, {"text": "there.", "start": 1303.502, "duration": 2.035}, {"text": "Hydrophobic, hydrophilic.", "start": 1305.537, "duration": 3.036}, {"text": "Well, those are other things\nyou can think about dissolving.", "start": 1308.573, "duration": 3.304}, {"text": "You can also dissolve\nsalt, and this is what", "start": 1311.877, "duration": 4.171}, {"text": "we're going to use as examples.", "start": 1316.048, "duration": 2.969}, {"text": "And this is a picture\nof a salt crystal.", "start": 1319.017, "duration": 2.002}, {"text": "So we show the sugar,\nand here's salt. Now,", "start": 1321.019, "duration": 3.47}, {"text": "so the thing about salt--", "start": 1324.489, "duration": 1.335}, {"text": "where's my sugar?", "start": 1325.824, "duration": 0.767}, {"text": "There's the sugar, and let's\nput salt underneath it.", "start": 1326.591, "duration": 4.271}, {"text": "The thing about\nsalt, which is really", "start": 1330.862, "duration": 3.704}, {"text": "just a general term for when\nyou have an ionic solid that", "start": 1334.566, "duration": 4.171}, {"text": "can be made from a mixture of\nacids and bases and dissolves", "start": 1338.737, "duration": 3.604}, {"text": "oftentimes a little\nbit, at least in water.", "start": 1342.341, "duration": 4.004}, {"text": "So a salt or an ionic solid--", "start": 1346.345, "duration": 6.506}, {"text": "let's say for now--", "start": 1352.851, "duration": 1.001}, {"text": "this gives something different,\nbecause this breaks apart", "start": 1357.422, "duration": 4.171}, {"text": "into positive and negative\nions that they contain.", "start": 1361.593, "duration": 9.977}, {"text": "So in the case of sodium and\nchlorine-- sodium chloride--", "start": 1371.57, "duration": 3.57}, {"text": "well, that's going\nto dissociate.", "start": 1375.14, "duration": 1.535}, {"text": "If you pour salt in water, then\nhere's the reaction for that.", "start": 1376.675, "duration": 4.304}, {"text": "You've got sodium\nchloride solid.", "start": 1380.979, "duration": 2.536}, {"text": "We put it in water.", "start": 1383.515, "duration": 2.502}, {"text": "That's going to go into ions.", "start": 1386.017, "duration": 1.268}, {"text": "So I put that in water, and\nit's different in the sense", "start": 1394.893, "duration": 3.237}, {"text": "that it doesn't break down\ninto the molecules that", "start": 1398.13, "duration": 3.169}, {"text": "made up the sugar.", "start": 1401.299, "duration": 1.669}, {"text": "It has a particle\nof sugar that's", "start": 1402.968, "duration": 1.635}, {"text": "got millions and millions\nof molecules in it.", "start": 1404.603, "duration": 2.569}, {"text": "Now they dissociate.", "start": 1407.172, "duration": 1.468}, {"text": "That's what the aq means.", "start": 1408.64, "duration": 2.803}, {"text": "Those are neutral.", "start": 1411.443, "duration": 1.034}, {"text": "Here, it's a solid, but\nyou can understand this", "start": 1412.477, "duration": 4.171}, {"text": "from looking at it\nand thinking about it.", "start": 1416.648, "duration": 1.668}, {"text": "Look at the way those water\nmolecules are oriented.", "start": 1418.316, "duration": 3.204}, {"text": "They're pointing to the\ncl with their positivity,", "start": 1421.52, "duration": 4.271}, {"text": "with positive charge.", "start": 1425.791, "duration": 1.468}, {"text": "And they're pointing to the\nsodium with the negative,", "start": 1427.259, "duration": 3.136}, {"text": "and that's how they find\nhappiness in water--", "start": 1430.395, "duration": 3.47}, {"text": "because they're ions, and\nwater can be either way.", "start": 1433.865, "duration": 4.371}, {"text": "It can point its\ndipole in either--", "start": 1438.236, "duration": 2.036}, {"text": "and so it can actually bond.", "start": 1440.272, "duration": 1.234}, {"text": "Remember, the hydrogen has\ngot a little positive charge", "start": 1441.506, "duration": 2.269}, {"text": "because the oxygen took it.", "start": 1443.775, "duration": 2.569}, {"text": "And so that's what\nthe-- it has a dipole,", "start": 1446.344, "duration": 2.203}, {"text": "and that's able to\nturn around and bond", "start": 1448.547, "duration": 2.535}, {"text": "and be happy with\neach of these ions.", "start": 1451.082, "duration": 1.869}, {"text": "That's why salt dissolves--", "start": 1452.951, "duration": 1.535}, {"text": "because it can\nfind a happy place.", "start": 1457.722, "duration": 2.636}, {"text": "Other reasons exist\noutside of this class,", "start": 1460.358, "duration": 2.336}, {"text": "like entropy, thermodynamics.", "start": 1462.694, "duration": 4.538}, {"text": "But this is how we're going\nto picture it as energetically", "start": 1467.232, "duration": 2.469}, {"text": "happy.", "start": 1469.701, "duration": 0.567}, {"text": "It can become happy.", "start": 1470.268, "duration": 1.202}, {"text": "So we've dissolved some things.", "start": 1475.34, "duration": 1.768}, {"text": "We've got to start\nthinking about the thing", "start": 1477.108, "duration": 2.436}, {"text": "that I mentioned before, which\nis how much can I dissolve?", "start": 1479.544, "duration": 4.371}, {"text": "How much can I dissolve?", "start": 1483.915, "duration": 1.735}, {"text": "And in that, it gets\ninto this table here.", "start": 1485.65, "duration": 5.139}, {"text": "There it is.", "start": 1490.789, "duration": 0.634}, {"text": "So that's how much.", "start": 1491.423, "duration": 1.835}, {"text": "And you see it's listed\nthere as moles per 100 grams.", "start": 1493.258, "duration": 5.005}, {"text": "And so that's one\nway to write it.", "start": 1498.263, "duration": 1.768}, {"text": "You could write it as--", "start": 1500.031, "duration": 2.636}, {"text": "it's often the max solubility is\noften what we're interested in.", "start": 1502.667, "duration": 11.612}, {"text": "And you could write it\nin moles per 100 grams.", "start": 1514.279, "duration": 4.705}, {"text": "You could write it\nin moles per liter.", "start": 1518.984, "duration": 4.104}, {"text": "Well that's something that\nwe've already learned.", "start": 1523.088, "duration": 3.17}, {"text": "That's m form last\nFriday, the molarity.", "start": 1526.258, "duration": 4.337}, {"text": "Or it could be in grams.", "start": 1530.595, "duration": 3.103}, {"text": "Sometimes you'll see\nit in grams per liter.", "start": 1533.698, "duration": 2.703}, {"text": "So don't get bogged\ndown by the units.", "start": 1536.401, "duration": 4.238}, {"text": "It's just how much of this\nstuff were you able to dissolve?", "start": 1540.639, "duration": 6.773}, {"text": "If we look at sugar--", "start": 1547.412, "duration": 1.768}, {"text": "here's sugar, here's salt--", "start": 1549.18, "duration": 1.802}, {"text": "how much sugar can dissolve?", "start": 1550.982, "duration": 1.302}, {"text": "I'm not going to cram it in.", "start": 1559.524, "duration": 1.268}, {"text": "So for sugar, the\nmax is 1,800, so I'm", "start": 1563.595, "duration": 10.277}, {"text": "going to do both those units--", "start": 1573.872, "duration": 2.135}, {"text": "1,800 grams per liter.", "start": 1576.007, "duration": 2.77}, {"text": "And if you convert that,\nit's 5.26 moles per liter.", "start": 1578.777, "duration": 5.305}, {"text": "That's how much sugar you\ncan dissolve in water.", "start": 1584.082, "duration": 3.804}, {"text": "By the way, I did a\nquick calculation,", "start": 1587.886, "duration": 1.835}, {"text": "and that's 429 teaspoons.", "start": 1589.721, "duration": 4.238}, {"text": "That's 429 teaspoons.", "start": 1593.959, "duration": 2.569}, {"text": "I don't know what\neverybody is saying--", "start": 1596.528, "duration": 1.902}, {"text": "Coke has so much sugar.", "start": 1598.43, "duration": 2.335}, {"text": "Coke's got only 26\nteaspoons per liter.", "start": 1600.765, "duration": 4.939}, {"text": "You could put a lot\nmore in, if they wanted.", "start": 1605.704, "duration": 3.336}, {"text": "I'll go the other way.", "start": 1609.04, "duration": 1.235}, {"text": "I challenge them to go\nnear the solubility limit.", "start": 1610.275, "duration": 5.505}, {"text": "They're not even close.", "start": 1615.78, "duration": 2.169}, {"text": "Too much sugar.", "start": 1617.949, "duration": 2.803}, {"text": "So salt-- you can also look\nat salt. For salt, what is it?", "start": 1620.752, "duration": 6.707}, {"text": "Salt is 359 grams per\nliter, and then that's it.", "start": 1627.459, "duration": 5.038}, {"text": "That's 6.14.", "start": 1632.497, "duration": 2.736}, {"text": "This is nacl.", "start": 1635.233, "duration": 0.567}, {"text": "It's interesting-- if you\ncompare sodium chloride with", "start": 1640.772, "duration": 3.17}, {"text": "sodium bromide--", "start": 1643.942, "duration": 2.235}, {"text": "so if you look at sodium\nbromide, it's going to be 8.9.", "start": 1646.177, "duration": 9.31}, {"text": "And sodium fluoride\nthere's only going to be 1.", "start": 1655.487, "duration": 4.037}, {"text": "Why?", "start": 1662.16, "duration": 1.134}, {"text": "Because it comes right\ndown to the picture.", "start": 1663.294, "duration": 3.17}, {"text": "I've got to make these happier.", "start": 1666.464, "duration": 2.87}, {"text": "I've got to make them happier.", "start": 1669.334, "duration": 1.501}, {"text": "If you've got the ions there,\nand the water likes it,", "start": 1670.835, "duration": 2.736}, {"text": "but what if they really didn't\nhave a strong ionic bond", "start": 1673.571, "duration": 3.304}, {"text": "to start with?", "start": 1676.875, "duration": 1.134}, {"text": "You can imagine you might\nbe able to get to a higher", "start": 1678.009, "duration": 2.97}, {"text": "amount of dissociation.", "start": 1680.979, "duration": 1.601}, {"text": "Or what if they had a\nvery strong ionic bond?", "start": 1682.58, "duration": 3.337}, {"text": "You might imagine\nthat less of it--", "start": 1685.917, "duration": 1.602}, {"text": "you've got a lower\nmaximum solubility.", "start": 1687.519, "duration": 2.502}, {"text": "So it all kind of goes\ntogether with the things", "start": 1690.021, "duration": 2.97}, {"text": "that we've learned.", "start": 1692.991, "duration": 0.801}, {"text": "But what we're\nreally talking about", "start": 1698.029, "duration": 2.569}, {"text": "is what I need to\ntell you about next.", "start": 1700.598, "duration": 2.369}, {"text": "And that is this idea that we've\nreached a dynamic equilibrium.", "start": 1702.967, "duration": 5.506}, {"text": "We've reached a\ndynamic equilibrium.", "start": 1708.473, "duration": 2.369}, {"text": "So what does that mean?", "start": 1710.842, "duration": 1.768}, {"text": "Well, if it's unsaturated--", "start": 1712.61, "duration": 2.503}, {"text": "so if it's unsaturated,\nI'm way before this limit.", "start": 1715.113, "duration": 4.471}, {"text": "This is salt. That's\nthe limit max.", "start": 1719.584, "duration": 3.871}, {"text": "Max.", "start": 1723.455, "duration": 2.569}, {"text": "What does it mean?", "start": 1726.024, "duration": 2.869}, {"text": "What does it mean\nto be below it?", "start": 1728.893, "duration": 2.536}, {"text": "Well, what does it mean to\neven have reached the maximum", "start": 1731.429, "duration": 2.603}, {"text": "itself?", "start": 1734.032, "duration": 0.5}, {"text": "What it means is not that\nthings aren't dissolving.", "start": 1737.102, "duration": 3.403}, {"text": "What it means is that things\nare reforming, recrystallizing", "start": 1740.505, "duration": 4.037}, {"text": "at the same rate that\nthey're dissolving.", "start": 1744.542, "duration": 3.137}, {"text": "That's what the maximum means,\nand that's an equilibrium.", "start": 1747.679, "duration": 4.171}, {"text": "And that's why we're\ngoing to talk about next.", "start": 1751.85, "duration": 1.902}, {"text": "So if it's unsaturated,\nthere's a nice little molecular", "start": 1753.752, "duration": 2.669}, {"text": "picture.", "start": 1756.421, "duration": 0.634}, {"text": "There's the thing you're\ndissolving, and look at them.", "start": 1757.055, "duration": 2.769}, {"text": "They're going away\ninto solution.", "start": 1759.824, "duration": 2.636}, {"text": "Maybe it's salt\nbreaking up into ions.", "start": 1762.46, "duration": 2.269}, {"text": "Maybe it's sugar.", "start": 1764.729, "duration": 2.002}, {"text": "They're going into solution\nand finding a happy place", "start": 1766.731, "duration": 2.236}, {"text": "around the water.", "start": 1768.967, "duration": 0.734}, {"text": "But once in a while,\none of them comes back.", "start": 1769.701, "duration": 2.169}, {"text": "You see that little\nparticle there coming back.", "start": 1771.87, "duration": 2.535}, {"text": "That happens.", "start": 1774.405, "duration": 1.369}, {"text": "But much more,\nthey're dissolving.", "start": 1775.774, "duration": 3.57}, {"text": "Then, you reach this point of\nsaturation where it cannot--", "start": 1779.344, "duration": 4.604}, {"text": "where it's going\nto recrystallize,", "start": 1783.948, "duration": 2.469}, {"text": "reform the solid at the\nsame rate that you dissolve.", "start": 1786.417, "duration": 3.104}, {"text": "And that's the place where\nyou can't dissolve anymore.", "start": 1789.521, "duration": 6.106}, {"text": "So what's really\nhappening is that you", "start": 1795.627, "duration": 2.235}, {"text": "have a solute plus a solvent,\nand it's not going one way", "start": 1797.862, "duration": 7.107}, {"text": "as we've been writing it down.", "start": 1804.969, "duration": 3.103}, {"text": "It's going both ways.", "start": 1808.072, "duration": 1.602}, {"text": "So it's actually the solute\nplus the solvent goes like this.", "start": 1809.674, "duration": 3.57}, {"text": "That is what we've\nbeen talking about.", "start": 1813.244, "duration": 1.569}, {"text": "That's dissolution, and that's\nthe predominant mechanism", "start": 1814.813, "duration": 4.904}, {"text": "on the left before\nyou've saturated.", "start": 1819.717, "duration": 2.903}, {"text": "But see, and that\ngoes to some solution.", "start": 1822.62, "duration": 3.504}, {"text": "But see, you can\nalso precipitate.", "start": 1826.124, "duration": 2.069}, {"text": "Precipitation.", "start": 1836.167, "duration": 3.17}, {"text": "And so at the saturated\nsolution, you have--", "start": 1839.337, "duration": 3.537}, {"text": "if it's saturated, then that's\nanother way of saying we've", "start": 1842.874, "duration": 6.406}, {"text": "reached the max possible\nconcentration of the solute.", "start": 1849.28, "duration": 10.01}, {"text": "Remember, the little brackets\nmeans concentration, molarity.", "start": 1859.29, "duration": 6.073}, {"text": "It means that these rates--", "start": 1865.363, "duration": 3.136}, {"text": "thinking back to Friday--", "start": 1868.499, "duration": 1.869}, {"text": "are the same.", "start": 1870.368, "duration": 2.035}, {"text": "It means these\nrates are the same.", "start": 1872.403, "duration": 2.937}, {"text": "This is a dynamic equilibrium.", "start": 1875.34, "duration": 2.736}, {"text": "And so that's what we need\nnow the tools to talk about.", "start": 1878.076, "duration": 3.403}, {"text": "And so we're going to\ntalk about three things--", "start": 1881.479, "duration": 4.037}, {"text": "the reaction quotient, the\nequilibrium constant k,", "start": 1885.516, "duration": 4.672}, {"text": "chemical equilibrium, and\nthen the solubility product.", "start": 1890.188, "duration": 3.603}, {"text": "Now if you think about--", "start": 1893.791, "duration": 2.503}, {"text": "I just said this is like\nthe forward reaction is", "start": 1896.294, "duration": 2.069}, {"text": "going in the same--", "start": 1898.363, "duration": 2.302}, {"text": "it's happening in the\nsame rate as the reverse.", "start": 1900.665, "duration": 2.636}, {"text": "And so if you think about\nthis as like a graph", "start": 1903.301, "duration": 4.671}, {"text": "of concentrations--", "start": 1907.972, "duration": 2.836}, {"text": "so I'll just put here\nconcentrations and time--", "start": 1910.808, "duration": 5.84}, {"text": "then maybe I have started--", "start": 1916.648, "duration": 2.135}, {"text": "I've put my salt. I pour a\nteaspoon of salt in water,", "start": 1918.783, "duration": 5.639}, {"text": "and the salt is dissolving.", "start": 1924.422, "duration": 4.805}, {"text": "So it's going into the products.", "start": 1929.227, "duration": 2.402}, {"text": "It starts out at\nzero in solution,", "start": 1931.629, "duration": 2.536}, {"text": "and then it becomes products.", "start": 1934.165, "duration": 3.437}, {"text": "At the same time, maybe\nI've started it up here,", "start": 1942.473, "duration": 4.104}, {"text": "and these are the reactants--", "start": 1946.577, "duration": 1.202}, {"text": "Gesundheit-- that\nlook like this--", "start": 1947.779, "duration": 2.435}, {"text": "Gesundheit-- and those\nwould be the reactants.", "start": 1950.214, "duration": 2.303}, {"text": "So the concentrations\nof these things--", "start": 1955.353, "duration": 2.603}, {"text": "at a certain point,\nthey're changing.", "start": 1957.956, "duration": 3.336}, {"text": "And then, at a certain\npoint, they're not changing.", "start": 1961.292, "duration": 3.637}, {"text": "But they're still reactions\nhappening back and forth", "start": 1964.929, "duration": 3.303}, {"text": "like I just showed you.", "start": 1968.232, "duration": 0.935}, {"text": "It's a dynamic equilibrium.", "start": 1969.167, "duration": 3.403}, {"text": "Now what we do is we write down\nfor some arbitrary reaction--", "start": 1972.57, "duration": 3.637}, {"text": "aa plus, so let's\ngo back to this one.", "start": 1976.207, "duration": 3.437}, {"text": "But now, we're going to\nwrite it going both ways--", "start": 1979.644, "duration": 3.07}, {"text": "cc plus dd.", "start": 1982.714, "duration": 3.236}, {"text": "You can define the\nreaction quotient q--", "start": 1985.95, "duration": 2.536}, {"text": "that's the first thing--", "start": 1988.486, "duration": 1.668}, {"text": "as the concentrations\nc of the products--", "start": 1990.154, "duration": 5.039}, {"text": "c to the c, d to the d,\nover a to the a, b to the b.", "start": 1995.193, "duration": 10.51}, {"text": "Please do not confuse\nthis with the rates.", "start": 2005.703, "duration": 4.638}, {"text": "Yeah.", "start": 2010.341, "duration": 0.501}, {"text": "I've been talking about\nthe rates being equal.", "start": 2010.842, "duration": 2.636}, {"text": "That's not from the rates.", "start": 2013.478, "duration": 1.701}, {"text": "Remember, the exponents\nof the rate law", "start": 2015.179, "duration": 4.071}, {"text": "come from experimental\nmeasurements.", "start": 2019.25, "duration": 4.438}, {"text": "The reaction quotient comes\nfrom the stoichiometric", "start": 2023.688, "duration": 3.37}, {"text": "coefficients.", "start": 2027.058, "duration": 2.803}, {"text": "Why?", "start": 2029.861, "duration": 1.001}, {"text": "These exponents here have to\ndo literally with probabilities", "start": 2030.862, "duration": 5.071}, {"text": "of reaction, of reacting.", "start": 2035.933, "duration": 3.204}, {"text": "It has to do with the fact\nthat if I've got two of c,", "start": 2039.137, "duration": 4.738}, {"text": "then you multiply the amount\nof c times another amount of c", "start": 2043.875, "duration": 4.905}, {"text": "in the same volume.", "start": 2048.78, "duration": 1.501}, {"text": "It has to do with\nprobabilities of reacting.", "start": 2050.281, "duration": 2.402}, {"text": "That's where you\nget those exponents,", "start": 2052.683, "duration": 1.735}, {"text": "and they're directly from the\nstoichiometric coefficients.", "start": 2054.418, "duration": 3.237}, {"text": "They do not need to be\nexperimentally measured.", "start": 2057.655, "duration": 3.47}, {"text": "Once you have this, you\nhave the reaction quotient.", "start": 2061.125, "duration": 3.003}, {"text": "Now, why is this useful,\nthis reaction quotient?", "start": 2066.764, "duration": 2.736}, {"text": "Well, it's useful because there\nis a very special place where", "start": 2069.5, "duration": 4.838}, {"text": "now it doesn't change anymore.", "start": 2074.338, "duration": 5.205}, {"text": "These concentrations\naren't changing.", "start": 2079.543, "duration": 1.669}, {"text": "Reactions are still happening,\nbut the concentrations", "start": 2081.212, "duration": 2.703}, {"text": "aren't changing-- no change.", "start": 2083.915, "duration": 2.636}, {"text": "If there is no change, then--", "start": 2089.821, "duration": 2.902}, {"text": "Gesundheit-- then q isn't\nchanging because it's just", "start": 2092.723, "duration": 3.204}, {"text": "a ratio of concentrations.", "start": 2095.927, "duration": 2.536}, {"text": "It's a ratio of concentrations\nequal to this whole thing, not", "start": 2098.463, "duration": 4.571}, {"text": "just the top line.", "start": 2103.034, "duration": 2.836}, {"text": "The reaction quotient is\nrelated to the concentrations.", "start": 2105.87, "duration": 5.639}, {"text": "So if the concentration\nzone changes", "start": 2111.509, "duration": 1.501}, {"text": "even if reactions are happening\nstill, it's a constant.", "start": 2113.01, "duration": 3.204}, {"text": "So at this point, q\nequals a constant,", "start": 2116.214, "duration": 5.705}, {"text": "and that is an\nequilibrium constant.", "start": 2121.919, "duration": 3.204}, {"text": "So we'll call it keq.", "start": 2125.123, "duration": 0.9}, {"text": "It's a dynamic equilibrium.", "start": 2130.094, "duration": 2.036}, {"text": "k represents a\ndynamic equilibrium.", "start": 2132.13, "duration": 4.738}, {"text": "And what's really useful about\nk is that for a given reaction,", "start": 2136.868, "duration": 5.839}, {"text": "k is a constant.", "start": 2142.707, "duration": 1.802}, {"text": "I just said it.", "start": 2144.509, "duration": 1.134}, {"text": "But it doesn't\nmatter-- if we're--", "start": 2145.643, "duration": 1.835}, {"text": "it depends on temperature.", "start": 2147.478, "duration": 2.202}, {"text": "But if I keep the temperature\nfixed, k won't change.", "start": 2149.68, "duration": 3.404}, {"text": "It's a constant.", "start": 2153.084, "duration": 2.536}, {"text": "It's the constant that tells\nme where equilibrium is.", "start": 2155.62, "duration": 5.672}, {"text": "It's the constant that tells\nme where equilibrium is.", "start": 2161.292, "duration": 2.202}, {"text": "Now there's one more thing\nthat we've got to write down--", "start": 2167.064, "duration": 3.204}, {"text": "that third one there.", "start": 2170.268, "duration": 1.268}, {"text": "I'm going to put it on here.", "start": 2171.536, "duration": 1.167}, {"text": "So k is an equilibrium constant.", "start": 2179.11, "duration": 1.668}, {"text": "That's a general constant.", "start": 2180.778, "duration": 1.468}, {"text": "But now, I'm going\nto turn my attention", "start": 2182.246, "duration": 2.269}, {"text": "from any old reaction--", "start": 2184.515, "duration": 2.603}, {"text": "my k is actually very general\nconcept for equilibrium.", "start": 2187.118, "duration": 3.003}, {"text": "We are in this class going\nto use it for solubility.", "start": 2190.121, "duration": 4.905}, {"text": "That's how we are using\nthe equilibrium constant.", "start": 2195.026, "duration": 2.469}, {"text": "And so the ksp is the\nsolubility product,", "start": 2200.298, "duration": 11.611}, {"text": "and it's an\nequilibrium constant.", "start": 2211.909, "duration": 4.071}, {"text": "Equilibrium constant that\nis related to solubility.", "start": 2215.98, "duration": 15.582}, {"text": "It is literally the product of\nsolubilities in equilibrium.", "start": 2231.562, "duration": 6.24}, {"text": "That is literally what it means.", "start": 2237.802, "duration": 1.368}, {"text": "So we're going to do some\nexamples to see that.", "start": 2239.17, "duration": 2.502}, {"text": "It's an equilibrium-- so it's\na constant of equilibrium.", "start": 2241.672, "duration": 4.505}, {"text": "And it's called--\nGesundheit-- it's", "start": 2246.177, "duration": 1.468}, {"text": "called the solubility\nproduct, because it's", "start": 2247.645, "duration": 1.935}, {"text": "related to the equilibrium\nof dissolving something,", "start": 2249.58, "duration": 5.773}, {"text": "dissolving some\nsolute in a solvent.", "start": 2255.353, "duration": 4.17}, {"text": "Now we're going to do\nexamples with salts.", "start": 2259.523, "duration": 3.304}, {"text": "So we're going to be\ndissolving salts and talking", "start": 2262.827, "duration": 2.035}, {"text": "about equilibrium constants\nin that dissolution,", "start": 2264.862, "duration": 4.772}, {"text": "otherwise known as the\nsolubility product.", "start": 2269.634, "duration": 2.302}, {"text": "It's just an\nequilibrium constant.", "start": 2271.936, "duration": 2.669}, {"text": "There are many.", "start": 2274.605, "duration": 1.201}, {"text": "This is the one we're\ngoing to care about,", "start": 2275.806, "duration": 1.802}, {"text": "and we're going to\ndo it for salts.", "start": 2277.608, "duration": 1.001}, {"text": "And so one of the\nthings you've got to--", "start": 2278.609, "duration": 1.669}, {"text": "so nacl-- that was kind of easy.", "start": 2280.278, "duration": 3.403}, {"text": "That became a cation and\nan anion in solution.", "start": 2283.681, "duration": 5.205}, {"text": "But salts can be made of\nmany, many different types", "start": 2288.886, "duration": 2.503}, {"text": "of cations, and there's lists\nthat go on and on and on.", "start": 2291.389, "duration": 3.97}, {"text": "Here are some, and\nthey get named.", "start": 2295.359, "duration": 3.037}, {"text": "So here's some of the anions.", "start": 2298.396, "duration": 2.135}, {"text": "Oh, chlorine-- we\njust did that one.", "start": 2300.531, "duration": 3.47}, {"text": "Bromine-- you can\nalso have a carbonate.", "start": 2304.001, "duration": 3.871}, {"text": "You could have chromates,\nhydroxides, oxalates,", "start": 2307.872, "duration": 2.502}, {"text": "sulfates, sulfides, and the\nlist goes on and on and on.", "start": 2310.374, "duration": 5.239}, {"text": "There are many, many of these.", "start": 2315.613, "duration": 1.735}, {"text": "They don't have to\nbe a single atom.", "start": 2317.348, "duration": 1.601}, {"text": "It can be a part of a salt\nthat breaks off and has", "start": 2318.949, "duration": 4.772}, {"text": "a negative charge.", "start": 2323.721, "duration": 0.834}, {"text": "That's an anion, and here\nare some of the cations--", "start": 2324.555, "duration": 3.203}, {"text": "sodium, potassium, calcium.", "start": 2327.758, "duration": 3.07}, {"text": "And you know about these things.", "start": 2330.828, "duration": 1.335}, {"text": "We've been talking\nabout these things.", "start": 2332.163, "duration": 3.904}, {"text": "And you know if it's sodium,\nthen you know it's only going", "start": 2336.067, "duration": 3.97}, {"text": "to lose-- it's only\ngoing to be na+.", "start": 2340.037, "duration": 2.67}, {"text": "It doesn't have a second\nweakly-bonded electron to lose.", "start": 2342.707, "duration": 5.105}, {"text": "So it's really only\ngoing to be na+.", "start": 2347.812, "duration": 1.968}, {"text": "But then you get--", "start": 2349.78, "duration": 1.135}, {"text": "and calcium is going\nto be calcium 2+.", "start": 2350.915, "duration": 2.836}, {"text": "It's got two, magnesium two.", "start": 2353.751, "duration": 1.635}, {"text": "And then transition metals\nare a little more complicated.", "start": 2355.386, "duration": 5.138}, {"text": "They can be a little\nmore complicated.", "start": 2360.524, "duration": 2.169}, {"text": "Iron can be 2+ or 3+.", "start": 2362.693, "duration": 1.669}, {"text": "It depends, and on and\non and on for those.", "start": 2364.362, "duration": 5.071}, {"text": "And so we'll do a few examples.", "start": 2369.433, "duration": 2.436}, {"text": "We'll do a few examples.", "start": 2371.869, "duration": 1.001}, {"text": "We'll get into the mood.", "start": 2375.673, "duration": 2.169}, {"text": "And I want to do it-- first, I'm\ngoing to do an example that's", "start": 2377.842, "duration": 2.569}, {"text": "actually a classic\nexample, because it", "start": 2380.411, "duration": 1.735}, {"text": "doesn't dissolve very well,\nbut it's silver chloride.", "start": 2382.146, "duration": 3.036}, {"text": "Now sodium chloride is--", "start": 2385.182, "duration": 2.203}, {"text": "sodium chloride goes all the way\nto the point where it basically", "start": 2387.385, "duration": 5.438}, {"text": "dissolves so well.", "start": 2392.823, "duration": 1.569}, {"text": "So you can imagine\nthe equilibrium", "start": 2396.994, "duration": 1.769}, {"text": "for sodium chloride\ngoes way to the right.", "start": 2398.763, "duration": 3.036}, {"text": "But for silver chloride,\nit's different.", "start": 2401.799, "duration": 2.569}, {"text": "For silver chloride,\nit's different.", "start": 2404.368, "duration": 1.502}, {"text": "So we're going to\nlook at this curve.", "start": 2405.87, "duration": 2.469}, {"text": "And I'll talk about this curve.", "start": 2408.339, "duration": 1.301}, {"text": "Don't worry.", "start": 2409.64, "duration": 0.567}, {"text": "We're coming to it.", "start": 2410.207, "duration": 1.368}, {"text": "We are coming to it.", "start": 2411.575, "duration": 1.235}, {"text": "Let me start in\nthe middle again.", "start": 2412.81, "duration": 3.704}, {"text": "Because what the\nequilibrium constant", "start": 2416.514, "duration": 2.702}, {"text": "does, given the definition\nthat I have just hidden,", "start": 2419.216, "duration": 3.07}, {"text": "unfortunately, is it allows\nus to go back and forth.", "start": 2422.286, "duration": 5.739}, {"text": "If I know the\nequilibrium constant,", "start": 2428.025, "duration": 2.202}, {"text": "then I can get how much one\nof these ions is soluble.", "start": 2430.227, "duration": 5.773}, {"text": "I can get the maximum\nsolubility of it.", "start": 2436.0, "duration": 3.103}, {"text": "So let's take an example.", "start": 2439.103, "duration": 2.269}, {"text": "So here's a question.", "start": 2441.372, "duration": 1.435}, {"text": "How much agcl dissolves\nin 1 liter of water?", "start": 2442.807, "duration": 16.049}, {"text": "That's such a good question.", "start": 2458.856, "duration": 2.169}, {"text": "I don't know.", "start": 2461.025, "duration": 1.334}, {"text": "But I do know that\nthe solubility product", "start": 2462.359, "duration": 3.27}, {"text": "that this equilibrium\nconstant for sodium chloride", "start": 2465.629, "duration": 2.57}, {"text": "is 1.7 times 10\nto the minus 10th.", "start": 2468.199, "duration": 5.839}, {"text": "Now if I write down the\ndissolution reaction,", "start": 2474.038, "duration": 5.672}, {"text": "sodium chloride solid\nis going to go to--", "start": 2479.71, "duration": 5.239}, {"text": "sorry, sodium silver--\nsilver plus in solution.", "start": 2487.618, "duration": 4.972}, {"text": "So we put the aqueous plus\nchlorine minus in solution.", "start": 2492.59, "duration": 4.004}, {"text": "And it is going to\ngo back and forth.", "start": 2499.763, "duration": 2.036}, {"text": "And so the ksp for this\nis going to equal--", "start": 2505.803, "duration": 3.904}, {"text": "I'm going to go with the\nequation that I wrote down--", "start": 2509.707, "duration": 2.936}, {"text": "the concentration of silver to\nthe 1 times the concentration", "start": 2512.643, "duration": 3.904}, {"text": "of chlorine minus--\nthese are ions--", "start": 2516.547, "duration": 1.935}, {"text": "divided by the concentration\nof silver chloride solid.", "start": 2518.482, "duration": 3.237}, {"text": "Now we get to another thing.", "start": 2526.223, "duration": 1.168}, {"text": "Remember, I got rid of water,\nbecause water is everywhere.", "start": 2527.391, "duration": 4.004}, {"text": "It's the solvent.", "start": 2531.395, "duration": 1.568}, {"text": "So you don't need to put it into\nthese equilibrium calculations.", "start": 2532.963, "duration": 3.904}, {"text": "Well, it's the same\nthing with the solid.", "start": 2536.867, "duration": 5.139}, {"text": "So if I think about\nthis a little bit,", "start": 2542.006, "duration": 3.203}, {"text": "this equilibrium is\nbetween dissolved.", "start": 2545.209, "duration": 4.571}, {"text": "It's between the ions\nthat are dissolving.", "start": 2549.78, "duration": 6.073}, {"text": "But there from this\nreaction, from the way", "start": 2555.853, "duration": 3.67}, {"text": "it's written there, I've got a\nsolid form of silver chloride.", "start": 2559.523, "duration": 5.639}, {"text": "So this is not-- so this is the\nconcentration of solid silver", "start": 2565.162, "duration": 4.905}, {"text": "chloride in the solid.", "start": 2570.067, "duration": 2.836}, {"text": "This is just a constant.", "start": 2572.903, "duration": 2.069}, {"text": "That's not going to change.", "start": 2574.972, "duration": 1.735}, {"text": "That's not going to change.", "start": 2576.707, "duration": 1.134}, {"text": "Common misunderstanding.", "start": 2577.841, "duration": 3.571}, {"text": "It doesn't change.", "start": 2581.412, "duration": 0.867}, {"text": "So we get rid of it, because it\ngets folded into the constant.", "start": 2582.279, "duration": 3.037}, {"text": "That's always the same.", "start": 2585.316, "duration": 2.102}, {"text": "The concentration of\nthis is always the same.", "start": 2587.418, "duration": 3.37}, {"text": "And so we get rid of it.", "start": 2590.788, "duration": 1.368}, {"text": "So now we have the ksp is\nequal to, in this case,", "start": 2592.156, "duration": 6.139}, {"text": "ag+ times cl-.", "start": 2598.295, "duration": 3.971}, {"text": "Talk about solubility product.", "start": 2602.266, "duration": 2.035}, {"text": "Solubilities concentrate.", "start": 2604.301, "duration": 2.236}, {"text": "The solubility is--\nwhen I add this in,", "start": 2606.537, "duration": 2.836}, {"text": "it reaches some\nequilibrium where they're", "start": 2609.373, "duration": 2.135}, {"text": "dissolving and reforming.", "start": 2611.508, "duration": 1.936}, {"text": "I wanted to know at what point\nthat is, what concentrations", "start": 2613.444, "duration": 3.103}, {"text": "is that going to be.", "start": 2616.547, "duration": 1.435}, {"text": "This is them.", "start": 2617.982, "duration": 3.403}, {"text": "So solubility\nproduct-- right there.", "start": 2621.385, "duration": 2.069}, {"text": "I used the definition\nof equilibrium constant.", "start": 2629.426, "duration": 3.604}, {"text": "And now I can use this reaction.", "start": 2633.03, "duration": 3.637}, {"text": "I can use this reaction because\nthe stoichiometric coefficients", "start": 2636.667, "duration": 4.137}, {"text": "tell me--", "start": 2640.804, "duration": 1.602}, {"text": "they tell me both what\nthe exponents there are--", "start": 2642.406, "duration": 2.669}, {"text": "1-- but they also tell me\nthe relative molar amounts", "start": 2645.075, "duration": 4.038}, {"text": "of these things.", "start": 2649.113, "duration": 0.867}, {"text": "It's the same.", "start": 2649.98, "duration": 2.569}, {"text": "So if x equals the\nconcentration of silver plus,", "start": 2652.549, "duration": 4.972}, {"text": "then it must also equal the\nconcentration of cl minus.", "start": 2657.521, "duration": 9.443}, {"text": "If you just let x equal\nthe concentration,", "start": 2666.964, "duration": 1.835}, {"text": "that comes from the reaction.", "start": 2668.799, "duration": 1.235}, {"text": "1 in front of silver,\n1 in front of chlorine.", "start": 2670.034, "duration": 3.003}, {"text": "And so that means now\nthat you can solve it", "start": 2673.037, "duration": 2.669}, {"text": "because x squared is equal to\n1.7 times 10 to the minus 10th,", "start": 2675.706, "duration": 10.544}, {"text": "and x equals 1.3 times\n10 to the minus fifth, m,", "start": 2686.25, "duration": 10.444}, {"text": "and that equals\nthese concentrations.", "start": 2696.694, "duration": 3.47}, {"text": "That equals the\nconcentration of silver plus.", "start": 2700.164, "duration": 1.868}, {"text": "So that is how much,\nin equilibrium-- this", "start": 2702.032, "duration": 2.302}, {"text": "is an equilibrium\nconstant-- that", "start": 2704.334, "duration": 1.369}, {"text": "is how much you will get of\nthese ions dissolved in water.", "start": 2705.703, "duration": 6.773}, {"text": "Now there is a nice way to\nset this up that is often", "start": 2712.476, "duration": 7.741}, {"text": "taught in high school.", "start": 2720.217, "duration": 1.268}, {"text": "I like it.", "start": 2721.485, "duration": 0.734}, {"text": "I think it's a good\nway to keep track.", "start": 2722.219, "duration": 2.97}, {"text": "And so if you were\nwanting to keep track,", "start": 2725.189, "duration": 3.103}, {"text": "and you like tables, there's\nsomething called the ICE table.", "start": 2728.292, "duration": 5.439}, {"text": "And in this case, it's a little\nbit boring, but as you'll see,", "start": 2733.731, "duration": 4.804}, {"text": "it can actually wind\nup being pretty useful,", "start": 2738.535, "duration": 5.339}, {"text": "especially when we\nadd other ions, which", "start": 2743.874, "duration": 2.302}, {"text": "are going to do soon.", "start": 2746.176, "duration": 3.404}, {"text": "So ICE is initial\nchange equilibrium.", "start": 2749.58, "duration": 5.172}, {"text": "Initial change equilibrium.", "start": 2754.752, "duration": 2.669}, {"text": "It's just a way of keeping\ntrack of what I just did,", "start": 2757.421, "duration": 2.703}, {"text": "because I started with\nsome amount of solid,", "start": 2760.124, "duration": 7.574}, {"text": "and I had zero.", "start": 2767.698, "duration": 1.701}, {"text": "I put it into water.", "start": 2769.399, "duration": 1.102}, {"text": "I had zero, but then I added\n1.3 times 10 to the minus fifth,", "start": 2770.501, "duration": 7.374}, {"text": "and I added 1.3 times\n10 to the minus fifth.", "start": 2777.875, "duration": 4.337}, {"text": "And so my equilibrium is a\nlittle less, a little less", "start": 2782.212, "duration": 6.64}, {"text": "solid.", "start": 2788.852, "duration": 2.77}, {"text": "And over here, it's\njust these numbers.", "start": 2791.622, "duration": 2.369}, {"text": "That was indeed boring,\nbut have no fear.", "start": 2797.728, "duration": 5.972}, {"text": "It becomes helpful.", "start": 2803.7, "duration": 2.503}, {"text": "It becomes helpful because\nwhat we're going to do next--", "start": 2806.203, "duration": 2.369}, {"text": "not right now--", "start": 2808.572, "duration": 1.235}, {"text": "but on Wednesday,\nwhat we're going to do", "start": 2809.807, "duration": 2.902}, {"text": "is we're going to mess\nwith this equilibrium.", "start": 2812.709, "duration": 4.038}, {"text": "Oh, equilibrium, I'm\ngoing to throw you off.", "start": 2816.747, "duration": 2.335}, {"text": "And equilibrium is\nsaying, no you're", "start": 2819.082, "duration": 1.469}, {"text": "not, because I'm equilibrium,\nand I will always be found.", "start": 2820.551, "duration": 4.838}, {"text": "And that's called Le Chatelier's\nPrinciple, and what that does", "start": 2825.389, "duration": 3.336}, {"text": "is it allows us\nto really go back,", "start": 2828.725, "duration": 1.802}, {"text": "and we get to actually add a\nbunch of chlorine ions to this,", "start": 2830.527, "duration": 5.105}, {"text": "and we're going to see what\nhappens to this balance.", "start": 2835.632, "duration": 3.437}, {"text": "It will find equilibrium.", "start": 2839.069, "duration": 2.436}, {"text": "And we have the tools now\nto know how to find it.", "start": 2841.505, "duration": 2.769}, {"text": "That's that green curve there.", "start": 2844.274, "duration": 2.202}, {"text": "This is what we're\ngoing to work with.", "start": 2846.476, "duration": 1.702}, {"text": "There's the concentration\nof chlorine.", "start": 2848.178, "duration": 1.635}, {"text": "There's a concentration\nof silver in ions.", "start": 2853.083, "duration": 2.503}, {"text": "You see the dissolved chlorine\non the x-axis, dissolved silver", "start": 2855.586, "duration": 2.769}, {"text": "on the y-axis.", "start": 2858.355, "duration": 0.567}, {"text": "And look at that.", "start": 2858.922, "duration": 1.001}, {"text": "I've got that point\nb there that is", "start": 2859.923, "duration": 4.171}, {"text": "where these things\nhave found equilibrium", "start": 2864.094, "duration": 2.369}, {"text": "when it's not messed with.", "start": 2866.463, "duration": 2.503}, {"text": "Now the thing is, if you\nwere a reaction happening,", "start": 2868.966, "duration": 3.47}, {"text": "and you hadn't gotten\nto equilibrium yet--", "start": 2872.436, "duration": 2.269}, {"text": "so I hadn't added\nmuch silver chloride--", "start": 2874.705, "duration": 2.802}, {"text": "if that was the case, then\nyou might be at point d.", "start": 2877.507, "duration": 3.571}, {"text": "Notice that the reaction\nquotient, q, is less", "start": 2881.078, "duration": 3.203}, {"text": "than the equilibrium constant.", "start": 2884.281, "duration": 3.437}, {"text": "q is less.", "start": 2887.718, "duration": 1.001}, {"text": "That means it's\ngoing to be driven", "start": 2888.719, "duration": 1.701}, {"text": "to dissolve more than\nit precipitates until it", "start": 2890.42, "duration": 2.77}, {"text": "gets to point B on this curve.", "start": 2893.19, "duration": 3.336}, {"text": "You could also be way, way out\nwith a much higher q point, e,", "start": 2896.526, "duration": 5.139}, {"text": "and you know it has\nto find equilibrium.", "start": 2901.665, "duration": 2.536}, {"text": "It's going to find\nequilibrium, which", "start": 2904.201, "duration": 1.601}, {"text": "is what we just calculated.", "start": 2905.802, "duration": 1.802}, {"text": "Those are the concentrations\nof equilibrium.", "start": 2907.604, "duration": 1.835}, {"text": "It has to get back to point\nB. It's going to do it", "start": 2909.439, "duration": 2.102}, {"text": "by precipitating out solid.", "start": 2911.541, "duration": 3.137}, {"text": "It's gone too far.", "start": 2914.678, "duration": 1.101}, {"text": "But you can see that\nequilibrium can also be had", "start": 2918.815, "duration": 3.07}, {"text": "and will be had.", "start": 2921.885, "duration": 1.001}, {"text": "It shall be had.", "start": 2922.886, "duration": 1.735}, {"text": "Because k never changes if\nyou fix the temperature.", "start": 2924.621, "duration": 3.37}, {"text": "k is the same.", "start": 2927.991, "duration": 2.069}, {"text": "So I can mess with\nthis in other ways.", "start": 2930.06, "duration": 2.135}, {"text": "I can go and add a\nwhole bunch of chlorine,", "start": 2932.195, "duration": 2.303}, {"text": "and it will come back down\nonto that green curve.", "start": 2934.498, "duration": 2.769}, {"text": "It will come back down\nonto that green curve,", "start": 2937.267, "duration": 1.902}, {"text": "which is the curve\nthat guarantees", "start": 2939.169, "duration": 2.002}, {"text": "k is the same constant.", "start": 2941.171, "duration": 1.969}, {"text": "That's what that green curve is.", "start": 2943.14, "duration": 2.402}, {"text": "And there's one last point\nI'm going to make today,", "start": 2945.542, "duration": 3.003}, {"text": "and that is units.", "start": 2948.545, "duration": 2.169}, {"text": "Units of k depend--", "start": 2950.714, "duration": 6.306}, {"text": "it was like the rate law.", "start": 2957.02, "duration": 1.702}, {"text": "It depends on the reaction.", "start": 2958.722, "duration": 7.641}, {"text": "Look, a concentration\nis a concentration.", "start": 2966.363, "duration": 4.404}, {"text": "That was deep.", "start": 2970.767, "duration": 1.602}, {"text": "Units are capital\nM moles per liter.", "start": 2972.369, "duration": 3.77}, {"text": "But that means that k--", "start": 2976.139, "duration": 3.07}, {"text": "k is two of those\nmultiplied together.", "start": 2979.209, "duration": 3.771}, {"text": "So in this case, k has\nunits of m squared.", "start": 2982.98, "duration": 7.34}, {"text": "It must, or it wouldn't work.", "start": 2990.32, "duration": 2.97}, {"text": "k can have units of m cubed.", "start": 2993.29, "duration": 1.601}, {"text": "We will pick up\nhere on Wednesday,", "start": 2997.494, "duration": 1.935}, {"text": "and we'll cover more\nof this, more examples", "start": 2999.429, "duration": 4.171}, {"text": "before we move on\nto acids and bases.", "start": 3003.6, "duration": 2.903}]
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+[{"text": "[SQUEAKING]\n[RUSTLING] [CLICKING]", "start": 0.0, "duration": 3.872}, {"text": "CASEY RODRIGUEZ: So last\ntime we spoke about--", "start": 13.07, "duration": 4.05}, {"text": "we covered sets and induction.", "start": 17.12, "duration": 2.13}, {"text": "This time, I want to ask\na question about sets,", "start": 19.25, "duration": 5.7}, {"text": "which turns out is actually\nquite a deep question.", "start": 24.95, "duration": 3.87}, {"text": "I mean, I didn't come\nup with it myself.", "start": 28.82, "duration": 2.31}, {"text": "This question is at least\n150 years old probably.", "start": 31.13, "duration": 6.8}, {"text": "So the question that I want to\nask is if A and B are sets--", "start": 37.93, "duration": 11.67}, {"text": "or let's phrase it this\nway, at least a little more", "start": 58.44, "duration": 3.03}, {"text": "efficiently.", "start": 61.47, "duration": 2.84}, {"text": "When do two sets, A and\nB, have the same size?", "start": 64.31, "duration": 15.345}, {"text": "Now, this is\nespecially interesting", "start": 86.06, "duration": 1.83}, {"text": "if these two sets\nare not finite,", "start": 87.89, "duration": 3.03}, {"text": "meaning there's\nnot five of them,", "start": 90.92, "duration": 2.22}, {"text": "there's not eight of them,\nbut there's infinitely", "start": 93.14, "duration": 4.2}, {"text": "many members,\nwhatever that means.", "start": 97.34, "duration": 1.68}, {"text": "And I'll actually\ndefine what that means.", "start": 99.02, "duration": 2.5}, {"text": "For example, do the natural\nnumbers and the integers", "start": 101.52, "duration": 2.81}, {"text": "have the same size?", "start": 104.33, "duration": 2.04}, {"text": "Do the natural numbers\nand the rational numbers", "start": 106.37, "duration": 2.94}, {"text": "have the same size?", "start": 109.31, "duration": 1.83}, {"text": "What about the rational\nnumbers and the real numbers?", "start": 111.14, "duration": 2.52}, {"text": "Even though we haven't\ndefined that yet,", "start": 113.66, "duration": 1.8}, {"text": "you can still keep in mind\nyour notion of the real numbers", "start": 115.46, "duration": 6.54}, {"text": "from calculus.", "start": 122.0, "duration": 1.515}, {"text": "And so this question is--", "start": 126.41, "duration": 3.759}, {"text": "why is it deep?", "start": 130.169, "duration": 2.101}, {"text": "Because it depends\non this word here,", "start": 132.27, "duration": 4.98}, {"text": "\"size,\" and what\nexactly that means.", "start": 137.25, "duration": 5.9}, {"text": "So I'm not-- so\nkind of an answer,", "start": 143.15, "duration": 11.05}, {"text": "this is due to George Cantor.", "start": 154.2, "duration": 1.725}, {"text": "He said that two sets--", "start": 158.64, "duration": 1.66}, {"text": "so not an answer, but\na way of defining size", "start": 160.3, "duration": 2.78}, {"text": "or a way of saying the two\nsets have the same size.", "start": 163.08, "duration": 3.12}, {"text": "He said two sets have the\nsame size when the two sets--", "start": 166.2, "duration": 17.73}, {"text": "the elements of the two sets\ncan be paired off, meaning--", "start": 183.93, "duration": 15.11}, {"text": "and I will make this much more\nprecise in a minute or so.", "start": 199.04, "duration": 5.13}, {"text": "What does he mean?", "start": 204.17, "duration": 2.58}, {"text": "Or what do I mean?", "start": 206.75, "duration": 1.3}, {"text": "For example, the set a, b,\nand c and the set 1, 2, and 3.", "start": 208.05, "duration": 7.46}, {"text": "So this one, this set, consists\nof three letters-- a, b, and c.", "start": 215.51, "duration": 3.45}, {"text": "This set consists\nof three integers--", "start": 218.96, "duration": 2.01}, {"text": "1, 2, and 3.", "start": 220.97, "duration": 1.05}, {"text": "They have the same size\nbecause I can essentially", "start": 222.02, "duration": 2.88}, {"text": "pair them off.", "start": 224.9, "duration": 0.765}, {"text": "So a and 1 go together,\nb and 2 go together,", "start": 229.59, "duration": 5.07}, {"text": "and c and 3 go together,\nmeaning each member of this set", "start": 234.66, "duration": 5.1}, {"text": "gets paired off with\nan element of this set.", "start": 239.76, "duration": 5.44}, {"text": "And every element of\nthis set gets paired off", "start": 245.2, "duration": 2.73}, {"text": "with a unique element\nfrom this set.", "start": 247.93, "duration": 1.62}, {"text": "Now, to make-- and so\nthis goes under the name", "start": 257.57, "duration": 8.29}, {"text": "of the theory of cardinality or\ncardinal numbers, if you like.", "start": 265.86, "duration": 9.78}, {"text": "But we won't go\ntoo deeply into it.", "start": 275.64, "duration": 2.8}, {"text": "So the way you make--", "start": 278.44, "duration": 2.18}, {"text": "or the way one makes\nthis pairing off business", "start": 280.62, "duration": 4.02}, {"text": "more precise is using the\nlanguage of functions.", "start": 284.64, "duration": 3.425}, {"text": "And you've been dealing\nwith functions since you've", "start": 288.065, "duration": 2.125}, {"text": "been doing calculus.", "start": 290.19, "duration": 3.21}, {"text": "So I'm just going to quickly\nreintroduce or review", "start": 293.4, "duration": 7.29}, {"text": "some terminology that goes\nalong with functions that", "start": 300.69, "duration": 4.08}, {"text": "will be the precise meaning\nof this pairing off business", "start": 304.77, "duration": 5.22}, {"text": "that I'm writing here.", "start": 309.99, "duration": 1.95}, {"text": "But just with an eye\ntowards the future,", "start": 311.94, "duration": 2.71}, {"text": "this is why I'm reviewing some\nof this terminology related", "start": 314.65, "duration": 4.91}, {"text": "to functions.", "start": 319.56, "duration": 1.11}, {"text": "So a brief review of some\nterminology for functions--", "start": 325.37, "duration": 3.43}, {"text": "so let me just recall\nthat if A and B are sets,", "start": 328.8, "duration": 10.55}, {"text": "then function f A B--", "start": 339.35, "duration": 8.57}, {"text": "so a function's usually written\nas f colon A arrow to B,", "start": 347.92, "duration": 4.62}, {"text": "meaning it takes elements\nfrom A into elements from B.", "start": 352.54, "duration": 4.62}, {"text": "This is a mapping that--", "start": 357.16, "duration": 9.605}, {"text": "or if you like, an assignment.", "start": 370.14, "duration": 1.77}, {"text": "It assigns to each x in\nA a unique element which", "start": 376.41, "duration": 10.16}, {"text": "we denote f of x in B.", "start": 386.57, "duration": 3.99}, {"text": "So one single input, x,\ngives me a single output.", "start": 390.56, "duration": 5.29}, {"text": "And the input does not\ngive me three outputs.", "start": 395.85, "duration": 2.9}, {"text": "Now, this is what one would call\na naive definition probably,", "start": 398.75, "duration": 4.47}, {"text": "not necessarily\ncompletely unambiguous.", "start": 403.22, "duration": 3.39}, {"text": "But for us, it suffices.", "start": 406.61, "duration": 1.71}, {"text": "In the textbook, you\ncan look up a function", "start": 408.32, "duration": 2.7}, {"text": "is unambiguously defined or as a\nsubset of the Cartesian product", "start": 411.02, "duration": 6.85}, {"text": "of A and B, which\nyou would recognize", "start": 417.87, "duration": 3.6}, {"text": "as essentially describing\nthe graph of the function.", "start": 421.47, "duration": 2.52}, {"text": "But then you never use\nthat definition of again.", "start": 423.99, "duration": 2.85}, {"text": "And you essentially\nuse this definition", "start": 426.84, "duration": 3.72}, {"text": "when you think about\nfunctions and when you", "start": 430.56, "duration": 2.46}, {"text": "prove properties of function.", "start": 433.02, "duration": 1.36}, {"text": "So this we will just\ntake as our definition.", "start": 434.38, "duration": 3.17}, {"text": "And it will be\nunambiguous enough for us.", "start": 437.55, "duration": 4.69}, {"text": "So let f be a\nfunction from A to B.", "start": 442.24, "duration": 15.0}, {"text": "If C is a subset of\nA, we define a set--", "start": 457.24, "duration": 9.2}, {"text": "so this is f of capital C.\nSo C is not an element of A.", "start": 466.44, "duration": 3.45}, {"text": "It's a subset of A.", "start": 469.89, "duration": 1.13}, {"text": "And this is a subset\nof B. This is--", "start": 471.02, "duration": 4.135}, {"text": "let me write it slightly\ndifferently here.", "start": 478.23, "duration": 3.27}, {"text": "This is a set of all\ny in B such that there", "start": 481.5, "duration": 4.08}, {"text": "exists an x in C such\nthat y equals to f of x.", "start": 485.58, "duration": 7.08}, {"text": "And I could write this a\nlittle more efficiently as this", "start": 492.66, "duration": 4.92}, {"text": "is the set of all\nelements f of x", "start": 497.58, "duration": 2.61}, {"text": "as x ranges over the\nelements of this subset C.", "start": 500.19, "duration": 10.08}, {"text": "And if D is a subset of B, we\ndefine the set f inverse of D.", "start": 510.27, "duration": 14.3}, {"text": "This is the set of guys\nthat get mapped into D.", "start": 524.57, "duration": 3.57}, {"text": "So I should say this is\nthe inverse image of D,", "start": 528.14, "duration": 4.98}, {"text": "not the inverse of\nthis function f.", "start": 533.12, "duration": 4.77}, {"text": "So the inverse, whatever\nthat means for now,", "start": 537.89, "duration": 5.19}, {"text": "does not necessarily\nalways exist.", "start": 543.08, "duration": 1.84}, {"text": "So this inverse image of\nthe set D always exists.", "start": 544.92, "duration": 3.77}, {"text": "This is the set of all elements\nin A such that f of x is in D.", "start": 548.69, "duration": 10.98}, {"text": "So for example, let me--", "start": 559.67, "duration": 11.73}, {"text": "so 1, 2, 3, 4 and a, b, c, d.", "start": 578.76, "duration": 9.33}, {"text": "And let's suppose 1 goes\nto a, 2 goes to a, 3 goes", "start": 588.09, "duration": 7.02}, {"text": "to c, 4 goes to d.", "start": 595.11, "duration": 2.7}, {"text": "Then f of the set 1,\n2, this is where--", "start": 602.16, "duration": 5.88}, {"text": "what is the set that gets--", "start": 608.04, "duration": 2.23}, {"text": "so this is the subset of--", "start": 610.27, "duration": 2.3}, {"text": "so this you should think of as\nB, a, b, and c, and D. And then", "start": 612.57, "duration": 7.65}, {"text": "1, 2, and 3, this is A.", "start": 620.22, "duration": 3.39}, {"text": "So f of the set of 1, 2--", "start": 623.61, "duration": 4.2}, {"text": "so 1 gets mapped to a.", "start": 627.81, "duration": 1.86}, {"text": "2 gets mapped to a.", "start": 629.67, "duration": 1.32}, {"text": "So this is just the set 2.", "start": 630.99, "duration": 3.48}, {"text": "f of the set--", "start": 634.47, "duration": 4.05}, {"text": "let's go with 1 and 3.", "start": 638.52, "duration": 3.3}, {"text": "1 gets mapped to a.", "start": 641.82, "duration": 2.16}, {"text": "So this should be a.", "start": 643.98, "duration": 3.66}, {"text": "1 gets mapped to a.", "start": 647.64, "duration": 2.256}, {"text": "And 3 gets mapped\ngets mapped to c.", "start": 649.896, "duration": 2.619}, {"text": "And so a couple of\ninverse images--", "start": 655.86, "duration": 3.27}, {"text": "if I look at the\ninverse image of a,", "start": 659.13, "duration": 5.23}, {"text": "this is equal to the set\nof all guys that map to a.", "start": 664.36, "duration": 3.68}, {"text": "This is, well, 1 maps\nto a and 2 maps to a.", "start": 668.04, "duration": 4.11}, {"text": "So this is 1, 2.", "start": 672.15, "duration": 1.95}, {"text": "Now, if I look at the\ninverse image of a,", "start": 676.89, "duration": 4.29}, {"text": "c, d, what elements get\nmapped to a, c, and d?", "start": 681.18, "duration": 6.24}, {"text": "Well, 1 and 2 get mapped to a.", "start": 687.42, "duration": 3.21}, {"text": "3 gets map to c.", "start": 690.63, "duration": 1.54}, {"text": "4 gets mapped to d.", "start": 692.17, "duration": 1.19}, {"text": "So everything maps\ninto a, C, and d.", "start": 693.36, "duration": 3.03}, {"text": "So this is just the\noriginal set or the set A--", "start": 696.39, "duration": 3.78}, {"text": "1, 2, 3, 4.", "start": 700.17, "duration": 2.61}, {"text": "All right, so there's\nmore terminology.", "start": 709.63, "duration": 5.94}, {"text": "And this is what we\nwill mean by when", "start": 715.57, "duration": 3.03}, {"text": "two sets can be paired off.", "start": 718.6, "duration": 2.34}, {"text": "Or this makes that more precise.", "start": 720.94, "duration": 1.65}, {"text": "Let f be a function from A to\nB. We say that f is injective,", "start": 727.024, "duration": 12.136}, {"text": "or I'll write one-to-one.", "start": 739.16, "duration": 2.145}, {"text": "It should be read\none-to-one if f satisfies", "start": 741.305, "duration": 6.407}, {"text": "the following property.", "start": 747.712, "duration": 0.958}, {"text": "f of x1 equals f of x2\nimplies x1 equals x2.", "start": 751.22, "duration": 8.58}, {"text": "So injective, or\none-to-one, means", "start": 759.8, "duration": 2.22}, {"text": "if I take two different inputs,\nI get two different outputs.", "start": 762.02, "duration": 4.575}, {"text": "That's essentially\nwhat this means.", "start": 769.56, "duration": 1.66}, {"text": "I mean, taking the equivalent--", "start": 771.22, "duration": 5.69}, {"text": "so equivalently, from\na logical standpoint,", "start": 776.91, "duration": 8.02}, {"text": "this statement\nimplying this statement", "start": 784.93, "duration": 1.62}, {"text": "is equivalent to the\nnegation of this statement", "start": 786.55, "duration": 2.04}, {"text": "implying the negation\nof this statement.", "start": 788.59, "duration": 2.47}, {"text": "So equivalently, this means x\nnot equal to x2 implies f of x1", "start": 791.06, "duration": 6.56}, {"text": "not equal to f of x2.", "start": 797.62, "duration": 2.82}, {"text": "So maybe this is clear.", "start": 800.44, "duration": 1.66}, {"text": "If I were to define f as\ninjective if it satisfies", "start": 802.1, "duration": 3.05}, {"text": "this property, maybe\nthat would have", "start": 805.15, "duration": 2.49}, {"text": "been clearer that f takes\ntwo different elements to two", "start": 807.64, "duration": 4.653}, {"text": "different elements.", "start": 812.293, "duration": 0.792}, {"text": "But this condition here is\ntypically easier to verify,", "start": 816.79, "duration": 3.75}, {"text": "or at least simpler\nto state and verify.", "start": 820.54, "duration": 2.235}, {"text": "So f is surjective or\nonto if the image of A", "start": 825.39, "duration": 19.48}, {"text": "is B. So let me write that\nstatement out a little bit", "start": 844.87, "duration": 6.58}, {"text": "more.", "start": 851.45, "duration": 0.5}, {"text": "Everything in the set B gets\nmapped to by something from A.", "start": 851.95, "duration": 12.4}, {"text": "So equivalently, this\nsays that for all y in B", "start": 864.35, "duration": 6.54}, {"text": "there exists an x in A\nso that f of x equals y.", "start": 870.89, "duration": 6.78}, {"text": "f is bijective if f is\none-to-one and onto.", "start": 886.104, "duration": 10.316}, {"text": "So f is bijective if it's\nboth injective and surjective.", "start": 896.42, "duration": 5.45}, {"text": "So for example, this map\nthat we just drew over here", "start": 907.55, "duration": 4.41}, {"text": "that sends 1 to a, 2 to b--", "start": 911.96, "duration": 4.75}, {"text": "I mean 2 to a, 3\nto c, 4, to d, this", "start": 916.71, "duration": 3.63}, {"text": "is neither injective\nnor surjective.", "start": 920.34, "duration": 2.28}, {"text": "It's not injective because it\ntakes two different elements", "start": 922.62, "duration": 4.11}, {"text": "to the image in B, namely a.", "start": 926.73, "duration": 2.55}, {"text": "So it takes 1 and 2 to a.", "start": 929.28, "duration": 1.9}, {"text": "It's not surjective\nbecause nothing gets", "start": 931.18, "duration": 2.6}, {"text": "mapped to the element b here.", "start": 933.78, "duration": 4.455}, {"text": "So we've seen that's\nnot surjective.", "start": 954.89, "duration": 1.68}, {"text": "Of course, this map, if I take--", "start": 956.57, "duration": 1.95}, {"text": "again, imagine this\nis 1, 2, 3 a, b, c, d.", "start": 958.52, "duration": 6.51}, {"text": "This map here, this function\nhere that takes 1 to a, 2", "start": 965.03, "duration": 5.19}, {"text": "to b, 3, to c, this is actually\ninjective but not surjective.", "start": 970.22, "duration": 4.77}, {"text": "And then of course, we\ncould change this slightly.", "start": 984.82, "duration": 3.95}, {"text": "And 1 goes to a, 2 goes\nto b, and 3 goes to b.", "start": 988.77, "duration": 10.21}, {"text": "Then this is surjective\nbut not injective.", "start": 998.98, "duration": 8.552}, {"text": "Now, the map that sends--", "start": 1012.21, "duration": 2.04}, {"text": "let's switch sides here--", "start": 1019.11, "duration": 2.22}, {"text": "a, b, and c, 1, 2, 3--", "start": 1021.33, "duration": 5.4}, {"text": "a to 1, b to 2, c to 3, this\nis a bijection, bijective.", "start": 1026.73, "duration": 10.42}, {"text": "So if I say something's\nan injection or surjection", "start": 1037.15, "duration": 3.09}, {"text": "or bijection, that just means\nit's a map that is injective,", "start": 1040.24, "duration": 3.27}, {"text": "or, surjective or\nbijective respectively.", "start": 1043.51, "duration": 7.35}, {"text": "And now, a definition--", "start": 1074.32, "duration": 10.3}, {"text": "so this is really--", "start": 1084.62, "duration": 1.25}, {"text": "there's not much\nto this definition,", "start": 1085.87, "duration": 1.5}, {"text": "but just defining a couple\nof related functions", "start": 1087.37, "duration": 7.87}, {"text": "that are related to\na given function.", "start": 1095.24, "duration": 3.25}, {"text": "If f goes from A to\nB, g goes from B to C,", "start": 1098.49, "duration": 9.05}, {"text": "the composition g of f is the\nfunction which goes from A to C", "start": 1107.54, "duration": 9.57}, {"text": "is defined by g of f of\nx equals g of f of x.", "start": 1117.11, "duration": 11.032}, {"text": "And 2, if f is bijective--", "start": 1132.214, "duration": 4.916}, {"text": "so this is the composition\nof two functions.", "start": 1140.25, "duration": 2.52}, {"text": "I didn't write the word\ncomposition, but g of f", "start": 1142.77, "duration": 3.09}, {"text": "means the composition, or is\nreferred to as a composition.", "start": 1145.86, "duration": 3.12}, {"text": "If f is bijective, then we\ndefine the inverse function", "start": 1148.98, "duration": 6.87}, {"text": "to f, B to A, by the following.", "start": 1155.85, "duration": 8.67}, {"text": "If y is in B, then\nf inverse of y in A", "start": 1167.74, "duration": 8.25}, {"text": "is the unique elements in A such\nthat if I take this element,", "start": 1175.99, "duration": 16.1}, {"text": "stick it into f, I get back y.", "start": 1192.09, "duration": 4.68}, {"text": "So the inverse of a\nfunction only exists", "start": 1196.77, "duration": 3.84}, {"text": "for bijective\nfunctions, or at least", "start": 1200.61, "duration": 3.09}, {"text": "is only defined for\nbijective functions.", "start": 1203.7, "duration": 4.08}, {"text": "Keep that in mind.", "start": 1207.78, "duration": 0.88}, {"text": "Don't confuse that with\nthe inverse image of sets.", "start": 1208.66, "duration": 5.03}, {"text": "Although, those two\nnotations look the same.", "start": 1213.69, "duration": 3.6}, {"text": "You have an inverse\nf to the minus 1.", "start": 1217.29, "duration": 4.955}, {"text": "f to the minus 1,\nif it's a function,", "start": 1222.245, "duration": 4.285}, {"text": "that is the inverse function.", "start": 1226.53, "duration": 1.93}, {"text": "However, if I'm taking f\nto the minus 1 of a set,", "start": 1228.46, "duration": 3.44}, {"text": "that means the inverse image of\nthat set as defined over there.", "start": 1231.9, "duration": 3.87}, {"text": "So bijections, meaning\nbijective functions,", "start": 1239.89, "duration": 5.76}, {"text": "will be what we mean when we\nsay two sets can be paired off.", "start": 1245.65, "duration": 5.73}, {"text": "It's what we mean when we--", "start": 1251.38, "duration": 2.67}, {"text": "or at least what Cantor's\nanswer to that original question", "start": 1254.05, "duration": 5.91}, {"text": "was, when did two sets\nhave the same size.", "start": 1259.96, "duration": 4.52}, {"text": "So this is the notion of\ncardinality that I alluded to.", "start": 1264.48, "duration": 9.67}, {"text": "So we say two\nsets, A and B, have", "start": 1274.15, "duration": 16.59}, {"text": "the same cardinality\nif there exists", "start": 1290.74, "duration": 13.27}, {"text": "a bijection or a bijective\nfunction f from A to B.", "start": 1304.01, "duration": 16.87}, {"text": "And so let me just make some\nnotation here. so this is not", "start": 1320.88, "duration": 13.62}, {"text": "really new objects I'm\ndefining or operations.", "start": 1334.5, "duration": 4.92}, {"text": "This is just some notation.", "start": 1339.42, "duration": 1.48}, {"text": "So when two sets have the\nsame cardinality, we write--", "start": 1340.9, "duration": 3.95}, {"text": "so this is just a shorthand way\nof writing that two functions", "start": 1362.03, "duration": 3.237}, {"text": "have the same cardinality.", "start": 1365.267, "duration": 1.083}, {"text": "You should not necessarily\nthink this means taking", "start": 1366.35, "duration": 3.42}, {"text": "the absolute value of a set.", "start": 1369.77, "duration": 1.86}, {"text": "That doesn't mean\nanything, all right?", "start": 1371.63, "duration": 2.43}, {"text": "This is just shorthand\nnotation for saying two", "start": 1374.06, "duration": 2.22}, {"text": "sets have the same cardinality.", "start": 1376.28, "duration": 1.56}, {"text": "If A has the same cardinality\nas the set 1, 2, 3 up to n,", "start": 1382.18, "duration": 13.42}, {"text": "we write A equals n.", "start": 1395.6, "duration": 4.46}, {"text": "That's just shorthand\nfor saying that a set has", "start": 1400.06, "duration": 2.61}, {"text": "the same cardinality as the\nnatural numbers up to n.", "start": 1402.67, "duration": 5.19}, {"text": "So if there exists an\ninjective function-- or I", "start": 1418.38, "duration": 11.85}, {"text": "will often say either\nfunction or map.", "start": 1430.23, "duration": 3.3}, {"text": "You should take\nthose as synonymous.", "start": 1433.53, "duration": 3.09}, {"text": "There exists an\ninjective function f--", "start": 1436.62, "duration": 3.72}, {"text": "if there exists an injective\nfunction f from A to B,", "start": 1440.34, "duration": 6.46}, {"text": "we write this thing.", "start": 1446.8, "duration": 5.74}, {"text": "Again, do not read this as\ntaking the absolute value", "start": 1452.54, "duration": 2.85}, {"text": "of some set and\nthat absolute value", "start": 1455.39, "duration": 2.55}, {"text": "is less than or equal to the\nabsolute value of the other set", "start": 1457.94, "duration": 2.64}, {"text": "because that's meaningless.", "start": 1460.58, "duration": 1.29}, {"text": "We haven't said what\nthat means even.", "start": 1461.87, "duration": 2.91}, {"text": "This is just shorthand notation.", "start": 1469.59, "duration": 1.41}, {"text": "And if there exists an\ninjection from A to B", "start": 1480.23, "duration": 12.21}, {"text": "but they don't have the same\ncardinality, we write this.", "start": 1492.44, "duration": 11.945}, {"text": "So even though this notation\nof these absolute value", "start": 1508.04, "duration": 4.17}, {"text": "things being on the\noutside of the set", "start": 1512.21, "duration": 2.64}, {"text": "makes you think absolute\nvalue or should be interpreted", "start": 1514.85, "duration": 4.92}, {"text": "as absolute value,\nit's OK to think", "start": 1519.77, "duration": 2.31}, {"text": "as a certain\nordering being there,", "start": 1522.08, "duration": 5.05}, {"text": "as A having smaller size than B.", "start": 1527.13, "duration": 4.8}, {"text": "We write this because there\nbeing an injection from one", "start": 1531.93, "duration": 3.6}, {"text": "set to the other means I\ncan pair off elements of A", "start": 1535.53, "duration": 5.55}, {"text": "with some elements\nof B. Maybe I don't", "start": 1541.08, "duration": 3.39}, {"text": "get all of the elements\nof B. But I can pair off", "start": 1544.47, "duration": 2.7}, {"text": "some of the elements of A with\nsome of the elements of B.", "start": 1547.17, "duration": 3.33}, {"text": "For example, that first\nmap we wrote up there,", "start": 1550.5, "duration": 3.36}, {"text": "that says that the\nset 1, 2, 3 in size", "start": 1553.86, "duration": 5.5}, {"text": "is less than or equal\nto the size of a, b, c,", "start": 1559.36, "duration": 2.7}, {"text": "d because we found an\ninjection, an injective map", "start": 1562.06, "duration": 2.76}, {"text": "from the first set\nto the second set.", "start": 1564.82, "duration": 2.805}, {"text": "This third map would say that\nthe size of the set a, b,c is", "start": 1570.35, "duration": 6.21}, {"text": "equal to 3, written here,\nor shorthand written here.", "start": 1576.56, "duration": 4.65}, {"text": "And in fact, that first map that\nwe wrote up there, again, is--", "start": 1584.08, "duration": 8.57}, {"text": "so from first map, this says\nthat the set of 1, 2, 3--", "start": 1592.65, "duration": 5.07}, {"text": "in our shorthand\nnotation, absolute value", "start": 1597.72, "duration": 3.45}, {"text": "is less than the\nsize of a, b, c, d.", "start": 1601.17, "duration": 4.2}, {"text": "So don't think of these as\nsaying the absolute value.", "start": 1605.37, "duration": 3.78}, {"text": "It's best to maybe think of\nthis as saying the size of.", "start": 1609.15, "duration": 2.985}, {"text": "All right, so if there exists\nan injective map or function", "start": 1615.07, "duration": 5.97}, {"text": "from one set to another,\nthen the size of A", "start": 1621.04, "duration": 2.88}, {"text": "is less than or equal to the\nsize of B. If the size of A", "start": 1623.92, "duration": 3.667}, {"text": "is less than or equal\nto the size of B", "start": 1627.587, "duration": 1.583}, {"text": "but the size of A and\nB are not the same,", "start": 1629.17, "duration": 2.22}, {"text": "we write the size of A is\nless than the size of B.", "start": 1631.39, "duration": 4.44}, {"text": "So best to think of those--", "start": 1635.83, "duration": 1.695}, {"text": "this absolute\nvalue looking thing", "start": 1640.12, "duration": 1.65}, {"text": "as being shorthand for\nsaying the words size of.", "start": 1641.77, "duration": 3.93}, {"text": "Now, I'm not going\nto prove this.", "start": 1652.33, "duration": 1.71}, {"text": "It goes a little bit beyond\nthe scope of this class.", "start": 1654.04, "duration": 5.78}, {"text": "But let me just say that this\nordering, this inequality,", "start": 1659.82, "duration": 5.73}, {"text": "these symbols that\nwe're writing does", "start": 1665.55, "duration": 4.46}, {"text": "bear some sort of semblance to\nthe ordering of real numbers", "start": 1670.01, "duration": 3.79}, {"text": "in that if I have two real\nnumbers, one is less than", "start": 1673.8, "duration": 3.26}, {"text": "or equal to the\nother and vice versa.", "start": 1677.06, "duration": 2.32}, {"text": "So A is less than or equal\nto B and B is less than", "start": 1679.38, "duration": 2.84}, {"text": "or equal to A, then\nA must equal B.", "start": 1682.22, "duration": 2.46}, {"text": "That is, in fact, true also\nfor this elementary notion", "start": 1684.68, "duration": 3.78}, {"text": "of size of sets.", "start": 1688.46, "duration": 1.74}, {"text": "And this is--", "start": 1690.2, "duration": 3.79}, {"text": "I mean, it shouldn't\nsurprise you for finite sets", "start": 1693.99, "duration": 7.08}, {"text": "necessarily.", "start": 1701.07, "duration": 0.75}, {"text": "If I have a pairing of A, if\nA is no bigger than n and n is", "start": 1701.82, "duration": 10.93}, {"text": "no bigger than the size of A,\nthen a should have n elements.", "start": 1712.75, "duration": 4.35}, {"text": "But it takes a little\nbit more to prove", "start": 1717.1, "duration": 2.49}, {"text": "for sets which are not finite.", "start": 1719.59, "duration": 3.06}, {"text": "So I forgot to write this down.", "start": 1722.65, "duration": 2.8}, {"text": "We also say that\nif the size of A", "start": 1725.45, "duration": 4.52}, {"text": "is equal to the size of\nthis finite set 1 through n,", "start": 1729.97, "duration": 3.51}, {"text": "we say A is finite.", "start": 1733.48, "duration": 4.755}, {"text": "So this theorem that\nI'm stating here", "start": 1742.45, "duration": 1.59}, {"text": "is the Cantor Schroeder\nBernstein theorem,", "start": 1744.04, "duration": 14.82}, {"text": "which states that\nif the size of A", "start": 1758.86, "duration": 5.55}, {"text": "is less than or equal to the\nsize of B and the size of B", "start": 1764.41, "duration": 5.79}, {"text": "is less than or equal to the\nsize of A, then the size of A", "start": 1770.2, "duration": 7.685}, {"text": "equals the size of B. So again,\nif you're thinking of these", "start": 1777.885, "duration": 5.175}, {"text": "in the context of real\nnumbers, one being less than", "start": 1783.06, "duration": 3.9}, {"text": "or equal to the\nother and vice versa,", "start": 1786.96, "duration": 2.37}, {"text": "of course, that implies that\nthose two real numbers are", "start": 1789.33, "duration": 2.49}, {"text": "equal to each other.", "start": 1791.82, "duration": 1.14}, {"text": "But we're not talking\nabout real numbers.", "start": 1792.96, "duration": 2.22}, {"text": "Again, this is just\nshorthand notation", "start": 1795.18, "duration": 2.97}, {"text": "for saying there exists a\nbijective map from A to B. This", "start": 1798.15, "duration": 4.98}, {"text": "means there exists a bijective\nmap from A to the set.", "start": 1803.13, "duration": 3.67}, {"text": "This means there exists an\ninjective map from A into this,", "start": 1806.8, "duration": 4.4}, {"text": "from a to this set.", "start": 1811.2, "duration": 3.18}, {"text": "So this is not a statement\nabout real numbers.", "start": 1814.38, "duration": 2.7}, {"text": "This is a statement about\ncardinality, all right?", "start": 1817.08, "duration": 3.54}, {"text": "OK.", "start": 1826.275, "duration": 0.5}, {"text": "So finite sets are sets that you\ncan count if you had n fingers.", "start": 1829.9, "duration": 11.03}, {"text": "Now, we would like to be\nable to define what it means", "start": 1840.93, "duration": 9.22}, {"text": "to be able to count a set.", "start": 1850.15, "duration": 2.22}, {"text": "So what do I mean\nby count a set?", "start": 1852.37, "duration": 2.16}, {"text": "Meaning, if I had\ninfinite time, I", "start": 1854.53, "duration": 3.36}, {"text": "could go through the\nset counting them--", "start": 1857.89, "duration": 3.24}, {"text": "1, 2, 3, 4, 5, 6, 7,\n8, 9, 10 and so on.", "start": 1861.13, "duration": 7.05}, {"text": "I don't need to go anymore.", "start": 1868.18, "duration": 1.59}, {"text": "But what does that\nprocess of counting mean?", "start": 1872.56, "duration": 3.76}, {"text": "That means, for each\nelement of the set", "start": 1876.32, "duration": 2.57}, {"text": "that I'm trying to\ncount, I can pair it off", "start": 1878.89, "duration": 2.91}, {"text": "with a natural number--", "start": 1881.8, "duration": 2.28}, {"text": "1, 2, 3, and so on.", "start": 1884.08, "duration": 2.02}, {"text": "So this is how we\ndefine countable sets.", "start": 1886.1, "duration": 5.64}, {"text": "So if A has the same size\nas the natural numbers,", "start": 1891.74, "duration": 5.91}, {"text": "meaning there exists a bijection\nfrom A to the natural numbers,", "start": 1897.65, "duration": 7.29}, {"text": "then we say A is\ncountably infinite.", "start": 1904.94, "duration": 10.44}, {"text": "If A is finite, or countably--", "start": 1922.07, "duration": 8.8}, {"text": "I also use a lot of shorthand,\nbut it's not clever shorthand.", "start": 1930.87, "duration": 4.02}, {"text": "So you should just be\nable to sound what--", "start": 1934.89, "duration": 3.0}, {"text": "if you just sound that out,\nyou'll get what word I mean,", "start": 1937.89, "duration": 2.46}, {"text": "countably, countably infinite.", "start": 1940.35, "duration": 4.13}, {"text": "We say A is countable.", "start": 1950.45, "duration": 7.63}, {"text": "So countably infinite means I\nneed all the natural numbers", "start": 1958.08, "duration": 3.42}, {"text": "to be able to count off\nthe elements of the set A.", "start": 1961.5, "duration": 4.14}, {"text": "Countable means maybe\nI stop after some point", "start": 1965.64, "duration": 3.21}, {"text": "and I've counted all them.", "start": 1968.85, "duration": 2.04}, {"text": "So A is finite or it's\ncountably infinite.", "start": 1970.89, "duration": 4.14}, {"text": "Otherwise, if a set\nis not countable,", "start": 1975.03, "duration": 2.49}, {"text": "we say it's uncountable.", "start": 1977.52, "duration": 1.32}, {"text": "OK, so let's take a look at\na couple of countable sets", "start": 1998.22, "duration": 9.63}, {"text": "that maybe don't come\noff as being countable.", "start": 2007.85, "duration": 4.59}, {"text": "The set of-- actually,\nthat's a homework problem.", "start": 2018.032, "duration": 6.848}, {"text": "The set of even\nintegers is countable.", "start": 2024.88, "duration": 7.32}, {"text": "The set of odd-- so I said\nintegers a minute ago.", "start": 2034.84, "duration": 5.22}, {"text": "Maybe I should just\nsay natural numbers.", "start": 2040.06, "duration": 2.22}, {"text": "The set of odd natural\nnumbers is countable.", "start": 2042.28, "duration": 9.22}, {"text": "So in fact-- so this\nis just an aside.", "start": 2051.5, "duration": 5.13}, {"text": "So these are two\ndisjoint subsets", "start": 2064.09, "duration": 3.35}, {"text": "that make up the\nnatural numbers, even", "start": 2067.44, "duration": 2.85}, {"text": "and odd natural numbers.", "start": 2070.29, "duration": 1.65}, {"text": "And they both have the same size\nas the set that they make up.", "start": 2071.94, "duration": 4.799}, {"text": "So it's almost like\nsaying the cardinality", "start": 2076.739, "duration": 5.871}, {"text": "of the natural numbers\nis twice the cardinality", "start": 2082.61, "duration": 2.339}, {"text": "of the natural numbers,\nsince you would think", "start": 2084.949, "duration": 2.73}, {"text": "that the size of N should\nbe the size of this set", "start": 2087.679, "duration": 3.451}, {"text": "plus the size of this set,\nsince they are disjoint", "start": 2091.13, "duration": 2.467}, {"text": "and they make up the set.", "start": 2093.597, "duration": 1.042}, {"text": "But that's not how\ncardinality works.", "start": 2097.64, "duration": 5.12}, {"text": "You don't just add cardinalities\nto get the cardinalities.", "start": 2102.76, "duration": 4.8}, {"text": "So this is a subtle, interesting\nthing about cardinalities", "start": 2107.56, "duration": 9.67}, {"text": "So Richard Feynman,\nwho won the Nobel Prize", "start": 2117.23, "duration": 2.37}, {"text": "in the '60s for his work\non QED, described this", "start": 2119.6, "duration": 7.02}, {"text": "as saying there are twice\nas many numbers as numbers.", "start": 2126.62, "duration": 17.69}, {"text": "OK, so let's prove this.", "start": 2148.99, "duration": 8.62}, {"text": "So what does this mean?", "start": 2157.61, "duration": 2.04}, {"text": "This means we have to be able\nto find a bijective function", "start": 2159.65, "duration": 4.1}, {"text": "from this set to this set or\nfrom this set to this set, one", "start": 2163.75, "duration": 6.93}, {"text": "or the other.", "start": 2170.68, "duration": 0.63}, {"text": "And so in fact, maybe I should--", "start": 2174.24, "duration": 8.42}, {"text": "well, I'll say something\nabout that in a minute.", "start": 2182.66, "duration": 2.7}, {"text": "Well, let me pause.", "start": 2188.62, "duration": 1.68}, {"text": "Let me pause this\njust for a minute.", "start": 2190.3, "duration": 4.38}, {"text": "And let me make a few\ncomments about cardinality,", "start": 2194.68, "duration": 3.84}, {"text": "which maybe I should have.", "start": 2198.52, "duration": 1.83}, {"text": "So this you can think\nof as a little theorem.", "start": 2203.54, "duration": 9.53}, {"text": "If I have two sets, A\nhas the same size as B,", "start": 2213.07, "duration": 7.39}, {"text": "then B has the same size\nas A. So remember, I mean,", "start": 2220.46, "duration": 4.11}, {"text": "what I just said in\nEnglish is not exactly", "start": 2224.57, "duration": 3.9}, {"text": "what those symbols mean.", "start": 2228.47, "duration": 1.32}, {"text": "Remember, this means there\nexists a bijection from A to B", "start": 2229.79, "duration": 4.5}, {"text": "This means there exists\na bijection from B to A.", "start": 2234.29, "duration": 3.36}, {"text": "So what is the proof\nof this statement?", "start": 2237.65, "duration": 5.56}, {"text": "So let's start off\nwith the hypothesis.", "start": 2243.21, "duration": 1.74}, {"text": "Suppose then there\nexists a bijective map,", "start": 2247.47, "duration": 14.66}, {"text": "bijective function\nf from A to B.", "start": 2262.13, "duration": 15.08}, {"text": "Now, if I have a bijection\nfrom A to B, then", "start": 2277.21, "duration": 3.63}, {"text": "what would be a bijection\ngoing from B to A?", "start": 2280.84, "duration": 2.278}, {"text": "That would just be the inverse.", "start": 2283.118, "duration": 1.292}, {"text": "So this is not the\ninverse image of sets,", "start": 2289.34, "duration": 2.63}, {"text": "like we described, but\nthe actual inverse,", "start": 2291.97, "duration": 1.9}, {"text": "which we defined over there.", "start": 2293.87, "duration": 1.655}, {"text": "Is a bijection.", "start": 2302.98, "duration": 1.35}, {"text": "So B has the same size as A.", "start": 2317.44, "duration": 24.0}, {"text": "One other statement-- so if A\nand B have the same size and B", "start": 2341.44, "duration": 10.2}, {"text": "and C have the same size--", "start": 2351.64, "duration": 3.43}, {"text": "so again, A, B, and C are sets.", "start": 2355.07, "duration": 1.43}, {"text": "I should have written\nthat at the beginning.", "start": 2356.5, "duration": 2.55}, {"text": "But from this context,\nyou should understand", "start": 2359.05, "duration": 1.965}, {"text": "that A, B, and C are sets--", "start": 2361.015, "duration": 2.025}, {"text": "then A and C have the same size.", "start": 2363.04, "duration": 4.845}, {"text": "So let's do a proof of that.", "start": 2378.45, "duration": 1.75}, {"text": "So let's start with\nthe hypothesis,", "start": 2380.2, "duration": 3.75}, {"text": "meaning A has the same size as\nB and B has the same size as C.", "start": 2383.95, "duration": 13.82}, {"text": "So what did these\ntwo statements mean", "start": 2397.77, "duration": 2.13}, {"text": "in terms of the definition?", "start": 2399.9, "duration": 1.5}, {"text": "That means there exists\na bijection from A to B", "start": 2401.4, "duration": 3.06}, {"text": "and a bijection from B to\nC. And this statement-- so", "start": 2404.46, "duration": 13.85}, {"text": "let me finish this.", "start": 2418.31, "duration": 0.91}, {"text": "And then I'll say what\nI was going to say.", "start": 2419.22, "duration": 1.75}, {"text": "Then there exists bijections f\nfrom A to B and g from B to C.", "start": 2420.97, "duration": 12.37}, {"text": "So perhaps I should have\nsaid a few more words", "start": 2433.34, "duration": 5.73}, {"text": "about why this is true.", "start": 2439.07, "duration": 2.79}, {"text": "But I'm going to leave\nthis as an exercise", "start": 2441.86, "duration": 4.05}, {"text": "just to pause the lecture\nand do it yourself.", "start": 2445.91, "duration": 3.24}, {"text": "And what I'll write shortly--", "start": 2449.15, "duration": 5.04}, {"text": "for this case,\nI'll actually prove", "start": 2454.19, "duration": 1.71}, {"text": "that the thing I'm going\nto define is bijection.", "start": 2455.9, "duration": 3.06}, {"text": "That should help you.", "start": 2458.96, "duration": 1.24}, {"text": "So let me draw over\nhere off to the side.", "start": 2460.2, "duration": 5.87}, {"text": "We have, again,\n1, 2, 3, a, b, c.", "start": 2466.07, "duration": 6.847}, {"text": "So think of this as f.", "start": 2476.74, "duration": 1.89}, {"text": "This is my set A.\nThis is my set B.", "start": 2478.63, "duration": 3.45}, {"text": "And then I have\nalpha, beta, gamma.", "start": 2482.08, "duration": 4.77}, {"text": "And a gets mapped to alpha,\nb, gets mapped to beta,", "start": 2486.85, "duration": 3.96}, {"text": "c gets mapped to gamma.", "start": 2490.81, "duration": 2.35}, {"text": "So what would be the map going\nfrom A down to the set C?", "start": 2493.16, "duration": 5.9}, {"text": "Well, perhaps the composition.", "start": 2499.06, "duration": 3.0}, {"text": "1 gets mapped to a, which\ngets mapped to alpha.", "start": 2502.06, "duration": 3.15}, {"text": "So 1 gets mapped to alpha.", "start": 2505.21, "duration": 1.68}, {"text": "2 gets mapped to beta.", "start": 2506.89, "duration": 1.56}, {"text": "3 gets mapped to gamma.", "start": 2508.45, "duration": 1.86}, {"text": "How do I build this function\nout of the things that I know,", "start": 2510.31, "duration": 2.82}, {"text": "namely this f and g?", "start": 2513.13, "duration": 2.88}, {"text": "Well, this function\ngoing from A to C", "start": 2516.01, "duration": 2.58}, {"text": "is just the composition\nof these two functions.", "start": 2518.59, "duration": 3.515}, {"text": "So this is off to the side.", "start": 2522.105, "duration": 1.125}, {"text": "This is not a part of the proof.", "start": 2523.23, "duration": 1.333}, {"text": "Let h go from A to C be\nthe function g of f of x.", "start": 2528.17, "duration": 18.89}, {"text": "So I claim that this\nfunction is a bijection.", "start": 2550.311, "duration": 5.339}, {"text": "So we want to prove that it's\none-to-one and onto, all right?", "start": 2555.65, "duration": 16.31}, {"text": "So let's do one-to-one first.", "start": 2571.96, "duration": 3.135}, {"text": "So we this is the\npart where I'm going", "start": 2581.81, "duration": 2.1}, {"text": "to put this in parentheses,\nmeaning what we're doing now.", "start": 2583.91, "duration": 2.74}, {"text": "So we're going to prove\nthat h is one-to-one.", "start": 2586.65, "duration": 4.61}, {"text": "So that means we have to\nverify the definition that I've", "start": 2591.26, "duration": 4.98}, {"text": "erased.", "start": 2596.24, "duration": 1.41}, {"text": "So remember the definition.", "start": 2597.65, "duration": 1.96}, {"text": "So let's write it all out.", "start": 2599.61, "duration": 5.68}, {"text": "We first show h is one-to-one.", "start": 2609.86, "duration": 7.08}, {"text": "And what this means, according\nto the definition that I'm now", "start": 2616.94, "duration": 4.14}, {"text": "writing over, if h of x1 equals\nh of x2, then x1 equals x2.", "start": 2621.08, "duration": 16.11}, {"text": "So this is what\nwe want to prove.", "start": 2637.19, "duration": 1.38}, {"text": "This is the definition\nof h being one-to-one.", "start": 2638.57, "duration": 3.66}, {"text": "So let's start.", "start": 2646.77, "duration": 0.915}, {"text": "If h of x1 equals h\nof x2, then, in terms", "start": 2650.53, "duration": 5.79}, {"text": "of how we've defined\nh, which is g", "start": 2656.32, "duration": 3.18}, {"text": "of f of x, so the composition,\nthen this means g of f of x1", "start": 2659.5, "duration": 8.9}, {"text": "equals g of f of x2.", "start": 2668.4, "duration": 1.665}, {"text": "That's just what h is.", "start": 2672.86, "duration": 2.54}, {"text": "Now, this statement here--", "start": 2675.4, "duration": 5.38}, {"text": "now g we know is a bijection.", "start": 2680.78, "duration": 3.5}, {"text": "We know g is one-to-one.", "start": 2684.28, "duration": 2.56}, {"text": "And since g of something equals\ng of something else and g", "start": 2686.84, "duration": 5.34}, {"text": "is one-to-one, this implies\nthat f of x1 equals f of x2.", "start": 2692.18, "duration": 8.14}, {"text": "This is since g is one-to-one.", "start": 2700.32, "duration": 4.42}, {"text": "So starting with this\nand the definition of h", "start": 2708.8, "duration": 2.64}, {"text": "being the composition,\nwe conclude that f of x1", "start": 2711.44, "duration": 4.37}, {"text": "has to equal f of x2\nbecause g is one-to-one.", "start": 2715.81, "duration": 4.26}, {"text": "Now, since f is\nalso one-to-one--", "start": 2720.07, "duration": 3.21}, {"text": "we are assuming that f\nand g are bijections.", "start": 2723.28, "duration": 2.94}, {"text": "Since f is one-to-one,\nthis implies x1 equals x2,", "start": 2726.22, "duration": 7.02}, {"text": "since f is one-to-one.", "start": 2733.24, "duration": 3.18}, {"text": "And this is what\nwe wanted to prove.", "start": 2741.88, "duration": 2.52}, {"text": "We wanted to start with\nassuming h of x1 equals h of x2", "start": 2744.4, "duration": 3.93}, {"text": "and prove x1 equals x2,\nwhich is what we've done.", "start": 2748.33, "duration": 2.97}, {"text": "So thus, we've proven\nthat h is one-to-one.", "start": 2751.3, "duration": 6.6}, {"text": "Now, we have to show that it's\nsurjective, that it's onto.", "start": 2757.9, "duration": 2.985}, {"text": "h of A equals C. And again,\nI'll write out what this means.", "start": 2772.58, "duration": 5.58}, {"text": "This means for all y in C--", "start": 2778.16, "duration": 3.64}, {"text": "all right, let me\ncall it [? z-- ?]", "start": 2781.8, "duration": 3.05}, {"text": "there exists an x in A\nsuch that h of x equals z.", "start": 2784.85, "duration": 7.83}, {"text": "Now, we used the\nfact that f and g", "start": 2797.85, "duration": 2.76}, {"text": "were injective to conclude that\nthe composition is injective.", "start": 2800.61, "duration": 5.62}, {"text": "So it stands to\nreason that we're", "start": 2806.23, "duration": 1.657}, {"text": "going to use the fact that\nthey're both surjective", "start": 2807.887, "duration": 2.083}, {"text": "to prove that h is surjective.", "start": 2809.97, "duration": 2.01}, {"text": "So we need to prove\nthat for all z in C", "start": 2815.02, "duration": 2.85}, {"text": "there exists an x in A as\nsuch that h of x equals z.", "start": 2817.87, "duration": 2.67}, {"text": "So let z be in C. Now,\nwe need to find some", "start": 2820.54, "duration": 4.77}, {"text": "x in A that gets mapped to z.", "start": 2825.31, "duration": 2.34}, {"text": "We'll use that g and\nf are both surjective.", "start": 2827.65, "duration": 4.41}, {"text": "And what's the picture\nthat goes along with this?", "start": 2836.53, "duration": 2.715}, {"text": "Here's the sets C, B, and\nA. We have some element of z", "start": 2846.1, "duration": 7.01}, {"text": "And we know that\nsince g is surjective,", "start": 2853.11, "duration": 6.22}, {"text": "there's some element in B\nthat gets mapped to z by G.", "start": 2859.33, "duration": 7.77}, {"text": "But now, since f going\nfrom A to B is surjective,", "start": 2867.1, "duration": 3.84}, {"text": "there exists some\nx which maps to y.", "start": 2870.94, "duration": 3.528}, {"text": "And then that's\nthe whole argument.", "start": 2877.112, "duration": 1.458}, {"text": "That's it.", "start": 2878.57, "duration": 2.31}, {"text": "I drew this picture.", "start": 2880.88, "duration": 1.11}, {"text": "But now, I just need\nto turn it into English", "start": 2881.99, "duration": 3.18}, {"text": "using the properties and\nassumptions that I have.", "start": 2885.17, "duration": 3.54}, {"text": "Since g is surjective, there\nexist a y in B such that g of y", "start": 2893.98, "duration": 11.4}, {"text": "equals z.", "start": 2905.38, "duration": 0.84}, {"text": "Since f is surjective, there\nexists an x in A so that f of x", "start": 2917.66, "duration": 13.24}, {"text": "equals y.", "start": 2930.9, "duration": 0.78}, {"text": "But then if I look\nat h of x, this", "start": 2934.78, "duration": 4.32}, {"text": "is equal to g of f of x,\nwhich is equal to g of y,", "start": 2939.1, "duration": 5.86}, {"text": "which is equal to z by\nhow we've defined y.", "start": 2944.96, "duration": 4.58}, {"text": "Remember, g of y equals z, how\nwe found y and how we found x.", "start": 2949.54, "duration": 3.76}, {"text": "Remember, f of x equals this y.", "start": 2953.3, "duration": 3.08}, {"text": "And therefore,\nthis map h is onto.", "start": 2956.38, "duration": 6.69}, {"text": "And therefore, h is a\nbijection, proving this theorem.", "start": 2963.07, "duration": 6.4}, {"text": "So that should help you.", "start": 2969.47, "duration": 2.968}, {"text": "I'll give you many\nexercises to prove", "start": 2972.438, "duration": 6.712}, {"text": "that the inverse of a\nbijection is a bijection.", "start": 2979.15, "duration": 3.48}, {"text": "So back to what we were\ndoing to begin with.", "start": 2989.91, "duration": 7.69}, {"text": "We want to show the set of\neven natural numbers has", "start": 2997.6, "duration": 4.31}, {"text": "the same size as\nthe natural numbers,", "start": 3001.91, "duration": 2.92}, {"text": "has the same cardinality, as\nthe natural numbers and the same", "start": 3004.83, "duration": 3.0}, {"text": "for the odd ones.", "start": 3007.83, "duration": 0.72}, {"text": "So I'm just going\nto do the odd ones.", "start": 3008.55, "duration": 2.04}, {"text": "Again, this will be a\nsmall exercise for you", "start": 3010.59, "duration": 2.94}, {"text": "to do to prove number 2, the\nstatement for the odd ones.", "start": 3013.53, "duration": 6.11}, {"text": "So I'm going to\ndo the even ones.", "start": 3019.64, "duration": 1.74}, {"text": "And you can do the odd ones.", "start": 3021.38, "duration": 3.09}, {"text": "You should, if you plan\non studying more math,", "start": 3024.47, "duration": 4.25}, {"text": "get used to the instructor,\nprofessor, research paper", "start": 3028.72, "duration": 6.33}, {"text": "writer, textbook author\ngiving out little exercises", "start": 3035.05, "duration": 5.53}, {"text": "to make sure that\nyou're following along", "start": 3040.58, "duration": 1.71}, {"text": "and that you can do some\nminor task at some point", "start": 3042.29, "duration": 5.69}, {"text": "during the discussion.", "start": 3047.98, "duration": 1.89}, {"text": "So we're going to find--", "start": 3052.79, "duration": 4.05}, {"text": "so we want to show that\nthe natural numbers has", "start": 3056.84, "duration": 17.42}, {"text": "the same size as the even\nnatural numbers, which", "start": 3074.26, "duration": 2.73}, {"text": "is the same as this statement\nby that first theorem I wrote up", "start": 3076.99, "duration": 2.61}, {"text": "there.", "start": 3079.6, "duration": 0.5}, {"text": "Now, that means we need\nto find a bijection", "start": 3084.51, "duration": 2.85}, {"text": "from the natural numbers to the\nset of even natural numbers.", "start": 3087.36, "duration": 7.78}, {"text": "This should be not too bad.", "start": 3095.14, "duration": 3.68}, {"text": "I mean, so again, this\nis off to the side.", "start": 3098.82, "duration": 4.495}, {"text": "This is not part of the proof.", "start": 3103.315, "duration": 1.25}, {"text": "What would be the map going\nfrom these guys to these guys?", "start": 3122.57, "duration": 5.04}, {"text": "Well, I mean, there's\nseveral you could choose.", "start": 3127.61, "duration": 3.18}, {"text": "But maybe the simplest\nis 1 gets mapped to 2,", "start": 3130.79, "duration": 2.77}, {"text": "2 gets mapped to 4,\n3 gets mapped to 6,", "start": 3133.56, "duration": 3.11}, {"text": "4 gets mapped to 8, 5 to 10,\n6 to 12, and so on, and so on.", "start": 3136.67, "duration": 6.18}, {"text": "Now, what is that map?", "start": 3142.85, "duration": 2.88}, {"text": "And now, I'll\ncontinue the proof.", "start": 3145.73, "duration": 3.84}, {"text": "Let f be the function into the\neven natural numbers defined", "start": 3155.12, "duration": 13.72}, {"text": "by f of n equals 2 times n.", "start": 3168.84, "duration": 6.03}, {"text": "And so n is a natural number.", "start": 3174.87, "duration": 4.24}, {"text": "So this is just formally writing\nthe function that takes 1 to 2,", "start": 3179.11, "duration": 4.04}, {"text": "2 to 4, 3 to 6, 4, to\n8, and so on, and so on.", "start": 3183.15, "duration": 5.65}, {"text": "I claim f is a bijection.", "start": 3188.8, "duration": 3.96}, {"text": "So I have to show that f\nis one-to-one and onto.", "start": 3192.76, "duration": 3.585}, {"text": "So we'll first show\nf is one-to-one.", "start": 3203.25, "duration": 5.73}, {"text": "So that means that I have to\nassume f of n1 equals f of n2", "start": 3211.93, "duration": 4.55}, {"text": "and conclude that n1 equals n2.", "start": 3216.48, "duration": 3.03}, {"text": "So let me actually write out\nwhat this means again for you", "start": 3219.51, "duration": 2.88}, {"text": "to say that f is one-to-one.", "start": 3222.39, "duration": 2.07}, {"text": "Is one to one-- i.e.", "start": 3224.46, "duration": 1.68}, {"text": "if f of n1 equals f of\nn2, then n1 equals n2.", "start": 3226.14, "duration": 9.72}, {"text": "But this is easy to\nverify for this function", "start": 3235.86, "duration": 2.7}, {"text": "that we've written down because\nif f of n1 equals f of n2-- so", "start": 3238.56, "duration": 8.87}, {"text": "remember, this is what we\nwant to show, all right?", "start": 3247.43, "duration": 3.0}, {"text": "So to show it, I start\nwith my assumption.", "start": 3250.43, "duration": 4.98}, {"text": "And I need to\nconclude n1 equals n2.", "start": 3255.41, "duration": 3.3}, {"text": "So suppose f of\nn1 equals f of n2,", "start": 3258.71, "duration": 5.85}, {"text": "my assumption, my hypothesis.", "start": 3264.56, "duration": 2.04}, {"text": "And I need to\nconclude n1 equals n2.", "start": 3266.6, "duration": 1.62}, {"text": "Then this implies, by\nthe definition of f,", "start": 3270.88, "duration": 2.925}, {"text": "2 times n2 equals\n2 times n2, which,", "start": 3273.805, "duration": 3.615}, {"text": "by algebra of just eliminating\nthe 2's, n1 equals n2, which", "start": 3277.42, "duration": 4.08}, {"text": "is the conclusion that I want.", "start": 3281.5, "duration": 3.15}, {"text": "So I've proven the statement\nthat if f of n1 equals f of n2,", "start": 3284.65, "duration": 4.41}, {"text": "then n1 equals n2.", "start": 3289.06, "duration": 1.41}, {"text": "Therefore, f is one-to-one.", "start": 3290.47, "duration": 3.04}, {"text": "So thus, f is one-to-one.", "start": 3293.51, "duration": 5.81}, {"text": "So now, we want to show\nf is onto, surjective.", "start": 3299.32, "duration": 12.3}, {"text": "I'll write this out again. i.e.", "start": 3311.62, "duration": 2.88}, {"text": "For all elements that\nn are an even number,", "start": 3314.5, "duration": 13.69}, {"text": "there exists an n such\nthat f of n equals m.", "start": 3328.19, "duration": 5.61}, {"text": "Now, let m be an even integer.", "start": 3340.71, "duration": 7.19}, {"text": "And so not to confuse us,\nlet me write 2 times k.", "start": 3347.9, "duration": 4.6}, {"text": "This is the same set.", "start": 3352.5, "duration": 1.73}, {"text": "I'm just using a different\ndummy variable instead of n", "start": 3354.23, "duration": 3.06}, {"text": "in my description of the\neven natural numbers.", "start": 3357.29, "duration": 2.415}, {"text": "And let's do that here as well.", "start": 3365.79, "duration": 1.62}, {"text": "Again, this is not\nchanging anything.", "start": 3375.47, "duration": 1.56}, {"text": "This is just changing\nthe letter I'm", "start": 3377.03, "duration": 1.5}, {"text": "using to describe the set,\nwhich is inconsequential.", "start": 3378.53, "duration": 6.29}, {"text": "But I don't want you to get the\nfalse impression that somehow", "start": 3384.82, "duration": 4.71}, {"text": "I'm not doing anything at all.", "start": 3389.53, "duration": 1.425}, {"text": "OK, so suppose I have an even\ninteger, then there exists--", "start": 3394.25, "duration": 5.52}, {"text": "simply by the\ndefinition of this set,", "start": 3399.77, "duration": 2.52}, {"text": "there exists an n natural number\nso that m equals 2 times n.", "start": 3402.29, "duration": 8.59}, {"text": "Then f of this natural number,\nwhich is 2 times n, equals m.", "start": 3413.71, "duration": 5.67}, {"text": "And therefore, I get\nsomething that maps to m.", "start": 3419.38, "duration": 3.495}, {"text": "Therefore, f is onto.", "start": 3432.49, "duration": 1.53}, {"text": "Therefore, f is a\nbijection and the two sets", "start": 3434.02, "duration": 3.84}, {"text": "have the same cardinality.", "start": 3437.86, "duration": 1.98}, {"text": "All right, so let's--", "start": 3449.26, "duration": 12.91}, {"text": "where are we at?", "start": 3462.17, "duration": 0.72}, {"text": "Where should I write?", "start": 3462.89, "duration": 1.56}, {"text": "Let's write here.", "start": 3464.45, "duration": 0.9}, {"text": "Maybe I'll leave that up\nbecause I don't want to--", "start": 3470.907, "duration": 2.083}, {"text": "now, using this-- and\nI'll probably put this", "start": 3491.17, "duration": 2.82}, {"text": "in the homework--", "start": 3493.99, "duration": 1.8}, {"text": "I mean, one can also show--", "start": 3495.79, "duration": 5.58}, {"text": "I should say using\nthis, but one can also", "start": 3504.04, "duration": 3.9}, {"text": "show that the integers\nhave the same size", "start": 3507.94, "duration": 7.47}, {"text": "as the natural numbers,\nwhich, again, is a little bit", "start": 3515.41, "duration": 4.88}, {"text": "surprising since the\nnatural numbers are", "start": 3520.29, "duration": 2.7}, {"text": "a strict subset of Z.", "start": 3522.99, "duration": 5.55}, {"text": "So what's the proof?", "start": 3528.54, "duration": 2.14}, {"text": "So I'm going to\ndraw a picture, then", "start": 3530.68, "duration": 3.14}, {"text": "I'm going to write\ndown the function,", "start": 3533.82, "duration": 1.8}, {"text": "and then I'm going\nto leave it as--", "start": 3535.62, "duration": 3.572}, {"text": "actually, I'm going to put\nit in the homework for you", "start": 3539.192, "duration": 2.208}, {"text": "to verify that this function\nis one-to-one and onto.", "start": 3541.4, "duration": 3.0}, {"text": "So let's say there's\nas many natural numbers", "start": 3544.4, "duration": 18.71}, {"text": "as I want to write and as many\nintegers as I want to write.", "start": 3563.11, "duration": 17.16}, {"text": "OK, so what would\nbe a way of mapping", "start": 3580.27, "duration": 6.24}, {"text": "the integers in a\none-to-one and onto fashion", "start": 3586.51, "duration": 4.83}, {"text": "onto the natural numbers?", "start": 3591.34, "duration": 1.095}, {"text": "Well, what we could do--", "start": 3594.99, "duration": 3.49}, {"text": "first off, let's send 0 to 1\njust to get 0 out of the way.", "start": 3598.48, "duration": 6.85}, {"text": "And from then on,\nnow we just need", "start": 3605.33, "duration": 3.06}, {"text": "to find a way to map\nthe positive integers", "start": 3608.39, "duration": 2.37}, {"text": "and the negative integers onto\nthe natural numbers bigger", "start": 3610.76, "duration": 3.81}, {"text": "than 2.", "start": 3614.57, "duration": 2.45}, {"text": "And in some way,\nmentally, we should", "start": 3617.02, "duration": 5.85}, {"text": "feel like we can do this because\nwe kind of did it over there,", "start": 3622.87, "duration": 5.04}, {"text": "but not explicitly.", "start": 3627.91, "duration": 1.86}, {"text": "So how about we take 1\nto 2, 2 to 4, 3 to 6?", "start": 3629.77, "duration": 11.52}, {"text": "4 would then go to 8.", "start": 3641.29, "duration": 3.57}, {"text": "And we'll take 1\nto 3, minus 2 to 5.", "start": 3644.86, "duration": 9.135}, {"text": "I'm getting crossed.", "start": 3653.995, "duration": 2.625}, {"text": "And then minus 3\nwould get sent to 7.", "start": 3656.62, "duration": 5.23}, {"text": "So you see that the\npositive integers", "start": 3661.85, "duration": 3.09}, {"text": "get mapped to the\neven natural numbers", "start": 3664.94, "duration": 2.76}, {"text": "and the negative integers\nget mapped to the odd natural", "start": 3667.7, "duration": 7.78}, {"text": "numbers bigger than 1.", "start": 3675.48, "duration": 1.29}, {"text": "So I'm not even going\nto write the proof.", "start": 3680.16, "duration": 1.75}, {"text": "This will be part\nof the homework.", "start": 3681.91, "duration": 6.49}, {"text": "Now, it is a bit surprising\nthat there are twice", "start": 3688.4, "duration": 5.57}, {"text": "as many numbers as\nnumbers, not too", "start": 3693.97, "duration": 2.94}, {"text": "surprising since these\nsubsets, if you picture them", "start": 3696.91, "duration": 5.16}, {"text": "as I've been doing as\nsubsets of the real line,", "start": 3702.07, "duration": 3.18}, {"text": "you know they're\nkind of discrete.", "start": 3705.25, "duration": 1.44}, {"text": "So you should be\nable to count them.", "start": 3706.69, "duration": 3.36}, {"text": "What is not-- what is\nmore surprising are--", "start": 3710.05, "duration": 5.4}, {"text": "is whether or not can count\nsubsets that, in some sense,", "start": 3715.45, "duration": 3.82}, {"text": "are not discrete.", "start": 3719.27, "duration": 1.07}, {"text": "For example, what about\nthe rational numbers?", "start": 3720.34, "duration": 3.91}, {"text": "So this is a theorem that--", "start": 3724.25, "duration": 6.74}, {"text": "and let me just look at those\npositive rational numbers.", "start": 3730.99, "duration": 3.12}, {"text": "In fact, I could take\nall rational numbers.", "start": 3734.11, "duration": 2.02}, {"text": "But for the statement\nof this theorem,", "start": 3736.13, "duration": 5.47}, {"text": "if I look at those rational\nnumbers which are positive,", "start": 3741.6, "duration": 10.1}, {"text": "then this has the same size\nas the natural numbers.", "start": 3751.7, "duration": 5.09}, {"text": "You can count the positive\nrational numbers, which is just", "start": 3756.79, "duration": 5.405}, {"text": "a bit crazy to me because\nhere, at least for let's say", "start": 3762.195, "duration": 6.115}, {"text": "the integers, once\nI'm at an integer,", "start": 3768.31, "duration": 3.27}, {"text": "I can move to a next biggest one\nand count that one in some way,", "start": 3771.58, "duration": 4.225}, {"text": "right?", "start": 3775.805, "duration": 0.5}, {"text": "And so that makes it believable\nthat I can count the integers.", "start": 3779.81, "duration": 6.258}, {"text": "The integers have the same\nsize as the natural numbers,", "start": 3786.068, "duration": 2.292}, {"text": "even though that,\nat first glance,", "start": 3788.36, "duration": 1.69}, {"text": "it looks like there's\ntwice as many.", "start": 3790.05, "duration": 3.44}, {"text": "But for rational\nnumbers, between any two", "start": 3793.49, "duration": 4.29}, {"text": "rational numbers, there's\nanother rational number", "start": 3797.78, "duration": 2.07}, {"text": "in between them.", "start": 3799.85, "duration": 1.14}, {"text": "You just take the average of\nthose two rational numbers.", "start": 3800.99, "duration": 5.85}, {"text": "So now, this idea of\nbeing at a rational number", "start": 3806.84, "duration": 3.45}, {"text": "and then moving to the next\nbig one, you can't do that now.", "start": 3810.29, "duration": 4.33}, {"text": "So now, it's a little bit up in\nthe air at least whether or not", "start": 3814.62, "duration": 4.34}, {"text": "can count the rational numbers.", "start": 3818.96, "duration": 2.97}, {"text": "And what I'm saying is\nthat indeed you can.", "start": 3821.93, "duration": 2.827}, {"text": "And this will be\npart of the homework.", "start": 3824.757, "duration": 1.583}, {"text": "I will at least give you an\nidea of how the proof will", "start": 3829.41, "duration": 8.09}, {"text": "go, what we will actually\nbe able to write down,", "start": 3837.5, "duration": 2.22}, {"text": "a map based on a simple fact.", "start": 3839.72, "duration": 4.08}, {"text": "So let me not write down proof,\nbut let me write down a remark.", "start": 3843.8, "duration": 8.73}, {"text": "So we'll actually be able\nto write down a map based", "start": 3852.53, "duration": 3.26}, {"text": "on one simple fact, which\nis this fundamental theorem", "start": 3855.79, "duration": 3.21}, {"text": "of arithmetic, which says that--", "start": 3859.0, "duration": 3.75}, {"text": "so this is just discussion now.", "start": 3862.75, "duration": 1.515}, {"text": "More stuff will be written\nin the homework about this.", "start": 3867.015, "duration": 2.655}, {"text": "So just try to follow along.", "start": 3869.67, "duration": 1.98}, {"text": "So the fundamental\ntheorem of arithmetic", "start": 3871.65, "duration": 1.68}, {"text": "says that if you have a\npositive natural number,", "start": 3873.33, "duration": 2.55}, {"text": "you can write it in a unique way\nas a product of prime numbers.", "start": 3875.88, "duration": 4.53}, {"text": "Now, for rational\nnumbers, using that,", "start": 3880.41, "duration": 4.661}, {"text": "that means you can write\nevery rational number uniquely", "start": 3885.071, "duration": 3.849}, {"text": "as a product of\nprime numbers divided", "start": 3888.92, "duration": 4.25}, {"text": "by another product\nof prime numbers", "start": 3893.17, "duration": 2.52}, {"text": "where no two prime numbers--", "start": 3895.69, "duration": 3.15}, {"text": "where the prime numbers up\ntop and the prime numbers", "start": 3898.84, "duration": 2.73}, {"text": "at the bottom,\nnone are in common,", "start": 3901.57, "duration": 2.47}, {"text": "meaning you've simplified\nas much as possible.", "start": 3904.04, "duration": 3.54}, {"text": "So instead of 15 over 3--", "start": 3907.58, "duration": 5.515}, {"text": "no, that's not good.", "start": 3913.095, "duration": 1.695}, {"text": "Let's say 15 over 30.", "start": 3914.79, "duration": 1.86}, {"text": "You have 1/2.", "start": 3916.65, "duration": 3.25}, {"text": "So the map that I would take--", "start": 3919.9, "duration": 3.75}, {"text": "so what I'm saying here is\nthat every rational number", "start": 3923.65, "duration": 16.37}, {"text": "can be written as some product.", "start": 3940.02, "duration": 6.46}, {"text": "So let me not use that\nnotation, but some product p", "start": 3946.48, "duration": 3.81}, {"text": "r1 pN rN q1 s1 qn sM where\np1, p2, and pN, these are all", "start": 3950.29, "duration": 17.04}, {"text": "primes.", "start": 3967.33, "duration": 0.5}, {"text": "q1 up to qN, they're all primes.", "start": 3967.83, "duration": 2.82}, {"text": "r1, rN, these are all exponents,\npositive natural numbers.", "start": 3970.65, "duration": 4.57}, {"text": "So rj, sk, these\nare natural numbers.", "start": 3975.22, "duration": 5.9}, {"text": "p1 pN q1 to qM are primes.", "start": 3981.12, "duration": 2.76}, {"text": "And for all jk, qj\ndoes not equal pk.", "start": 3983.88, "duration": 11.9}, {"text": "So there's no prime that appears\nboth up here and down here.", "start": 3995.78, "duration": 3.66}, {"text": "We've already\nsimplified that away.", "start": 3999.44, "duration": 2.61}, {"text": "So just so you don't\nthink I'm fooling you,", "start": 4016.4, "duration": 6.872}, {"text": "9/2, which is a positive\nrational number,", "start": 4023.272, "duration": 1.708}, {"text": "this is 3 squared over 2, yeah?", "start": 4024.98, "duration": 2.06}, {"text": "I'm not going to do any more.", "start": 4033.07, "duration": 1.21}, {"text": "That's it.", "start": 4034.28, "duration": 0.5}, {"text": "So the map that we will take\nfrom this rational number", "start": 4040.42, "duration": 5.51}, {"text": "to a natural number\nwill be this gets", "start": 4045.93, "duration": 4.86}, {"text": "mapped to the natural number\np1 to r1, pN to rN times now q1", "start": 4050.79, "duration": 13.57}, {"text": "to 2s 1 minus 1 qM 2Sn minus 1.", "start": 4064.36, "duration": 9.42}, {"text": "So basically, I map\nit to the integer that", "start": 4073.78, "duration": 3.51}, {"text": "has this expansion in terms\nof prime numbers, where now", "start": 4077.29, "duration": 5.4}, {"text": "the exponents of\nthese prime numbers", "start": 4082.69, "duration": 1.92}, {"text": "is even depending on\nthese exponents on top", "start": 4084.61, "duration": 3.24}, {"text": "and the exponents\nof this one are odd,", "start": 4087.85, "duration": 3.93}, {"text": "depending on this\nexponent on top.", "start": 4091.78, "duration": 3.51}, {"text": "So for example, 3 squared over\n2, this would get mapped to 3", "start": 4095.29, "duration": 8.79}, {"text": "to the 4 times 2.", "start": 4104.08, "duration": 2.7}, {"text": "So what we'll do in\nthe homework is show", "start": 4116.859, "duration": 2.04}, {"text": "that this map is, in\nfact, a bijection.", "start": 4118.899, "duration": 2.491}, {"text": "So those two theorems you\nwill prove in the homework.", "start": 4138.279, "duration": 4.441}, {"text": "They won't be too bad.", "start": 4142.72, "duration": 2.61}, {"text": "I will leave enough hints.", "start": 4145.33, "duration": 2.64}, {"text": "So we've dealt with z.", "start": 4147.97, "duration": 3.285}, {"text": "We've dealt with q, essentially.", "start": 4151.255, "duration": 2.295}, {"text": "I mean, so let me\nactually write down--", "start": 4166.26, "duration": 5.26}, {"text": "this is really a corollary\nof these two theorems", "start": 4171.52, "duration": 3.77}, {"text": "here, which I haven't\nproved, but you", "start": 4175.29, "duration": 3.41}, {"text": "will prove in the homework.", "start": 4178.7, "duration": 1.5}, {"text": "So this says that the\nrationals are countable,", "start": 4180.2, "duration": 8.47}, {"text": "all the rationales, not\njust the positive ones.", "start": 4188.67, "duration": 3.66}, {"text": "And what's the proof?", "start": 4192.33, "duration": 3.94}, {"text": "So we know that--", "start": 4196.27, "duration": 6.06}, {"text": "so I'm going to\ngive you a sketch.", "start": 4208.97, "duration": 4.96}, {"text": "Should I sketch it or\nshould I write it all out?", "start": 4213.93, "duration": 2.193}, {"text": "I'm running a little\nbit out of time.", "start": 4216.123, "duration": 1.542}, {"text": "So maybe I will just tell\nyou why this is true.", "start": 4224.17, "duration": 4.56}, {"text": "I mean, all the details\nare essentially here.", "start": 4228.73, "duration": 2.1}, {"text": "I'm just not going to write\nit as carefully as I've been", "start": 4230.83, "duration": 2.333}, {"text": "writing down the proofs before.", "start": 4233.163, "duration": 1.847}, {"text": "So let me write this\nas the proof sketch.", "start": 4235.01, "duration": 5.42}, {"text": "Of course, you can write these--", "start": 4243.41, "duration": 3.49}, {"text": "you can actually use the\ndefinitions and write this out.", "start": 4246.9, "duration": 2.67}, {"text": "But this is the essential idea.", "start": 4249.57, "duration": 2.23}, {"text": "So we have that the size\nof rational numbers--", "start": 4251.8, "duration": 14.0}, {"text": "so let me-- this has the same\nsize as the rational numbers", "start": 4265.8, "duration": 20.09}, {"text": "which are negative.", "start": 4285.89, "duration": 1.4}, {"text": "And how do we establish this?", "start": 4296.94, "duration": 4.38}, {"text": "Or instead of using\nthe same letter,", "start": 4301.32, "duration": 3.75}, {"text": "let's say r, since f\nof Q equals minus Q", "start": 4305.07, "duration": 10.05}, {"text": "is a bijection from the\nfirst set to the second set.", "start": 4315.12, "duration": 11.69}, {"text": "If I just take a rational\nnumber, positive 1,", "start": 4344.829, "duration": 2.611}, {"text": "take its minus, then I get\nan element of the second set.", "start": 4347.44, "duration": 3.72}, {"text": "And this is a bijection.", "start": 4351.16, "duration": 2.1}, {"text": "OK, so thus, since\nthis has the same size", "start": 4356.1, "duration": 13.35}, {"text": "as the natural numbers,\nand by that theorem", "start": 4369.45, "duration": 5.93}, {"text": "we proved over there,\nthe size of this set", "start": 4375.38, "duration": 2.18}, {"text": "is the same as the\nnatural numbers--", "start": 4377.56, "duration": 1.54}, {"text": "so it is countable--", "start": 4379.1, "duration": 2.797}, {"text": "then there exists\nbijections f going from Q--", "start": 4389.58, "duration": 11.305}, {"text": "so the positive\nrational numbers--", "start": 4400.885, "duration": 1.86}, {"text": "to the natural numbers and g\ngoing from the negative ones", "start": 4407.34, "duration": 20.87}, {"text": "to the natural numbers.", "start": 4428.21, "duration": 3.42}, {"text": "So the picture here is--", "start": 4431.63, "duration": 2.175}, {"text": "well, let's not draw\nthe picture yet.", "start": 4439.01, "duration": 3.9}, {"text": "OK, so I have these\ntwo bijections", "start": 4442.91, "duration": 2.28}, {"text": "from the positive\nrationales to the integers--", "start": 4445.19, "duration": 3.15}, {"text": "this one from the\nnegative rationales", "start": 4448.34, "duration": 3.75}, {"text": "to the natural numbers.", "start": 4452.09, "duration": 2.79}, {"text": "How do I get a map\nthat goes from all of q", "start": 4454.88, "duration": 3.08}, {"text": "now to the natural numbers?", "start": 4457.96, "duration": 1.61}, {"text": "Well, let's go in between\nand go to the integers.", "start": 4459.57, "duration": 3.48}, {"text": "Then I define a function h,\nwhich goes now from all of Q", "start": 4463.05, "duration": 10.5}, {"text": "to the integers by h of\nx equals 0 if x equals 0;", "start": 4473.55, "duration": 15.42}, {"text": "equals f of x if x is\npositive; and negative g", "start": 4488.97, "duration": 8.02}, {"text": "of x if x is negative.", "start": 4496.99, "duration": 3.53}, {"text": "And h is a bijection.", "start": 4506.32, "duration": 4.69}, {"text": "So everything up\nto this point has", "start": 4511.01, "duration": 4.32}, {"text": "been completely fine\nwith the exception", "start": 4515.33, "duration": 3.19}, {"text": "of me verifying that\nthis map is a bijection", "start": 4518.52, "duration": 3.33}, {"text": "and this map is a bijection.", "start": 4521.85, "duration": 1.69}, {"text": "So that's the only\nparts that I'm", "start": 4523.54, "duration": 1.4}, {"text": "leaving out for you to verify.", "start": 4524.94, "duration": 2.61}, {"text": "Then h is a bijection.", "start": 4527.55, "duration": 2.25}, {"text": "So Q has the same cardinality\nas integers, which we've shown", "start": 4529.8, "duration": 8.61}, {"text": "has the same cardinality\nas the natural numbers.", "start": 4538.41, "duration": 3.225}, {"text": "And therefore, the rationals\nhave the same cardinality", "start": 4544.56, "duration": 4.05}, {"text": "as the natural numbers.", "start": 4548.61, "duration": 1.15}, {"text": "So they are countably infinite.", "start": 4549.76, "duration": 1.73}, {"text": "So a natural question is--", "start": 4561.22, "duration": 5.505}, {"text": "I mean, is there anything\nbigger than the natural numbers?", "start": 4569.973, "duration": 2.417}, {"text": "Because everything\nI've written down,", "start": 4572.39, "duration": 1.89}, {"text": "this has the size of\nthe natural numbers.", "start": 4574.28, "duration": 1.965}, {"text": "We haven't really defined the\nreal numbers well enough yet", "start": 4579.51, "duration": 3.42}, {"text": "to make any sort of claim like\nthat about the real numbers.", "start": 4582.93, "duration": 9.9}, {"text": "And now, is there\njust any set that", "start": 4592.83, "duration": 7.96}, {"text": "is bigger in size than\nthe natural numbers?", "start": 4600.79, "duration": 2.65}, {"text": "The answer to that was unknown.", "start": 4603.44, "duration": 4.18}, {"text": "And it's pretty\nstrikingly yes, in fact.", "start": 4607.62, "duration": 6.23}, {"text": "So let me phrase that question.", "start": 4618.2, "duration": 6.44}, {"text": "Does there exist a set A\nsuch that A has strictly", "start": 4633.76, "duration": 12.29}, {"text": "bigger cardinality than\nthe natural numbers, so A", "start": 4646.05, "duration": 2.7}, {"text": "is uncountable?", "start": 4648.75, "duration": 0.93}, {"text": "So to answer this question\nastoundingly yes, let me first", "start": 4654.41, "duration": 4.32}, {"text": "define for a general object.", "start": 4658.73, "duration": 2.265}, {"text": "If A is a set, we\ndefine script p of A.", "start": 4665.71, "duration": 8.655}, {"text": "This is the power set of A.\nThis is a set that consists", "start": 4674.365, "duration": 14.115}, {"text": "of all subsets of A. So this is\na set of all sets B such that B", "start": 4688.48, "duration": 6.73}, {"text": "is a subset of A. So for\nexample, if A is the empty set,", "start": 4695.21, "duration": 16.65}, {"text": "the power set--", "start": 4711.86, "duration": 0.825}, {"text": "so A is empty.", "start": 4715.69, "duration": 1.65}, {"text": "What are the subsets\nof the empty set?", "start": 4717.34, "duration": 3.52}, {"text": "Well, there's only one subset\nof the empty set, the empty set.", "start": 4720.86, "duration": 5.17}, {"text": "And even though the\nempty set has no members,", "start": 4726.03, "duration": 2.13}, {"text": "its power set has one member.", "start": 4728.16, "duration": 1.425}, {"text": "If A equals 1,\nthen the power set", "start": 4733.73, "duration": 3.0}, {"text": "of A, the set of all subsets,\nconsists of the empty set", "start": 4736.73, "duration": 4.66}, {"text": "and the set itself, 1.", "start": 4741.39, "duration": 2.52}, {"text": "And let's do one more.", "start": 4746.94, "duration": 3.24}, {"text": "If A is the set 1, 2,\nthen the power set of A,", "start": 4750.18, "duration": 7.68}, {"text": "this is the set which\nconsists of the empty set,", "start": 4757.86, "duration": 5.0}, {"text": "because this is a\nsubset of this set,", "start": 4762.86, "duration": 3.97}, {"text": "the set consisting of 1, because\nthis is a subset of this set,", "start": 4766.83, "duration": 4.01}, {"text": "or 2, 1, 2.", "start": 4770.84, "duration": 6.33}, {"text": "Now, notice something.", "start": 4777.17, "duration": 1.74}, {"text": "This set had cardinality.", "start": 4778.91, "duration": 2.82}, {"text": "Strictly speaking, I\nshould have defined that", "start": 4781.73, "duration": 2.91}, {"text": "as having cardinality 0.", "start": 4784.64, "duration": 2.94}, {"text": "Yet, its power set\nhas cardinality 1.", "start": 4787.58, "duration": 3.36}, {"text": "A has size 1 because it's\nin one-to-one correspondence", "start": 4790.94, "duration": 4.62}, {"text": "with just 1.", "start": 4795.56, "duration": 1.89}, {"text": "And its power set\nhas two elements.", "start": 4797.45, "duration": 3.42}, {"text": "So it has cardinality 2.", "start": 4800.87, "duration": 3.44}, {"text": "I could count them off--", "start": 4804.31, "duration": 1.0}, {"text": "1, 2.", "start": 4805.31, "duration": 1.98}, {"text": "A has size 2, has two elements.", "start": 4807.29, "duration": 2.88}, {"text": "And the power set\nof A has size 4.", "start": 4810.17, "duration": 2.32}, {"text": "It has four different elements--\nthe empty set, 1, 2, 1, 2.", "start": 4812.49, "duration": 4.1}, {"text": "So what one can prove in\ngeneral and which will appear", "start": 4816.59, "duration": 9.43}, {"text": "on the homework is\nif A has size n--", "start": 4826.02, "duration": 7.11}, {"text": "so it's a finite set of size\nn, meaning it's in one-to-one", "start": 4833.13, "duration": 4.2}, {"text": "correspondence with\nthe numbers 1 up to n--", "start": 4837.33, "duration": 3.33}, {"text": "then its power\nset is also finite", "start": 4840.66, "duration": 7.35}, {"text": "and has cardinality 2 to the n.", "start": 4848.01, "duration": 3.84}, {"text": "And you can prove by induction,\nif you like, that 2 to the n", "start": 4851.85, "duration": 4.4}, {"text": "is always bigger than n.", "start": 4856.25, "duration": 1.29}, {"text": "And so a theorem I'll\nprove next time, which", "start": 4860.24, "duration": 7.1}, {"text": "will finish our discussion\nof sets and cardinality,", "start": 4867.34, "duration": 6.92}, {"text": "and then we'll move on\nto the real numbers,", "start": 4874.26, "duration": 2.58}, {"text": "is this theorem due\nto Cantor, which", "start": 4876.84, "duration": 8.31}, {"text": "says that not just\nfor finite sets", "start": 4885.15, "duration": 5.65}, {"text": "do we have the power set\nbeing, in some sense, strictly", "start": 4890.8, "duration": 2.55}, {"text": "bigger than the original\nset, but for any set.", "start": 4893.35, "duration": 3.33}, {"text": "So this theorem due to\nCantor is if A is a set,", "start": 4896.68, "duration": 8.29}, {"text": "then the cardinality of\nA is strictly smaller", "start": 4904.97, "duration": 5.16}, {"text": "than the cardinality\nof its power set.", "start": 4910.13, "duration": 4.22}, {"text": "So this definitely\nanswers our question.", "start": 4914.35, "duration": 4.56}, {"text": "Does there exist a set\nwith cardinality bigger", "start": 4918.91, "duration": 2.49}, {"text": "than the natural numbers?", "start": 4921.4, "duration": 1.54}, {"text": "So let me write\nthis as a remark.", "start": 4922.94, "duration": 1.625}, {"text": "In fact, maybe I'll state\nthis as another theorem, which", "start": 4928.55, "duration": 5.19}, {"text": "just follows immediately\nfrom this getting", "start": 4933.74, "duration": 2.91}, {"text": "used over and over again,\nis that the cardinality", "start": 4936.65, "duration": 5.22}, {"text": "of the natural\nnumbers, this is less", "start": 4941.87, "duration": 1.68}, {"text": "than the cardinality\nof the power", "start": 4943.55, "duration": 3.66}, {"text": "set of the natural\nnumbers, which is less", "start": 4947.21, "duration": 3.24}, {"text": "than the cardinality\nof the power", "start": 4950.45, "duration": 3.33}, {"text": "set of the power set of\nthe natural numbers, right?", "start": 4953.78, "duration": 3.36}, {"text": "I can now take this as a\nset and take its power set.", "start": 4957.14, "duration": 2.67}, {"text": "And I get a new set\nwith bigger size,", "start": 4959.81, "duration": 3.34}, {"text": "which is less than the power\nset of the power set where--", "start": 4963.15, "duration": 4.97}, {"text": "how many do we have now-- of the\npower set of natural numbers,", "start": 4968.12, "duration": 4.98}, {"text": "and so on.", "start": 4973.1, "duration": 0.93}, {"text": "And formally, this means there's\nan infinity of infinitudes.", "start": 4988.57, "duration": 16.97}, {"text": "There's an infinite\nnumber of infinite sizes,", "start": 5005.54, "duration": 4.95}, {"text": "one getting strictly--", "start": 5010.49, "duration": 1.77}, {"text": "in some sense, strictly\nbigger than the previous size.", "start": 5012.26, "duration": 2.415}, {"text": "And maybe you're wondering--", "start": 5017.47, "duration": 6.07}, {"text": "there's one more\nquestion that's kind", "start": 5023.54, "duration": 1.58}, {"text": "of sandwiched in between\nhere, pun intended, is--", "start": 5025.12, "duration": 8.97}, {"text": "let's look at this first guy.", "start": 5034.09, "duration": 2.73}, {"text": "Does there exist a set A\nsuch that it has size bigger", "start": 5046.02, "duration": 13.91}, {"text": "than natural numbers-- so\nit's uncountable-- but has", "start": 5059.93, "duration": 3.54}, {"text": "size strictly smaller\nthan the power", "start": 5063.47, "duration": 1.68}, {"text": "set of the natural numbers.", "start": 5065.15, "duration": 2.55}, {"text": "And this question is called\nthe continuum hypothesis,", "start": 5067.7, "duration": 11.726}, {"text": "hypothesis because it\nis independent from one", "start": 5079.426, "duration": 2.294}, {"text": "of the standard axiomatic\ntreatments of set theory.", "start": 5081.72, "duration": 6.72}, {"text": "But we will not\ntouch this question.", "start": 5088.44, "duration": 2.64}, {"text": "This is beyond the\nscope of this class,", "start": 5091.08, "duration": 3.115}, {"text": "but it's an interesting\nquestion that's", "start": 5094.195, "duration": 1.625}, {"text": "out there that people\njust don't know.", "start": 5095.82, "duration": 3.17}]
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+[{"text": "[SQUEAKING]", "start": 0.5, "duration": 3.412}, {"text": "PROFESSOR: Last time, we\nstarted discussing graph limits.", "start": 18.59, "duration": 3.13}, {"text": "And let me remind you some of\nthe notions and definitions", "start": 21.72, "duration": 3.188}, {"text": "that were involved.", "start": 24.908, "duration": 0.792}, {"text": "One of the main\nobjects in graph limits", "start": 35.59, "duration": 1.9}, {"text": "is that of a graphon, which are\nsymmetric, measurable functions", "start": 37.49, "duration": 9.18}, {"text": "from the unit squared\nto the unit interval.", "start": 46.67, "duration": 2.82}, {"text": "So here, symmetric means\nthat w of x, comma, y", "start": 58.89, "duration": 3.68}, {"text": "equals to w of y, comma, x.", "start": 62.57, "duration": 2.1}, {"text": "We define a notion\nof convergence", "start": 69.81, "duration": 1.71}, {"text": "for a sequence of graphons.", "start": 71.52, "duration": 2.46}, {"text": "And remember, the\nnotion of convergence", "start": 73.98, "duration": 7.1}, {"text": "is that a sequence is convergent\nif the sequence of homomorphism", "start": 81.08, "duration": 12.25}, {"text": "densities converges as n goes\nto infinity for every fixed", "start": 93.33, "duration": 10.0}, {"text": "F, every fixed graph.", "start": 103.33, "duration": 2.35}, {"text": "So this is how we\ndefine convergence.", "start": 109.48, "duration": 2.7}, {"text": "So a sequence of\ngraphs or graphons,", "start": 112.18, "duration": 1.74}, {"text": "they converge if all the\nhomomorphism densities--", "start": 113.92, "duration": 4.44}, {"text": "so you should think of this\nas subgraph statistics--", "start": 118.36, "duration": 2.84}, {"text": "if all of these\nstatistics converge.", "start": 121.2, "duration": 3.32}, {"text": "We also say that a sequence\nconverges to a particular limit", "start": 124.52, "duration": 5.66}, {"text": "if these homomorphism\ndensities converge", "start": 130.18, "duration": 6.0}, {"text": "to the corresponding\nhomomorphism density", "start": 136.18, "duration": 3.99}, {"text": "of the limit for every F.", "start": 140.17, "duration": 4.34}, {"text": "OK.", "start": 144.51, "duration": 0.5}, {"text": "So this is how we\ndefine convergence.", "start": 145.01, "duration": 2.73}, {"text": "We also define this\nnotion of a distance.", "start": 147.74, "duration": 2.13}, {"text": "And to do that, we\nfirst define the cut", "start": 153.14, "duration": 2.03}, {"text": "norm to be the following\nquantity defined", "start": 155.17, "duration": 6.73}, {"text": "by taking two subsets, S\nand T, which are measurable.", "start": 161.9, "duration": 7.44}, {"text": "Everything so far is\ngoing to be measurable.", "start": 169.34, "duration": 2.55}, {"text": "And look at what is the\nmaximum possible deviation", "start": 171.89, "duration": 3.93}, {"text": "of the integral of this\nfunction on this box, S cross T.", "start": 175.82, "duration": 4.53}, {"text": "And here, w, you should think\nof it as taking real values,", "start": 180.35, "duration": 3.45}, {"text": "allowing both positive\nand negative values,", "start": 183.8, "duration": 2.333}, {"text": "because otherwise,\nyou should just", "start": 186.133, "duration": 1.417}, {"text": "take S and T to be\nthe whole interval.", "start": 187.55, "duration": 3.86}, {"text": "OK.", "start": 191.41, "duration": 1.44}, {"text": "And this definition\nwas motivated", "start": 192.85, "duration": 2.1}, {"text": "by our discussion of discrepancy\ncoming from quasi randomness.", "start": 194.95, "duration": 4.67}, {"text": "Now, if I give you\ntwo graphs or graphons", "start": 199.62, "duration": 2.66}, {"text": "and ask you to\ncompare them, you are", "start": 202.28, "duration": 1.89}, {"text": "allowed to permute the\nvertices in some sense,", "start": 204.17, "duration": 4.38}, {"text": "so to find the best overlay.", "start": 208.55, "duration": 2.59}, {"text": "And that notion is\ncaptured in the definition", "start": 211.14, "duration": 2.9}, {"text": "of cut distance, which is\ndefined to be the following", "start": 214.04, "duration": 6.57}, {"text": "quantity, where we consider over\nall possible measure-preserving", "start": 220.61, "duration": 12.93}, {"text": "bijections from the interval\nto itself of the difference", "start": 233.54, "duration": 16.93}, {"text": "between these two\ngraphons if I rotate", "start": 250.47, "duration": 3.66}, {"text": "one of them using this\nmeasure-preserving bijection.", "start": 254.13, "duration": 4.62}, {"text": "So think of this as\npermuting the vertices.", "start": 266.46, "duration": 2.715}, {"text": "So these were the definitions\nthat were involved last time.", "start": 276.13, "duration": 3.53}, {"text": "And at the end of\nlast lecture, I", "start": 279.66, "duration": 1.75}, {"text": "stated three main theorems\nof graph limit theory.", "start": 281.41, "duration": 3.65}, {"text": "So I forgot to\nmention what are some", "start": 285.06, "duration": 2.17}, {"text": "of the histories of this theory.", "start": 287.23, "duration": 2.59}, {"text": "So there were a number\nof important papers", "start": 289.82, "duration": 2.54}, {"text": "that developed this very idea of\ngraph limits, which is actually", "start": 292.36, "duration": 4.89}, {"text": "somewhat-- if you think\nabout all of combinatorics,", "start": 297.25, "duration": 2.85}, {"text": "we like to deal with\ndiscrete objects.", "start": 300.1, "duration": 2.73}, {"text": "And even the idea of taking\na limit is rather novel.", "start": 302.83, "duration": 3.78}, {"text": "So this work is due\nto a number of people.", "start": 306.61, "duration": 5.22}, {"text": "In particular, Laszlo Lovasz\nplayed a very important", "start": 311.83, "duration": 3.0}, {"text": "central role in the\ndevelopment of this theory.", "start": 314.83, "duration": 2.37}, {"text": "And various people\ncame to this theory", "start": 317.2, "duration": 2.28}, {"text": "from different\nperspectives-- some", "start": 319.48, "duration": 1.98}, {"text": "from more pure\nperspectives, and some", "start": 321.46, "duration": 2.7}, {"text": "from more applied perspectives.", "start": 324.16, "duration": 2.13}, {"text": "And this theory is now getting\nused in more and more places,", "start": 326.29, "duration": 3.52}, {"text": "including statistics,\nmachine learning, and so on.", "start": 329.81, "duration": 3.22}, {"text": "And I'll explain where that\ncomes up just a little bit.", "start": 333.03, "duration": 4.96}, {"text": "At the end of last lecture,\nI stated three main theorems.", "start": 337.99, "duration": 2.88}, {"text": "And what I want to do\ntoday is develop some tools", "start": 340.87, "duration": 3.69}, {"text": "so that we can prove those\ntheorems in the next lecture.", "start": 344.56, "duration": 3.217}, {"text": "OK.", "start": 347.777, "duration": 0.5}, {"text": "So I want to develop some tools.", "start": 348.277, "duration": 1.633}, {"text": "In particular, you'll see some\nof the things that we've talked", "start": 349.91, "duration": 2.6}, {"text": "about in the chapter on\nSzemer\u00e9di's regularity lemma", "start": 352.51, "duration": 3.45}, {"text": "come up again in a slightly\ndifferent language.", "start": 355.96, "duration": 3.18}, {"text": "So much of what I will say\ntoday hopefully should already", "start": 359.14, "duration": 3.18}, {"text": "be familiar to you, but\nyou will see it again", "start": 362.32, "duration": 2.34}, {"text": "from the perspective\nof graph limits.", "start": 364.66, "duration": 4.03}, {"text": "But first, before telling\nyou about the tools,", "start": 368.69, "duration": 2.567}, {"text": "I want to give you\nsome more examples.", "start": 371.257, "duration": 1.583}, {"text": "So one of the ways that\nI motivated graph limits", "start": 375.58, "duration": 2.39}, {"text": "last time is this example of\nan Erdos-Renyi random graph", "start": 377.97, "duration": 4.41}, {"text": "or a sequence of quasi-random\ngraphs converging", "start": 382.38, "duration": 3.09}, {"text": "to a constant.", "start": 385.47, "duration": 1.07}, {"text": "The constant graphon\nis the limit.", "start": 386.54, "duration": 4.15}, {"text": "But what about generalizations?", "start": 390.69, "duration": 1.48}, {"text": "What about generalizations\nof that construction when", "start": 392.17, "duration": 2.42}, {"text": "your limit is not the constant?", "start": 394.59, "duration": 2.91}, {"text": "So this leads to this idea\nof a w random graph, which", "start": 397.5, "duration": 6.03}, {"text": "generalizes that of an\nErdos-Renyi random graph.", "start": 403.53, "duration": 5.72}, {"text": "So in Erdos-Renyi, we're\nlooking at every edge occurring", "start": 409.25, "duration": 9.14}, {"text": "with the same probability, p,\nuniform throughout the graph.", "start": 418.39, "duration": 4.87}, {"text": "But what I want to do now is\nallow you to change the edge", "start": 423.26, "duration": 3.99}, {"text": "probability somewhat.", "start": 427.25, "duration": 1.67}, {"text": "OK.", "start": 428.92, "duration": 0.5}, {"text": "So before giving you the\nmore general definition,", "start": 432.288, "duration": 2.042}, {"text": "a special case of this\nis an important model", "start": 434.33, "duration": 4.83}, {"text": "of random graphs known as\nthe stochastic block model.", "start": 439.16, "duration": 2.93}, {"text": "And in particular, a two-block\nmodel consists of the following", "start": 445.802, "duration": 5.898}, {"text": "data where I am looking\nat two types of vertices--", "start": 451.7, "duration": 7.63}, {"text": "let's call them red and blue--", "start": 464.75, "duration": 1.28}, {"text": "where the vertices are\nassigned to colors at random--", "start": 469.65, "duration": 5.18}, {"text": "for example, 50/50.", "start": 481.57, "duration": 1.48}, {"text": "But any other\nprobability is fine.", "start": 483.05, "duration": 2.64}, {"text": "And now I put down the edges\naccording to which colors", "start": 485.69, "duration": 4.64}, {"text": "the two endpoints are.", "start": 490.33, "duration": 2.01}, {"text": "So two red vertices are joined\nwith edge probability Prr.", "start": 492.34, "duration": 11.16}, {"text": "If I have a red\nand a blue, then I", "start": 503.5, "duration": 3.42}, {"text": "may have a different probability\njoining them, and likewise", "start": 506.92, "duration": 5.46}, {"text": "with blue-blue, like that.", "start": 512.38, "duration": 6.02}, {"text": "So in other words, I can encode\nthis probability information", "start": 518.4, "duration": 2.56}, {"text": "in the matrix, like that.", "start": 520.96, "duration": 9.93}, {"text": "So it's symmetric\nacross the diagonal.", "start": 530.89, "duration": 3.91}, {"text": "So this is a slightly\nmore general version", "start": 534.8, "duration": 2.42}, {"text": "of an Erdos-Renyi\nrandom graph where now I", "start": 537.22, "duration": 2.73}, {"text": "have potentially different\ntypes of vertices.", "start": 539.95, "duration": 2.37}, {"text": "And you can imagine\nthese kinds of models", "start": 542.32, "duration": 1.77}, {"text": "are very important in\napplied mathematics", "start": 544.09, "duration": 1.92}, {"text": "for modeling certain situations\nsuch as, for example,", "start": 546.01, "duration": 3.73}, {"text": "if you have people with\ndifferent political party", "start": 549.74, "duration": 5.15}, {"text": "affiliations.", "start": 554.89, "duration": 1.38}, {"text": "How likely are they\nto talk to each other?", "start": 556.27, "duration": 3.62}, {"text": "So you can imagine\nsome of these numbers", "start": 559.89, "duration": 2.16}, {"text": "might be bigger than others.", "start": 562.05, "duration": 2.65}, {"text": "And there's an important\nstatistical problem.", "start": 564.7, "duration": 2.66}, {"text": "If I give you a graph, can\nyou cluster or classify", "start": 567.36, "duration": 3.69}, {"text": "the vertices according\nto their types", "start": 571.05, "duration": 2.28}, {"text": "if I do not show you in advance\nwhat the colors are but show", "start": 573.33, "duration": 3.36}, {"text": "you what the output graph is?", "start": 576.69, "duration": 2.65}, {"text": "So these are important\nstatistical questions", "start": 579.34, "duration": 2.15}, {"text": "with lots of applications.", "start": 581.49, "duration": 4.26}, {"text": "This is an example of if\nyou have only two blocks.", "start": 585.75, "duration": 2.82}, {"text": "But of course, you can\nhave more than two blocks.", "start": 588.57, "duration": 3.46}, {"text": "And the graphon context\ntells us that we should not", "start": 592.03, "duration": 3.78}, {"text": "limit ourselves to just blocks.", "start": 595.81, "duration": 2.73}, {"text": "If I give you any\ngraphon w, I can also", "start": 598.54, "duration": 3.66}, {"text": "construct a random graph.", "start": 602.2, "duration": 3.84}, {"text": "So what I would like\nto do is to consider", "start": 606.04, "duration": 2.94}, {"text": "the following\nconstruction where--", "start": 608.98, "duration": 3.1}, {"text": "OK, so let's just call\nit w random graph denoted", "start": 612.08, "duration": 7.34}, {"text": "by g and w--", "start": 619.42, "duration": 4.5}, {"text": "where I form the graph\nusing the following process.", "start": 623.92, "duration": 4.59}, {"text": "First, the vertex set is\nlabeled by 1 through n.", "start": 628.51, "duration": 5.97}, {"text": "And let me draw the vertex types\nby taking uniform random x1", "start": 634.48, "duration": 10.16}, {"text": "through xn--", "start": 644.64, "duration": 2.306}, {"text": "OK, so uniform iid.", "start": 646.946, "duration": 4.134}, {"text": "So you think of them as the\nvertex colors, the vertex", "start": 651.08, "duration": 3.09}, {"text": "types.", "start": 654.17, "duration": 1.39}, {"text": "And I put an edge\nbetween i and j", "start": 655.56, "duration": 7.88}, {"text": "with probability\nexactly w of xi,", "start": 663.44, "duration": 7.394}, {"text": "xj, so for all i less\nthan j independently.", "start": 670.834, "duration": 6.548}, {"text": "That's the definition\nof a w random graph.", "start": 681.16, "duration": 2.79}, {"text": "And the two-block\nstochastic model", "start": 683.95, "duration": 2.84}, {"text": "is a special case of\nthis w random graph", "start": 686.79, "duration": 2.68}, {"text": "for the graphon,\nwhich corresponds", "start": 689.47, "duration": 2.25}, {"text": "to this red-blue picture here.", "start": 691.72, "duration": 3.59}, {"text": "So the generation process would\nbe I give you some x1, x2, x3,", "start": 698.65, "duration": 10.65}, {"text": "and then, likewise, x1, x3, x2.", "start": 709.3, "duration": 7.95}, {"text": "And then I evaluate, what\nis the value of this graphon", "start": 717.25, "duration": 4.01}, {"text": "at these points?", "start": 721.26, "duration": 1.49}, {"text": "And those are my\nedge probabilities.", "start": 731.45, "duration": 3.63}, {"text": "So what I described\nis a special case", "start": 735.08, "duration": 2.34}, {"text": "of this general w random graph.", "start": 737.42, "duration": 2.16}, {"text": "Any questions?", "start": 742.46, "duration": 3.11}, {"text": "So like before, an important\nstatistical question", "start": 745.57, "duration": 2.82}, {"text": "is if I show you\nthe graph, can you", "start": 748.39, "duration": 2.86}, {"text": "tell me a good model for\nwhere this graph came from?", "start": 751.25, "duration": 5.96}, {"text": "So that's one of the reasons\nwhy people in applied math", "start": 757.21, "duration": 4.25}, {"text": "might care about these\ntypes of constructions.", "start": 761.46, "duration": 4.51}, {"text": "Let me talk about some theorems.", "start": 765.97, "duration": 1.38}, {"text": "I've told you that the sequence\nof Erdos-Renyi random graphs", "start": 771.05, "duration": 3.75}, {"text": "converges to the\nconstant graphon p.", "start": 774.8, "duration": 2.97}, {"text": "So instead of taking\na constant graphon p,", "start": 777.77, "duration": 3.42}, {"text": "now I start with w random graph.", "start": 781.19, "duration": 3.0}, {"text": "And you should expect,\nand it is indeed true,", "start": 784.19, "duration": 2.67}, {"text": "that this sequence converges\nto w as their limit.", "start": 786.86, "duration": 5.64}, {"text": "So let w be a graphon.", "start": 792.5, "duration": 1.69}, {"text": "So let w be a graphon.", "start": 799.695, "duration": 2.135}, {"text": "And for each n, let me\ndraw this graph G sub", "start": 801.83, "duration": 6.62}, {"text": "n using the w random\ngraph model independently.", "start": 808.45, "duration": 6.022}, {"text": "Then with probability\n1, the sequence", "start": 817.64, "duration": 10.17}, {"text": "converges to the graphon w.", "start": 827.81, "duration": 2.67}, {"text": "So in the sense that I've\nshown above, described above.", "start": 833.68, "duration": 4.51}, {"text": "So this statement\ntells us a couple", "start": 838.19, "duration": 3.45}, {"text": "of things-- one, that w random\ngraphs converge to the limit w,", "start": 841.64, "duration": 3.26}, {"text": "as you should expect; and\ntwo, that every graphon w", "start": 844.9, "duration": 7.5}, {"text": "is the limit point of\nsome sequence of graphs.", "start": 852.4, "duration": 5.35}, {"text": "So this is something that\nwe never quite explicitly", "start": 857.75, "duration": 2.9}, {"text": "stated before.", "start": 860.65, "duration": 1.3}, {"text": "So let me make this remark.", "start": 861.95, "duration": 3.03}, {"text": "So in particular,\nevery w is the limit", "start": 864.98, "duration": 14.69}, {"text": "of some sequence of graphs,\njust like every real number,", "start": 879.67, "duration": 8.328}, {"text": "in analogy to what\nwe said last time.", "start": 887.998, "duration": 1.542}, {"text": "Every real number is\nthe limit of a sequence", "start": 889.54, "duration": 2.8}, {"text": "of rational numbers through\nrational approximation.", "start": 892.34, "duration": 3.42}, {"text": "And this is some form of\napproximation of a graphon", "start": 895.76, "duration": 3.81}, {"text": "by a sequence of graphs.", "start": 899.57, "duration": 1.855}, {"text": "OK.", "start": 901.425, "duration": 0.5}, {"text": "So I'm not going to\nprove this theorem.", "start": 901.925, "duration": 1.815}, {"text": "The proof is not difficult.\nSo using that definition", "start": 903.74, "duration": 4.68}, {"text": "of subgraph\nconvergence, the proof", "start": 908.42, "duration": 2.82}, {"text": "uses what's known as\nAzuma's inequality.", "start": 911.24, "duration": 5.65}, {"text": "So by an appropriate application\nof Azuma's inequality", "start": 916.89, "duration": 4.22}, {"text": "on the concentration\nof martingales,", "start": 921.11, "duration": 1.68}, {"text": "one can prove this\ntheorem here by estimating", "start": 922.79, "duration": 4.32}, {"text": "the probability that--", "start": 927.11, "duration": 1.86}, {"text": "to show that the probability\nthat the F density in Gn,", "start": 935.18, "duration": 6.78}, {"text": "it is very close to\nthe F density in w", "start": 941.96, "duration": 5.37}, {"text": "with high probability.", "start": 947.33, "duration": 2.006}, {"text": "OK.", "start": 952.252, "duration": 2.893}, {"text": "Any questions so far?", "start": 955.145, "duration": 0.875}, {"text": "So this is an important\nexample of one", "start": 958.82, "duration": 3.78}, {"text": "of the motivations\nof graph limits.", "start": 962.6, "duration": 3.62}, {"text": "But now, let's get back\nto what I said earlier.", "start": 966.22, "duration": 3.24}, {"text": "I would like to develop\na sequence of tools", "start": 969.46, "duration": 2.35}, {"text": "that will allow us to prove\nthe main theorem stated", "start": 971.81, "duration": 2.34}, {"text": "at the end of the last lecture.", "start": 974.15, "duration": 3.85}, {"text": "And this will sound\nvery familiar,", "start": 978.0, "duration": 1.47}, {"text": "because we're going to write\ndown some lemmas that we did", "start": 979.47, "duration": 4.14}, {"text": "back in the chapter of\nSzemer\u00e9di's regularity lemma", "start": 983.61, "duration": 2.88}, {"text": "but now in the\nlanguage of graphons.", "start": 986.49, "duration": 2.96}, {"text": "So the first is\na counting lemma.", "start": 989.45, "duration": 2.15}, {"text": "The goal of the\ncounting lemma is", "start": 998.27, "duration": 1.5}, {"text": "to show that if you\nhave two graphons which", "start": 999.77, "duration": 2.82}, {"text": "are close to each other in the\nsense of cut distance, then", "start": 1002.59, "duration": 7.47}, {"text": "their F densities are\nsimilar to each other.", "start": 1010.06, "duration": 5.47}, {"text": "So here's a statement.", "start": 1015.53, "duration": 1.66}, {"text": "So if w and u are\ngraphons and F is", "start": 1017.19, "duration": 8.213}, {"text": "a graph, then the F density\nof w minus the F density of u,", "start": 1025.403, "duration": 14.057}, {"text": "their difference is no more\nthan a constant-- so number", "start": 1039.46, "duration": 5.48}, {"text": "of edges of F times the cut\ndistance between u and w.", "start": 1044.94, "duration": 7.17}, {"text": "So maybe some of you already\nsee how to do this from", "start": 1057.67, "duration": 4.07}, {"text": "our discussion on\nSzemer\u00e9di's regularity lemma.", "start": 1061.74, "duration": 4.19}, {"text": "In any case, I want to just\nrewrite the proof again", "start": 1065.93, "duration": 2.86}, {"text": "in the language of graphons.", "start": 1068.79, "duration": 1.56}, {"text": "And this will hopefully--", "start": 1070.35, "duration": 1.84}, {"text": "so we did two proofs of the\ntriangle counting lemma.", "start": 1072.19, "duration": 3.51}, {"text": "One was hopefully more\nintuitive for you,", "start": 1075.7, "duration": 2.745}, {"text": "which is you pick a\ntypical vertex that", "start": 1078.445, "duration": 1.625}, {"text": "has lots of neighbors\non both sides", "start": 1080.07, "duration": 1.458}, {"text": "and therefore lots\nof edges between.", "start": 1081.528, "duration": 2.884}, {"text": "And then there was a\nsecond proof, which I said", "start": 1084.412, "duration": 1.958}, {"text": "was a more analytic\nproof, where you took out", "start": 1086.37, "duration": 2.1}, {"text": "one edge at a time.", "start": 1088.47, "duration": 1.95}, {"text": "And that proof, I think\nit's technically easier", "start": 1090.42, "duration": 3.03}, {"text": "to implement, especially\nfor general H.", "start": 1093.45, "duration": 2.933}, {"text": "But the first time\nyou see it, you", "start": 1096.383, "duration": 1.417}, {"text": "might not quite see what\nthe calculation was about.", "start": 1097.8, "duration": 2.88}, {"text": "So I want to do this exact\nsame calculation again", "start": 1100.68, "duration": 2.64}, {"text": "in the language of graphons.", "start": 1103.32, "duration": 1.227}, {"text": "And hopefully, it should\nbe clear this time.", "start": 1104.547, "duration": 1.833}, {"text": "So this is the same\nas the counting lemma", "start": 1109.6, "duration": 1.79}, {"text": "over epsilon-regular pairs.", "start": 1111.39, "duration": 3.41}, {"text": "So it suffices to\nprove the inequality", "start": 1114.8, "duration": 9.32}, {"text": "where the right-hand side\nis replaced not by the cut", "start": 1124.12, "duration": 5.21}, {"text": "distance but by the cut norm.", "start": 1129.33, "duration": 4.11}, {"text": "And the reason is that once\nyou have the second inequality", "start": 1133.44, "duration": 4.11}, {"text": "by taking an infimum over all\nmeasure-preserving bijections", "start": 1137.55, "duration": 6.86}, {"text": "phi--", "start": 1144.41, "duration": 0.88}, {"text": "and notice that that change\ndoes not affect the F density.", "start": 1145.29, "duration": 5.7}, {"text": "By taking an infimum\nover phi, you", "start": 1150.99, "duration": 1.91}, {"text": "recover the first inequality.", "start": 1152.9, "duration": 1.852}, {"text": "I want to give you a small\nreformulation of the cut norm", "start": 1157.59, "duration": 4.77}, {"text": "that will be useful for thinking\nabout this counting lemma.", "start": 1162.36, "duration": 3.246}, {"text": "Here's a reformulation\nof the cut norm--", "start": 1169.98, "duration": 7.77}, {"text": "namely, that I can\ndefine the cut norm.", "start": 1177.75, "duration": 4.72}, {"text": "So here, w is taking\nreal values, so", "start": 1182.47, "duration": 3.37}, {"text": "not necessarily non-negative.", "start": 1185.84, "duration": 2.79}, {"text": "So the cut norm\nwe saw earlier is", "start": 1188.63, "duration": 4.23}, {"text": "defined to be the supremum\nover all measurable subsets", "start": 1192.86, "duration": 9.08}, {"text": "of the 0, 1 interval of this\nintegral in absolute value.", "start": 1201.94, "duration": 6.96}, {"text": "But it turns out I can rewrite\nthis supremum over a slightly", "start": 1208.9, "duration": 5.88}, {"text": "larger set of objects.", "start": 1214.78, "duration": 2.07}, {"text": "Instead of just looking\nover measurable subsets", "start": 1216.85, "duration": 4.65}, {"text": "of the interval, let me now\nlook at measurable functions.", "start": 1221.5, "duration": 4.83}, {"text": "Little u.", "start": 1226.33, "duration": 2.8}, {"text": "So OK, let me look at functions.", "start": 1229.13, "duration": 3.44}, {"text": "So u and v from 0, 1 to 0, 1--", "start": 1232.57, "duration": 8.29}, {"text": "and as always, everything\nis measurable--", "start": 1240.86, "duration": 5.67}, {"text": "of the following integral.", "start": 1246.53, "duration": 3.12}, {"text": "So I claim this is true.", "start": 1261.57, "duration": 2.69}, {"text": "So I consider this integral.", "start": 1264.26, "duration": 5.11}, {"text": "Instead of integrating\nover a box,", "start": 1269.37, "duration": 2.11}, {"text": "now I'm integrating\nthis expression.", "start": 1271.48, "duration": 4.68}, {"text": "OK.", "start": 1276.16, "duration": 0.5}, {"text": "So why is this true?", "start": 1276.66, "duration": 2.72}, {"text": "Well, one of the\ndirections is easy to see,", "start": 1279.38, "duration": 4.29}, {"text": "because the right-hand side\nis strictly an enlargement", "start": 1283.67, "duration": 3.96}, {"text": "of the left-hand side.", "start": 1287.63, "duration": 1.44}, {"text": "So by taking u to be the\nindicator function of S", "start": 1289.07, "duration": 6.87}, {"text": "and v to be the indicator\nof function of T,", "start": 1295.94, "duration": 2.81}, {"text": "you see that the\nright-hand side, in fact,", "start": 1298.75, "duration": 1.93}, {"text": "includes the left-hand\nside in terms", "start": 1300.68, "duration": 2.01}, {"text": "of what you are allowed to do.", "start": 1302.69, "duration": 2.64}, {"text": "But what about the\nother direction?", "start": 1305.33, "duration": 2.83}, {"text": "So for the other\ndirection, the main thing", "start": 1308.16, "duration": 1.91}, {"text": "is to notice that the\nintegral or the integrand,", "start": 1310.07, "duration": 6.63}, {"text": "what's inside this integral,\nis bilinear in the values of u", "start": 1316.7, "duration": 9.1}, {"text": "and v. So in particular, the\nextrema of this integral,", "start": 1325.8, "duration": 6.59}, {"text": "as you allow to vary u\nand v, they are obtained.", "start": 1332.39, "duration": 4.82}, {"text": "So they are obtained\nfor u and v,", "start": 1337.21, "duration": 5.14}, {"text": "taking values in the\nendpoints 0, comma, 1.", "start": 1342.35, "duration": 9.26}, {"text": "It may be helpful to think about\nthe discrete setting, when,", "start": 1356.03, "duration": 3.13}, {"text": "instead of this integral, you\nhave a matrix and two vectors", "start": 1359.16, "duration": 2.91}, {"text": "multiplied from left and right.", "start": 1362.07, "duration": 1.8}, {"text": "And you had to decide,\nwhat are the coordinates", "start": 1363.87, "duration": 2.97}, {"text": "of those vectors?", "start": 1366.84, "duration": 1.72}, {"text": "It's a bilinear form.", "start": 1368.56, "duration": 1.7}, {"text": "How do you maximize\nit or minimize it?", "start": 1370.26, "duration": 2.83}, {"text": "You have to change every entry\nto one of its two endpoints.", "start": 1373.09, "duration": 4.81}, {"text": "Otherwise, it can never be--", "start": 1377.9, "duration": 2.76}, {"text": "you never lose by doing that.", "start": 1380.66, "duration": 3.95}, {"text": "OK, so think about it.", "start": 1384.61, "duration": 1.34}, {"text": "So this is not difficult once\nyou see it the right way.", "start": 1385.95, "duration": 6.66}, {"text": "But now, we have this cut\nnorm expressed over not sets,", "start": 1392.61, "duration": 6.02}, {"text": "but over bounded functions.", "start": 1398.63, "duration": 3.59}, {"text": "And now I'm ready to\nprove the counting lemma.", "start": 1402.22, "duration": 2.4}, {"text": "And instead of writing down\nthe whole proof for general H,", "start": 1412.4, "duration": 3.6}, {"text": "let me write down the\ncalculation that illustrates", "start": 1416.0, "duration": 4.65}, {"text": "this proof for triangles.", "start": 1420.65, "duration": 1.95}, {"text": "And the general\nproof is the same", "start": 1429.46, "duration": 1.38}, {"text": "once you understand how\nthis argument works.", "start": 1430.84, "duration": 3.66}, {"text": "And the argument works by\nconsidering the difference", "start": 1434.5, "duration": 6.27}, {"text": "between these two F densities.", "start": 1440.77, "duration": 9.12}, {"text": "And what I want to do is--", "start": 1449.89, "duration": 2.82}, {"text": "so this is some integral, right?", "start": 1452.71, "duration": 1.45}, {"text": "So this is this integral,\nwhich I'll write out.", "start": 1454.16, "duration": 2.93}, {"text": "So we would like to show\nthat this quantity here", "start": 1481.78, "duration": 4.86}, {"text": "is small if u and w\nare close in cut norm.", "start": 1486.64, "duration": 5.09}, {"text": "So let's write this integral\nas a telescoping sum", "start": 1491.73, "duration": 8.1}, {"text": "where the first term\nis obtained by--", "start": 1499.83, "duration": 4.07}, {"text": "so by this, I mean\nw of x, comma, y", "start": 1508.99, "duration": 2.16}, {"text": "minus u of x, comma, y.", "start": 1511.15, "duration": 1.29}, {"text": "And then the second term\nof the telescoping sum--", "start": 1524.44, "duration": 2.85}, {"text": "so you see what happens.", "start": 1527.29, "duration": 1.66}, {"text": "I change one factor at a time.", "start": 1528.95, "duration": 2.09}, {"text": "And finally, I change\nthe third factor.", "start": 1551.57, "duration": 3.24}, {"text": "So this is the identity.", "start": 1569.3, "duration": 1.0}, {"text": "If you expand out all\nof these differences,", "start": 1570.3, "duration": 1.98}, {"text": "you see that everything\nintermediate cancels out.", "start": 1572.28, "duration": 3.35}, {"text": "So it's a telescoping sum.", "start": 1575.63, "duration": 4.07}, {"text": "But now I want to show\nthat each term is small.", "start": 1579.7, "duration": 4.581}, {"text": "So how can I show that\neach term is small?", "start": 1584.281, "duration": 3.889}, {"text": "Look at this expression here.", "start": 1588.17, "duration": 4.23}, {"text": "I claim that for a\nfixed value of z--", "start": 1594.992, "duration": 3.288}, {"text": "so imagine fixing z.", "start": 1605.3, "duration": 2.19}, {"text": "And let x and y vary\nin this integral.", "start": 1607.49, "duration": 4.51}, {"text": "It has the form up there, right?", "start": 1612.0, "duration": 3.76}, {"text": "If you fix z, then\nyou have this u and v", "start": 1615.76, "duration": 4.92}, {"text": "coming from these two factors.", "start": 1620.68, "duration": 1.98}, {"text": "And they are both\nbounded between 0 and 1.", "start": 1622.66, "duration": 2.22}, {"text": "So for a fixed value of z,\nthis is at most w minus u--", "start": 1628.09, "duration": 10.08}, {"text": "the cut norm difference between\nw and u in absolute value.", "start": 1638.17, "duration": 5.12}, {"text": "So if I left z vary, it is\nstill bounded in absolute value", "start": 1647.52, "duration": 6.07}, {"text": "by that quantity.", "start": 1653.59, "duration": 2.86}, {"text": "So therefore each is\nbounded by w minus u cut", "start": 1656.45, "duration": 10.13}, {"text": "norm in absolute value.", "start": 1666.58, "duration": 3.33}, {"text": "Add all three of them together.", "start": 1669.91, "duration": 2.5}, {"text": "We find that the whole thing\nis bounded in absolute value", "start": 1672.41, "duration": 4.88}, {"text": "by 3 times the cut\nnormal difference.", "start": 1677.29, "duration": 2.673}, {"text": "OK, and that finishes the\nproof of the counting lemma.", "start": 1683.35, "duration": 3.31}, {"text": "For triangles, of course,\nif you have general H,", "start": 1686.66, "duration": 3.39}, {"text": "then you just have more terms.", "start": 1690.05, "duration": 2.55}, {"text": "You have a longer telescoping\nsum, and you have this bound.", "start": 1692.6, "duration": 5.44}, {"text": "OK.", "start": 1698.04, "duration": 0.5}, {"text": "So this is a counting lemma.", "start": 1698.54, "duration": 0.91}, {"text": "And I claim that it's exactly\nthe same proof as the second", "start": 1699.45, "duration": 2.63}, {"text": "proof of the counting lemma\nthat we did when we discussed", "start": 1702.08, "duration": 2.872}, {"text": "Szemer\u00e9di's regularity lemma\nand this counting lemma.", "start": 1704.952, "duration": 2.208}, {"text": "Any questions?", "start": 1710.22, "duration": 2.974}, {"text": "Yeah.", "start": 1713.194, "duration": 0.5}, {"text": "AUDIENCE: Why did it suffice\nto prove over the [INAUDIBLE]??", "start": 1717.082, "duration": 5.405}, {"text": "PROFESSOR: OK.", "start": 1722.487, "duration": 0.583}, {"text": "So let me answer\nthat in a second.", "start": 1723.07, "duration": 2.39}, {"text": "So first, this should\nbe H, not F. OK,", "start": 1725.46, "duration": 2.82}, {"text": "so your question\nwas, up there, why", "start": 1728.28, "duration": 6.72}, {"text": "was it sufficient to\nprove this version instead", "start": 1735.0, "duration": 4.35}, {"text": "of that version?", "start": 1739.35, "duration": 1.015}, {"text": "Is that the question?", "start": 1740.365, "duration": 0.875}, {"text": "AUDIENCE: Yeah.", "start": 1741.24, "duration": 0.937}, {"text": "PROFESSOR: OK.", "start": 1742.177, "duration": 0.583}, {"text": "Suppose I prove it\nfor this version.", "start": 1742.76, "duration": 2.21}, {"text": "So I know this is true.", "start": 1744.97, "duration": 1.9}, {"text": "Now I take infimum\nof both sides.", "start": 1746.87, "duration": 2.74}, {"text": "So now I consider\ninfimum of both sides.", "start": 1749.61, "duration": 8.38}, {"text": "So then this is true, right?", "start": 1757.99, "duration": 3.39}, {"text": "Because it's true for every phi.", "start": 1761.38, "duration": 3.06}, {"text": "But the left-hand side doesn't\nchange, because the F density", "start": 1764.44, "duration": 4.05}, {"text": "in a relabeling of the vertices,\nit's still the same quantity,", "start": 1768.49, "duration": 4.44}, {"text": "whereas this one\nhere is now that.", "start": 1772.93, "duration": 1.95}, {"text": "All right.", "start": 1780.226, "duration": 0.972}, {"text": "So what we see as a corollary\nof this counting lemma", "start": 1784.6, "duration": 8.72}, {"text": "is that if you are a Cauchy\nsequence with respect", "start": 1793.32, "duration": 5.22}, {"text": "to the cut distance,\nthen the sequence", "start": 1798.54, "duration": 8.4}, {"text": "is automatically convergent.", "start": 1806.94, "duration": 2.407}, {"text": "So recall the definition\nof convergence.", "start": 1815.663, "duration": 1.667}, {"text": "Convergence has to do with\nF densities converging.", "start": 1817.33, "duration": 3.59}, {"text": "And if you have a\nCauchy sequence,", "start": 1820.92, "duration": 2.02}, {"text": "then the F densities converge.", "start": 1822.94, "duration": 3.03}, {"text": "And also, a related\nbut different statement", "start": 1825.97, "duration": 3.03}, {"text": "is that if you have\na sequence wn that", "start": 1829.0, "duration": 6.18}, {"text": "converges to w in\ncut distance, then", "start": 1835.18, "duration": 5.86}, {"text": "it implies that wn\nconverges to w in the sense", "start": 1841.04, "duration": 4.77}, {"text": "as defined for F densities.", "start": 1845.81, "duration": 2.686}, {"text": "So qualitatively, what\nthe counting lemma says", "start": 1851.88, "duration": 3.39}, {"text": "is that the cut norm is stronger\nthan the notion of convergence", "start": 1855.27, "duration": 5.28}, {"text": "coming from subgraph densities.", "start": 1860.55, "duration": 4.71}, {"text": "So this is one part of\nthis regularity method, so", "start": 1865.26, "duration": 3.408}, {"text": "the counting lemma.", "start": 1868.668, "duration": 0.792}, {"text": "Of course, the other part is\nthe regularity lemma itself.", "start": 1869.46, "duration": 3.043}, {"text": "So that's the next\nthing we'll do.", "start": 1872.503, "duration": 1.417}, {"text": "And it turns out\nthat we actually", "start": 1877.02, "duration": 1.59}, {"text": "don't need the full strength\nof the regularity lemma.", "start": 1878.61, "duration": 2.58}, {"text": "We only need something called\na weak regularity lemma.", "start": 1881.19, "duration": 2.55}, {"text": "What the weak regularity\nlemma says is--", "start": 1897.66, "duration": 4.03}, {"text": "I mean, you still have a\npartition of the vertices.", "start": 1901.69, "duration": 3.16}, {"text": "So let me now state\nit for graphons.", "start": 1904.85, "duration": 1.52}, {"text": "So for a partition p--", "start": 1906.37, "duration": 6.74}, {"text": "so I have a partition\nof the vertex set--", "start": 1913.11, "duration": 3.81}, {"text": "and a symmetric,\nmeasurable function w--", "start": 1924.12, "duration": 8.98}, {"text": "I'm just going to omit the\nword \"measurable\" from now on.", "start": 1933.1, "duration": 2.98}, {"text": "Everything will be measurable.", "start": 1936.08, "duration": 2.91}, {"text": "What I can do is, OK,\nall of these assets", "start": 1938.99, "duration": 3.17}, {"text": "are also measurable.", "start": 1942.16, "duration": 2.303}, {"text": "I can define what's known as a\nstepping operator that sends w", "start": 1947.78, "duration": 10.35}, {"text": "to this object,\nw sub p, obtained", "start": 1958.13, "duration": 5.06}, {"text": "by averaging over\nthe steps si cross sj", "start": 1963.19, "duration": 12.02}, {"text": "and replacing that graphon by\nits average over each step.", "start": 1975.21, "duration": 6.28}, {"text": "Precisely, so I\nobtain a new graphon,", "start": 1981.49, "duration": 6.41}, {"text": "a new symmetric, measurable\nfunction, w sub p,", "start": 1987.9, "duration": 3.73}, {"text": "where the value on x,\ncomma, y is defined", "start": 1991.63, "duration": 8.47}, {"text": "to be the following quantity--", "start": 2000.1, "duration": 3.79}, {"text": "if x, comma, y lies\nin si cross sj.", "start": 2010.61, "duration": 8.43}, {"text": "So pictorially, what happens is\nthat you look at your graphon.", "start": 2019.04, "duration": 4.8}, {"text": "There's a partition\nof the vertex set,", "start": 2027.54, "duration": 3.722}, {"text": "so to speak, the interval.", "start": 2031.262, "duration": 1.591}, {"text": "Doesn't have to be a\npartition into intervals,", "start": 2032.853, "duration": 1.917}, {"text": "but for illustration,\nsuppose it looks like that.", "start": 2034.77, "duration": 3.08}, {"text": "And what I do is I take\nthis w, and I replace it", "start": 2037.85, "duration": 4.0}, {"text": "by a new graphon, a new\nsymmetric, measurable function,", "start": 2041.85, "duration": 4.74}, {"text": "w sub p, obtained by averaging.", "start": 2046.59, "duration": 6.159}, {"text": "Take each box.", "start": 2056.421, "duration": 1.179}, {"text": "Replace it by its average.", "start": 2057.6, "duration": 1.26}, {"text": "Put that average into the box.", "start": 2058.86, "duration": 3.45}, {"text": "So this is what w sub\np is supposed to be.", "start": 2062.31, "duration": 4.61}, {"text": "Just a few minor technicalities.", "start": 2066.92, "duration": 2.79}, {"text": "If this denominator is equal\nto 0, let's ignore the set.", "start": 2069.71, "duration": 9.98}, {"text": "I mean, then you have a\nzero measure set, anyway,", "start": 2079.69, "duration": 2.989}, {"text": "so we ignore that set.", "start": 2082.679, "duration": 2.141}, {"text": "So everything will be\ntreated up to measure zero,", "start": 2084.82, "duration": 2.51}, {"text": "changing the function\non measure zero sets.", "start": 2087.33, "duration": 2.52}, {"text": "So it doesn't really matter\nif you're not strictly", "start": 2089.85, "duration": 4.033}, {"text": "allowed to do this division.", "start": 2093.883, "duration": 1.167}, {"text": "OK.", "start": 2098.31, "duration": 0.89}, {"text": "So this operator plays\nan important role", "start": 2099.2, "duration": 2.79}, {"text": "in the regularity\nlemma, because it's", "start": 2101.99, "duration": 1.83}, {"text": "how we think about partitioning,\nwhat happens to a graph", "start": 2103.82, "duration": 3.23}, {"text": "under partitioning.", "start": 2107.05, "duration": 1.21}, {"text": "It has several other names if\nyou look at it from slightly", "start": 2108.26, "duration": 4.38}, {"text": "different perspectives.", "start": 2112.64, "duration": 1.42}, {"text": "So you can view\nit as a projection", "start": 2114.06, "duration": 5.34}, {"text": "in the sense of Hilbert space.", "start": 2119.4, "duration": 2.88}, {"text": "So in the Hilbert space of\nfunctions on the unit square,", "start": 2122.28, "duration": 12.89}, {"text": "the stepping operator is a\nprojection unto the subspace", "start": 2135.17, "duration": 9.67}, {"text": "of constants,\nsubspace of functions", "start": 2144.84, "duration": 7.25}, {"text": "that are constant on each step.", "start": 2152.09, "duration": 4.57}, {"text": "So that's one interpretation.", "start": 2165.21, "duration": 1.71}, {"text": "Another interpretation is\nthat this operation is also", "start": 2166.92, "duration": 2.94}, {"text": "a conditional expectation.", "start": 2169.86, "duration": 2.01}, {"text": "If you know what a conditional\nexpectation actually", "start": 2177.34, "duration": 4.56}, {"text": "is in the sense of\nprobability theory,", "start": 2181.9, "duration": 3.23}, {"text": "so then that's\nwhat happens here.", "start": 2185.13, "duration": 1.81}, {"text": "If you view 0, 1 squared\nas a probability space,", "start": 2186.94, "duration": 3.78}, {"text": "then what we're doing is we're\ndoing conditional expectation", "start": 2190.72, "duration": 4.62}, {"text": "relative to the sigma algebra\ngenerated by these steps.", "start": 2195.34, "duration": 4.41}, {"text": "So these are just a\ncouple of ways of thinking", "start": 2201.793, "duration": 1.917}, {"text": "about what's going on.", "start": 2203.71, "duration": 0.917}, {"text": "They might be somewhat\nhelpful later on", "start": 2204.627, "duration": 1.663}, {"text": "if you're familiar\nwith these notions.", "start": 2206.29, "duration": 1.583}, {"text": "But if you're not,\ndon't worry about it.", "start": 2207.873, "duration": 1.832}, {"text": "Concretely, it's what\nhappens up there.", "start": 2209.705, "duration": 1.625}, {"text": "OK.", "start": 2218.34, "duration": 0.65}, {"text": "So now let me state the\nweak regularity lemma.", "start": 2218.99, "duration": 2.94}, {"text": "So the weak regularity\nlemma is attributed", "start": 2233.53, "duration": 3.02}, {"text": "to Frieze and Kannan,\nalthough their work predates", "start": 2236.55, "duration": 9.25}, {"text": "the language of graphons.", "start": 2245.8, "duration": 1.74}, {"text": "So it's stated in the\nlanguage of graphs,", "start": 2247.54, "duration": 2.18}, {"text": "but it's the same proof.", "start": 2249.72, "duration": 1.0}, {"text": "So let me state it for you\nboth in terms of graphons", "start": 2250.72, "duration": 2.69}, {"text": "and in graphs.", "start": 2253.41, "duration": 1.66}, {"text": "What it says is that for every\nepsilon and every graphon w,", "start": 2255.07, "duration": 13.09}, {"text": "there exists a partition\ndenoted p of the 0, 1 interval.", "start": 2268.16, "duration": 12.6}, {"text": "And now I tell you how\nmany sets there are.", "start": 2280.76, "duration": 2.35}, {"text": "So it's a partition into--", "start": 2283.11, "duration": 2.21}, {"text": "so not a tower-type\nnumber of parts,", "start": 2285.32, "duration": 2.98}, {"text": "but only roughly an\nexponential number of parts--", "start": 2288.3, "duration": 3.62}, {"text": "4 to the 1 over epsilon\nsquared measurable sets such", "start": 2291.92, "duration": 10.33}, {"text": "that if we apply the stepping\noperator to this graphon,", "start": 2302.25, "duration": 7.46}, {"text": "we obtain an approximation of\nthe graphon in the cut norm.", "start": 2309.71, "duration": 5.828}, {"text": "So that's the statement of\nthe weak regularity lemma.", "start": 2320.52, "duration": 4.53}, {"text": "There exists a partition such\nthat if you do this stepping,", "start": 2325.05, "duration": 6.57}, {"text": "then you obtain\nan approximation.", "start": 2331.62, "duration": 1.84}, {"text": "So I want you to think about\nwhat this has to do with", "start": 2333.46, "duration": 2.66}, {"text": "the usual version of Szemer\u00e9di's\nregularity lemma that", "start": 2336.12, "duration": 2.48}, {"text": "you've seen earlier.", "start": 2338.6, "duration": 1.43}, {"text": "So hopefully, you\nshould realize, morally,", "start": 2340.03, "duration": 1.94}, {"text": "they're about the same\ntypes of statements.", "start": 2341.97, "duration": 2.69}, {"text": "But more importantly, how are\nthey different from each other?", "start": 2344.66, "duration": 3.32}, {"text": "And now let me state a version\nfor graphs, which is similar", "start": 2347.98, "duration": 4.64}, {"text": "but not exactly the same as\nwhat we just saw for graphons.", "start": 2352.62, "duration": 4.47}, {"text": "So let me state it.", "start": 2357.09, "duration": 2.43}, {"text": "So for graphs, the\nweak regularity lemma", "start": 2359.52, "duration": 6.78}, {"text": "says that, OK, so for graphs,\nlet me define a partition", "start": 2366.3, "duration": 10.12}, {"text": "p of the vertex set is\ncalled weakly epsilon regular", "start": 2376.42, "duration": 18.71}, {"text": "if the following is true.", "start": 2395.13, "duration": 3.23}, {"text": "If it is the case that whenever\nI look at two vertex subsets,", "start": 2398.36, "duration": 4.695}, {"text": "A and B, of the\nvertex set of g, then", "start": 2403.055, "duration": 5.595}, {"text": "the number of vertices\nbetween A and B", "start": 2408.65, "duration": 5.23}, {"text": "is what you should expect based\non the density information that", "start": 2413.88, "duration": 7.65}, {"text": "comes out of this partition.", "start": 2421.53, "duration": 3.18}, {"text": "Namely, if I sum over all\nthe parts of the partition,", "start": 2424.71, "duration": 8.12}, {"text": "look at how many vertices from A\nlie in the corresponding parts.", "start": 2432.83, "duration": 13.37}, {"text": "And then multiply by the edge\ndensity between these parts.", "start": 2446.2, "duration": 4.89}, {"text": "So that's your predicted\nvalue based on the data that", "start": 2451.09, "duration": 2.73}, {"text": "comes out of the partition.", "start": 2453.82, "duration": 2.08}, {"text": "So I claim that this is\nthe actual number of edges.", "start": 2455.9, "duration": 2.27}, {"text": "This is the predicted\nnumber of edges.", "start": 2458.17, "duration": 2.55}, {"text": "And those two numbers should\nbe similar to each other bt", "start": 2460.72, "duration": 6.675}, {"text": "at most epsilon n, where n\nis the number of vertices.", "start": 2467.395, "duration": 3.985}, {"text": "So this is the definition of\nwhat it means for a partition", "start": 2471.38, "duration": 3.3}, {"text": "to be weakly epsilon regular.", "start": 2474.68, "duration": 4.02}, {"text": "So it's important to think\nabout why this is weaker.", "start": 2478.7, "duration": 3.49}, {"text": "It's called weak, right?", "start": 2482.19, "duration": 1.0}, {"text": "So why is it weaker than a\nnotion of epsilon regularity?", "start": 2483.19, "duration": 4.96}, {"text": "So why is it weaker?", "start": 2488.15, "duration": 2.3}, {"text": "So previously, we had\nepsilon-regular partition", "start": 2490.45, "duration": 3.66}, {"text": "in the definition of\nSzemer\u00e9di's regularity lemma,", "start": 2494.11, "duration": 2.79}, {"text": "this epsilon-regular partition.", "start": 2496.9, "duration": 1.98}, {"text": "And here, notion of\nweakly epsilon regular.", "start": 2498.88, "duration": 4.47}, {"text": "So why is this a lot weaker?", "start": 2503.35, "duration": 1.27}, {"text": "It is not saying that\nindividual pairs of parts", "start": 2507.46, "duration": 4.59}, {"text": "are epsilon regular.", "start": 2512.05, "duration": 3.305}, {"text": "And eventually, we're going\nto have this number of parts.", "start": 2515.355, "duration": 2.375}, {"text": "So I'll state a\ntheorem in a second.", "start": 2517.73, "duration": 2.48}, {"text": "So the sizes of the\nparts are much smaller", "start": 2520.21, "duration": 3.86}, {"text": "than epsilon fraction.", "start": 2524.07, "duration": 3.31}, {"text": "But what this weak notion of\nregularity says, if you look", "start": 2527.38, "duration": 4.7}, {"text": "at it globally--", "start": 2532.08, "duration": 1.87}, {"text": "so not looking at\nspecific parts,", "start": 2533.95, "duration": 1.79}, {"text": "but looking at it globally--", "start": 2535.74, "duration": 1.71}, {"text": "then this partition is\na good approximation", "start": 2537.45, "duration": 2.22}, {"text": "of what's going on in the\nactual graph, whereas--", "start": 2539.67, "duration": 4.61}, {"text": "OK, so it's worth\nthinking about.", "start": 2544.28, "duration": 1.43}, {"text": "It's really worth\nthinking about what's", "start": 2545.71, "duration": 1.625}, {"text": "the difference between this weak\nnotion and the usual notion.", "start": 2547.335, "duration": 2.655}, {"text": "But first, let me state\nthis regularity lemma.", "start": 2549.99, "duration": 3.39}, {"text": "So the weak regularity\nlemma for graphs", "start": 2553.38, "duration": 9.95}, {"text": "says that for every\nepsilon and every graph G,", "start": 2563.33, "duration": 7.49}, {"text": "there exists a weakly\nepsilon-regular partition", "start": 2570.82, "duration": 12.54}, {"text": "of the vertex set\nof G into at most 4", "start": 2583.36, "duration": 5.73}, {"text": "to the 1 over epsilon\nsquared parts.", "start": 2589.09, "duration": 2.48}, {"text": "Now, you might wonder why\ndid Frieze and Kannan come up", "start": 2600.24, "duration": 4.4}, {"text": "with this notion of regularity.", "start": 2604.64, "duration": 4.37}, {"text": "It's a weaker result if you\ndon't care about the bounds,", "start": 2609.01, "duration": 3.0}, {"text": "because an epsilon-regular\npartition will be automatically", "start": 2612.01, "duration": 6.06}, {"text": "weakly epsilon regular.", "start": 2618.07, "duration": 3.29}, {"text": "So maybe with small\nchanges of epsilon", "start": 2621.36, "duration": 1.86}, {"text": "if you wish, but basically,\nthis is a weaker notion", "start": 2623.22, "duration": 3.15}, {"text": "compared to what we had before.", "start": 2626.37, "duration": 1.32}, {"text": "But of course, the advantage\nis that you have a much more", "start": 2630.78, "duration": 2.78}, {"text": "reasonable number of parts.", "start": 2633.56, "duration": 2.67}, {"text": "It's not a tower.", "start": 2636.23, "duration": 1.98}, {"text": "It's just a single exponential.", "start": 2638.21, "duration": 2.97}, {"text": "And this is important.", "start": 2641.18, "duration": 0.93}, {"text": "And their motivation was a\ncomputer science and algorithm", "start": 2642.11, "duration": 3.63}, {"text": "application.", "start": 2645.74, "duration": 1.02}, {"text": "So I want to take a\nbrief detour and mention", "start": 2646.76, "duration": 4.65}, {"text": "why you might care about weakly\nepsilon-regular partitions.", "start": 2651.41, "duration": 6.612}, {"text": "In particular, the problem\nthat is of interest", "start": 2662.18, "duration": 3.06}, {"text": "is in approximating\nsomething called a max cut.", "start": 2665.24, "duration": 5.74}, {"text": "So the max cut problem asks you\nto determine-- given a graph G,", "start": 2670.98, "duration": 7.08}, {"text": "find the maximum over\nall subsets of vertices,", "start": 2678.06, "duration": 8.3}, {"text": "the maximum number of\nvertices between a set", "start": 2686.36, "duration": 3.25}, {"text": "and its complement.", "start": 2689.61, "duration": 1.43}, {"text": "That's called a cut.", "start": 2691.04, "duration": 1.39}, {"text": "I give you a graph,\nand I want to know--", "start": 2692.43, "duration": 4.0}, {"text": "find this s so that it\ncan have as many edges", "start": 2696.43, "duration": 5.43}, {"text": "across this set as possible.", "start": 2701.86, "duration": 3.628}, {"text": "This is an important\nproblem in computer science,", "start": 2705.488, "duration": 2.042}, {"text": "extremely important problem.", "start": 2707.53, "duration": 1.59}, {"text": "And the status of\nthis problem is", "start": 2709.12, "duration": 3.33}, {"text": "that it is known to be difficult\nto get it even within 1%.", "start": 2712.45, "duration": 8.19}, {"text": "So the best algorithm is due\nto Goemans and Williamson.", "start": 2720.64, "duration": 3.548}, {"text": "It's an important\nalgorithm that was", "start": 2730.41, "duration": 1.71}, {"text": "one of the\nfoundational algorithms", "start": 2732.12, "duration": 1.44}, {"text": "in semidefinite\nprogramming, so related--", "start": 2733.56, "duration": 2.13}, {"text": "the words \"semidefinite\nprogramming\"", "start": 2735.69, "duration": 1.65}, {"text": "came up earlier in this course\nwhen we discussed growth index", "start": 2737.34, "duration": 2.73}, {"text": "inequality.", "start": 2740.07, "duration": 0.9}, {"text": "So they came up with an\napproximation algorithm.", "start": 2740.97, "duration": 2.85}, {"text": "So here, I'm only talking\nabout polynomial time,", "start": 2743.82, "duration": 3.28}, {"text": "so efficient algorithms.", "start": 2747.1, "duration": 1.73}, {"text": "Approximation algorithm\nwith approximation ratio", "start": 2748.83, "duration": 4.77}, {"text": "around 0.878.", "start": 2753.6, "duration": 2.52}, {"text": "So one can obtain a cut\nthat is within basically", "start": 2756.12, "duration": 7.78}, {"text": "13% of the maximum.", "start": 2763.9, "duration": 3.92}, {"text": "So it's an\napproximation algorithm.", "start": 2767.82, "duration": 2.72}, {"text": "However, it is known that it is\nhard in the sense of complexity", "start": 2770.54, "duration": 6.84}, {"text": "theory.", "start": 2777.38, "duration": 1.16}, {"text": "It'd be hard to approximate\nbeyond the ratio 16 over 17,", "start": 2778.54, "duration": 11.29}, {"text": "which is around 0.491.", "start": 2789.83, "duration": 7.17}, {"text": "And there is an\nimportant conjecture", "start": 2797.0, "duration": 1.98}, {"text": "in computer science called\na unique games conjecture", "start": 2798.98, "duration": 2.82}, {"text": "that, if that\nconjecture were true,", "start": 2801.8, "duration": 2.44}, {"text": "then it would be\ndifficult. It would", "start": 2804.24, "duration": 2.47}, {"text": "be hard to approximate beyond\nthe Goemans-Williamson ratio.", "start": 2806.71, "duration": 5.3}, {"text": "So this indicates the\nstatus of this problem.", "start": 2812.01, "duration": 2.06}, {"text": "It is difficult to do an\nepsilon approximation.", "start": 2814.07, "duration": 5.69}, {"text": "But if the graph I\ngive you is dense--", "start": 2819.76, "duration": 3.375}, {"text": "\"dense\" meaning a\nquadratic number", "start": 2830.46, "duration": 2.58}, {"text": "of edges, where n is\na number of vertices--", "start": 2833.04, "duration": 4.93}, {"text": "then it turns out that the\nregularity-type algorithms--", "start": 2837.97, "duration": 7.24}, {"text": "so that theorem combined\nwith the algorithmic versions", "start": 2845.21, "duration": 3.18}, {"text": "allows you to get polynomial\ntime approximation algorithms.", "start": 2848.39, "duration": 6.97}, {"text": "So this is polynomial time\napproximation schemes.", "start": 2855.36, "duration": 3.3}, {"text": "So one can approximate up\nto 1 minus epsilon ratio.", "start": 2861.62, "duration": 10.38}, {"text": "So one can approximate\nup to epsilon", "start": 2872.0, "duration": 5.94}, {"text": "n squared additive error\nin polynomial time.", "start": 2877.94, "duration": 9.856}, {"text": "So in particular, if I'm\nwilling to lose 0.01 n squared,", "start": 2887.796, "duration": 4.934}, {"text": "then there is an algorithm to\napproximate the size of the max", "start": 2892.73, "duration": 3.81}, {"text": "cut.", "start": 2896.54, "duration": 0.5}, {"text": "And that algorithm\nbasically comes from--", "start": 2897.04, "duration": 4.07}, {"text": "without giving you any\ndetails whatsoever,", "start": 2901.11, "duration": 2.21}, {"text": "the algorithm essentially comes\nfrom first finding a regularity", "start": 2903.32, "duration": 3.99}, {"text": "partition.", "start": 2907.31, "duration": 1.024}, {"text": "So the partition breaks\nthe set of vertices", "start": 2915.11, "duration": 5.01}, {"text": "into some number of pieces.", "start": 2920.12, "duration": 3.12}, {"text": "And now I search over\nall possible ratios", "start": 2923.24, "duration": 14.4}, {"text": "to divide each piece.", "start": 2937.64, "duration": 3.44}, {"text": "So there is a bounded\nnumber of parts.", "start": 2944.28, "duration": 1.93}, {"text": "Each one of those, I decide,\ndo I cut this up half-half?", "start": 2946.21, "duration": 3.11}, {"text": "Do I cut it up 1/3,\n2/3, and so on?", "start": 2949.32, "duration": 3.95}, {"text": "And those numbers alone,\nbecause of this definition", "start": 2953.27, "duration": 4.67}, {"text": "of weakly epsilon\nregular, once you", "start": 2957.94, "duration": 4.1}, {"text": "know what the intersection\nof A, B is, let's say,", "start": 2962.04, "duration": 4.965}, {"text": "a complement is with\nindividual sets,", "start": 2967.005, "duration": 2.775}, {"text": "then I basically know\nthe number of edges.", "start": 2969.78, "duration": 2.73}, {"text": "So I can approximate\nthe size of the max cut", "start": 2972.51, "duration": 4.29}, {"text": "using a weakly\nepsilon-regular partition.", "start": 2976.8, "duration": 4.5}, {"text": "So that was the motivation\nfor these weakly epsilon", "start": 2981.3, "duration": 6.06}, {"text": "partitions, at least the\nalgorithmic application.", "start": 2987.36, "duration": 4.46}, {"text": "OK.", "start": 2991.82, "duration": 0.5}, {"text": "Any questions?", "start": 2992.32, "duration": 1.1}, {"text": "OK.", "start": 2996.24, "duration": 0.5}, {"text": "So let's take a quick break.", "start": 2996.74, "duration": 1.41}, {"text": "And then afterwards,\nI want to show", "start": 2998.15, "duration": 1.95}, {"text": "you the proof of the\nweak regularity lemma.", "start": 3000.1, "duration": 3.06}, {"text": "All right.", "start": 3005.73, "duration": 0.5}, {"text": "So let me start the proof of\nthe weak regularity lemma.", "start": 3006.23, "duration": 6.33}, {"text": "And the proof is by this\nenergy increment argument.", "start": 3012.56, "duration": 2.215}, {"text": "So let's see what\nthis energy increment", "start": 3014.775, "duration": 1.625}, {"text": "argument looks like in\nthe language of graphons.", "start": 3016.4, "duration": 3.3}, {"text": "So energy now means L2,\nso L2 energy increment.", "start": 3019.7, "duration": 7.91}, {"text": "So the statement\nof this lemma is", "start": 3027.61, "duration": 1.99}, {"text": "that if you have w, a graphon,\nand p, a partition, of 0,", "start": 3029.6, "duration": 12.63}, {"text": "comma, 1 interval such that--", "start": 3042.23, "duration": 4.51}, {"text": "always measurable pieces.", "start": 3050.12, "duration": 1.14}, {"text": "I'm not going to even write it.", "start": 3051.26, "duration": 1.04}, {"text": "It's always measurable pieces--", "start": 3052.3, "duration": 1.292}, {"text": "such that the difference between\nw and w averaged over steps p", "start": 3057.32, "duration": 11.07}, {"text": "is bigger than epsilon.", "start": 3068.39, "duration": 3.03}, {"text": "So this is the notion\nof being not epsilon", "start": 3071.42, "duration": 2.97}, {"text": "regular in the weak sense,\nnot weakly epsilon regular.", "start": 3074.39, "duration": 7.89}, {"text": "Then there exists a\nrefinement, p prime of p,", "start": 3082.28, "duration": 10.82}, {"text": "dividing each part of p\ninto at most four parts", "start": 3093.1, "duration": 12.33}, {"text": "such that the true norm\nincreases by more than epsilon", "start": 3105.43, "duration": 11.95}, {"text": "squared under this refinement.", "start": 3117.38, "duration": 4.66}, {"text": "So it should be similar.", "start": 3122.04, "duration": 2.07}, {"text": "It should be familiar to\nyou, because we have similar", "start": 3124.11, "duration": 2.34}, {"text": "arguments from Szemer\u00e9di's\nregularity lemma.", "start": 3126.45, "duration": 3.236}, {"text": "So let's see the proof.", "start": 3129.686, "duration": 0.958}, {"text": "Because you have violation\nof weak epsilon regularity,", "start": 3133.49, "duration": 4.89}, {"text": "there exists sets S and T,\nmeasurable subsets of 0,", "start": 3138.38, "duration": 4.87}, {"text": "1 interval, such that this\nintegral evaluated over S", "start": 3143.25, "duration": 6.26}, {"text": "cross T is more than\nepsilon in absolute value.", "start": 3149.51, "duration": 9.63}, {"text": "So now let me take p prime to\nbe the common refinement of p", "start": 3159.14, "duration": 16.55}, {"text": "by introducing S and\nT into this partition.", "start": 3175.69, "duration": 12.2}, {"text": "So throw S and T in\nand break everything", "start": 3187.89, "duration": 3.01}, {"text": "according to S and T.", "start": 3190.9, "duration": 2.03}, {"text": "And so each part becomes\nat most four subparts.", "start": 3192.93, "duration": 8.21}, {"text": "So that's the at\nmost four subparts.", "start": 3201.14, "duration": 1.82}, {"text": "I now need to show that I\nhave an energy increment.", "start": 3205.78, "duration": 3.28}, {"text": "And to do this, let\nme first perform", "start": 3209.06, "duration": 4.28}, {"text": "the following calculation.", "start": 3213.34, "duration": 3.19}, {"text": "So remember, this symbol\nhere is the inner product", "start": 3216.53, "duration": 5.06}, {"text": "obtained by multiplying\nand integrating", "start": 3221.59, "duration": 2.64}, {"text": "over the entire box.", "start": 3224.23, "duration": 2.66}, {"text": "I claim that that\ninner product equals", "start": 3226.89, "duration": 5.51}, {"text": "to the inner product\nbetween wp and wp prime,", "start": 3232.4, "duration": 8.39}, {"text": "because what happens here is\nwe are looking at a situation", "start": 3240.79, "duration": 7.79}, {"text": "where wp prime is\nconstant on each part.", "start": 3248.58, "duration": 6.93}, {"text": "So when I do this inner product,\nI can replace w by its average.", "start": 3255.51, "duration": 5.41}, {"text": "And likewise, over here, I can\nalso replace it by its average.", "start": 3260.92, "duration": 2.89}, {"text": "And you end up having\nthe same average.", "start": 3263.81, "duration": 3.18}, {"text": "And these two averages\nare both just what happens", "start": 3266.99, "duration": 6.35}, {"text": "if you do stepping by p.", "start": 3273.34, "duration": 1.83}, {"text": "You also have that w has inner\nproduct with 1 sub S cross T", "start": 3278.44, "duration": 9.94}, {"text": "the same as that of p\nprime by the same reason,", "start": 3288.38, "duration": 6.4}, {"text": "because over S\ncross T. So S cross", "start": 3294.78, "duration": 6.01}, {"text": "T is a union of the\nparts of p prime.", "start": 3300.79, "duration": 5.21}, {"text": "So S is union of\nparts of p prime.", "start": 3306.0, "duration": 10.36}, {"text": "OK.", "start": 3316.36, "duration": 0.5}, {"text": "So let's see.", "start": 3316.86, "duration": 1.28}, {"text": "With those observations,\nyou find that--", "start": 3318.14, "duration": 3.63}, {"text": "so this is true.", "start": 3330.58, "duration": 3.0}, {"text": "This is from the first equality.", "start": 3333.58, "duration": 2.29}, {"text": "So now let me draw\nyou a right triangle.", "start": 3335.87, "duration": 4.925}, {"text": "So you have a right\nangle, because you have", "start": 3349.89, "duration": 1.95}, {"text": "an inner product that is 0.", "start": 3351.84, "duration": 2.61}, {"text": "So by Pythagorean theorem,\nso what is this hypotenuse?", "start": 3354.45, "duration": 10.08}, {"text": "So you add these two vectors.", "start": 3364.53, "duration": 1.99}, {"text": "And you find out this wp prime.", "start": 3366.52, "duration": 7.54}, {"text": "So by Pythagorean\ntheorem, you find", "start": 3374.06, "duration": 1.95}, {"text": "that the L2 norm\nof wp prime equals", "start": 3376.01, "duration": 4.53}, {"text": "to the L2 norm of the sum of\nthe L2 norm squares of the two", "start": 3380.54, "duration": 13.45}, {"text": "legs of this right triangle.", "start": 3393.99, "duration": 1.92}, {"text": "On the other hand,\nthis quantity here.", "start": 3403.42, "duration": 4.733}, {"text": "So let's think about\nthat quantity over there.", "start": 3408.153, "duration": 1.917}, {"text": "It's an L2 norm.", "start": 3412.81, "duration": 1.61}, {"text": "So in particular, it is at\nleast this quantity here,", "start": 3414.42, "duration": 22.16}, {"text": "which you can derive\nin one of many ways--", "start": 3436.58, "duration": 3.6}, {"text": "for example, by Cauchy-Schwarz\ninequality or go from L2 to L1", "start": 3440.18, "duration": 5.66}, {"text": "and then pass down to L1.", "start": 3445.84, "duration": 2.49}, {"text": "So this is true.", "start": 3448.33, "duration": 3.56}, {"text": "So let's say by Cauchy-Schwarz.", "start": 3451.89, "duration": 1.797}, {"text": "But this quantity here, we\nsaid was bigger than epsilon.", "start": 3469.57, "duration": 6.01}, {"text": "So as a result,\nthis final quantity,", "start": 3484.69, "duration": 7.49}, {"text": "this L2 norm of\nthe new refinement,", "start": 3492.18, "duration": 5.12}, {"text": "increases from the previous one\nby more than epsilon squared.", "start": 3497.3, "duration": 3.24}, {"text": "OK.", "start": 3504.62, "duration": 1.26}, {"text": "So this is the L2 energy\nincrement argument.", "start": 3505.88, "duration": 2.03}, {"text": "I claim it's the same\nargument, basically,", "start": 3507.91, "duration": 1.96}, {"text": "as the one that we did for\nSzemer\u00e9di's regularity lemma.", "start": 3509.87, "duration": 2.61}, {"text": "And I encourage you to\ngo back and compare them", "start": 3512.48, "duration": 2.22}, {"text": "to see why they're the same.", "start": 3514.7, "duration": 1.5}, {"text": "All right, moving on.", "start": 3520.28, "duration": 1.08}, {"text": "So the other part\nof regularity lemma", "start": 3521.36, "duration": 3.87}, {"text": "is to iterate this approach.", "start": 3525.23, "duration": 3.59}, {"text": "So if you have something\nwhich is not epsilon regular,", "start": 3528.82, "duration": 3.16}, {"text": "refine it.", "start": 3531.98, "duration": 0.81}, {"text": "And then iterate.", "start": 3532.79, "duration": 1.17}, {"text": "And you cannot perceive more\nthan a bounded number of times,", "start": 3533.96, "duration": 4.86}, {"text": "because energy is always\nbounded between 0 and 1.", "start": 3538.82, "duration": 3.57}, {"text": "So for every epsilon bigger\nthan 0 and graphon w,", "start": 3542.39, "duration": 6.87}, {"text": "suppose you have P0, a\npartition of 0, 1 interval", "start": 3549.26, "duration": 7.95}, {"text": "into measurable sets.", "start": 3557.21, "duration": 2.75}, {"text": "Then there exists a partition\np that cuts up each part of P0", "start": 3559.96, "duration": 18.32}, {"text": "into at most 4 to the\n1 over epsilon parts", "start": 3578.28, "duration": 9.18}, {"text": "such that w minus w sub\np is at most epsilon.", "start": 3587.46, "duration": 8.46}, {"text": "So I'm basically restating\nthe weak regularity lemma", "start": 3595.92, "duration": 3.7}, {"text": "over there but with a\nsmall difference, which", "start": 3599.62, "duration": 4.01}, {"text": "will become useful later on\nwhen we prove compactness.", "start": 3603.63, "duration": 3.39}, {"text": "Namely, I'm allowed to\nstart with any partition.", "start": 3607.02, "duration": 2.625}, {"text": "Instead of starting with\na trivial partition,", "start": 3609.645, "duration": 1.875}, {"text": "I can start with any partition.", "start": 3611.52, "duration": 2.58}, {"text": "This was also true when\nwe were talking about", "start": 3614.1, "duration": 2.282}, {"text": "Szemer\u00e9di's regularity lemma,\nalthough I didn't stress that", "start": 3616.382, "duration": 2.458}, {"text": "point.", "start": 3618.84, "duration": 1.48}, {"text": "That's certainly the case here.", "start": 3620.32, "duration": 1.538}, {"text": "I mean, the proof\nis exactly the same", "start": 3621.858, "duration": 1.542}, {"text": "with or without this extra.", "start": 3623.4, "duration": 2.85}, {"text": "This extra P0 really plays\nan insignificant role.", "start": 3626.25, "duration": 4.53}, {"text": "What happens, as in the proof\nof Szemer\u00e9di's regularity lemma,", "start": 3630.78, "duration": 3.74}, {"text": "is that we repeatedly apply\nthe previous lemma to obtain", "start": 3634.52, "duration": 8.25}, {"text": "the sequence of partitions\nof the 0, 1 interval where,", "start": 3642.77, "duration": 13.27}, {"text": "each step, either we find that\nwe obtain some partition p sub", "start": 3656.04, "duration": 14.12}, {"text": "i such that it's a good\napproximation of w,", "start": 3670.16, "duration": 5.63}, {"text": "in which case we stop, or the\nL2 energy increases by more than", "start": 3675.79, "duration": 17.36}, {"text": "epsilon squared.", "start": 3693.15, "duration": 1.6}, {"text": "And since the final energy\nis always at most 1--", "start": 3700.63, "duration": 9.26}, {"text": "so it's always bounded\nbetween 0 and 1--", "start": 3709.89, "duration": 2.73}, {"text": "we must stop after at\nmost 1 over epsilon steps.", "start": 3712.62, "duration": 8.44}, {"text": "And if you calculate\nthe number of parts,", "start": 3726.46, "duration": 7.7}, {"text": "each part is subdivided\ninto at most four parts", "start": 3734.16, "duration": 6.005}, {"text": "at each step, which\ngives you the conclusion", "start": 3740.165, "duration": 6.615}, {"text": "on the final number of parts.", "start": 3746.78, "duration": 2.8}, {"text": "OK, so very similar\nto what we did before.", "start": 3749.58, "duration": 2.06}, {"text": "All right.", "start": 3755.78, "duration": 0.94}, {"text": "So that concludes the discussion\nof the weak regularity lemma.", "start": 3756.72, "duration": 5.13}, {"text": "So basically the same proof.", "start": 3761.85, "duration": 2.51}, {"text": "Weaker conclusion and\nbetter quantitative balance.", "start": 3764.36, "duration": 4.043}, {"text": "The next thing and the final\nthing I want to discuss today", "start": 3768.403, "duration": 2.417}, {"text": "is a new ingredient which\nwe haven't seen before", "start": 3770.82, "duration": 4.32}, {"text": "but that will play an\nimportant role in the proof", "start": 3775.14, "duration": 2.97}, {"text": "of the compactness--", "start": 3778.11, "duration": 1.47}, {"text": "in particular, the proof of\nthe existence of the limit.", "start": 3779.58, "duration": 3.58}, {"text": "And this is something where I\nneed to discuss martingales.", "start": 3783.16, "duration": 5.12}, {"text": "So martingale gill is\nan important object", "start": 3792.41, "duration": 2.6}, {"text": "in probability theory.", "start": 3795.01, "duration": 1.545}, {"text": "And it's a random sequence.", "start": 3796.555, "duration": 2.31}, {"text": "So we'll look at discrete\nsequences, so indexed", "start": 3803.62, "duration": 4.73}, {"text": "by non-negative integers.", "start": 3808.35, "duration": 3.66}, {"text": "And is martingale is\nsuch a sequence where", "start": 3812.01, "duration": 4.61}, {"text": "if I'm interested in the\nexpectation of the next term", "start": 3816.62, "duration": 6.71}, {"text": "and even if you know\nall the previous terms--", "start": 3823.33, "duration": 4.39}, {"text": "so you have full knowledge of\nthe sequence before time n,", "start": 3827.72, "duration": 3.81}, {"text": "and you want to predict\non the expectation what", "start": 3831.53, "duration": 3.47}, {"text": "the nth term is--", "start": 3835.0, "duration": 1.44}, {"text": "then you cannot do better than\nsimply predicting the last term", "start": 3836.44, "duration": 8.39}, {"text": "that you saw.", "start": 3844.83, "duration": 1.97}, {"text": "So this is the definition\nof a martingale.", "start": 3846.8, "duration": 4.2}, {"text": "Now, to do this\nformally, I need to talk", "start": 3851.0, "duration": 2.73}, {"text": "about filtrations and what\nnot in measured theory.", "start": 3853.73, "duration": 4.35}, {"text": "But let me not do that.", "start": 3858.08, "duration": 2.622}, {"text": "OK, so this is how\nyou should think", "start": 3860.702, "duration": 1.458}, {"text": "about martingales and a\ncouple of important examples", "start": 3862.16, "duration": 3.8}, {"text": "of martingales.", "start": 3865.96, "duration": 1.12}, {"text": "So the first one comes\nfrom-- the reason", "start": 3867.08, "duration": 4.59}, {"text": "why these things are called\nmartingales is that there", "start": 3871.67, "duration": 3.33}, {"text": "is a gambling strategy\nwhich is related", "start": 3875.0, "duration": 2.28}, {"text": "to such a sequence where\nlet's say you consider", "start": 3877.28, "duration": 7.44}, {"text": "a sequence of fair coin tosses.", "start": 3884.72, "duration": 3.41}, {"text": "So here's what\nwe're going to do.", "start": 3888.13, "duration": 2.37}, {"text": "So suppose we consider\na betting strategy.", "start": 3890.5, "duration": 3.35}, {"text": "And x sub n is equal\nto your balance time n.", "start": 3903.24, "duration": 13.84}, {"text": "And suppose that we're\nlooking at a fair casino", "start": 3917.08, "duration": 4.04}, {"text": "where the expectation of\nevery game is exactly 0.", "start": 3921.12, "duration": 6.58}, {"text": "Then this is a martingale.", "start": 3927.7, "duration": 3.56}, {"text": "So imagine you have\na sequence of coin", "start": 3931.26, "duration": 1.74}, {"text": "flips, and you win $1 for each\nhead and lose $1 for each tail.", "start": 3933.0, "duration": 5.6}, {"text": "When you're at time five, you\nshould have $2 in your pocket.", "start": 3938.6, "duration": 3.45}, {"text": "Then time five\nplus 1, you expect", "start": 3942.05, "duration": 4.37}, {"text": "to also have that many dollars.", "start": 3946.42, "duration": 2.085}, {"text": "It might go up.", "start": 3948.505, "duration": 0.625}, {"text": "It might go down.", "start": 3949.13, "duration": 0.708}, {"text": "But in expectation,\nit doesn't change.", "start": 3949.838, "duration": 2.888}, {"text": "Is there a question?", "start": 3952.726, "duration": 0.944}, {"text": "OK.", "start": 3956.22, "duration": 0.5}, {"text": "So they're asking about,\nis there some independence", "start": 3956.72, "duration": 3.058}, {"text": "condition required?", "start": 3959.778, "duration": 0.792}, {"text": "And the answer is no.", "start": 3960.57, "duration": 1.62}, {"text": "So there's no independence\ncondition that is required.", "start": 3962.19, "duration": 2.35}, {"text": "So the definition\nof a martingale", "start": 3964.54, "duration": 1.73}, {"text": "is just if, even with complete\nknowledge of the sequence up", "start": 3966.27, "duration": 3.75}, {"text": "to a certain point, the\ndifference going forward", "start": 3970.02, "duration": 4.11}, {"text": "is 0 in expectation.", "start": 3974.13, "duration": 2.435}, {"text": "OK, so here's another\nexample of a martingale,", "start": 3982.57, "duration": 5.4}, {"text": "which actually turns out to\nbe more relevant to our use--", "start": 3987.97, "duration": 3.52}, {"text": "namely, that if I\nhave some hidden--", "start": 3994.25, "duration": 5.73}, {"text": "think of x as some hidden\nrandom variable, so something", "start": 3999.98, "duration": 4.56}, {"text": "that you have no idea.", "start": 4004.54, "duration": 2.34}, {"text": "But you can observe\nit at time n based", "start": 4006.88, "duration": 9.29}, {"text": "on information up to time n.", "start": 4016.17, "duration": 10.93}, {"text": "So for example, suppose\nyou have no idea who", "start": 4031.38, "duration": 5.22}, {"text": "is going to win the\npresidential election.", "start": 4036.6, "duration": 5.31}, {"text": "And really, nobody has any idea.", "start": 4041.91, "duration": 2.64}, {"text": "But as time proceeds, you\nmake an educated guess", "start": 4044.55, "duration": 4.44}, {"text": "based on the information\nthat you have,", "start": 4048.99, "duration": 1.8}, {"text": "all the information you\nhave up to that point.", "start": 4050.79, "duration": 3.1}, {"text": "And that information becomes\na larger and larger set", "start": 4053.89, "duration": 2.7}, {"text": "as time moves forward.", "start": 4056.59, "duration": 1.83}, {"text": "Your prediction is going to\nbe a random variable that", "start": 4058.42, "duration": 2.67}, {"text": "goes up and down.", "start": 4061.09, "duration": 2.7}, {"text": "And that will be a\nmartingale, because--", "start": 4063.79, "duration": 4.33}, {"text": "so how I predict\ntoday based on what", "start": 4068.12, "duration": 4.86}, {"text": "are all the possibilities\nhappening going forward,", "start": 4072.98, "duration": 3.68}, {"text": "well, one of many\nthings could happen.", "start": 4076.66, "duration": 3.64}, {"text": "But if I knew that my prediction\nis going to, in expectation,", "start": 4080.3, "duration": 5.51}, {"text": "shift upwards, then\nI shouldn't have", "start": 4085.81, "duration": 2.58}, {"text": "predicted what I predict today.", "start": 4088.39, "duration": 1.32}, {"text": "I should have predicted\nupwards anyway.", "start": 4089.71, "duration": 3.59}, {"text": "OK.", "start": 4093.3, "duration": 0.5}, {"text": "So this is another\nconstruction of martingales.", "start": 4093.8, "duration": 6.019}, {"text": "So this also comes up.", "start": 4099.819, "duration": 1.591}, {"text": "You could have other more pure\nmathematics-type explanations,", "start": 4101.41, "duration": 4.71}, {"text": "where suppose I\nwant to know what", "start": 4106.12, "duration": 3.81}, {"text": "is the chromatic number\nof a random graph.", "start": 4109.93, "duration": 4.56}, {"text": "And I show you that\ngraph one edge at a time.", "start": 4114.49, "duration": 4.47}, {"text": "You can predict the expectation.", "start": 4118.96, "duration": 2.31}, {"text": "You can find the expectation\nof this graph's statistic", "start": 4121.27, "duration": 3.27}, {"text": "based on what you've\nseen up to time n.", "start": 4124.54, "duration": 3.09}, {"text": "And that sequence\nwill be a martingale.", "start": 4127.63, "duration": 4.349}, {"text": "An important property\nof a martingale,", "start": 4131.979, "duration": 4.17}, {"text": "which is known as the\nmartingale convergence theorem--", "start": 4136.149, "duration": 3.841}, {"text": "and so that's what we'll need\nfor the proof of the existence", "start": 4139.99, "duration": 6.75}, {"text": "of the limit next time--", "start": 4146.74, "duration": 1.05}, {"text": "says that every\nbounded martingale--", "start": 4155.689, "duration": 4.67}, {"text": "so for example, suppose\nyour martingale only", "start": 4163.649, "duration": 3.58}, {"text": "takes values between 0 and 1.", "start": 4167.229, "duration": 2.361}, {"text": "So every bounded martingale\nconverges almost surely.", "start": 4169.59, "duration": 3.91}, {"text": "You cannot have a martingale\nwhich you expect to constantly", "start": 4182.87, "duration": 3.845}, {"text": "go up and down.", "start": 4186.715, "duration": 0.625}, {"text": "So I want to show you\na proof of this fact.", "start": 4193.04, "duration": 3.13}, {"text": "Let me just mention that\nthe bounded condition is", "start": 4196.17, "duration": 2.92}, {"text": "a little bit stronger than\nwhat we actually need.", "start": 4199.09, "duration": 2.4}, {"text": "From the proof, you'll\nsee that you really only", "start": 4201.49, "duration": 1.98}, {"text": "need them to be L1 bounded.", "start": 4203.47, "duration": 4.54}, {"text": "It's enough.", "start": 4208.01, "duration": 2.35}, {"text": "And more generally,\nthere is a condition", "start": 4210.36, "duration": 1.83}, {"text": "called uniform integrability,\nwhich I won't explain.", "start": 4212.19, "duration": 7.19}, {"text": "All right.", "start": 4222.368, "duration": 0.996}, {"text": "OK.", "start": 4226.12, "duration": 0.5}, {"text": "So let me show you a proof\nof the martingale convergence", "start": 4226.62, "duration": 2.63}, {"text": "theorem.", "start": 4229.25, "duration": 0.5}, {"text": "And I'm going to be somewhat\ninformal and somewhat cavalier,", "start": 4229.75, "duration": 3.77}, {"text": "because I don't want\nto get into some", "start": 4233.52, "duration": 2.13}, {"text": "of the fine details\nof probability theory.", "start": 4235.65, "duration": 2.9}, {"text": "But if you have taken something\nlike 18.675 probability theory,", "start": 4238.55, "duration": 5.29}, {"text": "then you can fill in\nall those details.", "start": 4243.84, "duration": 1.68}, {"text": "So I like this\nproof, because it's", "start": 4248.58, "duration": 1.71}, {"text": "kind of a proof by gambling.", "start": 4250.29, "duration": 1.29}, {"text": "So I want to tell you a story\nwhich should convince you that", "start": 4256.68, "duration": 3.39}, {"text": "a martingale cannot\nkeep going up and down.", "start": 4260.07, "duration": 4.31}, {"text": "It must converge almost surely.", "start": 4264.38, "duration": 1.74}, {"text": "So suppose x sub n\ndoesn't converge.", "start": 4268.64, "duration": 7.33}, {"text": "OK, so this is why\nI say I'm going", "start": 4279.863, "duration": 1.417}, {"text": "to be somewhat cavalier\nwith probability theory.", "start": 4281.28, "duration": 1.76}, {"text": "So when I say this\ndoesn't converge,", "start": 4283.04, "duration": 1.64}, {"text": "I mean a specific instance of\nthe sequence doesn't converge", "start": 4284.68, "duration": 3.38}, {"text": "or some specific realization.", "start": 4288.06, "duration": 1.99}, {"text": "If it doesn't converge,\nthen there exists a and b,", "start": 4290.05, "duration": 9.44}, {"text": "both rational numbers between\n0 and 1, such that the sequence", "start": 4299.49, "duration": 11.25}, {"text": "crosses the interval a,\nb infinitely many times.", "start": 4310.74, "duration": 8.3}, {"text": "So by crossing this interval,\nwhat I mean is the following.", "start": 4326.04, "duration": 5.02}, {"text": "OK.", "start": 4339.51, "duration": 0.5}, {"text": "So there's an\nimportant picture which", "start": 4340.01, "duration": 3.13}, {"text": "will help a lot in\nunderstanding this theorem.", "start": 4343.14, "duration": 2.76}, {"text": "So imagine I have this\ntime n, and I have a and b.", "start": 4351.55, "duration": 9.75}, {"text": "So I have this martingale.", "start": 4361.3, "duration": 1.83}, {"text": "It's realization curve\nwill be like that.", "start": 4363.13, "duration": 12.72}, {"text": "So that's an instance\nof this martingale.", "start": 4375.85, "duration": 2.54}, {"text": "And by crossing, I\nmean a sequence that--", "start": 4378.39, "duration": 5.56}, {"text": "OK, so here's what\nI mean by crossing.", "start": 4383.95, "duration": 3.44}, {"text": "I start below a and--", "start": 4387.39, "duration": 7.802}, {"text": "let me use a different color.", "start": 4395.192, "duration": 1.208}, {"text": "So I start below a, and I\ngo above b and then wait", "start": 4399.17, "duration": 7.15}, {"text": "until I come back below a.", "start": 4406.32, "duration": 4.11}, {"text": "And I go above b.", "start": 4410.43, "duration": 2.31}, {"text": "Wait until I come back.", "start": 4412.74, "duration": 3.3}, {"text": "So do like that.", "start": 4416.04, "duration": 1.46}, {"text": "Like that.", "start": 4425.592, "duration": 0.966}, {"text": "So I start below a until\nthe first time I go above b.", "start": 4432.86, "duration": 5.04}, {"text": "And then I stop that sequence.", "start": 4437.9, "duration": 1.8}, {"text": "So those are the upcrossings\nof this martingale.", "start": 4439.7, "duration": 6.005}, {"text": "So upcrossing is when\nyou start below a,", "start": 4452.98, "duration": 2.98}, {"text": "and then you end up above b.", "start": 4455.96, "duration": 2.76}, {"text": "So if you don't converge,\nthen there exists such a", "start": 4458.72, "duration": 7.32}, {"text": "and b such that there are\ninfinitely many such crossings.", "start": 4466.04, "duration": 4.32}, {"text": "So this is just a fact.", "start": 4470.36, "duration": 2.59}, {"text": "It's not hard to see.", "start": 4472.95, "duration": 3.96}, {"text": "And what we'll show is\nthat this doesn't happen", "start": 4476.91, "duration": 3.09}, {"text": "except with probability 0.", "start": 4480.0, "duration": 2.28}, {"text": "So we'll show that this\noccurs with probability 0.", "start": 4482.28, "duration": 11.05}, {"text": "And because there are\nonly countably many", "start": 4495.95, "duration": 6.98}, {"text": "rational numbers, we find\nthat x sub n converges", "start": 4502.93, "duration": 8.76}, {"text": "with probability 1.", "start": 4511.69, "duration": 1.31}, {"text": "So these are upcrossings.", "start": 4522.44, "duration": 1.19}, {"text": "So I didn't define\nit, but hopefully you", "start": 4523.63, "duration": 2.29}, {"text": "understood from my picture\nand my description.", "start": 4525.92, "duration": 3.24}, {"text": "And let me define\nby u sub n to be", "start": 4529.16, "duration": 7.11}, {"text": "the number of\nupcrossings up to time", "start": 4536.27, "duration": 8.35}, {"text": "n, so the number of\nsuch upcrossings.", "start": 4544.62, "duration": 8.587}, {"text": "Now let me consider\na betting strategy.", "start": 4555.95, "duration": 2.255}, {"text": "Basically, I want to make money.", "start": 4565.79, "duration": 1.98}, {"text": "And I want to make money by\nfollowing these upcrossings.", "start": 4567.77, "duration": 7.52}, {"text": "OK.", "start": 4575.29, "duration": 0.5}, {"text": "So every time you\ngive me a number and--", "start": 4575.79, "duration": 4.26}, {"text": "so think of this as\nthe stock market.", "start": 4580.05, "duration": 1.66}, {"text": "So it's a fair stock market\nwhere you tell me the price,", "start": 4581.71, "duration": 4.937}, {"text": "and I get to decide,\ndo I want to buy?", "start": 4586.647, "duration": 1.583}, {"text": "Or do I want to sell?", "start": 4588.23, "duration": 2.84}, {"text": "So consider the betting\nstrategy where at any time,", "start": 4591.07, "duration": 14.65}, {"text": "we're going to hold either 0\nor 1 share of the stock, which", "start": 4605.72, "duration": 8.81}, {"text": "has these moving prices.", "start": 4614.53, "duration": 3.06}, {"text": "And what we're going to do\nis if xn is less than a,", "start": 4617.59, "duration": 10.39}, {"text": "is less than the lower\nbound, then we're", "start": 4627.98, "duration": 4.08}, {"text": "going to buy and hold, meaning\n1, until the first time", "start": 4632.06, "duration": 15.83}, {"text": "that the price reaches\nabove b and then", "start": 4647.89, "duration": 14.56}, {"text": "sell as soon as the first time\nwe see the price goes above b.", "start": 4662.45, "duration": 5.602}, {"text": "So this is the betting strategy.", "start": 4670.95, "duration": 1.95}, {"text": "And it's something\nwhich you can implement.", "start": 4672.9, "duration": 2.06}, {"text": "If you see a sequence\nof prices, you", "start": 4674.96, "duration": 2.07}, {"text": "can implement this strategy.", "start": 4677.03, "duration": 2.1}, {"text": "And you already hopefully see,\nif you have many upcrossings,", "start": 4679.13, "duration": 3.87}, {"text": "then each upcrossing,\nyou make money.", "start": 4683.0, "duration": 2.31}, {"text": "Each upcrossing, you make money.", "start": 4685.31, "duration": 2.31}, {"text": "And this is almost\ntoo good to be true.", "start": 4687.62, "duration": 2.26}, {"text": "And in fact, we see that the\ntotal gain from this strategy--", "start": 4689.88, "duration": 5.28}, {"text": "so if you start with\nsome balance, what", "start": 4695.16, "duration": 2.14}, {"text": "you get at the end--", "start": 4697.3, "duration": 1.16}, {"text": "is at least this\ndifference from a", "start": 4698.46, "duration": 4.29}, {"text": "to b times the number\nof upcrossings.", "start": 4702.75, "duration": 4.702}, {"text": "You might start somewhere.", "start": 4711.27, "duration": 2.34}, {"text": "You buy, and then you\njust lose everything.", "start": 4713.61, "duration": 2.18}, {"text": "So there might be\nan initial cost.", "start": 4715.79, "duration": 3.05}, {"text": "And that cost is\nbounded, because we start", "start": 4718.84, "duration": 3.56}, {"text": "with a bounded martingale.", "start": 4722.4, "duration": 2.28}, {"text": "So suppose the martingale\nis always between 0 and 1.", "start": 4724.68, "duration": 8.1}, {"text": "We start with a\nbounded martingale.", "start": 4732.78, "duration": 2.135}, {"text": "But on the other hand,\nthere is a theorem", "start": 4737.53, "duration": 4.2}, {"text": "about martingales, which\nis not hard to deduce", "start": 4741.73, "duration": 2.94}, {"text": "from the definition, that\nno matter what the betting", "start": 4744.67, "duration": 3.03}, {"text": "strategy is, the gain\nat any particular time", "start": 4747.7, "duration": 3.45}, {"text": "must be 0 in expectation.", "start": 4751.15, "duration": 2.43}, {"text": "So this is just the\nproperty of the martingale.", "start": 4756.94, "duration": 2.3}, {"text": "So 0 equals the\nexpected gain, which", "start": 4759.24, "duration": 4.95}, {"text": "is at least b minus a\ntimes the expected number", "start": 4764.19, "duration": 3.33}, {"text": "of upcrossings minus 1.", "start": 4767.52, "duration": 3.11}, {"text": "And thus the expected number\nof upcrossings up to time n", "start": 4770.63, "duration": 4.8}, {"text": "is at most 1 over b minus a.", "start": 4775.43, "duration": 6.17}, {"text": "Now, we let n go to infinity.", "start": 4781.6, "duration": 5.54}, {"text": "And let u sub infinity be the\ntotal number of upcrossings.", "start": 4787.14, "duration": 10.64}, {"text": "By the monotone convergence\ntheorem in this limit,", "start": 4802.03, "duration": 15.4}, {"text": "the limit of these u sub\nn's, it can never go down.", "start": 4817.43, "duration": 2.88}, {"text": "It's always weakly increasing.", "start": 4820.31, "duration": 3.43}, {"text": "It converges to the\nexpectation of the total number", "start": 4823.74, "duration": 4.28}, {"text": "of upcrossings.", "start": 4828.02, "duration": 1.212}, {"text": "So now, in particular, you\nknow that the total number", "start": 4829.232, "duration": 2.208}, {"text": "of upcrossings is at\nmost some finite number.", "start": 4831.44, "duration": 6.68}, {"text": "So in particular,\nthe probability", "start": 4838.12, "duration": 2.18}, {"text": "that you have infinitely\nmany crossings is 0.", "start": 4840.3, "duration": 5.33}, {"text": "So with probability 0, you\ncross infinitely many times,", "start": 4845.63, "duration": 4.7}, {"text": "which proves the\nclaim over there", "start": 4850.33, "duration": 2.55}, {"text": "and which concludes\nthe proof of the claim", "start": 4852.88, "duration": 1.99}, {"text": "that the martingale\nconverges almost surely.", "start": 4854.87, "duration": 3.665}, {"text": "OK, so that proves the\nmartingale converge theorem.", "start": 4858.535, "duration": 2.125}, {"text": "So next time, we'll\ncombine everything", "start": 4860.66, "duration": 1.77}, {"text": "that we did today to prove the\nthree main theorems that we", "start": 4862.43, "duration": 3.21}, {"text": "stated last time\non graph limits.", "start": 4865.64, "duration": 3.59}]
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+[{"text": "[SQUEAKING]\n[RUSTLING] [CLICKING]", "start": 0.0, "duration": 11.34}, {"text": "SCOTT HUGHES: All right, so\nin today's recorded lecture,", "start": 11.34, "duration": 2.95}, {"text": "I would like to pick\nup where we started--", "start": 14.29, "duration": 2.97}, {"text": "excuse me.", "start": 17.26, "duration": 0.5}, {"text": "I'd like to pick up where\nwe stopped last time.", "start": 17.76, "duration": 2.64}, {"text": "So I discussed the\nEinstein field equations", "start": 20.4, "duration": 4.26}, {"text": "in the previous two lectures.", "start": 24.66, "duration": 1.35}, {"text": "I derived them first\nfrom the method", "start": 26.01, "duration": 3.51}, {"text": "that was used by Einstein in his\noriginal work on the subject.", "start": 29.52, "duration": 3.39}, {"text": "And then I laid out the way of\ncoming to the Einstein field", "start": 32.91, "duration": 4.05}, {"text": "equations using an\naction principle,", "start": 36.96, "duration": 1.98}, {"text": "using what we call the\nEinstein Hilbert action.", "start": 38.94, "duration": 3.42}, {"text": "Both of them lead us to this\nremarkably simple equation,", "start": 42.36, "duration": 8.56}, {"text": "if you think about it in terms\nsimply of the curvature tensor.", "start": 50.92, "duration": 5.81}, {"text": "This is saying that a particular\nversion of the curvature.", "start": 56.73, "duration": 5.13}, {"text": "You start with the\nRiemann tensor.", "start": 61.86, "duration": 1.61}, {"text": "You trace over two indices.", "start": 63.47, "duration": 2.13}, {"text": "You reverse the trace\nsuch that this whole thing", "start": 65.6, "duration": 4.02}, {"text": "has zero divergence.", "start": 69.62, "duration": 1.14}, {"text": "And you simply equate that\nto the stress energy tensor", "start": 70.76, "duration": 3.87}, {"text": "with a coupling factor\nwith a complex constant", "start": 74.63, "duration": 3.75}, {"text": "proportionality that\nensures that this", "start": 78.38, "duration": 1.74}, {"text": "recovers the Newtonian limit.", "start": 80.12, "duration": 2.31}, {"text": "The Einstein Hilbert\nexercise demonstrated", "start": 82.43, "duration": 2.52}, {"text": "that this is in a very\nquantifiable way, the simplest", "start": 84.95, "duration": 4.32}, {"text": "possible way of developing\na theory of gravity", "start": 89.27, "duration": 3.15}, {"text": "in this framework.", "start": 92.42, "duration": 2.108}, {"text": "The remainder of\nthis course is going", "start": 94.528, "duration": 1.542}, {"text": "to be dedicated to\nsolving this equation,", "start": 96.07, "duration": 2.71}, {"text": "and exploring the properties\nof the solutions that", "start": 98.78, "duration": 2.22}, {"text": "arise from this.", "start": 101.0, "duration": 1.578}, {"text": "And so let me continue\nthe discussion", "start": 102.578, "duration": 1.542}, {"text": "I began at the end of\nthe previous lecture.", "start": 104.12, "duration": 3.88}, {"text": "We are going to\nfind it very useful", "start": 108.0, "duration": 2.12}, {"text": "to regard this as a set\nof differential equations", "start": 110.12, "duration": 18.62}, {"text": "for the spacetime\nmetric given a source.", "start": 128.74, "duration": 8.35}, {"text": "That, after all,\nis how we typically", "start": 137.09, "duration": 3.99}, {"text": "think of solving for fields\ngiven a particular source.", "start": 141.08, "duration": 3.0}, {"text": "And just pardon me while\nI make sure this is on.", "start": 144.08, "duration": 2.0}, {"text": "It is.", "start": 146.08, "duration": 0.52}, {"text": "I give you a\ndistribution of mass.", "start": 149.33, "duration": 1.86}, {"text": "You compute the Newtonian\ngravitational potential", "start": 151.19, "duration": 2.16}, {"text": "for that.", "start": 153.35, "duration": 0.5}, {"text": "I give you a distribution\nof currents and fields.", "start": 153.85, "duration": 2.8}, {"text": "You calculate the electric\nand magnetic fields", "start": 156.65, "duration": 2.07}, {"text": "that arise from that.", "start": 158.72, "duration": 1.38}, {"text": "So I give you some distribution\nof mass and energy.", "start": 160.1, "duration": 3.12}, {"text": "You compute the spacetime\nthat arises from that.", "start": 163.22, "duration": 2.6}, {"text": "But let's stop before\nwe dig into this,", "start": 165.82, "duration": 1.87}, {"text": "and look at what\nthis actually means", "start": 167.69, "duration": 5.25}, {"text": "given the mathematical\nequations that we have.", "start": 172.94, "duration": 2.52}, {"text": "So G alpha beta is\nthe Einstein tensor.", "start": 175.46, "duration": 5.85}, {"text": "I construct it by taking several\nderivatives of the metric.", "start": 181.31, "duration": 3.75}, {"text": "I first make my\nChristoffel symbols.", "start": 185.06, "duration": 1.71}, {"text": "I combine those Christoffel\nsymbols and derivatives", "start": 186.77, "duration": 2.13}, {"text": "of the Christoffel symbols\nto make the Riemann tensor.", "start": 188.9, "duration": 2.7}, {"text": "I hit it with another\npower of the metric", "start": 191.6, "duration": 1.95}, {"text": "in order to trace and\nget the Ricci tensor.", "start": 193.55, "duration": 2.607}, {"text": "I combine it with the trace of\nthe Ricci tensor and the metric", "start": 196.157, "duration": 2.583}, {"text": "to get the Einstein.", "start": 198.74, "duration": 1.53}, {"text": "Schematically, I can\nthink of G alpha beta", "start": 200.27, "duration": 4.53}, {"text": "as some very\ncomplicated linear--", "start": 204.8, "duration": 4.62}, {"text": "excuse me, some very complicated\nnonlinear differential", "start": 209.42, "duration": 3.18}, {"text": "operator acting on the metric.", "start": 212.6, "duration": 4.04}, {"text": "So thinking about this is\njust a differential equation", "start": 235.91, "duration": 2.85}, {"text": "for the metric.", "start": 238.76, "duration": 0.99}, {"text": "The left hand side of this\nequation is a bit of a mess.", "start": 239.75, "duration": 3.61}, {"text": "Unfortunately, the right\nhand side can be a mess too.", "start": 243.36, "duration": 2.32}, {"text": "Let's think about this\nfor a particular example.", "start": 245.68, "duration": 2.0}, {"text": "Suppose I choose as my force--", "start": 247.68, "duration": 3.75}, {"text": "my source-- a perfect fluid.", "start": 251.43, "duration": 1.35}, {"text": "Well, then my right\nhand side is going", "start": 261.0, "duration": 6.653}, {"text": "to be something that involves\nthe density and the pressure", "start": 267.653, "duration": 2.417}, {"text": "of that fluid, the fluid\nvelocity, and then the metric.", "start": 270.07, "duration": 10.99}, {"text": "OK, so if I'm thinking\nabout this as a differential", "start": 281.06, "duration": 2.4}, {"text": "equation for the\nmetric, the metric", "start": 283.46, "duration": 2.4}, {"text": "is appearing under this\ndifferential operator", "start": 285.86, "duration": 3.22}, {"text": "on the left hand\nside, and explicitly", "start": 289.08, "duration": 1.95}, {"text": "in the source on\nthe right hand side.", "start": 291.03, "duration": 1.95}, {"text": "Oh, and by the way, don't\nforget my fluid needs", "start": 292.98, "duration": 2.73}, {"text": "to be normalized.", "start": 295.71, "duration": 0.78}, {"text": "My fluid flow velocity\nneeds to be normalized.", "start": 296.49, "duration": 2.55}, {"text": "So I have a further constraint,\nthat the complement to the four", "start": 299.04, "duration": 7.52}, {"text": "velocity are related to each\nother by the spacetime metric.", "start": 306.56, "duration": 3.81}, {"text": "So if I am going to regard this\nas just a differential equation", "start": 310.37, "duration": 4.02}, {"text": "for the space time metric.", "start": 314.39, "duration": 4.65}, {"text": "In general, we're in\nfor a world of pain.", "start": 319.04, "duration": 3.8}, {"text": "So as I described at the\nend of the previous lecture,", "start": 322.84, "duration": 4.88}, {"text": "we are going to examine\nhow to solve this equation.", "start": 327.72, "duration": 3.65}, {"text": "In what's left of\n8.962, we're going", "start": 331.37, "duration": 2.28}, {"text": "to look at three routes\nto solving this thing.", "start": 333.65, "duration": 3.2}, {"text": "The one that we will\nbegin to talk about today", "start": 336.85, "duration": 5.45}, {"text": "is we solve this for what I\nwill define a little bit more", "start": 342.3, "duration": 5.98}, {"text": "precisely in a moment\nas weak gravity.", "start": 348.28, "duration": 1.845}, {"text": "And what this is going\nto mean is that I only", "start": 355.67, "duration": 2.0}, {"text": "consider space times that are\nin a way that can be quantified", "start": 357.67, "duration": 7.65}, {"text": "close to flat space time.", "start": 365.32, "duration": 6.16}, {"text": "Method two will be to\nconsider symmetric solutions.", "start": 371.48, "duration": 3.87}, {"text": "Part of the reason the general\nframework is so complicated", "start": 383.46, "duration": 3.75}, {"text": "is that there are in\ngeneral, 10 of these", "start": 387.21, "duration": 3.12}, {"text": "coupled non-linear\ndifferential equations.", "start": 390.33, "duration": 2.52}, {"text": "When we introduce\nsymmetries, or we", "start": 392.85, "duration": 1.68}, {"text": "consider things like\nstatic solutions", "start": 394.53, "duration": 3.42}, {"text": "or stationary solutions that\ndon't have any time dynamics.", "start": 397.95, "duration": 3.78}, {"text": "That at least reduces\nthe number of equations", "start": 401.73, "duration": 2.012}, {"text": "we need to worry about.", "start": 403.742, "duration": 0.958}, {"text": "They may still be coupled\nnon-linear and complicated,", "start": 404.7, "duration": 4.89}, {"text": "but hopefully,\nmaybe we can reduce", "start": 409.59, "duration": 1.838}, {"text": "those from 10 of\nthese things we need", "start": 411.428, "duration": 1.542}, {"text": "to worry about to just a small\nnumber them, one, or two,", "start": 412.97, "duration": 3.31}, {"text": "or three.", "start": 416.28, "duration": 2.07}, {"text": "Makes it at least\na little easier.", "start": 418.35, "duration": 2.04}, {"text": "In truth, symmetric solutions--", "start": 420.39, "duration": 4.95}, {"text": "if you can then add techniques\nfor perturbing around them,", "start": 425.34, "duration": 7.97}, {"text": "these turn out to be\ntremendously powerful.", "start": 433.31, "duration": 1.97}, {"text": "My own research career is--", "start": 440.91, "duration": 3.3}, {"text": "uses this technique\na tremendous amount.", "start": 444.21, "duration": 2.16}, {"text": "Finally, just basically\nsay, you know what?", "start": 448.96, "duration": 4.753}, {"text": "Let's just dive in\nand solve this puppy.", "start": 453.713, "duration": 1.667}, {"text": "Just do a numerical solution\nof the whole monster,", "start": 461.15, "duration": 5.75}, {"text": "no simplifications.", "start": 466.9, "duration": 1.582}, {"text": "Eminent members of our field\nhave dedicated entire careers", "start": 475.1, "duration": 3.93}, {"text": "to item three.", "start": 479.03, "duration": 1.89}, {"text": "I will give you an introduction\nto the main concepts", "start": 480.92, "duration": 2.34}, {"text": "in the last lecture.", "start": 483.26, "duration": 2.4}, {"text": "But it's not\nsomething we're going", "start": 485.66, "duration": 1.58}, {"text": "to be able to explore in\nmuch detail in this class.", "start": 487.24, "duration": 3.97}, {"text": "We're going to do one in\na fair amount of detail.", "start": 491.21, "duration": 2.193}, {"text": "We will look at a couple\nof the most important", "start": 493.403, "duration": 1.917}, {"text": "symmetric solutions,\nso that you can", "start": 495.32, "duration": 1.5}, {"text": "see how these techniques work.", "start": 496.82, "duration": 4.495}, {"text": "And then in my\nlast two lectures,", "start": 501.315, "duration": 1.375}, {"text": "I'm going to describe\na little bit about what", "start": 502.69, "duration": 1.33}, {"text": "happens when you perturb\nsome of the most interesting", "start": 504.02, "duration": 2.232}, {"text": "symmetric solutions.", "start": 506.252, "duration": 0.833}, {"text": "And we'll talk about numerical\nsolutions for the general case.", "start": 507.085, "duration": 6.885}, {"text": "All right, so let's begin.", "start": 513.97, "duration": 1.88}, {"text": "We'll begin with choice one.", "start": 515.85, "duration": 1.52}, {"text": "Look at weak gravity,\nalso known as", "start": 517.37, "duration": 7.53}, {"text": "linearized general relativity.", "start": 524.9, "duration": 2.256}, {"text": "So linearized general\nrelativity is a situation", "start": 534.46, "duration": 3.09}, {"text": "in which we are only going\nto consider space times that", "start": 537.55, "duration": 2.55}, {"text": "are nearly flat.", "start": 540.1, "duration": 1.26}, {"text": "If I am in this situation,\nthen I can choose coordinates,", "start": 555.65, "duration": 12.6}, {"text": "such that my space time metric\nis the metric of flat space", "start": 568.25, "duration": 9.64}, {"text": "time plus a tensor H-alpha\nbeta, all of whose components--", "start": 577.89, "duration": 11.23}, {"text": "so this notation that I'm\nsort of inventing here,", "start": 592.338, "duration": 2.042}, {"text": "double bars around H-alpha beta.", "start": 594.38, "duration": 2.94}, {"text": "This means the magnitude of\nH-alpha beta's components.", "start": 597.32, "duration": 10.51}, {"text": "These all must be much,\nmuch less than one.", "start": 613.79, "duration": 4.98}, {"text": "When you are in such\na coordinate system", "start": 618.77, "duration": 3.42}, {"text": "you are in what we call\nnearly Lorenz coordinates.", "start": 622.19, "duration": 5.88}, {"text": "Such a coordinate\nsystem is as close", "start": 639.04, "duration": 2.07}, {"text": "to a globally inertial\ncoordinate system", "start": 641.11, "duration": 2.4}, {"text": "as is possible to make.", "start": 643.51, "duration": 2.1}, {"text": "There are other coordinate\nchoices we could make.", "start": 645.61, "duration": 2.05}, {"text": "So for instance, you're\nworking in a system like that.", "start": 647.66, "duration": 2.39}, {"text": "This basically boils\ndown to coordinates", "start": 650.05, "duration": 1.95}, {"text": "that are Cartesian like\non their spatial slices.", "start": 652.0, "duration": 4.32}, {"text": "You could work in other ones.", "start": 656.32, "duration": 1.92}, {"text": "These are particularly\nconvenient.", "start": 658.24, "duration": 1.5}, {"text": "Because for instance, if I work\nin a coordinate system whose", "start": 659.74, "duration": 2.94}, {"text": "spatial sector is\nspherical like,", "start": 662.68, "duration": 2.465}, {"text": "well, then there's going\nto be some components that", "start": 665.145, "duration": 2.125}, {"text": "grow very large as I go to\nlarge radius away from some--", "start": 667.27, "duration": 5.67}, {"text": "the source of my gravitation.", "start": 672.94, "duration": 2.34}, {"text": "And this just makes my\nanalysis quite convenient.", "start": 675.28, "duration": 3.45}, {"text": "In particular, where I'm going\nto take advantage of this.", "start": 678.73, "duration": 3.45}, {"text": "Whenever I come\nacross a term that", "start": 688.03, "duration": 2.37}, {"text": "involves the perturbations\nsquared or to a higher power,", "start": 690.4, "duration": 8.02}, {"text": "I'm just going\napproximate it as zero.", "start": 698.42, "duration": 1.62}, {"text": "I will always neglect\nterms beyond linear,", "start": 700.04, "duration": 3.81}, {"text": "hence the term linearized\nGR, in my analysis.", "start": 703.85, "duration": 9.66}, {"text": "Now, there are a\ncouple of properties,", "start": 726.98, "duration": 1.65}, {"text": "before I get into how to develop\nweak gravity, linearized GR.", "start": 728.63, "duration": 5.4}, {"text": "I want to discuss a little\nbit some of the properties", "start": 734.03, "duration": 3.36}, {"text": "of spacetimes of this form.", "start": 737.39, "duration": 4.71}, {"text": "What are the particularly\nimportant properties of these?", "start": 742.1, "duration": 3.61}, {"text": "So let's consider\ncoordinate transformations.", "start": 745.71, "duration": 2.559}, {"text": "My space time metric is\na tensor, like any other.", "start": 770.73, "duration": 4.14}, {"text": "And so the usual rules pertain\nhere, that I can change my", "start": 774.87, "duration": 5.43}, {"text": "coordinates using\nsome matrix that", "start": 780.3, "duration": 9.06}, {"text": "relates my original\ncoordinate system, which", "start": 789.36, "duration": 2.31}, {"text": "I've denoted without bars, to\nsome new coordinate system that", "start": 791.67, "duration": 6.1}, {"text": "is barred.", "start": 797.77, "duration": 0.51}, {"text": "Now, recall that when we\nworked in flat space time,", "start": 803.78, "duration": 5.62}, {"text": "there was one category of\ncoordinate transformations", "start": 809.4, "duration": 2.79}, {"text": "that was special.", "start": 812.19, "duration": 1.35}, {"text": "Those were the Lorentz\ntransformations.", "start": 813.54, "duration": 2.294}, {"text": "So we are not working\nin flat space time.", "start": 850.92, "duration": 4.19}, {"text": "So on the face of it, we don't\nexpect Lorentz transformations", "start": 855.11, "duration": 3.53}, {"text": "to play a particularly\nspecial role,", "start": 858.64, "duration": 1.5}, {"text": "except perhaps in the domain\nof a freely falling frame.", "start": 860.14, "duration": 3.12}, {"text": "But you know what?", "start": 867.13, "duration": 1.08}, {"text": "This is a nearly flat space\ntime, so just for giggles,", "start": 868.21, "duration": 3.1}, {"text": "let's see what happens\nif you apply the Lorentz", "start": 871.31, "duration": 2.9}, {"text": "transformation to your\nnearly flat spacetime.", "start": 874.21, "duration": 4.506}, {"text": "So if I look at G mu\nbar nu bar as being", "start": 893.62, "duration": 11.89}, {"text": "a Lorentz transformation applied\nto my nearly flat metric.", "start": 905.51, "duration": 15.23}, {"text": "Well, what I get\n[INAUDIBLE] side is this.", "start": 920.74, "duration": 18.753}, {"text": "Now, one of the reasons why\nthe Lorentz transformation was", "start": 939.493, "duration": 2.417}, {"text": "special in flat\nspacetime is that it", "start": 941.91, "duration": 2.91}, {"text": "leaves the metric of\nflat spacetime unchanged.", "start": 944.82, "duration": 4.92}, {"text": "And so this just\nmaps to eta mu nu.", "start": 949.74, "duration": 7.74}, {"text": "I'm going to define what\ncomes out here as h mu nu.", "start": 961.78, "duration": 4.07}, {"text": "I'm doing this in a fairly,\nI hope, obvious way.", "start": 971.6, "duration": 2.43}, {"text": "This is interesting.", "start": 983.19, "duration": 1.67}, {"text": "What this has told me is\nthat when I apply the Lorentz", "start": 984.86, "duration": 6.18}, {"text": "transformation to my\nnearly flat space time,", "start": 991.04, "duration": 4.56}, {"text": "the background is unchanged.", "start": 995.6, "duration": 3.73}, {"text": "And the perturbation\nto the background", "start": 999.33, "duration": 2.42}, {"text": "transforms just like\nany tensor field", "start": 1001.75, "duration": 3.51}, {"text": "would transform in flat space.", "start": 1005.26, "duration": 2.64}, {"text": "Now, it should be emphasized, we\nare not working in flat space.", "start": 1013.97, "duration": 3.3}, {"text": "We can compute\ncurvature tensors.", "start": 1020.53, "duration": 3.09}, {"text": "If we parallel transport--", "start": 1023.62, "duration": 2.249}, {"text": "If we consider two geodesics\nmoving through the space time,", "start": 1025.869, "duration": 3.541}, {"text": "we will see that parallel\ntransport along those two", "start": 1029.41, "duration": 2.74}, {"text": "geodesics, if they start\nout initially parallel,", "start": 1032.15, "duration": 2.0}, {"text": "they do not remain parallel.", "start": 1034.15, "duration": 1.75}, {"text": "So this is not flat space time.", "start": 1035.9, "duration": 2.73}, {"text": "But in many ways,\nit's close enough", "start": 1038.63, "duration": 3.41}, {"text": "that we can borrow many of\nthe mathematical tools that", "start": 1042.04, "duration": 3.539}, {"text": "were used in flat space time.", "start": 1045.579, "duration": 2.641}, {"text": "In particular, we can\nintroduce the following.", "start": 1048.22, "duration": 3.69}, {"text": "Think of it as a\nuseful fiction, which", "start": 1051.91, "duration": 8.08}, {"text": "is that in this\nframework, we can regard", "start": 1059.99, "duration": 8.21}, {"text": "the perturbation that\npushes us away from flat", "start": 1068.2, "duration": 3.06}, {"text": "spacetime as just an\nordinary tensor field", "start": 1071.26, "duration": 12.83}, {"text": "living in the manifold\nof special relativity,", "start": 1084.09, "duration": 2.61}, {"text": "living in the eta\nalpha beta metric.", "start": 1086.7, "duration": 2.46}, {"text": "It's worth bearing in mind in\na fundamental sense, it's not.", "start": 1092.38, "duration": 4.61}, {"text": "Space time is curved.", "start": 1096.99, "duration": 1.92}, {"text": "h alpha beta is telling\nme about that curvature.", "start": 1098.91, "duration": 3.33}, {"text": "But the mathematics\nworks in such a way", "start": 1102.24, "duration": 2.46}, {"text": "that you can borrow\na lot of tools", "start": 1104.7, "duration": 1.68}, {"text": "that we used in\nspecial relativity.", "start": 1106.38, "duration": 1.5}, {"text": "And just imagine h\nas a tensor field", "start": 1107.88, "duration": 2.61}, {"text": "living in that special\nrelativity manifold.", "start": 1110.49, "duration": 3.27}, {"text": "OK, so that's useful\nfact one that we", "start": 1119.53, "duration": 3.9}, {"text": "want to bear in mind as we work\nin this nearly flat space time.", "start": 1123.43, "duration": 8.04}, {"text": "Useful fact two is\nwe want to think", "start": 1131.47, "duration": 6.13}, {"text": "about what happens when we\nraise and lower indices.", "start": 1137.6, "duration": 3.38}, {"text": "So suppose now that\nI'm going to regard", "start": 1155.26, "duration": 2.37}, {"text": "h alpha beta as\nan ordinary tensor", "start": 1157.63, "duration": 2.31}, {"text": "field living in this thing.", "start": 1159.94, "duration": 2.1}, {"text": "I might want to\nknow what it looks", "start": 1162.04, "duration": 2.43}, {"text": "like with its indices raised.", "start": 1164.47, "duration": 2.675}, {"text": "So I'm going to\ndo what I usually", "start": 1167.145, "duration": 1.375}, {"text": "do when I want to raise\nthe indices on a tensor.", "start": 1168.52, "duration": 4.958}, {"text": "I hit it with the metric.", "start": 1173.478, "duration": 1.042}, {"text": "We're going to talk about\nwhat my upstairs metric looks", "start": 1178.19, "duration": 4.29}, {"text": "like in just a moment.", "start": 1182.48, "duration": 1.11}, {"text": "But clearly, it's\ngoing to be something", "start": 1183.59, "duration": 1.77}, {"text": "that looks like the metric\nof flat space time plus terms", "start": 1185.36, "duration": 4.08}, {"text": "that are on the order of h.", "start": 1189.44, "duration": 2.16}, {"text": "Because I always drop terms\nof order h squared and higher,", "start": 1191.6, "duration": 5.82}, {"text": "I can immediately say\nthat this must simply", "start": 1197.42, "duration": 5.79}, {"text": "be the metric of flat\nspace time with the indices", "start": 1203.21, "duration": 7.2}, {"text": "in the upstairs\nposition acting on h.", "start": 1210.41, "duration": 2.85}, {"text": "In other words,\nat least when I am", "start": 1213.26, "duration": 7.01}, {"text": "acting on tensors that are\nbuilt from the space time", "start": 1220.27, "duration": 4.56}, {"text": "metric itself, I'm\ngoing to always want", "start": 1224.83, "duration": 15.61}, {"text": "to raise and lower them using\nmy flat space time, eta alpha", "start": 1240.44, "duration": 16.11}, {"text": "beta.", "start": 1256.55, "duration": 1.32}, {"text": "Bearing this in\nmind, let's carefully", "start": 1257.87, "duration": 3.91}, {"text": "think about what the metric\ninverse actually looks like.", "start": 1261.78, "duration": 2.97}, {"text": "I actually used this in\none of my calculations", "start": 1271.05, "duration": 4.5}, {"text": "in the previous lecture.", "start": 1275.55, "duration": 1.27}, {"text": "And I said, I'm going to justify\nthis in the next lecture.", "start": 1276.82, "duration": 3.115}, {"text": "So here we are.", "start": 1279.935, "duration": 0.625}, {"text": "Now we're going to justify it.", "start": 1280.56, "duration": 2.29}, {"text": "So let's use this definition.", "start": 1282.85, "duration": 2.496}, {"text": "So the upstairs\nmetric is defined such", "start": 1292.8, "duration": 2.9}, {"text": "that when it contracts\nwith the downstairs metric,", "start": 1295.7, "duration": 2.46}, {"text": "I get the identity back.", "start": 1298.16, "duration": 1.65}, {"text": "This is the definition\nof the metric inverse.", "start": 1299.81, "duration": 6.78}, {"text": "Working in linear theory,\nI know that this thing", "start": 1306.59, "duration": 2.73}, {"text": "is going to be something\nlike eta alpha beta", "start": 1309.32, "duration": 4.59}, {"text": "plus a term of order h.", "start": 1313.91, "duration": 3.54}, {"text": "I don't know what that\nterm is yet, so let me just", "start": 1317.45, "duration": 2.25}, {"text": "give it a new name.", "start": 1319.7, "duration": 1.29}, {"text": "I'm going to call\nit m alpha beta.", "start": 1320.99, "duration": 5.416}, {"text": "Whoops.", "start": 1326.406, "duration": 0.5}, {"text": "Hopefully, the math\nwill soon show me", "start": 1340.288, "duration": 1.542}, {"text": "what this m actually is.", "start": 1341.83, "duration": 2.28}, {"text": "It will be of order h,\nbut as of yet, unknown.", "start": 1344.11, "duration": 3.225}, {"text": "OK, so you know what?", "start": 1376.5, "duration": 0.932}, {"text": "Let's rewrite that over here.", "start": 1377.432, "duration": 1.208}, {"text": "So let's now multiply\nthis guy out.", "start": 1391.99, "duration": 2.33}, {"text": "Eta alpha beta hitting\neta beta gamma.", "start": 1394.32, "duration": 4.02}, {"text": "That gives me delta alpha gamma.", "start": 1398.34, "duration": 3.52}, {"text": "m hitting eta.", "start": 1401.86, "duration": 1.91}, {"text": "Now, remember what I\njust said over here.", "start": 1403.77, "duration": 1.89}, {"text": "When I'm working with\nspacetime tensors,", "start": 1408.36, "duration": 1.8}, {"text": "I always raise and lower\nindices using eta alpha beta.", "start": 1410.16, "duration": 4.08}, {"text": "So when m alpha beta\nhits eta beta gamma,", "start": 1414.24, "duration": 4.26}, {"text": "this is going to give\nme m alpha gamma.", "start": 1418.5, "duration": 5.1}, {"text": "This eta hits that h.", "start": 1423.6, "duration": 4.26}, {"text": "I get h, alpha upstairs,\ngamma downstairs.", "start": 1427.86, "duration": 5.66}, {"text": "And then this guy is of order\nh, that guy is of order h.", "start": 1433.52, "duration": 3.6}, {"text": "So additional terms\nof order h squared.", "start": 1437.12, "duration": 3.82}, {"text": "So these guys cancel.", "start": 1444.29, "duration": 2.57}, {"text": "And what I am left\nwith is m alpha gamma", "start": 1446.86, "duration": 4.83}, {"text": "equals negative h alpha gamma.", "start": 1451.69, "duration": 5.25}, {"text": "I can raise my two indices,\nraise the gammas on both sides", "start": 1456.94, "duration": 3.46}, {"text": "here.", "start": 1460.4, "duration": 0.5}, {"text": "And we deduce from this\nthat my inverse metric", "start": 1460.9, "duration": 5.16}, {"text": "is eta alpha beta\nin the upstairs", "start": 1466.06, "duration": 2.16}, {"text": "position, minus h alpha beta.", "start": 1468.22, "duration": 5.07}, {"text": "At least two linear order in h.", "start": 1473.29, "duration": 1.65}, {"text": "I'll just comment\nthat what this is--", "start": 1485.56, "duration": 1.93}, {"text": "essentially, the matrix\nor tensor equivalent", "start": 1487.49, "duration": 3.24}, {"text": "of a binomial expansion.", "start": 1490.73, "duration": 2.4}, {"text": "1 over 1 plus epsilon is\napproximately 1 minus epsilon.", "start": 1493.13, "duration": 4.32}, {"text": "That's all this is.", "start": 1497.45, "duration": 1.94}, {"text": "But this is important to do.", "start": 1499.39, "duration": 1.99}, {"text": "In fact, I will just sort of\nremark somewhat anecdotally", "start": 1501.38, "duration": 4.56}, {"text": "that when I work with\ngraduate students on projects,", "start": 1505.94, "duration": 2.7}, {"text": "where we have to do things\nin linearized theory,", "start": 1508.64, "duration": 2.07}, {"text": "getting a sign wrong here is\none of the most common mistakes", "start": 1510.71, "duration": 2.7}, {"text": "that people make.", "start": 1513.41, "duration": 2.69}, {"text": "All right, one final detail.", "start": 1516.1, "duration": 2.29}, {"text": "So this detail, as\nI just labeled it,", "start": 1545.44, "duration": 3.73}, {"text": "is a particularly important one.", "start": 1549.17, "duration": 1.93}, {"text": "We talked about general\ncoordinate transformations.", "start": 1551.1, "duration": 4.715}, {"text": "And I immediately went\nin to discuss a Lorentz", "start": 1555.815, "duration": 1.975}, {"text": "transformation.", "start": 1557.79, "duration": 1.71}, {"text": "There's a different category\nof coordinate transformation", "start": 1559.5, "duration": 3.54}, {"text": "that plays a very important\nrole in understanding", "start": 1563.04, "duration": 7.23}, {"text": "the physics of systems that we\nanalyze in linearized theory.", "start": 1570.27, "duration": 3.623}, {"text": "So let's consider\na different kind", "start": 1573.893, "duration": 1.417}, {"text": "of coordinate transformation.", "start": 1575.31, "duration": 1.59}, {"text": "Let's consider a\ncoordinate shift,", "start": 1576.9, "duration": 10.89}, {"text": "which I'm going to\ndefine by x alpha prime.", "start": 1587.79, "duration": 8.34}, {"text": "Really, they should\nbe x prime alpha,", "start": 1596.13, "duration": 1.8}, {"text": "but you'll see why I need to\nname it this way right now.", "start": 1597.93, "duration": 3.15}, {"text": "So this is my original\ncoordinate, x alpha,", "start": 1601.08, "duration": 6.25}, {"text": "plus some little offset that's\na function of the coordinates x", "start": 1607.33, "duration": 5.16}, {"text": "beta.", "start": 1612.49, "duration": 0.75}, {"text": "So think of this as suppose\nI have a coordinate grid that", "start": 1613.24, "duration": 4.5}, {"text": "looks like this.", "start": 1617.74, "duration": 0.81}, {"text": "And I have some\nfunction that says,", "start": 1624.55, "duration": 2.79}, {"text": "I want to consider a different\nsystem of coordinates that", "start": 1627.34, "duration": 2.49}, {"text": "maybe pushes me a little bit\nalong away from each of these", "start": 1629.83, "duration": 4.32}, {"text": "coordinate lines in\na way that varies", "start": 1634.15, "duration": 2.698}, {"text": "as a function of position here.", "start": 1636.848, "duration": 1.292}, {"text": "This notation is kind of\nan abuse of the indices.", "start": 1641.96, "duration": 5.27}, {"text": "I am really not trying to\ndefine a coordinate invariant", "start": 1647.23, "duration": 2.59}, {"text": "relationship here.", "start": 1649.82, "duration": 0.9}, {"text": "I am just trying to\nconnect two quantities,", "start": 1650.72, "duration": 2.64}, {"text": "and I'm trying to\nconnect quantities in two", "start": 1653.36, "duration": 2.31}, {"text": "specific coordinate systems.", "start": 1655.67, "duration": 1.41}, {"text": "And as we'll see, even\nthough this is a bit ugly.", "start": 1657.08, "duration": 4.14}, {"text": "It works well for\nwhat we want to do.", "start": 1661.22, "duration": 2.785}, {"text": "So my coordinate\ntransformation matrix.", "start": 1664.005, "duration": 1.625}, {"text": "OK, so I just take\nthe matrix of--", "start": 1683.06, "duration": 3.7}, {"text": "I developed the\nJacobian-- my matrix", "start": 1686.76, "duration": 1.65}, {"text": "of partial derivatives--\nof the new coordinate", "start": 1688.41, "duration": 3.0}, {"text": "with respect to the old\ncoordinate in the usual way.", "start": 1691.41, "duration": 2.94}, {"text": "This is going to\nbe my first term.", "start": 1694.35, "duration": 4.18}, {"text": "It's just a Kronecker delta.", "start": 1698.53, "duration": 2.048}, {"text": "And then I'm going\nto get a term that", "start": 1700.578, "duration": 1.542}, {"text": "looks like matrix of\nderivatives of the function that", "start": 1702.12, "duration": 6.33}, {"text": "defines my infinitesimal--\ndefines my shift.", "start": 1708.45, "duration": 3.242}, {"text": "I just gave away what\nI was about to say.", "start": 1711.692, "duration": 1.708}, {"text": "I'm going to require [in?] my\nwork in these nearly Lorentz", "start": 1713.4, "duration": 2.79}, {"text": "coordinates, all of these\nentries need to be small.", "start": 1716.19, "duration": 3.0}, {"text": "These will all be\nmuch, much less than 1.", "start": 1724.0, "duration": 2.75}, {"text": "And so we call this\nan infinitesimal", "start": 1726.75, "duration": 1.77}, {"text": "coordinate transformation.", "start": 1728.52, "duration": 2.115}, {"text": "We are going to need to use\nthe inverse of this guy.", "start": 1748.98, "duration": 3.0}, {"text": "And using the definition\nof the inverse of this,", "start": 1764.57, "duration": 2.43}, {"text": "saying essentially that when\nI take this, and I contract--", "start": 1767.0, "duration": 3.58}, {"text": "Let me put it this way.", "start": 1770.58, "duration": 1.1}, {"text": "I'll just write it out.", "start": 1771.68, "duration": 1.77}, {"text": "So if I compute this.", "start": 1773.45, "duration": 6.76}, {"text": "I get my Kronecker delta back.", "start": 1780.21, "duration": 3.65}, {"text": "Taking advantage\nof the smallness", "start": 1783.86, "duration": 3.39}, {"text": "of the transformation.", "start": 1787.25, "duration": 3.61}, {"text": "It's not terribly hard\nto demonstrate that", "start": 1790.86, "duration": 16.7}, {"text": "what comes out of it is this.", "start": 1807.56, "duration": 2.01}, {"text": "The minus sign is the key thing\nwhich I want to emphasize here.", "start": 1818.81, "duration": 2.91}, {"text": "That minus sign is very\nsimilar to the minus sign", "start": 1821.72, "duration": 2.7}, {"text": "that I have here.", "start": 1824.42, "duration": 0.798}, {"text": "What we're doing\nis, again, just kind", "start": 1825.218, "duration": 1.542}, {"text": "of the matrix equivalent\nof expanding 1 over 1", "start": 1826.76, "duration": 4.11}, {"text": "plus epsilon for small epsilon.", "start": 1830.87, "duration": 1.62}, {"text": "The reason that I\nam doing this is", "start": 1835.88, "duration": 2.16}, {"text": "that I would now\nlike to look at how", "start": 1838.04, "duration": 2.88}, {"text": "the metric changes under this\ncoordinate transformation.", "start": 1840.92, "duration": 4.538}, {"text": "So what I'm going to\ndo is define g mu nu", "start": 1855.72, "duration": 5.19}, {"text": "in the new coordinate system.", "start": 1860.91, "duration": 1.32}, {"text": "Usual operation.", "start": 1871.65, "duration": 2.55}, {"text": "Let's now insert the many\ndifferent definitions", "start": 1874.2, "duration": 4.71}, {"text": "that we have introduced here.", "start": 1878.91, "duration": 3.0}, {"text": "Notice that what I am using\nfor my transformation matrix", "start": 1881.91, "duration": 5.37}, {"text": "there is the inverse\nthat I just wrote down.", "start": 1887.28, "duration": 2.22}, {"text": "So let's fill that in.", "start": 1905.29, "duration": 3.34}, {"text": "So I'm going to get\na term that involves", "start": 1908.63, "duration": 3.36}, {"text": "a Kronecker minus a matrix\nof partial derivatives.", "start": 1911.99, "duration": 7.43}, {"text": "My other one gives me a\nnether Kronecker matrix", "start": 1919.42, "duration": 7.65}, {"text": "of partial derivatives.", "start": 1927.07, "duration": 2.16}, {"text": "And then finally,\ndon't forget we", "start": 1929.23, "duration": 4.17}, {"text": "are working in this nearly\nflat space time metric.", "start": 1933.4, "duration": 3.75}, {"text": "And so I insert in my\nlast term, eta alpha", "start": 1941.01, "duration": 2.25}, {"text": "beta plus h alpha beta.", "start": 1943.26, "duration": 3.04}, {"text": "So now, let's go and expand\nall of these terms out.", "start": 1946.3, "duration": 4.32}, {"text": "My Kronecker,\nfirst, I get a term", "start": 1950.62, "duration": 1.82}, {"text": "where both of the Kroneckers hit\nthe metric of flat space time.", "start": 1952.44, "duration": 8.07}, {"text": "So what I get is eta mu nu.", "start": 1960.51, "duration": 2.3}, {"text": "Then I get a term which\nboth the Kroneckers hit,", "start": 1962.81, "duration": 2.43}, {"text": "the perturbation h alpha beta.", "start": 1965.24, "duration": 3.16}, {"text": "Gives me h mu nu.", "start": 1968.4, "duration": 2.34}, {"text": "Then, I'm going\nto get terms that", "start": 1970.74, "duration": 1.98}, {"text": "involve these matrices of\npartial derivatives hitting", "start": 1972.72, "duration": 6.48}, {"text": "the metric of flat space time.", "start": 1979.2, "duration": 1.25}, {"text": "And what that's going to do is\nin keeping with our principle", "start": 1982.98, "duration": 4.41}, {"text": "that when we're dealing with\nspacetime quantities, we raise", "start": 1987.39, "duration": 2.97}, {"text": "and lower indices with eta.", "start": 1990.36, "duration": 3.84}, {"text": "This is going to now give me--", "start": 1994.2, "duration": 3.215}, {"text": "pardon me just one moment--", "start": 1997.415, "duration": 1.125}, {"text": "a term that looks like partial--", "start": 2006.45, "duration": 2.413}, {"text": "everything in the\ndownstairs position, d", "start": 2008.863, "duration": 1.667}, {"text": "mu xi nu minus d nu xi mu.", "start": 2010.53, "duration": 4.56}, {"text": "And then all the other\nterms are on the order", "start": 2015.09, "duration": 4.83}, {"text": "of h times derivatives\nof the generators", "start": 2019.92, "duration": 7.08}, {"text": "of my coordinate transmission.", "start": 2027.0, "duration": 3.19}, {"text": "Small times small.", "start": 2030.19, "duration": 1.32}, {"text": "These are infinitesimal squared.", "start": 2031.51, "duration": 1.36}, {"text": "We are going to neglect them.", "start": 2032.87, "duration": 3.43}, {"text": "Suppose that I insist that\nI have gone from one nearly", "start": 2036.3, "duration": 2.67}, {"text": "flat spacetime to another.", "start": 2038.97, "duration": 2.157}, {"text": "Bear in mind this picture.", "start": 2041.127, "duration": 1.083}, {"text": "I'm just changing my\nrepresentation a little bit.", "start": 2042.21, "duration": 2.042}, {"text": "I've not changed the physics.", "start": 2044.252, "duration": 1.558}, {"text": "So if I write this as\neta mu prime nu prime,", "start": 2045.81, "duration": 7.829}, {"text": "plus h mu prime nu prime.", "start": 2053.639, "duration": 2.491}, {"text": "Well, I've got etas on both.", "start": 2056.13, "duration": 1.2}, {"text": "The thing which\nis interesting is", "start": 2063.96, "duration": 1.52}, {"text": "that I have generated a shift to\nmy perturbation to the metric.", "start": 2065.48, "duration": 4.89}, {"text": "Let's drop the\nprimes for a second.", "start": 2090.761, "duration": 1.458}, {"text": "And I'll just say\nthat my nu, h mu", "start": 2092.219, "duration": 2.201}, {"text": "nu is the old h mu nu minus\nthe symmetrized combination", "start": 2094.42, "duration": 15.56}, {"text": "of derivatives of--", "start": 2109.98, "duration": 2.58}, {"text": "the symmetrized combination of\nderivatives of infinitesimal", "start": 2112.56, "duration": 3.87}, {"text": "coordinate transformation.", "start": 2116.43, "duration": 1.383}, {"text": "Does this remind us of anything?", "start": 2122.65, "duration": 2.61}, {"text": "This is starkly\nreminiscent of the way", "start": 2125.26, "duration": 8.61}, {"text": "in which when we work with\nelectromagnetic fields,", "start": 2133.87, "duration": 4.24}, {"text": "I can take a\npotential, and shift it", "start": 2138.11, "duration": 10.37}, {"text": "by the gradient of some scalar\nto generate a new potential.", "start": 2148.48, "duration": 7.93}, {"text": "In so doing, what\nwe find is that this", "start": 2156.41, "duration": 2.73}, {"text": "leaves the fields unchanged.", "start": 2159.14, "duration": 4.23}, {"text": "If you compute your Faraday\ntensor associated with this,", "start": 2163.37, "duration": 4.11}, {"text": "it is unchanged.", "start": 2167.48, "duration": 1.84}, {"text": "Similarly, we're\ngoing to write out", "start": 2172.25, "duration": 1.62}, {"text": "the details of this\nin just a moment.", "start": 2173.87, "duration": 2.37}, {"text": "When I generate the Riemann\ncurvature from this,", "start": 2176.24, "duration": 15.6}, {"text": "we find that although the metric\nhas been tweaked a little bit", "start": 2191.84, "duration": 3.39}, {"text": "by this coordinate\ntransformation,", "start": 2195.23, "duration": 1.98}, {"text": "Riemann is left unchanged.", "start": 2197.21, "duration": 2.16}, {"text": "In acknowledgment of this,\nwe call an infinitesimal", "start": 2215.97, "duration": 5.02}, {"text": "coordinate transformation\nof this kind a gauge", "start": 2220.99, "duration": 3.03}, {"text": "transformation.", "start": 2224.02, "duration": 1.215}, {"text": "What the gauge\ntransformation does", "start": 2260.44, "duration": 1.77}, {"text": "is it allows us to\nchange the metric,", "start": 2262.21, "duration": 2.7}, {"text": "or change the way that we\nare representing our metric.", "start": 2264.91, "duration": 2.832}, {"text": "And it's going to\nturn out to leave", "start": 2267.742, "duration": 1.458}, {"text": "curvature tensors unchanged,\nin the same way that", "start": 2269.2, "duration": 3.51}, {"text": "changing the potential\nand electrodynamics", "start": 2272.71, "duration": 2.67}, {"text": "with a gauge transformation\nleaves our fields unchanged.", "start": 2275.38, "duration": 3.348}, {"text": "And we're going to exploit\nthis in exactly the same way", "start": 2278.728, "duration": 2.292}, {"text": "that we exploit this\nin electrodynamics.", "start": 2281.02, "duration": 1.68}, {"text": "We use this in\nelectrodynamics in order", "start": 2282.7, "duration": 2.79}, {"text": "to recast the equations\ngoverning our potentials", "start": 2285.49, "duration": 3.3}, {"text": "into a form that is maximally\nconvenient for whatever", "start": 2288.79, "duration": 2.85}, {"text": "calculation we are\ndoing right now.", "start": 2291.64, "duration": 1.458}, {"text": "We're going to find-- and then\nwe're going to derive this", "start": 2293.098, "duration": 2.375}, {"text": "probably in about 20 minutes--", "start": 2295.473, "duration": 1.597}, {"text": "that the equations\nthat govern h mu nu.", "start": 2297.07, "duration": 4.36}, {"text": "If we leave things as\ngeneral as possible,", "start": 2301.43, "duration": 1.78}, {"text": "they're a bit of a mess.", "start": 2303.21, "duration": 1.0}, {"text": "But by choosing\nthe right gauge, we", "start": 2304.21, "duration": 3.21}, {"text": "can simplify them,\nand wind up with a set", "start": 2307.42, "duration": 2.28}, {"text": "of equations that are--", "start": 2309.7, "duration": 2.94}, {"text": "they cover all physical\nsituations that matter,", "start": 2312.64, "duration": 2.85}, {"text": "and that allow us\nto just cast things", "start": 2315.49, "duration": 3.99}, {"text": "into a form that is much\nbetter for us to work with.", "start": 2319.48, "duration": 4.56}, {"text": "All right.", "start": 2324.04, "duration": 1.38}, {"text": "So we have now developed all\nof the sort of linguistics", "start": 2325.42, "duration": 4.71}, {"text": "of linearized geometry\nthat I want to use.", "start": 2330.13, "duration": 6.51}, {"text": "Let's now go from\nlinearized geometry", "start": 2336.64, "duration": 1.92}, {"text": "to linearized gravity by\nrunning this through, and making", "start": 2338.56, "duration": 2.85}, {"text": "some physics.", "start": 2341.41, "duration": 1.33}, {"text": "What I want to do\nis look at the field", "start": 2342.74, "duration": 2.99}, {"text": "equations in this framework.", "start": 2345.73, "duration": 2.303}, {"text": "I am not going to run through\nevery step of the next couple", "start": 2351.35, "duration": 2.91}, {"text": "calculations.", "start": 2354.26, "duration": 3.0}, {"text": "Doing so is a good illustration\nof the kind of calculation", "start": 2357.26, "duration": 3.81}, {"text": "that a physicist likes to call\nstraightforward but tedious.", "start": 2361.07, "duration": 2.61}, {"text": "So I'm going to just write down\nwhat the results turned out", "start": 2363.68, "duration": 2.49}, {"text": "to be.", "start": 2366.17, "duration": 1.42}, {"text": "So let's run the metric\nthrough the machinery", "start": 2367.59, "duration": 5.63}, {"text": "that we need to make all\nof our curvature tensors.", "start": 2373.22, "duration": 10.35}, {"text": "OK, I'll remind you when we\ndo this, we are linearizing.", "start": 2395.03, "duration": 3.32}, {"text": "So anytime we see a term that\nlooks like h squared, it dies.", "start": 2398.35, "duration": 3.12}, {"text": "So we're only keeping\nthings to linear order in h.", "start": 2401.47, "duration": 3.55}, {"text": "So the first thing we find\nis the Riemann tensor turns", "start": 2405.02, "duration": 9.25}, {"text": "into the following combination\nof partial derivatives", "start": 2414.27, "duration": 8.01}, {"text": "of the metric perturbation h.", "start": 2422.28, "duration": 1.56}, {"text": "In my notes, I have\nwritten out what", "start": 2443.22, "duration": 4.08}, {"text": "happens when you switch\nfrom some original tensor h", "start": 2447.3, "duration": 6.93}, {"text": "to a modified one using\nthis gauge transformation.", "start": 2454.23, "duration": 4.11}, {"text": "And what I show is that--", "start": 2458.34, "duration": 3.37}, {"text": "just a quick aside--", "start": 2461.71, "duration": 0.98}, {"text": "the gauge\ntransformation generates", "start": 2468.52, "duration": 5.04}, {"text": "a delta Riemann\nthat looks like it's", "start": 2473.56, "duration": 8.212}, {"text": "a whole bunch of-- let's see.", "start": 2481.772, "duration": 1.208}, {"text": "Let's count them up.", "start": 2482.98, "duration": 0.833}, {"text": "1, 2, 3, 4, 5, 6, 7, 8.", "start": 2483.813, "duration": 1.657}, {"text": "You have eight terms.", "start": 2485.47, "duration": 1.315}, {"text": "Of course there's eight,\nbecause there's four terms here,", "start": 2486.785, "duration": 2.375}, {"text": "and you get two\nmore for each one.", "start": 2489.16, "duration": 1.472}, {"text": "So you're going to wind up with\neight additional terms that", "start": 2490.632, "duration": 2.458}, {"text": "involve three partial\nderivatives of the gauge", "start": 2493.09, "duration": 2.52}, {"text": "generator.", "start": 2495.61, "duration": 0.937}, {"text": "So they're of the\nform d cubed on xi.", "start": 2508.74, "duration": 3.72}, {"text": "And it's not hard to show.", "start": 2512.46, "duration": 1.17}, {"text": "You just sort of look at them.", "start": 2513.63, "duration": 1.29}, {"text": "They cancel in pairs.", "start": 2514.92, "duration": 1.305}, {"text": "And so delta Riemann is zero.", "start": 2525.87, "duration": 3.1}, {"text": "The Riemann tensor is invariant\nto the gauge transformation.", "start": 2528.97, "duration": 4.382}, {"text": "All right, we want\nto take this Riemann", "start": 2537.42, "duration": 2.67}, {"text": "and use it to build\nthe Einstein tensor.", "start": 2540.09, "duration": 1.8}, {"text": "Our goal here is to\nmake the field equation", "start": 2541.89, "duration": 4.95}, {"text": "in linearized coordinates.", "start": 2546.84, "duration": 1.566}, {"text": "So let's start by\nmaking the Ricci tensor.", "start": 2562.02, "duration": 5.52}, {"text": "So we're going to\nraise and lower", "start": 2567.54, "duration": 1.47}, {"text": "indices in linearized theory\nwith the flat spacetime.", "start": 2569.01, "duration": 8.0}, {"text": "So when we make this\nguy, what we get is this.", "start": 2577.01, "duration": 10.68}, {"text": "I've introduced a couple\nof definitions here.", "start": 2606.84, "duration": 3.12}, {"text": "One of them, you've seen before.", "start": 2609.96, "duration": 1.98}, {"text": "The box operator is just a\nflat spacetime wave operator.", "start": 2611.94, "duration": 5.04}, {"text": "And h with no\nindices is what I get", "start": 2616.98, "duration": 5.92}, {"text": "when I trace over h using the\nflat background spacetime.", "start": 2622.9, "duration": 7.985}, {"text": "And let's do one more.", "start": 2633.773, "duration": 0.917}, {"text": "Evaluating r, I get one\nfurther contraction.", "start": 2641.52, "duration": 6.64}, {"text": "And this turns out to be\nd alpha, d mu, h alpha mu", "start": 2648.16, "duration": 8.98}, {"text": "minus box of h.", "start": 2657.14, "duration": 4.62}, {"text": "So we now have all\nthe pieces we need", "start": 2661.76, "duration": 2.91}, {"text": "to make the Einstein tensor.", "start": 2664.67, "duration": 2.588}, {"text": "So I'm going to\nwrite out the result.", "start": 2667.258, "duration": 1.542}, {"text": "And then we're going to stop and\njust look at it for a second.", "start": 2668.8, "duration": 2.583}, {"text": "Einstein is Ricci minus\n1/2 metric Ricci scalar.", "start": 2688.44, "duration": 7.92}, {"text": "Keeping things to\nleading order in h.", "start": 2696.36, "duration": 2.43}, {"text": "This becomes flat spacetime\nmetric going into there.", "start": 2701.694, "duration": 3.366}, {"text": "So when you put all these\ningredients together,", "start": 2708.17, "duration": 2.63}, {"text": "there's an overall\nprefactor of 1/2.", "start": 2710.8, "duration": 3.75}, {"text": "And then there are 1,\n2, 3, 4, 5, 6 terms.", "start": 2714.55, "duration": 3.593}, {"text": "Let me write them out.", "start": 2718.143, "duration": 0.917}, {"text": "OK.", "start": 2751.98, "duration": 0.5}, {"text": "So recall at the\nbeginning of the lecture,", "start": 2757.01, "duration": 3.01}, {"text": "I pointed out that when\none regards G alpha beta", "start": 2760.02, "duration": 4.01}, {"text": "as just a differential operator\non the spacetime metric,", "start": 2764.03, "duration": 2.95}, {"text": "it's kind of a mess.", "start": 2766.98, "duration": 2.15}, {"text": "Bearing in mind that what\nI have here is a simplified", "start": 2769.13, "duration": 3.24}, {"text": "version of that,\nI have discarded", "start": 2772.37, "duration": 1.75}, {"text": "all of the terms that are\nhigher order in h than linear.", "start": 2774.12, "duration": 4.29}, {"text": "This is already pretty much\na bloody mess as it is.", "start": 2778.41, "duration": 2.9}, {"text": "So you can sort of\nsee my point there.", "start": 2781.31, "duration": 1.89}, {"text": "If this were done in\nits full generality,", "start": 2783.2, "duration": 2.37}, {"text": "it would be kind of a disaster.", "start": 2785.57, "duration": 1.575}, {"text": "Now, in linearized theory, there\nis a bit of sleight of hand", "start": 2790.63, "duration": 6.3}, {"text": "that lets us clean\nthis up a little bit.", "start": 2796.93, "duration": 2.95}, {"text": "Let me emphasize that the next\nfew lines of calculation I'm", "start": 2799.88, "duration": 2.93}, {"text": "going to write down,\nthere's nothing profound.", "start": 2802.81, "duration": 2.64}, {"text": "All I'm going to\ndo is show a way", "start": 2805.45, "duration": 1.47}, {"text": "of reorganizing the\nterms, which simplifies", "start": 2806.92, "duration": 2.7}, {"text": "this in an important way.", "start": 2809.62, "duration": 1.51}, {"text": "So what we're going to do is\ndefine the following tensor.", "start": 2815.2, "duration": 3.47}, {"text": "h bar is h minus 1/2\neta alpha beta h.", "start": 2818.67, "duration": 11.72}, {"text": "So this is a good point to\ngo, well, who ordered that?", "start": 2830.39, "duration": 3.06}, {"text": "Let's take the trace of this.", "start": 2833.45, "duration": 2.67}, {"text": "Let's define h bar\nwith no indices", "start": 2836.12, "duration": 3.3}, {"text": "is what I get when\nI trace on this.", "start": 2839.42, "duration": 3.42}, {"text": "That's going to\nbe the trace of h.", "start": 2842.84, "duration": 2.953}, {"text": "This would be the\ntrace of h alpha beta,", "start": 2845.793, "duration": 1.667}, {"text": "so I just get h back,\nminus 1/2 h times the trace", "start": 2847.46, "duration": 7.74}, {"text": "of eta alpha beta.", "start": 2855.2, "duration": 1.42}, {"text": "And the trace of eta alpha beta.", "start": 2856.62, "duration": 1.64}, {"text": "This is what I get\nwhen I raise one index,", "start": 2858.26, "duration": 3.25}, {"text": "and sum over the diagonal.", "start": 2861.51, "duration": 1.67}, {"text": "That is 4.", "start": 2863.18, "duration": 0.81}, {"text": "So the trace of h bar is\nnegative the trace of h.", "start": 2867.87, "duration": 3.75}, {"text": "We call h bar alpha\nbeta the trace reversed", "start": 2877.15, "duration": 3.96}, {"text": "metric perturbation.", "start": 2881.11, "duration": 1.5}, {"text": "It's got exactly\nthe same information", "start": 2882.61, "duration": 2.46}, {"text": "as my original\nmetric perturbation,", "start": 2885.07, "duration": 1.9}, {"text": "but I've just redefined\na couple terms in order", "start": 2886.97, "duration": 3.83}, {"text": "to give it a trace that\nhas the opposite sign", "start": 2890.8, "duration": 5.43}, {"text": "of the original perturbation h.", "start": 2896.23, "duration": 2.94}, {"text": "The reason why this\nis useful is recall", "start": 2899.17, "duration": 2.85}, {"text": "the Einstein tensor is itself\nthe trace reversed Ricci", "start": 2902.02, "duration": 4.53}, {"text": "tensor.", "start": 2906.55, "duration": 1.65}, {"text": "What we're going to\nsee is that if we--", "start": 2908.2, "duration": 2.34}, {"text": "in acknowledgment that it's\nsort of a trace reverse thing,", "start": 2910.54, "duration": 3.33}, {"text": "if I plug in a trace\nreverse metric perturbation,", "start": 2913.87, "duration": 3.03}, {"text": "a couple of terms are\ngoing to get cleaned up.", "start": 2916.9, "duration": 2.62}, {"text": "So here's how we do this.", "start": 2919.52, "duration": 1.08}, {"text": "So let's now insert h bar.", "start": 2920.6, "duration": 5.96}, {"text": "This guy is going\nto be equal to--", "start": 2926.56, "duration": 2.26}, {"text": "oops, pardon me.", "start": 2928.82, "duration": 2.37}, {"text": "Insert h.", "start": 2931.19, "duration": 2.78}, {"text": "This guy is h bar plus\n1/2 eta alpha beta h.", "start": 2933.97, "duration": 9.38}, {"text": "So just move that\nto the other side.", "start": 2943.35, "duration": 2.01}, {"text": "All I'm doing is\ntaking the definition,", "start": 2945.36, "duration": 1.8}, {"text": "and I am moving part of\nit to the other side,", "start": 2947.16, "duration": 2.91}, {"text": "so that I can\nsubstitute in for h.", "start": 2950.07, "duration": 3.14}, {"text": "When you plug this\ninto here, you'll", "start": 2953.21, "duration": 1.62}, {"text": "see that there are\ncertain cancellations.", "start": 2954.83, "duration": 1.95}, {"text": "In particular, every term\nthat involves the trace of h,", "start": 2956.78, "duration": 4.35}, {"text": "h without any indices,\nis canceled out.", "start": 2961.13, "duration": 2.79}, {"text": "And so what you find doing this\nalgebra is that your Einstein", "start": 2978.87, "duration": 3.84}, {"text": "tensor turns into--", "start": 2982.71, "duration": 4.885}, {"text": "that can't be right.", "start": 2998.607, "duration": 0.833}, {"text": "OK.", "start": 3021.49, "duration": 1.09}, {"text": "So now, my Einstein tensor\nhas no trace of h in it.", "start": 3022.58, "duration": 3.12}, {"text": "Every h that appears\non its right hand side", "start": 3025.7, "duration": 3.06}, {"text": "is the tensor with\nboth of the indices.", "start": 3028.76, "duration": 2.13}, {"text": "But now, it's the trace\nreverse version of that.", "start": 3030.89, "duration": 4.13}, {"text": "This is still a bit of a mess.", "start": 3035.02, "duration": 4.98}, {"text": "Now, we're going to do something\nthat's got a little bit more--", "start": 3040.0, "duration": 4.81}, {"text": "it's not just sleight of hand.", "start": 3044.81, "duration": 1.42}, {"text": "This is something that's\ngot a little bit more", "start": 3046.23, "duration": 2.11}, {"text": "of sort of the meaning of\nsome of these manipulations", "start": 3048.34, "duration": 2.31}, {"text": "that we've worked out.", "start": 3050.65, "duration": 0.917}, {"text": "It's going to play a role in\nhelping us to understand this.", "start": 3051.567, "duration": 3.973}, {"text": "Notice this term involves\ndelta mu on h mu.", "start": 3055.54, "duration": 6.71}, {"text": "Excuse me, partial mu on\nh mu, partial mu on h mu.", "start": 3062.25, "duration": 5.13}, {"text": "Partial mu and\npartial nu on h mu.", "start": 3067.38, "duration": 4.16}, {"text": "This is the only term that does\nnot look like a divergence.", "start": 3071.54, "duration": 5.4}, {"text": "Three of the terms\nin my Einstein tensor", "start": 3088.1, "duration": 1.82}, {"text": "look like divergences of\nthe trace reverse metric.", "start": 3089.92, "duration": 9.74}, {"text": "Wouldn't it be nice if we\ncould eliminate them somehow?", "start": 3104.65, "duration": 3.195}, {"text": "Well, if you studied\ngauge transformations", "start": 3115.07, "duration": 2.07}, {"text": "and electrodynamics,\nyou'll note that there's", "start": 3117.14, "duration": 1.98}, {"text": "something similar that is done.", "start": 3119.12, "duration": 2.35}, {"text": "You can choose a gauge, such\nthe divergence of the vector", "start": 3121.47, "duration": 4.22}, {"text": "for potential vanishes.", "start": 3125.69, "duration": 0.99}, {"text": "Can we set the divergence\nof this guy equal to zero?", "start": 3132.17, "duration": 9.47}, {"text": "So if you look at this,\nmu is a dummy index.", "start": 3141.64, "duration": 4.02}, {"text": "This is four conditions\nthat we are trying to set.", "start": 3145.66, "duration": 3.57}, {"text": "This has to happen for mu--", "start": 3149.23, "duration": 2.195}, {"text": "well, we're going\nto sum over mu.", "start": 3151.425, "duration": 1.375}, {"text": "Pardon me.", "start": 3152.8, "duration": 0.5}, {"text": "It's going to happen\nfor nu equal time,", "start": 3153.3, "duration": 1.96}, {"text": "and for my three spaces.", "start": 3155.26, "duration": 3.45}, {"text": "These are four conditions.", "start": 3158.71, "duration": 1.793}, {"text": "My gauge generators, my xi\nnu are four free functions.", "start": 3168.24, "duration": 14.81}, {"text": "That suggests that the\ngauge generators give me", "start": 3192.42, "duration": 2.7}, {"text": "enough freedom that I\ncan adjust my gauge such", "start": 3195.12, "duration": 4.29}, {"text": "that if I start out\nwith some original,", "start": 3199.41, "duration": 3.54}, {"text": "I have an h old that\nis not divergence free.", "start": 3202.95, "duration": 4.35}, {"text": "Perhaps I can make\nan h new that is.", "start": 3207.3, "duration": 2.13}, {"text": "Well, let's try it.", "start": 3212.308, "duration": 0.792}, {"text": "So remember, I just erased it.", "start": 3235.91, "duration": 2.34}, {"text": "But in fact, I'll just\nwrite it down right now.", "start": 3238.25, "duration": 2.22}, {"text": "The shift to the metric\nperturbation arising", "start": 3240.47, "duration": 2.97}, {"text": "from the gauge\ntransformation, it's on h.", "start": 3243.44, "duration": 2.55}, {"text": "We need to look\nat how it affects", "start": 3245.99, "duration": 1.53}, {"text": "the trace reverse stage.", "start": 3247.52, "duration": 1.14}, {"text": "So if I start with\nmy new perturbation", "start": 3252.4, "duration": 3.92}, {"text": "is related to my old\nperturbation as follows.", "start": 3256.32, "duration": 5.35}, {"text": "It's not too hard to show\nthat your trace reversed", "start": 3267.27, "duration": 9.49}, {"text": "metric perturbation.", "start": 3276.76, "duration": 1.516}, {"text": "Pardon, pardon, pardon.", "start": 3285.092, "duration": 0.958}, {"text": "My trace reverse\nperturbation transforms", "start": 3289.2, "duration": 7.97}, {"text": "in almost the exact same way.", "start": 3297.17, "duration": 2.065}, {"text": "I get one extra term.", "start": 3299.235, "duration": 0.875}, {"text": "So now, what I\nwant to do is look", "start": 3308.94, "duration": 2.72}, {"text": "at how the divergence\nof this transforms.", "start": 3311.66, "duration": 4.05}, {"text": "So I'm going to get one\nterm here, d mu of this.", "start": 3329.77, "duration": 3.21}, {"text": "It gives me a wave operator\nacting on my gauge generator.", "start": 3332.98, "duration": 6.937}, {"text": "And then I get another\nterm here that looks like--", "start": 3342.78, "duration": 10.242}, {"text": "remember, partial\nderivatives commute.", "start": 3353.022, "duration": 1.583}, {"text": "So you can think of this as d nu\nof the divergence of xi, eta mu", "start": 3354.605, "duration": 17.605}, {"text": "nu acting on this\nchanges this into d", "start": 3372.21, "duration": 7.88}, {"text": "nu on the convergence of xi.", "start": 3380.09, "duration": 2.58}, {"text": "And I messed up the\nsign, my apologies.", "start": 3382.67, "duration": 3.55}, {"text": "That plus sign should\nhave come down here.", "start": 3386.22, "duration": 3.11}, {"text": "These are equal but opposite.", "start": 3389.33, "duration": 2.67}, {"text": "They cancel.", "start": 3392.0, "duration": 0.57}, {"text": "So let me just\nhighlight the result.", "start": 3395.85, "duration": 27.4}, {"text": "So what this tells me is if I\nchoose my gauge generators just", "start": 3423.25, "duration": 7.51}, {"text": "right, I can adjust my\ntrace reverse metric,", "start": 3430.76, "duration": 7.81}, {"text": "so that it is divergence free.", "start": 3438.57, "duration": 1.86}, {"text": "If I do that, then the first\nthree terms in my Einstein", "start": 3471.91, "duration": 7.06}, {"text": "tensor here vanish.", "start": 3478.97, "duration": 1.44}, {"text": "And if I do that, then\nhere is my Einstein tensor.", "start": 3491.32, "duration": 4.1}, {"text": "So just as in e and m, all\nthat you need to do is say,", "start": 3503.79, "duration": 6.85}, {"text": "I'm going to change\nmy gauge such", "start": 3510.64, "duration": 2.01}, {"text": "that the following\ncondition holds.", "start": 3512.65, "duration": 2.395}, {"text": "The condition that\ndescribes going", "start": 3518.53, "duration": 2.91}, {"text": "into this gauge such\nthat the divergence", "start": 3521.44, "duration": 2.46}, {"text": "of your trace reverse\nperturbation vanishes.", "start": 3523.9, "duration": 4.17}, {"text": "This is a simple wave equation.", "start": 3528.07, "duration": 2.1}, {"text": "So solutions to this\nare guaranteed to exist.", "start": 3530.17, "duration": 3.015}, {"text": "If you sit down\nand you ask, can I", "start": 3556.783, "duration": 1.417}, {"text": "come up with some kind of\na pathological spacetime,", "start": 3558.2, "duration": 2.4}, {"text": "or a pathological--", "start": 3560.6, "duration": 1.42}, {"text": "no.", "start": 3562.02, "duration": 0.85}, {"text": "Imagine I'm in some\noriginal spacetime", "start": 3562.87, "duration": 1.66}, {"text": "sufficiently pathological that\ndoesn't allow me to do this.", "start": 3564.53, "duration": 3.462}, {"text": "If you do that,\nyou're going end up", "start": 3567.992, "duration": 1.458}, {"text": "violating the conditions\nthat define weak spacetime.", "start": 3569.45, "duration": 3.0}, {"text": "You can't do that in\nlinearized gravity anyway.", "start": 3572.45, "duration": 2.52}, {"text": "So in practice, we can\nalways choose the gauge", "start": 3574.97, "duration": 3.54}, {"text": "that puts in linearized\ngravity my Einstein", "start": 3578.51, "duration": 3.09}, {"text": "tensor in this form.", "start": 3581.6, "duration": 2.89}, {"text": "This form is exactly\nanalogous to the Lorentz gauge", "start": 3584.49, "duration": 4.25}, {"text": "condition that is used\nin electrodynamics.", "start": 3588.74, "duration": 2.84}, {"text": "And so we call this Lorentz\ngauge in linearized gravity.", "start": 3591.58, "duration": 6.75}, {"text": "Once we've done that, here's\nwhat my Einstein field", "start": 3608.22, "duration": 10.72}, {"text": "equations turn into.", "start": 3618.94, "duration": 0.95}, {"text": "In the next lecture, we\nwill solve this exactly.", "start": 3663.6, "duration": 6.725}, {"text": "See, what you want\nto emphasize is", "start": 3673.02, "duration": 2.9}, {"text": "this is one of those\nsituations where the answer is", "start": 3675.92, "duration": 5.68}, {"text": "so easy and simple for\nus all to work out,", "start": 3681.6, "duration": 4.71}, {"text": "we don't actually really need to\neven do that much calculation.", "start": 3686.31, "duration": 3.4}, {"text": "I'll remind you that\nin electrodynamics,", "start": 3689.71, "duration": 8.48}, {"text": "if you work in Lorentz gauge\nof electrodynamics, the wave", "start": 3698.19, "duration": 8.97}, {"text": "equation that governs the\nelectromagnetic potential", "start": 3707.16, "duration": 11.86}, {"text": "turns out to be--", "start": 3719.02, "duration": 1.808}, {"text": "could be factors of c\nand things like that,", "start": 3720.828, "duration": 1.792}, {"text": "depending on which\nunits you're working in.", "start": 3722.62, "duration": 2.19}, {"text": "But we find an equation\nthat has exactly", "start": 3724.81, "duration": 2.91}, {"text": "the same mathematical structure.", "start": 3727.72, "duration": 2.43}, {"text": "Possibly there's a plus sign.", "start": 3730.15, "duration": 1.75}, {"text": "I should have looked that up.", "start": 3731.9, "duration": 2.63}, {"text": "Wave operator on my vector\npotential is a source.", "start": 3734.53, "duration": 4.09}, {"text": "And this is very\neasily solved using", "start": 3738.62, "duration": 2.038}, {"text": "what's called a radiative\nGreen's function.", "start": 3740.658, "duration": 1.792}, {"text": "I will discuss this\nin the next lecture.", "start": 3758.38, "duration": 2.29}, {"text": "You can look up the details in\nany advanced electrodynamics", "start": 3760.67, "duration": 4.02}, {"text": "textbook.", "start": 3764.69, "duration": 0.5}, {"text": "Jackson has very nice\ndiscussion of this.", "start": 3765.19, "duration": 3.45}, {"text": "I have an extra index.", "start": 3768.64, "duration": 1.59}, {"text": "I have a different coefficient.", "start": 3770.23, "duration": 1.56}, {"text": "But the mathematical\nstructure is identical.", "start": 3771.79, "duration": 4.45}, {"text": "So as far as linearized\ntheory is concerned,", "start": 3776.24, "duration": 2.46}, {"text": "we're basically done.", "start": 3778.7, "duration": 2.57}, {"text": "So I'm going to talk about\nthe exact solution of this", "start": 3781.27, "duration": 2.31}, {"text": "in the next lecture.", "start": 3783.58, "duration": 2.16}, {"text": "To wrap up today's lecture, to\nwrap up this current lecture.", "start": 3785.74, "duration": 3.43}, {"text": "Let me look at the solution\nof this in a particular limit.", "start": 3789.17, "duration": 4.25}, {"text": "So I'm going to\ntake my source to be", "start": 3815.13, "duration": 6.43}, {"text": "a static, non-relativistic,\nperfect fluid.", "start": 3821.56, "duration": 8.87}, {"text": "The fact that it is static means\nthat all of my time derivatives", "start": 3838.45, "duration": 4.35}, {"text": "will be zero.", "start": 3842.8, "duration": 0.6}, {"text": "And if that's true\nfor my source,", "start": 3848.245, "duration": 1.375}, {"text": "it has to be true for the\nfield that arises from it.", "start": 3849.62, "duration": 2.7}, {"text": "Non-relativistic tells me\nthat the fluid density greatly", "start": 3852.32, "duration": 10.98}, {"text": "exceeds its pressure.", "start": 3863.3, "duration": 2.86}, {"text": "And as a consequence, I\ncan write my stress energy", "start": 3866.16, "duration": 3.84}, {"text": "tensor as approximately density\nfour velocity four velocity.", "start": 3870.0, "duration": 8.99}, {"text": "And when you go and you look at\nthe magnitude of these things,", "start": 3878.99, "duration": 2.7}, {"text": "I sort of looked at\nthis a little bit", "start": 3881.69, "duration": 1.14}, {"text": "in the previous lecture.", "start": 3882.83, "duration": 1.0}, {"text": "T00 is approximately rho.", "start": 3886.53, "duration": 4.298}, {"text": "All others will be negligible.", "start": 3896.02, "duration": 3.54}, {"text": "Probably there's a small\ncorrection to this,", "start": 3899.56, "duration": 2.22}, {"text": "but we can neglect\nthat on a first pass.", "start": 3901.78, "duration": 2.31}, {"text": "So my field equation is\ndominated by the zero zero", "start": 3928.11, "duration": 7.86}, {"text": "component.", "start": 3935.97, "duration": 0.6}, {"text": "That's going to be the most\nimportant piece of this.", "start": 3943.46, "duration": 3.18}, {"text": "Since this is static,\nI can immediately say--", "start": 3946.64, "duration": 2.67}, {"text": "I can change that wave operator\ninto the plus operator.", "start": 3953.15, "duration": 4.409}, {"text": "And we now notice this\nis exactly the equation", "start": 3962.61, "duration": 4.41}, {"text": "governing the Newtonian\ngravitational potential,", "start": 3967.02, "duration": 3.59}, {"text": "modulo a factor of four.", "start": 3970.61, "duration": 1.27}, {"text": "Pardon me, factor of minus four.", "start": 3985.02, "duration": 2.23}, {"text": "And so we see from this\nthat h bar zero zero", "start": 3987.25, "duration": 5.11}, {"text": "is just negative 4 times\nthe Newtonian gravitational", "start": 3992.36, "duration": 3.34}, {"text": "potential.", "start": 3995.7, "duration": 0.959}, {"text": "At this order in\nthe calculation,", "start": 4004.81, "duration": 2.34}, {"text": "all other contributions to the\ntrace reverse metric are zero.", "start": 4007.15, "duration": 4.47}, {"text": "OK, so let's go from the\ntrace reverse metric back", "start": 4024.3, "duration": 3.21}, {"text": "to the metric.", "start": 4027.51, "duration": 0.6}, {"text": "We use the fact that h mu nu\nis the trace reversed h mu nu.", "start": 4031.2, "duration": 7.85}, {"text": "If we trace reverse it, we'll\nget the original metric back.", "start": 4039.05, "duration": 3.443}, {"text": "Basically, we trace\nreverse twice.", "start": 4042.493, "duration": 1.417}, {"text": "So the trace of this guy.", "start": 4051.12, "duration": 1.32}, {"text": "OK, and so putting all\nthese ingredients together,", "start": 4066.9, "duration": 3.1}, {"text": "what we see are that the only\nnon-zero contributions here", "start": 4070.0, "duration": 4.7}, {"text": "are 8 0 0.", "start": 4074.7, "duration": 1.053}, {"text": "Let's do this one carefully.", "start": 4075.753, "duration": 1.167}, {"text": "This is minus 4 times Newtonian\npotential minus 1/2 times 8 0 0", "start": 4076.92, "duration": 16.44}, {"text": "and 4 times Newtonian potential.", "start": 4093.36, "duration": 1.71}, {"text": "I have a c of minus sign here.", "start": 4095.07, "duration": 1.99}, {"text": "This turns into minus 2 phi n.", "start": 4097.06, "duration": 5.57}, {"text": "And h1 1 equals h2 2.", "start": 4102.63, "duration": 3.849}, {"text": "h equals h3 3.", "start": 4106.479, "duration": 2.581}, {"text": "This is going to be 0 minus\n1/2 times 1 times 4 phi n.", "start": 4109.06, "duration": 8.23}, {"text": "We put all these together.", "start": 4127.87, "duration": 1.26}, {"text": "And what we get is--", "start": 4159.25, "duration": 12.505}, {"text": "And I'll remind you.", "start": 4194.197, "duration": 0.833}, {"text": "This is a metric that I\nquoted in a previous lecture", "start": 4195.03, "duration": 3.96}, {"text": "that I said we would\nprove in an upcoming one.", "start": 4198.99, "duration": 2.54}, {"text": "Well, here it is.", "start": 4201.53, "duration": 1.33}, {"text": "This is the Newtonian limit\nof general relativity.", "start": 4202.86, "duration": 4.218}, {"text": "And it's worth remarking\nthat this thing--", "start": 4212.23, "duration": 5.13}, {"text": "we are now in the\nvery first lecture", "start": 4217.36, "duration": 2.67}, {"text": "after having derived the\nEinstein field equations.", "start": 4220.03, "duration": 4.22}, {"text": "20 years ago, almost all\nlaboratory tests, laboratory", "start": 4224.25, "duration": 4.69}, {"text": "and astronomical observational\ntests of general relativity", "start": 4228.94, "duration": 2.76}, {"text": "essentially came\nfrom this based on.", "start": 4231.7, "duration": 3.18}, {"text": "This ends up being\nthe foundation", "start": 4234.88, "duration": 1.89}, {"text": "of gravitational lensing.", "start": 4236.77, "duration": 1.62}, {"text": "This is used to look at\npost-Newtonian corrections", "start": 4238.39, "duration": 3.39}, {"text": "in our solar system.", "start": 4241.78, "duration": 2.31}, {"text": "To a good approximation, it\ndescribes a tremendous number", "start": 4244.09, "duration": 3.18}, {"text": "of binary systems that\nwe see in our galaxy", "start": 4247.27, "duration": 4.5}, {"text": "and in a few other galaxies.", "start": 4251.77, "duration": 1.74}, {"text": "You really need to look for\na much more extreme systems", "start": 4253.51, "duration": 4.14}, {"text": "before the way in which\nthe analysis changes", "start": 4257.65, "duration": 4.47}, {"text": "due to going beyond linear order\nstarts to become important.", "start": 4262.12, "duration": 5.31}, {"text": "There is an upcoming\nhomework exercise.", "start": 4267.43, "duration": 3.42}, {"text": "And for students taking this\ncourse in spring of 2020,", "start": 4270.85, "duration": 6.548}, {"text": "it remains to be\ndetermined how we", "start": 4277.398, "duration": 1.417}, {"text": "are going to do problem\nsets at this point.", "start": 4278.815, "duration": 1.935}, {"text": "I will be making a decision\non that in coming days.", "start": 4280.75, "duration": 2.58}, {"text": "But I want to tell you\nabout an exercise on P", "start": 4283.33, "duration": 3.54}, {"text": "set number 7, in which you do a\nvariation of this calculation.", "start": 4286.87, "duration": 6.13}, {"text": "So instead of just\nhaving a static body", "start": 4293.0, "duration": 6.2}, {"text": "with a body who has\nmassive density rho,", "start": 4299.2, "duration": 4.73}, {"text": "consider a rotating body.", "start": 4303.93, "duration": 1.43}, {"text": "And the thing which\nis interesting", "start": 4314.253, "duration": 1.417}, {"text": "here is that in\ngeneral relativity,", "start": 4315.67, "duration": 3.57}, {"text": "all forms, all fluxes\nof energy and momentum", "start": 4319.24, "duration": 5.34}, {"text": "contribute to gravity through\nthe stress energy tensor.", "start": 4324.58, "duration": 2.7}, {"text": "So if I have a body that\nis rotating about an axis,", "start": 4327.28, "duration": 3.45}, {"text": "there's a mass flow.", "start": 4330.73, "duration": 1.14}, {"text": "There are mass\ncurrents that arise.", "start": 4331.87, "duration": 2.55}, {"text": "And what you find if you do\nthis calculation correctly", "start": 4334.42, "duration": 2.61}, {"text": "is that there is a correction\nto the spacetime that", "start": 4337.03, "duration": 2.25}, {"text": "enters into here, which reflects\nthe fact that a rotating", "start": 4339.28, "duration": 6.4}, {"text": "body generates a\nunique contribution", "start": 4345.68, "duration": 2.31}, {"text": "to the gravity that is\nmanifested in this space time.", "start": 4347.99, "duration": 4.47}, {"text": "Now, when one looks\nat the behavior", "start": 4352.46, "duration": 2.4}, {"text": "of a body in a\nspacetime like the one", "start": 4354.86, "duration": 1.65}, {"text": "I've written down right here.", "start": 4356.51, "duration": 2.04}, {"text": "It's very reminiscent of--", "start": 4358.55, "duration": 2.095}, {"text": "well, it's just like\nNewtonian gravity.", "start": 4360.645, "duration": 1.625}, {"text": "It's the Newtonian limit.", "start": 4362.27, "duration": 1.56}, {"text": "And Newtonian gravity looks\na lot like the Coulomb", "start": 4363.83, "duration": 2.91}, {"text": "electric attraction.", "start": 4366.74, "duration": 1.68}, {"text": "So this is often called\na gravito electric field.", "start": 4368.42, "duration": 3.4}, {"text": "People use that term,\nparticularly when", "start": 4371.82, "duration": 1.625}, {"text": "they're talking about\nlinearized general relativity.", "start": 4373.445, "duration": 3.555}, {"text": "If I have a rotating body,\nI now have mass currents", "start": 4377.0, "duration": 3.18}, {"text": "flowing in this thing.", "start": 4380.18, "duration": 2.1}, {"text": "And the correction\nto the spacetime", "start": 4382.28, "duration": 2.25}, {"text": "that arises from this, it's\nqualitatively quite different", "start": 4384.53, "duration": 3.37}, {"text": "from us.", "start": 4387.9, "duration": 0.5}, {"text": "It doesn't have that simple\ngravito electric Coulombic type", "start": 4388.4, "duration": 3.45}, {"text": "of form.", "start": 4391.85, "duration": 1.11}, {"text": "It, in fact, looks a lot\nmore like a magnetic field.", "start": 4392.96, "duration": 3.52}, {"text": "And in fact, when\nyou ask, how does", "start": 4396.48, "duration": 2.09}, {"text": "this new term that is generated\naffect the motion of bodies?", "start": 4398.57, "duration": 3.93}, {"text": "You find something that looks\na lot like the magnetic Lorentz", "start": 4402.5, "duration": 2.67}, {"text": "force law describing its motion.", "start": 4405.17, "duration": 3.73}, {"text": "So this is a very,\nvery powerful tool.", "start": 4408.9, "duration": 4.31}, {"text": "But it's already not enough.", "start": 4413.21, "duration": 1.41}, {"text": "So we can go a lot\nfurther than this.", "start": 4414.62, "duration": 3.15}, {"text": "We have done so far, the\nsimplest possible thing", "start": 4417.77, "duration": 3.93}, {"text": "that we can do with this toolkit\nthat we have derived so far.", "start": 4421.7, "duration": 4.57}, {"text": "In the next lecture\nthat I will record,", "start": 4426.27, "duration": 2.0}, {"text": "we're going to return to my\nlinearized Einstein field", "start": 4428.27, "duration": 3.3}, {"text": "equations.", "start": 4431.57, "duration": 1.83}, {"text": "And I am going to explore\ngeneral solutions of this.", "start": 4433.4, "duration": 4.26}, {"text": "This is going to lead us\ninto a discussion of how", "start": 4437.66, "duration": 5.88}, {"text": "things behave when my\ngravitational source is", "start": 4443.54, "duration": 3.52}, {"text": "dynamic.", "start": 4447.06, "duration": 0.5}, {"text": "I do not want to lose the\ntime derivatives that are", "start": 4450.12, "duration": 3.2}, {"text": "present in that wave operator.", "start": 4453.32, "duration": 1.83}, {"text": "And so this is going to lead\nus quite naturally, then,", "start": 4455.15, "duration": 2.25}, {"text": "to a discussion of\ngravitational radiation.", "start": 4457.4, "duration": 3.15}, {"text": "And so after the\nnext lecture, we'll", "start": 4460.55, "duration": 1.93}, {"text": "spend a lecture or two\ndiscussing the nature", "start": 4462.48, "duration": 2.87}, {"text": "of gravitational radiation.", "start": 4465.35, "duration": 1.56}, {"text": "And there will be an\nupcoming homework assignment", "start": 4466.91, "duration": 2.43}, {"text": "or two in which you\nexplore the properties", "start": 4469.34, "duration": 3.0}, {"text": "of gravitational radiation.", "start": 4472.34, "duration": 2.45}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.445}, {"text": "[RUSTLING]", "start": 2.445, "duration": 1.956}, {"text": "[CLICKING]", "start": 4.401, "duration": 1.956}, {"text": "MICHAEL SIPSER: So,\nwelcome, everybody,", "start": 18.6, "duration": 3.06}, {"text": "to the Fall 2020 online\nIntroduction to the Theory", "start": 21.66, "duration": 6.48}, {"text": "of Computing 18.404/6.840.", "start": 28.14, "duration": 5.63}, {"text": "My name is Mike Sipser.", "start": 33.77, "duration": 2.52}, {"text": "I'm going to be your instructor\nfor the semester in this class.", "start": 36.29, "duration": 5.56}, {"text": "So let me just tell you\nwhat the course is about.", "start": 41.85, "duration": 3.17}, {"text": "Basically, it's going\nto be in two halves.", "start": 45.02, "duration": 2.605}, {"text": "We're going to be talking\nabout what are the capabilities", "start": 47.625, "duration": 2.375}, {"text": "and limitations of computers--\nof computer algorithms,", "start": 50.0, "duration": 2.85}, {"text": "really, computation.", "start": 52.85, "duration": 2.28}, {"text": "And the two parts of the\ncourse are more or less divided", "start": 55.13, "duration": 4.11}, {"text": "in half.", "start": 59.24, "duration": 2.328}, {"text": "The first half of\nthe course is going", "start": 61.568, "duration": 1.542}, {"text": "to talk about a subject called\ncomputability theory, which", "start": 63.11, "duration": 3.165}, {"text": "it really asks what\nyou can compute", "start": 66.275, "duration": 2.535}, {"text": "with an algorithm in principle.", "start": 68.81, "duration": 3.27}, {"text": "That's-- was an active area of\nresearch in the earlier part", "start": 72.08, "duration": 3.63}, {"text": "of the 20th century.", "start": 75.71, "duration": 1.38}, {"text": "It's pretty much closed\noff as a research subject", "start": 77.09, "duration": 2.97}, {"text": "these days, mainly\nbecause they answered", "start": 80.06, "duration": 3.27}, {"text": "all of their big questions.", "start": 83.33, "duration": 1.93}, {"text": "And so a mathematical\nfield really only", "start": 85.26, "duration": 3.59}, {"text": "stays vital when it\nhas problems to solve,", "start": 88.85, "duration": 3.6}, {"text": "and they really solved all of\ntheir interesting problems--", "start": 92.45, "duration": 3.36}, {"text": "for the most part, not 100%.", "start": 95.81, "duration": 1.47}, {"text": "But for the most part, it sort\nof finished off in the 1950s--", "start": 97.28, "duration": 5.103}, {"text": "just to say a little bit\nmore about what we're", "start": 102.383, "duration": 1.917}, {"text": "going to talk about there.", "start": 104.3, "duration": 1.5}, {"text": "When you're interested to\nknow what kinds of problems", "start": 105.8, "duration": 2.61}, {"text": "you can solve with\nan algorithm--", "start": 108.41, "duration": 2.13}, {"text": "there are problems\nthat you might", "start": 110.54, "duration": 1.74}, {"text": "want to solve that\nyou just can't solve.", "start": 112.28, "duration": 2.07}, {"text": "For example, given a\nspecification for a computer", "start": 114.35, "duration": 6.3}, {"text": "problem you want\nto solve, whatever", "start": 120.65, "duration": 3.21}, {"text": "that specification might be--", "start": 123.86, "duration": 1.65}, {"text": "say your algorithm\nactually is a sorting", "start": 125.51, "duration": 2.28}, {"text": "algorithm, for example--", "start": 127.79, "duration": 1.57}, {"text": "and you want to write\ndown that specification", "start": 129.36, "duration": 2.03}, {"text": "and have an automatic\nverifier that's", "start": 131.39, "duration": 2.1}, {"text": "going to check whether a\nprogram meets the specification.", "start": 133.49, "duration": 3.34}, {"text": "Well, that's just in\nprinciple impossible.", "start": 136.83, "duration": 3.5}, {"text": "You cannot make a verifier\nwhich is going to answer,", "start": 140.33, "duration": 6.03}, {"text": "in all cases, whether or not\na program meets a certain", "start": 146.36, "duration": 3.0}, {"text": "specification.", "start": 149.36, "duration": 1.59}, {"text": "So with things like that,\nwe will prove this semester.", "start": 150.95, "duration": 4.08}, {"text": "Questions about\nmathematical truth--", "start": 155.03, "duration": 2.7}, {"text": "if you're given a mathematical\nstatement, is it true", "start": 157.73, "duration": 2.25}, {"text": "or is it false?", "start": 159.98, "duration": 1.89}, {"text": "It'd be great if you can\nwrite a computer program that", "start": 161.87, "duration": 3.157}, {"text": "would answer that problem.", "start": 165.027, "duration": 1.083}, {"text": "Well, it would not be great\nif you were a mathematician,", "start": 166.11, "duration": 1.82}, {"text": "because that would put\nus all out of business.", "start": 167.93, "duration": 1.917}, {"text": "But you can imagine that\nmight be a nice thing to have,", "start": 169.847, "duration": 3.543}, {"text": "but you can't.", "start": 173.39, "duration": 0.81}, {"text": "I mean, there is no algorithm\nwhich can answer that question.", "start": 174.2, "duration": 2.542}, {"text": "Well, along the way, we're\ngoing to introduce models", "start": 179.09, "duration": 2.52}, {"text": "of computation, like finite\nautomata, which we'll", "start": 181.61, "duration": 2.31}, {"text": "see today, Turing machines,\nand some other models", "start": 183.92, "duration": 3.24}, {"text": "that we'll see along the way.", "start": 187.16, "duration": 1.83}, {"text": "The second half of\nthe course, which", "start": 188.99, "duration": 1.5}, {"text": "is going to be\nafter the midterm,", "start": 190.49, "duration": 1.47}, {"text": "we're going to\nshift gears and talk", "start": 191.96, "duration": 1.458}, {"text": "about complexity theory, which\nis instead of looking at what's", "start": 193.418, "duration": 2.982}, {"text": "computable in\nprinciple, you're going", "start": 196.4, "duration": 1.68}, {"text": "to look at what's computable\nin practice, so things", "start": 198.08, "duration": 2.82}, {"text": "that you can solve in a\nreasonable amount of time.", "start": 200.9, "duration": 2.8}, {"text": "And, for example,\nI'm sure many of you", "start": 203.7, "duration": 3.38}, {"text": "are aware of the factoring\nproblem, which has connections", "start": 207.08, "duration": 3.18}, {"text": "to the RSA cryptosystem,\ncryptography, and asks", "start": 210.26, "duration": 8.46}, {"text": "whether you can factor\nbig numbers quickly.", "start": 218.72, "duration": 4.14}, {"text": "That's a problem we\ndon't know the answer to.", "start": 222.86, "duration": 3.61}, {"text": "We just don't know how to\nfactor big numbers quickly.", "start": 226.47, "duration": 2.28}, {"text": "But it's possible that there\nare algorithms out there", "start": 228.75, "duration": 2.25}, {"text": "that we haven't discovered\nyet that can do so.", "start": 231.0, "duration": 2.22}, {"text": "It's connected with\nthis very famous problem", "start": 233.22, "duration": 2.07}, {"text": "in the intersection\nof computer science", "start": 235.29, "duration": 2.49}, {"text": "and mathematics called the\nP versus NP problem, which", "start": 237.78, "duration": 2.28}, {"text": "many of you may have heard of.", "start": 240.06, "duration": 1.25}, {"text": "We'll talk about that.", "start": 241.31, "duration": 1.09}, {"text": "We'll spend a lot of\ntime on that this term.", "start": 242.4, "duration": 3.9}, {"text": "And along the way, we'll\ntalk about different measures", "start": 246.3, "duration": 2.28}, {"text": "of complexity, of\ncomputation, time and space,", "start": 248.58, "duration": 3.54}, {"text": "time and memory, theoretical\nmemory, electrical space.", "start": 252.12, "duration": 4.589}, {"text": "That's going to be a big part\nof the course in the complexity", "start": 256.709, "duration": 3.541}, {"text": "theory part--", "start": 260.25, "duration": 0.87}, {"text": "introduce other\nmodels of computation,", "start": 261.12, "duration": 1.95}, {"text": "such as probabilistic and\ninteractive computation.", "start": 263.07, "duration": 3.93}, {"text": "Talk about the\nexpectations of the course.", "start": 267.0, "duration": 2.2}, {"text": "First of all, prerequisites.", "start": 269.2, "duration": 2.66}, {"text": "There are a bunch of\nprerequisites listed, 6.042,", "start": 271.86, "duration": 3.91}, {"text": "18.062 , or maybe some\nother subject as well.", "start": 275.77, "duration": 4.04}, {"text": "The real thing is that\nthis is a math class.", "start": 279.81, "duration": 3.33}, {"text": "This is a class where--", "start": 283.14, "duration": 1.86}, {"text": "and it's not a\nbeginning math class,", "start": 285.0, "duration": 1.53}, {"text": "this is a moderate-to-advanced\nmath class.", "start": 286.53, "duration": 2.64}, {"text": "And I'm expecting\npeople to have had", "start": 289.17, "duration": 2.04}, {"text": "some prior experience,\nof a substantial nature,", "start": 291.21, "duration": 4.08}, {"text": "with mathematical\ntheorems and proofs.", "start": 295.29, "duration": 4.8}, {"text": "We'll start off slow, but we're\ngoing to ramp up pretty fast.", "start": 300.09, "duration": 2.73}, {"text": "So if you haven't\nreally got the idea", "start": 302.82, "duration": 4.12}, {"text": "or gotten comfortable with\ndoing proofs, coming up", "start": 306.94, "duration": 2.61}, {"text": "with proofs to\nmathematical statements,", "start": 309.55, "duration": 2.46}, {"text": "that's going to be a concern.", "start": 312.01, "duration": 2.52}, {"text": "I would just be\nmonitoring yourself", "start": 314.53, "duration": 2.07}, {"text": "and seeing how you're doing.", "start": 316.6, "duration": 1.65}, {"text": "Because the homeworks\nand the exams", "start": 318.25, "duration": 3.18}, {"text": "are going to count on\nyour being able to produce", "start": 321.43, "duration": 2.04}, {"text": "proofs, and so you're\ngoing to be struggling", "start": 323.47, "duration": 4.62}, {"text": "if that's going to be a real--", "start": 328.09, "duration": 1.92}, {"text": "something that you haven't\nhad experience with.", "start": 330.01, "duration": 3.66}, {"text": "And let me talk a little\nbit about the role", "start": 333.67, "duration": 2.07}, {"text": "of theory in computer science.", "start": 335.74, "duration": 3.33}, {"text": "This is a theory\nclass, as you know.", "start": 339.07, "duration": 4.26}, {"text": "So before we jump\ninto the material,", "start": 343.33, "duration": 3.82}, {"text": "I just thought it would\nbe worth it for you", "start": 347.15, "duration": 1.82}, {"text": "to give you at\nleast my perspective", "start": 348.97, "duration": 1.59}, {"text": "on the role of theoretical\ncomputer science", "start": 350.56, "duration": 1.95}, {"text": "within the field.", "start": 352.51, "duration": 2.64}, {"text": "So I've been in computer\nscience for a long time.", "start": 355.15, "duration": 5.55}, {"text": "I go back-- I'm sure I'm\ngetting to be a dinosaur here--", "start": 360.7, "duration": 3.18}, {"text": "but I go back to the days\nwhen you had punch cards.", "start": 363.88, "duration": 3.0}, {"text": "That's what we did when\nI was an undergraduate.", "start": 366.88, "duration": 2.1}, {"text": "And, obviously, things\nare very different now.", "start": 368.98, "duration": 4.62}, {"text": "And you can argue\nthat computer science", "start": 373.6, "duration": 3.96}, {"text": "as a discipline has matured,\nand sort of the basic stuff", "start": 377.56, "duration": 4.41}, {"text": "has all been solved.", "start": 381.97, "duration": 1.8}, {"text": "Well, I would say there's\na certain truth to that,", "start": 383.77, "duration": 2.1}, {"text": "but there's a\ncertain way in which", "start": 385.87, "duration": 1.47}, {"text": "I would say that's not true.", "start": 387.34, "duration": 1.79}, {"text": "I think we're still\nat the very beginning,", "start": 389.13, "duration": 1.75}, {"text": "at least in certain\nrespects, of computer science", "start": 390.88, "duration": 2.91}, {"text": "as a discipline.", "start": 393.79, "duration": 1.62}, {"text": "For one thing, there\nare a lot of things", "start": 395.41, "duration": 1.86}, {"text": "that we do, a lot of things\nrelating to computation,", "start": 397.27, "duration": 5.22}, {"text": "that we just don't know\nthe answer to-- very", "start": 402.49, "duration": 2.67}, {"text": "fundamental things.", "start": 405.16, "duration": 0.96}, {"text": "Let's take as an example,\nhow does the brain work?", "start": 406.12, "duration": 3.72}, {"text": "Obviously, the brain computes\nin a certain fashion.", "start": 409.84, "duration": 2.34}, {"text": "And we've made good\nprogress, you can argue,", "start": 416.19, "duration": 2.37}, {"text": "with machine learning and all\nof those things that have very--", "start": 418.56, "duration": 5.47}, {"text": "very powerful and\ndoing very cool things.", "start": 424.03, "duration": 2.06}, {"text": "But I would also say that at\nsome deeper level, the methods", "start": 426.09, "duration": 8.94}, {"text": "that we have so far don't allow\nus to understand creativity.", "start": 435.03, "duration": 8.22}, {"text": "We're not close to being able to\ncreate a computer program that", "start": 443.25, "duration": 4.11}, {"text": "can do mathematics\nor that can do", "start": 447.36, "duration": 2.19}, {"text": "many of the creative\nkinds of things", "start": 449.55, "duration": 1.71}, {"text": "that human beings can do.", "start": 451.26, "duration": 1.14}, {"text": "I think machine learning,\npowerful as it is,", "start": 454.95, "duration": 2.22}, {"text": "is really successful only for\na very narrow set of tasks.", "start": 457.17, "duration": 4.63}, {"text": "And so I think there's probably\nsomething deeper and more", "start": 461.8, "duration": 7.07}, {"text": "fundamental going on\nthat we're missing.", "start": 468.87, "duration": 2.19}, {"text": "That would be my hunch.", "start": 471.06, "duration": 1.83}, {"text": "Now, whether something like\ntheoretical computer science is", "start": 472.89, "duration": 3.78}, {"text": "going to give you an answer\nthere-- or this kind of theory,", "start": 476.67, "duration": 2.46}, {"text": "or some kind of theory--", "start": 479.13, "duration": 1.68}, {"text": "I think some kind of theory\nhas at least a decent shot", "start": 480.81, "duration": 3.69}, {"text": "at playing a role in helping\nus to understand computation", "start": 484.5, "duration": 3.18}, {"text": "in a deeper way.", "start": 487.68, "duration": 1.56}, {"text": "And the fact that we can't\nunderstand something as basic", "start": 489.24, "duration": 2.73}, {"text": "as, can you factor a big\nnumber quickly or not?", "start": 491.97, "duration": 4.29}, {"text": "You can't really say you\nunderstand computation", "start": 496.26, "duration": 2.34}, {"text": "until you can answer\nquestions like that.", "start": 498.6, "duration": 3.16}, {"text": "So I would argue that\nwe have a really very", "start": 501.76, "duration": 2.45}, {"text": "primitive understanding of\ncomputation at this stage", "start": 504.21, "duration": 2.88}, {"text": "and that there is a lot that\nhas yet to be discovered,", "start": 507.09, "duration": 5.4}, {"text": "not just on the\ntechnological side,", "start": 512.49, "duration": 1.679}, {"text": "but just on the very fundamental\ntheoretical side that", "start": 514.169, "duration": 2.701}, {"text": "has a real shot at playing\na role in affecting", "start": 516.87, "duration": 2.46}, {"text": "the practice of how\nwe use computers.", "start": 519.33, "duration": 3.27}, {"text": "And so I think for\nthat reason-- again,", "start": 522.6, "duration": 2.07}, {"text": "I'm not sure what kind of theory\nis going to be the most useful,", "start": 524.67, "duration": 2.67}, {"text": "but the theory we're going\nto cover in this course", "start": 527.34, "duration": 2.22}, {"text": "is a particularly\nelegant theory,", "start": 529.56, "duration": 1.71}, {"text": "and it has already paid\noff in many applications", "start": 531.27, "duration": 2.97}, {"text": "and in terms of our\nunderstanding of computation.", "start": 534.24, "duration": 2.62}, {"text": "And I think, at least\nas a starting point,", "start": 536.86, "duration": 3.5}, {"text": "it's a good subject to learn.", "start": 540.36, "duration": 3.63}, {"text": "Certainly, I enjoy it, and\nI've spent a good chunk", "start": 543.99, "duration": 2.97}, {"text": "of my career doing that.", "start": 546.96, "duration": 4.18}, {"text": "So let's move on then and begin\nwith the subject material.", "start": 551.14, "duration": 13.63}, {"text": "So we're going to talk\nabout models of computation,", "start": 564.77, "duration": 5.0}, {"text": "as I mentioned.", "start": 569.77, "duration": 1.71}, {"text": "We want to try to\nunderstand computers,", "start": 571.48, "duration": 2.83}, {"text": "and we want to understand\nwhat computers can do.", "start": 574.31, "duration": 2.0}, {"text": "But computers in the real world\nare pretty complicated objects,", "start": 576.31, "duration": 2.85}, {"text": "and they're really not nice\nto talk about mathematically.", "start": 579.16, "duration": 2.74}, {"text": "So we're going to talk about\nabstract models of computers", "start": 581.9, "duration": 3.05}, {"text": "that are much simpler\nbut really capture--", "start": 584.95, "duration": 2.55}, {"text": "just like models in general--", "start": 587.5, "duration": 1.59}, {"text": "capture the important\naspects of the thing", "start": 589.09, "duration": 2.22}, {"text": "we're trying to understand.", "start": 591.31, "duration": 2.25}, {"text": "And so we're going to look\nat several different kinds", "start": 593.56, "duration": 3.87}, {"text": "of models that vary in their\ncapabilities and the way", "start": 597.43, "duration": 3.12}, {"text": "they approximate\nthe real computers", "start": 600.55, "duration": 3.35}, {"text": "that we deal with every day.", "start": 603.9, "duration": 1.81}, {"text": "And for starters, we're going\nto look at a very simple model", "start": 605.71, "duration": 4.49}, {"text": "called the finite automaton.", "start": 610.2, "duration": 1.8}, {"text": "And that's going to represent--", "start": 612.0, "duration": 3.21}, {"text": "you can think of it as\nrepresenting a computer that", "start": 615.21, "duration": 2.16}, {"text": "has a very small\namount of memory", "start": 617.37, "duration": 3.3}, {"text": "and a very limited and\nsmall amount of memory.", "start": 620.67, "duration": 2.52}, {"text": "And we're going to look\nat the capabilities", "start": 623.19, "duration": 1.86}, {"text": "of those kinds of machines.", "start": 625.05, "duration": 1.56}, {"text": "And what's nice about them is\nthat you can understand them", "start": 626.61, "duration": 2.46}, {"text": "very well.", "start": 629.07, "duration": 1.63}, {"text": "And so more powerful models that\nwe're going to look at later", "start": 630.7, "duration": 5.06}, {"text": "are going to be harder to\nunderstand in as deep a way.", "start": 635.76, "duration": 3.09}, {"text": "But for these, we can develop\na very comprehensive theory.", "start": 638.85, "duration": 7.165}, {"text": "And so that's what we're going\nto do for the next lecture", "start": 646.015, "duration": 2.375}, {"text": "and a half.", "start": 648.39, "duration": 2.15}, {"text": "So I'm starting off\nwith an example.", "start": 650.54, "duration": 2.83}, {"text": "I'm presenting a finite\nautomaton as a diagram--", "start": 653.37, "duration": 5.06}, {"text": "we call it a state diagram.", "start": 658.43, "duration": 1.62}, {"text": "It has these circles and\nlines and labels on the lines", "start": 660.05, "duration": 7.62}, {"text": "and also on these circles.", "start": 667.67, "duration": 2.05}, {"text": "So what's going on here?", "start": 669.72, "duration": 1.83}, {"text": "So this is a finite automaton.", "start": 671.55, "duration": 1.67}, {"text": "I'm giving it the name M1.", "start": 673.22, "duration": 1.74}, {"text": "And it has-- these\ncircles are called states.", "start": 674.96, "duration": 7.11}, {"text": "So in this case, there were\nthree states, q1, q2, and q3.", "start": 682.07, "duration": 3.17}, {"text": "Those are the labels there.", "start": 685.24, "duration": 1.68}, {"text": "There are arrows connecting\nstates with each other.", "start": 686.92, "duration": 4.78}, {"text": "So these we'll call transitions.", "start": 691.7, "duration": 2.99}, {"text": "And they're going\nto tell you how", "start": 694.69, "duration": 1.74}, {"text": "to compute with this device.", "start": 696.43, "duration": 2.52}, {"text": "And there's going to be a\nspecially-designated starting", "start": 698.95, "duration": 3.3}, {"text": "state, which has an arrow\ncoming in from nowhere.", "start": 702.25, "duration": 5.16}, {"text": "And there are other\nspecially-designated states", "start": 707.41, "duration": 3.39}, {"text": "called accepting\nstates, and that's", "start": 710.8, "duration": 1.59}, {"text": "going to have to do with\nhow the machine computes.", "start": 712.39, "duration": 2.1}, {"text": "But those are the ones that\nhave these double circles.", "start": 714.49, "duration": 3.21}, {"text": "And so talking about\nthe way it computes,", "start": 717.7, "duration": 3.03}, {"text": "the idea is pretty simple.", "start": 720.73, "duration": 2.14}, {"text": "The input is going to\nbe some finite string", "start": 722.87, "duration": 2.12}, {"text": "of 0's and 1's, in this case.", "start": 724.99, "duration": 1.87}, {"text": "We might have other types\nof symbols that are allowed", "start": 726.86, "duration": 2.75}, {"text": "for other automata, but the\nexample that I have here,", "start": 729.61, "duration": 4.08}, {"text": "it's going to be 0's and 1's.", "start": 733.69, "duration": 2.2}, {"text": "And the way you\ncompute with the thing", "start": 735.89, "duration": 1.85}, {"text": "is you first put your finger--", "start": 737.74, "duration": 3.04}, {"text": "which I can't do on Zoom,\nso I'll use the pointer--", "start": 740.78, "duration": 3.95}, {"text": "you put your pointer\non the starting state,", "start": 744.73, "duration": 2.64}, {"text": "the one that has the arrow\ncoming in from nowhere.", "start": 747.37, "duration": 3.06}, {"text": "First, you put\nyour pointer there.", "start": 750.43, "duration": 3.45}, {"text": "And then are you\nstart reading symbols", "start": 753.88, "duration": 3.76}, {"text": "from the input,\none after the next.", "start": 757.64, "duration": 2.53}, {"text": "So let's take an\nexample here, 01101.", "start": 760.17, "duration": 4.01}, {"text": "So you start reading\nthose symbols,", "start": 764.18, "duration": 2.61}, {"text": "and you follow\nthose transitions.", "start": 766.79, "duration": 2.02}, {"text": "So you go 0--", "start": 768.81, "duration": 2.09}, {"text": "and you go back\nto the same state.", "start": 770.9, "duration": 1.65}, {"text": "Then you go-- the\nnext symbol is a 1,", "start": 772.55, "duration": 2.34}, {"text": "so you go over to this\nstate, from q1 to q2.", "start": 774.89, "duration": 4.02}, {"text": "Now you have another\none that comes in.", "start": 778.91, "duration": 2.2}, {"text": "So now you're starting at\nq2, you have another one,", "start": 781.11, "duration": 2.66}, {"text": "so you follow its\nassociated transition.", "start": 783.77, "duration": 2.38}, {"text": "So if you notice,\nevery state has", "start": 786.15, "duration": 3.56}, {"text": "an outgoing transition for 1\nand another outgoing transition", "start": 789.71, "duration": 3.93}, {"text": "for 0.", "start": 793.64, "duration": 0.69}, {"text": "So there's always somewhere to\ngo every time you read symbols", "start": 794.33, "duration": 3.36}, {"text": "from the input.", "start": 797.69, "duration": 0.97}, {"text": "So now you're at q2.", "start": 798.66, "duration": 1.61}, {"text": "You read that next, that\nthird symbol, which is a 1.", "start": 800.27, "duration": 3.15}, {"text": "That's going to\ntake you over to q3.", "start": 803.42, "duration": 2.34}, {"text": "And now you have a\n0, which loops you", "start": 805.76, "duration": 2.28}, {"text": "back to where you were, and\nanother 1, which loops you", "start": 808.04, "duration": 4.8}, {"text": "back to where you were.", "start": 812.84, "duration": 1.17}, {"text": "And because you ended\nup at an accept,", "start": 814.01, "duration": 5.91}, {"text": "you say we accept that string.", "start": 819.92, "duration": 4.26}, {"text": "So that's going to be the\noutput of this finite automaton.", "start": 824.18, "duration": 4.92}, {"text": "For each string,\nit's either going", "start": 829.1, "duration": 1.74}, {"text": "to accept it or reject it.", "start": 830.84, "duration": 1.81}, {"text": "So it's just a binary decision\nthat is going to be made.", "start": 832.65, "duration": 2.97}, {"text": "It's sort of like\na 1 or a 0 output,", "start": 835.62, "duration": 1.79}, {"text": "but we're calling\nit accept or reject.", "start": 837.41, "duration": 2.44}, {"text": "So this one here,\nbecause it ended up", "start": 839.85, "duration": 3.23}, {"text": "at the accepting\nstate, is accepted.", "start": 843.08, "duration": 2.35}, {"text": "But if you look at the\nsecond example, 00101,", "start": 845.43, "duration": 5.13}, {"text": "so you're going to\nhave 0, 0, 1, 0, 1.", "start": 850.56, "duration": 5.75}, {"text": "Now we ended up at q2.", "start": 856.31, "duration": 2.19}, {"text": "That's not an accepting state.", "start": 858.5, "duration": 2.26}, {"text": "So therefore, we say\nwe reject this input.", "start": 860.76, "duration": 4.59}, {"text": "OK?", "start": 865.35, "duration": 0.5}, {"text": "Very simple.", "start": 865.85, "duration": 1.69}, {"text": "And now, for example,\none of the questions", "start": 867.54, "duration": 1.85}, {"text": "you might want to ask,\ngiven one of these things,", "start": 869.39, "duration": 2.042}, {"text": "is, well, which are\nexactly those strings", "start": 871.432, "duration": 2.668}, {"text": "that the machine accepts?", "start": 874.1, "duration": 2.46}, {"text": "And a little bit of\nthought will help", "start": 876.56, "duration": 6.17}, {"text": "you understand that\nthe only strings which", "start": 882.73, "duration": 3.33}, {"text": "are going to take you over\nto q3 are those strings that", "start": 886.06, "duration": 2.94}, {"text": "have a 11 appearing\nsomewhere along the way, two", "start": 889.0, "duration": 3.51}, {"text": "consecutive 1's, and you will\nend up at the accepting state.", "start": 892.51, "duration": 3.3}, {"text": "I encourage you to think\nabout that for a minute", "start": 898.82, "duration": 2.36}, {"text": "if not immediately obvious.", "start": 901.18, "duration": 1.71}, {"text": "But those are the\nstrings that are going", "start": 902.89, "duration": 2.28}, {"text": "to be accepted by this machine.", "start": 905.17, "duration": 3.3}, {"text": "And we call that\ncollection of strings", "start": 908.47, "duration": 3.39}, {"text": "the language of the machine.", "start": 911.86, "duration": 3.82}, {"text": "So that set A of\nthose strings that", "start": 915.68, "duration": 4.2}, {"text": "have a 11, for this particular\nmachine, is the language of M1.", "start": 919.88, "duration": 4.8}, {"text": "We also say that M1 recognizes\nthat language, recognizes A.", "start": 924.68, "duration": 5.32}, {"text": "And in terms of notation,\nwe write that A is L of M1.", "start": 930.0, "duration": 4.46}, {"text": "A is the language of M1.", "start": 934.46, "duration": 1.83}, {"text": "So the language of a machine\nis exactly the set of strings", "start": 936.29, "duration": 3.18}, {"text": "that machine accepts.", "start": 939.47, "duration": 3.34}, {"text": "OK?", "start": 942.81, "duration": 1.185}, {"text": "So one of the first things we're\ngoing to want to be able to do", "start": 943.995, "duration": 2.625}, {"text": "is take a machine\nand understand what", "start": 946.62, "duration": 2.1}, {"text": "its language is, what's\nthe set of strings", "start": 948.72, "duration": 1.86}, {"text": "that that machine accepts.", "start": 950.58, "duration": 1.32}, {"text": "Another thing we might want\nto do is, given a language,", "start": 951.9, "duration": 2.4}, {"text": "build a machine which\nrecognizes that language.", "start": 954.3, "duration": 5.07}, {"text": "And then understanding, what\nare the class of languages?", "start": 959.37, "duration": 2.61}, {"text": "Can you get any language\nfrom some machine,", "start": 961.98, "duration": 2.058}, {"text": "or are there going to be some\nlanguages that you can do", "start": 964.038, "duration": 2.292}, {"text": "and other languages\nthat you cannot do?", "start": 966.33, "duration": 1.842}, {"text": "So those are the\nkinds of questions", "start": 968.172, "duration": 1.458}, {"text": "we're going to be asking\nabout these finite automata.", "start": 969.63, "duration": 2.91}, {"text": "What kinds of things\ncan those machines do,", "start": 972.54, "duration": 2.64}, {"text": "and what can they not do?", "start": 975.18, "duration": 3.06}, {"text": "OK.", "start": 978.24, "duration": 2.28}, {"text": "Here's our next check-in.", "start": 980.52, "duration": 3.045}, {"text": "So wake up, everybody\nwho's not paying attention.", "start": 987.3, "duration": 3.66}, {"text": "A check-in is coming.", "start": 990.96, "duration": 2.22}, {"text": "So we have more\nquestions, though I", "start": 993.18, "duration": 1.77}, {"text": "can't keep-- are these\nthree statements equivalent?", "start": 994.95, "duration": 4.6}, {"text": "What three statements?", "start": 999.55, "duration": 3.18}, {"text": "AUDIENCE: At the\nbottom of the slide.", "start": 1002.73, "duration": 2.85}, {"text": "MICHAEL SIPSER: Oh,\noh, oh, oh, oh, yes.", "start": 1005.58, "duration": 1.77}, {"text": "Those three are equivalent.", "start": 1007.35, "duration": 2.22}, {"text": "A is the language-- yeah,\nthose mean the same thing.", "start": 1009.57, "duration": 2.44}, {"text": "Not only are they equivalent,\nbut they're just different ways", "start": 1012.01, "duration": 2.78}, {"text": "of saying the same thing.", "start": 1014.79, "duration": 2.94}, {"text": "That M1 recognizes\nthe language is", "start": 1017.73, "duration": 1.92}, {"text": "the same as saying that's\nthe language of the machine", "start": 1019.65, "duration": 2.47}, {"text": "and that A equals\nthat L of M. That's", "start": 1022.12, "duration": 3.53}, {"text": "all the same way of saying they\nall-- six of one, half a dozen", "start": 1025.65, "duration": 3.66}, {"text": "of the other.", "start": 1029.31, "duration": 0.6}, {"text": "It's two ways of\nsaying the same thing.", "start": 1029.91, "duration": 2.429}, {"text": "OK, so let's pop up our\npoll and get that started.", "start": 1032.339, "duration": 5.976}, {"text": "Whoops.", "start": 1038.315, "duration": 0.5}, {"text": "Still showing the old\none-- oh, here we go.", "start": 1041.43, "duration": 2.34}, {"text": "Move it to the next question.", "start": 1043.77, "duration": 2.245}, {"text": "OK.", "start": 1046.015, "duration": 0.5}, {"text": "OK, so you understand\nthe question here?", "start": 1051.81, "duration": 5.6}, {"text": "Where do we end up\nafter we read 101?", "start": 1057.41, "duration": 3.235}, {"text": "What state are we in?", "start": 1060.645, "duration": 0.875}, {"text": "Do we end up in\nstate q1, q2, or q3?", "start": 1066.28, "duration": 3.345}, {"text": "OK?", "start": 1072.3, "duration": 2.67}, {"text": "Go fast.", "start": 1074.97, "duration": 2.15}, {"text": "This is a--", "start": 1077.12, "duration": 0.66}, {"text": "OK, so I think we got\npretty much converged here.", "start": 1081.52, "duration": 6.68}, {"text": "I think almost\neverybody got it right.", "start": 1088.2, "duration": 4.08}, {"text": "The answer is indeed that\nyou ended up in state q2.", "start": 1092.28, "duration": 4.2}, {"text": "Because you go 1,\n0, 1, and that's", "start": 1096.48, "duration": 3.3}, {"text": "where you ended up, in state q2.", "start": 1099.78, "duration": 1.77}, {"text": "So is this string accepted?", "start": 1101.55, "duration": 2.64}, {"text": "No, because you didn't\nend up at an accept state.", "start": 1104.19, "duration": 3.03}, {"text": "So this machine rejects 101.", "start": 1107.22, "duration": 3.3}, {"text": "OK, let's keep going.", "start": 1110.52, "duration": 4.53}, {"text": "So now-- yeah.", "start": 1115.05, "duration": 3.56}, {"text": "OK, so now we gave\nit this informal idea", "start": 1121.68, "duration": 3.42}, {"text": "of a finite automaton.", "start": 1125.1, "duration": 1.32}, {"text": "We're going to have to try to\nget a formal definition now,", "start": 1126.42, "duration": 2.88}, {"text": "which is going to be a more\nmathematical way of saying", "start": 1129.3, "duration": 3.27}, {"text": "the same thing that I just said.", "start": 1132.57, "duration": 3.68}, {"text": "And the reason for having\na formal definition", "start": 1136.25, "duration": 2.88}, {"text": "is, for one thing, it allows\nus to be very precise.", "start": 1139.13, "duration": 3.24}, {"text": "Then we'll know exactly what\nwe mean by a finite automaton,", "start": 1142.37, "duration": 2.91}, {"text": "and it should answer any\nquestions about what counts", "start": 1145.28, "duration": 2.19}, {"text": "and what doesn't count.", "start": 1147.47, "duration": 1.32}, {"text": "It also is a way of\nproviding notation.", "start": 1148.79, "duration": 4.18}, {"text": "So it'll help us\ndescribe finite automata.", "start": 1152.97, "duration": 2.57}, {"text": "And sometimes there might be an\nautomaton where the picture is", "start": 1155.54, "duration": 4.32}, {"text": "just too big, so you might\nwant to be able to describe it", "start": 1159.86, "duration": 2.67}, {"text": "in some mathematical\nterminology rather", "start": 1162.53, "duration": 3.0}, {"text": "than by giving a picture.", "start": 1165.53, "duration": 1.14}, {"text": "Or maybe you're\ngoing to be asked", "start": 1166.67, "duration": 1.375}, {"text": "to give a family\nof automata, where", "start": 1168.045, "duration": 2.915}, {"text": "there is going to be a\nparameter, N, associated", "start": 1170.96, "duration": 4.44}, {"text": "with the class of\nlanguages you're trying", "start": 1175.4, "duration": 2.79}, {"text": "to describe with the automaton.", "start": 1178.19, "duration": 1.65}, {"text": "And then it'll be more\nhelpful to describe it", "start": 1179.84, "duration": 3.03}, {"text": "in this formal notation rather\nthan as a kind of a picture,", "start": 1182.87, "duration": 4.05}, {"text": "because it might be\ninfinitely many pictures that", "start": 1186.92, "duration": 3.06}, {"text": "are being needed.", "start": 1189.98, "duration": 2.02}, {"text": "So maybe examples of\nthat will come up now.", "start": 1192.0, "duration": 3.42}, {"text": "So a finite automaton,\nwe call it a 5-tuple.", "start": 1195.42, "duration": 3.11}, {"text": "Don't be put off by that.", "start": 1198.53, "duration": 1.5}, {"text": "A 5-tuple is just a\nlist of five things.", "start": 1200.03, "duration": 2.46}, {"text": "So a finite automaton,\nin our definition,", "start": 1202.49, "duration": 3.99}, {"text": "is going to have\nfive components.", "start": 1206.48, "duration": 2.61}, {"text": "It's going to have\nQ, which is going", "start": 1209.09, "duration": 2.88}, {"text": "to be a finite set\nof states, so it's", "start": 1211.97, "duration": 1.68}, {"text": "going to be a finite set,\nwhich we'll designate", "start": 1213.65, "duration": 3.75}, {"text": "as the states of the automaton.", "start": 1217.4, "duration": 2.49}, {"text": "Sigma is the alphabet\nsymbols of the automaton,", "start": 1219.89, "duration": 3.15}, {"text": "another finite set.", "start": 1223.04, "duration": 1.2}, {"text": "Delta is the\ntransition function.", "start": 1226.79, "duration": 2.67}, {"text": "That tells us how the automaton\nmoves from state to state.", "start": 1229.46, "duration": 3.84}, {"text": "Those describes how\nthose transition arrows--", "start": 1233.3, "duration": 4.35}, {"text": "those arrows which connected\nthe states with each other--", "start": 1237.65, "duration": 3.76}, {"text": "it describes them in\na mathematical way", "start": 1241.41, "duration": 1.88}, {"text": "instead in terms of a picture.", "start": 1243.29, "duration": 2.22}, {"text": "And the way I'm doing\nthat is with a function.", "start": 1245.51, "duration": 2.74}, {"text": "So delta is a function\nwhich takes two things.", "start": 1248.25, "duration": 3.18}, {"text": "So I'm hoping you've seen\nthis notation before.", "start": 1251.43, "duration": 2.36}, {"text": "I'll help you through\nit once, but this", "start": 1253.79, "duration": 2.712}, {"text": "is the kind of\nthing I would expect", "start": 1256.502, "duration": 1.458}, {"text": "you to have seen already.", "start": 1257.96, "duration": 1.33}, {"text": "So we have Q cross sigma.", "start": 1259.29, "duration": 2.63}, {"text": "So I'm going to give delta a\nstate and an alphabet symbol.", "start": 1261.92, "duration": 7.23}, {"text": "So Q is states, sigma\nis alphabet symbols.", "start": 1269.15, "duration": 2.73}, {"text": "So you're going to get a\nstate and an alphabet symbol,", "start": 1271.88, "duration": 3.63}, {"text": "and it's going to\ngive you back a state.", "start": 1275.51, "duration": 2.53}, {"text": "So describing it kind of\na little bit more detail,", "start": 1278.04, "duration": 8.94}, {"text": "delta, if you give it state\nq and symbol a equals r,", "start": 1286.98, "duration": 6.42}, {"text": "that means q, when you\nread an a, you go to r.", "start": 1293.4, "duration": 4.61}, {"text": "So that's the way this\npicture gets translated", "start": 1298.01, "duration": 2.94}, {"text": "into a mathematical\nfunction, which", "start": 1300.95, "duration": 3.54}, {"text": "describes those transitions.", "start": 1304.49, "duration": 2.93}, {"text": "And then now q0 is going\nto be the starting state.", "start": 1307.42, "duration": 3.18}, {"text": "That's the one with the\narrow coming in from nowhere.", "start": 1310.6, "duration": 2.46}, {"text": "And F is the set of\naccepting states.", "start": 1313.06, "duration": 3.45}, {"text": "So there's only going to\nbe one starting state,", "start": 1316.51, "duration": 2.85}, {"text": "but there might be\nseveral different--", "start": 1319.36, "duration": 1.62}, {"text": "or possibly even 0--", "start": 1320.98, "duration": 1.47}, {"text": "accepting states.", "start": 1322.45, "duration": 1.05}, {"text": "That's all legal when we\nhave a finite automaton.", "start": 1323.5, "duration": 4.05}, {"text": "And so in terms of\nusing the notation--", "start": 1327.55, "duration": 1.97}, {"text": "going back to the machine that\nwe just had from the previous", "start": 1329.52, "duration": 2.5}, {"text": "slide, which I've\ngiven you here again--", "start": 1332.02, "duration": 2.22}, {"text": "let me show you how\nI would describe", "start": 1334.24, "duration": 1.5}, {"text": "this using this notation that\ncomes out of the definition.", "start": 1335.74, "duration": 3.22}, {"text": "So here is M1 again.", "start": 1338.96, "duration": 2.09}, {"text": "It's this 5-tuple where Q\nnow is the set-- q1, q2, q3--", "start": 1341.05, "duration": 5.28}, {"text": "that's the set of states.", "start": 1346.33, "duration": 3.15}, {"text": "The input alphabet is 0, 1.", "start": 1349.48, "duration": 2.73}, {"text": "It might vary in other automata.", "start": 1352.21, "duration": 2.52}, {"text": "And f is the set q3,\nwhich has only the element", "start": 1354.73, "duration": 3.45}, {"text": "q3, because this has just\none accept state, q3.", "start": 1358.18, "duration": 4.86}, {"text": "So I hope that's helpful.", "start": 1363.04, "duration": 3.04}, {"text": "Oh, of course, I forgot the\ntransition function, which", "start": 1366.08, "duration": 3.35}, {"text": "here I'm describing as a table.", "start": 1369.43, "duration": 2.29}, {"text": "So the transition\nfunction says if you", "start": 1371.72, "duration": 6.71}, {"text": "have a state and\nan input alphabet,", "start": 1378.43, "duration": 3.15}, {"text": "you can look up in\nthe table where you're", "start": 1381.58, "duration": 2.49}, {"text": "supposed to go under\nthe transition function", "start": 1384.07, "duration": 2.67}, {"text": "according to the state\nand the alphabet symbol", "start": 1386.74, "duration": 5.7}, {"text": "that you're given.", "start": 1392.44, "duration": 1.39}, {"text": "So, for example, if we were\nin state q2 here getting a 0,", "start": 1393.83, "duration": 8.9}, {"text": "then q2 goes back to q1\nso that q2 on 0 is q1.", "start": 1402.73, "duration": 4.86}, {"text": "But q2 on 1 here is q3.", "start": 1407.59, "duration": 4.49}, {"text": "OK?", "start": 1412.08, "duration": 0.5}, {"text": "So that's how that table\ncaptures this picture.", "start": 1412.58, "duration": 4.41}, {"text": "OK?", "start": 1416.99, "duration": 0.548}, {"text": "And it's just a function.", "start": 1417.538, "duration": 1.042}, {"text": "It's a way of representing a\nfunction, a finite function,", "start": 1418.58, "duration": 6.78}, {"text": "in terms of this table here.", "start": 1425.36, "duration": 3.07}, {"text": "So I realize, for some\nof you, this may be slow.", "start": 1428.43, "duration": 5.49}, {"text": "We will ramp up\nin speed, but I'm", "start": 1433.92, "duration": 1.49}, {"text": "trying to get us all\ntogether in terms", "start": 1435.41, "duration": 2.37}, {"text": "of the language of the\ncourse here at the beginning.", "start": 1437.78, "duration": 3.84}, {"text": "OK, so now let's\ntalk about some more", "start": 1441.62, "duration": 6.18}, {"text": "the computation, so\nstrings and languages.", "start": 1447.8, "duration": 7.33}, {"text": "A string is just\na finite sequence", "start": 1455.13, "duration": 1.53}, {"text": "of symbols from the alphabet.", "start": 1456.66, "duration": 1.83}, {"text": "This class is not going to\ntalk about infinite strings.", "start": 1461.73, "duration": 3.27}, {"text": "All of our strings are\ngoing to be finite.", "start": 1465.0, "duration": 3.49}, {"text": "There's other mathematical\ntheories of automata", "start": 1468.49, "duration": 2.84}, {"text": "and so on that talk\nabout infinite inputs", "start": 1471.33, "duration": 1.95}, {"text": "and infinite strings.", "start": 1473.28, "duration": 0.93}, {"text": "We're not going to\ntalk about that.", "start": 1474.21, "duration": 1.59}, {"text": "Maybe rarely, we'll\nmake it very clear,", "start": 1479.12, "duration": 2.64}, {"text": "we'll talk about\nan infinite string,", "start": 1481.76, "duration": 1.5}, {"text": "but that's going\nto be an exception.", "start": 1483.26, "duration": 2.88}, {"text": "And a language is\na set of strings.", "start": 1486.14, "duration": 2.59}, {"text": "That's the traditional way\nthat people in this subject", "start": 1488.73, "duration": 7.46}, {"text": "refer to a set of strings.", "start": 1496.19, "duration": 1.32}, {"text": "They call it a language--\nreally because the subject", "start": 1497.51, "duration": 2.76}, {"text": "had its roots in\nlinguistics, actually.", "start": 1500.27, "duration": 2.688}, {"text": "And they were talking\nabout-- they're", "start": 1502.958, "duration": 1.542}, {"text": "trying to understand\nlanguages, human languages.", "start": 1504.5, "duration": 4.12}, {"text": "So this is just a\nhistorical fact,", "start": 1508.62, "duration": 1.88}, {"text": "and that's the\nterminology that's stuck.", "start": 1510.5, "duration": 2.73}, {"text": "OK, so two special string--", "start": 1513.23, "duration": 2.31}, {"text": "a special string and\na special language.", "start": 1515.54, "duration": 2.31}, {"text": "The empty string is\nthe string of length 0.", "start": 1517.85, "duration": 2.55}, {"text": "This is a totally\nlegitimate string", "start": 1520.4, "duration": 2.64}, {"text": "that you are going to\nrun into now and then.", "start": 1523.04, "duration": 2.31}, {"text": "And there's the\nempty language, which", "start": 1525.35, "duration": 1.86}, {"text": "is the set with no strings.", "start": 1527.21, "duration": 2.53}, {"text": "These are not the same.", "start": 1529.74, "duration": 1.57}, {"text": "They're not even of the\nsame type of object.", "start": 1531.31, "duration": 2.73}, {"text": "So don't confuse them\nwith one another.", "start": 1534.04, "duration": 3.18}, {"text": "I mean, you can have\na set, a language,", "start": 1537.22, "duration": 2.78}, {"text": "which has just one element,\nwhich is the empty string.", "start": 1540.0, "duration": 3.03}, {"text": "That is not the empty set.", "start": 1543.03, "duration": 1.65}, {"text": "That is a set-- that is\nnot the empty language.", "start": 1544.68, "duration": 2.19}, {"text": "That is a language that\nhas one element in it,", "start": 1546.87, "duration": 2.53}, {"text": "namely, the empty string.", "start": 1549.4, "duration": 1.61}, {"text": "So those are separate things.", "start": 1551.01, "duration": 3.01}, {"text": "OK, so here's a little bit of\na mouthful here on the slide,", "start": 1554.02, "duration": 4.41}, {"text": "defining what it means for an\nautomaton to accept its input--", "start": 1558.43, "duration": 5.16}, {"text": "accepts its input string w.", "start": 1563.59, "duration": 3.35}, {"text": "And we can define that formally.", "start": 1566.94, "duration": 1.68}, {"text": "And it's a little\ntechnical looking,", "start": 1568.62, "duration": 2.64}, {"text": "it's really not that bad.", "start": 1571.26, "duration": 2.89}, {"text": "So if you have your\ninput string w,", "start": 1574.15, "duration": 3.59}, {"text": "which you can write as\na sequence of symbols", "start": 1577.74, "duration": 2.13}, {"text": "in the alphabet-- w1, w2, dot\ndot dot, wn, so like 01001.", "start": 1579.87, "duration": 6.87}, {"text": "I'm just writing it out\nsymbol by symbol here.", "start": 1586.74, "duration": 4.14}, {"text": "So what does it mean for the\nmachine to accept that input?", "start": 1590.88, "duration": 4.2}, {"text": "So that means that there's\na sequence of states", "start": 1595.08, "duration": 3.05}, {"text": "in the machine, sequence of\nstates of members of Q. So", "start": 1598.13, "duration": 5.895}, {"text": "a sequence from Q,\nthese are the states", "start": 1604.025, "duration": 1.625}, {"text": "of the machine that satisfy\nthese three properties down", "start": 1605.65, "duration": 4.8}, {"text": "here.", "start": 1610.45, "duration": 0.78}, {"text": "First of all-- and I'm\nthinking about the sequence", "start": 1611.23, "duration": 3.99}, {"text": "that the machine goes through\nas it's processing the input w.", "start": 1615.22, "duration": 6.76}, {"text": "So when does it accept w?", "start": 1621.98, "duration": 2.79}, {"text": "If that sequence has the feature\nthat it starts at the start", "start": 1624.77, "duration": 3.45}, {"text": "state, each state legally\nfollows the previous state", "start": 1628.22, "duration": 5.51}, {"text": "according to the\ntransition function.", "start": 1633.73, "duration": 3.69}, {"text": "So that says the i-th\nmember of the sequence", "start": 1637.42, "duration": 5.15}, {"text": "is obtained by looking\nat the previous one--", "start": 1642.57, "duration": 2.73}, {"text": "the i minus first member of\nthat sequence, the i minus", "start": 1645.3, "duration": 4.02}, {"text": "first state in that\nsequence-- and then", "start": 1649.32, "duration": 2.37}, {"text": "looking at what happens when\nyou take the i-th input symbol.", "start": 1651.69, "duration": 4.58}, {"text": "So as you look at the previous\nstate and the next input", "start": 1656.27, "duration": 3.06}, {"text": "symbol, you should\nget the next state.", "start": 1659.33, "duration": 1.828}, {"text": "That's all that this is saying.", "start": 1661.158, "duration": 1.292}, {"text": "And this should happen for\neach one of these guys.", "start": 1662.45, "duration": 3.18}, {"text": "And lastly, for\nthis to be accepted,", "start": 1665.63, "duration": 2.94}, {"text": "the very last member\nhere, where we ended up", "start": 1668.57, "duration": 2.4}, {"text": "at the end of the input--", "start": 1670.97, "duration": 1.9}, {"text": "so you only care about this\nat the end of the input--", "start": 1672.87, "duration": 2.3}, {"text": "you have to be in\nan accepting state.", "start": 1675.17, "duration": 3.61}, {"text": "So you can mathematically\ncapture this notion", "start": 1678.78, "duration": 2.51}, {"text": "of going along this path.", "start": 1681.29, "duration": 1.425}, {"text": "And that's what--", "start": 1685.6, "duration": 1.7}, {"text": "I'm just trying to illustrate\nthat we could describe", "start": 1687.3, "duration": 2.69}, {"text": "all this very formally--", "start": 1689.99, "duration": 1.0}, {"text": "I'm not saying that's the\nbest way to think about it all", "start": 1690.99, "duration": 1.77}, {"text": "the time--", "start": 1692.76, "duration": 0.6}, {"text": "but that it can be done.", "start": 1693.36, "duration": 1.99}, {"text": "And I think that's something\nworth appreciating.", "start": 1695.35, "duration": 3.89}, {"text": "OK.", "start": 1699.24, "duration": 1.62}, {"text": "So now in terms of, again,\ngetting back-- we've", "start": 1700.86, "duration": 2.25}, {"text": "said this once\nalready, but in terms", "start": 1703.11, "duration": 1.5}, {"text": "of the languages that\nthe machine recognizes,", "start": 1704.61, "duration": 2.4}, {"text": "it's the collection of strings\nthat the machine accepts.", "start": 1707.01, "duration": 3.7}, {"text": "Every machine accepts-- it\nmight accept many strings,", "start": 1710.71, "duration": 4.53}, {"text": "but it always recognizes\none particular language,", "start": 1715.24, "duration": 4.65}, {"text": "even if the machine\naccepts no strings--", "start": 1719.89, "duration": 1.85}, {"text": "then it recognizes\nthe empty language.", "start": 1721.74, "duration": 2.59}, {"text": "So a machine always\nrecognizes one language,", "start": 1724.33, "duration": 4.1}, {"text": "but it may have many, many\nstrings that it's accepting.", "start": 1728.43, "duration": 3.54}, {"text": "And we call that language\nthe language of the machine.", "start": 1731.97, "duration": 2.79}, {"text": "And we say that M\nrecognizes that language.", "start": 1734.76, "duration": 3.06}, {"text": "These three things\nmean the same thing.", "start": 1737.82, "duration": 1.83}, {"text": "OK?", "start": 1742.28, "duration": 0.6}, {"text": "And now important definition--", "start": 1742.88, "duration": 1.29}, {"text": "I try to reserve the\nmost important things", "start": 1744.17, "duration": 2.16}, {"text": "or the highlighted things to\nbe in this light blue color,", "start": 1746.33, "duration": 2.85}, {"text": "if you can see that.", "start": 1749.18, "duration": 1.35}, {"text": "We say a language is\na regular language", "start": 1750.53, "duration": 3.78}, {"text": "if there's some finite\nautomaton that recognizes it.", "start": 1754.31, "duration": 4.94}, {"text": "OK?", "start": 1759.25, "duration": 0.84}, {"text": "So there are going to be some\nlanguages that have associated", "start": 1760.09, "duration": 2.94}, {"text": "to them finite automata that\nactually solve those languages,", "start": 1763.03, "duration": 3.09}, {"text": "that recognize those languages.", "start": 1766.12, "duration": 1.47}, {"text": "But there might be\nother languages--", "start": 1767.59, "duration": 1.5}, {"text": "and we'll see examples-- where\nyou just can't solve them.", "start": 1769.09, "duration": 2.43}, {"text": "You can't recognize them\nwith a finite automaton.", "start": 1771.52, "duration": 2.46}, {"text": "Those languages will not\nbe regular languages.", "start": 1773.98, "duration": 2.46}, {"text": "The regular ones are\nthe ones that you", "start": 1776.44, "duration": 1.83}, {"text": "can do with a finite automaton.", "start": 1778.27, "duration": 1.83}, {"text": "That's the traditional\nterminology.", "start": 1780.1, "duration": 3.67}, {"text": "OK, so let's continue.", "start": 1783.77, "duration": 1.62}, {"text": "Let's go on from there.", "start": 1785.39, "duration": 1.06}, {"text": "So let's do a\ncouple of examples.", "start": 1786.45, "duration": 2.0}, {"text": "Here, again, is that same--", "start": 1788.45, "duration": 1.56}, {"text": "getting to be an old\nfriend, that automaton M1.", "start": 1790.01, "duration": 3.72}, {"text": "Remember, its language\nhere is the set", "start": 1796.28, "duration": 2.49}, {"text": "of strings that have\nthe substring 11.", "start": 1798.77, "duration": 3.75}, {"text": "That is that\nlanguage A. Now, what", "start": 1802.52, "duration": 5.53}, {"text": "do we know about A from\nthe previous slide?", "start": 1808.05, "duration": 4.52}, {"text": "Think with me.", "start": 1812.57, "duration": 1.12}, {"text": "Don't just listen.", "start": 1813.69, "duration": 1.13}, {"text": "A is a regular language\nnow, because it's", "start": 1814.82, "duration": 4.08}, {"text": "recognized by some automaton.", "start": 1818.9, "duration": 3.76}, {"text": "So whenever you\nfind an automaton", "start": 1822.66, "duration": 5.25}, {"text": "for a language, a finite\nautomaton for language,", "start": 1827.91, "duration": 2.22}, {"text": "we know that that language\nis a regular language.", "start": 1830.13, "duration": 4.438}, {"text": "So let's look at a\ncouple of more examples.", "start": 1834.568, "duration": 1.792}, {"text": "So if you take the language--", "start": 1836.36, "duration": 1.73}, {"text": "let's call this one B, which\nis the strings that have", "start": 1838.09, "duration": 4.26}, {"text": "an even number of 1's in them.", "start": 1842.35, "duration": 2.71}, {"text": "So like the string 1101,\nwould that be in B?", "start": 1845.06, "duration": 6.31}, {"text": "No, because it has\nan odd number of 1's.", "start": 1851.37, "duration": 2.7}, {"text": "So the string 1111\nhas four 1's in it.", "start": 1854.07, "duration": 3.79}, {"text": "That's an even number, so\nthat string would be in B.", "start": 1857.86, "duration": 2.87}, {"text": "The 0's don't matter\nfor this language.", "start": 1860.73, "duration": 3.27}, {"text": "So strings that have\nan even number of 1's,", "start": 1864.0, "duration": 9.76}, {"text": "that's a regular language.", "start": 1873.76, "duration": 2.76}, {"text": "And the way you would\nknow that is you", "start": 1876.52, "duration": 1.68}, {"text": "would have to make a\nfinite automaton that", "start": 1878.2, "duration": 2.19}, {"text": "recognizes that language.", "start": 1880.39, "duration": 1.36}, {"text": "And I would encourage you to\ngo and make that automaton.", "start": 1881.75, "duration": 3.68}, {"text": "You can do it with two states.", "start": 1885.43, "duration": 1.26}, {"text": "It's a very simple automaton.", "start": 1886.69, "duration": 1.59}, {"text": "But if you haven't had\npractice with these,", "start": 1888.28, "duration": 2.28}, {"text": "I encourage you to do that.", "start": 1890.56, "duration": 1.51}, {"text": "And actually, there\nare lots of examples", "start": 1892.07, "duration": 2.15}, {"text": "that I ask you to solve at the\nend of chapter 1 in the book,", "start": 1894.22, "duration": 4.71}, {"text": "and you definitely should\nspend some time playing with it", "start": 1898.93, "duration": 3.39}, {"text": "if you have not yet seen\nfinite automata before.", "start": 1902.32, "duration": 5.13}, {"text": "You need to get comfortable with\nthese and be able to make them.", "start": 1907.45, "duration": 3.34}, {"text": "So we're going to start\nmaking some of them,", "start": 1910.79, "duration": 2.367}, {"text": "but we're going to\nbe talking about it", "start": 1913.157, "duration": 1.583}, {"text": "at a sort of a more\nabstract level in a minute.", "start": 1914.74, "duration": 2.01}, {"text": "Basically, the reason why\nyou can solve this problem,", "start": 1919.71, "duration": 3.51}, {"text": "you can make a finite automaton\nwhich recognizes the language", "start": 1923.22, "duration": 4.32}, {"text": "B, is because that\nfinite automaton", "start": 1927.54, "duration": 2.31}, {"text": "is going to keep track of the\nparity of the number of 1's", "start": 1929.85, "duration": 4.74}, {"text": "it's seen before.", "start": 1934.59, "duration": 1.53}, {"text": "This has two states,\none of them remembering", "start": 1936.12, "duration": 2.288}, {"text": "that it's seen an odd\nnumber of 1's so far,", "start": 1938.408, "duration": 1.792}, {"text": "the other one\nremembering it's seen", "start": 1940.2, "duration": 1.458}, {"text": "an even number of 1's before.", "start": 1941.658, "duration": 2.422}, {"text": "And that's going to be\ntypical for these automata,", "start": 1944.08, "duration": 2.3}, {"text": "finite automata.", "start": 1946.38, "duration": 1.11}, {"text": "There's going to be several\ndifferent possibilities", "start": 1947.49, "duration": 2.64}, {"text": "that you may have to keep track\nof as you're reading the input,", "start": 1950.13, "duration": 3.93}, {"text": "and there's going to\nbe a state associated", "start": 1954.06, "duration": 2.28}, {"text": "with each one of\nthose possibilities.", "start": 1956.34, "duration": 2.45}, {"text": "So if you're designing\nan automaton,", "start": 1958.79, "duration": 1.94}, {"text": "you have to think about--", "start": 1960.73, "duration": 1.47}, {"text": "as you're processing the input--", "start": 1962.2, "duration": 1.83}, {"text": "what things you have\nto keep track of.", "start": 1964.03, "duration": 1.62}, {"text": "And you're going to make\na state for each one", "start": 1965.65, "duration": 1.875}, {"text": "of those possibilities.", "start": 1967.525, "duration": 1.945}, {"text": "OK?", "start": 1969.47, "duration": 0.5}, {"text": "So you need to get\ncomfortable with that.", "start": 1969.97, "duration": 4.26}, {"text": "Let's look at another example,\nthe language C where the inputs", "start": 1974.23, "duration": 4.71}, {"text": "have an equal number\nof 0's and 1's.", "start": 1978.94, "duration": 3.7}, {"text": "That turns out to be\nnot a regular language.", "start": 1982.64, "duration": 4.12}, {"text": "So, in other words,\nwhat that means", "start": 1986.76, "duration": 2.45}, {"text": "is there's no way to\nrecognize that language", "start": 1989.21, "duration": 3.21}, {"text": "with a finite automaton.", "start": 1992.42, "duration": 1.17}, {"text": "You just can't do it.", "start": 1993.59, "duration": 1.48}, {"text": "That's beyond the capabilities\nof finite automata.", "start": 1995.07, "duration": 2.75}, {"text": "And that's a statement\nwe will prove later.", "start": 1997.82, "duration": 5.64}, {"text": "OK.", "start": 2003.46, "duration": 1.59}, {"text": "And our goal over the\nnext lecture or so", "start": 2005.05, "duration": 4.11}, {"text": "is to understand the regular\nlanguages, which you can", "start": 2009.16, "duration": 2.79}, {"text": "do in a very comprehensive way.", "start": 2011.95, "duration": 2.8}, {"text": "So we're going to\nstart to do that now.", "start": 2014.75, "duration": 3.28}, {"text": "So first, we're going to\nintroduce this concept", "start": 2018.03, "duration": 2.27}, {"text": "of regular expressions--", "start": 2020.3, "duration": 2.363}, {"text": "which, again, these\nare things you", "start": 2022.663, "duration": 1.417}, {"text": "may have run into in one\nway or another before.", "start": 2024.08, "duration": 3.13}, {"text": "So we're going to\nintroduce something", "start": 2027.21, "duration": 5.49}, {"text": "called the regular operations.", "start": 2032.7, "duration": 1.95}, {"text": "Now, I'm sure\nyou're familiar with", "start": 2034.65, "duration": 4.56}, {"text": "the arithmetical operations,\nlike plus and times.", "start": 2039.21, "duration": 5.28}, {"text": "Those apply to numbers.", "start": 2044.49, "duration": 3.62}, {"text": "The operations we're\ngoing to talk about", "start": 2048.11, "duration": 1.77}, {"text": "are operations that\napply to languages.", "start": 2049.88, "duration": 2.759}, {"text": "So they're going to take,\nlet's say, two languages,", "start": 2052.639, "duration": 3.361}, {"text": "you apply an\noperation, you're going", "start": 2056.0, "duration": 1.5}, {"text": "to get back another language.", "start": 2057.5, "duration": 1.5}, {"text": "Like the union\noperation, for example,", "start": 2059.0, "duration": 2.73}, {"text": "that's one you probably\nhave seen before.", "start": 2061.73, "duration": 3.449}, {"text": "The union of two\nlanguages here is", "start": 2065.179, "duration": 1.951}, {"text": "a collection of strings that\nare in either one or the other.", "start": 2067.13, "duration": 2.819}, {"text": "But there are other\noperations, which", "start": 2073.078, "duration": 1.542}, {"text": "you may not have seen before,\nthat we're going to look at--", "start": 2074.62, "duration": 2.849}, {"text": "the concatenation\noperation, for example.", "start": 2077.469, "duration": 2.621}, {"text": "So that says you're\ngoing to take", "start": 2080.09, "duration": 1.58}, {"text": "a string from the first\nlanguage and another string", "start": 2081.67, "duration": 3.42}, {"text": "from the second language\nand stick them together.", "start": 2085.09, "duration": 4.28}, {"text": "And it's called\nconcatenating them.", "start": 2089.37, "duration": 3.039}, {"text": "And you do that in\nall possible ways,", "start": 2092.409, "duration": 2.27}, {"text": "and you're going to get\nthe concatenation language", "start": 2094.679, "duration": 2.221}, {"text": "from these two languages\nthat you're starting with,", "start": 2096.9, "duration": 2.19}, {"text": "A and B. The symbol we\nuse for concatenation", "start": 2099.09, "duration": 3.84}, {"text": "is this little circle.", "start": 2102.93, "duration": 1.14}, {"text": "But often, we don't.", "start": 2104.07, "duration": 2.34}, {"text": "We just suppress that and\nwe write the two languages", "start": 2106.41, "duration": 3.06}, {"text": "next to one another with\nthe little circle implied.", "start": 2109.47, "duration": 3.11}, {"text": "So this also means concatenation\nover here, just like this does.", "start": 2112.58, "duration": 4.93}, {"text": "And the last of the\nregular operations", "start": 2117.51, "duration": 3.24}, {"text": "is the so-called star operation,\nwhich is a unary operation.", "start": 2120.75, "duration": 3.93}, {"text": "It applies to just\na single language.", "start": 2124.68, "duration": 2.5}, {"text": "And so what you do is now\nyou're going to take--", "start": 2127.18, "duration": 4.28}, {"text": "to get a member of\nthe star language,", "start": 2131.46, "duration": 3.15}, {"text": "you're going to take\na bunch of strings", "start": 2134.61, "duration": 1.77}, {"text": "in the original language,\nA, you stick them together.", "start": 2136.38, "duration": 3.6}, {"text": "Any number of members of\nA, you stick them together,", "start": 2139.98, "duration": 3.52}, {"text": "and that becomes an element\nof the star language.", "start": 2143.5, "duration": 3.05}, {"text": "And we'll do an example in a\nsecond if you didn't get that.", "start": 2146.55, "duration": 2.88}, {"text": "But one important element is\nthat when you have the star", "start": 2149.43, "duration": 2.82}, {"text": "language, you can\nalso allow it to stick", "start": 2152.25, "duration": 2.28}, {"text": "zero elements together, and\nthen you get the empty string.", "start": 2154.53, "duration": 5.56}, {"text": "So that's always a\nmember of the star", "start": 2160.09, "duration": 2.69}, {"text": "language, the empty string.", "start": 2162.78, "duration": 2.95}, {"text": "OK, so let's look\nat some examples.", "start": 2165.73, "duration": 2.43}, {"text": "Let's say A is the\nlanguage-- these are", "start": 2168.16, "duration": 2.46}, {"text": "two strings here-- good, bad.", "start": 2170.62, "duration": 1.89}, {"text": "And B is the language boy, girl.", "start": 2172.51, "duration": 1.77}, {"text": "Now, if we take the\nunion of those two,", "start": 2177.8, "duration": 3.58}, {"text": "we get good, bad, boy, girl.", "start": 2181.38, "duration": 4.36}, {"text": "That's kind of\nwhat you'd expect.", "start": 2185.74, "duration": 3.64}, {"text": "And now let's take a look\nat the concatenation.", "start": 2189.38, "duration": 8.79}, {"text": "Now, if you concatenate\nthe A and the B language,", "start": 2198.17, "duration": 3.09}, {"text": "you're going to get all\npossible ways of having an A", "start": 2201.26, "duration": 2.94}, {"text": "string followed by all possible\nways of having a B string.", "start": 2204.2, "duration": 2.65}, {"text": "So you can get goodboy,\ngoodgirl, badboy, badgirl.", "start": 2206.85, "duration": 3.11}, {"text": "Now, looking at the\nstar, well, that", "start": 2213.99, "duration": 7.25}, {"text": "applies to just one language.", "start": 2221.24, "duration": 1.66}, {"text": "So let's say it's the\ngood, bad language from A.", "start": 2222.9, "duration": 4.7}, {"text": "And so the A star\nthat you get from that", "start": 2227.6, "duration": 2.67}, {"text": "is all possible ways of sticking\ntogether the strings from A.", "start": 2230.27, "duration": 4.44}, {"text": "So using no strings, you\nalways get the empty string.", "start": 2234.71, "duration": 3.55}, {"text": "That's always guaranteed\nto be a member of A.", "start": 2238.26, "duration": 2.12}, {"text": "And then just taking\none element of A,", "start": 2240.38, "duration": 2.15}, {"text": "you get good, or\nanother element, bad.", "start": 2242.53, "duration": 2.26}, {"text": "But now two elements of A,\nyou get goodgood or goodbad,", "start": 2244.79, "duration": 3.3}, {"text": "and so on.", "start": 2248.09, "duration": 1.44}, {"text": "Or three elements of A,\ngoodgoodgood, goodgoodbad.", "start": 2249.53, "duration": 3.39}, {"text": "And so, in fact, A star is\ngoing to be an infinite language", "start": 2252.92, "duration": 4.21}, {"text": "if A itself contains\nany non-empty member.", "start": 2257.13, "duration": 9.4}, {"text": "So if A is the empty\nlanguage or if A contains", "start": 2266.53, "duration": 3.86}, {"text": "just the language empty\nstring, then A star", "start": 2270.39, "duration": 3.78}, {"text": "will be not an\ninfinite language.", "start": 2274.17, "duration": 2.31}, {"text": "It'll just be the\nlanguage empty string.", "start": 2276.48, "duration": 2.52}, {"text": "But otherwise, it'll be\nan infinite language.", "start": 2279.0, "duration": 3.02}, {"text": "I'm not even sure--", "start": 2282.02, "duration": 0.87}, {"text": "OK.", "start": 2287.78, "duration": 0.87}, {"text": "I'm not-- [LAUGHS]", "start": 2288.65, "duration": 1.23}, {"text": "I'm ignoring the chat here.", "start": 2289.88, "duration": 1.14}, {"text": "I'm hoping people\nare getting-- are you", "start": 2291.02, "duration": 1.65}, {"text": "guys are getting your\nquestions answered by our TAs?", "start": 2292.67, "duration": 3.18}, {"text": "How are we doing, Thomas?", "start": 2295.85, "duration": 1.59}, {"text": "AUDIENCE: One question is, are\nthe slides going to be posted?", "start": 2297.44, "duration": 3.737}, {"text": "MICHAEL SIPSER: Are the\nslides going to be posted?", "start": 2301.177, "duration": 2.083}, {"text": "Well, the whole lecture\nis going to be recorded.", "start": 2303.26, "duration": 4.887}, {"text": "Is it helpful to have\nthe slides separately?", "start": 2308.147, "duration": 1.833}, {"text": "I can post the slides.", "start": 2309.98, "duration": 3.15}, {"text": "Sure.", "start": 2313.13, "duration": 1.23}, {"text": "Remind me if I don't,\nbut I'll try to do that.", "start": 2314.36, "duration": 2.1}, {"text": "Yes, it is helpful.", "start": 2316.46, "duration": 0.9}, {"text": "I will do that.", "start": 2317.36, "duration": 1.17}, {"text": "Yeah.", "start": 2321.58, "duration": 1.86}, {"text": "Yeah, I will post the slides.", "start": 2323.44, "duration": 1.25}, {"text": "Just, Thomas, it's\nyour job to remind me.", "start": 2324.69, "duration": 3.118}, {"text": "AUDIENCE: OK.", "start": 2327.808, "duration": 0.542}, {"text": "MICHAEL SIPSER: All right, good.", "start": 2331.82, "duration": 2.01}, {"text": "So we talked about the\nregular operations.", "start": 2333.83, "duration": 1.78}, {"text": "Let's talk about the\nregular expressions.", "start": 2335.61, "duration": 2.13}, {"text": "So regular\nexpressions are-- just", "start": 2337.74, "duration": 1.76}, {"text": "like you have the\narithmetical operations,", "start": 2339.5, "duration": 2.07}, {"text": "then you can get\narithmetical expressions,", "start": 2341.57, "duration": 1.98}, {"text": "like 1 plus 3 times 7.", "start": 2343.55, "duration": 3.77}, {"text": "So now we're going to\nmake expressions out", "start": 2347.32, "duration": 1.75}, {"text": "of these operations.", "start": 2349.07, "duration": 1.17}, {"text": "First of all, you have,\nthe more atomic things,", "start": 2350.24, "duration": 2.88}, {"text": "the building blocks of\nthe expressions, which", "start": 2353.12, "duration": 2.01}, {"text": "are going to be like elements of\nsigma, elements of the alphabet", "start": 2355.13, "duration": 8.2}, {"text": "or the sigma itself\nas an alphabet symbol,", "start": 2363.33, "duration": 4.53}, {"text": "or the empty language\nor the empty string.", "start": 2367.86, "duration": 5.642}, {"text": "These are going to be\nthe building blocks", "start": 2373.502, "duration": 1.708}, {"text": "for the regular expressions.", "start": 2375.21, "duration": 1.26}, {"text": "We'll do an example in a second.", "start": 2376.47, "duration": 2.08}, {"text": "And then you combine\nthose basic elements", "start": 2378.55, "duration": 3.98}, {"text": "using the regular operations of\nunion, concatenation, and star.", "start": 2382.53, "duration": 3.33}, {"text": "So these are the\natomic expressions,", "start": 2385.86, "duration": 2.46}, {"text": "these are the\ncomposite expressions.", "start": 2388.32, "duration": 1.75}, {"text": "So, for example, if you look at\nthe expression 0 union 1 star--", "start": 2390.07, "duration": 7.87}, {"text": "so we can also write\nthat as sigma star.", "start": 2397.94, "duration": 2.46}, {"text": "Because if sigma is 0\nand 1, then sigma star", "start": 2400.4, "duration": 4.14}, {"text": "is the same thing as 0 union 1--\nsigma is the same as 0 union 1.", "start": 2404.54, "duration": 3.9}, {"text": "And that just gives all\npossible strings over sigma.", "start": 2408.44, "duration": 3.323}, {"text": "So this is something you're\ngoing to see frequently.", "start": 2411.763, "duration": 2.167}, {"text": "Sigma star means\nthis is the language", "start": 2413.93, "duration": 2.79}, {"text": "of all strings over\nthe alphabet we're", "start": 2416.72, "duration": 2.13}, {"text": "working with at that moment.", "start": 2418.85, "duration": 3.49}, {"text": "Now, if you take\nsigma star 1, you just", "start": 2422.34, "duration": 3.93}, {"text": "concatenate 1 onto all of\nthe elements of sigma star,", "start": 2426.27, "duration": 4.08}, {"text": "and that's going to give you\nall strings that end with a 1.", "start": 2430.35, "duration": 3.75}, {"text": "Technically, you might\nimagine writing this", "start": 2434.1, "duration": 2.1}, {"text": "with braces around the 1, but\ngenerally, we don't do that.", "start": 2436.2, "duration": 4.68}, {"text": "We just-- single element\nsets, single element strings,", "start": 2440.88, "duration": 4.5}, {"text": "we write without the\nbraces, because it's", "start": 2445.38, "duration": 2.52}, {"text": "clear enough without them,\nand it gets messy with them.", "start": 2447.9, "duration": 2.89}, {"text": "So sigma star 1 is all\nstrings that end with 1.", "start": 2450.79, "duration": 2.99}, {"text": "Or, for example,\nyou take sigma star", "start": 2453.78, "duration": 4.05}, {"text": "11 sigma star, that is all\nstrings that contain 11.", "start": 2457.83, "duration": 5.19}, {"text": "And we already saw that\nlanguage once before.", "start": 2463.02, "duration": 1.98}, {"text": "That's the language\nof that other machine", "start": 2465.0, "duration": 1.83}, {"text": "that we presented one\nor two slides back.", "start": 2466.83, "duration": 4.13}, {"text": "OK?", "start": 2470.96, "duration": 0.5}, {"text": "Right.", "start": 2474.945, "duration": 0.5}, {"text": "Yeah, but in terms of\nreadings-- by the way,", "start": 2480.377, "duration": 1.833}, {"text": "sorry, I don't know\nif it's helpful to you", "start": 2482.21, "duration": 1.43}, {"text": "for me to do these\ninterjections--", "start": 2483.64, "duration": 1.47}, {"text": "but the readings are listed\nalso on the homework.", "start": 2485.11, "duration": 5.13}, {"text": "So if you look at the\nposted homework 1,", "start": 2490.24, "duration": 3.33}, {"text": "it tells you which chapters\nyou should be reading now.", "start": 2493.57, "duration": 5.34}, {"text": "And also, if you look at the\ncourse schedule, which is also", "start": 2498.91, "duration": 3.51}, {"text": "on the home page, it has the\nwhole course plan and which", "start": 2502.42, "duration": 5.1}, {"text": "readings are for which dates.", "start": 2507.52, "duration": 2.37}, {"text": "So it's all there for you.", "start": 2509.89, "duration": 1.68}, {"text": "And so our goal here--\nthis is not an accident", "start": 2514.47, "duration": 2.64}, {"text": "that sigma star 11\nsigma star happens", "start": 2517.11, "duration": 3.18}, {"text": "to be the same language\nas we saw before", "start": 2520.29, "duration": 2.85}, {"text": "from the language of\nthat finite automaton M1.", "start": 2523.14, "duration": 4.29}, {"text": "In fact, that's a\ngeneral phenomenon.", "start": 2527.43, "duration": 2.82}, {"text": "Anything you can do with\na regular expression,", "start": 2530.25, "duration": 2.53}, {"text": "you can also do with a finite\nautomaton and vice versa.", "start": 2532.78, "duration": 4.02}, {"text": "They are equivalent\nin power with respect", "start": 2536.8, "duration": 2.87}, {"text": "to the class of\nlanguages they describe.", "start": 2539.67, "duration": 3.36}, {"text": "And we'll prove that.", "start": 2543.03, "duration": 1.34}, {"text": "OK?", "start": 2546.68, "duration": 0.5}, {"text": "So if you step back for\na second and just let", "start": 2550.54, "duration": 4.47}, {"text": "yourself appreciate this,\nit's kind of an amazing thing.", "start": 2555.01, "duration": 3.18}, {"text": "Because finite automata, with\nthe states and transitions,", "start": 2558.19, "duration": 2.97}, {"text": "and the regular expressions,\nwith these operations of union,", "start": 2561.16, "duration": 3.93}, {"text": "concatenation, and star,\nthey look totally different", "start": 2565.09, "duration": 2.58}, {"text": "from one another.", "start": 2567.67, "duration": 0.767}, {"text": "They look like they have\nnothing to do with one another.", "start": 2568.437, "duration": 2.333}, {"text": "But, in fact, they both describe\nexactly the regular languages,", "start": 2570.77, "duration": 3.11}, {"text": "the same class of languages.", "start": 2573.88, "duration": 2.37}, {"text": "And so it's kind of a cool\nfact that you can prove,", "start": 2576.25, "duration": 2.73}, {"text": "that these two very\ndifferent looking systems", "start": 2578.98, "duration": 2.52}, {"text": "actually are equivalent\nto one another.", "start": 2581.5, "duration": 1.74}, {"text": "Can we get empty\nstring from empty set?", "start": 2587.14, "duration": 3.64}, {"text": "Yeah.", "start": 2590.78, "duration": 0.66}, {"text": "There are a bunch of\nexotic cases, by the way.", "start": 2591.44, "duration": 4.08}, {"text": "So empty language star\nis the language which", "start": 2595.52, "duration": 3.75}, {"text": "has just the empty string.", "start": 2599.27, "duration": 1.92}, {"text": "If you don't get that,\nchew on that one.", "start": 2601.19, "duration": 2.46}, {"text": "But that is true.", "start": 2603.65, "duration": 1.74}, {"text": "OK, let's move on.", "start": 2608.21, "duration": 2.64}, {"text": "OK, let's talk about\nclosure properties now.", "start": 2610.85, "duration": 2.053}, {"text": "We're going to start doing\nsomething that has a little bit", "start": 2612.903, "duration": 2.417}, {"text": "more meat to it,\nin terms of we're", "start": 2615.32, "duration": 2.31}, {"text": "going to have our first theorem\nof the course coming here.", "start": 2617.63, "duration": 3.45}, {"text": "And this is not a baby theorem.", "start": 2621.08, "duration": 2.32}, {"text": "This is actually-- there's\ngoing to be some meat to this.", "start": 2623.4, "duration": 2.63}, {"text": "And you're going to\nhave to not totally--", "start": 2626.03, "duration": 7.05}, {"text": "this is not a toy.", "start": 2633.08, "duration": 1.2}, {"text": "We're proving something\nthat has real substance.", "start": 2634.28, "duration": 3.73}, {"text": "And the statement\nof this theorem", "start": 2638.01, "duration": 4.11}, {"text": "says that the regular languages\nare closed, that really,", "start": 2642.12, "duration": 6.0}, {"text": "the class of regular languages\nare closed under union, closed", "start": 2648.12, "duration": 3.39}, {"text": "under the union operation.", "start": 2651.51, "duration": 2.47}, {"text": "So what do I mean by that?", "start": 2653.98, "duration": 2.18}, {"text": "So when you say a\ncollection of objects", "start": 2656.16, "duration": 4.77}, {"text": "is closed under\nsome operation, that", "start": 2660.93, "duration": 2.49}, {"text": "means applying that\noperation to those objects", "start": 2663.42, "duration": 3.06}, {"text": "leaves you in the\nsame class of objects.", "start": 2666.48, "duration": 3.37}, {"text": "Like the positive integers,\nthe natural numbers,", "start": 2669.85, "duration": 7.94}, {"text": "that's closed under addition.", "start": 2677.79, "duration": 1.89}, {"text": "Because when you add\ntwo positive integers,", "start": 2679.68, "duration": 3.27}, {"text": "you get back a positive integer.", "start": 2682.95, "duration": 1.92}, {"text": "But they're not closed\nunder subtraction.", "start": 2684.87, "duration": 2.52}, {"text": "Because 2 minus 4, you\nget something which", "start": 2687.39, "duration": 3.6}, {"text": "is not a positive integer.", "start": 2690.99, "duration": 1.84}, {"text": "So closed means you leave\nyourself in the collection.", "start": 2692.83, "duration": 3.66}, {"text": "And the fact is that if you look\nat all the regular languages--", "start": 2696.49, "duration": 4.08}, {"text": "these are the languages that the\nfinite automata can recognize--", "start": 2700.57, "duration": 4.56}, {"text": "they are closed under\nthe union operation.", "start": 2705.13, "duration": 2.34}, {"text": "So if you start off with\ntwo regular languages", "start": 2707.47, "duration": 2.55}, {"text": "and you apply the union, you get\nback another regular language.", "start": 2710.02, "duration": 3.508}, {"text": "And that's what the\nstatement of this theorem is.", "start": 2713.528, "duration": 2.042}, {"text": "I hope that's clear enough\nin the way I've written it.", "start": 2715.57, "duration": 3.12}, {"text": "If A1 and A2 are regular, then\nA1 union A2 is also regular.", "start": 2718.69, "duration": 5.25}, {"text": "That's what the\nstatement of this is.", "start": 2723.94, "duration": 1.77}, {"text": "And it's just simply that--", "start": 2725.71, "duration": 2.31}, {"text": "that's proving that the\nclass of regular language", "start": 2728.02, "duration": 2.19}, {"text": "is closed under union.", "start": 2730.21, "duration": 0.99}, {"text": "So we're going to prove that.", "start": 2731.2, "duration": 2.77}, {"text": "So how do you\nprove such a thing?", "start": 2733.97, "duration": 2.53}, {"text": "So the way we're going\nto prove that is you", "start": 2736.5, "duration": 4.31}, {"text": "start off with what\nwe're assuming.", "start": 2740.81, "duration": 2.38}, {"text": "So our hypothesis is that we\nhave two regular languages.", "start": 2743.19, "duration": 4.11}, {"text": "And we have to prove\nour conclusion,", "start": 2747.3, "duration": 2.12}, {"text": "that the union is also regular.", "start": 2749.42, "duration": 2.88}, {"text": "Now, the hypothesis\nthat they're regular,", "start": 2752.3, "duration": 2.7}, {"text": "you have to unpack that and\nunderstand, what does that", "start": 2755.0, "duration": 3.78}, {"text": "get you?", "start": 2758.78, "duration": 1.23}, {"text": "And them being regular means\nthat there are finite automata", "start": 2760.01, "duration": 3.96}, {"text": "that recognize those languages.", "start": 2763.97, "duration": 1.78}, {"text": "So let's give those two\nfinite automata names.", "start": 2765.75, "duration": 2.51}, {"text": "So M1 and M2 are the\ntwo final automata", "start": 2768.26, "duration": 3.48}, {"text": "that recognize those two\nlanguages, A1 and A2.", "start": 2771.74, "duration": 2.258}, {"text": "That's what it means,\nthat they're regular,", "start": 2773.998, "duration": 1.792}, {"text": "that these automata exist.", "start": 2775.79, "duration": 3.26}, {"text": "So let's have those two\nautomata, M1 and M2,", "start": 2779.05, "duration": 3.11}, {"text": "using the components as we've\ndescribed, the respective state", "start": 2782.16, "duration": 3.96}, {"text": "sets, input alphabet,\ntransition functions, the two", "start": 2786.12, "duration": 3.24}, {"text": "starting states and the two\ncollections of accepting", "start": 2789.36, "duration": 2.52}, {"text": "states.", "start": 2791.88, "duration": 0.51}, {"text": "Here I'm assuming that they're\nover the same alphabet.", "start": 2792.39, "duration": 2.58}, {"text": "You could have\nautomata which operate", "start": 2794.97, "duration": 1.92}, {"text": "over different alphabets.", "start": 2796.89, "duration": 1.29}, {"text": "It's not interesting to do that.", "start": 2798.18, "duration": 1.98}, {"text": "It doesn't add anything.", "start": 2800.16, "duration": 1.21}, {"text": "The proof would be\nexactly the same.", "start": 2801.37, "duration": 1.83}, {"text": "So let's just not overcomplicate\nour lives and focus", "start": 2803.2, "duration": 2.84}, {"text": "on the more interesting\ncase, so assuming", "start": 2806.04, "duration": 1.8}, {"text": "that the two input alphabets\nare going to be the same.", "start": 2807.84, "duration": 4.15}, {"text": "And from these two\nautomata, we have", "start": 2811.99, "duration": 1.88}, {"text": "to show that this\nlanguage here, the union,", "start": 2813.87, "duration": 2.61}, {"text": "is also a regular language.", "start": 2816.48, "duration": 1.74}, {"text": "And we're going to do that\nby constructing the automaton", "start": 2818.22, "duration": 4.23}, {"text": "which recognizes the union.", "start": 2822.45, "duration": 1.53}, {"text": "That's really the only\nthing that we can do.", "start": 2823.98, "duration": 3.27}, {"text": "So we're going to build an\nautomaton out of M1 and M2", "start": 2827.25, "duration": 3.96}, {"text": "which recognizes the union\nlanguage A1 union A2.", "start": 2831.21, "duration": 4.03}, {"text": "And the task of M is that\nit should accept its input", "start": 2835.24, "duration": 4.32}, {"text": "if either M1 or M2 accept.", "start": 2839.56, "duration": 3.413}, {"text": "And now what I'd\nlike you to think", "start": 2842.973, "duration": 1.417}, {"text": "about doing that,\nhow in the world", "start": 2844.39, "duration": 1.98}, {"text": "are we going to come up with\nthis finite automaton M?", "start": 2846.37, "duration": 3.99}, {"text": "And the way we do that is\nto think about, how would", "start": 2850.36, "duration": 12.37}, {"text": "you do that union language?", "start": 2862.73, "duration": 3.38}, {"text": "If I ask you--", "start": 2866.11, "duration": 1.44}, {"text": "I give you two automata,\nM1 and M2, and I say,", "start": 2867.55, "duration": 3.3}, {"text": "here's an input, w.", "start": 2870.85, "duration": 1.17}, {"text": "Is w in the union language?", "start": 2874.82, "duration": 2.25}, {"text": "That's the job that M\nis supposed to solve.", "start": 2877.07, "duration": 2.7}, {"text": "And I suggest you\ntry to figure out", "start": 2879.77, "duration": 1.68}, {"text": "how you would solve it first.", "start": 2881.45, "duration": 2.37}, {"text": "I mean, this is a good\nstrategy for solving a lot", "start": 2883.82, "duration": 2.488}, {"text": "of the problems in this course.", "start": 2886.308, "duration": 1.292}, {"text": "Put yourself in the place of the\nmachine you're trying to build.", "start": 2887.6, "duration": 3.23}, {"text": "And so if you want to try to\nfigure out how to do that,", "start": 2890.83, "duration": 3.44}, {"text": "a natural thing is, well, you\ntake w, you feed it into M1,", "start": 2894.27, "duration": 4.14}, {"text": "and then you feed it into M2.", "start": 2898.41, "duration": 1.92}, {"text": "And if M1 accepts\nit, great, then you", "start": 2900.33, "duration": 2.287}, {"text": "know it's in the union.", "start": 2902.617, "duration": 1.163}, {"text": "And if not, you try it out in\nM2 and see if M2 accepts it.", "start": 2903.78, "duration": 4.938}, {"text": "Now, you have to be\na little careful,", "start": 2908.718, "duration": 1.542}, {"text": "because you want to have a\nstrategy that you can also", "start": 2910.26, "duration": 2.49}, {"text": "implement in a finite automaton.", "start": 2912.75, "duration": 4.69}, {"text": "And a finite automaton\nonly gets one shot", "start": 2917.44, "duration": 4.74}, {"text": "at looking at the input.", "start": 2922.18, "duration": 1.14}, {"text": "You can't sort of\nrewind the input.", "start": 2923.32, "duration": 1.92}, {"text": "You feed it first into M1\nand then you feed it into M2", "start": 2925.24, "duration": 3.75}, {"text": "and operate in a\nsequential way like that.", "start": 2928.99, "duration": 4.02}, {"text": "That's not going to be allowed\nin the way finite automata", "start": 2933.01, "duration": 4.68}, {"text": "work.", "start": 2937.69, "duration": 0.79}, {"text": "So you're going to have to\ntake it to the next level,", "start": 2938.48, "duration": 3.47}, {"text": "be a little bit more clever.", "start": 2941.95, "duration": 1.38}, {"text": "And instead of feeding\nit first into M1", "start": 2943.33, "duration": 2.55}, {"text": "and then and then\ninto M2, you feed them", "start": 2945.88, "duration": 2.07}, {"text": "into both in parallel.", "start": 2947.95, "duration": 3.53}, {"text": "So you take M1 and\nM2, and you run them", "start": 2951.48, "duration": 2.58}, {"text": "both in parallel on the input\nw, keeping track of which state", "start": 2954.06, "duration": 6.12}, {"text": "each of those two\nautomata are in.", "start": 2960.18, "duration": 4.27}, {"text": "And then at the end, you see\nif either one of those machines", "start": 2964.45, "duration": 3.62}, {"text": "is in an accepting state,\nand then you accept.", "start": 2968.07, "duration": 3.173}, {"text": "So that's the\nstrategy we're going", "start": 2971.243, "duration": 1.417}, {"text": "to employ in building the finite\nautomaton M out of M1 and M2.", "start": 2972.66, "duration": 5.77}, {"text": "So in terms of a picture,\nhere's M1 and M2.", "start": 2978.43, "duration": 4.72}, {"text": "Here is the automaton\nwe're trying to build.", "start": 2983.15, "duration": 2.523}, {"text": "We don't know how it's\ngoing to look like yet.", "start": 2985.673, "duration": 1.917}, {"text": "And yeah, so kind of getting\nahead of myself, but here", "start": 2987.59, "duration": 4.17}, {"text": "is a strategy, as I\njust described, for M.", "start": 2991.76, "duration": 8.94}, {"text": "M is going to keep track of\nwhich state that M1 is in", "start": 3000.7, "duration": 5.1}, {"text": "and which state M2 is\nin at any given moment.", "start": 3005.8, "duration": 2.94}, {"text": "As we're reading\nthe symbols of w,", "start": 3008.74, "duration": 2.34}, {"text": "we're going to feed that\ninto M1 and also into M2.", "start": 3011.08, "duration": 5.13}, {"text": "And so the possibilities we\nhave to keep track of in M", "start": 3016.21, "duration": 5.13}, {"text": "are all the pairs of states\nthat are in M1 and M2,", "start": 3021.34, "duration": 4.04}, {"text": "because you're going\nto really be tracking", "start": 3025.38, "duration": 1.75}, {"text": "M1 and M2 simultaneously.", "start": 3027.13, "duration": 1.99}, {"text": "So you have to remember\nwhich state M1 is in and also", "start": 3029.12, "duration": 2.45}, {"text": "which state M2 is in.", "start": 3031.57, "duration": 1.35}, {"text": "And so that really corresponds\nto what pair of states", "start": 3032.92, "duration": 2.25}, {"text": "to remember, one from M1\nand one from M2, and that's", "start": 3035.17, "duration": 3.21}, {"text": "why I've indicated it like that.", "start": 3038.38, "duration": 1.75}, {"text": "So M1 is in state\nq, M2 is in state r", "start": 3040.13, "duration": 2.84}, {"text": "at some given point in time.", "start": 3042.97, "duration": 1.92}, {"text": "And that's going to correspond\nto M being in the pair q comma", "start": 3044.89, "duration": 3.35}, {"text": "r.", "start": 3048.24, "duration": 0.76}, {"text": "That's just the label of\nthis particular state of m", "start": 3049.0, "duration": 3.3}, {"text": "that we're going to apply here.", "start": 3052.3, "duration": 3.615}, {"text": "OK?", "start": 3055.915, "duration": 0.5}, {"text": "And then M is going\nto accept if either M1", "start": 3059.13, "duration": 4.44}, {"text": "and M2 is an accepting state.", "start": 3063.57, "duration": 2.44}, {"text": "So it's going to be if either\nq or r is an accepting state,", "start": 3066.01, "duration": 3.92}, {"text": "we're going to make this\ninto an accepting state too.", "start": 3069.93, "duration": 3.91}, {"text": "OK?", "start": 3073.84, "duration": 1.58}, {"text": "Whoops.", "start": 3075.42, "duration": 0.63}, {"text": "There we go.", "start": 3076.05, "duration": 0.57}, {"text": "So let's describe\nthis formally instead", "start": 3079.725, "duration": 1.625}, {"text": "of by a picture, because\nwe can do it both ways.", "start": 3081.35, "duration": 2.407}, {"text": "And sometimes it's better to\ndo it one way and sometimes", "start": 3083.757, "duration": 2.333}, {"text": "the other way.", "start": 3086.09, "duration": 1.72}, {"text": "So now if we take--", "start": 3087.81, "duration": 1.34}, {"text": "the components of M now are the\npairs of states from M1 and M2.", "start": 3089.15, "duration": 5.67}, {"text": "Again, I'm writing this out\nliterally, explicitly here,", "start": 3094.82, "duration": 3.58}, {"text": "but you should make sure\nyou're comfortable with", "start": 3098.4, "duration": 2.09}, {"text": "this cross product notation.", "start": 3100.49, "duration": 1.84}, {"text": "So this is the collection of\npairs of states, q1 and q2,", "start": 3102.33, "duration": 2.93}, {"text": "where q1 is in the state\nof the first machine,", "start": 3105.26, "duration": 2.4}, {"text": "q2 is the state of\nthe second machine.", "start": 3107.66, "duration": 2.94}, {"text": "The start state is you\nstart at the two start", "start": 3110.6, "duration": 3.03}, {"text": "states of the two machines.", "start": 3113.63, "duration": 2.22}, {"text": "So this is q1, q2--", "start": 3115.85, "duration": 1.68}, {"text": "probably I should have\nnot reused the Q notation.", "start": 3117.53, "duration": 3.57}, {"text": "I should have called these r's--", "start": 3121.1, "duration": 1.432}, {"text": "now that I'm looking at that.", "start": 3122.532, "duration": 1.208}, {"text": "But, anyway, I hope you're\nnot confused by reusing this.", "start": 3123.74, "duration": 2.76}, {"text": "q1 and q2 here are the\nspecific start states", "start": 3126.5, "duration": 3.39}, {"text": "of the two machines.", "start": 3129.89, "duration": 2.26}, {"text": "These are just two other\nstates, representative states", "start": 3132.15, "duration": 3.5}, {"text": "of those machines.", "start": 3135.65, "duration": 2.13}, {"text": "Now, the transition\nfunction for the new machine", "start": 3137.78, "duration": 2.843}, {"text": "is going to be built out\nof the transition functions", "start": 3140.623, "duration": 2.167}, {"text": "from the previous machines.", "start": 3142.79, "duration": 2.08}, {"text": "So when I have a pair, q,\nr, and I have the symbol a,", "start": 3144.87, "duration": 5.63}, {"text": "where do we go?", "start": 3150.5, "duration": 1.02}, {"text": "Which new pair do we get?", "start": 3151.52, "duration": 1.75}, {"text": "Well, we just update\nthe state from M1", "start": 3153.27, "duration": 2.66}, {"text": "and update the state\nfrom M2 according", "start": 3155.93, "duration": 2.58}, {"text": "to their respective\ntransition functions,", "start": 3158.51, "duration": 1.763}, {"text": "and that's what's\nshown over here.", "start": 3160.273, "duration": 1.417}, {"text": "Now let's take a look at\nthe accepting states for M.", "start": 3165.41, "duration": 4.67}, {"text": "The natural thing to do is look\nat the set of pairs of states,", "start": 3170.08, "duration": 4.35}, {"text": "where we have a pair of states--", "start": 3174.43, "duration": 2.97}, {"text": "a pair of accepting states,\none from the first machine", "start": 3177.4, "duration": 5.43}, {"text": "and one from the second machine.", "start": 3182.83, "duration": 2.6}, {"text": "But if you're\nthinking with me, you", "start": 3185.43, "duration": 2.04}, {"text": "realize that this is\nnot the right thing.", "start": 3187.47, "duration": 2.115}, {"text": "What is DFAs?", "start": 3192.51, "duration": 0.66}, {"text": "Did I would call\nthem DFA somewhere?", "start": 3196.57, "duration": 2.19}, {"text": "Oh, somebody else is probably\ndoing that in the chat.", "start": 3198.76, "duration": 3.756}, {"text": "The DFA-- careful what\nnotation you're using.", "start": 3202.516, "duration": 3.024}, {"text": "We haven't introduced DFAs yet.", "start": 3205.54, "duration": 2.89}, {"text": "We'll do that next on Thursday.", "start": 3208.43, "duration": 1.94}, {"text": "But these are DFAs.", "start": 3210.37, "duration": 0.93}, {"text": "These are just finite automata,\nDeterministic Finite Automata.", "start": 3211.3, "duration": 3.0}, {"text": "That's why the D.", "start": 3214.3, "duration": 1.38}, {"text": "Anyway, so this is\nactually not right,", "start": 3215.68, "duration": 2.662}, {"text": "because if you think\nabout what this is saying,", "start": 3218.342, "duration": 1.958}, {"text": "it says that both components\nhave to be accepting.", "start": 3220.3, "duration": 3.96}, {"text": "And you want either\none to be accepting.", "start": 3224.26, "duration": 3.64}, {"text": "So this is not good.", "start": 3227.9, "duration": 2.15}, {"text": "This would be the wrong\nway of defining it.", "start": 3230.05, "duration": 3.51}, {"text": "That actually gives the\nintersection language.", "start": 3233.56, "duration": 1.95}, {"text": "And really, kind\nof along the way,", "start": 3235.51, "duration": 1.417}, {"text": "it's proving closure\nunder intersection,", "start": 3236.927, "duration": 1.835}, {"text": "which we don't care\nabout but might", "start": 3238.762, "duration": 1.458}, {"text": "be useful to have in our back\npocket sometime in the future.", "start": 3240.22, "duration": 4.47}, {"text": "In order to get\nclosure under a union,", "start": 3244.69, "duration": 2.31}, {"text": "we have to write it this\nslightly more complicated", "start": 3247.0, "duration": 2.1}, {"text": "looking way, which says the\npair, what you want to have is", "start": 3249.1, "duration": 5.61}, {"text": "either the first state is\nan accepting state and then", "start": 3254.71, "duration": 4.23}, {"text": "any state for the\nsecond element,", "start": 3258.94, "duration": 2.55}, {"text": "or any state for\nthe first element", "start": 3261.49, "duration": 2.19}, {"text": "and an accepting state\nfor the second element.", "start": 3263.68, "duration": 2.61}, {"text": "That's what it means to have the\nunion, to be doing the union.", "start": 3266.29, "duration": 4.8}, {"text": "OK?", "start": 3271.09, "duration": 0.6}, {"text": "So let's do-- oh,\nhere's a quick check-in.", "start": 3271.69, "duration": 3.33}, {"text": "So let's do another poll here.", "start": 3278.02, "duration": 2.34}, {"text": "We thought we were\ndone with these.", "start": 3280.36, "duration": 1.635}, {"text": "Again-- oh, here we go.", "start": 3284.66, "duration": 5.79}, {"text": "So it was too complicated to\nwrite it out in the polls,", "start": 3290.45, "duration": 2.87}, {"text": "so I actually put it up\non the slide for you.", "start": 3293.32, "duration": 2.16}, {"text": "So all I'm asking is\nthat if M1 has k1 states", "start": 3298.4, "duration": 4.01}, {"text": "and M2 has k2 states, how\nmany states does M have?", "start": 3302.41, "duration": 2.88}, {"text": "Is it the sum, the sum of\nthe squares, or the product?", "start": 3308.81, "duration": 3.445}, {"text": "OK, you have to think\nabout the states of M, what", "start": 3317.45, "duration": 2.88}, {"text": "do they look like?", "start": 3320.33, "duration": 2.46}, {"text": "And come on, guys.", "start": 3322.79, "duration": 3.93}, {"text": "All right, ending the\npoll, sharing results.", "start": 3329.33, "duration": 4.23}, {"text": "Yes, indeed, it is-- most\nof you got it correct.", "start": 3333.56, "duration": 3.9}, {"text": "It is C, the product.", "start": 3337.46, "duration": 2.58}, {"text": "Because when you look at the\nnumber of pairs of states", "start": 3340.04, "duration": 2.79}, {"text": "from M1 and M2, you\nneed all possible pairs.", "start": 3342.83, "duration": 3.45}, {"text": "And so it's the number of\nstates in M1 times the number", "start": 3346.28, "duration": 2.67}, {"text": "of states in M2.", "start": 3348.95, "duration": 1.0}, {"text": "So make sure you understand\nthat and think about that", "start": 3349.95, "duration": 5.66}, {"text": "so that you're\nfollowing and get this.", "start": 3355.61, "duration": 4.17}, {"text": "All right, so\nlet's move on here.", "start": 3359.78, "duration": 4.59}, {"text": "So we have another\nfive minutes or so.", "start": 3364.37, "duration": 1.7}, {"text": "Let's start thinking about\nclosure under concatenation.", "start": 3366.07, "duration": 5.57}, {"text": "So if we have two\nregular languages,", "start": 3371.64, "duration": 1.77}, {"text": "so is the\nconcatenation language.", "start": 3373.41, "duration": 3.99}, {"text": "We're going to\ntry to prove that.", "start": 3377.4, "duration": 1.41}, {"text": "We won't finish, but we'll at\nleast get our creative juices", "start": 3378.81, "duration": 2.97}, {"text": "going about it.", "start": 3381.78, "duration": 1.84}, {"text": "So we're going to do\nthe same scheme here.", "start": 3383.62, "duration": 2.0}, {"text": "We're going to take two\nmachines for A1 and A2", "start": 3385.62, "duration": 3.99}, {"text": "and build a machine for the\nconcatenation language out", "start": 3389.61, "duration": 2.28}, {"text": "of those two.", "start": 3391.89, "duration": 0.9}, {"text": "So here are the two machines\nfor A1 and A2 written down.", "start": 3392.79, "duration": 5.43}, {"text": "And now here is the\nconcatenation language.", "start": 3398.22, "duration": 5.1}, {"text": "And I'm going to propose\nto you a strategy--", "start": 3403.32, "duration": 2.92}, {"text": "which is not going\nto work, but it still", "start": 3406.24, "duration": 1.91}, {"text": "is going to be a good\nintuition to have.", "start": 3408.15, "duration": 2.44}, {"text": "So what I'm going to do is\nI'm going to make a copy of--", "start": 3410.59, "duration": 2.96}, {"text": "OK, let's understand what\nM is supposed to do first.", "start": 3413.55, "duration": 2.98}, {"text": "So M should accept its input.", "start": 3416.53, "duration": 1.64}, {"text": "So think about this.", "start": 3418.17, "duration": 0.87}, {"text": "M is doing the\nconcatenation language.", "start": 3419.04, "duration": 2.01}, {"text": "So it's given a string.", "start": 3421.05, "duration": 1.56}, {"text": "And it has to answer, is it\nin the concatenation language", "start": 3422.61, "duration": 4.77}, {"text": "A1A2 or not?", "start": 3427.38, "duration": 1.65}, {"text": "So it should accept it if\nthere's some way to divide w", "start": 3429.03, "duration": 4.53}, {"text": "into two pieces where M1 accepts\nthe first piece and M2 accepts", "start": 3433.56, "duration": 3.69}, {"text": "the second piece.", "start": 3437.25, "duration": 3.29}, {"text": "So here would be the picture.", "start": 3440.54, "duration": 2.75}, {"text": "OK?", "start": 3443.29, "duration": 0.51}, {"text": "And now we have to try to\nmake a machine which is", "start": 3443.8, "duration": 3.75}, {"text": "going to solve this intuition.", "start": 3447.55, "duration": 1.62}, {"text": "So how would you\ndo that yourself?", "start": 3449.17, "duration": 3.171}, {"text": "I'm giving you w.", "start": 3452.341, "duration": 2.239}, {"text": "And you can simulate M1 and M2.", "start": 3454.58, "duration": 2.83}, {"text": "So the natural thing\nis you're going", "start": 3457.41, "duration": 2.0}, {"text": "to start out by\nsimulating M1 for a while", "start": 3459.41, "duration": 2.37}, {"text": "and then shift into\nsimulating M2 for a while,", "start": 3461.78, "duration": 2.82}, {"text": "because that's what's\nsupposed to be happening", "start": 3464.6, "duration": 3.36}, {"text": "as you're processing the input.", "start": 3467.96, "duration": 1.3}, {"text": "So I'm going to suggest that in\nterms of the diagram like this.", "start": 3469.26, "duration": 5.32}, {"text": "So we have here M1\nand M2 copied here.", "start": 3474.58, "duration": 6.92}, {"text": "And what I propose doing\nis connecting M1 to M2", "start": 3481.5, "duration": 7.44}, {"text": "so that when M1 has\naccepted its input,", "start": 3488.94, "duration": 4.29}, {"text": "we're going to jump to\nM2, because that's perhaps", "start": 3493.23, "duration": 3.18}, {"text": "the first part of w.", "start": 3496.41, "duration": 1.44}, {"text": "And now we're going to have M2\nprocess the second part of w.", "start": 3497.85, "duration": 2.645}, {"text": "So the way I'm\ngoing to implement", "start": 3500.495, "duration": 1.375}, {"text": "that is by declassifying\nthe start state of M2,", "start": 3501.87, "duration": 4.23}, {"text": "having transition symbols from\nthe accepting states of M1", "start": 3506.1, "duration": 3.78}, {"text": "to M2, and then removing these\nguys here as accepting states.", "start": 3509.88, "duration": 7.345}, {"text": "And we would have to figure\nout what sort of labels", "start": 3517.225, "duration": 2.125}, {"text": "to apply here.", "start": 3519.35, "duration": 1.05}, {"text": "But, actually, this\nreasoning doesn't work.", "start": 3520.4, "duration": 4.57}, {"text": "It's tempting, but flawed.", "start": 3524.97, "duration": 2.43}, {"text": "Because-- what goes wrong?", "start": 3527.4, "duration": 3.12}, {"text": "What happens is that--", "start": 3530.52, "duration": 1.74}, {"text": "it might be that when M1 has\naccepted an initial part of w", "start": 3532.26, "duration": 7.04}, {"text": "and then it wants M2\nto accept the rest,", "start": 3539.3, "duration": 4.68}, {"text": "it might fail because M2\ndoesn't accept the rest.", "start": 3543.98, "duration": 4.02}, {"text": "And what you might have\nbeen better off doing", "start": 3548.0, "duration": 2.19}, {"text": "is waiting longer\nin M1, because there", "start": 3550.19, "duration": 3.18}, {"text": "might have been some\nother later place", "start": 3553.37, "duration": 2.07}, {"text": "to split w, which\nis still valid.", "start": 3555.44, "duration": 4.57}, {"text": "Splitting w in the\nfirst place where", "start": 3560.01, "duration": 2.7}, {"text": "you have M1 accepting\nan initial part", "start": 3562.71, "duration": 2.31}, {"text": "may not be the optimal\nplace to split w.", "start": 3565.02, "duration": 2.85}, {"text": "You might want to wait\nlater, and then you'll", "start": 3567.87, "duration": 1.98}, {"text": "have a better chance\nof accepting w.", "start": 3569.85, "duration": 4.38}, {"text": "So I'm not sure if\nyou quite follow that.", "start": 3574.23, "duration": 4.08}, {"text": "But, in fact, it doesn't work.", "start": 3578.31, "duration": 2.92}, {"text": "The question is\nwhere to split w,", "start": 3581.23, "duration": 1.55}, {"text": "and it's challenging,\nbecause how do you", "start": 3582.78, "duration": 3.27}, {"text": "know where to split w?", "start": 3586.05, "duration": 1.32}, {"text": "Because it depends upon what--", "start": 3587.37, "duration": 2.67}, {"text": "it depends on y, and\nyou haven't seen y yet.", "start": 3590.04, "duration": 4.45}, {"text": "So when you try to think about\nit that way, it looks hopeless.", "start": 3594.49, "duration": 3.49}, {"text": "But, in fact, it's still true.", "start": 3597.98, "duration": 1.86}, {"text": "And we'll see how to\ndo that on Thursday.", "start": 3599.84, "duration": 3.43}, {"text": "So just to recap\nwhat we did today,", "start": 3603.27, "duration": 4.76}, {"text": "we did our\nintroductory stuff, we", "start": 3608.03, "duration": 2.52}, {"text": "defined finite automata,\nregular languages.", "start": 3610.55, "duration": 3.7}, {"text": "We defined the regular\noperations and expressions.", "start": 3614.25, "duration": 3.38}, {"text": "We showed that the\nregular languages", "start": 3617.63, "duration": 1.5}, {"text": "are closed under union.", "start": 3619.13, "duration": 1.83}, {"text": "We started closure under\nintersection, to be continued.", "start": 3620.96, "duration": 3.68}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 0.985, "duration": 2.295}, {"text": "Commons License.", "start": 3.28, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.67, "duration": 2.21}, {"text": "continue to offer high quality\neducational resources for free.", "start": 6.88, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 10.97, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.54, "duration": 3.96}, {"text": "at ocw.mit.edu.", "start": 17.5, "duration": 0.88}, {"text": "MICHAEL SHORT: We've actually\ngot a special guest today.", "start": 21.427, "duration": 2.333}, {"text": "It's Jake Hecla, one\nof the seniors at NSE", "start": 23.76, "duration": 2.67}, {"text": "who's gone on to Chernobyl for\nthe second time, just returned", "start": 26.43, "duration": 3.63}, {"text": "from there two weeks ago.", "start": 30.06, "duration": 1.39}, {"text": "So if you remember\non Tuesday, we", "start": 31.45, "duration": 1.61}, {"text": "went through all of the\nphysics and intuition", "start": 33.06, "duration": 2.1}, {"text": "about why Chernobyl happened.", "start": 35.16, "duration": 1.47}, {"text": "And we left off on what\ndoes it look like today.", "start": 36.63, "duration": 2.65}, {"text": "So Jake is going to tell you\nwhat does it look like today.", "start": 39.28, "duration": 2.625}, {"text": "JAKE HECLA: All right,\nso first off I'm", "start": 41.905, "duration": 1.625}, {"text": "actually going to go over a bit\nof the reactor physics involved", "start": 43.53, "duration": 2.49}, {"text": "with the Chernobyl accident.", "start": 46.02, "duration": 0.96}, {"text": "I realize you guys have already\ncovered this to some extent.", "start": 46.98, "duration": 2.07}, {"text": "But I didn't plan for that.", "start": 49.05, "duration": 1.45}, {"text": "So it's in my presentation.", "start": 50.5, "duration": 1.197}, {"text": "MICHAEL SHORT: It'll\nbe a good review.", "start": 51.697, "duration": 1.583}, {"text": "JAKE HECLA: Yes, also\nI am a little sick.", "start": 53.28, "duration": 1.71}, {"text": "So I'm probably going to\nstart coughing, apologies.", "start": 54.99, "duration": 4.05}, {"text": "I'm not dying.", "start": 59.04, "duration": 0.93}, {"text": "It's just a cold.", "start": 59.97, "duration": 0.9}, {"text": "AUDIENCE: Radiation poisoning.", "start": 60.87, "duration": 1.282}, {"text": "JAKE HECLA: I have heard\nthat joke about eight times", "start": 62.152, "duration": 2.167}, {"text": "in the last two days.", "start": 64.319, "duration": 0.875}, {"text": "And I'm so done with it.", "start": 65.194, "duration": 1.016}, {"text": "But yes, it's not\nradiation poisoning.", "start": 66.21, "duration": 2.023}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 68.233, "duration": 0.917}, {"text": "JAKE HECLA: Yeah, all\nright, where is Chernobyl?", "start": 69.15, "duration": 4.67}, {"text": "Ah, dang it.", "start": 73.82, "duration": 0.97}, {"text": "Come on, no, go the other\nway, the other way, yep.", "start": 74.79, "duration": 3.47}, {"text": "OK, there.", "start": 78.26, "duration": 1.67}, {"text": "OK, so one of the\nfirst questions", "start": 79.93, "duration": 2.03}, {"text": "I got when I said I'm going to\ngo and visit Chernobyl is wait,", "start": 81.96, "duration": 2.76}, {"text": "isn't that a war zone?", "start": 84.72, "duration": 1.56}, {"text": "Not quite.", "start": 86.28, "duration": 0.9}, {"text": "So the Ukrainian,\nthe war in Ukraine", "start": 87.18, "duration": 4.62}, {"text": "is mostly in this\nportion over here.", "start": 91.8, "duration": 4.08}, {"text": "It's not entirely under\nRebel control in that area.", "start": 95.88, "duration": 3.3}, {"text": "And I say \"rebel\"\nin quotation marks", "start": 99.18, "duration": 1.65}, {"text": "because rebel means Russian.", "start": 100.83, "duration": 3.48}, {"text": "However, if you\nnotice those arrows,", "start": 104.31, "duration": 2.13}, {"text": "Russian forces are built\nup all along that border.", "start": 106.44, "duration": 2.55}, {"text": "So while it's not\nan active war zone,", "start": 108.99, "duration": 3.54}, {"text": "it's certainly not a\nplace to be spending", "start": 112.53, "duration": 2.01}, {"text": "a large amount of time.", "start": 114.54, "duration": 2.28}, {"text": "That said, Chernobyl is\nnorth of Kiev by about,", "start": 116.82, "duration": 7.95}, {"text": "I don't know, let's see,\n200, 250 kilometers.", "start": 124.77, "duration": 5.679}, {"text": "So it's not completely\nout in the sticks, right.", "start": 130.449, "duration": 4.221}, {"text": "Hopefully this gives you good\nsense of roughly where it is.", "start": 134.67, "duration": 4.27}, {"text": "All right, so what is the\nChernobyl nuclear power plant", "start": 138.94, "duration": 3.37}, {"text": "look like?", "start": 142.31, "duration": 1.32}, {"text": "It consists of four\nfinished reactors.", "start": 143.63, "duration": 2.79}, {"text": "There are two unfinished\nreactors, unit 5 and 6, that", "start": 146.42, "duration": 2.52}, {"text": "are not shown in this image.", "start": 148.94, "duration": 1.77}, {"text": "Units 1 and 2 are\nlocated at the right.", "start": 150.71, "duration": 3.93}, {"text": "Those were constructed in\nthe 1970s and early 1980s.", "start": 154.64, "duration": 4.65}, {"text": "All of these reactors\nor the RBMK type.", "start": 159.29, "duration": 3.8}, {"text": "Units 1 and 2 operated\nwith some success--", "start": 163.09, "duration": 3.47}, {"text": "I'll go into that later--", "start": 166.56, "duration": 1.97}, {"text": "for a number of years before the\naccident that happened in 1986.", "start": 168.53, "duration": 6.58}, {"text": "We also had some call\nouts up here that", "start": 175.11, "duration": 1.79}, {"text": "show the, some of the\nincidents that I'll", "start": 176.9, "duration": 3.66}, {"text": "talk about here a little bit\nlater in the presentation.", "start": 180.56, "duration": 2.31}, {"text": "But this just gives you a\ngeneral idea of the layout.", "start": 182.87, "duration": 2.8}, {"text": "So it's two separate\nbuildings for units 1 and 2.", "start": 185.67, "duration": 5.39}, {"text": "And then units 3 and 4 are in\none building, all connected", "start": 191.06, "duration": 3.63}, {"text": "by this turbo generator hall.", "start": 194.69, "duration": 1.95}, {"text": "So this is where\nthe generators that", "start": 196.64, "duration": 2.85}, {"text": "turn the steam from\nthe RBMK into power, r.", "start": 199.49, "duration": 3.93}, {"text": "This is one giant--", "start": 203.42, "duration": 2.0}, {"text": "well, before the accident, this\nwas one giant, not separated", "start": 205.42, "duration": 5.0}, {"text": "hallway, basically.", "start": 210.42, "duration": 1.24}, {"text": "So you could walk from one end\nto the other, theoretically.", "start": 211.66, "duration": 4.47}, {"text": "All right, so what is an RBMK?", "start": 216.13, "duration": 2.005}, {"text": "An RBMK is a light water-cooled,\ngraphite-moderated,", "start": 218.135, "duration": 5.075}, {"text": "channel-type reactor.", "start": 223.21, "duration": 1.69}, {"text": "This means that it does not\nhave a giant pressure vessel", "start": 224.9, "duration": 2.96}, {"text": "like you would see in a VVER\nor an equivalent American", "start": 227.86, "duration": 3.57}, {"text": "light water reactor.", "start": 231.43, "duration": 2.16}, {"text": "Why does that mean anything?", "start": 233.59, "duration": 1.27}, {"text": "Well, building giant pressure\nvessels is very difficult.", "start": 234.86, "duration": 3.26}, {"text": "If any of you've done\nresearch on manufacturing", "start": 238.12, "duration": 2.37}, {"text": "of nuclear reactors,\nyou'll find out", "start": 240.49, "duration": 2.49}, {"text": "that the equipment necessary\nto construct a reactor", "start": 242.98, "duration": 2.792}, {"text": "pressure vessel is\nnot actually something", "start": 245.772, "duration": 1.708}, {"text": "we even have in the US anymore.", "start": 247.48, "duration": 2.37}, {"text": "Is it Korea that\ndoes it for us now?", "start": 249.85, "duration": 1.97}, {"text": "MICHAEL SHORT:\nJapan Steel Works.", "start": 251.82, "duration": 1.375}, {"text": "JAKE HECLA: Japan\nthat does it now.", "start": 253.195, "duration": 2.355}, {"text": "In the Soviet times, it\nwas very, very difficult", "start": 255.55, "duration": 3.24}, {"text": "for the Soviet Union to\nproduce such pressure vessels", "start": 258.79, "duration": 5.07}, {"text": "at any kind of reasonable rate.", "start": 263.86, "duration": 1.62}, {"text": "So the RBMK got\naround this by using", "start": 265.48, "duration": 4.2}, {"text": "individual channels that were\ntheir own pressure vessel,", "start": 269.68, "duration": 2.82}, {"text": "so to speak.", "start": 272.5, "duration": 1.15}, {"text": "So the way this works is, let's\njust start on the cold side.", "start": 273.65, "duration": 3.05}, {"text": "You take in cold water, goes\nhere through these things.", "start": 276.7, "duration": 3.54}, {"text": "These are main\ncirculating pumps--", "start": 280.24, "duration": 2.1}, {"text": "MCPs, as you'll\nsee them referred", "start": 282.34, "duration": 1.65}, {"text": "to later in the presentation--", "start": 283.99, "duration": 1.77}, {"text": "goes up through the\nbottom up the core.", "start": 285.76, "duration": 2.17}, {"text": "These are the hot fuel rods.", "start": 287.93, "duration": 2.51}, {"text": "The water goes from liquid\nto steam phase as it's", "start": 290.44, "duration": 4.62}, {"text": "flowing through the\nchannels, comes out the top,", "start": 295.06, "duration": 4.23}, {"text": "goes to the steam\nwater separators.", "start": 299.29, "duration": 2.97}, {"text": "Steam goes to the turbines,\nturns the turbines,", "start": 302.26, "duration": 2.55}, {"text": "makes electricity.", "start": 304.81, "duration": 1.65}, {"text": "The important thing\nto remember here", "start": 306.46, "duration": 2.4}, {"text": "is that we've got a\ngiant graphite core.", "start": 308.86, "duration": 3.09}, {"text": "The graphite is what\nis doing the moderating", "start": 311.95, "duration": 1.89}, {"text": "in this circumstance.", "start": 313.84, "duration": 1.17}, {"text": "It is not the water.", "start": 315.01, "duration": 3.21}, {"text": "This allows you to run\nvery low-enriched uranium.", "start": 318.22, "duration": 2.77}, {"text": "So you could\ntheoretically run an RBMK", "start": 320.99, "duration": 3.89}, {"text": "on I believe it was 1.2 percent\nwas as low as they could go.", "start": 324.88, "duration": 5.46}, {"text": "But regardless, extremely\nlow-enriched uranium,", "start": 330.34, "duration": 2.81}, {"text": "which is convenient if you don't\nwant to waste a lot of time", "start": 333.15, "duration": 2.5}, {"text": "enriching uranium.", "start": 335.65, "duration": 0.75}, {"text": "The problem with this is\nthat you have a giant core.", "start": 339.91, "duration": 4.2}, {"text": "If you recall the scattering\ncross-section for graphite,", "start": 344.11, "duration": 3.04}, {"text": "it's pretty small.", "start": 347.15, "duration": 1.73}, {"text": "And the amount of energy\nlost per collision", "start": 348.88, "duration": 2.16}, {"text": "is likewise also fairly small.", "start": 351.04, "duration": 2.43}, {"text": "So the core on this thing\nis, let's see, 11, yeah,", "start": 353.47, "duration": 4.89}, {"text": "11.5 meters across.", "start": 358.36, "duration": 2.67}, {"text": "The core for an equivalent\nAmerican reactor--", "start": 361.03, "duration": 3.45}, {"text": "so well, there is no\nreal equivalent to this--", "start": 364.48, "duration": 2.7}, {"text": "but for, let's say,\nan AP 1000 reactor", "start": 367.18, "duration": 3.54}, {"text": "of equivalent electrical output,\nis about four meters across.", "start": 370.72, "duration": 3.96}, {"text": "So the core is huge.", "start": 374.68, "duration": 2.025}, {"text": "As I already discussed, this\nis what the individual pressure", "start": 379.66, "duration": 4.86}, {"text": "channels look like.", "start": 384.52, "duration": 1.02}, {"text": "So cool water comes in the\nbottom, goes by the fuel rods,", "start": 385.54, "duration": 3.48}, {"text": "pops out the top.", "start": 389.02, "duration": 3.22}, {"text": "The RBMK had some\nserious design flaws.", "start": 392.24, "duration": 2.48}, {"text": "So as I said, the core is huge.", "start": 394.72, "duration": 1.89}, {"text": "This allows local\npower anomalies", "start": 396.61, "duration": 1.98}, {"text": "to form really, really easily.", "start": 398.59, "duration": 3.36}, {"text": "If you look at the\ncore, one portion", "start": 401.95, "duration": 1.95}, {"text": "can be kind of neutronically\nseparated from the others", "start": 403.9, "duration": 2.79}, {"text": "because neutrons just don't\nmake it all that far when", "start": 406.69, "duration": 4.32}, {"text": "diffusing across the core.", "start": 411.01, "duration": 1.14}, {"text": "So you can have very, very\nhigh power in one corner", "start": 412.15, "duration": 2.25}, {"text": "and very low power in the other,\nwhich is not something that", "start": 414.4, "duration": 3.66}, {"text": "can develop in a physically\nsmaller core, which", "start": 418.06, "duration": 4.11}, {"text": "has a characteristic\nscale equivalent to that", "start": 422.17, "duration": 3.24}, {"text": "of the neutron being free path.", "start": 425.41, "duration": 1.38}, {"text": "Further, the encore flux\nmonitoring on the RBMK", "start": 429.86, "duration": 3.6}, {"text": "is seriously deficient.", "start": 433.46, "duration": 2.07}, {"text": "So there are a variety\nof neutron detectors", "start": 435.53, "duration": 2.73}, {"text": "that exist around the\nperiphery of the core.", "start": 438.26, "duration": 2.37}, {"text": "But they're wholly insufficient\nto catch these local power", "start": 440.63, "duration": 2.88}, {"text": "anomalies.", "start": 443.51, "duration": 1.41}, {"text": "Chernobyl actually found out\nthe hard way on this one.", "start": 444.92, "duration": 2.25}, {"text": "In 1982, unit 1 suffered a\nquote \"localized core melt,\"", "start": 447.17, "duration": 5.25}, {"text": "not really something that\ncan happen in LWR, really", "start": 452.42, "duration": 3.99}, {"text": "any other type of reactor.", "start": 456.41, "duration": 1.59}, {"text": "But a couple of\nthe fuel channels", "start": 458.0, "duration": 1.8}, {"text": "actually experienced\none of these local power", "start": 459.8, "duration": 2.52}, {"text": "anomalies and ended up melting.", "start": 462.32, "duration": 1.74}, {"text": "So if you go into the\ncontrol room of unit 1,", "start": 464.06, "duration": 3.6}, {"text": "you can see that on the fuel\nchannel cartogram on the wall,", "start": 467.66, "duration": 4.1}, {"text": "there are two of them that\nare just Sharpied out.", "start": 471.76, "duration": 2.11}, {"text": "And those are the\nones that melted.", "start": 473.87, "duration": 2.94}, {"text": "Further, it has a positive\nvoid reactivity coefficient.", "start": 476.81, "duration": 3.107}, {"text": "What does that mean?", "start": 479.917, "duration": 0.833}, {"text": "Well, when the water\nboils in the core,", "start": 480.75, "duration": 3.2}, {"text": "the density of the\nwater there goes down.", "start": 483.95, "duration": 2.43}, {"text": "And the power of\nthe reactor ends up", "start": 486.38, "duration": 2.28}, {"text": "going up because the\nwater is primarily", "start": 488.66, "duration": 2.28}, {"text": "acting not as moderator\nbut as a neutron absorber.", "start": 490.94, "duration": 2.97}, {"text": "This is bad for a whole\nvariety of reasons.", "start": 493.91, "duration": 4.32}, {"text": "And they found out\nquite catastrophically", "start": 498.23, "duration": 2.34}, {"text": "in 1986 exactly why.", "start": 500.57, "duration": 1.83}, {"text": "Further, the system is\nextremely unstable at low power.", "start": 502.4, "duration": 3.99}, {"text": "So how did the 1986\naccident happen?", "start": 510.47, "duration": 4.11}, {"text": "It was part of this thing called\na turbo generator rundown test.", "start": 514.58, "duration": 5.12}, {"text": "The general idea is that if you\nhave an off-site power failure,", "start": 519.7, "duration": 4.5}, {"text": "and your main circulating\npumps are no longer", "start": 524.2, "duration": 3.45}, {"text": "have off-site power,\nyou somehow need", "start": 527.65, "duration": 1.797}, {"text": "to keep water flowing\nthrough the core, such", "start": 529.447, "duration": 1.833}, {"text": "that the fuel does not melt.", "start": 531.28, "duration": 2.67}, {"text": "The problem is that the backup,\nlarge diesel generators,", "start": 533.95, "duration": 3.63}, {"text": "are just that.", "start": 537.58, "duration": 0.6}, {"text": "They're large.", "start": 538.18, "duration": 0.85}, {"text": "They're diesel.", "start": 539.03, "duration": 1.01}, {"text": "And therefore they're\nvery, very slow", "start": 540.04, "duration": 1.56}, {"text": "to come online and\ncome up to full power.", "start": 541.6, "duration": 3.12}, {"text": "The way that you\ncan bridge this gap", "start": 544.72, "duration": 2.07}, {"text": "is by using the energy that\nyou've stored in the turbines", "start": 546.79, "duration": 3.57}, {"text": "to effectively power the\nmain circulating pumps", "start": 550.36, "duration": 2.4}, {"text": "until the diesel generators\ncan come up online.", "start": 552.76, "duration": 3.18}, {"text": "When unit 4 was fully\nconstructed in 1983", "start": 555.94, "duration": 3.9}, {"text": "and turned on for\nthe first time,", "start": 559.84, "duration": 1.57}, {"text": "they had never\nactually done this test", "start": 561.41, "duration": 1.84}, {"text": "where they did a turbo\ngenerator rundown,", "start": 563.25, "duration": 1.96}, {"text": "despite the fact that it was\nrequired by law in the Soviet", "start": 565.21, "duration": 2.76}, {"text": "Union that all new\npower stations should", "start": 567.97, "duration": 2.7}, {"text": "have this test performed.", "start": 570.67, "duration": 1.7}, {"text": "It was delayed until 1986.", "start": 572.37, "duration": 3.52}, {"text": "And yeah, it was delayed until\n1986 is the long story short.", "start": 575.89, "duration": 8.05}, {"text": "The test procedure-- sorry for\nall the text on this slide--", "start": 583.94, "duration": 2.78}, {"text": "is basically as follows.", "start": 586.72, "duration": 1.72}, {"text": "So you would ramp\nthe reactor down.", "start": 588.44, "duration": 1.88}, {"text": "So you would bring it from\na normal thermal output", "start": 590.32, "duration": 2.49}, {"text": "of up to 2,400\nmegawatts thermal,", "start": 592.81, "duration": 3.42}, {"text": "down to 600 or 700 megawatts.", "start": 596.23, "duration": 3.01}, {"text": "You'd bring the turbo\ngenerators up to full speed.", "start": 599.24, "duration": 2.138}, {"text": "So you'd store as\nmuch energy in them", "start": 601.378, "duration": 1.542}, {"text": "as you possibly could, then\ncut off the steam supply such", "start": 602.92, "duration": 3.99}, {"text": "that now you are just extracting\nenergy from the spinning turbo", "start": 606.91, "duration": 2.85}, {"text": "generator.", "start": 609.76, "duration": 1.482}, {"text": "This would then be used to\npower the main circulating", "start": 611.242, "duration": 2.208}, {"text": "pumps, each of which\ntook about 40 megawatts.", "start": 613.45, "duration": 3.48}, {"text": "There are eight of them total.", "start": 616.93, "duration": 2.25}, {"text": "I believe six could be\nused for normal operation.", "start": 619.18, "duration": 4.77}, {"text": "The rundown would take\nsomewhere in the range", "start": 623.95, "duration": 2.13}, {"text": "of 60 to 70 seconds.", "start": 626.08, "duration": 1.86}, {"text": "And hopefully by this time\nyour diesel generators", "start": 627.94, "duration": 2.07}, {"text": "would be turned\non, pumping water,", "start": 630.01, "duration": 1.68}, {"text": "and everything would be fine.", "start": 631.69, "duration": 2.05}, {"text": "What happened in the test\nwas decidedly quite different", "start": 633.74, "duration": 3.2}, {"text": "from that.", "start": 636.94, "duration": 0.9}, {"text": "So on April 26,\n1986, they attempted", "start": 637.84, "duration": 5.58}, {"text": "to begin this test about\nsix hours behind schedule", "start": 643.42, "duration": 2.97}, {"text": "because there was an incident\nin another part of Ukraine,", "start": 646.39, "duration": 2.97}, {"text": "in which a coal power\nplant went offline.", "start": 649.36, "duration": 2.19}, {"text": "So what happened\nwas the authority", "start": 651.55, "duration": 3.9}, {"text": "for the grid in the area\nordered that Chernobyl", "start": 655.45, "duration": 3.0}, {"text": "should stay online at full power\nfor an additional six hours.", "start": 658.45, "duration": 5.52}, {"text": "They began the test by\nbringing power down.", "start": 663.97, "duration": 2.76}, {"text": "But as a result of running\nfor an extra six hours,", "start": 666.73, "duration": 4.74}, {"text": "they'd built up a significant\namount of xenon precursors", "start": 671.47, "duration": 2.79}, {"text": "in the core.", "start": 674.26, "duration": 1.03}, {"text": "So when they started\nturning the power down,", "start": 675.29, "duration": 2.6}, {"text": "the power started going\ndown, and down, and down.", "start": 677.89, "duration": 3.27}, {"text": "And they were unable\nto arrest its drop.", "start": 681.16, "duration": 4.89}, {"text": "What ended up happening was that\nthe power dropped all the way", "start": 686.05, "duration": 3.63}, {"text": "down to 30 megawatts thermal.", "start": 689.68, "duration": 2.19}, {"text": "And the reactor operators\nkind of panicked.", "start": 691.87, "duration": 3.46}, {"text": "Their response to this,\ninstead of canceling the test,", "start": 695.33, "duration": 3.02}, {"text": "was to pull out as\nmany control rods", "start": 698.35, "duration": 2.22}, {"text": "as they could get\ntheir hands on.", "start": 700.57, "duration": 1.65}, {"text": "They did so.", "start": 702.22, "duration": 0.72}, {"text": "And this managed to rescue the\nthermal output of the reactor.", "start": 702.94, "duration": 3.9}, {"text": "And it bumped up to around\n200 megawatts thermal.", "start": 706.84, "duration": 3.33}, {"text": "At this point, the reactor was\nin an extremely unstable state.", "start": 710.17, "duration": 3.27}, {"text": "Mind you, almost all of the rods\nthat they could get their hands", "start": 713.44, "duration": 2.73}, {"text": "on were out of the reactor.", "start": 716.17, "duration": 1.98}, {"text": "The only thing\nkeeping reactivity", "start": 718.15, "duration": 1.8}, {"text": "at a reasonable level\nwas all the xenon", "start": 719.95, "duration": 1.65}, {"text": "that was built up in the core.", "start": 721.6, "duration": 3.06}, {"text": "At this point, they began the\nturbo generator run down test.", "start": 724.66, "duration": 3.75}, {"text": "They shut off steam to the main\nturbine, or one of the turbines", "start": 728.41, "duration": 5.7}, {"text": "after it was run\nup to full power,", "start": 734.11, "duration": 3.45}, {"text": "and then attempted to run\nthe main circulating pump.", "start": 737.56, "duration": 2.79}, {"text": "The main circulating pump\nstarted drawing down the energy", "start": 740.35, "duration": 3.15}, {"text": "from the spinning turbine.", "start": 743.5, "duration": 3.54}, {"text": "And as a result, it\nran slower and slower,", "start": 747.04, "duration": 2.55}, {"text": "meaning that the\nflow through the core", "start": 749.59, "duration": 1.77}, {"text": "was less and less, more water\nboiled, going into steam,", "start": 751.36, "duration": 4.74}, {"text": "which increased the reactivity.", "start": 756.1, "duration": 3.21}, {"text": "As a result, the power\noutput of the court went up.", "start": 759.31, "duration": 3.9}, {"text": "It burned out more xenon.", "start": 763.21, "duration": 1.62}, {"text": "And the cycle continued.", "start": 764.83, "duration": 2.37}, {"text": "They noticed a power\nexcursion, about 40 seconds", "start": 767.2, "duration": 2.7}, {"text": "after they began the\ntest and at this point", "start": 769.9, "duration": 3.54}, {"text": "recognize they were\nin bad territory", "start": 773.44, "duration": 1.77}, {"text": "and hit the scram button.", "start": 775.21, "duration": 2.22}, {"text": "This would jam pretty much all\nof the available control rods", "start": 777.43, "duration": 2.79}, {"text": "into the core, including\nsome emergency extras,", "start": 780.22, "duration": 2.31}, {"text": "and shut everything down.", "start": 782.53, "duration": 1.8}, {"text": "In most circumstances, this\nwould be a fairly safe move.", "start": 784.33, "duration": 2.73}, {"text": "But in the case of the RBMK\nit was most certainly not.", "start": 787.06, "duration": 4.77}, {"text": "RBMK control rods have\na graphite tip on them.", "start": 791.83, "duration": 4.32}, {"text": "When jammed into the core,\nthey caused a localized power", "start": 796.15, "duration": 3.42}, {"text": "increase because the graphite\nis a great moderator.", "start": 799.57, "duration": 3.42}, {"text": "And it is displacing water,\nwhich is a great absorber.", "start": 802.99, "duration": 3.065}, {"text": "And as a result, after they\nmade it a couple meters", "start": 806.055, "duration": 2.125}, {"text": "into the core, the\nincreased pressure", "start": 808.18, "duration": 4.08}, {"text": "in the core from the\npower output, which", "start": 812.26, "duration": 4.02}, {"text": "was localized around the\ntips the control rods,", "start": 816.28, "duration": 2.25}, {"text": "ended up shattering the\ncontrol rod drive mechanisms.", "start": 818.53, "duration": 3.96}, {"text": "And instead of turning off, the\ncycle basically just continued,", "start": 822.49, "duration": 4.8}, {"text": "power continued to ramp up over\nthe next couple of seconds.", "start": 827.29, "duration": 2.7}, {"text": "It eventually reached\nsomewhere around 10 to 20", "start": 829.99, "duration": 2.64}, {"text": "times the maximum rated\nthermal output of the system.", "start": 832.63, "duration": 3.09}, {"text": "And a massive steam\nexplosion ended up", "start": 835.72, "duration": 1.77}, {"text": "ripping through the facility.", "start": 837.49, "duration": 2.31}, {"text": "It tossed the 2000\nton biological shield", "start": 839.8, "duration": 3.51}, {"text": "on top of the reactor through\nthe roof of the facility.", "start": 843.31, "duration": 3.84}, {"text": "It injected a significant\nportion of the fuel,", "start": 847.15, "duration": 2.82}, {"text": "as well as the\nmoderator in the core.", "start": 849.97, "duration": 2.49}, {"text": "And it started a massive\nfire around the facility.", "start": 852.46, "duration": 3.257}, {"text": "Just to give you a\ngood sense of scale,", "start": 858.2, "duration": 1.625}, {"text": "let's see, if I've got\nthe virtual laser pointer.", "start": 859.825, "duration": 2.985}, {"text": "That's a person right\nhere, this little guy.", "start": 862.81, "duration": 4.23}, {"text": "This is the top of\nthe biological shield,", "start": 867.04, "duration": 2.94}, {"text": "Elena shield.", "start": 869.98, "duration": 2.4}, {"text": "And then this is a model, a\ncutaway model of the Chernobyl", "start": 872.38, "duration": 5.04}, {"text": "reactor facility\nwith the shield,", "start": 877.42, "duration": 3.99}, {"text": "and with the flipped shield\nthat went up through the roof", "start": 881.41, "duration": 4.73}, {"text": "and came back down.", "start": 886.14, "duration": 1.62}, {"text": "So as you can see, it was an\nutterly massive explosion.", "start": 887.76, "duration": 3.02}, {"text": "So the damage to the reactor was\nimmediately quite catastrophic.", "start": 893.86, "duration": 4.62}, {"text": "Moderator blocks,\nfuel was spread", "start": 898.48, "duration": 1.86}, {"text": "all around the immediate area.", "start": 900.34, "duration": 1.95}, {"text": "If you look in this photo,\nit's rather difficult to see.", "start": 902.29, "duration": 2.62}, {"text": "But at the bottom of\nthat column of smoke", "start": 904.91, "duration": 2.42}, {"text": "you can actually see the bottom\nup the biological shield.", "start": 907.33, "duration": 4.08}, {"text": "Kind of gives you a\nsense of the scale", "start": 911.41, "duration": 2.25}, {"text": "of the damage to the reactor.", "start": 913.66, "duration": 2.18}, {"text": "After the explosion happened,\nactually none of the operators", "start": 915.84, "duration": 2.5}, {"text": "believe the reactor breached\nconfinement in any way.", "start": 918.34, "duration": 3.373}, {"text": "They didn't really\nhave an immediate way", "start": 921.713, "duration": 1.667}, {"text": "of seeing what had happened.", "start": 923.38, "duration": 1.74}, {"text": "So they open the door and went\nto the main turbo generator", "start": 925.12, "duration": 2.46}, {"text": "building to\ninvestigate the damage.", "start": 927.58, "duration": 1.74}, {"text": "They believed it was perhaps one\nor two ruptured fuel channels.", "start": 929.32, "duration": 3.27}, {"text": "As it happened at, I\nbelieve the Leningrad,", "start": 932.59, "duration": 2.093}, {"text": "I think it was the\nLeningrad power", "start": 934.683, "duration": 1.417}, {"text": "station a few years earlier.", "start": 936.1, "duration": 2.233}, {"text": "In the few seconds\nthat they were there,", "start": 938.333, "duration": 1.667}, {"text": "they received fatal doses\nand died in the hospital", "start": 940.0, "duration": 2.76}, {"text": "in May of 1986.", "start": 942.76, "duration": 2.28}, {"text": "This is a photo from\ncontrol room of reactor 4,", "start": 945.04, "duration": 3.0}, {"text": "showing a jammed control rod\ndrive at the 6 meter position.", "start": 948.04, "duration": 3.72}, {"text": "So this was probably\na rod, let's see,", "start": 951.76, "duration": 2.76}, {"text": "this is probably a rod coming\nup from the bottom, in that it,", "start": 954.52, "duration": 5.82}, {"text": "seven meters would\nbe all the way out.", "start": 960.34, "duration": 1.68}, {"text": "Zero meters would\nbe all the way in.", "start": 962.02, "duration": 1.5}, {"text": "The initial response to\nthis, despite the fact", "start": 967.01, "duration": 2.22}, {"text": "that the reactor\noperators were not", "start": 969.23, "duration": 2.55}, {"text": "yet dead, did\nrealize that it was", "start": 971.78, "duration": 1.83}, {"text": "a full breach of\ncontainment, was", "start": 973.61, "duration": 1.89}, {"text": "the response was to an accident\nthat was non-nuclear in nature.", "start": 975.5, "duration": 2.8}, {"text": "So when the fire department\ngot a call from the authority", "start": 978.3, "duration": 3.44}, {"text": "at Chernobyl, the message\nthat they received", "start": 981.74, "duration": 3.84}, {"text": "was there's a fire at\nthe reactor complex.", "start": 985.58, "duration": 2.91}, {"text": "As a result, what\nthey showed up with", "start": 988.49, "duration": 2.91}, {"text": "was not equipment suitable for\na hazmat situation in any way.", "start": 991.4, "duration": 7.11}, {"text": "That said, there's\npretty much nothing", "start": 998.51, "duration": 1.65}, {"text": "that could shield anyone from\nthe extremely high radiation", "start": 1000.16, "duration": 3.618}, {"text": "field that one would\nencounter around", "start": 1003.778, "duration": 1.542}, {"text": "the reactor in the immediate\naftermath of the accident.", "start": 1005.32, "duration": 2.5}, {"text": "But nonetheless, they\nwere extremely vulnerable.", "start": 1007.82, "duration": 6.38}, {"text": "It was night when this\naccident happened.", "start": 1014.2, "duration": 2.04}, {"text": "As I mentioned, this happened\nat 1:23 in the morning.", "start": 1016.24, "duration": 3.63}, {"text": "They actually couldn't see\nthe extent of the accident.", "start": 1019.87, "duration": 3.09}, {"text": "And they initially\nbelieved that it was just", "start": 1022.96, "duration": 2.1}, {"text": "a fire on the roof of the\nturbo generator building.", "start": 1025.06, "duration": 2.525}, {"text": "They attempted to\nfight the fire.", "start": 1027.585, "duration": 1.375}, {"text": "And some of them\nactually succumb", "start": 1028.96, "duration": 1.659}, {"text": "to acute radiation poisoning,\nor acute radiation syndrome,", "start": 1030.619, "duration": 3.381}, {"text": "almost immediately.", "start": 1034.0, "duration": 2.91}, {"text": "A number of firefighters\nwent up on the roof", "start": 1036.91, "duration": 1.9}, {"text": "and just didn't come back.", "start": 1038.81, "duration": 1.083}, {"text": "The aftermath of the\naccident, the cleanup", "start": 1044.4, "duration": 2.189}, {"text": "was handled by the Soviet Army.", "start": 1046.589, "duration": 2.791}, {"text": "The people that were\ninvolved in this", "start": 1049.38, "duration": 1.95}, {"text": "were known as the liquidators.", "start": 1051.33, "duration": 2.58}, {"text": "They would spend several minutes\non the rooftop of the turbo", "start": 1053.91, "duration": 3.54}, {"text": "generator building, or up\nnear where the reactor was,", "start": 1057.45, "duration": 3.39}, {"text": "the reactor containment\nbuilding was.", "start": 1060.84, "duration": 1.89}, {"text": "And they would receive a,\neffectively a lifetime dose,", "start": 1062.73, "duration": 5.71}, {"text": "which I believe was, I believe\ntheir limit was 50 REM.", "start": 1068.44, "duration": 4.31}, {"text": "And that would be a couple\nof minutes up there.", "start": 1072.75, "duration": 3.48}, {"text": "Let's see, this photo doesn't\nshow much evidence of it.", "start": 1076.23, "duration": 4.83}, {"text": "But I suppose it shows a\nlittle bit of evidence of it.", "start": 1081.06, "duration": 2.438}, {"text": "If you look around the\nbottom up the frame,", "start": 1083.498, "duration": 1.792}, {"text": "you can actually\nsee a little bit", "start": 1085.29, "duration": 1.68}, {"text": "of hazing in kind of\na periodic fashion.", "start": 1086.97, "duration": 2.34}, {"text": "Let's see if I can get my\npointer on it here, here, here,", "start": 1089.31, "duration": 6.13}, {"text": "here, and here.", "start": 1095.44, "duration": 1.13}, {"text": "That's the gear that\nmoves the film is actually", "start": 1096.57, "duration": 3.24}, {"text": "shielding the film\nfrom radiation", "start": 1099.81, "duration": 3.78}, {"text": "exposure at those points.", "start": 1103.59, "duration": 1.77}, {"text": "The radiation dose rate\nwas so high up there", "start": 1105.36, "duration": 2.52}, {"text": "that most of the pictures\nthat were taken just", "start": 1107.88, "duration": 2.19}, {"text": "didn't turn out whatsoever.", "start": 1110.07, "duration": 2.52}, {"text": "A few smarter photographers\nused a whole lot of lead", "start": 1112.59, "duration": 3.57}, {"text": "and were able to capture\nphotos like this.", "start": 1116.16, "duration": 1.9}, {"text": "But nonetheless, the dose\nrates were tremendous.", "start": 1118.06, "duration": 2.93}, {"text": "The reactor structure itself\nwas entombed in this thing", "start": 1123.94, "duration": 3.84}, {"text": "that we call the sarcophagus.", "start": 1127.78, "duration": 2.22}, {"text": "People in Ukraine call\nit the object shelter,", "start": 1130.0, "duration": 1.94}, {"text": "or the shelter object.", "start": 1131.94, "duration": 1.39}, {"text": "It was constructed in\nstarting almost immediately", "start": 1133.33, "duration": 3.48}, {"text": "after the accident, basically\nto keep radioactive graphite", "start": 1136.81, "duration": 4.98}, {"text": "and fuel fragments from\nleaving the reactor structure", "start": 1141.79, "duration": 3.51}, {"text": "and contaminating any more land.", "start": 1145.3, "duration": 2.5}, {"text": "This is a photo from when\nit was under construction.", "start": 1147.8, "duration": 3.95}, {"text": "Basically what it consisted of\nwere steel and concrete walls", "start": 1151.75, "duration": 3.33}, {"text": "that were erected\naround the reactor,", "start": 1155.08, "duration": 3.21}, {"text": "using a variety of technologies.", "start": 1158.29, "duration": 2.07}, {"text": "They at first attempted\nto use robots,", "start": 1160.36, "duration": 3.93}, {"text": "that were almost\nimmediately rendered useless", "start": 1164.29, "duration": 3.57}, {"text": "by the high radiation field.", "start": 1167.86, "duration": 2.49}, {"text": "Later on, they ended up using\nquote \"bio robots,\" people,", "start": 1170.35, "duration": 4.65}, {"text": "to move things into place.", "start": 1175.0, "duration": 3.72}, {"text": "As I've said before,\na whole lot of people", "start": 1178.72, "duration": 2.1}, {"text": "died in this accident both\nimmediately and after,", "start": 1180.82, "duration": 5.43}, {"text": "many during the construction\nof the sarcophagus.", "start": 1186.25, "duration": 3.3}, {"text": "Actually during the\ninitial firefighting,", "start": 1189.55, "duration": 2.01}, {"text": "or yeah, the initial\nfirefighting measures,", "start": 1191.56, "duration": 2.37}, {"text": "as the core remained burning\nfor a number of weeks", "start": 1193.93, "duration": 2.85}, {"text": "after the accident,\nthey attempted", "start": 1196.78, "duration": 3.69}, {"text": "to put it out with bags of\nsand dropped from helicopters.", "start": 1200.47, "duration": 4.14}, {"text": "And during that effort,\na helicopter actually", "start": 1204.61, "duration": 3.48}, {"text": "ended up hitting\none of the cranes", "start": 1208.09, "duration": 1.59}, {"text": "that they were attempting\nto use for this", "start": 1209.68, "duration": 1.92}, {"text": "and falling into the\nreactor, and a good portion", "start": 1211.6, "duration": 2.76}, {"text": "of its remains remain entombed\nwithin the sarcophagus,", "start": 1214.36, "duration": 3.03}, {"text": "from what I understand.", "start": 1217.39, "duration": 3.74}, {"text": "All right, so my visit to\nChernobyl, why would anyone", "start": 1221.13, "duration": 3.58}, {"text": "ever want to go there?", "start": 1224.71, "duration": 1.65}, {"text": "The primary focus\nwas to learn about", "start": 1226.36, "duration": 1.62}, {"text": "radiological\ndecontamination at the site,", "start": 1227.98, "duration": 3.24}, {"text": "basically how is\ncontamination control managed,", "start": 1231.22, "duration": 3.03}, {"text": "how do workers stay safe.", "start": 1234.25, "duration": 1.338}, {"text": "Mind you, there are\n3,000 people that", "start": 1235.588, "duration": 1.542}, {"text": "go to work there every day.", "start": 1237.13, "duration": 3.03}, {"text": "And what are the strengths?", "start": 1240.16, "duration": 1.47}, {"text": "And what are the shortcomings\nof their radiological program?", "start": 1241.63, "duration": 2.865}, {"text": "It was seven days total,\nfour of which were on site.", "start": 1244.495, "duration": 4.515}, {"text": "Other days were spent\nin Pripyat as well as", "start": 1249.01, "duration": 3.96}, {"text": "in some classroom training,\nwhich I've got great photos of.", "start": 1252.97, "duration": 4.35}, {"text": "So this is a slide stolen\ndirectly from the PowerPoint", "start": 1257.32, "duration": 2.94}, {"text": "that I was sent on day one.", "start": 1260.26, "duration": 2.47}, {"text": "But this was organized by\nthree people, Carl Willis,", "start": 1262.73, "duration": 3.92}, {"text": "Erik Kambarian, and Ed Geist.", "start": 1266.65, "duration": 2.16}, {"text": "I've known Carl for\na few years now.", "start": 1268.81, "duration": 1.59}, {"text": "He lives in\nAlbuquerque, New Mexico", "start": 1270.4, "duration": 2.67}, {"text": "and is a radiation safety\nofficer at a company", "start": 1273.07, "duration": 2.46}, {"text": "that, I think they do advanced\nenergy storage technologies.", "start": 1275.53, "duration": 4.5}, {"text": "I'm not exactly sure.", "start": 1280.03, "duration": 2.04}, {"text": "Erik is a firefighter and\nspecializes in radiation", "start": 1282.07, "duration": 4.23}, {"text": "emergency response.", "start": 1286.3, "duration": 1.2}, {"text": "And Edward works at\nthe Rand Corporation", "start": 1287.5, "duration": 3.33}, {"text": "and does nuclear history and\nnuclear security research.", "start": 1290.83, "duration": 3.105}, {"text": "This is the team this year.", "start": 1297.2, "duration": 2.56}, {"text": "So we've got, let's start here.", "start": 1299.76, "duration": 2.12}, {"text": "This is Lucas.", "start": 1301.88, "duration": 0.69}, {"text": "He does environmental\nradiation monitoring.", "start": 1302.57, "duration": 2.73}, {"text": "That's me after having no sleep\nbecause I did a 22.611 p-set", "start": 1305.3, "duration": 3.69}, {"text": "the night before.", "start": 1308.99, "duration": 1.78}, {"text": "I know.", "start": 1310.77, "duration": 0.5}, {"text": "I looked so happy to be there.", "start": 1311.27, "duration": 1.89}, {"text": "This is Nathan.", "start": 1313.16, "duration": 1.2}, {"text": "Nathan builds organs, as\nin the musical instrument.", "start": 1314.36, "duration": 4.98}, {"text": "He was along because\nhe's always been", "start": 1319.34, "duration": 1.56}, {"text": "interested in Chernobyl\nbut didn't really have", "start": 1320.9, "duration": 2.82}, {"text": "any experience in the field.", "start": 1323.72, "duration": 2.76}, {"text": "This is Stanislaus.", "start": 1326.48, "duration": 1.59}, {"text": "Stanislaus was our guide\nfrom the Chernobyl authority.", "start": 1328.07, "duration": 3.6}, {"text": "He's been working at\nthe plant since 1991", "start": 1331.67, "duration": 2.19}, {"text": "and is a fantastic\nresource for information.", "start": 1333.86, "duration": 3.54}, {"text": "This is Ed, who I believe\nI talked about earlier.", "start": 1337.4, "duration": 2.84}, {"text": "And this is Ryan Pierce.", "start": 1340.24, "duration": 2.02}, {"text": "I'm not really\nsure what he does.", "start": 1342.26, "duration": 1.41}, {"text": "This is Iris, who is a friend\nof Carl's and works in,", "start": 1343.67, "duration": 5.64}, {"text": "believe radiation oncology.", "start": 1349.31, "duration": 2.19}, {"text": "And then Danell Hogan, who's\nan educator based in Phoenix,", "start": 1351.5, "duration": 5.74}, {"text": "Arizona who works with the DOE.", "start": 1357.24, "duration": 1.37}, {"text": "By the way if you're\nwondering why we're all", "start": 1360.857, "duration": 1.833}, {"text": "wearing those absurd\nrobes before we", "start": 1362.69, "duration": 2.07}, {"text": "were going to go\nin to another room", "start": 1364.76, "duration": 3.3}, {"text": "and change into basically\ncoveralls, which", "start": 1368.06, "duration": 4.29}, {"text": "are easy to decontaminate.", "start": 1372.35, "duration": 2.945}, {"text": "One of the activities\nthat we did", "start": 1375.295, "duration": 1.375}, {"text": "was real decontamination\ntraining.", "start": 1376.67, "duration": 2.22}, {"text": "So that is a truck from\nthe Novarka work site,", "start": 1378.89, "duration": 3.72}, {"text": "which, by the way, that is\nme with a Geiger counter.", "start": 1382.61, "duration": 3.69}, {"text": "I'm surveying for contamination.", "start": 1386.3, "duration": 2.67}, {"text": "We then pressure\nwashed the truck.", "start": 1388.97, "duration": 2.387}, {"text": "As it turns out, there's\na very specific technique", "start": 1391.357, "duration": 2.083}, {"text": "one needs to use for pressure\nwashing when you're dealing", "start": 1393.44, "duration": 2.375}, {"text": "with a contaminated object, so\nas to not blast contaminated", "start": 1395.815, "duration": 3.835}, {"text": "dirt up back onto the truck.", "start": 1399.65, "duration": 2.53}, {"text": "This was a very interesting\nexperience and also", "start": 1402.18, "duration": 2.3}, {"text": "one that was very entertaining\nfor the workers involved,", "start": 1404.48, "duration": 2.64}, {"text": "because they don't actually\nwear that when they're", "start": 1407.12, "duration": 3.18}, {"text": "doing decontamination because\ntheir respect for safety", "start": 1410.3, "duration": 4.8}, {"text": "protocols are, shall we\nsay, a bit different.", "start": 1415.1, "duration": 3.12}, {"text": "So they got to see us\nwhere the absurd rubber", "start": 1418.22, "duration": 2.73}, {"text": "ducky suits while they stood\nby smoking and laughing at us.", "start": 1420.95, "duration": 5.94}, {"text": "I believe you can actually see\nthe corner of that guy's jacket", "start": 1426.89, "duration": 2.92}, {"text": "back there.", "start": 1429.81, "duration": 0.5}, {"text": "And he's just wearing\neveryday clothes.", "start": 1430.31, "duration": 2.55}, {"text": "We also went on the new\nsafe confinement work site.", "start": 1435.7, "duration": 2.94}, {"text": "So I haven't talked about it\nearlier in this presentation,", "start": 1438.64, "duration": 2.52}, {"text": "but I suppose I should have.", "start": 1441.16, "duration": 2.28}, {"text": "There is a object called\nthe New Safe Confinement", "start": 1443.44, "duration": 4.2}, {"text": "Arch that consists of basically\na giant stainless steel", "start": 1447.64, "duration": 5.25}, {"text": "structure on rails which is\nbeing slid over reactor 4", "start": 1452.89, "duration": 4.05}, {"text": "so as to prevent the spread\nof any sort of contamination", "start": 1456.94, "duration": 2.55}, {"text": "from it.", "start": 1459.49, "duration": 1.29}, {"text": "This is known as the New Safe\nConfinement, or NSC, arch.", "start": 1460.78, "duration": 4.77}, {"text": "It's been under\nconstruction since 2007.", "start": 1465.55, "duration": 2.88}, {"text": "And it just moved\nfor the first time,", "start": 1468.43, "duration": 3.15}, {"text": "actually while I was there,\nso on the 12th of November.", "start": 1471.58, "duration": 5.28}, {"text": "It's supposed to\nlast for 100 years.", "start": 1476.86, "duration": 4.08}, {"text": "And hopefully in that\nkind of time span", "start": 1480.94, "duration": 1.89}, {"text": "they'll be able to take apart\nwhat remains of the reactor.", "start": 1482.83, "duration": 3.6}, {"text": "So actually what you see here is\nthe corner of the sarcophagus.", "start": 1486.43, "duration": 5.34}, {"text": "And then if you were to pan\nover this way a little bit,", "start": 1491.77, "duration": 3.66}, {"text": "you'd see the right set\nof tracks for the New Safe", "start": 1495.43, "duration": 4.92}, {"text": "Confinement Arch.", "start": 1500.35, "duration": 2.69}, {"text": "We also did some\nclassroom training.", "start": 1503.04, "duration": 2.763}, {"text": "Admittedly, the\nclassroom training", "start": 1505.803, "duration": 1.417}, {"text": "was the most disappointing\npart of this.", "start": 1507.22, "duration": 3.27}, {"text": "The instructors were\nnot particularly", "start": 1510.49, "duration": 2.64}, {"text": "interested in showing\nus really anything", "start": 1513.13, "duration": 2.61}, {"text": "other than YouTube videos and\nother things that would just", "start": 1515.74, "duration": 5.64}, {"text": "waste our time.", "start": 1521.38, "duration": 1.38}, {"text": "That was the one part of this\ntrip that I did not enjoy.", "start": 1522.76, "duration": 3.507}, {"text": "Regardless, we did get\nto learn a little bit", "start": 1526.267, "duration": 1.833}, {"text": "about the various hazmat\ngetups that folks would", "start": 1528.1, "duration": 4.14}, {"text": "wear when working on site.", "start": 1532.24, "duration": 4.04}, {"text": "As I mentioned we also\ngot to visit Pripyat,", "start": 1536.28, "duration": 4.77}, {"text": "which I have more\nphotos of later,", "start": 1541.05, "duration": 2.04}, {"text": "as well as the reactor\n4 control room, which", "start": 1543.09, "duration": 2.88}, {"text": "is inside the sarcophagus,\nwhich is quite a treat to visit.", "start": 1545.97, "duration": 4.32}, {"text": "The reactor 4\ncontrol room is not", "start": 1550.29, "duration": 2.58}, {"text": "terribly contaminated as a\nresult of the decontamination", "start": 1552.87, "duration": 3.21}, {"text": "efforts.", "start": 1556.08, "duration": 1.11}, {"text": "During the accident,\nthe dose rate", "start": 1557.19, "duration": 1.86}, {"text": "would have been somewhere in the\nrange of 5 to 10 rem an hour.", "start": 1559.05, "duration": 4.05}, {"text": "But today, it's in the\nrange of 10 mrem an hour.", "start": 1563.1, "duration": 3.48}, {"text": "This is the New Safe\nConfinement Arch", "start": 1569.078, "duration": 1.542}, {"text": "that I've been talking about.", "start": 1570.62, "duration": 1.208}, {"text": "This is actually a photo from\n2015 with a clip art Statue", "start": 1571.828, "duration": 3.562}, {"text": "of Liberty on it, but to\ngive you an idea of how huge", "start": 1575.39, "duration": 2.82}, {"text": "it is, 5 meters taller\nthan the Statue of Liberty.", "start": 1578.21, "duration": 6.03}, {"text": "And it's on rails,\nwhich is interesting.", "start": 1584.24, "duration": 2.44}, {"text": "It's actually too\nbig for wheels.", "start": 1586.68, "duration": 1.85}, {"text": "So it's not on rails\nlike with wheels on them.", "start": 1588.53, "duration": 3.03}, {"text": "It's on rails with\ngiant Teflon scoots.", "start": 1591.56, "duration": 2.025}, {"text": "This is the inside of the\nturbo generator hallway.", "start": 1597.24, "duration": 2.115}, {"text": "Remember that long\nbuilding that I showed you", "start": 1599.355, "duration": 1.875}, {"text": "that connected reactors\n1 and 2 and 3 and 4?", "start": 1601.23, "duration": 3.75}, {"text": "This is right outside\nthe reactor 3 part of it.", "start": 1604.98, "duration": 2.55}, {"text": "There are-- I think I'll\nshow you these photos later.", "start": 1607.53, "duration": 3.15}, {"text": "There are chunks of the\nturbine from reactor 4", "start": 1610.68, "duration": 5.19}, {"text": "that are down here in this\narea that are quite visibly", "start": 1615.87, "duration": 5.22}, {"text": "radioactive and are very easy\nto detect if one swings a Geiger", "start": 1621.09, "duration": 3.99}, {"text": "counter about.", "start": 1625.08, "duration": 1.26}, {"text": "Within Pripyat we also\nvisited a hospital 126,", "start": 1626.34, "duration": 4.15}, {"text": "which is where the\nfirefighters went immediately", "start": 1630.49, "duration": 2.48}, {"text": "after the accident, that is, the\nones that made it off the roof.", "start": 1632.97, "duration": 5.04}, {"text": "This garment here,\nwe're not exactly", "start": 1638.01, "duration": 3.342}, {"text": "sure what it was\nbecause none of us", "start": 1641.352, "duration": 1.458}, {"text": "were going to really touch it.", "start": 1642.81, "duration": 1.32}, {"text": "But we think it might have\nbeen part of a cover--", "start": 1644.13, "duration": 3.12}, {"text": "it would go under one's helmet--", "start": 1647.25, "duration": 1.47}, {"text": "was extremely radioactive.", "start": 1648.72, "duration": 2.4}, {"text": "It was contaminated with\nalpha, beta, and gamma,", "start": 1651.12, "duration": 3.56}, {"text": "which is fairly unusual.", "start": 1654.68, "duration": 1.0}, {"text": "Alpha contamination is fairly\nrare around the Chernobyl site,", "start": 1655.68, "duration": 3.87}, {"text": "and was somewhere around 50\nto 75 mR an hour on contact.", "start": 1659.55, "duration": 3.84}, {"text": "I think I already showed\nyou photos the control room.", "start": 1667.28, "duration": 2.81}, {"text": "Yep, unit 4, that's\nthe cartogram,", "start": 1670.09, "duration": 1.83}, {"text": "so that would display various\nparameters of the reactor", "start": 1671.92, "duration": 3.97}, {"text": "for each fuel channel, depending\non how one configured it.", "start": 1675.89, "duration": 4.68}, {"text": "That's an external photo\nof the sarcophagus.", "start": 1680.57, "duration": 1.98}, {"text": "And I think that's it for\nthe PowerPoint slides.", "start": 1685.61, "duration": 3.93}, {"text": "I do have a bunch of\nphotos though that I think", "start": 1689.54, "duration": 2.21}, {"text": "you will find interesting.", "start": 1691.75, "duration": 1.57}, {"text": "I apologize if it's a\nlittle disorganized.", "start": 1693.32, "duration": 1.98}, {"text": "This was put together relatively\nrecently because, well, I", "start": 1698.27, "duration": 4.62}, {"text": "just got back from Chernobyl.", "start": 1702.89, "duration": 2.04}, {"text": "And then I went to a conference.", "start": 1704.93, "duration": 1.59}, {"text": "And then I came back here\nand tried to get work done.", "start": 1706.52, "duration": 2.73}, {"text": "Right, so these are in\nchronological order roughly.", "start": 1709.25, "duration": 4.02}, {"text": "I'll go through and\nhopefully tell you guys", "start": 1713.27, "duration": 2.1}, {"text": "a little bit about\nwhat the site's like.", "start": 1715.37, "duration": 2.645}, {"text": "MICHAEL SHORT: [INAUDIBLE].", "start": 1718.015, "duration": 1.125}, {"text": "JAKE HECLA: OK, so\nthis is on day one.", "start": 1719.14, "duration": 2.86}, {"text": "We're driving to the Chernobyl\nnuclear power plant site.", "start": 1722.0, "duration": 4.47}, {"text": "That blue and white\nbus is pretty much", "start": 1726.47, "duration": 2.16}, {"text": "what everyone uses for\ntransport around there.", "start": 1728.63, "duration": 1.98}, {"text": "All right, so we're\nnot really supposed", "start": 1733.37, "duration": 1.66}, {"text": "to be taking photos\nin this area.", "start": 1735.03, "duration": 1.32}, {"text": "So everything is\ntilted because it's", "start": 1736.35, "duration": 1.5}, {"text": "taking them out the window\nwith the camera like that.", "start": 1737.85, "duration": 2.76}, {"text": "That's the New Safe\nConfinement Arch.", "start": 1740.61, "duration": 2.52}, {"text": "It's in considerably\nbetter shape", "start": 1743.13, "duration": 1.5}, {"text": "than it was last\nyear at this time.", "start": 1744.63, "duration": 1.95}, {"text": "They have done a fantastic\njob of putting it together.", "start": 1746.58, "duration": 2.61}, {"text": "It's actually almost a\nyear ahead of schedule.", "start": 1749.19, "duration": 4.1}, {"text": "There it is, again.", "start": 1753.29, "duration": 0.85}, {"text": "You can see the sarcophagus\nwith the new support wall,", "start": 1754.14, "duration": 3.09}, {"text": "which is that right there.", "start": 1757.23, "duration": 3.5}, {"text": "All right, so this is our\nexcursion into Pripyat", "start": 1769.91, "duration": 2.37}, {"text": "on our second day.", "start": 1772.28, "duration": 1.71}, {"text": "So this is the group\nled by Stanislaus.", "start": 1773.99, "duration": 3.03}, {"text": "As you can see, there's\nnot very much left.", "start": 1777.02, "duration": 3.48}, {"text": "Just in comparison to\nwhat we saw last year,", "start": 1780.5, "duration": 2.28}, {"text": "the number of buildings\nthat had been taken apart", "start": 1782.78, "duration": 3.21}, {"text": "for scrap metal, illegally,\nof course, was pretty huge.", "start": 1785.99, "duration": 5.22}, {"text": "In, I don't know,\n5 or 10 years, it's", "start": 1791.21, "duration": 1.715}, {"text": "going to be very difficult to\nsee much of Pripyat at all,", "start": 1792.925, "duration": 2.375}, {"text": "frankly.", "start": 1795.3, "duration": 1.55}, {"text": "So this is a standard\napartment block in Pripyat.", "start": 1796.85, "duration": 3.36}, {"text": "As you can see, a lot\nof broken windows.", "start": 1800.21, "duration": 2.97}, {"text": "A lot of bricks have fallen off.", "start": 1803.18, "duration": 1.613}, {"text": "These things are\npretty dangerous.", "start": 1804.793, "duration": 1.417}, {"text": "A lot of tourists\ndo go into them.", "start": 1806.21, "duration": 1.74}, {"text": "If one decides to do a tourist\nexpedition to Chernobyl-- which", "start": 1807.95, "duration": 3.11}, {"text": "I don't particularly\nrecommend-- don't", "start": 1811.06, "duration": 2.23}, {"text": "go in the apartment blocks.", "start": 1813.29, "duration": 1.125}, {"text": "This is on the way to\none of the schools.", "start": 1817.37, "duration": 3.0}, {"text": "This is Lucas who has more\ndetectors than anyone I've ever", "start": 1820.37, "duration": 3.88}, {"text": "met.", "start": 1824.25, "duration": 0.5}, {"text": "He was wearing 7 at the time.", "start": 1824.75, "duration": 1.96}, {"text": "So I had to take a photo of him.", "start": 1826.71, "duration": 2.63}, {"text": "This is Iris imitating\nsome of the graffiti, which", "start": 1829.34, "duration": 2.7}, {"text": "unfortunately has popped\nup all over the place.", "start": 1832.04, "duration": 2.79}, {"text": "Pripyat itself is\nreally decaying quickly.", "start": 1834.83, "duration": 3.4}, {"text": "As I've said, there's a\nhuge problem with looting.", "start": 1838.23, "duration": 3.95}, {"text": "In addition, there's\na huge problem", "start": 1842.18, "duration": 1.5}, {"text": "with graffiti and vandalism.", "start": 1843.68, "duration": 2.55}, {"text": "It's really\ndepressing, honestly,", "start": 1846.23, "duration": 2.1}, {"text": "to go there and see how much\nhas changed just in a year.", "start": 1848.33, "duration": 5.76}, {"text": "So despite my\nearlier warning, we", "start": 1854.09, "duration": 1.83}, {"text": "did go in an apartment block.", "start": 1855.92, "duration": 1.23}, {"text": "This is just a\nmeasurement showing", "start": 1861.83, "duration": 1.95}, {"text": "that the background up there\nactually is not terribly high.", "start": 1863.78, "duration": 2.79}, {"text": "Yeah, that's Iris, not\nparticularly safety conscious", "start": 1869.33, "duration": 3.91}, {"text": "at times.", "start": 1873.24, "duration": 2.72}, {"text": "This gives you a good\nidea of how far away", "start": 1875.96, "duration": 1.75}, {"text": "Pripyat is from the reactor.", "start": 1877.71, "duration": 1.523}, {"text": "That is not very far,\nabout two kilometers.", "start": 1879.233, "duration": 1.792}, {"text": "So you can see the New\nSafe Confinement Arch", "start": 1881.025, "duration": 2.025}, {"text": "to the top left of the detector.", "start": 1883.05, "duration": 3.6}, {"text": "Background there is about,\nin this particular apartment", "start": 1886.65, "duration": 3.0}, {"text": "block, at this particular\ntime, was about four to five", "start": 1889.65, "duration": 2.88}, {"text": "times what you would see\nin downtown Cambridge.", "start": 1892.53, "duration": 3.762}, {"text": "There are wild\nanimals in Pripyat", "start": 1899.74, "duration": 2.26}, {"text": "and the rest of\nthe exclusion zone.", "start": 1902.0, "duration": 2.16}, {"text": "This is a huge problem.", "start": 1904.16, "duration": 1.41}, {"text": "So despite the fact that\nthe cats are very cute", "start": 1905.57, "duration": 2.73}, {"text": "and the puppies are very\ncute, they also have rabies,", "start": 1908.3, "duration": 3.47}, {"text": "not all of them, but a\nvery large number of them.", "start": 1911.77, "duration": 2.86}, {"text": "In 2009, five workers were\ninjured by, I kid you not,", "start": 1914.63, "duration": 3.51}, {"text": "a rabid wolf.", "start": 1918.14, "duration": 1.272}, {"text": "There's a YouTube\nvideo of this you", "start": 1919.412, "duration": 1.458}, {"text": "can look up on your own\ntime if you so wish.", "start": 1920.87, "duration": 3.45}, {"text": "This is because Ukraine\ndoesn't have a lot of money.", "start": 1924.32, "duration": 2.98}, {"text": "So they have not been able to\ncontinue with their vaccination", "start": 1927.3, "duration": 4.02}, {"text": "program.", "start": 1931.32, "duration": 0.5}, {"text": "They actually use baits that\nhave a rabies vaccine in them", "start": 1931.82, "duration": 5.88}, {"text": "to normally suppress rabies\nin wild animal populations.", "start": 1937.7, "duration": 4.59}, {"text": "But Ukraine doesn't\nhave any money.", "start": 1942.29, "duration": 1.53}, {"text": "They killed the program\nabout five years ago.", "start": 1943.82, "duration": 2.59}, {"text": "And as a result there's a\nhuge, huge problem with,", "start": 1946.41, "duration": 2.81}, {"text": "especially rabid foxes.", "start": 1949.22, "duration": 1.65}, {"text": "Because everyone thinks foxes\nare cute, especially tourists.", "start": 1950.87, "duration": 5.49}, {"text": "And foxes, when they\nget rabies, some of them", "start": 1956.36, "duration": 2.34}, {"text": "go through a stage in which\nthey appear to be very friendly.", "start": 1958.7, "duration": 2.7}, {"text": "As far as I know,\nno one has gotten", "start": 1961.4, "duration": 1.83}, {"text": "rabies from a rabid\nanimal at Chernobyl.", "start": 1963.23, "duration": 3.54}, {"text": "But it's certainly\na possibility.", "start": 1966.77, "duration": 3.48}, {"text": "So Stanislaus was being a very\nbad example by feeding one", "start": 1970.25, "duration": 4.29}, {"text": "of the wild cats.", "start": 1974.54, "duration": 2.94}, {"text": "So that's why I took\na picture of it.", "start": 1977.48, "duration": 2.945}, {"text": "This is one of\nthe many memorials", "start": 1980.425, "duration": 1.375}, {"text": "that you'll find in\ndowntown Slavutych.", "start": 1981.8, "duration": 1.65}, {"text": "We stayed in the city that\nwas built, effectively,", "start": 1983.45, "duration": 2.43}, {"text": "as a replacement for Pripyat.", "start": 1985.88, "duration": 1.65}, {"text": "It's actually a fantastic town.", "start": 1987.53, "duration": 2.13}, {"text": "I really enjoy Slavutych.", "start": 1989.66, "duration": 3.24}, {"text": "And as one might expect,\nthere are memorials", "start": 1992.9, "duration": 2.88}, {"text": "everywhere because the entire\npopulation is basically", "start": 1995.78, "duration": 3.03}, {"text": "the folks that were removed\nfrom the town of Pripyat.", "start": 1998.81, "duration": 5.25}, {"text": "This is the train we\nwould take every day.", "start": 2004.06, "duration": 2.64}, {"text": "Slavutych is\nseparated from Pripyat", "start": 2006.7, "duration": 4.05}, {"text": "by a little isthmus of\nBelarus that drops down.", "start": 2010.75, "duration": 3.49}, {"text": "So that's bad, because you\ncan't get a visa to Belarus.", "start": 2014.24, "duration": 3.8}, {"text": "It's not really a thing\nyou can do as an American.", "start": 2018.04, "duration": 3.2}, {"text": "I mean, you can apply for one.", "start": 2021.24, "duration": 1.25}, {"text": "You'll just never hear back.", "start": 2022.49, "duration": 1.82}, {"text": "Belarus is Europe's\nlast dictatorship.", "start": 2024.31, "duration": 2.4}, {"text": "And it's not some place one\nwants to go for any reason.", "start": 2026.71, "duration": 4.12}, {"text": "So when we would get on this\ntrain, the doors would shut.", "start": 2030.83, "duration": 3.437}, {"text": "We would go through\nBelarus and we would all", "start": 2034.267, "duration": 1.833}, {"text": "pray that didn't break\ndown because then we", "start": 2036.1, "duration": 2.435}, {"text": "would have to spend some\ntime to Belarus in prison.", "start": 2038.535, "duration": 2.125}, {"text": "But yeah, this is the train\nyard, bright and early.", "start": 2040.66, "duration": 2.13}, {"text": "The various zones on the\nreactor site for cleanliness,", "start": 2046.56, "duration": 3.57}, {"text": "so to speak,\nradiological cleanliness", "start": 2050.13, "duration": 1.799}, {"text": "are separated by these\nbenches effectively,", "start": 2051.929, "duration": 3.396}, {"text": "that you have to step over, so\nthat it reminds you that, hey,", "start": 2055.325, "duration": 3.084}, {"text": "this is the clean area.", "start": 2058.409, "duration": 1.711}, {"text": "You need to be wearing\nboot covers and at least", "start": 2060.12, "duration": 3.21}, {"text": "these garments in\norder to go here.", "start": 2063.33, "duration": 1.47}, {"text": "Sideways, for some reason,\nthis is part of the--", "start": 2068.0, "duration": 4.745}, {"text": "all right, I don't know\nwhy these are all sideways.", "start": 2072.745, "duration": 2.125}, {"text": "But regardless, you\nget the picture.", "start": 2074.87, "duration": 2.94}, {"text": "If you notice on the\ntop of the screen, which", "start": 2077.81, "duration": 2.22}, {"text": "should be the left\nof the screen,", "start": 2080.03, "duration": 1.379}, {"text": "let's see if I can rotate it.", "start": 2081.409, "duration": 1.711}, {"text": "That's a giant puddle of water.", "start": 2086.15, "duration": 1.98}, {"text": "This place is falling apart.", "start": 2088.13, "duration": 1.799}, {"text": "Despite the fact\nthat they have money", "start": 2089.929, "duration": 1.591}, {"text": "from the European bank on\nreconstruction and development", "start": 2091.52, "duration": 4.619}, {"text": "for the New Safe\nConfinement Arch,", "start": 2096.139, "duration": 1.831}, {"text": "the Chernobyl site itself\ndoes not have a lot of money.", "start": 2097.97, "duration": 3.79}, {"text": "And as a result things\nare falling apart.", "start": 2101.76, "duration": 2.45}, {"text": "And the amount of\ncontamination that", "start": 2104.21, "duration": 1.5}, {"text": "is getting into places where\nit very much shouldn't be,", "start": 2105.71, "duration": 2.58}, {"text": "like this quote \"clean\narea,\" is fairly high.", "start": 2108.29, "duration": 3.0}, {"text": "That puddle of water was pretty\ntoasty, something like 5 to 8", "start": 2111.29, "duration": 3.01}, {"text": "mR an hour on contact.", "start": 2114.3, "duration": 3.37}, {"text": "That's generally quite bad.", "start": 2117.67, "duration": 1.39}, {"text": "As I said, water is\ncoming in everywhere.", "start": 2122.4, "duration": 1.74}, {"text": "And in this case they were using\nleg covers to catch the water.", "start": 2124.14, "duration": 4.34}, {"text": "Another one of the hallways\nthat had water leak into it", "start": 2131.578, "duration": 2.292}, {"text": "and therefore all\nthe lights are out.", "start": 2133.87, "duration": 3.106}, {"text": "That's the footwear\nwhich we were issued,", "start": 2136.976, "duration": 2.194}, {"text": "which breaks after walking\nabout a kilometer, which is not", "start": 2139.17, "duration": 3.86}, {"text": "particularly encouraging if one\nwants to take their boots back.", "start": 2143.03, "duration": 4.41}, {"text": "Again, walking down\nthe hallway, you", "start": 2147.44, "duration": 2.31}, {"text": "notice this gold\ncorrugated material", "start": 2149.75, "duration": 2.01}, {"text": "that you see on the sides?", "start": 2151.76, "duration": 1.92}, {"text": "It's aluminum that is anodized.", "start": 2153.68, "duration": 2.67}, {"text": "And it's placed there\nbecause it covers up", "start": 2156.35, "duration": 1.8}, {"text": "all of the sheets of lead\nthat were affixed to the wall.", "start": 2158.15, "duration": 4.2}, {"text": "What happened is in the\naftermath of the accident,", "start": 2162.35, "duration": 3.33}, {"text": "the entire facility was just\nhopelessly contaminated.", "start": 2165.68, "duration": 3.03}, {"text": "And you can scrub all you\nwant, but ultimately it's", "start": 2168.71, "duration": 3.15}, {"text": "very difficult to get\nradioactive contamination off", "start": 2171.86, "duration": 2.64}, {"text": "of things.", "start": 2174.5, "duration": 0.86}, {"text": "So what they ended up\ndoing was getting it", "start": 2175.36, "duration": 1.75}, {"text": "down to a somewhat\nacceptable level,", "start": 2177.11, "duration": 2.19}, {"text": "and then fastening\nsheets of lead over it,", "start": 2179.3, "duration": 2.16}, {"text": "and then fastening this\nstuff over the top of that.", "start": 2181.46, "duration": 3.06}, {"text": "This is unit 2's control room.", "start": 2187.51, "duration": 1.65}, {"text": "So this is what a fully\nfleshed-out control", "start": 2189.16, "duration": 2.1}, {"text": "room looks like.", "start": 2191.26, "duration": 0.75}, {"text": "Unit 2 were shut down in 2000.", "start": 2195.01, "duration": 3.93}, {"text": "The reactors actually\ncontinued operating", "start": 2198.94, "duration": 2.22}, {"text": "after the 1986\nChernobyl accident", "start": 2201.16, "duration": 2.91}, {"text": "because Ukraine was in such\ndesperate need of power.", "start": 2204.07, "duration": 3.51}, {"text": "As a result, the fuel\nis still fairly hot.", "start": 2207.58, "duration": 3.15}, {"text": "It's producing a reasonable\namount of decay heat.", "start": 2210.73, "duration": 2.91}, {"text": "And there is a crew that\nsits in the control room", "start": 2213.64, "duration": 3.48}, {"text": "at all times monitoring it.", "start": 2217.12, "duration": 3.32}, {"text": "That's Nathan.", "start": 2220.44, "duration": 2.56}, {"text": "This is actually, I\ntook a picture of this", "start": 2223.0, "duration": 1.75}, {"text": "because it's a very good\ndiagram of the Chernobyl reactor", "start": 2224.75, "duration": 3.48}, {"text": "that's simplified.", "start": 2228.23, "duration": 2.34}, {"text": "It shows the core and\nthe relative locations", "start": 2230.57, "duration": 3.18}, {"text": "of these steam,\nwater separators.", "start": 2233.75, "duration": 5.51}, {"text": "OK, as I said, there is a\nteam that stays in there.", "start": 2239.26, "duration": 4.61}, {"text": "So there are people that work\non site and work in the reactor", "start": 2243.87, "duration": 3.8}, {"text": "control rooms, which\nI have to imagine", "start": 2247.67, "duration": 2.31}, {"text": "has to be a bit\nof a surreal job.", "start": 2249.98, "duration": 4.06}, {"text": "This is inside the main, inside\nthe turbo generator hall.", "start": 2254.04, "duration": 6.3}, {"text": "Those chunks that you see here\nare from the turbo generator", "start": 2260.34, "duration": 6.63}, {"text": "of reactor 4.", "start": 2266.97, "duration": 2.4}, {"text": "So they're quite contaminated\nand quite easy to detect.", "start": 2269.37, "duration": 3.0}, {"text": "Actually, there is a\ngood story behind this.", "start": 2272.37, "duration": 2.25}, {"text": "So we were trying to\nfigure out exactly what was", "start": 2274.62, "duration": 3.75}, {"text": "making the dose rate so high in\nthe area when we were up there.", "start": 2278.37, "duration": 4.56}, {"text": "So we got a group of us to stand\nin a circle, minus one person.", "start": 2282.93, "duration": 4.24}, {"text": "So there's a gap.", "start": 2287.17, "duration": 0.89}, {"text": "We got a person in the\ncenter with a scintillator.", "start": 2288.06, "duration": 2.72}, {"text": "And we all kind\nof rotated around", "start": 2290.78, "duration": 2.08}, {"text": "until we found in\nwhich direction", "start": 2292.86, "duration": 1.562}, {"text": "the scintillator reading was\nhigh enough, so basically made", "start": 2294.422, "duration": 2.458}, {"text": "like a 2 pi meat shield.", "start": 2296.88, "duration": 3.3}, {"text": "It worked fairly well.", "start": 2300.18, "duration": 1.17}, {"text": "It thoroughly baffled all of\nthe guides that were with us.", "start": 2301.35, "duration": 3.82}, {"text": "They were like, what are\nyou doing linking arms", "start": 2305.17, "duration": 2.75}, {"text": "and spinning around.", "start": 2307.92, "duration": 1.98}, {"text": "Regardless, that is a\ngood way to find sources", "start": 2309.9, "duration": 2.34}, {"text": "if you're in a pinch.", "start": 2312.24, "duration": 0.99}, {"text": "This is looking\nthe other direction", "start": 2315.79, "duration": 1.62}, {"text": "from that same vantage\npoint as in the last photo.", "start": 2317.41, "duration": 3.84}, {"text": "Behind those walls with a\nlittle radiation signs on them", "start": 2321.25, "duration": 2.76}, {"text": "are chunks of the ventilation\nstack, which is fairly iconic.", "start": 2324.01, "duration": 5.43}, {"text": "They've been fairly\nwell decontaminated.", "start": 2329.44, "duration": 2.43}, {"text": "At that fence area, the\ndose rate or more accurately", "start": 2331.87, "duration": 4.17}, {"text": "exposure rate,\nwas 10 mR an hour.", "start": 2336.04, "duration": 3.99}, {"text": "And yeah, that's another\nclose up photo of it.", "start": 2340.03, "duration": 2.73}, {"text": "And I managed to sneak by\nphone over the top of it", "start": 2342.76, "duration": 2.91}, {"text": "and get a good shot.", "start": 2345.67, "duration": 1.38}, {"text": "Unfortunately, none of\nthe pieces are uncovered.", "start": 2347.05, "duration": 2.16}, {"text": "I would really like to\nsee the orange and white", "start": 2349.21, "duration": 2.85}, {"text": "of the ventilation stack.", "start": 2352.06, "duration": 2.43}, {"text": "But I did not.", "start": 2354.49, "duration": 3.25}, {"text": "Again, same shot,\nslightly different", "start": 2357.74, "duration": 2.0}, {"text": "shot of the turbo generator\nhallway looking in the unit", "start": 2359.74, "duration": 2.4}, {"text": "1 2 direction.", "start": 2362.14, "duration": 3.43}, {"text": "More detritus, oh here's\na slightly better close", "start": 2365.57, "duration": 7.81}, {"text": "up of those components.", "start": 2373.38, "duration": 2.292}, {"text": "One of the interesting things\nI found out about the facility", "start": 2378.02, "duration": 2.5}, {"text": "is way that access\nis controlled.", "start": 2380.52, "duration": 1.96}, {"text": "So instead of having an RFID\ncard or something like that,", "start": 2382.48, "duration": 3.63}, {"text": "they've got cameras\nand operators.", "start": 2386.11, "duration": 1.83}, {"text": "So what you see\nhere is a camera.", "start": 2387.94, "duration": 5.42}, {"text": "So Stanislaus would scan a badge\nthat would automatically call", "start": 2393.36, "duration": 4.14}, {"text": "someone who is an operator.", "start": 2397.5, "duration": 2.52}, {"text": "Stanislaus would say,\nhey, I'm at this door.", "start": 2400.02, "duration": 2.25}, {"text": "I want to go into this location.", "start": 2402.27, "duration": 2.668}, {"text": "Will you let me in?", "start": 2404.938, "duration": 0.792}, {"text": "And then they would\nlook at the camera,", "start": 2405.73, "duration": 1.625}, {"text": "determine that yes,\nthat is Stanislaus.", "start": 2407.355, "duration": 2.145}, {"text": "He does want to\ngo into this area.", "start": 2409.5, "duration": 2.045}, {"text": "And then they would approve\nit and let him through.", "start": 2411.545, "duration": 2.125}, {"text": "Walking through the\ncorridors of the sarcophagus.", "start": 2417.01, "duration": 2.79}, {"text": "You can actually see up\nhere those lead sheets", "start": 2419.8, "duration": 2.16}, {"text": "I was talking about.", "start": 2421.96, "duration": 2.072}, {"text": "I don't know how thick\nthey are on there,", "start": 2424.032, "duration": 1.708}, {"text": "or how close they are to\nfalling off, for that matter.", "start": 2425.74, "duration": 2.37}, {"text": "But I'm sure several\nthousand pounds of lead", "start": 2428.11, "duration": 3.06}, {"text": "is right there alone.", "start": 2431.17, "duration": 2.67}, {"text": "These are main circulating\npumps, about one-half", "start": 2433.84, "duration": 3.6}, {"text": "of the main circulating\npumps for reactor 2.", "start": 2437.44, "duration": 5.64}, {"text": "And each one of\nthese things takes", "start": 2443.08, "duration": 1.62}, {"text": "something around, something\naround 40 megawatts", "start": 2444.7, "duration": 3.27}, {"text": "to actually operate.", "start": 2447.97, "duration": 2.82}, {"text": "These are aligned\ndifferently and are", "start": 2450.79, "duration": 3.63}, {"text": "of a different type than\nthe ones used in reactor 4", "start": 2454.42, "duration": 3.45}, {"text": "because reactors 1 and 2\nwere of an earlier design.", "start": 2457.87, "duration": 3.57}, {"text": "Ironically enough,\nreactors 1 and 2 actually", "start": 2461.44, "duration": 2.49}, {"text": "don't have all of\nthe safety measures", "start": 2463.93, "duration": 1.77}, {"text": "that reactor 4 does, which is\na bit terrifying to think of.", "start": 2465.7, "duration": 4.35}, {"text": "Yet more photos, right, as I\nsaid, dog problem at Chernobyl.", "start": 2472.77, "duration": 5.49}, {"text": "This is right outside the\nentrance to a clean facility.", "start": 2478.26, "duration": 2.7}, {"text": "And occasionally these\ndogs would wander in.", "start": 2480.96, "duration": 1.95}, {"text": "Unfortunately dogs are large\nfurry piles of easily airborne", "start": 2482.91, "duration": 4.59}, {"text": "contamination.", "start": 2487.5, "duration": 1.3}, {"text": "So they would walk in.", "start": 2488.8, "duration": 1.91}, {"text": "People would go\nto shoo them out.", "start": 2490.71, "duration": 1.5}, {"text": "They would shake their\ncoats or whatever.", "start": 2492.21, "duration": 1.77}, {"text": "And then clean up\non aisle three,", "start": 2493.98, "duration": 2.46}, {"text": "because now there's\ncontamination everywhere.", "start": 2496.44, "duration": 4.86}, {"text": "More sad looking puppies.", "start": 2501.3, "duration": 3.03}, {"text": "New Safe Confinement, yet again,\nto give you an idea of scale,", "start": 2504.33, "duration": 3.42}, {"text": "let's play find the workers.", "start": 2507.75, "duration": 1.605}, {"text": "Those are workers right there.", "start": 2526.56, "duration": 3.84}, {"text": "Can you guys see them?", "start": 2530.4, "duration": 1.32}, {"text": "AUDIENCE: Barely.", "start": 2531.72, "duration": 1.26}, {"text": "JAKE HECLA: Yeah, they're\nreally, really small", "start": 2532.98, "duration": 4.83}, {"text": "next to this facility.", "start": 2537.81, "duration": 2.514}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 2540.324, "duration": 1.956}, {"text": "JAKE HECLA: Yeah, I think I've\ngot a slightly better shot", "start": 2542.28, "duration": 4.89}, {"text": "here.", "start": 2547.17, "duration": 0.5}, {"text": "That's a guy right there.", "start": 2551.39, "duration": 2.58}, {"text": "There's also another\ndude right here.", "start": 2553.97, "duration": 3.58}, {"text": "Yeah, this place is,\nor this structure", "start": 2557.55, "duration": 2.75}, {"text": "is absolutely enormous.", "start": 2560.3, "duration": 1.043}, {"text": "It's really hard\nto wrap your head", "start": 2561.343, "duration": 1.417}, {"text": "around exactly how large it is.", "start": 2562.76, "duration": 2.67}, {"text": "So this is in an area\ncalled the local zone.", "start": 2565.43, "duration": 3.687}, {"text": "So it's the immediate\nseveral hundred meters", "start": 2569.117, "duration": 1.833}, {"text": "surrounding the reactor.", "start": 2570.95, "duration": 1.92}, {"text": "As you can see, the\nhazmat equipment", "start": 2572.87, "duration": 1.742}, {"text": "that we're wearing\nthere is significantly", "start": 2574.612, "duration": 1.708}, {"text": "different from what we would\nwear inside the reactor", "start": 2576.32, "duration": 2.38}, {"text": "or inside the\nsarcophagus, mostly", "start": 2578.7, "duration": 2.18}, {"text": "because the threat from dust\nin this area is pretty huge.", "start": 2580.88, "duration": 3.06}, {"text": "As you can see, we're\nwalking on fill.", "start": 2587.51, "duration": 1.68}, {"text": "It's actually meters\nand meters of fill", "start": 2589.19, "duration": 1.92}, {"text": "because the ground\nwas so contaminated", "start": 2591.11, "duration": 1.71}, {"text": "that they scraped it\naway, put fill in there,", "start": 2592.82, "duration": 3.15}, {"text": "put fill on top of that because\njust the residual contamination", "start": 2595.97, "duration": 3.15}, {"text": "was enough to make it hazardous\nto use as a work site.", "start": 2599.12, "duration": 3.06}, {"text": "Though they're not\nshown in this image,", "start": 2602.18, "duration": 2.64}, {"text": "or I believe any\nimages here, there", "start": 2604.82, "duration": 4.285}, {"text": "are little concrete\nand lead structures", "start": 2609.105, "duration": 2.375}, {"text": "that these workers\ntake breaks behind", "start": 2611.48, "duration": 2.79}, {"text": "because you have a dose\nlimit that is enforced", "start": 2614.27, "duration": 4.23}, {"text": "while you're working there.", "start": 2618.5, "duration": 1.41}, {"text": "And if you're going\nto take a smoke", "start": 2619.91, "duration": 1.71}, {"text": "break, as a huge fraction\nof the population of Ukraine", "start": 2621.62, "duration": 2.49}, {"text": "smokes, or you're going to\ntake a break of another sort,", "start": 2624.11, "duration": 5.412}, {"text": "they don't want you racking\nup dose during that time.", "start": 2629.522, "duration": 2.208}, {"text": "So you basically hide in\na little concrete shack", "start": 2631.73, "duration": 2.67}, {"text": "for a while with a\nfew inches of lead", "start": 2634.4, "duration": 1.8}, {"text": "between you and the reactor.", "start": 2636.2, "duration": 2.94}, {"text": "Yet another shot\ninside the sarcophagus,", "start": 2639.14, "duration": 4.8}, {"text": "Ed explaining something\nabout which I'm not sure.", "start": 2643.94, "duration": 2.77}, {"text": "As you can see these\nplaces are not exactly", "start": 2651.0, "duration": 2.04}, {"text": "in the best condition\non the inside.", "start": 2653.04, "duration": 1.89}, {"text": "And one thing that\ndid concern me a lot", "start": 2654.93, "duration": 1.89}, {"text": "was the amount of dust\nthat was very, very", "start": 2656.82, "duration": 2.58}, {"text": "easy to kick up in the area.", "start": 2659.4, "duration": 2.52}, {"text": "This is inside control\nroom of reactor 4.", "start": 2661.92, "duration": 4.37}, {"text": "Selfie, which I didn't\nmean to have in this album.", "start": 2666.29, "duration": 2.97}, {"text": "Control room 4 hasn't changed\na whole lot since last year.", "start": 2673.46, "duration": 3.6}, {"text": "But there is a\ndividing wall that", "start": 2677.06, "duration": 3.09}, {"text": "actually separates\nreactors 3 and 4 that's", "start": 2680.15, "duration": 2.37}, {"text": "being put together.", "start": 2682.52, "duration": 1.26}, {"text": "And it cuts right through the\nedge of the fourth control", "start": 2683.78, "duration": 3.41}, {"text": "room.", "start": 2687.19, "duration": 0.5}, {"text": "And for a while, we actually\ndidn't know whether or not", "start": 2687.69, "duration": 2.995}, {"text": "we were going to be able\nto visit it at all because", "start": 2690.685, "duration": 2.125}, {"text": "of ongoing construction.", "start": 2692.81, "duration": 1.11}, {"text": "I'm very glad that\nwe were able to.", "start": 2693.92, "duration": 3.72}, {"text": "Most of the instruments\nhave been removed.", "start": 2697.64, "duration": 2.64}, {"text": "It's unclear as to why.", "start": 2700.28, "duration": 2.31}, {"text": "We've been told that some of it\nwas because of contamination.", "start": 2702.59, "duration": 2.76}, {"text": "But the pattern doesn't\nreally make sense.", "start": 2705.35, "duration": 3.81}, {"text": "This is the reactor control\nroom cartogram, excuse me,", "start": 2709.16, "duration": 6.16}, {"text": "reactor core cartogram,\nwhich, as I said", "start": 2715.32, "duration": 2.16}, {"text": "was lit and could display\nvarious parameters regarding", "start": 2717.48, "duration": 3.54}, {"text": "the various fuel channels.", "start": 2721.02, "duration": 3.4}, {"text": "There is only two control\nrod indicator, well, yeah.", "start": 2724.42, "duration": 5.66}, {"text": "There are really only these\ncontrol rod indicators left.", "start": 2730.08, "duration": 4.79}, {"text": "And we believe that\nactually some of these", "start": 2734.87, "duration": 1.75}, {"text": "might not be original.", "start": 2736.62, "duration": 0.96}, {"text": "Someone might have\nstolen the real one", "start": 2737.58, "duration": 1.583}, {"text": "and put another one back.", "start": 2739.163, "duration": 3.33}, {"text": "I don't have any\nevidence to support it.", "start": 2742.493, "duration": 1.667}, {"text": "But I suspect that there's\nsignificant looting that", "start": 2744.16, "duration": 1.82}, {"text": "happens in here.", "start": 2745.98, "duration": 0.667}, {"text": "This is a rather\nentertaining photo.", "start": 2751.97, "duration": 2.4}, {"text": "That means smoking area.", "start": 2754.37, "duration": 3.39}, {"text": "That's in the control room.", "start": 2757.76, "duration": 1.288}, {"text": "You shouldn't be smoking.", "start": 2759.048, "duration": 1.042}, {"text": "You shouldn't take your\nmask off for any reason.", "start": 2760.09, "duration": 2.2}, {"text": "That's a high gamma\nradiation warning sign.", "start": 2768.47, "duration": 2.54}, {"text": "It was in fact, not that\nhigh of a dose rate,", "start": 2771.01, "duration": 2.13}, {"text": "somewhere in the range\nof 30 mR an hour.", "start": 2773.14, "duration": 1.74}, {"text": "We also explored a little bit\noutside of the more formal part", "start": 2778.9, "duration": 6.03}, {"text": "of the reactor\npremises, namely we", "start": 2784.93, "duration": 3.6}, {"text": "went to this place called\nBuriakivka 2, which", "start": 2788.53, "duration": 2.88}, {"text": "is a burial facility for\nwaste from the reactor,", "start": 2791.41, "duration": 5.61}, {"text": "not waste as in nuclear waste\nbut waste is in chunks of metal", "start": 2797.02, "duration": 3.57}, {"text": "and other things that are\ncontaminated and therefore", "start": 2800.59, "duration": 2.31}, {"text": "removed when the New Safe\nConfinement Arch was being", "start": 2802.9, "duration": 3.0}, {"text": "built, or when, let's say, they\nwere building the separation", "start": 2805.9, "duration": 4.05}, {"text": "wall between reactors 3 and 4.", "start": 2809.95, "duration": 2.282}, {"text": "And there were some\nincredibly hot spots.", "start": 2812.232, "duration": 1.708}, {"text": "So I might, I think I have\nsome more photos later.", "start": 2813.94, "duration": 5.01}, {"text": "But just under that\nlittle triangle,", "start": 2818.95, "duration": 3.39}, {"text": "the dose rate was 150 mR an\nhour, so 0.15 rem an hour.", "start": 2822.34, "duration": 6.51}, {"text": "It's extremely high.", "start": 2828.85, "duration": 1.57}, {"text": "And that was just in a field\nbasically, not controlled, not", "start": 2830.42, "duration": 6.41}, {"text": "patrolled, no warning signs.", "start": 2836.83, "duration": 2.35}, {"text": "Getting dressed up, lots of fun.", "start": 2841.84, "duration": 3.73}, {"text": "That was the truck we were\nsent to decontaminate.", "start": 2845.57, "duration": 3.977}, {"text": "Honestly it wasn't\nparticularly contaminated", "start": 2849.547, "duration": 1.833}, {"text": "in the first place.", "start": 2851.38, "duration": 0.792}, {"text": "They weren't going to give us\nreal fun things to play with.", "start": 2852.172, "duration": 3.698}, {"text": "That's all of us.", "start": 2855.87, "duration": 0.92}, {"text": "And then as you notice,\nthe real workers", "start": 2856.79, "duration": 2.31}, {"text": "here are not wearing even\na fraction of what we are.", "start": 2859.1, "duration": 3.48}, {"text": "More decontamination,\nyeah, see, barely anything.", "start": 2867.22, "duration": 9.23}, {"text": "These are chunks of metal that\nhave come out of the reactor.", "start": 2876.45, "duration": 2.5}, {"text": "We're not exactly sure what\npart, what parts they are.", "start": 2878.95, "duration": 4.32}, {"text": "No one was really able to\nanswer our questions about them.", "start": 2883.27, "duration": 3.03}, {"text": "But they were also\nrather contaminated,", "start": 2886.3, "duration": 2.13}, {"text": "somewhere in the\nrange of 50 to 75 mR", "start": 2888.43, "duration": 2.31}, {"text": "an hour on contact\nin some spots.", "start": 2890.74, "duration": 4.42}, {"text": "More photos of Chernobyl, or\nof Chernobyl from Pripyat.", "start": 2895.16, "duration": 3.792}, {"text": "MICHAEL SHORT: Dr. Jake, I\nwant to take a quick break", "start": 2898.952, "duration": 2.208}, {"text": "and ask folks if they\nhave any questions on what", "start": 2901.16, "duration": 3.45}, {"text": "the experience was\nlike [INAUDIBLE]..", "start": 2904.61, "duration": 1.974}, {"text": "JAKE HECLA: Yes?", "start": 2911.823, "duration": 0.667}, {"text": "AUDIENCE: Did you suffer\nany adverse health", "start": 2912.49, "duration": 1.792}, {"text": "effects or anything?", "start": 2914.282, "duration": 1.338}, {"text": "JAKE HECLA: Only the cold I\npicked up on the way back.", "start": 2915.62, "duration": 4.26}, {"text": "The total dose that I received\non this entire expedition,", "start": 2919.88, "duration": 3.57}, {"text": "minus the flights there and\nback, was 0.6 millisieverts.", "start": 2923.45, "duration": 4.39}, {"text": "So effectively, nothing.", "start": 2927.84, "duration": 4.25}, {"text": "MICHAEL SHORT: [INAUDIBLE].", "start": 2932.09, "duration": 1.62}, {"text": "JAKE HECLA: Well, all of\nthe high radiation areas", "start": 2933.71, "duration": 3.48}, {"text": "that we were in, we were\nencouraged to walk quickly,", "start": 2937.19, "duration": 3.97}, {"text": "is basically what\nit comes down to.", "start": 2941.16, "duration": 2.72}, {"text": "The time portion of time,\ndistance, and shielding", "start": 2943.88, "duration": 2.1}, {"text": "was emphasized.", "start": 2945.98, "duration": 3.32}, {"text": "Further questions?", "start": 2949.3, "duration": 1.71}, {"text": "Yeah.", "start": 2951.01, "duration": 1.102}, {"text": "AUDIENCE: Are there [INAUDIBLE]\nradiation area versus", "start": 2952.112, "duration": 3.178}, {"text": "[INAUDIBLE].", "start": 2955.29, "duration": 0.942}, {"text": "Do they use the same\nlevels [INAUDIBLE]??", "start": 2956.232, "duration": 1.708}, {"text": "JAKE HECLA: No, radiological\ncontrol in Ukraine", "start": 2957.94, "duration": 3.63}, {"text": "is a totally different\ngame than it is in the US.", "start": 2961.57, "duration": 4.38}, {"text": "There are the same\ntypes of controls", "start": 2965.95, "duration": 3.24}, {"text": "that exist in the US just\ndon't exist at that site.", "start": 2969.19, "duration": 5.46}, {"text": "For areas that are immediately\ndangerous to your health,", "start": 2974.65, "duration": 4.2}, {"text": "you know, 10 rad\nan hour, something", "start": 2978.85, "duration": 2.4}, {"text": "like that, from what I\nunderstand that there", "start": 2981.25, "duration": 2.88}, {"text": "are locked doors that prevent\none from accessing those", "start": 2984.13, "duration": 3.72}, {"text": "accidentally.", "start": 2987.85, "duration": 1.08}, {"text": "And there are warning signs\nin a variety of locations.", "start": 2988.93, "duration": 2.32}, {"text": "But I don't think that there\nis a the same standardization", "start": 2991.25, "duration": 4.31}, {"text": "of 5 mR an hours is a radiation\narea, et cetera, et cetera.", "start": 2995.56, "duration": 6.166}, {"text": "Yeah.", "start": 3001.726, "duration": 0.5}, {"text": "Further?", "start": 3005.53, "duration": 1.043}, {"text": "MICHAEL SHORT: And\nare folks still going", "start": 3006.573, "duration": 1.667}, {"text": "to be running these tours\npretty continuously?", "start": 3008.24, "duration": 1.96}, {"text": "JAKE HECLA: No.", "start": 3010.2, "duration": 0.74}, {"text": "You won't be able to see the\nsarcophagus itself because it", "start": 3010.94, "duration": 3.3}, {"text": "will be contained within the\nNew Safe Confinement Arch", "start": 3014.24, "duration": 3.63}, {"text": "pretty much now.", "start": 3017.87, "duration": 2.02}, {"text": "It's 75, right, let's see.", "start": 3019.89, "duration": 2.66}, {"text": "Last I checked, the New\nSafe Confinement Arch", "start": 3022.55, "duration": 1.92}, {"text": "was 75 percent of the way\nover the reactor itself.", "start": 3024.47, "duration": 5.19}, {"text": "Regular tourist\nvisits to Pripyat", "start": 3029.66, "duration": 2.37}, {"text": "will continue to happen.", "start": 3032.03, "duration": 2.82}, {"text": "This program that I went on\nis something very special.", "start": 3034.85, "duration": 2.79}, {"text": "Carl, Ed, and Erik have done\nthis type of thing once before.", "start": 3040.37, "duration": 5.43}, {"text": "That was the trip I\nwent on last year.", "start": 3045.8, "duration": 2.11}, {"text": "And they intend on doing it\nonce a year as long as they can.", "start": 3047.91, "duration": 5.507}, {"text": "But that's pretty much\nyour only opportunity", "start": 3053.417, "duration": 1.833}, {"text": "to get that kind of\naccess to the reactor.", "start": 3055.25, "duration": 2.19}, {"text": "It takes a lot of work.", "start": 3057.44, "duration": 1.11}, {"text": "MICHAEL SHORT: Anyone else\nhave questions for Jake?", "start": 3062.84, "duration": 2.44}, {"text": "It's rare to meet someone that's\nactually gone to Chernobyl to", "start": 3065.28, "duration": 3.24}, {"text": "[INAUDIBLE].", "start": 3068.52, "duration": 0.52}, {"text": "Yeah?", "start": 3069.04, "duration": 1.05}, {"text": "AUDIENCE: Do you\nthink it's haunted?", "start": 3070.09, "duration": 1.88}, {"text": "JAKE HECLA: No.", "start": 3071.97, "duration": 2.53}, {"text": "There's a rather haunting\nlocation, though,", "start": 3074.5, "duration": 2.58}, {"text": "the Khodemchuk Memorial.", "start": 3077.08, "duration": 2.4}, {"text": "So when the accident happened\nthere was one guy who was--", "start": 3079.48, "duration": 3.27}, {"text": "depending on how you look at\nit, either lucky or unlucky--", "start": 3082.75, "duration": 3.33}, {"text": "in that he wasn't killed\nby radiation poisoning.", "start": 3086.08, "duration": 2.31}, {"text": "He was killed by being\nflattened in the explosion.", "start": 3088.39, "duration": 4.38}, {"text": "And his remains are\nwithin the reactor", "start": 3092.77, "duration": 2.88}, {"text": "and within the sarcophagus,\nnever really recovered him.", "start": 3095.65, "duration": 3.512}, {"text": "Better than dying of\nradiation poisoning.", "start": 3099.162, "duration": 1.708}, {"text": "But nonetheless, not\na fantastic way to go.", "start": 3100.87, "duration": 3.93}, {"text": "The memorial that is\nwithin the sarcophagus", "start": 3104.8, "duration": 3.42}, {"text": "is pretty interesting to\nvisit, and rather somber.", "start": 3108.22, "duration": 5.55}, {"text": "Makes you reflect a little\nbit on the enormous human toll", "start": 3113.77, "duration": 3.15}, {"text": "that the accident had.", "start": 3116.92, "duration": 2.3}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.475}, {"text": "[RUSTLING]", "start": 2.475, "duration": 1.98}, {"text": "[CLICKING]", "start": 4.455, "duration": 3.465}, {"text": "ROBERT TOWNSEND: So today\nis a review session.", "start": 10.91, "duration": 4.71}, {"text": "But let me start by looking\nat the class schedule.", "start": 15.62, "duration": 4.34}, {"text": "And today is the review session.", "start": 19.96, "duration": 2.11}, {"text": "So there's no\nreadings for today.", "start": 22.07, "duration": 2.42}, {"text": "Note the lectures are\nnumbered seven, eight,", "start": 24.49, "duration": 3.93}, {"text": "so today doesn't count somehow.", "start": 28.42, "duration": 2.7}, {"text": "But it does show up\non the class schedule.", "start": 31.12, "duration": 3.11}, {"text": "It does not show up as a\nnumbered lecture on the reading", "start": 34.23, "duration": 2.56}, {"text": "list.", "start": 36.79, "duration": 0.93}, {"text": "I find these, going over\nrandomly selected questions", "start": 37.72, "duration": 3.81}, {"text": "on the study guide,\nto be very helpful.", "start": 41.53, "duration": 3.63}, {"text": "Taking a bit of time to go over,\nas we usually do, in this case", "start": 45.16, "duration": 4.29}, {"text": "after the end of lecture seven,\nis definitely worthwhile.", "start": 49.45, "duration": 4.15}, {"text": "So this question was\nalready asked of me.", "start": 53.6, "duration": 4.73}, {"text": "So granted, it's kind of a hard\nquestion to write and maybe", "start": 58.33, "duration": 3.27}, {"text": "not so obvious how to answer.", "start": 61.6, "duration": 2.19}, {"text": "Go back to the medieval\nvillage economy", "start": 63.79, "duration": 2.43}, {"text": "and think about how\nyou would model it", "start": 66.22, "duration": 1.95}, {"text": "in general equilibrium terms.", "start": 68.17, "duration": 3.06}, {"text": "Volunteer.", "start": 71.23, "duration": 2.75}, {"text": "How do we model the\nmedieval village economy", "start": 73.98, "duration": 3.93}, {"text": "in general equilibrium terms?", "start": 77.91, "duration": 3.73}, {"text": "And he's ready to answer this\nbut we already talked about it.", "start": 81.64, "duration": 3.96}, {"text": "Yes, who's speaking?", "start": 85.6, "duration": 2.47}, {"text": "STUDENT: I was going\nto say that it includes", "start": 88.07, "duration": 2.72}, {"text": "the possible consumption set,\nand the production vectors that", "start": 90.79, "duration": 4.65}, {"text": "are possible, and the\nendowment for that economy.", "start": 95.44, "duration": 5.9}, {"text": "ROBERT TOWNSEND:\nAnd the preferences.", "start": 101.34, "duration": 2.61}, {"text": "STUDENT: Yeah, and that.", "start": 103.95, "duration": 1.35}, {"text": "ROBERT TOWNSEND:\nYeah, so that's good.", "start": 105.3, "duration": 2.37}, {"text": "So then what aspects\nof the medieval economy", "start": 107.67, "duration": 4.11}, {"text": "do you remember\nfrom figures and so", "start": 111.78, "duration": 4.14}, {"text": "on that look like\none of those things?", "start": 115.92, "duration": 3.555}, {"text": "What about production?", "start": 123.22, "duration": 2.15}, {"text": "Well, either this question\nis too hard or too easy.", "start": 133.22, "duration": 2.58}, {"text": "I'm not sure which.", "start": 135.8, "duration": 0.84}, {"text": "So one answer I didn't\ngive, the key just now,", "start": 139.78, "duration": 2.19}, {"text": "is we actually thought\nabout the medieval village", "start": 141.97, "duration": 5.42}, {"text": "when we did the dynamics\nof storage, and starvation,", "start": 147.39, "duration": 3.37}, {"text": "and so on.", "start": 150.76, "duration": 1.32}, {"text": "And we wrote down a\nproduction technology", "start": 152.08, "duration": 3.56}, {"text": "mapping inputs and outputs.", "start": 155.64, "duration": 1.65}, {"text": "So we were doing production,\nand we took a stand on utility.", "start": 160.78, "duration": 5.36}, {"text": "And so that was an example of\na medieval village economy,", "start": 166.14, "duration": 3.89}, {"text": "except there was only\none person in it.", "start": 170.03, "duration": 1.875}, {"text": "But--", "start": 171.905, "duration": 0.5}, {"text": "If you go back to\nthose pictures,", "start": 180.59, "duration": 1.97}, {"text": "we have a map with\na given person", "start": 182.56, "duration": 5.39}, {"text": "having its plots spread out all\nover the map of the village.", "start": 187.95, "duration": 5.83}, {"text": "So do you think they have the\nsame production technologies", "start": 198.79, "duration": 2.61}, {"text": "or different production\ntechnologies?", "start": 201.4, "duration": 1.95}, {"text": "Anybody can answer.", "start": 207.34, "duration": 1.287}, {"text": "This is a little\ndiscussion period.", "start": 208.627, "duration": 1.458}, {"text": "Well, if it were the same\nproduction technology,", "start": 222.87, "duration": 2.43}, {"text": "then why on Earth would they\nbe spreading their land out", "start": 225.3, "duration": 2.76}, {"text": "over the village\ninto different spots?", "start": 228.06, "duration": 1.83}, {"text": "So it seems likely they're\ndifferent production", "start": 238.22, "duration": 2.01}, {"text": "technologies.", "start": 240.23, "duration": 0.658}, {"text": "In what way do you think\nthey might be different?", "start": 240.888, "duration": 2.042}, {"text": "I'm going to call on someone.", "start": 249.132, "duration": 1.208}, {"text": "This isn't working.", "start": 250.34, "duration": 1.02}, {"text": "Ewan, can you try\nto answer that--", "start": 251.36, "duration": 2.91}, {"text": "in what reasonable\nway do you think", "start": 254.27, "duration": 1.74}, {"text": "the production\ntechnology is different", "start": 256.01, "duration": 1.769}, {"text": "across different plots?", "start": 257.779, "duration": 2.356}, {"text": "STUDENT: Maybe the\nmultiplier that", "start": 263.58, "duration": 2.55}, {"text": "determines the state of\nthe world is independent,", "start": 266.13, "duration": 3.84}, {"text": "or there are fewer correlations\nthe further out you go.", "start": 269.97, "duration": 2.943}, {"text": "ROBERT TOWNSEND: Yeah, good.", "start": 272.913, "duration": 1.167}, {"text": "OK.", "start": 274.08, "duration": 1.32}, {"text": "So what in the\nstorage economy was", "start": 275.4, "duration": 1.83}, {"text": "that epsilon might have\ndifferent realizations", "start": 277.23, "duration": 3.75}, {"text": "for different plots,\nand then we get", "start": 280.98, "duration": 1.98}, {"text": "into all that stuff about\ncorrelations, and covariances,", "start": 282.96, "duration": 5.07}, {"text": "and so on.", "start": 288.03, "duration": 2.52}, {"text": "Yeah.", "start": 290.55, "duration": 2.02}, {"text": "So as I was saying, the\nkey at the beginning, this", "start": 292.57, "duration": 4.02}, {"text": "is kind of a difficult question.", "start": 296.59, "duration": 1.95}, {"text": "That's why she asked me at\nright when we logged on at 2:30.", "start": 298.54, "duration": 4.44}, {"text": "It's difficult-- why?", "start": 302.98, "duration": 1.56}, {"text": "Because you're so\nused to seeing me", "start": 304.54, "duration": 2.1}, {"text": "show you slides of things,\nlike here's the model,", "start": 306.64, "duration": 5.31}, {"text": "and then you're,\nlike, OK, I guess", "start": 311.95, "duration": 1.53}, {"text": "I better learn this model.", "start": 313.48, "duration": 2.53}, {"text": "And I just put you in the\ndifferent position of asking", "start": 316.01, "duration": 2.79}, {"text": "you to choose the model.", "start": 318.8, "duration": 2.89}, {"text": "That is a very interesting\nskill and it is not something", "start": 321.69, "duration": 3.15}, {"text": "you get to practice very often.", "start": 324.84, "duration": 1.53}, {"text": "That's why I think this\nquestion is hard in the sense", "start": 329.2, "duration": 3.42}, {"text": "that you're not\nused to doing that.", "start": 332.62, "duration": 1.69}, {"text": "But that's the way economists\nhave to think about things.", "start": 334.31, "duration": 2.39}, {"text": "We make decisions.", "start": 336.7, "duration": 1.72}, {"text": "It's not like God is giving\nus preferences, endowments,", "start": 338.42, "duration": 2.96}, {"text": "and technology.", "start": 341.38, "duration": 1.23}, {"text": "We're kind of making it up,\nhopefully for good reason.", "start": 342.61, "duration": 7.13}, {"text": "All right, so that's why I\nearmarked that question today.", "start": 349.74, "duration": 4.82}, {"text": "For the set of feasible\nallocations in an Edgeworth box", "start": 354.56, "duration": 3.09}, {"text": "economy, which allocations are\nPareto optimal and which not?", "start": 357.65, "duration": 6.45}, {"text": "And if we had the whiteboard,\nI would ask you to draw it,", "start": 364.1, "duration": 2.875}, {"text": "but I'm not going to\nbe that ambitious.", "start": 366.975, "duration": 1.625}, {"text": "So can someone just\ntell me in words?", "start": 368.6, "duration": 4.18}, {"text": "How about Paolo.", "start": 372.78, "duration": 2.88}, {"text": "Can you take a stab at this.", "start": 375.66, "duration": 1.847}, {"text": "STUDENT: Yeah, sure.", "start": 377.507, "duration": 0.833}, {"text": "So the set of all Pareto optimal\nallocations inside of the box", "start": 378.34, "duration": 5.69}, {"text": "are the set of points for\nwhich the indifference", "start": 384.03, "duration": 3.21}, {"text": "curves for person one and person\ntwo are tangent to each other", "start": 387.24, "duration": 4.47}, {"text": "because then you can optimize.", "start": 391.71, "duration": 1.41}, {"text": "There's no lens-shaped\nregion for you", "start": 393.12, "duration": 2.31}, {"text": "to do something that's better.", "start": 395.43, "duration": 1.5}, {"text": "And everything else is just\nlike a non-Pareto optimal", "start": 396.93, "duration": 2.52}, {"text": "allocation.", "start": 399.45, "duration": 1.16}, {"text": "ROBERT TOWNSEND: OK, that's\ngreat, excellent answer.", "start": 400.61, "duration": 2.805}, {"text": "And maybe if we get that\nfar in our review session,", "start": 406.84, "duration": 4.015}, {"text": "all the way back here\nto lecture seven,", "start": 410.855, "duration": 1.625}, {"text": "we can take a look at\nsome of those pictures.", "start": 412.48, "duration": 2.55}, {"text": "Here's another one.", "start": 420.28, "duration": 0.91}, {"text": "What is the relationship\nbetween maximized linear welfare", "start": 421.19, "duration": 3.41}, {"text": "functions and Pareto optimality?", "start": 424.6, "duration": 2.82}, {"text": "STUDENT: So whenever we maximize\na linear welfare function,", "start": 431.1, "duration": 5.19}, {"text": "the resulting\nallocation is guaranteed", "start": 436.29, "duration": 2.25}, {"text": "to be Pareto optimal.", "start": 438.54, "duration": 2.53}, {"text": "And I think conversely, any\nPareto-optimal allocation", "start": 441.07, "duration": 5.33}, {"text": "optimizes some linear\nsocial welfare function.", "start": 446.4, "duration": 2.372}, {"text": "ROBERT TOWNSEND: Perfect answer.", "start": 448.772, "duration": 1.333}, {"text": "Now I'm a happy camper.", "start": 452.73, "duration": 1.29}, {"text": "Thank you.", "start": 454.02, "duration": 1.65}, {"text": "You guys do really well on\nthese more precisely worded", "start": 455.67, "duration": 4.2}, {"text": "questions.", "start": 459.87, "duration": 1.77}, {"text": "That's a very good answer.", "start": 461.64, "duration": 1.17}, {"text": "Thank you so much.", "start": 462.81, "duration": 0.75}, {"text": "And let's see-- that's\nprobably enough of that.", "start": 466.32, "duration": 2.205}, {"text": "So I'm going to scroll\nthrough these lectures", "start": 471.65, "duration": 4.77}, {"text": "with two goals in mind.", "start": 476.42, "duration": 1.84}, {"text": "One, as I go through the slides,\nsometimes pretty quickly,", "start": 478.26, "duration": 4.79}, {"text": "please let me know if\nyou have a question.", "start": 483.05, "duration": 2.95}, {"text": "Even if you didn't\nplan to ask it,", "start": 486.0, "duration": 1.58}, {"text": "you might think of something.", "start": 487.58, "duration": 1.377}, {"text": "It might come back to you when\nyou're looking at the material.", "start": 488.957, "duration": 2.583}, {"text": "And secondly, I will try to\nsummarize a bit in key spots", "start": 491.54, "duration": 4.44}, {"text": "and draw some connections of\none lecture to another one.", "start": 495.98, "duration": 3.52}, {"text": "So that's the plan.", "start": 499.5, "duration": 1.67}, {"text": "The substance of\nthis first lecture", "start": 501.17, "duration": 2.52}, {"text": "had to do with economics as\na science of experiments.", "start": 503.69, "duration": 4.2}, {"text": "And I covered these\nfour different authors.", "start": 507.89, "duration": 3.06}, {"text": "Let me just not dwell on it.", "start": 510.95, "duration": 1.92}, {"text": "The point was economics\nas an experiment,", "start": 512.87, "duration": 3.57}, {"text": "in the sense of physics and\ncombining various disciplines", "start": 516.44, "duration": 4.739}, {"text": "to do this.", "start": 521.179, "duration": 0.75}, {"text": "And Koopmans is\nmaking this point", "start": 521.929, "duration": 2.101}, {"text": "that it's much more\nthan just measurement.", "start": 524.03, "duration": 2.55}, {"text": "And constantly in the\ncourse, I am showing you", "start": 526.58, "duration": 3.24}, {"text": "measurements of things, facts,\nand statistics, and so on.", "start": 529.82, "duration": 3.4}, {"text": "But like Koopmans,\nthat's not enough.", "start": 533.22, "duration": 2.52}, {"text": "We want to have a good sense\nof the context of the problem", "start": 535.74, "duration": 3.65}, {"text": "or economy, but we want to\ngo on and understand behavior", "start": 539.39, "duration": 4.23}, {"text": "and then make predictions.", "start": 543.62, "duration": 2.64}, {"text": "I guess the best\nillustration of our", "start": 546.26, "duration": 2.43}, {"text": "doing this so far might be\nthe medieval storage problem,", "start": 548.69, "duration": 4.32}, {"text": "where we wrote that we took\nthe medieval village we were", "start": 553.01, "duration": 3.18}, {"text": "discussing earlier, talked\nabout preferences, endowments,", "start": 556.19, "duration": 4.2}, {"text": "and technology.", "start": 560.39, "duration": 0.9}, {"text": "We did some calibration\nto put in serious numbers", "start": 561.29, "duration": 3.51}, {"text": "representing risk, and\nreturns, and so on.", "start": 564.8, "duration": 2.86}, {"text": "And then we\nsimulated the economy", "start": 567.66, "duration": 2.99}, {"text": "and pretty much got\nit to match the data.", "start": 570.65, "duration": 2.41}, {"text": "So that was, I guess, the\nmost full-blown application", "start": 573.06, "duration": 4.13}, {"text": "we've done so far in this\ntradition of Koopmans,", "start": 577.19, "duration": 4.74}, {"text": "although Koopmans goes on to\ntalk about what he thinks is", "start": 581.93, "duration": 3.78}, {"text": "the real goal, which is policy.", "start": 585.71, "duration": 2.31}, {"text": "And we did not do any\npolicy simulations in that.", "start": 588.02, "duration": 3.3}, {"text": "We didn't change\nsomething and ask", "start": 591.32, "duration": 2.34}, {"text": "if we could remedy the\nproblem, for example.", "start": 593.66, "duration": 3.0}, {"text": "But we will be doing much more\nof that as the class goes on.", "start": 596.66, "duration": 4.14}, {"text": "Matzkin has this language\nabout exogenous and endogenous", "start": 600.8, "duration": 3.66}, {"text": "variables.", "start": 604.46, "duration": 0.54}, {"text": "And we've, again in that\nmedieval village economy,", "start": 605.0, "duration": 3.03}, {"text": "I think I was using\nthat terminology--", "start": 608.03, "duration": 3.84}, {"text": "things that are taken\nas given versus things", "start": 611.87, "duration": 3.18}, {"text": "we want to explain.", "start": 615.05, "duration": 2.13}, {"text": "Angrist was talking about\nrandomized controlled trials", "start": 617.18, "duration": 3.57}, {"text": "and comparing them to\nquasi-natural experiments.", "start": 620.75, "duration": 3.78}, {"text": "This first example was\npaying bicycle messengers", "start": 624.53, "duration": 4.74}, {"text": "a higher wage.", "start": 629.27, "duration": 1.53}, {"text": "And a couple of\ncomments on that--", "start": 630.8, "duration": 2.46}, {"text": "when we get to utility functions\nand utility maximization", "start": 633.26, "duration": 4.77}, {"text": "subject to budgets, we\nactually had a picture", "start": 638.03, "duration": 3.51}, {"text": "of someone choosing how\nmuch labor to supply", "start": 641.54, "duration": 2.94}, {"text": "as a function of the wage.", "start": 644.48, "duration": 1.81}, {"text": "So this should not\nbe abstract anymore.", "start": 646.29, "duration": 2.87}, {"text": "And we actually\ndid look at an RCT", "start": 649.16, "duration": 3.63}, {"text": "in China that had\nto do with changing", "start": 652.79, "duration": 2.79}, {"text": "the price of a staple commodity,\nwhich was featured in problem", "start": 655.58, "duration": 4.35}, {"text": "set one.", "start": 659.93, "duration": 1.08}, {"text": "So what am I doing?", "start": 661.01, "duration": 2.13}, {"text": "What on Earth am\nI doing right now?", "start": 663.14, "duration": 1.75}, {"text": "I'm not trying to give\nthis lecture again.", "start": 664.89, "duration": 2.57}, {"text": "I'm trying to tell you that\nwe're delivering on it.", "start": 667.46, "duration": 3.18}, {"text": "I mentioned these concepts\nin the very first lecture,", "start": 670.64, "duration": 2.85}, {"text": "was probably quite abstract.", "start": 673.49, "duration": 1.56}, {"text": "But now we're already\nbeginning to be", "start": 675.05, "duration": 2.37}, {"text": "able to fill in with the\nmaterial that came afterwards.", "start": 677.42, "duration": 3.81}, {"text": "Yeah, I think this is\nmore issues of modeling.", "start": 681.23, "duration": 6.36}, {"text": "Lucas artificial\neconomies-- I'll", "start": 687.59, "duration": 1.95}, {"text": "go back to that\ndynamic lecture where", "start": 689.54, "duration": 2.61}, {"text": "I said they could be\nfeeding grain to the animals", "start": 692.15, "duration": 5.01}, {"text": "or turning it into beer.", "start": 697.16, "duration": 2.07}, {"text": "And I said we would ignore that.", "start": 699.23, "duration": 2.13}, {"text": "That represented a\nchoice so that we", "start": 701.36, "duration": 2.19}, {"text": "could focus on what\narguably were the two", "start": 703.55, "duration": 2.58}, {"text": "most important storage devices.", "start": 706.13, "duration": 2.17}, {"text": "So we constructed an\nartificial economy", "start": 708.3, "duration": 2.6}, {"text": "to compare to the real data.", "start": 710.9, "duration": 2.43}, {"text": "And Lucas mentioned computation.", "start": 713.33, "duration": 2.37}, {"text": "And you can see\nthrough these lectures", "start": 715.7, "duration": 2.28}, {"text": "that I have not shied\naway from telling you", "start": 717.98, "duration": 2.82}, {"text": "how to determine solutions.", "start": 720.8, "duration": 2.64}, {"text": "We did this with\nLagrangian stuff,", "start": 723.44, "duration": 2.88}, {"text": "with a set of\nfirst-order conditions", "start": 726.32, "duration": 2.04}, {"text": "you could use to help predict\nand understand the solution.", "start": 728.36, "duration": 3.27}, {"text": "And then we went\nto linear programs.", "start": 731.63, "duration": 2.67}, {"text": "We went to dynamic programs.", "start": 734.3, "duration": 2.43}, {"text": "And we'll do more\nas we go along,", "start": 736.73, "duration": 2.52}, {"text": "depending on what we need to\ndo, depending on the lecture.", "start": 739.25, "duration": 3.24}, {"text": "And then this list\nof economies--", "start": 742.49, "duration": 2.34}, {"text": "we had a great discussion\nabout this on the last slide", "start": 744.83, "duration": 4.08}, {"text": "of the dynamic problem.", "start": 748.91, "duration": 1.65}, {"text": "We shifted gears, and went\nto a modern US economy", "start": 750.56, "duration": 4.29}, {"text": "with some credit instruments.", "start": 754.85, "duration": 1.74}, {"text": "And I'll come back to that.", "start": 756.59, "duration": 1.65}, {"text": "But this first economy, the\nmedieval village economy,", "start": 758.24, "duration": 3.15}, {"text": "you've obviously seen depicted\nin about three different", "start": 761.39, "duration": 3.45}, {"text": "lectures so far.", "start": 764.84, "duration": 1.68}, {"text": "The Thai village\neconomy has entered", "start": 766.52, "duration": 3.21}, {"text": "into the discussion,\neconomies where they didn't", "start": 769.73, "duration": 3.33}, {"text": "try to diversify\nex ante, and they", "start": 773.06, "duration": 3.15}, {"text": "need to potentially\nto share risk ex post.", "start": 776.21, "duration": 3.72}, {"text": "And we haven't done\nmuch with trade yet,", "start": 779.93, "duration": 1.83}, {"text": "although we haven't touched\nthese other two yet.", "start": 781.76, "duration": 3.57}, {"text": "The Lucas trees we did\nin that dynamic lecture", "start": 785.33, "duration": 3.42}, {"text": "because we talked about yield\nto seed ratios, how much harvest", "start": 788.75, "duration": 4.17}, {"text": "they're getting per unit\nof land planted in seed.", "start": 792.92, "duration": 2.85}, {"text": "And then I turned again,\nat the end of that lecture,", "start": 795.77, "duration": 2.67}, {"text": "to a dynamic problem in a\ndifferent economy, where", "start": 798.44, "duration": 3.57}, {"text": "they had an asset that was\nlike a borrowing or lending", "start": 802.01, "duration": 4.17}, {"text": "contract with its own return.", "start": 806.18, "duration": 2.5}, {"text": "So we went from farming\nto financial assets.", "start": 808.68, "duration": 3.63}, {"text": "So hopefully, that's an example.", "start": 812.31, "duration": 2.15}, {"text": "This we just did--", "start": 814.46, "duration": 1.98}, {"text": "what's an economy?", "start": 816.44, "duration": 1.11}, {"text": "Preferences, endowments,\nand technology.", "start": 817.55, "duration": 2.82}, {"text": "We've now got examples of it and\nwe developed notation for it.", "start": 820.37, "duration": 4.98}, {"text": "And throughout, I keep\ntrying to emphasize", "start": 825.35, "duration": 3.57}, {"text": "this can be applied to economies\nwith dynamics with geography", "start": 828.92, "duration": 6.09}, {"text": "and with uncertainty.", "start": 835.01, "duration": 1.65}, {"text": "Hopefully, you're getting\nbored with my comments,", "start": 836.66, "duration": 3.36}, {"text": "in the sense of yeah,\nyeah, yeah, we know.", "start": 840.02, "duration": 3.57}, {"text": "I hope you do know,\nbut my experience", "start": 843.59, "duration": 2.73}, {"text": "has been these things\nbear repeating.", "start": 846.32, "duration": 2.91}, {"text": "What are we going to do?", "start": 849.23, "duration": 1.48}, {"text": "We did that in the first\nlecture, then we did it .", "start": 850.71, "duration": 3.14}, {"text": "And now we're coming\nback to what did we do.", "start": 853.85, "duration": 2.98}, {"text": "So it is a review, after all.", "start": 856.83, "duration": 4.38}, {"text": "Lecture two was about\nconsumer choice.", "start": 861.21, "duration": 3.3}, {"text": "And we reviewed what's\nan economy-- preference,", "start": 864.51, "duration": 3.12}, {"text": "endowments, and technology--", "start": 867.63, "duration": 1.98}, {"text": "as if to say now we're going\nto focus only on preferences.", "start": 869.61, "duration": 4.2}, {"text": "Motivationally, I'm very nervous\nabout this part of the course", "start": 873.81, "duration": 4.74}, {"text": "and also the same\nslide for production,", "start": 878.55, "duration": 3.06}, {"text": "because then we kind of forget\nthe whole general economy", "start": 881.61, "duration": 3.36}, {"text": "thing, which is the prize\nthat we want to get to.", "start": 884.97, "duration": 3.12}, {"text": "But we can't get\nto the big picture", "start": 888.09, "duration": 1.53}, {"text": "with all the\ningredients combined", "start": 889.62, "duration": 1.86}, {"text": "until we understand the pieces.", "start": 891.48, "duration": 2.44}, {"text": "So this piece was\nabout the consumer.", "start": 893.92, "duration": 2.63}, {"text": "And we applied it, though we\ndid try to not just make things", "start": 896.55, "duration": 4.32}, {"text": "to memorize or theory.", "start": 900.87, "duration": 1.44}, {"text": "We tried to apply it at\nthe end of this lecture", "start": 902.31, "duration": 2.79}, {"text": "and in the following two--", "start": 905.1, "duration": 1.62}, {"text": "maximization of utility\nsubject to budgets.", "start": 906.72, "duration": 3.61}, {"text": "So we described the consumption\nset, various special versions", "start": 910.33, "duration": 4.35}, {"text": "that have time and geography.", "start": 914.68, "duration": 1.8}, {"text": "And we've talked about this.", "start": 916.48, "duration": 1.3}, {"text": "This is, again, one of the\ngreat, little questions", "start": 917.78, "duration": 2.33}, {"text": "we had at the beginning\nof the following class.", "start": 920.11, "duration": 2.73}, {"text": "And we talked about\nconsumer preferences,", "start": 922.84, "duration": 2.4}, {"text": "rank-ordering goods,\ndefined rational choice", "start": 925.24, "duration": 3.21}, {"text": "as preferences which are\ncomplete, transitive,", "start": 928.45, "duration": 2.22}, {"text": "and continuous.", "start": 930.67, "duration": 1.53}, {"text": "And then we talked\nabout a utility function", "start": 932.2, "duration": 2.67}, {"text": "representing preferences.", "start": 934.87, "duration": 1.8}, {"text": "A couple of things\ncame up here--", "start": 936.67, "duration": 2.1}, {"text": "it was ordinal and not cardinal,\nand we talked about that.", "start": 938.77, "duration": 3.75}, {"text": "But we will and did need\ncardinal representations", "start": 942.52, "duration": 3.33}, {"text": "when we got to uncertainty\nand dynamic decision problems.", "start": 945.85, "duration": 3.9}, {"text": "Second thing is this\nwas a chat on Piazza.", "start": 949.75, "duration": 4.11}, {"text": "This slide goes from having\na continuous utility.", "start": 953.86, "duration": 4.83}, {"text": "Any preference that\ncan be represented", "start": 958.69, "duration": 2.43}, {"text": "by a continuous\nutility function is", "start": 961.12, "duration": 2.94}, {"text": "rational in the sense\nof the definition", "start": 964.06, "duration": 2.07}, {"text": "of the previous slide.", "start": 966.13, "duration": 1.14}, {"text": "And then someone initiated\nthe obvious question,", "start": 967.27, "duration": 3.99}, {"text": "does it also go the other way--\nthat any rational preference", "start": 971.26, "duration": 3.75}, {"text": "function can be represented\nas a continuous utility?", "start": 975.01, "duration": 3.57}, {"text": "And the answer was,\nyes, although there", "start": 978.58, "duration": 1.65}, {"text": "was a good discussion about\ndistinguishing continuity", "start": 980.23, "duration": 3.42}, {"text": "on the one hand from the\nother two ingredients--", "start": 983.65, "duration": 2.13}, {"text": "completeness and transitivity.", "start": 985.78, "duration": 1.83}, {"text": "So that was a great\ndiscussion on Piazza.", "start": 987.61, "duration": 3.3}, {"text": "Local nonsatiation--\nthis is kind", "start": 990.91, "duration": 2.37}, {"text": "of a definition of being\nclose by and getting better.", "start": 993.28, "duration": 3.58}, {"text": "I talked about no bliss points.", "start": 996.86, "duration": 2.03}, {"text": "I think in words, we talked\nabout utility functions", "start": 998.89, "duration": 2.79}, {"text": "with bliss points, but we\nnever put any pictures in.", "start": 1001.68, "duration": 3.57}, {"text": "You might be thinking,\ncould I draw a picture", "start": 1005.25, "duration": 2.85}, {"text": "with a bliss point, and\nwhat would it look like?", "start": 1008.1, "duration": 2.64}, {"text": "More is preferred to less.", "start": 1010.74, "duration": 1.53}, {"text": "Largely I'm scrolling through\nthis, and hopefully quickly,", "start": 1012.27, "duration": 3.42}, {"text": "just to make sure if you\nhave questions or not.", "start": 1015.69, "duration": 2.91}, {"text": "Indifference curves, the whole\nfamily of indifference curves.", "start": 1018.6, "duration": 3.75}, {"text": "Indifferent serves can't\ncross because then they", "start": 1022.35, "duration": 2.55}, {"text": "wouldn't be transitive.", "start": 1024.9, "duration": 1.23}, {"text": "Margin rates of substitution\nwere defined, typically", "start": 1026.13, "duration": 3.36}, {"text": "diminishing, although\nnot necessarily.", "start": 1029.49, "duration": 3.089}, {"text": "And various displays of into\nfamilies of indifference", "start": 1032.579, "duration": 3.51}, {"text": "for different utility\nfunctions, running all the way", "start": 1036.089, "duration": 2.221}, {"text": "from perfect substitutes\nto perfect complements.", "start": 1038.31, "duration": 3.539}, {"text": "This one over here, the\nright-angled indifference", "start": 1041.849, "duration": 3.27}, {"text": "curves, represent\nLeontiefian preferences", "start": 1045.119, "duration": 3.991}, {"text": "where there's no\nsubstitutability.", "start": 1049.11, "duration": 2.76}, {"text": "We're about to get to maximizing\nutility subject to budgets.", "start": 1051.87, "duration": 3.023}, {"text": "You might play\naround a little bit", "start": 1054.893, "duration": 1.417}, {"text": "and see what happens with\nthese particular preferences", "start": 1056.31, "duration": 3.78}, {"text": "when you do that.", "start": 1060.09, "duration": 1.27}, {"text": "What happens when\nyou change prices?", "start": 1061.36, "duration": 1.7}, {"text": "That would be an\ninteresting experiment", "start": 1063.06, "duration": 1.83}, {"text": "to conduct because you'll get\nreally sharp predictions that", "start": 1064.89, "duration": 4.29}, {"text": "are distinct from what\nyou would get in this more", "start": 1069.18, "duration": 2.88}, {"text": "typical smooth case.", "start": 1072.06, "duration": 1.89}, {"text": "And I'm anticipating reviewing\nthe production lecture", "start": 1073.95, "duration": 4.14}, {"text": "in two lectures away.", "start": 1078.09, "duration": 1.98}, {"text": "So now, you're able to go\nback and forth between what", "start": 1080.07, "duration": 3.78}, {"text": "do indifference curves\nlook like and consumption", "start": 1083.85, "duration": 2.67}, {"text": "versus isoquants or isoproduct\nlines in production.", "start": 1086.52, "duration": 5.94}, {"text": "This one, the Leontief thing,\nwe didn't talk about it much", "start": 1092.46, "duration": 4.65}, {"text": "in consumer theory but we did\ntalk about it in production,", "start": 1097.11, "duration": 3.45}, {"text": "and you probably didn't\nmake the connection.", "start": 1100.56, "duration": 2.56}, {"text": "But I'll try to remember to\npoint out where we actually", "start": 1103.12, "duration": 3.95}, {"text": "used it in production.", "start": 1107.07, "duration": 2.38}, {"text": "These are examples of utility\nfunctions and definitions", "start": 1109.45, "duration": 4.16}, {"text": "of convexity and\nquasi-concavity.", "start": 1113.61, "duration": 3.72}, {"text": "There are a lot of\ndifferent concepts here.", "start": 1117.33, "duration": 2.43}, {"text": "They were all illustrated\nas holding or not", "start": 1119.76, "duration": 2.91}, {"text": "holding, depending on how\nwe draw these pictures.", "start": 1122.67, "duration": 3.21}, {"text": "Convexity turns out\nto be important,", "start": 1125.88, "duration": 2.74}, {"text": "especially when we're\ndrawing pictures", "start": 1128.62, "duration": 2.18}, {"text": "of tangencies and optimization.", "start": 1130.8, "duration": 2.64}, {"text": "Things can really\ngo kind of crazy", "start": 1133.44, "duration": 2.31}, {"text": "when you don't have convexity.", "start": 1135.75, "duration": 1.62}, {"text": "Here, it's convexity of the\nweak upper contour set of it,", "start": 1137.37, "duration": 3.87}, {"text": "weakly preferred bundles.", "start": 1141.24, "duration": 1.95}, {"text": "A little more technical\nderivation of the marginal rate", "start": 1143.19, "duration": 2.73}, {"text": "of substitution, and something\nabout homothetic preferences,", "start": 1145.92, "duration": 3.93}, {"text": "where the slope of the\nindifference curves", "start": 1149.85, "duration": 2.01}, {"text": "are determined entirely by\nthe ratio of the two goods.", "start": 1151.86, "duration": 4.23}, {"text": "We kept coming back to this\npicture in different ways.", "start": 1156.09, "duration": 2.88}, {"text": "In the next lecture\nin fact, there's", "start": 1158.97, "duration": 2.31}, {"text": "something about angles\ncurves, and necessities,", "start": 1161.28, "duration": 3.21}, {"text": "and Giffen goods, and so on.", "start": 1164.49, "duration": 1.77}, {"text": "Suffice it to say\nthat if you're moving", "start": 1166.26, "duration": 2.55}, {"text": "outwards along this ray--", "start": 1168.81, "duration": 1.65}, {"text": "because maybe your income\nis increased, holding prices", "start": 1170.46, "duration": 3.54}, {"text": "constant-- the goods x1 and x2\nare increasing proportionally", "start": 1174.0, "duration": 4.8}, {"text": "with the distance\nalong this ray.", "start": 1178.8, "duration": 2.1}, {"text": "And likewise, since\nprices are fixed,", "start": 1180.9, "duration": 3.09}, {"text": "expenditure is also moving\nproportionally along this ray.", "start": 1183.99, "duration": 4.65}, {"text": "The preferences\nwere not homothetic.", "start": 1188.64, "duration": 1.92}, {"text": "Then this would not be\na line from the origin.", "start": 1190.56, "duration": 2.37}, {"text": "It would start to bend.", "start": 1192.93, "duration": 1.62}, {"text": "And that actually\nwas what was going", "start": 1194.55, "duration": 2.46}, {"text": "on when we talked about income\neffects and substitution", "start": 1197.01, "duration": 2.91}, {"text": "effects.", "start": 1199.92, "duration": 0.57}, {"text": "That's coming up in\nthe next lecture.", "start": 1200.49, "duration": 2.58}, {"text": "We haven't used this\nutility function very much,", "start": 1203.07, "duration": 2.49}, {"text": "although it will appear soon.", "start": 1205.56, "duration": 2.99}, {"text": "And we did talk about\nutility functions", "start": 1208.55, "duration": 2.31}, {"text": "which are completely linear.", "start": 1210.86, "duration": 1.89}, {"text": "So finally, we get to the\nutility maximization problem--", "start": 1212.75, "duration": 3.39}, {"text": "max utility is\nsubject to a budget--", "start": 1216.14, "duration": 2.04}, {"text": "and defined homogeneity in\nthis consumer theory context,", "start": 1218.18, "duration": 4.5}, {"text": "and started to generate these\npictures of income budget", "start": 1222.68, "duration": 3.33}, {"text": "lines, and the set of\nall possible purchases", "start": 1226.01, "duration": 3.0}, {"text": "in and under the budget line,\nand the utility-maximizing", "start": 1229.01, "duration": 4.86}, {"text": "positions.", "start": 1233.87, "duration": 0.75}, {"text": "Although again, this is kind\nof the classic smooth diagram", "start": 1234.62, "duration": 3.54}, {"text": "that sometimes is the\nonly diagram you see.", "start": 1238.16, "duration": 2.97}, {"text": "I'm bending over\nbackwards to show you", "start": 1241.13, "duration": 2.37}, {"text": "different pictures like this\none, where the maximum is not", "start": 1243.5, "duration": 4.11}, {"text": "interior.", "start": 1247.61, "duration": 1.68}, {"text": "You do want to keep an eye out\nabout whether they would be", "start": 1249.29, "duration": 3.93}, {"text": "happy with this quantity of y,\nor whether they would actually", "start": 1253.22, "duration": 4.35}, {"text": "like to go negative\nand just cannot do it", "start": 1257.57, "duration": 2.16}, {"text": "because of the consumption set.", "start": 1259.73, "duration": 1.83}, {"text": "And we formalize\nthat as an example", "start": 1261.56, "duration": 3.89}, {"text": "of the use of the\nLagrangian, where", "start": 1265.45, "duration": 2.49}, {"text": "you write out this expression\nwith all the constraints.", "start": 1267.94, "duration": 4.17}, {"text": "And this is the generalized\nroutine for optimization,", "start": 1272.11, "duration": 5.1}, {"text": "and actually applying\nit to the case", "start": 1277.21, "duration": 2.34}, {"text": "where we have these\nnon-negativity constraints", "start": 1279.55, "duration": 3.3}, {"text": "on the two goods.", "start": 1282.85, "duration": 2.14}, {"text": "This is the most general way\nto deal with the problem.", "start": 1284.99, "duration": 3.45}, {"text": "It doesn't mean all these\nconstraints to are binding.", "start": 1288.44, "duration": 3.65}, {"text": "They may be binding\nand may be not.", "start": 1292.09, "duration": 2.67}, {"text": "Typically with non-satiation, a\nhousehold with this constraint", "start": 1294.76, "duration": 3.36}, {"text": "will want to spend\nall its income,", "start": 1298.12, "duration": 1.81}, {"text": "so that's usually\nbinding, although you", "start": 1299.93, "duration": 2.57}, {"text": "could try to draw a\npicture where it's not.", "start": 1302.5, "duration": 2.04}, {"text": "Back, by the way,\nto the bliss point,", "start": 1304.54, "duration": 2.34}, {"text": "but I've never shown you that.", "start": 1306.88, "duration": 1.69}, {"text": "And just because it says\n\"greater than or equal to,\"", "start": 1308.57, "duration": 2.96}, {"text": "in other words,\nnon-negative, doesn't", "start": 1311.53, "duration": 1.74}, {"text": "mean they would want\nit to go negative.", "start": 1313.27, "duration": 2.04}, {"text": "That depends on what\nthis picture looks like.", "start": 1315.31, "duration": 4.94}, {"text": "And then we did the\nexample utility functions.", "start": 1320.25, "duration": 4.33}, {"text": "This is Cobb-Douglas.", "start": 1324.58, "duration": 1.38}, {"text": "And you do the algebra,\nand you get this result", "start": 1325.96, "duration": 5.1}, {"text": "that pX times X is\ntotal expenditures on X.", "start": 1331.06, "duration": 4.68}, {"text": "And it's a constant,\nalpha times income.", "start": 1335.74, "duration": 3.58}, {"text": "So this is an example of\nbudget shares being constant.", "start": 1339.32, "duration": 4.84}, {"text": "As income vary, X\nand Y will vary.", "start": 1344.16, "duration": 4.66}, {"text": "The amount spent\nwill vary, but it's", "start": 1348.82, "duration": 2.64}, {"text": "going to vary in a linear way.", "start": 1351.46, "duration": 1.65}, {"text": "It's one-to-one with income.", "start": 1353.11, "duration": 1.425}, {"text": "And that Cobb-Douglas,\nthis guy here,", "start": 1357.44, "duration": 3.34}, {"text": "that's homothetic preferences.", "start": 1360.78, "duration": 2.03}, {"text": "I don't think I said that\nwhen I was lecturing on this.", "start": 1362.81, "duration": 3.0}, {"text": "Maybe I did.", "start": 1365.81, "duration": 2.38}, {"text": "So in this case, you can\nalmost see it in the algebra--", "start": 1368.19, "duration": 3.59}, {"text": "the marginal rate of\nsubstitution, which is here,", "start": 1371.78, "duration": 5.2}, {"text": "depends only on the ratio of\nY to X because this alpha is", "start": 1376.98, "duration": 5.18}, {"text": "a constant.", "start": 1382.16, "duration": 0.82}, {"text": "So this is a homothetic\nutility function.", "start": 1382.98, "duration": 2.78}, {"text": "And finally, we got\nto labor supply,", "start": 1385.76, "duration": 2.44}, {"text": "which is like an\napplication, since I", "start": 1388.2, "duration": 2.96}, {"text": "was worried that you'll\nlose the context of what", "start": 1391.16, "duration": 2.85}, {"text": "we're trying to do.", "start": 1394.01, "duration": 1.84}, {"text": "So we had this picture, this\nbeautiful picture, of someone", "start": 1395.85, "duration": 5.27}, {"text": "starting with leisure.", "start": 1401.12, "duration": 2.43}, {"text": "This was the first time I think\nwe talked about an endowment.", "start": 1403.55, "duration": 3.84}, {"text": "So they're endowed with 24\nhours a day or less sleep time.", "start": 1407.39, "duration": 5.95}, {"text": "I don't know if you\nsleep eight hours,", "start": 1413.34, "duration": 2.8}, {"text": "but now we're down to 16.", "start": 1416.14, "duration": 1.92}, {"text": "And they can take that time\nand enjoy it in leisure", "start": 1418.06, "duration": 4.14}, {"text": "or run it to 0 and work.", "start": 1422.2, "duration": 2.4}, {"text": "This diagram is in the space\nof goods that consumers want.", "start": 1424.6, "duration": 4.17}, {"text": "They're going to\nend up consuming", "start": 1428.77, "duration": 1.38}, {"text": "positive amounts of\nleisure, positive amounts", "start": 1430.15, "duration": 3.0}, {"text": "of consumption, like\nx1, x2, with both", "start": 1433.15, "duration": 3.3}, {"text": "of them being positive.", "start": 1436.45, "duration": 1.47}, {"text": "The slope of the budget\nline represents the wage.", "start": 1437.92, "duration": 2.97}, {"text": "You might play\naround a bit and ask", "start": 1440.89, "duration": 2.31}, {"text": "if you could draw the picture\nwhere the choice is not", "start": 1443.2, "duration": 4.44}, {"text": "over leisure but\nlabor, in which case", "start": 1447.64, "duration": 2.67}, {"text": "you'd be moving\nto the left here.", "start": 1450.31, "duration": 1.77}, {"text": "And then you'd have to\ndraw the budget line--", "start": 1452.08, "duration": 2.94}, {"text": "it's going to look similar--", "start": 1455.02, "duration": 1.39}, {"text": "and then draw preferences.", "start": 1456.41, "duration": 2.095}, {"text": "I'll show you what\nI have in mind", "start": 1458.505, "duration": 1.375}, {"text": "when we get back to that\nRobinson Crusoe economy.", "start": 1459.88, "duration": 3.63}, {"text": "Now let's go to lecture three.", "start": 1463.51, "duration": 3.01}, {"text": "I'm going to spend a little\nbit less time on this", "start": 1466.52, "duration": 2.75}, {"text": "in terms of going through\neach and every slide,", "start": 1469.27, "duration": 2.14}, {"text": "but try to focus more on\nsome of the key aspects.", "start": 1471.41, "duration": 3.79}, {"text": "So we had this demand system.", "start": 1475.2, "duration": 2.12}, {"text": "This would represent\ndata, but we're", "start": 1477.32, "duration": 2.437}, {"text": "going to assume right\naway it's coming", "start": 1479.757, "duration": 1.583}, {"text": "from utility maximization.", "start": 1481.34, "duration": 2.34}, {"text": "So you can think about\nthis as restrictions", "start": 1483.68, "duration": 2.52}, {"text": "on data implied by\nutility maximization.", "start": 1486.2, "duration": 4.99}, {"text": "This is in the spirit\nof Frisch and RCTs", "start": 1491.19, "duration": 4.62}, {"text": "and various other things.", "start": 1495.81, "duration": 1.27}, {"text": "So we're increasing income.", "start": 1497.08, "duration": 1.19}, {"text": "What would happen?", "start": 1498.27, "duration": 1.77}, {"text": "This is the linear\nexpansion path.", "start": 1500.04, "duration": 3.33}, {"text": "But it doesn't have\nto look like that.", "start": 1503.37, "duration": 1.72}, {"text": "It could look like this.", "start": 1505.09, "duration": 2.21}, {"text": "So this actually\nhas a negative slope", "start": 1507.3, "duration": 3.36}, {"text": "as you increase income because\nthe amount purchased of goods", "start": 1510.66, "duration": 3.48}, {"text": "is going down.", "start": 1514.14, "duration": 1.59}, {"text": "It could be entirely\nvertical, actually.", "start": 1515.73, "duration": 3.12}, {"text": "I think you could imagine\nhow to draw it that way.", "start": 1518.85, "duration": 3.21}, {"text": "That utility function\nI said we didn't", "start": 1522.06, "duration": 2.07}, {"text": "do much, which was transferable\nutility, x1 plus log", "start": 1524.13, "duration": 3.57}, {"text": "x2, that would give you a\nvertical line like this,", "start": 1527.7, "duration": 4.95}, {"text": "or horizontal.", "start": 1532.65, "duration": 1.29}, {"text": "I don't remember\nwhich good was which,", "start": 1533.94, "duration": 1.62}, {"text": "but now the quantities\nare going down or up", "start": 1535.56, "duration": 4.5}, {"text": "and the prices are constant.", "start": 1540.06, "duration": 1.59}, {"text": "Because all we're\ndoing is moving income.", "start": 1541.65, "duration": 2.61}, {"text": "Hence, the\nexpenditure shares are", "start": 1544.26, "duration": 1.98}, {"text": "moving in this diagram,\nnot just the quantities,", "start": 1546.24, "duration": 3.78}, {"text": "because of the nature\nof the experiment.", "start": 1550.02, "duration": 1.96}, {"text": "So we defined inferior goods and\nnormal goods, and got to Engel.", "start": 1551.98, "duration": 5.94}, {"text": "Engel's law being,\nin particular,", "start": 1557.92, "duration": 2.37}, {"text": "proportion of total\nexpenditure on food", "start": 1560.29, "duration": 2.49}, {"text": "goes down as income goes up.", "start": 1562.78, "duration": 1.83}, {"text": "So someone asks me--", "start": 1564.61, "duration": 1.29}, {"text": "I think it was in the Piazza\nchat or was it in class--", "start": 1565.9, "duration": 3.52}, {"text": "no, it was in class.", "start": 1569.42, "duration": 1.01}, {"text": "One of you asked\nme, are we talking", "start": 1570.43, "duration": 2.73}, {"text": "about quantities or\nshares of expenses?", "start": 1573.16, "duration": 3.76}, {"text": "So it's kind of related.", "start": 1576.92, "duration": 1.07}, {"text": "In order for Engel's\nthings to be true,", "start": 1577.99, "duration": 2.38}, {"text": "some good must be, by\ndefinition, a necessity.", "start": 1580.37, "duration": 3.44}, {"text": "But necessities were\ndefined by this diagram", "start": 1583.81, "duration": 3.48}, {"text": "where we just changed income\nand didn't change prices.", "start": 1587.29, "duration": 3.51}, {"text": "Just trying to tie these\nloose ends together.", "start": 1590.8, "duration": 3.12}, {"text": "Then we showed you what's\ngoing on in the US.", "start": 1593.92, "duration": 2.67}, {"text": "One of you made a great\ncomment about this diagram,", "start": 1596.59, "duration": 3.99}, {"text": "it's kind of being tautological.", "start": 1600.58, "duration": 1.71}, {"text": "And my answer was\nyes, but it's also", "start": 1602.29, "duration": 2.13}, {"text": "quantifying the differences.", "start": 1604.42, "duration": 1.6}, {"text": "And here we did the income\nand substitution effects", "start": 1606.02, "duration": 3.05}, {"text": "from price changes, in\nparticular emphasizing", "start": 1609.07, "duration": 3.27}, {"text": "the income effect of price\nchanges for increases", "start": 1612.34, "duration": 3.63}, {"text": "and decreases in prices, and\nplotted out the demand curves.", "start": 1615.97, "duration": 3.75}, {"text": "Some people just start with\ndemand curves, like this.", "start": 1619.72, "duration": 3.16}, {"text": "So where did it come from?", "start": 1622.88, "duration": 1.7}, {"text": "In particular with\naggregate demand,", "start": 1624.58, "duration": 2.34}, {"text": "is it down-sloping like this?", "start": 1626.92, "duration": 2.04}, {"text": "What's going to\nhappen in the economy", "start": 1628.96, "duration": 1.59}, {"text": "as a function of the virus has\nto do with these elasticities", "start": 1630.55, "duration": 3.15}, {"text": "and so on.", "start": 1633.7, "duration": 1.21}, {"text": "But I prefer not to start\nwith this as a primitive.", "start": 1634.91, "duration": 2.63}, {"text": "I prefer to derive it and\nput restrictions on it", "start": 1637.54, "duration": 4.05}, {"text": "from these underlying\nfirst principles.", "start": 1641.59, "duration": 2.85}, {"text": "Then we defined\nGiffen's paradox--", "start": 1644.44, "duration": 2.22}, {"text": "that in the famine, the Irish--", "start": 1646.66, "duration": 1.77}, {"text": "which destroyed the potatoes,\nthey were eating more potatoes.", "start": 1648.43, "duration": 3.96}, {"text": "We decided that couldn't\nliterally be factually true,", "start": 1652.39, "duration": 3.3}, {"text": "and that Giffen's thing, I\nthought, had never been tested.", "start": 1655.69, "duration": 3.36}, {"text": "And then I discovered\nJensen and Miller,", "start": 1659.05, "duration": 3.69}, {"text": "and they shared their data.", "start": 1662.74, "duration": 1.47}, {"text": "And of course, the paper\nwas published and so on.", "start": 1664.21, "duration": 2.86}, {"text": "So this was an important part\nof the course for two reasons.", "start": 1667.07, "duration": 4.07}, {"text": "It's meant to bring the\nconcepts of Giffen goods,", "start": 1671.14, "duration": 3.21}, {"text": "and hence the distinction\nbetween income and substitution", "start": 1674.35, "duration": 2.58}, {"text": "effects, to life in real data.", "start": 1676.93, "duration": 2.37}, {"text": "It was also, as I said earlier,\nan example of an actual RCT", "start": 1679.3, "duration": 5.46}, {"text": "in practice.", "start": 1684.76, "duration": 1.18}, {"text": "So it's not just as if we\nwere running an experiment.", "start": 1685.94, "duration": 2.9}, {"text": "They ran the experiment.", "start": 1688.84, "duration": 1.35}, {"text": "They actually did it.", "start": 1690.19, "duration": 1.78}, {"text": "They had households\nthat were treated,", "start": 1691.97, "duration": 2.09}, {"text": "households that were\ncontrol, looked at behavior,", "start": 1694.06, "duration": 3.78}, {"text": "and they did find Giffen goods.", "start": 1697.84, "duration": 2.35}, {"text": "So it's an important part\nto bring the theory to life.", "start": 1700.19, "duration": 4.11}, {"text": "The second thing is it was a\nbig part of problem set one.", "start": 1704.3, "duration": 4.52}, {"text": "And that came with the\nexperience of reading", "start": 1708.82, "duration": 3.18}, {"text": "a professional paper,\nhaving the data there ready", "start": 1712.0, "duration": 3.33}, {"text": "for you to manipulate,\nrun some code", "start": 1715.33, "duration": 2.85}, {"text": "to replicate what these\nguys did, and to extend it.", "start": 1718.18, "duration": 3.63}, {"text": "And many of you answered\nthose questions.", "start": 1721.81, "duration": 2.01}, {"text": "Some of you did not or\ndidn't answer all of it.", "start": 1723.82, "duration": 4.28}, {"text": "At a minimum for now,\nyou should understand", "start": 1728.1, "duration": 2.1}, {"text": "what it was that these guys\ndid, and why they did it,", "start": 1730.2, "duration": 3.82}, {"text": "and what they found, quite apart\nfrom answering that problem.", "start": 1734.02, "duration": 3.57}, {"text": "So uncompensated and\ncompensated demand,", "start": 1737.59, "duration": 4.34}, {"text": "also known as Hicksian\nversus Marshallian demand.", "start": 1741.93, "duration": 4.05}, {"text": "This eliminates income effects.", "start": 1745.98, "duration": 2.26}, {"text": "So you move along indifference\ncurves when you change prices,", "start": 1748.24, "duration": 3.23}, {"text": "so it's all driven\nby assumptions", "start": 1751.47, "duration": 2.46}, {"text": "about the marginal\nrate of substitution.", "start": 1753.93, "duration": 2.95}, {"text": "We tended to draw these\nsmooth indifference curves", "start": 1756.88, "duration": 3.29}, {"text": "with declining marginal rates\nof substitution, which is", "start": 1760.17, "duration": 3.21}, {"text": "the right way to get started.", "start": 1763.38, "duration": 1.23}, {"text": "But this concept should\nwork as well when you have", "start": 1764.61, "duration": 2.61}, {"text": "linear indifference curves.", "start": 1767.22, "duration": 1.24}, {"text": "So that links back to that other\ndiagram that I was mentioning,", "start": 1768.46, "duration": 3.92}, {"text": "the one with the almost-linear\nindifference curve", "start": 1772.38, "duration": 3.03}, {"text": "and the price.", "start": 1775.41, "duration": 1.29}, {"text": "But in this case, we'd be\ndoing that and also changing", "start": 1776.7, "duration": 3.18}, {"text": "the price ratio.", "start": 1779.88, "duration": 1.66}, {"text": "So we have compensated\nand uncompensated demand,", "start": 1781.54, "duration": 3.5}, {"text": "leading to Slutsky's equation.", "start": 1785.04, "duration": 2.77}, {"text": "And I don't know if\nI helped or hurt,", "start": 1787.81, "duration": 2.24}, {"text": "but I actually jumped ahead\nto lecture 18 or something,", "start": 1790.05, "duration": 3.99}, {"text": "and showed you eventually\nhow we're going to use that.", "start": 1794.04, "duration": 2.71}, {"text": "But I also told you\nto ignore that detour", "start": 1796.75, "duration": 4.73}, {"text": "if it was confusing.", "start": 1801.48, "duration": 2.41}, {"text": "But this whole lecture is\nabout making predictions", "start": 1803.89, "duration": 3.71}, {"text": "as prices change\nor income change.", "start": 1807.6, "duration": 3.33}, {"text": "And this Slutsky\nequation turns out", "start": 1810.93, "duration": 3.66}, {"text": "to be something you\ncan measure in data.", "start": 1814.59, "duration": 2.19}, {"text": "Even though we never see\nthe compensated demand,", "start": 1816.78, "duration": 5.01}, {"text": "the compensated\ndemand has properties", "start": 1821.79, "duration": 3.15}, {"text": "because the expenditure\nfunction is concave.", "start": 1824.94, "duration": 3.03}, {"text": "So we can actually put\nsome sign restrictions", "start": 1827.97, "duration": 3.03}, {"text": "on the Marshallian\ndemand in this way.", "start": 1831.0, "duration": 3.6}, {"text": "It's all a bit surprising,\nbut more on that later.", "start": 1834.6, "duration": 3.72}, {"text": "Anyway, it's about\nmaking predictions.", "start": 1838.32, "duration": 2.35}, {"text": "And then we did duality,\nwhich I was just", "start": 1840.67, "duration": 2.03}, {"text": "alluding to, minimizing\nexpenditures subject to--", "start": 1842.7, "duration": 5.31}, {"text": "here's the picture.", "start": 1848.01, "duration": 1.26}, {"text": "So this was the\nfirst time we talked", "start": 1849.27, "duration": 2.94}, {"text": "about maximizing utilities\nsubject to budgets, hand", "start": 1852.21, "duration": 3.12}, {"text": "in hand with minimizing\nexpenditures to achieve", "start": 1855.33, "duration": 3.51}, {"text": "a certain level of utility.", "start": 1858.84, "duration": 2.38}, {"text": "So we defined a dual\nproblem relative", "start": 1861.22, "duration": 2.54}, {"text": "to the primary problem, and got\nsome useful characteristics out", "start": 1863.76, "duration": 4.05}, {"text": "of the dual.", "start": 1867.81, "duration": 1.53}, {"text": "Although in fact, if\nit's a very teeny,", "start": 1869.34, "duration": 2.7}, {"text": "weeny change, and it's all\nlocal, nothing happens.", "start": 1872.04, "duration": 2.88}, {"text": "They're equivalent.", "start": 1874.92, "duration": 1.87}, {"text": "At least, they're equivalent\nwith these other underlying", "start": 1876.79, "duration": 2.6}, {"text": "assumptions--", "start": 1879.39, "duration": 1.32}, {"text": "nice, smooth indifference\ncurves, no bliss points,", "start": 1880.71, "duration": 2.55}, {"text": "et cetera.", "start": 1883.26, "duration": 1.11}, {"text": "You could experiment with\nputting in local satiation.", "start": 1884.37, "duration": 4.32}, {"text": "And then you will\ndiscover that these things", "start": 1888.69, "duration": 1.95}, {"text": "don't have to be the same.", "start": 1890.64, "duration": 2.16}, {"text": "Maximizing utility\nsubject to a budget", "start": 1892.8, "duration": 3.03}, {"text": "and minimizing\nexpenditure to achieve", "start": 1895.83, "duration": 2.55}, {"text": "a certain level of\nutility will not", "start": 1898.38, "duration": 2.94}, {"text": "be the same when you\nviolate the assumption", "start": 1901.32, "duration": 4.41}, {"text": "of local non-satiation.", "start": 1905.73, "duration": 3.54}, {"text": "Anyway, we developed\nall this in the math,", "start": 1909.27, "duration": 5.16}, {"text": "in the end of this\nlecture, and then", "start": 1914.43, "duration": 4.05}, {"text": "ended just the way we did the\nprevious one, with, hopefully,", "start": 1918.48, "duration": 3.63}, {"text": "another attempt to bring\nthis stuff to life, which", "start": 1922.11, "duration": 2.46}, {"text": "is to give the household\nmoney incomes denoted", "start": 1924.57, "duration": 3.3}, {"text": "by a first date or\nsecond date, and then", "start": 1927.87, "duration": 2.67}, {"text": "talk about price changes.", "start": 1930.54, "duration": 2.44}, {"text": "So it is about the distinction\nbetween income and substitution", "start": 1932.98, "duration": 4.22}, {"text": "effects.", "start": 1937.2, "duration": 0.85}, {"text": "But here, unlike income as\nexogenous and moving around,", "start": 1938.05, "duration": 6.15}, {"text": "you have money incomes\nin the two dates.", "start": 1944.2, "duration": 2.42}, {"text": "All we're doing is\nchanging prices.", "start": 1946.62, "duration": 2.52}, {"text": "We're changing the price\nof the good at date two", "start": 1949.14, "duration": 2.7}, {"text": "relative to the price\nof the good at date one.", "start": 1951.84, "duration": 2.73}, {"text": "So there were two\ndifferent pictures here", "start": 1954.57, "duration": 2.13}, {"text": "depending on whether initially,\nthe household, as here,", "start": 1956.7, "duration": 3.54}, {"text": "is a lender, eating less\nthan its initial endowment.", "start": 1960.24, "duration": 6.66}, {"text": "We talked about\nan income effect.", "start": 1966.9, "duration": 2.11}, {"text": "You can see that as we move\nfrom the solid blue line", "start": 1969.01, "duration": 3.32}, {"text": "to the pale blue line, in\nthis upper quadrant at least,", "start": 1972.33, "duration": 3.96}, {"text": "the new budget line lies\nfurther toward the northeast", "start": 1976.29, "duration": 3.93}, {"text": "than the original one.", "start": 1980.22, "duration": 1.48}, {"text": "And since they started\nhere, locally the effect", "start": 1981.7, "duration": 2.99}, {"text": "of the interest change is\nto give them more income.", "start": 1984.69, "duration": 3.33}, {"text": "But they don't have\nto end up with higher", "start": 1988.02, "duration": 2.34}, {"text": "consumption of the second good.", "start": 1990.36, "duration": 1.38}, {"text": "They could have ended up\nwith lower consumption.", "start": 1991.74, "duration": 2.31}, {"text": "It's really hard\nto focus in there.", "start": 1994.05, "duration": 1.87}, {"text": "I have to put it right\nthere or something.", "start": 1995.92, "duration": 2.37}, {"text": "So it would be a little bit\nlower than it was initially,", "start": 1998.29, "duration": 3.68}, {"text": "and that's despite the\nincrease in income.", "start": 2001.97, "duration": 3.31}, {"text": "So that's the case\nwhere the substitution", "start": 2005.28, "duration": 2.72}, {"text": "effect is getting washed out.", "start": 2008.0, "duration": 2.01}, {"text": "So again, here, they\nstart out as a borrower,", "start": 2010.01, "duration": 4.65}, {"text": "and now when the\ninterest rate goes up,", "start": 2014.66, "duration": 3.78}, {"text": "they clearly have less income,\nwhich intuitively makes sense", "start": 2018.44, "duration": 3.66}, {"text": "because they were\nalready borrowing.", "start": 2022.1, "duration": 1.5}, {"text": "And an increase in\nthe interest rate", "start": 2023.6, "duration": 1.98}, {"text": "can only increase the amount\nof debt if they stay put.", "start": 2025.58, "duration": 3.48}, {"text": "But they would not stay put.", "start": 2029.06, "duration": 2.64}, {"text": "Then the two effects have to\ndo with income and substitution", "start": 2031.7, "duration": 2.82}, {"text": "effects.", "start": 2034.52, "duration": 0.81}, {"text": "They have the same sign\nfor consumption today,", "start": 2035.33, "duration": 4.23}, {"text": "but opposing signs for\nconsumption tomorrow.", "start": 2039.56, "duration": 5.36}, {"text": "So I think I went\nback the next class", "start": 2044.92, "duration": 1.7}, {"text": "and made the comment that this\nis an important stepping stone", "start": 2046.62, "duration": 4.5}, {"text": "toward modeling entire\neconomies because we're giving", "start": 2051.12, "duration": 3.3}, {"text": "the household an endowment.", "start": 2054.42, "duration": 1.35}, {"text": "In the labor example,\nwe gave the household", "start": 2055.77, "duration": 2.73}, {"text": "an endowment of time.", "start": 2058.5, "duration": 2.04}, {"text": "Here, we're giving the household\nan endowment of money income", "start": 2060.54, "duration": 2.94}, {"text": "in each of two periods.", "start": 2063.48, "duration": 2.14}, {"text": "So the endowments are\npart of an economy.", "start": 2065.62, "duration": 2.15}, {"text": "Preferences are clearly\nbeing described here.", "start": 2067.77, "duration": 3.03}, {"text": "Production was suppressed\nbecause it's just", "start": 2070.8, "duration": 3.18}, {"text": "a consumer problem.", "start": 2073.98, "duration": 3.13}, {"text": "So that was lecture three.", "start": 2077.11, "duration": 3.209}, {"text": "Next up is lecture four.", "start": 2083.19, "duration": 3.35}, {"text": "So I may speed up a little bit.", "start": 2086.54, "duration": 3.15}, {"text": "That said, there's a ton\nof stuff in lecture four,", "start": 2089.69, "duration": 2.18}, {"text": "and we did not get through it\ndeliberately the first time.", "start": 2091.87, "duration": 3.51}, {"text": "There's three or four\nslides at the end", "start": 2095.38, "duration": 3.75}, {"text": "that we moved to\nthe next lecture.", "start": 2099.13, "duration": 4.15}, {"text": "Because by topic,\nit's about production,", "start": 2103.28, "duration": 2.1}, {"text": "but there are just too\nmany important concepts.", "start": 2105.38, "duration": 2.79}, {"text": "Repeat-- preferences,\nendowment, technology-- now", "start": 2108.17, "duration": 2.82}, {"text": "zero in on technology.", "start": 2110.99, "duration": 2.25}, {"text": "That question that\nwe were discussing", "start": 2113.24, "duration": 2.1}, {"text": "about describe medieval\nvillages as an economy also", "start": 2115.34, "duration": 4.32}, {"text": "made reference to Northern\nThai villages as an economy.", "start": 2119.66, "duration": 2.88}, {"text": "Here's the picture.", "start": 2122.54, "duration": 1.15}, {"text": "So what's the technology here?", "start": 2123.69, "duration": 2.75}, {"text": "Land, labor, and capital\nare used as inputs", "start": 2126.44, "duration": 2.82}, {"text": "to produce this crop.", "start": 2129.26, "duration": 1.47}, {"text": "So this, in many respects,\nshould not have been hard.", "start": 2130.73, "duration": 2.97}, {"text": "But then again,\nI'm not asking you", "start": 2133.7, "duration": 1.56}, {"text": "to memorize all these\nbeautiful pictures,", "start": 2135.26, "duration": 2.64}, {"text": "just saying that because\nI took this picture.", "start": 2137.9, "duration": 2.13}, {"text": "Sorry.", "start": 2140.03, "duration": 0.6}, {"text": "So production-- we have\ninputs and negative, outputs,", "start": 2140.63, "duration": 3.46}, {"text": "which are positive, and vectors,\nand indexed by particular goods", "start": 2144.09, "duration": 6.08}, {"text": "and by firms, potentially.", "start": 2150.17, "duration": 1.77}, {"text": "We have this production\npossibility set,", "start": 2151.94, "duration": 2.85}, {"text": "where inputs being negative,\nlike labor over here,", "start": 2154.79, "duration": 3.24}, {"text": "and outputs being positive.", "start": 2158.03, "duration": 1.77}, {"text": "This one displays a region\nof increasing and decreasing", "start": 2159.8, "duration": 4.17}, {"text": "returns to scale, to\nbe defined momentarily.", "start": 2163.97, "duration": 3.54}, {"text": "We went through these properties\nof production functions.", "start": 2167.51, "duration": 2.88}, {"text": "And there was a good\ndiscussion coming up, namely", "start": 2170.39, "duration": 4.32}, {"text": "decreasing constant and\nincreasing returns to scale.", "start": 2174.71, "duration": 4.11}, {"text": "This was the picture of\ndecreasing returns to scale.", "start": 2178.82, "duration": 3.3}, {"text": "This is a picture of\nincreasing returns.", "start": 2182.12, "duration": 2.49}, {"text": "This is a \"typo\" because\naccording to the definition,", "start": 2184.61, "duration": 4.45}, {"text": "you should take a point\nin the production set", "start": 2189.06, "duration": 2.84}, {"text": "and multiply it by a\nlambda greater than 1,", "start": 2191.9, "duration": 3.12}, {"text": "which I mentioned in class.", "start": 2195.02, "duration": 1.59}, {"text": "We have not tried to\ncorrect the picture.", "start": 2196.61, "duration": 2.46}, {"text": "That's because\nwhat this displays", "start": 2199.07, "duration": 1.62}, {"text": "is a violation of\ndecreasing returns", "start": 2200.69, "duration": 3.15}, {"text": "relative to them being\nsatisfied on the left.", "start": 2203.84, "duration": 2.88}, {"text": "They're not satisfied\non the right.", "start": 2206.72, "duration": 1.63}, {"text": "So the picture is\nnot wrong, it's just", "start": 2208.35, "duration": 1.88}, {"text": "not a direct use of the\ndefinition of increasing", "start": 2210.23, "duration": 2.49}, {"text": "returns, and this\nwas constant returns.", "start": 2212.72, "duration": 4.36}, {"text": "So this is aggregating\nproduction sets.", "start": 2217.08, "duration": 3.53}, {"text": "This one plus this one equals\nthis one plus the endowments.", "start": 2220.61, "duration": 4.15}, {"text": "So there was a lovely\ndiscussion on Piazza", "start": 2224.76, "duration": 2.45}, {"text": "about this thing, which is,\nhave we generated a free lunch?", "start": 2227.21, "duration": 5.96}, {"text": "Evidently from the\npicture, the answer", "start": 2233.17, "duration": 1.74}, {"text": "is no because there is that\nfinite production possibilities", "start": 2234.91, "duration": 5.1}, {"text": "frontier over here.", "start": 2240.01, "duration": 1.763}, {"text": "Depending on where\nyou are, you're", "start": 2241.773, "duration": 1.417}, {"text": "using one as an\ninput and the other", "start": 2243.19, "duration": 1.68}, {"text": "as an output or vice versa.", "start": 2244.87, "duration": 2.55}, {"text": "The possibility is\ncreated here, however,", "start": 2247.42, "duration": 3.21}, {"text": "that you use x as the input,\ngetting y as the output.", "start": 2250.63, "duration": 5.1}, {"text": "Take y as the output,\nput it in as an input", "start": 2255.73, "duration": 2.85}, {"text": "in the second technology.", "start": 2258.58, "duration": 1.95}, {"text": "Take y as the input,\nget x as the output.", "start": 2260.53, "duration": 4.3}, {"text": "So if you kept going like that,\nand you got more in output", "start": 2264.83, "duration": 3.83}, {"text": "than you used in input after\ngoing through one cycle,", "start": 2268.66, "duration": 3.57}, {"text": "you could go to infinity.", "start": 2272.23, "duration": 1.62}, {"text": "There'd be no end to it.", "start": 2273.85, "duration": 2.39}, {"text": "It would not only\nbe a free lunch,", "start": 2276.24, "duration": 1.68}, {"text": "it'd be an infinite lunch.", "start": 2277.92, "duration": 2.13}, {"text": "You could just keep\ngoing, in which case,", "start": 2280.05, "duration": 3.0}, {"text": "although it's not\nentirely obvious,", "start": 2283.05, "duration": 1.89}, {"text": "you could never\ndraw this picture", "start": 2284.94, "duration": 1.56}, {"text": "because there'd be no boundary.", "start": 2286.5, "duration": 2.01}, {"text": "You'd always be in the interior.", "start": 2288.51, "duration": 1.44}, {"text": "You could always do\nbetter just by cloning.", "start": 2289.95, "duration": 3.03}, {"text": "And then we define the firm's\nproblem, maximizing profits.", "start": 2292.98, "duration": 4.26}, {"text": "We drew these pictures.", "start": 2297.24, "duration": 1.41}, {"text": "Again, you get into the\nhabit, if you're an economist-", "start": 2298.65, "duration": 3.72}, {"text": "maximize subject to.", "start": 2302.37, "duration": 1.68}, {"text": "Maximize linear function\nsubject to convex constraints.", "start": 2304.05, "duration": 4.32}, {"text": "You end up with\nthese tangent cases.", "start": 2308.37, "duration": 1.83}, {"text": "In this case, these\nare isoprofit lines", "start": 2310.2, "duration": 2.52}, {"text": "not isobudget lines.", "start": 2312.72, "duration": 1.56}, {"text": "We want to move out as far as\nwe can on the isoprofit line.", "start": 2314.28, "duration": 3.45}, {"text": "But the tangency\nis a similar thing", "start": 2317.73, "duration": 3.36}, {"text": "if we move across these\napplications from consumer", "start": 2321.09, "duration": 3.18}, {"text": "theory to producer theory.", "start": 2324.27, "duration": 2.03}, {"text": "So hopefully, it's starting\nto become second nature.", "start": 2326.3, "duration": 3.19}, {"text": "We defined properties of\nthe production function,", "start": 2329.49, "duration": 4.5}, {"text": "including convexity.", "start": 2333.99, "duration": 1.23}, {"text": "And we proved it.", "start": 2335.22, "duration": 0.9}, {"text": "And then almost out of order,\nthis definition of homogeneity", "start": 2336.12, "duration": 4.44}, {"text": "popped up.", "start": 2340.56, "duration": 0.87}, {"text": "So one thing we didn't do\nwas link these definitions", "start": 2341.43, "duration": 3.18}, {"text": "of homogeneity of functions\nback to the discussion", "start": 2344.61, "duration": 3.51}, {"text": "of increasing, decreasing,\nand constant returns to scale.", "start": 2348.12, "duration": 3.99}, {"text": "But you should be\nable to do that.", "start": 2352.11, "duration": 2.23}, {"text": "This was a proof of\nHotelling's lemma.", "start": 2354.34, "duration": 2.7}, {"text": "And it was an illustration\nof the envelope", "start": 2357.04, "duration": 3.2}, {"text": "theorem, which is\nanother tool that's", "start": 2360.24, "duration": 2.64}, {"text": "going to keep popping up.", "start": 2362.88, "duration": 1.53}, {"text": "Special versions of\nprofit maximization,", "start": 2364.41, "duration": 3.27}, {"text": "cost minimization--", "start": 2367.68, "duration": 1.92}, {"text": "so this is like the dual, except\nthis one's going to get used,", "start": 2369.6, "duration": 3.63}, {"text": "not just to show equivalence.", "start": 2373.23, "duration": 2.82}, {"text": "What I mean by that is this--", "start": 2376.05, "duration": 2.08}, {"text": "so we have this isoproduction\ncurve called isoquant,", "start": 2378.13, "duration": 4.67}, {"text": "and we're going to try to find\nthe cost-minimizing bundle that", "start": 2382.8, "duration": 5.88}, {"text": "allows you to achieve that\ngiven level of output.", "start": 2388.68, "duration": 3.173}, {"text": "Then you could do\ntwo experiments.", "start": 2391.853, "duration": 1.417}, {"text": "Just like with the\nhousehold, we varied", "start": 2393.27, "duration": 2.85}, {"text": "income and varied prices.", "start": 2396.12, "duration": 1.77}, {"text": "Here, you can vary prices.", "start": 2397.89, "duration": 2.43}, {"text": "And that's the\nWalt Disney thing.", "start": 2400.32, "duration": 1.68}, {"text": "So the input mix would change.", "start": 2402.0, "duration": 2.31}, {"text": "What you could also\ndo, although we", "start": 2404.31, "duration": 1.95}, {"text": "decided not to\noverwhelm you, is pick", "start": 2406.26, "duration": 3.27}, {"text": "a different level of output--", "start": 2409.53, "duration": 2.19}, {"text": "a higher level-- and find the\ncost-minimizing combination", "start": 2411.72, "duration": 4.29}, {"text": "of inputs to support\nthat higher output.", "start": 2416.01, "duration": 2.37}, {"text": "And the definition of a\ncost curve was defined.", "start": 2418.38, "duration": 5.4}, {"text": "Cost function takes the\ninput prices as given,", "start": 2423.78, "duration": 3.51}, {"text": "but also the output.", "start": 2427.29, "duration": 1.36}, {"text": "So this is kind of\nobvious when you say it.", "start": 2428.65, "duration": 2.82}, {"text": "This is the cost of\nproducing a given output.", "start": 2431.47, "duration": 2.15}, {"text": "Yes, that's true.", "start": 2433.62, "duration": 1.44}, {"text": "But we never showed the picture.", "start": 2435.06, "duration": 3.18}, {"text": "But we did show the costs.", "start": 2438.24, "duration": 1.92}, {"text": "They're sitting\nhere in this slide.", "start": 2440.16, "duration": 2.37}, {"text": "Average cost, marginal\ncosts, and what", "start": 2442.53, "duration": 2.79}, {"text": "happens when you change prices\nwith constant returns to scale?", "start": 2445.32, "duration": 4.08}, {"text": "If the price were\ntoo high, the outcome", "start": 2449.4, "duration": 3.57}, {"text": "would not be well\ndefined because they", "start": 2452.97, "duration": 2.1}, {"text": "would make infinite profit.", "start": 2455.07, "duration": 1.83}, {"text": "And then when I presented\nthis, I said there was a typo,", "start": 2456.9, "duration": 4.41}, {"text": "and there is no typo.", "start": 2461.31, "duration": 1.41}, {"text": "So I apologize twice.", "start": 2462.72, "duration": 2.16}, {"text": "It's fine.", "start": 2464.88, "duration": 1.08}, {"text": "What's going on is the\ndialogue in the text below is", "start": 2465.96, "duration": 4.02}, {"text": "moving from here to the\nintermediate line to this line.", "start": 2469.98, "duration": 4.78}, {"text": "So when price of the\noutput is going up,", "start": 2474.76, "duration": 3.89}, {"text": "this thing is going down.", "start": 2478.65, "duration": 1.17}, {"text": "These lines are getting flatter.", "start": 2479.82, "duration": 1.8}, {"text": "And when they get sufficiently\nflat, then you go ballistic", "start": 2481.62, "duration": 4.23}, {"text": "and you can make infinite\nprofits, which is", "start": 2485.85, "duration": 2.76}, {"text": "consistent with this diagram.", "start": 2488.61, "duration": 1.83}, {"text": "Except that it's never\ndefined at a higher price", "start": 2490.44, "duration": 2.76}, {"text": "because there is no\ndeterminate outcome.", "start": 2493.2, "duration": 3.77}, {"text": "Then this thing\nI will set aside,", "start": 2496.97, "duration": 2.79}, {"text": "but again, I asked you to try\nto write down a little bit", "start": 2499.76, "duration": 4.29}, {"text": "better proof that these input\nratios are constant when you", "start": 2504.05, "duration": 4.05}, {"text": "have constant returns to scale.", "start": 2508.1, "duration": 2.16}, {"text": "Although this is a version\nof in consumer theory,", "start": 2510.26, "duration": 3.9}, {"text": "the idea that with\nhomothetic utility,", "start": 2514.16, "duration": 3.09}, {"text": "the expenditure shares\ndon't move, and so on.", "start": 2517.25, "duration": 3.34}, {"text": "So it is related to that.", "start": 2520.59, "duration": 2.48}, {"text": "This was a picture\nof Robinson Crusoe.", "start": 2523.07, "duration": 2.55}, {"text": "This was the first general\nequilibrium economy", "start": 2525.62, "duration": 3.69}, {"text": "although it was only one\nperson, with a production", "start": 2529.31, "duration": 2.88}, {"text": "set and preferences.", "start": 2532.19, "duration": 1.74}, {"text": "When I said you should be\nable to take that labor supply", "start": 2533.93, "duration": 3.75}, {"text": "and convert it by making\nthe labor supply negative,", "start": 2537.68, "duration": 4.56}, {"text": "I had this in mind, except\nthat unlike a production set,", "start": 2542.24, "duration": 4.18}, {"text": "you just have a straight budget\nline emanating from the origin,", "start": 2546.42, "duration": 4.61}, {"text": "and then you would\nmaximize utility.", "start": 2551.03, "duration": 2.52}, {"text": "You're just basically flipping\nthe diagram from right", "start": 2553.55, "duration": 3.45}, {"text": "to left like an overlay.", "start": 2557.0, "duration": 2.23}, {"text": "But here, there is production.", "start": 2559.23, "duration": 1.55}, {"text": "And this was an exciting\npart because we got to trade.", "start": 2560.78, "duration": 3.99}, {"text": "So now we're talking about a\nreal, live economy with two", "start": 2564.77, "duration": 3.57}, {"text": "goods, agriculture and\noutput, and looking", "start": 2568.34, "duration": 3.42}, {"text": "at what the consumer would do\nif they were maximizing utility", "start": 2571.76, "duration": 3.3}, {"text": "subject to that production\nset, as opposed to what", "start": 2575.06, "duration": 3.09}, {"text": "they would do if they were able\nto trade in the world economy.", "start": 2578.15, "duration": 4.33}, {"text": "They would produce more\nof the manufacturing good,", "start": 2582.48, "duration": 3.98}, {"text": "and export it, and consume\nboth goods in such a way", "start": 2586.46, "duration": 4.5}, {"text": "that their utility is higher.", "start": 2590.96, "duration": 2.62}, {"text": "So this is-- I can't\nremember if I emphasized it,", "start": 2593.58, "duration": 2.72}, {"text": "but this illustrates\nthe gains to trade.", "start": 2596.3, "duration": 3.06}, {"text": "It's the gains to trade for a\nsingle consumer like Robinson", "start": 2599.36, "duration": 3.48}, {"text": "Crusoe, which you\ncan see evidently", "start": 2602.84, "duration": 2.61}, {"text": "has higher utility\nbecause they get", "start": 2605.45, "duration": 2.52}, {"text": "to trade away from the origin.", "start": 2607.97, "duration": 2.7}, {"text": "Of course, we\nshould ask ourselves", "start": 2610.67, "duration": 1.53}, {"text": "whether this is a realistic\ndescription of the economy", "start": 2612.2, "duration": 3.27}, {"text": "or whether we should\npopulate it with more people,", "start": 2615.47, "duration": 2.64}, {"text": "and potentially have\nheterogeneous utility", "start": 2618.11, "duration": 2.46}, {"text": "functions.", "start": 2620.57, "duration": 0.682}, {"text": "And for that, we're going\nto need to talk about", "start": 2621.252, "duration": 1.958}, {"text": "whether or not we\ncan aggregate up,", "start": 2623.21, "duration": 2.01}, {"text": "which comes up in lecture 15\nor 16, or something like that.", "start": 2625.22, "duration": 4.75}, {"text": "And this is the US and England\ntrading with one another.", "start": 2629.97, "duration": 4.76}, {"text": "Questions?", "start": 2634.73, "duration": 3.47}, {"text": "So I'm going to be brief.", "start": 2638.2, "duration": 1.25}, {"text": "Otherwise, we're\ngoing to go over.", "start": 2639.45, "duration": 2.04}, {"text": "This is decision making\nunder uncertainty, and also", "start": 2641.49, "duration": 3.24}, {"text": "illustrative of linear programs.", "start": 2644.73, "duration": 2.68}, {"text": "So I think on this\none in particular,", "start": 2647.41, "duration": 2.79}, {"text": "I want you to let me know\nif you have questions.", "start": 2650.2, "duration": 2.96}, {"text": "It is a bit unnatural.", "start": 2653.16, "duration": 1.24}, {"text": "This part's all very natural.", "start": 2654.4, "duration": 2.13}, {"text": "It just has to do with\na household evaluating", "start": 2656.53, "duration": 3.77}, {"text": "nontrivial lotteries\nover prizes, although we", "start": 2660.3, "duration": 4.89}, {"text": "used it to define means\nand variances, coefficients", "start": 2665.19, "duration": 3.78}, {"text": "of variation, and\nvariances, and correlations.", "start": 2668.97, "duration": 3.09}, {"text": "We did all of that.", "start": 2672.06, "duration": 1.63}, {"text": "But then we went back to\nthe award or the prize", "start": 2673.69, "duration": 2.78}, {"text": "being two-dimensional, in\nthis case, goods X1 and X2.", "start": 2676.47, "duration": 3.3}, {"text": "So this is a discrete,\nnon-convex consumption set.", "start": 2679.77, "duration": 3.3}, {"text": "And miraculously, we turned\nit into a convex-looking set.", "start": 2683.07, "duration": 4.29}, {"text": "And we had a good\ndiscussion at the beginning", "start": 2687.36, "duration": 2.61}, {"text": "of the following class\nabout how to do that.", "start": 2689.97, "duration": 3.01}, {"text": "But I want to make sure\nyou all understand it,", "start": 2692.98, "duration": 2.39}, {"text": "because we're going to build\non it in subsequent lectures.", "start": 2695.37, "duration": 3.04}, {"text": "So one of you asked\nme in my office hours,", "start": 2698.41, "duration": 3.01}, {"text": "it's kind of weird--\nin finance, you", "start": 2701.42, "duration": 1.87}, {"text": "take as given the returns on\nthe assets or their beliefs", "start": 2703.29, "duration": 3.45}, {"text": "about the returns.", "start": 2706.74, "duration": 1.05}, {"text": "We don't talk about\nchoosing the returns.", "start": 2707.79, "duration": 3.34}, {"text": "But here you do, because\nyou're choosing the lottery.", "start": 2711.13, "duration": 2.88}, {"text": "You're choosing a\nrandom way, although it", "start": 2714.01, "duration": 2.27}, {"text": "could be subject to a budget.", "start": 2716.28, "duration": 2.93}, {"text": "I'm practically out of time.", "start": 2719.21, "duration": 1.83}, {"text": "We went to concave utility.", "start": 2721.04, "duration": 1.65}, {"text": "We talked about behavior\nunder risk, different types", "start": 2722.69, "duration": 2.88}, {"text": "of utility functions,\nthis tree that we", "start": 2725.57, "duration": 2.43}, {"text": "keep coming back to that was\nat the end of the lecture", "start": 2728.0, "duration": 2.55}, {"text": "last time.", "start": 2730.55, "duration": 1.05}, {"text": "This is Arrow-Debreu security,\nso in this case, instead", "start": 2731.6, "duration": 3.66}, {"text": "of having a pure borrowing and\nlending economy or borrowing", "start": 2735.26, "duration": 2.908}, {"text": "subject to a credit limit,\nwe could have had them", "start": 2738.168, "duration": 2.042}, {"text": "trading in an asset which\nyields a return of 1", "start": 2740.21, "duration": 3.33}, {"text": "in one state and nothing\nin the other states.", "start": 2743.54, "duration": 3.0}, {"text": "And you could be either making\nthat promise as a borrower,", "start": 2746.54, "duration": 3.82}, {"text": "so to speak, or buying\nit as an investor.", "start": 2750.36, "duration": 3.93}, {"text": "So we can go from\nmedieval villages", "start": 2754.29, "duration": 2.69}, {"text": "to sophisticated securities.", "start": 2756.98, "duration": 2.67}, {"text": "And then we kind of talked about\nthis at the beginning of class.", "start": 2759.65, "duration": 5.11}, {"text": "And this class ended with\nlinear programming problems", "start": 2764.76, "duration": 3.77}, {"text": "and how they crop up in\ngeneral in utility maximization", "start": 2768.53, "duration": 4.68}, {"text": "and linear activity analysis.", "start": 2773.21, "duration": 2.16}, {"text": "This linear activity analysis\nis the Leontief thing", "start": 2775.37, "duration": 3.72}, {"text": "I was alluding to when\nwe went over preferences.", "start": 2779.09, "duration": 2.89}, {"text": "These are constants.", "start": 2781.98, "duration": 1.19}, {"text": "These A a j is the amount\nof good i, input i,", "start": 2783.17, "duration": 3.39}, {"text": "required to produce good\nj, and it's a constant.", "start": 2786.56, "duration": 3.27}, {"text": "The rate of substitution\nisn't varying", "start": 2789.83, "duration": 2.73}, {"text": "that delivers these\nl-shaped isoquants.", "start": 2792.56, "duration": 3.81}, {"text": "All right, so I'm going to have\nto stop because otherwise we're", "start": 2796.37, "duration": 3.5}, {"text": "going to go over.", "start": 2799.87, "duration": 1.59}, {"text": "So we almost got to the end.", "start": 2801.46, "duration": 4.65}, {"text": "I don't think I have anything\nusually uncovered anyway.", "start": 2806.11, "duration": 4.02}, {"text": "Because the other\ntwo lectures were", "start": 2810.13, "duration": 2.37}, {"text": "the dynamics, which should be\nfresh in your mind-- we just", "start": 2812.5, "duration": 3.15}, {"text": "covered it recently--\nand the one", "start": 2815.65, "duration": 2.49}, {"text": "that we did and reviewed at\nthe beginning of the lecture", "start": 2818.14, "duration": 2.76}, {"text": "today on Pareto-optimal\nallocations.", "start": 2820.9, "duration": 4.25}]
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+[{"text": "Today, we're going to just start\nby talking about what glass is", "start": 16.649, "duration": 3.304}, {"text": "and what its properties are.", "start": 19.953, "duration": 1.301}, {"text": "But before we do, this came in--", "start": 24.057, "duration": 2.569}, {"text": "we've been talking\nabout defects, OK.", "start": 26.626, "duration": 2.669}, {"text": "And vacancies, point defects,\nand then on Wednesday,", "start": 29.295, "duration": 5.806}, {"text": "we did line defects.", "start": 35.101, "duration": 1.135}, {"text": "Remember those?", "start": 36.236, "duration": 0.767}, {"text": "Right, and they create\nthese planes that come in.", "start": 37.003, "duration": 3.604}, {"text": "They're slip planes\nthat allow atoms", "start": 40.607, "duration": 2.102}, {"text": "to slide across each other that\nallows you to plasticly deform", "start": 42.709, "duration": 4.805}, {"text": "a material.", "start": 47.514, "duration": 1.735}, {"text": "And so OK, but with regards to\nvacancies, I got this by email.", "start": 49.249, "duration": 5.372}, {"text": "I'm at the Heathrow\nAirport in London,", "start": 54.621, "duration": 2.235}, {"text": "and even this aerial sculpture\nhas vacancy point defects", "start": 56.856, "duration": 3.404}, {"text": "in its pattern.", "start": 60.26, "duration": 1.067}, {"text": "Look at that.", "start": 61.327, "duration": 0.601}, {"text": "There you go.", "start": 61.928, "duration": 1.235}, {"text": "And there you go.", "start": 63.163, "duration": 1.268}, {"text": "This is a beautiful\nthing, right?", "start": 64.431, "duration": 2.602}, {"text": "Thank you, Sophia.", "start": 67.033, "duration": 0.801}, {"text": "And notice that she's looking\nat it with her periodic table,", "start": 70.503, "duration": 3.671}, {"text": "of course, right.", "start": 74.174, "duration": 2.035}, {"text": "That's a no-brainer.", "start": 76.209, "duration": 2.202}, {"text": "But even such structures\ncan't escape the fact", "start": 78.411, "duration": 4.304}, {"text": "that you always have vacancies.", "start": 82.715, "duration": 3.003}, {"text": "That was cool.", "start": 85.718, "duration": 0.668}, {"text": "OK, now where were we?", "start": 86.386, "duration": 1.168}, {"text": "Right, so we're going\nto talk about glass.", "start": 87.554, "duration": 2.502}, {"text": "Now, this is glass,\nand I'll start", "start": 90.056, "duration": 2.77}, {"text": "with just how cool glass is.", "start": 92.826, "duration": 1.735}, {"text": "But this is also not just--", "start": 94.561, "duration": 2.202}, {"text": "this isn't all that glass is.", "start": 96.763, "duration": 2.803}, {"text": "And I want to make\nsure we get that", "start": 99.566, "duration": 2.469}, {"text": "by the end of this lecture.", "start": 102.035, "duration": 1.134}, {"text": "This is not the only\nthing that glass means.", "start": 103.169, "duration": 2.569}, {"text": "But this is what we think of.", "start": 105.738, "duration": 1.202}, {"text": "So here's a really cool video.", "start": 106.94, "duration": 2.836}, {"text": "OK.", "start": 109.776, "duration": 1.034}, {"text": "No and yes.", "start": 110.81, "duration": 2.536}, {"text": "[VIDEO PLAYBACK]", "start": 113.346, "duration": 0.667}, {"text": "There they are.", "start": 114.013, "duration": 0.633}, {"text": "Look at that molten\n[INAUDIBLE] and it's--", "start": 114.646, "duration": 3.637}, {"text": "oh, he just added something.", "start": 118.283, "duration": 1.169}, {"text": "We'll talk about that.", "start": 119.452, "duration": 1.301}, {"text": "Oh, and now he's mixing it.", "start": 120.753, "duration": 1.135}, {"text": "- Table man carefully mixes\nthis glass [INAUDIBLE]..", "start": 121.888, "duration": 3.47}, {"text": "Once the glass is blended\nto his specifications--", "start": 129.362, "duration": 2.035}, {"text": "OK, there it is.", "start": 131.397, "duration": 0.768}, {"text": "Is it a liquid?", "start": 132.165, "duration": 1.368}, {"text": "Is it a solid?", "start": 133.533, "duration": 0.968}, {"text": "- [INAUDIBLE]", "start": 134.501, "duration": 2.602}, {"text": "And then he just puts it\nthrough a little roller.", "start": 137.103, "duration": 3.604}, {"text": "- That will mash that\nglass flat [INAUDIBLE]", "start": 140.707, "duration": 2.469}, {"text": "Mash it flat, and there\nis your piece of glass.", "start": 143.176, "duration": 4.271}, {"text": "OK, and we'll see another one.", "start": 147.447, "duration": 1.401}, {"text": "I'll show you another\nvideo of a larger scale--", "start": 148.848, "duration": 3.37}, {"text": "don't keep going.", "start": 152.218, "duration": 1.068}, {"text": "[END PLAYBACK]", "start": 153.286, "duration": 0.567}, {"text": "OK.", "start": 153.853, "duration": 0.868}, {"text": "So what was it that\nthey were just mixing?", "start": 154.721, "duration": 2.068}, {"text": "Why does it have the\nproperties that it has?", "start": 156.789, "duration": 3.304}, {"text": "Why can they just\ntake this thing", "start": 160.093, "duration": 1.802}, {"text": "that's not really\nliquid and not really", "start": 161.895, "duration": 2.002}, {"text": "solid, it's some viscous\nthing, and roll it through,", "start": 163.897, "duration": 3.603}, {"text": "and then it comes into\nthis really beautiful sheet", "start": 167.5, "duration": 2.836}, {"text": "that we all call glass?", "start": 170.336, "duration": 2.903}, {"text": "And it all has to do with\nwhat I showed you before,", "start": 173.239, "duration": 3.671}, {"text": "and what we've\nbeen talking about,", "start": 176.91, "duration": 1.401}, {"text": "which is order or disorder.", "start": 178.311, "duration": 4.004}, {"text": "And so we did this already.", "start": 182.315, "duration": 1.468}, {"text": "We covered, OK, a solid that\nwhich is dimensionally stable.", "start": 183.783, "duration": 3.404}, {"text": "That's cool.", "start": 187.187, "duration": 0.967}, {"text": "Classification, oh ordered,\nregular, long-range order, BCC,", "start": 188.154, "duration": 7.074}, {"text": "FCC.", "start": 195.228, "duration": 1.468}, {"text": "All right.", "start": 196.696, "duration": 0.901}, {"text": "OK, long-range.", "start": 197.597, "duration": 1.101}, {"text": "Remember, we said it just keeps\ngoing and going and going.", "start": 198.698, "duration": 2.603}, {"text": "And then we say, well, it\nmay be once in a while,", "start": 201.301, "duration": 2.369}, {"text": "once every 1,000, 10,000,\n100,000, there's a vacancy.", "start": 203.67, "duration": 4.838}, {"text": "OK, so we started\nmessing with it.", "start": 208.508, "duration": 1.668}, {"text": "But it still had this long\nrange-- gesundheit-- order.", "start": 210.176, "duration": 3.604}, {"text": "And so they were\ncalled crystalline,", "start": 213.78, "duration": 1.868}, {"text": "crystalline with defects,\nmaybe, but still crystalline.", "start": 215.648, "duration": 3.537}, {"text": "That is not what glass is.", "start": 219.185, "duration": 2.002}, {"text": "Glass is disordered.", "start": 221.187, "duration": 2.669}, {"text": "And so that is the topic of\ntoday and next Wednesday.", "start": 223.856, "duration": 3.204}, {"text": "What happens when you go\nfrom an ordered structure,", "start": 227.06, "duration": 3.537}, {"text": "like this, oh maybe\nit's got some--", "start": 230.597, "duration": 3.336}, {"text": "oh these are 2D defects,\nright, the whole things", "start": 233.933, "duration": 3.103}, {"text": "are kind of-- so it's\npoly crystalline,", "start": 237.036, "duration": 1.602}, {"text": "but it's still kind\nof crystalline,", "start": 238.638, "duration": 1.468}, {"text": "and it's very ordered,\nto totally disordered.", "start": 240.106, "duration": 3.337}, {"text": "All right.", "start": 243.443, "duration": 0.5}, {"text": "And so a disordered solid\nlooks random, certainly", "start": 243.943, "duration": 5.506}, {"text": "over long range.", "start": 249.449, "duration": 1.902}, {"text": "There might be\nshort range order.", "start": 251.351, "duration": 2.669}, {"text": "There might be some short range\norder, but over a long range,", "start": 254.02, "duration": 2.636}, {"text": "it's going to be disordered.", "start": 256.656, "duration": 1.969}, {"text": "It's going to look random.", "start": 258.625, "duration": 1.201}, {"text": "This is called amorphous\nas opposed to crystalline.", "start": 259.826, "duration": 3.97}, {"text": "This is also called glass.", "start": 263.796, "duration": 4.138}, {"text": "This is also called glass.", "start": 267.934, "duration": 1.435}, {"text": "So one of the first things we've\ngot, this is really important,", "start": 269.369, "duration": 3.603}, {"text": "glass is not just the window,\nor the thing on your phone", "start": 272.972, "duration": 4.104}, {"text": "that keeps cracking.", "start": 277.076, "duration": 1.702}, {"text": "No.", "start": 278.778, "duration": 0.934}, {"text": "Glass is equal to\nan amorphous solid.", "start": 279.712, "duration": 4.872}, {"text": "Well, so it's bigger.", "start": 289.522, "duration": 2.636}, {"text": "It's broader.", "start": 292.158, "duration": 1.535}, {"text": "It's bolder.", "start": 293.693, "duration": 1.068}, {"text": "You can have glass\nmetal, metallic glass.", "start": 294.761, "duration": 3.303}, {"text": "It's a thing.", "start": 298.064, "duration": 2.069}, {"text": "Any solid that doesn't have long\nrange order that's amorphous", "start": 300.133, "duration": 4.971}, {"text": "is a glass.", "start": 305.104, "duration": 1.402}, {"text": "OK.", "start": 306.506, "duration": 1.468}, {"text": "Now in this class we\nwill use SiO2 as--", "start": 307.974, "duration": 6.306}, {"text": "so what we're going\nto do is we're", "start": 314.28, "duration": 1.835}, {"text": "going to talk about\nglass with an example.", "start": 316.115, "duration": 3.07}, {"text": "We will use the\nkind that winds up", "start": 319.185, "duration": 3.303}, {"text": "being in the\nwindshield of your car", "start": 322.488, "duration": 2.169}, {"text": "or in the window of your\nhouse and on your phone.", "start": 324.657, "duration": 2.302}, {"text": "And that is called quartz.", "start": 326.959, "duration": 2.136}, {"text": "So the chemistry\nthat we're going", "start": 329.095, "duration": 1.368}, {"text": "to use is quartz, or\nSiO2 OK, and what we're", "start": 330.463, "duration": 9.209}, {"text": "going to talk about is\nhow processing effects", "start": 339.672, "duration": 3.904}, {"text": "that chemistry, affects the--", "start": 343.576, "duration": 1.635}, {"text": "sorry, the solid that forms.", "start": 345.211, "duration": 2.002}, {"text": "So processing.", "start": 347.213, "duration": 1.135}, {"text": "And there is lots of\nprocessing parameters", "start": 348.348, "duration": 3.803}, {"text": "and we can talk about.", "start": 352.151, "duration": 1.335}, {"text": "What I want to focus on\ntoday is the cooling,", "start": 353.486, "duration": 3.77}, {"text": "the cooling rate in particular.", "start": 357.256, "duration": 1.635}, {"text": "So that's going to\nbe the focus today.", "start": 358.891, "duration": 2.87}, {"text": "We'll talk about the chemistry.", "start": 361.761, "duration": 1.902}, {"text": "We'll talk about the processing.", "start": 363.663, "duration": 1.334}, {"text": "And we'll talk\nabout how those go", "start": 364.997, "duration": 1.402}, {"text": "back and forth to create glass.", "start": 366.399, "duration": 2.436}, {"text": "Now, OK, what am\nI starting with?", "start": 371.504, "duration": 2.703}, {"text": "I'm starting with a crystal.", "start": 374.207, "duration": 3.069}, {"text": "This is quartz.", "start": 377.276, "duration": 2.336}, {"text": "This is how you see quartz.", "start": 379.612, "duration": 1.335}, {"text": "Now, quartz is this\nbeautiful, beautiful crystal.", "start": 380.947, "duration": 3.837}, {"text": "And it is ordered.", "start": 384.784, "duration": 1.335}, {"text": "That's why I'm saying\nthe word crystal.", "start": 386.119, "duration": 1.935}, {"text": "I'm not saying the word glass.", "start": 388.054, "duration": 1.835}, {"text": "All right.", "start": 389.889, "duration": 0.501}, {"text": "This is an ordered solid.", "start": 390.39, "duration": 2.102}, {"text": "It's not cubic.", "start": 392.492, "duration": 1.001}, {"text": "So it's not one of the\nones we've learned.", "start": 393.493, "duration": 1.768}, {"text": "But it's still\nperiodically repeating.", "start": 395.261, "duration": 3.737}, {"text": "All right.", "start": 398.998, "duration": 0.534}, {"text": "And so it's a crystal.", "start": 399.532, "duration": 0.968}, {"text": "It's got long range order.", "start": 400.5, "duration": 1.101}, {"text": "It's called quartz.", "start": 401.601, "duration": 0.967}, {"text": "It's SiO2 So I'm\ngoing to hand this out", "start": 402.568, "duration": 3.17}, {"text": "so you can just see it.", "start": 405.738, "duration": 1.869}, {"text": "And that's what I want to\nstart, I want to talk about,", "start": 407.607, "duration": 2.569}, {"text": "is that crystal,\nOK, because that's", "start": 410.176, "duration": 3.704}, {"text": "what we're going to be messing\nup and creating short-range.", "start": 413.88, "duration": 5.772}, {"text": "We're going to go from\nlong-range to short-range.", "start": 419.652, "duration": 3.47}, {"text": "OK, so what is it?", "start": 423.122, "duration": 1.035}, {"text": "Well, let's see.", "start": 424.157, "duration": 2.135}, {"text": "In this class, how do we\nthink about chemistry?", "start": 426.292, "duration": 2.136}, {"text": "Well you can think about\nit now in different ways.", "start": 428.428, "duration": 2.936}, {"text": "Let's pick Lewis.", "start": 431.364, "duration": 2.035}, {"text": "All right, OK.", "start": 433.399, "duration": 1.035}, {"text": "So I say, OK, I got\nsilicon, silicon, silicon,", "start": 434.434, "duration": 6.573}, {"text": "if I think about\nsilicon as it's Lewis,", "start": 441.007, "duration": 4.304}, {"text": "you know, dots,\nthen it's got four.", "start": 445.311, "duration": 3.137}, {"text": "It's got four valence\nelectrons ready to bond.", "start": 448.448, "duration": 5.605}, {"text": "You can see that now if I\nhave oxygen, what does oxygen", "start": 454.053, "duration": 3.036}, {"text": "look like?", "start": 457.089, "duration": 0.501}, {"text": "So oxygen has six.", "start": 457.59, "duration": 2.803}, {"text": "I'm going to put\nthose like that.", "start": 460.393, "duration": 1.935}, {"text": "So oxygen has six.", "start": 462.328, "duration": 1.802}, {"text": "Maybe it's got a\ncouple lone pairs,", "start": 464.13, "duration": 2.135}, {"text": "which has six valence\nelectrons, not four.", "start": 466.265, "duration": 3.704}, {"text": "Now so if I had--", "start": 469.969, "duration": 2.736}, {"text": "so when you look at this,\nyou think, you know,", "start": 472.705, "duration": 2.803}, {"text": "silicon looks like it wants\nfour bonds when you look at it.", "start": 475.508, "duration": 5.205}, {"text": "And in fact, we know that\nthe crystal in silicon", "start": 480.713, "duration": 2.77}, {"text": "as we've talked\nabout-- gesundheit--", "start": 483.483, "duration": 2.569}, {"text": "is tetrahedral because of this.", "start": 486.052, "duration": 2.502}, {"text": "Right, it's tetrahedral.", "start": 488.554, "duration": 1.001}, {"text": "Remember, it's a two atom\nbasis FCC lattice which is", "start": 489.555, "duration": 4.505}, {"text": "is diamond.", "start": 494.06, "duration": 2.502}, {"text": "But what if I just\nlook at it with oxygen,", "start": 496.562, "duration": 2.202}, {"text": "come at this with oxygen\nand say, well, you know,", "start": 498.764, "duration": 2.236}, {"text": "I want to have four bonds.", "start": 501.0, "duration": 2.469}, {"text": "One way to do that would\nbe to add four oxygens.", "start": 503.469, "duration": 3.771}, {"text": "So what if I did this?", "start": 507.24, "duration": 1.034}, {"text": "What if I did\nsilicon and oxygen,", "start": 508.274, "duration": 3.736}, {"text": "and I did plus 4\ntimes the oxygen.", "start": 512.01, "duration": 5.273}, {"text": "Well, then you could\nsee, what could you do?", "start": 517.283, "duration": 2.069}, {"text": "You could do this, OK, and\nthis and this and this.", "start": 519.352, "duration": 6.072}, {"text": "But now, OK, the oxygens,\nhow would they be left?", "start": 525.424, "duration": 2.937}, {"text": "They'd be left like this.", "start": 528.361, "duration": 1.468}, {"text": "And you'll see why I'm focusing\non this SiO4 group in a minute.", "start": 529.829, "duration": 7.14}, {"text": "That's what I got.", "start": 536.969, "duration": 1.302}, {"text": "Now, OK, if I go back in\nand I put my Lewis cap on,", "start": 538.271, "duration": 3.737}, {"text": "silicon is very happy\nit's obeying octet,", "start": 542.008, "duration": 3.837}, {"text": "but the oxygens\naren't quite there.", "start": 545.845, "duration": 2.736}, {"text": "So they need one more\nelectron, one more electron.", "start": 548.581, "duration": 4.805}, {"text": "I'm going to make it a little\nbolder because I've added it.", "start": 553.386, "duration": 3.27}, {"text": "All right.", "start": 556.656, "duration": 0.5}, {"text": "So I've added an electron\nto each of those.", "start": 557.156, "duration": 2.302}, {"text": "So if I had SiO4,\nand I added 4--", "start": 559.458, "duration": 4.738}, {"text": "if I had SiO4, and I added\nfour electrons to it,", "start": 564.196, "duration": 6.207}, {"text": "I get a really nice\nstable Lewis structure.", "start": 570.403, "duration": 2.969}, {"text": "Right.", "start": 573.372, "duration": 0.968}, {"text": "That's called a silicate.", "start": 574.34, "duration": 1.902}, {"text": "That's a silicate group.", "start": 576.242, "duration": 1.134}, {"text": "SiO4.", "start": 581.013, "duration": 0.935}, {"text": "And I need those four\nelectrons, as you", "start": 581.948, "duration": 2.202}, {"text": "can see just from looking\nat the simple dot diagram.", "start": 584.15, "duration": 2.636}, {"text": "I need those four\nelectrons to make it happy.", "start": 586.786, "duration": 2.903}, {"text": "OK.", "start": 589.689, "duration": 1.167}, {"text": "By the way, just\nspeaking of naming, OK,", "start": 590.856, "duration": 1.969}, {"text": "so let's see silicate,\nright silica, SiO2,", "start": 592.825, "duration": 5.239}, {"text": "we can talk about, so what we do\nis when we have oxide, silicon", "start": 598.064, "duration": 3.537}, {"text": "oxide, just in terms\nof naming, you know,", "start": 601.601, "duration": 3.503}, {"text": "like if you have an oxide,\noften, you kind of add an a,", "start": 605.104, "duration": 5.439}, {"text": "right, so like silicon went\nfrom SiO2, we call it silica.", "start": 610.543, "duration": 6.339}, {"text": "So in Al2O3, let's see, Al2O3\nis also an oxide, right?", "start": 622.455, "duration": 5.105}, {"text": "And so we called that--\nthis is something", "start": 627.56, "duration": 1.735}, {"text": "we've already done, alumina.", "start": 629.295, "duration": 3.236}, {"text": "All right, and so on,\nexcept for sometimes.", "start": 632.531, "duration": 4.472}, {"text": "And so sometimes,\nlike for example,", "start": 637.003, "duration": 3.069}, {"text": "if you do calcium oxide,\nwell, that's called lime.", "start": 640.072, "duration": 7.174}, {"text": "It's called lime, calcium oxide.", "start": 647.246, "duration": 3.771}, {"text": "Well, what about sodium?", "start": 651.017, "duration": 1.301}, {"text": "Well, sodium, if you\ndo sodium, you're", "start": 652.318, "duration": 3.07}, {"text": "going to need it I'm\nassuming the oxygen might", "start": 655.388, "duration": 3.536}, {"text": "break off and become to--", "start": 658.924, "duration": 1.736}, {"text": "so you've got to think\nabout the charge again.", "start": 660.66, "duration": 1.935}, {"text": "So Na20 would be the\none that works there.", "start": 662.595, "duration": 4.371}, {"text": "All right, and this\nis sodium oxide.", "start": 666.966, "duration": 3.737}, {"text": "But see, sodium\noxide, but sometimes,", "start": 670.703, "duration": 6.206}, {"text": "it's called soda, because--", "start": 676.909, "duration": 3.537}, {"text": "and this is an extra step,\nbecause soda comes from calcium", "start": 680.446, "duration": 5.672}, {"text": "from--", "start": 686.118, "duration": 0.834}, {"text": "let's see, Na2O from--", "start": 686.952, "duration": 4.638}, {"text": "how do you make it?", "start": 691.59, "duration": 0.801}, {"text": "You make it from Na2CO3, which\nis actually what is soda?", "start": 692.391, "duration": 9.71}, {"text": "Sodium carbonate.", "start": 702.101, "duration": 2.169}, {"text": "But because we make Na2O,\nthat oxide from something", "start": 704.27, "duration": 6.206}, {"text": "that we call soda, sometimes\npeople just call in Na2O soda,", "start": 710.476, "duration": 3.971}, {"text": "it's not.", "start": 714.447, "duration": 1.234}, {"text": "But sometimes you see that.", "start": 715.681, "duration": 1.101}, {"text": "So I just want to kind of make\nyou aware some of these names.", "start": 716.782, "duration": 2.469}, {"text": "Why am I writing it there?", "start": 719.251, "duration": 1.101}, {"text": "We're coming back to that.", "start": 720.352, "duration": 1.769}, {"text": "We're going to use those later.", "start": 722.121, "duration": 2.035}, {"text": "That's partly why I want\nthem to be on the board,", "start": 724.156, "duration": 2.202}, {"text": "and also tell you\nabout the names.", "start": 726.358, "duration": 2.47}, {"text": "So Na2O is sodium oxide.", "start": 728.828, "duration": 2.335}, {"text": "But it's made from sodium\ncarbonate, which is soda.", "start": 731.163, "duration": 3.671}, {"text": "OK.", "start": 734.834, "duration": 1.167}, {"text": "All right.", "start": 736.001, "duration": 0.501}, {"text": "Now, OK, now, here's the thing.", "start": 736.502, "duration": 2.102}, {"text": "That's an isolated molecule.", "start": 738.604, "duration": 3.504}, {"text": "Look at what I'm\npassing around here.", "start": 742.108, "duration": 1.668}, {"text": "Oh, I wanted to tell\nyou about the window.", "start": 743.776, "duration": 3.704}, {"text": "I almost forgot.", "start": 747.48, "duration": 2.035}, {"text": "In this class, in\nthis class, we don't", "start": 749.515, "duration": 3.17}, {"text": "go around saying that windows\nare thicker on the bottom,", "start": 752.685, "duration": 3.503}, {"text": "than on the top, because\nglass flows like a liquid.", "start": 756.188, "duration": 4.171}, {"text": "No.", "start": 760.359, "duration": 1.101}, {"text": "That is not true.", "start": 761.46, "duration": 1.935}, {"text": "That is not true.", "start": 763.395, "duration": 1.102}, {"text": "That may be true\ndown the street.", "start": 764.497, "duration": 1.468}, {"text": "That is not true here.", "start": 765.965, "duration": 2.869}, {"text": "We do the calculation.", "start": 768.834, "duration": 1.769}, {"text": "Glass is not a liquid, not once\nit's cooled down into a solid.", "start": 770.603, "duration": 7.34}, {"text": "It's a solid.", "start": 777.943, "duration": 0.901}, {"text": "If you do the calculation,\nand it's a centimeter thick,", "start": 778.844, "duration": 4.505}, {"text": "a window pane, for\nthat piece of glass,", "start": 783.349, "duration": 4.504}, {"text": "under normal diffusion\nand temperature conditions", "start": 787.853, "duration": 2.67}, {"text": "for that piece of\nglass at the bottom", "start": 790.523, "duration": 2.035}, {"text": "to become thicker\nby one nanometer", "start": 792.558, "duration": 3.003}, {"text": "would take 10 billion years.", "start": 795.561, "duration": 2.736}, {"text": "OK.", "start": 798.297, "duration": 1.368}, {"text": "So no, it's not flowing under\nits own weight in a window.", "start": 799.665, "duration": 4.938}, {"text": "What happened?", "start": 804.603, "duration": 0.935}, {"text": "What happened is\npeople didn't know", "start": 805.538, "duration": 2.035}, {"text": "how to make glass\nuniformly way back when,", "start": 807.573, "duration": 3.136}, {"text": "and so they came out\nun-uniform, non uniform.", "start": 810.709, "duration": 5.039}, {"text": "What's easier?", "start": 815.748, "duration": 1.167}, {"text": "To install it with\nthe heavier side", "start": 816.915, "duration": 1.969}, {"text": "up or the heavier side down?", "start": 818.884, "duration": 3.203}, {"text": "It's easier to install it if\nit's heavier on the bottom.", "start": 822.087, "duration": 3.17}, {"text": "Class doesn't flow.", "start": 825.257, "duration": 2.236}, {"text": "OK.", "start": 827.493, "duration": 0.667}, {"text": "All right.", "start": 828.16, "duration": 0.501}, {"text": "I wanted to get that done early.", "start": 828.661, "duration": 2.636}, {"text": "Yeah.", "start": 831.297, "duration": 1.034}, {"text": "Oh, here we go.", "start": 832.331, "duration": 1.301}, {"text": "OK, so this is quartz.", "start": 833.632, "duration": 2.603}, {"text": "This is crystalline silica.", "start": 836.235, "duration": 2.736}, {"text": "This is groups of\nSiO2, not SiO4.", "start": 838.971, "duration": 6.006}, {"text": "This was how we made\na molecule happy.", "start": 844.977, "duration": 3.237}, {"text": "But watch what happens now when\nI go from that picture to SiO2.", "start": 848.214, "duration": 7.273}, {"text": "So now, I've got these--", "start": 855.487, "duration": 2.37}, {"text": "let's suppose I've got these\nmolecules of-- and I'm just", "start": 857.857, "duration": 3.236}, {"text": "going to not draw it 3D, but\nI'm going to draw it 2D, and OK,", "start": 861.093, "duration": 4.838}, {"text": "there's--", "start": 865.931, "duration": 0.501}, {"text": "gesundheit-- there's\nall these charges there.", "start": 866.432, "duration": 2.135}, {"text": "So now these are\nthese molecules,", "start": 868.567, "duration": 2.77}, {"text": "these silicate groups.", "start": 871.337, "duration": 1.701}, {"text": "And they're kind of happy,\nand they're on their own.", "start": 873.038, "duration": 2.169}, {"text": "But now look what happens here.", "start": 875.207, "duration": 3.404}, {"text": "See, those two oxygen, what\nif instead of each of these", "start": 878.611, "duration": 4.237}, {"text": "being separate,\nthey came together?", "start": 882.848, "duration": 3.203}, {"text": "All right.", "start": 886.051, "duration": 0.668}, {"text": "Well, you can see that--", "start": 886.719, "duration": 1.735}, {"text": "you see, if they shared\nthe same oxygen here,", "start": 888.454, "duration": 4.871}, {"text": "if they shared the\nsame oxygen here,", "start": 893.325, "duration": 2.336}, {"text": "then that oxygen is\nactually now Lewis", "start": 895.661, "duration": 3.036}, {"text": "happy without the extra charge.", "start": 898.697, "duration": 3.003}, {"text": "So this oxygen,\nthis bridge, oxygen,", "start": 904.637, "duration": 9.609}, {"text": "doesn't need that extra\nelectron to be happy.", "start": 914.246, "duration": 10.944}, {"text": "What does to be happy mean?", "start": 925.19, "duration": 1.202}, {"text": "Well, we know what that means.", "start": 926.392, "duration": 2.235}, {"text": "And if we're talking about Lewis\nand speaking in those terms,", "start": 928.627, "duration": 2.803}, {"text": "it means you've got your octet.", "start": 931.43, "duration": 1.535}, {"text": "All right.", "start": 932.965, "duration": 0.934}, {"text": "So now the bridge oxygen--", "start": 933.899, "duration": 1.602}, {"text": "oh, but that is what\nI'm passing around.", "start": 935.501, "duration": 2.302}, {"text": "That is what quartz is.", "start": 937.803, "duration": 2.402}, {"text": "It's all the oxygen is\nhappy without needing", "start": 940.205, "duration": 2.703}, {"text": "the extra charge, because\nthey are all bridged.", "start": 942.908, "duration": 2.369}, {"text": "So that's what we've done.", "start": 948.18, "duration": 1.101}, {"text": "We've made silica\nby thinking about it", "start": 949.281, "duration": 3.871}, {"text": "in terms of these\nsilicate groups, OK,", "start": 953.152, "duration": 4.504}, {"text": "and just bridging\nthem all together.", "start": 957.656, "duration": 1.935}, {"text": "And I can't draw it.", "start": 959.591, "duration": 1.268}, {"text": "But you have it\nthere, and 3D models", "start": 960.859, "duration": 2.403}, {"text": "are the easiest way to see it.", "start": 963.262, "duration": 2.669}, {"text": "And they all act as bridges\nbetween silicate groups.", "start": 965.931, "duration": 4.938}, {"text": "OK.", "start": 970.869, "duration": 0.768}, {"text": "So why am I--", "start": 971.637, "duration": 1.168}, {"text": "why do I keep this\nsilicate group?", "start": 972.805, "duration": 2.002}, {"text": "So a lot of times if you\nlook up the structure,", "start": 974.807, "duration": 2.102}, {"text": "and this is the\n3D structure, you", "start": 976.909, "duration": 1.368}, {"text": "see every single\noxygen is a bridge.", "start": 978.277, "duration": 3.503}, {"text": "Every single oxygen is a bridge.", "start": 981.78, "duration": 2.87}, {"text": "And it's nice to think\nabout it in terms", "start": 984.65, "duration": 2.035}, {"text": "of the silicate groups.", "start": 986.685, "duration": 1.368}, {"text": "Why?", "start": 988.053, "duration": 0.501}, {"text": "Why did I start with that?", "start": 988.554, "duration": 2.569}, {"text": "I started with that because\nthese groups are very strong.", "start": 991.123, "duration": 4.404}, {"text": "They stay together.", "start": 995.527, "duration": 2.536}, {"text": "And they kind of act as\nbuilding blocks for the glass", "start": 998.063, "duration": 3.504}, {"text": "and for the quartz.", "start": 1001.567, "duration": 1.401}, {"text": "And you now know those\nare two different things,", "start": 1002.968, "duration": 2.636}, {"text": "quartz is silicate groups\nordered in a crystal.", "start": 1005.604, "duration": 4.138}, {"text": "Glass is what we're\ngoing to get to.", "start": 1009.742, "duration": 2.102}, {"text": "It's when they're disordered.", "start": 1011.844, "duration": 2.736}, {"text": "OK.", "start": 1014.58, "duration": 0.667}, {"text": "And why is that?", "start": 1015.247, "duration": 1.034}, {"text": "Well, because these oxygen, you\nsee the silica, the tetrahedron", "start": 1016.281, "duration": 3.871}, {"text": "with the silicon atom and\nthose oxygens is pretty robust.", "start": 1020.152, "duration": 3.103}, {"text": "But the bond between\nthe oxygens is-- well,", "start": 1023.255, "duration": 1.968}, {"text": "there's a whole lot of\nrotation that can happen here.", "start": 1025.223, "duration": 3.203}, {"text": "You see that?", "start": 1028.426, "duration": 1.97}, {"text": "That thing can rotate around.", "start": 1030.396, "duration": 2.568}, {"text": "So that's a good\nway to picture this.", "start": 1032.964, "duration": 1.701}, {"text": "That's a good way\nto picture quartz", "start": 1034.665, "duration": 2.136}, {"text": "is these silicate groups\nthat are bonded together", "start": 1036.801, "duration": 2.97}, {"text": "through these bridge\noxygens, but they", "start": 1039.771, "duration": 1.969}, {"text": "have a lot of rotational\nand distortion", "start": 1041.74, "duration": 3.337}, {"text": "relative one with respect to\none another, that is possible.", "start": 1045.077, "duration": 6.173}, {"text": "So I take those\nsilicate groups, OK.", "start": 1051.25, "duration": 4.371}, {"text": "Here they are up top, and\nI bring them together,", "start": 1055.621, "duration": 3.303}, {"text": "and I make a perfect crystal.", "start": 1058.924, "duration": 1.602}, {"text": "That is what's\nbeing passed around.", "start": 1060.526, "duration": 1.434}, {"text": "But look, because there's\nso much possibility", "start": 1061.96, "duration": 2.97}, {"text": "for rotation and distortion,\nmaybe that didn't happen.", "start": 1064.93, "duration": 3.937}, {"text": "Maybe as they start to form\nor they find each other,", "start": 1068.867, "duration": 2.67}, {"text": "and they start bridging, maybe\nthey didn't quite make it.", "start": 1071.537, "duration": 4.905}, {"text": "And you can imagine these\nthings are kind of bulky groups", "start": 1076.442, "duration": 3.77}, {"text": "coming together and\ntwisting around.", "start": 1080.212, "duration": 2.236}, {"text": "You missed the mark, it\nmight be hard to get back.", "start": 1082.448, "duration": 4.304}, {"text": "So how does one\nhappen over the other?", "start": 1086.752, "duration": 4.104}, {"text": "All right, that's the crystal.", "start": 1090.856, "duration": 1.501}, {"text": "That's the not\ncrystal, the glass.", "start": 1092.357, "duration": 3.437}, {"text": "And it depends on\na couple of things.", "start": 1095.794, "duration": 1.835}, {"text": "And that's what I want\nto talk about next.", "start": 1097.629, "duration": 1.735}, {"text": "It depends on the\ntemperature and the cooling.", "start": 1099.364, "duration": 3.537}, {"text": "Depends on the temperature\nand the cooling.", "start": 1102.901, "duration": 2.503}, {"text": "So how does temperature come in?", "start": 1105.404, "duration": 1.868}, {"text": "So temperature comes\nin because temperature", "start": 1107.272, "duration": 3.537}, {"text": "makes everything vibrate.", "start": 1110.809, "duration": 1.669}, {"text": "Right.", "start": 1112.478, "duration": 0.5}, {"text": "It gives these atoms and\nthese groups kinetic energy.", "start": 1112.978, "duration": 4.805}, {"text": "OK.", "start": 1117.783, "duration": 0.5}, {"text": "So let's look at that.", "start": 1118.283, "duration": 1.001}, {"text": "So if we were to plot,\nfor example, temperature", "start": 1119.284, "duration": 6.807}, {"text": "versus the volume\nper mole, so this is,", "start": 1126.091, "duration": 4.138}, {"text": "you know, for a given number\nof these atoms, much volume", "start": 1130.229, "duration": 5.372}, {"text": "do they take?", "start": 1135.601, "duration": 0.567}, {"text": "Well, you can imagine that\nthat is actually related", "start": 1136.168, "duration": 3.27}, {"text": "to how much energy they have.", "start": 1139.438, "duration": 2.002}, {"text": "All right.", "start": 1141.44, "duration": 0.5}, {"text": "So like if I had like\na crystal, you know,", "start": 1141.94, "duration": 3.671}, {"text": "maybe I'll start it here.", "start": 1145.611, "duration": 2.035}, {"text": "And if I have a\ncrystal, you know,", "start": 1147.646, "duration": 2.569}, {"text": "and I increase the\ntemperature a little bit,", "start": 1150.215, "duration": 1.936}, {"text": "maybe they're\ngoing to move more.", "start": 1152.151, "duration": 2.569}, {"text": "And as they move more,\nthey need more room.", "start": 1154.72, "duration": 3.036}, {"text": "And this is just a\nsimple-- you can just", "start": 1160.159, "duration": 1.668}, {"text": "think of like a\nsimple atom, connected", "start": 1161.827, "duration": 3.236}, {"text": "to another on a spring.", "start": 1165.063, "duration": 2.336}, {"text": "And more kinetic energy, more\ntemperature, it goes further.", "start": 1167.399, "duration": 5.539}, {"text": "And now you're all thinking,\nwell, wait a second,", "start": 1172.938, "duration": 2.069}, {"text": "doesn't it go in as\nfar as it goes out?", "start": 1175.007, "duration": 2.936}, {"text": "Why?", "start": 1177.943, "duration": 1.401}, {"text": "Does it need more volume?", "start": 1179.344, "duration": 2.636}, {"text": "Well, that is because of what\nwe have already talked about,", "start": 1181.98, "duration": 4.505}, {"text": "which is this energy curve\nbetween two atoms, or two", "start": 1186.485, "duration": 6.94}, {"text": "silicate groups.", "start": 1193.425, "duration": 1.335}, {"text": "This potential energy\ncurve that plots", "start": 1194.76, "duration": 3.136}, {"text": "the energy between\nthose two groups", "start": 1197.896, "duration": 2.269}, {"text": "and, say, the\ndistance between them,", "start": 1200.165, "duration": 2.669}, {"text": "has something very\nimportant about it,", "start": 1202.834, "duration": 3.337}, {"text": "has something very important.", "start": 1206.171, "duration": 1.468}, {"text": "This is the spring.", "start": 1207.639, "duration": 0.968}, {"text": "OK, so I'm in there, and\nI'm at T equals 0 here.", "start": 1208.607, "duration": 6.239}, {"text": "That would be like T equals 0.", "start": 1214.846, "duration": 2.603}, {"text": "The absolute ground\nstate, the place", "start": 1217.449, "duration": 2.636}, {"text": "where everything is just\nin its minimum energy,", "start": 1220.085, "duration": 2.302}, {"text": "but now I start\nmaking things move.", "start": 1222.387, "duration": 3.07}, {"text": "All right, I put\nkinetic energy into it,", "start": 1225.457, "duration": 2.102}, {"text": "I increase the\ntemperature, what happens?", "start": 1227.559, "duration": 3.904}, {"text": "The energy goes up.", "start": 1231.463, "duration": 1.869}, {"text": "But look, it doesn't go up.", "start": 1233.332, "duration": 2.235}, {"text": "It goes like this.", "start": 1235.567, "duration": 1.035}, {"text": "The average-- I'm a little\nbit higher in energy,", "start": 1236.602, "duration": 3.336}, {"text": "right, I'm a little\nbit higher in energy.", "start": 1239.938, "duration": 2.136}, {"text": "So where I am is\nthere, on average.", "start": 1242.074, "duration": 1.902}, {"text": "Now I'm a little bit higher\nin energy, and so where I am", "start": 1243.976, "duration": 3.169}, {"text": "is there, and now I'm a little\nbit higher, and where I am", "start": 1247.145, "duration": 3.404}, {"text": "is there.", "start": 1250.549, "duration": 0.5}, {"text": "This is what happens\nto the average.", "start": 1251.049, "duration": 4.371}, {"text": "That's why solids expand.", "start": 1255.42, "duration": 2.036}, {"text": "It's because of the asymmetry\nin this potential energy", "start": 1260.392, "duration": 3.871}, {"text": "curve, which we have\nalready talked about.", "start": 1264.263, "duration": 3.003}, {"text": "It's because of the asymmetry.", "start": 1267.266, "duration": 2.002}, {"text": "You see.", "start": 1269.268, "duration": 0.867}, {"text": "This is going out differently\nthan this goes up.", "start": 1270.135, "duration": 4.838}, {"text": "That's why you have\nthermal expansion.", "start": 1274.973, "duration": 2.603}, {"text": "All right.", "start": 1277.576, "duration": 0.701}, {"text": "Things are vibrating.", "start": 1278.277, "duration": 2.535}, {"text": "But more often than not, they're\ngoing to be farther apart.", "start": 1280.812, "duration": 2.937}, {"text": "And so this happens.", "start": 1283.749, "duration": 1.301}, {"text": "And so this happens.", "start": 1285.05, "duration": 0.934}, {"text": "So we've just understood\nthis from an atomic--", "start": 1285.984, "duration": 2.536}, {"text": "so this would be like\nif I had a crystal,", "start": 1288.52, "duration": 2.236}, {"text": "and I'm going to save three\nletters and write xtal.", "start": 1290.756, "duration": 4.204}, {"text": "That's so efficient.", "start": 1294.96, "duration": 2.402}, {"text": "And then I keep going.", "start": 1297.362, "duration": 2.136}, {"text": "And by the way,\nthe slope of this", "start": 1299.498, "duration": 1.668}, {"text": "is called slope is called the\nthermal expansion coefficient.", "start": 1301.166, "duration": 6.673}, {"text": "Thermal expansion.", "start": 1307.839, "duration": 5.573}, {"text": "That is the definition of the\nthermal expansion coefficient.", "start": 1313.412, "duration": 3.57}, {"text": "Sometimes we use alpha.", "start": 1319.685, "duration": 1.201}, {"text": "That's the slope of this line.", "start": 1323.488, "duration": 1.535}, {"text": "It's the volume per\nmole divided by--", "start": 1325.023, "duration": 2.469}, {"text": "over the temperature,\nthe change in the volume", "start": 1327.492, "duration": 1.902}, {"text": "or the change in temperature.", "start": 1329.394, "duration": 1.235}, {"text": "It's the thermal expansion\ncoefficient of the material.", "start": 1330.629, "duration": 2.436}, {"text": "OK, so I'm adding\ntemperature, and I'm expanding", "start": 1333.065, "duration": 3.57}, {"text": "and I'm expanding and\nthen I get to this point.", "start": 1336.635, "duration": 2.769}, {"text": "I get to this point.", "start": 1339.404, "duration": 1.936}, {"text": "This point here is where\neverything changes.", "start": 1341.34, "duration": 5.872}, {"text": "Everything changes.", "start": 1347.212, "duration": 1.935}, {"text": "That's the melting\npoint of the solid.", "start": 1349.147, "duration": 3.704}, {"text": "That's the melting point.", "start": 1352.851, "duration": 1.335}, {"text": "Now at the melting\npoint, as we know,", "start": 1354.186, "duration": 4.504}, {"text": "the whole thing goes\nthrough a transition.", "start": 1358.69, "duration": 3.237}, {"text": "It goes through a\nphase transition.", "start": 1361.927, "duration": 4.538}, {"text": "And it becomes a liquid.", "start": 1366.465, "duration": 1.034}, {"text": "And the thermal\nexpansion of the liquid", "start": 1370.035, "duration": 2.502}, {"text": "is different than the\nsolid, because those, now,", "start": 1372.537, "duration": 3.137}, {"text": "you think about those\nmolecules are not rigidly", "start": 1375.674, "duration": 4.738}, {"text": "bonded to each other anymore.", "start": 1380.412, "duration": 2.269}, {"text": "They're more weakly bonded,\nand they're moving around", "start": 1382.681, "duration": 2.636}, {"text": "with a lot of kinetic energy.", "start": 1385.317, "duration": 2.569}, {"text": "And so when they get\nmore kinetic energy,", "start": 1387.886, "duration": 1.702}, {"text": "they can expand even more.", "start": 1389.588, "duration": 1.701}, {"text": "That's why those\nslopes are different.", "start": 1391.289, "duration": 1.735}, {"text": "But as we know, there's\nalso a big volume change.", "start": 1395.694, "duration": 3.07}, {"text": "There's a sudden volume change.", "start": 1398.764, "duration": 2.936}, {"text": "In going from a\nsolid to a liquid,", "start": 1401.7, "duration": 3.336}, {"text": "there's a sudden volume change.", "start": 1405.036, "duration": 2.737}, {"text": "And it would be the same thing\nif I went back the other way.", "start": 1407.773, "duration": 3.737}, {"text": "Right, I'm cooling it\ndown and cooling it down,", "start": 1411.51, "duration": 2.936}, {"text": "and all of a sudden, I get to\nthe solidification temperature", "start": 1414.446, "duration": 4.171}, {"text": "of the material, and\nI become a crystal.", "start": 1418.617, "duration": 5.138}, {"text": "Except when I don't.", "start": 1423.755, "duration": 2.803}, {"text": "Except when I don't.", "start": 1426.558, "duration": 2.202}, {"text": "And when I don't, that's\nwhen I become a glass.", "start": 1428.76, "duration": 3.971}, {"text": "And that's what we\nhave to talk about now", "start": 1432.731, "duration": 1.702}, {"text": "is, how do we go from this\nvery simple picture of being", "start": 1434.433, "duration": 3.903}, {"text": "a glass--", "start": 1438.336, "duration": 1.135}, {"text": "being a liquid or being a\nsolid, a crystalline solid,", "start": 1439.471, "duration": 3.337}, {"text": "how do we go from\nthat to being a glass?", "start": 1442.808, "duration": 4.671}, {"text": "And to explain this,\nto start, I want", "start": 1447.479, "duration": 3.303}, {"text": "to show you something\nreally cool that can happen.", "start": 1450.782, "duration": 2.77}, {"text": "That actually wasn't\nan intentional pun.", "start": 1453.552, "duration": 2.102}, {"text": "But it has to do with\ncooling, and it's really cool,", "start": 1455.654, "duration": 4.171}, {"text": "because sometimes, if\nyou cool a liquid down,", "start": 1459.825, "duration": 4.037}, {"text": "it doesn't solidify right there.", "start": 1463.862, "duration": 2.536}, {"text": "Then that's called\nsuper cooling.", "start": 1466.398, "duration": 1.435}, {"text": "So you can actually cool\nthe liquid down like that,", "start": 1467.833, "duration": 2.669}, {"text": "and have it stay a liquid.", "start": 1470.502, "duration": 1.268}, {"text": "That's called super cooling.", "start": 1474.406, "duration": 1.868}, {"text": "By the way, so this is\ncalled super cooling.", "start": 1476.274, "duration": 7.074}, {"text": "By the way, you can\ndo that with water.", "start": 1483.348, "duration": 3.47}, {"text": "And so I want to show you\nlike one of the coolest things", "start": 1486.818, "duration": 2.536}, {"text": "you could do tonight.", "start": 1489.354, "duration": 1.135}, {"text": "It's a Friday night.", "start": 1490.489, "duration": 1.134}, {"text": "You're going to\nhave guests over,", "start": 1491.623, "duration": 1.802}, {"text": "or you'll be out at that\nsame restaurant that", "start": 1493.425, "duration": 2.335}, {"text": "knows about you,\nbecause you asked them", "start": 1495.76, "duration": 2.069}, {"text": "already all about the\ncandle and the oxygen.", "start": 1497.829, "duration": 5.105}, {"text": "And you always come with\nyour periodic table,", "start": 1502.934, "duration": 1.869}, {"text": "and this time, you sit down\nand you say I don't want water.", "start": 1504.803, "duration": 2.669}, {"text": "Do you want\nsparkling or regular?", "start": 1507.472, "duration": 1.402}, {"text": "I want super cooled.", "start": 1508.874, "duration": 2.102}, {"text": "This is what you're\ngoing to get.", "start": 1510.976, "duration": 1.601}, {"text": "This is what they'll bring you.", "start": 1512.577, "duration": 1.302}, {"text": "They should.", "start": 1513.879, "duration": 0.5}, {"text": "If it's a good restaurant, this\nis what they would bring you.", "start": 1514.379, "duration": 4.104}, {"text": "You know, so here's who is\nsupercooled water being poured.", "start": 1518.483, "duration": 3.437}, {"text": "This is what you should\nsee in your glass.", "start": 1524.623, "duration": 2.469}, {"text": "Now, that is a liquid\nthat is stable, for now,", "start": 1527.092, "duration": 7.641}, {"text": "below its melting point, below\nits solidification point.", "start": 1534.733, "duration": 4.171}, {"text": "So what happens is as\nsoon as it hits the glass,", "start": 1538.904, "duration": 4.504}, {"text": "it's like, whoa, wait a second,\nI am supposed to be a crystal,", "start": 1543.408, "duration": 4.705}, {"text": "and it immediately solidifies.", "start": 1548.113, "duration": 2.102}, {"text": "All right, so it\nimmediately went like this.", "start": 1550.215, "duration": 3.303}, {"text": "Now, by the way, it's not that\nhard to make supercooled water.", "start": 1553.518, "duration": 2.603}, {"text": "If anybody's interested, I'd be\nhappy to tell you how to do it.", "start": 1556.121, "duration": 3.503}, {"text": "You can't just put\nbottles in a freezer.", "start": 1559.624, "duration": 2.036}, {"text": "That won't work.", "start": 1561.66, "duration": 1.067}, {"text": "But it's not that hard to do.", "start": 1562.727, "duration": 3.47}, {"text": "Now, OK, back and\nforth, melting point,", "start": 1566.197, "duration": 6.841}, {"text": "supercooled-- oh,\nit's playing again.", "start": 1573.038, "duration": 3.303}, {"text": "And it starts freezing.", "start": 1576.341, "duration": 1.168}, {"text": "You can also take a bottle\nof supercooled water", "start": 1577.509, "duration": 3.203}, {"text": "and just go like this.", "start": 1580.712, "duration": 0.901}, {"text": "It's liquid inside\nand just tap it,", "start": 1581.613, "duration": 2.169}, {"text": "and the whole thing\nfreezes instantly.", "start": 1583.782, "duration": 2.102}, {"text": "It's really cool.", "start": 1585.884, "duration": 1.301}, {"text": "It's really cool.", "start": 1587.185, "duration": 1.635}, {"text": "OK.", "start": 1588.82, "duration": 0.501}, {"text": "OK.", "start": 1595.627, "duration": 1.034}, {"text": "Now, why am I\ntalking about this?", "start": 1596.661, "duration": 4.672}, {"text": "Because you can super\ncool and go down.", "start": 1601.333, "duration": 7.974}, {"text": "You could go below\nthat transition point", "start": 1609.307, "duration": 3.17}, {"text": "and go and go down,\nlike I just did there", "start": 1612.477, "duration": 2.736}, {"text": "and become a crystal right\naway, but you could also not.", "start": 1615.213, "duration": 6.874}, {"text": "You could also become a solid,\nso you could become a crystal,", "start": 1622.087, "duration": 4.905}, {"text": "or you could also\nbecome a solid.", "start": 1626.992, "duration": 2.235}, {"text": "And I'm going to need\nanother plot to do this.", "start": 1629.227, "duration": 3.203}, {"text": "And you could become a\nsolid right where you were.", "start": 1632.43, "duration": 2.603}, {"text": "You might not go down\nto the crystal curve,", "start": 1635.033, "duration": 3.837}, {"text": "but you might start a new curve.", "start": 1638.87, "duration": 2.903}, {"text": "And that will be a glass.", "start": 1641.773, "duration": 3.47}, {"text": "And so we're going to draw this\nagain and show you a glass,", "start": 1645.243, "duration": 2.603}, {"text": "but this is what we need is\nthis framework to understand", "start": 1647.846, "duration": 4.504}, {"text": "when a glass forms.", "start": 1652.35, "duration": 0.834}, {"text": "So this was our picture,\ncrystalline, crystalline,", "start": 1653.184, "duration": 2.369}, {"text": "glass, amorphous equals glass.", "start": 1655.553, "duration": 3.137}, {"text": "When does it form?", "start": 1658.69, "duration": 1.969}, {"text": "Now I think the best--", "start": 1660.659, "duration": 1.668}, {"text": "I'll show you that\none in a second.", "start": 1662.327, "duration": 1.468}, {"text": "I think the best way\nto think about it", "start": 1663.795, "duration": 2.469}, {"text": "is let's draw the\nplot again, and I", "start": 1666.264, "duration": 3.337}, {"text": "think the best way\nto think about it", "start": 1669.601, "duration": 1.501}, {"text": "is an analogy that has been\nused before, and let's see--", "start": 1671.102, "duration": 9.143}, {"text": "and this is temperature.", "start": 1680.245, "duration": 2.702}, {"text": "This is volume per mole.", "start": 1682.947, "duration": 4.572}, {"text": "By the way, that could\nbe energy, or enthalpy.", "start": 1687.519, "duration": 3.27}, {"text": "Yeah, because as the atoms\naren't packed in as well,", "start": 1690.789, "duration": 3.97}, {"text": "we know this, right, as\nthey're not packed in as well,", "start": 1694.759, "duration": 2.503}, {"text": "they're also going to\nbe higher in energy.", "start": 1697.262, "duration": 3.303}, {"text": "Right, the bonding\nwon't be as strong.", "start": 1700.565, "duration": 1.702}, {"text": "But I think that one of the\nbest analogies to think about", "start": 1704.769, "duration": 2.736}, {"text": "is so I'm coming in as a\nliquid, so I'm now a liquid.", "start": 1707.505, "duration": 3.003}, {"text": "And here's my melting point for\nthe crystal, for the crystal.", "start": 1713.278, "duration": 6.206}, {"text": "But I went past it.", "start": 1719.484, "duration": 2.369}, {"text": "And I went past it,\nand now, instead of--", "start": 1721.853, "duration": 3.637}, {"text": "I'm just going to\ndraw this out here.", "start": 1725.49, "duration": 2.035}, {"text": "There's the crystal.", "start": 1727.525, "duration": 0.834}, {"text": "Instead of going down to\nbecome a crystal, suddenly", "start": 1730.962, "duration": 6.94}, {"text": "or super cooling, and\nthen becoming a crystal,", "start": 1737.902, "duration": 2.87}, {"text": "no, I super cool, and then\nI just become a solid.", "start": 1740.772, "duration": 5.639}, {"text": "And then I just become a solid.", "start": 1746.411, "duration": 3.036}, {"text": "OK.", "start": 1749.447, "duration": 0.968}, {"text": "Now that-- this is a glass.", "start": 1750.415, "duration": 3.103}, {"text": "You know that it's a solid.", "start": 1756.154, "duration": 3.303}, {"text": "It's got the same\nslope as the crystal.", "start": 1759.457, "duration": 2.936}, {"text": "The thermal expansion\nof this thing", "start": 1762.393, "duration": 1.502}, {"text": "is the same as the\ncrystal or very similar.", "start": 1763.895, "duration": 2.236}, {"text": "So that's enough to tell\nyou this is a solid, right?", "start": 1769.234, "duration": 3.603}, {"text": "It should be a good indicator.", "start": 1772.837, "duration": 2.136}, {"text": "It should have been a nice\nstraight line just for now.", "start": 1774.973, "duration": 4.337}, {"text": "OK.", "start": 1779.31, "duration": 0.968}, {"text": "Yeah, but it didn't get--", "start": 1780.278, "duration": 4.771}, {"text": "those silicate blocks\ndidn't find the lattice.", "start": 1785.049, "duration": 4.205}, {"text": "They didn't find the lattice.", "start": 1789.254, "duration": 2.035}, {"text": "As you're cool-- here,\nthey've got all this freedom.", "start": 1791.289, "duration": 3.17}, {"text": "I mean, they're a\nliquid, silicate, happy.", "start": 1794.459, "duration": 3.17}, {"text": "Maybe it's an even\nhigher temperature,", "start": 1797.629, "duration": 1.568}, {"text": "and the silicons are even\ndissociated from the oxygen.", "start": 1799.197, "duration": 2.436}, {"text": "Let's just assume they're\nin these silicate groups,", "start": 1801.633, "duration": 2.169}, {"text": "and they're floating around in a\nliquid, and I start cooling it.", "start": 1803.802, "duration": 5.205}, {"text": "I think one of the best\nanalogies that I've heard", "start": 1809.007, "duration": 2.035}, {"text": "is that of musical chairs.", "start": 1811.042, "duration": 2.87}, {"text": "How many of you have\nplayed musical chairs?", "start": 1813.912, "duration": 2.402}, {"text": "OK, you've got to\nfix this tonight.", "start": 1816.314, "duration": 2.035}, {"text": "For those of you who\ndidn't raise your hand,", "start": 1818.349, "duration": 1.802}, {"text": "that's going on\nthe menu tonight,", "start": 1820.151, "duration": 3.203}, {"text": "because it's a really fun game.", "start": 1823.354, "duration": 3.471}, {"text": "With supercooled\nwater, of course.", "start": 1826.825, "duration": 1.634}, {"text": "You line up some chairs, and\nyou get around in a group", "start": 1831.196, "duration": 3.603}, {"text": "and you walk around\nit as the music plays", "start": 1834.799, "duration": 3.57}, {"text": "and then the music stops and\neverybody has to find a chair,", "start": 1838.369, "duration": 5.739}, {"text": "but there's a chair missing.", "start": 1844.108, "duration": 2.203}, {"text": "So you've got to go fast, or\nyou might not get to a chair.", "start": 1846.311, "duration": 3.537}, {"text": "Well, you see the silicate,\nlet's put it below here,", "start": 1853.952, "duration": 4.537}, {"text": "the silicates are you.", "start": 1858.489, "duration": 1.569}, {"text": "You are the silicates.", "start": 1860.058, "duration": 2.302}, {"text": "People equals silicate.", "start": 1862.36, "duration": 4.104}, {"text": "And the chair equal\nlattice sites.", "start": 1869.701, "duration": 8.575}, {"text": "And now you can really feel it.", "start": 1882.313, "duration": 1.602}, {"text": "You can really feel it, because\nthe speed around the chairs.", "start": 1883.915, "duration": 3.303}, {"text": "How fast are you moving?", "start": 1887.218, "duration": 2.002}, {"text": "Right.", "start": 1889.22, "duration": 0.768}, {"text": "So the speed, well, if it's\nspeed around the chair,", "start": 1889.988, "duration": 7.674}, {"text": "OK, if that's fast, then\nit's, you know, high mobility,", "start": 1897.662, "duration": 7.908}, {"text": "so let's see, speed around\nchair, let's do this.", "start": 1905.57, "duration": 3.07}, {"text": "High mobility, maybe\nyou'd find, you know, find", "start": 1908.64, "duration": 9.409}, {"text": "lattice sites easier, or\nfaster, at least, but see,", "start": 1918.049, "duration": 9.977}, {"text": "if you have a high\n1 over mobility--", "start": 1928.026, "duration": 4.237}, {"text": "by the way, that's\nalso viscosity,", "start": 1932.263, "duration": 2.369}, {"text": "if you have a high\n1 over mobility.", "start": 1934.632, "duration": 3.704}, {"text": "So if you have a high\nviscosity, [INAUDIBLE]..", "start": 1938.336, "duration": 2.97}, {"text": "High 1 over mobility, high\nviscosity, then it's slow.", "start": 1946.377, "duration": 6.173}, {"text": "And that's how you have a\nhigher chance of forming glass.", "start": 1952.55, "duration": 4.171}, {"text": "So I'm going to talk about\nwhat would make a glass form.", "start": 1956.721, "duration": 6.573}, {"text": "If you're just\nwalking around slowly,", "start": 1963.294, "duration": 2.603}, {"text": "like this, everyone\nelse is running,", "start": 1965.897, "duration": 1.968}, {"text": "but maybe you're\nall walking slowly,", "start": 1967.865, "duration": 2.069}, {"text": "and now the music stops, and I'm\nlike, yeah, I'll take my time,", "start": 1969.934, "duration": 4.071}, {"text": "it's going to be hard to get\nto the open lattice site.", "start": 1974.005, "duration": 4.237}, {"text": "I might just get stuck.", "start": 1978.242, "duration": 1.936}, {"text": "OK, so what else?", "start": 1980.178, "duration": 0.867}, {"text": "Well, OK, so how\nabout the arrangement?", "start": 1981.045, "duration": 2.569}, {"text": "So the chair\narrangement, that has", "start": 1983.614, "duration": 8.909}, {"text": "to do with the\ncrystal complexity.", "start": 1992.523, "duration": 2.203}, {"text": "And you can imagine that\nif the chairs are arranged", "start": 1998.696, "duration": 2.536}, {"text": "in a straight line, and you're\ngoing around the chairs,", "start": 2001.232, "duration": 2.302}, {"text": "and it's is kind\nof an easy loop,", "start": 2003.534, "duration": 2.503}, {"text": "right, now I don't have\nto concentrate too much", "start": 2006.037, "duration": 3.77}, {"text": "on where I'm going, and it's\nkind of-- there's nothing", "start": 2009.807, "duration": 2.269}, {"text": "really blocking me,\nI hope, but what", "start": 2012.076, "duration": 2.102}, {"text": "if those chairs were arranged\nin a really complicated way.", "start": 2014.178, "duration": 4.672}, {"text": "So how hard is it to\nget around these chairs?", "start": 2018.85, "duration": 3.27}, {"text": "How hard is it to find them?", "start": 2022.12, "duration": 1.534}, {"text": "How complex is the lattice?", "start": 2023.654, "duration": 2.536}, {"text": "And you can imagine\nthat it is higher.", "start": 2026.19, "duration": 4.538}, {"text": "So let's see.", "start": 2030.728, "duration": 3.337}, {"text": "More-- I'll just draw an arrow.", "start": 2034.065, "duration": 1.535}, {"text": "Higher would lead to glass.", "start": 2035.6, "duration": 3.003}, {"text": "OK, so it fits.", "start": 2038.603, "duration": 1.868}, {"text": "Higher complexity\nof the lattice.", "start": 2040.471, "duration": 4.471}, {"text": "It might be harder\nto find the lattice", "start": 2044.942, "duration": 2.103}, {"text": "sites in this musical chairs.", "start": 2047.045, "duration": 2.469}, {"text": "OK, one more, and\nI'll put it here,", "start": 2049.514, "duration": 2.536}, {"text": "so that it's close\nby, because I've", "start": 2052.05, "duration": 2.068}, {"text": "got no more room on that board.", "start": 2054.118, "duration": 1.435}, {"text": "The third one is how\nfast you stop the music.", "start": 2058.356, "duration": 2.936}, {"text": "So this would be like\n1, 2, and then 3.", "start": 2061.292, "duration": 7.206}, {"text": "How fast do we stop music?", "start": 2068.498, "duration": 3.103}, {"text": "OK.", "start": 2075.106, "duration": 0.6}, {"text": "So you can imagine if\nI, you know, if I slowly", "start": 2075.706, "duration": 5.406}, {"text": "were playing musical chairs,\nand I am walking around,", "start": 2081.112, "duration": 3.17}, {"text": "and I slowly fade\nthe music, all right,", "start": 2084.282, "duration": 4.471}, {"text": "well, then you got lots of time.", "start": 2088.753, "duration": 1.667}, {"text": "You got lots of time, but\nwhat if I just stop it.", "start": 2090.42, "duration": 3.071}, {"text": "Now, everybody's scrambling.", "start": 2093.491, "duration": 2.902}, {"text": "So how fast do you stop the\nmusic is the cooling rate.", "start": 2096.393, "duration": 2.937}, {"text": "It's how quickly you\ncool this material.", "start": 2103.201, "duration": 2.802}, {"text": "It's how fast you\nstop the music,", "start": 2106.003, "duration": 1.402}, {"text": "and you can imagine that\nif it's faster, faster,", "start": 2107.405, "duration": 5.372}, {"text": "you are more likely\nto form a glass.", "start": 2112.777, "duration": 2.803}, {"text": "You're more likely\nto form a glass,", "start": 2119.083, "duration": 1.468}, {"text": "and so we go back\nto our picture.", "start": 2120.551, "duration": 3.304}, {"text": "Well, maybe I'll draw one over\nhere, because I need more room,", "start": 2123.855, "duration": 2.936}, {"text": "and I don't want to\nblock what's there.", "start": 2126.791, "duration": 4.871}, {"text": "We go back to our picture and\nhere it is, drawn out for you.", "start": 2131.662, "duration": 3.37}, {"text": "You see that is--", "start": 2135.032, "duration": 2.837}, {"text": "OK, there is the\nliquid line, coming in,", "start": 2137.869, "duration": 2.168}, {"text": "volume, OK, enthalpy,\nvisage, and we'll", "start": 2140.037, "duration": 3.604}, {"text": "keep thinking\nabout it as volume.", "start": 2143.641, "duration": 1.635}, {"text": "The liquid line comes in.", "start": 2145.276, "duration": 1.268}, {"text": "You're cooling it down.", "start": 2146.544, "duration": 0.968}, {"text": "There's the thermal expansion.", "start": 2147.512, "duration": 1.568}, {"text": "It's reducing,\nreducing, and now I", "start": 2149.08, "duration": 1.435}, {"text": "get to the melting temperature,\nand I become a crystal.", "start": 2150.515, "duration": 2.268}, {"text": "That's if it can\nbecome a crystal,", "start": 2152.783, "duration": 2.536}, {"text": "but all of these\nfactors, now, matter.", "start": 2155.319, "duration": 4.038}, {"text": "The melting point of the crystal\nis always the same number.", "start": 2163.528, "duration": 5.905}, {"text": "It's always the same number.", "start": 2169.433, "duration": 1.168}, {"text": "The melting point,\nwhere the crystal melts,", "start": 2170.601, "duration": 3.771}, {"text": "because the crystal\nis always the same.", "start": 2174.372, "duration": 3.069}, {"text": "Right.", "start": 2177.441, "duration": 0.501}, {"text": "Now, where that melts is\nalways the same temperature.", "start": 2177.942, "duration": 4.938}, {"text": "But notice now,\nwhat have I done?", "start": 2182.88, "duration": 2.036}, {"text": "I've super cooled\nthe liquid down,", "start": 2184.916, "duration": 2.902}, {"text": "and on a, I've got a glass\nthat looks like this.", "start": 2187.818, "duration": 3.671}, {"text": "These are glasses.", "start": 2191.489, "duration": 1.401}, {"text": "And on b, I've got a glass\nthat looks like that.", "start": 2192.89, "duration": 2.102}, {"text": "Those are different.", "start": 2194.992, "duration": 2.77}, {"text": "And they have different\nsolidification temperatures.", "start": 2197.762, "duration": 4.738}, {"text": "And what do we call it?", "start": 2202.5, "duration": 0.967}, {"text": "We have a special\nname for it, too.", "start": 2203.467, "duration": 2.203}, {"text": "We have a special name for it,\nbecause it's not crystallizing.", "start": 2205.67, "duration": 4.905}, {"text": "Right, so if this is\nthe volume per mole,", "start": 2210.575, "duration": 2.936}, {"text": "and this is the temperature,\nit's not crystallizing.", "start": 2213.511, "duration": 4.504}, {"text": "No.", "start": 2218.015, "duration": 1.101}, {"text": "What is it doing?", "start": 2219.116, "duration": 0.734}, {"text": "So that would be\nthe melting point.", "start": 2219.85, "duration": 2.903}, {"text": "It is turning into a glass,\nand so we call this the glass", "start": 2222.753, "duration": 7.741}, {"text": "transition temperature.", "start": 2230.494, "duration": 1.268}, {"text": "It's a glass transition.", "start": 2231.762, "duration": 1.969}, {"text": "What that means is it\nis still becoming--", "start": 2233.731, "duration": 3.77}, {"text": "gesundheit-- a solid, but\nit's an amorphous solid.", "start": 2237.501, "duration": 5.506}, {"text": "It's not a crystal.", "start": 2243.007, "duration": 2.669}, {"text": "Why did it become\nan amorphous solid?", "start": 2245.676, "duration": 1.669}, {"text": "Well, maybe I cooled\nit really fast.", "start": 2247.345, "duration": 4.137}, {"text": "Or maybe it's a really\ncomplex structure, right?", "start": 2251.482, "duration": 4.071}, {"text": "Or maybe the viscosity of\nthe material is very high,", "start": 2255.553, "duration": 3.07}, {"text": "and it just--", "start": 2258.623, "duration": 0.7}, {"text": "as I'm cooling it\ndown, it just couldn't", "start": 2259.323, "duration": 1.669}, {"text": "find the crystal lattice,\nwhich is all the way down here.", "start": 2260.992, "duration": 3.436}, {"text": "And you can see from\nthis, that you know,", "start": 2267.565, "duration": 3.236}, {"text": "imagine I take\nthe extreme limit,", "start": 2270.801, "duration": 3.237}, {"text": "and I got my liquid\nof my silicate groups,", "start": 2274.038, "duration": 3.437}, {"text": "and right as I get below here,\nI'm like you're all frozen.", "start": 2277.475, "duration": 4.905}, {"text": "I'd literally-- I'd make a glass\nright here, right up there,", "start": 2282.38, "duration": 4.671}, {"text": "all right.", "start": 2287.051, "duration": 2.269}, {"text": "So I can make glasses that\nare different from each other.", "start": 2289.32, "duration": 3.103}, {"text": "And you can see that\nthe volume per mole", "start": 2292.423, "duration": 4.471}, {"text": "is increasing as\nI go up, and you", "start": 2296.894, "duration": 2.469}, {"text": "can understand that, because\nlook, I took a glass.", "start": 2299.363, "duration": 3.137}, {"text": "I didn't let--", "start": 2302.5, "duration": 0.734}, {"text": "I took a liquid here.", "start": 2303.234, "duration": 1.268}, {"text": "This is the liquid.", "start": 2304.502, "duration": 1.168}, {"text": "I didn't let any of it\nfind crystals sites.", "start": 2305.67, "duration": 2.636}, {"text": "It's a liquid.", "start": 2308.306, "duration": 0.9}, {"text": "But I said, ha, you're frozen.", "start": 2309.206, "duration": 2.803}, {"text": "And it became frozen and stuck\nat a high volume per mole.", "start": 2312.009, "duration": 4.571}, {"text": "Because it's totally\nrandom and amorphous.", "start": 2316.58, "duration": 3.471}, {"text": "It's coming right from all\nthose random liquid degrees", "start": 2320.051, "duration": 3.536}, {"text": "of freedom are just frozen in.", "start": 2323.587, "duration": 3.504}, {"text": "Yeah, but now, I cool it slower.", "start": 2327.091, "duration": 3.37}, {"text": "Maybe that's what\nhappened here, right?", "start": 2330.461, "duration": 2.102}, {"text": "And I give it more time.", "start": 2332.563, "duration": 2.169}, {"text": "And I give it more time to find\nsome of those lattice sites,", "start": 2334.732, "duration": 4.071}, {"text": "and it finds some lattice sites,\nbut then it became a glass", "start": 2338.803, "duration": 4.504}, {"text": "at this temperature, the\nglass transition temperature,", "start": 2343.307, "duration": 2.669}, {"text": "and everything\nelse is frozen in.", "start": 2345.976, "duration": 2.103}, {"text": "So if I label this, so let's\nlabel it the same as there,", "start": 2350.881, "duration": 2.837}, {"text": "if I label a as this\none and b as this one,", "start": 2353.718, "duration": 5.338}, {"text": "and this is the crystal,\nnope, the crystal", "start": 2359.056, "duration": 4.672}, {"text": "would have to go all\nthe way up to here.", "start": 2363.728, "duration": 2.369}, {"text": "There we go.", "start": 2366.097, "duration": 1.067}, {"text": "Right.", "start": 2367.164, "duration": 2.67}, {"text": "So if that's a, that's glass\na, and that's glass b, then", "start": 2369.834, "duration": 3.37}, {"text": "which one did I cool faster?", "start": 2373.204, "duration": 3.303}, {"text": "Well, I had to call\nthis one slower--", "start": 2376.507, "duration": 2.002}, {"text": "if all I changed between\nthem is cooling rates,", "start": 2378.509, "duration": 3.837}, {"text": "then this one is cooled faster.", "start": 2382.346, "duration": 3.704}, {"text": "So let me write it here.", "start": 2386.05, "duration": 1.601}, {"text": "a cooled slower than b.", "start": 2387.651, "duration": 6.273}, {"text": "Right.", "start": 2397.161, "duration": 0.5}, {"text": "Because I get-- and\nthat's this one here.", "start": 2397.661, "duration": 2.369}, {"text": "How fast did you stop the music?", "start": 2400.03, "duration": 1.535}, {"text": "Right.", "start": 2401.565, "duration": 0.501}, {"text": "It's the cooling rate.", "start": 2402.066, "duration": 1.668}, {"text": "OK, so this plot, this volume\nversus temperature really", "start": 2403.734, "duration": 6.073}, {"text": "allows us to understand how\nglass forms, or at least we can", "start": 2409.807, "duration": 4.004}, {"text": "plot, you know, what happened,\nand then try to understand it.", "start": 2413.811, "duration": 6.406}, {"text": "And if it did get all\nthe way to the crystal,", "start": 2420.217, "duration": 2.803}, {"text": "then maybe it means that it's\nnot very viscous as a liquid,", "start": 2423.02, "duration": 3.871}, {"text": "it doesn't have a\ncomplex lattice site,", "start": 2426.891, "duration": 3.336}, {"text": "and maybe it didn't even matter\nhow quickly-- oh, metals.", "start": 2430.227, "duration": 5.272}, {"text": "But that's why it's hard to\nmake glasses out of metals.", "start": 2435.499, "duration": 4.605}, {"text": "Because metals have an easy time\nfinding their lattice sites.", "start": 2440.104, "duration": 6.44}, {"text": "Metals as liquids typically\naren't very viscous.", "start": 2446.544, "duration": 4.004}, {"text": "And so even if you cool\nit faster, it's got time.", "start": 2450.548, "duration": 4.504}, {"text": "The musical chairs\nof metals is easy.", "start": 2455.052, "duration": 2.302}, {"text": "It's an easy game.", "start": 2457.354, "duration": 2.703}, {"text": "That's why the silicates\nnever played musical chairs", "start": 2460.057, "duration": 2.836}, {"text": "with metals.", "start": 2462.893, "duration": 0.534}, {"text": "But I can still\ndo it, and the way", "start": 2466.063, "duration": 1.602}, {"text": "you make a glass out\nof a metal, the way", "start": 2467.665, "duration": 1.701}, {"text": "you make a metallic glass,\nwhich is a really cool material", "start": 2469.366, "duration": 3.07}, {"text": "is you freeze it really quickly.", "start": 2472.436, "duration": 3.57}, {"text": "You will lower the temperature\nas quickly as you can,", "start": 2476.006, "duration": 3.17}, {"text": "really, really fast, and\nyou freeze in the disorder,", "start": 2479.176, "duration": 2.236}, {"text": "and you make a metallic glass.", "start": 2481.412, "duration": 2.235}, {"text": "OK, so those are the two curves\nI just talked about there.", "start": 2483.647, "duration": 3.671}, {"text": "That's the glass curve.", "start": 2487.318, "duration": 1.368}, {"text": "This would be the crystal curve.", "start": 2488.686, "duration": 1.968}, {"text": "OK, two different\ncooling rates on here.", "start": 2490.654, "duration": 4.839}, {"text": "OK, now, here's a\npicture of float glass.", "start": 2495.493, "duration": 4.971}, {"text": "This is the kind of glass--", "start": 2500.464, "duration": 1.502}, {"text": "we're going to move from\nunderstanding what glass is", "start": 2501.966, "duration": 5.338}, {"text": "and understanding in terms of\nthis temperature versus volume", "start": 2507.304, "duration": 3.037}, {"text": "plot and amorphous\nsolids, and we're", "start": 2510.341, "duration": 4.371}, {"text": "going to move\ntowards understanding", "start": 2514.712, "duration": 1.434}, {"text": "how to modify it,\nhow to control it,", "start": 2516.146, "duration": 2.002}, {"text": "because we do a lot of that.", "start": 2518.148, "duration": 1.702}, {"text": "Here's an example\nof a factor right--", "start": 2519.85, "duration": 1.535}, {"text": "I like this.", "start": 2521.385, "duration": 0.501}, {"text": "This is flow glass.", "start": 2521.886, "duration": 0.867}, {"text": "So this is like when you\nbuy, you know, your windows,", "start": 2522.753, "duration": 2.87}, {"text": "or you know, a\nlot of times, when", "start": 2525.623, "duration": 1.668}, {"text": "you need a very clear,\nbeautiful piece of glass,", "start": 2527.291, "duration": 3.704}, {"text": "you go up to very\nhigh temperatures.", "start": 2530.995, "duration": 2.202}, {"text": "All right, so you're\ntaking those silicates.", "start": 2533.197, "duration": 2.235}, {"text": "You make them into a liquid.", "start": 2535.432, "duration": 1.168}, {"text": "Here he is, measuring\nthe temperature.", "start": 2536.6, "duration": 2.369}, {"text": "I don't know what he's\ndoing actually, whatever.", "start": 2538.969, "duration": 2.603}, {"text": "Oh and this isn't\nshowing up very well.", "start": 2541.572, "duration": 3.27}, {"text": "And there's no\nvolume, so double--", "start": 2544.842, "duration": 1.935}, {"text": "OK, there it is.", "start": 2546.777, "duration": 0.801}, {"text": "So there's the liquid glass.", "start": 2547.578, "duration": 1.435}, {"text": "Why is it called float glass?", "start": 2549.013, "duration": 1.201}, {"text": "[VIDEO PLAYBACK]", "start": 2550.214, "duration": 0.067}, {"text": "[INTERPOSING VOICES]", "start": 2550.281, "duration": 0.033}, {"text": "- The process is monitored\ncontinuously by technicians", "start": 2550.314, "duration": 2.636}, {"text": "to ensure quality.", "start": 2552.95, "duration": 1.401}, {"text": "But because it floats on\ntop of another liquid.", "start": 2554.351, "duration": 5.172}, {"text": "That's how you get the glass\nbecause so incredibly smooth.", "start": 2559.523, "duration": 3.17}, {"text": "- And ensure uniformity--", "start": 2562.693, "duration": 1.335}, {"text": "And there it is coming out.", "start": 2564.028, "duration": 1.434}, {"text": "There's a nice wide piece\nof glass coming out,", "start": 2565.462, "duration": 2.97}, {"text": "and what he says at the end of\nthis, there it is coming out.", "start": 2568.432, "duration": 3.137}, {"text": "[END PLAYBACK]", "start": 2571.569, "duration": 0.567}, {"text": "They can do kilometers\nand kilometers", "start": 2572.136, "duration": 1.635}, {"text": "per day of this float glass.", "start": 2573.771, "duration": 2.569}, {"text": "You float it over molten tin.", "start": 2576.34, "duration": 2.402}, {"text": "The tin acts like this\nreally nice smooth surface", "start": 2578.742, "duration": 3.838}, {"text": "that you put the\nglass on top of.", "start": 2582.58, "duration": 2.369}, {"text": "So one liquid on top of\nanother makes a very nice", "start": 2584.949, "duration": 2.535}, {"text": "smooth interface.", "start": 2587.484, "duration": 1.469}, {"text": "And what he talks about, which\nis what I wanted to capture,", "start": 2588.953, "duration": 2.469}, {"text": "is how important\nthat cooling is.", "start": 2591.422, "duration": 2.169}, {"text": "So the line has to go\nin a very particular way", "start": 2593.591, "duration": 3.37}, {"text": "after it comes out,\nas you cool it,", "start": 2596.961, "duration": 1.868}, {"text": "and because it's all\nabout the cooling.", "start": 2598.829, "duration": 2.87}, {"text": "As you come all the way back\ndown to here, room temperature,", "start": 2601.699, "duration": 5.105}, {"text": "right, or as I--", "start": 2606.804, "duration": 1.401}, {"text": "maybe as I went through\nthis transition,", "start": 2608.205, "duration": 2.636}, {"text": "what's happening inside?", "start": 2610.841, "duration": 2.903}, {"text": "Am I creating a lot of stress?", "start": 2613.744, "duration": 2.369}, {"text": "We just learned about stress.", "start": 2616.113, "duration": 1.502}, {"text": "Am I creating a lot of stress?", "start": 2617.615, "duration": 1.267}, {"text": "Right, or is it going\nto cool in a nice way?", "start": 2618.882, "duration": 2.97}, {"text": "Are there going to\nbe cracks that form?", "start": 2621.852, "duration": 2.703}, {"text": "So that is one of the\nmost important processing", "start": 2624.555, "duration": 2.836}, {"text": "parameters.", "start": 2627.391, "duration": 2.102}, {"text": "What we'll learn next week is\nthat chemistry is also a really", "start": 2629.493, "duration": 4.404}, {"text": "important pressing parameter.", "start": 2633.897, "duration": 1.235}, {"text": "And that's why you have\nsuch good phone screens.", "start": 2635.132, "duration": 2.169}, {"text": "Actually, you don't really,\nbecause they always break,", "start": 2637.301, "duration": 2.836}, {"text": "but they would break even more\nif it weren't for chemistry.", "start": 2640.137, "duration": 3.504}, {"text": "OK, but certainly cooling\nspeed is really important.", "start": 2643.641, "duration": 3.47}, {"text": "So let's go to the--", "start": 2647.111, "duration": 1.601}, {"text": "OK, now how--", "start": 2648.712, "duration": 1.635}, {"text": "OK, if you look\nat glass, remember", "start": 2650.347, "duration": 3.203}, {"text": "I said that it's got order or no\norder, crystalline, amorphous,", "start": 2653.55, "duration": 3.938}, {"text": "crystalline, amorphous.", "start": 2657.488, "duration": 1.868}, {"text": "How do you tell\nwhich one you have?", "start": 2659.356, "duration": 1.735}, {"text": "Who can tell me?", "start": 2661.091, "duration": 2.67}, {"text": "You just learned about it.", "start": 2663.761, "duration": 3.503}, {"text": "What do you do to see if\nsomething is a crystal", "start": 2667.264, "duration": 2.269}, {"text": "and which crystal it is?", "start": 2669.533, "duration": 2.402}, {"text": "You shine x-rays on it.", "start": 2671.935, "duration": 1.435}, {"text": "You go to your x-ray source,\nand you just shine it on,", "start": 2673.37, "duration": 2.536}, {"text": "and you measure\nwhere it bounces off.", "start": 2675.906, "duration": 2.302}, {"text": "But see-- so if you did that,\nso if you look in the circle,", "start": 2678.208, "duration": 3.337}, {"text": "they look the same.", "start": 2681.545, "duration": 2.336}, {"text": "They look the same.", "start": 2683.881, "duration": 1.234}, {"text": "That's crystalline.", "start": 2685.115, "duration": 1.101}, {"text": "That's quartz.", "start": 2686.216, "duration": 0.901}, {"text": "This is glass.", "start": 2687.117, "duration": 1.201}, {"text": "Quartz, glass,\ncrystalline, amorphous.", "start": 2688.318, "duration": 2.236}, {"text": "Right, but if you go to the long\nrange order, there isn't any.", "start": 2690.554, "duration": 3.57}, {"text": "So if I shine x-rays, these are\ntwo different types of solids.", "start": 2694.124, "duration": 3.27}, {"text": "Think about it like DCC\nFCC, but they're not.", "start": 2697.394, "duration": 2.169}, {"text": "They're more complicated\nof quartz or of silicates.", "start": 2699.563, "duration": 5.806}, {"text": "This is what glass\nwould look like.", "start": 2705.369, "duration": 2.402}, {"text": "Look at that.", "start": 2707.771, "duration": 1.302}, {"text": "There's still like a little\nbit of a peak there, but not", "start": 2709.073, "duration": 2.335}, {"text": "really, right, because this\nis from the short range order,", "start": 2711.408, "duration": 2.936}, {"text": "but here's the important\npart, which is where--", "start": 2714.344, "duration": 3.704}, {"text": "you can still, even\nthough it's not", "start": 2718.048, "duration": 2.236}, {"text": "that everything is where\nyou think it is, right,", "start": 2720.284, "duration": 2.669}, {"text": "because it in a crystal, you\nknow everything's BCC or FCC.", "start": 2722.953, "duration": 4.004}, {"text": "Every lattice is the same.", "start": 2726.957, "duration": 1.201}, {"text": "You know you can\ncount on it for 10", "start": 2728.158, "duration": 1.468}, {"text": "to the 20 second repetitions.", "start": 2729.626, "duration": 2.303}, {"text": "Here you can't.", "start": 2731.929, "duration": 0.934}, {"text": "You can still control\nthe properties.", "start": 2732.863, "duration": 2.87}, {"text": "You can still control\nthe properties.", "start": 2735.733, "duration": 1.634}, {"text": "So the properties can\nbe highly engineered.", "start": 2737.367, "duration": 3.738}, {"text": "And here's an example.", "start": 2741.105, "duration": 1.034}, {"text": "So these are different\ntypes of glass.", "start": 2745.976, "duration": 1.902}, {"text": "This is a glass cup, and\nthis is a glass bottle.", "start": 2747.878, "duration": 5.305}, {"text": "And you might think,\nit's just glass.", "start": 2753.183, "duration": 2.236}, {"text": "No.", "start": 2755.419, "duration": 2.035}, {"text": "It's not just glass.", "start": 2757.454, "duration": 1.068}, {"text": "It's very complicated mixtures\nof silica with other things.", "start": 2758.522, "duration": 7.608}, {"text": "Notice, it's got soda.", "start": 2766.13, "duration": 1.901}, {"text": "This is-- like I said,\nthis is not soda,", "start": 2768.031, "duration": 1.836}, {"text": "but it comes from soda, so\nit's called soda, sodium", "start": 2769.867, "duration": 2.135}, {"text": "oxide in Na2O.", "start": 2772.002, "duration": 2.603}, {"text": "Lime CaO, magnesia, alumina.", "start": 2774.605, "duration": 5.639}, {"text": "All the glass-- you know, unless\nyou pay a whole lot of money", "start": 2780.244, "duration": 3.303}, {"text": "for something made of quartz,\nalmost all the glass you buy", "start": 2783.547, "duration": 5.339}, {"text": "has this kind of stuff in it.", "start": 2788.886, "duration": 2.335}, {"text": "In fact, 90% of all glass\nis called soda glass,", "start": 2791.221, "duration": 3.537}, {"text": "because it's got--", "start": 2794.758, "duration": 0.834}, {"text": "that's this one here.", "start": 2795.592, "duration": 0.868}, {"text": "That's this cup, because\nit's got sodium oxide in it.", "start": 2796.46, "duration": 4.438}, {"text": "And the question is why.", "start": 2800.898, "duration": 1.902}, {"text": "Why do we put these\nthings in glass?", "start": 2802.8, "duration": 2.435}, {"text": "Why did we used to\nput lead in glass?", "start": 2805.235, "duration": 2.703}, {"text": "In fact, the history is pretty--", "start": 2807.938, "duration": 3.103}, {"text": "goes back thousands of years.", "start": 2811.041, "duration": 1.535}, {"text": "And I found this.", "start": 2812.576, "duration": 0.901}, {"text": "If you go to ancient\nRome, they made glass,", "start": 2813.477, "duration": 3.036}, {"text": "and you can look at what\nthey made glass out of.", "start": 2816.513, "duration": 2.002}, {"text": "They had a little\nbit less silica.", "start": 2818.515, "duration": 1.635}, {"text": "But they mixed all\nsorts of things in.", "start": 2820.15, "duration": 2.803}, {"text": "They did not have\n3091 back then,", "start": 2822.953, "duration": 4.538}, {"text": "so they didn't really\nknow why this was doing", "start": 2827.491, "duration": 2.803}, {"text": "something useful, but it was.", "start": 2830.294, "duration": 3.57}, {"text": "Now we mix all these oxides,\nremember I wrote some of them", "start": 2833.864, "duration": 2.97}, {"text": "up here, lime, soda.", "start": 2836.834, "duration": 2.602}, {"text": "We mix those in, and we mix\nall sorts of other things in,", "start": 2839.436, "duration": 3.404}, {"text": "but now we know why.", "start": 2842.84, "duration": 2.635}, {"text": "And the reason why is\nall about the chemistry,", "start": 2845.475, "duration": 3.371}, {"text": "and it all goes back to\nthis picture right here.", "start": 2848.846, "duration": 3.903}, {"text": "It all goes back to exactly this\nLewis structure that I started", "start": 2852.749, "duration": 4.305}, {"text": "with, which is not on the--", "start": 2857.054, "duration": 2.569}, {"text": "stop it.", "start": 2859.623, "duration": 1.101}, {"text": "No.", "start": 2860.724, "duration": 1.301}, {"text": "It's stuck here.", "start": 2862.025, "duration": 2.169}, {"text": "Maybe it's here.", "start": 2864.194, "duration": 1.669}, {"text": "Yes.", "start": 2865.863, "duration": 2.335}, {"text": "That made me happy.", "start": 2868.198, "duration": 2.102}, {"text": "This all goes back\nto the chemistry.", "start": 2870.3, "duration": 3.704}, {"text": "If I deliver, if I deliver\ninto this system something that", "start": 2874.004, "duration": 6.673}, {"text": "gives me charged oxygens,\nsomething that provides", "start": 2880.677, "duration": 4.605}, {"text": "a little bit of O\nminus or O2 minus,", "start": 2885.282, "duration": 3.57}, {"text": "then I could cut this bond back.", "start": 2888.852, "duration": 2.202}, {"text": "I can cut this all the way\nback to the original silicate,", "start": 2891.054, "duration": 3.904}, {"text": "sort of.", "start": 2894.958, "duration": 1.635}, {"text": "If I had an oxygen\nwith charge on it,", "start": 2896.593, "duration": 2.269}, {"text": "I can go from here back to\nwhere I started, right there,", "start": 2898.862, "duration": 6.073}, {"text": "at least for that bond, right?", "start": 2904.935, "duration": 2.669}, {"text": "And so what every single one\nof these things has in common", "start": 2907.604, "duration": 3.304}, {"text": "is that it can provide\ninto the system", "start": 2910.908, "duration": 3.37}, {"text": "a charged oxygen, a\ncharged oxygen atom.", "start": 2914.278, "duration": 3.103}, {"text": "If this dissociates, it gives\nwe Ca2 plus and O2 minus.", "start": 2917.381, "duration": 3.837}, {"text": "If this dissociates, it gives me\ntwo Na pluses and an O2 minus.", "start": 2921.218, "duration": 3.437}, {"text": "Oh, a pattern is forming\nhere, O2 minus, O2 minus,", "start": 2924.655, "duration": 4.904}, {"text": "O2 minus all the way down.", "start": 2929.559, "duration": 2.603}, {"text": "So these modifiers, these things\nthat we use to engineer glass,", "start": 2932.162, "duration": 3.804}, {"text": "they give me the O2 minus,\nand that is the knife", "start": 2935.966, "duration": 6.273}, {"text": "that I use to cut this\nglass apart and modify", "start": 2942.239, "duration": 4.371}, {"text": "its properties, and\nit's where we're", "start": 2946.61, "duration": 1.501}, {"text": "going to pick up on Wednesday.", "start": 2948.111, "duration": 1.435}, {"text": "But because it's a Friday, I\nwant to throw t-shirts out.", "start": 2949.546, "duration": 2.97}, {"text": "We'll do more next week.", "start": 2953.65, "duration": 1.468}, {"text": "Have a really good\nholiday weekend.", "start": 2955.118, "duration": 3.337}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.992}, {"text": "[RUSTLING]", "start": 1.992, "duration": 0.996}, {"text": "[CLICKING]", "start": 2.988, "duration": 0.996}, {"text": "DAVID HSU: Welcome to\nanother lecture in my series", "start": 10.47, "duration": 2.25}, {"text": "on urban energy\nsystems and policy.", "start": 12.72, "duration": 3.07}, {"text": "Welcome back.", "start": 15.79, "duration": 0.78}, {"text": "Today I'd like to talk about\ncities and building energy", "start": 16.57, "duration": 5.59}, {"text": "policies.", "start": 22.16, "duration": 1.45}, {"text": "This is an area that I think is\nreally interesting for cities,", "start": 23.61, "duration": 3.09}, {"text": "but also representative\nof energy efficiency", "start": 26.7, "duration": 2.9}, {"text": "efforts in general.", "start": 29.6, "duration": 1.345}, {"text": "And so what I'll take\nyou through today", "start": 30.945, "duration": 1.625}, {"text": "is how me and many other\npeople in New York City", "start": 32.57, "duration": 4.86}, {"text": "help develop building energy\npolicies that we see continue", "start": 37.43, "duration": 2.91}, {"text": "to be aggressive today.", "start": 40.34, "duration": 2.53}, {"text": "And just to give you a sense\nof how this fits in a larger", "start": 42.87, "duration": 3.95}, {"text": "landscape around environmental\npolicy instruments and energy", "start": 46.82, "duration": 2.76}, {"text": "efficiency, this is from a\nchapter by Peter May in 2003.", "start": 49.58, "duration": 5.28}, {"text": "This is the sort of thing I'd\nread in graduate school quite", "start": 54.86, "duration": 2.73}, {"text": "a bit, maybe, at the time.", "start": 57.59, "duration": 1.95}, {"text": "And a lot of the\ndebate at the time", "start": 59.54, "duration": 2.04}, {"text": "was about command and\ncontrol regulation.", "start": 61.58, "duration": 2.22}, {"text": "What could government\nsimply command", "start": 63.8, "duration": 2.76}, {"text": "the industry or\nprivate actors to do?", "start": 66.56, "duration": 2.392}, {"text": "And of course, a lot of\ndebate at the time when", "start": 68.952, "duration": 1.958}, {"text": "I was in graduate school\nwas around charges", "start": 70.91, "duration": 2.1}, {"text": "and special taxes, most\nnotably carbon taxes.", "start": 73.01, "duration": 3.27}, {"text": "There had been a lot of\nsuccess in the 1980s and '90s", "start": 76.28, "duration": 3.12}, {"text": "with sulfur dioxide\nabatement taxes.", "start": 79.4, "duration": 2.82}, {"text": "It started during the\nfirst Bush administration.", "start": 82.22, "duration": 3.18}, {"text": "And a lot of economists\nlooked at this", "start": 85.4, "duration": 1.65}, {"text": "as an incredibly\neconomically efficient way", "start": 87.05, "duration": 1.98}, {"text": "to achieve environmental\npolicy outcomes.", "start": 89.03, "duration": 2.64}, {"text": "Of course, command\nand control regulation", "start": 91.67, "duration": 3.12}, {"text": "and charges and\nspecial taxes are not", "start": 94.79, "duration": 1.71}, {"text": "the only ways to achieve our\nenvironmental policy goals.", "start": 96.5, "duration": 4.05}, {"text": "Other ways are\neconomic regulation.", "start": 100.55, "duration": 3.12}, {"text": "Instead of incentivizing\nindustry to do certain things,", "start": 103.67, "duration": 3.4}, {"text": "we could also simply\npass standards, standards", "start": 107.07, "duration": 3.2}, {"text": "over what kinds of\ngoods can be sold", "start": 110.27, "duration": 1.86}, {"text": "or how certain services\ncan be delivered.", "start": 112.13, "duration": 3.742}, {"text": "We could give incentives\nor subsidies directly,", "start": 115.872, "duration": 1.958}, {"text": "including tax credits,\na notable feature", "start": 117.83, "duration": 2.43}, {"text": "of the Inflation Reduction Act.", "start": 120.26, "duration": 1.752}, {"text": "And of course,\ngovernment insurance", "start": 122.012, "duration": 1.458}, {"text": "is a way to subsidize\nhigh-risk industries.", "start": 123.47, "duration": 2.31}, {"text": "For example, the\nnuclear industry", "start": 125.78, "duration": 1.8}, {"text": "is heavily insured\nby the government.", "start": 127.58, "duration": 2.5}, {"text": "Even then, it has not\nproven to be cost effective.", "start": 130.08, "duration": 3.38}, {"text": "Of course, other ways\nthat we provide services", "start": 133.46, "duration": 2.1}, {"text": "or vital services\nthrough government,", "start": 135.56, "duration": 1.89}, {"text": "the government can directly\nprovide those services.", "start": 137.45, "duration": 2.62}, {"text": "We can also have government\ncorporations and enterprises.", "start": 140.07, "duration": 3.71}, {"text": "Both examples exist, where\nthe government owns utilities,", "start": 143.78, "duration": 4.23}, {"text": "something we'll\ntalk about later.", "start": 148.01, "duration": 2.19}, {"text": "About 30% of electric utilities\nare owned by governments.", "start": 150.2, "duration": 3.9}, {"text": "And about 60% or 70%\nof water utilities", "start": 154.1, "duration": 2.88}, {"text": "are owned by governments.", "start": 156.98, "duration": 1.17}, {"text": "That's essentially direct\ngovernment provision.", "start": 158.15, "duration": 2.76}, {"text": "We can set up government\ncorporations--", "start": 160.91, "duration": 2.23}, {"text": "Amtrak is a government\ncorporation--", "start": 163.14, "duration": 2.45}, {"text": "or special enterprises.", "start": 165.59, "duration": 1.32}, {"text": "For example, if your city\nowns an airport or a utility,", "start": 166.91, "duration": 3.84}, {"text": "it may often be\non its own balance", "start": 170.75, "duration": 2.4}, {"text": "sheet, which is to say that\nit runs its own agency.", "start": 173.15, "duration": 2.52}, {"text": "It can issue its own bonds.", "start": 175.67, "duration": 1.5}, {"text": "It's run for hopefully\na profit for the city.", "start": 177.17, "duration": 3.21}, {"text": "But it essentially\nis an enterprise", "start": 180.38, "duration": 2.28}, {"text": "set up to serve the city.", "start": 182.66, "duration": 1.84}, {"text": "Of course, we know\nthat cities, because", "start": 184.5, "duration": 1.73}, {"text": "of their economic activity,\nand wealth, and population,", "start": 186.23, "duration": 3.21}, {"text": "have tremendous\npower to influence", "start": 189.44, "duration": 1.8}, {"text": "the market through\ncontracting and purchasing.", "start": 191.24, "duration": 2.4}, {"text": "Finally, there's\nother ways that we", "start": 196.38, "duration": 1.59}, {"text": "can try to achieve our\nmarket policy goals.", "start": 197.97, "duration": 2.04}, {"text": "We can implement\nsocial regulations.", "start": 200.01, "duration": 2.91}, {"text": "Vouchers are something\nthat's used quite a bit,", "start": 202.92, "duration": 2.02}, {"text": "let's say, in school choice, but\nsomething that could be used,", "start": 204.94, "duration": 3.08}, {"text": "let's say, in other\nareas of our policy.", "start": 208.02, "duration": 3.18}, {"text": "And tort liability\nis another aspect", "start": 211.2, "duration": 2.13}, {"text": "where, again, we can try\nto limit the liability", "start": 213.33, "duration": 2.79}, {"text": "of certain industries.", "start": 216.12, "duration": 1.14}, {"text": "That's essentially\nanother way to provide", "start": 217.26, "duration": 1.95}, {"text": "insurance or limited liability\nfor certain industries", "start": 219.21, "duration": 3.45}, {"text": "that we think might be high\nrisk or we want to encourage.", "start": 222.66, "duration": 3.255}, {"text": "And the thing I plan to\nspend most of my time", "start": 225.915, "duration": 1.875}, {"text": "talking about today\nis public information.", "start": 227.79, "duration": 2.46}, {"text": "We know the government has a\ntremendous role in providing", "start": 230.25, "duration": 2.55}, {"text": "information to the market.", "start": 232.8, "duration": 1.65}, {"text": "We know sometimes if the\nmarket doesn't have--", "start": 234.45, "duration": 2.22}, {"text": "or the market lacks information,\nit will not actually grow.", "start": 236.67, "duration": 3.09}, {"text": "Or it's very difficult\nfor private actors", "start": 239.76, "duration": 2.28}, {"text": "to accumulate the information\nthey need to make decisions.", "start": 242.04, "duration": 3.12}, {"text": "A good example, of\ncourse, is the census,", "start": 245.16, "duration": 1.83}, {"text": "which is embedded in\nthe US Constitution.", "start": 246.99, "duration": 2.13}, {"text": "We know the census is basically\nan essential instrument", "start": 249.12, "duration": 4.86}, {"text": "or essential data set\nfor many businesses", "start": 253.98, "duration": 2.88}, {"text": "to make their decisions.", "start": 256.86, "duration": 1.39}, {"text": "This is why the census\nis so important.", "start": 258.25, "duration": 3.315}, {"text": "And so this is\nsomething that also I've", "start": 261.565, "duration": 1.625}, {"text": "argued in many papers,\nbut just to highlight", "start": 263.19, "duration": 2.37}, {"text": "one paper I wrote in 2017.", "start": 265.56, "duration": 2.07}, {"text": "I hope the title is\ndirect and to the point.", "start": 267.63, "duration": 2.43}, {"text": "It's called Further\nOpportunities", "start": 270.06, "duration": 1.65}, {"text": "to Reduce the Energy\nUse and Greenhouse Gas", "start": 271.71, "duration": 2.13}, {"text": "Emissions of Buildings.", "start": 273.84, "duration": 1.47}, {"text": "It's in the Journal of Planning\nEducation and Research.", "start": 275.31, "duration": 2.37}, {"text": "My co-authors and I\nargued, essentially,", "start": 277.68, "duration": 2.58}, {"text": "that cities actually have many\nmore opportunities to reduce", "start": 280.26, "duration": 3.03}, {"text": "the energy use and greenhouse\ngas emissions of buildings,", "start": 283.29, "duration": 2.52}, {"text": "an area that I've argued\nto actually result", "start": 285.81, "duration": 2.67}, {"text": "in a lot of greenhouse gas\nemissions for countries.", "start": 288.48, "duration": 3.683}, {"text": "So to give you an\nexample of where", "start": 292.163, "duration": 1.417}, {"text": "they might have additional\npowers that we might not", "start": 293.58, "duration": 2.125}, {"text": "be using, cities collect\nabout 70% of local tax revenue", "start": 295.705, "duration": 4.895}, {"text": "and about 30% of all state\nand local taxes in the US.", "start": 300.6, "duration": 3.21}, {"text": "So through their tax power, they\nhave quite a bit of leverage", "start": 303.81, "duration": 3.42}, {"text": "over the private sector.", "start": 307.23, "duration": 3.3}, {"text": "In terms of infrastructure,\ncities and state and local", "start": 310.53, "duration": 2.82}, {"text": "governments own about\n50% or more than 50%", "start": 313.35, "duration": 2.79}, {"text": "of all infrastructure.", "start": 316.14, "duration": 1.35}, {"text": "They do about 75% of the\nspending on infrastructure.", "start": 317.49, "duration": 3.86}, {"text": "And as I mentioned before,\nwe often through cities", "start": 321.35, "duration": 2.85}, {"text": "own about a third of\nelectric utilities and 2/3", "start": 324.2, "duration": 2.97}, {"text": "of water utilities.", "start": 327.17, "duration": 1.683}, {"text": "And just to give you an\nexample of departments", "start": 328.853, "duration": 1.917}, {"text": "that you could work in in the\nfuture that might have leverage", "start": 330.77, "duration": 2.82}, {"text": "over potential decarbonization\nopportunities, the Department", "start": 333.59, "duration": 4.32}, {"text": "of Finance.", "start": 337.91, "duration": 0.99}, {"text": "The Department of\nFinance, again, this", "start": 338.9, "duration": 2.01}, {"text": "is where all those tax revenues\nare gathered and then disbursed", "start": 340.91, "duration": 4.2}, {"text": "into the city government.", "start": 345.11, "duration": 1.38}, {"text": "That gives you a\ntremendous amount of power", "start": 346.49, "duration": 1.83}, {"text": "if you control where\nthe money is raised", "start": 348.32, "duration": 2.143}, {"text": "and where it flows to.", "start": 350.463, "duration": 0.917}, {"text": "Also has tremendous\nimplications for equity.", "start": 351.38, "duration": 3.06}, {"text": "The law department is\nessential to find out--", "start": 354.44, "duration": 3.87}, {"text": "or to craft laws or policies\nthat are lawful and effective.", "start": 358.31, "duration": 4.99}, {"text": "The fire department\nobviously has", "start": 363.3, "duration": 1.4}, {"text": "codes over how buildings\nare built. Power, water,", "start": 364.7, "duration": 3.54}, {"text": "housing authorities.", "start": 368.24, "duration": 1.47}, {"text": "New York City in particular\nowns a tremendous amount", "start": 369.71, "duration": 2.88}, {"text": "of housing stock.", "start": 372.59, "duration": 0.9}, {"text": "Other large cities own\na lot of housing stock.", "start": 373.49, "duration": 2.73}, {"text": "And schools--\nschool buildings are", "start": 376.22, "duration": 1.68}, {"text": "where kids spend a lot of time.", "start": 377.9, "duration": 3.75}, {"text": "We have tremendous opportunities\nto improve the environment", "start": 381.65, "duration": 2.79}, {"text": "of school buildings.", "start": 384.44, "duration": 1.18}, {"text": "So to give you an example\nof some of the departments", "start": 385.62, "duration": 2.18}, {"text": "involved just in New York\nCity with the building sector,", "start": 387.8, "duration": 3.51}, {"text": "there's the Department of\nCitywide Administrative", "start": 391.31, "duration": 2.37}, {"text": "Services, DCAS; the Department\nof Design and Construction,", "start": 393.68, "duration": 3.57}, {"text": "DDC; the Department\nof Buildings, DOB;", "start": 397.25, "duration": 3.57}, {"text": "the Department of Finance,\nDOF; the Office of Long-Term", "start": 400.82, "duration": 3.51}, {"text": "Planning and Sustainability--\nat the time, it was OLTPS--", "start": 404.33, "duration": 3.54}, {"text": "and the New York City\nHousing Authority, NYCHA.", "start": 407.87, "duration": 2.46}, {"text": "All have a role to play\nin governing the building", "start": 410.33, "duration": 4.11}, {"text": "stock of New York City.", "start": 414.44, "duration": 2.96}, {"text": "So just to take a\ntrip down memory lane,", "start": 417.4, "duration": 2.85}, {"text": "there have been a variety of New\nYork City sustainability plans.", "start": 420.25, "duration": 2.7}, {"text": "I actually wrote that one on\nthe left, Sustainable New York", "start": 422.95, "duration": 2.55}, {"text": "City.", "start": 425.5, "duration": 0.6}, {"text": "I wrote it as a fellow for the\ndesign trust of New York City.", "start": 426.1, "duration": 4.17}, {"text": "It was one of the first\nsustainability plans written", "start": 430.27, "duration": 3.45}, {"text": "for New York City.", "start": 433.72, "duration": 1.77}, {"text": "I also worked as\na fellow on one of", "start": 435.49, "duration": 1.8}, {"text": "the first internal government\nsustainability plans,", "start": 437.29, "duration": 2.13}, {"text": "started in 2003.", "start": 439.42, "duration": 2.04}, {"text": "And in 2005, the\ncity of New York", "start": 441.46, "duration": 2.61}, {"text": "issued their first what\nthey called PlaNYC 2030.", "start": 444.07, "duration": 4.14}, {"text": "It reads as Plan NYC.", "start": 448.21, "duration": 2.58}, {"text": "It was issued in 2005\nor developed in 2005", "start": 450.79, "duration": 2.88}, {"text": "and I think issued 2006.", "start": 453.67, "duration": 1.83}, {"text": "But it was a comprehensive suite\nof plans from the Bloomberg", "start": 455.5, "duration": 3.09}, {"text": "administration to try to improve\nthe environment in New York", "start": 458.59, "duration": 3.15}, {"text": "City and frankly to\nestablish New York City", "start": 461.74, "duration": 2.31}, {"text": "as an environmental leader.", "start": 464.05, "duration": 1.98}, {"text": "The plan was updated\nin 2011, which", "start": 466.03, "duration": 2.37}, {"text": "is the cover on the right.", "start": 468.4, "duration": 3.01}, {"text": "And so to take us back\nfor a second where", "start": 471.41, "duration": 2.81}, {"text": "the environmental discussion\nwas at the time, this,", "start": 474.22, "duration": 2.43}, {"text": "again, is the McKinsey 2007\ngreenhouse gas reduction", "start": 476.65, "duration": 3.18}, {"text": "report that I showed you.", "start": 479.83, "duration": 1.23}, {"text": "This the marginal\nabatement curve.", "start": 481.06, "duration": 1.92}, {"text": "The argument I made to\nyou last time in class", "start": 482.98, "duration": 2.4}, {"text": "was that you should be on the\nleft-hand side of the curve", "start": 485.38, "duration": 2.43}, {"text": "because these are\nall negative costs.", "start": 487.81, "duration": 1.71}, {"text": "These should be easy things\nfor you to sell in your career.", "start": 489.52, "duration": 3.15}, {"text": "These right-hand side\nthings may be necessary", "start": 492.67, "duration": 2.55}, {"text": "but are harder to sell\nsimply because it costs money", "start": 495.22, "duration": 2.43}, {"text": "to reduce greenhouse\ngas emissions.", "start": 497.65, "duration": 1.5}, {"text": "Again, on the left-hand side,\nwe can save money and reduce", "start": 499.15, "duration": 3.42}, {"text": "greenhouse gas emissions.", "start": 502.57, "duration": 1.218}, {"text": "But if you look\nclosely at everything", "start": 503.788, "duration": 1.542}, {"text": "on the left-hand side, you'll\nnotice that everything here is", "start": 505.33, "duration": 2.97}, {"text": "essentially buildings related.", "start": 508.3, "duration": 1.44}, {"text": "We have residential electronics,\nresidential buildings,", "start": 509.74, "duration": 2.59}, {"text": "commercial buildings,\nresidential water heaters,", "start": 512.33, "duration": 2.63}, {"text": "commercial buildings\ncontrol systems,", "start": 514.96, "duration": 1.98}, {"text": "and more commercial electronics,\nvirtual lighting, and so on.", "start": 516.94, "duration": 3.31}, {"text": "So many things on\nthe left-hand side", "start": 520.25, "duration": 1.909}, {"text": "save money, reduce\ngreenhouse gas emissions,", "start": 522.159, "duration": 2.281}, {"text": "and are related to buildings.", "start": 524.44, "duration": 2.51}, {"text": "And so just to again\nmaybe emphasize", "start": 526.95, "duration": 2.52}, {"text": "the importance of the New\nYork City building sector,", "start": 529.47, "duration": 2.207}, {"text": "we know it's some of the\nmost valuable real estate", "start": 531.677, "duration": 2.083}, {"text": "in the world.", "start": 533.76, "duration": 0.85}, {"text": "And just to break it down\nfor a moment, at the time,", "start": 534.61, "duration": 3.98}, {"text": "the New York City\ngovernment thought about 75%", "start": 538.59, "duration": 2.7}, {"text": "of all greenhouse gas\nemissions come from buildings.", "start": 541.29, "duration": 3.0}, {"text": "The sector size is roughly\nabout 1 million total buildings", "start": 544.29, "duration": 3.09}, {"text": "in New York City.", "start": 547.38, "duration": 1.26}, {"text": "And a key point that\ninfluenced the policymaking", "start": 548.64, "duration": 3.57}, {"text": "around how to affect\nexisting buildings", "start": 552.21, "duration": 2.79}, {"text": "was that one estimate was that\n85% of all buildings in New", "start": 555.0, "duration": 3.6}, {"text": "York City that would be\nthere in 2030 already exist.", "start": 558.6, "duration": 3.39}, {"text": "And I think roughly 70%\nof all the buildings", "start": 561.99, "duration": 2.55}, {"text": "that will be there in\n2050 are already existing.", "start": 564.54, "duration": 2.64}, {"text": "So if you want to influence the\nenergy use or greenhouse gas", "start": 567.18, "duration": 3.39}, {"text": "emissions of buildings, you have\nto influence the buildings that", "start": 570.57, "duration": 2.88}, {"text": "are already there.", "start": 573.45, "duration": 0.81}, {"text": "We know New York City's\nalready tremendously dense.", "start": 574.26, "duration": 2.125}, {"text": "It's already\ntremendously valuable.", "start": 576.385, "duration": 1.605}, {"text": "How do we get these owners and\nthese privately owned buildings", "start": 577.99, "duration": 3.92}, {"text": "to change their energy use?", "start": 581.91, "duration": 2.7}, {"text": "And again there's one\npoint that came out", "start": 584.61, "duration": 2.37}, {"text": "of some of the analyses\nof the property tax data.", "start": 586.98, "duration": 3.42}, {"text": "It was large versus\nsmall buildings.", "start": 590.4, "duration": 1.98}, {"text": "Only 2% of all buildings New\nYork City are above 50,000", "start": 592.38, "duration": 3.18}, {"text": "square feet, but they\nrepresented about 50-- a half--", "start": 595.56, "duration": 3.36}, {"text": "50% of all New York\nCity square footage.", "start": 598.92, "duration": 2.97}, {"text": "And one estimate\nwas they roughly", "start": 601.89, "duration": 2.55}, {"text": "were responsible for about\n48% of all the energy", "start": 604.44, "duration": 2.46}, {"text": "use in the city.", "start": 606.9, "duration": 0.9}, {"text": "I can't actually find\na source for that.", "start": 607.8, "duration": 1.89}, {"text": "And honestly, some of\nthese numbers at the time,", "start": 609.69, "duration": 3.07}, {"text": "looking back at it, I'm not sure\nhow strong the sourcing was.", "start": 612.76, "duration": 3.08}, {"text": "But this definitely influenced\nhow environmental policies", "start": 615.84, "duration": 2.67}, {"text": "were made in New York City.", "start": 618.51, "duration": 1.235}, {"text": "And of course, we know\nthere's tremendous diversity", "start": 619.745, "duration": 2.125}, {"text": "in buildings in New York City.", "start": 621.87, "duration": 1.355}, {"text": "We have commercial buildings,\nindustrial buildings,", "start": 623.225, "duration": 2.125}, {"text": "institutional buildings,\nlike hospitals and schools.", "start": 625.35, "duration": 2.97}, {"text": "We have multifamily residential.", "start": 628.32, "duration": 1.5}, {"text": "We have mixed-use buildings.", "start": 629.82, "duration": 1.2}, {"text": "And those are the\nlarge buildings alone.", "start": 631.02, "duration": 1.78}, {"text": "We know that of the\nmillion buildings,", "start": 632.8, "duration": 1.64}, {"text": "a lot of those\nmillion buildings may", "start": 634.44, "duration": 1.5}, {"text": "be single-family\nhomes or relatively", "start": 635.94, "duration": 1.68}, {"text": "small multifamily buildings\nin the outer boroughs.", "start": 637.62, "duration": 3.09}, {"text": "But we know that the large\nbuildings are also themselves", "start": 640.71, "duration": 3.21}, {"text": "tremendously diverse.", "start": 643.92, "duration": 1.17}, {"text": "Just take, for example, a\ncampus like Columbia or NYU.", "start": 645.09, "duration": 3.81}, {"text": "Those campuses have large\nnumbers of buildings,", "start": 648.9, "duration": 2.25}, {"text": "a lot of real estate.", "start": 651.15, "duration": 0.92}, {"text": "And even their buildings are\nused for many different things,", "start": 652.07, "duration": 2.5}, {"text": "both for University\npurposes and also,", "start": 654.57, "duration": 2.01}, {"text": "let's say, for rental or lease.", "start": 656.58, "duration": 2.49}, {"text": "And so the question\nI want to get to", "start": 659.07, "duration": 1.86}, {"text": "is, how do you know which\nbuildings to implement", "start": 660.93, "duration": 2.49}, {"text": "energy efficiency in?", "start": 663.42, "duration": 1.81}, {"text": "I've talked about\npolicy analysis", "start": 665.23, "duration": 1.49}, {"text": "in terms of\nefficiency and equity.", "start": 666.72, "duration": 2.22}, {"text": "But ultimately, you have\nto think back to maybe", "start": 668.94, "duration": 2.64}, {"text": "about 15 years\nago, when we first", "start": 671.58, "duration": 1.89}, {"text": "started looking at\nthe sector, people", "start": 673.47, "duration": 1.8}, {"text": "didn't actually have any\ndata about the energy", "start": 675.27, "duration": 2.19}, {"text": "use in buildings.", "start": 677.46, "duration": 1.08}, {"text": "The utility only had energy\ntracked to the meter.", "start": 678.54, "duration": 4.47}, {"text": "But in general, because of\nthe tenant-landlord problem", "start": 683.01, "duration": 2.25}, {"text": "that we've talked about\nbefore, only tenants often", "start": 685.26, "duration": 3.0}, {"text": "get their electricity bills.", "start": 688.26, "duration": 1.59}, {"text": "Or in some cases, only\nlandlords get electricity bills.", "start": 689.85, "duration": 2.49}, {"text": "So tenants don't always know\nwhat energy the landlords are", "start": 692.34, "duration": 3.69}, {"text": "paying for, let's say, in a\nsmall multifamily building.", "start": 696.03, "duration": 3.21}, {"text": "Or if you're in a large\ncommercial building,", "start": 699.24, "duration": 1.89}, {"text": "and you're a landlord,\nyou didn't actually", "start": 701.13, "duration": 1.75}, {"text": "know what the tenants\nwere paying for.", "start": 702.88, "duration": 1.76}, {"text": "Even if they're, let's say,\na large bank or law firm,", "start": 704.64, "duration": 2.46}, {"text": "you had no sense of how much\nenergy they were paying for.", "start": 707.1, "duration": 3.06}, {"text": "So you had this kind of\nfragmented information", "start": 710.16, "duration": 2.31}, {"text": "landscape.", "start": 712.47, "duration": 2.61}, {"text": "And so a lot of the data\nwe started to gather--", "start": 715.08, "duration": 3.9}, {"text": "I'll go through the policies\nthat created the data first.", "start": 718.98, "duration": 2.83}, {"text": "But there was a lot of\nexcitement about New York", "start": 721.81, "duration": 2.0}, {"text": "City in the early\ndays about gathering", "start": 723.81, "duration": 2.22}, {"text": "the data because the New\nYork City laws that were", "start": 726.03, "duration": 2.43}, {"text": "passed mandated gathering data.", "start": 728.46, "duration": 3.09}, {"text": "So just to give\ncredit where it's due,", "start": 731.55, "duration": 3.24}, {"text": "first, the Institute for Market\nTransformation on the left", "start": 734.79, "duration": 3.36}, {"text": "started publishing reports\non the opportunities", "start": 738.15, "duration": 3.27}, {"text": "for building energy\ntransparency.", "start": 741.42, "duration": 1.923}, {"text": "And they really started\nto develop a framework", "start": 743.343, "duration": 1.917}, {"text": "for implementing US commercial\nenergy rating and disclosure", "start": 745.26, "duration": 3.0}, {"text": "policies.", "start": 748.26, "duration": 1.3}, {"text": "They also I think deserve\na tremendous amount", "start": 749.56, "duration": 2.21}, {"text": "of credit for going to\nlots of cities and states,", "start": 751.77, "duration": 4.74}, {"text": "showing them how it\ncould work, and helping", "start": 756.51, "duration": 2.16}, {"text": "to write legislation\nfor how it could work.", "start": 758.67, "duration": 1.952}, {"text": "So essentially, I\nthink they are lobbying", "start": 760.622, "duration": 1.708}, {"text": "for a great\nenvironmental policy.", "start": 762.33, "duration": 1.83}, {"text": "And Cliff Majersik, Andrew\nBurr, Caroline Keicher,", "start": 764.16, "duration": 2.85}, {"text": "and David Leipziger all deserve\na tremendous amount of credit.", "start": 767.01, "duration": 4.17}, {"text": "New York City, the law I'll\nfocus on mostly is local Law", "start": 771.18, "duration": 3.36}, {"text": "84, a benchmarking report.", "start": 774.54, "duration": 2.55}, {"text": "A lot of work was done by Laurie\nKerr, John Lee, Hilary Bieber,", "start": 777.09, "duration": 4.14}, {"text": "Donna Hope, Stacy Lee, and Jenny\nCooper at the City of New York.", "start": 781.23, "duration": 3.75}, {"text": "And then a variety of\npeople worked on it", "start": 784.98, "duration": 3.03}, {"text": "from various sectors, including\nme, Constantine Kontokosta", "start": 788.01, "duration": 3.96}, {"text": "from NYU, Adam Hinge\nfrom Sustainable Building", "start": 791.97, "duration": 2.61}, {"text": "Partnerships, and Alexandra\nSullivan from the EPA.", "start": 794.58, "duration": 2.88}, {"text": "And then just most recently,\na lot of work on this area", "start": 797.46, "duration": 2.49}, {"text": "has been done by Urban\nGreen Council, including", "start": 799.95, "duration": 2.28}, {"text": "Sean Brennan, Adam Schiabor,\nSheena Thiruselvan, Chris", "start": 802.23, "duration": 4.47}, {"text": "Anjesky, and John Mandyck\nfrom the Urban Green Council.", "start": 806.7, "duration": 3.78}, {"text": "So how do we get to this data?", "start": 810.48, "duration": 5.07}, {"text": "The key point was\nNew York City passed", "start": 815.55, "duration": 2.64}, {"text": "a series of building policies.", "start": 818.19, "duration": 1.77}, {"text": "And the key point I want to\nmake is that many buildings", "start": 819.96, "duration": 2.55}, {"text": "were already--", "start": 822.51, "duration": 2.02}, {"text": "many building\nowners were already", "start": 824.53, "duration": 1.61}, {"text": "doing a lot of things\nfor energy efficiency.", "start": 826.14, "duration": 2.13}, {"text": "As I said before, New\nYork City has jurisdiction", "start": 828.27, "duration": 2.82}, {"text": "over buildings-- the\nDepartment of Finance,", "start": 831.09, "duration": 1.83}, {"text": "the Department of Buildings.", "start": 832.92, "duration": 1.63}, {"text": "But what happened after\nPlaNYC 2030 came out in 2006", "start": 834.55, "duration": 4.49}, {"text": "was developed what's called the\nGreater Greener Buildings Plan.", "start": 839.04, "duration": 3.78}, {"text": "And that passed\na series of laws.", "start": 842.82, "duration": 2.85}, {"text": "The New York City Energy\nEfficiency Corporation, NYCEEC,", "start": 845.67, "duration": 2.73}, {"text": "was set up.", "start": 848.4, "duration": 1.89}, {"text": "Local Law 85 in 2009 was set up\nto pass a New York City energy", "start": 850.29, "duration": 4.44}, {"text": "conservation code, NYCECC.", "start": 854.73, "duration": 4.8}, {"text": "Local Law 88 was\nalso passed in 2009", "start": 859.53, "duration": 2.82}, {"text": "to encourage a more efficient\nlighting and sub metering.", "start": 862.35, "duration": 3.96}, {"text": "To think back to the\nenergy efficiency lecture", "start": 866.31, "duration": 2.67}, {"text": "from last time,\nconservation codes", "start": 868.98, "duration": 2.58}, {"text": "have been around a\nlong time, since 1970s.", "start": 871.56, "duration": 2.7}, {"text": "As I said to you,\naround 2008, 2009,", "start": 874.26, "duration": 2.605}, {"text": "there's a tremendous\namount of interest", "start": 876.865, "duration": 1.625}, {"text": "in making building codes much\nmore aggressive to deliver", "start": 878.49, "duration": 3.42}, {"text": "faster energy savings.", "start": 881.91, "duration": 1.83}, {"text": "For example, City of Seattle,\nwhere I used to work,", "start": 883.74, "duration": 2.61}, {"text": "has had since the 1970s or '80s\na person in charge of energy", "start": 886.35, "duration": 4.38}, {"text": "code who did tremendous work.", "start": 890.73, "duration": 2.43}, {"text": "But the energy code\nis only designed", "start": 893.16, "duration": 1.5}, {"text": "to deliver about 1% or\n2% improvement per year.", "start": 894.66, "duration": 2.85}, {"text": "In 2008, 2009, the\nObama administration", "start": 897.51, "duration": 2.73}, {"text": "and many cities starting looking\nto building codes to develop--", "start": 900.24, "duration": 3.78}, {"text": "deliver much more aggressive\nsavings, more than 3%", "start": 904.02, "duration": 3.33}, {"text": "a year at times.", "start": 907.35, "duration": 2.31}, {"text": "Lighting and submetering, again,\nis essentially a no-brainer.", "start": 909.66, "duration": 3.24}, {"text": "Because of the rise of light\nemitting diodes, or LEDs,", "start": 912.9, "duration": 3.57}, {"text": "we have much more efficient\nlighting than we did before.", "start": 916.47, "duration": 2.83}, {"text": "And submetering was designed\nto give buildings control", "start": 919.3, "duration": 3.32}, {"text": "over subareas of the building.", "start": 922.62, "duration": 2.323}, {"text": "Of course, this is\nessentially something", "start": 924.943, "duration": 1.667}, {"text": "that's built into\nmost modern buildings.", "start": 926.61, "duration": 2.29}, {"text": "So this is something that\nsome high-value buildings", "start": 928.9, "duration": 4.28}, {"text": "were already doing.", "start": 933.18, "duration": 0.97}, {"text": "And so you want to reward\nowners for doing those things.", "start": 934.15, "duration": 3.76}, {"text": "The policy I'll talk about\ntoday is Local Law 84 in 2009.", "start": 937.91, "duration": 4.2}, {"text": "It's the benchmarking\nand disclosure policy.", "start": 942.11, "duration": 2.7}, {"text": "It essentially sought to solve\nthe landlord-tenant problem", "start": 944.81, "duration": 2.79}, {"text": "that I talked about before.", "start": 947.6, "duration": 1.347}, {"text": "It essentially simply said, if\nyou're the owner of a building,", "start": 948.947, "duration": 2.583}, {"text": "you have to go gather the\nbills for your tenants.", "start": 951.53, "duration": 2.22}, {"text": "It's not actually that hard.", "start": 953.75, "duration": 1.47}, {"text": "You simply have to send a\nmessage to your tenants,", "start": 955.22, "duration": 3.0}, {"text": "gather the data, maybe\nhire a consultant to put it", "start": 958.22, "duration": 2.76}, {"text": "into the EPA database together.", "start": 960.98, "duration": 2.228}, {"text": "But a lot of the\ninfrastructure was already", "start": 963.208, "duration": 1.792}, {"text": "built by the EPA for the\nEnergy Star rating system.", "start": 965.0, "duration": 4.232}, {"text": "But I'll talk more about\nwhat the effects of this law", "start": 969.232, "duration": 2.208}, {"text": "were later on.", "start": 971.44, "duration": 2.0}, {"text": "And of course, Local\nLaw 87 passed in 2009.", "start": 973.44, "duration": 3.03}, {"text": "It required energy audits\nand retro-commissioning.", "start": 976.47, "duration": 2.55}, {"text": "An energy audit is a much\nmore detailed, in-depth view", "start": 979.02, "duration": 3.57}, {"text": "of a building.", "start": 982.59, "duration": 0.75}, {"text": "Think of it as\ngetting a car tune-up.", "start": 983.34, "duration": 2.31}, {"text": "You take it to the\nshop, and the mechanic", "start": 985.65, "duration": 2.79}, {"text": "tells you all the\nthings that work", "start": 988.44, "duration": 2.07}, {"text": "and don't work\nwith your building.", "start": 990.51, "duration": 1.95}, {"text": "Retro-commissioning\nis the next step.", "start": 992.46, "duration": 1.95}, {"text": "That's essentially\na process where", "start": 994.41, "duration": 1.74}, {"text": "you turn all the dials in a\nbuilding to tune it up again.", "start": 996.15, "duration": 3.038}, {"text": "In other words, once you know\nwhat's wrong with the building,", "start": 999.188, "duration": 2.542}, {"text": "you read the manual.", "start": 1001.73, "duration": 1.11}, {"text": "You make sure it's performing\nas the designers intended it to.", "start": 1002.84, "duration": 3.81}, {"text": "Local Law 87 requires I\nthink 10% of buildings", "start": 1006.65, "duration": 3.69}, {"text": "in a given year to\nundergo an energy audit", "start": 1010.34, "duration": 2.43}, {"text": "retro-commissioning.", "start": 1012.77, "duration": 0.96}, {"text": "This is a much more\nin-depth procedure.", "start": 1013.73, "duration": 2.113}, {"text": "But we have plenty\nof empirical evidence", "start": 1015.843, "duration": 1.667}, {"text": "that energy audits and\nretro-commissioning is also", "start": 1017.51, "duration": 3.21}, {"text": "beneficial.", "start": 1020.72, "duration": 0.81}, {"text": "I think Evan Mills from Lawrence\nBerkeley National Labs in 2011", "start": 1021.53, "duration": 3.75}, {"text": "wrote a paper arguing that,\nbased on 600 buildings or so,", "start": 1025.28, "duration": 4.89}, {"text": "retro-commissioning on average\nwould deliver about 20%,", "start": 1030.17, "duration": 2.899}, {"text": "25% savings in energy.", "start": 1033.069, "duration": 1.991}, {"text": "That is a non-trivial amount.", "start": 1035.06, "duration": 2.49}, {"text": "Local Law 33 passed in 2017.", "start": 1037.55, "duration": 3.24}, {"text": "Gave letter grades for\nbuilding performance.", "start": 1040.79, "duration": 2.1}, {"text": "Just like you see on New\nYork City restaurants", "start": 1042.89, "duration": 2.429}, {"text": "an A, B, or, god\nforbid, a C grade,", "start": 1045.319, "duration": 4.741}, {"text": "buildings themselves would\nget grades for their energy", "start": 1050.06, "duration": 2.25}, {"text": "performance.", "start": 1052.31, "duration": 0.822}, {"text": "And you could think about\nhow benchmarking and letter", "start": 1053.132, "duration": 2.208}, {"text": "grades are meant to work.", "start": 1055.34, "duration": 1.105}, {"text": "Think about what\nyou'd do if you didn't", "start": 1056.445, "duration": 1.625}, {"text": "have this kind of information.", "start": 1058.07, "duration": 1.71}, {"text": "If you're a tenant\nseeking to, let's say,", "start": 1059.78, "duration": 2.49}, {"text": "rent a space in New York\nCity, and you don't actually", "start": 1062.27, "duration": 3.18}, {"text": "know how energy efficient\nany of the spaces are,", "start": 1065.45, "duration": 2.34}, {"text": "why would you pay\nmore for any space", "start": 1067.79, "duration": 2.4}, {"text": "if it's more energy efficient?", "start": 1070.19, "duration": 1.48}, {"text": "So actually,\nthere's no incentive", "start": 1071.67, "duration": 1.64}, {"text": "for the landlord to\ninvest energy efficiency", "start": 1073.31, "duration": 2.05}, {"text": "in the first place.", "start": 1075.36, "duration": 1.35}, {"text": "We'll talk more about that also.", "start": 1076.71, "duration": 2.09}, {"text": "Local Law 97 passed in 2019.", "start": 1078.8, "duration": 3.18}, {"text": "Was part of a, quote,\nunquote, \"Green New Deal\"", "start": 1081.98, "duration": 3.15}, {"text": "package meant to establish\nvery aggressive carbon", "start": 1085.13, "duration": 3.178}, {"text": "budgets for buildings.", "start": 1088.308, "duration": 0.917}, {"text": "It is something the New York\nCity government is working", "start": 1089.225, "duration": 2.295}, {"text": "on right now to implement.", "start": 1091.52, "duration": 2.7}, {"text": "So just to give you a sense\nalso where the energy efficiency", "start": 1094.22, "duration": 2.84}, {"text": "landscape was in\nabout 2009, 2010,", "start": 1097.06, "duration": 3.51}, {"text": "on the left-hand side, the\ncodes that were being upgraded.", "start": 1100.57, "duration": 3.72}, {"text": "You can see this kind\nof green landscape.", "start": 1104.29, "duration": 2.04}, {"text": "The darker green indicates\nthe more aggressive codes", "start": 1106.33, "duration": 3.63}, {"text": "in Florida and Massachusetts.", "start": 1109.96, "duration": 1.8}, {"text": "But you can see across\nthe country in 2009", "start": 1111.76, "duration": 2.97}, {"text": "that there is a Building Codes\nAssistance Project funded", "start": 1114.73, "duration": 3.33}, {"text": "by the Department of Energy.", "start": 1118.06, "duration": 1.26}, {"text": "And they're assisting\nall these jurisdictions,", "start": 1119.32, "duration": 2.82}, {"text": "all these states, in developing\nmore aggressive codes.", "start": 1122.14, "duration": 3.45}, {"text": "And the spectrum\nat the lower left", "start": 1125.59, "duration": 1.68}, {"text": "shows you how those\ncodes are getting", "start": 1127.27, "duration": 2.16}, {"text": "more aggressive over time.", "start": 1129.43, "duration": 1.98}, {"text": "In 2013, this map\non the right, you", "start": 1131.41, "duration": 3.01}, {"text": "can see that there are\nsome disclosure laws that", "start": 1134.42, "duration": 2.0}, {"text": "are nascent across the country.", "start": 1136.42, "duration": 1.47}, {"text": "It looks like about 15 or\n20 cities and states have", "start": 1137.89, "duration": 3.63}, {"text": "passed these disclosure laws.", "start": 1141.52, "duration": 2.01}, {"text": "But in 2013, none\nof the states--", "start": 1143.53, "duration": 2.34}, {"text": "none of the cities had really\ndeveloped a lot of data yet.", "start": 1145.87, "duration": 3.193}, {"text": "This is part of the reason why\nwe focused on New York City", "start": 1149.063, "duration": 2.417}, {"text": "so much.", "start": 1151.48, "duration": 0.66}, {"text": "New York City, as\nthe biggest city,", "start": 1152.14, "duration": 1.95}, {"text": "developed the largest\ndata sets that we", "start": 1154.09, "duration": 1.92}, {"text": "can do the most analysis on.", "start": 1156.01, "duration": 2.577}, {"text": "So just to give you a\nsense of how these two", "start": 1158.587, "duration": 1.833}, {"text": "different policies work,\non the left-hand side,", "start": 1160.42, "duration": 2.94}, {"text": "this is a famous graph\nyou might have seen.", "start": 1163.36, "duration": 2.14}, {"text": "It's called the diffusion\nof innovation curve.", "start": 1165.5, "duration": 3.11}, {"text": "You might have heard the\nphrase early adopters.", "start": 1168.61, "duration": 2.46}, {"text": "And it's essentially\na bell curve,", "start": 1171.07, "duration": 1.99}, {"text": "where the bell curve is divided\ninto one standard deviation,", "start": 1173.06, "duration": 3.23}, {"text": "two standard\ndeviation differences.", "start": 1176.29, "duration": 1.98}, {"text": "On the far left-hand side,\ninnovators are the 2.5%", "start": 1178.27, "duration": 4.72}, {"text": "of the population that are\ntwo standard deviations ahead", "start": 1182.99, "duration": 2.69}, {"text": "of the curve.", "start": 1185.68, "duration": 0.72}, {"text": "They're innovating,\ntrying new things.", "start": 1186.4, "duration": 2.46}, {"text": "The early adopters,\nthe one to two", "start": 1188.86, "duration": 2.64}, {"text": "standard deviation\npart of the population,", "start": 1191.5, "duration": 2.07}, {"text": "are people who are\nadopting new technology.", "start": 1193.57, "duration": 2.13}, {"text": "And of course, the rest\nare the early majority,", "start": 1195.7, "duration": 2.16}, {"text": "and the late majority,\nand the laggards.", "start": 1197.86, "duration": 2.23}, {"text": "But this is where\nbenchmarking is", "start": 1200.09, "duration": 1.46}, {"text": "meant to reward some\ngroups over others.", "start": 1201.55, "duration": 2.65}, {"text": "For example, if you're an\ninnovator or early adopter,", "start": 1204.2, "duration": 2.9}, {"text": "it may cost money.", "start": 1207.1, "duration": 1.3}, {"text": "It may cost time for\nyou to do those things.", "start": 1208.4, "duration": 1.967}, {"text": "And if there's no\ninformation in the market,", "start": 1210.367, "duration": 1.833}, {"text": "you won't be rewarded for it.", "start": 1212.2, "duration": 1.93}, {"text": "But if we release the data\nto the public about which", "start": 1214.13, "duration": 3.2}, {"text": "buildings are more energy\nefficient or less energy using", "start": 1217.33, "duration": 2.97}, {"text": "than others, then\nyou have an incentive", "start": 1220.3, "duration": 1.95}, {"text": "to be an innovator\nor early adopter.", "start": 1222.25, "duration": 2.07}, {"text": "At the same time, on the\nright-hand side of the curve,", "start": 1224.32, "duration": 2.46}, {"text": "the laggards are the\npeople who are, let's say,", "start": 1226.78, "duration": 4.05}, {"text": "doing less or doing\nthe bare minimum.", "start": 1230.83, "duration": 2.61}, {"text": "That's where building codes are\nmeant to bring up the floor.", "start": 1233.44, "duration": 2.91}, {"text": "They're meant to get\nthe laggards to perform", "start": 1236.35, "duration": 2.07}, {"text": "to a minimum standard.", "start": 1238.42, "duration": 1.29}, {"text": "So benchmarking and\ncodes essentially", "start": 1239.71, "duration": 1.95}, {"text": "work on different\nsides of this curve.", "start": 1241.66, "duration": 3.14}, {"text": "And so what we found in our\nfirst look at the data--", "start": 1244.8, "duration": 3.23}, {"text": "I guess I've quoted the New York\nCity 2013 year two Local Law 84", "start": 1248.03, "duration": 4.14}, {"text": "report--", "start": 1252.17, "duration": 0.81}, {"text": "is you see tremendous\nvariation in all these sectors.", "start": 1252.98, "duration": 2.97}, {"text": "In other words,\ndepending on the sector--", "start": 1255.95, "duration": 2.25}, {"text": "multifamily buildings, office\nbuildings, retail, hotel,", "start": 1258.2, "duration": 2.85}, {"text": "education-- you can\nsee that there's", "start": 1261.05, "duration": 1.86}, {"text": "huge variation between the\nbest performers and the worst", "start": 1262.91, "duration": 2.34}, {"text": "performers.", "start": 1265.25, "duration": 0.69}, {"text": "In the retail sector, let's\nsay, there's a 5.6 times", "start": 1265.94, "duration": 4.59}, {"text": "difference between\ntypically good performers", "start": 1270.53, "duration": 3.3}, {"text": "and bad performers.", "start": 1273.83, "duration": 1.68}, {"text": "An office building is\na 5.8 times difference.", "start": 1275.51, "duration": 3.4}, {"text": "And you can see that\nthere's basically", "start": 1278.91, "duration": 2.667}, {"text": "tremendous variation between the\nbest performers and the worst", "start": 1281.577, "duration": 2.583}, {"text": "performers.", "start": 1284.16, "duration": 0.78}, {"text": "And what you want to do is give\nincentives or reward the best", "start": 1284.94, "duration": 4.08}, {"text": "performers and tell the poor\nperformers how to improve.", "start": 1289.02, "duration": 5.44}, {"text": "And so this kind of ties into\na larger empirical literature", "start": 1294.46, "duration": 3.98}, {"text": "about what the market\nfor energy efficiency is.", "start": 1298.44, "duration": 3.15}, {"text": "For the past 40 years,\nsince the 1970s,", "start": 1301.59, "duration": 2.577}, {"text": "there's been a tremendous\namount of interest", "start": 1304.167, "duration": 1.833}, {"text": "in energy efficiency.", "start": 1306.0, "duration": 1.29}, {"text": "But there's also been\na gap in investments.", "start": 1307.29, "duration": 2.83}, {"text": "And so the argument\nis that there's", "start": 1310.12, "duration": 1.58}, {"text": "been underinvestment in these\nenergy efficiency technologies", "start": 1311.7, "duration": 3.6}, {"text": "compared to the significant\npotential returns.", "start": 1315.3, "duration": 2.82}, {"text": "And frankly, neither\nengineers or economists", "start": 1318.12, "duration": 2.34}, {"text": "explain this gap\nparticularly well.", "start": 1320.46, "duration": 2.22}, {"text": "Is this a rational or\nirrational process?", "start": 1322.68, "duration": 3.15}, {"text": "Economists would argue that--", "start": 1325.83, "duration": 2.19}, {"text": "have argued in many papers\nthat this is actually", "start": 1328.02, "duration": 3.0}, {"text": "a rational gap, that the\nsavings of energy efficiency", "start": 1331.02, "duration": 2.91}, {"text": "are not necessarily\nthere because people", "start": 1333.93, "duration": 2.332}, {"text": "choose not to invest in them.", "start": 1336.262, "duration": 1.208}, {"text": "So therefore, there\nmust be a reason", "start": 1337.47, "duration": 2.13}, {"text": "why people have chosen not to\ninvest in energy efficiency.", "start": 1339.6, "duration": 3.03}, {"text": "And engineers have\nfocused on the fact", "start": 1342.63, "duration": 2.06}, {"text": "that this is irrational.", "start": 1344.69, "duration": 1.0}, {"text": "They say, well, the\nsavings are clearly there", "start": 1345.69, "duration": 2.31}, {"text": "from well-understood\ntechnologies.", "start": 1348.0, "duration": 2.17}, {"text": "So this is irrational for\npeople to be using more energy", "start": 1350.17, "duration": 2.63}, {"text": "than they have to.", "start": 1352.8, "duration": 1.23}, {"text": "But the paper we read for class\ntoday, the Bernstein et al.", "start": 1354.03, "duration": 2.88}, {"text": "1980 paper, is called\n\"Overcoming Social", "start": 1356.91, "duration": 3.61}, {"text": "and Institutional Barriers\nto Energy Conservation.\"", "start": 1360.52, "duration": 2.93}, {"text": "It focuses on six different\nbarriers, including misplaced", "start": 1363.45, "duration": 4.32}, {"text": "or split incentives, like\nthe tenant-landlord problem", "start": 1367.77, "duration": 2.91}, {"text": "I mentioned to you earlier,\nthe lack of or misinformation", "start": 1370.68, "duration": 4.02}, {"text": "among decision makers.", "start": 1374.7, "duration": 2.22}, {"text": "If you don't understand\nhow much better", "start": 1376.92, "duration": 2.01}, {"text": "a green building or an\nefficient appliance can perform,", "start": 1378.93, "duration": 3.42}, {"text": "you won't take that action.", "start": 1382.35, "duration": 1.8}, {"text": "There may be existing\ncustoms and regulation.", "start": 1384.15, "duration": 2.67}, {"text": "I talked too last time\nabout how some buildings", "start": 1386.82, "duration": 2.775}, {"text": "exist for many different uses.", "start": 1389.595, "duration": 2.385}, {"text": "The energy efficiency may\nnot be the principal concern", "start": 1391.98, "duration": 3.39}, {"text": "of the owner.", "start": 1395.37, "duration": 1.35}, {"text": "Market structure\nmay inhibit people", "start": 1396.72, "duration": 2.64}, {"text": "from investing in\nenergy efficiency.", "start": 1399.36, "duration": 2.79}, {"text": "For example, if you're in a\nhighly competitive market,", "start": 1402.15, "duration": 2.55}, {"text": "you may simply not choose to\ninvest in energy efficiency,", "start": 1404.7, "duration": 2.76}, {"text": "because none of your\ncompetitors are.", "start": 1407.46, "duration": 2.16}, {"text": "You may lack available\nfinancing and capital", "start": 1409.62, "duration": 3.27}, {"text": "to help you make those energy\nefficiency investments.", "start": 1412.89, "duration": 2.43}, {"text": "And you simply may be\nmyopic, which is, of course,", "start": 1415.32, "duration": 3.07}, {"text": "a natural human characteristic.", "start": 1418.39, "duration": 2.76}, {"text": "So I teach this paper\nevery single year,", "start": 1421.15, "duration": 2.67}, {"text": "this paper that's 42 years old,\nbecause I would argue to you,", "start": 1423.82, "duration": 3.29}, {"text": "and I think you all probably\nrecognize, that many", "start": 1427.11, "duration": 2.67}, {"text": "of these barriers still exist.", "start": 1429.78, "duration": 1.78}, {"text": "They're still barriers\nwe need to overcome.", "start": 1431.56, "duration": 2.64}, {"text": "And so the question we had was,\nif all of these barriers vary", "start": 1434.2, "duration": 4.34}, {"text": "greatly by individuals--\nwhether or not you're a tenant,", "start": 1438.54, "duration": 2.76}, {"text": "or what kind of owner you are,\nor what kind of individual you", "start": 1441.3, "duration": 2.76}, {"text": "are--", "start": 1444.06, "duration": 0.54}, {"text": "how do I identify who's\naffected by which barrier?", "start": 1444.6, "duration": 2.95}, {"text": "And how do we target\nour policies better?", "start": 1447.55, "duration": 2.94}, {"text": "So this brings me to\nhow benchmarking works.", "start": 1450.49, "duration": 2.88}, {"text": "And it's really an argument\nabout market transformation", "start": 1453.37, "duration": 2.58}, {"text": "heterogeneity.", "start": 1455.95, "duration": 0.99}, {"text": "So if you start in the\nupper-left-hand corner,", "start": 1456.94, "duration": 2.38}, {"text": "you start with the diffusion\nof innovation curve.", "start": 1459.32, "duration": 2.54}, {"text": "And information\nenables us to identify", "start": 1461.86, "duration": 3.78}, {"text": "who's an innovator,\nwho's an early adopter,", "start": 1465.64, "duration": 1.92}, {"text": "and who's a laggard.", "start": 1467.56, "duration": 1.32}, {"text": "But the fundamental question\nwe're trying to get at", "start": 1468.88, "duration": 2.125}, {"text": "is, what information\nwill cause action?", "start": 1471.005, "duration": 2.525}, {"text": "When you move to the\nupper-right-hand side,", "start": 1473.53, "duration": 1.84}, {"text": "you can see building owners.", "start": 1475.37, "duration": 1.58}, {"text": "And the question\nfor building owners", "start": 1476.95, "duration": 1.77}, {"text": "is, well, how efficient\nis my building?", "start": 1478.72, "duration": 2.28}, {"text": "Do I know how fresh\nmy building is?", "start": 1481.0, "duration": 1.62}, {"text": "And who will I be judged\nagainst in a marketplace?", "start": 1482.62, "duration": 2.7}, {"text": "So the question\nfor building owners", "start": 1485.32, "duration": 1.53}, {"text": "is, what building\nshould I be compared to?", "start": 1486.85, "duration": 2.7}, {"text": "Now, if you know you're\ncompared to other buildings,", "start": 1489.55, "duration": 2.17}, {"text": "and if you know that\nyour building can perform", "start": 1491.72, "duration": 1.917}, {"text": "six times better,\nthen you actually", "start": 1493.637, "duration": 2.333}, {"text": "want to understand, how do I\nmake my building work better?", "start": 1495.97, "duration": 2.89}, {"text": "And so that you want to\ngo see what other building", "start": 1498.86, "duration": 2.27}, {"text": "is performing well.", "start": 1501.13, "duration": 1.45}, {"text": "So if the data was\npublic, you can not only", "start": 1502.58, "duration": 3.65}, {"text": "have an incentive\nto invest, you'd", "start": 1506.23, "duration": 2.16}, {"text": "also have an incentive\nto go find out what", "start": 1508.39, "duration": 2.1}, {"text": "works for a similar building.", "start": 1510.49, "duration": 1.77}, {"text": "And that leads us to\nthe question of, what", "start": 1512.26, "duration": 1.89}, {"text": "investments are cost effective?", "start": 1514.15, "duration": 1.927}, {"text": "And if you make those\ninvestments that", "start": 1516.077, "duration": 1.583}, {"text": "are cost effective,\nthen, if you skip", "start": 1517.66, "duration": 2.61}, {"text": "to the lower-left-hand corner,\nyou can see potential buyers.", "start": 1520.27, "duration": 3.72}, {"text": "Potential buyers will\nreward you for having", "start": 1523.99, "duration": 2.62}, {"text": "a more energy-efficient\nbuilding if it saves them", "start": 1526.61, "duration": 2.18}, {"text": "money, which leads us\nkind of a circle back to,", "start": 1528.79, "duration": 2.88}, {"text": "what determines\nthe building energy", "start": 1531.67, "duration": 1.8}, {"text": "performance we're seeing in the\nfirst place in our information?", "start": 1533.47, "duration": 5.01}, {"text": "If this information\ndoesn't exist", "start": 1538.48, "duration": 1.8}, {"text": "in the upper-right-hand\ncorner, then this whole cycle", "start": 1540.28, "duration": 2.91}, {"text": "can't work.", "start": 1543.19, "duration": 0.54}, {"text": "And this is a virtuous cycle.", "start": 1543.73, "duration": 1.96}, {"text": "But if the government\npassed a law,", "start": 1545.69, "duration": 1.79}, {"text": "as it did with Local Law 84,\nto gather the information", "start": 1547.48, "duration": 3.87}, {"text": "or compel building owners\nto gather information", "start": 1551.35, "duration": 2.49}, {"text": "at relatively low cost, once\nyou inject the information", "start": 1553.84, "duration": 2.76}, {"text": "to the market, you can\nget building owners", "start": 1556.6, "duration": 1.98}, {"text": "to act towards investment.", "start": 1558.58, "duration": 1.598}, {"text": "You can get potential buyers to\nreward those building owners.", "start": 1560.178, "duration": 2.542}, {"text": "It becomes a virtuous cycle.", "start": 1562.72, "duration": 3.42}, {"text": "So what we found in some\nof the initial reports", "start": 1566.14, "duration": 2.42}, {"text": "was that different\nproperty types", "start": 1568.56, "duration": 1.8}, {"text": "comprise very different\nportions of the total energy", "start": 1570.36, "duration": 4.35}, {"text": "use of the city.", "start": 1574.71, "duration": 1.41}, {"text": "But even more\ninteresting to us was", "start": 1576.12, "duration": 2.628}, {"text": "that if you looked\nat the buildings--", "start": 1578.748, "duration": 1.542}, {"text": "and we coded them to keep\nthem anonymous on the bottom.", "start": 1580.29, "duration": 3.06}, {"text": "But also, on the\nhorizontal axis,", "start": 1583.35, "duration": 1.92}, {"text": "we actually grouped\nthem by consultant.", "start": 1585.27, "duration": 2.17}, {"text": "You can see that different\ngroups of consultants", "start": 1587.44, "duration": 2.0}, {"text": "actually came up with really\ndifferent results for what", "start": 1589.44, "duration": 3.0}, {"text": "the energy use was\nin the buildings.", "start": 1592.44, "duration": 1.69}, {"text": "And this is simply\nbecause people", "start": 1594.13, "duration": 1.4}, {"text": "have different processes.", "start": 1595.53, "duration": 1.11}, {"text": "They measure different things.", "start": 1596.64, "duration": 1.59}, {"text": "They also look at\nthe data differently.", "start": 1598.23, "duration": 3.28}, {"text": "And so it was interesting.", "start": 1601.51, "duration": 1.2}, {"text": "We actually would get all\nthe consultants in a room.", "start": 1602.71, "duration": 2.167}, {"text": "And we'd show them this graph.", "start": 1604.877, "duration": 1.423}, {"text": "And we'd show them how\nmuch their energy use", "start": 1606.3, "duration": 2.943}, {"text": "they measured was different.", "start": 1609.243, "duration": 1.167}, {"text": "And we were trying to\nimprove the data quality.", "start": 1610.41, "duration": 2.37}, {"text": "So this is to say\nthat if you are trying", "start": 1612.78, "duration": 2.16}, {"text": "to affect the overall\nmarket, we first", "start": 1614.94, "duration": 2.49}, {"text": "want to work through building\nowners to gather the data.", "start": 1617.43, "duration": 2.587}, {"text": "But then we recognize there\nis a relatively small number", "start": 1620.017, "duration": 2.333}, {"text": "of consultants servicing\nall these owners.", "start": 1622.35, "duration": 2.77}, {"text": "So in New York\nCity, when we first", "start": 1625.12, "duration": 3.56}, {"text": "implemented this law,\nwhen New York City first", "start": 1628.68, "duration": 1.95}, {"text": "implemented this law for\nbuildings over 50,000", "start": 1630.63, "duration": 3.48}, {"text": "square feet, it only affected\nabout 10,000 buildings.", "start": 1634.11, "duration": 3.48}, {"text": "But those 10,000 buildings\nwere serviced by a much smaller", "start": 1637.59, "duration": 2.7}, {"text": "consultant industry--", "start": 1640.29, "duration": 1.47}, {"text": "I think roughly\n500 consultants so.", "start": 1641.76, "duration": 2.59}, {"text": "Still a very large number.", "start": 1644.35, "duration": 1.8}, {"text": "But if you think\nabout the fact you're", "start": 1646.15, "duration": 1.67}, {"text": "trying to affect a\nmillion buildings,", "start": 1647.82, "duration": 1.86}, {"text": "it's much easier to work through\n10,000 building owners and 500", "start": 1649.68, "duration": 3.18}, {"text": "consultants than it is to\ntry to tackle the entire city", "start": 1652.86, "duration": 4.65}, {"text": "or make it a public\ninformation campaign.", "start": 1657.51, "duration": 2.5}, {"text": "Having said that, you know that\nall your building owners are", "start": 1660.01, "duration": 3.51}, {"text": "owned--", "start": 1663.52, "duration": 0.6}, {"text": "your office buildings are owned\nby a relatively small number", "start": 1664.12, "duration": 2.5}, {"text": "of owners, whereas\nmultifamily buildings,", "start": 1666.62, "duration": 1.94}, {"text": "there's many more buildings,\nbut also, many more owners", "start": 1668.56, "duration": 3.0}, {"text": "or many different\nkinds of owners.", "start": 1671.56, "duration": 1.53}, {"text": "This suggests you need\ndifferent kinds of campaigns", "start": 1673.09, "duration": 2.76}, {"text": "to target this information\nto different owners.", "start": 1675.85, "duration": 3.37}, {"text": "So to give you a sense of some\nof the results from this law,", "start": 1679.22, "duration": 4.65}, {"text": "this is something I\nfound in a 2017 paper,", "start": 1683.87, "duration": 2.6}, {"text": "that the first three or four\nyears, my co-authors and I", "start": 1686.47, "duration": 4.05}, {"text": "found that this law\nactually reduced energy use", "start": 1690.52, "duration": 3.0}, {"text": "intensity, which is the\nenergy use per square foot,", "start": 1693.52, "duration": 2.58}, {"text": "by about 12% to 14% over\nthe first three years.", "start": 1696.1, "duration": 3.67}, {"text": "We were quite surprised how much\nenergy reduction it delivered", "start": 1699.77, "duration": 4.922}, {"text": "because that's much more\naggressive than the building", "start": 1704.692, "duration": 2.208}, {"text": "codes I told you about before.", "start": 1706.9, "duration": 1.32}, {"text": "That's roughly about 3% or\n4% per year at a minimum.", "start": 1708.22, "duration": 3.99}, {"text": "If you look over the\nlast 10 years of data,", "start": 1712.21, "duration": 2.94}, {"text": "from the benchmarked\nemissions and energy trends,", "start": 1715.15, "duration": 3.12}, {"text": "you can see that site energy\nuse and total emissions", "start": 1718.27, "duration": 3.15}, {"text": "have steadily decreased\nover the last 10 years.", "start": 1721.42, "duration": 2.73}, {"text": "This is from a report from the\nUrban Green Council in 2022.", "start": 1724.15, "duration": 4.19}, {"text": "To make the point again\nthat this is unusual data,", "start": 1728.34, "duration": 3.22}, {"text": "or this is a new data\nset that we really", "start": 1731.56, "duration": 1.92}, {"text": "didn't have 10 years\nago, this is a data", "start": 1733.48, "duration": 3.21}, {"text": "from the effects of COVID-19.", "start": 1736.69, "duration": 2.25}, {"text": "And you can see that the Urban\nGreen Council graphs it here.", "start": 1738.94, "duration": 3.54}, {"text": "We saw that energy\nuse had decreased", "start": 1742.48, "duration": 2.49}, {"text": "in January and February and\ndecreased in April and May", "start": 1744.97, "duration": 2.97}, {"text": "between 2019 and 2020.", "start": 1747.94, "duration": 2.39}, {"text": "And we knew that from\nthe electric utility", "start": 1750.33, "duration": 1.75}, {"text": "because the electric utility\ndelivers all the power.", "start": 1752.08, "duration": 2.58}, {"text": "But what we didn't know before\ndeveloping this benchmarking", "start": 1754.66, "duration": 3.03}, {"text": "data set was how it\naffected different buildings", "start": 1757.69, "duration": 3.69}, {"text": "and how it affected different\nbuildings in different places", "start": 1761.38, "duration": 2.46}, {"text": "in New York City.", "start": 1763.84, "duration": 1.66}, {"text": "For example, we knew that\nenergy use was going down", "start": 1765.5, "duration": 3.42}, {"text": "at the beginning of COVID.", "start": 1768.92, "duration": 1.29}, {"text": "And we knew that\nestimated occupancy", "start": 1770.21, "duration": 2.01}, {"text": "went down quite a bit.", "start": 1772.22, "duration": 1.37}, {"text": "But we didn't\nnecessarily know where.", "start": 1776.34, "duration": 2.73}, {"text": "Some of the benchmarking\ndata revealed to us", "start": 1779.07, "duration": 2.07}, {"text": "for the first time\nthat water energy use", "start": 1781.14, "duration": 2.49}, {"text": "decreased in Manhattan\nand increased", "start": 1783.63, "duration": 2.143}, {"text": "in the outer boroughs.", "start": 1785.773, "duration": 0.917}, {"text": "This is clearly\nbecause people aren't", "start": 1786.69, "duration": 1.65}, {"text": "commuting into Manhattan.", "start": 1788.34, "duration": 1.32}, {"text": "Roughly 4 million people\nused to come into Manhattan", "start": 1789.66, "duration": 3.21}, {"text": "every single day.", "start": 1792.87, "duration": 1.14}, {"text": "And we know that some\nManhattan residents", "start": 1794.01, "duration": 1.77}, {"text": "were more likely to\ndecamp for places", "start": 1795.78, "duration": 2.22}, {"text": "outside of New York City\nwhen the pandemic occurred.", "start": 1798.0, "duration": 3.17}, {"text": "So we can actually\nsee in a localized way", "start": 1801.17, "duration": 3.16}, {"text": "where energy and water use\nare increasing or decreasing.", "start": 1804.33, "duration": 5.04}, {"text": "And so what we've seen\nover the last 10 years", "start": 1809.37, "duration": 2.45}, {"text": "is an explosion of\nthese benchmarking laws.", "start": 1811.82, "duration": 3.54}, {"text": "When I first got\ninvolved in this", "start": 1815.36, "duration": 1.5}, {"text": "I think about 10\nyears ago, there", "start": 1816.86, "duration": 1.42}, {"text": "were about five\nor six cities that", "start": 1818.28, "duration": 1.58}, {"text": "had passed benchmarking laws and\nhad not yet implemented them.", "start": 1819.86, "duration": 3.262}, {"text": "New York City wasn't the\nfirst to pass the law.", "start": 1823.122, "duration": 1.958}, {"text": "I think San Francisco was.", "start": 1825.08, "duration": 1.777}, {"text": "But New York City\nwas one of the first", "start": 1826.857, "duration": 1.583}, {"text": "to really put that\ndata into action.", "start": 1828.44, "duration": 2.01}, {"text": "And because New York City\nhas the most buildings,", "start": 1830.45, "duration": 2.22}, {"text": "it was the most interesting\ndata set for me and others", "start": 1832.67, "duration": 3.27}, {"text": "to analyze.", "start": 1835.94, "duration": 0.9}, {"text": "You can see at this\npoint, benchmarking", "start": 1836.84, "duration": 2.07}, {"text": "has spread to about\n40 or 50 cities.", "start": 1838.91, "duration": 3.3}, {"text": "This is a very popular map\nthat the Institute for Market", "start": 1842.21, "duration": 2.49}, {"text": "Transformation keeps\nupdated because they've", "start": 1844.7, "duration": 2.58}, {"text": "helped pass these laws\nin many of these places", "start": 1847.28, "duration": 2.52}, {"text": "through lobbying and through\neducation of public officials.", "start": 1849.8, "duration": 5.16}, {"text": "And so to give you another\nsense of how important building", "start": 1854.96, "duration": 3.36}, {"text": "energy efficiency policies\nare and where they're going,", "start": 1858.32, "duration": 3.18}, {"text": "this is always a report\nI'd like to show.", "start": 1861.5, "duration": 2.34}, {"text": "This is another graph\nthat McKinsey consultants", "start": 1863.84, "duration": 3.18}, {"text": "use quite a bit, but also other\nbusiness-type consultants use.", "start": 1867.02, "duration": 3.99}, {"text": "It's called a waterfall graph.", "start": 1871.01, "duration": 2.04}, {"text": "It shows you where you start--", "start": 1873.05, "duration": 2.04}, {"text": "let's say, in 2050,\nbusiness as usual--", "start": 1875.09, "duration": 2.65}, {"text": "and what steps\nyou'd have to take", "start": 1877.74, "duration": 1.7}, {"text": "to reduce to your goal,\nwhich is 2050 carbon", "start": 1879.44, "duration": 3.51}, {"text": "reductions, deep carbon\nreductions by 2050 for New York", "start": 1882.95, "duration": 3.3}, {"text": "City.", "start": 1886.25, "duration": 0.93}, {"text": "The somewhat entertaining\nthing I find about this report", "start": 1887.18, "duration": 2.61}, {"text": "is that this is\nfrom a report called", "start": 1889.79, "duration": 1.5}, {"text": "\"New York City's Pathways\nto Deep Carbon Reductions.\"", "start": 1891.29, "duration": 3.36}, {"text": "It was issued on\nDecember 30 of 2013,", "start": 1894.65, "duration": 3.15}, {"text": "essentially the last day\nthat Michael Bloomberg", "start": 1897.8, "duration": 2.01}, {"text": "was in office.", "start": 1899.81, "duration": 1.02}, {"text": "And he issued this report\nbecause he'd already", "start": 1900.83, "duration": 2.61}, {"text": "done a lot to try to pass\n[INAUDIBLE] policies.", "start": 1903.44, "duration": 2.897}, {"text": "But this is kind of the\nequivalent of the midnight", "start": 1906.337, "duration": 2.083}, {"text": "report you pass for\nyour predecessor", "start": 1908.42, "duration": 1.95}, {"text": "to have to deal with.", "start": 1910.37, "duration": 1.705}, {"text": "Bill de Blasio, when\nhe came to office,", "start": 1912.075, "duration": 1.625}, {"text": "actually increased the climate\ncommitments of New York City.", "start": 1913.7, "duration": 3.27}, {"text": "But the crucial thing I\nwant to show in this report", "start": 1916.97, "duration": 2.4}, {"text": "is that the 2050\nbusiness-as-usual case", "start": 1919.37, "duration": 3.03}, {"text": "is a very slight reduction\nfrom the 2005 emissions levels", "start": 1922.4, "duration": 3.54}, {"text": "that the Kyoto Protocol\nmeasures against.", "start": 1925.94, "duration": 3.36}, {"text": "But you can see of the 55.7\nmillion metric tons of carbon", "start": 1929.3, "duration": 4.5}, {"text": "dioxide equivalent just\nfrom New York City,", "start": 1933.8, "duration": 3.09}, {"text": "of the savings to get\nto the 80-by-50 goals,", "start": 1936.89, "duration": 2.91}, {"text": "or the 80% reduction by\n2050, roughly half of that", "start": 1939.8, "duration": 3.24}, {"text": "is going to come\nfrom buildings alone.", "start": 1943.04, "duration": 2.04}, {"text": "Most of it is going to come\nfrom existing buildings' energy", "start": 1945.08, "duration": 2.55}, {"text": "efficiency.", "start": 1947.63, "duration": 0.9}, {"text": "Some is going to come from\nfuel switching in buildings.", "start": 1948.53, "duration": 2.88}, {"text": "And a little bit is going to\ncome from making new buildings", "start": 1951.41, "duration": 2.55}, {"text": "energy efficient.", "start": 1953.96, "duration": 0.96}, {"text": "That again reinforces\nthe point that most", "start": 1954.92, "duration": 2.49}, {"text": "the buildings we're going to\nhave in 2050 are already built.", "start": 1957.41, "duration": 2.76}, {"text": "We need to change the\nbehavior of people", "start": 1960.17, "duration": 1.95}, {"text": "living in those buildings\nor owning those buildings.", "start": 1962.12, "duration": 2.747}, {"text": "The power sector-- we're\ngoing to get some savings", "start": 1964.867, "duration": 2.083}, {"text": "from clean power and\ndistributed generation.", "start": 1966.95, "duration": 2.43}, {"text": "For the transportation\nsector, we're", "start": 1969.38, "duration": 1.5}, {"text": "going to get some savings.", "start": 1970.88, "duration": 1.47}, {"text": "We're going to get\nrelatively little savings", "start": 1972.35, "duration": 2.13}, {"text": "from solid waste.", "start": 1974.48, "duration": 1.05}, {"text": "But you add the buildings,\nthe power, the transportation", "start": 1975.53, "duration": 3.33}, {"text": "sector together, and you get to\nfairly deep carbon reductions", "start": 1978.86, "duration": 3.27}, {"text": "for New York City--", "start": 1982.13, "duration": 1.44}, {"text": "more than 80% reduction by 2050,\nwhich was the original Paris", "start": 1983.57, "duration": 4.86}, {"text": "Agreement goal.", "start": 1988.43, "duration": 1.65}, {"text": "Now our goals have\nbecome net zero", "start": 1990.08, "duration": 2.1}, {"text": "by 2050, which is\nmore aggressive still.", "start": 1992.18, "duration": 3.54}, {"text": "To give you a sense of how\nsome of this kind of analysis", "start": 1995.72, "duration": 3.42}, {"text": "percolated into\ncity-level reports,", "start": 1999.14, "duration": 2.79}, {"text": "this should be a\nfamiliar graph to you.", "start": 2001.93, "duration": 1.95}, {"text": "This is a marginal\nabatement cost curve.", "start": 2003.88, "duration": 2.7}, {"text": "But this is specifically\nfor the building sector", "start": 2006.58, "duration": 2.16}, {"text": "in New York City.", "start": 2008.74, "duration": 1.29}, {"text": "So you can see that\nthey've measured out", "start": 2010.03, "duration": 1.89}, {"text": "all the possible savings\nyou can have in buildings.", "start": 2011.92, "duration": 3.7}, {"text": "These are all the negative ones.", "start": 2015.62, "duration": 1.67}, {"text": "Almost everything\nis negative compared", "start": 2017.29, "duration": 1.83}, {"text": "to this few interventions\nthat are relatively--", "start": 2019.12, "duration": 3.93}, {"text": "cost more.", "start": 2023.05, "duration": 1.26}, {"text": "But I would argue that anything\nbelow about $150 per ton", "start": 2024.31, "duration": 5.743}, {"text": "essentially is something that\nwe should do because it's lower", "start": 2030.053, "duration": 2.542}, {"text": "than the social cost of carbon.", "start": 2032.595, "duration": 3.145}, {"text": "That pretty much\ndescribes about 23", "start": 2035.74, "duration": 7.83}, {"text": "of the 28 total metric\ntons carbon dioxide", "start": 2043.57, "duration": 4.02}, {"text": "equivalent per year potential.", "start": 2047.59, "duration": 2.19}, {"text": "You can look at the\nbiggest area is probably", "start": 2049.78, "duration": 2.07}, {"text": "residential freezers.", "start": 2051.85, "duration": 1.53}, {"text": "Again, not necessarily a topic\nyou thought you might focus on,", "start": 2053.38, "duration": 3.359}, {"text": "but a topic that has\nvery high impact.", "start": 2056.739, "duration": 3.621}, {"text": "And so to get to the\nmost recent New York City", "start": 2060.36, "duration": 2.54}, {"text": "law, passed in 2019, these are\ncarbon budgets for buildings.", "start": 2062.9, "duration": 5.94}, {"text": "The highlights are that it\naffects buildings greater", "start": 2068.84, "duration": 2.22}, {"text": "than 25,000 square feet.", "start": 2071.06, "duration": 2.389}, {"text": "It sets increasingly\nstringent limits", "start": 2073.449, "duration": 2.681}, {"text": "on carbon emissions per\nsquare foot in 2024 and 2030.", "start": 2076.13, "duration": 4.569}, {"text": "So in two years, we're coming\nup on the first marker, which", "start": 2080.699, "duration": 3.978}, {"text": "is not the most aggressive one.", "start": 2084.677, "duration": 1.292}, {"text": "2030 is a much tougher\ntarget to meet.", "start": 2085.969, "duration": 3.181}, {"text": "It gives building\nowners the flexibility", "start": 2089.15, "duration": 1.71}, {"text": "to comply with this law through\nrenewable energy credits", "start": 2090.86, "duration": 2.819}, {"text": "or emissions offsets.", "start": 2093.679, "duration": 1.5}, {"text": "And notably, the\ncity of Cambridge", "start": 2095.179, "duration": 2.671}, {"text": "is considering similar\ncarbon budgets for buildings.", "start": 2097.85, "duration": 2.92}, {"text": "But they're not allowing\nrenewable energy credits,", "start": 2100.77, "duration": 2.16}, {"text": "which means that a\nbuilding owner can't just", "start": 2102.93, "duration": 1.833}, {"text": "go on the market and purchase a\nrenewable energy credit, which", "start": 2104.763, "duration": 4.787}, {"text": "may not have the decarbonizing\nimpact we want it to have.", "start": 2109.55, "duration": 2.803}, {"text": "I'll talk about\nrenewable energy credits", "start": 2112.353, "duration": 1.667}, {"text": "more in a few lectures from now.", "start": 2114.02, "duration": 2.61}, {"text": "It allows for some\naffordable housing", "start": 2116.63, "duration": 1.8}, {"text": "to choose low-cost\nenergy savings", "start": 2118.43, "duration": 1.92}, {"text": "measures instead of meeting\nthese emissions limits.", "start": 2120.35, "duration": 3.98}, {"text": "It sets up a new Office\nof Building Energy", "start": 2124.33, "duration": 1.955}, {"text": "and Emissions Performance at\nthe Department of Buildings,", "start": 2126.285, "duration": 2.375}, {"text": "again, spreading this\nthroughout the city government.", "start": 2128.66, "duration": 3.27}, {"text": "It has a strong advisory\nboard to help refine emissions", "start": 2131.93, "duration": 2.49}, {"text": "metrics and limits.", "start": 2134.42, "duration": 1.59}, {"text": "And also, crucially, it calls\nfor creating a carbon trading", "start": 2136.01, "duration": 3.96}, {"text": "study and implementation\nplan because even relatively", "start": 2139.97, "duration": 4.77}, {"text": "new buildings in New\nYork City will not be", "start": 2144.74, "duration": 1.98}, {"text": "able to meet the 2030 limits.", "start": 2146.72, "duration": 1.86}, {"text": "Let's say you built a\nnew building around 2000.", "start": 2148.58, "duration": 3.9}, {"text": "And you got a LEED\ngold certification", "start": 2152.48, "duration": 2.46}, {"text": "even though your\nbuilding had natural gas.", "start": 2154.94, "duration": 1.8}, {"text": "Or natural gas at the\ntime was relatively clean", "start": 2156.74, "duration": 2.52}, {"text": "compared to consuming\nother forms of fuel.", "start": 2159.26, "duration": 3.06}, {"text": "By 2030, that building\nmay be out of compliance.", "start": 2162.32, "duration": 2.97}, {"text": "And so what you\nmight do is actually", "start": 2165.29, "duration": 1.5}, {"text": "choose to trade carbon credits.", "start": 2166.79, "duration": 1.92}, {"text": "This is essentially a\ncap-and-trade program", "start": 2168.71, "duration": 2.1}, {"text": "just for buildings.", "start": 2170.81, "duration": 1.23}, {"text": "You may choose to spend\nyour money not on upgrading", "start": 2172.04, "duration": 2.88}, {"text": "your 20-year-old natural\ngas system, but upgrading,", "start": 2174.92, "duration": 3.06}, {"text": "let's say, 10 buildings in--", "start": 2177.98, "duration": 2.31}, {"text": "10 multifamily buildings in the\nouter boroughs because that's", "start": 2180.29, "duration": 3.51}, {"text": "relatively cost effective and\nhas the exact same greenhouse", "start": 2183.8, "duration": 3.18}, {"text": "gas emissions abatement\npotential, which is to say it's", "start": 2186.98, "duration": 3.06}, {"text": "cap and trade for buildings.", "start": 2190.04, "duration": 2.22}, {"text": "We want to look for\nthe lowest-cost,", "start": 2192.26, "duration": 1.9}, {"text": "highest-impact alternatives.", "start": 2194.16, "duration": 2.73}, {"text": "And it does give very stringent\npenalties for non-compliance", "start": 2196.89, "duration": 3.29}, {"text": "and also gives variances for\nfinancial hardship for owners.", "start": 2200.18, "duration": 4.88}, {"text": "With the Urban Green\nCouncil, in 2019,", "start": 2205.06, "duration": 2.22}, {"text": "I analyzed the economic\nand employment effects", "start": 2207.28, "duration": 5.62}, {"text": "for this city.", "start": 2212.9, "duration": 2.03}, {"text": "It does affect the total\noutput of the city.", "start": 2214.93, "duration": 2.46}, {"text": "And it does affect the\nearnings of the city.", "start": 2217.39, "duration": 2.31}, {"text": "But crucially,\nlook at the number", "start": 2219.7, "duration": 1.71}, {"text": "of jobs in 2024 and 2030.", "start": 2221.41, "duration": 3.06}, {"text": "To meet the less\nstringent 2024 goals,", "start": 2224.47, "duration": 2.67}, {"text": "we were going to-- it's expected\nto create nearly 20,000 jobs.", "start": 2227.14, "duration": 4.53}, {"text": "But to meet the 2030\ngoals, it's expected", "start": 2231.67, "duration": 2.79}, {"text": "to create, but also\nrequire, 180,000 more jobs.", "start": 2234.46, "duration": 5.01}, {"text": "We talk about this as a good\nthing in terms of green jobs,", "start": 2239.47, "duration": 2.67}, {"text": "to create 200,000 jobs.", "start": 2242.14, "duration": 2.25}, {"text": "But it could also be a\npotential constraint,", "start": 2244.39, "duration": 2.05}, {"text": "which is to say\nthat if you can't", "start": 2246.44, "duration": 2.18}, {"text": "get enough affordable housing\nor enough people to fill", "start": 2248.62, "duration": 2.61}, {"text": "these 200,000 jobs, this\ncarbon budget may not happen.", "start": 2251.23, "duration": 4.0}, {"text": "So this is to say that\nworkforce is considered", "start": 2255.23, "duration": 3.47}, {"text": "to be one of the biggest\npossible obstacles to achieving", "start": 2258.7, "duration": 2.73}, {"text": "the carbon budgets\nfor buildings.", "start": 2261.43, "duration": 2.34}, {"text": "We can increase the\nvalue of the buildings.", "start": 2263.77, "duration": 2.28}, {"text": "We can increase output and\nearnings in New York City.", "start": 2266.05, "duration": 2.575}, {"text": "Building owners may\nbe willing to do it", "start": 2268.625, "duration": 1.625}, {"text": "because it's cost effective.", "start": 2270.25, "duration": 1.48}, {"text": "But if you can't\nfind the workers,", "start": 2271.73, "duration": 1.94}, {"text": "the policy may not be effective.", "start": 2273.67, "duration": 3.11}]
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+[{"text": "BARBARA IMPERIALI:\nWhat I'm going", "start": 15.395, "duration": 1.375}, {"text": "to do first of all for today,\nthe bulk of today's lecture", "start": 16.77, "duration": 4.62}, {"text": "will be on HIV\nand Ebola viruses,", "start": 21.39, "duration": 3.21}, {"text": "with more time spent on HIV\nbecause it's potentially", "start": 24.6, "duration": 3.78}, {"text": "one of the mechanistically best\nunderstood of the retroviruses.", "start": 28.38, "duration": 5.49}, {"text": "And it also has offered\nnumerous opportunities", "start": 33.87, "duration": 3.39}, {"text": "for therapeutic intervention.", "start": 37.26, "duration": 2.13}, {"text": "And there are a lot\nof themes and terms", "start": 39.39, "duration": 1.92}, {"text": "that I can bring up as I talk\nto you about the HIV virus,", "start": 41.31, "duration": 4.62}, {"text": "because it's just a great\nexemplar of the viruses.", "start": 45.93, "duration": 6.32}, {"text": "OK.", "start": 52.25, "duration": 0.5}, {"text": "So HIV is what is\nknown as a retrovirus.", "start": 52.75, "duration": 3.632}, {"text": "So that sort of designates\nthat there's something working", "start": 64.129, "duration": 3.241}, {"text": "backwards in this retrovirus.", "start": 67.37, "duration": 2.34}, {"text": "Based on its number in the\nBaltimore Classification,", "start": 69.71, "duration": 2.97}, {"text": "it is the most recently\nidentified mechanism", "start": 72.68, "duration": 3.54}, {"text": "of viruses.", "start": 76.22, "duration": 1.44}, {"text": "HIV stands for Human\nImmunodeficiency Virus.", "start": 77.66, "duration": 6.33}, {"text": "And when you hear\nthe term HIV, you'll", "start": 94.47, "duration": 2.48}, {"text": "often hear HIV/AIDS where the\nAIDS part stands for Acquired", "start": 96.95, "duration": 7.42}, {"text": "Immunodeficiency Syndrome.", "start": 104.37, "duration": 1.545}, {"text": "So what you can start\nto tell about the name--", "start": 114.99, "duration": 4.12}, {"text": "why am I hunching down--", "start": 119.11, "duration": 2.36}, {"text": "is there's something related to\nthe immune system with respect", "start": 129.34, "duration": 4.07}, {"text": "to this virus.", "start": 133.41, "duration": 1.54}, {"text": "And in particular, it is\nthat this virus targets,", "start": 134.95, "duration": 3.41}, {"text": "very specifically, a\npopulation of the cells that", "start": 138.36, "duration": 3.81}, {"text": "are critical in immunity.", "start": 142.17, "duration": 2.37}, {"text": "And when the virus\nattacks those cells,", "start": 144.54, "duration": 2.97}, {"text": "the person infected with the\nvirus becomes immunodeficit.", "start": 147.51, "duration": 4.59}, {"text": "So I've talked to you\nabout different viruses.", "start": 152.1, "duration": 2.08}, {"text": "Some go to the liver.", "start": 154.18, "duration": 1.76}, {"text": "Some go for other organs.", "start": 155.94, "duration": 1.44}, {"text": "So like the liver,\nthe viruses that", "start": 157.38, "duration": 4.89}, {"text": "really cause a\ndeficiency in liver", "start": 162.27, "duration": 3.54}, {"text": "function, but this one is\nvery specifically deficiencies", "start": 165.81, "duration": 3.6}, {"text": "in immune function.", "start": 169.41, "duration": 1.62}, {"text": "And it has been a tremendous\nchallenge developing vaccines", "start": 171.03, "duration": 4.53}, {"text": "against HIV/AIDS because of the\nproblem with the immune system.", "start": 175.56, "duration": 5.11}, {"text": "The other thing that I mentioned\nto you in the last class", "start": 180.67, "duration": 3.44}, {"text": "was that HIV is often\nfound co-infecting", "start": 184.11, "duration": 3.45}, {"text": "with TB patients, people with\nthose microbial infections.", "start": 187.56, "duration": 3.84}, {"text": "And that's because the\nimmunodeficiency makes you more", "start": 191.4, "duration": 3.21}, {"text": "susceptible to tuberculosis.", "start": 194.61, "duration": 2.56}, {"text": "And oftentimes\nthere's a co-infection", "start": 197.17, "duration": 3.2}, {"text": "with the two diseases.", "start": 200.37, "duration": 2.37}, {"text": "And it makes the people\nwith TB really even", "start": 202.74, "duration": 2.73}, {"text": "less able to combat\nthe TB infection.", "start": 205.47, "duration": 3.58}, {"text": "So that is really what gets\na lot of the TB patients.", "start": 209.05, "duration": 4.49}, {"text": "So that's an important\naspect to know.", "start": 213.54, "duration": 2.81}, {"text": "And it's also an\nimportant aspect", "start": 216.35, "duration": 2.35}, {"text": "to be aware of when treating\npeople for any infection", "start": 218.7, "duration": 4.72}, {"text": "is if there's an HIV\ncomponent, the body", "start": 223.42, "duration": 5.0}, {"text": "is much less able to\ndeal with mounting", "start": 228.42, "duration": 3.84}, {"text": "an immune response\nbecause of the fact", "start": 232.26, "duration": 2.04}, {"text": "that the immune\ncells are targeted.", "start": 234.3, "duration": 2.13}, {"text": "So HIV is an envelope virus.", "start": 236.43, "duration": 4.725}, {"text": "That means it has a\nmembrane around it.", "start": 245.79, "duration": 4.69}, {"text": "It is this sort\nof peculiar shape", "start": 250.48, "duration": 4.52}, {"text": "where the outside of\nthe membrane is coated--", "start": 255.0, "duration": 3.92}, {"text": "the outside of the virus\nis coated with membrane.", "start": 258.92, "duration": 3.64}, {"text": "And then stuck in that membrane\nare particular proteins", "start": 262.56, "duration": 4.95}, {"text": "that are very critical\nfor interaction", "start": 267.51, "duration": 2.94}, {"text": "with the human host cells.", "start": 270.45, "duration": 2.2}, {"text": "So these are often\ntermed GP proteins.", "start": 272.65, "duration": 7.58}, {"text": "And the one very\nimportant one is GP140.", "start": 280.23, "duration": 3.3}, {"text": "And that GP stands\nfor glycoprotein.", "start": 283.53, "duration": 7.56}, {"text": "Now, an important aspect,\nremember, of virus lifestyle", "start": 291.09, "duration": 5.0}, {"text": "is that they\nbasically exploit all", "start": 296.09, "duration": 2.94}, {"text": "of the human cellular\nmachinery for their benefit", "start": 299.03, "duration": 3.33}, {"text": "to make their proteins for all\nof the basic needs of a cell.", "start": 302.36, "duration": 4.84}, {"text": "So these glycoproteins\nlook like the glycoproteins", "start": 307.2, "duration": 3.71}, {"text": "that are made by\nhumans, because they're", "start": 310.91, "duration": 2.28}, {"text": "being made by the\nsame machinery that we", "start": 313.19, "duration": 2.79}, {"text": "would make the glycoproteins.", "start": 315.98, "duration": 2.1}, {"text": "In bacteria, when we\ntalked about them,", "start": 318.08, "duration": 2.31}, {"text": "it's a different machinery\nthat glycoproteins", "start": 320.39, "duration": 2.52}, {"text": "and glycoconjugates\nlook different.", "start": 322.91, "duration": 2.43}, {"text": "But in HIV, the glycoproteins\nlook like our glycoproteins.", "start": 325.34, "duration": 4.95}, {"text": "And therefore, you\ncould more or less", "start": 330.29, "duration": 1.68}, {"text": "consider the HIV virus particle\nto be coated with things", "start": 331.97, "duration": 4.98}, {"text": "that look sort of human.", "start": 336.95, "duration": 2.23}, {"text": "So that's a kind of\ndecoy to the human system", "start": 339.18, "duration": 3.62}, {"text": "anyway with respect to\nrecognizing a foreign entity.", "start": 342.8, "duration": 3.96}, {"text": "So often the glycans\nthere serve as decoys", "start": 346.76, "duration": 3.63}, {"text": "to make the human body\nthink, well, there's", "start": 350.39, "duration": 2.13}, {"text": "nothing wrong here.", "start": 352.52, "duration": 1.48}, {"text": "Now within the\nvirus, there is RNA.", "start": 354.0, "duration": 4.88}, {"text": "And it's single-stranded\nbut negative strand RNA,", "start": 358.88, "duration": 6.36}, {"text": "so that's what puts it into--", "start": 365.24, "duration": 2.41}, {"text": "Sorry.", "start": 367.65, "duration": 0.5}, {"text": "Positive strand.", "start": 368.15, "duration": 2.31}, {"text": "Positive.", "start": 370.46, "duration": 0.827}, {"text": "So what puts it into\na separate category", "start": 373.91, "duration": 3.09}, {"text": "is the fact that the genetic\nmaterial in the retroviruses", "start": 377.0, "duration": 4.44}, {"text": "is single-stranded RNA and\nit's the positive strand.", "start": 381.44, "duration": 3.69}, {"text": "So far we've talked\nabout two other types", "start": 385.13, "duration": 2.61}, {"text": "of virus mechanisms--", "start": 387.74, "duration": 1.65}, {"text": "the double-stranded\nDNA-- remember", "start": 389.39, "duration": 1.95}, {"text": "that was as an example.", "start": 391.34, "duration": 1.83}, {"text": "That was smallpox--\nand we've also", "start": 393.17, "duration": 2.16}, {"text": "talked about the single-stranded\nRNA negative strand.", "start": 395.33, "duration": 3.96}, {"text": "And our best example there\nwas the influenza virus,", "start": 399.29, "duration": 4.26}, {"text": "which is a segmented genome.", "start": 403.55, "duration": 2.82}, {"text": "What you'll learn\nabout HIV is that it", "start": 406.37, "duration": 3.45}, {"text": "has a non-segmented genome.", "start": 409.82, "duration": 7.755}, {"text": "Meaning that this strand\nof RNA is one continuous", "start": 420.32, "duration": 3.75}, {"text": "strand rather than\nseparate pieces", "start": 424.07, "duration": 2.88}, {"text": "as we saw in the\ninfluenza virus, which", "start": 426.95, "duration": 2.16}, {"text": "was the last example at\nthe end of the last class.", "start": 429.11, "duration": 3.27}, {"text": "Now, let me just\ntake a quick look.", "start": 432.38, "duration": 1.92}, {"text": "So every virion, that would\nbe a single viral particle,", "start": 434.3, "duration": 6.86}, {"text": "therefore will contain\nwithin its structure the RNA.", "start": 441.16, "duration": 4.71}, {"text": "And it will also contain two\ncopies of a particular enzyme", "start": 448.88, "duration": 5.1}, {"text": "that are absolutely critical.", "start": 453.98, "duration": 1.95}, {"text": "When the virus infects\na cell, there's", "start": 455.93, "duration": 2.28}, {"text": "no time for it to make anything.", "start": 458.21, "duration": 1.71}, {"text": "It needs a particular\nenzyme to get", "start": 459.92, "duration": 2.73}, {"text": "going with replicating\nthat initial strand of RNA", "start": 462.65, "duration": 5.31}, {"text": "to start to come to make a DNA,\ndouble-stranded DNA copy of it,", "start": 467.96, "duration": 4.38}, {"text": "and then make a messenger RNA.", "start": 472.34, "duration": 2.29}, {"text": "So the enzyme that's\nimportant and there", "start": 474.63, "duration": 1.97}, {"text": "are two copies of an enzyme\nknown as reverse transcriptase.", "start": 476.6, "duration": 8.59}, {"text": "So basically, the virus\nstructure is fairly simple.", "start": 493.16, "duration": 4.05}, {"text": "There's a capsid\ninside with the RNA", "start": 497.21, "duration": 3.58}, {"text": "plus the reverse transcriptase\nthat I'm just showing", "start": 500.79, "duration": 3.26}, {"text": "as a filled circle here.", "start": 504.05, "duration": 2.19}, {"text": "And then surrounding the\nvirion is a membrane bilayer", "start": 506.24, "duration": 6.0}, {"text": "with GP proteins stuck into\nthat membrane bilayer that", "start": 512.24, "duration": 4.703}, {"text": "are going to be\nimportant when one", "start": 516.943, "duration": 1.417}, {"text": "starts to think about the\ninfectivity by the virus.", "start": 518.36, "duration": 4.23}, {"text": "All right.", "start": 522.59, "duration": 0.66}, {"text": "There's a second glycoprotein\nthat's also important,", "start": 523.25, "duration": 5.47}, {"text": "which is known as GP41.", "start": 528.72, "duration": 2.21}, {"text": "And these are very specifically\npart of this complex,", "start": 530.93, "duration": 4.94}, {"text": "but associated with the GP140.", "start": 535.87, "duration": 3.12}, {"text": "All right.", "start": 538.99, "duration": 0.74}, {"text": "So now let's take a\nlook at the virus life--", "start": 539.73, "duration": 3.2}, {"text": "or details of this virus.", "start": 542.93, "duration": 3.73}, {"text": "But first of all, I want you\nto take a look at T-cells.", "start": 546.66, "duration": 4.05}, {"text": "You've heard a\nlot about T-cells.", "start": 550.71, "duration": 2.32}, {"text": "They're a major component\nof the immune system.", "start": 553.03, "duration": 3.18}, {"text": "So I'm going to home\nyou right in on what", "start": 556.21, "duration": 2.57}, {"text": "the virus, the virion,\nrecognizes on T-cells", "start": 558.78, "duration": 4.2}, {"text": "and what makes it\nsuch a disaster", "start": 562.98, "duration": 1.83}, {"text": "for the human immune system.", "start": 564.81, "duration": 1.87}, {"text": "OK.", "start": 566.68, "duration": 0.5}, {"text": "So here are typical\nT-cell receptors", "start": 567.18, "duration": 3.39}, {"text": "on the surface of T-cells.", "start": 570.57, "duration": 2.1}, {"text": "Just as a recap, I want you\nto remember T-cells produce", "start": 572.67, "duration": 3.53}, {"text": "unique antigen binding\nproteins that are", "start": 576.2, "duration": 4.36}, {"text": "put onto the T-cell surface.", "start": 580.56, "duration": 3.18}, {"text": "And they provide\ncell-mediated immunity", "start": 583.74, "duration": 3.03}, {"text": "by destroying antigens\nsuch as viruses.", "start": 586.77, "duration": 3.93}, {"text": "But what the HIV virus\ndoes is it really", "start": 590.7, "duration": 3.09}, {"text": "homes in on the cell-surface\nreceptors of the T-cells,", "start": 593.79, "duration": 4.53}, {"text": "specifically the HIV virus\nrecognizes the CD4 receptor,", "start": 598.32, "duration": 7.57}, {"text": "which is a glycoprotein on\nthe surface of some T-cells", "start": 605.89, "duration": 3.71}, {"text": "that are designated as\nCD4 positive T-cells.", "start": 609.6, "duration": 4.12}, {"text": "So if you have\ncirculating T-cells,", "start": 613.72, "duration": 3.35}, {"text": "that would be the first place\nwhere the HIV virus attaches", "start": 617.07, "duration": 5.76}, {"text": "to the T-cell to\ncause infectivity,", "start": 622.83, "duration": 3.3}, {"text": "thus debilitating\nthe ability to mount", "start": 626.13, "duration": 3.93}, {"text": "the type of immune responses\nthat T-cells are involved in.", "start": 630.06, "duration": 3.66}, {"text": "So it's very important\nto now understand", "start": 633.72, "duration": 2.7}, {"text": "why the physiology of\nthis virus is to knock out", "start": 636.42, "duration": 5.49}, {"text": "the thing that's\nthere to protect us", "start": 641.91, "duration": 2.37}, {"text": "from foreign antigens,\nwhich makes it so serious.", "start": 644.28, "duration": 4.42}, {"text": "Now, HIV first started to\nemerge in the early '80s.", "start": 648.7, "duration": 5.84}, {"text": "It was more or less designated\nas a death sentence.", "start": 654.54, "duration": 3.12}, {"text": "As you may be aware,\nHIV circulated", "start": 657.66, "duration": 2.97}, {"text": "around the gay community\nin the San Francisco area", "start": 660.63, "duration": 3.63}, {"text": "very rapidly.", "start": 664.26, "duration": 1.33}, {"text": "But it then became\nincredibly widespread.", "start": 665.59, "duration": 4.29}, {"text": "There's a possibility\nthat the jump", "start": 669.88, "duration": 1.82}, {"text": "of the virus from primates\nto humans, the virus", "start": 671.7, "duration": 5.97}, {"text": "might have originated in Africa.", "start": 677.67, "duration": 2.25}, {"text": "There's a lot of work done\non the origin of this virus,", "start": 679.92, "duration": 3.42}, {"text": "but it sort of came\nout of nowhere.", "start": 683.34, "duration": 2.24}, {"text": "It was something that was\nunexpected, unanticipated,", "start": 685.58, "duration": 3.52}, {"text": "and hitting people\njust like a cannonball.", "start": 689.1, "duration": 3.69}, {"text": "And it was literally a\ndeath sentence early on.", "start": 692.79, "duration": 3.9}, {"text": "As the mechanism of the\nvirus became understood,", "start": 696.69, "duration": 4.02}, {"text": "a number of strategies could\nbe put in place with respect", "start": 700.71, "duration": 3.3}, {"text": "to antiviral therapeutics to\ntarget this particular virus.", "start": 704.01, "duration": 4.8}, {"text": "And what we will see\nis the four types", "start": 708.81, "duration": 2.1}, {"text": "of targets that have\nbeen named as targets", "start": 710.91, "duration": 4.14}, {"text": "for therapeutic agents, why\nthey work, how they work.", "start": 715.05, "duration": 3.49}, {"text": "And we'll see the mechanisms\nof those as to how", "start": 718.54, "duration": 2.63}, {"text": "they pertain to the HIV virus.", "start": 721.17, "duration": 3.51}, {"text": "And we'll talk about things\nlike combination therapies.", "start": 724.68, "duration": 2.94}, {"text": "So early on, there\nwas really nothing.", "start": 727.62, "duration": 3.15}, {"text": "Gradually early, therapeutic\napproaches started to emerge,", "start": 730.77, "duration": 4.54}, {"text": "but they were\ndevastating treatments", "start": 735.31, "duration": 2.99}, {"text": "because the drugs were so\npoor against the HIV virus,", "start": 738.3, "duration": 4.08}, {"text": "people were taking massive\nhandfuls of medications a day", "start": 742.38, "duration": 4.08}, {"text": "to try to stay\nahead of the virus.", "start": 746.46, "duration": 2.4}, {"text": "As time has progressed,\nthese therapeutic agents", "start": 748.86, "duration": 3.51}, {"text": "have been improved and improved.", "start": 752.37, "duration": 2.04}, {"text": "And now they're relatively\nsimple therapeutic agents", "start": 754.41, "duration": 3.96}, {"text": "where you don't have to\ntake massive doses of fairly", "start": 758.37, "duration": 3.09}, {"text": "non-specific therapeutic agents.", "start": 761.46, "duration": 2.58}, {"text": "But they're quite\nsort of workable.", "start": 764.04, "duration": 4.17}, {"text": "The problem is,\nand you'll see why,", "start": 768.21, "duration": 2.67}, {"text": "people have to take these\ntherapeutic agents for life.", "start": 770.88, "duration": 3.42}, {"text": "Once cells are\ninfected with HIV,", "start": 774.3, "duration": 2.67}, {"text": "there will always\nbe a population", "start": 776.97, "duration": 2.67}, {"text": "of the virus genetic\nmaterial in the human genome.", "start": 779.64, "duration": 4.12}, {"text": "So you can't just say,\nI feel way better,", "start": 783.76, "duration": 2.57}, {"text": "not taking these drugs anymore,\nbecause there is the chance", "start": 786.33, "duration": 3.6}, {"text": "that in some repository\nin some of your cells", "start": 789.93, "duration": 3.24}, {"text": "the virus genetic\nmaterial is still there.", "start": 793.17, "duration": 2.16}, {"text": "And you'll see which enzymes in\nHIV are responsible for that.", "start": 795.33, "duration": 4.29}, {"text": "OK?", "start": 799.62, "duration": 1.17}, {"text": "So let's take a look\nhere at the Group VI", "start": 800.79, "duration": 4.14}, {"text": "retrovirus named HIV/AIDS.", "start": 804.93, "duration": 4.23}, {"text": "In 2015, there were 37\nmillion people infected.", "start": 809.16, "duration": 6.96}, {"text": "Nowhere near enough in\ntreatment, about half", "start": 816.12, "duration": 2.46}, {"text": "of those in treatment.", "start": 818.58, "duration": 1.32}, {"text": "And about 1.2 million deaths.", "start": 819.9, "duration": 1.86}, {"text": "This may account also for\npeople coinfected with TB.", "start": 821.76, "duration": 4.5}, {"text": "I mentioned to you\nwhen we started", "start": 826.26, "duration": 2.13}, {"text": "talking about\ninfectious disease,", "start": 828.39, "duration": 2.43}, {"text": "I really encourage you to\ngo to the NIAID website.", "start": 830.82, "duration": 3.93}, {"text": "There is tons of really\ninteresting information,", "start": 834.75, "duration": 3.36}, {"text": "not just from a\nclinical perspective", "start": 838.11, "duration": 2.22}, {"text": "but from a mechanistic\nperspective,", "start": 840.33, "duration": 2.1}, {"text": "from a treatment perspective.", "start": 842.43, "duration": 1.24}, {"text": "There's really important things.", "start": 843.67, "duration": 1.7}, {"text": "So I really encourage\nyou if you are", "start": 845.37, "duration": 1.86}, {"text": "interested in infectious\ndisease, the National", "start": 847.23, "duration": 3.75}, {"text": "Institute of Allergies and\nInfectious Diseases Component", "start": 850.98, "duration": 6.42}, {"text": "of the NIH is the one\nresponsible for all", "start": 857.4, "duration": 3.09}, {"text": "the research on\ninfectious disease.", "start": 860.49, "duration": 3.37}, {"text": "And in fact, for\nmany, many years", "start": 863.86, "duration": 2.39}, {"text": "during the crisis\nwith HIV, there", "start": 866.25, "duration": 2.37}, {"text": "were special earmarked\nfunds for any research", "start": 868.62, "duration": 4.35}, {"text": "towards the development\nof therapeutic agents.", "start": 872.97, "duration": 2.91}, {"text": "So what happens?", "start": 875.88, "duration": 1.38}, {"text": "How does this virus,\nthis little particle", "start": 877.26, "duration": 1.95}, {"text": "that I've shown you here--", "start": 879.21, "duration": 2.1}, {"text": "I should really show\nyou this is the capsid.", "start": 881.31, "duration": 3.5}, {"text": "And I should really show you\nthe membrane a little bit more", "start": 884.81, "duration": 3.19}, {"text": "encircling that with\nthe capsid inside.", "start": 888.0, "duration": 2.49}, {"text": "So the cartoon that you see\non the screen is more correct.", "start": 890.49, "duration": 4.53}, {"text": "So here's the virion particle.", "start": 895.02, "duration": 2.43}, {"text": "It has inside it the\ncapsid that includes", "start": 897.45, "duration": 4.02}, {"text": "the single-stranded RNA.", "start": 901.47, "duration": 2.22}, {"text": "It only needs to code\nfor very few proteins,", "start": 903.69, "duration": 3.04}, {"text": "remember, because the virus\njust exploits everything", "start": 906.73, "duration": 2.99}, {"text": "else from the human host.", "start": 909.72, "duration": 1.83}, {"text": "And GP120-- sorry for that\ntypo, please correct that.", "start": 911.55, "duration": 10.54}, {"text": "And GP120 is displayed on\nthe surface of the virion.", "start": 922.09, "duration": 4.89}, {"text": "And in fact, it's\nGP120 that interacts", "start": 926.98, "duration": 3.33}, {"text": "with the CD4 receptor on\nthe surface of a target host", "start": 930.31, "duration": 3.96}, {"text": "cell, a T-cell.", "start": 934.27, "duration": 1.89}, {"text": "Now there is a second receptor\nthat's quite important.", "start": 936.16, "duration": 3.7}, {"text": "It was not discovered\nuntil quite a bit later on.", "start": 939.86, "duration": 3.78}, {"text": "It's designated\nas the coreceptor.", "start": 943.64, "duration": 2.69}, {"text": "And the interaction of the\nvirion with the host cell", "start": 946.33, "duration": 4.32}, {"text": "is only good when there's\nboth the CD4 receptor", "start": 950.65, "duration": 3.69}, {"text": "plus the coreceptor.", "start": 954.34, "duration": 1.89}, {"text": "And this was found through\ncareful biology that", "start": 956.23, "duration": 2.67}, {"text": "realized there was\nanother critical component", "start": 958.9, "duration": 2.85}, {"text": "for the infectious disease.", "start": 961.75, "duration": 1.78}, {"text": "And that is designated as\nthe CCR5 receptor or CXCR4", "start": 963.53, "duration": 4.67}, {"text": "receptor.", "start": 968.2, "duration": 0.87}, {"text": "So both receptors on\nthe surface, the virus", "start": 969.07, "duration": 4.26}, {"text": "has evolved or selected\nout, to recognize", "start": 973.33, "duration": 3.27}, {"text": "cells that have both of\nthose types of receptors", "start": 976.6, "duration": 2.7}, {"text": "on the surface which ends\nup making them very targeted", "start": 979.3, "duration": 4.08}, {"text": "towards the T-cells.", "start": 983.38, "duration": 1.77}, {"text": "Once that association\noccurs, then", "start": 985.15, "duration": 3.69}, {"text": "becomes the process of fusion.", "start": 988.84, "duration": 3.42}, {"text": "So remember, I told you that\nlarge things can get into cells", "start": 992.26, "duration": 4.71}, {"text": "by merging a membrane\nwith the membrane", "start": 996.97, "duration": 4.47}, {"text": "on the surface of the cell.", "start": 1001.44, "duration": 1.84}, {"text": "So what is happening as those\ntwo receptors are engaged", "start": 1003.28, "duration": 3.71}, {"text": "is the virus membrane is coming\nclose to the host cell membrane", "start": 1006.99, "duration": 6.12}, {"text": "and starting to fuse\nthrough the action of GP120", "start": 1013.11, "duration": 5.07}, {"text": "along with the CD4\nreceptor and coreceptor.", "start": 1018.18, "duration": 3.937}, {"text": "And I'm going to\nshow you a movie that", "start": 1022.117, "duration": 1.583}, {"text": "shows that part of the\nfusion, because it's really", "start": 1023.7, "duration": 2.79}, {"text": "cool to see it in action.", "start": 1026.49, "duration": 2.129}, {"text": "Once that fusion occurs,\nthe virus membrane", "start": 1028.619, "duration": 4.5}, {"text": "actually just merges with the\nremainder of the host cell", "start": 1033.119, "duration": 3.631}, {"text": "membrane.", "start": 1036.75, "duration": 0.839}, {"text": "And you drop that capsid into\nthe cell, which then becomes", "start": 1037.589, "duration": 3.601}, {"text": "on packaged to release the\nsingle-stranded RNA that's", "start": 1041.19, "duration": 4.5}, {"text": "the contents of that.", "start": 1045.69, "duration": 1.62}, {"text": "And what's important to know--\nwhoops going backwards--", "start": 1047.31, "duration": 4.6}, {"text": "is that the minute the\nsingle-stranded RNA", "start": 1051.91, "duration": 3.66}, {"text": "gets into the cell, that\nneeds to be processed.", "start": 1055.57, "duration": 8.0}, {"text": "But it needs to be processed\nwith an enzyme that is", "start": 1063.57, "duration": 3.51}, {"text": "completely unique to the virus.", "start": 1067.08, "duration": 2.47}, {"text": "And that's the\nreverse transcriptase.", "start": 1069.55, "duration": 2.93}, {"text": "Without the reverse\ntranscriptase being there,", "start": 1072.48, "duration": 2.54}, {"text": "it's just RNA that's just going\nto get chewed up in the cell.", "start": 1075.02, "duration": 4.4}, {"text": "So what reverse transcriptase\ndoes it reverse transcribes RNA", "start": 1079.42, "duration": 5.42}, {"text": "into DNA.", "start": 1084.84, "duration": 1.71}, {"text": "So that gets you on the track\nto the infectious process.", "start": 1086.55, "duration": 3.81}, {"text": "In the absence of RT,\nyou don't get there.", "start": 1090.36, "duration": 2.79}, {"text": "You're not able to make\na DNA copy to then make", "start": 1093.15, "duration": 4.11}, {"text": "a copy of the RNA and so on.", "start": 1097.26, "duration": 1.98}, {"text": "So reverse\ntranscriptase, that is", "start": 1099.24, "duration": 2.22}, {"text": "why the reverse transcriptase\nhas to be delivered along", "start": 1101.46, "duration": 4.74}, {"text": "with the virus.", "start": 1106.2, "duration": 0.91}, {"text": "It can't be just a virus\nwith the genetic material.", "start": 1107.11, "duration": 2.91}, {"text": "It's got to have this\nparticular enzyme with it.", "start": 1110.02, "duration": 2.63}, {"text": "So reverse transcriptase is\nresponsible for converting RNA", "start": 1112.65, "duration": 6.0}, {"text": "into DNA.", "start": 1118.65, "duration": 1.41}, {"text": "And as you all know, that\nis not the usual direction", "start": 1120.06, "duration": 4.68}, {"text": "with respect to\nthe central dogma.", "start": 1124.74, "duration": 1.74}, {"text": "We're always talking\nabout DNA to RNA.", "start": 1126.48, "duration": 2.85}, {"text": "But you've also heard\nthroughout the course,", "start": 1129.33, "duration": 2.46}, {"text": "how handy this reverse\ntranscriptase is material is.", "start": 1131.79, "duration": 4.65}, {"text": "When we talk about arrays\nand loads of biotechnology,", "start": 1136.44, "duration": 4.11}, {"text": "using reverse transcriptase\nis super valuable.", "start": 1140.55, "duration": 2.99}, {"text": "Let's say, for example, we\ndon't want to sequence a genome,", "start": 1143.54, "duration": 3.64}, {"text": "we want to look at the\ntranscriptome, the part", "start": 1147.18, "duration": 2.88}, {"text": "of the genome that's really\nimportant for being translated", "start": 1150.06, "duration": 2.97}, {"text": "into proteins.", "start": 1153.03, "duration": 1.41}, {"text": "What we do is we collect\nthe transcriptome", "start": 1154.44, "duration": 2.94}, {"text": "but reverse transcribe\nit into DNA,", "start": 1157.38, "duration": 2.88}, {"text": "which is a much more\nstable, tractable material", "start": 1160.26, "duration": 3.6}, {"text": "for sequencing and\nso on and so forth.", "start": 1163.86, "duration": 2.47}, {"text": "So RT has become kind of\na gift to biotechnology", "start": 1166.33, "duration": 3.62}, {"text": "and biological research.", "start": 1169.95, "duration": 1.62}, {"text": "And it was inspired from\nthe RT in the HIV virus.", "start": 1171.57, "duration": 4.29}, {"text": "So that's very important.", "start": 1175.86, "duration": 1.96}, {"text": "So the reverse\ntranscriptase, then,", "start": 1177.82, "duration": 2.36}, {"text": "makes a DNA copy of the RNA.", "start": 1180.18, "duration": 4.17}, {"text": "And then a second\ncomplementary copy", "start": 1184.35, "duration": 2.97}, {"text": "of that DNA is made to make\ndouble-stranded DNA which", "start": 1187.32, "duration": 4.44}, {"text": "represents the viral\ngenome, but in the format", "start": 1191.76, "duration": 3.18}, {"text": "of a double-stranded DNA.", "start": 1194.94, "duration": 2.13}, {"text": "That DNA can be, then, taken--", "start": 1197.07, "duration": 4.53}, {"text": "here's the fun part.", "start": 1201.6, "duration": 1.56}, {"text": "That DNA is actually, then,\ntaken into the nucleus", "start": 1203.16, "duration": 4.5}, {"text": "and it's zippered in\nto the host genome", "start": 1207.66, "duration": 4.05}, {"text": "by an enzyme known as integrase.", "start": 1211.71, "duration": 2.58}, {"text": "So it's not that you\nhave this virus junk", "start": 1214.29, "duration": 2.82}, {"text": "and then you send\nit back out again", "start": 1217.11, "duration": 2.19}, {"text": "with the mature\nparticles, you actually", "start": 1219.3, "duration": 2.37}, {"text": "put this in the permanent copy\nof your DNA in the nucleus.", "start": 1221.67, "duration": 5.91}, {"text": "And that is why people don't\nget cured from HIV/AIDS.", "start": 1227.58, "duration": 6.24}, {"text": "They have to take treatment\nfor the rest of their life,", "start": 1233.82, "duration": 2.58}, {"text": "because that DNA is permanently\nin the copy of your genome", "start": 1236.4, "duration": 4.23}, {"text": "that gets replicated every time\nyour cells divide and so on.", "start": 1240.63, "duration": 3.66}, {"text": "So you can understand the\nseriousness of that event.", "start": 1244.29, "duration": 3.63}, {"text": "So that gets taken\ninto the genome.", "start": 1247.92, "duration": 4.2}, {"text": "But also when it's time\nto make new virions,", "start": 1252.12, "duration": 3.96}, {"text": "the DNA is transcribed\ninto messenger RNA.", "start": 1256.08, "duration": 4.44}, {"text": "The messenger RNA\nleaves the nucleus,", "start": 1260.52, "duration": 3.3}, {"text": "gets translated into proteins.", "start": 1263.82, "duration": 2.97}, {"text": "And those proteins\nform the basis", "start": 1266.79, "duration": 2.28}, {"text": "of the new virion particles.", "start": 1269.07, "duration": 2.22}, {"text": "Now, I mentioned\nsomewhere here that it", "start": 1271.29, "duration": 2.91}, {"text": "is a non-segmented genome.", "start": 1274.2, "duration": 2.58}, {"text": "So initially, the messenger\nRNA is a single segment", "start": 1276.78, "duration": 8.06}, {"text": "that then gets translated into\na single segment of protein,", "start": 1284.84, "duration": 5.8}, {"text": "which is known as a polyprotein.", "start": 1290.64, "duration": 1.66}, {"text": "So there are no stops between\nthe various genes encoding", "start": 1295.17, "duration": 4.89}, {"text": "frames within the messenger RNA.", "start": 1300.06, "duration": 2.68}, {"text": "So that gets transcribed\nby the host machinery", "start": 1302.74, "duration": 4.07}, {"text": "straight into a polyprotein\nthat's all glued together", "start": 1306.81, "duration": 4.86}, {"text": "in a single long piece.", "start": 1311.67, "duration": 1.99}, {"text": "But then there is another\nimportant HIV enzyme,", "start": 1313.66, "duration": 6.33}, {"text": "the protease, that chops those\nportions of the polyprotein", "start": 1319.99, "duration": 6.77}, {"text": "up into useful and\nusable portions.", "start": 1326.76, "duration": 3.54}, {"text": "So you also need the\nprotease readily available", "start": 1330.3, "duration": 3.72}, {"text": "rapidly to start dicing up the\npolyprotein into usable protein", "start": 1334.02, "duration": 4.89}, {"text": "segments for the\nnew virus assembly.", "start": 1338.91, "duration": 2.64}, {"text": "So let's take a look\nhere what happens.", "start": 1341.55, "duration": 3.42}, {"text": "The messenger\nleaves the nucleus.", "start": 1344.97, "duration": 1.575}, {"text": "You make a polyprotein that gets\ndigested into protein segments.", "start": 1350.04, "duration": 3.93}, {"text": "And then everything accumulates\nat the inside surface", "start": 1353.97, "duration": 3.9}, {"text": "of the membrane and starts\nbudding off the virion.", "start": 1357.87, "duration": 4.47}, {"text": "When it's first budded off,\nit's not really ready to go.", "start": 1362.34, "duration": 3.22}, {"text": "It's not intact.", "start": 1365.56, "duration": 1.07}, {"text": "It has to develop a\nlittle bit further", "start": 1366.63, "duration": 2.52}, {"text": "to become a mature\nvirion moving forward", "start": 1369.15, "duration": 3.06}, {"text": "to go infect another cell.", "start": 1372.21, "duration": 2.13}, {"text": "So the initial stage, that\nbudded stage, of the virion", "start": 1374.34, "duration": 5.19}, {"text": "is not completely\ncompetent to go infect.", "start": 1379.53, "duration": 2.76}, {"text": "And in fact, there\nhas been some thoughts", "start": 1382.29, "duration": 2.52}, {"text": "about can you ensure that the\nimmature virion doesn't develop", "start": 1384.81, "duration": 5.37}, {"text": "into the mature virion,\nbecause that would be one", "start": 1390.18, "duration": 2.58}, {"text": "way of targeting the system.", "start": 1392.76, "duration": 1.72}, {"text": "OK.", "start": 1394.48, "duration": 0.5}, {"text": "So there are a few\ndifferent pieces--", "start": 1394.98, "duration": 3.03}, {"text": "the reverse transcriptase,\nthe integrase, the protease,", "start": 1398.01, "duration": 10.82}, {"text": "and then, finally--", "start": 1408.83, "duration": 0.795}, {"text": "these are all critical\nprocesses that", "start": 1412.61, "duration": 2.55}, {"text": "have been the targets\nof therapeutic agents.", "start": 1415.16, "duration": 3.13}, {"text": "They are molecular\ntargets, such as enzymes.", "start": 1418.29, "duration": 2.66}, {"text": "And we know how to address\nenzymes with inhibitors.", "start": 1420.95, "duration": 6.06}, {"text": "And one last feature\nof the virus life cycle", "start": 1427.01, "duration": 4.23}, {"text": "that has been focused on\nrespect to therapeutics", "start": 1431.24, "duration": 4.26}, {"text": "is the viral fusion.", "start": 1435.5, "duration": 1.065}, {"text": "So there have also been\nefforts at a molecular level", "start": 1441.87, "duration": 4.22}, {"text": "to try to inhibit this process\nwhere your virus particle docks", "start": 1446.09, "duration": 6.72}, {"text": "down on the cell and\nsomehow the membranes fuse", "start": 1452.81, "duration": 4.2}, {"text": "and then the virus dumps\nits contents into the cell.", "start": 1457.01, "duration": 3.45}, {"text": "OK.", "start": 1460.46, "duration": 0.78}, {"text": "This is just sort of a quick\nsort of more beautiful view.", "start": 1461.24, "duration": 4.89}, {"text": "But in a minute, I'm\ngoing to show you a video.", "start": 1466.13, "duration": 2.64}, {"text": "But I thought it was kind\nof nice because it really", "start": 1468.77, "duration": 2.31}, {"text": "allows you to look at the\ndifferent steps in the virus", "start": 1471.08, "duration": 3.49}, {"text": "life cycle--", "start": 1474.57, "duration": 2.09}, {"text": "recognition, fusion, delivery,\nmaking the double-stranded DNA,", "start": 1476.66, "duration": 5.7}, {"text": "integrated the DNA\ninto the genome,", "start": 1482.36, "duration": 2.76}, {"text": "and making new viral proteins.", "start": 1485.12, "duration": 1.8}, {"text": "So those steps,\nthey're pretty logical.", "start": 1486.92, "duration": 2.25}, {"text": "It's just like step one,\ngot to find my target.", "start": 1489.17, "duration": 3.15}, {"text": "Step two, I've got to\nstick to my target.", "start": 1492.32, "duration": 2.1}, {"text": "Step three, I've got to\ndeliver my genomic content", "start": 1494.42, "duration": 3.57}, {"text": "into my target and so on.", "start": 1497.99, "duration": 2.04}, {"text": "So I don't want you\nto think this is", "start": 1500.03, "duration": 2.01}, {"text": "a bunch of steps to memorize.", "start": 1502.04, "duration": 1.53}, {"text": "They all sort of make sense in\na logical progression of events", "start": 1503.57, "duration": 3.6}, {"text": "to make the virus be able to go\nall the way through to budding", "start": 1507.17, "duration": 4.08}, {"text": "off new, immature, and\nthen mature virions.", "start": 1511.25, "duration": 4.53}, {"text": "And so as I\nmentioned over there,", "start": 1515.78, "duration": 1.93}, {"text": "these are the four\ntargets that I'm", "start": 1517.71, "duration": 1.52}, {"text": "going to describe\nto you with respect", "start": 1519.23, "duration": 1.74}, {"text": "to therapeutic development.", "start": 1520.97, "duration": 2.07}, {"text": "And this is where\nthey all work--", "start": 1523.04, "duration": 1.74}, {"text": "the fusion early on, the\nreverse transcriptase", "start": 1524.78, "duration": 4.2}, {"text": "taking that single-stranded\nRNA to a DNA copy,", "start": 1528.98, "duration": 5.85}, {"text": "the integrase which zips\nthe genomic material", "start": 1534.83, "duration": 3.51}, {"text": "into the genome, and the\nprotease that cleaves up", "start": 1538.34, "duration": 4.14}, {"text": "the long polyprotein to make\nmature pieces of protein that", "start": 1542.48, "duration": 4.92}, {"text": "are part of the virus.", "start": 1547.4, "duration": 0.975}, {"text": "OK.", "start": 1552.9, "duration": 0.69}, {"text": "So let's talk first of\nall about viral fusion.", "start": 1553.59, "duration": 2.64}, {"text": "And as I mentioned, when\nI get to showing you--", "start": 1556.23, "duration": 2.43}, {"text": "it's a really beautiful\nvideo from the Howard Hughes", "start": 1558.66, "duration": 4.89}, {"text": "Institute that really\nshows the fusion very well.", "start": 1563.55, "duration": 3.18}, {"text": "But I want to describe\nthe fusion to you", "start": 1566.73, "duration": 2.85}, {"text": "at a molecular level.", "start": 1569.58, "duration": 1.5}, {"text": "And then later, you'll see it\na little bit more real life.", "start": 1571.08, "duration": 4.78}, {"text": "So what I said to you is\nthat GP120 and GP41, which", "start": 1575.86, "duration": 5.0}, {"text": "are these proteins that are\nin the surface of the envelope", "start": 1580.86, "duration": 5.01}, {"text": "then recognize the coreceptor\nand CD41 and form a complex.", "start": 1585.87, "duration": 6.69}, {"text": "So it's a complex that\ninvolves what's on the virus.", "start": 1592.56, "duration": 3.28}, {"text": "It's actually in a\ntrimeric structure", "start": 1595.84, "duration": 2.24}, {"text": "with the two receptors\nthat are on the host cell.", "start": 1598.08, "duration": 2.97}, {"text": "And they form a\npretty close union.", "start": 1601.05, "duration": 2.64}, {"text": "And then what\nhappens is there are", "start": 1603.69, "duration": 1.68}, {"text": "a series of events that tug\nthe two membranes together,", "start": 1605.37, "duration": 4.53}, {"text": "mechanically linked to\nconformational changes", "start": 1609.9, "duration": 3.48}, {"text": "of the protein, and basically\nsplosh the two membranes", "start": 1613.38, "duration": 4.14}, {"text": "together for a fusion event.", "start": 1617.52, "duration": 2.1}, {"text": "So it's through the\nconfirmational dynamics", "start": 1619.62, "duration": 3.81}, {"text": "of that large complex\nhappening in sequence", "start": 1623.43, "duration": 3.03}, {"text": "after the first interactions\nthat get you to a fusion event.", "start": 1626.46, "duration": 4.47}, {"text": "So these initially\nlook like this,", "start": 1630.93, "duration": 2.67}, {"text": "but then they start\nchanging their shape,", "start": 1633.6, "duration": 2.64}, {"text": "and making a fusion event.", "start": 1636.24, "duration": 1.89}, {"text": "So you could look at\nit as, initially, you", "start": 1638.13, "duration": 2.46}, {"text": "have the complex formed,\nbut then, later on, there's", "start": 1640.59, "duration": 3.33}, {"text": "been a twisting\nof the structures,", "start": 1643.92, "duration": 1.86}, {"text": "the large macromolecular\nstructures", "start": 1645.78, "duration": 1.8}, {"text": "to fuse the membranes.", "start": 1647.58, "duration": 1.84}, {"text": "So for quite a few years--", "start": 1649.42, "duration": 2.3}, {"text": "and I don't think it\nwas the most successful", "start": 1651.72, "duration": 2.64}, {"text": "of the approaches with\nrespect to therapeutics--", "start": 1654.36, "duration": 2.85}, {"text": "people thought that maybe you\ncould inhibit the interaction", "start": 1657.21, "duration": 4.23}, {"text": "between GP120 and\nthose receptors", "start": 1661.44, "duration": 2.88}, {"text": "with small molecules that\nmight inhibit the progress", "start": 1664.32, "duration": 3.48}, {"text": "through the fusion process.", "start": 1667.8, "duration": 2.13}, {"text": "So that was deemed\na viable target.", "start": 1669.93, "duration": 2.85}, {"text": "It's not the same\nas an enzyme target,", "start": 1672.78, "duration": 2.52}, {"text": "but it's definitely a critical\npoint in viral infections.", "start": 1675.3, "duration": 3.81}, {"text": "And what was made\nwere short peptides", "start": 1679.11, "duration": 2.82}, {"text": "that might stabilize\nthis complex", "start": 1681.93, "duration": 2.76}, {"text": "and avoid the structure\nmoving forward", "start": 1684.69, "duration": 4.35}, {"text": "to the fusion-related complex.", "start": 1689.04, "duration": 2.55}, {"text": "So that was one sort\nof series of events.", "start": 1691.59, "duration": 2.64}, {"text": "So those peptides were\ndesignated a C-peptide.", "start": 1694.23, "duration": 3.84}, {"text": "They would bind to\nthis portion up here", "start": 1698.07, "duration": 2.67}, {"text": "that's pointed to with\nthe N. They'd stick", "start": 1700.74, "duration": 2.4}, {"text": "and they'd basically\njam the cogs.", "start": 1703.14, "duration": 2.4}, {"text": "They'd stopped that event\noccurring by binding", "start": 1705.54, "duration": 4.23}, {"text": "quite tightly to part\nof the fusion complex.", "start": 1709.77, "duration": 2.715}, {"text": "OK?", "start": 1712.485, "duration": 2.265}, {"text": "The drugs, the therapeutic\nagents, in that case", "start": 1714.75, "duration": 3.48}, {"text": "were peptidic, kind of large.", "start": 1718.23, "duration": 2.67}, {"text": "They don't diffuse into cells,\nbut that's not a problem", "start": 1720.9, "duration": 3.21}, {"text": "because this target\nis outside the cell.", "start": 1724.11, "duration": 2.86}, {"text": "So there's no need for that to\nget into cells for its effect.", "start": 1726.97, "duration": 3.5}, {"text": "All of the other therapeutic\nagents I'll describe to you", "start": 1730.47, "duration": 3.34}, {"text": "are molecules that need\nto get into cells in order", "start": 1733.81, "duration": 2.93}, {"text": "to do their job.", "start": 1736.74, "duration": 1.87}, {"text": "But this particular strategy\ndidn't involve that.", "start": 1738.61, "duration": 3.35}, {"text": "Which was why it was\nfairly attractive early on,", "start": 1741.96, "duration": 3.39}, {"text": "because it was a very different\ntarget from the others.", "start": 1745.35, "duration": 3.27}, {"text": "So the next step I\nwant to describe to you", "start": 1748.62, "duration": 3.36}, {"text": "is inhibition of\nreserve transcriptase.", "start": 1751.98, "duration": 5.22}, {"text": "So this is a RNA-dependent\nDNA polymerase.", "start": 1757.2, "duration": 12.49}, {"text": "OK?", "start": 1769.69, "duration": 0.5}, {"text": "So different from the\nother DNA polymerases.", "start": 1770.19, "duration": 3.09}, {"text": "We have DNA-dependent\nDNA polymerases,", "start": 1773.28, "duration": 2.52}, {"text": "but we don't have the\nRNA-dependent ones.", "start": 1775.8, "duration": 3.39}, {"text": "And so the types of strategies\nthat were used initially", "start": 1779.19, "duration": 3.78}, {"text": "was to use types of\nanalogs of the nucleosides", "start": 1782.97, "duration": 4.41}, {"text": "that will be used\nin polymerization.", "start": 1787.38, "duration": 3.12}, {"text": "So the reverse transcriptase,\nthe first types of targets--", "start": 1790.5, "duration": 6.16}, {"text": "what's going on down there--\nthe first types of targets", "start": 1796.66, "duration": 3.83}, {"text": "were nucleoside\nanalogs because they", "start": 1800.49, "duration": 3.43}, {"text": "can inhibit the polymerization.", "start": 1803.92, "duration": 2.12}, {"text": "And you're going to realize you\nknow quite a bit about these", "start": 1806.04, "duration": 2.5}, {"text": "when we first look\nat the structure.", "start": 1808.54, "duration": 1.783}, {"text": "So I'm going to\ndescribe to you what are", "start": 1810.323, "duration": 1.667}, {"text": "known as nucleoside analogs.", "start": 1811.99, "duration": 4.14}, {"text": "What does this term mean?", "start": 1820.57, "duration": 2.16}, {"text": "Nucleoside means it's a\nnuclear base plus a sugar.", "start": 1822.73, "duration": 4.47}, {"text": "There's no phosphates.", "start": 1827.2, "duration": 1.23}, {"text": "Because, remember,\nthere's an s there.", "start": 1828.43, "duration": 2.54}, {"text": "And it's an analog meaning it's\nnot one of the native ones,", "start": 1830.97, "duration": 3.7}, {"text": "but it--", "start": 1834.67, "duration": 1.985}, {"text": "that looks good.", "start": 1836.655, "duration": 1.511}, {"text": "AUDIENCE: I'm looking\nfor [INAUDIBLE]", "start": 1838.166, "duration": 5.587}, {"text": "BARBARA IMPERIALI: OK.", "start": 1843.753, "duration": 0.917}, {"text": "I'll grab her.", "start": 1844.67, "duration": 0.69}, {"text": "And you get the bag.", "start": 1845.36, "duration": 0.96}, {"text": "[LAUGHTER]", "start": 1846.32, "duration": 3.27}, {"text": "OK.", "start": 1849.59, "duration": 0.5}, {"text": "So it's a nucleoside\nanalog meaning", "start": 1850.09, "duration": 2.26}, {"text": "it isn't the\nstandard nucleosides", "start": 1852.35, "duration": 3.21}, {"text": "that you put into your DNA.", "start": 1855.56, "duration": 1.98}, {"text": "And the most critical first line\nactually became azidothymidine.", "start": 1857.54, "duration": 5.43}, {"text": "So look, that's the thymide\nnuclear base, hits a sugar,", "start": 1862.97, "duration": 4.38}, {"text": "but it's different from\nthe regular ribose that's", "start": 1867.35, "duration": 2.94}, {"text": "either in RNA or DNA.", "start": 1870.29, "duration": 3.06}, {"text": "And it's two deoxys so it looks\nmore like a DNA building block.", "start": 1873.35, "duration": 4.02}, {"text": "But check it out.", "start": 1877.37, "duration": 0.9}, {"text": "On the three prime\nsite, there is azide.", "start": 1878.27, "duration": 3.413}, {"text": "What do you think\nthis thing does?", "start": 1881.683, "duration": 1.417}, {"text": "Or have I already told you?", "start": 1883.1, "duration": 1.21}, {"text": "Yeah.", "start": 1884.31, "duration": 0.5}, {"text": "What do you think\nthis thing does", "start": 1884.81, "duration": 1.375}, {"text": "to stop the virus marching\nforward and turning", "start": 1886.185, "duration": 3.665}, {"text": "its RNA into a DNA copy?", "start": 1889.85, "duration": 2.01}, {"text": "Can it polymerase?", "start": 1894.39, "duration": 3.05}, {"text": "No.", "start": 1897.44, "duration": 0.61}, {"text": "So what do you think?", "start": 1898.05, "duration": 1.11}, {"text": "So what how does it work?", "start": 1899.16, "duration": 1.36}, {"text": "AUDIENCE: It blocks [INAUDIBLE]", "start": 1900.52, "duration": 1.37}, {"text": "BARBARA IMPERIALI: Yeah.", "start": 1901.89, "duration": 1.21}, {"text": "Yeah.", "start": 1903.1, "duration": 0.5}, {"text": "It just grinds to a\nhalt. What technology", "start": 1903.6, "duration": 3.36}, {"text": "does this remind you of?", "start": 1906.96, "duration": 3.46}, {"text": "Yeah?", "start": 1910.42, "duration": 0.575}, {"text": "AUDIENCE: The sequencing\nwith the [INAUDIBLE]..", "start": 1910.995, "duration": 4.29}, {"text": "BARBARA IMPERIALI:\nSo it's really cool.", "start": 1915.285, "duration": 1.625}, {"text": "I mean, we're using\nsomething like this", "start": 1916.91, "duration": 2.33}, {"text": "for sequencing blocking the\nchain growth to get pieces", "start": 1919.24, "duration": 3.39}, {"text": "so we can tell the\nsequence, but this", "start": 1922.63, "duration": 2.04}, {"text": "is a very viable drug for\nreverse transcriptase for kind", "start": 1924.67, "duration": 4.15}, {"text": "of similar reasons, because\nit stops translation.", "start": 1928.82, "duration": 4.49}, {"text": "It stops polymerization.", "start": 1933.31, "duration": 2.455}, {"text": "Now, there's one\nimportant thing that I", "start": 1935.765, "duration": 1.625}, {"text": "need to tell you about this AZT,\nas it's termed, azidothymidine.", "start": 1937.39, "duration": 7.14}, {"text": "AZT is what is known in\nthe industry as a prodrug.", "start": 1944.53, "duration": 9.315}, {"text": "It's not the actual drug.", "start": 1960.35, "duration": 1.44}, {"text": "Why is it a prodrug?", "start": 1961.79, "duration": 1.08}, {"text": "What has to happen\nto it to be useful?", "start": 1962.87, "duration": 2.89}, {"text": "Why is it handy\nto have a prodrug?", "start": 1965.76, "duration": 2.06}, {"text": "I know there's a lot\nof questions there,", "start": 1967.82, "duration": 1.81}, {"text": "but they all kind\nof tie together.", "start": 1969.63, "duration": 1.83}, {"text": "So it's a prodrug.", "start": 1971.46, "duration": 1.88}, {"text": "It can get into cells, right?", "start": 1973.34, "duration": 2.46}, {"text": "What has to happen to it for\nit to be useful in inhibiting", "start": 1975.8, "duration": 4.32}, {"text": "reverse transcriptase?", "start": 1980.12, "duration": 3.01}, {"text": "Because it won't do\nit all on its own.", "start": 1983.13, "duration": 1.59}, {"text": "Look at that structure.", "start": 1984.72, "duration": 1.14}, {"text": "There's something missing\nin that structure.", "start": 1985.86, "duration": 3.9}, {"text": "What are the building\nblocks in the polymerases?", "start": 1989.76, "duration": 5.36}, {"text": "Are they nucleosides?", "start": 1995.12, "duration": 2.93}, {"text": "No.", "start": 1998.05, "duration": 1.78}, {"text": "Up there.", "start": 1999.83, "duration": 1.24}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2001.07, "duration": 2.15}, {"text": "BARBARA IMPERIALI: Yes, exactly.", "start": 2003.22, "duration": 1.65}, {"text": "So you have to convert\nthis neutral molecule that", "start": 2004.87, "duration": 2.91}, {"text": "can sneak into a cell by kinases\nthat put phosphate groups", "start": 2007.78, "duration": 4.98}, {"text": "onto that molecule.", "start": 2012.76, "duration": 1.98}, {"text": "So that that molecule can get\nengaged in polymerization,", "start": 2014.74, "duration": 3.93}, {"text": "you can put one nucleotide\nonto a growing strand,", "start": 2018.67, "duration": 3.39}, {"text": "but then it can't go any further\nbecause of that azido group", "start": 2022.06, "duration": 3.69}, {"text": "at 3, which would be the\nnormal place you grow.", "start": 2025.75, "duration": 3.27}, {"text": "So prodrug strategies\nare very useful.", "start": 2029.02, "duration": 3.46}, {"text": "It's a way of having drugs\nthat aren't quite drugs yet", "start": 2032.48, "duration": 3.14}, {"text": "but they become drugs once\nthey are at their location.", "start": 2035.62, "duration": 3.81}, {"text": "It's not handy to use the\ntriphosphate of AZT as a drug,", "start": 2039.43, "duration": 5.19}, {"text": "because it can't\nget in the cell.", "start": 2044.62, "duration": 1.78}, {"text": "So we deliver a cellulary\navailable molecule.", "start": 2046.4, "duration": 3.5}, {"text": "We let the promiscuous\nenzymes in the cell", "start": 2049.9, "duration": 3.029}, {"text": "convert it to a triphosphate.", "start": 2052.929, "duration": 2.071}, {"text": "And then it becomes a\nreal drug, a mature drug.", "start": 2055.0, "duration": 2.98}, {"text": "So I think that's a\nvery important thing", "start": 2057.98, "duration": 1.82}, {"text": "about these types of\ntherapeutic agents.", "start": 2059.8, "duration": 4.07}, {"text": "And what I want you to know\nis that many, many viruses", "start": 2063.87, "duration": 3.28}, {"text": "are treated with nucleoside\nanalogs performing", "start": 2067.15, "duration": 4.14}, {"text": "similar sorts of things.", "start": 2071.29, "duration": 1.86}, {"text": "But in some cases, there's a lot\nof different tailoring goes on", "start": 2073.15, "duration": 4.41}, {"text": "with the nucleoside analog.", "start": 2077.56, "duration": 1.92}, {"text": "It doesn't always work to\nhave the azide at C3 prime.", "start": 2079.48, "duration": 5.88}, {"text": "Some of these features\ndon't always work.", "start": 2085.36, "duration": 1.87}, {"text": "So these have to be\ntailored in different ways", "start": 2087.23, "duration": 3.02}, {"text": "to target different viruses.", "start": 2090.25, "duration": 2.28}, {"text": "Because in this case, AZT\nhits reverse transcriptase.", "start": 2092.53, "duration": 3.68}, {"text": "But there may be a different\nflavor of polymerase enzyme", "start": 2096.21, "duration": 4.99}, {"text": "that you need to inhibit\nin other organisms.", "start": 2101.2, "duration": 2.65}, {"text": "So it's a lot, lot,\nlot of options.", "start": 2103.85, "duration": 1.97}, {"text": "Yeah.", "start": 2105.82, "duration": 1.1}, {"text": "AUDIENCE: Does it\nonly affect RT?", "start": 2106.92, "duration": 1.9}, {"text": "Or could there be side\neffects of the cell,", "start": 2108.82, "duration": 2.85}, {"text": "like an old using\nit by accident?", "start": 2111.67, "duration": 3.427}, {"text": "BARBARA IMPERIALI:\nThere can be, but I", "start": 2115.097, "duration": 1.583}, {"text": "think the most important thing\nis that RT is very promiscuous.", "start": 2116.68, "duration": 6.61}, {"text": "So it's much more likely to\npop this building block in.", "start": 2123.29, "duration": 3.99}, {"text": "And that doesn't\nhave the mechanisms", "start": 2127.28, "duration": 2.18}, {"text": "to reverse that reaction, all\nof the clean up that gets done", "start": 2129.46, "duration": 3.81}, {"text": "with normal DNA polymerase.", "start": 2133.27, "duration": 2.05}, {"text": "So our DNA polymerase is\ngoing to be a lot more tuned", "start": 2135.32, "duration": 3.65}, {"text": "up to avoid these mistakes.", "start": 2138.97, "duration": 2.14}, {"text": "But the viral\nreverse transcriptase", "start": 2141.11, "duration": 2.21}, {"text": "just churn through in making it.", "start": 2143.32, "duration": 2.5}, {"text": "So we're protected by our own\nproofreading and other types", "start": 2145.82, "duration": 4.88}, {"text": "of mechanisms to avoid it\nreally messing up replication.", "start": 2150.7, "duration": 5.28}, {"text": "But that's a very good point.", "start": 2155.98, "duration": 2.4}, {"text": "OK.", "start": 2158.38, "duration": 0.65}, {"text": "So remember the central dogma.", "start": 2159.03, "duration": 2.68}, {"text": "And this is why this\nprocess confounds that.", "start": 2161.71, "duration": 3.81}, {"text": "And that's azidothymidine.", "start": 2165.52, "duration": 1.41}, {"text": "And we've already\ndiscussed that.", "start": 2166.93, "duration": 4.03}, {"text": "So the next enzyme that became\nquite an important target,", "start": 2170.96, "duration": 6.93}, {"text": "because it was a new\ntarget, was integrase.", "start": 2177.89, "duration": 3.9}, {"text": "So I will tell you, though,\nthat reverse transcriptase", "start": 2181.79, "duration": 3.39}, {"text": "inhibitors like AZT\nwere used early on,", "start": 2185.18, "duration": 4.02}, {"text": "but people with the virus\nrapidly developed resistance", "start": 2189.2, "duration": 5.79}, {"text": "to that therapeutic agent.", "start": 2194.99, "duration": 2.73}, {"text": "It was one enzyme that was\njust mutating like crazy.", "start": 2197.72, "duration": 3.45}, {"text": "And the organism could\nslip through that net.", "start": 2201.17, "duration": 3.54}, {"text": "So the development\nof therapeutic agents", "start": 2204.71, "duration": 3.33}, {"text": "didn't stop with AZT.", "start": 2208.04, "duration": 2.04}, {"text": "It was, like, we need to\nhit other targets for us", "start": 2210.08, "duration": 3.12}, {"text": "to have a therapeutically\nviable combination of therapies", "start": 2213.2, "duration": 4.35}, {"text": "that can really stop\nthis virus effectively.", "start": 2217.55, "duration": 3.19}, {"text": "So a next enzyme that was\ntargeted is integrase.", "start": 2220.74, "duration": 4.73}, {"text": "So this is the one that's\nbeen targeted most recently.", "start": 2225.47, "duration": 3.12}, {"text": "And there are currently\nseveral integrase inhibitors.", "start": 2228.59, "duration": 4.8}, {"text": "Integrase is a\nfascinating enzyme", "start": 2233.39, "duration": 2.43}, {"text": "because it really is the\nenzyme that actually stitches", "start": 2235.82, "duration": 5.55}, {"text": "that piece of viral DNA\nright into the human genome", "start": 2241.37, "duration": 7.0}, {"text": "just so it's able to be\nreplicated, transcribed,", "start": 2248.37, "duration": 4.19}, {"text": "and translated at any time.", "start": 2252.56, "duration": 2.19}, {"text": "So integrase has been targeted.", "start": 2254.75, "duration": 2.59}, {"text": "It was a tricky target to hit.", "start": 2257.34, "duration": 2.03}, {"text": "But as you can see with\nseveral of these drugs,", "start": 2259.37, "duration": 3.84}, {"text": "they are successful drugs.", "start": 2263.21, "duration": 2.76}, {"text": "One thing I want to\nremind you about,", "start": 2265.97, "duration": 1.92}, {"text": "a lot of the names\nof the agents,", "start": 2267.89, "duration": 5.11}, {"text": "if you see A-V-I-R within the\nname of a therapeutic agent,", "start": 2273.0, "duration": 7.85}, {"text": "it means it's an antiviral.", "start": 2280.85, "duration": 1.61}, {"text": "So that's a clue that\nall of these compounds", "start": 2282.46, "duration": 3.13}, {"text": "are given names--", "start": 2285.59, "duration": 2.04}, {"text": "raltegravir, blah.", "start": 2287.63, "duration": 2.1}, {"text": "I don't know who comes up with\nthese names, but nevertheless,", "start": 2289.73, "duration": 2.91}, {"text": "they're all names\nthat end in A-V-I-R.", "start": 2292.64, "duration": 3.09}, {"text": "So if you see a medicine\nand it ends in A-V-I-R,", "start": 2295.73, "duration": 3.72}, {"text": "it's an antiviral agent.", "start": 2299.45, "duration": 2.4}, {"text": "Now, the last of the\nreally fascinating enzymes", "start": 2301.85, "duration": 2.94}, {"text": "that was targeted\nis the HIV protease,", "start": 2304.79, "duration": 4.08}, {"text": "because the HIV protease\nis very, very different", "start": 2308.87, "duration": 2.55}, {"text": "from many proteases\nin mammalian biology.", "start": 2311.42, "duration": 3.34}, {"text": "It's a simple dimeric structure.", "start": 2314.76, "duration": 4.37}, {"text": "So it has quaternary structure.", "start": 2319.13, "duration": 1.98}, {"text": "It has two monomers that\nare 99 amino acids each.", "start": 2321.11, "duration": 6.03}, {"text": "And each monomer\ncontributes an aspartic acid", "start": 2327.14, "duration": 5.67}, {"text": "to an active site.", "start": 2332.81, "duration": 1.38}, {"text": "And those are involved\nin the mechanism.", "start": 2334.19, "duration": 2.19}, {"text": "And what generally happens when\nsubstrates or inhibitors bind", "start": 2336.38, "duration": 3.75}, {"text": "is these two flaps--", "start": 2340.13, "duration": 1.86}, {"text": "one of them I've\nshown you in magenta--", "start": 2341.99, "duration": 2.04}, {"text": "close down and close\nup the active site.", "start": 2344.03, "duration": 3.78}, {"text": "And ritonavir was one of the\nfirst generation protease", "start": 2347.81, "duration": 3.51}, {"text": "inhibitors that sat\nin the place where", "start": 2351.32, "duration": 4.56}, {"text": "the substrate would normally\nsit in the HIV protease.", "start": 2355.88, "duration": 3.39}, {"text": "And remember that\nthe HIV protease", "start": 2359.27, "duration": 1.92}, {"text": "is critical for\nmaturity of the virus", "start": 2361.19, "duration": 2.88}, {"text": "because it chops\nup the polyprotein", "start": 2364.07, "duration": 2.97}, {"text": "into the necessary enzymes.", "start": 2367.04, "duration": 2.04}, {"text": "They can't be functional\nenzymes in the polyprotein.", "start": 2369.08, "duration": 3.12}, {"text": "They have to cut up into\nthe appropriate pieces.", "start": 2372.2, "duration": 3.93}, {"text": "So the HIV protease had\nunusual specificity.", "start": 2376.13, "duration": 3.27}, {"text": "And as soon as it was discovered\nand structurally characterized,", "start": 2379.4, "duration": 3.36}, {"text": "every major pharmaceutical\ncompany jumped on-- this was", "start": 2382.76, "duration": 3.66}, {"text": "in the late '80s--", "start": 2386.42, "duration": 1.41}, {"text": "to make successful\nprotease inhibitors that", "start": 2387.83, "duration": 3.06}, {"text": "just got better and better.", "start": 2390.89, "duration": 1.86}, {"text": "Ritonavir is an example\nof first generation,", "start": 2392.75, "duration": 2.98}, {"text": "but I think now we're on third\ngeneration-type inhibitors", "start": 2395.73, "duration": 3.41}, {"text": "which are just a better\nand better and much", "start": 2399.14, "duration": 2.76}, {"text": "more selective and specific\nfor the HIV protease.", "start": 2401.9, "duration": 3.92}, {"text": "And because they're\nmuch more potent,", "start": 2405.82, "duration": 2.29}, {"text": "instead of needing grams\nand grams of an inhibitor,", "start": 2408.11, "duration": 3.54}, {"text": "you can get away with\nmilligrams of inhibitor,", "start": 2411.65, "duration": 2.64}, {"text": "which made the therapeutic\ndosing for HIV much more", "start": 2414.29, "duration": 4.71}, {"text": "palatable is sort\nof a good word.", "start": 2419.0, "duration": 2.22}, {"text": "Because when you have a very\npromiscuous protease inhibitor,", "start": 2421.22, "duration": 3.96}, {"text": "like the early ones\nthat were discovered,", "start": 2425.18, "duration": 2.47}, {"text": "they mess up your entire\nGI because your GI", "start": 2427.65, "duration": 3.05}, {"text": "runs on proteases\nthat digest your food.", "start": 2430.7, "duration": 2.64}, {"text": "So the original, the\nearly protease inhibitors", "start": 2433.34, "duration": 2.91}, {"text": "had a lot of side effects.", "start": 2436.25, "duration": 1.74}, {"text": "The most modern third\ngeneration are very viable.", "start": 2437.99, "duration": 3.63}, {"text": "And this just shows\nyou what other topic I", "start": 2441.62, "duration": 2.28}, {"text": "want to hit on next is here's\nthe green and cyan two monomer", "start": 2443.9, "duration": 5.57}, {"text": "units of HIV protease.", "start": 2449.47, "duration": 2.56}, {"text": "In yellow is an\ninhibitor that is bound.", "start": 2452.03, "duration": 3.36}, {"text": "And just on one monomer\nof the two monomers,", "start": 2455.39, "duration": 3.13}, {"text": "I've highlighted, in red,\ndifferent resistance sites.", "start": 2458.52, "duration": 3.68}, {"text": "So when any of\nthose sites mutates,", "start": 2462.2, "duration": 3.27}, {"text": "the protease stops being\ninhibited by the HIV protease", "start": 2465.47, "duration": 5.65}, {"text": "inhibitors.", "start": 2471.12, "duration": 1.09}, {"text": "Because you want\nto think about it,", "start": 2472.21, "duration": 1.82}, {"text": "one mutation in one\nsubunit, actually,", "start": 2474.03, "duration": 2.7}, {"text": "will have a corresponding\nmutation in the partner subunit", "start": 2476.73, "duration": 4.71}, {"text": "that is in the dimer.", "start": 2481.44, "duration": 1.26}, {"text": "So each mutation ends\nup being two mutations", "start": 2482.7, "duration": 3.33}, {"text": "in the full enzyme that\nhas quaternary restructure.", "start": 2486.03, "duration": 5.13}, {"text": "So these are major.", "start": 2491.16, "duration": 2.58}, {"text": "They go all the way out to\nthe outer parts of the enzyme.", "start": 2493.74, "duration": 4.81}, {"text": "It's not just around\nthe active site.", "start": 2498.55, "duration": 1.67}, {"text": "It's just all over the enzyme\nyou can get mutations that", "start": 2500.22, "duration": 5.07}, {"text": "stop the typical drugs that\nare targeted at the protease's", "start": 2505.29, "duration": 3.72}, {"text": "binding", "start": 2509.01, "duration": 1.02}, {"text": "So here I just\nshow you these are", "start": 2510.03, "duration": 1.95}, {"text": "data that show for\nthe protease and", "start": 2511.98, "duration": 2.76}, {"text": "for the reverse transcriptase.", "start": 2514.74, "duration": 1.95}, {"text": "Within the length\nof the protease,", "start": 2516.69, "duration": 1.86}, {"text": "for example, there's\nmutations all the way along.", "start": 2518.55, "duration": 3.68}, {"text": "I don't know why this is 101.", "start": 2522.23, "duration": 1.21}, {"text": "The numbering system is a little\ndifferent in some variants.", "start": 2523.44, "duration": 3.3}, {"text": "But you can see which mutations\nwill add to drug resistance.", "start": 2526.74, "duration": 4.92}, {"text": "And there's a similar picture\nhere for reverse transcriptase.", "start": 2531.66, "duration": 3.76}, {"text": "OK?", "start": 2535.42, "duration": 0.62}, {"text": "So this is a very serious issue.", "start": 2536.04, "duration": 3.55}, {"text": "So now I'm going to give\nyou a little break here.", "start": 2539.59, "duration": 3.073}, {"text": "[VIDEO PLAYBACK]", "start": 2542.663, "duration": 0.667}, {"text": "- So this is HIV.", "start": 2543.33, "duration": 1.2}, {"text": "It's a typical\nretrovirus, meaning", "start": 2544.53, "duration": 2.01}, {"text": "that it has an outer envelope.", "start": 2546.54, "duration": 2.04}, {"text": "And in the center, it\nhas two copies of RNA,", "start": 2548.58, "duration": 2.79}, {"text": "as well as an\nenzyme here in blue", "start": 2551.37, "duration": 2.4}, {"text": "that's reverse transcriptase,\nwhich will ultimately", "start": 2553.77, "duration": 3.03}, {"text": "turn that RNA into DNA.", "start": 2556.8, "duration": 3.34}, {"text": "The virus itself, with\nthis outer envelope", "start": 2560.14, "duration": 2.99}, {"text": "PROTEIN actually directly\ninfects T-helper cells.", "start": 2563.13, "duration": 6.36}, {"text": "The way that it does this is\nthat as it comes up to the cell", "start": 2569.49, "duration": 3.84}, {"text": "surface, it uses receptors\nthat are on T-helper cells", "start": 2573.33, "duration": 4.17}, {"text": "and exclusive to T-helper cells,\nwhich are CD4 molecule which", "start": 2577.5, "duration": 4.77}, {"text": "really defines T-helper cells.", "start": 2582.27, "duration": 1.83}, {"text": "It's a surface receptor that\nbinds to the envelope protein.", "start": 2584.1, "duration": 4.35}, {"text": "That causes a\nconformational change", "start": 2588.45, "duration": 2.67}, {"text": "and allows a second receptor\nto grab hold of the envelope.", "start": 2591.12, "duration": 3.49}, {"text": "This is the\nchemokine coreceptor.", "start": 2594.61, "duration": 1.94}, {"text": "It's also called CCR5.", "start": 2596.55, "duration": 1.77}, {"text": "And we'll talk about that more.", "start": 2598.32, "duration": 1.95}, {"text": "What happens now is that the\nstock of the envelope protein", "start": 2600.27, "duration": 4.77}, {"text": "pierces through from the\nvirus into the host cell", "start": 2605.04, "duration": 5.4}, {"text": "and starts to draw the cell\nmembrane and the viral membrane", "start": 2610.44, "duration": 4.17}, {"text": "together.", "start": 2614.61, "duration": 1.02}, {"text": "And what ultimately happens is\nfusion of those two membranes", "start": 2615.63, "duration": 3.48}, {"text": "and the viral genetic material\nis injected, essentially,", "start": 2619.11, "duration": 3.87}, {"text": "into the cell.", "start": 2622.98, "duration": 1.02}, {"text": "And the envelope protein is\nleft at the cell surface.", "start": 2624.0, "duration": 2.91}, {"text": "- So that's the fusion process\nthat's so hard to explain.", "start": 2626.91, "duration": 2.43}, {"text": "- The virus has a matrix and\na capsid protein, shown here", "start": 2629.34, "duration": 3.15}, {"text": "in green and red, that\nessentially are digested", "start": 2632.49, "duration": 3.48}, {"text": "when it enters into the cell.", "start": 2635.97, "duration": 2.28}, {"text": "That releases the viral\nenzymes and the viral RNA.", "start": 2638.25, "duration": 4.65}, {"text": "And here we have\nreverse transcriptase,", "start": 2642.9, "duration": 1.86}, {"text": "which takes the viral RNA,\nand using host nucleotides", "start": 2644.76, "duration": 5.43}, {"text": "converts that viral RNA\ninto a single strand of DNA.", "start": 2650.19, "duration": 4.47}, {"text": "While it does that, it\nmakes some random errors,", "start": 2654.66, "duration": 3.22}, {"text": "which is characteristic\nof reverse transcriptase.", "start": 2657.88, "duration": 2.54}, {"text": "It has very poor\nproofreading activity.", "start": 2660.42, "duration": 3.97}, {"text": "That single-stranded DNA, now,\nis again reverse transcribed", "start": 2664.39, "duration": 4.41}, {"text": "into a double-stranded DNA.", "start": 2668.8, "duration": 1.82}, {"text": "At that point,\nanother enzyme that", "start": 2673.29, "duration": 2.37}, {"text": "has come in with the virus\nin the beginning, called", "start": 2675.66, "duration": 2.49}, {"text": "integrase,\nessentially grabs hold", "start": 2678.15, "duration": 2.52}, {"text": "of that double-stranded\nDNA and carries it", "start": 2680.67, "duration": 3.03}, {"text": "through a nuclear pore into\nthe nucleus of the cell.", "start": 2683.7, "duration": 5.07}, {"text": "Within the nucleus of the cell,\nit finds the host chromosome.", "start": 2688.77, "duration": 3.87}, {"text": "And basically, the\nintegrase enzyme,", "start": 2692.64, "duration": 2.49}, {"text": "makes a nick in the host's\nDNA and allows for HIV", "start": 2695.13, "duration": 4.41}, {"text": "to insert itself into\nthe host chromosome.", "start": 2699.54, "duration": 3.21}, {"text": "And that right there is what\nestablishes lifelong infection.", "start": 2702.75, "duration": 5.83}, {"text": "Now, RNA polymerase comes along\nand makes its messenger RNA.", "start": 2708.58, "duration": 3.56}, {"text": "- That's the host polymerase,\nit's just back to normal now.", "start": 2712.14, "duration": 3.18}, {"text": "- Those messenger RNAs encode\nfor different viral proteins.", "start": 2715.32, "duration": 4.17}, {"text": "They end up associating\nwith ribosomes", "start": 2719.49, "duration": 3.18}, {"text": "at the surface of the rough\nendoplasmic reticulum.", "start": 2722.67, "duration": 3.18}, {"text": "And here is a piece\nof mRNA that's", "start": 2725.85, "duration": 1.98}, {"text": "making envelope protein\nwhich is directly produced", "start": 2727.83, "duration": 3.54}, {"text": "into the endoplasmic reticulum.", "start": 2731.37, "duration": 2.46}, {"text": "And its shuttled, then, through\nthe endoplasmic reticulum", "start": 2733.83, "duration": 3.33}, {"text": "and taken to the cell surface,\nwhere, at the cell surface,", "start": 2737.16, "duration": 4.03}, {"text": "it becomes embedded in\nthe cellular membrane.", "start": 2741.19, "duration": 2.66}, {"text": "And at this point, coalescing\nwith other envelope proteins", "start": 2743.85, "duration": 3.63}, {"text": "that have been produced\nyou have this cluster", "start": 2747.48, "duration": 1.95}, {"text": "of envelope proteins now on the\nsurface of this infected cell.", "start": 2749.43, "duration": 6.0}, {"text": "At the same time, there\nare other messenger RNAs", "start": 2755.43, "duration": 4.14}, {"text": "that are being produced\nthat allow for translation", "start": 2759.57, "duration": 3.33}, {"text": "of other viral proteins.", "start": 2762.9, "duration": 2.47}, {"text": "So here are additional\nviral proteins being made", "start": 2765.37, "duration": 2.96}, {"text": "which are going to\nbe used to make up", "start": 2768.33, "duration": 2.94}, {"text": "the key components that\nthe virus, ultimately,", "start": 2771.27, "duration": 2.79}, {"text": "is going to need.", "start": 2774.06, "duration": 2.01}, {"text": "These are transported\nagain to the cell surface,", "start": 2776.07, "duration": 2.46}, {"text": "to the area where these\nenvelope proteins are.", "start": 2778.53, "duration": 3.03}, {"text": "And a strand of RNA, as\nwell as some of the enzymes", "start": 2781.56, "duration": 4.32}, {"text": "are part of that complex.", "start": 2785.88, "duration": 3.76}, {"text": "This then buds off at the\ncell surface at this point,", "start": 2789.64, "duration": 3.09}, {"text": "but it's still not\na mature virion", "start": 2792.73, "duration": 1.98}, {"text": "because the polyprotein chain\nneeds to still be digested", "start": 2794.71, "duration": 5.46}, {"text": "into its component parts.", "start": 2800.17, "duration": 2.16}, {"text": "That's done by an\nenzyme called protease.", "start": 2802.33, "duration": 2.63}, {"text": "Protease breaks up\nthose polyprotein chains", "start": 2804.96, "duration": 3.97}, {"text": "and, ultimately, allows for\nthem to coalesce and form", "start": 2808.93, "duration": 3.78}, {"text": "the mature structures that\nmake up the final virion.", "start": 2812.71, "duration": 4.68}, {"text": "And now you have a\nmature infectious virion", "start": 2817.39, "duration": 2.97}, {"text": "that can go on now to\ninfect other cells.", "start": 2820.36, "duration": 4.48}, {"text": "Once that happens, now, the cell\ncan produce tons of viruses.", "start": 2824.84, "duration": 4.53}, {"text": "And this is really what, then,\nkeeps the whole process going.", "start": 2829.37, "duration": 3.375}, {"text": "[END PLAYBACK]", "start": 2832.745, "duration": 0.615}, {"text": "BARBARA IMPERIALI: OK.", "start": 2833.36, "duration": 0.93}, {"text": "All right.", "start": 2834.29, "duration": 0.5}, {"text": "So I have gone\nmonstrously long on HIV.", "start": 2834.79, "duration": 3.04}, {"text": "So sadly, I cannot\nget you to Ebola.", "start": 2837.83, "duration": 4.56}, {"text": "But I'll post those\nslides anyway.", "start": 2842.39, "duration": 3.66}, {"text": "This question just speaks\nto combination therapies.", "start": 2846.05, "duration": 4.02}, {"text": "So combination therapies\nare very, very important,", "start": 2850.07, "duration": 3.91}, {"text": "particularly in cases\nwhere resistance", "start": 2853.98, "duration": 2.24}, {"text": "to individual therapeutic agents\nagainst an individual target", "start": 2856.22, "duration": 5.55}, {"text": "can happen.", "start": 2861.77, "duration": 0.84}, {"text": "So HIV mutates its proteins\nvery, very rapidly.", "start": 2862.61, "duration": 4.29}, {"text": "But the likelihood that\nit will simultaneously", "start": 2866.9, "duration": 5.04}, {"text": "mutate two targets in\none cell is much lower.", "start": 2871.94, "duration": 4.03}, {"text": "So combination\ntherapies basically", "start": 2875.97, "duration": 2.96}, {"text": "are there to avoid\ndrug resistance that", "start": 2878.93, "duration": 3.3}, {"text": "occurs, usually, because\nof the high mutation rate,", "start": 2882.23, "duration": 2.43}, {"text": "not because one drug has\na short half life, not", "start": 2884.66, "duration": 3.84}, {"text": "so that multiple\nstrains can be targeted,", "start": 2888.5, "duration": 2.49}, {"text": "or to decrease the\nnumber of side effects.", "start": 2890.99, "duration": 2.52}, {"text": "Obviously, combination therapies\ngive you more side effects,", "start": 2893.51, "duration": 3.69}, {"text": "but they are really important\nin mitigating the disease.", "start": 2897.2, "duration": 4.36}, {"text": "So I was going to talk to you\nabout vaccine development,", "start": 2901.56, "duration": 3.68}, {"text": "but I will discuss this\nwith Professor Martin", "start": 2905.24, "duration": 2.67}, {"text": "to see if he wants\nto take that over.", "start": 2907.91, "duration": 4.17}, {"text": "But I want to leave you\nwith one last thing.", "start": 2912.08, "duration": 4.25}, {"text": "OK.", "start": 2921.33, "duration": 1.88}, {"text": "Three small points.", "start": 2923.21, "duration": 1.71}, {"text": "On next Wednesday, this\nis Fred Flintstone.", "start": 2924.92, "duration": 4.17}, {"text": "I tend to channel Fred\nFlintstone because he", "start": 2929.09, "duration": 2.55}, {"text": "wears this nice blue scarf.", "start": 2931.64, "duration": 2.31}, {"text": "Next Wednesday is the\nlast of the classes.", "start": 2933.95, "duration": 3.72}, {"text": "We've got some good\nstuff lined up for you.", "start": 2937.67, "duration": 2.38}, {"text": "We're going to have\nthe topoisomerase demo", "start": 2940.05, "duration": 2.54}, {"text": "from some people who\nsubmitted a topo demo for us.", "start": 2942.59, "duration": 3.87}, {"text": "And then we're going\nto do 7.016 Jeopardy.", "start": 2946.46, "duration": 2.31}, {"text": "Now, don't think this\nis going to be cheesy.", "start": 2948.77, "duration": 2.04}, {"text": "It's going to be tough.", "start": 2950.81, "duration": 1.35}, {"text": "And it's going to be fun.", "start": 2952.16, "duration": 1.5}, {"text": "And we're all going\nto be involved.", "start": 2953.66, "duration": 1.95}, {"text": "Professor Martin and\nI will be the hosts.", "start": 2955.61, "duration": 1.98}, {"text": "He's promised to dress up.", "start": 2957.59, "duration": 1.822}, {"text": "Ha ha ha.", "start": 2959.412, "duration": 2.718}, {"text": "Jackie will help\nme run the program,", "start": 2962.13, "duration": 2.75}, {"text": "because it's in a\nreal Jeopardy program.", "start": 2964.88, "duration": 2.58}, {"text": "And Hannah and David\nwill keep scores.", "start": 2967.46, "duration": 2.64}, {"text": "And we'd like to encourage you\nwho come to be in teams of two.", "start": 2970.1, "duration": 4.41}, {"text": "Otherwise, there will\nbe kind of a lot of you.", "start": 2974.51, "duration": 2.22}, {"text": "So if when you come in, if you\nsit on that side of the room,", "start": 2976.73, "duration": 3.25}, {"text": "put your two names\non these boards.", "start": 2979.98, "duration": 2.87}, {"text": "And if you're on the other\nside, put them on these boards", "start": 2982.85, "duration": 2.91}, {"text": "because Hannah and David will\nbe posted there to keep score.", "start": 2985.76, "duration": 4.05}, {"text": "And we will muster up some\nsmall prize for the winner here.", "start": 2989.81, "duration": 5.01}, {"text": "So, yes, question.", "start": 2994.82, "duration": 1.655}, {"text": "AUDIENCE: Will this\ncount as the final?", "start": 2996.475, "duration": 1.625}, {"text": "BARBARA IMPERIALI: No.", "start": 2998.1, "duration": 2.42}, {"text": "That would be a heck of\nan incentive, wouldn't it?", "start": 3000.52, "duration": 2.7}, {"text": "What this will do\nfor you is actually", "start": 3003.22, "duration": 2.55}, {"text": "kind of help you\nrefresh a lot of things,", "start": 3005.77, "duration": 2.85}, {"text": "maybe identify blind spots.", "start": 3008.62, "duration": 1.95}, {"text": "It was worth asking.", "start": 3010.57, "duration": 0.942}, {"text": "It was a good question, yeah.", "start": 3011.512, "duration": 1.208}, {"text": "So I'll post the questions\nafterwards as well.", "start": 3015.49, "duration": 2.28}, {"text": "So you'll be able\nto kind of say, guy,", "start": 3017.77, "duration": 2.32}, {"text": "I don't know what this\nquestion was about at all.", "start": 3020.09, "duration": 2.48}, {"text": "And you can go and review\na little of the material.", "start": 3022.57, "duration": 2.58}, {"text": "Nice try, though.", "start": 3025.15, "duration": 1.03}, {"text": "Oh, and there was\none other thing.", "start": 3028.81, "duration": 2.28}, {"text": "I just want to remind you\nthat a vote is a vote.", "start": 3031.09, "duration": 3.09}, {"text": "This is a democratic society.", "start": 3034.18, "duration": 2.1}, {"text": "So you should please take time\nto fill in the evaluations", "start": 3036.28, "duration": 4.38}, {"text": "on the course.", "start": 3040.66, "duration": 0.91}, {"text": "OK.", "start": 3041.57, "duration": 1.55}]
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@@ -0,0 +1 @@
+[{"text": "OK.", "start": 15.966, "duration": 1.568}, {"text": "Let's get started.", "start": 17.534, "duration": 2.736}, {"text": "How's everyone doing?", "start": 20.27, "duration": 1.535}, {"text": "Wonderful.", "start": 21.805, "duration": 0.867}, {"text": "Come on, let's do\nbetter than that.", "start": 22.672, "duration": 1.935}, {"text": "How is everyone doing?", "start": 24.607, "duration": 1.702}, {"text": "Wonderful!", "start": 26.309, "duration": 0.768}, {"text": "Thank you.", "start": 27.077, "duration": 1.268}, {"text": "Welcome to 3.091.", "start": 28.345, "duration": 3.136}, {"text": "This is the first day.", "start": 31.481, "duration": 2.236}, {"text": "And I'm really excited.", "start": 33.717, "duration": 1.668}, {"text": "I hope you are too.", "start": 35.385, "duration": 1.868}, {"text": "In this very first\nlecture, we're", "start": 37.253, "duration": 2.203}, {"text": "going to do a little\nbit of administration,", "start": 39.456, "duration": 2.969}, {"text": "tell you a little bit about\nthe class and how it's set up.", "start": 42.425, "duration": 3.804}, {"text": "And then we'll give\na little mini--", "start": 46.229, "duration": 1.735}, {"text": "we'll have time for a mini\nlecture in the second part", "start": 47.964, "duration": 2.77}, {"text": "of the lecture today.", "start": 50.734, "duration": 1.368}, {"text": "So I thought I'd\nstart by inducing me.", "start": 52.102, "duration": 2.836}, {"text": "My name is Jeff Grossman.", "start": 54.938, "duration": 2.069}, {"text": "I am in Course Three, that's the\nDepartment of Material Science", "start": 57.007, "duration": 2.802}, {"text": "and Engineering.", "start": 59.809, "duration": 1.602}, {"text": "My background, I went\nto Hopkins, undergrad,", "start": 61.411, "duration": 3.036}, {"text": "moved my way towards the\nwest coast, Illinois PhD.", "start": 64.447, "duration": 4.271}, {"text": "And I did a post-doc\nat Berkeley.", "start": 68.718, "duration": 2.77}, {"text": "And then I came here to\nMIT about nine years ago", "start": 71.488, "duration": 2.702}, {"text": "when I joined the faculty.", "start": 74.19, "duration": 2.303}, {"text": "My own passion, my own\ninterest in research", "start": 76.493, "duration": 3.436}, {"text": "is in materials for energy and\nwater and chemical processes", "start": 79.929, "duration": 6.34}, {"text": "and separations.", "start": 86.269, "duration": 1.101}, {"text": "So I thought I'd just give\nyou a little example of what", "start": 87.37, "duration": 2.302}, {"text": "I mean by that.", "start": 89.672, "duration": 0.701}, {"text": "So I get really excited\nabout the ability", "start": 90.373, "duration": 2.368}, {"text": "to take the material\nand make it do something", "start": 92.741, "duration": 2.971}, {"text": "that it can't do\nnow, but that it", "start": 95.712, "duration": 1.868}, {"text": "needs to do to solve a problem.", "start": 97.58, "duration": 1.828}, {"text": "Maybe it needs to be cheaper.", "start": 99.408, "duration": 1.208}, {"text": "Maybe it needs to\nbe more efficient.", "start": 100.616, "duration": 3.036}, {"text": "So one example is\nin this material.", "start": 103.652, "duration": 2.604}, {"text": "This is a barrel of oil.", "start": 106.256, "duration": 2.869}, {"text": "And what we do today\nwith this barrel of oil", "start": 109.125, "duration": 2.569}, {"text": "is we mostly burn it.", "start": 111.694, "duration": 1.902}, {"text": "A lot of what we do is burn it.", "start": 113.596, "duration": 1.302}, {"text": "Now if you do that,\nand you think about it", "start": 114.898, "duration": 1.75}, {"text": "in terms of energy, that's\n159 liters of this material.", "start": 116.648, "duration": 4.823}, {"text": "And if you think\nabout what you're", "start": 121.471, "duration": 1.435}, {"text": "carrying about as energy,\nyou get 1.73 megawatt hours", "start": 122.906, "duration": 3.069}, {"text": "of energy out of that.", "start": 125.975, "duration": 2.297}, {"text": "But see, I like to think about\nmaterials, again, and ask them", "start": 128.272, "duration": 2.542}, {"text": "what they can do differently\nfor me, for these problems.", "start": 130.814, "duration": 3.87}, {"text": "And so if you think\nabout that and you say,", "start": 134.684, "duration": 1.802}, {"text": "well, OK, let's just\ntake 1% of the carbon", "start": 136.486, "duration": 2.202}, {"text": "in that barrel of oil\nand do something with it.", "start": 138.688, "duration": 2.469}, {"text": "Let's make thin\nfilm solar cells.", "start": 141.157, "duration": 2.636}, {"text": "Well, if you do that and\nthey're not very good,", "start": 143.793, "duration": 2.036}, {"text": "they're 5% efficient, they\ncompletely die in a year,", "start": 145.829, "duration": 2.702}, {"text": "you get 10,000 times as\nmuch energy over that year", "start": 148.531, "duration": 3.103}, {"text": "than burning it.", "start": 151.634, "duration": 0.768}, {"text": "So it's an example\nof what you can", "start": 152.402, "duration": 1.435}, {"text": "do when you think about\nusing elements differently.", "start": 153.837, "duration": 2.968}, {"text": "That's what I get really\nexcited about in my research.", "start": 156.805, "duration": 2.904}, {"text": "And that's just one example.", "start": 159.709, "duration": 2.002}, {"text": "You can take that\nsame carbon and you", "start": 161.711, "duration": 3.771}, {"text": "can make a thermoelectric,\nthat's on top.", "start": 165.482, "duration": 2.636}, {"text": "Or you can make the\nworld's thinnest filter.", "start": 168.118, "duration": 2.702}, {"text": "That's a piece of graphene\nwith a hole in it.", "start": 170.82, "duration": 2.269}, {"text": "And that's still working with\njust one element, carbon.", "start": 173.089, "duration": 3.47}, {"text": "All right?", "start": 176.559, "duration": 0.852}, {"text": "So there are many,\nmany things you", "start": 177.411, "duration": 1.417}, {"text": "can do once you understand\nwhat these elements are", "start": 178.828, "duration": 3.47}, {"text": "and how they combine together.", "start": 182.298, "duration": 1.435}, {"text": "And that's what\nwe're going to talk", "start": 183.733, "duration": 1.468}, {"text": "about in this class\nover the fall.", "start": 185.201, "duration": 2.236}, {"text": "How many elements\nare in your phone?", "start": 187.437, "duration": 1.501}, {"text": "Listen, we just talked\nabout one element.", "start": 188.938, "duration": 1.869}, {"text": "Anybody know how many\nelements are in your phone?", "start": 190.807, "duration": 3.036}, {"text": "How many?", "start": 193.843, "duration": 0.501}, {"text": "Take a guess.", "start": 194.344, "duration": 1.468}, {"text": "Seven.", "start": 195.812, "duration": 1.568}, {"text": "27.", "start": 197.38, "duration": 1.935}, {"text": "OK, it depends.", "start": 199.315, "duration": 1.302}, {"text": "It depends.", "start": 200.617, "duration": 1.201}, {"text": "Do you have the Samsung?", "start": 201.818, "duration": 3.136}, {"text": "If you've got the\nSamsung whatever,", "start": 204.954, "duration": 2.469}, {"text": "it might light on fire.", "start": 207.423, "duration": 1.168}, {"text": "If you've got the\nnewer one, it won't.", "start": 208.591, "duration": 1.969}, {"text": "Do you have an iPhone?", "start": 210.56, "duration": 1.001}, {"text": "Well you know what?", "start": 211.561, "duration": 0.801}, {"text": "In the iPhone, there's 63.", "start": 212.362, "duration": 2.002}, {"text": "63 elements.", "start": 214.364, "duration": 5.038}, {"text": "So we have these\nlectures in Course Three,", "start": 219.402, "duration": 2.035}, {"text": "they're called the wolf lecture.", "start": 221.437, "duration": 1.335}, {"text": "And I gave one a\ncouple of years ago.", "start": 222.772, "duration": 1.702}, {"text": "If you're interested in\nhearing a little bit more", "start": 224.474, "duration": 1.234}, {"text": "about what I do or what\nsome other people do who", "start": 225.708, "duration": 2.002}, {"text": "think about materials\nin this way,", "start": 227.71, "duration": 1.454}, {"text": "you can use Google\nwolf lecture and you'll", "start": 229.164, "duration": 1.75}, {"text": "get to some of the videos.", "start": 230.914, "duration": 2.335}, {"text": "And I'll mention it when they\ncome around during the year.", "start": 233.249, "duration": 2.703}, {"text": "OK, so that's a\nlittle intro to me.", "start": 235.952, "duration": 4.23}, {"text": "What about the class?", "start": 240.182, "duration": 0.875}, {"text": "So as I said, the class--\nat the heart of the class", "start": 241.057, "duration": 2.569}, {"text": "is kind of what\nI just described.", "start": 243.626, "duration": 3.47}, {"text": "But in order to do that, we need\nto know some very basic things.", "start": 247.096, "duration": 4.538}, {"text": "We need to know how\natoms are arranged,", "start": 251.634, "duration": 5.772}, {"text": "the atomic arrangement\nright there.", "start": 257.406, "duration": 2.73}, {"text": "But we also need to know\nwhat atoms are there", "start": 260.136, "duration": 1.875}, {"text": "in the first place.", "start": 262.011, "duration": 0.834}, {"text": "So if we know that, if\nwe know those things,", "start": 262.845, "duration": 4.205}, {"text": "then we can build,\nthen we can build.", "start": 267.05, "duration": 3.036}, {"text": "We can get properties.", "start": 270.086, "duration": 1.235}, {"text": "We can get structure.", "start": 271.321, "duration": 1.401}, {"text": "We can get processing.", "start": 272.722, "duration": 1.635}, {"text": "We can get performance.", "start": 274.357, "duration": 1.068}, {"text": "And we can talk about\nhow all of these things", "start": 275.425, "duration": 2.194}, {"text": "relate to each other.", "start": 277.619, "duration": 0.875}, {"text": "They're all correlated.", "start": 278.494, "duration": 1.435}, {"text": "If I change the\nprocessing of something,", "start": 279.929, "duration": 1.769}, {"text": "I change the properties.", "start": 281.698, "duration": 2.102}, {"text": "How do you know how\nit changes when you've", "start": 283.8, "duration": 1.768}, {"text": "got to know these things?", "start": 285.568, "duration": 1.268}, {"text": "And at the core of\nit all is really", "start": 286.836, "duration": 2.136}, {"text": "the thesis of this\nclass, which is", "start": 288.972, "duration": 4.304}, {"text": "that the electronic structure--", "start": 293.276, "duration": 5.138}, {"text": "Paul will be talking\nabout this-- structure", "start": 298.414, "duration": 3.633}, {"text": "of the elements holds\nthe key to understanding.", "start": 302.047, "duration": 13.318}, {"text": "That really is what\nthis class is about.", "start": 315.365, "duration": 5.071}, {"text": "Holds the key.", "start": 320.436, "duration": 0.901}, {"text": "The electronic structure of\nthe elements holds the key.", "start": 321.337, "duration": 3.304}, {"text": "That's what we're\nhere to talk about.", "start": 324.641, "duration": 1.901}, {"text": "And the first part of this class\nis really the basic foundations", "start": 326.542, "duration": 3.471}, {"text": "of chemistry.", "start": 330.013, "duration": 2.269}, {"text": "Some of you may have\nseen some of this before.", "start": 332.282, "duration": 1.935}, {"text": "We're going to build\nthese elements.", "start": 334.217, "duration": 1.501}, {"text": "We're going to talk about them.", "start": 335.718, "duration": 0.868}, {"text": "We're going to learn\nabout the electrons", "start": 336.586, "duration": 1.668}, {"text": "and the electronic structure.", "start": 338.254, "duration": 1.869}, {"text": "But then we're going to\nmake solids out of them", "start": 340.123, "duration": 2.912}, {"text": "and we're going to talk\nabout what those do", "start": 343.035, "duration": 1.792}, {"text": "and how the chemistry\nrelates to the solids", "start": 344.827, "duration": 2.77}, {"text": "and to the properties\nof those solids.", "start": 347.597, "duration": 3.203}, {"text": "Now, I want you to\nknow, again, this", "start": 350.8, "duration": 1.535}, {"text": "is the sort of\nadministrative introduction.", "start": 352.335, "duration": 2.069}, {"text": "You are not alone.", "start": 354.404, "duration": 1.635}, {"text": "On this journey, you have\nmany, many resources.", "start": 356.039, "duration": 5.538}, {"text": "And we are here to help you,\nto help you learn this material", "start": 361.577, "duration": 5.072}, {"text": "and do the best you can.", "start": 366.649, "duration": 2.703}, {"text": "So first you have me.", "start": 369.352, "duration": 1.935}, {"text": "You have your TA.", "start": 371.287, "duration": 1.201}, {"text": "We'll talk about\nthem in a second.", "start": 372.488, "duration": 1.468}, {"text": "You have Laura.", "start": 373.956, "duration": 1.435}, {"text": "Oh, we're going to talk\nabout Laura in a second.", "start": 375.391, "duration": 2.002}, {"text": "You have the textbook\nand the internet.", "start": 377.393, "duration": 2.136}, {"text": "I hear there's stuff\non the internet.", "start": 379.529, "duration": 3.171}, {"text": "And you have each other.", "start": 382.7, "duration": 1.0}, {"text": "And I really want\nyou to work together.", "start": 383.7, "duration": 3.336}, {"text": "Thank you.", "start": 387.036, "duration": 0.668}, {"text": "Who said --that was...", "start": 387.704, "duration": 1.167}, {"text": "I was like, that hit made right\nhere, right in the first 10", "start": 388.871, "duration": 2.603}, {"text": "minutes of class.", "start": 391.474, "duration": 2.135}, {"text": "So the textbook is Averill.", "start": 393.609, "duration": 1.802}, {"text": "It's a really good textbook.", "start": 395.411, "duration": 2.636}, {"text": "It's a really good textbook.", "start": 398.047, "duration": 1.168}, {"text": "Please use it.", "start": 399.215, "duration": 1.468}, {"text": "Please.", "start": 400.683, "duration": 1.201}, {"text": "It's available here.", "start": 401.884, "duration": 1.354}, {"text": "Notes, like I said, will\nbe posted on the same day", "start": 403.238, "duration": 2.083}, {"text": "of each lecture.", "start": 405.321, "duration": 0.667}, {"text": "I'll post whatever you\nsee on this screen.", "start": 405.988, "duration": 1.969}, {"text": "I will post.", "start": 407.957, "duration": 1.668}, {"text": "All right, good.", "start": 409.625, "duration": 1.235}, {"text": "The goody bag.", "start": 410.86, "duration": 1.201}, {"text": "So the goody bag is another\npart of your homework.", "start": 412.061, "duration": 5.239}, {"text": "And these will be\ngiven out nine weeks.", "start": 417.3, "duration": 4.204}, {"text": "So sort of like the quizzes.", "start": 421.504, "duration": 2.135}, {"text": "And in each goody\nbag, which I'm going", "start": 423.639, "duration": 2.269}, {"text": "to talk about in a second,\nthere are things to do.", "start": 425.908, "duration": 3.304}, {"text": "This is a hands on compliment\nto 309.1 lecturers and all", "start": 429.212, "duration": 6.339}, {"text": "the other materials.", "start": 435.551, "duration": 2.469}, {"text": "Now, these goody bags\nare really important.", "start": 438.02, "duration": 6.04}, {"text": "And one of the two\nquiz questions,", "start": 444.06, "duration": 2.169}, {"text": "every week that there's a\nquiz, there are two questions.", "start": 446.229, "duration": 4.337}, {"text": "And one of them will be\ndirectly related to something", "start": 450.566, "duration": 2.603}, {"text": "that you're supposed\nto do in the goody bag.", "start": 453.169, "duration": 1.835}, {"text": "And in fact, we\nwill most times ask", "start": 455.004, "duration": 2.703}, {"text": "you to bring something into\nthe quiz that is in the bag.", "start": 457.707, "duration": 4.671}, {"text": "So don't throw it\naway and please do it.", "start": 462.378, "duration": 2.77}, {"text": "Because one of the\ntwo quiz questions", "start": 465.148, "duration": 1.801}, {"text": "will be very related\nto the goody bag.", "start": 466.949, "duration": 1.802}, {"text": "And the other will be related\nto problems, you know, lecture.", "start": 468.751, "duration": 3.637}, {"text": "Everything's related to lecture.", "start": 472.388, "duration": 2.669}, {"text": "But at least one will be\nrelated to what's in the bag.", "start": 475.057, "duration": 2.313}, {"text": "So this, we really\ntake this seriously.", "start": 477.37, "duration": 1.625}, {"text": "This is a very important\npart of your homework.", "start": 478.995, "duration": 3.236}, {"text": "And oh, there it is.", "start": 482.231, "duration": 1.302}, {"text": "Some of which you need\nto bring to the quiz.", "start": 483.533, "duration": 1.868}, {"text": "And we'll tell you what\nthat is before the quiz.", "start": 485.401, "duration": 2.903}, {"text": "I want to tell you a thing,\nthough, because here's", "start": 488.304, "duration": 2.769}, {"text": "the thing, goody bags are--\nit's a little bit of what's", "start": 491.073, "duration": 4.389}, {"text": "going on here?", "start": 495.462, "duration": 0.583}, {"text": "This is a lecture class.", "start": 496.045, "duration": 1.001}, {"text": "Why are we getting goody bags?", "start": 497.046, "duration": 4.371}, {"text": "And it's because I believe\nin the soul of MIT.", "start": 501.417, "duration": 6.006}, {"text": "I believe in the soul of MIT.", "start": 507.423, "duration": 2.236}, {"text": "And that is that we learn\nbest by thinking and doing,", "start": 509.659, "duration": 5.572}, {"text": "by thinking and doing.", "start": 515.231, "duration": 2.101}, {"text": "And even though this\nis a lecture class,", "start": 517.332, "duration": 1.903}, {"text": "I still want you to do.", "start": 519.235, "duration": 1.201}, {"text": "I want you to have\nstuff in your hands", "start": 520.436, "duration": 2.302}, {"text": "so that you can play\nwith the chemistry", "start": 522.738, "duration": 1.702}, {"text": "that we're learning about.", "start": 524.44, "duration": 4.271}, {"text": "Now, this goes back.", "start": 528.711, "duration": 1.769}, {"text": "I said the soul of MIT.", "start": 530.48, "duration": 1.101}, {"text": "What do I mean?", "start": 531.581, "duration": 1.067}, {"text": "This goes back, all the way back\nto before MIT was born, 1850s.", "start": 532.648, "duration": 7.341}, {"text": "You've got a group of\nreally smart people.", "start": 539.989, "duration": 2.296}, {"text": "They're getting together\nand they're meeting.", "start": 542.285, "duration": 1.875}, {"text": "And they're saying,\nOK, we're going", "start": 544.16, "duration": 1.468}, {"text": "to start up a new university.", "start": 545.628, "duration": 1.802}, {"text": "What should we do?", "start": 547.43, "duration": 2.235}, {"text": "And they wrote out a plan.", "start": 549.665, "duration": 2.002}, {"text": "They wrote out a plan.", "start": 551.667, "duration": 0.935}, {"text": "And it's called\nthe institute plan.", "start": 552.602, "duration": 1.458}, {"text": "That makes sense, 1860.", "start": 554.06, "duration": 1.778}, {"text": "It's a great read.", "start": 555.838, "duration": 2.154}, {"text": "But I want to pull\nout one part that's", "start": 557.992, "duration": 1.583}, {"text": "really important,\nthat what they wanted", "start": 559.575, "duration": 2.603}, {"text": "to do with this great new\ninstitution was to do something", "start": 562.178, "duration": 5.872}, {"text": "that would serve the interests\nof the commerce and the arts,", "start": 568.05, "duration": 3.704}, {"text": "as well as of general\neducation, call for the most", "start": 571.754, "duration": 3.504}, {"text": "earnest cooperation\nof intelligent culture", "start": 575.258, "duration": 2.435}, {"text": "with industrial pursuits,\nintelligent culture,", "start": 577.693, "duration": 2.736}, {"text": "industrial pursuits.", "start": 580.429, "duration": 1.702}, {"text": "That is Mens et Manus.", "start": 582.131, "duration": 2.77}, {"text": "That is Mens et Manus.", "start": 584.901, "duration": 3.036}, {"text": "Mind and Hand.", "start": 587.937, "duration": 2.569}, {"text": "It's so important to MIT\nthat we put it on our logo.", "start": 590.506, "duration": 5.272}, {"text": "We put it on our logo.", "start": 595.778, "duration": 1.401}, {"text": "That's how important it is.", "start": 597.179, "duration": 2.37}, {"text": "We don't put some\nanimal on our logo.", "start": 599.549, "duration": 5.238}, {"text": "We put what matters,\nmens et manus.", "start": 604.787, "duration": 4.671}, {"text": "We don't put the word truth.", "start": 609.458, "duration": 4.972}, {"text": "Veritas, veritas, I mean,\nI'm not going to name names,", "start": 614.43, "duration": 6.206}, {"text": "Harvard.", "start": 620.636, "duration": 2.269}, {"text": "But I mean, isn't that\nsetting the bar kind of low?", "start": 622.905, "duration": 3.837}, {"text": "You know, were\nthey lying before?", "start": 626.742, "duration": 6.974}, {"text": "I don't know.", "start": 633.716, "duration": 1.301}, {"text": "I'm not-- look,\nhonestly I don't know.", "start": 635.017, "duration": 3.47}, {"text": "I don't know.", "start": 638.487, "duration": 0.768}, {"text": "But what I know is that what\nwe know is that, of course,", "start": 639.255, "duration": 3.904}, {"text": "the goal is truth.", "start": 643.159, "duration": 1.034}, {"text": "The difference is, we\nknow how to get it.", "start": 644.193, "duration": 4.638}, {"text": "Mens et manus is how to get it.", "start": 648.831, "duration": 3.137}, {"text": "Let me ask you a question.", "start": 651.968, "duration": 2.335}, {"text": "Why are you here?", "start": 654.303, "duration": 2.569}, {"text": "Not here in this classroom.", "start": 656.872, "duration": 1.936}, {"text": "I know you're in the classroom\nbecause you signed up for it.", "start": 658.808, "duration": 2.502}, {"text": "Why are you at MIT?", "start": 661.31, "duration": 1.969}, {"text": "Why are you here at MIT?", "start": 663.279, "duration": 3.704}, {"text": "I can tell you, you\nare here because you", "start": 666.983, "duration": 3.503}, {"text": "are some of the brightest, most\ngifted, most talented students", "start": 670.486, "duration": 3.203}, {"text": "on the planet.", "start": 673.689, "duration": 2.202}, {"text": "Right?", "start": 675.891, "duration": 0.501}, {"text": "Thank you, whoever said that.", "start": 676.392, "duration": 1.602}, {"text": "Agreement.", "start": 677.994, "duration": 1.635}, {"text": "That was like a like online.", "start": 679.629, "duration": 2.235}, {"text": "But you are here\nbecause you want", "start": 681.864, "duration": 2.169}, {"text": "to use those talents to make\nthe world a better place.", "start": 684.033, "duration": 4.504}, {"text": "You are here because you know\nhow to answer any question.", "start": 688.537, "duration": 6.006}, {"text": "But you are also here\nbecause you are going", "start": 694.543, "duration": 3.204}, {"text": "to experience a transition.", "start": 697.747, "duration": 2.168}, {"text": "You are going to experience\na transition here.", "start": 699.915, "duration": 2.403}, {"text": "You are going to\nmake the transition", "start": 702.318, "duration": 2.035}, {"text": "from knowing how to answer\nany question to knowing", "start": 704.353, "duration": 3.27}, {"text": "which question to ask.", "start": 707.623, "duration": 1.468}, {"text": "And that is the transition\nfrom student to scholar.", "start": 709.091, "duration": 4.204}, {"text": "That is MIT.", "start": 713.295, "duration": 1.502}, {"text": "That's mens et manus.", "start": 714.797, "duration": 3.503}, {"text": "Now, it's not easy.", "start": 718.3, "duration": 3.437}, {"text": "You don't come here-- nobody\ncomes to MIT to phone it in.", "start": 721.737, "duration": 5.105}, {"text": "If universities\nwere restaurants,", "start": 726.842, "duration": 3.17}, {"text": "this wouldn't be that fancy one\nwhere you go in and you order,", "start": 730.012, "duration": 3.404}, {"text": "and then somebody cooks\nand brings you your food.", "start": 733.416, "duration": 2.135}, {"text": "This would be the one where we\nall go back into the kitchen", "start": 735.551, "duration": 2.503}, {"text": "and together we make the\nbest meal we've ever had.", "start": 738.054, "duration": 4.004}, {"text": "That's the MIT way.", "start": 742.058, "duration": 1.801}, {"text": "That's the MIT way.", "start": 743.859, "duration": 1.569}, {"text": "And it's not about-- you don't\nroam the halls here and bask", "start": 745.428, "duration": 5.693}, {"text": "in this reputation and think\nof it as some privilege", "start": 751.121, "duration": 3.516}, {"text": "to be here, because you\nare MIT's reputation.", "start": 754.637, "duration": 5.972}, {"text": "Freshmen, raise your hand.", "start": 760.609, "duration": 2.536}, {"text": "Yeah.", "start": 763.145, "duration": 0.501}, {"text": "Starting-- There's a few of you.", "start": 763.646, "duration": 2.836}, {"text": "Starting today, you\nare MIT's reputation.", "start": 766.482, "duration": 4.605}, {"text": "Starting today.", "start": 771.087, "duration": 2.502}, {"text": "It's on you.", "start": 773.589, "duration": 0.868}, {"text": "So we don't walk around these\ngreat halls and feel privilege.", "start": 774.457, "duration": 6.506}, {"text": "We feel responsibility.", "start": 780.963, "duration": 2.102}, {"text": "That's what it means to be here.", "start": 783.065, "duration": 1.702}, {"text": "OK?", "start": 784.767, "duration": 3.47}, {"text": "All right.", "start": 788.237, "duration": 1.168}, {"text": "Good.", "start": 789.405, "duration": 0.867}, {"text": "Well, now that we've got\nthat all straightened out,", "start": 790.272, "duration": 3.07}, {"text": "let's move on.", "start": 793.342, "duration": 0.601}, {"text": "That's the end of my\nadministrative stuff.", "start": 793.943, "duration": 4.638}, {"text": "And with the last\n20, 25 minutes,", "start": 798.581, "duration": 4.871}, {"text": "I want to do a little bit of\nan introduction to chemistry.", "start": 803.452, "duration": 5.606}, {"text": "And I'm not going to\never test you on history.", "start": 809.058, "duration": 9.242}, {"text": "But I want to just kind of\nget ourselves in the mood", "start": 818.3, "duration": 5.239}, {"text": "by going back.", "start": 823.539, "duration": 2.336}, {"text": "So I'll give you a little bit\nof history here in a few slides.", "start": 825.875, "duration": 5.071}, {"text": "So we are interested in\nsolid state chemistry", "start": 830.946, "duration": 5.706}, {"text": "because chemistry is\nthat essential ingredient", "start": 836.652, "duration": 4.071}, {"text": "to understanding\nthe natural world.", "start": 840.723, "duration": 2.335}, {"text": "And the solid state is the link\nbetween that and materials,", "start": 843.058, "duration": 4.505}, {"text": "and engineering.", "start": 847.563, "duration": 2.202}, {"text": "That is the link.", "start": 849.765, "duration": 1.301}, {"text": "And so we'll talk a lot\nabout this all the time.", "start": 851.066, "duration": 3.17}, {"text": "Oh oh.", "start": 854.236, "duration": 1.835}, {"text": "Come on out, Jerome.", "start": 856.071, "duration": 2.903}, {"text": "But where did chemistry begin?", "start": 858.974, "duration": 2.803}, {"text": "OK, now hold on.", "start": 861.777, "duration": 5.005}, {"text": "I've got a pen.", "start": 866.782, "duration": 0.667}, {"text": "Oh no, I got a--", "start": 867.449, "duration": 0.901}, {"text": "OK, that's better.", "start": 868.35, "duration": 1.335}, {"text": "I thought it was a pen.", "start": 869.685, "duration": 2.903}, {"text": "Where did it begin?", "start": 872.588, "duration": 1.602}, {"text": "Where did it begin?", "start": 874.19, "duration": 2.168}, {"text": "Well, people were mixing\nstuff a long time ago.", "start": 876.358, "duration": 1.969}, {"text": "But really, and there's\nsome debate about this,", "start": 878.327, "duration": 2.035}, {"text": "you know, the word\nchem itself, you know,", "start": 880.362, "duration": 2.47}, {"text": "it may have come from\nchem, the land of chem,", "start": 882.832, "duration": 1.901}, {"text": "which means sort of\nthe rich soil in Egypt.", "start": 884.733, "duration": 3.204}, {"text": "Or maybe it came\nfrom chemea in Greek,", "start": 887.937, "duration": 2.235}, {"text": "which meant sort of mixing\nand pouring together.", "start": 890.172, "duration": 3.337}, {"text": "But the point is that\nwhat they were doing was", "start": 893.509, "duration": 1.935}, {"text": "they were taking stuff and\nmaking other stuff out of it.", "start": 895.444, "duration": 4.638}, {"text": "That dagger there is\nfrom ancient Egypt.", "start": 900.082, "duration": 3.103}, {"text": "It's from around 3,000 BC.", "start": 903.185, "duration": 1.568}, {"text": "And the way they made that was\nby taking stuff from a meteor.", "start": 904.753, "duration": 6.173}, {"text": "It was iron and some nickel\nand some other things.", "start": 910.926, "duration": 2.102}, {"text": "But from a meteor.", "start": 913.028, "duration": 1.202}, {"text": "And they were able to make a\nreally, really strong weapon", "start": 914.23, "duration": 3.069}, {"text": "out of it.", "start": 917.299, "duration": 1.235}, {"text": "They called those\ndaggers from heaven.", "start": 918.534, "duration": 2.736}, {"text": "But the point is\nthat what chemistry", "start": 921.27, "duration": 2.235}, {"text": "is about is it's about\nhow you mix these things", "start": 923.505, "duration": 3.137}, {"text": "and what are you mixing\nin the first place.", "start": 926.642, "duration": 2.502}, {"text": "What was it that you\ntook out of the meteor?", "start": 929.144, "duration": 2.57}, {"text": "And why did it make\nthat instead of that?", "start": 931.714, "duration": 1.902}, {"text": "How did I get that dagger?", "start": 933.616, "duration": 2.335}, {"text": "That's really what\nthis is about.", "start": 935.951, "duration": 1.802}, {"text": "And so if we go back to\nsort of the first people who", "start": 937.753, "duration": 3.437}, {"text": "really started\ndiscussing this, we", "start": 941.19, "duration": 2.269}, {"text": "start with Plato and Aristotle.", "start": 943.459, "duration": 2.836}, {"text": "And Plato had this idea,\nprobably some of you", "start": 946.295, "duration": 7.708}, {"text": "may have heard it, so\nwhat is stuff made of?", "start": 954.003, "duration": 3.303}, {"text": "What is like the\nessence of things?", "start": 957.306, "duration": 3.236}, {"text": "They really thought about\nthis and they debated it.", "start": 960.542, "duration": 2.703}, {"text": "And you know, Plato-- well,\nPlato said there's four things.", "start": 963.245, "duration": 5.506}, {"text": "And some of you may\nhave heard this.", "start": 968.751, "duration": 1.501}, {"text": "There's earth.", "start": 970.252, "duration": 2.603}, {"text": "There's fire.", "start": 972.855, "duration": 3.136}, {"text": "There's air.", "start": 975.991, "duration": 2.236}, {"text": "And there's water.", "start": 978.227, "duration": 5.605}, {"text": "And everything is\nmade out of that.", "start": 983.832, "duration": 2.369}, {"text": "Now, you can see that's\na little limiting.", "start": 986.201, "duration": 4.371}, {"text": "Aristotle came along\nand said, wait a second.", "start": 990.572, "duration": 1.902}, {"text": "Hold on.", "start": 992.474, "duration": 0.895}, {"text": "If I look out into the stars,\nthey don't seem to change much.", "start": 993.369, "duration": 2.542}, {"text": "So there must be something\nelse that's not quote,", "start": 995.911, "duration": 2.136}, {"text": "\"earthly and corruptible.\"", "start": 998.047, "duration": 3.336}, {"text": "And he called that ether.", "start": 1001.383, "duration": 1.068}, {"text": "But anyway, the point is,\nit's hard to kind of explain", "start": 1002.451, "duration": 3.737}, {"text": "everything with this.", "start": 1006.188, "duration": 1.068}, {"text": "How are you going to\nbuild a world out of--", "start": 1007.256, "duration": 1.802}, {"text": "We can't even explain\nthe Boston weather", "start": 1009.058, "duration": 1.835}, {"text": "with just these four words.", "start": 1010.893, "duration": 3.737}, {"text": "So it was limiting.", "start": 1014.63, "duration": 1.168}, {"text": "But then along came these\nguys, Democritus and Leucippus,", "start": 1015.798, "duration": 6.006}, {"text": "who was his teacher.", "start": 1021.804, "duration": 1.101}, {"text": "And Democritus said, OK look,\nthere's something fundamental.", "start": 1022.905, "duration": 4.471}, {"text": "So Democritus, he said, look I\nbelieve there's something more", "start": 1027.376, "duration": 5.606}, {"text": "than these four things.", "start": 1032.982, "duration": 2.434}, {"text": "Democritus.", "start": 1035.416, "duration": 4.339}, {"text": "And he said there are\nthese things called atoms.", "start": 1039.755, "duration": 3.136}, {"text": "So he was an atomist.", "start": 1042.891, "duration": 2.303}, {"text": "And atom is indivisible.", "start": 1045.194, "duration": 5.138}, {"text": "Indivisible, that's the meaning.", "start": 1050.332, "duration": 2.136}, {"text": "Atomist in Greek, it\nmeant indivisible, atom.", "start": 1052.468, "duration": 6.673}, {"text": "And they fought about this.", "start": 1059.141, "duration": 1.735}, {"text": "They fought about this a lot.", "start": 1060.876, "duration": 1.468}, {"text": "And Plato, it's said, was\nso upset about Democritus", "start": 1062.344, "duration": 3.537}, {"text": "that he wanted all\nof his books burned.", "start": 1065.881, "duration": 4.104}, {"text": "That's a-- back in the day,\nthat was a serious diss.", "start": 1069.985, "duration": 3.837}, {"text": "It would be like if I blocked\nsomebody on Instagram.", "start": 1073.822, "duration": 4.805}, {"text": "Can I do that?", "start": 1078.627, "duration": 0.634}, {"text": "Is that a thing?", "start": 1079.261, "duration": 0.667}, {"text": "No, Snapchat.", "start": 1079.928, "duration": 1.435}, {"text": "What?", "start": 1081.363, "duration": 0.634}, {"text": "I don't know.", "start": 1081.997, "duration": 0.801}, {"text": "I was right.", "start": 1082.798, "duration": 0.534}, {"text": "See!", "start": 1083.332, "duration": 1.101}, {"text": "That's how-- I'm blocking you.", "start": 1084.433, "duration": 2.703}, {"text": "Burn your books.", "start": 1087.136, "duration": 2.702}, {"text": "Seriously dissing each other.", "start": 1089.838, "duration": 4.305}, {"text": "Democritus.", "start": 1094.143, "duration": 0.8}, {"text": "Now, it really happened\nquickly from there.", "start": 1094.943, "duration": 4.105}, {"text": "A mere 2,000 years later\nwe get to modern chemistry.", "start": 1099.048, "duration": 5.472}, {"text": "Why did it take 2,000 years?", "start": 1104.52, "duration": 2.736}, {"text": "It took 2,000 years because\nwe were missing something.", "start": 1107.256, "duration": 3.103}, {"text": "So we had a lot of alchemy.", "start": 1110.359, "duration": 1.435}, {"text": "The thing about alchemy,\nthere are actually", "start": 1111.794, "duration": 1.801}, {"text": "some really interesting\ndiscoveries in alchemy", "start": 1113.595, "duration": 2.57}, {"text": "but they always tied it to\nsomething very non-rigorous,", "start": 1116.165, "duration": 3.737}, {"text": "like oh, this works\nbecause of the phases", "start": 1119.902, "duration": 2.169}, {"text": "of the moon or the tides.", "start": 1122.071, "duration": 4.304}, {"text": "And so it really needed\nsome rigorous way", "start": 1126.375, "duration": 3.904}, {"text": "to study what things were made\nof, what things were made of.", "start": 1130.279, "duration": 5.505}, {"text": "And that came, oh, inevitable\nthat that might happen.", "start": 1135.784, "duration": 6.073}, {"text": "Here we go.", "start": 1141.857, "duration": 0.734}, {"text": "That came with the\nscientific method", "start": 1142.591, "duration": 1.635}, {"text": "in the 1600s and\nSir Francis Bacon.", "start": 1144.226, "duration": 4.538}, {"text": "And I think a lot of you have\nseen the scientific method.", "start": 1148.764, "duration": 4.237}, {"text": "But it was pivotal\nfor chemistry.", "start": 1153.001, "duration": 1.635}, {"text": "It was pivotal.", "start": 1154.636, "duration": 1.335}, {"text": "Because it allowed\npeople to think", "start": 1155.971, "duration": 1.635}, {"text": "about this question\nof what stuff", "start": 1157.606, "duration": 1.635}, {"text": "is made of but using\na rigorous approach.", "start": 1159.241, "duration": 4.738}, {"text": "Making observation,\nform a hypothesis,", "start": 1163.979, "duration": 2.469}, {"text": "do an experiment, record.", "start": 1166.448, "duration": 2.269}, {"text": "And that's what\npeople started doing.", "start": 1168.717, "duration": 2.236}, {"text": "That is what, for\nexample, Robert Boyle", "start": 1170.953, "duration": 2.169}, {"text": "did, one of the earlier\nones to think about things", "start": 1173.122, "duration": 3.336}, {"text": "and talk about the element.", "start": 1176.458, "duration": 1.368}, {"text": "They were all going\nback to thinking", "start": 1177.826, "duration": 2.269}, {"text": "about these same issues,\nwhat are things made of?", "start": 1180.095, "duration": 4.638}, {"text": "An element can't be broken\ndown into two or more", "start": 1184.733, "duration": 3.504}, {"text": "simpler substances\nby chemical means.", "start": 1188.237, "duration": 2.936}, {"text": "So he was at that.", "start": 1191.173, "duration": 0.901}, {"text": "He was going for that core.", "start": 1192.074, "duration": 2.035}, {"text": "What is at the core?", "start": 1194.109, "duration": 1.635}, {"text": "Oh, and then you had Priestly.", "start": 1195.744, "duration": 4.505}, {"text": "Priestly discovered oxygen and\nhe did it by burning things.", "start": 1200.249, "duration": 6.172}, {"text": "He did it by burning things.", "start": 1206.421, "duration": 2.803}, {"text": "Just mentioning that word\nmakes me want to put those on.", "start": 1209.224, "duration": 6.44}, {"text": "And so he really\nstudied combustion.", "start": 1215.664, "duration": 3.57}, {"text": "He studied these reactions\nthat were happening with oxygen", "start": 1219.234, "duration": 2.903}, {"text": "and carbon containing matter.", "start": 1222.137, "duration": 3.17}, {"text": "It was combustion.", "start": 1225.307, "duration": 1.702}, {"text": "So he burned stuff.", "start": 1227.009, "duration": 0.8}, {"text": "He burned this.", "start": 1227.809, "duration": 0.901}, {"text": "He burned that.", "start": 1228.71, "duration": 0.901}, {"text": "He burned that.", "start": 1229.611, "duration": 0.634}, {"text": "And he said, what\nhappens when I do that?", "start": 1230.245, "duration": 2.703}, {"text": "That was another way.", "start": 1232.948, "duration": 1.068}, {"text": "Priestly-- sorry, Boyle played\nwith pressure and volume.", "start": 1234.016, "duration": 4.938}, {"text": "Pressure and volume\nrelationships", "start": 1238.954, "duration": 1.401}, {"text": "for gases, that was\nhis way to try to get", "start": 1240.355, "duration": 2.203}, {"text": "at what things are made of.", "start": 1242.558, "duration": 1.334}, {"text": "Priestley wanted\nto blow stuff up.", "start": 1243.892, "duration": 3.671}, {"text": "Oh, and he also\nworked with beer.", "start": 1247.563, "duration": 3.963}, {"text": "He actually worked with beer.", "start": 1251.526, "duration": 1.208}, {"text": "And he discovered\nthat the same gas that", "start": 1252.734, "duration": 2.436}, {"text": "comes out of fermenting\nbeer is the gas that", "start": 1255.17, "duration": 2.569}, {"text": "comes out of combusting.", "start": 1257.739, "duration": 2.269}, {"text": "So you got a guy who's\nworking on lighting stuff", "start": 1260.008, "duration": 3.27}, {"text": "on fire and beer.", "start": 1263.278, "duration": 2.803}, {"text": "And you can imagine\nmaybe that wasn't going", "start": 1266.081, "duration": 2.669}, {"text": "to be a good day at some point.", "start": 1268.75, "duration": 2.336}, {"text": "And what happened is,\nactually, his experiments did--", "start": 1271.086, "duration": 2.703}, {"text": "this is true, they slowed down\nwhen he fell into a vat of beer", "start": 1273.789, "duration": 3.77}, {"text": "during one of his experiments.", "start": 1277.559, "duration": 2.703}, {"text": "Now, the thing is, though,\nthat he studied combustion.", "start": 1280.262, "duration": 3.203}, {"text": "And that makes me\nthink about combustion.", "start": 1283.465, "duration": 3.036}, {"text": "And I feel like oh\noh, I feel like this", "start": 1286.501, "duration": 6.04}, {"text": "is a good time for my goody bag,\nwhich is to illustrate a point.", "start": 1292.541, "duration": 8.542}, {"text": "Oh, thank you, Jerome.", "start": 1301.083, "duration": 5.972}, {"text": "That's going to\nsome feed somewhere.", "start": 1307.055, "duration": 2.236}, {"text": "OK, now the thing is that\nwhen you go to a restaurant", "start": 1309.291, "duration": 4.905}, {"text": "and they have real candles,\nI get really happy about it.", "start": 1314.196, "duration": 2.335}, {"text": "We'll tell candle stories\nlater in the term as well.", "start": 1316.531, "duration": 3.938}, {"text": "And this is what you're doing.", "start": 1320.469, "duration": 1.902}, {"text": "You are lighting\na candle on fire.", "start": 1322.371, "duration": 2.502}, {"text": "Now, when you do that,\nyou see, here's the thing.", "start": 1324.873, "duration": 3.37}, {"text": "You're actually-- I don't\nwant you to think about it", "start": 1328.243, "duration": 2.836}, {"text": "as lighting a candle.", "start": 1331.079, "duration": 1.335}, {"text": "I want you to now from\nnow on think about it", "start": 1332.414, "duration": 2.569}, {"text": "as lighting C25H52.", "start": 1334.983, "duration": 1.721}, {"text": "And in fact, if you\ngo to a restaurant", "start": 1336.704, "duration": 1.583}, {"text": "and you want to ask them\nif they have real candles,", "start": 1338.287, "duration": 1.901}, {"text": "I don't care if you're\nout with friends", "start": 1340.188, "duration": 1.135}, {"text": "or maybe you're on a\ndate, raise your hand.", "start": 1341.323, "duration": 2.169}, {"text": "Ask the waiter and say,\ndo you have any C25H52?", "start": 1343.492, "duration": 4.104}, {"text": "And see if they know, see if\nthey've taken some chemistry.", "start": 1347.596, "duration": 3.97}, {"text": "What you're doing is\nyou're doing that.", "start": 1351.566, "duration": 1.702}, {"text": "You're combusting that fuel.", "start": 1353.268, "duration": 2.636}, {"text": "See, the whole world runs\nby lighting things on fire.", "start": 1355.904, "duration": 3.67}, {"text": "You could light propane on fire.", "start": 1359.574, "duration": 2.169}, {"text": "Or you could light\nhydrogen on fire.", "start": 1361.743, "duration": 3.037}, {"text": "That's where we said, yo, hands\non is a good way to learn.", "start": 1364.78, "duration": 4.271}, {"text": "So let's see what that's like.", "start": 1369.051, "duration": 1.268}, {"text": "There's the candle,\nwhich is tilting.", "start": 1370.319, "duration": 1.901}, {"text": "I'm watching it.", "start": 1372.22, "duration": 2.136}, {"text": "Really?", "start": 1374.356, "duration": 1.034}, {"text": "Oh, OK.", "start": 1375.39, "duration": 2.903}, {"text": "Or you could light\nhydrogen on fire.", "start": 1378.293, "duration": 1.935}, {"text": "And if you do that,\nthis is what happens.", "start": 1380.228, "duration": 3.871}, {"text": "So, OK, let's do that again.", "start": 1384.099, "duration": 1.902}, {"text": "These bubbles aren't-- oh,\nI should have kept this on.", "start": 1386.001, "duration": 3.303}, {"text": "There we go.", "start": 1389.304, "duration": 3.337}, {"text": "That's really, really fun.", "start": 1392.641, "duration": 3.837}, {"text": "But I'm going to stop.", "start": 1396.478, "duration": 0.934}, {"text": "Oh, I'm not going to\nstop because you just", "start": 1397.412, "duration": 1.944}, {"text": "turned it on again.", "start": 1399.356, "duration": 0.792}, {"text": "Now you're coaxing\nme to do more.", "start": 1400.148, "duration": 3.37}, {"text": "Well, these are bigger bubbles.", "start": 1403.518, "duration": 1.302}, {"text": "These are bigger boulders.", "start": 1404.82, "duration": 1.083}, {"text": "Let's see if this\ngets a nice flame.", "start": 1405.903, "duration": 2.52}, {"text": "Oh, thank you.", "start": 1408.423, "duration": 2.202}, {"text": "There we go.", "start": 1410.625, "duration": 2.336}, {"text": "OK, now that's my\ngoody bag for today.", "start": 1412.961, "duration": 7.074}, {"text": "We run our world by\ndoing this, I mean,", "start": 1420.035, "duration": 1.868}, {"text": "not by lighting hydrogen\nbubbles on fire,", "start": 1421.903, "duration": 4.238}, {"text": "but when you put your\nphone in to charge it,", "start": 1426.141, "duration": 3.27}, {"text": "you are lighting a fire.", "start": 1429.411, "duration": 1.001}, {"text": "Think about that.", "start": 1430.412, "duration": 0.708}, {"text": "You might not feel it.", "start": 1431.12, "duration": 2.795}, {"text": "You are.", "start": 1433.915, "duration": 0.501}, {"text": "No, I'm-- I love that reaction.", "start": 1434.416, "duration": 1.835}, {"text": "I love that reaction.", "start": 1436.251, "duration": 1.068}, {"text": "You are lighting a fire.", "start": 1437.319, "duration": 1.535}, {"text": "It may not be you, but\nsomebody else's down the street", "start": 1438.854, "duration": 2.869}, {"text": "at a power plant.", "start": 1441.723, "duration": 1.335}, {"text": "This is how we run our\nworld, we burn things.", "start": 1443.058, "duration": 2.169}, {"text": "And so this study of combustion\nwas extremely important.", "start": 1445.227, "duration": 3.803}, {"text": "And it's going to be\nour first reaction.", "start": 1449.03, "duration": 4.372}, {"text": "So what's happening?", "start": 1453.402, "duration": 1.534}, {"text": "When you light C25H52 on\nfire, what's happening", "start": 1454.936, "duration": 5.473}, {"text": "is that you're reacting.", "start": 1460.409, "duration": 1.534}, {"text": "You're doing--\nremember, Priestley", "start": 1461.943, "duration": 3.444}, {"text": "discovered H52 plus oxygen.\nHe discovered oxygen.", "start": 1465.387, "duration": 5.332}, {"text": "And he also, remember,\nthis comes off of beer too.", "start": 1470.719, "duration": 4.538}, {"text": "He also discovered these\nother gases coming out.", "start": 1475.257, "duration": 3.603}, {"text": "Right?", "start": 1478.86, "duration": 2.169}, {"text": "And that's the\nchemical reaction.", "start": 1481.029, "duration": 2.97}, {"text": "Is it the chemical reaction?", "start": 1483.999, "duration": 2.135}, {"text": "It's not done yet.", "start": 1486.134, "duration": 2.936}, {"text": "It's not balanced.", "start": 1489.07, "duration": 1.168}, {"text": "It's not balanced.", "start": 1490.238, "duration": 1.902}, {"text": "Mass is being lost\nleft and right.", "start": 1492.14, "duration": 2.102}, {"text": "Not OK.", "start": 1494.242, "duration": 1.969}, {"text": "Not OK.", "start": 1496.211, "duration": 1.101}, {"text": "So we must, when we\nwrite down things", "start": 1497.312, "duration": 3.07}, {"text": "that happen in chemistry like a\nreaction, we must find balance.", "start": 1500.382, "duration": 4.604}, {"text": "It's also important in life.", "start": 1504.986, "duration": 2.636}, {"text": "But it's very\nimportant in chemistry.", "start": 1507.622, "duration": 1.902}, {"text": "And so if you balance this,\nyou're going to put a 2.", "start": 1509.524, "duration": 4.271}, {"text": "Because here's the deal and I'll\ntalk about this more in a sec,", "start": 1513.795, "duration": 4.738}, {"text": "C25H52 plus-- anybody\nknow how many O2s?", "start": 1518.533, "duration": 10.544}, {"text": "38, whoever said\nthat, 38 is going", "start": 1529.077, "duration": 3.103}, {"text": "to go to 25CO2 plus 26H2O.", "start": 1532.18, "duration": 11.045}, {"text": "These are the kinds of\nthings that are perfect,", "start": 1543.225, "duration": 2.802}, {"text": "perfect to keep doing exercises\non though your problems,", "start": 1546.027, "duration": 3.437}, {"text": "through your goody bags,\nin your recitation.", "start": 1549.464, "duration": 3.904}, {"text": "These are exactly the--\nhow did you do that?", "start": 1553.368, "duration": 2.703}, {"text": "If you don't know,\nyou will soon.", "start": 1556.071, "duration": 1.835}, {"text": "You'll get help, practice.", "start": 1557.906, "duration": 5.305}, {"text": "I know, I know.", "start": 1563.211, "duration": 1.535}, {"text": "I wrote this down.", "start": 1564.746, "duration": 2.402}, {"text": "I'm just testing you.", "start": 1567.148, "duration": 2.77}, {"text": "I made a mistake.", "start": 1569.918, "duration": 1.234}, {"text": "Because the 2 was supposed\nto go to the propane one", "start": 1571.152, "duration": 5.406}, {"text": "because I wanted to write\nthat one and I got excited.", "start": 1576.558, "duration": 2.569}, {"text": "And I went to that instead.", "start": 1579.127, "duration": 3.47}, {"text": "And that would be 13O2.", "start": 1582.597, "duration": 2.002}, {"text": "And that would be\n8CO2, and so on, 10H2O.", "start": 1584.599, "duration": 6.206}, {"text": "These are balanced.", "start": 1590.805, "duration": 2.203}, {"text": "These are balanced.", "start": 1593.008, "duration": 2.435}, {"text": "And balancing\nreactions is important.", "start": 1595.443, "duration": 5.439}, {"text": "Why?", "start": 1600.882, "duration": 0.501}, {"text": "Because it balances the mass\nand it tells us something else.", "start": 1601.383, "duration": 5.305}, {"text": "Once we count atoms, you'll see.", "start": 1606.688, "duration": 2.402}, {"text": "We're going to count\natoms on Friday.", "start": 1609.09, "duration": 3.604}, {"text": "But it's telling us that\nyou can't just lose stuff.", "start": 1612.694, "duration": 3.837}, {"text": "You can't just lose stuff.", "start": 1616.531, "duration": 1.201}, {"text": "You've got to have the--", "start": 1617.732, "duration": 1.068}, {"text": "Oh, and that, by\nthe way, is what--", "start": 1618.8, "duration": 3.937}, {"text": "Lavoisier, Lavoisier.", "start": 1622.737, "duration": 1.202}, {"text": "Where is Jerome?", "start": 1623.939, "duration": 1.368}, {"text": "Oh, yeah.", "start": 1625.307, "duration": 1.434}, {"text": "No.", "start": 1626.741, "duration": 1.135}, {"text": "Shoot.", "start": 1627.876, "duration": 0.5}, {"text": "Isn't that butane, not propane?", "start": 1628.376, "duration": 1.936}, {"text": "Butane not propane.", "start": 1630.312, "duration": 0.967}, {"text": "It very well might have been.", "start": 1631.279, "duration": 1.769}, {"text": "C4 H10, yes.", "start": 1633.048, "duration": 2.002}, {"text": "I believe that is butane.", "start": 1635.05, "duration": 1.268}, {"text": "Thank you.", "start": 1636.318, "duration": 4.437}, {"text": "Oh, Jerome, come back.", "start": 1640.755, "duration": 1.802}, {"text": "Jerome helps the class\nand he helps my French.", "start": 1642.557, "duration": 2.669}, {"text": "Lavoisier?", "start": 1645.226, "duration": 1.435}, {"text": "No.", "start": 1646.661, "duration": 2.002}, {"text": "OK, say it.", "start": 1648.663, "duration": 2.87}, {"text": "Lavoisier.", "start": 1651.533, "duration": 3.87}, {"text": "OK, I tried.", "start": 1655.403, "duration": 1.835}, {"text": "But now he said, look,\nyou've got to conserve mass.", "start": 1657.238, "duration": 5.973}, {"text": "You can't lose-- you can't\ncreate or destroy matter", "start": 1663.211, "duration": 4.104}, {"text": "when you do chemistry.", "start": 1667.315, "duration": 1.502}, {"text": "When you do this, when you\ndo this you cannot create", "start": 1668.817, "duration": 3.937}, {"text": "or destroy matter.", "start": 1672.754, "duration": 3.937}, {"text": "Conservation of mass, Lavoisier.", "start": 1676.691, "duration": 6.807}, {"text": "It means that if I-- you\nknow, you get a little more", "start": 1683.498, "duration": 3.269}, {"text": "than that, see\nthis is balancing.", "start": 1686.767, "duration": 4.038}, {"text": "But you also can think about\nwhether you have anything--", "start": 1690.805, "duration": 4.772}, {"text": "I probably should blow that out.", "start": 1695.577, "duration": 3.003}, {"text": "Whether you have anything-- did\nyou have too much, too little?", "start": 1698.58, "duration": 4.738}, {"text": "Did I mix it just right?", "start": 1703.318, "duration": 1.201}, {"text": "So like if you take-- let's\ntake another reaction just", "start": 1704.519, "duration": 2.665}, {"text": "as an example.", "start": 1707.184, "duration": 0.839}, {"text": "If I mix iron and oxygen to make\nferric oxide, oh, not balanced.", "start": 1708.023, "duration": 11.044}, {"text": "Two, three, four.", "start": 1719.067, "duration": 4.371}, {"text": "And I tell you, for example,\nthat I've got 10 grams of iron", "start": 1723.438, "duration": 5.239}, {"text": "reacts with, let's see--", "start": 1728.677, "duration": 6.406}, {"text": "OK, I'm going to give it\nto you a different way.", "start": 1735.083, "duration": 2.002}, {"text": "I'm going to say that it gives\nyou, reacts with O2 to give", "start": 1737.085, "duration": 7.24}, {"text": "18.2 grams of FE203.", "start": 1744.325, "duration": 7.208}, {"text": "This is an example\nfrom the textbook.", "start": 1751.533, "duration": 3.37}, {"text": "Then I know because\nof conservation", "start": 1754.903, "duration": 2.427}, {"text": "of mass from Lavoisier that 8.2\ngrams-- if this reacts fully,", "start": 1757.33, "duration": 8.446}, {"text": "right, if iron reacts\nfully, it all goes away.", "start": 1765.776, "duration": 4.709}, {"text": "There's none left.", "start": 1770.485, "duration": 1.401}, {"text": "Then I must have, if I got\n18.2 grams of ferric acid,", "start": 1771.886, "duration": 3.604}, {"text": "I must have reacted\n8.2 grams of oxygen.", "start": 1775.49, "duration": 3.27}, {"text": "That's conservation of mass.", "start": 1778.76, "duration": 2.135}, {"text": "But there's another thing\nyou can do with this.", "start": 1780.895, "duration": 3.137}, {"text": "So I must have reacted\n8.2 grams of oxygen.", "start": 1784.032, "duration": 9.009}, {"text": "But there's another thing\nbecause if I started, you know,", "start": 1793.041, "duration": 3.904}, {"text": "if I started now with 10 grams\nof O2 and 10 grams of iron,", "start": 1796.945, "duration": 12.379}, {"text": "aha, I'm going to have excess.", "start": 1809.324, "duration": 3.069}, {"text": "I know that.", "start": 1812.393, "duration": 1.135}, {"text": "I know that now.", "start": 1813.528, "duration": 0.901}, {"text": "I'm going to have excess.", "start": 1814.429, "duration": 1.068}, {"text": "And the thing is that there's\nsomething that's limiting here.", "start": 1815.497, "duration": 3.336}, {"text": "What's in excess?", "start": 1818.833, "duration": 3.103}, {"text": "The oxygen because I started\nwith the same amount of iron.", "start": 1821.936, "duration": 3.137}, {"text": "There is more-- but\nthat means that we've", "start": 1825.073, "duration": 2.302}, {"text": "got another term, which is that\niron is the limiting reagent.", "start": 1827.375, "duration": 6.131}, {"text": "You see that?", "start": 1833.506, "duration": 0.542}, {"text": "Because now I'm limited,\nmeaning this reaction", "start": 1834.048, "duration": 6.64}, {"text": "goes and goes and goes and\nsomething runs out first.", "start": 1840.688, "duration": 3.137}, {"text": "That is the limiting reagent.", "start": 1843.825, "duration": 3.503}, {"text": "And this was just by thinking\nabout Lavoisier's conservation", "start": 1847.328, "duration": 4.305}, {"text": "of mass.", "start": 1851.633, "duration": 1.301}, {"text": "I can't create or destroy\natoms in a reaction,", "start": 1852.934, "duration": 3.003}, {"text": "not in this class.", "start": 1855.937, "duration": 1.301}, {"text": "You can take nuclear\nsomewhere else.", "start": 1857.238, "duration": 1.569}, {"text": "But not here.", "start": 1858.807, "duration": 0.967}, {"text": "Here we don't destroy\nor create matter.", "start": 1859.774, "duration": 2.669}, {"text": "Limiting reagent,\nbalancing reactions,", "start": 1862.443, "duration": 2.103}, {"text": "very, very fundamental\nfirst chemical concepts.", "start": 1864.546, "duration": 4.604}, {"text": "Now, these guys were\nplaying around with stuff", "start": 1869.15, "duration": 3.537}, {"text": "and really trying to\nfigure out, again,", "start": 1872.687, "duration": 2.069}, {"text": "they're going back\nto Democritus.", "start": 1874.756, "duration": 2.702}, {"text": "What are these indivisible\nelements, atoms, what are they?", "start": 1877.458, "duration": 5.216}, {"text": "And all these guys were\nstarting to mess with that.", "start": 1882.674, "duration": 2.125}, {"text": "Once they had the\nscientific method,", "start": 1884.799, "duration": 1.862}, {"text": "they were willing\nto go very far.", "start": 1886.661, "duration": 1.375}, {"text": "Here's Lavoisier's\nlist, 33 elements.", "start": 1888.036, "duration": 4.471}, {"text": "And he tried to organize them.", "start": 1892.507, "duration": 2.636}, {"text": "And in some cases, he\nsucceeded fairly well.", "start": 1895.143, "duration": 3.37}, {"text": "Look at this.", "start": 1898.513, "duration": 0.6}, {"text": "This is a, OK, where is Jerome?", "start": 1899.113, "duration": 3.003}, {"text": "This is a Tableau\ndes Substances...", "start": 1902.116, "duration": 6.04}, {"text": "No, not even close.", "start": 1908.156, "duration": 2.502}, {"text": "But look, \"Simples...\"", "start": 1910.658, "duration": 3.037}, {"text": "Simple, fundamental atoms.", "start": 1913.695, "duration": 4.538}, {"text": "What are those things\nthat we're mixing together", "start": 1918.233, "duration": 2.402}, {"text": "that we've been mixing together\nfor thousands of years?", "start": 1920.635, "duration": 3.704}, {"text": "What is that thing I'm\npulling out of this oar", "start": 1924.339, "duration": 2.536}, {"text": "and making stuff out of?", "start": 1926.875, "duration": 1.835}, {"text": "And he was trying to classify\nthem using these experiments.", "start": 1928.71, "duration": 4.571}, {"text": "And some of these are actually\nreally good discoveries.", "start": 1933.281, "duration": 6.173}, {"text": "I want you to experience this.", "start": 1939.454, "duration": 2.002}, {"text": "I want you to go\nback to this time.", "start": 1941.456, "duration": 2.269}, {"text": "And that is what the\nfirst goody bag is about.", "start": 1943.725, "duration": 3.637}, {"text": "So what I have given\nyou in this goody bag", "start": 1947.362, "duration": 2.736}, {"text": "is the most accurate measuring\ndevice ever created and branded", "start": 1950.098, "duration": 6.139}, {"text": "309.1.", "start": 1956.237, "duration": 1.702}, {"text": "It's a ruler.", "start": 1957.939, "duration": 2.97}, {"text": "I've given you\nfive metal strips.", "start": 1960.909, "duration": 1.401}, {"text": "And I want you to pretend that\nyou don't know what these are.", "start": 1962.31, "duration": 2.703}, {"text": "How do you find out?", "start": 1965.013, "duration": 2.636}, {"text": "You do nothing\nwith fire, nothing.", "start": 1967.649, "duration": 5.338}, {"text": "But I gave you vinegar.", "start": 1972.987, "duration": 3.17}, {"text": "And you do lots with vinegar.", "start": 1976.157, "duration": 1.902}, {"text": "Pour it on them.", "start": 1978.059, "duration": 0.767}, {"text": "Measure it, weigh it.", "start": 1978.826, "duration": 1.102}, {"text": "Look at it.", "start": 1979.928, "duration": 1.601}, {"text": "Shiny, not shiny.", "start": 1981.529, "duration": 1.235}, {"text": "Different color, densities.", "start": 1982.764, "duration": 2.068}, {"text": "Think about what\nthe differences are.", "start": 1984.832, "duration": 3.804}, {"text": "And I want to put you\nback in that time.", "start": 1988.636, "duration": 1.702}, {"text": "And I want to make a\npoint here, goody bags", "start": 1990.338, "duration": 2.035}, {"text": "are not just about\nthe questions I ask.", "start": 1992.373, "duration": 2.069}, {"text": "I hope that you think\neven beyond the Goody bag.", "start": 1994.442, "duration": 3.77}, {"text": "So if you use that vinegar and\none of those things reacts,", "start": 1998.212, "duration": 3.07}, {"text": "let's just suppose,\nwith the vinegar,", "start": 2001.282, "duration": 4.738}, {"text": "think about what that is\nand maybe vinegar is a test.", "start": 2006.02, "duration": 2.703}, {"text": "Maybe it's a test\nand you can react--", "start": 2008.723, "duration": 1.935}, {"text": "you can pour vinegar and make\nreactions with other things.", "start": 2010.658, "duration": 3.304}, {"text": "Maybe you should be thinking\nabout where that thing is", "start": 2013.962, "duration": 2.302}, {"text": "in the Infinite Corridor and\nthe whole Infinite Corridor", "start": 2016.264, "duration": 2.335}, {"text": "should smell like vinegar.", "start": 2018.599, "duration": 1.702}, {"text": "But we won't tell\nPresident Reif about that.", "start": 2020.301, "duration": 5.806}, {"text": "But that's what I mean, maybe\nnot the Infinite-- but explore.", "start": 2026.107, "duration": 3.604}, {"text": "These are meant to be--", "start": 2029.711, "duration": 1.201}, {"text": "I want you to really use\nthese as an adventure.", "start": 2030.912, "duration": 3.203}, {"text": "You know, think outside the box.", "start": 2034.115, "duration": 2.603}, {"text": "So you've got this most\naccurate measuring device.", "start": 2036.718, "duration": 2.869}, {"text": "You've got these\nstrips of pipette.", "start": 2039.587, "duration": 1.602}, {"text": "And you've got some gloves.", "start": 2041.189, "duration": 2.269}, {"text": "And that is your\nfirst goody bag.", "start": 2043.458, "duration": 4.204}, {"text": "OK, now though the\nlast thing that I'm", "start": 2047.662, "duration": 3.57}, {"text": "going to tell you about\nis why this matters.", "start": 2051.232, "duration": 2.168}, {"text": "And just like the goody bags,\nwhen I started teaching class", "start": 2053.4, "duration": 3.605}, {"text": "three years ago, I\nwanted to also protect", "start": 2057.005, "duration": 4.404}, {"text": "a certain fundamental\npart of each lecture.", "start": 2061.409, "duration": 3.437}, {"text": "And I call it my why\nthis matters moment.", "start": 2064.846, "duration": 2.668}, {"text": "Sometimes it goes on\nfor more than a moment.", "start": 2067.514, "duration": 3.27}, {"text": "But I really, really\nwant every lecture", "start": 2070.784, "duration": 2.971}, {"text": "to connect what we just\nlearned to a big picture.", "start": 2073.755, "duration": 4.471}, {"text": "Most of the time,\nit's some application", "start": 2078.226, "duration": 1.634}, {"text": "or some global challenge.", "start": 2079.86, "duration": 2.603}, {"text": "Right I want you to\nsee those connections,", "start": 2082.463, "duration": 3.236}, {"text": "that what you're\nlearning is directly", "start": 2085.699, "duration": 1.902}, {"text": "relevant to some big thing.", "start": 2087.601, "duration": 3.404}, {"text": "So my why this matters\nmoment is really related", "start": 2091.005, "duration": 2.87}, {"text": "to these discoveries themselves.", "start": 2093.875, "duration": 2.902}, {"text": "Please give me till 11:55.", "start": 2096.777, "duration": 1.802}, {"text": "I will always let you\ngo on time, 11:55.", "start": 2098.579, "duration": 2.13}, {"text": "But please don't start\nputting stuff away", "start": 2100.709, "duration": 1.708}, {"text": "because it's distracting\nto everybody.", "start": 2102.417, "duration": 2.068}, {"text": "So two and a half minutes.", "start": 2104.485, "duration": 4.371}, {"text": "We name the age we live in often\nby the element, by the atom,", "start": 2108.856, "duration": 4.738}, {"text": "by the material, by\nthe material that", "start": 2113.594, "duration": 3.904}, {"text": "was most useful at the time.", "start": 2117.498, "duration": 3.237}, {"text": "The Stone Age, the\nBronze Age, the Iron Age.", "start": 2120.735, "duration": 3.637}, {"text": "I would say we've moved\nthrough the industrial age,", "start": 2124.372, "duration": 2.235}, {"text": "the age of plastics,\nthe age of silicon.", "start": 2126.607, "duration": 2.303}, {"text": "As a material scientist\nand engineer, I love this.", "start": 2128.91, "duration": 2.736}, {"text": "I love that you name the age\nyou live in by the material that", "start": 2131.646, "duration": 3.47}, {"text": "mattered.", "start": 2135.116, "duration": 1.168}, {"text": "But I also love that we will\nnever do that again, ever.", "start": 2136.284, "duration": 4.871}, {"text": "And the reason is that we live\nin a truly unique age now,", "start": 2141.155, "duration": 3.07}, {"text": "a different age, one in\nwhich we can put atoms,", "start": 2144.225, "duration": 3.737}, {"text": "we can realize Feynman's dream\nand put atoms anywhere we want.", "start": 2147.962, "duration": 4.238}, {"text": "The question is not,\ncan we make it as much", "start": 2152.2, "duration": 4.304}, {"text": "any more as it is,\nwhat should we make?", "start": 2156.504, "duration": 2.736}, {"text": "We live in the age\nof atomic design.", "start": 2159.24, "duration": 3.704}, {"text": "And that is really important.", "start": 2162.944, "duration": 1.234}, {"text": "And I mentioned the phone\nand the 63 elements.", "start": 2164.178, "duration": 4.004}, {"text": "You know, look, this\nis called a revolution.", "start": 2168.182, "duration": 3.771}, {"text": "This is called a revolution.", "start": 2171.953, "duration": 3.003}, {"text": "You went in 50 years\nfrom $1 per transistor,", "start": 2174.956, "duration": 4.104}, {"text": "eight orders of\nmagnitude cheaper.", "start": 2179.06, "duration": 2.969}, {"text": "In 2012, it became cheaper to\nprint a transistor on a chip", "start": 2182.029, "duration": 4.505}, {"text": "than a character in a newspaper.", "start": 2186.534, "duration": 3.27}, {"text": "That's a revolution\nbut that revolution,", "start": 2189.804, "duration": 1.935}, {"text": "it started as a\nprocessing revolution", "start": 2191.739, "duration": 2.302}, {"text": "with one really important\nelement, silicon.", "start": 2194.041, "duration": 3.003}, {"text": "And now it's a materials\nrevolution, with 63.", "start": 2197.044, "duration": 4.805}, {"text": "It's a chemistry revolution.", "start": 2201.849, "duration": 2.503}, {"text": "And the reason this matters so\nmuch, what are these things,", "start": 2204.352, "duration": 3.87}, {"text": "is because so many of\nthe problems that we face", "start": 2208.222, "duration": 4.538}, {"text": "in this world today, so many\nof the global challenges,", "start": 2212.76, "duration": 3.904}, {"text": "will rely on new chemistry\nand on new materials.", "start": 2216.664, "duration": 5.372}, {"text": "Those are the bottlenecks.", "start": 2222.036, "duration": 2.269}, {"text": "Those are the bottlenecks\nin costs, in efficiency,", "start": 2224.305, "duration": 2.102}, {"text": "in processing, in properties.", "start": 2226.407, "duration": 2.929}, {"text": "And those are the\nkinds of things", "start": 2229.336, "duration": 1.375}, {"text": "that we're going to be talking\nabout all throughout the fall.", "start": 2230.711, "duration": 2.67}, {"text": "And that is our\nconstruction set.", "start": 2233.381, "duration": 3.003}, {"text": "And we will build\nthis on Friday.", "start": 2236.384, "duration": 3.436}, {"text": "So see you guys all on Friday.", "start": 2239.82, "duration": 1.802}, {"text": "[INTERPOSING VOICES]", "start": 2241.622, "duration": 1.967}]
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+[{"text": "Today, clearly,\nI am a noble gas.", "start": 17.417, "duration": 5.539}, {"text": "Thanks to-- it was\nactually the TAs' idea.", "start": 25.025, "duration": 4.004}, {"text": "And I was like, of course,\nthat sounds awesome.", "start": 29.029, "duration": 2.702}, {"text": "So I hope you guys have\na fantastic Halloween.", "start": 31.731, "duration": 5.139}, {"text": "Obviously, what you want\nto do is any kind of trick", "start": 36.87, "duration": 3.436}, {"text": "or treating or partying,\nyou know the drill,", "start": 40.306, "duration": 2.937}, {"text": "you bring your periodic\ntable, because you never know.", "start": 43.243, "duration": 3.87}, {"text": "And that's what happened--", "start": 47.113, "duration": 1.769}, {"text": "so on Sunday right before\nthe exam, I got this.", "start": 48.882, "duration": 5.005}, {"text": "And so this is\nCharles and Raymond.", "start": 53.887, "duration": 2.736}, {"text": "And they're saying we\nwanted to celebrate the Sox", "start": 56.623, "duration": 2.736}, {"text": "victory in Boston, but because\nthe midterm was the next day,", "start": 59.359, "duration": 4.137}, {"text": "we brought along our\nperiodic table to study.", "start": 63.496, "duration": 2.403}, {"text": "There were so many\npeople moving around it", "start": 65.899, "duration": 1.735}, {"text": "felt like we were in\na sea of electrons.", "start": 67.634, "duration": 3.336}, {"text": "And of course, the\nonly thing that", "start": 70.97, "duration": 1.502}, {"text": "could have improved\non that was actually", "start": 72.472, "duration": 1.668}, {"text": "like a little dance video.", "start": 74.14, "duration": 1.201}, {"text": "But that will probably come.", "start": 75.341, "duration": 1.168}, {"text": "I'm sure there on that next.", "start": 76.509, "duration": 2.169}, {"text": "But you see, they brought it\nnot just to study for the exam,", "start": 78.678, "duration": 2.736}, {"text": "because they didn't know if\nit was going to be important", "start": 81.414, "duration": 2.67}, {"text": "or not at the rally.", "start": 84.084, "duration": 1.534}, {"text": "You never know.", "start": 85.618, "duration": 2.236}, {"text": "So make sure you have your\nperiodic table with you.", "start": 87.854, "duration": 3.704}, {"text": "Now, OK, oh, yeah, they\nmentioned the exam.", "start": 91.558, "duration": 6.139}, {"text": "So speaking of the exam.", "start": 97.697, "duration": 3.404}, {"text": "Here are the results.", "start": 101.101, "duration": 1.401}, {"text": "And you can see that there is\na pretty wide distribution.", "start": 102.502, "duration": 5.272}, {"text": "You can also see\nthe averages is 77.", "start": 107.774, "duration": 2.235}, {"text": "And just to remind you--\nthat's about here--", "start": 110.009, "duration": 2.803}, {"text": "just to remind you, these\nmarks, 85, that's the A range.", "start": 112.812, "duration": 4.872}, {"text": "This is the B range.", "start": 117.684, "duration": 1.401}, {"text": "So the average was in the\nsolid B range territory.", "start": 119.085, "duration": 3.203}, {"text": "And so it goes.", "start": 123.556, "duration": 2.369}, {"text": "The standard deviation was 12.", "start": 125.925, "duration": 4.572}, {"text": "Now I could tell-- you\nknow, the exam 1,", "start": 130.497, "duration": 5.872}, {"text": "the topics of exam 1 many\nof you had already seen.", "start": 136.369, "duration": 3.403}, {"text": "And I think in this\nexam, some of you had not", "start": 139.772, "duration": 3.17}, {"text": "seen some of these\ntopics, especially", "start": 142.942, "duration": 1.535}, {"text": "like the\ncrystallography, but also", "start": 144.477, "duration": 2.536}, {"text": "even the molecular orbitals,\nthe band structure.", "start": 147.013, "duration": 3.604}, {"text": "And I could tell that, you know,\nsome people had to work harder,", "start": 150.617, "duration": 6.473}, {"text": "maybe a little bit stressed,\nand I could sense, some of that.", "start": 157.09, "duration": 4.304}, {"text": "But when I get\nstressed what I do", "start": 161.394, "duration": 3.17}, {"text": "is I need to kind of\nde-stress somehow.", "start": 164.564, "duration": 2.469}, {"text": "And sometimes some\npeople listen to music,", "start": 167.033, "duration": 2.069}, {"text": "some of the other things.", "start": 169.102, "duration": 1.101}, {"text": "I always like comedy\nas a way of relaxing.", "start": 170.203, "duration": 4.705}, {"text": "And so what I do\nis I'll Google like", "start": 174.908, "duration": 1.635}, {"text": "for articles about Harvard.", "start": 176.543, "duration": 2.469}, {"text": "And so I found this one.", "start": 179.012, "duration": 5.105}, {"text": "This is actually an\narticle in The Crimson", "start": 184.117, "duration": 3.07}, {"text": "from a few years ago.", "start": 187.187, "duration": 1.334}, {"text": "And the most common\ngrade at Harvard", "start": 188.521, "duration": 3.17}, {"text": "is actually an A, a solid\nA, the most common grade.", "start": 191.691, "duration": 4.838}, {"text": "Suspicion that the college\nemploys a softer grading", "start": 199.632, "duration": 2.803}, {"text": "standard than many of\nits peer institutions.", "start": 202.435, "duration": 2.202}, {"text": "You think?", "start": 204.637, "duration": 1.569}, {"text": "I mean, if everyone's\ngetting an A, you think?", "start": 206.206, "duration": 5.071}, {"text": "So what I wanted to point\nout is there's a difference.", "start": 211.277, "duration": 3.771}, {"text": "And it's not just about\nyour privileged, therefore,", "start": 215.048, "duration": 3.436}, {"text": "you deserve an A, whereas\nwe know that that actually", "start": 218.484, "duration": 4.038}, {"text": "takes work.", "start": 222.522, "duration": 1.268}, {"text": "That's not the point\nI want to make.", "start": 223.79, "duration": 2.202}, {"text": "The point I want to make\nis that we know also", "start": 225.992, "duration": 1.902}, {"text": "what to do when we miss things.", "start": 227.894, "duration": 3.136}, {"text": "We know what to do when\nwe don't get things right.", "start": 231.03, "duration": 3.037}, {"text": "That's when you do the work.", "start": 234.067, "duration": 2.469}, {"text": "So wherever you\nare on this curve,", "start": 236.536, "duration": 2.069}, {"text": "go back and figure\nout what didn't work.", "start": 238.605, "duration": 2.535}, {"text": "What did you miss?", "start": 241.14, "duration": 1.001}, {"text": "Figure that out, because\nthat's where you learn.", "start": 242.141, "duration": 3.671}, {"text": "Thomas Edison who said,\nI never failed, I just", "start": 245.812, "duration": 3.069}, {"text": "did 10,000 experiments\nthat didn't work.", "start": 248.881, "duration": 4.572}, {"text": "You've got to get through that.", "start": 253.453, "duration": 1.301}, {"text": "You've got to know that\nit takes hard work.", "start": 254.754, "duration": 1.801}, {"text": "And that's the thing\nthat we know here.", "start": 256.555, "duration": 1.669}, {"text": "That's the difference.", "start": 258.224, "duration": 0.934}, {"text": "So please make sure you\ndo that with exam 2.", "start": 259.158, "duration": 3.17}, {"text": "We are all here to help\nyou continue learning.", "start": 262.328, "duration": 3.27}, {"text": "I'm a noble gas.", "start": 265.598, "duration": 0.734}, {"text": "And speaking of continuing\nto learn, where were we?", "start": 270.003, "duration": 4.704}, {"text": "X-rays.", "start": 274.707, "duration": 0.5}, {"text": "On Friday, we had sort of\nsome other things going on.", "start": 279.846, "duration": 3.703}, {"text": "But I also was trying to\nteach you guys about X-rays.", "start": 283.549, "duration": 2.303}, {"text": "And what we did is we learned\nhow they're generated.", "start": 289.422, "duration": 3.403}, {"text": "Remember that?", "start": 292.825, "duration": 0.568}, {"text": "The Roentgen experiments.", "start": 293.393, "duration": 3.57}, {"text": "And so I want to pick up\nhere with the kinds of X-rays", "start": 296.963, "duration": 2.969}, {"text": "that we have.", "start": 299.932, "duration": 0.601}, {"text": "There are two kinds of X-rays.", "start": 300.533, "duration": 1.268}, {"text": "And we learned about\nthose on Friday.", "start": 304.637, "duration": 3.771}, {"text": "And I want to just\nremind you about those.", "start": 308.408, "duration": 2.502}, {"text": "And I also want to show you\na video to kind of recapture", "start": 310.91, "duration": 6.206}, {"text": "what they are.", "start": 317.116, "duration": 2.069}, {"text": "The first kind of\nX-ray, remember,", "start": 319.185, "duration": 4.938}, {"text": "we plotted this as intensity.", "start": 324.123, "duration": 2.336}, {"text": "And I'm not going to\ndraw the cathode ray", "start": 326.459, "duration": 5.205}, {"text": "tube again and the experiment\nthat Roentgen did and all that.", "start": 331.664, "duration": 3.17}, {"text": "But I'm going to just jump\nto the two kinds of x-rays", "start": 334.834, "duration": 2.436}, {"text": "that you get.", "start": 337.27, "duration": 1.735}, {"text": "And so if you plot\nthe wavelength", "start": 339.005, "duration": 3.603}, {"text": "of the X-ray versus the\nintensity of the X-ray,", "start": 342.608, "duration": 3.904}, {"text": "then one kind is\nthe Bremsstrahlung,", "start": 346.512, "duration": 3.07}, {"text": "which comes from that that\nelectron getting slowed down.", "start": 349.582, "duration": 4.772}, {"text": "And if it slows down,\nit emits radiation", "start": 354.354, "duration": 3.003}, {"text": "in a continuous spectrum.", "start": 357.357, "duration": 1.701}, {"text": "And remember, we\nsort of drew these.", "start": 362.895, "duration": 3.17}, {"text": "And this would be like the\nincident electron energy.", "start": 369.068, "duration": 6.373}, {"text": "Let's say incident\nenergy of the electron.", "start": 375.441, "duration": 6.44}, {"text": "Maybe like that's, OK, I\ndon't know, like 10 keV.", "start": 381.881, "duration": 2.736}, {"text": "And then up here the incident\nenergy of the electron", "start": 387.653, "duration": 3.137}, {"text": "was you know something\nlike maybe 30 keV.", "start": 390.79, "duration": 4.371}, {"text": "And so you see that as you\nhit that anode, remember what", "start": 395.161, "duration": 4.972}, {"text": "Roentgen did, he took\na cathode ray tube", "start": 400.133, "duration": 3.87}, {"text": "and he upped the voltage.", "start": 404.003, "duration": 1.935}, {"text": "So he really cranked\nup the voltage.", "start": 405.938, "duration": 1.502}, {"text": "So those electrons\ncoming off the cathode", "start": 407.44, "duration": 2.269}, {"text": "are going really fast.", "start": 409.709, "duration": 2.769}, {"text": "And then what he did is he put\na piece of metal in their way.", "start": 412.478, "duration": 3.771}, {"text": "And what happened is those\nreally high energy electrons,", "start": 416.249, "duration": 3.77}, {"text": "they see those metal\natoms and sometimes they", "start": 420.019, "duration": 3.47}, {"text": "get inside the electron\ncloud and they turn.", "start": 423.489, "duration": 2.536}, {"text": "And that's when they give off\nthis continuous radiation.", "start": 426.025, "duration": 3.971}, {"text": "But we also know that\nthere is a limit here.", "start": 429.996, "duration": 4.07}, {"text": "Remember that?", "start": 434.066, "duration": 0.801}, {"text": "We talked about that?", "start": 434.867, "duration": 1.135}, {"text": "And that this limit is\nset by this maximum.", "start": 436.002, "duration": 12.245}, {"text": "It's just the maximum\namount of energy", "start": 448.247, "duration": 5.372}, {"text": "that you could get\nout of a photon being", "start": 453.619, "duration": 1.669}, {"text": "emitted this way would be\nequal to the incoming electron.", "start": 455.288, "duration": 3.669}, {"text": "The incoming electron\ntransferred all of its energy", "start": 458.957, "duration": 3.404}, {"text": "to the photon.", "start": 462.361, "duration": 1.001}, {"text": "So that's why\nthere is a maximum.", "start": 463.362, "duration": 1.669}, {"text": "And it's also why it increases--\nremember, shorter wavelength,", "start": 465.031, "duration": 4.604}, {"text": "higher energy--", "start": 469.635, "duration": 1.535}, {"text": "so it increases as you\nincrease the energy", "start": 471.17, "duration": 2.803}, {"text": "of the instant an electron.", "start": 473.973, "duration": 1.134}, {"text": "That is Bremsstrahlung.", "start": 477.844, "duration": 1.434}, {"text": "Let's watch a video,\nbecause this is actually", "start": 479.278, "duration": 1.869}, {"text": "a very nicely done video that\ncaptures it with animation.", "start": 481.147, "duration": 4.137}, {"text": "So OK, here's your CRT.", "start": 489.021, "duration": 3.003}, {"text": "Now here they come.", "start": 492.024, "duration": 1.335}, {"text": "Those are those electrons.", "start": 493.359, "duration": 1.702}, {"text": "And that voltage is high.", "start": 495.061, "duration": 1.701}, {"text": "So they're coming out.", "start": 496.762, "duration": 0.901}, {"text": "Look at them coming\nout really fast.", "start": 497.663, "duration": 2.603}, {"text": "Lots of kinetic energy.", "start": 500.266, "duration": 3.237}, {"text": "And then they go.", "start": 503.503, "duration": 1.534}, {"text": "And then this is\nwhat Roentgen did.", "start": 505.037, "duration": 1.936}, {"text": "He put a little piece\nof metal in there.", "start": 506.973, "duration": 2.135}, {"text": "So now those electrons\nare hitting the metal.", "start": 509.108, "duration": 2.569}, {"text": "So those are the two things\nthat he did differently.", "start": 511.677, "duration": 2.169}, {"text": "Remember, the room lit up even\nwhen all the lights were off.", "start": 513.846, "duration": 4.038}, {"text": "There they are.", "start": 517.884, "duration": 1.101}, {"text": "Nice.", "start": 518.985, "duration": 0.833}, {"text": "Good electrons.", "start": 519.818, "duration": 0.702}, {"text": "Oh, and here they go.", "start": 520.52, "duration": 1.067}, {"text": "And there's a metal atom.", "start": 521.587, "duration": 2.87}, {"text": "And oh look at that.", "start": 524.457, "duration": 1.601}, {"text": "Now what are these?", "start": 526.058, "duration": 1.569}, {"text": "Those are x-rays coming off.", "start": 527.627, "duration": 1.701}, {"text": "Those are the electrons\nhitting the metal.", "start": 529.328, "duration": 1.769}, {"text": "And here's the metal atom.", "start": 531.097, "duration": 2.135}, {"text": "And as the electron\ncomes in, remember", "start": 533.232, "duration": 1.935}, {"text": "it sees the charge\nof the nucleus.", "start": 535.167, "duration": 3.037}, {"text": "And it gets deflected.", "start": 538.204, "duration": 2.669}, {"text": "And that deflection\nloses energy.", "start": 540.873, "duration": 2.636}, {"text": "And that loss of energy\ngoes into a photon.", "start": 543.509, "duration": 2.069}, {"text": "Now, because these electrons\nhave such high energy", "start": 545.578, "duration": 2.803}, {"text": "to start with, the energies\nof the photons are very high.", "start": 548.381, "duration": 8.675}, {"text": "They're x-rays.", "start": 557.056, "duration": 0.767}, {"text": "And so here's the wavelength.", "start": 561.994, "duration": 1.502}, {"text": "And you can see that--", "start": 563.496, "duration": 0.967}, {"text": "well, it's sort of a little\nhard to see this blue range.", "start": 564.463, "duration": 2.336}, {"text": "But see higher energy,\nshorter wavelength.", "start": 566.799, "duration": 2.269}, {"text": "Lower energy, longer wavelength.", "start": 569.068, "duration": 1.802}, {"text": "Very nice.", "start": 570.87, "duration": 0.934}, {"text": "So that's the animation\nof Bremsstrahlung.", "start": 571.804, "duration": 3.771}, {"text": "OK.", "start": 575.575, "duration": 0.7}, {"text": "Good.", "start": 576.275, "duration": 0.934}, {"text": "Now the thing is\nwhat we also learned", "start": 577.209, "duration": 2.47}, {"text": "is that there is\nanother type of X-ray.", "start": 579.679, "duration": 2.969}, {"text": "There's another type of X-ray.", "start": 582.648, "duration": 1.602}, {"text": "And in fact, if you crank\nthis up high enough,", "start": 584.25, "duration": 5.005}, {"text": "you can get that other type.", "start": 589.255, "duration": 1.168}, {"text": "So now, we go higher.", "start": 590.423, "duration": 1.367}, {"text": "Oh, we didn't see it here.", "start": 591.79, "duration": 1.836}, {"text": "It just looks like\nthat and that and that.", "start": 593.626, "duration": 2.069}, {"text": "And then all of a sudden we go\nup to 40 keV and we see this.", "start": 595.695, "duration": 5.472}, {"text": "Why?", "start": 606.439, "duration": 0.8}, {"text": "What happened here?", "start": 607.239, "duration": 1.635}, {"text": "And what happened here is a\ntotally different mechanism", "start": 608.874, "duration": 2.403}, {"text": "for generating X-rays.", "start": 611.277, "duration": 1.935}, {"text": "And that was the second type\nthat we talked about on Friday.", "start": 613.212, "duration": 2.703}, {"text": "Those are called characteristic.", "start": 615.915, "duration": 4.004}, {"text": "And the reason is that--\nremember, we have these levels,", "start": 619.919, "duration": 5.205}, {"text": "which now that we are\ntalking about X-rays,", "start": 625.124, "duration": 3.203}, {"text": "we give them\nletters, K, L, M, N.", "start": 628.327, "duration": 3.27}, {"text": "But it's just the\nquantum numbers.", "start": 631.597, "duration": 1.935}, {"text": "n equals 1.", "start": 633.532, "duration": 1.635}, {"text": "n equals 2.", "start": 635.167, "duration": 3.037}, {"text": "n equals 3.", "start": 638.204, "duration": 1.735}, {"text": "n equals 4.", "start": 639.939, "duration": 2.469}, {"text": "And what we said is that\nthe weight characteristic", "start": 642.408, "duration": 2.402}, {"text": "X-rays are labeled is\nthat if an electron is", "start": 644.81, "duration": 4.104}, {"text": "excited from this lower level,\nif an electron is knocked out", "start": 648.914, "duration": 6.674}, {"text": "of here, then there's a place\nfor an electron from here", "start": 655.588, "duration": 2.803}, {"text": "to go down.", "start": 658.391, "duration": 2.035}, {"text": "Maybe the electron is excited.", "start": 660.426, "duration": 1.635}, {"text": "Maybe the electron\nis kicked out.", "start": 662.061, "duration": 1.768}, {"text": "And then something\nhere can come down.", "start": 663.829, "duration": 2.703}, {"text": "And when that happens, just\nlike in the Bohr model,", "start": 666.532, "duration": 6.64}, {"text": "you get radiation.", "start": 673.172, "duration": 2.569}, {"text": "But now, unlike\nhydrogen 13.6 electrons,", "start": 675.741, "duration": 3.671}, {"text": "these are keV of energy.", "start": 679.412, "duration": 1.968}, {"text": "These are very high energies.", "start": 681.38, "duration": 2.002}, {"text": "Why?", "start": 683.382, "duration": 0.501}, {"text": "Because it's the one S electron.", "start": 683.883, "duration": 2.736}, {"text": "And we know that once you\nget down to those metals,", "start": 686.619, "duration": 3.703}, {"text": "those one s electrons,\nyou go further", "start": 690.322, "duration": 1.968}, {"text": "down the periodic table,\n1s electrons are seriously", "start": 692.29, "duration": 3.004}, {"text": "tightly bound.", "start": 695.294, "duration": 2.703}, {"text": "And those levels have\na difference down there", "start": 697.997, "duration": 3.837}, {"text": "that is pretty high in energy.", "start": 701.834, "duration": 1.235}, {"text": "It's X-ray high in energy.", "start": 703.069, "duration": 2.135}, {"text": "That's the point.", "start": 705.204, "duration": 1.268}, {"text": "So now, when that\ncascade happens,", "start": 706.472, "duration": 3.77}, {"text": "we call that a k alpha.", "start": 710.242, "duration": 2.937}, {"text": "And if it were to\nhave come from here,", "start": 713.179, "duration": 2.869}, {"text": "it would be called a k beta.", "start": 716.048, "duration": 1.435}, {"text": "And those are transitions, that\nunlike this continuous energy,", "start": 721.954, "duration": 5.572}, {"text": "those transitions only happen\nat very specific energies,", "start": 727.526, "duration": 4.271}, {"text": "delta energies.", "start": 731.797, "duration": 1.468}, {"text": "The change in\nenergy from L to K--", "start": 733.265, "duration": 3.204}, {"text": "or for K beta it would\nbe going from M to K.", "start": 736.469, "duration": 4.271}, {"text": "It's k alpha, k beta.", "start": 740.74, "duration": 2.402}, {"text": "We use the k because that's the\nfinal place the electron goes", "start": 743.142, "duration": 3.47}, {"text": "when it decays down.", "start": 746.612, "duration": 3.17}, {"text": "So if I just showed\nyou these, well, that", "start": 749.782, "duration": 3.77}, {"text": "would be like k alpha, and\nthat would be like k beta", "start": 753.552, "duration": 4.672}, {"text": "because you know the k beta\nis going to be a higher energy", "start": 758.224, "duration": 3.904}, {"text": "photon because it came\nup from a higher level.", "start": 762.128, "duration": 3.87}, {"text": "Well, you would also have\non here some other peaks.", "start": 765.998, "duration": 3.937}, {"text": "You would have the L peaks.", "start": 769.935, "duration": 3.504}, {"text": "So you'd have like\nL alpha, L beta.", "start": 773.439, "duration": 9.309}, {"text": "So as you crank the\nenergy up, then you", "start": 782.748, "duration": 3.37}, {"text": "can knock out those\ncore electrons", "start": 786.118, "duration": 2.102}, {"text": "and these cascades happen and\nyou get these discrete peaks.", "start": 788.22, "duration": 3.404}, {"text": "Notice, they will only come\nwhen you have enough energy", "start": 791.624, "duration": 5.005}, {"text": "in that incident electron\nto knock this electron out", "start": 796.629, "duration": 3.57}, {"text": "from the core.", "start": 800.199, "duration": 1.335}, {"text": "So that's why they\ndon't appear until you", "start": 801.534, "duration": 2.235}, {"text": "get to a certain\nincident electron energy.", "start": 803.769, "duration": 2.736}, {"text": "They don't appear until you\nget to that certain energy.", "start": 806.505, "duration": 3.27}, {"text": "And so we have a video on that,\nwhich also I will narrate.", "start": 809.775, "duration": 6.14}, {"text": "Is this it?", "start": 819.351, "duration": 1.068}, {"text": "There we go.", "start": 820.419, "duration": 1.802}, {"text": "So there it is.", "start": 822.221, "duration": 1.001}, {"text": "It's a metal atom.", "start": 823.222, "duration": 0.901}, {"text": "I don't know which one.", "start": 824.123, "duration": 3.336}, {"text": "OK, there's the\nincident electron.", "start": 827.459, "duration": 1.535}, {"text": "You fired it.", "start": 828.994, "duration": 0.701}, {"text": "And look at that.", "start": 829.695, "duration": 0.734}, {"text": "It knocked out a\ncore 1s electron,", "start": 830.429, "duration": 2.236}, {"text": "because it had enough\nenergy, very high energy.", "start": 832.665, "duration": 2.636}, {"text": "That's what Roentgen\ndid, cranked up", "start": 835.301, "duration": 1.568}, {"text": "the voltage, higher keV.", "start": 836.869, "duration": 1.702}, {"text": "And there it is.", "start": 838.571, "duration": 0.767}, {"text": "A cascade down and\nan X-ray comes out.", "start": 839.338, "duration": 2.636}, {"text": "You see that?", "start": 841.974, "duration": 0.534}, {"text": "Is that all?", "start": 846.679, "duration": 0.834}, {"text": "Oh, yeah, and then\nit's going to draw--", "start": 847.513, "duration": 1.668}, {"text": "because of those, you get\nthese characteristic peaks.", "start": 849.181, "duration": 2.536}, {"text": "Now, we call them\ncharacteristic,", "start": 851.717, "duration": 2.035}, {"text": "because now you see why.", "start": 853.752, "duration": 1.569}, {"text": "So unlike the\ncontinuous radiation,", "start": 855.321, "duration": 3.97}, {"text": "these peaks depend on\nthe atom, because they", "start": 859.291, "duration": 3.871}, {"text": "depend on the energy\nlevels of the atom.", "start": 863.162, "duration": 3.036}, {"text": "And so that's why like\nif you looked this up,", "start": 866.198, "duration": 2.236}, {"text": "you say, well, OK, let's look\nat the k alpha radiation.", "start": 868.434, "duration": 2.903}, {"text": "Let's look at the\nk alpha peaks that", "start": 871.337, "duration": 2.302}, {"text": "come out of different atoms.", "start": 873.639, "duration": 2.502}, {"text": "They're going to be different.", "start": 876.141, "duration": 1.268}, {"text": "So you have very\nsharp lines of x-rays", "start": 879.945, "duration": 4.838}, {"text": "at very specific energies.", "start": 884.783, "duration": 2.236}, {"text": "For copper, it's 8 keV.", "start": 887.019, "duration": 2.469}, {"text": "For molybdenum it's 17.5.", "start": 889.488, "duration": 2.369}, {"text": "Silver tungsten, it changes.", "start": 891.857, "duration": 1.769}, {"text": "And you can see that it goes\nup, as that 1s electron is", "start": 893.626, "duration": 5.839}, {"text": "lower and lower energy because\nI'm adding all these protons.", "start": 899.465, "duration": 2.569}, {"text": "So it all makes sense from\nthe concepts we've learned.", "start": 902.034, "duration": 3.637}, {"text": "Oh but see, now\nthat's really useful.", "start": 905.671, "duration": 3.337}, {"text": "That is really useful,\nbecause now I've", "start": 909.008, "duration": 2.669}, {"text": "got a way to have\na source of X-rays", "start": 911.677, "duration": 3.77}, {"text": "that is super well defined.", "start": 915.447, "duration": 2.169}, {"text": "It's super clear.", "start": 917.616, "duration": 0.701}, {"text": "It's always this--\nthat's so cool.", "start": 918.317, "duration": 2.869}, {"text": "As long as I have the same\nmetal, it's always the same.", "start": 921.186, "duration": 4.004}, {"text": "I can increase or decrease--", "start": 925.19, "duration": 1.802}, {"text": "well, I can't go\nbelow the threshold.", "start": 926.992, "duration": 1.535}, {"text": "But I can't go above it.", "start": 928.527, "duration": 1.468}, {"text": "And that peak is\ncharacteristic of the metal.", "start": 929.995, "duration": 4.071}, {"text": "So it doesn't change.", "start": 934.066, "duration": 1.301}, {"text": "That's really useful because\nI've got now a flashlight.", "start": 935.367, "duration": 4.238}, {"text": "I've got an X-ray\nflashlight where", "start": 939.605, "duration": 2.636}, {"text": "the energy that I'm\nsending out is always", "start": 942.241, "duration": 2.302}, {"text": "exactly what I know it to be.", "start": 944.543, "duration": 1.935}, {"text": "I can predict what it is.", "start": 946.478, "duration": 1.135}, {"text": "And it always will be that\ndepending on which medal", "start": 947.613, "duration": 2.969}, {"text": "I put in there.", "start": 950.582, "duration": 1.502}, {"text": "So that's a useful thing.", "start": 952.084, "duration": 3.537}, {"text": "Why is that useful?", "start": 955.621, "duration": 1.835}, {"text": "Well, that gets to the topic\nthat is the topic of today", "start": 957.456, "duration": 4.071}, {"text": "and of Friday, which is what\nare we doing with these X-rays?", "start": 961.527, "duration": 3.97}, {"text": "Well, first, we're\ngenerating them.", "start": 965.497, "duration": 1.502}, {"text": "So that's what we've\ntalked about so far.", "start": 966.999, "duration": 2.636}, {"text": "But now, we're going\nto actually use", "start": 969.635, "duration": 2.936}, {"text": "them to determine the\ncrystal that we have.", "start": 972.571, "duration": 3.804}, {"text": "We're going to\nactually use them.", "start": 976.375, "duration": 1.368}, {"text": "We're going to use\nthat flashlight.", "start": 977.743, "duration": 3.17}, {"text": "And so you can see why\nthis would be useful,", "start": 980.913, "duration": 2.736}, {"text": "because this is the range--", "start": 983.649, "duration": 2.736}, {"text": "we've showed this before--", "start": 986.385, "duration": 1.735}, {"text": "of X-rays.", "start": 988.12, "duration": 0.968}, {"text": "So they have these\nenergies of keV.", "start": 989.088, "duration": 2.202}, {"text": "And they have wavelengths\nright around a few Angstrom.", "start": 991.29, "duration": 3.403}, {"text": "That is a little less than an\nAngstrom, maybe 2 Angstroms.", "start": 994.693, "duration": 2.87}, {"text": "See where those wavelengths are?", "start": 997.563, "duration": 1.568}, {"text": "Well, those are atomic spacings.", "start": 999.131, "duration": 3.036}, {"text": "Those are like distances\nbetween layers.", "start": 1002.167, "duration": 4.805}, {"text": "And so if we could\nshine these on a crystal", "start": 1006.972, "duration": 2.703}, {"text": "and somehow figure out what\nit is with that light--", "start": 1009.675, "duration": 3.97}, {"text": "oh, there's a way\nwe can do that.", "start": 1013.645, "duration": 1.902}, {"text": "It's called diffraction.", "start": 1015.547, "duration": 2.436}, {"text": "Because what happens is--", "start": 1017.983, "duration": 1.969}, {"text": "and we know this\nfrom many fields.", "start": 1019.952, "duration": 2.335}, {"text": "You can think about this just\nas a water wave, any way.", "start": 1022.287, "duration": 4.504}, {"text": "If the wavelength is similar\nin size to the features,", "start": 1026.791, "duration": 6.874}, {"text": "then you get constructive\nand destructive interference", "start": 1033.665, "duration": 3.938}, {"text": "as a result of the\ninteraction between the wave", "start": 1037.603, "duration": 2.869}, {"text": "and the features.", "start": 1040.472, "duration": 1.735}, {"text": "So that's called diffraction.", "start": 1042.207, "duration": 2.703}, {"text": "And you can see it here with\nthis very simple picture", "start": 1044.91, "duration": 2.936}, {"text": "of say a water-- this\ncould be like a water", "start": 1047.846, "duration": 1.802}, {"text": "wave, a sound wave.", "start": 1049.648, "duration": 1.201}, {"text": "And there it is.", "start": 1050.849, "duration": 0.901}, {"text": "And it's interfering\nboth constructively", "start": 1051.75, "duration": 3.137}, {"text": "and destructively\nalong these lines.", "start": 1054.887, "duration": 4.604}, {"text": "You can do this test yourself.", "start": 1059.491, "duration": 1.869}, {"text": "You can take--", "start": 1061.36, "duration": 1.968}, {"text": "I highly recommend this--\ntake a laser pointer.", "start": 1063.328, "duration": 2.236}, {"text": "Now if I just had\na piece of metal--", "start": 1069.501, "duration": 1.936}, {"text": "I don't have a piece\nof metal, but if I did,", "start": 1071.437, "duration": 3.203}, {"text": "then I would shine it on it.", "start": 1074.64, "duration": 1.701}, {"text": "And what you'd see is\nthat the dot would just", "start": 1076.341, "duration": 2.436}, {"text": "reflect off the piece of metal.", "start": 1078.777, "duration": 2.436}, {"text": "So I just would\nget the dot back.", "start": 1081.213, "duration": 2.369}, {"text": "But now I've got\nthis thing here.", "start": 1083.582, "duration": 3.036}, {"text": "Many of you may\nnot know what this.", "start": 1086.618, "duration": 2.87}, {"text": "This is called a CD.", "start": 1089.488, "duration": 1.268}, {"text": "But it turns out that a\nCD has features in it.", "start": 1093.859, "duration": 3.737}, {"text": "It's got trenches that are like\na little less than a micron", "start": 1097.596, "duration": 4.338}, {"text": "apart, 100 nanometers.", "start": 1101.934, "duration": 2.135}, {"text": "And this is 500 nanometer light.", "start": 1104.069, "duration": 2.369}, {"text": "So you would expect\nthere to be diffraction.", "start": 1106.438, "duration": 2.536}, {"text": "You would expect there to be\nconstructive and destructive", "start": 1108.974, "duration": 3.036}, {"text": "interference.", "start": 1112.01, "duration": 0.734}, {"text": "And when I bounce it off\nof this, look at that.", "start": 1112.744, "duration": 2.436}, {"text": "There it is.", "start": 1115.18, "duration": 1.402}, {"text": "This never gets old.", "start": 1116.582, "duration": 2.769}, {"text": "I'm not getting just\none reflection here.", "start": 1119.351, "duration": 4.538}, {"text": "I'm getting a whole scatter of\nthem that have constructively", "start": 1123.889, "duration": 3.537}, {"text": "interfered, because of\nthe feature sizes being", "start": 1127.426, "duration": 2.803}, {"text": "the same as the wavelength.", "start": 1130.229, "duration": 4.004}, {"text": "But now, I want to\ndo that with X-rays.", "start": 1134.233, "duration": 2.068}, {"text": "And I want to do\nit onto crystals.", "start": 1136.301, "duration": 4.004}, {"text": "So how do we do that?", "start": 1140.305, "duration": 1.969}, {"text": "So let's think about that.", "start": 1142.274, "duration": 1.468}, {"text": "And we're going to think\nabout it in terms of what", "start": 1143.742, "duration": 2.069}, {"text": "the Bragg father-son pair, who\nwon the Nobel Prize and are", "start": 1145.811, "duration": 3.337}, {"text": "on a stamp.", "start": 1149.148, "duration": 1.001}, {"text": "That's what you get when you\nwin a Nobel Prize I guess.", "start": 1150.149, "duration": 4.27}, {"text": "And what they did is they\nfigured out how to do this.", "start": 1154.419, "duration": 4.438}, {"text": "So let's go through that just so\nwe understand it conceptually.", "start": 1158.857, "duration": 3.27}, {"text": "So I'm going to say that\nI have a set of atoms.", "start": 1166.064, "duration": 6.307}, {"text": "Now, I'm not going to\nworry about what they are.", "start": 1172.371, "duration": 4.905}, {"text": "But I'm just going to say that\nthere's some plane of atoms", "start": 1177.276, "duration": 3.069}, {"text": "here.", "start": 1180.345, "duration": 0.634}, {"text": "And there's another plane\nof atoms beneath that.", "start": 1180.979, "duration": 3.938}, {"text": "So there is another one\nand so on and so on.", "start": 1184.917, "duration": 3.803}, {"text": "And now, these would\nbe Miller planes.", "start": 1188.72, "duration": 4.638}, {"text": "These would be Miller\nplanes in the crystal.", "start": 1193.358, "duration": 1.969}, {"text": "And let's just assume\nthey're very, very simple,", "start": 1195.327, "duration": 2.402}, {"text": "this plane and that plane.", "start": 1197.729, "duration": 1.235}, {"text": "And now what I'm going to do is\nI'm going to have some x-rays.", "start": 1198.964, "duration": 2.769}, {"text": "I'm going to have some\nlight shining on this.", "start": 1201.733, "duration": 3.737}, {"text": "And it's going to be incident.", "start": 1205.47, "duration": 2.403}, {"text": "And it's going to be reflected.", "start": 1207.873, "duration": 2.035}, {"text": "But see, I'm going to\nhave another wave here.", "start": 1209.908, "duration": 4.271}, {"text": "OK, let's see if I can\nget through this drawing,", "start": 1214.179, "duration": 3.937}, {"text": "sort of, almost, kind of.", "start": 1218.116, "duration": 3.938}, {"text": "Now, here's the deal,\nthese are waves.", "start": 1222.054, "duration": 4.204}, {"text": "So if I want to\ndraw this as a wave,", "start": 1229.328, "duration": 2.969}, {"text": "I might draw it like that.", "start": 1232.297, "duration": 1.302}, {"text": "And if these waves are\nconstructively interfering,", "start": 1233.599, "duration": 6.306}, {"text": "let's just complete that, then\nthis wave would look like that.", "start": 1239.905, "duration": 6.64}, {"text": "If they're in phase, then that's\nwhat they would look like.", "start": 1246.545, "duration": 2.836}, {"text": "Now, this one's getting\nreflected off the surface.", "start": 1249.381, "duration": 2.736}, {"text": "So I'm going to do\nthat reflection here.", "start": 1252.117, "duration": 1.735}, {"text": "And if I wanted to come\nback off of the surface,", "start": 1256.622, "duration": 3.57}, {"text": "and this one got\nthrough the first layer,", "start": 1260.192, "duration": 3.103}, {"text": "this didn't get reflected.", "start": 1263.295, "duration": 1.101}, {"text": "It's going down.", "start": 1264.396, "duration": 0.834}, {"text": "And if I want it\nto come back up,", "start": 1265.23, "duration": 1.769}, {"text": "then this one must also look\nlike that to be in phase.", "start": 1266.999, "duration": 4.204}, {"text": "They must be in\nphases they come out,", "start": 1271.203, "duration": 2.536}, {"text": "or else they're not going\nto interfere constructively.", "start": 1273.739, "duration": 2.736}, {"text": "You see that?", "start": 1276.475, "duration": 0.7}, {"text": "So those are my X-rays.", "start": 1277.175, "duration": 1.402}, {"text": "They're waves.", "start": 1278.577, "duration": 1.001}, {"text": "They're just waves.", "start": 1279.578, "duration": 2.135}, {"text": "Oh, but this is\nthe whole secret,", "start": 1281.713, "duration": 3.304}, {"text": "because if this angle here is\ntheta, then what that means", "start": 1285.017, "duration": 8.708}, {"text": "is that this angle is theta.", "start": 1293.725, "duration": 1.302}, {"text": "And if that's true,\nthen this distance", "start": 1298.03, "duration": 3.403}, {"text": "is d sine theta,\nwhere this is d.", "start": 1301.433, "duration": 5.906}, {"text": "That's just some\nsimple geometry.", "start": 1307.339, "duration": 4.504}, {"text": "So what you know then\nis, OK, now we're", "start": 1311.843, "duration": 3.504}, {"text": "getting somewhere, because\nyou know if I had a wave,", "start": 1315.347, "duration": 4.471}, {"text": "this is one wavelength.", "start": 1319.818, "duration": 3.47}, {"text": "So if I had a wave come\nin like this and one", "start": 1323.288, "duration": 4.171}, {"text": "of them is going to get\nreflected off of this lower", "start": 1327.459, "duration": 2.135}, {"text": "surface and the other one\ngot reflected on this,", "start": 1329.594, "duration": 2.636}, {"text": "but I don't want them\nto interfere in any way", "start": 1332.23, "duration": 2.436}, {"text": "but constructively, that's what\nBragg said, Bragg and Bragg.", "start": 1334.666, "duration": 5.439}, {"text": "That's what they said.", "start": 1340.105, "duration": 1.034}, {"text": "Then the only way\nfor that to happen", "start": 1341.139, "duration": 2.536}, {"text": "is if this distance\nplus that distance--", "start": 1343.675, "duration": 3.203}, {"text": "so d sine theta\nplus d sine theta", "start": 1346.878, "duration": 2.87}, {"text": "is equal to some multiple\nof the wavelength.", "start": 1349.748, "duration": 2.903}, {"text": "It has to be.", "start": 1352.651, "duration": 2.002}, {"text": "And so what you get is-- well,\nthat's what they have there,", "start": 1354.653, "duration": 4.004}, {"text": "n lambda, some multiple\nof the wavelength,", "start": 1358.657, "duration": 2.035}, {"text": "equals 2d sine theta,\nwhere theta is the incident", "start": 1360.692, "duration": 5.706}, {"text": "angle of that X-ray.", "start": 1366.398, "duration": 3.57}, {"text": "So this is incident--", "start": 1369.968, "duration": 1.969}, {"text": "just to be clear--\nincident X-ray.", "start": 1371.937, "duration": 3.837}, {"text": "And these are reflected X-rays.", "start": 1375.774, "duration": 5.606}, {"text": "Now to keep it\nsimple in this class,", "start": 1384.883, "duration": 2.536}, {"text": "we're just going to say n\nequals 1 for 3.091, just", "start": 1387.419, "duration": 8.775}, {"text": "to keep things simple,\nbecause I want to grasp", "start": 1396.194, "duration": 3.737}, {"text": "the basic concepts here.", "start": 1399.931, "duration": 2.636}, {"text": "We're not using X-rays to\nget the structure of DNA.", "start": 1402.567, "duration": 2.903}, {"text": "But we're going to use X-rays\nto figure out cubic crystal", "start": 1405.47, "duration": 2.87}, {"text": "structures.", "start": 1408.34, "duration": 1.068}, {"text": "I'm going to show\nhow that works.", "start": 1409.408, "duration": 1.534}, {"text": "So this must be true for--", "start": 1413.779, "duration": 4.27}, {"text": "so this is in parentheses--", "start": 1418.049, "duration": 1.936}, {"text": "for constructive interference.", "start": 1419.985, "duration": 2.569}, {"text": "Those dots that\nyou saw interface--", "start": 1428.293, "duration": 3.07}, {"text": "interface, no\ninterference, interference.", "start": 1431.363, "duration": 4.504}, {"text": "This is true for\nconstructive interference.", "start": 1439.671, "duration": 2.469}, {"text": "Of course, you could write\nany equation you want.", "start": 1442.14, "duration": 2.036}, {"text": "But if you want them to be\nconstructively interfering", "start": 1444.176, "duration": 2.836}, {"text": "when they come out,\nthat has to be true.", "start": 1447.012, "duration": 1.835}, {"text": "And that's what the Braggs said.", "start": 1448.847, "duration": 1.335}, {"text": "But we're not there yet\nright, because now we've", "start": 1450.182, "duration": 2.869}, {"text": "got to do experiments.", "start": 1453.051, "duration": 2.77}, {"text": "So we've got to do experiments.", "start": 1455.821, "duration": 1.301}, {"text": "So what does this mean?", "start": 1457.122, "duration": 2.436}, {"text": "Well, OK, I'm going to\ntake X-rays of some lambda.", "start": 1459.558, "duration": 9.175}, {"text": "And I'm going to shine\nthem on a sample.", "start": 1468.733, "duration": 4.839}, {"text": "And I'm going to measure.", "start": 1473.572, "duration": 1.902}, {"text": "So what I'm going to do--", "start": 1475.474, "duration": 1.634}, {"text": "well, I think I have a picture--", "start": 1477.108, "duration": 1.535}, {"text": "I'm going to measure--", "start": 1478.643, "duration": 1.168}, {"text": "there it is.", "start": 1479.811, "duration": 0.934}, {"text": "This is what an X-ray\ndiffraction experiment", "start": 1480.745, "duration": 4.672}, {"text": "looks like.", "start": 1485.417, "duration": 1.635}, {"text": "So I've got some sample.", "start": 1487.052, "duration": 2.335}, {"text": "And I shine x-rays.", "start": 1489.387, "duration": 1.469}, {"text": "I've got a source of x-rays.", "start": 1490.856, "duration": 1.167}, {"text": "We now know how to\nmake that source.", "start": 1492.023, "duration": 4.138}, {"text": "And we'll just filter\nout one of these lines.", "start": 1496.161, "duration": 4.304}, {"text": "So I've got that source,\nand I can change the angle.", "start": 1500.465, "duration": 3.771}, {"text": "And then I've got a detector.", "start": 1504.236, "duration": 1.935}, {"text": "And I can measure did I\nget interference or not?", "start": 1506.171, "duration": 3.07}, {"text": "It's just like the dots.", "start": 1509.241, "duration": 2.602}, {"text": "So now, we know that if I\ndo that and I say I scan--", "start": 1511.843, "duration": 5.739}, {"text": "so I've got intensity.", "start": 1522.32, "duration": 2.269}, {"text": "And now I'm plotting\nit with angle.", "start": 1524.589, "duration": 3.203}, {"text": "So now I'm moving the angle\naround and I'm changing it.", "start": 1527.792, "duration": 4.905}, {"text": "And, bam, I get interference.", "start": 1532.697, "duration": 2.002}, {"text": "And I see a spot in my detector.", "start": 1534.699, "duration": 2.069}, {"text": "So literally it\nwould look like this.", "start": 1536.768, "duration": 2.703}, {"text": "You would get some angle\nwhere there's interference.", "start": 1539.471, "duration": 3.37}, {"text": "And the detector would say\nding, ding, ding, ding, ding,", "start": 1542.841, "duration": 2.335}, {"text": "I see a lot of\nx-rays coming off.", "start": 1545.176, "duration": 2.97}, {"text": "And now you change the\nangle a few degrees", "start": 1548.146, "duration": 1.835}, {"text": "and I don't see anything,\nbecause it's all", "start": 1549.981, "duration": 2.937}, {"text": "destructive from\nthese crystal planes.", "start": 1552.918, "duration": 2.836}, {"text": "So it seems like then if I just\nvary theta, am I there yet?", "start": 1558.924, "duration": 5.839}, {"text": "The problem is that\nI might not know d.", "start": 1564.763, "duration": 5.438}, {"text": "A, ha, but we do know d.", "start": 1570.201, "duration": 3.237}, {"text": "We do know d, because\nwe learned about d.", "start": 1573.438, "duration": 3.203}, {"text": "For cubic crystals, we know d.", "start": 1576.641, "duration": 3.07}, {"text": "Because for cubic\nsystems, we know", "start": 1579.711, "duration": 3.437}, {"text": "that d of hkl of any plane, the\ndistance between those planes", "start": 1583.148, "duration": 7.073}, {"text": "is equal to a over the\nsquare root of h squared", "start": 1590.221, "duration": 4.905}, {"text": "plus k squared plus l squared.", "start": 1595.126, "duration": 2.503}, {"text": "And that's something\nthat we learned.", "start": 1597.629, "duration": 1.601}, {"text": "This is distance between\nMiller planes in cubic crystal.", "start": 1599.23, "duration": 12.046}, {"text": "I'm saving time.", "start": 1614.346, "duration": 0.8}, {"text": "I wrote xtal.", "start": 1615.146, "duration": 2.002}, {"text": "I saved a lot of\ntime, which I just", "start": 1617.148, "duration": 2.336}, {"text": "wasted by being so proud of it.", "start": 1619.484, "duration": 1.969}, {"text": "I know d.", "start": 1625.557, "duration": 0.6}, {"text": "Well, OK, so what\ndoes that mean?", "start": 1626.157, "duration": 1.635}, {"text": "Well, let's take a\nlook, because now I'm", "start": 1627.792, "duration": 2.77}, {"text": "going to go back my equation.", "start": 1630.562, "duration": 5.672}, {"text": "And I'm going to say,\nOK, lambda equals 2d--", "start": 1636.234, "duration": 3.303}, {"text": "and I'm saying n equals 1.", "start": 1639.537, "duration": 2.369}, {"text": "And I'm not going\nto be very specific.", "start": 1641.906, "duration": 1.569}, {"text": "This is now a d that comes\nfrom the spacing between planes", "start": 1643.475, "duration": 4.538}, {"text": "that are specified\nby the Miller indices", "start": 1648.013, "duration": 2.836}, {"text": "times the sine of theta.", "start": 1650.849, "duration": 4.371}, {"text": "And I'm putting hkl on the theta\nas well, and you'll see why.", "start": 1655.22, "duration": 4.938}, {"text": "Because here's the thing,\nnow I've got constants.", "start": 1660.158, "duration": 5.005}, {"text": "Now I've got constants,\nbecause look,", "start": 1665.163, "duration": 2.202}, {"text": "this is fixed by the source.", "start": 1667.365, "duration": 6.607}, {"text": "So this is a constant.", "start": 1673.972, "duration": 2.536}, {"text": "If I have copper, then\nit's 1.54 Angstroms.", "start": 1676.508, "duration": 4.437}, {"text": "This is a constant.", "start": 1680.945, "duration": 1.836}, {"text": "This is fixed by the crystal.", "start": 1682.781, "duration": 2.702}, {"text": "That's also a constant.", "start": 1685.483, "duration": 2.136}, {"text": "Fixed by the crystal,\nbecause that's also", "start": 1687.619, "duration": 5.739}, {"text": "a constants, because it's\nthe lattice constant.", "start": 1693.358, "duration": 1.968}, {"text": "We're not changing that.", "start": 1695.326, "duration": 1.635}, {"text": "So for a given set of\nplanes that these waves", "start": 1696.961, "duration": 3.771}, {"text": "are bouncing off of and maybe\nconstructively interfering", "start": 1700.732, "duration": 5.539}, {"text": "with, that depending\non the theta,", "start": 1706.271, "duration": 4.838}, {"text": "then these are constants.", "start": 1711.109, "duration": 2.302}, {"text": "So if I regroup then-- so\nI'm going to regroup them.", "start": 1716.081, "duration": 3.603}, {"text": "And so I'm going to say that--", "start": 1719.684, "duration": 2.669}, {"text": "let's see, d-- so I'm going to\nsubstitute in that expression", "start": 1722.353, "duration": 4.872}, {"text": "up there down here.", "start": 1727.225, "duration": 3.27}, {"text": "And I'm going to\nuse a copper source.", "start": 1730.495, "duration": 2.436}, {"text": "So I'm going to say-- well,\nlet me go through this one step", "start": 1732.931, "duration": 2.435}, {"text": "at a time.", "start": 1735.366, "duration": 0.501}, {"text": "So d equals 1.54\nAngstroms over--", "start": 1735.867, "duration": 5.505}, {"text": "let's see-- 2 sine theta hkl.", "start": 1744.209, "duration": 5.939}, {"text": "Now what have I done here?", "start": 1750.148, "duration": 1.668}, {"text": "This is for a copper source.", "start": 1751.816, "duration": 3.637}, {"text": "So I'm fixing in the constant.", "start": 1755.453, "duration": 5.539}, {"text": "So that's the Bragg condition.", "start": 1760.992, "duration": 1.268}, {"text": "But I also know\nthat d is equal to--", "start": 1762.26, "duration": 4.638}, {"text": "I don't want to write it again.", "start": 1769.467, "duration": 1.402}, {"text": "It's also equal to that.", "start": 1770.869, "duration": 2.602}, {"text": "OK, good.", "start": 1773.471, "duration": 1.702}, {"text": "OK, so let's put that together.", "start": 1775.173, "duration": 1.835}, {"text": "We'll do a little division.", "start": 1777.008, "duration": 1.568}, {"text": "And what we get is 1.54\nAngstroms over 2a squared,", "start": 1778.576, "duration": 9.543}, {"text": "the whole thing squared.", "start": 1788.119, "duration": 1.001}, {"text": "I'm squaring it-- I don't\nwant the square root--", "start": 1789.12, "duration": 2.336}, {"text": "equals sine squared\ntheta hkl over h", "start": 1791.456, "duration": 6.573}, {"text": "squared plus k squared\nplus l squared for--", "start": 1798.029, "duration": 4.471}, {"text": "let's be very specific-- for\nconstructive interference", "start": 1802.5, "duration": 11.578}, {"text": "and a copper source.", "start": 1814.078, "duration": 2.603}, {"text": "So now, I'm getting\nspecific because this", "start": 1816.681, "duration": 1.802}, {"text": "is how experiments with\nX-ray diffraction are done.", "start": 1818.483, "duration": 2.369}, {"text": "But now the last time\nI checked, if you", "start": 1824.389, "duration": 3.27}, {"text": "got something equal\nto a constant,", "start": 1827.659, "duration": 4.337}, {"text": "then that something\nalso is a constant.", "start": 1831.996, "duration": 3.037}, {"text": "And this is a constant.", "start": 1835.033, "duration": 2.869}, {"text": "And so what I need to\ndo now is figure out I'm", "start": 1837.902, "duration": 4.338}, {"text": "going to measure these data\nis where I get a signal.", "start": 1842.24, "duration": 4.805}, {"text": "Remember, I'm going\nto now change theta so", "start": 1847.045, "duration": 2.502}, {"text": "that I see where I get signals.", "start": 1849.547, "duration": 3.07}, {"text": "Now, those thetas\ndivided by the hkl", "start": 1852.617, "duration": 7.407}, {"text": "that they are bouncing\noff of must be a constant.", "start": 1860.024, "duration": 3.404}, {"text": "They must not change.", "start": 1863.428, "duration": 1.501}, {"text": "That is at the heart\nof X-ray diffraction.", "start": 1864.929, "duration": 3.203}, {"text": "That is at the heart of it.", "start": 1868.132, "duration": 2.903}, {"text": "And so we're going to do\nthat with a specific example", "start": 1871.035, "duration": 5.039}, {"text": "today and Friday.", "start": 1876.074, "duration": 1.168}, {"text": "But before we do that,\nthere's another thing", "start": 1877.242, "duration": 2.369}, {"text": "that we can observe.", "start": 1879.611, "duration": 0.834}, {"text": "There's another thing\nthat we can observe.", "start": 1880.445, "duration": 1.768}, {"text": "Oh, this is what\nit would look like.", "start": 1882.213, "duration": 1.635}, {"text": "So here it is.", "start": 1883.848, "duration": 2.269}, {"text": "So now I I've changed--\nnow, why do we do 2 theta?", "start": 1886.117, "duration": 2.903}, {"text": "It's kind of historical.", "start": 1889.02, "duration": 1.435}, {"text": "You plot X-ray\ndiffraction spectra.", "start": 1890.455, "duration": 4.171}, {"text": "So this is an XRD, X-ray\ndiffraction spectrum.", "start": 1894.626, "duration": 3.236}, {"text": "This is the intensity\nof the peaks.", "start": 1897.862, "duration": 2.669}, {"text": "And these are the peaks.", "start": 1900.531, "duration": 1.802}, {"text": "This is a beautiful thing.", "start": 1902.333, "duration": 1.101}, {"text": "I'm seeing a crystal here.", "start": 1903.434, "duration": 2.169}, {"text": "I'm seeing a crystal.", "start": 1905.603, "duration": 0.968}, {"text": "And by Friday, you will\nbe seeing a crystal.", "start": 1906.571, "duration": 3.136}, {"text": "Those aren't just peaks.", "start": 1909.707, "duration": 1.001}, {"text": "Those are planes in a crystal.", "start": 1910.708, "duration": 2.736}, {"text": "Those are planes in a\ncrystal, which tells me", "start": 1913.444, "duration": 2.536}, {"text": "not only that I\nhave these planes,", "start": 1915.98, "duration": 2.102}, {"text": "but it tells me\nwhat crystal I have.", "start": 1918.082, "duration": 1.902}, {"text": "But that's not how we start.", "start": 1919.984, "duration": 2.136}, {"text": "The way we start is we\ndo these measurements", "start": 1922.12, "duration": 2.169}, {"text": "and we just read off angles.", "start": 1924.289, "duration": 1.568}, {"text": "So we got to get from there to\nthere, to crystal structure.", "start": 1925.857, "duration": 3.336}, {"text": "So what I want to determine\nis the crystal structure", "start": 1929.193, "duration": 3.504}, {"text": "and the lattice constant.", "start": 1932.697, "duration": 1.034}, {"text": "That's my goal.", "start": 1933.731, "duration": 1.302}, {"text": "What I have is a\nspectrum that looks", "start": 1935.033, "duration": 1.968}, {"text": "like this where\nall I've done here", "start": 1937.001, "duration": 1.502}, {"text": "is put these\nspecific angles here.", "start": 1938.503, "duration": 3.503}, {"text": "And you have to be given--", "start": 1942.006, "duration": 3.003}, {"text": "so this is the\naluminum XRD spectrum.", "start": 1945.009, "duration": 2.97}, {"text": "So if you shine\nX-rays on aluminum,", "start": 1947.979, "duration": 3.303}, {"text": "this is what you\nget if you know also", "start": 1951.282, "duration": 3.137}, {"text": "that those X-rays are\nfrom copper, which", "start": 1954.419, "duration": 2.769}, {"text": "means that lambda is fixed.", "start": 1957.188, "duration": 2.77}, {"text": "So this should be like the\ninformation you get to start.", "start": 1959.958, "duration": 4.504}, {"text": "You'd be given this\nspectrum, given these peaks.", "start": 1964.462, "duration": 2.636}, {"text": "And you've be giving\nthis information here.", "start": 1967.098, "duration": 1.802}, {"text": "It's a copper target.", "start": 1968.9, "duration": 1.501}, {"text": "And from that, we can\ndetermine the crystal structure", "start": 1970.401, "duration": 2.236}, {"text": "in the lattice constant.", "start": 1972.637, "duration": 1.001}, {"text": "Now, there's something--\noh, why do we do 2 theta?", "start": 1973.638, "duration": 6.273}, {"text": "Well, it's historical.", "start": 1979.911, "duration": 1.401}, {"text": "It could have been theta to\nmake all those dividing by 2s", "start": 1981.312, "duration": 3.57}, {"text": "go away.", "start": 1984.882, "duration": 0.468}, {"text": "But instead, you can see\nthat as I rotate this,", "start": 1985.35, "duration": 3.67}, {"text": "this changes by theta.", "start": 1989.02, "duration": 1.768}, {"text": "The detector changes by 2 theta.", "start": 1990.788, "duration": 2.169}, {"text": "So that's why extra spectra\nare given in 2 theta.", "start": 1992.957, "duration": 3.604}, {"text": "There's no other real\ngood reason for it,", "start": 1996.561, "duration": 3.403}, {"text": "even though in the Bragg\ncondition, it's not 2 theta,", "start": 1999.964, "duration": 2.636}, {"text": "it's theta.", "start": 2002.6, "duration": 1.001}, {"text": "This comes from\ngeometry of the planes.", "start": 2003.601, "duration": 3.604}, {"text": "And this just comes\nfrom historical setups", "start": 2007.205, "duration": 4.07}, {"text": "and how you move the detector.", "start": 2011.275, "duration": 2.77}, {"text": "So what's measured and\nplotted is the 2 theta.", "start": 2014.045, "duration": 4.237}, {"text": "But before we go, before\nwe do this transformation,", "start": 2018.282, "duration": 3.037}, {"text": "where we take an X-ray\nspectrum like this", "start": 2021.319, "duration": 2.335}, {"text": "and we get the information we\nwant, there's one more thing.", "start": 2023.654, "duration": 3.504}, {"text": "And that is not all\nreflections are allowed.", "start": 2027.158, "duration": 4.671}, {"text": "Not all reflections are allowed.", "start": 2031.829, "duration": 1.869}, {"text": "And so let's talk about\nthat, and then we'll", "start": 2033.698, "duration": 3.603}, {"text": "come back to the spectrum.", "start": 2037.301, "duration": 2.77}, {"text": "Now, you can kind\nof understand this", "start": 2040.071, "duration": 3.003}, {"text": "by looking at just a simple\nkind of comparison here.", "start": 2043.074, "duration": 4.504}, {"text": "So these are the hkl's.", "start": 2050.38, "duration": 1.102}, {"text": "Remember, that's the\nhkl for a Miller plane.", "start": 2051.482, "duration": 3.304}, {"text": "This is h squared plus k\nsquared plus l squared.", "start": 2054.786, "duration": 2.235}, {"text": "Why do we put that?", "start": 2057.021, "duration": 1.335}, {"text": "Because we know we're\ngoing to need it.", "start": 2058.356, "duration": 1.735}, {"text": "There it is right there.", "start": 2060.091, "duration": 1.401}, {"text": "So we know we're\ngoing to need it.", "start": 2061.492, "duration": 3.07}, {"text": "But if you look at the simple\ncubic, that's simple cubic.", "start": 2064.562, "duration": 4.637}, {"text": "Any combination of hkl is OK.", "start": 2069.199, "duration": 3.471}, {"text": "There is no combination that\nwould give you interference", "start": 2072.67, "duration": 5.372}, {"text": "along those plains stacking.", "start": 2078.042, "duration": 3.203}, {"text": "You may say, well, OK, yeah,\nwhat are you talking about?", "start": 2081.245, "duration": 3.336}, {"text": "Why are you even\nbringing this up?", "start": 2084.581, "duration": 1.402}, {"text": "Well, when you see the\nother two crystal structures", "start": 2085.983, "duration": 2.502}, {"text": "you'll see what I mean.", "start": 2088.485, "duration": 1.836}, {"text": "So now we have the case of BCC--", "start": 2090.321, "duration": 3.237}, {"text": "when you see this,\nyou see BCC and FCC.", "start": 2093.558, "duration": 2.969}, {"text": "And what I'm showing you\nhere isn't the 100 plane.", "start": 2096.527, "duration": 3.237}, {"text": "It's the 200 plane.", "start": 2099.764, "duration": 1.835}, {"text": "So this is the family--", "start": 2101.599, "duration": 1.034}, {"text": "remember, the family--\nof 200 planes.", "start": 2102.633, "duration": 1.802}, {"text": "There they are.", "start": 2104.435, "duration": 0.634}, {"text": "But now you see\nthat what happens--", "start": 2108.206, "duration": 4.671}, {"text": "and I have a picture\nhere to show you,", "start": 2112.877, "duration": 1.602}, {"text": "but I'll tell you first--", "start": 2114.479, "duration": 1.034}, {"text": "what happens is\nthe light comes in.", "start": 2115.513, "duration": 2.669}, {"text": "So there's those\nsquiggly X-rays.", "start": 2118.182, "duration": 2.436}, {"text": "It comes in.", "start": 2120.618, "duration": 0.901}, {"text": "And there is, OK,\nd, which depends", "start": 2121.519, "duration": 2.769}, {"text": "on the lattice\nconstant, is related", "start": 2124.288, "duration": 1.735}, {"text": "to the lattice constant.", "start": 2126.023, "duration": 1.001}, {"text": "But look.", "start": 2127.024, "duration": 0.601}, {"text": "Now there's another\nplane in between.", "start": 2127.625, "duration": 2.636}, {"text": "There's another\nplane in between.", "start": 2130.261, "duration": 1.368}, {"text": "And in fact, with\nthe 200 planes,", "start": 2131.629, "duration": 2.069}, {"text": "that plane in between\nexactly cancels out", "start": 2133.698, "duration": 2.669}, {"text": "the constructive interference.", "start": 2136.367, "duration": 1.235}, {"text": "Here it is.", "start": 2137.602, "duration": 1.468}, {"text": "So there's what\nI would have had.", "start": 2139.07, "duration": 3.837}, {"text": "If you want to think about this\nas the 100, there's the 200s.", "start": 2142.907, "duration": 5.339}, {"text": "But notice when I go from 100 to\n200s, I add this plane in here.", "start": 2148.246, "duration": 5.538}, {"text": "And because that\nplane has atoms in it,", "start": 2153.784, "duration": 3.437}, {"text": "because that plane has atoms\nin it, it acts like a mirror,", "start": 2157.221, "duration": 3.504}, {"text": "and it can also reflect.", "start": 2160.725, "duration": 3.57}, {"text": "And so what happens is I would\nhave had this nice-- there", "start": 2164.295, "duration": 3.37}, {"text": "it is.", "start": 2167.665, "duration": 0.501}, {"text": "There's a picture I drew.", "start": 2168.166, "duration": 1.034}, {"text": "There's that first\nX-ray bouncing off.", "start": 2169.2, "duration": 2.302}, {"text": "There's the second\none bouncing off.", "start": 2171.502, "duration": 1.602}, {"text": "And those are nicely in phase.", "start": 2173.104, "duration": 1.568}, {"text": "So I would see that.", "start": 2174.672, "duration": 1.635}, {"text": "If that's the angle\nthat gave that to me,", "start": 2176.307, "duration": 1.735}, {"text": "I'd see that in the detector.", "start": 2178.042, "duration": 1.401}, {"text": "But now, for BCC or FCC, I've\ngot something in the middle.", "start": 2179.443, "duration": 4.905}, {"text": "And that something in the\nmiddle is exactly canceling out.", "start": 2184.348, "duration": 3.604}, {"text": "You see that?", "start": 2187.952, "duration": 0.701}, {"text": "So now, it cancels that out.", "start": 2188.653, "duration": 1.635}, {"text": "In fact, that's\ncalled forbidden.", "start": 2190.288, "duration": 2.335}, {"text": "You won't see a signal.", "start": 2192.623, "duration": 1.001}, {"text": "And so these are\ncalled selection rules.", "start": 2196.694, "duration": 4.037}, {"text": "And for a simple cubic, you\ncan see there's nothing inside.", "start": 2200.731, "duration": 5.172}, {"text": "So there's nothing in this\nunit cell that could do this.", "start": 2205.903, "duration": 3.871}, {"text": "So everything's allowed.", "start": 2209.774, "duration": 1.101}, {"text": "Whether there's a plane in\nthere or not, it doesn't matter.", "start": 2210.875, "duration": 2.469}, {"text": "The selection rule is\nwhether it's ever allowed.", "start": 2213.344, "duration": 4.204}, {"text": "And for a simple\ncubic, everything's", "start": 2217.548, "duration": 1.935}, {"text": "fine, because nothing\nwould cancel out.", "start": 2219.483, "duration": 2.403}, {"text": "But in here, you see\nin this 200 case,", "start": 2221.886, "duration": 2.836}, {"text": "you can see very clearly\nfrom that picture", "start": 2224.722, "duration": 2.202}, {"text": "how it cancels out.", "start": 2226.924, "duration": 0.801}, {"text": "But there's many other\nkinds of angles or planes", "start": 2227.725, "duration": 5.005}, {"text": "that might also do that.", "start": 2232.73, "duration": 2.269}, {"text": "And so I'm going\nto just give you", "start": 2234.999, "duration": 1.435}, {"text": "what the selection rules are.", "start": 2236.434, "duration": 1.201}, {"text": "We won't go through\nand derive them all.", "start": 2237.635, "duration": 3.47}, {"text": "But let's see, they are\nactually quite simple.", "start": 2241.105, "duration": 5.472}, {"text": "And so I'm going\nto write them down.", "start": 2246.577, "duration": 2.302}, {"text": "So if we look at\nallowed reflections,", "start": 2248.879, "duration": 10.511}, {"text": "and then we look at\nforbidden reflections--", "start": 2259.39, "duration": 7.774}, {"text": "so this is what the\nselection rules tell us--", "start": 2267.164, "duration": 3.704}, {"text": "so if it's simple cubic,\nthen it's any h, k, and l.", "start": 2270.868, "duration": 11.445}, {"text": "And there's no\nforbidden reflections.", "start": 2282.313, "duration": 3.904}, {"text": "But if we go through BCC\nand FCC, then what we find", "start": 2286.217, "duration": 7.407}, {"text": "is that for BCC\nthe selection rule", "start": 2293.624, "duration": 2.403}, {"text": "is that h plus k\nplus l equals even.", "start": 2296.027, "duration": 4.838}, {"text": "If that is even-- and\nwe won't derive these,", "start": 2300.865, "duration": 3.403}, {"text": "but it comes from the\nsame very simple picture", "start": 2304.268, "duration": 2.136}, {"text": "I just showed you.", "start": 2306.404, "duration": 1.167}, {"text": "If something is in there\nthat can cancel out", "start": 2307.571, "duration": 2.603}, {"text": "the constructive interference,\nit's going to be forbidden.", "start": 2310.174, "duration": 4.037}, {"text": "Otherwise, it can\nconstructively interfere.", "start": 2314.211, "duration": 3.07}, {"text": "And that's what this tells us.", "start": 2317.281, "duration": 1.335}, {"text": "For BCC, it turns out\nto be h plus k plus l.", "start": 2318.616, "duration": 2.769}, {"text": "And so here, what's\nforbidden for BCC", "start": 2321.385, "duration": 2.636}, {"text": "is h plus k plus l is odd.", "start": 2324.021, "duration": 3.137}, {"text": "And for FCC it's h, k,\nl, all odd or all even.", "start": 2327.158, "duration": 10.277}, {"text": "And the forbidden FCC is\nh, k, l, mixed odd/even.", "start": 2340.104, "duration": 10.777}, {"text": "These are the selection rules.", "start": 2350.881, "duration": 1.235}, {"text": "So if I were to give you the\nplanes that you see, then", "start": 2356.921, "duration": 6.339}, {"text": "right away from\nan X-ray spectrum,", "start": 2363.26, "duration": 3.537}, {"text": "you could just use\nthese selection rules", "start": 2366.797, "duration": 2.136}, {"text": "right away to know something,\nto know something about it.", "start": 2368.933, "duration": 3.904}, {"text": "And if you work this\nout and you look at,", "start": 2372.837, "duration": 1.735}, {"text": "OK, so we have simple cubic.", "start": 2374.572, "duration": 3.336}, {"text": "So h squared plus k squared\nplus 1, 100, BCC, FCC, you're", "start": 2377.908, "duration": 5.206}, {"text": "not going to see it.", "start": 2383.114, "duration": 1.868}, {"text": "That doesn't mean that there is\nno 100 plane in those crystals.", "start": 2384.982, "duration": 3.57}, {"text": "It just means that if\nyou shine X-rays on it,", "start": 2388.552, "duration": 2.403}, {"text": "you will not see it.", "start": 2390.955, "duration": 0.867}, {"text": "OK, so the 110,\nthough, now here, OK,", "start": 2394.892, "duration": 3.437}, {"text": "so we see our-- by the way,\nmixed, even, odd, and it", "start": 2398.329, "duration": 4.838}, {"text": "adds to odd.", "start": 2403.167, "duration": 1.134}, {"text": "That's why neither\none of these works.", "start": 2404.301, "duration": 1.936}, {"text": "Here we go, adds\nto even, BCC OK,", "start": 2406.237, "duration": 2.836}, {"text": "but it's still mixed\neven odd, won't be FCC.", "start": 2409.073, "duration": 4.004}, {"text": "3, it's not mixed, so it can\nbe a allowable reflection", "start": 2413.077, "duration": 7.441}, {"text": "for FCC, but not for BBC.", "start": 2420.518, "duration": 3.536}, {"text": "Because if you add\nthem up, it's on odd,", "start": 2424.054, "duration": 3.104}, {"text": "and so forth and so forth.", "start": 2427.158, "duration": 1.368}, {"text": "And look it, 7 doesn't exist,\nbecause you can't do it.", "start": 2428.526, "duration": 2.869}, {"text": "No matter how hard you\ntry, you can't get 7.", "start": 2431.395, "duration": 3.337}, {"text": "That's OK.", "start": 2434.732, "duration": 1.134}, {"text": "And there's 8 and\n9 and so forth.", "start": 2435.866, "duration": 1.835}, {"text": "So 9 also-- so\nhere it's allowed,", "start": 2437.701, "duration": 3.804}, {"text": "but it's not allowed\nin either of these,", "start": 2441.505, "duration": 2.336}, {"text": "because you can't get either\nof these to be satisfied.", "start": 2443.841, "duration": 9.309}, {"text": "This is what selection\nrules give us.", "start": 2453.15, "duration": 2.169}, {"text": "And it comes,\nagain, from simple--", "start": 2455.319, "duration": 5.539}, {"text": "oh, OK, well, that\nthat's another thing.", "start": 2460.858, "duration": 1.868}, {"text": "I said a simple, I have\nto tell you something,", "start": 2462.726, "duration": 2.703}, {"text": "because the Bragg condition,\nit relies on an assumption", "start": 2465.429, "duration": 6.206}, {"text": "that's mostly true.", "start": 2471.635, "duration": 1.969}, {"text": "But the Bragg condition\nrequires that the reflection", "start": 2473.604, "duration": 12.746}, {"text": "is independent--", "start": 2486.35, "duration": 2.069}, {"text": "some of you may be thinking\nI did I draw it onto the atom", "start": 2488.419, "duration": 3.503}, {"text": "or did I draw it\nin between atoms?", "start": 2491.922, "duration": 1.802}, {"text": "Where did that thing--", "start": 2493.724, "duration": 1.101}, {"text": "does it have to\nreflect off an atom?", "start": 2494.825, "duration": 1.602}, {"text": "We're not going there.", "start": 2496.427, "duration": 1.501}, {"text": "With the Bragg condition,\nit's independent of the atom", "start": 2497.928, "duration": 6.941}, {"text": "positions in a plane.", "start": 2504.869, "duration": 1.835}, {"text": "And the second\nthing which is what", "start": 2512.843, "duration": 1.935}, {"text": "I've been sort of alluding\nto is that the atomic planes", "start": 2514.778, "duration": 4.739}, {"text": "are mirror like.", "start": 2519.517, "duration": 0.834}, {"text": "I mean, this is sort of\nan obvious assumption", "start": 2530.794, "duration": 2.103}, {"text": "since I've been assuming\nthey've been mirrors.", "start": 2532.897, "duration": 2.902}, {"text": "But if you start thinking\nabout atom position,", "start": 2535.799, "duration": 6.44}, {"text": "you might go back to that\nselection rule picture", "start": 2542.239, "duration": 3.837}, {"text": "and say, well, wait\na second, does it", "start": 2546.076, "duration": 2.636}, {"text": "always have to hit the atom?", "start": 2548.712, "duration": 1.502}, {"text": "What if this one was over\nor something like that?", "start": 2550.214, "duration": 2.336}, {"text": "No, no, we assume it's\njust one continuous plane", "start": 2552.55, "duration": 3.47}, {"text": "if there are atoms in it.", "start": 2556.02, "duration": 4.104}, {"text": "If there's no atom in it, then\nit's not a reflective plane.", "start": 2560.124, "duration": 4.704}, {"text": "But it's continuous in the\nassumption of the Bragg", "start": 2564.828, "duration": 2.57}, {"text": "condition.", "start": 2567.398, "duration": 0.934}, {"text": "Now we go back to our picture.", "start": 2572.903, "duration": 1.735}, {"text": "So what we want to do\nis, again, our goal,", "start": 2574.638, "duration": 5.439}, {"text": "should we choose, our goal is\nto go from this spectrum knowing", "start": 2580.077, "duration": 8.308}, {"text": "this information--", "start": 2588.385, "duration": 1.535}, {"text": "it's a copper target and being\nable to read off the peak--", "start": 2589.92, "duration": 3.904}, {"text": "our goal is to determine\nthe crystal structure", "start": 2593.824, "duration": 2.669}, {"text": "and the lattice constant.", "start": 2596.493, "duration": 1.569}, {"text": "That's our goal.", "start": 2598.062, "duration": 2.802}, {"text": "And let me let me\njust write this again,", "start": 2600.864, "duration": 2.436}, {"text": "because it's\nextremely important.", "start": 2603.3, "duration": 2.603}, {"text": "So maybe I'll keep that one.", "start": 2605.903, "duration": 3.637}, {"text": "I'm going to erase this and\nput it right in the middle,", "start": 2609.54, "duration": 3.036}, {"text": "because this is what drives XRD.", "start": 2612.576, "duration": 6.006}, {"text": "This is what drives\nXRD, which is", "start": 2618.582, "duration": 3.437}, {"text": "that our goal is figure out\nwhat makes this constant always.", "start": 2622.019, "duration": 25.959}, {"text": "Now, you say what is\nthis constant always?", "start": 2647.978, "duration": 2.236}, {"text": "This is the expression, which\nI'm going to write again.", "start": 2652.783, "duration": 4.705}, {"text": "So what I have if\nit's a copper source", "start": 2657.488, "duration": 3.603}, {"text": "is 1.54 Angstroms\ndivided by 2 a squared.", "start": 2661.091, "duration": 5.239}, {"text": "That's a constant.", "start": 2666.33, "duration": 3.236}, {"text": "That equals sine squared of the\ntheta for some plane divided", "start": 2669.566, "duration": 7.208}, {"text": "by h squared plus k\nsquared plus l squared.", "start": 2676.774, "duration": 5.538}, {"text": "So I'm just kind of\nrepeating what I've said", "start": 2682.312, "duration": 1.836}, {"text": "and what I've written elsewhere,\nbut that is really it.", "start": 2684.148, "duration": 2.269}, {"text": "That is what we do\nin X-ray diffraction.", "start": 2686.417, "duration": 2.969}, {"text": "What makes this?", "start": 2689.386, "duration": 1.702}, {"text": "Well, by this what I mean\nis this term on the right.", "start": 2691.088, "duration": 6.039}, {"text": "How do I make sure that this\nnever changes its value?", "start": 2697.127, "duration": 4.672}, {"text": "Because the thing on the\nleft never changes its value.", "start": 2701.799, "duration": 4.004}, {"text": "And just making sure that\nyou've got that concept,", "start": 2705.803, "duration": 2.769}, {"text": "that is this, oh, yeah.", "start": 2708.572, "duration": 1.735}, {"text": "And it turns out I got a recipe\nfor you to follow to do this.", "start": 2714.144, "duration": 6.54}, {"text": "And it's on the previous slide.", "start": 2720.684, "duration": 1.802}, {"text": "And so we'll start\nthinking about it now.", "start": 2722.486, "duration": 2.502}, {"text": "And we've got five more minutes.", "start": 2724.988, "duration": 1.502}, {"text": "And then on Friday, we\nwill finish this and then", "start": 2726.49, "duration": 3.136}, {"text": "talk about what to do with\nthose continuous X-rays.", "start": 2729.626, "duration": 4.638}, {"text": "So what do I do?", "start": 2734.264, "duration": 2.436}, {"text": "Well, the way you do\nthis is systematically.", "start": 2736.7, "duration": 1.835}, {"text": "And the first thing\nyou do is you read off", "start": 2743.173, "duration": 1.969}, {"text": "the 2 theta values that generate\na set of sine squared value.", "start": 2745.142, "duration": 5.339}, {"text": "So that the X-ray\nspectrum measures 2 theta.", "start": 2750.481, "duration": 2.702}, {"text": "But you know from here\nthat I need sine squared.", "start": 2753.183, "duration": 3.203}, {"text": "So I'm going to write down\nthe sine squared values.", "start": 2756.386, "duration": 3.671}, {"text": "So that's a first step.", "start": 2760.057, "duration": 1.301}, {"text": "So for the first one,\nI've got the first peak.", "start": 2768.465, "duration": 5.572}, {"text": "So I would start to log my data.", "start": 2774.037, "duration": 2.403}, {"text": "The first peak and\nthe 2 theta is 38.43.", "start": 2776.44, "duration": 7.04}, {"text": "And the sine squared theta is--", "start": 2783.48, "duration": 3.937}, {"text": "and I'm just going\nto do that math--", "start": 2787.417, "duration": 1.502}, {"text": "0.1083.", "start": 2788.919, "duration": 3.704}, {"text": "OK, good.", "start": 2792.623, "duration": 0.901}, {"text": "And the next one, the\nnext peak is 44.67.", "start": 2793.524, "duration": 6.606}, {"text": "And the sine square of\nthat is 0.1444 so on.", "start": 2800.13, "duration": 5.873}, {"text": "So you read off all the peaks\nand you make those columns.", "start": 2806.003, "duration": 3.403}, {"text": "So I've gone through.", "start": 2809.406, "duration": 1.001}, {"text": "Now the second one,\nnormalize the sine", "start": 2810.407, "duration": 2.169}, {"text": "squared theta values\nby the smallest value.", "start": 2812.576, "duration": 3.437}, {"text": "You say, so why am I doing that?", "start": 2816.013, "duration": 1.501}, {"text": "Trust me, this will\nachieve our goal.", "start": 2817.514, "duration": 2.936}, {"text": "This will get us there.", "start": 2820.45, "duration": 1.602}, {"text": "This is a nice simple\nrecipe to achieve our goal.", "start": 2822.052, "duration": 2.903}, {"text": "So the next column\nwould simply be", "start": 2824.955, "duration": 2.636}, {"text": "sine squared theta divided\nby sine squared theta min.", "start": 2827.591, "duration": 12.713}, {"text": "Well, I ran out of\nroom there, but that's", "start": 2840.304, "duration": 1.768}, {"text": "going to be obviously 1.", "start": 2842.072, "duration": 2.469}, {"text": "And this would be\n1.333 and so on.", "start": 2844.541, "duration": 6.407}, {"text": "So that's the next one.", "start": 2850.948, "duration": 0.967}, {"text": "So I'm just setting\nthat the top row to 1.", "start": 2851.915, "duration": 5.372}, {"text": "I'm setting the top row to 1.", "start": 2857.287, "duration": 3.804}, {"text": "Good.", "start": 2861.091, "duration": 0.501}, {"text": "Now, I'm going to\nclear fractions.", "start": 2861.592, "duration": 1.735}, {"text": "So I've normalized, and now\nI'm going to clear fractions.", "start": 2863.327, "duration": 2.836}, {"text": "And if I do that,\nI clear fractions.", "start": 2866.163, "duration": 4.337}, {"text": "Well, you say, what does\nclearing fractions mean?", "start": 2870.5, "duration": 4.071}, {"text": "It means just what it implies.", "start": 2874.571, "duration": 1.435}, {"text": "I don't want fractions anymore.", "start": 2876.006, "duration": 2.469}, {"text": "It means I just need to multiply\nthe whole set of numbers", "start": 2878.475, "duration": 3.47}, {"text": "by something that gets\nrid of the fractions.", "start": 2881.945, "duration": 3.037}, {"text": "And it turns out that\nin this case it is 3.", "start": 2884.982, "duration": 3.703}, {"text": "So 3 times sine squared theta\nover sine squared theta min,", "start": 2888.685, "duration": 10.144}, {"text": "and that is going to be 3.", "start": 2898.829, "duration": 3.103}, {"text": "And that is going\nto be 4 and so on.", "start": 2901.932, "duration": 5.405}, {"text": "We're almost there.", "start": 2911.975, "duration": 2.102}, {"text": "We're almost there.", "start": 2914.077, "duration": 0.835}, {"text": "And we're not going\nto finish today,", "start": 2914.912, "duration": 1.501}, {"text": "but we're getting real close.", "start": 2916.413, "duration": 2.002}, {"text": "That's good.", "start": 2918.415, "duration": 0.667}, {"text": "It leaves us with a sense of\nanticipation and excitement.", "start": 2919.082, "duration": 5.039}, {"text": "So, OK, I got clear fractions.", "start": 2924.121, "duration": 2.702}, {"text": "What values of h, k, l,\nif I have this h squared", "start": 2926.823, "duration": 4.538}, {"text": "plus k squared plus l\nsquared, would give me", "start": 2931.361, "duration": 2.169}, {"text": "the sequence of clear fractions?", "start": 2933.53, "duration": 1.935}, {"text": "What values of h squared?", "start": 2935.465, "duration": 1.702}, {"text": "Now, remember, you say,\nwhy am I doing this?", "start": 2937.167, "duration": 3.137}, {"text": "Again, go back to this.", "start": 2940.304, "duration": 2.068}, {"text": "This is why.", "start": 2942.372, "duration": 2.069}, {"text": "I have a simple recipe for\nyou to accomplish this goal.", "start": 2944.441, "duration": 4.471}, {"text": "That's where we're\ngoing with this.", "start": 2948.912, "duration": 3.037}, {"text": "So I'm now going to see\nwith those clear fractions,", "start": 2951.949, "duration": 3.069}, {"text": "now it's very easy\nto see what h, k,", "start": 2955.018, "duration": 2.87}, {"text": "l's would give me-- h squared\nplus k squared plus l squared", "start": 2957.888, "duration": 4.137}, {"text": "equals that clear\nfraction value.", "start": 2962.025, "duration": 3.203}, {"text": "So for example, here,\nwell, if this is h", "start": 2965.228, "duration": 4.939}, {"text": "squared plus k squared plus\nl squared, maybe this is 111.", "start": 2970.167, "duration": 3.103}, {"text": "And This might be\n200, for example.", "start": 2973.27, "duration": 10.31}, {"text": "So we're almost there.", "start": 2983.58, "duration": 1.735}, {"text": "We're so close.", "start": 2985.315, "duration": 1.502}, {"text": "What we're going\nto do is I'm going", "start": 2986.817, "duration": 1.902}, {"text": "to start on Friday I'll\nput this up on the board", "start": 2988.719, "duration": 2.502}, {"text": "and we'll finish filling it\nout and going from this matrix", "start": 2991.221, "duration": 4.171}, {"text": "to the crystal structure\nand the lattice constant.", "start": 2995.392, "duration": 2.636}, {"text": "OK, have a great Halloween.", "start": 2998.028, "duration": 2.469}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 0.0, "duration": 2.49}, {"text": "Commons license.", "start": 2.49, "duration": 1.24}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 3.73, "duration": 2.39}, {"text": "continue to offer high-quality\neducational resources for free.", "start": 6.12, "duration": 3.97}, {"text": "To make a donation or to\nview additional materials", "start": 10.09, "duration": 2.63}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 12.72, "duration": 3.465}, {"text": "at ocw.mit.edu.", "start": 16.185, "duration": 1.375}, {"text": "RAMESH RASKAR: All right.", "start": 20.708, "duration": 1.042}, {"text": "So let me switch\nover to this topic.", "start": 21.75, "duration": 4.35}, {"text": "And let's see some cool demos.", "start": 26.1, "duration": 1.26}, {"text": "So this particular project that\nKimo Johnson and [INAUDIBLE]", "start": 32.729, "duration": 4.201}, {"text": "Adelson built, called\nretrographic sensor,", "start": 36.93, "duration": 4.68}, {"text": "also won the best\ndemo award at CVPR.", "start": 41.61, "duration": 4.75}, {"text": "So we saw this chart last time.", "start": 46.36, "duration": 3.95}, {"text": "They're already selling\n2.5 billion sensors", "start": 50.31, "duration": 6.43}, {"text": "in the next year\nor two per year.", "start": 56.74, "duration": 3.58}, {"text": "And this is the forecast\nmade in 2006, 2007.", "start": 60.32, "duration": 2.9}, {"text": "So it might have changed.", "start": 63.22, "duration": 3.77}, {"text": "And if you see the integration\nof cameras in mobile phones,", "start": 66.99, "duration": 4.53}, {"text": "a natural question\nis, will we have--", "start": 71.52, "duration": 5.79}, {"text": "will we even think about\nour digital still camera", "start": 77.31, "duration": 5.04}, {"text": "as a standalone entity\nin coming years?", "start": 82.35, "duration": 4.81}, {"text": "And if you think about the\nwristwatch, I think most of us", "start": 87.16, "duration": 2.54}, {"text": "don't wear wristwatches anymore.", "start": 89.7, "duration": 1.62}, {"text": "Knowing what time it is is not\na difficult problem anymore.", "start": 91.32, "duration": 6.73}, {"text": "I don't need to\nspend a lot of money.", "start": 98.05, "duration": 2.48}, {"text": "Or I don't have to tether\nmyself to an additional device", "start": 100.53, "duration": 5.25}, {"text": "to know what time it is.", "start": 105.78, "duration": 2.58}, {"text": "And will we be in a similar\nsituation about image?", "start": 108.36, "duration": 4.53}, {"text": "Will we even have a standalone\ncamera for any purpose?", "start": 112.89, "duration": 5.59}, {"text": "So I just want to take\na couple of minutes", "start": 118.48, "duration": 1.97}, {"text": "to see what opinions you have.", "start": 120.45, "duration": 3.54}, {"text": "According to Nokia,\nmore than 50%", "start": 123.99, "duration": 3.95}, {"text": "of the people who\nbought N95 got rid", "start": 127.94, "duration": 3.039}, {"text": "of their point-and-shoot\ncamera And Nokia", "start": 130.979, "duration": 4.191}, {"text": "sells about a million\nphones every day.", "start": 135.17, "duration": 5.93}, {"text": "They sell 400 million\nphones a year.", "start": 141.1, "duration": 2.53}, {"text": "So they sell more than a\nmillion phones every day.", "start": 143.63, "duration": 4.72}, {"text": "So these are staggering numbers.", "start": 148.35, "duration": 2.735}, {"text": "Which is the largest camera\ncompany in the world?", "start": 155.838, "duration": 2.042}, {"text": "AUDIENCE: Nokia?", "start": 160.45, "duration": 0.75}, {"text": "RAMESH RASKAR: Sorry?", "start": 161.2, "duration": 0.36}, {"text": "AUDIENCE: Nokia [INAUDIBLE].", "start": 161.56, "duration": 0.88}, {"text": "RAMESH RASKAR: Nokia, right.", "start": 162.44, "duration": 1.167}, {"text": "It's not a traditional\ncamera company.", "start": 163.607, "duration": 2.333}, {"text": "And the same answer for, which\nis the largest computer company", "start": 165.94, "duration": 4.98}, {"text": "in the world?", "start": 170.92, "duration": 1.34}, {"text": "AUDIENCE: Flextronics.", "start": 172.26, "duration": 1.47}, {"text": "RAMESH RASKAR: Oh, yeah,\nNokia doesn't build anything", "start": 173.73, "duration": 3.41}, {"text": "of their own, of course.", "start": 177.14, "duration": 1.0}, {"text": "They owe EM everything.", "start": 178.14, "duration": 2.46}, {"text": "But still, they're the\nlargest camera and computer", "start": 180.6, "duration": 3.69}, {"text": "company in the world as well.", "start": 184.29, "duration": 2.882}, {"text": "So all right.", "start": 187.172, "duration": 1.168}, {"text": "When do you think of camera\nas a standalone device", "start": 188.34, "duration": 3.51}, {"text": "will completely disappear?", "start": 191.85, "duration": 3.65}, {"text": "AUDIENCE: It'll never\ncompletely disappear.", "start": 195.5, "duration": 1.83}, {"text": "RAMESH RASKAR: And\nby completely, I", "start": 197.33, "duration": 0.95}, {"text": "mean less than 0.1% of\nthe population carries it,", "start": 198.28, "duration": 2.41}, {"text": "basically.", "start": 200.69, "duration": 1.052}, {"text": "Something that's-- it's like\nsaying whether the film camera", "start": 201.742, "duration": 2.458}, {"text": "will disappear.", "start": 204.2, "duration": 0.73}, {"text": "And I believe it's gone.", "start": 204.93, "duration": 1.01}, {"text": "AUDIENCE: Oh, but they're going\nto be gone in different ways.", "start": 208.788, "duration": 2.542}, {"text": "So camera and digital\ncameras are going to be gone.", "start": 211.33, "duration": 2.125}, {"text": "And then, they're\ngoing to be everywhere.", "start": 213.455, "duration": 1.945}, {"text": "And film cameras are gone\nin that nobody uses them.", "start": 215.4, "duration": 3.508}, {"text": "AUDIENCE: What?", "start": 218.908, "duration": 1.272}, {"text": "RAMESH RASKAR: I'm sorry", "start": 220.18, "duration": 1.0}, {"text": "[INTERPOSING VOICES]", "start": 221.18, "duration": 1.6}, {"text": "[LAUGHTER]", "start": 222.78, "duration": 4.222}, {"text": "RAMESH RASKAR: I'll give\nyou an invented thing.", "start": 227.002, "duration": 1.958}, {"text": "You don't want to answer\nthe film camera question.", "start": 228.96, "duration": 1.74}, {"text": "You'll love it.", "start": 230.7, "duration": 0.625}, {"text": "But when will the digital\ncamera disappear altogether?", "start": 231.325, "duration": 2.415}, {"text": "You don't have anything\nagainst digital cameras,", "start": 233.74, "duration": 2.0}, {"text": "though, do you?", "start": 235.74, "duration": 1.782}, {"text": "AUDIENCE: Well, no,\nI don't have anything", "start": 237.522, "duration": 1.708}, {"text": "against digital cameras.", "start": 239.23, "duration": 1.0}, {"text": "But it depends on your\ndefinition of a digital camera.", "start": 240.23, "duration": 3.14}, {"text": "If you're just talking about\npoint-and-shoot cameras--", "start": 243.37, "duration": 2.25}, {"text": "RAMESH RASKAR: A standalone--\na camera-- a device that's", "start": 245.62, "duration": 2.333}, {"text": "built specifically for the\npurpose of taking photos.", "start": 247.953, "duration": 4.807}, {"text": "AUDIENCE: So if\nyou're not going to be", "start": 252.76, "duration": 2.19}, {"text": "a professional photographer,\nthen the average consumer,", "start": 254.95, "duration": 3.84}, {"text": "it's probably just going to\ndisappear maybe in 10 years?", "start": 258.79, "duration": 5.3}, {"text": "RAMESH RASKAR: 10 years.", "start": 264.09, "duration": 1.0}, {"text": "AUDIENCE: Five years?", "start": 265.09, "duration": 0.6}, {"text": "RAMESH RASKAR: All right.", "start": 265.69, "duration": 1.042}, {"text": "And either--\nanybody thinks it'll", "start": 266.732, "duration": 1.568}, {"text": "happen in less than 10 years?", "start": 268.3, "duration": 3.66}, {"text": "Let's take someone over there.", "start": 271.96, "duration": 1.408}, {"text": "AUDIENCE: Yeah, I think\naround five [INAUDIBLE]..", "start": 273.368, "duration": 2.042}, {"text": "RAMESH RASKAR: In five years?", "start": 275.41, "duration": 1.26}, {"text": "There'll be no standalone\nconsumer digital cameras.", "start": 276.67, "duration": 3.358}, {"text": "AUDIENCE: Yeah, I think\nin just a couple of years", "start": 280.028, "duration": 2.042}, {"text": "because if you think about it--", "start": 282.07, "duration": 1.08}, {"text": "RAMESH RASKAR: In two years?", "start": 283.15, "duration": 0.9}, {"text": "AUDIENCE: Yeah.", "start": 284.05, "duration": 0.3}, {"text": "RAMESH RASKAR: Wow.", "start": 284.35, "duration": 0.792}, {"text": "[LAUGHTER]", "start": 285.142, "duration": 2.628}, {"text": "Let's call all the\ncamera companies.", "start": 287.77, "duration": 1.65}, {"text": "[LAUGHTER]", "start": 289.42, "duration": 1.29}, {"text": "[INTERPOSING VOICES]", "start": 290.71, "duration": 0.883}, {"text": "AUDIENCE: --she's\nalready switching over", "start": 291.593, "duration": 1.667}, {"text": "to emphasizing video.", "start": 293.26, "duration": 1.86}, {"text": "And then also, SLRs are\nstarting to be video", "start": 295.12, "duration": 2.19}, {"text": "also because they're not\njust normal cameras anymore.", "start": 297.31, "duration": 2.7}, {"text": "RAMESH RASKAR: Right.", "start": 300.01, "duration": 0.24}, {"text": "But I meant, video cameras are\nstill cameras, the same thing.", "start": 300.25, "duration": 2.68}, {"text": "I'm just saying, will we\nhave standalone devices that", "start": 302.93, "duration": 4.73}, {"text": "only goes to--", "start": 307.66, "duration": 0.99}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 308.65, "duration": 0.888}, {"text": "RAMESH RASKAR: Yes?", "start": 309.538, "duration": 0.792}, {"text": "AUDIENCE: There are cameras\nthat allow you to upload your", "start": 310.33, "duration": 3.21}, {"text": "[INAUDIBLE].", "start": 313.54, "duration": 0.82}, {"text": "RAMESH RASKAR: Right.", "start": 317.195, "duration": 0.875}, {"text": "AUDIENCE: And there's\nno reason why it just", "start": 318.07, "duration": 0.9}, {"text": "wouldn't be on a\ncomputer, the actual", "start": 318.97, "duration": 1.65}, {"text": "[INAUDIBLE] device [INAUDIBLE].", "start": 320.62, "duration": 1.472}, {"text": "RAMESH RASKAR: Exactly.", "start": 322.092, "duration": 0.958}, {"text": "AUDIENCE: So basically,\nit's converting", "start": 323.05, "duration": 1.65}, {"text": "both the cameras [INAUDIBLE],,\nnot just the acquisition.", "start": 324.7, "duration": 2.975}, {"text": "RAMESH RASKAR: Right.", "start": 327.675, "duration": 0.875}, {"text": "AUDIENCE: And the\nother [INAUDIBLE]..", "start": 328.55, "duration": 2.155}, {"text": "RAMESH RASKAR: Right.", "start": 330.705, "duration": 0.875}, {"text": "You're right.", "start": 331.58, "duration": 0.51}, {"text": "It's going to be\nsome, kind of, fusion.", "start": 332.09, "duration": 1.625}, {"text": "But is the camera going\nto become a phone?", "start": 333.715, "duration": 2.085}, {"text": "Or the phone is going\nto become a camera?", "start": 335.8, "duration": 1.708}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 337.508, "duration": 1.103}, {"text": "[LAUGHTER]", "start": 338.611, "duration": 1.473}, {"text": "RAMESH RASKAR: I\nthink in the back.", "start": 342.05, "duration": 1.556}, {"text": "AUDIENCE: I would say a century.", "start": 343.606, "duration": 1.564}, {"text": "RAMESH RASKAR: A century.", "start": 345.17, "duration": 1.19}, {"text": "Wow.", "start": 346.36, "duration": 0.5}, {"text": "AUDIENCE: Yeah, the\nsame way that computers", "start": 346.86, "duration": 2.15}, {"text": "brought us the paperless\noffice and the end of books.", "start": 349.01, "duration": 3.93}, {"text": "And we no longer have a\nstage, theater, or cinema.", "start": 352.94, "duration": 5.34}, {"text": "We've been predicting that\nfor a long time [INAUDIBLE]..", "start": 358.28, "duration": 4.63}, {"text": "RAMESH RASKAR: So that's a\nvery interesting comment.", "start": 362.91, "duration": 3.48}, {"text": "What's unique about paper or\nwatching movies that may or may", "start": 366.39, "duration": 4.59}, {"text": "not apply to a device?", "start": 370.98, "duration": 4.26}, {"text": "AUDIENCE: But in response\nto what you said,", "start": 375.24, "duration": 3.87}, {"text": "the need to capture\nimages won't disappear.", "start": 379.11, "duration": 3.3}, {"text": "But the fact that\nthere is going to be", "start": 382.41, "duration": 1.65}, {"text": "one device that its sole\npurpose is to capture images", "start": 384.06, "duration": 3.42}, {"text": "will disappear.", "start": 387.48, "duration": 1.05}, {"text": "And it will be a device\nthat it's either a phone,", "start": 388.53, "duration": 2.49}, {"text": "and capture this, and\n[INAUDIBLE],, and [INAUDIBLE]..", "start": 391.02, "duration": 5.257}, {"text": "AUDIENCE: Yeah, the way we\nprint things has changed.", "start": 396.277, "duration": 2.463}, {"text": "But we still have [INAUDIBLE].", "start": 398.74, "duration": 1.25}, {"text": "[INTERPOSING VOICES]", "start": 399.99, "duration": 0.88}, {"text": "AUDIENCE: That's why\nyou're doing the image,", "start": 400.87, "duration": 0.83}, {"text": "though, because you're\nshooting stuff on a screen", "start": 401.7, "duration": 2.302}, {"text": "because you want\nthe image quality.", "start": 404.002, "duration": 1.458}, {"text": "So maybe you\n[INAUDIBLE] enough or", "start": 405.46, "duration": 2.39}, {"text": "simulate it that [INAUDIBLE].", "start": 407.85, "duration": 2.32}, {"text": "RAMESH RASKAR: Yeah, but it\nis a hypothetical scenario.", "start": 413.37, "duration": 2.55}, {"text": "If I can buy a phone whose\nimage quality is sufficiently", "start": 415.92, "duration": 4.95}, {"text": "good compared to a\nstandalone still camera,", "start": 420.87, "duration": 7.5}, {"text": "that's the question.", "start": 428.37, "duration": 1.05}, {"text": "Yeah, assuming that\nthe image quality", "start": 429.42, "duration": 1.68}, {"text": "is going to be good enough.", "start": 431.1, "duration": 2.14}, {"text": "Let's ask somebody down here.", "start": 433.24, "duration": 2.047}, {"text": "AUDIENCE: Sorry, go.", "start": 435.287, "duration": 0.833}, {"text": "RAMESH RASKAR: Yeah.", "start": 436.12, "duration": 0.26}, {"text": "AUDIENCE: Yeah, I actually\nreally agree with what he said.", "start": 436.38, "duration": 2.417}, {"text": "I actually think it'll\nnever really disappear", "start": 438.797, "duration": 3.913}, {"text": "for a couple of reasons.", "start": 442.71, "duration": 1.08}, {"text": "I think--", "start": 443.79, "duration": 0.5}, {"text": "RAMESH RASKAR: 0.1%\nof the population.", "start": 444.29, "duration": 2.057}, {"text": "AUDIENCE: All right.", "start": 446.347, "duration": 0.833}, {"text": "So I actually will be\ncurious today how many people", "start": 447.18, "duration": 2.1}, {"text": "carry phone cameras.", "start": 449.28, "duration": 0.84}, {"text": "I'm curious.", "start": 450.12, "duration": 1.65}, {"text": "RAMESH RASKAR:\nOne billion people", "start": 451.77, "duration": 1.65}, {"text": "carry a camera in the pocket.", "start": 453.42, "duration": 1.92}, {"text": "AUDIENCE: But so\none reason I think", "start": 455.34, "duration": 2.52}, {"text": "is that there's not\nonly image quality.", "start": 457.86, "duration": 3.33}, {"text": "But there's the\nergonomic interaction.", "start": 461.19, "duration": 2.667}, {"text": "AUDIENCE: Yes.", "start": 463.857, "duration": 0.583}, {"text": "AUDIENCE: And I think the\nreason why a lot of people", "start": 464.44, "duration": 2.167}, {"text": "carry DSLR is not just\nfor the image quality,", "start": 466.607, "duration": 2.458}, {"text": "but for having things\navailable, and buttons,", "start": 469.065, "duration": 1.875}, {"text": "and having human hands that\nare certain sizes, and people", "start": 470.94, "duration": 2.937}, {"text": "[INTERPOSING VOICES]", "start": 473.877, "duration": 0.833}, {"text": "RAMESH RASKAR: Sometimes, that's\nheavy enough and something", "start": 474.71, "duration": 2.458}, {"text": "to look cool with and so on.", "start": 477.168, "duration": 1.402}, {"text": "[INTERPOSING VOICES]", "start": 478.57, "duration": 0.1}, {"text": "[LAUGHTER]", "start": 478.67, "duration": 0.5}, {"text": "AUDIENCE: So--", "start": 479.17, "duration": 0.62}, {"text": "RAMESH RASKAR: Is it\nfor function or just for", "start": 479.79, "duration": 1.68}, {"text": "[INTERPOSING VOICES]", "start": 481.47, "duration": 0.23}, {"text": "AUDIENCE: No, the heaviness\ndoes add a function", "start": 481.7, "duration": 2.14}, {"text": "because it stabilizes\nthe image a little bit.", "start": 483.84, "duration": 2.748}, {"text": "AUDIENCE: Yeah, but I also\nthink that there's something", "start": 486.588, "duration": 2.292}, {"text": "else too.", "start": 488.88, "duration": 0.5}, {"text": "I'm actually\nunconvinced in general", "start": 489.38, "duration": 2.05}, {"text": "that devices converging\nis necessarily good.", "start": 491.43, "duration": 4.11}, {"text": "Friends of mine that\nI tell this to say", "start": 495.54, "duration": 1.69}, {"text": "that I'm an exception because\nI carry two cell phones.", "start": 497.23, "duration": 2.25}, {"text": "And I think I'm carrying\nthree cameras right now.", "start": 499.48, "duration": 1.96}, {"text": "RAMESH RASKAR: Yeah, two cell\nphones will never converge.", "start": 501.44, "duration": 2.375}, {"text": "[LAUGHTER]", "start": 503.815, "duration": 1.341}, {"text": "AUDIENCE: Well, the amount of\nphones that have two Sim cards", "start": 505.156, "duration": 3.028}, {"text": "[INTERPOSING VOICES]", "start": 508.184, "duration": 0.833}, {"text": "[LAUGHTER]", "start": 509.017, "duration": 0.427}, {"text": "RAMESH RASKAR: [INAUDIBLE]", "start": 509.444, "duration": 0.856}, {"text": "AUDIENCE: No, I think there\nare certain advantages", "start": 510.3, "duration": 2.083}, {"text": "to having, actually, redundancy\nin devices and things.", "start": 512.383, "duration": 3.557}, {"text": "So I definitely agree\nthat digital cameras", "start": 515.94, "duration": 2.31}, {"text": "might have WiFi connectivity\nor other things.", "start": 518.25, "duration": 2.58}, {"text": "But I suspect that\na lot of people", "start": 520.83, "duration": 1.92}, {"text": "will carry separate\nthings that are", "start": 522.75, "duration": 2.46}, {"text": "their primary purpose as imaging\nand a separate thing itself.", "start": 525.21, "duration": 3.075}, {"text": "RAMESH RASKAR: Right.", "start": 528.285, "duration": 0.875}, {"text": "AUDIENCE: And then, they\nalso have a camera in it.", "start": 529.16, "duration": 1.4}, {"text": "RAMESH RASKAR: Well,\nthere will always", "start": 530.56, "duration": 1.583}, {"text": "be a film camera in\n[INAUDIBLE] house.", "start": 532.143, "duration": 1.887}, {"text": "[LAUGHTER]", "start": 534.03, "duration": 2.07}, {"text": "Even 20 years from now.", "start": 536.1, "duration": 2.08}, {"text": "But we're talking about 0.1%.", "start": 538.18, "duration": 2.76}, {"text": "So let's take a quick\nvote and move on.", "start": 540.94, "duration": 1.86}, {"text": "So how many people think it's--", "start": 542.8, "duration": 2.9}, {"text": "let's do the reverse.", "start": 545.7, "duration": 0.88}, {"text": "So we'll say, two\nyears from now,", "start": 546.58, "duration": 4.19}, {"text": "how many of you think\nwill a standalone imaging", "start": 550.77, "duration": 4.89}, {"text": "device will disappear?", "start": 555.66, "duration": 2.142}, {"text": "Kevin?", "start": 557.802, "duration": 0.848}, {"text": "No?", "start": 558.65, "duration": 0.83}, {"text": "All right.", "start": 559.48, "duration": 0.5}, {"text": "We have one.", "start": 559.98, "duration": 0.69}, {"text": "AUDIENCE: No.", "start": 560.67, "duration": 1.695}, {"text": "RAMESH RASKAR: Do you want\nto say very quickly why?", "start": 562.365, "duration": 2.125}, {"text": "Because you--", "start": 564.49, "duration": 0.728}, {"text": "[LAUGHTER]", "start": 565.218, "duration": 0.936}, {"text": "AUDIENCE: It would be--", "start": 566.154, "duration": 1.326}, {"text": "so far, the image quality\nhas been the problem.", "start": 567.48, "duration": 2.695}, {"text": "RAMESH RASKAR: Right.", "start": 570.175, "duration": 0.875}, {"text": "AUDIENCE: There's just not quite\nenough reliance on the sensors", "start": 571.05, "duration": 2.64}, {"text": "that you can fit into a phone.", "start": 573.69, "duration": 1.38}, {"text": "But I think people\nare finding ways", "start": 575.07, "duration": 2.01}, {"text": "to get around that with\nsoftware and with optics.", "start": 577.08, "duration": 3.935}, {"text": "RAMESH RASKAR: Right.", "start": 581.015, "duration": 0.875}, {"text": "Oh, by the way, this--", "start": 581.89, "duration": 0.78}, {"text": "AUDIENCE: And with\nthe sensor, actually.", "start": 582.67, "duration": 0.87}, {"text": "There's a whole new generation\nof sensors coming out", "start": 583.54, "duration": 2.167}, {"text": "that allows you to [INAUDIBLE].", "start": 585.707, "duration": 4.223}, {"text": "RAMESH RASKAR:\nRemember, right now,", "start": 589.93, "duration": 1.92}, {"text": "the total standalone devices\nfor imaging is 10% already.", "start": 591.85, "duration": 7.05}, {"text": "This is optical mouse, which\nis not really a camera.", "start": 598.9, "duration": 3.19}, {"text": "We can ignore that.", "start": 602.09, "duration": 1.47}, {"text": "But mobile phone camera,\n[INAUDIBLE] cameras,", "start": 603.56, "duration": 2.12}, {"text": "gaming and so on.", "start": 605.68, "duration": 0.91}, {"text": "So it's already 10%.", "start": 606.59, "duration": 1.19}, {"text": "And we're talking about 0.1%.", "start": 607.78, "duration": 2.11}, {"text": "So let's move on.", "start": 609.89, "duration": 1.01}, {"text": "And just, let's\ntake a quick poll.", "start": 610.9, "duration": 1.83}, {"text": "So two years, we have\nonly [INAUDIBLE]..", "start": 612.73, "duration": 1.77}, {"text": "AUDIENCE: Quick\nquestion, I guess.", "start": 614.5, "duration": 1.44}, {"text": "Is that even a decent metric?", "start": 615.94, "duration": 2.1}, {"text": "Would it be better to say,\nhow many photos are taken?", "start": 618.04, "duration": 3.48}, {"text": "Because a lot of people\ncarry cell phone cameras,", "start": 621.52, "duration": 2.13}, {"text": "but are using the [INAUDIBLE].", "start": 623.65, "duration": 2.07}, {"text": "My mom doesn't use\nher cell phone.", "start": 625.72, "duration": 1.89}, {"text": "RAMESH RASKAR: Right.", "start": 627.61, "duration": 0.3}, {"text": "AUDIENCE: But she has one.", "start": 627.91, "duration": 0.855}, {"text": "AUDIENCE: Yeah.", "start": 628.765, "duration": 0.625}, {"text": "RAMESH RASKAR: The next\nclass, we'll talk about,", "start": 629.39, "duration": 2.06}, {"text": "how long will it take\nbefore photos disappear?", "start": 631.45, "duration": 2.5}, {"text": "But--", "start": 633.95, "duration": 0.5}, {"text": "[LAUGHTER]", "start": 634.45, "duration": 1.6}, {"text": "--that's the next conversation.", "start": 636.05, "duration": 2.248}, {"text": "[LAUGHTER]", "start": 638.298, "duration": 1.452}, {"text": "So it's like saying,\nhow many people", "start": 641.69, "duration": 2.78}, {"text": "write with their\nown handwriting?", "start": 644.47, "duration": 2.188}, {"text": "It's the same situation\nwe want to see very soon.", "start": 646.658, "duration": 2.042}, {"text": "But that's for the next class.", "start": 648.7, "duration": 1.5}, {"text": "So two years, we have only one.", "start": 653.81, "duration": 1.58}, {"text": "Five years?", "start": 655.39, "duration": 0.675}, {"text": "Three or four.", "start": 659.4, "duration": 1.566}, {"text": "10 years?", "start": 660.966, "duration": 0.729}, {"text": "15 years?", "start": 665.37, "duration": 2.61}, {"text": "So I guess almost\neverybody because--", "start": 667.98, "duration": 2.76}, {"text": "and never?", "start": 670.74, "duration": 2.844}, {"text": "Wow.", "start": 673.584, "duration": 1.404}, {"text": "Wow.", "start": 674.988, "duration": 1.872}, {"text": "All the power to you.", "start": 676.86, "duration": 1.26}, {"text": "AUDIENCE: I say one\nadditional comment.", "start": 678.12, "duration": 1.8}, {"text": "We're thinking about\nthis population.", "start": 679.92, "duration": 1.95}, {"text": "But here, in most of the world,\npeople cannot go and afford", "start": 681.87, "duration": 3.81}, {"text": "this separate camera.", "start": 685.68, "duration": 1.237}, {"text": "They're going to buy a phone.", "start": 686.917, "duration": 1.208}, {"text": "RAMESH RASKAR: A similar point.", "start": 688.125, "duration": 0.735}, {"text": "An excellent point.", "start": 688.86, "duration": 1.2}, {"text": "AUDIENCE: [INAUDIBLE] 1%.", "start": 690.06, "duration": 2.01}, {"text": "RAMESH RASKAR: Yeah.", "start": 692.07, "duration": 0.9}, {"text": "AUDIENCE: It doesn't\nchange that much.", "start": 692.97, "duration": 0.81}, {"text": "RAMESH RASKAR: When the\nremaining five billion", "start": 693.78, "duration": 1.917}, {"text": "come on board.", "start": 695.697, "duration": 0.693}, {"text": "AUDIENCE: Right.", "start": 696.39, "duration": 1.14}, {"text": "RAMESH RASKAR: Yeah, that's\na good point, actually.", "start": 697.53, "duration": 1.64}, {"text": "AUDIENCE: So in camera phones.", "start": 699.17, "duration": 1.25}, {"text": "RAMESH RASKAR: Right.", "start": 700.42, "duration": 2.08}, {"text": "Yes, Jeremy?", "start": 702.5, "duration": 0.6}, {"text": "AUDIENCE: Yeah, I\nhave a prediction.", "start": 703.1, "duration": 1.5}, {"text": "I think that people will\nstill have many devices,", "start": 704.6, "duration": 2.49}, {"text": "like an Apple device.", "start": 707.09, "duration": 1.43}, {"text": "And if you look at Steve Jobs,\nyou have the iPhone with camera", "start": 708.52, "duration": 4.79}, {"text": "and the iPod Touch with camera.", "start": 713.31, "duration": 1.775}, {"text": "RAMESH RASKAR: Right.", "start": 715.085, "duration": 0.875}, {"text": "AUDIENCE: Now they are an\niPhone without [INAUDIBLE]..", "start": 715.96, "duration": 2.675}, {"text": "RAMESH RASKAR: Right.", "start": 718.635, "duration": 0.875}, {"text": "AUDIENCE: So it's interesting.", "start": 719.51, "duration": 1.05}, {"text": "RAMESH RASKAR: That's\njust a marketing gimmick.", "start": 720.56, "duration": 1.08}, {"text": "But--", "start": 721.64, "duration": 0.5}, {"text": "AUDIENCE: Yeah, but it's\ninteresting to think", "start": 722.14, "duration": 2.17}, {"text": "of marketing in this respect.", "start": 724.31, "duration": 2.38}, {"text": "And I think the point\nis they [INAUDIBLE]..", "start": 726.69, "duration": 1.896}, {"text": "RAMESH RASKAR: Right.", "start": 728.586, "duration": 0.875}, {"text": "AUDIENCE: Some people\ncan [INAUDIBLE] device.", "start": 729.461, "duration": 2.254}, {"text": "RAMESH RASKAR: Right.", "start": 731.715, "duration": 0.875}, {"text": "AUDIENCE: And the\nmobile phone makes", "start": 732.59, "duration": 1.5}, {"text": "sense because communication\nis really [INAUDIBLE]..", "start": 734.09, "duration": 4.147}, {"text": "RAMESH RASKAR: Yeah,\nvery soon, you'll", "start": 738.237, "duration": 1.583}, {"text": "be able to buy a burger\nwith a camera in it.", "start": 739.82, "duration": 2.1}, {"text": "[LAUGHTER]", "start": 741.92, "duration": 2.526}, {"text": "That's your--", "start": 744.446, "duration": 1.314}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 747.888, "duration": 0.875}, {"text": "RAMESH RASKAR: What's the\ntoy called for chicken?", "start": 748.763, "duration": 2.042}, {"text": "The happy toy.", "start": 750.805, "duration": 0.843}, {"text": "AUDIENCE: The Happy Meal.", "start": 751.648, "duration": 1.042}, {"text": "RAMESH RASKAR: The Happy Meal.", "start": 752.69, "duration": 1.05}, {"text": "[LAUGHTER]", "start": 753.74, "duration": 0.45}, {"text": "And you'll know what you\nate and how many calories", "start": 754.19, "duration": 1.8}, {"text": "[INTERPOSING VOICES]", "start": 755.99, "duration": 0.833}, {"text": "[LAUGHTER]", "start": 756.823, "duration": 0.5}, {"text": "RAMESH RASKAR: It's a lot.", "start": 757.323, "duration": 1.083}, {"text": "But--", "start": 758.406, "duration": 0.654}, {"text": "[INTERPOSING VOICES]", "start": 759.06, "duration": 0.34}, {"text": "AUDIENCE: It will\ntrace the burger", "start": 759.4, "duration": 1.6}, {"text": "through your digestive system?", "start": 761.0, "duration": 1.56}, {"text": "RAMESH RASKAR: Yeah,\nit will show you", "start": 762.56, "duration": 0.84}, {"text": "how happy you were and--", "start": 763.4, "duration": 1.23}, {"text": "AUDIENCE: And then, when you\nget it out, it's [INAUDIBLE]..", "start": 764.63, "duration": 2.513}, {"text": "AUDIENCE: Great.", "start": 767.143, "duration": 0.667}, {"text": "RAMESH RASKAR: Right.", "start": 767.81, "duration": 0.48}, {"text": "[LAUGHTER]", "start": 768.29, "duration": 0.48}, {"text": "AUDIENCE: Yeah, in this\ngraph, the number [INAUDIBLE]", "start": 768.77, "duration": 2.208}, {"text": "has also increased followed\nby the same proportion", "start": 770.978, "duration": 2.442}, {"text": "as the number of mobile phones.", "start": 773.42, "duration": 1.292}, {"text": "RAMESH RASKAR: Exactly.", "start": 774.712, "duration": 0.958}, {"text": "It's mostly mobile right now.", "start": 775.67, "duration": 1.38}, {"text": "AUDIENCE: Yeah, but see, the\nnetwork of digital cameras", "start": 777.05, "duration": 2.292}, {"text": "is really part of the", "start": 779.342, "duration": 0.978}, {"text": "[INTERPOSING VOICES]", "start": 780.32, "duration": 0.45}, {"text": "RAMESH RASKAR: It's not\ngrowing at the same rate,", "start": 780.77, "duration": 2.07}, {"text": "unfortunately.", "start": 782.84, "duration": 2.52}, {"text": "So--", "start": 785.36, "duration": 1.398}, {"text": "AUDIENCE: [INAUDIBLE] you\ncan't buy a phone without it.", "start": 786.758, "duration": 2.292}, {"text": "It's hard to find a\nhome without a camera.", "start": 789.05, "duration": 1.77}, {"text": "So it is unfair to look at that.", "start": 790.82, "duration": 3.257}, {"text": "RAMESH RASKAR: But that's the\nwhole point of this class.", "start": 794.077, "duration": 2.333}, {"text": "I think we are at a stage\nwhere people are saying,", "start": 796.41, "duration": 2.68}, {"text": "oh, cameras are cheap enough.", "start": 799.09, "duration": 1.25}, {"text": "By the way, do you have an idea\nof how cheap a camera is today?", "start": 800.34, "duration": 6.208}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 806.548, "duration": 1.742}, {"text": "RAMESH RASKAR: For\na device maker,", "start": 808.29, "duration": 2.07}, {"text": "how much does it cost\nthem to pay for a camera?", "start": 810.36, "duration": 3.197}, {"text": "If they would attach a\ncamera, how much does it cost?", "start": 813.557, "duration": 2.208}, {"text": "AUDIENCE: $1 [INAUDIBLE].", "start": 815.765, "duration": 1.585}, {"text": "RAMESH RASKAR: $1.", "start": 817.35, "duration": 0.75}, {"text": "Anybody else?", "start": 818.1, "duration": 0.6}, {"text": "AUDIENCE: [INAUDIBLE] $5.", "start": 818.7, "duration": 1.042}, {"text": "RAMESH RASKAR: It's $0.20.", "start": 819.742, "duration": 2.023}, {"text": "AUDIENCE: What?", "start": 821.765, "duration": 0.625}, {"text": "[CHATTER]", "start": 822.39, "duration": 0.53}, {"text": "RAMESH RASKAR: So when I said\nit will come with your burger,", "start": 822.92, "duration": 2.5}, {"text": "I'm not joking.", "start": 825.42, "duration": 2.06}, {"text": "All right?", "start": 827.48, "duration": 0.5}, {"text": "Yeah, of course, it\ndoesn't have power.", "start": 827.98, "duration": 1.34}, {"text": "It has electronics.", "start": 829.32, "duration": 0.792}, {"text": "It has objects.", "start": 830.112, "duration": 0.648}, {"text": "It has sensors.", "start": 830.76, "duration": 0.93}, {"text": "And it has a compression engine.", "start": 831.69, "duration": 3.37}, {"text": "All right?", "start": 835.06, "duration": 0.5}, {"text": "It's $0.20.", "start": 835.56, "duration": 2.65}, {"text": "So things are changing rapidly.", "start": 838.21, "duration": 1.55}, {"text": "And to answer your\nquestion on, OK,", "start": 839.76, "duration": 1.83}, {"text": "you cannot buy a device\nwithout a camera in it anymore,", "start": 841.59, "duration": 4.45}, {"text": "the problem is, right now, we\ndon't have enough services that", "start": 846.04, "duration": 3.89}, {"text": "go on top of those cameras.", "start": 849.93, "duration": 1.47}, {"text": "But imagine if people\nin this room say,", "start": 851.4, "duration": 2.25}, {"text": "wow, a billion\npeople have a camera.", "start": 853.65, "duration": 3.12}, {"text": "Let me try to see if\nI can build something", "start": 856.77, "duration": 2.25}, {"text": "that really exploits that.", "start": 859.02, "duration": 2.31}, {"text": "Or let me see if I can\nchange the game a little bit,", "start": 861.33, "duration": 2.97}, {"text": "add a little bit extra\nfeatures, maybe add", "start": 864.3, "duration": 1.77}, {"text": "a thermal sensor to it,\nmaybe add UV light to it,", "start": 866.07, "duration": 3.27}, {"text": "whatever it is.", "start": 869.34, "duration": 0.84}, {"text": "Maybe I'll make it into a\ncamera so that instead of $0.20,", "start": 870.18, "duration": 3.36}, {"text": "now it costs me $0.23.", "start": 873.54, "duration": 3.39}, {"text": "It'll completely\nchange the game.", "start": 876.93, "duration": 2.82}, {"text": "And the same way we get\naddicted to our devices", "start": 879.75, "duration": 2.4}, {"text": "and we just can't live\nwithout them anymore.", "start": 882.15, "duration": 1.93}, {"text": "Hopefully, cameras will\nplay a similar role,", "start": 884.08, "duration": 2.72}, {"text": "that you will be forced\nto use the camera", "start": 886.8, "duration": 2.39}, {"text": "and it won't be just\nan additional feature", "start": 889.19, "duration": 1.81}, {"text": "that never gets used.", "start": 891.0, "duration": 2.91}, {"text": "So--", "start": 893.91, "duration": 0.72}, {"text": "AUDIENCE: Did you hope\nthis or [INAUDIBLE]??", "start": 894.63, "duration": 2.04}, {"text": "RAMESH RASKAR: About what?", "start": 896.67, "duration": 1.36}, {"text": "AUDIENCE: That you'll be\nforced to use a camera?", "start": 898.03, "duration": 2.203}, {"text": "RAMESH RASKAR: Not forced,\nbut you'll be encouraged.", "start": 900.233, "duration": 2.167}, {"text": "How about that?", "start": 902.4, "duration": 0.756}, {"text": "[LAUGHTER]", "start": 903.156, "duration": 1.944}, {"text": "It's like saying, are you being\nforced to use a credit card?", "start": 905.1, "duration": 4.81}, {"text": "AUDIENCE: Yeah, that's what I\nactually felt like [INAUDIBLE]..", "start": 909.91, "duration": 3.02}, {"text": "RAMESH RASKAR: Yeah.", "start": 912.93, "duration": 0.833}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 913.763, "duration": 0.875}, {"text": "RAMESH RASKAR: That's another\ndiscussion I'm going to have", "start": 914.638, "duration": 2.417}, {"text": "[INAUDIBLE].", "start": 917.055, "duration": 0.69}, {"text": "[LAUGHTER]", "start": 917.745, "duration": 1.171}, {"text": "All right.", "start": 920.17, "duration": 0.5}, {"text": "So taking notes.", "start": 920.67, "duration": 2.695}, {"text": "As you can see, a\nlot of our discussion", "start": 923.365, "duration": 1.625}, {"text": "will be not on the slides.", "start": 924.99, "duration": 2.34}, {"text": "So Sam's taking the notes today.", "start": 927.33, "duration": 3.24}, {"text": "And what you need to do is\nthe slides will be online.", "start": 930.57, "duration": 3.72}, {"text": "So you don't need to capture\nwhat's on the slides.", "start": 934.29, "duration": 2.17}, {"text": "And you don't need to capture\nall the information that's", "start": 936.46, "duration": 2.15}, {"text": "coming up.", "start": 938.61, "duration": 0.5}, {"text": "For example, JB had a\ncomment on a new camera", "start": 939.11, "duration": 2.87}, {"text": "or the other\ncomments in the back.", "start": 941.98, "duration": 1.86}, {"text": "So you want to capture that\nin the slides or anything", "start": 943.84, "duration": 3.53}, {"text": "I mentioned.", "start": 947.37, "duration": 2.138}, {"text": "And also, summarize some of the\nquestion and answer sessions.", "start": 949.508, "duration": 2.542}, {"text": "And we'll draw some--", "start": 952.05, "duration": 1.89}, {"text": "we'll have some demos,\n[INAUDIBLE] pictures.", "start": 953.94, "duration": 3.21}, {"text": "And I'll do some doodles on\nthe board, and take a photo,", "start": 957.15, "duration": 4.26}, {"text": "and so on.", "start": 961.41, "duration": 0.66}, {"text": "And we'll have one student\nassigned for each class", "start": 962.07, "duration": 3.75}, {"text": "if you're taking for credit.", "start": 965.82, "duration": 1.59}, {"text": "And I encourage you to just use\na laptop because you can, one,", "start": 967.41, "duration": 3.99}, {"text": "take notes faster.", "start": 971.4, "duration": 0.9}, {"text": "And you can also look up some\ninformation very quickly.", "start": 972.3, "duration": 2.75}, {"text": "And then, you can work\nwith me over the weekend.", "start": 975.05, "duration": 2.0}, {"text": "And on one day, we'll\npost it on Stellar.", "start": 977.05, "duration": 4.04}, {"text": "Is everybody familiar with\nStellar website for MIT?", "start": 981.09, "duration": 4.08}, {"text": "How many of you know\nabout the Stellar webpage?", "start": 985.17, "duration": 3.06}, {"text": "Everybody is familiar?", "start": 988.23, "duration": 1.35}, {"text": "And if you don't have\naccess, if you're not", "start": 989.58, "duration": 2.07}, {"text": "taking the class for\ncredit, then you may not--", "start": 991.65, "duration": 2.118}, {"text": "I think you should\nbe able to access.", "start": 993.768, "duration": 1.542}, {"text": "It's open to anybody\nin the world.", "start": 995.31, "duration": 2.173}, {"text": "So you can even send\nit to your friends.", "start": 997.483, "duration": 1.667}, {"text": "And they can look\nat just the slides.", "start": 999.15, "duration": 2.4}, {"text": "They won't get a lot of the\nother information, of course.", "start": 1001.55, "duration": 3.905}, {"text": "But if you cannot access\nit, just send me an email.", "start": 1005.455, "duration": 2.125}, {"text": "And I can explicitly add you as\na guest on the Stellar website.", "start": 1007.58, "duration": 6.27}, {"text": "The one benefit of\nadding explicitly", "start": 1013.85, "duration": 2.31}, {"text": "is that, sometimes,\nthe announcements", "start": 1016.16, "duration": 1.59}, {"text": "go only to the people who are\ntaking the class for credit.", "start": 1017.75, "duration": 3.75}, {"text": "It could be about\nexams or other things.", "start": 1021.5, "duration": 2.68}, {"text": "And if you want to\nbe part-- if you", "start": 1024.18, "duration": 2.03}, {"text": "want to participate\nin that, then you'll", "start": 1026.21, "duration": 1.867}, {"text": "get those emails as well.", "start": 1028.077, "duration": 1.042}, {"text": "So assignment one\nwas about lighting.", "start": 1032.2, "duration": 2.399}, {"text": "And that's what we'll\nbe talking about today,", "start": 1034.599, "duration": 2.431}, {"text": "very different ways\nof capturing light.", "start": 1037.03, "duration": 2.408}, {"text": "Does anybody have questions?", "start": 1039.438, "duration": 1.167}, {"text": "Because there's have a\nfew things you had to do.", "start": 1040.605, "duration": 2.0}, {"text": "You had to have a\ncommitted source code.", "start": 1042.605, "duration": 2.285}, {"text": "Or if you used a GUI-based\napproach, Photoshop", "start": 1044.89, "duration": 4.65}, {"text": "or something, then\nyou need to show", "start": 1049.54, "duration": 1.8}, {"text": "me a lot of intermediate\nresults, input and output", "start": 1051.34, "duration": 2.28}, {"text": "images.", "start": 1053.62, "duration": 0.78}, {"text": "The images should be captured by\nyourself with your own camera.", "start": 1054.4, "duration": 4.35}, {"text": "If you don't have--", "start": 1058.75, "duration": 1.272}, {"text": "for the first\nassignment, maybe you", "start": 1060.022, "duration": 1.458}, {"text": "can use a cell phone camera.", "start": 1061.48, "duration": 1.23}, {"text": "But see if you can buy a cheap\ncamera that has a manual mode.", "start": 1062.71, "duration": 3.87}, {"text": "You can buy a pretty good\ncamera for less than $150.", "start": 1066.58, "duration": 4.14}, {"text": "I recommend the Canon A series.", "start": 1070.72, "duration": 3.48}, {"text": "It usually has a manual mode.", "start": 1074.2, "duration": 1.98}, {"text": "And another benefit\nof the Canon series", "start": 1076.18, "duration": 2.67}, {"text": "is that we have very good SDK.", "start": 1078.85, "duration": 2.31}, {"text": "So you can control the\ncamera from your laptop", "start": 1081.16, "duration": 3.78}, {"text": "or from your PC.", "start": 1084.94, "duration": 1.26}, {"text": "So I recommend the\nCanon A series to buy.", "start": 1086.2, "duration": 4.86}, {"text": "And then, you must\ncreate a webpage", "start": 1091.06, "duration": 2.31}, {"text": "where you will host your\nsolutions for your assignments.", "start": 1093.37, "duration": 4.53}, {"text": "And then, you should\nsend me a link.", "start": 1097.9, "duration": 1.56}, {"text": "And what you update on the\nStellar is just a link.", "start": 1099.46, "duration": 3.57}, {"text": "You're not going to upload\nall the images and so on.", "start": 1103.03, "duration": 4.21}, {"text": "And then, it's perfectly fine\nto use software you find online.", "start": 1107.24, "duration": 6.83}, {"text": "It's perfectly fine.", "start": 1114.07, "duration": 1.48}, {"text": "Don't use your\ncolleague's software", "start": 1115.55, "duration": 3.12}, {"text": "in this class or software people\nwrote in this class last year.", "start": 1118.67, "duration": 4.49}, {"text": "But you can go online.", "start": 1123.16, "duration": 1.17}, {"text": "Go to MATLAB repository.", "start": 1124.33, "duration": 1.71}, {"text": "And if they have a\nfunction for doing x, y, z,", "start": 1126.04, "duration": 2.26}, {"text": "it's perfectly fine to use it.", "start": 1128.3, "duration": 1.25}, {"text": "And then, we have a\nFlickr group page.", "start": 1132.08, "duration": 2.48}, {"text": "I believe you got an email from\nme about the Flickr group page.", "start": 1134.56, "duration": 2.73}, {"text": "And all your final results,\nsorry, input and final results", "start": 1137.29, "duration": 3.75}, {"text": "will be on the Flickr page\nso everybody can see it.", "start": 1141.04, "duration": 2.55}, {"text": "And we can write comments\nabout each other's work.", "start": 1143.59, "duration": 3.73}, {"text": "And this will be a good trial\nrun towards our final project,", "start": 1147.32, "duration": 5.9}, {"text": "where we will be doing\na lot of commenting", "start": 1153.22, "duration": 2.07}, {"text": "on each other's work, giving a\nlot of feedback, and critiques,", "start": 1155.29, "duration": 2.835}, {"text": "and so on.", "start": 1158.125, "duration": 1.245}, {"text": "So three things, Stellar,\nyour own webpage,", "start": 1159.37, "duration": 5.55}, {"text": "and the Flickr page.", "start": 1164.92, "duration": 3.4}, {"text": "Any questions?", "start": 1168.32, "duration": 2.81}, {"text": "All right.", "start": 1171.13, "duration": 0.57}, {"text": "So this was simple.", "start": 1171.7, "duration": 4.05}, {"text": "And if you have more\ntime, you probably", "start": 1175.75, "duration": 2.58}, {"text": "want to do in your\nassignment something that", "start": 1178.33, "duration": 2.46}, {"text": "looks like this, where you\ncan do some beautiful light.", "start": 1180.79, "duration": 5.17}, {"text": "All right.", "start": 1185.96, "duration": 0.5}, {"text": "So some of the assignments, I\nthink we already discussed it,", "start": 1186.46, "duration": 3.33}, {"text": "will look like this.", "start": 1189.79, "duration": 1.35}, {"text": "And let's start with\nsome interesting ways you", "start": 1194.69, "duration": 3.8}, {"text": "can think about illumination.", "start": 1198.49, "duration": 4.05}, {"text": "So here's a photo from\nOne Kendall Square.", "start": 1202.54, "duration": 5.61}, {"text": "This is [INAUDIBLE]\nhere and so on.", "start": 1208.15, "duration": 2.61}, {"text": "And even if you have been to\nKendall Square, this photo,", "start": 1210.76, "duration": 5.19}, {"text": "it's somewhat difficult to\nunderstand what's going on.", "start": 1215.95, "duration": 3.07}, {"text": "You don't even know\nhow many stories this,", "start": 1219.02, "duration": 1.94}, {"text": "I guess it's the\n[? Treper Labs ?] building,", "start": 1220.96, "duration": 2.04}, {"text": "has, for example, from\nthis photo and so on.", "start": 1223.0, "duration": 3.79}, {"text": "So imagine if,\nmagically, you can", "start": 1226.79, "duration": 2.06}, {"text": "convert this photo into this\nphoto from here to here?", "start": 1228.85, "duration": 9.84}, {"text": "What are some tricks\nyou can use to do that?", "start": 1238.69, "duration": 3.85}, {"text": "AUDIENCE: Wait 12 hours?", "start": 1242.54, "duration": 1.0}, {"text": "[LAUGHTER]", "start": 1243.54, "duration": 2.208}, {"text": "RAMESH RASKAR: [INAUDIBLE]", "start": 1245.748, "duration": 1.083}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 1246.831, "duration": 2.205}, {"text": "They have Photoshop's\nShadow Highlights feature.", "start": 1249.036, "duration": 2.842}, {"text": "RAMESH RASKAR: Yeah, you can\ntry to stretch the [INAUDIBLE]..", "start": 1251.878, "duration": 2.542}, {"text": "Or you can try to take a\nreally long exposure photo.", "start": 1254.42, "duration": 3.27}, {"text": "But yeah, this is\nreally, really dark.", "start": 1257.69, "duration": 1.972}, {"text": "There's almost nothing there.", "start": 1259.662, "duration": 1.208}, {"text": "AUDIENCE: [INAUDIBLE] another\nphoto, you can [INAUDIBLE]..", "start": 1260.87, "duration": 2.88}, {"text": "RAMESH RASKAR: Exactly.", "start": 1263.75, "duration": 1.32}, {"text": "Who's saying that?", "start": 1265.07, "duration": 1.165}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1266.235, "duration": 0.875}, {"text": "RAMESH RASKAR: All right.", "start": 1267.11, "duration": 0.27}, {"text": "Good.", "start": 1267.38, "duration": 1.2}, {"text": "So you just cheat.", "start": 1268.58, "duration": 1.48}, {"text": "This was actually taken\nwhen I was working at MERL.", "start": 1270.06, "duration": 3.92}, {"text": "And this will be from\nmy office, actually.", "start": 1273.98, "duration": 1.89}, {"text": "It's a much nicer building than\nthe office I have right now.", "start": 1275.87, "duration": 2.5}, {"text": "[LAUGHTER]", "start": 1278.37, "duration": 1.3}, {"text": "AUDIENCE: This campus is nice.", "start": 1279.67, "duration": 1.335}, {"text": "RAMESH RASKAR: Sorry?", "start": 1281.005, "duration": 0.875}, {"text": "AUDIENCE: This campus is nice.", "start": 1281.88, "duration": 1.25}, {"text": "RAMESH RASKAR: Yeah, I\nlike the brick texture.", "start": 1283.13, "duration": 1.86}, {"text": "It's beautiful.", "start": 1284.99, "duration": 0.66}, {"text": "[LAUGHTER]", "start": 1285.65, "duration": 1.77}, {"text": "And just take the photo after\n12 hours, in the morning.", "start": 1287.42, "duration": 5.08}, {"text": "Actually, I took\na photo at 6:00 AM", "start": 1292.5, "duration": 3.83}, {"text": "when there were very\nfew cars on the street.", "start": 1296.33, "duration": 3.78}, {"text": "And somehow, you want to fuse\nthese two photos into a photo", "start": 1300.11, "duration": 3.69}, {"text": "that looks like that.", "start": 1303.8, "duration": 1.48}, {"text": "So the static parts are\ncaptured from daytime.", "start": 1305.28, "duration": 3.68}, {"text": "And all the dynamic parts with\nthe cars, and the Christmas", "start": 1308.96, "duration": 4.35}, {"text": "lights, and so on are\ncaptured from the nighttime.", "start": 1313.31, "duration": 3.04}, {"text": "So you want to make some\nintelligent decision, which", "start": 1316.35, "duration": 2.36}, {"text": "when-- which pixel\ncomes from where?", "start": 1318.71, "duration": 3.72}, {"text": "AUDIENCE: The color\ntemperature is off.", "start": 1322.43, "duration": 1.68}, {"text": "RAMESH RASKAR: And the\ncolor temperature is off.", "start": 1324.11, "duration": 2.0}, {"text": "And you ought to make some\nartistic decisions about that.", "start": 1326.11, "duration": 4.12}, {"text": "And you'll always have\nsome issues, like this one.", "start": 1330.23, "duration": 3.12}, {"text": "I think this guy, I\nwaited all night long.", "start": 1333.35, "duration": 2.01}, {"text": "But he was part of my class.", "start": 1335.36, "duration": 1.83}, {"text": "He just didn't move.", "start": 1337.19, "duration": 1.17}, {"text": "So you can see that.", "start": 1338.36, "duration": 1.452}, {"text": "[LAUGHTER]", "start": 1339.812, "duration": 0.5}, {"text": "You can see that.", "start": 1340.312, "duration": 3.388}, {"text": "So it's a\ncontext-enhanced image.", "start": 1343.7, "duration": 2.85}, {"text": "And we're really exploiting\nnatural illumination", "start": 1346.55, "duration": 2.94}, {"text": "to capture a new photo.", "start": 1349.49, "duration": 1.81}, {"text": "Yeah?", "start": 1351.3, "duration": 0.5}, {"text": "AUDIENCE: So how was this\n[INAUDIBLE] to you what", "start": 1351.8, "duration": 2.85}, {"text": "[INAUDIBLE] algorithm or--", "start": 1354.65, "duration": 4.462}, {"text": "RAMESH RASKAR: Yeah, it\nhas to be an algorithm.", "start": 1359.112, "duration": 1.958}, {"text": "So this is what you can\ndo, just one approach.", "start": 1361.07, "duration": 4.21}, {"text": "But maybe in your\nassignments, you'll", "start": 1365.28, "duration": 2.39}, {"text": "come up with another approach.", "start": 1367.67, "duration": 2.85}, {"text": "In this case, you\ncan just take--", "start": 1370.52, "duration": 1.83}, {"text": "just compute the scene contrast.", "start": 1372.35, "duration": 1.99}, {"text": "You can just take a\nfive-by-five window", "start": 1374.34, "duration": 2.36}, {"text": "and find pixels that\nhave very high-variance.", "start": 1376.7, "duration": 3.07}, {"text": "And you can create\na stencil like this", "start": 1379.77, "duration": 3.02}, {"text": "that says, oh, all these\npixels look interesting.", "start": 1382.79, "duration": 2.28}, {"text": "And this part here,\nclearly, there's nothing.", "start": 1385.07, "duration": 2.4}, {"text": "So I should not take that\nfrom the nighttime image.", "start": 1387.47, "duration": 3.6}, {"text": "And then, I can create--", "start": 1391.07, "duration": 2.22}, {"text": "I can use the stencil.", "start": 1393.29, "duration": 1.56}, {"text": "The black pixels will\ncome from daytime.", "start": 1394.85, "duration": 1.92}, {"text": "And the white pixels\nwill come from nighttime.", "start": 1396.77, "duration": 2.1}, {"text": "And if you just\ncombine that, combine", "start": 1398.87, "duration": 1.8}, {"text": "those two using\nthat stencil, you", "start": 1400.67, "duration": 2.76}, {"text": "get a reasonable image already.", "start": 1403.43, "duration": 1.38}, {"text": "But it will look extremely\nugly because the transition", "start": 1404.81, "duration": 4.11}, {"text": "from here to here, from\nnighttime to the daytime,", "start": 1408.92, "duration": 2.82}, {"text": "will not look very natural.", "start": 1411.74, "duration": 3.308}, {"text": "So what can you do?", "start": 1415.048, "duration": 0.792}, {"text": "Any solutions?", "start": 1415.84, "duration": 0.87}, {"text": "AUDIENCE: Blur the\nmask [INAUDIBLE]..", "start": 1419.54, "duration": 1.65}, {"text": "RAMESH RASKAR: Blur the mask.", "start": 1421.19, "duration": 0.69}, {"text": "You can do that.", "start": 1421.88, "duration": 0.667}, {"text": "But then, the edges\nof the building", "start": 1422.547, "duration": 2.003}, {"text": "will get very fuzzy because it\nlooks like part of the building", "start": 1424.55, "duration": 2.82}, {"text": "was in the daytime and\npart of the building", "start": 1427.37, "duration": 1.792}, {"text": "was in the nighttime.", "start": 1429.162, "duration": 1.553}, {"text": "AUDIENCE: Could you just\nstart-- could you just say", "start": 1430.715, "duration": 2.125}, {"text": "how you made the mask again?", "start": 1432.84, "duration": 1.33}, {"text": "I--", "start": 1434.17, "duration": 0.5}, {"text": "RAMESH RASKAR: This mask?", "start": 1434.67, "duration": 0.51}, {"text": "AUDIENCE: Yeah.", "start": 1435.18, "duration": 0.625}, {"text": "RAMESH RASKAR: So in\nthe simplest case,", "start": 1435.805, "duration": 2.565}, {"text": "you can just say, given the\npixels aren't bright enough.", "start": 1438.37, "duration": 3.77}, {"text": "That is, imagine zero to 255.", "start": 1442.14, "duration": 2.44}, {"text": "Anything over 150,\nmark it as [INAUDIBLE]..", "start": 1444.58, "duration": 3.017}, {"text": "That's the simplest thing.", "start": 1447.597, "duration": 1.083}, {"text": "But it's not so good.", "start": 1448.68, "duration": 2.49}, {"text": "A slightly better way\nof doing that is you", "start": 1451.17, "duration": 2.73}, {"text": "go in a window of, say,\nfive-by-five pixels.", "start": 1453.9, "duration": 2.85}, {"text": "And if all the 25 pixels\nare the same, then", "start": 1456.75, "duration": 3.24}, {"text": "maybe it's not very interesting.", "start": 1459.99, "duration": 1.77}, {"text": "Here, all 25 pixels\nare the same.", "start": 1461.76, "duration": 1.65}, {"text": "Or in this region, all\n25 pixels are the same.", "start": 1463.41, "duration": 3.075}, {"text": "But if there's enough\nvariation between them,", "start": 1466.485, "duration": 1.875}, {"text": "if I just take the variance\nor the standard deviation", "start": 1468.36, "duration": 2.91}, {"text": "of those 25 pixels\nand it's high enough,", "start": 1471.27, "duration": 2.64}, {"text": "that looks like there's some\ninformation in those 25 pixels", "start": 1473.91, "duration": 3.39}, {"text": "in a five-by-five window.", "start": 1477.3, "duration": 1.11}, {"text": "And you'll have that center\nof that five-by-five window", "start": 1478.41, "duration": 3.81}, {"text": "as something that's interesting.", "start": 1482.22, "duration": 2.25}, {"text": "Yep?", "start": 1484.47, "duration": 0.567}, {"text": "AUDIENCE: One thing you could\ndo for [INAUDIBLE] the buildings", "start": 1485.037, "duration": 2.583}, {"text": "is that you would shrink\nthe components that are not", "start": 1487.62, "duration": 4.55}, {"text": "[INAUDIBLE].", "start": 1492.17, "duration": 2.483}, {"text": "RAMESH RASKAR: So\nyou can use some", "start": 1494.653, "duration": 1.417}, {"text": "a graph card approach and\nfind some connected components", "start": 1496.07, "duration": 3.0}, {"text": "and so on, like that?", "start": 1499.07, "duration": 1.512}, {"text": "AUDIENCE: [INAUDIBLE]\na little bit,", "start": 1500.582, "duration": 1.458}, {"text": "you could have taken any\nimmersive photos and just,", "start": 1502.04, "duration": 3.455}, {"text": "between them, defined\nmotion or [INAUDIBLE]..", "start": 1505.495, "duration": 2.162}, {"text": "RAMESH RASKAR: Great idea.", "start": 1507.657, "duration": 1.083}, {"text": "Great idea, especially\nfor something", "start": 1508.74, "duration": 1.81}, {"text": "that's moving to find that.", "start": 1510.55, "duration": 1.627}, {"text": "[INTERPOSING VOICES]", "start": 1512.177, "duration": 0.833}, {"text": "RAMESH RASKAR:\nBut you still have", "start": 1513.01, "duration": 1.375}, {"text": "to take some data images to\nfill in the static parts that", "start": 1514.385, "duration": 3.345}, {"text": "are dark.", "start": 1517.73, "duration": 0.5}, {"text": "AUDIENCE: Yeah.", "start": 1518.23, "duration": 0.24}, {"text": "RAMESH RASKAR: But that's right.", "start": 1518.47, "duration": 1.333}, {"text": "In fact, that you have\nto do that for cars", "start": 1519.803, "duration": 2.267}, {"text": "because some cars, the center\nof this car is too dark.", "start": 1522.07, "duration": 3.42}, {"text": "But it's still important to us.", "start": 1525.49, "duration": 2.86}, {"text": "So this is what simple\nprocessing would do.", "start": 1528.35, "duration": 2.99}, {"text": "But maybe you want to\ndo something smart.", "start": 1531.34, "duration": 3.27}, {"text": "So this is just a zoomed\nin version of that.", "start": 1534.61, "duration": 4.92}, {"text": "It's trying to capture--", "start": 1539.53, "duration": 1.26}, {"text": "all these windows did not\nhave lights on, you see here.", "start": 1540.79, "duration": 5.34}, {"text": "But there's one window\nwith a light on.", "start": 1546.13, "duration": 2.28}, {"text": "I think this is the scaled up\nafter biogen building, Amgen", "start": 1548.41, "duration": 4.01}, {"text": "building.", "start": 1552.42, "duration": 1.71}, {"text": "And it captures that.", "start": 1554.13, "duration": 2.7}, {"text": "But then, it creates this\nugly artifact around that.", "start": 1556.83, "duration": 2.735}, {"text": "So you want a very nice\ntransition between the two.", "start": 1559.565, "duration": 2.125}, {"text": "So the solution for\nthat is actually", "start": 1564.98, "duration": 3.26}, {"text": "called a gradient dom infusion.", "start": 1568.24, "duration": 3.12}, {"text": "And that's just a\nfancy way of saying", "start": 1571.36, "duration": 1.62}, {"text": "that instead of worrying\nabout absolute intensities,", "start": 1572.98, "duration": 3.78}, {"text": "I'm going to worry\nabout differences", "start": 1576.76, "duration": 2.58}, {"text": "between every pixel.", "start": 1579.34, "duration": 2.14}, {"text": "So I'm going to take a\npixel x plus one and pixel x", "start": 1581.48, "duration": 3.47}, {"text": "and find the difference\nbetween them.", "start": 1584.95, "duration": 1.81}, {"text": "And I'm going to\nblend those ones.", "start": 1586.76, "duration": 2.87}, {"text": "So this is what would happen if\nyou just blend the intensities.", "start": 1589.63, "duration": 3.87}, {"text": "And this is what would happen\nif you blend the differences.", "start": 1593.5, "duration": 3.45}, {"text": "Now if you blend the\ndifferences, which is just", "start": 1596.95, "duration": 2.74}, {"text": "the forward difference, then\nthe image that you will get", "start": 1599.69, "duration": 2.9}, {"text": "will be also made up\nof forward differences.", "start": 1602.59, "duration": 2.32}, {"text": "So to go from a forward\ndifference back to the signal,", "start": 1604.91, "duration": 2.57}, {"text": "we must do integration.", "start": 1607.48, "duration": 2.04}, {"text": "And in 1D, it's very easy.", "start": 1609.52, "duration": 2.41}, {"text": "And we'll study that later.", "start": 1611.93, "duration": 1.95}, {"text": "But in 2D, it's\nquite challenging.", "start": 1613.88, "duration": 2.1}, {"text": "So it's basically\ndoing a 2D integration", "start": 1615.98, "duration": 2.27}, {"text": "from all the forward differences\nand putting the two together.", "start": 1618.25, "duration": 3.222}, {"text": "Again, I'm not going\nthrough the details.", "start": 1621.472, "duration": 1.708}, {"text": "We'll study this more.", "start": 1623.18, "duration": 3.29}, {"text": "It turns out you can\ncreate various very", "start": 1626.47, "duration": 3.48}, {"text": "aesthetically pleasing\nfusions or blending", "start": 1629.95, "duration": 3.87}, {"text": "between different parts.", "start": 1633.82, "duration": 1.15}, {"text": "Yeah?", "start": 1634.97, "duration": 0.5}, {"text": "AUDIENCE: What if-- this is just\nan example of a night and day.", "start": 1635.47, "duration": 4.14}, {"text": "And what if you multiply the\nimages and then normalize them?", "start": 1639.61, "duration": 3.843}, {"text": "RAMESH RASKAR: You could\ntry different things.", "start": 1643.453, "duration": 1.917}, {"text": "AUDIENCE: Because the dark\nparts would come through.", "start": 1645.37, "duration": 2.45}, {"text": "And the light parts from the\nday would also come through.", "start": 1647.82, "duration": 2.536}, {"text": "And they might actually merge\na little bit [INAUDIBLE]..", "start": 1650.356, "duration": 2.334}, {"text": "RAMESH RASKAR: Right.", "start": 1652.69, "duration": 0.875}, {"text": "So, Nina, these are\nsome of the things--", "start": 1653.565, "duration": 1.823}, {"text": "it could work in one\nscenario, but not the other.", "start": 1655.388, "duration": 2.042}, {"text": "You're right.", "start": 1657.43, "duration": 0.6}, {"text": "And this is exactly what I want\nyou to do in the assignment.", "start": 1658.03, "duration": 2.76}, {"text": "The assignment gives you a very\nsimple and very easy problem.", "start": 1660.79, "duration": 5.79}, {"text": "But instead of taking pictures\nunder two different flash table", "start": 1666.58, "duration": 4.95}, {"text": "lab conditions, you\ncould take a picture", "start": 1671.53, "duration": 1.89}, {"text": "under two time instances,\none in the daytime,", "start": 1673.42, "duration": 3.43}, {"text": "one in the nighttime,\nor under two", "start": 1676.85, "duration": 1.55}, {"text": "different polarizations or\nanything, and then fuse them.", "start": 1678.4, "duration": 2.79}, {"text": "Instead of fusing\ncolor channels,", "start": 1681.19, "duration": 1.62}, {"text": "you can fuse intensity channels.", "start": 1682.81, "duration": 2.64}, {"text": "Or you can fuse the forward\ndifference channels and so on.", "start": 1685.45, "duration": 3.81}, {"text": "One great software,\nit's on the website,", "start": 1689.26, "duration": 3.46}, {"text": "I would like you to use for\ntesting is called HDR Shop.", "start": 1692.72, "duration": 6.38}, {"text": "And it's available for free.", "start": 1702.364, "duration": 2.086}, {"text": "It's from a group at\nUSC led by Paul Debevec.", "start": 1704.45, "duration": 5.19}, {"text": "And I highly recommend\nthat because it certainly", "start": 1709.64, "duration": 2.0}, {"text": "isn't Photoshop.", "start": 1711.64, "duration": 1.5}, {"text": "If you use HDR Shop,\nagain, even if you're", "start": 1713.14, "duration": 3.48}, {"text": "doing MATLAB assignments,\nyou can download HDR Shop.", "start": 1716.62, "duration": 3.0}, {"text": "And it allows you to\ndo some [INAUDIBLE]..", "start": 1719.62, "duration": 2.64}, {"text": "You can sample\nimages [INAUDIBLE]..", "start": 1722.26, "duration": 2.61}, {"text": "You can subtract images.", "start": 1724.87, "duration": 1.44}, {"text": "You can do forward differences.", "start": 1726.31, "duration": 1.74}, {"text": "You can do volume densities\nand all those things.", "start": 1728.05, "duration": 2.62}, {"text": "So it's a really good software\nfor doing arithmetic on images.", "start": 1730.67, "duration": 7.1}, {"text": "And the other [INAUDIBLE]\nis done in floating point.", "start": 1737.77, "duration": 3.99}, {"text": "It's not trapped [INAUDIBLE].", "start": 1741.76, "duration": 2.98}, {"text": "So let's say you want\nto multiply two images.", "start": 1744.74, "duration": 2.36}, {"text": "And the intensities\nare at 200 and 200.", "start": 1747.1, "duration": 3.93}, {"text": "It's 40,000 [INAUDIBLE].", "start": 1751.03, "duration": 2.49}, {"text": "And Photoshop only supports\nfloating point numbers.", "start": 1753.52, "duration": 4.69}, {"text": "But HDR Shop will support that.", "start": 1758.21, "duration": 3.325}, {"text": "[INAUDIBLE]", "start": 1761.535, "duration": 0.855}, {"text": "So even before,\nsometimes, you're", "start": 1765.64, "duration": 1.82}, {"text": "writing a MATLAB program,\nyou can very quickly", "start": 1767.46, "duration": 2.22}, {"text": "do some visual inspection\non this and [INAUDIBLE]..", "start": 1769.68, "duration": 5.94}, {"text": "Another thing a lot\nof people forget", "start": 1775.62, "duration": 1.5}, {"text": "about when you're doing\nassignments or projects that", "start": 1777.12, "duration": 4.68}, {"text": "involve images is don't\nwork on the whole image.", "start": 1781.8, "duration": 4.11}, {"text": "Work on a very tiny\npart of the image.", "start": 1785.91, "duration": 2.4}, {"text": "Just take a 100 pixel\nby 100 pixel crop,", "start": 1788.31, "duration": 2.88}, {"text": "largest size, but just a crop.", "start": 1791.19, "duration": 1.8}, {"text": "So you have some two\nmegapixel images.", "start": 1792.99, "duration": 3.06}, {"text": "Don't try to run your core\non a two-megapixel image.", "start": 1796.05, "duration": 2.46}, {"text": "It might take forever.", "start": 1798.51, "duration": 1.41}, {"text": "Just take a very tiny part\nfrom a very interesting part.", "start": 1799.92, "duration": 3.33}, {"text": "[INAUDIBLE] run all\nyour code on that.", "start": 1803.25, "duration": 3.27}, {"text": "And when you feel that all\nyour procedures are working", "start": 1806.52, "duration": 3.9}, {"text": "[INAUDIBLE],, then you\ncan go back to maybe", "start": 1810.42, "duration": 3.33}, {"text": "some larger [? optical ?] image.", "start": 1813.75, "duration": 1.52}, {"text": "So when I was working on\nthis portrait, actually,", "start": 1821.22, "duration": 3.9}, {"text": "I was very inspired by this\nsurrealism, AR surrealism,", "start": 1825.12, "duration": 8.37}, {"text": "where Ren\u00e9 Magritte and all\nthat came up with Empire", "start": 1833.49, "duration": 3.15}, {"text": "of the Lights.", "start": 1836.64, "duration": 1.18}, {"text": "I'm sure a lot of you have\nseen this painting, where", "start": 1837.82, "duration": 2.87}, {"text": "he created this very stark,\ndisconcerting positioning.", "start": 1840.69, "duration": 9.1}, {"text": "You have bright daylight here.", "start": 1849.79, "duration": 3.39}, {"text": "But the bottom part of the\nimage is a nighttime scene.", "start": 1853.18, "duration": 5.85}, {"text": "And he played with a lot of this\njuxtaposing of disconcerting", "start": 1859.03, "duration": 5.67}, {"text": "elements.", "start": 1864.7, "duration": 0.66}, {"text": "And the question\nis, can photography", "start": 1865.36, "duration": 3.36}, {"text": "create something that is\nsurrrealistic, not always", "start": 1868.72, "duration": 5.25}, {"text": "photorealistic,\nbut surrrealistic?", "start": 1873.97, "duration": 3.58}, {"text": "And when we come to\na discussion about,", "start": 1877.55, "duration": 3.23}, {"text": "will photos survive\nin the future,", "start": 1880.78, "duration": 2.37}, {"text": "this is exactly the question\nthat painters ask themselves", "start": 1883.15, "duration": 6.0}, {"text": "when cameras are measured.", "start": 1889.15, "duration": 1.45}, {"text": "There was a lot of\ninterest in creating", "start": 1890.6, "duration": 2.51}, {"text": "photorealistic paintings.", "start": 1893.11, "duration": 3.84}, {"text": "And when camera came around,\nthey all scratched their heads", "start": 1896.95, "duration": 2.91}, {"text": "and said, wow, we need to\nmove on and do something else.", "start": 1899.86, "duration": 3.09}, {"text": "We cannot create photorealistic\npaintings anymore.", "start": 1902.95, "duration": 2.83}, {"text": "And then, we had\npointillism and surrealism.", "start": 1905.78, "duration": 2.51}, {"text": "And now, it's just abstract.", "start": 1908.29, "duration": 2.31}, {"text": "We don't even care about\nrepresenting geometry,", "start": 1910.6, "duration": 2.55}, {"text": "and reflectance, and so on.", "start": 1913.15, "duration": 2.2}, {"text": "And the question\nis, should cameras", "start": 1915.35, "duration": 3.02}, {"text": "worry about capturing intensity,\nand shapes, and geometry?", "start": 1918.37, "duration": 5.85}, {"text": "When I check on\nFlickr, there are", "start": 1924.22, "duration": 1.53}, {"text": "hundreds of images of\nbuildings like this.", "start": 1925.75, "duration": 2.64}, {"text": "What's so great about taking\nyet another photo of yet", "start": 1928.39, "duration": 3.9}, {"text": "another building?", "start": 1932.29, "duration": 1.71}, {"text": "What I want to create is\nimages that are somehow", "start": 1934.0, "duration": 3.24}, {"text": "more expressive and more real.", "start": 1937.24, "duration": 2.52}, {"text": "So that's another debate,\nwhether photos [INAUDIBLE]..", "start": 1939.76, "duration": 4.86}, {"text": "I personally, by the way, have\ncompletely given up on camera.", "start": 1944.62, "duration": 2.55}, {"text": "I don't-- I barely take photos\nwhen I travel and so on.", "start": 1947.17, "duration": 7.57}, {"text": "It's just one of those things.", "start": 1954.74, "duration": 1.25}, {"text": "I'm well beyond the\nstage of taking photos.", "start": 1955.99, "duration": 3.08}, {"text": "And I rarely get impressed\nwith beautiful photos.", "start": 1959.07, "duration": 3.997}, {"text": "But these look nice.", "start": 1963.067, "duration": 0.833}, {"text": "But I never get\nimpressed with that.", "start": 1963.9, "duration": 2.65}, {"text": "And hopefully, the\nremaining six billion", "start": 1966.55, "duration": 3.02}, {"text": "people will also\nstart challenging", "start": 1969.57, "duration": 3.75}, {"text": "the notion of camera as a device\nthat captures photorealism.", "start": 1973.32, "duration": 6.71}, {"text": "People will\nchallenge that notion", "start": 1980.03, "duration": 2.01}, {"text": "just like the painters\ndid during the Renaissance", "start": 1982.04, "duration": 5.06}, {"text": "and [INAUDIBLE].", "start": 1987.1, "duration": 1.86}, {"text": "So any thoughts, [INAUDIBLE]?", "start": 1988.96, "duration": 2.996}, {"text": "AUDIENCE: Huh?", "start": 1991.956, "duration": 0.754}, {"text": "RAMESH RASKAR: Any thoughts?", "start": 1992.71, "duration": 1.737}, {"text": "[INTERPOSING VOICES]", "start": 1994.447, "duration": 0.833}, {"text": "AUDIENCE: There--\nyou've never seen", "start": 1995.28, "duration": 4.7}, {"text": "a photo done by a\nphotographer, let's", "start": 1999.98, "duration": 3.085}, {"text": "say, Richard Avedon or Ansel\nAdams that you really liked,", "start": 2003.065, "duration": 3.72}, {"text": "that", "start": 2006.785, "duration": 0.5}, {"text": "[INTERPOSING VOICES]", "start": 2007.285, "duration": 0.275}, {"text": "RAMESH RASKAR: It's beautiful.", "start": 2007.56, "duration": 0.63}, {"text": "But I'm not impressed.", "start": 2008.19, "duration": 1.425}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2009.615, "duration": 1.503}, {"text": "RAMESH RASKAR: Can\nyou say it louder?", "start": 2011.118, "duration": 1.542}, {"text": "She said, what about\nAnsel Adams and so on?", "start": 2012.66, "duration": 3.6}, {"text": "Yeah, back then--", "start": 2016.26, "duration": 1.087}, {"text": "[INTERPOSING VOICES]", "start": 2017.347, "duration": 0.833}, {"text": "RAMESH RASKAR: --when they\ndid it, it was impressive.", "start": 2018.18, "duration": 2.208}, {"text": "But now, if somebody shows\nme something as good as Ansel", "start": 2020.388, "duration": 2.682}, {"text": "Adams, it's great.", "start": 2023.07, "duration": 1.77}, {"text": "But it's not interesting.", "start": 2024.84, "duration": 2.8}, {"text": "AUDIENCE: Well, you should look\nat some of Richard Avedon's", "start": 2027.64, "duration": 4.51}, {"text": "more recent works.", "start": 2032.15, "duration": 2.4}, {"text": "He does some pretty\ncreative things.", "start": 2034.55, "duration": 2.74}, {"text": "There's one, he use a skeleton\nin some of his photos.", "start": 2037.29, "duration": 2.763}, {"text": "And it's very serious.", "start": 2040.053, "duration": 0.917}, {"text": "RAMESH RASKAR: Yeah, so\nthe content sometimes", "start": 2040.97, "duration": 2.037}, {"text": "is impressive.", "start": 2043.007, "duration": 0.583}, {"text": "AUDIENCE: Right, yeah.", "start": 2043.59, "duration": 0.917}, {"text": "RAMESH RASKAR: But the\nart of photography.", "start": 2044.507, "duration": 4.071}, {"text": "Comment back there?", "start": 2048.578, "duration": 0.792}, {"text": "Somebody had a\ncomment back there?", "start": 2052.31, "duration": 1.5}, {"text": "All right.", "start": 2053.81, "duration": 0.5}, {"text": "AUDIENCE: I had one [INAUDIBLE].", "start": 2054.31, "duration": 2.197}, {"text": "I'm not sure you can\nseparate both the technique", "start": 2056.507, "duration": 2.652}, {"text": "from the content.", "start": 2059.159, "duration": 2.593}, {"text": "So this is really discretion.", "start": 2061.752, "duration": 2.058}, {"text": "But I think they\ncan come together", "start": 2063.81, "duration": 2.49}, {"text": "in creating and influencing\neach other's thoughts.", "start": 2066.3, "duration": 3.16}, {"text": "RAMESH RASKAR: You definitely\nneed better and better tools", "start": 2069.46, "duration": 3.44}, {"text": "and technologies to be\nable to create something", "start": 2072.9, "duration": 3.27}, {"text": "that's really\nexpressive, really,", "start": 2076.17, "duration": 1.87}, {"text": "really beautiful and creative.", "start": 2078.04, "duration": 5.0}, {"text": "But there was a time when\nphotographers could impress us", "start": 2083.04, "duration": 5.369}, {"text": "based on their techniques.", "start": 2088.409, "duration": 1.471}, {"text": "The guy with the\nbiggest camera was", "start": 2089.88, "duration": 2.94}, {"text": "called a professional\nphotographer, not the guy", "start": 2092.82, "duration": 2.91}, {"text": "with the best eye and\nsomebody who has the patience,", "start": 2095.73, "duration": 4.92}, {"text": "and aesthetics, and\nall of those things.", "start": 2100.65, "duration": 2.1}, {"text": "And hopefully, now we\nhave separated the two.", "start": 2102.75, "duration": 2.88}, {"text": "Just because the guy\nhas the best gear", "start": 2105.63, "duration": 3.21}, {"text": "doesn't mean he's a great\nphotographer anymore.", "start": 2108.84, "duration": 2.615}, {"text": "And that's what I mean by--", "start": 2111.455, "duration": 1.125}, {"text": "yes?", "start": 2115.92, "duration": 0.5}, {"text": "AUDIENCE: [? Great book ?]\non that topic", "start": 2116.42, "duration": 0.93}, {"text": "as well, going back to\nold master techniques.", "start": 2117.35, "duration": 1.875}, {"text": "It's called Secret\nKnowledge by David Hockney.", "start": 2119.225, "duration": 2.302}, {"text": "I don't know if everybody\nelse has read that", "start": 2121.527, "duration": 1.833}, {"text": "[INAUDIBLE] all the different", "start": 2123.36, "duration": 1.42}, {"text": "[INTERPOSING VOICES]", "start": 2124.78, "duration": 0.27}, {"text": "RAMESH RASKAR: Can\nyou just repeat?", "start": 2125.05, "duration": 1.458}, {"text": "Is David Hockney--", "start": 2126.508, "duration": 0.792}, {"text": "AUDIENCE: David Hockney.", "start": 2127.3, "duration": 1.0}, {"text": "It's called Secret Knowledge.", "start": 2128.3, "duration": 1.49}, {"text": "And it's going through all--", "start": 2129.79, "duration": 2.34}, {"text": "he worked backwards\nbased on weird artifacts", "start": 2132.13, "duration": 2.255}, {"text": "and their paintings\nto figure out", "start": 2134.385, "duration": 1.375}, {"text": "how they would make weird\noptical devices that could", "start": 2135.76, "duration": 3.183}, {"text": "create the original artwork.", "start": 2138.943, "duration": 1.167}, {"text": "And that goes back\nto the same concept", "start": 2140.11, "duration": 1.84}, {"text": "of technique, and artists,\nand where those two", "start": 2141.95, "duration": 2.487}, {"text": "[INTERPOSING VOICES]", "start": 2144.437, "duration": 0.833}, {"text": "AUDIENCE: So there\nwere from Ricoh?", "start": 2145.27, "duration": 1.48}, {"text": "RAMESH RASKAR: What's that?", "start": 2146.75, "duration": 1.125}, {"text": "AUDIENCE: From Ricoh?", "start": 2147.875, "duration": 0.889}, {"text": "RAMESH RASKAR: What do you mean?", "start": 2148.764, "duration": 0.457}, {"text": "What?", "start": 2149.221, "duration": 0.5}, {"text": "AUDIENCE: The company\nRicoh, he's from that.", "start": 2149.721, "duration": 2.328}, {"text": "RAMESH RASKAR: What?", "start": 2152.049, "duration": 0.833}, {"text": "David Hockney.", "start": 2152.882, "duration": 0.824}, {"text": "AUDIENCE: The painter.", "start": 2153.706, "duration": 0.414}, {"text": "RAMESH RASKAR: Yeah.", "start": 2154.12, "duration": 0.42}, {"text": "AUDIENCE: He's a famous painter.", "start": 2154.54, "duration": 1.333}, {"text": "RAMESH RASKAR: Oh, sorry.", "start": 2155.873, "duration": 1.997}, {"text": "Who's the guy from Rico who\ndid all the same analysis?", "start": 2157.87, "duration": 2.25}, {"text": "But this is the one\nwhere they looked at--", "start": 2163.7, "duration": 4.103}, {"text": "AUDIENCE: It's an\ninteresting read", "start": 2167.803, "duration": 1.417}, {"text": "if anybody's interested\non the history of how", "start": 2169.22, "duration": 2.61}, {"text": "these optical techniques\nplayed into the role of artists", "start": 2171.83, "duration": 3.042}, {"text": "[INAUDIBLE].", "start": 2174.872, "duration": 0.5}, {"text": "It's controversial", "start": 2175.372, "duration": 0.478}, {"text": "[INTERPOSING VOICES]", "start": 2175.85, "duration": 0.48}, {"text": "RAMESH RASKAR: Yes, exactly.", "start": 2176.33, "duration": 1.167}, {"text": "I think we're talking\nabout the same thing.", "start": 2177.497, "duration": 2.603}, {"text": "It's very controversial.", "start": 2180.1, "duration": 1.0}, {"text": "And he claims that\nthe painters knew", "start": 2181.1, "duration": 2.94}, {"text": "about perspective and so on\neven before the Renaissance", "start": 2184.04, "duration": 4.68}, {"text": "and so on.", "start": 2188.72, "duration": 0.66}, {"text": "AUDIENCE: Yeah, there's a\nlot of interesting backwards", "start": 2189.38, "duration": 2.25}, {"text": "scientific discoveries\nthat he did", "start": 2191.63, "duration": 1.417}, {"text": "based off your artifacts\nin perspective.", "start": 2193.047, "duration": 2.406}, {"text": "AUDIENCE: Yeah, I\nthink it's David Stork.", "start": 2195.453, "duration": 1.947}, {"text": "RAMESH RASKAR: David Stork", "start": 2197.4, "duration": 0.48}, {"text": "[INTERPOSING VOICES]", "start": 2197.88, "duration": 1.17}, {"text": "AUDIENCE: --Ricoh.", "start": 2199.05, "duration": 0.39}, {"text": "RAMESH RASKAR: Exactly.", "start": 2199.44, "duration": 0.285}, {"text": "AUDIENCE: Yeah.", "start": 2199.725, "duration": 0.615}, {"text": "RAMESH RASKAR: Is that the\nsame thing we're talking about?", "start": 2200.34, "duration": 1.71}, {"text": "AUDIENCE: Different\nbut maybe related?", "start": 2202.05, "duration": 1.89}, {"text": "AUDIENCE: I think they\ndo similar things.", "start": 2203.94, "duration": 2.44}, {"text": "David Stork writes about\noptical projections for planes.", "start": 2206.38, "duration": 3.515}, {"text": "And so it's probably similar.", "start": 2209.895, "duration": 2.695}, {"text": "RAMESH RASKAR: So David\nStork and David Hockney.", "start": 2212.59, "duration": 2.352}, {"text": "All right.", "start": 2214.942, "duration": 2.948}, {"text": "My laptop is recording again.", "start": 2217.89, "duration": 1.34}, {"text": "That's fine.", "start": 2219.23, "duration": 2.56}, {"text": "So yeah, so I think\nthat's a great challenge", "start": 2221.79, "duration": 4.12}, {"text": "we have about how--", "start": 2225.91, "duration": 1.61}, {"text": "the same way a camera put\nphotorealistic paintings.", "start": 2227.52, "duration": 7.95}, {"text": "They made them boring and\nbasically put that breed", "start": 2235.47, "duration": 4.41}, {"text": "of painters out of business.", "start": 2239.88, "duration": 2.55}, {"text": "What will be the\nnext imaging paradigm", "start": 2242.43, "duration": 4.74}, {"text": "that we'll put to\nthis camera that", "start": 2247.17, "duration": 4.4}, {"text": "would make these cameras boring,\nobsolete, and out of business?", "start": 2251.57, "duration": 6.23}, {"text": "Because there's\nonly so far you can", "start": 2257.8, "duration": 2.04}, {"text": "go with a device that\nrecords light and tries", "start": 2259.84, "duration": 6.93}, {"text": "to be realistic with a\ngood signal-to-noise ratio", "start": 2266.77, "duration": 4.68}, {"text": "converting photons\ninto electrons.", "start": 2271.45, "duration": 2.89}, {"text": "That's not what humans do.", "start": 2274.34, "duration": 2.9}, {"text": "We don't see with\nour eyes at all.", "start": 2277.24, "duration": 3.17}, {"text": "We just record with our eyes.", "start": 2280.41, "duration": 1.85}, {"text": "And we see with our brain.", "start": 2282.26, "duration": 2.61}, {"text": "And right now,\nthere is very little", "start": 2284.87, "duration": 2.67}, {"text": "suppression in our\nimaging devices", "start": 2287.54, "duration": 3.06}, {"text": "about sensing and seeing.", "start": 2290.6, "duration": 5.85}, {"text": "But the whole concept behind\ncomputational photography", "start": 2296.45, "duration": 4.14}, {"text": "is that these two processes\nare completely separate.", "start": 2300.59, "duration": 3.15}, {"text": "They can be decoupled.", "start": 2303.74, "duration": 1.5}, {"text": "You can sense in some crazy\nway with some crazy mechanism", "start": 2305.24, "duration": 3.6}, {"text": "and then use a\nlot of computation", "start": 2308.84, "duration": 2.07}, {"text": "to create images or create\nvisual experiences that", "start": 2310.91, "duration": 5.34}, {"text": "are very different.", "start": 2316.25, "duration": 3.1}, {"text": "And if you look at--", "start": 2319.35, "duration": 2.3}, {"text": "Dan in my group and\nothers have put up", "start": 2321.65, "duration": 2.13}, {"text": "together this really beautiful\ndigital totem in our area.", "start": 2323.78, "duration": 4.47}, {"text": "And it's constantly streaming\nthe most interesting images", "start": 2328.25, "duration": 3.09}, {"text": "on Flickr.", "start": 2331.34, "duration": 1.17}, {"text": "And you stand in\nfront of that, you", "start": 2332.51, "duration": 1.98}, {"text": "will realize that\nif anybody is saying", "start": 2334.49, "duration": 4.2}, {"text": "that the goal of a camera\nis to mimic a human eye,", "start": 2338.69, "duration": 3.82}, {"text": "and that's what makes\nit a good camera,", "start": 2342.51, "duration": 3.557}, {"text": "that notion will be\nchallenged, because most", "start": 2346.067, "duration": 1.833}, {"text": "of those photos which are\ntagged interesting by thousands", "start": 2347.9, "duration": 4.17}, {"text": "of people on Flickr\nare actually the photos", "start": 2352.07, "duration": 2.97}, {"text": "you don't see with your eyes.", "start": 2355.04, "duration": 3.27}, {"text": "It has some really crazy focus.", "start": 2358.31, "duration": 3.57}, {"text": "It has very different\ncolor response curves.", "start": 2361.88, "duration": 6.94}, {"text": "It has very different\nzoom and so on.", "start": 2368.82, "duration": 3.54}, {"text": "It's basically\nthings-- people think", "start": 2372.36, "duration": 1.79}, {"text": "it's interesting when\nit's not what you", "start": 2374.15, "duration": 3.6}, {"text": "see with your own naked eye.", "start": 2377.75, "duration": 1.98}, {"text": "And that's what the goal--\nif you take the concept for--", "start": 2379.73, "duration": 4.17}, {"text": "right now, people are\ntrying to use cameras", "start": 2383.9, "duration": 1.95}, {"text": "that are built to\nmimic the human eye", "start": 2385.85, "duration": 2.01}, {"text": "and pushing them\nto create things", "start": 2387.86, "duration": 2.19}, {"text": "that don't mimic the human eye.", "start": 2390.05, "duration": 2.13}, {"text": "If you take that\nfurther, why not", "start": 2392.18, "duration": 3.24}, {"text": "start building\nimaging platforms that", "start": 2395.42, "duration": 2.34}, {"text": "have nothing to do with\ncapturing a 2D perspective", "start": 2397.76, "duration": 4.81}, {"text": "photo?", "start": 2402.57, "duration": 1.56}, {"text": "And that's what\nwe'll see real soon.", "start": 2404.13, "duration": 1.5}, {"text": "So I'm looking towards an\nimaging platform that can just", "start": 2405.63, "duration": 3.56}, {"text": "create abstract visual art.", "start": 2409.19, "duration": 2.158}, {"text": "I don't know what that will be.", "start": 2411.348, "duration": 1.292}, {"text": "But go ahead.", "start": 2412.64, "duration": 1.794}, {"text": "AUDIENCE: I guess this\nis more of a question", "start": 2414.434, "duration": 2.868}, {"text": "or a topic for your discussion.", "start": 2417.302, "duration": 1.912}, {"text": "But what do you imagine the--", "start": 2419.214, "duration": 3.492}, {"text": "what is the fundamental\nphotography or class", "start": 2422.706, "duration": 3.839}, {"text": "of images that makes it lasting\nas opposed to the art tied", "start": 2426.545, "duration": 7.155}, {"text": "to technology, which is batty.", "start": 2433.7, "duration": 4.38}, {"text": "In the past year or so,\n[INAUDIBLE] photography.", "start": 2438.08, "duration": 3.238}, {"text": "And they", "start": 2441.318, "duration": 1.209}, {"text": "[INTERPOSING VOICES]", "start": 2442.527, "duration": 0.833}, {"text": "[LAUGHTER]", "start": 2443.36, "duration": 1.12}, {"text": "RAMESH RASKAR: Right.", "start": 2444.48, "duration": 0.13}, {"text": "AUDIENCE: So it's entering\nthe life of kitsch.", "start": 2444.61, "duration": 1.94}, {"text": "RAMESH RASKAR: Right.", "start": 2446.55, "duration": 1.23}, {"text": "AUDIENCE: Or even in\nHDR, you see a lot of--", "start": 2447.78, "duration": 4.02}, {"text": "it was in the beginning.", "start": 2451.8, "duration": 3.27}, {"text": "And now, it feels like\nit's run its course.", "start": 2455.07, "duration": 3.798}, {"text": "RAMESH RASKAR: Yes.", "start": 2458.868, "duration": 0.792}, {"text": "AUDIENCE: And so\nbut there's still", "start": 2459.66, "duration": 1.47}, {"text": "photography in the\ntraditional sense of capturing", "start": 2461.13, "duration": 4.05}, {"text": "what the human eye sees is\nfundamental in some way, which", "start": 2465.18, "duration": 4.85}, {"text": "is separate from the technique,\nthings like [INAUDIBLE]..", "start": 2470.03, "duration": 6.93}, {"text": "So I guess the question\nthat I have is,", "start": 2476.96, "duration": 2.43}, {"text": "what is the fundamental of\nthe photographic medium?", "start": 2479.39, "duration": 3.96}, {"text": "And in terms of\ntechnology, what would", "start": 2483.35, "duration": 2.88}, {"text": "be the fundamental technological\n[? ability ?] as opposed", "start": 2486.23, "duration": 3.82}, {"text": "to separating that from kitsch?", "start": 2490.05, "duration": 1.832}, {"text": "RAMESH RASKAR: I agree.", "start": 2491.882, "duration": 0.958}, {"text": "I agree.", "start": 2492.84, "duration": 0.52}, {"text": "I think the camera, to\nme, it's just a sensor.", "start": 2493.36, "duration": 5.27}, {"text": "It's just a transducer.", "start": 2498.63, "duration": 1.77}, {"text": "And people say,\nwow, if the camera", "start": 2500.4, "duration": 3.57}, {"text": "is going to change,\nfundamentally,", "start": 2503.97, "duration": 3.36}, {"text": "it's still going to\nconvert electrons", "start": 2507.33, "duration": 2.28}, {"text": "into photons and photons into--", "start": 2509.61, "duration": 2.57}, {"text": "sorry, photons into\nelectrons, and electrons", "start": 2512.18, "duration": 2.35}, {"text": "into pixels, and so on.", "start": 2514.53, "duration": 2.64}, {"text": "The laws of physics are not\ngoing to change anytime soon.", "start": 2517.17, "duration": 4.03}, {"text": "So how we use it, though, it's\ngoing to change altogether.", "start": 2521.2, "duration": 7.61}, {"text": "And this notion that once you\ntake a picture, that's set,", "start": 2528.81, "duration": 4.23}, {"text": "use the best possible\noptics and sensor", "start": 2533.04, "duration": 3.81}, {"text": "so that it captured image\nand that you can see later", "start": 2536.85, "duration": 3.03}, {"text": "is changing.", "start": 2539.88, "duration": 0.84}, {"text": "So it will shift.", "start": 2540.72, "duration": 1.427}, {"text": "I'm glad you brought it\nup because that's the very", "start": 2542.147, "duration": 2.083}, {"text": "next thing I was going to show.", "start": 2544.23, "duration": 1.292}, {"text": "This is going before that.", "start": 2548.37, "duration": 1.62}, {"text": "I'll come to this.", "start": 2549.99, "duration": 2.35}, {"text": "[INAUDIBLE] some other\ninteresting images", "start": 2552.34, "duration": 2.66}, {"text": "are time lapse mosaics.", "start": 2555.0, "duration": 1.11}, {"text": "So again, I sat in my office and\ntook these time lapse pictures.", "start": 2556.11, "duration": 5.22}, {"text": "And on the left\nside, it's daytime.", "start": 2561.33, "duration": 2.05}, {"text": "Bright time, it's nighttime.", "start": 2563.38, "duration": 2.24}, {"text": "And all I'm doing is just\npicking up strips of the images", "start": 2565.62, "duration": 5.1}, {"text": "from different times of day.", "start": 2570.72, "duration": 1.8}, {"text": "And [INAUDIBLE]\nannoying artifacts", "start": 2572.52, "duration": 2.73}, {"text": "because it's on\nsome other exposure.", "start": 2575.25, "duration": 2.16}, {"text": "But using a gradient\ndomain technique,", "start": 2577.41, "duration": 2.818}, {"text": "you can create a very\nsmooth transition.", "start": 2580.228, "duration": 1.667}, {"text": "AUDIENCE: [INAUDIBLE] cop car.", "start": 2581.895, "duration": 2.055}, {"text": "AUDIENCE: Yeah, cop cars and--", "start": 2583.95, "duration": 2.422}, {"text": "RAMESH RASKAR: Yeah, exactly.", "start": 2586.372, "duration": 1.208}, {"text": "It still has those problems.", "start": 2587.58, "duration": 2.16}, {"text": "So I don't have\nas much patience.", "start": 2589.74, "duration": 1.44}, {"text": "And I'm only doing it\nsitting in my office.", "start": 2591.18, "duration": 2.37}, {"text": "But it's just a tool that\nphotographers could create,", "start": 2593.55, "duration": 6.15}, {"text": "create images that have a very\ndifferent notion than what", "start": 2599.7, "duration": 4.08}, {"text": "your eye will see if you're\nthere sitting in an office.", "start": 2603.78, "duration": 2.405}, {"text": "Of course, hopefully,\nthis can be", "start": 2606.185, "duration": 1.375}, {"text": "done in Times Square or some\nreally interesting places.", "start": 2607.56, "duration": 3.6}, {"text": "And by the way, this one is\nalso catching up now on Flickr,", "start": 2611.16, "duration": 3.12}, {"text": "a lot of people who\nare trying to do this.", "start": 2614.28, "duration": 1.95}, {"text": "We did this in 2002.", "start": 2616.23, "duration": 2.688}, {"text": "But--", "start": 2618.918, "duration": 0.912}, {"text": "AUDIENCE: So in lots of\nexamples we saw here,", "start": 2619.83, "duration": 3.21}, {"text": "the final result is an image\nlike a final master in sound,", "start": 2623.04, "duration": 5.82}, {"text": "where you do all equalizing.", "start": 2628.86, "duration": 3.78}, {"text": "There is one sound.", "start": 2632.64, "duration": 1.08}, {"text": "And lots of techniques now\ncould be also interactive.", "start": 2633.72, "duration": 2.82}, {"text": "You could actually go\nand those will be made.", "start": 2636.54, "duration": 3.575}, {"text": "It goes through\nevery part of it,", "start": 2640.115, "duration": 1.375}, {"text": "because that is the final\ngoal is to understand it.", "start": 2641.49, "duration": 3.82}, {"text": "There is this idea that there\nis something complex about who", "start": 2645.31, "duration": 2.63}, {"text": "[INAUDIBLE].", "start": 2647.94, "duration": 1.386}, {"text": "And it could be\ninteractive as well.", "start": 2649.326, "duration": 1.519}, {"text": "RAMESH RASKAR: Right.", "start": 2650.845, "duration": 0.875}, {"text": "AUDIENCE: So in one sense,\nthe [INAUDIBLE] goal", "start": 2651.72, "duration": 2.04}, {"text": "is always to create a new\nstatic image or media.", "start": 2653.76, "duration": 5.52}, {"text": "The interactive parts\nwould be so interesting.", "start": 2659.28, "duration": 3.012}, {"text": "RAMESH RASKAR:\nYeah, I think you're", "start": 2662.292, "duration": 1.458}, {"text": "pointing to a very important\nfundamental, again,", "start": 2663.75, "duration": 3.54}, {"text": "constraint we have\nput on ourselves.", "start": 2667.29, "duration": 1.5}, {"text": "That an imaging device should\ncreate, eventually, a 2D photo.", "start": 2668.79, "duration": 4.925}, {"text": "AUDIENCE: Yeah.", "start": 2673.715, "duration": 0.625}, {"text": "RAMESH RASKAR: And that's very\nlimiting, extremely limiting.", "start": 2674.34, "duration": 3.21}, {"text": "And we will be spending\na little bit of time", "start": 2677.55, "duration": 3.36}, {"text": "near the end of the semester\ntalking about display", "start": 2680.91, "duration": 2.25}, {"text": "technologies,\nbecause unless there", "start": 2683.16, "duration": 3.54}, {"text": "is corresponding innovation,\nand research, and products,", "start": 2686.7, "duration": 4.62}, {"text": "and services in display, it\ndoesn't make sense to spend", "start": 2691.32, "duration": 3.39}, {"text": "a lot of time on sensors.", "start": 2694.71, "duration": 3.12}, {"text": "So yeah, the two have\nto go hand-in-hand.", "start": 2697.83, "duration": 1.915}, {"text": "And there are some\nexciting directions there.", "start": 2699.745, "duration": 1.875}, {"text": "So the last chapter\nof our book talks", "start": 2701.62, "duration": 2.09}, {"text": "all about these other\nparallel developments", "start": 2703.71, "duration": 2.85}, {"text": "that's going to change\nhow we-- so for example,", "start": 2706.56, "duration": 2.1}, {"text": "we have 60 displayed now.", "start": 2708.66, "duration": 1.11}, {"text": "AUDIENCE: Because even\nin the simple 2D display,", "start": 2709.77, "duration": 3.15}, {"text": "there is this project\ncalled Photos Projector.", "start": 2712.92, "duration": 2.34}, {"text": "Maybe you know.", "start": 2715.26, "duration": 0.625}, {"text": "That's also in this, where\nyou can find any [INAUDIBLE]", "start": 2715.885, "duration": 5.825}, {"text": "in time.", "start": 2721.71, "duration": 1.26}, {"text": "So it's another way of\nalso exploring this.", "start": 2722.97, "duration": 2.02}, {"text": "It's", "start": 2724.99, "duration": 0.5}, {"text": "[INTERPOSING VOICES]", "start": 2725.49, "duration": 0.432}, {"text": "RAMESH RASKAR: Exactly.", "start": 2725.922, "duration": 0.958}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2726.88, "duration": 1.13}, {"text": "RAMESH RASKAR: Exactly.", "start": 2728.01, "duration": 0.958}, {"text": "AUDIENCE: And by taking--", "start": 2728.968, "duration": 1.262}, {"text": "giving the controls to the user,\nit will be used to empower him.", "start": 2730.23, "duration": 2.805}, {"text": "RAMESH RASKAR: Right.", "start": 2733.035, "duration": 0.875}, {"text": "AUDIENCE: Then just\nto one final comment", "start": 2733.91, "duration": 2.77}, {"text": "representation [INAUDIBLE].", "start": 2736.68, "duration": 1.262}, {"text": "RAMESH RASKAR: Exactly.", "start": 2737.942, "duration": 0.958}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2738.9, "duration": 1.11}, {"text": "RAMESH RASKAR: Exactly.", "start": 2740.01, "duration": 0.958}, {"text": "So navigating through\nphotos is a great way.", "start": 2740.968, "duration": 3.902}, {"text": "But at the same time--", "start": 2744.87, "duration": 1.23}, {"text": "I love this process.", "start": 2746.1, "duration": 0.833}, {"text": "At the same time,\nwe want to think", "start": 2746.933, "duration": 1.417}, {"text": "about something that scales.", "start": 2748.35, "duration": 1.2}, {"text": "AUDIENCE: Yes.", "start": 2749.55, "duration": 0.33}, {"text": "RAMESH RASKAR: And build\nit so people can use it.", "start": 2749.88, "duration": 1.44}, {"text": "AUDIENCE: Yes.", "start": 2751.32, "duration": 0.67}, {"text": "RAMESH RASKAR: So that's\nanother challenge.", "start": 2751.99, "duration": 1.88}, {"text": "So let's shift.", "start": 2753.87, "duration": 1.83}, {"text": "I'm glad you brought it up.", "start": 2755.7, "duration": 1.74}, {"text": "This is the latest\nfad on Flickr.", "start": 2757.44, "duration": 4.05}, {"text": "I think, yeah, the HDR,\nit's reaching its--", "start": 2761.49, "duration": 5.01}, {"text": "it's bottoming out now.", "start": 2766.5, "duration": 2.64}, {"text": "But this is tilt-shift\nimaging, where this looks", "start": 2769.14, "duration": 5.34}, {"text": "like a tabletop toy scene.", "start": 2774.48, "duration": 5.13}, {"text": "But it's actually taken from\nhundreds of meters away.", "start": 2779.61, "duration": 3.39}, {"text": "This is in Rajasthan, the city\nof Jodhpur, the Blue City.", "start": 2783.0, "duration": 4.29}, {"text": "And that's when you haven't\nused the tilt-shift class.", "start": 2787.29, "duration": 4.89}, {"text": "So in the basic principles,\nyou want to create--", "start": 2792.18, "duration": 7.07}, {"text": "instead of making-- keeping\nthe lens, and the image plane,", "start": 2799.25, "duration": 3.06}, {"text": "and the plane of focus\nparallel to each other,", "start": 2802.31, "duration": 2.52}, {"text": "if you tilt the lens with\nrespect to the sensor,", "start": 2804.83, "duration": 2.91}, {"text": "then it turns out the plane\nat which things are in focus,", "start": 2807.74, "duration": 3.43}, {"text": "the plane of focus, also tilts.", "start": 2811.17, "duration": 2.48}, {"text": "And this is based on the\nshift-tilt principle.", "start": 2813.65, "duration": 2.46}, {"text": "And credit this in detail\nwhen we come back to optics", "start": 2816.11, "duration": 2.91}, {"text": "and light [INAUDIBLE].", "start": 2819.02, "duration": 2.04}, {"text": "But I just wanted to bring\nthis up because it's fun.", "start": 2821.06, "duration": 4.95}, {"text": "And you can play with it.", "start": 2826.01, "duration": 2.64}, {"text": "All right.", "start": 2828.65, "duration": 1.02}, {"text": "So let's talk about\nsome other things.", "start": 2829.67, "duration": 6.94}, {"text": "So illumination.", "start": 2836.61, "duration": 1.88}, {"text": "You can use it in\nvery interesting ways.", "start": 2841.97, "duration": 3.46}, {"text": "Here's the project, I\nbelieve, from Georgia Tech,", "start": 2845.43, "duration": 5.24}, {"text": "where they created an\nanti-paparazzi flash.", "start": 2850.67, "duration": 2.985}, {"text": "[LAUGHTER]", "start": 2853.655, "duration": 1.045}, {"text": "And as you can see,\nthe way it works", "start": 2855.91, "duration": 1.98}, {"text": "is the paparazzi will take a\nphoto of a celebrity coming", "start": 2857.89, "duration": 5.22}, {"text": "out.", "start": 2863.11, "duration": 1.44}, {"text": "As soon as the\nflash goes off, it's", "start": 2864.55, "duration": 2.94}, {"text": "detected by some\nelectronic device.", "start": 2867.49, "duration": 4.11}, {"text": "And it will blast more\nlight so that what", "start": 2871.6, "duration": 5.43}, {"text": "the paparazzi will get in the\ncamera is some blown out photo.", "start": 2877.03, "duration": 4.59}, {"text": "How does it work?", "start": 2884.73, "duration": 2.97}, {"text": "You can-- so let's say this is--", "start": 2887.7, "duration": 3.48}, {"text": "let me make sure I understand.", "start": 2891.18, "duration": 1.29}, {"text": "So it comes out a\ntraditional camera.", "start": 2892.47, "duration": 3.0}, {"text": "Especially a [INAUDIBLE] camera\nis actually a retroreflector.", "start": 2895.47, "duration": 4.8}, {"text": "I'll explain that in a minute.", "start": 2900.27, "duration": 2.86}, {"text": "So if you take a flash photo,\nespecially a cell phone camera,", "start": 2903.13, "duration": 7.85}, {"text": "then it appears as a bright\nspot in the flash photography.", "start": 2910.98, "duration": 6.18}, {"text": "So what we're going to do is\nthis guy here is actually--", "start": 2917.16, "duration": 3.78}, {"text": "it's going to be a camera\nwith a ring of LED lights,", "start": 2920.94, "duration": 4.44}, {"text": "which is this one here.", "start": 2925.38, "duration": 2.95}, {"text": "And right next to it is\ngoing to be a projector.", "start": 2928.33, "duration": 3.41}, {"text": "So this is mounted in the\nceiling, a camera with LED", "start": 2931.74, "duration": 4.5}, {"text": "lights and a projector.", "start": 2936.24, "duration": 2.7}, {"text": "Now these LED lights\nare on all the time.", "start": 2938.94, "duration": 2.13}, {"text": "And a paparazzi's camera\nwill appear as a bright spot", "start": 2941.07, "duration": 8.82}, {"text": "because it's a retroreflector.", "start": 2949.89, "duration": 2.91}, {"text": "And this projector\nthen, which is", "start": 2952.8, "duration": 2.4}, {"text": "right below the mounted camera,\nwill turn on the lights,", "start": 2955.2, "duration": 4.86}, {"text": "turn on some pixels that are\npointed towards this paparazzi.", "start": 2960.06, "duration": 6.27}, {"text": "And so basically, you'll always\nsee this very bright light,", "start": 2966.33, "duration": 3.27}, {"text": "bright spotlight, being put on\n[? hand. ?] At the same time,", "start": 2969.6, "duration": 3.062}, {"text": "the rest of the scene\nis going to be dark", "start": 2972.662, "duration": 1.708}, {"text": "because only those pixels of the\nprojector are being turned on.", "start": 2974.37, "duration": 4.14}, {"text": "And that's why your camera,\nwhen it takes a picture, where", "start": 2978.51, "duration": 4.14}, {"text": "it will just see this really\nbright source that's blowing", "start": 2982.65, "duration": 3.96}, {"text": "out the rest of the scene.", "start": 2986.61, "duration": 2.56}, {"text": "Yes?", "start": 2989.17, "duration": 0.68}, {"text": "AUDIENCE: What about\nsurveillance cameras?", "start": 2989.85, "duration": 3.3}, {"text": "We don't want to bomb them?", "start": 2993.15, "duration": 2.967}, {"text": "RAMESH RASKAR: So\nsurveillance cameras are--", "start": 2996.117, "duration": 1.833}, {"text": "what's the question?", "start": 3004.88, "duration": 0.91}, {"text": "AUDIENCE: I--", "start": 3005.79, "duration": 0.706}, {"text": "[LAUGHTER]", "start": 3006.496, "duration": 2.011}, {"text": "Are they-- if, for example,\nwe want surveillance cameras", "start": 3008.507, "duration": 3.573}, {"text": "to just monitor that\nregion, and then", "start": 3012.08, "duration": 2.7}, {"text": "we have this device there that\nbombs every camera that it", "start": 3014.78, "duration": 3.21}, {"text": "finds, then probably we are\nnot capturing any information.", "start": 3017.99, "duration": 2.94}, {"text": "RAMESH RASKAR: Yeah, exactly.", "start": 3020.93, "duration": 0.675}, {"text": "All right.", "start": 3021.605, "duration": 0.5}, {"text": "So the point is, can you--", "start": 3022.105, "duration": 2.207}, {"text": "[INTERPOSING VOICES]", "start": 3024.312, "duration": 0.833}, {"text": "RAMESH RASKAR: --defeat\nsurveillance cameras", "start": 3025.145, "duration": 1.833}, {"text": "[INAUDIBLE]?", "start": 3026.978, "duration": 1.062}, {"text": "Yeah, there are-- we will\nlearn a lot of interesting ways", "start": 3028.04, "duration": 3.21}, {"text": "you can beat traffic cameras\nor those cameras in this class.", "start": 3031.25, "duration": 3.9}, {"text": "But that will all happen\nat the very [? chance. ?]", "start": 3035.15, "duration": 2.31}, {"text": "[LAUGHTER]", "start": 3037.46, "duration": 1.924}, {"text": "[INAUDIBLE]", "start": 3039.384, "duration": 2.886}, {"text": "So what is there to reflect?", "start": 3042.27, "duration": 2.57}, {"text": "And we'll look at those.", "start": 3044.84, "duration": 2.61}, {"text": "Can you guys all\nsee this over here?", "start": 3047.45, "duration": 2.055}, {"text": "[INAUDIBLE]", "start": 3049.505, "duration": 0.885}, {"text": "So if you have a traditional\nsurface, like a wall,", "start": 3056.89, "duration": 3.71}, {"text": "light comes in.", "start": 3060.6, "duration": 1.78}, {"text": "And it gets reflected\nin our direction.", "start": 3062.38, "duration": 3.03}, {"text": "And you've got a\ndiffuse [INAUDIBLE]..", "start": 3065.41, "duration": 3.11}, {"text": "If you have a mirror, then\nlight comes in and gets", "start": 3068.52, "duration": 3.39}, {"text": "reflected symmetric\naround the [INAUDIBLE]..", "start": 3071.91, "duration": 6.94}, {"text": "But most surfaces,\nlike this surface", "start": 3078.85, "duration": 4.87}, {"text": "here, over here, light comes in.", "start": 3083.72, "duration": 2.03}, {"text": "And it doesn't reflect\nin a uniform way.", "start": 3085.75, "duration": 5.76}, {"text": "And it doesn't\nbehave like a mirror.", "start": 3091.51, "duration": 1.53}, {"text": "It's somewhere in between.", "start": 3093.04, "duration": 1.27}, {"text": "So you get a bright spot.", "start": 3094.31, "duration": 2.0}, {"text": "But you also get some other\n[INAUDIBLE] and so on.", "start": 3096.31, "duration": 4.35}, {"text": "Is that clear?", "start": 3100.66, "duration": 1.98}, {"text": "So diffuse, light comes in,\ngets tilted in all directions.", "start": 3102.64, "duration": 3.6}, {"text": "Mirror goes in one direction.", "start": 3106.24, "duration": 1.83}, {"text": "And a shiny surface is\nsomewhere in between.", "start": 3108.07, "duration": 3.06}, {"text": "There's other surfaces\nwhere light comes in", "start": 3113.86, "duration": 4.09}, {"text": "and it reflects back\nin the same direction.", "start": 3117.95, "duration": 2.27}, {"text": "And same surface, the\nlight comes in and reflects", "start": 3123.1, "duration": 2.85}, {"text": "back again to the same place.", "start": 3125.95, "duration": 3.15}, {"text": "And this is retroreflective.", "start": 3129.1, "duration": 1.68}, {"text": "And this is very useful material\nthat you can use in many cases.", "start": 3135.64, "duration": 4.16}, {"text": "Anybody know where this is used?", "start": 3139.8, "duration": 2.535}, {"text": "[INTERPOSING VOICES]", "start": 3142.335, "duration": 1.575}, {"text": "RAMESH RASKAR: The back of\nyour backpack [INAUDIBLE]..", "start": 3143.91, "duration": 4.74}, {"text": "That's reflector\nof the [INAUDIBLE]..", "start": 3148.65, "duration": 2.06}, {"text": "AUDIENCE: [INAUDIBLE]\nsystem [INAUDIBLE]..", "start": 3153.53, "duration": 3.717}, {"text": "RAMESH RASKAR: Oh, that's right.", "start": 3157.247, "duration": 1.333}, {"text": "[INAUDIBLE], yeah.", "start": 3158.58, "duration": 2.07}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3160.65, "duration": 2.45}, {"text": "RAMESH RASKAR: [INAUDIBLE] on\nsame principle as the camera", "start": 3163.1, "duration": 2.98}, {"text": "and the signal [INAUDIBLE].", "start": 3166.08, "duration": 2.4}, {"text": "So human eyes also reflect.", "start": 3168.48, "duration": 3.57}, {"text": "And we'll see what happens.", "start": 3172.05, "duration": 1.72}, {"text": "So this is a principle\nof retroreflection.", "start": 3173.77, "duration": 2.703}, {"text": "How it may work, there\nare multiple ways", "start": 3176.473, "duration": 1.667}, {"text": "you can make it happen.", "start": 3178.14, "duration": 0.958}, {"text": "You can just have a so-called\n[INAUDIBLE] situation.", "start": 3179.098, "duration": 3.452}, {"text": "If I put a [INAUDIBLE],,\nwhich is the mirror,", "start": 3182.55, "duration": 3.93}, {"text": "then it comes out no matter\nwhich direction light comes in.", "start": 3186.48, "duration": 3.82}, {"text": "It goes back in\nthe same direction.", "start": 3190.3, "duration": 2.43}, {"text": "It comes from here.", "start": 3192.73, "duration": 1.602}, {"text": "And here, it goes back\nthe same direction.", "start": 3194.332, "duration": 3.808}, {"text": "So [INAUDIBLE] is a very\nuseful retroreflector.", "start": 3198.14, "duration": 3.15}, {"text": "In fact, if you go to many\nshops, especially tiny shops", "start": 3201.29, "duration": 4.5}, {"text": "which put mirrors on\ntheir walls to make", "start": 3205.79, "duration": 2.13}, {"text": "it look like it's much larger\n[INAUDIBLE] reflections,", "start": 3207.92, "duration": 5.4}, {"text": "and you stand at the corner\nof such [INAUDIBLE] shops,", "start": 3213.32, "duration": 6.05}, {"text": "you look at the corner, you\nwill see your own mirror", "start": 3219.37, "duration": 2.77}, {"text": "image, which is strange because\nthey say this is a shop.", "start": 3222.14, "duration": 5.13}, {"text": "And there's a mirror here.", "start": 3227.27, "duration": 1.74}, {"text": "And you're standing here.", "start": 3229.01, "duration": 1.67}, {"text": "You'll see your own reflection\nhere in this mirror.", "start": 3230.68, "duration": 2.56}, {"text": "And you'll also see your own\nreflection here in this mirror.", "start": 3233.24, "duration": 3.43}, {"text": "But you'll also see you have\none image here in the corner.", "start": 3236.67, "duration": 4.98}, {"text": "And as you move around, this\nimage will move with you.", "start": 3241.65, "duration": 4.43}, {"text": "This image will move with you.", "start": 3246.08, "duration": 1.38}, {"text": "But this image will\nalways be in the corner.", "start": 3247.46, "duration": 4.47}, {"text": "It's retroreflection.", "start": 3251.93, "duration": 1.42}, {"text": "I look at the corner,\nI always see myself.", "start": 3253.35, "duration": 5.3}, {"text": "So I'm surprised we don't have\nmirrors like this in our house", "start": 3258.65, "duration": 2.552}, {"text": "so that I don't have to actually\ngo in front of the mirror.", "start": 3261.202, "duration": 2.458}, {"text": "I could be anywhere in the room.", "start": 3263.66, "duration": 1.5}, {"text": "And I will still see\nmyself no matter what I do.", "start": 3265.16, "duration": 3.787}, {"text": "So you could build\na mirror like that.", "start": 3268.947, "duration": 1.583}, {"text": "It's just that you [INAUDIBLE].", "start": 3270.53, "duration": 3.32}, {"text": "Yes?", "start": 3273.85, "duration": 0.5}, {"text": "AUDIENCE: Can you use it also\nfor measuring [INAUDIBLE]", "start": 3274.35, "duration": 2.22}, {"text": "laser?", "start": 3276.57, "duration": 0.42}, {"text": "RAMESH RASKAR: Yes.", "start": 3276.99, "duration": 0.792}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3277.782, "duration": 0.978}, {"text": "RAMESH RASKAR: Exactly.", "start": 3278.76, "duration": 0.255}, {"text": "[INTERPOSING VOICES]", "start": 3279.015, "duration": 0.833}, {"text": "RAMESH RASKAR: [INAUDIBLE]", "start": 3279.848, "duration": 2.902}, {"text": "AUDIENCE: Very good\nangles [INAUDIBLE] for", "start": 3282.75, "duration": 4.96}, {"text": "[INTERPOSING VOICES]", "start": 3287.71, "duration": 1.04}, {"text": "AUDIENCE: Yeah.", "start": 3288.75, "duration": 0.625}, {"text": "RAMESH RASKAR: Yeah, so\nthat's one way of doing it.", "start": 3289.375, "duration": 2.225}, {"text": "Yes?", "start": 3291.6, "duration": 0.38}, {"text": "AUDIENCE: Is [INAUDIBLE]\nreduction also required?", "start": 3291.98, "duration": 2.042}, {"text": "Because rhetorically--", "start": 3294.022, "duration": 1.088}, {"text": "RAMESH RASKAR: Very good point.", "start": 3295.11, "duration": 0.66}, {"text": "Very good point.", "start": 3295.77, "duration": 0.667}, {"text": "So whether reduction is\nlike [INAUDIBLE],, you see--", "start": 3296.437, "duration": 3.323}, {"text": "and the color red is because\nthe chemicals are [INAUDIBLE]", "start": 3299.76, "duration": 7.13}, {"text": "AUDIENCE: [INAUDIBLE]\nalso, [INAUDIBLE]..", "start": 3306.89, "duration": 1.778}, {"text": "RAMESH RASKAR: Huh?", "start": 3308.668, "duration": 0.792}, {"text": "AUDIENCE: That\ncould [INAUDIBLE]..", "start": 3309.46, "duration": 1.962}, {"text": "RAMESH RASKAR: Exactly.", "start": 3311.422, "duration": 0.958}, {"text": "Now both of those are\nanother way of doing it.", "start": 3312.38, "duration": 2.21}, {"text": "So you-- so once [INAUDIBLE]\nthe other way is--", "start": 3314.59, "duration": 4.56}, {"text": "[INAUDIBLE] property\nof this one is", "start": 3319.15, "duration": 2.01}, {"text": "you know how people will say,\nin the mirror, you get confused.", "start": 3321.16, "duration": 2.617}, {"text": "If you move your left hand,\nyour right hand moves.", "start": 3323.777, "duration": 2.083}, {"text": "And you move the right\nhand, the right hand moves.", "start": 3325.86, "duration": 2.35}, {"text": "The [INAUDIBLE],,\nthat doesn't happen.", "start": 3328.21, "duration": 1.81}, {"text": "You can move this\nhand [INAUDIBLE]..", "start": 3330.02, "duration": 3.52}, {"text": "You can move this\nhand so your image,", "start": 3333.54, "duration": 6.67}, {"text": "it's not clear [INAUDIBLE].", "start": 3340.21, "duration": 1.605}, {"text": "Is there a shop around here\nwith mirrors like this?", "start": 3346.205, "duration": 2.125}, {"text": "You use the [INAUDIBLE].", "start": 3351.22, "duration": 1.285}, {"text": "All right.", "start": 3355.82, "duration": 0.5}, {"text": "So other one is false.", "start": 3356.32, "duration": 2.08}, {"text": "If I just take a shiny--", "start": 3358.4, "duration": 3.86}, {"text": "this is the last\n[INAUDIBLE],, actually.", "start": 3362.26, "duration": 2.4}, {"text": "Night comes in.", "start": 3364.66, "duration": 1.94}, {"text": "It reflects because\nof this refraction.", "start": 3366.6, "duration": 6.34}, {"text": "And then, it reflects\nagain because, of course,", "start": 3372.94, "duration": 1.96}, {"text": "we need another reflection.", "start": 3374.9, "duration": 1.125}, {"text": "There's a refractive\nindex here [INAUDIBLE]..", "start": 3376.025, "duration": 4.16}, {"text": "And then, it goes back out.", "start": 3380.185, "duration": 2.485}, {"text": "And then [INAUDIBLE].", "start": 3382.67, "duration": 3.76}, {"text": "So that's how a glass bead-based\nretroreflector would work.", "start": 3386.43, "duration": 5.29}, {"text": "And then, of course, you'll\nhave a bunch of these.", "start": 3391.72, "duration": 2.67}, {"text": "So you can [INAUDIBLE].", "start": 3394.39, "duration": 2.63}, {"text": "All right?", "start": 3397.02, "duration": 0.5}, {"text": "And this is exactly\nhow a rainbow works.", "start": 3397.52, "duration": 3.213}, {"text": "So you see a rainbow after\nyou've had this rain.", "start": 3400.733, "duration": 4.927}, {"text": "This is how a rainbow works.", "start": 3405.66, "duration": 2.28}, {"text": "If you ever see a\nrainbow with maximum--", "start": 3407.94, "duration": 5.292}, {"text": "most vivid colors, what\nconditions you are satisfying?", "start": 3417.06, "duration": 4.41}, {"text": "This is for the sun.", "start": 3421.47, "duration": 1.56}, {"text": "And this is for the\nhigh-humidity here.", "start": 3423.03, "duration": 8.23}, {"text": "What's the [INAUDIBLE]\ncondition [INAUDIBLE]??", "start": 3431.26, "duration": 3.428}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3434.688, "duration": 1.762}, {"text": "RAMESH RASKAR: [INAUDIBLE]", "start": 3436.45, "duration": 1.083}, {"text": "AUDIENCE: [INAUDIBLE], yeah.", "start": 3437.533, "duration": 1.277}, {"text": "RAMESH RASKAR: So\nthis is the sky.", "start": 3438.81, "duration": 2.74}, {"text": "The sun is just setting.", "start": 3441.55, "duration": 2.42}, {"text": "You are here.", "start": 3443.97, "duration": 0.63}, {"text": "And you're going\nto see it exactly", "start": 3447.39, "duration": 1.708}, {"text": "in the opposite direction here.", "start": 3449.098, "duration": 1.292}, {"text": "So the rainbow is here.", "start": 3450.39, "duration": 2.13}, {"text": "So very common.", "start": 3452.52, "duration": 1.32}, {"text": "You would go to some\nplace with a waterfall.", "start": 3453.84, "duration": 3.21}, {"text": "And you want to see the rainbow.", "start": 3457.05, "duration": 1.588}, {"text": "In case of a challenge,\nyou can see it sometimes.", "start": 3458.638, "duration": 2.042}, {"text": "You don't see it sometimes.", "start": 3460.68, "duration": 1.17}, {"text": "All you have to make sure is\nthat the sun-- so usually, it's", "start": 3461.85, "duration": 3.375}, {"text": "high enough.", "start": 3465.225, "duration": 1.505}, {"text": "You can see the rainbow.", "start": 3466.73, "duration": 1.0}, {"text": "Because you can imagine if the\nsun is pretty high in the sky,", "start": 3467.73, "duration": 5.22}, {"text": "you'll never see a rainbow\nbecause it's occluded", "start": 3472.95, "duration": 2.46}, {"text": "by the surface of the Earth.", "start": 3475.41, "duration": 2.28}, {"text": "But when the sun is low\nenough, you will see a rainbow.", "start": 3477.69, "duration": 3.85}, {"text": "On the other hand, you\njust have a mountain,", "start": 3481.54, "duration": 3.11}, {"text": "then even in the\ndaytime, you could see", "start": 3484.65, "duration": 2.04}, {"text": "the rainbow if the [INAUDIBLE].", "start": 3486.69, "duration": 4.08}, {"text": "The lowest point by\nthis are allowing", "start": 3490.77, "duration": 2.73}, {"text": "you to see the retroreflection.", "start": 3493.5, "duration": 2.61}, {"text": "And we're coming to,\nwhy this rainbow?", "start": 3496.11, "duration": 1.89}, {"text": "Because the refractive index\nfor different times [INAUDIBLE]..", "start": 3498.0, "duration": 3.845}, {"text": "So that's why we\nsee [INAUDIBLE]..", "start": 3501.845, "duration": 2.34}, {"text": "So it's all fascinating\n[INAUDIBLE],, retroreflection.", "start": 3507.11, "duration": 3.73}, {"text": "So in case of, why does the\nhuman eye have red eye or a cat", "start": 3510.84, "duration": 7.13}, {"text": "has these bright spots?", "start": 3517.97, "duration": 4.465}, {"text": "It's the same reason.", "start": 3522.435, "duration": 0.875}, {"text": "So all you want is [INAUDIBLE].", "start": 3526.668, "duration": 1.292}, {"text": "Light goes in, comes back\nin the same direction.", "start": 3527.96, "duration": 3.12}, {"text": "So if you have\nnow a [INAUDIBLE]..", "start": 3531.08, "duration": 7.23}, {"text": "So now, if you have, let's\nsay, a camera for now.", "start": 3541.63, "duration": 5.01}, {"text": "And human eye was almost\nsimilar [INAUDIBLE]..", "start": 3546.64, "duration": 2.8}, {"text": "And there's a bright\nspot, bright light.", "start": 3549.44, "duration": 2.82}, {"text": "I'm going to stand\nright next to it.", "start": 3552.26, "duration": 2.33}, {"text": "Light goes in.", "start": 3554.59, "duration": 2.07}, {"text": "And this gets focused.", "start": 3556.66, "duration": 1.77}, {"text": "That's the point.", "start": 3558.43, "duration": 0.92}, {"text": "And as you can imagine,\nif you're a sensor,", "start": 3563.5, "duration": 3.54}, {"text": "it actually has a shiny\n[INAUDIBLE] in front of it.", "start": 3567.04, "duration": 2.395}, {"text": "If you look at a\nsensor, you'll realize", "start": 3569.435, "duration": 1.625}, {"text": "it's pretty shiny\nbecause [INAUDIBLE]..", "start": 3571.06, "duration": 4.24}, {"text": "Light goes in and reflects.", "start": 3575.3, "duration": 2.57}, {"text": "And no matter where light\ncomes out from, because", "start": 3577.87, "duration": 2.715}, {"text": "of the geometry\nof the light, you", "start": 3580.585, "duration": 1.595}, {"text": "can go back to the same spot.", "start": 3582.18, "duration": 1.33}, {"text": "Now [INAUDIBLE] for\nthe focus, you do not", "start": 3586.77, "duration": 2.64}, {"text": "see it because [INAUDIBLE].", "start": 3589.41, "duration": 2.76}, {"text": "But if the point was in\nsharp focus, on the sensor,", "start": 3592.17, "duration": 2.82}, {"text": "it will reflect back.", "start": 3594.99, "duration": 1.23}, {"text": "And it will come back\nin the same place.", "start": 3596.22, "duration": 2.86}, {"text": "And so this is the\nsame reason why", "start": 3599.08, "duration": 2.06}, {"text": "for a human eye, again, in a\nsituation like [INAUDIBLE],,", "start": 3601.14, "duration": 4.04}, {"text": "it reflects and comes back\nin the same direction.", "start": 3605.18, "duration": 4.114}, {"text": "[INAUDIBLE]", "start": 3609.294, "duration": 0.976}, {"text": "So the reason why\nI tell you, what's", "start": 3610.27, "duration": 2.75}, {"text": "the new strategy for\nremoving a red light?", "start": 3613.02, "duration": 3.45}, {"text": "What should you do?", "start": 3616.47, "duration": 1.55}, {"text": "AUDIENCE: Flash\nphase or [INAUDIBLE]..", "start": 3618.02, "duration": 1.84}, {"text": "RAMESH RASKAR: Flash out.", "start": 3619.86, "duration": 1.042}, {"text": "Or if you have a cheap\ncamera, where you--", "start": 3620.902, "duration": 2.006}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3622.908, "duration": 0.876}, {"text": "RAMESH RASKAR:\n[INAUDIBLE] camera.", "start": 3623.784, "duration": 2.106}, {"text": "Because you're not\nlooking at the camera,", "start": 3625.89, "duration": 1.86}, {"text": "you have-- the\nimage that we formed", "start": 3627.75, "duration": 1.86}, {"text": "is forming something that's\nmade of the light [INAUDIBLE]..", "start": 3629.61, "duration": 4.32}, {"text": "And so you're not referring\nback to the camera.", "start": 3633.93, "duration": 3.01}, {"text": "AUDIENCE: So the\nanti-paparazzi system will also", "start": 3636.94, "duration": 2.36}, {"text": "blind everybody [INAUDIBLE].", "start": 3639.3, "duration": 2.112}, {"text": "RAMESH RASKAR: If it was--", "start": 3641.412, "duration": 2.608}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3644.02, "duration": 1.0}, {"text": "RAMESH RASKAR: If the--", "start": 3645.02, "duration": 0.958}, {"text": "[LAUGHTER]", "start": 3645.978, "duration": 1.542}, {"text": "If the city-mounted light\nwas omnidirectional,", "start": 3649.25, "duration": 4.72}, {"text": "then that would matter.", "start": 3653.97, "duration": 1.17}, {"text": "But because the\nprojector had constrained", "start": 3655.14, "duration": 2.43}, {"text": "light only at [INAUDIBLE]\npoints [INAUDIBLE] this point.", "start": 3657.57, "duration": 4.12}, {"text": "[INTERPOSING VOICES]", "start": 3661.69, "duration": 1.5}, {"text": "RAMESH RASKAR: Yes.", "start": 3664.638, "duration": 0.792}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3665.43, "duration": 0.875}, {"text": "RAMESH RASKAR: Or this camera.", "start": 3666.305, "duration": 2.815}, {"text": "We don't want to [INAUDIBLE].", "start": 3669.12, "duration": 1.593}, {"text": "AUDIENCE: I think the\npoint JD was bringing up", "start": 3670.713, "duration": 1.917}, {"text": "is that human eyes are\nalso retroreflective.", "start": 3672.63, "duration": 1.833}, {"text": "So if you look at a spot, it\nwill potentially flash you.", "start": 3674.463, "duration": 3.117}, {"text": "RAMESH RASKAR: Is that\nwhat you're saying?", "start": 3677.58, "duration": 0.63}, {"text": "AUDIENCE: Yes.", "start": 3678.21, "duration": 0.39}, {"text": "RAMESH RASKAR: Yeah, so--", "start": 3678.6, "duration": 0.81}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3679.41, "duration": 0.96}, {"text": "RAMESH RASKAR: It's true.", "start": 3680.37, "duration": 0.57}, {"text": "It's true.", "start": 3680.94, "duration": 0.72}, {"text": "So this is among the rules.", "start": 3681.66, "duration": 1.28}, {"text": "[LAUGHTER]", "start": 3682.94, "duration": 2.06}, {"text": "So just don't go there\nwith [INAUDIBLE]..", "start": 3685.0, "duration": 2.615}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3687.615, "duration": 3.105}, {"text": "RAMESH RASKAR: So also, you\nknow that [INAUDIBLE] are", "start": 3690.72, "duration": 3.9}, {"text": "a very technical environment.", "start": 3694.62, "duration": 1.975}, {"text": "Usually, [INAUDIBLE]\nhave more problems", "start": 3696.595, "duration": 1.625}, {"text": "with [INAUDIBLE] don't have\na problem with [INAUDIBLE]..", "start": 3698.22, "duration": 4.26}, {"text": "And that's just because\nof the pigment and so on.", "start": 3702.48, "duration": 3.67}, {"text": "But you're right, that If\nthe system works really well,", "start": 3706.15, "duration": 3.438}, {"text": "it will also blind\nall the [INAUDIBLE]..", "start": 3709.588, "duration": 1.667}, {"text": "[LAUGHTER]", "start": 3711.255, "duration": 0.675}, {"text": "AUDIENCE: So if you have\nthe masks, something", "start": 3711.93, "duration": 2.25}, {"text": "to put into your lens, then\nthis will seem, obviously,", "start": 3714.18, "duration": 4.38}, {"text": "[INAUDIBLE].", "start": 3718.56, "duration": 2.19}, {"text": "RAMESH RASKAR: Oh, yeah,\nthat's the next [INAUDIBLE],,", "start": 3720.75, "duration": 2.67}, {"text": "how to beat [INAUDIBLE].", "start": 3723.42, "duration": 2.038}, {"text": "AUDIENCE: And", "start": 3725.458, "duration": 0.542}, {"text": "[INTERPOSING VOICES]", "start": 3726.0, "duration": 0.36}, {"text": "AUDIENCE: You can use the flash.", "start": 3726.36, "duration": 1.333}, {"text": "[LAUGHTER]", "start": 3727.693, "duration": 0.873}, {"text": "Use a camera with a\nhigh-ISO [INAUDIBLE]..", "start": 3728.566, "duration": 3.454}, {"text": "RAMESH RASKAR: Yeah,\nthere's a lot of ways", "start": 3732.02, "duration": 1.75}, {"text": "to get around it, always.", "start": 3733.77, "duration": 2.64}, {"text": "If you want to have a very\nnice discussion on how", "start": 3736.41, "duration": 3.0}, {"text": "to change your license\nplate so that the--", "start": 3739.41, "duration": 3.078}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3742.488, "duration": 2.232}, {"text": "RAMESH RASKAR: --high-speed--\nwhatever, the--", "start": 3744.72, "duration": 2.425}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3747.145, "duration": 0.875}, {"text": "RAMESH RASKAR:\n--speeding cameras", "start": 3748.02, "duration": 1.375}, {"text": "will not be able to see it.", "start": 3749.395, "duration": 1.775}, {"text": "You ought to buy me a beer.", "start": 3751.17, "duration": 1.363}, {"text": "[LAUGHTER]", "start": 3752.533, "duration": 0.927}, {"text": "All right?", "start": 3754.78, "duration": 0.5}, {"text": "AUDIENCE: Yeah.", "start": 3755.28, "duration": 0.39}, {"text": "RAMESH RASKAR: You're up for it?", "start": 3755.67, "duration": 0.63}, {"text": "AUDIENCE: Yeah.", "start": 3756.3, "duration": 0.625}, {"text": "RAMESH RASKAR: You're over 18?", "start": 3756.925, "duration": 1.485}, {"text": "[LAUGHTER]", "start": 3758.41, "duration": 0.5}, {"text": "AUDIENCE: Yeah, 21 [INAUDIBLE].", "start": 3758.91, "duration": 1.74}, {"text": "RAMESH RASKAR: I\ndid not say age.", "start": 3760.65, "duration": 2.19}, {"text": "All right.", "start": 3762.84, "duration": 0.8}, {"text": "Good.", "start": 3763.64, "duration": 0.5}, {"text": "So before we take a\nshort break and go", "start": 3764.14, "duration": 3.98}, {"text": "into the illumination,\nmore discussion,", "start": 3768.12, "duration": 2.01}, {"text": "I just want to give\nyou the final projects", "start": 3770.13, "duration": 2.73}, {"text": "you could be working on.", "start": 3772.86, "duration": 1.09}, {"text": "Remember, we are really here\nto do something that's cool", "start": 3773.95, "duration": 3.38}, {"text": "as well as novel.", "start": 3777.33, "duration": 2.46}, {"text": "So many times, I'm\ngoing to bring up", "start": 3779.79, "duration": 1.68}, {"text": "a list of the projects\nthat are not cool.", "start": 3781.47, "duration": 3.374}, {"text": "All right?", "start": 3784.844, "duration": 0.766}, {"text": "And again, no offense\nto somebody who", "start": 3785.61, "duration": 2.22}, {"text": "might be working\nin a similar field.", "start": 3787.83, "duration": 1.83}, {"text": "But just, let's be honest.", "start": 3789.66, "duration": 1.83}, {"text": "Let's do something nice.", "start": 3791.49, "duration": 1.63}, {"text": "So here are some suggestions\nfor types of fun projects", "start": 3793.12, "duration": 4.16}, {"text": "you could be doing.", "start": 3797.28, "duration": 2.61}, {"text": "You have beautiful user\ninteraction devices", "start": 3799.89, "duration": 3.33}, {"text": "that are always fun.", "start": 3803.22, "duration": 1.61}, {"text": "You start using a\n2D sensor camera.", "start": 3804.83, "duration": 2.83}, {"text": "Maybe use the [INAUDIBLE]\ncamera for the finished camera,", "start": 3807.66, "duration": 4.14}, {"text": "which can be, by the way,\ncreated from a flatbed scanner.", "start": 3811.8, "duration": 2.64}, {"text": "You can buy a flatbed\nscanner for under $100.", "start": 3814.44, "duration": 3.12}, {"text": "And it's actually a\nmultithousand frame rate", "start": 3817.56, "duration": 3.27}, {"text": "camera.", "start": 3820.83, "duration": 1.8}, {"text": "You can just hold\nit in one place.", "start": 3822.63, "duration": 1.93}, {"text": "And if you walk in\nfront of it, you'll", "start": 3824.56, "duration": 1.91}, {"text": "basically create a\nphoto finished camera.", "start": 3826.47, "duration": 2.07}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3828.54, "duration": 2.042}, {"text": "RAMESH RASKAR: Yeah,\nthere are a lot of issues.", "start": 3830.582, "duration": 1.958}, {"text": "But we'll help you on that.", "start": 3832.54, "duration": 1.59}, {"text": "We'll help you on that.", "start": 3834.13, "duration": 2.7}, {"text": "Yeah, like Dino was\nsaying, it's not", "start": 3836.83, "duration": 2.22}, {"text": "something you can just\nbuy and just plug it in.", "start": 3839.05, "duration": 2.71}, {"text": "You have to get your hands\ndirty in [INAUDIBLE]..", "start": 3841.76, "duration": 4.67}, {"text": "Or just use photodetectors,\nsingle-pixel cameras.", "start": 3846.43, "duration": 2.67}, {"text": "You can do a lot of\ninteresting things with it.", "start": 3849.1, "duration": 2.64}, {"text": "You can include some\ninteresting illumination.", "start": 3851.74, "duration": 2.82}, {"text": "Capture the invisible.", "start": 3854.56, "duration": 1.11}, {"text": "It's always my fascination on,\nhow can we capture something", "start": 3855.67, "duration": 2.64}, {"text": "that cannot be seen\nwith the naked eye?", "start": 3858.31, "duration": 2.62}, {"text": "So maybe bring some\ntomography machine", "start": 3860.93, "duration": 1.94}, {"text": "that can see inside the\nbody, some structure like 3D", "start": 3862.87, "duration": 3.45}, {"text": "scanning or fluorescence.", "start": 3866.32, "duration": 2.13}, {"text": "And we'll see that experiment\nhere just in a minute.", "start": 3868.45, "duration": 3.64}, {"text": "And this is a question\nyou were asking earlier.", "start": 3872.09, "duration": 2.03}, {"text": "Are there cameras\nin other domains,", "start": 3874.12, "duration": 1.83}, {"text": "electromagnetic, or\naudio, or resistant.", "start": 3875.95, "duration": 2.55}, {"text": "So how about an audio\ncamera, or a magnetic camera,", "start": 3878.5, "duration": 3.75}, {"text": "or a capacitive camera?", "start": 3882.25, "duration": 1.23}, {"text": "So we won't be discussing\nit a lot in the class.", "start": 3883.48, "duration": 2.97}, {"text": "But I think it's a great\nway to do a final project.", "start": 3886.45, "duration": 4.27}, {"text": "Thermal lab camera,\nwe can help you.", "start": 3890.72, "duration": 1.94}, {"text": "Maybe a thermal lab camera\nthat detects emotions.", "start": 3892.66, "duration": 3.18}, {"text": "Multispectral\ncamera, cameras that", "start": 3895.84, "duration": 2.52}, {"text": "can distinguish between two\nvery similar colored objects.", "start": 3898.36, "duration": 3.87}, {"text": "There's a lot of us interested\nin distinguishing camel", "start": 3902.23, "duration": 3.18}, {"text": "from sand.", "start": 3905.41, "duration": 1.26}, {"text": "So can you create\nsome mechanisms", "start": 3906.67, "duration": 3.6}, {"text": "so that two very similar\nlooking objects can", "start": 3910.27, "duration": 3.55}, {"text": "be completely distinguished?", "start": 3913.82, "duration": 2.79}, {"text": "There's a lot of market in\nthe golf business, where", "start": 3916.61, "duration": 2.19}, {"text": "people want to spot their golf\nball on a green background.", "start": 3918.8, "duration": 6.93}, {"text": "So you just put this--", "start": 3925.73, "duration": 1.29}, {"text": "you know what to do?", "start": 3927.02, "duration": 2.388}, {"text": "Yeah, they sell it for\nhundreds of dollars.", "start": 3929.408, "duration": 1.792}, {"text": "All you need is a blue filter.", "start": 3931.2, "duration": 1.565}, {"text": "If you put a blue filter on\nthe grass, which is green,", "start": 3932.765, "duration": 2.85}, {"text": "it looks black.", "start": 3935.615, "duration": 1.935}, {"text": "But your ball, which is\nnot green, stands up.", "start": 3937.55, "duration": 5.248}, {"text": "So you have a black background.", "start": 3942.798, "duration": 1.292}, {"text": "And anything that's not\ngreen will really stand out.", "start": 3944.09, "duration": 4.77}, {"text": "You can-- there are lots of\nother businesses [INAUDIBLE]..", "start": 3948.86, "duration": 4.8}, {"text": "Illumination.", "start": 3953.66, "duration": 1.365}, {"text": "[INAUDIBLE] photography,\nI think we saw earlier.", "start": 3955.025, "duration": 2.985}, {"text": "A lot of fun.", "start": 3958.01, "duration": 0.92}, {"text": "All, kinds of, strobing.", "start": 3958.93, "duration": 1.0}, {"text": "Nonimaging elements such\nas gyros, GPS, interaction", "start": 3963.35, "duration": 6.06}, {"text": "between two cameras.", "start": 3969.41, "duration": 0.92}, {"text": "Maybe there is some\nlighting communication", "start": 3970.33, "duration": 1.75}, {"text": "or Wi-Fi communication\nbetween them.", "start": 3972.08, "duration": 2.67}, {"text": "Optics is always a lot of fun,\ncamera areas, light fields,", "start": 3974.75, "duration": 3.9}, {"text": "portrait aperture.", "start": 3978.65, "duration": 1.65}, {"text": "Maybe try to mimic a vision\nof one of the animals.", "start": 3980.3, "duration": 5.16}, {"text": "Or study.", "start": 3985.46, "duration": 1.17}, {"text": "Bring some worms\nor bring some cats.", "start": 3986.63, "duration": 2.13}, {"text": "And cats are, by the way,\nreally beautiful mechanisms", "start": 3988.76, "duration": 3.42}, {"text": "of how they work.", "start": 3992.18, "duration": 2.28}, {"text": "And we'll have a whole\nlecture on animal eyes.", "start": 3994.46, "duration": 2.37}, {"text": "I think seventh\nor eighth lecture.", "start": 3996.83, "duration": 2.5}, {"text": "So we'll study that.", "start": 3999.33, "duration": 2.21}, {"text": "And time.", "start": 4001.54, "duration": 0.81}, {"text": "Timelapse photos,\nthere's so much", "start": 4002.35, "duration": 2.64}, {"text": "information in\ntime lapse photos.", "start": 4004.99, "duration": 1.83}, {"text": "I wish I could go on Google\nEarth or Google Street View", "start": 4006.82, "duration": 3.418}, {"text": "and it will show me time lapse.", "start": 4010.238, "duration": 1.292}, {"text": "It can't be that\ndifficult. They'd", "start": 4011.53, "duration": 1.74}, {"text": "have to scale\ntheir database only", "start": 4013.27, "duration": 1.77}, {"text": "by a factor of 24, which is\nnot that much more, I think.", "start": 4015.04, "duration": 4.207}, {"text": "But it'd be nice to\nsee the same place", "start": 4019.247, "duration": 1.583}, {"text": "in the daytime and\nnighttime, and what,", "start": 4020.83, "duration": 2.22}, {"text": "kind of, traffic it has, and\nwhat, kind of, people it has.", "start": 4023.05, "duration": 3.06}, {"text": "Right now, it's very static\nabout its appearance.", "start": 4026.11, "duration": 4.23}, {"text": "Somebody had a very nice\nidea for time lapse photos", "start": 4030.34, "duration": 2.82}, {"text": "for Google Street\nMap, which is--", "start": 4033.16, "duration": 3.48}, {"text": "sometimes, you don't need a\nvideo of what's going on there.", "start": 4036.64, "duration": 2.76}, {"text": "But the world, at\nleast man-made world,", "start": 4039.4, "duration": 3.51}, {"text": "usually, it will only\nhave a few discrete steps.", "start": 4042.91, "duration": 2.46}, {"text": "If there's a traffic\nlight, it just", "start": 4045.37, "duration": 3.75}, {"text": "switches between three\ndifferent colors.", "start": 4049.12, "duration": 2.04}, {"text": "If there's a bridge on the\nriver, that drawbridge,", "start": 4051.16, "duration": 4.26}, {"text": "it's either this position\nor this position.", "start": 4055.42, "duration": 2.28}, {"text": "There are a lot of\nthese discrete things", "start": 4057.7, "duration": 2.34}, {"text": "that happen in man-made world.", "start": 4060.04, "duration": 1.63}, {"text": "So it'd be nice if\nin Google Street,", "start": 4061.67, "duration": 1.76}, {"text": "you can see all those discrete\nsteps, discrete situations", "start": 4063.43, "duration": 4.14}, {"text": "in [INAUDIBLE].", "start": 4067.57, "duration": 1.29}, {"text": "You can create this\ndirect global separation.", "start": 4072.22, "duration": 3.42}, {"text": "I think we saw that earlier.", "start": 4075.64, "duration": 1.74}, {"text": "Create new types of\ncameras that are over 10--", "start": 4077.38, "duration": 2.97}, {"text": "these are all suggestions\nfor final products.", "start": 4080.35, "duration": 3.06}, {"text": "Mimic animal eyes.", "start": 4083.41, "duration": 2.25}, {"text": "Play with photonic crystals.", "start": 4085.66, "duration": 1.17}, {"text": "They're are very\neasy to make now.", "start": 4086.83, "duration": 2.37}, {"text": "Photonic crystals,\nbasically, in simple words,", "start": 4089.2, "duration": 3.54}, {"text": "these are ordered arrays\nof materials that have", "start": 4092.74, "duration": 9.21}, {"text": "different refractive indexes.", "start": 4101.95, "duration": 1.92}, {"text": "In the simplest case, it\ncould be just glass and air.", "start": 4103.87, "duration": 3.93}, {"text": "So if you could just create\nmicron-scaled holes in glass,", "start": 4107.8, "duration": 3.69}, {"text": "it behaves in very\ninteresting ways.", "start": 4111.49, "duration": 1.81}, {"text": "So maybe somebody will play with\nthat [INAUDIBLE] photography", "start": 4113.3, "duration": 4.01}, {"text": "and [INAUDIBLE].", "start": 4117.31, "duration": 0.733}, {"text": "AUDIENCE: Ramesh?", "start": 4118.043, "duration": 0.254}, {"text": "RAMESH RASKAR: Yeah?", "start": 4118.297, "duration": 0.513}, {"text": "AUDIENCE: You say\nit's very simple.", "start": 4118.81, "duration": 1.458}, {"text": "How do you do that?", "start": 4120.268, "duration": 1.895}, {"text": "RAMESH RASKAR: By\nsimple, I mean--", "start": 4122.163, "duration": 1.417}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4123.58, "duration": 0.239}, {"text": "RAMESH RASKAR: Yeah, the\nidea is fairly simple.", "start": 4123.819, "duration": 2.311}, {"text": "Actually, when photonic crystals\nwere invented in Bell Labs,", "start": 4126.13, "duration": 3.66}, {"text": "they literally took CNC\nC machines in metal.", "start": 4129.79, "duration": 3.84}, {"text": "And they just punched holes.", "start": 4133.63, "duration": 1.422}, {"text": "AUDIENCE: You can get access\nto that or [INAUDIBLE]??", "start": 4135.052, "duration": 2.208}, {"text": "RAMESH RASKAR: We have a\nmicroelectronics laboratory.", "start": 4137.26, "duration": 2.37}, {"text": "I think Quinn knows about it.", "start": 4139.63, "duration": 3.93}, {"text": "And we can-- I think\nthere's some charge.", "start": 4143.56, "duration": 1.98}, {"text": "But I can easily take care\nof the funding for that.", "start": 4145.54, "duration": 4.59}, {"text": "And I think you pay a fixed\none-hour rental for it.", "start": 4150.13, "duration": 4.513}, {"text": "But if it's a research\nproject, maybe we", "start": 4154.643, "duration": 1.667}, {"text": "can even get around that.", "start": 4156.31, "duration": 1.509}, {"text": "So in fact, you can buy now\nnanomaterials and photonic", "start": 4157.819, "duration": 7.191}, {"text": "crystals just online.", "start": 4165.01, "duration": 1.95}, {"text": "You can get two-micron\nbeads and six-micron beads--", "start": 4166.96, "duration": 3.72}, {"text": "sorry, two-nanometer beads and\nsix-nanometer beads online.", "start": 4170.68, "duration": 4.95}, {"text": "Very toxic.", "start": 4175.63, "duration": 0.78}, {"text": "A little bit dangerous.", "start": 4176.41, "duration": 1.92}, {"text": "But there are certain varieties\nthat you can just use.", "start": 4178.33, "duration": 4.734}, {"text": "So it's a lot of fun\nto play with that.", "start": 4183.064, "duration": 1.625}, {"text": "And here are some\nsample projects", "start": 4187.165, "duration": 1.375}, {"text": "from last year's class.", "start": 4188.54, "duration": 1.92}, {"text": "In our [INAUDIBLE]\nphotography, again,", "start": 4190.46, "duration": 1.62}, {"text": "this was the only\nundergrad in the class.", "start": 4192.08, "duration": 2.19}, {"text": "And he won the best award,\nBest Project Award, from Nokia.", "start": 4194.27, "duration": 3.9}, {"text": "Jessie from\nmechanical engineering", "start": 4200.93, "duration": 1.62}, {"text": "did a camera array for\nparticle image velocimetry.", "start": 4202.55, "duration": 3.27}, {"text": "And now, it has\nbecome his PhD thesis.", "start": 4205.82, "duration": 3.0}, {"text": "And he's applying for\nhundreds of thousands", "start": 4208.82, "duration": 3.24}, {"text": "of dollars in grants.", "start": 4212.06, "duration": 1.8}, {"text": "Bidirectional screen was a\nproject by Matt, Matt Hirsch.", "start": 4213.86, "duration": 3.3}, {"text": "Again, it has become\nhis master's thesis,", "start": 4217.16, "duration": 2.25}, {"text": "SIGGRAPH paper, and so on.", "start": 4219.41, "duration": 3.561}, {"text": "[INAUDIBLE] Kermani,\nin my group,", "start": 4222.971, "duration": 1.537}, {"text": "he just looked at the\ntheory, he didn't have time", "start": 4224.508, "duration": 2.042}, {"text": "to build anything at\nthat time, but looking", "start": 4226.55, "duration": 1.95}, {"text": "around a corner, which is,\nagain, a paper this year.", "start": 4228.5, "duration": 3.39}, {"text": "Somebody is building a\ntomography machine and so on.", "start": 4231.89, "duration": 2.41}, {"text": "Lots of cool things.", "start": 4234.3, "duration": 1.55}, {"text": "As you can imagine,\nlast year, the emphasis", "start": 4235.85, "duration": 2.28}, {"text": "was a little bit more\nhardware-intensive", "start": 4238.13, "duration": 3.09}, {"text": "because the people who\nare taking the classes", "start": 4241.22, "duration": 2.64}, {"text": "were interested in that.", "start": 4243.86, "duration": 1.89}, {"text": "But this year, we have a\nmore diverse crowd here.", "start": 4245.75, "duration": 3.36}, {"text": "So I'm expecting projects\nin just art or photography,", "start": 4249.11, "duration": 3.96}, {"text": "beautiful synthesis of images,\nreal-time XCS systems, maybe", "start": 4253.07, "duration": 8.97}, {"text": "some different types\nof scientific imaging,", "start": 4262.04, "duration": 2.37}, {"text": "maybe a new microscope,\nanything of that variety.", "start": 4264.41, "duration": 5.52}, {"text": "And we'll spend a\nlot of time together.", "start": 4269.93, "duration": 1.66}, {"text": "We have four or five\nmentors assigned.", "start": 4271.59, "duration": 2.21}, {"text": "We're working with you\non the final projects.", "start": 4273.8, "duration": 4.24}, {"text": "All right.", "start": 4278.04, "duration": 0.81}, {"text": "So let's take a short break.", "start": 4278.85, "duration": 1.245}, {"text": "And the short break, we\nare going to show you", "start": 4280.095, "duration": 1.875}, {"text": "some cool fluorescent\ndemos here.", "start": 4281.97, "duration": 5.46}, {"text": "And then, we'll start\nback in about 10 minutes", "start": 4287.43, "duration": 2.31}, {"text": "to talk about other\ntypes of image.", "start": 4289.74, "duration": 3.15}, {"text": "So here's a big question\nfor photography.", "start": 4296.63, "duration": 5.45}, {"text": "1930s, we had big cameras.", "start": 4302.08, "duration": 1.887}, {"text": "The guy had to get under\nthe cloth to take a picture.", "start": 4303.967, "duration": 2.208}, {"text": "AUDIENCE: That's\nactually a press camera.", "start": 4306.175, "duration": 2.085}, {"text": "It's pretty small.", "start": 4308.26, "duration": 1.08}, {"text": "And people", "start": 4309.34, "duration": 0.6}, {"text": "[INTERPOSING VOICES]", "start": 4309.94, "duration": 0.5}, {"text": "RAMESH RASKAR: This\nis more recent.", "start": 4310.44, "duration": 1.63}, {"text": "But I'm guessing\nyou have cameras", "start": 4312.07, "duration": 1.855}, {"text": "that are bigger than this?", "start": 4313.925, "duration": 1.115}, {"text": "AUDIENCE: Yeah.", "start": 4315.04, "duration": 0.625}, {"text": "RAMESH RASKAR: And\nthere's nothing wrong", "start": 4318.28, "duration": 1.92}, {"text": "in having large\ncameras [INAUDIBLE]..", "start": 4320.2, "duration": 3.42}, {"text": "And that has shrunk down to\nsomething, this, and this,", "start": 4323.62, "duration": 6.81}, {"text": "and $0.20 with all the\nelectronics, and processing,", "start": 4330.43, "duration": 3.49}, {"text": "and so on.", "start": 4333.92, "duration": 0.93}, {"text": "But when you think about\nlighting, not much has changed.", "start": 4334.85, "duration": 5.45}, {"text": "It has definitely\nnot reduced in size.", "start": 4340.3, "duration": 2.22}, {"text": "It definitely has not reduced in\ncost or convenience and so on.", "start": 4342.52, "duration": 5.35}, {"text": "And in a way, what really\ndistinguishes consumer", "start": 4347.87, "duration": 6.5}, {"text": "photography from\nprofessional photography", "start": 4354.37, "duration": 2.04}, {"text": "is not the camera\nanymore, but the lighting.", "start": 4356.41, "duration": 4.33}, {"text": "So this is a challenge\nfor our community, who", "start": 4360.74, "duration": 3.633}, {"text": "we like to think about\nmaking everything", "start": 4364.373, "duration": 1.667}, {"text": "programmable and easy to use.", "start": 4366.04, "duration": 3.33}, {"text": "The same revolution will\nnot happen for illumination.", "start": 4369.37, "duration": 3.145}, {"text": "So we're going to explore\nthat a little bit into today's", "start": 4376.21, "duration": 2.82}, {"text": "class, then come back and talk\nsome more in the next class.", "start": 4379.03, "duration": 4.48}, {"text": "So when it's all\nabout cameras, we", "start": 4383.51, "duration": 2.36}, {"text": "try to make it very\nsmart with the lenses,", "start": 4385.87, "duration": 2.65}, {"text": "and different sensors,\nand new processing.", "start": 4388.52, "duration": 2.39}, {"text": "But the light source\nis still a flash.", "start": 4390.91, "duration": 1.92}, {"text": "Maybe it has fancy\numbrellas and so on.", "start": 4392.83, "duration": 2.2}, {"text": "But it's mostly a flash.", "start": 4395.03, "duration": 3.17}, {"text": "So what we want to\ndo is replace that", "start": 4398.2, "duration": 2.37}, {"text": "into a more programmable\nillumination", "start": 4400.57, "duration": 3.03}, {"text": "in a very high-dimensional way.", "start": 4403.6, "duration": 1.62}, {"text": "It's geometry recorded\nfor the illumination", "start": 4405.22, "duration": 2.58}, {"text": "field in time and color.", "start": 4407.8, "duration": 3.61}, {"text": "All right?", "start": 4411.41, "duration": 0.74}, {"text": "So some of the earliest\nexamples, and this whole field", "start": 4412.15, "duration": 3.84}, {"text": "is called computational\nillumination,", "start": 4415.99, "duration": 2.207}, {"text": "we're going to use computing\neven in the lighting.", "start": 4418.197, "duration": 2.083}, {"text": "And maybe the pioneer was\nEdgerton, Dr. Edgerton", "start": 4422.95, "duration": 4.29}, {"text": "right here.", "start": 4427.24, "duration": 1.41}, {"text": "Very famous examples of bullets\ngoing through through an apple.", "start": 4428.65, "duration": 5.19}, {"text": "And Santiago saying,\nyou have this one or--", "start": 4433.84, "duration": 3.0}, {"text": "AUDIENCE: The three balloons.", "start": 4436.84, "duration": 1.32}, {"text": "RAMESH RASKAR: Three\nballoons, yeah.", "start": 4438.16, "duration": 1.5}, {"text": "So [INAUDIBLE] has beautiful,\nbeautiful pictures.", "start": 4439.66, "duration": 3.63}, {"text": "Are they in your dorm room?", "start": 4443.29, "duration": 1.19}, {"text": "AUDIENCE: I've seen one.", "start": 4444.48, "duration": 1.0}, {"text": "RAMESH RASKAR: The same one?", "start": 4445.48, "duration": 0.72}, {"text": "Yeah, great.", "start": 4446.2, "duration": 0.66}, {"text": "So beautiful pictures.", "start": 4446.86, "duration": 1.23}, {"text": "But they were not captured\nwith smart cameras.", "start": 4448.09, "duration": 3.415}, {"text": "They were captured\nwith smart lighting.", "start": 4451.505, "duration": 1.625}, {"text": "You have an ordinary\ncamera, where the shutter", "start": 4456.79, "duration": 2.07}, {"text": "is open for a certain duration.", "start": 4458.86, "duration": 2.37}, {"text": "But then, you have a flash that\nfreezes that motion, which,", "start": 4461.23, "duration": 5.1}, {"text": "as I recall, was troublesome.", "start": 4466.33, "duration": 2.25}, {"text": "And in this particular case, you\nhave a sequential strobe that", "start": 4468.58, "duration": 4.86}, {"text": "captures this whole circle.", "start": 4473.44, "duration": 2.018}, {"text": "Nothing smart about the camera.", "start": 4475.458, "duration": 1.292}, {"text": "Really smart strobed lighting.", "start": 4476.75, "duration": 4.22}, {"text": "And of course,\n[? Doc ?] Edgerton", "start": 4480.97, "duration": 1.44}, {"text": "came up with chemical processes\nto create very sharp duration", "start": 4482.41, "duration": 4.95}, {"text": "light sources.", "start": 4487.36, "duration": 1.81}, {"text": "But now, we have LEDs\nand solid state devices.", "start": 4489.17, "duration": 4.01}, {"text": "We can control light down to a\nfew picoseconds or nanoseconds.", "start": 4493.18, "duration": 4.8}, {"text": "All this can be done very\neasily in your house.", "start": 4497.98, "duration": 6.78}, {"text": "So again, this is what\ndistinguishes consumers", "start": 4504.76, "duration": 3.66}, {"text": "from professionals.", "start": 4508.42, "duration": 2.22}, {"text": "And we look at\nthis step-by-step.", "start": 4510.64, "duration": 4.48}, {"text": "And this will be a more\ntechnical discussion", "start": 4515.12, "duration": 2.12}, {"text": "about what parameters\nof light we can change.", "start": 4517.24, "duration": 5.7}, {"text": "So let's think about,\nwhat are the things we", "start": 4522.94, "duration": 2.37}, {"text": "can change about light?", "start": 4525.31, "duration": 1.34}, {"text": "One is clearly the brightness.", "start": 4526.65, "duration": 2.69}, {"text": "What are some other\nthings we can change?", "start": 4529.34, "duration": 3.53}, {"text": "AUDIENCE: Color.", "start": 4532.87, "duration": 0.88}, {"text": "RAMESH RASKAR: Color.", "start": 4533.75, "duration": 1.686}, {"text": "AUDIENCE: The coordination.", "start": 4535.436, "duration": 1.224}, {"text": "RAMESH RASKAR: The cone.", "start": 4536.66, "duration": 1.482}, {"text": "AUDIENCE: [INAUDIBLE]\npolarizing.", "start": 4538.142, "duration": 1.728}, {"text": "RAMESH RASKAR: Polarization.", "start": 4539.87, "duration": 2.1}, {"text": "AUDIENCE: Coherence length.", "start": 4541.97, "duration": 1.23}, {"text": "RAMESH RASKAR: Go ahead\nand slant a little bit more", "start": 4543.2, "duration": 2.125}, {"text": "exotic, yes.", "start": 4545.325, "duration": 1.015}, {"text": "AUDIENCE: Diffusion.", "start": 4546.34, "duration": 1.0}, {"text": "AUDIENCE: The direction.", "start": 4547.34, "duration": 1.02}, {"text": "RAMESH RASKAR: The\ndirection, yes.", "start": 4548.36, "duration": 1.155}, {"text": "AUDIENCE: Color.", "start": 4549.515, "duration": 0.667}, {"text": "RAMESH RASKAR: Maybe it's not\neven a single cone, but just", "start": 4550.182, "duration": 2.468}, {"text": "a projector.", "start": 4552.65, "duration": 0.78}, {"text": "Different directions have\na different intensity.", "start": 4553.43, "duration": 4.45}, {"text": "AUDIENCE: Time.", "start": 4557.88, "duration": 0.69}, {"text": "RAMESH RASKAR: Time.", "start": 4558.57, "duration": 0.833}, {"text": "So strobing, or duration,\nor synchronization", "start": 4559.403, "duration": 4.147}, {"text": "with the captured image.", "start": 4563.55, "duration": 3.39}, {"text": "AUDIENCE: Relative fades.", "start": 4566.94, "duration": 1.4}, {"text": "RAMESH RASKAR: Relative\nfades, of course.", "start": 4568.34, "duration": 1.78}, {"text": "AUDIENCE: The lenses on\nyour lighting [INAUDIBLE]..", "start": 4570.12, "duration": 2.43}, {"text": "RAMESH RASKAR: For\nlenses, exactly.", "start": 4572.55, "duration": 1.5}, {"text": "Don't think of your flash\nas just a light source.", "start": 4574.05, "duration": 2.31}, {"text": "But put fancy optics or masks\nin front of them to control,", "start": 4576.36, "duration": 4.68}, {"text": "again, direction and so on.", "start": 4581.04, "duration": 1.23}, {"text": "AUDIENCE: You can put inside\nthe object [INAUDIBLE]..", "start": 4582.27, "duration": 3.083}, {"text": "RAMESH RASKAR: Yeah, you\ncan change the environment,", "start": 4585.353, "duration": 2.167}, {"text": "not just illuminate\nthe environment,", "start": 4587.52, "duration": 1.53}, {"text": "but change the\nenvironment by putting", "start": 4589.05, "duration": 1.542}, {"text": "some interesting\nlighting inside there.", "start": 4590.592, "duration": 3.348}, {"text": "So this is, by the\nway, another great way", "start": 4593.94, "duration": 3.15}, {"text": "to come up with new ideas.", "start": 4597.09, "duration": 3.36}, {"text": "And you say, this picture\nreally bothers me.", "start": 4600.45, "duration": 4.68}, {"text": "What can I do?", "start": 4605.13, "duration": 0.867}, {"text": "And if you want to do\nresearch in this area,", "start": 4605.997, "duration": 1.833}, {"text": "you ask this question\nyourself, what", "start": 4607.83, "duration": 1.86}, {"text": "are all the ways I can control\nthe lighting parameters?", "start": 4609.69, "duration": 3.3}, {"text": "And I'm going to go\nthrough one-by-one", "start": 4612.99, "duration": 2.46}, {"text": "and see how I can attack them.", "start": 4615.45, "duration": 2.55}, {"text": "And we'll see examples of\nexactly how that has happened", "start": 4618.0, "duration": 3.69}, {"text": "over the last several years.", "start": 4621.69, "duration": 2.08}, {"text": "So the simplest one is I\ncan have light or no light.", "start": 4623.77, "duration": 4.49}, {"text": "The simplest [INAUDIBLE].", "start": 4628.26, "duration": 1.88}, {"text": "The next parameter\nis duration, how long", "start": 4630.14, "duration": 2.59}, {"text": "it's on or its brightness and\nso on, its position, its color,", "start": 4632.73, "duration": 5.58}, {"text": "using it as a projector,\nespecially angle,", "start": 4638.31, "duration": 3.87}, {"text": "modulation in space,\nmodulation in time,", "start": 4642.18, "duration": 2.13}, {"text": "and sometimes just natural\nlight, just time lapse,", "start": 4644.31, "duration": 2.55}, {"text": "which we saw.", "start": 4646.86, "duration": 0.85}, {"text": "All right?", "start": 4647.71, "duration": 0.5}, {"text": "So we'll just look at a few\nprojects to get us motivated.", "start": 4648.21, "duration": 4.5}, {"text": "And we saw this one last\ntime, a multiflash camera,", "start": 4652.71, "duration": 2.94}, {"text": "where we're really trying\nto solve a new problem.", "start": 4655.65, "duration": 4.59}, {"text": "If I want to tell you\nwhat's inside my car,", "start": 4660.24, "duration": 3.18}, {"text": "I can just take a photo\nand send it to you.", "start": 4663.42, "duration": 3.78}, {"text": "But when car companies\nwant to do the same thing,", "start": 4667.2, "duration": 2.61}, {"text": "they hire artists.", "start": 4669.81, "duration": 2.81}, {"text": "So the question is, why do we\nhire artists to draw something", "start": 4672.62, "duration": 4.35}, {"text": "that can be photographed?", "start": 4676.97, "duration": 1.414}, {"text": "Yes?", "start": 4682.74, "duration": 0.528}, {"text": "AUDIENCE: They might know\nwhat's more important or less", "start": 4683.268, "duration": 2.292}, {"text": "important [INAUDIBLE].", "start": 4685.56, "duration": 1.26}, {"text": "RAMESH RASKAR: The semantics\nis very important, yes.", "start": 4686.82, "duration": 3.74}, {"text": "Yes?", "start": 4690.56, "duration": 0.81}, {"text": "AUDIENCE: [INAUDIBLE]\nreflection, so like edges.", "start": 4691.37, "duration": 3.358}, {"text": "RAMESH RASKAR: So yeah,\nreflections are annoying.", "start": 4694.728, "duration": 2.042}, {"text": "And they don't really\nadd any information.", "start": 4696.77, "duration": 1.9}, {"text": "And edges just felt\nmore important.", "start": 4698.67, "duration": 2.465}, {"text": "AUDIENCE: In that picture,\nso the central elements", "start": 4701.135, "duration": 4.185}, {"text": "are highlighted.", "start": 4705.32, "duration": 1.502}, {"text": "RAMESH RASKAR: Exactly.", "start": 4706.822, "duration": 0.958}, {"text": "The hand is brighter\nthan the rest of the car.", "start": 4707.78, "duration": 3.073}, {"text": "Is that what you mean?", "start": 4710.853, "duration": 0.917}, {"text": "AUDIENCE: Yeah.", "start": 4711.77, "duration": 0.625}, {"text": "RAMESH RASKAR: Yeah.", "start": 4712.395, "duration": 1.385}, {"text": "AUDIENCE: Some unnecessary\nwires or [INAUDIBLE] can be--", "start": 4713.78, "duration": 3.43}, {"text": "[LAUGHTER]", "start": 4717.21, "duration": 0.5}, {"text": "RAMESH RASKAR: Yeah, all these\nthings, it's just clutter.", "start": 4717.71, "duration": 3.0}, {"text": "It's not critical to\nexplaining what's in the car.", "start": 4720.71, "duration": 4.72}, {"text": "It just looks wonderful.", "start": 4725.43, "duration": 1.11}, {"text": "So yeah, unnecessary\nshadows, clutters,", "start": 4726.54, "duration": 3.15}, {"text": "too many colors as opposed\nto highlighting the shape,", "start": 4729.69, "duration": 3.25}, {"text": "and just marking what's\nmoving, and using very simple,", "start": 4732.94, "duration": 2.42}, {"text": "basic colors.", "start": 4735.36, "duration": 0.93}, {"text": "Yes?", "start": 4736.29, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]\nstrategy [INAUDIBLE]??", "start": 4736.79, "duration": 2.86}, {"text": "[LAUGHTER]", "start": 4739.65, "duration": 0.804}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4740.454, "duration": 1.206}, {"text": "RAMESH RASKAR: There are\nsome other names for it.", "start": 4741.66, "duration": 2.042}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4743.702, "duration": 1.358}, {"text": "RAMESH RASKAR: Not\nfor [INAUDIBLE]..", "start": 4745.06, "duration": 1.5}, {"text": "So imagine if you can\njust build a camera that", "start": 4746.56, "duration": 3.41}, {"text": "gives you an image on the\nwhite as opposed to black.", "start": 4749.97, "duration": 2.37}, {"text": "We are not trying to put\nthe artists out of business.", "start": 4752.34, "duration": 3.28}, {"text": "But we are trying\nto create tools", "start": 4755.62, "duration": 1.49}, {"text": "so that they don't end up\ntime rotoscoping and drawing", "start": 4757.11, "duration": 3.72}, {"text": "the lines.", "start": 4760.83, "duration": 0.75}, {"text": "They get all the line\nmaps very quickly.", "start": 4761.58, "duration": 2.4}, {"text": "And then beyond that, the\ncreative process starts.", "start": 4763.98, "duration": 4.15}, {"text": "So get rid of this tedious\ntask of finding the edges,", "start": 4768.13, "duration": 3.83}, {"text": "and marking, and so on, like all\nthe magic scissors and so on.", "start": 4771.96, "duration": 4.2}, {"text": "So of course, the first solution\nwould be just take the photo", "start": 4779.69, "duration": 3.23}, {"text": "and try to find intensity edges.", "start": 4782.92, "duration": 2.05}, {"text": "It turns out it\ndoesn't work very well.", "start": 4784.97, "duration": 3.48}, {"text": "And this is the problem you\nface in XCI all the time.", "start": 4788.45, "duration": 3.71}, {"text": "You have some gestures\nwith your hand.", "start": 4792.16, "duration": 3.49}, {"text": "We might have some challenging\nbackground lighting.", "start": 4795.65, "duration": 3.41}, {"text": "Then a typical method is to\nmaybe do some edge detection,", "start": 4799.06, "duration": 3.54}, {"text": "color detection.", "start": 4802.6, "duration": 1.05}, {"text": "And you just hope\nthat they are not--", "start": 4803.65, "duration": 3.99}, {"text": "the lighting is just right\nwhen you're showing the demo", "start": 4807.64, "duration": 2.82}, {"text": "and you have matched--", "start": 4810.46, "duration": 1.65}, {"text": "controlled the\nbackground just enough so", "start": 4812.11, "duration": 1.68}, {"text": "that everything works out.", "start": 4813.79, "duration": 1.47}, {"text": "Or you can be smart\nabout it and use--", "start": 4815.26, "duration": 4.59}, {"text": "distinguish within\nreflectance edges, which", "start": 4819.85, "duration": 2.1}, {"text": "are edges between\ndifferent materials,", "start": 4821.95, "duration": 3.69}, {"text": "and distinguish them\nfrom depth edges,", "start": 4825.64, "duration": 3.6}, {"text": "which are real geometric edges.", "start": 4829.24, "duration": 2.94}, {"text": "So these are all\nintensity edges.", "start": 4832.18, "duration": 2.58}, {"text": "And these are all\njust geometry edges.", "start": 4834.76, "duration": 2.31}, {"text": "So imagine if I could take a\nphoto of this and get this out.", "start": 4837.07, "duration": 3.5}, {"text": "It would be much easier for me\nto write an interactive system", "start": 4840.57, "duration": 5.86}, {"text": "that's based on it.", "start": 4846.43, "duration": 1.96}, {"text": "AUDIENCE: Well, this is really\nlike a computer-based question,", "start": 4848.39, "duration": 3.02}, {"text": "actually.", "start": 4851.41, "duration": 0.51}, {"text": "The example with\nthe car [INAUDIBLE]", "start": 4851.92, "duration": 2.13}, {"text": "maybe a professional meeting\nbecause a human being knows", "start": 4854.05, "duration": 3.18}, {"text": "what to abstract", "start": 4857.23, "duration": 0.84}, {"text": "[INTERPOSING VOICES]", "start": 4858.07, "duration": 1.26}, {"text": "AUDIENCE: --to normally\nemphasize [INAUDIBLE]..", "start": 4859.33, "duration": 1.958}, {"text": "RAMESH RASKAR: Yes,\nit's multiple goals.", "start": 4861.288, "duration": 3.242}, {"text": "So one goal is a\ndiminished reality--", "start": 4864.53, "duration": 2.72}, {"text": "[LAUGHTER]", "start": 4867.25, "duration": 1.35}, {"text": "--trademarked by--", "start": 4868.6, "duration": 1.526}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 4870.126, "duration": 1.355}, {"text": "RAMESH RASKAR: Sorry?", "start": 4871.481, "duration": 0.875}, {"text": "AUDIENCE: [INAUDIBLE]\nthe internet.", "start": 4872.356, "duration": 1.884}, {"text": "RAMESH RASKAR: All right.", "start": 4874.24, "duration": 1.32}, {"text": "So [INAUDIBLE],, who's a\nscientist in our group,", "start": 4875.56, "duration": 4.33}, {"text": "has a very interesting\nway of putting this.", "start": 4879.89, "duration": 4.02}, {"text": "He says, photography,\nit's well-known.", "start": 4883.91, "duration": 3.86}, {"text": "Photography is the\nart of exclusion,", "start": 4887.77, "duration": 7.26}, {"text": "de-emphasizing things that--", "start": 4895.03, "duration": 2.07}, {"text": "the photographer\nmakes a decision", "start": 4897.1, "duration": 1.44}, {"text": "on what to de-emphasize\neither by using focus", "start": 4898.54, "duration": 2.61}, {"text": "or by cropping it and so on\nso that the photographer can", "start": 4901.15, "duration": 3.84}, {"text": "convey to the viewer\nwhat's most important.", "start": 4904.99, "duration": 3.99}, {"text": "But what we're doing\ncomputationally now", "start": 4908.98, "duration": 3.33}, {"text": "is adding another\nlevel of exclusion.", "start": 4912.31, "duration": 3.6}, {"text": "In this case, we're\nexcluding the intensity edges", "start": 4915.91, "duration": 2.46}, {"text": "and just keeping depth edges\nand all these other things.", "start": 4918.37, "duration": 3.37}, {"text": "So computationally,\nwe would extend", "start": 4921.74, "duration": 2.9}, {"text": "the concept of exclusion.", "start": 4924.64, "duration": 2.362}, {"text": "So one could be for\nnonphotorealistic rendering", "start": 4927.002, "duration": 1.958}, {"text": "for creating cartoons.", "start": 4928.96, "duration": 1.53}, {"text": "One could be for XCI.", "start": 4930.49, "duration": 1.5}, {"text": "And there are lots\nof other things.", "start": 4931.99, "duration": 1.98}, {"text": "Right now, this is being\nused in Mitsubishi products", "start": 4933.97, "duration": 2.43}, {"text": "for some really bizarre things.", "start": 4936.4, "duration": 2.01}, {"text": "So we saw the idea last time.", "start": 4942.41, "duration": 1.43}, {"text": "You get the slivers of shadows.", "start": 4943.84, "duration": 2.19}, {"text": "And by analyzing\nthe shadows, you", "start": 4946.03, "duration": 2.49}, {"text": "can continue-- compute\nthe depth discontinuities.", "start": 4948.52, "duration": 3.66}, {"text": "And some people like\nto call it slivers.", "start": 4952.18, "duration": 2.73}, {"text": "Some people like to call it\noccluding contours or shape", "start": 4954.91, "duration": 2.79}, {"text": "boundaries.", "start": 4957.7, "duration": 0.78}, {"text": "But they're not so precise.", "start": 4958.48, "duration": 1.98}, {"text": "And depth\ndiscontinuities is what", "start": 4960.46, "duration": 1.68}, {"text": "we're really talking about.", "start": 4962.14, "duration": 1.18}, {"text": "So when I take a\nphoto, then the depth", "start": 4963.32, "duration": 3.35}, {"text": "of this pixel and\ndepth of the pixel", "start": 4966.67, "duration": 2.7}, {"text": "on the other side of this\nscreen has a [INAUDIBLE]", "start": 4969.37, "duration": 4.02}, {"text": "discontinuity.", "start": 4973.39, "duration": 1.17}, {"text": "And that's really what\nwe're talking about as", "start": 4974.56, "duration": 2.76}, {"text": "opposed to slivers,\nwhere it's usually", "start": 4977.32, "duration": 3.69}, {"text": "about just the external part.", "start": 4981.01, "duration": 1.57}, {"text": "Well, if I put my\nhand over here,", "start": 4982.58, "duration": 1.73}, {"text": "this is still a\ndepth discontinuity", "start": 4984.31, "duration": 2.49}, {"text": "from my hand to my body.", "start": 4986.8, "duration": 1.71}, {"text": "So I would like to capture that.", "start": 4988.51, "duration": 3.12}, {"text": "And shape boundaries is\nalso not very precise.", "start": 4991.63, "duration": 3.61}, {"text": "So depth discontinuity is\nreally what we're talking about.", "start": 4995.24, "duration": 2.96}, {"text": "And imagine if this is in the\nSony EyeToy or the Microsoft", "start": 4998.2, "duration": 5.18}, {"text": "Natal.", "start": 5003.38, "duration": 0.52}, {"text": "Then if you have a depth camera,\nif I put my hand really close", "start": 5003.9, "duration": 3.36}, {"text": "to my body, it cannot\ndistinguish the depth with", "start": 5007.26, "duration": 2.57}, {"text": "respect to the camera of\nmy body versus my hand.", "start": 5009.83, "duration": 2.59}, {"text": "But with this\ncamera, I can still", "start": 5012.42, "duration": 1.65}, {"text": "continue to detect that\nthere's a shadow that's", "start": 5014.07, "duration": 4.41}, {"text": "created from that.", "start": 5018.48, "duration": 1.53}, {"text": "AUDIENCE: How about\nthat laser from--", "start": 5020.01, "duration": 2.043}, {"text": "RAMESH RASKAR: Sorry?", "start": 5022.053, "duration": 0.907}, {"text": "AUDIENCE: The laser\nprojector camera?", "start": 5022.96, "duration": 1.49}, {"text": "RAMESH RASKAR: Yeah, so\nactually, the Microsoft Natal", "start": 5024.45, "duration": 2.208}, {"text": "uses this PrimeSense sensor,\nwhich is not time of flight,", "start": 5026.658, "duration": 3.492}, {"text": "but based on triangulation.", "start": 5030.15, "duration": 2.55}, {"text": "But anything that\nsenses depth as", "start": 5032.7, "duration": 2.1}, {"text": "opposed to depth discontinuity\nwill have the same problem", "start": 5034.8, "duration": 3.03}, {"text": "because, as you get\ncloser and closer,", "start": 5037.83, "duration": 1.8}, {"text": "you'll not be able\nto detect that.", "start": 5039.63, "duration": 1.11}, {"text": "AUDIENCE: If you were\ntesting for a piece of paper,", "start": 5040.74, "duration": 1.54}, {"text": "it seems pretty good.", "start": 5042.28, "duration": 1.34}, {"text": "RAMESH RASKAR: It was very good.", "start": 5043.62, "duration": 0.69}, {"text": "Yeah, it was very good.", "start": 5044.31, "duration": 0.958}, {"text": "Yeah, so if it's a really\ngood depth-sensing camera,", "start": 5045.268, "duration": 3.272}, {"text": "then you're all set.", "start": 5048.54, "duration": 1.36}, {"text": "But it has poor resolution.", "start": 5049.9, "duration": 1.19}, {"text": "And it's a much\nmore complex device.", "start": 5051.09, "duration": 2.58}, {"text": "So again, shadows to the right,\nshadows to the left, and so on.", "start": 5058.43, "duration": 4.75}, {"text": "But then, look at the shadows.", "start": 5063.18, "duration": 1.25}, {"text": "They are not just\none-pixel-wide.", "start": 5064.43, "duration": 3.06}, {"text": "Depending on the\ndepth difference,", "start": 5067.49, "duration": 1.71}, {"text": "they could be very\nwide or very narrow.", "start": 5069.2, "duration": 2.49}, {"text": "So you want to create an output\nthat's exactly one-pixel-wide.", "start": 5071.69, "duration": 3.42}, {"text": "So how does this work?", "start": 5075.11, "duration": 1.75}, {"text": "So before we go there, I guess,\nis there intensity in this?", "start": 5076.86, "duration": 2.69}, {"text": "These are [INAUDIBLE].", "start": 5079.55, "duration": 1.797}, {"text": "And we can just put\nthat together and create", "start": 5081.347, "duration": 1.833}, {"text": "a cartoon in real-time.", "start": 5083.18, "duration": 2.75}, {"text": "In fact, we demonstrated this.", "start": 5085.93, "duration": 3.1}, {"text": "So yeah, this is another\nexample, my old '93 Honda", "start": 5089.03, "duration": 2.37}, {"text": "Civic.", "start": 5091.4, "duration": 0.84}, {"text": "And this is what you will get if\nyou use the intensity detector.", "start": 5092.24, "duration": 4.14}, {"text": "This is what you get\nfrom the four flashes.", "start": 5096.38, "duration": 2.4}, {"text": "And you will see\nthe Honda sign here.", "start": 5098.78, "duration": 1.65}, {"text": "That's barely visible here.", "start": 5100.43, "duration": 2.29}, {"text": "That's because the\nHonda sign has a relief.", "start": 5102.72, "duration": 5.36}, {"text": "It's a height field.", "start": 5108.08, "duration": 1.24}, {"text": "It's a geometric\nrather than texture.", "start": 5109.32, "duration": 2.15}, {"text": "And all these scratch marks\nand rusting is just texture.", "start": 5111.47, "duration": 6.25}, {"text": "It does not contribute\nto the geometry.", "start": 5117.72, "duration": 2.6}, {"text": "And if you try to locate the\nspark plugs or the dipstick,", "start": 5120.32, "duration": 4.68}, {"text": "it's barely visible here.", "start": 5125.0, "duration": 2.49}, {"text": "But again, here, you\ncan see it right there.", "start": 5127.49, "duration": 3.54}, {"text": "So the shapes are what\nwe're really looking for.", "start": 5131.03, "duration": 3.31}, {"text": "And we've got the four images,\ninput images, just four images.", "start": 5134.34, "duration": 2.87}, {"text": "You can see to the\nnaked eye, they", "start": 5137.21, "duration": 3.27}, {"text": "look identical to\na naive observer.", "start": 5140.48, "duration": 3.24}, {"text": "But you look at the shadows.", "start": 5143.72, "duration": 2.13}, {"text": "Here, the shadows are to\nthe right of these pipes.", "start": 5145.85, "duration": 3.06}, {"text": "Here, the shadow are to\nthe left of these pipes.", "start": 5148.91, "duration": 2.46}, {"text": "Here, the shadows\nare at the top.", "start": 5151.37, "duration": 2.23}, {"text": "And here, the shadows\nare at the bottom.", "start": 5153.6, "duration": 2.09}, {"text": "And by analyzing the shadows,\nyou can find the [INAUDIBLE]..", "start": 5155.69, "duration": 4.56}, {"text": "Yeah?", "start": 5160.25, "duration": 0.63}, {"text": "AUDIENCE: In practice,\nhonestly, the farther", "start": 5160.88, "duration": 3.06}, {"text": "continuous from\n12 feet away, it's", "start": 5163.94, "duration": 2.37}, {"text": "not as effective because your\nflashes are pretty close to the", "start": 5166.31, "duration": 2.797}, {"text": "[INTERPOSING VOICES]", "start": 5169.107, "duration": 0.833}, {"text": "RAMESH RASKAR: Right.", "start": 5169.94, "duration": 0.42}, {"text": "Exactly.", "start": 5170.36, "duration": 0.48}, {"text": "So we'll talk a little\nbit about what parameters", "start": 5170.84, "duration": 2.0}, {"text": "you are to choose to get\nan optimal performance.", "start": 5172.84, "duration": 2.77}, {"text": "And yeah, there's\ndefinitely a sweet spot", "start": 5175.61, "duration": 1.83}, {"text": "where it works in the system.", "start": 5177.44, "duration": 2.433}, {"text": "Some more examples here.", "start": 5183.24, "duration": 2.34}, {"text": "And I just want to describe\nto you very quickly", "start": 5185.58, "duration": 3.03}, {"text": "the geometric parameters\nthat make it happen.", "start": 5188.61, "duration": 2.94}, {"text": "But we were showing\nthis live at SIGGRAPH.", "start": 5191.55, "duration": 3.51}, {"text": "And you can stand in front\nof this camera, where", "start": 5195.06, "duration": 2.58}, {"text": "every iconic fourth frame had a\ndifferent flashlight going off.", "start": 5197.64, "duration": 5.09}, {"text": "They put in the lead-in.", "start": 5202.73, "duration": 1.0}, {"text": "You can stand in front of it.", "start": 5203.73, "duration": 1.208}, {"text": "And it's a cartoon.", "start": 5204.938, "duration": 1.852}, {"text": "And I'm a big fan of the\nA-ha video from the 1980s,", "start": 5206.79, "duration": 5.43}, {"text": "\"Take On Me.\"", "start": 5212.22, "duration": 0.88}, {"text": "[LAUGHTER]", "start": 5213.1, "duration": 0.5}, {"text": "You remember that?", "start": 5213.6, "duration": 0.69}, {"text": "AUDIENCE: Yeah.", "start": 5214.29, "duration": 0.625}, {"text": "AUDIENCE: Wow.", "start": 5214.915, "duration": 1.098}, {"text": "RAMESH RASKAR: I thought I was\ntoo old to appreciate that.", "start": 5216.013, "duration": 2.417}, {"text": "But so in the A-ha\nvideo, there's", "start": 5218.43, "duration": 3.9}, {"text": "this very beautiful effect\nwhere on one side of the glass", "start": 5222.33, "duration": 4.08}, {"text": "screen, the world is cartoon.", "start": 5226.41, "duration": 1.89}, {"text": "And the other side, it's real.", "start": 5228.3, "duration": 1.99}, {"text": "And so when we were showing\nthis, it goes on for four days,", "start": 5230.29, "duration": 6.567}, {"text": "after the end of the\nfirst day, people", "start": 5236.857, "duration": 1.583}, {"text": "started saying,\noh, this reminds us", "start": 5238.44, "duration": 1.458}, {"text": "of the A-ha video, the\n\"Take On Me\" video.", "start": 5239.898, "duration": 2.922}, {"text": "And I said, yeah,\nthat's really true.", "start": 5242.82, "duration": 2.01}, {"text": "So we got really sick\nof those comments.", "start": 5244.83, "duration": 2.28}, {"text": "And on our demo,\ninstead of calling it--", "start": 5247.11, "duration": 3.09}, {"text": "we had some really\nboring technical name.", "start": 5250.2, "duration": 2.28}, {"text": "We said, this is the A-ha\ndemo, \"Take On Me\" demo.", "start": 5252.48, "duration": 3.03}, {"text": "And we had it in big\nletters on a huge screen.", "start": 5255.51, "duration": 5.13}, {"text": "And then, on the second day, the\ncurator of the show came to me.", "start": 5260.64, "duration": 5.993}, {"text": "And she introduced\nme to this guy.", "start": 5266.633, "duration": 1.417}, {"text": "And she said, this is, I forget\nhis name, David Patterson.", "start": 5268.05, "duration": 6.307}, {"text": "This David Patterson,\ndo you know him?", "start": 5274.357, "duration": 1.583}, {"text": "I said, I don't know him.", "start": 5275.94, "duration": 1.042}, {"text": "He said, he was the music\nvideo director of A-ha.", "start": 5276.982, "duration": 2.978}, {"text": "[LAUGHTER]", "start": 5279.96, "duration": 2.46}, {"text": "And so I said,\nwow, that's great.", "start": 5282.42, "duration": 2.07}, {"text": "We're really inspired\nby your video.", "start": 5284.49, "duration": 1.5}, {"text": "He looks up on the screen.", "start": 5285.99, "duration": 2.46}, {"text": "And our demo was\ninside a closed quote.", "start": 5288.45, "duration": 2.172}, {"text": "And they're showing\nthe live output", "start": 5290.622, "duration": 1.458}, {"text": "of that on the big screen.", "start": 5292.08, "duration": 2.263}, {"text": "And he said, what are\nyou showing there?", "start": 5294.343, "duration": 1.667}, {"text": "I said, this is live.", "start": 5296.01, "duration": 0.875}, {"text": "We can go inside.", "start": 5296.885, "duration": 0.985}, {"text": "And this is being\ncomputed in real-time.", "start": 5297.87, "duration": 4.21}, {"text": "And he said, that's impossible\nbecause when we were doing it", "start": 5302.08, "duration": 2.81}, {"text": "in the mid-80s, every frame\ntook them a whole day--", "start": 5304.89, "duration": 3.81}, {"text": "[LAUGHTER]", "start": 5308.7, "duration": 2.16}, {"text": "--to rotoscope and so on.", "start": 5310.86, "duration": 3.96}, {"text": "And so we were excited.", "start": 5314.82, "duration": 3.03}, {"text": "Patterson is here.", "start": 5317.85, "duration": 0.84}, {"text": "So he comes inside.", "start": 5318.69, "duration": 1.11}, {"text": "He acts very cool.", "start": 5319.8, "duration": 1.925}, {"text": "He looks right there.", "start": 5321.725, "duration": 0.875}, {"text": "He looks at the images.", "start": 5322.6, "duration": 1.19}, {"text": "And we take-- we\nget very excited.", "start": 5323.79, "duration": 1.58}, {"text": "We take pictures with him.", "start": 5325.37, "duration": 1.63}, {"text": "He leaves.", "start": 5327.0, "duration": 1.63}, {"text": "But after 1/2 an hour, he\nbrings his son with him.", "start": 5328.63, "duration": 4.555}, {"text": "And he started\nexplaining to him.", "start": 5333.185, "duration": 1.375}, {"text": "His son is two or\nthree years old.", "start": 5334.56, "duration": 1.92}, {"text": "He said, wow, remember in the\n1980s, I worked on this video?", "start": 5336.48, "duration": 3.03}, {"text": "These guys are doing\nit in real-time now.", "start": 5339.51, "duration": 2.43}, {"text": "And we said, welcome.", "start": 5341.94, "duration": 1.783}, {"text": "We're pretty happy\nyou brought your son.", "start": 5343.723, "duration": 1.667}, {"text": "You must be excited.", "start": 5345.39, "duration": 1.26}, {"text": "After a couple of hours,\nhe brings his wife.", "start": 5346.65, "duration": 1.95}, {"text": "[LAUGHTER]", "start": 5348.6, "duration": 2.575}, {"text": "And then, it just\ngoes on all day long.", "start": 5351.175, "duration": 1.625}, {"text": "He just keeps bringing people\nto show them how this works.", "start": 5352.8, "duration": 3.94}, {"text": "So that was a high-point\nof that [INAUDIBLE]..", "start": 5356.74, "duration": 3.26}, {"text": "So how does it work?", "start": 5360.0, "duration": 1.35}, {"text": "So you have a camera.", "start": 5361.35, "duration": 2.88}, {"text": "And you have your flashlight,\nwhich is shown as P here.", "start": 5364.23, "duration": 3.66}, {"text": "And then, because of the\nparallax between the lights", "start": 5367.89, "duration": 3.6}, {"text": "and between the lens\nand the light source,", "start": 5371.49, "duration": 2.7}, {"text": "you're going to cast a\nshadow of this object.", "start": 5374.19, "duration": 3.33}, {"text": "If the flash is to\nthe left, the shadow", "start": 5377.52, "duration": 2.01}, {"text": "is going to be\ncast on the right.", "start": 5379.53, "duration": 2.38}, {"text": "And if you just freeze the\nrig from the light source", "start": 5381.91, "duration": 3.05}, {"text": "to the object to\nthe shadow, it's", "start": 5384.96, "duration": 2.91}, {"text": "going to be projected\nin the image", "start": 5387.87, "duration": 1.86}, {"text": "as this particular vector.", "start": 5389.73, "duration": 3.24}, {"text": "Now what's interesting\nis that it turns out", "start": 5392.97, "duration": 4.62}, {"text": "we need at least\nthree light sources.", "start": 5397.59, "duration": 1.545}, {"text": "You don't have to use four.", "start": 5399.135, "duration": 1.125}, {"text": "But you need at least\nthree light sources.", "start": 5400.26, "duration": 2.01}, {"text": "And let's say you have three\nlight sources, P1, P2, P3.", "start": 5402.27, "duration": 2.97}, {"text": "And the image of the light\nsource is denoted by E.", "start": 5405.24, "duration": 4.17}, {"text": "So the shadow, it\nturns out, lies", "start": 5409.41, "duration": 2.88}, {"text": "along a so-called\n[INAUDIBLE],, those", "start": 5412.29, "duration": 1.8}, {"text": "of you who are familiar with\nthe [INAUDIBLE] geometry.", "start": 5414.09, "duration": 3.52}, {"text": "And as long as we make\nsure that for any given", "start": 5417.61, "duration": 6.59}, {"text": "silhouette, any\ngiven depth edge,", "start": 5424.2, "duration": 1.8}, {"text": "there is at least one light\nthat's on one side of that edge", "start": 5426.0, "duration": 3.66}, {"text": "and there's at least\none light that's", "start": 5429.66, "duration": 1.59}, {"text": "on the other side\nof that edge, we", "start": 5431.25, "duration": 2.55}, {"text": "can guarantee that at\nleast in one image,", "start": 5433.8, "duration": 2.82}, {"text": "you will see a shadow.", "start": 5436.62, "duration": 1.65}, {"text": "And at least in one image,\nyou will not see a shadow.", "start": 5438.27, "duration": 5.13}, {"text": "And while being\nable to compare--", "start": 5443.4, "duration": 2.265}, {"text": "so out of four, in our\ncase, at least one of them", "start": 5445.665, "duration": 2.673}, {"text": "will have a shadow.", "start": 5448.338, "duration": 0.792}, {"text": "And at least one of them\nwill not have a shadow.", "start": 5449.13, "duration": 3.06}, {"text": "So by guaranteeing that, we\ncan analyze the four images", "start": 5452.19, "duration": 4.8}, {"text": "and compute how that works.", "start": 5456.99, "duration": 1.96}, {"text": "So here's a very simple example.", "start": 5458.95, "duration": 4.31}, {"text": "It flashed to the left.", "start": 5463.26, "duration": 1.39}, {"text": "So the shadow is on the right.", "start": 5464.65, "duration": 1.25}, {"text": "Here, the flash is on the right.", "start": 5465.9, "duration": 1.333}, {"text": "So the shadow is on the left.", "start": 5467.233, "duration": 1.247}, {"text": "And all you do is take these two\nimages, find the max operator,", "start": 5468.48, "duration": 6.06}, {"text": "take the max of every pixel.", "start": 5474.54, "duration": 2.07}, {"text": "And this is what you\ncan do with HDR Shop.", "start": 5476.61, "duration": 1.86}, {"text": "I don't know if you can\ndo it with Photoshop.", "start": 5478.47, "duration": 1.5}, {"text": "Can you just take two\nimages in Photoshop", "start": 5479.97, "duration": 1.9}, {"text": "and find the max of the two?", "start": 5481.87, "duration": 2.04}, {"text": "At every pixel, I want to\ncompare the two pixels.", "start": 5483.91, "duration": 3.18}, {"text": "And I want to take the\nmaximum of the two.", "start": 5487.09, "duration": 2.395}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 5489.485, "duration": 0.875}, {"text": "RAMESH RASKAR: You can do that?", "start": 5490.36, "duration": 0.51}, {"text": "AUDIENCE: Well, I\nlearned that there", "start": 5490.87, "duration": 1.74}, {"text": "are filters that you can do that\nwith one layer and the layer", "start": 5492.61, "duration": 2.76}, {"text": "behind it and [INAUDIBLE].", "start": 5495.37, "duration": 1.96}, {"text": "I don't know if\nit's exactly that.", "start": 5497.33, "duration": 1.617}, {"text": "RAMESH RASKAR: Yeah.", "start": 5498.947, "duration": 0.833}, {"text": "AUDIENCE: But [INAUDIBLE].", "start": 5499.78, "duration": 1.942}, {"text": "RAMESH RASKAR: Exactly.", "start": 5501.722, "duration": 0.958}, {"text": "But nobody cares about\ndoing nice, simple", "start": 5502.68, "duration": 2.08}, {"text": "mathematical operations.", "start": 5504.76, "duration": 2.17}, {"text": "So HDR Shop is great\nfor these things.", "start": 5506.93, "duration": 2.248}, {"text": "All these things, you\ncan do it in HDR Shop", "start": 5509.178, "duration": 1.792}, {"text": "in 15 seconds [INAUDIBLE].", "start": 5510.97, "duration": 2.97}, {"text": "AUDIENCE: Another\n[INAUDIBLE] introduced it.", "start": 5513.94, "duration": 2.16}, {"text": "But [INAUDIBLE]\nimage processing,", "start": 5516.1, "duration": 1.83}, {"text": "ImageJ is really a nice--", "start": 5517.93, "duration": 1.569}, {"text": "RAMESH RASKAR: ImageJ?", "start": 5519.499, "duration": 0.917}, {"text": "AUDIENCE: ImageJ.", "start": 5520.416, "duration": 0.814}, {"text": "It's Java-based and\nall open-source.", "start": 5521.23, "duration": 1.5}, {"text": "So if you want to take a look\nat the code, it's all there.", "start": 5522.73, "duration": 2.43}, {"text": "RAMESH RASKAR: Excellent.", "start": 5525.16, "duration": 0.36}, {"text": "AUDIENCE: And also, you can\nscript all of these functions", "start": 5525.52, "duration": 2.79}, {"text": "with a lot of images\nusing JavaScript--", "start": 5528.31, "duration": 2.01}, {"text": "RAMESH RASKAR: Excellent.", "start": 5530.32, "duration": 0.63}, {"text": "AUDIENCE: --which\nis really useful.", "start": 5530.95, "duration": 0.93}, {"text": "RAMESH RASKAR: Just send a\nlink to the class or to Sam", "start": 5531.88, "duration": 1.91}, {"text": "so it'll go in the notes.", "start": 5533.79, "duration": 1.042}, {"text": "AUDIENCE: Cool.", "start": 5534.832, "duration": 0.625}, {"text": "RAMESH RASKAR: ImageJ.", "start": 5535.457, "duration": 0.917}, {"text": "I know there's OpenCV\nand all those things.", "start": 5536.374, "duration": 1.876}, {"text": "So I'm sure you'll use them.", "start": 5538.25, "duration": 1.37}, {"text": "In MATLAB, again, it's one-line\ncommand, max a, b, a vector,", "start": 5539.62, "duration": 5.76}, {"text": "b vector.", "start": 5545.38, "duration": 0.5}, {"text": "But basically, one-line code\nto take a max of two images.", "start": 5545.88, "duration": 3.31}, {"text": "In Photoshop, every 30 minutes.", "start": 5549.19, "duration": 3.93}, {"text": "So all you do is take\nthe max of the two", "start": 5553.12, "duration": 2.16}, {"text": "and take the ratio of this\nimage by the max image, which", "start": 5555.28, "duration": 3.81}, {"text": "I call normalized.", "start": 5559.09, "duration": 1.475}, {"text": "And then, we want\nto divide that.", "start": 5560.565, "duration": 1.375}, {"text": "And if you divide it, all\nthe texture goes away.", "start": 5561.94, "duration": 2.59}, {"text": "And only the shadows are left.", "start": 5564.53, "duration": 1.25}, {"text": "Wherever there was no shadow,\nyou'll get a value of one.", "start": 5565.78, "duration": 3.15}, {"text": "The ratio is one.", "start": 5568.93, "duration": 0.96}, {"text": "Wherever there's\na shadow, you'll", "start": 5569.89, "duration": 1.56}, {"text": "get a value that's\nclose to zero.", "start": 5571.45, "duration": 2.0}, {"text": "It's not always zero because\nthere's some other lighting.", "start": 5573.45, "duration": 3.31}, {"text": "And now, all you have to do is\nif you take one scan line here,", "start": 5576.76, "duration": 4.76}, {"text": "this is how you plot it.", "start": 5581.52, "duration": 1.0}, {"text": "And you can see the\nshadows very clearly.", "start": 5582.52, "duration": 1.74}, {"text": "And same here.", "start": 5584.26, "duration": 1.5}, {"text": "In the left image, just\nscan from left to right.", "start": 5585.76, "duration": 2.52}, {"text": "And wherever you see a jump\nfrom lit area to an unlit area,", "start": 5588.28, "duration": 2.865}, {"text": "it has to be a\n[INAUDIBLE] touch.", "start": 5591.145, "duration": 1.965}, {"text": "In the right image, you\nscan from right to left.", "start": 5593.11, "duration": 2.58}, {"text": "And wherever, again, you see\nfrom lit area to unlit area,", "start": 5595.69, "duration": 3.42}, {"text": "that's a [INAUDIBLE] touch.", "start": 5599.11, "duration": 1.51}, {"text": "So in every one of\nthose four images,", "start": 5600.62, "duration": 2.17}, {"text": "you'll be able to find\n[INAUDIBLE] touches", "start": 5602.79, "duration": 1.75}, {"text": "from different orientations.", "start": 5604.54, "duration": 1.5}, {"text": "And then, we can take a union\nof all these four images.", "start": 5606.04, "duration": 4.08}, {"text": "And that gives you a full\n[INAUDIBLE] touch image.", "start": 5610.12, "duration": 4.09}, {"text": "So in this case, for example,\nall these internal edges", "start": 5614.21, "duration": 2.6}, {"text": "are completely ignored.", "start": 5616.81, "duration": 1.29}, {"text": "And all you see is silhouettes.", "start": 5618.1, "duration": 3.03}, {"text": "And in MATLAB, that's\nall there is, 15 lines", "start": 5621.13, "duration": 3.36}, {"text": "of code and no parameters.", "start": 5624.49, "duration": 3.66}, {"text": "No tuning required.", "start": 5628.15, "duration": 1.98}, {"text": "There's no constant\nthat's used anyway.", "start": 5630.13, "duration": 3.5}, {"text": "So it's extremely easy to use.", "start": 5633.63, "duration": 1.36}, {"text": "You can implement this.", "start": 5634.99, "duration": 1.1}, {"text": "You can use it.", "start": 5636.09, "duration": 0.75}, {"text": "I'll give it as an option\nfor one of the class", "start": 5636.84, "duration": 2.64}, {"text": "assignments so you have\na choice to use this.", "start": 5639.48, "duration": 4.56}, {"text": "Any questions on this one?", "start": 5646.69, "duration": 2.03}, {"text": "Yes?", "start": 5648.72, "duration": 0.5}, {"text": "AUDIENCE: So you said outline.", "start": 5649.22, "duration": 2.42}, {"text": "The boundary is only\na one-pixel line.", "start": 5651.64, "duration": 2.1}, {"text": "But if you actually provide\nmore than one pixel,", "start": 5653.74, "duration": 3.3}, {"text": "depending on how\nthick the shadow is,", "start": 5657.04, "duration": 2.13}, {"text": "can we get more\ndepth [INAUDIBLE]??", "start": 5659.17, "duration": 2.01}, {"text": "RAMESH RASKAR: That's\na very good point.", "start": 5661.18, "duration": 1.667}, {"text": "So depending on how far things\nare, so here, for example,", "start": 5662.847, "duration": 3.323}, {"text": "the shadow is wider than here.", "start": 5666.17, "duration": 2.745}, {"text": "And that's because\nthe depth difference", "start": 5668.915, "duration": 1.625}, {"text": "is larger or smaller.", "start": 5670.54, "duration": 0.908}, {"text": "So you are already right.", "start": 5671.448, "duration": 1.042}, {"text": "That thickness of\nthe shadow actually", "start": 5672.49, "duration": 2.237}, {"text": "tells you a little bit\nabout the depth difference,", "start": 5674.727, "duration": 2.083}, {"text": "not the depth itself,\nbut the depth difference.", "start": 5676.81, "duration": 2.655}, {"text": "AUDIENCE: So you get more\n3D information out of it.", "start": 5679.465, "duration": 2.125}, {"text": "RAMESH RASKAR: So you could get\na little bit of 3D information", "start": 5681.59, "duration": 2.03}, {"text": "as well.", "start": 5683.62, "duration": 0.5}, {"text": "Yeah, that would be nice.", "start": 5684.12, "duration": 1.11}, {"text": "AUDIENCE: [INAUDIBLE] capture?", "start": 5685.23, "duration": 6.61}, {"text": "So [INAUDIBLE] like a\nmachine in the shop.", "start": 5691.84, "duration": 3.605}, {"text": "RAMESH RASKAR: Right.", "start": 5695.445, "duration": 0.875}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 5696.32, "duration": 0.875}, {"text": "RAMESH RASKAR: Yes.", "start": 5697.195, "duration": 0.792}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 5697.987, "duration": 0.883}, {"text": "RAMESH RASKAR: They just use\na laser scanner, usually.", "start": 5698.87, "duration": 1.54}, {"text": "AUDIENCE: Yeah.", "start": 5700.41, "duration": 0.39}, {"text": "RAMESH RASKAR:\nYeah, unfortunately.", "start": 5700.8, "duration": 1.458}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 5702.258, "duration": 1.147}, {"text": "RAMESH RASKAR: You can just\ncapture the silhouette.", "start": 5703.405, "duration": 2.125}, {"text": "But remember, we are\nnot capturing depth.", "start": 5705.53, "duration": 2.31}, {"text": "We're only capturing\ndepth edges.", "start": 5707.84, "duration": 2.537}, {"text": "AUDIENCE: Yes.", "start": 5710.377, "duration": 0.583}, {"text": "RAMESH RASKAR: It's like saying,\nI'm not capturing intensities.", "start": 5710.96, "duration": 2.625}, {"text": "I'm just capturing\nintensity edges.", "start": 5713.585, "duration": 2.308}, {"text": "AUDIENCE: But [INAUDIBLE].", "start": 5715.893, "duration": 1.389}, {"text": "RAMESH RASKAR: So this\nwork has really taken off.", "start": 5720.198, "duration": 2.042}, {"text": "There have been lots of\npapers that are based", "start": 5722.24, "duration": 2.01}, {"text": "on this particular technique.", "start": 5724.25, "duration": 1.23}, {"text": "And so people have\ntried to do [INAUDIBLE]..", "start": 5725.48, "duration": 3.81}, {"text": "Some people have\ntried to do some--", "start": 5729.29, "duration": 2.31}, {"text": "it's still open.", "start": 5731.6, "duration": 0.69}, {"text": "It's very new.", "start": 5732.29, "duration": 0.672}, {"text": "Or it's some three,\nfour years old.", "start": 5732.962, "duration": 1.458}, {"text": "And people are trying to\ndo different color lights.", "start": 5734.42, "duration": 4.89}, {"text": "So there's a lot you can do.", "start": 5739.31, "duration": 1.17}, {"text": "Question up there?", "start": 5740.48, "duration": 1.005}, {"text": "AUDIENCE: Could you\nactually capture depth?", "start": 5741.485, "duration": 1.792}, {"text": "Or at least the difference\nbetween different edges", "start": 5743.277, "duration": 2.923}, {"text": "so you can study\nthe [INAUDIBLE]??", "start": 5746.2, "duration": 1.875}, {"text": "RAMESH RASKAR: If you can\nprocess the shadow width.", "start": 5748.075, "duration": 2.125}, {"text": "But remember, it's not\ngoing to be as robust,", "start": 5750.2, "duration": 2.22}, {"text": "because if you\nlook at this plot,", "start": 5752.42, "duration": 3.94}, {"text": "you have to estimate how wide\nthis region is that's shadowed.", "start": 5756.36, "duration": 3.21}, {"text": "So if you can do that\nfast enough, then yes,", "start": 5759.57, "duration": 3.38}, {"text": "you could do that.", "start": 5762.95, "duration": 0.82}, {"text": "So it's not-- in\ncertain conditions,", "start": 5763.77, "duration": 2.06}, {"text": "maybe it's possible.", "start": 5765.83, "duration": 1.44}, {"text": "For skin, it's very easy\nbecause the shadow color is not", "start": 5767.27, "duration": 4.02}, {"text": "going to interfere.", "start": 5771.29, "duration": 0.84}, {"text": "If something was\nblack in the scene,", "start": 5772.13, "duration": 1.5}, {"text": "then that could be\ndetected as a shadow.", "start": 5773.63, "duration": 2.58}, {"text": "But in this matter, even\nif the object is black,", "start": 5776.21, "duration": 3.21}, {"text": "it doesn't matter.", "start": 5779.42, "duration": 0.99}, {"text": "You'll still get\nvery nice edges.", "start": 5780.41, "duration": 2.8}, {"text": "But if you try to\nestimate the shadow width,", "start": 5783.21, "duration": 2.42}, {"text": "then you have a little\nbit of [INAUDIBLE]..", "start": 5785.63, "duration": 1.87}, {"text": "AUDIENCE: Again, all\nof these techniques", "start": 5787.5, "duration": 1.667}, {"text": "assume that you have one\n[INAUDIBLE] image, which", "start": 5789.167, "duration": 2.703}, {"text": "could have [INAUDIBLE].", "start": 5791.87, "duration": 2.73}, {"text": "You can-- then this one--", "start": 5794.6, "duration": 1.26}, {"text": "RAMESH RASKAR: Hey, now you're\nthinking like a researcher.", "start": 5795.86, "duration": 2.417}, {"text": "Yeah, now we thought\nabout all the ways", "start": 5798.277, "duration": 2.593}, {"text": "you can change the\nlighting parameters.", "start": 5800.87, "duration": 1.975}, {"text": "Now you're saying,\nin addition to that,", "start": 5802.845, "duration": 1.625}, {"text": "can we change camera parameters\nand do something more?", "start": 5804.47, "duration": 2.25}, {"text": "That's the thinking I want\nyou to have in this class.", "start": 5806.72, "duration": 2.435}, {"text": "AUDIENCE: Yeah.", "start": 5809.155, "duration": 0.625}, {"text": "RAMESH RASKAR: Yeah,\nalways take an idea, x,", "start": 5809.78, "duration": 2.25}, {"text": "and think about how\nyou can do the next x.", "start": 5812.03, "duration": 3.63}, {"text": "And I posted some\nslides on how to come up", "start": 5815.66, "duration": 2.43}, {"text": "with new ideas on\nthe Stellar webpage.", "start": 5818.09, "duration": 2.67}, {"text": "If you're inspired by\nan idea x, how do you", "start": 5820.76, "duration": 3.36}, {"text": "come up with the next idea?", "start": 5824.12, "duration": 1.33}, {"text": "And then, there's a\nsystematic process", "start": 5825.45, "duration": 3.08}, {"text": "of how you can come\nup with great ideas.", "start": 5828.53, "duration": 2.34}, {"text": "And also, the same\nslides tell you,", "start": 5830.87, "duration": 2.95}, {"text": "if you come up\nwith a great idea,", "start": 5833.82, "duration": 1.88}, {"text": "whether to decide whether\nto pursue it or not.", "start": 5835.7, "duration": 2.95}, {"text": "So I'm curious\nabout your comments.", "start": 5838.65, "duration": 3.32}, {"text": "It's just a work in progress.", "start": 5841.97, "duration": 1.6}, {"text": "I have been putting it together\nover the last several months.", "start": 5843.57, "duration": 3.77}, {"text": "So again, that allows you\nto do this in real-time.", "start": 5851.69, "duration": 5.71}, {"text": "What are some other\nthings people are doing?", "start": 5857.4, "duration": 2.45}, {"text": "You take a flash photo.", "start": 5859.85, "duration": 2.91}, {"text": "The person is very brightly lit.", "start": 5862.76, "duration": 1.59}, {"text": "The background is\nnot so well-lit.", "start": 5864.35, "duration": 2.37}, {"text": "You take a no-flash photo.", "start": 5866.72, "duration": 3.33}, {"text": "What has changed in the two?", "start": 5870.05, "duration": 3.194}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 5873.244, "duration": 0.875}, {"text": "RAMESH RASKAR: She didn't blink.", "start": 5874.119, "duration": 1.333}, {"text": "Remember, this part\nof [INAUDIBLE] flash.", "start": 5875.452, "duration": 2.118}, {"text": "But anyway, that's\na different point.", "start": 5877.57, "duration": 2.55}, {"text": "What information can\nyou recover from this?", "start": 5880.12, "duration": 2.833}, {"text": "AUDIENCE: You can separate the\nforeground from background.", "start": 5882.953, "duration": 2.417}, {"text": "RAMESH RASKAR: You can separate\nforeground from background", "start": 5885.37, "duration": 2.417}, {"text": "because the foreground\nis well-lit.", "start": 5887.787, "duration": 2.903}, {"text": "But the background\ndoesn't change.", "start": 5890.69, "duration": 2.96}, {"text": "If I just take the\nratio of the two images,", "start": 5893.65, "duration": 3.22}, {"text": "it will look something like this\nif I do one minus the ratio.", "start": 5896.87, "duration": 4.5}, {"text": "So the background\nhasn't changed.", "start": 5901.37, "duration": 3.51}, {"text": "And the foreground has\nchanged dramatically.", "start": 5904.88, "duration": 4.65}, {"text": "So this particular paper\nis called flash mapping.", "start": 5909.53, "duration": 2.37}, {"text": "As simple as that.", "start": 5911.9, "duration": 0.96}, {"text": "That was the idea for a\nSIGGRAPH paper in 2006.", "start": 5912.86, "duration": 3.608}, {"text": "They went a little bit\nbeyond that and just said,", "start": 5916.468, "duration": 2.042}, {"text": "if we just take pure ratios,\nthen you cannot get the strands", "start": 5918.51, "duration": 3.38}, {"text": "of the hair and so on.", "start": 5921.89, "duration": 2.11}, {"text": "So they used some gradient\ndomain techniques,", "start": 5924.0, "duration": 3.75}, {"text": "some graphical techniques to\nsolve this mapping equation of,", "start": 5927.75, "duration": 4.893}, {"text": "what's foreground and\nwhat's background?", "start": 5932.643, "duration": 1.667}, {"text": "And they can also detect\nthese very subpixel features,", "start": 5934.31, "duration": 4.91}, {"text": "strands of hair.", "start": 5939.22, "duration": 2.2}, {"text": "And then, of course,\nyou can take that", "start": 5941.42, "duration": 2.1}, {"text": "and replace the background.", "start": 5943.52, "duration": 2.13}, {"text": "So it was mostly well-lit.", "start": 5945.65, "duration": 1.26}, {"text": "It does pretty well here.", "start": 5946.91, "duration": 1.15}, {"text": "There's some small artifacts.", "start": 5948.06, "duration": 1.4}, {"text": "But it looks pretty good.", "start": 5949.46, "duration": 2.49}, {"text": "So just by changing the light,\nalso, this presence and absence", "start": 5951.95, "duration": 3.9}, {"text": "of light, you can create some\nreally interesting [INAUDIBLE]", "start": 5955.85, "duration": 3.6}, {"text": "or interactions.", "start": 5959.45, "duration": 1.355}, {"text": "AUDIENCE: It's\nthe same technique", "start": 5960.805, "duration": 1.375}, {"text": "with a flashing\n[INAUDIBLE] video.", "start": 5962.18, "duration": 3.112}, {"text": "RAMESH RASKAR:\nThat's a great idea.", "start": 5965.292, "duration": 1.458}, {"text": "So you could do\nalternate frames.", "start": 5966.75, "duration": 2.3}, {"text": "And you won't-- it won't\nbe disturbing for the user.", "start": 5969.05, "duration": 3.84}, {"text": "And you can just distinguish\nforeground from background.", "start": 5972.89, "duration": 5.42}, {"text": "So very simple examples.", "start": 5978.31, "duration": 1.14}, {"text": "We'll progressively become\nmore and more complex, I guess,", "start": 5979.45, "duration": 3.55}, {"text": "here.", "start": 5983.0, "duration": 0.5}, {"text": "But let's stop here for today.", "start": 5983.5, "duration": 1.83}, {"text": "And we'll talk about all these\nother cool things next time.", "start": 5985.33, "duration": 4.17}]
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+[{"text": "NANCY KANWISHER: So we won't\nget through the whole attention", "start": 10.2, "duration": 2.55}, {"text": "lecture.", "start": 12.75, "duration": 0.36}, {"text": "I saw this coming.", "start": 13.11, "duration": 0.75}, {"text": "I just felt like that last\nbit was important enough.", "start": 13.86, "duration": 2.167}, {"text": "We'll cut as needed.", "start": 16.027, "duration": 1.403}, {"text": "But I do want to\ntalk about attention.", "start": 17.43, "duration": 1.95}, {"text": "And let me start by\nsharing with you some", "start": 19.38, "duration": 3.33}, {"text": "of the key ideas about\nwhat attention is.", "start": 22.71, "duration": 3.72}, {"text": "OK, so to get into the mode\nof thinking about this,", "start": 26.43, "duration": 3.15}, {"text": "let's consider the\nfollowing question.", "start": 29.58, "duration": 2.64}, {"text": "How do you feel about\npeople driving while talking", "start": 32.22, "duration": 2.31}, {"text": "on their cell phones?", "start": 34.53, "duration": 2.17}, {"text": "Smart, not smart?", "start": 36.7, "duration": 2.84}, {"text": "And while you're thinking about\nthat, also consider the case--", "start": 39.54, "duration": 3.45}, {"text": "like let's suppose\nthat you have had", "start": 42.99, "duration": 2.49}, {"text": "a hands-free setup,\nso you don't have", "start": 45.48, "duration": 2.28}, {"text": "to be looking down\non your cell phone", "start": 47.76, "duration": 2.43}, {"text": "or typing away or\nholding your cell phone.", "start": 50.19, "duration": 5.55}, {"text": "Maybe that's OK.", "start": 55.74, "duration": 1.62}, {"text": "What do you think?", "start": 57.36, "duration": 1.35}, {"text": "Is there no problem with driving\nwhile talking on your cell", "start": 58.71, "duration": 3.03}, {"text": "phone, provided you're\nnot looking down", "start": 61.74, "duration": 1.83}, {"text": "and pecking away at it?", "start": 63.57, "duration": 1.35}, {"text": "Yes?", "start": 69.44, "duration": 0.6}, {"text": "What do you think?", "start": 70.04, "duration": 0.75}, {"text": "I want to know what\nyou really think.", "start": 73.078, "duration": 1.542}, {"text": "I know what all the PR says.", "start": 74.62, "duration": 3.57}, {"text": "Is it fine?", "start": 78.19, "duration": 1.65}, {"text": "Yes?", "start": 79.84, "duration": 1.14}, {"text": "AUDIENCE: I would say it depends\non whether you're driving--", "start": 80.98, "duration": 2.97}, {"text": "Like if the road is clear and\nit's like your usual path,", "start": 83.95, "duration": 2.55}, {"text": "like driving is pretty\nautomatic at that point.", "start": 86.5, "duration": 2.1}, {"text": "But it it's like high\ntraffic or a new area,", "start": 88.6, "duration": 2.22}, {"text": "then I think it would have\na significant affects,", "start": 90.82, "duration": 2.23}, {"text": "so you shouldn't.", "start": 93.05, "duration": 1.46}, {"text": "NANCY KANWISHER: Totally.", "start": 94.51, "duration": 1.14}, {"text": "My rule is, if I am\ntalking on my cell phone,", "start": 95.65, "duration": 2.97}, {"text": "certainly, if I'm turning\nleft, I put the damn cell phone", "start": 98.62, "duration": 2.76}, {"text": "on my lap.", "start": 101.38, "duration": 0.78}, {"text": "And I tell whoever it\nis, I can't talk to you", "start": 102.16, "duration": 3.27}, {"text": "and turn left at the same time.", "start": 105.43, "duration": 1.62}, {"text": "All right, turning left is\nthe hardest thing we do.", "start": 107.05, "duration": 2.19}, {"text": "Self-driving cars\ncan't turn left.", "start": 109.24, "duration": 1.873}, {"text": "Have I mentioned this?", "start": 111.113, "duration": 0.917}, {"text": "How does a self-driving\ncar turn left?", "start": 112.03, "duration": 1.77}, {"text": "It turns right three times.", "start": 113.8, "duration": 1.98}, {"text": "Why is that?", "start": 115.78, "duration": 0.57}, {"text": "Because turning left\nis social cognition.", "start": 116.35, "duration": 2.49}, {"text": "It's like, do they see me?", "start": 118.84, "duration": 2.22}, {"text": "Do they know I'm here?", "start": 121.06, "duration": 1.085}, {"text": "Are they looking\nat my indicator?", "start": 122.145, "duration": 1.375}, {"text": "Do they realize I'm\ngoing to turn left?", "start": 123.52, "duration": 1.625}, {"text": "This is hard.", "start": 125.145, "duration": 0.565}, {"text": "This is social cognition.", "start": 125.71, "duration": 1.08}, {"text": "Nobody's mastered that yet.", "start": 126.79, "duration": 1.59}, {"text": "Anyway, it's hard for us too.", "start": 128.38, "duration": 2.73}, {"text": "Anyway, the real\nquestion here is not", "start": 131.11, "duration": 3.03}, {"text": "for me to lecture you about\ndriving but to think about,", "start": 134.14, "duration": 3.27}, {"text": "why is that a problem?", "start": 137.41, "duration": 3.24}, {"text": "Why can't you talk to a person\nand pay attention to driving?", "start": 140.65, "duration": 4.05}, {"text": "What is the big deal, right?", "start": 144.7, "duration": 3.27}, {"text": "And so the intuition is we have\nsome kind of limited processing", "start": 147.97, "duration": 4.29}, {"text": "ability.", "start": 152.26, "duration": 0.93}, {"text": "OK, we're not like super\nsupercomputers who can just", "start": 153.19, "duration": 3.24}, {"text": "do millions of things at once.", "start": 156.43, "duration": 1.8}, {"text": "We have some kind of limit in\nhow much stuff we can handle,", "start": 158.23, "duration": 2.92}, {"text": "OK?", "start": 161.15, "duration": 0.5}, {"text": "And I think everybody\nwill have this intuition.", "start": 161.65, "duration": 4.56}, {"text": "You can't think about lots\nof different things at once.", "start": 166.21, "duration": 2.52}, {"text": "I like to think of this as the\ntoaster model of cognition.", "start": 168.73, "duration": 4.05}, {"text": "That is, you plug in the\ntoaster, and the lights dim,", "start": 172.78, "duration": 2.79}, {"text": "right?", "start": 175.57, "duration": 0.69}, {"text": "So if everything's\non the same circuit,", "start": 176.26, "duration": 1.77}, {"text": "there's some kind of unitary\nthing, resource that's limited.", "start": 178.03, "duration": 3.78}, {"text": "And if some more of it goes\nhere, less if it goes here.", "start": 181.81, "duration": 3.21}, {"text": "OK, so obviously we don't\nhave simple circuits", "start": 185.02, "duration": 2.252}, {"text": "like that in our brain.", "start": 187.272, "duration": 0.958}, {"text": "And the relevant\nscarce commodity", "start": 188.23, "duration": 3.3}, {"text": "isn't just electricity.", "start": 191.53, "duration": 1.62}, {"text": "It's not electrons.", "start": 193.15, "duration": 0.93}, {"text": "It's some other kind of thing\nwe don't totally understand.", "start": 194.08, "duration": 3.93}, {"text": "But there's still some sense in\nwhich of our mental processes", "start": 198.01, "duration": 4.95}, {"text": "are on the same circuit.", "start": 202.96, "duration": 1.62}, {"text": "OK?", "start": 204.58, "duration": 1.23}, {"text": "I'm assuming everybody is\nsharing this intuition here.", "start": 205.81, "duration": 3.31}, {"text": "So think about this.", "start": 209.12, "duration": 1.158}, {"text": "How many people feel like\nyou can listen to music", "start": 210.278, "duration": 2.042}, {"text": "and read difficult\nstuff at the same time?", "start": 212.32, "duration": 2.138}, {"text": "Raise your-- I'm curious.", "start": 214.458, "duration": 1.042}, {"text": "How many people feel\nlike they can do that?", "start": 215.5, "duration": 2.73}, {"text": "Only a few.", "start": 218.23, "duration": 1.86}, {"text": "That's so interesting.", "start": 220.09, "duration": 1.89}, {"text": "Sort of.", "start": 221.98, "duration": 0.75}, {"text": "Yeah, I can't do it\nat all, like at all,", "start": 222.73, "duration": 2.58}, {"text": "like even background\nmusic that I don't even", "start": 225.31, "duration": 2.43}, {"text": "care that much about.", "start": 227.74, "duration": 2.16}, {"text": "Someday-- I mean, I\nthink these are really", "start": 229.9, "duration": 1.83}, {"text": "stunning individual differences.", "start": 231.73, "duration": 1.36}, {"text": "I don't know if there's\nany good work on it.", "start": 233.09, "duration": 1.74}, {"text": "I haven't seen it.", "start": 234.83, "duration": 0.75}, {"text": "But I think it's\nreally interesting.", "start": 235.58, "duration": 2.61}, {"text": "Some people can.", "start": 238.19, "duration": 0.71}, {"text": "Some people can't.", "start": 238.9, "duration": 0.75}, {"text": "I don't know what's\nup with that.", "start": 239.65, "duration": 3.09}, {"text": "How about recognizing faces\nand scenes at the same time?", "start": 242.74, "duration": 4.603}, {"text": "Can you do that?", "start": 247.343, "duration": 0.667}, {"text": "Yeah?", "start": 248.01, "duration": 0.45}, {"text": "How many people feel like\nyou can recognize a face", "start": 248.46, "duration": 2.083}, {"text": "and a scene at the same time?", "start": 250.543, "duration": 1.552}, {"text": "All right.", "start": 252.095, "duration": 3.115}, {"text": "In fact, Michael Cohen,\nwho gave that lecture", "start": 255.21, "duration": 2.64}, {"text": "on brain-computer interfaces\na month ago or so,", "start": 257.85, "duration": 4.14}, {"text": "showed some beautiful\nwork that, actually, you", "start": 261.99, "duration": 3.24}, {"text": "are better at recognizing a\nface and a scene presented", "start": 265.23, "duration": 4.47}, {"text": "simultaneously than two\nfaces or two scenes.", "start": 269.7, "duration": 5.85}, {"text": "Can you think why that might be?", "start": 275.55, "duration": 2.88}, {"text": "Yeah, Isabelle?", "start": 278.43, "duration": 1.29}, {"text": "AUDIENCE: Context.", "start": 279.72, "duration": 1.257}, {"text": "NANCY KANWISHER: Say more.", "start": 280.977, "duration": 1.083}, {"text": "AUDIENCE: If you see somebody,\neven a familiar face,", "start": 284.88, "duration": 6.08}, {"text": "you can either--", "start": 290.96, "duration": 1.82}, {"text": "it helps identify them as,\noh, I know that person.", "start": 292.78, "duration": 3.19}, {"text": "Then, obviously, they're there.", "start": 295.97, "duration": 1.442}, {"text": "NANCY KANWISHER: Right.", "start": 297.412, "duration": 0.958}, {"text": "So they can go together\ninto a thing, maybe chunk", "start": 298.37, "duration": 2.34}, {"text": "it as a thing or something.", "start": 300.71, "duration": 1.275}, {"text": "That's a good answer.", "start": 301.985, "duration": 0.875}, {"text": "It wasn't the one\nI was fishing for.", "start": 302.86, "duration": 2.35}, {"text": "Yeah, Jimmy?", "start": 305.21, "duration": 2.04}, {"text": "AUDIENCE: If people and\nplaces are separate things", "start": 307.25, "duration": 5.7}, {"text": "that your brain calculates,\nif it's two faces,", "start": 312.95, "duration": 3.03}, {"text": "you have to calculate this\nthing with a face number one", "start": 315.98, "duration": 3.27}, {"text": "before going to face number two.", "start": 319.25, "duration": 1.98}, {"text": "Whereas if it's [INAUDIBLE]", "start": 321.23, "duration": 2.91}, {"text": "NANCY KANWISHER: Exactly.", "start": 324.14, "duration": 1.5}, {"text": "Exactly.", "start": 325.64, "duration": 0.72}, {"text": "And you do, right?", "start": 326.36, "duration": 1.11}, {"text": "You have an FFA and a PPA.", "start": 327.47, "duration": 1.35}, {"text": "And they're friends, right?", "start": 328.82, "duration": 1.8}, {"text": "So what Michael showed\nis not just that you", "start": 330.62, "duration": 2.85}, {"text": "can recognize a face and\nhold it in working memory,", "start": 333.47, "duration": 2.79}, {"text": "a face and a scene better\nthan two faces or two scenes,", "start": 336.26, "duration": 3.45}, {"text": "but the degree to which\nyou have that cost", "start": 339.71, "duration": 2.61}, {"text": "of doing two things\nin one category", "start": 342.32, "duration": 1.68}, {"text": "rather than spreading\nover two categories", "start": 344.0, "duration": 2.22}, {"text": "is linearly proportional to\nhow different the activation", "start": 346.22, "duration": 3.99}, {"text": "patterns are for\nthose categories", "start": 350.21, "duration": 1.5}, {"text": "in the ventral visual pathway.", "start": 351.71, "duration": 1.68}, {"text": "So faces and scenes are totally\ndifferent from each other.", "start": 353.39, "duration": 2.65}, {"text": "And so you get a big benefit\nfor separating your two items", "start": 356.04, "duration": 4.82}, {"text": "across faces and scenes.", "start": 360.86, "duration": 2.67}, {"text": "Other things that are more\nsimilar in their pattern", "start": 363.53, "duration": 2.13}, {"text": "of response in the ventral\npathway, like faces and bodies,", "start": 365.66, "duration": 3.3}, {"text": "you get a smaller benefit.", "start": 368.96, "duration": 1.66}, {"text": "OK?", "start": 370.62, "duration": 0.5}, {"text": "So it's consistent\nwith this idea", "start": 371.12, "duration": 1.375}, {"text": "that, to the degree that we\nhave separate processors,", "start": 372.495, "duration": 2.735}, {"text": "you can do, to some extent,\nprocessing in parallel, OK?", "start": 375.23, "duration": 5.79}, {"text": "It doesn't explain why not\neverybody can read and listen", "start": 381.02, "duration": 4.107}, {"text": "to music at the same time.", "start": 385.127, "duration": 1.083}, {"text": "Because, as I argued\na few weeks ago,", "start": 386.21, "duration": 1.542}, {"text": "these things don't\noverlap at all.", "start": 387.752, "duration": 1.791}, {"text": "So there are many mysteries.", "start": 389.543, "duration": 1.167}, {"text": "But there's some\nintuition there.", "start": 390.71, "duration": 2.95}, {"text": "OK, to get a little\nmore intuition", "start": 393.66, "duration": 2.25}, {"text": "about limited processing\ncapacity, can you guys see?", "start": 395.91, "duration": 2.623}, {"text": "When I was sitting\nover there last time,", "start": 398.533, "duration": 1.667}, {"text": "I couldn't see\nthe screen at all.", "start": 400.2, "duration": 1.9}, {"text": "Can you guys see it?", "start": 402.1, "duration": 1.26}, {"text": "It's OK?", "start": 403.36, "duration": 0.5}, {"text": "All right.", "start": 403.86, "duration": 0.54}, {"text": "Yeah?", "start": 404.4, "duration": 0.785}, {"text": "AUDIENCE: Do you think\nthe problem is [INAUDIBLE]", "start": 405.185, "duration": 5.878}, {"text": "NANCY KANWISHER: Not for me.", "start": 411.063, "duration": 1.167}, {"text": "Instrumental music, no\nlyrics still a problem.", "start": 412.23, "duration": 2.89}, {"text": "So I don't know.", "start": 415.12, "duration": 0.713}, {"text": "I mean, I'm sure there's\na literature on this.", "start": 415.833, "duration": 1.917}, {"text": "I just don't happen to know it.", "start": 417.75, "duration": 0.99}, {"text": "I'm just trying to\nshare the intuition.", "start": 418.74, "duration": 1.87}, {"text": "So I don't-- it's not\nthe only thing for me.", "start": 420.61, "duration": 2.63}, {"text": "OK, so what I'm going to do--\nthis is a super low-tech demo.", "start": 426.52, "duration": 2.7}, {"text": "I'm going to show you an\narray of colored letters.", "start": 429.22, "duration": 2.393}, {"text": "Grab a piece of\npaper or something", "start": 431.613, "duration": 1.417}, {"text": "where you can write\ndown a few letters.", "start": 433.03, "duration": 1.77}, {"text": "And I'm just going to flash\nup one array very quickly.", "start": 434.8, "duration": 2.55}, {"text": "And I want you to write down\nas many of the blue letters", "start": 437.35, "duration": 3.39}, {"text": "as you can.", "start": 440.74, "duration": 1.08}, {"text": "OK, ready?", "start": 441.82, "duration": 0.69}, {"text": "There's only a few of them.", "start": 450.275, "duration": 1.125}, {"text": "So you can.", "start": 451.4, "duration": 0.98}, {"text": "OK, ready?", "start": 452.38, "duration": 0.6}, {"text": "Here we go.", "start": 452.98, "duration": 0.57}, {"text": "OK, write them down.", "start": 456.277, "duration": 0.833}, {"text": "Last year, everyone\ngot all of them.", "start": 459.82, "duration": 1.5}, {"text": "So I tried to go a\nlittle faster this time.", "start": 461.32, "duration": 2.24}, {"text": "OK.", "start": 463.56, "duration": 2.378}, {"text": "OK, we're going to do it again.", "start": 465.938, "duration": 1.292}, {"text": "Ready?", "start": 467.23, "duration": 0.77}, {"text": "There's going to\nbe another display,", "start": 468.0, "duration": 1.11}, {"text": "and you're going to write\ndown all the blue letters.", "start": 469.11, "duration": 1.62}, {"text": "Everyone ready?", "start": 470.73, "duration": 0.99}, {"text": "Here we go.", "start": 471.72, "duration": 0.51}, {"text": "OK, just wanted to\nshare the intuition.", "start": 478.52, "duration": 2.31}, {"text": "The probability-- did\nanyone miss the N here?", "start": 480.83, "duration": 3.22}, {"text": "OK, how many people got the N?", "start": 484.05, "duration": 2.705}, {"text": "Nobody's going to admit it.", "start": 486.755, "duration": 1.125}, {"text": "I wanted a few people\nto miss the N, right?", "start": 490.78, "duration": 2.37}, {"text": "I really did zip through.", "start": 493.15, "duration": 1.06}, {"text": "I probably cheated and\nmade this one go faster.", "start": 494.21, "duration": 2.107}, {"text": "You missed it?", "start": 496.317, "duration": 0.583}, {"text": "OK, thank you.", "start": 496.9, "duration": 0.747}, {"text": "I'm sure a few others did.", "start": 497.647, "duration": 1.083}, {"text": "OK, anyway, the point\nis that, if you do this", "start": 498.73, "duration": 6.03}, {"text": "properly in a lab,\nthe probability", "start": 504.76, "duration": 1.74}, {"text": "of detecting it here is\nmuch less than there, right?", "start": 506.5, "duration": 3.84}, {"text": "So what does this show?", "start": 510.34, "duration": 2.975}, {"text": "It shows that we have\nlimited capacity.", "start": 513.315, "duration": 1.625}, {"text": "We can't process all\nof those blue letters", "start": 514.94, "duration": 2.489}, {"text": "in parallel, right?", "start": 517.429, "duration": 2.341}, {"text": "When there's a single\none, you get it just fine.", "start": 519.77, "duration": 2.139}, {"text": "But when there's a bunch,\nyou don't necessarily", "start": 521.909, "duration": 2.211}, {"text": "get it, right?", "start": 524.12, "duration": 1.5}, {"text": "OK.", "start": 525.62, "duration": 1.47}, {"text": "It also shows that we\nhave ability to select", "start": 527.09, "duration": 2.61}, {"text": "the information, right?", "start": 529.7, "duration": 1.83}, {"text": "So you weren't bothered\nby the red letters.", "start": 531.53, "duration": 2.165}, {"text": "If I'd asked you right\nafter about the red letters,", "start": 533.695, "duration": 2.125}, {"text": "you probably couldn't report\nany of them at all, right?", "start": 535.82, "duration": 3.15}, {"text": "It's a whole field\nthat studies that.", "start": 538.97, "duration": 1.83}, {"text": "We won't get into that.", "start": 540.8, "duration": 1.65}, {"text": "OK.", "start": 542.45, "duration": 1.86}, {"text": "So in fact, the\nprobability of reporting", "start": 544.31, "duration": 2.43}, {"text": "the N in these two displays\nis independent of the number", "start": 546.74, "duration": 3.48}, {"text": "of red letters.", "start": 550.22, "duration": 1.2}, {"text": "They just don't matter.", "start": 551.42, "duration": 1.51}, {"text": "They are not entering into that\nlimitation, whatever it is.", "start": 552.93, "duration": 3.11}, {"text": "The limitation is\nonly for the ones", "start": 556.04, "duration": 1.59}, {"text": "you're paying attention\nto, the blue ones, OK?", "start": 557.63, "duration": 5.77}, {"text": "OK, so why is our\nmental capacity limited?", "start": 563.4, "duration": 5.97}, {"text": "OK?", "start": 569.37, "duration": 1.26}, {"text": "Nobody really knows an answer.", "start": 570.63, "duration": 1.47}, {"text": "And I actually think this is\na really unsatisfying part", "start": 572.1, "duration": 2.79}, {"text": "of attention research because\nit sort of seems obvious.", "start": 574.89, "duration": 2.89}, {"text": "But I think it's not.", "start": 577.78, "duration": 1.34}, {"text": "So sometime in the\nnext 10 or 20 years,", "start": 579.12, "duration": 3.0}, {"text": "some smart computational person\nwill analyze this well and get", "start": 582.12, "duration": 3.66}, {"text": "a more satisfying answer.", "start": 585.78, "duration": 1.18}, {"text": "But right now,\nhere's where we are.", "start": 586.96, "duration": 1.458}, {"text": "The standard story is, well,\nwe have only so many neurons", "start": 590.76, "duration": 4.53}, {"text": "and so much capacity.", "start": 595.29, "duration": 1.08}, {"text": "And you can't do\neverything at once, right?", "start": 596.37, "duration": 3.36}, {"text": "So we can't process everything\nin the whole visual field", "start": 599.73, "duration": 2.55}, {"text": "at once.", "start": 602.28, "duration": 2.51}, {"text": "That's the standard story.", "start": 604.79, "duration": 2.13}, {"text": "But the reason I find\nthis unsatisfying is like,", "start": 606.92, "duration": 2.15}, {"text": "why the hell not, right?", "start": 609.07, "duration": 1.0}, {"text": "We have all this parallel stuff\nor the whole visual field,", "start": 610.07, "duration": 3.24}, {"text": "at least in the first\nfew stages of processing.", "start": 613.31, "duration": 2.28}, {"text": "And we have quite a degree\nof parallelism after that.", "start": 615.59, "duration": 2.85}, {"text": "So I think that's\nthe standard story.", "start": 618.44, "duration": 1.83}, {"text": "But I'm just marking that I\ndon't find it very satisfying.", "start": 620.27, "duration": 3.21}, {"text": "Yeah?", "start": 623.48, "duration": 2.61}, {"text": "A second answer, which\nI think is also not", "start": 626.09, "duration": 2.4}, {"text": "totally satisfying but also\na little bit right at least,", "start": 628.49, "duration": 3.48}, {"text": "is that, typically, you're\nonly going to do one action.", "start": 631.97, "duration": 3.34}, {"text": "Right?", "start": 635.31, "duration": 0.5}, {"text": "You're going around\nin the world.", "start": 635.81, "duration": 1.375}, {"text": "Let's forget colored letters\non a display in a lab.", "start": 637.185, "duration": 2.895}, {"text": "Let's think about a person\nwalking around in a busy city", "start": 640.08, "duration": 3.11}, {"text": "street doing something, right?", "start": 643.19, "duration": 1.96}, {"text": "There's typically only\none or a very small number", "start": 645.15, "duration": 3.05}, {"text": "of things you're going to\ndo next, like walk down", "start": 648.2, "duration": 2.25}, {"text": "the sidewalk and\nnot bump into people", "start": 650.45, "duration": 1.77}, {"text": "or pick up this object, right?", "start": 652.22, "duration": 2.52}, {"text": "You don't need to act towards\nall the things in your world.", "start": 654.74, "duration": 3.69}, {"text": "And in fact, if you\nhad to, so given", "start": 658.43, "duration": 2.73}, {"text": "that you're only going\nto do one thing, why", "start": 661.16, "duration": 2.07}, {"text": "distract the whole rest of\nyour motor-planning system", "start": 663.23, "duration": 2.49}, {"text": "by feeding it all this\ninformation that's is just", "start": 665.72, "duration": 2.25}, {"text": "going to clutter\nit with garbage?", "start": 667.97, "duration": 1.5}, {"text": "Why not give it just the\ninformation it needs?", "start": 669.47, "duration": 2.715}, {"text": "OK, so that's the\nstandard story.", "start": 672.185, "duration": 1.375}, {"text": "It's very squishy and vague\nbut hopefully intuitive.", "start": 673.56, "duration": 4.85}, {"text": "And there's some nice,\ncompelling examples", "start": 678.41, "duration": 3.93}, {"text": "that illustrate this.", "start": 682.34, "duration": 1.09}, {"text": "So there's a fish\ncalled the pike fish", "start": 683.43, "duration": 2.3}, {"text": "that preys on smaller\nfish called sticklebacks.", "start": 685.73, "duration": 2.73}, {"text": "OK?", "start": 688.46, "duration": 1.05}, {"text": "And if you stick a pike fish\nin a tank with sticklebacks,", "start": 689.51, "duration": 5.13}, {"text": "it will catch the\nfirst stickleback", "start": 694.64, "duration": 1.86}, {"text": "faster if there's only\none in the tank with it", "start": 696.5, "duration": 3.12}, {"text": "than if there are 10\nin the tank with it.", "start": 699.62, "duration": 3.07}, {"text": "OK?", "start": 702.69, "duration": 0.5}, {"text": "You might think, you've\ngot 10 to choose from.", "start": 703.19, "duration": 2.52}, {"text": "You'll get a fish faster.", "start": 705.71, "duration": 2.1}, {"text": "But 10 is more\ndistracting, right?", "start": 707.81, "duration": 2.61}, {"text": "And so maybe our\naction-planning systems also", "start": 710.42, "duration": 2.28}, {"text": "prefer the single stickleback.", "start": 712.7, "duration": 2.73}, {"text": "Again, there's no\ncomputational precision.", "start": 715.43, "duration": 2.01}, {"text": "I'm just sharing\nintuitions with you.", "start": 717.44, "duration": 2.67}, {"text": "OK, so let me give you some\nmore evidence that there really", "start": 720.11, "duration": 3.78}, {"text": "are significant capacity\nlimits in perception", "start": 723.89, "duration": 5.487}, {"text": "and that, in fact, there's a lot\nof stuff right in front of us", "start": 729.377, "duration": 2.583}, {"text": "that comes right onto our\nretina that we don't see.", "start": 731.96, "duration": 3.84}, {"text": "OK?", "start": 735.8, "duration": 1.2}, {"text": "So I'm going to\nshow you an example.", "start": 737.0, "duration": 2.35}, {"text": "I'm going to show you a\npicture for just a few seconds.", "start": 739.35, "duration": 2.39}, {"text": "And I want you to\njust look at it.", "start": 741.74, "duration": 1.23}, {"text": "And then I'm going to ask\nyou some questions about it.", "start": 742.97, "duration": 1.8}, {"text": "OK?", "start": 744.77, "duration": 0.3}, {"text": "Here we go.", "start": 745.07, "duration": 0.57}, {"text": "OK, so how rich a\npercept did you get?", "start": 748.71, "duration": 4.59}, {"text": "Did you see lots of stuff\nand get lots of detail?", "start": 753.3, "duration": 4.035}, {"text": "Or do you just\nfeel like you just", "start": 757.335, "duration": 1.375}, {"text": "have the vaguest sense of a few\nbuildings, a street, that's it?", "start": 758.71, "duration": 3.69}, {"text": "How many feel like they got\na lot of pretty good detail?", "start": 762.4, "duration": 5.05}, {"text": "No one does.", "start": 767.45, "duration": 0.772}, {"text": "Or everyone's bored.", "start": 768.222, "duration": 0.833}, {"text": "I don't know which.", "start": 769.055, "duration": 2.523}, {"text": "AUDIENCE: What do\nyou mean good detail?", "start": 771.578, "duration": 2.622}, {"text": "NANCY KANWISHER: The colors\nof buildings, the presence", "start": 774.2, "duration": 2.25}, {"text": "of objects, details on\nthe architectural styles,", "start": 776.45, "duration": 3.39}, {"text": "where an awning was,\nthat kind of thing.", "start": 779.84, "duration": 3.038}, {"text": "AUDIENCE: I feel like\nI got [INAUDIBLE]", "start": 782.878, "duration": 5.35}, {"text": "NANCY KANWISHER: Well, most\npeople looking at this feel", "start": 788.228, "duration": 2.292}, {"text": "like--", "start": 790.52, "duration": 0.24}, {"text": "I mean, who knows what it means?", "start": 790.76, "duration": 1.14}, {"text": "I mean, we're just\nsharing intuitions here.", "start": 791.9, "duration": 1.792}, {"text": "But most feel like,\nthat was pretty rich.", "start": 793.692, "duration": 1.803}, {"text": "I have a sense of it.", "start": 795.495, "duration": 0.875}, {"text": "I have a sense of maybe\nwhat country that's", "start": 796.37, "duration": 1.792}, {"text": "in and what kind\nof stuff is there", "start": 798.162, "duration": 1.448}, {"text": "and what kind the style is.", "start": 799.61, "duration": 1.872}, {"text": "You get a feel for the place,\nall that kind of thing.", "start": 801.482, "duration": 2.208}, {"text": "Maybe not every damn\ndetail, but lots, right?", "start": 803.69, "duration": 3.24}, {"text": "So the general intuition\nmost people have", "start": 806.93, "duration": 1.95}, {"text": "is a fair amount of detail.", "start": 808.88, "duration": 2.52}, {"text": "OK?", "start": 811.4, "duration": 1.65}, {"text": "Well, let's look\nat that some more.", "start": 813.05, "duration": 1.5}, {"text": "This is actually a very,\nvery heated topic right now.", "start": 814.55, "duration": 4.32}, {"text": "Me and Michael Cohen published\na paper a couple of years", "start": 818.87, "duration": 2.73}, {"text": "ago called The Bandwidth of\nPerception, which is an effort", "start": 821.6, "duration": 2.43}, {"text": "to grapple with this question\nof how much information is there", "start": 824.03, "duration": 2.91}, {"text": "in your current\npercept right now.", "start": 826.94, "duration": 1.77}, {"text": "And there are many different\nperspectives on this.", "start": 828.71, "duration": 2.65}, {"text": "Let's find out a little\nmore with a further demo.", "start": 831.36, "duration": 3.45}, {"text": "So what I'm going\nto do is I'm going", "start": 834.81, "duration": 2.57}, {"text": "to show you that picture again.", "start": 837.38, "duration": 3.66}, {"text": "And it's going to flash\non a number of times.", "start": 841.04, "duration": 2.65}, {"text": "And each time it\nflashes on, there", "start": 843.69, "duration": 1.46}, {"text": "might be something\nthat's different.", "start": 845.15, "duration": 1.9}, {"text": "So take notes on any\ndifferences you might detect.", "start": 847.05, "duration": 3.59}, {"text": "OK?", "start": 850.64, "duration": 2.045}, {"text": "OK.", "start": 852.685, "duration": 0.5}, {"text": "OK, what things changed?", "start": 880.38, "duration": 1.9}, {"text": "Yeah?", "start": 882.28, "duration": 0.5}, {"text": "AUDIENCE: There was a woman\nwalking down the sidewalk.", "start": 882.78, "duration": 2.25}, {"text": "NANCY KANWISHER: And?", "start": 885.03, "duration": 1.26}, {"text": "AUDIENCE: That's all I got.", "start": 886.29, "duration": 1.308}, {"text": "NANCY KANWISHER:\nOK, but she changed.", "start": 887.598, "duration": 1.542}, {"text": "What changed about her?", "start": 889.14, "duration": 2.7}, {"text": "AUDIENCE: Other\nthan her clothes?", "start": 891.84, "duration": 2.953}, {"text": "NANCY KANWISHER: Yeah.", "start": 894.793, "duration": 0.917}, {"text": "Over the successive\npresentations,", "start": 895.71, "duration": 1.74}, {"text": "was she there sometimes\nand not others?", "start": 897.45, "duration": 1.74}, {"text": "Did she change?", "start": 899.19, "duration": 0.63}, {"text": "Yeah, she appeared\nor disappeared.", "start": 899.82, "duration": 1.68}, {"text": "OK, good.", "start": 901.5, "duration": 0.51}, {"text": "What else, Isabel?", "start": 902.01, "duration": 1.384}, {"text": "AUDIENCE: The awnings changed.", "start": 903.394, "duration": 1.452}, {"text": "The buildings changed colors.", "start": 904.846, "duration": 1.989}, {"text": "NANCY KANWISHER: Very good.", "start": 906.835, "duration": 1.125}, {"text": "Very good.", "start": 907.96, "duration": 0.75}, {"text": "How many people saw\nan awning change?", "start": 908.71, "duration": 4.08}, {"text": "Maybe half of you.", "start": 912.79, "duration": 1.77}, {"text": "OK.", "start": 914.56, "duration": 0.81}, {"text": "What else changed?", "start": 915.37, "duration": 2.508}, {"text": "AUDIENCE: The car.", "start": 917.878, "duration": 1.36}, {"text": "AUDIENCE: The model of the car.", "start": 919.238, "duration": 1.292}, {"text": "NANCY KANWISHER: The\nmodel of the car.", "start": 920.53, "duration": 1.11}, {"text": "Very good.", "start": 921.64, "duration": 0.75}, {"text": "Yeah?", "start": 922.39, "duration": 0.51}, {"text": "AUDIENCE: I feel like\nthe shops changed.", "start": 922.9, "duration": 2.4}, {"text": "But I don't know when or how.", "start": 925.3, "duration": 2.63}, {"text": "NANCY KANWISHER: OK.", "start": 927.93, "duration": 2.66}, {"text": "OK.", "start": 930.59, "duration": 0.5}, {"text": "You want to see\nhow they changed?", "start": 931.09, "duration": 1.68}, {"text": "OK, here's how it ended.", "start": 932.77, "duration": 1.83}, {"text": "Here's how it started.", "start": 934.6, "duration": 1.86}, {"text": "Are you surprised how much?", "start": 936.46, "duration": 1.68}, {"text": "Raise your hand if you're\nsurprised how much changed.", "start": 938.14, "duration": 2.46}, {"text": "Yeah, a lot, right?", "start": 940.6, "duration": 2.81}, {"text": "OK, so what does that tell us?", "start": 943.41, "duration": 2.5}, {"text": "It tells us that\neither the sense", "start": 945.91, "duration": 3.77}, {"text": "we have that we really saw a\nlot of what's going on there", "start": 949.68, "duration": 3.27}, {"text": "was wrong.", "start": 952.95, "duration": 0.51}, {"text": "We didn't see as\nmuch as we thought.", "start": 953.46, "duration": 1.5}, {"text": "Because if we saw as\nmuch as we thought,", "start": 954.96, "duration": 1.95}, {"text": "we should notice massive\nchanges like that.", "start": 956.91, "duration": 2.433}, {"text": "If you didn't see the\nawning, look over there.", "start": 959.343, "duration": 1.917}, {"text": "I mean, how could-- look\nat the color changes.", "start": 961.26, "duration": 3.3}, {"text": "Pretty major, right?", "start": 964.56, "duration": 2.07}, {"text": "Or we perceive all that\nstuff in the instant,", "start": 966.63, "duration": 2.73}, {"text": "and it just goes poof by the\ntime the next one comes along.", "start": 969.36, "duration": 2.895}, {"text": "That's one of the things\nthe field is finding", "start": 972.255, "duration": 1.875}, {"text": "about those things are\nvery hard to tell apart,", "start": 974.13, "duration": 1.958}, {"text": "not impossible, but hard.", "start": 976.088, "duration": 1.552}, {"text": "Yeah.", "start": 977.64, "duration": 2.07}, {"text": "OK, so most people feel\nlike, wow, much more changed", "start": 979.71, "duration": 3.48}, {"text": "than I thought.", "start": 983.19, "duration": 1.26}, {"text": "I can't resist one\nmore hilarious demo.", "start": 984.45, "duration": 3.78}, {"text": "So have you already\nseen this like in 9.00?", "start": 988.23, "duration": 2.76}, {"text": "How many people have\nseen this before?", "start": 990.99, "duration": 2.09}, {"text": "Oh, I don't want to bore you.", "start": 993.08, "duration": 1.423}, {"text": "Do you mind seeing it again?", "start": 994.503, "duration": 1.167}, {"text": "We could skip it.", "start": 995.67, "duration": 1.02}, {"text": "It's kind of fun.", "start": 996.69, "duration": 1.42}, {"text": "Sorry?", "start": 998.11, "duration": 0.5}, {"text": "Do it?", "start": 998.61, "duration": 0.27}, {"text": "OK.", "start": 998.88, "duration": 0.54}, {"text": "OK.", "start": 999.42, "duration": 2.02}, {"text": "OK.", "start": 1001.44, "duration": 0.5}, {"text": "So you're just going to\nwatch this video and just", "start": 1001.94, "duration": 2.37}, {"text": "track things\nbecause there may be", "start": 1004.31, "duration": 1.595}, {"text": "changes happening\nhere and there,", "start": 1005.905, "duration": 1.375}, {"text": "and you want to notice them, OK?", "start": 1007.28, "duration": 1.81}, {"text": "Here we go.", "start": 1009.09, "duration": 0.5}, {"text": "[MUSIC PLAYING]", "start": 1009.59, "duration": 3.583}, {"text": "[VIDEO PLAYBACK]", "start": 1013.173, "duration": 0.667}, {"text": "- Clearly, somebody in this\nroom murdered Lord Smythe,", "start": 1013.84, "duration": 3.51}, {"text": "who, at precisely\n3:34 this afternoon,", "start": 1017.35, "duration": 3.51}, {"text": "was brutally bludgeoned to\ndeath with a blunt instrument.", "start": 1020.86, "duration": 3.91}, {"text": "I want each of you to\ntell me your whereabouts", "start": 1024.77, "duration": 3.2}, {"text": "at precisely the time that\nthis dastardly deed took place.", "start": 1027.97, "duration": 5.32}, {"text": "- I was polishing the brass\nin the master bedroom.", "start": 1033.29, "duration": 3.779}, {"text": "- I was buttering his lordship's\nscones below stairs, sir.", "start": 1037.069, "duration": 4.311}, {"text": "- I was planting my petunias\nin the potting shed.", "start": 1041.38, "duration": 3.42}, {"text": "- Constable, arrest Lady Smythe.", "start": 1044.8, "duration": 4.54}, {"text": "- How did you know?", "start": 1049.34, "duration": 0.8}, {"text": "- Madam, as any\nhorticulturist will tell you,", "start": 1050.14, "duration": 2.11}, {"text": "one does not plant\npetunias until May is out.", "start": 1052.25, "duration": 2.81}, {"text": "Take her away.", "start": 1055.06, "duration": 1.95}, {"text": "It's just a matter\nof observation.", "start": 1057.01, "duration": 2.07}, {"text": "The real question is,\nhow observant were you?", "start": 1059.08, "duration": 3.36}, {"text": "Clearly, somebody in this\nroom murdered Lord Smythe,", "start": 1071.38, "duration": 3.54}, {"text": "who at precisely\n3:34 this afternoon,", "start": 1074.92, "duration": 3.57}, {"text": "was brutally bludgeoned to\ndeath with a blunt instrument.", "start": 1078.49, "duration": 3.79}, {"text": "I want each of you to\ntell me your whereabouts", "start": 1082.28, "duration": 3.26}, {"text": "at precisely the time that\nthis dastardly deed took place.", "start": 1085.54, "duration": 3.047}, {"text": "[END PLAYBACK]", "start": 1088.587, "duration": 0.583}, {"text": "NANCY KANWISHER:\nTotally different guy.", "start": 1089.17, "duration": 0.9}, {"text": "[VIDEO PLAYBACK]", "start": 1090.07, "duration": 0.667}, {"text": "- I was polishing the brass\nin the master bedroom.", "start": 1090.737, "duration": 3.773}, {"text": "- I was buttering his lordship's\nscones below stairs, sir.", "start": 1094.51, "duration": 4.38}, {"text": "- I was planting my petunias\nin the potting shed.", "start": 1098.89, "duration": 3.39}, {"text": "- Constable, arrest Lady Smythe.", "start": 1102.28, "duration": 3.24}, {"text": "[END PLAYBACK]", "start": 1109.091, "duration": 0.583}, {"text": "NANCY KANWISHER:\nIt's actually an ad.", "start": 1109.674, "duration": 1.542}, {"text": "But it doesn't hurt\nto get its message.", "start": 1111.216, "duration": 1.894}, {"text": "All right, it's a British ad\nwith an important message.", "start": 1116.48, "duration": 5.79}, {"text": "But it's a pretty impressive\ndemo too, isn't it?", "start": 1122.27, "duration": 2.545}, {"text": "How many people feel\nlike lots of stuff", "start": 1124.815, "duration": 1.625}, {"text": "changed that they didn't notice?", "start": 1126.44, "duration": 2.28}, {"text": "Yeah, that's intuition.", "start": 1128.72, "duration": 2.22}, {"text": "So the idea here is that all\nthat stuff hits your retina.", "start": 1130.94, "duration": 3.69}, {"text": "All of it kind of gets\nprocessed to some degree.", "start": 1134.63, "duration": 2.67}, {"text": "But it's amazing how much\nof it goes unnoticed.", "start": 1137.3, "duration": 3.51}, {"text": "OK?", "start": 1140.81, "duration": 1.25}, {"text": "All right, oops.", "start": 1142.06, "duration": 0.96}, {"text": "Sorry.", "start": 1143.02, "duration": 1.47}, {"text": "OK, you might think, OK, is\nthis something that only happens", "start": 1144.49, "duration": 3.56}, {"text": "when it doesn't really matter?", "start": 1148.05, "duration": 1.25}, {"text": "OK, you were\nlooking for changes.", "start": 1149.3, "duration": 1.49}, {"text": "But your life\ndidn't depend on it.", "start": 1150.79, "duration": 1.95}, {"text": "What about commercial pilots?", "start": 1152.74, "duration": 2.16}, {"text": "So here's a classic\nstudy where they", "start": 1154.9, "duration": 1.71}, {"text": "brought in actual\nreal commercial pilots", "start": 1156.61, "duration": 3.33}, {"text": "with thousands of hours\nof flying experience.", "start": 1159.94, "duration": 3.27}, {"text": "And they had them fly\nin a flight simulator.", "start": 1163.21, "duration": 2.7}, {"text": "They had them land a plane on a\nrunway in the flight simulator", "start": 1165.91, "duration": 4.95}, {"text": "under foggy conditions.", "start": 1170.86, "duration": 2.22}, {"text": "And I forget what percent.", "start": 1173.08, "duration": 1.77}, {"text": "I have to cheat and\nlook at my notes.", "start": 1174.85, "duration": 2.195}, {"text": "It doesn't say.", "start": 1177.045, "duration": 1.225}, {"text": "It does.", "start": 1178.27, "duration": 0.54}, {"text": "I'm just not seeing it.", "start": 1178.81, "duration": 0.958}, {"text": "Some large percent\nof the pilots never", "start": 1179.768, "duration": 3.452}, {"text": "saw this plane sitting\nright there on the runway.", "start": 1183.22, "duration": 3.66}, {"text": "They landed the planes\nin the simulator right", "start": 1186.88, "duration": 3.0}, {"text": "through that plane.", "start": 1189.88, "duration": 1.262}, {"text": "And when they were\nshown it subsequently,", "start": 1191.142, "duration": 1.708}, {"text": "they were shocked\nand couldn't believe", "start": 1192.85, "duration": 1.583}, {"text": "they didn't see it, right?", "start": 1194.433, "duration": 1.387}, {"text": "They were using a\nheads-up display", "start": 1195.82, "duration": 1.61}, {"text": "that tells them\ntheir orientation", "start": 1197.43, "duration": 1.375}, {"text": "to where the runway is.", "start": 1198.805, "duration": 1.095}, {"text": "And they're paying\nattention to this stuff,", "start": 1199.9, "duration": 1.8}, {"text": "landing on the runway.", "start": 1201.7, "duration": 1.02}, {"text": "And they just do not even see\nthat very relevant thing, OK?", "start": 1202.72, "duration": 4.11}, {"text": "So it's not just something that\nhappens in like weird psych", "start": 1206.83, "duration": 3.33}, {"text": "demos and funny movies.", "start": 1210.16, "duration": 2.28}, {"text": "Even for very important things,\npeople miss absolutely major,", "start": 1212.44, "duration": 5.04}, {"text": "important information.", "start": 1217.48, "duration": 2.12}, {"text": "OK, so what all this\ntells us is attention", "start": 1219.6, "duration": 3.9}, {"text": "is a filter that lets some\ninformation into our awareness", "start": 1223.5, "duration": 4.56}, {"text": "but completely filters\nout of awareness", "start": 1228.06, "duration": 2.7}, {"text": "a lot of other\ninformation that lands", "start": 1230.76, "duration": 2.13}, {"text": "on your retina or your cochlea.", "start": 1232.89, "duration": 2.52}, {"text": "OK?", "start": 1235.41, "duration": 2.25}, {"text": "And there's two key\nproperties of attention", "start": 1237.66, "duration": 2.22}, {"text": "that go hand-in-hand.", "start": 1239.88, "duration": 1.23}, {"text": "One, those capacity limits\nwe've been talking about.", "start": 1241.11, "duration": 2.25}, {"text": "You can't do everything at once.", "start": 1243.36, "duration": 1.93}, {"text": "And two, selectivity,\nthat is there's", "start": 1245.29, "duration": 2.87}, {"text": "some way some subset\nof that information", "start": 1248.16, "duration": 2.31}, {"text": "comes in some way\nto select it, OK?", "start": 1250.47, "duration": 3.53}, {"text": "All right, so let's say a\nlittle bit more about attention.", "start": 1254.0, "duration": 3.03}, {"text": "There's lots of different\nways and forms of attention.", "start": 1257.03, "duration": 2.73}, {"text": "So let me give you a few key\ndistinctions about attention.", "start": 1259.76, "duration": 4.66}, {"text": "So far, it's just kind\nof a vague word that gets", "start": 1264.42, "duration": 2.0}, {"text": "used lots of different ways.", "start": 1266.42, "duration": 2.44}, {"text": "So long ago, the great Helmholtz\nthought about attention", "start": 1268.86, "duration": 4.76}, {"text": "and realized that there were two\ndifferent kinds of attention.", "start": 1273.62, "duration": 3.03}, {"text": "So he noted way back\nin 1860, our attention", "start": 1276.65, "duration": 4.23}, {"text": "is quite independent of the\nposition and accommodation", "start": 1280.88, "duration": 2.88}, {"text": "of the eyes and of any known\nalteration in these organs", "start": 1283.76, "duration": 4.08}, {"text": "and free to direct itself by a\nconscious and voluntary effort", "start": 1287.84, "duration": 4.02}, {"text": "upon any selected portion of a\ndark and undifferentiated field", "start": 1291.86, "duration": 3.54}, {"text": "of view.", "start": 1295.4, "duration": 1.06}, {"text": "This is one of the most\nimportant observations", "start": 1296.46, "duration": 2.0}, {"text": "for a future theory\nof attention.", "start": 1298.46, "duration": 2.43}, {"text": "Indeed, it is, right?", "start": 1300.89, "duration": 2.16}, {"text": "So his point-- I think we did\nthis at some earlier lecture.", "start": 1303.05, "duration": 2.73}, {"text": "His point is you can fixate\non my nose right now.", "start": 1305.78, "duration": 3.57}, {"text": "OK, everybody fixate on my nose.", "start": 1309.35, "duration": 2.19}, {"text": "Not that it's that\nfabulous a nose.", "start": 1311.54, "duration": 1.53}, {"text": "It'll just serve for\nthe demo right now.", "start": 1313.07, "duration": 1.95}, {"text": "And if I hold up different\nnumbers of fingers out here--", "start": 1315.02, "duration": 3.84}, {"text": "keep fixating on my nose.", "start": 1318.86, "duration": 1.26}, {"text": "No cheating.", "start": 1320.12, "duration": 1.41}, {"text": "OK?", "start": 1321.53, "duration": 1.17}, {"text": "How many fingers are off\nto the left side of my nose", "start": 1322.7, "duration": 3.87}, {"text": "from your perspective?", "start": 1326.57, "duration": 1.71}, {"text": "OK.", "start": 1328.28, "duration": 0.78}, {"text": "How many fingers are\noff to the right side?", "start": 1329.06, "duration": 2.19}, {"text": "OK.", "start": 1331.25, "duration": 0.81}, {"text": "You can do that.", "start": 1332.06, "duration": 0.96}, {"text": "You can pull up this information\nor pull up that information", "start": 1333.02, "duration": 2.73}, {"text": "without moving your eyes.", "start": 1335.75, "duration": 1.89}, {"text": "OK?", "start": 1337.64, "duration": 0.54}, {"text": "That's called covert attention\nbecause the input is identical.", "start": 1338.18, "duration": 4.2}, {"text": "And you are just\nsomehow adjusting", "start": 1342.38, "duration": 1.86}, {"text": "the dials on your\nperceptual system", "start": 1344.24, "duration": 1.56}, {"text": "to pull up this or pull up that.", "start": 1345.8, "duration": 2.77}, {"text": "OK?", "start": 1348.57, "duration": 0.51}, {"text": "So that's called\ncovert attention.", "start": 1349.08, "duration": 2.76}, {"text": "To be unconfounded\nfrom overt attention,", "start": 1351.84, "duration": 2.31}, {"text": "which is actually the most\npowerful kind of attention.", "start": 1354.15, "duration": 2.28}, {"text": "Overt attention, you\nmove your eyes from point", "start": 1356.43, "duration": 2.46}, {"text": "to point to select\ndifferent information.", "start": 1358.89, "duration": 2.94}, {"text": "OK, so overt attention is a\nmuch more powerful filter.", "start": 1361.83, "duration": 4.59}, {"text": "And we make about two to\nfour eye movements a second.", "start": 1366.42, "duration": 3.15}, {"text": "And it's very powerful\nbecause the center of gaze", "start": 1369.57, "duration": 2.43}, {"text": "has very high\nresolution information.", "start": 1372.0, "duration": 1.89}, {"text": "Remember high density\nof photoreceptors", "start": 1373.89, "duration": 1.95}, {"text": "at the fovea in\nthe center of gaze,", "start": 1375.84, "duration": 2.19}, {"text": "and the density tails\noff in the periphery.", "start": 1378.03, "duration": 3.04}, {"text": "So we have much better\ninformation in the fovea", "start": 1381.07, "duration": 2.99}, {"text": "than in the periphery.", "start": 1384.06, "duration": 1.98}, {"text": "OK, so it's both\nphotoreceptor density,", "start": 1386.04, "duration": 1.95}, {"text": "and it's also cortical area.", "start": 1387.99, "duration": 2.55}, {"text": "So in retinotopic\ncortex, back here,", "start": 1390.54, "duration": 2.37}, {"text": "primary visual cortex,\nV1, V2, those regions,", "start": 1392.91, "duration": 3.39}, {"text": "you have about 20 square\ncentimeters of cortex,", "start": 1396.3, "duration": 3.96}, {"text": "like that area of cortex--", "start": 1400.26, "duration": 1.74}, {"text": "pretty big-- something like\nthat processing the central two", "start": 1402.0, "duration": 3.75}, {"text": "degrees of vision.", "start": 1405.75, "duration": 1.6}, {"text": "OK?", "start": 1407.35, "duration": 0.5}, {"text": "Huge cortical area devoted\nto a tiny little part", "start": 1407.85, "duration": 2.97}, {"text": "of the visual world.", "start": 1410.82, "duration": 1.3}, {"text": "And much less per degree\nfor the periphery.", "start": 1412.12, "duration": 4.22}, {"text": "OK, so both at the\nphotoreceptor stage", "start": 1416.34, "duration": 1.89}, {"text": "and at higher-level\nprocessing stages,", "start": 1418.23, "duration": 1.83}, {"text": "we vastly over represent\nthe center of gaze.", "start": 1420.06, "duration": 3.12}, {"text": "OK?", "start": 1423.18, "duration": 0.75}, {"text": "That's why if you have loss\nof foveal vision and macular", "start": 1423.93, "duration": 2.76}, {"text": "degeneration, it's really awful.", "start": 1426.69, "duration": 1.5}, {"text": "You can't read or\nrecognize faces.", "start": 1428.19, "duration": 1.8}, {"text": "That's where you need\nthis fine-grained foveal", "start": 1429.99, "duration": 2.01}, {"text": "information.", "start": 1432.0, "duration": 1.26}, {"text": "OK, so that means\nthat moving your fovea", "start": 1433.26, "duration": 3.6}, {"text": "and parking it on different\nparts of the array", "start": 1436.86, "duration": 2.07}, {"text": "is an extremely\npowerful way to select", "start": 1438.93, "duration": 2.43}, {"text": "different kinds of information.", "start": 1441.36, "duration": 1.99}, {"text": "So to give you a feel for\nhow much people do this", "start": 1443.35, "duration": 2.99}, {"text": "and how they select\ninformation, here's a video.", "start": 1446.34, "duration": 4.68}, {"text": "This is taken from a\nhead-mounted camera", "start": 1451.02, "duration": 1.8}, {"text": "of a person who is\nwatching these two people.", "start": 1452.82, "duration": 2.49}, {"text": "And the yellow dot is\nwhere their fovea is.", "start": 1455.31, "duration": 2.82}, {"text": "So they're talking to\nmy former postdoc Matt.", "start": 1458.13, "duration": 2.34}, {"text": "And they're fixating on\nhis face as he talks.", "start": 1460.47, "duration": 2.91}, {"text": "And sometimes they take a\npeek at the other person.", "start": 1463.38, "duration": 3.15}, {"text": "And you can see there's very\nfine-grained adjustments", "start": 1466.53, "duration": 2.85}, {"text": "of where they look\nas this goes on.", "start": 1469.38, "duration": 1.818}, {"text": "And now they're walking down\nthe hall in this building,", "start": 1471.198, "duration": 2.292}, {"text": "and they're following her.", "start": 1473.49, "duration": 1.425}, {"text": "Watch what happens when\nthey turn the corner.", "start": 1474.915, "duration": 1.875}, {"text": "Check out the signs.", "start": 1476.79, "duration": 1.32}, {"text": "Read the little notices.", "start": 1478.11, "duration": 2.04}, {"text": "Look down the hall.", "start": 1480.15, "duration": 1.09}, {"text": "And then watch what happens\nwhen they go around the corner.", "start": 1481.24, "duration": 2.458}, {"text": "Oh, new person.", "start": 1483.698, "duration": 0.802}, {"text": "Look at the new person.", "start": 1484.5, "duration": 1.51}, {"text": "Right?", "start": 1486.01, "duration": 0.5}, {"text": "Sorry, it's too dark to\nsee what's going on here.", "start": 1489.31, "duration": 2.1}, {"text": "Oh, this is a little\nfixation patch", "start": 1491.41, "duration": 1.53}, {"text": "where they're recalibrating\nthe eye tracker to figure out", "start": 1492.94, "duration": 3.48}, {"text": "to make sure it's working.", "start": 1496.42, "duration": 1.28}, {"text": "Here comes a new person.", "start": 1497.7, "duration": 1.0}, {"text": "They look at his face.", "start": 1498.7, "duration": 1.41}, {"text": "Saccade back and forth\nbetween the two faces, right?", "start": 1500.11, "duration": 3.78}, {"text": "Whoever's talking,\nyou look at them.", "start": 1503.89, "duration": 1.8}, {"text": "And you collect\nhigh-resolution information", "start": 1505.69, "duration": 2.16}, {"text": "from that person's face.", "start": 1507.85, "duration": 1.108}, {"text": "With both head turns, you\ncan see their both head", "start": 1508.958, "duration": 2.042}, {"text": "turns and eye movements.", "start": 1511.0, "duration": 4.52}, {"text": "OK, you get the idea.", "start": 1515.52, "duration": 1.62}, {"text": "I didn't totally explain.", "start": 1517.14, "duration": 1.11}, {"text": "So this is a head-mounted\ncamera and eye tracker, OK,", "start": 1518.25, "duration": 4.672}, {"text": "of a person who was\nwalking around the building", "start": 1522.922, "duration": 1.958}, {"text": "encountering people.", "start": 1524.88, "duration": 0.89}, {"text": "And it was showing you both\nwhat was in their field of view", "start": 1525.77, "duration": 2.458}, {"text": "and where they were fixating\ntheir eyes in that view.", "start": 1528.228, "duration": 2.662}, {"text": "So you can see there's really\nfine-grained, moment-to-moment", "start": 1530.89, "duration": 2.81}, {"text": "sampling of visual\ninformation all", "start": 1533.7, "duration": 1.92}, {"text": "the time with overt attention\nwith eye movements, OK?", "start": 1535.62, "duration": 3.18}, {"text": "Make sense?", "start": 1538.8, "duration": 1.32}, {"text": "OK.", "start": 1540.12, "duration": 0.962}, {"text": "OK, first, so that's the first\ndistinction about attention,", "start": 1541.082, "duration": 2.458}, {"text": "covert versus overt.", "start": 1543.54, "duration": 1.95}, {"text": "OK?", "start": 1545.49, "duration": 1.29}, {"text": "Now, you might say,\nwhy would we bother", "start": 1546.78, "duration": 1.92}, {"text": "with this subtle, sophisticated\ncovert attention when", "start": 1548.7, "duration": 3.42}, {"text": "we can just move our eyes\nand do overt attention?", "start": 1552.12, "duration": 3.98}, {"text": "And I think there's a\nbunch of reasons for that.", "start": 1556.1, "duration": 2.0}, {"text": "One is other people can\nsee where you're looking.", "start": 1558.1, "duration": 3.62}, {"text": "And there's sometimes you want\nto attend to stuff over there", "start": 1561.72, "duration": 2.97}, {"text": "and not let people know, right?", "start": 1564.69, "duration": 2.7}, {"text": "So there are many examples of\nthis from elevator eyes, people", "start": 1567.39, "duration": 4.23}, {"text": "who look you up and down.", "start": 1571.62, "duration": 1.582}, {"text": "It's not politically correct.", "start": 1573.202, "duration": 1.208}, {"text": "It's not nice.", "start": 1574.41, "duration": 0.84}, {"text": "It's not considerate.", "start": 1575.25, "duration": 1.23}, {"text": "People notice if you do that.", "start": 1576.48, "duration": 2.35}, {"text": "So don't do it.", "start": 1578.83, "duration": 0.77}, {"text": "You can covertly attend\nbelow the face, if you like.", "start": 1579.6, "duration": 3.48}, {"text": "But don't overtly move\nyour eyes down there", "start": 1583.08, "duration": 2.37}, {"text": "because they will know.", "start": 1585.45, "duration": 1.38}, {"text": "OK?", "start": 1586.83, "duration": 0.57}, {"text": "We primates are\nvery, very attuned", "start": 1587.4, "duration": 1.98}, {"text": "to where each other are looking.", "start": 1589.38, "duration": 2.22}, {"text": "We are the only primate who\nhas whites around the eyes.", "start": 1591.6, "duration": 3.75}, {"text": "I just heard a talk last\nweek by Michael Tomasello,", "start": 1595.35, "duration": 2.31}, {"text": "who's one of the\nmajor primatologists.", "start": 1597.66, "duration": 2.34}, {"text": "And he says that\nthe fact that humans", "start": 1600.0, "duration": 2.25}, {"text": "have whites of their eyes that\nmake it so easy to tell where", "start": 1602.25, "duration": 2.52}, {"text": "they're looking must\nmean that we mostly", "start": 1604.77, "duration": 2.7}, {"text": "want to share information\nwith each other about where", "start": 1607.47, "duration": 2.687}, {"text": "we're looking.", "start": 1610.157, "duration": 0.583}, {"text": "We're a very cooperative,\ncommunicative species.", "start": 1610.74, "duration": 3.66}, {"text": "But not always.", "start": 1614.4, "duration": 0.963}, {"text": "Sometimes we want to\nsneak a peek at something", "start": 1615.363, "duration": 1.917}, {"text": "where people don't know.", "start": 1617.28, "duration": 1.23}, {"text": "The case that I\nnotice all the time is", "start": 1618.51, "duration": 1.65}, {"text": "I'm at a conference and\nsome very familiar face", "start": 1620.16, "duration": 2.13}, {"text": "comes along and\nsays, hey, Nancy.", "start": 1622.29, "duration": 1.65}, {"text": "How are you?", "start": 1623.94, "duration": 0.51}, {"text": "And I'm thinking,\nwho the hell is this?", "start": 1624.45, "duration": 2.07}, {"text": "And the whole time, I'm thinking\nI can see the name right there.", "start": 1626.52, "duration": 2.94}, {"text": "I can't quite resolve it.", "start": 1629.46, "duration": 1.14}, {"text": "I know that if saccade\ndown for a half a second,", "start": 1630.6, "duration": 2.88}, {"text": "they will see it.", "start": 1633.48, "duration": 0.72}, {"text": "And I will be busted.", "start": 1634.2, "duration": 1.59}, {"text": "And so I'm sitting there with\na name right there racking", "start": 1635.79, "duration": 2.52}, {"text": "my brain trying to think\nwho the hell it is.", "start": 1638.31, "duration": 1.98}, {"text": "Anyway, so there are many\ncases like this where we don't", "start": 1640.29, "duration": 2.333}, {"text": "want to be caught looking.", "start": 1642.623, "duration": 2.144}, {"text": "So those are all\ncases where you might", "start": 1644.767, "duration": 1.583}, {"text": "want to use covert attention.", "start": 1646.35, "duration": 2.52}, {"text": "Also, sometimes\nyou want to track", "start": 1648.87, "duration": 1.8}, {"text": "lots of things in parallel, and\nyou can't foveate all of them.", "start": 1650.67, "duration": 3.57}, {"text": "You can only foveate one thing.", "start": 1654.24, "duration": 2.26}, {"text": "So I don't know\nanything about sports.", "start": 1656.5, "duration": 1.73}, {"text": "But think of your favorite\ncomplicated sports example", "start": 1658.23, "duration": 2.25}, {"text": "where there are multiple\nplayers moving at once", "start": 1660.48, "duration": 1.958}, {"text": "and you need to keep\ntrack of all of them.", "start": 1662.438, "duration": 1.832}, {"text": "That would be a classic\ncase of covert attention", "start": 1664.27, "duration": 2.0}, {"text": "because you could covertly\nattend to several of them", "start": 1666.27, "duration": 2.13}, {"text": "at once.", "start": 1668.4, "duration": 0.5}, {"text": "And you have only one fovea.", "start": 1668.9, "duration": 1.82}, {"text": "Well, you have two, but\nthey go to the same place.", "start": 1670.72, "duration": 3.14}, {"text": "OK, so that's the\nsecond distinction overt", "start": 1673.86, "duration": 1.86}, {"text": "versus covert--", "start": 1675.72, "duration": 2.43}, {"text": "or the first one.", "start": 1678.15, "duration": 0.78}, {"text": "Right?", "start": 1678.93, "duration": 0.5}, {"text": "So the next basic distinction\nof different kinds of attention", "start": 1679.43, "duration": 3.67}, {"text": "are the kind where\nwe decide where", "start": 1683.1, "duration": 2.25}, {"text": "we want to look versus the\nkind where the stimulus draws", "start": 1685.35, "duration": 4.05}, {"text": "our attention, OK?", "start": 1689.4, "duration": 1.83}, {"text": "So there are lots of examples.", "start": 1691.23, "duration": 2.28}, {"text": "Like web pop ups\nare all designed", "start": 1693.51, "duration": 2.37}, {"text": "to pull your attention,\novert and covert.", "start": 1695.88, "duration": 2.67}, {"text": "Even you don't want to\nlook at that damn thing.", "start": 1698.55, "duration": 2.16}, {"text": "But the weird, little\ndancing figure,", "start": 1700.71, "duration": 2.16}, {"text": "they're all optimized to pull\nyour attention over and make", "start": 1702.87, "duration": 3.84}, {"text": "you read the ad, right?", "start": 1706.71, "duration": 1.942}, {"text": "And they're pretty effective.", "start": 1708.652, "duration": 1.208}, {"text": "OK, so that's called\nstimulus-driven attention", "start": 1709.86, "duration": 3.0}, {"text": "or exogenous attention.", "start": 1712.86, "duration": 1.167}, {"text": "It comes from the outside.", "start": 1714.027, "duration": 1.083}, {"text": "And it pulls you in.", "start": 1715.11, "duration": 1.56}, {"text": "OK?", "start": 1716.67, "duration": 2.28}, {"text": "Another classic\nexample is pop-out.", "start": 1718.95, "duration": 2.13}, {"text": "If you look at this\ndisplay, it's very hard", "start": 1721.08, "duration": 1.8}, {"text": "not to notice and have\nyour attention drawn", "start": 1722.88, "duration": 1.83}, {"text": "to that red thing.", "start": 1724.71, "duration": 1.74}, {"text": "Certain properties\nof stimuli that just", "start": 1726.45, "duration": 1.89}, {"text": "automatically capture\nyour attention.", "start": 1728.34, "duration": 2.49}, {"text": "OK, that is to be\ncontrasted with", "start": 1730.83, "duration": 2.37}, {"text": "voluntary controlled attention.", "start": 1733.2, "duration": 1.513}, {"text": "That's like the case\nwe did before where", "start": 1734.713, "duration": 1.667}, {"text": "you were fixating on my nose.", "start": 1736.38, "duration": 1.65}, {"text": "It was totally up to\nyou whether attend--", "start": 1738.03, "duration": 2.053}, {"text": "I mean, I told you to.", "start": 1740.083, "duration": 0.917}, {"text": "But you could have\nmade up your own mind", "start": 1741.0, "duration": 1.35}, {"text": "and attended to neither.", "start": 1742.35, "duration": 1.11}, {"text": "And I wouldn't\nhave known, right?", "start": 1743.46, "duration": 1.89}, {"text": "So you can decide what you\nwant to pay attention to.", "start": 1745.35, "duration": 2.56}, {"text": "And as I think I\nmentioned in I don't", "start": 1747.91, "duration": 1.61}, {"text": "know what context\na few weeks ago,", "start": 1749.52, "duration": 2.52}, {"text": "thank God we can decide\nwhat to pay attention to.", "start": 1752.04, "duration": 2.148}, {"text": "Because there's lots of stuff\nthat goes on in the world", "start": 1754.188, "duration": 2.292}, {"text": "that we don't want to have\ndominate our mental life.", "start": 1756.48, "duration": 2.49}, {"text": "And controlled or\nvoluntary attention", "start": 1758.97, "duration": 3.42}, {"text": "is one way that we can have\nour mental life dominated", "start": 1762.39, "duration": 3.54}, {"text": "more by things we want it\nto be dominated by and less", "start": 1765.93, "duration": 2.49}, {"text": "by things we don't, right?", "start": 1768.42, "duration": 3.75}, {"text": "So that's that notion here.", "start": 1772.17, "duration": 1.62}, {"text": "Like for example,\nyou're sitting here.", "start": 1773.79, "duration": 2.4}, {"text": "And it's like noon.", "start": 1776.19, "duration": 0.99}, {"text": "And you're just thinking,\nOK, I'm really hungry.", "start": 1777.18, "duration": 1.68}, {"text": "I'm really hungry.", "start": 1778.86, "duration": 0.87}, {"text": "If you were my dog Charlie,\nyour entire mental life", "start": 1779.73, "duration": 2.4}, {"text": "for the whole next half an\nhour would be, I'm so hungry.", "start": 1782.13, "duration": 1.95}, {"text": "I'm so hungry.", "start": 1784.08, "duration": 0.583}, {"text": "I'm so hungry.", "start": 1784.663, "duration": 1.097}, {"text": "But you're a person.", "start": 1785.76, "duration": 1.24}, {"text": "And so that thought may\nimpinge now and then,", "start": 1787.0, "duration": 2.235}, {"text": "but you can drive it away and\nthink about something else.", "start": 1789.235, "duration": 2.375}, {"text": "Because it's not going\nto get you anywhere", "start": 1791.61, "duration": 2.01}, {"text": "to focus on how hungry you are.", "start": 1793.62, "duration": 1.293}, {"text": "I know I just made it worse.", "start": 1794.913, "duration": 1.167}, {"text": "I'm sorry about that.", "start": 1796.08, "duration": 3.09}, {"text": "OK.", "start": 1799.17, "duration": 1.67}, {"text": "OK, the way that\nscientists have typically", "start": 1800.84, "duration": 3.91}, {"text": "studied voluntary attention is\nthey ask subjects to do this.", "start": 1804.75, "duration": 4.08}, {"text": "And much like the\ncase we just did,", "start": 1808.83, "duration": 1.47}, {"text": "here's kind of very\nbasic paradigm.", "start": 1810.3, "duration": 2.28}, {"text": "You have subjects\nfixating on a cross.", "start": 1812.58, "duration": 1.8}, {"text": "And typically, in covert\nattention experiments,", "start": 1814.38, "duration": 3.03}, {"text": "you want to make sure there\naren't overt eye movements.", "start": 1817.41, "duration": 2.55}, {"text": "And so you'll have an\neye tracker to make sure", "start": 1819.96, "duration": 1.5}, {"text": "the subject is keeping\ntheir eye on that cross.", "start": 1821.46, "duration": 2.01}, {"text": "OK?", "start": 1823.47, "duration": 1.002}, {"text": "And then you give\nthem a little cue", "start": 1824.472, "duration": 1.458}, {"text": "that says pay attention\noff to the right,", "start": 1825.93, "duration": 2.1}, {"text": "but don't move your eyes, OK?", "start": 1828.03, "duration": 2.67}, {"text": "And then shortly thereafter,\na little cue comes up.", "start": 1830.7, "duration": 3.03}, {"text": "And you have to hit\na button quickly", "start": 1833.73, "duration": 1.5}, {"text": "that you detected the target.", "start": 1835.23, "duration": 1.35}, {"text": "OK?", "start": 1836.58, "duration": 0.27}, {"text": "It comes out at variable delays.", "start": 1836.85, "duration": 1.333}, {"text": "So you can't just\nhit the button.", "start": 1838.183, "duration": 2.267}, {"text": "OK, if you do that, you\nfind that the reaction", "start": 1840.45, "duration": 2.61}, {"text": "time to detect that target, if\nit's where you're attending,", "start": 1843.06, "duration": 2.7}, {"text": "is really fast, not much\nmore than 200 milliseconds,", "start": 1845.76, "duration": 3.1}, {"text": "which is damned fast, right?", "start": 1848.86, "duration": 2.66}, {"text": "Now consider a case where you're\ninstructed to attend over here.", "start": 1851.52, "duration": 3.245}, {"text": "And the way you get\nthese experiments to work", "start": 1854.765, "duration": 1.875}, {"text": "is that these cues are\nvalid 80% of the time.", "start": 1856.64, "duration": 2.527}, {"text": "So there's a reason for\nsubject to-- there's", "start": 1859.167, "duration": 1.833}, {"text": "a motivation for them to\nfollow your instruction.", "start": 1861.0, "duration": 2.12}, {"text": "So they're trying\nto answer quickly.", "start": 1863.12, "duration": 1.26}, {"text": "And there's like,\nOK, they're ready.", "start": 1864.38, "duration": 0.96}, {"text": "It's almost certainly\ngoing to be over here.", "start": 1865.34, "duration": 1.35}, {"text": "But oops.", "start": 1866.69, "duration": 0.57}, {"text": "It's not.", "start": 1867.26, "duration": 0.9}, {"text": "OK?", "start": 1868.16, "duration": 1.02}, {"text": "Then reaction time is almost\n100 milliseconds slower,", "start": 1869.18, "duration": 3.42}, {"text": "which is a huge effect in\npsychology, 100 milliseconds.", "start": 1872.6, "duration": 3.75}, {"text": "OK?", "start": 1876.35, "duration": 0.96}, {"text": "OK, so you're much slower\nto detect something", "start": 1877.31, "duration": 3.57}, {"text": "if it's at an\nunattended location.", "start": 1880.88, "duration": 2.44}, {"text": "OK?", "start": 1883.32, "duration": 0.5}, {"text": "And if you have a neutral trial,\nyou're somewhere in the middle.", "start": 1883.82, "duration": 3.09}, {"text": "OK, so that is exogenous\nor voluntary attention.", "start": 1886.91, "duration": 6.21}, {"text": "OK, and again, this\nis covert attention.", "start": 1893.12, "duration": 2.22}, {"text": "No eye movements.", "start": 1895.34, "duration": 2.07}, {"text": "All right, so third\ndistinction, the example", "start": 1897.41, "duration": 4.05}, {"text": "I just gave you was\nspatial attention.", "start": 1901.46, "duration": 1.77}, {"text": "You're attending to this\nlocation or that location", "start": 1903.23, "duration": 2.91}, {"text": "in space.", "start": 1906.14, "duration": 1.27}, {"text": "OK?", "start": 1907.41, "duration": 0.5}, {"text": "That's probably the most\npowerful and common kind", "start": 1907.91, "duration": 2.43}, {"text": "of attention is\nusually the things", "start": 1910.34, "duration": 2.092}, {"text": "you're interested in are\nin a particular place.", "start": 1912.432, "duration": 1.958}, {"text": "And you attend to that place.", "start": 1914.39, "duration": 1.208}, {"text": "And there you go.", "start": 1915.598, "duration": 1.762}, {"text": "But it's not the only kind.", "start": 1917.36, "duration": 1.77}, {"text": "You can have\nfeature-based attention.", "start": 1919.13, "duration": 2.23}, {"text": "So if your utensil drawer is\na hell of a mess like mine", "start": 1921.36, "duration": 3.32}, {"text": "is, like this, if your task\nis to find the black vegetable", "start": 1924.68, "duration": 4.86}, {"text": "peeler, best of luck to you.", "start": 1929.54, "duration": 2.49}, {"text": "It'll take quite a while.", "start": 1932.03, "duration": 1.68}, {"text": "It's in there.", "start": 1933.71, "duration": 0.67}, {"text": "It's right there.", "start": 1934.38, "duration": 0.708}, {"text": "But it takes a while, right?", "start": 1935.088, "duration": 1.712}, {"text": "In contrast, if the task is find\nthe purple rubber spatula, duh,", "start": 1936.8, "duration": 4.86}, {"text": "right?", "start": 1941.66, "duration": 0.78}, {"text": "OK, so that's\nfeature-based attention.", "start": 1942.44, "duration": 1.74}, {"text": "You don't know the\nlocation in advance.", "start": 1944.18, "duration": 1.77}, {"text": "You know something about the\nfeature you're looking for,", "start": 1945.95, "duration": 2.333}, {"text": "that it's black or that it's\npurple or round or square", "start": 1948.283, "duration": 2.857}, {"text": "or whatever the feature is.", "start": 1951.14, "duration": 1.47}, {"text": "OK, so different\nkinds of filters", "start": 1952.61, "duration": 2.46}, {"text": "you can set on your\nattention system.", "start": 1955.07, "duration": 2.97}, {"text": "OK, so that's just\nto give you some", "start": 1958.04, "duration": 1.77}, {"text": "of the phenomenology of the\ndifferent kinds of attention.", "start": 1959.81, "duration": 2.83}, {"text": "How does all this\nwork in the brain?", "start": 1962.64, "duration": 1.605}, {"text": "I'm not going to tell\nyou how it works.", "start": 1964.245, "duration": 1.625}, {"text": "We'll just focus mostly on\nwhat the brain regions are.", "start": 1965.87, "duration": 4.05}, {"text": "OK, so let's go back to this\ncase here, voluntary attention.", "start": 1969.92, "duration": 5.83}, {"text": "So now the question is, what\nhappens when you get this cue?", "start": 1975.75, "duration": 3.41}, {"text": "You're not going\nto move your eyes.", "start": 1979.16, "duration": 1.53}, {"text": "But you're kind of cranking\nup that part of space.", "start": 1980.69, "duration": 3.21}, {"text": "OK, what's going on in\nthe brain right there", "start": 1983.9, "duration": 3.12}, {"text": "before the stimulus comes on?", "start": 1987.02, "duration": 2.13}, {"text": "Everybody get the question?", "start": 1989.15, "duration": 1.71}, {"text": "OK, you can sort of\nfeel it happening.", "start": 1990.86, "duration": 2.04}, {"text": "But what does that mean?", "start": 1992.9, "duration": 1.93}, {"text": "Well, this is very amenable\nto a simple functional MRI", "start": 1994.83, "duration": 3.26}, {"text": "experiment.", "start": 1998.09, "duration": 1.02}, {"text": "And in the early days\nof functional MRI,", "start": 1999.11, "duration": 2.25}, {"text": "a whole bunch of people at\nonce realize, oh, right, we", "start": 2001.36, "duration": 2.85}, {"text": "can answer this\nlongstanding question", "start": 2004.21, "duration": 1.98}, {"text": "of whether early retinotopic\nparts of the visual system", "start": 2006.19, "duration": 3.45}, {"text": "are affected just\nby a cue like that,", "start": 2009.64, "duration": 2.97}, {"text": "even before the stimulus\ncomes on, right?", "start": 2012.61, "duration": 3.54}, {"text": "And I think it was 1998.", "start": 2016.15, "duration": 2.28}, {"text": "A whole bunch of people\nstarted doing this in 1997.", "start": 2018.43, "duration": 2.55}, {"text": "I was one of them.", "start": 2020.98, "duration": 1.44}, {"text": "But a whole bunch\ndid it once in 1998.", "start": 2022.42, "duration": 1.92}, {"text": "I think like six\npapers were published", "start": 2024.34, "duration": 2.307}, {"text": "all doing versions of\nthis next thing, which", "start": 2026.647, "duration": 1.833}, {"text": "is one of those obvious ideas.", "start": 2028.48, "duration": 2.67}, {"text": "We got scooped.", "start": 2031.15, "duration": 0.75}, {"text": "But anyway, everybody\ngot the same result.", "start": 2031.9, "duration": 2.83}, {"text": "So basically, if you just\ndo a simple comparison--", "start": 2034.73, "duration": 2.34}, {"text": "this is the version they have.", "start": 2037.07, "duration": 1.25}, {"text": "Subjects are fixating here.", "start": 2038.32, "duration": 1.2}, {"text": "There's two stimuli.", "start": 2039.52, "duration": 1.89}, {"text": "They're looking in V1 and V2.", "start": 2041.41, "duration": 2.01}, {"text": "And if you just do a contrast\nof the case where you're", "start": 2043.42, "duration": 2.76}, {"text": "looking here and you're\nattending, waiting for a target", "start": 2046.18, "duration": 2.459}, {"text": "here versus waiting for a target\nthere without moving your eyes,", "start": 2048.639, "duration": 3.871}, {"text": "you get a big contralateral\nmodulation in V1 and V2.", "start": 2052.51, "duration": 4.919}, {"text": "This is a slice near the\nback of the head here.", "start": 2057.429, "duration": 2.321}, {"text": "So this is a piece\nof calcarine sulcus", "start": 2059.75, "duration": 2.51}, {"text": "or primary visual cortex, right?", "start": 2062.26, "duration": 2.669}, {"text": "And so you can see, even before\nthe target stimulus comes on,", "start": 2064.929, "duration": 3.691}, {"text": "just attending over there gives\nyou a big baseline increase", "start": 2068.62, "duration": 4.019}, {"text": "in neural activity.", "start": 2072.639, "duration": 0.931}, {"text": "Everybody clear\nwhat's going on here?", "start": 2073.57, "duration": 2.01}, {"text": "And of course, you can\ndo the opposite one", "start": 2075.58, "duration": 1.9}, {"text": "and see that it shifts to\nthe opposite side of space.", "start": 2077.48, "duration": 2.929}, {"text": "OK?", "start": 2080.409, "duration": 1.341}, {"text": "OK, so that's all before\nthe stimulus comes on.", "start": 2081.75, "duration": 2.85}, {"text": "You can think of it as priming\nthe brain, kind of juicing up", "start": 2084.6, "duration": 2.76}, {"text": "those neurons getting\nthem ready to go,", "start": 2087.36, "duration": 1.66}, {"text": "so that, when that stimulus\ncomes through, boom.", "start": 2089.02, "duration": 2.0}, {"text": "Your reaction time is faster.", "start": 2091.02, "duration": 2.179}, {"text": "OK?", "start": 2093.199, "duration": 2.371}, {"text": "OK, so that's modulating\nparts of visual cortex", "start": 2095.57, "duration": 4.35}, {"text": "before a stimulus comes\non to get it ready.", "start": 2099.92, "duration": 3.18}, {"text": "But we can also look\nat, what is the effect", "start": 2103.1, "duration": 1.92}, {"text": "on a stimulus once\nit comes through,", "start": 2105.02, "duration": 1.98}, {"text": "an attended stimulus or\nan unattended stimulus?", "start": 2107.0, "duration": 2.665}, {"text": "To show you that,\nI'm going to show you", "start": 2109.665, "duration": 1.625}, {"text": "a kind of feature-based\nattention and an ancient-- this", "start": 2111.29, "duration": 5.07}, {"text": "is a paper we published\nin 1998, I think.", "start": 2116.36, "duration": 3.18}, {"text": "This is a nonspatial version.", "start": 2119.54, "duration": 1.92}, {"text": "So we gave subjects--\nguess what-- faces", "start": 2121.46, "duration": 2.49}, {"text": "and houses and a\nlittle crosshair.", "start": 2123.95, "duration": 2.31}, {"text": "And we had subjects\nin different blocks", "start": 2126.26, "duration": 2.49}, {"text": "say whether the two\narms of the cross", "start": 2128.75, "duration": 2.37}, {"text": "were the same or\ndifferent length, OK?", "start": 2131.12, "duration": 3.21}, {"text": "So vertical one is\ndifferent length.", "start": 2134.33, "duration": 1.525}, {"text": "So that's a different case.", "start": 2135.855, "duration": 1.325}, {"text": "Whether the two houses\nare same or different", "start": 2137.18, "duration": 3.24}, {"text": "or whether the two faces\nare same or different.", "start": 2140.42, "duration": 2.35}, {"text": "OK, so actually, it's\nspatial and feature,", "start": 2142.77, "duration": 1.91}, {"text": "when you think of it, because\nthey're in different places.", "start": 2144.68, "duration": 2.565}, {"text": "OK?", "start": 2147.245, "duration": 0.855}, {"text": "So we then looked in\na bunch of regions.", "start": 2148.1, "duration": 2.25}, {"text": "I'll show you the data from\nthe fusiform face area.", "start": 2150.35, "duration": 2.79}, {"text": "And the key thing about\nthis is, in all three tasks,", "start": 2153.14, "duration": 3.6}, {"text": "we had the identical stimuli.", "start": 2156.74, "duration": 2.56}, {"text": "So there's always\nfaces and houses", "start": 2159.3, "duration": 2.27}, {"text": "and crosses in the same\nplace in your visual field,", "start": 2161.57, "duration": 2.76}, {"text": "in all of those blocks.", "start": 2164.33, "duration": 1.5}, {"text": "It's just a matter of\nwhich of those things", "start": 2165.83, "duration": 1.86}, {"text": "you're paying attention to.", "start": 2167.69, "duration": 2.01}, {"text": "OK?", "start": 2169.7, "duration": 0.905}, {"text": "So what do you think we'll\nsee in the fusiform face", "start": 2170.605, "duration": 2.125}, {"text": "area in this experiment?", "start": 2172.73, "duration": 3.51}, {"text": "Is it going to care whether\nyou're attending to faces", "start": 2176.24, "duration": 3.93}, {"text": "or attending to houses or\nattending to the crosshair?", "start": 2180.17, "duration": 3.42}, {"text": "Same stimulus all the time.", "start": 2183.59, "duration": 1.605}, {"text": "Yeah, Jimmy?", "start": 2189.84, "duration": 1.36}, {"text": "AUDIENCE: [INAUDIBLE]\nwhen you're not attending.", "start": 2191.2, "duration": 2.0}, {"text": "But when you're\nattending, [INAUDIBLE]", "start": 2193.2, "duration": 2.84}, {"text": "NANCY KANWISHER:\nExactly what happens.", "start": 2196.04, "duration": 1.823}, {"text": "OK, everybody hear\nthe prediction?", "start": 2197.863, "duration": 1.417}, {"text": "You'll still get something.", "start": 2199.28, "duration": 1.5}, {"text": "But you'll get more when\nyou're paying attention to it.", "start": 2200.78, "duration": 3.06}, {"text": "OK, so here's the FFA\nresponse over time.", "start": 2203.84, "duration": 3.85}, {"text": "Here's the time course.", "start": 2207.69, "duration": 1.43}, {"text": "And these gray blocks\nare the blocks.", "start": 2209.12, "duration": 2.28}, {"text": "These are the different\nattending to houses, faces,", "start": 2211.4, "duration": 2.16}, {"text": "color, houses, faces, crosshair,\nhouses, faces, crosshair.", "start": 2213.56, "duration": 3.81}, {"text": "The gray bars are\nwhen the subjects", "start": 2217.37, "duration": 1.95}, {"text": "are attending to faces.", "start": 2219.32, "duration": 2.85}, {"text": "Now, here, I actually\ncan't quite tell.", "start": 2222.17, "duration": 6.85}, {"text": "Yeah, I can sort of tell.", "start": 2229.02, "duration": 1.46}, {"text": "You can't see it on the screen.", "start": 2230.48, "duration": 1.35}, {"text": "But there are little rest\nperiods between those blocks.", "start": 2231.83, "duration": 2.388}, {"text": "So I'm trying to\nfigure out if you're", "start": 2234.218, "duration": 1.542}, {"text": "right that there's some\nresponse greater than baseline.", "start": 2235.76, "duration": 3.87}, {"text": "I think there's actually very\nlittle selective response", "start": 2239.63, "duration": 2.34}, {"text": "greater than baseline.", "start": 2241.97, "duration": 1.32}, {"text": "By design, we made this\na whopping attentional", "start": 2243.29, "duration": 3.21}, {"text": "manipulation, so that all of\nthe tasks are really difficult.", "start": 2246.5, "duration": 3.443}, {"text": "And when you're\ndoing one of them,", "start": 2249.943, "duration": 1.417}, {"text": "you just barely feel\naware of anything else.", "start": 2251.36, "duration": 2.32}, {"text": "In fact, I vividly\nremember the first time", "start": 2253.68, "duration": 2.42}, {"text": "we ran this experiment, I\nwas a subject in the scanner.", "start": 2256.1, "duration": 2.61}, {"text": "And I did the first block.", "start": 2258.71, "duration": 2.01}, {"text": "And I was doing just crosshairs.", "start": 2260.72, "duration": 3.18}, {"text": "And I went through the\nwhole crosshair thing.", "start": 2263.9, "duration": 2.537}, {"text": "And it wasn't till the end\nof the experiment I realized,", "start": 2266.437, "duration": 2.333}, {"text": "oh, right, there\nwere faces there.", "start": 2268.77, "duration": 1.417}, {"text": "I was just completely\nunaware of them.", "start": 2270.187, "duration": 1.673}, {"text": "So we designed it to really\nso tie up your mental capacity", "start": 2271.86, "duration": 4.91}, {"text": "that you just didn't have\nprocessing resources left", "start": 2276.77, "duration": 2.46}, {"text": "for anything else.", "start": 2279.23, "duration": 0.97}, {"text": "And so if there is a response\nto everything else here,", "start": 2280.2, "duration": 2.78}, {"text": "it's really low.", "start": 2282.98, "duration": 0.91}, {"text": "But you can see, certainly, the\nattended thing is much more.", "start": 2283.89, "duration": 2.78}, {"text": "It's much stronger\nin the attended case", "start": 2286.67, "duration": 1.69}, {"text": "than the unattended case.", "start": 2288.36, "duration": 1.52}, {"text": "OK?", "start": 2289.88, "duration": 0.84}, {"text": "So this is a general property.", "start": 2290.72, "duration": 1.68}, {"text": "Like basically, all of\nthe perceptual regions", "start": 2292.4, "duration": 2.04}, {"text": "we've talked about are strongly\nmodulable by attention,", "start": 2294.44, "duration": 4.05}, {"text": "OK, from retinotopic\nregions on up.", "start": 2298.49, "duration": 4.83}, {"text": "OK, including V1 and, in fact,\neven including the lateral", "start": 2303.32, "duration": 5.98}, {"text": "geniculate nucleus.", "start": 2309.3, "duration": 2.38}, {"text": "So one synapse up\nfrom the retina,", "start": 2311.68, "duration": 2.84}, {"text": "you're already modulating\nactivity there by attention.", "start": 2314.52, "duration": 3.87}, {"text": "OK?", "start": 2318.39, "duration": 2.49}, {"text": "I know I said this, but\nit maybe went by briefly.", "start": 2320.88, "duration": 2.79}, {"text": "You have 10 times as\nmany connections down", "start": 2323.67, "duration": 2.28}, {"text": "from cortex down to the LGN\nas you have going forward.", "start": 2325.95, "duration": 4.24}, {"text": "OK?", "start": 2330.19, "duration": 0.5}, {"text": "One of the things they're\ndoing is setting up", "start": 2330.69, "duration": 2.1}, {"text": "selective filters, so that only\nthe stuff you want to process", "start": 2332.79, "duration": 3.87}, {"text": "makes it to higher stages.", "start": 2336.66, "duration": 2.59}, {"text": "OK, Yes?", "start": 2339.25, "duration": 2.062}, {"text": "AUDIENCE: So does this\nsort of phenomenon", "start": 2341.312, "duration": 1.708}, {"text": "generalize across\nthe brain areas?", "start": 2343.02, "duration": 2.21}, {"text": "I mean, it's like--", "start": 2345.23, "duration": 0.94}, {"text": "NANCY KANWISHER: It's\ngenerally true of pretty much", "start": 2346.17, "duration": 2.125}, {"text": "everywhere, yeah.", "start": 2348.295, "duration": 1.19}, {"text": "AUDIENCE: It might be\nthe intuitive physics", "start": 2349.485, "duration": 1.795}, {"text": "thing is justified.", "start": 2351.28, "duration": 1.3}, {"text": "So it's better to see\nthe same stimulus.", "start": 2352.58, "duration": 3.028}, {"text": "NANCY KANWISHER: Exactly.", "start": 2355.608, "duration": 1.042}, {"text": "It's an instance of\nthis, exactly right.", "start": 2356.65, "duration": 2.16}, {"text": "Exactly right.", "start": 2358.81, "duration": 0.75}, {"text": "It gives us one\nof our paradigms.", "start": 2359.56, "duration": 2.55}, {"text": "In functional MRI studies,\nhave the same stimulus,", "start": 2362.11, "duration": 2.55}, {"text": "vary the task.", "start": 2364.66, "duration": 1.39}, {"text": "OK?", "start": 2366.05, "duration": 1.078}, {"text": "Some things don't work\nas well, things that", "start": 2367.128, "duration": 1.792}, {"text": "are just very dominant stimuli.", "start": 2368.92, "duration": 2.11}, {"text": "In this experiment, if we hadn't\nput the faces in the periphery", "start": 2371.03, "duration": 2.87}, {"text": "and given subjects a\ndamn difficult task,", "start": 2373.9, "duration": 3.0}, {"text": "the modulation\nwouldn't have worked.", "start": 2376.9, "duration": 1.5}, {"text": "Because faces are\njust so dominant,", "start": 2378.4, "duration": 1.5}, {"text": "they're going to punch through\neven if you don't want to, OK?", "start": 2379.9, "duration": 3.09}, {"text": "Like web pop ups. You also--", "start": 2382.99, "duration": 1.607}, {"text": "I'm going to skip this\nbecause we won't have time.", "start": 2384.597, "duration": 2.083}, {"text": "You could get very\nsimilar things", "start": 2386.68, "duration": 1.5}, {"text": "in primary auditory cortex\nlistening to high frequencies", "start": 2388.18, "duration": 2.82}, {"text": "or low frequencies.", "start": 2391.0, "duration": 1.14}, {"text": "These are all the same stimuli.", "start": 2392.14, "duration": 1.66}, {"text": "This is voxel selected\nfor low frequencies, voxel", "start": 2393.8, "duration": 3.06}, {"text": "selected for high frequencies.", "start": 2396.86, "duration": 1.25}, {"text": "You have a high frequency\ninput in one ear,", "start": 2398.11, "duration": 1.83}, {"text": "low frequency in the other.", "start": 2399.94, "duration": 1.14}, {"text": "As you switch between,\nthose responses toggle.", "start": 2401.08, "duration": 4.13}, {"text": "OK, so all of that tells you\nthe effects of attention,", "start": 2405.21, "duration": 3.18}, {"text": "how it modulates activity\nall over the brain.", "start": 2408.39, "duration": 2.62}, {"text": "But what is the source of\nattention signals in the brain?", "start": 2411.01, "duration": 3.5}, {"text": "And that source is\na set of regions", "start": 2414.51, "duration": 1.86}, {"text": "we have encountered\nbefore, sometimes called", "start": 2416.37, "duration": 2.76}, {"text": "the frontal-parietal\nattention network,", "start": 2419.13, "duration": 1.92}, {"text": "these blue and green\nbits up in here,", "start": 2421.05, "duration": 2.13}, {"text": "back here in the parietal lobe,\nup here in the frontal lobe.", "start": 2423.18, "duration": 3.66}, {"text": "And they are active\nwhen you shift attention", "start": 2426.84, "duration": 2.52}, {"text": "from one location to another,\nfrom one feature to another,", "start": 2429.36, "duration": 3.06}, {"text": "or when you do any difficult\nattention-demanding task.", "start": 2432.42, "duration": 3.84}, {"text": "We've also talked about\nthem in the other context", "start": 2436.26, "duration": 2.4}, {"text": "of the multiple demand system.", "start": 2438.66, "duration": 1.41}, {"text": "It's pretty much the same\nset of cortical regions.", "start": 2440.07, "duration": 2.34}, {"text": "That pretty much any time\nyou do a difficult task,", "start": 2442.41, "duration": 2.43}, {"text": "almost no matter what the task\nis, these regions turn on.", "start": 2444.84, "duration": 3.4}, {"text": "So they're not just\nabout visual attention.", "start": 2448.24, "duration": 2.12}, {"text": "They're kind of about basically\ncontrolling your mind, right,", "start": 2450.36, "duration": 4.53}, {"text": "selecting information, making\nyourself do difficult things.", "start": 2454.89, "duration": 4.92}, {"text": "Who knows what that\nis computationally.", "start": 2459.81, "duration": 2.1}, {"text": "But these regions are very\nsystematically engaged.", "start": 2461.91, "duration": 3.42}, {"text": "And they're particularly\nsystematically engaged", "start": 2465.33, "duration": 2.22}, {"text": "when you're shifting attention\nover different locations.", "start": 2467.55, "duration": 3.42}, {"text": "OK, so just to remind you\nin contrast, everything else", "start": 2470.97, "duration": 2.31}, {"text": "we've talked about, face areas,\nmusic areas, language areas,", "start": 2473.28, "duration": 3.33}, {"text": "they're very specific\nfor one mental process,", "start": 2476.61, "duration": 2.37}, {"text": "domain specific.", "start": 2478.98, "duration": 0.96}, {"text": "These are the opposite.", "start": 2479.94, "duration": 1.06}, {"text": "They're ludicrously\ndomain general.", "start": 2481.0, "duration": 2.69}, {"text": "OK?", "start": 2483.69, "duration": 1.59}, {"text": "All right, I'm going\nto skip the video.", "start": 2485.28, "duration": 3.3}, {"text": "When the system is\ndamaged bilaterally,", "start": 2488.58, "duration": 1.92}, {"text": "all kinds of weird\nstuff happens.", "start": 2490.5, "duration": 2.86}, {"text": "OK?", "start": 2493.36, "duration": 0.5}, {"text": "I'll post this.", "start": 2493.86, "duration": 0.72}, {"text": "If you guys send me\nan email to remind me,", "start": 2494.58, "duration": 1.92}, {"text": "I'll post this clip in.", "start": 2496.5, "duration": 1.11}, {"text": "Balint's syndrome, where\nyou have bilateral damage", "start": 2497.61, "duration": 2.94}, {"text": "back there in these\nparietal regions,", "start": 2500.55, "duration": 1.89}, {"text": "people can only see\none object at a time.", "start": 2502.44, "duration": 2.95}, {"text": "OK?", "start": 2505.39, "duration": 0.5}, {"text": "They're looking at a\ncomplicated thing like this.", "start": 2505.89, "duration": 2.34}, {"text": "And they would see, I see Shosh.", "start": 2508.23, "duration": 2.22}, {"text": "See anything else?", "start": 2510.45, "duration": 0.87}, {"text": "No just Shosh.", "start": 2511.32, "duration": 1.2}, {"text": "Nothing else there?", "start": 2512.52, "duration": 0.87}, {"text": "No.", "start": 2513.39, "duration": 0.5}, {"text": "Just Shosh, right?", "start": 2513.89, "duration": 0.79}, {"text": "Totally weird.", "start": 2514.68, "duration": 0.66}, {"text": "Anyway, so they get\nlocked on one thing.", "start": 2515.34, "duration": 1.83}, {"text": "They can't shift attention.", "start": 2517.17, "duration": 1.86}, {"text": "OK.", "start": 2519.03, "duration": 2.52}, {"text": "OK, I want to talk at least\nbriefly about awareness.", "start": 2521.55, "duration": 3.67}, {"text": "So let's talk a little bit about\nneural correlates of awareness.", "start": 2525.22, "duration": 4.56}, {"text": "And so first question\nis, if we want", "start": 2529.78, "duration": 3.44}, {"text": "to study perceptual awareness\nand not just perception,", "start": 2533.22, "duration": 4.77}, {"text": "how are we going to\nuncouple those things?", "start": 2537.99, "duration": 2.58}, {"text": "We've sort of talked about a\nfew examples with attention.", "start": 2540.57, "duration": 3.15}, {"text": "With attention, the\nthing you're attending to", "start": 2543.72, "duration": 2.22}, {"text": "is at least much more\ndominant in your awareness", "start": 2545.94, "duration": 2.28}, {"text": "than the stuff you're\nnot attending to,", "start": 2548.22, "duration": 1.86}, {"text": "even if the other stuff\nseeps in a little bit.", "start": 2550.08, "duration": 3.22}, {"text": "So that's one way, where you\nhave the identical stimulus.", "start": 2553.3, "duration": 6.17}, {"text": "But you were varying\nthe degree of awareness.", "start": 2559.47, "duration": 2.67}, {"text": "But another way-- oh, I need you\nguys to pass out the glasses.", "start": 2562.14, "duration": 3.597}, {"text": "You want to both do\nthat at different sides?", "start": 2565.737, "duration": 1.833}, {"text": "OK, so I'm going to\nshow you a stimulus.", "start": 2567.57, "duration": 1.947}, {"text": "These guys are going\nto pass around glasses.", "start": 2569.517, "duration": 1.833}, {"text": "And let me say in\nadvance, I want them back.", "start": 2571.35, "duration": 1.59}, {"text": "I use these every year.", "start": 2572.94, "duration": 0.96}, {"text": "So drop them off\nhere when you leave.", "start": 2573.9, "duration": 1.922}, {"text": "OK, so what you're going to\ndo, you put them on either way.", "start": 2575.822, "duration": 2.458}, {"text": "Doesn't matter.", "start": 2578.28, "duration": 1.47}, {"text": "OK, so first, we're\ngoing to do optics.", "start": 2579.75, "duration": 1.95}, {"text": "Nothing interesting.", "start": 2581.7, "duration": 1.56}, {"text": "So look at this stimulus\nand close one eye.", "start": 2583.26, "duration": 4.17}, {"text": "OK, now look at it\nthrough the glasses.", "start": 2587.43, "duration": 1.98}, {"text": "Look at it through the\nglasses, and close one eye.", "start": 2589.41, "duration": 2.28}, {"text": "And you should see just\na face or just a house.", "start": 2591.69, "duration": 2.94}, {"text": "And if you close the other eye,\nyou should see the opposite.", "start": 2594.63, "duration": 2.77}, {"text": "Does everybody get that?", "start": 2597.4, "duration": 1.28}, {"text": "OK, that's not psychology.", "start": 2598.68, "duration": 1.23}, {"text": "That's optics.", "start": 2599.91, "duration": 0.84}, {"text": "The glasses are just\nfiltering one image", "start": 2600.75, "duration": 1.98}, {"text": "into one eye and another\nimage into the other eye, OK?", "start": 2602.73, "duration": 3.655}, {"text": "This is all this is is a way\nto get different information", "start": 2606.385, "duration": 2.375}, {"text": "to your two eyes.", "start": 2608.76, "duration": 1.35}, {"text": "OK, now just look\nwith both eyes.", "start": 2610.11, "duration": 2.58}, {"text": "And don't do anything.", "start": 2612.69, "duration": 1.2}, {"text": "Just kind of look.", "start": 2613.89, "duration": 1.38}, {"text": "And if anything cool happens,\nyou can kind of go, ooh, aah.", "start": 2615.27, "duration": 4.09}, {"text": "Or you can tell me\nwhat's happening.", "start": 2623.48, "duration": 1.68}, {"text": "Just watch.", "start": 2625.16, "duration": 0.75}, {"text": "Doesn't always\nhappen immediately.", "start": 2625.91, "duration": 1.59}, {"text": "Yeah, Kwylie, what's happening?", "start": 2627.5, "duration": 2.274}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2629.774, "duration": 1.386}, {"text": "NANCY KANWISHER: Sorry.", "start": 2631.16, "duration": 0.33}, {"text": "What's that?", "start": 2631.49, "duration": 0.5}, {"text": "AUDIENCE: Every time I blink,\nit changes from the house", "start": 2631.99, "duration": 2.38}, {"text": "to the face.", "start": 2634.37, "duration": 0.5}, {"text": "NANCY KANWISHER: Aha.", "start": 2634.87, "duration": 1.05}, {"text": "OK, it changes from the house\nto the face only when you blink.", "start": 2635.92, "duration": 2.73}, {"text": "Yeah, Kwylie?", "start": 2638.65, "duration": 0.615}, {"text": "AUDIENCE: So at first\nwhen I first put it on,", "start": 2639.265, "duration": 1.875}, {"text": "I was like I saw the house\nand the face superimposed.", "start": 2641.14, "duration": 3.87}, {"text": "And then you told\nus put one eye.", "start": 2645.01, "duration": 1.68}, {"text": "And then I opened both eyes,\nand it went from the house", "start": 2646.69, "duration": 3.255}, {"text": "to the face.", "start": 2649.945, "duration": 1.145}, {"text": "NANCY KANWISHER: Uh huh.", "start": 2651.09, "duration": 1.0}, {"text": "Uh huh.", "start": 2652.09, "duration": 0.57}, {"text": "And then did it stay there?", "start": 2652.66, "duration": 1.125}, {"text": "Or does it keep flipping?", "start": 2653.785, "duration": 2.295}, {"text": "OK, if this is not working\nfor you, don't panic.", "start": 2656.08, "duration": 2.16}, {"text": "There's nothing wrong with you.", "start": 2658.24, "duration": 1.292}, {"text": "It's hard to get everybody's\nred-green balance the same.", "start": 2659.532, "duration": 3.038}, {"text": "Yeah.", "start": 2662.57, "duration": 0.5}, {"text": "Sorry.", "start": 2663.07, "duration": 0.3}, {"text": "Question?", "start": 2663.37, "duration": 0.67}, {"text": "Shardul, yeah?", "start": 2664.04, "duration": 0.7}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2664.74, "duration": 2.65}, {"text": "NANCY KANWISHER: So I\nshare your intuition.", "start": 2667.39, "duration": 2.16}, {"text": "I think I can choose too.", "start": 2669.55, "duration": 1.32}, {"text": "But there's actually a\nwhole literature on that.", "start": 2670.87, "duration": 2.17}, {"text": "And the guy I was collaborating\nwith on this project,", "start": 2673.04, "duration": 2.72}, {"text": "20 years ago, insists\nthat, actually, that's", "start": 2675.76, "duration": 2.46}, {"text": "a wrong intuition.", "start": 2678.22, "duration": 0.85}, {"text": "You can't choose.", "start": 2679.07, "duration": 0.71}, {"text": "And I said, oh, the hell.", "start": 2679.78, "duration": 1.11}, {"text": "The hell I can't.", "start": 2680.89, "duration": 1.4}, {"text": "I'm in the scanner\nbeing your best subject", "start": 2682.29, "duration": 1.75}, {"text": "ever because I'm\nswitching exactly when you", "start": 2684.04, "duration": 1.77}, {"text": "want me to switch.", "start": 2685.81, "duration": 0.63}, {"text": "Don't tell me I can't switch.", "start": 2686.44, "duration": 0.96}, {"text": "He said, no, the\nliterature says you don't.", "start": 2687.4, "duration": 1.44}, {"text": "Anyway, I don't know\nthe latest on that.", "start": 2688.84, "duration": 1.92}, {"text": "Yeah?", "start": 2690.76, "duration": 0.77}, {"text": "AUDIENCE: Kind of related,\nit feels a lot harder", "start": 2691.53, "duration": 3.1}, {"text": "to see the house than the face.", "start": 2694.63, "duration": 1.363}, {"text": "NANCY KANWISHER: Yeah.", "start": 2695.993, "duration": 0.917}, {"text": "AUDIENCE: I can see the face\na lot easier than switching.", "start": 2696.91, "duration": 2.06}, {"text": "NANCY KANWISHER: Yes.", "start": 2698.97, "duration": 0.875}, {"text": "It's not optimally set up, so\nthat it's perfect for each.", "start": 2699.845, "duration": 3.305}, {"text": "Really the reason I do this\nis to amuse myself looking", "start": 2703.15, "duration": 2.73}, {"text": "at all of you with your--", "start": 2705.88, "duration": 3.15}, {"text": "thank you.", "start": 2709.03, "duration": 1.65}, {"text": "OK, so you can keep\nlooking or not,", "start": 2710.68, "duration": 1.582}, {"text": "but I'm going to tell\nyou what's going on here.", "start": 2712.262, "duration": 1.958}, {"text": "The cool thing\nabout this is when--", "start": 2714.22, "duration": 2.07}, {"text": "if it didn't switch\nfor you, the person--", "start": 2716.29, "duration": 1.94}, {"text": "is there anybody for\nwhom it didn't switch?", "start": 2718.23, "duration": 3.23}, {"text": "One.", "start": 2721.46, "duration": 0.5}, {"text": "OK, so maybe your color\nvision or who knows what.", "start": 2721.96, "duration": 3.19}, {"text": "But anyway.", "start": 2725.15, "duration": 1.49}, {"text": "OK, if it doesn't switch,\nthere's nothing wrong with you.", "start": 2726.64, "duration": 2.97}, {"text": "The percept everyone else has is\nit just flips every few seconds", "start": 2729.61, "duration": 3.48}, {"text": "from one to the other.", "start": 2733.09, "duration": 1.05}, {"text": "OK.", "start": 2734.14, "duration": 0.84}, {"text": "So what's cool about this\nis, when it switches,", "start": 2734.98, "duration": 3.15}, {"text": "nothing changes on your retina.", "start": 2738.13, "duration": 2.22}, {"text": "Only your state of\nawareness changes.", "start": 2740.35, "duration": 2.28}, {"text": "And that gives us\na wonderful lever", "start": 2742.63, "duration": 2.61}, {"text": "to study what goes on in the\nbrain when awareness switches,", "start": 2745.24, "duration": 3.51}, {"text": "unconfounded from the stimulus.", "start": 2748.75, "duration": 2.94}, {"text": "OK?", "start": 2751.69, "duration": 0.99}, {"text": "It's like varying attention,\nbut it's more powerful.", "start": 2752.68, "duration": 2.79}, {"text": "So of course, we put\npeople in the scanner.", "start": 2755.47, "duration": 3.33}, {"text": "We put mostly me\nand a few others.", "start": 2758.8, "duration": 1.81}, {"text": "But anyway.", "start": 2760.61, "duration": 0.56}, {"text": "We popped ourselves\nin the scanner.", "start": 2761.17, "duration": 1.86}, {"text": "We just taped these\nthings on our forehead,", "start": 2763.03, "duration": 1.98}, {"text": "nice low-tech experiment.", "start": 2765.01, "duration": 1.08}, {"text": "And we looked at\nthat exact stimulus.", "start": 2766.09, "duration": 1.89}, {"text": "OK?", "start": 2767.98, "duration": 1.05}, {"text": "And we scanned the\nbrain while people", "start": 2769.03, "duration": 2.64}, {"text": "sat there watching the\nstimulus flip back and forth.", "start": 2771.67, "duration": 3.63}, {"text": "OK?", "start": 2775.3, "duration": 0.66}, {"text": "So this is a stimulus\nfor the whole experiment.", "start": 2775.96, "duration": 2.67}, {"text": "This is the percept.", "start": 2778.63, "duration": 1.11}, {"text": "It switches back and forth.", "start": 2779.74, "duration": 1.392}, {"text": "The subject has a little\nbutton box, so they can say,", "start": 2781.132, "duration": 2.208}, {"text": "now I see the face.", "start": 2783.34, "duration": 0.99}, {"text": "Now I see the house.", "start": 2784.33, "duration": 1.6}, {"text": "Now, of course, the choice\nof a face and a house", "start": 2785.93, "duration": 2.0}, {"text": "was not random.", "start": 2787.93, "duration": 1.59}, {"text": "Why did we choose\na face and a house?", "start": 2789.52, "duration": 1.95}, {"text": "So that we could\nlook at the response", "start": 2791.47, "duration": 1.68}, {"text": "in the FFA and the PPA.", "start": 2793.15, "duration": 2.1}, {"text": "FFA loves faces, hates houses.", "start": 2795.25, "duration": 1.83}, {"text": "PPA loves houses, hates faces.", "start": 2797.08, "duration": 1.74}, {"text": "Perfect.", "start": 2798.82, "duration": 1.2}, {"text": "Right?", "start": 2800.02, "duration": 0.93}, {"text": "So the question\nis, are they going", "start": 2800.95, "duration": 1.59}, {"text": "to switch when your percept\nswitches, even though nothing's", "start": 2802.54, "duration": 2.91}, {"text": "changing on your retina?", "start": 2805.45, "duration": 1.59}, {"text": "What do you guys think?", "start": 2807.04, "duration": 1.62}, {"text": "Switch?", "start": 2808.66, "duration": 0.82}, {"text": "Switch?", "start": 2809.48, "duration": 0.5}, {"text": "How many people think\nit's going to switch?", "start": 2809.98, "duration": 2.16}, {"text": "How many people think\nit's not going to switch?", "start": 2812.14, "duration": 2.29}, {"text": "A few.", "start": 2814.43, "duration": 0.87}, {"text": "OK, all right, so\nthat's what we did.", "start": 2815.3, "duration": 3.12}, {"text": "Here is now the raw MRI time\ncourse averaged over the FFA", "start": 2818.42, "duration": 3.57}, {"text": "and averaged over the PPA for\none five-minute experiment", "start": 2821.99, "duration": 3.81}, {"text": "or three-minute\nexperiment in one subject.", "start": 2825.8, "duration": 1.83}, {"text": "Probably me.", "start": 2827.63, "duration": 0.54}, {"text": "I forget.", "start": 2828.17, "duration": 1.35}, {"text": "Again, stimulus is the\nsame the whole time.", "start": 2829.52, "duration": 1.86}, {"text": "The letters are the times when\nthe subject pressed the button.", "start": 2831.38, "duration": 3.96}, {"text": "And you can sort of get\na sense that there's", "start": 2835.34, "duration": 1.98}, {"text": "a little bit of maybe like\nhere's a phase the FFA", "start": 2837.32, "duration": 3.45}, {"text": "response goes up.", "start": 2840.77, "duration": 1.17}, {"text": "Here again the house goes up.", "start": 2841.94, "duration": 2.49}, {"text": "But it's kind of hard to tell.", "start": 2844.43, "duration": 1.71}, {"text": "So really, the way\nto analyze these data", "start": 2846.14, "duration": 2.28}, {"text": "is to take all the face\nto house flips, right,", "start": 2848.42, "duration": 4.83}, {"text": "and align them and signal\naverage to get rid of noise.", "start": 2853.25, "duration": 3.52}, {"text": "OK?", "start": 2856.77, "duration": 0.5}, {"text": "So we can look at, what happens\nbefore and after a switch", "start": 2857.27, "duration": 4.44}, {"text": "from face to house?", "start": 2861.71, "duration": 1.2}, {"text": "And what happens in the\nopposite direction switch?", "start": 2862.91, "duration": 2.19}, {"text": "Everybody get the idea?", "start": 2865.1, "duration": 1.48}, {"text": "It's just a way to\nclean up the noise here.", "start": 2866.58, "duration": 2.51}, {"text": "And here's what happens.", "start": 2869.09, "duration": 1.32}, {"text": "This is time zero.", "start": 2870.41, "duration": 1.09}, {"text": "The subject presses\na button saying", "start": 2871.5, "duration": 2.18}, {"text": "that their percept has flipped\nbetween a house to a face.", "start": 2873.68, "duration": 3.6}, {"text": "The response in\nthe FFA shoots up.", "start": 2877.28, "duration": 2.34}, {"text": "And the response in\nthe PPA shoots down.", "start": 2879.62, "duration": 3.735}, {"text": "Isn't that cool?", "start": 2883.355, "duration": 2.075}, {"text": "OK, now why are these peaks and\nvalleys after the button press?", "start": 2885.43, "duration": 5.43}, {"text": "Yeah.", "start": 2894.28, "duration": 0.5}, {"text": "Evan, right.", "start": 2894.78, "duration": 0.54}, {"text": "There's a delayed signal, right?", "start": 2895.32, "duration": 2.13}, {"text": "OK?", "start": 2897.45, "duration": 2.19}, {"text": "This is harder.", "start": 2899.64, "duration": 0.99}, {"text": "Why do they come back\ntogether out there?", "start": 2900.63, "duration": 2.25}, {"text": "Yeah, because it flips back.", "start": 2907.06, "duration": 1.77}, {"text": "It flips back.", "start": 2908.83, "duration": 1.47}, {"text": "And all we've done is signal\naverage to one button press.", "start": 2910.3, "duration": 2.97}, {"text": "But there are different\ndurations of percepts.", "start": 2913.27, "duration": 2.05}, {"text": "Sometimes it lasts\nthree seconds.", "start": 2915.32, "duration": 1.58}, {"text": "Sometimes it lasts 10 seconds,\neverything in between.", "start": 2916.9, "duration": 2.58}, {"text": "By the time you're\n12 seconds out,", "start": 2919.48, "duration": 1.77}, {"text": "most people have flipped again.", "start": 2921.25, "duration": 1.5}, {"text": "That's why it goes back.", "start": 2922.75, "duration": 1.8}, {"text": "OK, make sense?", "start": 2924.55, "duration": 0.885}, {"text": "Yeah?", "start": 2928.42, "duration": 0.817}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2929.237, "duration": 15.803}, {"text": "NANCY KANWISHER: I don't know.", "start": 2945.04, "duration": 1.25}, {"text": "And I'm not sure that\nthat was generally true.", "start": 2946.29, "duration": 2.76}, {"text": "I hadn't noticed that before.", "start": 2949.05, "duration": 1.62}, {"text": "But we should\nscrutinize the images.", "start": 2950.67, "duration": 2.16}, {"text": "I can't actually remember if\nthis was averaged over subjects", "start": 2952.83, "duration": 3.21}, {"text": "or if this is one subject.", "start": 2956.04, "duration": 1.11}, {"text": "I suspect that's a fluke.", "start": 2957.15, "duration": 1.38}, {"text": "But we could look at it and see.", "start": 2958.53, "duration": 3.11}, {"text": "OK, so the point of all of this\nis that these regions, the face", "start": 2961.64, "duration": 4.67}, {"text": "area and the place area,\ncare about what you", "start": 2966.31, "duration": 2.28}, {"text": "are experiencing,\nunconfounded from what's", "start": 2968.59, "duration": 2.7}, {"text": "hitting your retina, right?", "start": 2971.29, "duration": 1.83}, {"text": "They are reflecting the\ncontents of your awareness,", "start": 2973.12, "duration": 2.5}, {"text": "not just what's coming into\nyour eyes, which is cool.", "start": 2975.62, "duration": 5.75}, {"text": "OK, so that shows that\nthese regions kind", "start": 2981.37, "duration": 4.06}, {"text": "of track awareness.", "start": 2985.43, "duration": 2.28}, {"text": "OK?", "start": 2987.71, "duration": 0.96}, {"text": "But can we find any\nevidence for perception", "start": 2988.67, "duration": 3.66}, {"text": "without awareness\nusing neuroimaging?", "start": 2992.33, "duration": 3.3}, {"text": "OK?", "start": 2995.63, "duration": 0.93}, {"text": "So to make this point, I'm\ngoing to accelerate slightly,", "start": 2996.56, "duration": 2.67}, {"text": "but I think there's\njust barely time.", "start": 2999.23, "duration": 1.738}, {"text": "There are lots and lots\nof studies of this genre.", "start": 3000.968, "duration": 2.042}, {"text": "And I'll tell you about one.", "start": 3003.01, "duration": 1.74}, {"text": "So I'm going to show you.", "start": 3004.75, "duration": 1.05}, {"text": "I'm going to flash up a\nvery rapid series of digits.", "start": 3005.8, "duration": 2.31}, {"text": "You have to get ready\nto write stuff down.", "start": 3008.11, "duration": 2.49}, {"text": "Your task is to see if there\nare any letters in the digit.", "start": 3010.6, "duration": 5.01}, {"text": "There might be zero.", "start": 3015.61, "duration": 0.87}, {"text": "There might be one.", "start": 3016.48, "duration": 0.72}, {"text": "There might be a few.", "start": 3017.2, "duration": 0.72}, {"text": "Write down any letters you see.", "start": 3017.92, "duration": 1.41}, {"text": "It's going to go by really fast.", "start": 3019.33, "duration": 1.63}, {"text": "OK, everyone ready?", "start": 3020.96, "duration": 2.54}, {"text": "OK.", "start": 3023.5, "duration": 2.43}, {"text": "Here we go.", "start": 3025.93, "duration": 0.57}, {"text": "OK, write down any\nletters you may have seen.", "start": 3030.08, "duration": 3.24}, {"text": "OK?", "start": 3033.32, "duration": 1.86}, {"text": "All right, let's do another one.", "start": 3035.18, "duration": 2.46}, {"text": "Everyone ready?", "start": 3037.64, "duration": 0.75}, {"text": "OK, write down any\nletters you may have seen.", "start": 3043.63, "duration": 3.51}, {"text": "OK?", "start": 3047.14, "duration": 1.34}, {"text": "OK, raise your hand if you\nsaw both the A and the P", "start": 3048.48, "duration": 4.08}, {"text": "in the first sequence.", "start": 3052.56, "duration": 2.47}, {"text": "A few of you.", "start": 3055.03, "duration": 0.6}, {"text": "Less than half.", "start": 3055.63, "duration": 1.5}, {"text": "Raise your hand if you saw both\nthe X and the H in the second.", "start": 3057.13, "duration": 2.97}, {"text": "Almost everyone.", "start": 3060.1, "duration": 1.5}, {"text": "All right, well, I\ncheated slightly.", "start": 3061.6, "duration": 2.07}, {"text": "But never mind how I cheated.", "start": 3063.67, "duration": 1.98}, {"text": "The way you cheat in demos--", "start": 3065.65, "duration": 1.5}, {"text": "you guys will be\nteaching someday.", "start": 3067.15, "duration": 1.8}, {"text": "You have the one you want\npeople to get wrong first.", "start": 3068.95, "duration": 2.68}, {"text": "It's a total cheat.", "start": 3071.63, "duration": 0.98}, {"text": "So it's slightly cheated.", "start": 3072.61, "duration": 1.05}, {"text": "But if you do it right--", "start": 3073.66, "duration": 2.058}, {"text": "it didn't work last year.", "start": 3075.718, "duration": 1.042}, {"text": "That's why I cheated.", "start": 3076.76, "duration": 0.875}, {"text": "Anyway, even if you do\nit right in the lab,", "start": 3077.635, "duration": 1.875}, {"text": "you get a really strong effect.", "start": 3079.51, "duration": 3.03}, {"text": "There was only one\ndigit between the A", "start": 3082.54, "duration": 2.37}, {"text": "and the P in the first sequence.", "start": 3084.91, "duration": 2.04}, {"text": "And it's like your brain\nis still dealing with the A", "start": 3086.95, "duration": 2.67}, {"text": "when the P comes along.", "start": 3089.62, "duration": 1.363}, {"text": "You just don't even see the\nP. You're looking for letters.", "start": 3090.983, "duration": 2.417}, {"text": "You don't see it.", "start": 3093.4, "duration": 1.35}, {"text": "Whereas there were three\ndigits between the X", "start": 3094.75, "duration": 2.16}, {"text": "and the H in the\nsecond sequence.", "start": 3096.91, "duration": 2.46}, {"text": "And just to show\nyou some real data.", "start": 3099.37, "duration": 2.56}, {"text": "So this has been done\nlots of different ways.", "start": 3101.93, "duration": 2.1}, {"text": "Here's an example\nof this experiment.", "start": 3104.03, "duration": 2.06}, {"text": "And this is the time that people\nget the second letter when they", "start": 3106.09, "duration": 4.648}, {"text": "don't have to report the first.", "start": 3110.738, "duration": 1.292}, {"text": "Well, the first\none's colored, right?", "start": 3112.03, "duration": 1.32}, {"text": "So you either have to\nreport the colored letter", "start": 3113.35, "duration": 2.13}, {"text": "and detect the letter\nafter it or just", "start": 3115.48, "duration": 1.95}, {"text": "detect the letter after\nthe colored thing.", "start": 3117.43, "duration": 2.56}, {"text": "So if you don't have to\nreport the first one,", "start": 3119.99, "duration": 2.13}, {"text": "there's no dip in accuracy.", "start": 3122.12, "duration": 1.41}, {"text": "Oh, sorry.", "start": 3123.53, "duration": 0.5}, {"text": "This is a function of the\ndistance between the two", "start": 3124.03, "duration": 2.31}, {"text": "items in the sequence.", "start": 3126.34, "duration": 1.66}, {"text": "But if you do,\nthere's a big dip.", "start": 3128.0, "duration": 2.57}, {"text": "That's maximal with\none intervening item.", "start": 3130.57, "duration": 3.24}, {"text": "Yeah?", "start": 3133.81, "duration": 1.66}, {"text": "OK, well, here it\nsays two or three.", "start": 3135.47, "duration": 4.5}, {"text": "But anyway.", "start": 3139.97, "duration": 2.4}, {"text": "OK, so that's called\nthe attentional blink.", "start": 3142.37, "duration": 2.155}, {"text": "And the idea is there isn't\na physical blink of the eyes.", "start": 3144.525, "duration": 2.375}, {"text": "But your attention\nsystem is tied up", "start": 3146.9, "duration": 1.893}, {"text": "processing the first target.", "start": 3148.793, "duration": 1.167}, {"text": "And it doesn't get\nthe second one, OK?", "start": 3149.96, "duration": 2.34}, {"text": "So there are dozens,\nprobably hundreds", "start": 3152.3, "duration": 2.032}, {"text": "of papers on this phenomenon.", "start": 3154.332, "duration": 1.208}, {"text": "It's pretty cool.", "start": 3155.54, "duration": 1.65}, {"text": "But for present purposes,\nwe're going to use it to say,", "start": 3157.19, "duration": 4.26}, {"text": "does that unseen second\ntarget get into the brain?", "start": 3161.45, "duration": 3.72}, {"text": "Presumably, it\nlands on the retina", "start": 3165.17, "duration": 1.44}, {"text": "because you didn't blink.", "start": 3166.61, "duration": 1.198}, {"text": "So it could probably get there.", "start": 3167.808, "duration": 1.292}, {"text": "Probably got to V1.", "start": 3169.1, "duration": 1.11}, {"text": "How far up the\nsystem did it get?", "start": 3170.21, "duration": 3.72}, {"text": "Can you think of how we might\ntest this using functional MRI.", "start": 3173.93, "duration": 4.2}, {"text": "How would we see how\nfar those stimuli", "start": 3178.13, "duration": 3.96}, {"text": "go in an experiment like this?", "start": 3182.09, "duration": 1.8}, {"text": "What would we use?", "start": 3187.75, "duration": 0.75}, {"text": "What would we measure\nthe MRI response to?", "start": 3188.5, "duration": 3.27}, {"text": "How could we design\na version of this", "start": 3191.77, "duration": 1.657}, {"text": "that you could do\nwith functional MRI?", "start": 3193.427, "duration": 1.583}, {"text": "We need some MRI response,\nwhere, if we get that response,", "start": 3199.69, "duration": 4.35}, {"text": "we know that it's a response\nto a given stimulus.", "start": 3204.04, "duration": 2.415}, {"text": "What would we measure?", "start": 3209.56, "duration": 2.43}, {"text": "And what stimuli would we use?", "start": 3211.99, "duration": 1.26}, {"text": "AUDIENCE: Well, we could\nuse faces or something.", "start": 3215.83, "duration": 2.123}, {"text": "NANCY KANWISHER: Yeah.", "start": 3217.953, "duration": 0.917}, {"text": "It's always the same.", "start": 3218.87, "duration": 1.05}, {"text": "Yeah.", "start": 3219.92, "duration": 0.54}, {"text": "Faces and houses.", "start": 3220.46, "duration": 1.47}, {"text": "Lots of ways to do this.", "start": 3221.93, "duration": 1.26}, {"text": "But it's not even my experiment,\nand they used faces and houses.", "start": 3223.19, "duration": 3.797}, {"text": "OK, so they did a version\nof that very same thing.", "start": 3226.987, "duration": 2.083}, {"text": "This is a bunch of\ngarbage flashing on.", "start": 3229.07, "duration": 2.16}, {"text": "Early on, there's a face.", "start": 3231.23, "duration": 1.24}, {"text": "The subjects have to\nsay which of those three", "start": 3232.47, "duration": 1.875}, {"text": "faces they've studied it is.", "start": 3234.345, "duration": 1.575}, {"text": "And then after that,\na scene comes on,", "start": 3235.92, "duration": 2.6}, {"text": "or it doesn't come on.", "start": 3238.52, "duration": 1.77}, {"text": "OK, they have to just\nsay, was there a scene?", "start": 3240.29, "duration": 2.82}, {"text": "First of all, which face was it?", "start": 3243.11, "duration": 1.68}, {"text": "And was there a\nscene afterwards?", "start": 3244.79, "duration": 2.56}, {"text": "OK, so it's a variant of\nthe thing you just did.", "start": 3247.35, "duration": 2.65}, {"text": "So here's the behavioral data.", "start": 3250.0, "duration": 2.81}, {"text": "If you don't have\nto report the face,", "start": 3252.81, "duration": 1.95}, {"text": "then you are very accurate\nreporting the scene.", "start": 3254.76, "duration": 2.82}, {"text": "If you do have to\nreport the face,", "start": 3257.58, "duration": 1.8}, {"text": "then you're very bad at it if\nthe scene comes right after.", "start": 3259.38, "duration": 3.6}, {"text": "But if there's a big\ninterval in between,", "start": 3262.98, "duration": 1.71}, {"text": "you do OK with the scene.", "start": 3264.69, "duration": 1.05}, {"text": "Same thing we saw before but\nnow with faces and scenes.", "start": 3265.74, "duration": 2.52}, {"text": "OK, that's the behavioral data.", "start": 3268.26, "duration": 2.13}, {"text": "What do you see\nin the PPA, right?", "start": 3270.39, "duration": 2.31}, {"text": "The second target\nis always a scene.", "start": 3272.7, "duration": 2.22}, {"text": "So what you see\nin the PPA, here's", "start": 3274.92, "duration": 2.58}, {"text": "a response in the PPA to that\nsecond scene if it's a hit.", "start": 3277.5, "duration": 4.59}, {"text": "That is if you detect it, right?", "start": 3282.09, "duration": 1.59}, {"text": "You correctly say, yes, there\nwas a scene in that trial.", "start": 3283.68, "duration": 2.82}, {"text": "Here's a response\nwith a correct reject.", "start": 3286.5, "duration": 1.99}, {"text": "There was no scene\nin that trial.", "start": 3288.49, "duration": 1.46}, {"text": "And you correctly\nsaid there was not.", "start": 3289.95, "duration": 2.34}, {"text": "OK, so that difference\nshows you the response", "start": 3292.29, "duration": 2.82}, {"text": "in the PPA to a scene\nthat you've seen,", "start": 3295.11, "duration": 3.21}, {"text": "that you detected consciously.", "start": 3298.32, "duration": 2.04}, {"text": "But here's a critical case.", "start": 3300.36, "duration": 2.542}, {"text": "I don't know why there's\na little pop up there.", "start": 3302.902, "duration": 1.958}, {"text": "Anyway, this is a case\nwhere there was a scene,", "start": 3304.86, "duration": 3.39}, {"text": "but you've said there wasn't.", "start": 3308.25, "duration": 2.12}, {"text": "OK?", "start": 3310.37, "duration": 0.5}, {"text": "That's called a miss.", "start": 3310.87, "duration": 0.875}, {"text": "You missed it.", "start": 3311.745, "duration": 0.625}, {"text": "It was there, and\nyou didn't see it.", "start": 3312.37, "duration": 2.34}, {"text": "And what it shows you\nis two cool things.", "start": 3314.71, "duration": 3.12}, {"text": "Well, first of all, it tells\nyou that the more aware you", "start": 3317.83, "duration": 3.66}, {"text": "are of the stimulus,\nthe stronger response.", "start": 3321.49, "duration": 2.52}, {"text": "But the crucial\nthing it shows you", "start": 3324.01, "duration": 3.11}, {"text": "is this difference right\nhere, which is significant.", "start": 3327.12, "duration": 2.76}, {"text": "This is a kind of perception\nwithout awareness.", "start": 3329.88, "duration": 3.15}, {"text": "You did not detect the scene.", "start": 3333.03, "duration": 1.62}, {"text": "You said there was no scene.", "start": 3334.65, "duration": 1.35}, {"text": "But your PPA detected\nthe difference.", "start": 3336.0, "duration": 2.85}, {"text": "Everybody get that?", "start": 3338.85, "duration": 2.08}, {"text": "So we have evidence\nfor perception", "start": 3340.93, "duration": 1.97}, {"text": "by the PPA at least of a\nscene without awareness.", "start": 3342.9, "duration": 4.26}, {"text": "That make sense?", "start": 3347.16, "duration": 1.57}, {"text": "So there are many, many\nstudies like this that kind of", "start": 3348.73, "duration": 2.92}, {"text": "take it every which way.", "start": 3351.65, "duration": 1.0}, {"text": "This is just one\nlittle example of how", "start": 3352.65, "duration": 1.98}, {"text": "you can use neuroimaging to\nask, how far up the system", "start": 3354.63, "duration": 3.57}, {"text": "does an unseen stimulus get?", "start": 3358.2, "duration": 2.91}, {"text": "Make sense?", "start": 3361.11, "duration": 2.32}, {"text": "OK, so we are about out of time.", "start": 3363.43, "duration": 2.37}, {"text": "And I just gave\nyou a little taste", "start": 3365.8, "duration": 2.07}, {"text": "of some of the work on neural\ncorrelates of awareness,", "start": 3367.87, "duration": 2.52}, {"text": "showed you, with binocular\nrivalry, a neural response", "start": 3370.39, "duration": 3.57}, {"text": "that's correlated with awareness\nunconfounded from the stimulus,", "start": 3373.96, "duration": 3.45}, {"text": "uncoupling, again, perceptual\nawareness from what's", "start": 3377.41, "duration": 2.61}, {"text": "hitting your retina, and, in the\ncase of the attentional blink,", "start": 3380.02, "duration": 3.63}, {"text": "some evidence for\nperceptual representation", "start": 3383.65, "duration": 3.6}, {"text": "without awareness.", "start": 3387.25, "duration": 1.9}, {"text": "OK?", "start": 3389.15, "duration": 1.55}]
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+[{"text": "The following content is provided under a\nCreative Commons license. Your support will", "start": 0.94, "duration": 4.37}, {"text": "help MIT OpenCourseWare continue to offer\nhigh-quality educational resources for free.", "start": 5.31, "duration": 5.59}, {"text": "To make a donation or to view additional materials\nfrom hundreds of MIT courses, visit MIT OpenCourseWare", "start": 10.9, "duration": 7.54}, {"text": "at ocw.mit.edu.", "start": 18.44, "duration": 1.75}, {"text": "TADGE DRYJA: OK, so today I'll talk about\nCoinJoin, signature aggregation, well before", "start": 20.19, "duration": 7.76}, {"text": "that privacy, but privacy, CoinJoin, CoinShuffle,\nsignature aggregation, and how these all connect.", "start": 27.95, "duration": 5.699}, {"text": "It's a little bit of a leap to put these both\nin the same class, but not really. They're", "start": 33.649, "duration": 4.631}, {"text": "connected. But they are somewhat separate\nthings. Today, I'll talk about privacy, CoinJoin,", "start": 38.28, "duration": 6.809}, {"text": "and various ways to do that, and then aggregate\nsignatures, so Schnorr multi-signatures, and", "start": 45.089, "duration": 5.81}, {"text": "then aggregation, and attacks on the system.", "start": 50.899, "duration": 3.8}, {"text": "OK, so the idea is privacy. And there's a\nbunch of terms we can use here, like anonymity", "start": 54.699, "duration": 7.901}, {"text": "and fungibility. And whatever the term for\nthis, I don't need any, because I have nothing", "start": 62.6, "duration": 5.11}, {"text": "to hide.", "start": 67.71, "duration": 1.01}, {"text": "So I don't need any privacy. I don't need\nany anonymity. I'm a good person. I don't", "start": 68.72, "duration": 4.069}, {"text": "break the law. I'm a boring guy. I don't do\nanything crazy.", "start": 72.789, "duration": 3.791}, {"text": "I'm joking, but-- no, I'm not joking about\nbeing boring and not doing anything crazy.", "start": 76.58, "duration": 6.06}, {"text": "That is actually pretty true. I mostly just\nwork on this stuff.", "start": 82.64, "duration": 4.43}, {"text": "But, yeah, that's a fairly common thing that\npeople say. And the sort of clearest example", "start": 87.07, "duration": 9.14}, {"text": "is if you don't have anything to hide, you\ndon't have any bitcoin, because literally,", "start": 96.21, "duration": 4.46}, {"text": "if you don't hide your private key, someone\nwill just immediately take your bitcoin. So", "start": 100.67, "duration": 4.88}, {"text": "you do have secrets.", "start": 105.55, "duration": 2.48}, {"text": "Your secret is your private key and your password.\nAnd if bitcoin and these types of systems", "start": 108.03, "duration": 6.03}, {"text": "really take off, potentially most of your\nmoney and a lot of your wealth could be tied", "start": 114.06, "duration": 5.36}, {"text": "up in what is a secret. So if you're not able\nto keep your secrets you could lose a lot", "start": 119.42, "duration": 5.741}, {"text": "of money. And larger, I sort of think that\ngoing forward-- this is very thought leader,", "start": 125.161, "duration": 7.158}, {"text": "future kind of thing.", "start": 132.319, "duration": 1.451}, {"text": "But going forward, it seems like sort of all\nyou have is your secrets. To the extent that", "start": 133.77, "duration": 5.96}, {"text": "you can own anything, the thing that you really\nhave control of, you're like, OK, I got these", "start": 139.73, "duration": 3.78}, {"text": "things in my head that no one else knows.\nAnd maybe I own my car. But that's also sort", "start": 143.51, "duration": 6.48}, {"text": "of property rights, and legal systems, and\nmaybe you can get repossessed.", "start": 149.99, "duration": 3.51}, {"text": "Maybe I own this land. But, again, that's\nsort of this thing with the state. But I definitely", "start": 153.5, "duration": 4.5}, {"text": "really have the stuff in my head. And I can\nat least try to keep that.", "start": 158.0, "duration": 6.39}, {"text": "So even if you think you have nothing to hide,\nyou do have your private keys to hide. And", "start": 164.39, "duration": 5.02}, {"text": "that's sort of the obvious one. But larger,\nyou want privacy because, in general, you", "start": 169.41, "duration": 7.07}, {"text": "don't want to reveal stuff about your coins.\nThis is specific to bitcoin.", "start": 176.48, "duration": 3.93}, {"text": "But my philosophy is I generally don't want\nto reveal stuff ever. And it's a lot of times", "start": 180.41, "duration": 6.35}, {"text": "at stores. I remember like Radio Shack, when\nit was still a thing when I was in high school,", "start": 186.76, "duration": 5.08}, {"text": "they would always ask you your phone number\nwhen you bought anything. And when I was little,", "start": 191.84, "duration": 3.94}, {"text": "I would just tell them my parents phone number\nat my house, because they asked.", "start": 195.78, "duration": 4.24}, {"text": "But then once I was in college, I was like,\nwait, no I'm just going to make something", "start": 200.02, "duration": 2.91}, {"text": "up. And now I do that all the time. And it\nsometimes gets annoying for other people,", "start": 202.93, "duration": 6.13}, {"text": "because I would like go to a restaurant. They\nask to put my name down. I'll say I'm Fred.", "start": 209.06, "duration": 4.98}, {"text": "And then my other friend comes. And she was\nlike, wait, you're not listed. And then she", "start": 214.04, "duration": 4.98}, {"text": "put her name in. I'm like, no, I'm already\nthere. I'm Fred, and confusing things like", "start": 219.02, "duration": 6.87}, {"text": "that.", "start": 225.89, "duration": 1.0}, {"text": "And I hope, and I sort of think that we're\nstarting to see this kind of thing. Like,", "start": 226.89, "duration": 8.79}, {"text": "there's like Facebook hearings now. And people\nare all shocked that the company Facebook", "start": 235.68, "duration": 3.83}, {"text": "can read everyone's messages and see everything.\nWell, yeah, that's how it works. You're giving", "start": 239.51, "duration": 4.61}, {"text": "it all to their servers.", "start": 244.12, "duration": 3.33}, {"text": "So I think it's starting to be, like where\nbefore companies would all be like, we just", "start": 247.45, "duration": 3.74}, {"text": "want to get all the user data possible, hopefully\ngoing forward data will be seen more as a", "start": 251.19, "duration": 3.879}, {"text": "liability and less as an asset. We're not\nthere yet, because the companies who get sort", "start": 255.069, "duration": 6.401}, {"text": "of hacked and lose all this user data don't\nreally get punished. So the Equifax thing,", "start": 261.47, "duration": 6.35}, {"text": "and all these different data breaches, there's\nnot a ton of consequences yet.", "start": 267.82, "duration": 3.87}, {"text": "Maybe there will be in the future. And maybe\ncompanies will start to not want all this", "start": 271.69, "duration": 3.15}, {"text": "data. But it's not as clean cut as, well,\nI didn't do anything wrong, so I don't want", "start": 274.84, "duration": 7.91}, {"text": "to hide anything.", "start": 282.75, "duration": 1.0}, {"text": "Sort of default hide is my stance. And there's\nso many conflicting interests where every", "start": 283.75, "duration": 5.69}, {"text": "time you're on the websites, it's like, this\nwebsite wants your location. And you're like,", "start": 289.44, "duration": 3.87}, {"text": "wait, how do I always disable that? I don't\nknow the settings. But everyone wants this", "start": 293.31, "duration": 6.26}, {"text": "stuff.", "start": 299.57, "duration": 1.0}, {"text": "So another reason, specifically in the case\nof money, is what's called fungibility. And", "start": 300.57, "duration": 7.46}, {"text": "it sounds like a weird word. It just means\nthat every bitcoin is the same, or every dollar", "start": 308.03, "duration": 4.85}, {"text": "is the same.", "start": 312.88, "duration": 1.34}, {"text": "So dollars are fungible, in that, physically,\nthis $20 bill and this $20 bill are worth", "start": 314.22, "duration": 6.78}, {"text": "the same. And different denominations, so\nI will give you a 20 for two 10's. And anyone", "start": 321.0, "duration": 6.12}, {"text": "will do that. They're worth the same.", "start": 327.12, "duration": 2.25}, {"text": "You don't have, well, this dollar is not worth\nquite as much. And sometimes that happens,", "start": 329.37, "duration": 5.7}, {"text": "even with dollar bills. Like in other countries,\nI think in the Philippines when the new $100", "start": 335.07, "duration": 6.15}, {"text": "bills were issued that have the like little\nblue shiny thing, people didn't like them.", "start": 341.22, "duration": 4.449}, {"text": "And people were like, no, I won't trade my\nold $100 bill for your new $100 bill. I don't", "start": 345.669, "duration": 4.091}, {"text": "trust this new one. Eventually, they got used\nto it.", "start": 349.76, "duration": 2.78}, {"text": "But there's things, that even money can be\nnot fungible. So the classic example is, OK,", "start": 352.54, "duration": 4.94}, {"text": "gold is fungible. Diamonds are not. Diamonds,\nI have little experience with diamonds they", "start": 357.48, "duration": 5.67}, {"text": "seem kind of silly, but they're all unique.", "start": 363.15, "duration": 3.81}, {"text": "They've got different grades, and different\ncuts, and different sizes, and carrots, and", "start": 366.96, "duration": 3.53}, {"text": "little inclusions, and imperfections. And\nyou've got this whole industry, where people", "start": 370.49, "duration": 5.31}, {"text": "with these little eye things look at the diamonds,\nand figure out, oh, this is a good one. And", "start": 375.8, "duration": 3.99}, {"text": "this one is so, so.", "start": 379.79, "duration": 1.689}, {"text": "Whereas gold is, sort of also has essayists,\nand good delivery standards, and all these", "start": 381.479, "duration": 5.801}, {"text": "things for the gold bars. But it's much more\nof a standard. There's no judgment calls.", "start": 387.28, "duration": 4.139}, {"text": "It's like, OK, this is gold. It's 99.95% pure.\nIt weighs this much. This is how much it's", "start": 391.419, "duration": 5.601}, {"text": "worth. And you can chop gold up and-- sorry,\ndivisibility is different than fungibility.", "start": 397.02, "duration": 6.56}, {"text": "So if diamonds were all identical but not\ndivisible, they could still maybe function", "start": 403.58, "duration": 5.1}, {"text": "as money. You would just need a lot of little\ndiamonds. But the fact that gold is also divisible", "start": 408.68, "duration": 5.75}, {"text": "is really is a bonus. But the fungibility\nis really what's nice about it, and what makes", "start": 414.43, "duration": 3.66}, {"text": "it sort of used as money.", "start": 418.09, "duration": 3.59}, {"text": "Currency's fungibility is actually-- I'm not\na lawyer, but I hang out with them. It's enforced", "start": 421.68, "duration": 7.79}, {"text": "by the law itself. So there's an interesting\ncase, Crawford v. The Royal Bank, in Scotland", "start": 429.47, "duration": 6.14}, {"text": "a couple hundred years ago, where there was\na guy.", "start": 435.61, "duration": 3.4}, {"text": "And he wrote his name on a 20 pound note.\nIt's like Crawford. This is his money. And", "start": 439.01, "duration": 5.249}, {"text": "I think he was trying to mail it someone.\nHe lost it.", "start": 444.259, "duration": 3.751}, {"text": "Years later, the note shows up at a bank.\nAnd he's like, no, see that was my money.", "start": 448.01, "duration": 3.749}, {"text": "I lost it. And he demands the money back.", "start": 451.759, "duration": 3.351}, {"text": "I lost that money. This is my property. Give\nit back. It's got my name on it. I can prove", "start": 455.11, "duration": 4.279}, {"text": "it.", "start": 459.389, "duration": 1.06}, {"text": "And then the court says no, no, no, that's\nnot how money works. The bank has the money.", "start": 460.449, "duration": 4.101}, {"text": "You can't just write your name on money and\nthen have it be yours.", "start": 464.55, "duration": 6.71}, {"text": "And this is very different from property.\nSo if you steal a bicycle, and then you go", "start": 471.26, "duration": 6.379}, {"text": "go sell it on-- sorry, if someone steals a\nbicycle, sells it on Craigslist, and you buy", "start": 477.639, "duration": 5.221}, {"text": "it, and you didn't know, it was just, whatever,\nsome guy's selling a bike on Craigslist. The", "start": 482.86, "duration": 3.97}, {"text": "police show up, and say, hey, that bicycle\nwas stolen. We're taking it back.", "start": 486.83, "duration": 2.8}, {"text": "And you're like, well, I didn't know. I just\nbought it on Craigslist. I paid a couple hundred", "start": 489.63, "duration": 4.73}, {"text": "bucks. Police are like, sorry, you're not\nin trouble. We're not going to charge you", "start": 494.36, "duration": 3.621}, {"text": "with a crime.", "start": 497.981, "duration": 1.0}, {"text": "But these are stolen goods. We're taking them\nback, giving it to the rightful owner. And", "start": 498.981, "duration": 4.619}, {"text": "that's how the law works. You can try to complain\nabout it, but they're taking it.", "start": 503.6, "duration": 4.56}, {"text": "Money is different. If you're running a pizza\nstore, someone comes in, gives you a 20, and", "start": 508.16, "duration": 5.189}, {"text": "buys a pizza, and then presumably eats it\nor whatever, and then a couple hours later", "start": 513.349, "duration": 4.771}, {"text": "the police come in and say, hey, that guy\nstole that $20 bill. And we're taking it back,", "start": 518.12, "duration": 5.589}, {"text": "and giving it to its rightful owner.", "start": 523.709, "duration": 1.521}, {"text": "As the shopkeeper, you're like, I don't even\nknow which $20 bill. Even though there are", "start": 525.23, "duration": 4.61}, {"text": "serial numbers, and the police could say,\nit was this $20 bill. We're taking it back,", "start": 529.84, "duration": 3.98}, {"text": "or returning it to the person he stole it\nfrom, legally they can't do that.", "start": 533.82, "duration": 8.93}, {"text": "So this is from talking to lawyer people.\nSo money's different. Money is not property,", "start": 542.75, "duration": 4.73}, {"text": "in the same sense. And the fungibility is\nenforced by the state.", "start": 547.48, "duration": 4.71}, {"text": "And the divisibility and fungibility are enforced\nby the banks. The US dollar isn't worth anything.", "start": 552.19, "duration": 9.21}, {"text": "The government and the banks don't have to\ngive you anything for $1.", "start": 561.4, "duration": 3.91}, {"text": "They used to sort of have this agreement,\nwhere, OK you give us $35. And we'll give", "start": 565.31, "duration": 4.78}, {"text": "you an ounce of gold. That agreement is longer\nis in place. But they do have to give you", "start": 570.09, "duration": 5.41}, {"text": "a change.", "start": 575.5, "duration": 1.08}, {"text": "So they do have a duty where if you have a\nbunch of old, beatup $20 bills, the bank sort", "start": 576.58, "duration": 4.9}, {"text": "of does have to honor those and give you new\n$20 bills. And that's one of the things that", "start": 581.48, "duration": 4.01}, {"text": "the Bureau of Engraving and Printing, and\nthe Fed, they all have this system. So they", "start": 585.49, "duration": 3.81}, {"text": "maintain the currency, in that sense.", "start": 589.3, "duration": 3.75}, {"text": "So there's all these things that like you\ndon't really think about in that how money", "start": 593.05, "duration": 3.68}, {"text": "operates. But fungibility, divisibility, those\nare really important. And most of it is enforced", "start": 596.73, "duration": 5.07}, {"text": "by the legal system.", "start": 601.8, "duration": 2.05}, {"text": "Bitcoin does not have these legal protections.\nIf want bitcoin to work, even where it's not", "start": 603.85, "duration": 6.13}, {"text": "legally recognized as being money, and our\ngoal is to make it like money. So if they're", "start": 609.98, "duration": 7.491}, {"text": "stolen bitcoins, and you can trace them, the\nlaw enforcement can say, no, those bitcoins", "start": 617.471, "duration": 5.129}, {"text": "are stolen. We're recovering them.", "start": 622.6, "duration": 3.04}, {"text": "So it's not treated as a currency. It's also\nnot controlled as fungible. So in the absence", "start": 625.64, "duration": 8.1}, {"text": "of these sort of protections from the legal\nsystem, the software needs to help enforce", "start": 633.74, "duration": 4.97}, {"text": "the fungibility and divisibility of these\nthings. So you can sort of treat the bitcoin", "start": 638.71, "duration": 5.48}, {"text": "software and ruleset as sort of a legal--\nit's not a legal system.", "start": 644.19, "duration": 4.31}, {"text": "But it's a system of rules that governs how\nthe bitcoin transactions work. And so the", "start": 648.5, "duration": 4.86}, {"text": "fungibility has got to be in the system. Right\nSo gold, for example, they don't have-- I", "start": 653.36, "duration": 5.67}, {"text": "don't want to say they don't have rules about\ngold. There's probably all sorts of old laws", "start": 659.03, "duration": 3.53}, {"text": "about gold.", "start": 662.56, "duration": 1.02}, {"text": "But you don't really need a law enforcing\nthe fungibility of gold, in that you can sort", "start": 663.58, "duration": 6.53}, {"text": "of melt it down, and it's untraceable. If\nyou have this old gold coin from this empire,", "start": 670.11, "duration": 4.82}, {"text": "and this other gold coin from this empire,\nyou melt the gold, you put it into a new coin,", "start": 674.93, "duration": 4.9}, {"text": "no one can tell. So, similarly, bitcoin needs\nto enforce fungibility that way.", "start": 679.83, "duration": 6.23}, {"text": "OK, so any questions so far about these definitions\nor objections? I don't think bitcoin should", "start": 686.06, "duration": 5.61}, {"text": "be fungible.", "start": 691.67, "duration": 1.21}, {"text": "AUDIENCE: So bitcoin is more like gold than\ndiamonds. But, in a sense, right after your", "start": 692.88, "duration": 11.84}, {"text": "transaction happens, the probability that\nit-- say it's only one block deep. I don't", "start": 704.72, "duration": 5.38}, {"text": "think it's actually treated this way.", "start": 710.1, "duration": 2.47}, {"text": "But someone could potentially, oh, I'll just\nconsider that 90% of one bitcoin, because", "start": 712.57, "duration": 8.543}, {"text": "the probability or whatever--", "start": 721.113, "duration": 1.437}, {"text": "TADGE DRYJA: They're not valued the same,\nbecause they haven't been fully confirmed.", "start": 722.55, "duration": 4.26}, {"text": "Yeah, that's an interesting way to look at\nit. I'm not talking about sort of the time-based", "start": 726.81, "duration": 5.22}, {"text": "things here, because I guess in many cases\nyou say, OK, I'm going to wait a day.", "start": 732.03, "duration": 4.99}, {"text": "If it's got 100 confirmations, it's good.\nI'll consider it full value. But, yeah, there", "start": 737.02, "duration": 4.101}, {"text": "could be things where you look at the probability\nof a double spend, and then sort of assign", "start": 741.121, "duration": 4.679}, {"text": "value to it, increasing as time passes or\nsomething. That's sort of a unique thing to", "start": 745.8, "duration": 6.23}, {"text": "bitcoin, where the sort of finality of the\ntransfer increases with time, which is not", "start": 752.03, "duration": 5.499}, {"text": "really the case with gold or dollars, where\nyou're like, oh, I got it.", "start": 757.529, "duration": 3.511}, {"text": "The fact that I've had it for one minute or\n10 minutes doesn't really change that I've", "start": 761.04, "duration": 5.01}, {"text": "got it. So that's an interesting point. I'm\nnot really addressing it here.", "start": 766.05, "duration": 5.87}, {"text": "In this conversation, just assume you wait\na day. And then all the probability of it", "start": 771.92, "duration": 4.44}, {"text": "going back is sort of negligible. But it's\nmore the fungibility in that you can trace", "start": 776.36, "duration": 6.33}, {"text": "where it came from, and so assign values to\ndifferent coins based on that.", "start": 782.69, "duration": 7.9}, {"text": "So there's a real world example of this. I\ndon't want to name specific names. But customer", "start": 790.59, "duration": 4.72}, {"text": "buys some coins. You go to exchange. You send\nthem a couple hundred bucks.", "start": 795.31, "duration": 3.54}, {"text": "You say, I want to buy some bitcoins. And\nthe customer buys the bitcoins, and then transfers", "start": 798.85, "duration": 4.59}, {"text": "the coins to a betting shop, a betting company\nin the UK, and bets on a soccer game, for", "start": 803.44, "duration": 5.91}, {"text": "example. And he wins.", "start": 809.35, "duration": 1.58}, {"text": "Great, so he bought a coin, sent it over to\nthis UK gambling company, bet on a soccer", "start": 810.93, "duration": 6.33}, {"text": "game, or football I guess they call it, wins.\nNow, he has two coins. Transfers those two", "start": 817.26, "duration": 6.06}, {"text": "coins back to the US exchange.", "start": 823.32, "duration": 3.069}, {"text": "And he wants to sell them. Before he can click\nsell, his account is closed. And the exchange", "start": 826.389, "duration": 4.741}, {"text": "website says, no, you violated our terms of\nservice. We're closing your account.", "start": 831.13, "duration": 3.889}, {"text": "Take your bitcoins. We've sent all your dollars\nback to your bank. Withdraw your bitcoins.", "start": 835.019, "duration": 7.301}, {"text": "We're out.", "start": 842.32, "duration": 2.4}, {"text": "This happens. So whether you agree with gambling\nbeing legal-- so in the UK, however, there's", "start": 844.72, "duration": 9.94}, {"text": "no law violated. And as a United States--\nso this is sort of the gray area. I'm pretty", "start": 854.66, "duration": 5.39}, {"text": "sure that if I'm a US citizen, I take a plane\nover to London, I go to a-- I don't know the", "start": 860.05, "duration": 6.779}, {"text": "lingo, punters shop, betting shop? And then\nI bet on something, and I win.", "start": 866.829, "duration": 6.431}, {"text": "Well, I'm pretty sure I have to pay capital\ngains on those winnings to the US, IRS. But", "start": 873.26, "duration": 5.81}, {"text": "I haven't broken a law, because I'm not in\nthe US when I'm doing this thing. So, similarly,", "start": 879.07, "duration": 5.949}, {"text": "if casino gambling is illegal in Massachusetts,\nsort of, I can go to Las Vegas. I can gamble.", "start": 885.019, "duration": 4.711}, {"text": "And I can come back to Massachusetts, and\nit's OK.", "start": 889.73, "duration": 4.47}, {"text": "So this is probably a gray area. I don't know\nif there's actual court cases about this,", "start": 894.2, "duration": 4.41}, {"text": "where you're still sitting in Massachusetts\nat your computer. But you've sent your money", "start": 898.61, "duration": 4.1}, {"text": "to the United Kingdom. I don't know. I don't\nknow of anyone who's gotten in trouble for", "start": 902.71, "duration": 7.629}, {"text": "this.", "start": 910.339, "duration": 1.0}, {"text": "I don't know if there's been prosecution against\nUK betting shops for this kind of thing. But", "start": 911.339, "duration": 4.381}, {"text": "this happens. A lot of companies run betting\nshops like this.", "start": 915.72, "duration": 5.46}, {"text": "But I have seen that US exchanges will shut\ndown accounts because of this. And they say,", "start": 921.18, "duration": 3.62}, {"text": "look, you can buy bitcoins. But if you're\nusing these to gamble, we don't want to get", "start": 924.8, "duration": 4.15}, {"text": "involved. It's just more risk for us.", "start": 928.95, "duration": 3.35}, {"text": "And so they close the accounts. So the problem\nhere is-- what did I say next? From the perspective", "start": 932.3, "duration": 7.089}, {"text": "of the legal system, for the user it's obviously\na problem, because it's annoying.", "start": 939.389, "duration": 4.151}, {"text": "What's the problem for bitcoin here? Why should\nbitcoin care about this, like as people working", "start": 943.54, "duration": 5.54}, {"text": "on bitcoin? Why do I care?", "start": 949.08, "duration": 4.1}, {"text": "AUDIENCE: Two reasons. It's the usability\nof bitcoin, that bitcoin is not usable that's", "start": 953.18, "duration": 7.29}, {"text": "public and private. So that's the different\nbetween fiat currencies, that can be like", "start": 960.47, "duration": 8.57}, {"text": "government, state. But, two, is then what\nhappens to these two bitcoins? Do they just", "start": 969.04, "duration": 6.2}, {"text": "get burned?", "start": 975.24, "duration": 1.0}, {"text": "They're suspended until there's some decision\nas to what to happen. They're not owned by", "start": 976.24, "duration": 3.789}, {"text": "the exchange.", "start": 980.029, "duration": 1.0}, {"text": "TADGE DRYJA: They gave them back. But, yeah,\nthe real thing is these two bitcoins are sort", "start": 981.029, "duration": 4.011}, {"text": "of worth less than two other bitcoins. Now,\nyou've got a sort of different value for these,", "start": 985.04, "duration": 5.1}, {"text": "where these two bitcoins are hot. And I need\nto get rid of them, and launder them, or something.", "start": 990.14, "duration": 5.19}, {"text": "AUDIENCE: That happens with $100 bills too.", "start": 995.33, "duration": 1.0}, {"text": "TADGE DRYJA: Really? OK, well.", "start": 996.33, "duration": 1.0}, {"text": "AUDIENCE: I had a suitcase full of them in\nBogota.", "start": 997.33, "duration": 4.1}, {"text": "TADGE DRYJA: You had a suitcase full of hundreds,\nand you just walk to the Bank of America,", "start": 1001.43, "duration": 11.31}, {"text": "and say, here, I want to deposit this, probably\nyou've got some problems.", "start": 1012.74, "duration": 5.959}, {"text": "AUDIENCE: [INAUDIBLE] 1% into the banking\nsystem, to move it from fiat to digital, digital", "start": 1018.699, "duration": 7.15}, {"text": "fiat.", "start": 1025.849, "duration": 1.0}, {"text": "TADGE DRYJA: Yeah, like actual physical currency\nnotes.", "start": 1026.849, "duration": 1.121}, {"text": "AUDIENCE: That's not money laundering.", "start": 1027.97, "duration": 2.8}, {"text": "TADGE DRYJA: So, yeah, so now you've got the\nsort of money laundering that now people are", "start": 1030.77, "duration": 5.97}, {"text": "going to try to do using bitcoin. It would\nbe preferable if-- so the way that they can", "start": 1036.74, "duration": 6.868}, {"text": "tell about this, is that people reuse addresses.\nBitcoin is not inherently as fungible as,", "start": 1043.608, "duration": 6.342}, {"text": "say, gold.", "start": 1049.95, "duration": 1.959}, {"text": "Dollar bills have these serial numbers. And\nI don't know to what extent people track these", "start": 1051.909, "duration": 4.24}, {"text": "things. But bitcoins are much more like the\ndollar bills with serial numbers. And it's", "start": 1056.149, "duration": 4.671}, {"text": "all on the internet. It's all on the computer.\nSo it's really easy to track things this way.", "start": 1060.82, "duration": 4.01}, {"text": "AUDIENCE: [INAUDIBLE] could just simply transfer\nthem to a new address, and no one would know", "start": 1064.83, "duration": 6.363}, {"text": "it was still him until it was spent.", "start": 1071.193, "duration": 3.356}, {"text": "TADGE DRYJA: Well, yes and no. So you say,\nOK, I'm at the exchange. They've got a giant", "start": 1074.549, "duration": 7.36}, {"text": "pool of addresses. I transfer to the casino.", "start": 1081.909, "duration": 5.62}, {"text": "And then the casino, in many of these cases,\nreuses addresses extensively. So it's really", "start": 1087.529, "duration": 5.14}, {"text": "easy to see that this is the casino. And then\nfrom the casino, goes to the exchange again.", "start": 1092.669, "duration": 5.87}, {"text": "Exchange flags that and says, hey, we know\nwhere this came from.", "start": 1098.539, "duration": 2.481}, {"text": "Instead, you say, OK, I go to User A. And\nthen I go to the exchange. In some cases,", "start": 1101.02, "duration": 6.469}, {"text": "that might-- if their algorithm is, hey, just\nlook at where it came from, sure. But if you", "start": 1107.489, "duration": 4.31}, {"text": "say, wait, there was one output. This transaction\nis one input, one output.", "start": 1111.799, "duration": 5.151}, {"text": "So we know exactly where it came from. You\ncan trace it back that way. So it depends.", "start": 1116.95, "duration": 4.839}, {"text": "Would the coins be worth less? This is un-money\nlike.", "start": 1121.789, "duration": 4.061}, {"text": "And since legal tender is a whole other thing.\nAnd I'm pretty sure bitcoin will never be", "start": 1125.85, "duration": 4.409}, {"text": "legal tender anywhere, in terms of debts can\nbe settled. But at least fungibility, we want.", "start": 1130.259, "duration": 6.03}, {"text": "So we want to make bitcoin more money like,\nhow do we fix this? The first, and simplest,", "start": 1136.289, "duration": 5.041}, {"text": "and possibly the biggest is, address reuse.\nSo if the casino keeps using the same address", "start": 1141.33, "duration": 5.979}, {"text": "over and over, it's really obvious.", "start": 1147.309, "duration": 3.271}, {"text": "And so things like vanity addresses, so a\nlot of them will use vanity addresses. A vanity", "start": 1150.58, "duration": 4.539}, {"text": "address is when you continually perform computations\nto try to get a human readable address. The", "start": 1155.119, "duration": 6.87}, {"text": "addresses are random numbers.", "start": 1161.989, "duration": 1.18}, {"text": "So for example, I ain't rich. So Greg Maxwell\nhas this address, which is 1gMaxwellbo8. So", "start": 1163.169, "duration": 9.541}, {"text": "you can see that the first part of that addresses\nis Jim Maxwell.", "start": 1172.71, "duration": 4.189}, {"text": "And you get that just by continually attempting\nmillions and millions, or billions, of different", "start": 1176.899, "duration": 4.5}, {"text": "keys, and seeing which turn into the address\nyou want. So people do that. People spend", "start": 1181.399, "duration": 6.76}, {"text": "a lot of resources on making cool addresses.", "start": 1188.159, "duration": 1.931}, {"text": "And then the casino can say, OK, this is my\naddress. But that really hurts the fungibility", "start": 1190.09, "duration": 4.799}, {"text": "and privacy, because now it's clear when a\ncustomer sends to that address, everyone in", "start": 1194.889, "duration": 6.561}, {"text": "the world can see. Yeah?", "start": 1201.45, "duration": 1.78}, {"text": "AUDIENCE: Does the casino just do this, because\nit's cool? Because it's not like it's easier", "start": 1203.23, "duration": 8.189}, {"text": "to type in, because--", "start": 1211.419, "duration": 1.75}, {"text": "TADGE DRYJA: You still have the stuff. It's\nbranding, vanity address, it cool I guess.", "start": 1213.169, "duration": 5.32}, {"text": "But, yeah, Satoshi Dice does this too, right?\nOr did.", "start": 1218.489, "duration": 7.25}, {"text": "So the Satoshi Dice address is-- yeah, it\nalways starts with one dice. So branding,", "start": 1225.739, "duration": 13.32}, {"text": "I guess, makes it easier for-- it does make\nit easier for people to recognize. If they", "start": 1239.059, "duration": 4.11}, {"text": "have a list of the addresses, they're like,\noh, that's the casino address. I want to deposit", "start": 1243.169, "duration": 3.151}, {"text": "to the casino, and just copy and paste that\nin there.", "start": 1246.32, "duration": 3.729}, {"text": "So it does help usability. And that's one\nof the issues in bitcoin. It's like, having", "start": 1250.049, "duration": 5.62}, {"text": "these giant, ugly addresses that you have\nto get right, and not sent to the wrong, it's", "start": 1255.669, "duration": 5.99}, {"text": "not a great user experience kind of thing.\nSo I can see that vanity addresses do improve", "start": 1261.659, "duration": 5.34}, {"text": "the user experience a little bit.", "start": 1266.999, "duration": 1.721}, {"text": "But it really hurts the privacy of the system.\nAnd address reuse is a problem, because people", "start": 1268.72, "duration": 6.62}, {"text": "keep using it. It looks cool. Also web explorers,\nso if you look", "start": 1275.34, "duration": 12.089}, {"text": "at blockchain.info. This is advanced mode,\nenable, disable.", "start": 1287.429, "duration": 8.17}, {"text": "Even with advanced mode, it'll give you a\nlink to the output. So no one is going to", "start": 1295.599, "duration": 3.861}, {"text": "click that. Anyway, so the idea is this shows,\noh, here's a transaction. It's coming from", "start": 1299.46, "duration": 5.48}, {"text": "two addresses, sending to two addresses.", "start": 1304.94, "duration": 4.089}, {"text": "And it even gives you a helpful, hey, this\nis Greg Maxwell. And I'll give you a link", "start": 1309.029, "duration": 6.84}, {"text": "to-- where does this link go? You're being\nredirected. OK, well, go for it. Gmax-- OK,", "start": 1315.869, "duration": 11.19}, {"text": "so it's Greg's account on bitcoin talk. Interesting.", "start": 1327.059, "duration": 9.33}, {"text": "So you guys know enough about the system now,\nthat this is not true. If you click on an", "start": 1336.389, "duration": 5.191}, {"text": "address, and now it gives you all the transactions,\nway too many, that were involved in this.", "start": 1341.58, "duration": 4.669}, {"text": "But if you click on a transaction, it's not\nspending from addresses and to addresses.", "start": 1346.249, "duration": 7.63}, {"text": "It's spending from transaction outputs, and\nspending to addresses that can later be consumed.", "start": 1353.879, "duration": 5.601}, {"text": "So the way that web explorers-- and it'll\nshow a balance. If I click on an address,", "start": 1359.48, "duration": 5.559}, {"text": "it says, hey, here's the number of transactions\ninvolved. Here's the final balance. And you", "start": 1365.039, "duration": 4.33}, {"text": "can look at the current balance, and things\nlike that.", "start": 1369.369, "duration": 3.981}, {"text": "But that's not actually how the system works.\nAnd it hurts privacy and vulnerability, to", "start": 1373.35, "duration": 4.169}, {"text": "have this idea of, oh, this is sort of my\naccount. And it's got a balance that can increase", "start": 1377.519, "duration": 4.001}, {"text": "and decrease, because then that implies that\nI'm going to keep using it. Whereas, really,", "start": 1381.52, "duration": 5.749}, {"text": "if they're one-time use, that really makes\nit harder to trace things.", "start": 1387.269, "duration": 4.721}, {"text": "So another aspect that hurts this, if you\nwant to trace things-- so if it's one input,", "start": 1391.99, "duration": 5.019}, {"text": "one output, right here, it's real easy. But\neven if it's not one input, one output-- so,", "start": 1397.009, "duration": 6.54}, {"text": "for example, imagine a transaction where the\ninput has 10 coins in it. There's output a,", "start": 1403.549, "duration": 4.151}, {"text": "which is one coin, output b, which is 8.9997\ncoins.", "start": 1407.7, "duration": 4.849}, {"text": "Which do you think is the change address?\nThey're all different addresses. But OK, whoever", "start": 1412.549, "duration": 11.61}, {"text": "is doing this, they're sending one coin. And\nthe remainder, minus the fee, is this.", "start": 1424.159, "duration": 5.97}, {"text": "So it's often pretty clear, even though looking\nat it, all the addresses are different. OK,", "start": 1430.129, "duration": 6.25}, {"text": "are any of these change addresses? Is it just\na sending to b and c? Is it a sending to b,", "start": 1436.379, "duration": 4.581}, {"text": "and back to a? Often, it's pretty easy to\nfigure out.", "start": 1440.96, "duration": 3.449}, {"text": "And you're guessing. But you can get the guessing\npretty good. OK, so what we're going to talk", "start": 1444.409, "duration": 5.4}, {"text": "about now-- anonymity sets.", "start": 1449.809, "duration": 2.831}, {"text": "So bitcoin is not actually anonymous. There\nare sort of identities attached to these things,", "start": 1452.64, "duration": 4.879}, {"text": "in that you have addresses. The addresses\nare not your name.", "start": 1457.519, "duration": 3.11}, {"text": "But you can think of them as a pseudonym.\nAnd you can create a bunch of pseudonyms.", "start": 1460.629, "duration": 3.77}, {"text": "But there are these keys. There are these\npublicly known addresses.", "start": 1464.399, "duration": 5.49}, {"text": "And so we want to expand an anonymity set.\nAnd so the idea of an anonymity set is, how", "start": 1469.889, "duration": 6.801}, {"text": "many possible different identities could be\nthe owner of these coins? And the idea of", "start": 1476.69, "duration": 9.419}, {"text": "expanding your anonymity set-- so even if\nbitcoin were perfectly anonymous, in terms", "start": 1486.109, "duration": 3.53}, {"text": "of the anonymity set was everyone who had\nBitcoin, that's still actually not that many", "start": 1489.639, "duration": 4.311}, {"text": "people.", "start": 1493.95, "duration": 1.0}, {"text": "So if you see a bitcoin, you're like, well,\nI don't know who owns it. But I know that", "start": 1494.95, "duration": 3.839}, {"text": "the person who owns it, owns bitcoin. And,\nactually, there's not that many people who", "start": 1498.789, "duration": 3.46}, {"text": "own bitcoin. So I've just eliminated 99% of\nthe people, my suspects, just by doing that.", "start": 1502.249, "duration": 6.091}, {"text": "So just having more people using bitcoin makes\nit more anonymous, in that sense. If it's", "start": 1508.34, "duration": 6.309}, {"text": "very niche kind of thing, and then the police\nsay, OK, well whoever did this crime, they're", "start": 1514.649, "duration": 5.32}, {"text": "a bitcoin user. Well, now you can find-- there's\nnot that many bitcoin users. So you want to", "start": 1519.969, "duration": 4.63}, {"text": "try to increase your anonymity set for a specific\ntransaction.", "start": 1524.599, "duration": 4.05}, {"text": "So the traditional-- I don't want to say traditional--\nthe way you do this is basically money laundering.", "start": 1528.649, "duration": 5.23}, {"text": "It's a bitcoin mixer. And these mixers still\nexist. I'm pretty sure, right? They're still", "start": 1533.879, "duration": 6.701}, {"text": "around?", "start": 1540.58, "duration": 1.0}, {"text": "They're still around. I don't know why. But\na lot of times they use Tor. I mean, I know", "start": 1541.58, "duration": 5.319}, {"text": "why. But it's like, there's so many better\nways to do this.", "start": 1546.899, "duration": 3.25}, {"text": "So you've got coins at address A. And you\nsay, OK, I'm going to send 10 coins to the", "start": 1550.149, "duration": 3.671}, {"text": "mixer, which has address me. And then later,\nsome different, not from that output, but", "start": 1553.82, "duration": 4.979}, {"text": "somewhere else in this sort of giant mixer\naccount, four coins get sent to address C,", "start": 1558.799, "duration": 5.041}, {"text": "and six coins to address D. So you basically\npool all the coins into this mixer, which", "start": 1563.84, "duration": 6.019}, {"text": "uses lots of different addresses, and then\nsplit it up over time, different amounts.", "start": 1569.859, "duration": 6.04}, {"text": "And it gets really hard to figure out where\nthe coins came from.", "start": 1575.899, "duration": 3.89}, {"text": "So your anonymity set is bigger. The problem\nis mixers were well. Potential anonymity set", "start": 1579.789, "duration": 6.211}, {"text": "is all the other users of the mixer, if it's\nwell designed. The problem, the mixers disappear", "start": 1586.0, "duration": 4.34}, {"text": "with everyone's money, very consistently.", "start": 1590.34, "duration": 2.719}, {"text": "The mixers are certainly not publicly regulated\ncompanies. I'm pretty sure you couldn't do", "start": 1593.059, "duration": 7.47}, {"text": "that. So they're just sort of these anonymous,\nlike, hey, I'm a mixer, bitcoin cloud, or", "start": 1600.529, "duration": 4.77}, {"text": "bitcoin fog, or whatever. And a lot of times\nthey're on Tor. So you don't even know where", "start": 1605.299, "duration": 4.46}, {"text": "the mixer exists. And you sort of hope for\nthe best and send your money. Yeah?", "start": 1609.759, "duration": 4.61}, {"text": "AUDIENCE: Do they take a transaction fee?", "start": 1614.369, "duration": 2.271}, {"text": "TADGE DRYJA: Yes, of them take fees. The big\nfee is when they keep all your money and don't", "start": 1616.64, "duration": 2.659}, {"text": "give it back. But a lot of times, they will\ntake a small cut. But it's not actually hard.", "start": 1619.299, "duration": 8.12}, {"text": "The cost is pretty minimal. Need some kind\nof Tor service. And then you just have some", "start": 1627.419, "duration": 4.771}, {"text": "software that just runs this, and allows deposits\nand withdrawals.", "start": 1632.19, "duration": 4.4}, {"text": "The conference in Puerto Rico, Financial Cryptos,\nthere was a talk about a-- what was the word", "start": 1636.59, "duration": 5.529}, {"text": "they used? Not traceable, a mixer that you\ncould prove defrauded you. So you could have", "start": 1642.119, "duration": 13.341}, {"text": "these proofs that, oh, I can prove that they\nstole my coins, which is I thought was kind", "start": 1655.46, "duration": 5.12}, {"text": "of useless, because the whole idea is they're\nanonymous.", "start": 1660.58, "duration": 2.399}, {"text": "And maybe you can prove that they ripped you\noff. But they still ripped you off. OK, so", "start": 1662.979, "duration": 4.93}, {"text": "then the better idea than a mixer is I taint\nrich was a blog post from Greg. That's why", "start": 1667.909, "duration": 8.32}, {"text": "I've got this up.", "start": 1676.229, "duration": 1.381}, {"text": "In 2013, and it was kind of fun. Ever since\nI was a wee lad, I had a dream, a dream of", "start": 1677.61, "duration": 5.47}, {"text": "being incorrectly assessed as impossibly rich\nby a braindead automated analysis. Now, with", "start": 1683.08, "duration": 3.93}, {"text": "your help, I can be.", "start": 1687.01, "duration": 1.57}, {"text": "So he wanted to mix inputs from different\npeople within the same transaction. So you", "start": 1688.58, "duration": 8.029}, {"text": "could have two different people in the same\ntransaction. And in bitcoin, this is secure,", "start": 1696.609, "duration": 3.68}, {"text": "because the signature signs the whole transaction.", "start": 1700.289, "duration": 3.64}, {"text": "So you say, OK, I'm user A. I have my 10 coin\ninput. I'll match up with user B, who's got", "start": 1703.929, "duration": 7.321}, {"text": "his two coin input. And we both sign this\nwhole transaction, which sends two coins to", "start": 1711.25, "duration": 5.229}, {"text": "C, and 10 coins to D. So now, you can't trace\nwhere these coins went right. Right? Well,", "start": 1716.479, "duration": 8.54}, {"text": "you sort of can.", "start": 1725.019, "duration": 2.091}, {"text": "But if you just look at the graph of transactions,\nit's not as obvious. So the first transaction", "start": 1727.11, "duration": 3.659}, {"text": "is really fun. I remember seeing this.", "start": 1730.769, "duration": 4.66}, {"text": "So there's three inputs, 40,000 bitcoins,\n0.1337 bitcoins, and 1 bitcoin from Greg,", "start": 1735.429, "duration": 7.97}, {"text": "and then 40,000, and 31337, and then 0.82.\nFor some reason, it was even more-- yeah,", "start": 1743.399, "duration": 9.431}, {"text": "40,000 bitcoins is pretty good today. It was\nno less impressive at the time in 2013, even", "start": 1752.83, "duration": 6.151}, {"text": "though I guess it was only worth about half\na million dollars at that time.", "start": 1758.981, "duration": 4.729}, {"text": "But it was like-- it was pretty cool. And\nthen Greg was like, wow, I've never seen that", "start": 1763.71, "duration": 3.839}, {"text": "much money. Yeah, so the guy who posted the\n40,000 coins, he's called loaded. And nobody", "start": 1767.549, "duration": 10.09}, {"text": "knows who he is. But he shows up from time\nto time, and has a lot of money.", "start": 1777.639, "duration": 6.5}, {"text": "So, yeah, then Greg made a transaction with\nLoaded. I've handled pricey assets before,", "start": 1784.139, "duration": 5.182}, {"text": "the most I've ever moved on a single key press.\nSo it's pretty cool. This was very manual.", "start": 1789.321, "duration": 8.379}, {"text": "That was on a message board, sort of goofing\naround. But there's no risk. You're not sending", "start": 1797.7, "duration": 4.849}, {"text": "money to someone, and then getting it back.\nYou're just saying, I'll sign off on this", "start": 1802.549, "duration": 4.94}, {"text": "transaction. And then transactions are atomic.", "start": 1807.489, "duration": 2.32}, {"text": "You can't say, oh, I'm going to cut off this\nbottom part, and only have 10 coins going", "start": 1809.809, "duration": 3.79}, {"text": "in, and two coins come up. The whole transaction\nis the thing that gets signed. OK, so what's", "start": 1813.599, "duration": 4.93}, {"text": "the problem with this model?", "start": 1818.529, "duration": 1.7}, {"text": "Any way to get a mapping from C and D, to\nA and B? There's one really obvious one on", "start": 1820.229, "duration": 7.8}, {"text": "this screen. It's an x, right? Yeah, well,\ngee, I think it's A goes to D, and B goes", "start": 1828.029, "duration": 7.921}, {"text": "to C, because the amounts are completely different.\nAnd, actually, we'll talk about amounts next", "start": 1835.95, "duration": 5.059}, {"text": "week.", "start": 1841.009, "duration": 1.0}, {"text": "But how about this? Well, you've got 10 coins\ncoming in, two coins coming in here. And I've", "start": 1842.009, "duration": 5.13}, {"text": "got address C, D, E, and F, 1, 7, 1, and 3.\nBetter, maybe? No, nice try. You can still", "start": 1847.139, "duration": 8.231}, {"text": "easily.", "start": 1855.37, "duration": 1.0}, {"text": "The 7 goes to the 10, the 7 to 3, the 1 and\n1. I don't think there's any way it could", "start": 1856.37, "duration": 7.78}, {"text": "be anything else. How about this?", "start": 1864.15, "duration": 3.969}, {"text": "Address C has two coins. Address D has two\ncoins. Address E has eight coins. Well, now,", "start": 1868.119, "duration": 3.55}, {"text": "that actually works, right? It's not clear\nif C is from A or B, same with D.", "start": 1871.669, "duration": 7.73}, {"text": "These two have some anonymity, in that you're\nnot sure which user it's from. E, on the other", "start": 1879.399, "duration": 6.4}, {"text": "hand, is obviously from A. But B's coins are\nnow sort of-- the anonymity set has doubled.", "start": 1885.799, "duration": 8.801}, {"text": "You don't know whether it's C or D. B's address\nis now unclear.", "start": 1894.6, "duration": 4.209}, {"text": "So that's kind of cool. How do we scale this?\nWell, have more users, and a bigger anonymity", "start": 1898.809, "duration": 6.86}, {"text": "set. So one issue with this is, as you scale\nto more users-- let's say you do 10 different", "start": 1905.669, "duration": 6.32}, {"text": "users, where they all put in their inputs.", "start": 1911.989, "duration": 2.67}, {"text": "They all put in their set of outputs. And\nnow, you've got this big transaction, where", "start": 1914.659, "duration": 5.44}, {"text": "it's hard to tell what the mapping is. The\nproblem, as you gain numbers of inputs, numbers", "start": 1920.099, "duration": 4.69}, {"text": "of users, the users themselves know the mapping,\nbecause someone's actually doing the, I put", "start": 1924.789, "duration": 5.22}, {"text": "in my thing, you put in yours.", "start": 1930.009, "duration": 2.431}, {"text": "So there's a user that knows the mapping.\nAnd they can leak that info. And that hurts", "start": 1932.44, "duration": 3.799}, {"text": "the anonymity. So maybe just the transaction\ngraph itself won't tell you, but somebody", "start": 1936.239, "duration": 10.231}, {"text": "knows.", "start": 1946.47, "duration": 1.0}, {"text": "And they can reveal that at a later date.\nSo that's not good. So there's a really cool", "start": 1947.47, "duration": 6.299}, {"text": "protocol called CoinShuffle, so pre-CoinJoin\nmessaging to shuffle the inputs and outputs.", "start": 1953.769, "duration": 6.26}, {"text": "And this allows you to have 10, 20, 30 different\npeople doing it. And if at least two participants", "start": 1960.029, "duration": 6.1}, {"text": "are honest, then the mapping cannot be determined.\nThe way it works-- this is super quick, because", "start": 1966.129, "duration": 7.03}, {"text": "I don't have time.", "start": 1973.159, "duration": 2.9}, {"text": "Everyone has their inputs that they want to\nput into the transaction. And they also have", "start": 1976.059, "duration": 4.23}, {"text": "the output addresses that they want as their\noutputs. So they make a new set of public", "start": 1980.289, "duration": 4.831}, {"text": "keys that they're not going to use on bitcoin\nat all.", "start": 1985.12, "duration": 2.739}, {"text": "They're just making public keys for encryption\npurposes for this game. And they also tell", "start": 1987.859, "duration": 6.78}, {"text": "everyone, here's my inputs. My input is A.\nMy input is B. So the inputs are known to", "start": 1994.639, "duration": 5.75}, {"text": "the people participating.", "start": 2000.389, "duration": 1.0}, {"text": "And then the idea is, OK, I know everyone's\npublicly that they've given. So I encrypt", "start": 2001.389, "duration": 5.931}, {"text": "my output. So I've got an input I've told\neveryone. I've got my output.", "start": 2007.32, "duration": 4.549}, {"text": "And I encrypt that, the address itself and\nthe amount, with everyone's public keys sequentially.", "start": 2011.869, "duration": 5.42}, {"text": "So, for example, I use encryption on key C\nto encrypt the thing on encryption on key", "start": 2017.289, "duration": 5.23}, {"text": "B, encrypt the encryption on key A of my output.\nAnd then I hand this to user A.", "start": 2022.519, "duration": 6.83}, {"text": "So this is like onion routing, sort of onion\nencryption, where you take a plaintext, encrypt", "start": 2029.349, "duration": 4.401}, {"text": "it, encrypt it again, encrypt it again. So\nI receive these encrypted outputs. I shuffle", "start": 2033.75, "duration": 9.42}, {"text": "them. I receive one from A, one from B, one\nfrom C.", "start": 2043.17, "duration": 3.499}, {"text": "Actually, I receive the whole set. I shuffle\nthe order. And then I use my key to decrypt", "start": 2046.669, "duration": 6.341}, {"text": "one layer. It's still going to be encrypted,\nbecause I just see, here's a bunch of encrypted", "start": 2053.01, "duration": 5.359}, {"text": "data.", "start": 2058.369, "duration": 1.0}, {"text": "I decrypt it. It's still encrypted with the\nnext person's key. And then I hand it to them,", "start": 2059.369, "duration": 3.99}, {"text": "and they shuffle, and decrypt. So the final\nuser gets the outputs.", "start": 2063.359, "duration": 4.88}, {"text": "And the final user-- so in this case, user\nC, can decrypt. And now, he's got my output.", "start": 2068.239, "duration": 6.1}, {"text": "But it's been shuffled around with everyone\nelse's output, at every step of the way.", "start": 2074.339, "duration": 5.911}, {"text": "So they can't tell who's went to whom. And\nthen they have this final transaction, which", "start": 2080.25, "duration": 4.84}, {"text": "has all the outputs in some random order,\nbecause everyone contributed to randomizing", "start": 2085.09, "duration": 4.42}, {"text": "the order of the outputs. So this is really\ncool.", "start": 2089.51, "duration": 3.54}, {"text": "As long as two parties are honest-- if there's\nonly one honest party, it doesn't work, because", "start": 2093.05, "duration": 4.89}, {"text": "then every dishonest party colludes, and says,\nwell, we know everything but the honest party's", "start": 2097.94, "duration": 6.889}, {"text": "output. So we can figure out which one it\nis. But if there's two users actually doing", "start": 2104.829, "duration": 7.94}, {"text": "this, then you can't determine the order.", "start": 2112.769, "duration": 1.931}, {"text": "So that's pretty cool. I think it's being\nused for Join Market. Do they use something", "start": 2114.7, "duration": 4.589}, {"text": "like this? I don't know.", "start": 2119.289, "duration": 2.751}, {"text": "So there's cool techniques for this kind of.\nThing OK, real world, though, some people", "start": 2122.04, "duration": 5.75}, {"text": "use this. Join Market exists. I don't know\nhow popular it is.", "start": 2127.79, "duration": 4.489}, {"text": "Problem, which people use this. Who uses this?\nIt's got a limited anonymity set of the people", "start": 2132.279, "duration": 5.881}, {"text": "who really want anonymity, which is not the\nanonymity set the people who want anonymity", "start": 2138.16, "duration": 5.64}, {"text": "want, which is kind of confusing. But the\nidea is, I don't want to just be in this group", "start": 2143.8, "duration": 6.299}, {"text": "of people who want anonymity, because those\nare the people I don't want to be associated", "start": 2150.099, "duration": 4.571}, {"text": "with.", "start": 2154.67, "duration": 1.0}, {"text": "I would rather associate myself with the people\nwho don't particularly want anonymity. This", "start": 2155.67, "duration": 6.34}, {"text": "is a big problem. People don't care about\nprivacy. People don't want to do these kinds", "start": 2162.01, "duration": 7.66}, {"text": "of things.", "start": 2169.67, "duration": 1.0}, {"text": "And this costs money too, in this case. If\nyou're doing these transactions, this isn't", "start": 2170.67, "duration": 4.699}, {"text": "really a payment. This is just superfluous\ntransaction to turn your money around to get", "start": 2175.369, "duration": 5.041}, {"text": "some more privacy. This is one of the big\nissues with, OK, we want anonymity.", "start": 2180.41, "duration": 5.55}, {"text": "But if anonymity is opt in, it's not very\nuseful, because then it's sort of like Tor,", "start": 2185.96, "duration": 6.93}, {"text": "where if I'm using Tor, everyone's like, why\nare you using Tor? And so at this point, encryption", "start": 2192.89, "duration": 11.449}, {"text": "is now sort of ubiquitous. And it's like the\nstandard. But yeah?", "start": 2204.339, "duration": 5.151}, {"text": "AUDIENCE: Given that most transactions happen\non exchanges, why not just lobby a few exchanges", "start": 2209.49, "duration": 7.059}, {"text": "to try and implement this?", "start": 2216.549, "duration": 2.51}, {"text": "TADGE DRYJA: Well, wait, most actual bitcoin\ntransactions are in and out from exchanges?", "start": 2219.059, "duration": 4.351}, {"text": "I don't know--", "start": 2223.41, "duration": 1.0}, {"text": "AUDIENCE: If that's true.", "start": 2224.41, "duration": 1.0}, {"text": "TADGE DRYJA: There's a lot. But I don't know\nif it's a majority. I think it's a decent", "start": 2225.41, "duration": 3.75}, {"text": "percentage. But I think it's less than half.\nBut, yeah, there's a lot.", "start": 2229.16, "duration": 2.85}, {"text": "It'd be awesome. So exchanges are actually\nuniquely positioned, where something like", "start": 2232.01, "duration": 5.93}, {"text": "CoinShuffle, you could really easily do an\noblivious withdrawal. Where you say, I want", "start": 2237.94, "duration": 5.271}, {"text": "to withdraw my coins. And I'm not going to\ntell you where to. But I'll give you this", "start": 2243.211, "duration": 4.398}, {"text": "encrypted thing that gets shuffled around\nwith different users.", "start": 2247.609, "duration": 2.681}, {"text": "And then at the end, I sign off on it. And\nthe exchange can say, well, we're fulfilling", "start": 2250.29, "duration": 3.92}, {"text": "all our customers' withdrawals. But we don't\nknow where the coins are going. You could", "start": 2254.21, "duration": 4.069}, {"text": "totally do that. That's not a conversation\nthat happens at any exchange. Yeah?", "start": 2258.279, "duration": 5.74}, {"text": "AUDIENCE: I also think that the bulk of exchanges\nare now getting caught up in some regulatory,", "start": 2264.019, "duration": 6.761}, {"text": "in Japan, soon to be in the US, for know your\ncustomer, anti-money laundering. So for the", "start": 2270.78, "duration": 9.059}, {"text": "exchange business model, they're going to\nhave to give this Coinbase to the FBI some", "start": 2279.839, "duration": 6.101}, {"text": "data.", "start": 2285.94, "duration": 1.0}, {"text": "TADGE DRYJA: Yeah, and whether that data is,\nhere is this user's name, and address, his", "start": 2286.94, "duration": 3.95}, {"text": "house home address, and his social security\nnumber, and here's what he bought and sold.", "start": 2290.89, "duration": 3.84}, {"text": "Versus, does that also have, and here's where\nthe addresses where he withdrew his coins", "start": 2294.73, "duration": 4.54}, {"text": "to? I don't think the IRs-- the IRS thing,\nI think it was mostly we want to get people", "start": 2299.27, "duration": 7.86}, {"text": "for not reporting their gains.", "start": 2307.13, "duration": 1.5}, {"text": "AUDIENCE: That's the IRS point, but the other\npart--", "start": 2308.63, "duration": 1.899}, {"text": "TADGE DRYJA: Right, FinCEN.", "start": 2310.529, "duration": 1.0}, {"text": "AUDIENCE: Financial Crimes Unit, FinCEN would\nwant the addresses.", "start": 2311.529, "duration": 4.391}, {"text": "TADGE DRYJA: FinCEN would want to map bitcoin\naddresses to human names, so they could see", "start": 2315.92, "duration": 6.48}, {"text": "who did what. IRS just wants to know who sold\nand didn't report gains. By the way, this", "start": 2322.4, "duration": 5.06}, {"text": "weekend, if you sold any coins last year,\nyou got to tell the IRS. I've actually got", "start": 2327.46, "duration": 7.751}, {"text": "to pay a little bit of tax on that.", "start": 2335.211, "duration": 3.019}, {"text": "Yeah, so anonymity is tricky. Like, you could\ntry to go through exchanges, probably not", "start": 2338.23, "duration": 6.52}, {"text": "the best. They're not going to do it. It's\nhard to do even research on this kind of stuff", "start": 2344.75, "duration": 7.14}, {"text": "when you're a company.", "start": 2351.89, "duration": 2.05}, {"text": "There's a lot of sort of chilling effects\nand stuff. That's sort of why I like working", "start": 2353.94, "duration": 3.72}, {"text": "at MIT, in that if I want to research crazy\nanonymity stuff, totally fine. Whereas if", "start": 2357.66, "duration": 5.48}, {"text": "I'm working at a VC-funded company in San\nFrancisco, and I'm like, hey, we're making", "start": 2363.14, "duration": 5.689}, {"text": "these anonymity protocols. Are you sure you\nwant to do it?", "start": 2368.829, "duration": 4.24}, {"text": "It can be an awkward conversation, in some\ncases. So people don't care about privacy.", "start": 2373.069, "duration": 8.161}, {"text": "It's sort of an externality. If you say, I'm\nreusing addresses. But that only hurts my", "start": 2381.23, "duration": 4.579}, {"text": "privacy.", "start": 2385.809, "duration": 1.0}, {"text": "That's actually not true. In the simplest\nsense, you're reducing the anonymity set for", "start": 2386.809, "duration": 5.651}, {"text": "everyone else. So if I I say, OK, where are\nJames' coins? Well, I know they're not at", "start": 2392.46, "duration": 6.879}, {"text": "1Gmaxwell909, because that's Greg Maxwell's\ncoin.", "start": 2399.339, "duration": 3.46}, {"text": "So when you use publicly identifiable addresses,\nand vanity addresses, you're actually reducing", "start": 2402.799, "duration": 5.241}, {"text": "the anonymity set for everyone else. It's\nsort of an externality, where the people who", "start": 2408.04, "duration": 4.19}, {"text": "say, I don't care about privacy are not paying\nthe cost of harming the people who do care", "start": 2412.23, "duration": 5.66}, {"text": "about privacy. So this is a tricky problem.", "start": 2417.89, "duration": 3.31}, {"text": "And there's no solution. But one cool thing,\none way forward, is, well, everyone likes", "start": 2421.2, "duration": 9.29}, {"text": "cheaper transactions. Everyone likes saving\nmoney.", "start": 2430.49, "duration": 3.26}, {"text": "So can we make it cheaper to improve anonymity?\nAnd so privacy and scalability, in some cases,", "start": 2433.75, "duration": 7.019}, {"text": "are at odds. So in things like ring signatures,\nwhich I don't think I have time to go-- but", "start": 2440.769, "duration": 7.06}, {"text": "Monero is a sort of privacy focused currency\nthat uses ring signatures where, where you", "start": 2447.829, "duration": 5.27}, {"text": "can point to-- a ring signature is, I can\npoint to two public keys.", "start": 2453.099, "duration": 4.23}, {"text": "And say, OK, there's public key A and public\nkey B. I'm signing message M on one of those", "start": 2457.329, "duration": 5.25}, {"text": "two public keys. But I'm not telling you which.\nAnd you can verify that, OK, one of these", "start": 2462.579, "duration": 3.701}, {"text": "keys signed. But I don't know which.", "start": 2466.28, "duration": 2.94}, {"text": "And the signer had to have one of the private\nkeys, or both. If you have both keys, you", "start": 2469.22, "duration": 4.69}, {"text": "can obviously make a ring signature. It doesn't\nhave to be two. It can 5, 10, whatever. You", "start": 2473.91, "duration": 5.82}, {"text": "pick a bunch of public keys, sign with one\nof them.", "start": 2479.73, "duration": 3.039}, {"text": "So that's pretty cool. That expands the size\nof signatures, I believe, with like 0 of n.", "start": 2482.769, "duration": 6.151}, {"text": "So if you have 10 keys you're pointing to,\nand you make a signature on one of them, the", "start": 2488.92, "duration": 5.25}, {"text": "signature actually gets bigger.", "start": 2494.17, "duration": 2.51}, {"text": "So for Monero, they use all these different\nsystems. And scalability is one of the biggest", "start": 2496.68, "duration": 5.03}, {"text": "problems with there-- I mean, it's a problem\nwith bitcoin as well. It's a problem with", "start": 2501.71, "duration": 3.68}, {"text": "everything.", "start": 2505.39, "duration": 1.0}, {"text": "But it's even worse in Monero because of the\nchoices and the different algorithms they", "start": 2506.39, "duration": 4.23}, {"text": "use. So in some cases, privacy and scalability\nare at odds. But in some cases, it works together,", "start": 2510.62, "duration": 6.12}, {"text": "where you can say, we just want to have less\ninformation about these transactions. So if", "start": 2516.74, "duration": 4.69}, {"text": "you have less information to store, there's\nless information to link the users to their", "start": 2521.43, "duration": 4.98}, {"text": "coins.", "start": 2526.41, "duration": 1.78}, {"text": "So an idea here is aggregate signatures. So,\ncurrently, when you sign, you have this input.", "start": 2528.19, "duration": 8.329}, {"text": "And you say, OK, here's user's A signature,\nhere's user's B signature. And you're doing", "start": 2536.519, "duration": 5.08}, {"text": "this ineffective CoinJoin thing here.", "start": 2541.599, "duration": 3.68}, {"text": "The goal would be we want to aggregate these\nsignatures. So we don't have a signature for", "start": 2545.279, "duration": 5.431}, {"text": "this input. We just have a single signature\non key C, which is just, somehow, the combination", "start": 2550.71, "duration": 7.67}, {"text": "of A and B's signature.", "start": 2558.38, "duration": 3.36}, {"text": "And then you can save space, because there's\nonly one signature that stays the same size,", "start": 2561.74, "duration": 4.17}, {"text": "but still prove that both A-- so this is not\na ring signature. This is aggregate is A and", "start": 2565.91, "duration": 5.909}, {"text": "B both signed, and produced a single signature\ntogether. And that can validate the whole", "start": 2571.819, "duration": 5.451}, {"text": "thing.", "start": 2577.27, "duration": 1.0}, {"text": "OK, so how can we make this signature? We\nknow pub keys A and B. They're both signing", "start": 2578.27, "duration": 7.589}, {"text": "the same message, which is really important.\nThere's other terms for these things.", "start": 2585.859, "duration": 5.111}, {"text": "There's multi-signatures, aggregate signatures,\nkey aggregation. And no one agrees on-- like,", "start": 2590.97, "duration": 5.899}, {"text": "I've had discussions with people. And I'm\nlike, wait, that's what you call it? I was", "start": 2596.869, "duration": 2.97}, {"text": "calling it something else. And there's not\nreally good terms for this.", "start": 2599.839, "duration": 4.091}, {"text": "But in this case, what we want is we're signing\nthe same message. So that makes it easier.", "start": 2603.93, "duration": 4.439}, {"text": "We're not trying to combine different signatures\non different messages from different pub keys", "start": 2608.369, "duration": 5.99}, {"text": "and combine it to the same signature. That's\neven harder, although that is possible in", "start": 2614.359, "duration": 3.551}, {"text": "some ways.", "start": 2617.91, "duration": 2.26}, {"text": "But in this case, A and B are signing the\nsame message with their two different keys.", "start": 2620.17, "duration": 4.06}, {"text": "And they need one signature. And the signature\nis going to be R and S.", "start": 2624.23, "duration": 4.799}, {"text": "So the equation that we had, that we've done\na couple of times, the signature is k, some", "start": 2629.029, "duration": 6.412}, {"text": "random number, minus the hash of the message,\nand k times gr, times the private key. And", "start": 2635.441, "duration": 7.428}, {"text": "to verify, r minus the hash of the message\nand r, times the public key. Now, if you share", "start": 2642.869, "duration": 11.021}, {"text": "the private keys with each other, it's kind\nof easy.", "start": 2653.89, "duration": 4.56}, {"text": "Alice just say, here's my key, Bob. And then\nthe Bob can compute everything. You can do", "start": 2658.45, "duration": 3.73}, {"text": "that with ECSA. But you really don't want\nto share private keys, because as soon as", "start": 2662.18, "duration": 4.56}, {"text": "you give someone else your private key, maybe\nthey don't sign this aggregate signature of", "start": 2666.74, "duration": 4.43}, {"text": "the thing you want to sign, they sign something\nelse, giving them all the money. So you want", "start": 2671.17, "duration": 3.73}, {"text": "to be involved in this process.", "start": 2674.9, "duration": 3.639}, {"text": "So the simplest sort of multi-signature system\nfor Schnorr signatures-- first, you want to", "start": 2678.539, "duration": 6.73}, {"text": "share an r value. So this r is also going\nto have to have contributions from both users.", "start": 2685.269, "duration": 9.76}, {"text": "Who comes up with what here? If c is the combination\nof both Alice and Bob's public key, the message", "start": 2695.029, "duration": 5.57}, {"text": "we have already agreed on. But this r value\nis the question.", "start": 2700.599, "duration": 5.49}, {"text": "So the idea is, Alice comes up with k sub\na, computes r sub a, and gives it to Bob.", "start": 2706.089, "duration": 7.111}, {"text": "Bob makes k sub b, computes r sub b, and gives\nthat to Alice. Then both of them can say,", "start": 2713.2, "duration": 6.77}, {"text": "OK, well, we know the real r that we're going\nto use for the signature is the sum of r sub", "start": 2719.97, "duration": 4.96}, {"text": "a and r sub b.", "start": 2724.93, "duration": 1.0}, {"text": "Then, they want to compute their own s's.\nSo for Alice, s sub a is going to be equal", "start": 2725.93, "duration": 10.419}, {"text": "to k sub a, that only she knows. She shared\nr sub a, but not k sub a, with Bob. Minus", "start": 2736.349, "duration": 5.631}, {"text": "the hash of the message, and this aggregate,\nthis summed r, times her private key.", "start": 2741.98, "duration": 5.129}, {"text": "For Bob, it's s sub b, equals k sub b, minus\nthe hash of the message, and r, times little", "start": 2747.109, "duration": 7.141}, {"text": "be. And then they give each other a really--\nonly one party needs to do this, right? Either", "start": 2754.25, "duration": 6.099}, {"text": "Alice gives s sub a to Bob, or Bob gives s\nsub a to Alice. But they don't have them both", "start": 2760.349, "duration": 5.641}, {"text": "do it, because then the final step is you\njust add the s's.", "start": 2765.99, "duration": 4.839}, {"text": "So this aggregate s is s sub a, plus s sub\nb, which is k sub a, plus k sub b, minus the", "start": 2770.829, "duration": 9.081}, {"text": "hash of m and r, times a, minus the hash of\nm and r, times b, which is, you can call this", "start": 2779.91, "duration": 7.22}, {"text": "k. That's the discrete log of r, because they\nsummed it. And then you can factor out the", "start": 2787.13, "duration": 5.5}, {"text": "a and b here.", "start": 2792.63, "duration": 1.88}, {"text": "And so this is the sum of their private keys.\nThis is the sum of their k values. And then", "start": 2794.51, "duration": 6.12}, {"text": "this single verification step will work. And\nthat works. Awesome. OK, questions about this?", "start": 2800.63, "duration": 8.82}, {"text": "Basically make sense? There's all sorts of\nminefield caveat sort of watch out things.", "start": 2809.45, "duration": 10.599}, {"text": "For example, if they learn your k value, they\nwill learn your private key, once they get", "start": 2820.049, "duration": 6.361}, {"text": "this. Normally, you make deterministic k values,\nwhere you compute k as the hash of your message", "start": 2826.41, "duration": 11.54}, {"text": "being signed and your private key. That's\ndangerous to do in this case, because they", "start": 2837.95, "duration": 4.061}, {"text": "might get a k value from you, and then give\nyou a different r value, and get another k", "start": 2842.011, "duration": 5.988}, {"text": "value, and find your private key.", "start": 2847.999, "duration": 1.941}, {"text": "So there's all sorts of watch out things.\nSo the idea is, OK, now cool, we've got output,", "start": 2849.94, "duration": 8.03}, {"text": "which needs a signature from a. We've got\nan output which needs a signature from b.", "start": 2857.97, "duration": 3.389}, {"text": "We'll use those as inputs, and just have this\nsum c signature. And that shows that both", "start": 2861.359, "duration": 5.391}, {"text": "parties signed.", "start": 2866.75, "duration": 1.25}, {"text": "So we're good. Now, we have way less data.\nThese signatures are like 65 bytes. So instead", "start": 2868.0, "duration": 9.39}, {"text": "of having it twice, you just have one that\ncovers the whole transaction. Great.", "start": 2877.39, "duration": 4.699}, {"text": "And it doesn't have to be two. You can see\nhow this would extend to three, four, or five", "start": 2882.089, "duration": 5.43}, {"text": "different people. They would all have to compute\ntheir own k value, give it to everyone else,", "start": 2887.519, "duration": 6.131}, {"text": "everyone computes this combined r value, and\nthen does their own s's, and then sums them", "start": 2893.65, "duration": 6.49}, {"text": "all up. And this would work with any number\nof participants.", "start": 2900.14, "duration": 4.359}, {"text": "Problem-- you've got a bunch of coins, that\n40,000 coins from before. And then one day,", "start": 2904.499, "duration": 5.451}, {"text": "you see, wait, I'm user A. User B came up\nwith a user A and B signature and sent it", "start": 2909.95, "duration": 6.85}, {"text": "all to address E. I never signed anything.\nI didn't do this process with him.", "start": 2916.8, "duration": 6.61}, {"text": "How did he steal all my coins? This is bad.\nSo any idea of how you could do this with", "start": 2923.41, "duration": 5.119}, {"text": "the equations we?", "start": 2928.529, "duration": 2.991}, {"text": "OK, so what you do is you say, hey, here's\nkey A on the network. And, normally, you see", "start": 2931.52, "duration": 7.91}, {"text": "pub key hashes. But a lot of times you see\npub keys. And, anyway, you definitely see", "start": 2939.43, "duration": 3.099}, {"text": "the pub key once people try to spend it.", "start": 2942.529, "duration": 3.06}, {"text": "So maybe you have to do this quickly. But\nyou can do this real quick. So you say, OK,", "start": 2945.589, "duration": 3.72}, {"text": "I'm going to make Q, a random private key,\ncompute q times G to be big Q. And then I'll", "start": 2949.309, "duration": 6.76}, {"text": "compute key B, which is q minus A. Then I\nwill send some coins to B.", "start": 2956.069, "duration": 5.98}, {"text": "And now, note that I don't know the private\nkey for B. The private key for B is going", "start": 2962.049, "duration": 5.01}, {"text": "to be this little q, minus little a. I don't\nknow little a, so I don't know what little", "start": 2967.059, "duration": 4.871}, {"text": "b is.", "start": 2971.93, "duration": 2.06}, {"text": "But that's OK. I don't send too many coins\nto key b. And, anyway, I'll get them back.", "start": 2973.99, "duration": 6.849}, {"text": "I don't know b. I can't sign with it.", "start": 2980.839, "duration": 2.02}, {"text": "However, I want to spend from b and a together.\nI don't know a little b. I don't little a.", "start": 2982.859, "duration": 6.4}, {"text": "I don't know the private key for either. But\nI do know the private key for both, which", "start": 2989.259, "duration": 3.421}, {"text": "is sort of confusing.", "start": 2992.68, "duration": 1.169}, {"text": "But the idea is, well, C, is going to be a\nplus b, which is a, plus q minus a, which", "start": 2993.849, "duration": 4.182}, {"text": "is just q. So in this case, I can observe\na key, make this rogue key, and then spend", "start": 2998.031, "duration": 10.159}, {"text": "from both of them, without knowing the actual\nkey that I wanted to steal from. So this is", "start": 3008.19, "duration": 6.0}, {"text": "a huge problem. You can't have this. This\nwould make signature aggregation completely", "start": 3014.19, "duration": 4.22}, {"text": "insecure. What are some ideas of how to fix\nthat?", "start": 3018.41, "duration": 10.099}, {"text": "So the interesting thing is in all the literature\nabout multi-signature, this problem sort of", "start": 3028.509, "duration": 5.75}, {"text": "still persists. And the new papers about how\nto use this in bitcoin are the ones that are", "start": 3034.259, "duration": 5.461}, {"text": "actually addressing it. So the general idea\nwas, well, make b sign. Make b prove that", "start": 3039.72, "duration": 7.819}, {"text": "he actually can sign with key b.", "start": 3047.539, "duration": 2.601}, {"text": "Before you start doing these things, have\nAlice and Bob talk to each other. And Bob", "start": 3050.14, "duration": 4.25}, {"text": "says, OK, here's a signature with key b. And\nAlice says, OK, here's a signature with key", "start": 3054.39, "duration": 4.189}, {"text": "a. And, now you've proven that they actually\ncan sign, and they're not doing these kinds", "start": 3058.579, "duration": 3.891}, {"text": "of rogue attacks.", "start": 3062.47, "duration": 2.51}, {"text": "So that's the straight straightforward way\nto do it, where, OK, if you don't know b and", "start": 3064.98, "duration": 5.599}, {"text": "can't sign, we're not going to continue with\nthis process. That's interactive, though.", "start": 3070.579, "duration": 4.54}, {"text": "So make b sign a message before combining\nkeys. Easy, that's what people sort of thought", "start": 3075.119, "duration": 4.811}, {"text": "about for years.", "start": 3079.93, "duration": 1.81}, {"text": "But the whole point here is to aggregate signatures.\nAnd so if you require b to create a signature", "start": 3081.74, "duration": 3.98}, {"text": "and post it into the transaction, you've just\neliminated all the gains, all the space saving,", "start": 3085.72, "duration": 6.05}, {"text": "for this technique. So we can't have that.\nWe want it to be non-interactive.", "start": 3091.77, "duration": 4.56}, {"text": "We want any existing keys to be usable in\nthis system, without pre-committing to anything.", "start": 3096.33, "duration": 7.499}, {"text": "You can also make it interactive, where--\nwell, anyway, there's actually a better way", "start": 3103.829, "duration": 5.861}, {"text": "to do it. You de-linearize the signatures.\nSo you redefine the signatures.", "start": 3109.69, "duration": 4.669}, {"text": "You still send to, for example, key a or key\nb. Your outputs are still pub keys. But when", "start": 3114.359, "duration": 6.92}, {"text": "you require a signature, you don't require\na signature from that pub key. You require", "start": 3121.279, "duration": 6.08}, {"text": "a signature from that pub key, times the hash\nof that pub key.", "start": 3127.359, "duration": 4.431}, {"text": "So you say, OK, I'm sending to a. But when\nnormally I have sig a, signature from key", "start": 3131.79, "duration": 5.76}, {"text": "a. Instead, I say, no, I want a signature\nfrom a, times the hash of a. So anyone who", "start": 3137.55, "duration": 11.341}, {"text": "knows the private key for a will know the\nprivate key for this, because this is public.", "start": 3148.891, "duration": 5.968}, {"text": "Everyone can see what the hash of a is.", "start": 3154.859, "duration": 2.67}, {"text": "And then so it's just little a, times the\nhas of little a. This is a scalar multiplication.", "start": 3157.529, "duration": 8.75}, {"text": "So the scalar multiplication works the same\nfor the-- sorry, this is the point multiplication.", "start": 3166.279, "duration": 6.371}, {"text": "And it works the same for the scalar down\nhere.", "start": 3172.65, "duration": 2.689}, {"text": "So this doesn't hurt. It doesn't make it any\nharder to sign. You just have to perform a", "start": 3175.339, "duration": 3.871}, {"text": "hash operation and a multiplication, which\nis quick. But what it does is it prevents", "start": 3179.21, "duration": 6.069}, {"text": "this kind of attack.", "start": 3185.279, "duration": 1.421}, {"text": "So instead of signing with a plus b, sign\nwith a, times the hash of a, plus b times", "start": 3186.7, "duration": 5.26}, {"text": "the hash of b. Since, in this case, in bitcoin,\nyou can see what public keys are being signed", "start": 3191.96, "duration": 7.63}, {"text": "and aggregated, so you say, OK, well I'm going\nto try to do this technique again. c is a,", "start": 3199.59, "duration": 4.85}, {"text": "times the hash of a, plus b times the hash\nof b.", "start": 3204.44, "duration": 3.139}, {"text": "The private key is going to be a, times the\nhash of the pub key, plus little b times the", "start": 3207.579, "duration": 5.831}, {"text": "hash of pub key big B. I know b, which is\nq minus a-- sorry, I don't know b. I know", "start": 3213.41, "duration": 10.81}, {"text": "q. And I constructed sort of this b is q minus\na. But I don't know it.", "start": 3224.22, "duration": 10.68}, {"text": "So c is now going to be a, times the hash\nof a, plus q minus a, times the hash of q", "start": 3234.9, "duration": 7.33}, {"text": "minus a. That's what b is. I can't cancel\nout this little a anymore, because it's got", "start": 3242.23, "duration": 7.839}, {"text": "a different coefficient. Maybe it's easier\nif you sort of move them on the other side.", "start": 3250.069, "duration": 5.071}, {"text": "I've now got these coefficients in front of\nmy private keys that are not the same, and", "start": 3255.14, "duration": 4.87}, {"text": "won't cancel out anymore.", "start": 3260.01, "duration": 2.92}, {"text": "Before, the system is times 1. So the idea\nwas a, times 1, plus q minus a, times 1. Since", "start": 3262.93, "duration": 8.241}, {"text": "the coefficients are the same, 1, I can factor\nthem out, and now apply these, and remove", "start": 3271.171, "duration": 6.188}, {"text": "the a.", "start": 3277.359, "duration": 1.0}, {"text": "So if the coefficients are the same-- if it\nwas a, times the hash of a, plus q minus a", "start": 3278.359, "duration": 4.332}, {"text": "times the hash of a, I'm good. I can still\nfactor out that coefficient and cancel out", "start": 3282.691, "duration": 4.358}, {"text": "a. But now, the coefficients are different.\nAnd so I can't do that subtraction. And now,", "start": 3287.049, "duration": 5.82}, {"text": "I'm stuck. I cannot sign with this little\nc, just from knowing q. Questions about this?", "start": 3292.869, "duration": 6.931}, {"text": "AUDIENCE: So how do come up with q?", "start": 3299.8, "duration": 6.59}, {"text": "TADGE DRYJA: In this attack, q is just any\nrandom number. But the idea is here, q being", "start": 3306.39, "duration": 10.56}, {"text": "any random number doesn't help you, because\nyou've sent money to b. You're trying to sign", "start": 3316.95, "duration": 5.329}, {"text": "with q minus a. But you don't actually know\nthe private key, q minus a. So you're stuck.", "start": 3322.279, "duration": 6.861}, {"text": "Even if you did, in this case, it wouldn't\nhelp, because you still have that either.", "start": 3329.14, "duration": 5.06}, {"text": "So this prevents that kind of straightforward\nattack. You can't get rid of the a times h", "start": 3334.2, "duration": 7.419}, {"text": "term.", "start": 3341.619, "duration": 1.051}, {"text": "This actually is not enough. There's a paper\ncalled Wagner, Wagner's paper, some guy at", "start": 3342.67, "duration": 6.81}, {"text": "California, UC Berkeley, I think, a generalized\nbirthday problem. And it's a hard paper to", "start": 3349.48, "duration": 6.81}, {"text": "read. But if you're working on these kinds\nof things, it's a good paper to read, because", "start": 3356.29, "duration": 4.219}, {"text": "it comes up again and again with these kinds\nof attacks.", "start": 3360.509, "duration": 4.231}, {"text": "Collisions-- I don't think we ever talked\nabout. So the idea of colliding, for example,", "start": 3364.74, "duration": 6.569}, {"text": "a hash function, or in this case a public\nkey, usually it takes half the work that you--", "start": 3371.309, "duration": 9.75}, {"text": "the reason it's called a birthday paradox\nis because-- do people know this birthday", "start": 3381.059, "duration": 7.321}, {"text": "thing. Like, how many people need to be in\na room before two people have the same birthday?", "start": 3388.38, "duration": 4.219}, {"text": "And it's like 22 or something.", "start": 3392.599, "duration": 1.901}, {"text": "It's really low. And it's surprising, because\nyou think, well, maybe 365 divided by 2, so", "start": 3394.5, "duration": 5.81}, {"text": "like 180 or something. But it's actually 22,\nI think, because of the way like for every", "start": 3400.31, "duration": 8.95}, {"text": "new person added, there's a possibility they\ncollide with every already existing person's", "start": 3409.26, "duration": 6.079}, {"text": "birthday.", "start": 3415.339, "duration": 1.27}, {"text": "And so the collisions are more common than\nyou think. So in the case of colliding a hash", "start": 3416.609, "duration": 5.571}, {"text": "function, even if the hash function is 2 to\nthe 256 bits, you only need 2 of the 128 attempts", "start": 3422.18, "duration": 8.879}, {"text": "to collide and find two that are the same.\nAnd that's if you store all the old hashes.", "start": 3431.059, "duration": 4.971}, {"text": "And so keep coming up with new ones after\nthe square root of the number of attempts,", "start": 3436.03, "duration": 4.44}, {"text": "you'll find it. And then there's some techniques\nwith cycle finding, where you don't have to", "start": 3440.47, "duration": 4.34}, {"text": "store them all, things like that. So usually,\nyou think, OK, 2 to the n over 2 time to find", "start": 3444.81, "duration": 6.1}, {"text": "a collision. But that's a collision between\ntwo things.", "start": 3450.91, "duration": 3.699}, {"text": "And Wagner's attack is sort of, yeah, find\na and b, such that a equals b, kind of the", "start": 3454.609, "duration": 7.301}, {"text": "normal collision. Now, find a0, a1, up to\nai. So find i things on this side, and j things", "start": 3461.91, "duration": 7.879}, {"text": "on this side, such that the sum of a equals\nthe sum of b. And in the case of elliptic", "start": 3469.789, "duration": 7.041}, {"text": "curve points, it would actually be the sum.\nYou'd do addition.", "start": 3476.83, "duration": 2.57}, {"text": "In the case of hashes, it might be xor, or\nsome other operation. But the idea is if you", "start": 3479.4, "duration": 5.44}, {"text": "have a lot of different things that you can\npick and choose on both sides, you can potentially", "start": 3484.84, "duration": 4.999}, {"text": "find collisions with much less time. And in\nthe case of these elliptic curve points, it", "start": 3489.839, "duration": 6.121}, {"text": "probably would be practical. You'd need dozens,\n20, 30, 40, different keys.", "start": 3495.96, "duration": 5.95}, {"text": "But you could potentially say, OK, there's\na key with a lot of coins. I'm going to find", "start": 3501.91, "duration": 5.959}, {"text": "a set of a whole bunch of keys, such that\nthat I can cancel that key out, even with", "start": 3507.869, "duration": 4.541}, {"text": "this multiplying by a different coefficient,\nbecause I've got so much search space. It's", "start": 3512.41, "duration": 9.78}, {"text": "a cool paper. You should look through it,\nif you're interested.", "start": 3522.19, "duration": 3.329}, {"text": "But that's a problem. You can sort of make\nprogress, is the basic idea. I can keep getting", "start": 3525.519, "duration": 6.661}, {"text": "closer and closer to canceling this thing\nout.", "start": 3532.18, "duration": 3.069}, {"text": "So instead, we have this improved delinearization.\nAnd this is talked about in the paper from", "start": 3535.249, "duration": 7.791}, {"text": "like January. You take the hash of all the\nkeys concatenated together, in some specified", "start": 3543.04, "duration": 6.17}, {"text": "order. So you sort the keys some way. And\nyou say OK, z is the hash of a and b, or if", "start": 3549.21, "duration": 6.57}, {"text": "there's more keys a, and b, and c, just all\nconcatenated.", "start": 3555.78, "duration": 3.12}, {"text": "And then you sign with a, times the hash of\nz, and a 0, plus b times the hash of z, and", "start": 3558.9, "duration": 6.369}, {"text": "a 1. So you make the coefficients distinct.\nBut you also make the coefficients commit", "start": 3565.269, "duration": 5.08}, {"text": "to every single part of the set. Every key\nin the set needs to be in this coefficient.", "start": 3570.349, "duration": 7.031}, {"text": "And the MuSig sort of explains why that works.\nSo the attack in this case is, well, I've", "start": 3577.38, "duration": 10.81}, {"text": "got these different coefficients. But the\ncoefficient here only depends on this key", "start": 3588.19, "duration": 4.75}, {"text": "here.", "start": 3592.94, "duration": 1.02}, {"text": "So maybe I can find a bunch of different keys\nwith different coefficients, such that these", "start": 3593.96, "duration": 4.52}, {"text": "coefficients will cancel out, or these coefficients\nwill sum, or multiply, or sum up to hash of", "start": 3598.48, "duration": 8.4}, {"text": "a. So it seems hard. I can't find different\nhashes that will equal the hash of a. That's", "start": 3606.88, "duration": 6.79}, {"text": "a hash collision.", "start": 3613.67, "duration": 1.609}, {"text": "But if I have any number of different things,\nI may be able to. And so the idea is, if you", "start": 3615.279, "duration": 6.911}, {"text": "do this, now every time I'm adding or removing\na key from my attempt, I have to change z.", "start": 3622.19, "duration": 8.25}, {"text": "So I can't leave this here, and start adding\nthings, and try to work on it that way, because", "start": 3630.44, "duration": 5.38}, {"text": "every time I add a c or d, z changes.", "start": 3635.82, "duration": 3.749}, {"text": "And so I have to start over from scratch.\nSo anyway, that's my general intuition of", "start": 3639.569, "duration": 5.78}, {"text": "how the delinearization works for MuSig. And\nthen, yeah, it used to be like z, and then", "start": 3645.349, "duration": 6.76}, {"text": "put a in here, because now that makes it unique.\nBut you can actually just number them.", "start": 3652.109, "duration": 5.01}, {"text": "You just need them to be distinct. And since\nit's hash, function just say like 0, 1, 2,", "start": 3657.119, "duration": 3.73}, {"text": "3, 4, is good enough. OK, any questions about\nthis?", "start": 3660.849, "duration": 4.801}, {"text": "I realize it's kind of complicated, and the\nsoftware is kind of crazy. But the idea is", "start": 3665.65, "duration": 5.09}, {"text": "that it prevents a bunch of these attacks\nso that you can securely use aggregate signatures.", "start": 3670.74, "duration": 9.759}, {"text": "Questions?", "start": 3680.499, "duration": 3.25}, {"text": "And you wouldn't have to program it. Yeah\nso you could say, OK, it saves face. The first", "start": 3683.749, "duration": 9.881}, {"text": "use case will be in single wallets. It's interactive.\nSo you have to do that thing where I come", "start": 3693.63, "duration": 8.33}, {"text": "up with different k values, I share the different\nr values. I come up with the s values. I add", "start": 3701.96, "duration": 4.73}, {"text": "those up, sure.", "start": 3706.69, "duration": 2.31}, {"text": "If it's all doing it yourself, where it's\njust there happened to be two different pub", "start": 3709.0, "duration": 4.45}, {"text": "keys that you control both of, you can basically\nskip all of that. And you can just say, no,", "start": 3713.45, "duration": 5.099}, {"text": "I'm just going to add the two points here.\nAnd I'll use the same k value. That's just", "start": 3718.549, "duration": 5.68}, {"text": "me.", "start": 3724.229, "duration": 1.02}, {"text": "So this happens a lot in bitcoin wallets,\nwhere you're making a transaction with multiple", "start": 3725.249, "duration": 5.74}, {"text": "inputs. They're all controlled by you. But\nyou might have two coins here, and three coins", "start": 3730.989, "duration": 4.37}, {"text": "there, and you want to send someone four coins.\nSo you've got to use both of these inputs.", "start": 3735.359, "duration": 4.021}, {"text": "Currently, in bitcoin you're going to have\nmultiple signatures. With this new signature", "start": 3739.38, "duration": 6.13}, {"text": "aggregation, you can say, OK, I'm picking\nthese two inputs. I'm signing for all of them", "start": 3745.51, "duration": 5.519}, {"text": "with a single signature. And in the case of\nit all being years, you don't even have to", "start": 3751.029, "duration": 4.301}, {"text": "do the two operations and add them, because\nyou know the all the keys. So that's going", "start": 3755.33, "duration": 7.769}, {"text": "to be the first use case.", "start": 3763.099, "duration": 1.211}, {"text": "And that's much easier to program, because\nit's all just within the same computer. And", "start": 3764.31, "duration": 5.49}, {"text": "this is easy. That's cool.", "start": 3769.8, "duration": 1.819}, {"text": "And then a cooler use is, OK, use it with\nCoinJoin, where users A, B, C, and D all contribute.", "start": 3771.619, "duration": 9.761}, {"text": "They all have an input with the same amount\nof coins, great. And they're doing CoinShuffle", "start": 3781.38, "duration": 5.489}, {"text": "to shuffle the order of these outputs.", "start": 3786.869, "duration": 2.14}, {"text": "So A knows, oh, mine is G. But I have no idea\nabout E, F, and H. I don't know the mapping", "start": 3789.009, "duration": 6.141}, {"text": "other than my own. But, hey, my output is\nin there. So whatever everyone else is doing,", "start": 3795.15, "duration": 6.429}, {"text": "I don't care.", "start": 3801.579, "duration": 1.0}, {"text": "But I'm good with this transaction. And they\ncan contribute their own k value on their", "start": 3802.579, "duration": 4.691}, {"text": "own s value. And then, finally, you put the\nsignature at the bottom. And it verifies that", "start": 3807.27, "duration": 6.209}, {"text": "all these participants have signed.", "start": 3813.479, "duration": 2.8}, {"text": "And this is really nice because it's smaller.\nThis would be 250 bytes worth of signature", "start": 3816.279, "duration": 9.731}, {"text": "data. Now, it's just 65 bytes sorts of signature\ndata at the bottom. So you save on fees. You", "start": 3826.01, "duration": 5.41}, {"text": "save on space.", "start": 3831.42, "duration": 2.21}, {"text": "Everyone likes this. Yeah, it's cheaper than\na solo transaction. And so that potentially", "start": 3833.63, "duration": 6.199}, {"text": "helps scalability and privacy, in that if\npeople say, I want to do something cheaply,", "start": 3839.829, "duration": 4.209}, {"text": "I will connect to other people and aggregate\nmy signature with theirs.", "start": 3844.038, "duration": 5.281}, {"text": "And so we'd save some space and save some\nmoney. And maybe I don't really care about", "start": 3849.319, "duration": 4.611}, {"text": "the anonymity thing. Maybe I'm entering into\na transaction, and there's some people doing", "start": 3853.93, "duration": 6.47}, {"text": "shady deals in this transaction. But I don't\ncare.", "start": 3860.4, "duration": 3.209}, {"text": "My thing gets in and out. And I save money.\nSo the extension of this would be, what if", "start": 3863.609, "duration": 5.211}, {"text": "you had just one giant transaction in every\nblock, which is all the inputs and all the", "start": 3868.82, "duration": 5.19}, {"text": "outputs, and there's a single signature? That\nwould be really cool.", "start": 3874.01, "duration": 6.2}, {"text": "There are techniques to do that. Maybe next\ntime. So the issue is it's interactive, in", "start": 3880.21, "duration": 11.119}, {"text": "that you have to know about all the other\ninputs and all the other outputs.", "start": 3891.329, "duration": 4.461}, {"text": "So if it were non-interactive, then I could\nsay, oh, well there's this transaction where", "start": 3895.79, "duration": 4.63}, {"text": "D is sending coins to H. And there's also\nthis other transaction where C sounds going", "start": 3900.42, "duration": 5.089}, {"text": "to G. And they've got their own signatures.", "start": 3905.509, "duration": 4.951}, {"text": "I'm not either of these people. I didn't do\nanything with these signatures. But if I could", "start": 3910.46, "duration": 3.47}, {"text": "take those two things and combine the signature\nnon-interactively, then I could just basically", "start": 3913.93, "duration": 5.23}, {"text": "take all the transactions in my meme pool,\nsquish them into one transaction with one", "start": 3919.16, "duration": 3.959}, {"text": "signature, and put that in my block. That\nwould be really cool.", "start": 3923.119, "duration": 5.021}, {"text": "But the issue there is, one, the signatures\nhave to be interactive. And, two, they're", "start": 3928.14, "duration": 4.93}, {"text": "on different messages. So in the case of C\nsending to G, it's a message of C to G. And", "start": 3933.07, "duration": 6.279}, {"text": "then D sending to H, It's on that message.", "start": 3939.349, "duration": 3.64}, {"text": "There are techniques, though. So BLS signatures\ndo allow you to do this, so non-interactive", "start": 3942.989, "duration": 9.161}, {"text": "aggregation of signatures. Which would be\nreally cool, because then a block would only", "start": 3952.15, "duration": 4.25}, {"text": "need one signature. And then BLS signatures\nthemselves are a single point, not a point", "start": 3956.4, "duration": 5.32}, {"text": "in a scalar. So it would just be 32 bytes.", "start": 3961.72, "duration": 3.639}, {"text": "Well, you'd probably use a different curve.\nYou'd have to. But, yeah, the idea of having", "start": 3965.359, "duration": 5.95}, {"text": "these tiny signatures that's satisfy proof\nfor the entire set is really cool.", "start": 3971.309, "duration": 7.67}, {"text": "So this is a cool idea. So you saying there\nisn't software? Or it's not on GitHub?", "start": 3978.979, "duration": 10.461}, {"text": "OK, so the idea is, there is a bunch of software\nfor this that mostly SIPPA-- or Peter Wool,", "start": 3989.44, "duration": 8.919}, {"text": "his name on the internet is SIPPA. And he\ntold me what that stood for. And it was some", "start": 3998.359, "duration": 5.131}, {"text": "like super cheesy thing he made when he was\nin middle school.", "start": 4003.49, "duration": 3.798}, {"text": "Anyway, he has been working on this kind of\nsoftware. So has Greg, that guy who five years", "start": 4007.288, "duration": 6.771}, {"text": "ago wrote about this stuff. A couple of people\nhave been working on this.", "start": 4014.059, "duration": 6.321}, {"text": "It's not publicly available code, which is\nkind of weird. But the reason is that they're", "start": 4020.38, "duration": 4.44}, {"text": "working on Schnorr signatures and aggregation.\nAnd it was on GitHub in like a branch of lib", "start": 4024.82, "duration": 5.779}, {"text": "sec p, the repo they're using. And then all\nthese altcoins were taking the code, and putting", "start": 4030.599, "duration": 6.101}, {"text": "it into their altcoins, and saying, hey, we\nsupport Schnorr signatures.", "start": 4036.7, "duration": 4.639}, {"text": "So for example the rogue key attack, it was\nthe simple version, which didn't have this", "start": 4041.339, "duration": 4.351}, {"text": "multiplied by the hash of the pub key. And\nthey were like, wait, no, don't, we're working", "start": 4045.69, "duration": 5.589}, {"text": "on this software. But we know all of these\nproblems with it.", "start": 4051.279, "duration": 4.041}, {"text": "You can't actually use this for signature\naggregation. We're just sort of playing around,", "start": 4055.32, "duration": 4.509}, {"text": "and trying different things. And so they actually\npulled it from GitHub.", "start": 4059.829, "duration": 6.5}, {"text": "And so I have seen it. You can see the old\nstuff. Yeah, the three years ago stuff that", "start": 4066.329, "duration": 8.23}, {"text": "doesn't have any of this delinearization,\nor this thing that prevent Wagner's attack,", "start": 4074.559, "duration": 5.0}, {"text": "all of that stuff is not in there.", "start": 4079.559, "duration": 4.51}, {"text": "AUDIENCE: That's something that sounds really\ncool. But that's something [INAUDIBLE].", "start": 4084.069, "duration": 4.841}, {"text": "TADGE DRYJA: No that's not what they-- OK,\nmaybe that's a cool attack. But they were", "start": 4088.91, "duration": 6.22}, {"text": "like, oh, shoot, no. But it said in their\nrepo, do not use this. This is research code.", "start": 4095.13, "duration": 4.88}, {"text": "Do not use this in production. There are known\nvulnerabilities.", "start": 4100.01, "duration": 3.639}, {"text": "But people are like, whatever, people didn't\ncare. Well, yeah, there's some esoteric edge", "start": 4103.649, "duration": 5.089}, {"text": "case vulnerability, but I'm going to solve\nthat, because xyz. So they actually pulled", "start": 4108.738, "duration": 4.161}, {"text": "the code.", "start": 4112.899, "duration": 2.041}, {"text": "They are working on the code. I mean, the\ncode works. I've seen it. But they are very", "start": 4114.94, "duration": 6.539}, {"text": "sort of like, we don't want to put it publicly\nuntil we're sort of saying, OK, here's our", "start": 4121.479, "duration": 4.53}, {"text": "final version that we want to put in bitcoin,\nbecause they know as soon as they sort of", "start": 4126.009, "duration": 3.64}, {"text": "put it out there for review, all these altcoins\nwill take-- I mean, you've implemented this", "start": 4129.649, "duration": 4.891}, {"text": "in-- yeah. Not in vertcoin, in crypto kernel.\nAnd you do use the u sig?", "start": 4134.54, "duration": 10.049}, {"text": "AUDIENCE: I will do now.", "start": 4144.589, "duration": 2.081}, {"text": "TADGE DRYJA: Oh, OK, cool, let me know. So\nthey know that people are going to use this,", "start": 4146.67, "duration": 5.648}, {"text": "because it's a cool signature scheme. And\nI've talked about this multiple times before.", "start": 4152.318, "duration": 5.122}, {"text": "Once you have this Schnorr signature equation,\nthere's all these other cool things you can", "start": 4157.44, "duration": 3.78}, {"text": "do with your addresses and things like that.", "start": 4161.22, "duration": 4.059}, {"text": "And so the idea here is scalability is one\nthat, OK, now we can combine things, make", "start": 4165.279, "duration": 5.641}, {"text": "it smaller. And also, we can hopefully help\nprivacy this way, in that people who are not", "start": 4170.92, "duration": 4.939}, {"text": "particularly concerned with their anonymity\nwill say, yeah, I still want to use it, because", "start": 4175.859, "duration": 4.48}, {"text": "I can save $1 on fees. So, yeah, I'll join\nthis transaction with a bunch of other people.", "start": 4180.339, "duration": 6.581}, {"text": "And then you've got the people who actually\nwant anonymity are like, great, these are", "start": 4186.92, "duration": 4.0}, {"text": "exactly the people I want to be associated\nwith, the people who don't particularly care", "start": 4190.92, "duration": 4.84}, {"text": "about anonymity. So it seems like a win-win.", "start": 4195.76, "duration": 3.52}, {"text": "Right now, all the software requires a regular\nold signature. So, for example, if these are", "start": 4199.28, "duration": 10.08}, {"text": "outputs that are currently being used, and\nyou do this, I'd validate the output one at", "start": 4209.36, "duration": 5.311}, {"text": "a time.", "start": 4214.671, "duration": 1.0}, {"text": "And I say, OK, I'm looking at this output,\nlooking at this input, there's no signature", "start": 4215.671, "duration": 3.289}, {"text": "at all, fail. OK, the whole transaction fails.\nSo you need a new output type, which says,", "start": 4218.96, "duration": 5.19}, {"text": "OK, I'm using this new aggregate signature.\nSo, actually, look at all the inputs. Don't", "start": 4224.15, "duration": 6.981}, {"text": "validate them at all, and just validate at\nthe end at the bottom.", "start": 4231.131, "duration": 5.139}, {"text": "So that's going to be some different code.\nAnd you can't retroactively say, OK, all the", "start": 4236.27, "duration": 8.039}, {"text": "existing outputs we can now spend with this\nnew signature scheme. You can't really do", "start": 4244.309, "duration": 3.33}, {"text": "that. So we'll have to make new addresses.", "start": 4247.639, "duration": 3.5}, {"text": "And the new addresses will be bc1v, instead\nof q, new address type. And then we send to", "start": 4251.139, "duration": 6.301}, {"text": "that. And now, you're allowed to spend from\nit using aggregate signatures. So all that", "start": 4257.44, "duration": 4.13}, {"text": "software is mostly there.", "start": 4261.57, "duration": 2.21}, {"text": "But it might take a while. You've got to get\neveryone on board. I'm curious to see what", "start": 4263.78, "duration": 5.77}, {"text": "people will complain about. Segwit was a little\nbit more like, there's a lot to complain about.", "start": 4269.55, "duration": 6.379}, {"text": "Even I don't like parts of Segwit. There's\na lot of parts I don't like and won't use.", "start": 4275.929, "duration": 7.15}, {"text": "But this seems like a sort of clear win, where\nit's like, great, you can aggregate signatures,", "start": 4283.079, "duration": 3.511}, {"text": "do all these cool things. I'm guessing there\nwill be people saying, this is bad. And saying,", "start": 4286.59, "duration": 6.64}, {"text": "no, because Satoshi's vision is one signature,\none input. A coin is a chain of signatures.", "start": 4293.23, "duration": 8.82}, {"text": "And this coin has no signatures.", "start": 4302.05, "duration": 1.6}, {"text": "I'm guessing. I don't know what'll happen.\nOr maybe it might be smooth, and everyone", "start": 4303.65, "duration": 4.95}, {"text": "is sort of like, yeah, this is obviously better,\ngreat paper, great math, great idea. Let's", "start": 4308.6, "duration": 5.869}, {"text": "all activate it and use bitcoin this way.\nWho knows?", "start": 4314.469, "duration": 4.641}, {"text": "So we'll see. It's pretty cool software, though.\nAnd you can use it in other projects. So Crypto", "start": 4319.11, "duration": 7.19}, {"text": "Kernel is using Schnorr signatures, probably\na bunch of different coins who are sort of", "start": 4326.3, "duration": 4.31}, {"text": "more agile, in that it's easier to make changes,\nwill probably start using this.", "start": 4330.61, "duration": 4.17}, {"text": "Ethereum is still ECDSA though, right? There's\nno coins that are actually implementing this", "start": 4334.78, "duration": 8.48}, {"text": "yet. Monera uses ED25509, which is essentially\na Schnorr signature. And I think Ripple can", "start": 4343.26, "duration": 7.89}, {"text": "use ED25509. So there's some different schemes\nthat are more similar to this, but still don't", "start": 4351.15, "duration": 7.049}, {"text": "have the definitions for aggregation.", "start": 4358.199, "duration": 1.79}, {"text": "So, anyway, so this is cool stuff. Next time,\nI will talk about-- next one, I'm not looking", "start": 4359.989, "duration": 7.741}, {"text": "forward to making slides, because it's like\na really complicated one that I don't even", "start": 4367.73, "duration": 3.81}, {"text": "understand. Like, I sort of get it, but it's\nlike, wait, how? OK, but how to mix different", "start": 4371.54, "duration": 6.3}, {"text": "amounts.", "start": 4377.84, "duration": 4.73}, {"text": "In this case, hey, it's great. But in many\ncases, you can see, I said the reason it doesn't", "start": 4382.57, "duration": 8.02}, {"text": "work is because it's really obvious. But what\nif you could hide the amounts, but still enforce", "start": 4390.59, "duration": 7.589}, {"text": "that the amounts were correct?", "start": 4398.179, "duration": 1.931}, {"text": "So that's the idea of confidential transactions,\nwhich I'll talk about next time. And then", "start": 4400.11, "duration": 4.75}, {"text": "it leads to MimbleWimble, which is even more\ncomplicated. I'm not going to promise that", "start": 4404.86, "duration": 5.089}, {"text": "I'll explain the whole thing. But I'll touch\non the ideas.", "start": 4409.949, "duration": 3.691}]
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+[{"text": "[SQUEAKING]\n[RUSTLING] [CLICKING]", "start": 0.0, "duration": 6.581}, {"text": "ISAAC METCALF: In\nthis video, we'll", "start": 6.581, "duration": 1.458}, {"text": "be discussing Goodie Bag\n7, or crystalline defects.", "start": 8.039, "duration": 3.391}, {"text": "The objectives are to\nvisualize zero dimensional, one", "start": 11.43, "duration": 2.55}, {"text": "dimensional, and two\ndimensional defects", "start": 13.98, "duration": 1.77}, {"text": "in crystalline materials.", "start": 15.75, "duration": 1.89}, {"text": "You'll need a double-sided\nstrip of adhesive,", "start": 17.64, "duration": 2.22}, {"text": "two Plexiglas panels, and\n500 1/16th-inch metal beads.", "start": 19.86, "duration": 4.29}, {"text": "First, pull off\nthe protective film", "start": 24.15, "duration": 1.77}, {"text": "on the top of your\nacrylic sheet.", "start": 25.92, "duration": 2.34}, {"text": "Take four pieces of\ndouble-sided tape", "start": 28.26, "duration": 2.4}, {"text": "and put one piece on each of\nthe edges of the acrylic sheet.", "start": 30.66, "duration": 3.99}, {"text": "Then carefully put your balls\nin the middle of the square made", "start": 34.65, "duration": 4.47}, {"text": "by the four pieces of tape.", "start": 39.12, "duration": 1.95}, {"text": "Finally remove the film on the\ntop of the other acrylic sheet", "start": 41.07, "duration": 3.48}, {"text": "and put it on top.", "start": 44.55, "duration": 1.8}, {"text": "When you're finished, you\nshould have a completed defect", "start": 46.35, "duration": 2.52}, {"text": "modeling kit.", "start": 48.87, "duration": 1.492}, {"text": "CAROLYN JONS: Now that\nyou've built your model,", "start": 50.362, "duration": 1.958}, {"text": "let's use it to visualize how\nmaterial processing impacts", "start": 52.32, "duration": 2.85}, {"text": "the number of defects\nvisible in a crystal.", "start": 55.17, "duration": 2.61}, {"text": "When looking at our\noriginal crystal,", "start": 57.78, "duration": 1.59}, {"text": "you can see several defects.", "start": 59.37, "duration": 1.65}, {"text": "These are a vacancy,\nline defect,", "start": 61.02, "duration": 2.14}, {"text": "and grain boundary defect.", "start": 63.16, "duration": 2.06}, {"text": "Material processing can lead\nto both increases and decreases", "start": 65.22, "duration": 3.45}, {"text": "in the number of\ndefects in the material.", "start": 68.67, "duration": 2.22}, {"text": "A process that leads to an\nincreased number of defects", "start": 70.89, "duration": 2.7}, {"text": "is extrusion or rolling,\nbecause when we extrude or roll", "start": 73.59, "duration": 2.88}, {"text": "a material, we force the atoms\nto go into certain places", "start": 76.47, "duration": 3.18}, {"text": "and those aren't necessarily\nthe most energetically", "start": 79.65, "duration": 2.13}, {"text": "favorable states.", "start": 81.78, "duration": 1.6}, {"text": "Let's look at our\nmodel to understand", "start": 83.38, "duration": 1.64}, {"text": "how material processing leads to\nan increased number of defects.", "start": 85.02, "duration": 3.96}, {"text": "When we shake the model,\nwe're able to add defects", "start": 88.98, "duration": 2.46}, {"text": "to the system.", "start": 91.44, "duration": 1.272}, {"text": "As you can see now, our\nmodel has an increased number", "start": 92.712, "duration": 2.208}, {"text": "of vacancies, line defects,\nand grain boundary defects.", "start": 94.92, "duration": 3.69}, {"text": "Other material\nprocessing methods", "start": 98.61, "duration": 1.65}, {"text": "allow for a decrease in\nthe number of vacancies.", "start": 100.26, "duration": 2.49}, {"text": "One possibility for\nthis is annealing.", "start": 102.75, "duration": 1.95}, {"text": "When we anneal, we\nheat the material up,", "start": 104.7, "duration": 2.1}, {"text": "and then we cool it slowly and\nallow the atoms to move back", "start": 106.8, "duration": 2.67}, {"text": "to their more favorable states.", "start": 109.47, "duration": 2.37}, {"text": "To illustrate annealing,\nlet's tap gently", "start": 111.84, "duration": 2.19}, {"text": "on the side of our model.", "start": 114.03, "duration": 1.98}, {"text": "As you can see, the number\nof defects in our material", "start": 116.01, "duration": 2.4}, {"text": "has been substantially reduced.", "start": 118.41, "duration": 3.1}, {"text": "In this Goodie Bag, we\nwere able to visualize", "start": 121.51, "duration": 2.15}, {"text": "some of the defects\nseen in many crystals,", "start": 123.66, "duration": 2.17}, {"text": "and we were also able to see\nhow processing conditions impact", "start": 125.83, "duration": 3.26}, {"text": "the number of\ndefects in a crystal.", "start": 129.09, "duration": 2.659}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 0.0, "duration": 2.49}, {"text": "Commons license.", "start": 2.49, "duration": 1.24}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 3.73, "duration": 2.39}, {"text": "continue to offer high quality\neducational resources for free.", "start": 6.12, "duration": 3.97}, {"text": "To make a donation or to\nview additional materials", "start": 10.09, "duration": 2.63}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 12.72, "duration": 3.93}, {"text": "at ocw.mit.edu.", "start": 16.65, "duration": 1.33}, {"text": "RAMESH RASKAR: All right,\neveryone, let's get started.", "start": 20.84, "duration": 2.74}, {"text": "I am Ramesh Raskar.", "start": 23.58, "duration": 1.14}, {"text": "And this is--", "start": 24.72, "duration": 1.82}, {"text": "AUDIENCE: I don't know.", "start": 26.54, "duration": 2.95}, {"text": "RAMESH RASKAR: --MAS 131 and\n531, computational camera", "start": 29.49, "duration": 4.2}, {"text": "and photography.", "start": 33.69, "duration": 1.68}, {"text": "And we have, I think, about $50\nto $60,000 worth of equipment", "start": 35.37, "duration": 4.8}, {"text": "right here.", "start": 40.17, "duration": 1.007}, {"text": "So please hold on to the\ndoor if something goes on", "start": 41.177, "duration": 2.083}, {"text": "I really need your help to\nprotect all these things.", "start": 43.26, "duration": 3.06}, {"text": "It's going to be a lot of fun.", "start": 46.32, "duration": 1.81}, {"text": "We're going to see\ncrazy kinds of cameras,", "start": 48.13, "duration": 2.21}, {"text": "crazy kind of photography,\nmedical imaging,", "start": 50.34, "duration": 2.52}, {"text": "and applications in\ndifferent domains.", "start": 52.86, "duration": 3.03}, {"text": "I just wanted to show this\nreally beautiful picture", "start": 55.89, "duration": 2.31}, {"text": "that some of you may\nhave seen on blogs.", "start": 58.2, "duration": 4.98}, {"text": "This is a real photo taken by\nan iPhone camera of a propeller", "start": 63.18, "duration": 6.33}, {"text": "blades on an aircraft.", "start": 69.51, "duration": 3.12}, {"text": "Anybody knows what's going on?", "start": 72.63, "duration": 3.33}, {"text": "AUDIENCE: The sensor\ntakes line by line images.", "start": 75.96, "duration": 2.34}, {"text": "And by the time it goes to the\nnext line, next vertical line,", "start": 78.3, "duration": 2.805}, {"text": "those propellers have moved.", "start": 81.105, "duration": 1.455}, {"text": "So it faces the [INAUDIBLE]\ndirections are not exact", "start": 82.56, "duration": 4.14}, {"text": "location--", "start": 86.7, "duration": 0.5}, {"text": "RAMESH RASKAR: Excellent.", "start": 87.2, "duration": 1.042}, {"text": "AUDIENCE: [INAUDIBLE]\nseparated [INAUDIBLE]..", "start": 88.242, "duration": 2.058}, {"text": "RAMESH RASKAR: Exactly, so\nwhen we think about an image,", "start": 90.3, "duration": 2.333}, {"text": "we think about this as some\nkind of a snapshot, some kind", "start": 92.633, "duration": 3.067}, {"text": "of a progressive photo.", "start": 95.7, "duration": 1.62}, {"text": "But there are two\nmotions going on here.", "start": 97.32, "duration": 2.2}, {"text": "One is the motion of the\nblade, which is circular,", "start": 99.52, "duration": 4.43}, {"text": "and with radial blades.", "start": 103.95, "duration": 1.86}, {"text": "And then there is\nmotion effectively", "start": 105.81, "duration": 4.71}, {"text": "of the sampler, which is\nmoving from up to down.", "start": 110.52, "duration": 2.82}, {"text": "It's a rolling shutter.", "start": 113.34, "duration": 3.12}, {"text": "There's a very nice\nanimation of that.", "start": 116.46, "duration": 3.87}, {"text": "So this is the rolling\nshutter the camera", "start": 124.05, "duration": 2.27}, {"text": "is exposing approximately\njust one line at a time.", "start": 126.32, "duration": 3.58}, {"text": "And as the blades\nrotate around, you", "start": 129.9, "duration": 3.5}, {"text": "can see that it's\ntracing this course.", "start": 133.4, "duration": 3.81}, {"text": "So this example should show\nyou that we can't take anything", "start": 137.21, "duration": 4.98}, {"text": "for granted when it comes\nto this modern photography.", "start": 142.19, "duration": 6.24}, {"text": "And this is mostly an artifact\nof a really cheap sensor", "start": 148.43, "duration": 3.45}, {"text": "that cell phone cameras use.", "start": 151.88, "duration": 1.41}, {"text": "Because of bandwidth\nconstraints it's much easier", "start": 153.29, "duration": 2.46}, {"text": "to roll and read\none line at a time", "start": 155.75, "duration": 2.19}, {"text": "than reading the whole buffer\nof the camera at the same time.", "start": 157.94, "duration": 2.91}, {"text": "So you get just\nbeautiful artifacts.", "start": 160.85, "duration": 2.04}, {"text": "And one open question\nis if camera makers", "start": 162.89, "duration": 4.23}, {"text": "start supporting or\nstart cheaping out on", "start": 167.12, "duration": 4.41}, {"text": "rather than just\none line at a time--", "start": 171.53, "duration": 2.1}, {"text": "if they come up with\neven cheaper mechanisms", "start": 173.63, "duration": 2.64}, {"text": "where they're explaining and\nsome random sequence or--", "start": 176.27, "duration": 4.11}, {"text": "any artifacts they create,\nhover photographers", "start": 180.38, "duration": 3.21}, {"text": "exploit that to create this\nstunning and beautiful imagery.", "start": 183.59, "duration": 5.88}, {"text": "More on the scientific\nside, let's see the lighting", "start": 189.47, "duration": 2.45}, {"text": "is [INAUDIBLE] here.", "start": 191.92, "duration": 2.08}, {"text": "Let's see if you\ncan play with that.", "start": 194.0, "duration": 2.56}, {"text": "Yeah, I'll do that.", "start": 196.56, "duration": 1.79}, {"text": "See if there's another switch\nthat doesn't like the back--", "start": 198.35, "duration": 2.86}, {"text": "No.", "start": 201.21, "duration": 0.5}, {"text": "We're going to learn a lot\nabout computational illumination", "start": 204.65, "duration": 2.94}, {"text": "in this [INAUDIBLE].", "start": 207.59, "duration": 1.093}, {"text": "That maybe OK for now.", "start": 208.683, "duration": 0.917}, {"text": "And we'll switch it back.", "start": 209.6, "duration": 2.17}, {"text": "So imagine you have somebody\nout here behind a shower curtain", "start": 211.77, "duration": 6.26}, {"text": "and you want to take a photo.", "start": 218.03, "duration": 1.778}, {"text": "And you may be able to\ncome up with a photo", "start": 219.808, "duration": 1.792}, {"text": "where you just see the shower\ncurtain behind the person", "start": 221.6, "duration": 2.7}, {"text": "behind without the person\nbehind the shower curtain.", "start": 224.3, "duration": 5.16}, {"text": "But maybe you can\nalso create a photo", "start": 229.46, "duration": 2.13}, {"text": "where you realize it was\nbehind the shower curtain.", "start": 231.59, "duration": 5.8}, {"text": "And this is a trick\nthat's achieved using", "start": 237.39, "duration": 3.93}, {"text": "a special type of a flash.", "start": 241.32, "duration": 2.04}, {"text": "And as you'll see, we\nwill generalize the flash", "start": 243.36, "duration": 2.58}, {"text": "to a very highly\nprogrammable illumination.", "start": 245.94, "duration": 3.9}, {"text": "And with that, photography of\nthis kind is also possible.", "start": 249.84, "duration": 3.81}, {"text": "What else?", "start": 253.65, "duration": 1.39}, {"text": "Here's a great example\nI'd like to show.", "start": 255.04, "duration": 2.989}, {"text": "Imagine you have a scene\nand instead of a camera", "start": 258.029, "duration": 3.271}, {"text": "you just have a\nsingle photodetector.", "start": 261.3, "duration": 2.72}, {"text": "OK, It could be a light\nsensor of your SLR camera.", "start": 264.02, "duration": 4.69}, {"text": "Those of you like to think about\nthese photodiodes, just one", "start": 268.71, "duration": 3.42}, {"text": "photodiode.", "start": 272.13, "duration": 0.72}, {"text": "And instead of taking a\nphoto, what I'm going to do", "start": 272.85, "duration": 2.79}, {"text": "is turn on one pixel of\nthis projector at a time", "start": 275.64, "duration": 3.18}, {"text": "and record this.", "start": 278.82, "duration": 1.47}, {"text": "If the projector has\none million pixels,", "start": 280.29, "duration": 2.28}, {"text": "I'm going to take one\nmillion measurements", "start": 282.57, "duration": 2.19}, {"text": "by turning on one at a time.", "start": 284.76, "duration": 1.77}, {"text": "What picture will I get here?", "start": 286.53, "duration": 1.59}, {"text": "Will I get a picture from\nthose 1 million measurements?", "start": 290.76, "duration": 4.452}, {"text": "Anybody?", "start": 295.212, "duration": 2.568}, {"text": "No, you get a photo that looks\nlike the camera was placed", "start": 297.78, "duration": 3.48}, {"text": "here instead of over here.", "start": 301.26, "duration": 3.45}, {"text": "And it's exactly how a barcode\nscanner at checkout counter", "start": 304.71, "duration": 3.557}, {"text": "works as well.", "start": 308.267, "duration": 0.583}, {"text": "The barcode scanner\ndoesn't have a camera.", "start": 308.85, "duration": 2.35}, {"text": "It just has a sweeping laser.", "start": 311.2, "duration": 2.99}, {"text": "In the same apparatus there's\nalso a single photodetector.", "start": 314.19, "duration": 2.82}, {"text": "So if the barcode scanner\nhits the 1010 patterns", "start": 317.01, "duration": 3.42}, {"text": "of the printed code, when\nit hits the black spot,", "start": 320.43, "duration": 3.78}, {"text": "it doesn't reflect much light\nand it hits the white spot.", "start": 324.21, "duration": 2.55}, {"text": "It reflects much light.", "start": 326.76, "duration": 1.35}, {"text": "And in this way,\na barcode scanner", "start": 328.11, "duration": 2.7}, {"text": "without having to worry about\nfocus and dynamic range and all", "start": 330.81, "duration": 3.42}, {"text": "those issues can figure\nout what the barcode is.", "start": 334.23, "duration": 2.808}, {"text": "AUDIENCE: Isn't it\nimportant, though,", "start": 337.038, "duration": 1.542}, {"text": "that the barcode scanner\nis a laser, which keeps", "start": 338.58, "duration": 2.19}, {"text": "the pixels spatially localized?", "start": 340.77, "duration": 2.013}, {"text": "RAMESH RASKAR: Very focused.", "start": 342.783, "duration": 1.167}, {"text": "AUDIENCE: Right.", "start": 343.95, "duration": 0.667}, {"text": "Whereas here if you have\nan incoherent light source,", "start": 344.617, "duration": 2.543}, {"text": "and you're illuminating\na real scene,", "start": 347.16, "duration": 1.86}, {"text": "you'll illuminate the whole\nscene kind of diffusely.", "start": 349.02, "duration": 2.243}, {"text": "RAMESH RASKAR: That's\na very good point.", "start": 351.263, "duration": 1.667}, {"text": "So that's why we have\nto use a projector.", "start": 352.93, "duration": 1.708}, {"text": "So we are turning on only\none pixel of the projector.", "start": 354.638, "duration": 2.482}, {"text": "So as in very simple\nwords, it's turning", "start": 357.12, "duration": 2.64}, {"text": "on only one ray in the scene.", "start": 359.76, "duration": 2.79}, {"text": "The projector is not flat field.", "start": 362.55, "duration": 2.04}, {"text": "Not all the pixels\nare on it at a time.", "start": 364.59, "duration": 2.55}, {"text": "That's why we had to take one\nmillion readings while turning", "start": 367.14, "duration": 3.45}, {"text": "on one pixel at a time.", "start": 370.59, "duration": 2.97}, {"text": "So that's straightforward.", "start": 373.56, "duration": 1.48}, {"text": "This is very well known.", "start": 375.04, "duration": 2.21}, {"text": "What are some other\nthings you can do", "start": 377.25, "duration": 1.8}, {"text": "with this particular duality?", "start": 379.05, "duration": 3.6}, {"text": "If you replace the\nphotodetector with a camera,", "start": 382.65, "duration": 3.66}, {"text": "you can do something similar.", "start": 386.31, "duration": 1.23}, {"text": "You can turn on one pixel at\na time and take a full photo.", "start": 387.54, "duration": 3.46}, {"text": "So again, I'm going\nto turn on one", "start": 391.0, "duration": 1.97}, {"text": "pixel of the projector at\na time and in this case,", "start": 392.97, "duration": 3.0}, {"text": "take 1 million photos.", "start": 395.97, "duration": 4.11}, {"text": "Now, once you do that,\nwhat I will be able to do", "start": 400.08, "duration": 2.85}, {"text": "is create a relationship\nbetween what", "start": 402.93, "duration": 2.13}, {"text": "happens when I turn on exactly\none pixel of this projector.", "start": 405.06, "duration": 4.77}, {"text": "One pixel is turned on.", "start": 409.83, "duration": 1.23}, {"text": "A photo is taken.", "start": 411.06, "duration": 0.93}, {"text": "I can measure what happens\nto this particular pixel", "start": 411.99, "duration": 2.46}, {"text": "of the camera.", "start": 414.45, "duration": 1.48}, {"text": "And in this way, you will\ncreate a four-dimensional", "start": 415.93, "duration": 2.9}, {"text": "relationship, 2D for the\ncamera and 2D for the--", "start": 418.83, "duration": 6.72}, {"text": "so 2D for the projector\nand 2D for the camera.", "start": 425.55, "duration": 2.38}, {"text": "So a million photos here\nand a million pixels here.", "start": 427.93, "duration": 3.17}, {"text": "So you're going to have a\ntrillion measurements, 10", "start": 431.1, "duration": 4.41}, {"text": "to the 12.", "start": 435.51, "duration": 2.04}, {"text": "Now, we can invert that\nand ask for a single pixel", "start": 437.55, "duration": 5.64}, {"text": "of the camera, which projector\npixels are contributing.", "start": 443.19, "duration": 4.41}, {"text": "So the question to\nask is I'm going", "start": 447.6, "duration": 2.52}, {"text": "to turn on one pixel at a time.", "start": 450.12, "duration": 2.14}, {"text": "If I turn on just this\narray, for example,", "start": 452.26, "duration": 2.37}, {"text": "it will only contribute\nto, say, this pixel.", "start": 454.63, "duration": 2.36}, {"text": "But if there was\nsome intersection,", "start": 456.99, "duration": 1.74}, {"text": "it will also contribute to\nsome other pixel and so on.", "start": 458.73, "duration": 2.66}, {"text": "So you're going to have this\nglobal transport of light.", "start": 461.39, "duration": 2.65}, {"text": "And from that you can ask this\nquestion, for a given camera", "start": 464.04, "duration": 3.93}, {"text": "pixel, what are the other\nprojector pixels that", "start": 467.97, "duration": 2.19}, {"text": "are contributing to it?", "start": 470.16, "duration": 2.2}, {"text": "And so you can do\nthis inversion,", "start": 472.36, "duration": 2.49}, {"text": "which is relatively\nstraightforward to do.", "start": 474.85, "duration": 5.42}, {"text": "And then you can do\nexperiments like this,", "start": 480.27, "duration": 2.4}, {"text": "how can you read your opponent's\ncards from across the table?", "start": 482.67, "duration": 4.5}, {"text": "You can turn on the projector\none pixel at a time,", "start": 487.17, "duration": 3.43}, {"text": "look at the reflection,\nand it's in the camera,", "start": 490.6, "duration": 2.78}, {"text": "then on the next\npixel, and so on.", "start": 493.38, "duration": 3.61}, {"text": "And after you\nallow your opponent", "start": 496.99, "duration": 2.39}, {"text": "to take a million\nphotos of him, you'll", "start": 499.38, "duration": 3.48}, {"text": "be able to read the\ncard although it", "start": 502.86, "duration": 2.43}, {"text": "[? will ?] not directly visible\nfrom your point of view.", "start": 505.29, "duration": 4.51}, {"text": "So you can kind of\nlook around an uploader", "start": 509.8, "duration": 3.499}, {"text": "and what's behind a corner.", "start": 513.299, "duration": 2.401}, {"text": "What's the-- what's the\nflaw in this argument", "start": 515.7, "duration": 1.959}, {"text": "that you can look in a corner?", "start": 517.659, "duration": 1.25}, {"text": "Yes.", "start": 521.98, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 522.48, "duration": 1.112}, {"text": "RAMESH RASKAR: Exactly.", "start": 523.592, "duration": 0.958}, {"text": "There's some device\nthat you have", "start": 524.55, "duration": 1.375}, {"text": "to place that's actually\nlooking at that card.", "start": 525.925, "duration": 4.385}, {"text": "So this is a beautiful\nproject from Stanford.", "start": 530.31, "duration": 3.57}, {"text": "And one of their funding\nagencies, of course, the army--", "start": 533.88, "duration": 3.262}, {"text": "and they would like to know\nwhat's around the corner.", "start": 537.142, "duration": 2.208}, {"text": "But of course you\nhave to go and place", "start": 539.35, "duration": 1.583}, {"text": "a projector in the enemy\nline to be able to figure out", "start": 540.933, "duration": 3.347}, {"text": "who's out there.", "start": 544.28, "duration": 2.18}, {"text": "So this is the\nmessage of this class.", "start": 546.46, "duration": 4.43}, {"text": "Pure digital cameras\nare extremely boring.", "start": 550.89, "duration": 3.178}, {"text": "And if you look at these\ntwo cameras, one of them", "start": 554.068, "duration": 2.042}, {"text": "is digital.", "start": 556.11, "duration": 0.54}, {"text": "One of them is phone.", "start": 556.65, "duration": 1.74}, {"text": "Can you really figure\nout which one is which?", "start": 558.39, "duration": 3.24}, {"text": "Left is digital.", "start": 561.63, "duration": 2.4}, {"text": "Right is digital.", "start": 564.03, "duration": 2.01}, {"text": "OK, and the rest are confused.", "start": 566.04, "duration": 2.79}, {"text": "So hardly any\ndifference between them,", "start": 568.83, "duration": 2.76}, {"text": "zoom, focus, aperture exposure,\nall the same old boring stuff.", "start": 571.59, "duration": 4.19}, {"text": "There's not much extra going on.", "start": 575.78, "duration": 1.66}, {"text": "And if somebody claims that\ndigital camera have spawned", "start": 577.44, "duration": 3.24}, {"text": "a new art form, probably not.", "start": 580.68, "duration": 1.412}, {"text": "I mean, you could just\ntake film cameras,", "start": 582.092, "duration": 1.708}, {"text": "scan them, and play with that.", "start": 583.8, "duration": 3.0}, {"text": "They're just faster,\nbetter, and cheaper.", "start": 586.8, "duration": 4.02}, {"text": "So when people think about\ncomputational photography", "start": 590.82, "duration": 5.34}, {"text": "and computational camera,\nthey start thinking about,", "start": 596.16, "duration": 2.79}, {"text": "wow, OK I have this\ncamera that doesn't", "start": 598.95, "duration": 2.73}, {"text": "do a very good job of dynamic\nrange and field of view", "start": 601.68, "duration": 4.87}, {"text": "and so on.", "start": 606.55, "duration": 1.24}, {"text": "So what I'm going to\ndo is somehow improve", "start": 607.79, "duration": 1.75}, {"text": "the performance of this camera.", "start": 609.54, "duration": 2.46}, {"text": "One common is by boosting\nthe dynamic range", "start": 612.0, "duration": 2.91}, {"text": "by taking multiple photo\nby exposure bracketing", "start": 614.91, "duration": 4.2}, {"text": "or having a larger\ndepth of field", "start": 619.11, "duration": 2.31}, {"text": "by taking multiple photo by\ntaking focus bracketing and so", "start": 621.42, "duration": 3.9}, {"text": "on.", "start": 625.32, "duration": 0.6}, {"text": "So to increase\nthe field of view,", "start": 625.92, "duration": 1.68}, {"text": "you're going to do a panorama\nand then stitch it together.", "start": 627.6, "duration": 3.76}, {"text": "If you want to increase\nthe frame rate,", "start": 631.36, "duration": 1.73}, {"text": "you're going to play with\nexposure time and so on.", "start": 633.09, "duration": 3.34}, {"text": "So this is what a lot of people\nthink about as computation", "start": 636.43, "duration": 3.08}, {"text": "camera and photography.", "start": 639.51, "duration": 1.62}, {"text": "I just want to emphasize\nthat this is not", "start": 641.13, "duration": 2.13}, {"text": "what we're going to talk\nabout in this class.", "start": 643.26, "duration": 2.4}, {"text": "These are concepts\nliterally easy to understand", "start": 645.66, "duration": 4.32}, {"text": "and I have a lot of lecture,\nnotes, and videos online.", "start": 649.98, "duration": 3.3}, {"text": "You can look it up.", "start": 653.28, "duration": 1.2}, {"text": "In a couple of hours.", "start": 654.48, "duration": 1.02}, {"text": "You will get a pretty good\noverview of all the things", "start": 655.5, "duration": 2.55}, {"text": "that can be done in this space.", "start": 658.05, "duration": 2.08}, {"text": "And if you go to\nFlickr, there are", "start": 660.13, "duration": 3.32}, {"text": "groups that are just\nexploring high dynamic range", "start": 663.45, "duration": 2.25}, {"text": "imaging, et cetera.", "start": 665.7, "duration": 1.08}, {"text": "So we are not really\ngoing to talk about that", "start": 666.78, "duration": 2.13}, {"text": "because all these\ntechniques are just", "start": 668.91, "duration": 1.8}, {"text": "trying to improve the\nperformance of a camera.", "start": 670.71, "duration": 3.03}, {"text": "It's not trying to change\nthe game of photography.", "start": 673.74, "duration": 4.79}, {"text": "So generalizing it even further,\nwhat we're going to look at", "start": 678.53, "duration": 3.5}, {"text": "is cameras that are not just\n2D sensors mimicking film.", "start": 682.03, "duration": 4.05}, {"text": "But they could be\nzero-dimensional sensors that", "start": 686.08, "duration": 2.58}, {"text": "are, as I said in\nbarcode scanner,", "start": 688.66, "duration": 2.43}, {"text": "and we'll look at time of\nflight, motion detection.", "start": 691.09, "duration": 3.3}, {"text": "One these sensors that you\nsee in flatbed scanners or fax", "start": 694.39, "duration": 2.85}, {"text": "machines or line scan cameras\nthat are used in photo finish", "start": 697.24, "duration": 4.02}, {"text": "at sports events, 2\nand 1/2 new sensors.", "start": 701.26, "duration": 3.69}, {"text": "3D sensors are a different kind\nand very quickly into 4D and 6D", "start": 704.95, "duration": 5.49}, {"text": "devices that are exploiting\ndeconvolution and tomography", "start": 710.44, "duration": 5.31}, {"text": "in medical imaging or scientific\nimaging and also displays", "start": 715.75, "duration": 3.24}, {"text": "that are four-dimensional\nand six-dimensional.", "start": 718.99, "duration": 3.86}, {"text": "So earlier we saw that you\ncan look around the corner", "start": 722.85, "duration": 4.02}, {"text": "by placing a device\nin the line of sight,", "start": 726.87, "duration": 3.73}, {"text": "which is the projector.", "start": 730.6, "duration": 2.3}, {"text": "Well, that was done three years\nago or four years ago, 2005.", "start": 732.9, "duration": 4.92}, {"text": "Do we have some\nnew machinery now", "start": 737.82, "duration": 2.16}, {"text": "that will allow us to\nlook around the corner?", "start": 739.98, "duration": 3.0}, {"text": "You're out here.", "start": 742.98, "duration": 0.675}, {"text": "The meetings are called.", "start": 746.77, "duration": 2.456}, {"text": "It's a good day.", "start": 749.226, "duration": 0.824}, {"text": "You're out here,\nand you want to see", "start": 754.19, "duration": 2.01}, {"text": "what's inside with a door\nthat's partially open.", "start": 756.2, "duration": 4.002}, {"text": "Is this possible?", "start": 760.202, "duration": 0.708}, {"text": "Or imagine your cameras that\nare right now in mobile devices.", "start": 764.62, "duration": 7.57}, {"text": "You have this thing that's\nshrinking every day,", "start": 772.19, "duration": 3.89}, {"text": "getting cheaper but also\nshrinking and actually", "start": 776.08, "duration": 2.46}, {"text": "degrading its signal to\nnoise ratio performance.", "start": 778.54, "duration": 3.57}, {"text": "But imagine if your whole\nLCD becomes photosensitive,", "start": 782.11, "duration": 5.58}, {"text": "so every pixel that's\nemitting on your LCD", "start": 787.69, "duration": 2.7}, {"text": "also becomes photosensitive--", "start": 790.39, "duration": 2.55}, {"text": "and companies like Sharp and\nPlanar are already doing that.", "start": 792.94, "duration": 3.33}, {"text": "So they have this\nLCD array where", "start": 796.27, "duration": 4.08}, {"text": "if you put a finger\ndirectly on top of the LCD,", "start": 800.35, "duration": 2.55}, {"text": "you can even look at the\nridges on this finger.", "start": 802.9, "duration": 5.91}, {"text": "So there's some very\nbeautiful opportunities.", "start": 808.81, "duration": 2.1}, {"text": "And I just saw\nKimo and Ted here.", "start": 810.91, "duration": 1.96}, {"text": "They have also a\nvery exciting project", "start": 812.87, "duration": 1.97}, {"text": "where they can use\nan ordinary camera", "start": 814.84, "duration": 1.8}, {"text": "to look at right down to the\nresolution of your ridges.", "start": 816.64, "duration": 5.43}, {"text": "Now the question is,\nif we redefine a camera", "start": 822.07, "duration": 5.35}, {"text": "not to be this\nperspective device that", "start": 827.42, "duration": 2.37}, {"text": "behaves like a pinhole camera--", "start": 829.79, "duration": 1.74}, {"text": "but the whole screen\nis like sensing.", "start": 831.53, "duration": 2.895}, {"text": "There's a fusion of\nsensor and optics.", "start": 837.02, "duration": 4.68}, {"text": "Think about in the\ndisplay domain a CRT.", "start": 841.7, "duration": 3.81}, {"text": "There is an emitter, the\nelectron beam, and then", "start": 845.51, "duration": 3.66}, {"text": "the receiver, which is\nthe phosphorescent screen.", "start": 849.17, "duration": 2.85}, {"text": "There's always a separation\nbetween what's emitting it", "start": 852.02, "duration": 3.27}, {"text": "and what's receiving it.", "start": 855.29, "duration": 1.78}, {"text": "And over time, of course,\nwe have a LCDs where", "start": 857.07, "duration": 4.25}, {"text": "everything is fused together.", "start": 861.32, "duration": 1.563}, {"text": "And if you think about\ncameras, it's the same.", "start": 862.883, "duration": 1.917}, {"text": "You have a lens\nthat's collecting,", "start": 864.8, "duration": 2.28}, {"text": "and then you have a\nsensor that's receiving.", "start": 867.08, "duration": 2.46}, {"text": "And we haven't thought\nthat there's always", "start": 869.54, "duration": 2.88}, {"text": "has to be some distance\nsufficient distance.", "start": 872.42, "duration": 2.52}, {"text": "If you have a 35\nmillimeter camera,", "start": 874.94, "duration": 1.71}, {"text": "you ought to have roughly 35\nmillimeters between your lens", "start": 876.65, "duration": 4.35}, {"text": "and your sensor.", "start": 881.0, "duration": 1.65}, {"text": "And we can throw away all\nthose constraints and all", "start": 882.65, "duration": 2.67}, {"text": "those assumptions,\nand we might be", "start": 885.32, "duration": 1.71}, {"text": "able to come up\nwith devices where", "start": 887.03, "duration": 1.92}, {"text": "the lens and the optics and the\nsensor is all just one thing.", "start": 888.95, "duration": 3.99}, {"text": "And that would be kind of the\nLCD equivalent of a camera.", "start": 892.94, "duration": 4.15}, {"text": "So this is something\nwe can think about.", "start": 897.09, "duration": 3.39}, {"text": "And these devices\nare coming mainly", "start": 900.48, "duration": 1.73}, {"text": "because they want to\nsupport touch sensing.", "start": 902.21, "duration": 2.76}, {"text": "But imagine the future if\nyou have your mobile device,", "start": 904.97, "duration": 3.28}, {"text": "and you can just wave\nit and take a picture--", "start": 908.25, "duration": 3.27}, {"text": "and because your\nsensor is so large,", "start": 911.52, "duration": 2.03}, {"text": "you'll be able to\ncollect a lot of light.", "start": 913.55, "duration": 2.34}, {"text": "And right now this it's\nnot even megapixel yet.", "start": 915.89, "duration": 3.49}, {"text": "But this will be a\nmegapixel, 10 megapixel.", "start": 919.38, "duration": 2.21}, {"text": "And you'll be able to multiplex\nthose pixels for color", "start": 921.59, "duration": 4.21}, {"text": "and infrared and all\nkinds of beautiful things,", "start": 925.8, "duration": 4.07}, {"text": "different speeds, and so on.", "start": 929.87, "duration": 2.23}, {"text": "So that's how we're going\nto think about in this class", "start": 932.1, "duration": 2.69}, {"text": "about cameras and photography.", "start": 934.79, "duration": 4.08}, {"text": "And the same with\nmedical imaging.", "start": 938.87, "duration": 2.82}, {"text": "Right now medical\nimaging is thought as--", "start": 941.69, "duration": 2.49}, {"text": "medical imaging today is\nvery similar to photography", "start": 944.18, "duration": 3.51}, {"text": "in the 1930s.", "start": 947.69, "duration": 1.98}, {"text": "The guy who took the photo was\nmore important than the people", "start": 949.67, "duration": 3.72}, {"text": "whose photo was being\ntaken sometimes,", "start": 953.39, "duration": 1.74}, {"text": "because those people\nhave to go to the sky", "start": 955.13, "duration": 2.34}, {"text": "and stand for some time.", "start": 957.47, "duration": 2.05}, {"text": "And he had this one specialized\ndevice called a camera.", "start": 959.52, "duration": 3.53}, {"text": "Everybody has to stand\nstill for a few seconds.", "start": 963.05, "duration": 2.37}, {"text": "You take a picture,\nand then you go home.", "start": 965.42, "duration": 2.46}, {"text": "And after a couple of days,\nyou get your photo back.", "start": 967.88, "duration": 2.76}, {"text": "And that's exactly what medical\nimaging is all about today.", "start": 970.64, "duration": 3.6}, {"text": "We have to go to\na special location", "start": 974.24, "duration": 2.04}, {"text": "to get our CAT scan or\nultrasound scan done.", "start": 976.28, "duration": 4.05}, {"text": "And our time is completely--", "start": 980.33, "duration": 3.39}, {"text": "our time is considered\nnot so important.", "start": 983.72, "duration": 2.58}, {"text": "The guy who's\nrunning the machine,", "start": 986.3, "duration": 1.44}, {"text": "he's very important\nbecause we have", "start": 987.74, "duration": 1.458}, {"text": "to make an appointment\nwith this guy.", "start": 989.198, "duration": 3.442}, {"text": "So can we bring--", "start": 992.64, "duration": 3.56}, {"text": "will medical imaging\nevolve to a stage", "start": 996.2, "duration": 2.34}, {"text": "where it's like\nphotography today?", "start": 998.54, "duration": 2.49}, {"text": "Clearly, when we take a photo\nif somebody spills a coffee,", "start": 1001.03, "duration": 4.05}, {"text": "we take a photo.", "start": 1005.08, "duration": 0.94}, {"text": "It's a very casual way of\nthinking about photography.", "start": 1006.02, "duration": 2.69}, {"text": "And then medical imaging\nevolved to a stage", "start": 1008.71, "duration": 2.28}, {"text": "where we can do that.", "start": 1010.99, "duration": 1.58}, {"text": "And it turns out we can.", "start": 1012.57, "duration": 1.0}, {"text": "There are certain directions,\ncertain computational methods", "start": 1013.57, "duration": 3.06}, {"text": "that we will be able to\ndevelop that will get rid", "start": 1016.63, "duration": 4.05}, {"text": "of older mindsets of how medical\ndevices are being developed.", "start": 1020.68, "duration": 6.83}, {"text": "So a very brief\nintroduction of where", "start": 1027.51, "duration": 3.24}, {"text": "I come from and our group\nhere Camera Culture.", "start": 1030.75, "duration": 3.97}, {"text": "So in the past I\nhave worked a lot", "start": 1034.72, "duration": 1.76}, {"text": "on [? conventional ?]\nillumination, different types", "start": 1036.48, "duration": 2.339}, {"text": "of projectors, creating\nmulti projector displays,", "start": 1038.819, "duration": 3.631}, {"text": "creating virtual reality\nsetups, augmented", "start": 1042.45, "duration": 4.139}, {"text": "reality, a lot of work\non pocket projectors", "start": 1046.589, "duration": 2.641}, {"text": "and augmented reality with\npocket projectors, interaction", "start": 1049.23, "duration": 3.3}, {"text": "paradigms, work with\nRFIDs and so on.", "start": 1052.53, "duration": 4.06}, {"text": "And in the last eight years or\nso, a lot of work in cameras", "start": 1056.59, "duration": 4.13}, {"text": "playing with shutter aperture,\nlight fields, illumination", "start": 1060.72, "duration": 4.89}, {"text": "wavelength, and\nsensors and so on.", "start": 1065.61, "duration": 3.79}, {"text": "And some of the questions we\ndiscuss in our group are this.", "start": 1069.4, "duration": 4.79}, {"text": "And what will the camera\nlook like in 10 or 20 years", "start": 1074.19, "duration": 4.02}, {"text": "from now?", "start": 1078.21, "duration": 0.96}, {"text": "I already gave you one\nkind of possible direction", "start": 1079.17, "duration": 3.99}, {"text": "where it might be\njust a flat screen,", "start": 1083.16, "duration": 2.43}, {"text": "or maybe it's just\nyour credit card.", "start": 1085.59, "duration": 1.72}, {"text": "But it could even be a\nretina display retinal sensor", "start": 1087.31, "duration": 4.91}, {"text": "and digital sensors.", "start": 1092.22, "duration": 2.22}, {"text": "How will the next\nbillion cameras", "start": 1094.44, "duration": 2.28}, {"text": "change our social fabric\nor social culture?", "start": 1096.72, "duration": 4.44}, {"text": "If you think about the--", "start": 1101.16, "duration": 1.482}, {"text": "if you think about\nthe internet, it", "start": 1102.642, "duration": 1.458}, {"text": "has been transformed by\nthe ability to search.", "start": 1104.1, "duration": 3.84}, {"text": "That includes indexing and\nsegmenting and sorting and all", "start": 1107.94, "duration": 4.8}, {"text": "those beautiful problems.", "start": 1112.74, "duration": 1.68}, {"text": "But image search even\ntoday remains an extremely", "start": 1114.42, "duration": 2.82}, {"text": "challenging problem.", "start": 1117.24, "duration": 2.32}, {"text": "So maybe we can change the\ngame and modify our devices,", "start": 1119.56, "duration": 6.86}, {"text": "modify our cameras,\nmodify our displays,", "start": 1126.42, "duration": 2.16}, {"text": "modify our storage\ndevices and so on.", "start": 1128.58, "duration": 2.95}, {"text": "So that image search\ncan become simpler.", "start": 1131.53, "duration": 4.43}, {"text": "OK.", "start": 1135.96, "duration": 0.57}, {"text": "If they magically\nhave a camera that's", "start": 1136.53, "duration": 2.28}, {"text": "100 megapixel, when\nI take your photo,", "start": 1138.81, "duration": 3.54}, {"text": "I can Zoom in all the\nway down to your iris.", "start": 1142.35, "duration": 3.03}, {"text": "And if I have an\niris detector, then I", "start": 1145.38, "duration": 2.28}, {"text": "have very easy identification.", "start": 1147.66, "duration": 1.29}, {"text": "And all the photos I take\nof Dina, for example,", "start": 1148.95, "duration": 2.28}, {"text": "they're all indexed\nwith her iris code.", "start": 1151.23, "duration": 4.89}, {"text": "So that's kind of a\nvery [INAUDIBLE] level", "start": 1156.12, "duration": 2.79}, {"text": "way of thinking about\nsimplifying image search.", "start": 1158.91, "duration": 3.06}, {"text": "But we'll look at a\nvery interesting example", "start": 1161.97, "duration": 1.95}, {"text": "that exploit thermal IR imaging,\nelectric cameras and so on.", "start": 1163.92, "duration": 6.24}, {"text": "What will happen when for\nthis recording is being", "start": 1170.16, "duration": 3.03}, {"text": "used not just by\nthe big brother,", "start": 1173.19, "duration": 1.71}, {"text": "but it's actually being used\nfor some beneficial purposes", "start": 1174.9, "duration": 3.12}, {"text": "in commercial settings?", "start": 1178.02, "duration": 1.53}, {"text": "So imagine a scenario something\nlike Google Earth live", "start": 1179.55, "duration": 4.83}, {"text": "where right now you\ncan go to Google Earth", "start": 1184.38, "duration": 3.09}, {"text": "and fire up the browser, and you\ncan go to any part of the world", "start": 1187.47, "duration": 4.65}, {"text": "and see how it looks about\nsix months ago or a year ago.", "start": 1192.12, "duration": 6.63}, {"text": "But imagine if you can\njust fire up your browser", "start": 1198.75, "duration": 2.31}, {"text": "and go to this location\nlive as it's happening now.", "start": 1201.06, "duration": 4.658}, {"text": "And of course, you can move your\nslider and go back and forth", "start": 1205.718, "duration": 2.542}, {"text": "and back.", "start": 1208.26, "duration": 1.42}, {"text": "So if you have a camera on\nevery street pole, every bus,", "start": 1209.68, "duration": 4.19}, {"text": "every taxi, every person\nand all those data", "start": 1213.87, "duration": 3.51}, {"text": "all that data is being\nstreamed on the network,", "start": 1217.38, "duration": 3.87}, {"text": "so you can go to any part\nof the world and see it,", "start": 1221.25, "duration": 3.81}, {"text": "how will that world look like?", "start": 1225.06, "duration": 1.92}, {"text": "I'm sure many of you\nare definitely scared--", "start": 1226.98, "duration": 4.32}, {"text": "and given all the privacy\nand security notions of it.", "start": 1231.3, "duration": 4.86}, {"text": "But this could become\nvery similar to the safety", "start": 1236.16, "duration": 4.53}, {"text": "we have a little bit\nin our financial system", "start": 1240.69, "duration": 3.49}, {"text": "our financial transactions.", "start": 1244.18, "duration": 1.22}, {"text": "When I use my card in a\nrestaurant, a bunch of people", "start": 1245.4, "duration": 3.39}, {"text": "actually see my credit card\nnumber and all the information.", "start": 1248.79, "duration": 2.835}, {"text": "The waitress looks at the card.", "start": 1251.625, "duration": 2.145}, {"text": "And the owner knows it.", "start": 1253.77, "duration": 1.08}, {"text": "The bank knows it.", "start": 1254.85, "duration": 1.23}, {"text": "The credit card\ncompany knows it.", "start": 1256.08, "duration": 1.487}, {"text": "And the government, of\ncourse, knows it and so on.", "start": 1257.567, "duration": 2.083}, {"text": "And a lot of people know about\nyour financial transactions.", "start": 1259.65, "duration": 2.458}, {"text": "But somehow you are\ncompletely comfortable sharing", "start": 1262.108, "duration": 3.242}, {"text": "your financial data.", "start": 1265.35, "duration": 1.83}, {"text": "And similarly can we create\ncameras and photography", "start": 1267.18, "duration": 3.66}, {"text": "and imaging infrastructure\nso that if you walk down", "start": 1270.84, "duration": 3.24}, {"text": "the street, and all these\ncameras are looking at you,", "start": 1274.08, "duration": 2.97}, {"text": "anybody in the world could\nbe looking at your live?", "start": 1277.05, "duration": 2.22}, {"text": "You feel completely\nsecure that it's", "start": 1279.27, "duration": 2.19}, {"text": "being used only by the right\npeople for the right reasons.", "start": 1281.46, "duration": 3.16}, {"text": "And if you don't\nwant them to see it,", "start": 1284.62, "duration": 1.55}, {"text": "you have some switch on you that\nsays, I'm completely invisible.", "start": 1286.17, "duration": 3.57}, {"text": "And you should be able\nto walk down the street.", "start": 1289.74, "duration": 3.09}, {"text": "Can we create such an\nimaging infrastructure?", "start": 1292.83, "duration": 2.63}, {"text": "Think about high speed cameras\nand high resolution cameras.", "start": 1298.1, "duration": 2.49}, {"text": "Maybe we'll have microscopes\nand nano scopes with us", "start": 1300.59, "duration": 2.76}, {"text": "that will again change the way\nwe think about medical imaging.", "start": 1303.35, "duration": 4.2}, {"text": "And what about movie\nmaking and news reporting?", "start": 1307.55, "duration": 3.15}, {"text": "As you know it has dramatically\nchanged over the last three", "start": 1310.7, "duration": 3.84}, {"text": "or four years because,\nagain, a billion people", "start": 1314.54, "duration": 2.01}, {"text": "have cameras out there.", "start": 1316.55, "duration": 1.65}, {"text": "Whether there is an\nin Tibet or there's", "start": 1318.2, "duration": 3.75}, {"text": "a satellite image of\nwhat's going on in Burma", "start": 1321.95, "duration": 3.15}, {"text": "or a plane that's about to\ncrash, you get amazing videos.", "start": 1325.1, "duration": 5.25}, {"text": "And they're not captured by CNN.", "start": 1330.35, "duration": 1.8}, {"text": "They're captured\nby other people.", "start": 1332.15, "duration": 1.39}, {"text": "So how are we going\nto, again, change", "start": 1333.54, "duration": 3.5}, {"text": "this imaging infrastructure,\nthe whole pipeline,", "start": 1337.04, "duration": 3.12}, {"text": "to think about the future of\nmoviemaking and news reporting?", "start": 1340.16, "duration": 7.53}, {"text": "So overall in this\ncourse, we're not", "start": 1347.69, "duration": 2.43}, {"text": "going to think purely\nabout software.", "start": 1350.12, "duration": 2.53}, {"text": "We're going to think about\nhow we can change the camera,", "start": 1352.65, "duration": 4.55}, {"text": "not just use the camera.", "start": 1357.2, "duration": 1.23}, {"text": "So that involves\noptics and illumination", "start": 1358.43, "duration": 1.92}, {"text": "and sensor and\nmotion of the sensor,", "start": 1360.35, "duration": 2.37}, {"text": "motion of the optics, the\ndifferent wavelengths, 3D", "start": 1362.72, "duration": 5.31}, {"text": "cameras, polarization, probes\nand actuators and also priors", "start": 1368.03, "duration": 5.25}, {"text": "and online collections,\nthe network.", "start": 1373.28, "duration": 5.34}, {"text": "And one kind of\ntheme you'll see is", "start": 1378.62, "duration": 4.41}, {"text": "after years of research\nin computer vision, one", "start": 1383.03, "duration": 3.24}, {"text": "could argue that we have\nexhausted the bits that", "start": 1386.27, "duration": 3.68}, {"text": "are available in pixels.", "start": 1389.95, "duration": 1.0}, {"text": "There's still a lot to be done.", "start": 1390.95, "duration": 1.21}, {"text": "There's a lot to be done.", "start": 1392.16, "duration": 1.042}, {"text": "Still challenging even today\nwith sophisticated computing", "start": 1395.6, "duration": 2.7}, {"text": "algorithms, it's challenging.", "start": 1398.3, "duration": 1.63}, {"text": "So maybe we can build\nfeature revealing cameras", "start": 1399.93, "duration": 3.32}, {"text": "that will go hand in hand with\nexisting or modern [INAUDIBLE]", "start": 1403.25, "duration": 6.48}, {"text": "algorithms so that we can\nprocess photons and create", "start": 1409.73, "duration": 4.02}, {"text": "this meta structure for\nour imaging pipeline.", "start": 1413.75, "duration": 5.38}, {"text": "So what we're going\nto do today is", "start": 1419.13, "duration": 3.14}, {"text": "I'll briefly describe\nwhat this course is about,", "start": 1422.27, "duration": 3.06}, {"text": "do some introductions.", "start": 1425.33, "duration": 1.59}, {"text": "And the second half,\nwe will come around", "start": 1426.92, "duration": 2.25}, {"text": "and do a fast forward preview\nof the [? core ?] groups, OK.", "start": 1429.17, "duration": 6.82}, {"text": "So in the next few\nslides, I'm just", "start": 1435.99, "duration": 2.0}, {"text": "going to give you a\nquick kind of rundown", "start": 1437.99, "duration": 2.49}, {"text": "of what this course\nis about, the layout.", "start": 1440.48, "duration": 2.61}, {"text": "Here's a nice overview of the\nbiological successful vision", "start": 1452.86, "duration": 7.89}, {"text": "in the animal eyes.", "start": 1460.75, "duration": 1.71}, {"text": "And there's a nice\npaper in Science.", "start": 1462.46, "duration": 3.18}, {"text": "And you can take all the\nsuccessful biological vision", "start": 1465.64, "duration": 3.93}, {"text": "and place that in kind\nof eight categories.", "start": 1469.57, "duration": 4.14}, {"text": "You have eyes based on\nshadows, based on refraction,", "start": 1473.71, "duration": 3.84}, {"text": "based on reflection,\nsingle chambered eyes,", "start": 1477.55, "duration": 4.02}, {"text": "or compound eyes\nsometimes with apposition,", "start": 1481.57, "duration": 3.78}, {"text": "sometimes with\nsuperposition, and so on.", "start": 1485.35, "duration": 2.55}, {"text": "We'll come back and\ndiscuss this more.", "start": 1487.9, "duration": 1.8}, {"text": "If you look at the\neyes of a scallop,", "start": 1489.7, "duration": 5.22}, {"text": "it's based on a\nmirror, not on a lens.", "start": 1494.92, "duration": 2.28}, {"text": "So you have a mirror down here,\nand the sensor is up here.", "start": 1497.2, "duration": 4.77}, {"text": "And light actually reflects\nfrom this concave mirror.", "start": 1501.97, "duration": 4.29}, {"text": "And the image is\nfound on the detector.", "start": 1506.26, "duration": 2.79}, {"text": "And the future camera in your\nmobile device on a flat sensor", "start": 1509.05, "duration": 6.24}, {"text": "could be on this architecture.", "start": 1515.29, "duration": 2.43}, {"text": "It doesn't have to be on this\nsingle chamber high refraction.", "start": 1517.72, "duration": 3.85}, {"text": "So the human vision is\nin this corner here.", "start": 1521.57, "duration": 3.77}, {"text": "It's a single chamber\ndesign with lenses.", "start": 1525.34, "duration": 3.495}, {"text": "And all the cameras, at least\nall the standard cameras", "start": 1528.835, "duration": 3.465}, {"text": "that we know of are in\nthis particular part.", "start": 1532.3, "duration": 4.45}, {"text": "But this is a lot to explore.", "start": 1536.75, "duration": 2.3}, {"text": "And that doesn't even\nexplore computation.", "start": 1539.05, "duration": 1.86}, {"text": "This is pretty much raw imaging\nthat these animals are using.", "start": 1540.91, "duration": 4.8}, {"text": "So film light, traditional\nphotography, light", "start": 1545.71, "duration": 4.29}, {"text": "comes in through the lens.", "start": 1550.0, "duration": 1.63}, {"text": "It falls on the\ndetector of the film,", "start": 1551.63, "duration": 2.057}, {"text": "and that's the end of the story.", "start": 1553.687, "duration": 1.333}, {"text": "That's your photon.", "start": 1555.02, "duration": 0.792}, {"text": "And you just\ntransfer it digitally", "start": 1555.812, "duration": 2.168}, {"text": "or by chemical processing,\nand you should see it.", "start": 1557.98, "duration": 4.77}, {"text": "Computational camera is\na little bit different.", "start": 1562.75, "duration": 2.8}, {"text": "We're going to have\nsome crazy optics that's", "start": 1565.55, "duration": 3.29}, {"text": "going to think about how\nrays and wavelengths are", "start": 1568.84, "duration": 2.31}, {"text": "manipulated.", "start": 1571.15, "duration": 1.29}, {"text": "We're going to have a sensor\nthat's not just mimicking film.", "start": 1572.44, "duration": 3.24}, {"text": "It's not going to be\na [? flag ?] sensor.", "start": 1575.68, "duration": 1.83}, {"text": "It'll have its own geometry\nand spectrum and so on.", "start": 1577.51, "duration": 5.13}, {"text": "And what you see finally\nwill not be just a raw image", "start": 1582.64, "duration": 4.47}, {"text": "but will have some\nreconstruction and computation", "start": 1587.11, "duration": 3.54}, {"text": "on top.", "start": 1590.65, "duration": 0.54}, {"text": "So that's computational camera.", "start": 1591.19, "duration": 1.292}, {"text": "That would be what's in\nthe conventional camera.", "start": 1597.41, "duration": 2.213}, {"text": "But there's also\nan element that's", "start": 1599.623, "duration": 1.417}, {"text": "outside the camera,\nwhich is like--", "start": 1601.04, "duration": 1.89}, {"text": "and it's sort of\njust a flashlight.", "start": 1602.93, "duration": 2.4}, {"text": "You're going to\nhave a flashlight", "start": 1605.33, "duration": 1.89}, {"text": "with sophisticated modulators\nthat are changing the intensity", "start": 1607.22, "duration": 3.75}, {"text": "and phase and polarization of\nlight in different directions,", "start": 1610.97, "duration": 4.84}, {"text": "different kinds of\nadditional optics, and so on.", "start": 1615.81, "duration": 3.0}, {"text": "So once you have a\nprogrammable light", "start": 1618.81, "duration": 1.94}, {"text": "and a computational\ncamera, we have a framework", "start": 1620.75, "duration": 3.06}, {"text": "to really exploit and\nunderstand the light transport", "start": 1623.81, "duration": 4.62}, {"text": "in the scene.", "start": 1628.43, "duration": 2.74}, {"text": "So something interesting is\nhappening in the camera work.", "start": 1631.17, "duration": 5.16}, {"text": "We are here 2008, 2009.", "start": 1636.33, "duration": 3.02}, {"text": "About a billion\ncameras are being", "start": 1639.35, "duration": 2.49}, {"text": "sold every year, which is fine.", "start": 1641.84, "duration": 4.71}, {"text": "Most people know that.", "start": 1646.55, "duration": 1.05}, {"text": "But if you just go\nback about six years,", "start": 1647.6, "duration": 2.96}, {"text": "2001, 2002, 0 cameras were sold\nembedded in a mobile phone.", "start": 1650.56, "duration": 7.62}, {"text": "So we have gone from 0 to a\nbillion in just six years.", "start": 1658.18, "duration": 7.06}, {"text": "So it's just an amazing\ntime to think about imaging.", "start": 1665.24, "duration": 5.88}, {"text": "And this is very\nmuch like all the fun", "start": 1671.12, "duration": 2.99}, {"text": "in networking and\ncommunication back", "start": 1674.11, "duration": 1.71}, {"text": "in the '90s when millions of\npeople were coming on board", "start": 1675.82, "duration": 3.75}, {"text": "and thousands of\nwebsites were going on.", "start": 1679.57, "duration": 3.39}, {"text": "And that was computing.", "start": 1682.96, "duration": 3.57}, {"text": "And this is the time\nfor visual computing.", "start": 1686.53, "duration": 2.97}, {"text": "And because this game\nis changing so fast", "start": 1689.5, "duration": 2.64}, {"text": "in terms of cost, in\nterms of performance,", "start": 1692.14, "duration": 4.32}, {"text": "applications where\nimaging was considered", "start": 1696.46, "duration": 5.001}, {"text": "not the perfect\nsolution is changing.", "start": 1701.461, "duration": 3.489}, {"text": "We are seeing cameras being used\nin some really casual and very", "start": 1704.95, "duration": 4.35}, {"text": "strange ways.", "start": 1709.3, "duration": 2.67}, {"text": "And here's an indication\nof where that's going.", "start": 1711.97, "duration": 2.67}, {"text": "So where are these cameras?", "start": 1714.64, "duration": 1.77}, {"text": "Remember, cameras are not just\n2D sensors for photography,", "start": 1716.41, "duration": 4.44}, {"text": "but they're used\nin various ways.", "start": 1720.85, "duration": 4.09}, {"text": "So we are here, 2008, 2009.", "start": 1724.94, "duration": 4.4}, {"text": "The pink here is because\nof mobile phones.", "start": 1729.34, "duration": 3.54}, {"text": "About a billion\nsensors are being sold.", "start": 1732.88, "duration": 3.9}, {"text": "Any guesses about what\nthese other slivers", "start": 1736.78, "duration": 2.79}, {"text": "are, the blue one, the\ngreen one, and so on?", "start": 1739.57, "duration": 4.11}, {"text": "There are a couple\nof million here.", "start": 1743.68, "duration": 4.47}, {"text": "About 100 million\nhere are being sold.", "start": 1748.15, "duration": 3.882}, {"text": "I guess [INAUDIBLE].", "start": 1752.032, "duration": 2.138}, {"text": "Sorry.", "start": 1754.17, "duration": 0.5}, {"text": "AUDIENCE: Optical mouse.", "start": 1754.67, "duration": 1.32}, {"text": "RAMESH RASKAR: Optical\nmouse, very good, very good.", "start": 1755.99, "duration": 2.826}, {"text": "AUDIENCE: Gaming.", "start": 1758.816, "duration": 0.787}, {"text": "RAMESH RASKAR: Gaming.", "start": 1759.603, "duration": 0.917}, {"text": "So if you think about--", "start": 1760.52, "duration": 1.44}, {"text": "we, I think, sold like\n30 million remotes.", "start": 1761.96, "duration": 3.84}, {"text": "30 million remotes were sold.", "start": 1765.8, "duration": 1.507}, {"text": "And this chart is\nactually made before that.", "start": 1767.307, "duration": 1.833}, {"text": "So that's not even here, but\nthat's going to be big, yes.", "start": 1769.14, "duration": 3.74}, {"text": "And of course, there is\ntraditional photography.", "start": 1772.88, "duration": 3.21}, {"text": "But I'm glad you got\noptical mouse because that's", "start": 1776.09, "duration": 3.21}, {"text": "one of the largest markets.", "start": 1779.3, "duration": 1.41}, {"text": "It's basically a\nvery low resolution,", "start": 1780.71, "duration": 2.4}, {"text": "usually 20x20 or 32x32\npixel camera that's", "start": 1783.11, "duration": 3.42}, {"text": "running 1,000 or 2,000 Hz.", "start": 1786.53, "duration": 2.25}, {"text": "It's a high speed camera\nthat's doing optical flow", "start": 1788.78, "duration": 2.34}, {"text": "to figure out where your\nmouse is even if you put it", "start": 1791.12, "duration": 2.52}, {"text": "on a very clear surface.", "start": 1793.64, "duration": 4.17}, {"text": "And the mobile phones\nand digital cameras--", "start": 1797.81, "duration": 2.43}, {"text": "and all this worry about big\nbrother, think about security.", "start": 1800.24, "duration": 4.68}, {"text": "It's a very, very tiny sliver.", "start": 1804.92, "duration": 3.76}, {"text": "And if you think about the\nfirst three categories here,", "start": 1808.68, "duration": 3.89}, {"text": "optical mouse mobile phones,\nand digital and video cameras,", "start": 1812.57, "duration": 5.4}, {"text": "these are all personal devices.", "start": 1817.97, "duration": 1.65}, {"text": "And this is going to scale\nwith the number of people", "start": 1819.62, "duration": 2.37}, {"text": "in the world.", "start": 1821.99, "duration": 1.08}, {"text": "So this will easily become\n6 billion or 6.5 billion,", "start": 1823.07, "duration": 3.12}, {"text": "whatever we have.", "start": 1826.19, "duration": 1.59}, {"text": "But these other slivers\nmay or may not grow.", "start": 1827.78, "duration": 2.31}, {"text": "Gaming, for example, could\nstill grow very rapidly", "start": 1830.09, "duration": 2.64}, {"text": "because almost every\nperson individually", "start": 1832.73, "duration": 2.49}, {"text": "might own a game console.", "start": 1835.22, "duration": 3.01}, {"text": "So very interesting here.", "start": 1838.23, "duration": 3.68}, {"text": "If we look around the\ninternet, cameras are being--", "start": 1841.91, "duration": 4.86}, {"text": "sometimes it's just silly.", "start": 1846.77, "duration": 2.76}, {"text": "You may know about\nthis do it yourself", "start": 1849.53, "duration": 2.67}, {"text": "green screen effects\ncompany, U-Start.", "start": 1852.2, "duration": 2.94}, {"text": "And they want to be the Guitar\nHero in the visual domain.", "start": 1855.14, "duration": 4.12}, {"text": "So instead of\nplaying music that's", "start": 1859.26, "duration": 2.06}, {"text": "synchronized with some\nprerecorded data, here", "start": 1861.32, "duration": 3.51}, {"text": "they have pre-recorded\nvideo segments.", "start": 1864.83, "duration": 1.92}, {"text": "And then you can\nstar in this movie.", "start": 1866.75, "duration": 1.98}, {"text": "It's pretty big.", "start": 1868.73, "duration": 2.1}, {"text": "If you go to their\nwebsite, a lot of people", "start": 1870.83, "duration": 2.5}, {"text": "are uploading their\nvideos with their software", "start": 1873.33, "duration": 2.963}, {"text": "and their experience screen.", "start": 1876.293, "duration": 1.167}, {"text": "All they give you is a\ncamera, a simple camera,", "start": 1877.46, "duration": 2.23}, {"text": "not even a studio pair,\njust a simple camera", "start": 1879.69, "duration": 2.3}, {"text": "and a big plastic green screen.", "start": 1881.99, "duration": 2.16}, {"text": "And they have some software for\ndoing screen mapping and so on.", "start": 1884.15, "duration": 4.84}, {"text": "You may be familiar\nwith this video.", "start": 1888.99, "duration": 4.293}, {"text": "Which company is that?", "start": 1893.283, "duration": 0.917}, {"text": "I forgot.", "start": 1894.2, "duration": 0.87}, {"text": "It's starts with M.\nIt's a studio webcam.", "start": 1895.07, "duration": 3.36}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 1898.43, "duration": 1.26}, {"text": "RAMESH RASKAR: It's a\nJapanese company, OK.", "start": 1899.69, "duration": 2.61}, {"text": "Some other interesting\nones, look at this one here.", "start": 1902.3, "duration": 2.28}, {"text": "Panasonic Beauty\nAppliance, what does it do?", "start": 1904.58, "duration": 2.76}, {"text": "Any guesses?", "start": 1907.34, "duration": 0.585}, {"text": "It's a pretty big camera.", "start": 1913.85, "duration": 2.28}, {"text": "It's a personal\nbeauty appliance where", "start": 1916.13, "duration": 3.75}, {"text": "it provides humidification\nin a very local spot.", "start": 1919.88, "duration": 3.66}, {"text": "So you can sit there and sit\nall day around and it I guess", "start": 1923.54, "duration": 4.05}, {"text": "maintains the right level of\nmoisture and humidity around.", "start": 1927.59, "duration": 4.1}, {"text": "So your skin won't get very dry.", "start": 1931.69, "duration": 2.057}, {"text": "What about this one?", "start": 1933.747, "duration": 0.833}, {"text": "The camera is not anywhere\nnear the eyesight.", "start": 1934.58, "duration": 2.82}, {"text": "But the camera is\nactually on the ear.", "start": 1937.4, "duration": 3.077}, {"text": "Can I look inside this?", "start": 1940.477, "duration": 0.958}, {"text": "I was reading up on this.", "start": 1945.44, "duration": 1.42}, {"text": "It wasn't very clear what\nthe applications are.", "start": 1946.86, "duration": 1.97}, {"text": "But you can think of it.", "start": 1948.83, "duration": 1.32}, {"text": "I mean, if you're\nwalking down the street", "start": 1950.15, "duration": 1.89}, {"text": "and you want to be safe,\nsomething's coming at you.", "start": 1952.04, "duration": 2.955}, {"text": "Maybe it tells you.", "start": 1954.995, "duration": 0.975}, {"text": "Or if there's somebody\nyou don't like--", "start": 1955.97, "duration": 2.52}, {"text": "they're walking towards you--", "start": 1958.49, "duration": 1.77}, {"text": "don't turn around.", "start": 1960.26, "duration": 3.015}, {"text": "Yeah.", "start": 1963.275, "duration": 0.675}, {"text": "And that's going to happen more\nand more, more crazy places.", "start": 1963.95, "duration": 4.32}, {"text": "I like this GigaPan\nEpic 100 which is", "start": 1968.27, "duration": 3.0}, {"text": "for creating panoramic imagery.", "start": 1971.27, "duration": 1.77}, {"text": "But it's actually basically\na tiny, tiny robotic platform", "start": 1973.04, "duration": 3.69}, {"text": "about $300 for an [INAUDIBLE].", "start": 1976.73, "duration": 3.0}, {"text": "And it has a physical lever that\npresses on the shutter as it", "start": 1979.73, "duration": 6.18}, {"text": "rotates around.", "start": 1985.91, "duration": 1.11}, {"text": "It's pretty amazing.", "start": 1987.02, "duration": 2.04}, {"text": "And of course Fuji is doing\nsome fantastic work just", "start": 1989.06, "duration": 4.11}, {"text": "starting with the studio pair.", "start": 1993.17, "duration": 1.335}, {"text": "And they're trying to provide a\nwhole pipeline all the way down", "start": 1994.505, "duration": 2.625}, {"text": "to printing on a\nlenticular screen", "start": 1997.13, "duration": 2.31}, {"text": "so you can enjoy\nthis studio box.", "start": 1999.44, "duration": 4.29}, {"text": "OK, so after you look\nat all this camera,", "start": 2003.73, "duration": 3.247}, {"text": "they say, OK, what\nelse is there to do", "start": 2006.977, "duration": 1.583}, {"text": "because you don't have\nto do much research to do", "start": 2008.56, "duration": 3.12}, {"text": "any one of these projects.", "start": 2011.68, "duration": 1.26}, {"text": "You don't have to take a class\nto build these applications.", "start": 2012.94, "duration": 5.86}, {"text": "So let's think about\nsomething trying to improve", "start": 2018.8, "duration": 2.07}, {"text": "the camera just a little bit.", "start": 2020.87, "duration": 1.85}, {"text": "All I want is depth per\npixel, something humans", "start": 2022.72, "duration": 4.44}, {"text": "seem to be doing very well.", "start": 2027.16, "duration": 1.992}, {"text": "We can use our two eyes and\nfigure out how far things are.", "start": 2029.152, "duration": 4.128}, {"text": "At least we think we\nknow how things are.", "start": 2033.28, "duration": 2.412}, {"text": "There's a lot of\nprior information.", "start": 2035.692, "duration": 1.458}, {"text": "But for a camera just to get\ndepth is extremely challenging.", "start": 2037.15, "duration": 5.43}, {"text": "After 34 years of research\nin computer vision,", "start": 2042.58, "duration": 3.36}, {"text": "still you can't go\nout there and buy", "start": 2045.94, "duration": 2.219}, {"text": "a camera that's a\nreasonable cost, which", "start": 2048.159, "duration": 3.391}, {"text": "runs at a reasonable\nspeed and gives you", "start": 2051.55, "duration": 2.07}, {"text": "that perfect [INAUDIBLE].", "start": 2053.62, "duration": 2.9}, {"text": "It's amazing.", "start": 2056.52, "duration": 1.35}, {"text": "So we'll show you what\nthe state of the art", "start": 2057.87, "duration": 2.13}, {"text": "is using this multi-thousand\ndollar camera.", "start": 2060.0, "duration": 5.269}, {"text": "This was donated to\nus by [INAUDIBLE]..", "start": 2065.269, "duration": 5.111}, {"text": "And [INAUDIBLE].", "start": 2070.38, "duration": 2.996}, {"text": "So this is camera that uses\ntime of flight to [INAUDIBLE]..", "start": 2076.84, "duration": 10.69}, {"text": "Oh, we don't use\n[INAUDIBLE] cameras as much.", "start": 2087.53, "duration": 3.55}, {"text": "OK, so this is time of flight.", "start": 2091.08, "duration": 3.18}, {"text": "All those alleles are being--", "start": 2094.26, "duration": 1.95}, {"text": "those of you who have a\ncell phone camera, just", "start": 2096.21, "duration": 2.55}, {"text": "look at this lights\nthrough your camera.", "start": 2098.76, "duration": 3.91}, {"text": "You'll see all of them\nare lit up in the air.", "start": 2102.67, "duration": 5.31}, {"text": "And as you can see here--", "start": 2107.98, "duration": 3.194}, {"text": "what is it looking at?", "start": 2111.174, "duration": 1.256}, {"text": "Is it [INAUDIBLE]?", "start": 2112.43, "duration": 1.172}, {"text": "OK, so the people\nin the front are", "start": 2116.26, "duration": 1.92}, {"text": "marked in green and somebody\nin the back over there.", "start": 2118.18, "duration": 3.3}, {"text": "Yeah, Martin.", "start": 2121.48, "duration": 1.47}, {"text": "So it's giving you some\nestimate of depth by doing", "start": 2122.95, "duration": 5.07}, {"text": "a time of light calculation.", "start": 2128.02, "duration": 1.59}, {"text": "Now that is the camera.", "start": 2129.61, "duration": 2.5}, {"text": "And it works OK.", "start": 2132.11, "duration": 1.01}, {"text": "But as you can see\nthe quality even", "start": 2133.12, "duration": 2.37}, {"text": "in this relatively\neasy configuration,", "start": 2135.49, "duration": 3.3}, {"text": "most of the objects\nare diffused.", "start": 2138.79, "duration": 2.04}, {"text": "There is no resistance.", "start": 2140.83, "duration": 1.26}, {"text": "The movement doesn't\nhave some light", "start": 2142.09, "duration": 1.92}, {"text": "to overwhelm this active light.", "start": 2144.01, "duration": 2.1}, {"text": "And even then the quality is OK.", "start": 2146.11, "duration": 2.55}, {"text": "It's not that great.", "start": 2148.66, "duration": 2.86}, {"text": "And I forget the exact\ncost of this one,", "start": 2151.52, "duration": 2.15}, {"text": "but they cost about\n$10,000, these cameras.", "start": 2153.67, "duration": 4.89}, {"text": "Go ahead.", "start": 2158.56, "duration": 0.5}, {"text": "AUDIENCE: What's is it called?", "start": 2159.06, "duration": 1.11}, {"text": "RAMESH RASKAR: This\none is Canesta.", "start": 2160.17, "duration": 1.53}, {"text": "Yeah, but during\nthe later classes", "start": 2161.7, "duration": 3.99}, {"text": "we'll learn about\nall the different 3D", "start": 2165.69, "duration": 2.55}, {"text": "cameras, whether they're based\non active light or stereo", "start": 2168.24, "duration": 3.54}, {"text": "or structured light,\npolarization, and so on.", "start": 2171.78, "duration": 3.8}, {"text": "So this one is going to start.", "start": 2175.58, "duration": 1.25}, {"text": "The other company is\n3DV, which was recently", "start": 2176.83, "duration": 7.33}, {"text": "bought by Microsoft.", "start": 2184.16, "duration": 1.11}, {"text": "And then there's a couple\nof companies in Germany", "start": 2187.82, "duration": 4.77}, {"text": "who are building 3D cameras.", "start": 2192.59, "duration": 2.76}, {"text": "And apparently\nthis market is now", "start": 2195.35, "duration": 2.22}, {"text": "being driven by game\nconsoles because PlayStation", "start": 2197.57, "duration": 3.3}, {"text": "and Xbox are all\ninterested in using", "start": 2200.87, "duration": 2.97}, {"text": "3D cameras in the\nhouse for gaming,", "start": 2203.84, "duration": 4.93}, {"text": "for interacting with gestures.", "start": 2208.77, "duration": 1.44}, {"text": "So they want to distinguish\nthis from this, for example,", "start": 2210.21, "duration": 3.32}, {"text": "because right now all the\ngames are in the gulag.", "start": 2213.53, "duration": 2.82}, {"text": "The hands are away from\nyour body to play the games.", "start": 2216.35, "duration": 3.21}, {"text": "I-toy and Xbox and so on.", "start": 2219.56, "duration": 2.32}, {"text": "But the new ones will\nallow you to do gestures", "start": 2221.88, "duration": 3.74}, {"text": "that are more intricate.", "start": 2225.62, "duration": 4.06}, {"text": "So there are too\nmany challenges just", "start": 2229.68, "duration": 3.59}, {"text": "to get 3D because we have to\nuse some kind of active light", "start": 2233.27, "duration": 4.26}, {"text": "to compensate for\nambient scenes.", "start": 2237.53, "duration": 3.72}, {"text": "You have to stitch geometric\ncapture from multiple views.", "start": 2241.25, "duration": 5.88}, {"text": "If you have something\nlike marble or skin,", "start": 2247.13, "duration": 3.82}, {"text": "it has subsurface scattering.", "start": 2250.95, "duration": 1.31}, {"text": "So that's difficult\nto deal with.", "start": 2252.26, "duration": 1.65}, {"text": "I cannot do triangulation.", "start": 2253.91, "duration": 2.37}, {"text": "And objects that are diffused\nhave diffuse reflection", "start": 2256.28, "duration": 4.98}, {"text": "component.", "start": 2261.26, "duration": 0.69}, {"text": "If you go into something\nthat has glass or are dark,", "start": 2261.95, "duration": 3.69}, {"text": "it's just out of caution.", "start": 2265.64, "duration": 2.34}, {"text": "So computational camera,\nit should do something", "start": 2267.98, "duration": 4.86}, {"text": "more than just\ncapturing a 2D image.", "start": 2272.84, "duration": 3.45}, {"text": "And those of you who are\nhere building real time and C", "start": 2276.29, "duration": 4.11}, {"text": "applications for robotics,\nanything like that.", "start": 2280.4, "duration": 5.73}, {"text": "There's no camera\nright now that can", "start": 2286.13, "duration": 2.85}, {"text": "deal with objects like this.", "start": 2288.98, "duration": 1.26}, {"text": "This is amazing.", "start": 2290.24, "duration": 1.71}, {"text": "So we have a billion\ncameras out there.", "start": 2291.95, "duration": 2.26}, {"text": "But none of those cameras\ncan solve this problem.", "start": 2294.21, "duration": 3.06}, {"text": "So that's what I want to\nlook at in this class.", "start": 2297.27, "duration": 2.17}, {"text": "AUDIENCE: Can I ask a\nquick question about that?", "start": 2299.44, "duration": 2.0}, {"text": "RAMESH RASKAR: Yeah.", "start": 2301.44, "duration": 0.26}, {"text": "AUDIENCE: So I'm\njust thinking back", "start": 2301.7, "duration": 1.53}, {"text": "to the traditional\nfilm type camera that", "start": 2303.23, "duration": 3.03}, {"text": "has autofocus sensors\nthat are contrast based", "start": 2306.26, "duration": 3.09}, {"text": "or a rangefinder type thing.", "start": 2309.35, "duration": 1.62}, {"text": "So that in a way gives you depth\nby moving optical elements.", "start": 2310.97, "duration": 5.58}, {"text": "But this doesn't have any\nmoving parts, I guess.", "start": 2316.55, "duration": 3.435}, {"text": "Does that count as a way to\ntry to make a camera that", "start": 2319.985, "duration": 3.717}, {"text": "perceives depth by\nhaving something", "start": 2323.702, "duration": 1.458}, {"text": "that scans physical optics--", "start": 2325.16, "duration": 2.342}, {"text": "RAMESH RASKAR: Exactly.", "start": 2327.502, "duration": 0.958}, {"text": "AUDIENCE: --around.", "start": 2328.46, "duration": 0.39}, {"text": "RAMESH RASKAR: I\nthink you're asking", "start": 2328.85, "duration": 1.5}, {"text": "a very important question.", "start": 2330.35, "duration": 1.11}, {"text": "Let's see if I have a slide.", "start": 2331.46, "duration": 1.167}, {"text": "So if you think\nabout a different way", "start": 2332.627, "duration": 3.543}, {"text": "of scanning in 3D.", "start": 2336.17, "duration": 0.87}, {"text": "And this is by the way--", "start": 2337.04, "duration": 1.35}, {"text": "it's one of our\nvisiting students", "start": 2338.39, "duration": 2.07}, {"text": "Doug Lanman and Gabriel Taubin.", "start": 2340.46, "duration": 2.73}, {"text": "They have a beautiful\ncourse at SIGGRAPH", "start": 2343.19, "duration": 2.19}, {"text": "on all different ways\nof doing 3D scanning.", "start": 2345.38, "duration": 4.35}, {"text": "And they're contact based\nand then non-contact based.", "start": 2349.73, "duration": 3.6}, {"text": "And right now we're talking\nabout mostly active by using", "start": 2353.33, "duration": 3.06}, {"text": "time of flight and so on.", "start": 2356.39, "duration": 1.21}, {"text": "But they're of course passive\nas well studio and motion", "start": 2357.6, "duration": 3.86}, {"text": "and so on based on\nfocus and defocus.", "start": 2361.46, "duration": 2.24}, {"text": "That may be a good segue way\nto actually look at this camera", "start": 2363.7, "duration": 2.5}, {"text": "here.", "start": 2366.2, "duration": 0.73}, {"text": "And Ms. Emily, you\nwant to run it?", "start": 2366.93, "duration": 1.76}, {"text": "AUDIENCE: Yeah, [INAUDIBLE]", "start": 2368.69, "duration": 0.69}, {"text": "RAMESH RASKAR: Yeah.", "start": 2369.38, "duration": 0.833}, {"text": "So this camera is\ncompletely passive.", "start": 2370.213, "duration": 2.977}, {"text": "It's like a full\ncamera, which has--", "start": 2373.19, "duration": 3.801}, {"text": "You want to talk about it.", "start": 2376.991, "duration": 2.019}, {"text": "AUDIENCE: Yeah, basically\nit's 25 separate images,", "start": 2379.01, "duration": 2.38}, {"text": "each one of these is\na separate camera.", "start": 2381.39, "duration": 1.625}, {"text": "RAMESH RASKAR: Which\nis on a single chassis.", "start": 2383.015, "duration": 1.833}, {"text": "AUDIENCE: Yeah, and they're\njust 25 to 30 minutes.", "start": 2384.848, "duration": 2.212}, {"text": "But each one's from a slightly\ndifferent perspective.", "start": 2389.91, "duration": 3.67}, {"text": "So you can do things like\nadd all the images together", "start": 2393.58, "duration": 2.27}, {"text": "but slightly shift them.", "start": 2395.85, "duration": 2.31}, {"text": "So I can focus down at infinity\ntowards the end of the table.", "start": 2398.16, "duration": 5.34}, {"text": "Or I can change the\nfocus by just simply", "start": 2403.5, "duration": 3.75}, {"text": "by shifting or moving the\nimages to focus right there.", "start": 2407.25, "duration": 4.0}, {"text": "RAMESH RASKAR: So remember\nhe's doing all this operation", "start": 2411.25, "duration": 2.45}, {"text": "in software.", "start": 2413.7, "duration": 1.44}, {"text": "You can take those 25 images.", "start": 2415.14, "duration": 1.77}, {"text": "And then in software you can\nrefocus it anywhere you want.", "start": 2416.91, "duration": 3.16}, {"text": "And then, again, based\non maximum contrast", "start": 2420.07, "duration": 5.57}, {"text": "or one of those operators.", "start": 2425.64, "duration": 1.41}, {"text": "You could potentially\nfigure out what's in front", "start": 2427.05, "duration": 3.672}, {"text": "or what's behind.", "start": 2430.722, "duration": 0.708}, {"text": "But of course, if you put\nin some transparent object,", "start": 2431.43, "duration": 3.4}, {"text": "it's going to be quite\nchallenging to figure out", "start": 2434.83, "duration": 2.0}, {"text": "where this is.", "start": 2436.83, "duration": 0.99}, {"text": "If I just put something\nthat's really flat,", "start": 2437.82, "duration": 3.37}, {"text": "then it wouldn't know\nwhether it's in focus", "start": 2441.19, "duration": 1.85}, {"text": "or not in focus in the\nmiddle of the paper.", "start": 2443.04, "duration": 1.86}, {"text": "It might be able to do an OK job\non the boundaries of the paper.", "start": 2444.9, "duration": 3.99}, {"text": "Or in the middle of the\npaper it always looks", "start": 2448.89, "duration": 1.89}, {"text": "like it's low frequency.", "start": 2450.78, "duration": 3.76}, {"text": "So these kind of\ncameras are coming.", "start": 2454.54, "duration": 3.69}, {"text": "You can buy this camera for\nabout $20,000 from U-Plus.", "start": 2458.23, "duration": 5.43}, {"text": "So far we are up to\nwhat, 30, up to 30K.", "start": 2463.66, "duration": 4.06}, {"text": "We did 10, 120.", "start": 2467.72, "duration": 2.15}, {"text": "The next one will be--", "start": 2469.87, "duration": 1.32}, {"text": "we'll get to 60s\nvery quickly, 60K.", "start": 2471.19, "duration": 3.6}, {"text": "And if you, again, think\nabout your cell phone camera,", "start": 2474.79, "duration": 5.76}, {"text": "the current mindset\nin camera makers", "start": 2480.55, "duration": 3.187}, {"text": "is that they want to shrink\nit, something that's smaller", "start": 2483.737, "duration": 2.333}, {"text": "and smaller and smaller.", "start": 2486.07, "duration": 2.01}, {"text": "But if you want to\ncreate enough baseline,", "start": 2488.08, "duration": 1.89}, {"text": "create some kind of focus\nbased depth extraction,", "start": 2489.97, "duration": 3.9}, {"text": "for example, as we're\nlooking at here,", "start": 2493.87, "duration": 1.74}, {"text": "we must have some\nbaseline between them.", "start": 2495.61, "duration": 1.715}, {"text": "And that's what\nthis camera does.", "start": 2497.325, "duration": 1.375}, {"text": "It's still pretty compact.", "start": 2498.7, "duration": 1.18}, {"text": "I forget.", "start": 2499.88, "duration": 0.5}, {"text": "I think 6 centimeters\ntotal, something like that.", "start": 2500.38, "duration": 3.11}, {"text": "I don't know.", "start": 2503.49, "duration": 1.03}, {"text": "It could be on your phone.", "start": 2504.52, "duration": 2.01}, {"text": "It does have that much space.", "start": 2506.53, "duration": 1.99}, {"text": "So if they would just turn it\naround and make all the pixels", "start": 2508.52, "duration": 5.03}, {"text": "as sensing pixels, you\nhave enough baseline", "start": 2513.55, "duration": 3.12}, {"text": "from the left edge\nof the camera,", "start": 2516.67, "duration": 2.25}, {"text": "left edge of this\ncell phone camera", "start": 2518.92, "duration": 2.49}, {"text": "to the right edge of\nthe cell phone camera", "start": 2521.41, "duration": 2.46}, {"text": "to create those effects.", "start": 2523.87, "duration": 1.78}, {"text": "But that mindset has to change.", "start": 2525.65, "duration": 1.7}, {"text": "Right now, as we will\nsee in the class later", "start": 2527.35, "duration": 3.45}, {"text": "on the section on sensors,\nthere is tremendous innovation", "start": 2530.8, "duration": 6.36}, {"text": "in how photons--", "start": 2537.16, "duration": 2.49}, {"text": "sorry, image sensors\nare being built", "start": 2539.65, "duration": 2.13}, {"text": "that are wafer level cameras\nback start elimination,", "start": 2541.78, "duration": 4.56}, {"text": "3D VLSI, and so on.", "start": 2546.34, "duration": 3.51}, {"text": "I mean, it's all great,\nand it's going to help us.", "start": 2549.85, "duration": 2.43}, {"text": "But unfortunately all of them\nhave a single tract mind.", "start": 2552.28, "duration": 4.53}, {"text": "They just want to\nmake a higher signal", "start": 2556.81, "duration": 2.01}, {"text": "to noise ratio that must collect\nas many photons as you can.", "start": 2558.82, "duration": 3.03}, {"text": "And they want to shrink the\nsensor as small as you can", "start": 2561.85, "duration": 3.3}, {"text": "so that they can sell\nit for a cheap cost.", "start": 2565.15, "duration": 5.04}, {"text": "But if you think about--", "start": 2570.19, "duration": 2.25}, {"text": "if somebody had told\nyou 30 years ago", "start": 2572.44, "duration": 3.0}, {"text": "that the TVs are\nreally expensive,", "start": 2575.44, "duration": 3.28}, {"text": "so what we're going to do\nis start building TVs that", "start": 2578.72, "duration": 2.51}, {"text": "are smaller and smaller because\nthey'll be cheaper and cheaper,", "start": 2581.23, "duration": 3.72}, {"text": "all right--", "start": 2584.95, "duration": 0.96}, {"text": "but that's not how it works.", "start": 2585.91, "duration": 1.62}, {"text": "People want larger\nand larger TVs.", "start": 2587.53, "duration": 2.52}, {"text": "And they're willing to pay\nfor 40 inch and 50 inch TVs.", "start": 2590.05, "duration": 4.89}, {"text": "And there will come a\ntime when people say,", "start": 2594.94, "duration": 2.43}, {"text": "it's OK if I have to\npay a little bit more,", "start": 2597.37, "duration": 3.0}, {"text": "but make my sensor and make my\nsensor array larger and larger", "start": 2600.37, "duration": 4.39}, {"text": "so that it's almost the\nsize of the whole device.", "start": 2604.76, "duration": 4.715}, {"text": "Even for a camera\nlike an SLR camera,", "start": 2609.475, "duration": 3.705}, {"text": "not the whole camera is sensor.", "start": 2613.18, "duration": 2.04}, {"text": "Only a small part\nof it is sensor.", "start": 2615.22, "duration": 2.1}, {"text": "But once we get\naround this notion", "start": 2617.32, "duration": 1.92}, {"text": "that silicon is\nreally expensive.", "start": 2619.24, "duration": 1.95}, {"text": "And we have to shrink it, and\nwe have to create this wafer.", "start": 2621.19, "duration": 2.97}, {"text": "We can slice and\ndice it into millions", "start": 2624.16, "duration": 2.22}, {"text": "of tiny sensors for cameras.", "start": 2626.38, "duration": 4.05}, {"text": "Hopefully things\nwill change around", "start": 2630.43, "duration": 1.8}, {"text": "and we won't be watching\nthose tiny TVs as they", "start": 2632.23, "duration": 3.87}, {"text": "have predicted some time ago.", "start": 2636.1, "duration": 1.23}, {"text": "So that's kind of where\nsome of these things are.", "start": 2640.22, "duration": 3.57}, {"text": "So let me go back--", "start": 2643.79, "duration": 3.22}, {"text": "so getting 3D very challenging,\nand that I would say", "start": 2647.01, "duration": 4.04}, {"text": "is kind of version 0.1\nof a computation camera.", "start": 2651.05, "duration": 3.93}, {"text": "I mean, it has to sense\nthe three-dimensional world", "start": 2654.98, "duration": 2.745}, {"text": "to do anything interesting.", "start": 2657.725, "duration": 3.105}, {"text": "And it is being used\nin other scenarios,", "start": 2660.83, "duration": 2.19}, {"text": "I mean, [INAUDIBLE] challenge.", "start": 2663.02, "duration": 2.77}, {"text": "This is an animation\nfor movies.--", "start": 2665.79, "duration": 2.94}, {"text": "where you can\nbuild vehicles that", "start": 2668.73, "duration": 4.46}, {"text": "can navigate through\nany kind of terrain,", "start": 2673.19, "duration": 5.73}, {"text": "including urban neighborhoods.", "start": 2678.92, "duration": 3.33}, {"text": "So the first version of\nthe [INAUDIBLE] challenge", "start": 2682.25, "duration": 2.31}, {"text": "actually had a lot of cameras.", "start": 2684.56, "duration": 2.7}, {"text": "But the sad aspect from\na camera point of view", "start": 2687.26, "duration": 3.33}, {"text": "is that the second\nversion that was--", "start": 2690.59, "duration": 4.53}, {"text": "Stanford was the\nwinner in that one.", "start": 2695.12, "duration": 3.69}, {"text": "In the traditional\ndefinition of a camera,", "start": 2698.81, "duration": 2.04}, {"text": "there were no cameras\non the whole vehicle.", "start": 2700.85, "duration": 3.84}, {"text": "There were zero\ncameras on a car that's", "start": 2704.69, "duration": 3.54}, {"text": "built to navigate in a city.", "start": 2708.23, "duration": 3.653}, {"text": "It's pretty sad.", "start": 2711.883, "duration": 0.667}, {"text": "I mean, if you think about\nit, a human driver driving", "start": 2712.55, "duration": 4.5}, {"text": "through a city--", "start": 2717.05, "duration": 1.56}, {"text": "I would say almost\nall our input,", "start": 2718.61, "duration": 3.24}, {"text": "all our actions are based\non visual information.", "start": 2721.85, "duration": 3.72}, {"text": "But cameras are so primitive\nto build this self navigating", "start": 2725.57, "duration": 5.7}, {"text": "vehicle that no traditional\ncameras are used.", "start": 2731.27, "duration": 2.46}, {"text": "Now, of course, I'm\ntaking it to the extreme", "start": 2733.73, "duration": 1.92}, {"text": "because the kind\nof devices they did", "start": 2735.65, "duration": 1.5}, {"text": "use were similar to\nrange scanning devices.", "start": 2737.15, "duration": 3.75}, {"text": "They had laser scanners\nLIDAR, reducing time of flight", "start": 2740.9, "duration": 3.51}, {"text": "and so on.", "start": 2744.41, "duration": 0.79}, {"text": "And in a way they're\ncapturing information", "start": 2745.2, "duration": 3.14}, {"text": "that's sensitive to\ndifferent directions.", "start": 2748.34, "duration": 2.41}, {"text": "So in a way, it's\na camera, but it's", "start": 2750.75, "duration": 2.6}, {"text": "not a traditional visible range\ncamera that they're using.", "start": 2753.35, "duration": 4.02}, {"text": "It's a detector, a\nsingle pixel detector", "start": 2757.37, "duration": 2.37}, {"text": "that's measuring light coming\nfrom different directions.", "start": 2759.74, "duration": 4.947}, {"text": "And on the other extreme,\nthat's one extreme", "start": 2764.687, "duration": 1.833}, {"text": "where cameras are not good\nenough to self navigate.", "start": 2766.52, "duration": 2.7}, {"text": "On the other extreme, you\nhave lots of people online--", "start": 2769.22, "duration": 4.41}, {"text": "again, this is a slide from Doug\nLanman building their own 3D", "start": 2773.63, "duration": 5.71}, {"text": "scanners.", "start": 2779.34, "duration": 0.5}, {"text": "So of course, you can\ntake a Logitech webcam", "start": 2779.84, "duration": 2.76}, {"text": "and put some [INAUDIBLE].", "start": 2782.6, "duration": 1.29}, {"text": "You can calibrate that\nand move it around", "start": 2783.89, "duration": 2.7}, {"text": "to create 3D models\nand a whole bunch of--", "start": 2786.59, "duration": 5.04}, {"text": "We'll look at this during the--", "start": 2791.63, "duration": 2.19}, {"text": "people are using\njust a wineglass", "start": 2793.82, "duration": 3.54}, {"text": "to create laser stripes.", "start": 2797.36, "duration": 1.5}, {"text": "So I can take a laser pointer\nand shine it at a wineglass", "start": 2798.86, "duration": 4.08}, {"text": "to create a laser stripe.", "start": 2802.94, "duration": 1.35}, {"text": "I don't even have to\nbuy expensive optics.", "start": 2804.29, "duration": 2.01}, {"text": "And they just scan it\nand develop a cheap DV", "start": 2806.3, "duration": 3.09}, {"text": "Cam to create 3D scanners.", "start": 2809.39, "duration": 2.16}, {"text": "This one is probably\nmost interesting.", "start": 2811.55, "duration": 2.46}, {"text": "They want to create,\nagain, a very accurate", "start": 2814.01, "duration": 2.7}, {"text": "3D model from a LEGO rig.", "start": 2816.71, "duration": 2.94}, {"text": "And this is how it works.", "start": 2819.65, "duration": 2.378}, {"text": "You can probably guess\nit from the picture.", "start": 2822.028, "duration": 1.792}, {"text": "There is a milk pot.", "start": 2823.82, "duration": 1.68}, {"text": "They want to take a\ncharacter and scan it.", "start": 2825.5, "duration": 1.98}, {"text": "They'll put this\ncharacter in a milk pot.", "start": 2827.48, "duration": 2.64}, {"text": "And take a photo\nfrom above doing", "start": 2830.12, "duration": 1.71}, {"text": "a very simple segmentation.", "start": 2831.83, "duration": 1.26}, {"text": "And then over\ntime, they're going", "start": 2833.09, "duration": 1.53}, {"text": "to put a little bit more milk\nso that the level of the fluid", "start": 2834.62, "duration": 6.48}, {"text": "will rise in this square bucket\nand this rectangular bucket.", "start": 2841.1, "duration": 4.44}, {"text": "And they'll continue\nto take pictures", "start": 2845.54, "duration": 1.56}, {"text": "and they'll create this 3D\nmodel section by section.", "start": 2847.1, "duration": 4.74}, {"text": "Pretty amazing.", "start": 2851.84, "duration": 0.778}, {"text": "AUDIENCE: They did it\nin New York with humans.", "start": 2852.618, "duration": 1.917}, {"text": "RAMESH RASKAR: Sorry?", "start": 2854.535, "duration": 0.875}, {"text": "AUDIENCE: They did it\nin New York with humans.", "start": 2855.41, "duration": 2.31}, {"text": "They go in the\nmilk and scan you.", "start": 2857.72, "duration": 2.66}, {"text": "[INAUDIBLE]", "start": 2860.38, "duration": 1.992}, {"text": "RAMESH RASKAR: Excellent,\nI would imagine", "start": 2862.372, "duration": 1.708}, {"text": "going the other way is easier.", "start": 2864.08, "duration": 1.25}, {"text": "Just drink.", "start": 2865.33, "duration": 2.29}, {"text": "Just straight up\n[INAUDIBLE] and drain it.", "start": 2867.62, "duration": 2.03}, {"text": "It will go out\nalmost concentrated.", "start": 2869.65, "duration": 1.84}, {"text": "AUDIENCE: True.", "start": 2871.49, "duration": 2.22}, {"text": "RAMESH RASKAR: But, yeah, this\ncould be a great class project.", "start": 2873.71, "duration": 2.85}, {"text": "So here's a slightly\ndifferent direction", "start": 2882.47, "duration": 3.42}, {"text": "that some people are taking.", "start": 2885.89, "duration": 1.41}, {"text": "And I really like this work\nfrom [INAUDIBLE] Washington.", "start": 2887.3, "duration": 3.88}, {"text": "Some of you are--", "start": 2891.18, "duration": 1.11}, {"text": "OK, let me state the question\nfirst and see if anyone of you", "start": 2892.29, "duration": 3.56}, {"text": "has an answer to that.", "start": 2895.85, "duration": 1.17}, {"text": "Let's say you go to\nRome, and you are", "start": 2897.02, "duration": 1.95}, {"text": "in front of the Trevi Fountain.", "start": 2898.97, "duration": 2.91}, {"text": "You take a photo, and\nyou don't know anything", "start": 2901.88, "duration": 2.94}, {"text": "about Trevi Fountain and\nall the hype about it.", "start": 2904.82, "duration": 3.15}, {"text": "You want to take a\nphoto and figure out", "start": 2907.97, "duration": 2.04}, {"text": "which part of this\nphoto is interesting", "start": 2910.01, "duration": 3.21}, {"text": "according to everybody else.", "start": 2913.22, "duration": 2.41}, {"text": "So why am I here?", "start": 2915.63, "duration": 1.73}, {"text": "Should I be looking at--", "start": 2917.36, "duration": 1.74}, {"text": "if I go to the Old\nTown Square in Prague,", "start": 2919.1, "duration": 3.39}, {"text": "I'm not going to look\nat a fountain here.", "start": 2922.49, "duration": 1.86}, {"text": "I'm going to look at\nanother part of the castle.", "start": 2924.35, "duration": 3.6}, {"text": "But somehow when I'm\nat Trevi Fountain,", "start": 2927.95, "duration": 2.04}, {"text": "I'm not looking\nat the buildings.", "start": 2929.99, "duration": 1.5}, {"text": "I'm looking at the Fountain.", "start": 2931.49, "duration": 1.35}, {"text": "So how would I determine without\nlooking in my guidebook which", "start": 2932.84, "duration": 5.31}, {"text": "part is most interesting?", "start": 2938.15, "duration": 1.806}, {"text": "Any clues, any answers?", "start": 2943.15, "duration": 0.99}, {"text": "AUDIENCE: I don't know\nif I should answer.", "start": 2953.31, "duration": 1.75}, {"text": "RAMESH RASKAR: Go ahead.", "start": 2955.06, "duration": 1.0}, {"text": "You're [INAUDIBLE] yeah.", "start": 2956.06, "duration": 1.3}, {"text": "AUDIENCE: One thing\nyou could perhaps do", "start": 2957.36, "duration": 2.19}, {"text": "is take a consensus\nfor all the photos", "start": 2959.55, "duration": 2.25}, {"text": "that have been\ntaken of this object", "start": 2961.8, "duration": 2.24}, {"text": "and basically see where\nthe feature tracks overlap.", "start": 2964.04, "duration": 3.705}, {"text": "An alert [INAUDIBLE] sort of.", "start": 2971.08, "duration": 2.708}, {"text": "RAMESH RASKAR: Excellent.", "start": 2973.788, "duration": 1.042}, {"text": "So this is actually an offshoot\nof the photo tourism Microsoft", "start": 2974.83, "duration": 5.13}, {"text": "Photosynth project where\nyou have millions of photos", "start": 2979.96, "duration": 3.06}, {"text": "of the same tourist location.", "start": 2983.02, "duration": 2.74}, {"text": "And once you have\nregistered them in 3D,", "start": 2985.76, "duration": 3.62}, {"text": "then you can just\nshoot the rays back", "start": 2989.38, "duration": 1.86}, {"text": "to see which rays will\nintersect the pixels.", "start": 2991.24, "duration": 3.15}, {"text": "If most of the rays seem to be\nshooting you just kind of just", "start": 2994.39, "duration": 5.37}, {"text": "a histogram, you'll realize\nthat most of the photos", "start": 2999.76, "duration": 3.36}, {"text": "are looking at the fountain.", "start": 3003.12, "duration": 1.3}, {"text": "And in this case,\nwhat the photos", "start": 3004.42, "duration": 1.375}, {"text": "are looking up at the top\npart of the [INAUDIBLE]..", "start": 3005.795, "duration": 2.215}, {"text": "AUDIENCE: So maybe it's\nwhat is popular here.", "start": 3008.01, "duration": 1.95}, {"text": "Everything might be a\ndifferent [INAUDIBLE]..", "start": 3009.96, "duration": 1.68}, {"text": "RAMESH RASKAR: You're\nright, you're right.", "start": 3011.64, "duration": 1.75}, {"text": "So the next question\nis, how can we--", "start": 3013.39, "duration": 1.55}, {"text": "it's like popular versus\ninteresting on Flickr.", "start": 3014.94, "duration": 2.56}, {"text": "AUDIENCE: Yes, that's true.", "start": 3017.5, "duration": 3.05}, {"text": "RAMESH RASKAR: So here's our\nquestion, how can we ask--", "start": 3020.55, "duration": 3.0}, {"text": "how can we answer this question?", "start": 3023.55, "duration": 1.585}, {"text": "AUDIENCE: There may\nbe certain features", "start": 3025.135, "duration": 1.625}, {"text": "that the human visual system\nfinds particularly interesting,", "start": 3026.76, "duration": 3.48}, {"text": "things with high levels\nof non-repetitive detail", "start": 3030.24, "duration": 2.49}, {"text": "or certain shapes or ratios.", "start": 3032.73, "duration": 3.298}, {"text": "RAMESH RASKAR: Yeah, certainly.", "start": 3036.028, "duration": 1.292}, {"text": "So I think there's\na lot to be done.", "start": 3037.32, "duration": 2.35}, {"text": "So maybe if we want to build\na camera that directly detects", "start": 3039.67, "duration": 3.65}, {"text": "the building pattern, it\ndoesn't care about finding it,", "start": 3043.32, "duration": 2.4}, {"text": "capturing a real photo.", "start": 3045.72, "duration": 1.44}, {"text": "But it does a very\ngood job of finding out", "start": 3047.16, "duration": 2.7}, {"text": "if there are patterns we\nfind interesting whether it's", "start": 3049.86, "duration": 2.58}, {"text": "symmetry or repetition or the\nright scales the right aspect", "start": 3052.44, "duration": 5.79}, {"text": "ratio and so on.", "start": 3058.23, "duration": 1.29}, {"text": "And the same project.", "start": 3064.7, "duration": 2.85}, {"text": "So this is the\nPantheon again in Rome.", "start": 3067.55, "duration": 2.8}, {"text": "These are all the places from\nwhich people take photos.", "start": 3070.35, "duration": 3.02}, {"text": "And if I just tell you this\nis the view of the Pantheon,", "start": 3073.37, "duration": 4.5}, {"text": "and you usually are--\nup here is a fountain.", "start": 3077.87, "duration": 3.45}, {"text": "People start from here and\nthen go in and roam around", "start": 3081.32, "duration": 3.48}, {"text": "and take a picture of this\nbig hole in the Pantheon.", "start": 3084.8, "duration": 4.14}, {"text": "So the question is if I take\na picture here at the entrance", "start": 3088.94, "duration": 5.07}, {"text": "and from inside the\npantheon looking out", "start": 3094.01, "duration": 3.09}, {"text": "at the door and a\npicture from outside,", "start": 3097.1, "duration": 2.76}, {"text": "what's the part that would\nconnect these two photos?", "start": 3099.86, "duration": 4.47}, {"text": "It's not a straight line path.", "start": 3104.33, "duration": 1.41}, {"text": "I don't have an image.", "start": 3109.023, "duration": 0.917}, {"text": "I don't have it.", "start": 3112.77, "duration": 2.83}, {"text": "But if you actually have\nthis, again, voting scheme,", "start": 3115.6, "duration": 3.438}, {"text": "you've realized the best\nway to go from this view", "start": 3119.038, "duration": 2.042}, {"text": "to this view is follow\nthis particular path.", "start": 3121.08, "duration": 3.73}, {"text": "So this is data that's been\ncaptured from visual media,", "start": 3124.81, "duration": 5.39}, {"text": "like photographs, but inherently\nit's more about geometry.", "start": 3130.2, "duration": 3.18}, {"text": "And I would call it--", "start": 3133.38, "duration": 0.9}, {"text": "it's almost non-visual.", "start": 3134.28, "duration": 2.61}, {"text": "So that was\ncomputational camera,", "start": 3136.89, "duration": 1.86}, {"text": "and let's think about\ncomputational photography.", "start": 3138.75, "duration": 3.93}, {"text": "And computational photography\nand my collaborator Jack", "start": 3142.68, "duration": 6.51}, {"text": "Tumblin at Northwestern.", "start": 3149.19, "duration": 2.4}, {"text": "This is how we like to\ndefine the two parts.", "start": 3151.59, "duration": 2.19}, {"text": "We want to capture\nthe scene, and we", "start": 3153.78, "duration": 2.32}, {"text": "want to synthesize this thing.", "start": 3156.1, "duration": 1.25}, {"text": "And when we capture,\nwe want to capture it", "start": 3157.35, "duration": 2.73}, {"text": "in an extremely rich fashion\nso that it's machine readable", "start": 3160.08, "duration": 2.568}, {"text": "and the machine can\nunderstand what's", "start": 3162.648, "duration": 1.542}, {"text": "out there and re-synthesize.", "start": 3164.19, "duration": 2.37}, {"text": "We want to synthesize in\na hyper realistic manner", "start": 3166.56, "duration": 2.52}, {"text": "so that it represents\nthe essence", "start": 3169.08, "duration": 3.69}, {"text": "of our visual experience.", "start": 3172.77, "duration": 3.16}, {"text": "And within that there\nare three major teams.", "start": 3175.93, "duration": 3.45}, {"text": "One is epsilon photography,\nwhich is basically generalized", "start": 3179.38, "duration": 4.5}, {"text": "bracketing.", "start": 3183.88, "duration": 0.5}, {"text": "So whether I want\nHDR or panorama,", "start": 3184.38, "duration": 4.23}, {"text": "I'm going to take my camera,\nGoogle's exposure bracketing", "start": 3188.61, "duration": 3.15}, {"text": "or focus bracketing\nor view bracketing", "start": 3191.76, "duration": 3.24}, {"text": "and so on and just create\na very nice picture", "start": 3195.0, "duration": 3.24}, {"text": "and mostly to overcome the\nlimitations of a camera.", "start": 3198.24, "duration": 3.27}, {"text": "That's just epsilon photography.", "start": 3201.51, "duration": 1.41}, {"text": "I'm going to change the\nparameters of the camera", "start": 3202.92, "duration": 2.46}, {"text": "within an epsilon neighborhood.", "start": 3205.38, "duration": 3.96}, {"text": "And then people think of\nthat as the ultimate camera.", "start": 3209.34, "duration": 2.64}, {"text": "But again we're not going\nto focus much on this part", "start": 3211.98, "duration": 2.88}, {"text": "in this course.", "start": 3214.86, "duration": 1.65}, {"text": "The next part-- that's\nquite interesting--", "start": 3216.51, "duration": 2.07}, {"text": "is so-called coated photography.", "start": 3218.58, "duration": 2.38}, {"text": "So the comment we had\nearlier I really care", "start": 3220.96, "duration": 3.29}, {"text": "about some mid-level feature.", "start": 3224.25, "duration": 2.85}, {"text": "I want to know if\nthey're symmetric.", "start": 3227.1, "duration": 1.59}, {"text": "I want to if there's\na repeating pattern.", "start": 3228.69, "duration": 1.92}, {"text": "I want to know\nwhere the edges are.", "start": 3230.61, "duration": 2.49}, {"text": "I want to know how the regions\ncan be segmented and so on.", "start": 3233.1, "duration": 3.36}, {"text": "And it's worth taking multiple\nphotos such as in bracketing.", "start": 3236.46, "duration": 2.85}, {"text": "I just want to take one or maybe\ntwo photos which are reversible", "start": 3239.31, "duration": 3.81}, {"text": "and of course the information\nof what the world in my image.", "start": 3243.12, "duration": 4.62}, {"text": "And the image may not\nbe a single 2D image.", "start": 3247.74, "duration": 2.65}, {"text": "It could be a light\nfield camera where", "start": 3250.39, "duration": 1.72}, {"text": "you have 25 images\nor a single snapshot", "start": 3252.11, "duration": 2.98}, {"text": "or you could have a\ntime of flight camera", "start": 3255.09, "duration": 1.8}, {"text": "where you really\ncan't call it a photo", "start": 3256.89, "duration": 2.13}, {"text": "because it's actually\nmeasuring the amount of time", "start": 3259.02, "duration": 4.29}, {"text": "it takes for light to travel\nback and forth in a given", "start": 3263.31, "duration": 2.82}, {"text": "direction and so on.", "start": 3266.13, "duration": 3.15}, {"text": "And it would be very\nuseful for scene analysis.", "start": 3269.28, "duration": 2.68}, {"text": "So a lot of our course would be\nactually discussing this part.", "start": 3271.96, "duration": 5.78}, {"text": "And the last part is\n[? instance ?] photography", "start": 3277.74, "duration": 2.04}, {"text": "which is really to\nsee if we can go", "start": 3279.78, "duration": 3.21}, {"text": "beyond this low level of\nfeatures, pixels and mid-level", "start": 3282.99, "duration": 4.53}, {"text": "features such as motion and\nforeground and background", "start": 3287.52, "duration": 3.63}, {"text": "and symmetry and so on to a\nhigher level understanding.", "start": 3291.15, "duration": 4.35}, {"text": "So that it's not just\nmimicking human eye,", "start": 3295.5, "duration": 2.4}, {"text": "but it's doing possibly\nthings like this,", "start": 3297.9, "duration": 3.93}, {"text": "telling me what's\npopular for example.", "start": 3301.83, "duration": 3.24}, {"text": "And I claim that only when\nwe have computational cameras", "start": 3308.26, "duration": 5.68}, {"text": "and computational\nphotography supporting this,", "start": 3313.94, "duration": 2.77}, {"text": "we'll be able to create\nnew visual art forms.", "start": 3316.71, "duration": 2.825}, {"text": "So within that, this\nis a chart that we'll", "start": 3322.8, "duration": 4.92}, {"text": "be talking about\nthroughout this class.", "start": 3327.72, "duration": 1.8}, {"text": "I won't go into too\nmuch detail right now.", "start": 3329.52, "duration": 1.86}, {"text": "But we have certain goals,\nthe mid-level features,", "start": 3331.38, "duration": 2.7}, {"text": "low level features, high\nlevel features, and so on.", "start": 3334.08, "duration": 2.74}, {"text": "And we have certain tools that\ncan capture the raw image.", "start": 3336.82, "duration": 3.98}, {"text": "We can capture the\nincident angle and spectrum", "start": 3340.8, "duration": 3.48}, {"text": "such as UV and thermal IR.", "start": 3344.28, "duration": 2.91}, {"text": "We can capture high\ndimensional reflectance field.", "start": 3347.19, "duration": 2.46}, {"text": "We have non-visual data such\nas GPS and identity, metadata,", "start": 3349.65, "duration": 5.01}, {"text": "image priors and so on.", "start": 3354.66, "duration": 2.53}, {"text": "And with that we're going\nto explore this whole space", "start": 3357.19, "duration": 2.93}, {"text": "of camera and photography.", "start": 3360.12, "duration": 2.67}, {"text": "Of course high dynamic range\nand so on is right here.", "start": 3362.79, "duration": 3.33}, {"text": "We're not going to spend\ntoo much time on that.", "start": 3366.12, "duration": 1.99}, {"text": "But we're going to\nthink about how can we", "start": 3368.11, "duration": 1.708}, {"text": "insert a virtual object,\nhow can you take a photo", "start": 3369.818, "duration": 2.602}, {"text": "and relight, change the\nlighting in the scene and so on.", "start": 3372.42, "duration": 5.79}, {"text": "Material editing for example\nfrom a single photon, Ted Olson", "start": 3378.21, "duration": 4.23}, {"text": "is here, and he's done a\nlot of work in this space.", "start": 3382.44, "duration": 4.96}, {"text": "And if you look\nat this chart, you", "start": 3387.4, "duration": 4.16}, {"text": "realize that even the\nhuman vision is not", "start": 3391.56, "duration": 4.98}, {"text": "at the top right\nof this diagram.", "start": 3396.54, "duration": 3.36}, {"text": "With human vision I cannot\nlook around the corner.", "start": 3399.9, "duration": 3.39}, {"text": "I cannot see what's\ninside the body.", "start": 3403.29, "duration": 1.75}, {"text": "I cannot tell you what's\nbehind the curtain.", "start": 3405.04, "duration": 2.78}, {"text": "I cannot tell you when I'm\nin Rome what's interesting", "start": 3407.82, "duration": 4.71}, {"text": "and so on.", "start": 3412.53, "duration": 0.94}, {"text": "So you really want to create\nthis augmented human experience", "start": 3413.47, "duration": 3.32}, {"text": "by using these tools and\nusing the mechanisms that we", "start": 3416.79, "duration": 5.04}, {"text": "have available.", "start": 3421.83, "duration": 0.82}, {"text": "So we'll be coming back to this.", "start": 3422.65, "duration": 2.21}, {"text": "Just keep this in mind.", "start": 3424.86, "duration": 1.05}, {"text": "And a lot of this is actually\navailable in the book", "start": 3428.67, "duration": 3.12}, {"text": "that I and Jack\nTumblin have published.", "start": 3431.79, "duration": 3.6}, {"text": "The PDF of this book\nwill be available", "start": 3435.39, "duration": 2.04}, {"text": "throughout the course.", "start": 3437.43, "duration": 0.99}, {"text": "And the real book\nshould be out any time.", "start": 3438.42, "duration": 2.1}, {"text": "All right.", "start": 3444.44, "duration": 0.79}, {"text": "So just a couple of more\nslides, and we'll take a break.", "start": 3445.23, "duration": 4.373}, {"text": "Let me skip over\nthis one for now,", "start": 3449.603, "duration": 1.417}, {"text": "some of my favorite examples.", "start": 3451.02, "duration": 3.56}, {"text": "All right.", "start": 3454.58, "duration": 0.66}, {"text": "So we also got to spend\na lot of time thinking", "start": 3455.24, "duration": 3.3}, {"text": "about cameras that, again,\nshow what's not seen.", "start": 3458.54, "duration": 6.21}, {"text": "And I realized that\nMathias is here.", "start": 3464.75, "duration": 2.79}, {"text": "His company is the founder of\nRedshift, a thermal imaging", "start": 3467.54, "duration": 4.11}, {"text": "company.", "start": 3471.65, "duration": 1.17}, {"text": "And you want to say\na couple of words?", "start": 3472.82, "duration": 3.84}, {"text": "MATHIAS OMOTOLA: Sure.", "start": 3476.66, "duration": 1.38}, {"text": "So this was my second\nstartup, and the idea", "start": 3478.04, "duration": 3.12}, {"text": "was to build an ultra low\ncost thermal imaging camera", "start": 3481.16, "duration": 3.54}, {"text": "and do it using a\nstandard cell phone", "start": 3484.7, "duration": 3.75}, {"text": "camera as, actually,\nthe image sensor", "start": 3488.45, "duration": 2.37}, {"text": "and using a little thermally\ntunable film as a translator", "start": 3490.82, "duration": 6.54}, {"text": "between infrared and visible.", "start": 3497.36, "duration": 2.222}, {"text": "RAMESH RASKAR: Exactly.", "start": 3499.582, "duration": 0.958}, {"text": "And the goal is to\ndramatically bring down", "start": 3500.54, "duration": 2.16}, {"text": "the cost of a thermal camera.", "start": 3502.7, "duration": 3.87}, {"text": "So let's bring in our next toy.", "start": 3506.57, "duration": 3.501}, {"text": "Will you need some\ntime to set up?", "start": 3510.071, "duration": 1.449}, {"text": "GUEST SPEAKER: Oh, yes I need--", "start": 3511.52, "duration": 1.5}, {"text": "RAMESH RASKAR: OK.", "start": 3513.02, "duration": 0.82}, {"text": "Yeah.", "start": 3513.84, "duration": 0.74}, {"text": "I we'll set up this other time,\nwhich will very quickly take us", "start": 3514.58, "duration": 3.63}, {"text": "towards the 60K.", "start": 3518.21, "duration": 3.18}, {"text": "And you can do some\namazing things.", "start": 3521.39, "duration": 2.45}, {"text": "So this is not from\nMathias's company.", "start": 3523.84, "duration": 3.82}, {"text": "Is that a maker or just a--", "start": 3527.66, "duration": 3.27}, {"text": "they actually make cameras\nor they're just integrators?", "start": 3530.93, "duration": 3.39}, {"text": "And they can use it\nin sports analysis?", "start": 3534.32, "duration": 2.7}, {"text": "This is in the game of cricket\nwhere you want to figure out", "start": 3537.02, "duration": 3.87}, {"text": "if the ball was hitting\nthe pad or the pad", "start": 3540.89, "duration": 3.3}, {"text": "and it's a very difficult\ncall for the referee", "start": 3544.19, "duration": 2.94}, {"text": "but if they have a thermal\nimaging camera, then", "start": 3547.13, "duration": 4.62}, {"text": "the ball here if\nit hits the bag,", "start": 3551.75, "duration": 2.76}, {"text": "it will leave a hot\nspot on the bat.", "start": 3554.51, "duration": 2.102}, {"text": "But if it hits the bat, it will\nleave a hotspot on the pad.", "start": 3556.612, "duration": 2.458}, {"text": "So just by looking\nat an image a couple", "start": 3559.07, "duration": 1.83}, {"text": "of seconds after the ball\nhas left, the player,", "start": 3560.9, "duration": 3.45}, {"text": "you can figure out\nif the ball hit the--", "start": 3564.35, "duration": 3.82}, {"text": "the ball hit the bat or the bat.", "start": 3568.17, "duration": 3.74}, {"text": "And this is major.", "start": 3571.91, "duration": 1.17}, {"text": "People get really angry\nand all the sports analysts", "start": 3573.08, "duration": 2.79}, {"text": "will be writing or the\nreferee next day in the press.", "start": 3575.87, "duration": 8.55}, {"text": "This really saves their life.", "start": 3584.42, "duration": 2.67}, {"text": "But the goal for Mathias\nand other companies", "start": 3587.09, "duration": 2.82}, {"text": "is to make it available\npossibly at the same cost", "start": 3589.91, "duration": 3.81}, {"text": "as your traditional camera.", "start": 3593.72, "duration": 1.68}, {"text": "I mean, if you think about\na cost of a digital SLR,", "start": 3595.4, "duration": 2.73}, {"text": "it was $30,000 dollars.", "start": 3598.13, "duration": 1.95}, {"text": "And now it's worth about $500.", "start": 3600.08, "duration": 3.03}, {"text": "It's just silicon.", "start": 3603.11, "duration": 1.05}, {"text": "It's not that expensive.", "start": 3604.16, "duration": 1.41}, {"text": "If Canon or Nokia\ndecides to have", "start": 3605.57, "duration": 4.89}, {"text": "a thermal camera in\nevery cell phone,", "start": 3610.46, "duration": 2.22}, {"text": "they will be available for\nvery low cost, very extreme low", "start": 3612.68, "duration": 4.11}, {"text": "cost.", "start": 3616.79, "duration": 0.588}, {"text": "What is your guess?", "start": 3617.378, "duration": 0.792}, {"text": "What would be the\ncost in five years?", "start": 3618.17, "duration": 2.91}, {"text": "AUDIENCE: Five years?", "start": 3621.08, "duration": 2.27}, {"text": "It's still $500.", "start": 3623.35, "duration": 1.54}, {"text": "RAMESH RASKAR: $500.", "start": 3624.89, "duration": 0.85}, {"text": "That's not bad, right?", "start": 3625.74, "duration": 1.49}, {"text": "And as you'll see\nlater in the class", "start": 3627.23, "duration": 2.46}, {"text": "and you'll see in this demo--", "start": 3629.69, "duration": 1.87}, {"text": "we can do this in\nthe break as well.", "start": 3631.56, "duration": 1.5}, {"text": "So take your time.", "start": 3633.06, "duration": 2.87}, {"text": "It can do some amazing things.", "start": 3635.93, "duration": 2.01}, {"text": "All right.", "start": 3637.94, "duration": 0.66}, {"text": "So that was computational camera\nand computational photography.", "start": 3638.6, "duration": 4.68}, {"text": "And in this class we're going\nto look at both aspects.", "start": 3643.28, "duration": 2.85}, {"text": "This is how we're\ngoing to do it.", "start": 3646.13, "duration": 2.55}, {"text": "We have two numbers 131\nfor undergraduate and 531", "start": 3648.68, "duration": 3.75}, {"text": "for graduate.", "start": 3652.43, "duration": 1.65}, {"text": "The main difference is\nwe have four assignments", "start": 3654.08, "duration": 3.0}, {"text": "for the graduate version\nand three assignments", "start": 3657.08, "duration": 2.55}, {"text": "for the undergraduate version.", "start": 3659.63, "duration": 2.04}, {"text": "And we have a midterm\nexam where there", "start": 3661.67, "duration": 2.55}, {"text": "will be fewer questions for\nthe undergraduate version other", "start": 3664.22, "duration": 3.48}, {"text": "than that, the rest of the\ncourse is very similar.", "start": 3667.7, "duration": 3.97}, {"text": "So in the assignments\nwe're playing with hands", "start": 3671.67, "duration": 3.95}, {"text": "on with optics and illumination\nand sensors and other elements.", "start": 3675.62, "duration": 4.66}, {"text": "And we'll have all these\ntoys available for you.", "start": 3680.28, "duration": 3.17}, {"text": "We'll have projectors,\ndifferent light sources, lasers,", "start": 3683.45, "duration": 5.07}, {"text": "and things like\nthat to play with.", "start": 3688.52, "duration": 3.48}, {"text": "I will also have a\nbest project award.", "start": 3692.0, "duration": 3.15}, {"text": "At the end last year\nthere was exactly", "start": 3695.15, "duration": 2.91}, {"text": "one undergraduate\nstudent, and he", "start": 3698.06, "duration": 3.27}, {"text": "won the best project\naward, pretty impressive,", "start": 3701.33, "duration": 3.66}, {"text": "pretty impressive.", "start": 3704.99, "duration": 1.48}, {"text": "He did an amazing job\nbecause last year we did not", "start": 3706.47, "duration": 2.09}, {"text": "have an undergraduate version.", "start": 3708.56, "duration": 1.92}, {"text": "It was only a graduate version.", "start": 3710.48, "duration": 3.96}, {"text": "Midterm exam will\nbe early November.", "start": 3714.44, "duration": 5.17}, {"text": "A big component of the\nclass and your work", "start": 3719.61, "duration": 3.56}, {"text": "would be a final project, which\nshould be novel as well as cool", "start": 3723.17, "duration": 3.78}, {"text": "unlike a lot of other fields.", "start": 3726.95, "duration": 2.01}, {"text": "It is possible to\ncome up with an idea", "start": 3728.96, "duration": 1.98}, {"text": "that nobody else has even\nthought about in this field.", "start": 3730.94, "duration": 3.7}, {"text": "So you could come up with ideas\nthat are not just incremental", "start": 3734.64, "duration": 2.93}, {"text": "but that could be game changing.", "start": 3737.57, "duration": 1.77}, {"text": "And I'll tell you later\nthat three projects,", "start": 3739.34, "duration": 6.36}, {"text": "final projects from last year\nled to SIGGRAPH or ICCP papers.", "start": 3745.7, "duration": 5.1}, {"text": "And two of the projects are\nbecoming multi hundred thousand", "start": 3750.8, "duration": 4.17}, {"text": "dollar projects.", "start": 3754.97, "duration": 2.5}, {"text": "So it is possible to come\nup in this class with ideas", "start": 3757.47, "duration": 3.32}, {"text": "that are game changing.", "start": 3760.79, "duration": 3.54}, {"text": "If you are taking\nthe class for credit,", "start": 3764.33, "duration": 1.86}, {"text": "you'll also take class\nnotes for the lectures.", "start": 3766.19, "duration": 4.5}, {"text": "We'll have plenty of guest talks\nin line and online discussion.", "start": 3770.69, "duration": 4.83}, {"text": "This class, most of the\nmaterials is on slides.", "start": 3778.04, "duration": 3.42}, {"text": "But starting next week,\nabout half the material", "start": 3781.46, "duration": 3.12}, {"text": "will be on slides,\nand the other half", "start": 3784.58, "duration": 2.46}, {"text": "will be just on whiteboards\nand demos and so on.", "start": 3787.04, "duration": 3.745}, {"text": "So if you're looking\nat a slide, you'll", "start": 3790.785, "duration": 1.625}, {"text": "get an idea of the type of\nmaterial we're covering,", "start": 3792.41, "duration": 2.62}, {"text": "but what I realized\nlast year was", "start": 3795.03, "duration": 4.55}, {"text": "most of the discussion\nwas actually not", "start": 3799.58, "duration": 2.94}, {"text": "captured in the slides.", "start": 3802.52, "duration": 1.005}, {"text": "And if you're a listener--", "start": 3806.48, "duration": 2.49}, {"text": "and I a lot of you\nare going to be", "start": 3808.97, "duration": 1.71}, {"text": "listeners in this class,\nwhich is perfectly fine.", "start": 3810.68, "duration": 3.22}, {"text": "But what I would like to do\nis participate in discussion.", "start": 3813.9, "duration": 4.64}, {"text": "Bring in a new viewpoint.", "start": 3818.54, "duration": 1.62}, {"text": "I want to learn from you.", "start": 3820.16, "duration": 1.53}, {"text": "I'm glad Mathias is\nhere, for example.", "start": 3821.69, "duration": 2.4}, {"text": "He's the world expert world's\nexpert on thermal imaging.", "start": 3824.09, "duration": 2.46}, {"text": "So I want all of you\nto who are taking", "start": 3826.55, "duration": 4.44}, {"text": "it, who are just listening in,\nto contribute to the discussion", "start": 3830.99, "duration": 4.23}, {"text": "and give a new viewpoint.", "start": 3835.22, "duration": 1.53}, {"text": "I will not be offended\nat all if you jump in", "start": 3836.75, "duration": 3.03}, {"text": "and give a new perspective\nor a new reference", "start": 3839.78, "duration": 3.42}, {"text": "about what we are discussing.", "start": 3843.2, "duration": 3.42}, {"text": "And if you are a graduate\nstudent or a postdoc,", "start": 3846.62, "duration": 5.4}, {"text": "then I would also like\nto spend some time", "start": 3852.02, "duration": 3.06}, {"text": "in sharing with us one short\npresentation, maybe a cool idea", "start": 3855.08, "duration": 6.78}, {"text": "or some new work you're doing.", "start": 3861.86, "duration": 2.58}, {"text": "But that's what I would\nexpect if you are not", "start": 3864.44, "duration": 2.25}, {"text": "taking this class for credit.", "start": 3866.69, "duration": 3.54}, {"text": "In terms of the credit\nbreakdown, we have about four", "start": 3870.23, "duration": 4.05}, {"text": "or three assignments\ndepending on which version you", "start": 3874.28, "duration": 2.31}, {"text": "are taking 40%, final project,\n30%, midterm 40% and class", "start": 3876.59, "duration": 5.31}, {"text": "participation.", "start": 3881.9, "duration": 0.69}, {"text": "That includes discussions\noften online as well as", "start": 3882.59, "duration": 3.45}, {"text": "taking the notes.", "start": 3886.04, "duration": 2.67}, {"text": "Pre-requisites.", "start": 3888.71, "duration": 2.78}, {"text": "Let's see if I have--", "start": 3891.49, "duration": 1.36}, {"text": "I'll come back to\nthat, another slide.", "start": 3892.85, "duration": 3.68}, {"text": "The emphasis for\nthis class is really", "start": 3896.53, "duration": 2.67}, {"text": "on fundamental\ntechniques in imaging.", "start": 3899.2, "duration": 3.115}, {"text": "Yeah, it's coming up.", "start": 3902.315, "duration": 0.875}, {"text": "It's going to be fun.", "start": 3903.19, "duration": 3.48}, {"text": "And in class as\nwell as in homework,", "start": 3906.67, "duration": 2.58}, {"text": "emphasis is on techniques.", "start": 3909.25, "duration": 3.0}, {"text": "And they include all these\nkey words, signal processing,", "start": 3912.25, "duration": 2.76}, {"text": "applied optics graphics vision,\nonline photo collection,", "start": 3915.01, "duration": 3.21}, {"text": "statistical techniques,\nelectronics, visual arts,", "start": 3918.22, "duration": 3.46}, {"text": "and so on.", "start": 3921.68, "duration": 0.5}, {"text": "And so in that sense it's\nnot a discussion class.", "start": 3922.18, "duration": 2.65}, {"text": "We're going to learn\nabout techniques.", "start": 3924.83, "duration": 3.12}, {"text": "All right, there is\nentertainment here.", "start": 3927.95, "duration": 4.89}, {"text": "It's very addictive\nto play with cameras.", "start": 3932.84, "duration": 3.07}, {"text": "OK.", "start": 3935.91, "duration": 0.69}, {"text": "So if you can just focus\nhere for a couple of minutes.", "start": 3936.6, "duration": 2.25}, {"text": "And there are three areas\nwe want to focus on.", "start": 3941.34, "duration": 4.2}, {"text": "And just keep this in\nmind and know this.", "start": 3945.54, "duration": 3.0}, {"text": "We're going to focus\non photography.", "start": 3948.54, "duration": 1.77}, {"text": "We're going to focus on\nactive techniques, real time", "start": 3950.31, "duration": 2.98}, {"text": "Techniques.", "start": 3953.29, "duration": 0.5}, {"text": "And we're going to focus\non scientific imaging.", "start": 3953.79, "duration": 2.52}, {"text": "So within photography,\nwe're going", "start": 3956.31, "duration": 1.89}, {"text": "to think in higher dimensions.", "start": 3958.2, "duration": 2.19}, {"text": "We're not going to\nthink about just HDR", "start": 3960.39, "duration": 2.58}, {"text": "or focus stack and so on.", "start": 3962.97, "duration": 1.75}, {"text": "We're going to think about\nhigh dimensional imaging light", "start": 3964.72, "duration": 2.63}, {"text": "fields, thermal imaging\nrange cameras, and so on.", "start": 3967.35, "duration": 5.28}, {"text": "And active computer\nvision, we're", "start": 3972.63, "duration": 2.49}, {"text": "going to think about\nHCI applications,", "start": 3975.12, "duration": 2.34}, {"text": "robotics, tracking\nand segmentation", "start": 3977.46, "duration": 2.31}, {"text": "and how we can change\nthe game by using", "start": 3979.77, "duration": 2.67}, {"text": "feature revealing cameras.", "start": 3982.44, "duration": 2.1}, {"text": "And a lot of concepts\nfrom scientific imaging", "start": 3984.54, "duration": 2.64}, {"text": "such as composition\nsensing, wavefront", "start": 3987.18, "duration": 2.22}, {"text": "coding, deconvolution,\ntomography, point square", "start": 3989.4, "duration": 2.82}, {"text": "function, and so on--", "start": 3992.22, "duration": 2.17}, {"text": "And at first glance, these three\nareas might look very distinct", "start": 3994.39, "duration": 4.13}, {"text": "and have very\ndifferent techniques.", "start": 3998.52, "duration": 3.0}, {"text": "But fortunately they all\nuse very similar principles.", "start": 4001.52, "duration": 3.63}, {"text": "And what we realized\nover the course", "start": 4005.15, "duration": 2.65}, {"text": "is that this fusion of\nthis dissimilar ideas--", "start": 4007.8, "duration": 4.19}, {"text": "I mean, tomography\nand wavefront coding", "start": 4011.99, "duration": 2.43}, {"text": "seem very far away from\ntraditional photography or HCI.", "start": 4014.42, "duration": 3.36}, {"text": "But you'll realize that\nmany of the problems you", "start": 4017.78, "duration": 2.61}, {"text": "may be encountering and\nmany of the visual arts", "start": 4020.39, "duration": 5.28}, {"text": "that you might be interested\nin could be impacted from some", "start": 4025.67, "duration": 4.65}, {"text": "of these new techniques.", "start": 4030.32, "duration": 4.15}, {"text": "So in terms of\nthe prerequisites.", "start": 4034.47, "duration": 3.701}, {"text": "The last time I\ntaught this course,", "start": 4038.171, "duration": 2.629}, {"text": "there was a request to\nbe supportive of students", "start": 4040.8, "duration": 3.38}, {"text": "with different backgrounds.", "start": 4044.18, "duration": 1.392}, {"text": "So this is what\nwe're going to try.", "start": 4045.572, "duration": 1.458}, {"text": "We're going to try to\ntracks, a software only tract", "start": 4047.03, "duration": 4.23}, {"text": "and a software, hardware tract.", "start": 4051.26, "duration": 2.85}, {"text": "And software intensive\ntract is for those of you", "start": 4054.11, "duration": 2.88}, {"text": "who just because\nof your interests", "start": 4056.99, "duration": 2.88}, {"text": "or want to do things\nin a particular way--", "start": 4059.87, "duration": 3.72}, {"text": "and you may be able to use\nsome key based software.", "start": 4063.59, "duration": 3.99}, {"text": "And the software hardware\ntract you will be using a lot", "start": 4067.58, "duration": 3.03}, {"text": "of programming, OpenCV, MATLAB,\nC++ , Flash, whatever you like,", "start": 4070.61, "duration": 5.88}, {"text": "Java.", "start": 4076.49, "duration": 0.72}, {"text": "It doesn't really matter to me.", "start": 4077.21, "duration": 1.292}, {"text": "But you'll be doing\na lot of programming.", "start": 4078.502, "duration": 2.788}, {"text": "And those of you who might be\nthinking about the software", "start": 4081.29, "duration": 2.46}, {"text": "only track--", "start": 4083.75, "duration": 1.26}, {"text": "and you might be\ntrying to use GUI.", "start": 4085.01, "duration": 1.59}, {"text": "Actually it will be\na lot of work also.", "start": 4086.6, "duration": 2.77}, {"text": "And those of you\nwho use Photoshop", "start": 4089.37, "duration": 2.12}, {"text": "know very well that if you want\nto do simple edits to a photo,", "start": 4091.49, "duration": 3.27}, {"text": "you take an hour, two\nhour, sometimes six hours.", "start": 4094.76, "duration": 3.179}, {"text": "And you'll realize\nthat sometimes writing", "start": 4097.939, "duration": 1.741}, {"text": "a small program you can\ndo that task much faster,", "start": 4099.68, "duration": 4.02}, {"text": "but it's your cost.", "start": 4103.7, "duration": 2.38}, {"text": "What is helpful\nbut not absolutely", "start": 4106.08, "duration": 2.0}, {"text": "necessary is some knowledge\nin linear algebra,", "start": 4108.08, "duration": 3.72}, {"text": "signal processing,\nimage processing.", "start": 4111.8, "duration": 2.67}, {"text": "But what's critical is that you\nshould be able to think in 3D.", "start": 4114.47, "duration": 5.7}, {"text": "And this is a skill that's\nabsolutely necessary.", "start": 4120.17, "duration": 5.13}, {"text": "If you're going to think\nabout in higher dimensions.", "start": 4125.3, "duration": 2.889}, {"text": "3D is just a beginning,\nbut [? we're ?] thinking", "start": 4128.189, "duration": 2.0}, {"text": "about 40, 60, 80 and so on.", "start": 4130.189, "duration": 4.571}, {"text": "Now we're trying to keep the\nmath to basic essentials.", "start": 4134.76, "duration": 4.46}, {"text": "I like to use a lot of\ndiagrams and visual analogies", "start": 4139.22, "duration": 5.099}, {"text": "in the visual analogies\nto explain the concepts.", "start": 4144.319, "duration": 4.201}, {"text": "But when you're doing\nyour own assignments,", "start": 4148.52, "duration": 1.95}, {"text": "you will have to go\nback to the questions.", "start": 4150.47, "duration": 2.309}, {"text": "I might just flash\nthe question, but I'll", "start": 4152.779, "duration": 1.891}, {"text": "try to explain that again\nby drawing on the board.", "start": 4154.67, "duration": 6.899}, {"text": "But it's possible for you to\ngo through the whole class", "start": 4161.569, "duration": 3.931}, {"text": "without actually writing\ndown a lot of equations.", "start": 4165.5, "duration": 3.779}, {"text": "At the same time, many of\nthese concepts are complex,", "start": 4169.279, "duration": 3.841}, {"text": "and they will arrive\nat a very fast pace.", "start": 4173.12, "duration": 3.094}, {"text": "And we'll be discussing\na lot of concepts.", "start": 4176.214, "duration": 2.395}, {"text": "Now, if you're the kind\nof person who can just sit", "start": 4178.609, "duration": 2.701}, {"text": "back and watch a presentation\nand grasp a concept,", "start": 4181.31, "duration": 3.469}, {"text": "where you ask questions.", "start": 4184.779, "duration": 1.0}, {"text": "It's interactive.", "start": 4185.779, "duration": 1.381}, {"text": "This is an ideal class.", "start": 4187.16, "duration": 2.332}, {"text": "On the other hand, if\nyou're the kind of person", "start": 4189.492, "duration": 1.958}, {"text": "who likes to really\nlook at the math", "start": 4191.45, "duration": 1.5}, {"text": "and see what the relationship\nbetween the variables", "start": 4192.95, "duration": 4.08}, {"text": "is and so on,\nthat's fine as well.", "start": 4197.03, "duration": 2.92}, {"text": "So you need to have\none of those two skills", "start": 4199.95, "duration": 1.82}, {"text": "to be able to do\nwell in this class.", "start": 4201.77, "duration": 4.48}, {"text": "Now assignments for\nthis class is also", "start": 4206.25, "duration": 2.422}, {"text": "going to be a little\nbit different.", "start": 4208.672, "duration": 1.458}, {"text": "As I said during\nthe class, you'll", "start": 4210.13, "duration": 1.94}, {"text": "be listening to a lot of\nadvanced and complex concepts.", "start": 4212.07, "duration": 3.03}, {"text": "But the assignments are\nstructured in such a way", "start": 4215.1, "duration": 3.12}, {"text": "that they have increasing\nlevel of sophistication.", "start": 4218.22, "duration": 3.19}, {"text": "So you can do pretty well\nwithout much background", "start": 4221.41, "duration": 3.44}, {"text": "for up to the first 60%\nor 70% of the assignment.", "start": 4224.85, "duration": 2.88}, {"text": "But to do the last 10% or 20%\nyou will need a good background", "start": 4227.73, "duration": 5.49}, {"text": "in some of these areas.", "start": 4233.22, "duration": 1.295}, {"text": "So that's another\nway of thinking", "start": 4234.515, "duration": 1.375}, {"text": "about how you might be\nable to take this class,", "start": 4235.89, "duration": 3.61}, {"text": "even if you don't have very\nstrong mathematical, algebra,", "start": 4239.5, "duration": 4.01}, {"text": "or signal processing background.", "start": 4243.51, "duration": 1.38}, {"text": "So you can do pretty well,\nup to the 60% or 70% of.", "start": 4244.89, "duration": 3.12}, {"text": "It and again in the superior\nof supporting students", "start": 4248.01, "duration": 3.09}, {"text": "with varying background,\nwhat I will do", "start": 4251.1, "duration": 2.22}, {"text": "is I will normalize\nyour performance", "start": 4253.32, "duration": 3.36}, {"text": "in those homeworks based on\nwhat background you have.", "start": 4256.68, "duration": 3.01}, {"text": "So if I know that you don't have\na linear algebra background,", "start": 4259.69, "duration": 3.8}, {"text": "and you're taking\nthis class, I will", "start": 4263.49, "duration": 1.74}, {"text": "think that if you reach\n70% of that assignment", "start": 4265.23, "duration": 3.51}, {"text": "you have done a pretty good job.", "start": 4268.74, "duration": 1.69}, {"text": "So I'll normalize\nit again by how much", "start": 4270.43, "duration": 2.09}, {"text": "you know in that particular--", "start": 4272.52, "duration": 4.57}, {"text": "the knowledge required for\nthat particular assignment.", "start": 4277.09, "duration": 2.72}, {"text": "So you can really pick your\nlevel of how you want to do it.", "start": 4279.81, "duration": 4.745}, {"text": "And we did this last time,\nand it worked out pretty well.", "start": 4284.555, "duration": 2.375}, {"text": "So we'll see if we\ncan do the same thing.", "start": 4286.93, "duration": 3.27}, {"text": "And those of you who\nare taking the 131", "start": 4290.2, "duration": 2.63}, {"text": "class for undergraduate,\nplease come and talk to me.", "start": 4292.83, "duration": 2.61}, {"text": "And we can similarly\nfigure out based", "start": 4295.44, "duration": 1.77}, {"text": "on the classes you have already\ntaken, how we can structure", "start": 4297.21, "duration": 3.03}, {"text": "those assignments.", "start": 4300.24, "duration": 0.99}, {"text": "For all those assignments,\nthe four or three assignments,", "start": 4304.11, "duration": 2.61}, {"text": "there's always an option.", "start": 4306.72, "duration": 1.47}, {"text": "There are two assignments, and\nyou can pick any one of them.", "start": 4308.19, "duration": 2.74}, {"text": "So that gives you,\nagain, an ability", "start": 4310.93, "duration": 2.18}, {"text": "to pick an assignment that's\nappropriate for your level", "start": 4313.11, "duration": 3.99}, {"text": "of understanding.", "start": 4317.1, "duration": 3.03}, {"text": "All right, so let's see.", "start": 4320.13, "duration": 2.94}, {"text": "Any programming environment\nis fine, OnePlus notes.", "start": 4323.07, "duration": 4.86}, {"text": "Send me an email,\nraskar@media.mit.edu,", "start": 4327.93, "duration": 3.24}, {"text": "to put you on the mailing list.", "start": 4331.17, "duration": 1.92}, {"text": "And we also have a\nsign up sheet that I'll", "start": 4333.09, "duration": 2.213}, {"text": "pass around in the break.", "start": 4335.303, "duration": 1.042}, {"text": "And, remember, our class runs\ninto the happy hour on Friday.", "start": 4339.09, "duration": 3.82}, {"text": "So after the class, we'll all\ngo over to the marriage house", "start": 4342.91, "duration": 3.62}, {"text": "and continue our discussion\nover beer, if you are over 18.", "start": 4346.53, "duration": 5.67}, {"text": "No, 21.", "start": 4352.2, "duration": 1.53}, {"text": "Is it 21?", "start": 4353.73, "duration": 0.66}, {"text": "So that's at 4:30.", "start": 4358.85, "duration": 2.76}, {"text": "This is a rough outline of\nhow we're going to proceed.", "start": 4361.61, "duration": 6.24}, {"text": "We finish on December 4th.", "start": 4367.85, "duration": 2.91}, {"text": "It's funny because the\nclasses end on December 10th.", "start": 4370.76, "duration": 3.93}, {"text": "And our last class would\nhave been December 11th.", "start": 4374.69, "duration": 2.55}, {"text": "So I think having a Friday\nclass with no final exam", "start": 4377.24, "duration": 4.53}, {"text": "means you finish\nreally, really early.", "start": 4381.77, "duration": 2.64}, {"text": "So the semester ends\non December 4th,", "start": 4384.41, "duration": 1.71}, {"text": "which means final projects.", "start": 4386.12, "duration": 1.23}, {"text": "Unfortunately, the week\nbefore that is thanksgiving.", "start": 4387.35, "duration": 3.06}, {"text": "So many of you\nwill be thanking me", "start": 4390.41, "duration": 2.13}, {"text": "for the delay and the\nprocrastination that", "start": 4392.54, "duration": 5.16}, {"text": "led you to work through\nthe Thanksgiving break.", "start": 4397.7, "duration": 3.64}, {"text": "Yeah, there's just a list here.", "start": 4401.34, "duration": 1.83}, {"text": "All right.", "start": 4403.17, "duration": 0.5}, {"text": "So one of the things we will\nnot cover or cover not in detail", "start": 4403.67, "duration": 6.6}, {"text": "are the art and aesthetics\nof photography, the 4343.", "start": 4410.27, "duration": 7.23}, {"text": "Software image\nmanipulation, there's", "start": 4417.5, "duration": 2.82}, {"text": "a great course by Fredo Durand\non digital computational", "start": 4420.32, "duration": 4.08}, {"text": "photography which is\ncompletely focused on software.", "start": 4424.4, "duration": 2.62}, {"text": "So these two classes,\nfirst class and my class,", "start": 4427.02, "duration": 3.02}, {"text": "is actually a very good\ncomplement of each other", "start": 4430.04, "duration": 2.58}, {"text": "because in this class,\nthe emphasis is more", "start": 4432.62, "duration": 2.13}, {"text": "on hardware and\noptics and sensors", "start": 4434.75, "duration": 2.73}, {"text": "and of course, software.", "start": 4437.48, "duration": 1.38}, {"text": "But emphasis is on\nthe hands on elements.", "start": 4438.86, "duration": 3.33}, {"text": "And I believe Fredo's not going\nto teach the class in spring.", "start": 4442.19, "duration": 5.04}, {"text": "But Will Freeman, who's\nalso a great instructor,", "start": 4447.23, "duration": 3.21}, {"text": "is going to teach\nthe class in spring.", "start": 4450.44, "duration": 2.658}, {"text": "That's what I hear.", "start": 4453.098, "duration": 0.792}, {"text": "I haven't confirmed it.", "start": 4453.89, "duration": 2.76}, {"text": "And there are excellent\nclasses in computer vision.", "start": 4456.65, "duration": 3.01}, {"text": "I think, Ted, you are teaching\na class on scene perception.", "start": 4459.66, "duration": 3.38}, {"text": "TED: Shape.", "start": 4463.04, "duration": 0.552}, {"text": "RAMESH RASKAR: For\nshape perception", "start": 4463.592, "duration": 1.458}, {"text": "that's on Mondays, just Mondays.", "start": 4465.05, "duration": 3.375}, {"text": "TED: No, we don't know when.", "start": 4468.425, "duration": 1.167}, {"text": "RAMESH RASKAR: All right.", "start": 4469.592, "duration": 1.041}, {"text": "TED: First class is\nMonday, [INAUDIBLE]..", "start": 4470.633, "duration": 1.917}, {"text": "RAMESH RASKAR: OK, but I already\nsent an email about Ted's class", "start": 4472.55, "duration": 3.15}, {"text": "on the mailing list.", "start": 4475.7, "duration": 1.36}, {"text": "So once I hear from you,\nI'll send it out again.", "start": 4477.06, "duration": 2.93}, {"text": "There are a couple of\ngreat optics classes.", "start": 4479.99, "duration": 2.58}, {"text": "This class is not about optics.", "start": 4482.57, "duration": 1.59}, {"text": "You'll be learning\na lot of concept.", "start": 4484.16, "duration": 1.5}, {"text": "But the emphasis\nis not on optics.", "start": 4485.66, "duration": 1.98}, {"text": "The emphasis is on\nimaging and photography.", "start": 4487.64, "duration": 3.39}, {"text": "We will not learn\nabout Photoshop.", "start": 4491.03, "duration": 1.59}, {"text": "Actually, I don't even know\nPhotoshop that very well.", "start": 4492.62, "duration": 2.598}, {"text": "So if you're going to do your\nassignments in Photoshop,", "start": 4495.218, "duration": 2.292}, {"text": "please come and tell me.", "start": 4497.51, "duration": 1.26}, {"text": "I'll look forward to it.", "start": 4498.77, "duration": 2.7}, {"text": "And we won't talk\nabout anything that's", "start": 4501.47, "duration": 1.77}, {"text": "included in the instruction\nmanual of the camera.", "start": 4503.24, "duration": 2.31}, {"text": "So you will not learn about\nhow to set the exposure", "start": 4505.55, "duration": 2.94}, {"text": "and how to change the aperture.", "start": 4508.49, "duration": 1.53}, {"text": "I'm happy to do a separate crash\ncourse, one of the evenings.", "start": 4510.02, "duration": 3.99}, {"text": "And we can all sit\ntogether and do a course.", "start": 4514.01, "duration": 5.22}, {"text": "On the many people\nhere it is super expert", "start": 4519.23, "duration": 2.28}, {"text": "with all kinds of\ncameras, and he'll", "start": 4521.51, "duration": 2.67}, {"text": "be happy to do that as well.", "start": 4524.18, "duration": 1.18}, {"text": "So there are a lot of\nresources available if you", "start": 4525.36, "duration": 2.0}, {"text": "have those questions.", "start": 4527.36, "duration": 0.96}, {"text": "But this class is\nnot really a program.", "start": 4528.32, "duration": 3.64}, {"text": "So as I said a few\nclasses I teach a class", "start": 4531.96, "duration": 3.42}, {"text": "that's more discussion\noriented in spring,", "start": 4535.38, "duration": 3.57}, {"text": "the computational photography\nclass and optics class.", "start": 4538.95, "duration": 3.87}, {"text": "And Professor Han, I don't if\nhe's teaching it in Spring.", "start": 4542.82, "duration": 5.16}, {"text": "Yeah, I don't know.", "start": 4547.98, "duration": 2.31}, {"text": "All right, so any questions\nabout the structure", "start": 4550.29, "duration": 2.58}, {"text": "of the class and\nwhat you expect?", "start": 4552.87, "duration": 4.93}, {"text": "Rose, yes.", "start": 4557.8, "duration": 0.515}, {"text": "AUDIENCE: Will you be posting\nthe assignments in advance", "start": 4558.315, "duration": 3.075}, {"text": "so we can kind of\nsee what sort of work", "start": 4561.39, "duration": 1.88}, {"text": "will we be doing and\nengaging with during class?", "start": 4563.27, "duration": 2.313}, {"text": "RAMESH RASKAR:\nExcellent question.", "start": 4565.583, "duration": 1.417}, {"text": "The question was, will I be\nposting assignments in advance?", "start": 4567.0, "duration": 4.11}, {"text": "What's going to happen is based\non the feedback I receive.", "start": 4571.11, "duration": 2.82}, {"text": "Some of the assignments\nwill change.", "start": 4573.93, "duration": 1.6}, {"text": "But if you look at the OCW page\nfrom last year for this course,", "start": 4575.53, "duration": 7.89}, {"text": "which is only an\nindication by the way", "start": 4583.42, "duration": 2.03}, {"text": "because of course it's changing\nsignificantly this year,", "start": 4585.45, "duration": 2.53}, {"text": "you will see the--", "start": 4587.98, "duration": 1.82}, {"text": "let's see the projects.", "start": 4589.8, "duration": 0.96}, {"text": "You'll see the\ntype of assignments", "start": 4596.35, "duration": 1.95}, {"text": "that were given out.", "start": 4598.3, "duration": 1.42}, {"text": "It has all the details as well.", "start": 4599.72, "duration": 2.15}, {"text": "So four assignments,\nwriting and so on.", "start": 4601.87, "duration": 4.15}, {"text": "So you can already get a sense\nof the type of assignments", "start": 4606.02, "duration": 2.63}, {"text": "that were given.", "start": 4608.65, "duration": 0.91}, {"text": "And so, again, the options.", "start": 4609.56, "duration": 5.64}, {"text": "There is 4A and 4B for example.", "start": 4615.2, "duration": 2.22}, {"text": "So you can choose which\none you would like to do.", "start": 4617.42, "duration": 3.99}, {"text": "Again, the OpenCourseWare page\nis for last year's course.", "start": 4621.41, "duration": 3.87}, {"text": "And we are recording\nit for this year.", "start": 4625.28, "duration": 2.13}, {"text": "But it's not up\nhere till next fall.", "start": 4627.41, "duration": 3.58}, {"text": "So there's a long delay\nbefore the model appears.", "start": 4630.99, "duration": 3.77}, {"text": "And next year we'll be doing\nsomething entirely different", "start": 4634.76, "duration": 3.46}, {"text": "again.", "start": 4638.22, "duration": 0.5}, {"text": "Other questions?", "start": 4642.8, "duration": 0.81}, {"text": "All right, so let's go\naround very briefly.", "start": 4648.47, "duration": 2.42}, {"text": "I realize there are\nquite a few people.", "start": 4650.89, "duration": 2.46}, {"text": "So maybe 30 seconds\nper person no more than", "start": 4653.35, "duration": 4.08}, {"text": "that just to get a\nsense of who's here", "start": 4657.43, "duration": 4.08}, {"text": "and why you are here.", "start": 4661.51, "duration": 2.29}, {"text": "So before we get started.", "start": 4663.8, "duration": 2.64}, {"text": "Are you a photographer?", "start": 4666.44, "duration": 1.65}, {"text": "All right, almost everybody.", "start": 4671.31, "duration": 1.27}, {"text": "How many of you\nare videographer?", "start": 4672.58, "duration": 1.76}, {"text": "You create videos.", "start": 4674.34, "duration": 0.795}, {"text": "It's funny.", "start": 4678.28, "duration": 0.6}, {"text": "Why there's a distinction\nbetween photographers", "start": 4678.88, "duration": 1.958}, {"text": "and videographers?", "start": 4680.838, "duration": 2.152}, {"text": "Do you use cameras\nfor computer vision.", "start": 4682.99, "duration": 5.26}, {"text": "Pretty good.", "start": 4688.25, "duration": 1.36}, {"text": "Do you use cameras for\nreal time processing", "start": 4689.61, "duration": 2.92}, {"text": "like HCI or robotics and so on?", "start": 4692.53, "duration": 3.64}, {"text": "OK.", "start": 4696.17, "duration": 1.77}, {"text": "Do you have background\nin optics or sensors?", "start": 4697.94, "duration": 3.83}, {"text": "OK, all right.", "start": 4701.77, "duration": 0.97}, {"text": "So we have pretty good\ndistribution here.", "start": 4702.74, "duration": 2.29}, {"text": "So so let's start\nand very quickly go", "start": 4705.03, "duration": 2.3}, {"text": "to the just your\nname, department here,", "start": 4707.33, "duration": 5.76}, {"text": "and why you're here,\njust 30 seconds.", "start": 4713.09, "duration": 2.34}, {"text": "I take this opportunity to\nsay that Professor Oliveira is", "start": 4721.44, "duration": 3.33}, {"text": "the top scientist in graphics\nand vision from Brazil,", "start": 4724.77, "duration": 2.55}, {"text": "and he'll be in our group.", "start": 4727.32, "duration": 1.38}, {"text": "And we are sending him\nand Professor Mukaigawa", "start": 4728.7, "duration": 3.87}, {"text": "who is a famous researcher\nfrom Osaka University", "start": 4732.57, "duration": 3.96}, {"text": "and both of them, as\nwell as Ankit Mohan, who", "start": 4736.53, "duration": 3.03}, {"text": "is a scientist, those 3\nand some additional people", "start": 4739.56, "duration": 3.12}, {"text": "will be the mentors\nfor this class.", "start": 4742.68, "duration": 2.62}, {"text": "So if you have any\nquestions, you can come to me", "start": 4745.3, "duration": 2.15}, {"text": "or if you want to brainstorm\nabout projects or ideas", "start": 4747.45, "duration": 3.84}, {"text": "or have questions, they\nwill be available as well", "start": 4751.29, "duration": 2.64}, {"text": "during the week.", "start": 4753.93, "duration": 1.34}, {"text": "Oh, this is amazing,\njust an amazing set", "start": 4761.3, "duration": 1.8}, {"text": "of people, chemistry, arts,\ncommunication, vision, HCI.", "start": 4763.1, "duration": 6.745}, {"text": "It's going to be fun.", "start": 4769.845, "duration": 0.875}, {"text": "Night vision goggles.", "start": 4770.72, "duration": 2.43}, {"text": "Night vision goggles.", "start": 4773.15, "duration": 1.122}, {"text": "That would have\ntaken us over 100k.", "start": 4774.272, "duration": 1.458}, {"text": "All right.", "start": 4778.83, "duration": 0.5}, {"text": "So let me just quickly make\na couple of announcements,", "start": 4779.33, "duration": 3.0}, {"text": "and we'll break.", "start": 4782.33, "duration": 2.7}, {"text": "So there's a great\nopportunity for those of you", "start": 4785.03, "duration": 3.21}, {"text": "who are taking this\nclass or credit.", "start": 4788.24, "duration": 1.5}, {"text": "And there's a conference on\ncomputational photography", "start": 4789.74, "duration": 3.75}, {"text": "which is the second edition of\nFredo Durand who some of you", "start": 4793.49, "duration": 3.63}, {"text": "may know from CSAIL.", "start": 4797.12, "duration": 1.95}, {"text": "And Mark LeVoy and Eric\nZaleski from Microsoft", "start": 4799.07, "duration": 4.74}, {"text": "did the first one, which\nwas this year in April.", "start": 4803.81, "duration": 3.33}, {"text": "And myself and [INAUDIBLE] from\nToronto and Raphael Bastion", "start": 4807.14, "duration": 4.47}, {"text": "from Colorado was one\nof the world's experts", "start": 4811.61, "duration": 2.52}, {"text": "in wavefront coding.", "start": 4814.13, "duration": 2.01}, {"text": "Three of us are doing the second\nedition of this conference.", "start": 4816.14, "duration": 4.72}, {"text": "And it will be held\nhere in the new building", "start": 4820.86, "duration": 3.5}, {"text": "in the last week of March.", "start": 4824.36, "duration": 3.63}, {"text": "And the papers are\ndue in November.", "start": 4827.99, "duration": 3.31}, {"text": "So if you're doing\nwell in this class,", "start": 4831.3, "duration": 1.86}, {"text": "and one of the project\nideas is interesting,", "start": 4833.16, "duration": 3.14}, {"text": "you could even attempt\nto submit a paper", "start": 4836.3, "duration": 3.66}, {"text": "for this particular\nconference or at least", "start": 4839.96, "duration": 2.56}, {"text": "as a demo or a poster\nor something like that.", "start": 4842.52, "duration": 2.19}, {"text": "So it's right here on campus.", "start": 4844.71, "duration": 2.36}, {"text": "And most likely we'll have\nadditional opportunities", "start": 4847.07, "duration": 3.06}, {"text": "who are not in the\npeer review track", "start": 4850.13, "duration": 2.78}, {"text": "to show off your work as well.", "start": 4852.91, "duration": 1.91}, {"text": "So this is really catching on.", "start": 4854.82, "duration": 2.18}, {"text": "A lot of big companies\nlike Nokia and Samsung", "start": 4857.0, "duration": 3.72}, {"text": "and Canon and HP all have\nstarted big research groups", "start": 4860.72, "duration": 5.25}, {"text": "in computational photography\nand computational cameras.", "start": 4865.97, "duration": 2.7}, {"text": "So there's a lot of interest.", "start": 4868.67, "duration": 4.74}, {"text": "Another thing we're going\nto do in this class is--", "start": 4873.41, "duration": 4.2}, {"text": "as I said, it is\npossible to come up", "start": 4877.61, "duration": 1.77}, {"text": "with completely new\nideas in this field.", "start": 4879.38, "duration": 1.9}, {"text": "It's such a new field\nbecause of the intersection", "start": 4881.28, "duration": 2.585}, {"text": "of lots of interesting domains.", "start": 4883.865, "duration": 3.205}, {"text": "So we're going to learn how\nto come up with new ideas.", "start": 4887.07, "duration": 3.5}, {"text": "And we're going to learn\nhow to write a good paper.", "start": 4890.57, "duration": 3.18}, {"text": "We're not going to do it\nexactly it in the class.", "start": 4893.75, "duration": 2.58}, {"text": "But toward the semester\nduring discussions", "start": 4896.33, "duration": 2.79}, {"text": "with me and your mentors,\nwe will help you actually", "start": 4899.12, "duration": 4.08}, {"text": "write a good quality paper.", "start": 4903.2, "duration": 2.91}, {"text": "And writing a good\nquality paper actually", "start": 4906.11, "duration": 2.31}, {"text": "has really simple\nmethodologies which is amazing.", "start": 4908.42, "duration": 3.64}, {"text": "We never learn about\nit in a formal class.", "start": 4912.06, "duration": 2.31}, {"text": "So we'll try to do\nthat in this class", "start": 4914.37, "duration": 3.05}, {"text": "because the final project\nis really important.", "start": 4917.42, "duration": 2.37}, {"text": "So just deciding if an\nidea is worth pursuing", "start": 4919.79, "duration": 3.9}, {"text": "is half the battle.", "start": 4923.69, "duration": 1.42}, {"text": "And we'll help you do that,\nyou can actually just use", "start": 4925.11, "duration": 3.02}, {"text": "the Heilmeier's rules\nwhich the military uses", "start": 4928.13, "duration": 3.63}, {"text": "to decide whether they\nshould pursue a project.", "start": 4931.76, "duration": 2.445}, {"text": "And raise simple questions.", "start": 4934.205, "duration": 1.125}, {"text": "If we answer those questions,\nyou can very quickly", "start": 4935.33, "duration": 2.46}, {"text": "make a decision whether you\nshould pursue that project.", "start": 4937.79, "duration": 3.42}, {"text": "And as I said last year was\nextremely, extremely beautiful.", "start": 4941.21, "duration": 2.97}, {"text": "There were papers that\nbecame SIGGRAPH submissions.", "start": 4944.18, "duration": 5.79}, {"text": "Matt Hirsch, who took\nthis class last year,", "start": 4949.97, "duration": 2.07}, {"text": "went to SIGGRAPH and also in\nthe student research competition", "start": 4952.04, "duration": 3.72}, {"text": "this year based on the\nlast project he did.", "start": 4955.76, "duration": 2.64}, {"text": "And there are two\nmajor research teams", "start": 4958.4, "duration": 2.49}, {"text": "that are coming out one\nin mechanical engineering.", "start": 4960.89, "duration": 2.762}, {"text": "Some students, they're starting\nthis multi hundred thousand", "start": 4963.652, "duration": 2.458}, {"text": "dollar project based on the\nclass project here and so on.", "start": 4966.11, "duration": 2.77}, {"text": "So we really want you to\nfocus on novel ideas that", "start": 4968.88, "duration": 3.29}, {"text": "are cool and publishable.", "start": 4972.17, "duration": 3.51}, {"text": "Of course, those of you who\nhave a design background or art", "start": 4975.68, "duration": 2.49}, {"text": "background, we also will try\nto think about how they can", "start": 4978.17, "duration": 3.36}, {"text": "be given the right exposure.", "start": 4981.53, "duration": 3.638}, {"text": "And when it comes to\ntechnical publication,", "start": 4985.168, "duration": 1.792}, {"text": "there are some\nsimple rules that you", "start": 4986.96, "duration": 1.71}, {"text": "can follow to write a\nreasonable quality paper.", "start": 4988.67, "duration": 3.15}, {"text": "So will help you do that.", "start": 4991.82, "duration": 2.59}, {"text": "So let me stop there\nwith this image", "start": 4994.41, "duration": 3.68}, {"text": "to make you go a\nlittle bit dizzy.", "start": 4998.09, "duration": 2.07}, {"text": "And then we'll reconvene\nin about 10 minutes.", "start": 5000.16, "duration": 3.39}, {"text": "And in the second half, we will\nhave a fast forward preview", "start": 5003.55, "duration": 3.48}, {"text": "of the whole class.", "start": 5007.03, "duration": 1.66}, {"text": "So we'll spend\nabout 2 to 3 minutes", "start": 5008.69, "duration": 3.32}, {"text": "on each of the projects.", "start": 5012.01, "duration": 1.35}, {"text": "We have 12 classes.", "start": 5013.36, "duration": 1.98}, {"text": "We'll spend about 5\nminutes on each class,", "start": 5015.34, "duration": 1.89}, {"text": "and we will see all the pieces.", "start": 5017.23, "duration": 2.59}, {"text": "So in the break, we'll\nalso have the IR.", "start": 5019.82, "duration": 2.96}, {"text": "camera you can try that.", "start": 5022.78, "duration": 2.67}, {"text": "And Dan [? Sarkis ?] suggested\nfor all of us to build this--", "start": 5025.45, "duration": 7.83}, {"text": "what do you call it?", "start": 5033.28, "duration": 1.72}, {"text": "A pinhole camera from\njust a piece of paper.", "start": 5035.0, "duration": 3.507}, {"text": "So you can just take\na piece of paper,", "start": 5038.507, "duration": 1.583}, {"text": "cut it up, and build\na pinhole camera.", "start": 5040.09, "duration": 2.83}, {"text": "So if you want to do some\nprojects in that space--", "start": 5042.92, "duration": 3.658}, {"text": "AUDIENCE: Hi.", "start": 5046.578, "duration": 0.542}, {"text": "[SIDE CONVERSATION]", "start": 5047.12, "duration": 2.56}]
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+[{"text": "[SOUND EFFECTS]", "start": 0.5, "duration": 3.42}, {"text": "PROFESSOR: OK, I just want to\njust highlight your attention", "start": 16.68, "duration": 3.66}, {"text": "to things.", "start": 20.34, "duration": 0.96}, {"text": "Like every day, I get\nthat MIT news feed.", "start": 21.3, "duration": 2.16}, {"text": "I get a couple of\nother news feeds.", "start": 23.46, "duration": 1.71}, {"text": "And I just thought this was\nreally sort of a striking image", "start": 25.17, "duration": 3.36}, {"text": "and I think a great way to\nconvey science and engineering", "start": 28.53, "duration": 4.53}, {"text": "is through sort of really\neye catching imagery.", "start": 33.06, "duration": 4.24}, {"text": "This is a synapse, which\nis where nerves contact", "start": 37.3, "duration": 3.89}, {"text": "to other nerves or to the\nneuromuscular junction", "start": 41.19, "duration": 2.55}, {"text": "in order to trigger activity.", "start": 43.74, "duration": 3.15}, {"text": "And this is a piece of research\nout of the Cima-- whoops,", "start": 46.89, "duration": 5.16}, {"text": "go back one-- whoops,\ngo back one more--", "start": 52.05, "duration": 3.39}, {"text": "between the Cima\nand Langer labs,", "start": 55.44, "duration": 3.54}, {"text": "where they've designed\nlittle tiny microchip probes.", "start": 58.98, "duration": 4.1}, {"text": "They're about 10 microns big.", "start": 63.08, "duration": 2.59}, {"text": "They can be planted in the\nbrain in different sites,", "start": 65.67, "duration": 3.75}, {"text": "hopefully non-invasively.", "start": 69.42, "duration": 2.74}, {"text": "And they can report\non concentrations", "start": 72.16, "duration": 2.69}, {"text": "of this neurotransmitter,\ndopamine.", "start": 74.85, "duration": 2.68}, {"text": "And the reason you might\nwant to be able to do that", "start": 77.53, "duration": 2.33}, {"text": "is that there is a\ndopamine deficit in a lot", "start": 79.86, "duration": 2.7}, {"text": "of neurologic disorders.", "start": 82.56, "duration": 1.84}, {"text": "So you would like to understand\nwhat the deficits are", "start": 84.4, "duration": 3.14}, {"text": "and pinpoint points of the\nbrain where there may be issues.", "start": 87.54, "duration": 4.78}, {"text": "And in fact, they used it to\ntrack Parkinson's disease.", "start": 92.32, "duration": 6.32}, {"text": "Because Parkinson's\ndisease, some", "start": 98.64, "duration": 2.25}, {"text": "of the therapeutic approaches\ninvolve deep brain stimulation.", "start": 100.89, "duration": 4.8}, {"text": "But you can't\nreally tell if it's", "start": 105.69, "duration": 1.53}, {"text": "working unless you\ncan measure something.", "start": 107.22, "duration": 2.49}, {"text": "And the thing that\nyou could measure", "start": 109.71, "duration": 1.53}, {"text": "would be the absolute levels\nof this neurotransmitter,", "start": 111.24, "duration": 3.6}, {"text": "dopamine, which, by the way, is\noriginated from the amino acid", "start": 114.84, "duration": 5.7}, {"text": "tyrosine.", "start": 120.54, "duration": 1.44}, {"text": "You could sort of spot\nsome of the parts of that.", "start": 121.98, "duration": 2.67}, {"text": "That would be the carbon.", "start": 124.65, "duration": 2.76}, {"text": "Becomes a c-- there's a\ncarboxylate and an amine.", "start": 127.41, "duration": 4.38}, {"text": "Oh, I've drawn the alcohol.", "start": 131.79, "duration": 2.32}, {"text": "This should be an NH2.", "start": 134.11, "duration": 1.45}, {"text": "Sorry, I just added\nthis at last minute.", "start": 135.56, "duration": 2.08}, {"text": "So dopamine actually though\noriginates from tyrosine.", "start": 137.64, "duration": 4.05}, {"text": "So I just thought you would\nbe interested because when", "start": 141.69, "duration": 2.7}, {"text": "I talk about the highlighting\nthings that are in the news,", "start": 144.39, "duration": 3.33}, {"text": "I mean things like this where\nwe're all kind of interested.", "start": 147.72, "duration": 3.99}, {"text": "It's cool.", "start": 151.71, "duration": 0.63}, {"text": "It's relevant to what we do.", "start": 152.34, "duration": 2.28}, {"text": "And it really\ncombines the efforts", "start": 154.62, "duration": 3.36}, {"text": "of scientists and engineers\nto make tools and methods", "start": 157.98, "duration": 4.2}, {"text": "and invent methods\nto make measurements", "start": 162.18, "duration": 2.82}, {"text": "that are quantitative\nenough to guide", "start": 165.0, "duration": 2.31}, {"text": "the analysis of a disorder.", "start": 167.31, "duration": 3.7}, {"text": "So I just want to wrap up a\nlittle bit on the aspects.", "start": 171.01, "duration": 3.93}, {"text": "I was showing you the energy\ndiagrams in the last class", "start": 174.94, "duration": 3.5}, {"text": "and telling you how enzymes\naffect the course of a reaction", "start": 178.44, "duration": 5.28}, {"text": "by lowering the\nenergy of activation,", "start": 183.72, "duration": 2.76}, {"text": "by stabilizing a transition\nstate or a high energy", "start": 186.48, "duration": 3.24}, {"text": "intermediate state.", "start": 189.72, "duration": 1.65}, {"text": "So the energy of\nactivation becomes", "start": 191.37, "duration": 1.91}, {"text": "smaller in the\ncatalyzed reaction,", "start": 193.28, "duration": 2.39}, {"text": "therefore faster than\nany uncatalyzed reaction.", "start": 195.67, "duration": 3.26}, {"text": "And I did not give you\nthis number last time.", "start": 198.93, "duration": 2.52}, {"text": "Enzymes catalyze\nreactions through about 10", "start": 201.45, "duration": 4.44}, {"text": "to the 6, a million\n10 to the 10-fold.", "start": 205.89, "duration": 3.84}, {"text": "So these are dramatic\nincreases in rates", "start": 209.73, "duration": 3.12}, {"text": "that are really physio-- we\ndepend on physiologically.", "start": 212.85, "duration": 3.81}, {"text": "They ensure specificity.", "start": 216.66, "duration": 1.68}, {"text": "And they're essential\nin all systems.", "start": 218.34, "duration": 2.16}, {"text": "And the way we discuss energetic\nchanges in reaction diagrams", "start": 220.5, "duration": 6.54}, {"text": "is by looking at what's\nknown as the delta", "start": 227.04, "duration": 2.13}, {"text": "G. It's the change\nin free energy.", "start": 229.17, "duration": 2.97}, {"text": "What I show you here is an\nexergonic reaction, where", "start": 232.14, "duration": 4.23}, {"text": "it is a negative delta G. I\ndidn't reinforce that point", "start": 236.37, "duration": 3.75}, {"text": "enough last time.", "start": 240.12, "duration": 1.41}, {"text": "The energy of the products\nis lower than the energy", "start": 241.53, "duration": 3.45}, {"text": "of the substrates.", "start": 244.98, "duration": 1.3}, {"text": "So energy is given out at the\nend of the transformation.", "start": 246.28, "duration": 3.62}, {"text": "That means the reaction\nis favorable with respect", "start": 249.9, "duration": 3.45}, {"text": "to an equilibrium, a\nthermodynamic parameter.", "start": 253.35, "duration": 3.299}, {"text": "And then it's the\nenzyme that takes", "start": 256.649, "duration": 2.101}, {"text": "care of the kinetic\naspects of the reaction.", "start": 258.75, "duration": 5.05}, {"text": "So just to sort of\nshow you the correlate,", "start": 263.8, "duration": 2.83}, {"text": "an endergonic reaction\nwould look like this,", "start": 266.63, "duration": 3.34}, {"text": "where the delta G is positive.", "start": 269.97, "duration": 2.28}, {"text": "The products are less stable\nthan the starting materials,", "start": 272.25, "duration": 3.13}, {"text": "which would mean the\nreaction is not favorable.", "start": 275.38, "duration": 2.81}, {"text": "But it will still proceed in\nthe presence of a catalyst.", "start": 278.19, "duration": 2.94}, {"text": "And in this next\nsmall bit where we", "start": 281.13, "duration": 1.56}, {"text": "talk about pathways\nand different aspects", "start": 282.69, "duration": 3.42}, {"text": "of metabolism, I'm\ngoing to tell you", "start": 286.11, "duration": 2.52}, {"text": "how we get around the\nunfavorable equilibrium", "start": 288.63, "duration": 3.01}, {"text": "problem.", "start": 291.64, "duration": 0.5}, {"text": "Because that's obviously a big\npredicament in biochemistry.", "start": 292.14, "duration": 3.72}, {"text": "If reactions aren't\nfavorable, why", "start": 295.86, "duration": 2.31}, {"text": "do they go far enough to be\nuseful to us in metabolism?", "start": 298.17, "duration": 6.16}, {"text": "So that reaction would\nhave a positive delta G.", "start": 304.33, "duration": 4.46}, {"text": "And then I also mentioned\nthese two terms.", "start": 308.79, "duration": 2.67}, {"text": "Anabolic refers to the\nendergonic reactions.", "start": 311.46, "duration": 4.13}, {"text": "I don't know why you're\ndoing this to me--", "start": 315.59, "duration": 1.75}, {"text": "the endergonic reactions.", "start": 317.34, "duration": 1.83}, {"text": "And catabolic refers to\nthe exergonic reactions.", "start": 319.17, "duration": 4.56}, {"text": "OK, then this last point--", "start": 323.73, "duration": 2.04}, {"text": "I showed you this\nslide last time.", "start": 325.77, "duration": 2.25}, {"text": "But I think it was\nimportant to think about,", "start": 328.02, "duration": 2.34}, {"text": "why are enzymes so big?", "start": 330.36, "duration": 2.1}, {"text": "And I want to give one example\nof an additional genetic", "start": 332.46, "duration": 4.38}, {"text": "mutation that causes a human\ndisorder, where I at least show", "start": 336.84, "duration": 4.41}, {"text": "you how the mutations\nare spread quite", "start": 341.25, "duration": 2.91}, {"text": "a distance from\nthe reaction center", "start": 344.16, "duration": 2.79}, {"text": "to show you that all of\nthat structure that you see", "start": 346.95, "duration": 3.66}, {"text": "in an enzyme as it interacts\nwith a small substrate", "start": 350.61, "duration": 4.41}, {"text": "is critical for catalysis.", "start": 355.02, "duration": 2.25}, {"text": "So we see small\nsubstrates in each case.", "start": 357.27, "duration": 3.37}, {"text": "But we have this\nvery large enzyme,", "start": 360.64, "duration": 2.39}, {"text": "which is many, many times its\nsize, all engaged in catalysis.", "start": 363.03, "duration": 4.86}, {"text": "But what's the proof of that?", "start": 367.89, "duration": 2.95}, {"text": "So why are enzymes so big?", "start": 370.84, "duration": 1.49}, {"text": "So phenylketonuria\nis a human disorder.", "start": 372.33, "duration": 3.45}, {"text": "It's one of those\ndisorders that neonates,", "start": 375.78, "duration": 3.84}, {"text": "brand newborns are tested for.", "start": 379.62, "duration": 2.45}, {"text": "They are checked for\nthe genetic signal", "start": 382.07, "duration": 3.34}, {"text": "that shows that the\nprotein will have", "start": 385.41, "duration": 2.04}, {"text": "mutations in its structure.", "start": 387.45, "duration": 2.19}, {"text": "And there are many mutations\nassociated with a defect", "start": 389.64, "duration": 4.44}, {"text": "in this particular protein.", "start": 394.08, "duration": 1.74}, {"text": "And the protein that\nI'm talking about", "start": 395.82, "duration": 2.13}, {"text": "is phenylalanine hydroxylase.", "start": 397.95, "duration": 2.61}, {"text": "So the disorder is\nrelated to defects", "start": 400.56, "duration": 3.3}, {"text": "in phenylalanine hydroxylase.", "start": 403.86, "duration": 1.74}, {"text": "Now what does that enzyme do?", "start": 405.6, "duration": 1.77}, {"text": "It takes phenylalanine and\ninstalls a hydroxyl group", "start": 407.37, "duration": 4.14}, {"text": "opposite to where it's\nattached to the amino acid.", "start": 411.51, "duration": 2.79}, {"text": "So this is the hydrophobic\namino acid phenylalanine.", "start": 414.3, "duration": 3.24}, {"text": "And this is another one of\nthe hydrophobic amino acids", "start": 417.54, "duration": 2.82}, {"text": "in a similar family\nthat's tyrosine.", "start": 420.36, "duration": 2.58}, {"text": "And in fact, it's the precursor\nto dopamine physiologically.", "start": 422.94, "duration": 4.14}, {"text": "Now it turns out\nthere can always", "start": 427.08, "duration": 2.34}, {"text": "be too much of a good thing.", "start": 429.42, "duration": 2.05}, {"text": "So if you have too\nmuch phenylalanine,", "start": 431.47, "duration": 2.45}, {"text": "it has to be converted to\na different amino acid.", "start": 433.92, "duration": 3.18}, {"text": "Because the build\nup of phenylalanine", "start": 437.1, "duration": 2.31}, {"text": "gets to a certain stage\nwhere it is converted itself", "start": 439.41, "duration": 3.18}, {"text": "to a toxic byproduct\nthat actually", "start": 442.59, "duration": 2.67}, {"text": "causes severe mental\ndisorders and seizures.", "start": 445.26, "duration": 4.0}, {"text": "So the body needs to monitor\nthe levels of phenylalanine.", "start": 449.26, "duration": 4.61}, {"text": "And at a certain stage,\nphenylalanine hydroxylase", "start": 453.87, "duration": 3.03}, {"text": "will convert it to tyrosine.", "start": 456.9, "duration": 1.86}, {"text": "So even though\nphenylalanine is essential,", "start": 458.76, "duration": 2.34}, {"text": "too much phenylalanine\nis a bad thing.", "start": 461.1, "duration": 2.8}, {"text": "So that enzyme is the one that\nis associated with defects--", "start": 463.9, "duration": 4.73}, {"text": "with mutations.", "start": 468.63, "duration": 1.31}, {"text": "The lower the activity of\nthe phenylalanine hydroxylase", "start": 469.94, "duration": 3.75}, {"text": "and end you up accumulating\nphenylalanine too high.", "start": 473.69, "duration": 4.48}, {"text": "And so the PAH\nregulates the clearance", "start": 478.17, "duration": 3.84}, {"text": "from the body converting\nit to tyrosine.", "start": 482.01, "duration": 2.46}, {"text": "So why-- you know, I told you\nI would give you some insight", "start": 484.47, "duration": 4.5}, {"text": "into how entire enzymes are in\nfact critical for cat lysis.", "start": 488.97, "duration": 5.88}, {"text": "So what I'm showing you\non this a little movie is", "start": 494.85, "duration": 3.18}, {"text": "that the sites shown in magenta\nall around this protein,", "start": 498.03, "duration": 4.17}, {"text": "the active site would be\nwhere this big ball is.", "start": 502.2, "duration": 2.37}, {"text": "It's actually cofactor iron.", "start": 504.57, "duration": 2.91}, {"text": "But the sites that are involved\nin the reduction of activity", "start": 507.48, "duration": 3.42}, {"text": "of phenylalanine hydroxylase\nare way out on the protein,", "start": 510.9, "duration": 3.81}, {"text": "out on its perimeters.", "start": 514.71, "duration": 1.41}, {"text": "So this protein is\nabout 49 angstroms,", "start": 516.12, "duration": 4.47}, {"text": "4.9 nanometers across.", "start": 520.59, "duration": 2.86}, {"text": "But the sites that cause\na reduction in activity", "start": 523.45, "duration": 2.93}, {"text": "are a long way away,\n10 angstroms longer,", "start": 526.38, "duration": 3.53}, {"text": "15 angstroms, 16.", "start": 529.91, "duration": 2.14}, {"text": "So it turns out that\nenzymes as catalysts", "start": 532.05, "duration": 2.52}, {"text": "don't just use the local\nenvironment right near where", "start": 534.57, "duration": 2.97}, {"text": "chemistry happens.", "start": 537.54, "duration": 1.29}, {"text": "The entire protein collaborates\nto make the changes happen", "start": 538.83, "duration": 4.8}, {"text": "in catalysis.", "start": 543.63, "duration": 1.32}, {"text": "So enzymes are big,\nbecause you're not just", "start": 544.95, "duration": 2.43}, {"text": "using this inner shell\nof functional groups", "start": 547.38, "duration": 2.7}, {"text": "where the substrate binds.", "start": 550.08, "duration": 1.38}, {"text": "You're actually using a lot\nof the dynamics of the enzyme", "start": 551.46, "duration": 3.87}, {"text": "to promote catalysis.", "start": 555.33, "duration": 2.19}, {"text": "And just this sort\nof visual shows you", "start": 557.52, "duration": 3.48}, {"text": "how far away things\ncan be where they", "start": 561.0, "duration": 2.52}, {"text": "suppress the\nactivity of a protein", "start": 563.52, "duration": 2.43}, {"text": "and make it a poorer catalyst.", "start": 565.95, "duration": 1.74}, {"text": "OK.", "start": 567.69, "duration": 1.77}, {"text": "So as I said, this is\none of the disorders,", "start": 569.46, "duration": 4.97}, {"text": "the genetic mutations that\nis tested for at birth.", "start": 574.43, "duration": 3.43}, {"text": "If you have one of\nthese set of mutations,", "start": 577.86, "duration": 2.91}, {"text": "you immediately have to\nbe put on a diet that's", "start": 580.77, "duration": 3.93}, {"text": "low in phenylalanine, so\nyou don't bombard your body", "start": 584.7, "duration": 3.03}, {"text": "with too much phenylalanine,\nnot allowing the phenylalanine", "start": 587.73, "duration": 5.82}, {"text": "to build up too much.", "start": 593.55, "duration": 1.35}, {"text": "But I don't know if\nany of you have lately", "start": 594.9, "duration": 2.58}, {"text": "grabbed a can of\nCoca-Cola that's", "start": 597.48, "duration": 2.04}, {"text": "got aspartame as a sweetener.", "start": 599.52, "duration": 2.55}, {"text": "It turns out that sweetener,\nNutraSweet rather,", "start": 602.07, "duration": 3.51}, {"text": "is a dipeptide.", "start": 605.58, "duration": 2.23}, {"text": "See?", "start": 607.81, "duration": 0.77}, {"text": "But it contains phenylalanine.", "start": 608.58, "duration": 2.22}, {"text": "So if you drink a ton of diet\ndrinks that include NutraSweet,", "start": 610.8, "duration": 4.8}, {"text": "you are actually\nbombing yourself", "start": 615.6, "duration": 2.31}, {"text": "with high levels\nof phenylalanine", "start": 617.91, "duration": 2.53}, {"text": "that the body can't deal with.", "start": 620.44, "duration": 1.52}, {"text": "So people who have\nphenylketonuria,", "start": 621.96, "duration": 2.19}, {"text": "i.e. a defect in that enzyme,\nshouldn't be drinking or using", "start": 624.15, "duration": 4.29}, {"text": "NutraSweet type sweeteners.", "start": 628.44, "duration": 1.92}, {"text": "Because they actually\ngive you too much", "start": 630.36, "duration": 1.95}, {"text": "phenylalanine at once, that\nyou can mitigate the levels of.", "start": 632.31, "duration": 4.08}, {"text": "So I want to just tell you\nabout these genetic disorders.", "start": 636.39, "duration": 3.66}, {"text": "There's a fairly decent set\nthat are tested for at birth.", "start": 640.05, "duration": 3.93}, {"text": "But the ones that are\ntested are for ones", "start": 643.98, "duration": 2.1}, {"text": "that you can make dietary\nmodifications or lifestyle", "start": 646.08, "duration": 3.06}, {"text": "modifications and\nmitigate the symptoms.", "start": 649.14, "duration": 3.97}, {"text": "And so that's a very\nimportant thing to know.", "start": 653.11, "duration": 3.08}, {"text": "You're not tested for things\nyou don't know how to fix,", "start": 656.19, "duration": 3.57}, {"text": "because that wouldn't\nbe appropriate.", "start": 659.76, "duration": 2.67}, {"text": "All right, any\nquestions about that?", "start": 662.43, "duration": 4.34}, {"text": "Yeah.", "start": 666.77, "duration": 0.671}, {"text": "STUDENT: [INAUDIBLE]", "start": 667.441, "duration": 2.871}, {"text": "PROFESSOR: Yes.", "start": 670.312, "duration": 0.625}, {"text": "STUDENT: [INAUDIBLE]", "start": 670.937, "duration": 1.403}, {"text": "PROFESSOR: Oh, you know, that\nwas me being clunky with--", "start": 672.34, "duration": 2.55}, {"text": "of course you guys\nnotice everything.", "start": 674.89, "duration": 1.804}, {"text": "This morning, I was making--", "start": 679.42, "duration": 1.713}, {"text": "all right, let's go forward.", "start": 681.133, "duration": 1.167}, {"text": "One, two, and that and that.", "start": 682.3, "duration": 3.3}, {"text": "I know exactly what\nyou're talking about.", "start": 685.6, "duration": 1.77}, {"text": "This little curb\ndown, yeah that's", "start": 687.37, "duration": 2.73}, {"text": "me shaking when I'm doing\nthe ChemDraw drawing.", "start": 690.1, "duration": 3.42}, {"text": "It should be flat.", "start": 693.52, "duration": 1.83}, {"text": "But thank you for noticing that.", "start": 695.35, "duration": 1.41}, {"text": "Just so that's not ambiguity,\nthere should not be-- there", "start": 696.76, "duration": 3.15}, {"text": "could be, actually, a little\ndip when substrates bind", "start": 699.91, "duration": 2.37}, {"text": "to enzymes.", "start": 702.28, "duration": 0.57}, {"text": "But I didn't mean to imply it.", "start": 702.85, "duration": 1.78}, {"text": "OK, anything else?", "start": 704.63, "duration": 1.1}, {"text": "OK, so what I want to talk about\nnow is the equilibrium problem.", "start": 709.59, "duration": 5.02}, {"text": "And what is that?", "start": 714.61, "duration": 0.97}, {"text": "So if we have reactions\nthat are endergonic--", "start": 725.66, "duration": 10.9}, {"text": "so we have one of\nthese situations", "start": 736.56, "duration": 2.04}, {"text": "where we have a substrate\ngoing to a product that's", "start": 738.6, "duration": 3.54}, {"text": "higher energy.", "start": 742.14, "duration": 0.705}, {"text": "What that means is, at\nequilibrium between substrate", "start": 745.36, "duration": 3.74}, {"text": "and product, which is\ndefined by the delta G,", "start": 749.1, "duration": 3.72}, {"text": "you have substrate\ngoing to product.", "start": 752.82, "duration": 4.17}, {"text": "But mostly, you've\ngot a lot of substrate", "start": 756.99, "duration": 3.13}, {"text": "there, which is\nthe amount of each", "start": 760.12, "duration": 1.89}, {"text": "of these is defined by\nthis energy difference.", "start": 762.01, "duration": 2.88}, {"text": "OK.", "start": 764.89, "duration": 0.81}, {"text": "So how do we survive with\nthese kinds of transformations", "start": 765.7, "duration": 3.61}, {"text": "when we really want\nthe flux for an enzyme", "start": 769.31, "duration": 3.47}, {"text": "to be in the forward direction?", "start": 772.78, "duration": 3.0}, {"text": "Because if we need the product,\nwe need to move things forward.", "start": 775.78, "duration": 3.67}, {"text": "So nature deals with this\nby coupling reactions", "start": 779.45, "duration": 3.23}, {"text": "to other reactions.", "start": 782.68, "duration": 1.54}, {"text": "So it finds ways around\nthe equilibrium problem", "start": 784.22, "duration": 3.29}, {"text": "by, for example, putting\na series of reactions.", "start": 787.51, "duration": 3.3}, {"text": "For example, let's\ngo from A to B to C.", "start": 790.81, "duration": 5.52}, {"text": "So these are three intermediates\ncatalyzed by enzyme 1,", "start": 796.33, "duration": 5.61}, {"text": "enzyme 2.", "start": 801.94, "duration": 1.27}, {"text": "OK.", "start": 803.21, "duration": 1.04}, {"text": "And let's just say this\nhas an unfavorable delta G.", "start": 804.25, "duration": 4.11}, {"text": "So we don't make-- we have a\nlot of A. We have very little B.", "start": 808.36, "duration": 7.55}, {"text": "And then what happens?", "start": 815.91, "duration": 1.53}, {"text": "How are we going\nto-- and then let's", "start": 817.44, "duration": 1.5}, {"text": "just say, for example,\nthis reaction is favorable.", "start": 818.94, "duration": 4.77}, {"text": "So let's see.", "start": 823.71, "duration": 0.78}, {"text": "The delta G here is positive.", "start": 824.49, "duration": 3.46}, {"text": "The delta G here is negative.", "start": 827.95, "duration": 3.74}, {"text": "So by plus VE, I mean\npositive and negative.", "start": 831.69, "duration": 3.34}, {"text": "So this is a favorable\nreaction, whereas this", "start": 835.03, "duration": 4.47}, {"text": "is an unfavorable reaction.", "start": 839.5, "duration": 2.13}, {"text": "How does putting two\nreactions adjacent", "start": 841.63, "duration": 3.36}, {"text": "to each other happening\non the same substrate", "start": 844.99, "duration": 2.91}, {"text": "and moving through\nhelp that situation?", "start": 847.9, "duration": 2.31}, {"text": "Yeah.", "start": 852.83, "duration": 1.08}, {"text": "STUDENT: [INAUDIBLE]", "start": 853.91, "duration": 4.748}, {"text": "PROFESSOR: Perfect.", "start": 858.658, "duration": 0.792}, {"text": "So the answer here is that, as\nyou take whatever B you have", "start": 859.45, "duration": 5.04}, {"text": "and turn it into C, A has to--", "start": 864.49, "duration": 3.65}, {"text": "A1 has to make more B. So you\nsolve the equilibrium problem", "start": 868.14, "duration": 4.51}, {"text": "in that way to a certain\nextent by just opening the tap", "start": 872.65, "duration": 3.0}, {"text": "at the other end of the series.", "start": 875.65, "duration": 1.78}, {"text": "And nature organizes a ton\nof reactions in sequential", "start": 877.43, "duration": 3.32}, {"text": "pathways to get around\nthese kinds of problems.", "start": 880.75, "duration": 3.82}, {"text": "So this is done by\ncoupling reactions.", "start": 884.57, "duration": 2.83}, {"text": "And so there are\nsome reactions that", "start": 893.7, "duration": 2.02}, {"text": "are highly favorable,\nhighly exothermic,", "start": 895.72, "duration": 3.66}, {"text": "where you can really\nsort of guarantee flux", "start": 899.38, "duration": 2.88}, {"text": "through that enzyme.", "start": 902.26, "duration": 1.32}, {"text": "A lot of these enzymes\nare ATP dependent.", "start": 903.58, "duration": 4.22}, {"text": "They use and burn ATP.", "start": 910.89, "duration": 2.04}, {"text": "So you get a lot of energy out.", "start": 912.93, "duration": 1.92}, {"text": "And they drive the flux\nthrough enzyme one,", "start": 914.85, "duration": 2.79}, {"text": "by enzyme to being an\nexergonic reaction,", "start": 917.64, "duration": 3.25}, {"text": "while the enzyme one\nis and endergonic.", "start": 920.89, "duration": 1.7}, {"text": "So flux is guaranteed.", "start": 922.59, "duration": 1.65}, {"text": "And a lot of pathways sort\nof set up to be in this way", "start": 924.24, "duration": 4.38}, {"text": "with this coupling\nof the chemistries.", "start": 928.62, "duration": 2.58}, {"text": "What else?", "start": 933.9, "duration": 1.63}, {"text": "So what we find is that\nenzymes, first of all,", "start": 935.53, "duration": 8.06}, {"text": "work in pathways where they are\nco-located in certain places.", "start": 943.59, "duration": 7.3}, {"text": "They may be, for\nexample, co-localized", "start": 950.89, "duration": 6.92}, {"text": "to certain organelles\nin a human cell.", "start": 957.81, "duration": 2.22}, {"text": "They may be co-localized\nin the mitochondria", "start": 960.03, "duration": 3.06}, {"text": "or in some organelle.", "start": 963.09, "duration": 4.3}, {"text": "And we'll talk more about\norganelles and mitochondria", "start": 967.39, "duration": 2.87}, {"text": "later.", "start": 970.26, "duration": 1.13}, {"text": "They could be co-localized\nat a membrane.", "start": 971.39, "duration": 3.045}, {"text": "And so you ensure that\nthe enzymes are together", "start": 977.87, "duration": 2.67}, {"text": "by putting them\nin the same place.", "start": 980.54, "duration": 2.1}, {"text": "And then nature\nalso evolves ways", "start": 982.64, "duration": 2.88}, {"text": "where the enzymes physically\ninteract with each other,", "start": 985.52, "duration": 3.24}, {"text": "either covalently\nor non-covalently.", "start": 988.76, "duration": 2.91}, {"text": "So they could be\nassociated in the pathway", "start": 991.67, "duration": 4.05}, {"text": "by some kind of\nnon-covalent interaction.", "start": 995.72, "duration": 3.6}, {"text": "Or you may actually link enzymes\nto make them single species.", "start": 999.32, "duration": 9.07}, {"text": "So if this is enzyme one\nand this is enzyme two,", "start": 1008.39, "duration": 5.43}, {"text": "here you have an enzyme\none, enzyme two single", "start": 1013.82, "duration": 7.02}, {"text": "long polypeptide chain\nthat has two domains.", "start": 1020.84, "duration": 3.773}, {"text": "They can't get away from\neach other, because they're", "start": 1024.613, "duration": 2.167}, {"text": "joined covalently.", "start": 1026.78, "duration": 1.62}, {"text": "And they catalyze\nsequential reactions.", "start": 1028.4, "duration": 2.219}, {"text": "This just doesn't happen\nwith just three enzymes.", "start": 1030.619, "duration": 2.791}, {"text": "It can happen with\n10 enzymes or more.", "start": 1033.41, "duration": 2.459}, {"text": "So there are very clever\nways to ensure the flux", "start": 1035.869, "duration": 3.121}, {"text": "occurs through pathways.", "start": 1038.99, "duration": 3.0}, {"text": "OK.", "start": 1041.99, "duration": 0.5}, {"text": "But don't forget, all along,\nthat each of these enzymes", "start": 1046.609, "duration": 3.601}, {"text": "is responsible for a\nsingle transformation.", "start": 1050.21, "duration": 2.52}, {"text": "That's important.", "start": 1052.73, "duration": 1.35}, {"text": "There's another phenomenon that\nhaving flux through pathways", "start": 1054.08, "duration": 3.39}, {"text": "is very useful for, is to\ndeal with toxic intermediates.", "start": 1057.47, "duration": 6.66}, {"text": "Because that makes\nit very advantageous,", "start": 1069.98, "duration": 2.41}, {"text": "again, to couple reactions.", "start": 1072.39, "duration": 2.53}, {"text": "So let's say product B is toxic.", "start": 1074.92, "duration": 4.285}, {"text": "We don't want it\nhanging around much.", "start": 1082.23, "duration": 1.87}, {"text": "We don't want it released\nfrom an enzyme to go do damage", "start": 1084.1, "duration": 3.4}, {"text": "somewhere in the cell.", "start": 1087.5, "duration": 1.66}, {"text": "So having flux through\na pathway basically", "start": 1089.16, "duration": 2.6}, {"text": "ensures the B never\ngets out of the game.", "start": 1091.76, "duration": 2.4}, {"text": "It just goes straight\nto enzyme two.", "start": 1094.16, "duration": 2.34}, {"text": "So that's another physical\nadvantage of those processes", "start": 1096.5, "duration": 3.75}, {"text": "being linked together.", "start": 1100.25, "duration": 2.04}, {"text": "And finally, the process also\nensures a very nice opportunity", "start": 1102.29, "duration": 5.76}, {"text": "to do regulation.", "start": 1108.05, "duration": 1.71}, {"text": "So here we on this\nslide, I show you", "start": 1109.76, "duration": 2.73}, {"text": "this sort of mega mess\nof metabolic pathways", "start": 1112.49, "duration": 3.21}, {"text": "in physiology.", "start": 1115.7, "duration": 0.75}, {"text": "That there would\nbe the Krebs cycle.", "start": 1116.45, "duration": 2.64}, {"text": "But all the metabolic pathways\nthat are all interlinked.", "start": 1119.09, "duration": 3.48}, {"text": "And many of these pathways\nwill be co-locali--", "start": 1122.57, "duration": 3.15}, {"text": "steps in these pathways will\nbe co-localized as clusters.", "start": 1125.72, "duration": 4.08}, {"text": "And so that deal tells you how\nwe can solve the equilibrium", "start": 1129.8, "duration": 5.25}, {"text": "problem by linking enzymes--", "start": 1135.05, "duration": 2.46}, {"text": "the flux through pathways.", "start": 1137.51, "duration": 1.89}, {"text": "And one of the best examples\nis in aerobic glycolysis,", "start": 1139.4, "duration": 3.84}, {"text": "where in the early\nsteps, they're", "start": 1143.24, "duration": 1.65}, {"text": "not energetically favorable.", "start": 1144.89, "duration": 2.22}, {"text": "You use ATP to start\nto break down glucose.", "start": 1147.11, "duration": 4.11}, {"text": "Then you get to a\ncertain intermediate", "start": 1151.22, "duration": 1.89}, {"text": "where it's conversion\nto a smaller molecule", "start": 1153.11, "duration": 3.42}, {"text": "generates ATP with very\nfavorable reactions.", "start": 1156.53, "duration": 3.25}, {"text": "So glycolysis is a really\ngreat example of this.", "start": 1159.78, "duration": 4.58}, {"text": "Now the other thing that I\njust want to describe to you", "start": 1164.36, "duration": 2.85}, {"text": "is the issue of feedback.", "start": 1167.21, "duration": 4.85}, {"text": "And I've described this\nhere on this slide.", "start": 1172.06, "duration": 4.86}, {"text": "And so we'll talk\nabout it on this slide.", "start": 1176.92, "duration": 2.09}, {"text": "So if we are working\nwith a pathway", "start": 1179.01, "duration": 3.32}, {"text": "that goes through multiple steps\nto make an end product, five", "start": 1182.33, "duration": 5.01}, {"text": "steps, three steps or whatever.", "start": 1187.34, "duration": 2.08}, {"text": "And you've made\ntoo much of that.", "start": 1189.42, "duration": 1.57}, {"text": "You've already made a\nlot of that product.", "start": 1190.99, "duration": 1.75}, {"text": "And you don't need anymore.", "start": 1192.74, "duration": 1.95}, {"text": "Nature also has in place\na regulatory mechanism", "start": 1194.69, "duration": 4.44}, {"text": "to feedback and stop\nflux through the pathway.", "start": 1199.13, "duration": 3.18}, {"text": "You don't just stop\nall the enzymes.", "start": 1202.31, "duration": 2.04}, {"text": "You find a way to\nstop the first enzyme.", "start": 1204.35, "duration": 3.16}, {"text": "So this is a very important\nparadigm in biochemistry.", "start": 1207.51, "duration": 4.64}, {"text": "And that's called\nnegative feedback.", "start": 1212.15, "duration": 2.25}, {"text": "So I'm showing you it here\njust in a very simple cartoon", "start": 1214.4, "duration": 3.51}, {"text": "form in the isoleucine\nbiosynthesis pathway.", "start": 1217.91, "duration": 3.72}, {"text": "That's one of the\nhydrophobic amino acids.", "start": 1221.63, "duration": 2.52}, {"text": "This is an intermediate\nthat is on its way", "start": 1224.15, "duration": 2.97}, {"text": "from this amino acid that\nis polar but not charged,", "start": 1227.12, "duration": 4.41}, {"text": "threonine.", "start": 1231.53, "duration": 0.87}, {"text": "So threonine gets\nconverted to isoleucine.", "start": 1232.4, "duration": 2.88}, {"text": "We need threonine\nto make isoleucine.", "start": 1235.28, "duration": 2.67}, {"text": "But once we got a\nlot of isoleucine,", "start": 1237.95, "duration": 2.33}, {"text": "it binds to the very first\nenzyme in the pathway and acts", "start": 1240.28, "duration": 5.23}, {"text": "as an allosteric regulator\nthat dampens activity.", "start": 1245.51, "duration": 4.35}, {"text": "So in this case, I\njust want to point out", "start": 1249.86, "duration": 2.19}, {"text": "to you that I'm showing a very\ncommon way we notate things.", "start": 1252.05, "duration": 4.44}, {"text": "When we are talking about\ninhibiting a reaction,", "start": 1256.49, "duration": 4.35}, {"text": "we draw it like this.", "start": 1260.84, "duration": 1.32}, {"text": "We align and then align\nto the so the arrow,", "start": 1266.7, "duration": 3.36}, {"text": "see which means you've\nstopped the activity.", "start": 1270.06, "duration": 2.74}, {"text": "So you'll see this\nagain and again.", "start": 1272.8, "duration": 1.95}, {"text": "You're going to see it a\nlot in signaling pathways,", "start": 1274.75, "duration": 2.55}, {"text": "because things often feedback.", "start": 1277.3, "duration": 1.89}, {"text": "So another thing that\nnature ensures, in addition", "start": 1279.19, "duration": 3.45}, {"text": "to not building\nup toxic products", "start": 1282.64, "duration": 1.95}, {"text": "and dealing with\nequilibria, is that you", "start": 1284.59, "duration": 2.13}, {"text": "don't want a ton of enzymes\nworking to make something", "start": 1286.72, "duration": 2.64}, {"text": "you don't need anymore.", "start": 1289.36, "duration": 1.56}, {"text": "So you might as well\ntake the end product", "start": 1290.92, "duration": 2.55}, {"text": "and use it to stop\nthe first enzyme.", "start": 1293.47, "duration": 2.4}, {"text": "As that in product\nbecomes scarce,", "start": 1295.87, "duration": 3.07}, {"text": "it dissociates from\nthe first enzyme.", "start": 1298.94, "duration": 1.97}, {"text": "And it turns the\npathway back on again.", "start": 1300.91, "duration": 2.26}, {"text": "And I think that's a really\nneat way of making that happen.", "start": 1303.17, "duration": 4.18}, {"text": "And also, in these\ncases, the enzymes", "start": 1307.35, "duration": 2.29}, {"text": "have to be clustered as a group.", "start": 1309.64, "duration": 1.56}, {"text": "Because you wouldn't get\nthose local concentrations", "start": 1311.2, "duration": 2.88}, {"text": "to be so advantageous if the\nenzymes weren't co-localized.", "start": 1314.08, "duration": 3.71}, {"text": "So does that make sense?", "start": 1317.79, "duration": 1.81}, {"text": "If they weren't in a really\nnear location, the enzyme that", "start": 1319.6, "duration": 3.45}, {"text": "present produces\nisoleucine, that isoleucine", "start": 1323.05, "duration": 3.18}, {"text": "couldn't bind back to the\nfirst enzyme in the pathway", "start": 1326.23, "duration": 2.91}, {"text": "if they were in different\ncompartments of the cell.", "start": 1329.14, "duration": 3.15}, {"text": "OK, everyone good with that?", "start": 1332.29, "duration": 3.76}, {"text": "Good.", "start": 1336.05, "duration": 1.0}, {"text": "All right.", "start": 1337.05, "duration": 2.03}, {"text": "OK, so now we are moving\non to carbohydrates.", "start": 1339.08, "duration": 3.94}, {"text": "It's a pretty strange\nword, carbohydrate.", "start": 1361.34, "duration": 3.15}, {"text": "But actually, it relates\nto early findings", "start": 1364.49, "duration": 2.87}, {"text": "that glucose is a carbohydrate.", "start": 1367.36, "duration": 3.94}, {"text": "And its molecular\nformula is C6H12O6.", "start": 1371.3, "duration": 2.52}, {"text": "So they called it\na hydrate of carbon", "start": 1376.85, "duration": 3.94}, {"text": "before when they knew the\nelemental composition but they", "start": 1380.79, "duration": 3.27}, {"text": "didn't know anything\nabout the structure.", "start": 1384.06, "duration": 1.92}, {"text": "There's a lot of carbohydrates\nthat don't obey this rule.", "start": 1385.98, "duration": 3.63}, {"text": "But that's where the name comes\nfrom, a hydrate of carbon.", "start": 1389.61, "duration": 4.15}, {"text": "All right now\ncarbohydrates account", "start": 1393.76, "duration": 3.41}, {"text": "for-- what did I have here?", "start": 1397.17, "duration": 3.37}, {"text": "25% of the mass of\nmacromolecules, so", "start": 1400.54, "duration": 5.43}, {"text": "a good amount.", "start": 1405.97, "duration": 1.5}, {"text": "They are very, very\nimportant, carbohydrates", "start": 1407.47, "duration": 2.7}, {"text": "in central metabolism.", "start": 1410.17, "duration": 1.53}, {"text": "We use carbohydrates\nas a source of energy.", "start": 1411.7, "duration": 3.75}, {"text": "But also, carbohydrates\nare a part", "start": 1415.45, "duration": 2.43}, {"text": "of storage of energy in the\nform of polymeric structures,", "start": 1417.88, "duration": 4.44}, {"text": "that I'll describe to you.", "start": 1422.32, "duration": 1.45}, {"text": "There are different ones\nin plants and in humans.", "start": 1423.77, "duration": 3.44}, {"text": "One is glycogen.\nOne is cellulose.", "start": 1427.21, "duration": 4.41}, {"text": "But carbohydrates have an\nincreasingly important role", "start": 1431.62, "duration": 3.66}, {"text": "in the extracellular matrix\nin these polymers that", "start": 1435.28, "duration": 3.3}, {"text": "are wrapped around your cells\nand also as signaling entities", "start": 1438.58, "duration": 4.41}, {"text": "both inside and\noutside the cell.", "start": 1442.99, "duration": 2.47}, {"text": "So we used to think\nof carbohydrates", "start": 1445.46, "duration": 1.91}, {"text": "and straight away connect\nthis with metabolism.", "start": 1447.37, "duration": 2.82}, {"text": "But the story is far\ngreater than that.", "start": 1450.19, "duration": 2.52}, {"text": "And I'll try to\nexplain to you why.", "start": 1452.71, "duration": 2.01}, {"text": "And it's because of the\nrichness of functional groups", "start": 1454.72, "duration": 2.46}, {"text": "in a carbohydrate.", "start": 1457.18, "duration": 1.65}, {"text": "So the simplest carbohydrate,\nbefore I go up there,", "start": 1458.83, "duration": 6.08}, {"text": "is a three carbon molecule.", "start": 1464.91, "duration": 2.37}, {"text": "This would actually be\ncalled glyceraldehyde.", "start": 1470.81, "duration": 3.03}, {"text": "But don't worry about\nthat other name for it.", "start": 1473.84, "duration": 2.38}, {"text": "It's a three carbon\ncarbohydrate.", "start": 1476.22, "duration": 3.51}, {"text": "And this molecule would\nbe called a triose.", "start": 1485.19, "duration": 4.93}, {"text": "So we've got a couple\nof new-- a new suffix.", "start": 1490.12, "duration": 3.225}, {"text": "Because anything that\nis a carbohydrate", "start": 1496.68, "duration": 2.85}, {"text": "ends with the suffix\n\"ose,\" not to be", "start": 1499.53, "duration": 2.61}, {"text": "confused with the suffix\n\"ase,\" which is an enzyme.", "start": 1502.14, "duration": 3.7}, {"text": "So look carefully whether it's\nan \"a\" or \"o,\" because it's", "start": 1505.84, "duration": 2.47}, {"text": "the difference between a\nbig protein that catalyzes", "start": 1508.31, "duration": 2.68}, {"text": "a reaction and a carbohydrate.", "start": 1510.99, "duration": 2.28}, {"text": "So a triose would\nbe a carbohydrate", "start": 1513.27, "duration": 2.82}, {"text": "with three carbons.", "start": 1516.09, "duration": 1.65}, {"text": "They have an aldehyde.", "start": 1517.74, "duration": 2.33}, {"text": "Or let's just say they have\na carbonyl functionality.", "start": 1520.07, "duration": 2.95}, {"text": "So remember, there would be lone\npair electrons on those OHs,", "start": 1525.72, "duration": 5.85}, {"text": "similarly on these.", "start": 1531.57, "duration": 1.92}, {"text": "And remember, that\neach of these vertices", "start": 1533.49, "duration": 3.21}, {"text": "corresponds to a carbon.", "start": 1536.7, "duration": 2.96}, {"text": "It's some-- the way you\nrecognize carbohydrates is most", "start": 1539.66, "duration": 4.96}, {"text": "commonly--", "start": 1544.62, "duration": 1.29}, {"text": "is that they are rich\nin carbon dash OH", "start": 1545.91, "duration": 7.11}, {"text": "bonds, which are hydroxyls.", "start": 1553.02, "duration": 1.798}, {"text": "Which makes them\npolar molecules,", "start": 1557.746, "duration": 2.864}, {"text": "likely to be highly solvated\nin water and very different", "start": 1560.61, "duration": 4.02}, {"text": "for from the compounds that\nare rich in just CH bonds that", "start": 1564.63, "duration": 3.69}, {"text": "don't have such opportunities.", "start": 1568.32, "duration": 2.14}, {"text": "So if you see a molecule\nand it's got a bunch of CHs", "start": 1570.46, "duration": 3.2}, {"text": "but not a bunch of OHs,\nit's probably a lipid.", "start": 1573.66, "duration": 2.78}, {"text": "If you see a compound\nthat's rich in OHs,", "start": 1576.44, "duration": 3.37}, {"text": "it's likely to be\na carbohydrate.", "start": 1579.81, "duration": 2.61}, {"text": "The story gets a little\nbit more interesting", "start": 1582.42, "duration": 2.37}, {"text": "as we move up to some of the\ndifferent carbohydrates, which", "start": 1584.79, "duration": 3.27}, {"text": "I've shown you there\non that screen.", "start": 1588.06, "duration": 1.5}, {"text": "And I'm going to go forward\nto talk about those.", "start": 1589.56, "duration": 2.55}, {"text": "Because this triose is\nimportant in primary metabolism.", "start": 1592.11, "duration": 5.13}, {"text": "We break down\ncarbon carbohydrates", "start": 1597.24, "duration": 2.79}, {"text": "that have six sugars to small\ncarbohydrates that have three--", "start": 1600.03, "duration": 4.71}, {"text": "excuse me,\ncarbohydrates that have", "start": 1604.74, "duration": 1.86}, {"text": "six carbons to carbohydrates\nthat have three carbons.", "start": 1606.6, "duration": 3.25}, {"text": "And that's where these three\ncarbon entities crop up.", "start": 1609.85, "duration": 3.14}, {"text": "But I want to focus you in\non two sets of carbohydrates,", "start": 1612.99, "duration": 5.82}, {"text": "the hexoses and the pentoses.", "start": 1618.81, "duration": 2.05}, {"text": "So we immediately know\nthey're carbohydrates, right?", "start": 1624.75, "duration": 4.26}, {"text": "\"Ose.\"", "start": 1629.01, "duration": 1.59}, {"text": "The hexoses obviously\nhave six carbons.", "start": 1630.6, "duration": 4.51}, {"text": "And the pentoses\nhave five carbons.", "start": 1635.11, "duration": 3.06}, {"text": "And these are the most\nimportant of the carbohydrates.", "start": 1638.17, "duration": 2.88}, {"text": "Yes, there are carbohydrates\nwith four carbons.", "start": 1641.05, "duration": 2.76}, {"text": "And then there were ones with\nseven, eight, nine carbons.", "start": 1643.81, "duration": 3.42}, {"text": "But these are the\nones will totally", "start": 1647.23, "duration": 1.5}, {"text": "focus on in 7016,\nbecause these are", "start": 1648.73, "duration": 2.82}, {"text": "very important in\ndifferent biopolymers.", "start": 1651.55, "duration": 3.0}, {"text": "And the hexoses are important\ncomponents, for example,", "start": 1654.55, "duration": 4.67}, {"text": "of cellulose and glycogen. But\nwhere are the pentose carbons?", "start": 1659.22, "duration": 11.35}, {"text": "And why are they so important?", "start": 1670.57, "duration": 2.75}, {"text": "Actually, I need to draw this\nis its straight chain version.", "start": 1673.32, "duration": 2.642}, {"text": "Because I'll drive you crazy.", "start": 1675.962, "duration": 1.208}, {"text": "So this sugar here is a\npentose, one, two, three, four,", "start": 1687.58, "duration": 3.84}, {"text": "five carbons, a bunch of\nOHs, aldehyde at one end.", "start": 1691.42, "duration": 4.47}, {"text": "Commonly, carbohydrates will\nfold up into a cyclic structure", "start": 1695.89, "duration": 4.112}, {"text": "through an equilibrium.", "start": 1700.002, "duration": 0.958}, {"text": "I won't worry you too\nmuch with the chemistry.", "start": 1700.96, "duration": 2.7}, {"text": "But I'm just going to\nshow you that structure.", "start": 1703.66, "duration": 4.58}, {"text": "It looks like this,\na five-membered ring.", "start": 1708.24, "duration": 2.36}, {"text": "The interconversion of these\ntwo is an equilibrium process.", "start": 1713.37, "duration": 3.89}, {"text": "And those carbohydrates are\nincredibly important where?", "start": 1717.26, "duration": 4.6}, {"text": "Yeah, nucleic acids.", "start": 1721.86, "duration": 3.07}, {"text": "So your phosphodiester\nbackbone is", "start": 1724.93, "duration": 3.95}, {"text": "attached to sugars that are\nattached a bit to purines", "start": 1728.88, "duration": 5.94}, {"text": "and pyrimidines.", "start": 1734.82, "duration": 0.69}, {"text": "And we'll see those\nstructures later.", "start": 1735.51, "duration": 2.01}, {"text": "But an absolutely essential\nfeature of that polymer", "start": 1737.52, "duration": 4.53}, {"text": "is the five-membered\nring carbohydrates", "start": 1742.05, "duration": 2.91}, {"text": "that are known as ribose,\nwhich is what that guy is,", "start": 1744.96, "duration": 6.81}, {"text": "and two deoxyribose,\nwhere one of the hydroxyls", "start": 1751.77, "duration": 9.39}, {"text": "is actually a hydrogen.\nIt's not a hydroxyl.", "start": 1761.16, "duration": 2.68}, {"text": "And it's this one.", "start": 1763.84, "duration": 3.23}, {"text": "So instead of being\nan OH, it's an H.", "start": 1767.07, "duration": 4.07}, {"text": "And we number carbohydrates.", "start": 1771.14, "duration": 1.56}, {"text": "And I'll reinforce\nthis much more", "start": 1772.7, "duration": 2.16}, {"text": "when we talk about carbohydrate,\nabout nucleic acids.", "start": 1774.86, "duration": 3.51}, {"text": "There's a numbering system.", "start": 1778.37, "duration": 1.52}, {"text": "So two deoxyribose\nis in your DNA.", "start": 1779.89, "duration": 3.34}, {"text": "And ribose itself\nis in your RNA.", "start": 1786.92, "duration": 5.06}, {"text": "OK, so obviously, we need\nto worry about carbohydrates", "start": 1791.98, "duration": 2.855}, {"text": "and learn a little\nbit about them", "start": 1794.835, "duration": 1.375}, {"text": "based on that key criterion.", "start": 1796.21, "duration": 2.05}, {"text": "OK, let's move now\nto the hexoses.", "start": 1798.26, "duration": 4.07}, {"text": "I'm not going to make you keep\ndrawing hexoses and things.", "start": 1802.33, "duration": 3.33}, {"text": "I'm going to just tell you\na little bit about them", "start": 1805.66, "duration": 2.43}, {"text": "with respect to\ntheir structures.", "start": 1808.09, "duration": 2.13}, {"text": "So I've shown you on the board\nthe cyclic form of a pentose.", "start": 1810.22, "duration": 5.85}, {"text": "This is the linear form\nand the cyclic form.", "start": 1816.07, "duration": 2.282}, {"text": "Let me write that down.", "start": 1818.352, "duration": 0.958}, {"text": "And by the way, in your DNA,\nit's always in the cyclic form.", "start": 1825.06, "duration": 3.39}, {"text": "It's not in the linear form.", "start": 1828.45, "duration": 1.86}, {"text": "And the hexoses also have\na linear and a cyclic form.", "start": 1830.31, "duration": 4.41}, {"text": "And I show you that\nequilibrium for glucose.", "start": 1834.72, "duration": 3.6}, {"text": "You see six carbons.", "start": 1838.32, "duration": 1.89}, {"text": "I've got them numbered.", "start": 1840.21, "duration": 1.32}, {"text": "And they form favorably\ninto the six-membered ring.", "start": 1841.53, "duration": 3.69}, {"text": "This is the cyclic\nform of glucose.", "start": 1845.22, "duration": 2.25}, {"text": "This is the linear\nform of glucose.", "start": 1847.47, "duration": 2.4}, {"text": "When glucose associates\ninto polymers,", "start": 1849.87, "duration": 3.21}, {"text": "it becomes these things\nlike cellulose or glycogen.", "start": 1853.08, "duration": 3.81}, {"text": "And it depends a lot on the\nlinkages in those polymers", "start": 1856.89, "duration": 3.03}, {"text": "to define which one it is.", "start": 1859.92, "duration": 2.08}, {"text": "Now, as I mentioned,\ncarbohydrates aren't always", "start": 1862.0, "duration": 5.12}, {"text": "just a series of OH groups.", "start": 1867.12, "duration": 2.31}, {"text": "There's sometimes\nother functionality.", "start": 1869.43, "duration": 3.088}, {"text": "So I'm just going to\nquickly draw those.", "start": 1872.518, "duration": 1.667}, {"text": "And if you've got\nthem on your handouts,", "start": 1877.03, "duration": 5.28}, {"text": "you can play along with me here.", "start": 1882.31, "duration": 2.33}, {"text": "So sometimes,\nthere's an NH2 there.", "start": 1889.23, "duration": 6.78}, {"text": "That's called glucose\namine, very creatively.", "start": 1896.01, "duration": 3.84}, {"text": "Sometimes that NH2 is\nconverted to an amide,", "start": 1899.85, "duration": 6.99}, {"text": "like that bond in a peptide.", "start": 1906.84, "duration": 1.59}, {"text": "So it's glucose amide.", "start": 1908.43, "duration": 2.88}, {"text": "And sometimes-- so you can\ndraw these on your handout,", "start": 1911.31, "duration": 3.33}, {"text": "because the six-membered\nrings are there.", "start": 1914.64, "duration": 2.43}, {"text": "This stays as an OH.", "start": 1917.07, "duration": 2.72}, {"text": "But this OH here is at a\ndifferent oxidation state.", "start": 1919.79, "duration": 4.81}, {"text": "Don't worry about\nthat terminology.", "start": 1924.6, "duration": 1.71}, {"text": "But what's important,\nit's glucuronic acid.", "start": 1926.31, "duration": 3.61}, {"text": "So it can be negatively charged,\npositively charged, neutral.", "start": 1929.92, "duration": 3.77}, {"text": "So there are variations\non a lot of our hexoses,", "start": 1933.69, "duration": 3.69}, {"text": "basically meaning this\ncarbohydrate molecular formula", "start": 1937.38, "duration": 3.0}, {"text": "doesn't work anymore.", "start": 1940.38, "duration": 0.96}, {"text": "But the term has stuck.", "start": 1941.34, "duration": 1.95}, {"text": "So there's quite a variety\nof different carbohydrates", "start": 1943.29, "duration": 3.63}, {"text": "with slight differences.", "start": 1946.92, "duration": 1.59}, {"text": "And the intriguing thing\nis that the carbohydrates", "start": 1948.51, "duration": 3.33}, {"text": "that you and I use in all\nof our physiologic processes", "start": 1951.84, "duration": 3.87}, {"text": "are much simpler than\nthe carbohydrates", "start": 1955.71, "duration": 2.07}, {"text": "that bacteria use.", "start": 1957.78, "duration": 1.67}, {"text": "There is an expansion of\nlike 10 to the 2 or 10", "start": 1959.45, "duration": 2.8}, {"text": "to the 3 in the variety of\nsugars that bacteria use.", "start": 1962.25, "duration": 4.44}, {"text": "And that's definitely a\nstory for another day.", "start": 1966.69, "duration": 2.59}, {"text": "So let me now move on to\nthinking about carbohydrates", "start": 1969.28, "duration": 3.89}, {"text": "not as the monomers\nthat you metabolize,", "start": 1973.17, "duration": 3.6}, {"text": "but rather as the\npolymers that are", "start": 1976.77, "duration": 1.95}, {"text": "involved in many other\ndifferent types of processes.", "start": 1978.72, "duration": 3.21}, {"text": "And when we think\nabout the polymers,", "start": 1981.93, "duration": 1.83}, {"text": "we want to think about\nhow their polymers differ", "start": 1983.76, "duration": 3.09}, {"text": "from the polymers of\nnucleic acids or proteins.", "start": 1986.85, "duration": 4.44}, {"text": "Because this will tell\nyou why carbohydrates", "start": 1991.29, "duration": 2.97}, {"text": "are so complicated.", "start": 1994.26, "duration": 2.37}, {"text": "When you take a bunch of amino\nacids and make a polymer,", "start": 1996.63, "duration": 4.56}, {"text": "it's a linear polymer.", "start": 2001.19, "duration": 2.44}, {"text": "Every unit is joined\nto the next by a name.", "start": 2003.63, "duration": 2.31}, {"text": "There's no branching there.", "start": 2005.94, "duration": 1.39}, {"text": "It's just a linear polymer.", "start": 2007.33, "duration": 1.66}, {"text": "So the diversity\nis not enormous.", "start": 2008.99, "duration": 2.97}, {"text": "Or-- it's pretty enormous.", "start": 2011.96, "duration": 1.23}, {"text": "But it's not as\nbig as it could be", "start": 2013.19, "duration": 1.77}, {"text": "if it were a branch polymer with\ndifferent types of side chains.", "start": 2014.96, "duration": 3.42}, {"text": "We will see next week that the\npolymers of the nucleic acids--", "start": 2018.38, "duration": 4.36}, {"text": "here's the basic structure.", "start": 2022.74, "duration": 1.39}, {"text": "There's the ribose, by the way.", "start": 2024.13, "duration": 1.78}, {"text": "The R could be an OH or an H\nattached to a base of purine", "start": 2025.91, "duration": 3.86}, {"text": "or pyrimidine-- you don't\nneed to know that yet;", "start": 2029.77, "duration": 2.3}, {"text": "you'll know it next week--", "start": 2032.07, "duration": 1.19}, {"text": "and then to a phosphate.", "start": 2033.26, "duration": 1.47}, {"text": "But those again,\nare linear polymers.", "start": 2034.73, "duration": 3.668}, {"text": "You don't have branching.", "start": 2038.398, "duration": 1.042}, {"text": "You just have a single\ncontinuous chain.", "start": 2039.44, "duration": 2.58}, {"text": "The crazy thing about\nsugars is they can", "start": 2042.02, "duration": 2.31}, {"text": "branch from any of those OHs.", "start": 2044.33, "duration": 2.35}, {"text": "So there's much more diversity\nof structure and function", "start": 2046.68, "duration": 4.82}, {"text": "wrapped in the\ncarbohydrates, which makes", "start": 2051.5, "duration": 2.25}, {"text": "them real trouble to study.", "start": 2053.75, "duration": 2.32}, {"text": "OK, I want to now introduce\nyou to another feature.", "start": 2056.07, "duration": 4.2}, {"text": "The other thing is,\nwhen we join amino acids", "start": 2060.27, "duration": 2.389}, {"text": "or we join nucleic acid\nbuilding blocks, nucleosides,", "start": 2062.659, "duration": 4.531}, {"text": "there's no difference in\nthe shapes that we can form.", "start": 2067.19, "duration": 2.94}, {"text": "We don't have variety there.", "start": 2070.13, "duration": 1.74}, {"text": "But in sugars, we can make\ndifferent kinds of linkages", "start": 2071.87, "duration": 3.809}, {"text": "depending on how two OH\ngroups in a sugar are joined.", "start": 2075.679, "duration": 4.23}, {"text": "So for example, if\nyou join two glucoses,", "start": 2079.909, "duration": 3.611}, {"text": "in this kind of linkage,\nthat would give you maltose.", "start": 2083.52, "duration": 3.27}, {"text": "But if you join two glucoses\nin that kind of linkage,", "start": 2086.79, "duration": 4.047}, {"text": "it would give you lactose.", "start": 2090.837, "duration": 1.083}, {"text": "And those are\ndifferent compounds.", "start": 2091.92, "duration": 2.219}, {"text": "They serve different types\nof physiologic roles.", "start": 2094.139, "duration": 3.921}, {"text": "And there are enzymes that\nwill make these bonds and then", "start": 2098.06, "duration": 4.69}, {"text": "enzymes that will\nbreak these bonds.", "start": 2102.75, "duration": 3.1}, {"text": "There is a common disorder that\npeople have as they grow older.", "start": 2105.85, "duration": 5.19}, {"text": "The enzyme that breaks\nthe lactose bond the gets", "start": 2111.04, "duration": 5.15}, {"text": "turned off.", "start": 2116.19, "duration": 0.6}, {"text": "It doesn't work anymore.", "start": 2116.79, "duration": 1.42}, {"text": "And that's the enzyme, lactose.", "start": 2118.21, "duration": 2.3}, {"text": "So when people are\nintolerant to sugars--", "start": 2120.51, "duration": 4.2}, {"text": "lactose is the sugar in milk.", "start": 2124.71, "duration": 2.46}, {"text": "And they can't digest\ndairy products.", "start": 2127.17, "duration": 1.98}, {"text": "Because lactase\ndoesn't work anymore.", "start": 2129.15, "duration": 2.31}, {"text": "Or you can take supplements.", "start": 2131.46, "duration": 1.23}, {"text": "So that's how that\nrelates to physiology.", "start": 2132.69, "duration": 3.54}, {"text": "The reaction\nbetween two glucoses", "start": 2136.23, "duration": 2.76}, {"text": "to make the disaccharide\nis actually a condensation.", "start": 2138.99, "duration": 3.6}, {"text": "Because when you join\nthat bond, you kick out", "start": 2142.59, "duration": 2.88}, {"text": "water as a side product.", "start": 2145.47, "duration": 2.28}, {"text": "Or when you break that\nbond, you release water.", "start": 2147.75, "duration": 3.61}, {"text": "So this is another one of\nthe condensation reactions.", "start": 2151.36, "duration": 3.14}, {"text": "So underline that on the slide.", "start": 2154.5, "duration": 2.19}, {"text": "Because condensation\nmeans a reaction", "start": 2156.69, "duration": 2.25}, {"text": "that precedes and produces\nyou a molecule of water.", "start": 2158.94, "duration": 3.21}, {"text": "And this just sums up\nthe lactase problem,", "start": 2168.03, "duration": 2.58}, {"text": "where you can digest\nlactose, the milk sugar.", "start": 2170.61, "duration": 3.18}, {"text": "OK, so those are monomers.", "start": 2173.79, "duration": 2.19}, {"text": "Now let's think about polymers\nand complex structures", "start": 2175.98, "duration": 3.57}, {"text": "of sugars.", "start": 2179.55, "duration": 1.32}, {"text": "And I put these\nall on the slides,", "start": 2180.87, "duration": 1.71}, {"text": "because it's just impossible\nfor you to keep drawing them.", "start": 2182.58, "duration": 3.22}, {"text": "And I'm just going to give you\nsort of one of my pet peeves.", "start": 2185.8, "duration": 2.735}, {"text": "I draw sugars like this.", "start": 2191.07, "duration": 3.6}, {"text": "A lot of other people\ndraw sugars like that.", "start": 2194.67, "duration": 4.35}, {"text": "And I don't like that.", "start": 2201.7, "duration": 0.96}, {"text": "Because this is\nwhat they look like.", "start": 2202.66, "duration": 1.69}, {"text": "So if you see this\nand you go, I haven't", "start": 2204.35, "duration": 2.18}, {"text": "seen sugars looking\nlike that before, it's", "start": 2206.53, "duration": 3.21}, {"text": "because this is the way to draw\nthem that actually represents", "start": 2209.74, "duration": 6.09}, {"text": "their shape.", "start": 2215.83, "duration": 0.75}, {"text": "So if it's unusual\nformat to you,", "start": 2216.58, "duration": 2.52}, {"text": "I'm not going to ask\nyou to construct these.", "start": 2219.1, "duration": 2.95}, {"text": "I just want you to be familiar\nwith looking at them like this", "start": 2222.05, "duration": 3.26}, {"text": "rather than like this.", "start": 2225.31, "duration": 1.44}, {"text": "Because, to me, that's the\nbest way to render them.", "start": 2226.75, "duration": 4.46}, {"text": "OK, so polymers of sugar.", "start": 2231.21, "duration": 1.75}, {"text": "I just mentioned\nto you, there are", "start": 2232.96, "duration": 1.83}, {"text": "polymers of sugars that\nare important to storage.", "start": 2234.79, "duration": 3.51}, {"text": "So when we have\nexcess glucose, we", "start": 2238.3, "duration": 2.97}, {"text": "store glucose as glycogen.\nIt's often stored in the liver.", "start": 2241.27, "duration": 5.25}, {"text": "And later on in\nthe semester, we'll", "start": 2246.52, "duration": 1.62}, {"text": "see how a bolt of\nadrenaline sets", "start": 2248.14, "duration": 3.27}, {"text": "all the processes in\nmotion to chew up glycogen,", "start": 2251.41, "duration": 3.15}, {"text": "to release more glucose so\nyou can have a lot of energy", "start": 2254.56, "duration": 3.3}, {"text": "quickly.", "start": 2257.86, "duration": 1.74}, {"text": "So in that polymer, the sugars\nare linked in a different way.", "start": 2259.6, "duration": 4.68}, {"text": "The common polymer in\nplants and, in fact,", "start": 2264.28, "duration": 3.78}, {"text": "accounts for a massive\nproportion of the biomass,", "start": 2268.06, "duration": 3.3}, {"text": "is a different\npolymer of glucose", "start": 2271.36, "duration": 2.31}, {"text": "where the linkages are beta--", "start": 2273.67, "duration": 2.97}, {"text": "we would call this\na beta linkage.", "start": 2276.64, "duration": 1.6}, {"text": "But that's the way it looks.", "start": 2278.24, "duration": 1.28}, {"text": "And that would be cellulose.", "start": 2279.52, "duration": 1.68}, {"text": "And it's a linear polymer.", "start": 2281.2, "duration": 1.71}, {"text": "Coming down here, glycogen\nis often a branched polymer", "start": 2282.91, "duration": 4.38}, {"text": "with different kinds of\nlinkages with different aspects", "start": 2287.29, "duration": 3.47}, {"text": "or different shapes.", "start": 2290.76, "duration": 1.46}, {"text": "So the glycogen that we\nstore and can break down", "start": 2292.22, "duration": 3.89}, {"text": "in order to produce glucose\nto make energy is glycogen.", "start": 2296.11, "duration": 4.68}, {"text": "We cannot break down cellulose.", "start": 2300.79, "duration": 3.15}, {"text": "We don't digest plant\ncellulose, because we", "start": 2303.94, "duration": 2.67}, {"text": "don't have those\nenzymes, which is", "start": 2306.61, "duration": 1.95}, {"text": "why we don't get\nnutritional value out", "start": 2308.56, "duration": 2.19}, {"text": "of the cellulose the same way\nwe can put forces in action", "start": 2310.75, "duration": 4.44}, {"text": "to break down glucose.", "start": 2315.19, "duration": 1.78}, {"text": "So the way those bonds look\nis absolutely critical for how", "start": 2316.97, "duration": 5.21}, {"text": "you can use the energy that's\nwithin them by using enzymes", "start": 2322.18, "duration": 3.57}, {"text": "to break those bonds.", "start": 2325.75, "duration": 1.14}, {"text": "OK, so in general--", "start": 2329.83, "duration": 2.87}, {"text": "I've just said that.", "start": 2332.7, "duration": 1.24}, {"text": "Glucose can be stored a\ncellulose or as glycogen.", "start": 2333.94, "duration": 5.16}, {"text": "The process of photosynthesis\nconverts energy and sunlight", "start": 2339.1, "duration": 5.4}, {"text": "into glucose.", "start": 2344.5, "duration": 3.69}, {"text": "And then you can make\nthe polymers of glucose.", "start": 2348.19, "duration": 2.97}, {"text": "And what I'm showing you\nhere in these polymers", "start": 2351.16, "duration": 2.25}, {"text": "is a simplified view.", "start": 2353.41, "duration": 2.31}, {"text": "I want to introduce\nto you one other term.", "start": 2355.72, "duration": 3.18}, {"text": "And that term is glycan.", "start": 2358.9, "duration": 1.35}, {"text": "And that basically\nrefers to something", "start": 2363.96, "duration": 2.68}, {"text": "that is more than one\nsugar, one carbohydrate.", "start": 2366.64, "duration": 2.94}, {"text": "I was looking at the\nvideos of my lectures.", "start": 2375.398, "duration": 1.792}, {"text": "I realized my\nhandwriting is horrible.", "start": 2377.19, "duration": 1.93}, {"text": "So I'm really trying very\nhard to make it a little bit", "start": 2379.12, "duration": 2.33}, {"text": "neater today.", "start": 2381.45, "duration": 1.29}, {"text": "So glycan is just the name\nfor a polymer of sugars.", "start": 2382.74, "duration": 3.33}, {"text": "But they can also be\ncalled polysaccharides.", "start": 2386.07, "duration": 4.81}, {"text": "But glycan now is the\ncommonly accepted term", "start": 2396.55, "duration": 2.79}, {"text": "for a lot of sugars.", "start": 2399.34, "duration": 1.27}, {"text": "Now, I told you\nabout energy storage.", "start": 2400.61, "duration": 2.57}, {"text": "I've told you about\nsimple disaccharides", "start": 2403.18, "duration": 2.19}, {"text": "and monosaccharides\nand metabolism.", "start": 2405.37, "duration": 2.31}, {"text": "But what I want to\ndo now is give you", "start": 2407.68, "duration": 1.89}, {"text": "a little overview of all\nthe different places where", "start": 2409.57, "duration": 3.81}, {"text": "sugars feature in a cell.", "start": 2413.38, "duration": 1.758}, {"text": "Because I think it's\nreally important", "start": 2415.138, "duration": 1.542}, {"text": "to realize that sugars\nform a great sort of set", "start": 2416.68, "duration": 3.99}, {"text": "of molecules for communication.", "start": 2420.67, "duration": 2.97}, {"text": "So I'm going to go\naround this sort", "start": 2423.64, "duration": 1.56}, {"text": "of funny looking square cell.", "start": 2425.2, "duration": 2.66}, {"text": "And this would be\na eukaryotic cell,", "start": 2427.86, "duration": 1.81}, {"text": "because it's got a nucleus.", "start": 2429.67, "duration": 1.56}, {"text": "And there are\ndifferent compartments.", "start": 2431.23, "duration": 1.92}, {"text": "So within the\ncell, the cell sits", "start": 2433.15, "duration": 3.36}, {"text": "in what's known as an\nextracellular matrix.", "start": 2436.51, "duration": 2.79}, {"text": "It's a mesh work\nof sugar polymers", "start": 2439.3, "duration": 3.63}, {"text": "that actually is\nimportant for the cells", "start": 2442.93, "duration": 2.05}, {"text": "and important for trapping\nsignals that come from cells", "start": 2444.98, "duration": 3.2}, {"text": "and go to other cells.", "start": 2448.18, "duration": 1.54}, {"text": "So those are all predominantly\nmade up of carbohydrate.", "start": 2449.72, "duration": 4.22}, {"text": "The next thing to\nlook at is that there", "start": 2453.94, "duration": 1.8}, {"text": "are proteins within the cell.", "start": 2455.74, "duration": 3.14}, {"text": "They can become modified with\na sugar and go to the nucleus", "start": 2458.88, "duration": 4.24}, {"text": "or leave the nucleus.", "start": 2463.12, "duration": 1.3}, {"text": "So there is a type of signaling\nthat is based on adding a sugar", "start": 2464.42, "duration": 3.92}, {"text": "or taking it off a protein.", "start": 2468.34, "duration": 2.16}, {"text": "We'll see later in the semester\nhow also phosphorylation", "start": 2470.5, "duration": 3.45}, {"text": "does a lot of functions\nthat look like that.", "start": 2473.95, "duration": 3.12}, {"text": "There are sugars that are\ndisplayed on the cell surface", "start": 2477.07, "duration": 3.27}, {"text": "polymers.", "start": 2480.34, "duration": 1.11}, {"text": "And that's where signaling\nbecomes important.", "start": 2481.45, "duration": 2.16}, {"text": "Because sugars may be\nattached to lipids.", "start": 2483.61, "duration": 2.88}, {"text": "You remember, we've\ntalked about phospholipids", "start": 2486.49, "duration": 2.49}, {"text": "being part of the membrane.", "start": 2488.98, "duration": 1.65}, {"text": "Sugars can be attached to\nlipids that sit in the membrane", "start": 2490.63, "duration": 3.18}, {"text": "and face out.", "start": 2493.81, "duration": 0.84}, {"text": "And it's how cell-cell\ncommunication", "start": 2494.65, "duration": 3.0}, {"text": "occurs in some instances.", "start": 2497.65, "duration": 2.28}, {"text": "Or they may be\nattached to proteins", "start": 2499.93, "duration": 3.03}, {"text": "that are also displayed on\nthe surface of the cell.", "start": 2502.96, "duration": 2.98}, {"text": "So this tells you a\nlittle bit about where", "start": 2505.94, "duration": 2.45}, {"text": "we put these sugars is what's\nresponsible for communication.", "start": 2508.39, "duration": 3.72}, {"text": "Because they're on the surface\nof the cell with their sides", "start": 2512.11, "duration": 3.45}, {"text": "out.", "start": 2515.56, "duration": 2.8}, {"text": "And then the final thing\nI want to talk about", "start": 2518.36, "duration": 2.13}, {"text": "is the blood group system.", "start": 2520.49, "duration": 1.78}, {"text": "So a lot of you may be\naware of blood groups.", "start": 2522.27, "duration": 3.5}, {"text": "There are four\nprincipal blood groups.", "start": 2525.77, "duration": 3.09}, {"text": "The differences between the\nblood in a A, B, AB and O blood", "start": 2528.86, "duration": 3.99}, {"text": "groups are differences in just\nthe sugars that are attached", "start": 2532.85, "duration": 3.87}, {"text": "to the surface of the cell.", "start": 2536.72, "duration": 1.72}, {"text": "So let me describe those.", "start": 2538.44, "duration": 1.52}, {"text": "And then we'll talk about\nblood groups and things that", "start": 2539.96, "duration": 2.4}, {"text": "are being done to enhance the\nsupplies of red blood cells", "start": 2542.36, "duration": 4.89}, {"text": "in cases of emergency.", "start": 2547.25, "duration": 1.34}, {"text": "I have a nice little video\nI'm hoping to get to.", "start": 2548.59, "duration": 2.83}, {"text": "So on the surface\nof the cell, you", "start": 2551.42, "duration": 1.89}, {"text": "might have different sugars.", "start": 2553.31, "duration": 1.84}, {"text": "This is a trisaccharide.", "start": 2555.15, "duration": 2.78}, {"text": "All right, you can see\none, two, three sugars.", "start": 2557.93, "duration": 2.75}, {"text": "They have different linkages.", "start": 2560.68, "duration": 1.26}, {"text": "But you can pick out the sugars.", "start": 2561.94, "duration": 1.77}, {"text": "And they are joined by a\nbond called a glycoside bond", "start": 2563.71, "duration": 9.54}, {"text": "and those join sugars.", "start": 2573.25, "duration": 1.155}, {"text": "So what do you think the enzyme\nthat cleaves the glycoside is?", "start": 2579.7, "duration": 2.67}, {"text": "STUDENT: Glycosidase.", "start": 2586.362, "duration": 1.998}, {"text": "PROFESSOR: Glycosidase.", "start": 2588.36, "duration": 1.68}, {"text": "You would say glycosidase.", "start": 2590.04, "duration": 1.26}, {"text": "I would say glycosidase.", "start": 2591.3, "duration": 1.23}, {"text": "But if they are the same thing.", "start": 2592.53, "duration": 1.41}, {"text": "And that's going to be\npertinent in a minute.", "start": 2596.89, "duration": 2.42}, {"text": "So remember, if in doubt,\nguess and stick \"ase\"", "start": 2602.75, "duration": 3.22}, {"text": "at the end if I ask you\nthe name of an enzyme,", "start": 2605.97, "duration": 2.0}, {"text": "because that works pretty well.", "start": 2607.97, "duration": 1.6}, {"text": "So if you have O\nblood group, you", "start": 2609.57, "duration": 2.3}, {"text": "would have exclusively this\ntrisaccharide on your red blood", "start": 2611.87, "duration": 4.95}, {"text": "cells.", "start": 2616.82, "duration": 0.97}, {"text": "If you have the A\nblood group, you", "start": 2617.79, "duration": 2.27}, {"text": "have an extra sugar attached\nto that trisaccharide.", "start": 2620.06, "duration": 2.49}, {"text": "And it's a glucosamide sugar.", "start": 2622.55, "duration": 4.92}, {"text": "There's an extra carbonyl\ngroup on an amide.", "start": 2627.47, "duration": 5.91}, {"text": "And if you have B blood\ngroup, it's gluco--", "start": 2633.38, "duration": 3.61}, {"text": "it's a sugar.", "start": 2636.99, "duration": 0.78}, {"text": "It's actually called galactose.", "start": 2637.77, "duration": 1.64}, {"text": "That has all OH groups.", "start": 2639.41, "duration": 2.79}, {"text": "So the differences\nbetween if you're O group,", "start": 2642.2, "duration": 2.91}, {"text": "if you're A group,\nor if you're B group,", "start": 2645.11, "duration": 2.48}, {"text": "adjust those\ndifferences in sugars.", "start": 2647.59, "duration": 2.68}, {"text": "And then people who have AB\nblood group have a composite.", "start": 2650.27, "duration": 3.69}, {"text": "They have a mixture of the\nA and the B blood group.", "start": 2653.96, "duration": 3.93}, {"text": "So do you-- yeah, question.", "start": 2657.89, "duration": 2.934}, {"text": "STUDENT: [INAUDIBLE]", "start": 2660.824, "duration": 1.776}, {"text": "PROFESSOR: That's\na second marker,", "start": 2662.6, "duration": 4.05}, {"text": "which we won't talk about.", "start": 2666.65, "duration": 1.8}, {"text": "So it's A plus another\nmarker that's either", "start": 2668.45, "duration": 3.66}, {"text": "one type or another type.", "start": 2672.11, "duration": 1.95}, {"text": "But the AB and O are\ndefined by the sugars.", "start": 2674.06, "duration": 2.37}, {"text": "Yeah, good question.", "start": 2676.43, "duration": 2.13}, {"text": "OK, so do people know\ntheir blood group?", "start": 2678.56, "duration": 4.25}, {"text": "It's good to know, frankly.", "start": 2682.81, "duration": 1.53}, {"text": "Because someone-- you know,\nyou may you cut yourself.", "start": 2684.34, "duration": 2.452}, {"text": "And someone says, do you\nknow your blood group?", "start": 2686.792, "duration": 1.958}, {"text": "And you'll go, yes.", "start": 2688.75, "duration": 0.792}, {"text": "And they'll give you\nan on-site transfusion.", "start": 2689.542, "duration": 2.203}, {"text": "I've been watching\ntoo much Jack Bauer.", "start": 2691.745, "duration": 1.625}, {"text": "But, you know, that's a story\nfor another day as well.", "start": 2693.37, "duration": 5.58}, {"text": "So it turns out that\ndepending on blood groups,", "start": 2698.95, "duration": 2.25}, {"text": "you can either be a universal\ndonor or a universal acceptor.", "start": 2701.2, "duration": 4.3}, {"text": "So the people with\nthe O blood group", "start": 2705.5, "duration": 2.36}, {"text": "can give anyone their blood.", "start": 2707.86, "duration": 2.7}, {"text": "People with O, A, B, and AB.", "start": 2710.56, "duration": 2.82}, {"text": "But unfortunately for the poor\npeople with O blood group is", "start": 2713.38, "duration": 3.98}, {"text": "that they cannot receive blood\nfrom blood group A, B, or AB.", "start": 2717.36, "duration": 4.72}, {"text": "And I wanted to show this.", "start": 2722.08, "duration": 1.68}, {"text": "And I hope I can get it working.", "start": 2723.76, "duration": 1.89}, {"text": "Because we have just the\nright amount of time,", "start": 2725.65, "duration": 2.02}, {"text": "which makes me really happy.", "start": 2727.67, "duration": 2.15}, {"text": "Because I don't really program\nthings that well sometimes.", "start": 2729.82, "duration": 3.21}, {"text": "There was a pay-- there was--", "start": 2733.03, "duration": 3.31}, {"text": "the latest American chemist--", "start": 2736.34, "duration": 1.79}, {"text": "NARRATOR: --or other disaster.", "start": 2738.13, "duration": 1.25}, {"text": "Those who are affected\nby crisis usually", "start": 2739.38, "duration": 1.92}, {"text": "need four vital things, food,\nshelter, water and blood.", "start": 2741.3, "duration": 4.44}, {"text": "In particular, O-type blood,\nbecause it can be safely given", "start": 2745.74, "duration": 2.85}, {"text": "to any patient.", "start": 2748.59, "duration": 1.2}, {"text": "Now, scientists say they\nhave identified enzymes", "start": 2749.79, "duration": 2.46}, {"text": "from the human gut that can turn\ntype A and B blood into type", "start": 2752.25, "duration": 3.36}, {"text": "O up to 30 times more\nefficiently than previously", "start": 2755.61, "duration": 2.7}, {"text": "studied enzymes.", "start": 2758.31, "duration": 1.41}, {"text": "Type A or B blood\nhas specific sugars", "start": 2759.72, "duration": 2.103}, {"text": "on the outside of its cells.", "start": 2761.823, "duration": 1.167}, {"text": "PROFESSOR: I just described--", "start": 2762.99, "duration": 0.66}, {"text": "NARRATOR: These\nsugars are recognized", "start": 2763.65, "duration": 1.23}, {"text": "by the immune system.", "start": 2764.88, "duration": 1.052}, {"text": "And if they don't\nmatch the type of blood", "start": 2765.932, "duration": 1.708}, {"text": "that's already in an individual,\nthose cells are destroyed.", "start": 2767.64, "duration": 3.24}, {"text": "Because these sugars\nare recognized", "start": 2770.88, "duration": 1.71}, {"text": "by the immune system,\nthey're called antigens.", "start": 2772.59, "duration": 2.43}, {"text": "Type AB blood has both antigens.", "start": 2775.02, "duration": 2.34}, {"text": "And type O blood has none.", "start": 2777.36, "duration": 1.74}, {"text": "The researchers\npresented these findings", "start": 2779.1, "duration": 1.8}, {"text": "at the recent American\nChemical Society", "start": 2780.9, "duration": 1.89}, {"text": "National Meeting in Boston.", "start": 2782.79, "duration": 1.83}, {"text": "Stephen Withers from the\nUniversity of British Columbia", "start": 2784.62, "duration": 2.97}, {"text": "has been studying enzymes\nthat remove A or B", "start": 2787.59, "duration": 2.49}, {"text": "antigens from red blood cells.", "start": 2790.08, "duration": 2.11}, {"text": "If those antigens\ncan be removed,", "start": 2792.19, "duration": 1.76}, {"text": "then type A or B can be\nconverted to type O blood.", "start": 2793.95, "duration": 3.24}, {"text": "To find the enzymes\nmore quickly,", "start": 2797.19, "duration": 1.71}, {"text": "Withers and a colleague at his\ninstitution used a technique", "start": 2798.9, "duration": 2.79}, {"text": "called metagenomics,\nwhich allows scientists", "start": 2801.69, "duration": 2.64}, {"text": "to sample the genes of\nmillions of microorganisms", "start": 2804.33, "duration": 2.55}, {"text": "without the need\nfor individual c--", "start": 2806.88, "duration": 2.19}, {"text": "PROFESSOR: So that\ntells you something", "start": 2809.07, "duration": 1.65}, {"text": "about technology and engineering\nand understanding structures.", "start": 2810.72, "duration": 4.38}, {"text": "So it would be\nreally advantageous.", "start": 2815.1, "duration": 2.71}, {"text": "The stage at which you\nreally need blood supplies", "start": 2817.81, "duration": 2.78}, {"text": "is to take all the\nblood in the blood banks", "start": 2820.59, "duration": 2.01}, {"text": "and turn everything\ninto a universal donor.", "start": 2822.6, "duration": 3.12}, {"text": "But the blood banks keep\nthese differentiated supplies", "start": 2825.72, "duration": 3.09}, {"text": "of blood.", "start": 2828.81, "duration": 0.81}, {"text": "But what if you need something\nthat you can give everyone", "start": 2829.62, "duration": 3.54}, {"text": "safely?", "start": 2833.16, "duration": 1.14}, {"text": "And so there are\nenzymes in the gut.", "start": 2834.3, "duration": 2.7}, {"text": "There are bacteria in the\ngut that actually live off", "start": 2837.0, "duration": 3.81}, {"text": "of sugars that\nthey chop off cells", "start": 2840.81, "duration": 1.98}, {"text": "in the matrix in the GI system.", "start": 2842.79, "duration": 7.9}, {"text": "And so what the\nWithers group did", "start": 2850.69, "duration": 1.91}, {"text": "was to screen a lot\nof different enzymes", "start": 2852.6, "duration": 3.27}, {"text": "from bacteria in\nthe gut and find", "start": 2855.87, "duration": 3.54}, {"text": "ones that had a really good\nspecificity for removing", "start": 2859.41, "duration": 3.12}, {"text": "those sugars.", "start": 2862.53, "duration": 1.29}, {"text": "Then they did\nprotein engineering", "start": 2863.82, "duration": 1.92}, {"text": "work to make them\nmore efficient,", "start": 2865.74, "duration": 2.67}, {"text": "thus creating something\nthat was proposed", "start": 2868.41, "duration": 2.04}, {"text": "a long time ago as could\nbe useful, but now really", "start": 2870.45, "duration": 3.24}, {"text": "making it useful.", "start": 2873.69, "duration": 1.17}, {"text": "Because those enzymes\nare much more efficient.", "start": 2874.86, "duration": 2.52}, {"text": "They really catalyze\nreactions at great speed.", "start": 2877.38, "duration": 2.67}, {"text": "So they're much more\nefficient engineering enzymes", "start": 2880.05, "duration": 3.03}, {"text": "to treat your blood\ncells, to make", "start": 2883.08, "duration": 1.68}, {"text": "sure you get rid\nof all the features", "start": 2884.76, "duration": 3.63}, {"text": "that are characteristic of the\nA, the B, and the AB antigens.", "start": 2888.39, "duration": 3.91}, {"text": "Because if you don't\ndo a good job of it,", "start": 2892.3, "duration": 2.45}, {"text": "then the human\nimmune system will", "start": 2894.75, "duration": 1.89}, {"text": "recognize the little\nbits that sneak in", "start": 2896.64, "duration": 2.58}, {"text": "and start triggering\nan immune response.", "start": 2899.22, "duration": 2.56}, {"text": "So the efficiency of the enzymes\nthat cleave those sugars off", "start": 2901.78, "duration": 2.99}, {"text": "is absolutely paramount.", "start": 2904.77, "duration": 1.96}, {"text": "And that's what I\nhave for you today.", "start": 2906.73, "duration": 2.94}, {"text": "I will see you Monday,\nso don't forget.", "start": 2909.67, "duration": 1.67}, {"text": "The Pset's due at 3:00.", "start": 2911.34, "duration": 2.97}, {"text": "Monday, I would like for you\nto have a preview of the--", "start": 2914.31, "duration": 5.31}, {"text": "whoops, come on-- of the\nDNA reading material.", "start": 2919.62, "duration": 5.202}, {"text": "I don't know if\nany of you do this.", "start": 2924.822, "duration": 1.458}, {"text": "But I think it's really handy.", "start": 2926.28, "duration": 1.74}, {"text": "So there's just some\nvery little sections", "start": 2928.02, "duration": 2.09}, {"text": "that will give you a bit of\nexposure to nucleic acids.", "start": 2930.11, "duration": 3.49}, {"text": "It'll just make the\nlecture a little bit more", "start": 2933.6, "duration": 2.13}, {"text": "kind of familiar.", "start": 2935.73, "duration": 0.88}, {"text": "But that's what\nwe're up for Monday.", "start": 2936.61, "duration": 2.74}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 0.85, "duration": 2.37}, {"text": "Commons license.", "start": 3.22, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.61, "duration": 2.21}, {"text": "continue to offer high quality\neducational resources for free.", "start": 6.82, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 10.91, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.48, "duration": 3.96}, {"text": "at ocw.mit.edu.", "start": 17.44, "duration": 0.873}, {"text": "ALIN TOMESCU: My name is Alin.", "start": 22.1, "duration": 1.25}, {"text": "I work in Stata, in\nthe Stata Center.", "start": 23.35, "duration": 2.24}, {"text": "I'm a PhD student\nthere in my fifth year.", "start": 25.59, "duration": 2.17}, {"text": "And today we're going\nto be talking about one", "start": 27.76, "duration": 2.97}, {"text": "of our research\nproject called Catena.", "start": 30.73, "duration": 2.01}, {"text": "And Catena is a really\nnice way of using bitcoin", "start": 32.74, "duration": 2.28}, {"text": "to build append-only logs.", "start": 35.02, "duration": 2.37}, {"text": "Bitcoin itself is\nan append-only log.", "start": 37.39, "duration": 1.86}, {"text": "And a lot of people have been\nusing it to put data in it.", "start": 39.25, "duration": 4.02}, {"text": "And I'll describe a\nreally efficient way", "start": 43.27, "duration": 1.77}, {"text": "of doing that and\nits applications.", "start": 45.04, "duration": 2.16}, {"text": "And if there is time, we'll talk\nabout a tax and maybe colored", "start": 47.2, "duration": 2.73}, {"text": "coins and some other stuff.", "start": 49.93, "duration": 1.65}, {"text": "We'll talk about the\nwhat, the how and the why.", "start": 51.58, "duration": 2.25}, {"text": "And that's the overview\nof the presentation.", "start": 53.83, "duration": 3.21}, {"text": "So let's talk about this\nproblem called the equivocation", "start": 57.04, "duration": 2.74}, {"text": "problem.", "start": 59.78, "duration": 0.5}, {"text": "So what is this?", "start": 60.28, "duration": 2.1}, {"text": "In general, non-equivocation\nmeans saying the same thing", "start": 62.38, "duration": 3.36}, {"text": "to everybody.", "start": 65.74, "duration": 1.11}, {"text": "So for example, if you\nhave a malicious service", "start": 66.85, "duration": 2.31}, {"text": "and you have Alice\nand Bob, the service", "start": 69.16, "duration": 2.82}, {"text": "should say the same\nthing to Alice and Bob.", "start": 71.98, "duration": 2.19}, {"text": "So it would make a\nbunch of statements.", "start": 74.17, "duration": 1.89}, {"text": "Let's say s1, s2, s3 over\ntime and Alice and Bob", "start": 76.06, "duration": 3.12}, {"text": "would see all of\nthese statements.", "start": 79.18, "duration": 1.867}, {"text": "So this is very similar to\nwhat bitcoin provides, right?", "start": 81.047, "duration": 2.333}, {"text": "In bitcoin you see block\none, block two, block three.", "start": 83.38, "duration": 2.67}, {"text": "And everybody agrees on these\nblocks in sequence, right?", "start": 86.05, "duration": 2.52}, {"text": "Does that make sense?", "start": 88.57, "duration": 1.66}, {"text": "So this is non-equivocation\nand in some sense", "start": 90.23, "duration": 2.06}, {"text": "this is what bitcoin\nalready offers.", "start": 92.29, "duration": 2.55}, {"text": "And in general with\nnon-equivocation,", "start": 94.84, "duration": 2.523}, {"text": "what you might get is\nsome of these statements", "start": 97.363, "duration": 1.917}, {"text": "might actually be\nfalse or incorrect.", "start": 99.28, "duration": 2.17}, {"text": "Non-equivocation\ndoesn't guarantee you", "start": 101.45, "duration": 1.79}, {"text": "that this statement is\na correct statement.", "start": 103.24, "duration": 1.892}, {"text": "But it just guarantees\nyou that everybody", "start": 105.132, "duration": 1.708}, {"text": "sees the same statements.", "start": 106.84, "duration": 1.042}, {"text": "And then they can detect\nincorrect statements.", "start": 107.882, "duration": 2.018}, {"text": "In bitcoin you get\na little bit more.", "start": 109.9, "duration": 1.32}, {"text": "You actually know that\nif this is a block,", "start": 111.22, "duration": 1.75}, {"text": "it's a valid block, assuming\nthere are enough blocks on top", "start": 112.97, "duration": 2.96}, {"text": "of it, right?", "start": 115.93, "duration": 1.47}, {"text": "So equivocation means saying\nthe same thing to everybody.", "start": 117.4, "duration": 3.12}, {"text": "So for example, this malicious\nservice at time four,", "start": 120.52, "duration": 3.09}, {"text": "he might show Bob a different\nstatement than Alice.", "start": 123.61, "duration": 2.91}, {"text": "So Bob sees s4 and\nAlice sees s4 prime.", "start": 126.52, "duration": 3.03}, {"text": "This is what happens\nin bitcoin sometimes.", "start": 129.55, "duration": 2.04}, {"text": "And that's how you can\ndouble spend in bitcoin", "start": 131.59, "duration": 2.16}, {"text": "by putting the transaction here\nsending money to the merchant,", "start": 133.75, "duration": 2.91}, {"text": "and then putting\nanother transaction", "start": 136.66, "duration": 1.5}, {"text": "here sending money back to you.", "start": 138.16, "duration": 1.95}, {"text": "Right, are you guys\nfamiliar with this?", "start": 140.11, "duration": 1.85}, {"text": "Yeah, OK.", "start": 141.96, "duration": 1.86}, {"text": "All right, so why\ndoes this matter?", "start": 143.82, "duration": 1.54}, {"text": "Let me give you a silly example.", "start": 145.36, "duration": 1.44}, {"text": "Suppose we have Jimmy and we\nhave Jimmy's mom and Jimmy's", "start": 146.8, "duration": 3.06}, {"text": "dad, right?", "start": 149.86, "duration": 0.835}, {"text": "And Jimmy wants to\ngo outside and play.", "start": 150.695, "duration": 1.625}, {"text": "But he knows that mom and dad\nusually don't let him play.", "start": 152.32, "duration": 3.75}, {"text": "So what he does is he\ntells dad, hey dad,", "start": 156.07, "duration": 3.33}, {"text": "mom said I can go outside.", "start": 159.4, "duration": 1.81}, {"text": "Right, and then he\ntells mom, hey mom.", "start": 161.21, "duration": 2.9}, {"text": "Dad said I can go outside.", "start": 164.11, "duration": 1.36}, {"text": "And let's say mom and dad\nare in different rooms", "start": 165.47, "duration": 2.0}, {"text": "and they're watching soap\noperas and they're not", "start": 167.47, "duration": 1.44}, {"text": "talking to one another.", "start": 168.91, "duration": 1.11}, {"text": "So they can actually\nconfirm that.", "start": 170.02, "duration": 2.51}, {"text": "You know, mom can confirm\nthat dad really said that.", "start": 172.53, "duration": 2.183}, {"text": "And dad can really confirm\nthat mom said that.", "start": 174.713, "duration": 1.917}, {"text": "But they both trust Jimmy.", "start": 176.63, "duration": 2.012}, {"text": "So you see how equivocation\ncan be really problematic", "start": 178.642, "duration": 2.208}, {"text": "because now mom and\ndad will say sure,", "start": 180.85, "duration": 1.89}, {"text": "go outside as long as the\nother person said that, right?", "start": 182.74, "duration": 3.12}, {"text": "But let me give you a\nmore practical example.", "start": 185.86, "duration": 2.68}, {"text": "So let's look at something\ncalled a public-key directory.", "start": 188.54, "duration": 3.04}, {"text": "A public-key directory allows\nyou to map user's public keys--", "start": 191.58, "duration": 3.62}, {"text": "a user name to a public key.", "start": 195.2, "duration": 1.167}, {"text": "Right, so here I have\nthe public key for Alice", "start": 196.367, "duration": 1.916}, {"text": "and here I have the\npublic key for Bob.", "start": 198.283, "duration": 1.647}, {"text": "And they look up each other's\nkeys in this directory.", "start": 199.93, "duration": 2.208}, {"text": "And then they can set\nup a secure channel.", "start": 202.138, "duration": 2.352}, {"text": "How many of you guys use\nWhatsapp, for example?", "start": 204.49, "duration": 2.88}, {"text": "So the Whatsapp server has\na public-key directory.", "start": 207.37, "duration": 2.97}, {"text": "And when I want to\nsend you a message,", "start": 210.34, "duration": 1.71}, {"text": "I look up your phone\nnumber in that directory", "start": 212.05, "duration": 2.43}, {"text": "and I get your\npublic key, right?", "start": 214.48, "duration": 1.62}, {"text": "If that directory equivocates,\nthe following thing can happen.", "start": 216.1, "duration": 2.84}, {"text": "What the directory can do is\nit can create a new directory", "start": 218.94, "duration": 2.65}, {"text": "at time two where he puts\na fake public key for Bob", "start": 221.59, "duration": 3.06}, {"text": "and he shows this\nto Alice, right?", "start": 224.65, "duration": 3.0}, {"text": "And at time two also, he creates\nanother directory for Bob", "start": 227.65, "duration": 4.08}, {"text": "where he puts a fake public\nkey for Alice, right?", "start": 231.73, "duration": 3.27}, {"text": "So now the problem\nhere is that when", "start": 235.0, "duration": 2.43}, {"text": "Alice checks in this directory,\nshe looks at her own public key", "start": 237.43, "duration": 3.21}, {"text": "to make sure she's\nnot impersonated.", "start": 240.64, "duration": 2.055}, {"text": "And Alice looks in this\nversion and sees, OK.", "start": 242.695, "duration": 1.875}, {"text": "That is my public key.", "start": 244.57, "duration": 0.82}, {"text": "I'm good.", "start": 245.39, "duration": 0.38}, {"text": "She looks in this version, OK.", "start": 245.77, "duration": 1.17}, {"text": "This is my public key.", "start": 246.94, "duration": 0.917}, {"text": "I'm good.", "start": 247.857, "duration": 0.638}, {"text": "So now I'm ready to\nuse this directory.", "start": 248.495, "duration": 1.625}, {"text": "And I'll look up Bob and\nI'll get his public key.", "start": 250.12, "duration": 2.46}, {"text": "But Alice will actually\nget the wrong public key.", "start": 252.58, "duration": 2.1}, {"text": "Does everybody see that?", "start": 254.68, "duration": 2.39}, {"text": "And similarly Bob\nwill do the same.", "start": 257.07, "duration": 2.35}, {"text": "So Bob will look in his fork\nof the directory, right?", "start": 259.42, "duration": 3.57}, {"text": "And he looks up his key\nhere and his key here.", "start": 262.99, "duration": 2.503}, {"text": "And he thinks he's OK.", "start": 265.493, "duration": 0.917}, {"text": "He's not impersonated.", "start": 266.41, "duration": 0.917}, {"text": "But in fact, Alice has\nimpersonated there.", "start": 267.327, "duration": 2.983}, {"text": "OK?", "start": 270.31, "duration": 1.23}, {"text": "And now as a result, they\nwill obtain fake keys", "start": 271.54, "duration": 3.78}, {"text": "for each other.", "start": 275.32, "duration": 1.02}, {"text": "And this man in the\nmiddle, attacker", "start": 276.34, "duration": 1.62}, {"text": "who knows the\ncorresponding secret keys", "start": 277.96, "duration": 2.01}, {"text": "for these public\nkeys can basically", "start": 279.97, "duration": 2.22}, {"text": "read all of their\ncommunications.", "start": 282.19, "duration": 3.7}, {"text": "Any questions about this?", "start": 285.89, "duration": 1.57}, {"text": "This is just one example\nof how equivocation", "start": 287.46, "duration": 2.39}, {"text": "can be really disastrous.", "start": 289.85, "duration": 1.83}, {"text": "So in a public-key directory,\nif you can equivocate,", "start": 291.68, "duration": 2.22}, {"text": "you can show fake\npublic keys for people", "start": 293.9, "duration": 2.01}, {"text": "and impersonate them.", "start": 295.91, "duration": 2.353}, {"text": "So in other words,\nit's really important", "start": 298.263, "duration": 1.667}, {"text": "that Alice and Bob both\nsee the same directory.", "start": 299.93, "duration": 2.79}, {"text": "Because if Bob saw\nthis directory,", "start": 302.72, "duration": 1.8}, {"text": "the same one Alice saw, then Bob\nwould notice that this is not", "start": 304.52, "duration": 3.51}, {"text": "the public key he had.", "start": 308.03, "duration": 1.605}, {"text": "He would notice his\nfirst public key and then", "start": 309.635, "duration": 1.875}, {"text": "that there's a second one there.", "start": 311.51, "duration": 1.47}, {"text": "And then he would know\nhe's impersonated.", "start": 312.98, "duration": 1.708}, {"text": "And he could let's say,\ntalk to the New York Times,", "start": 314.688, "duration": 2.582}, {"text": "and say, look.", "start": 317.27, "duration": 0.93}, {"text": "This directory is\nimpersonating me.", "start": 318.2, "duration": 1.84}, {"text": "So in conclusion, equivocation\ncan be pretty bad.", "start": 323.33, "duration": 2.31}, {"text": "So this idea that you\nsay different things", "start": 325.64, "duration": 1.75}, {"text": "to different people can\nbe pretty disastrous.", "start": 327.39, "duration": 1.97}, {"text": "And what Catena does\nis it prevents that.", "start": 329.36, "duration": 2.59}, {"text": "So in general, if you have\nthis malicious service that is", "start": 331.95, "duration": 3.2}, {"text": "backed by Catena, if it\nwants to say different things", "start": 335.15, "duration": 3.385}, {"text": "to different people.\nit cannot do that.", "start": 338.535, "duration": 1.625}, {"text": "It has to show the same\nthing to everybody.", "start": 340.16, "duration": 2.82}, {"text": "And the way we achieve that is\nby building on top of bitcoin.", "start": 342.98, "duration": 2.91}, {"text": "And that's what we're going\nto be talking about today.", "start": 345.89, "duration": 2.41}, {"text": "So any questions about\nsort of the general setting", "start": 348.3, "duration": 3.02}, {"text": "of the problem and\nour goals here?", "start": 351.32, "duration": 2.71}, {"text": "So let's move on then.", "start": 354.03, "duration": 1.23}, {"text": "So why does this matter?", "start": 355.26, "duration": 1.665}, {"text": "So this matters for a\nbunch of other reasons,", "start": 356.925, "duration": 1.875}, {"text": "not just public-key directories\nand secure messaging.", "start": 358.8, "duration": 2.43}, {"text": "It matters because when you want\nto do secure software update,", "start": 361.23, "duration": 3.66}, {"text": "equivocation is a problem.", "start": 364.89, "duration": 1.23}, {"text": "And I'll talk about that later.", "start": 366.12, "duration": 1.42}, {"text": "So for example, at\nsome point bitcoin", "start": 367.54, "duration": 1.61}, {"text": "was concerned about\nmalicious bitcoin binaries", "start": 369.15, "duration": 3.09}, {"text": "being published on\nthe web and people", "start": 372.24, "duration": 2.0}, {"text": "like you and me\ndownloading those binaries", "start": 374.24, "duration": 1.75}, {"text": "and getting our coins stolen.", "start": 375.99, "duration": 1.82}, {"text": "Right, and it turns out that\nthat's an equivocation problem.", "start": 377.81, "duration": 2.5}, {"text": "Somebody is equivocating, right?", "start": 380.31, "duration": 2.31}, {"text": "It's equivocating about\nthe bitcoin binary.", "start": 382.62, "duration": 1.99}, {"text": "It's showing us a\nfake version and maybe", "start": 384.61, "duration": 2.06}, {"text": "other people the real version.", "start": 386.67, "duration": 2.088}, {"text": "Secure messaging,\nlike I said before,", "start": 388.758, "duration": 1.542}, {"text": "has applications here and.", "start": 390.3, "duration": 3.24}, {"text": "Not just secure messaging\nbut also the web.", "start": 393.54, "duration": 1.8}, {"text": "Like when you go\non Facebook.com,", "start": 395.34, "duration": 1.375}, {"text": "you're looking up\nFacebook's public key.", "start": 396.715, "duration": 1.902}, {"text": "And if somebody lies to\nyou about that public key,", "start": 398.617, "duration": 2.083}, {"text": "you could be going to\na malicious service", "start": 400.7, "duration": 2.32}, {"text": "and you could be giving\nthem your Facebook password.", "start": 403.02, "duration": 3.37}, {"text": "Does that make sense?", "start": 406.39, "duration": 2.54}, {"text": "And also it has\napplications in the sense", "start": 408.93, "duration": 1.93}, {"text": "that if you have a way of\nbuilding a append-only log,", "start": 410.86, "duration": 2.97}, {"text": "you really have a way of\nbuilding a blockchain right", "start": 413.83, "duration": 2.64}, {"text": "for whatever purpose you want.", "start": 416.47, "duration": 1.81}, {"text": "And we'll talk\nabout that as well.", "start": 418.28, "duration": 2.55}, {"text": "So the 10,000 feet\nview of the system", "start": 420.83, "duration": 3.11}, {"text": "is we built this bitcoin\nbased append-only log.", "start": 423.94, "duration": 3.12}, {"text": "And the way to think about\nis that bitcoin is already", "start": 427.06, "duration": 2.32}, {"text": "an append-only log.", "start": 429.38, "duration": 1.452}, {"text": "It's just that it's kind\nof inefficient to look", "start": 430.832, "duration": 1.958}, {"text": "in that log.", "start": 432.79, "duration": 0.515}, {"text": "If you want to pick certain\nthings from the Bitcoin", "start": 433.305, "duration": 2.125}, {"text": "blockchain, like you put your\ncertain bits and pieces of data", "start": 435.43, "duration": 2.58}, {"text": "there, you have to\nkind of download", "start": 438.01, "duration": 1.05}, {"text": "the whole thing to make sure\nyou're not missing anything.", "start": 439.06, "duration": 2.375}, {"text": "And I'll tell you why soon.", "start": 441.435, "duration": 1.585}, {"text": "So instead of\nputting stuff naively", "start": 443.02, "duration": 2.43}, {"text": "in the Bitcoin\nblockchain, we put it", "start": 445.45, "duration": 1.5}, {"text": "in a more principled way.", "start": 446.95, "duration": 1.77}, {"text": "And in a sense we get\na log and another log.", "start": 448.72, "duration": 2.82}, {"text": "We get our log and\nthe bitcoin log.", "start": 451.54, "duration": 3.12}, {"text": "And this generalizes to\nother cryptocurrencies.", "start": 454.66, "duration": 2.25}, {"text": "Like you could do\nthis in light coin,", "start": 456.91, "duration": 1.62}, {"text": "for example, or\neven in ethereum.", "start": 458.53, "duration": 1.685}, {"text": "Though I don't\nthink you guys yet", "start": 460.215, "duration": 1.375}, {"text": "talked about how the\nethereum blockchain works.", "start": 461.59, "duration": 3.5}, {"text": "And the cool thing about this\nCatena log that we're building", "start": 465.09, "duration": 3.22}, {"text": "is that the Catena log is as\nhard to fork as the bitcoin", "start": 468.31, "duration": 3.25}, {"text": "blockchain.", "start": 471.56, "duration": 0.5}, {"text": "If you want to fork our log,\nyou have to fork bitcoin.", "start": 472.06, "duration": 2.82}, {"text": "However, unlike the\nBitcoin blockchain,", "start": 474.88, "duration": 1.86}, {"text": "Catena is super\nefficient to verify.", "start": 476.74, "duration": 2.4}, {"text": "So in particular, remember,\nI described the log", "start": 479.14, "duration": 3.63}, {"text": "in terms of the\nstatements in it.", "start": 482.77, "duration": 1.48}, {"text": "So if you have 10\nstatements, each statement", "start": 484.25, "duration": 3.59}, {"text": "will be 600 bytes to audit.", "start": 487.84, "duration": 1.732}, {"text": "So you don't have to\ndownload the whole Bitcoin", "start": 489.572, "duration": 1.958}, {"text": "blockchain to make sure you're\nnot missing a statement.", "start": 491.53, "duration": 3.29}, {"text": "And you also have to download\n80 bytes per bitcoin block.", "start": 494.82, "duration": 3.37}, {"text": "And we have a Java\nimplementation of this.", "start": 498.19, "duration": 1.83}, {"text": "And if you guys are curious,\nyou can go to my GitHub page,", "start": 500.02, "duration": 3.69}, {"text": "and take a look at the code.", "start": 503.71, "duration": 1.92}, {"text": "All right, so before we\nstart, I know you guys already", "start": 505.63, "duration": 2.25}, {"text": "know a lot about how\nthe Bitcoin blockchain,", "start": 507.88, "duration": 1.53}, {"text": "but it's important that I\nreintroduce some terminology", "start": 509.41, "duration": 2.31}, {"text": "just so we're on the same page.", "start": 511.72, "duration": 1.77}, {"text": "So this is the\nbitcoin blockchain.", "start": 513.49, "duration": 1.51}, {"text": "We have a bunch of\nblocks connected", "start": 515.0, "duration": 1.49}, {"text": "by hash chain pointers.", "start": 516.49, "duration": 1.2}, {"text": "And we have Merkle\ntrees of transactions.", "start": 517.69, "duration": 3.15}, {"text": "And you know, these arrows\nindicate hash pointers.", "start": 520.84, "duration": 2.77}, {"text": "It means that block n stores a\nhash of block n minus 1 in it,", "start": 523.61, "duration": 4.23}, {"text": "right?", "start": 527.84, "duration": 0.5}, {"text": "So in that sense.", "start": 528.34, "duration": 1.35}, {"text": "Block n has a hash pointer\nto block n minus 1.", "start": 529.69, "duration": 2.81}, {"text": "All right, and like I said,\neach tree has a Merkle tree.", "start": 535.32, "duration": 2.482}, {"text": "Each block has a Merkle tree.", "start": 537.802, "duration": 1.208}, {"text": "And everybody\nagrees on this chain", "start": 539.01, "duration": 1.95}, {"text": "of blocks via proof of work\nconsensus, which all of you", "start": 540.96, "duration": 2.91}, {"text": "already know.", "start": 543.87, "duration": 1.29}, {"text": "And importantly, in the Merkle\ntrees, we have transactions.", "start": 545.16, "duration": 3.51}, {"text": "And transactions\ncan do two things.", "start": 548.67, "duration": 1.56}, {"text": "Right, a transaction can\nmint coins, create new coins.", "start": 550.23, "duration": 2.82}, {"text": "So here I have transaction a.", "start": 553.05, "duration": 1.54}, {"text": "It created four coins by\nstoring them in an output.", "start": 554.59, "duration": 3.08}, {"text": "Are you familiar with outputs?", "start": 557.67, "duration": 1.25}, {"text": "So you guys already discussed\ntransaction outputs and inputs.", "start": 558.92, "duration": 2.542}, {"text": "So that's what we're going\nover here again real quick.", "start": 561.462, "duration": 3.798}, {"text": "So an output specifies\nthe number of coins", "start": 565.26, "duration": 2.19}, {"text": "and the public key of\nthe owner of those coins,", "start": 567.45, "duration": 2.85}, {"text": "as you already know.", "start": 570.3, "duration": 1.5}, {"text": "And the second purpose\nof transactions", "start": 571.8, "duration": 1.83}, {"text": "is that they can transfer\ncoins, right, and pay fees", "start": 573.63, "duration": 2.31}, {"text": "in the process.", "start": 575.94, "duration": 0.96}, {"text": "So here if you have\na transaction b,", "start": 576.9, "duration": 2.25}, {"text": "this transaction b\nmight say, hey, here's", "start": 579.15, "duration": 3.36}, {"text": "a signature from the\nowner of these coins here.", "start": 582.51, "duration": 3.24}, {"text": "Here's a signature\nand transaction b.", "start": 585.75, "duration": 2.1}, {"text": "And here's the new\nowner with public key", "start": 587.85, "duration": 1.82}, {"text": "b of three of those four coins.", "start": 589.67, "duration": 2.53}, {"text": "And one of those coins\nI'll just give it", "start": 592.2, "duration": 1.89}, {"text": "to the miners as\na transaction fee.", "start": 594.09, "duration": 3.685}, {"text": "Does this make sense?", "start": 597.775, "duration": 0.875}, {"text": "How many of you are with me?", "start": 598.65, "duration": 1.97}, {"text": "All right, any questions\nabout how transaction inputs", "start": 600.62, "duration": 3.15}, {"text": "and outputs work?", "start": 603.77, "duration": 0.888}, {"text": "So if you remember\nin the input here,", "start": 604.658, "duration": 1.542}, {"text": "you have a hash pointer\nto the output here.", "start": 606.2, "duration": 3.32}, {"text": "All right.", "start": 609.52, "duration": 2.95}, {"text": "So and the high\nlevel idea here is", "start": 612.47, "duration": 1.793}, {"text": "that the output\nis just the number", "start": 614.263, "duration": 1.417}, {"text": "of coins in a public key.", "start": 615.68, "duration": 1.197}, {"text": "And the input is a hash\npointer to an output", "start": 616.877, "duration": 1.833}, {"text": "plus a digital signature from\nthat output's public key, OK?", "start": 618.71, "duration": 5.7}, {"text": "And yeah, so what\nhappens here is", "start": 624.41, "duration": 1.77}, {"text": "that transaction b is spending\ntransaction a's first output.", "start": 626.18, "duration": 4.74}, {"text": "Right, that's the terminology\nthat we're going to use.", "start": 630.92, "duration": 2.495}, {"text": "And I think you\nguys have already", "start": 633.415, "duration": 1.375}, {"text": "used terminology like this.", "start": 634.79, "duration": 3.0}, {"text": "And in addition, what we're\ngoing to talk about today", "start": 637.79, "duration": 2.64}, {"text": "is the fact that in these\nbitcoin transactions", "start": 640.43, "duration": 2.01}, {"text": "you can actually embed data.", "start": 642.44, "duration": 1.23}, {"text": "And I think you touched briefly\non this concept of op return", "start": 643.67, "duration": 4.41}, {"text": "transaction outputs.", "start": 648.08, "duration": 1.98}, {"text": "Right, so this is an output that\nsends coins to a public key.", "start": 650.06, "duration": 4.68}, {"text": "But here I can have an output\nthat sends coins to nobody.", "start": 654.74, "duration": 3.06}, {"text": "It just specifies some data.", "start": 657.8, "duration": 2.01}, {"text": "And in fact, I'll use that\ndata to specify the statements", "start": 659.81, "duration": 2.67}, {"text": "that I was talking\nabout earlier.", "start": 662.48, "duration": 2.39}, {"text": "So that the high\nlevel point here", "start": 664.87, "duration": 1.42}, {"text": "is that you can embed data\nin bitcoin transactions using", "start": 666.29, "duration": 4.05}, {"text": "these operations.", "start": 670.34, "duration": 0.762}, {"text": "And there's a bunch of other\nways to do it, actually.", "start": 671.102, "duration": 2.208}, {"text": "Like initially\nwhat people did is", "start": 673.31, "duration": 2.19}, {"text": "they put the data\nas the public key.", "start": 675.5, "duration": 1.772}, {"text": "They just set the\npublic key to the data.", "start": 677.272, "duration": 1.708}, {"text": "And in that sense, they\nkind of wasted bitcoins.", "start": 678.98, "duration": 3.59}, {"text": "Right, they said hey,\nsend these three bitcoins", "start": 682.57, "duration": 2.71}, {"text": "to this public key, which\nis just some random data.", "start": 685.28, "duration": 2.61}, {"text": "But nobody would know the\ncorresponding secret key", "start": 687.89, "duration": 2.19}, {"text": "of that public key.", "start": 690.08, "duration": 1.5}, {"text": "So therefore those\ncoins would be burned.", "start": 691.58, "duration": 2.28}, {"text": "Did you did you cover\nthis in class already?", "start": 693.86, "duration": 2.91}, {"text": "Maybe, maybe a little bit.", "start": 696.77, "duration": 1.11}, {"text": "So but that's kind\nof inefficient", "start": 697.88, "duration": 1.722}, {"text": "because if you\nremember, the miners", "start": 699.602, "duration": 1.458}, {"text": "have to build this UTXO set.", "start": 701.06, "duration": 2.4}, {"text": "And they have to\nkeep this output that", "start": 703.46, "duration": 2.31}, {"text": "has this bad public\nkey in their memory", "start": 705.77, "duration": 2.16}, {"text": "forever because nobody's\ngoing to be able to spend it.", "start": 707.93, "duration": 2.743}, {"text": "So we don't want to do that.", "start": 710.673, "duration": 1.167}, {"text": "We want to build a nice system,\na system that treats bitcoin", "start": 711.84, "duration": 3.89}, {"text": "nicely, the bitcoin miners.", "start": 715.73, "duration": 1.33}, {"text": "So that's why we use\nthese return outputs.", "start": 717.06, "duration": 3.205}, {"text": "All right, so the\nhigh level here", "start": 720.265, "duration": 1.375}, {"text": "is that Alice gives\nBob three bitcoins.", "start": 721.64, "duration": 1.65}, {"text": "And the miners collect\na bitcoin as a fee.", "start": 723.29, "duration": 2.793}, {"text": "And of course, you can\nkeep doing this, right?", "start": 726.083, "duration": 1.917}, {"text": "Like Bob can give Carol these\ntwo bitcoins later by creating", "start": 728.0, "duration": 2.94}, {"text": "another transaction with an\ninput referring to that output", "start": 730.94, "duration": 3.52}, {"text": "and with an output specifying\nCarol's public key.", "start": 734.46, "duration": 3.37}, {"text": "All right, and the high level\nidea of bitcoin is that you", "start": 737.83, "duration": 3.1}, {"text": "don't-- you cannot\ndouble spend coins.", "start": 740.93, "duration": 1.68}, {"text": "And what that means is that\na transaction output can only", "start": 742.61, "duration": 3.03}, {"text": "be referred to by a\nsingle transaction input.", "start": 745.64, "duration": 2.852}, {"text": "So this thing right here in\nbitcoin where I have two inputs", "start": 748.492, "duration": 2.458}, {"text": "spending an output\ncannot happen, right?", "start": 750.95, "duration": 3.49}, {"text": "How many of you are\nfamiliar with this already?", "start": 754.44, "duration": 2.43}, {"text": "OK, good.", "start": 756.87, "duration": 0.625}, {"text": "So actually this is\nthe essential trick", "start": 757.495, "duration": 1.625}, {"text": "that Catena leverages.", "start": 759.12, "duration": 1.05}, {"text": "And we'll talk about it soon.", "start": 760.17, "duration": 1.84}, {"text": "And yeah, the\nmoral of the story,", "start": 762.01, "duration": 1.55}, {"text": "the reason I told you all\nof this is because you know,", "start": 763.56, "duration": 2.73}, {"text": "basically if you have proof of\nwork consensus in the bitcoin", "start": 766.29, "duration": 2.7}, {"text": "sense, you cannot\ndo double spends.", "start": 768.99, "duration": 1.71}, {"text": "So this thing right\nhere, that I said before,", "start": 770.7, "duration": 2.19}, {"text": "just cannot occur in the Bitcoin\nblockchain unless you break", "start": 772.89, "duration": 3.267}, {"text": "the assumptions, right, unless\nyou have more mining power than", "start": 776.157, "duration": 2.583}, {"text": "you should.", "start": 778.74, "duration": 2.31}, {"text": "In that case, you either\nhave to tx2 or tx2", "start": 781.05, "duration": 2.22}, {"text": "prime, but not both, right?", "start": 783.27, "duration": 2.48}, {"text": "And what Catena\nreally realizes is", "start": 785.75, "duration": 3.13}, {"text": "that if I put statements\nin these transactions now,", "start": 788.88, "duration": 2.91}, {"text": "what that means is that I can\nonly have a second statement.", "start": 791.79, "duration": 2.58}, {"text": "I cannot have two\nsecond statements.", "start": 794.37, "duration": 1.74}, {"text": "I cannot equivocate about the\nsecond statements if I just", "start": 796.11, "duration": 3.0}, {"text": "restrict my way of issuing\nstatements in this way.", "start": 799.11, "duration": 3.627}, {"text": "I put the first statement\nin the transaction", "start": 802.737, "duration": 1.833}, {"text": "and the second\nstatement I put it", "start": 804.57, "duration": 1.375}, {"text": "in a transaction that\nspends the first one.", "start": 805.945, "duration": 2.885}, {"text": "So does everybody agree that\nif I do things in this way", "start": 808.83, "duration": 2.573}, {"text": "and I want to equivocate\nabout the second statement,", "start": 811.403, "duration": 2.167}, {"text": "I would have to double spend?", "start": 813.57, "duration": 2.95}, {"text": "So that's the key insight\nbehind our system.", "start": 816.52, "duration": 4.16}, {"text": "Any questions about this so far?", "start": 820.68, "duration": 1.54}, {"text": "You know it's really hard to\ntalk if you guys talk back,", "start": 826.147, "duration": 2.333}, {"text": "it's way easier.", "start": 828.48, "duration": 2.67}, {"text": "Yeah?", "start": 831.15, "duration": 0.5}, {"text": "AUDIENCE: A question.", "start": 831.65, "duration": 0.875}, {"text": "And maybe, I think I'm\ngetting this right.", "start": 832.525, "duration": 2.553}, {"text": "If you're setting up\nthe first transaction,", "start": 835.078, "duration": 1.792}, {"text": "then you're adding data on?", "start": 836.87, "duration": 2.02}, {"text": "You're burning bitcoins\nevery time you're doing it,", "start": 838.89, "duration": 2.24}, {"text": "so at some point,\nyou're going to run out.", "start": 841.13, "duration": 1.75}, {"text": "ALIN TOMESCU: That's\nan excellent question.", "start": 842.88, "duration": 0.93}, {"text": "So let's-- we'll go over that.", "start": 843.81, "duration": 1.98}, {"text": "But the idea is\nthat in this output,", "start": 845.79, "duration": 2.16}, {"text": "I won't burn any bitcoins.", "start": 847.95, "duration": 2.31}, {"text": "I'll actually specify\nmy own public key here.", "start": 850.26, "duration": 2.35}, {"text": "And I'll just send the\nbitcoins back to myself.", "start": 852.61, "duration": 2.21}, {"text": "And in the process I'll pay a\nfee to issue this transaction.", "start": 854.82, "duration": 3.63}, {"text": "Does that make sense?", "start": 858.45, "duration": 1.41}, {"text": "Yeah?", "start": 859.86, "duration": 0.54}, {"text": "And we'll talk about it later.", "start": 860.4, "duration": 2.29}, {"text": "OK, so real quickly,\nwhat did previous work", "start": 862.69, "duration": 2.59}, {"text": "do regarding this?", "start": 865.28, "duration": 0.75}, {"text": "So how many of you are\nfamiliar with blockstack?", "start": 866.03, "duration": 3.06}, {"text": "1, 2, only two people?", "start": 869.09, "duration": 2.81}, {"text": "OK how many of you are\nfamiliar with Keybase?", "start": 871.9, "duration": 1.92}, {"text": "OK, so blockstack and Keybase\nactually post statements", "start": 873.82, "duration": 4.13}, {"text": "in the Bitcoin blockchain.", "start": 877.95, "duration": 1.29}, {"text": "And they're both\npublic directories.", "start": 879.24, "duration": 1.97}, {"text": "They map user names\nto public keys.", "start": 881.21, "duration": 2.17}, {"text": "And for example, Keybase,\nwhat Keybase does", "start": 883.38, "duration": 2.49}, {"text": "is they take this\nMerkle route hash,", "start": 885.87, "duration": 2.052}, {"text": "and they put it in\nthe transaction.", "start": 887.922, "duration": 1.458}, {"text": "And then six hours later,\nthey take the new route hash,", "start": 889.38, "duration": 2.34}, {"text": "and they put it in another\ntransaction, and so on.", "start": 891.72, "duration": 2.31}, {"text": "Every six hours, they\npost the transaction.", "start": 894.03, "duration": 2.25}, {"text": "But unfortunately, they don't\nactually do what Catena does.", "start": 896.28, "duration": 3.36}, {"text": "So they don't have their new\ntransaction spend the old one.", "start": 899.64, "duration": 3.72}, {"text": "And as a result,\nif you're trying", "start": 903.36, "duration": 1.65}, {"text": "to make sure you see all of\nthe statements for Keybase,", "start": 905.01, "duration": 4.2}, {"text": "you don't have a lot\nof recourse other", "start": 909.21, "duration": 1.65}, {"text": "than just downloading each\nblock and looking in the block", "start": 910.86, "duration": 4.05}, {"text": "for all of the\nrelevant transactions.", "start": 914.91, "duration": 2.842}, {"text": "Another thing you could\ndo is you could sort of", "start": 917.752, "duration": 1.958}, {"text": "trust the bitcoin miners--", "start": 919.71, "duration": 2.04}, {"text": "the bitcoin full nodes to\nfilter the blocks for you.", "start": 921.75, "duration": 3.45}, {"text": "So you could contact a\nbunch of bitcoin full nodes", "start": 925.2, "duration": 3.677}, {"text": "and say, look.", "start": 928.877, "duration": 0.583}, {"text": "I'm only interested\nin transactions", "start": 929.46, "duration": 1.8}, {"text": "that have a certain IP\nreturn prefix in the data.", "start": 931.26, "duration": 3.218}, {"text": "And they could do that for you.", "start": 934.478, "duration": 1.292}, {"text": "But unfortunately,\nbitcoin full nodes", "start": 935.77, "duration": 1.542}, {"text": "could also lie to\nyou very easily.", "start": 937.312, "duration": 1.748}, {"text": "And there is no cost\nfor them to lie to you.", "start": 939.06, "duration": 1.98}, {"text": "Everybody can be a\nbitcoin full node.", "start": 941.04, "duration": 2.04}, {"text": "So then it becomes a very\nbandwidth intensive process", "start": 943.08, "duration": 2.22}, {"text": "because you have to\nask a lot of full nodes", "start": 945.3, "duration": 3.54}, {"text": "to deal with the fact that\nsomeone might lie to you.", "start": 948.84, "duration": 2.47}, {"text": "But you either need to\ndownload full blocks", "start": 951.31, "duration": 2.03}, {"text": "to find let's say, a missing\nstatement like this one", "start": 953.34, "duration": 2.59}, {"text": "that a bitcoin full node\nmight hide from you,", "start": 955.93, "duration": 2.575}, {"text": "or you can trust the majority\nof bitcoin full nodes", "start": 958.505, "duration": 2.125}, {"text": "to not hide statements, which\nis not very good, right?", "start": 960.63, "duration": 2.672}, {"text": "So I don't want to\ntrust these full nodes", "start": 963.302, "duration": 1.708}, {"text": "because all of you guys\ncould run a full node right", "start": 965.01, "duration": 1.74}, {"text": "now in the bitcoin network.", "start": 966.75, "duration": 0.88}, {"text": "It doesn't cost you anything.", "start": 967.63, "duration": 1.208}, {"text": "And if I talk to your malicious\nfull node, I could be screwed.", "start": 968.838, "duration": 3.382}, {"text": "So our work just says, look.", "start": 972.22, "duration": 3.53}, {"text": "Instead of issuing\ntransactions in sort", "start": 975.75, "duration": 3.6}, {"text": "of an uncorrelated fashion,\njust do the following thing.", "start": 979.35, "duration": 4.08}, {"text": "Every transaction you issue\nshould spend the previous one.", "start": 983.43, "duration": 2.43}, {"text": "So as a result, if someone\nwants to equivocate", "start": 985.86, "duration": 1.92}, {"text": "about the third\nstatement, they have", "start": 987.78, "duration": 1.74}, {"text": "to double spend\nlike I said before.", "start": 989.52, "duration": 3.36}, {"text": "Right?", "start": 992.88, "duration": 0.69}, {"text": "Yeah?", "start": 993.57, "duration": 0.78}, {"text": "AUDIENCE: So what's\nthe connection back", "start": 994.35, "duration": 1.625}, {"text": "to Keybase and blockstack again?", "start": 995.975, "duration": 2.075}, {"text": "ALIN TOMESCU: Yeah, so\nKeybase and blockstack", "start": 998.05, "duration": 3.84}, {"text": "are public directories.", "start": 1001.89, "duration": 1.04}, {"text": "And what they do is they want\nto prevent themselves from--", "start": 1002.93, "duration": 4.87}, {"text": "is there a whiteboard\nI can draw here?", "start": 1007.8, "duration": 2.19}, {"text": "Yeah so, let's say, you know,\nif you remember the picture", "start": 1009.99, "duration": 5.0}, {"text": "from the beginning, I can\nhave a public directory", "start": 1014.99, "duration": 2.37}, {"text": "that evolves over time, right?", "start": 1017.36, "duration": 1.86}, {"text": "So this is v1 of the\ndirectory, and it", "start": 1019.22, "duration": 1.98}, {"text": "might have the right public\nkeys for Alice and Bob.", "start": 1021.2, "duration": 2.59}, {"text": "But at v2, the\ndirectory might do this.", "start": 1023.79, "duration": 1.98}, {"text": "It might do v2.", "start": 1025.77, "duration": 2.12}, {"text": "It might have Alice, Bob, but\nthen put a fake key for Alice.", "start": 1027.89, "duration": 3.09}, {"text": "And at V2 prime, it might\ndo Alice, Bob as before,", "start": 1030.98, "duration": 3.389}, {"text": "and put a fake key for Bob.", "start": 1034.369, "duration": 1.74}, {"text": "So in other words it keeps\nthe directory append-only.", "start": 1036.109, "duration": 2.941}, {"text": "But it just adds fake public\nkeys for the right people", "start": 1039.05, "duration": 3.42}, {"text": "in the right version.", "start": 1042.47, "duration": 1.03}, {"text": "So here this one\nis shown to Bob.", "start": 1043.5, "duration": 3.15}, {"text": "And here this one\nis shown to Alice.", "start": 1046.65, "duration": 2.21}, {"text": "So now Alice will use\nthis fake key for Bob.", "start": 1048.86, "duration": 3.33}, {"text": "So she'll encrypt a message\nwith b prime for Bob.", "start": 1052.19, "duration": 4.14}, {"text": "And now the attacker can\neasily decrypt this message", "start": 1056.33, "duration": 4.65}, {"text": "because he has the secret key.", "start": 1060.98, "duration": 1.8}, {"text": "So what the attacker can\ndo then is re-encrypt it", "start": 1062.78, "duration": 3.03}, {"text": "with the right\npublic key for Bob", "start": 1065.81, "duration": 2.76}, {"text": "and now he can read\nAlice's messages.", "start": 1068.57, "duration": 2.252}, {"text": "And the whole idea is\nthat the attacker--", "start": 1070.822, "duration": 1.708}, {"text": "you know, this b prime is the\npublic key, is pk b prime,", "start": 1072.53, "duration": 5.16}, {"text": "let's say.", "start": 1077.69, "duration": 0.72}, {"text": "But the attacker\nhas this sk b prime.", "start": 1078.41, "duration": 2.73}, {"text": "He knows sk b prime because\nthe attacker put this in there.", "start": 1081.14, "duration": 2.97}, {"text": "The attacker being really,\nblockstack or Keybase.", "start": 1084.11, "duration": 2.458}, {"text": "And of course, they're\nnot attackers in the sense", "start": 1086.568, "duration": 2.042}, {"text": "that they want to be good guys.", "start": 1088.61, "duration": 1.12}, {"text": "But they're going to be\ncompromised eventually.", "start": 1089.73, "duration": 1.91}, {"text": "So they want to\nprevent themselves", "start": 1091.64, "duration": 1.417}, {"text": "from doing things like these.", "start": 1093.057, "duration": 1.693}, {"text": "Is that sort of\nanswer your question?", "start": 1094.75, "duration": 2.55}, {"text": "Yeah.", "start": 1097.3, "duration": 1.57}, {"text": "All right, so yeah, a\nreally simple summary.", "start": 1098.87, "duration": 3.26}, {"text": "If I had two slides to summarize\nour work, this would be it.", "start": 1102.13, "duration": 2.5}, {"text": "Right, they would be these two.", "start": 1104.63, "duration": 1.68}, {"text": "Look, don't do things this way.", "start": 1106.31, "duration": 1.42}, {"text": "Do them this way.", "start": 1107.73, "duration": 1.45}, {"text": "All right, so let's see,\nlet's look a little bit", "start": 1109.18, "duration": 2.86}, {"text": "at the design.", "start": 1112.04, "duration": 0.6}, {"text": "So remember we have\nthese authorities that", "start": 1112.64, "duration": 3.75}, {"text": "could equivocate about\nstatements they issued", "start": 1116.39, "duration": 2.0}, {"text": "like blockstack and Keybase.", "start": 1118.39, "duration": 1.19}, {"text": "So what we propose is\nlook, these authorities", "start": 1119.58, "duration": 3.02}, {"text": "can run a lock server,\na Catena lock server.", "start": 1122.6, "duration": 3.33}, {"text": "And they start with some\nfunds locked in some output.", "start": 1125.93, "duration": 4.013}, {"text": "And what they can\ndo first is they", "start": 1129.943, "duration": 1.417}, {"text": "can issue this\ngenesis transaction", "start": 1131.36, "duration": 2.58}, {"text": "to start a new lock.", "start": 1133.94, "duration": 1.35}, {"text": "So for example, Keybase would\nissue this genesis transaction", "start": 1135.29, "duration": 2.79}, {"text": "starting the log of their\npublic directory Merkle routes.", "start": 1138.08, "duration": 4.23}, {"text": "And this genesis\ntransaction can be", "start": 1142.31, "duration": 1.77}, {"text": "thought of as the\npublic key of the log.", "start": 1144.08, "duration": 1.68}, {"text": "Once you have this\ngenesis transaction,", "start": 1145.76, "duration": 2.49}, {"text": "you know it's transaction ID.", "start": 1148.25, "duration": 2.58}, {"text": "You can verify any\nfuture statements,", "start": 1150.83, "duration": 1.92}, {"text": "and you can implicitly prevent\nequivocation about statements.", "start": 1152.75, "duration": 4.86}, {"text": "And what the lock\nserver is going to do", "start": 1157.61, "duration": 2.68}, {"text": "is it's going to\ntake these coins", "start": 1160.29, "duration": 1.49}, {"text": "and send them back to the\nserver to answer your question.", "start": 1161.78, "duration": 2.67}, {"text": "So if there was a public\nkey, if these coins", "start": 1164.45, "duration": 1.833}, {"text": "are owned by some\npublic key, they're", "start": 1166.283, "duration": 1.542}, {"text": "just sent back to\nsame public key here", "start": 1167.825, "duration": 1.675}, {"text": "and paying some\nfees in the process.", "start": 1169.5, "duration": 2.81}, {"text": "Right, so we're not\nburning coins in the sense", "start": 1172.31, "duration": 1.92}, {"text": "that we're just\npaying fees that are", "start": 1174.23, "duration": 1.5}, {"text": "miners, which we have to do.", "start": 1175.73, "duration": 1.167}, {"text": "OK, so now what you\ncan do is if you", "start": 1180.22, "duration": 1.9}, {"text": "want to issue the\nfirst statements,", "start": 1182.12, "duration": 1.458}, {"text": "you create a transaction.", "start": 1183.578, "duration": 2.442}, {"text": "You send the coins from this\noutput to this other output.", "start": 1186.02, "duration": 2.46}, {"text": "You pay some fees\nin the process.", "start": 1188.48, "duration": 1.375}, {"text": "You put your statement\nin an op return output.", "start": 1189.855, "duration": 3.995}, {"text": "And as a result, if this lock\nserver wants to equivocate,", "start": 1193.85, "duration": 2.91}, {"text": "it has to again,\ndouble spend here,", "start": 1196.76, "duration": 2.38}, {"text": "which it cannot do unless\nit has enough mining power.", "start": 1199.14, "duration": 3.32}, {"text": "So Keybase and\nblockstack, if they", "start": 1202.46, "duration": 1.77}, {"text": "were to use a system\nlike this, they", "start": 1204.23, "duration": 1.5}, {"text": "could prevent themselves\nfrom equivocating.", "start": 1205.73, "duration": 2.788}, {"text": "And this can keep going, right?", "start": 1208.518, "duration": 1.292}, {"text": "So you issue\nanother transaction.", "start": 1209.81, "duration": 1.375}, {"text": "Spend the previous output.", "start": 1211.185, "duration": 1.475}, {"text": "Put the new statement.", "start": 1212.66, "duration": 1.02}, {"text": "Yes?", "start": 1213.68, "duration": 0.51}, {"text": "AUDIENCE: This doesn't\nseem like a new problem.", "start": 1214.19, "duration": 1.958}, {"text": "How have authorities prevented\nequivocation in the past?", "start": 1216.148, "duration": 4.647}, {"text": "ALIN TOMESCU: This doesn't\nseem like a new problem.", "start": 1220.795, "duration": 2.125}, {"text": "How did authorities do it?", "start": 1222.92, "duration": 1.26}, {"text": "The problem is not new.", "start": 1224.18, "duration": 1.02}, {"text": "The problem is eternal.", "start": 1225.2, "duration": 1.95}, {"text": "So you are correct there.", "start": 1227.15, "duration": 1.11}, {"text": "How did they do it in the past?", "start": 1228.26, "duration": 1.6}, {"text": "They just used a Byzantine\nconsensus algorithm.", "start": 1229.86, "duration": 2.718}, {"text": "So in some sense this is what\nwe're doing here as well.", "start": 1232.578, "duration": 2.292}, {"text": "We're just piggybacking\non top of Bitcoin's", "start": 1234.87, "duration": 3.07}, {"text": "Byzantine consensus algorithm.", "start": 1237.94, "duration": 1.75}, {"text": "AUDIENCE: So you're rolling down\nto a newer Byzantine consensus", "start": 1239.69, "duration": 3.27}, {"text": "algorithm basically.", "start": 1242.96, "duration": 1.67}, {"text": "ALIN TOMESCU: Sure, I'm not\nsure what rolling down means.", "start": 1244.63, "duration": 2.375}, {"text": "But yeah, we're piggybacking\non top of bitcoin.", "start": 1247.005, "duration": 2.192}, {"text": "The idea is that look,\na byzantine consensus", "start": 1249.197, "duration": 1.833}, {"text": "is actually quite\ncomplex to get right.", "start": 1251.03, "duration": 2.49}, {"text": "We already have a publicly\nverifiable business consensus", "start": 1253.52, "duration": 3.4}, {"text": "algorithm.", "start": 1256.92, "duration": 0.5}, {"text": "It's bitcoin.", "start": 1257.42, "duration": 1.08}, {"text": "Why can't we use it to verify,\nlet's say, a log of statements", "start": 1258.5, "duration": 3.78}, {"text": "super efficiently?", "start": 1262.28, "duration": 1.32}, {"text": "So up until our work, people\ndidn't seem to do this.", "start": 1263.6, "duration": 3.78}, {"text": "So Keybase didn't do this.", "start": 1267.38, "duration": 1.17}, {"text": "Blockstack didn't do this.", "start": 1268.55, "duration": 1.35}, {"text": "They kind of forced it to\ndownload the entire bitcoin", "start": 1269.9, "duration": 2.25}, {"text": "block chain to verify let's\nsay, three statements.", "start": 1272.15, "duration": 2.425}, {"text": "So in our case, you only have\nto download a few kilobytes", "start": 1274.575, "duration": 2.375}, {"text": "of data to verify\nthese three statements,", "start": 1276.95, "duration": 1.92}, {"text": "assuming you have the\nbitcoin block headers, right,", "start": 1278.87, "duration": 2.25}, {"text": "which we think is\na step forward.", "start": 1281.12, "duration": 2.532}, {"text": "And it's sort of\nlike the right way", "start": 1283.652, "duration": 1.458}, {"text": "to use these systems\nshould be you", "start": 1285.11, "duration": 3.15}, {"text": "know, the efficient way,\nnot the inefficient way.", "start": 1288.26, "duration": 2.07}, {"text": "Because bandwidth\nis expensive, right?", "start": 1290.33, "duration": 1.765}, {"text": "Computation is cheap.", "start": 1292.095, "duration": 0.875}, {"text": "Bandwidth is expensive.", "start": 1292.97, "duration": 1.25}, {"text": "All right, so anyway the idea is\nthat if the lock server becomes", "start": 1296.86, "duration": 3.82}, {"text": "malicious, if Keybase or\nblockstack gets hacked,", "start": 1300.68, "duration": 2.46}, {"text": "they cannot equivocate\nabout the third statement.", "start": 1303.14, "duration": 2.91}, {"text": "They can only issue one\nunique third statement.", "start": 1306.05, "duration": 3.27}, {"text": "And the advantages\nare, you know,", "start": 1309.32, "duration": 1.5}, {"text": "it's hard to fork this lock.", "start": 1310.82, "duration": 1.28}, {"text": "It's hard to equivocate\nabout third statement.", "start": 1312.1, "duration": 2.102}, {"text": "But it's efficient to verify.", "start": 1314.202, "duration": 1.208}, {"text": "And I'll walk you through\nhow clients verify soon.", "start": 1315.41, "duration": 2.083}, {"text": "The disadvantages\nare that if I want", "start": 1320.59, "duration": 2.43}, {"text": "to know that this is the\nsecond statement in the log,", "start": 1323.02, "duration": 2.37}, {"text": "I have to wait for\nsix more blocks", "start": 1325.39, "duration": 1.86}, {"text": "to be built on top of this\nstatement's block, right?", "start": 1327.25, "duration": 3.582}, {"text": "Just like in bitcoin, you\nhave to wait for six blocks", "start": 1330.832, "duration": 2.208}, {"text": "to make sure a transaction\nis confirmed, right?", "start": 1333.04, "duration": 2.34}, {"text": "Why do you do that?", "start": 1335.38, "duration": 0.8}, {"text": "The reason you do that\nis because there could", "start": 1336.18, "duration": 1.875}, {"text": "be another transaction\nhere, double spending", "start": 1338.055, "duration": 1.975}, {"text": "because sometimes there are\naccidental forks in bitcoin", "start": 1340.03, "duration": 3.25}, {"text": "and things like that.", "start": 1343.28, "duration": 3.05}, {"text": "What are some\nother disadvantages", "start": 1346.33, "duration": 1.56}, {"text": "that you guys can point out?", "start": 1347.89, "duration": 1.167}, {"text": "Yeah?", "start": 1352.6, "duration": 0.624}, {"text": "AUDIENCE: It's going\nto be expensive.", "start": 1353.224, "duration": 1.816}, {"text": "ALIN TOMESCU: It's going\nto be expensive to issue", "start": 1355.04, "duration": 1.41}, {"text": "these trends.", "start": 1356.45, "duration": 0.542}, {"text": "So Alin-- Alin and I\nshare the same name.", "start": 1356.992, "duration": 3.248}, {"text": "So Alin is pointing\nout that you know,", "start": 1360.24, "duration": 1.64}, {"text": "every time I issue\nthese statements,", "start": 1361.88, "duration": 1.5}, {"text": "I have to pay a fee, right?", "start": 1363.38, "duration": 1.355}, {"text": "And if you remember, the\nfees were quite ridiculous", "start": 1364.735, "duration": 2.125}, {"text": "in bitcoin.", "start": 1366.86, "duration": 1.38}, {"text": "So that's a problem, right?", "start": 1368.24, "duration": 1.29}, {"text": "So let's see, is\nthat the next thing?", "start": 1369.53, "duration": 1.8}, {"text": "The next thing was\nyou have to issue--", "start": 1371.33, "duration": 2.07}, {"text": "you can only issue a statement\nevery 10 minutes, right?", "start": 1373.4, "duration": 2.77}, {"text": "So if you want to issue\nstatements really fast.", "start": 1376.17, "duration": 1.958}, {"text": "you can't do that.", "start": 1378.128, "duration": 1.122}, {"text": "All right, like Alin said you\nhave to pay bitcoin transaction", "start": 1379.25, "duration": 4.9}, {"text": "fees.", "start": 1384.15, "duration": 0.75}, {"text": "And the other problem is\nthat you don't get freshness", "start": 1384.9, "duration": 2.61}, {"text": "in the sense that it's kind\nof easy for this lock server", "start": 1387.51, "duration": 3.99}, {"text": "to hide from you the\nlatest statement.", "start": 1391.5, "duration": 1.853}, {"text": "You know, unless you have\na lot of these log servers", "start": 1393.353, "duration": 2.167}, {"text": "and you ask many of them, hey,\nwhat's the latest statement?", "start": 1395.52, "duration": 2.58}, {"text": "And they show you back\nthe latest statement.", "start": 1398.1, "duration": 2.772}, {"text": "If there is just one log\nserver and it's compromised,", "start": 1400.872, "duration": 2.208}, {"text": "it could always\npretend no, no, no.", "start": 1403.08, "duration": 1.458}, {"text": "This is the latest statement.", "start": 1404.538, "duration": 1.312}, {"text": "And if you don't trust it,\nthe best recourse you have", "start": 1405.85, "duration": 1.91}, {"text": "is to download the full block\nand look for the statement", "start": 1407.76, "duration": 2.49}, {"text": "yourself.", "start": 1410.25, "duration": 1.11}, {"text": "So you don't get freshness.", "start": 1411.36, "duration": 2.67}, {"text": "Those are some disadvantages.", "start": 1414.03, "duration": 1.21}, {"text": "Now let's look at how\nclients audit this log?", "start": 1415.24, "duration": 2.78}, {"text": "So I was claiming that\nit's very efficient", "start": 1418.02, "duration": 1.908}, {"text": "to get these statements\nand make sure", "start": 1419.928, "duration": 1.542}, {"text": "that no equivocation happened.", "start": 1421.47, "duration": 2.617}, {"text": "So let's say, you\nhave a Catena client", "start": 1424.087, "duration": 1.583}, {"text": "and you're running on your\nphone with this client.", "start": 1425.67, "duration": 2.083}, {"text": "And your goal is to get\nthat list of statements.", "start": 1427.753, "duration": 2.837}, {"text": "And there's the Catena log\nserver over there in the back.", "start": 1430.59, "duration": 2.43}, {"text": "And there's the\nbitcoin peer to peer", "start": 1433.02, "duration": 1.5}, {"text": "network which at the moment\nhas about 11,000 nodes.", "start": 1434.52, "duration": 3.585}, {"text": "And remember, I said\nthe first thing you need", "start": 1438.105, "duration": 1.875}, {"text": "is the genesis transaction.", "start": 1439.98, "duration": 3.81}, {"text": "Does everybody\nsort of understand", "start": 1443.79, "duration": 1.9}, {"text": "that if you get the wrong\nGenesis transaction,", "start": 1445.69, "duration": 2.46}, {"text": "you're completely\nscrewed, right?", "start": 1448.15, "duration": 1.65}, {"text": "Because it's very\neasy to equivocate", "start": 1449.8, "duration": 2.188}, {"text": "if you have the wrong\nGenesis transaction, right?", "start": 1451.988, "duration": 2.042}, {"text": "I mean, you know there's the\nright GTX here where you have,", "start": 1454.03, "duration": 4.69}, {"text": "let's say, a s1.", "start": 1458.72, "duration": 0.8}, {"text": "And then you have s2 in their\nown transactions, right?", "start": 1459.52, "duration": 3.66}, {"text": "But if there's another GTX prime\nhere and you're using that one,", "start": 1463.18, "duration": 3.63}, {"text": "you're going to get s1 prime,\ns2 prime, different statements.", "start": 1466.81, "duration": 4.16}, {"text": "So if Alice uses GTX\nbut Bob uses GTX prime,", "start": 1470.97, "duration": 4.64}, {"text": "Alice and Bob are\nback to square one.", "start": 1475.61, "duration": 2.627}, {"text": "So in some sense, you might ask,\nOK, so then what's the point?", "start": 1478.237, "duration": 2.583}, {"text": "What have you solved here?", "start": 1480.82, "duration": 1.083}, {"text": "I still need to get\nthis GTX, right?", "start": 1481.903, "duration": 2.037}, {"text": "So what we claim is that this is\na step forward because you only", "start": 1483.94, "duration": 2.88}, {"text": "have to do this once.", "start": 1486.82, "duration": 0.905}, {"text": "Once you've got\nthis GTX, you can", "start": 1487.725, "duration": 1.375}, {"text": "be sure you're never\nequivocated to, right?", "start": 1489.1, "duration": 2.91}, {"text": "Whereas in the\npast, you would have", "start": 1492.01, "duration": 1.74}, {"text": "to for each\nindividual statement,", "start": 1493.75, "duration": 2.07}, {"text": "you'd have to do\nadditional checks", "start": 1495.82, "duration": 1.74}, {"text": "to make sure you're\nnot being equivocated", "start": 1497.56, "duration": 1.708}, {"text": "to, like you would have to\nask in a full node, let's say.", "start": 1499.268, "duration": 2.912}, {"text": "Right, so as long as you have\nthe right GTX, you're good.", "start": 1502.18, "duration": 2.855}, {"text": "And how do you\nget the right GTX?", "start": 1505.035, "duration": 1.375}, {"text": "Well, usually you ship it with\nthe software on your phone.", "start": 1506.41, "duration": 2.993}, {"text": "And there's some\nproblems there as well,", "start": 1509.403, "duration": 1.667}, {"text": "like there is no problem\nsolved in computer", "start": 1511.07, "duration": 2.763}, {"text": "science in some sense.", "start": 1513.833, "duration": 0.917}, {"text": "But you know, we're trying\nto make progress here.", "start": 1514.75, "duration": 3.72}, {"text": "OK, so let's say you have\nthe right GTX because it", "start": 1518.47, "duration": 2.22}, {"text": "got shipped with your software.", "start": 1520.69, "duration": 1.712}, {"text": "Now the next thing you want to\ndo is get the block headers.", "start": 1522.402, "duration": 2.458}, {"text": "So you have header\ni, but there are", "start": 1524.86, "duration": 2.01}, {"text": "some new headers being posted.", "start": 1526.87, "duration": 1.568}, {"text": "Let's say the bitcoin peer to\npeer network sends them to you.", "start": 1528.438, "duration": 2.542}, {"text": "You have these headers.", "start": 1530.98, "duration": 0.958}, {"text": "You verify the proof\nof work, right?", "start": 1531.938, "duration": 1.562}, {"text": "So this only costs you 80\nbytes per header, right?", "start": 1533.5, "duration": 2.45}, {"text": "Does everyone see that\nthis is very cheap?", "start": 1535.95, "duration": 2.38}, {"text": "So far, so far I have the GTX,\nwhich is let's say 235 bytes.", "start": 1538.33, "duration": 4.71}, {"text": "And now I'm downloading\nsome headers.", "start": 1543.04, "duration": 1.61}, {"text": "And now I'm ready to ask\nthe log server what's", "start": 1544.65, "duration": 1.917}, {"text": "the first statement\nin the log, right?", "start": 1546.567, "duration": 2.136}, {"text": "And what the log\nserver will do is", "start": 1548.703, "duration": 1.417}, {"text": "he's going to reply\nwith the transaction", "start": 1550.12, "duration": 2.25}, {"text": "with the statement, which is\n600 bytes and the Merkle proof.", "start": 1552.37, "duration": 3.0}, {"text": "So all of this is\n600 bytes, actually.", "start": 1555.37, "duration": 3.06}, {"text": "Right, and now what the\nCatena client will do", "start": 1558.43, "duration": 2.85}, {"text": "is he'll check the\nMerkle proof against one", "start": 1561.28, "duration": 2.25}, {"text": "of the headers so to see in\nwhich headers does it fit.", "start": 1563.53, "duration": 3.21}, {"text": "And then he'll also\ncheck that the input here", "start": 1566.74, "duration": 2.46}, {"text": "has a valid signature from the\npublic key in the output here.", "start": 1569.2, "duration": 3.75}, {"text": "All right, I want at least\none question about this.", "start": 1576.0, "duration": 2.87}, {"text": "Yeah?", "start": 1578.87, "duration": 0.57}, {"text": "AUDIENCE: Sorry I came in\nlate, but is the Catena client", "start": 1579.44, "duration": 2.333}, {"text": "over there similar to the SPV?", "start": 1581.773, "duration": 2.167}, {"text": "ALIN TOMESCU: Yeah,\nso that exactly.", "start": 1583.94, "duration": 1.5}, {"text": "It's an SPV client.", "start": 1585.44, "duration": 1.02}, {"text": "Yeah, so the idea is\nthat we want SPV clients.", "start": 1586.46, "duration": 2.59}, {"text": "We don't want these\nmobile phone clients", "start": 1589.05, "duration": 2.09}, {"text": "to download 150\ngigabytes of data.", "start": 1591.14, "duration": 3.36}, {"text": "We want them to download let's\nsay 40 megabytes worth of block", "start": 1594.5, "duration": 3.06}, {"text": "headers, which they can discard\nvery quickly as they verify.", "start": 1597.56, "duration": 3.485}, {"text": "And then we want\nthem to download", "start": 1601.045, "duration": 1.375}, {"text": "600 bytes per\nstatement, but still", "start": 1602.42, "duration": 2.19}, {"text": "be sure that they saw all of\nthe statements in sequence,", "start": 1604.61, "duration": 2.76}, {"text": "and that there was\nno equivocation.", "start": 1607.37, "duration": 1.47}, {"text": "Yeah?", "start": 1611.55, "duration": 0.5}, {"text": "AUDIENCE: So in our\nprevious classes,", "start": 1613.988, "duration": 1.542}, {"text": "we discussed, if you can have\na full node and an SPV node,", "start": 1615.53, "duration": 4.36}, {"text": "do these sort of vulnerabilities\nexist with the [INAUDIBLE]", "start": 1619.89, "duration": 3.42}, {"text": "client?", "start": 1623.31, "duration": 0.69}, {"text": "ALIN TOMESCU: So\nwhich vulnerabilities", "start": 1624.0, "duration": 1.583}, {"text": "that you did talk about?", "start": 1625.583, "duration": 1.247}, {"text": "AUDIENCE: I forget.", "start": 1626.83, "duration": 1.1}, {"text": "ALIN TOMESCU: Did\nyou talk about--", "start": 1627.93, "duration": 0.66}, {"text": "AUDIENCE: There was just a\nbox that was like less secure.", "start": 1628.59, "duration": 2.43}, {"text": "And then there was another box\nthat was something else bad.", "start": 1631.02, "duration": 3.42}, {"text": "There was one about [INAUDIBLE].", "start": 1634.44, "duration": 3.77}, {"text": "The clients would\nlie to you about--", "start": 1638.21, "duration": 2.95}, {"text": "If you say, here's\nsome transactions", "start": 1641.16, "duration": 3.52}, {"text": "or here are some\nunspent outputs,", "start": 1644.68, "duration": 1.56}, {"text": "then they could just tell\nyou something different.", "start": 1646.24, "duration": 3.04}, {"text": "ALIN TOMESCU: Yes.", "start": 1649.28, "duration": 0.75}, {"text": "Yeah?", "start": 1650.03, "duration": 0.41}, {"text": "Sorry.", "start": 1650.44, "duration": 0.29}, {"text": "AUDIENCE: Well,\nthey can't tell you", "start": 1650.73, "duration": 1.458}, {"text": "that transactions\nexist or don't exist.", "start": 1652.188, "duration": 1.792}, {"text": "They can just not tell you--", "start": 1653.98, "duration": 1.713}, {"text": "ALIN TOMESCU: Yeah, they\ncan hide transactions", "start": 1655.693, "duration": 1.917}, {"text": "from you, which gets back\nto the freshness issue", "start": 1657.61, "duration": 2.31}, {"text": "that we could discussed.", "start": 1659.92, "duration": 1.2}, {"text": "They could also--\nthis block header", "start": 1661.12, "duration": 2.34}, {"text": "could be an header\nfor an invalid block.", "start": 1663.46, "duration": 3.15}, {"text": "But remember, that before\nyou accept this tx1,", "start": 1666.61, "duration": 3.24}, {"text": "you wait for enough\nproof of work,", "start": 1669.85, "duration": 2.01}, {"text": "you wait for more block\nheaders on top of this guy", "start": 1671.86, "duration": 2.85}, {"text": "to sort of get some\nassurance that no, this", "start": 1674.71, "duration": 2.04}, {"text": "was a valid block because a\nbunch of other miners built", "start": 1676.75, "duration": 2.52}, {"text": "on top of it.", "start": 1679.27, "duration": 1.1}, {"text": "Right?", "start": 1680.37, "duration": 0.5}, {"text": "So as long as you're willing\nto trust that the miners do", "start": 1683.037, "duration": 2.333}, {"text": "the right thing, which\nthey have an incentive", "start": 1685.37, "duration": 2.07}, {"text": "to do the right thing,\nyou should be good.", "start": 1687.44, "duration": 2.31}, {"text": "But like you said,\nwhat's your name?", "start": 1689.75, "duration": 2.6}, {"text": "AUDIENCE: Anne.", "start": 1692.35, "duration": 0.82}, {"text": "ALIN TOMESCU: Anne?", "start": 1693.17, "duration": 0.792}, {"text": "Like Anne said, there are\nactually bigger problems", "start": 1693.962, "duration": 2.298}, {"text": "with SPV clients.", "start": 1696.26, "duration": 0.788}, {"text": "And if there is time,\nwe can talk about it.", "start": 1697.048, "duration": 1.792}, {"text": "But it's actually easier to\ntrick SPV clients to fork them.", "start": 1698.84, "duration": 3.81}, {"text": "And there's something called a\ngeneralized vector 76 attack.", "start": 1702.65, "duration": 3.45}, {"text": "Have any of your guys\nheard about this?", "start": 1706.1, "duration": 2.55}, {"text": "So it's like a pre-mining\nattack but it's", "start": 1708.65, "duration": 1.77}, {"text": "a bit easier to pull off.", "start": 1710.42, "duration": 2.07}, {"text": "Actually, it's a lot easier\nto pull off on an SPV node", "start": 1712.49, "duration": 2.25}, {"text": "than on a full node.", "start": 1714.74, "duration": 0.8}, {"text": "And if there's time at the\nend, we can talk about it.", "start": 1715.54, "duration": 2.208}, {"text": "If there isn't, you\ncan read our paper,", "start": 1717.748, "duration": 2.062}, {"text": "which is online on my website.", "start": 1719.81, "duration": 1.45}, {"text": "And you can read about\nthese pre-mining attacks", "start": 1721.26, "duration": 2.9}, {"text": "that work easier for SPV nodes.", "start": 1724.16, "duration": 2.485}, {"text": "But anyway, this can\nkeep going, right?", "start": 1726.645, "duration": 1.625}, {"text": "You get block headers,\n80 bytes each.", "start": 1728.27, "duration": 2.44}, {"text": "You ask the log\nserver, hey what's", "start": 1730.71, "duration": 1.86}, {"text": "the next statement in the log?", "start": 1732.57, "duration": 1.26}, {"text": "You get a Merkle proof\nin a transaction.", "start": 1733.83, "duration": 2.31}, {"text": "And then you verify\nthe Merkle proof.", "start": 1736.14, "duration": 1.86}, {"text": "You put this transaction\nin one of these blocks", "start": 1738.0, "duration": 2.43}, {"text": "and you verify that it\nspends the previous one.", "start": 1740.43, "duration": 2.78}, {"text": "Right, and as a\nresult, you implicitly", "start": 1743.21, "duration": 2.11}, {"text": "by doing this verification,\nby checking that hey,", "start": 1745.32, "duration": 2.413}, {"text": "this is a transaction\nand a valid block.", "start": 1747.733, "duration": 1.667}, {"text": "This block has enough\nstuff built on top of it", "start": 1749.4, "duration": 2.37}, {"text": "and this transaction\nspends this guy here,", "start": 1751.77, "duration": 2.25}, {"text": "you implicitly\nprevent equivocation.", "start": 1754.02, "duration": 2.022}, {"text": "Right, then you don't have\nto download anything else.", "start": 1756.042, "duration": 2.208}, {"text": "Right, you only have to\ndownload these Merkle proofs", "start": 1758.25, "duration": 2.96}, {"text": "and transactions in\nthese block headers.", "start": 1761.21, "duration": 2.2}, {"text": "Whereas in previous work, you\ncould be missing these s1's,", "start": 1763.41, "duration": 2.83}, {"text": "these s2's, they\ncould be hidden away", "start": 1766.24, "duration": 1.76}, {"text": "in some other branch\nof the Merkle tree.", "start": 1768.0, "duration": 2.28}, {"text": "And you'd have to do\npeer to peer bloom", "start": 1770.28, "duration": 2.1}, {"text": "filtering on the full nodes.", "start": 1772.38, "duration": 1.89}, {"text": "And those full nodes\ncould lie to you.", "start": 1774.27, "duration": 1.822}, {"text": "Yeah, so the bandwidth\nis actually very small.", "start": 1779.023, "duration": 1.917}, {"text": "So suppose we have\n500k block headers--", "start": 1780.94, "duration": 2.31}, {"text": "I think bitcoin has a\nbit more right now--", "start": 1783.25, "duration": 2.07}, {"text": "which are 80 bytes\neach and we have", "start": 1785.32, "duration": 1.5}, {"text": "10,000 statements in this\nlog, which are 600 bytes each.", "start": 1786.82, "duration": 2.97}, {"text": "Then we only need now\nwith 46 megabytes, right?", "start": 1789.79, "duration": 3.267}, {"text": "What's the what's the\nother way of doing it?", "start": 1793.057, "duration": 1.833}, {"text": "You have to download\nhundreds of gigabytes.", "start": 1794.89, "duration": 4.52}, {"text": "All right, so let's talk about\nscalability a little bit.", "start": 1799.41, "duration": 2.91}, {"text": "So suppose the system\ngets deployed widely.", "start": 1802.32, "duration": 2.43}, {"text": "Let's say Whatsapp starts to\nuse the system to witness--", "start": 1804.75, "duration": 5.15}, {"text": "to publish their public\ndirectory in bitcoin, right?", "start": 1809.9, "duration": 3.1}, {"text": "And everybody, a lot of\nyou here have Whatsapp.", "start": 1813.0, "duration": 2.1}, {"text": "And this is you guys.", "start": 1815.1, "duration": 1.17}, {"text": "Let's say there are 200,000\npeople using Whatsapp.", "start": 1816.27, "duration": 2.175}, {"text": "I think there's\nmore like a billion.", "start": 1818.445, "duration": 2.265}, {"text": "So what are they going to do?", "start": 1820.71, "duration": 1.27}, {"text": "Remember that part of\nthe verification protocol", "start": 1821.98, "duration": 2.75}, {"text": "is asking for\nthese block headers", "start": 1824.73, "duration": 1.44}, {"text": "from the peer to\npeer network, right?", "start": 1826.17, "duration": 2.28}, {"text": "And in fact, if\nyou're SPV clients,", "start": 1828.45, "duration": 1.72}, {"text": "you usually open up around\neight connections to the peer", "start": 1830.17, "duration": 2.6}, {"text": "to peer network.", "start": 1832.77, "duration": 1.41}, {"text": "And if you're a full node in the\nbitcoin peer to peer network,", "start": 1834.18, "duration": 3.12}, {"text": "you usually have around\n117 incoming connections.", "start": 1837.3, "duration": 4.61}, {"text": "That that's how\nmuch you support.", "start": 1841.91, "duration": 1.39}, {"text": "You support 117 incoming\nconnections as a full node.", "start": 1843.3, "duration": 3.095}, {"text": "So that means in total,\nyou support about a million", "start": 1846.395, "duration": 2.125}, {"text": "incoming connections.", "start": 1848.52, "duration": 1.41}, {"text": "So you know, this guy\nsupports a million.", "start": 1849.93, "duration": 1.77}, {"text": "But we need about 1.6\nmillion connections", "start": 1851.7, "duration": 4.14}, {"text": "from these 200,000\nclients, right?", "start": 1855.84, "duration": 1.99}, {"text": "So it's a bit of\na problem if you", "start": 1857.83, "duration": 2.0}, {"text": "deploy Catena and it\nbecomes wildly popular.", "start": 1859.83, "duration": 4.19}, {"text": "Being a bit optimistic\nhere, but you know,", "start": 1864.02, "duration": 1.75}, {"text": "let's say that happened, right?", "start": 1865.77, "duration": 2.67}, {"text": "So how can we fix this?", "start": 1868.44, "duration": 1.36}, {"text": "How can we avoid this problem\nbecause in this case, what", "start": 1869.8, "duration": 2.75}, {"text": "we would basically\nbe doing is we", "start": 1872.55, "duration": 1.56}, {"text": "would be accidentally\nDDOSing bitcoin.", "start": 1874.11, "duration": 1.92}, {"text": "And we don't want to do that.", "start": 1876.03, "duration": 1.47}, {"text": "Does everybody see that there's\na problem here, first of all?", "start": 1877.5, "duration": 2.542}, {"text": "OK, so the idea is very simple.", "start": 1883.31, "duration": 1.96}, {"text": "We just introduced something\ncalled a header relay network.", "start": 1885.27, "duration": 2.735}, {"text": "And what that means is\nlook, you don't really", "start": 1888.005, "duration": 1.875}, {"text": "have to ask for these block\nheaders from the Bitcoin peer", "start": 1889.88, "duration": 2.52}, {"text": "to peer network.", "start": 1892.4, "duration": 0.96}, {"text": "You could just outsource\nthese block headers anywhere", "start": 1893.36, "duration": 2.85}, {"text": "because they're\npublicly verifiable.", "start": 1896.21, "duration": 1.69}, {"text": "Right, the block headers\nhave proof of work on them.", "start": 1897.9, "duration": 3.15}, {"text": "So you can use volunteer\nnodes that sort of push block", "start": 1901.05, "duration": 5.48}, {"text": "headers to whoever\nasks for them.", "start": 1906.53, "duration": 2.7}, {"text": "You could use blockchain\nexplorers like blockchain.info,", "start": 1909.23, "duration": 2.34}, {"text": "right?", "start": 1911.57, "duration": 0.78}, {"text": "You could use Facebook.", "start": 1912.35, "duration": 1.23}, {"text": "You could just post block\nheaders on Facebook.", "start": 1913.58, "duration": 2.77}, {"text": "Right, like in a Facebook feed.", "start": 1916.35, "duration": 1.638}, {"text": "You could use Twitter for that.", "start": 1917.988, "duration": 1.292}, {"text": "You could use GitHub gists.", "start": 1919.28, "duration": 2.14}, {"text": "You know, so you could--", "start": 1921.42, "duration": 1.473}, {"text": "there's a lot of ways\nto implement this.", "start": 1922.893, "duration": 1.667}, {"text": "The simplest way is\nhave servers and have", "start": 1924.56, "duration": 2.67}, {"text": "them send these headers\nto whoever asks for them.", "start": 1927.23, "duration": 3.84}, {"text": "So it's easy to\nscale in that sense", "start": 1931.07, "duration": 1.83}, {"text": "because if you now\nask these header relay", "start": 1932.9, "duration": 2.37}, {"text": "network for the\nblock headers, you", "start": 1935.27, "duration": 2.307}, {"text": "know, it's much easier to scale\nthis than to scale the bitcoin", "start": 1937.577, "duration": 2.583}, {"text": "peer to peer network, which\nhas to do a bit more than just", "start": 1940.16, "duration": 3.03}, {"text": "block headers.", "start": 1943.19, "duration": 0.63}, {"text": "They have to verify blocks.", "start": 1943.82, "duration": 1.23}, {"text": "They have to verify signatures.", "start": 1945.05, "duration": 3.28}, {"text": "Yeah?", "start": 1948.33, "duration": 0.63}, {"text": "AUDIENCE: Did you\nconsider having", "start": 1948.96, "duration": 0.905}, {"text": "the clients being peer to peer?", "start": 1949.865, "duration": 1.367}, {"text": "ALIN TOMESCU: ,\nYes so another way.", "start": 1951.232, "duration": 1.458}, {"text": "And I think we'll talk\nabout that in the paper--", "start": 1952.69, "duration": 3.82}, {"text": "is you can implement the header\nrelay network as a peer to peer", "start": 1956.51, "duration": 3.09}, {"text": "network on top of the clients.", "start": 1959.6, "duration": 2.02}, {"text": "Yeah, so that's\nanother way to do it.", "start": 1961.62, "duration": 4.3}, {"text": "There's some subtleties there\nthat you have to get right.", "start": 1965.92, "duration": 2.43}, {"text": "But you can do it, I think.", "start": 1968.35, "duration": 1.34}, {"text": "Yeah?", "start": 1969.69, "duration": 0.15}, {"text": "AUDIENCE: Would you you expect\nthat if a company like Whatsapp", "start": 1969.84, "duration": 2.583}, {"text": "decided adopt Catena, they\nwould run their own servers", "start": 1972.423, "duration": 3.247}, {"text": "to make sure that there\nwas the capacity for it?", "start": 1975.67, "duration": 2.248}, {"text": "ALIN TOMESCU: For the\nheader relay network?", "start": 1977.918, "duration": 1.792}, {"text": "AUDIENCE: Yes.", "start": 1979.71, "duration": 1.12}, {"text": "ALIN TOMESCU: I mean, I\nwould be just be speculating,", "start": 1980.83, "duration": 2.43}, {"text": "wishful thinking.", "start": 1983.26, "duration": 2.49}, {"text": "They could.", "start": 1985.75, "duration": 1.98}, {"text": "There is some problem with this\nheader relay network as well.", "start": 1987.73, "duration": 2.76}, {"text": "And we talk about\nit in the paper", "start": 1990.49, "duration": 1.375}, {"text": "because this had a really\nnetwork could withhold", "start": 1991.865, "duration": 2.095}, {"text": "block headers from you.", "start": 1993.96, "duration": 0.97}, {"text": "So you do have to distribute it.", "start": 1994.93, "duration": 1.59}, {"text": "Like usually you don't\nwant to just trust", "start": 1996.52, "duration": 1.8}, {"text": "Whatsapp who's also doing\nthe statements, who's", "start": 1998.32, "duration": 2.73}, {"text": "also pushing the statements\nin the blockchain.", "start": 2001.05, "duration": 2.31}, {"text": "You don't want to trust\nthem to also give you", "start": 2003.36, "duration": 2.1}, {"text": "the block headers.", "start": 2005.46, "duration": 0.75}, {"text": "You actually want to fetch\nthem from a different source", "start": 2006.21, "duration": 2.52}, {"text": "that Whatsapp\ndoesn't collude with.", "start": 2008.73, "duration": 2.16}, {"text": "Yeah, Anne, you had a question?", "start": 2010.89, "duration": 1.832}, {"text": "AUDIENCE: Are there other\nheader relay networks", "start": 2012.722, "duration": 1.958}, {"text": "that are deployed already?", "start": 2014.68, "duration": 1.968}, {"text": "ALIN TOMESCU: Yeah, there\nwas actually one on ethereum.", "start": 2016.648, "duration": 2.292}, {"text": "There's a smart\ncontract in ethereum,", "start": 2018.94, "duration": 1.947}, {"text": "I think, that if you submit\nbitcoin block headers to it,", "start": 2020.887, "duration": 2.333}, {"text": "you get something back.", "start": 2023.22, "duration": 1.68}, {"text": "And then you can just\nquery bitcoin block headers", "start": 2024.9, "duration": 2.07}, {"text": "from the ethereum blockchain.", "start": 2026.97, "duration": 2.02}, {"text": "Is anyone familiar with this?", "start": 2028.99, "duration": 1.7}, {"text": "So I guess I didn't\ninclude it here.", "start": 2030.69, "duration": 1.5}, {"text": "But another way to do it is\nto just publish the header", "start": 2032.19, "duration": 2.25}, {"text": "is in an ethereum\nsmart contract.", "start": 2034.44, "duration": 1.79}, {"text": "Yeah.", "start": 2036.23, "duration": 1.06}, {"text": "So there's crazy ways\nyou could do this too.", "start": 2037.29, "duration": 2.37}, {"text": "Yeah?", "start": 2039.66, "duration": 0.96}, {"text": "AUDIENCE: Will that\none go out of gas?", "start": 2040.62, "duration": 2.29}, {"text": "I don't know, my understanding\nof ethereum is pretty decent,", "start": 2042.91, "duration": 2.653}, {"text": "but would that smart contract\neventually run out of gas", "start": 2045.563, "duration": 3.017}, {"text": "and not publish anymore?", "start": 2048.58, "duration": 1.51}, {"text": "ALIN TOMESCU: So to fetch from\nit, you don't need to pay gas.", "start": 2050.09, "duration": 4.5}, {"text": "But I suspect to push\nin it, I actually", "start": 2054.59, "duration": 4.401}, {"text": "don't know who\nfunds that contract.", "start": 2058.991, "duration": 1.458}, {"text": "So I guess you fund that\nwhen you push maybe.", "start": 2060.449, "duration": 2.873}, {"text": "Maybe not because then you\nalso want something back.", "start": 2063.322, "duration": 2.167}, {"text": "Why would you push?", "start": 2065.489, "duration": 2.159}, {"text": "I'm not sure.", "start": 2067.648, "duration": 0.542}, {"text": "But we can look at it after.", "start": 2068.19, "duration": 2.6}, {"text": "Yeah.", "start": 2070.79, "duration": 1.849}, {"text": "It's a good question.", "start": 2072.639, "duration": 2.411}, {"text": "So anyway, even if this header\nrelay network is compromised,", "start": 2075.05, "duration": 2.5}, {"text": "if you implement it\nin the right way,", "start": 2077.55, "duration": 1.542}, {"text": "you've distributed on a\nsufficient number of parties,", "start": 2079.092, "duration": 3.678}, {"text": "you can still get all of the\nproperties that you need to,", "start": 2082.77, "duration": 3.313}, {"text": "meaning freshness for\nthe block headers.", "start": 2086.083, "duration": 1.667}, {"text": "That's really the only\nproperty that you need to.", "start": 2087.75, "duration": 1.79}, {"text": "The header relay\nnetwork should always", "start": 2089.54, "duration": 1.583}, {"text": "reply with the\nlatest block headers.", "start": 2091.123, "duration": 2.087}, {"text": "So let's look at costs since\nAlin was mentioning the costs.", "start": 2093.21, "duration": 4.4}, {"text": "So to open a statement, you have\nto issue a transaction, right?", "start": 2097.61, "duration": 3.88}, {"text": "And the size of our transactions\nare around 235 bytes.", "start": 2101.49, "duration": 4.74}, {"text": "So and the fee as of December\n13 was $16.24 for transactions", "start": 2106.23, "duration": 5.61}, {"text": "if you guys remember\nthose great bitcoin times.", "start": 2111.84, "duration": 2.52}, {"text": "I think it went up to\n$40 at some point too.", "start": 2114.36, "duration": 3.33}, {"text": "So it was it was really hard\nfor me to talk to people", "start": 2117.69, "duration": 2.82}, {"text": "about this research back then.", "start": 2120.51, "duration": 1.31}, {"text": "But guess what,\nthe fees are today?", "start": 2121.82, "duration": 1.458}, {"text": "So today, this\nmorning I checked.", "start": 2126.66, "duration": 1.44}, {"text": "And there were $0.78, right?", "start": 2128.1, "duration": 2.55}, {"text": "When we wrote the paper,\nthey were like $0.12.", "start": 2130.65, "duration": 4.02}, {"text": "So you know, here I\nam standing in front", "start": 2134.67, "duration": 1.95}, {"text": "of you pitching our work.", "start": 2136.62, "duration": 2.1}, {"text": "In two minutes they could be\nback to $100, but who knows?", "start": 2138.72, "duration": 3.12}, {"text": "Yes, you had a question.", "start": 2141.84, "duration": 1.21}, {"text": "AUDIENCE: Maybe I'm wrong,\nbut in a transaction,", "start": 2143.05, "duration": 2.0}, {"text": "you can have some outputs.", "start": 2145.05, "duration": 1.47}, {"text": "Can you have several\nstatements in there?", "start": 2146.52, "duration": 2.753}, {"text": "ALIN TOMESCU: So\nthat's a good question.", "start": 2149.273, "duration": 1.667}, {"text": "So can you batch statements?", "start": 2150.94, "duration": 1.595}, {"text": "And then the answer is yes.", "start": 2152.535, "duration": 1.125}, {"text": "You can definitely\nbatch statements.", "start": 2153.66, "duration": 2.1}, {"text": "What we've said so far\nis in a transaction--", "start": 2155.76, "duration": 3.39}, {"text": "in a Catena transaction,\nyou have this output.", "start": 2159.15, "duration": 3.24}, {"text": "And you have this\nop return output", "start": 2162.39, "duration": 1.73}, {"text": "where you put the\nstatement, right?", "start": 2164.12, "duration": 2.5}, {"text": "And you know, it spends\na previous transaction.", "start": 2166.62, "duration": 3.96}, {"text": "But as a matter of fact, what\nyou can do and some of you", "start": 2170.58, "duration": 6.09}, {"text": "may already notice this.", "start": 2176.67, "duration": 3.28}, {"text": "There is no reason to put\njust one statement in here.", "start": 2179.95, "duration": 2.54}, {"text": "There is some reason--\nso the only reason", "start": 2182.49, "duration": 2.04}, {"text": "is that it only fits 80 bytes.", "start": 2184.53, "duration": 2.62}, {"text": "So you could put easily, let's\nsay, two or three statements", "start": 2187.15, "duration": 2.72}, {"text": "in there if you hashed them\nwith the right hash function.", "start": 2189.87, "duration": 2.648}, {"text": "But a better way to do\nit is why didn't you", "start": 2192.518, "duration": 1.792}, {"text": "put here a Merkle root hash?", "start": 2194.31, "duration": 2.31}, {"text": "And then you can have\nas many statements", "start": 2196.62, "duration": 2.76}, {"text": "as you want in the leafs\nof that Merkle tree, right?", "start": 2199.38, "duration": 4.25}, {"text": "In fact, here you could\nhave I don't know,", "start": 2203.63, "duration": 1.75}, {"text": "billions of statements.", "start": 2205.38, "duration": 4.22}, {"text": "So keep in mind,\nyou will only be", "start": 2209.6, "duration": 2.72}, {"text": "able to issue billions of\nstatements every 10 minutes.", "start": 2212.32, "duration": 3.06}, {"text": "But you can definitely\nhave billions", "start": 2215.38, "duration": 1.5}, {"text": "of statements in a\nsingle transaction", "start": 2216.88, "duration": 2.13}, {"text": "if you just batch them.", "start": 2219.01, "duration": 1.26}, {"text": "So now, remember the blockchain\nwill only store the root hash.", "start": 2220.27, "duration": 3.48}, {"text": "This Merkle tree will be stored\nby the log server perhaps", "start": 2223.75, "duration": 3.09}, {"text": "or by a different party.", "start": 2226.84, "duration": 2.04}, {"text": "They don't have to\nbe the same party.", "start": 2228.88, "duration": 2.4}, {"text": "Does that make sense?", "start": 2231.28, "duration": 1.63}, {"text": "Does that answer your question?", "start": 2232.91, "duration": 1.46}, {"text": "Yeah.", "start": 2234.37, "duration": 0.5}, {"text": "Right, that was my next point.", "start": 2237.45, "duration": 2.65}, {"text": "Statements can be batched\nwith Merkle trees.", "start": 2240.1, "duration": 2.41}, {"text": "OK, so let's talk about\nthe why since so far", "start": 2242.51, "duration": 2.39}, {"text": "we've been talking abstractly\nabout these statements.", "start": 2244.9, "duration": 2.25}, {"text": "But what could these\nstatements actually be.", "start": 2247.15, "duration": 2.34}, {"text": "So let's look at a\nsecure software update.", "start": 2249.49, "duration": 1.8}, {"text": "So how do you do\nsecure software update?", "start": 2251.29, "duration": 2.85}, {"text": "An example attack on a\nsoftware update scheme", "start": 2254.14, "duration": 2.4}, {"text": "is that somebody compromises\nthe bitcoin.org domain.", "start": 2256.54, "duration": 4.79}, {"text": "And they change the bitcoin\nbinary to a malicious binary.", "start": 2261.33, "duration": 3.06}, {"text": "And they wait for people to\ninstall that malicious binary.", "start": 2264.39, "duration": 3.027}, {"text": "And then they steal their coins.", "start": 2267.417, "duration": 1.333}, {"text": "They steal their data.", "start": 2268.75, "duration": 1.07}, {"text": "They could execute\narbitrary code.", "start": 2269.82, "duration": 2.07}, {"text": "And an example of this was\nsort of this binary safety", "start": 2271.89, "duration": 2.34}, {"text": "warning on the bitcoin website.", "start": 2274.23, "duration": 1.645}, {"text": "At some point, they\nwere very concerned", "start": 2275.875, "duration": 1.625}, {"text": "that a state actor is going\nto mess with the DNS servers", "start": 2277.5, "duration": 3.63}, {"text": "and redirect clients\nto a different server", "start": 2281.13, "duration": 2.88}, {"text": "and make them download\na bad bitcoin binary.", "start": 2284.01, "duration": 3.28}, {"text": "So does the attack make sense?", "start": 2287.29, "duration": 1.25}, {"text": "Does everybody see\nwhy this is possible?", "start": 2288.54, "duration": 1.87}, {"text": "You do need to sort of accept\nthat the DNS service that we", "start": 2290.41, "duration": 5.18}, {"text": "currently have on the internet\nis fundamentally flawed.", "start": 2295.59, "duration": 2.34}, {"text": "It's not built for security.", "start": 2297.93, "duration": 3.7}, {"text": "So the typical defense the\ntypical defense for this", "start": 2301.63, "duration": 3.05}, {"text": "is that the Bitcoin developers--\nthey sign the bitcoin", "start": 2304.68, "duration": 2.28}, {"text": "binaries with some secret key.", "start": 2306.96, "duration": 2.31}, {"text": "And they protect\nthat secret key.", "start": 2309.27, "duration": 2.55}, {"text": "And then there's a\npublic key associated", "start": 2311.82, "duration": 2.635}, {"text": "with the secret key that's\nposted on the bitcoin website,", "start": 2314.455, "duration": 2.375}, {"text": "right?", "start": 2316.83, "duration": 0.84}, {"text": "And maybe some of you'll\nnotice that sometimes it's", "start": 2317.67, "duration": 2.125}, {"text": "also very easy to change the\npublic key on the website,", "start": 2319.795, "duration": 2.292}, {"text": "you know, if you\ncan just redirect", "start": 2322.087, "duration": 1.493}, {"text": "the victim to another website.", "start": 2323.58, "duration": 1.71}, {"text": "And another problem is that not\neveryone checks the signature.", "start": 2325.29, "duration": 2.7}, {"text": "Even if let's say you have the\npublic key on your computer,", "start": 2327.99, "duration": 2.458}, {"text": "you know what the\nright public key is,", "start": 2330.448, "duration": 1.855}, {"text": "only if you're\nlike an expert user", "start": 2332.303, "duration": 1.417}, {"text": "and you know how to use GPG,\nyou will check that signature,", "start": 2333.72, "duration": 3.66}, {"text": "right?", "start": 2337.38, "duration": 1.05}, {"text": "And the other problem\nthat's probably I", "start": 2338.43, "duration": 1.715}, {"text": "think a much, much\nbigger problem", "start": 2340.145, "duration": 1.375}, {"text": "is that for the bitcoin\ndevs themselves,", "start": 2341.52, "duration": 2.25}, {"text": "it's very hard to detect if\nsomeone stole their secret key.", "start": 2343.77, "duration": 2.51}, {"text": "Like if I'm a state actor\nand I break your computer", "start": 2346.28, "duration": 3.22}, {"text": "and I steal your secret key, I\nwill sign this bitcoin binary.", "start": 2349.5, "duration": 2.94}, {"text": "And I'll give it to\nlet's say, one guy.", "start": 2352.44, "duration": 1.83}, {"text": "I'll give it to you.", "start": 2354.27, "duration": 1.012}, {"text": "You know, and I'll just\ntarget you individually", "start": 2355.282, "duration": 1.958}, {"text": "because I'm really--", "start": 2357.24, "duration": 1.08}, {"text": "I know you have\na lot of bitcoin.", "start": 2358.32, "duration": 1.47}, {"text": "Right, and then the bitcoin devs\nwill never find out about it", "start": 2359.79, "duration": 3.257}, {"text": "unless you know you kind\nof realize what happened.", "start": 2363.047, "duration": 2.083}, {"text": "Then you take your\nbitcoin binary", "start": 2365.13, "duration": 1.555}, {"text": "and you go with it\nto the bitcoin devs.", "start": 2366.685, "duration": 1.625}, {"text": "And they check the signature\non it and they say, oh wow.", "start": 2368.31, "duration": 2.518}, {"text": "This is a valid signature\nand we never signed it.", "start": 2370.828, "duration": 2.042}, {"text": "So somebody must have\nstolen our secret key.", "start": 2372.87, "duration": 3.57}, {"text": "So this is really a bad--", "start": 2376.44, "duration": 3.113}, {"text": "kind of the core\nof the problem is", "start": 2379.553, "duration": 1.417}, {"text": "that it's hard for\nwhoever publishes software", "start": 2380.97, "duration": 2.352}, {"text": "to detect that\ntheir secret key has", "start": 2383.322, "duration": 1.458}, {"text": "been stolen-- to detect\nmalicious signatures", "start": 2384.78, "duration": 2.58}, {"text": "on their binaries.", "start": 2387.36, "duration": 0.84}, {"text": "Does that make sense?", "start": 2388.2, "duration": 1.33}, {"text": "So the solution, of course,\nis you know, publish", "start": 2389.53, "duration": 2.33}, {"text": "the signatures of bitcoin\nbinaries in a Catena log", "start": 2391.86, "duration": 3.6}, {"text": "So now if there's a malicious\nbinary being published", "start": 2395.46, "duration": 2.37}, {"text": "by a state actor, people\nwon't accept that binary", "start": 2397.83, "duration": 2.94}, {"text": "unless it's in the\nCatena log, which", "start": 2400.77, "duration": 2.01}, {"text": "means people in the bitcoin\ndevs will see the same binary.", "start": 2402.78, "duration": 4.27}, {"text": "Right, so let me let me show\nyou what I mean with a picture.", "start": 2407.05, "duration": 2.75}, {"text": "So we have this Catena\nlog for Bitcoin binaries.", "start": 2409.8, "duration": 3.81}, {"text": "And let's say, the\nfirst transaction", "start": 2413.61, "duration": 1.5}, {"text": "has a hash of the bitcoin\n0.001 tar file, right,", "start": 2415.11, "duration": 6.15}, {"text": "the bitcoin binaries.", "start": 2421.26, "duration": 2.58}, {"text": "And this hash here\nis implicitly signed", "start": 2423.84, "duration": 3.39}, {"text": "by the signature in\nthis input because it", "start": 2427.23, "duration": 2.55}, {"text": "signs the whole transaction.", "start": 2429.78, "duration": 2.73}, {"text": "So now if I put this\nhash in a Catena log,", "start": 2432.51, "duration": 2.7}, {"text": "I get a signature\non it for free.", "start": 2435.21, "duration": 3.03}, {"text": "And now, if let's say, a state\nactor compromises the log", "start": 2438.24, "duration": 4.08}, {"text": "server, gets the\nsecret key, he can", "start": 2442.32, "duration": 2.4}, {"text": "publish this second malicious\nbinary in the log, right?", "start": 2444.72, "duration": 3.39}, {"text": "But what that malicious\nstate actor will want to do,", "start": 2448.11, "duration": 2.98}, {"text": "he will want to hide this\nfrom the Bitcoin devs", "start": 2451.09, "duration": 2.15}, {"text": "and show it to all of you guys.", "start": 2453.24, "duration": 1.38}, {"text": "All right, so he'll\nwant to equivocate.", "start": 2454.62, "duration": 2.577}, {"text": "So as a result, he will want to\ncreate a different transaction", "start": 2457.197, "duration": 2.583}, {"text": "with the right\nbitcoin binary there,", "start": 2459.78, "duration": 2.64}, {"text": "show this to the bitcoin devs\nwhile showing this to you guys.", "start": 2462.42, "duration": 2.93}, {"text": "All right, so the bitcoin\ndevs would think they're good.", "start": 2465.35, "duration": 2.89}, {"text": "This is the binary they wanted\nto publish while you guys would", "start": 2468.24, "duration": 3.3}, {"text": "be using this malicious binary\npublished by the state actor.", "start": 2471.54, "duration": 5.995}, {"text": "Of course this cannot happen\nbecause in Catena you cannot", "start": 2477.535, "duration": 2.375}, {"text": "equivocate.", "start": 2479.91, "duration": 1.406}, {"text": "Right?", "start": 2481.316, "duration": 2.874}, {"text": "Does everybody see this?", "start": 2484.19, "duration": 3.17}, {"text": "Right, any questions about this?", "start": 2487.36, "duration": 1.472}, {"text": "There has to be a\nquestion on this.", "start": 2488.832, "duration": 1.458}, {"text": "No?", "start": 2497.122, "duration": 1.968}, {"text": "So this mechanism is called\nsoftware transparency.", "start": 2499.09, "duration": 3.15}, {"text": "It's this idea that rather\nthan just downloading software", "start": 2502.24, "duration": 3.48}, {"text": "like a crazy person from the\ninternet and installing it,", "start": 2505.72, "duration": 4.32}, {"text": "we should just be\npublishing these binaries", "start": 2510.04, "duration": 1.89}, {"text": "in a log that everybody can see,\nincluding the software vendors", "start": 2511.93, "duration": 3.06}, {"text": "that created those binaries.", "start": 2514.99, "duration": 1.78}, {"text": "So in this way, if somebody\ncompromises a software vendor,", "start": 2516.77, "duration": 3.177}, {"text": "that vendor can\nnotice that in the log", "start": 2519.947, "duration": 1.583}, {"text": "there's a new version\nfor their software", "start": 2521.53, "duration": 1.667}, {"text": "that they didn't publish.", "start": 2523.197, "duration": 1.153}, {"text": "So you know, this isn't to say\nthat it'll prevent attacks.", "start": 2524.35, "duration": 3.54}, {"text": "You know, what a state\nactor can do anyway", "start": 2527.89, "duration": 3.0}, {"text": "is they can just do this.", "start": 2530.89, "duration": 1.29}, {"text": "They can post this\nH2 prime in here,", "start": 2532.18, "duration": 1.77}, {"text": "show it to you guys\nincluding the bitcoin devs", "start": 2533.95, "duration": 2.82}, {"text": "and still screw everyone over.", "start": 2536.77, "duration": 2.19}, {"text": "But at least these attacks\nthen go undetected anymore.", "start": 2538.96, "duration": 2.93}, {"text": "All right, so it's a step\nforward in that sense.", "start": 2541.89, "duration": 5.435}, {"text": "Yes, so the idea\nis that you have", "start": 2547.325, "duration": 1.375}, {"text": "to double spend to equivocate.", "start": 2548.7, "duration": 1.89}, {"text": "And the other\nexample that really--", "start": 2550.59, "duration": 4.17}, {"text": "the reason I wanted\nto start this research", "start": 2554.76, "duration": 1.92}, {"text": "had to do with public\nkey distribution.", "start": 2556.68, "duration": 1.66}, {"text": "So let's say we have\nAlice and we have Bob.", "start": 2558.34, "duration": 2.21}, {"text": "And they both have\ntheir public keys.", "start": 2560.55, "duration": 1.98}, {"text": "And I'm using this\nletter b to denote", "start": 2562.53, "duration": 2.118}, {"text": "Bob and his public\nkey and the letter", "start": 2564.648, "duration": 1.542}, {"text": "a to denote Alice\nand her public key.", "start": 2566.19, "duration": 2.31}, {"text": "And they have their\ncorresponding secret keys,", "start": 2568.5, "duration": 2.04}, {"text": "right?", "start": 2570.54, "duration": 0.57}, {"text": "And Alice and Bob, they want\nto chat securely, right?", "start": 2571.11, "duration": 2.208}, {"text": "So they want to set\nup a secure channel.", "start": 2573.318, "duration": 5.262}, {"text": "And there's this directory\nwhich stores their public keys.", "start": 2578.58, "duration": 2.7}, {"text": "So this guy stores\nAlice, pk Alice.", "start": 2581.28, "duration": 2.04}, {"text": "This guy stores Bob, pk Bob.", "start": 2583.32, "duration": 1.98}, {"text": "All right, and the directory\ngets updated over time,", "start": 2585.3, "duration": 4.14}, {"text": "maybe Karl, Ellen\nand Dan registered.", "start": 2589.44, "duration": 4.23}, {"text": "And if you have\nnon-equivocation,", "start": 2593.67, "duration": 3.42}, {"text": "if the attacker wants to\nimpersonate Alice and Bob,", "start": 2597.09, "duration": 2.85}, {"text": "he kind of has to put\ntheir public keys,", "start": 2599.94, "duration": 2.79}, {"text": "the fake public keys\nin the same directory,", "start": 2602.73, "duration": 1.84}, {"text": "which means that when\nAlice and Bob monitor--", "start": 2604.57, "duration": 3.23}, {"text": "they check their\nown public keys,", "start": 2607.8, "duration": 2.07}, {"text": "they both notice they've\nbeen impersonated, right?", "start": 2609.87, "duration": 4.16}, {"text": "So again, the idea is\nthat you can detect.", "start": 2614.03, "duration": 3.39}, {"text": "Now how can this\nattacker still trick", "start": 2617.42, "duration": 3.61}, {"text": "Alice to send an\nencrypted message to Bob", "start": 2621.03, "duration": 2.61}, {"text": "with Bob's fake public key?", "start": 2623.64, "duration": 1.95}, {"text": "Is there a way even if\nyou have non-equivocation?", "start": 2625.59, "duration": 2.467}, {"text": "So what's the attack?", "start": 2630.98, "duration": 1.05}, {"text": "Even I have\nnon-equivocation and I", "start": 2632.03, "duration": 1.745}, {"text": "claim that the\nattacker can still", "start": 2633.775, "duration": 1.375}, {"text": "get Alice to send a fake,\nan encrypted message to Bob", "start": 2635.15, "duration": 4.56}, {"text": "that the attacker can decrypt.", "start": 2639.71, "duration": 1.863}, {"text": "What should the attacker do?", "start": 2641.573, "duration": 1.167}, {"text": "So pretend that we are\nhere without the ability", "start": 2642.74, "duration": 5.01}, {"text": "to equivocate.", "start": 2647.75, "duration": 1.112}, {"text": "So the attacker\ncannot equivocate.", "start": 2651.453, "duration": 1.417}, {"text": "But I claimed that\nthe attacker can still", "start": 2652.87, "duration": 1.92}, {"text": "trick Alice into\nsending a message to Bob", "start": 2654.79, "duration": 2.28}, {"text": "that the attacker can read.", "start": 2657.07, "duration": 2.72}, {"text": "So now it's time to see if\nyou guys paid attention.", "start": 2659.79, "duration": 2.376}, {"text": "Somebody?", "start": 2668.01, "duration": 1.91}, {"text": "Alin?", "start": 2669.92, "duration": 1.12}, {"text": "Oh, you?", "start": 2671.04, "duration": 1.057}, {"text": "AUDIENCE: Does the attacker\nhave to have the secret key?", "start": 2672.097, "duration": 2.333}, {"text": "ALIN TOMESCU: No, no.", "start": 2674.43, "duration": 0.63}, {"text": "He does not.", "start": 2675.06, "duration": 0.62}, {"text": "Yeah.", "start": 2675.68, "duration": 1.24}, {"text": "He does not have to\nhave the secret key.", "start": 2676.92, "duration": 2.192}, {"text": "The attacker just\ncreates fake public keys.", "start": 2681.84, "duration": 2.687}, {"text": "Here's a hint.", "start": 2684.527, "duration": 0.583}, {"text": "AUDIENCE: If you only\nchanged one person to choose,", "start": 2688.29, "duration": 2.72}, {"text": "they don't know that it's a\nfake key so they could send it", "start": 2691.01, "duration": 2.955}, {"text": "to a fake key for a bit?", "start": 2693.965, "duration": 1.995}, {"text": "ALIN TOMESCU: Yeah, so\nwhose person should they", "start": 2695.96, "duration": 2.082}, {"text": "attack or change the key for?", "start": 2698.042, "duration": 1.208}, {"text": "AUDIENCE: Like if they\nchange Bob's, Alice", "start": 2699.25, "duration": 1.62}, {"text": "will still think\nBob's is correct", "start": 2700.87, "duration": 1.375}, {"text": "so she'll send it to the\nfake Bob until Bob checks it.", "start": 2702.245, "duration": 2.628}, {"text": "ALIN TOMESCU: Exactly.", "start": 2704.873, "duration": 0.917}, {"text": "So that's exactly right.", "start": 2705.79, "duration": 1.56}, {"text": "So what's your name?", "start": 2707.35, "duration": 1.133}, {"text": "AUDIENCE: Lucas.", "start": 2708.483, "duration": 0.667}, {"text": "ALIN TOMESCU: Lucas.", "start": 2709.15, "duration": 0.833}, {"text": "So what Lucas is saying is\nlook, even without equivocation,", "start": 2709.983, "duration": 5.827}, {"text": "I had this directory at T1.", "start": 2715.81, "duration": 2.58}, {"text": "I had another one at T2.", "start": 2718.39, "duration": 1.56}, {"text": "But at T3 and both of these had\nkeys for Alice and Bob, right?", "start": 2719.95, "duration": 5.64}, {"text": "But at T3, Lucas is saying look,\njust put the fake key for Bob", "start": 2725.59, "duration": 4.6}, {"text": "here.", "start": 2730.19, "duration": 0.5}, {"text": "And that's it.", "start": 2730.69, "duration": 1.44}, {"text": "Don't put a fake key for\nAlice there, just for Bob.", "start": 2732.13, "duration": 3.18}, {"text": "And now when Alice looks up\nthis public key for Bob here,", "start": 2735.31, "duration": 6.025}, {"text": "she sends a query to\nthe directory hey,", "start": 2741.335, "duration": 1.625}, {"text": "what's Bob's public key?", "start": 2742.96, "duration": 1.98}, {"text": "She gets back b prime,\nwhich is equal to Bob pk", "start": 2744.94, "duration": 5.34}, {"text": "Bob prime, right?", "start": 2750.28, "duration": 3.7}, {"text": "Alice can't tell if that's\nreally Bob's fake public key.", "start": 2753.98, "duration": 3.188}, {"text": "That's the reason she's\nusing the directory", "start": 2757.168, "duration": 1.792}, {"text": "in the first place.", "start": 2758.96, "duration": 1.2}, {"text": "She wants sort of a trustworthy\nplace to get it from.", "start": 2760.16, "duration": 2.76}, {"text": "Bob can tell if Bob looks.", "start": 2762.92, "duration": 1.69}, {"text": "But by the time Bob looks,\nit might be too late.", "start": 2764.61, "duration": 2.0}, {"text": "Alice might have already\nencrypted a message, right?", "start": 2766.61, "duration": 2.27}, {"text": "So again, what's the point\nof doing all of this?", "start": 2768.88, "duration": 2.0}, {"text": "It's not like you're\npreventing attacks, right?", "start": 2770.88, "duration": 3.223}, {"text": "And the point of\ndoing all of this", "start": 2774.103, "duration": 1.417}, {"text": "is that you get transparency.", "start": 2775.52, "duration": 1.32}, {"text": "Bob can detect, whereas\nright now Bob has no hope.", "start": 2776.84, "duration": 2.97}, {"text": "In fact, so you said, a\nlot of you use Whatsapp.", "start": 2779.81, "duration": 3.3}, {"text": "So you know in\nWhatsapp, if you really", "start": 2783.11, "duration": 1.683}, {"text": "want to be sure, so I\nhave a conversation here", "start": 2784.793, "duration": 1.917}, {"text": "with Alin Dragos.", "start": 2786.71, "duration": 1.86}, {"text": "So, Alin, do you what to\nto bring your phone here?", "start": 2788.57, "duration": 2.49}, {"text": "Do you have Whatsapp?", "start": 2791.06, "duration": 1.89}, {"text": "So if you really want\nto be sure that you're", "start": 2792.95, "duration": 2.49}, {"text": "talking to the real Alin\nand not some other guy,", "start": 2795.44, "duration": 2.257}, {"text": "you have to go on\nthis encryption tab.", "start": 2797.697, "duration": 1.583}, {"text": "Can you tape this?", "start": 2799.28, "duration": 3.268}, {"text": "So my phone is black and white.", "start": 2802.548, "duration": 1.292}, {"text": "It's going through\na depression phase.", "start": 2803.84, "duration": 1.92}, {"text": "I apologize.", "start": 2805.76, "duration": 2.13}, {"text": "So you have to go here and\nthere's a code here, right?", "start": 2807.89, "duration": 2.25}, {"text": "And Alin, can you\ndo the same thing?", "start": 2810.14, "duration": 1.5}, {"text": "You know what I'm talking about?", "start": 2811.64, "duration": 1.333}, {"text": "I really hope I don't get some\nweird text message right now", "start": 2816.25, "duration": 3.24}, {"text": "with the camera on the phone.", "start": 2819.49, "duration": 2.44}, {"text": "OK, so now with Alin's\nphone, is that the same code?", "start": 2821.93, "duration": 3.165}, {"text": "Can somebody tell me?", "start": 2825.095, "duration": 0.875}, {"text": "I can't see it.", "start": 2825.97, "duration": 1.44}, {"text": "AUDIENCE: It's hard to see.", "start": 2827.41, "duration": 2.33}, {"text": "ALIN TOMESCU: OK, so\nwe have 27836 and yeah.", "start": 2829.74, "duration": 2.593}, {"text": "So it's the same code.", "start": 2832.333, "duration": 0.917}, {"text": "Can you see it on the camera?", "start": 2833.25, "duration": 1.8}, {"text": "So now because we have\nthe same code here.", "start": 2835.05, "duration": 1.865}, {"text": "With this code\nhere, it really is", "start": 2836.915, "duration": 1.375}, {"text": "a hash of my public key\nand Alin's public key.", "start": 2838.29, "duration": 2.383}, {"text": "And if we've got the same hash\nof both of our public keys,", "start": 2840.673, "duration": 2.417}, {"text": "then we know we're\ntalking to one another.", "start": 2843.09, "duration": 1.75}, {"text": "But we won't really know that's\nthe case until we actually", "start": 2844.84, "duration": 2.45}, {"text": "meet in person and do\nthis exchange, right?", "start": 2847.29, "duration": 2.07}, {"text": "So what this system\ndoes instead is", "start": 2849.36, "duration": 2.52}, {"text": "it allows Alin to check\nhis own public key", "start": 2851.88, "duration": 1.83}, {"text": "and it allows me to\ncheck my own public key.", "start": 2853.71, "duration": 2.7}, {"text": "This way if we check\nour own public key,", "start": 2856.41, "duration": 1.668}, {"text": "we'll always know when we're\nimpersonated even though I", "start": 2858.078, "duration": 2.292}, {"text": "might send an encrypted\nmessage to the wrong Alin,", "start": 2860.37, "duration": 2.76}, {"text": "Alin will eventually find out.", "start": 2863.13, "duration": 1.573}, {"text": "It's a bit confusing because\nwe're both called Alin.", "start": 2864.703, "duration": 2.167}, {"text": "So does that sort\nof makes sense?", "start": 2870.505, "duration": 1.375}, {"text": "Yeah?", "start": 2871.88, "duration": 0.5}, {"text": "AUDIENCE: So what do\nyou do when you realize", "start": 2872.38, "duration": 1.91}, {"text": "that your key is the wrong key?", "start": 2874.29, "duration": 1.653}, {"text": "ALIN TOMESCU: Good question.", "start": 2875.943, "duration": 1.167}, {"text": "So that's really the\ncrucial question.", "start": 2877.11, "duration": 1.29}, {"text": "What the hell can you do?", "start": 2878.4, "duration": 1.042}, {"text": "Right, so this directory\nimpersonated you.", "start": 2879.442, "duration": 2.048}, {"text": "In fact, you can't even--", "start": 2881.49, "duration": 2.298}, {"text": "here's the problem.", "start": 2883.788, "duration": 0.792}, {"text": "If you're Bob here and you\nsee this fake public key.", "start": 2884.58, "duration": 3.133}, {"text": "And you go to the New\nYork Times and you", "start": 2887.713, "duration": 1.667}, {"text": "say hey, New York Times,\nthis Whatsapp directory", "start": 2889.38, "duration": 2.73}, {"text": "started impersonating me.", "start": 2892.11, "duration": 1.71}, {"text": "And the New York Times\ncan go to the directory", "start": 2893.82, "duration": 2.1}, {"text": "and say, hey directory, why\ndid you impersonate Bob?", "start": 2895.92, "duration": 2.167}, {"text": "And the directory can say,\nno, I did not impersonate Bob.", "start": 2898.087, "duration": 2.375}, {"text": "Bob really just ask\nfor a new public key.", "start": 2900.462, "duration": 1.818}, {"text": "And this was the public\nkey that Bob gave me.", "start": 2902.28, "duration": 2.34}, {"text": "And it's just a he said, they\nsaid, kind of a thing, right?", "start": 2904.62, "duration": 3.513}, {"text": "So it's really a sort\nof an open research area", "start": 2908.133, "duration": 1.917}, {"text": "to figure out what's the right\nway to whistle blow here.", "start": 2910.05, "duration": 2.91}, {"text": "So for example, one project\nthat we're trying to work on", "start": 2912.96, "duration": 2.61}, {"text": "is there a way to track\nthe directory somehow", "start": 2915.57, "duration": 3.12}, {"text": "so that when he does\nstuff like this,", "start": 2918.69, "duration": 1.95}, {"text": "you get a publicly verifiable\ncryptographic proof that he", "start": 2920.64, "duration": 4.228}, {"text": "really misbehaved, right?", "start": 2924.868, "duration": 1.042}, {"text": "No, there's no\ncryptographic proof.", "start": 2925.91, "duration": 1.21}, {"text": "The fact that that\npublic key is there", "start": 2927.12, "duration": 1.74}, {"text": "could have come from\nthe malicious directory", "start": 2928.86, "duration": 1.833}, {"text": "or could have come\nfrom an honest Bob who", "start": 2930.693, "duration": 1.737}, {"text": "just changed his public key.", "start": 2932.43, "duration": 2.29}, {"text": "So yeah.", "start": 2934.72, "duration": 0.84}, {"text": "So again, a step forward\nbut we're not there.", "start": 2935.56, "duration": 1.88}, {"text": "You know, it's just that there's\nmuch more work to do here.", "start": 2937.44, "duration": 3.22}, {"text": "And I think you\nalso had a question.", "start": 2940.66, "duration": 2.092}, {"text": "AUDIENCE: Can't Alice just\nask Bob if this is you?", "start": 2942.752, "duration": 3.608}, {"text": "ALIN TOMESCU: So that's a\nchicken and an egg, right?", "start": 2946.36, "duration": 2.57}, {"text": "So we have Alice.", "start": 2948.93, "duration": 1.86}, {"text": "We have Bob.", "start": 2950.79, "duration": 0.81}, {"text": "And we have the attacker.", "start": 2951.6, "duration": 1.53}, {"text": "Alice asks Bob, is\nthis your public key?", "start": 2953.13, "duration": 4.38}, {"text": "You know, let's say, b prime.", "start": 2957.51, "duration": 3.22}, {"text": "Let me make this more readable.", "start": 2960.73, "duration": 1.85}, {"text": "So attacker, right?", "start": 2962.58, "duration": 2.28}, {"text": "So Alice asks, hey Bob.", "start": 2964.86, "duration": 1.5}, {"text": "Is this b prime your public key?", "start": 2966.36, "duration": 2.13}, {"text": "The attacker changes it.", "start": 2968.49, "duration": 1.92}, {"text": "Hey Bob, is b your public key?", "start": 2970.41, "duration": 2.52}, {"text": "The attacker-- Bob says yes.", "start": 2972.93, "duration": 2.53}, {"text": "Attacker forwards\nyes to Alice, right?", "start": 2975.46, "duration": 2.57}, {"text": "Remember, Bob and Alice\ndon't have a secure channel.", "start": 2978.03, "duration": 2.328}, {"text": "That's the problem we're trying\nto solve with this directory,", "start": 2980.358, "duration": 2.542}, {"text": "right?", "start": 2982.9, "duration": 2.01}, {"text": "So the attacker can always\nman in the middle people.", "start": 2984.91, "duration": 2.7}, {"text": "Well, people like Alice and Bob.", "start": 2987.61, "duration": 1.42}, {"text": "If the attacker can man\nin the middle everything,", "start": 2989.03, "duration": 2.07}, {"text": "then there's really no hope.", "start": 2991.1, "duration": 1.22}, {"text": "And we're living in a very sad,\nsad world if that's the case.", "start": 2992.32, "duration": 4.01}, {"text": "Yeah, it actually might\nbe the case but we'll see.", "start": 2996.33, "duration": 4.59}, {"text": "Anyway, so yeah, so I claim here\nthat this is a step forward.", "start": 3000.92, "duration": 3.55}, {"text": "But there's still\nmuch work to do.", "start": 3004.47, "duration": 1.423}, {"text": "All right, so we\nget transparency.", "start": 3005.893, "duration": 1.417}, {"text": "Bob can detect.", "start": 3007.31, "duration": 0.78}, {"text": "He'll know.", "start": 3008.09, "duration": 0.84}, {"text": "He won't be able to\nconvince anybody.", "start": 3008.93, "duration": 1.77}, {"text": "But if a lot of Bobs\nget compromised,", "start": 3010.7, "duration": 2.61}, {"text": "you're still like in a\nplace where everybody", "start": 3013.31, "duration": 2.3}, {"text": "knows that something's off and\nwill all stop using Whatsapp,", "start": 3015.61, "duration": 2.5}, {"text": "for example.", "start": 3018.11, "duration": 0.63}, {"text": "Right?", "start": 3018.74, "duration": 0.618}, {"text": "By the way, Whatsapp\nis a great tool.", "start": 3019.358, "duration": 1.542}, {"text": "You should continue using it.", "start": 3020.9, "duration": 2.19}, {"text": "I'm just saying it's\ndifficult to use right", "start": 3023.09, "duration": 1.96}, {"text": "like if somebody really\nwants to target it,", "start": 3025.05, "duration": 1.87}, {"text": "they can play a lot of\ntricks to still trick you.", "start": 3026.92, "duration": 4.54}, {"text": "So yeah, so all right, we\nalready talked about this.", "start": 3031.46, "duration": 3.27}, {"text": "And yeah, again if the director\ncan equivocate, then you know,", "start": 3034.73, "duration": 3.24}, {"text": "all bets are off because now\nBob will look in this directory,", "start": 3037.97, "duration": 3.33}, {"text": "he'll think he's\nnot impersonated.", "start": 3041.3, "duration": 1.463}, {"text": "Alice will look\nin this directory.", "start": 3042.763, "duration": 1.417}, {"text": "She'll think she's not\nimpersonated, right?", "start": 3044.18, "duration": 2.06}, {"text": "So the reason we\nstarted this research", "start": 3046.24, "duration": 1.9}, {"text": "is because I really want to--", "start": 3048.14, "duration": 1.56}, {"text": "my thesis is on building\nthese directories that", "start": 3049.7, "duration": 2.61}, {"text": "are efficiently auditable and\nhave a hard time impersonating", "start": 3052.31, "duration": 3.06}, {"text": "people.", "start": 3055.37, "duration": 0.778}, {"text": "So that's why we decided\nto look at how could you", "start": 3056.148, "duration": 2.042}, {"text": "do this with Bitcoin.", "start": 3058.19, "duration": 1.77}, {"text": "Yeah, so of course there's\none project called KeyChat", "start": 3059.96, "duration": 2.64}, {"text": "that we're working on with\nsome high school students.", "start": 3062.6, "duration": 2.34}, {"text": "And we're using the key\nbased public key directory.", "start": 3064.94, "duration": 2.125}, {"text": "And we're witnessing\nit in a Catena log", "start": 3067.065, "duration": 1.985}, {"text": "so that stuff like\nthat doesn't happen.", "start": 3069.05, "duration": 4.32}, {"text": "OK, so now let's talk\nabout the blockchains.", "start": 3073.37, "duration": 3.33}, {"text": "In general, people\nnowadays like to say I", "start": 3076.7, "duration": 2.01}, {"text": "need a blockchain for x, right?", "start": 3078.71, "duration": 2.23}, {"text": "I need a blockchain for\nsupply chain management.", "start": 3080.94, "duration": 2.0}, {"text": "I mean a blockchain\nfor cats, for whatever.", "start": 3082.94, "duration": 2.88}, {"text": "I've heard a lot\nof crazy stories.", "start": 3085.82, "duration": 1.95}, {"text": "IOT, self-driving\ncars, blah, blah, blah.", "start": 3087.77, "duration": 2.66}, {"text": "And I think the right way\nto think about blockchain", "start": 3090.43, "duration": 4.69}, {"text": "is to never ever say\nthat word unless you", "start": 3095.12, "duration": 2.19}, {"text": "use quotes, first of all.", "start": 3097.31, "duration": 1.54}, {"text": "And second of all, to\nunderstand what Byzantine state", "start": 3098.85, "duration": 3.02}, {"text": "machine replication is.", "start": 3101.87, "duration": 1.315}, {"text": "Right, and if you understand\nwhat Byzantine state machine", "start": 3103.185, "duration": 2.375}, {"text": "replication is or a\nByzantine consensus,", "start": 3105.56, "duration": 2.127}, {"text": "you understand blockchain.", "start": 3107.687, "duration": 1.083}, {"text": "And you understand all the hype.", "start": 3108.77, "duration": 1.44}, {"text": "And then you can make some\nprogress in solving problems.", "start": 3110.21, "duration": 2.58}, {"text": "In the sense that\nwhat is blockchain?", "start": 3112.79, "duration": 1.56}, {"text": "So what we're\ndoing here is we're", "start": 3114.35, "duration": 1.387}, {"text": "doing a Byzantine\nconsensus algorithm.", "start": 3115.737, "duration": 1.583}, {"text": "We're agreeing on a\nlog of operations.", "start": 3117.32, "duration": 2.2}, {"text": "Right, by the way, that's\nwhat Catena does too", "start": 3119.52, "duration": 2.03}, {"text": "by piggybacking on bitcoin.", "start": 3121.55, "duration": 2.41}, {"text": "It agrees on a lot on\na log of operations.", "start": 3123.96, "duration": 3.12}, {"text": "Right, but the other thing that\nSMR or Byzantine consensus does", "start": 3127.08, "duration": 4.31}, {"text": "is that it also\nallows you to agree", "start": 3131.39, "duration": 1.95}, {"text": "on the execution of\nthe ops in that log.", "start": 3133.34, "duration": 3.18}, {"text": "So in Catena, you don't\nagree on the execution,", "start": 3136.52, "duration": 2.01}, {"text": "you just agree on\nthe statements.", "start": 3138.53, "duration": 1.9}, {"text": "But there is no execution of\nthose statements in the sense", "start": 3140.43, "duration": 2.6}, {"text": "that you can't build\nanother bitcoin", "start": 3143.03, "duration": 2.52}, {"text": "on top of bitcoin in Catena\nbecause you can't prevent", "start": 3145.55, "duration": 4.32}, {"text": "double spends of\ntransactions that", "start": 3149.87, "duration": 3.69}, {"text": "are Catena statements, right?", "start": 3153.56, "duration": 1.208}, {"text": "Like the Catena statements,\nyou have to look in each one", "start": 3154.768, "duration": 2.334}, {"text": "and tell if it's correct.", "start": 3157.102, "duration": 1.158}, {"text": "So to detect a double spend in\na Catena backed cryptocurrency,", "start": 3158.26, "duration": 3.1}, {"text": "you would have to download\nall of the transactions", "start": 3161.36, "duration": 2.15}, {"text": "and because you cannot execute\nit like the bitcoin miners do", "start": 3163.51, "duration": 3.34}, {"text": "and build this UTXO set.", "start": 3166.85, "duration": 2.58}, {"text": "I'm not sure this is\nmaking a lot of sense.", "start": 3169.43, "duration": 1.86}, {"text": "But let's put it another way.", "start": 3171.29, "duration": 2.77}, {"text": "In bitcoin, you have\nblock one and then", "start": 3174.06, "duration": 3.617}, {"text": "you have block two, right?", "start": 3177.677, "duration": 1.083}, {"text": "And there's a hash pointer and\nthere's a bunch of transactions", "start": 3181.307, "duration": 2.583}, {"text": "here, right?", "start": 3183.89, "duration": 1.56}, {"text": "And remember that what prevents\nme from double spending", "start": 3185.45, "duration": 3.12}, {"text": "something here--", "start": 3188.57, "duration": 1.2}, {"text": "I can have two\ntransactions in this block", "start": 3189.77, "duration": 1.74}, {"text": "that double spend\nthe same one here.", "start": 3191.51, "duration": 2.16}, {"text": "What prevents me from doing\nthat is exactly this execution", "start": 3193.67, "duration": 2.67}, {"text": "stage, right?", "start": 3196.34, "duration": 1.8}, {"text": "Because in the execution stage,\nwhen I try to I execute this", "start": 3198.14, "duration": 2.97}, {"text": "first transaction and I\nmark this output as spent,", "start": 3201.11, "duration": 2.91}, {"text": "when I execute the\nsecond transaction,", "start": 3204.02, "duration": 1.89}, {"text": "I cannot spend that\noutput anymore, right?", "start": 3205.91, "duration": 1.75}, {"text": "In Catena, you can't do anything\nlike that with the statements.", "start": 3207.66, "duration": 2.625}, {"text": "You just agree on\nthe statements.", "start": 3210.285, "duration": 1.455}, {"text": "In Catena, you would\nput this transaction", "start": 3211.74, "duration": 1.43}, {"text": "in the log, this one and then\nthat one and someone would", "start": 3213.17, "duration": 2.333}, {"text": "have to detect that the second\none is a bad one by actually", "start": 3215.503, "duration": 2.557}, {"text": "downloading it.", "start": 3218.06, "duration": 0.64}, {"text": "That's kind of what\nI'm trying to say here.", "start": 3218.7, "duration": 2.275}, {"text": "So in general,\nthe way should you", "start": 3220.975, "duration": 1.375}, {"text": "should be thinking\nabout blockchain", "start": 3222.35, "duration": 1.458}, {"text": "is through the lens of\nByzantine consensus.", "start": 3223.808, "duration": 1.932}, {"text": "And that'll get you\nahead of the curve", "start": 3225.74, "duration": 2.49}, {"text": "in this overly\nhyped space, right,", "start": 3228.23, "duration": 1.87}, {"text": "because it's really just this.", "start": 3230.1, "duration": 1.25}, {"text": "You're agreeing on\na log of operations.", "start": 3231.35, "duration": 1.36}, {"text": "And then you're agreeing on the\nexecution of those operations", "start": 3232.71, "duration": 2.3}, {"text": "according to some rules.", "start": 3235.01, "duration": 1.02}, {"text": "The rules in bitcoin\nare transaction cannot--", "start": 3236.03, "duration": 3.36}, {"text": "there cannot be two inputs\nspending the same output more", "start": 3239.39, "duration": 3.49}, {"text": "or less.", "start": 3242.88, "duration": 0.5}, {"text": "There's other things too.", "start": 3243.38, "duration": 1.8}, {"text": "What that gives you\nis it allows you", "start": 3245.18, "duration": 1.5}, {"text": "to agree on a final state\nwhich in bitcoin are", "start": 3246.68, "duration": 2.83}, {"text": "the valid transactions.", "start": 3249.51, "duration": 1.25}, {"text": "That's the final state right.", "start": 3250.76, "duration": 1.585}, {"text": "In ethereum, for\nexample, the final state", "start": 3252.345, "duration": 2.165}, {"text": "are the valid transactions,\nand the account", "start": 3254.51, "duration": 2.01}, {"text": "balances of everything,\nand the smart contract", "start": 3256.52, "duration": 2.97}, {"text": "state for everything.", "start": 3259.49, "duration": 1.44}, {"text": "And I guess you'll\nlearn about that later.", "start": 3260.93, "duration": 2.11}, {"text": "So you can build\narbitrarily complex things", "start": 3263.04, "duration": 2.42}, {"text": "with Byzantine consensus\nor with blockchains.", "start": 3265.46, "duration": 3.56}, {"text": "And the high level bit, if you\nwant to look at it another way,", "start": 3269.02, "duration": 2.65}, {"text": "is that you have a program p,\nright, which could be anything,", "start": 3271.67, "duration": 3.72}, {"text": "could be a cryptocurrency.", "start": 3275.39, "duration": 1.418}, {"text": "And then, instead of\nrunning this program p", "start": 3276.808, "duration": 1.792}, {"text": "on a single server s,\nwhat do you do is you", "start": 3278.6, "duration": 2.94}, {"text": "distribute it on a bunch of\nservers, s1, s2, s3, s4, right?", "start": 3281.54, "duration": 5.84}, {"text": "And now as a result, to\nmess with this program p,", "start": 3287.38, "duration": 2.23}, {"text": "it's not enough to\ncompromise one server,", "start": 3289.61, "duration": 1.71}, {"text": "you have to compromise\na bunch of them.", "start": 3291.32, "duration": 2.54}, {"text": "right?", "start": 3293.86, "duration": 1.36}, {"text": "OK so, and some\nof you might also", "start": 3295.22, "duration": 2.4}, {"text": "be familiar with this term\npermissioned blockchain.", "start": 3297.62, "duration": 2.61}, {"text": "So when you distribute this\nprogram o amongst n servers", "start": 3300.23, "duration": 3.66}, {"text": "where n is equal let's\nsay, three f plus 1 and f", "start": 3303.89, "duration": 3.87}, {"text": "is equal to 1 in\nthis particular case.", "start": 3307.76, "duration": 2.54}, {"text": "In a permission blockchain,\nthis n is fixed, right?", "start": 3310.3, "duration": 2.92}, {"text": "Once you've set n to\n4, it has to stay 4.", "start": 3313.22, "duration": 2.76}, {"text": "These servers have\nto know one another.", "start": 3315.98, "duration": 1.66}, {"text": "They need to know each\nother's public keys.", "start": 3317.64, "duration": 2.0}, {"text": "And only one of the servers,\nf is equal to 1, can fail.", "start": 3319.64, "duration": 4.08}, {"text": "If more than one server\nfails, then all bets are off.", "start": 3323.72, "duration": 2.79}, {"text": "Your program can start\ndoing arbitrary things.", "start": 3326.51, "duration": 2.33}, {"text": "In particular, if your\nprogram is bitcoin,", "start": 3328.84, "duration": 1.75}, {"text": "it can start double spending.", "start": 3330.59, "duration": 2.58}, {"text": "I'm moving a little bit fast,\nso I'll take some questions up", "start": 3333.17, "duration": 3.22}, {"text": "until this point before I go on.", "start": 3336.39, "duration": 2.936}, {"text": "Yes?", "start": 3339.326, "duration": 0.989}, {"text": "AUDIENCE: In a\npermissioned blockchain,", "start": 3340.315, "duration": 1.625}, {"text": "do they use proof of work?", "start": 3341.94, "duration": 1.33}, {"text": "ALIN TOMESCU: No,\nyou don't have to.", "start": 3343.27, "duration": 1.5}, {"text": "And that's kind of\nwhat the hype is about.", "start": 3344.77, "duration": 2.63}, {"text": "This stuff, there is like--", "start": 3347.4, "duration": 2.4}, {"text": "the first interesting\npaper on this", "start": 3349.8, "duration": 2.76}, {"text": "was 1976 or something like that.", "start": 3352.56, "duration": 2.64}, {"text": "So this is 40-30,\n40-year-old research.", "start": 3355.2, "duration": 3.22}, {"text": "We've known how to do\npermissioned consensus-- we", "start": 3358.42, "duration": 2.09}, {"text": "used to call it Byzantine\nconsensus for 30 or 40", "start": 3360.51, "duration": 2.55}, {"text": "years, right?", "start": 3363.06, "duration": 1.5}, {"text": "So there's nothing new there.", "start": 3364.56, "duration": 1.47}, {"text": "It's just that it's very useful\nnowadays to say blockchain then", "start": 3366.03, "duration": 3.545}, {"text": "to say consensus\nbecause then you", "start": 3369.575, "duration": 1.375}, {"text": "get 10 more million from your\nventure capitalist folks.", "start": 3370.95, "duration": 3.293}, {"text": "AUDIENCE: But if you don't\nhave to do proof of work,", "start": 3374.243, "duration": 2.167}, {"text": "do they ever do proof of work?", "start": 3376.41, "duration": 3.03}, {"text": "ALIN TOMESCU: It would\nbe such a bad idea", "start": 3379.44, "duration": 2.22}, {"text": "technically to do prefer\nworking a permissioned consensus", "start": 3381.66, "duration": 2.43}, {"text": "algorithm.", "start": 3384.09, "duration": 0.5}, {"text": "It just-- completely\nunnecessary, plus probably", "start": 3384.59, "duration": 5.92}, {"text": "insecure too.", "start": 3390.51, "duration": 1.94}, {"text": "Yeah, so now the reason\nyou do proof of work", "start": 3392.45, "duration": 3.64}, {"text": "is because in a\npermissionless blockchain,", "start": 3396.09, "duration": 3.42}, {"text": "this n is not fixed.", "start": 3399.51, "duration": 1.32}, {"text": "n could go, let's say, n was 4.", "start": 3400.83, "duration": 2.25}, {"text": "It could go to 8.", "start": 3403.08, "duration": 2.25}, {"text": "Then it could go to 3.", "start": 3405.33, "duration": 2.43}, {"text": "Then it could go to 12.", "start": 3407.76, "duration": 2.99}, {"text": "In other words, people\nare joining and leaving", "start": 3410.75, "duration": 2.71}, {"text": "as they please.", "start": 3413.46, "duration": 1.578}, {"text": "And the reason you\nneed proof of work", "start": 3415.038, "duration": 1.542}, {"text": "in bitcoin, one way\nyou can look at it", "start": 3416.58, "duration": 3.45}, {"text": "is that you're really turning\na permissioned consensus", "start": 3420.03, "duration": 3.06}, {"text": "algorithm into a\npermissionless one.", "start": 3423.09, "duration": 2.19}, {"text": "And a consensus\nalgorithm is just voting.", "start": 3425.28, "duration": 2.82}, {"text": "These n folks are just voting.", "start": 3428.1, "duration": 2.34}, {"text": "And you need 2f plus 1 votes\nto sort of move on, right?", "start": 3430.44, "duration": 5.73}, {"text": "And if this n changes over time,\nlike if the n becomes bigger,", "start": 3436.17, "duration": 4.35}, {"text": "it's very easy to take over\na majority of the voters.", "start": 3440.52, "duration": 3.15}, {"text": "If I can just add fake voters\nto a permissioned consensus", "start": 3443.67, "duration": 3.06}, {"text": "algorithm, I can just take\nover the consensus algorithm.", "start": 3446.73, "duration": 3.19}, {"text": "In other words, I can take\nover more than f nodes.", "start": 3449.92, "duration": 2.6}, {"text": "Right, so the trick\nthere is you have", "start": 3452.52, "duration": 2.94}, {"text": "to prevent that from happening.", "start": 3455.46, "duration": 1.9}, {"text": "And the only way to\nprevent that is to say,", "start": 3457.36, "duration": 1.91}, {"text": "look if you're going to join\nand then make my n bigger,", "start": 3459.27, "duration": 3.18}, {"text": "you better do some work.", "start": 3462.45, "duration": 1.008}, {"text": "So that it's not\neasy for you to join", "start": 3463.458, "duration": 1.542}, {"text": "because if you're a bad guy\nand you want to join, you know,", "start": 3465.0, "duration": 3.54}, {"text": "you can do that\nvery easily unless I", "start": 3468.54, "duration": 1.5}, {"text": "require you to do some work.", "start": 3470.04, "duration": 3.687}, {"text": "So that's kind of\nthe trick in turning", "start": 3473.727, "duration": 1.583}, {"text": "a permissioned\nconsensus algorithm", "start": 3475.31, "duration": 1.66}, {"text": "into a permissionless one.", "start": 3476.97, "duration": 1.49}, {"text": "And in fact, the way these\npermissioned animals work", "start": 3478.46, "duration": 2.58}, {"text": "is completely\ndifferent than bitcoin.", "start": 3481.04, "duration": 1.875}, {"text": "They are much more complex.", "start": 3482.915, "duration": 1.125}, {"text": "Bitcoin is incredibly simple\nas a consensus algorithm.", "start": 3484.04, "duration": 3.45}, {"text": "If you ever read a\nconsensus algorithm paper,", "start": 3487.49, "duration": 2.49}, {"text": "you know, it's a bit insane.", "start": 3489.98, "duration": 1.248}, {"text": "Also to implement,\nit's a bit insane.", "start": 3491.228, "duration": 1.542}, {"text": "Bitcoin is very simple\nto implement compared", "start": 3492.77, "duration": 1.85}, {"text": "to these other things,\nI mean, bitcoin is,", "start": 3494.62, "duration": 1.75}, {"text": "of course, a complex\nbeast as well.", "start": 3496.37, "duration": 1.48}, {"text": "But you should look at let's\nsay, practical Byzantine fault", "start": 3497.85, "duration": 3.32}, {"text": "tolerant paper, PBFT, and\ntry and implement that.", "start": 3501.17, "duration": 4.71}, {"text": "So anyway, why am I\ntelling you all of this?", "start": 3508.177, "duration": 1.833}, {"text": "The reason I'm telling\nyou all of this", "start": 3510.01, "duration": 1.583}, {"text": "is because if you want to\ndo a permissioned blockchain", "start": 3511.593, "duration": 2.327}, {"text": "for whatever reason,\none way to do", "start": 3513.92, "duration": 1.982}, {"text": "that is to use your favorite\nByzantine consensus algorithm.", "start": 3515.902, "duration": 2.458}, {"text": "So that would be--", "start": 3518.36, "duration": 1.14}, {"text": "let's say pbft.", "start": 3519.5, "duration": 1.5}, {"text": "This was 1999 from MIT.", "start": 3521.0, "duration": 5.473}, {"text": "So you could use that.", "start": 3526.473, "duration": 0.917}, {"text": "You could have a lot\nof fun implementing it.", "start": 3527.39, "duration": 2.86}, {"text": "Another thing you could do is\nyou could take your program p", "start": 3530.25, "duration": 2.72}, {"text": "and just give it to an\nethereum smart contract.", "start": 3532.97, "duration": 2.552}, {"text": "And you know, that the\nethereum smart contract,", "start": 3535.522, "duration": 1.958}, {"text": "if the ethereum security\nassumption holds,", "start": 3537.48, "duration": 3.455}, {"text": "it will do the right thing.", "start": 3540.935, "duration": 1.125}, {"text": "It will execute your\nprogram p correctly, right?", "start": 3542.06, "duration": 2.842}, {"text": "But the other thing that\nyou could do actually,", "start": 3544.902, "duration": 1.958}, {"text": "is you could use Catena\nto agree on these logs,", "start": 3546.86, "duration": 3.15}, {"text": "on the log of operations\nfor your program.", "start": 3550.01, "duration": 3.27}, {"text": "And then you could use another\n2f plus 1 servers or replicas", "start": 3553.28, "duration": 4.35}, {"text": "to do the execution\nstuff so that you", "start": 3557.63, "duration": 2.25}, {"text": "can agree on the final state.", "start": 3559.88, "duration": 2.615}, {"text": "And this gives you a very simple\nByzantine consensus algorithm.", "start": 3562.495, "duration": 2.625}, {"text": "So remember Catena doesn't\ngive you execution.", "start": 3565.12, "duration": 2.32}, {"text": "It allows you to agree\non the log of ops.", "start": 3567.44, "duration": 1.8}, {"text": "To get the execution, you'd\nbasically take a majority vote.", "start": 3569.24, "duration": 3.45}, {"text": "If you see you have 2f\nplus 1 replica servers", "start": 3572.69, "duration": 5.1}, {"text": "and if you see f plus 1\nvotes on a final state,", "start": 3577.79, "duration": 3.99}, {"text": "you know that's the right\nstate because only f of them", "start": 3581.78, "duration": 4.29}, {"text": "are malicious.", "start": 3586.07, "duration": 0.78}, {"text": "So in fact, if you use Catena\nwith 2f plus 1 replicas,", "start": 3591.32, "duration": 2.28}, {"text": "I claim that you can get sort of\na permissioned blockchain that", "start": 3593.6, "duration": 3.03}, {"text": "sort of leverages the bitcoin\nblockchain to do the agreement", "start": 3596.63, "duration": 3.57}, {"text": "on the log of ops.", "start": 3600.2, "duration": 1.08}, {"text": "So in that sense, it's sort\nof a mix of a permissioned", "start": 3601.28, "duration": 1.77}, {"text": "and permissionless.", "start": 3603.05, "duration": 0.93}, {"text": "We haven't studied\nthis like we don't know", "start": 3603.98, "duration": 1.75}, {"text": "what properties it would have.", "start": 3605.73, "duration": 2.12}, {"text": "So that's future work.", "start": 3607.85, "duration": 2.59}, {"text": "And if you don't need the\nexecution, for example,", "start": 3610.44, "duration": 3.96}, {"text": "if all you're doing\nis you're agreeing", "start": 3614.4, "duration": 2.12}, {"text": "on a public key directory--\nlike here, there's no execution.", "start": 3616.52, "duration": 2.55}, {"text": "This directory just is\nsupposed to stay append-only,", "start": 3619.07, "duration": 2.85}, {"text": "we have some\nresearch that allows", "start": 3621.92, "duration": 2.1}, {"text": "you to prove that\nevery transition is", "start": 3624.02, "duration": 2.43}, {"text": "an append-only directory.", "start": 3626.45, "duration": 2.382}, {"text": "And if you only\nneed execution, you", "start": 3628.832, "duration": 1.458}, {"text": "can just use Catena\ndirectly as I already", "start": 3630.29, "duration": 2.61}, {"text": "told you guys for the\nsoftware transparency", "start": 3632.9, "duration": 2.13}, {"text": "application for the public\nkey directory application.", "start": 3635.03, "duration": 4.83}, {"text": "And if you want to do a\npermissionless blockchain then,", "start": 3639.86, "duration": 3.16}, {"text": "of course, you would\nhave to roll your own.", "start": 3643.02, "duration": 3.32}, {"text": "But you have to proceed\nwith caution there, right?", "start": 3646.34, "duration": 2.43}, {"text": "It's not an easy thing to do.", "start": 3648.77, "duration": 2.37}, {"text": "OK, so let's conclude now.", "start": 3651.14, "duration": 1.8}, {"text": "What we did here is that we\nenabled these applications", "start": 3652.94, "duration": 2.46}, {"text": "to efficiently leverage\nbitcoin's consensus, right?", "start": 3655.4, "duration": 3.69}, {"text": "So clients can download\ntransactions selectively", "start": 3659.09, "duration": 3.15}, {"text": "rather than full blockchain\nand prevent equivocation.", "start": 3662.24, "duration": 3.12}, {"text": "Right, and you only need\nto get 46 megabytes instead", "start": 3665.36, "duration": 2.58}, {"text": "of gigabytes from the\nBitcoin blockchain.", "start": 3667.94, "duration": 3.48}, {"text": "So why does this matter?", "start": 3671.42, "duration": 1.803}, {"text": "These are just I think\nthe three killer apps--", "start": 3673.223, "duration": 1.917}, {"text": "secure software update,\npublic key directories--", "start": 3675.14, "duration": 2.41}, {"text": "by the way, the\npublic directories", "start": 3677.55, "duration": 1.417}, {"text": "also are applicable to https.", "start": 3678.967, "duration": 2.293}, {"text": "So when you go on\nFacebook, you have", "start": 3681.26, "duration": 1.5}, {"text": "to get Facebook's public key.", "start": 3682.76, "duration": 1.565}, {"text": "The certificate authorities\nthat sign the public keys", "start": 3684.325, "duration": 2.545}, {"text": "are often compromised.", "start": 3686.87, "duration": 1.663}, {"text": "So they're often fake\nsearch for Google,", "start": 3688.533, "duration": 1.667}, {"text": "for big companies like that.", "start": 3690.2, "duration": 1.98}, {"text": "And you might use it.", "start": 3692.18, "duration": 1.24}, {"text": "But if you have a\npublic key directory,", "start": 3693.42, "duration": 2.042}, {"text": "Facebook and Google\ncan immediately", "start": 3695.462, "duration": 1.458}, {"text": "notice those fake sorts.", "start": 3696.92, "duration": 3.06}, {"text": "It's a step forward.", "start": 3699.98, "duration": 1.24}, {"text": "And for more, of course,\nyou can read our paper.", "start": 3701.22, "duration": 3.34}, {"text": "It appeared in a IEEE\nsecurity and privacy 2017.", "start": 3704.56, "duration": 4.42}, {"text": "And I'll post the\nslide on GitHub too.", "start": 3708.98, "duration": 2.44}, {"text": "So there are links there.", "start": 3711.42, "duration": 1.45}, {"text": "Yeah so, again this is the high\nlevel overview of everything", "start": 3712.87, "duration": 3.16}, {"text": "that's previous\nwork and our work.", "start": 3716.03, "duration": 2.31}, {"text": "The difference is very small.", "start": 3718.34, "duration": 3.6}, {"text": "And now we can also\ntalk about other stuff.", "start": 3721.94, "duration": 2.82}, {"text": "In fact, I have\nmore stuff to talk.", "start": 3724.76, "duration": 1.64}, {"text": "But before we do, I'd like to\nhave a discussion with you guys", "start": 3726.4, "duration": 3.52}, {"text": "if you have questions.", "start": 3729.92, "duration": 1.58}, {"text": "So?", "start": 3731.5, "duration": 0.91}, {"text": "AUDIENCE: So could you implement\nCatena in the actual bitcoin", "start": 3732.41, "duration": 4.64}, {"text": "node?", "start": 3737.05, "duration": 1.46}, {"text": "Would that be something\nthat they would want?", "start": 3738.51, "duration": 2.78}, {"text": "It seems like it would\nbe a good feature to add?", "start": 3741.29, "duration": 5.19}, {"text": "Or is it strictly separate?", "start": 3746.48, "duration": 2.043}, {"text": "ALIN TOMESCU: Yeah, I\ndon't think you need to.", "start": 3748.523, "duration": 1.917}, {"text": "That's the whole point, right?", "start": 3750.44, "duration": 1.36}, {"text": "The whole point\nof the research is", "start": 3751.8, "duration": 1.417}, {"text": "how do we use bitcoin without\ngetting the miners to accept", "start": 3753.217, "duration": 3.3}, {"text": "a new version of bitcoin,\nwithout changing bitcoin", "start": 3756.517, "duration": 2.083}, {"text": "in any way?", "start": 3758.6, "duration": 2.39}, {"text": "So no, I don't think--\nthere's nothing to do really,", "start": 3760.99, "duration": 2.62}, {"text": "we're just--", "start": 3763.61, "duration": 1.045}, {"text": "we're taking bitcoin\nas it is and we're", "start": 3764.655, "duration": 1.625}, {"text": "piggybacking on top of it.", "start": 3766.28, "duration": 2.46}, {"text": "We couldn't change it.", "start": 3768.74, "duration": 1.15}, {"text": "I mean, there's a lot of things\nyou can do in some sense.", "start": 3769.89, "duration": 1.52}, {"text": "But then you get a\nvery different system.", "start": 3771.41, "duration": 2.19}, {"text": "Very different, we can talk\nabout it more if you want.", "start": 3773.6, "duration": 2.83}, {"text": "Yeah?", "start": 3776.43, "duration": 0.84}, {"text": "AUDIENCE: You were talking about\nhow you can use this system", "start": 3777.27, "duration": 2.75}, {"text": "to verify software\nbinaries and how", "start": 3780.02, "duration": 3.04}, {"text": "you want this to run in\nSPV modes on phones So", "start": 3783.06, "duration": 3.16}, {"text": "how do you install\nsoftware on the phones say,", "start": 3786.22, "duration": 2.487}, {"text": "through apple and the app store.", "start": 3788.707, "duration": 1.333}, {"text": "Is there a way to sign the\nbinary that you actually", "start": 3790.04, "duration": 2.43}, {"text": "get from the app store?", "start": 3792.47, "duration": 1.95}, {"text": "ALIN TOMESCU: I think your\nquestion is really about how", "start": 3794.42, "duration": 2.31}, {"text": "do appstore binaries--", "start": 3796.73, "duration": 3.458}, {"text": "how do you Verify\nApp store binaries?", "start": 3800.188, "duration": 1.542}, {"text": "It's a chicken and an\negg in some sense right,", "start": 3801.73, "duration": 1.53}, {"text": "is that what you're saying?", "start": 3803.26, "duration": 1.125}, {"text": "Yeah, you're right.", "start": 3804.385, "duration": 3.255}, {"text": "Eventually, I mean\nin the best case,", "start": 3807.64, "duration": 2.97}, {"text": "wishful thinking would\nbe to say that look,", "start": 3810.61, "duration": 1.83}, {"text": "the app store does this\nalready for all of the binaries", "start": 3812.44, "duration": 3.03}, {"text": "that they publish, allowing the\ndevelopers to make sure nobody", "start": 3815.47, "duration": 6.65}, {"text": "is posting malicious binaries\non the app store for them.", "start": 3822.12, "duration": 2.36}, {"text": "Yes?", "start": 3828.12, "duration": 1.324}, {"text": "AUDIENCE: Who do you\nenvision running it?", "start": 3829.444, "duration": 2.328}, {"text": "ALIN TOMESCU: So I'd really\nlike to see Keybase run Catena,", "start": 3831.772, "duration": 2.458}, {"text": "it seems like a\nmissed opportunity", "start": 3834.23, "duration": 1.83}, {"text": "that they don't do this.", "start": 3836.06, "duration": 1.32}, {"text": "I'm sure they have better stuff\nto do but it's just really", "start": 3837.38, "duration": 5.37}, {"text": "easily allow Keybase--", "start": 3842.75, "duration": 1.7}, {"text": "let's say Keybase has\na mobile phone app,", "start": 3844.45, "duration": 1.75}, {"text": "it would allow that mobile phone\napp to verify the directory", "start": 3846.2, "duration": 2.91}, {"text": "and get much, much,\nmuch more security.", "start": 3849.11, "duration": 2.38}, {"text": "You know, no equivocation as\nlong as nobody forks bitcoin.", "start": 3851.49, "duration": 3.59}, {"text": "Since Keybase is already\npublishing these digests", "start": 3855.08, "duration": 2.07}, {"text": "but they cannot be audited\nefficiently on a mobile phone.", "start": 3857.15, "duration": 2.88}, {"text": "I mean they can but\nnot securely you know,", "start": 3860.03, "duration": 1.95}, {"text": "because full nodes can lie.", "start": 3861.98, "duration": 1.5}, {"text": "So there's a big problem with\neverything I said so far.", "start": 3873.09, "duration": 3.36}, {"text": "And nobody caught it.", "start": 3876.45, "duration": 1.5}, {"text": "So one problem is\nthat what do you", "start": 3877.95, "duration": 2.76}, {"text": "do when you run out of funds?", "start": 3880.71, "duration": 3.537}, {"text": "Remember I said the log server\nstarts with two bitcoins.", "start": 3884.247, "duration": 2.333}, {"text": "Let's say it issues\nthousands of transactions,", "start": 3886.58, "duration": 2.64}, {"text": "starts paying those $40 fees\nand it runs out of funds.", "start": 3889.22, "duration": 3.665}, {"text": "What do you do?", "start": 3892.885, "duration": 0.625}, {"text": "Then Yeah?", "start": 3893.51, "duration": 2.31}, {"text": "AUDIENCE: You can maybe\nreload the new transactions", "start": 3895.82, "duration": 3.454}, {"text": "with this transaction\n[INAUDIBLE]..", "start": 3899.274, "duration": 3.914}, {"text": "ALIN TOMESCU: What's your name?", "start": 3903.188, "duration": 1.292}, {"text": "AUDIENCE: Raul.", "start": 3904.48, "duration": 0.69}, {"text": "ALIN TOMESCU: Raul.", "start": 3905.17, "duration": 0.94}, {"text": "So Raul is saying\nyou can reload.", "start": 3906.11, "duration": 1.45}, {"text": "And that's exactly right.", "start": 3907.56, "duration": 1.19}, {"text": "We just have to change the\ntransaction format slightly.", "start": 3908.75, "duration": 4.93}, {"text": "We talk about this\nin the paper as well.", "start": 3913.68, "duration": 2.18}, {"text": "But just to demonstrate\nreal quickly.", "start": 3915.86, "duration": 3.33}, {"text": "Suppose, let's take a ridiculous\nexample which hopefully", "start": 3919.19, "duration": 4.32}, {"text": "will never happen in bitcoin.", "start": 3923.51, "duration": 1.71}, {"text": "But suppose that the\nBitcoin fee is 1 bitcoin.", "start": 3925.22, "duration": 4.08}, {"text": "So now I have one bitcoin here.", "start": 3932.45, "duration": 2.62}, {"text": "And I have s1 here.", "start": 3935.07, "duration": 2.31}, {"text": "And now I have\nzero bitcoins here.", "start": 3937.38, "duration": 3.26}, {"text": "All right, so zero\nbitcoins in this output.", "start": 3944.86, "duration": 4.41}, {"text": "And maybe s2 here.", "start": 3949.27, "duration": 2.827}, {"text": "So that would be terrible.", "start": 3952.097, "duration": 1.083}, {"text": "Right, now I can't go on.", "start": 3953.18, "duration": 2.61}, {"text": "Does everybody see\nthis as a problem?", "start": 3955.79, "duration": 2.86}, {"text": "Right, so what Raul is saying\nis look at another input", "start": 3958.65, "duration": 3.16}, {"text": "here and make it take coins\nfrom some other transaction", "start": 3961.81, "duration": 5.32}, {"text": "whatever, 20 bitcoins.", "start": 3967.13, "duration": 1.48}, {"text": "And now you get\n20 bitcoins here.", "start": 3968.61, "duration": 2.48}, {"text": "Right, so you can easily\nrefund transactions.", "start": 3971.09, "duration": 2.892}, {"text": "There is a bit more\nsubtlety there in the sense", "start": 3979.07, "duration": 2.85}, {"text": "that you don't\nwant to join logs--", "start": 3981.92, "duration": 4.26}, {"text": "let's say if you have two\nlogs, GTX and GTX prime", "start": 3986.18, "duration": 5.28}, {"text": "for different applications.", "start": 3991.46, "duration": 2.17}, {"text": "Right, and they start\nissuing statements-- s1, s2.", "start": 3993.63, "duration": 3.08}, {"text": "You don't want to\nbe able to join--", "start": 3996.71, "duration": 1.95}, {"text": "I'm sorry, s1, s1 prime--", "start": 3998.66, "duration": 2.19}, {"text": "these two locks to a single\nlog for certain reasons right.", "start": 4000.85, "duration": 4.35}, {"text": "But this doesn't actually\nallow you to join them", "start": 4005.2, "duration": 2.76}, {"text": "in the sense that--", "start": 4007.96, "duration": 1.005}, {"text": "let's say you actually\ndo this and join them.", "start": 4008.965, "duration": 1.875}, {"text": "Right, so let's say\nthis transaction here", "start": 4010.84, "duration": 3.15}, {"text": "came from GTX prime, right?", "start": 4013.99, "duration": 4.85}, {"text": "And there was an s1 prime here.", "start": 4018.84, "duration": 2.13}, {"text": "And you did this, right?", "start": 4024.428, "duration": 3.952}, {"text": "So the problem is this is\nno longer a valid Catena", "start": 4028.38, "duration": 2.23}, {"text": "transaction for this log\nbecause a valid Casino", "start": 4030.61, "duration": 4.95}, {"text": "transaction-- the\nfirst input spends", "start": 4035.56, "duration": 2.28}, {"text": "the previous\ntransactions output.", "start": 4037.84, "duration": 2.61}, {"text": "But in this chain, it's\nthe second input that", "start": 4040.45, "duration": 3.66}, {"text": "spends the previous output.", "start": 4044.11, "duration": 1.98}, {"text": "So I cannot join logs.", "start": 4046.09, "duration": 2.19}, {"text": "And this matters for\na bunch of reasons", "start": 4048.28, "duration": 2.52}, {"text": "that we don't have to go into.", "start": 4050.8, "duration": 2.31}, {"text": "Yeah, so we talked about the\nabout batching statements.", "start": 4057.35, "duration": 4.418}, {"text": "I want to show you guys\nsome previous work,", "start": 4061.768, "duration": 1.792}, {"text": "so how did some previous\nwork do this since there", "start": 4063.56, "duration": 3.63}, {"text": "we seem to have a bit of time.", "start": 4067.19, "duration": 1.962}, {"text": "OK, so there are\nsome previous work", "start": 4069.152, "duration": 1.458}, {"text": "called liar, liar,\ncoins on fire.", "start": 4070.61, "duration": 3.06}, {"text": "Have you guys seen this?", "start": 4073.67, "duration": 1.71}, {"text": "So the idea here is that it\nis a really nice piece of work", "start": 4075.38, "duration": 2.91}, {"text": "and lots of people in\nthe bitcoin community", "start": 4078.29, "duration": 1.95}, {"text": "already know about this.", "start": 4080.24, "duration": 2.5}, {"text": "And I think it was an idea\nbefore the paper or maybe not,", "start": 4082.74, "duration": 3.09}, {"text": "I'm not sure.", "start": 4085.83, "duration": 1.5}, {"text": "But Tadge has a similar idea.", "start": 4087.33, "duration": 3.0}, {"text": "So for example, suppose\nwe have this authority.", "start": 4090.33, "duration": 5.12}, {"text": "Imagine this is a\nCatena block server", "start": 4095.45, "duration": 1.65}, {"text": "and it publishes a transaction\nwhich locks to bitcoin", "start": 4097.1, "duration": 4.049}, {"text": "and locks those bitcoins\nto that public key.", "start": 4101.149, "duration": 3.271}, {"text": "And this authority\nsometimes will want", "start": 4104.42, "duration": 2.053}, {"text": "to say two different things.", "start": 4106.473, "duration": 1.167}, {"text": "It will want to say\ns and s prime, right?", "start": 4107.64, "duration": 3.61}, {"text": "And it will sign the statements\nwith their secret key.", "start": 4111.25, "duration": 4.069}, {"text": "But the secret key\nthat the authority", "start": 4117.99, "duration": 1.98}, {"text": "uses to sign statements is\nalso a bitcoin secret key.", "start": 4119.97, "duration": 4.32}, {"text": "It's the same secret\nkey that the authority", "start": 4124.29, "duration": 2.279}, {"text": "used to lock to bitcoins,\nso $20,000 or something.", "start": 4126.569, "duration": 3.901}, {"text": "I'm not sure if bitcoin\nplummeted since yesterday,", "start": 4130.47, "duration": 2.94}, {"text": "can never be sure.", "start": 4133.41, "duration": 1.47}, {"text": "Does the setting make sense?", "start": 4134.88, "duration": 1.68}, {"text": "So I have an authority.", "start": 4136.56, "duration": 1.16}, {"text": "It issues statements\njust like before.", "start": 4137.72, "duration": 1.99}, {"text": "And it numbers them\nwith i, let's say.", "start": 4139.71, "duration": 4.939}, {"text": "And we want to prevent this\nauthority from equivocating.", "start": 4144.649, "duration": 2.886}, {"text": "We're not actually\ngoing to prevent it.", "start": 4147.535, "duration": 1.625}, {"text": "We're just going to\ndisincentivize it in the sense", "start": 4149.16, "duration": 3.18}, {"text": "that if this authority\nequivocates like this", "start": 4152.34, "duration": 3.09}, {"text": "for the same statement\ni, what I claim", "start": 4155.43, "duration": 3.27}, {"text": "is that anybody can then\nsteal that authority's", "start": 4158.7, "duration": 2.79}, {"text": "bitcoin because\nequivocating like this", "start": 4161.49, "duration": 2.31}, {"text": "reveals the secret key.", "start": 4163.8, "duration": 2.173}, {"text": "And the reason it\nreveals the secret key", "start": 4165.973, "duration": 1.667}, {"text": "is because the signature\nshares the same i here.", "start": 4167.64, "duration": 5.11}, {"text": "So how many of you\nguys actually, you", "start": 4172.75, "duration": 2.52}, {"text": "did cover Schnorr\nsignatures, right?", "start": 4175.27, "duration": 2.07}, {"text": "So did Tadge talk about how\nto do this with Schnorr?", "start": 4177.34, "duration": 4.372}, {"text": "AUDIENCE: This is\nthe [INAUDIBLE]..", "start": 4181.712, "duration": 1.458}, {"text": "ALIN TOMESCU: But\ndid Tadge cover it?", "start": 4186.27, "duration": 1.66}, {"text": "AUDIENCE: Yes.", "start": 4187.93, "duration": 0.59}, {"text": "ALIN TOMESCU: OK, great.", "start": 4188.52, "duration": 1.08}, {"text": "So yeah so let's go\nover that less briefly.", "start": 4189.6, "duration": 3.48}, {"text": "So again, the idea is that\nif someone observes these two", "start": 4193.08, "duration": 3.36}, {"text": "signatures on conflicting\nstatements for the same i,", "start": 4196.44, "duration": 3.0}, {"text": "there is this box where you\ncan put the two signatures", "start": 4199.44, "duration": 2.58}, {"text": "and get back the secret key.", "start": 4202.02, "duration": 1.63}, {"text": "And once you have\nthe secret key,", "start": 4203.65, "duration": 1.48}, {"text": "we can spend this\ntransaction and get", "start": 4205.13, "duration": 1.63}, {"text": "that authority's bitcoins.", "start": 4206.76, "duration": 2.565}, {"text": "And then there's\na lot of details", "start": 4209.325, "duration": 1.375}, {"text": "to get it right because\nyou might notice", "start": 4210.7, "duration": 2.31}, {"text": "that if the authority does\nthis, before they do this,", "start": 4213.01, "duration": 3.85}, {"text": "they might already be spending\nthis transaction themselves", "start": 4216.86, "duration": 2.42}, {"text": "so as to prevent\nyou from taking it.", "start": 4219.28, "duration": 3.69}, {"text": "And details on how to prevent\nthe authority from doing that", "start": 4222.97, "duration": 2.52}, {"text": "are in those paper.", "start": 4225.49, "duration": 1.86}, {"text": "Yeah, and then you\nknow, whoever discovered", "start": 4227.35, "duration": 2.52}, {"text": "this can spend those bitcoins.", "start": 4229.87, "duration": 2.08}, {"text": "And the idea is that this\ndisincentivizes equivocation", "start": 4231.95, "duration": 4.22}, {"text": "by locking these funds\nunder the secret key", "start": 4236.17, "duration": 2.03}, {"text": "of the bad authority.", "start": 4238.2, "duration": 1.99}, {"text": "But it does not prevent it.", "start": 4240.19, "duration": 1.23}, {"text": "Right, so in Catena we\nactually prevent equivocation.", "start": 4241.42, "duration": 2.73}, {"text": "We say, if you\nwant to equivocate,", "start": 4244.15, "duration": 2.07}, {"text": "you better fork bitcoin.", "start": 4246.22, "duration": 2.32}, {"text": "Here they say, if you\nwant to equivocate,", "start": 4248.54, "duration": 3.56}, {"text": "you're going to lose $20,000.", "start": 4252.1, "duration": 2.65}, {"text": "Right?", "start": 4254.75, "duration": 2.12}, {"text": "But you have to\nunderstand like this", "start": 4256.87, "duration": 1.65}, {"text": "could be a good authority\nthat locked $20,000 here.", "start": 4258.52, "duration": 2.352}, {"text": "But the attackers are going\nto be-- they're not going", "start": 4260.872, "duration": 2.208}, {"text": "to care about those $20,000.", "start": 4263.08, "duration": 1.53}, {"text": "They're just going to\nsteal the secret key,", "start": 4264.61, "duration": 2.01}, {"text": "equivocate and\nthen the authority", "start": 4266.62, "duration": 2.16}, {"text": "is going to be\nleft without money.", "start": 4268.78, "duration": 2.91}, {"text": "If the authority\nis the attacker,", "start": 4271.69, "duration": 1.513}, {"text": "then this makes sense.", "start": 4273.203, "duration": 0.917}, {"text": "But if the attacker\nis not the authority,", "start": 4274.12, "duration": 1.708}, {"text": "then this makes less sense\nbecause the authority sort", "start": 4275.828, "duration": 2.282}, {"text": "of risking their bitcoins\non the assumption", "start": 4278.11, "duration": 3.96}, {"text": "that no attacker can compromise\nthem, which you know,", "start": 4282.07, "duration": 2.592}, {"text": "if you could do that\nin computer science,", "start": 4284.662, "duration": 1.708}, {"text": "I wouldn't be sitting\nhere talking to you guys.", "start": 4286.37, "duration": 1.958}, {"text": "OK, so now how do you do this?", "start": 4290.33, "duration": 2.9}, {"text": "So do you remember Schnorr\nsignatures real quickly?", "start": 4293.23, "duration": 3.27}, {"text": "An easy way to do this is\nusing Schnorr signatures.", "start": 4299.05, "duration": 5.65}, {"text": "And I think--", "start": 4304.7, "duration": 1.06}, {"text": "I could be wrong, but\nI think this new SegWit", "start": 4305.76, "duration": 2.69}, {"text": "update to bitcoin allows\nSchnorr signatures, right?", "start": 4308.45, "duration": 5.91}, {"text": "So with SegWit and\nwith Schnorr signature,", "start": 4314.36, "duration": 3.8}, {"text": "as you can definitely do this.", "start": 4318.16, "duration": 1.59}, {"text": "And the idea is that\nSchnorr signature", "start": 4319.75, "duration": 2.73}, {"text": "if you recall, is just k\nplus h of m, g to the k s,", "start": 4322.48, "duration": 8.73}, {"text": "where s is the secret key.", "start": 4331.21, "duration": 1.95}, {"text": "Right, so this is a Schnorr\nsignature on m, right?", "start": 4333.16, "duration": 3.07}, {"text": "How many recall this?", "start": 4338.84, "duration": 1.942}, {"text": "Right, and of course,\nit's not just this.", "start": 4340.782, "duration": 1.708}, {"text": "I mean, the signature is\nreally this and this h of m,", "start": 4342.49, "duration": 9.39}, {"text": "g to the k.", "start": 4351.88, "duration": 1.83}, {"text": "So it's these two things, right.", "start": 4353.71, "duration": 3.03}, {"text": "But now I want to show you that\nif I sign two different things,", "start": 4356.74, "duration": 8.13}, {"text": "I can actually get s.", "start": 4364.87, "duration": 2.85}, {"text": "But if I sign them\nin a certain way--", "start": 4367.72, "duration": 2.31}, {"text": "so remember what I said before\nis I would like this authority", "start": 4370.03, "duration": 3.3}, {"text": "to sign i m and i m prime.", "start": 4373.33, "duration": 6.16}, {"text": "Right, and if the\nauthority does this,", "start": 4379.49, "duration": 3.71}, {"text": "I claim that I can get\nthe secret key out.", "start": 4383.2, "duration": 1.95}, {"text": "But I have to have the same i.", "start": 4385.15, "duration": 1.95}, {"text": "So we relax this in a\nsense that we're not", "start": 4387.1, "duration": 3.24}, {"text": "going to use i here, we're just\ngoing to use this g to the k.", "start": 4390.34, "duration": 5.61}, {"text": "So if the authority uses\nthe same g to the k to sign,", "start": 4395.95, "duration": 3.37}, {"text": "then we can extract\nthe secret key.", "start": 4399.32, "duration": 1.47}, {"text": "And the way we can do that\nis I'll just show an example,", "start": 4400.79, "duration": 2.41}, {"text": "sig1 would be k plus\nh of m1 g to the k.", "start": 4403.2, "duration": 8.92}, {"text": "And it'll be sig 1 and I\nguess the associated hash", "start": 4412.12, "duration": 4.83}, {"text": "E1 would be h m1, g to the k.", "start": 4416.95, "duration": 4.42}, {"text": "Does everybody see this?", "start": 4421.37, "duration": 2.12}, {"text": "And then sig2 would be k\nplus h of m 2 g to the k.", "start": 4423.49, "duration": 6.54}, {"text": "So again, oh, you guys are\nclearly not paying attention.", "start": 4430.03, "duration": 3.41}, {"text": "I forgot the secret key.", "start": 4433.44, "duration": 1.0}, {"text": "E2 is hash of m2 g to the k.", "start": 4437.2, "duration": 3.76}, {"text": "OK, so I'm using the same\ng to the k and the same k.", "start": 4440.96, "duration": 4.13}, {"text": "So now how can I\nextract the secret key?", "start": 4452.52, "duration": 1.8}, {"text": "Does anybody see a\nsolution to this?", "start": 4454.32, "duration": 1.5}, {"text": "AUDIENCE: It's now just system\nof two equations and two", "start": 4458.97, "duration": 2.447}, {"text": "variables where k and s\nare the unknown variables.", "start": 4461.417, "duration": 2.083}, {"text": "ALIN TOMESCU: So I think\nwhat Rahul always saying", "start": 4463.5, "duration": 2.042}, {"text": "is that s is just sig1 minus\nsig2 divided by e1 minus e2.", "start": 4465.542, "duration": 6.958}, {"text": "Is that right?", "start": 4472.5, "duration": 0.64}, {"text": "Yeah.", "start": 4473.14, "duration": 0.5}, {"text": "See this, because if I\nsubtract this from this,", "start": 4479.14, "duration": 3.09}, {"text": "I just get h m1--", "start": 4482.23, "duration": 6.24}, {"text": "I'm not going to\nhave space here.", "start": 4488.47, "duration": 1.77}, {"text": "I get-- let's say it here--", "start": 4490.24, "duration": 4.23}, {"text": "h of m1, g to the k minus h\nof m2 g into the k times s.", "start": 4494.47, "duration": 11.68}, {"text": "All right?", "start": 4506.15, "duration": 2.53}, {"text": "And now I take this\nhere in the denominator", "start": 4508.68, "duration": 3.91}, {"text": "and I simplify and I get s.", "start": 4512.59, "duration": 1.99}, {"text": "All right.", "start": 4514.58, "duration": 0.5}, {"text": "So it turns out that\nthat's kind of the trick", "start": 4518.43, "duration": 2.4}, {"text": "that this word leverage\nis more or less.", "start": 4520.83, "duration": 2.07}, {"text": "The only sort of caveat here\nis that remember I said,", "start": 4522.9, "duration": 4.1}, {"text": "there is a position\ni for the statement.", "start": 4527.0, "duration": 2.08}, {"text": "But now I'm saying, there's\nno longer a position.", "start": 4529.08, "duration": 2.25}, {"text": "We have to use this g to the k.", "start": 4531.33, "duration": 1.8}, {"text": "And how do we map positions\nthat are g to the k", "start": 4533.13, "duration": 2.16}, {"text": "is another trick that you\nhave to do but you can do it.", "start": 4535.29, "duration": 2.8}, {"text": "And if you want more details,\nyou can read the paper", "start": 4538.09, "duration": 2.167}, {"text": "and I'm sure Tadge will tell you\neven more details about this.", "start": 4540.257, "duration": 3.673}, {"text": "I think the lightning\nnetwork also leverages", "start": 4543.93, "duration": 1.92}, {"text": "this trick in some cases.", "start": 4545.85, "duration": 2.7}, {"text": "All right now, let's talk a\nlittle bit about some attacks", "start": 4551.85, "duration": 3.3}, {"text": "if there is time.", "start": 4555.15, "duration": 1.23}, {"text": "The most interesting attack\nwould be the generalized vector", "start": 4556.38, "duration": 3.57}, {"text": "76 attack.", "start": 4559.95, "duration": 0.798}, {"text": "So this is a screenshot\nfrom a paper.", "start": 4560.748, "duration": 1.542}, {"text": "Can everybody see this?", "start": 4562.29, "duration": 2.73}, {"text": "So the generalized vector 76\nattack is very interesting.", "start": 4565.02, "duration": 4.05}, {"text": "So you have you have\nan attacker, right?", "start": 4569.07, "duration": 2.13}, {"text": "And remember, the goal of\nthe attacker is to replace--", "start": 4571.2, "duration": 3.77}, {"text": "let's say this\nTX1 with that TX2.", "start": 4574.97, "duration": 4.15}, {"text": "It's going to show this TX1\nto a merchant saying hey,", "start": 4579.12, "duration": 3.06}, {"text": "I paid you money.", "start": 4582.18, "duration": 1.38}, {"text": "And then it's going to show\nthis TX2 to the merchant sending", "start": 4583.56, "duration": 3.0}, {"text": "the money back to himself.", "start": 4586.56, "duration": 1.14}, {"text": "So the whole trick is to fork\nthe merchant on this side", "start": 4587.7, "duration": 2.94}, {"text": "and then to switch him\nback to that, right.", "start": 4590.64, "duration": 2.34}, {"text": "It's a sort of a pre-mining\nattack and this attack is much", "start": 4592.98, "duration": 4.05}, {"text": "easier to pull on SPV notes\nbecause what the attacker does", "start": 4597.03, "duration": 3.75}, {"text": "is--", "start": 4600.78, "duration": 0.51}, {"text": "let's see-- he works on the\nsecret chain with TX1 in it.", "start": 4601.29, "duration": 4.73}, {"text": "And at some point, the main\nchain might take him over,", "start": 4606.02, "duration": 2.39}, {"text": "might win.", "start": 4608.41, "duration": 0.5}, {"text": "So the attacker kind of\ngives up and keeps trying.", "start": 4608.91, "duration": 2.34}, {"text": "But at some point the\nattacker gets ahead,", "start": 4611.25, "duration": 2.49}, {"text": "right in the second chain.", "start": 4613.74, "duration": 1.127}, {"text": "He gets ahead of the main chain.", "start": 4614.867, "duration": 1.333}, {"text": "This stuff is not posted yet.", "start": 4616.2, "duration": 1.74}, {"text": "And let's see this merchant only\nfor some reason because they're", "start": 4617.94, "duration": 3.66}, {"text": "silly, they only need one\nconfirmation to accept the TX1.", "start": 4621.6, "duration": 4.59}, {"text": "And for other silly\nreasons, this merchant", "start": 4626.19, "duration": 1.75}, {"text": "is an SPV merchant, right?", "start": 4627.94, "duration": 3.02}, {"text": "Let's draw a figure here.", "start": 4630.96, "duration": 1.77}, {"text": "So this merchant\nis an SPV merchant", "start": 4632.73, "duration": 1.56}, {"text": "that only needs one confirmation\nto accept the transaction.", "start": 4634.29, "duration": 5.396}, {"text": "So we have the attacker.", "start": 4643.97, "duration": 1.905}, {"text": "And we have let's\nsay, the SPV merchant.", "start": 4649.55, "duration": 1.92}, {"text": "Right, and now the\nattacker's sent you know,", "start": 4655.67, "duration": 2.63}, {"text": "this was the main block\nthere, let's say, this was bi.", "start": 4658.3, "duration": 4.45}, {"text": "And the attacker forked it.", "start": 4662.75, "duration": 1.54}, {"text": "He put TX1 here.", "start": 4664.29, "duration": 2.94}, {"text": "And then had a\nconfirmation on it, right?", "start": 4667.23, "duration": 2.49}, {"text": "So he sends this\nchain to the merchant.", "start": 4669.72, "duration": 3.06}, {"text": "And the other miners\nhaven't found anything yet.", "start": 4672.78, "duration": 2.357}, {"text": "Right, so the attacker\nis a bit ahead.", "start": 4675.137, "duration": 1.583}, {"text": "So he's pre-mining.", "start": 4676.72, "duration": 1.52}, {"text": "So far, so good.", "start": 4678.24, "duration": 1.08}, {"text": "Are you all with me?", "start": 4679.32, "duration": 2.19}, {"text": "And remember that he really\njust is showing block headers.", "start": 4681.51, "duration": 4.11}, {"text": "So these are not full blocks.", "start": 4685.62, "duration": 1.317}, {"text": "He's just showing block headers.", "start": 4686.937, "duration": 1.333}, {"text": "They're much smaller\nblocks, 80 bytes.", "start": 4688.27, "duration": 3.35}, {"text": "And the blocks are missing.", "start": 4691.62, "duration": 2.54}, {"text": "All right, so when\nhe shows TX1, he", "start": 4694.16, "duration": 1.78}, {"text": "is just showing like a Merkle\npath to TX1 to the merchant.", "start": 4695.94, "duration": 5.4}, {"text": "You guys with me?", "start": 4701.34, "duration": 1.86}, {"text": "OK, so now he did\nthis to the merchant.", "start": 4703.2, "duration": 1.82}, {"text": "And now what the\nattacker is going to do,", "start": 4705.02, "duration": 1.83}, {"text": "he's going to relax,\nsit back, and post", "start": 4706.85, "duration": 2.58}, {"text": "the TX2 the mines--\ngive TX2 to the miners.", "start": 4709.43, "duration": 3.81}, {"text": "Let's say the miners are here.", "start": 4713.24, "duration": 2.46}, {"text": "Hes going to post\nTX2 to the miners.", "start": 4715.7, "duration": 2.67}, {"text": "And he'll stop\nmining the attacker.", "start": 4718.37, "duration": 1.56}, {"text": "He's not going to mine anymore.", "start": 4719.93, "duration": 1.17}, {"text": "But he got the merchant\nto accept the payment.", "start": 4721.1, "duration": 1.917}, {"text": "And the merchant\nshipped the goods.", "start": 4723.017, "duration": 1.713}, {"text": "Maybe this is an\nonline purchase.", "start": 4724.73, "duration": 2.49}, {"text": "And so now the miners, they will\nfind the next block bi plus 1.", "start": 4727.22, "duration": 5.52}, {"text": "They'll put TX2 here.", "start": 4732.74, "duration": 2.85}, {"text": "They'll find the next block\nand then the next block.", "start": 4735.59, "duration": 3.06}, {"text": "And they'll take over.", "start": 4738.65, "duration": 1.11}, {"text": "Their chain will\nbe the main chain.", "start": 4739.76, "duration": 1.625}, {"text": "And eventually\nthis merchant will", "start": 4741.385, "duration": 1.375}, {"text": "hear about this main chain.", "start": 4742.76, "duration": 2.01}, {"text": "And he'll just see the\nheaders, of course,", "start": 4744.77, "duration": 2.06}, {"text": "because he's an SPV merchant.", "start": 4746.83, "duration": 1.52}, {"text": "So now the SPV merchant\njust got double spent.", "start": 4748.35, "duration": 2.51}, {"text": "Does everybody see this?", "start": 4750.86, "duration": 1.76}, {"text": "That I just double\nspent the merchant?", "start": 4752.62, "duration": 1.72}, {"text": "And sort of the\nfundamental problem", "start": 4754.34, "duration": 2.13}, {"text": "here is that the merchant\nonly received block headers.", "start": 4756.47, "duration": 4.29}, {"text": "So he cannot take these block\nheaders and broadcast them", "start": 4760.76, "duration": 2.49}, {"text": "to the miners because miners\ndon't mine on top of block", "start": 4763.25, "duration": 3.21}, {"text": "headers.", "start": 4766.46, "duration": 1.05}, {"text": "Miners mine on top\nof full blocks.", "start": 4767.51, "duration": 2.25}, {"text": "So this merchant cannot has\nno protection against this", "start": 4769.76, "duration": 2.58}, {"text": "if he's doing SPV--", "start": 4772.34, "duration": 1.81}, {"text": "if he's accepting SPV payments.", "start": 4774.15, "duration": 1.81}, {"text": "If these were full blocks, what\nthe merchant could have done", "start": 4775.96, "duration": 3.25}, {"text": "was the following.", "start": 4779.21, "duration": 2.063}, {"text": "The merchant would\nhave would have", "start": 4781.273, "duration": 1.417}, {"text": "received the full block here\nwith the transaction in it,", "start": 4782.69, "duration": 8.37}, {"text": "right.", "start": 4791.06, "duration": 0.5}, {"text": "So again the attacker got ahead.", "start": 4791.56, "duration": 1.83}, {"text": "But now the merchant\nbecause he saw a block,", "start": 4793.39, "duration": 2.55}, {"text": "he's going to ship this\nblock with TX1 to the miners", "start": 4795.94, "duration": 3.96}, {"text": "because he's a full node.", "start": 4799.9, "duration": 1.11}, {"text": "Full nodes do that.", "start": 4801.01, "duration": 0.9}, {"text": "When they hear about a\nblock, they broadcast it.", "start": 4801.91, "duration": 3.09}, {"text": "So now the miners\nknow about this block.", "start": 4805.0, "duration": 2.37}, {"text": "They're going to continue\nmining on top of it.", "start": 4807.37, "duration": 2.11}, {"text": "And in fact, the merchant\nwill send both blocks,", "start": 4809.48, "duration": 2.0}, {"text": "right to the miners.", "start": 4811.48, "duration": 1.2}, {"text": "So now miners will\ncontinue building here.", "start": 4812.68, "duration": 3.12}, {"text": "So now the attacker has a bit of\na tougher problem on his hands.", "start": 4815.8, "duration": 5.58}, {"text": "There is still a way to\ntrick even full nodes,", "start": 4821.38, "duration": 2.1}, {"text": "even if this guy\nis a full node, you", "start": 4823.48, "duration": 1.98}, {"text": "can sort of leverage\nsome timing assumptions", "start": 4825.46, "duration": 2.27}, {"text": "to still trick the full node.", "start": 4827.73, "duration": 1.32}, {"text": "And the details are in\nthat paper over there.", "start": 4829.05, "duration": 2.95}, {"text": "But that's one way--", "start": 4832.0, "duration": 3.193}, {"text": "somebody was asking, I think\nyou were asking Anne, right--", "start": 4835.193, "duration": 2.417}, {"text": "about SPV nodes and how\nthey're less secure.", "start": 4837.61, "duration": 1.56}, {"text": "And this is one fundamental way\nin which they're less secure.", "start": 4839.17, "duration": 2.542}, {"text": "If you accept payments\nwith SPV nodes", "start": 4841.712, "duration": 2.798}, {"text": "you're really playing with fire.", "start": 4844.51, "duration": 1.9}, {"text": "You know, you do need a\nsufficiently powerful attacker", "start": 4846.41, "duration": 4.52}, {"text": "who can get ahead.", "start": 4850.93, "duration": 1.75}, {"text": "But yeah.", "start": 4852.68, "duration": 1.48}, {"text": "OK, so with that I think that\nkind of concludes the lecture.", "start": 4854.16, "duration": 4.85}, {"text": "Any final questions?", "start": 4859.01, "duration": 1.25}, {"text": "All right, cool.", "start": 4865.19, "duration": 1.06}, {"text": "Thank you guys.", "start": 4866.25, "duration": 1.72}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 2.42}, {"text": "[RUSTLING]", "start": 2.42, "duration": 1.936}, {"text": "[CLICKING]", "start": 4.356, "duration": 2.42}, {"text": "ERIK DEMAINE: Good morning.", "start": 14.425, "duration": 1.125}, {"text": "AUDIENCE: Morning!", "start": 15.55, "duration": 1.45}, {"text": "ERIK DEMAINE: Welcome to 006,\nIntroduction to Algorithms,", "start": 17.0, "duration": 2.63}, {"text": "lecture two.", "start": 19.63, "duration": 1.02}, {"text": "I am Erik Demaine and\nI love algorithms.", "start": 20.65, "duration": 3.21}, {"text": "Are you with me?", "start": 23.86, "duration": 0.78}, {"text": "[APPLAUSE]", "start": 24.64, "duration": 0.5}, {"text": "Yeah.", "start": 25.14, "duration": 1.87}, {"text": "Today, we're not\ndoing algorithms.", "start": 27.01, "duration": 1.83}, {"text": "No, we're doing data structures.", "start": 28.84, "duration": 2.08}, {"text": "It's OK.", "start": 30.92, "duration": 0.5}, {"text": "There's lots of algorithms\nin each data structure.", "start": 31.42, "duration": 2.22}, {"text": "It's like multiple\nalgorithms for free.", "start": 33.64, "duration": 2.64}, {"text": "We're going to talk\nabout sequences,", "start": 36.28, "duration": 1.5}, {"text": "and sets, and linked\nlists, and dynamic arrays.", "start": 37.78, "duration": 4.53}, {"text": "Fairly simple data\nstructures today.", "start": 42.31, "duration": 1.59}, {"text": "This is the beginning of\nseveral data structures", "start": 43.9, "duration": 2.58}, {"text": "we'll be talking about\nin the next few lectures.", "start": 46.48, "duration": 2.44}, {"text": "But before we actually\nstart with one,", "start": 48.92, "duration": 2.66}, {"text": "let me tell you/remind remind\nyou of the difference between", "start": 51.58, "duration": 5.94}, {"text": "an interface-- which\nyou might call an API", "start": 57.52, "duration": 2.76}, {"text": "if you're a programmer, or\nan ADT if you're an ancient", "start": 60.28, "duration": 2.73}, {"text": "algorithms person like me--", "start": 63.01, "duration": 1.83}, {"text": "versus a data structure.", "start": 64.84, "duration": 2.362}, {"text": "These are useful distinctions.", "start": 71.45, "duration": 3.2}, {"text": "The idea is that an interface\nsays what you want to do.", "start": 74.65, "duration": 3.84}, {"text": "A data structure\nsays how you do it.", "start": 78.49, "duration": 2.35}, {"text": "So you might call\nthis a specification.", "start": 80.84, "duration": 2.06}, {"text": "And in the context\nof data structures,", "start": 85.6, "duration": 1.74}, {"text": "we're trying to store some data.", "start": 87.34, "duration": 1.36}, {"text": "So the interface will specify\nwhat data you can store,", "start": 88.7, "duration": 6.88}, {"text": "whereas the data\nstructure will give you", "start": 95.58, "duration": 1.86}, {"text": "an actual representation and\ntell you how to store it.", "start": 97.44, "duration": 3.25}, {"text": "This is pretty boring.", "start": 108.14, "duration": 2.01}, {"text": "Just storing data\nis really easy.", "start": 110.15, "duration": 1.57}, {"text": "You just throw it in\na file or something.", "start": 111.72, "duration": 2.93}, {"text": "What makes it interesting is\nhaving operations on that data.", "start": 114.65, "duration": 5.28}, {"text": "In the interface, you specify\nwhat the operations do,", "start": 119.93, "duration": 5.7}, {"text": "what operations are\nsupported, and in some sense,", "start": 125.63, "duration": 10.735}, {"text": "what they mean.", "start": 136.365, "duration": 0.625}, {"text": "And the data structure\nactually gives you algorithms--", "start": 142.72, "duration": 3.71}, {"text": "this is where the\nalgorithms come in--", "start": 146.43, "duration": 1.96}, {"text": "for how to support\nthose operations.", "start": 148.39, "duration": 1.92}, {"text": "All right.", "start": 162.87, "duration": 1.98}, {"text": "In this class, we're going to\nfocus on two main interfaces", "start": 164.85, "duration": 6.66}, {"text": "and various special of them.", "start": 171.51, "duration": 3.6}, {"text": "The idea is to separate what you\nwant to do versus how to do it.", "start": 175.11, "duration": 2.94}, {"text": "Because-- you can think of\nthis as the problem statement.", "start": 178.05, "duration": 4.2}, {"text": "Yesterday-- or, last class,\nJason talked about problems", "start": 182.25, "duration": 4.62}, {"text": "and defined what a problem was\nversus algorithmic solutions", "start": 186.87, "duration": 4.53}, {"text": "to the problem.", "start": 191.4, "duration": 1.6}, {"text": "And this is the analogous notion\nfor data structures, where", "start": 193.0, "duration": 2.72}, {"text": "we want to maintain\nsome data according", "start": 195.72, "duration": 2.82}, {"text": "to various operations.", "start": 198.54, "duration": 2.94}, {"text": "The same problem can be\nsolved by many different data", "start": 201.48, "duration": 2.34}, {"text": "structures.", "start": 203.82, "duration": 0.54}, {"text": "And we're going to see that.", "start": 204.36, "duration": 1.08}, {"text": "And different data\nstructures are going", "start": 205.44, "duration": 1.56}, {"text": "to have different advantages.", "start": 207.0, "duration": 1.02}, {"text": "They might support some\noperations faster than others.", "start": 208.02, "duration": 2.37}, {"text": "And depending on\nwhat you actually", "start": 210.39, "duration": 1.44}, {"text": "use those data\nstructures for, you", "start": 211.83, "duration": 1.417}, {"text": "choose the right data structure.", "start": 213.247, "duration": 2.513}, {"text": "But you can maintain\nthe same interface.", "start": 215.76, "duration": 2.76}, {"text": "We're going to think\nabout two data structures.", "start": 218.52, "duration": 2.08}, {"text": "One is called a set and\none is called a sequence.", "start": 220.6, "duration": 5.18}, {"text": "These are highly loaded terms.", "start": 225.78, "duration": 1.255}, {"text": "Set means something\nto a mathematician.", "start": 227.035, "duration": 1.625}, {"text": "It means something else\nto a Python programmer.", "start": 228.66, "duration": 2.64}, {"text": "Sequence, similarly.", "start": 231.3, "duration": 1.8}, {"text": "I guess there's not a Python\nsequence data type built in.", "start": 233.1, "duration": 5.19}, {"text": "The idea is, we want\nto store n things.", "start": 238.29, "duration": 3.0}, {"text": "The things will be\nfairly arbitrary.", "start": 241.29, "duration": 2.25}, {"text": "Think of them as\nintegers or strings.", "start": 243.54, "duration": 2.88}, {"text": "And on the one hand, we\ncare about their values.", "start": 246.42, "duration": 3.69}, {"text": "And maybe we want to\nmaintain them in sorted order", "start": 250.11, "duration": 2.73}, {"text": "and be able to search\nfor a given value, which", "start": 252.84, "duration": 2.51}, {"text": "we'll call a key.", "start": 255.35, "duration": 1.27}, {"text": "And on the other hand, we\ncare about representing", "start": 256.62, "duration": 3.149}, {"text": "a particular sequence\nthat we care about.", "start": 259.769, "duration": 3.211}, {"text": "Maybe we want to represent\nthe numbers 5, 2, 9,", "start": 262.98, "duration": 4.47}, {"text": "7 in that order and store that.", "start": 267.45, "duration": 2.61}, {"text": "In Python, you could store\nthat in a list, for example.", "start": 270.06, "duration": 3.36}, {"text": "And it will keep\ntrack of that order.", "start": 273.42, "duration": 1.63}, {"text": "And this is the first item,\nthe second item, the last item.", "start": 275.05, "duration": 3.98}, {"text": "Today, we're going to be\nfocusing on this sequence data", "start": 279.03, "duration": 3.21}, {"text": "structure, although\nat the end, I'll", "start": 282.24, "duration": 1.5}, {"text": "mention the interface for sets.", "start": 283.74, "duration": 2.61}, {"text": "But we're going to be actually\nsolving sequences today.", "start": 286.35, "duration": 2.49}, {"text": "And in the next\nseveral lectures,", "start": 288.84, "duration": 1.432}, {"text": "we'll be bouncing back\nand forth between these.", "start": 290.272, "duration": 1.958}, {"text": "They're closely related.", "start": 292.23, "duration": 2.22}, {"text": "Pretty abstract at the moment.", "start": 294.45, "duration": 2.8}, {"text": "On the other hand, we're\ngoing to have two main--", "start": 297.25, "duration": 2.57}, {"text": "let's call them data\nstructure tools or approaches.", "start": 303.08, "duration": 4.43}, {"text": "One is arrays and the\nother is pointers--", "start": 313.98, "duration": 7.22}, {"text": "pointer-based or\nlinked data structures.", "start": 321.2, "duration": 4.4}, {"text": "You may have seen these.", "start": 325.6, "duration": 1.21}, {"text": "They're used a lot in\nprogramming, of course.", "start": 326.81, "duration": 2.618}, {"text": "But we're going to see\nboth of these today.", "start": 329.428, "duration": 1.792}, {"text": "I'll come back to this sort\nof highlight in a moment.", "start": 331.22, "duration": 3.52}, {"text": "Let's jump into the sequence\ninterface, which I conveniently", "start": 334.74, "duration": 4.07}, {"text": "have part of here.", "start": 338.81, "duration": 2.8}, {"text": "There's a few different\nlevels of sequences", "start": 341.61, "duration": 2.098}, {"text": "that we might care about.", "start": 343.708, "duration": 1.042}, {"text": "I'm going to start with the\nstatic sequence interface.", "start": 344.75, "duration": 3.06}, {"text": "This is where the number\nof items doesn't change,", "start": 347.81, "duration": 6.35}, {"text": "though the actual items might.", "start": 354.16, "duration": 2.47}, {"text": "Here, we have n items.", "start": 356.63, "duration": 1.89}, {"text": "I'm going to label them x 0\nto x n minus 1, as in Python.", "start": 358.52, "duration": 3.87}, {"text": "So the number of items is n.", "start": 362.39, "duration": 1.8}, {"text": "And the operations I want\nto support are build,", "start": 364.19, "duration": 2.28}, {"text": "length, iteration, get, and set.", "start": 366.47, "duration": 4.32}, {"text": "So what do these do?", "start": 370.79, "duration": 2.04}, {"text": "Build is how you get started.", "start": 372.83, "duration": 1.38}, {"text": "To build a data structure\nin this interface,", "start": 374.21, "duration": 2.85}, {"text": "you call build of x.", "start": 377.06, "duration": 2.22}, {"text": "Exactly how you specify x isn't\ntoo important, but the idea is,", "start": 379.28, "duration": 3.51}, {"text": "I give you some\nitems in some order.", "start": 382.79, "duration": 2.22}, {"text": "In Python, this\nwould be an iterable.", "start": 385.01, "duration": 2.04}, {"text": "I'm going to want to\nalso know its length.", "start": 387.05, "duration": 2.52}, {"text": "And I want to make a new\ndata structure of size", "start": 389.57, "duration": 2.43}, {"text": "and a new static\nsequence of size n", "start": 392.0, "duration": 2.16}, {"text": "that has those\nitems in that order.", "start": 394.16, "duration": 2.06}, {"text": "So that's how you\nbuild one of these.", "start": 396.22, "duration": 2.608}, {"text": "Because somehow, we\nhave to specify n", "start": 398.828, "duration": 1.542}, {"text": "to this data structure,\nbecause n is not", "start": 400.37, "duration": 1.667}, {"text": "going to be allowed to change.", "start": 402.037, "duration": 2.113}, {"text": "I'm going to give\nyou a length method.", "start": 404.15, "duration": 2.28}, {"text": "Methods are the\nobject-oriented way", "start": 409.3, "duration": 2.7}, {"text": "of thinking of operations\nthat your interface supports.", "start": 412.0, "duration": 5.85}, {"text": "Length will just return\nthis fixed value n.", "start": 417.85, "duration": 2.25}, {"text": "Iter sequence.", "start": 420.1, "duration": 0.775}, {"text": "This is the sense in which we\nwant to maintain the order.", "start": 420.875, "duration": 2.375}, {"text": "I want to be able to output\nx 0 through x n minus 1", "start": 423.25, "duration": 3.24}, {"text": "in the sequence order,\nin that specified order", "start": 426.49, "duration": 2.46}, {"text": "that they were built in\nor that it was changed to.", "start": 428.95, "duration": 4.8}, {"text": "This is going to iterate\nthrough all of the items.", "start": 433.75, "duration": 3.72}, {"text": "So it's going to take at least\nlinear time to output that.", "start": 437.47, "duration": 2.94}, {"text": "But more interesting is, we\ncan dynamically access anywhere", "start": 440.41, "duration": 3.36}, {"text": "in the middle of the sequence.", "start": 443.77, "duration": 2.08}, {"text": "We can get the ith item,\nx i, given the value i,", "start": 445.85, "duration": 3.47}, {"text": "and we can change x i\nto a given new item.", "start": 449.32, "duration": 4.61}, {"text": "OK.", "start": 453.93, "duration": 0.5}, {"text": "So that's called\nget_at and set_at.", "start": 454.43, "duration": 2.61}, {"text": "Pretty straightforward.", "start": 457.04, "duration": 1.11}, {"text": "This should remind you\nvery closely of something--", "start": 458.15, "duration": 4.49}, {"text": "a data structure.", "start": 462.64, "duration": 1.25}, {"text": "So this is an interface.", "start": 463.89, "duration": 1.2}, {"text": "This is something I\nmight want to solve.", "start": 465.09, "duration": 2.097}, {"text": "But what is the\nobvious data structure", "start": 467.187, "duration": 1.583}, {"text": "that solves this problem?", "start": 468.77, "duration": 1.33}, {"text": "Yeah?", "start": 470.1, "duration": 0.5}, {"text": "AUDIENCE: A list.", "start": 470.6, "duration": 1.015}, {"text": "ERIK DEMAINE: A list.", "start": 471.615, "duration": 0.875}, {"text": "In Python, it's called a list.", "start": 472.49, "duration": 2.04}, {"text": "I prefer to call it an\narray, but to each their own.", "start": 474.53, "duration": 3.807}, {"text": "We're going to use \"list.\"", "start": 478.337, "duration": 1.083}, {"text": "List could mean many\nthings, but the solution", "start": 479.42, "duration": 8.31}, {"text": "to this interface problem--", "start": 487.73, "duration": 2.19}, {"text": "the natural solution-- is\nwhat I'll call a static array.", "start": 489.92, "duration": 10.41}, {"text": "Jason mentioned\nthese in lecture one.", "start": 503.18, "duration": 5.433}, {"text": "It's a little\ntricky because there", "start": 508.613, "duration": 1.417}, {"text": "are no static arrays in Python.", "start": 510.03, "duration": 1.292}, {"text": "There are only\ndynamic arrays, which", "start": 511.322, "duration": 1.5}, {"text": "is something we will get to.", "start": 512.822, "duration": 1.258}, {"text": "But I want to talk about, what\nis a static array, really?", "start": 514.08, "duration": 4.66}, {"text": "And this relates\nto our notion of--", "start": 518.74, "duration": 3.74}, {"text": "our model of computation,\nJason also talked about,", "start": 522.48, "duration": 3.33}, {"text": "which we call the\nword RAM, remember?", "start": 525.81, "duration": 3.57}, {"text": "The idea, in word RAM,\nis that your memory", "start": 538.58, "duration": 4.56}, {"text": "is an array of w-bit words.", "start": 543.14, "duration": 5.222}, {"text": "This is a bit circular.", "start": 548.362, "duration": 0.958}, {"text": "I'm going to define an array\nin terms of the word RAM, which", "start": 549.32, "duration": 2.46}, {"text": "is defined in terms of arrays.", "start": 551.78, "duration": 1.25}, {"text": "But I think you know the idea.", "start": 553.03, "duration": 5.75}, {"text": "So we have a big memory which\ngoes off to infinity, maybe.", "start": 558.78, "duration": 4.4}, {"text": "It's divided into words.", "start": 563.18, "duration": 3.21}, {"text": "Each word here is w bits long.", "start": 566.39, "duration": 3.54}, {"text": "This is word 0, word 1, word 2.", "start": 569.93, "duration": 2.31}, {"text": "And you can access\nthis array randomly--", "start": 572.24, "duration": 3.21}, {"text": "random access memory.", "start": 575.45, "duration": 1.39}, {"text": "So I can give you the number\n5 and get 0 1, 2, 3, 4,", "start": 576.84, "duration": 4.37}, {"text": "5, the fifth word in this RAM.", "start": 581.21, "duration": 3.78}, {"text": "That's how actual memories work.", "start": 584.99, "duration": 4.17}, {"text": "You can access any of\nthem equally quickly.", "start": 589.16, "duration": 4.38}, {"text": "OK, so that's memory.", "start": 593.54, "duration": 3.76}, {"text": "And so what we want to do\nis, when we say an array,", "start": 597.3, "duration": 5.9}, {"text": "we want this to be a\nconsecutive chunk of memory.", "start": 603.2, "duration": 7.95}, {"text": "Let me get color.", "start": 616.46, "duration": 1.2}, {"text": "Let's say I have an array\nof size 4 and it lives here.", "start": 622.18, "duration": 4.05}, {"text": "Jason can't spell,\nbut I can't count.", "start": 629.69, "duration": 2.22}, {"text": "So I think that's four.", "start": 631.91, "duration": 2.46}, {"text": "We've got-- so the array starts\nhere and it ends over here.", "start": 634.37, "duration": 5.94}, {"text": "It's of size 4.", "start": 640.31, "duration": 2.5}, {"text": "And it's consecutive,\nwhich means,", "start": 642.81, "duration": 2.64}, {"text": "if I want to access\nthe array at position--", "start": 645.45, "duration": 7.47}, {"text": "at index i, then this\nis the same thing", "start": 652.92, "duration": 4.8}, {"text": "as accessing my memory\narray at position--", "start": 657.72, "duration": 5.73}, {"text": "wherever the array\nstarts, which I'll", "start": 663.45, "duration": 2.01}, {"text": "call the address of the array--", "start": 665.46, "duration": 4.98}, {"text": "in Python, this is ID of array--", "start": 670.44, "duration": 3.03}, {"text": "plus i.", "start": 673.47, "duration": 2.8}, {"text": "OK.", "start": 676.27, "duration": 0.5}, {"text": "This is just simple\noffset arithmetic.", "start": 676.77, "duration": 2.7}, {"text": "If I want to know the\n0th item of the array,", "start": 679.47, "duration": 2.04}, {"text": "it's right here,\nwhere it starts.", "start": 681.51, "duration": 1.53}, {"text": "The first item is\none after that.", "start": 683.04, "duration": 1.65}, {"text": "The second item\nis one after that.", "start": 684.69, "duration": 1.93}, {"text": "So as long as I store my\narray consecutively in memory,", "start": 686.62, "duration": 3.62}, {"text": "I can access the array\nin constant time.", "start": 690.24, "duration": 3.45}, {"text": "I can do get_at and\nset_at as quickly", "start": 693.69, "duration": 2.7}, {"text": "as I can randomly access\nthe memory and get value--", "start": 696.39, "duration": 3.9}, {"text": "or set a value-- which we're\nassuming is constant time.", "start": 700.29, "duration": 2.77}, {"text": "My array access\nis constant time.", "start": 710.87, "duration": 3.6}, {"text": "This is what allows\na static array", "start": 717.88, "duration": 2.28}, {"text": "to actually solve this problem\nin constant time per get_at", "start": 720.16, "duration": 6.15}, {"text": "and set_at operation.", "start": 726.31, "duration": 2.73}, {"text": "This may seem simple, but we're\nreally going to need this model", "start": 729.04, "duration": 3.57}, {"text": "and really rely on this model\nincreasingly as we get to more", "start": 732.61, "duration": 3.0}, {"text": "interesting data structures.", "start": 735.61, "duration": 1.48}, {"text": "This is the first time\nwe're actually needing it.", "start": 737.09, "duration": 3.8}, {"text": "Let's see.", "start": 740.89, "duration": 0.96}, {"text": "Length is also constant time.", "start": 741.85, "duration": 1.86}, {"text": "We're just going to\nstore that number", "start": 743.71, "duration": 1.75}, {"text": "n, along with its address.", "start": 745.46, "duration": 3.77}, {"text": "And build is going\nto take linear time.", "start": 749.23, "duration": 2.97}, {"text": "Iteration will take linear time.", "start": 752.2, "duration": 2.49}, {"text": "Pretty straightforward.", "start": 763.35, "duration": 2.47}, {"text": "I guess one thing\nhere, when defining", "start": 765.82, "duration": 2.21}, {"text": "build, I need to introduce\na little bit more", "start": 768.03, "duration": 1.92}, {"text": "of our model of\ncomputation, which", "start": 769.95, "duration": 1.44}, {"text": "is, how do you create an\narray in the beginning?", "start": 771.39, "duration": 3.59}, {"text": "I claim I could do\nit in linear time,", "start": 774.98, "duration": 2.34}, {"text": "but that's just\npart of the model.", "start": 777.32, "duration": 1.92}, {"text": "This is called the\nmemory allocation model.", "start": 779.24, "duration": 2.13}, {"text": "There are a few\npossible choices here,", "start": 789.45, "duration": 1.597}, {"text": "but the cleanest one\nis just to assume", "start": 791.047, "duration": 1.583}, {"text": "that you can allocate an array\nof size n in theta n time.", "start": 792.63, "duration": 13.0}, {"text": "So it takes linear time to\nmake an array of size n.", "start": 805.63, "duration": 3.547}, {"text": "You could imagine\nthis being constant.", "start": 809.177, "duration": 1.583}, {"text": "It doesn't really matter much.", "start": 810.76, "duration": 1.64}, {"text": "But it does take work.", "start": 812.4, "duration": 1.53}, {"text": "And in particular, if you just\nallocate some chunk of memory,", "start": 813.93, "duration": 2.61}, {"text": "you have no idea whether\nit's initialized.", "start": 816.54, "duration": 1.75}, {"text": "So initializing that array\nto 0s will cost linear time.", "start": 818.29, "duration": 2.9}, {"text": "It won't really matter,\nconstant versus linear,", "start": 821.19, "duration": 2.19}, {"text": "but a nice side effect of\nthis model is that space--", "start": 823.38, "duration": 4.5}, {"text": "if you're just\nallocating arrays,", "start": 827.88, "duration": 2.462}, {"text": "the amount of space you use\nis, at most, the amount of time", "start": 830.342, "duration": 2.458}, {"text": "you use.", "start": 832.8, "duration": 0.78}, {"text": "Or, I guess, big O of that.", "start": 833.58, "duration": 3.66}, {"text": "So that's a nice feature.", "start": 837.24, "duration": 3.05}, {"text": "It's pretty weird\nif you imagine--", "start": 840.29, "duration": 1.63}, {"text": "it's unrealistic to imagine you\ncan allocate an array that's", "start": 841.92, "duration": 2.97}, {"text": "infinite size and then just\nuse a few items out of it.", "start": 844.89, "duration": 2.94}, {"text": "That won't give you a\ngood data structure.", "start": 847.83, "duration": 2.71}, {"text": "So we'll assume it costs\nto allocate memory.", "start": 850.54, "duration": 3.47}, {"text": "OK, great.", "start": 854.01, "duration": 0.57}, {"text": "We solved the sequence problem.", "start": 854.58, "duration": 2.31}, {"text": "Very simple, kind of boring.", "start": 856.89, "duration": 1.56}, {"text": "These are optimal running times.", "start": 858.45, "duration": 3.3}, {"text": "Now, let's make it interesting--\nmake sure I didn't miss", "start": 861.75, "duration": 3.03}, {"text": "anything--", "start": 864.78, "duration": 1.81}, {"text": "and talk about-- oh,\nthere is one thing I want", "start": 866.59, "duration": 5.87}, {"text": "to talk about in the word RAM.", "start": 872.46, "duration": 3.0}, {"text": "A side effect of this assumption\nthat array access should", "start": 875.46, "duration": 3.81}, {"text": "take constant time, and that\naccessing these positions", "start": 879.27, "duration": 4.14}, {"text": "in my memory should\ntake constant time,", "start": 883.41, "duration": 2.25}, {"text": "is that we need to assume\nw is at least log n or so.", "start": 885.66, "duration": 9.75}, {"text": "w, remember, is the\nmachine word size.", "start": 898.45, "duration": 2.43}, {"text": "In real computers,\nthis is currently 64--", "start": 900.88, "duration": 3.66}, {"text": "or 256, in some\nbizarre instructions.", "start": 904.54, "duration": 3.88}, {"text": "But we don't usually\nthink of the machine", "start": 908.42, "duration": 2.33}, {"text": "as getting bigger over time, but\nyou should think of the machine", "start": 910.75, "duration": 2.913}, {"text": "as getting bigger over time.", "start": 913.663, "duration": 1.167}, {"text": "This is a statement\nthat says, the word", "start": 914.83, "duration": 2.28}, {"text": "size has to grow with n.", "start": 917.11, "duration": 2.04}, {"text": "It might faster\nthan log n, but it", "start": 919.15, "duration": 1.5}, {"text": "has to grow at least\nas fast as log n.", "start": 920.65, "duration": 1.95}, {"text": "Why do I say that?", "start": 922.6, "duration": 1.36}, {"text": "Because if I have n things\nthat I'm dealing with-- n,", "start": 923.96, "duration": 2.6}, {"text": "here, is the problem size.", "start": 926.56, "duration": 1.38}, {"text": "Maybe it's the array I'm\ntrying to store-- whatever.", "start": 927.94, "duration": 2.64}, {"text": "If I'm having to deal with\nn things in my memory,", "start": 930.58, "duration": 3.03}, {"text": "at the very least, I need\nto be able to address them.", "start": 933.61, "duration": 2.59}, {"text": "I should be able to\nsay, give me the ith one", "start": 936.2, "duration": 2.12}, {"text": "and represent that\nnumber i in a word.", "start": 938.32, "duration": 2.25}, {"text": "Otherwise-- because the machine\nis designed to only work", "start": 940.57, "duration": 2.67}, {"text": "with w-bit words\nin constant time,", "start": 943.24, "duration": 1.652}, {"text": "they'll want to be\nable to access the ith", "start": 944.892, "duration": 1.708}, {"text": "word in constant time,\nI need a word size", "start": 946.6, "duration": 2.32}, {"text": "that's at least log n just\nto address that and n things", "start": 948.92, "duration": 2.63}, {"text": "in my input.", "start": 951.55, "duration": 1.248}, {"text": "So this is a totally\nreasonable assumption.", "start": 952.798, "duration": 1.792}, {"text": "It may seem weird because\nyou think of a real machine", "start": 954.59, "duration": 2.208}, {"text": "as having constant\nsize, but a real machine", "start": 956.798, "duration": 2.402}, {"text": "has constant size RAM, also.", "start": 959.2, "duration": 2.19}, {"text": "My machine has 24 gigs\nof RAM, or whatever.", "start": 961.39, "duration": 3.06}, {"text": "That laptop has 8.", "start": 964.45, "duration": 1.32}, {"text": "But you don't think of\nthat as changing over time.", "start": 965.77, "duration": 2.797}, {"text": "But of course, if you want\nit to process a larger input,", "start": 968.567, "duration": 2.333}, {"text": "you would buy more RAM.", "start": 970.9, "duration": 1.59}, {"text": "So eventually, when our\nn's get really, really big,", "start": 972.49, "duration": 3.84}, {"text": "we're going to have\nto increase w just", "start": 976.33, "duration": 1.65}, {"text": "so we can address that RAM.", "start": 977.98, "duration": 2.5}, {"text": "That's the intuition here.", "start": 980.48, "duration": 1.87}, {"text": "But this is a way to\nbridge reality, which are", "start": 982.35, "duration": 2.87}, {"text": "fixed machines, with theory.", "start": 985.22, "duration": 2.29}, {"text": "In.", "start": 987.51, "duration": 0.5}, {"text": "Algorithms, we care about\nscalability for very large n.", "start": 988.01, "duration": 2.73}, {"text": "We want to know what that\ngrowth function is and ignore", "start": 990.74, "duration": 2.58}, {"text": "the lead constant factor.", "start": 993.32, "duration": 1.38}, {"text": "That's what asymptotic\nnotation is all about.", "start": 994.7, "duration": 2.71}, {"text": "And for that, we need a notion\nof word size also changing", "start": 997.41, "duration": 3.29}, {"text": "in this asymptotic way.", "start": 1000.7, "duration": 1.92}, {"text": "All right.", "start": 1002.62, "duration": 1.71}, {"text": "That would be more\nimportant next week,", "start": 1004.33, "duration": 1.89}, {"text": "when we talk about\nhashing and why hashing", "start": 1006.22, "duration": 2.4}, {"text": "is a reasonable thing to do.", "start": 1008.62, "duration": 3.26}, {"text": "But let's move on to\ndynamic sequences, which is", "start": 1011.88, "duration": 5.6}, {"text": "where things get interesting.", "start": 1017.48, "duration": 1.545}, {"text": "I have the update here.", "start": 1021.73, "duration": 2.58}, {"text": "We start with static sequences.", "start": 1024.31, "duration": 3.0}, {"text": "All of these\noperations are still", "start": 1027.31, "duration": 2.495}, {"text": "something we want to support\nin a dynamic sequence,", "start": 1029.805, "duration": 2.125}, {"text": "but we add two\ndynamic operations--", "start": 1031.93, "duration": 3.06}, {"text": "somewhat controversial\noperations, very exciting.", "start": 1034.99, "duration": 3.3}, {"text": "I want to be able to insert\nin the middle of my sequence", "start": 1038.29, "duration": 3.24}, {"text": "and I want to be able to delete\nfrom the middle of my sequence.", "start": 1041.53, "duration": 3.569}, {"text": "Here's my sequence, which I'm\ngoing to think of in a picture.", "start": 1045.099, "duration": 3.636}, {"text": "I'm going to draw\nit as an array.", "start": 1048.735, "duration": 1.375}, {"text": "But it's stored\nhowever it's stored.", "start": 1050.11, "duration": 1.53}, {"text": "We don't know.", "start": 1051.64, "duration": 0.9}, {"text": "This is an interface,\nnot an implementation.", "start": 1052.54, "duration": 1.99}, {"text": "So we have x 0, x 1, x 2, x 3.", "start": 1054.53, "duration": 4.13}, {"text": "And let's say I\ninsert at position 2.", "start": 1061.84, "duration": 5.1}, {"text": "Position 2 is here.", "start": 1066.94, "duration": 2.13}, {"text": "So I come in with\nmy new x, and I", "start": 1069.07, "duration": 2.73}, {"text": "would like x to be the\nnew x 2, but I don't", "start": 1071.8, "duration": 2.1}, {"text": "want to lose any information.", "start": 1073.9, "duration": 1.23}, {"text": "If I did set_at 2, then I\nwould erase this and replace it", "start": 1075.13, "duration": 3.54}, {"text": "with x.", "start": 1078.67, "duration": 0.763}, {"text": "But I want to do insert_at,\nwhich means all of these guys,", "start": 1079.433, "duration": 2.417}, {"text": "conceptually, are\ngoing to shift over", "start": 1081.85, "duration": 1.542}, {"text": "by 1 in terms of their indices.", "start": 1083.392, "duration": 2.358}, {"text": "Then, I would get this\npicture that's one bigger.", "start": 1085.75, "duration": 3.54}, {"text": "And now I've got the new x.", "start": 1093.51, "duration": 1.4}, {"text": "I've got what was the\nold x 2, which I don't--", "start": 1094.91, "duration": 3.93}, {"text": "I hesitate to call x 2 because\nthat's its old name, not", "start": 1098.84, "duration": 2.88}, {"text": "its new name.", "start": 1101.72, "duration": 0.61}, {"text": "I'm going to draw arrows to\nsay, these guys get copied over.", "start": 1102.33, "duration": 5.29}, {"text": "These ones are\ndefinitely unchanged.", "start": 1107.62, "duration": 2.58}, {"text": "Our new x 2, which\nprime is x This", "start": 1110.2, "duration": 4.02}, {"text": "is x3 prime, 4 prime, and so on.", "start": 1114.22, "duration": 4.5}, {"text": "I want to be careful here--\nand of course, the new n prime", "start": 1118.72, "duration": 4.05}, {"text": "is n plus 1.", "start": 1122.77, "duration": 1.2}, {"text": "I want to be careful about the\nlabeling, because the key--", "start": 1126.653, "duration": 2.417}, {"text": "what makes insert_at interesting\nis that, later, when I call", "start": 1129.07, "duration": 2.8}, {"text": "get_at, it's with\nthe new indexing.", "start": 1131.87, "duration": 2.81}, {"text": "So previously, if I did get_at\nat 2, I would get this value.", "start": 1134.68, "duration": 4.92}, {"text": "And afterwards, if\nI did get_at at 2,", "start": 1139.6, "duration": 1.827}, {"text": "I would get the new value.", "start": 1141.427, "duration": 1.083}, {"text": "If I did get_at\nat 3 down here, I", "start": 1142.51, "duration": 2.01}, {"text": "would get the value\nthat used to be X 2.", "start": 1144.52, "duration": 3.76}, {"text": "That's maybe hard to track.", "start": 1148.28, "duration": 1.61}, {"text": "But this is a conceptually\nvery useful thing", "start": 1149.89, "duration": 3.03}, {"text": "to do, especially when\nyou're inserting or deleting", "start": 1152.92, "duration": 3.42}, {"text": "at the ends.", "start": 1156.34, "duration": 1.33}, {"text": "So we're going to define, in\nparticular, insert and delete", "start": 1157.67, "duration": 8.82}, {"text": "first and last.", "start": 1166.49, "duration": 2.745}, {"text": "These are sometimes given--\nif you have an insert,", "start": 1173.27, "duration": 4.59}, {"text": "it has an x.", "start": 1177.86, "duration": 1.74}, {"text": "If you do a delete,\nit has no argument.", "start": 1179.6, "duration": 3.96}, {"text": "This means insert_at the\nbeginning of the array, which", "start": 1183.56, "duration": 2.97}, {"text": "would be like adding it here.", "start": 1186.53, "duration": 2.1}, {"text": "And insert_last means\nadding it on here.", "start": 1188.63, "duration": 3.48}, {"text": "insert_last doesn't\nchange the indices", "start": 1192.11, "duration": 1.74}, {"text": "of any of the old items.", "start": 1193.85, "duration": 1.18}, {"text": "That's a nice feature\nof insert_last.", "start": 1195.03, "duration": 1.542}, {"text": "Insert-first\nchanges all of them.", "start": 1196.572, "duration": 2.888}, {"text": "They all get incremented by 1.", "start": 1199.46, "duration": 3.0}, {"text": "And we're also interested\nin the similar things here.", "start": 1202.46, "duration": 3.06}, {"text": "We could do get-first or\n-last or set-first or -last,", "start": 1205.52, "duration": 17.03}, {"text": "which are the obvious special\ncases of get_at and set_at.", "start": 1222.55, "duration": 3.21}, {"text": "Now, these special\ncases are particularly", "start": 1225.76, "duration": 1.8}, {"text": "interesting in an\nalgorithms context.", "start": 1227.56, "duration": 2.048}, {"text": "If you were a mathematician,\nyou would say, well,", "start": 1229.608, "duration": 2.042}, {"text": "why do I even bother?", "start": 1231.65, "duration": 0.98}, {"text": "This is just shorthand for a\nparticular call to get or set.", "start": 1232.63, "duration": 4.92}, {"text": "But what makes it interesting\nfrom a data structures", "start": 1237.55, "duration": 2.79}, {"text": "perspective is that we care\nabout algorithms for supporting", "start": 1240.34, "duration": 3.03}, {"text": "these operations.", "start": 1243.37, "duration": 0.75}, {"text": "And maybe, the\nalgorithm for supporting", "start": 1244.12, "duration": 2.55}, {"text": "get-first or set-first, or in\nparticular, insert-first or", "start": 1246.67, "duration": 3.51}, {"text": "insert_last, might\nbe more efficient.", "start": 1250.18, "duration": 2.73}, {"text": "Maybe we can solve\nthis problem better", "start": 1252.91, "duration": 2.01}, {"text": "than we can solve insert_at.", "start": 1254.92, "duration": 1.89}, {"text": "So while, ideally,\nwe could solve", "start": 1256.81, "duration": 1.56}, {"text": "the entire dynamic sequence\ninterface constant time", "start": 1258.37, "duration": 2.85}, {"text": "preparation, that's\nnot actually possible.", "start": 1261.22, "duration": 1.83}, {"text": "You can prove that.", "start": 1263.05, "duration": 1.44}, {"text": "But special cases of\nit-- where we're just", "start": 1264.49, "duration": 1.86}, {"text": "inserting and leading from\nthe end, say-- we can do that.", "start": 1266.35, "duration": 3.84}, {"text": "That's why it's interesting to\nintroduce special cases that we", "start": 1270.19, "duration": 3.06}, {"text": "care about.", "start": 1273.25, "duration": 2.93}, {"text": "Cool.", "start": 1276.18, "duration": 0.51}, {"text": "That's the definition of the\ndynamic sequence interface.", "start": 1276.69, "duration": 2.677}, {"text": "Now, we're going to\nactually solve it.", "start": 1279.367, "duration": 1.583}, {"text": "Our first data structure for\nthis is called linked lists.", "start": 1287.83, "duration": 4.56}, {"text": "You've taken, probably-- you've\nprobably seen linked lists", "start": 1292.39, "duration": 7.42}, {"text": "before at some point.", "start": 1299.81, "duration": 1.33}, {"text": "But the main new\npart here is, we're", "start": 1301.14, "duration": 2.0}, {"text": "going to actually analyze them\nand see how efficiently they", "start": 1303.14, "duration": 3.51}, {"text": "implement all of these\noperations we might care about.", "start": 1306.65, "duration": 2.73}, {"text": "First, review.", "start": 1309.38, "duration": 1.35}, {"text": "What is a linked list?", "start": 1310.73, "duration": 1.89}, {"text": "We store our items\nin a bunch of nodes.", "start": 1312.62, "duration": 8.29}, {"text": "Each node has an item\nin it and a next field.", "start": 1332.47, "duration": 7.68}, {"text": "So you can think of\nthese as class objects", "start": 1340.15, "duration": 2.76}, {"text": "with two class variables, the\nitem and the next pointer.", "start": 1342.91, "duration": 5.43}, {"text": "And we assemble those into\nthis kind of structure", "start": 1348.34, "duration": 2.64}, {"text": "where we store--", "start": 1350.98, "duration": 1.38}, {"text": "in the item fields, we're going\nto store the actual values", "start": 1352.36, "duration": 3.57}, {"text": "that we want to represent\nin our sequence, x 0", "start": 1355.93, "duration": 2.37}, {"text": "through x n minus 1, in order.", "start": 1358.3, "duration": 3.39}, {"text": "And then we're going to use\nthe next pointers to link these", "start": 1361.69, "duration": 3.09}, {"text": "all together in that order.", "start": 1364.78, "duration": 1.81}, {"text": "So the next pointers are what\nactually give us the order.", "start": 1366.59, "duration": 2.39}, {"text": "And in addition, we're going\nto keep track of what's", "start": 1368.98, "duration": 2.34}, {"text": "called the head of the list.", "start": 1371.32, "duration": 2.52}, {"text": "The data structure is going\nto be represented by a head.", "start": 1373.84, "duration": 2.88}, {"text": "If you wanted to, you\ncould also store length.", "start": 1376.72, "duration": 3.793}, {"text": "This could be the\ndata structure itself.", "start": 1380.513, "duration": 1.667}, {"text": "And it's pointing to all of\nthese types of data structures.", "start": 1384.83, "duration": 3.18}, {"text": "Notice, we've just seen an\narray-based data structure,", "start": 1388.01, "duration": 2.68}, {"text": "which is just a static\narray, and we've", "start": 1390.69, "duration": 3.65}, {"text": "seen a pointer-based\ndata structure.", "start": 1394.34, "duration": 3.37}, {"text": "And we're relying on the fact\nthat pointers can be stored", "start": 1397.71, "duration": 4.47}, {"text": "in a single word, which means\nwe can de-reference them--", "start": 1402.18, "duration": 2.55}, {"text": "we can see what's on the\nother side of the pointer--", "start": 1404.73, "duration": 2.91}, {"text": "in constant time in\nour word RAM model.", "start": 1407.64, "duration": 3.06}, {"text": "In reality, each of these\nnodes is stored somewhere", "start": 1410.7, "duration": 3.63}, {"text": "in the array of the computer.", "start": 1414.33, "duration": 3.82}, {"text": "So maybe each one\nis two words long,", "start": 1418.15, "duration": 2.27}, {"text": "so maybe one node is--\nthe first node is here.", "start": 1420.42, "duration": 3.91}, {"text": "Maybe the second node is here.", "start": 1424.33, "duration": 1.25}, {"text": "The third node is here.", "start": 1425.58, "duration": 1.29}, {"text": "They're in some arbitrary order.", "start": 1426.87, "duration": 1.71}, {"text": "We're using this fact, that we\ncan allocate an array of size n", "start": 1428.58, "duration": 5.61}, {"text": "in linear time--\nin this case, we're", "start": 1434.19, "duration": 1.62}, {"text": "going to have arrays of size 2.", "start": 1435.81, "duration": 1.74}, {"text": "We can just say, oh, please\ngive me a new array of size 2.", "start": 1437.55, "duration": 3.25}, {"text": "And that will make us\none of these nodes.", "start": 1440.8, "duration": 5.03}, {"text": "And then we're storing pointers.", "start": 1445.83, "duration": 1.65}, {"text": "Pointers are just indices\ninto the giant memory array.", "start": 1447.48, "duration": 3.9}, {"text": "They're just, what is the\naddress of this little array?", "start": 1451.38, "duration": 3.582}, {"text": "If you've ever wondered how\npointers are implemented,", "start": 1454.962, "duration": 2.208}, {"text": "they're just numbers that\nsay where, in memory, is", "start": 1457.17, "duration": 3.03}, {"text": "this thing over here?", "start": 1460.2, "duration": 1.14}, {"text": "And in memory, they're\nin arbitrary order.", "start": 1461.34, "duration": 2.61}, {"text": "This is really nice because\nit's easy to manipulate", "start": 1463.95, "duration": 3.03}, {"text": "the order of a linked\nlist without actually", "start": 1466.98, "duration": 1.8}, {"text": "physically moving nodes around,\nwhereas arrays are problematic.", "start": 1468.78, "duration": 6.12}, {"text": "Maybe it's worth mentioning.", "start": 1474.9, "duration": 2.37}, {"text": "Let's start analyzing things.", "start": 1477.27, "duration": 1.53}, {"text": "So we care about these\ndynamic sequence operations.", "start": 1478.8, "duration": 4.17}, {"text": "And we could try to apply\nit to the static array data", "start": 1482.97, "duration": 4.17}, {"text": "structure, or we could try\nto implement these operations", "start": 1487.14, "duration": 5.46}, {"text": "in a static array.", "start": 1492.6, "duration": 1.35}, {"text": "It's possible, just not\ngoing to be very good.", "start": 1493.95, "duration": 3.78}, {"text": "And we can try to implement\nit with linked lists.", "start": 1497.73, "duration": 2.34}, {"text": "And it's also not\ngoing to be that great.", "start": 1500.07, "duration": 2.92}, {"text": "Let's go over here.", "start": 1502.99, "duration": 2.18}, {"text": "Our goal is the\nnext data structure,", "start": 1511.11, "duration": 2.17}, {"text": "which is dynamic arrays.", "start": 1513.28, "duration": 1.7}, {"text": "But linked lists and\nstatic arrays each", "start": 1514.98, "duration": 1.71}, {"text": "have their advantages.", "start": 1516.69, "duration": 1.44}, {"text": "Let's first analyze dynamic\nsequence operations,", "start": 1522.56, "duration": 11.17}, {"text": "first on a static array\nand then on a linked list.", "start": 1533.73, "duration": 7.71}, {"text": "On a static array,\nI think you all see,", "start": 1546.89, "duration": 3.63}, {"text": "if I try to insert at the\nbeginning of the static array--", "start": 1550.52, "duration": 3.69}, {"text": "that's kind of the worst case.", "start": 1554.21, "duration": 1.5}, {"text": "If I insert first, then\neverybody has to shift over.", "start": 1555.71, "duration": 4.26}, {"text": "If I'm going to\nmaintain this invariant,", "start": 1559.97, "duration": 1.95}, {"text": "that the ith item in\nthe array represents--", "start": 1561.92, "duration": 2.88}, {"text": "I guess I didn't write\nit anywhere here.", "start": 1564.8, "duration": 4.08}, {"text": "Maybe here.", "start": 1568.88, "duration": 0.9}, {"text": "Static array.", "start": 1574.61, "duration": 1.23}, {"text": "We're going to maintain\nthis invariant that a of i", "start": 1575.84, "duration": 2.37}, {"text": "represents x i.", "start": 1578.21, "duration": 1.155}, {"text": "If I want to maintain\nthat at all times, when", "start": 1582.05, "duration": 2.123}, {"text": "I insert a new\nthing in the front,", "start": 1584.173, "duration": 1.417}, {"text": "because the indices of all\nthe previous items change,", "start": 1585.59, "duration": 2.28}, {"text": "I have to spend time\nto copy those over.", "start": 1587.87, "duration": 2.28}, {"text": "You can do it in linear\ntime, but no better.", "start": 1590.15, "duration": 2.37}, {"text": "Static array.", "start": 1596.03, "duration": 3.12}, {"text": "Insert and delete anywhere\ncosts theta n time--", "start": 1599.15, "duration": 13.85}, {"text": "actually, for two reasons.", "start": 1615.87, "duration": 2.8}, {"text": "Reason number one is that,\nif we're near the front,", "start": 1618.67, "duration": 4.89}, {"text": "then we have to do shifting.", "start": 1623.56, "duration": 1.805}, {"text": "What about insert or delete\nthe last element of an array?", "start": 1627.96, "duration": 5.68}, {"text": "Is that any easier?", "start": 1633.64, "duration": 1.71}, {"text": "Because then, if I insert\nthe very last element,", "start": 1635.35, "duration": 2.49}, {"text": "none of the indices change.", "start": 1637.84, "duration": 1.21}, {"text": "I'm just adding a new element.", "start": 1639.05, "duration": 1.28}, {"text": "So I don't have to do shifting.", "start": 1644.158, "duration": 1.292}, {"text": "So can I do insert and\ndelete last in constant time", "start": 1648.62, "duration": 3.21}, {"text": "in a static array?", "start": 1651.83, "duration": 0.76}, {"text": "Yeah?", "start": 1656.92, "duration": 1.222}, {"text": "AUDIENCE: No, because\nthe size is constant.", "start": 1658.142, "duration": 1.953}, {"text": "ERIK DEMAINE: No, because\nthe size is constant.", "start": 1660.095, "duration": 1.958}, {"text": "So our model is that\nremember allocation model is", "start": 1662.053, "duration": 3.787}, {"text": "that we can allocate a\nstatic array of size em", "start": 1665.84, "duration": 4.5}, {"text": "but it's just a size\nn I can't just say", "start": 1670.34, "duration": 2.07}, {"text": "please make it bigger\nby 1 I need I need space", "start": 1672.41, "duration": 3.09}, {"text": "to store this extra element.", "start": 1675.5, "duration": 1.63}, {"text": "And if you think about where\nthings are in memory, when", "start": 1677.13, "duration": 3.02}, {"text": "you call to this\nmemory allocator, which", "start": 1680.15, "duration": 2.045}, {"text": "is part of your\noperating system,", "start": 1682.195, "duration": 1.375}, {"text": "you say, please give\nme a chunk of memory.", "start": 1683.57, "duration": 4.5}, {"text": "It's going to place them in\nvarious places in memory,", "start": 1688.07, "duration": 2.46}, {"text": "and some of them might\nbe next to each other.", "start": 1690.53, "duration": 2.45}, {"text": "So if I try to grow\nthis array by 1,", "start": 1692.98, "duration": 1.685}, {"text": "there might already\nbe something there.", "start": 1694.665, "duration": 1.625}, {"text": "And that's not possible\nwithout first shifting.", "start": 1696.29, "duration": 2.268}, {"text": "So even though, in\nthe array, I don't", "start": 1698.558, "duration": 1.542}, {"text": "have to do any\nshifting, in memory,", "start": 1700.1, "duration": 1.458}, {"text": "I might have to do shifting.", "start": 1701.558, "duration": 1.222}, {"text": "And that's outside the model.", "start": 1702.78, "duration": 1.542}, {"text": "So we're going to stick\nto this model of just--", "start": 1704.322, "duration": 1.958}, {"text": "you can allocate memory.", "start": 1706.28, "duration": 1.09}, {"text": "You can also de-allocate memory,\njust to keep space usage small.", "start": 1707.37, "duration": 4.16}, {"text": "But the only way\nto get more space", "start": 1711.53, "duration": 2.97}, {"text": "is to ask for a new array.", "start": 1714.5, "duration": 1.11}, {"text": "And that new array won't be\ncontiguous to your old one.", "start": 1715.61, "duration": 3.61}, {"text": "Question?", "start": 1719.22, "duration": 0.873}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1720.093, "duration": 1.972}, {"text": "ERIK DEMAINE: What\nis the dynamic array", "start": 1726.455, "duration": 1.625}, {"text": "will be the next topic, so\nmaybe we'll come back to that.", "start": 1728.08, "duration": 2.61}, {"text": "Yeah?", "start": 1730.69, "duration": 1.71}, {"text": "In a static array, you're just\nnot allowed to make it bigger.", "start": 1732.4, "duration": 2.94}, {"text": "And so you have to\nallocate a new array, which", "start": 1735.34, "duration": 5.16}, {"text": "we say takes linear time.", "start": 1740.5, "duration": 1.26}, {"text": "Even if allocating the new\narray didn't take linear time,", "start": 1741.76, "duration": 3.33}, {"text": "you have to copy all\nthe elements over", "start": 1745.09, "duration": 2.213}, {"text": "from the old array\nto the new one.", "start": 1747.303, "duration": 1.417}, {"text": "Then you can throw\naway the old one.", "start": 1748.72, "duration": 3.75}, {"text": "Just the copying\nfrom an array of size", "start": 1752.47, "duration": 2.22}, {"text": "n to an array of size n plus\n1, that will take linear time.", "start": 1754.69, "duration": 2.95}, {"text": "So static arrays are really\nbad for dynamic operations--", "start": 1757.64, "duration": 3.38}, {"text": "no surprise.", "start": 1761.02, "duration": 0.66}, {"text": "But you could do them.", "start": 1761.68, "duration": 2.29}, {"text": "That's static array.", "start": 1763.97, "duration": 2.03}, {"text": "Now, linked lists are going\nto be almost the opposite--", "start": 1766.0, "duration": 3.96}, {"text": "well, almost.", "start": 1769.96, "duration": 3.36}, {"text": "If we store the length, OK,\nwe can compute the length", "start": 1773.32, "duration": 3.18}, {"text": "of the array very quickly.", "start": 1776.5, "duration": 2.97}, {"text": "We can insert and delete at\nthe front really efficiently.", "start": 1779.47, "duration": 5.04}, {"text": "If I want to add a new item as\na new first item, then what do?", "start": 1784.51, "duration": 6.57}, {"text": "I do I allocate a new\nnode, which I'll call x.", "start": 1791.08, "duration": 3.51}, {"text": "This is insert-first of x.", "start": 1794.59, "duration": 6.47}, {"text": "I'll allocate a new\narray of size 2.", "start": 1801.06, "duration": 2.75}, {"text": "I'm going to change--", "start": 1803.81, "duration": 1.51}, {"text": "let me do it in red.", "start": 1805.32, "duration": 2.79}, {"text": "I'm going to change\nthis head pointer.", "start": 1808.11, "duration": 2.97}, {"text": "Maybe I should do that later.", "start": 1811.08, "duration": 2.46}, {"text": "I'm going to set the next\npointer here to this one,", "start": 1813.54, "duration": 2.857}, {"text": "and then I'm going\nto change this head", "start": 1816.397, "duration": 1.583}, {"text": "pointer to point to here.", "start": 1817.98, "duration": 2.7}, {"text": "And, boom, now I've\ngot a linked list.", "start": 1820.68, "duration": 2.41}, {"text": "Again, we don't know anything\nabout the order and memory", "start": 1823.09, "duration": 2.51}, {"text": "of these lists.", "start": 1825.6, "duration": 1.092}, {"text": "We just care about\nthe order that's", "start": 1826.692, "duration": 1.458}, {"text": "represented implicitly\nby following", "start": 1828.15, "duration": 1.71}, {"text": "the next pointers repeatedly.", "start": 1829.86, "duration": 2.84}, {"text": "Now, I've got a new list that\nhas x in front, and then x 0,", "start": 1832.7, "duration": 3.12}, {"text": "and then x 1, and so on.", "start": 1835.82, "duration": 1.63}, {"text": "So insert- and delete_first,\nat least are really efficient.", "start": 1837.45, "duration": 3.595}, {"text": "We won't get much\nmore than that,", "start": 1841.045, "duration": 1.375}, {"text": "but the linked list, insert- and\ndelete_first are constant time.", "start": 1842.42, "duration": 12.59}, {"text": "So that's cool.", "start": 1860.35, "duration": 2.68}, {"text": "However, everything else\nis going to be slow.", "start": 1863.03, "duration": 2.09}, {"text": "If I want to get the 10th\nitem in a linked list,", "start": 1865.12, "duration": 5.37}, {"text": "I have to follow these\npointers 10 times.", "start": 1870.49, "duration": 3.0}, {"text": "I go 0, 1, 2, 3, and so on.", "start": 1873.49, "duration": 4.02}, {"text": "Follow 10 next pointers\nand I'll get the 10th item.", "start": 1877.51, "duration": 3.42}, {"text": "Accessing the ith item is\ngoing to take order i time.", "start": 1880.93, "duration": 2.55}, {"text": "Get- and set_at need i time,\nwhich, in the worst case,", "start": 1889.09, "duration": 11.41}, {"text": "is theta n.", "start": 1900.5, "duration": 0.72}, {"text": "We have sort of complementary\ndata structures here.", "start": 1908.83, "duration": 2.5}, {"text": "On the one hand, a static\narray can do constant time", "start": 1911.33, "duration": 3.14}, {"text": "get_at/set_at.", "start": 1914.47, "duration": 0.98}, {"text": "So it's very fast at\nthe random access aspect", "start": 1915.45, "duration": 2.26}, {"text": "because it's an array.", "start": 1917.71, "duration": 1.44}, {"text": "Linked lists are very\nbad at random access,", "start": 1919.15, "duration": 2.32}, {"text": "but they're better\nat being dynamic.", "start": 1921.47, "duration": 2.69}, {"text": "We can insert and delete--\nat the beginning, at least--", "start": 1924.16, "duration": 2.46}, {"text": "in constant time.", "start": 1926.62, "duration": 2.34}, {"text": "Now, if we want to\nactually insert and delete", "start": 1928.96, "duration": 2.28}, {"text": "at a particular position,\nthat's still hard,", "start": 1931.24, "duration": 2.43}, {"text": "because we have to\nwalk to that position.", "start": 1933.67, "duration": 1.95}, {"text": "Even inserting and leading\nat the end of the list", "start": 1935.62, "duration": 2.19}, {"text": "is hard, although\nthat's fixable.", "start": 1937.81, "duration": 2.625}, {"text": "And maybe I'll leave that for\nproblem session or problem set.", "start": 1943.15, "duration": 3.54}, {"text": "But an easy-- here's\na small puzzle.", "start": 1946.69, "duration": 4.48}, {"text": "Suppose you wanted\nto solve get-last", "start": 1951.17, "duration": 4.5}, {"text": "efficiently in a linked list.", "start": 1955.67, "duration": 3.12}, {"text": "How would you solve\nthat in constant time?", "start": 1958.79, "duration": 1.92}, {"text": "Yeah?", "start": 1963.53, "duration": 0.602}, {"text": "AUDIENCE: Doubly linked list.", "start": 1964.132, "duration": 1.208}, {"text": "ERIK DEMAINE:\nDoubly linked list.", "start": 1965.34, "duration": 1.375}, {"text": "It's a good idea, but\nactually not the right answer.", "start": 1966.715, "duration": 2.735}, {"text": "That's an answer to the\nnext question I might ask.", "start": 1969.45, "duration": 2.58}, {"text": "Yeah?", "start": 1972.03, "duration": 0.861}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1972.891, "duration": 2.759}, {"text": "ERIK DEMAINE: [INAUDIBLE]\npointer to the last element.", "start": 1975.65, "duration": 2.25}, {"text": "That's all we need here.", "start": 1977.9, "duration": 1.5}, {"text": "And often, a doubly\nlinked list has this.", "start": 1979.4, "duration": 3.75}, {"text": "They usually call this\nthe tail-- head and tail.", "start": 1983.15, "duration": 3.07}, {"text": "And if we always just store\na pointer to the last list--", "start": 1986.22, "duration": 3.5}, {"text": "this is what we call data\nstructure augmentation,", "start": 1989.72, "duration": 2.67}, {"text": "where we add some extra\ninformation to the data", "start": 1992.39, "duration": 2.07}, {"text": "structure and--", "start": 1994.46, "duration": 0.96}, {"text": "we have to keep it up\nto date all the time.", "start": 1995.42, "duration": 2.74}, {"text": "So if we do an\ninsert_last or something,", "start": 1998.16, "duration": 2.24}, {"text": "insert_last also becomes\neasy because I can just", "start": 2000.4, "duration": 2.52}, {"text": "add a new node here and\nupdate the pointer here.", "start": 2002.92, "duration": 3.03}, {"text": "delete_last is trickier.", "start": 2005.95, "duration": 1.32}, {"text": "That's where you get\na doubly linked list.", "start": 2007.27, "duration": 2.43}, {"text": "But whenever I add something\nto the end of this list,", "start": 2009.7, "duration": 2.43}, {"text": "I have to update the\ntail pointer also.", "start": 2012.13, "duration": 2.31}, {"text": "As long as I maintain this,\nnow, suddenly get-last", "start": 2014.44, "duration": 2.4}, {"text": "is fast in constant time.", "start": 2016.84, "duration": 1.357}, {"text": "So linked lists are great if\nyou're working on the ends,", "start": 2018.197, "duration": 2.333}, {"text": "even dynamically.", "start": 2020.53, "duration": 1.53}, {"text": "Arrays are great if you're\ndoing random access and nothing", "start": 2022.06, "duration": 2.88}, {"text": "dynamic--", "start": 2024.94, "duration": 0.58}, {"text": "nothing adding or deleting\nat the ends or in the middle.", "start": 2025.52, "duration": 2.93}, {"text": "Our final goal for\ntoday is to get", "start": 2031.27, "duration": 2.94}, {"text": "sort of the best of both\nworlds with dynamic arrays.", "start": 2034.21, "duration": 2.64}, {"text": "We're going to try to get\nall of the good running times", "start": 2036.85, "duration": 3.118}, {"text": "of linked lists and all\nof the good running times", "start": 2039.968, "duration": 2.042}, {"text": "of static arrays.", "start": 2042.01, "duration": 1.318}, {"text": "We won't get quite all of\nthem, but most of them.", "start": 2043.328, "duration": 2.042}, {"text": "And in some sense,\nanother way to describe", "start": 2052.06, "duration": 7.92}, {"text": "what these introductory\nlectures are about", "start": 2059.98, "duration": 3.09}, {"text": "is telling you about how\nPython is implemented.", "start": 2063.07, "duration": 3.899}, {"text": "What we're going to talk\nabout next, dynamic arrays,", "start": 2066.969, "duration": 4.17}, {"text": "I've alluded to many times.", "start": 2071.139, "duration": 1.951}, {"text": "But these are what\nPython calls lists.", "start": 2073.09, "duration": 4.77}, {"text": "You don't have to implement\na dynamic array by hand", "start": 2083.3, "duration": 2.91}, {"text": "because it's already built\ninto many fancy new languages", "start": 2086.21, "duration": 4.529}, {"text": "for free, because\nthey're so darn useful.", "start": 2090.739, "duration": 2.821}, {"text": "This lecture is about how\nthese are actually implemented", "start": 2093.56, "duration": 2.579}, {"text": "and why they're efficient.", "start": 2096.139, "duration": 2.941}, {"text": "And in recitation\nnodes, you'll see", "start": 2099.08, "duration": 1.742}, {"text": "how to actually\nimplement them if all you", "start": 2100.822, "duration": 1.708}, {"text": "had were static arrays.", "start": 2102.53, "duration": 1.89}, {"text": "But luckily, we\nhave dynamic arrays,", "start": 2104.42, "duration": 1.71}, {"text": "so we don't have to\nactually implement them.", "start": 2106.13, "duration": 2.28}, {"text": "But inside the\nPython interpreter,", "start": 2108.41, "duration": 3.07}, {"text": "this is exactly\nwhat's happening.", "start": 2111.48, "duration": 3.02}, {"text": "The idea is to relax\nthe constraint--", "start": 2114.5, "duration": 8.7}, {"text": "or the invariant, whatever--", "start": 2123.2, "duration": 1.95}, {"text": "that the size of\nthe array we use", "start": 2125.15, "duration": 5.19}, {"text": "equals n, which is the number\nof items in the sequence.", "start": 2130.34, "duration": 6.81}, {"text": "Remember, in the\nsequence problem,", "start": 2140.773, "duration": 1.417}, {"text": "we're supposed to\nrepresent n items.", "start": 2142.19, "duration": 2.37}, {"text": "With a static array, we\nallocated an array of size", "start": 2144.56, "duration": 2.46}, {"text": "exactly n.", "start": 2147.02, "duration": 1.71}, {"text": "So let's relax that.", "start": 2148.73, "duration": 1.05}, {"text": "Let's not make it exactly n.", "start": 2149.78, "duration": 1.62}, {"text": "Let's make it roughly n.", "start": 2151.4, "duration": 2.7}, {"text": "How roughly, you can\nthink about for a while.", "start": 2154.1, "duration": 2.79}, {"text": "But from an algorithms\nperspective,", "start": 2156.89, "duration": 2.91}, {"text": "usually, when we say\nroughly, we mean throw away", "start": 2159.8, "duration": 2.61}, {"text": "constant factors.", "start": 2162.41, "duration": 0.81}, {"text": "And that turns out to be\nthe right answer here.", "start": 2163.22, "duration": 1.35}, {"text": "It's not always\nthe right answer.", "start": 2164.57, "duration": 1.47}, {"text": "But we're going to enforce\nthat the size of the array", "start": 2166.04, "duration": 5.94}, {"text": "is theta n--", "start": 2171.98, "duration": 2.25}, {"text": "probably also greater\nthan or equal to n.", "start": 2174.23, "duration": 1.71}, {"text": "0.5 n would not be very helpful.", "start": 2175.94, "duration": 2.26}, {"text": "So it's going to be\nat least n, and it's", "start": 2178.2, "duration": 3.17}, {"text": "going to be at most\nsome constant times n.", "start": 2181.37, "duration": 4.06}, {"text": "2n, 10n, 1.1 times n.", "start": 2185.43, "duration": 2.795}, {"text": "Any of these\nconstants will work.", "start": 2188.225, "duration": 1.375}, {"text": "I'm going to use 2n here, but\nthere are lots of options.", "start": 2189.6, "duration": 3.24}, {"text": "And now, things\nalmost work for free.", "start": 2195.43, "duration": 3.31}, {"text": "There's going to be\none subtlety here.", "start": 2198.74, "duration": 2.83}, {"text": "And I'm going to focus on--", "start": 2201.57, "duration": 2.74}, {"text": "we're still going to maintain\nthat the ith item of the array", "start": 2204.31, "duration": 6.68}, {"text": "represents x i.", "start": 2210.99, "duration": 3.47}, {"text": "This data structure--\nlet me draw a picture.", "start": 2214.46, "duration": 3.78}, {"text": "We've got an array of some size.", "start": 2218.24, "duration": 1.89}, {"text": "The first few items are\nused to store the sequence.", "start": 2220.13, "duration": 7.72}, {"text": "But then, there's going to be\nsome blank ones at the end.", "start": 2227.85, "duration": 3.72}, {"text": "Maybe we'll keep track of this--", "start": 2231.57, "duration": 1.87}, {"text": "so the data structure itself is\ngoing to have an array and it's", "start": 2233.44, "duration": 3.2}, {"text": "going to have a length.", "start": 2236.64, "duration": 2.46}, {"text": "Something like this.", "start": 2239.1, "duration": 1.055}, {"text": "We're also going to keep\ntrack of the length.", "start": 2240.155, "duration": 1.875}, {"text": "So we know that the\nfirst length items", "start": 2242.03, "duration": 2.47}, {"text": "are where the data is, and\nthe remainder are meaningless.", "start": 2244.5, "duration": 6.0}, {"text": "So now, if I want to go and do\nan insert_last, what do I do?", "start": 2250.5, "duration": 9.26}, {"text": "I just go to a of\nlength and set it to x.", "start": 2259.76, "duration": 3.83}, {"text": "And then I increment length.", "start": 2268.48, "duration": 3.72}, {"text": "Boom.", "start": 2272.2, "duration": 0.5}, {"text": "Easy.", "start": 2272.7, "duration": 0.5}, {"text": "Constant time.", "start": 2273.2, "duration": 0.65}, {"text": "Yeah?", "start": 2273.85, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2274.35, "duration": 2.42}, {"text": "ERIK DEMAINE: How do\nyou have enough room.", "start": 2276.77, "duration": 1.75}, {"text": "Indeed, I don't.", "start": 2278.52, "duration": 0.87}, {"text": "This was an incorrect algorithm.", "start": 2279.39, "duration": 2.13}, {"text": "But it's usually correct.", "start": 2281.52, "duration": 1.59}, {"text": "As long as I have\nextra space, this", "start": 2283.11, "duration": 1.65}, {"text": "is all I need to\ndo for insert_last.", "start": 2284.76, "duration": 3.24}, {"text": "But I am also going to\nstore the size of the array.", "start": 2288.0, "duration": 6.1}, {"text": "This is the actual--", "start": 2294.1, "duration": 1.4}, {"text": "this whole thing is size,\nand this part is length.", "start": 2295.5, "duration": 7.36}, {"text": "Length is always going to be\nless than or equal to size.", "start": 2302.86, "duration": 3.78}, {"text": "And so there's a problem.", "start": 2306.64, "duration": 1.23}, {"text": "If length equals size, then\nI don't have any space.", "start": 2307.87, "duration": 3.42}, {"text": "Just add to end\nunless n equals size.", "start": 2316.04, "duration": 12.03}, {"text": "I'm using n length\nfor the same thing.", "start": 2328.07, "duration": 3.88}, {"text": "So length here is the same as n.", "start": 2331.95, "duration": 3.91}, {"text": "That's our actual\nnumber of things", "start": 2335.86, "duration": 1.65}, {"text": "we're trying to represent.", "start": 2337.51, "duration": 1.69}, {"text": "And size-- this is great.", "start": 2339.2, "duration": 1.46}, {"text": "This is the interface size.", "start": 2340.66, "duration": 2.645}, {"text": "This is what we're\ntrying to represent.", "start": 2343.305, "duration": 1.625}, {"text": "And this is the\nrepresentation size.", "start": 2344.93, "duration": 2.99}, {"text": "This is the size of my array.", "start": 2347.92, "duration": 1.235}, {"text": "These are the\nnumber of items I'm", "start": 2349.155, "duration": 1.375}, {"text": "trying to store in that array.", "start": 2350.53, "duration": 1.69}, {"text": "This is the interface\nversus data structure.", "start": 2352.22, "duration": 2.055}, {"text": "Here's the interface.", "start": 2354.275, "duration": 0.875}, {"text": "Here's the data structure.", "start": 2355.15, "duration": 2.01}, {"text": "OK, cool.", "start": 2357.16, "duration": 1.52}, {"text": "What do I do in the\ncase when n equals size?", "start": 2362.56, "duration": 2.835}, {"text": "I'm going to have to\nmake my array bigger.", "start": 2373.28, "duration": 2.83}, {"text": "This should sound just\nlike static arrays.", "start": 2376.11, "duration": 3.965}, {"text": "For static arrays, we made\nour array bigger every time", "start": 2380.075, "duration": 2.925}, {"text": "we inserted.", "start": 2383.0, "duration": 1.23}, {"text": "And that was this linear\ncost of allocation.", "start": 2384.23, "duration": 5.19}, {"text": "We're going to do\nthat sometimes.", "start": 2389.42, "duration": 1.47}, {"text": "With static arrays, we had\nto do it every single time,", "start": 2390.89, "duration": 2.25}, {"text": "because size equaled n.", "start": 2393.14, "duration": 2.31}, {"text": "Now, we have some flexibility.", "start": 2395.45, "duration": 1.47}, {"text": "We're only going\nto do it sometimes.", "start": 2396.92, "duration": 2.86}, {"text": "It's like, cookies are a\nsometimes food, apparently,", "start": 2399.78, "duration": 3.99}, {"text": "according to modern\nCookie Monster.", "start": 2403.77, "duration": 2.76}, {"text": "I don't understand.", "start": 2406.53, "duration": 1.33}, {"text": "But if n equals\nsize, we're going", "start": 2407.86, "duration": 4.61}, {"text": "to allocate a new\narray of size--", "start": 2412.47, "duration": 13.155}, {"text": "any suggestions?", "start": 2430.19, "duration": 0.87}, {"text": "AUDIENCE: Bigger.", "start": 2431.06, "duration": 0.955}, {"text": "ERIK DEMAINE: Bigger.", "start": 2432.015, "duration": 0.875}, {"text": "I like it.", "start": 2432.89, "duration": 0.87}, {"text": "Greater than size.", "start": 2433.76, "duration": 1.98}, {"text": "How much bigger?", "start": 2435.74, "duration": 1.05}, {"text": "AUDIENCE: Twice.", "start": 2436.79, "duration": 1.76}, {"text": "ERIK DEMAINE: Twice.", "start": 2438.55, "duration": 1.453}, {"text": "JASON KU: Five things.", "start": 2440.003, "duration": 0.917}, {"text": "ERIK DEMAINE: Five things.", "start": 2440.92, "duration": 2.1}, {"text": "Size plus 5?", "start": 2443.02, "duration": 1.62}, {"text": "Come on, Jason.", "start": 2444.64, "duration": 2.46}, {"text": "Trolling me.", "start": 2447.1, "duration": 1.6}, {"text": "All right.", "start": 2448.7, "duration": 0.5}, {"text": "There are a couple of\nnatural choices here.", "start": 2449.2, "duration": 2.29}, {"text": "One is a constant factor larger.", "start": 2451.49, "duration": 1.76}, {"text": "You could use 1.1, or\n1.01, or two, or 5, or 10.", "start": 2453.25, "duration": 4.29}, {"text": "They will all work.", "start": 2457.54, "duration": 1.32}, {"text": "Or you could use Jason's\ntrolling answer of size", "start": 2458.86, "duration": 3.57}, {"text": "plus a constant, like 5.", "start": 2462.43, "duration": 3.99}, {"text": "Why is this bad?", "start": 2466.42, "duration": 0.9}, {"text": "Yeah?", "start": 2470.39, "duration": 0.5}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2470.89, "duration": 2.4}, {"text": "ERIK DEMAINE: You'll\nhave to do it again.", "start": 2478.072, "duration": 1.708}, {"text": "You'll have to\nresize frequently.", "start": 2479.78, "duration": 2.28}, {"text": "When?", "start": 2482.06, "duration": 0.87}, {"text": "Five steps later.", "start": 2482.93, "duration": 2.67}, {"text": "In the original\nstatic array, we were", "start": 2485.6, "duration": 1.59}, {"text": "reallocating every single time.", "start": 2487.19, "duration": 2.22}, {"text": "That's like n plus 1.", "start": 2489.41, "duration": 1.56}, {"text": "If we do n plus 5, that\nreally doesn't change things", "start": 2490.97, "duration": 2.37}, {"text": "if we ignore constant factors.", "start": 2493.34, "duration": 1.62}, {"text": "Now, we'll have to spend linear\ntime every five steps instead", "start": 2494.96, "duration": 2.88}, {"text": "of linear time every one step.", "start": 2497.84, "duration": 1.65}, {"text": "That's still linear time\nper operation, just,", "start": 2499.49, "duration": 2.76}, {"text": "we're changing the\nconstant factor.", "start": 2502.25, "duration": 2.46}, {"text": "Whereas 2 times\nsize, well, now we", "start": 2504.71, "duration": 2.1}, {"text": "have to think a\nlittle bit harder.", "start": 2506.81, "duration": 2.53}, {"text": "Let's just think\nabout the case where", "start": 2509.34, "duration": 2.03}, {"text": "we're inserting at\nthe end of an array.", "start": 2511.37, "duration": 3.0}, {"text": "Let's say we do n insert_lasts\nfrom an empty array.", "start": 2514.37, "duration": 11.1}, {"text": "When do we resize?", "start": 2532.01, "duration": 1.26}, {"text": "Well, at the beginning--", "start": 2533.27, "duration": 1.575}, {"text": "I guess I didn't say what\nwe do for an empty array.", "start": 2534.845, "duration": 2.125}, {"text": "Let's say size equals 1.", "start": 2536.97, "duration": 1.7}, {"text": "We can insert one item for free.", "start": 2538.67, "duration": 1.65}, {"text": "As soon as we insert the second\nitem, then we have to resize.", "start": 2540.32, "duration": 3.18}, {"text": "That seems bad.", "start": 2543.5, "duration": 0.96}, {"text": "Immediately, we have to resize.", "start": 2544.46, "duration": 1.62}, {"text": "Then we insert the third item.", "start": 2546.08, "duration": 1.47}, {"text": "OK, now let's draw a picture.", "start": 2547.55, "duration": 2.56}, {"text": "So we start with one item.", "start": 2550.11, "duration": 1.22}, {"text": "We fill it up.", "start": 2551.33, "duration": 1.93}, {"text": "Then, we grow to size 2,\nbecause that's twice 1.", "start": 2553.26, "duration": 3.74}, {"text": "Then we fill it up.", "start": 2557.0, "duration": 0.96}, {"text": "Immediately, we have\nto resize again.", "start": 2557.96, "duration": 1.56}, {"text": "But now we start to\nget some benefit.", "start": 2559.52, "duration": 1.77}, {"text": "Now, we have size 4, and\nso we can insert two items", "start": 2561.29, "duration": 3.81}, {"text": "before we have to resize.", "start": 2565.1, "duration": 1.77}, {"text": "And now, we're\nsize 8, and we get", "start": 2566.87, "duration": 3.87}, {"text": "to insert four items\nbefore we refill.", "start": 2570.74, "duration": 4.77}, {"text": "This is going to resize--", "start": 2575.51, "duration": 2.46}, {"text": "and again, resizes\nare expensive both", "start": 2577.97, "duration": 2.22}, {"text": "because we have to pay to\nallocate the new array--", "start": 2580.19, "duration": 2.43}, {"text": "I drew it as just extending\nit, but in fact, we're", "start": 2582.62, "duration": 2.27}, {"text": "creating a whole\nnew array, and then", "start": 2584.89, "duration": 1.84}, {"text": "we have to copy all\nof the items over.", "start": 2586.73, "duration": 2.563}, {"text": "So there's the allocation cost\nand then the copying costs.", "start": 2589.293, "duration": 2.417}, {"text": "It's linear either way.", "start": 2591.71, "duration": 1.89}, {"text": "But we're going to resize\nat n equals 1, 2, 4, 8,", "start": 2593.6, "duration": 6.9}, {"text": "16-- you know this sequence.", "start": 2600.5, "duration": 1.68}, {"text": "All the powers of 2,\nbecause we're doubling.", "start": 2602.18, "duration": 3.0}, {"text": "That is exactly powers of 2.", "start": 2605.18, "duration": 3.06}, {"text": "So we pay a linear cost.", "start": 2608.24, "duration": 3.45}, {"text": "This resize cost, the\nallocation and the copying,", "start": 2611.69, "duration": 5.46}, {"text": "is going to be-- it's\nlinear each time.", "start": 2617.15, "duration": 2.92}, {"text": "So it's 1 plus 2 plus\n4 plus 8 plus 16.", "start": 2620.07, "duration": 6.41}, {"text": "Really, I should write\nthis as sum from i", "start": 2626.48, "duration": 4.59}, {"text": "equals 1 to roughly log n.", "start": 2631.07, "duration": 2.61}, {"text": "Log base 2 of n is\nlG of 2 to the i.", "start": 2633.68, "duration": 4.59}, {"text": "If you want a terminus\nhere, it's roughly n.", "start": 2641.16, "duration": 3.54}, {"text": "It's actually the next--", "start": 2644.7, "duration": 1.44}, {"text": "the previous power of\n2 of n, or something.", "start": 2646.14, "duration": 2.97}, {"text": "But that won't matter.", "start": 2649.11, "duration": 1.077}, {"text": "That will just affect\nthings by a constant factor.", "start": 2650.187, "duration": 2.083}, {"text": "What is the sum of 2 to the i?", "start": 2652.27, "duration": 4.24}, {"text": "This is a geometric series.", "start": 2656.51, "duration": 2.282}, {"text": "Anyone know the answer?", "start": 2658.792, "duration": 0.958}, {"text": "Yeah?", "start": 2665.69, "duration": 0.835}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2666.525, "duration": 2.855}, {"text": "ERIK DEMAINE: 2 to the\ntop limit plus 1 minus 1.", "start": 2669.38, "duration": 4.42}, {"text": "Yeah.", "start": 2673.8, "duration": 0.5}, {"text": "So this is the identity.", "start": 2674.3, "duration": 2.22}, {"text": "Sum of 2 to the i from i equals\n1 to k is 2 to the k plus 1,", "start": 2676.52, "duration": 9.24}, {"text": "plus 1 minus 1.", "start": 2685.76, "duration": 2.07}, {"text": "So the plus 1 is upstairs.", "start": 2687.83, "duration": 1.293}, {"text": "The minus one is downstairs.", "start": 2689.123, "duration": 1.167}, {"text": "An easy way to remember this\nis if you think in binary--", "start": 2690.29, "duration": 3.0}, {"text": "as we all should.", "start": 2693.29, "duration": 0.93}, {"text": "We're computer scientists.", "start": 2694.22, "duration": 1.65}, {"text": "2 to the i means you\nset the ith bit to 1.", "start": 2695.87, "duration": 4.98}, {"text": "Here's a bit string.", "start": 2700.85, "duration": 1.44}, {"text": "This is the ith bit.", "start": 2702.29, "duration": 0.96}, {"text": "This is 2 to the i.", "start": 2703.25, "duration": 1.23}, {"text": "0 is down here.", "start": 2704.48, "duration": 1.47}, {"text": "If I sum them all up, what that\nmeans is, I'm putting 1s here.", "start": 2705.95, "duration": 5.55}, {"text": "And if you think about what this\nmeans, this is up to k from 0--", "start": 2711.5, "duration": 4.32}, {"text": "sorry, I should\ndo 0 to be proper.", "start": 2715.82, "duration": 3.93}, {"text": "If I write-- that's\nthe left-hand side.", "start": 2719.75, "duration": 3.36}, {"text": "The right-hand side is 2 to the\nk plus 1, which is a 1 here,", "start": 2723.11, "duration": 4.59}, {"text": "and the rest 0s.", "start": 2727.7, "duration": 2.4}, {"text": "So if you know your\nbinary arithmetic,", "start": 2730.1, "duration": 1.8}, {"text": "you subtract-- if you add\n1 to this, you get this.", "start": 2731.9, "duration": 2.43}, {"text": "Or if you subtract 1\nfrom this, you get this.", "start": 2734.33, "duration": 2.34}, {"text": "This is why this identity holds.", "start": 2736.67, "duration": 2.94}, {"text": "Or the higher-level\nthing is to say, oh,", "start": 2739.61, "duration": 2.43}, {"text": "this is a geometric series.", "start": 2742.04, "duration": 2.08}, {"text": "So I know-- you\nshould know this.", "start": 2744.12, "duration": 2.3}, {"text": "I'm telling you now.", "start": 2746.42, "duration": 1.02}, {"text": "Geometric series are dominated\nby the last term-- the biggest", "start": 2747.44, "duration": 3.55}, {"text": "term.", "start": 2750.99, "duration": 0.5}, {"text": "If you have any series you can\nidentify as geometric, which", "start": 2751.49, "duration": 2.458}, {"text": "means it's growing at\nleast exponentially,", "start": 2753.948, "duration": 2.432}, {"text": "then in terms of\ntheta notation, you", "start": 2756.38, "duration": 2.755}, {"text": "can just look at the last term\nand put a theta around it,", "start": 2759.135, "duration": 2.375}, {"text": "and you're done.", "start": 2761.51, "duration": 1.54}, {"text": "So this is theta\nof the last term,", "start": 2763.05, "duration": 2.24}, {"text": "like 2 to the log\nn, which is theta n.", "start": 2765.29, "duration": 4.05}, {"text": "Cool.", "start": 2772.92, "duration": 1.11}, {"text": "Linear time.", "start": 2774.03, "duration": 1.68}, {"text": "Linear time for all\nof my operations.", "start": 2775.71, "duration": 2.43}, {"text": "I'm doing n operations here,\nand I spent linear total time", "start": 2778.14, "duration": 3.66}, {"text": "to do all of the resizing.", "start": 2781.8, "duration": 2.22}, {"text": "That's good.", "start": 2784.02, "duration": 0.6}, {"text": "That's like constant\neach, kind of.", "start": 2784.62, "duration": 3.781}, {"text": "The \"kind of\" is\nan important notion", "start": 2788.401, "duration": 3.449}, {"text": "which we call amortization.", "start": 2791.85, "duration": 4.14}, {"text": "I want to say an\noperation takes t of n", "start": 2805.36, "duration": 10.2}, {"text": "amortized time if, let's say,\nany k of those operations", "start": 2815.56, "duration": 17.98}, {"text": "take, at most, k\ntimes t of n time.", "start": 2833.54, "duration": 6.25}, {"text": "This is a little bit\nsloppy, but be good enough.", "start": 2839.79, "duration": 3.29}, {"text": "The idea is here, if\nthis works for n or k,", "start": 2843.08, "duration": 3.03}, {"text": "to do n operations from\nan empty array here", "start": 2846.11, "duration": 3.06}, {"text": "takes linear time,\nwhich means I would", "start": 2849.17, "duration": 4.11}, {"text": "call this constant amortized.", "start": 2853.28, "duration": 3.39}, {"text": "Amortized means a particular\nkind of averaging--", "start": 2856.67, "duration": 5.72}, {"text": "averaging over the\nsequence of operations.", "start": 2862.39, "duration": 2.32}, {"text": "So while individual\noperations will be expensive,", "start": 2864.71, "duration": 2.48}, {"text": "one near the end, when I\nhave to resize the array,", "start": 2867.19, "duration": 2.79}, {"text": "is going to take linear time\njust for that one operation.", "start": 2869.98, "duration": 2.85}, {"text": "But most of the\noperations are cheap.", "start": 2872.83, "duration": 1.6}, {"text": "Most of them are constant.", "start": 2874.43, "duration": 1.68}, {"text": "So I can think of\ncharging that high cost", "start": 2876.11, "duration": 4.4}, {"text": "to all of the other operations\nthat made it happen.", "start": 2880.51, "duration": 4.11}, {"text": "This is averaging over\nthe operation sequence.", "start": 2884.62, "duration": 7.26}, {"text": "Every insert_last over there\nonly takes constant time,", "start": 2891.88, "duration": 5.28}, {"text": "on average, over the sequence\nof operations that we do.", "start": 2897.16, "duration": 6.59}, {"text": "And so it's almost constant.", "start": 2903.75, "duration": 1.31}, {"text": "It's not quite as good\nas constant, worst case,", "start": 2905.06, "duration": 2.25}, {"text": "but it's almost as good.", "start": 2907.31, "duration": 1.44}, {"text": "And it's as good\nas you could hope", "start": 2908.75, "duration": 1.53}, {"text": "to do in this dynamic\narray allocation model.", "start": 2910.28, "duration": 4.8}, {"text": "Let me put this into a table.", "start": 2915.08, "duration": 2.53}, {"text": "And you'll find these in\nthe lecture notes, also.", "start": 2917.61, "duration": 2.33}, {"text": "We have, on the top,\nthe main operations", "start": 2919.94, "duration": 2.19}, {"text": "of sequence interface, which we\nwill revisit in lecture seven.", "start": 2922.13, "duration": 3.0}, {"text": "We'll see some other\ndata structures for this.", "start": 2925.13, "duration": 2.04}, {"text": "Get_at and set_at\nin the first column.", "start": 2927.17, "duration": 1.997}, {"text": "Insert_ and delete_first,\ninsert_ and delete_last,", "start": 2929.167, "duration": 2.083}, {"text": "insert_ and delete_at\nan arbitrary position.", "start": 2931.25, "duration": 3.09}, {"text": "We've seen three\ndata structures now.", "start": 2934.34, "duration": 2.37}, {"text": "Arrays were really\ngood at get_at/set_at.", "start": 2936.71, "duration": 2.61}, {"text": "They took constant time.", "start": 2939.32, "duration": 1.44}, {"text": "That's the blue one.", "start": 2940.76, "duration": 1.29}, {"text": "We're omitting the thetas here.", "start": 2942.05, "duration": 2.025}, {"text": "All of the other operations\ntook linear time,", "start": 2944.075, "duration": 1.875}, {"text": "no matter where they were.", "start": 2945.95, "duration": 1.41}, {"text": "Linked lists were really good\nat insert- and delete_first.", "start": 2947.36, "duration": 2.517}, {"text": "They took constant time,\nbut everything else", "start": 2949.877, "duration": 1.833}, {"text": "took linear time,\nin the worst case.", "start": 2951.71, "duration": 1.98}, {"text": "These new dynamic arrays\nachieve get_at and set_at", "start": 2953.69, "duration": 4.2}, {"text": "in constant time because they\nmaintain this invariant here", "start": 2957.89, "duration": 6.17}, {"text": "that a of i equals x i.", "start": 2964.06, "duration": 1.35}, {"text": "So we can still do get-\nand set_at quickly.", "start": 2965.41, "duration": 4.51}, {"text": "And we also just\nshowed that insert_last", "start": 2969.92, "duration": 2.15}, {"text": "is constant amortized.", "start": 2972.07, "duration": 1.47}, {"text": "delete_last, you don't\nhave to resize the array.", "start": 2973.54, "duration": 4.96}, {"text": "You could just decrease\nlength and, boom,", "start": 2978.5, "duration": 2.25}, {"text": "you've deleted the last item.", "start": 2980.75, "duration": 2.38}, {"text": "It's not so satisfying,\nbecause if you insert n items", "start": 2983.13, "duration": 2.3}, {"text": "and then delete n\nitems, you'll still", "start": 2985.43, "duration": 1.86}, {"text": "have an array of size theta n,\neven though your current value", "start": 2987.29, "duration": 2.91}, {"text": "of n is 0.", "start": 2990.2, "duration": 1.92}, {"text": "You can get around that\nwith a little bit more", "start": 2992.12, "duration": 2.13}, {"text": "trickery, which are described\nin the lecture notes.", "start": 2994.25, "duration": 2.125}, {"text": "But it's beyond the-- we're\nonly going to do very simple", "start": 2996.375, "duration": 3.155}, {"text": "amortized analysis\nin this class--", "start": 2999.53, "duration": 1.92}, {"text": "to prove that that\nalgorithm is also constant", "start": 3001.45, "duration": 2.1}, {"text": "amortized, which it is.", "start": 3003.55, "duration": 1.77}, {"text": "You'll see in 046, or you\ncan find it in the CLRS book.", "start": 3005.32, "duration": 4.5}, {"text": "That's it for today.", "start": 3009.82, "duration": 2.0}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 1.12, "duration": 2.37}, {"text": "Commons license.", "start": 3.49, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.88, "duration": 2.21}, {"text": "continue to offer high quality\neducational resources for free.", "start": 7.09, "duration": 4.09}, {"text": "To make a donation or to\nview additional materials", "start": 11.18, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.75, "duration": 3.93}, {"text": "at ocw.mit.edu.", "start": 17.68, "duration": 0.906}, {"text": "GARY GENSLER: All right,\nso we're going to try to--", "start": 23.07, "duration": 2.43}, {"text": "I was giving a little bit\nmore time for more people", "start": 25.5, "duration": 2.95}, {"text": "to show up--", "start": 28.45, "duration": 1.46}, {"text": "chat about what did we\ncover this semester.", "start": 29.91, "duration": 2.16}, {"text": "So I'm going to\ntry to talk about--", "start": 32.07, "duration": 2.94}, {"text": "we started out--\nmoney and ledgers,", "start": 35.01, "duration": 1.91}, {"text": "and why does that matter, and\nif you go away from all this.", "start": 36.92, "duration": 4.6}, {"text": "Satoshi Nakamoto's innovation--\nwhat is that again?", "start": 41.52, "duration": 6.3}, {"text": "The economics of\nblockchain technology,", "start": 47.82, "duration": 2.43}, {"text": "why the financial sector is\nso entwined in all of this,", "start": 50.25, "duration": 4.15}, {"text": "though it's not the\nonly place we're going.", "start": 54.4, "duration": 2.38}, {"text": "A little bit about crypto\nfinance and public policy", "start": 56.78, "duration": 3.01}, {"text": "frameworks, and then wrap\nit up with a quote from Ben", "start": 59.79, "duration": 4.89}, {"text": "Franklin-- will be the last\nthing we talk about at the end,", "start": 64.68, "duration": 2.94}, {"text": "about paying it forward.", "start": 67.62, "duration": 1.17}, {"text": "I don't know how\nmany people read", "start": 71.43, "duration": 1.59}, {"text": "the article I wrote\nfor Coin Desk, which", "start": 73.02, "duration": 3.67}, {"text": "will run in a day\nor two or something,", "start": 76.69, "duration": 1.83}, {"text": "but that, too, just like helped\nme wrap up the whole semester.", "start": 78.52, "duration": 8.91}, {"text": "As I told you, I'm neither a\nmaximalist or a minimalist,", "start": 87.43, "duration": 3.24}, {"text": "but in a few\nminutes, I'm probably", "start": 90.67, "duration": 1.59}, {"text": "going to ask you all to kind of\nlet me know where you ended up.", "start": 92.26, "duration": 5.31}, {"text": "So the role of money.", "start": 97.57, "duration": 1.29}, {"text": "Anybody remember\nthe role of money", "start": 98.86, "duration": 2.94}, {"text": "in an economy, the three things?", "start": 101.8, "duration": 1.77}, {"text": "AUDIENCE: Medium of\nexchange, unit of account,", "start": 106.432, "duration": 2.298}, {"text": "store of value.", "start": 108.73, "duration": 1.26}, {"text": "GARY GENSLER: Medium of\nexchange, unit of account,", "start": 109.99, "duration": 2.37}, {"text": "store of value.", "start": 112.36, "duration": 0.99}, {"text": "I don't think we\nreally know, when", "start": 115.9, "duration": 2.01}, {"text": "we go through all the history\nand the archeology of it,", "start": 117.91, "duration": 3.45}, {"text": "which came first, but\nall three really matter.", "start": 121.36, "duration": 4.3}, {"text": "So how many people\nthink that Bitcoin--", "start": 125.66, "duration": 3.5}, {"text": "just Bitcoin.", "start": 129.16, "duration": 0.9}, {"text": "I'm not talking about\nthe other 1,600 tokens--", "start": 130.06, "duration": 2.88}, {"text": "Bitcoin fulfills these\nthree roles of money?", "start": 132.94, "duration": 7.35}, {"text": "James, was that a hand up?", "start": 140.29, "duration": 1.345}, {"text": "AUDIENCE: Yeah.", "start": 141.635, "duration": 0.625}, {"text": "Yep.", "start": 142.26, "duration": 0.817}, {"text": "GARY GENSLER: You're saying yes.", "start": 143.077, "duration": 1.333}, {"text": "AUDIENCE: Yes.", "start": 144.41, "duration": 1.405}, {"text": "GARY GENSLER: Alexis?", "start": 145.815, "duration": 0.875}, {"text": "Oh, we got two.", "start": 146.69, "duration": 0.73}, {"text": "Hugo?", "start": 147.42, "duration": 0.5}, {"text": "Somebody take the other side.", "start": 150.96, "duration": 2.13}, {"text": "Tom?", "start": 153.09, "duration": 0.69}, {"text": "AUDIENCE: Nope.", "start": 153.78, "duration": 1.28}, {"text": "GARY GENSLER: That's it?", "start": 155.06, "duration": 1.0}, {"text": "That's it?", "start": 156.06, "duration": 0.5}, {"text": "A whole semester, and\nall you can say is nope?", "start": 156.56, "duration": 2.205}, {"text": "AUDIENCE: Yeah.", "start": 158.765, "duration": 0.625}, {"text": "GARY GENSLER: Nope?", "start": 159.39, "duration": 0.36}, {"text": "All right.", "start": 159.75, "duration": 0.86}, {"text": "Anybody want to give more?", "start": 160.61, "duration": 2.38}, {"text": "Brotish?", "start": 162.99, "duration": 1.456}, {"text": "AUDIENCE: So not a store of\nvalue because of [INAUDIBLE]..", "start": 164.446, "duration": 3.294}, {"text": "GARY GENSLER: So Brotish\nsays not a store of value,", "start": 167.74, "duration": 2.54}, {"text": "but isn't it $60 billion\nof value right now?", "start": 170.28, "duration": 3.03}, {"text": "AUDIENCE: [INAUDIBLE].", "start": 173.31, "duration": 1.68}, {"text": "So there is a value,\nbut it's too volatile.", "start": 174.99, "duration": 3.62}, {"text": "GARY GENSLER: James?", "start": 178.61, "duration": 1.165}, {"text": "AUDIENCE: I\nrespectfully disagree.", "start": 179.775, "duration": 3.435}, {"text": "It's volatile when you think\nof it in exchange of a dollar,", "start": 183.21, "duration": 3.15}, {"text": "but if you move your\nmindset, a bitcoin", "start": 186.36, "duration": 2.58}, {"text": "is a bitcoin is a bitcoin.", "start": 188.94, "duration": 1.35}, {"text": "Right?", "start": 190.29, "duration": 0.64}, {"text": "It's only volatile if you\nthink [INAUDIBLE] a dollar.", "start": 190.93, "duration": 4.888}, {"text": "GARY GENSLER: Oh, my god.", "start": 195.818, "duration": 1.042}, {"text": "Here we go.", "start": 196.86, "duration": 2.19}, {"text": "Ross?", "start": 199.05, "duration": 1.43}, {"text": "AUDIENCE: But that same\nthing is true of corn, right?", "start": 200.48, "duration": 2.525}, {"text": "A bushel of corn is--", "start": 203.005, "duration": 1.675}, {"text": "I'm with Brotish on this.", "start": 204.68, "duration": 1.042}, {"text": "GARY GENSLER: I'm\nsorry, were you", "start": 205.722, "duration": 1.375}, {"text": "in the no camp or the yes camp?", "start": 207.097, "duration": 1.823}, {"text": "That it's a store of value.", "start": 208.92, "duration": 1.23}, {"text": "AUDIENCE: I'm in the no camp.", "start": 210.15, "duration": 1.08}, {"text": "GARY GENSLER: No?", "start": 211.23, "duration": 0.708}, {"text": "Is it a medium of exchange?", "start": 211.938, "duration": 1.302}, {"text": "AUDIENCE: Yes.", "start": 213.24, "duration": 0.81}, {"text": "GARY GENSLER: Oh,\nmedium of exchange.", "start": 214.05, "duration": 1.24}, {"text": "Sean?", "start": 215.29, "duration": 0.51}, {"text": "AUDIENCE: In response\nto [INAUDIBLE] none", "start": 215.8, "duration": 4.095}, {"text": "of the currency can\nactually be treated", "start": 219.895, "duration": 1.625}, {"text": "as a stand alone currency.", "start": 221.52, "duration": 1.15}, {"text": "Everything has to be\ntreated as a pair.", "start": 222.67, "duration": 3.11}, {"text": "So everything's a\nrelative comparison.", "start": 225.78, "duration": 2.68}, {"text": "So you can't really treat\nBitcoin on a standalone basis.", "start": 228.46, "duration": 3.26}, {"text": "AUDIENCE: I don't know\nif I agree with that.", "start": 235.457, "duration": 1.833}, {"text": "But I would say that pretty much\nanything can fit into all three", "start": 237.29, "duration": 2.89}, {"text": "of these buckets.", "start": 240.18, "duration": 0.82}, {"text": "It just depends on\nhow dependable it is.", "start": 241.0, "duration": 2.43}, {"text": "In those three buckets,\nwith US dollar's", "start": 243.43, "duration": 2.27}, {"text": "very good at being\nmedium of exchange,", "start": 245.7, "duration": 2.01}, {"text": "very good at being a\ndependable store of value,", "start": 247.71, "duration": 1.98}, {"text": "and a steady unit of account.", "start": 249.69, "duration": 1.8}, {"text": "But you could also have a\nbushel of wheat or something.", "start": 251.49, "duration": 5.377}, {"text": "It would be all three\nof these things,", "start": 256.867, "duration": 1.583}, {"text": "but it wouldn't be equality.", "start": 258.45, "duration": 0.87}, {"text": "GARY GENSLER: Right, but--", "start": 259.32, "duration": 1.23}, {"text": "please, Jihee.", "start": 260.55, "duration": 0.969}, {"text": "AUDIENCE: So the fiat\ncurrency-- the reason why", "start": 261.519, "duration": 4.341}, {"text": "I think US dollar is\nstable is because there", "start": 265.86, "duration": 2.05}, {"text": "is a US central bank that\nactually backs up that.", "start": 267.91, "duration": 3.74}, {"text": "Because it's just\nthat fiat currency.", "start": 271.65, "duration": 1.8}, {"text": "It is a liability\nof the central bank,", "start": 273.45, "duration": 3.45}, {"text": "whereas Bitcoin\ndoesn't have a center", "start": 276.9, "duration": 4.098}, {"text": "to worry that banks have.", "start": 280.998, "duration": 1.042}, {"text": "GARY GENSLER: Nice music\nthat we're getting.", "start": 282.04, "duration": 1.734}, {"text": "[INAUDIBLE] a serenade.", "start": 283.774, "duration": 0.936}, {"text": "AUDIENCE: So therefore,\nI don't think", "start": 284.71, "duration": 1.542}, {"text": "the store of value\nargument will work.", "start": 286.252, "duration": 2.111}, {"text": "GARY GENSLER: So you think--", "start": 288.363, "duration": 1.167}, {"text": "[INAUDIBLE] saying,\nwell, there's", "start": 289.53, "duration": 1.375}, {"text": "no central bank behind it,\nso maybe it doesn't hold up.", "start": 290.905, "duration": 3.405}, {"text": "But if you take anything\naway from the class--", "start": 294.31, "duration": 2.81}, {"text": "and I'm going to have\nsome other takeaways, too.", "start": 297.12, "duration": 3.51}, {"text": "Remember, the three things\nthat about the role of money--", "start": 300.63, "duration": 3.84}, {"text": "but it's a social construct.", "start": 304.47, "duration": 2.4}, {"text": "Even with a central bank--", "start": 306.87, "duration": 1.56}, {"text": "a central bank is, ultimately--\nwe enshrined in law.", "start": 308.43, "duration": 3.54}, {"text": "We enshrine it in a big\ninstitution, and bricks,", "start": 311.97, "duration": 3.45}, {"text": "and mortar, and columns usually.", "start": 315.42, "duration": 3.35}, {"text": "You always have to\nhave those columns.", "start": 318.77, "duration": 2.75}, {"text": "But it's still a\nsocial construct.", "start": 321.52, "duration": 3.23}, {"text": "And Bitcoin does, in some\nways, have all three of these.", "start": 324.75, "duration": 7.41}, {"text": "It's just not\nbroadly acceptable.", "start": 332.16, "duration": 2.1}, {"text": "It's rarely used as\na unit of account,", "start": 334.26, "duration": 2.77}, {"text": "but it is sometimes\nused as a unit account", "start": 337.03, "duration": 2.36}, {"text": "in some initial coin offerings.", "start": 339.39, "duration": 2.71}, {"text": "It's not used, generally,\nas a medium of exchange.", "start": 342.1, "duration": 3.08}, {"text": "But some people are\npaid in Bitcoin some.", "start": 345.18, "duration": 2.28}, {"text": "Software developers are\nactually paid in Bitcoin.", "start": 347.46, "duration": 5.55}, {"text": "And it's $60 billion.", "start": 353.01, "duration": 1.02}, {"text": "It might be volatile.", "start": 354.03, "duration": 1.41}, {"text": "It has a store value.", "start": 355.44, "duration": 2.02}, {"text": "So I'm not trying to take\nmaximalist or minimalist,", "start": 357.46, "duration": 3.44}, {"text": "but I'm probably\nbetween Tom and James,", "start": 360.9, "duration": 2.76}, {"text": "because it does have\nall of those qualities", "start": 363.66, "duration": 3.63}, {"text": "in to some extent in there.", "start": 367.29, "duration": 5.1}, {"text": "Early money-- remember some\nof our walk down memory lane.", "start": 372.39, "duration": 4.05}, {"text": "Some of these early monies\nfell apart, became extinct,", "start": 376.44, "duration": 6.18}, {"text": "when they got debased.", "start": 382.62, "duration": 1.808}, {"text": "And we talked about,\nearly in the semester,", "start": 384.428, "duration": 1.792}, {"text": "even the story about it.", "start": 386.22, "duration": 1.68}, {"text": "It was, I think, a British--", "start": 387.9, "duration": 3.09}, {"text": "when the British got\nto the island of Yap,", "start": 390.99, "duration": 2.97}, {"text": "they went off a couple miles\nand quarried the stones", "start": 393.96, "duration": 2.94}, {"text": "and kept bringing\nmore yap stones there.", "start": 396.9, "duration": 2.55}, {"text": "And all of a sudden,\nit got debased.", "start": 399.45, "duration": 2.79}, {"text": "And then, of course, money\nturned to paper money.", "start": 402.24, "duration": 3.47}, {"text": "And in the bottom\nleft-hand corner,", "start": 405.71, "duration": 2.24}, {"text": "it started as\nwarehouse receipts.", "start": 407.95, "duration": 2.78}, {"text": "So the paper was\njust a representation", "start": 410.73, "duration": 2.31}, {"text": "of the store of value--", "start": 413.04, "duration": 1.59}, {"text": "the metal, or the corn, or\nthe wheat that we had earlier.", "start": 414.63, "duration": 4.68}, {"text": "Another important\nthing was ledgers.", "start": 419.31, "duration": 3.15}, {"text": "Who wants to remind the\nclass what a ledger is?", "start": 422.46, "duration": 2.47}, {"text": "Why do ledgers matter?", "start": 424.93, "duration": 3.58}, {"text": "Anybody want to-- ledgers?", "start": 428.51, "duration": 1.8}, {"text": "All right, clearly I\ndidn't make it on ledgers.", "start": 430.31, "duration": 3.555}, {"text": "Hugo?", "start": 436.79, "duration": 1.815}, {"text": "AUDIENCE: It's transaction\nhistory, basically.", "start": 438.605, "duration": 3.175}, {"text": "GARY GENSLER: A store\ntransaction history.", "start": 441.78, "duration": 1.85}, {"text": "What else is there?", "start": 443.63, "duration": 2.99}, {"text": "AUDIENCE: Balances.", "start": 446.62, "duration": 0.84}, {"text": "GARY GENSLER: Balances of?", "start": 447.46, "duration": 1.852}, {"text": "AUDIENCE: Accounts.", "start": 449.312, "duration": 1.328}, {"text": "GARY GENSLER: Accounts.", "start": 450.64, "duration": 1.17}, {"text": "So it stores a balance\nand a transaction.", "start": 451.81, "duration": 2.61}, {"text": "So you can think of it\nas a flow and a balance.", "start": 454.42, "duration": 3.56}, {"text": "The flow is the transaction--", "start": 457.98, "duration": 2.53}, {"text": "I give Hugo money.", "start": 460.51, "duration": 2.87}, {"text": "Regardless of who gives Hugo\nmoney, here's his balance.", "start": 463.38, "duration": 3.09}, {"text": "So an income statement\nand a balance sheet", "start": 466.47, "duration": 2.94}, {"text": "is a flow and a balance.", "start": 469.41, "duration": 1.8}, {"text": "But ledgers and keeping ledgers\ngo back thousands of years.", "start": 471.21, "duration": 6.23}, {"text": "So blockchain technology\nis really about money,", "start": 477.44, "duration": 3.11}, {"text": "but it's also about a\ndatabase that has ledgers.", "start": 480.55, "duration": 2.31}, {"text": "And ledgers usually\nstore things of value.", "start": 482.86, "duration": 1.89}, {"text": "So then we got to fiat currency.", "start": 487.27, "duration": 1.86}, {"text": "And fiat currency,\nas Jihee said,", "start": 489.13, "duration": 2.33}, {"text": "they were represented by\ncentral bank notes, central bank", "start": 491.46, "duration": 2.98}, {"text": "reserves, and bank deposits.", "start": 494.44, "duration": 1.845}, {"text": "So there's three things.", "start": 496.285, "duration": 1.515}, {"text": "Does anybody want\nto see if anybody", "start": 497.8, "duration": 3.15}, {"text": "listened in those classes?", "start": 500.95, "duration": 1.53}, {"text": "[LAUGHS] I'm kidding around.", "start": 502.48, "duration": 1.65}, {"text": "Elan, you're going to say,\nwhy is it those three things?", "start": 504.13, "duration": 2.55}, {"text": "They're all forms of fiat money.", "start": 506.68, "duration": 3.192}, {"text": "AUDIENCE: I thought\nyou were asking", "start": 509.872, "duration": 1.458}, {"text": "about the illicit\nactivity in that list.", "start": 511.33, "duration": 3.62}, {"text": "Is that the question?", "start": 514.95, "duration": 1.03}, {"text": "GARY GENSLER: All right,\nanswer the question", "start": 515.98, "duration": 1.5}, {"text": "you want to answer.", "start": 517.48, "duration": 0.86}, {"text": "AUDIENCE: Yeah.", "start": 518.34, "duration": 0.625}, {"text": "[LAUGHTER]", "start": 518.965, "duration": 0.995}, {"text": "[INAUDIBLE] there\nare things that", "start": 519.96, "duration": 1.375}, {"text": "are important in fiat\ncurrency, or is helpful.", "start": 521.335, "duration": 4.131}, {"text": "Fiat currency is important\nfor paying taxes.", "start": 525.466, "duration": 4.974}, {"text": "And it is allegedly backed\nby the social understanding", "start": 530.44, "duration": 5.79}, {"text": "that the central bank will\nrespect those notes at the end.", "start": 536.23, "duration": 4.477}, {"text": "GARY GENSLER: Right.", "start": 540.707, "duration": 0.833}, {"text": "So it's actually--\nyou're on to this.", "start": 541.54, "duration": 2.31}, {"text": "It's accepted for taxes.", "start": 543.85, "duration": 2.28}, {"text": "It's legal tender.", "start": 546.13, "duration": 1.2}, {"text": "So actually, society\ngets together,", "start": 547.33, "duration": 1.953}, {"text": "through its parliament,\nthrough its executive,", "start": 549.283, "duration": 1.917}, {"text": "and passes a law that\nsays it's legal tender.", "start": 551.2, "duration": 2.54}, {"text": "That gives it a huge leg up.", "start": 553.74, "duration": 1.54}, {"text": "But this is what\nit's really about.", "start": 555.28, "duration": 2.16}, {"text": "It has huge network effects.", "start": 557.44, "duration": 2.46}, {"text": "And I wrote this in\nthe CoinDesk article.", "start": 559.9, "duration": 1.99}, {"text": "The question I have\nfor any new currency", "start": 561.89, "duration": 4.55}, {"text": "is, how does it compete with\nthose incredible network", "start": 566.44, "duration": 2.34}, {"text": "effects?", "start": 568.78, "duration": 1.47}, {"text": "And we talk about Facebook\nhas incredible network effects", "start": 570.25, "duration": 3.15}, {"text": "because--", "start": 573.4, "duration": 1.11}, {"text": "two billion members.", "start": 574.51, "duration": 1.89}, {"text": "But even money, as a\ntechnology, has a network effect", "start": 576.4, "duration": 3.48}, {"text": "because people readily accept\nit as a unit of account,", "start": 579.88, "duration": 3.21}, {"text": "a medium of exchange,\na store of value.", "start": 583.09, "duration": 4.39}, {"text": "And it only loses that\nnetwork effect, usually,", "start": 587.48, "duration": 3.72}, {"text": "when it gets\ndebased, when people", "start": 591.2, "duration": 2.85}, {"text": "can't be confident that\nit's a good store of value", "start": 594.05, "duration": 2.79}, {"text": "because somebody else\ncan mint a lot of it,", "start": 596.84, "duration": 2.4}, {"text": "or print a lot of it, or a king\nstarts to print too much of it.", "start": 599.24, "duration": 6.93}, {"text": "But it has an extraordinary\nnetwork effect.", "start": 606.17, "duration": 3.21}, {"text": "On the other hand,\nsometimes currencies", "start": 609.38, "duration": 1.65}, {"text": "are a little bit challenged,\nlike the euro right now.", "start": 611.03, "duration": 2.82}, {"text": "Will the euro ultimately work?", "start": 613.85, "duration": 2.08}, {"text": "That's for a different class\nand a different lecture,", "start": 615.93, "duration": 2.3}, {"text": "but will the euro\nultimately work long term?", "start": 618.23, "duration": 3.42}, {"text": "I have my doubts whether it\nwill work for decades to come,", "start": 621.65, "duration": 4.65}, {"text": "because there's so\nmany jurisdictions.", "start": 626.3, "duration": 3.32}, {"text": "And there's not a\nunified fiscal account,", "start": 629.62, "duration": 2.61}, {"text": "not a unified economy, and not\ntruly free movement of labor", "start": 632.23, "duration": 8.56}, {"text": "across that continent.", "start": 640.79, "duration": 4.06}, {"text": "So that's fiat currency.", "start": 644.85, "duration": 1.74}, {"text": "It's sort of the game in town\nthat then Satoshi Nakamoto", "start": 646.59, "duration": 4.38}, {"text": "is was addressing.", "start": 650.97, "duration": 2.1}, {"text": "And you all read the\neight-page paper,", "start": 653.07, "duration": 2.83}, {"text": "but that was the first line.", "start": 655.9, "duration": 1.64}, {"text": "\"Been working on a\nnew electronic cash", "start": 657.54, "duration": 1.678}, {"text": "system that's fully\npeer-to-peer, with no trusted", "start": 659.218, "duration": 2.042}, {"text": "third party.\"", "start": 661.26, "duration": 1.02}, {"text": "Basically, as Jihee\nsaid, no central bank.", "start": 662.28, "duration": 2.19}, {"text": "Forget about that central bank.", "start": 664.47, "duration": 1.98}, {"text": "That was the core\ninspiration that was there.", "start": 666.45, "duration": 5.55}, {"text": "But interestingly, it\nwasn't the first try.", "start": 672.0, "duration": 3.18}, {"text": "And we talked early\nin the semester", "start": 675.18, "duration": 1.98}, {"text": "about at least a handful\nof early attempts", "start": 677.16, "duration": 3.57}, {"text": "that all failed\nbecause they were still", "start": 680.73, "duration": 3.67}, {"text": "centralized-- like DigiCash\nwas still very centralized.", "start": 684.4, "duration": 4.92}, {"text": "Or they couldn't solve\nthe double spending.", "start": 689.32, "duration": 2.55}, {"text": "On the internet, you\ncan send an email twice.", "start": 691.87, "duration": 2.64}, {"text": "It doesn't need a\ncentral authority.", "start": 694.51, "duration": 2.58}, {"text": "So what if it gets copied?", "start": 697.09, "duration": 1.53}, {"text": "But the double spending\nis the big issue.", "start": 698.62, "duration": 3.52}, {"text": "So how did he solve\nit, or she solve it?", "start": 702.14, "duration": 5.8}, {"text": "Does anybody still not know\nwho Satoshi Nakamoto is?", "start": 707.94, "duration": 4.12}, {"text": "No?", "start": 712.06, "duration": 0.5}, {"text": "All right.", "start": 712.56, "duration": 1.26}, {"text": "I was hoping, I was hoping.", "start": 713.82, "duration": 1.47}, {"text": "So we talked about\nblocks of data", "start": 717.98, "duration": 6.18}, {"text": "using cryptography\nand consensus.", "start": 724.16, "duration": 4.495}, {"text": "So if you're at a\ndinner party, and you", "start": 728.655, "duration": 1.625}, {"text": "can't remember anything else\nfrom this class, [LAUGHS]", "start": 730.28, "duration": 3.487}, {"text": "maybe just remember,\noh, yeah, there's", "start": 733.767, "duration": 1.583}, {"text": "something about blocks of data\nusing a bunch of cryptography", "start": 735.35, "duration": 4.22}, {"text": "and consensus.", "start": 739.57, "duration": 1.99}, {"text": "These slides are on Canvas.", "start": 741.56, "duration": 1.35}, {"text": "Download this one slide,\nyou're the expert.", "start": 742.91, "duration": 3.44}, {"text": "Neha Nerula actually\ncreated this slide,", "start": 746.35, "duration": 2.395}, {"text": "and I've been using it a lot.", "start": 748.745, "duration": 3.315}, {"text": "But anybody remember who\ninvented this whole concept", "start": 752.06, "duration": 3.36}, {"text": "of blocks of data?", "start": 755.42, "duration": 1.13}, {"text": "James?", "start": 759.97, "duration": 0.5}, {"text": "AUDIENCE: Adam someone?", "start": 760.47, "duration": 1.17}, {"text": "Back?", "start": 761.64, "duration": 0.5}, {"text": "GARY GENSLER: Adam\nBack is a good name,", "start": 762.14, "duration": 1.625}, {"text": "but he's not the guy\nthat invented this.", "start": 763.765, "duration": 2.375}, {"text": "He invented something else,\nwhich was proof-of-work.", "start": 766.14, "duration": 3.832}, {"text": "Timestamp append-only\nlogs-- what's", "start": 772.69, "duration": 1.91}, {"text": "the longest running\nblockchain in the world?", "start": 774.6, "duration": 3.24}, {"text": "AUDIENCE: New York Times?", "start": 777.84, "duration": 1.26}, {"text": "GARY GENSLER: New York Times.", "start": 779.1, "duration": 0.555}, {"text": "[INTERPOSING VOICES]", "start": 779.655, "duration": 0.945}, {"text": "AUDIENCE: Crossword.", "start": 780.6, "duration": 0.833}, {"text": "GARY GENSLER: All\nright, here he is.", "start": 781.433, "duration": 4.267}, {"text": "So two Bell Labs scientists--\nthis is one of them.", "start": 785.7, "duration": 4.78}, {"text": "Two Bell Labs scientists\ncame up with this concept", "start": 790.48, "duration": 4.08}, {"text": "that you could take a bunch\nof data, put it through what's", "start": 794.56, "duration": 4.44}, {"text": "called a cryptographic\nhash function,", "start": 799.0, "duration": 4.32}, {"text": "and that's a commitment scheme.", "start": 803.32, "duration": 1.317}, {"text": "You couldn't change it, because\nif you changed anything,", "start": 804.637, "duration": 2.333}, {"text": "the hash function would change.", "start": 806.97, "duration": 3.39}, {"text": "So what's a cryptographic\nhash function?", "start": 810.36, "duration": 2.07}, {"text": "That's when I use\nthis idea of you", "start": 812.43, "duration": 1.92}, {"text": "can take the entire\nlibrary of Congress,", "start": 814.35, "duration": 2.73}, {"text": "and put it into a little\nthing called a hash function,", "start": 817.08, "duration": 2.7}, {"text": "and end up with a\nstring of characters,", "start": 819.78, "duration": 5.37}, {"text": "a hexadecimal output.", "start": 825.15, "duration": 7.13}, {"text": "But a hash function is the key\nto what this guy figured out.", "start": 832.28, "duration": 7.51}, {"text": "And, of course, this.", "start": 839.79, "duration": 2.87}, {"text": "That's the key.", "start": 842.66, "duration": 1.71}, {"text": "There was only two\nbits of cryptography", "start": 844.37, "duration": 2.52}, {"text": "in this whole class.", "start": 846.89, "duration": 1.77}, {"text": "And I know that it seemed like,\noh, why are we teaching this?", "start": 848.66, "duration": 4.05}, {"text": "But it's this idea that you\ncan take a whole bunch of data,", "start": 852.71, "duration": 3.16}, {"text": "put it into this thing\ncalled a hash function,", "start": 855.87, "duration": 1.94}, {"text": "and it commits to it.", "start": 857.81, "duration": 1.53}, {"text": "Because if you change\nany piece of the data--", "start": 859.34, "duration": 3.18}, {"text": "any individual\npiece-- you're going", "start": 862.52, "duration": 2.18}, {"text": "to get a different output.", "start": 864.7, "duration": 3.68}, {"text": "And so it's really the key to\nit is that it commits something.", "start": 868.38, "duration": 4.548}, {"text": "You can do it with the New\nYork Times crossword puzzle,", "start": 872.928, "duration": 2.292}, {"text": "and that was just my\nobservation on it.", "start": 875.22, "duration": 6.27}, {"text": "So it's about data commitment.", "start": 881.49, "duration": 1.89}, {"text": "The other thing that\nSatoshi Nakamoto used", "start": 883.38, "duration": 3.48}, {"text": "was asymmetric cryptography,\nor digital signatures.", "start": 886.86, "duration": 4.89}, {"text": "I pulled one of the graphics\nthat we talked about.", "start": 891.75, "duration": 2.91}, {"text": "But the idea being that,\nlong ago, cryptography", "start": 894.66, "duration": 5.19}, {"text": "was, how do I encrypt\nsomething because I'm", "start": 899.85, "duration": 2.13}, {"text": "in a military campaign?", "start": 901.98, "duration": 2.93}, {"text": "And I would, maybe,\njust transpose.", "start": 904.91, "duration": 2.61}, {"text": "The simplest cryptography\nfrom thousands of years", "start": 907.52, "duration": 3.03}, {"text": "ago was transposing\nevery letter.", "start": 910.55, "duration": 3.0}, {"text": "An A becomes a B,\na B becomes a C.", "start": 913.55, "duration": 2.58}, {"text": "That would be a\ntransposition of one.", "start": 916.13, "duration": 2.61}, {"text": "Well, that's pretty hard to\nimagine that anybody got away", "start": 918.74, "duration": 4.9}, {"text": "with that.", "start": 923.64, "duration": 0.5}, {"text": "But that was early cryptography,\nthousands of years ago-- just", "start": 924.14, "duration": 2.85}, {"text": "simple transposition.", "start": 926.99, "duration": 2.79}, {"text": "By the mid-20th\ncentury, there was", "start": 929.78, "duration": 2.55}, {"text": "very complex\ntranspositions, which", "start": 932.33, "duration": 2.82}, {"text": "were called keys and enigma.", "start": 935.15, "duration": 3.09}, {"text": "If you ever go back and watch\nthat movie Imitation Games,", "start": 938.24, "duration": 3.66}, {"text": "there was five metal rotors--", "start": 941.9, "duration": 3.21}, {"text": "they were electronic rotors--", "start": 945.11, "duration": 1.8}, {"text": "that changed.", "start": 946.91, "duration": 1.25}, {"text": "And every day, the Germans\nwould change the five rotors.", "start": 948.16, "duration": 5.95}, {"text": "But still, they were\nsymmetric cryptography.", "start": 954.11, "duration": 2.79}, {"text": "The U boats actually\nhad the same five rotors", "start": 956.9, "duration": 6.0}, {"text": "as high command out of--", "start": 962.9, "duration": 3.54}, {"text": "Berlin, let's say.", "start": 966.44, "duration": 2.63}, {"text": "So somebody came\nalong in the 1970s", "start": 969.07, "duration": 2.44}, {"text": "and said, what if\nthe key is different?", "start": 971.51, "duration": 1.71}, {"text": "It's asymmetric.", "start": 973.22, "duration": 0.99}, {"text": "There's a private\nkey, and a public key.", "start": 974.21, "duration": 1.93}, {"text": "The public key, everybody gets,\nbut the private key, you keep.", "start": 976.14, "duration": 5.41}, {"text": "And some of those\ncomputer sites--", "start": 981.55, "duration": 2.25}, {"text": "cryptographers-- are\nhere, right here, at MIT.", "start": 983.8, "duration": 2.88}, {"text": "Ron Rivest teaches a\ncourse in cryptography.", "start": 986.68, "duration": 4.05}, {"text": "But that invention, in\nthe 1970s, is really key.", "start": 990.73, "duration": 3.71}, {"text": "So it's hash functions,\nand this concept", "start": 994.44, "duration": 2.08}, {"text": "of a private key\nand a public key,", "start": 996.52, "duration": 2.59}, {"text": "and of course a digital\nsignature that goes with it.", "start": 999.11, "duration": 3.39}, {"text": "You probably don't even need to\nremember much about this class", "start": 1002.5, "duration": 3.54}, {"text": "about this.", "start": 1006.04, "duration": 0.517}, {"text": "But just know there's\nsomething called", "start": 1006.557, "duration": 1.583}, {"text": "a private key and a public key.", "start": 1008.14, "duration": 2.67}, {"text": "And then, Nakamoto's\nreal innovation", "start": 1010.81, "duration": 3.93}, {"text": "was off of Adam Back.", "start": 1014.74, "duration": 1.74}, {"text": "And Adam Back said, if I use\nsome computational work--", "start": 1016.48, "duration": 4.86}, {"text": "if I use computational work\nto find a hash function that", "start": 1021.34, "duration": 3.87}, {"text": "has a predetermined\nnumber of zeros,", "start": 1025.21, "duration": 3.72}, {"text": "it's not much of a puzzle.", "start": 1028.93, "duration": 1.38}, {"text": "It's a random number generation.", "start": 1030.31, "duration": 2.07}, {"text": "People will say proof-of-work\nis a computational puzzle.", "start": 1032.38, "duration": 3.719}, {"text": "It is simply running--", "start": 1036.099, "duration": 3.051}, {"text": "this thing called mining\nis running-- electricity", "start": 1039.15, "duration": 2.62}, {"text": "until you get the right\nnumber of leading zeros.", "start": 1041.77, "duration": 2.684}, {"text": "But it can be\nefficiently verified.", "start": 1047.14, "duration": 2.13}, {"text": "So the characteristics of\nproof-of-work is of work is--", "start": 1049.27, "duration": 3.54}, {"text": "invented in 1997.", "start": 1052.81, "duration": 1.95}, {"text": "Blockchains were\ninvented in 1991.", "start": 1054.76, "duration": 3.6}, {"text": "But what Satoshi Nakamoto--", "start": 1058.36, "duration": 2.34}, {"text": "what she did was she pulled that\ntogether after like 20 or 30", "start": 1060.7, "duration": 4.8}, {"text": "failed attempts to have a\ndigital, non-central money", "start": 1065.5, "duration": 4.68}, {"text": "and said, that that's where\nblockchain inspiration is.", "start": 1070.18, "duration": 3.75}, {"text": "And so proof of work--", "start": 1076.47, "duration": 2.73}, {"text": "I use this little visual.", "start": 1079.2, "duration": 1.45}, {"text": "But each block-- do you\nremember what the word nonce is?", "start": 1080.65, "duration": 5.78}, {"text": "What's a nonce?", "start": 1086.43, "duration": 1.33}, {"text": "Ross?", "start": 1087.76, "duration": 2.59}, {"text": "Make me proud, somebody.", "start": 1090.35, "duration": 2.65}, {"text": "Can't remember.", "start": 1093.0, "duration": 0.665}, {"text": "AUDIENCE: And once.", "start": 1093.665, "duration": 0.802}, {"text": "GARY GENSLER: What's that?", "start": 1094.467, "duration": 1.083}, {"text": "AUDIENCE: And once.", "start": 1095.55, "duration": 1.38}, {"text": "GARY GENSLER: And\nonce-- a number once.", "start": 1096.93, "duration": 1.935}, {"text": "AUDIENCE: Number used once.", "start": 1098.865, "duration": 1.125}, {"text": "AUDIENCE: Once.", "start": 1099.99, "duration": 0.678}, {"text": "GARY GENSLER: Number used once.", "start": 1100.668, "duration": 1.292}, {"text": "And so why is a nonce\nimportant for proof of work?", "start": 1104.49, "duration": 3.58}, {"text": "AUDIENCE: Because\nit's a unique number.", "start": 1108.07, "duration": 1.73}, {"text": "GARY GENSLER: It's\na unique number.", "start": 1109.8, "duration": 1.65}, {"text": "AUDIENCE: And so\nestablishing the integrity", "start": 1111.45, "duration": 3.36}, {"text": "of that [INAUDIBLE].", "start": 1114.81, "duration": 1.11}, {"text": "GARY GENSLER: So all this\nwhole proof of work--", "start": 1115.92, "duration": 2.28}, {"text": "I'm just going back as a review,\nbut the whole proof of work", "start": 1118.2, "duration": 2.73}, {"text": "is your computer is\ngoing to randomly keep", "start": 1120.93, "duration": 3.0}, {"text": "picking one thing that changes.", "start": 1123.93, "duration": 3.15}, {"text": "All the data, all the\ntransactions are the same,", "start": 1127.08, "duration": 2.55}, {"text": "but keep changing this\nthing called a nonce", "start": 1129.63, "duration": 4.1}, {"text": "until I get some\nleading number of zeros.", "start": 1133.73, "duration": 4.59}, {"text": "And the whole Bitcoin\nnetwork around the globe--", "start": 1138.32, "duration": 3.42}, {"text": "all it's really doing is running\na random number generation,", "start": 1141.74, "duration": 3.12}, {"text": "or nonces, until\nthe hash function", "start": 1144.86, "duration": 4.32}, {"text": "is solved to have 18\nleading zeros right now.", "start": 1149.18, "duration": 4.42}, {"text": "Or I should say--", "start": 1153.6, "duration": 1.35}, {"text": "18 leading zeros when Bitcoin's\nvalue was $6,500 a Bitcoin.", "start": 1154.95, "duration": 5.718}, {"text": "It wouldn't surprise\nme if it's going", "start": 1160.668, "duration": 1.542}, {"text": "to fall down to 17 leading\nzeros, or 16 leading zeros,", "start": 1162.21, "duration": 3.98}, {"text": "because that would\nmake it easier to find.", "start": 1166.19, "duration": 2.67}, {"text": "All of that cryptography is just\nto make the database structure.", "start": 1171.77, "duration": 4.92}, {"text": "This database structure\nthat is in blockchain--", "start": 1176.69, "duration": 5.6}, {"text": "to make this work.", "start": 1182.29, "duration": 1.27}, {"text": "All that cryptography of hash\nfunctions, digital signatures,", "start": 1183.56, "duration": 3.3}, {"text": "and a little proof\nof work is to make it", "start": 1186.86, "duration": 2.58}, {"text": "what's called nearly immutable.", "start": 1189.44, "duration": 3.57}, {"text": "And I'm putting the word\n\"nearly\" in because nothing's", "start": 1193.01, "duration": 2.58}, {"text": "truly immutable.", "start": 1195.59, "duration": 1.0}, {"text": "You could overwhelm even\nthe Bitcoin network.", "start": 1196.59, "duration": 4.18}, {"text": "Questions about the technology?", "start": 1200.77, "duration": 3.975}, {"text": "[INAUDIBLE]", "start": 1204.745, "duration": 0.685}, {"text": "AUDIENCE: Could you just go\nover the number of leading zeros", "start": 1205.43, "duration": 2.5}, {"text": "concept again?", "start": 1207.93, "duration": 1.58}, {"text": "GARY GENSLER: So the concept\nbehind the proof of work", "start": 1209.51, "duration": 6.29}, {"text": "that Adam Back came up with\nin the late 1990s was--", "start": 1215.8, "duration": 9.76}, {"text": "gotta run some data\nthrough a hash function.", "start": 1225.56, "duration": 5.22}, {"text": "In his case, in Adam\nBack's case, it was emails.", "start": 1230.78, "duration": 3.24}, {"text": "Literally run an email all the\nway through a hash function,", "start": 1234.02, "duration": 5.01}, {"text": "and then add an additional\nbit of data to it--", "start": 1239.03, "duration": 3.78}, {"text": "this nonce, a number\nthat's used once--", "start": 1242.81, "duration": 4.12}, {"text": "and run that nonce randomly\nuntil the hash that comes out.", "start": 1246.93, "duration": 4.96}, {"text": "And my little\nvisual at the bottom", "start": 1251.89, "duration": 1.81}, {"text": "there has some\nleading zeros to it.", "start": 1253.7, "duration": 3.09}, {"text": "AUDIENCE: So\nbeginning of the hash", "start": 1259.86, "duration": 1.5}, {"text": "will be its number of zeros?", "start": 1261.36, "duration": 2.25}, {"text": "GARY GENSLER: Yes.", "start": 1263.61, "duration": 0.75}, {"text": "So in this case,\nfour leading zeros--", "start": 1264.36, "duration": 2.99}, {"text": "in that little visual there.", "start": 1267.35, "duration": 2.44}, {"text": "All the data that\ngoes into a block--", "start": 1269.79, "duration": 2.49}, {"text": "in Bitcoin, 1,000 to 1,500\ntransactions all go in.", "start": 1272.28, "duration": 4.68}, {"text": "They're rolled up in this\nthing called a Merkle tree,", "start": 1276.96, "duration": 2.4}, {"text": "but it all goes in.", "start": 1279.36, "duration": 2.34}, {"text": "And the only thing\nthat's changing", "start": 1281.7, "duration": 1.74}, {"text": "is the miners are trying\nto find a random nonce", "start": 1283.44, "duration": 5.14}, {"text": "until the hash has certain\nnumber of leading zeros.", "start": 1288.58, "duration": 5.23}, {"text": "When Nakamoto wrote the paper,\nthe difficulty was, I think,", "start": 1293.81, "duration": 4.77}, {"text": "10 leading zeros.", "start": 1298.58, "duration": 2.05}, {"text": "And you could solve\nthat on a laptop.", "start": 1300.63, "duration": 3.185}, {"text": "With eight more leading zeros--", "start": 1307.36, "duration": 2.92}, {"text": "and since it's hexadecimal--", "start": 1310.28, "duration": 2.04}, {"text": "I guess it's 16 to\nthe eighth power", "start": 1312.32, "duration": 4.38}, {"text": "harder, or something like\nseven trillion times harder.", "start": 1316.7, "duration": 7.777}, {"text": "AUDIENCE: Yes.", "start": 1324.477, "duration": 0.583}, {"text": "AUDIENCE: Let's assume\nthat you and I were trying", "start": 1330.46, "duration": 2.12}, {"text": "to have a transaction today.", "start": 1332.58, "duration": 2.06}, {"text": "And I'm going to\nkeep some coins.", "start": 1334.64, "duration": 4.209}, {"text": "And I'm [INAUDIBLE]\nthese for everyone", "start": 1338.849, "duration": 3.211}, {"text": "who's transacting\nmany, many times", "start": 1342.06, "duration": 2.06}, {"text": "and adding layers of difficulty\nto the transaction that we had.", "start": 1344.12, "duration": 6.25}, {"text": "If I want to use my\nbalance in five years,", "start": 1350.37, "duration": 4.84}, {"text": "how do we know\nwhat my balance is?", "start": 1355.21, "duration": 2.59}, {"text": "I need to go back\nthrough all the history", "start": 1357.8, "duration": 3.2}, {"text": "to know that I have a balance?", "start": 1361.0, "duration": 1.25}, {"text": "GARY GENSLER: So at the heart\nof the blockchain technology,", "start": 1362.25, "duration": 5.1}, {"text": "the Bitcoin network, but\nalso all the other networks,", "start": 1367.35, "duration": 3.06}, {"text": "is the entire transaction\nhistory is public.", "start": 1370.41, "duration": 3.72}, {"text": "This both gives us its\nstrength, but it's also", "start": 1374.13, "duration": 2.1}, {"text": "one of its challenges.", "start": 1376.23, "duration": 2.64}, {"text": "And so, yes, even\nfive years from now,", "start": 1378.87, "duration": 3.6}, {"text": "if you want to use\none of your Bitcoins--", "start": 1382.47, "duration": 5.83}, {"text": "which are stored\non the blockchain--", "start": 1388.3, "duration": 3.38}, {"text": "you have to be able to show\nthat here is a transaction", "start": 1391.68, "duration": 3.21}, {"text": "output from five years ago.", "start": 1394.89, "duration": 1.5}, {"text": "If you remember, there is both\ntransaction output models--", "start": 1396.39, "duration": 5.32}, {"text": "Bitcoin is a system that keeps\nall the individual transactions", "start": 1401.71, "duration": 4.77}, {"text": "in a set called the UTXO--", "start": 1406.48, "duration": 2.3}, {"text": "the Unspent\nTransaction Output Set.", "start": 1408.78, "duration": 4.14}, {"text": "You'd have to be able to show\nthat you have that in 25 years,", "start": 1412.92, "duration": 4.38}, {"text": "you said?", "start": 1417.3, "duration": 0.75}, {"text": "2023-- in 2023, you'd have\nto be able to show that.", "start": 1418.05, "duration": 6.15}, {"text": "AUDIENCE: So it's\nalso a balance.", "start": 1424.2, "duration": 2.61}, {"text": "They all spent this balance\nin the transaction [INAUDIBLE]", "start": 1426.81, "duration": 4.45}, {"text": "a record.", "start": 1431.26, "duration": 1.8}, {"text": "GARY GENSLER: It is\na record of an output", "start": 1433.06, "duration": 2.21}, {"text": "from an individual transaction.", "start": 1435.27, "duration": 2.56}, {"text": "So yes, it is like a balance.", "start": 1437.83, "duration": 3.79}, {"text": "But because Bitcoin does not\nadd up all of those individual--", "start": 1441.62, "duration": 5.99}, {"text": "if you had 13\nindividual outputs,", "start": 1447.61, "duration": 4.8}, {"text": "the Bitcoin network will\nnot add up those 13.", "start": 1452.41, "duration": 4.04}, {"text": "You'd have to use each of those\nindividually as new inputs.", "start": 1456.45, "duration": 4.776}, {"text": "AUDIENCE: And that one is\non the last block, as well.", "start": 1461.226, "duration": 4.944}, {"text": "But I'd have to go\nback [INAUDIBLE]..", "start": 1466.17, "duration": 2.457}, {"text": "GARY GENSLER: All right,\nso the question is,", "start": 1468.627, "duration": 1.833}, {"text": "does the last block--", "start": 1470.46, "duration": 1.14}, {"text": "Bitcoin has 550-some 1,000\nblocks of data right now.", "start": 1471.6, "duration": 4.59}, {"text": "Does the last block\nstore all of the data?", "start": 1476.19, "duration": 3.85}, {"text": "And the answer is, no, but\nit does store a hash function", "start": 1480.04, "duration": 5.67}, {"text": "from the previous block,\nwhich stores a hash function", "start": 1485.71, "duration": 3.45}, {"text": "from the previous block.", "start": 1489.16, "duration": 1.94}, {"text": "So your transaction output might\nbe on block number 420,000,", "start": 1491.1, "duration": 6.35}, {"text": "130,000 blocks ago.", "start": 1497.45, "duration": 4.31}, {"text": "But what shows that\nit's verifiable", "start": 1501.76, "duration": 2.67}, {"text": "is that each one of these blocks\nare linked to another block", "start": 1504.43, "duration": 4.05}, {"text": "through this thing called\na commitment scheme", "start": 1508.48, "duration": 1.98}, {"text": "called a hash function.", "start": 1510.46, "duration": 2.33}, {"text": "So technically speaking,\nthe latest block", "start": 1512.79, "duration": 4.33}, {"text": "has a number in it--", "start": 1517.12, "duration": 2.75}, {"text": "a hexadecimal number,\nbut a number in it--", "start": 1519.87, "duration": 2.88}, {"text": "called a hash function\nthat is committed to.", "start": 1522.75, "duration": 2.91}, {"text": "Because all the data\nthat's come before it--", "start": 1525.66, "duration": 3.21}, {"text": "all the millions of\ntransactions before it--", "start": 1528.87, "duration": 2.9}, {"text": "if somebody even\nchanges one of them,", "start": 1531.77, "duration": 2.29}, {"text": "you'll know that\nit's been tampered.", "start": 1534.06, "duration": 3.612}, {"text": "AUDIENCE: Let's say I want\nto use that balance I have.", "start": 1537.672, "duration": 3.788}, {"text": "Where do the blockchain\nverify that I have that?", "start": 1541.46, "duration": 4.04}, {"text": "Is it on the last\nblock, or does it", "start": 1545.5, "duration": 2.68}, {"text": "go back as long as it\nfinds the [INAUDIBLE]??", "start": 1548.18, "duration": 5.315}, {"text": "GARY GENSLER: In\nessence, it does", "start": 1553.495, "duration": 1.375}, {"text": "both, because the last\nblock better be valid.", "start": 1554.87, "duration": 4.55}, {"text": "But for you to\nspend something, it", "start": 1559.42, "duration": 2.03}, {"text": "has to really go back and find\nthat the input that you now", "start": 1561.45, "duration": 8.73}, {"text": "want to use is an output\nthat has not yet been spent.", "start": 1570.18, "duration": 5.24}, {"text": "Eric, did you have something\nthat you were trying to--", "start": 1575.42, "duration": 3.15}, {"text": "AUDIENCE: Yeah, it was\na very nice explanation.", "start": 1578.57, "duration": 3.09}, {"text": "You have to go all the way\nwhere your transaction-- where", "start": 1581.66, "duration": 3.12}, {"text": "you got the Bitcoin\nwas, whatever", "start": 1584.78, "duration": 4.585}, {"text": "block it is [INAUDIBLE]\nthrough the blockchain.", "start": 1589.365, "duration": 2.86}, {"text": "If you would try\nto get those coins", "start": 1592.225, "duration": 3.245}, {"text": "and use them as a [INAUDIBLE]\nfor whatever transaction", "start": 1595.47, "duration": 5.69}, {"text": "you want to do, you have\nto go all the way back.", "start": 1601.16, "duration": 2.885}, {"text": "GARY GENSLER: And\nthis complexity", "start": 1604.045, "duration": 1.375}, {"text": "is part of the\nreason why it doesn't", "start": 1605.42, "duration": 1.89}, {"text": "have the same performance--", "start": 1607.31, "duration": 1.8}, {"text": "doesn't have the same\nscalability-- yet.", "start": 1609.11, "duration": 4.02}, {"text": "I'm one that believes in a--", "start": 1613.13, "duration": 3.42}, {"text": "I'm optimistic that some\nof these scalability", "start": 1616.55, "duration": 2.55}, {"text": "and performance issues\nwill be overcome.", "start": 1619.1, "duration": 2.13}, {"text": "But it might take three,\nfive, seven years.", "start": 1621.23, "duration": 2.82}, {"text": "And it's not three\nor seven months.", "start": 1624.05, "duration": 3.463}, {"text": "But you're absolutely\nright, because you", "start": 1627.513, "duration": 1.667}, {"text": "have to kind of look back--", "start": 1629.18, "duration": 3.03}, {"text": "way back.", "start": 1632.21, "duration": 2.03}, {"text": "The Ethereum network doesn't\njust do it on transactions.", "start": 1634.24, "duration": 4.62}, {"text": "It has balances.", "start": 1638.86, "duration": 0.978}, {"text": "And so it's a little bit\nmore efficient that way,", "start": 1639.838, "duration": 2.042}, {"text": "and has other inefficiencies--", "start": 1641.88, "duration": 2.77}, {"text": "many other big inefficiencies,\nbut in some ways it--", "start": 1644.65, "duration": 5.8}, {"text": "We talked about smart contracts.", "start": 1650.45, "duration": 1.65}, {"text": "Larry Lessig actually spoke to\nus also about smart contracts.", "start": 1652.1, "duration": 4.26}, {"text": "Nick Szabo wrote\nabout this in 1996.", "start": 1656.36, "duration": 2.61}, {"text": "I like to talk about\nthe history to say,", "start": 1658.97, "duration": 2.01}, {"text": "it's not all about this one\nperson that we don't know--", "start": 1660.98, "duration": 3.69}, {"text": "Satoshi Nakamoto--\nbut a set of promises", "start": 1664.67, "duration": 2.79}, {"text": "specified in digital form,\nincluding protocols, where", "start": 1667.46, "duration": 3.09}, {"text": "parties keep their promises.", "start": 1670.55, "duration": 1.83}, {"text": "Think about it as a\nmodern way to automate.", "start": 1672.38, "duration": 2.79}, {"text": "So if you're out in\nbusiness in the future,", "start": 1675.17, "duration": 2.205}, {"text": "you're thinking about\ninvesting, and somebody", "start": 1677.375, "duration": 1.875}, {"text": "raises a smart contract issue.", "start": 1679.25, "duration": 3.45}, {"text": "Even if you're a\nBitcoin minimalist,", "start": 1682.7, "duration": 2.747}, {"text": "you might say, wait, wait, wait.", "start": 1685.447, "duration": 1.333}, {"text": "There might be some\nway I can automate", "start": 1686.78, "duration": 2.22}, {"text": "that which is currently\ndone by lawyers,", "start": 1689.0, "duration": 3.57}, {"text": "or by back-office\nfolks, or accountants.", "start": 1692.57, "duration": 4.805}, {"text": "So there's still\nsomething there.", "start": 1697.375, "duration": 1.375}, {"text": "And we talked about a\nuse case where the SDA--", "start": 1698.75, "duration": 2.67}, {"text": "the Swap Derivatives\nAssociation--", "start": 1701.42, "duration": 3.84}, {"text": "is looking at smart\ncontracts to try", "start": 1705.26, "duration": 2.01}, {"text": "to automate some of the\npreviously written mechanisms.", "start": 1707.27, "duration": 7.7}, {"text": "So smart contracts,\nwhich have come out", "start": 1714.97, "duration": 3.62}, {"text": "of this whole blockchain\ntechnology movement,", "start": 1718.59, "duration": 4.89}, {"text": "actually predates\nblockchain technology.", "start": 1723.48, "duration": 2.603}, {"text": "But blockchain technology,\nagain, as well-- maybe we", "start": 1726.083, "duration": 2.167}, {"text": "can do this in a verifiable,\nnearly immutable way, as well.", "start": 1728.25, "duration": 5.53}, {"text": "So moving value or\nautomating some forms", "start": 1733.78, "duration": 3.02}, {"text": "of contractual arrangement.", "start": 1736.8, "duration": 3.27}, {"text": "But remember,\nthey're not so smart,", "start": 1740.07, "duration": 1.88}, {"text": "and they're not\nso much contracts.", "start": 1741.95, "duration": 3.72}, {"text": "You probably still\nneed the courts,", "start": 1745.67, "duration": 1.84}, {"text": "and there's still some\nambiguity that can't", "start": 1747.51, "duration": 1.98}, {"text": "be pushed into these documents.", "start": 1749.49, "duration": 3.3}, {"text": "So then, we talked a\nlot about the economics", "start": 1752.79, "duration": 1.92}, {"text": "of blockchain technology.", "start": 1754.71, "duration": 1.92}, {"text": "And it's around verification\ncosts and networking costs.", "start": 1756.63, "duration": 4.41}, {"text": "But it's about lowering\nverification costs.", "start": 1761.04, "duration": 2.31}, {"text": "And some of those\nverification costs", "start": 1763.35, "duration": 1.56}, {"text": "might just be the economic\nrents of the current incumbents.", "start": 1764.91, "duration": 3.15}, {"text": "So blockchain technology may\nbe a really important way", "start": 1768.06, "duration": 4.17}, {"text": "to lower direct verification\ncosts and deal with censorship.", "start": 1772.23, "duration": 5.4}, {"text": "And I think that was a lot of\nwhat Nakamoto's innovation was", "start": 1777.63, "duration": 3.18}, {"text": "about, was dealing with\ncensorship that somebody", "start": 1780.81, "duration": 2.04}, {"text": "could deny me the right\nto use my money when", "start": 1782.85, "duration": 2.55}, {"text": "I want to use my money.", "start": 1785.4, "duration": 2.01}, {"text": "But it could also be about\nlowering economic rents.", "start": 1787.41, "duration": 2.4}, {"text": "Any questions?", "start": 1792.88, "duration": 1.262}, {"text": "And then we said, how do\nyou assess a use case?", "start": 1797.45, "duration": 2.13}, {"text": "And this was at the core of\neven my CoinDesk article.", "start": 1799.58, "duration": 4.5}, {"text": "Before you get to anything\nelse is, how is it going to be,", "start": 1804.08, "duration": 3.42}, {"text": "really?", "start": 1807.5, "duration": 0.65}, {"text": "It's what's the value\ncreation proposition?", "start": 1808.15, "duration": 1.99}, {"text": "Again, what are the verification\nand networking costs that", "start": 1810.14, "duration": 2.76}, {"text": "are really going to be reduced?", "start": 1812.9, "duration": 1.81}, {"text": "And what are competitors doing?", "start": 1814.71, "duration": 1.94}, {"text": "With a keen eye on--", "start": 1816.65, "duration": 1.77}, {"text": "in trade finance,\nthere's 20 or 30 efforts,", "start": 1818.42, "duration": 3.39}, {"text": "so it's worthwhile\nlooking at those 20 or 30.", "start": 1821.81, "duration": 2.58}, {"text": "I don't know which\nfield you all go into,", "start": 1827.33, "duration": 3.03}, {"text": "but if you're in a field where\nnobody has used blockchain", "start": 1830.36, "duration": 2.58}, {"text": "technology, no competitor,\nthen ask the question,", "start": 1832.94, "duration": 2.97}, {"text": "well, how are competitors\nusing traditional databases?", "start": 1835.91, "duration": 4.38}, {"text": "And that might be the\nopportunity for you.", "start": 1840.29, "duration": 3.05}, {"text": "And it might be a\ngolden opportunity.", "start": 1843.34, "duration": 2.01}, {"text": "But always look-- what's\nthe value proposition?", "start": 1845.35, "duration": 3.31}, {"text": "What verification\nand networking cost?", "start": 1848.66, "duration": 2.1}, {"text": "What's the competition?", "start": 1850.76, "duration": 1.5}, {"text": "And then, you get into\nthe sort of tough details.", "start": 1852.26, "duration": 6.013}, {"text": "And if you're\ninvesting, if you're", "start": 1858.273, "duration": 1.417}, {"text": "a venture capitalist\nand somebody", "start": 1859.69, "duration": 1.71}, {"text": "can't really tell you why\nmultiple stakeholders need", "start": 1861.4, "duration": 3.81}, {"text": "to write to the ledger,\nand what's their data--", "start": 1865.21, "duration": 3.66}, {"text": "what data are they going to\nbe storing on this append-only", "start": 1868.87, "duration": 2.91}, {"text": "log--", "start": 1871.78, "duration": 1.6}, {"text": "then I might suggest you\ninvest in something else.", "start": 1873.38, "duration": 4.14}, {"text": "I mean, you can always\ninvest in something", "start": 1877.52, "duration": 1.75}, {"text": "because you think that\nit's a momentum play.", "start": 1879.27, "duration": 3.45}, {"text": "And if you invest, it's\nan early seed investment,", "start": 1882.72, "duration": 3.42}, {"text": "and somebody will bail you out.", "start": 1886.14, "duration": 1.968}, {"text": "But most venture\ncapitalists-- you're", "start": 1888.108, "duration": 1.542}, {"text": "investing for three to six\nyears, or three to five years.", "start": 1889.65, "duration": 3.73}, {"text": "And so I wouldn't\nalways expect somebody", "start": 1893.38, "duration": 1.97}, {"text": "is going to bail you out.", "start": 1895.35, "duration": 1.87}, {"text": "Ask the tough questions.", "start": 1897.22, "duration": 1.37}, {"text": "Jihee?", "start": 1898.59, "duration": 0.792}, {"text": "AUDIENCE: But just because\nthat is the best solution,", "start": 1899.382, "duration": 2.208}, {"text": "it doesn't mean that they're\ngoing to be successful later,", "start": 1901.59, "duration": 3.63}, {"text": "right?", "start": 1905.22, "duration": 0.81}, {"text": "There are multiple examples\nof products, or services,", "start": 1906.03, "duration": 5.25}, {"text": "or [INAUDIBLE] that are\nclearly not the best solution", "start": 1911.28, "duration": 2.55}, {"text": "but have taken dominant\nposition in a market.", "start": 1913.83, "duration": 3.93}, {"text": "So I was curious, should\nit be the best solution?", "start": 1917.76, "duration": 5.85}, {"text": "GARY GENSLER: Well, I think\nthat's one of the questions.", "start": 1923.61, "duration": 4.1}, {"text": "But you're saying, well, what\nif it's not the best solution?", "start": 1927.71, "duration": 2.895}, {"text": "Going back to what\nJeff Sprecher said,", "start": 1934.34, "duration": 2.8}, {"text": "can it do something\ncheaper, faster, or better?", "start": 1937.14, "duration": 5.91}, {"text": "And it might not be\nthe best solution.", "start": 1943.05, "duration": 2.418}, {"text": "But if it can at least\nanswer the question,", "start": 1945.468, "duration": 1.792}, {"text": "is it cheaper,\nbetter, or faster,", "start": 1947.26, "duration": 5.05}, {"text": "you're probably not\ngoing to be successful.", "start": 1952.31, "duration": 2.07}, {"text": "And in some cases, it's\nnot the best data solution,", "start": 1954.38, "duration": 2.69}, {"text": "but there's such\nhigh economic rents", "start": 1957.07, "duration": 3.31}, {"text": "that however the mortgage\nproduct, the health care", "start": 1960.38, "duration": 2.6}, {"text": "product, the product that\nis being delivered now,", "start": 1962.98, "duration": 2.25}, {"text": "the payment solution\nthat you're saying, ah,", "start": 1965.23, "duration": 3.85}, {"text": "it's not the best solution.", "start": 1969.08, "duration": 1.21}, {"text": "But this is my solution on how\nI'm going to do it cheaper,", "start": 1970.29, "duration": 3.62}, {"text": "because they have so\nmany economic rents.", "start": 1973.91, "duration": 3.09}, {"text": "So maybe that the\nword should say,", "start": 1977.0, "duration": 2.76}, {"text": "why is this a better solution,\nrather than best solution.", "start": 1979.76, "duration": 4.14}, {"text": "I'll agree with that.", "start": 1983.9, "duration": 2.394}, {"text": "Other queries?", "start": 1986.294, "duration": 1.596}, {"text": "And then, if there's\na native token,", "start": 1990.49, "duration": 3.06}, {"text": "I think that's where\nyou start to lose May.", "start": 1993.55, "duration": 2.94}, {"text": "But now, I'm going\nto ask the class.", "start": 1996.49, "duration": 3.36}, {"text": "How many people have come\nout of this semester thinking", "start": 1999.85, "duration": 3.18}, {"text": "there's a lot of\ninitial coin offerings", "start": 2003.03, "duration": 3.42}, {"text": "that you'd want to\npersonally invest in?", "start": 2006.45, "duration": 3.528}, {"text": "[LAUGHTER]", "start": 2009.978, "duration": 1.342}, {"text": "All right, is there\nanybody in the class", "start": 2011.32, "duration": 2.27}, {"text": "that owns an initial coin\noffering-- a non-Bitcoin token?", "start": 2013.59, "duration": 4.75}, {"text": "OK, do you want to tell us why?", "start": 2018.34, "duration": 4.401}, {"text": "AUDIENCE: Yeah.", "start": 2022.741, "duration": 1.589}, {"text": "GARY GENSLER: Give us the value\nproposition, or the pitch.", "start": 2024.33, "duration": 4.5}, {"text": "AUDIENCE: So I went to work\nfor a startup, [INAUDIBLE]", "start": 2028.83, "duration": 3.88}, {"text": "this summer.", "start": 2032.71, "duration": 1.07}, {"text": "And after the summer,\nthey paid me US dollars.", "start": 2033.78, "duration": 3.27}, {"text": "But after the summer, they gave\nme a lot of tokens they have.", "start": 2037.05, "duration": 4.88}, {"text": "And I saved a\nlittle bit of them.", "start": 2041.93, "duration": 1.59}, {"text": "GARY GENSLER: All right.", "start": 2043.52, "duration": 1.0}, {"text": "So you got paid in tokens.", "start": 2044.52, "duration": 1.86}, {"text": "AUDIENCE: No, I was\npaid in US dollars.", "start": 2046.38, "duration": 2.65}, {"text": "After the summer, they\ngave me most of the--", "start": 2049.03, "duration": 3.37}, {"text": "like a bunch of--\nsome of the tokens.", "start": 2052.4, "duration": 3.63}, {"text": "GARY GENSLER: As a bonus or?", "start": 2056.03, "duration": 1.379}, {"text": "AUDIENCE: As a bonus, yeah.", "start": 2057.409, "duration": 0.631}, {"text": "GARY GENSLER: I see.", "start": 2058.04, "duration": 0.32}, {"text": "As a bonus, you got--", "start": 2058.36, "duration": 1.299}, {"text": "all right.", "start": 2059.659, "duration": 0.511}, {"text": "And you sold some of them?", "start": 2060.17, "duration": 1.44}, {"text": "AUDIENCE: Some of\nthem, sold them.", "start": 2061.61, "duration": 1.65}, {"text": "GARY GENSLER: And I see.", "start": 2063.26, "duration": 1.169}, {"text": "AUDIENCE: Some of them\nI still [INAUDIBLE]..", "start": 2064.429, "duration": 1.841}, {"text": "GARY GENSLER: All right.", "start": 2066.27, "duration": 1.0}, {"text": "And do you think that there's\na use for these native tokens?", "start": 2067.27, "duration": 5.03}, {"text": "AUDIENCE: This specific startup?", "start": 2072.3, "duration": 1.426}, {"text": "GARY GENSLER: Yeah.", "start": 2073.726, "duration": 0.978}, {"text": "Names will not be repeated.", "start": 2074.704, "duration": 1.276}, {"text": "It's being filmed.", "start": 2075.98, "duration": 0.932}, {"text": "AUDIENCE: I don't know.", "start": 2076.912, "duration": 0.958}, {"text": "GARY GENSLER: I don't know.", "start": 2077.87, "duration": 1.125}, {"text": "Sean.", "start": 2078.995, "duration": 0.765}, {"text": "AUDIENCE: So I\nthought of it-- well,", "start": 2079.76, "duration": 1.979}, {"text": "I just thought a little\nof like Tron, which is a--", "start": 2081.739, "duration": 2.781}, {"text": "GARY GENSLER: Tron.", "start": 2084.52, "duration": 1.639}, {"text": "AUDIENCE: Yeah, it's a gaming.", "start": 2086.159, "duration": 1.25}, {"text": "GARY GENSLER: Gaming site.", "start": 2087.409, "duration": 1.411}, {"text": "AUDIENCE: Which is a--\nbasically a company", "start": 2088.82, "duration": 2.03}, {"text": "started by a friend of mine.", "start": 2090.85, "duration": 1.61}, {"text": "So it's kind of a\ntoken of support", "start": 2092.46, "duration": 1.52}, {"text": "instead of like [INAUDIBLE].", "start": 2093.98, "duration": 1.239}, {"text": "GARY GENSLER: All right.", "start": 2095.219, "duration": 1.0}, {"text": "So you bought some tokens\nas a token of support", "start": 2096.219, "duration": 2.801}, {"text": "for a friend, who\nstarted a company.", "start": 2099.02, "duration": 2.61}, {"text": "Do you think they have some use?", "start": 2101.63, "duration": 2.7}, {"text": "Can you use the token?", "start": 2104.33, "duration": 1.41}, {"text": "AUDIENCE: I don't\nthink there's-- well--", "start": 2105.74, "duration": 2.038}, {"text": "[LAUGHTER]", "start": 2107.778, "duration": 1.482}, {"text": "Well, it's supposed to be the--", "start": 2109.26, "duration": 2.54}, {"text": "building up to the biggest\ngaming network [INAUDIBLE]..", "start": 2111.8, "duration": 3.085}, {"text": "GARY GENSLER: But is\nit pre-functional,", "start": 2114.885, "duration": 1.625}, {"text": "or is it functional?", "start": 2116.51, "duration": 1.695}, {"text": "It's pre-functional.", "start": 2118.205, "duration": 1.585}, {"text": "Hugo?", "start": 2119.79, "duration": 0.89}, {"text": "AUDIENCE: Yeah.", "start": 2120.68, "duration": 0.895}, {"text": "GARY GENSLER: You\nhave-- you are?", "start": 2121.575, "duration": 1.375}, {"text": "AUDIENCE: I have-- yeah.", "start": 2122.95, "duration": 1.38}, {"text": "GARY GENSLER: All right.", "start": 2124.33, "duration": 1.0}, {"text": "You don't-- all right.", "start": 2125.33, "duration": 0.917}, {"text": "He's got a whole portfolio.", "start": 2126.247, "duration": 1.273}, {"text": "I can tell.", "start": 2127.52, "duration": 1.322}, {"text": "AUDIENCE: I don't know.", "start": 2128.842, "duration": 0.958}, {"text": "I've been interested in\nthis for over a year now.", "start": 2129.8, "duration": 3.062}, {"text": "So I wanted to make\na whole radical", "start": 2132.862, "duration": 1.458}, {"text": "of like, oh, this one looks\nlike it's going to go well,", "start": 2134.32, "duration": 2.292}, {"text": "but this one's a scam.", "start": 2136.612, "duration": 1.068}, {"text": "And there are some that seem\nlike sure-- in the long run,", "start": 2137.68, "duration": 7.13}, {"text": "they may retain some value.", "start": 2144.81, "duration": 2.95}, {"text": "But I probably made\nsome bad investments.", "start": 2147.76, "duration": 2.207}, {"text": "GARY GENSLER: Right.", "start": 2149.967, "duration": 0.833}, {"text": "So I don't want to make you sort\nof grieve those bad investment", "start": 2150.8, "duration": 3.54}, {"text": "decisions, but are any of\nyour tokens that you have held", "start": 2154.34, "duration": 3.48}, {"text": "or hold currently-- are\nany of them functional?", "start": 2157.82, "duration": 3.17}, {"text": "Like, they can be\nused on a network?", "start": 2160.99, "duration": 2.54}, {"text": "AUDIENCE: Yeah.", "start": 2163.53, "duration": 0.67}, {"text": "And I actually use\nat least one of them.", "start": 2164.2, "duration": 3.205}, {"text": "GARY GENSLER: All right.", "start": 2167.405, "duration": 1.425}, {"text": "Here.", "start": 2168.83, "duration": 1.928}, {"text": "Are you an owner, or\nyou've got a question?", "start": 2170.758, "duration": 1.792}, {"text": "AUDIENCE: I'm an\nowner, but not--", "start": 2172.55, "duration": 1.47}, {"text": "I haven't voted.", "start": 2174.02, "duration": 1.49}, {"text": "Both the tokens-- I'm\nmining the tokens.", "start": 2175.51, "duration": 1.9}, {"text": "But in any case, I\nwouldn't disregard maybe", "start": 2177.41, "duration": 5.02}, {"text": "tokens that's a valid way of\ngenerating a means to jumpstart", "start": 2182.43, "duration": 5.43}, {"text": "a network and create\nsome sort of valid way", "start": 2187.86, "duration": 6.98}, {"text": "to drive collective action for\nsome disintermediation effort,", "start": 2194.84, "duration": 6.43}, {"text": "because I mean I--", "start": 2201.27, "duration": 1.96}, {"text": "and I think it's a\nlittle bit unfair", "start": 2203.23, "duration": 2.59}, {"text": "to ask if we kind of\njoin or support ICOs", "start": 2205.82, "duration": 5.1}, {"text": "in the context of there's\nhuge amount of scams", "start": 2210.92, "duration": 3.477}, {"text": "that are [INAUDIBLE]\nright now in the media.", "start": 2214.397, "duration": 1.833}, {"text": "But I wouldn't disregard the\nwhole concept of tokens here.", "start": 2216.23, "duration": 3.807}, {"text": "GARY GENSLER: [INAUDIBLE].", "start": 2220.037, "duration": 1.083}, {"text": "I admit it might have\nbeen an unfair question.", "start": 2221.12, "duration": 2.25}, {"text": "I was just trying to get--", "start": 2223.37, "duration": 1.35}, {"text": "I was just trying to get some\nsupport in the room for tokens.", "start": 2224.72, "duration": 5.02}, {"text": "AUDIENCE: The concept for\nme is absolutely valid.", "start": 2229.74, "duration": 2.81}, {"text": "I would explore,\nseriously explore--", "start": 2232.55, "duration": 2.76}, {"text": "if I launch a startup\nin the blockchain space,", "start": 2235.31, "duration": 3.54}, {"text": "seriously explore\nthe possibility", "start": 2238.85, "duration": 2.04}, {"text": "of using maybe tokens in the\npermissionless environment.", "start": 2240.89, "duration": 4.14}, {"text": "So I suppose the permission--", "start": 2245.03, "duration": 1.47}, {"text": "GARY GENSLER: So I think\nthat there is definitely", "start": 2246.5, "duration": 5.22}, {"text": "a future in this overall\ntechnology of making", "start": 2251.72, "duration": 6.11}, {"text": "a database harder\nto tamper with,", "start": 2257.83, "duration": 4.99}, {"text": "more immutable on\na scale, maybe not", "start": 2262.82, "duration": 2.64}, {"text": "100% immutable, but\ncloser to that immutable", "start": 2265.46, "duration": 3.37}, {"text": "and inverifiable.", "start": 2268.83, "duration": 2.75}, {"text": "I think that native tokens\ncould help jump start a network.", "start": 2271.58, "duration": 4.48}, {"text": "What I think the challenge\nis I think the challenge is,", "start": 2276.06, "duration": 3.68}, {"text": "how do you compete\nwith fiat currency", "start": 2279.74, "duration": 2.75}, {"text": "that has such extraordinary\nnetwork effects?", "start": 2282.49, "duration": 4.62}, {"text": "So the Ernst & Young study,\nthe recent study, I think", "start": 2287.11, "duration": 3.68}, {"text": "captures this a bit when they\nlooked at the 140 largest ICOs", "start": 2290.79, "duration": 4.08}, {"text": "from 2017.", "start": 2294.87, "duration": 2.16}, {"text": "Only about I think\nit was 17 of 140", "start": 2297.03, "duration": 3.36}, {"text": "have a functioning\nnetwork right now,", "start": 2300.39, "duration": 2.46}, {"text": "where you can use\nthe token, 13%.", "start": 2302.85, "duration": 3.48}, {"text": "But of those 17, I\nthink seven of them,", "start": 2306.33, "duration": 3.78}, {"text": "the networks that are\nlive, instead of, well,", "start": 2310.11, "duration": 2.25}, {"text": "guess what, we'll also take\nfiat currency for this service", "start": 2312.36, "duration": 3.36}, {"text": "that we're providing,\nwhether they're providing", "start": 2315.72, "duration": 2.13}, {"text": "file storage or something else.", "start": 2317.85, "duration": 1.75}, {"text": "So they definitely\nused a native token", "start": 2319.6, "duration": 1.97}, {"text": "to jumpstart the network\nas a crowdfunding,", "start": 2321.57, "duration": 3.48}, {"text": "but then when they got to\nthe later functional stage,", "start": 2325.05, "duration": 4.5}, {"text": "the operator, the\nentrepreneur says,", "start": 2329.55, "duration": 2.16}, {"text": "I don't want to limit my users.", "start": 2331.71, "duration": 2.03}, {"text": "I'm going to also take fiat\ncurrency to buy or secure", "start": 2333.74, "duration": 3.52}, {"text": "whatever service I'm having.", "start": 2337.26, "duration": 2.46}, {"text": "And I think that's the\nbusiness model challenge.", "start": 2339.72, "duration": 3.12}, {"text": "And it may well be that\nthere are networks,", "start": 2345.52, "duration": 4.59}, {"text": "just like in gaming sites,\nwhere you want skins or shields,", "start": 2350.11, "duration": 3.78}, {"text": "and there's something about\nonly trading those tokens.", "start": 2353.89, "duration": 3.54}, {"text": "But to date, that's\nbeen a limited class.", "start": 2360.58, "duration": 2.67}, {"text": "That's where I probably\nwill declare myself.", "start": 2363.25, "duration": 5.43}, {"text": "I think, of course, there's\na bunch of tradeoffs", "start": 2368.68, "duration": 3.18}, {"text": "over the next three\nto seven years", "start": 2371.86, "duration": 2.25}, {"text": "that will be sorted out around\nperformance, privacy, security.", "start": 2374.11, "duration": 4.24}, {"text": "We talked about layer 2.", "start": 2378.35, "duration": 1.62}, {"text": "If any of you are actually\ninterested in work", "start": 2379.97, "duration": 3.26}, {"text": "in the blockchain\ntechnology field,", "start": 2383.23, "duration": 1.86}, {"text": "you're going to learn a\nlot about layer 2 solutions", "start": 2385.09, "duration": 2.58}, {"text": "and side chains and all the\nperformance scalability things", "start": 2387.67, "duration": 3.96}, {"text": "that colleagues over at the\nDigital Currency Initiative", "start": 2391.63, "duration": 2.79}, {"text": "are spending a lot of time\non this question right here.", "start": 2394.42, "duration": 4.59}, {"text": "And then, of course,\nthis is a business model.", "start": 2399.01, "duration": 2.61}, {"text": "Just purely as a\nventure capitalist,", "start": 2401.62, "duration": 1.882}, {"text": "you have to think about,\nhow do I get adoption?", "start": 2403.502, "duration": 1.958}, {"text": "How do-- what's my\ncustomer user interface?", "start": 2405.46, "duration": 2.31}, {"text": "I'm sure, Iman, you're thinking\na lot about this, right?", "start": 2407.77, "duration": 3.15}, {"text": "You could have the best\nidea on a data structure.", "start": 2410.92, "duration": 2.94}, {"text": "You could have a really\nnifty idea on a native token.", "start": 2413.86, "duration": 3.6}, {"text": "But you still have\nto deal with whatever", "start": 2417.46, "duration": 2.13}, {"text": "venture capitalist has to do is,\nhow do I get users to use this?", "start": 2419.59, "duration": 4.68}, {"text": "Adoption.", "start": 2424.27, "duration": 0.63}, {"text": "What's my UI?", "start": 2424.9, "duration": 2.22}, {"text": "And it's sort of a much\nmore generic set of issues.", "start": 2427.12, "duration": 5.19}, {"text": "Iman.", "start": 2432.31, "duration": 0.5}, {"text": "AUDIENCE: That was\nmy answer to Jihee.", "start": 2432.81, "duration": 2.17}, {"text": "She's totally right.", "start": 2434.98, "duration": 1.92}, {"text": "It's all about-- it's a tension\nbetween adoption and quality", "start": 2436.9, "duration": 6.48}, {"text": "of product.", "start": 2443.38, "duration": 1.26}, {"text": "And that's why we\nmoved from Ethereum", "start": 2444.64, "duration": 3.548}, {"text": "to the public blockchain.", "start": 2448.188, "duration": 1.042}, {"text": "But we didn't think that\nit will be mass adopt by--", "start": 2449.23, "duration": 4.48}, {"text": "massively adopted\nby the incumbents.", "start": 2453.71, "duration": 2.84}, {"text": "So we moved to a\npermission blockchain", "start": 2456.55, "duration": 3.03}, {"text": "because of the adoption.", "start": 2459.58, "duration": 2.005}, {"text": "GARY GENSLER: And I can't\nremember if you're able to say.", "start": 2461.585, "duration": 2.375}, {"text": "Which are you using--", "start": 2463.96, "duration": 1.47}, {"text": "Hyperledger Fabric or Corda or?", "start": 2465.43, "duration": 2.61}, {"text": "AUDIENCE: We're using Corda\nbecause of the state channels", "start": 2468.04, "duration": 2.71}, {"text": "solution that they provide.", "start": 2470.75, "duration": 3.36}, {"text": "GARY GENSLER: So we\ntalked about frameworks.", "start": 2474.11, "duration": 3.15}, {"text": "Over time, it's my thought that\nthat orange line, the slope", "start": 2477.26, "duration": 4.17}, {"text": "of that will come down,\nand we'll move more", "start": 2481.43, "duration": 2.13}, {"text": "towards the decentralized side.", "start": 2483.56, "duration": 2.34}, {"text": "But for the orange line, the\nslope to come down, in essence,", "start": 2485.9, "duration": 4.2}, {"text": "the costs of the scalability,\nsecurity, even the coordination", "start": 2490.1, "duration": 4.44}, {"text": "needs to come down.", "start": 2494.54, "duration": 1.2}, {"text": "It's always going to be some\nchallenge on governance.", "start": 2495.74, "duration": 3.18}, {"text": "In essence, who is going\nto pay for the software", "start": 2498.92, "duration": 3.57}, {"text": "development in a truly\ndecentralized network?", "start": 2502.49, "duration": 4.68}, {"text": "And Bitcoin has been supported,\nfor instance, by, really,", "start": 2507.17, "duration": 5.73}, {"text": "an incredible group of\nBitcoin Core developers,", "start": 2512.9, "duration": 3.3}, {"text": "in part because\nthey just believe", "start": 2516.2, "duration": 2.19}, {"text": "in it, in part that\nsome are funded", "start": 2518.39, "duration": 2.13}, {"text": "by institutions like MIT.", "start": 2520.52, "duration": 4.01}, {"text": "But it's still-- it's always\na challenge in a truly", "start": 2524.53, "duration": 3.19}, {"text": "decentralized space.", "start": 2527.72, "duration": 1.59}, {"text": "Who's going to fund--", "start": 2529.31, "duration": 1.26}, {"text": "who's got the economic interest\nto fund the continued updates", "start": 2530.57, "duration": 4.11}, {"text": "and software?", "start": 2534.68, "duration": 1.17}, {"text": "I think Uber could be completely\na decentralized network.", "start": 2535.85, "duration": 5.43}, {"text": "And probably, drivers\nwould get paid more.", "start": 2541.28, "duration": 3.93}, {"text": "But then where would\nbe the incentive?", "start": 2545.21, "duration": 2.28}, {"text": "Who would work on the\nsoftware development", "start": 2547.49, "duration": 2.22}, {"text": "to update their ride app?", "start": 2549.71, "duration": 3.71}, {"text": "So there's a key tradeoff there.", "start": 2553.42, "duration": 3.89}, {"text": "The financial sector--\nwell, it moves and allocates", "start": 2557.31, "duration": 3.03}, {"text": "money and risk.", "start": 2560.34, "duration": 1.17}, {"text": "We talked about that.", "start": 2561.51, "duration": 1.38}, {"text": "But it relies on a\nsystem of ledgers,", "start": 2562.89, "duration": 2.28}, {"text": "and it's always had a symbiotic\nrelationship with technology.", "start": 2565.17, "duration": 5.22}, {"text": "The opportunities-- these\nare the key opportunities,", "start": 2570.39, "duration": 3.06}, {"text": "which I think any\nthought fintech--", "start": 2573.45, "duration": 2.01}, {"text": "it's not just blockchain but\neven AI and machine learning--", "start": 2575.46, "duration": 3.6}, {"text": "has around finances.", "start": 2579.06, "duration": 2.31}, {"text": "The customer\ninterfaces-- there's", "start": 2581.37, "duration": 1.53}, {"text": "a lot of legacy\ncustomer interfaces", "start": 2582.9, "duration": 1.95}, {"text": "that you can actually\ncompete with,", "start": 2584.85, "duration": 1.56}, {"text": "if you're doing a startup.", "start": 2586.41, "duration": 1.74}, {"text": "The economic rents are high.", "start": 2588.15, "duration": 2.6}, {"text": "There's 7 and 1/2 percent\nof the economy is finance.", "start": 2590.75, "duration": 2.98}, {"text": "Not all of the 7 and\n1/2 percent is rents,", "start": 2593.73, "duration": 2.61}, {"text": "but there is a lot of extra--", "start": 2596.34, "duration": 3.13}, {"text": "excuse the expression-- a\nlot of extra vig or juice", "start": 2599.47, "duration": 2.75}, {"text": "in that model.", "start": 2602.22, "duration": 4.11}, {"text": "And, of course, we've\nhad repeated crises", "start": 2606.33, "duration": 2.97}, {"text": "and instability.", "start": 2609.3, "duration": 0.96}, {"text": "And financial inclusion--\nwe talked about products", "start": 2610.26, "duration": 3.54}, {"text": "like Alipay and M-Pesa\nthat were really", "start": 2613.8, "duration": 3.18}, {"text": "about financial inclusion\nusing new technologies.", "start": 2616.98, "duration": 4.45}, {"text": "So what are the\ntechnologies in our time?", "start": 2621.43, "duration": 2.51}, {"text": "I just put up a nice\nlittle graphic here.", "start": 2623.94, "duration": 3.9}, {"text": "I'm doing some work\nwith a group called", "start": 2627.84, "duration": 1.95}, {"text": "FinTech at CSAIL, the Computer\nScience and AI Lab here.", "start": 2629.79, "duration": 4.02}, {"text": "And when we leave with\nthe funding companies,", "start": 2633.81, "duration": 2.37}, {"text": "the big funding companies\nof that unit over there,", "start": 2636.18, "duration": 4.6}, {"text": "blockchain is on their list,\nbut it's not number one.", "start": 2640.78, "duration": 2.855}, {"text": "To just put it in context, in\nterms of their technologies,", "start": 2643.635, "duration": 2.99}, {"text": "they're thinking\nabout machine learning", "start": 2646.625, "duration": 1.625}, {"text": "and AI would probably\nbe the biggest piece.", "start": 2648.25, "duration": 4.02}, {"text": "But just to give a flavor for--", "start": 2652.27, "duration": 3.03}, {"text": "but it's one of the\ntop three or four.", "start": 2655.3, "duration": 3.69}, {"text": "But as we've talked about,\nthey have challenges.", "start": 2658.99, "duration": 3.06}, {"text": "The financial sector\nsees a lot of challenges.", "start": 2662.05, "duration": 2.99}, {"text": "AUDIENCE: I just want to\ngo back to previous slides,", "start": 2665.04, "duration": 2.5}, {"text": "and how would the virtual\nreality impact finance?", "start": 2667.54, "duration": 3.39}, {"text": "I'm not sure.", "start": 2670.93, "duration": 1.73}, {"text": "[INAUDIBLE]", "start": 2672.66, "duration": 0.5}, {"text": "GARY GENSLER: That\nhas happened--", "start": 2673.16, "duration": 1.375}, {"text": "AUDIENCE: AR and VR,\n[INAUDIBLE] tech, finance.", "start": 2674.535, "duration": 2.115}, {"text": "GARY GENSLER: I'm not\nfamiliar with the projects", "start": 2681.15, "duration": 2.0}, {"text": "in that space.", "start": 2683.15, "duration": 1.74}, {"text": "But where-- and I'm\nsure I'm getting now,", "start": 2684.89, "duration": 3.513}, {"text": "you're going to inspire\nme to do some research", "start": 2688.403, "duration": 1.917}, {"text": "in the next day or two to shoot\nyour email with some projects.", "start": 2690.32, "duration": 3.45}, {"text": "But virtual reality\nand hearing it does", "start": 2693.77, "duration": 7.32}, {"text": "allow for more\nfinancial inclusion.", "start": 2701.09, "duration": 2.25}, {"text": "And the question really\nis, can you just, rather--", "start": 2703.34, "duration": 4.41}, {"text": "think of the user experience.", "start": 2707.75, "duration": 1.71}, {"text": "If you can find an enjoyable\nway to spend more money", "start": 2709.46, "duration": 8.07}, {"text": "through virtual reality,\nthe banking system", "start": 2717.53, "duration": 3.0}, {"text": "wants to tap into that.", "start": 2720.53, "duration": 2.37}, {"text": "It's not one of the top\nthings at FinTech at CSAIL,", "start": 2722.9, "duration": 4.11}, {"text": "I'd say AI, machine learning,\nbiometrics, and blockchain.", "start": 2727.01, "duration": 4.05}, {"text": "Everything's in the\ncloud, so they're not", "start": 2731.06, "duration": 1.74}, {"text": "asking, right now, MIT to\nhelp them with cloud issues.", "start": 2732.8, "duration": 4.23}, {"text": "Open API is a really big\nissue, particularly in London", "start": 2737.03, "duration": 3.09}, {"text": "and in the UK, where it's been\nregulated that the banks need", "start": 2740.12, "duration": 3.78}, {"text": "to use Open API.", "start": 2743.9, "duration": 2.01}, {"text": "So I'd say AR and\nvirtual reality", "start": 2745.91, "duration": 3.18}, {"text": "is probably eighth\non the list there.", "start": 2749.09, "duration": 4.02}, {"text": "And I just include it,\nbecause I kind of think it's--", "start": 2753.11, "duration": 2.94}, {"text": "they'll find a way to\nchange a user interface.", "start": 2756.05, "duration": 4.14}, {"text": "We talked about there's\na bunch of issues,", "start": 2760.19, "duration": 2.76}, {"text": "and that's really\nleading to the use.", "start": 2762.95, "duration": 2.88}, {"text": "We talked about traditional\ndatabases, which--", "start": 2765.83, "duration": 2.73}, {"text": "where parties can just\ncreate, read, write,", "start": 2768.56, "duration": 3.66}, {"text": "the ledger, the private\nblockchain, which,", "start": 2772.22, "duration": 2.43}, {"text": "of course, is what most of\ntrade finance, most of payments,", "start": 2774.65, "duration": 6.57}, {"text": "all the big central banks\nthat have looked at it", "start": 2781.22, "duration": 2.25}, {"text": "or moved from Ethereum to\ndoing Hyperledger projects--", "start": 2783.47, "duration": 3.83}, {"text": "Singapore and Canada's Jasper--", "start": 2787.3, "duration": 3.19}, {"text": "and maybe permissionless.", "start": 2790.49, "duration": 2.16}, {"text": "But the finance is really in\nthe second bucket right now.", "start": 2792.65, "duration": 6.65}, {"text": "Eric, it's not to say that\nnative tokens won't take off", "start": 2799.3, "duration": 3.18}, {"text": "and, Hugo, that your portfolio\nwill be worth something, maybe.", "start": 2802.48, "duration": 3.82}, {"text": "So here, we went through\na bunch of use cases.", "start": 2809.24, "duration": 5.31}, {"text": "But the biggest use case so far\nhas been the $20 to $30 billion", "start": 2814.55, "duration": 3.2}, {"text": "that's been raised through ICOs.", "start": 2817.75, "duration": 4.08}, {"text": "I personally think that's\ngoing to come down, way down.", "start": 2821.83, "duration": 5.12}, {"text": "But payment systems--", "start": 2826.95, "duration": 2.46}, {"text": "I mean we might differ on\nthe views of XRP, a token,", "start": 2829.41, "duration": 5.29}, {"text": "but Ripple and\nother companies have", "start": 2834.7, "duration": 1.98}, {"text": "done a lot to try to be a\ncatalyst for change and payment", "start": 2836.68, "duration": 3.54}, {"text": "systems.", "start": 2840.22, "duration": 1.03}, {"text": "We talked a lot\nabout trade finance.", "start": 2841.25, "duration": 1.7}, {"text": "Again, they're more\nin the permissions", "start": 2842.95, "duration": 1.77}, {"text": "than the permissionless.", "start": 2844.72, "duration": 1.26}, {"text": "Clearing and settling--\nwhat's going on in Australia.", "start": 2849.19, "duration": 2.8}, {"text": "Again, permissionless, not--\nI mean permissioned, not", "start": 2851.99, "duration": 3.98}, {"text": "permissionless.", "start": 2855.97, "duration": 2.94}, {"text": "And then some of\nthe non-financial--", "start": 2858.91, "duration": 4.33}, {"text": "had a lively discussion about\nsupply chain management,", "start": 2863.24, "duration": 3.05}, {"text": "and James, I'll forever remember\nthat you're not a fan of it.", "start": 2866.29, "duration": 4.87}, {"text": "But Walmart and Cargo\nmight disagree with James.", "start": 2871.16, "duration": 4.17}, {"text": "And they have active\nprojects on it.", "start": 2875.33, "duration": 3.15}, {"text": "And Lauren gave--\nwhere's Lauren?", "start": 2878.48, "duration": 2.68}, {"text": "She's here, maybe--\ngave a reason why", "start": 2881.16, "duration": 2.63}, {"text": "in supply chain\nsustainability that you", "start": 2883.79, "duration": 2.7}, {"text": "might be on the other side.", "start": 2886.49, "duration": 1.59}, {"text": "Digital ID was the last\nthing we talked about.", "start": 2888.08, "duration": 6.1}, {"text": "So there's a lot going on, and\nwhen there's $20 or $30 billion", "start": 2894.18, "duration": 3.71}, {"text": "raised, there's going\nto be-- these projects", "start": 2897.89, "duration": 2.04}, {"text": "will have some life to them.", "start": 2899.93, "duration": 1.69}, {"text": "We'll learn a lot from\nthem along the way.", "start": 2901.62, "duration": 4.79}, {"text": "Crypto finance-- when I\nfirst put this slide up,", "start": 2906.41, "duration": 2.31}, {"text": "it wasn't $110 billion.", "start": 2908.72, "duration": 1.63}, {"text": "And gosh knows I\ndid this yesterday,", "start": 2910.35, "duration": 2.24}, {"text": "so I don't even know\nwhat it is today.", "start": 2912.59, "duration": 2.76}, {"text": "Pretty volatile market.", "start": 2915.35, "duration": 1.44}, {"text": "Interestingly, Bitcoin staggered\nabout 55% or 57% of the market.", "start": 2916.79, "duration": 4.69}, {"text": "So there's a high correlation,\nthough Ethereum slid, and XRP", "start": 2921.48, "duration": 6.97}, {"text": "is number two in that market\nsince we first got together", "start": 2928.45, "duration": 6.06}, {"text": "in September.", "start": 2934.51, "duration": 2.13}, {"text": "Here, what I think the\nchallenge is, as an investor--", "start": 2936.64, "duration": 4.65}, {"text": "I'm not trying to pick on\nyou, Hugo, but you know,", "start": 2941.29, "duration": 2.55}, {"text": "an investor.", "start": 2943.84, "duration": 1.32}, {"text": "But I think that's the\nnumber one challenge.", "start": 2945.16, "duration": 2.61}, {"text": "I really do.", "start": 2947.77, "duration": 1.73}, {"text": "What's the viability\nof that token?", "start": 2949.5, "duration": 1.93}, {"text": "And Eric, I'll agree with you.", "start": 2951.43, "duration": 1.25}, {"text": "Some tokens will\nbe worth something.", "start": 2952.68, "duration": 2.44}, {"text": "But it's assessing that.", "start": 2955.12, "duration": 1.58}, {"text": "But the markets are readily\nsusceptible to fraud.", "start": 2956.7, "duration": 3.24}, {"text": "How do I keep custody\nfor the private key?", "start": 2959.94, "duration": 2.22}, {"text": "Fidelity has announced\nthey're going", "start": 2962.16, "duration": 1.72}, {"text": "to have a new\nprivate key solution,", "start": 2963.88, "duration": 2.12}, {"text": "so it's interesting that big\nincumbents are coming in.", "start": 2966.0, "duration": 2.94}, {"text": "It's not just the Zappos and the\nearly stage custody solutions.", "start": 2968.94, "duration": 5.55}, {"text": "Even Backed, the\nIntercontinental Exchange,", "start": 2974.49, "duration": 3.84}, {"text": "has put a lot of money into it.", "start": 2978.33, "duration": 1.5}, {"text": "And they'll, in essence,\nhave a custody solution,", "start": 2979.83, "duration": 2.55}, {"text": "because you could buy\nBitcoin, one day futures,", "start": 2982.38, "duration": 3.21}, {"text": "have a Bitcoin, and then\nthey would, in essence,", "start": 2985.59, "duration": 2.37}, {"text": "hold custody for you.", "start": 2987.96, "duration": 1.25}, {"text": "And then we talked\nabout crypto exchanges.", "start": 2991.97, "duration": 2.98}, {"text": "And the key thing-- and\nif you take anything away", "start": 2994.95, "duration": 2.81}, {"text": "about exchanges, other than\nright now they're unregulated", "start": 2997.76, "duration": 2.7}, {"text": "and they're probably highly\nsusceptible to front running", "start": 3000.46, "duration": 3.06}, {"text": "and manipulation, is that\nthey're a little bit different,", "start": 3003.52, "duration": 3.36}, {"text": "because they're\nnot just matching", "start": 3006.88, "duration": 2.25}, {"text": "agents, which the London Stock\nExchange or the New York Stock", "start": 3009.13, "duration": 3.24}, {"text": "Exchange are [INAUDIBLE],, but\nthey also are counterparties", "start": 3012.37, "duration": 3.06}, {"text": "and custodians.", "start": 3015.43, "duration": 1.08}, {"text": "The other thing to take\naway about crypto exchanges", "start": 3019.33, "duration": 3.42}, {"text": "is they're highly centralized.", "start": 3022.75, "duration": 1.68}, {"text": "So it's a central irony that\nSatoshi Nakamoto is trying", "start": 3024.43, "duration": 3.9}, {"text": "to have decentralization,\nand yet there's", "start": 3028.33, "duration": 3.86}, {"text": "an awful lot of centralization.", "start": 3032.19, "duration": 2.9}, {"text": "So I'm just thinking\nabout core takeaways.", "start": 3035.09, "duration": 2.49}, {"text": "If you're ever investing, or\nyou're thinking about this,", "start": 3037.58, "duration": 2.4}, {"text": "or you're just involved in\na dinner party conversation,", "start": 3039.98, "duration": 2.58}, {"text": "that central irony in\na decentralized space,", "start": 3042.56, "duration": 3.06}, {"text": "95% of the real transactions are\nhappening on crypto exchanges.", "start": 3045.62, "duration": 5.91}, {"text": "My thought about\ncrypto exchanges--", "start": 3054.14, "duration": 1.99}, {"text": "they'll not be 200 of them\nthat much longer either.", "start": 3056.13, "duration": 3.86}, {"text": "We talked about\nInitial Coin Offerings.", "start": 3059.99, "duration": 2.07}, {"text": "Central takeaway is they're\nfundraising vehicles.", "start": 3062.06, "duration": 3.61}, {"text": "Whether you believe\nin or not believe", "start": 3065.67, "duration": 1.76}, {"text": "in the US and Canadian\napproach under the Howey Test,", "start": 3067.43, "duration": 3.99}, {"text": "but they help build a network,\nraise money in anticipation", "start": 3071.42, "duration": 5.34}, {"text": "the tokens are issued\nbefore it's functional.", "start": 3076.76, "duration": 3.225}, {"text": "I think the latest\nstudy was that--", "start": 3079.985, "duration": 4.125}, {"text": "what was it-- 1 and 1/2 percent\nare actually functional,", "start": 3084.11, "duration": 2.46}, {"text": "and 98 and 1/2 percent\nare issued pre-functional.", "start": 3086.57, "duration": 2.64}, {"text": "So that's not a problem.", "start": 3089.21, "duration": 2.34}, {"text": "It's just-- that's the--", "start": 3091.55, "duration": 3.06}, {"text": "means it's probably an\ninvestment vehicle, not", "start": 3094.61, "duration": 2.22}, {"text": "a utility token.", "start": 3096.83, "duration": 1.44}, {"text": "And that whole thing\nabout utility token", "start": 3098.27, "duration": 1.99}, {"text": "versus security tokens, it\nstretched pretty darn thin.", "start": 3100.26, "duration": 5.75}, {"text": "We talked about public\npolicy frameworks,", "start": 3106.01, "duration": 2.67}, {"text": "guarding against illicit\nactivity, financial stability,", "start": 3108.68, "duration": 2.52}, {"text": "investing public.", "start": 3111.2, "duration": 1.41}, {"text": "My overall thought on this--", "start": 3112.61, "duration": 3.48}, {"text": "and I accept that others\nwill have other views--", "start": 3116.09, "duration": 3.12}, {"text": "is that any new technology, if\nit grows to be economy-wide,", "start": 3119.21, "duration": 6.03}, {"text": "needs to live within\npublic policy frameworks,", "start": 3125.24, "duration": 3.39}, {"text": "or society will change those\npublic policy frameworks", "start": 3128.63, "duration": 3.93}, {"text": "modestly.", "start": 3132.56, "duration": 1.63}, {"text": "But you still want\nto protect the public", "start": 3134.19, "duration": 1.88}, {"text": "against core social goods.", "start": 3136.07, "duration": 2.72}, {"text": "It happened when the\nrailroad came along.", "start": 3138.79, "duration": 1.8}, {"text": "It happened when telegram came\nalong in the 19th century.", "start": 3140.59, "duration": 2.64}, {"text": "It happened with the internet.", "start": 3143.23, "duration": 2.38}, {"text": "Societies don't\nhave technologies", "start": 3145.61, "duration": 2.16}, {"text": "fully outside of whatever\nsocial fabric we want to create.", "start": 3147.77, "duration": 6.1}, {"text": "And we do that\nsocial fabric stuff", "start": 3153.87, "duration": 1.98}, {"text": "through politics and parliaments\nand executives and regulators.", "start": 3155.85, "duration": 4.92}, {"text": "But we don't leave big parts\nof our economy outside of it.", "start": 3160.77, "duration": 4.72}, {"text": "This stuff is still small.", "start": 3165.49, "duration": 2.055}, {"text": "It's $100 billion.", "start": 3167.545, "duration": 1.695}, {"text": "The worldwide capital markets\nare over $300 trillion.", "start": 3169.24, "duration": 5.0}, {"text": "But it's gained a lot\nof public attention.", "start": 3174.24, "duration": 3.69}, {"text": "And particularly, we want to\nguard against illicit activity.", "start": 3177.93, "duration": 3.81}, {"text": "Most folks do.", "start": 3181.74, "duration": 2.91}, {"text": "Maybe not everybody.", "start": 3184.65, "duration": 1.14}, {"text": "But most do.", "start": 3185.79, "duration": 1.52}, {"text": "No, I recognize.", "start": 3187.31, "duration": 1.54}, {"text": "Hopefully, you all do.", "start": 3188.85, "duration": 1.14}, {"text": "Well, I don't know.", "start": 3189.99, "duration": 0.81}, {"text": "So we talked about the US\nSecurities Law, the Howey Test.", "start": 3193.32, "duration": 3.47}, {"text": "It's not-- if you forget the\nHowey Test, it's totally fine.", "start": 3196.79, "duration": 4.3}, {"text": "But it's core to these\ninitial coin offerings,", "start": 3201.09, "duration": 3.48}, {"text": "and it was that four-part test--", "start": 3204.57, "duration": 1.92}, {"text": "investment of money in\na common enterprise,", "start": 3206.49, "duration": 2.01}, {"text": "expectation of profits.", "start": 3208.5, "duration": 2.53}, {"text": "So if you get into\nsome debate, and you", "start": 3211.03, "duration": 1.73}, {"text": "want to have some\nfun with somebody,", "start": 3212.76, "duration": 1.57}, {"text": "you can say you\nknow the Howey Test.", "start": 3214.33, "duration": 1.52}, {"text": "But it's really more this.", "start": 3218.55, "duration": 1.84}, {"text": "I prefer the Duck Test.", "start": 3220.39, "duration": 2.06}, {"text": "Just use common sense.", "start": 3222.45, "duration": 1.83}, {"text": "This course has been more\nabout critical reasoning skills", "start": 3224.28, "duration": 3.18}, {"text": "than anything.", "start": 3227.46, "duration": 1.23}, {"text": "So if somebody's trying to sell\nyou something or hustle you", "start": 3228.69, "duration": 2.76}, {"text": "on something, and you are\nnow a venture capitalist,", "start": 3231.45, "duration": 2.85}, {"text": "and you're investing,\nuse the Duck Test.", "start": 3234.3, "duration": 3.57}, {"text": "You can even remember\nthe Duck Test", "start": 3237.87, "duration": 1.56}, {"text": "about whether they're trying\nto sell you something,", "start": 3239.43, "duration": 2.34}, {"text": "and it has nothing\nto do with the law.", "start": 3241.77, "duration": 2.32}, {"text": "It just-- so where do I think\ncrypto exchanges will go?", "start": 3244.09, "duration": 6.92}, {"text": "I think that they'll have to\nfix this whole custodial duty", "start": 3251.01, "duration": 4.38}, {"text": "stuff.", "start": 3255.39, "duration": 0.72}, {"text": "They might all use\nFidelity's product.", "start": 3256.11, "duration": 3.64}, {"text": "Or they'll keep it\nin-house or spin it off.", "start": 3259.75, "duration": 5.03}, {"text": "I think they'll have to start\ncomplying with any money", "start": 3264.78, "duration": 3.01}, {"text": "laundering.", "start": 3267.79, "duration": 0.5}, {"text": "We saw one study that said\na quarter of all exchanges", "start": 3268.29, "duration": 3.6}, {"text": "don't even have any AML.", "start": 3271.89, "duration": 2.64}, {"text": "I think two years from\nnow, that will be way down.", "start": 3274.53, "duration": 4.44}, {"text": "I think margins\nwill compress, and I", "start": 3278.97, "duration": 3.18}, {"text": "don't think there'll\nbe 200 exchanges", "start": 3282.15, "duration": 1.83}, {"text": "two or three years from now.", "start": 3283.98, "duration": 1.86}, {"text": "There'll be five or\n10 relevant exchanges", "start": 3285.84, "duration": 2.73}, {"text": "at some point in time.", "start": 3288.57, "duration": 2.79}, {"text": "On Initial Coin\nOfferings, I think", "start": 3291.36, "duration": 1.582}, {"text": "we're going to keep seeing\na high failure rate.", "start": 3292.942, "duration": 1.958}, {"text": "There's still about 200 a\nmonth, but there'll probably", "start": 3294.9, "duration": 2.25}, {"text": "be fewer of them.", "start": 3297.15, "duration": 2.58}, {"text": "I think that there's going to\nbe a lot of enforcement actions.", "start": 3299.73, "duration": 3.45}, {"text": "Occasionally, you'll\nsee something--", "start": 3303.18, "duration": 1.68}, {"text": "the Securities and Exchange\nCommission or some other--", "start": 3304.86, "duration": 2.57}, {"text": "maybe it will be in\nJapan or elsewhere will", "start": 3307.43, "duration": 1.81}, {"text": "be bringing more cases.", "start": 3309.24, "duration": 2.07}, {"text": "And what will be interesting\nin 2019 is to watch,", "start": 3311.31, "duration": 3.36}, {"text": "does any of the\nbig ones go live?", "start": 3314.67, "duration": 2.91}, {"text": "And I think this\nwill be a real test.", "start": 3317.58, "duration": 2.16}, {"text": "Does Filecoin figure\nout what to do?", "start": 3319.74, "duration": 2.25}, {"text": "They raised a quarter\nof a billion dollars.", "start": 3321.99, "duration": 2.7}, {"text": "Telegram raised $1.7 billion.", "start": 3324.69, "duration": 4.73}, {"text": "Do they figure out\nwhat to do and make", "start": 3329.42, "duration": 2.01}, {"text": "a real live effort in 2019?", "start": 3331.43, "duration": 2.61}, {"text": "And it will test the economics.", "start": 3334.04, "duration": 2.1}, {"text": "And by the way, Eric,\nit might pull me more", "start": 3336.14, "duration": 1.92}, {"text": "towards where you are, right?", "start": 3338.06, "duration": 2.58}, {"text": "I mean Telegram's-- they got a\nlot of smart folks over there", "start": 3340.64, "duration": 2.97}, {"text": "working on this.", "start": 3343.61, "duration": 1.71}, {"text": "And by the way, Facebook\nhas advertisements out", "start": 3345.32, "duration": 2.5}, {"text": "hiring people on\nblockchain technology.", "start": 3347.82, "duration": 2.56}, {"text": "So there's a lot of very\nbig tech companies hiring", "start": 3350.38, "duration": 2.9}, {"text": "and recruiting in this space.", "start": 3353.28, "duration": 1.78}, {"text": "But I think 2019 will be\ninteresting to see, what does--", "start": 3355.06, "duration": 2.87}, {"text": "what is Telegram?", "start": 3357.93, "duration": 0.75}, {"text": "What is Filecoin?", "start": 3358.68, "duration": 0.9}, {"text": "What do some of the big,\nhopefully, well-meaning", "start": 3359.58, "duration": 3.42}, {"text": "companies do with these tokens?", "start": 3363.0, "duration": 3.99}, {"text": "Central banks-- mostly\nin the monitor phase.", "start": 3366.99, "duration": 3.66}, {"text": "But I'd say the thing\nto watch is Sweden.", "start": 3370.65, "duration": 2.298}, {"text": "It'll be really\ninteresting what they", "start": 3372.948, "duration": 1.542}, {"text": "do with their E-krona project.", "start": 3374.49, "duration": 1.88}, {"text": "Do they go live and say,\ninspired by blockchain?", "start": 3376.37, "duration": 4.24}, {"text": "The E-krona project is\nnot blockchain technology,", "start": 3380.61, "duration": 2.88}, {"text": "but it's completely inspired by\nSatoshi Nakamoto saying, well,", "start": 3383.49, "duration": 4.44}, {"text": "we, the central bank, Jihee's\nthe central bank says,", "start": 3387.93, "duration": 5.07}, {"text": "we're going to do what\nSatoshi Nakamoto's--", "start": 3393.0, "duration": 3.24}, {"text": "we're going to have a\ncentral bank digital token.", "start": 3396.24, "duration": 3.39}, {"text": "You can use it at Starbucks.", "start": 3399.63, "duration": 1.51}, {"text": "You can use it wherever.", "start": 3401.14, "duration": 1.49}, {"text": "I'd watch that.", "start": 3402.63, "duration": 0.78}, {"text": "I think Venezuela will\nprobably fail on the other end.", "start": 3403.41, "duration": 4.28}, {"text": "But it'll be interesting.", "start": 3407.69, "duration": 1.09}, {"text": "There might be some distressed\ncountry that does something.", "start": 3408.78, "duration": 5.94}, {"text": "So how would I conclude?", "start": 3414.72, "duration": 2.59}, {"text": "I think blockchain does--", "start": 3417.31, "duration": 1.37}, {"text": "this is my disclosure.", "start": 3418.68, "duration": 2.43}, {"text": "I think it does provide a\nreal peer-to-peer alternative.", "start": 3421.11, "duration": 3.45}, {"text": "I think it's a legit\nlive application.", "start": 3424.56, "duration": 4.08}, {"text": "It might not be the best, but\nis it better than some others?", "start": 3428.64, "duration": 3.22}, {"text": "Is it something you could use?", "start": 3431.86, "duration": 2.69}, {"text": "Verification and\nnetworking cost--", "start": 3434.55, "duration": 2.126}, {"text": "I'm going to repeat on that--", "start": 3436.676, "duration": 2.434}, {"text": "is the key.", "start": 3439.11, "duration": 2.22}, {"text": "But you always, I think,\nhave to assess, is it", "start": 3441.33, "duration": 2.19}, {"text": "the right use case?", "start": 3443.52, "duration": 1.41}, {"text": "Is this use case\nthe right use case?", "start": 3444.93, "duration": 3.083}, {"text": "But as we've talked,\nI think there", "start": 3448.013, "duration": 1.417}, {"text": "are real use cases\nmore in permissioned", "start": 3449.43, "duration": 3.51}, {"text": "than permissionless.", "start": 3452.94, "duration": 1.57}, {"text": "Remember anything.", "start": 3457.27, "duration": 0.84}, {"text": "Money is just-- we all\nhumans, the 7 billion", "start": 3458.11, "duration": 4.68}, {"text": "of us that live now,\nhave to thank somebody", "start": 3462.79, "duration": 2.94}, {"text": "about 10,000 years ago, but came\nup with this technology called", "start": 3465.73, "duration": 4.29}, {"text": "money.", "start": 3470.02, "duration": 1.35}, {"text": "Store value, medium\nof exchange, unit", "start": 3471.37, "duration": 2.19}, {"text": "of account-- it's just a\nsocial construct, which", "start": 3473.56, "duration": 2.31}, {"text": "is a reason why I say, we\ncould have a social construct", "start": 3475.87, "duration": 2.61}, {"text": "that is decentralized money.", "start": 3478.48, "duration": 2.9}, {"text": "I absolutely believe\nwe could have that.", "start": 3481.38, "duration": 2.95}, {"text": "But we'd all have to accept it.", "start": 3484.33, "duration": 1.8}, {"text": "Where I have less\noptimism is that you'd", "start": 3486.13, "duration": 3.03}, {"text": "want to accept it for a\nclosed, bounded ecosystem", "start": 3489.16, "duration": 4.2}, {"text": "only for file storage.", "start": 3493.36, "duration": 1.98}, {"text": "That's where I'm a\nlittle challenged as to,", "start": 3495.34, "duration": 3.09}, {"text": "what is the real\neconomics of that?", "start": 3498.43, "duration": 5.5}, {"text": "Financial sector's\ncharacteristics", "start": 3503.93, "duration": 1.89}, {"text": "and challenges--", "start": 3505.82, "duration": 1.74}, {"text": "is it good?", "start": 3507.56, "duration": 1.52}, {"text": "It's fertile ground, because\nfinance is built on ledgers.", "start": 3509.08, "duration": 4.45}, {"text": "And finance is big--", "start": 3513.53, "duration": 1.56}, {"text": "7 and 1/2 percent\nof our economy.", "start": 3515.09, "duration": 3.35}, {"text": "And around the globe,\nit's anywhere from 5%", "start": 3518.44, "duration": 2.77}, {"text": "to probably 8% of\nthose economies.", "start": 3521.21, "duration": 2.21}, {"text": "Most other countries,\nit's less than the US,", "start": 3523.42, "duration": 2.09}, {"text": "but it's still-- it's big.", "start": 3525.51, "duration": 3.68}, {"text": "Incumbents are,\nof course, looking", "start": 3529.19, "duration": 1.5}, {"text": "at permissioned blockchains.", "start": 3530.69, "duration": 2.28}, {"text": "And unfortunately,\ncrypto finance", "start": 3532.97, "duration": 1.77}, {"text": "has a bunch of scams and frauds.", "start": 3534.74, "duration": 3.06}, {"text": "And that hurts the development.", "start": 3537.8, "duration": 4.06}, {"text": "But I think adoption\nwill come, but it", "start": 3541.86, "duration": 3.87}, {"text": "rests on solving a bunch\nof technical issues,", "start": 3545.73, "duration": 2.34}, {"text": "like the Digital Currency\nInitiative's trying to solve.", "start": 3548.07, "duration": 3.73}, {"text": "What are the commercial use\ncases and the public policy?", "start": 3551.8, "duration": 2.76}, {"text": "I wouldn't lead\nwith public policy.", "start": 3554.56, "duration": 1.55}, {"text": "I don't think that's\nthe main issue here.", "start": 3556.11, "duration": 2.27}, {"text": "But if this is ever\ngoing to be anything,", "start": 3558.38, "duration": 2.82}, {"text": "it's got to get over that.", "start": 3561.2, "duration": 3.2}, {"text": "So mostly, it's probably going\nto be a catalyst for change,", "start": 3564.4, "duration": 2.52}, {"text": "more than actual real thoughts.", "start": 3566.92, "duration": 4.79}, {"text": "Questions?", "start": 3571.71, "duration": 1.012}, {"text": "Thoughts?", "start": 3575.82, "duration": 1.8}, {"text": "Eric.", "start": 3577.62, "duration": 0.565}, {"text": "AUDIENCE: On the\nthird point, I--", "start": 3578.185, "duration": 3.468}, {"text": "GARY GENSLER: Use\ncases must address why", "start": 3581.653, "duration": 1.667}, {"text": "versus a traditional database.", "start": 3583.32, "duration": 1.74}, {"text": "AUDIENCE: I always\nhad the feeling", "start": 3585.06, "duration": 1.47}, {"text": "that it seemed the\npermissioned space, where", "start": 3586.53, "duration": 2.94}, {"text": "you have the most or the\nbiggest urge to prove where--", "start": 3589.47, "duration": 4.72}, {"text": "if your submission needs a\nblockchain solution as opposed", "start": 3594.19, "duration": 6.44}, {"text": "to a traditional--", "start": 3600.63, "duration": 1.295}, {"text": "I mean making a case against\nthe centralized database", "start": 3601.925, "duration": 3.115}, {"text": "is kind of easy, versus\na distributed database.", "start": 3605.04, "duration": 3.715}, {"text": "I think it's a little bit tough.", "start": 3608.755, "duration": 2.455}, {"text": "But in the\npermissionless space, I", "start": 3611.21, "duration": 2.777}, {"text": "think you don't have\nto struggle much,", "start": 3613.987, "duration": 1.583}, {"text": "because it's absolutely\njustified that you can--", "start": 3615.57, "duration": 3.24}, {"text": "because you're dealing with a\ndecentralized configuration,", "start": 3618.81, "duration": 4.2}, {"text": "where there's no one in\ncharge of guaranteeing", "start": 3623.01, "duration": 4.89}, {"text": "that we have a--", "start": 3627.9, "duration": 2.12}, {"text": "GARY GENSLER: So Eric's\nraising the question,", "start": 3630.02, "duration": 2.29}, {"text": "why not use a\ntraditional database?", "start": 3632.31, "duration": 2.17}, {"text": "Why ever use a permissioned--", "start": 3634.48, "duration": 1.64}, {"text": "AUDIENCE: In the\npermissioned space,", "start": 3636.12, "duration": 1.5}, {"text": "because permissionless\nis perfectly justified.", "start": 3637.62, "duration": 2.46}, {"text": "But in the\npermissioned space, I'm", "start": 3640.08, "duration": 1.47}, {"text": "not saying it's not justified.", "start": 3641.55, "duration": 2.95}, {"text": "The point is being\nthat in our project,", "start": 3644.5, "duration": 4.34}, {"text": "we argued for a\npermissioned system.", "start": 3648.84, "duration": 2.97}, {"text": "We made some justifications\nin that space,", "start": 3651.81, "duration": 2.1}, {"text": "so the point is that I just\nwanted to get your thoughts so", "start": 3653.91, "duration": 6.06}, {"text": "that in the\npermissionless spaces,", "start": 3659.97, "duration": 1.79}, {"text": "you don't have to\nstruggle much in that.", "start": 3661.76, "duration": 2.38}, {"text": "GARY GENSLER: Permissionless\nblockchain technology,", "start": 3664.14, "duration": 4.66}, {"text": "looking forward a\nnumber of years,", "start": 3668.8, "duration": 1.68}, {"text": "looking forward to when some of\nthe scalability and performance", "start": 3670.48, "duration": 3.09}, {"text": "gets better, can give\nyou verification costs.", "start": 3673.57, "duration": 3.97}, {"text": "And it's censorship-resistant\nor practically", "start": 3677.54, "duration": 5.18}, {"text": "censorship-resistant, unless\nsomebody does a 51% attack.", "start": 3682.72, "duration": 4.29}, {"text": "But so I think that the truly\ndecentralized distributed", "start": 3687.01, "duration": 4.11}, {"text": "permissionless system has\na lot of-- a lot to offer.", "start": 3691.12, "duration": 5.36}, {"text": "But it comes with a lot of\ncosts, too, and challenges--", "start": 3696.48, "duration": 3.23}, {"text": "hard to do the governance and\nhard to get coordinated action.", "start": 3699.71, "duration": 4.53}, {"text": "And as you've heard\nme say, I think", "start": 3704.24, "duration": 2.46}, {"text": "there's only probably going\nto be a very limited use", "start": 3706.7, "duration": 2.7}, {"text": "cases for native tokens,\nnative product-specific tokens", "start": 3709.4, "duration": 7.0}, {"text": "like a Filecoin or a restaurant\nreview coin or a health care", "start": 3716.4, "duration": 7.29}, {"text": "coin.", "start": 3723.69, "duration": 1.05}, {"text": "I have-- I have my\ndoubts about that.", "start": 3724.74, "duration": 3.33}, {"text": "An economy-wide coin, a\ncryptocurrency like Bitcoin--", "start": 3728.07, "duration": 3.75}, {"text": "I think there's more\nuse, particularly", "start": 3731.82, "duration": 2.37}, {"text": "if you have a weak central\nbank, a weak fiscal policy.", "start": 3734.19, "duration": 3.33}, {"text": "A country like Venezuela in the\nfuture might adopt something.", "start": 3737.52, "duration": 5.1}, {"text": "I think there's a lot to\nbe said for permissionless,", "start": 3742.62, "duration": 2.22}, {"text": "but permissioned systems versus\ntraditional databases, I think,", "start": 3744.84, "duration": 3.75}, {"text": "also gives something.", "start": 3748.59, "duration": 1.59}, {"text": "And I'll use the Australian\nstock exchange for one,", "start": 3750.18, "duration": 2.97}, {"text": "but they know their customers.", "start": 3753.15, "duration": 1.8}, {"text": "They know they have--", "start": 3754.95, "duration": 0.96}, {"text": "I think the number\nwas 77 members.", "start": 3755.91, "duration": 2.73}, {"text": "They can take their database\nand decentralize it and put it", "start": 3758.64, "duration": 3.87}, {"text": "on all 77 member companies,\nif that's the right number,", "start": 3762.51, "duration": 5.22}, {"text": "and say, you're\nnow sharing that.", "start": 3767.73, "duration": 3.45}, {"text": "And so then there's no\nsingle point of failure,", "start": 3771.18, "duration": 2.43}, {"text": "and we can lower what's\ncalled reconciliation costs,", "start": 3773.61, "duration": 2.76}, {"text": "because you all needed\nsome of that data anyway.", "start": 3776.37, "duration": 3.0}, {"text": "The historic data-keeping,\nthe historic nature of it", "start": 3779.37, "duration": 5.25}, {"text": "came up with each\nof those 77 members", "start": 3784.62, "duration": 2.61}, {"text": "having individual databases.", "start": 3787.23, "duration": 2.14}, {"text": "So I could see that there is\na real benefit in probably", "start": 3789.37, "duration": 3.17}, {"text": "efficiency and\nlowering costs, which", "start": 3792.54, "duration": 3.27}, {"text": "means lowering costs\nof verification,", "start": 3795.81, "duration": 2.84}, {"text": "lowering networking\ncosts, because there's", "start": 3798.65, "duration": 1.75}, {"text": "77 members, trade finance.", "start": 3800.4, "duration": 2.85}, {"text": "I could see some\nof that as well.", "start": 3803.25, "duration": 1.78}, {"text": "So that-- but you\nmight be right.", "start": 3805.03, "duration": 2.21}, {"text": "Oracle might be\nable to just adopt", "start": 3807.24, "duration": 1.68}, {"text": "that in a traditional database.", "start": 3808.92, "duration": 1.37}, {"text": "Sabrina.", "start": 3810.29, "duration": 0.575}, {"text": "AUDIENCE: Yeah, so\nit seems like you're", "start": 3810.865, "duration": 1.625}, {"text": "describing that they have some\nform of distributed consensus.", "start": 3812.49, "duration": 3.31}, {"text": "And that's the\nmain reason, right?", "start": 3815.8, "duration": 1.59}, {"text": "But there's--", "start": 3817.39, "duration": 1.446}, {"text": "GARY GENSLER: And\ndistributed the data", "start": 3818.836, "duration": 2.054}, {"text": "stored on multiple nodes,\nbecause it's multiple copies", "start": 3820.89, "duration": 3.09}, {"text": "of the same data.", "start": 3823.98, "duration": 1.06}, {"text": "AUDIENCE: Right, but yeah.", "start": 3825.04, "duration": 2.54}, {"text": "There's-- I mean if that still\ncan be implemented without", "start": 3827.58, "duration": 3.11}, {"text": "watching.", "start": 3830.69, "duration": 1.08}, {"text": "I'm playing the Aleem\ntoday, since he's not here.", "start": 3831.77, "duration": 2.686}, {"text": "But there's no--", "start": 3834.456, "duration": 1.061}, {"text": "GARY GENSLER: No, but we--", "start": 3835.517, "duration": 1.083}, {"text": "AUDIENCE: That's been a long\nsolved problem of how consensus", "start": 3836.6, "duration": 3.07}, {"text": "algorithms that--\nor you can replicate", "start": 3839.67, "duration": 1.69}, {"text": "state on the same state\non both the machines", "start": 3841.36, "duration": 5.02}, {"text": "and tolerate some [INAUDIBLE]\nnumber of failures.", "start": 3846.38, "duration": 3.11}, {"text": "So I personally don't really\nsee the use of blockchain", "start": 3849.49, "duration": 4.98}, {"text": "in permissioned systems, but\nI do see a lot of potential", "start": 3854.47, "duration": 4.52}, {"text": "for permissionless systems,\njust because those algorithms", "start": 3858.99, "duration": 2.79}, {"text": "already exist out there\nto do [INAUDIBLE]..", "start": 3861.78, "duration": 2.76}, {"text": "GARY GENSLER: So what\nSabrina's raising--", "start": 3864.54, "duration": 2.01}, {"text": "you can take the Sabrina seat.", "start": 3866.55, "duration": 1.86}, {"text": "You're-- Sabrina's a master's\nstudent at computer science", "start": 3868.41, "duration": 5.65}, {"text": "at MIT, so she probably knows\nwhat she's talking about--", "start": 3874.06, "duration": 4.1}, {"text": "is really saying, well,\nyou can do a lot of that.", "start": 3878.16, "duration": 3.75}, {"text": "You can have\ndistributed databases", "start": 3881.91, "duration": 2.73}, {"text": "without blockchain technology.", "start": 3884.64, "duration": 2.61}, {"text": "You can have-- and\nthere's ways that", "start": 3887.25, "duration": 2.13}, {"text": "this Byzantine-fought\ntolerance has been addressed", "start": 3889.38, "duration": 3.0}, {"text": "in distributed\ndatabases that you don't", "start": 3892.38, "duration": 3.48}, {"text": "need blockchain technology.", "start": 3895.86, "duration": 1.65}, {"text": "The concept of a block,\ncommitment hash, block,", "start": 3897.51, "duration": 4.545}, {"text": "a commitment hash,\nblock technology.", "start": 3902.055, "duration": 4.045}, {"text": "And I accept that.", "start": 3906.1, "duration": 1.14}, {"text": "But I'm not going\nto accept it to say", "start": 3907.24, "duration": 3.65}, {"text": "that there's no space for\npermissioned blockchain", "start": 3910.89, "duration": 2.94}, {"text": "technology.", "start": 3913.83, "duration": 1.68}, {"text": "What there is space\nfor is the 80 of you", "start": 3915.51, "duration": 2.37}, {"text": "in this room to have different\nopinions on all of this.", "start": 3917.88, "duration": 3.88}, {"text": "You want to close out?", "start": 3921.76, "duration": 1.005}, {"text": "I want to-- I have one\nmore slide I want to--", "start": 3922.765, "duration": 1.875}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3924.64, "duration": 1.988}, {"text": "GARY GENSLER: So this is,\nof course, about money,", "start": 3926.628, "duration": 2.042}, {"text": "so I went back and found a\nquote from Benjamin Franklin", "start": 3928.67, "duration": 3.09}, {"text": "that I like.", "start": 3931.76, "duration": 0.99}, {"text": "And to me, it's about a concept\nthat I hope you all live by.", "start": 3932.75, "duration": 3.57}, {"text": "It's paying it forward.", "start": 3936.32, "duration": 2.6}, {"text": "Paying forward is partly\nbecause all of us in this room", "start": 3938.92, "duration": 4.6}, {"text": "are privileged.", "start": 3943.52, "duration": 0.84}, {"text": "We're at MIT or Harvard or\nWellesley, but we're at MIT.", "start": 3944.36, "duration": 6.81}, {"text": "And so what did\nBen Franklin say?", "start": 3951.17, "duration": 1.8}, {"text": "And it does close on money.", "start": 3952.97, "duration": 2.46}, {"text": "\"I do not pretend\nto give such a deed.", "start": 3955.43, "duration": 1.83}, {"text": "I only lend it to you.", "start": 3957.26, "duration": 2.49}, {"text": "When you meet another honest\nman in similar distress,", "start": 3959.75, "duration": 2.79}, {"text": "you must pay me by\nlending this sum to him", "start": 3962.54, "duration": 4.44}, {"text": "and joining him to discharge\nthe debt by a like operation,\"", "start": 3966.98, "duration": 4.41}, {"text": "paying it forward, basically.", "start": 3971.39, "duration": 3.38}, {"text": "\"He should be able and shall\nmeet another opportunity,", "start": 3974.77, "duration": 2.25}, {"text": "I hope, that this may,\nthough many hands.\"", "start": 3977.02, "duration": 3.67}, {"text": "So Benjamin Franklin,\nover 200 years ago,", "start": 3980.69, "duration": 2.22}, {"text": "he closes, this\nis a trick of mine", "start": 3982.91, "duration": 1.86}, {"text": "of doing a deal good\nwith a little money.", "start": 3984.77, "duration": 3.77}]
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+[{"text": "BARBARA IMPERIALI: So what\nwe're going to do today", "start": 15.947, "duration": 2.083}, {"text": "is we're going to finish\nup a bit of transcription,", "start": 18.03, "duration": 3.0}, {"text": "and then I'm going\nto talk largely", "start": 21.03, "duration": 1.62}, {"text": "about transcription control.", "start": 22.65, "duration": 1.59}, {"text": "Because it's tremendously\nimportant that we actually", "start": 24.24, "duration": 3.51}, {"text": "not just know how to\ntranscribe, but we", "start": 27.75, "duration": 2.52}, {"text": "know how it's controlled,\nand how ultimately", "start": 30.27, "duration": 3.63}, {"text": "the appropriate messenger RNA\nis sent out for a translation", "start": 33.9, "duration": 5.16}, {"text": "into proteins.", "start": 39.06, "duration": 0.85}, {"text": "So transcription control is\na very important component.", "start": 39.91, "duration": 3.71}, {"text": "So let me just start\nwith this first.", "start": 43.62, "duration": 3.61}, {"text": "So these are typical\nof questions.", "start": 47.23, "duration": 2.66}, {"text": "And they look like, gosh, I\ndon't have enough information", "start": 49.89, "duration": 2.67}, {"text": "to answer this question.", "start": 52.56, "duration": 1.65}, {"text": "And it's basically about what's\nknown as the transcription", "start": 54.21, "duration": 3.96}, {"text": "bubble, which is the portion of\nthe double-stranded DNA, where", "start": 58.17, "duration": 4.77}, {"text": "transcription is occurring.", "start": 62.94, "duration": 2.14}, {"text": "And so a transiently,\nthe double-stranded DNA", "start": 65.08, "duration": 3.11}, {"text": "is opened up for the\nRNA polymerase, which", "start": 68.19, "duration": 4.35}, {"text": "remember has inbuilt\nhelicase activity to start", "start": 72.54, "duration": 3.39}, {"text": "transcribing the gene.", "start": 75.93, "duration": 1.99}, {"text": "So let's just say we have\nthe information we might give", "start": 77.92, "duration": 2.96}, {"text": "you is that\ntranscription starts here", "start": 80.88, "duration": 3.27}, {"text": "at this point on the\ndouble-stranded DNA.", "start": 84.15, "duration": 3.3}, {"text": "And what we want you\nto know is that you", "start": 87.45, "duration": 3.6}, {"text": "have all the information you\nneed to know which of the two", "start": 91.05, "duration": 3.06}, {"text": "strands is copied.", "start": 94.11, "duration": 1.82}, {"text": "Have you had a chance\nto think about that?", "start": 95.93, "duration": 1.75}, {"text": "Does anyone want to give\nme a good answer to that?", "start": 97.68, "duration": 3.24}, {"text": "Yes, here.", "start": 100.92, "duration": 1.11}, {"text": "AUDIENCE: The\nbottom [INAUDIBLE]..", "start": 102.03, "duration": 1.5}, {"text": "BARBARA IMPERIALI:\nAnd why is that?", "start": 103.53, "duration": 1.458}, {"text": "AUDIENCE: Because\nit's [INAUDIBLE]..", "start": 104.988, "duration": 1.7}, {"text": "BARBARA IMPERIALI: Right.", "start": 106.688, "duration": 1.042}, {"text": "So that reading things\n3 prime to 5 prime,", "start": 107.73, "duration": 3.27}, {"text": "and making things\n5 prime to 3 prime,", "start": 111.0, "duration": 3.42}, {"text": "is all you need to know\nto answer this question.", "start": 114.42, "duration": 3.58}, {"text": "So you would\nstraightaway know, OK,", "start": 118.0, "duration": 2.09}, {"text": "we're going to start\nsomewhere here,", "start": 120.09, "duration": 2.64}, {"text": "but we're actually\ngoing to start", "start": 122.73, "duration": 2.04}, {"text": "on the lower strand,\nbecause that's the one 3", "start": 124.77, "duration": 2.13}, {"text": "prime to 5 prime.", "start": 126.9, "duration": 1.35}, {"text": "And we're going to\nmake the new transcript", "start": 128.25, "duration": 4.62}, {"text": "in the appropriate direction,\nand know what it's going to be.", "start": 132.87, "duration": 3.18}, {"text": "So you can only read the\nbottom strand in this case.", "start": 136.05, "duration": 3.99}, {"text": "But watch out,\nbecause you might be", "start": 140.04, "duration": 2.16}, {"text": "reading the top strand in the\nappropriate direction as well.", "start": 142.2, "duration": 4.96}, {"text": "But what we've told you already\nis where the start site is.", "start": 147.16, "duration": 3.41}, {"text": "So you're going to\nknow that information.", "start": 150.57, "duration": 2.07}, {"text": "If we'd put, for example, that\nthe start site was over here,", "start": 152.64, "duration": 4.27}, {"text": "you might have different\nanswers to this question.", "start": 156.91, "duration": 3.0}, {"text": "So the only singular piece\nof information you need", "start": 159.91, "duration": 3.32}, {"text": "is that you read 3 to\n5, and you make 5 to 3.", "start": 163.23, "duration": 3.54}, {"text": "Then you can also\nfill in the bases", "start": 166.77, "duration": 3.21}, {"text": "to know what the transcribed\nsequence looks like.", "start": 169.98, "duration": 3.78}, {"text": "And I always recommend when\nyou're filling in bases,", "start": 173.76, "duration": 2.61}, {"text": "you just write 5\nprime to 3 prime.", "start": 176.37, "duration": 2.4}, {"text": "So you really are following\nproperly which is being read,", "start": 178.77, "duration": 3.81}, {"text": "and the direction\nit's being read.", "start": 182.58, "duration": 2.04}, {"text": "And so if you were asked what\nthe new messenger RNA sequence", "start": 184.62, "duration": 4.29}, {"text": "would be, you'd get it right.", "start": 188.91, "duration": 1.79}, {"text": "And here I just\nhave a few questions", "start": 190.7, "duration": 2.17}, {"text": "that will help highlight\nthe differences", "start": 192.87, "duration": 3.15}, {"text": "between the transcription\nprocess and the replication", "start": 196.02, "duration": 3.96}, {"text": "process.", "start": 199.98, "duration": 0.9}, {"text": "So can you guys just\nread each of these,", "start": 200.88, "duration": 2.43}, {"text": "and see whether\nthey look like rules", "start": 203.31, "duration": 2.1}, {"text": "that apply to\ntranscription, or they're", "start": 205.41, "duration": 2.37}, {"text": "things that are not true\nabout transcription.", "start": 207.78, "duration": 2.86}, {"text": "So just give you one second\nto think about that, who?", "start": 210.64, "duration": 4.34}, {"text": "OK, who would like\nto give me an answer?", "start": 214.98, "duration": 5.12}, {"text": "Someone over in this\npart of the room,", "start": 220.1, "duration": 1.85}, {"text": "I haven't heard as much-- yes?", "start": 221.95, "duration": 2.031}, {"text": "AUDIENCE: Makes a complete\ncopy of one strata.", "start": 223.981, "duration": 2.481}, {"text": "BARBARA IMPERIALI: DNA.", "start": 226.462, "duration": 0.958}, {"text": "OK, so the correct answer\nis that we only transcribe", "start": 227.42, "duration": 4.2}, {"text": "about 1.5% of the genomic DNA.", "start": 231.62, "duration": 4.05}, {"text": "We're not transcribing\nthe whole thing.", "start": 235.67, "duration": 2.37}, {"text": "We're only transcribing the bits\nthat we need to make proteins.", "start": 238.04, "duration": 4.18}, {"text": "So the correct answer\nis C, because we", "start": 242.22, "duration": 4.04}, {"text": "don't make a copy of the\nwhole of genomic DNA.", "start": 246.26, "duration": 3.39}, {"text": "But these are all right.", "start": 249.65, "duration": 1.0}, {"text": "We have a different\nset of nucleotides,", "start": 250.65, "duration": 1.91}, {"text": "or rather a difference in one\nof the nucleotide triphosphate", "start": 252.56, "duration": 3.39}, {"text": "building blocks.", "start": 255.95, "duration": 2.19}, {"text": "Remember that RNA polymerase\ndoes not require a primer.", "start": 258.14, "duration": 3.75}, {"text": "That was a complication when\nwe looked at replication,", "start": 261.89, "duration": 2.97}, {"text": "because we had to paste\nin primers, made often", "start": 264.86, "duration": 2.88}, {"text": "by the primase, RNA primase.", "start": 267.74, "duration": 3.65}, {"text": "All RNA polymerase is much\ncleverer than DNA polymerase,", "start": 271.39, "duration": 5.02}, {"text": "because it has the\npolymerase activity.", "start": 276.41, "duration": 2.49}, {"text": "It has the helicase activity.", "start": 278.9, "duration": 2.34}, {"text": "There isn't needed\na topoisomerase,", "start": 281.24, "duration": 2.64}, {"text": "because we're only\nopening a little bit", "start": 283.88, "duration": 2.1}, {"text": "of the double-stranded to copy.", "start": 285.98, "duration": 1.71}, {"text": "I'll show you a\nmovie in a second.", "start": 287.69, "duration": 3.03}, {"text": "And it also has a 3\nprime exonuclease,", "start": 290.72, "duration": 3.66}, {"text": "which means that RNA is able to\ndo its own proofreading, just", "start": 294.38, "duration": 7.08}, {"text": "like the DNA polymerase.", "start": 301.46, "duration": 2.53}, {"text": "So the error rate is\nsimilar to the error", "start": 303.99, "duration": 4.19}, {"text": "rate with the\nexonuclease activity for.", "start": 308.18, "duration": 2.25}, {"text": "DNA so that's about 1 in 10\nto the 5 to 10 to the sixth.", "start": 310.43, "duration": 7.253}, {"text": "Now I'm going to\ntalk in a minute.", "start": 317.683, "duration": 1.417}, {"text": "There's not the same\ncadre of repair enzymes", "start": 319.1, "duration": 4.26}, {"text": "that we have for DNA.", "start": 323.36, "duration": 1.89}, {"text": "And that's a curious thing,\nuntil you start thinking", "start": 325.25, "duration": 2.31}, {"text": "about what the reality is.", "start": 327.56, "duration": 2.17}, {"text": "So let me try to lead\nyou to my thinking.", "start": 329.73, "duration": 2.67}, {"text": "So with genomic\nDNA, that's the copy", "start": 332.4, "duration": 2.66}, {"text": "of the DNA that's in the\nnucleus that has to stay good.", "start": 335.06, "duration": 3.57}, {"text": "So if there's any mistakes,\nwe need them cleaned up.", "start": 338.63, "duration": 3.0}, {"text": "Because otherwise\nwhen we replicate", "start": 341.63, "duration": 3.21}, {"text": "a set of all of the\ndouble-stranded DNA,", "start": 344.84, "duration": 2.34}, {"text": "there will be an error in the\nprogeny, the daughter cells.", "start": 347.18, "duration": 4.89}, {"text": "For transcribing RNA,\nan error rate of about 1", "start": 352.07, "duration": 3.96}, {"text": "in 10 to the 5 to 1 in\n10 to a 6, is just fine.", "start": 356.03, "duration": 5.76}, {"text": "That piece of RNA ends up,\nafter a few of the processing", "start": 361.79, "duration": 4.95}, {"text": "steps that I'll describe to\nyou, ends up leaving the nucleus", "start": 366.74, "duration": 3.69}, {"text": "to be made into proteins.", "start": 370.43, "duration": 2.28}, {"text": "And it's not such a bad thing\nif you have a little bit", "start": 372.71, "duration": 3.18}, {"text": "more error in that RNA.", "start": 375.89, "duration": 2.1}, {"text": "Why is that?", "start": 377.99, "duration": 2.97}, {"text": "Over here, or up there actually.", "start": 380.96, "duration": 1.98}, {"text": "Yeah?", "start": 382.94, "duration": 0.64}, {"text": "AUDIENCE: It has a\nshorter life, so it's not", "start": 383.58, "duration": 3.242}, {"text": "going to mess up everything\nfor the rest of its life.", "start": 386.822, "duration": 3.83}, {"text": "BARBARA IMPERIALI: Right, so\nif you have a bit of an error,", "start": 390.652, "duration": 2.458}, {"text": "maybe you make a new protein,\nbut it's not full length,", "start": 393.11, "duration": 3.87}, {"text": "or the protein you make\nisn't perfect; it's OK.", "start": 396.98, "duration": 3.81}, {"text": "Because there'll be other\ntranscripts that are correct,", "start": 400.79, "duration": 3.03}, {"text": "and then after you've\ndone making the protein,", "start": 403.82, "duration": 3.34}, {"text": "then you're just\ngoing to destroy", "start": 407.16, "duration": 2.27}, {"text": "that RNA, because it has a\ntransient lifetime because", "start": 409.43, "duration": 3.48}, {"text": "of the structure of the\nRNA, and the nucleases that", "start": 412.91, "duration": 2.94}, {"text": "chew up the RNA.", "start": 415.85, "duration": 1.42}, {"text": "So this is an acceptable\nerror rate for RNA polymerase.", "start": 417.27, "duration": 4.49}, {"text": "Remember, it's not an\nacceptable error rate", "start": 421.76, "duration": 2.52}, {"text": "to have in your genome.", "start": 424.28, "duration": 1.38}, {"text": "OK, it's just too big.", "start": 425.66, "duration": 1.62}, {"text": "Any questions about that?", "start": 427.28, "duration": 1.05}, {"text": "Does that all make sense?", "start": 428.33, "duration": 2.73}, {"text": "OK.", "start": 431.06, "duration": 0.5}, {"text": "All right, so now\nwe want to talk", "start": 434.23, "duration": 1.39}, {"text": "about transcription control.", "start": 435.62, "duration": 2.41}, {"text": "But before I do that, I do\nwant to very quickly show you", "start": 438.03, "duration": 2.84}, {"text": "something, because I feel\nlike it really caps off", "start": 440.87, "duration": 4.29}, {"text": "the transcription part.", "start": 445.16, "duration": 2.98}, {"text": "And I'm going to\nshow you only about", "start": 448.14, "duration": 1.68}, {"text": "a minute of this,\nbecause once again, I", "start": 449.82, "duration": 3.693}, {"text": "love the sound effects here.", "start": 453.513, "duration": 1.167}, {"text": "And I can't turn\ndown the volume.", "start": 457.97, "duration": 1.57}, {"text": "This is one of those animations\nshowing transcription.", "start": 459.54, "duration": 3.8}, {"text": "And it basically shows on\nthe double-stranded DNA,", "start": 463.34, "duration": 2.62}, {"text": "lot of things accumulating to\nmake a decision with respect", "start": 465.96, "duration": 4.05}, {"text": "to starting.", "start": 470.01, "duration": 1.32}, {"text": "But now, the whole\ncomplex, the RNA polymerase", "start": 471.33, "duration": 4.23}, {"text": "is just screeching through the\nDNA, making that messenger RNA.", "start": 475.56, "duration": 5.19}, {"text": "And you're only unraveling\njust a little bit of DNA", "start": 480.75, "duration": 4.47}, {"text": "around that\ntranscription bubble.", "start": 485.22, "duration": 1.75}, {"text": "So you wouldn't need\ntopoisomerase in this case.", "start": 486.97, "duration": 3.59}, {"text": "You're only copying\none of the two strands.", "start": 490.56, "duration": 3.14}, {"text": "We saw how to identify which.", "start": 493.7, "duration": 2.47}, {"text": "And thus, the new RNA\nstrand is basically", "start": 496.17, "duration": 3.33}, {"text": "falling out of the complex.", "start": 499.5, "duration": 1.71}, {"text": "You can see [INAUDIBLE]\nit's moving a lot.", "start": 501.21, "duration": 2.874}, {"text": "So that gives you\na feel for things.", "start": 504.084, "duration": 2.395}, {"text": "When I hear that\nmusic, I'm just sort of", "start": 510.293, "duration": 1.667}, {"text": "waiting for the whole\nthing to crash somewhere.", "start": 511.96, "duration": 1.98}, {"text": "But who would know, right?", "start": 513.94, "duration": 4.099}, {"text": "All right.", "start": 518.039, "duration": 0.551}, {"text": "So at the beginning\nof that animation", "start": 518.59, "duration": 3.3}, {"text": "a few things were\nhighlighted, where", "start": 521.89, "duration": 2.039}, {"text": "there's the double-stranded DNA,\nand a collection of entities", "start": 523.929, "duration": 3.691}, {"text": "starts clustering around\nwhere the reading is", "start": 527.62, "duration": 2.82}, {"text": "going to take place.", "start": 530.44, "duration": 1.54}, {"text": "So this thin, black strand\nis the double-stranded DNA.", "start": 531.98, "duration": 4.1}, {"text": "So some of the entities\naccumulate quite close", "start": 536.08, "duration": 3.72}, {"text": "to the start site.", "start": 539.8, "duration": 1.47}, {"text": "There is a section of\nDNA known as a TATA box", "start": 541.27, "duration": 2.91}, {"text": "that we spoke about, at the\nvery end of the last lecture.", "start": 544.18, "duration": 3.84}, {"text": "But there are a number\nof transcription factors", "start": 548.02, "duration": 3.06}, {"text": "that are quite important.", "start": 551.08, "duration": 1.71}, {"text": "But then you might also,\nif you go back and look", "start": 552.79, "duration": 2.22}, {"text": "at that animation, there\nare sections of DNA", "start": 555.01, "duration": 3.57}, {"text": "that are at quite a distance\nthat also help really regulate", "start": 558.58, "duration": 5.43}, {"text": "and promote transcription.", "start": 564.01, "duration": 2.05}, {"text": "So many factors regulate where\nthe transcription occurs.", "start": 566.06, "duration": 3.26}, {"text": "First of all, is there\na promoter site right", "start": 569.32, "duration": 2.76}, {"text": "near where we need to start?", "start": 572.08, "duration": 1.26}, {"text": "That causes a fair\namount of collecting", "start": 573.34, "duration": 3.45}, {"text": "of complex components.", "start": 576.79, "duration": 2.25}, {"text": "But then there may be\nother things at a distance.", "start": 579.04, "duration": 2.76}, {"text": "So the promoter region\nmight be located quite", "start": 581.8, "duration": 3.06}, {"text": "near the transcription\nstart site,", "start": 584.86, "duration": 2.52}, {"text": "but then there\nare also enhancers", "start": 587.38, "duration": 2.31}, {"text": "that can be located at\nquite a big distance", "start": 589.69, "duration": 2.67}, {"text": "away from the start site\nthat also play a role.", "start": 592.36, "duration": 4.14}, {"text": "Why do we need\nthis much control?", "start": 596.5, "duration": 2.28}, {"text": "Because we don't\nneed to be making", "start": 598.78, "duration": 2.16}, {"text": "the RNA for every protein\nall at the same time.", "start": 600.94, "duration": 4.02}, {"text": "Certain times in cell\ncycle you'll see,", "start": 604.96, "duration": 2.4}, {"text": "I only need to make one\nprotein or a different protein.", "start": 607.36, "duration": 3.36}, {"text": "So we need all of this control\nto decide when transcription", "start": 610.72, "duration": 4.71}, {"text": "occurs, when do we need\nto make the messenger", "start": 615.43, "duration": 3.42}, {"text": "RNA to make our favorite new\nprotein that needs to be made.", "start": 618.85, "duration": 4.37}, {"text": "And you'll learn a lot in\nsignal transduction and cell", "start": 623.22, "duration": 3.52}, {"text": "cycle, where we\nreally show you how", "start": 626.74, "duration": 2.67}, {"text": "a lot of the housekeeping\ngenes are all fine.", "start": 629.41, "duration": 2.46}, {"text": "The proteins are all there.", "start": 631.87, "duration": 1.165}, {"text": "But at a certain\nstage, we need to make", "start": 633.035, "duration": 1.625}, {"text": "more of a particular protein.", "start": 634.66, "duration": 2.01}, {"text": "And that's when the\ntranscription control", "start": 636.67, "duration": 2.58}, {"text": "comes into play.", "start": 639.25, "duration": 1.77}, {"text": "And you'll commonly\nhear about things", "start": 641.02, "duration": 1.83}, {"text": "called transcription factors.", "start": 642.85, "duration": 1.275}, {"text": "And those may be the\nproteins, for example,", "start": 652.59, "duration": 3.85}, {"text": "that regulate that\ntranscription should start.", "start": 656.44, "duration": 2.97}, {"text": "In other cases, there\nmay be times when", "start": 659.41, "duration": 2.52}, {"text": "transcription is turned down.", "start": 661.93, "duration": 2.82}, {"text": "So we have things that activate.", "start": 664.75, "duration": 2.04}, {"text": "So we start transcription,\nwe make that happen,", "start": 670.02, "duration": 3.42}, {"text": "or others that repress.", "start": 673.44, "duration": 1.2}, {"text": "So they turn down transcription.", "start": 677.75, "duration": 2.2}, {"text": "So it's all about when\nyou need to start,", "start": 679.95, "duration": 3.8}, {"text": "which is controlled\nby external factors", "start": 683.75, "duration": 2.73}, {"text": "acting on the\ndouble-stranded DNA", "start": 686.48, "duration": 1.98}, {"text": "to send the transcription\ncomplex, making the new entity.", "start": 688.46, "duration": 3.9}, {"text": "All right, does that make sense?", "start": 692.36, "duration": 1.47}, {"text": "We can't have a dysregulated\nsystem, or if we do,", "start": 693.83, "duration": 3.69}, {"text": "then we have problems\nwith, for example,", "start": 697.52, "duration": 3.0}, {"text": "proliferation of cells.", "start": 700.52, "duration": 2.67}, {"text": "All right, so what\nI want to talk about", "start": 703.19, "duration": 1.98}, {"text": "are the key things that\nregulate transcription,", "start": 705.17, "duration": 3.42}, {"text": "and the key things that we do to\nthe messenger that's been made.", "start": 708.59, "duration": 4.2}, {"text": "So what you're seeing\nhere on this slide", "start": 712.79, "duration": 1.98}, {"text": "is just where we\nare in the process.", "start": 714.77, "duration": 2.58}, {"text": "We've seen replication.", "start": 717.35, "duration": 1.38}, {"text": "We're now at the\ntranscription step.", "start": 718.73, "duration": 1.92}, {"text": "But there are many steps\nto go in eukaryotes", "start": 720.65, "duration": 4.56}, {"text": "before that transcript\ncan leave the nucleus.", "start": 725.21, "duration": 2.94}, {"text": "All right?", "start": 728.15, "duration": 1.13}, {"text": "And I want you to\nremember the difference", "start": 729.28, "duration": 4.85}, {"text": "between eukaryotic\nand prokaryotic cells.", "start": 734.13, "duration": 3.27}, {"text": "This was just a picture\nwe saw very early on.", "start": 737.4, "duration": 2.79}, {"text": "Prokaryotic cells,\nlike bacteria,", "start": 740.19, "duration": 2.73}, {"text": "do not have a nucleus.", "start": 742.92, "duration": 1.69}, {"text": "They have an area\ncalled a nucleoid,", "start": 744.61, "duration": 2.39}, {"text": "but they don't have a discrete\nmembrane encased organelle,", "start": 747.0, "duration": 5.04}, {"text": "where the processes of\nreplication and transcription", "start": 752.04, "duration": 3.99}, {"text": "occur.", "start": 756.03, "duration": 0.9}, {"text": "In contrast, in\neukaryotes, there", "start": 756.93, "duration": 2.52}, {"text": "is a discrete area of\nthe cell, the nucleus,", "start": 759.45, "duration": 3.33}, {"text": "that includes all the\nmachinery for replication", "start": 762.78, "duration": 3.36}, {"text": "and transcription.", "start": 766.14, "duration": 1.71}, {"text": "And it also includes\nthe machinery", "start": 767.85, "duration": 2.25}, {"text": "that takes a pre-messenger\nRNA into a mature messenger", "start": 770.1, "duration": 13.52}, {"text": "RNA that can leave the nucleus.", "start": 783.62, "duration": 2.22}, {"text": "If you send that\npre-messenger out there,", "start": 790.86, "duration": 1.96}, {"text": "it's going to have a lot\nof stuff wrong with it.", "start": 792.82, "duration": 2.0}, {"text": "It's not going to\nbe ready to face", "start": 794.82, "duration": 1.88}, {"text": "the outside of the nucleus.", "start": 796.7, "duration": 1.65}, {"text": "It's going to be\nreadily degraded.", "start": 798.35, "duration": 1.96}, {"text": "It's not going to have\nthe full information.", "start": 800.31, "duration": 1.95}, {"text": "So I want to talk to you\nabout the processes that", "start": 802.26, "duration": 2.93}, {"text": "are put in place\nfor this conversion", "start": 805.19, "duration": 2.28}, {"text": "from the pre-messenger RNA\nto the messenger RNA, which", "start": 807.47, "duration": 4.38}, {"text": "we don't have to think\nabout in prokaryotes,", "start": 811.85, "duration": 2.88}, {"text": "the small organisms\nwithout organelles.", "start": 814.73, "duration": 7.02}, {"text": "All right, so, and\nthis is the foundation", "start": 821.75, "duration": 4.02}, {"text": "of transcriptional control.", "start": 825.77, "duration": 2.445}, {"text": "All right.", "start": 831.16, "duration": 0.796}, {"text": "So, we've talked about\npromoters and enhancers.", "start": 837.55, "duration": 7.83}, {"text": "Those happen early.", "start": 848.11, "duration": 1.41}, {"text": "That's all about making\nthe pre-messenger RNA.", "start": 849.52, "duration": 4.71}, {"text": "But now we have to discuss\nsome aspects that are also", "start": 854.23, "duration": 3.9}, {"text": "critical for making the initial\npre-messenger RNA, and that's", "start": 858.13, "duration": 5.97}, {"text": "chromatin remodelers,\nor chromatin remodeling.", "start": 864.1, "duration": 10.67}, {"text": "Because in order to\ntranscribe anything,", "start": 874.77, "duration": 3.75}, {"text": "there's a lot of ground to\ncover with respect to unwrapping", "start": 878.52, "duration": 4.5}, {"text": "the chromatin, the chromosomes.", "start": 883.02, "duration": 2.04}, {"text": "Because they're all\npacked up in such a way", "start": 885.06, "duration": 2.14}, {"text": "that you can't possibly do\nany transcription there,", "start": 887.2, "duration": 3.29}, {"text": "because they're too\ntightly packed in order", "start": 890.49, "duration": 2.4}, {"text": "to be accessible for the\ntranscription machinery", "start": 892.89, "duration": 3.0}, {"text": "to tackle it.", "start": 895.89, "duration": 1.14}, {"text": "So I show you parts of\nthat machinery up here.", "start": 897.03, "duration": 2.67}, {"text": "These are the nucleosomes\nthat make up chromatin,", "start": 899.7, "duration": 3.6}, {"text": "which makes up the chromosomes.", "start": 903.3, "duration": 2.04}, {"text": "And in order for you to even\nbe able to start transcribing,", "start": 905.34, "duration": 3.87}, {"text": "you have to unravel that part,\nthose complex structures that", "start": 909.21, "duration": 5.76}, {"text": "are tightly wrapped up.", "start": 914.97, "duration": 1.32}, {"text": "You've got make the\ndouble-stranded DNA accessible,", "start": 916.29, "duration": 3.72}, {"text": "otherwise you can't\nbreak into it.", "start": 920.01, "duration": 1.92}, {"text": "So there are two things\nthat also contribute", "start": 921.93, "duration": 3.84}, {"text": "to allowing transcription, and\nthose occur both at the DNA", "start": 925.77, "duration": 6.96}, {"text": "level, and the histone level.", "start": 932.73, "duration": 3.67}, {"text": "And I'm going to talk about the\nhistone level changes first.", "start": 936.4, "duration": 3.62}, {"text": "I want you to recall that\nhistones are proteins that", "start": 940.02, "duration": 5.28}, {"text": "have a lot of positive charge,\nby virtue of the fact that they", "start": 945.3, "duration": 5.01}, {"text": "include two of the positively\ncharged amino acids, arginine", "start": 950.31, "duration": 6.27}, {"text": "and lysine.", "start": 956.58, "duration": 1.11}, {"text": "And if you're curious\nabout those structures,", "start": 957.69, "duration": 1.95}, {"text": "you can go look back at the\ntable of the amino acids", "start": 959.64, "duration": 3.27}, {"text": "and see that those guys are\nalways positively charged.", "start": 962.91, "duration": 3.24}, {"text": "The reason we use histones as\nthe core of the nucleus home", "start": 966.15, "duration": 4.89}, {"text": "structure, is they're\nvery positively charged,", "start": 971.04, "duration": 2.75}, {"text": "and they neutralize the\ndense negative charge", "start": 973.79, "duration": 2.95}, {"text": "of the nucleic acid.", "start": 976.74, "duration": 1.17}, {"text": "Otherwise we couldn't pack\nit up as tightly as we do.", "start": 977.91, "duration": 3.21}, {"text": "So changes that occur\nat the histone level,", "start": 981.12, "duration": 4.21}, {"text": "and their remodeling\nof the chromatin", "start": 985.33, "duration": 2.33}, {"text": "in order to promote\ntranscription", "start": 987.66, "duration": 2.64}, {"text": "is modification oftentimes\nto neutralize those charges.", "start": 990.3, "duration": 9.55}, {"text": "So the one most obvious one\nI'll show you, and then there", "start": 999.85, "duration": 3.12}, {"text": "are others where you\nadd methyl groups that", "start": 1002.97, "duration": 3.69}, {"text": "dampen down the charge.", "start": 1006.66, "duration": 1.17}, {"text": "But I'm just going to show\nyou the very obvious one.", "start": 1007.83, "duration": 2.91}, {"text": "So let's just look at\nlysine in a protein.", "start": 1010.74, "duration": 8.4}, {"text": "That looks like this.", "start": 1022.74, "duration": 0.99}, {"text": "That is a terrible drawing.", "start": 1023.73, "duration": 2.339}, {"text": "It has a positive\ncharge for bonds", "start": 1026.069, "duration": 2.25}, {"text": "to nitrogen. In order to\nneutralize that charge,", "start": 1028.319, "duration": 3.79}, {"text": "there are enzymes that\nacylate, or transfer", "start": 1032.109, "duration": 3.201}, {"text": "an acyl group to turn this\npositively charged amine", "start": 1035.31, "duration": 4.049}, {"text": "into a neutral amide.", "start": 1039.359, "duration": 2.281}, {"text": "Let me draw that side\nchain, because I think", "start": 1041.64, "duration": 1.86}, {"text": "it makes much more\nsense to understand it,", "start": 1043.5, "duration": 3.119}, {"text": "this particular thing from\na chemical perspective.", "start": 1046.619, "duration": 2.941}, {"text": "So we still have the n but\nit is now part of an amide.", "start": 1049.56, "duration": 5.67}, {"text": "So the charge has been\nneutralized on the nitrogen.", "start": 1059.79, "duration": 4.2}, {"text": "If the charge is neutralized on\nthe positively charged residues", "start": 1063.99, "duration": 4.53}, {"text": "in the histones, the\nDNA will be encouraged", "start": 1068.52, "duration": 3.27}, {"text": "to unravel from those.", "start": 1071.79, "duration": 2.28}, {"text": "It makes good chemical\nsense that that's a good way", "start": 1074.07, "duration": 2.94}, {"text": "to start on packaging DNA.", "start": 1077.01, "duration": 2.91}, {"text": "The other modification\noccurs at the DNA level", "start": 1079.92, "duration": 3.3}, {"text": "and it's methylation\nof cytosine.", "start": 1083.22, "duration": 6.34}, {"text": "A little harder to explain\nfrom a chemical sense,", "start": 1092.88, "duration": 3.03}, {"text": "but up there in the\ncorner of this slide", "start": 1095.91, "duration": 2.67}, {"text": "I've shown you the pictures.", "start": 1098.58, "duration": 2.25}, {"text": "So methylation on cytosine\nwould look like this.", "start": 1100.83, "duration": 3.87}, {"text": "This encourages stabilization\nof the chromatin.", "start": 1104.7, "duration": 4.15}, {"text": "So what would that do\nto transcription if I've", "start": 1116.55, "duration": 2.07}, {"text": "stabilized the chromatin?", "start": 1118.62, "duration": 3.34}, {"text": "It represses it.", "start": 1121.96, "duration": 0.95}, {"text": "It turns it down.", "start": 1122.91, "duration": 1.62}, {"text": "So these are pairs of changes\nthat act in opposite direction.", "start": 1124.53, "duration": 4.37}, {"text": "So we'd go down-regulate\ntranscription.", "start": 1128.9, "duration": 8.51}, {"text": "OK, so DNA methylation\ncauses the chromatin", "start": 1137.41, "duration": 4.43}, {"text": "to be a bit more\ncompact, more stable.", "start": 1141.84, "duration": 2.91}, {"text": "It's much harder\nto unravel the DNA.", "start": 1144.75, "duration": 3.0}, {"text": "It's obviously then harder\nto start transcription.", "start": 1147.75, "duration": 3.66}, {"text": "In contrast, modification\nof the histone proteins", "start": 1151.41, "duration": 4.56}, {"text": "to neutralize their charges\ndestabilizes and up-regulates", "start": 1155.97, "duration": 8.52}, {"text": "transcription,\nbecause it's allowing", "start": 1164.49, "duration": 2.55}, {"text": "us to open up the\nnucleosomes in order", "start": 1167.04, "duration": 3.21}, {"text": "to make the DNA available.", "start": 1170.25, "duration": 2.198}, {"text": "Does that all make sense?", "start": 1172.448, "duration": 1.042}, {"text": "So we have two counter-balances\nthat play in each direction.", "start": 1173.49, "duration": 5.57}, {"text": "OK?", "start": 1179.06, "duration": 0.5}, {"text": "All right, so that's\nchromatic remodeling.", "start": 1183.21, "duration": 2.606}, {"text": "The next two transformations\nI'll show you", "start": 1193.44, "duration": 3.28}, {"text": "may certainly look\nfairly complicated.", "start": 1196.72, "duration": 2.83}, {"text": "But I'm going to\ndescribe them to you,", "start": 1199.55, "duration": 2.18}, {"text": "and show you what\nthe changes are,", "start": 1201.73, "duration": 2.19}, {"text": "and how they would contribute\nto stabilizing the transcript", "start": 1203.92, "duration": 4.26}, {"text": "and finishing the\ntranscript up, to make", "start": 1208.18, "duration": 2.43}, {"text": "it ready to leave the\nnucleus, to go out", "start": 1210.61, "duration": 2.97}, {"text": "to the cytoplasm, where the\nmachinery to translate proteins", "start": 1213.58, "duration": 3.58}, {"text": "is.", "start": 1217.16, "duration": 0.5}, {"text": "Because you want to\nremember the ribosomes", "start": 1217.66, "duration": 1.75}, {"text": "that we're going to use on\nFriday aren't in the nucleus.", "start": 1219.41, "duration": 2.65}, {"text": "They're in the cytoplasm.", "start": 1222.06, "duration": 1.73}, {"text": "So there is a variety of events.", "start": 1223.79, "duration": 2.75}, {"text": "There is what's known\nas 5 prime capping.", "start": 1226.54, "duration": 2.115}, {"text": "So that is going to be a change.", "start": 1235.858, "duration": 3.642}, {"text": "Let's just say this goes down.", "start": 1239.5, "duration": 7.01}, {"text": "This is the base.", "start": 1246.51, "duration": 1.49}, {"text": "Remember 1, 2, 3 prime,\n4 prime, 5 prime.", "start": 1248.0, "duration": 6.6}, {"text": "It's something that's happening\nto this end of the messenger", "start": 1254.6, "duration": 4.74}, {"text": "RNA that stabilizes it.", "start": 1259.34, "duration": 2.26}, {"text": "So 5 prime capping is\nimportant for one end.", "start": 1261.6, "duration": 5.21}, {"text": "And then at the other end\nthere is polyadenylation", "start": 1266.81, "duration": 9.02}, {"text": "of the 3 prime end.", "start": 1275.83, "duration": 2.07}, {"text": "OK, so let's just look\nat these one at a time.", "start": 1277.9, "duration": 2.91}, {"text": "And let me convince\nyou that they", "start": 1280.81, "duration": 1.96}, {"text": "are important changes in the\ntranscript that will preserve", "start": 1282.77, "duration": 3.93}, {"text": "its identity, and in fact,\ngive it a little bit more", "start": 1286.7, "duration": 2.55}, {"text": "information.", "start": 1289.25, "duration": 1.05}, {"text": "Because indeed, the 5 prime\ncapping modification actually", "start": 1290.3, "duration": 3.51}, {"text": "is a signal later on, when the\ntranscript leaves the nucleus", "start": 1293.81, "duration": 4.92}, {"text": "for protein translation.", "start": 1298.73, "duration": 1.74}, {"text": "But in general, both\nof these changes", "start": 1300.47, "duration": 2.43}, {"text": "mechanically protect the\nends of the part of the gene", "start": 1302.9, "duration": 5.16}, {"text": "that you're going to\nwant to translate.", "start": 1308.06, "duration": 2.4}, {"text": "They basically leave\nthat piece of gene", "start": 1310.46, "duration": 2.1}, {"text": "in the middle, where it's\nnot going to be nibbled up,", "start": 1312.56, "duration": 2.61}, {"text": "it's not going to be degraded.", "start": 1315.17, "duration": 1.71}, {"text": "Because the biggest\nthreat to the messenger", "start": 1316.88, "duration": 2.64}, {"text": "RNA are things known\nas exonucleases.", "start": 1319.52, "duration": 4.118}, {"text": "Exonucleases chew down nucleic\nacids from the two ends.", "start": 1327.77, "duration": 5.07}, {"text": "All right.", "start": 1332.84, "duration": 0.84}, {"text": "So let's look\nfirst, and it's kind", "start": 1333.68, "duration": 2.01}, {"text": "of wild and crazy chemistry,\nat the 5 prime capping.", "start": 1335.69, "duration": 4.335}, {"text": "And then we'll\ndiscuss the other two.", "start": 1343.71, "duration": 2.02}, {"text": "And then I will finish\nthese types of changes", "start": 1345.73, "duration": 2.57}, {"text": "with splicing, which is really\ncool and extremely important.", "start": 1348.3, "duration": 3.48}, {"text": "But the transcript,\nthe pre-messenger RNA", "start": 1351.78, "duration": 2.91}, {"text": "has to go through\nall of these steps", "start": 1354.69, "duration": 2.28}, {"text": "before it's ready\nfor nuclear export.", "start": 1356.97, "duration": 2.7}, {"text": "So in 5 prime capping,\nyou have this strand", "start": 1359.67, "duration": 2.82}, {"text": "of pre-messenger RNA.", "start": 1362.49, "duration": 1.86}, {"text": "Everything looks pretty happy.", "start": 1364.35, "duration": 1.35}, {"text": "It's all in one piece.", "start": 1365.7, "duration": 1.54}, {"text": "But the first thing that\nhappens is three phosphates", "start": 1367.24, "duration": 3.32}, {"text": "are added to that\n5 prime OH group.", "start": 1370.56, "duration": 3.15}, {"text": "So that's the start\nof this process.", "start": 1373.71, "duration": 2.37}, {"text": "And this process\nactually happens", "start": 1376.08, "duration": 3.21}, {"text": "while you're still transcribing\nthe double-stranded DNA.", "start": 1379.29, "duration": 3.87}, {"text": "It's actually already going on.", "start": 1383.16, "duration": 1.35}, {"text": "As soon as that component\nof the newly transcribed", "start": 1384.51, "duration": 3.72}, {"text": "pre-messenger RNA\nis made, things", "start": 1388.23, "duration": 2.37}, {"text": "start happening at the 5\nprime end to protect it.", "start": 1390.6, "duration": 4.65}, {"text": "At that stage, then once\nthose three phosphates", "start": 1395.25, "duration": 2.85}, {"text": "are put on there, and\nnucleobase is added backwards.", "start": 1398.1, "duration": 4.92}, {"text": "So there's a couple\nof functions.", "start": 1403.02, "duration": 1.68}, {"text": "This all looks pretty strange.", "start": 1404.7, "duration": 2.07}, {"text": "The rest of this still\nlooks quite good.", "start": 1406.77, "duration": 2.07}, {"text": "It looks fairly intact.", "start": 1408.84, "duration": 2.04}, {"text": "But then the next\nthing that happens", "start": 1410.88, "duration": 3.29}, {"text": "is that the guanine\nthat's here is--", "start": 1414.17, "duration": 4.41}, {"text": "you do not have to remember this\nstuff, I couldn't remember it.", "start": 1418.58, "duration": 2.94}, {"text": "I just want to show you\nhow weird and different", "start": 1421.52, "duration": 3.18}, {"text": "the 5 prime end looks.", "start": 1424.7, "duration": 1.38}, {"text": "It doesn't look like\na strand of RNA.", "start": 1426.08, "duration": 2.56}, {"text": "So the guanine is methylated.", "start": 1428.64, "duration": 2.57}, {"text": "And then a couple\nof the riboses,", "start": 1431.21, "duration": 3.06}, {"text": "those sugars that have\nan OH usually at 2 prime,", "start": 1434.27, "duration": 3.0}, {"text": "get methylated.", "start": 1437.27, "duration": 1.29}, {"text": "So we've created this entire\nthing at the 5 prime end,", "start": 1438.56, "duration": 4.05}, {"text": "known as the 5 prime\ncap that looks nothing", "start": 1442.61, "duration": 3.45}, {"text": "like regular messenger RNA.", "start": 1446.06, "duration": 2.59}, {"text": "And that protects that\nend of the messenger,", "start": 1448.65, "duration": 3.11}, {"text": "and makes it safe from\na variety of insults.", "start": 1451.76, "duration": 4.28}, {"text": "So let's take a look.", "start": 1456.04, "duration": 0.88}, {"text": "Why does it happen?", "start": 1456.92, "duration": 1.45}, {"text": "So the first thing is it\nstops nuclease activity.", "start": 1458.37, "duration": 2.78}, {"text": "Because the nuclease\ncould look at it, and go,", "start": 1461.15, "duration": 2.35}, {"text": "I don't recognize any\nof this happy mess.", "start": 1463.5, "duration": 2.12}, {"text": "I'm not going to chop\ndown this component.", "start": 1465.62, "duration": 2.7}, {"text": "It's too foreign to me.", "start": 1468.32, "duration": 1.62}, {"text": "So that's the primary thing.", "start": 1469.94, "duration": 2.04}, {"text": "But then it's actually quite\nimportant for regulation", "start": 1471.98, "duration": 3.33}, {"text": "of when that messenger\nneeds to leave the nucleus.", "start": 1475.31, "duration": 2.86}, {"text": "There are proteins\ninvolved in helping export", "start": 1478.17, "duration": 2.96}, {"text": "the messenger RNA, when\nit's ready from the nucleus.", "start": 1481.13, "duration": 3.73}, {"text": "So it's an important signal\nor recognition element.", "start": 1484.86, "duration": 4.13}, {"text": "It marks this thing\nas a messenger RNA", "start": 1488.99, "duration": 3.69}, {"text": "that's going to be\nimportant in translation.", "start": 1492.68, "duration": 2.49}, {"text": "It gives it an identity.", "start": 1495.17, "duration": 2.01}, {"text": "And then finally, it can\nactually in the next step", "start": 1497.18, "duration": 3.0}, {"text": "promote translation.", "start": 1500.18, "duration": 1.68}, {"text": "So all of these\nthings are useful.", "start": 1501.86, "duration": 1.92}, {"text": "So we do a number of these\nunusual transformations,", "start": 1503.78, "duration": 3.45}, {"text": "but they all have a\nreason, and they all", "start": 1507.23, "duration": 2.19}, {"text": "carried out in the\nnucleus purposed", "start": 1509.42, "duration": 3.54}, {"text": "to protect the 5 prime\ncap of the messenger,", "start": 1512.96, "duration": 3.87}, {"text": "and actually make it\nready for its next tasks.", "start": 1516.83, "duration": 3.03}, {"text": "All right?", "start": 1519.86, "duration": 1.17}, {"text": "The next thing that\nhappens is what's", "start": 1521.03, "duration": 3.12}, {"text": "known as polyadenylation.", "start": 1524.15, "duration": 2.11}, {"text": "So here's it.", "start": 1526.26, "duration": 0.86}, {"text": "This would be the 5 prime cap.", "start": 1527.12, "duration": 2.1}, {"text": "In the middle would be\nyour gene that you're", "start": 1529.22, "duration": 2.19}, {"text": "going to transcribe.", "start": 1531.41, "duration": 1.47}, {"text": "But at the other end there is\nan enzyme that puts on a lot", "start": 1532.88, "duration": 3.57}, {"text": "of adenine nucleotides, and\nbasically adds to the other end", "start": 1536.45, "duration": 4.74}, {"text": "a lot of A's.", "start": 1541.19, "duration": 0.795}, {"text": "And when I say a lot,\nit can be hundreds.", "start": 1545.42, "duration": 3.36}, {"text": "And it just promiscuously\nkeeps on adenylating.", "start": 1548.78, "duration": 2.49}, {"text": "And now what's this bit for?", "start": 1551.27, "duration": 2.43}, {"text": "Once again, it protects\nfrom exonuclease activity", "start": 1553.7, "duration": 3.03}, {"text": "from the other\nend of the strand.", "start": 1556.73, "duration": 2.31}, {"text": "Because if you have\nexonuclease activity,", "start": 1559.04, "duration": 2.79}, {"text": "you might start munching\naway at these As.", "start": 1561.83, "duration": 2.79}, {"text": "But these aren't the important\nparts of the messenger, right?", "start": 1564.62, "duration": 3.06}, {"text": "These are just add-ons.", "start": 1567.68, "duration": 1.56}, {"text": "It's kind of a buffer.", "start": 1569.24, "duration": 0.99}, {"text": "It's like something to\ndo while you're waiting.", "start": 1570.23, "duration": 2.105}, {"text": "Oh, I'm going to\nchew up some As.", "start": 1572.335, "duration": 1.375}, {"text": "But you're not messing\nup the messenger RNA", "start": 1573.71, "duration": 2.76}, {"text": "that you need at the end.", "start": 1576.47, "duration": 1.38}, {"text": "So it's adding\nsome dummy sequence", "start": 1577.85, "duration": 2.94}, {"text": "that will be handy there.", "start": 1580.79, "duration": 3.57}, {"text": "It contributes to stability.", "start": 1584.36, "duration": 2.76}, {"text": "The tail is shortened over\ntime, but it's non-coding,", "start": 1587.12, "duration": 2.92}, {"text": "so that's OK.", "start": 1590.04, "duration": 1.21}, {"text": "And actually though, when\nthe tail is short enough,", "start": 1591.25, "duration": 3.25}, {"text": "the polyadenine tail kind\nof acts as a bit of a timer.", "start": 1594.5, "duration": 3.72}, {"text": "Because once the\ntail gets short,", "start": 1598.22, "duration": 1.54}, {"text": "you start chewing\ninto the transcript,", "start": 1599.76, "duration": 2.81}, {"text": "and you basically end up with a\ndegradation of the transcript.", "start": 1602.57, "duration": 3.36}, {"text": "But it gives you time in\nthe cytoplasm for the gene", "start": 1605.93, "duration": 4.02}, {"text": "to be translated into protein.", "start": 1609.95, "duration": 2.018}, {"text": "Does that all make sense?", "start": 1611.968, "duration": 1.042}, {"text": "So it's basically like an egg\ntimer, just watching, watching;", "start": 1613.01, "duration": 3.6}, {"text": "back, back, back.", "start": 1616.61, "duration": 1.05}, {"text": "OK, this transcript has\nbeen out here long enough.", "start": 1617.66, "duration": 3.3}, {"text": "We've made all the\nprotein we need.", "start": 1620.96, "duration": 1.99}, {"text": "Now we're going to chew\nup the coding part.", "start": 1622.95, "duration": 2.7}, {"text": "And then finally it's\nactually a good marker", "start": 1625.65, "duration": 3.74}, {"text": "again for leaving the nucleus.", "start": 1629.39, "duration": 2.1}, {"text": "And then finally it's kind of\na cool tool for technology,", "start": 1631.49, "duration": 3.84}, {"text": "because there's lots of interest\nin characterizing what's", "start": 1635.33, "duration": 11.09}, {"text": "known as the transcriptome.", "start": 1646.42, "duration": 1.57}, {"text": "OK, it's all well and good\nto characterize a genome.", "start": 1655.41, "duration": 3.6}, {"text": "But it's a lot of work,\n3.2 billion base pairs.", "start": 1659.01, "duration": 4.05}, {"text": "And only a part of\nit, a tiny part of it,", "start": 1663.06, "duration": 3.15}, {"text": "are parts of the genes\nthat encode the proteins.", "start": 1666.21, "duration": 3.61}, {"text": "So what you'd\nreally want to know,", "start": 1669.82, "duration": 1.79}, {"text": "if you want to\nanalyze the genes that", "start": 1671.61, "duration": 2.46}, {"text": "are going to become the proteins\nand maybe look for defects,", "start": 1674.07, "duration": 3.38}, {"text": "is look at the things that\nare going to be transcribed.", "start": 1677.45, "duration": 3.32}, {"text": "So you can use the\nfact that there", "start": 1680.77, "duration": 2.57}, {"text": "is this poly-A tail on\nthe transcripts that", "start": 1683.34, "duration": 4.29}, {"text": "are going to leave the\nnucleus with something that", "start": 1687.63, "duration": 4.14}, {"text": "will pull them out of the mix.", "start": 1691.77, "duration": 2.04}, {"text": "What would I use?", "start": 1693.81, "duration": 1.05}, {"text": "Let's say I've got a\nresin bead, polystyrene", "start": 1694.86, "duration": 6.51}, {"text": "or some favorable polymer.", "start": 1701.37, "duration": 2.55}, {"text": "And I can attach covalently\nnucleic acids to that bead.", "start": 1703.92, "duration": 5.43}, {"text": "What would I add there\nto fish this lot out?", "start": 1709.35, "duration": 4.23}, {"text": "Yeah, up here?", "start": 1713.58, "duration": 1.33}, {"text": "Yeah.", "start": 1714.91, "duration": 0.512}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1715.422, "duration": 1.116}, {"text": "BARBARA IMPERIALI:\nYeah, a lot of Ts.", "start": 1716.538, "duration": 1.542}, {"text": "So I'm going to make this.", "start": 1718.08, "duration": 1.1}, {"text": "I'm going to put on a bunch of\nTs, and I can do this a lot.", "start": 1719.18, "duration": 5.45}, {"text": "This is done very,\nvery commonly.", "start": 1724.63, "duration": 2.09}, {"text": "And then I'm just\ngoing to fish out", "start": 1726.72, "duration": 2.37}, {"text": "everything that is part of the\ntranscriptome, not the genome.", "start": 1729.09, "duration": 5.37}, {"text": "So I've got a much smaller\njob then to find out errors", "start": 1734.46, "duration": 3.78}, {"text": "in the genes that\nencode the proteins,", "start": 1738.24, "duration": 2.46}, {"text": "than if I was going to start\nwith the entire genome.", "start": 1740.7, "duration": 3.25}, {"text": "So pretty cool tool,\nand later on we're", "start": 1743.95, "duration": 2.3}, {"text": "going to see how\nthis can be used.", "start": 1746.25, "duration": 2.08}, {"text": "It's actually used in concert\nwith an interesting enzyme", "start": 1748.33, "duration": 2.96}, {"text": "that comes from viruses\ncalled reverse transcriptase.", "start": 1751.29, "duration": 3.51}, {"text": "But that's a story\nfor a later day.", "start": 1754.8, "duration": 1.68}, {"text": "But it is a cool story.", "start": 1756.48, "duration": 1.89}, {"text": "Now the last thing that\nwe do in the nucleus", "start": 1758.37, "duration": 6.06}, {"text": "is arguably the most important.", "start": 1764.43, "duration": 2.31}, {"text": "And that is splicing.", "start": 1766.74, "duration": 0.975}, {"text": "OK, all right.", "start": 1772.44, "duration": 5.05}, {"text": "Once again, this is a picture\nwith a lot of moving parts.", "start": 1777.49, "duration": 3.76}, {"text": "But I want to convey to\nyou the point of splicing,", "start": 1781.25, "duration": 3.11}, {"text": "as opposed to you knowing\nall the little details.", "start": 1784.36, "duration": 3.39}, {"text": "It was noticed for a long\ntime that the messenger didn't", "start": 1787.75, "duration": 5.67}, {"text": "always correspond to\nthe original transcript.", "start": 1793.42, "duration": 2.55}, {"text": "And this is the case\neukaryotes, not in bacteria.", "start": 1795.97, "duration": 3.05}, {"text": "But that there was quite\na lot of processing", "start": 1799.02, "duration": 2.32}, {"text": "done, not just to cap the\nends, but by cutting out", "start": 1801.34, "duration": 5.22}, {"text": "chunks of the transcript,\nso removal of segments", "start": 1806.56, "duration": 12.26}, {"text": "of the transcript.", "start": 1818.82, "duration": 0.96}, {"text": "And a lot of the\nseminal work was", "start": 1823.84, "duration": 2.22}, {"text": "done by Phillip Sharp, who\nis a member of our faculty", "start": 1826.06, "duration": 3.06}, {"text": "in the Biology Department.", "start": 1829.12, "duration": 1.26}, {"text": "So we're very proud of this.", "start": 1830.38, "duration": 1.65}, {"text": "This was actually the topic\nof a Nobel Prize in the '90s.", "start": 1832.03, "duration": 5.65}, {"text": "And so what was noticed is that\nif you had a gene, and let's", "start": 1837.68, "duration": 5.33}, {"text": "just put it here,\n5 prime to 3 prime.", "start": 1843.01, "duration": 10.21}, {"text": "And I'm going to name these.", "start": 1853.22, "duration": 1.5}, {"text": "And then I'll explain\nto you what they are.", "start": 1854.72, "duration": 2.19}, {"text": "These would be called exons.", "start": 1856.91, "duration": 3.3}, {"text": "These would be called intros.", "start": 1860.21, "duration": 1.336}, {"text": "And this is another exon.", "start": 1864.94, "duration": 2.79}, {"text": "Outside, inside; that's\nthe way to remember them.", "start": 1867.73, "duration": 3.0}, {"text": "And what happens in\nsplicing is that the introns", "start": 1870.73, "duration": 2.6}, {"text": "are chopped out.", "start": 1873.33, "duration": 1.38}, {"text": "OK, so your gene\nthen ends up being,", "start": 1874.71, "duration": 2.59}, {"text": "if this is exon\n1 and exon 2, not", "start": 1877.3, "duration": 2.94}, {"text": "represented by\nthis entire thing,", "start": 1880.24, "duration": 2.25}, {"text": "but eliminating that\nmiddle component.", "start": 1882.49, "duration": 2.4}, {"text": "And remember all the time\nwe have the cap at 5,", "start": 1898.185, "duration": 4.365}, {"text": "we have the poly-A tail ad\ninfinitum, the 3 prime end.", "start": 1902.55, "duration": 6.92}, {"text": "So we've just\nchanged the middle.", "start": 1909.47, "duration": 2.38}, {"text": "And it was recognized through\nbioinformatics analysis that", "start": 1911.85, "duration": 3.93}, {"text": "basically noticed the\npieces that was chopped out", "start": 1915.78, "duration": 4.05}, {"text": "and the pieces that\nended up being joined.", "start": 1919.83, "duration": 2.6}, {"text": "And protein splicing\noccurs as a sequence", "start": 1922.43, "duration": 3.01}, {"text": "of events that ends you up\nwith the protein being spliced", "start": 1925.44, "duration": 4.5}, {"text": "together through a\nseries of rearrangements", "start": 1929.94, "duration": 3.06}, {"text": "that occur on the structure\nof the messenger RNA.", "start": 1933.0, "duration": 5.32}, {"text": "So there is an\ninternal rearrangement.", "start": 1938.32, "duration": 2.63}, {"text": "A new phosphate is made.", "start": 1940.95, "duration": 1.92}, {"text": "And then there's\nanother rearrangement,", "start": 1942.87, "duration": 2.16}, {"text": "where there's a new\nbond made between one", "start": 1945.03, "duration": 2.76}, {"text": "end of the pre-messenger\nRNA, and the other end", "start": 1947.79, "duration": 6.8}, {"text": "of the pre-messenger\nRNA, to give you", "start": 1954.59, "duration": 4.21}, {"text": "the exon rejoined, ready\nto be read in translation.", "start": 1958.8, "duration": 4.54}, {"text": "Now why is this so important?", "start": 1963.34, "duration": 1.68}, {"text": "So I want to go here\nto a few numbers", "start": 1965.02, "duration": 2.33}, {"text": "that I think are\nvery pertinent, which", "start": 1967.35, "duration": 1.89}, {"text": "I had to drill my\ncolleagues for,", "start": 1969.24, "duration": 1.59}, {"text": "because I didn't\nknow all the numbers.", "start": 1970.83, "duration": 1.6}, {"text": "So when the genome\nwas sequenced,", "start": 1972.43, "duration": 3.02}, {"text": "we were a bit stunned,\nbecause the number", "start": 1975.45, "duration": 2.82}, {"text": "of coding things\nthat are genes that", "start": 1978.27, "duration": 2.49}, {"text": "are going to be\nturned into proteins", "start": 1980.76, "duration": 1.98}, {"text": "was much smaller\nthan we anticipated.", "start": 1982.74, "duration": 2.25}, {"text": "For man, it's currently\nat about 20,000 genes.", "start": 1984.99, "duration": 3.84}, {"text": "That's 20,000 mature transcripts\nthat could make proteins.", "start": 1988.83, "duration": 5.79}, {"text": "Fly?", "start": 1994.62, "duration": 0.6}, {"text": "Not much smaller, arguably\nthey're pretty smart, 16,000.", "start": 1995.22, "duration": 4.18}, {"text": "Yeast 6,000, a\nbacteria at 4,000.", "start": 1999.4, "duration": 2.9}, {"text": "There doesn't seem to be\nenough of a difference.", "start": 2002.3, "duration": 3.3}, {"text": "But a huge amount\nof diversity is", "start": 2005.6, "duration": 3.3}, {"text": "introduced into the transcripts\nby different splicing events.", "start": 2008.9, "duration": 4.59}, {"text": "Because if you make\none transcript,", "start": 2013.49, "duration": 1.68}, {"text": "that would count as one gene.", "start": 2015.17, "duration": 2.8}, {"text": "But if there is a lot of\nopportunities for difference", "start": 2017.97, "duration": 3.08}, {"text": "splicing activity,\nyou can piece together", "start": 2021.05, "duration": 3.48}, {"text": "new transcripts that will\nencode proteins differently.", "start": 2024.53, "duration": 4.33}, {"text": "And I think this next\nslide will show you", "start": 2028.86, "duration": 3.86}, {"text": "an example of a transcript that\nhas several different introns", "start": 2032.72, "duration": 4.55}, {"text": "and exons.", "start": 2037.27, "duration": 1.36}, {"text": "So you can see here\nacross, there's", "start": 2038.63, "duration": 2.31}, {"text": "a blue, green, red, another\nblue, and an orange exon.", "start": 2040.94, "duration": 5.16}, {"text": "But depending on which\npieces are spliced out,", "start": 2046.1, "duration": 3.18}, {"text": "we'll have different\nproteins end up.", "start": 2049.28, "duration": 2.22}, {"text": "So it could be a\nway, for example,", "start": 2051.5, "duration": 2.909}, {"text": "to think of a practical use, to\nhave a protein that is either", "start": 2054.409, "duration": 3.391}, {"text": "secreted as a soluble\nprotein, or left", "start": 2057.8, "duration": 3.3}, {"text": "in the membrane with a\nmembrane association domain,", "start": 2061.1, "duration": 3.52}, {"text": "or left in the cytoplasm because\nit has no way to be secreted.", "start": 2064.62, "duration": 3.74}, {"text": "So it could be a way to\nmake three proteins that", "start": 2068.36, "duration": 2.22}, {"text": "are in completely\ndifferent places of a cell,", "start": 2070.58, "duration": 2.7}, {"text": "or have different functions.", "start": 2073.28, "duration": 1.98}, {"text": "It's also very\nimportant in tissues,", "start": 2075.26, "duration": 3.37}, {"text": "because we splice proteins\ndifferently in muscle,", "start": 2078.63, "duration": 3.319}, {"text": "or liver, or heart to\nachieve different outcomes", "start": 2081.949, "duration": 3.241}, {"text": "in the proteins that we make.", "start": 2085.19, "duration": 1.799}, {"text": "So basically, it's a\nsource of huge diversity,", "start": 2086.989, "duration": 3.631}, {"text": "and it gives us the\ngenetic diversity", "start": 2090.62, "duration": 2.4}, {"text": "that means this 20,000 can\nbe a much bigger number.", "start": 2093.02, "duration": 3.48}, {"text": "And then with the\npost-translational", "start": 2096.5, "duration": 1.5}, {"text": "modifications I talk about\nwhen we come back later on,", "start": 2098.0, "duration": 4.56}, {"text": "you'll see we've got lots of\nways to diversify that 20,000.", "start": 2102.56, "duration": 5.03}, {"text": "That mean these aren't\nliteral numbers.", "start": 2107.59, "duration": 2.9}, {"text": "They're quite varied.", "start": 2110.49, "duration": 0.98}, {"text": "But what you want to remember\nis E. coli doesn't do splicing.", "start": 2111.47, "duration": 4.09}, {"text": "There's no opportunity there.", "start": 2115.56, "duration": 1.76}, {"text": "It's much more limited\nin yeast, so is", "start": 2117.32, "duration": 2.22}, {"text": "the post-translational\nmodification.", "start": 2119.54, "duration": 1.93}, {"text": "So these numbers settle\nout quite differently", "start": 2121.47, "duration": 2.54}, {"text": "from what they look\nlike by looking directly", "start": 2124.01, "duration": 2.19}, {"text": "at those numbers.", "start": 2126.2, "duration": 1.95}, {"text": "And I wanted to\ngive you an example.", "start": 2128.15, "duration": 1.84}, {"text": "You don't have this\nin your slides,", "start": 2129.99, "duration": 1.54}, {"text": "but I was thinking\nabout it the other day.", "start": 2131.53, "duration": 1.75}, {"text": "A colleague of mine, Professor\nPentelute in chemistry,", "start": 2133.28, "duration": 3.69}, {"text": "works on trying\nto reprogram genes", "start": 2136.97, "duration": 3.0}, {"text": "to overcome a disease known as\nDuchenne muscular dystrophy.", "start": 2139.97, "duration": 4.62}, {"text": "It's another genetic disorder.", "start": 2144.59, "duration": 2.43}, {"text": "It's X-linked.", "start": 2147.02, "duration": 1.53}, {"text": "So it's much more serious\nin males than in females.", "start": 2148.55, "duration": 3.63}, {"text": "Because if you only have\none bad copy of the gene,", "start": 2152.18, "duration": 2.37}, {"text": "you can do OK with this disease.", "start": 2154.55, "duration": 3.75}, {"text": "Whereas in the male,\nyou'd only have", "start": 2158.3, "duration": 2.88}, {"text": "the component of the gene\nthat's on the X chromosome.", "start": 2161.18, "duration": 3.7}, {"text": "And it's a defect in RNA\nsplicing, so directly there.", "start": 2164.88, "duration": 5.25}, {"text": "So this is a biopsy\nof muscle where", "start": 2170.13, "duration": 4.1}, {"text": "red would be good muscle\ncells, whereas the white would", "start": 2174.23, "duration": 3.72}, {"text": "be fat cells.", "start": 2177.95, "duration": 4.62}, {"text": "And they actually weaken\nthe integrity of the muscle,", "start": 2182.57, "duration": 2.993}, {"text": "because the muscle\ndoesn't develop", "start": 2185.563, "duration": 1.417}, {"text": "to have all the well-defined\nmuscle cells that", "start": 2186.98, "duration": 3.91}, {"text": "are important for\nmuscle tensile strength,", "start": 2190.89, "duration": 2.73}, {"text": "and contractility, and\neverything else that muscles", "start": 2193.62, "duration": 2.28}, {"text": "do.", "start": 2195.9, "duration": 0.6}, {"text": "And it's all related to a\nprotein known as dystrophin,", "start": 2196.5, "duration": 3.75}, {"text": "which is a huge protein.", "start": 2200.25, "duration": 1.59}, {"text": "And it's a critical\nstructural protein", "start": 2201.84, "duration": 2.16}, {"text": "that's important to maintain\nthe cellular membranes", "start": 2204.0, "duration": 3.57}, {"text": "within the muscle cells.", "start": 2207.57, "duration": 1.24}, {"text": "So if dystrophin is no good,\nthe cell membrane integrity", "start": 2208.81, "duration": 4.19}, {"text": "is no good.", "start": 2213.0, "duration": 0.9}, {"text": "And you just end up\nwith losing the muscle", "start": 2213.9, "duration": 1.89}, {"text": "cells, a cost of replacing them\nwith fat cells in the muscle.", "start": 2215.79, "duration": 4.53}, {"text": "And here's a really\namazing number.", "start": 2220.32, "duration": 2.76}, {"text": "The gene that encodes\ndystrophin has 79 exons.", "start": 2223.08, "duration": 4.65}, {"text": "So you can picture the\nopportunities for things", "start": 2227.73, "duration": 2.79}, {"text": "to go wrong, and it's\nactually a defect in the place", "start": 2230.52, "duration": 3.6}, {"text": "where the splicing happens.", "start": 2234.12, "duration": 1.59}, {"text": "So a splicing event\ncannot happen.", "start": 2235.71, "duration": 2.62}, {"text": "And so the protein at the\nend of the day is not good.", "start": 2238.33, "duration": 3.92}, {"text": "So there's a lot of\nefforts going on,", "start": 2242.25, "duration": 2.88}, {"text": "antisense efforts, and even\nother gene therapy efforts,", "start": 2245.13, "duration": 5.55}, {"text": "and also nowadays there's\nobviously a large focus", "start": 2250.68, "duration": 3.3}, {"text": "on CRISPR-based gene editing.", "start": 2253.98, "duration": 1.92}, {"text": "But remember this is\na serious debilitating", "start": 2255.9, "duration": 3.27}, {"text": "disease of all muscle tissue.", "start": 2259.17, "duration": 2.31}, {"text": "It starts to be noticed when\nthe babies are toddlers,", "start": 2261.48, "duration": 3.048}, {"text": "because that's really\nwhen they start", "start": 2264.528, "duration": 1.542}, {"text": "to engage muscle strength.", "start": 2266.07, "duration": 2.14}, {"text": "So around the age of four\nit's actually noticed.", "start": 2268.21, "duration": 3.32}, {"text": "And then the life\nexpectancy is in the 30", "start": 2271.53, "duration": 3.48}, {"text": "to 40-years-old range.", "start": 2275.01, "duration": 2.49}, {"text": "But it's also a\nterrible lifestyle,", "start": 2277.5, "duration": 2.37}, {"text": "because the lungs don't work.", "start": 2279.87, "duration": 2.64}, {"text": "So many things rely\non muscle strength.", "start": 2282.51, "duration": 2.52}, {"text": "OK, good.", "start": 2285.03, "duration": 1.35}, {"text": "All right, so I believe\nthat's the end of that.", "start": 2286.38, "duration": 2.88}, {"text": "But I want to give you an\nintroduction to translation,", "start": 2289.26, "duration": 3.51}, {"text": "so you'll see what we\nhave in store for Friday.", "start": 2292.77, "duration": 3.09}, {"text": "And just get you\nback to this picture,", "start": 2295.86, "duration": 2.37}, {"text": "we've done everything we need.", "start": 2298.23, "duration": 1.48}, {"text": "We've done all the processing.", "start": 2299.71, "duration": 2.09}, {"text": "We're here, and then\nthe mature messenger RNA", "start": 2301.8, "duration": 4.14}, {"text": "can finally leave the nucleus\nto be ready for translation.", "start": 2305.94, "duration": 4.14}, {"text": "And the cap-- there\nis a complex that", "start": 2310.08, "duration": 2.22}, {"text": "binds the 5 prime\ncap that's tasked", "start": 2312.3, "duration": 5.85}, {"text": "with helping export\nthat transcript", "start": 2318.15, "duration": 6.87}, {"text": "through the nuclear pore, which\nis a fairly large opening,", "start": 2325.02, "duration": 3.48}, {"text": "outside into the cytoplasm.", "start": 2328.5, "duration": 2.57}, {"text": "And I want to show\nyou one other thing", "start": 2331.07, "duration": 1.75}, {"text": "and I hope I can\nget this reliably,", "start": 2332.82, "duration": 4.08}, {"text": "because with this I'm\ngoing to actually show you", "start": 2336.9, "duration": 2.7}, {"text": "some of the moving parts.", "start": 2339.6, "duration": 1.77}, {"text": "There's a little\nthing on the sidebar", "start": 2341.37, "duration": 1.72}, {"text": "now, called a short translation.", "start": 2343.09, "duration": 4.21}, {"text": "And so what you're seeing\nhere, the black line", "start": 2347.3, "duration": 4.28}, {"text": "is the messenger RNA.", "start": 2351.58, "duration": 1.69}, {"text": "OK, so that's the thing\nthat's finally out", "start": 2353.27, "duration": 2.03}, {"text": "there in the cytoplasm ready.", "start": 2355.3, "duration": 2.28}, {"text": "The pale green and yellow\nare the two components", "start": 2357.58, "duration": 2.88}, {"text": "of the ribosome, which is\na soluble organelle that", "start": 2360.46, "duration": 3.24}, {"text": "assembles on the double-stranded\nDNA based on a few cues.", "start": 2363.7, "duration": 4.59}, {"text": "The dark blue components\nare transfer RNAs", "start": 2368.29, "duration": 4.87}, {"text": "that bring in new amino acids.", "start": 2373.16, "duration": 2.6}, {"text": "And what you see\nthreading out here", "start": 2375.76, "duration": 2.46}, {"text": "is a new protein strand\nthat is being translated.", "start": 2378.22, "duration": 4.32}, {"text": "This particular translation is\nto make a protein that becomes", "start": 2382.54, "duration": 3.78}, {"text": "membrane bound and secreted.", "start": 2386.32, "duration": 1.59}, {"text": "So I'm not going to\ngo further than that.", "start": 2387.91, "duration": 2.53}, {"text": "But there's a lot of\nthose light blue proteins", "start": 2390.44, "duration": 2.57}, {"text": "that are actually helping\nescort the transfer", "start": 2393.01, "duration": 3.06}, {"text": "RNAs to where they're needed to\ncontinue building the proteins.", "start": 2396.07, "duration": 4.35}, {"text": "So we've seen the messenger.", "start": 2400.42, "duration": 2.28}, {"text": "We'll learn more\nabout the ribosome,", "start": 2402.7, "duration": 2.19}, {"text": "and will learn about\nthe transfer RNAs.", "start": 2404.89, "duration": 3.33}, {"text": "And you can also watch this\nto your heart's content.", "start": 2408.22, "duration": 4.5}, {"text": "I just find it just a\nuseful simple cartoon", "start": 2412.72, "duration": 2.88}, {"text": "that tells us a lot.", "start": 2415.6, "duration": 3.24}, {"text": "So what I really want\nto encourage you to do", "start": 2418.84, "duration": 2.88}, {"text": "is read this section 14.5,\nbecause the next parts will", "start": 2421.72, "duration": 4.32}, {"text": "make a great deal more sense.", "start": 2426.04, "duration": 2.2}, {"text": "So what I want to do\nthough now is first of all,", "start": 2428.24, "duration": 5.4}, {"text": "start with describing the\nplayers in translation,", "start": 2433.64, "duration": 4.26}, {"text": "and just the way we\ndid for replication,", "start": 2437.9, "duration": 2.48}, {"text": "we're going to systematically\nascribe the importance", "start": 2440.38, "duration": 3.25}, {"text": "to each of these players.", "start": 2443.63, "duration": 1.8}, {"text": "So what you see, there\nare molecular players", "start": 2445.43, "duration": 2.79}, {"text": "and there are key steps.", "start": 2448.22, "duration": 1.53}, {"text": "So the molecular\nplayers are shown here.", "start": 2449.75, "duration": 2.31}, {"text": "So far, we've focused very\nstrongly on the messenger RNA.", "start": 2452.06, "duration": 3.95}, {"text": "You know all about that.", "start": 2456.01, "duration": 1.0}, {"text": "You know where it's from.", "start": 2457.01, "duration": 1.14}, {"text": "You know it's stable in\nthe cytoplasm for a while.", "start": 2458.15, "duration": 2.61}, {"text": "You know it's got signals\nthat tell the complexes where", "start": 2460.76, "duration": 3.15}, {"text": "to go down.", "start": 2463.91, "duration": 1.89}, {"text": "Then we need transfer\nRNAs and amino acids,", "start": 2465.8, "duration": 3.39}, {"text": "and we need the ribosomes.", "start": 2469.19, "duration": 1.83}, {"text": "And ribosomes are made of\na composite of nucleic acid", "start": 2471.02, "duration": 3.87}, {"text": "and protein wrapped together.", "start": 2474.89, "duration": 2.46}, {"text": "There's quite a big\ndifference in prokaryotes", "start": 2477.35, "duration": 2.31}, {"text": "and eukaryotic\nribosomes, and I'll", "start": 2479.66, "duration": 2.04}, {"text": "mention that when we get to it.", "start": 2481.7, "duration": 1.86}, {"text": "But I want to focus for a\nfew moments, first of all,", "start": 2483.56, "duration": 3.03}, {"text": "on the landmarks that got us to\nfinally in 2009 the structure", "start": 2486.59, "duration": 5.46}, {"text": "of the ribosome.", "start": 2492.05, "duration": 0.87}, {"text": "It's a cool development\nfor everyone.", "start": 2492.92, "duration": 2.58}, {"text": "But also where we came\nfrom in the '60s, when", "start": 2495.5, "duration": 3.36}, {"text": "Crick and Brenner finally\ncracked the genetic code,", "start": 2498.86, "duration": 3.57}, {"text": "and found out that three\nbases on that messenger", "start": 2502.43, "duration": 3.18}, {"text": "RNA will encode\neach new amino acid", "start": 2505.61, "duration": 3.63}, {"text": "that gets put into\nyour protein sequence.", "start": 2509.24, "duration": 2.55}, {"text": "So I want to introduce you\nto the transfer RNAs that", "start": 2511.79, "duration": 5.61}, {"text": "are really the most\nimportant element", "start": 2517.4, "duration": 3.45}, {"text": "to start thinking about.", "start": 2520.85, "duration": 1.35}, {"text": "And you can call these\nguys the decoders,", "start": 2528.11, "duration": 6.24}, {"text": "because what the\ntransfer RNA does", "start": 2534.35, "duration": 3.06}, {"text": "is it can carry an amino acid\non one end of its nucleic acid.", "start": 2537.41, "duration": 5.22}, {"text": "But on one of the other\nloops within the transfer", "start": 2542.63, "duration": 2.73}, {"text": "RNA is what's known\nas an anticodon that", "start": 2545.36, "duration": 3.39}, {"text": "recognizes a codon\nin the messenger RNA,", "start": 2548.75, "duration": 3.86}, {"text": "and basically prescribes\nwhat amino acids get put in.", "start": 2552.61, "duration": 4.28}, {"text": "So it was always a wonder how\nyou went from the nucleic acid", "start": 2556.89, "duration": 3.44}, {"text": "world to the protein world.", "start": 2560.33, "duration": 2.44}, {"text": "The answer is you\nuse a nucleic acid", "start": 2562.77, "duration": 3.19}, {"text": "that you can load\nwith an amino acid,", "start": 2565.96, "duration": 2.35}, {"text": "but it can also recognize\nthe messenger RNA that codes", "start": 2568.31, "duration": 4.08}, {"text": "for the protein sequence.", "start": 2572.39, "duration": 2.07}, {"text": "And that's why I like to\nthink of them as decoders.", "start": 2574.46, "duration": 3.09}, {"text": "But what this picture\nof the RNA shows you,", "start": 2577.55, "duration": 7.32}, {"text": "is the beautiful\nstructure of RNA,", "start": 2584.87, "duration": 2.6}, {"text": "where at one end is where an\namino acid would be attached.", "start": 2587.47, "duration": 3.58}, {"text": "There's this cool kind\nof cloverleaf structure.", "start": 2591.05, "duration": 3.03}, {"text": "And then at the other\nend is the anticodon loop", "start": 2594.08, "duration": 3.12}, {"text": "that will actually recognize\nyour messenger RNA.", "start": 2597.2, "duration": 3.76}, {"text": "So I'm going to stop now.", "start": 2600.96, "duration": 1.37}, {"text": "But I really want to\nencourage you, just skim", "start": 2602.33, "duration": 3.51}, {"text": "through that small section.", "start": 2605.84, "duration": 2.46}, {"text": "It'll make a lot\nmore sense on Friday.", "start": 2608.3, "duration": 2.82}, {"text": "I've been waiting to talk to\nyou about protein translation", "start": 2611.12, "duration": 3.35}, {"text": "since we started this class.", "start": 2614.47, "duration": 1.42}, {"text": "But it'll make a lot more sense.", "start": 2615.89, "duration": 2.89}, {"text": "And there's some super cool\ninitiatives in chemical biology", "start": 2618.78, "duration": 3.62}, {"text": "now, where people have been\nable to completely hijack", "start": 2622.4, "duration": 3.87}, {"text": "protein translation,\nand not put in just", "start": 2626.27, "duration": 2.55}, {"text": "20 regular boring amino\nacids, but actually", "start": 2628.82, "duration": 3.18}, {"text": "put in all kinds of\nother amino acids.", "start": 2632.0, "duration": 2.77}, {"text": "So we understand the system\nwell enough to manipulate it.", "start": 2634.77, "duration": 4.37}, {"text": "And this really hearkens\nto the Feynman quotes,", "start": 2639.14, "duration": 3.24}, {"text": "\"If you can build it,\nyou can understand it.\"", "start": 2642.38, "duration": 2.4}, {"text": "That's the level to which\nwe understand translation", "start": 2644.78, "duration": 2.82}, {"text": "nowadays.", "start": 2647.6, "duration": 0.9}, {"text": "That's it for today.", "start": 2648.5, "duration": 2.0}]
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+[{"text": "The following content is\nprovided under a Creative", "start": 0.95, "duration": 2.37}, {"text": "Commons license.", "start": 3.32, "duration": 1.39}, {"text": "Your support will help\nMIT OpenCourseWare", "start": 4.71, "duration": 2.21}, {"text": "continue to offer high-quality\neducational resources for free.", "start": 6.92, "duration": 4.09}, {"text": "To make a donation, or to\nview additional materials", "start": 11.01, "duration": 2.57}, {"text": "from hundreds of MIT courses,\nvisit MIT OpenCourseWare", "start": 13.58, "duration": 3.96}, {"text": "at ocw.mit.edu.", "start": 17.54, "duration": 0.886}, {"text": "PROFESSOR: So I got much\nmore than one request", "start": 23.024, "duration": 4.396}, {"text": "to do some stuff on\nnuclear materials,", "start": 27.42, "duration": 2.04}, {"text": "and I think it's just\nabout the right time.", "start": 29.46, "duration": 2.38}, {"text": "That you guys know\nenough about radiation", "start": 31.84, "duration": 2.265}, {"text": "interacting with\nmatter and everything,", "start": 34.105, "duration": 1.625}, {"text": "and stopping power,\nand processing,", "start": 35.73, "duration": 1.705}, {"text": "to actually make sense of\nnuclear materials and radiation", "start": 37.435, "duration": 2.865}, {"text": "damage.", "start": 40.3, "duration": 0.5}, {"text": "And this is my whole\ntheme, so happy", "start": 40.8, "duration": 2.632}, {"text": "to come talk to\nyou guys about this", "start": 43.432, "duration": 1.458}, {"text": "and show you why I\nthink it's interesting.", "start": 44.89, "duration": 1.75}, {"text": "Because it all goes--", "start": 46.64, "duration": 1.89}, {"text": "this slide kind of gets onto it.", "start": 48.53, "duration": 2.63}, {"text": "It starts off with the\nsingle-atom atomic defects", "start": 51.16, "duration": 3.02}, {"text": "that make up the basic\nbuilding blocks of damage", "start": 54.18, "duration": 2.82}, {"text": "and ends up with things that\nbreak in nuclear reactors", "start": 57.0, "duration": 3.09}, {"text": "under radiation.", "start": 60.09, "duration": 1.098}, {"text": "And so to understand\nthe whole thing,", "start": 61.188, "duration": 1.542}, {"text": "you've got to know everything\nfrom the single atoms", "start": 62.73, "duration": 2.729}, {"text": "on the sort of\nfemtosecond scale,", "start": 65.459, "duration": 1.946}, {"text": "all the way up to\nthe engineering scale", "start": 67.405, "duration": 1.625}, {"text": "where things evolve over\nyears or even decades.", "start": 69.03, "duration": 3.9}, {"text": "So we'll be talking--", "start": 72.93, "duration": 0.91}, {"text": "first, probably\ntoday, we're going", "start": 73.84, "duration": 1.19}, {"text": "to go over a material\nscience primer.", "start": 75.03, "duration": 1.66}, {"text": "So who here has had any\ncourses in material science?", "start": 76.69, "duration": 3.81}, {"text": "No one.", "start": 80.5, "duration": 0.5}, {"text": "That's good because I'm\nassuming that there is a--", "start": 81.0, "duration": 2.95}, {"text": "see, no one knows anything here.", "start": 83.95, "duration": 1.405}, {"text": "I know there's a couple material\nscientists in the class,", "start": 85.355, "duration": 2.375}, {"text": "and I'll apologize ahead of\ntime if it's a bit of a review.", "start": 87.73, "duration": 2.7}, {"text": "But we'll be going mostly\nthrough what are materials", "start": 90.43, "duration": 2.82}, {"text": "and what are the defects\nthat change their material", "start": 93.25, "duration": 2.31}, {"text": "properties, and\nhow do they behave.", "start": 95.56, "duration": 2.29}, {"text": "That'll take us\nthrough about today.", "start": 97.85, "duration": 1.86}, {"text": "So then tomorrow, we can see how\nradiation causes those defects", "start": 99.71, "duration": 3.44}, {"text": "and actually changes\nmaterial properties.", "start": 103.15, "duration": 4.268}, {"text": "So there's a whole laundry\nlist of different ways", "start": 107.418, "duration": 2.042}, {"text": "that materials\nfail, and most folks", "start": 109.46, "duration": 2.16}, {"text": "are concerned with\nall of these--", "start": 111.62, "duration": 2.89}, {"text": "everything from simple\noverload, which means you", "start": 114.51, "duration": 2.87}, {"text": "stress something too\nmuch and it just breaks,", "start": 117.38, "duration": 2.52}, {"text": "to all the different\nforms of corrosion.", "start": 119.9, "duration": 2.1}, {"text": "That's a whole field in itself.", "start": 122.0, "duration": 1.788}, {"text": "And then there's\nthe things that just", "start": 123.788, "duration": 1.542}, {"text": "we have to worry about\nbecause they're only activated", "start": 125.33, "duration": 2.82}, {"text": "with radiation damage.", "start": 128.15, "duration": 1.95}, {"text": "And in this case, this isn't\nquite ionization by radiation,", "start": 130.1, "duration": 3.07}, {"text": "but it's actual radiation\nslamming into nuclei", "start": 133.17, "duration": 2.75}, {"text": "and moving atoms\nout of their place.", "start": 135.92, "duration": 2.89}, {"text": "And we've got one figure\nthat we had recently", "start": 138.81, "duration": 2.04}, {"text": "in a paper that sums up the\nentire multi-scale picture", "start": 140.85, "duration": 3.0}, {"text": "of radiation damage, from the\nfemtosecond to, let's say,", "start": 143.85, "duration": 3.96}, {"text": "the megasecond scale.", "start": 147.81, "duration": 1.108}, {"text": "Or I think it's more than that.", "start": 148.918, "duration": 1.292}, {"text": "Maybe gigasecond would be\nthe right word for that.", "start": 150.21, "duration": 2.46}, {"text": "And all the way down from the\nangstrom to the meter scale.", "start": 152.67, "duration": 3.3}, {"text": "And I want to walk you\nthrough sort of a lens scale", "start": 155.97, "duration": 3.78}, {"text": "by lens scale depiction\nof radiation damage.", "start": 159.75, "duration": 3.09}, {"text": "It all starts with knocking\natoms out of place.", "start": 162.84, "duration": 3.035}, {"text": "We've mentioned\nthis a little bit", "start": 165.875, "duration": 1.375}, {"text": "when we talked about\nnuclear stopping power,", "start": 167.25, "duration": 2.37}, {"text": "and this is where it\nactually comes into play.", "start": 169.62, "duration": 1.98}, {"text": "Sometimes an incoming\nneutron or photon or ion", "start": 171.6, "duration": 3.57}, {"text": "can displace an atom\nfrom its original site,", "start": 175.17, "duration": 3.57}, {"text": "and we call that a physical--\nit's a displacement.", "start": 178.74, "duration": 3.09}, {"text": "And then that atom comes\noff with quite a bit", "start": 181.83, "duration": 2.13}, {"text": "of kinetic energy and can\nknock into a whole bunch", "start": 183.96, "duration": 3.63}, {"text": "of other atoms.", "start": 187.59, "duration": 1.5}, {"text": "Now this loss of the solid\ncrystalline structure,", "start": 189.09, "duration": 3.15}, {"text": "you can't really tell what the\noriginal structure looked like,", "start": 192.24, "duration": 3.27}, {"text": "right?", "start": 195.51, "duration": 1.2}, {"text": "It actually comprises a\nvery small, localized zone", "start": 196.71, "duration": 2.88}, {"text": "of melting called\na thermal spike.", "start": 199.59, "duration": 2.46}, {"text": "If you think about,\nall these atoms", "start": 202.05, "duration": 1.71}, {"text": "are vibrating at\nfractions of an eV--", "start": 203.76, "duration": 2.61}, {"text": "at thermal energies,\nlike the thermal neutrons", "start": 206.37, "duration": 1.95}, {"text": "we talked about in the reactor.", "start": 208.32, "duration": 1.65}, {"text": "Then you hit them\nwith an MeV neutron.", "start": 209.97, "duration": 2.31}, {"text": "They might transfer\n100 keV of energy.", "start": 212.28, "duration": 2.88}, {"text": "And a bunch of these\natoms will then", "start": 215.16, "duration": 1.5}, {"text": "be moving about at, let's\nsay, a few hundred eV.", "start": 216.66, "duration": 3.78}, {"text": "That's way beyond\nliquid temperature.", "start": 220.44, "duration": 2.91}, {"text": "So actually, it's been\ntheorized that there's", "start": 223.35, "duration": 2.31}, {"text": "a little pocket of atoms around\nthree to five nanometers wide", "start": 225.66, "duration": 3.36}, {"text": "that reaches, like, 10,000\nKelvin for a very, very", "start": 229.02, "duration": 3.18}, {"text": "short amount of time--", "start": 232.2, "duration": 2.07}, {"text": "less than a picosecond.", "start": 234.27, "duration": 1.56}, {"text": "Because almost\ninstantly, those atoms", "start": 235.83, "duration": 1.86}, {"text": "knock into the ones\naround them, and this", "start": 237.69, "duration": 2.4}, {"text": "is how the process of\nheat transfer occurs.", "start": 240.09, "duration": 2.85}, {"text": "And so, very quickly,\nyou get what's", "start": 242.94, "duration": 1.5}, {"text": "called the quench, where\nmost of those atoms", "start": 244.44, "duration": 2.61}, {"text": "very quickly knock\ninto other ones,", "start": 247.05, "duration": 1.68}, {"text": "slowing down, finding their\nequilibrium positions again,", "start": 248.73, "duration": 3.45}, {"text": "but not every one.", "start": 252.18, "duration": 2.07}, {"text": "You can see there's a few\nplaces where the atoms are still", "start": 254.25, "duration": 3.06}, {"text": "out of their original location.", "start": 257.31, "duration": 1.769}, {"text": "And it's those residual\ndefects that actually", "start": 259.079, "duration": 2.371}, {"text": "comprise radiation damage.", "start": 261.45, "duration": 2.64}, {"text": "And as those defects build\nup, they start to move.", "start": 264.09, "duration": 3.77}, {"text": "They can diffuse.", "start": 267.86, "duration": 1.38}, {"text": "They can be transported\nballistically", "start": 269.24, "duration": 1.8}, {"text": "by more radiation damage.", "start": 271.04, "duration": 1.937}, {"text": "They can move by all sorts\nof different mechanisms", "start": 272.977, "duration": 2.083}, {"text": "and eventually find each other,\nforming what's called clusters.", "start": 275.06, "duration": 3.948}, {"text": "So a bunch of those missing\natoms could find each other", "start": 279.008, "duration": 2.292}, {"text": "and make a hole,\nwhich we call a void.", "start": 281.3, "duration": 2.19}, {"text": "A bunch of the extra\natoms shoved in", "start": 283.49, "duration": 1.83}, {"text": "between the other\nones can form things", "start": 285.32, "duration": 2.55}, {"text": "called interstitial clusters.", "start": 287.87, "duration": 2.1}, {"text": "We say interstitial because\nit's like in the space", "start": 289.97, "duration": 2.19}, {"text": "in between where you'd\nnormally find some atoms.", "start": 292.16, "duration": 3.93}, {"text": "So let's say you had a whole\nbunch of those missing atoms", "start": 296.09, "duration": 3.18}, {"text": "come together, forming a void.", "start": 299.27, "duration": 2.25}, {"text": "This is an actual Transmission\nElectron Microscope,", "start": 301.52, "duration": 2.54}, {"text": "or TEM, image of a void--", "start": 304.06, "duration": 2.32}, {"text": "pockets of vacuum in materials.", "start": 306.38, "duration": 3.0}, {"text": "Notice anything interesting\nabout its shape?", "start": 309.38, "duration": 2.883}, {"text": "AUDIENCE: It's, like, rounded.", "start": 312.263, "duration": 1.847}, {"text": "PROFESSOR: It's rounded, but\nwhat's most striking to me", "start": 314.11, "duration": 3.24}, {"text": "is it isn't actually round.", "start": 317.35, "duration": 2.5}, {"text": "So you would expect a void or a\nbubble to be kind of spherical,", "start": 319.85, "duration": 3.31}, {"text": "right?", "start": 323.16, "duration": 0.5}, {"text": "That's the minimum energy\nconfiguration of most things.", "start": 323.66, "duration": 4.08}, {"text": "Not so when you have a\nlittle pocket of vacuum.", "start": 327.74, "duration": 2.86}, {"text": "It's where crystallinity\ncomes into play.", "start": 330.6, "duration": 2.77}, {"text": "And these voids can end up\nforming superstructures.", "start": 333.37, "duration": 2.98}, {"text": "What curious thing\ndo you notice here?", "start": 336.35, "duration": 2.22}, {"text": "For this whole\nensemble of voids.", "start": 341.38, "duration": 1.395}, {"text": "Yeah?", "start": 345.76, "duration": 0.5}, {"text": "AUDIENCE: It seems like\nthey're all in line.", "start": 346.26, "duration": 1.96}, {"text": "PROFESSOR: They are all\nin the same direction.", "start": 348.22, "duration": 2.607}, {"text": "Kind of funny.", "start": 350.827, "duration": 0.583}, {"text": "That's definitely not\nan accident, right?", "start": 351.41, "duration": 1.772}, {"text": "That's not like they're\nrandomly aligned.", "start": 353.182, "duration": 1.708}, {"text": "There's a reason\nfor this, that we'll", "start": 354.89, "duration": 1.542}, {"text": "go into in a couple slides.", "start": 356.432, "duration": 1.198}, {"text": "Yeah?", "start": 357.63, "duration": 0.5}, {"text": "AUDIENCE: What's\nthe size scale here?", "start": 358.13, "duration": 1.85}, {"text": "PROFESSOR: The size scale?", "start": 359.98, "duration": 1.8}, {"text": "I think these are on the\norder of 20 nanometers or so.", "start": 361.78, "duration": 3.438}, {"text": "Yeah, I cropped these images\njust to get points across.", "start": 365.218, "duration": 2.292}, {"text": "Let's see if it says\nin the older one.", "start": 367.51, "duration": 2.1}, {"text": "Not quite.", "start": 369.61, "duration": 0.84}, {"text": "Yeah, but these voids can get\nupwards of tens of nanometers.", "start": 370.45, "duration": 3.66}, {"text": "As small as single atoms.", "start": 374.11, "duration": 1.19}, {"text": "Yeah?", "start": 375.3, "duration": 0.5}, {"text": "AUDIENCE: Sorry, what is this?", "start": 375.8, "duration": 2.45}, {"text": "PROFESSOR: This is\nthe accumulation", "start": 378.25, "duration": 1.83}, {"text": "of radiation defects\ninto what's called voids.", "start": 380.08, "duration": 3.88}, {"text": "Yeah.", "start": 383.96, "duration": 0.5}, {"text": "Don't worry, we'll go over\nit in more detail again.", "start": 384.46, "duration": 3.93}, {"text": "And if you get little pockets\nof vacuum in your material,", "start": 388.39, "duration": 2.75}, {"text": "you're not creating\nor destroying mass.", "start": 391.14, "duration": 1.75}, {"text": "You're just moving it.", "start": 392.89, "duration": 1.44}, {"text": "So those voids, where that mass\nwas has to go somewhere else,", "start": 394.33, "duration": 3.66}, {"text": "and you actually get\nthings that swell", "start": 397.99, "duration": 1.74}, {"text": "in the reactor on their own.", "start": 399.73, "duration": 1.75}, {"text": "They don't change mass\nbut they change volume.", "start": 401.48, "duration": 2.3}, {"text": "They just kind of puff up\nlike Swiss cheese, sometimes", "start": 403.78, "duration": 3.03}, {"text": "upwards of 20% or 30% changes\nin diameter and length", "start": 406.81, "duration": 3.66}, {"text": "for some tubing.", "start": 410.47, "duration": 1.17}, {"text": "Now if you're depending\non these fuel rods", "start": 411.64, "duration": 2.31}, {"text": "being a certain space\napart in a reactor", "start": 413.95, "duration": 2.79}, {"text": "and they start to swell,\nsqueezing out the coolant,", "start": 416.74, "duration": 3.18}, {"text": "you lose the ability\nto cool the reactor.", "start": 419.92, "duration": 2.075}, {"text": "Because then how can you\nget water around something", "start": 421.995, "duration": 2.125}, {"text": "where the tubes have\nthen swelled together?", "start": 424.12, "duration": 2.128}, {"text": "There's lots of other bad\nthings that can happen,", "start": 426.248, "duration": 2.042}, {"text": "which we'll get into.", "start": 428.29, "duration": 2.0}, {"text": "And so then that's the\norigin of void swelling.", "start": 430.29, "duration": 2.1}, {"text": "From single missing\natoms called vacancies,", "start": 432.39, "duration": 2.655}, {"text": "they can cluster\ninto voids which", "start": 435.045, "duration": 2.835}, {"text": "then cause physical dimensional\nchanges of materials", "start": 437.88, "duration": 3.24}, {"text": "on the scale of\ncentimeters to meters.", "start": 441.12, "duration": 2.53}, {"text": "And that's why we say it's\nthis full multi-scale picture", "start": 443.65, "duration": 2.96}, {"text": "of radiation damage.", "start": 446.61, "duration": 1.94}, {"text": "But to understand,\nwhat is damage,", "start": 448.55, "duration": 1.68}, {"text": "you have to know what is\nan undamaged structure", "start": 450.23, "duration": 2.19}, {"text": "to begin with.", "start": 452.42, "duration": 1.088}, {"text": "So it doesn't make sense to say,\nhow does a structure change,", "start": 453.508, "duration": 2.542}, {"text": "if you don't know\nhow it behaves.", "start": 456.05, "duration": 2.53}, {"text": "So I want to give a very quick\nprimer to material science.", "start": 458.58, "duration": 3.77}, {"text": "And apologies to any material\nscientists in the room", "start": 462.35, "duration": 2.31}, {"text": "because this is going\nto seem really basic,", "start": 464.66, "duration": 2.25}, {"text": "but this is a very quick\nintro to this whole field.", "start": 466.91, "duration": 3.15}, {"text": "I want to go over quickly,\nwhat is a crystalline solid?", "start": 470.06, "duration": 3.16}, {"text": "A perfectly undamaged\nmaterial would", "start": 473.22, "duration": 2.3}, {"text": "be a set of atoms lined up\nin a very regular lattice", "start": 475.52, "duration": 3.99}, {"text": "and of regular array, where you\nmove over a certain distance", "start": 479.51, "duration": 3.24}, {"text": "and you find another atom.", "start": 482.75, "duration": 1.53}, {"text": "And this extends forever\nand ever and ever,", "start": 484.28, "duration": 2.49}, {"text": "all the way out to when\nyou reach the free surface.", "start": 486.77, "duration": 2.647}, {"text": "And so this is what we would\ncall an undamaged material.", "start": 489.417, "duration": 2.333}, {"text": "A pristine, perfect,\nsingle crystal.", "start": 491.75, "duration": 3.57}, {"text": "By crystal, I mean\nan arrangement", "start": 495.32, "duration": 2.19}, {"text": "of atoms in a certain direction.", "start": 497.51, "duration": 2.32}, {"text": "So notice here, all of the atoms\nare lined up in, let's say,", "start": 499.83, "duration": 3.26}, {"text": "some cubic xyz way.", "start": 503.09, "duration": 2.64}, {"text": "That's what we would call\none crystal or one grain.", "start": 505.73, "duration": 3.24}, {"text": "You'll hear both of those.", "start": 508.97, "duration": 2.58}, {"text": "And you'll notice also that\nthe arrangement of the atoms", "start": 511.55, "duration": 3.09}, {"text": "tends to determine what the\nphysical objects look like.", "start": 514.64, "duration": 3.96}, {"text": "Or we like to say\nthat form follows", "start": 518.6, "duration": 3.569}, {"text": "structure in material science.", "start": 522.169, "duration": 2.611}, {"text": "So for materials\nlike pyrite, which", "start": 524.78, "duration": 2.76}, {"text": "follows a simple cubic\nstructure, that's the crystals", "start": 527.54, "duration": 2.97}, {"text": "you pull out of the ground.", "start": 530.51, "duration": 1.47}, {"text": "They mimic their\natomic configurations", "start": 531.98, "duration": 1.98}, {"text": "in physical\ncentimeter-sized space.", "start": 533.96, "duration": 3.07}, {"text": "For gold atoms, they adopt a\nslightly different structure.", "start": 537.03, "duration": 3.54}, {"text": "It's still cubic\nbut there is atoms", "start": 540.57, "duration": 2.16}, {"text": "shoved into the cube faces.", "start": 542.73, "duration": 1.98}, {"text": "It's what we call\nFace-Centered Cubic, or FCC.", "start": 544.71, "duration": 2.94}, {"text": "And you start to see\ncube-looking structures", "start": 547.65, "duration": 2.52}, {"text": "all over single\ncrystals of gold.", "start": 550.17, "duration": 3.23}, {"text": "Another one, gypsum.", "start": 553.4, "duration": 1.38}, {"text": "It's got a very different type\nof structure called monoclinic,", "start": 554.78, "duration": 2.88}, {"text": "where none of the sides of\nthis parallelogram are the same", "start": 557.66, "duration": 3.51}, {"text": "and there are some funny angles.", "start": 561.17, "duration": 1.432}, {"text": "But if you look at the\narrangement of the atoms", "start": 562.602, "duration": 1.958}, {"text": "and the actual crystals\nof gypsum that grow,", "start": 564.56, "duration": 3.2}, {"text": "you see a striking similarity,\nwhich I find pretty neat.", "start": 567.76, "duration": 4.012}, {"text": "I also want to mention, what\nis the absence of structure", "start": 571.772, "duration": 3.468}, {"text": "in material science?", "start": 575.24, "duration": 0.87}, {"text": "We call that something\nthat's amorphous.", "start": 576.11, "duration": 2.25}, {"text": "Amorphous means without form.", "start": 578.36, "duration": 2.07}, {"text": "So for example, crystalline\nindium phosphide", "start": 580.43, "duration": 3.627}, {"text": "would have this regular\nstructure like this.", "start": 584.057, "duration": 1.833}, {"text": "You move over a\ncertain distance,", "start": 585.89, "duration": 1.38}, {"text": "you see another green atom,\nand so on and so on and so on.", "start": 587.27, "duration": 3.52}, {"text": "In an amorphous material,\nit can still be a solid,", "start": 590.79, "duration": 2.36}, {"text": "but there is no fixed distance\nbetween any certain types", "start": 593.15, "duration": 3.69}, {"text": "of atoms.", "start": 596.84, "duration": 1.17}, {"text": "And radiation can cause a\nlot of this amorphization", "start": 598.01, "duration": 3.21}, {"text": "by knocking the atoms about\nand having them freeze", "start": 601.22, "duration": 2.1}, {"text": "in random configurations.", "start": 603.32, "duration": 1.98}, {"text": "This is one of the ways\nthat radiation damage can", "start": 605.3, "duration": 2.87}, {"text": "embrittle materials because--", "start": 608.17, "duration": 2.49}, {"text": "well, we'll get into that.", "start": 610.66, "duration": 2.06}, {"text": "So now let's talk\nabout the defects", "start": 612.72, "duration": 2.33}, {"text": "that can be created\nin a perfect crystal.", "start": 615.05, "duration": 2.692}, {"text": "The simplest ones, we\ncall point defects.", "start": 617.742, "duration": 1.708}, {"text": "They're zero-dimensional\nbecause they're just", "start": 619.45, "duration": 2.32}, {"text": "single atoms out of place.", "start": 621.77, "duration": 2.22}, {"text": "You can have what's called\na vacancy, where if you had,", "start": 623.99, "duration": 2.5}, {"text": "let's say, a face-centered\ncubic lattice of atoms,", "start": 626.49, "duration": 3.29}, {"text": "where you have atoms on every\ncube corner and every face,", "start": 629.78, "duration": 3.162}, {"text": "if you just pull\none out somewhere,", "start": 632.942, "duration": 1.458}, {"text": "we refer to that as a vacancy.", "start": 634.4, "duration": 2.54}, {"text": "A missing atom.", "start": 636.94, "duration": 1.272}, {"text": "It had to go somewhere,\nthough, and we'll", "start": 638.212, "duration": 1.708}, {"text": "get to where it is\nin just a second.", "start": 639.92, "duration": 2.36}, {"text": "So it might be kind of hard\nto conceptualize, how do we", "start": 642.28, "duration": 2.4}, {"text": "know that there are missing\natoms in all these little cubes", "start": 644.68, "duration": 3.84}, {"text": "or lattices?", "start": 648.52, "duration": 1.44}, {"text": "We do have direct evidence.", "start": 649.96, "duration": 3.02}, {"text": "They're what's called\nquenching studies,", "start": 652.98, "duration": 1.67}, {"text": "where you can measure the\nresistance or resistivity", "start": 654.65, "duration": 3.36}, {"text": "of a piece of material\nafter heating it", "start": 658.01, "duration": 2.01}, {"text": "to a certain temperature.", "start": 660.02, "duration": 1.57}, {"text": "Because it turns out that the\nhotter you make something,", "start": 661.59, "duration": 2.45}, {"text": "the more of those vacancies\njust naturally occur.", "start": 664.04, "duration": 3.27}, {"text": "You won't actually ever\nfind an absolutely perfect", "start": 667.31, "duration": 3.3}, {"text": "single crystal\nanywhere in nature,", "start": 670.61, "duration": 2.85}, {"text": "unless you go to zero\nKelvin for infinite time,", "start": 673.46, "duration": 2.43}, {"text": "then the atoms arrange\nthemselves thusly.", "start": 675.89, "duration": 2.43}, {"text": "There's always some amount\nof atomic vibration going on.", "start": 678.32, "duration": 3.45}, {"text": "And there's actually some\nthermodynamic energy gain", "start": 681.77, "duration": 4.35}, {"text": "to having a few defects\nin your structure.", "start": 686.12, "duration": 2.79}, {"text": "And that number of\ndefects increases", "start": 688.91, "duration": 3.21}, {"text": "with increasing temperature.", "start": 692.12, "duration": 1.61}, {"text": "Once you get to the melting\npoint of a material,", "start": 693.73, "duration": 2.0}, {"text": "or like right before something\nmelts, you can have up to 1", "start": 695.73, "duration": 3.02}, {"text": "in 10,000 atoms just missing.", "start": 698.75, "duration": 2.25}, {"text": "Moved somewhere else.", "start": 701.0, "duration": 1.59}, {"text": "We call that the\nthermal equilibrium", "start": 702.59, "duration": 1.77}, {"text": "vacancy concentration.", "start": 704.36, "duration": 1.58}, {"text": "And we can measure that using\nthese resistivity measurements,", "start": 705.94, "duration": 3.48}, {"text": "where you heat materials up to\nhigher and higher temperatures,", "start": 709.42, "duration": 3.22}, {"text": "cool them down suddenly\nin, like, liquid nitrogen", "start": 712.64, "duration": 2.28}, {"text": "or liquid helium, and measure\nthe change in resistivity.", "start": 714.92, "duration": 3.9}, {"text": "The more defects there are,\nthe harder it is for electrons", "start": 718.82, "duration": 2.68}, {"text": "to flow through.", "start": 721.5, "duration": 0.775}, {"text": "And the only thing that could\nreally be responsible there", "start": 722.275, "duration": 2.375}, {"text": "in a single element\nwould be vacancies.", "start": 724.65, "duration": 4.38}, {"text": "So we do know that\nthese really exist.", "start": 729.03, "duration": 3.14}, {"text": "They can also cluster up.", "start": 732.17, "duration": 1.86}, {"text": "It turns out that\nevery time you have", "start": 734.03, "duration": 1.68}, {"text": "a vacancy in a material,\nthe other atoms", "start": 735.71, "duration": 2.1}, {"text": "move in a little bit towards\nit, relaxing the pressure they", "start": 737.81, "duration": 3.36}, {"text": "feel from the atoms nearby.", "start": 741.17, "duration": 2.1}, {"text": "And one way for a whole\nbunch of vacancies", "start": 743.27, "duration": 2.07}, {"text": "to lower the stress of the\nwhole atomic configuration", "start": 745.34, "duration": 3.36}, {"text": "is to cluster together.", "start": 748.7, "duration": 2.02}, {"text": "So if you have a whole\nbunch of vacancies,", "start": 750.72, "duration": 2.15}, {"text": "they may not allow as\nmuch stress accommodation", "start": 752.87, "duration": 3.51}, {"text": "as if they were separate,\nwhen they're together.", "start": 756.38, "duration": 3.99}, {"text": "Now you might ask, what\nhappened to the original atoms?", "start": 760.37, "duration": 3.887}, {"text": "You can't just take atoms\naway and then go nowhere", "start": 764.257, "duration": 2.083}, {"text": "because you can't just\ndestroy matter, right?", "start": 766.34, "duration": 2.118}, {"text": "Unless you turn it\ninto energy, which", "start": 768.458, "duration": 1.542}, {"text": "is what we do in\nnuclear engineering.", "start": 770.0, "duration": 2.07}, {"text": "So in the material\nscience world,", "start": 772.07, "duration": 2.94}, {"text": "they end up as what's\ncalled interstitials,", "start": 775.01, "duration": 2.4}, {"text": "where you kind of have a\nvacancy created from somewhere", "start": 777.41, "duration": 2.94}, {"text": "that knocks that\natom out, and it", "start": 780.35, "duration": 1.86}, {"text": "gets stuck in the next biggest\nspace between some other atoms.", "start": 782.21, "duration": 4.83}, {"text": "And we refer to those\nas interstitials.", "start": 787.04, "duration": 1.71}, {"text": "And those can cluster up, too,\nto reduce their total stress", "start": 788.75, "duration": 4.86}, {"text": "in the lattice.", "start": 793.61, "duration": 1.64}, {"text": "They can cluster up into\nwhat's called split dumbbell", "start": 795.25, "duration": 2.49}, {"text": "interstitials.", "start": 797.74, "duration": 1.2}, {"text": "Instead of having one\nextra atom shoved in here,", "start": 798.94, "duration": 2.88}, {"text": "you might rearrange\na couple so there's", "start": 801.82, "duration": 1.65}, {"text": "two atoms in the center\nof a cube instead of one.", "start": 803.47, "duration": 2.79}, {"text": "And that tends to be a lower\nenergy or a more stable", "start": 806.26, "duration": 3.06}, {"text": "configuration.", "start": 809.32, "duration": 3.002}, {"text": "So let's look a little bit at\nthe energetics of these point", "start": 812.322, "duration": 2.458}, {"text": "defects because\nunderstanding how they move", "start": 814.78, "duration": 2.1}, {"text": "and why will tell us a lot about\nhow radiation damage happens.", "start": 816.88, "duration": 3.923}, {"text": "So it turns out\nthat interstitials", "start": 820.803, "duration": 1.417}, {"text": "are very hard to make.", "start": 822.22, "duration": 1.77}, {"text": "It's really hard\nto shove an atom", "start": 823.99, "duration": 1.68}, {"text": "where it doesn't want to be.", "start": 825.67, "duration": 1.63}, {"text": "But once you get it there,\nit moves very easily.", "start": 827.3, "duration": 5.05}, {"text": "Let's draw a quick,\nsimple cubic lattice", "start": 832.35, "duration": 3.13}, {"text": "to do a little\nthought experiment", "start": 835.48, "duration": 1.98}, {"text": "and explore why that might be.", "start": 837.46, "duration": 1.47}, {"text": "Let's say I want to shove\nan interstitial atom in here", "start": 841.63, "duration": 3.96}, {"text": "between these other atoms.", "start": 845.59, "duration": 1.74}, {"text": "Well their electron\nclouds are going to repel,", "start": 847.33, "duration": 2.79}, {"text": "and it's going to push\nall the nearby atoms away", "start": 850.12, "duration": 2.22}, {"text": "by just a little bit.", "start": 852.34, "duration": 1.35}, {"text": "And these ones might\npush the other atoms away", "start": 853.69, "duration": 2.91}, {"text": "by just a little bit,\nstretching out the lattice,", "start": 856.6, "duration": 5.06}, {"text": "or adding some\ncompressive stress", "start": 861.66, "duration": 1.62}, {"text": "wherever that interstitial is.", "start": 863.28, "duration": 2.55}, {"text": "But then how would it move?", "start": 865.83, "duration": 2.425}, {"text": "What's the biggest\nbarrier it has", "start": 868.255, "duration": 1.375}, {"text": "to overcome to get to the\nnext adjacent location?", "start": 869.63, "duration": 3.03}, {"text": "Well, which direction\nwould it go?", "start": 878.753, "duration": 1.417}, {"text": "Would it go this way?", "start": 880.17, "duration": 2.288}, {"text": "Probably not.", "start": 882.458, "duration": 0.542}, {"text": "There's an atom in the way.", "start": 883.0, "duration": 1.71}, {"text": "So it's going to find the\npath of least resistance", "start": 884.71, "duration": 3.44}, {"text": "to try to get over here,\nbecause like we've talked about", "start": 888.15, "duration": 3.54}, {"text": "before, all atoms\nare always in motion.", "start": 891.69, "duration": 2.43}, {"text": "Vibrating.", "start": 894.12, "duration": 1.038}, {"text": "Some of them will\nbe energetic enough", "start": 895.158, "duration": 1.542}, {"text": "to squeeze through\nthese two atoms", "start": 896.7, "duration": 2.44}, {"text": "and get over to the next site.", "start": 899.14, "duration": 1.25}, {"text": "And that turns out to be\na pretty easy process.", "start": 900.39, "duration": 3.0}, {"text": "We can look at the energy\nrequired for an interstitial", "start": 903.39, "duration": 3.45}, {"text": "to move.", "start": 906.84, "duration": 0.96}, {"text": "We notice it's really small\nfractions of an electron volt,", "start": 907.8, "duration": 3.72}, {"text": "whereas creating them takes\ntwo or three electron volts.", "start": 911.52, "duration": 2.79}, {"text": "In atomic land, that's a\nvery high energy penalty.", "start": 914.31, "duration": 4.2}, {"text": "Now let's look at vacancies.", "start": 918.51, "duration": 1.22}, {"text": "They're quite the opposite.", "start": 919.73, "duration": 1.91}, {"text": "They're rather easy\nto make but they're", "start": 921.64, "duration": 2.21}, {"text": "very hard to move,\ncompared to interstitials.", "start": 923.85, "duration": 3.51}, {"text": "Notice that the\nenergy of movement", "start": 927.36, "duration": 1.53}, {"text": "is about the same as the energy\nof formation for vacancies.", "start": 928.89, "duration": 3.18}, {"text": "To take an atom out\nor to pluck it out,", "start": 932.07, "duration": 1.86}, {"text": "you have to break every\nbond between nearby atoms.", "start": 933.93, "duration": 3.93}, {"text": "So you actually have to put\nenergy in to break those bonds", "start": 937.86, "duration": 5.45}, {"text": "and then remove the\natoms somewhere else.", "start": 943.31, "duration": 3.24}, {"text": "Now these things are\nusually made in pairs,", "start": 946.55, "duration": 2.77}, {"text": "so if you think about\nhow much energy would it", "start": 949.32, "duration": 2.42}, {"text": "take to cause a single radiation\ndamage event where you have", "start": 951.74, "duration": 3.57}, {"text": "one vacancy, which let's say\nwould have been right here,", "start": 955.31, "duration": 3.56}, {"text": "and one interstitial, it takes\nthe sum of these two energies--", "start": 958.87, "duration": 4.24}, {"text": "usually about four\nelectron volts.", "start": 963.11, "duration": 2.37}, {"text": "That's not something\nthat tends to happen", "start": 965.48, "duration": 2.4}, {"text": "chemically or from stress\nor from something like that.", "start": 967.88, "duration": 3.48}, {"text": "But radiation coming\nin with hundreds of keV", "start": 971.36, "duration": 2.97}, {"text": "or even MeV neutrons,\nanything's on the table", "start": 974.33, "duration": 3.42}, {"text": "because it's high enough energy.", "start": 977.75, "duration": 3.12}, {"text": "Yeah?", "start": 980.87, "duration": 0.62}, {"text": "AUDIENCE: What would take\nabout three or four eV?", "start": 981.49, "duration": 2.17}, {"text": "PROFESSOR: So it would\ntake about three or four", "start": 983.66, "duration": 1.958}, {"text": "eV to make a pair of a\nvacancy and an interstitial.", "start": 985.618, "duration": 3.102}, {"text": "If you just add these two up.", "start": 988.72, "duration": 1.5}, {"text": "It comes usually to about three\nor four eV, or electron volts.", "start": 990.22, "duration": 3.89}, {"text": "And that's a very\ndifficult thing", "start": 994.11, "duration": 1.48}, {"text": "to do in sort of chemical world,\nwhere reactions might proceed", "start": 995.59, "duration": 4.41}, {"text": "with fractions of\nan electron volt.", "start": 1000.0, "duration": 2.07}, {"text": "But when you have MeV\nneutrons coming in,", "start": 1002.07, "duration": 2.94}, {"text": "they do whatever they want.", "start": 1005.01, "duration": 2.1}, {"text": "They'll do whatever they will.", "start": 1007.11, "duration": 1.845}, {"text": "So someone actually\nasked me yesterday,", "start": 1008.955, "duration": 1.625}, {"text": "what sort of materials can\nyou put in the way of neutrons", "start": 1010.58, "duration": 3.6}, {"text": "to stop them from doing damage?", "start": 1014.18, "duration": 2.19}, {"text": "And the answer is,\npretty much nothing.", "start": 1016.37, "duration": 3.1}, {"text": "Fast neutrons tend to travel\nabout 10 centimeters, even", "start": 1019.47, "duration": 3.74}, {"text": "in things like steel\nor water, and they're", "start": 1023.21, "duration": 2.7}, {"text": "going to hit what\nthey're going to hit.", "start": 1025.91, "duration": 1.72}, {"text": "There's not much you can do\nbut put more things in the way.", "start": 1027.63, "duration": 3.35}, {"text": "And we can only get to a certain\ndensity with regular matter.", "start": 1030.98, "duration": 2.639}, {"text": "And I think osmium has\nupwards of, like, 22 grams", "start": 1033.619, "duration": 3.571}, {"text": "per cubic centimeter density.", "start": 1037.19, "duration": 1.77}, {"text": "That's not enough\nto stop neutrons,", "start": 1038.96, "duration": 2.1}, {"text": "even over a\nconsiderable distance.", "start": 1041.06, "duration": 2.13}, {"text": "Unless you had, like,\nliquid neutron star,", "start": 1043.19, "duration": 2.28}, {"text": "that you could pack nuclei in\nat a way higher number density,", "start": 1045.47, "duration": 3.337}, {"text": "not much you can do.", "start": 1048.807, "duration": 0.833}, {"text": "So moving up in the\ndimensions, there's", "start": 1052.3, "duration": 2.55}, {"text": "another type of defect\ncalled a dislocation, where", "start": 1054.85, "duration": 3.18}, {"text": "it's actually energetically\nfavorable to slide", "start": 1058.03, "duration": 2.91}, {"text": "an extra half-plane of atoms\nin between two sets in here", "start": 1060.94, "duration": 4.98}, {"text": "in the crystal lattice, creating\na sort of bulged-out structure", "start": 1065.92, "duration": 3.3}, {"text": "like you see right here.", "start": 1069.22, "duration": 1.79}, {"text": "And dislocations are one of\nthe most important defects", "start": 1071.01, "duration": 2.92}, {"text": "in material science\nand radiation damage.", "start": 1073.93, "duration": 2.28}, {"text": "They're what I like to call\nthe agents of plasticity.", "start": 1076.21, "duration": 2.91}, {"text": "If you deform a material\nenough that it doesn't just", "start": 1079.12, "duration": 3.03}, {"text": "spring back, then most likely,\nyou were creating and moving", "start": 1082.15, "duration": 5.46}, {"text": "dislocations in the material.", "start": 1087.61, "duration": 1.82}, {"text": "If you think about a\ncouple of different ways", "start": 1089.43, "duration": 2.29}, {"text": "to cause deformation--", "start": 1091.72, "duration": 2.13}, {"text": "let's bring our\nperfect lattice back", "start": 1093.85, "duration": 1.56}, {"text": "without all these\nextra notations.", "start": 1095.41, "duration": 4.87}, {"text": "If you want to slide or shear\ntwo planes of atoms across,", "start": 1100.28, "duration": 5.07}, {"text": "and they're all\nbonded to each other,", "start": 1105.35, "duration": 7.853}, {"text": "what do you\nphysically have to do?", "start": 1113.203, "duration": 1.417}, {"text": "How can you get these atoms\nto slide across each other?", "start": 1120.028, "duration": 2.292}, {"text": "What sort of energy do\nyou have to put into it?", "start": 1122.32, "duration": 2.55}, {"text": "Yeah?", "start": 1127.94, "duration": 0.577}, {"text": "AUDIENCE: [INAUDIBLE] energy.", "start": 1128.517, "duration": 1.223}, {"text": "PROFESSOR: Yep.", "start": 1129.74, "duration": 0.93}, {"text": "Because all these atoms\nare bonded to each other,", "start": 1130.67, "duration": 2.22}, {"text": "if you want them\nto move, you have", "start": 1132.89, "duration": 1.89}, {"text": "to break every\nbond on that plane.", "start": 1134.78, "duration": 3.3}, {"text": "That's a lot of\natomic bonds to break", "start": 1138.08, "duration": 2.52}, {"text": "and it's extremely unlikely\nthat that would happen.", "start": 1140.6, "duration": 2.58}, {"text": "In fact, if you broke\nan entire plane of bonds", "start": 1143.18, "duration": 3.42}, {"text": "in some material like this, what\nwould you physically do to it?", "start": 1146.6, "duration": 4.564}, {"text": "You'd snap it in half.", "start": 1151.164, "duration": 2.696}, {"text": "That would be fracture.", "start": 1153.86, "duration": 1.73}, {"text": "So if you broke every\nbond down this plane,", "start": 1155.59, "duration": 3.13}, {"text": "you would then have two\npieces of this fuel rod.", "start": 1158.72, "duration": 2.76}, {"text": "That's usually a pretty\nhigh-energy thing to try to do.", "start": 1161.48, "duration": 2.79}, {"text": "So instead, if you\nshove an extra half", "start": 1164.27, "duration": 5.71}, {"text": "plane of atoms in\nthere, and the bonds", "start": 1169.98, "duration": 4.87}, {"text": "are kind of funny like so,\nright at that extra half-plane", "start": 1174.85, "duration": 5.7}, {"text": "location, then what you can\nactually do is break one.", "start": 1180.55, "duration": 6.38}, {"text": "Let's say you break this\none, form the next one,", "start": 1186.93, "duration": 2.1}, {"text": "then break this one\nand form the next one.", "start": 1189.03, "duration": 2.85}, {"text": "And for a few\natoms to move over,", "start": 1191.88, "duration": 2.31}, {"text": "you only have to break a\nline of bonds, not a plane.", "start": 1194.19, "duration": 3.78}, {"text": "So it's much less\nenergy-intensive to get", "start": 1197.97, "duration": 3.48}, {"text": "a dislocation to move than to\njust break something in half.", "start": 1201.45, "duration": 4.35}, {"text": "Now you might ask, well, then\nwhy do things actually break?", "start": 1205.8, "duration": 3.01}, {"text": "Whether or not things\ndeform or break", "start": 1208.81, "duration": 1.86}, {"text": "is a balance between this\nprocess, which we call slip,", "start": 1210.67, "duration": 5.51}, {"text": "and breaking an entire plane of\natoms, which we call fracture.", "start": 1216.18, "duration": 5.12}, {"text": "So this one's called slip.", "start": 1221.3, "duration": 1.17}, {"text": "The other mode is fracture.", "start": 1225.75, "duration": 2.89}, {"text": "We would rather materials to\nform in systems like reactors", "start": 1228.64, "duration": 3.96}, {"text": "by slip, just\nmoving a little bit,", "start": 1232.6, "duration": 1.68}, {"text": "then just breaking altogether.", "start": 1234.28, "duration": 1.92}, {"text": "Unfortunately, when enough\nradiation hits materials,", "start": 1236.2, "duration": 3.0}, {"text": "you can fracture things\nin a brutal manner,", "start": 1239.2, "duration": 2.19}, {"text": "and we'll see what happens then.", "start": 1241.39, "duration": 2.53}, {"text": "There's a couple\nkinds of dislocations.", "start": 1243.92, "duration": 3.03}, {"text": "One of them is called\na screw dislocation.", "start": 1246.95, "duration": 2.53}, {"text": "So imagine you had a whole\nbunch of sheets of atoms,", "start": 1249.48, "duration": 2.6}, {"text": "and you made a cut\nhalfway through that sheet", "start": 1252.08, "duration": 2.55}, {"text": "and then moved every\nplane up by one position.", "start": 1254.63, "duration": 3.45}, {"text": "You then got what's called\na screw dislocation--", "start": 1258.08, "duration": 2.07}, {"text": "kind of a spiral parking\ngarage of atoms surrounding", "start": 1260.15, "duration": 3.93}, {"text": "that core right there.", "start": 1264.08, "duration": 1.913}, {"text": "You can also have what's called\nan edge dislocation, which", "start": 1265.993, "duration": 2.417}, {"text": "is like the one I've\ngot here on the board", "start": 1268.41, "duration": 2.7}, {"text": "right here, where you just have\nan extra half plane of atoms", "start": 1271.11, "duration": 3.06}, {"text": "shoved in right there.", "start": 1274.17, "duration": 2.25}, {"text": "So there's two types, and they\nmove in two different ways.", "start": 1276.42, "duration": 3.7}, {"text": "The edge dislocation behaves\nlike you may physically expect.", "start": 1280.12, "duration": 3.98}, {"text": "If you kind of push like\nthis on two planes of atoms,", "start": 1284.1, "duration": 4.17}, {"text": "it moves in the\ndirection you push it.", "start": 1288.27, "duration": 2.44}, {"text": "Screw dislocations\nare kind of screwy.", "start": 1290.71, "duration": 2.46}, {"text": "If you push like this,\nit moves perpendicular.", "start": 1293.17, "duration": 5.055}, {"text": "Not going to get into\nwhy, but just remember,", "start": 1298.225, "duration": 1.875}, {"text": "screw dislocations are\nfairly screwy in the way", "start": 1300.1, "duration": 2.1}, {"text": "that they behave.", "start": 1302.2, "duration": 1.86}, {"text": "Not quite intuitive.", "start": 1304.06, "duration": 1.68}, {"text": "But that's OK.", "start": 1305.74, "duration": 0.67}, {"text": "We don't have to\nworry about those.", "start": 1306.41, "duration": 3.13}, {"text": "And the way that\nthey actually move,", "start": 1309.54, "duration": 1.86}, {"text": "like we showed right here, is\nby what's called glide, or slip,", "start": 1311.4, "duration": 3.15}, {"text": "where dislocations can slide\njust by one plane of atoms", "start": 1314.55, "duration": 5.13}, {"text": "or one atomic position\nin a mechanism that", "start": 1319.68, "duration": 3.24}, {"text": "looks something like this.", "start": 1322.92, "duration": 1.96}, {"text": "Where, as that\ndislocation moves,", "start": 1324.88, "duration": 2.09}, {"text": "you only have to\nbreak a line of bonds", "start": 1326.97, "duration": 1.92}, {"text": "and then reform a\nline of bonds, which", "start": 1328.89, "duration": 1.92}, {"text": "is a much easier\nprocess than breaking", "start": 1330.81, "duration": 1.65}, {"text": "an entire plane at once.", "start": 1332.46, "duration": 1.998}, {"text": "It's like you have to\nbreak the square root", "start": 1334.458, "duration": 1.792}, {"text": "of the same number of bonds.", "start": 1336.25, "duration": 1.167}, {"text": "I'm going to skip ahead\nthrough some of that.", "start": 1340.545, "duration": 1.875}, {"text": "There's one other mechanism\nof dislocation movement", "start": 1342.42, "duration": 2.4}, {"text": "that's important to\nus in radiation damage", "start": 1344.82, "duration": 2.52}, {"text": "and that's called climb.", "start": 1347.34, "duration": 1.507}, {"text": "This is when you\nstart to think about,", "start": 1348.847, "duration": 1.583}, {"text": "what happens if you have\na dislocation, which we'll", "start": 1350.43, "duration": 3.48}, {"text": "give this symbol right here,\nand you also have a vacancy,", "start": 1353.91, "duration": 6.39}, {"text": "let's say created\nby radiation damage.", "start": 1360.3, "duration": 2.61}, {"text": "If that vacancy can\nmove, it's going", "start": 1362.91, "duration": 1.68}, {"text": "to find the most stressed-out\npart of this lattice.", "start": 1364.59, "duration": 3.06}, {"text": "Most likely, the\nvacancy will move here.", "start": 1367.65, "duration": 4.06}, {"text": "In other words, the atom\nwill move over there,", "start": 1371.71, "duration": 4.84}, {"text": "leaving this vacancy over there.", "start": 1376.55, "duration": 2.922}, {"text": "It's kind of funny to\nthink, like, what does it", "start": 1379.472, "duration": 1.958}, {"text": "mean that a vacancy moves?", "start": 1381.43, "duration": 1.738}, {"text": "Has anyone ever done\nanything with semiconductors", "start": 1383.168, "duration": 2.042}, {"text": "and talked about electron\nand hole movement?", "start": 1385.21, "duration": 3.07}, {"text": "OK, yeah.", "start": 1388.28, "duration": 0.51}, {"text": "So what does it really mean\nfor a hole to move, right?", "start": 1388.79, "duration": 3.27}, {"text": "A hole's not a thing.", "start": 1392.06, "duration": 1.18}, {"text": "A vacancy's also not a thing.", "start": 1393.24, "duration": 1.35}, {"text": "It's an absence of an atom.", "start": 1394.59, "duration": 2.07}, {"text": "But here, we can say\nthat the vacancy moves", "start": 1396.66, "duration": 2.03}, {"text": "in this direction when the\ncorresponding atom moves", "start": 1398.69, "duration": 2.97}, {"text": "in the exact opposite direction.", "start": 1401.66, "duration": 2.1}, {"text": "And then what\nyou've actually done", "start": 1403.76, "duration": 1.89}, {"text": "is moved your dislocation up.", "start": 1405.65, "duration": 3.59}, {"text": "Instead of moving in\nthe slip direction,", "start": 1409.24, "duration": 2.55}, {"text": "you've now moved it in a\nperpendicular direction.", "start": 1411.79, "duration": 4.25}, {"text": "This is usually not\npossible without things", "start": 1416.04, "duration": 2.94}, {"text": "like radiation damage or\nvery high temperature.", "start": 1418.98, "duration": 2.538}, {"text": "And then, to make\nthings even crazier,", "start": 1423.907, "duration": 1.583}, {"text": "you can also have\nwhat's called loops", "start": 1425.49, "duration": 1.57}, {"text": "of dislocation, some videos\nof which I'll actually", "start": 1427.06, "duration": 2.083}, {"text": "get to show you.", "start": 1429.143, "duration": 1.217}, {"text": "You can have a dislocation that\nhas part edge character, part", "start": 1430.36, "duration": 3.33}, {"text": "screw character.", "start": 1433.69, "duration": 1.042}, {"text": "If you look at how the\natoms are arranged here,", "start": 1434.732, "duration": 1.958}, {"text": "you're looking from\nsort of the top-down.", "start": 1436.69, "duration": 2.347}, {"text": "You can see that\nthere's an extra half", "start": 1439.037, "duration": 1.583}, {"text": "plane of these white atoms\nshoved in in the black ones,", "start": 1440.62, "duration": 3.42}, {"text": "and this right here would be\na completely edge dislocation.", "start": 1444.04, "duration": 4.17}, {"text": "You can have a\ngradual transition,", "start": 1448.21, "duration": 1.74}, {"text": "where about 90 degrees\nlater, it looks like a spiral", "start": 1449.95, "duration": 3.69}, {"text": "and that's a screw dislocation.", "start": 1453.64, "duration": 2.2}, {"text": "And the net effect\nof that is when", "start": 1455.84, "duration": 2.0}, {"text": "you push in this direction\non an edge dislocation,", "start": 1457.84, "duration": 2.76}, {"text": "it moves that way.", "start": 1460.6, "duration": 1.77}, {"text": "When you push this direction\non a screw dislocation,", "start": 1462.37, "duration": 2.38}, {"text": "it moves that way.", "start": 1464.75, "duration": 2.77}, {"text": "So when you stress out\na dislocation loop,", "start": 1467.52, "duration": 2.26}, {"text": "it just grows.", "start": 1469.78, "duration": 1.82}, {"text": "You're not actually creating\nor destroying matter,", "start": 1471.6, "duration": 2.64}, {"text": "but what you're doing is causing\nthis small loop of extra half", "start": 1474.24, "duration": 3.93}, {"text": "plane of atoms to grow further\nand further until it actually", "start": 1478.17, "duration": 2.67}, {"text": "reaches some obstacle or\nthe outside of a crystal.", "start": 1480.84, "duration": 5.16}, {"text": "And these dislocations\ncan actually", "start": 1486.0, "duration": 2.4}, {"text": "feel the force from each other.", "start": 1488.4, "duration": 2.4}, {"text": "If I draw a clean one because I\nthink it'll be easier to see--", "start": 1490.8, "duration": 3.42}, {"text": "if I draw a small\nlattice of atoms", "start": 1496.77, "duration": 1.81}, {"text": "here and then a dislocation\ncore right there.", "start": 1498.58, "duration": 8.96}, {"text": "So that's our dislocation core.", "start": 1507.54, "duration": 2.09}, {"text": "This region of space right\nhere is compressively stressed.", "start": 1509.63, "duration": 5.72}, {"text": "There's more atoms in that\nspace than there want to be", "start": 1515.35, "duration": 2.92}, {"text": "and so it's kind of\ncrammed in there.", "start": 1518.27, "duration": 1.79}, {"text": "While this region\nright here is in what's", "start": 1520.06, "duration": 4.19}, {"text": "called tensile stress.", "start": 1524.25, "duration": 1.83}, {"text": "There's almost some space,\nlike right here, where", "start": 1526.08, "duration": 3.15}, {"text": "there's too few atoms and they\nkind of want there to be more.", "start": 1529.23, "duration": 3.99}, {"text": "And these dislocations can\nfeel neighboring stress fields.", "start": 1533.22, "duration": 3.96}, {"text": "Let's say there was\nanother one right over here", "start": 1537.18, "duration": 2.64}, {"text": "that had its own\ncompressive stress field.", "start": 1539.82, "duration": 3.68}, {"text": "They'll actually\nrepel each other", "start": 1543.5, "duration": 2.8}, {"text": "because you don't want to add\neven more compressive stress", "start": 1546.3, "duration": 2.82}, {"text": "to anywhere in this\ngroup of atoms.", "start": 1549.12, "duration": 2.04}, {"text": "So they'll actually repel\neach other to the point", "start": 1551.16, "duration": 2.287}, {"text": "where, if you get\ntwo dislocations too", "start": 1553.447, "duration": 1.583}, {"text": "close to each other, they'll\nwhat's called pile-up,", "start": 1555.03, "duration": 4.6}, {"text": "or they'll refuse to move a bit.", "start": 1559.63, "duration": 2.483}, {"text": "So I want to show\nyou some videos.", "start": 1562.113, "duration": 1.417}, {"text": "We can actually see\nthese dislocations.", "start": 1563.53, "duration": 2.01}, {"text": "In this one, you see that faint\nline right there originating", "start": 1565.54, "duration": 3.66}, {"text": "from this area?", "start": 1569.2, "duration": 1.74}, {"text": "That's actually a\ndislocation loop under stress", "start": 1570.94, "duration": 3.33}, {"text": "and that's actually growing.", "start": 1574.27, "duration": 1.33}, {"text": "So what you're seeing\nhere is an image", "start": 1575.6, "duration": 2.33}, {"text": "of electrons passing\nthrough material", "start": 1577.93, "duration": 2.52}, {"text": "and looking at regions\nof different contrast.", "start": 1580.45, "duration": 2.49}, {"text": "So wherever there is more\natoms or fewer atoms,", "start": 1582.94, "duration": 2.07}, {"text": "it looks darker or lighter,\nand that can tell you", "start": 1585.01, "duration": 3.18}, {"text": "what sort of defects there are.", "start": 1588.19, "duration": 1.32}, {"text": "You guys all see that\nfaint line right there?", "start": 1589.51, "duration": 2.642}, {"text": "Notice how the\nloop's just growing.", "start": 1592.152, "duration": 1.458}, {"text": "It's not like you're\nmoving a line,", "start": 1593.61, "duration": 1.458}, {"text": "but you're literally\ngrowing a line out", "start": 1595.068, "duration": 1.662}, {"text": "of what looks like nothing.", "start": 1596.73, "duration": 1.125}, {"text": "There's another one we\ncall a Frank-Read source.", "start": 1601.32, "duration": 2.79}, {"text": "It's a source of\ndislocation loop.", "start": 1604.11, "duration": 2.4}, {"text": "So what you're seeing\nhere, each of these lines", "start": 1606.51, "duration": 2.52}, {"text": "is a single dislocation.", "start": 1609.03, "duration": 1.26}, {"text": "And then right there, you\nsee that loop suddenly form?", "start": 1610.29, "duration": 4.23}, {"text": "Let's show you that one again.", "start": 1614.52, "duration": 1.59}, {"text": "I'll point on where to look.", "start": 1616.11, "duration": 2.877}, {"text": "By stressing out\nmaterials, you can actually", "start": 1618.987, "duration": 1.833}, {"text": "create additional dislocation\nloops, right around here.", "start": 1620.82, "duration": 4.341}, {"text": "And there it is.", "start": 1625.161, "duration": 1.839}, {"text": "You guys see that one?", "start": 1627.0, "duration": 1.41}, {"text": "Yeah.", "start": 1628.41, "duration": 0.513}, {"text": "Out of what looks like\nnothing but is actually", "start": 1628.923, "duration": 1.917}, {"text": "just a couple of\natomic defects, you", "start": 1630.84, "duration": 2.13}, {"text": "can create a dislocation\nloop and allow more plastic", "start": 1632.97, "duration": 2.94}, {"text": "deformation to take place,\nwhich I think is awesome.", "start": 1635.91, "duration": 5.445}, {"text": "Look at this one.", "start": 1641.355, "duration": 0.795}, {"text": "Another dislocation\nsource in germanium.", "start": 1642.15, "duration": 2.01}, {"text": "It's a little\neasier to see, also", "start": 1644.16, "duration": 1.98}, {"text": "because it's making this sort\nof spiral set of dislocations", "start": 1646.14, "duration": 3.66}, {"text": "a little slower.", "start": 1649.8, "duration": 1.53}, {"text": "So you can track its\nmotion a little easier.", "start": 1651.33, "duration": 3.17}, {"text": "Notice how they all kind of line\nup on certain atomic planes.", "start": 1654.5, "duration": 3.83}, {"text": "Yeah?", "start": 1658.33, "duration": 0.5}, {"text": "AUDIENCE: Does the topology\nof these things ever change,", "start": 1658.83, "duration": 2.333}, {"text": "or is it always just\na slow [INAUDIBLE]", "start": 1661.163, "duration": 2.987}, {"text": "PROFESSOR: The\ntopology will change.", "start": 1664.15, "duration": 1.727}, {"text": "Let's say, if it\nhits another obstacle", "start": 1665.877, "duration": 1.583}, {"text": "or another\ndislocation, yeah, they", "start": 1667.46, "duration": 1.417}, {"text": "can slam into each other\nand change topology.", "start": 1668.877, "duration": 2.633}, {"text": "AUDIENCE: Breaking\ntoo [INAUDIBLE]", "start": 1671.51, "duration": 2.88}, {"text": "PROFESSOR: All sorts\nof things, yeah.", "start": 1674.39, "duration": 2.057}, {"text": "That's a subject for a\nwhole other class, I'd say.", "start": 1676.447, "duration": 2.083}, {"text": "I want to skip\nahead to the pile-up", "start": 1681.23, "duration": 2.34}, {"text": "because I think this kind\nof gets the point across.", "start": 1683.57, "duration": 3.57}, {"text": "But actually, we can\nsee direct evidence", "start": 1687.14, "duration": 2.19}, {"text": "that dislocations feel\neach other's stress fields.", "start": 1689.33, "duration": 2.64}, {"text": "When you get enough of them\nlined up, they won't overlap.", "start": 1691.97, "duration": 3.03}, {"text": "They actually push each other\nin a kind of dislocation traffic", "start": 1695.0, "duration": 3.18}, {"text": "jam.", "start": 1698.18, "duration": 2.1}, {"text": "Because what's happening\non the atomic level is,", "start": 1700.28, "duration": 2.46}, {"text": "they feel each\nother's stress fields.", "start": 1702.74, "duration": 1.56}, {"text": "There might be a source of\ndislocations further away,", "start": 1704.3, "duration": 2.645}, {"text": "but when they get too\nclose to each other,", "start": 1706.945, "duration": 2.005}, {"text": "it literally is a\ndislocation traffic jam.", "start": 1708.95, "duration": 2.55}, {"text": "I mean, if you try and hit\nthe car in front of you,", "start": 1711.5, "duration": 2.16}, {"text": "the repulsion of the electrons\nbetween your and their bumper", "start": 1713.66, "duration": 3.24}, {"text": "will prevent the cars from\ngetting a certain distance", "start": 1716.9, "duration": 3.0}, {"text": "closer to each other.", "start": 1719.9, "duration": 1.47}, {"text": "Same kind of thing here.", "start": 1721.37, "duration": 1.02}, {"text": "Moving onto grain boundaries,\na two-dimensional defect.", "start": 1725.89, "duration": 3.21}, {"text": "Any time you have\na perfect crystal", "start": 1729.1, "duration": 2.85}, {"text": "of atoms that meets\nanother perfect crystal", "start": 1731.95, "duration": 3.03}, {"text": "at a different orientation,\nor where the atoms", "start": 1734.98, "duration": 2.13}, {"text": "are arranged in a\ndifferent direction,", "start": 1737.11, "duration": 1.77}, {"text": "you end up with a\nboundary between them", "start": 1738.88, "duration": 2.04}, {"text": "that we refer to as\na grain boundary.", "start": 1740.92, "duration": 3.07}, {"text": "So you can actually see, this\nis a direct physical image", "start": 1743.99, "duration": 2.96}, {"text": "of atoms of two different\ncrystals meaning at the grain", "start": 1746.95, "duration": 3.33}, {"text": "boundary.", "start": 1750.28, "duration": 0.84}, {"text": "Again, taken in the transmission\nelectron microscope.", "start": 1751.12, "duration": 2.31}, {"text": "So for those who\ndidn't know, yes,", "start": 1753.43, "duration": 1.417}, {"text": "we can see individual atoms\nand the defects between them.", "start": 1754.847, "duration": 4.238}, {"text": "I definitely didn't know\nthat in high school.", "start": 1759.085, "duration": 1.875}, {"text": "They didn't even\nmention that whatsoever.", "start": 1760.96, "duration": 1.708}, {"text": "Did you guys ever\nsee images like this?", "start": 1762.668, "duration": 2.692}, {"text": "Anyone?", "start": 1765.36, "duration": 0.63}, {"text": "Yes?", "start": 1765.99, "duration": 0.5}, {"text": "Raise your hand.", "start": 1766.49, "duration": 1.27}, {"text": "Just one, OK.", "start": 1767.76, "duration": 1.38}, {"text": "So yeah.", "start": 1769.14, "duration": 0.69}, {"text": "It's important for\nyou guys to know", "start": 1769.83, "duration": 1.23}, {"text": "that we can have direct evidence\nfor all this blackboard stuff", "start": 1771.06, "duration": 2.583}, {"text": "because you can see atoms\nin the transmission electron", "start": 1773.643, "duration": 2.817}, {"text": "microscope and see what happens\nwhen the two of them meet.", "start": 1776.46, "duration": 3.42}, {"text": "You see this kind of regular\nstructure of empty space", "start": 1779.88, "duration": 3.36}, {"text": "where this grain\nboundary meets, right?", "start": 1783.24, "duration": 3.04}, {"text": "You can actually model it as\na line of 1-D dislocations,", "start": 1786.28, "duration": 3.55}, {"text": "because if you take\na line of 1-D lines,", "start": 1789.83, "duration": 2.81}, {"text": "you end up with a\n2-D boundary, which", "start": 1792.64, "duration": 2.19}, {"text": "you can see very clearly here.", "start": 1794.83, "duration": 1.3}, {"text": "It's almost like there's an\nextra half plane right there.", "start": 1796.13, "duration": 2.375}, {"text": "Another one there, another one\nthere, and another one there.", "start": 1798.505, "duration": 3.915}, {"text": "And we call that a\ntilt grain boundary.", "start": 1802.42, "duration": 2.77}, {"text": "Grain boundaries are nice in\nthat they can accommodate lots", "start": 1805.19, "duration": 2.82}, {"text": "of these little\nzero-dimensional defects,", "start": 1808.01, "duration": 2.85}, {"text": "moving to them without\ngetting destroyed.", "start": 1810.86, "duration": 3.03}, {"text": "So grain boundaries\nare one of those ways", "start": 1813.89, "duration": 1.74}, {"text": "that radiation damage\ncan be removed.", "start": 1815.63, "duration": 3.51}, {"text": "And that's one of the reasons\nwhy most small-grain materials", "start": 1819.14, "duration": 2.64}, {"text": "are really--", "start": 1821.78, "duration": 0.78}, {"text": "nano-grain materials are more\nresistant to radiation damage", "start": 1822.56, "duration": 3.42}, {"text": "than large-grain\nones because they", "start": 1825.98, "duration": 2.04}, {"text": "act as what's called sinks or\ndestroyers of radiation damage.", "start": 1828.02, "duration": 5.37}, {"text": "There's another kind of 2-D\ndefect called a twin, where", "start": 1833.39, "duration": 4.47}, {"text": "you can actually get a little\nchunk of atoms sort of switch", "start": 1837.86, "duration": 3.84}, {"text": "orientation.", "start": 1841.7, "duration": 0.93}, {"text": "And you can see these very\nclearly in, again, TEM", "start": 1842.63, "duration": 3.27}, {"text": "micrographs, and the evidence\nactually that the twin actually", "start": 1845.9, "duration": 4.86}, {"text": "is a different physical\narrangement of atoms,", "start": 1850.76, "duration": 1.92}, {"text": "even though you can't see\nthe atoms in this little band", "start": 1852.68, "duration": 3.75}, {"text": "right there.", "start": 1856.43, "duration": 1.35}, {"text": "Look at the way the\ndislocations line up.", "start": 1857.78, "duration": 2.76}, {"text": "Those dislocations\ntend to line up", "start": 1860.54, "duration": 1.65}, {"text": "in energetically-favorable\ndirections, and in this grain,", "start": 1862.19, "duration": 3.0}, {"text": "they're all this\nway, and in the twin,", "start": 1865.19, "duration": 3.09}, {"text": "they're all lined up like that.", "start": 1868.28, "duration": 4.733}, {"text": "And then finally, there's\nthe most intuitive defect,", "start": 1873.013, "duration": 2.167}, {"text": "inclusions.", "start": 1875.18, "duration": 1.2}, {"text": "A 3-D piece of some other\nmaterial inside what", "start": 1876.38, "duration": 3.36}, {"text": "would otherwise be\na pure material.", "start": 1879.74, "duration": 2.14}, {"text": "This one, I actually pulled\nout of the rotor that powers", "start": 1881.88, "duration": 3.65}, {"text": "the Alcator fusion reactor.", "start": 1885.53, "duration": 1.71}, {"text": "I was asked to do some\nanalysis to find out,", "start": 1887.24, "duration": 2.55}, {"text": "is the structure of\nthat rotor changing,", "start": 1889.79, "duration": 2.88}, {"text": "because General Electric who\nwas insuring this rotor said,", "start": 1892.67, "duration": 3.952}, {"text": "we don't want to\ninsure it anymore.", "start": 1896.622, "duration": 1.458}, {"text": "Thanks for the premiums, but\nwe're not insuring it anymore.", "start": 1898.08, "duration": 3.32}, {"text": "And we said, why?", "start": 1901.4, "duration": 1.0}, {"text": "And they said, oh, it's\nstructurally unsound.", "start": 1902.4, "duration": 2.0}, {"text": "So we said, oh yeah?", "start": 1904.4, "duration": 1.44}, {"text": "We'll be back in a year\nand we'll talk about it.", "start": 1905.84, "duration": 2.31}, {"text": "And we did a lot of\nthis work to find out", "start": 1908.15, "duration": 2.165}, {"text": "that, actually, the structure\nhadn't really changed", "start": 1910.315, "duration": 2.125}, {"text": "since 1954 when it was made.", "start": 1912.44, "duration": 2.58}, {"text": "But what we did also\nsee is we could pop out", "start": 1915.02, "duration": 2.58}, {"text": "little precipitates\nof manganese sulfide.", "start": 1917.6, "duration": 3.72}, {"text": "So there's always\nsulfur in iron,", "start": 1921.32, "duration": 2.43}, {"text": "and sulfur tends to\nbe a bad actor when it", "start": 1923.75, "duration": 1.8}, {"text": "comes to material properties.", "start": 1925.55, "duration": 2.04}, {"text": "You throw manganese\ninto iron to scoop up", "start": 1927.59, "duration": 2.58}, {"text": "that sulfur in the form of\nthese little precipitates", "start": 1930.17, "duration": 2.88}, {"text": "or inclusions, which we\nwere able to see perfectly", "start": 1933.05, "duration": 3.12}, {"text": "when we did an x-ray\nmap, just like the one we", "start": 1936.17, "duration": 1.98}, {"text": "did after the first exam.", "start": 1938.15, "duration": 2.25}, {"text": "It's like we were looking at\nChris' copper silver alloy,", "start": 1940.4, "duration": 3.51}, {"text": "mapping out where is\nthe copper and silver.", "start": 1943.91, "duration": 2.037}, {"text": "I made this image the\nsame way, mapping out,", "start": 1945.947, "duration": 1.833}, {"text": "where is there iron,\nmanganese and sulfur.", "start": 1947.78, "duration": 1.902}, {"text": "That's how you can\ntell what it is.", "start": 1949.682, "duration": 1.458}, {"text": "And so dislocations and\ndefects can actually interact.", "start": 1954.43, "duration": 2.73}, {"text": "Let's say this is\nthe interaction", "start": 1957.16, "duration": 1.38}, {"text": "of a 1-D defect, a dislocation,\nwith a 3-D defect, a void.", "start": 1958.54, "duration": 6.66}, {"text": "If you have a material\nthat's deforming plastically,", "start": 1965.2, "duration": 2.64}, {"text": "very smoothly, and isn't\ngoing to undergo fracture,", "start": 1967.84, "duration": 2.49}, {"text": "you want the dislocations\nto be able to move.", "start": 1970.33, "duration": 2.58}, {"text": "If you put anything in their\nway, they tend to get stuck.", "start": 1972.91, "duration": 4.08}, {"text": "It's not easy for\nthat dislocation", "start": 1976.99, "duration": 1.86}, {"text": "to shear through a whole\nbunch of extra atoms.", "start": 1978.85, "duration": 2.41}, {"text": "And in some cases, you can\nstop that motion and favor", "start": 1981.26, "duration": 4.97}, {"text": "fracture over slip.", "start": 1986.23, "duration": 3.71}, {"text": "So any time you\nmake slip harder,", "start": 1989.94, "duration": 2.43}, {"text": "it means that you're making\nfracture more likely.", "start": 1992.37, "duration": 2.298}, {"text": "I didn't say you're\nmaking it easier,", "start": 1994.668, "duration": 1.542}, {"text": "but you're making\nit more likely.", "start": 1996.21, "duration": 1.86}, {"text": "And you would\nprefer for materials", "start": 1998.07, "duration": 1.5}, {"text": "to deform a little bit by a slip\nthan just break by fracture.", "start": 1999.57, "duration": 6.37}, {"text": "So I think now is a good point\nto go over a few key material", "start": 2005.94, "duration": 3.38}, {"text": "properties.", "start": 2009.32, "duration": 1.79}, {"text": "All of these are sometimes\nused to describe the same thing", "start": 2011.11, "duration": 3.93}, {"text": "in colloquial speech.", "start": 2015.04, "duration": 1.71}, {"text": "That is wrong.", "start": 2016.75, "duration": 2.503}, {"text": "Has anyone here thought\nthat, let's say,", "start": 2019.253, "duration": 1.667}, {"text": "stiffness or toughness or\nstrength meant the same thing?", "start": 2020.92, "duration": 4.68}, {"text": "No.", "start": 2025.6, "duration": 0.5}, {"text": "OK.", "start": 2026.1, "duration": 0.83}, {"text": "A few people.", "start": 2026.93, "duration": 0.64}, {"text": "It's OK.", "start": 2027.57, "duration": 0.93}, {"text": "Because it's used wrong all\nthe time in colloquial speech.", "start": 2028.5, "duration": 3.51}, {"text": "These actually refer to\ndifferent material properties", "start": 2032.01, "duration": 2.46}, {"text": "with different units.", "start": 2034.47, "duration": 1.098}, {"text": "And we're going to go into\na little bit about what they", "start": 2035.568, "duration": 2.292}, {"text": "are and then show\nyou a few videos", "start": 2037.86, "duration": 2.82}, {"text": "to test your intuition about\nthe differences between them.", "start": 2040.68, "duration": 3.93}, {"text": "So first, I want to mention\nwhat you're seeing right here.", "start": 2044.61, "duration": 3.08}, {"text": "It's called a\nstress-strain curve.", "start": 2047.69, "duration": 2.549}, {"text": "Stress is simple.", "start": 2050.239, "duration": 1.5}, {"text": "Stress is just a force\ndivided by an area.", "start": 2051.739, "duration": 2.221}, {"text": "And usually, the\ncriterion for will", "start": 2057.92, "duration": 1.77}, {"text": "a material deform\nor will it break", "start": 2059.69, "duration": 2.34}, {"text": "is does it reach\na certain stress.", "start": 2062.03, "duration": 2.31}, {"text": "It doesn't matter just how\nmuch force you put on it,", "start": 2064.34, "duration": 2.29}, {"text": "but it's like, how\nmuch force per atom", "start": 2066.63, "duration": 1.85}, {"text": "or how much force per area\ndetermines whether bonds", "start": 2068.48, "duration": 2.82}, {"text": "are going to break.", "start": 2071.3, "duration": 1.56}, {"text": "And so on the y-axis is stress.", "start": 2072.86, "duration": 1.589}, {"text": "Let's say the amount of force\nper area we're putting in.", "start": 2074.449, "duration": 4.081}, {"text": "And strain is the\namount of deformation.", "start": 2078.53, "duration": 4.919}, {"text": "So that's stress.", "start": 2083.449, "duration": 0.971}, {"text": "And strain is, let's\nsay, the change in length", "start": 2084.42, "duration": 4.68}, {"text": "over the original length\nof some material in what's", "start": 2089.1, "duration": 3.36}, {"text": "called the engineering\nor simplified notation.", "start": 2092.46, "duration": 2.989}, {"text": "And so something\nthat is stiff means", "start": 2095.449, "duration": 2.291}, {"text": "you can put a lot\nof force into it", "start": 2097.74, "duration": 2.62}, {"text": "but it won't deform very much.", "start": 2100.36, "duration": 1.4}, {"text": "That's kind of the easiest\nproperty to understand.", "start": 2101.76, "duration": 2.535}, {"text": "Is something that's\nvery stiff will", "start": 2104.295, "duration": 2.385}, {"text": "have what's called a\nhigh Young's modulus,", "start": 2106.68, "duration": 1.86}, {"text": "or a high slope right here.", "start": 2108.54, "duration": 2.94}, {"text": "Something that's super\nstiff, like a ceramic,", "start": 2111.48, "duration": 2.46}, {"text": "you could really push\non it quite a bit,", "start": 2113.94, "duration": 3.13}, {"text": "but you won't get it to deform\nlike you would this metal.", "start": 2117.07, "duration": 3.59}, {"text": "So the opposite of stiff,\nI would call compliant.", "start": 2120.66, "duration": 3.06}, {"text": "Not soft.", "start": 2123.72, "duration": 1.44}, {"text": "This is one of those\ntricky things right there.", "start": 2125.16, "duration": 1.98}, {"text": "Something that's stiff, you try\nand flex it and it won't flex.", "start": 2127.14, "duration": 3.27}, {"text": "Something that's compliant,\nyou put a little bit of force", "start": 2130.41, "duration": 2.61}, {"text": "into it and it undergoes\nsome amount of strain.", "start": 2133.02, "duration": 4.82}, {"text": "And that slope right\nthere between the stress", "start": 2137.84, "duration": 2.59}, {"text": "and the strain, we call\nthe Young's modulus.", "start": 2140.43, "duration": 3.87}, {"text": "We also note that\nthis part right here", "start": 2144.3, "duration": 2.04}, {"text": "is what's called the elastic\nregion of deformation.", "start": 2146.34, "duration": 3.45}, {"text": "By elastic, we mean reversible,\nor it snaps right back.", "start": 2149.79, "duration": 3.26}, {"text": "So right here, when I bend this\nbar and it snaps right back,", "start": 2153.05, "duration": 4.24}, {"text": "that's called\nelastic deformation.", "start": 2157.29, "duration": 1.74}, {"text": "And it's reversible,\nbecause you can bend one way", "start": 2159.03, "duration": 3.06}, {"text": "and it snaps right back.", "start": 2162.09, "duration": 1.56}, {"text": "If I bent it more,\nwhich I don't want", "start": 2163.65, "duration": 2.07}, {"text": "to do because this is a nice\nzirconium fuel cladding rod,", "start": 2165.72, "duration": 3.57}, {"text": "you would deform\nit irreversibly.", "start": 2169.29, "duration": 1.59}, {"text": "You'd bend it permanently.", "start": 2170.88, "duration": 2.07}, {"text": "And to undergo what's called\nplastic deformation, when", "start": 2172.95, "duration": 3.3}, {"text": "you deviate from the slope, and\nthen a little bit more stress", "start": 2176.25, "duration": 3.54}, {"text": "can cause a lot\nmore deformation.", "start": 2179.79, "duration": 2.09}, {"text": "Have any of you guys ever\ntried pulling copper wire", "start": 2181.88, "duration": 2.29}, {"text": "apart before?", "start": 2184.17, "duration": 0.66}, {"text": "That's something I'd recommend\nyou try, for thin wire", "start": 2187.312, "duration": 2.208}, {"text": "so you don't cut your hands.", "start": 2189.52, "duration": 1.73}, {"text": "What you may notice is that\nit's awfully hard to get", "start": 2191.25, "duration": 2.97}, {"text": "the copper deforming\nin the first place,", "start": 2194.22, "duration": 2.52}, {"text": "but as soon as it starts to\nstretch, it gets really easy.", "start": 2196.74, "duration": 3.425}, {"text": "So this is something\nI recommend.", "start": 2200.165, "duration": 1.375}, {"text": "Go to the electronics\nshop or wherever", "start": 2201.54, "duration": 1.92}, {"text": "and try it out on some\nreally thin copper wire.", "start": 2203.46, "duration": 2.5}, {"text": "If it's thick, you'll\nslice through your fingers", "start": 2205.96, "duration": 2.0}, {"text": "and you don't want to do that.", "start": 2207.96, "duration": 2.39}, {"text": "Strength, however, that's\na different metric.", "start": 2210.35, "duration": 3.74}, {"text": "Whereas stiffness\ndescribes the slope here,", "start": 2214.09, "duration": 2.98}, {"text": "strength describes the height,\nor the stress at which you", "start": 2217.07, "duration": 4.38}, {"text": "start to plastically deform.", "start": 2221.45, "duration": 1.68}, {"text": "They're in different units.", "start": 2223.13, "duration": 2.29}, {"text": "Stiffness is in\nstress over strain,", "start": 2225.42, "duration": 3.12}, {"text": "whereas strength is\ngiven as a stress.", "start": 2228.54, "duration": 4.33}, {"text": "So when you hear\nthings like the yield", "start": 2232.87, "duration": 1.74}, {"text": "stress or the ultimate\ntensile strength,", "start": 2234.61, "duration": 1.83}, {"text": "that's referring to how\nstrong something is,", "start": 2236.44, "duration": 2.37}, {"text": "which may have nothing to\ndo with how stiff it is.", "start": 2238.81, "duration": 3.2}, {"text": "Toughness is another property.", "start": 2242.01, "duration": 2.55}, {"text": "Toughness is actually kind of\nlike the area under this curve,", "start": 2244.56, "duration": 4.2}, {"text": "because if you do a force\nand apply it over a distance,", "start": 2248.76, "duration": 3.96}, {"text": "that's like putting\nwork into the material", "start": 2252.72, "duration": 2.28}, {"text": "and it ends up being\na unit of energy.", "start": 2255.0, "duration": 2.72}, {"text": "So toughness will tell\nyou how much energy", "start": 2257.72, "duration": 1.91}, {"text": "you have to put into\nsomething before creating", "start": 2259.63, "duration": 2.58}, {"text": "a new free surface,\notherwise known as fracture.", "start": 2262.21, "duration": 3.72}, {"text": "And ductility is how much can\nyou deform it before it breaks.", "start": 2265.93, "duration": 4.01}, {"text": "So it would be like this point\nright here on the strain axis.", "start": 2269.94, "duration": 4.86}, {"text": "So I'll give a little\nbit more examples", "start": 2274.8, "duration": 1.68}, {"text": "of what this is all about.", "start": 2276.48, "duration": 3.34}, {"text": "Toughness, again,\nis actually measured", "start": 2279.82, "duration": 2.34}, {"text": "as an energy required\nto form a free surface,", "start": 2282.16, "duration": 3.99}, {"text": "or propagate a crack, let's say.", "start": 2286.15, "duration": 2.82}, {"text": "Whereas something\nthat's ductile,", "start": 2288.97, "duration": 1.907}, {"text": "it doesn't necessarily\nmean that it's tough.", "start": 2290.877, "duration": 1.833}, {"text": "Like, if you have a piece\nof chewed chewing gum,", "start": 2292.71, "duration": 2.64}, {"text": "you can stretch it quite a\nlot with very little energy.", "start": 2295.35, "duration": 3.06}, {"text": "And then you can say it's\nextremely ductile but not", "start": 2298.41, "duration": 2.7}, {"text": "very strong.", "start": 2301.11, "duration": 1.54}, {"text": "A piece of copper\nwire, you can also", "start": 2302.65, "duration": 2.18}, {"text": "stretch it an\nextremely far distance,", "start": 2304.83, "duration": 2.49}, {"text": "but it takes more\nenergy to do so.", "start": 2307.32, "duration": 2.04}, {"text": "So that's both\nductile and strong.", "start": 2309.36, "duration": 3.3}, {"text": "And then if you apply that\nforce over a certain distance,", "start": 2312.66, "duration": 2.49}, {"text": "stretching out the\nwire, you can also", "start": 2315.15, "duration": 2.25}, {"text": "reveal some of its toughness\nand how much energy", "start": 2317.4, "duration": 2.19}, {"text": "it takes to stretch that\nwire before it breaks.", "start": 2319.59, "duration": 4.58}, {"text": "Hardness is the last material\nproperty I want to mention,", "start": 2324.17, "duration": 2.65}, {"text": "which is not any of\nthe ones that I showed", "start": 2326.82, "duration": 3.38}, {"text": "on the stress-strain curve.", "start": 2330.2, "duration": 2.18}, {"text": "Hardness is the\nresistance to a little bit", "start": 2332.38, "duration": 1.86}, {"text": "of plastic deformation.", "start": 2334.24, "duration": 1.92}, {"text": "So assuming that\nyou're already here,", "start": 2336.16, "duration": 2.85}, {"text": "how much more energy\ndo you have to put in", "start": 2339.01, "duration": 1.8}, {"text": "to get the material\nto deform plastic?", "start": 2340.81, "duration": 1.645}, {"text": "So very different\nmaterial properties.", "start": 2345.46, "duration": 1.59}, {"text": "I'll try and mention\nall what they are.", "start": 2347.05, "duration": 4.27}, {"text": "So if we have a\nstress-strain curve like so,", "start": 2351.32, "duration": 5.34}, {"text": "and it follows\nthe elastic region", "start": 2356.66, "duration": 2.49}, {"text": "and then deforms\nplastically, this point", "start": 2359.15, "duration": 3.33}, {"text": "here is what we call\nthe yield strength.", "start": 2362.48, "duration": 2.25}, {"text": "Whatever that point\non the stress axis is.", "start": 2371.3, "duration": 3.9}, {"text": "This point right here,\nour strain to failure,", "start": 2375.2, "duration": 4.14}, {"text": "we can use as a\nmeasure of ductility.", "start": 2379.34, "duration": 4.6}, {"text": "This slope right here\nrefers to the stiffness.", "start": 2383.94, "duration": 6.53}, {"text": "And finally, this\nenergy right here", "start": 2390.47, "duration": 4.44}, {"text": "is something like the toughness.", "start": 2394.91, "duration": 1.58}, {"text": "And the hardness isn't\nquite on this plot.", "start": 2399.16, "duration": 3.11}, {"text": "So I want to see if\nyou guys intuitively", "start": 2402.27, "duration": 2.67}, {"text": "understand this, because\nthe next lecture,", "start": 2404.94, "duration": 1.94}, {"text": "I'm going to be throwing around\nthe words like stiffness,", "start": 2406.88, "duration": 2.95}, {"text": "toughness, ductility,\nhardness, compliance,", "start": 2409.83, "duration": 2.61}, {"text": "hard, soft, whatever,\nand I want to make sure", "start": 2412.44, "duration": 2.25}, {"text": "that you just at least\nintuitively understand.", "start": 2414.69, "duration": 2.67}, {"text": "There's a few videos you\nmay have seen before.", "start": 2417.36, "duration": 1.95}, {"text": "Anyone here watch the\nhydraulic press channel?", "start": 2419.31, "duration": 2.95}, {"text": "There we go.", "start": 2422.26, "duration": 0.6}, {"text": "Finally, something that\nhalf the class does.", "start": 2422.86, "duration": 2.29}, {"text": "We're going to\npredict what's going", "start": 2425.15, "duration": 1.67}, {"text": "to happen in each of these\ncases based on these material", "start": 2426.82, "duration": 3.39}, {"text": "properties.", "start": 2430.21, "duration": 1.14}, {"text": "So in this case, this is a\npressurized cylinder of CO2.", "start": 2431.35, "duration": 4.02}, {"text": "It's made of aluminum, which\nis a very ductile material.", "start": 2435.37, "duration": 4.09}, {"text": "It's also a very tough material.", "start": 2439.46, "duration": 2.225}, {"text": "How do you think it will\ndeform when smashed?", "start": 2441.685, "duration": 1.875}, {"text": "Anyone ever tried this?", "start": 2450.672, "duration": 0.958}, {"text": "Squishing aluminum stuff.", "start": 2451.63, "duration": 1.36}, {"text": "What happens?", "start": 2452.99, "duration": 1.084}, {"text": "AUDIENCE: You compress it.", "start": 2454.074, "duration": 1.961}, {"text": "PROFESSOR: You compress it.", "start": 2456.035, "duration": 1.125}, {"text": "And then what happens?", "start": 2457.16, "duration": 0.917}, {"text": "AUDIENCE: Fracture?", "start": 2460.772, "duration": 1.828}, {"text": "PROFESSOR: Will it fracture?", "start": 2462.6, "duration": 1.282}, {"text": "AUDIENCE: After a while.", "start": 2463.882, "duration": 1.14}, {"text": "PROFESSOR: After a while, OK.", "start": 2465.022, "duration": 1.208}, {"text": "If you put a lot of energy\ninto it, eventually,", "start": 2466.23, "duration": 2.34}, {"text": "when you reach this strain to\nfailure, it should fracture.", "start": 2468.57, "duration": 3.21}, {"text": "But in your personal\nhands-on experience,", "start": 2471.78, "duration": 2.58}, {"text": "does aluminum tend to fracture\nwhen you bend it a little bit?", "start": 2474.36, "duration": 2.657}, {"text": "AUDIENCE: No.", "start": 2477.017, "duration": 1.493}, {"text": "PROFESSOR: So then what words\nwould you use to describe it?", "start": 2478.51, "duration": 4.8}, {"text": "Based on this curve right here.", "start": 2483.31, "duration": 2.1}, {"text": "Yep?", "start": 2488.48, "duration": 0.5}, {"text": "AUDIENCE: Ductile.", "start": 2488.98, "duration": 0.81}, {"text": "PROFESSOR: Ductile.", "start": 2489.79, "duration": 0.792}, {"text": "I would say ductile\nand not brittle", "start": 2490.582, "duration": 2.018}, {"text": "because you can bend it quite\na bit or stretch it quite a bit", "start": 2492.6, "duration": 3.21}, {"text": "before it fractures.", "start": 2495.81, "duration": 1.67}, {"text": "How about stiffness?", "start": 2497.48, "duration": 1.06}, {"text": "Is it really hard or really\neasy to get aluminum bending?", "start": 2498.54, "duration": 2.46}, {"text": "AUDIENCE: It's pretty easy.", "start": 2503.69, "duration": 1.125}, {"text": "PROFESSOR: It's fairly easy.", "start": 2504.815, "duration": 1.167}, {"text": "So would you call that\nstiff or compliant?", "start": 2505.982, "duration": 1.758}, {"text": "AUDIENCE: Compliant.", "start": 2507.74, "duration": 0.833}, {"text": "PROFESSOR: Compliant.", "start": 2508.573, "duration": 0.875}, {"text": "OK.", "start": 2509.448, "duration": 0.632}, {"text": "What about strength?", "start": 2510.08, "duration": 1.35}, {"text": "How hard is it to start\ndeforming aluminum", "start": 2511.43, "duration": 2.4}, {"text": "irreversibly, compared\nto something like steel?", "start": 2513.83, "duration": 2.97}, {"text": "AUDIENCE: Not very.", "start": 2516.8, "duration": 1.26}, {"text": "PROFESSOR: Not very.", "start": 2518.06, "duration": 1.02}, {"text": "Especially pure aluminum.", "start": 2519.08, "duration": 1.05}, {"text": "You can chew through it.", "start": 2520.13, "duration": 2.19}, {"text": "If you guys ever got a\none yen coin from Japan,", "start": 2522.32, "duration": 2.67}, {"text": "you can chew through it.", "start": 2524.99, "duration": 2.49}, {"text": "Not very strong.", "start": 2527.48, "duration": 1.68}, {"text": "Then again, your bite force\nis also incredibly strong.", "start": 2529.16, "duration": 3.132}, {"text": "But anyway, let's\nsee what actually", "start": 2532.292, "duration": 1.458}, {"text": "happens when you compress a\nrather ductile, compliant,", "start": 2533.75, "duration": 4.8}, {"text": "and not that strong\naluminum canister.", "start": 2538.55, "duration": 2.925}, {"text": "Is it actually going?", "start": 2544.364, "duration": 1.436}, {"text": "Oh, it actually skipped ahead.", "start": 2545.8, "duration": 2.97}, {"text": "That's what I wanted,\nwas their sound.", "start": 2548.77, "duration": 1.98}, {"text": "It was also\npressurized with CO2.", "start": 2557.92, "duration": 1.765}, {"text": "But notice what's left.", "start": 2562.46, "duration": 1.71}, {"text": "So actually watch in slow-mo.", "start": 2564.17, "duration": 1.29}, {"text": "Look how much you can compress\nthat, even after the explosion.", "start": 2565.46, "duration": 3.75}, {"text": "No fracture.", "start": 2569.21, "duration": 2.648}, {"text": "If you had done that with,\nlet's say, a glass canister,", "start": 2571.858, "duration": 2.292}, {"text": "what do you guys think\nwould have happened?", "start": 2574.15, "duration": 1.08}, {"text": "AUDIENCE: It would\nhave shattered.", "start": 2575.23, "duration": 0.91}, {"text": "PROFESSOR: It would\nhave shattered.", "start": 2576.14, "duration": 1.2}, {"text": "Yeah, we'll see that in\na bit with a material", "start": 2577.34, "duration": 1.94}, {"text": "that may surprise you.", "start": 2579.28, "duration": 1.86}, {"text": "AUDIENCE: So it basically\ndoesn't fracture, right?", "start": 2581.14, "duration": 3.475}, {"text": "PROFESSOR: It will\nfracture eventually,", "start": 2584.615, "duration": 1.625}, {"text": "but the hydraulic press can't\nget it that far in compression.", "start": 2586.24, "duration": 3.48}, {"text": "So that would be something\nthat's extremely ductile, not", "start": 2589.72, "duration": 2.76}, {"text": "that strong--", "start": 2592.48, "duration": 0.79}, {"text": "so it wasn't that\nhard to deform.", "start": 2593.27, "duration": 1.76}, {"text": "Certainly we know it wasn't\nstronger than the steel base", "start": 2595.03, "duration": 3.18}, {"text": "plate that they used\nto do the smashing.", "start": 2598.21, "duration": 2.88}, {"text": "Because whatever's\nthe softer material", "start": 2601.09, "duration": 1.59}, {"text": "is going to deform more.", "start": 2602.68, "duration": 1.292}, {"text": "So here he's going to have--\nwell I'll let him describe it,", "start": 2603.972, "duration": 2.458}, {"text": "and then I'll let you guess\nwhat's going to happen.", "start": 2606.43, "duration": 2.802}, {"text": "What do you guys think\nis going to happen?", "start": 2632.2, "duration": 1.75}, {"text": "You've got what looks like\nbrass and copper coins", "start": 2636.55, "duration": 2.38}, {"text": "on a steel base plate.", "start": 2638.93, "duration": 2.54}, {"text": "Anyone have any idea?", "start": 2641.47, "duration": 2.7}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2644.17, "duration": 1.206}, {"text": "PROFESSOR: Yeah.", "start": 2645.376, "duration": 1.294}, {"text": "Everyone's making\nthis motion, which", "start": 2646.67, "duration": 1.5}, {"text": "means everything's going\nto flatten out, right?", "start": 2648.17, "duration": 3.45}, {"text": "Let's find out.", "start": 2651.62, "duration": 0.99}, {"text": "Not nearly as much as\nyou might have expected.", "start": 2664.423, "duration": 1.917}, {"text": "Is anyone surprised by this?", "start": 2685.97, "duration": 3.09}, {"text": "What happened there?", "start": 2689.06, "duration": 2.48}, {"text": "What actually happened there\nwas already described up here.", "start": 2691.54, "duration": 3.78}, {"text": "When you get enough dislocations\npiling up against each other", "start": 2695.32, "duration": 2.97}, {"text": "during plastic deformation,\nyou can undergo a process", "start": 2698.29, "duration": 3.12}, {"text": "called work hardening.", "start": 2701.41, "duration": 1.601}, {"text": "That process can be\nphysically described", "start": 2708.42, "duration": 1.86}, {"text": "by a lot of those dislocations\npiling up and making", "start": 2710.28, "duration": 2.55}, {"text": "it more and more difficult\nto continue that deformation.", "start": 2712.83, "duration": 3.887}, {"text": "So what happened here is\nthe brass and the copper,", "start": 2716.717, "duration": 2.083}, {"text": "which started out quite soft,\nnot that hard, quite ductile,", "start": 2718.8, "duration": 4.35}, {"text": "as you can see, and not that\nstrong actually got stronger", "start": 2723.15, "duration": 5.25}, {"text": "as they were deformed.", "start": 2728.4, "duration": 2.42}, {"text": "Interesting, huh?", "start": 2730.82, "duration": 1.23}, {"text": "Did anyone expect\nthis to happen?", "start": 2732.05, "duration": 2.65}, {"text": "OK.", "start": 2734.7, "duration": 1.36}, {"text": "Let's go to one that I think\neveryone can guess what's", "start": 2736.06, "duration": 2.25}, {"text": "going to happen, a lead ball.", "start": 2738.31, "duration": 3.02}, {"text": "So has anyone ever tried\nplaying with lead before?", "start": 2741.33, "duration": 3.07}, {"text": "Hopefully not.", "start": 2744.4, "duration": 1.94}, {"text": "I have quite a--", "start": 2746.34, "duration": 0.68}, {"text": "OK good, I'm not alone.", "start": 2747.02, "duration": 1.773}, {"text": "How would you describe lead\nin terms of the material", "start": 2748.793, "duration": 2.167}, {"text": "properties here?", "start": 2750.96, "duration": 0.75}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 2755.702, "duration": 1.998}, {"text": "PROFESSOR: Yep.", "start": 2757.7, "duration": 0.74}, {"text": "It's not very stiff.", "start": 2758.44, "duration": 1.01}, {"text": "It doesn't take much energy\nto start deforming it.", "start": 2759.45, "duration": 2.26}, {"text": "How else?", "start": 2761.71, "duration": 0.6}, {"text": "Was it hard or soft?", "start": 2765.71, "duration": 1.44}, {"text": "AUDIENCE: Soft.", "start": 2767.15, "duration": 0.94}, {"text": "PROFESSOR: OK.", "start": 2768.09, "duration": 0.63}, {"text": "Do you think it's\nductile or brittle?", "start": 2768.72, "duration": 3.6}, {"text": "Yeah?", "start": 2772.32, "duration": 0.552}, {"text": "AUDIENCE: It's brittle.", "start": 2772.872, "duration": 0.958}, {"text": "PROFESSOR: You\nthink it's brittle.", "start": 2773.83, "duration": 1.57}, {"text": "So by that, you mean it's just\ngoing to break apart, right?", "start": 2775.4, "duration": 3.06}, {"text": "If you deform it?", "start": 2778.46, "duration": 3.09}, {"text": "OK, cool.", "start": 2781.55, "duration": 1.25}, {"text": "And would you say it\nis tough or not tough?", "start": 2782.8, "duration": 2.48}, {"text": "Not a lot of folks have\nhands-on experience with lead.", "start": 2788.47, "duration": 2.4}, {"text": "It's probably good\nfor your brains.", "start": 2790.87, "duration": 2.13}, {"text": "Let's find out.", "start": 2793.0, "duration": 0.69}, {"text": "Lead pancake.", "start": 2817.9, "duration": 1.05}, {"text": "So what words would you use to\ndescribe what just happened?", "start": 2818.95, "duration": 3.753}, {"text": "AUDIENCE: It's ductile.", "start": 2822.703, "duration": 0.967}, {"text": "PROFESSOR: Ductile indeed.", "start": 2823.67, "duration": 1.563}, {"text": "I don't know what\nsort of brittle lead--", "start": 2825.233, "duration": 1.667}, {"text": "was it an alloy that you had\nbeen playing with, maybe?", "start": 2826.9, "duration": 2.441}, {"text": "AUDIENCE: It was\nlike a little sheet.", "start": 2829.341, "duration": 1.542}, {"text": "It was just easy to snap.", "start": 2830.883, "duration": 1.227}, {"text": "PROFESSOR: Aha, OK.", "start": 2832.11, "duration": 1.18}, {"text": "So it was a sheet of lead\nthat was easy to snap.", "start": 2833.29, "duration": 2.58}, {"text": "So I would not call lead\nas a very tough material", "start": 2835.87, "duration": 2.79}, {"text": "because you didn't have to\nput a lot of energy into it,", "start": 2838.66, "duration": 2.79}, {"text": "but did it deform quite a bit\nbefore you snapped it or did", "start": 2841.45, "duration": 2.97}, {"text": "it just crumble apart?", "start": 2844.42, "duration": 1.537}, {"text": "AUDIENCE: Oh, it deformed.", "start": 2845.957, "duration": 1.463}, {"text": "PROFESSOR: OK.", "start": 2847.42, "duration": 0.87}, {"text": "So in that case, I would call\nit ductile because it deformed", "start": 2848.29, "duration": 3.45}, {"text": "a lot before breaking,\nbut I would not", "start": 2851.74, "duration": 2.88}, {"text": "call it tough because it took\nvery little energy to get it", "start": 2854.62, "duration": 3.06}, {"text": "to that breaking point.", "start": 2857.68, "duration": 1.86}, {"text": "And it wasn't that stiff because\nit was quite easy to get it--", "start": 2859.54, "duration": 2.77}, {"text": "let's say it's the\namount of stress", "start": 2862.31, "duration": 3.05}, {"text": "you put in versus the strain.", "start": 2865.36, "duration": 1.64}, {"text": "It could be quite low.", "start": 2867.0, "duration": 1.8}, {"text": "And it would not be\nvery strong because it", "start": 2868.8, "duration": 1.75}, {"text": "didn't take a lot of energy\nor stress to get it moving.", "start": 2870.55, "duration": 4.14}, {"text": "Let's look at another ball.", "start": 2874.69, "duration": 1.65}, {"text": "In this case, a\nsteel ball bearing.", "start": 2876.34, "duration": 3.87}, {"text": "What do you guys think\nis going to happen here?", "start": 2880.21, "duration": 2.052}, {"text": "AUDIENCE: It's going to shatter.", "start": 2882.262, "duration": 1.728}, {"text": "PROFESSOR: It's\ngoing to shatter.", "start": 2883.99, "duration": 1.375}, {"text": "So you're guessing that the\nsteel is brittle, right?", "start": 2885.365, "duration": 3.645}, {"text": "What else?", "start": 2889.01, "duration": 0.54}, {"text": "AUDIENCE: Probably\npretty stiff and strong.", "start": 2896.538, "duration": 1.792}, {"text": "PROFESSOR: Probably quite\nstiff and strong, yeah.", "start": 2898.33, "duration": 2.89}, {"text": "I think so, too, but\nI don't think the guy", "start": 2901.22, "duration": 1.75}, {"text": "that did this expected that.", "start": 2902.97, "duration": 1.819}, {"text": "[INTERPOSING VOICES]", "start": 2928.025, "duration": 2.893}, {"text": "PROFESSOR: Yeah.", "start": 2930.918, "duration": 0.667}, {"text": "Did that surprise anybody?", "start": 2931.585, "duration": 1.913}, {"text": "Yeah.", "start": 2963.77, "duration": 0.5}, {"text": "Quite a surprise, right?", "start": 2964.27, "duration": 1.53}, {"text": "So in this case, materials\nlike hardened steel", "start": 2965.8, "duration": 2.49}, {"text": "aren't necessarily that brittle.", "start": 2968.29, "duration": 1.71}, {"text": "In fact, you wouldn't want a\nball bearing to be brittle.", "start": 2970.0, "duration": 3.48}, {"text": "If you get some small chip in it\nor a little bit of grit or sand", "start": 2973.48, "duration": 3.9}, {"text": "in the bearings, you would\nshatter the ball bearing", "start": 2977.38, "duration": 2.4}, {"text": "and cause instantaneous failure\nof the rotating component.", "start": 2979.78, "duration": 3.24}, {"text": "So what you actually want out\nof a high-strength ball bearing", "start": 2983.02, "duration": 3.12}, {"text": "is something that's\nextremely hard.", "start": 2986.14, "duration": 1.56}, {"text": "Resists deformation\nso it doesn't undergo,", "start": 2987.7, "duration": 3.03}, {"text": "let's say, change of shape\nthat would prevent it", "start": 2990.73, "duration": 2.37}, {"text": "from rolling without friction\nor with very little friction.", "start": 2993.1, "duration": 2.932}, {"text": "You want it to be quite\nstiff because you don't", "start": 2996.032, "duration": 1.958}, {"text": "want the load of whatever you're\nloading onto it to deform it,", "start": 2997.99, "duration": 3.24}, {"text": "but you also don't\nwant it to be brittle.", "start": 3001.23, "duration": 2.55}, {"text": "So it's got to be somewhat\ntough and ductile to prevent", "start": 3003.78, "duration": 3.18}, {"text": "sudden failure.", "start": 3006.96, "duration": 1.2}, {"text": "You'd rather it compress a tiny\nbit than just cracking in half.", "start": 3008.16, "duration": 4.16}, {"text": "So you can make things like\nceramic ball bearings, which", "start": 3012.32, "duration": 3.23}, {"text": "are very brittle, very stiff,\nnot that tough, but also very", "start": 3015.55, "duration": 4.98}, {"text": "strong, and you just\nhave to make sure", "start": 3020.53, "duration": 2.4}, {"text": "that whatever part\nyou make is not", "start": 3022.93, "duration": 1.47}, {"text": "going to reach any sort of yield\nstrength criterion or crack", "start": 3024.4, "duration": 5.22}, {"text": "or anything.", "start": 3029.62, "duration": 1.79}, {"text": "Now the last one that's\nprobably the most surprising.", "start": 3031.41, "duration": 3.48}, {"text": "They bought a $4,000 diamond.", "start": 3034.89, "duration": 3.24}, {"text": "It's a diamond like that big.", "start": 3038.13, "duration": 2.14}, {"text": "What do you know about\ndiamonds as a material in terms", "start": 3040.27, "duration": 2.34}, {"text": "of these properties?", "start": 3042.61, "duration": 1.08}, {"text": "AUDIENCE: They're hard.", "start": 3043.69, "duration": 1.96}, {"text": "PROFESSOR: Yep, both is right.", "start": 3045.65, "duration": 1.25}, {"text": "They're extremely stiff.", "start": 3046.9, "duration": 1.71}, {"text": "It's the hardest material\nthat we know of, almost.", "start": 3048.61, "duration": 2.85}, {"text": "We've made slightly\nharder ones artificially.", "start": 3051.46, "duration": 2.355}, {"text": "It's the hardest natural\nmaterial we know of.", "start": 3053.815, "duration": 1.875}, {"text": "What else?", "start": 3055.69, "duration": 1.38}, {"text": "Do you know whether\nthey're strong or tough?", "start": 3057.07, "duration": 2.686}, {"text": "AUDIENCE: They're not tough.", "start": 3059.756, "duration": 1.284}, {"text": "PROFESSOR: They're not tough.", "start": 3061.04, "duration": 1.208}, {"text": "Why do you say that?", "start": 3062.248, "duration": 1.104}, {"text": "AUDIENCE: Because\nit will shatter.", "start": 3063.352, "duration": 2.068}, {"text": "PROFESSOR: Have\nyou seen the video?", "start": 3065.42, "duration": 0.78}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3066.2, "duration": 0.78}, {"text": "PROFESSOR: Oh wow.", "start": 3066.98, "duration": 0.83}, {"text": "OK.", "start": 3067.81, "duration": 1.45}, {"text": "What else do we have?", "start": 3069.26, "duration": 0.9}, {"text": "Yeah.", "start": 3070.16, "duration": 0.84}, {"text": "So you're saying it's not tough.", "start": 3071.0, "duration": 1.597}, {"text": "AUDIENCE: You can\ncut diamonds, right?", "start": 3072.597, "duration": 1.583}, {"text": "PROFESSOR: You can cut\ndiamonds with other diamonds.", "start": 3074.18, "duration": 2.82}, {"text": "So the cutting action\nusually depends", "start": 3077.0, "duration": 1.8}, {"text": "on the relative hardness\nof the material.", "start": 3078.8, "duration": 3.01}, {"text": "So if you want to polish or\ncut something abrasively,", "start": 3081.81, "duration": 2.87}, {"text": "you need to use\na harder material", "start": 3084.68, "duration": 1.53}, {"text": "because then the grit\nitself won't wear away", "start": 3086.21, "duration": 2.97}, {"text": "before the material\nit's trying to cut.", "start": 3089.18, "duration": 2.24}, {"text": "But what's going to happen here\nis we're going to put a diamond", "start": 3091.42, "duration": 3.28}, {"text": "and try compressing\nit, and we'll", "start": 3094.7, "duration": 1.987}, {"text": "see what its stress-strain\ncurve looks like.", "start": 3096.687, "duration": 1.833}, {"text": "So votes on what's\ngoing to happen.", "start": 3098.52, "duration": 1.94}, {"text": "Who says, like Monica,\nit's going to shatter?", "start": 3100.46, "duration": 3.081}, {"text": "Who thinks it's going\nto break the tools?", "start": 3103.541, "duration": 3.799}, {"text": "Who thinks it's going\nto deform plastically?", "start": 3107.34, "duration": 2.464}, {"text": "Yeah, I've never seen a\ndiamond deform plastically.", "start": 3109.804, "duration": 2.961}, {"text": "AUDIENCE: They still have\npretty big chunks, though.", "start": 3165.133, "duration": 2.167}, {"text": "PROFESSOR: Oh yeah, they could\nprobably still sell those.", "start": 3167.3, "duration": 2.74}, {"text": "Absolutely no deformation.", "start": 3170.04, "duration": 3.21}, {"text": "It just rotates and explodes.", "start": 3173.25, "duration": 3.16}, {"text": "Yeah.", "start": 3176.41, "duration": 0.5}, {"text": "This would be a\nmaterial that we would", "start": 3176.91, "duration": 1.71}, {"text": "say has almost zero ductility.", "start": 3178.62, "duration": 3.6}, {"text": "Despite being\nextremely hard, I don't", "start": 3182.22, "duration": 2.1}, {"text": "know if there would\neven been enough", "start": 3184.32, "duration": 1.5}, {"text": "deformation to have a slight\ndent in the tool itself.", "start": 3185.82, "duration": 3.098}, {"text": "There's probably a little hole\nwhere the point of the diamond", "start": 3188.918, "duration": 2.542}, {"text": "poked in, but once there was\nenough stress on that diamond,", "start": 3191.46, "duration": 3.57}, {"text": "its stress-strain curve would\nlook something like that.", "start": 3195.03, "duration": 4.25}, {"text": "Maybe like that.", "start": 3199.28, "duration": 2.2}, {"text": "Yeah.", "start": 3201.48, "duration": 1.43}, {"text": "So it's important\nthat you intuitively", "start": 3202.91, "duration": 1.62}, {"text": "understand the differences\nbetween strength, ductility,", "start": 3204.53, "duration": 3.39}, {"text": "hardness, toughness, and\nstiffness, because then", "start": 3207.92, "duration": 3.57}, {"text": "next class, we can explain\nhow radiation changes them.", "start": 3211.49, "duration": 4.38}, {"text": "So any questions on the\nmaterials and properties", "start": 3215.87, "duration": 2.7}, {"text": "from today?", "start": 3218.57, "duration": 0.54}, {"text": "Yeah?", "start": 3223.62, "duration": 1.1}, {"text": "AUDIENCE: Can you clarify why\nsomething is, for example,", "start": 3224.72, "duration": 3.07}, {"text": "ductile versus brittle?", "start": 3227.79, "duration": 1.915}, {"text": "PROFESSOR: Mhm.", "start": 3229.705, "duration": 0.625}, {"text": "So the reason something\nwould be ductile", "start": 3230.33, "duration": 1.667}, {"text": "versus brittle is whether or not\nyou can plastically deform it,", "start": 3231.997, "duration": 3.445}, {"text": "and that means whether or\nnot it's more energetically", "start": 3235.442, "duration": 2.208}, {"text": "favorable for dislocations\nto keep moving", "start": 3237.65, "duration": 2.55}, {"text": "versus just breaking a plane\nof atoms in any irregular", "start": 3240.2, "duration": 3.69}, {"text": "direction and causing fracture.", "start": 3243.89, "duration": 2.22}, {"text": "So again, ductility\nversus embrittlement", "start": 3246.11, "duration": 2.37}, {"text": "is the interplay between\nslip and fracture.", "start": 3248.48, "duration": 5.19}, {"text": "Slip is normally done\nby dislocation movement.", "start": 3253.67, "duration": 3.0}, {"text": "Any defects created by anything,\nespecially radiation damage,", "start": 3256.67, "duration": 3.45}, {"text": "will make slip harder so that\nany continued energy you put in", "start": 3260.12, "duration": 3.57}, {"text": "will not move dislocations\nbut move towards fracture.", "start": 3263.69, "duration": 2.938}, {"text": "If there's no other\nquestions, we'll", "start": 3269.496, "duration": 2.524}, {"text": "look at the\nstress-strain curves of", "start": 3272.02, "duration": 2.4}, {"text": "some other familiar materials.", "start": 3274.42, "duration": 2.323}, {"text": "It is 10:00, in case you guys\nhave to go to other classes.", "start": 3276.743, "duration": 2.417}, {"text": "AUDIENCE: Are you taking any\nnuclear activation stuff today?", "start": 3283.38, "duration": 2.5}, {"text": "PROFESSOR: Yes.", "start": 3285.88, "duration": 0.625}, {"text": "If you guys have things for a\nnuclear activation analysis,", "start": 3286.505, "duration": 2.435}, {"text": "hand it in.", "start": 3288.94, "duration": 1.78}, {"text": "You guys bring stuff in?", "start": 3290.72, "duration": 2.943}, {"text": "We're running out of\nopportunities to do this.", "start": 3293.663, "duration": 1.917}, {"text": "All right.", "start": 3298.26, "duration": 0.5}, {"text": "In that case, the\nentry fee for the quiz", "start": 3298.76, "duration": 4.5}, {"text": "will be your nuclear\nactivation analysis sample.", "start": 3303.26, "duration": 3.53}]
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+[{"text": "We are going to be\nleaving the territory of--", "start": 17.666, "duration": 5.071}, {"text": "some of you have had\nhigh school chemistry.", "start": 22.737, "duration": 1.802}, {"text": "We're going to be starting\nto leave that territory", "start": 24.539, "duration": 2.669}, {"text": "and get into some of the things\nI've talked about before,", "start": 27.208, "duration": 5.239}, {"text": "that you may have never seen.", "start": 32.447, "duration": 1.401}, {"text": "So for example, today we'll be\ntalking about semiconductors", "start": 33.848, "duration": 5.072}, {"text": "and what happens when you\ntake all these atomic orbitals", "start": 38.92, "duration": 3.904}, {"text": "and you put them into a solid.", "start": 42.824, "duration": 2.469}, {"text": "And then, by the end of the\nweek, we'll talk about metals.", "start": 45.293, "duration": 3.904}, {"text": "And then next week, we're\ngoing to talk about crystals.", "start": 49.197, "duration": 2.436}, {"text": "So that's what's coming.", "start": 51.633, "duration": 1.368}, {"text": "OK, now there's one\ntype of bonding--", "start": 53.001, "duration": 0.067}, {"text": "Before we get into\nsemiconductors and solids,", "start": 53.068, "duration": 7.007}, {"text": "there's one type of bonding\nwe covered but I didn't", "start": 60.075, "duration": 2.135}, {"text": "put the stats up on the column.", "start": 62.21, "duration": 2.535}, {"text": "So I just wanted to kind of\nmake sure that we finish that,", "start": 64.745, "duration": 3.938}, {"text": "and that was hydrogen bonding.", "start": 68.683, "duration": 2.202}, {"text": "And there's a little video--", "start": 70.885, "duration": 1.535}, {"text": "you know, water,\nwe're not going to go", "start": 72.42, "duration": 2.603}, {"text": "into all the amazing\nproperties of water.", "start": 75.023, "duration": 2.102}, {"text": "But if you're interested,\nthis is a really cool website", "start": 77.125, "duration": 2.703}, {"text": "that talks about all\nthe anomalies of water.", "start": 79.828, "duration": 3.236}, {"text": "And many of water's\nproperties are anomalous.", "start": 83.064, "duration": 5.205}, {"text": "And much of the reason for that\nis the last type of bonding", "start": 88.269, "duration": 3.77}, {"text": "we talked about,\nintermolecular bonds", "start": 92.039, "duration": 2.07}, {"text": "we talked about last Friday,\nwhich is the hydrogen bond.", "start": 94.109, "duration": 3.737}, {"text": "So remember our table, I just\nwanted to fill out the table", "start": 97.846, "duration": 3.803}, {"text": "because I didn't fill\nout the table, right.", "start": 101.649, "duration": 2.002}, {"text": "That's the type of bond.", "start": 103.651, "duration": 1.368}, {"text": "And the model was some\nkind of electronegative--", "start": 105.019, "duration": 3.871}, {"text": "it was some kind of highly\nelectronegative atom.", "start": 111.493, "duration": 2.936}, {"text": "Like a was oxygen or\nnitrogen or fluorine.", "start": 114.429, "duration": 5.339}, {"text": "So that you drew a lot of\ncharge off of that hydrogen", "start": 119.768, "duration": 3.57}, {"text": "and you left it with a\nreally strong delta plus", "start": 123.338, "duration": 4.171}, {"text": "so that it could then\nbond to some other atom.", "start": 127.509, "duration": 4.504}, {"text": "It might be the\nsame, by the way.", "start": 132.013, "duration": 1.568}, {"text": "It was in the cases\nthat we talked about.", "start": 133.581, "duration": 3.27}, {"text": "Actually, I'll just use the same\natom because we use HF and H2O,", "start": 136.851, "duration": 3.504}, {"text": "so then it would\nbe the O or the F.", "start": 140.355, "duration": 1.902}, {"text": "But it's to a lone\npair on that atom.", "start": 142.257, "duration": 4.104}, {"text": "That was the hydrogen bond.", "start": 146.361, "duration": 2.302}, {"text": "And the range of attraction is\nin kilojoules per mole of bonds", "start": 148.663, "duration": 8.909}, {"text": "is something like,\nlet's see, 10 to 40.", "start": 157.572, "duration": 4.571}, {"text": "So it's pretty strong,\nyou know, compared", "start": 162.143, "duration": 1.902}, {"text": "to some of the weaker\nthings like London,", "start": 164.045, "duration": 2.202}, {"text": "the hydrogen bond\ncan be pretty strong.", "start": 166.247, "duration": 2.77}, {"text": "And one of the examples\nthat is the classic example", "start": 169.017, "duration": 3.103}, {"text": "would be", "start": 172.12, "duration": 2.169}, {"text": "Hydrogen, hydrogen, there's\nthe hydrogen bond right there,", "start": 174.289, "duration": 5.438}, {"text": "you see?", "start": 179.727, "duration": 0.701}, {"text": "Hydrogen bond between another\noxygen with its hydrogens", "start": 180.428, "duration": 5.406}, {"text": "as well.", "start": 185.834, "duration": 0.533}, {"text": "Now, we talked about\nhow water is so special", "start": 186.367, "duration": 4.572}, {"text": "because in the case of water,\nnot only do I have exactly two", "start": 190.939, "duration": 4.738}, {"text": "hydrogens in each molecule that\nhave caused this strong delta", "start": 195.677, "duration": 3.837}, {"text": "plus, but I've also\ngot two lone pairs.", "start": 199.514, "duration": 2.803}, {"text": "So the numbers work.", "start": 202.317, "duration": 1.935}, {"text": "In HF, that's also\na hydrogen bonded--", "start": 204.252, "duration": 3.737}, {"text": "it can hydrogen bond\nto itself, but I've", "start": 207.989, "duration": 2.703}, {"text": "got three lone pairs on\neach F and only one hydrogen", "start": 210.692, "duration": 2.536}, {"text": "that I've taken that\ncharge away from.", "start": 213.228, "duration": 1.568}, {"text": "So you still get the\nhydrogen bonding,", "start": 214.796, "duration": 1.601}, {"text": "but this is the\nbeautiful balance.", "start": 216.397, "duration": 2.97}, {"text": "And there's a video showing\nwater bonded to each other.", "start": 219.367, "duration": 4.538}, {"text": "Oh, there it is.", "start": 223.905, "duration": 1.568}, {"text": "Because there's nothing like\njust imagining what a hydrogen", "start": 225.473, "duration": 2.936}, {"text": "bond looks like.", "start": 228.409, "duration": 1.068}, {"text": "And so of course, a\nhydrogen bond will--", "start": 229.477, "duration": 3.036}, {"text": "OK, charges.", "start": 232.513, "duration": 0.935}, {"text": "Oh, it's French.", "start": 233.448, "duration": 1.034}, {"text": "[SPEAKING FRENCH] OK.", "start": 234.482, "duration": 3.704}, {"text": "Oh, that's what it looks like.", "start": 238.186, "duration": 1.568}, {"text": "Really, if you could\nget down there,", "start": 239.754, "duration": 1.502}, {"text": "it would be a ray of\na laser beam light.", "start": 241.256, "duration": 3.903}, {"text": "It's a liaison hydrogene.", "start": 245.159, "duration": 3.237}, {"text": "And there it is.", "start": 248.396, "duration": 2.736}, {"text": "And this is what's\ngoing on in the liquid.", "start": 251.132, "duration": 2.236}, {"text": "They're kind of\nseeing each other.", "start": 253.368, "duration": 1.434}, {"text": "And they're talking.", "start": 254.802, "duration": 1.035}, {"text": "But they feel this strong,\nstrong hydrogen bond.", "start": 255.837, "duration": 4.738}, {"text": "And that's happening\nall over the place.", "start": 260.575, "duration": 1.668}, {"text": "And in a liquid, they are making\nand breaking all the time.", "start": 262.243, "duration": 4.638}, {"text": "Question?", "start": 266.881, "duration": 1.368}, {"text": "STUDENT: Why do they separate?", "start": 268.249, "duration": 2.503}, {"text": "Yeah.", "start": 270.752, "duration": 0.667}, {"text": "Yeah, because--\nwell, it depends.", "start": 271.419, "duration": 2.135}, {"text": "It depends.", "start": 273.554, "duration": 0.601}, {"text": "It's a great question.", "start": 274.155, "duration": 1.468}, {"text": "Why do they separate?", "start": 275.623, "duration": 2.469}, {"text": "Well, they don't in ice.", "start": 278.092, "duration": 2.57}, {"text": "So in ice, I mean,\nyou know, they can.", "start": 280.662, "duration": 2.636}, {"text": "But in ice, it's a solid, so\nthey're sort of locked in.", "start": 283.298, "duration": 4.004}, {"text": "And so in there, you're going\nto have pretty much each water", "start": 287.302, "duration": 3.503}, {"text": "molecule has four--", "start": 290.805, "duration": 1.401}, {"text": "look at this.", "start": 292.206, "duration": 1.168}, {"text": "It's you know from VESPR, right?", "start": 293.374, "duration": 2.136}, {"text": "Four possible bonds.", "start": 295.51, "duration": 2.803}, {"text": "You can make tetrahedral.", "start": 298.313, "duration": 2.235}, {"text": "But there's actually\nlots of ways", "start": 300.548, "duration": 1.368}, {"text": "you can orient them in a solid.", "start": 301.916, "duration": 1.668}, {"text": "There's many forms of\nice, 12 different ways", "start": 303.584, "duration": 2.97}, {"text": "to make a solid of ice.", "start": 306.554, "duration": 2.169}, {"text": "But see, here-- gesundheit.", "start": 308.723, "duration": 4.271}, {"text": "So here in the liquid\nat room temperature,", "start": 312.994, "duration": 3.103}, {"text": "with the laser beams, they're\ncoming in and they're bonding,", "start": 316.097, "duration": 4.171}, {"text": "but they have enough energy\nto break the bond, too.", "start": 320.268, "duration": 3.17}, {"text": "So they stick and they\nunstick because there's", "start": 323.438, "duration": 2.335}, {"text": "enough thermal energy in the\nsystem to continuously break", "start": 325.773, "duration": 3.737}, {"text": "them and remake them.", "start": 329.51, "duration": 0.935}, {"text": "That's when it's a liquid.", "start": 330.445, "duration": 2.836}, {"text": "When is it a liquid\nversus a gas?", "start": 333.281, "duration": 2.569}, {"text": "Right, the boiling\npoint, remember,", "start": 335.85, "duration": 1.902}, {"text": "that is a proxy we\ntalked about last Friday.", "start": 337.752, "duration": 2.669}, {"text": "That is a proxy for\nthe bonding strength", "start": 340.421, "duration": 2.703}, {"text": "between these molecules.", "start": 343.124, "duration": 2.302}, {"text": "If it's a stronger bonding,\nthen the boiling point", "start": 345.426, "duration": 2.937}, {"text": "will be higher and higher.", "start": 348.363, "duration": 1.601}, {"text": "Oh, water should have boiled\nat a much lower temperature", "start": 349.964, "duration": 3.771}, {"text": "if it didn't have this very\nspecial hydrogen bond, which", "start": 353.735, "duration": 2.869}, {"text": "is not a dipole-dipole.", "start": 356.604, "duration": 2.136}, {"text": "People try to write the physics\nof the hydrogen bond as 1", "start": 358.74, "duration": 3.503}, {"text": "over r cubed.", "start": 362.243, "duration": 0.768}, {"text": "That is not true.", "start": 363.011, "duration": 1.234}, {"text": "That is not just as simple as,\nit's another dipole-dipole type", "start": 364.245, "duration": 4.138}, {"text": "interaction.", "start": 368.383, "duration": 0.667}, {"text": "It's complicated.", "start": 369.05, "duration": 2.402}, {"text": "Complicated.", "start": 371.452, "duration": 2.703}, {"text": "Remember, we had covalent\nbonds were complicated too.", "start": 374.155, "duration": 4.171}, {"text": "So we're not going\nto put a simple one", "start": 378.326, "duration": 2.736}, {"text": "over r something dependence\nfor the hydrogen bond.", "start": 381.062, "duration": 3.87}, {"text": "OK, good question.", "start": 384.932, "duration": 1.469}, {"text": "OK now, all right, so that's\nan intermolecular-- now", "start": 386.401, "duration": 3.236}, {"text": "we're going to\nmove on to solids.", "start": 389.637, "duration": 1.735}, {"text": "So that was our last\nintermolecular interaction.", "start": 391.372, "duration": 2.77}, {"text": "Oh, before I do,\nthere's actually", "start": 394.142, "duration": 1.635}, {"text": "an example question I put there\nthat you could now answer,", "start": 395.777, "duration": 5.105}, {"text": "which this is actually--", "start": 400.882, "duration": 1.2}, {"text": "I just want to show\nyou the type of--", "start": 402.082, "duration": 1.903}, {"text": "so we covered all these\nintermolecular bonds.", "start": 403.985, "duration": 2.402}, {"text": "Here's a question\nfrom a quiz last year.", "start": 406.387, "duration": 2.503}, {"text": "List the intermolecular forces\nin each substance, methane,", "start": 408.89, "duration": 3.57}, {"text": "and then you've got that CH3OH.", "start": 412.46, "duration": 2.369}, {"text": "And then you've got the CH3CL.", "start": 414.829, "duration": 3.136}, {"text": "And so you can do this\nnow because for methane", "start": 417.965, "duration": 3.07}, {"text": "all you've got is London.", "start": 421.035, "duration": 2.036}, {"text": "It's not a polar molecule.", "start": 423.071, "duration": 1.201}, {"text": "All you've got is London.", "start": 424.272, "duration": 1.101}, {"text": "There's no hydrogen bond.", "start": 425.373, "duration": 3.07}, {"text": "But for CH3OH, do you\nhave hydrogen bonding?", "start": 428.443, "duration": 6.239}, {"text": "Yeah, you do.", "start": 434.682, "duration": 1.135}, {"text": "Because if you draw--", "start": 435.817, "duration": 1.201}, {"text": "because you've got an H\nthat's had the charge taken", "start": 437.018, "duration": 3.87}, {"text": "from it by oxygen, a highly\nelectronegative atom, and then", "start": 440.888, "duration": 4.939}, {"text": "and then you've got lone\npairs on that same oxygen.", "start": 445.827, "duration": 2.435}, {"text": "So you can hydrogen bond\nand you've also got London.", "start": 448.262, "duration": 4.338}, {"text": "All right, now is that it?", "start": 452.6, "duration": 1.268}, {"text": "Is there anything else?", "start": 453.868, "duration": 2.102}, {"text": "CH3OH.", "start": 455.97, "duration": 1.168}, {"text": "What else?", "start": 457.138, "duration": 0.5}, {"text": "Is there any other type of bond?", "start": 457.638, "duration": 3.904}, {"text": "Well, the last question\nyou need to ask", "start": 461.542, "duration": 1.769}, {"text": "is, is there a dipole\nmoment in the molecule?", "start": 463.311, "duration": 3.136}, {"text": "Because if that molecule\nhad a permanent dipole,", "start": 466.447, "duration": 2.77}, {"text": "then there is another type of\nintermolecular interaction,", "start": 469.217, "duration": 2.502}, {"text": "like we talked\nabout, dipole-dipole.", "start": 471.719, "duration": 2.102}, {"text": "So you'd have three.", "start": 473.821, "duration": 3.27}, {"text": "And for CH3CO, well there, you\nalso-- you know that for CH3CO,", "start": 477.091, "duration": 6.14}, {"text": "you're going to have\na dipole moment.", "start": 483.231, "duration": 1.534}, {"text": "Remember, we compared\ndipole moments of molecules.", "start": 484.765, "duration": 3.237}, {"text": "And if you have a diaper\nmoment in a molecule,", "start": 488.002, "duration": 1.902}, {"text": "then that dipole moment can\ntalk to another dipole moment", "start": 489.904, "duration": 3.17}, {"text": "and be interacting with it.", "start": 493.074, "duration": 1.635}, {"text": "So that's a kind of bond.", "start": 494.709, "duration": 2.002}, {"text": "And is that it?", "start": 496.711, "duration": 1.168}, {"text": "London, London is always there.", "start": 501.149, "duration": 3.236}, {"text": "It's always there.", "start": 504.385, "duration": 1.068}, {"text": "We've also got\nLondon, don't forget.", "start": 505.453, "duration": 1.968}, {"text": "So you'd have dipole-dipole\nplus London here.", "start": 507.421, "duration": 3.471}, {"text": "Dipole-dipole London and\nhydrogen, just London.", "start": 510.892, "duration": 4.804}, {"text": "So this is the kind\nof way I want--", "start": 515.696, "duration": 2.002}, {"text": "and you might be able\nto think about, well,", "start": 517.698, "duration": 1.802}, {"text": "would a trend-- if\nyou think about,", "start": 519.5, "duration": 1.934}, {"text": "like, OK well, if\na molecule just", "start": 521.434, "duration": 1.802}, {"text": "has London, then what\ndoes London depend on?", "start": 523.236, "duration": 4.506}, {"text": "All right, well, it depends\non the polarizability", "start": 527.742, "duration": 3.737}, {"text": "of the charge.", "start": 531.479, "duration": 0.701}, {"text": "So that can be\nsomething [INAUDIBLE]..", "start": 532.18, "duration": 1.568}, {"text": "It depends on the size because\nthat tells you how much--", "start": 533.748, "duration": 2.669}, {"text": "if I say, well, what about\nSIH4 compared to CH4?", "start": 536.417, "duration": 5.472}, {"text": "Which is going to be\nmore strongly bonded?", "start": 541.889, "duration": 3.203}, {"text": "You can answer that\nbecause you know", "start": 545.092, "duration": 1.769}, {"text": "the only force there is London.", "start": 546.861, "duration": 1.768}, {"text": "And you know for London, it's\nhow much contact area you have", "start": 548.629, "duration": 3.704}, {"text": "is going to be one\nof the factors.", "start": 552.333, "duration": 1.435}, {"text": "The more contact area, the\nmore chances these things", "start": 553.768, "duration": 2.269}, {"text": "can get close\nenough and polarize.", "start": 556.037, "duration": 2.536}, {"text": "And then polarizability\nwould be the other.", "start": 558.573, "duration": 3.87}, {"text": "All right, now we're\ngoing on to solids.", "start": 562.443, "duration": 2.302}, {"text": "Now, the big picture\nis pretty awesome.", "start": 564.745, "duration": 5.072}, {"text": "If you look at the\nbig picture, we", "start": 569.817, "duration": 1.502}, {"text": "have done the\nelectronic structure", "start": 571.319, "duration": 2.269}, {"text": "of atoms and molecules.", "start": 573.588, "duration": 2.402}, {"text": "So we've gone through\nand we've worked our way", "start": 575.99, "duration": 2.236}, {"text": "through the Bohr atom, the\natomic model, quantum numbers,", "start": 578.226, "duration": 3.636}, {"text": "Aufbau, what happens when\nyou go from one electron", "start": 581.862, "duration": 2.903}, {"text": "to many, and octet stability,\nwhich is Lewis and Vesper.", "start": 584.765, "duration": 4.872}, {"text": "We have also now talked about\nhow molecules come together", "start": 589.637, "duration": 3.637}, {"text": "in different ways, how the atoms\ncome together in the molecule,", "start": 593.274, "duration": 2.636}, {"text": "and how the molecules come\ntogether in different ways.", "start": 595.91, "duration": 2.436}, {"text": "Dipole-dipole, London\ndispersion, hydrogen bonding.", "start": 598.346, "duration": 4.07}, {"text": "And then there's these\nforms of aggregation,", "start": 602.416, "duration": 1.869}, {"text": "gas, liquid, and solid.", "start": 604.285, "duration": 1.034}, {"text": "And of course, we're\nexcited about this.", "start": 605.319, "duration": 2.403}, {"text": "So I put my little emoji\nthere, because that's", "start": 607.722, "duration": 4.004}, {"text": "what we're going to do now.", "start": 611.726, "duration": 1.301}, {"text": "We're actually going to take--", "start": 613.027, "duration": 1.702}, {"text": "we talked a little bit\nabout solids already,", "start": 614.729, "duration": 1.835}, {"text": "but now we're going to take the\nelectronic structure that we've", "start": 616.564, "duration": 3.737}, {"text": "built up, these orbitals.", "start": 620.301, "duration": 2.836}, {"text": "And we're going to make\nsolids out of them.", "start": 623.137, "duration": 2.669}, {"text": "So this is the week where these\nare the next two weeks, right,", "start": 625.806, "duration": 5.072}, {"text": "where we're going to\ntalk a lot about solids.", "start": 630.878, "duration": 3.237}, {"text": "And this week, this\nweek we're going", "start": 634.115, "duration": 7.607}, {"text": "to do the electronic structure.", "start": 641.722, "duration": 3.504}, {"text": "And next week, we're\ngoing to do atoms.", "start": 645.226, "duration": 5.705}, {"text": "So that's our plan.", "start": 650.931, "duration": 3.07}, {"text": "And next week Friday, we're\ngoing to break a bunch of stuff", "start": 654.001, "duration": 2.469}, {"text": "with parents.", "start": 656.47, "duration": 1.235}, {"text": "So this week we're [INAUDIBLE].", "start": 657.705, "duration": 1.668}, {"text": "What do electrons do in solids?", "start": 659.373, "duration": 2.002}, {"text": "Next week, how do atoms\narrange in solids?", "start": 661.375, "duration": 2.202}, {"text": "And together, that gives\nus so much understanding", "start": 663.577, "duration": 2.87}, {"text": "of how chemistry effects\nproperties in solids.", "start": 666.447, "duration": 5.072}, {"text": "So that's the big picture.", "start": 671.519, "duration": 1.234}, {"text": "Now, here's the thing,\nwhy does that matter?", "start": 672.753, "duration": 2.536}, {"text": "Well, because so many\nproperties can vary by so much", "start": 675.289, "duration": 5.172}, {"text": "depending on what I just said.", "start": 680.461, "duration": 1.869}, {"text": "How does chemistry affect\nproperties in solids?", "start": 682.33, "duration": 3.003}, {"text": "Well, it's complicated,\nbut look at this variation.", "start": 685.333, "duration": 4.004}, {"text": "28 orders of magnitude of\nconnectivity, electrical", "start": 689.337, "duration": 3.103}, {"text": "conductivity.", "start": 692.44, "duration": 1.6}, {"text": "28 orders of magnitude,\nthat's a lot of zeros.", "start": 694.04, "duration": 4.973}, {"text": "[INAUDIBLE]", "start": 699.013, "duration": 0.5}, {"text": "These are the electrical\nconductivities", "start": 699.513, "duration": 1.602}, {"text": "of different atoms,\ndifferent materials.", "start": 701.115, "duration": 4.838}, {"text": "And you can see that it's going\nto depend on what you have,", "start": 705.953, "duration": 4.238}, {"text": "but it's also going to depend\non-- so that's the chemistry.", "start": 710.191, "duration": 2.736}, {"text": "But it's also going to\ndepend on the bonding.", "start": 712.927, "duration": 2.202}, {"text": "It's going to depend on how\nthe electronic structure comes", "start": 715.129, "duration": 3.17}, {"text": "together.", "start": 718.299, "duration": 0.7}, {"text": "And it's going to depend on\nhow the atoms come together.", "start": 718.999, "duration": 2.436}, {"text": "That is what will explain\n28 orders of magnitude.", "start": 721.435, "duration": 4.438}, {"text": "That is a lot of variation.", "start": 725.873, "duration": 3.07}, {"text": "So we start by thinking about\nhow electrons see these solids.", "start": 728.943, "duration": 4.671}, {"text": "That's how we're going to start.", "start": 733.614, "duration": 1.735}, {"text": "Now, the thing is that\nthese good old days", "start": 735.349, "duration": 3.37}, {"text": "of molecular orbital\ntheory are going to end.", "start": 738.719, "duration": 4.304}, {"text": "They're going to\nhave to end today.", "start": 743.023, "duration": 1.435}, {"text": "No, they're not ending for\nlike quizzes and exams.", "start": 744.458, "duration": 3.704}, {"text": "Don't forget about them.", "start": 748.162, "duration": 1.235}, {"text": "But we've got to move\non because this is just", "start": 749.397, "duration": 2.569}, {"text": "two atoms, two atoms.", "start": 751.966, "duration": 4.638}, {"text": "But what happens when\nwe have like a solid?", "start": 756.604, "duration": 4.037}, {"text": "How many atoms do we have?", "start": 760.641, "duration": 2.069}, {"text": "We've got a lot.", "start": 762.71, "duration": 1.101}, {"text": "We've got a lot.", "start": 763.811, "duration": 0.734}, {"text": "So let's go-- we'll go here.", "start": 764.545, "duration": 2.736}, {"text": "OK, now, if you think about\nthat picture, that was our--", "start": 767.281, "duration": 4.972}, {"text": "I'm going to take 1s orbitals.", "start": 772.253, "duration": 3.103}, {"text": "And let's just think\nabout this for a second.", "start": 775.356, "duration": 4.471}, {"text": "If we take 1s\norbitals and you have", "start": 779.827, "duration": 2.97}, {"text": "two atoms that come\ntogether, well, they're", "start": 782.797, "duration": 3.637}, {"text": "going to do just what\nyou see there where", "start": 786.434, "duration": 6.206}, {"text": "you've got your 1s and your 1s.", "start": 792.64, "duration": 2.435}, {"text": "I'm not even going\nto fill these out,", "start": 795.075, "duration": 1.569}, {"text": "and they're sigma\nand sigma star.", "start": 796.644, "duration": 3.103}, {"text": "And so that would be like two\n1s orbitals that I have either--", "start": 799.747, "duration": 4.705}, {"text": "OK, so up here, I took one.", "start": 804.452, "duration": 2.902}, {"text": "It was a positive\nand I subtracted one.", "start": 807.354, "duration": 2.903}, {"text": "And here, I took\none and I added one.", "start": 810.257, "duration": 4.972}, {"text": "And remember, this\ngave us this and this.", "start": 815.229, "duration": 3.67}, {"text": "And this gave us the\nbonding orbital, right?", "start": 818.899, "duration": 3.904}, {"text": "Bonding, anti-bonding.", "start": 822.803, "duration": 2.002}, {"text": "It all came from LCAO.", "start": 824.805, "duration": 2.002}, {"text": "LCAO is the linear combination\nof atomic orbitals.", "start": 826.807, "duration": 2.87}, {"text": "That's the theory\nwe use to build", "start": 829.677, "duration": 1.434}, {"text": "up our [INAUDIBLE] theory.", "start": 831.111, "duration": 1.836}, {"text": "But now, we've got\nto go a lot further.", "start": 832.947, "duration": 3.336}, {"text": "So I'm going to--\nbecause I don't", "start": 836.283, "duration": 2.203}, {"text": "want to keep adding things here\nand here, it gets complicated.", "start": 838.486, "duration": 4.07}, {"text": "I'm trying to find the MOs for\nmore, and more, and more atoms", "start": 842.556, "duration": 5.739}, {"text": "because I've got to put a\nwhole lot into my solid.", "start": 848.295, "duration": 3.837}, {"text": "So I'm going to write\nthem just on one side.", "start": 852.132, "duration": 2.169}, {"text": "If I write the two\nhere like that,", "start": 854.301, "duration": 4.838}, {"text": "and that would be\nsigma and sigma star,", "start": 859.139, "duration": 2.169}, {"text": "then you know what\nI'm talking about.", "start": 861.308, "duration": 1.535}, {"text": "I'm taking the two\nand I'm combining them", "start": 862.843, "duration": 1.535}, {"text": "in two different ways.", "start": 864.378, "duration": 1.034}, {"text": "But what if I had three?", "start": 865.412, "duration": 1.602}, {"text": "Well see, if I had three--", "start": 867.014, "duration": 2.536}, {"text": "so I've got three\ns orbitals now.", "start": 869.55, "duration": 2.936}, {"text": "So if I've got three s orbitals,\nthen if you think about it,", "start": 872.486, "duration": 5.906}, {"text": "I could also add them like that.", "start": 878.392, "duration": 4.938}, {"text": "That would be a very\nnice bonding orbital.", "start": 883.33, "duration": 2.636}, {"text": "If you add them,\nyou see that they're", "start": 885.966, "duration": 1.702}, {"text": "going to have the same kind\nof really nice bonding.", "start": 887.668, "duration": 2.536}, {"text": "But I can also subtract\none in the middle.", "start": 890.204, "duration": 2.736}, {"text": "And if I did that--", "start": 892.94, "duration": 2.135}, {"text": "so I had a plus,\nminus, plus there.", "start": 895.075, "duration": 4.405}, {"text": "So those are the signs,\nplus s, minus s, plus s.", "start": 899.48, "duration": 4.304}, {"text": "Then you can see that in-between\nthose, as I add these together,", "start": 903.784, "duration": 3.504}, {"text": "you have nodes.", "start": 907.288, "duration": 1.735}, {"text": "So this is not going to look\nlike a very happy bonding", "start": 909.023, "duration": 3.737}, {"text": "situation.", "start": 912.76, "duration": 0.667}, {"text": "I'm going to have\nsomething in there", "start": 913.427, "duration": 1.768}, {"text": "and then something in there.", "start": 915.195, "duration": 1.769}, {"text": "That's what that's going to\nlook like as I bring them closer", "start": 916.964, "duration": 2.502}, {"text": "and try to add them.", "start": 919.466, "duration": 1.235}, {"text": "I made two nodes here.", "start": 920.701, "duration": 2.97}, {"text": "Well, there's one other\nway you could do this.", "start": 923.671, "duration": 2.469}, {"text": "And we know that the number\nof molecular orbitals", "start": 926.14, "duration": 3.136}, {"text": "has to equal the number\nof atomic orbitals.", "start": 929.276, "duration": 3.003}, {"text": "We know that.", "start": 932.279, "duration": 0.734}, {"text": "So there's one\nmore that we mean,", "start": 933.013, "duration": 1.969}, {"text": "because I started\nwith three s's.", "start": 934.982, "duration": 2.235}, {"text": "And you can kind of see that.", "start": 937.217, "duration": 1.802}, {"text": "You can see that because\nif I had a plus and a plus,", "start": 939.019, "duration": 5.306}, {"text": "if I had done it that way\nor maybe the other way,", "start": 944.325, "duration": 3.069}, {"text": "maybe this was\nover there, but you", "start": 947.394, "duration": 2.203}, {"text": "see I got a little bonding\ngoing on in here between them.", "start": 949.597, "duration": 2.902}, {"text": "And I got an anti-bonding there.", "start": 952.499, "duration": 2.336}, {"text": "It's almost like it\nkind of cancels out.", "start": 954.835, "duration": 2.002}, {"text": "So you can imagine that\nthat combination of s", "start": 956.837, "duration": 3.837}, {"text": "orbitals, if I add and\nsubtract them this way,", "start": 960.674, "duration": 2.036}, {"text": "it's going to be somewhere\nright in the middle.", "start": 962.71, "duration": 3.203}, {"text": "Maybe not so bonding,\nmaybe not so anti-bonding.", "start": 965.913, "duration": 2.636}, {"text": "OK, good.", "start": 968.549, "duration": 2.469}, {"text": "All right, well let's do four.", "start": 971.018, "duration": 2.035}, {"text": "So if I had four, if\nI started with four--", "start": 973.053, "duration": 3.571}, {"text": "this is like four\nhydrogen atoms, let's say,", "start": 976.624, "duration": 2.235}, {"text": "although I'm not filling it yet.", "start": 978.859, "duration": 1.502}, {"text": "But so four 1s orbitals.", "start": 980.361, "duration": 2.902}, {"text": "Well now you see,\nI could do this.", "start": 983.263, "duration": 3.504}, {"text": "I can add them all up and get\nthis super awesome bonding", "start": 986.767, "duration": 3.237}, {"text": "state.", "start": 990.004, "duration": 0.5}, {"text": "I could also alternate\nthem so that everything", "start": 993.674, "duration": 6.139}, {"text": "is anti-bonding.", "start": 999.813, "duration": 1.836}, {"text": "Look at that.", "start": 1001.649, "duration": 1.067}, {"text": "These are going to cancel\nas you bring them together", "start": 1002.716, "duration": 2.536}, {"text": "and you're going to get\nanti-bonding, anti-bonding.", "start": 1005.252, "duration": 3.036}, {"text": "But there's also two other\noptions that are in between.", "start": 1008.288, "duration": 4.739}, {"text": "Right here, I can add\n2 and then subtract 2.", "start": 1013.027, "duration": 5.105}, {"text": "And you can see, these\nare both negative.", "start": 1018.132, "duration": 2.736}, {"text": "And as they come\ntogether, they're", "start": 1020.868, "duration": 1.401}, {"text": "going to overlap\nconstructively, so will these.", "start": 1022.269, "duration": 2.435}, {"text": "But in the middle\nhere, they're going", "start": 1024.704, "duration": 1.702}, {"text": "to be kind of\ndestructive interference.", "start": 1026.406, "duration": 3.871}, {"text": "And so you're going to have\nthis one node in between.", "start": 1030.277, "duration": 3.337}, {"text": "But in general, you\ncan imagine, this", "start": 1033.614, "duration": 1.568}, {"text": "will be more bonding\nthan anti-bonding,", "start": 1035.182, "duration": 2.435}, {"text": "so we draw it down\nbelow the middle.", "start": 1037.617, "duration": 2.236}, {"text": "Whereas up here, you could\nalso imagine something", "start": 1039.853, "duration": 3.303}, {"text": "like this, where you\nstart with a plus", "start": 1043.156, "duration": 2.87}, {"text": "and you put two minuses in\nthere and a plus over there.", "start": 1046.026, "duration": 3.804}, {"text": "I'm just adding and subtracting.", "start": 1049.83, "duration": 1.668}, {"text": "I'm just taking LCAO\ntheory and moving it", "start": 1051.498, "duration": 2.836}, {"text": "to more than two orbitals.", "start": 1054.334, "duration": 2.837}, {"text": "OK, so now you can\nactually understand this", "start": 1057.171, "duration": 3.169}, {"text": "from a number of nodes, right?", "start": 1060.34, "duration": 1.402}, {"text": "This is like three nodes.", "start": 1061.742, "duration": 3.337}, {"text": "This is two nodes over there.", "start": 1065.079, "duration": 4.804}, {"text": "This is one node.", "start": 1069.883, "duration": 3.404}, {"text": "And zero nodes.", "start": 1073.287, "duration": 2.169}, {"text": "This is exactly\nthe kind of thing", "start": 1075.456, "duration": 2.002}, {"text": "we talked about already,\nbut for only two orbitals.", "start": 1077.458, "duration": 2.435}, {"text": "Now we're just\ncontinuing it along.", "start": 1079.893, "duration": 2.503}, {"text": "OK, you can see why the good\nold days are over, because see,", "start": 1082.396, "duration": 4.604}, {"text": "now we've got to\njump this up a level.", "start": 1087.0, "duration": 3.37}, {"text": "And we've got to think,\nhow many s orbitals", "start": 1090.37, "duration": 2.47}, {"text": "do I have in a typical\npiece of matter?", "start": 1092.84, "duration": 3.403}, {"text": "How many do you think?", "start": 1096.243, "duration": 3.437}, {"text": "Take a guess.", "start": 1099.68, "duration": 0.667}, {"text": "Roughly?", "start": 1103.851, "duration": 1.701}, {"text": "Take a chunk of\nhydrogen this big.", "start": 1105.552, "duration": 2.67}, {"text": "How many atoms do I have?", "start": 1108.222, "duration": 3.603}, {"text": "A mole, exactly.", "start": 1111.825, "duration": 1.669}, {"text": "That's why we\ninvented the mole, so", "start": 1113.494, "duration": 2.936}, {"text": "that we could count big numbers\nby just saying 1, 1 mole.", "start": 1116.43, "duration": 5.138}, {"text": "But if I have a mole,\nthen I've got like 10", "start": 1121.568, "duration": 1.835}, {"text": "to the 24th of these.", "start": 1123.403, "duration": 1.869}, {"text": "I just went to four.", "start": 1125.272, "duration": 2.202}, {"text": "I just went to four.", "start": 1127.474, "duration": 2.303}, {"text": "But it just keeps on going.", "start": 1129.777, "duration": 1.601}, {"text": "So [INAUDIBLE].", "start": 1131.378, "duration": 1.335}, {"text": "So here is like, OK,\n1, orbital of atom.", "start": 1132.713, "duration": 5.072}, {"text": "Boy, I labeled that well.", "start": 1137.785, "duration": 1.768}, {"text": "2, bonding, anti-bonding\norbitals of molecules.", "start": 1139.553, "duration": 3.203}, {"text": "And then you see, OK, there's 3.", "start": 1142.756, "duration": 2.236}, {"text": "There's 4, 5.", "start": 1144.992, "duration": 1.768}, {"text": "Then you keep on going.", "start": 1146.76, "duration": 1.602}, {"text": "OK, they got a\nlittle tired and then", "start": 1148.362, "duration": 1.501}, {"text": "they wrote 30, 30 orbitals.", "start": 1149.863, "duration": 5.272}, {"text": "30 is still way, way far away.", "start": 1155.135, "duration": 2.836}, {"text": "But if you had 30s\norbitals, you might still", "start": 1157.971, "duration": 3.204}, {"text": "be able to kind of see\nthese lines discretely.", "start": 1161.175, "duration": 3.003}, {"text": "Remember, this is energy space.", "start": 1164.178, "duration": 1.334}, {"text": "There might actually--\nremember, like,", "start": 1165.512, "duration": 1.568}, {"text": "these energies are\nreally important,", "start": 1167.08, "duration": 1.669}, {"text": "the lines between the deltas.", "start": 1168.749, "duration": 1.501}, {"text": "But if you have a mole,\nif you have a mole,", "start": 1170.25, "duration": 4.805}, {"text": "it looks like one\ncontinuous set of lines.", "start": 1175.055, "duration": 2.369}, {"text": "These don't really\nlook discrete anymore.", "start": 1177.424, "duration": 4.138}, {"text": "These don't look discrete.", "start": 1181.562, "duration": 2.569}, {"text": "And so if you have a mole of\natoms, so if you have a solid,", "start": 1184.131, "duration": 5.238}, {"text": "we call that collection\nof orbitals that", "start": 1189.369, "duration": 5.072}, {"text": "are all stuck in here a band.", "start": 1194.441, "duration": 2.536}, {"text": "We call that a band.", "start": 1196.977, "duration": 2.236}, {"text": "OK, so if I take--", "start": 1199.213, "duration": 2.135}, {"text": "Now, I'm not going to\ndraw 10 to the 24th.", "start": 1201.348, "duration": 5.706}, {"text": "10 to the 24th s orbitals.", "start": 1207.054, "duration": 2.736}, {"text": "But pretend, pretend that\nthat's what I have here.", "start": 1209.79, "duration": 4.838}, {"text": "Then what happens?", "start": 1214.628, "duration": 1.401}, {"text": "What I do is I form a continuum\nof states, a continuum", "start": 1218.866, "duration": 4.27}, {"text": "of levels for those electrons.", "start": 1223.136, "duration": 2.036}, {"text": "And this, they're\nso packed together,", "start": 1225.172, "duration": 2.869}, {"text": "we don't even draw\nthem as lines.", "start": 1228.041, "duration": 1.368}, {"text": "We can't.", "start": 1229.409, "duration": 1.569}, {"text": "So this is called the 1s band.", "start": 1230.978, "duration": 4.271}, {"text": "Oh, band.", "start": 1235.249, "duration": 2.168}, {"text": "It's a band.", "start": 1237.417, "duration": 1.335}, {"text": "It's a band of states.", "start": 1238.752, "duration": 2.002}, {"text": "It's a band of states.", "start": 1240.754, "duration": 1.969}, {"text": "It's the 1s band.", "start": 1242.723, "duration": 2.769}, {"text": "Now, there are some\nimportant rules", "start": 1245.492, "duration": 3.537}, {"text": "that are really just the same\nbut we follow them here too.", "start": 1249.029, "duration": 4.071}, {"text": "And so I want to emphasize them.", "start": 1253.1, "duration": 1.935}, {"text": "We've already learned\nthem for molecules.", "start": 1255.035, "duration": 2.035}, {"text": "They holds for bands and solids.", "start": 1257.07, "duration": 2.77}, {"text": "All right, so now, for example,\nlet's think about this.", "start": 1259.84, "duration": 5.705}, {"text": "Each of these orbitals could\noccupy how many electrons?", "start": 1265.545, "duration": 6.374}, {"text": "Two.", "start": 1271.919, "duration": 1.301}, {"text": "So I have two electrons\nfor each s orbital, s orb.", "start": 1273.22, "duration": 8.709}, {"text": "Well, you know, if you think\nabout that, then for n atoms,", "start": 1281.929, "duration": 6.239}, {"text": "and here what did I\nsay, 10 to the 24.", "start": 1288.168, "duration": 2.703}, {"text": "Because there is one s orbital\nthat comes from each atom.", "start": 1290.871, "duration": 3.37}, {"text": "So for n atoms, then I\nwould have 2n electrons", "start": 1294.241, "duration": 8.642}, {"text": "can go into the one s band.", "start": 1302.883, "duration": 6.406}, {"text": "So if I have--", "start": 1309.289, "duration": 1.802}, {"text": "that makes sense, right?", "start": 1311.091, "duration": 1.101}, {"text": "Because I had two for each\norbital, and I had that many.", "start": 1312.192, "duration": 2.436}, {"text": "So if I know how many atoms I\nhave that make up this solid,", "start": 1314.628, "duration": 5.605}, {"text": "then that's how many electrons\nthat band can have in it.", "start": 1320.233, "duration": 2.903}, {"text": "All we did is go from the atomic\norbital picture to the solid", "start": 1323.136, "duration": 3.871}, {"text": "to the mole.", "start": 1327.007, "duration": 1.668}, {"text": "OK, why am I saying that?", "start": 1328.675, "duration": 2.303}, {"text": "Because filling is\nincredibly important", "start": 1330.978, "duration": 6.84}, {"text": "And it happens in the\nsame way-- just like it", "start": 1337.818, "duration": 2.102}, {"text": "was so important for\nmolecular orbitals,", "start": 1339.92, "duration": 2.469}, {"text": "it's also critical for bands.", "start": 1342.389, "duration": 2.035}, {"text": "So filling is like MOs.", "start": 1344.424, "duration": 5.472}, {"text": "It's just like in MOs,\nstart from lowest energy.", "start": 1349.896, "duration": 9.743}, {"text": "Then fill up.", "start": 1363.777, "duration": 1.134}, {"text": "So you know, if you\nthink about this,", "start": 1368.081, "duration": 2.503}, {"text": "if I had-- now I'm\ngoing to actually say,", "start": 1370.584, "duration": 2.436}, {"text": "well, OK, I made the one s band\nby combining these orbitals.", "start": 1373.02, "duration": 3.37}, {"text": "Now I'm going to\nsee what I have,", "start": 1376.39, "duration": 2.202}, {"text": "which tells me how to fill it.", "start": 1378.592, "duration": 1.468}, {"text": "Now I have hydrogen. So\nif this is the one s band", "start": 1380.06, "duration": 8.608}, {"text": "and I have hydrogen, hydrogen\nhas, for each hydrogen,", "start": 1388.668, "duration": 9.276}, {"text": "I've got one electron.", "start": 1397.944, "duration": 2.236}, {"text": "But I just said that\nin the one band,", "start": 1400.18, "duration": 2.502}, {"text": "for each atom I could\nhave put two electrons.", "start": 1402.682, "duration": 2.203}, {"text": "So you know if this is made\nof hydrogen, it's half filled,", "start": 1404.885, "duration": 3.637}, {"text": "which is exactly what\nthat picture shows.", "start": 1408.522, "duration": 3.77}, {"text": "That's the filling.", "start": 1412.292, "duration": 0.801}, {"text": "You see it's filled half way.", "start": 1413.093, "duration": 1.635}, {"text": "The band is filled halfway.", "start": 1414.728, "duration": 1.802}, {"text": "It's like the MO\npicture, but it's not", "start": 1416.53, "duration": 6.573}, {"text": "because I've made a\ncontinuous band out of it.", "start": 1423.103, "duration": 2.269}, {"text": "So instead of putting\nlines here, lines there,", "start": 1425.372, "duration": 2.502}, {"text": "and then occupying\nthem with arrows,", "start": 1427.874, "duration": 2.269}, {"text": "I fill them up with 10\nto the 24-ish electrons.", "start": 1430.143, "duration": 5.539}, {"text": "So we fill bands up like that.", "start": 1435.682, "duration": 1.301}, {"text": "And we know that\nit's half filled", "start": 1436.983, "duration": 1.368}, {"text": "because it's hydrogen.\nAnother thing", "start": 1438.351, "duration": 2.837}, {"text": "that we know is\nthat the energy--", "start": 1441.188, "duration": 4.304}, {"text": "remember this?", "start": 1445.492, "duration": 2.736}, {"text": "This is also important.", "start": 1448.228, "duration": 4.371}, {"text": "That energy is related to\ninteraction and overlap.", "start": 1452.599, "duration": 8.108}, {"text": "This is something we talked\nabout, interaction and overlap", "start": 1460.707, "duration": 5.739}, {"text": "of the orbitals.", "start": 1466.446, "duration": 1.101}, {"text": "How much does that band\ngo up and down in energy?", "start": 1467.547, "duration": 5.706}, {"text": "This is something\nwe've talked about.", "start": 1473.253, "duration": 1.535}, {"text": "How much that band\ngoes up and in energy,", "start": 1474.788, "duration": 1.702}, {"text": "it's just like in\nthe H2 molecule.", "start": 1476.49, "duration": 4.738}, {"text": "One s, one s,\nsigma, sigma, star.", "start": 1481.228, "duration": 2.168}, {"text": "How far apart are\nsigma star and energy?", "start": 1483.396, "duration": 2.503}, {"text": "Well, it depends on the\ninteraction strength", "start": 1485.899, "duration": 2.369}, {"text": "and the overlap\nbetween those orbitals.", "start": 1488.268, "duration": 2.736}, {"text": "The same is true in solids.", "start": 1491.004, "duration": 2.503}, {"text": "Same is true in solids.", "start": 1493.507, "duration": 1.034}, {"text": "So what is the\nwidth of that band?", "start": 1494.541, "duration": 4.671}, {"text": "How spread out\nover energy is it?", "start": 1499.212, "duration": 2.97}, {"text": "OK, so those are\nsome ground rules.", "start": 1502.182, "duration": 3.437}, {"text": "Now, what else can we say?", "start": 1505.619, "duration": 2.435}, {"text": "OK, so there's the\nabsolute least bonding", "start": 1508.054, "duration": 2.403}, {"text": "state, anti-bonding, all the\nway up there, the most bonding.", "start": 1510.457, "duration": 3.103}, {"text": "And then you've got\nalmost infinite number", "start": 1513.56, "duration": 2.469}, {"text": "of possibilities in between.", "start": 1516.029, "duration": 1.268}, {"text": "But the thing is that filling\ndetermines the properties.", "start": 1519.9, "duration": 7.173}, {"text": "You can't just know the\nbands or the band structure,", "start": 1527.073, "duration": 4.672}, {"text": "as it's called.", "start": 1531.745, "duration": 2.068}, {"text": "But you have to\nknow the filling.", "start": 1533.813, "duration": 1.736}, {"text": "And when you have a\nsituation like this--", "start": 1535.549, "duration": 3.837}, {"text": "so let's write this down.", "start": 1539.386, "duration": 1.434}, {"text": "When you have partial\nfilling, partially", "start": 1543.49, "duration": 6.606}, {"text": "filled band is a metal.", "start": 1550.096, "duration": 5.439}, {"text": "And I will talk about\nmetals on Friday.", "start": 1559.339, "duration": 3.403}, {"text": "So we will come\nback to that concept", "start": 1562.742, "duration": 2.236}, {"text": "and the electronic structure\nof metals on Friday.", "start": 1564.978, "duration": 4.271}, {"text": "But today, I want to talk about\nsomething else that happens,", "start": 1569.249, "duration": 3.804}, {"text": "which is when you fill not\nin the middle of a band,", "start": 1573.053, "duration": 5.272}, {"text": "not in the middle, but maybe\nall the way up to the top.", "start": 1578.325, "duration": 2.535}, {"text": "And there's a gap.", "start": 1580.86, "duration": 1.702}, {"text": "That's a different\nkind of material.", "start": 1582.562, "duration": 2.536}, {"text": "So if filling stops somewhere\npartially in the band,", "start": 1585.098, "duration": 2.302}, {"text": "in the middle of a\nband, if you're filling,", "start": 1587.4, "duration": 1.802}, {"text": "you're counting, and you\ndidn't go all the way up,", "start": 1589.202, "duration": 3.57}, {"text": "then you have a metal.", "start": 1592.772, "duration": 2.736}, {"text": "But the thing is,\nhere we've only", "start": 1595.508, "duration": 1.368}, {"text": "talked about one kind of band.", "start": 1596.876, "duration": 2.169}, {"text": "This is the s band.", "start": 1599.045, "duration": 1.502}, {"text": "But every single one of these--", "start": 1600.547, "duration": 4.171}, {"text": "look at this, I can\ntake a mole of orbitals", "start": 1604.718, "duration": 3.503}, {"text": "and make an s band, like that.", "start": 1608.221, "duration": 3.237}, {"text": "And then, oh, that was 1s.", "start": 1611.458, "duration": 1.701}, {"text": "Here's 2s.", "start": 1613.159, "duration": 2.103}, {"text": "And look at this, I can take the\np electrons and make a p band.", "start": 1615.262, "duration": 6.673}, {"text": "2p band.", "start": 1621.935, "duration": 1.301}, {"text": "I can do this with\nevery single--", "start": 1623.236, "duration": 2.736}, {"text": "2s, 1s, right?", "start": 1625.972, "duration": 3.203}, {"text": "So depending on a\nbunch of factors,", "start": 1629.175, "duration": 7.174}, {"text": "these bands could\nlook different.", "start": 1636.349, "duration": 3.704}, {"text": "What does it depend on?", "start": 1640.053, "duration": 1.168}, {"text": "So this is-- the way these\nbands are organized, right,", "start": 1641.221, "duration": 5.472}, {"text": "we know now that\nthese orbitals will", "start": 1646.693, "duration": 3.537}, {"text": "come together like I've drawn\nthere and there and form bands.", "start": 1650.23, "duration": 4.838}, {"text": "What is the difference\nbetween these?", "start": 1655.068, "duration": 2.97}, {"text": "Did they overlap, maybe?", "start": 1658.038, "duration": 2.836}, {"text": "Are they very far in energy?", "start": 1660.874, "duration": 2.369}, {"text": "These things depend on atom--", "start": 1663.243, "duration": 3.637}, {"text": "depends on the atom and the\nbonding and the structure.", "start": 1670.05, "duration": 11.678}, {"text": "How do those bands look?", "start": 1688.368, "duration": 2.502}, {"text": "Well, it depends.", "start": 1690.87, "duration": 1.469}, {"text": "And we'll be talking\nabout some examples.", "start": 1692.339, "duration": 2.469}, {"text": "But for now, I want to focus\non that filling thing again.", "start": 1694.808, "duration": 6.039}, {"text": "What happens if I--", "start": 1700.847, "duration": 4.204}, {"text": "if I fill this 1s up to\nhalf way, it's a metal.", "start": 1705.051, "duration": 3.437}, {"text": "If I keep filling,\nkeep adding electrons,", "start": 1708.488, "duration": 2.169}, {"text": "and I fill this up\nhalfway, it's a metal.", "start": 1710.657, "duration": 4.071}, {"text": "But if I stop filling,\nyou know, if I fill this", "start": 1714.728, "duration": 4.704}, {"text": "and then I fill this, and then\nthere's some space in energy", "start": 1719.432, "duration": 4.538}, {"text": "and I didn't fill any\nmore, that's not a metal.", "start": 1723.97, "duration": 2.97}, {"text": "That's not a metal.", "start": 1726.94, "duration": 1.468}, {"text": "So if there's a gap--", "start": 1728.408, "duration": 1.134}, {"text": "so there can be gaps between\nbands, which I just showed you.", "start": 1729.542, "duration": 3.337}, {"text": "That's between an\ns and a p band.", "start": 1732.879, "duration": 3.27}, {"text": "And then the filling\ndetermines the properties.", "start": 1736.149, "duration": 1.969}, {"text": "And they're so important.", "start": 1738.118, "duration": 1.768}, {"text": "They're so important.", "start": 1739.886, "duration": 1.468}, {"text": "So let's talk about that.", "start": 1741.354, "duration": 1.068}, {"text": "I want to talk about these.", "start": 1742.422, "duration": 1.435}, {"text": "What we're going to\ndo is we're talking", "start": 1743.857, "duration": 2.102}, {"text": "about semiconductors today\nand Wednesday, and metals", "start": 1745.959, "duration": 6.072}, {"text": "on Friday.", "start": 1752.031, "duration": 1.569}, {"text": "And we're going to see it\nthrough the vantage point", "start": 1753.6, "duration": 2.369}, {"text": "of these electronic levels.", "start": 1755.969, "duration": 1.635}, {"text": "And then next week, we'll\nsee it through the vantage", "start": 1757.604, "duration": 2.169}, {"text": "point of atoms.", "start": 1759.773, "duration": 1.301}, {"text": "So, if you have a gap between--", "start": 1764.444, "duration": 4.738}, {"text": "well, you always have\ngaps, the question,", "start": 1769.182, "duration": 1.668}, {"text": "again, comes to filling.", "start": 1770.85, "duration": 2.236}, {"text": "If the filling stops--", "start": 1773.086, "duration": 1.068}, {"text": "I want to define this\nvery important-- so", "start": 1779.192, "duration": 3.036}, {"text": "if the filling stops,\nthen you have this highest", "start": 1782.228, "duration": 4.838}, {"text": "occupied level.", "start": 1787.066, "duration": 1.035}, {"text": "So let's suppose\nI have filling--", "start": 1788.101, "duration": 3.27}, {"text": "this is some band.", "start": 1791.371, "duration": 2.369}, {"text": "And this is some band.", "start": 1793.74, "duration": 1.668}, {"text": "And this is unoccupied.", "start": 1795.408, "duration": 2.903}, {"text": "So unoccupied by electrons.", "start": 1798.311, "duration": 4.037}, {"text": "This is fully\noccupied by electrons.", "start": 1802.348, "duration": 4.138}, {"text": "So what's going to happen?", "start": 1809.489, "duration": 1.668}, {"text": "Well, first of all, let's\njust get some terms.", "start": 1811.157, "duration": 3.337}, {"text": "The last band that I filled,\nthe last band that I filled,", "start": 1814.494, "duration": 4.037}, {"text": "is called the valence band.", "start": 1818.531, "duration": 1.368}, {"text": "Valence band.", "start": 1824.037, "duration": 2.269}, {"text": "And we use vb for short.", "start": 1826.306, "duration": 3.303}, {"text": "And the first band\nthat I don't fill", "start": 1829.609, "duration": 3.637}, {"text": "is called the conduction band.", "start": 1833.246, "duration": 1.969}, {"text": "And as we talk more\nabout these materials,", "start": 1835.215, "duration": 5.138}, {"text": "you will see why\nthey're called that.", "start": 1840.353, "duration": 2.402}, {"text": "Conduction band.", "start": 1842.755, "duration": 0.668}, {"text": "But for now, just trust\nme in the labeling.", "start": 1846.759, "duration": 3.27}, {"text": "So the conduction band\nand the valence band", "start": 1850.029, "duration": 3.204}, {"text": "depend on the filling.", "start": 1853.233, "duration": 2.002}, {"text": "Because again, it's, you\nknow, it's where I filled to.", "start": 1855.235, "duration": 3.57}, {"text": "Now, the top level, the very,\nvery top level out of these 10", "start": 1858.805, "duration": 4.037}, {"text": "to the 24 level, that very\ntop one has a special name.", "start": 1862.842, "duration": 4.204}, {"text": "It's the vb maximum.", "start": 1867.046, "duration": 3.337}, {"text": "That makes sense, right?", "start": 1870.383, "duration": 1.001}, {"text": "It's the top valence\nband, or the vbn.", "start": 1871.384, "duration": 3.937}, {"text": "And the one down here\nalso has a special name,", "start": 1875.321, "duration": 2.903}, {"text": "it's the cb minimum, or cbm.", "start": 1878.224, "duration": 8.776}, {"text": "So the valence band maximum\nand the conduction band minimum", "start": 1887.0, "duration": 3.236}, {"text": "are, you know, it tells\nyou, if you think about it,", "start": 1890.236, "duration": 2.336}, {"text": "it tells you if you\nsubtracted those energies", "start": 1892.572, "duration": 2.936}, {"text": "between those parts\nof the band, you'd", "start": 1895.508, "duration": 2.603}, {"text": "get the distance and energy\nbetween the two bands.", "start": 1898.111, "duration": 2.269}, {"text": "So the conduction band\nminimum is this energy level", "start": 1903.55, "duration": 2.535}, {"text": "here and the valence\nband maximum energy is--", "start": 1906.085, "duration": 2.636}, {"text": "Now remember, valence electro--\nit's called the valence band.", "start": 1908.721, "duration": 2.703}, {"text": "It makes sense because\nvalence electrons, remember,", "start": 1911.424, "duration": 2.336}, {"text": "are those ones, as we talked\nabout with Louis, where you've", "start": 1913.76, "duration": 3.136}, {"text": "got kind of the bonding and\nthe action and the chemistry", "start": 1916.896, "duration": 2.336}, {"text": "happening.", "start": 1919.232, "duration": 0.934}, {"text": "And so this is\nthat top most state", "start": 1920.166, "duration": 3.07}, {"text": "of the top most valence band.", "start": 1923.236, "duration": 2.736}, {"text": "This is the valence\nband top most state.", "start": 1925.972, "duration": 1.668}, {"text": "And there's one more definition\nwe got to know about.", "start": 1930.343, "duration": 2.569}, {"text": "This is why we're\nsetting this up,", "start": 1932.912, "duration": 1.435}, {"text": "which is that that energy\ndifference here, oh, that", "start": 1934.347, "duration": 3.637}, {"text": "is really important.", "start": 1937.984, "duration": 2.336}, {"text": "So the energy of the\nconduction band minimum,", "start": 1940.32, "duration": 4.938}, {"text": "minus the energy of the\nvalence band maximum,", "start": 1945.258, "duration": 3.97}, {"text": "is equal to something called\nthe bandgap, energy gap.", "start": 1949.228, "duration": 6.507}, {"text": "It's the band gap.", "start": 1955.735, "duration": 0.734}, {"text": "This is an extremely important\nproperty of materials,", "start": 1960.54, "duration": 5.806}, {"text": "the electronic band gap.", "start": 1966.346, "duration": 1.468}, {"text": "What is the energy difference\nbetween the highest", "start": 1970.75, "duration": 2.269}, {"text": "occupied electrons and the\nlowest unoccupied electrons?", "start": 1973.019, "duration": 5.205}, {"text": "That's what we're talking about.", "start": 1978.224, "duration": 3.103}, {"text": "So if that filling,\nif that distance--", "start": 1981.327, "duration": 6.473}, {"text": "OK, so here's an\nelement, carbon,", "start": 1987.8, "duration": 2.837}, {"text": "in the diamond structure.", "start": 1990.637, "duration": 1.868}, {"text": "And just-- purple is filled\nand not purple is not filled.", "start": 1992.505, "duration": 4.938}, {"text": "So you know that that's\nthe connection band.", "start": 1997.443, "duration": 2.403}, {"text": "And that's the valence band.", "start": 1999.846, "duration": 1.268}, {"text": "And the band gap, which\nwe've just defined here,", "start": 2001.114, "duration": 3.703}, {"text": "is the energy difference\nbetween those.", "start": 2004.817, "duration": 4.305}, {"text": "And for diamond,\nit's really large.", "start": 2009.122, "duration": 2.002}, {"text": "For diamond, it's really large.", "start": 2011.124, "duration": 2.335}, {"text": "So you can see that, in\nfact, the gap is over--", "start": 2013.459, "duration": 4.338}, {"text": "if we converted this\nto electron-volts,", "start": 2017.797, "duration": 1.635}, {"text": "is more than five\nelectron-volts.", "start": 2019.432, "duration": 3.036}, {"text": "Now, I mentioned\nthermal energy in answer", "start": 2025.505, "duration": 3.67}, {"text": "to the question about water.", "start": 2029.175, "duration": 3.17}, {"text": "And room temperature--\nso room temperature,", "start": 2032.345, "duration": 6.306}, {"text": "the energy of room temperature,\nif you think about temperature", "start": 2038.651, "duration": 3.37}, {"text": "as an energy of like vibrational\nmotion, and you can do that.", "start": 2042.021, "duration": 5.906}, {"text": "You use something called\nthe Boltzmann constant", "start": 2047.927, "duration": 3.569}, {"text": "and you can get what the\nroom temperature energy is.", "start": 2051.496, "duration": 2.537}, {"text": "And it's something like\n0.025 electron-volts.", "start": 2054.033, "duration": 5.005}, {"text": "Seems pretty small.", "start": 2059.038, "duration": 1.634}, {"text": "So the point is, if that's the\nenergy, the thermal energy I", "start": 2060.672, "duration": 4.471}, {"text": "have at room temperature,\nthen if my bandgap is so much", "start": 2065.143, "duration": 5.473}, {"text": "larger than that, is\nso much larger than", "start": 2070.616, "duration": 2.536}, {"text": "that, it means those electrons\nare always going to be stuck.", "start": 2073.152, "duration": 3.904}, {"text": "They're never going to,\neven in some accident,", "start": 2077.056, "duration": 3.237}, {"text": "have enough thermal energy\nto come up and be excited.", "start": 2080.293, "duration": 4.337}, {"text": "We'll talk about this later.", "start": 2084.63, "duration": 3.971}, {"text": "So they're really stuck.", "start": 2088.601, "duration": 1.301}, {"text": "And if an electron is\nin the valence band,", "start": 2089.902, "duration": 3.17}, {"text": "it can't move very well.", "start": 2093.072, "duration": 2.036}, {"text": "It can't move-- it's kind\nof stuck in those bonds.", "start": 2095.108, "duration": 3.269}, {"text": "It's kind of stuck\nin those bonds.", "start": 2098.377, "duration": 1.802}, {"text": "And so here, if there is\nelectrons all stuck here,", "start": 2100.179, "duration": 4.138}, {"text": "and they never have a\nchance to go up here", "start": 2104.317, "duration": 2.002}, {"text": "where they can\ntravel freely, this", "start": 2106.319, "duration": 2.903}, {"text": "is really going to\nbe an insulator.", "start": 2109.222, "duration": 1.635}, {"text": "This is not going to carry\nelectrons through the material.", "start": 2110.857, "duration": 4.337}, {"text": "So that's an insulator.", "start": 2115.194, "duration": 0.968}, {"text": "When you have a very\nlarge bandgap like that,", "start": 2116.162, "duration": 2.569}, {"text": "we call that an insulator.", "start": 2118.731, "duration": 3.037}, {"text": "OK, but see if we compare--", "start": 2121.768, "duration": 1.501}, {"text": "and this is\ninteresting, you're just", "start": 2123.269, "duration": 1.502}, {"text": "going down in the periodic\ntable if you compare diamond", "start": 2124.771, "duration": 3.737}, {"text": "to silicon to germanium.", "start": 2128.508, "duration": 4.137}, {"text": "Well, see, what happens is\nthe bandgap gets smaller.", "start": 2132.645, "duration": 3.203}, {"text": "I'm still filling them all the\nway up to the top of a band.", "start": 2135.848, "duration": 4.038}, {"text": "So I'm not a metal.", "start": 2139.886, "duration": 2.802}, {"text": "If I'm a metal, it's because\nmy filling stopped somewhere", "start": 2142.688, "duration": 2.57}, {"text": "in the middle of the band.", "start": 2145.258, "duration": 1.535}, {"text": "I'm not a metal.", "start": 2146.793, "duration": 1.501}, {"text": "I'm a semi conductor\nand not an insulator.", "start": 2148.294, "duration": 3.136}, {"text": "And the reason I'm\na semi conductor", "start": 2151.43, "duration": 1.902}, {"text": "is that my bandgap\nis kind of small", "start": 2153.332, "duration": 2.036}, {"text": "enough so that electrons\ncan kind of jump from here", "start": 2155.368, "duration": 3.804}, {"text": "up to there, sometimes.", "start": 2159.172, "duration": 4.237}, {"text": "Sometimes.", "start": 2163.409, "duration": 2.002}, {"text": "That's why it's called\na semi conductor.", "start": 2165.411, "duration": 4.204}, {"text": "They kind of conduct electrons.", "start": 2169.615, "duration": 2.436}, {"text": "So the electron can get\nup to the conduction", "start": 2172.051, "duration": 3.937}, {"text": "band in a semiconductor more\neasily than an insulator.", "start": 2175.988, "duration": 3.671}, {"text": "And that's why it can conduct\nelectricity much better", "start": 2179.659, "duration": 3.203}, {"text": "than an insulator, many, many,\nmany orders of magnitude.", "start": 2182.862, "duration": 4.504}, {"text": "But the way that we have\ntalked about getting", "start": 2187.366, "duration": 2.002}, {"text": "electrons excited,\ngetting electrons excited,", "start": 2189.368, "duration": 3.871}, {"text": "is with light.", "start": 2193.239, "duration": 1.568}, {"text": "And we can do that\nfor solids, too.", "start": 2194.807, "duration": 2.636}, {"text": "We can do the same\nthing for solids.", "start": 2197.443, "duration": 2.736}, {"text": "And so if I plot the\nabsorption, if I take a solid", "start": 2200.179, "duration": 8.042}, {"text": "and I shine a light\non it, there's", "start": 2208.221, "duration": 3.069}, {"text": "something called the absorption\ncoefficient, which is really", "start": 2211.29, "duration": 8.042}, {"text": "just a measure of how\nfar down into the solid", "start": 2219.332, "duration": 6.673}, {"text": "did that light have to go\nbefore some electron got excited", "start": 2226.005, "duration": 4.771}, {"text": "by it?", "start": 2230.776, "duration": 1.702}, {"text": "How well does it-- well,\nOK, different solids", "start": 2232.478, "duration": 2.403}, {"text": "can absorb electrons\ndifferently.", "start": 2234.881, "duration": 2.068}, {"text": "But the main point is, if\nI plot that versus energy", "start": 2236.949, "duration": 4.271}, {"text": "for something like silicon, the\nbandgap of silicon is 1.1 ev,", "start": 2241.22, "duration": 6.607}, {"text": "so that's what it would\nlook like for silicon", "start": 2247.827, "duration": 1.868}, {"text": "because you know--", "start": 2249.695, "duration": 3.704}, {"text": "this should be wavelength.", "start": 2253.399, "duration": 1.568}, {"text": "Because you know-- because\nas you get to lower--", "start": 2258.905, "duration": 6.006}, {"text": "so you know that above--", "start": 2264.911, "duration": 3.536}, {"text": "it's exactly like for atoms.", "start": 2268.447, "duration": 2.002}, {"text": "If I shine light, like\nremember the Bohr model,", "start": 2270.449, "duration": 3.07}, {"text": "if I shine light on an atom that\nhas enough energy to promote it", "start": 2273.519, "duration": 4.371}, {"text": "up, then it can go.", "start": 2277.89, "duration": 3.67}, {"text": "But the difference here is\nthat for silicon, for silicon,", "start": 2281.56, "duration": 6.507}, {"text": "that's right there,\nfor silicon there's", "start": 2288.067, "duration": 1.802}, {"text": "this big empty\nspace with no bands.", "start": 2289.869, "duration": 2.302}, {"text": "It's just like the atom.", "start": 2292.171, "duration": 1.502}, {"text": "When there's no states, I\ncannot have an electron there.", "start": 2293.673, "duration": 5.138}, {"text": "I'm stuck.", "start": 2298.811, "duration": 1.301}, {"text": "So the electron can be\nhere or it can be here.", "start": 2300.112, "duration": 2.57}, {"text": "And so the light, the\nenergy of the light,", "start": 2302.682, "duration": 1.735}, {"text": "has to be at least the\nbandgap to get it up.", "start": 2304.417, "duration": 4.037}, {"text": "At least the bandgap\nto get it up.", "start": 2308.454, "duration": 3.604}, {"text": "So what that means\nis that if I had--", "start": 2312.058, "duration": 2.936}, {"text": "so, why does this go to zero\nwith increasing wavelength?", "start": 2314.994, "duration": 4.338}, {"text": "What it means is that if my\nvalence band looks like this", "start": 2319.332, "duration": 4.537}, {"text": "and my conduction\nband looks like this,", "start": 2323.869, "duration": 3.037}, {"text": "and now my light is coming\nand I want to take an electron", "start": 2326.906, "duration": 3.503}, {"text": "and promote it up.", "start": 2330.409, "duration": 2.102}, {"text": "Well, it cannot be--", "start": 2332.511, "duration": 2.102}, {"text": "the electron cannot exist\ninside the band gap.", "start": 2334.613, "duration": 10.177}, {"text": "There is no states there.", "start": 2344.79, "duration": 1.669}, {"text": "It's just like we\ntalked about with atoms.", "start": 2346.459, "duration": 1.768}, {"text": "But now we've got almost\ninfinite states here,", "start": 2348.227, "duration": 2.97}, {"text": "no states there.", "start": 2351.197, "duration": 1.168}, {"text": "And then again we start\nwith infinite places", "start": 2352.365, "duration": 1.835}, {"text": "where it can be.", "start": 2354.2, "duration": 0.7}, {"text": "What that means is that\nif I shine light on it,", "start": 2357.67, "duration": 2.202}, {"text": "the only way silicon, the only\nway it can absorb this light", "start": 2359.872, "duration": 4.705}, {"text": "is if the light has energy\ngreater than the band gap,", "start": 2364.577, "duration": 4.504}, {"text": "or wavelength less\nthan the bandgap.", "start": 2369.081, "duration": 2.836}, {"text": "That's why I drew it that way.", "start": 2371.917, "duration": 2.169}, {"text": "So it goes to\nzero-- so it's going", "start": 2374.086, "duration": 1.435}, {"text": "to absorb in wavelength\nup to a certain point.", "start": 2375.521, "duration": 2.269}, {"text": "And then if I go\nhigher in wavelength,", "start": 2377.79, "duration": 1.802}, {"text": "those are energies\nthat are too small.", "start": 2379.592, "duration": 1.601}, {"text": "It's going to try to absorb here\nbut there's nowhere to absorb", "start": 2381.193, "duration": 2.57}, {"text": "to, so it can't.", "start": 2383.763, "duration": 3.236}, {"text": "But if it has enough\nenergy, oh, look at this.", "start": 2386.999, "duration": 2.369}, {"text": "This is also different.", "start": 2389.368, "duration": 1.235}, {"text": "I could absorb here\nor here or here.", "start": 2390.603, "duration": 3.703}, {"text": "I can take all those\nhigher energies", "start": 2394.306, "duration": 2.703}, {"text": "and absorb light\nkind of continuously,", "start": 2397.009, "duration": 4.238}, {"text": "unlike in the atom\nwhere it could only", "start": 2401.247, "duration": 1.835}, {"text": "be the level to hop you from\nn equals 2 to n equals 4.", "start": 2403.082, "duration": 4.004}, {"text": "But here I have an almost\ncontinuous set of states,", "start": 2407.086, "duration": 4.104}, {"text": "except in the band gap,\nwhere I have no states.", "start": 2411.19, "duration": 4.238}, {"text": "So that's what the absorption\nwould look like for silicon.", "start": 2415.428, "duration": 3.67}, {"text": "And if you look at the bandgap,\nthis very, very important", "start": 2419.098, "duration": 3.503}, {"text": "quantity, there is carbon.", "start": 2422.601, "duration": 1.802}, {"text": "There's diamond.", "start": 2424.403, "duration": 1.435}, {"text": "There's silicon.", "start": 2425.838, "duration": 1.201}, {"text": "There's germanium.", "start": 2427.039, "duration": 2.036}, {"text": "And you can see that as you\ngo to heavier and heavier", "start": 2429.075, "duration": 3.903}, {"text": "elements, you change the gap.", "start": 2432.978, "duration": 5.039}, {"text": "And you can understand\nthis from what", "start": 2438.017, "duration": 1.568}, {"text": "you know about the\nelectron levels in atoms.", "start": 2439.585, "duration": 2.903}, {"text": "Because in an atom, remember,\nif I get heavier and heavier,", "start": 2442.488, "duration": 8.442}, {"text": "those electrons all the way on\nthe outer edges of the atom,", "start": 2450.93, "duration": 4.404}, {"text": "they're more weakly\nbonded to the atom.", "start": 2455.334, "duration": 3.203}, {"text": "They're weaker and\nweaker and weaker.", "start": 2458.537, "duration": 4.038}, {"text": "So the energy is\nhigher and higher.", "start": 2462.575, "duration": 2.836}, {"text": "Remember, so instead of being\nthese deeper energy levels that", "start": 2465.411, "duration": 3.603}, {"text": "have more bonding, more energy\nin them, lower in energy,", "start": 2469.014, "duration": 3.304}, {"text": "they're less and less energy.", "start": 2472.318, "duration": 3.37}, {"text": "So you can imagine,\nnow, that those", "start": 2475.688, "duration": 3.47}, {"text": "are what you're starting with.", "start": 2479.158, "duration": 1.668}, {"text": "Those are what you're\nstarting with, these.", "start": 2480.826, "duration": 2.102}, {"text": "Right these are the atom levels\nthat you're starting with.", "start": 2482.928, "duration": 2.469}, {"text": "So if you're going to make\nyour atom have electrons that", "start": 2485.397, "duration": 2.77}, {"text": "are more weakly bound with\nenergies that are higher,", "start": 2488.167, "duration": 4.771}, {"text": "that aren't as deep and\ndon't have as much distance", "start": 2492.938, "duration": 2.236}, {"text": "between them in the\nenergy landscape,", "start": 2495.174, "duration": 3.904}, {"text": "then the gaps will get smaller.", "start": 2499.078, "duration": 1.935}, {"text": "Now, that is a\nvery simple picture", "start": 2501.013, "duration": 4.605}, {"text": "of why the gaps get smaller.", "start": 2505.618, "duration": 1.268}, {"text": "It happens to work\nfor this column.", "start": 2506.886, "duration": 2.636}, {"text": "So if you look at\nthis-- and some people", "start": 2509.522, "duration": 2.268}, {"text": "would even call this\na metal because that's", "start": 2511.79, "duration": 2.737}, {"text": "such a small gap, but I like\nto call it a semiconductor.", "start": 2514.527, "duration": 4.037}, {"text": "But if your gap is zero,\nif you're band gap is zero,", "start": 2518.564, "duration": 3.604}, {"text": "it means there is no gap.", "start": 2522.168, "duration": 2.369}, {"text": "So by definition, you're\nin the middle of a band.", "start": 2524.537, "duration": 3.937}, {"text": "You're somewhere in\nthe middle of a band.", "start": 2528.474, "duration": 1.735}, {"text": "And if you're in the middle\nof a band, you're a metal.", "start": 2530.209, "duration": 3.37}, {"text": "You didn't fill that\nband all the way up.", "start": 2533.579, "duration": 3.003}, {"text": "But if you filled it\nup and then there's", "start": 2536.582, "duration": 1.635}, {"text": "a little gap between\nyou and the next level,", "start": 2538.217, "duration": 2.436}, {"text": "then you're a semiconductor.", "start": 2540.653, "duration": 1.201}, {"text": "Or if it's much greater,\nlike greater than three", "start": 2541.854, "duration": 3.337}, {"text": "electron volts, 3 and\n1/2 electron volts,", "start": 2545.191, "duration": 2.869}, {"text": "then you're an insulator.", "start": 2548.06, "duration": 3.67}, {"text": "Now, so you can\nimagine now why--", "start": 2551.73, "duration": 2.77}, {"text": "so as the interactions\nget stronger,", "start": 2554.5, "duration": 2.869}, {"text": "you can imagine those\ndistances can get larger.", "start": 2557.369, "duration": 3.671}, {"text": "And so you could have\nlarger and larger gaps,", "start": 2561.04, "duration": 3.103}, {"text": "which can explain this trend.", "start": 2564.143, "duration": 1.535}, {"text": "But as I said before,\nwhere did I put it,", "start": 2565.678, "duration": 2.802}, {"text": "it depends, not just on the atom\nand the original energy levels,", "start": 2568.48, "duration": 5.406}, {"text": "but on how those bond together.", "start": 2573.886, "duration": 2.336}, {"text": "And we'll talk about\nthat on Wednesday.", "start": 2576.222, "duration": 2.135}, {"text": "And it also depends on\nthe structure, which", "start": 2578.357, "duration": 2.135}, {"text": "we'll talk about next week.", "start": 2580.492, "duration": 1.502}, {"text": "So it's not just\nas simple as that", "start": 2581.994, "duration": 1.702}, {"text": "but you can understand\nbasic trends this way", "start": 2583.696, "duration": 3.537}, {"text": "for some of the columns.", "start": 2587.233, "duration": 2.335}, {"text": "OK, we'll get to that on Friday.", "start": 2589.568, "duration": 4.805}, {"text": "Now, the goodie bag gives\nyou a way to probe this.", "start": 2594.373, "duration": 3.07}, {"text": "So what's in the goodie bag?", "start": 2597.443, "duration": 1.434}, {"text": "The goodie bag has a way\nof measuring conductivity.", "start": 2598.877, "duration": 5.573}, {"text": "Now, I just told you that you\ncannot get connectivity unless", "start": 2604.45, "duration": 3.003}, {"text": "you have electrons that\nare able to make this jump,", "start": 2607.453, "duration": 5.272}, {"text": "to make this jump.", "start": 2612.725, "duration": 1.635}, {"text": "They've got to be able to\ngo up from the valence band", "start": 2614.36, "duration": 3.637}, {"text": "to the conduction band.", "start": 2617.997, "duration": 1.534}, {"text": "If they don't do that,\nthey're not free.", "start": 2619.531, "duration": 2.436}, {"text": "They're stuck in these bonds.", "start": 2621.967, "duration": 2.536}, {"text": "You've got to get them free so\nthey can roam around and not", "start": 2624.503, "duration": 4.138}, {"text": "be stuck in this\nbond or that bond.", "start": 2628.641, "duration": 3.203}, {"text": "This measures that.", "start": 2631.844, "duration": 1.234}, {"text": "This measures that.", "start": 2633.078, "duration": 1.101}, {"text": "This measures whether electrons\nare in the conduction band.", "start": 2634.179, "duration": 3.771}, {"text": "You've also got some\nLEDs and some LEDs.", "start": 2637.95, "duration": 3.337}, {"text": "And this is a\ncritical piece here.", "start": 2641.287, "duration": 2.869}, {"text": "Why do you have\ntwo kinds of LEDs?", "start": 2644.156, "duration": 3.971}, {"text": "Because on the one\nhand, what you're doing,", "start": 2648.127, "duration": 3.069}, {"text": "I'm giving you a way\nto excite electrons.", "start": 2651.196, "duration": 2.803}, {"text": "So I'm giving you a way to\nactually promote electrons.", "start": 2653.999, "duration": 5.973}, {"text": "So you've got 10 to the 24\nelectrons in this valence band.", "start": 2659.972, "duration": 3.704}, {"text": "This would be the vb and\nthis would be the cb.", "start": 2663.676, "duration": 3.403}, {"text": "And what you're doing\nis you're shining light", "start": 2667.079, "duration": 4.738}, {"text": "with different frequencies,\nwhich means different energies.", "start": 2671.817, "duration": 5.005}, {"text": "That's what the right\nhand side gives you.", "start": 2676.822, "duration": 1.768}, {"text": "It gives you different\nenergies of the photons.", "start": 2678.59, "duration": 4.071}, {"text": "So you have a way,\nnow, of shining energy", "start": 2682.661, "duration": 2.903}, {"text": "on a semiconductor.", "start": 2685.564, "duration": 1.401}, {"text": "And that's the second piece.", "start": 2686.965, "duration": 2.436}, {"text": "The semiconductor\nis what an LED is.", "start": 2689.401, "duration": 3.203}, {"text": "It's a semiconductor.", "start": 2692.604, "duration": 2.77}, {"text": "If LEDs were insulators,\nthey wouldn't work.", "start": 2695.374, "duration": 2.135}, {"text": "And if they were metals,\nthey wouldn't work.", "start": 2697.509, "duration": 2.503}, {"text": "Because the way an LED works\nis actually just the opposite.", "start": 2700.012, "duration": 4.871}, {"text": "Here, I'm shining light so\nthat an electron gets promoted", "start": 2704.883, "duration": 4.171}, {"text": "and I can measure that\nwith my voltmeter.", "start": 2709.054, "duration": 3.07}, {"text": "But I could also put\nelectrons in with a current.", "start": 2712.124, "duration": 4.037}, {"text": "That gets them up\nhere and then they", "start": 2716.161, "duration": 1.835}, {"text": "drop down and emit a photon.", "start": 2717.996, "duration": 2.036}, {"text": "That's what an LED is.", "start": 2720.032, "duration": 2.402}, {"text": "That's what an LED is,\nit's just the reverse.", "start": 2722.434, "duration": 2.336}, {"text": "And so what I've\ngiven you on the left", "start": 2724.77, "duration": 2.502}, {"text": "are different semiconductors.", "start": 2727.272, "duration": 3.537}, {"text": "Because you see, just like\na different-- you know,", "start": 2730.809, "duration": 3.337}, {"text": "if I'm running current through\nlike I am on the right,", "start": 2734.146, "duration": 3.036}, {"text": "you see, those are\ndifferent colors.", "start": 2737.182, "duration": 2.069}, {"text": "That means that I must\nhave different gaps.", "start": 2739.251, "duration": 5.339}, {"text": "You know that.", "start": 2744.59, "duration": 0.634}, {"text": "You know that\nalready from the work", "start": 2745.224, "duration": 1.434}, {"text": "we did with Bohr and the\ncolor or frequency of light", "start": 2746.658, "duration": 3.704}, {"text": "that you can get out of\ndifferent transitions.", "start": 2750.362, "duration": 2.202}, {"text": "But it's the same here.", "start": 2752.564, "duration": 1.602}, {"text": "Did an electron-- you know,\ndid I put an electron up here", "start": 2754.166, "duration": 3.003}, {"text": "and then it fell down\nand gave off some lambda?", "start": 2757.169, "duration": 5.272}, {"text": "That lambda has to equal\nthe difference between the--", "start": 2762.441, "duration": 6.406}, {"text": "it just equals the band gap.", "start": 2768.847, "duration": 2.002}, {"text": "It equals the band gap because\nthe electron was put up", "start": 2770.849, "duration": 4.171}, {"text": "to here in the cbm and then\nit drops down to the vbm", "start": 2775.02, "duration": 2.836}, {"text": "and it emits a photon.", "start": 2777.856, "duration": 0.968}, {"text": "That's what's happening\non the right hand side.", "start": 2778.824, "duration": 1.935}, {"text": "But see, you've also got,\non the left hand side,", "start": 2780.759, "duration": 2.469}, {"text": "you've got sensors because\nit's just LEDs on the left.", "start": 2783.228, "duration": 6.04}, {"text": "But if I hook those\nup, if I hook those up", "start": 2789.268, "duration": 4.037}, {"text": "to the volt meter,\nwell, I'm hooking up", "start": 2793.305, "duration": 3.704}, {"text": "a semiconductor to a voltmeter.", "start": 2797.009, "duration": 2.002}, {"text": "So I'm hooking this up and I'm\nreading, is there any current.", "start": 2799.011, "duration": 5.172}, {"text": "And the answer in\na dark room is no,", "start": 2804.183, "duration": 2.802}, {"text": "unless you make it\nreally, really hot.", "start": 2806.985, "duration": 1.869}, {"text": "Don't, because you have to\ngo to very high temperatures.", "start": 2808.854, "duration": 2.703}, {"text": "Well, what if I shine\nlight on this now?", "start": 2811.557, "duration": 3.27}, {"text": "Well, if I shine light\nthat has the right energy", "start": 2814.827, "duration": 3.203}, {"text": "to put electrons up in\nthe cbm from the vbm,", "start": 2818.03, "duration": 4.304}, {"text": "then I'll read something\non the voltmeter.", "start": 2822.334, "duration": 2.469}, {"text": "So by giving you different\nLEDs on the left,", "start": 2824.803, "duration": 3.003}, {"text": "I'm giving you\ndifferent band gaps.", "start": 2827.806, "duration": 1.769}, {"text": "You have in your hands different\nsemiconductor band gaps.", "start": 2829.575, "duration": 3.97}, {"text": "And by reading whether there\nare electrons in here or not,", "start": 2833.545, "duration": 3.07}, {"text": "you can tell what frequency\nof light I shined on them.", "start": 2836.615, "duration": 3.17}, {"text": "So they're both emitters\nof photons and detectors", "start": 2839.785, "duration": 3.737}, {"text": "of photons.", "start": 2843.522, "duration": 1.468}, {"text": "And it all comes\ntogether because you", "start": 2844.99, "duration": 2.703}, {"text": "have a semiconductor, which\nhappens because you took 10", "start": 2847.693, "duration": 3.503}, {"text": "to the 24 states, you\nput them together,", "start": 2851.196, "duration": 2.636}, {"text": "you had gaps between them,\nand you filled all the way up", "start": 2853.832, "duration": 2.67}, {"text": "to one of those gaps, and that\ngap was around 1 or 2 electron", "start": 2856.502, "duration": 4.304}, {"text": "volts.", "start": 2860.806, "duration": 1.435}, {"text": "We will pick this up on\nFriday and go further--", "start": 2862.241, "duration": 4.237}, {"text": "I mean on Wednesday,\non Wednesday.", "start": 2866.478, "duration": 1.602}]
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@@ -0,0 +1 @@
+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.92}, {"text": "[RUSTLING]", "start": 1.92, "duration": 1.92}, {"text": "[CLICKING]", "start": 3.84, "duration": 1.44}, {"text": "ROBERT M. TOWNSEND: Let me\nremind you from the reading", "start": 11.54, "duration": 2.34}, {"text": "list where we are.", "start": 13.88, "duration": 1.69}, {"text": "We did the introductory\nlecture, of course,", "start": 15.57, "duration": 3.09}, {"text": "about economic science.", "start": 18.66, "duration": 2.51}, {"text": "And last time, we did our\nfirst nuts and bolts lecture", "start": 21.17, "duration": 4.32}, {"text": "on preferences, consumer theory,\nwith the associated starred", "start": 25.49, "duration": 5.67}, {"text": "readings.", "start": 31.16, "duration": 1.44}, {"text": "And today, we're\ngoing to do more", "start": 32.6, "duration": 3.42}, {"text": "the way we ended the last\nclass on consumer behavior.", "start": 36.02, "duration": 3.69}, {"text": "I'm showing this reading\nlist because I just", "start": 39.71, "duration": 3.27}, {"text": "want to remind you that these\nstarred articles do exist.", "start": 42.98, "duration": 3.45}, {"text": "The Nicholson and\nSchneider chapter 5,", "start": 46.43, "duration": 2.58}, {"text": "from which this is drawn,\nalthough not entirely.", "start": 49.01, "duration": 2.52}, {"text": "And also, this Jensen\nand Miller paper,", "start": 51.53, "duration": 3.91}, {"text": "which I will say a few words\nabout today because it fits", "start": 55.44, "duration": 3.17}, {"text": "into this lecture, but\nalso, as I probably", "start": 58.61, "duration": 3.0}, {"text": "mentioned too many\ntimes, that's also", "start": 61.61, "duration": 2.519}, {"text": "a big part of your first\nproblem set and involves", "start": 64.129, "duration": 4.621}, {"text": "getting that paper, reading the\nyellow markings as highlights,", "start": 68.75, "duration": 4.62}, {"text": "accessing the data\nthat these guys used,", "start": 73.37, "duration": 3.45}, {"text": "and running through some\nof their calculations.", "start": 76.82, "duration": 4.09}, {"text": "So that's the part of\nthe starred readings", "start": 80.91, "duration": 3.68}, {"text": "for this lecture.", "start": 84.59, "duration": 1.96}, {"text": "So in terms of the study\nguide, Consumer Theory,", "start": 86.55, "duration": 5.14}, {"text": "as I was alerting you\nlast time, there's", "start": 91.69, "duration": 3.35}, {"text": "a pretty good thorough review\nof what you should have learned", "start": 95.04, "duration": 4.62}, {"text": "or are learning from\nthe topic of last time.", "start": 99.66, "duration": 3.75}, {"text": "And I will not go\nthrough all of this,", "start": 103.41, "duration": 2.16}, {"text": "but I will ask a\nfew questions, get", "start": 105.57, "duration": 2.34}, {"text": "a few volunteers, maybe even\ncall on a couple of you.", "start": 107.91, "duration": 4.24}, {"text": "So this one, give a plausible\nexample of a commodity point", "start": 112.15, "duration": 5.18}, {"text": "that could not be in a\ntypical consumption set.", "start": 117.33, "duration": 4.07}, {"text": "And I'll take\nvolunteers on that.", "start": 121.4, "duration": 1.62}, {"text": "It's partly remembering\nthe slide where I showed", "start": 123.02, "duration": 3.6}, {"text": "examples of consumption sets.", "start": 126.62, "duration": 1.799}, {"text": "Does anyone remember?", "start": 128.419, "duration": 2.421}, {"text": "The question is-- yes?", "start": 130.84, "duration": 2.852}, {"text": "AUDIENCE: One infeasible\nconsumption site", "start": 133.692, "duration": 1.708}, {"text": "is consuming 25 hours in a\nday or something like that.", "start": 135.4, "duration": 3.54}, {"text": "ROBERT M. TOWNSEND: That's good.", "start": 138.94, "duration": 1.86}, {"text": "Yep, that was one of\nthe diagrams where", "start": 140.8, "duration": 2.79}, {"text": "the amount of leisure\navailable for work or leisure,", "start": 143.59, "duration": 5.04}, {"text": "the sum could not exceed 25.", "start": 148.63, "duration": 2.7}, {"text": "There was another one,\nwhich you might not", "start": 151.33, "duration": 1.8}, {"text": "have thought of given\nthe way this is worded,", "start": 153.13, "duration": 2.4}, {"text": "which is consumption of\nbread in New York at noon", "start": 155.53, "duration": 3.78}, {"text": "and consumption in\nBoston at noon of bread.", "start": 159.31, "duration": 3.27}, {"text": "And you're not allowed to\nhave bread in the interior", "start": 162.58, "duration": 5.13}, {"text": "because you can't\nconsume simultaneously", "start": 167.71, "duration": 3.33}, {"text": "in both New York and Boston.", "start": 171.04, "duration": 1.75}, {"text": "So that was another example.", "start": 172.79, "duration": 1.43}, {"text": "But your answer was great.", "start": 174.22, "duration": 3.37}, {"text": "So can someone\nvolunteer to give me", "start": 177.59, "duration": 3.3}, {"text": "the definition of\nlocal non-satiation?", "start": 180.89, "duration": 4.98}, {"text": "AUDIENCE: That\nmeans that there's", "start": 185.87, "duration": 1.96}, {"text": "in that-- so if you have a\nbundle, in any neighborhood", "start": 187.83, "duration": 5.61}, {"text": "of that bundle, there is\nsome other bundle that's", "start": 193.44, "duration": 3.45}, {"text": "preferred to the bundle\nyou originally had.", "start": 196.89, "duration": 2.34}, {"text": "There are no bliss points.", "start": 199.23, "duration": 2.37}, {"text": "ROBERT M. TOWNSEND:\nThat's right.", "start": 201.6, "duration": 2.58}, {"text": "That's an excellent answer.", "start": 204.18, "duration": 2.18}, {"text": "Yeah, I can't remember\nwhether we did X or Y.", "start": 206.36, "duration": 2.56}, {"text": "But for any X in\nthe consumption set,", "start": 208.92, "duration": 5.46}, {"text": "there's some other Y,\nno matter how close", "start": 214.38, "duration": 4.77}, {"text": "we are to X, which is\npreferred to X and-- well,", "start": 219.15, "duration": 5.28}, {"text": "and Y has to be in\nthe consumption set.", "start": 224.43, "duration": 2.07}, {"text": "So both things have to be true.", "start": 226.5, "duration": 1.93}, {"text": "It has to be available in this\nlittle ball or circle around X,", "start": 228.43, "duration": 4.82}, {"text": "and it has to be preferred.", "start": 233.25, "duration": 3.93}, {"text": "And you gave a good\ncounter-example.", "start": 237.18, "duration": 2.27}, {"text": "If there were a\nbliss point, that", "start": 239.45, "duration": 1.53}, {"text": "means there's something\nthat is maximal utility", "start": 240.98, "duration": 6.67}, {"text": "among all possible points.", "start": 247.65, "duration": 1.66}, {"text": "So if we do a\ncircle around that,", "start": 249.31, "duration": 2.9}, {"text": "everything else\nwould be inferior.", "start": 252.21, "duration": 1.935}, {"text": "If you went beyond the bliss\npoint, northeast of it,", "start": 256.85, "duration": 4.679}, {"text": "you have too much\nof all the goods.", "start": 261.529, "duration": 3.331}, {"text": "But then, ironically, you\nalso have local non-satiation", "start": 264.86, "duration": 4.38}, {"text": "because, given any point X,\nthere's another point Y, which", "start": 269.24, "duration": 6.84}, {"text": "involves less than both goods.", "start": 276.08, "duration": 3.45}, {"text": "That would be strictly\npreferred because you're", "start": 279.53, "duration": 1.98}, {"text": "moving to the bliss point.", "start": 281.51, "duration": 2.64}, {"text": "So anyway, the point of\nthis little discussion", "start": 284.15, "duration": 2.37}, {"text": "is that local non-satiation\nand global non-satiation", "start": 286.52, "duration": 4.86}, {"text": "are two different things.", "start": 291.38, "duration": 3.12}, {"text": "Thank you.", "start": 294.5, "duration": 1.62}, {"text": "OK, let's-- what does it mean\nfor a preference relation to be", "start": 296.12, "duration": 4.49}, {"text": "represented by a\nutility function?", "start": 300.61, "duration": 2.055}, {"text": "Given a preference\nrelation, is the utility", "start": 305.38, "duration": 2.16}, {"text": "function that\nrepresents it unique?", "start": 307.54, "duration": 2.88}, {"text": "Yes or no, and explain.", "start": 310.42, "duration": 4.39}, {"text": "AUDIENCE: Yeah, so we say that\na utility function represents", "start": 314.81, "duration": 5.4}, {"text": "a preference if, for example,\nfor any consumption bundle, X,", "start": 320.21, "duration": 5.16}, {"text": "any two consumption bundles, X\nand Y, if X is preferred to Y,", "start": 325.37, "duration": 4.24}, {"text": "then U of X is\ngreater than U of Y.", "start": 329.61, "duration": 4.43}, {"text": "And the utility\nfunction is not unique.", "start": 334.04, "duration": 2.23}, {"text": "It just has to respect the given\nordering of the preferences.", "start": 336.27, "duration": 2.78}, {"text": "So we could have U, or\nU squared, or U cubed,", "start": 339.05, "duration": 3.75}, {"text": "and all of those would work.", "start": 342.8, "duration": 1.75}, {"text": "ROBERT M. TOWNSEND: Excellent.", "start": 344.55, "duration": 1.25}, {"text": "Perfect answer.", "start": 345.8, "duration": 3.06}, {"text": "Any other comments or\nquestions about that?", "start": 348.86, "duration": 2.775}, {"text": "AUDIENCE: I had a question.", "start": 355.45, "duration": 1.62}, {"text": "On this slide, it\nhad said that it", "start": 357.07, "duration": 2.73}, {"text": "was unique only up to an order\npreserving transformation.", "start": 359.8, "duration": 3.72}, {"text": "What exactly does\nthat, I guess, mean?", "start": 363.52, "duration": 4.51}, {"text": "ROBERT M. TOWNSEND: Well,\nif you had three points,", "start": 368.03, "duration": 3.23}, {"text": "ordering them from\nlow to high in terms", "start": 371.26, "duration": 2.1}, {"text": "of preference relation--", "start": 373.36, "duration": 2.37}, {"text": "say, X1, X2, X3, where\nX3 is preferred to X2", "start": 375.73, "duration": 4.83}, {"text": "is preferred to X1,\nall we need to do", "start": 380.56, "duration": 3.24}, {"text": "is to assign a higher number\nto the best one, a lower number", "start": 383.8, "duration": 4.14}, {"text": "to the intermediate one.", "start": 387.94, "duration": 1.2}, {"text": "So something like 15, 5, 1\npreserves the rank ordering.", "start": 389.14, "duration": 6.0}, {"text": "Those are utility\nnumber assignments.", "start": 395.14, "duration": 2.82}, {"text": "But we could multiply by 2,\nand then we have 30, 10, 2.", "start": 397.96, "duration": 8.99}, {"text": "But we're still assigning\nnumbers from high to low", "start": 406.95, "duration": 4.86}, {"text": "to preserve the\nsame rank ordering.", "start": 411.81, "duration": 1.74}, {"text": "Does that help?", "start": 413.55, "duration": 1.06}, {"text": "AUDIENCE: Yeah, thank you.", "start": 414.61, "duration": 2.0}, {"text": "ROBERT M. TOWNSEND: OK.", "start": 416.61, "duration": 2.73}, {"text": "Yes, go on.", "start": 419.34, "duration": 1.2}, {"text": "AUDIENCE: Do you eventually\nneed to, I guess,", "start": 420.54, "duration": 2.7}, {"text": "reintroduce some\nconcept of magnitude--", "start": 423.24, "duration": 3.21}, {"text": "or not magnitude,\nbut have something", "start": 426.45, "duration": 1.71}, {"text": "beyond just ordering if you want\nto start talking about gambling", "start": 428.16, "duration": 2.88}, {"text": "or expected value?", "start": 431.04, "duration": 1.38}, {"text": "ROBERT M. TOWNSEND:\nYes, absolutely.", "start": 432.42, "duration": 1.59}, {"text": "And we're going to do\nthat in two lectures.", "start": 434.01, "duration": 2.8}, {"text": "So there, the utility\nfunction will--", "start": 436.81, "duration": 4.68}, {"text": "the ordinal\nrepresentation matters.", "start": 441.49, "duration": 4.33}, {"text": "And the question will be, how\nmuch more utility do you get", "start": 445.82, "duration": 4.02}, {"text": "or how much less, depending\non an adverse event?", "start": 449.84, "duration": 5.49}, {"text": "So that the curvature literally\nrepresents your willingness", "start": 455.33, "duration": 6.82}, {"text": "to take gambles.", "start": 462.15, "duration": 2.44}, {"text": "Whereas with an\nordinal function,", "start": 464.59, "duration": 2.19}, {"text": "a linear function is fine.", "start": 466.78, "duration": 1.83}, {"text": "Linear function\nwhen you're facing", "start": 468.61, "duration": 2.4}, {"text": "gambles means\nyou're risk-neutral,", "start": 471.01, "duration": 2.46}, {"text": "and you just rank based\non expected values.", "start": 473.47, "duration": 3.84}, {"text": "That's all a little bit early.", "start": 477.31, "duration": 1.273}, {"text": "It's a great question.", "start": 478.583, "duration": 0.917}, {"text": "And we're going to get\nthere in two lectures.", "start": 479.5, "duration": 3.78}, {"text": "We got time for one more here.", "start": 483.28, "duration": 2.055}, {"text": "What does it mean for\npreferences to be homothetic?", "start": 489.0, "duration": 3.06}, {"text": "AUDIENCE: The MRS is just\ndepending on the ratio", "start": 494.96, "duration": 4.83}, {"text": "of two goods, right?", "start": 499.79, "duration": 2.52}, {"text": "Not depending on the absolute\nquantity of each good.", "start": 502.31, "duration": 5.91}, {"text": "ROBERT M. TOWNSEND:\nYep, perfect.", "start": 508.22, "duration": 2.93}, {"text": "Wow, I'm very happy,\nvery impressed.", "start": 511.15, "duration": 3.0}, {"text": "Thank you, all.", "start": 514.15, "duration": 1.05}, {"text": "That's tremendous.", "start": 515.2, "duration": 0.849}, {"text": "OK, so again, these are just\nsomewhat randomly selected.", "start": 516.049, "duration": 4.071}, {"text": "I do go over these\nbefore class to help", "start": 520.12, "duration": 3.84}, {"text": "me decide, since I\ncan't ask them all,", "start": 523.96, "duration": 2.97}, {"text": "which one I would ask in class.", "start": 526.93, "duration": 2.7}, {"text": "There are some of these\nthat say draw a graph", "start": 529.63, "duration": 2.22}, {"text": "or so on and so forth.", "start": 531.85, "duration": 2.76}, {"text": "So I didn't ask about those.", "start": 534.61, "duration": 1.84}, {"text": "But none of them are\nsupposed to be terribly hard.", "start": 536.45, "duration": 4.07}, {"text": "But it is always a good\nreview, at a minimum.", "start": 540.52, "duration": 4.77}, {"text": "OK, so today is a lecture\non income and substitution", "start": 545.29, "duration": 6.03}, {"text": "effects.", "start": 551.32, "duration": 1.05}, {"text": "Or really, it's about\nconsumer-maximizing behavior.", "start": 552.37, "duration": 5.32}, {"text": "And so when we solve the\nconsumers utility maximization", "start": 557.69, "duration": 7.2}, {"text": "problem, we get individual\ndemand functions.", "start": 564.89, "duration": 3.85}, {"text": "It should say function\nwith an S because if there", "start": 568.74, "duration": 4.01}, {"text": "are n goods, little n, then\nthere's a demand for good 1,", "start": 572.75, "duration": 4.08}, {"text": "good 2, good n, and so on.", "start": 576.83, "duration": 3.49}, {"text": "And what are the arguments\nin these demand functions?", "start": 580.32, "duration": 3.26}, {"text": "The entire vector of\nPrices, denoted P1", "start": 583.58, "duration": 3.27}, {"text": "through Pn, and\nIncome, denoted as I.", "start": 586.85, "duration": 4.5}, {"text": "And you can think about\nprices and income denominated", "start": 591.35, "duration": 3.18}, {"text": "in dollars or some\nunit of account.", "start": 594.53, "duration": 3.76}, {"text": "We're going to be\nspending time looking", "start": 598.29, "duration": 2.43}, {"text": "at how the price of\ngood k changes when", "start": 600.72, "duration": 3.18}, {"text": "we change the price of good k.", "start": 603.9, "duration": 2.61}, {"text": "But of necessity, other goods\nwill be changing as well.", "start": 606.51, "duration": 5.1}, {"text": "It's at best, the implicit\nhappenings in the diagrams.", "start": 611.61, "duration": 4.89}, {"text": "So here is a little\nbit of a repeat", "start": 616.5, "duration": 3.06}, {"text": "but expanded from last time.", "start": 619.56, "duration": 2.19}, {"text": "We've got two goods\ndenoted, X and Y.", "start": 621.75, "duration": 2.64}, {"text": "And this household has a certain\namount of income, I, say, I2.", "start": 624.39, "duration": 5.88}, {"text": "If income were I2,\nto this would be", "start": 630.27, "duration": 1.83}, {"text": "the budget line, which has\na slope of PX over PY minus.", "start": 632.1, "duration": 5.7}, {"text": "And this is the tangency which\nis the maximum utility point", "start": 637.8, "duration": 3.81}, {"text": "denoted X2,Y2, associated\nwith income I2.", "start": 641.61, "duration": 5.07}, {"text": "What this diagram is\nfeaturing, though,", "start": 646.68, "duration": 1.99}, {"text": "is not a single maximization.", "start": 648.67, "duration": 2.42}, {"text": "It's how the maximization point\nchanges if you increase income.", "start": 651.09, "duration": 4.03}, {"text": "So you would move from\nX2,Y2 to X3,Y3, for example.", "start": 655.12, "duration": 5.6}, {"text": "And likewise, if your\nincome were less,", "start": 660.72, "duration": 3.6}, {"text": "if this household's income were\nless, they would move to Y1,X1.", "start": 664.32, "duration": 5.22}, {"text": "So you could connect these dots.", "start": 669.54, "duration": 3.45}, {"text": "And as only income is\nvarying and the price ratio", "start": 672.99, "duration": 3.81}, {"text": "is held fixed, we could\ncall the connected dots", "start": 676.8, "duration": 3.06}, {"text": "an income expansion path.", "start": 679.86, "duration": 2.13}, {"text": "And I'll show you some\nexamples of that momentarily.", "start": 681.99, "duration": 4.17}, {"text": "Here is a different experiment.", "start": 686.16, "duration": 3.24}, {"text": "Did we miss something?", "start": 689.4, "duration": 1.32}, {"text": "Well, in this one,\nyou'll get lulled", "start": 690.72, "duration": 3.25}, {"text": "into thinking that,\nas income changes,", "start": 693.97, "duration": 2.4}, {"text": "the amount spent on both\ngoods has to change, increase.", "start": 696.37, "duration": 3.63}, {"text": "But that's not\nnecessarily the case.", "start": 700.0, "duration": 2.86}, {"text": "So here, again, we're\ngoing from I1 to I2 to I3", "start": 702.86, "duration": 5.24}, {"text": "and tracing out the quantities\nfrom ZY1, ZY2 to ZY3.", "start": 708.1, "duration": 8.13}, {"text": "And here, the quantity demanded\nof good Y is increasing,", "start": 716.23, "duration": 6.12}, {"text": "but the quantity demanded of\ngood Z is actually decreasing.", "start": 722.35, "duration": 4.15}, {"text": "So there's nothing terribly\npeculiar about the shape", "start": 726.5, "duration": 3.8}, {"text": "of these indifference curves.", "start": 730.3, "duration": 1.46}, {"text": "We didn't have to struggle too\nhard to get this phenomenon", "start": 731.76, "duration": 3.28}, {"text": "to happen.", "start": 735.04, "duration": 1.23}, {"text": "But anyway, this\nphenomenon has a name.", "start": 736.27, "duration": 3.06}, {"text": "Namely, the good Y over here\nwould be called a normal good,", "start": 739.33, "duration": 5.52}, {"text": "and good Z would be called an\ninferior good or a necessity", "start": 744.85, "duration": 5.97}, {"text": "because the amount\nthat you consume of it", "start": 750.82, "duration": 2.16}, {"text": "diminishes as income goes up.", "start": 752.98, "duration": 4.21}, {"text": "So here are those\ndefinitions, a good", "start": 757.19, "duration": 2.75}, {"text": "for which the demand\nof good i goes down", "start": 759.94, "duration": 3.45}, {"text": "as income-- capital I-- goes up\nis said to be an inferior good.", "start": 763.39, "duration": 4.74}, {"text": "It doesn't have to happen over\nthe entire range of income", "start": 768.13, "duration": 3.84}, {"text": "and prices.", "start": 771.97, "duration": 0.9}, {"text": "But if it happens locally,\nit's called an inferior good", "start": 772.87, "duration": 3.43}, {"text": "locally.", "start": 776.3, "duration": 0.5}, {"text": "And likewise, if the derivative\nwith respect to income", "start": 776.8, "duration": 3.12}, {"text": "is positive, then we\ncall, in some range,", "start": 779.92, "duration": 2.85}, {"text": "the good to be a normal\ngood or noninferior good.", "start": 782.77, "duration": 4.6}, {"text": "So there's something\ncalled Engel's Law.", "start": 787.37, "duration": 2.64}, {"text": "And with the caveat that\nthis is not one household,", "start": 790.01, "duration": 3.96}, {"text": "it's actually comparing\nacross households that", "start": 793.97, "duration": 3.45}, {"text": "differ in their annual income.", "start": 797.42, "duration": 2.83}, {"text": "So here, we're going from\nan annual income of $225", "start": 800.25, "duration": 6.29}, {"text": "to-- this is written\nin 1920, by the way.", "start": 806.54, "duration": 2.4}, {"text": "Don't be too alarmed.", "start": 808.94, "duration": 1.17}, {"text": "There's been a lot of inflation.", "start": 810.11, "duration": 3.01}, {"text": "So this, in real\npurchasing power,", "start": 813.12, "duration": 1.85}, {"text": "was more than you\nthought, $300--", "start": 814.97, "duration": 3.18}, {"text": "or this range, 450 to\n600 or 750 to 1,000.", "start": 818.15, "duration": 6.06}, {"text": "And what you can\nsee is the percent", "start": 824.21, "duration": 2.047}, {"text": "spent of the budget\non food declines", "start": 826.257, "duration": 5.963}, {"text": "as we move to\nthese income groups", "start": 832.22, "duration": 2.91}, {"text": "with higher and higher income.", "start": 835.13, "duration": 1.87}, {"text": "So in some sense, if all\nconsumers were alike,", "start": 837.0, "duration": 3.33}, {"text": "and some had more\nincome than others,", "start": 840.33, "duration": 2.3}, {"text": "we'd be looking at what an\nindividual household would", "start": 842.63, "duration": 3.18}, {"text": "do as its income changed.", "start": 845.81, "duration": 2.86}, {"text": "And in this case, food\nwould be an inferior good.", "start": 848.67, "duration": 3.08}, {"text": "You're saying, what's going up?", "start": 851.75, "duration": 1.38}, {"text": "Clothing, not by much.", "start": 853.13, "duration": 2.22}, {"text": "Lodging, not at all.", "start": 855.35, "duration": 2.37}, {"text": "What really expands\nas income goes up", "start": 857.72, "duration": 2.76}, {"text": "is services, education, health,\nlegal, and other services.", "start": 860.48, "duration": 3.71}, {"text": "In fact, in the US\neconomy, looking", "start": 864.19, "duration": 2.92}, {"text": "over decades, the fraction\nof services produced in GDP", "start": 867.11, "duration": 5.04}, {"text": "just keeps going\nup, and up, and up,", "start": 872.15, "duration": 1.57}, {"text": "which is reflective of the\nfact that, as households", "start": 873.72, "duration": 2.99}, {"text": "have more income, they demand\nmore services than less food.", "start": 876.71, "duration": 3.375}, {"text": "So that's pretty dated, 1920.", "start": 882.76, "duration": 1.98}, {"text": "So I went on the web and looked\nthis thing up, Engel's Law", "start": 884.74, "duration": 3.78}, {"text": "today.", "start": 888.52, "duration": 1.23}, {"text": "Here, we're dividing\nhouseholds into quintiles,", "start": 889.75, "duration": 3.15}, {"text": "five groups, an equal number\nof households in each group.", "start": 892.9, "duration": 4.54}, {"text": "And we plot the fraction\nof so-called luxuries", "start": 897.44, "duration": 4.16}, {"text": "and necessities for each group.", "start": 901.6, "duration": 2.2}, {"text": "Now, this is a bit\nproblematic in the sense", "start": 903.8, "duration": 2.39}, {"text": "that necessities are\ndefined as goods or services", "start": 906.19, "duration": 3.21}, {"text": "where consumption is\nproportionately lower", "start": 909.4, "duration": 3.57}, {"text": "as a person's income increases.", "start": 912.97, "duration": 2.08}, {"text": "So again, necessity\nor non-normal goods", "start": 915.05, "duration": 3.53}, {"text": "or as we defined it in\nthe last three slides.", "start": 918.58, "duration": 3.21}, {"text": "Not too surprisingly, the\nhighest income groups,", "start": 921.79, "duration": 3.69}, {"text": "the top 20% of the population,\nthe proportion of expenditure", "start": 925.48, "duration": 4.92}, {"text": "on luxuries is a lot\nhigher than on necessities.", "start": 930.4, "duration": 3.48}, {"text": "And that gap lowers\nuntil you get", "start": 933.88, "duration": 3.15}, {"text": "to the lowest group,\nin which case,", "start": 937.03, "duration": 2.98}, {"text": "the fraction spent\non necessities", "start": 940.01, "duration": 2.51}, {"text": "is a lot higher than luxuries.", "start": 942.52, "duration": 2.94}, {"text": "Now, when I grabbed this,\nthere was an whole article", "start": 945.46, "duration": 2.34}, {"text": "about how poor people\nare extravagant", "start": 947.8, "duration": 2.67}, {"text": "because they're still spending\nmoney on luxury goods.", "start": 950.47, "duration": 3.09}, {"text": "Well, I mean, narrowly\nspeaking, yes, that's true.", "start": 953.56, "duration": 3.78}, {"text": "But again, it's a\nlittle bit harsh", "start": 957.34, "duration": 1.593}, {"text": "because it doesn't mean\nthey're driving around", "start": 958.933, "duration": 1.917}, {"text": "in a Mercedes Benz.", "start": 960.85, "duration": 1.14}, {"text": "It just means they're\neating some fraction of what", "start": 961.99, "duration": 3.06}, {"text": "they spend on are normal goods.", "start": 965.05, "duration": 3.6}, {"text": "AUDIENCE: Wait.", "start": 968.65, "duration": 2.19}, {"text": "Can you-- is there a little bit\nof issue with how those two--", "start": 970.84, "duration": 7.12}, {"text": "I guess, how the two\nlines are defined?", "start": 977.96, "duration": 1.88}, {"text": "Because the way\nyou defined them,", "start": 979.84, "duration": 2.58}, {"text": "it seems like you said luxuries\nare just what rich people buy,", "start": 982.42, "duration": 2.97}, {"text": "and necessities are\nwhat poor people buy.", "start": 985.39, "duration": 2.1}, {"text": "So doesn't this kind\nof get confirmed just", "start": 987.49, "duration": 2.79}, {"text": "by how you define it?", "start": 990.28, "duration": 1.02}, {"text": "ROBERT M. TOWNSEND: Yes, I\nthink that's exactly right.", "start": 991.3, "duration": 2.25}, {"text": "It's almost tautological.", "start": 993.55, "duration": 2.16}, {"text": "I mean, the way\nthey defined it, it", "start": 995.71, "duration": 1.77}, {"text": "has to be true that this blue\nline is going up and up as you", "start": 997.48, "duration": 3.63}, {"text": "go across the quantiles.", "start": 1001.11, "duration": 1.83}, {"text": "So I agree with that comment.", "start": 1002.94, "duration": 1.5}, {"text": "But I still think the graphs--", "start": 1004.44, "duration": 2.55}, {"text": "how much is it going up,\nwhat's the difference,", "start": 1006.99, "duration": 2.44}, {"text": "and so on, could go up\njust a teeny little bit,", "start": 1009.43, "duration": 2.6}, {"text": "in which case, that blue\nline would not move much.", "start": 1012.03, "duration": 3.6}, {"text": "Other questions?", "start": 1015.63, "duration": 3.41}, {"text": "Well, one takeaway from\nthis is different households", "start": 1019.04, "duration": 4.29}, {"text": "that differ in income do\nnot spend the same fraction", "start": 1023.33, "duration": 3.66}, {"text": "of their money on goods.", "start": 1026.99, "duration": 3.03}, {"text": "So let me take a\nchance at the risk of--", "start": 1030.02, "duration": 3.809}, {"text": "preview of coming\nattractions, this", "start": 1033.829, "duration": 2.49}, {"text": "is way back in lecture\n18, where we're", "start": 1036.319, "duration": 3.54}, {"text": "going to talk about aggregation,\nwhich has to do with whether we", "start": 1039.859, "duration": 4.411}, {"text": "can represent demand\nfunctions as if they came", "start": 1044.27, "duration": 3.299}, {"text": "from a single maximizing\nrepresentative", "start": 1047.569, "duration": 3.331}, {"text": "household or weaker, that\nthere is a group of households,", "start": 1050.9, "duration": 3.93}, {"text": "like the lower quintile,\nand they're all alike.", "start": 1054.83, "duration": 2.94}, {"text": "And we could take a\nrepresentative low-quintile", "start": 1057.77, "duration": 3.15}, {"text": "household and talk\nabout the demand", "start": 1060.92, "duration": 2.34}, {"text": "as if it were coming\nfrom that one person.", "start": 1063.26, "duration": 3.21}, {"text": "What is a necessary and\nsufficient assumption", "start": 1066.47, "duration": 2.82}, {"text": "for us to be able to do\nthat kind of aggregation?", "start": 1069.29, "duration": 3.48}, {"text": "It is that these income--", "start": 1072.77, "duration": 2.04}, {"text": "in this case, denoted\nwealth expansion paths--", "start": 1074.81, "duration": 2.73}, {"text": "are linear and have\nexactly the same slope.", "start": 1077.54, "duration": 5.11}, {"text": "So these guys will spend--", "start": 1082.65, "duration": 2.45}, {"text": "and I'm not trying to go\nthrough the entire lecture.", "start": 1085.1, "duration": 2.79}, {"text": "I'm just really\ntrying to motivate you", "start": 1087.89, "duration": 2.19}, {"text": "that we looked at\nsome micro data,", "start": 1090.08, "duration": 1.99}, {"text": "and later, we'll make\nsome assumptions.", "start": 1092.07, "duration": 1.91}, {"text": "It's good to put the microdata\nabout the assumptions", "start": 1093.98, "duration": 3.18}, {"text": "on the table at the same\ntime and compare them.", "start": 1097.16, "duration": 3.93}, {"text": "What's going on here is that,\nif these income expansion", "start": 1101.09, "duration": 3.75}, {"text": "paths are parallel, then\nwhen we increase income", "start": 1104.84, "duration": 4.05}, {"text": "for one household, it's\nexpenditure would go up.", "start": 1108.89, "duration": 3.09}, {"text": "But because this\nline is parallel,", "start": 1111.98, "duration": 2.35}, {"text": "when we decrease\nexpenditure for another one,", "start": 1114.33, "duration": 2.99}, {"text": "it's expenditures will go down\nin exactly the same amount", "start": 1117.32, "duration": 3.54}, {"text": "that this guy's went up.", "start": 1120.86, "duration": 1.45}, {"text": "So those income effects\nare completely offsetting.", "start": 1122.31, "duration": 2.75}, {"text": "And that turns out to be\nnecessary and sufficient to add", "start": 1125.06, "duration": 3.93}, {"text": "up all of income\nand drive demand", "start": 1128.99, "duration": 1.98}, {"text": "as if we've given all of\nincome to one household.", "start": 1130.97, "duration": 3.48}, {"text": "All right.", "start": 1134.45, "duration": 0.5}, {"text": "Well, it was with\nsome trepidation", "start": 1134.95, "duration": 1.92}, {"text": "that I showed you\nthis picture, but I", "start": 1136.87, "duration": 2.16}, {"text": "thought you might like\nto know what's coming.", "start": 1139.03, "duration": 2.52}, {"text": "And we'll review all of\nthat when we get to 18.", "start": 1141.55, "duration": 2.84}, {"text": "OK, so let's talk about income\nand substitution effects now.", "start": 1144.39, "duration": 4.15}, {"text": "Instead of changing income,\nwe want to change a price.", "start": 1148.54, "duration": 4.71}, {"text": "We're going to focus on\ngood X. We're going to look", "start": 1153.25, "duration": 3.21}, {"text": "at an initial point,\nwhich is Y*,X*.", "start": 1156.46, "duration": 5.81}, {"text": "And then we're going to\nlower the price of good X", "start": 1162.27, "duration": 4.05}, {"text": "and not touch good Y.", "start": 1166.32, "duration": 2.34}, {"text": "One way to quickly\nconvince yourself", "start": 1168.66, "duration": 3.33}, {"text": "that the diagram is correct\nis that this point over here", "start": 1171.99, "duration": 3.69}, {"text": "on the Y-axis is\ntaking all your income", "start": 1175.68, "duration": 2.73}, {"text": "and devoting it to the purchase\nof good Y. The price of Y", "start": 1178.41, "duration": 3.36}, {"text": "hasn't changed, so this\npoint hasn't changed.", "start": 1181.77, "duration": 2.58}, {"text": "But the price of\nX is going down.", "start": 1184.35, "duration": 3.18}, {"text": "And logically, the set of\nthings you can buy is expanding.", "start": 1187.53, "duration": 4.95}, {"text": "So this budget line\nshifts to the right,", "start": 1192.48, "duration": 2.7}, {"text": "but not in a parallel fashion.", "start": 1195.18, "duration": 2.35}, {"text": "So what is the new purchase?", "start": 1197.53, "duration": 2.54}, {"text": "The new purchase is a\ntangency, Y** and X**.", "start": 1200.07, "duration": 4.44}, {"text": "And we're going to break that\nmovement from the initial point", "start": 1204.51, "duration": 3.84}, {"text": "to the subsequent\npoint into two pieces--", "start": 1208.35, "duration": 3.54}, {"text": "one, a price effect, and\ntwo, an income effect.", "start": 1211.89, "duration": 4.87}, {"text": "So since the price\nof good X goes down,", "start": 1216.76, "duration": 3.08}, {"text": "PX over PY in absolute\nvalue is going down.", "start": 1219.84, "duration": 5.04}, {"text": "So there's a new budget\nline with a lower", "start": 1224.88, "duration": 3.57}, {"text": "slope that is pivoting on the\ninitial indifference curve, U1.", "start": 1228.45, "duration": 7.51}, {"text": "So setting aside income effects,\nwhich we'll get to momentarily,", "start": 1235.96, "duration": 5.28}, {"text": "the natural impact of\nlowering the price of good X", "start": 1241.24, "duration": 4.08}, {"text": "is to increase the\nexpenditure of good X", "start": 1245.32, "duration": 2.76}, {"text": "and decrease the\nexpenditure of good Y.", "start": 1248.08, "duration": 2.82}, {"text": "So that's called the\nsubstitution effect.", "start": 1250.9, "duration": 2.31}, {"text": "And it's a movement from X*,Y*\nto B. But in fact, of course,", "start": 1253.21, "duration": 5.8}, {"text": "income--", "start": 1259.01, "duration": 0.77}, {"text": "effectively, purchasing\npower has gone up.", "start": 1259.78, "duration": 2.61}, {"text": "Even though nominal income has\nnot moved, one good, at least,", "start": 1262.39, "duration": 3.6}, {"text": "is cheaper.", "start": 1265.99, "duration": 1.05}, {"text": "So their effect of\nincome has gone up,", "start": 1267.04, "duration": 2.8}, {"text": "and that's represented by\nthis parallel shift from B", "start": 1269.84, "duration": 3.95}, {"text": "to X**,Y**.", "start": 1273.79, "duration": 3.09}, {"text": "And that last bit\nfrom B to there", "start": 1276.88, "duration": 2.52}, {"text": "is called the income effect.", "start": 1279.4, "duration": 2.02}, {"text": "So the global movement is from\nX* to X** with a corresponding", "start": 1281.42, "duration": 6.23}, {"text": "movement from Y* to Y**.", "start": 1287.65, "duration": 2.28}, {"text": "And it's broken into two pieces,\nthis substitution effect, which", "start": 1289.93, "duration": 4.41}, {"text": "corresponds with movement\nalong the original indifference", "start": 1294.34, "duration": 3.33}, {"text": "curve, and the income\neffect of having higher", "start": 1297.67, "duration": 2.85}, {"text": "effective purchasing power.", "start": 1300.52, "duration": 3.01}, {"text": "OK?", "start": 1303.53, "duration": 1.52}, {"text": "A lot of today's\nlecture is just going", "start": 1305.05, "duration": 2.13}, {"text": "over this in various ways.", "start": 1307.18, "duration": 2.76}, {"text": "You can get mesmerized\nwith the price decrease.", "start": 1309.94, "duration": 4.08}, {"text": "Here is a price increase.", "start": 1314.02, "duration": 3.15}, {"text": "They're starting\nout with a tangency.", "start": 1317.17, "duration": 3.85}, {"text": "The price of good X still\ngoes, in this case, up.", "start": 1321.02, "duration": 5.92}, {"text": "Their purchasing\npower goes down.", "start": 1326.94, "duration": 2.58}, {"text": "The budget line rotates from\nthis initial point, inward.", "start": 1329.52, "duration": 3.75}, {"text": "So the total demand of the\nprice increase is going down,", "start": 1337.02, "duration": 5.13}, {"text": "a reduction in X.", "start": 1342.15, "duration": 1.59}, {"text": "But again, we can break\nthat into two pieces.", "start": 1343.74, "duration": 3.55}, {"text": "One is a substitution effect,\nthe movement away from good X--", "start": 1347.29, "duration": 3.83}, {"text": "because it has a higher\nprice relative to good Y--", "start": 1351.12, "duration": 3.06}, {"text": "to point B. And now\nwe take into account", "start": 1354.18, "duration": 4.02}, {"text": "the loss of effective\npurchasing power, which", "start": 1358.2, "duration": 3.06}, {"text": "is a shift in this budget line,\nthe dotted tangency line, which", "start": 1361.26, "duration": 4.56}, {"text": "is tangent at B, to the\nactual new, lower budget line.", "start": 1365.82, "duration": 6.09}, {"text": "So here, we denote the\ncombination of the substitution", "start": 1371.91, "duration": 3.89}, {"text": "and income effect.", "start": 1375.8, "duration": 1.51}, {"text": "This is really the previous\ndiagram in reverse.", "start": 1377.31, "duration": 3.41}, {"text": "But I think it's\nuseful to show both.", "start": 1380.72, "duration": 3.78}, {"text": "Of course, we can also start\nchanging the price of Y. Let's", "start": 1384.5, "duration": 3.96}, {"text": "not do that right away.", "start": 1388.46, "duration": 1.27}, {"text": "I'll come back to that later.", "start": 1389.73, "duration": 1.32}, {"text": "But the principles\nremain the same.", "start": 1391.05, "duration": 4.4}, {"text": "So let's construct\nsome demand curves,", "start": 1395.45, "duration": 4.53}, {"text": "as in the equation\nsystem we had initially.", "start": 1399.98, "duration": 3.06}, {"text": "If we keep lowering the price,\nmoving in this direction,", "start": 1403.04, "duration": 4.89}, {"text": "we trace out this tangency.", "start": 1407.93, "duration": 3.8}, {"text": "And those will be the demand\nat the associated prices.", "start": 1411.73, "duration": 3.79}, {"text": "So here, we have,\nsay, X prime at price,", "start": 1415.52, "duration": 5.77}, {"text": "P prime, X double prime\nat price P double prime--", "start": 1421.29, "duration": 6.82}, {"text": "and this would have\nbeen even better", "start": 1428.11, "duration": 3.12}, {"text": "if these things were lined up\nas they were intended to be--", "start": 1431.23, "duration": 4.17}, {"text": "X triple prime at\nprice P triple prime.", "start": 1435.4, "duration": 6.8}, {"text": "Now, again, price is going\ndown, and demand is going up.", "start": 1442.2, "duration": 6.82}, {"text": "Now, just to alert\nyou, I don't know", "start": 1452.98, "duration": 2.91}, {"text": "where this got started,\nwith Marshall or whatever.", "start": 1455.89, "duration": 3.36}, {"text": "But usually, we plot Y\nis a function of X, where", "start": 1459.25, "duration": 4.26}, {"text": "X is on the Y-axis, and\nY, the dependent variable,", "start": 1463.51, "duration": 3.21}, {"text": "is on the Y-axis.", "start": 1466.72, "duration": 2.01}, {"text": "This is actually\nplotted in reverse", "start": 1468.73, "duration": 2.01}, {"text": "because we're varying price\nas an exogenous variable", "start": 1470.74, "duration": 3.66}, {"text": "and plotting the demand.", "start": 1474.4, "duration": 2.61}, {"text": "No big deal.", "start": 1477.01, "duration": 1.3}, {"text": "I don't think I can\nplot it the other way.", "start": 1478.31, "duration": 2.69}, {"text": "Actually, I could.", "start": 1481.0, "duration": 0.96}, {"text": "But you'll see why\nthis can get confusing.", "start": 1481.96, "duration": 4.24}, {"text": "I just thought I'd point\nit out along the way.", "start": 1486.2, "duration": 3.55}, {"text": "OK.", "start": 1489.75, "duration": 1.2}, {"text": "Now we come to Giffen's Paradox.", "start": 1490.95, "duration": 2.85}, {"text": "If the income effect of a\nprice change is strong enough,", "start": 1493.8, "duration": 3.76}, {"text": "the change in the price\nand the resulting change", "start": 1497.56, "duration": 2.66}, {"text": "in the quantity\ndemanded could actually", "start": 1500.22, "duration": 2.28}, {"text": "move in the same direction.", "start": 1502.5, "duration": 2.7}, {"text": "So let me give you\nan example that's", "start": 1505.2, "duration": 1.55}, {"text": "attributed to Robert\nGiffen, who claimed", "start": 1506.75, "duration": 3.33}, {"text": "to observe this in Ireland,\nwhere they had a famine.", "start": 1510.08, "duration": 3.79}, {"text": "So the potato crop was failing,\nand the price of potatoes", "start": 1513.87, "duration": 3.35}, {"text": "was rising.", "start": 1517.22, "duration": 1.32}, {"text": "And despite the rise in\nprice, people consumed more.", "start": 1518.54, "duration": 3.94}, {"text": "So the demand curve\nwas upward-sloping, not", "start": 1522.48, "duration": 2.06}, {"text": "downward-sloping.", "start": 1524.54, "duration": 1.59}, {"text": "His explanation was, potatoes\nare a big part of the budget.", "start": 1526.13, "duration": 3.69}, {"text": "When their price goes up, the\neffect of income goes down.", "start": 1529.82, "duration": 4.11}, {"text": "And that income\neffect dominates.", "start": 1533.93, "duration": 2.37}, {"text": "The lower income effect is what\nlowers the demand for the good.", "start": 1536.3, "duration": 4.17}, {"text": "But in effect, prices\ngo up, and demand goes--", "start": 1540.47, "duration": 3.93}, {"text": "well, income's going down.", "start": 1544.4, "duration": 2.53}, {"text": "But this good is a necessity.", "start": 1546.93, "duration": 2.46}, {"text": "So you get a negative\nsign on the income effect,", "start": 1549.39, "duration": 3.21}, {"text": "so the demand is going up.", "start": 1552.6, "duration": 1.73}, {"text": "So price and income are\ngoing up at the same time.", "start": 1554.33, "duration": 3.85}, {"text": "It's a bit of a mouthful.", "start": 1558.18, "duration": 1.4}, {"text": "No pun intended.", "start": 1559.58, "duration": 1.2}, {"text": "Actually, this could\nnot have happened.", "start": 1560.78, "duration": 2.32}, {"text": "It would require\nthat potatoes be", "start": 1563.1, "duration": 2.36}, {"text": "an important part of the budget,\nthat potatoes be a necessity.", "start": 1565.46, "duration": 3.3}, {"text": "But what doesn't fit the facts\nis, how are they consuming more", "start": 1568.76, "duration": 3.03}, {"text": "potatoes when, in fact,\nthere was a blight,", "start": 1571.79, "duration": 3.18}, {"text": "and there were no more\npotatoes to be had?", "start": 1574.97, "duration": 3.61}, {"text": "So something doesn't\nadd up, literally.", "start": 1578.58, "duration": 3.05}, {"text": "Anyway, all intermediate\nmicro classes", "start": 1581.63, "duration": 3.57}, {"text": "typically feature Giffen\ngoods and then move on.", "start": 1585.2, "duration": 4.74}, {"text": "And you may be left\nwondering if it ever", "start": 1589.94, "duration": 2.13}, {"text": "really happens in practice.", "start": 1592.07, "duration": 1.68}, {"text": "So searching around, I\ndiscovered Jensen and Miller,", "start": 1593.75, "duration": 5.52}, {"text": "who actually ran an experiment.", "start": 1599.27, "duration": 4.11}, {"text": "So this is literally a\nrandomized controlled trial.", "start": 1603.38, "duration": 4.17}, {"text": "They went to China, two\ndifferent provinces,", "start": 1607.55, "duration": 3.15}, {"text": "looked at relatively\npoor households,", "start": 1610.7, "duration": 2.73}, {"text": "and changed the price of\nthe staple food item that", "start": 1613.43, "duration": 4.44}, {"text": "was a big part of their budget.", "start": 1617.87, "duration": 2.61}, {"text": "Now, in order to\nmake the comparison,", "start": 1620.48, "duration": 2.55}, {"text": "you've got to change the price.", "start": 1623.03, "duration": 1.66}, {"text": "So it was a randomized\ncontrolled trial,", "start": 1624.69, "duration": 2.43}, {"text": "meaning, randomly, some\nhouseholds were exposed", "start": 1627.12, "duration": 3.59}, {"text": "to a lower price because\nthey were given vouchers", "start": 1630.71, "duration": 2.64}, {"text": "so that when they\nwent to the store,", "start": 1633.35, "duration": 2.1}, {"text": "the sum of U unpaid\nplus vouchers", "start": 1635.45, "duration": 3.21}, {"text": "equaled the stated price.", "start": 1638.66, "duration": 2.055}, {"text": "But they didn't have to\npay for the vouchers.", "start": 1640.715, "duration": 1.875}, {"text": "So effectively, from\ntheir point of view,", "start": 1642.59, "duration": 2.28}, {"text": "the price was lowered,\ngiven the vouchers.", "start": 1644.87, "duration": 3.12}, {"text": "And the control group\ndid not receive vouchers.", "start": 1647.99, "duration": 3.27}, {"text": "So the control group faced\nthe normal market price.", "start": 1651.26, "duration": 3.54}, {"text": "And what Jensen and\nMiller are doing", "start": 1654.8, "duration": 2.28}, {"text": "is comparing the control group\nwith the treatment group.", "start": 1657.08, "duration": 3.6}, {"text": "And what they discovered\nwas, in Hunan, in the South,", "start": 1660.68, "duration": 3.75}, {"text": "rice was the staple good.", "start": 1664.43, "duration": 2.16}, {"text": "In Guangzhou, it's wheat.", "start": 1666.59, "duration": 2.49}, {"text": "They did surveys,\nlike Engel, before,", "start": 1669.08, "duration": 3.58}, {"text": "during, and after the subsidy\non both treatment and control", "start": 1672.66, "duration": 3.35}, {"text": "groups.", "start": 1676.01, "duration": 0.73}, {"text": "And they found strong evidence\nthat poor households in Hunan", "start": 1676.74, "duration": 3.92}, {"text": "experienced this Giffen\nbehavior with respect to rice.", "start": 1680.66, "duration": 3.33}, {"text": "That is to say, when the\nprice of rice went down,", "start": 1683.99, "duration": 3.99}, {"text": "households reduced\ntheir demand for rice.", "start": 1687.98, "duration": 3.48}, {"text": "The evidence was mixed\nin the other province.", "start": 1691.46, "duration": 3.81}, {"text": "And I think I will choose not\nto say very much about this.", "start": 1695.27, "duration": 4.92}, {"text": "There were groups, the very\npoorest and the least poor", "start": 1700.19, "duration": 3.51}, {"text": "that responded in what you might\nthink to be the ordinary way,", "start": 1703.7, "duration": 3.6}, {"text": "with price--", "start": 1707.3, "duration": 0.9}, {"text": "with demand down-sloping.", "start": 1708.2, "duration": 1.56}, {"text": "But there was a group in the\nmiddle between the very poorest", "start": 1709.76, "duration": 3.84}, {"text": "and the least poor which\nexhibited Giffen behavior.", "start": 1713.6, "duration": 3.87}, {"text": "As it's written on the slide,\nthis is a bit of a mystery.", "start": 1717.47, "duration": 3.48}, {"text": "Why is it that we're\ngetting this difference", "start": 1720.95, "duration": 1.92}, {"text": "across the three groups,\nor two groups plus one?", "start": 1722.87, "duration": 3.96}, {"text": "And I leave that for you\nbecause, again, the problem set", "start": 1726.83, "duration": 3.81}, {"text": "features the entire article.", "start": 1730.64, "duration": 1.86}, {"text": "We try to make it easy\nby highlighting the text.", "start": 1732.5, "duration": 4.02}, {"text": "But somewhere in that\npaper is a discussion", "start": 1736.52, "duration": 2.76}, {"text": "of why this result, which is\na bit hard to interpret here,", "start": 1739.28, "duration": 4.08}, {"text": "does happen.", "start": 1743.36, "duration": 1.41}, {"text": "The authors did give\nit an interpretation.", "start": 1744.77, "duration": 2.68}, {"text": "So that's advertising to go\nand grab that paper, which", "start": 1747.45, "duration": 3.83}, {"text": "I think I already have.", "start": 1751.28, "duration": 1.23}, {"text": "Yes, question?", "start": 1752.51, "duration": 1.5}, {"text": "AUDIENCE: Yeah, so is the\ndemand the amount of potatoes", "start": 1754.01, "duration": 4.38}, {"text": "or rice you're consuming,\nor the proportion", "start": 1758.39, "duration": 2.4}, {"text": "that is of your income\nthat's increasing?", "start": 1760.79, "duration": 3.517}, {"text": "ROBERT M. TOWNSEND:\nIt's the quantity.", "start": 1764.307, "duration": 1.583}, {"text": "But obviously, they\nhave the prices.", "start": 1765.89, "duration": 2.16}, {"text": "So you can look at both.", "start": 1768.05, "duration": 3.63}, {"text": "But the definition we've been\nusing of a Giffen good, it's--", "start": 1771.68, "duration": 6.315}, {"text": "well, actually, it never showed.", "start": 1781.78, "duration": 2.72}, {"text": "But it is the quantity-- in this\ncase, the quantity of potatoes,", "start": 1784.5, "duration": 3.81}, {"text": "not expenditure on potatoes.", "start": 1788.31, "duration": 1.635}, {"text": "All right.", "start": 1796.66, "duration": 2.58}, {"text": "OK, so now I want to get\nto something, effectively,", "start": 1799.24, "duration": 3.51}, {"text": "we've already been doing,\nwhich is compensated", "start": 1802.75, "duration": 3.9}, {"text": "versus uncompensated demands.", "start": 1806.65, "duration": 3.74}, {"text": "So the uncompensated\ndemand is the total demand,", "start": 1810.39, "duration": 3.26}, {"text": "sometimes called the Marshallian\ndemand from Marshall,", "start": 1813.65, "duration": 4.51}, {"text": "who was an early\nEnglish economist.", "start": 1818.16, "duration": 2.45}, {"text": "It shows the relationship\nbetween price of the good", "start": 1820.61, "duration": 2.52}, {"text": "and the quantity purchased,\nassuming that all other prices", "start": 1823.13, "duration": 3.21}, {"text": "and income are held constant.", "start": 1826.34, "duration": 1.89}, {"text": "The compensated demand,\nsometimes called the Hicksian", "start": 1828.23, "duration": 2.97}, {"text": "demand, shows the relationship\nbetween price and quantity.", "start": 1831.2, "duration": 3.66}, {"text": "It continues to assume that\nall the other prices are", "start": 1834.86, "duration": 3.21}, {"text": "held fixed.", "start": 1838.07, "duration": 0.66}, {"text": "But instead of holding income\nfixed, utility is held fixed.", "start": 1838.73, "duration": 3.85}, {"text": "So to go back to\nthe earlier slides,", "start": 1842.58, "duration": 2.24}, {"text": "we were featuring the\nsubstitution effect", "start": 1844.82, "duration": 2.97}, {"text": "as the movement along\nan indifference curve--", "start": 1847.79, "duration": 3.18}, {"text": "i.e., holding utility fixed.", "start": 1850.97, "duration": 2.34}, {"text": "So when we looked at how\nmuch demand would change", "start": 1853.31, "duration": 3.03}, {"text": "one way or the other as a\nfunction of the price change,", "start": 1856.34, "duration": 3.18}, {"text": "and we went along the initial\nbaseline indifference curve,", "start": 1859.52, "duration": 4.41}, {"text": "that was the compensated demand.", "start": 1863.93, "duration": 3.95}, {"text": "So more dramatically, if\nwe fix the initial point", "start": 1867.88, "duration": 4.95}, {"text": "and change the price, we\nwould be, for a lower price,", "start": 1872.83, "duration": 4.92}, {"text": "pivoting along this\nindifference curve, U2.", "start": 1877.75, "duration": 3.84}, {"text": "By construction, we keep\nutility constant at U2.", "start": 1881.59, "duration": 4.98}, {"text": "And then plot the demands,\nwhich are going up,", "start": 1886.57, "duration": 3.51}, {"text": "and we put that on the\nprice quantity diagram,", "start": 1890.08, "duration": 2.91}, {"text": "and the demand curve\nis sloping down.", "start": 1892.99, "duration": 2.32}, {"text": "But this is the Hicksian\ndemand at little h", "start": 1895.31, "duration": 3.32}, {"text": "to remind us that it's Hicks.", "start": 1898.63, "duration": 3.51}, {"text": "So putting both types of\ndemand on the same diagram,", "start": 1902.14, "duration": 5.57}, {"text": "we'd have the normal demand,\nor the Marshallian demand,", "start": 1907.71, "duration": 4.59}, {"text": "and h for the Hicksian demand.", "start": 1912.3, "duration": 2.56}, {"text": "So as price goes\ndown, demand goes up,", "start": 1914.86, "duration": 3.86}, {"text": "but the demand goes up\nfrom two different effects.", "start": 1918.72, "duration": 3.01}, {"text": "One is the substitution effect\nholding utility constant,", "start": 1921.73, "duration": 3.8}, {"text": "and that's a point on\nthe Hicksian demand.", "start": 1925.53, "duration": 3.94}, {"text": "And then the rest of it is this\nmovement to the Marshallian", "start": 1929.47, "duration": 4.01}, {"text": "demand, or ordinary demand,\nwhich is the income effect that", "start": 1933.48, "duration": 3.33}, {"text": "comes from the lower price.", "start": 1936.81, "duration": 3.02}, {"text": "And obviously, we can go\nin the other direction.", "start": 1939.83, "duration": 2.82}, {"text": "Starting here as a baseline,\nif we increase the price,", "start": 1942.65, "duration": 5.85}, {"text": "we would pivot along\nthe indifference curve", "start": 1948.5, "duration": 2.43}, {"text": "and get a lower demand due\nto the substitution effect.", "start": 1950.93, "duration": 3.28}, {"text": "But effective income\nhas gone down,", "start": 1954.21, "duration": 2.12}, {"text": "so this negative\nincome effect kicks in,", "start": 1956.33, "duration": 3.15}, {"text": "and demand is even less.", "start": 1959.48, "duration": 2.23}, {"text": "So kind of intuitively,\nthe Hicksian demand", "start": 1961.71, "duration": 4.22}, {"text": "is steeper than the\nordinary demand curve", "start": 1965.93, "duration": 4.02}, {"text": "because it has included\nthose income effects.", "start": 1969.95, "duration": 3.9}, {"text": "Or putting in another way,\nthe ordinary demand curve", "start": 1973.85, "duration": 3.72}, {"text": "is, quote, flatter\nwith a lower slope", "start": 1977.57, "duration": 3.42}, {"text": "because there's a more dramatic\nlarger change in the quantity", "start": 1980.99, "duration": 4.98}, {"text": "as we change the price.", "start": 1985.97, "duration": 1.77}, {"text": "Either the income\neffect is positive,", "start": 1987.74, "duration": 2.22}, {"text": "and demand goes up all\nthe more, or the income", "start": 1989.96, "duration": 2.37}, {"text": "effect is negative, and the\ndemand decreases all the more.", "start": 1992.33, "duration": 4.72}, {"text": "So we could say-- be\ncareful about this--", "start": 1997.05, "duration": 2.4}, {"text": "that, in some sense,\nthe ordinary demand", "start": 1999.45, "duration": 2.4}, {"text": "curve is more elastic.", "start": 2001.85, "duration": 1.62}, {"text": "At least here, it has\na higher derivative.", "start": 2003.47, "duration": 4.67}, {"text": "So there's a\nmathematical expression", "start": 2008.14, "duration": 3.98}, {"text": "for the difference between\nthe Hicksian demand", "start": 2012.12, "duration": 2.94}, {"text": "and the ordinary demand.", "start": 2015.06, "duration": 2.19}, {"text": "Namely, the derivative\nof demand of good X", "start": 2017.25, "duration": 3.75}, {"text": "as we change the price of X,\nthe slope of the ordinary demand", "start": 2021.0, "duration": 3.51}, {"text": "curve, is first term,\nthe substitution effect", "start": 2024.51, "duration": 4.59}, {"text": "of the price change, PX,\nbut then this income effect", "start": 2029.1, "duration": 4.02}, {"text": "kicks in.", "start": 2033.12, "duration": 1.17}, {"text": "And there's two pieces\nto the income effect.", "start": 2034.29, "duration": 3.18}, {"text": "One has to do with how high\nis the marginal change in X", "start": 2037.47, "duration": 4.5}, {"text": "as you change income.", "start": 2041.97, "duration": 1.78}, {"text": "The other is, how much X you\nwere eating to begin with.", "start": 2043.75, "duration": 3.86}, {"text": "Think of potatoes, and\nso on, or those budget", "start": 2047.61, "duration": 3.359}, {"text": "shares, either Engel\nor-- but this is X.", "start": 2050.969, "duration": 2.73}, {"text": "This is the quantity.", "start": 2053.699, "duration": 1.331}, {"text": "So it looks, from this, since\nwe're subtracting-- say,", "start": 2055.03, "duration": 3.74}, {"text": "the income effect is\npositive, and X is positive.", "start": 2058.77, "duration": 3.31}, {"text": "Then we're subtracting\na positive number.", "start": 2062.08, "duration": 2.34}, {"text": "So it looks like this minus\nthis must be lower than this.", "start": 2064.42, "duration": 4.02}, {"text": "So it looks like\nthe ordinary demand", "start": 2068.44, "duration": 1.85}, {"text": "should have a lower slope if\nthis equation is accurate.", "start": 2070.29, "duration": 3.76}, {"text": "But in fact, as I just said,\nit's the other way around.", "start": 2074.05, "duration": 2.87}, {"text": "Puzzle, puzzle, puzzle.", "start": 2076.92, "duration": 1.44}, {"text": "What's going on?", "start": 2078.36, "duration": 1.2}, {"text": "Well, it's this stupid\nway that we traditionally", "start": 2079.56, "duration": 3.36}, {"text": "plot the dependent\nvariable on the X-axis.", "start": 2082.92, "duration": 3.43}, {"text": "So this is dX/dP, the response\nof the dependent variable", "start": 2086.35, "duration": 4.639}, {"text": "to the independent\nvariable, which", "start": 2090.989, "duration": 1.891}, {"text": "is 1 over the slope of this.", "start": 2092.88, "duration": 2.73}, {"text": "So this diagram is consistent\nwith this equation.", "start": 2095.61, "duration": 3.18}, {"text": "It just takes a little bit\nof juggling to realize why.", "start": 2098.79, "duration": 3.72}, {"text": "Anyway, this is called\nSlutsky's equation.", "start": 2102.51, "duration": 3.03}, {"text": "And again, at the risk of\ntrying to do too much too", "start": 2105.54, "duration": 3.15}, {"text": "fast, but on the\nother hand, providing", "start": 2108.69, "duration": 2.31}, {"text": "some motivation for\nwhere we're going,", "start": 2111.0, "duration": 2.28}, {"text": "eventually, we'll get to\nlecture 19 and talk about", "start": 2113.28, "duration": 3.39}, {"text": "whether there are retractable\nrestrictions on data, as", "start": 2116.67, "duration": 4.44}, {"text": "in the science lecture.", "start": 2121.11, "duration": 1.35}, {"text": "We have a model.", "start": 2122.46, "duration": 1.11}, {"text": "Does the model fit\nthe data or not?", "start": 2123.57, "duration": 1.86}, {"text": "Can you even reject the model?", "start": 2125.43, "duration": 2.49}, {"text": "Is it providing some guidance?", "start": 2127.92, "duration": 1.8}, {"text": "Or you can always tweak things,\nso the model is always true.", "start": 2129.72, "duration": 3.67}, {"text": "So this lecture 19\nis about restrictions", "start": 2133.39, "duration": 3.29}, {"text": "that can be tested.", "start": 2136.68, "duration": 1.59}, {"text": "And there's something\ncalled Slutsky, same guy,", "start": 2138.27, "duration": 3.99}, {"text": "Slutsky's Decomposition\nthis equation is", "start": 2142.26, "duration": 3.21}, {"text": "a generalization of the\none I was just showing you,", "start": 2145.47, "duration": 2.7}, {"text": "with the exception that\nwe put this substitution", "start": 2148.17, "duration": 3.03}, {"text": "effect on the left and\nthe regular derivative", "start": 2151.2, "duration": 3.12}, {"text": "on the right.", "start": 2154.32, "duration": 0.85}, {"text": "So it looks like the\nsigns are changing.", "start": 2155.17, "duration": 2.0}, {"text": "This becomes a plus.", "start": 2157.17, "duration": 1.78}, {"text": "This is a generalization\nin a number of respects.", "start": 2158.95, "duration": 3.44}, {"text": "We're looking at the\ndemand for good L", "start": 2162.39, "duration": 3.06}, {"text": "as we change the price of\nanother good, good K, not", "start": 2165.45, "duration": 3.54}, {"text": "the own effect of one good\nwith respect to its own price,", "start": 2168.99, "duration": 3.45}, {"text": "but a cross-partial derivative.", "start": 2172.44, "duration": 2.25}, {"text": "Although we still have this\nincome effect over here,", "start": 2174.69, "duration": 2.49}, {"text": "and we're still weighting it by\nthe initial quantity purchased.", "start": 2177.18, "duration": 3.15}, {"text": "So it turns out that\nwhat we want to do", "start": 2180.33, "duration": 3.27}, {"text": "is ask whether observe demands--", "start": 2183.6, "duration": 3.9}, {"text": "this guy, these guys, really--", "start": 2187.5, "duration": 3.15}, {"text": "how demand is changing\nwith prices and income,", "start": 2190.65, "duration": 3.07}, {"text": "whether there are patterns\nwhich could be rejected as being", "start": 2193.72, "duration": 3.29}, {"text": "inconsistent with a model.", "start": 2197.01, "duration": 1.75}, {"text": "And the problem is\nthat the restrictions", "start": 2198.76, "duration": 2.15}, {"text": "are on these Hicksian demands,\nand we don't see those.", "start": 2200.91, "duration": 3.15}, {"text": "We see the regular demands.", "start": 2204.06, "duration": 1.38}, {"text": "We don't see the\nHicksian demands.", "start": 2205.44, "duration": 2.28}, {"text": "And I'll say more\nabout this in a minute.", "start": 2207.72, "duration": 2.52}, {"text": "It turns out that,\nwith some math,", "start": 2210.24, "duration": 2.22}, {"text": "you can actually\ngo back and forth", "start": 2212.46, "duration": 1.86}, {"text": "between the regular demand\nand the Hicksian in demand,", "start": 2214.32, "duration": 2.73}, {"text": "and there are restrictions.", "start": 2217.05, "duration": 1.62}, {"text": "So anyway, I'm\nrunning an experiment", "start": 2218.67, "duration": 2.52}, {"text": "now because I'm\nshowing you things", "start": 2221.19, "duration": 2.52}, {"text": "that are more toward\nthe end of the class", "start": 2223.71, "duration": 2.91}, {"text": "set of lectures than\nat the beginning.", "start": 2226.62, "duration": 2.07}, {"text": "But since we're introducing\nSlutsky's equation today,", "start": 2228.69, "duration": 3.72}, {"text": "I thought I'd show you that\nwe will come back to it", "start": 2232.41, "duration": 2.43}, {"text": "and use it in a\nsubsequent lecture.", "start": 2234.84, "duration": 2.76}, {"text": "This is a lot simpler notation.", "start": 2237.6, "duration": 2.52}, {"text": "And don't worry about either\nthe income expansion paths", "start": 2240.12, "duration": 3.6}, {"text": "or this generalization\nof Slutsky.", "start": 2243.72, "duration": 2.64}, {"text": "That was meant to be a\npreview of coming attractions", "start": 2246.36, "duration": 2.97}, {"text": "and motivation, not something\nyou should be worried", "start": 2249.33, "duration": 2.49}, {"text": "about learning right away.", "start": 2251.82, "duration": 2.65}, {"text": "So now I want to introduce\nsomething called duality.", "start": 2254.47, "duration": 3.71}, {"text": "This looks like an\nincome expansion path.", "start": 2258.18, "duration": 2.94}, {"text": "As we increase income, we\nget more and more points.", "start": 2261.12, "duration": 3.84}, {"text": "I think this is identical\nwith the figure I showed you", "start": 2264.96, "duration": 2.7}, {"text": "earlier.", "start": 2267.66, "duration": 1.64}, {"text": "But I want to use it\nfor a different purpose.", "start": 2269.3, "duration": 2.46}, {"text": "I want to say, suppose\nwe're at this point", "start": 2271.76, "duration": 3.35}, {"text": "with this intermediate\nincome, I2.", "start": 2275.11, "duration": 3.36}, {"text": "And we could be maximizing\nutility subject to that income", "start": 2278.47, "duration": 3.72}, {"text": "level holding prices fixed.", "start": 2282.19, "duration": 2.43}, {"text": "And X2,Y2 would be the\nmaximum point of utility.", "start": 2284.62, "duration": 5.1}, {"text": "But suppose we did a\ndifferent experiment.", "start": 2289.72, "duration": 2.59}, {"text": "Suppose we wanted to\nachieve this utility", "start": 2292.31, "duration": 3.32}, {"text": "level, U2, by spending\nas little as possible.", "start": 2295.63, "duration": 3.97}, {"text": "The amount spent\nwould be captured", "start": 2299.6, "duration": 1.67}, {"text": "by these various\npossible budget lines.", "start": 2301.27, "duration": 2.58}, {"text": "So something called a\nminimizing expenditure problem,", "start": 2303.85, "duration": 3.63}, {"text": "minimal expenditure\nproblem, would", "start": 2307.48, "duration": 2.4}, {"text": "be to find the\nbudget line, which", "start": 2309.88, "duration": 2.13}, {"text": "is lowest, closest to 0,0,\nand still allows the household", "start": 2312.01, "duration": 4.74}, {"text": "to get the utility level U2.", "start": 2316.75, "duration": 2.28}, {"text": "So at this point, it's clear.", "start": 2319.03, "duration": 2.91}, {"text": "You could think of this as\nmaximizing utility subject", "start": 2321.94, "duration": 2.94}, {"text": "to a fixed budget or\nminimizing the expenses to get", "start": 2324.88, "duration": 3.42}, {"text": "to a fixed level of utility.", "start": 2328.3, "duration": 2.04}, {"text": "Both things are true and,\nyou can go back and forth.", "start": 2330.34, "duration": 3.31}, {"text": "And that is the essential\nidea of duality.", "start": 2333.65, "duration": 4.67}, {"text": "OK, let's do it a bit\nmore with notation.", "start": 2338.32, "duration": 4.41}, {"text": "Let's take a consumer\nwith a consumption", "start": 2342.73, "duration": 2.21}, {"text": "set in L-dimensional\ncommodity space", "start": 2344.94, "duration": 3.6}, {"text": "with the preferences represented\nby a continuous utility", "start": 2348.54, "duration": 4.8}, {"text": "function.", "start": 2353.34, "duration": 1.63}, {"text": "And let's look at the\nUtility Maximization Problem,", "start": 2354.97, "duration": 4.05}, {"text": "UMP for short,\nwhich is to maximize", "start": 2359.02, "duration": 3.96}, {"text": "utility subject to\nbeing within the budget.", "start": 2362.98, "duration": 3.66}, {"text": "So this says, choose a point\nin the consumption set,", "start": 2366.64, "duration": 3.045}, {"text": "all of the positive [INAUDIBLE],,\nwhich maximizes that utility", "start": 2369.685, "duration": 6.105}, {"text": "function subject to, the points\nunder consideration have to be", "start": 2375.79, "duration": 4.08}, {"text": "such that, when you take\nthe dot product of P and X,", "start": 2379.87, "duration": 3.21}, {"text": "P1,X1 plus P2,X2, dot, dot,\ndot, it cannot exceed wealth", "start": 2383.08, "duration": 5.49}, {"text": "or income.", "start": 2388.57, "duration": 1.12}, {"text": "So that's the utility\nmaximization problem.", "start": 2389.69, "duration": 4.7}, {"text": "The result of solving\nthe maximization problem", "start": 2394.39, "duration": 4.47}, {"text": "can be substituted\ninto utility--", "start": 2398.86, "duration": 2.46}, {"text": "in other words, utility\nat the maximal solution.", "start": 2401.32, "duration": 4.12}, {"text": "And we're going to call\nthat the value function", "start": 2405.44, "duration": 2.72}, {"text": "or indirect utility function.", "start": 2408.16, "duration": 2.8}, {"text": "Note that the maximized utility\nis a function of the parameters", "start": 2410.96, "duration": 4.25}, {"text": "or the exogenous\nvariables of the problem--", "start": 2415.21, "duration": 2.88}, {"text": "namely, the Price\nvector, p, and Wealth, w.", "start": 2418.09, "duration": 5.53}, {"text": "Now, in contrast, the\nExpenditure Minimization", "start": 2423.62, "duration": 3.93}, {"text": "Problem, EMP, is to--", "start": 2427.55, "duration": 4.5}, {"text": "given a certain\nlevel of utility--", "start": 2432.05, "duration": 2.94}, {"text": "minimize expenditures,\nthe dot product P.X,", "start": 2434.99, "duration": 6.19}, {"text": "that allows you to achieve\nat least that utility.", "start": 2441.18, "duration": 4.46}, {"text": "Getting more is fine.", "start": 2445.64, "duration": 1.3}, {"text": "But in most of the\nfigures we show,", "start": 2446.94, "duration": 3.11}, {"text": "this will be at an equality.", "start": 2450.05, "duration": 1.53}, {"text": "But just like you could\nspend less than your income", "start": 2451.58, "duration": 4.29}, {"text": "in principle, here,\nyou could achieve", "start": 2455.87, "duration": 2.43}, {"text": "a higher level of utility.", "start": 2458.3, "duration": 1.77}, {"text": "But whatever you're doing here\nin the expenditure minimization", "start": 2460.07, "duration": 4.11}, {"text": "problem, you're trying to\nminimize total expenditures.", "start": 2464.18, "duration": 2.73}, {"text": "And we call the solution to\nthat the E for Expenditure--", "start": 2466.91, "duration": 6.16}, {"text": "minimized expenditure\nat the optimum--", "start": 2473.07, "duration": 3.51}, {"text": "is a function of the parameters\nof the problem, the same price", "start": 2476.58, "duration": 3.75}, {"text": "vector p.", "start": 2480.33, "duration": 1.14}, {"text": "But now what's taken as a\ngiven is u, not w, but u.", "start": 2481.47, "duration": 5.7}, {"text": "So we'll have this notation for\nvalue function and expenditure", "start": 2487.17, "duration": 3.99}, {"text": "functions.", "start": 2491.16, "duration": 1.08}, {"text": "Expenditure functions and\ndemands, for that matter,", "start": 2492.24, "duration": 3.24}, {"text": "have certain properties.", "start": 2495.48, "duration": 1.98}, {"text": "It turns out, the expenditure\nfunction is concave,", "start": 2497.46, "duration": 3.42}, {"text": "and the derivative of the\nexpenditure function is demand.", "start": 2500.88, "duration": 4.72}, {"text": "So when you take the second\nderivative of demand,", "start": 2505.6, "duration": 3.08}, {"text": "it picks up the concavity of\nthe level expenditure function.", "start": 2508.68, "duration": 4.63}, {"text": "And that's why that\nSlutsky equation", "start": 2513.31, "duration": 3.35}, {"text": "holds because we're\nlooking at the matrix", "start": 2516.66, "duration": 3.15}, {"text": "of second-order\nconditions, effectively.", "start": 2519.81, "duration": 2.87}, {"text": "But again, just ignore\nme if that's confusing.", "start": 2522.68, "duration": 3.27}, {"text": "We'll get there in\nthat lecture 19.", "start": 2525.95, "duration": 2.49}, {"text": "For now, I just want to\nfocus on this relationship,", "start": 2528.44, "duration": 3.75}, {"text": "this duality.", "start": 2532.19, "duration": 1.11}, {"text": "And there's a number\nof ways to put it.", "start": 2533.3, "duration": 2.16}, {"text": "The notation is\nsurprisingly subtle.", "start": 2535.46, "duration": 2.37}, {"text": "But if you work\nthrough it, it's fine.", "start": 2537.83, "duration": 2.04}, {"text": "So suppose we're given a\ncontinuous utility function", "start": 2539.87, "duration": 2.91}, {"text": "representing locally nonsatiated\npreferences with a consumption", "start": 2542.78, "duration": 4.08}, {"text": "set, strictly\npositive price vector.", "start": 2546.86, "duration": 2.67}, {"text": "If x* star is optimal under the\nutility max problem for a given", "start": 2549.53, "duration": 4.65}, {"text": "wealth at those prices, then x*\nis optimal in the expenditure", "start": 2554.18, "duration": 4.23}, {"text": "minimization problem when\nthe required utility level is", "start": 2558.41, "duration": 4.47}, {"text": "the utility you achieve under\nthe utility maximization", "start": 2562.88, "duration": 4.14}, {"text": "problem.", "start": 2567.02, "duration": 1.05}, {"text": "I showed you a picture of\nthat just a minute ago.", "start": 2568.07, "duration": 3.43}, {"text": "And the minimized expenditure\nwhen you solve the EMP", "start": 2571.5, "duration": 4.4}, {"text": "is exactly the wealth that you\nhad in the utility maximization", "start": 2575.9, "duration": 5.37}, {"text": "problem.", "start": 2581.27, "duration": 1.27}, {"text": "Let me go back.", "start": 2582.54, "duration": 1.26}, {"text": "So I started here.", "start": 2583.8, "duration": 1.71}, {"text": "We had income I.\nPrices were given.", "start": 2585.51, "duration": 3.2}, {"text": "You maximized utility, ended\nup at U2, given I and P.", "start": 2588.71, "duration": 6.48}, {"text": "We had a certain optimizing\nsolution here called X2,Y2 that", "start": 2595.19, "duration": 6.81}, {"text": "solves the utility\nmaximization problem.", "start": 2602.0, "duration": 3.06}, {"text": "And then I said, what if we\nfix the utility level instead", "start": 2605.06, "duration": 5.49}, {"text": "and solve the expenditure\nminimization problem, which", "start": 2610.55, "duration": 3.0}, {"text": "is finding the expenditure\nlevel earmarked by these budget", "start": 2613.55, "duration": 3.33}, {"text": "lines, which is minimal and,\nyet, allows us to achieve", "start": 2616.88, "duration": 4.74}, {"text": "the utility level U2.", "start": 2621.62, "duration": 2.16}, {"text": "So this budget line, which was\na budget line for the utility", "start": 2623.78, "duration": 3.54}, {"text": "maximization problem, is kind\nof the minimized expenditure", "start": 2627.32, "duration": 4.59}, {"text": "line for the expenditure\nminimization problem.", "start": 2631.91, "duration": 4.358}, {"text": "I don't know.", "start": 2636.268, "duration": 0.542}, {"text": "Maybe the picture\nis just easier.", "start": 2636.81, "duration": 2.37}, {"text": "But the notation says that.", "start": 2639.18, "duration": 2.34}, {"text": "And it actually\ngoes the other way.", "start": 2641.52, "duration": 2.71}, {"text": "If x* were solving the\nexpenditure minimization", "start": 2644.23, "duration": 3.74}, {"text": "problem, when the required\nutility level is parameter u", "start": 2647.97, "duration": 5.46}, {"text": "then x* is also optimal--", "start": 2653.43, "duration": 3.15}, {"text": "the same x-- in the utility\nmaximization problem,", "start": 2656.58, "duration": 3.36}, {"text": "where we give the\nguys wealth equal", "start": 2659.94, "duration": 2.28}, {"text": "to the minimized expenditure.", "start": 2662.22, "duration": 3.15}, {"text": "And when they solve the\nutility maximization problem", "start": 2665.37, "duration": 3.57}, {"text": "at that level of wealth,\nthey end up exactly", "start": 2668.94, "duration": 3.21}, {"text": "with the u we started with in\nthe expenditure minimization", "start": 2672.15, "duration": 3.57}, {"text": "problem.", "start": 2675.72, "duration": 2.69}, {"text": "Relatedly-- and this is\nthe most compact notation", "start": 2678.41, "duration": 3.99}, {"text": "of all that's kind of cool.", "start": 2682.4, "duration": 3.28}, {"text": "Another way to state\nthe proposition", "start": 2685.68, "duration": 2.03}, {"text": "is to say that, given equation\n3, when we start, given a price", "start": 2687.71, "duration": 5.88}, {"text": "vector p, we are\nfixing prices p,", "start": 2693.59, "duration": 4.41}, {"text": "we give the guy\nincome or wealth, w.", "start": 2698.0, "duration": 3.24}, {"text": "We solve the utility\nmaximization problem.", "start": 2701.24, "duration": 2.85}, {"text": "We substitute the maximizing\ndemands into utility.", "start": 2704.09, "duration": 3.99}, {"text": "We get the indirect\nutility function.", "start": 2708.08, "duration": 2.88}, {"text": "Now, starting with\nthat level of utility,", "start": 2710.96, "duration": 2.58}, {"text": "we do the expenditure\nminimization problem", "start": 2713.54, "duration": 3.03}, {"text": "and the minimized\nexpenditures at that", "start": 2716.57, "duration": 2.67}, {"text": "the in particular utility\nlevel is W all over again.", "start": 2719.24, "duration": 3.67}, {"text": "So it's like feeding\nback to itself.", "start": 2722.91, "duration": 1.745}, {"text": "Likewise here, we start with\nthe parameterized level of u", "start": 2728.11, "duration": 4.44}, {"text": "in the expenditure minimization\nproblem, taking, again, p.", "start": 2732.55, "duration": 3.69}, {"text": "Vector p is given.", "start": 2736.24, "duration": 1.74}, {"text": "At that level u, we solve for\nthe minimized expenditure,", "start": 2737.98, "duration": 4.26}, {"text": "which we called e of p and u.", "start": 2742.24, "duration": 2.73}, {"text": "And if we take that minimized\nexpenditure and substituted it", "start": 2744.97, "duration": 3.84}, {"text": "as a wealth term and solve\nthe utility maximization", "start": 2748.81, "duration": 3.6}, {"text": "problem at that\nwealth, we would get", "start": 2752.41, "duration": 2.4}, {"text": "that the indirect\nutility is exactly", "start": 2754.81, "duration": 2.64}, {"text": "the u that we started with.", "start": 2757.45, "duration": 2.2}, {"text": "So it is a bit of a mouthful.", "start": 2759.65, "duration": 2.93}, {"text": "The notation is quite\ncompact, and you may just", "start": 2762.58, "duration": 3.09}, {"text": "have a white-out\nmoment when you see it.", "start": 2765.67, "duration": 2.92}, {"text": "But it is repeating in different\nways in related notation.", "start": 2768.59, "duration": 5.52}, {"text": "Oh, this also means that e and\nv are inverses of one another", "start": 2774.11, "duration": 5.0}, {"text": "in the sense that take e and\nmultiply by some imagined e", "start": 2779.11, "duration": 3.93}, {"text": "inverse, and you'd get rid\nof e on the left-hand side", "start": 2783.04, "duration": 3.45}, {"text": "and have an e inverse\non the right-hand side.", "start": 2786.49, "duration": 2.53}, {"text": "So you'd have the\nvalue of function", "start": 2789.02, "duration": 2.39}, {"text": "is an inverse of v. Sorry,\nI said that wrong, actually.", "start": 2791.41, "duration": 6.54}, {"text": "If you take e and get rid\nof it by taking e inverse,", "start": 2797.95, "duration": 4.71}, {"text": "when you take the inverse\nof the expenditure function,", "start": 2802.66, "duration": 2.73}, {"text": "you end up with\na value function.", "start": 2805.39, "duration": 2.37}, {"text": "And likewise, when you take the\ninverse of the value function,", "start": 2807.76, "duration": 3.54}, {"text": "you'll end up with the\nexpenditure function.", "start": 2811.3, "duration": 3.0}, {"text": "OK, I said it\nright at that time.", "start": 2814.3, "duration": 2.883}, {"text": "There's a question.", "start": 2817.183, "duration": 0.792}, {"text": "AUDIENCE: You keep saying\nindirect utility function--", "start": 2822.865, "duration": 2.633}, {"text": "or, I guess, what do you\nmean when you say indirect?", "start": 2825.498, "duration": 2.167}, {"text": "ROBERT M. TOWNSEND:\nIt has a label.", "start": 2830.062, "duration": 1.458}, {"text": "I mean, v looks like value.", "start": 2831.52, "duration": 2.31}, {"text": "You say, value function.", "start": 2833.83, "duration": 1.26}, {"text": "But it's called the\nindirect utility function", "start": 2835.09, "duration": 2.55}, {"text": "in the literature.", "start": 2837.64, "duration": 1.168}, {"text": "AUDIENCE: OK.", "start": 2838.808, "duration": 0.542}, {"text": "ROBERT M. TOWNSEND: That's\nthe name that we give it.", "start": 2839.35, "duration": 3.87}, {"text": "So Hicksian Demand is solving\nthe expenditure minimization", "start": 2843.22, "duration": 4.98}, {"text": "problem.", "start": 2848.2, "duration": 1.18}, {"text": "And we have the Hicksian\ndemand or demand correspondence", "start": 2849.38, "duration": 3.59}, {"text": "if there's more\nthan one solution.", "start": 2852.97, "duration": 2.01}, {"text": "And then the diagram, so\nthere's been a unique solution.", "start": 2854.98, "duration": 3.34}, {"text": "This looks like\nit's a new slide.", "start": 2858.32, "duration": 2.27}, {"text": "But actually, right\nfrom the very beginning,", "start": 2860.59, "duration": 2.94}, {"text": "where we were talking about\nprice effects and income", "start": 2863.53, "duration": 2.67}, {"text": "effects, and we defined the\nprice effect as a substitution", "start": 2866.2, "duration": 2.97}, {"text": "effect, we were moving along\na given indifference curve.", "start": 2869.17, "duration": 2.86}, {"text": "So we were really talking about\nHicksian demands all along.", "start": 2872.03, "duration": 3.14}, {"text": "And again, for\nthe third time, we", "start": 2875.17, "duration": 2.31}, {"text": "have a different way\nof stating the problem,", "start": 2877.48, "duration": 2.22}, {"text": "that the ordinary demand is\nequal to the Hicksian demand", "start": 2879.7, "duration": 5.52}, {"text": "evaluated at a\nutility level, which", "start": 2885.22, "duration": 2.19}, {"text": "is the indirect utility of the\nutility maximization problem.", "start": 2887.41, "duration": 3.9}, {"text": "And likewise, for the\nexpenditure minimization", "start": 2891.31, "duration": 2.82}, {"text": "problem.", "start": 2894.13, "duration": 0.9}, {"text": "This is, as I've been saying,\ntrue starting at this point.", "start": 2895.03, "duration": 5.29}, {"text": "You start looking at it\none way or the other.", "start": 2900.32, "duration": 2.18}, {"text": "You end up with\nexactly the same point.", "start": 2902.5, "duration": 3.74}, {"text": "But if we start actually\ntaking discrete changes,", "start": 2906.24, "duration": 3.93}, {"text": "things are a bit different.", "start": 2910.17, "duration": 1.3}, {"text": "And in fact, we were actually\ndoing that at the beginning,", "start": 2911.47, "duration": 3.03}, {"text": "right?", "start": 2914.5, "duration": 0.5}, {"text": "We were talking about\na non-trivial decrease", "start": 2915.0, "duration": 3.33}, {"text": "in the price of X.", "start": 2918.33, "duration": 3.45}, {"text": "So let's talk about discrete\nchanges and compensated demand.", "start": 2921.78, "duration": 6.08}, {"text": "We start with p and w.", "start": 2927.86, "duration": 1.5}, {"text": "We have the maximized\ndemand, x, for that given w.", "start": 2929.36, "duration": 6.18}, {"text": "But we change p\nfrom p to p prime.", "start": 2935.54, "duration": 3.81}, {"text": "Then w prime would, say, be\nthe minimized expenditure", "start": 2939.35, "duration": 5.91}, {"text": "at the level of utility,\nu, the initial level", "start": 2945.26, "duration": 3.99}, {"text": "of utility at the baseline but\nwith the new different price", "start": 2949.25, "duration": 5.73}, {"text": "vector, p prime.", "start": 2954.98, "duration": 1.65}, {"text": "And we call that new wealth\nas opposed to old wealth.", "start": 2956.63, "duration": 3.57}, {"text": "Call it w prime.", "start": 2960.2, "duration": 1.45}, {"text": "So in words, that level\nof income or wealth", "start": 2961.65, "duration": 3.59}, {"text": "w prime is the one that, under\nthe new price vector p prime,", "start": 2965.24, "duration": 4.56}, {"text": "would minimize the expenses\nat p prime of achieving", "start": 2969.8, "duration": 4.68}, {"text": "the old utility level.", "start": 2974.48, "duration": 1.38}, {"text": "Remember, when we\nchange the price,", "start": 2975.86, "duration": 1.53}, {"text": "we just rotate it along\nthe indifference curve", "start": 2977.39, "duration": 2.64}, {"text": "going one way or the other.", "start": 2980.03, "duration": 2.28}, {"text": "That's all this English and\nall this notation means.", "start": 2982.31, "duration": 4.29}, {"text": "We're just compensating\nthe agent for the change", "start": 2986.6, "duration": 3.45}, {"text": "in purchasing power.", "start": 2990.05, "duration": 2.93}, {"text": "But of course, demand doesn't\nstay constant because the new", "start": 2992.98, "duration": 3.56}, {"text": "demand, x*, will be different\nas the prices are different.", "start": 2996.54, "duration": 5.13}, {"text": "And the Hicksian demand includes\nthe price substitution effect,", "start": 3001.67, "duration": 4.53}, {"text": "is defined by it.", "start": 3006.2, "duration": 2.23}, {"text": "So the Hicksian demand, at the\nold utility level and prices p", "start": 3008.43, "duration": 4.77}, {"text": "prime, is different from the\noriginal baseline purchase.", "start": 3013.2, "duration": 6.47}, {"text": "Anyway, if you understood the\nincome and substitution effects", "start": 3019.67, "duration": 3.24}, {"text": "at the beginning,\nthat's all this slide", "start": 3022.91, "duration": 2.07}, {"text": "is saying, where we have\nnontrivial discrete changes", "start": 3024.98, "duration": 3.66}, {"text": "in the price.", "start": 3028.64, "duration": 1.05}, {"text": "Here's the picture again.", "start": 3029.69, "duration": 2.73}, {"text": "But be forewarned that, somehow,\nto make it more interesting,", "start": 3032.42, "duration": 5.58}, {"text": "we're going to change the price\nof good 2 instead of good 1.", "start": 3038.0, "duration": 3.99}, {"text": "And we are going to\nincrease the price.", "start": 3041.99, "duration": 4.59}, {"text": "So the original baseline\nbudget is from w to w over p2.", "start": 3046.58, "duration": 8.16}, {"text": "Why just w?", "start": 3054.74, "duration": 1.98}, {"text": "Well, there's an assumption\ndown here that we only", "start": 3056.72, "duration": 4.24}, {"text": "care about the price ratio.", "start": 3060.96, "duration": 2.32}, {"text": "So let's denominate everything\nin units of good on the X-axis.", "start": 3063.28, "duration": 5.24}, {"text": "p1, the first good, equals 1.", "start": 3068.52, "duration": 3.87}, {"text": "So we don't need\nto worry anymore", "start": 3072.39, "duration": 1.65}, {"text": "about the price of the\nfirst good because it's 1.", "start": 3074.04, "duration": 3.288}, {"text": "And the question\nis, what's the price", "start": 3077.328, "duration": 1.542}, {"text": "of the second good\nrelative to 1?", "start": 3078.87, "duration": 3.12}, {"text": "In this case, the price of the\nsecond good, p2, is going up.", "start": 3081.99, "duration": 4.93}, {"text": "So you would go from w\nover p2 attainable to w", "start": 3086.92, "duration": 5.46}, {"text": "over p2 prime attainable\nwhen you go from a price p2", "start": 3092.38, "duration": 4.17}, {"text": "to p2 prime.", "start": 3096.55, "duration": 1.95}, {"text": "This is like the\nearlier diagram,", "start": 3098.5, "duration": 2.49}, {"text": "where we fixed a\npoint on the Y-axis", "start": 3100.99, "duration": 2.73}, {"text": "and pivoted on the X-axis.", "start": 3103.72, "duration": 2.41}, {"text": "But this is the other\nway around because we're", "start": 3106.13, "duration": 2.15}, {"text": "changing the price of good 2\nand not the price of good 1.", "start": 3108.28, "duration": 3.51}, {"text": "OK, so we start here, and we\nhave an income, a lower budget", "start": 3115.51, "duration": 4.17}, {"text": "line.", "start": 3119.68, "duration": 0.96}, {"text": "Now we want to break that\ninto two pieces, namely", "start": 3120.64, "duration": 3.15}, {"text": "the substitution effect\nand the income effect.", "start": 3123.79, "duration": 3.45}, {"text": "What is the substitution effect?", "start": 3127.24, "duration": 2.31}, {"text": "At this higher price of\np2, it's p1, over p2,", "start": 3129.55, "duration": 4.14}, {"text": "If you remember the slope.", "start": 3133.69, "duration": 1.84}, {"text": "So as p2 goes up,\nthat slope goes down.", "start": 3135.53, "duration": 3.54}, {"text": "So we're going to rotate\nalong this indifference curve", "start": 3139.07, "duration": 3.65}, {"text": "and effectively\nmaximize utility,", "start": 3142.72, "duration": 3.76}, {"text": "which is giving you this point.", "start": 3146.48, "duration": 1.97}, {"text": "What's the maximum\nutility you can get", "start": 3148.45, "duration": 3.12}, {"text": "or the minimized expenditure?", "start": 3151.57, "duration": 1.95}, {"text": "Rotating along this\nindifference curve.", "start": 3153.52, "duration": 3.03}, {"text": "And then the income effect\nis moving from here,", "start": 3156.55, "duration": 3.75}, {"text": "a parallel shift back to here.", "start": 3160.3, "duration": 3.22}, {"text": "So our initial level of wealth,\nw, was on this good 1 axis,", "start": 3163.52, "duration": 5.78}, {"text": "and our new level of wealth\nis this minimized expenditure", "start": 3169.3, "duration": 5.52}, {"text": "at the new prices, p prime,\ngiven utility level u.", "start": 3174.82, "duration": 4.2}, {"text": "So we've gone from w to w prime.", "start": 3179.02, "duration": 3.33}, {"text": "That's the change in\nwealth in terms of good 1.", "start": 3182.35, "duration": 4.02}, {"text": "Initial wealth, new\nwealth in terms of good 1,", "start": 3186.37, "duration": 3.03}, {"text": "this must therefore be\nthe change in wealth.", "start": 3189.4, "duration": 3.09}, {"text": "And that's the change in\nwealth, which is positive,", "start": 3192.49, "duration": 3.88}, {"text": "which you may have\nbeen wondering about,", "start": 3196.37, "duration": 1.74}, {"text": "which is necessary to compensate\nthe agent for the fact", "start": 3198.11, "duration": 3.83}, {"text": "that the price of\ngood 2 has gone up.", "start": 3201.94, "duration": 2.77}, {"text": "We have to compensate the agent\nfor the adverse price change", "start": 3204.71, "duration": 4.37}, {"text": "by giving him or\nher more income.", "start": 3209.08, "duration": 3.48}, {"text": "And this is that\nlevel of income.", "start": 3212.56, "duration": 1.65}, {"text": "OK, so as I keep saying, but\nit's probably been more or less", "start": 3217.306, "duration": 5.114}, {"text": "an abstract\nstatement, I'm really", "start": 3222.42, "duration": 2.28}, {"text": "interested in real\neconomies, where", "start": 3224.7, "duration": 3.45}, {"text": "we have something\ngoing on over time,", "start": 3228.15, "duration": 2.61}, {"text": "or something with the\ngeography, or something having", "start": 3230.76, "duration": 3.75}, {"text": "to do with uncertainty,\nand gambles,", "start": 3234.51, "duration": 2.07}, {"text": "and states of the world.", "start": 3236.58, "duration": 2.02}, {"text": "So having memorized or\nshown you all those figures", "start": 3238.6, "duration": 4.55}, {"text": "with some very interesting\nconcepts and a little bit", "start": 3243.15, "duration": 2.58}, {"text": "of data along the way,\none may, nevertheless,", "start": 3245.73, "duration": 3.39}, {"text": "walk away with the\nimpression that we're", "start": 3249.12, "duration": 2.16}, {"text": "talking about a\nstatic world, where", "start": 3251.28, "duration": 1.98}, {"text": "we have rice and other goods\nor potatoes and other goods.", "start": 3253.26, "duration": 3.9}, {"text": "And we're just comparing wheat\nto apples as we change prices.", "start": 3257.16, "duration": 4.62}, {"text": "But no, the framework\napplies to any goods,", "start": 3261.78, "duration": 4.23}, {"text": "including goods that\nare earmarked by time.", "start": 3266.01, "duration": 2.71}, {"text": "So suppose we have\ntwo time periods only.", "start": 3268.72, "duration": 5.0}, {"text": "And we'll call consumption C1--", "start": 3273.72, "duration": 2.85}, {"text": "consumption and date 1, and\nC2, consumption and date 2.", "start": 3276.57, "duration": 3.84}, {"text": "And we're going to give\nincome as an endowment,", "start": 3280.41, "duration": 3.72}, {"text": "meaning how much income they\nhave in the first date, 1,", "start": 3284.13, "duration": 4.92}, {"text": "and how much income they\nhave in the second date, 2.", "start": 3289.05, "duration": 3.9}, {"text": "Using income is\na bit tricky here", "start": 3292.95, "duration": 2.22}, {"text": "because we used that before\nin the static optimization", "start": 3295.17, "duration": 3.57}, {"text": "problem.", "start": 3298.74, "duration": 0.91}, {"text": "So think of it as money, then--", "start": 3299.65, "duration": 2.18}, {"text": "money in date 1,\nmoney at date 2.", "start": 3301.83, "duration": 3.87}, {"text": "Now, what is the budget line?", "start": 3305.7, "duration": 1.9}, {"text": "Well, if they just\neat their money,", "start": 3307.6, "duration": 3.26}, {"text": "they would have consumption\nequal to m1 and m2.", "start": 3310.86, "duration": 3.21}, {"text": "But the way this is drawn,\nthey don't want to do that.", "start": 3314.07, "duration": 3.13}, {"text": "They want to move in one\ndirection or another.", "start": 3317.2, "duration": 3.5}, {"text": "So what is this budget line?", "start": 3320.7, "duration": 1.94}, {"text": "This budget line\nreflects the possibility", "start": 3322.64, "duration": 3.42}, {"text": "of giving up money tomorrow\nand getting more consumption", "start": 3326.06, "duration": 3.33}, {"text": "today--", "start": 3329.39, "duration": 1.05}, {"text": "that's borrowing-- or\ngiving up money today", "start": 3330.44, "duration": 3.54}, {"text": "and getting more consumption\ntomorrow-- that's lending.", "start": 3333.98, "duration": 3.36}, {"text": "So the slope of\nthis heavy blue line", "start": 3337.34, "duration": 2.94}, {"text": "represents the tradeoff\nof the price of goods", "start": 3340.28, "duration": 3.57}, {"text": "today for the price of good\ntomorrow, which you knew", "start": 3343.85, "duration": 3.45}, {"text": "all along but probably forgot.", "start": 3347.3, "duration": 2.16}, {"text": "Why?", "start": 3349.46, "duration": 0.57}, {"text": "Because the slope of the\nbudget line is p1 over p2--", "start": 3350.03, "duration": 3.47}, {"text": "p1 being consumption\nat date one, p2", "start": 3353.5, "duration": 2.8}, {"text": "to being-- sorry-- the price\nof consumption at date two.", "start": 3356.3, "duration": 3.18}, {"text": "But the economics of the problem\ndoesn't write p1 over p2.", "start": 3359.48, "duration": 4.65}, {"text": "It writes r as an interest rate.", "start": 3364.13, "duration": 2.56}, {"text": "Why is it the interest rate?", "start": 3366.69, "duration": 1.46}, {"text": "Because if you gave up\nsome of your money today", "start": 3368.15, "duration": 3.63}, {"text": "and put it in the bank,\nyou would get the principal", "start": 3371.78, "duration": 3.33}, {"text": "and interest back tomorrow.", "start": 3375.11, "duration": 1.8}, {"text": "So 1 plus r, which is also\nthe slope of this line,", "start": 3376.91, "duration": 4.59}, {"text": "reflects the tradeoff\nbetween consumption today", "start": 3381.5, "duration": 3.48}, {"text": "and consumption tomorrow as made\npossible by this interest rate.", "start": 3384.98, "duration": 4.36}, {"text": "So then, as per\nthe entire lecture,", "start": 3389.34, "duration": 2.66}, {"text": "we try to change a price.", "start": 3392.0, "duration": 2.07}, {"text": "Over here, let's increase\nthe interest rate.", "start": 3394.07, "duration": 2.47}, {"text": "So it's still possible to eat\nyour money in both periods.", "start": 3396.54, "duration": 3.59}, {"text": "But now that the interest\nrate has gone up,", "start": 3400.13, "duration": 2.01}, {"text": "the budget line is steeper.", "start": 3402.14, "duration": 1.95}, {"text": "For a given surrendering\nof one unit of consumption", "start": 3404.09, "duration": 3.51}, {"text": "today, you get a higher\n1 plus r tomorrow.", "start": 3407.6, "duration": 3.96}, {"text": "So this paler blue line crosses\nthrough the endowment point,", "start": 3411.56, "duration": 3.72}, {"text": "but it's steeper.", "start": 3415.28, "duration": 1.02}, {"text": "And as drawn with these\nindifference curves,", "start": 3416.3, "duration": 2.94}, {"text": "the household would move from\nthis point to this point.", "start": 3419.24, "duration": 3.16}, {"text": "So let's talk about income\nand substitution effects.", "start": 3422.4, "duration": 4.19}, {"text": "Consumption, tomorrow, at\ndate 2, goes up and up.", "start": 3426.59, "duration": 4.77}, {"text": "Why?", "start": 3431.36, "duration": 0.94}, {"text": "Two effects, and they're both\nmoving in the same direction.", "start": 3432.3, "duration": 3.35}, {"text": "The increase in\nthe interest rate", "start": 3435.65, "duration": 1.62}, {"text": "effectively means\nthey have more income.", "start": 3437.27, "duration": 2.8}, {"text": "They can take their\nendowment of money tomorrow,", "start": 3440.07, "duration": 2.54}, {"text": "and it will be worth more.", "start": 3442.61, "duration": 1.38}, {"text": "So there's an income\neffect associated", "start": 3443.99, "duration": 2.04}, {"text": "with the price change.", "start": 3446.03, "duration": 2.1}, {"text": "Not only that, there's\na substitution effect.", "start": 3448.13, "duration": 2.59}, {"text": "Why?", "start": 3450.72, "duration": 0.65}, {"text": "Because as the\ninterest rate goes up,", "start": 3451.37, "duration": 1.98}, {"text": "the opportunity cost of\neating today goes up.", "start": 3453.35, "duration": 3.09}, {"text": "It's more painful to eat\ntoday because you could", "start": 3456.44, "duration": 2.94}, {"text": "get even more tomorrow by\nputting the money in the bank", "start": 3459.38, "duration": 2.91}, {"text": "at a higher interest rate.", "start": 3462.29, "duration": 1.6}, {"text": "So the substitution\neffect moves them", "start": 3463.89, "duration": 2.87}, {"text": "with these nice,\nsmooth indifference", "start": 3466.76, "duration": 1.5}, {"text": "curves away from\nconsumption today", "start": 3468.26, "duration": 2.61}, {"text": "toward higher\nconsumption tomorrow.", "start": 3470.87, "duration": 2.52}, {"text": "So the income and substitution\neffects in this diagram", "start": 3473.39, "duration": 3.03}, {"text": "work in the same\ndirection for good 2,", "start": 3476.42, "duration": 2.64}, {"text": "but it's not true\nfor good 1 at date 1.", "start": 3479.06, "duration": 5.16}, {"text": "Or at least, it\ncould be ambiguous.", "start": 3484.22, "duration": 2.64}, {"text": "Why?", "start": 3486.86, "duration": 1.23}, {"text": "There's an income effect, which\nshould increase consumption", "start": 3488.09, "duration": 3.12}, {"text": "at date 1.", "start": 3491.21, "duration": 1.41}, {"text": "But there's a price\neffect, which should", "start": 3492.62, "duration": 1.8}, {"text": "decrease consumption at date 1.", "start": 3494.42, "duration": 2.52}, {"text": "And those can, in principle,\nmove in opposite directions.", "start": 3496.94, "duration": 4.12}, {"text": "In this case, date 1\nconsumption is going down,", "start": 3501.06, "duration": 3.47}, {"text": "so the substitution effect is\ndominating the income effect.", "start": 3504.53, "duration": 4.86}, {"text": "But it didn't have\nto go that way.", "start": 3509.39, "duration": 1.89}, {"text": "You could have drawn\nthe indifference curves", "start": 3511.28, "duration": 2.1}, {"text": "and gotten an increase in\nthe consumption of date", "start": 3513.38, "duration": 2.88}, {"text": "of that good.", "start": 3516.26, "duration": 1.32}, {"text": "OK, let's start out with a\ndifferent but related diagram.", "start": 3517.58, "duration": 4.2}, {"text": "Suppose they have money today\nand tomorrow as endowments.", "start": 3521.78, "duration": 3.45}, {"text": "And this guy is\nactually doing what?", "start": 3525.23, "duration": 2.46}, {"text": "Originally, borrowing,\ngetting more consumption today", "start": 3527.69, "duration": 3.36}, {"text": "than the money he or she has\nat the expense of paying it", "start": 3531.05, "duration": 3.27}, {"text": "back with interest\ntomorrow, therefore", "start": 3534.32, "duration": 1.95}, {"text": "having less consumption than the\nmoney that he or she originally", "start": 3536.27, "duration": 3.5}, {"text": "had.", "start": 3539.77, "duration": 0.5}, {"text": "So we'd end up\nwith this tangency.", "start": 3540.27, "duration": 3.02}, {"text": "And now we still increase\nthe interest rate.", "start": 3543.29, "duration": 2.97}, {"text": "That makes this pale\nblue line steeper.", "start": 3546.26, "duration": 4.59}, {"text": "And you can see consumption\nis moving inwards.", "start": 3550.85, "duration": 3.36}, {"text": "So actually, consumption of\nboth goods in the diagram", "start": 3554.21, "duration": 3.33}, {"text": "is going down.", "start": 3557.54, "duration": 1.18}, {"text": "But let's think about income\nand substitution effects.", "start": 3558.72, "duration": 2.9}, {"text": "Because they were\nborrowing originally,", "start": 3561.62, "duration": 2.58}, {"text": "as opposed to\nlending, intuitively,", "start": 3564.2, "duration": 2.55}, {"text": "an increase in the interest rate\nis a bad situation for them.", "start": 3566.75, "duration": 3.93}, {"text": "They were borrowing, and now\nthe interest rate is higher.", "start": 3570.68, "duration": 2.68}, {"text": "So the income\neffect is negative.", "start": 3573.36, "duration": 1.94}, {"text": "And that could show\nup with both goods.", "start": 3575.3, "duration": 2.95}, {"text": "On the other hand, the\nsubstitution effect", "start": 3578.25, "duration": 1.97}, {"text": "should still push them in the\ndirection of higher consumption", "start": 3580.22, "duration": 2.94}, {"text": "tomorrow.", "start": 3583.16, "duration": 0.66}, {"text": "That's the substitution effect.", "start": 3583.82, "duration": 2.32}, {"text": "So for one of these\ngoods, consumption today", "start": 3586.14, "duration": 2.99}, {"text": "is unambiguous.", "start": 3589.13, "duration": 1.11}, {"text": "But consumption\ntomorrow is ambiguous,", "start": 3590.24, "duration": 2.46}, {"text": "despite the way it's\ndrawn, because the income", "start": 3592.7, "duration": 2.46}, {"text": "and substitution effects work\nin the opposite direction.", "start": 3595.16, "duration": 3.43}, {"text": "So take a look at those.", "start": 3598.59, "duration": 1.4}, {"text": "There's a lot going on.", "start": 3599.99, "duration": 1.24}, {"text": "In fact, that's\nkind of the point,", "start": 3601.23, "duration": 1.58}, {"text": "that when we move\nfrom apples, wheats,", "start": 3602.81, "duration": 2.76}, {"text": "and so on with prices and\nincome to an applied problem,", "start": 3605.57, "duration": 3.66}, {"text": "like what's happening in\nthe US with these lower", "start": 3609.23, "duration": 3.03}, {"text": "and lower interest\nrates, well, if we", "start": 3612.26, "duration": 2.55}, {"text": "look at consumer behavior,\nthere's income effects.", "start": 3614.81, "duration": 3.09}, {"text": "There's substitution effects.", "start": 3617.9, "duration": 2.13}, {"text": "You can go in different\ndirections and be in conflict.", "start": 3620.03, "duration": 2.79}, {"text": "And that's an important part\nof understanding the impact", "start": 3622.82, "duration": 3.36}, {"text": "on the households and the\nimpact on the economy.", "start": 3626.18, "duration": 2.61}, {"text": "And it's actually\na lot more work", "start": 3628.79, "duration": 2.58}, {"text": "to go through this slide\nand the previous one", "start": 3631.37, "duration": 1.92}, {"text": "than you might\nhave imagined, even", "start": 3633.29, "duration": 1.65}, {"text": "though, say, you\nwere totally sure you", "start": 3634.94, "duration": 2.4}, {"text": "could shift these curves around\nin whatever way you wanted.", "start": 3637.34, "duration": 2.88}, {"text": "When we get to the\neconomic application,", "start": 3640.22, "duration": 2.82}, {"text": "we kind of do it all over again\nwith the new realistic labels.", "start": 3643.04, "duration": 3.72}, {"text": "And it brings that tool to life.", "start": 3646.76, "duration": 3.85}, {"text": "OK, well, that's the\nlast slide for today.", "start": 3650.61, "duration": 2.82}, {"text": "That's the end of this lecture.", "start": 3653.43, "duration": 3.0}, {"text": "All right, thank you very much.", "start": 3656.43, "duration": 2.84}]
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+[{"text": "[SQUEAKING]", "start": 0.0, "duration": 1.944}, {"text": "[RUSTLING]", "start": 1.944, "duration": 1.458}, {"text": "[CLICKING]", "start": 3.402, "duration": 3.402}, {"text": "NORVIN RICHARDS: Today, we\nare going to finish syntax,", "start": 13.12, "duration": 3.29}, {"text": "not in the sense that you\nwill now know everything", "start": 16.41, "duration": 2.98}, {"text": "there is to know about syntax.", "start": 19.39, "duration": 1.25}, {"text": "People spend their\nlives studying syntax.", "start": 20.64, "duration": 3.51}, {"text": "In fact, that's what I'm doing.", "start": 24.15, "duration": 2.85}, {"text": "But you'll know\nenough for 24.900.", "start": 27.0, "duration": 2.79}, {"text": "And if you're interested\nin these things,", "start": 29.79, "duration": 2.04}, {"text": "there is 24.902, which\nis all about syntax--", "start": 31.83, "duration": 3.36}, {"text": "introduction-- more of an\nintroduction to syntax.", "start": 35.19, "duration": 3.72}, {"text": "So I was in the middle\nof talking, last time,", "start": 38.91, "duration": 1.98}, {"text": "about shortest move, and so I'm\ngoing to back up a little bit", "start": 40.89, "duration": 3.48}, {"text": "and we'll talk through\nthe cases that I", "start": 44.37, "duration": 1.68}, {"text": "was talking about last time.", "start": 46.05, "duration": 3.08}, {"text": "Before I do that,\nthough, I wanted to say,", "start": 49.13, "duration": 1.75}, {"text": "I got a really interesting\nquestion after class last time", "start": 50.88, "duration": 3.84}, {"text": "from someone who basically\nwanted to know whether it could", "start": 54.72, "duration": 2.85}, {"text": "be shown that the kinds of\nuniversals that I was showing", "start": 57.57, "duration": 4.74}, {"text": "you, observations like there's\nwh- movement to the left,", "start": 62.31, "duration": 4.29}, {"text": "but there isn't wh- movement\nto the right, or there's V2,", "start": 66.6, "duration": 3.66}, {"text": "but there isn't anti-V2--", "start": 70.26, "duration": 1.913}, {"text": "Somebody wanted\nto know whether it", "start": 72.173, "duration": 1.417}, {"text": "could be shown that the\nabsence of these things", "start": 73.59, "duration": 1.958}, {"text": "was statistically significant.", "start": 75.548, "duration": 1.262}, {"text": "That is, if you look at\nthe languages of the world,", "start": 76.81, "duration": 2.93}, {"text": "would we expect to find\nanti-V2 is V2 common enough", "start": 79.74, "duration": 3.84}, {"text": "that it's surprising that\nthe anti-V2 is absent.", "start": 83.58, "duration": 3.55}, {"text": "So I am working on\nworking up some stats,", "start": 87.13, "duration": 3.35}, {"text": "and I will probably\nsend out an announcement", "start": 90.48, "duration": 2.34}, {"text": "about that stuff later.", "start": 92.82, "duration": 1.15}, {"text": "So keep your eyes\npeeled for that.", "start": 93.97, "duration": 3.98}, {"text": "In working up some stats, I'm\nhaving a look at a website,", "start": 97.95, "duration": 3.88}, {"text": "which I can recommend.", "start": 101.83, "duration": 1.755}, {"text": "It's called WALS-- oh dear,\nI was about to write the URL,", "start": 103.585, "duration": 2.375}, {"text": "and then I realized\nI don't know how.", "start": 105.96, "duration": 1.542}, {"text": "If you Google WALS--", "start": 107.502, "duration": 1.758}, {"text": "WALS stands for the World\nAtlas of Language Structures.", "start": 109.26, "duration": 7.393}, {"text": "And I think it's something\ndumb like WALS.com or something", "start": 116.653, "duration": 2.417}, {"text": "like that.", "start": 119.07, "duration": 2.322}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 121.392, "duration": 1.318}, {"text": "NORVIN RICHARDS: WALS dot what?", "start": 122.71, "duration": 1.325}, {"text": "AUDIENCE: Dot info.", "start": 124.035, "duration": 0.792}, {"text": "NORVIN RICHARDS: Info, huh?", "start": 124.827, "duration": 1.173}, {"text": "No wonder I don't know the URL.", "start": 126.0, "duration": 3.15}, {"text": "Language Structures-- Thank you.", "start": 129.15, "duration": 2.5}, {"text": "It is a typological\ndatabase, gathering", "start": 131.65, "duration": 5.93}, {"text": "typological information about\na bunch of different languages.", "start": 137.58, "duration": 3.28}, {"text": "So it has thousands of\nlanguages, observations", "start": 140.86, "duration": 4.76}, {"text": "by various linguists who\nwork on them categorized", "start": 145.62, "duration": 3.21}, {"text": "by various phenomena.", "start": 148.83, "duration": 1.32}, {"text": "So there are all\nthese parameters", "start": 150.15, "duration": 1.71}, {"text": "that you can look up.", "start": 151.86, "duration": 1.06}, {"text": "You can find out\nhow many of these", "start": 152.92, "duration": 1.42}, {"text": "languages have the\nverb before the object.", "start": 154.34, "duration": 1.75}, {"text": "How many of them have the\nobject before the verb.", "start": 156.09, "duration": 2.042}, {"text": "You can get it to make you a\nmap of where these languages are", "start": 158.132, "duration": 2.788}, {"text": "and all that cute stuff.", "start": 160.92, "duration": 1.26}, {"text": "And they take a stab at\nhaving a typlogically balanced", "start": 162.18, "duration": 4.08}, {"text": "genealogically-balanced\nsurvey, I guess.", "start": 166.26, "duration": 2.11}, {"text": "So the languages are\nnot all Indo-European.", "start": 168.37, "duration": 1.857}, {"text": "They're from all over the world.", "start": 170.227, "duration": 1.333}, {"text": "There's just all\nkinds of stuff there.", "start": 171.56, "duration": 2.325}, {"text": "Some of the generalizations\nthat I was showing you,", "start": 173.885, "duration": 2.125}, {"text": "it's trivial to show that they\nare statistically significant.", "start": 176.01, "duration": 4.18}, {"text": "So, for example, there\nare according to WALS,", "start": 180.19, "duration": 3.23}, {"text": "roughly a third of\nthe world's languages", "start": 183.42, "duration": 2.28}, {"text": "have wh- movement to the left.", "start": 185.7, "duration": 1.77}, {"text": "That is, they're like English.", "start": 187.47, "duration": 2.31}, {"text": "And the other 2/3\nhave wh- in situ.", "start": 189.78, "duration": 2.85}, {"text": "So if that is wh- goes wherever\nthe wh- would normally go,", "start": 192.63, "duration": 3.69}, {"text": "it doesn't move.", "start": 196.32, "duration": 1.56}, {"text": "So when I told you that there\nis wh- movement to the left", "start": 197.88, "duration": 2.76}, {"text": "and there isn't wh-\nmovement to the right,", "start": 200.64, "duration": 2.82}, {"text": "I'm not a\nmathematician, but that", "start": 203.46, "duration": 2.19}, {"text": "looks statistically\nsignificant, given", "start": 205.65, "duration": 2.1}, {"text": "that they're studying thousands\nand thousands of languages.", "start": 207.75, "duration": 3.06}, {"text": "It's surprising if you thought\nthat wh- movement to the right", "start": 210.81, "duration": 5.46}, {"text": "was, should be, just as common\nas the movement to the left.", "start": 216.27, "duration": 3.42}, {"text": "The absence of that in any of\nthe languages we've studied", "start": 219.69, "duration": 2.4}, {"text": "is surprising and significant.", "start": 222.09, "duration": 2.35}, {"text": "But as I say, I'll write up\nsome stats and send them to you.", "start": 224.44, "duration": 5.93}, {"text": "Questions about that or anything\nelse that we did last time?", "start": 230.37, "duration": 4.3}, {"text": "OK.", "start": 234.67, "duration": 1.5}, {"text": "This, as I said, we had\ngotten started on this,", "start": 236.17, "duration": 2.01}, {"text": "and I'll just back up and\ngo through this again.", "start": 238.18, "duration": 3.96}, {"text": "We were talking last time\nabout restrictions on movement.", "start": 242.14, "duration": 3.24}, {"text": "So I've given you the\nbeginnings of some reasons", "start": 245.38, "duration": 2.82}, {"text": "to believe that\nthere are cases where", "start": 248.2, "duration": 2.7}, {"text": "forming a tree for a sentence,\nforming a syntactic structure,", "start": 250.9, "duration": 3.6}, {"text": "isn't just a matter of\nmerging things to each other,", "start": 254.5, "duration": 2.485}, {"text": "but that, sometimes, you take\nsomething which has already", "start": 256.985, "duration": 2.375}, {"text": "been merged and you\nmove it someplace else.", "start": 259.36, "duration": 2.38}, {"text": "And we've talked about\ndifferent kinds of movement.", "start": 261.74, "duration": 2.48}, {"text": "And last time, towards\nthe end of last time,", "start": 264.22, "duration": 2.07}, {"text": "I was starting to show you\nexamples kinds of movement", "start": 266.29, "duration": 3.39}, {"text": "that you couldn't do.", "start": 269.68, "duration": 1.77}, {"text": "So I think one of\nthe examples we", "start": 271.45, "duration": 2.91}, {"text": "talked about, you can\nsay things like \"She", "start": 274.36, "duration": 5.64}, {"text": "ordered a hamburger and fries.\"", "start": 280.0, "duration": 9.33}, {"text": "But that if you were to take\n\"fries,\" replace it with a wh-", "start": 289.33, "duration": 3.75}, {"text": "phrase, and tried\nto wh- move it,", "start": 293.08, "duration": 4.08}, {"text": "giving you \"What did she\norder a hamburger and?\"--", "start": 297.16, "duration": 5.79}, {"text": "even if you spell\n\"did\" correctly,", "start": 302.95, "duration": 1.68}, {"text": "which is surprisingly\nchallenging!--", "start": 304.63, "duration": 3.48}, {"text": "the result is very bad.", "start": 308.11, "duration": 1.96}, {"text": "So I showed you some\nexamples like that,", "start": 310.07, "duration": 1.85}, {"text": "where if you\narrange to put a wh-", "start": 311.92, "duration": 3.54}, {"text": "phrase in a certain\nkind of structure,", "start": 315.46, "duration": 1.71}, {"text": "it somehow can't escape, calling\nthose structures islands.", "start": 317.17, "duration": 3.07}, {"text": "There's some kinds\nof wh- movement", "start": 320.24, "duration": 1.732}, {"text": "that you just can't do.", "start": 321.972, "duration": 0.958}, {"text": "Does this sound familiar at all?", "start": 322.93, "duration": 1.333}, {"text": "We were doing this last time.", "start": 324.263, "duration": 2.187}, {"text": "And then I said, so\nthere's big literature", "start": 326.45, "duration": 3.35}, {"text": "on syntax identifying\nthese islands", "start": 329.8, "duration": 1.89}, {"text": "and trying to figure out what\nare the structures that you", "start": 331.69, "duration": 2.375}, {"text": "can't move out of.", "start": 334.065, "duration": 1.135}, {"text": "There's actually--\nand then attempts", "start": 335.2, "duration": 2.13}, {"text": "to develop theories of why\ncertain things are islands.", "start": 337.33, "duration": 2.82}, {"text": "Why are certain kinds of\nthings opaque to extraction.", "start": 340.15, "duration": 2.86}, {"text": "And I wanted to show you one\ntheory of one particular set", "start": 343.01, "duration": 4.07}, {"text": "of examples like this, examples\nof places that you cannot move", "start": 347.08, "duration": 5.1}, {"text": "out of, because, well, they--", "start": 352.18, "duration": 2.88}, {"text": "the explanation for why these\nparticular things are opaque", "start": 355.06, "duration": 3.75}, {"text": "is particularly straightforward.", "start": 358.81, "duration": 3.58}, {"text": "So old observation,\nactually, that a number", "start": 362.39, "duration": 2.27}, {"text": "of the restrictions on\nmovement that people have found", "start": 364.66, "duration": 2.73}, {"text": "can be unified into a\nsingle condition that", "start": 367.39, "duration": 2.82}, {"text": "has been called various things\nand formalized various ways.", "start": 370.21, "duration": 2.88}, {"text": "But today, I'll call\nit shortest move.", "start": 373.09, "duration": 1.92}, {"text": "It says, basically, if you have\na choice between two movement", "start": 375.01, "duration": 3.18}, {"text": "operations, you should\npick the shorter one.", "start": 378.19, "duration": 3.34}, {"text": "So pick short moves\nover long moves.", "start": 381.53, "duration": 2.93}, {"text": "And I gave you this\ndefinition of \"short.\"", "start": 384.46, "duration": 4.89}, {"text": "So one of the things people\ndo in this literature", "start": 389.35, "duration": 2.16}, {"text": "is try to figure out exactly\nhow we ought to define \"short.\"", "start": 391.51, "duration": 2.61}, {"text": "So one way to define it would be\nto say, one movement is shorter", "start": 394.12, "duration": 4.14}, {"text": "than another movement,\nif it crosses", "start": 398.26, "duration": 2.01}, {"text": "a smaller number of nodes.", "start": 400.27, "duration": 1.69}, {"text": "So you start off dominated\nby a certain number of nodes,", "start": 401.96, "duration": 3.47}, {"text": "and you move to a\nposition where you are not", "start": 405.43, "duration": 2.13}, {"text": "dominated by some of the nodes\nthat used to dominate you.", "start": 407.56, "duration": 3.18}, {"text": "Let's call that your path.", "start": 410.74, "duration": 1.53}, {"text": "So the path is the\nset of nodes that", "start": 412.27, "duration": 3.03}, {"text": "dominate the position the\nmoved item came from and don't", "start": 415.3, "duration": 2.82}, {"text": "dominate the position\nwhere it lands.", "start": 418.12, "duration": 2.678}, {"text": "And what we're saying\nis you want your path", "start": 420.798, "duration": 1.792}, {"text": "to be as short as possible.", "start": 422.59, "duration": 1.36}, {"text": "So if you're\ncomparing two moves,", "start": 423.95, "duration": 2.557}, {"text": "and then there are various\nways to formalize this,", "start": 426.507, "duration": 2.083}, {"text": "but one is, if you're\ncomparing to moves,", "start": 428.59, "duration": 1.83}, {"text": "count the nodes in the\npaths, and pick the one", "start": 430.42, "duration": 2.61}, {"text": "that has the smaller number.", "start": 433.03, "duration": 2.05}, {"text": "Another way to\nformalize it is to say,", "start": 435.08, "duration": 1.85}, {"text": "this only works if you're\ncomparing two nodes that", "start": 436.93, "duration": 2.55}, {"text": "have overlapping\npaths and you are", "start": 439.48, "duration": 2.22}, {"text": "supposed to pick the one that\nis a subset, the path that's", "start": 441.7, "duration": 2.7}, {"text": "a subset.", "start": 444.4, "duration": 2.49}, {"text": "So that's a story to tell here.", "start": 446.89, "duration": 2.23}, {"text": "I'll show you some examples.", "start": 449.12, "duration": 1.5}, {"text": "The first example, which\nI showed you last time,", "start": 450.62, "duration": 2.0}, {"text": "was the head\nmovement constraint.", "start": 452.62, "duration": 1.45}, {"text": "So you can move heads but only\nover very short distances.", "start": 454.07, "duration": 5.7}, {"text": "So English forms yes/no\nquestions by moving T into C.", "start": 459.77, "duration": 6.8}, {"text": "So you can say, ask questions,\nlike \"Will Mary type novels?\"", "start": 466.57, "duration": 3.81}, {"text": "where you take what's\nin T, which is \"will,\"", "start": 470.38, "duration": 3.163}, {"text": "and move it into C.\nThat's a way to form", "start": 473.543, "duration": 1.667}, {"text": "that kind of yes/no question.", "start": 475.21, "duration": 1.59}, {"text": "But I said, you\ndo not, in English", "start": 476.8, "duration": 3.54}, {"text": "or in any language, form yes/no\nquestions by moving the verb", "start": 480.34, "duration": 4.08}, {"text": "into C past the auxiliary.", "start": 484.42, "duration": 2.16}, {"text": "So English can't ask questions\nlike \"Type Mary will novels?\"", "start": 486.58, "duration": 4.83}, {"text": "This is out.", "start": 491.41, "duration": 1.95}, {"text": "I'm showing you this with\nyes/no questions in English.", "start": 493.36, "duration": 2.25}, {"text": "I could have shown\nit to you with V2.", "start": 495.61, "duration": 2.01}, {"text": "So the same thing holds in V2,\nverb second, German phenomenon,", "start": 497.62, "duration": 4.5}, {"text": "and many other languages in\nwhich something has to be in C.", "start": 502.12, "duration": 6.3}, {"text": "And what happens is, whatever\nhead is highest, moves into C.", "start": 508.42, "duration": 3.33}, {"text": "You do the shortest move.", "start": 511.75, "duration": 1.74}, {"text": "In German, you\nmove the auxiliary,", "start": 513.49, "duration": 1.74}, {"text": "and if there is no auxiliary,\nyou move the main verb.", "start": 515.23, "duration": 2.22}, {"text": "If there are\nmultiple auxiliaries,", "start": 517.45, "duration": 1.417}, {"text": "you move the highest one.", "start": 518.867, "duration": 2.333}, {"text": "So this is one example\nof shortest move.", "start": 521.2, "duration": 2.52}, {"text": "Oh, I did it again.", "start": 526.3, "duration": 0.84}, {"text": "Sorry, I haven't fixed this yet.", "start": 527.14, "duration": 1.53}, {"text": "The path from I to C, which is\nreally the path from T to C,", "start": 528.67, "duration": 3.51}, {"text": "sorry, the path from where\nwill is to where C is,", "start": 532.18, "duration": 3.54}, {"text": "consists of T bar and TP.", "start": 535.72, "duration": 1.92}, {"text": "That is, those are the nodes\nthat dominate T and don't", "start": 537.64, "duration": 3.03}, {"text": "dominate C.", "start": 540.67, "duration": 1.68}, {"text": "But the path from\nV to C consists", "start": 542.35, "duration": 2.85}, {"text": "of VP, as well as T bar and TP.", "start": 545.2, "duration": 3.157}, {"text": "Do people see that, even\nthough I wrote the wrong things", "start": 548.357, "duration": 2.333}, {"text": "on the slide?", "start": 550.69, "duration": 0.67}, {"text": "So please mentally\nsearch, replace I with T,", "start": 551.36, "duration": 2.42}, {"text": "on this slide.", "start": 553.78, "duration": 1.08}, {"text": "I'm using an old\nterm for IP, which", "start": 554.86, "duration": 2.52}, {"text": "I meant to go back and fix.", "start": 557.38, "duration": 2.29}, {"text": "There are no IPs anymore.", "start": 559.67, "duration": 2.65}, {"text": "So this is an example\nof how you use", "start": 562.32, "duration": 1.62}, {"text": "paths to explain\nto yourself what", "start": 563.94, "duration": 3.48}, {"text": "you mean when you say that one\nmove is shorter than another.", "start": 567.42, "duration": 2.53}, {"text": "As you can see, this is also a\ncase in which one of the paths", "start": 569.95, "duration": 2.09}, {"text": "is a subset of the other.", "start": 572.04, "duration": 1.042}, {"text": "And then the second\nkind of case,", "start": 576.26, "duration": 1.59}, {"text": "which we talked about last time,\nand this is one of the reasons", "start": 577.85, "duration": 3.03}, {"text": "that this is only\nas far as we got", "start": 580.88, "duration": 1.47}, {"text": "because this case is a little\nshakier than the first one.", "start": 582.35, "duration": 2.638}, {"text": "The head movement constraint\nis extremely strong.", "start": 584.988, "duration": 2.042}, {"text": "If you violate the head\nmovement constraint,", "start": 587.03, "duration": 1.833}, {"text": "then your sentences are\nalmost uninterpretable.", "start": 588.863, "duration": 2.967}, {"text": "Superiority--\nthere are all kinds", "start": 591.83, "duration": 2.67}, {"text": "of complicated\nsemantic things going", "start": 594.5, "duration": 1.59}, {"text": "on that allow you to\nsometimes violate superiority.", "start": 596.09, "duration": 4.5}, {"text": "But, at least in some\ncases, out of the blue, if I", "start": 600.59, "duration": 3.0}, {"text": "ask you \"Who bought what?\"", "start": 603.59, "duration": 2.25}, {"text": "that's better than asking\n\"What did who buy?\"", "start": 605.84, "duration": 2.25}, {"text": "And I was getting general\nagreement with that last time.", "start": 608.09, "duration": 2.85}, {"text": "One of the things I said last\ntime, and I think this is true,", "start": 610.94, "duration": 3.69}, {"text": "is that superiority judgments\nare particularly strong if you", "start": 614.63, "duration": 6.39}, {"text": "are talking about--", "start": 621.02, "duration": 0.99}, {"text": "if there are only two answers.", "start": 624.53, "duration": 1.92}, {"text": "So wh- questions--\nmultiple wh- questions,", "start": 626.45, "duration": 3.18}, {"text": "what you're asking for is\na list of pairs, usually.", "start": 629.63, "duration": 4.41}, {"text": "So if I ask you\n\"Who bought what?\"", "start": 634.04, "duration": 1.74}, {"text": "the answer is going\nto be, well, you know,", "start": 635.78, "duration": 2.67}, {"text": "\"Sally bought chocolate,\nand Bill novels,", "start": 638.45, "duration": 3.12}, {"text": "and Mary bought a computer.\"", "start": 641.57, "duration": 2.64}, {"text": "So it'll be a list\nof people and things,", "start": 644.21, "duration": 2.52}, {"text": "such that the people\nbought the things.", "start": 646.73, "duration": 2.133}, {"text": "Superiority-- we talked\nabout this last time--", "start": 648.863, "duration": 1.917}, {"text": "but superiority\njudgments are strongest", "start": 650.78, "duration": 1.8}, {"text": "when there's only one pair.", "start": 652.58, "duration": 2.08}, {"text": "So if you see two\npeople fighting,", "start": 654.66, "duration": 6.32}, {"text": "you might ask \"Who\nhit who first?\"", "start": 660.98, "duration": 4.77}, {"text": "Compare that with \"Who\ndid who hit first?\"", "start": 668.48, "duration": 5.445}, {"text": "For me, at least, that's a\nparticularly strong judgment.", "start": 676.76, "duration": 2.82}, {"text": "Are there people\nwho prefer one--", "start": 679.58, "duration": 1.95}, {"text": "let's see.", "start": 681.53, "duration": 0.51}, {"text": "Let's see a show of hands,\nwho prefers the first of these", "start": 682.04, "duration": 2.7}, {"text": "to the second?", "start": 684.74, "duration": 1.83}, {"text": "Who prefers the\nsecond to the first?", "start": 686.57, "duration": 2.37}, {"text": "Who finds them both fine and\nis not sure why some of you", "start": 688.94, "duration": 2.58}, {"text": "raised your hands\nthe first time?", "start": 691.52, "duration": 1.44}, {"text": "So there are a few of you\nwho don't care whether there", "start": 692.96, "duration": 3.99}, {"text": "is only a single pair.", "start": 696.95, "duration": 1.14}, {"text": "But for many of you, this\none is better than this one.", "start": 698.09, "duration": 3.78}, {"text": "There's something\nwrong with this.", "start": 701.87, "duration": 3.52}, {"text": "So this is a phenomenon which\nis not as strong as the head", "start": 705.39, "duration": 2.575}, {"text": "movement constraint but\nresembles the head movement", "start": 707.965, "duration": 2.125}, {"text": "constraint, in that,\nthere's a preference when", "start": 710.09, "duration": 3.09}, {"text": "you've got a choice between two\nthings which of them to move.", "start": 713.18, "duration": 2.847}, {"text": "There's a preference for moving\nthe higher one, the first one.", "start": 716.027, "duration": 2.583}, {"text": "And then here's the\ncase number three, which", "start": 721.637, "duration": 1.833}, {"text": "we didn't get to last time.", "start": 723.47, "duration": 2.43}, {"text": "These are what are\ncalled wh- islands.", "start": 725.9, "duration": 2.55}, {"text": "\"Island,\" again, is\na name syntacticians", "start": 728.45, "duration": 2.88}, {"text": "use for these positions\nthat you can't move out of.", "start": 731.33, "duration": 2.37}, {"text": "There's this metaphor, I guess,\nthat involves wh- phrases", "start": 733.7, "duration": 2.94}, {"text": "not being able to swim.", "start": 736.64, "duration": 1.59}, {"text": "If they're stuck on an\nisland, then they're stuck.", "start": 738.23, "duration": 3.42}, {"text": "So here's a sentence with\nan embedded wh- question.", "start": 741.65, "duration": 5.49}, {"text": "\"I wonder what\nBill gave to Fred.\"", "start": 747.14, "duration": 2.94}, {"text": "So this whole sentence\nis not a question really.", "start": 750.08, "duration": 3.33}, {"text": "It's a statement.", "start": 753.41, "duration": 0.84}, {"text": "I'm telling you something\nabout my mental state.", "start": 754.25, "duration": 2.52}, {"text": "My mental state is one in\nwhich I don't know the answer", "start": 756.77, "duration": 2.88}, {"text": "to a particular question.", "start": 759.65, "duration": 2.05}, {"text": "And that question is, \"What\ndid Bill give to Fred?\"", "start": 761.7, "duration": 2.69}, {"text": "So there's wh-\nmovements happening", "start": 764.39, "duration": 2.01}, {"text": "in the embedded clause.", "start": 766.4, "duration": 1.14}, {"text": "What has moved to the edge\nof the embedded clause.", "start": 767.54, "duration": 2.34}, {"text": "Is that clear?", "start": 769.88, "duration": 1.23}, {"text": "Does that make sense?", "start": 771.11, "duration": 1.56}, {"text": "That's what's going\non in this sentence.", "start": 772.67, "duration": 2.29}, {"text": "Now observation about\nembedded questions.", "start": 774.96, "duration": 4.03}, {"text": "If I ask you, \"Who do you\nwonder what Bill gave to?\"", "start": 778.99, "duration": 2.31}, {"text": "you are upset.", "start": 784.08, "duration": 3.9}, {"text": "So what did I do.", "start": 787.98, "duration": 1.6}, {"text": "Well, I turned Fred into a\nwh- question, a wh- word, zap.", "start": 789.58, "duration": 6.17}, {"text": "Now Fred is who,\nand I moved \"who\"", "start": 795.75, "duration": 3.84}, {"text": "out of the embedded clause\ninto the matrix clause.", "start": 799.59, "duration": 3.39}, {"text": "\"Who do you wonder\nwhat Bill gave to?\"", "start": 802.98, "duration": 1.63}, {"text": "where the answer is,\nwell, I'm wondering", "start": 804.61, "duration": 2.09}, {"text": "what Bill gave to Fred.", "start": 806.7, "duration": 2.385}, {"text": "It ought to be able to\nmean that, but it really,", "start": 809.085, "duration": 2.365}, {"text": "really can't.", "start": 811.45, "duration": 1.38}, {"text": "There's something badly\nwrong with this sentence.", "start": 812.83, "duration": 4.4}, {"text": "So this is called a wh- island.", "start": 817.23, "duration": 1.8}, {"text": "A wh- question, like \"what Bill\ngave to Fred,\" is an island.", "start": 819.03, "duration": 3.66}, {"text": "You can form that.", "start": 822.69, "duration": 0.75}, {"text": "That's what the\nfirst sentence says.", "start": 823.44, "duration": 1.78}, {"text": "\"I wonder what\nBill gave to Fred.\"", "start": 825.22, "duration": 1.417}, {"text": "But you can't wh-\nextract out of it.", "start": 826.637, "duration": 3.263}, {"text": "The proposal people have made--", "start": 829.9, "duration": 2.57}, {"text": "well, look, there are at\nleast two possible things", "start": 832.47, "duration": 2.25}, {"text": "that could be wrong with\nthe green arrow there,", "start": 834.72, "duration": 1.59}, {"text": "the one that's going\nfrom the embedded clause", "start": 836.31, "duration": 1.875}, {"text": "into the matrix clause.", "start": 838.185, "duration": 1.515}, {"text": "One is, here I am\nin the matrix CP,", "start": 839.7, "duration": 3.84}, {"text": "and I'm trying to\ndecide what to move.", "start": 843.54, "duration": 2.5}, {"text": "And there are two wh- phrases.", "start": 846.04, "duration": 2.36}, {"text": "There's \"what\"\nand there's \"who.\"", "start": 848.4, "duration": 1.44}, {"text": "I should really\nhave a tree here.", "start": 849.84, "duration": 2.32}, {"text": "Let me draw a quasi tree.", "start": 852.16, "duration": 3.155}, {"text": "To \"wonder\"...", "start": 864.442, "duration": 0.583}, {"text": "Here we have \"what.\"", "start": 870.55, "duration": 2.9}, {"text": "Then, I'm out of words, so\nI'll just use a triangle here,", "start": 873.45, "duration": 3.34}, {"text": "to who.", "start": 876.79, "duration": 2.79}, {"text": "So this is \"You wonder\nwhat John gave to who.\"", "start": 879.58, "duration": 4.313}, {"text": "I know my handwriting\nis terrible,", "start": 883.893, "duration": 1.417}, {"text": "but can people see that that's\nwhat that tree is meant to be?", "start": 885.31, "duration": 2.61}, {"text": "So this is the\ntree for what you--", "start": 887.92, "duration": 2.898}, {"text": "for the second sentence, this\nis going to be my attempt", "start": 890.818, "duration": 2.292}, {"text": "to draw the second sentence.", "start": 893.11, "duration": 1.54}, {"text": "So \"Who do you wonder\nwhat Bill gave to?\"", "start": 894.65, "duration": 2.96}, {"text": "So we've got-- we can fill\nin some of the gaps here.", "start": 897.61, "duration": 3.51}, {"text": "\"Bill gave (blank) to who.\"", "start": 901.12, "duration": 4.2}, {"text": "So we first moved \"what\" into\nthe specifier of the embedded", "start": 905.32, "duration": 3.15}, {"text": "CP.", "start": 908.47, "duration": 1.62}, {"text": "And now, this is one of\nthe few times in my life", "start": 910.09, "duration": 4.29}, {"text": "I wish I had colored chalk.", "start": 914.38, "duration": 2.46}, {"text": "Now we're going to\n\"who,\" and we're", "start": 916.84, "duration": 1.8}, {"text": "going to move it up to here.", "start": 918.64, "duration": 3.3}, {"text": "And there's something\nwrong with this.", "start": 921.94, "duration": 2.04}, {"text": "Try to figure out\nwhat's wrong with it.", "start": 923.98, "duration": 1.907}, {"text": "The shortest move story\nabout what's wrong with it", "start": 925.887, "duration": 2.083}, {"text": "goes like this.", "start": 927.97, "duration": 0.64}, {"text": "Well, actually,\nthere are two things", "start": 928.61, "duration": 1.25}, {"text": "that you could blame this on.", "start": 929.86, "duration": 1.208}, {"text": "One is, when we're\nhere and we're", "start": 931.068, "duration": 1.852}, {"text": "trying to decide what to\nmove into this position,", "start": 932.92, "duration": 2.37}, {"text": "well, at this point,\nthere are two wh- phrases,", "start": 935.29, "duration": 2.46}, {"text": "\"what\" and \"who.\"", "start": 937.75, "duration": 0.99}, {"text": "And \"what\" is higher.", "start": 938.74, "duration": 2.85}, {"text": "So maybe one thing\nthat's wrong with it", "start": 941.59, "duration": 2.58}, {"text": "is, basically,\nsuperiority over again.", "start": 944.17, "duration": 2.785}, {"text": "You've got two wh- phrases.", "start": 946.955, "duration": 1.355}, {"text": "You have to pick\nwhich one to move.", "start": 948.31, "duration": 1.458}, {"text": "You should move the\nhigher one, if you didn't.", "start": 949.768, "duration": 2.852}, {"text": "So that you didn't\npick the shorter move.", "start": 952.62, "duration": 3.833}, {"text": "And the other objection you\nmight have to this green arrow", "start": 956.453, "duration": 2.417}, {"text": "goes like this.", "start": 958.87, "duration": 1.65}, {"text": "The wh- movement is\nto the spec of CP.", "start": 960.52, "duration": 1.95}, {"text": "Here's \"who\" sitting here.", "start": 962.47, "duration": 1.65}, {"text": "If you're going to\nmove \"who,\" well,", "start": 964.12, "duration": 2.4}, {"text": "you shouldn't move it here.", "start": 966.52, "duration": 1.47}, {"text": "You should move it here.", "start": 967.99, "duration": 2.005}, {"text": "Sorry.", "start": 969.995, "duration": 0.5}, {"text": "Let me do that without\nputting my body in the way.", "start": 970.495, "duration": 1.905}, {"text": "You shouldn't move it here.", "start": 972.4, "duration": 1.125}, {"text": "Here's a spec of CP to\nwhich it's going to land.", "start": 973.525, "duration": 2.295}, {"text": "But really what you\nshould do is move it here.", "start": 975.82, "duration": 1.92}, {"text": "And you can't, because\nthere's a wh- phrase here.", "start": 977.74, "duration": 2.88}, {"text": "This phrase is stuck.", "start": 980.62, "duration": 1.5}, {"text": "So the ill-formedness of\nthe sentence, the star,", "start": 982.12, "duration": 5.25}, {"text": "is this feeling\nyou're having trying", "start": 987.37, "duration": 4.98}, {"text": "to satisfy multiple\nconflicting requirements.", "start": 992.35, "duration": 4.02}, {"text": "There's a Greek\ntragedy going on here.", "start": 996.37, "duration": 1.93}, {"text": "\"Who\" absolutely\nneeds to land here,", "start": 998.3, "duration": 2.03}, {"text": "but there's \"what\" in the way.", "start": 1000.33, "duration": 1.39}, {"text": "And so, \"who\" wants to kill its\nfather and marry its mother,", "start": 1001.72, "duration": 3.38}, {"text": "and then, bad things happen.", "start": 1005.1, "duration": 2.31}, {"text": "You can't do everything\nthat you want to do.", "start": 1007.41, "duration": 2.388}, {"text": "So this wants to make the\nshortest possible move and it", "start": 1009.798, "duration": 2.292}, {"text": "can't.", "start": 1012.09, "duration": 0.6}, {"text": "And it's unhappy and it pouts.", "start": 1012.69, "duration": 1.77}, {"text": "And that's got the\nshape of a star.", "start": 1014.46, "duration": 2.49}, {"text": "That's a story, anyway, about\nwhy wh- islands are islands.", "start": 1016.95, "duration": 3.78}, {"text": "Do people see the problem?", "start": 1020.73, "duration": 1.956}, {"text": "That, that sentence is bad.", "start": 1022.686, "duration": 1.474}, {"text": "And it's not like it's\nunclear what it means,", "start": 1024.16, "duration": 2.15}, {"text": "but you just can't say that.", "start": 1026.31, "duration": 2.86}, {"text": "Yeah?", "start": 1029.17, "duration": 0.728}, {"text": "AUDIENCE: How would you say it?", "start": 1029.898, "duration": 1.292}, {"text": "NORVIN RICHARDS: You can't.", "start": 1031.19, "duration": 2.129}, {"text": "\"Who do you wonder\nwhat Bill gave to?\"", "start": 1033.319, "duration": 2.01}, {"text": "The closest you can come\nto saying it in English", "start": 1035.329, "duration": 2.25}, {"text": "is to say things\nlike, \"Who is it", "start": 1037.579, "duration": 1.981}, {"text": "that you're wondering what\nBill gave to him or her.\"", "start": 1039.56, "duration": 5.049}, {"text": "So sometimes, for some\npeople, putting in a pronoun", "start": 1044.609, "duration": 3.531}, {"text": "improves these sentences.", "start": 1048.14, "duration": 2.04}, {"text": "For me, the effect\nis not so strong.", "start": 1050.18, "duration": 2.76}, {"text": "There isn't a very\ngood way to say this.", "start": 1052.94, "duration": 2.31}, {"text": "There are languages\nin which this is OK,", "start": 1055.25, "duration": 2.07}, {"text": "which is an interesting--\nthere are questions about why.", "start": 1057.32, "duration": 3.69}, {"text": "But in English, not so much.", "start": 1061.01, "duration": 1.86}, {"text": "Yes?", "start": 1062.87, "duration": 1.05}, {"text": "AUDIENCE: What about \"What do\nyou wonder Bill gave to who?\"", "start": 1063.92, "duration": 3.77}, {"text": "NORVIN RICHARDS: \"What do\nyou wonder Bill gave to who?\"", "start": 1067.69, "duration": 2.94}, {"text": "So the point-- so one of\nthe things I just said was,", "start": 1070.63, "duration": 14.54}, {"text": "when we're asking what went\nwrong with the sentence that", "start": 1085.17, "duration": 3.122}, {"text": "I've got up there, \"Who do you\nwonder what Bill gave to?\"--", "start": 1088.292, "duration": 2.458}, {"text": "one thing that you could blame\nit on is, you moved \"who,\"", "start": 1093.48, "duration": 3.15}, {"text": "and \"what\" is closer.", "start": 1096.63, "duration": 1.32}, {"text": "What you should really\nhave done is moved \"what.\"", "start": 1097.95, "duration": 3.9}, {"text": "I don't know about\nyou guys, but, for me,", "start": 1101.85, "duration": 1.92}, {"text": "\"What do you wonder\nBill gave to who?\"", "start": 1103.77, "duration": 2.95}, {"text": "I can't say.", "start": 1106.72, "duration": 2.9}, {"text": "So this is another one of\nthese Greek tragedy things.", "start": 1109.62, "duration": 2.97}, {"text": "Shortest move really wants this\nto be the thing that moves.", "start": 1112.59, "duration": 3.96}, {"text": "But the result is\nthat, let's think", "start": 1116.55, "duration": 2.28}, {"text": "about what wh- movement does.", "start": 1118.83, "duration": 1.29}, {"text": "It makes questions, right?", "start": 1120.12, "duration": 1.65}, {"text": "So when you move\n\"what\" here, you're", "start": 1121.77, "duration": 1.8}, {"text": "making this into a question.", "start": 1123.57, "duration": 1.56}, {"text": "You wonder what Bill gave to\nBill-- to Fred or whatever.", "start": 1125.13, "duration": 3.81}, {"text": "If you move it up here, you're\nmaking this into a question.", "start": 1128.94, "duration": 2.46}, {"text": "And maybe what we're seeing\nis that you can't do both.", "start": 1131.4, "duration": 3.6}, {"text": "And we could demonstrate that\nwithout doing an wh- island.", "start": 1135.0, "duration": 3.44}, {"text": "So it's also bad,\nat least for me.", "start": 1138.44, "duration": 1.77}, {"text": "I'm going to star this.", "start": 1140.21, "duration": 1.26}, {"text": "It's also bad, at least\nfor me, to say things", "start": 1141.47, "duration": 1.875}, {"text": "like what do you wonder\nBill gave to Fred.", "start": 1143.345, "duration": 6.98}, {"text": "This is also out.", "start": 1152.95, "duration": 1.53}, {"text": "So it's just independently\nimpossible for \"what\"", "start": 1154.48, "duration": 2.19}, {"text": "to start here, move\nhere, and then move here.", "start": 1156.67, "duration": 3.21}, {"text": "It's as though \"what\" can't be--", "start": 1159.88, "duration": 4.38}, {"text": "you're attempting to form two\nquestions with a single wh-", "start": 1164.26, "duration": 2.76}, {"text": "word, and you can't.", "start": 1167.02, "duration": 2.871}, {"text": "AUDIENCE: I thought\nthe last one is OK.", "start": 1169.891, "duration": 2.146}, {"text": "NORVIN RICHARDS: \"What do you\nwonder Bill gave to Fred?\"", "start": 1172.037, "duration": 2.333}, {"text": "AUDIENCE: No. you\ncould say \"What do you", "start": 1174.37, "duration": 1.667}, {"text": "wonder whether Bill gave to\nFred\" is more normal to me,", "start": 1176.037, "duration": 4.233}, {"text": "but also [INAUDIBLE].", "start": 1180.27, "duration": 1.71}, {"text": "NORVIN RICHARDS: Yeah.", "start": 1181.98, "duration": 1.05}, {"text": "For me, at least,\nI can't say this.", "start": 1183.03, "duration": 1.928}, {"text": "But I agree with you, that if\nI were to make it, \"What do you", "start": 1184.958, "duration": 2.542}, {"text": "wonder if Bill gave to Fred\"--", "start": 1187.5, "duration": 1.95}, {"text": "that's still bad, but\nit's better than this.", "start": 1189.45, "duration": 2.46}, {"text": "That's my feeling about it.", "start": 1191.91, "duration": 2.0}, {"text": "Joseph?", "start": 1193.91, "duration": 0.5}, {"text": "AUDIENCE: \"Wonder\" replaced with\n\"think\" seems perfectly fine.", "start": 1197.74, "duration": 3.34}, {"text": "So [INAUDIBLE].", "start": 1201.08, "duration": 3.17}, {"text": "NORVIN RICHARDS: So notice--", "start": 1204.25, "duration": 2.91}, {"text": "good point.", "start": 1207.16, "duration": 0.66}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 1211.2, "duration": 2.29}, {"text": "NORVIN RICHARDS:\nRight, that's it.", "start": 1213.49, "duration": 1.59}, {"text": "So \"wonder\" selects for\nan interrogative CP.", "start": 1215.08, "duration": 3.69}, {"text": "You can say \"I wonder who left?\"", "start": 1218.77, "duration": 3.66}, {"text": "\"why they left,\" \"where\nthey went,\" but not--", "start": 1222.43, "duration": 8.29}, {"text": "or \"whether they left.\"", "start": 1230.72, "duration": 4.02}, {"text": "There are various things you can\nsay, but they're all questions.", "start": 1234.74, "duration": 3.15}, {"text": "So \"wonder\" selects\nfor a question.", "start": 1237.89, "duration": 2.04}, {"text": "And \"that she left\" is no good.", "start": 1239.93, "duration": 5.22}, {"text": "\"Think\" is the opposite.", "start": 1245.15, "duration": 4.74}, {"text": "You can say, \"I think that\nshe left,\" but not, \"I", "start": 1249.89, "duration": 5.94}, {"text": "think whether she left,\"\nor \"I think we left.\"", "start": 1255.83, "duration": 4.302}, {"text": "Things like that.", "start": 1260.132, "duration": 0.708}, {"text": "Yeah, so you're\nabsolutely right.", "start": 1260.84, "duration": 1.84}, {"text": "If I make that \"think,\" \"What\ndo you think Bill gave to Fred?\"", "start": 1262.68, "duration": 3.03}, {"text": "then \"what\" is going to\nbe able to move up here,", "start": 1265.71, "duration": 2.0}, {"text": "because \"think\"\ndoesn't care, in fact,", "start": 1267.71, "duration": 2.19}, {"text": "doesn't want this\nto be a question.", "start": 1269.9, "duration": 1.59}, {"text": "But \"wonder\" does want\nthis to be a question,", "start": 1271.49, "duration": 2.07}, {"text": "with the consequence\nthat if \"what\" goes here,", "start": 1273.56, "duration": 1.92}, {"text": "it's as though it's stuck.", "start": 1275.48, "duration": 1.56}, {"text": "It's got a job.", "start": 1277.04, "duration": 0.99}, {"text": "It needs to make\nthis a question.", "start": 1278.03, "duration": 1.59}, {"text": "If it moves, then it\nisn't a question anymore.", "start": 1279.62, "duration": 2.498}, {"text": "Something has gone wrong.", "start": 1282.118, "duration": 1.042}, {"text": "So we have two\nconflicting things.", "start": 1285.71, "duration": 2.3}, {"text": "Your shortest move that\nsays, in this example,", "start": 1288.01, "duration": 2.95}, {"text": "\"what\" should move up to\nhere should really be \"what.\"", "start": 1290.96, "duration": 2.42}, {"text": "And then, you have\n\"wonder,\" which says, \"No,", "start": 1293.38, "duration": 1.62}, {"text": "'what,' you have to stay here.", "start": 1295.0, "duration": 1.25}, {"text": "You have a job.\"", "start": 1296.25, "duration": 1.79}, {"text": "And these two things\ncan't be reconciled.", "start": 1298.04, "duration": 3.555}, {"text": "Notice that we are out of the\ndomain of optimality theory", "start": 1301.595, "duration": 2.375}, {"text": "here.", "start": 1303.97, "duration": 0.708}, {"text": "So if you remember\noptimality theory,", "start": 1304.678, "duration": 1.542}, {"text": "back when we were\ndoing phonology,", "start": 1306.22, "duration": 1.26}, {"text": "we were talking as\nthough, sometimes,", "start": 1307.48, "duration": 1.59}, {"text": "when you have two things\nand they're fighting,", "start": 1309.07, "duration": 1.917}, {"text": "you just try to find\nsome middle ground.", "start": 1310.987, "duration": 2.193}, {"text": "You find the thing\nthat's best or you", "start": 1313.18, "duration": 1.68}, {"text": "decide who's more important.", "start": 1314.86, "duration": 1.65}, {"text": "That's not the way I usually\nsettle fights between people,", "start": 1316.51, "duration": 2.7}, {"text": "but apparently, in optimality\ntheory, that's what you do.", "start": 1319.21, "duration": 2.4}, {"text": "You decide which of\nthese requirements", "start": 1321.61, "duration": 1.71}, {"text": "is the most important one.", "start": 1323.32, "duration": 1.74}, {"text": "The way I'm talking\nhere is not that.", "start": 1325.06, "duration": 1.95}, {"text": "This is more like, here you\nhave two conflicting constraints", "start": 1327.01, "duration": 3.45}, {"text": "and so you die.", "start": 1330.46, "duration": 1.2}, {"text": "You can't do anything.", "start": 1331.66, "duration": 1.465}, {"text": "There's no way to\nmake everybody happy.", "start": 1333.125, "duration": 1.625}, {"text": "So this has been an\nexercise in, well, first,", "start": 1339.07, "duration": 2.73}, {"text": "showing you some other places\nwhere movement is barred,", "start": 1341.8, "duration": 2.73}, {"text": "and then, also,\ngiving you just a hint", "start": 1344.53, "duration": 3.905}, {"text": "of a very large and\ninteresting literature in which", "start": 1348.435, "duration": 2.125}, {"text": "syntacticians look at\na variety of phenomena", "start": 1350.56, "duration": 3.51}, {"text": "and try to unify them.", "start": 1354.07, "duration": 1.95}, {"text": "So head movement constraint,\nand superiority, and wh- islands", "start": 1356.02, "duration": 4.067}, {"text": "are all things that were\ndiscovered independently,", "start": 1360.087, "duration": 2.083}, {"text": "at different times,\nby different people.", "start": 1362.17, "duration": 1.59}, {"text": "And then another\ngeneration of syntacticians", "start": 1363.76, "duration": 1.89}, {"text": "came along and said, no, these\nall belong in the same box.", "start": 1365.65, "duration": 2.94}, {"text": "And that's where we\nare at this point.", "start": 1368.59, "duration": 2.4}, {"text": "Lots more work like\nthis to talk about.", "start": 1374.14, "duration": 1.8}, {"text": "But this is 24.900, and\nalthough I am a syntactician--", "start": 1375.94, "duration": 2.488}, {"text": "I looked at the\nsyllabus, by the way,", "start": 1378.428, "duration": 1.542}, {"text": "and we're actually,\nmore or less, on track.", "start": 1379.97, "duration": 1.792}, {"text": "I was astonished.", "start": 1381.762, "duration": 0.778}, {"text": "We're supposed to stop\ntalking about syntax today,", "start": 1382.54, "duration": 2.273}, {"text": "and so, we will.", "start": 1384.813, "duration": 0.667}, {"text": "One more thing for me to\nshow you about syntax.", "start": 1388.22, "duration": 2.22}, {"text": "It's actually kind of connected\nto this, to Joseph's point.", "start": 1390.44, "duration": 3.33}, {"text": "Here's a sentence.", "start": 1393.77, "duration": 1.48}, {"text": "\"She will say that we\nshould buy kumquats.\"", "start": 1395.25, "duration": 3.45}, {"text": "Questions about this sentence?", "start": 1398.7, "duration": 1.25}, {"text": "Does this make sense?", "start": 1399.95, "duration": 1.41}, {"text": "Did I put anything\nin here that's", "start": 1401.36, "duration": 1.53}, {"text": "surprising or disturbing?", "start": 1402.89, "duration": 4.045}, {"text": "I think I have a new thing\nin T, which is \"should,\"", "start": 1406.935, "duration": 2.125}, {"text": "but maybe that's\nnot so alarming.", "start": 1409.06, "duration": 3.18}, {"text": "And now what happens if we\nchange \"kumquats\" into a wh-", "start": 1412.24, "duration": 3.45}, {"text": "word, stop, and we wh-\nmove it to the beginning", "start": 1415.69, "duration": 3.203}, {"text": "of the sentence.", "start": 1418.893, "duration": 0.667}, {"text": "Well, so that's me turning\n\"kumquats\" into \"what,", "start": 1419.56, "duration": 4.56}, {"text": "and also turning the\nTP into a triangle,", "start": 1424.12, "duration": 1.86}, {"text": "because I was\nrunning out of room.", "start": 1425.98, "duration": 1.51}, {"text": "And then we're going to move\nwhat into the matrix clause,", "start": 1427.49, "duration": 4.13}, {"text": "so we'll get what will she\nsay that we should buy.", "start": 1431.62, "duration": 2.32}, {"text": "So we've done wh-\nmovement of \"what,\"", "start": 1433.94, "duration": 1.7}, {"text": "and we've also done\nhead movement of \"will\"", "start": 1435.64, "duration": 2.25}, {"text": "from T into C. I haven't\ndrawn an arrow for that.", "start": 1437.89, "duration": 3.61}, {"text": "And that's how we form\nthat wh- question.", "start": 1441.5, "duration": 3.61}, {"text": "But given everything I just\nsaid about shortest move,", "start": 1445.11, "duration": 4.19}, {"text": "you might worry.", "start": 1449.3, "duration": 1.51}, {"text": "You might say to\nyourself, but wait,", "start": 1450.81, "duration": 2.8}, {"text": "isn't CT a closer\nplace to land--", "start": 1453.61, "duration": 2.16}, {"text": "that lower CT,\nthat we should buy,", "start": 1455.77, "duration": 1.643}, {"text": "isn't that a closer\nplace to land?", "start": 1457.413, "duration": 1.417}, {"text": "After all, wh- words move\nto the specifier of CP.", "start": 1458.83, "duration": 4.83}, {"text": "Here is an example of\nwhere there are two CPs.", "start": 1463.66, "duration": 2.31}, {"text": "So what should we do?", "start": 1465.97, "duration": 3.12}, {"text": "And there are various theories\nyou can have about that.", "start": 1469.09, "duration": 3.12}, {"text": "One would be to say,\nyeah, a wh- phrase has", "start": 1472.21, "duration": 1.8}, {"text": "moved to specifer of CP,\nbut it's specifically", "start": 1474.01, "duration": 2.34}, {"text": "interrogative CP.", "start": 1476.35, "duration": 1.02}, {"text": "They form questions.", "start": 1477.37, "duration": 1.41}, {"text": "So not that kind of CP.", "start": 1478.78, "duration": 2.87}, {"text": "But another kind of\ntheory we could have,", "start": 1481.65, "duration": 3.63}, {"text": "would be to say, no,\nshortest move is correct.", "start": 1485.28, "duration": 3.6}, {"text": "The fact that \"what\"\ncan, in principle,", "start": 1488.88, "duration": 2.37}, {"text": "land in the specifer of\nCP, means that it must.", "start": 1491.25, "duration": 3.48}, {"text": "So it's not possible to do the\narrow-- bless you-- the longer", "start": 1494.73, "duration": 2.94}, {"text": "arrow that I showed you\non the previous slide,", "start": 1497.67, "duration": 1.95}, {"text": "where \"what\" just starts\ndown there and moves", "start": 1499.62, "duration": 1.92}, {"text": "in one hop up to there.", "start": 1501.54, "duration": 1.95}, {"text": "Movement is always-- the name\nfor this is successive cyclic.", "start": 1503.49, "duration": 4.38}, {"text": "It's always in little hops.", "start": 1507.87, "duration": 2.34}, {"text": "You can't move from one CP, out\nof that CP, into another CP,", "start": 1510.21, "duration": 4.77}, {"text": "without stopping at the edge of\nthe CP that you started out in.", "start": 1514.98, "duration": 4.26}, {"text": "This is something that was\nproposed by Noam Chomsky, who,", "start": 1519.24, "duration": 3.75}, {"text": "decades ago--", "start": 1522.99, "duration": 0.9}, {"text": "and when he first\nproposed it, it", "start": 1523.89, "duration": 2.07}, {"text": "was met with\nwidespread derision.", "start": 1525.96, "duration": 2.555}, {"text": "People were like \"Just\nbecause of the shortest move", "start": 1528.515, "duration": 2.125}, {"text": "constraint, you're\ngoing to say that we're", "start": 1530.64, "duration": 1.11}, {"text": "doing all these little hops.\"", "start": 1531.75, "duration": 1.47}, {"text": "And then, there was immediately\na flood of really good evidence", "start": 1533.22, "duration": 4.17}, {"text": "that this is true.", "start": 1537.39, "duration": 1.742}, {"text": "It really does work this way.", "start": 1539.132, "duration": 1.208}, {"text": "I'm going to show you\none piece of evidence", "start": 1540.34, "duration": 1.792}, {"text": "that this is how\nwh- movement works.", "start": 1542.132, "duration": 1.551}, {"text": "It's going to be\nkind of involved,", "start": 1543.683, "duration": 1.417}, {"text": "so I'll try to go\nthrough it slowly.", "start": 1545.1, "duration": 2.51}, {"text": "Did you have a question?", "start": 1547.61, "duration": 1.0}, {"text": "AUDIENCE: Yeah.", "start": 1548.61, "duration": 0.625}, {"text": "So if we moved it up\nto where the CP is,", "start": 1549.235, "duration": 3.115}, {"text": "then it would be like, \"She will\nsay what that we should buy.\"", "start": 1552.35, "duration": 5.2}, {"text": "I feel like that sounds weird.", "start": 1557.55, "duration": 2.28}, {"text": "I would say like, \"She will\nsay what we should buy,\"", "start": 1559.83, "duration": 4.367}, {"text": "or something--", "start": 1564.197, "duration": 0.583}, {"text": "I don't know.", "start": 1564.78, "duration": 0.49}, {"text": "NORVIN RICHARDS: Yes.", "start": 1565.27, "duration": 0.59}, {"text": "No, you're right.", "start": 1565.86, "duration": 0.87}, {"text": "So \"say,\" and we talked about--\nthere are verbs, like \"wonder,\"", "start": 1566.73, "duration": 4.393}, {"text": "that need to question.", "start": 1571.123, "duration": 0.917}, {"text": "There are verbs\nlike \"think\" that", "start": 1572.04, "duration": 1.38}, {"text": "need to not have a question.", "start": 1573.42, "duration": 1.2}, {"text": "\"Say\" can have either one.", "start": 1574.62, "duration": 1.74}, {"text": "So you can say, \"She will\nsay that it is raining.\"", "start": 1576.36, "duration": 5.55}, {"text": "Or She will say who left.\"", "start": 1581.91, "duration": 4.56}, {"text": "So \"say\" has both options.", "start": 1586.47, "duration": 3.045}, {"text": "It can have either a\nquestion or a statement.", "start": 1589.515, "duration": 1.875}, {"text": "But actually, the\nevidence that I'm", "start": 1591.39, "duration": 2.28}, {"text": "going to show you about\nsuccessive cyclic movement", "start": 1593.67, "duration": 2.28}, {"text": "shows that it actually\ndoesn't matter", "start": 1595.95, "duration": 3.3}, {"text": "whether the higher verb can\nselect for a question or not.", "start": 1599.25, "duration": 6.0}, {"text": "That even for\nverbs like \"think,\"", "start": 1605.25, "duration": 2.04}, {"text": "that have to select\nfor statements,", "start": 1607.29, "duration": 1.92}, {"text": "you get successive\ncyclic movement.", "start": 1609.21, "duration": 2.44}, {"text": "So you're raising a very\ngood point, which is--", "start": 1611.65, "duration": 2.15}, {"text": "I'm sorry, I'm going\nto hijack your point.", "start": 1613.8, "duration": 2.7}, {"text": "This movement, this\nfirst movement,", "start": 1616.5, "duration": 2.16}, {"text": "it's not driven by the\nneed to form a question.", "start": 1618.66, "duration": 3.9}, {"text": "It's not that this wh-\nphrase is moving here", "start": 1622.56, "duration": 2.07}, {"text": "to make that embedded\nclause a question.", "start": 1624.63, "duration": 2.43}, {"text": "It's just moving there.", "start": 1627.06, "duration": 2.028}, {"text": "And then there's this question\nabout why, like why does", "start": 1629.088, "duration": 2.292}, {"text": "successive cyclic\nmovement happen.", "start": 1631.38, "duration": 1.89}, {"text": "But what I'll try to show you\nnow is that it does happen.", "start": 1633.27, "duration": 2.38}, {"text": "And so, we need to get used to\nit and try to understand why.", "start": 1635.65, "duration": 2.5}, {"text": "But we need a theory of\nwhy, because it's true.", "start": 1638.15, "duration": 3.01}, {"text": "It does happen.", "start": 1641.16, "duration": 2.16}, {"text": "I haven't yet shown you have\nany evidence that this is true.", "start": 1643.32, "duration": 2.5}, {"text": "So far, all I'm\ndoing is asserting", "start": 1645.82, "duration": 2.6}, {"text": "through the force\nof my personality", "start": 1648.42, "duration": 1.77}, {"text": "that this is how the\nwh- movement works.", "start": 1650.19, "duration": 2.25}, {"text": "Let me now show\nyou some evidence.", "start": 1652.44, "duration": 1.77}, {"text": "The evidence involves--\ndo we have evidence", "start": 1657.72, "duration": 3.648}, {"text": "that this is right?", "start": 1661.368, "duration": 0.792}, {"text": "Yes.", "start": 1662.16, "duration": 0.95}, {"text": "The evidence comes-- there's\nlots of evidence for this.", "start": 1663.11, "duration": 2.63}, {"text": "But I want to show you one of\nmy favorite pieces of evidence.", "start": 1665.74, "duration": 1.7}, {"text": "It comes from a\nlanguage called Dinka,", "start": 1667.44, "duration": 1.59}, {"text": "which is a Nilotic language.", "start": 1669.03, "duration": 1.32}, {"text": "It's spoken in South\nSudan and in lots", "start": 1670.35, "duration": 2.88}, {"text": "of diaspora communities,\nincluding a big community", "start": 1673.23, "duration": 2.46}, {"text": "here in Boston, by\nabout 2 million people.", "start": 1675.69, "duration": 4.43}, {"text": "Its phonology is lots of fun.", "start": 1680.12, "duration": 2.08}, {"text": "We did a field methods class\non Dinka few years ago.", "start": 1682.2, "duration": 5.18}, {"text": "It has all kinds of shenanigans\nit gets up to with vowels.", "start": 1687.38, "duration": 4.32}, {"text": "Actually, let me see, I can play\nyou these shenanigans in a way", "start": 1691.7, "duration": 4.86}, {"text": "that you can hear.", "start": 1696.56, "duration": 1.08}, {"text": "And I will see whether\nthis works or not.", "start": 1697.64, "duration": 1.77}, {"text": "So it has long and short\nvowels, which itself, is not", "start": 1703.26, "duration": 5.12}, {"text": "all that unusual.", "start": 1708.38, "duration": 0.99}, {"text": "But it has three different\nlevels of vowel length.", "start": 1709.37, "duration": 2.97}, {"text": "So there are short\nvowels and long vowels", "start": 1712.34, "duration": 1.77}, {"text": "and really long vowels.", "start": 1714.11, "duration": 1.23}, {"text": "So here are three\nminimal triple.", "start": 1715.34, "duration": 3.81}, {"text": "You've got \"mouse\" and\n\"charcoal\" and \"pieces", "start": 1719.15, "duration": 2.76}, {"text": "of charcoal,\" both\nsingular and plural.", "start": 1721.91, "duration": 2.038}, {"text": "So here's the word for \"mouse.\"", "start": 1723.948, "duration": 1.292}, {"text": "Let's see if I can play\nit so you can hear it.", "start": 1725.24, "duration": 3.19}, {"text": "No, I can't.", "start": 1728.43, "duration": 0.56}, {"text": "[SPEECH SOUND]", "start": 1731.92, "duration": 2.752}, {"text": "Oh, I think I know\nwhat happened.", "start": 1737.51, "duration": 1.47}, {"text": "I will put these--", "start": 1742.39, "duration": 2.655}, {"text": "[SPEECH SOUND] if\npeople will be quiet,", "start": 1745.045, "duration": 2.125}, {"text": "they may be able to hear this.", "start": 1747.17, "duration": 1.25}, {"text": "[SPEECH SOUND] And here\nis the longer version.", "start": 1748.42, "duration": 2.97}, {"text": "[SPEECH SOUND] That's\na longer vowel.", "start": 1751.39, "duration": 2.353}, {"text": "And then we also,\nsomewhere around here,", "start": 1753.743, "duration": 1.667}, {"text": "have a really long vowel.", "start": 1755.41, "duration": 1.492}, {"text": "[SPEECH SOUND] There.", "start": 1756.902, "duration": 1.78}, {"text": "I'll put those sound\nfiles on the website", "start": 1758.682, "duration": 1.708}, {"text": "so that you can hear them.", "start": 1760.39, "duration": 1.65}, {"text": "Basically, the word for\n\"mouse\" is [SPEECH SOUND]..", "start": 1762.04, "duration": 2.168}, {"text": "The word for \"charcoal\"\nis [SPEECH SOUND]..", "start": 1764.208, "duration": 1.792}, {"text": "And the word for pieces of\n\"charcoal\" is [SPEECH SOUND]..", "start": 1766.0, "duration": 3.78}, {"text": "It also has tone.", "start": 1769.78, "duration": 3.51}, {"text": "And it has a contrast\nbetween what are called", "start": 1773.29, "duration": 1.95}, {"text": "creaky and breathy voice.", "start": 1775.24, "duration": 2.34}, {"text": "And I'll play those sound\nclips for you as well.", "start": 1777.58, "duration": 2.31}, {"text": "Actually, here, let's see\nif I can get this to work.", "start": 1779.89, "duration": 4.56}, {"text": "No.", "start": 1784.45, "duration": 0.5}, {"text": "No.", "start": 1784.95, "duration": 0.5}, {"text": "No.", "start": 1785.45, "duration": 0.73}, {"text": "No.", "start": 1786.18, "duration": 0.99}, {"text": "No.", "start": 1787.17, "duration": 0.625}, {"text": "No.", "start": 1787.795, "duration": 0.5}, {"text": "I'm sorry.", "start": 1790.92, "duration": 0.5}, {"text": "My theory is that\nthis was not working", "start": 1797.14, "duration": 3.847}, {"text": "because I didn't have it plugged\nin when I opened the program.", "start": 1800.987, "duration": 2.583}, {"text": "Let's see whether that's true.", "start": 1803.57, "duration": 1.25}, {"text": "Doo.", "start": 1808.05, "duration": 0.5}, {"text": "Doo.", "start": 1808.55, "duration": 0.09}, {"text": "Doo.", "start": 1808.64, "duration": 0.15}, {"text": "Doo.", "start": 1808.79, "duration": 0.15}, {"text": "Doo.", "start": 1808.94, "duration": 0.5}, {"text": "Ah.", "start": 1811.99, "duration": 1.688}, {"text": "[SPEECH SOUND] There we go.", "start": 1813.678, "duration": 2.032}, {"text": "[SPEECH SOUND] So\nthat's creaky voice.", "start": 1815.71, "duration": 1.92}, {"text": "That's the word for \"berries.\"", "start": 1817.63, "duration": 1.758}, {"text": "Here's the word for \"women.\"", "start": 1819.388, "duration": 1.167}, {"text": "[SPEECH SOUND] [SPEECH SOUND].", "start": 1825.85, "duration": 2.61}, {"text": "So you do fancy things\nwith your vocal cords", "start": 1828.46, "duration": 2.732}, {"text": "when you speak this language.", "start": 1831.192, "duration": 1.208}, {"text": "You either have to have-- it\nhas different dialects of Dinka", "start": 1832.4, "duration": 3.125}, {"text": "have different numbers\nof voice qualities.", "start": 1835.525, "duration": 3.825}, {"text": "But in this dialect,\nthere are two.", "start": 1839.35, "duration": 1.77}, {"text": "There's creaky voice\nwhere your vocal cords", "start": 1841.12, "duration": 3.03}, {"text": "are under a lot of tension,\nI guess, as you're speaking.", "start": 1844.15, "duration": 3.3}, {"text": "[SPEECH SOUND] [VOWEL SOUND].", "start": 1847.45, "duration": 1.295}, {"text": "So that's the word\nfor \"berries.\"", "start": 1848.745, "duration": 1.375}, {"text": "Here's the word for \"women.\"", "start": 1850.12, "duration": 1.68}, {"text": "[SPEECH SOUND] [SPEECH SOUND]\nwhere the voice is breathy.", "start": 1851.8, "duration": 4.05}, {"text": "There's actually a more\nminimal pair in here somewhere,", "start": 1855.85, "duration": 3.45}, {"text": "but I'm not finding it.", "start": 1859.3, "duration": 1.46}, {"text": "Never mind.", "start": 1860.76, "duration": 1.33}, {"text": "So that's what\nDinka sounds like.", "start": 1862.09, "duration": 2.52}, {"text": "It is lots of fun\nto try to study,", "start": 1864.61, "duration": 3.63}, {"text": "partly because a lot of\nits morphology is tonal,", "start": 1868.24, "duration": 5.28}, {"text": "involves changes to tone or\nto creaky or breathy voice,", "start": 1873.52, "duration": 3.9}, {"text": "or to vowel length.", "start": 1877.42, "duration": 1.08}, {"text": "So you can see, for example,\nthat the word for charcoal", "start": 1878.5, "duration": 2.58}, {"text": "forms its plural by\nlengthening the vowel, which", "start": 1881.08, "duration": 2.49}, {"text": "is already long.", "start": 1883.57, "duration": 0.87}, {"text": "And also making\nit low tone, so it", "start": 1884.44, "duration": 1.62}, {"text": "changes from [SPEECH SOUND]\nto [SPEECH SOUND]..", "start": 1886.06, "duration": 4.71}, {"text": "We lived in fear that we were\nmissing half of the morphemes.", "start": 1890.77, "duration": 2.535}, {"text": "[LAUGHING]", "start": 1893.305, "duration": 2.545}, {"text": "So that's enough\nabout Dinka phonology.", "start": 1895.85, "duration": 1.64}, {"text": "Let me tell you something\nthings about Dinka syntax.", "start": 1897.49, "duration": 2.96}, {"text": "Dinka is V2 language.", "start": 1900.45, "duration": 3.04}, {"text": "So you can see\nsome examples here.", "start": 1903.49, "duration": 2.84}, {"text": "If you want to say\nthings like \"Can", "start": 1906.33, "duration": 2.31}, {"text": "will buy Bol some\nclothes in the town,\"", "start": 1908.64, "duration": 4.182}, {"text": "there's a position\nat the beginning", "start": 1912.822, "duration": 1.458}, {"text": "of the sentence that has to\nget filled by some phrase.", "start": 1914.28, "duration": 3.0}, {"text": "It can be filled by \"Can\" or\nby \"town,\" or by \"clothes.\"", "start": 1917.28, "duration": 3.303}, {"text": "You can pick any of these\nthings and move them", "start": 1920.583, "duration": 1.917}, {"text": "into the first position.", "start": 1922.5, "duration": 2.1}, {"text": "That phrase is then\nfollowed by an auxiliary", "start": 1924.6, "duration": 2.46}, {"text": "in all of these examples.", "start": 1927.06, "duration": 1.08}, {"text": "If there isn't an\nauxiliary, then you", "start": 1928.14, "duration": 1.542}, {"text": "get the verb in that position.", "start": 1929.682, "duration": 1.316}, {"text": "And then you have the\nrest of the sentence.", "start": 1930.998, "duration": 1.792}, {"text": "Dinka is unlike German\nin one or two ways.", "start": 1932.79, "duration": 4.11}, {"text": "German doesn't have creaky and\nbreathy voice, for one thing.", "start": 1936.9, "duration": 2.88}, {"text": "But also, the verb\nin German, we saw,", "start": 1939.78, "duration": 3.0}, {"text": "goes at the end of\nthe verb phrase.", "start": 1942.78, "duration": 2.07}, {"text": "The verb in Dinka goes\nearlier in the verb phrases.", "start": 1944.85, "duration": 2.76}, {"text": "It's head initial.", "start": 1947.61, "duration": 1.05}, {"text": "It's followed by its complement,\nwith some complications,", "start": 1948.66, "duration": 3.0}, {"text": "as we'll see.", "start": 1951.66, "duration": 1.06}, {"text": "So you can say \"Can will Bol\nbuy clothes in the town,\"", "start": 1952.72, "duration": 5.87}, {"text": "or you can say \"Clothes will\nC\u00e1n Bol buy in the town,\"", "start": 1958.59, "duration": 3.66}, {"text": "or you can say \"town\"--", "start": 1962.25, "duration": 1.17}, {"text": "you can take any\nof these phrases", "start": 1963.42, "duration": 1.375}, {"text": "and move them into\nfirst position.", "start": 1964.795, "duration": 2.045}, {"text": "Dinka is also\ndifferent from German", "start": 1966.84, "duration": 1.5}, {"text": "in that there's a\nmorpheme in Dinka that", "start": 1968.34, "duration": 1.98}, {"text": "tells you the number\nof the thing you've", "start": 1970.32, "duration": 2.46}, {"text": "put in first position.", "start": 1972.78, "duration": 1.3}, {"text": "So you can see\nthat the auxiliary", "start": 1974.08, "duration": 3.86}, {"text": "in the first and the third\nexamples starts with ah.", "start": 1977.94, "duration": 5.46}, {"text": "And in the second\nexample, starts with ah.", "start": 1983.4, "duration": 3.84}, {"text": "So the ah, in the\nsecond example,", "start": 1987.24, "duration": 1.89}, {"text": "is indicating that the\nclothes are plural,", "start": 1989.13, "duration": 1.845}, {"text": "that the thing in first\nposition is plural.", "start": 1990.975, "duration": 2.805}, {"text": "So German doesn't have that.", "start": 1993.78, "duration": 1.963}, {"text": "There are other alternations\nthat you can see there, which", "start": 1995.743, "duration": 2.417}, {"text": "I won't try to talk about.", "start": 1998.16, "duration": 1.52}, {"text": "Oh, well.", "start": 1999.68, "duration": 0.653}, {"text": "So you can also see\nthere's a difference", "start": 2000.333, "duration": 1.667}, {"text": "between the auxiliary\nand the first example,", "start": 2002.0, "duration": 2.95}, {"text": "which is [SPEECH SOUND].", "start": 2004.95, "duration": 1.34}, {"text": "That tells you that the\nthing in first position", "start": 2006.29, "duration": 2.43}, {"text": "is the subject,\nwhereas the auxiliary", "start": 2008.72, "duration": 2.532}, {"text": "in the second and\nthird examples is", "start": 2011.252, "duration": 1.458}, {"text": "B is telling you that the\nthing in first position", "start": 2012.71, "duration": 2.13}, {"text": "is not the subject.", "start": 2014.84, "duration": 1.03}, {"text": "So there's all this\nmorphology, and as you can see,", "start": 2015.87, "duration": 2.125}, {"text": "it's tricky to keep track of.", "start": 2017.995, "duration": 2.455}, {"text": "So it's V2.", "start": 2023.31, "duration": 1.82}, {"text": "The last example\ndemonstrates this.", "start": 2025.13, "duration": 2.28}, {"text": "So it's ungrammatical to just\nhave nothing in first position.", "start": 2027.41, "duration": 3.9}, {"text": "You have to put something\nin first position.", "start": 2031.31, "duration": 2.49}, {"text": "V2 language.", "start": 2033.8, "duration": 0.615}, {"text": "Now there is another\nposition in the Dinka clause", "start": 2036.96, "duration": 2.7}, {"text": "that has to get occupied.", "start": 2039.66, "duration": 1.26}, {"text": "So if you want to say in Dinka,\n\"I saw a giraffe,\" you can say,", "start": 2040.92, "duration": 5.34}, {"text": "[SPEAKING DINKA].", "start": 2046.26, "duration": 2.07}, {"text": "No, sorry, [SPEAKING DINKA],,\nso C is breathy.", "start": 2048.33, "duration": 5.79}, {"text": "You've got \"I,\" the word for\n\"I,\" in first position here,", "start": 2054.12, "duration": 3.3}, {"text": "it is satisfying\nthe V2 requirement.", "start": 2057.42, "duration": 1.739}, {"text": "And throughout,\nI'm going to make", "start": 2059.159, "duration": 1.98}, {"text": "things in the V2 requirement,\nthings in the specifier", "start": 2061.139, "duration": 2.261}, {"text": "or CP, things satisfying\nthat need for there", "start": 2063.4, "duration": 2.172}, {"text": "to be something\nin first position,", "start": 2065.572, "duration": 1.417}, {"text": "I'll make those things blue.", "start": 2066.989, "duration": 1.831}, {"text": "There is another position that\nhas to get occupied though.", "start": 2068.82, "duration": 4.14}, {"text": "So you can say \"I\n(auxiliary) giraffe saw.\"", "start": 2072.96, "duration": 3.21}, {"text": "That's how you say\n\"I saw a giraffe.\"", "start": 2076.17, "duration": 1.95}, {"text": "You can't leave\n\"giraffe\" after the verb.", "start": 2078.12, "duration": 2.384}, {"text": "If you-- basically,\nthe generalization", "start": 2083.08, "duration": 2.57}, {"text": "is that if there is\na deep, an NP object,", "start": 2085.65, "duration": 3.15}, {"text": "the NP object has to\ngo before the verb.", "start": 2088.8, "duration": 2.25}, {"text": "Everything else\ngoes after the verb.", "start": 2091.05, "duration": 1.62}, {"text": "But the NP object\ngoes before the verb.", "start": 2092.67, "duration": 2.77}, {"text": "So there's another\nposition down there.", "start": 2095.44, "duration": 1.76}, {"text": "I won't try to talk\nabout how we figure out", "start": 2097.2, "duration": 2.337}, {"text": "where that is in the tree.", "start": 2099.537, "duration": 1.083}, {"text": "That won't matter for what\nI'm about to show you.", "start": 2100.62, "duration": 2.042}, {"text": "But I want you to\nknow about it, partly", "start": 2102.662, "duration": 2.241}, {"text": "because it will make things\nslightly less confusing,", "start": 2104.903, "duration": 2.167}, {"text": "I hope.", "start": 2107.07, "duration": 1.23}, {"text": "If you have two objects,\nlike you say things like,", "start": 2108.3, "duration": 2.31}, {"text": "\"I gave Ayen a book,\" you\ncan choose either of them", "start": 2110.61, "duration": 4.65}, {"text": "to go in first position.", "start": 2115.26, "duration": 1.3}, {"text": "So you can say either, \"I\nhave a book given Ayen,\"", "start": 2116.56, "duration": 4.4}, {"text": "or \"I have Ayen given the book.\"", "start": 2120.96, "duration": 2.25}, {"text": "One of those two objects\nhas to go before \"give.\"", "start": 2123.21, "duration": 2.49}, {"text": "You can't leave them\nboth after \"give.\"", "start": 2125.7, "duration": 1.74}, {"text": "I don't think I have this\nanywhere on the slide,", "start": 2127.44, "duration": 2.0}, {"text": "but you also can't put\nthem both before \"give.\"", "start": 2129.44, "duration": 2.92}, {"text": "So it's a V2 language.", "start": 2132.36, "duration": 0.937}, {"text": "Something has to be\nin first position.", "start": 2133.297, "duration": 1.583}, {"text": "And there's another position\nright before the verb", "start": 2134.88, "duration": 2.31}, {"text": "that also has to get\noccupied, if there", "start": 2137.19, "duration": 1.89}, {"text": "is a noun-phrase object.", "start": 2139.08, "duration": 1.313}, {"text": "If there is no\nnoun-phrase object,", "start": 2140.393, "duration": 1.417}, {"text": "then nothing goes in\nthat second position.", "start": 2141.81, "duration": 3.66}, {"text": "That lower position,\nthe red position.", "start": 2145.47, "duration": 3.036}, {"text": "OK so far?", "start": 2148.506, "duration": 3.534}, {"text": "This is all set up.", "start": 2152.04, "duration": 1.96}, {"text": "So Dinka has two positions\nin the clause that", "start": 2154.0, "duration": 3.42}, {"text": "absolutely have to be filled.", "start": 2157.42, "duration": 1.74}, {"text": "There's the specifier of\nCP, so it's a V2 language.", "start": 2159.16, "duration": 3.63}, {"text": "The blue position, the\nposition at the beginning", "start": 2162.79, "duration": 3.18}, {"text": "of every clause, has to\nget filled by some phrase.", "start": 2165.97, "duration": 2.55}, {"text": "And Dinka is V2,\nso it can be filled", "start": 2168.52, "duration": 1.95}, {"text": "by a variety of\ndifferent phrases.", "start": 2170.47, "duration": 1.98}, {"text": "And then there is\nanother position", "start": 2172.45, "duration": 1.5}, {"text": "that's right before the\nverb that also absolutely", "start": 2173.95, "duration": 2.042}, {"text": "has to get filled.", "start": 2175.992, "duration": 1.418}, {"text": "So if you say in\nDinka, \"Yaar told Ayen", "start": 2177.41, "duration": 2.954}, {"text": "that Bol sent Deng\nto the cattle camp\"--", "start": 2180.364, "duration": 3.396}, {"text": "The cattle camp is\nwhere the cattle are.", "start": 2183.76, "duration": 2.73}, {"text": "Young people go to\nthe cattle camp.", "start": 2186.49, "duration": 1.5}, {"text": "Our consultant told us\nthat the cattle camp", "start": 2187.99, "duration": 1.8}, {"text": "is where young people\nget to know each other.", "start": 2189.79, "duration": 1.875}, {"text": "So men and women mostly don't\nmix, but at the cattle camp,", "start": 2191.665, "duration": 3.435}, {"text": "then they do.", "start": 2195.1, "duration": 0.66}, {"text": "So Yaar and Ayen--", "start": 2198.37, "duration": 3.35}, {"text": "I'm trying to remember, \"Yaar\"\nand \"Ayen\" are women's names.", "start": 2201.72, "duration": 2.95}, {"text": "And \"Bol\" and \"Deng\"\nare men's names.", "start": 2204.67, "duration": 2.04}, {"text": "\"Bol\"-- I think \"Bol\"\nmeans \"a person who", "start": 2206.71, "duration": 2.67}, {"text": "is born after a set of twins.\"", "start": 2209.38, "duration": 2.19}, {"text": "It's apparently a\nreally common name.", "start": 2211.57, "duration": 1.65}, {"text": "Twins, I guess, are really\ncommon among the Dinka.", "start": 2213.22, "duration": 3.75}, {"text": "\"Ayen\" is a name for\na color, just like a--", "start": 2216.97, "duration": 3.99}, {"text": "yeah, anyway.", "start": 2220.96, "duration": 2.31}, {"text": "So here's a sentence.", "start": 2223.27, "duration": 2.43}, {"text": "The main clause and\nthe embedded clause", "start": 2225.7, "duration": 2.49}, {"text": "both have their subjects\nin the first position.", "start": 2228.19, "duration": 2.38}, {"text": "So you've got Yaar before the\nauxiliary in the main clause", "start": 2230.57, "duration": 3.05}, {"text": "and you've got Bol\nbefore the auxiliary", "start": 2233.62, "duration": 2.04}, {"text": "in the embedded clause.", "start": 2235.66, "duration": 3.25}, {"text": "And in the main\nclause, you've got", "start": 2238.91, "duration": 3.15}, {"text": "Ayen, the person\nwho's being told,", "start": 2242.06, "duration": 1.89}, {"text": "going before the verb \"told,\"\nfollowing that red position.", "start": 2243.95, "duration": 3.893}, {"text": "And in the embedded\nclause, you've", "start": 2247.843, "duration": 1.417}, {"text": "got Deng, the person who's\nbeing sent, preceding the verb,", "start": 2249.26, "duration": 5.7}, {"text": "filling that red position.", "start": 2254.96, "duration": 1.725}, {"text": "OK so far?", "start": 2256.685, "duration": 2.325}, {"text": "So now a little bit of Dinka.", "start": 2259.01, "duration": 2.85}, {"text": "Here's the thing,\nif you wh- extract--", "start": 2261.86, "duration": 4.2}, {"text": "so suppose you want to ask,\n\"Who did Yaar tell Ayen that Bol", "start": 2266.06, "duration": 4.875}, {"text": "sent to the cattle camp?\"--", "start": 2270.935, "duration": 1.125}, {"text": "So here we've changed\nDeng into a wh- word,", "start": 2272.06, "duration": 3.0}, {"text": "and we're going to move\nDeng into the main clause.", "start": 2275.06, "duration": 4.14}, {"text": "So the object of \"send\"\nis going to be a wh- word", "start": 2279.2, "duration": 2.64}, {"text": "and it's going to go\nin the main clause.", "start": 2281.84, "duration": 1.92}, {"text": "The whole thing is\ngoing to be a question.", "start": 2283.76, "duration": 2.26}, {"text": "Here's the observation.", "start": 2286.02, "duration": 1.02}, {"text": "If you do that, all\nof those positions", "start": 2287.04, "duration": 2.61}, {"text": "that normally absolutely have\nto be filled have to be empty.", "start": 2289.65, "duration": 4.59}, {"text": "So \"who\" started off as\nthe object of \"send.\"", "start": 2294.24, "duration": 5.98}, {"text": "And so that rightmost\nred position,", "start": 2300.22, "duration": 2.69}, {"text": "the one that \"Deng\"\nused to be in, is empty.", "start": 2302.91, "duration": 2.138}, {"text": "That's not so surprising.", "start": 2305.048, "duration": 1.042}, {"text": "That's where \"who\" came from.", "start": 2306.09, "duration": 3.27}, {"text": "But what's interesting is\nthat the blue position right", "start": 2309.36, "duration": 2.49}, {"text": "above that, the one\nbefore the auxiliary", "start": 2311.85, "duration": 1.83}, {"text": "of the embedded clause,\nthe one that's normally--", "start": 2313.68, "duration": 2.73}, {"text": "that was filled by \"Bol\"\nin the first example,", "start": 2316.41, "duration": 3.06}, {"text": "can't be filled by \"Bol.\"", "start": 2319.47, "duration": 2.37}, {"text": "\"Bol\" has to not\nbe there anymore.", "start": 2321.84, "duration": 2.67}, {"text": "And similarly, the red\nposition before \"tell,\"", "start": 2324.51, "duration": 3.63}, {"text": "the first red position in\nthe second example there,", "start": 2328.14, "duration": 2.76}, {"text": "the one that's an empty\nbox, has to be empty.", "start": 2330.9, "duration": 2.85}, {"text": "Normally it would\nbe filled by \"Ayen.\"", "start": 2333.75, "duration": 2.107}, {"text": "That's what's it's being\nfilled by in the first example.", "start": 2335.857, "duration": 2.333}, {"text": "But if you wh- move across\nit, it has to be empty.", "start": 2338.19, "duration": 4.69}, {"text": "So these positions that\nordinarily absolutely,", "start": 2342.88, "duration": 2.27}, {"text": "absolutely have to be filled,\ncannot leave them empty,", "start": 2345.15, "duration": 2.85}, {"text": "suddenly they have to be\nempty if you're moving a wh-", "start": 2348.0, "duration": 2.43}, {"text": "phrase across them.", "start": 2350.43, "duration": 2.22}, {"text": "Well we can understand\nwhy if we're", "start": 2352.65, "duration": 5.06}, {"text": "willing to believe in\nsuccessive cyclic movement.", "start": 2357.71, "duration": 2.52}, {"text": "So we just have to be willing\nto believe the wh- movement is", "start": 2360.23, "duration": 4.05}, {"text": "obliged to move not\nin one mighty leap,", "start": 2364.28, "duration": 3.93}, {"text": "but in a series of little hops.", "start": 2368.21, "duration": 2.76}, {"text": "It has to land in all\nof these open positions.", "start": 2370.97, "duration": 2.31}, {"text": "And that's why they\ncan't be filled the way", "start": 2373.28, "duration": 1.86}, {"text": "they normally would be\nif you're doing long wh-", "start": 2375.14, "duration": 3.27}, {"text": "movement across them.", "start": 2378.41, "duration": 0.94}, {"text": "So there's an explanation\nfor why these positions are", "start": 2379.35, "duration": 2.33}, {"text": "emptied out.", "start": 2381.68, "duration": 1.833}, {"text": "I'll show you one other\ncool thing about Dinka", "start": 2383.513, "duration": 1.917}, {"text": "and then I think\nwe're done with Dinka.", "start": 2385.43, "duration": 3.45}, {"text": "Dinka has a distinction\nbetween singular and plural", "start": 2388.88, "duration": 3.69}, {"text": "versions of wh- words.", "start": 2392.57, "duration": 2.46}, {"text": "So there's \"ye\u014b\u00e0\" which\nis the word for \"who,\"", "start": 2395.03, "duration": 2.91}, {"text": "and then there's \"y\u00e8y\u00ed\u014b\u00e0,\" which\nis the word for \"who\" plural,", "start": 2397.94, "duration": 3.36}, {"text": "\"who all.\"", "start": 2401.3, "duration": 0.555}, {"text": "English doesn't have a\nword for \"who\" plural,", "start": 2401.855, "duration": 1.875}, {"text": "but plenty of languages\ndo, and Dinka is one.", "start": 2403.73, "duration": 3.33}, {"text": "If you ask a plural\nquestion, you", "start": 2407.06, "duration": 5.28}, {"text": "put that \"who\" at the\nbeginning in the spec of CP,", "start": 2412.34, "duration": 3.0}, {"text": "of the clause that you're in.", "start": 2415.34, "duration": 2.14}, {"text": "But you're required to\nleave behind the plural", "start": 2417.48, "duration": 2.54}, {"text": "morpheme in the red positions,\nthe positions before the verb.", "start": 2420.02, "duration": 4.84}, {"text": "So \"Who all did Bol see?\"", "start": 2424.86, "duration": 1.962}, {"text": "You've got this \"who\"\nplural in first position.", "start": 2426.822, "duration": 1.958}, {"text": "But you've also got this \"k\u00e9\"\nthat goes in the red position,", "start": 2428.78, "duration": 3.04}, {"text": "the position that's\nbefore the verb.", "start": 2431.82, "duration": 1.5}, {"text": "If you wh- extract something\nfrom the verb phrase,", "start": 2433.32, "duration": 2.9}, {"text": "like an object, you have to\nleave this plural morpheme", "start": 2436.22, "duration": 3.0}, {"text": "behind.", "start": 2439.22, "duration": 1.8}, {"text": "So interesting fact, if\nyou do a longer question", "start": 2441.02, "duration": 3.81}, {"text": "than that, like \"Who all do\nyou think that Bol saw?\"--", "start": 2444.83, "duration": 3.0}, {"text": "So you've got \"who\"\nplural at the beginning,", "start": 2447.83, "duration": 1.89}, {"text": "and you've got \"k\u00e9,\" in both\nof the red positions along", "start": 2449.72, "duration": 3.18}, {"text": "the way.", "start": 2452.9, "duration": 1.44}, {"text": "As you wh- move up\nthe clause, it's", "start": 2454.34, "duration": 2.04}, {"text": "like you leave\nbehind this little--", "start": 2456.38, "duration": 2.29}, {"text": "this was plural thing,\nas you move along.", "start": 2458.67, "duration": 5.18}, {"text": "So you get multiple\n\"k\u00e9\"s as you go up.", "start": 2463.85, "duration": 3.99}, {"text": "\"K\u00e9\" sort of resembles the\nthird-person plural pronoun,", "start": 2467.84, "duration": 5.697}, {"text": "which is [SPEAKING DINKA].", "start": 2473.537, "duration": 1.083}, {"text": "So that's the word for they.", "start": 2474.62, "duration": 2.1}, {"text": "So we figure it's\nsomehow related to this.", "start": 2476.72, "duration": 2.74}, {"text": "So Dinka gives us some evidence\nfor this idea, this wacky idea", "start": 2479.46, "duration": 3.89}, {"text": "of Chomsky's from the\n'70's that wh- movement has", "start": 2483.35, "duration": 3.71}, {"text": "to be successive cyclic, that\nit's not possible to just move", "start": 2487.06, "duration": 2.5}, {"text": "in one big jump.", "start": 2489.56, "duration": 0.667}, {"text": "You have to move in a\nbunch of little hops.", "start": 2490.227, "duration": 2.273}, {"text": "So Dinka has a\ndetector for landing", "start": 2492.5, "duration": 3.75}, {"text": "in positions-- two\ndetectors, actually.", "start": 2496.25, "duration": 2.25}, {"text": "One is this \"k\u00e9\" thing.", "start": 2498.5, "duration": 1.432}, {"text": "And the other is just\nwhether certain positions", "start": 2499.932, "duration": 1.958}, {"text": "are filled or empty.", "start": 2501.89, "duration": 1.63}, {"text": "So these positions that\nnormally have to be filled,", "start": 2503.52, "duration": 2.577}, {"text": "have to empty\nthemselves out if you're", "start": 2506.097, "duration": 1.583}, {"text": "going to wh- move through\nthem, by hypothesis,", "start": 2507.68, "duration": 2.43}, {"text": "because the wh- word\nis landing in them", "start": 2510.11, "duration": 2.25}, {"text": "and moving on the way up.", "start": 2512.36, "duration": 3.12}, {"text": "One piece of evidence.", "start": 2515.48, "duration": 1.11}, {"text": "There are zillions of\npieces of evidence for this.", "start": 2516.59, "duration": 2.16}, {"text": "This is one of my favorites.", "start": 2518.75, "duration": 1.39}, {"text": "Now we are done with syntax.", "start": 2524.09, "duration": 2.51}, {"text": "Let us have a moment\nof silence for syntax.", "start": 2526.6, "duration": 3.367}, {"text": "Does anybody have any\nquestions about syntax", "start": 2529.967, "duration": 1.833}, {"text": "before we leave syntax\nbehind and begin", "start": 2531.8, "duration": 2.28}, {"text": "talking about something else?", "start": 2534.08, "duration": 1.96}, {"text": "So if you are looking\nat the syllabus,", "start": 2536.04, "duration": 4.25}, {"text": "there was going to\nbe a day on dialect.", "start": 2540.29, "duration": 2.94}, {"text": "I will move that day to\nthe end of semantics.", "start": 2543.23, "duration": 2.047}, {"text": "So we're now, more or less,\ncaught up with the syllabus.", "start": 2545.277, "duration": 2.333}, {"text": "We're going to spend some\ntime doing semantics.", "start": 2547.61, "duration": 1.958}, {"text": "And then, we will have\na grab bag of topics", "start": 2549.568, "duration": 2.512}, {"text": "after we're done with\nsemantics, on various things.", "start": 2552.08, "duration": 3.0}, {"text": "Any questions about syntax\nbefore we leave syntax behind?", "start": 2555.08, "duration": 2.4}, {"text": "All right.", "start": 2560.32, "duration": 1.59}, {"text": "Let us start in\non semantics then.", "start": 2561.91, "duration": 4.12}, {"text": "So we've done morphology,\nwhich is the building", "start": 2566.03, "duration": 3.15}, {"text": "up of words out of morphemes.", "start": 2569.18, "duration": 2.1}, {"text": "We've done syntax, which is\nthe building of a sentences out", "start": 2571.28, "duration": 2.49}, {"text": "of words.", "start": 2573.77, "duration": 1.15}, {"text": "We're now going to\ndo semantics, which", "start": 2574.92, "duration": 1.91}, {"text": "is the study of how\nyou make meanings out", "start": 2576.83, "duration": 3.39}, {"text": "of smaller meanings.", "start": 2580.22, "duration": 2.58}, {"text": "That's what semantics\nis all about.", "start": 2582.8, "duration": 3.55}, {"text": "There's a going\nhypothesis, which is that--", "start": 2586.35, "duration": 2.36}, {"text": "something like if you\ncompletely understand", "start": 2588.71, "duration": 3.12}, {"text": "the meanings of the various\nparts of the sentence,", "start": 2591.83, "duration": 2.64}, {"text": "the various morphemes\nthat combine,", "start": 2594.47, "duration": 1.71}, {"text": "that there ought to be a\nsimple set of rules for how", "start": 2596.18, "duration": 2.79}, {"text": "to combine meanings,\nthat would give you", "start": 2598.97, "duration": 2.28}, {"text": "the meaning of the sentence.", "start": 2601.25, "duration": 1.17}, {"text": "It's called-- this idea is\ncalled compositionality.", "start": 2602.42, "duration": 2.125}, {"text": "It's the idea that we should\npay a lot of attention", "start": 2604.545, "duration": 3.725}, {"text": "to specifying very completely\nwhat particular morphemes mean.", "start": 2608.27, "duration": 3.9}, {"text": "That if we'll do that, we can\nhave simple rules to generate", "start": 2612.17, "duration": 3.51}, {"text": "the meanings of sentences.", "start": 2615.68, "duration": 1.74}, {"text": "So we're going to\ndo some semantics.", "start": 2617.42, "duration": 1.95}, {"text": "I'm going introduce\nyou to semantics.", "start": 2619.37, "duration": 2.01}, {"text": "And semantics is going to be\nlike the other topics we've", "start": 2621.38, "duration": 2.34}, {"text": "talked about in this\nclass, in that, I", "start": 2623.72, "duration": 1.583}, {"text": "hope to tell you enough about\nit to make it sound interesting.", "start": 2625.303, "duration": 2.707}, {"text": "And then I will abandon you and\nlet you study it on your own.", "start": 2628.01, "duration": 5.28}, {"text": "Go take-- there is an\nundergrad intro syntax class--", "start": 2633.29, "duration": 2.85}, {"text": "semantics class that I\nencourage you to take,", "start": 2636.14, "duration": 2.557}, {"text": "if you find the stuff\nthat we're going", "start": 2638.697, "duration": 1.583}, {"text": "to talk about interesting.", "start": 2640.28, "duration": 1.71}, {"text": "There's lots of interesting\nwork in semantics.", "start": 2641.99, "duration": 3.09}, {"text": "So let's talk about some meaning\nrelations, some classics,", "start": 2645.08, "duration": 4.44}, {"text": "like meaning relations\ninvolving words.", "start": 2649.52, "duration": 3.33}, {"text": "So we can say that words\nare synonyms, if they", "start": 2652.85, "duration": 1.95}, {"text": "seem to mean the same thing.", "start": 2654.8, "duration": 1.28}, {"text": "So words like\n\"purchase\" and \"buy.\"", "start": 2656.08, "duration": 2.32}, {"text": "And that words are\nantonyms if they", "start": 2658.4, "duration": 1.71}, {"text": "seem to mean opposite things.", "start": 2660.11, "duration": 3.51}, {"text": "This is an antiquated example.", "start": 2663.62, "duration": 1.47}, {"text": "I should fix this.", "start": 2665.09, "duration": 0.93}, {"text": "So \"male\" and \"female.\"", "start": 2666.02, "duration": 2.76}, {"text": "But there are fancier\nthings to say about meaning.", "start": 2668.78, "duration": 2.59}, {"text": "So let's consider the\nvarious ways someone might", "start": 2671.37, "duration": 2.81}, {"text": "want to refer to me.", "start": 2674.18, "duration": 1.65}, {"text": "So people usually say at\nthe beginning of classes--", "start": 2675.83, "duration": 3.398}, {"text": "\"It doesn't matter to\nme what you call me.\"", "start": 2679.228, "duration": 1.792}, {"text": "Some people call me Professor\nRichards or call me Professor.", "start": 2681.02, "duration": 3.09}, {"text": "Some people call me Norvin,\nwhich is my first name.", "start": 2684.11, "duration": 3.93}, {"text": "If you can't remember\nmy name, there", "start": 2688.04, "duration": 1.808}, {"text": "are other things you\nmight want to call me.", "start": 2689.848, "duration": 1.792}, {"text": "[LAUGHING]", "start": 2691.64, "duration": 0.5}, {"text": "All right.", "start": 2692.14, "duration": 0.585}, {"text": "There's a variety of things\nthat you might say about me,", "start": 2692.725, "duration": 3.115}, {"text": "depending on the circumstances.", "start": 2695.84, "duration": 3.45}, {"text": "And to say that these\nare all things that you", "start": 2699.29, "duration": 3.81}, {"text": "can use to refer to me is to\nsay that it's usually true", "start": 2703.1, "duration": 4.74}, {"text": "if you have a\nsentence and it has", "start": 2707.84, "duration": 2.73}, {"text": "one of those expressions\nin it, if you change just", "start": 2710.57, "duration": 4.02}, {"text": "that expression to\nanother expression,", "start": 2714.59, "duration": 2.01}, {"text": "that the sentence, the meaning\nof the sentence won't change.", "start": 2716.6, "duration": 3.3}, {"text": "In particular, if it was true\nbefore, it'll still be true.", "start": 2719.9, "duration": 3.12}, {"text": "If it was false before,\nit'll still be false.", "start": 2723.02, "duration": 2.14}, {"text": "So here's a sentence.", "start": 2725.16, "duration": 1.01}, {"text": "\"Professor Richards\nis from Alabama.\"", "start": 2726.17, "duration": 1.542}, {"text": "That sentence is true.", "start": 2727.712, "duration": 1.098}, {"text": "I am from Alabama.", "start": 2728.81, "duration": 2.16}, {"text": "And if you were to switch out\nthe red expression for any", "start": 2730.97, "duration": 4.71}, {"text": "of the other red\nexpressions, the sentence", "start": 2735.68, "duration": 1.89}, {"text": "would still be true.", "start": 2737.57, "duration": 1.03}, {"text": "So to say that these all\nmean the same thing--", "start": 2738.6, "duration": 2.21}, {"text": "to say that \"Professor\nRichards\" and \"Norvin\"", "start": 2740.81, "duration": 1.875}, {"text": "and \"that guy with\nthe beard\" can all", "start": 2742.685, "duration": 1.542}, {"text": "refer to the same\nperson, is to say", "start": 2744.227, "duration": 1.623}, {"text": "that if the first\nsentence is true,", "start": 2745.85, "duration": 2.83}, {"text": "then changing from one\nof these to another one", "start": 2748.68, "duration": 2.18}, {"text": "is not going to change that.", "start": 2750.86, "duration": 1.2}, {"text": "If it's false, it's not\ngoing to change that.", "start": 2752.06, "duration": 2.4}, {"text": "Sound right?", "start": 2754.46, "duration": 0.6}, {"text": "We have to be\ncareful, because it's", "start": 2759.76, "duration": 2.012}, {"text": "possible to get a little fancier\nwith the meanings of words", "start": 2761.772, "duration": 2.458}, {"text": "and phrases.", "start": 2764.23, "duration": 2.37}, {"text": "People sometimes\ntalk about what's", "start": 2766.6, "duration": 2.1}, {"text": "called the \"intension\" and\nthe \"extension\" of the meaning", "start": 2768.7, "duration": 4.98}, {"text": "of a phrase or a word.", "start": 2773.68, "duration": 2.4}, {"text": "Maybe the easiest way to think\nabout this, at least for me,", "start": 2776.08, "duration": 3.09}, {"text": "goes like this.", "start": 2779.17, "duration": 1.92}, {"text": "The intension of\na word, if you ask", "start": 2781.09, "duration": 3.36}, {"text": "what the intension of a word\nis, what you're asking me for", "start": 2784.45, "duration": 3.42}, {"text": "is the procedure\nthat you will use.", "start": 2787.87, "duration": 3.557}, {"text": "I'm going to give you examples\nof this in just a second.", "start": 2791.427, "duration": 2.333}, {"text": "But the intension\nis the procedure", "start": 2793.76, "duration": 2.18}, {"text": "that you will use to determine\nwhat that word or that phrase", "start": 2795.94, "duration": 3.12}, {"text": "refers to.", "start": 2799.06, "duration": 1.38}, {"text": "Whereas the extension\nof a word or phrase", "start": 2800.44, "duration": 2.43}, {"text": "is the value, the\nthing you will get", "start": 2802.87, "duration": 3.24}, {"text": "if you apply that procedure,\nthe value of that function.", "start": 2806.11, "duration": 2.62}, {"text": "Let me show you what the\nheck I'm talking about.", "start": 2808.73, "duration": 2.21}, {"text": "So the phrase \"the President\nof the United States\"", "start": 2810.94, "duration": 5.26}, {"text": "has an intension\nand an extension.", "start": 2816.2, "duration": 2.67}, {"text": "The intension of that phrase,\n\"the President of the United", "start": 2818.87, "duration": 2.67}, {"text": "States\" is the\nprocedure that you", "start": 2821.54, "duration": 3.18}, {"text": "should use to find out\nwho that phrase refers to.", "start": 2824.72, "duration": 2.76}, {"text": "So what you should\ndo is find out", "start": 2827.48, "duration": 1.71}, {"text": "who won the election,\nwho won the most", "start": 2829.19, "duration": 3.0}, {"text": "recent election for president.", "start": 2832.19, "duration": 2.71}, {"text": "That's the intention\nof that phrase.", "start": 2834.9, "duration": 2.06}, {"text": "The extension of\nthat phrase is, well,", "start": 2836.96, "duration": 3.12}, {"text": "what you'll get if you\napply that procedure, which,", "start": 2840.08, "duration": 2.58}, {"text": "right now, is Joe Biden.", "start": 2842.66, "duration": 3.4}, {"text": "Where similarly, the phrase,\n\"the current temperature\"", "start": 2846.06, "duration": 3.39}, {"text": "has an intension\nand an extension.", "start": 2849.45, "duration": 1.86}, {"text": "The intension is\nthe procedure we", "start": 2851.31, "duration": 2.37}, {"text": "will use to find out what\nthe current temperature is,", "start": 2853.68, "duration": 2.28}, {"text": "like go look at the thermometer,\ngo on to weather.com,", "start": 2855.96, "duration": 4.2}, {"text": "or whatever.", "start": 2860.16, "duration": 1.33}, {"text": "And then it has an\nextension, which", "start": 2861.49, "duration": 1.697}, {"text": "is, well, whatever it is--", "start": 2863.187, "duration": 1.083}, {"text": "45 degrees, let's say.", "start": 2864.27, "duration": 1.864}, {"text": "So I said before, when we\nsay that these phrases mean", "start": 2870.22, "duration": 5.58}, {"text": "the same thing, to say that\nis to say that you could", "start": 2875.8, "duration": 4.02}, {"text": "take a sentence that's true\nand switch one of the phrases", "start": 2879.82, "duration": 4.17}, {"text": "and still have a\nsentence that's true.", "start": 2883.99, "duration": 2.44}, {"text": "We have to be careful,\nthough, about things", "start": 2886.43, "duration": 2.39}, {"text": "like intensions and extensions.", "start": 2888.82, "duration": 2.05}, {"text": "So when we say \"The\ntemperature is 45 degrees,\"", "start": 2890.87, "duration": 3.59}, {"text": "or \"That guy with the beard\nis Professor Richards,\"", "start": 2894.46, "duration": 3.93}, {"text": "it's true that \"that\nguy with the beard\"", "start": 2898.39, "duration": 1.77}, {"text": "and \"Professor\nRichards\" are mostly", "start": 2900.16, "duration": 1.458}, {"text": "substitutable for each other.", "start": 2901.618, "duration": 2.322}, {"text": "But we have to be careful with\nphrases like \"the temperature\"", "start": 2903.94, "duration": 3.93}, {"text": "and \"45 degrees.\"", "start": 2907.87, "duration": 1.09}, {"text": "So the temperature has an\nintension and an extension.", "start": 2908.96, "duration": 3.02}, {"text": "And its extension\nmight be 45 degrees,", "start": 2911.98, "duration": 2.85}, {"text": "but its intension\nisn't necessarily,", "start": 2914.83, "duration": 2.25}, {"text": "which means that, for\nexample, even if it's true", "start": 2917.08, "duration": 3.19}, {"text": "that the temperature\nis rising, it", "start": 2920.27, "duration": 3.82}, {"text": "doesn't follow that\n45 degrees is rising,", "start": 2924.09, "duration": 3.69}, {"text": "even if it's true that the\ntemperature is 45 degrees", "start": 2927.78, "duration": 2.73}, {"text": "and that the\ntemperature is rising.", "start": 2930.51, "duration": 1.98}, {"text": "So here's a place where it seems\nas though you can't substitute", "start": 2932.49, "duration": 3.51}, {"text": "in one phrase for another.", "start": 2936.0, "duration": 1.92}, {"text": "That's because rising is\ninteracting, specifically,", "start": 2937.92, "duration": 5.88}, {"text": "with the intension.", "start": 2943.8, "duration": 0.96}, {"text": "It's telling you something\nabout what you will see", "start": 2944.76, "duration": 2.083}, {"text": "if you look at the thermometer.", "start": 2946.843, "duration": 1.774}, {"text": "It's not telling you\nsomething about the extension", "start": 2948.617, "duration": 2.083}, {"text": "of the phrase, the temperature.", "start": 2950.7, "duration": 3.73}, {"text": "So there are places where\nyou can confuse yourself", "start": 2954.43, "duration": 4.13}, {"text": "with intensions and extensions.", "start": 2958.56, "duration": 1.62}, {"text": "Let's extend the focus a little\nbit and talk about sentences.", "start": 2963.27, "duration": 4.16}, {"text": "So that's the beginnings\nof some things", "start": 2967.43, "duration": 2.593}, {"text": "we'll have to watch\nout for when we look", "start": 2970.023, "duration": 1.667}, {"text": "at the meanings of phrases.", "start": 2971.69, "duration": 1.757}, {"text": "When we start talking\nseriously about the meanings", "start": 2973.447, "duration": 2.083}, {"text": "of sentences, there\nare some relations", "start": 2975.53, "duration": 1.95}, {"text": "between sentences\nthat it's going", "start": 2977.48, "duration": 1.53}, {"text": "to be useful to keep track of.", "start": 2979.01, "duration": 3.15}, {"text": "So one of them is entailment.", "start": 2982.16, "duration": 1.97}, {"text": "So we say that a sentence\nA \"entails\" a sentence B,", "start": 2984.13, "duration": 4.5}, {"text": "if whenever A is\ntrue, B must be true.", "start": 2988.63, "duration": 3.94}, {"text": "So if John killed the\nant, it has to be true", "start": 2992.57, "duration": 3.62}, {"text": "that the ant is dead.", "start": 2996.19, "duration": 1.23}, {"text": "That's what \"kill\" means.", "start": 2997.42, "duration": 1.38}, {"text": "Yes?", "start": 2998.8, "duration": 2.35}, {"text": "AUDIENCE: For this\ntemperature example,", "start": 3001.15, "duration": 1.625}, {"text": "we have the intensions\nand the extensions,", "start": 3002.775, "duration": 3.075}, {"text": "and the intension\nis not fixed, right?", "start": 3005.85, "duration": 3.283}, {"text": "NORVIN RICHARDS: Yeah.", "start": 3009.133, "duration": 0.917}, {"text": "AUDIENCE: It is 45 degrees\nnow, up to 50 degrees.", "start": 3010.05, "duration": 2.33}, {"text": "NORVIN RICHARDS: Sure.", "start": 3012.38, "duration": 0.6}, {"text": "AUDIENCE: Next day.", "start": 3012.98, "duration": 0.78}, {"text": "NORVIN RICHARDS: Yeah.", "start": 3013.76, "duration": 0.917}, {"text": "AUDIENCE: If we said \"the winner\nof the previous election,\"", "start": 3014.677, "duration": 3.733}, {"text": "would that be always\nsubstitutable for \"Joe Biden\"?", "start": 3018.41, "duration": 5.88}, {"text": "NORVIN RICHARDS: So--\noh, \"the winner\"--", "start": 3024.29, "duration": 2.65}, {"text": "so let's see now.", "start": 3026.94, "duration": 1.37}, {"text": "The phrase that-- let's\ngo back to Joe Biden.", "start": 3028.31, "duration": 4.02}, {"text": "Here he is.", "start": 3032.33, "duration": 2.22}, {"text": "It's not always going to\nbe true that \"the winner", "start": 3034.55, "duration": 3.96}, {"text": "of the previous election\"\nis substitutable for \"Joe", "start": 3038.51, "duration": 3.21}, {"text": "Biden,\" because I can say things\nlike \"In 1945, the President", "start": 3041.72, "duration": 6.72}, {"text": "of the United States\ndeclared war on Japan.\"", "start": 3048.44, "duration": 3.12}, {"text": "And that phrase,\nand it's probably", "start": 3051.56, "duration": 2.31}, {"text": "the wrong year, that phrase--", "start": 3053.87, "duration": 2.498}, {"text": "even if that sentence is true,\nI don't get to substitute that", "start": 3056.368, "duration": 2.542}, {"text": "in for \"Joe Biden.\"", "start": 3058.91, "duration": 1.47}, {"text": "That's a case where it\nrefers to a different person,", "start": 3060.38, "duration": 4.47}, {"text": "to the person who won the\nelection previous to that.", "start": 3064.85, "duration": 3.6}, {"text": "Am I getting at your--", "start": 3068.45, "duration": 1.93}, {"text": "AUDIENCE: I feel like it\ncould stickier than that?", "start": 3070.38, "duration": 2.16}, {"text": "NORVIN RICHARDS: Probably.", "start": 3072.54, "duration": 1.83}, {"text": "This is day one of semantics.", "start": 3074.37, "duration": 1.29}, {"text": "But yes, you're right.", "start": 3075.66, "duration": 2.25}, {"text": "This is mainly meant to make\nyou wary about expressions", "start": 3077.91, "duration": 4.498}, {"text": "like \"the meaning of a phrase.\"", "start": 3082.408, "duration": 1.292}, {"text": "So the meaning of a phrase\nhas more than one dimension.", "start": 3083.7, "duration": 4.03}, {"text": "You have to be careful about\nwhat kinds of predicates", "start": 3087.73, "duration": 2.51}, {"text": "it's interacting with.", "start": 3090.24, "duration": 1.095}, {"text": "I mean, similarly,\nif I say something", "start": 3093.99, "duration": 3.75}, {"text": "like, \"The President\nof the United States", "start": 3097.74, "duration": 3.6}, {"text": "has always been\nmale,\" that's true.", "start": 3101.34, "duration": 3.73}, {"text": "It's also true of Joe\nBiden, as far as I know.", "start": 3105.07, "duration": 2.81}, {"text": "But it's-- those\naren't the same claim.", "start": 3107.88, "duration": 2.465}, {"text": "Rising-- ants-- dead ants.", "start": 3122.57, "duration": 3.42}, {"text": "Yes, so entailment--\none sentence", "start": 3125.99, "duration": 2.49}, {"text": "entails another\nsentence, if whenever", "start": 3128.48, "duration": 1.74}, {"text": "the first sentence is true, the\nsecond sentence has to be true.", "start": 3130.22, "duration": 2.625}, {"text": "That's what entailment means.", "start": 3132.845, "duration": 2.245}, {"text": "Similarly, to say\n\"Norman is Don's nephew,\"", "start": 3135.09, "duration": 2.69}, {"text": "is to say that \"Don\nis Norman's uncle.\"", "start": 3137.78, "duration": 3.21}, {"text": "The first of those sentences\nentails the second--", "start": 3140.99, "duration": 2.76}, {"text": "no, it doesn't.", "start": 3147.35, "duration": 0.625}, {"text": "Actually, this is a lie!", "start": 3154.19, "duration": 2.22}, {"text": "Neither of these sentences\nentails the other,", "start": 3156.41, "duration": 2.73}, {"text": "unless you know that Norman\nand Don are both male.", "start": 3159.14, "duration": 3.46}, {"text": "If you know that Norman\nand Don are both male,", "start": 3162.6, "duration": 2.13}, {"text": "then they entail each other.", "start": 3164.73, "duration": 2.68}, {"text": "Otherwise, not.", "start": 3167.41, "duration": 2.71}, {"text": "I should fix that.", "start": 3170.12, "duration": 0.87}, {"text": "I think this one does work.", "start": 3175.04, "duration": 1.47}, {"text": "\"If John is here, then Mary\nis here, and John is here.\"", "start": 3176.51, "duration": 3.99}, {"text": "That first sentence,\nthat long sentence,", "start": 3180.5, "duration": 2.19}, {"text": "entails that \"Mary is here.\"", "start": 3182.69, "duration": 2.83}, {"text": "So if that first\nsentence is true,", "start": 3185.52, "duration": 1.47}, {"text": "the second sentence is true.", "start": 3186.99, "duration": 3.24}, {"text": "So these are\nentailment relations.", "start": 3190.23, "duration": 2.93}, {"text": "Entailment relations\nare not about", "start": 3193.16, "duration": 1.53}, {"text": "whether their sentences\nactually are true.", "start": 3194.69, "duration": 2.29}, {"text": "So to say that sentence A\nentails sentence B is just", "start": 3196.98, "duration": 3.5}, {"text": "to say, if you imagine that A\nis true, then B is also true.", "start": 3200.48, "duration": 4.42}, {"text": "So \"Joe Biden is a\nbachelor\" entails", "start": 3204.9, "duration": 5.63}, {"text": "that \"Joe Biden is unmarried.\"", "start": 3210.53, "duration": 3.57}, {"text": "They're both false, but if\nthe first sentence were true,", "start": 3214.1, "duration": 2.92}, {"text": "the second sentence\nwould be true.", "start": 3217.02, "duration": 3.23}, {"text": "Does the second sentence\nentail the first?", "start": 3220.25, "duration": 4.07}, {"text": "AUDIENCE: What is a bachelor?", "start": 3224.32, "duration": 1.47}, {"text": "NORVIN RICHARDS:\nAn unmarried man.", "start": 3225.79, "duration": 2.31}, {"text": "AUDIENCE: If Joe Biden\nis a man and unmarried", "start": 3228.1, "duration": 3.17}, {"text": "he may be a bachelor,\nbut Joe Biden could", "start": 3231.27, "duration": 2.29}, {"text": "be a woman for all we know.", "start": 3233.56, "duration": 1.26}, {"text": "NORVIN RICHARDS: Right.", "start": 3234.82, "duration": 0.78}, {"text": "Yeah.", "start": 3235.6, "duration": 0.5}, {"text": "That's an example.", "start": 3236.1, "duration": 1.3}, {"text": "And actually, I\nthink I misspoke when", "start": 3237.4, "duration": 1.59}, {"text": "I said that a bachelor\nwas an unmarried man.", "start": 3238.99, "duration": 1.833}, {"text": "If his wife had died,\nhe would be unmarried,", "start": 3240.823, "duration": 2.547}, {"text": "I guess, but not a bachelor.", "start": 3243.37, "duration": 1.65}, {"text": "I think a bachelor is someone\nwho has never married.", "start": 3245.02, "duration": 2.46}, {"text": "Yeah.", "start": 3247.48, "duration": 0.75}, {"text": "Also false.", "start": 3248.23, "duration": 1.15}, {"text": "So he's actually married.", "start": 3249.38, "duration": 3.7}, {"text": "So entailment relations are\nnot necessarily symmetrical.", "start": 3253.08, "duration": 2.79}, {"text": "It's possible for A to entail\nB, and for B to not entail A.", "start": 3255.87, "duration": 3.57}, {"text": "And entailment\nrelations are about what", "start": 3259.44, "duration": 2.73}, {"text": "life would be like if the\nfirst sentence were true.", "start": 3262.17, "duration": 2.22}, {"text": "It's not about\nwhether it is true.", "start": 3264.39, "duration": 4.01}, {"text": "And we say that A and B are\nin an equivalence relation,", "start": 3268.4, "duration": 2.64}, {"text": "if they entail each other.", "start": 3271.04, "duration": 2.303}, {"text": "We can also say that\nthey're synonymous.", "start": 3273.343, "duration": 1.667}, {"text": "So \"Mary ate the bagel\" and\n\"The bagel was eaten by Mary.\"", "start": 3275.01, "duration": 3.357}, {"text": "The first sentence\nentails the second.", "start": 3278.367, "duration": 1.583}, {"text": "And the second\nentails the first.", "start": 3279.95, "duration": 1.56}, {"text": "These are equivalent sentences.", "start": 3281.51, "duration": 1.92}, {"text": "And we say that they contradict\neach other if each entails", "start": 3285.813, "duration": 2.417}, {"text": "that the other is false.", "start": 3288.23, "duration": 1.51}, {"text": "So as long as \"Noam\" always\nrefers to the same person,", "start": 3289.74, "duration": 6.4}, {"text": "if Noam is here, that\nentails that it is not true", "start": 3296.14, "duration": 3.9}, {"text": "that Noam is not here.", "start": 3300.04, "duration": 2.45}, {"text": "And if Noam is not here, that\nentails that it is not true", "start": 3302.49, "duration": 3.86}, {"text": "that Naom is here.", "start": 3306.35, "duration": 3.63}, {"text": "I'm waiting for\nsomebody to work hard", "start": 3309.98, "duration": 1.71}, {"text": "on the meaning of\n\"here,\" which I", "start": 3311.69, "duration": 2.19}, {"text": "guess we could\nsuppose he's halfway", "start": 3313.88, "duration": 1.95}, {"text": "into the room or something.", "start": 3315.83, "duration": 1.44}, {"text": "But forget about that\nstuff for a second.", "start": 3317.27, "duration": 2.76}, {"text": "Let's pretend that people are\neither here or there, not here.", "start": 3320.03, "duration": 5.47}, {"text": "So we say that A and B\ncontradict each other,", "start": 3325.5, "duration": 2.06}, {"text": "if they each entail the\nfalsehood of the other.", "start": 3327.56, "duration": 5.74}, {"text": "Yeah?", "start": 3333.3, "duration": 0.5}, {"text": "AUDIENCE: I assume that\nit's possible for A--", "start": 3333.8, "duration": 3.79}, {"text": "is it possible for A to\ncontradict B, but B not", "start": 3337.59, "duration": 3.62}, {"text": "contradict A as false?", "start": 3341.21, "duration": 2.5}, {"text": "NORVIN RICHARDS: So for A\nto entail that B is false,", "start": 3343.71, "duration": 2.4}, {"text": "but for B to not\nentail that A is false?", "start": 3346.11, "duration": 2.43}, {"text": "Yeah.", "start": 3348.54, "duration": 1.5}, {"text": "So if you go back to\nthis slide, because I", "start": 3350.04, "duration": 7.16}, {"text": "feel as though if we arrange\nthings, correctly-- yeah.", "start": 3357.2, "duration": 3.03}, {"text": "So \"If Joe Biden\nis a bachelor\"...", "start": 3360.23, "duration": 5.64}, {"text": "nope.", "start": 3369.72, "duration": 1.475}, {"text": "What's a better example?", "start": 3371.195, "duration": 1.0}, {"text": "So if-- so we're looking for a\ncase of a subset relation where", "start": 3375.54, "duration": 6.11}, {"text": "all--", "start": 3381.65, "duration": 1.838}, {"text": "AUDIENCE: \"If the\nrectangle is a square...\"", "start": 3383.488, "duration": 1.792}, {"text": "NORVIN RICHARDS: Is a\nrectangle and square-- yeah,", "start": 3385.28, "duration": 1.23}, {"text": "that's better, isn't it?", "start": 3386.51, "duration": 1.05}, {"text": "Yeah, go ahead.", "start": 3387.56, "duration": 0.66}, {"text": "Give us the rectangle\nand square example.", "start": 3388.22, "duration": 1.708}, {"text": "AUDIENCE: If you say that\nsomething is not a rectangle,", "start": 3393.202, "duration": 4.018}, {"text": "that doesn't necessarily\nmean that it isn't square.", "start": 3397.22, "duration": 2.22}, {"text": "NORVIN RICHARDS: Yeah.", "start": 3399.44, "duration": 0.27}, {"text": "AUDIENCE: If it\nisn't a square, that", "start": 3399.71, "duration": 1.62}, {"text": "means it's definitely\nnot rectangle.", "start": 3401.33, "duration": 1.5}, {"text": "NORVIN RICHARDS: Yeah.", "start": 3402.83, "duration": 0.3}, {"text": "OK.", "start": 3403.13, "duration": 0.5}, {"text": "That's--", "start": 3403.63, "duration": 0.7}, {"text": "AUDIENCE: Other way around.", "start": 3404.33, "duration": 0.51}, {"text": "NORVIN RICHARDS: OK,\nother way around.", "start": 3404.84, "duration": 0.99}, {"text": "Good.", "start": 3405.83, "duration": 0.6}, {"text": "Yes.", "start": 3406.43, "duration": 0.51}, {"text": "AUDIENCE: I think\nthat the logic rules", "start": 3406.94, "duration": 1.95}, {"text": "are like if you have something\nlike, \"if p, then q,\" then", "start": 3408.89, "duration": 5.07}, {"text": "it follows that \"not\nq implies not p.\"", "start": 3413.96, "duration": 3.57}, {"text": "But you have no idea\nwhether q implies p or not.", "start": 3417.53, "duration": 3.895}, {"text": "NORVIN RICHARDS: Yes.", "start": 3421.425, "duration": 0.875}, {"text": "Yes.", "start": 3422.3, "duration": 0.51}, {"text": "Yes.", "start": 3422.81, "duration": 0.5}, {"text": "Yes, that's true.", "start": 3423.31, "duration": 0.82}, {"text": "So that is what people\nsay about [INAUDIBLE]..", "start": 3424.13, "duration": 4.47}, {"text": "Yeah, you're right.", "start": 3428.6, "duration": 2.85}, {"text": "Yes.", "start": 3431.45, "duration": 0.99}, {"text": "OK, good.", "start": 3432.44, "duration": 2.93}, {"text": "I'm going to move\naway from entailment", "start": 3435.37, "duration": 1.83}, {"text": "and start talking\nabout presupposition.", "start": 3437.2, "duration": 3.27}, {"text": "Presupposition is another kind\nof relation between sentences.", "start": 3440.47, "duration": 2.625}, {"text": "Again, it doesn't matter whether\nthe sentences are true or not,", "start": 3443.095, "duration": 2.625}, {"text": "you're being invited\nto imagine what life", "start": 3445.72, "duration": 1.71}, {"text": "would be if they were true.", "start": 3447.43, "duration": 2.53}, {"text": "So a sentence like \"The\npresent King of France is bald\"", "start": 3449.96, "duration": 5.41}, {"text": "presupposes that there is\na present King of France.", "start": 3455.37, "duration": 5.38}, {"text": "So this is different\nfrom entailment, in ways", "start": 3460.75, "duration": 3.935}, {"text": "that I think I illustrate\non the next slides.", "start": 3464.685, "duration": 1.875}, {"text": "Yes.", "start": 3466.56, "duration": 1.008}, {"text": "Crucially different\nfrom entitlement.", "start": 3467.568, "duration": 1.542}, {"text": "So if I say \"The present\nKing of France is bald,\"", "start": 3469.11, "duration": 4.65}, {"text": "or if I say \"The present\nKing of France is not bald,\"", "start": 3473.76, "duration": 3.7}, {"text": "or if I say-- if I ask you,\n\"Is the present King of France", "start": 3477.46, "duration": 2.79}, {"text": "bald,\" all of those have this\nrelation of presupposition", "start": 3480.25, "duration": 4.53}, {"text": "to there is a present\nKing of France.", "start": 3484.78, "duration": 2.28}, {"text": "That is-- we can stick\nto the first two--", "start": 3487.06, "duration": 2.52}, {"text": "If I say \"The present\nKing of France is bald,\"", "start": 3489.58, "duration": 1.92}, {"text": "or if I say \"The present\nKing of France is not bald,\"", "start": 3491.5, "duration": 2.328}, {"text": "for either of those\nto be true, there", "start": 3493.828, "duration": 1.542}, {"text": "has to be a present\nKing of France.", "start": 3495.37, "duration": 3.28}, {"text": "That's different\nfrom entailment.", "start": 3498.65, "duration": 2.37}, {"text": "So for entailment,\nwhen we did things", "start": 3501.02, "duration": 3.3}, {"text": "like \"John killed an\nant,\" and \"The ant died,\"", "start": 3504.32, "duration": 9.48}, {"text": "that's an entailment relation.", "start": 3513.8, "duration": 1.65}, {"text": "If I say \"John didn't\nkill an ant,\" well,", "start": 3515.45, "duration": 3.66}, {"text": "if John didn't kill\nan ant, then the ant", "start": 3519.11, "duration": 2.01}, {"text": "didn't die, at least,\nnot necessarily.", "start": 3521.12, "duration": 2.28}, {"text": "It might be alive.", "start": 3523.4, "duration": 0.93}, {"text": "So to say that John killed an\nant entails that the ant died.", "start": 3524.33, "duration": 3.942}, {"text": "And if I negate\nthe first sentence,", "start": 3528.272, "duration": 1.458}, {"text": "I no longer entail\nwhat I used to entail.", "start": 3529.73, "duration": 3.21}, {"text": "But if you negate a sentence\nthat presupposes something,", "start": 3532.94, "duration": 3.28}, {"text": "so if you add not--", "start": 3536.22, "duration": 0.96}, {"text": "if you go from \"The\npresent King France", "start": 3537.18, "duration": 1.625}, {"text": "is bald\" to \"The present\nKing of France is not bald,\"", "start": 3538.805, "duration": 2.085}, {"text": "you still have the\npreposition-- the preposition--", "start": 3540.89, "duration": 2.16}, {"text": "the presuppositions\nthat you used to have.", "start": 3543.05, "duration": 2.07}, {"text": "You still presuppose--\nit still has", "start": 3545.12, "duration": 1.68}, {"text": "to be true that there is\na present King of France.", "start": 3546.8, "duration": 3.18}, {"text": "Yes?", "start": 3549.98, "duration": 1.218}, {"text": "AUDIENCE: Let's say there is\nno current King of France.", "start": 3551.198, "duration": 2.292}, {"text": "NORVIN RICHARDS:\nYes, which is true,", "start": 3553.49, "duration": 1.523}, {"text": "by the way, if\nanybody is learning", "start": 3555.013, "duration": 1.417}, {"text": "about the world from this class.", "start": 3556.43, "duration": 2.983}, {"text": "AUDIENCE: [INAUDIBLE]", "start": 3559.413, "duration": 1.727}, {"text": "NORVIN RICHARDS: Oh.", "start": 3562.107, "duration": 0.833}, {"text": "So if there is no present\nKing of France, ah.", "start": 3562.94, "duration": 2.88}, {"text": "If there is no present\nKing of France--", "start": 3565.82, "duration": 3.0}, {"text": "good point-- their truth\nvalue becomes difficult.", "start": 3568.82, "duration": 9.0}, {"text": "This is sometimes called\npresupposition failure.", "start": 3577.82, "duration": 2.74}, {"text": "So if I say a sentence that\npresupposes something false--", "start": 3580.56, "duration": 5.073}, {"text": "we're actually going\nto talk about this,", "start": 3585.633, "duration": 1.667}, {"text": "I think, on the next slide--", "start": 3587.3, "duration": 2.1}, {"text": "your cognitive state\nbecomes difficult.", "start": 3589.4, "duration": 2.59}, {"text": "So this is a classic of--", "start": 3591.99, "duration": 5.38}, {"text": "it's used in politics\nand also in comedy.", "start": 3597.37, "duration": 3.54}, {"text": "Unfortunate example\nfrom the Marx brothers--", "start": 3600.91, "duration": 1.987}, {"text": "the Marx brothers\nasked at some point,", "start": 3602.897, "duration": 1.583}, {"text": "\"Have you stopped\nbeating your wife?\"", "start": 3604.48, "duration": 1.542}, {"text": "The point of the question is\nthat there's no good answer.", "start": 3608.41, "duration": 4.32}, {"text": "If you say, yes or no, you're\naccepting the presupposition", "start": 3612.73, "duration": 5.64}, {"text": "that you used to beat your wife.", "start": 3618.37, "duration": 1.35}, {"text": "That's what this\nquestion does, right?", "start": 3619.72, "duration": 3.27}, {"text": "The corresponding statement\nhas the same presupposition.", "start": 3622.99, "duration": 3.15}, {"text": "So \"He stopped\nsmoking\" presupposes", "start": 3626.14, "duration": 7.44}, {"text": "that he used to smoke.", "start": 3633.58, "duration": 2.61}, {"text": "And that means that\nif I presuppose", "start": 3636.19, "duration": 5.85}, {"text": "something which is\nfalse, so if you ask me,", "start": 3642.04, "duration": 1.98}, {"text": "have you stopped smoking,\nyou're presupposing", "start": 3644.02, "duration": 2.635}, {"text": "that I used to smoke.", "start": 3646.655, "duration": 0.875}, {"text": "And if that's false,\nit's not enough", "start": 3647.53, "duration": 1.68}, {"text": "for me to either say yes or no.", "start": 3649.21, "duration": 1.71}, {"text": "I inherit your presupposition.", "start": 3650.92, "duration": 2.61}, {"text": "I have to say something.", "start": 3653.53, "duration": 1.48}, {"text": "I have to say something\nlike, \"Wait, I never", "start": 3655.01, "duration": 2.21}, {"text": "smoked in the first place.", "start": 3657.22, "duration": 1.8}, {"text": "Your presupposition is false\"--", "start": 3659.02, "duration": 2.197}, {"text": "something like that.", "start": 3661.217, "duration": 0.833}, {"text": "There's-- in the\nliterature on Zen Buddhism,", "start": 3662.05, "duration": 4.35}, {"text": "which I'm not an expert on,\nthere's a kind of exchange", "start": 3666.4, "duration": 3.75}, {"text": "between teachers and students\nthat happens a lot where", "start": 3670.15, "duration": 3.18}, {"text": "a teacher will ask a\nstudent the question.", "start": 3673.33, "duration": 2.397}, {"text": "The teacher-- the student\nwill ask something", "start": 3675.727, "duration": 1.833}, {"text": "like, \"Does the dog\nhave the Buddha nature?\"", "start": 3677.56, "duration": 3.63}, {"text": "or something like that.", "start": 3681.19, "duration": 1.0}, {"text": "And the teacher,\nby way of answer,", "start": 3682.19, "duration": 2.72}, {"text": "will haul off and\nslap the student,", "start": 3684.91, "duration": 2.64}, {"text": "or pour cold water on the\nstudent, or shout \"mu!\"", "start": 3687.55, "duration": 4.32}, {"text": "and the student is enlightened.", "start": 3691.87, "duration": 2.28}, {"text": "This is a kind of story you\nsee a lot in the Zen Buddhism", "start": 3694.15, "duration": 2.82}, {"text": "literature.", "start": 3696.97, "duration": 1.437}, {"text": "I don't know a whole\nlot about Zen Buddhism,", "start": 3698.407, "duration": 1.833}, {"text": "but I've always\nwondered whether \"mu!\"", "start": 3700.24, "duration": 2.07}, {"text": "means you are making a\nfalse presupposition.", "start": 3702.31, "duration": 3.55}, {"text": "Because it's an interesting\nfact about languages", "start": 3705.86, "duration": 2.0}, {"text": "that we have words\nlike \"yes\" or \"no\"", "start": 3707.86, "duration": 2.04}, {"text": "that say things like\n\"The statement that", "start": 3709.9, "duration": 4.17}, {"text": "underlies your question\nis true or false.\"", "start": 3714.07, "duration": 2.7}, {"text": "If I ask you \"Is it raining?\"", "start": 3716.77, "duration": 1.62}, {"text": "you're asking me to evaluate\nthe truth or falsehood of \"It", "start": 3718.39, "duration": 3.12}, {"text": "is raining?\"", "start": 3721.51, "duration": 0.81}, {"text": "And I'm supposed to\nsay either \"Yes, it's", "start": 3722.32, "duration": 2.22}, {"text": "true that it is\nraining,\" or \"No,", "start": 3724.54, "duration": 1.5}, {"text": "it's false that it's raining.\"", "start": 3726.04, "duration": 1.97}, {"text": "You ask me \"Have you\nstopped smoking?\"", "start": 3728.01, "duration": 2.492}, {"text": "the statement that you're\nasking me to evaluate", "start": 3730.502, "duration": 1.958}, {"text": "is \"You have stopped smoking.\"", "start": 3732.46, "duration": 1.6}, {"text": "And I have \"yes\" and \"no\"\nas my standard options.", "start": 3734.06, "duration": 3.71}, {"text": "But I don't have an\noption that says there", "start": 3737.77, "duration": 2.04}, {"text": "is a false presupposition.", "start": 3739.81, "duration": 1.62}, {"text": "And most languages don't.", "start": 3741.43, "duration": 2.062}, {"text": "It's not common for\nlanguages to have something", "start": 3743.492, "duration": 1.958}, {"text": "to say that means you have\nmade a false presupposition.", "start": 3745.45, "duration": 4.11}, {"text": "And so it's interesting\nthat language work this way.", "start": 3749.56, "duration": 3.42}, {"text": "AUDIENCE: That's interesting,\nbecause I think in math,", "start": 3752.98, "duration": 3.18}, {"text": "like in formal logic, if the--", "start": 3756.16, "duration": 4.62}, {"text": "if this, then that, then\nif this is just false,", "start": 3760.78, "duration": 2.77}, {"text": "then it's the whole thing\nis true just by default.", "start": 3763.55, "duration": 3.86}, {"text": "And the thing I'm\nwondering is like,", "start": 3767.41, "duration": 1.77}, {"text": "does this mean that\nwhen you ask a question,", "start": 3769.18, "duration": 2.73}, {"text": "you aren't actually\nasking, like \"Have", "start": 3771.91, "duration": 1.888}, {"text": "you stopped beating your wife?\"", "start": 3773.798, "duration": 1.292}, {"text": "You're asking, like, \"Are\nall the presuppositions", "start": 3775.09, "duration": 3.03}, {"text": "in this true, and\nis this also true?\"", "start": 3778.12, "duration": 3.113}, {"text": "NORVIN RICHARDS:\nSo that's just it", "start": 3781.233, "duration": 1.417}, {"text": "though, I'm not asking you\nwhether the presuppositions are", "start": 3782.65, "duration": 2.4}, {"text": "true.", "start": 3785.05, "duration": 0.5}, {"text": "That's why if I ask\nyou this question--", "start": 3785.55, "duration": 3.79}, {"text": "let's change it to \"Have\nyou stopped smoking?\"--", "start": 3789.34, "duration": 3.18}, {"text": "If I ask you \"Have\nyou stopped smoking?\"", "start": 3792.52, "duration": 2.07}, {"text": "you can't say no\nand have that mean--", "start": 3794.59, "duration": 4.47}, {"text": "and have me interpret that\nas meaning you never smoked", "start": 3799.06, "duration": 3.018}, {"text": "in the first place.", "start": 3802.078, "duration": 0.792}, {"text": "You're absolutely right\nthat if you were--", "start": 3802.87, "duration": 5.76}, {"text": "this is the kind of thing\nthat robots and aliens", "start": 3808.63, "duration": 2.55}, {"text": "get wrong, standardly, in\nscience fiction stories,", "start": 3811.18, "duration": 2.7}, {"text": "that false presuppositions\nlead to ungrammaticality,", "start": 3813.88, "duration": 4.44}, {"text": "or something like that.", "start": 3818.32, "duration": 1.29}, {"text": "There's something\nweird going on.", "start": 3819.61, "duration": 2.13}, {"text": "Did I get it, the\nanswer to your question?", "start": 3821.74, "duration": 2.59}, {"text": "So presupposition\nfailure, this case", "start": 3824.33, "duration": 1.73}, {"text": "where I say something that\nhas a false presupposition, it", "start": 3826.06, "duration": 3.06}, {"text": "doesn't make the sentence false,\nit makes the sentence weird.", "start": 3829.12, "duration": 3.81}, {"text": "Yeah, that's the expression,\nor the feeling that we have.", "start": 3832.93, "duration": 4.62}, {"text": "I skipped some slides\nto get to this one.", "start": 3837.55, "duration": 1.78}, {"text": "So let me go back a bit.", "start": 3839.33, "duration": 1.0}, {"text": "So \"The present King\nof France is bald\"", "start": 3844.01, "duration": 3.66}, {"text": "presupposes that there is\na present King of France.", "start": 3847.67, "duration": 2.23}, {"text": "It entails that the\npresent King of France", "start": 3849.9, "duration": 1.75}, {"text": "has no hair, because\nthat's what it means.", "start": 3851.65, "duration": 3.53}, {"text": "And so, if I say \"The present\nKing of France is not bald,\"", "start": 3855.18, "duration": 5.15}, {"text": "that no longer entails\nthat he has no hair.", "start": 3860.33, "duration": 2.34}, {"text": "That's the difference\nbetween entailments", "start": 3862.67, "duration": 1.92}, {"text": "and presuppositions.", "start": 3864.59, "duration": 1.11}, {"text": "Entailments don't\nsurvive negation.", "start": 3865.7, "duration": 3.42}, {"text": "If you add \"not,\" then\nyou lose the entailments", "start": 3869.12, "duration": 2.58}, {"text": "that you used to have.", "start": 3871.7, "duration": 1.2}, {"text": "But you still have\nthe presuppositions", "start": 3872.9, "duration": 1.92}, {"text": "that you used to have.", "start": 3874.82, "duration": 1.68}, {"text": "Yeah?", "start": 3876.5, "duration": 0.96}, {"text": "AUDIENCE: Did that say\nthat entails the opposite?", "start": 3877.46, "duration": 3.98}, {"text": "NORVIN RICHARDS: Say it again.", "start": 3881.44, "duration": 1.25}, {"text": "AUDIENCE: Did you then\njust say that entailment", "start": 3882.69, "duration": 1.57}, {"text": "is the opposite?", "start": 3884.26, "duration": 0.667}, {"text": "Like it entails\nthat he has hair?", "start": 3884.927, "duration": 2.143}, {"text": "NORVIN RICHARDS: Oh, in\nthis particular case?", "start": 3887.07, "duration": 1.875}, {"text": "Yes.", "start": 3892.17, "duration": 1.47}, {"text": "I think we're going to find\nexamples where A entails B,", "start": 3893.64, "duration": 6.94}, {"text": "But not A does not entail\nnot B. So yeah, if something", "start": 3900.58, "duration": 5.28}, {"text": "is a rectangle, then it-- no.", "start": 3905.86, "duration": 3.838}, {"text": "If something is a square,\nthen it is a rectangle.", "start": 3909.698, "duration": 2.042}, {"text": "Did I get that right?", "start": 3911.74, "duration": 1.8}, {"text": "But if something\nis not a square,", "start": 3913.54, "duration": 3.21}, {"text": "that doesn't mean that\nit's not a rectangle.", "start": 3916.75, "duration": 2.17}, {"text": "So yes, that's a case where A\nentails B, but not A doesn't", "start": 3918.92, "duration": 3.77}, {"text": "entail not B. Yeah, good.", "start": 3922.69, "duration": 3.22}, {"text": "Phew.", "start": 3925.91, "duration": 0.5}, {"text": "And then presuppositions--\nyeah, presuppositions are funny.", "start": 3936.12, "duration": 2.56}, {"text": "So if depending on\nthe presupposition--", "start": 3938.68, "duration": 4.82}, {"text": "so if we hear scratching\nat the door, I could say,", "start": 3943.5, "duration": 2.55}, {"text": "\"The cat is at the\ndoor,\" out of the blue.", "start": 3946.05, "duration": 3.375}, {"text": "But there's a\npresupposition there,", "start": 3949.425, "duration": 2.185}, {"text": "which is that \"There is a cat.\"", "start": 3951.61, "duration": 1.61}, {"text": "It's kind of like \"The present\nKing of France is bald\"", "start": 3953.22, "duration": 2.52}, {"text": "presupposes that there\nis a King of France.", "start": 3955.74, "duration": 3.33}, {"text": "There's a process, what's called\naccommodating presuppositions,", "start": 3959.07, "duration": 3.39}, {"text": "and this is why\npresuppositions are so handy", "start": 3962.46, "duration": 2.19}, {"text": "in comedy and in politics.", "start": 3964.65, "duration": 1.92}, {"text": "You make-- you say things that\npresuppose things, and then", "start": 3966.57, "duration": 5.31}, {"text": "people accommodate your\npresuppositions sometimes", "start": 3971.88, "duration": 2.25}, {"text": "without realizing it.", "start": 3974.13, "duration": 1.18}, {"text": "So if I, out of the blue,\nsay, \"The cat is at the door,\"", "start": 3975.31, "duration": 2.943}, {"text": "you didn't know before\nthat I had a cat.", "start": 3978.253, "duration": 1.667}, {"text": "I hadn't mentioned a cat before.", "start": 3979.92, "duration": 1.333}, {"text": "But my sentence presupposes\nthat there is a cat.", "start": 3981.253, "duration": 3.947}, {"text": "And so you learn from my\nsentence that there is a cat", "start": 3985.2, "duration": 2.76}, {"text": "and you add that to\nyour knowledge base.", "start": 3987.96, "duration": 4.62}, {"text": "If I were to instead say,\n\"The giraffe is at the door,\"", "start": 3992.58, "duration": 3.72}, {"text": "you'd probably be less\npeaceful about it.", "start": 3996.3, "duration": 3.09}, {"text": "So if I make you\npresuppose something", "start": 3999.39, "duration": 2.73}, {"text": "that's easy to presuppose,\nyou do it without noticing it.", "start": 4002.12, "duration": 3.45}, {"text": "It's not like you consciously\ngo through a state of,", "start": 4005.57, "duration": 5.61}, {"text": "if I say \"The cat\nis at the door,\"", "start": 4011.18, "duration": 1.48}, {"text": "it's not like you\nthink to yourself,", "start": 4012.66, "duration": 1.5}, {"text": "\"Ah, he must have a cat.", "start": 4014.16, "duration": 3.338}, {"text": "Write down in your mental\nnotebook he must have a cat.\"", "start": 4017.498, "duration": 2.292}, {"text": "Maybe that's happening\non some very fast level,", "start": 4019.79, "duration": 2.25}, {"text": "but you're not conscious of it.", "start": 4022.04, "duration": 2.035}, {"text": "On the other hand, if I say\n\"The giraffe is at the door,\"", "start": 4024.075, "duration": 2.375}, {"text": "then you have the\nsensation of having", "start": 4026.45, "duration": 2.13}, {"text": "learned something significant.", "start": 4028.58, "duration": 1.59}, {"text": "Right, and similarly, \"I regret\nhaving been born in 1857.\"", "start": 4034.42, "duration": 3.39}, {"text": "If I say that and\nsomebody objects,", "start": 4037.81, "duration": 2.34}, {"text": "I say, OK, \"I don't regret\nhaving been born in 1857.\"", "start": 4040.15, "duration": 3.69}, {"text": "Either of these presupposes\nthat I was born in 1857.", "start": 4043.84, "duration": 3.48}, {"text": "And in order for\nsomebody to object,", "start": 4047.32, "duration": 2.977}, {"text": "they have to say\n\"No, wait, surely you", "start": 4050.297, "duration": 1.583}, {"text": "were not born in 1857.\"", "start": 4051.88, "duration": 3.52}, {"text": "So that's entailments\nand presuppositions.", "start": 4055.4, "duration": 2.49}, {"text": "There are also implicatures,\nwhich I think we have time for.", "start": 4057.89, "duration": 2.82}, {"text": "The implicatures\nare things that you", "start": 4060.71, "duration": 1.95}, {"text": "might tend to infer\nfrom hearing a sentence", "start": 4062.66, "duration": 2.4}, {"text": "but that might not\nbe true at all.", "start": 4065.06, "duration": 2.2}, {"text": "So, for example, if I\nask you a question, like", "start": 4067.26, "duration": 4.04}, {"text": "\"Can you open the window?\"", "start": 4071.3, "duration": 2.532}, {"text": "there's an implicature\nthat I would", "start": 4073.832, "duration": 1.458}, {"text": "like you to open the window.", "start": 4075.29, "duration": 2.81}, {"text": "It's not entailed\nor presupposed.", "start": 4078.1, "duration": 2.94}, {"text": "But you, when you\nhear me say that,", "start": 4081.04, "duration": 2.04}, {"text": "you're likely to\nconclude that I wish", "start": 4083.08, "duration": 1.83}, {"text": "that you would open the window.", "start": 4084.91, "duration": 1.32}, {"text": "Or if I ask you,\n\"Where's the salt?\"", "start": 4086.23, "duration": 4.86}, {"text": "there is a minimally\ncooperative answer to that", "start": 4091.09, "duration": 3.3}, {"text": "in which you point, you know.", "start": 4094.39, "duration": 2.639}, {"text": "But what I really want you\nto do is give me some salt.", "start": 4097.029, "duration": 3.54}, {"text": "Or if I say I am 21,\nthere is an implication", "start": 4100.569, "duration": 4.561}, {"text": "that I am 21, that, I'm,\nin fact, exactly 21.", "start": 4105.13, "duration": 3.045}, {"text": "21 is my age.", "start": 4108.175, "duration": 2.595}, {"text": "Or if I say \"Mary ate\nsome of the cookies,\"", "start": 4110.77, "duration": 3.39}, {"text": "there's an implicature that\nthere are some cookies left.", "start": 4114.16, "duration": 4.319}, {"text": "But all of these\nthings could be false,", "start": 4118.479, "duration": 2.431}, {"text": "under the right circumstances.", "start": 4120.91, "duration": 1.81}, {"text": "So if I ask you, \"Can\nyou open the window?\"", "start": 4122.72, "duration": 3.29}, {"text": "probably what I-- under most\ncircumstances, what I want", "start": 4126.01, "duration": 2.67}, {"text": "you to do is open the window.", "start": 4128.68, "duration": 1.41}, {"text": "But maybe what I'm\ndoing is making", "start": 4130.09, "duration": 2.46}, {"text": "a study of physical\nfitness in MIT students", "start": 4132.55, "duration": 2.08}, {"text": "and I want to know\nwhether you're", "start": 4134.63, "duration": 1.375}, {"text": "capable of opening the window.", "start": 4136.005, "duration": 1.735}, {"text": "Or \"Where's the salt?\"--\nmaybe, in most circumstances,", "start": 4137.74, "duration": 3.35}, {"text": "what I want you to do\nis hand me the salt,", "start": 4141.09, "duration": 1.75}, {"text": "but maybe I'm making\na map of the kitchen.", "start": 4142.84, "duration": 2.49}, {"text": "Or there are circumstances\nin which I could say,", "start": 4145.33, "duration": 2.609}, {"text": "I, personally, could\nsay, I'm 21, namely,", "start": 4147.939, "duration": 3.031}, {"text": "when I'm trying to go\ninto a bar or something,", "start": 4150.97, "duration": 2.13}, {"text": "and they tell you \"You can't\ncome in here unless you're 21.\"", "start": 4153.1, "duration": 3.27}, {"text": "I could say \"I'm 21.\"", "start": 4156.37, "duration": 3.37}, {"text": "In fact, I'm 50.", "start": 4159.74, "duration": 2.23}, {"text": "But what I mean is, I\nsatisfy the requirement.", "start": 4161.97, "duration": 5.537}, {"text": "Do people agree with that?", "start": 4167.507, "duration": 1.083}, {"text": "There's another kind of example\nlike this that people give.", "start": 4171.16, "duration": 3.63}, {"text": "Imagine that the\ngovernment is going", "start": 4174.79, "duration": 1.83}, {"text": "to have a tax break for people\nwith two children, two or more.", "start": 4176.62, "duration": 8.25}, {"text": "And so, I claim this\ntax benefit on my taxes.", "start": 4184.87, "duration": 6.449}, {"text": "And then someone from the\ngovernment comes by and says,", "start": 4191.319, "duration": 2.521}, {"text": "you claimed this benefit.", "start": 4193.84, "duration": 1.38}, {"text": "You're claiming to\nhave two children.", "start": 4195.22, "duration": 1.64}, {"text": "I say, I do have two children.", "start": 4196.86, "duration": 1.25}, {"text": "In fact, I have six.", "start": 4198.11, "duration": 0.833}, {"text": "This is something that people\nseem to think about-- numbers,", "start": 4201.64, "duration": 3.81}, {"text": "that numbers imply\nexactly the number,", "start": 4205.45, "duration": 4.86}, {"text": "but they don't entail\nexactly the number.", "start": 4210.31, "duration": 2.28}, {"text": "They just imply\nit very strongly.", "start": 4212.59, "duration": 2.16}, {"text": "And under the right\ncircumstances,", "start": 4214.75, "duration": 1.882}, {"text": "you can convince yourself\nthat what they really", "start": 4216.632, "duration": 1.958}, {"text": "mean, what they actually\nentail is that number or more.", "start": 4218.59, "duration": 4.45}, {"text": "These kinds of circumstances\nlead people to think that.", "start": 4223.04, "duration": 3.12}, {"text": "Yeah?", "start": 4226.16, "duration": 0.63}, {"text": "AUDIENCE: I wonder\nif in languages", "start": 4226.79, "duration": 2.19}, {"text": "where instead of saying\nthings like \"I am 21,\"", "start": 4228.98, "duration": 2.43}, {"text": "you're saying \"I have\n21 years,\" whether it", "start": 4231.41, "duration": 2.55}, {"text": "be more likely that you\naccept like oh yeah,", "start": 4233.96, "duration": 2.58}, {"text": "like if you're 50, you have\n50, then you probably have 25.", "start": 4236.54, "duration": 4.42}, {"text": "Like maybe, because\nwe think of it", "start": 4240.96, "duration": 1.7}, {"text": "as an identity\nthing [INAUDIBLE]..", "start": 4242.66, "duration": 1.455}, {"text": "NORVIN RICHARDS: It would be\ninteresting to study that.", "start": 4244.115, "duration": 3.345}, {"text": "So people, when I\nsaid that I could", "start": 4247.46, "duration": 1.77}, {"text": "say to the guy at\nthe bar \"I'm 21\"--", "start": 4249.23, "duration": 2.34}, {"text": "yeah.", "start": 4251.57, "duration": 0.6}, {"text": "I'm sorry, I'm stepping\non what you're saying.", "start": 4252.17, "duration": 2.19}, {"text": "You're absolutely right.", "start": 4254.36, "duration": 0.54}, {"text": "There are languages out\nthere, like Spanish,", "start": 4254.9, "duration": 1.833}, {"text": "in which to say I'm 21,\nyou say \"I have 21 years,\"", "start": 4256.733, "duration": 2.157}, {"text": "or something like that.", "start": 4258.89, "duration": 0.958}, {"text": "Were people just\nbeing polite when", "start": 4262.19, "duration": 1.44}, {"text": "I said to-- that I could say\nto the guy at the bar I'm 21?", "start": 4263.63, "duration": 5.22}, {"text": "Did people want to\nobject that would", "start": 4268.85, "duration": 2.13}, {"text": "be a weird thing for me to say?", "start": 4270.98, "duration": 2.25}, {"text": "Some people think that would\nbe a weird thing for me to say.", "start": 4273.23, "duration": 2.5}, {"text": "What should I say?", "start": 4275.73, "duration": 2.09}, {"text": "I'm 50.", "start": 4277.82, "duration": 2.12}, {"text": "Yeah?", "start": 4279.94, "duration": 1.47}, {"text": "AUDIENCE: [INAUDIBLE]\nlike, \"I'm over 21.\"", "start": 4281.41, "duration": 2.142}, {"text": "NORVIN RICHARDS:\nOh, \"I'm over 21.\"", "start": 4283.552, "duration": 1.458}, {"text": "Suppose the guy has just\nsaid to me, you have to be 21", "start": 4285.01, "duration": 2.01}, {"text": "to get inside.", "start": 4287.02, "duration": 0.75}, {"text": "First of all, notice,\nhe can say that.", "start": 4287.77, "duration": 1.81}, {"text": "He can say you have to\nbe 21 to get inside.", "start": 4289.58, "duration": 1.94}, {"text": "He doesn't mean we don't\nallow 22-year-olds, right?", "start": 4291.52, "duration": 4.92}, {"text": "He means you have\nto be 21 or higher.", "start": 4296.44, "duration": 2.88}, {"text": "And what I'm saying is I\nsatisfy your requirement.", "start": 4299.32, "duration": 4.652}, {"text": "But I take your point.", "start": 4307.83, "duration": 2.35}, {"text": "All of you go to bars\nand try this out.", "start": 4310.18, "duration": 1.86}, {"text": "No--", "start": 4312.04, "duration": 0.5}, {"text": "[LAUGHS]", "start": 4312.54, "duration": 1.172}, {"text": "Oh, darn, I've been\nrecorded saying that.", "start": 4313.712, "duration": 1.708}, {"text": "This is bad.", "start": 4315.42, "duration": 0.51}, {"text": "Oh yeah, and \"Mary ate\nsome of the cookies\"", "start": 4323.92, "duration": 1.922}, {"text": "implies that she didn't eat\nall of them, but maybe she did.", "start": 4325.842, "duration": 2.458}, {"text": "So presuppositions are\ndifferent from this.", "start": 4330.88, "duration": 3.73}, {"text": "So I can say things\nlike \"I'm 21.", "start": 4334.61, "duration": 3.26}, {"text": "In fact, I'm 50.\"", "start": 4337.87, "duration": 1.08}, {"text": "Or \"Mary ate some\nof the cookies.", "start": 4338.95, "duration": 1.99}, {"text": "In fact, to be perfectly\nfrank, she ate them all,", "start": 4340.94, "duration": 3.14}, {"text": "just so you know.\"", "start": 4344.08, "duration": 1.32}, {"text": "And that's, perhaps, a slightly\nodd way of telling you that,", "start": 4345.4, "duration": 2.87}, {"text": "but I can tell you that.", "start": 4348.27, "duration": 1.0}, {"text": "There's nothing too\nsurprising about it.", "start": 4349.27, "duration": 2.2}, {"text": "On the other hand, if I say\n\"The King of France is bald, oh,", "start": 4351.47, "duration": 2.54}, {"text": "and by the way, there\nis no King of France,\"", "start": 4354.01, "duration": 2.16}, {"text": "then I am very weird.", "start": 4356.17, "duration": 2.52}, {"text": "And I know.", "start": 4358.69, "duration": 0.69}, {"text": "I have spent a lifetime\nresearching ways", "start": 4359.38, "duration": 1.89}, {"text": "to be very weird.", "start": 4361.27, "duration": 0.78}, {"text": "This is one of the best ones.", "start": 4362.05, "duration": 1.23}, {"text": "So saying something\nthat presupposes--", "start": 4363.28, "duration": 3.12}, {"text": "saying A that\npresupposes B, and then,", "start": 4366.4, "duration": 2.19}, {"text": "saying oh, and B\nis false, that's", "start": 4368.59, "duration": 2.67}, {"text": "just like a very\npeculiar thing to do.", "start": 4371.26, "duration": 3.84}, {"text": "So to summarize, we've\ntalked about three kinds", "start": 4375.1, "duration": 3.26}, {"text": "of relations between sentences.", "start": 4378.36, "duration": 1.87}, {"text": "So a sentence can\nhave entailments.", "start": 4380.23, "duration": 2.78}, {"text": "So the entailments\nof a sentence A,", "start": 4383.01, "duration": 2.43}, {"text": "have to be true if A is true.", "start": 4385.44, "duration": 3.66}, {"text": "Presuppositions have\nto be true for A", "start": 4389.1, "duration": 1.83}, {"text": "to be either true or false.", "start": 4390.93, "duration": 2.41}, {"text": "So \"The King of France\nis bald\" presupposes", "start": 4393.34, "duration": 4.07}, {"text": "that there is a King of France.", "start": 4397.41, "duration": 1.42}, {"text": "So there has to be a\nKing of France for it", "start": 4398.83, "duration": 2.24}, {"text": "to be either true or false that\n\"The King of France is bald.\"", "start": 4401.07, "duration": 4.63}, {"text": "And then implicatures are\nthings that yeah, could be true.", "start": 4405.7, "duration": 3.387}, {"text": "You might be inclined to think\nthat they're true if A is true,", "start": 4409.087, "duration": 2.583}, {"text": "but they might be false.", "start": 4411.67, "duration": 1.29}, {"text": "And if I say A and then\nsay oh and by the way,", "start": 4412.96, "duration": 2.64}, {"text": "this implicature is false,\nyou're not distraught.", "start": 4415.6, "duration": 4.98}, {"text": "Or to put it another\nway, if you're", "start": 4420.58, "duration": 2.16}, {"text": "asking about one\nsentence P, is P", "start": 4422.74, "duration": 2.64}, {"text": "an entailment, or\na presupposition,", "start": 4425.38, "duration": 1.68}, {"text": "or an implicature\nof A, the thing", "start": 4427.06, "duration": 1.77}, {"text": "to ask yourself is, \"Does\nP have to be true for A", "start": 4428.83, "duration": 3.99}, {"text": "to be either true or false?\"", "start": 4432.82, "duration": 2.05}, {"text": "If so, then it's\na presupposition.", "start": 4434.87, "duration": 2.84}, {"text": "\"Does P have to be true\njust if A is true?\"", "start": 4437.71, "duration": 2.98}, {"text": "If so, it's an entailment.", "start": 4440.69, "duration": 2.31}, {"text": "So it's not a presupposition.", "start": 4443.0, "duration": 2.66}, {"text": "It's an entailment.", "start": 4445.66, "duration": 1.41}, {"text": "And then \"Does P have\nto be true at all,", "start": 4447.07, "duration": 2.58}, {"text": "or is it just something you\nmight be inclined to think?\"", "start": 4449.65, "duration": 3.0}, {"text": "So then it's an implicature.", "start": 4452.65, "duration": 3.8}, {"text": "I want to practice this\nfor like two minutes.", "start": 4456.45, "duration": 2.83}, {"text": "So if I say, \"Bill isn't\naware that Susan is pregnant,\"", "start": 4459.28, "duration": 3.98}, {"text": "that's a sentence.", "start": 4463.26, "duration": 1.08}, {"text": "And now here are two\nsentences that we", "start": 4464.34, "duration": 2.672}, {"text": "can talk about the relationship\nbetween the first sentence,", "start": 4467.012, "duration": 2.458}, {"text": "and the second, and the third.", "start": 4469.47, "duration": 1.57}, {"text": "So \"Bill isn't aware\nthat Susan is pregnant.\"", "start": 4471.04, "duration": 2.36}, {"text": "What's the relationship\nbetween that and the sentence", "start": 4473.4, "duration": 3.69}, {"text": "\"Susan is pregnant?\"", "start": 4477.09, "duration": 1.23}, {"text": "Is that presupposition or\nentailment or implicature?", "start": 4478.32, "duration": 4.198}, {"text": "AUDIENCE: Presupposition.", "start": 4482.518, "duration": 1.042}, {"text": "NORVIN RICHARDS:\nPresupposition, why?", "start": 4483.56, "duration": 1.542}, {"text": "AUDIENCE: Well because whether\nBill is aware of or not aware", "start": 4488.72, "duration": 4.01}, {"text": "that Susan is\npregnant, they both", "start": 4492.73, "duration": 3.037}, {"text": "mean Susan is pregnant versus--", "start": 4495.767, "duration": 2.575}, {"text": "NORVIN RICHARDS: Right.", "start": 4498.342, "duration": 0.958}, {"text": "That's the way to\ndemonstrate that.", "start": 4499.3, "duration": 1.63}, {"text": "So both the sentence--\nfor either \"Bill", "start": 4500.93, "duration": 4.04}, {"text": "isn't aware that\nSusan is pregnant\"", "start": 4504.97, "duration": 1.74}, {"text": "or \"Bill is aware that Susan\nis pregnant\" to be true,", "start": 4506.71, "duration": 3.87}, {"text": "Susan has to be pregnant.", "start": 4510.58, "duration": 1.32}, {"text": "It has to be true that\nSusan is pregnant.", "start": 4511.9, "duration": 2.008}, {"text": "What about the second\nsentence, or last sentence,", "start": 4513.908, "duration": 2.042}, {"text": "\"You should tell Bill\nthat Susan is pregnant.\"", "start": 4515.95, "duration": 3.42}, {"text": "That's an implicature.", "start": 4519.37, "duration": 1.2}, {"text": "So there could be\ncircumstances under which I", "start": 4520.57, "duration": 2.85}, {"text": "would say that first sentence\non order to communicate to you", "start": 4523.42, "duration": 3.0}, {"text": "that last sentence, but it\ndoesn't have to be true.", "start": 4526.42, "duration": 3.69}, {"text": "It's just the kind of\nthing you might conclude.", "start": 4530.11, "duration": 2.285}, {"text": "So that's a presupposition.", "start": 4532.395, "duration": 1.125}, {"text": "That's implicature.", "start": 4533.52, "duration": 2.58}, {"text": "We will do much more\nof this next time.", "start": 4536.1, "duration": 2.5}, {"text": "Have a good weekend.", "start": 4538.6, "duration": 1.72}]
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